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                                   EPA-650/2-74-030
   AN  INTERPRETATIVE  COMPILATION
        OF  EPA  STUDIES RELATED
TO  COAL  QUALITY  AND  CLEANABILITY
                        by

           L. Hoffman, J.B. Truett, and S.J. Aresco

                  The Mitre Corporation
                 Westgate Research Park
                 McLean, Virginia 22101
                 Contract No. 68-02-1352
                  ROAP No. 21AFJ-27
               Program Element No. LAB013
              EPA Project Officer: T.K. Janes

                Control Systems Laboratory
            National Environmental Research Center
             Research Triangle Park, N.C. 27711
                    Prepared for

           OFFICE OF RESEARCH AND DEVELOPMENT
          U.S. ENVIRONMENTAL PROTECTION AGENCY
                WASHINGTON, D-C. 20460

                      May 1974

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This report has been reviewed by the Environmental Protection Agency
and approved for publication.  Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.

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                               ABSTRACT




     This report provides an interpretative compilation of the overall




EPA coal cleaning effort in the form of indepth analysis, evaluation,




and examination of the interrelationships among elements comprising the




EPA coal program.  The report basically addresses coal (1) washability




studies, (2) sulfur reduction by cleaning processes including plant




design and associated economics, and (3) the utilization of reject




sulfur and coal values from the cleaning processes.
                                     iii

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                        ACKNOWLEDGMENTS






     The authors gratefully acknowledge the assistance,




technical support, and consultations provided by Mr. T. K. Janes




of the U. S. Environmental Protection Agency, Mr. A. W. Deurbrouck




of the U. S. Department of Interior, Bureau of Mines and




Dr. J. Burton, Mr. L. Rosenberg and Mrs.  B. Stokes,of The MITRE




Corporation, in the preparation of this study.

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                           TABLE OF CONTENTS
LIST OF ILLUSTRATIONS                                               x

1.0  INTRODUCTION                                                   1

2.0  SUMMARY                                                        12

2.1  Introduction                                                   12
2.2  Washability Studies                                            13
2.3  Laboratory and Pilot Studies Evaluating Processes For Pyrite
     Removal from Fine Coals                                        25

     2.3.1  Principal Findings                                      26

2.4  Prototype Coal Cleaning Plant                                  29
2.5  Pyrite Utilization Economic Studies                            31

     2.5.1  The Bechtel Corporation Study                           32
     2.5.2  The A. D. Little Study                                  33
     2.5.3  The Chemico Study                                       38

3.0  CONCLUSIONS               '                                     42

4.0  WASHABILITY STUDIES                                            48

4.1  Experimental Procedure - Collection of Coal Mine Samples       49
4.2  Procedure for the Conduct of the Washability Studies           49
4.3  Results of Washability Data - Washability Computer Program     52
4.4  Program Results                                                53

     4.4.1  Northern Appalachian Region                             57

            4.4.1.1  Sewickley Coal Bed                             60
            4.4.1.2  Pittsburgh Coal Bed                            60
            4.4.1.3  Upper Freeport Coal Bed                        61
            4.4.1.4  Lower Freeport Coal Bed                        62
            4.4.1.5  Upper Kittanning Coal Bed                      63
            4.4.1.6  Middle Kittanning Coal Bed                     64
            4.4.1.7  Lower Kittanning Coal Bed                      65

     4.4.2  Southern Appalachian Region Coals                       65
     4.4.3  Alabama Region Coals                                    68
     4.4.4  Midwest Region Coals                                    68

            4.4.4.1  Kentucky No. 9 Coal Bed                        70
            4.4.4.2  Illinois Coal Beds                             70
                                    vii

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                      TABLE OF CONTENTS (Cont'd)
     4.4.5  Illinois  Geological  Survey Studies                      72
     4.4.6  Western Coal                                             73
     4.4.7  Extension of  Float-Sink Test  to Finer Grinds            74
     4.4.8  Comparability of  Core Samples and Face Samples          76

5.0  LABORATORY AND PILOT STUDIES EVALUATING PROCESSES FOR PYRITE
     REMOVAL FROM FINE COALS                                         8*

5.1  Wet Concentrating Table                                         85
5.2  Concentrating Spiral                                           90
5.3  Water Cyclone                                                  98
5.4  Air Classifier                                                 103
5.5  Electrokinetics                                                 103
5.6  Agglomo-Separation (Oil)                                       107
5.7  Froth Flotation                                                 113
5.8  Concentration of Pyrite  from Refuse                             117

6.0  PROTOTYPE COAL CLEANING  PLANTS                                 120

6.1  Classification and Selection of Coals                          123
6.2  Design of Roberts and Schaefer Prototype Cleaning Plant,
     Test Plan, and Costs                                           125

     6.2.1  Roberts and Schaefer Plant Design                       125
     6.2.2  Roberts and Schaefer Test-Program                       130
     6.2.3  Roberts and Schaefer Capital  and Operating Costs        135

6.3  Design of the McNally Pittsburg Prototype Cleaning Plant,
     Test Plan and Costs

     6.3.1  McNally Pittsburg Plant Design                          139
     6.3.2  McNally Pittsburg Test-Program                          ^43
     6.3.3  McNally Pittsburg Capital and Operating Costs           147
                                                \
6.4  Data Evaluation                                                ,10

     6.4.1  Details of Presently Available Computer Programs        151
     6.4.2  Correlation of Coal Characteristics with Cleaning
            Results (Multiple Regression  Analysis)                  i CA

7.0  PYRITE UTILIZATION ECONOMIC STUDY                              . .,
                                                                    156
7.1  Purposes of the  Study; Overview and  Approach                   , c/-
7.2  Description of Candidate Recovery Processes

     7.2.1  Brief Description of Recovery Processes                 , ._
     7.2.2  Preliminary Economic Studies  of Selected Processes      ice
     7.2.3  Processes Selected for Detailed Cost Studies


                                  viii

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                      TABLE OF CONTENTS (Cont'd)

                                                                   Page

7.3  Sulfuric Acid Market Analysis                                  173
7.4  Further Analysis of Two Selected Processes                     180

     7.4.1  Refuse-Combustion/Sulfur-Oxide-Removal (Technical
            Aspects)                                                182
     7.4.2  Refuse-Combustion/Sulfur-Oxide-Removal (Economic
            Aspects)                                                184
     7.4.3  Fluidized Bed Roasting of Pyrite, followed by
            Catalytic Oxidation of Sulfur Dioxide - (Technical
            Aspects)                                                198
     7.4.4  Fluidized Bed Roasting of Pyrite Concentrate (Economic
            Aspects)                                                209

7.5  Findings                                                       219

8.0  THE HIGH SULFUR COMBUSTOR — A STUDY OF SYSTEMS FOR
     UTILIZATION OF COAL CLEANING REJECT MATERIAL                   223

8.1  Objectives and Approach                                        223
8.2  Types of Coal and Effects of Coal Cleaning                     225
8.3  High Sulfur Fuel Characteristics                               226
8.4  Performance Requirements for Recovery Systems—Base Parameters
     for Five Case Studies                                          228
8.5  Selection of Equipment and Fuel Compositions                   231

     8.5.1  High Sulfur Fuels                                       231
     8.5.2  Furnace Types                                           233
     8.5.3  Boiles, Burners, and Combustion Systems                 234
     8.5.4  Electric Generating Equipment                           235
     8.5.5  Processes for Recovery of Sulfur Values                 235
     8.5.6  Process Description and Fuel Composition for Each
            Case Study                                              238

8.6  Economic Analyses of the Five System Designs                   238

     8.6.1  Method for Valuation of High-Sulfur Fuels               245
     8.6.2  Capital Costs                                           246
     8.6.3  Operating Costs                                         246
     8.6.4  Operating Economics:  Cost of High-Sulfur Fuel          249

8.7  Findings                                                       253

REFERENCES                                                          257
                                   ix

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                          LIST OF ILLUSTRATIONS

                                                                   Page
FIGURE NUMBER

     1          FUEL UTILIZATION                                    6

     2          PYRITE COAL PROGRAM                                 8

     3          WASHABILITY SUMMARY OF ALL COALS                    15

     4          EFFECT OF CRUSHING ON LIBERATION OF TOTAL SULFUR,
                SUMMARY OF ALL COALS                                16

     5          AVERAGE TOTAL SULFUR CONTENT,  + 1 STANDARD
                DEVIATION AT 3/8 INCH TOP SIZE, SUMMARY OF
                ALL COALS                                           I?

     6          AVERAGE PYRITIC SULFUR CONTENT, + 1 STANDARD
                DEVIATION AT 3/8 INCH TOP SIZE, SUMMARY OF
                ALL COALS                                           18

     7          AVERAGE PERCENT TOTAL SULFUR REDUCTION + 1
                STANDARD DEVIATION AT 3/8 INCH TOP SIZE,
                SUMMARY OF ALL COALS                                19

     8          AVERAGE PERCENT PYRITIC SULFUR REDUCTION, + 1
                STANDARD DEVIATION AT 3/8 INCH TOP SIZE,
                SUMMARY OF ALL COALS                                20

     9          WASHABILITY OF NORTHERN APPALACHIAN REGION COALS    22

     10         WASHABILITY OF SOUTHERN APPALACHIAN REGION COALS    23

     11         WASHABILITY OF MIDWEST REGION COALS                 24

     12         ESTIMATED PHYSICAL DESULFURIZATION POTENTIAL OF
                EASTERN BITUMINOUS STEAM COAL PRODUCTION            44

     13         FLOW DIAGRAM SHOWING PREPARATION OF GROSS SAMPLE    50

     14         WASHABILITY SUMMARY OF ALL COALS                    55

     15         WASHABILITY OF NORTHERN APPALACHIAN REGION COALS    59

     16         WASHABILITY OF SOUTHERN APPALACHIAN REGION COALS    67

     17         WASHABILITY OF MIDWEST REGION COALS                 71

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                    LIST OF ILLUSTRATIONS (Cont'd)

FIGURE NUMBER                                                      Page

   .  18         TOTAL SULFUR REDUCTION AT 1.60 SPECIFIC GRAVITY
                AS RELATED TO SIZE FOR 70 W. PENNSYLVANIA,
                E. OHIO, AND ILLINOIS COALS                         77

     19         TOTAL SULFUR REDUCTION AT 1.60 SPECIFIC GRAVITY
                AS RELATED TO SIZE FOR 20 SOUTHERN, WESTERN,
                AND MID-WESTERN COALS                               78

     20         WASHABILITY CHARACTERISTICS OF SAMPLE 20            82

     21         WASHABILITY CHARACTERISTICS OF SAMPLE 22            83

     22         DISTRIBUTION OF CLEAN COAL, MIDDLINGS, AND
                REFUSE ON THE WET CONCENTRATING TABLE               86

     23         HUMPHREYS SPIRAL CONCENTRATOR CLOSED CIRCUIT
                TEST UNIT                                           93

     24         COMPOUND WATER CYCLONE                              102

     25         REFUSE PROCESSES                                    160

     26         REFUSE-COMBUSTION/SULFUR-OXIDES-REMOVAL FLOW
                CHART                                               183

     27         DUAL PLANT SCHEME                                   185

     28         TOTAL REFUSE VALUE-REFUSE POWER PLANT CAPACITY-
                REFUSE COMPOSITION                                  193

     29         TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-
                SULFURIC ACID PRICE  (REFUSE ASH CONCENTRATION,
                34.0%)                                              194

     30         TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-
                REFUSE POWER PLANT CAPITAL COSTS (REFUSE ASH
                CONCENTRATION, 34 PERCENT; SULFURIC ACID PRICE,
                $12.50/TON)                                         195

     31         TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-
                SULFUR RECOVERY PLANT INVESTMENT (REFUSE ASH
                CONCENTRATION, 34 PERCENT; SULFURIC ACID PRICE,
                $12.50 TON)                                         196
                                  xi

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                    LIST OF ILLUSTRATIONS (Cont'd)
FIGURE NUMBER
     32
                                                                   Page
     33


     34


     35

     36


     37
 TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-
 RATE OF  RETURN ON INVESTMENT  (REFUSE ASH
 CONCENTRATION, 34 PERCENT; SULFURIC ACID PRICE,
 $12.50/TON)
                                                                    197
 TOTAL REFUSE VALUE COMPONENTS  (300 Mw REFUSE
 POWER PLANT; REFUSE ASH CONCENTRATION, 34 PERCENT)   199
 TOTAL REFUSE VALUE SENSITIVITY, 300-Mw REFUSE
 POWER PLANT

 PYRITE-REMOVAL PROCESS

 FLOW DIAGRAM OF FLUOSOLIDS PYRITE-ROASTING/
 SULFURIC-ACID PLANT PLANT TYPE 1-A
200

203


204
 ESTIMATED VALUE OF PYRITE FOR SUPPLYING SULFURIC
 ACID TO PHOSPHATE FERTILIZER PLANT AT CAIRO,
 ILLINOIS AS A FUNCTION OF- 1.  PREVAILING
 PRICE OF PRBtSTONE (ELEMENTAL SULFUR); 2.  LOCATION
 OF BRIMSTONE - BASED PHOSPHATE PLANT - BATON
 ROUGE, LA., OR CAIRO, ILL.                           218
TABLE NUMBER

     I

    II


   III


    IV


     V


    VI


   VII
VALUE OF REFUSE                                      34

HSC FUEL COMPOSITIONS, PRODUCTS, INVESTMENT, AND
OPERATING COSTS                                      40

TABLE OF FLOAT SINK TEST SIZES WITH SPECIFIC
GRAVITIES                                            51

COMPARISON OF WASHABILITIES OF SMALL AND LARGE
SAMPLES                                              80

PRODUCT ANALYSIS OF A 1/4 INCH BY 0 SIZE COAL
WASHED ON A WET CONCENTRATING TABLE                  88

PRODUCT ANALYSIS OF A 35 MESH BY 0 SIZE COAL
WASHED ON A WET CONCENTRATING TABLE                  89

ANALYSIS OF COALS SELECTED FOR CONCENTRATING
TABLE LISTS                                          91
                                  xii

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                    LIST OF ILLUSTRATIONS (Cont'd)
TABLE NUMBER

  VIII

    IX


     X


    XI
   XII


  XIII


   XIV


    XV



   XVI



  XVII



'XVIII


   XIX


    XX

   XXI

  XXII
                                                   Page
CONCENTRATING TABLE TESTS                           92

PRODUCT ANALYSIS OF 35 MESH BY 0 MIDDLE KIT-
TANNING BED COAL WASHED OVER THE COAL SPIRAL        95

CONCENTRATING TABLE AND SPIRAL CONCENTRATOR
TESTS EFFECTS OF TWO-STAGE CLEANING                 97

COMPARISON OF CONCENTRATING TABLE RUNS AND
COMPOUND WATER CYCLONE RUN WITH 30 MESH X 0,
R.O.M., OHIO NO. 6-A SEAM                           99

CONCENTRATING TABLE AND COMPOUND WATER CYCLONE
TESTS-EFFECTS OF TWO-STAGE CLEANING                 100

PYRITIC SULFUR REDUCTION IN MAJOR AIR
CLASSIFICATION TESTS                                104

SULFUR REDUCTION IN ALPINE ZIGZAG CLASSIFIER
TESTS                                               105

FRACTIONATION OF A SAMPLE OF 100 BY 325 MESH
LOWER FREEPORT BED COAL IN AN ELECTROPHORESIS
COLUMN                                              108

EVALUATION OF THE AGGLOMO-SEPARATION PROCESS
FOR THE LOWER FREEPORT BED COAL USING FOUR
PROCESS VARIABLES                                   110

EVALUATION OF THE AGGLOMO-SEPARATION PROCESS
FOR THE PITTSBURGH BED COAL USING FOUR
PROCESS VARIABLES                                   111

TWO-STAGE FLOTATION RESULTS WITH LOWER FREEPORT
BED COAL SLURRY                                     115

TWO-STAGE FLOTATION RESULTS WITH MIDDLE KITTANNING
BED COAL SLURRY                                     116
SULFUR RECOVERY IN PYRITE CONCENTRATION TESTS

COST ESTIMATES FOR FIFTY-TWO MONTH PROGRAM

COST ESTIMATES FOR 44 MONTH PROGRAM
119

136

138
                                  xiii

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 TABLE NUMBER

  XXIII

   XXIV

    XXV

   XXVI


  XXVII

 XXVIII


   XXIX


    XXX


   XXXI

  XXXII

 XXXIII

  XXXIV

   XXXV


  XXXVI


 XXXVII



XXXVIII



  XXXIX

     XL
    LIST OF ILLUSTRATIONS (Cont'd)



SUMMARY OF PROCESSES FOR UTILIZING COAL REFUSE

COST EVALUATION SUMMARY

ASSUMPTIONS FOR PRELIMINARY ECONOMIC ESTIMATES

ESTIMATED REGIONAL PRODUCTION AND DISPOSITION
OF SULFURIC ACID, 1966

SULFURIC ACID DISTRIBUTION BY END USE

GROWTH IN MAJOR SULFURIC ACID END USES,
UNITED STATES

ESTIMATED SULFURIC ACID END-USE PATTERN IN
SELECTED STATES, 1966

SULFURIC ACID SUPPLY-DEMAND SITUATION IN
SELECTED STATES, 1966

750-MW BASE POWER PLANT SUMMARY

REFUSE POWER PLANT SUMMARY

SULFUR RECOVERY PLANT INVESTMENT

STANDARD CONDITIONS 300-MW REFUSE POWER PLANTS

BATTERY LIMIT COSTS AND TOTAL CAPITAL INVESTMENTS
VS. CAPACITY AND FEED CONSUMPTION

TOTAL PROCESSING COSTS VS. FEED PLANT COMPOSITION
AND PLANT CAPACITY

THE PRICE THAT CAN BE PAID FOR PYRITES TO YIELD
THE SAME SULFURIC ACID MANUFACTURING COST AS WHEN
USING BRIMSTONE AT VARIOUS PRICES

ALLOWABLE PRICES FOR 85 PERCENT PYRITE DELIVERED
TO CAIRO PLANT UNDER VARIOUS RETURN-ON-INVESTMENT
REQUIREMENTS*

SUMMARY OF CASE A

SUMMARY OF CASE B
Page

 166

 169

 170


 176

 177


 178


 179


 181

 188

 188

 190

 201


 212


 214



 216



 220

 239

 240
                                    xiv

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TABLE NUMBER

   XLI

  XLII

 XLIII

  XLIV


   XLV

  XLVI

 XLVII


XLVIII
    LIST OF ILLUSTRATIONS (Cont'd)



SUMMARY OF CASE C

SUMMARY OF CASE D

SUMMARY OF CASE E

SUMMARY OF INPUTS AND OUTPUTS FOR FIVE CASE
STUDIES

ESTIMATED CAPITAL COST

CASE C SYSTEM ESTIMATED OPERATING COST

INCOME FROM SALES COSTS OF OPERATION AND
PRODUCTS GAIN OR LOSS FROM OPERATION

VALUE OF HSC FUELS, OFFSET TO CLEANING COST,
PAYOUT OF INVESTMENT
Page

 241

 242

 243


 244

 247

 248


 250


 251
                                   xv

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1.0  INTRODUCTION




     The exponential technical and economic growth of  the  last  25  years




has resulted in serious adverse effects on the quality of  the Nation's




air.  A concern for preserving the quality of the environment resulted




in the Air Quality Act of 1963 which initiated a concerted effort  by




federal, state, and local governments for the preservation of the  Na-




tion's air quality.  This Act called for an expanded federal research




and development program and placed special emphasis on the problem of




sulfur oxides emissions from the combustion of coal and oil in  station-




ary plants.




     .Coal provides for 20.5 percent  (calendar year 1971) of the  total




fossil fuel energy consumed by stationary sources (utility, industrial,




commercial, and residential).  In the utility industry, over 53  per-




cent  (calendar year 1971) of the fossil fuel energy requirement  is




supplied by coal.  Of the 33.2 million tons of sulfur  oxides emitted




into the atmosphere in 1968, 20.1 million tons were from coal-fired




utility operations.  The ever-increasing demand for electrical  energy,




the shortage of the available oil-gas reserves, and the delay in the




construction and development of breeder-reactor nuclear power plants




have resulted and will continue to result in increasing use of  coal




as a major source of energy for the utility industry.   Coal consumption




by utilities could reach 500 million tons    in 1980 and could  be  over




a billion tons in the year 2000-  Because pollution from fuel has  long




been recognized as a problem, both by EPA and its predecessor organiza-

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tions,* major emphasis has been placed on the development  of  methods

for controlling sulfur oxides emissions.

     Currently available methods for controlling sulfur oxides  emissions

from coal-fired stationary combustion sources fall into the following

categories:

     1.   The use of low sulfur coal either naturally occur ing  or

          physically cleaned;

     2.   Chemical treatment to extract sulfur from coal;

     3.   Removal of sulfur compounds during the combustion process;

     4.   Removal of sulfur oxides from the combustion flue gas;

     5.   Conversion of coal to a clean fuel by such processes  as

          gasification and liquefaction.

Of these methods, physical removal of pyritic sulfur  (principally

FeS2) is the lowest cost and has the most developed technology.

     Sulfur as coal exists in two principal forms, organic and  inorganic.

The organic sulfur is bound chemically to the coal substance  and cannot

be physically removed.   However, inorganic sulfur  (i.e., pyritic)  is not

bound chemically with the coal substance and may be removed to  varying

extents by crushing and physical cleaning.  The degree of  removal  is

dependent upon pyrite size and distribution, coal  size, and other

physical characteristics.
throughout this report, the acronym "EPA" is used  to  designate the U.S.
 Environmental Protection Agency (especially its component  organization,
 the Office of Air Programs), as well as its predecessor  agency, the
 National Air Pollution Control Administration of the  Department of
 Health,  Education and Welfare.

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     Physical cleaning of coal has been used for many years.   Its




principal purpose has been to reduce the so-called ash-forming  im-




purities.  The process in common use for reducing such  impurities is  a




combination of stage crushing and specific gravity separation.   Shale




and coal having different specific gravities may be  separated.   Froth




flotation, dependent on differences in surface characteristics  of coal




and coal impurities, is used for removing ash from fine size  coal.




Existing cleaning processes, while removing impurities  from coal, also




reduce the total BTU recovery  (i.e., a portion of the heat content  of




the feed will be lost with the refuse).  As a result, the BTU content




per unit weight of the processed product increases due  to removal of




low heat value impurities.  In practice an economic  balance must be




achieved between the BTU loss and the improvement in coal quality.




This balance may be further influenced by environmental considerations.




     In 1965, EPA sponsored a study to quantify the  impact that coal




cleaning, optimized for pyrite removal, could have on the control of




sulfur oxide emissions.  This study found that it was impossible to




quantify the impact of coal cleaning on sulfur oxide emissions  because




Of large gaps in available information.  The study identified the fol-




lowing areas where required information was either not  available or




was inadequate for appraising this impact:




     •    Knowledge of the distribution of sulfur forms in  (all) major




          high-sulfur coalbeds in the United States;

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      •     Effectiveness  of  available  commercial  coal  preparation methods




           for  pyrite  separation,  together with the development  or modi-




           fication  of  these techniques  to maximize sulfur  reduction;




      •     Identification and assessment of processes  that  could econom-




           ically utilize coal cleaning  reject material  for byproduct




           recovery, thereby aiding the  overall cleaning economics and




           reducing  potential air, water, and solid pollution.




      The findings of  the 1965 study led EPA to proceed  with implemen-




 tation  of a  comprehensive program designed to define  the potential role




 of  coal cleaning in controlling sulfur  oxides emissions from coal-fired




 sources.   The  individual program  elements were structured  to supply the




 basic information required.   The  program permitted flexibility  for tailor-




 ing new program  elements in accordance with findings  of previous or on-




 going studies.   An important  part of  the program was  to determine the




 extent  to  which  the sulfur  content of U.S. coals could  be  reduced by  coal




 cleaning  processes based on differences in physical properties.   While




 pyritic  sulfur is amenable  to  removal by such processes, the other major




 form of  sulfur (organic  sulfur compounds) is not.  A  good  indicator of




 the "cleanability" of pyrites  from coal is the float-sink, or washabil-




 ity, test  in which crushed  coal is tested at various  gravities  to sepa-




rate the different specific  gravity fractions.   The coal fractions float




and the heavier  fractions sink.   Such washability tests form an important




element  of the total program.  The overall study concept included the




following elements:

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     •    A data base of coal cleanability, containing results of pyrite




          (and ash) washability studies, to determine the sulfur-release




          potential of coals from principal utility-coal-producing beds




          of the United States;




     •    In-depth studies of existing physical cleaning techniques to




          obtain maximum pyrite removal;




     •    The modification of existing methods and evaluation of new




          methods for sulfur reduction;




     •    Studies covering pyrite utilization and related economics;




     •    A feasibility study (with costs) of a prototype cleaning




          plant to evaluate both economic and technical factors asso-




          ciated with maximizing sulfur reduction;




     •    A feasibility study with costs of a high-sulfur combustor




          for utilizing reject material from coal cleaning.




     The overall basic program concept  (Figure 1) has been to develop




a means for achieving full utilization of all values in the coal.  The




deep-cleaning of coal to maximize sulfur reduction could result in reject




material high in coal and sulfur values.  This refuse material could be




reprocessed into various products:  non-polluting refuse for disposal;




a pyrite concentrate that could be converted into sulfuric acid; and




coal products of various sulfur levels for utilization with flue gas




cleaning systems to generate electrical energy.  The full utilization of




these values could result not only in lower cost fuels, but also in the




conservation of the Nation's fossil fuel resources.

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                             RAW COAL
                               1
                               COAL
                           PREPARATION
 CLEAN FUEL
 (LOW SULFUR/LOW ASH)
                          CLEANING REJECT
                              REJECT
                             PROCESSING
      SHALE,  SANDSTONE,
INTERMEDIATE SULFUR FUEL
(SULFUR 1-4%;  ASH 5-20%)
                                                 CLAYEY SUBSTANCES
CONCENTRATED PYRITE
(SULFUR >35%)
                      HIGH SULFUR  FUEL
                      (SULFUR 6-15%, HIGH ASH)
                             FIGURE 1
                        FUEL UTILIZATION

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     A diagram identifying the major  elements of the program sponsored
by EPA  (in whole  or  part)  to  develop  the information necessary to quantify
the potential  role of  coal cleaning in the control of sulfur oxides
emissions and  to  define  the relative  attractiveness of cleaning options
is given in  Figure 2.  This figure indicates the interrelations among
the various  program  elements, together with the beginning date for each
funded  effort  and the  identification  of future efforts required to reach
demonstration  of  commercial applicabilities of considered techniques.
     The initial  EPA-sponsored washability study began in 1965.  Repre-
sentative samples were collected from mines of major producers of coal
primarily for  use by the utilities.  The samples were stage crushed to
three  top sizes;  coarse  - 1^  inch; intermediate - 3/8 inch, and fine -
14 mesh.  Washability  studies were performed on the various sized frac-
tions with organic liquids of standardized specific gravities to de-
termine the  effects  of top size and specific gravity parameters upon
pyrite  liberation and  separation.
     Because of the  the  large number  of coals to be tested and the need
to accelerate  their  evaluation, EPA expanded the testing program by sup-
"porting three  additional organizations.  The first of these concentrated
on regions where  preliminary  data  indicate the presence of coals clean-
able for major sulfur  reduction.
     In another study, EPA cooperatively supported a two-year investiga-
tion to evaluate  all active.ly mined coal beds in the state of Illinois,
which has the  largest  bituminous coal reserves in the United States.
This effort  determined the important  physical and chemical properties of
                                    7

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PYRITIC SULFUR
WASHABILITY /
STUDIES
PYRITE
REMOVAL
PROCESSES
PYRITE
UTILIZATION
ECONOMIC STUDY
5/67
COMMERCIAL
TESTING AND
ENGINEERING
COMPANY
5/67
ILLINOIS
GEOLOGICAL
SURVEY
7/65
U.S. BUREAU
OF MINES
6/67
BITUMINOUS
COAL
RESEARCH
6/67
A. D. LITTLE
AND
DORR-OLIVER
6/67
BECHTEL AND
STANFORD
RES. INST.
       6/68
PROTOTYPE COAL CLEANING
                  5/70
  1.   ROBERTS AND
      SCHAEFER
      COMPANY
  2.   McNALLY
      PITTSBURG
      MFG.  CORP.
        ROBERTS AND
        SCHAEFER CO.
        AND U.S. BUREAU
        OF MINES
                      DETAILED DESIGN    PROTOTYPE
                      AND EXPERIMENTAL   PLANT
                      TEST PROGRAM
 FEASIBILITY  STUDY
                HIGH  SULFUR COMBUSTOR
      7/69
                                                              FULL-SCALE
                                                              UNITS
FEASIBILITY STUDY
      DETAILED
      DESIGN
PROTOTYPE
PLANT
              FIGURE 2
       PYRITE COAL PROGRAM

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Illinois coal, including its washability and distribution of sulfur




forms.




     To further develop basic data on the effects of size reduction on




pyrite liberation, selected samples  (in a separate effort) were further




reduced in top size to 30 mesh and 60 mesh and evaluated by float-sink




evaluation.  Although the cleaning of this size material by specific




gravity methods is not normal commercial practice, this information




would define the maximum effects of  size reduction on pyrite liberation




and separation.




     The four funded washability studies contributed to the development




of a substantial body of data on the cleanability of U.S. coals.  This




information is stored in a computerized data bank to facilitate retrieval,




updating, and analysis.




     Concurrent with the washability studies, EPA sponsored two separate




investigations of techniques for separating and concentrating pyrites




from fine coal.  One of these evaluated the effectiveness of commercially




available equipment; the wet concentrating table, the compound water




cyclone, and the concentrating spiral.  The other evaluated conventional




techniques to define operating parameters, modification of these  tech-




niques to maximize sulfur reduction, and the development of new tech-




niques .




     In 1967, EPA sponsored two preliminary studies that investigated




the economics of recovering by-products from the reject material  result-




ing from coal cleaning.  One of these included a review and analysis







                                     9

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of commercially applicable processes for recovering sulfur and the ap




plicability of these processes utilizing coal cleaning refuse.  The




second was a detailed feasibility study of fluid bed roasting with con-




version to sulfuric acid, plus a market analysis for its principal




product, commercial grade sulfuric acid.  The study findings indicated




that the high-sulfur combustor had the highest economic viability po-




tential.




     After the preliminary economic studies were completed, EPA funded




a feasibility study of a high-sulfur combustor capable of burning the




reject.material to recover its energy and sulfur values.  This study




produced an engineering design and cost analysis associated with the




utilization of high sulfur reject material to generate power and re-




cover  sulfuric acid or elemental sulfur.




     In order to determine the scope and cost of conducting investiga-




tions and demonstrations of pyrite removal using commercial equipment




on a scale approximating commercial capacity, EPA in 1968 funded two




independent and competing engineering studies.  These efforts, predi-




cated on findings of the washability investigations, were for designing




a prototype coal cleaning plant and for estimating capital and operating




cost for the plant.  Two studies were required to identify the most ac-




ceptable design/cost option due to plant and operational complexities.




     These various studies are described and their results summarized




in the following chapters of this report.  The economics, technologies,




etc.,  provided in this report are those of the addressed studies.   It
                                    10

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should be noted that since the reported studies were performed condi-




tions have changed and the economic findings and conclusions of the var-




ious efforts may not be currently valid.
                                     11

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2.0  SUMMARY


2.1  Introduction


     This study provides an interpretative evaluation of the EPA  (and


its predecessor organizations) coal cleaning program.  The EPA coal clean-


ing effort ostensibly began in 1965 when EPA sponsored a study to quan-


tify the impact that coal cleaning, optimized for pyrite removal, could

                                              (2)
have on the control of sulfur oxide emissions.     This study found that


it was impossible to quantify the impact of coal cleaning on sulfur


oxide emissions due to large gaps in available information.


     The findings of the 1965 study led to the establishment of a com-


prehensive program designed to define the potential role of coal clean-


ing in controlling sulfur oxide emissions from coal-fired sources.  Prin-


cipal elements of the resulting program were:


     •  A data base of coal cleanability, based on findings of pyrite


        washability studies, to determine the sulfur-release potential


        of coals from principal utility coal producing beds of the


        United States;


     •  An in-depth study of pyrite removal processes;


     •  Studies covering pyrite utilization and related economics;


     •  Feasibility studies of a prototype cleaning plant to evaluate


        the economic and technical factors associated with maximizing


        sulfur reduction;


     •  A feasibility study of a high-sulfur combustor for utilizing


        reject material from coal cleaning.
                                   12

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     In essence, the overall program concept was  to develop methods  for




achieving utilization of all values in the coal.  The deep cleaning  of




coal to maximize sulfur reduction could result  in a reject material  high




in coal and sulfur values.  This refuse  (reject)  material could be pro-




cessed into various products:  non-polluting refuse for disposal; a




pyrite concentrate that could be converted into sulfuric acid; and coal




products of various sulfur levels for utilizing with flue gas cleaning




systems to generate electrical energy.




     The principal elements that comprized the  EPA program are summarized




below.




2.2  Washability Studies




     Sulfur is  found in raw coal in two major forms:  organic and in-




organic (pyritic) sulfur.  Organic sulfur is chemically bound to the




organic structure of the coal and cannot be removed by use of conven-




tional washing  methods.  The pyritic sulfur occurs in particles of




varying size mixed with the coal.  By crushing  (to liberate the pyritic




sulfur) and washing  (to remove the liberated particles), the total




amount of sulfur in the coal may be reduced.  The degree of removal  of




the pyritic sulfur is dependent on the size of  the particles of pyrites;




the finer the particles, the more difficult to  remove by washing.  The




total sulfur reduction, therefore, is dependent on the amount of organic




sulfur and the  effects of crushing to liberate  the pyritic sulfur.   The




desulfurization process results  (as do most beneficiation processes) in




some loss in total heat content of the processed  coal.







                                   13

-------
      A summary of 322 washability tests reported by the Bureau of Mines
 shows that the organic sulfur and the effects of crushing (Figures 3 and
 4) vary widely, as would be expected, when washability data of coals

 throughout the United States are combined.
      The average total sulfur content of all coal studied in the Bureau
 of Mines reported investigation of coal washability is 3,23 percent at
 a raw coal top size of 3/8 inch (Figure 5).  When washed to a 90 percent
 yield, this average was reduced to 1.95 percent; reducing the yield to
 60 percent results in a 1.82 percent average value.  Figure 6 shows the
 average pyritic sulfur content of the raw coal is 2.05 percent.  At 90
 percent yield this average was reduced to 0.75 percent; at 60 percent
 yield it was reduced to 0.51 percent.   On the average, regardless of
 yield, the organic sulfur content of the coals was 1.2 percent.  The
 average percent total sulfur reduction and the average percent pyritic
 sulfur reduction at the varied yields are shown in Figures 7 and 8.  Fig-
 ure 3 shows that at a 60 percent  yield only 20 to 25 percent of the coals
 sampled could produce a one percent  or less total sulfur washed coal.
      The production of  one  percent or less total sulfur coal by means of

 physical  cleaning is  governed  by  the amount of organic sulfur and part-
 icle  sizes  of  the  pyrite in the coals (the fine, intimately mixed pyrite

 particles are  impossible to remove by conventional washing processes),
 regardless  of  cost.   In general,  the lower the level of total sulfur re-
 quired  in the washed  coal,  the higher the cost of cleaning due to the
lower recovery of  the washed coal  (i.e.,  greater loss of coal values
during washing).
                                    14

-------
w
w
PJ
CO
H
                    90 PERCENT YIELD
                       i   i    i   i
                                              80 PERCENT YIELD
                                             i   i    i
                   70 PERCENT  YIELD
                          i    i   i
                                             60 PERCENT YIELD
                                                 i    i   i    i
(a)
(b)
(c)
(d)
                     56780   12
                           SULFUR, PERCENT

RAW COAL TOTAL SULFUR CONTENT CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS  1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS  14 MESH.
                               FIGURES
                WASHABILITY SUMMARY OF ALL COALS
345678


 SOURCE:  REFERENCE 8
                                  15

-------
   100
    90
    80
    70
en


3  60
H
O
H



S  50
H
U
C3
Q


3  40
W
e^   30
    20
    10 h-
      60
70           80


  PERCENT YIELD
90
                                    SOURCE:  REFERENCE 8
                   FIGURE 4
EFFECT OF CRUSHING ON LIBERATION OF TOTAL SULFUR,
             SUMMARY OF ALL COALS
                     16

-------
1
H

I
W
                             80

                      PERCENT YIELD
90
                                   SOURCE:  REFERENCE 8
100
                        FIGURES
   AVERAGE TOTAL SULFUR CONTENT, ±1 STANDARD DEVIATION
         AT 3/8 INCH TOP SIZE, SUMMARY OF ALL COALS
                          17

-------
               70
       80

PERCENT YIELD
                                        90
100
                                      SOURCE:  REFERENCE 8
                      FIGURES
AVERAGE PYRITIC SULFUR CONTENT, ±1 STANDARD DEVIATION
       AT 3/8 INCH TOP SIZE, SUMMARY OF ALL COALS
                        18

-------
                    70           80

                    PERCENT YIELD
90
                              SOURCE:  REFERENCE 8
                     FIGURE?
AVERAGE PERCENT TOTAL SULFUR REDUCTION ±1 STANDARD
 DEVIATION AT 3/8 INCH TOP SIZE, SUMMARY OF ALL COALS
                       19

-------
     •100
   g
   OT
  E


  §
  M
  H
  O

  g
  PM
                     70            80


                      PERCENT YIELD
90
                                  SOURCE:  REFERENCE 8
                       FIGURES

AVERAGE PERCENT PYRITIC SULFUR REDUCTION, ±1 STANDARD

  DEVIATION AT 3/8 INCH TOP SIZE, SUMMARY OF ALL COALS
                          20

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     The three regions indicating a potential  for washing  to  a total




sulfur content of one percent or less are  the  Northern Appalachian




(Figure 9), the Southern Appalachian  (Figure 10), and Eastern Interior




or Midwest Region (Figure 11).  The remaining  coal  producing  regions




given less attention or excluded are:   the Western  Interior  (the  coals




in this region are characteristically high in  sulfur content  regardless




of the physical treatment used) and Northern and  Southern  Rocky Mountain




(these coals are generally of low sulfur content).




     As shown by Figures 4 and 5, coal  crushed to 3/8-inch top size and




cleaned to yield in the order of 90 percent will  provide the  predominant




benefit.  The figures show that, on the average,  sulfur content will de-




crease by less than ten percent with an additional  yield sacrifice of




30 percent (i.e., 90 to 60 percent).  Even so,  it must be  emphasized




that individual cases may vary and must be independently assessed.




     In addition to the Bureau of Mines reported  washability  studies,




67 washability tests on Illinois coals  were reported by the Illinois




Geological Survey.  The test samples were  taken from Illinois coal mines




located in significant mining areas in  the state.   The Illinois Geo-




logical Survey tests indicated that most Illinois coals have  3 to 5




percent total sulfur and only in those  coals having a relatively  low-




sulfur content as mined could the total sulfur content be  reduced to




1.5 percent or less by washing techniques.  Of the  67 coal samples




tested, 6 could be washed to a total sulfur level of 1 percent and 10




could be washed to 1.5 percent with an  80  percent minimum  recovery.
                                    21

-------
 w
 £
 w
 w
 53
90 PERCENT YIELD
      i
                   70 PERCENT YIELD
                      i    i   i    i
                             60 PERCENT YIELD
(a)
(b)
(c)
(d)
                             345678


                              SOURCE:   REFERENCE 8
                        678012
                          SULFUR,  PERCENT
RAW COAL TOTAL SULFUR  CONTENT CURVE;
RAW COAL ORGANIC  SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                              FIGURE 9
         WASHABILITY OF NORTHERN APPALACHIAN REGION COALS
                                  22

-------
w
w
p-
w
S3
(a)
(b)
(c)
(d)
                    90 PERCENT YIELD
                   i   i    i   i    i
                   70 PERCENT YIELD
                                 I
       80 PERCENT YIELD
       i	i	i    i   i
       60 PERCENT YIELD
I   i    i   i    lit
       3   A   5  6   7  8

       SOURCE:  REFERENCES
       12345678012
                          SULFUR, PERCENT
RAW COAL TOTAL SULFUR CONTENT CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT  COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.

                        FIGURE 10
  WASHABILITY OF SOUTHERN APPALACHIAN REGION COALS
                                23

-------
 w
 w
 PL.
a
M
SB
100

 90

 80

 70

 60

 50

 40

 30

 20

 10

   0
100

 90

 80

 70

 60

 50

 40

 30

 20

 10

  0
                       PERCENT  YIELD
                       i	i    i   i
                   70 PERCENT YIELD
                   i    i   i   i   i
(a)
(b)
(c)
(d)
       12345678012,
                          SULFUR, PERCENT
RAW COAL TOTAL SULFUR CONTENT CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                              FIGURE 11
                WASHABILITY OF MIDWEST REGION COALS
345678

 SOURCE:   REFERENCE 8
                                  24

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2.3  Laboratory and Pilot Studies Evaluating Processes For Pyrite Re-
     moval From Fine Coals

     The goals of EPA-sponsored laboratory and pilot study projects

conducted by the Bureau of Mines and Bituminous Coal Research,  Incor-

porated were:

     1)   to determine the operating parameters for maximum pyrite sep-

          aration,

     2)   to modify existing techniques and/or develop new techniques

          to separate pyrite from fine coal, and

     3)   to evaluate methods to process coal cleaning rejects  so as

          to concentrate the pyrite and reclaim clean coal products.

     The Bureau of Mines concentrated on equipment operational  para-

meters and the development of new techniques while the Bituminous Coal

Research effort concentrated on the applicability of equipment  to var-

ious coals.  The following equipment or processes were evaluated by the

two contractor organizations.

     EQUIPMENT/PROCESS                          INVESTIGATED BY
                                          BUREAU OF      BITUMINOUS COAL
                                            MINES         RESEARCH. INC.

Wet Concentrating Table  (Deister)            X                  X

Concentrating Spiral (Humphrey)              X                  X

Hydrocyclones                                X                  X
                                     25

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     EQUIPMENT/PROCESS                          -53                 CQAL
       	'	                   BUREAU OF      BITUMINOUS COAL

                                          MINES __       RESEARCH. INC.


                                                                v
Air Classifiers


Electrokinetic Techniques                   Y


Agglomo-Separation                          X,Y


Froth Flotation                             X,Y


            X - designates pilot plant tests


            Y - designates laboratory-scale tests


     2.3.1  Principal Findings


     Wet Concentrating Table


     In tests, the wet concentrating table proved effective in removing


free pyrite from coal.  Coals with a high proportion of pyritic sulfur


relative to organic sulfur are particularly amenable to sulfur reduction


by this process.  Two-stage cleaning tests, in which a coarse sample was


tabled and the clean fraction pulverized and retabled, indicated that


pyrite removal can be enhanced by use of the concentrating table in two


stages.


     Concentrating Spiral


     The concentrating spiral experienced a rapid deterioration of wash-


ing efficiency with feed size below 35 mesh, this being a normal char-


acteristic of specific gravity separators.


     Overall, the excellent results the concentrating spiral provided on


fine-size coal suggest that it should be considered as a "rougher" clean-


ing unit to remove pyrite from high sulfur coals prior to flotation.
                                   26

-------
Double-stage cleaning indicate that for  some  coals  the  spiral  process




produces similar reductions and yields to  those obtained  with  the  wet




concentrating table.




     Water-Only Cyclone




     Preliminary results of the Bureau of Mines water cyclone  perfor-




mance evaluation tests showed excellent  pyritic sulfur  reductions  were




obtainable.  The clean coal recoveries were highly  dependent on  the




size of the material.  Clean coal recovery of plus  48 .mesh material was




low while most of the minus 100 mesh material reported  to the  clean coal




product.




     Water cyclone  tests were also conducted  by Bituminous Coal  Research,




Inc. (BCR, Inc.).   Feed coals were pulverized to minus  30 mesh prior to




test runs.  BCR, Inc., results indicated that in general  the compound




water cyclone provided smaller sulfur reductions than were achieved by




the concentrating table.  However, BCR,  Inc., believes  that improved re-




sults in total sulfur reduction could be obtained by using a closer-




sized feed to the water cyclone.




     Air Classifier




     Air is used to separate relatively  coarse grind of pulverized coal




into a fine fraction and a coarse, pyrite  rich fraction using  the  BCR-




Majac and Alpine zigzag air classifiers.   Pyrite could  then be removed




from coarse fractions by wet-coal preparation techniques.
                                    27

-------
      The  reduction of  total  sulfur  through  use  of  the  Majac unit ranged




 from 20.1 to  51.7  percent  for  10  samples.   Only one  coal  was processed




 on the  Alpine zigzag unit.




      Electrokinetics



      The  electrokinetic  process for  the  physical cleaning of coal uses




 the technique of electrophoresis  for separating the  pyrite from the coal.




 The laboratory-scale investigation  indicated  that  pyrite  and other im-




 purities  such as silica  could  be  separated  from 'the  coal.   The technique,




 unfortunately,  was deemed  uneconomical for  scaling up  to  the pilot stage




 as a coal cleaning procedure.




      Agglomo-Separation  (Oil)




      An oil agglomeration  process for the recovery of  clean coal from




 slime size material and  the  sulfur and ash  reduction potential of this




 process was investigated by  the Bureau of Mines.   This process provided




 negligible reduction in  sulfur; however, the  reduction in coal ash con-




 tent  was  good.




      Froth Flotation




      Froth flotation is a  process for separating fine-size particles by




 selective  attachment of air  bubbles  to coal particles, causing the coal




 to be buoyed  up into a froth while leaving  the  refuse  particles in the




water.  Of the several innovative processes for pyrite separation in-




vestigated under the EPA Clean Coal  Program,  the froth flotation tech-




nique appears to show the  greatest potential  for scale-up to commercial




operation.
                                    28

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     Concentration of Pyrite from Refuse




     Studies were performed to determine the potential of fine-cleaning




techniques for preparing a concentrated grade of pyrite from coal clean-




ing reject material.  Coals from six mines were cleaned and the reject




concentrated by staged separation with a wet concentrating table and a




hydraulic classifier.  The results indicate that pyrite concentrates with




sufficiently high total sulfur content for conventional acid-making pro-



cesses were achieved for all coals tested, sometimes at the expense of




percentage of sulfur recovered.  Total sulfur in the pyrite concentrates




ranged from 35.6 to 48.6 percent.




2.4  Prototype Coal Cleaning Plant




     The washability studies and pilot plant investigations indicated




the amenability of a wide range of coals to physical desulfurization




under carefully controlled conditions.  Although testing for pyrite re-




moval could be conducted to a limited degree in some existing prepara-




tion plants, the equipment and cleaning circuits of such plants are not




normally arranged to maximize sulfur reduction but to meet ash and BTU




specifications.  Ideally, a plant to be used for investigating and demon-




strating desulfurization methods at high through-put capacities would




provide flexibility of equipment configurations, cleaning circuits, and




operating conditions.



     In order to determine the scope and cost of conducting investiga-




tions and demonstrations of pyrite removal using commercial cleaning
                                    29

-------
 equipment  on  a scale  approximating  commercial  capacity,  EPA funded two




 independent and competitive  studies for  designing  a  prototype coal clean-




 ing  plant  of  50-100 tons  per hour capacity  and for estimating the cap-




 ital and operating cost for  the plant.   The  study  objectives were to




 produce a  prototype plant design, together with cost estimates for




 building,  equipping and operating a plant capable  of reducing the sulfur




 of coals having widely variable washability  characteristics.




      The prototype plant  design and cost studies were conducted by the




 McNally Pittsburg Manufacturing Corporation  and the  Roberts and Schaefer




 Company of Chicago.   The  major difference in the two studies was plant




 design; Roberts and Schaefer's design was the  more complex  of the two;




 however, it offered the most  flexibility.




      The Roberts and  Schaefer cost  estimate  for a  fifty-two month pro-




 gram covering  plant cost,  operating  cost, laboratory services,  and con-




 tractor's fee  came to $16,457,965.   In addition, a cost  estimate was




 provided for a  modified,  alternate,  lower price program  that would not




 unduly sacrifice program  objectives.  The cost  estimate  for the alter-




 nate  forty-four month program (instead of the  fifty-two  month basic pro-




 gram) amounted  to $8,923,200.




     The McNally Pittsburg cost estimate for a  fifty-four month program




covering plant cost and operating cost, which  include laboratory services,




amounted to $11,406,775.   Even though not specifically stated,  it is as-




sumed that  the contractor's fee charge is included in the above amount.
                                    30

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2.5  Pyrite Utilization Economic Studies
     The purposes of the Pyrite Utilization Economic Study portion of
EPA's overall pyrite coal program are:
     1.   To investigate the economics of utilizing the pyrites ob-
          tained from coal beneficiation;
     2.   To evaluate the applicability of alternative commercial
          processes for recovering energy and chemical values from
          coal cleaning reject material; and
     3,   To design, construct, and operate a plant that would demon-
          strate the technical and economic feasibility of the pro-
          cesses.
     Investigations concerned with the first two purposes were conducted
concurrently.  In 1967, EPA contracted with the Bechtel Corporation to
perform a general review and evaluation of costs and technology of other
available processes for pyrite—coal utilization.  Also in 1967, a con-
tract was awarded to A. D. Little, Inc. (assisted by Dorr-Oliver) to
determine the costs and benefits associated with the processing of
pyrite removed from coal.  This study effort was concentrated on the
technology and economics of fluidized-bed roasting of pyrite-coal
followed by conversion of sulfur dioxide to sulfuric acid by the con-
tact process.  On the basis of the resulting technical and economic
data, EPA decided to look more closely at a system for burning the high-
sulfur, high-ash material produced by coal desulfurization.  The re-
sulting effort was performed by the Chemical Construction Company
(Chemico); a summary is presented in Section 2.5.3.
                                   31

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     2.5.1  The Bechtel Corporation Study



     Eight processes were selected by the Bechtel Corporation for invest-




igating the recovery of chemical and energy values from pyrite-coal refuse.




After initial study, two of the eight processes were selected for analy-




sis at a more detailed level.  The selected processes were the "Combus-




tion/ Sulfur-Oxides-Removal Process" and the "Fluidized-Bed Pyrite Roast-




ing Process".  These two, in the order listed, had the most favorable




economics.  The overall economics of the "Combustion/Sulfur-Oxides-Removal




Process" indicated the possibility of an economic benefit while the




"Fluidized-Bed Pyrite Roasting Process" indicated the likelihood of a




small cost penalty.  The study was predicated on a maximum sulfur level




of washed coal of 1.0 percent and coal washing refuse containing from




about 4 to 25 percent sulfur and ash levels of 20 to 90 percent.




     The Bechtel findings are based on examining two general classes




of processes for utilizing coal refuse.   These are:




     1.    The feed is the entire refuse stream from coal preparation,




          and




     2.    A concentrated feed is used.




     The study (at time of performance)  indicated that:




     1.    None of  the processes which use the entire refuse stream




          has reached commercial status,




     2.    Processes which feed a pyrite concentrate are commercial




          but have not  been operated with pyrite-coal mixtures, and
                                    32

-------
     3.   The Combustion/Sulfur-Oxides-Removal Process shows the most




          favorable economic outlook and its technology appears sound.




The Monsanto process for removing sulfur oxides from flue gas was se-




lected for the economic estimates because of its advanced development




state and simplicity.




     For the study, a method was developed to calculate the value of




coal refuse as a function of numerous variables.  The method assumes




that coal refuse is bought jointly by the owners of a closely integrated




electric utility and sulfuric acid plant; wherein each of the two in-




vestors would pay for his share of the refuse value (fuel or sulfur).




The owner of the coal preparation plant could use this income to offset




part or all the cost of coal cleaning.  Table I shows the results of




an estimate for values of the two refuse compositions for specific assump-




tions.




     The study indicated that refuse value depends on many variables, the




most important being refuse power plant capital cost and sulfuric acid




sales price.  Other factors affecting refuse values are:




     •    Refuse ash concentration,




     •    Refuse power plant operating and maintenance cost,




     •    Sulfuric acid recovery plant investment, and




     •    Rate of return on acid recovery plant.




     2.5.2  The A. D. Little Study




     As previously indicated, the A. D. Little effort was predicated on
                                    33

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                       TABLE I

                   VALUE OF REFUSE
REFUSE
SULFUR
CONCENT.
(PERCENT)
6.38

6.38

10.62

10.62

SULFURIC
ACID
PRICE
($/TON)
10.00

15.00

10.00

15.00

NET REFUSE
ENERGY VALUE
(CENTS/
106 BTU)
4.0

4.0

4.0

4.0

NET REFUSE
SULFUR VALUE
($/TON
SULFUR)
-10.24

7.70

7.18

25.10

TOTAL REFUSE
VALUE
($/TON
REFUSE)
-0.06

1.09

1.35

3.25

(CENTS/
106 BTU)
nil

7.3

9.2

22.2

CHANGE IN
COAL PREP,
COST
(PERCENT)
2.5
increase
45.4
decrease
56.2
decrease
135.4
decrease
                    ASSUMPTIONS

 Refuse Power Plant Capacity
 Refuse Power Plant Capital Cost*
 Return On Book Value

 Refuse Ash Concentration
 Refuse Moisture

 Sulfur Oxides Recovery Plant
  Investment (in terms of refuse
  power plant capacity)
Discounted Rate of Return

Coal Preparation Plant Yield
Coal Preparation Cost
300 Mw (net)
170 $/kw
8.0 percent

34.0 percent
15.0 percent
42 $/kw
12.5 percent

80 percent
$0.60/ton clean coal
*Does not include cost for SO- recovery plant,
                       34

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fluid-bed roasting of pyrite-coal  followed by  conversion of  sulfur diox-




ide to sulfuric acid by  the  contact  process.   The  study found that the




economic feasibility of  the  process,  i.e., the amount  that  can be paid




for pyrite feed  (coal cleaning  reject),  depends on a number  of inter-




related factors including:   the price of elemental sulfur and sulfuric




acid, the location of the acid  plant  relative  to pyrite deposits, the




expected return on investment,  and the markets for sulfuric  acid.  Tak-




ing these and  other considerations (including  an f.o.b.  price for ele-




mental sulfur  of  $38 per long ton) into  account, it was estimated that




the net financial benefit to coal  operators for producing low-sulfur




(1 percent or  less) coal and an acceptable pyrite  feed material could




range from $1.16  to $1.57 per ton  of  coal processed.   The results are




based on the following:




     •    It is reasonable  to expect  that a premium of $1.10 to $1.20




          per  ton of coal should be  obtained by mines  supplying less




          than 1 percent sulfur coal  to  utilities  subject to stringent




          air  pollution  abatement  restrictions;




     •    Coal companies should obtain a benefit of approximately $0.15




          per  ton of coal processes  resulting  from reduced  disposal re-




          quirements and reduced air  and water pollution.




     In order  to support a 1500 ton  per  day sulfuric acid plant (the




minimum size believed suitable  for economic manufacture), considerable




tonnages of pyrite-bearing coal must  be  processed.   The amount required




would probably come from more than one mine.
                                    35

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      Costs  associated  with  the manufacture  of  sulfuric  acid from a pynte




 feed  will vary  primarily  as a function  of three major variables:   plant




 size, plant type,  and  feed  composition.  Plant size  and type will be de-




 termined to a considerable  degree by market conditions  projected  over




 plant life.  Even  so,  feed  stream characteristics  could change in accord-




 ance  with raw material resources and beneficiation processes.




      For the study a broad  range of possible pyrite  feed compositions




 were  arbitrarily selected and evaluated.  The pyrite feed composition




 has a pronounced effect on  almost all of the process requirements in




 both  the pyrite roasting  section and the contact acid section.  While




 the cost of  pyrite-coal beneficiation must  ultimately be taken into




 account, for practical purposes a feed  composition of no worse than 70




 percent  pyrite, 10  percent  coal, and 20 percent gangue  was assumed for




 acid  manufacture.   For the  study a feed of  85 percent pyrite,  10  percent




 coal,  and 5  percent inerts  was used.




      On  the  basis  of the  three major parameters — plant capacity, feed




 composition, and plant type — investment and operating costs  were cal-




 culated  for  each possible combination.  Manufacturing costs (excluding




 cost  of  pyrite)  ranged from $5.51 to $25.40  per ton  of  98 percent sul-




 furic acid.   Plant  investment cost ranged from $3.7  million to $35.5




million.




     For purposes of the  study effort,  1500  tons per day acid  produc-




tion capacity and a feed of  85 percent pyrite, 10  percent coal, and 5




percent gangue were chosen.  Estimated processing  cost  (excluding raw







                                    36

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material costs and any by-product credit,  i.e.  low-pressure  steam)  for




this type of plant is $7.63 per  ton  of  98  percent  produced,  with  an




estimated plant investment of  $14.54 million.




     Because of its comparatively high  weight and  low price,  sulfuric




acid is ordinarily marketed within a radius  of  150 to 200 miles.  With-




in the eight-state area covered  by the  investigation, the major outlet




for sulfuric acid today and in the foreseeable  future is and will be the




phosphate fertilizer industry, which presently  consumes approximately 40




percent of all sulfuric acid  in  the  United States.   Of the other  uses of




sulfuric acid, ammonium sulfate  (also used extensively in fertilizer man-




ufacture), titanium dioxide,  petroleum  refining, and steel making are




the most significant.




     To evaluate the need for  a  pyrite-based sulfuric acid plant, four




major marketing areas which are  reasonably close to the potential pyrite




source areas were investigated.  The investigated  areas were:  Pittsburgh,




Pennsylvania; Cairo, Illinois; St. Louis,  Missouri; and Chicago,  Illinois,




Pittsburgh is too far away to  serve  as  an  economic supply point to  the




Midwest fertilizer market.  The  other three  areas  offer reasonably  attrac-




tive possibilities for a large,  new  sulfuric acid  plant, so  long  as all




or a major portion of production would  be  captive  and related to  ferti-




lizer production.. For an acid plant to be advantageously located with




respect to potential pyrite supply and  still be in a position to  com-




pete effectively in the,fertilizer industry, the St. Louis and Cairo




areas were judged preferable.  Since Cairo is closer to possible  pyrite
                                    37

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 sources  in  Pennsylvania  and  southern  Illinois  (thereby minimizing po-




 tential  freight  costs) it was  selected  as  the  location to  consider for




 an  integrated  pyrite-based fertilizer operation.



      In  order  to evaluate the  economic  effect  of  a  pyrite-based opera-




 tion  contrasted  with  a brims tone-based  operation, a hypothetical situ-




 ation was developed wherein  phosphate fertilizer  would be  produced at




 Cairo, using pyrite feed obtained  either from  southern Illinois or the




 Pennsylvania region.  To assess the competitive situation,  an alterna-




 tive  was calculated,  involving a similar phosphate  fertilizer plant




 using brimstone  (elemental sulfur), and located in  Cairo or Baton




 Rouge, Louisiana.  The price of brimstone  was  assumed  to be $38 per long




 ton,  f.o.b. Gulf Coast port  (December 1967 quoted price).   Under the




 conditions  assumed, the  net  price  payable  to a coal company for an 85




 percent  pyrite feed may  range  from a negative  value of $1.50 per ton




 to  approximately $3.73 per ton, f.o.b.  the fertilizer  plant.  If an




 additional  penalty is imposed  on the pyrite operation  to reflect the




 risk  associated  with  the higher capital cost required, the price pay-



 able  for pyrite  becomes  lower.




      2.5.3  The  Chemico  Study




      The Chemico  "High Sulfur  Combustor Study" examined preliminary




 designs and evaluations  of several combustion  and flue gas treating




 systems for processing high  sulfur fuels that  may be drawn off from




 the rejects of coal washing.   These fuels  (i.e.,  washing rejects) will




need to be tailored to specifications that depend first on the require*-
                                     38

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ments of available processes  for  sulfur  value  recovery  and  second on  the

limitations of combustion  equipment  with respect  to  ash.  The  High Sulfur

Combustion  (HSC) fuel specifications can evidently be satisfied  by ap-

propriately re-combining selected portions  of  reject material  from deep

cleaning of coal.

     Four sample HSC fuel  compositions are  tabulated in Table  II to-

gether with product and cost  data on six processing  systems for  these

fuels.  The operating context in  each case  is  one of a  number  of typi-

cal site possibilities in  the bituminous coal-producing area comprised

of Pennsylvania, Ohio, West Virginia, Indiana,  and Illinois.

     Forward  estimates of  selling prices of the four products  are:

               Steam per M  pounds           $ 0.65

               Electricity  per KWH           0.0075

               Sulfur per long ton          25.00

               Sulfuric acid per net  ton     12.75

     If these prices prevail, the estimates of economic benefit, if any,

treated as  credits to coal cleaning  costs,  are as shown below:
Gain after Tax
Clean Coal
M Ton /Year
CASE
A
M$
1,760
7,100
CASE
B
M$
(420)
2,300
CASE
C
M$
(1,960)

920
CASE
D
M$
690

7,100
CASE
D3
M$
4,700

7,100
CASE
E
M$
4,230
3,500
Netback per Ton
 of Clean Coal   $0.25   ($0.18)    ($2.13)    $0.10     0.66    $1.21
                                     39

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CASE
_A 	

33.1
61.0
1.8
6.0
500

CASE
_B 	

18.3
42.5
0.4
2.0
500

CASE
C
PROTOTYPE
11.7
33.8
0.2
1.2
500
50
CASE
_D 	

11.7
33.8
0.2
1.2
3,500
500
CASE
D3

11.7
33.8
0.2
1.2
3,500
500
CASE
_E 	

7.9
28.8
0.12
0,7
3,500
500
                                                                          TABLE II
                                            HSC FUEL COMPOSITrONS, PRODUCTS, INVESTMENT, AND OPERATING COSTS
High Sulfur Fuel Composition

     % Total Sulfur
     % Total Ash

     Sulfur to Coal Weight Ratio

Percent S02 in Flue Gas

Products for Sale

     Energy as Steam - M Lbs/Hr
     Energy as Electric Capacity - Megawatts

     Sulfur Value as Sulfuric Acid - M Net Tons  per Year     610          208                                   753         473
     Sulfur Value as Sulfur - M Long Tons per year                                     31           233

Co-Produced Clean Coal

     M Tons per year

TOTAL INVESTMENT IN HSC SYSTEMS

ANNUAL COST OF OPERATION BEFORE U.S. INCOME TAX

COST OF ENERGY EXTRACTION

     Steam per M Lbs
     Electricity per MWH

COST OF SULFUR VALUE EXTRACTION

     Sulfuric Acid per Net Ton
     Sulfur per Long Ton



                  NOTE:   "Cost" does not  include any charge for the HSC Fuels.   Unit  costs  of  products reflect an adjustment for "pollution control"

                         In CASE A and CASE B the cost of sulfuric acid manufacture is less than  the cost of pollution control, hence the figures
                         in () parenthesis.


                  SOURCE:  Reference 25.
7
M$18
6
$

($

,100
,340
,990
3.00

8.20)

2,300
M$18,600
6,060
$ 1

($ 2

920
M$29,270
7,530
.60
S 14.50
.00)
S 57.00
7,100
M$128,520
34,500

5 7.

$ 28.
7,100
M$126,520
29,000

00 S 7
$ 3
00
3,500
M$125,700
27,900

.00 S 5.W
-.50 $ 10.00


-------
     Case C is intended for possible construction as a prototype  or




demonstration plant.  The four other case studies,  taken  together,




amount to a preliminary exploration of  the range of possible  operating




conditions.  Any specific coal cleaning situation will need to be ex-




amined in detail for applicability to the high  sulfur combustor con-




cept.  Washability of the coal and proximity  to sulfuric  acid consumers




were found to be major determinants of  the choice of technology and




economic expectations.  The manufacture of sulfur for conversion  to




sulfuric acid after shipment  compares unfavorably with manufacture and




direct shipment of sulfuric acid  unless very  large  tonnages are to be




shipped long distances by rail.
                                     41

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 3.0  CONCLUSIONS
     1.   Information was developed on the sulfur forms and distribution
 of sulfur  in coal samples from mines which were producers of utility
 coal.  Related washability studies were performed to assess the
 effects  of specific gravity and size reduction on the liberation and
 separation of pyritic sulfur and ash from coals.  Data on 322 samples
 were reported by the Bureau of Mines and data on 67 samples were re-
 ported by  the Illinois Geological Survey.  This effort is continuing.
     2.  An evaluation of the data from 322 mines sampled showed that
 approximately 30 percent of these mines have coal that washed to a  total
 sulfur content of 1 percent or less.  Both the distribution and release
 potential  of the sulfur in coals varies between the regions and coals
 within the region.
     3.  The Illinois Geological Survey data indicated that there are
 only a few Illinois coals whose sulfur content can be reduced to 1.5 per-
 cent or  less.  Coals capable of this amount of sulfur reduction had only
 2 percent  or less sulfur in the raw coal samples.
     4.  An evaluation of data obtained from 195 coal samples from  the
 Appalachian region coal bed showed that significant total sulfur reduc-
 tions are  obtainable at yields of 70 to 80 percent.
     5.  An evaluation of data obtained from 13 coal samples from the
 Southern Appalachian region showed percentage reductions in pyritic
 sulfur contents (via washing) similar to those for Northern Appalachian
coals.   However, due to the low pyritic sulfur content of the southern
coals,  the attractiveness for cleaning is not as great.
                                    42

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     6.  The Illinois Geological Survey concluded that, for the  (Illinois)


coals tested for washability, two-inch-diameter core sample data correlated


very closely with face sample data.


     7.  All existing commercial coal cleaning processes with the excep-


tion of froth flotation proved effective in separating liberated pyrite


from coal.  Of the several innovative processes for pyrite liberation


investigated, the two-stage flotation technique appears to show the


greatest potential for scale-up to commercial operation.  The degree of


sulfur reduction was dependent on equipment, operating characteristics,


and, of course, the characteristics of the coal being tested.,  The


studies defined how sulfur reduction could be optimized.


     8.  Based on float-sink test  results, an estimate was made of the

                                                                    (9)
physical desulfurization potential of eastern bituminous steam coal.


The estimate was based on washing at 3/8 inch top size with a 90 per-


cent Btu recovery.  The resulting estimates of cumulative availability


by sulfur content for both clean and raw coal are given in Figure 12.


     9.  The technology exists for utilizing reject and middling pro-


ducts to recover sulfur values and generate energy.  The variables are


such (e.g., market for sulfur values, cost of coal, cleaning cost, trans-


portation economics, plant cost) that economic generalizations are not


possible and each case must be individually examined.


     10.   Physical cleaning, in general, will provide a higher Btu,


lower ash, more uniform product.  Monetary benefits will result from


using physically cleaned coal.  These benefits are attributable to




                                    43

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       (ALL COAL WASHED)   V
                          SOURCE:  DERIVED FROM DATA IN REFERENCE 2
0
12345

   TOTAL  SULFUR CONTENT - PERCENT BY WEIGHT
                            FIGURE 12
    ESTIMATED PHYSICAL DESULFURIZATION POTENTIAL OF EASTERN
               BITUMINOUS STEAM COAL PRODUCTION

-------
higher Btu content  (of cleaned coal), an effective  transportation  cost




saving, an ash disposal cost saving, a grinding cost  saving, and a




plant maintenance cost saving.




     11.  Physical  cleaning the higher sulfur  content coals, thereby




providing a higher  BTU and lower ash product at high  yield and reason-




able cost, could provide fuel for a combustor  employing a moderate-




cost/moderate-capability supplemental stack gas cleaning system.   This




use of physical cleaning and flue gas cleaning could  reduce the overall




SC>2 emission control cost.




     12.  Physical  cleaning of coal is essentially  a  proven technique




with only degree  (levels and amounts) to be quantified.  The process is




capable of providing a near-term, even though  limited, benefit.




     13.  Physical  cleaning of coal as a means to control sulfur oxides




emissions will have the least impact on the economy.  Wide-spread  com-




merical application of physical cleaning will  help  maintain a viable




coal industry and will permit increased use of coal,  by far our most




abundant fossil fuel resource.




     14-  Studies performed by the Bechtel Corporation and A. D. Little,




Incorporated indicate that adequate technology exists, in the form of




several commercially-used and proven processes, for recovery of sulfur




values of pyrite materials as elemental sulfur or sulfuric acid and




energy values as steam or electric power.  These processes have been




applied to mined pyrites but have not yet been applied to utilizing




pyrite-bearing refuse from coal preparation plants  as feedstock.







                                    45

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      15.   The Bechtel Corporation study indicates that several examined




 processes are technically  capable of  accepting coal cleaning refuse as




 feedstock,  although  certain of  these  processes require concentration of




 the refuse to increase its pyrite content.




      16.   All the  processes considered  by A. D.  Little,  Incorporated and




 the Bechtel Corporation for utilizing coal  cleaning refuse require some




 degree of modification to  accommodate the relatively low-pyrite,  high-




 ash feedstock.  Modification can  be minimized  by enriching the input air




 with pure oxygen.




      17.   There is a large and  a  relatively stable  market  for sulfuric




 acid.   The  attractiveness  of processes  for  converting the  sulfur  content




 of  coal preparation  plant  refuse  to sulfuric acid is highly dependent on




 the market  value of  elemented sulfur.




      18.  Under conditions  prevailing at the time of the A. D. Little,




 Inc.  and  the  Bechtel  Corp.  studies, the refuse-combustion/sulfur-oxides-




 removal process and  the  fluid-bed  roasting  process  were  found to  be




 economically  viable.




     19.  The Chemico  study  indicated (i.e., at  the time of the study)




 that by the use of high-sulfur refuse fuel  of  tailored composition to




meet the requirements  of especially designed combustors  and commercially




available boilers,  generators and  sulfur recovery processes,  it appears




possible to extract the energy and sulfur values  of high-sulfur fuels




on a commercial basis.
                                     46

-------
     20.  In view of the shipping costs resulting from  the heavy weight




of sulfuric acid, it may be highly advantageous  for  a sulfur  recovery




plant to be capable of producing sulfur as  several different  compounds




(or in elemental form) especially in  cases  where the sulfur must be




shipped to different points of  consumption.

-------
4.0  WASHABILITY STUDIES



     This section outlines the  procedures  employed,  details the number




of samples obtained from various  locations,  summarizes the results of




the washability studies, and reports  on the  findings of an effort that




examined the comparability of coal  core samples  and  face samples.  The




comparability of core samples and face  samples effort was to determine




whether useful washability data could be obtained  from 2-inch diameter




core samples.  A more detailed  description of sampling and washability




procedures and an in-depth discussion of results can be found in




References 3, 4, 5, 6,  7,  and 8.




     The principal purpose of the effort was to  determine the sulfur




forms and distribution of  sulfur  in coal samples from mines which were




principally utility coal producers.   Coal  samples  were obtained from




the following coal regions:




     1.    Northern Appalachian  region:   the  states of Maryland, Pennsyl-




          vania (bituminous), and Ohio  and counties  located in central




          and northern  West  Virginia.




     2.    Southern Appalachian  region:   the  states of Tennessee,  Virginia,




          and eastern Kentucky  and  some of the southern West Virginia



          counties.




     3.    Alabama  region:  the  state  of Alabama.




     4.    Midwest  region:  the  states of Illinois, Indiana,  and western



          Kentucky.




     5.    Western  region:  all  states west of the  Mississippi.
                                   48

-------
     Generally, the washability data on the coals indicated that the




total sulfur could be reduced by using some combination of stage crush-




ing and specific gravity separation.  The washability data were analyzed




with the use of a specifically designed computer program.




4.1  Experimental Procedure - Collection of Coal Mine Samples




     Coal samples were collected either from a fresh face in the mine or




from the tipple (raw R.O.M.).  The face samples were obtained by cutting




channels approximately ten inches deep and wide enough to provide a sample




of approximately 600 pounds.^- '  Each channel was selected so as to be




as representative as possible of coal being mined.  Tipple samples were




collected by taking increments at fixed time and/or weight intervals so




as to insure that all working faces were represented in the gross sample.




4.2  Procedure for the Conduct of the Washability Studies




     The sample preparation procedures by investigator with specific




gravity test points for the washability studies are provided in Figure




13 and Table III.  Each gross sample was air-dried and crushed to 1 1/2




inch top size using a single roll tooth crusher.  The coal was then




divided into required portions by means of cone and quartering.  The pre-




paration of each coal portion for float and sink tests was as indicated




in Figure 13.  The 100 mesh x 0 material, separated by screening from the




coal fraction used for float and sink tests, was analyzed for ash,




pyritic sulfur, and total sulfur.
                                    49

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tn
o
                                                                                                1,2,3,4
                                                                                                  SCREEN-
, 3/8" x
MESH
14

14 x 100
MESH
                                                                                                                                 REFERENCE NUMBER OF INVESTIGATION

                                                                                                                                 1 - BUREAU OF MINES
                                                                                                                                 2 - COMMERCIAL TESTING AND ENGINEERING
                                                                                                                                 3 - BITUMINOUS COAL RESEARCH
                                                                                                                                 4 - ILLINOIS GEOLOGICAL SURVEY
                              INDICATES FLOAT-SINK TEST
                                                                         FIGURE 13
                                                   FLOW DIAGRAM SHOWING PREPARATION OF GROSS SAMPLE

-------
                                         TABLE III
                 TABLE OF FLOAT SINK TEST SIZES WITH SPECIFIC GRAVITIES
Investigator
Bureau of Mines
Commercial Testing
and Engineering
Company
Bituminous Coal
Research, Inc.

Illinois State
Geological
Survey
 Sizes Washed

1 1/2 in. x 100 mesh
3/8 in. x 100 mesh
14 mesh x 0
1 1/2 in. x 100 mesh
3/8 in. x 100 mesh
14 mesh x 0
30 mesh x 0
60 mesh x 0  (p.c.)
1 1/2 in. x 0
3/8 in. x 14 mesh
14 mesh x 100 mesh
     Test Points
(Specific Gravities)
1.25-1.29 1.30 1.30-1.39 1.40
x x
X X
X X
X X
X X
X X


X XX
X XX
X XX
1.60
X
X
X
X
X
X
X
X
X
X
X
1.



X
X
X






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     The float and sink analyses were conducted on the various fractions




at specific gravities as indicated by Table III.   After completing the




float-and-sink analysis, the specific gravity fractions of the samples




were analyzed for ash, pyritic sulfur, and total sulfur content.





     Additional  details of  the  float-sink  tests are provided  in Refer-




 ence 8.




 4.3  Results  of  Washability Data  - Washability Computer Program




     A  computer  program was used  to  interpolate the washability data  to




 find the theoretical  specific gravity of separation,  yield, ash content,




 and  pyritic and  total sulfur contents for  specific levels of  yield or




 total sulfur.  The values of the  sulfur and yield interpolants  were read




 into the computer and stored.   In addition, the following data  were




 entered  for each mine sample:   "state, county, town,  mine, and  bed codes;




 laboratory number, and laboratory identification code, bed-bench and  size




 fraction codes;  year  of sample  collection; company name, mine name, and




 county name;  the specific gravity fractions of separation and their




 associated levels with the  variables, ash, pyritic and total  sulfur."^




 Using these data, three tables  are printed out for each mine.   These




 tables are:   (1)  the  original cumulative washability  data;   (2) values




 of specific gravity of separation, yield,  ash, and pyritic sulfur for




 requested  levels of total sulfur; and  (3)  values of specific  gravity  of




 separation, yield, ash, pyritic sulfur, and total sulfur for  the request-




 ed levels  of yield.
                                   52

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     A second computer program was written to make a statistical evalua-

tion of the washability data.  This program calculated averages and the

standard deviation (sigma) values.

     The computer program was used to calculate the percentages of total

recovery of ash, pyritic sulfur, and total sulfur for the desired levels

of interpolation.  Next, the program was used to calculate the averages

and standard deviations of the ash, pyritic sulfur, and total sulfur.

These averages and standard deviation values were found for each bed and

the required data accumulated for similar averages for the region.  Also,

the averages and standard deviation values were calculated for each set

of interpolated values at the various yield levels.

4.4  Program Results

     The average composition of the coals evaluated in the Bureau of

Mines study*was 14.4 percent ash, 2.05 percent pyritic sulfur and 3.23

percent total sulfur.' '  The results generally indicated that the largest

reduction in ash and sulfur through washing was obtained by reducing

coal top size from 1 1/2 inches to 3/8 inch.  Crushing from 3/8 inch to 14

mesh showed relatively lower ash and sulfur reduction.
 *Data from the Commercial Testing and Engineering Company investigations are
  reported by the Bureau of Mines.
                                   53

-------
     Summary data covering the 322 coal samples evaluated by  the  Bureau  of

                     fO\
Mines are as follows:v
                    Ash, Percent
                   (Raw Avg.: 14.4,
„     ^  XT    *      Sigma: 5.8)
Percent  No. of        °
Yield    Samples  Average   Sigma*
                             Pyritic Sulfur,
                                Percent
                            (Raw Avg.:  2.05,
                              Sigma: 1.35)
 Total Sulfur,
   Percent
(Raw Avg.: 3.23,
  Sigma:  1.75)
  60
  70
  80
  90
   60
   70
   80
   90
   60
   70
   80
   90
260
290
284
168
25.
287
277
145
270
298
274
136
                            Average    Sigma     Average

                           1 1/2 Inch Top Size
5.8
6.4
7.1
7.2
2.3
2.7
2.8
2.4
0.72
0.79
0.89
1.00
0.57
0.59
0.65
0.68
1.95
2.03
2.13
2.27
1.06
1.07
1.12
1.21
                                        3/8 Inch Top Size
5.1
5.6
6.3
6.5

4.6
5.2
5.9
6.0
2.2
2.4
2.4
2.2

2.1
2.3
2.2
2.0
0.57
0.61
0.68
0.75
14 Mesh
0.46
0.50
0.57
0.59
0.48
0.48
0.49
0.56
Top Size
0.40
0.39
0.42
0.48
1.82
1.83
1.92
1.95

1.70
1.72
1.79
1.79
1.04
1.00
1.04
1.12

0.98
0.96
0.99
1.07
       The sulfur reductions of these coals attained by washing are further

  summarized in Figure 14.  This figure indicates that significant total sulfur

  reductions are attainable by removing heavy impurities.  At 60 percent

  yield, 20 to 25 percent of the mine samples showed a 1 percent or less

  total sulfur product.
   *Sigma (cr)  is  the standard deviation value.
                                     54

-------
w
OT
W
                    90 PERCENT YIELD
                i   i    i   i    i
                                              80 PERCENT YIELD
                   70 PERCENT YIELD
                                             60 PERCENT YIELD
                                                 i    i   i    i
(a)
(b)
(c)
(d)
                         678012
                           SULFUR, PERCENT
RAW COAL TOTAL SULFUR CONTENT CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS llj INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                               FIGURE 14
                WASHABILITY SUMMARY OF ALL COALS
345678


 SOURCE:  REFERENCE 8
                                 55

-------
     An evaluation of the data from  the  322 mines sampled showed that




approximately 30 percent of these mines  have  coal that washed to a total




sulfur content of 1 percent or less.  On crushing to 1 1/2 inch top size,




significant reductions in sulfur content were attainable by removing 10




or 20 percent of the heaviest material.   Furthermore,  the total sulfur




content was reduced by approximately 50  percent  in more than half  of the




samples collected by crushing of the coal prior  to removing the heaviest




impurities.  Both the distribution and release potential of the sulfur




in coals varies between the regions and  the coals within the region.




     The Illinois Geological Survey washability  studies indicated  that




most Illinois coals have a total sulfur  content  of 3  to 5 percent  and




there are only a few Illinois coals whose sulfur  content can be reduced




to 1.5 percent or less.  The coals capable of this amount of sulfur re-




duction had only 2 percent or less sulfur in  the  raw  coal samples.




     With regard to the forms of sulfur  in the coals,  it was found that




approximately 50 percent of the sulfur in the average  Illinois  coal was




in the pyritic form.  The average pyritic sulfur  reduction was  approxi-




mately 60 percent with an 80 percent yield and 75 percent  with  a 40 per-




cent yield.





     Usually, the float coal fractions had less sulfur when  the  coal  was




crushed to finer sizes.  In many of the coals tested, however,  the  differ-




ences were not great enough to warrant grinding the coals  to finer  sizes




for sulfur reduction.
                                     56

-------
    4.4.1  Northern Appalachian Region


     One hundred and ninety-five coal bed samples were collected from

the following four states of the Appalachian region:

     1.   Maryland - 32 samples

     2.   Ohio - 48 samples

     3.   Pennsylvania - 90 samples

     4.   Northern West Virginia - 25 samples.

The average composition of the raw coal of the region was 14.7 percent

ash, 2.03 percent pyritic sulfur, and 3.07 percent total sulfur.  An

analysis of the data indicated that crushing the raw coal to 1 1/2 inch

top size resulted in an average pyritic sulfur reduction of 0.95 per-

centage points at 90 percent yield and 1.12 percentage points at 80 per-

cent yield.  Crushing the coal to 3/8 inch top size resulted in an

average pyritic sulfur reduction compared to raw coal of 1.25 percentage

points at 90 percent yield and 1.4 percentage points at 80 percent yield.

Crushing the coal to 14 mesh top size resulted in an average pyritic

sulfur reduction compared to raw coal of 1.46 percentage points at 90

percent yield and 1.52 percentage points at 80 percent yield.

     Summary data covering the 195 Northern Appalachian region coal
                                                        /Q\
samples evaluated by the Bureau of Mines are as follows:
                                57

-------
  Percent  No.  of
   Yield    Samples
                       Ash, Percent
                     (Raw Avg.:  14.7,
                       Sigma: 6.0)
                      Pyritic  Sulfur,
                        Percent
                       (Raw Avg.:  2.03,
                        Sigma: 1.24)
 Total Sulfur,
   Percent
(Raw Avg.: 3.07,
  Sigma:  1.59)
Average    Sigma      Average     Sigma    Average    Sigma
                                         1 1/2 Inch TOP Size
60
70
80
90

60
70
80
90
169
180
169
99

159
179
163
86
5.8
6.6
7.4
7.4

5.2
5.8
6.5
6.7
2.6
2.9
3.0
2.4

2.4
2.7
2.6
2.2
0.68
0.79
0.91
1.08
3/8 Inch
0.50
0.57
0.63
0.78
0.54
0.59
0.70
0.67
Top Size
0.45
0.49
0.49
0.57
1.73
1.83
1.96
2.25

1.57
1.62
; 1.68
1.90
0.96
1.00
1.11
1.15

0.93
0.94
0.98
1.11
14 Mesh Top Size
60
70
80
90
163
181
161
81
4.7
5.4
6.0
6.2
2.2
2.6
2.3
2.0
0.39
0.44
0.51
0.57
0.35
0.39
0.40
0.45
1.45
1.49
1.55
1.69
0.86
0.87
0.91
1.01
      Figure 15 shows  the percentage  of  mines  versus sulfur content re-

 lationship derived from analyses  of  coals  collected from the Northern Ap-

 palachian region.   This figure  indicates that 32  percent of the mines

 sampled  contained  coal  with  less  than 2 percent total  sulfur.   Upon

 crushing to 1  1/2  inch  top size with 90 percent yield,  43 percent  of  the

 mines  sampled  contained less than 2  percent total sulfur.   At  80 percent

yield the value increased to 68 percent with less than 2 percent sulfur.

In general, significant total sulfur reductions are obtainable  at yields

of 70 to 80 percent.

     The results of sampling various coal beds of the Northern Appalachian

region are discussed in the following sections.

                                    58

-------
w
W
w
100
 90
 80
 70
 60
 50
 40
 30
 20
 10
  0
100
 90
 80
 70
 60
 50
 40
 30
 20
 10
  0
                    90 PERCENT YIELD
                   i	i	i   i   i
                   70 PERCENT YIELD
                      i    i   i    i
                                             80 PERCENT YIELD
                                             i	i	i    i   i
                                             60 PERCENT YIELD
                                         iii   iii
(a)
(b)
(c)
(d)
                                            345678

                                             SOURCE:  REFERENCES
                     56780   12
                          SULFUR, PERCENT
RAW COAL TOTAL SULFUR CONTENT  CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT  COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                              FIGURE 15
        WASHABILITY OF NORTHERN APPALACHIAN REGION COALS
                                 59

-------
     4.4.1.1  Sewickley Coal Bed.  Thirteen Sewickley coal bed samples
were collected from the following four Northern Appalachian states:

       1.   Maryland -  2 samples
       2.   Ohio - 9 samples
       3.   Pennsylvania - 1 sample
       4.   West Virginia - 1 sample
  The total sulfur content of this coal is high,  averaging over 2.5 percent
  (with o- «1.37) at 60 percent yield.   In general,  this coal was quite
  refractory, providing small to only  moderate reductions of ash and total
  sulfur contents as a result of crushing.  However,  the pyritic sulfur
  reduction was high due to the coarseness of  the pyrite which reported to
  the high specific gravity material.
       The organic sulfur content of coals from the Sewickley  bed varied
  considerably and was generally over  1.5  percent.  The  high percentage
  reduction in pyritic sulfur was reflected in total  sulfur  reductions
  ranging  from 23 percentage points at 90  percent yield  to 33  percentage
  points at 60 percent yield when the  coals were crushed to  3/8 inch top
  size.  Further crushing did not significantly reduce  total sulfur content.
       4.4.1.2  Pittsburgh Coal Bed.   Thirty-six  samples from the Pittsburgh
  coal bed were collected from the following four Northern Appalachian
  Region states:
       1.   Maryland -  1 sample
       2.   Ohio - 16 samples
       3.   Pennsylvania - 5 samples
       4.   West Virginia - 14 samples
                                    60

-------
The average characteristics of the raw samples collected from the Pittsburgh
coal bed are 12.4 percent ash  (tr = 5.8),  2.16 percent pyritic sulfur  (a- = 0.92),
and 3.61 percent total sulfur  (cr - 1.21).  Crushing these coals to 1  1/2 inch
top size provided 90 percent average yield values of 6.7 percent ash  (
-------
The  average  characteristics of  raw samples collected from the Upper Freeport

coal bed  are 17.2  percent  ash (cr = 5.3),  1.72 percent pyritic sulfur  (cr = 0.9;

and  2.42  percent total  sulfur (cr = 1.10).   Crushing these coals to 1 1/2

inch top  size provided  90  percent yield values of 9.1 percent ash (cr = 2.9),

1.05 percent pyritic  sulfur (cr  = 0.72), and 1.81 percent total sulfur

(
-------
The average characteristics of the raw  samples collected  from  the Lower




Freeport coal bed are 12.9 percent ash  (cr = 3.5),  1.72 percent pyritic




sulfur (
-------
 sulfur (or= 1.19),  and 2.37 percent total sulfur (or =  1.29).   Crushing




 these coals to 1 1/2 inch top size provided 80  percent yield  values of




 7.1 percent ash (cr = 0.5),  0.48 percent pyritic sulfur (0-== 0.39),  and




 1.07 percent total  sulfur ( cr= 0.46).   Crushing to 3/8 inch top size




 provided 80 percent yield values of 6.4 percent ash (cr =  0.5),  0.33 per-




 cent pyritic sulfur ( a-= 0.33), and 0.89 percent total sulfur (cr =  0.37).




 Further crushing to 14 mesh top size proved to  be of no practical value.




      The sampled data indicated that Upper Kittanning  coal is a good




 example of coal that can be significantly desulfurized.   The  average




 sulfur content of these coals decreased from the raw coal value of  2.37




 percent to 0.89 percent upon crushing  to 3/8 inch top  size and processing




 to provide an 80 percent yield.




      4.4.1.6  Middle Kittanning Coal Bed.  Twenty-three coal  samples




 were collected from the following three states:




      1.  Ohio - 11 samples




      2.  Pennsylvania - 10 samples




      3.  West Virginia - 2 samples.




The average characteristics of the raw coal samples collected  from the




 Middle Kittanning coal bed are 12.7 percent ash (cr = 5.2), 2.25 percent




 pyritic sulfur (cr = 1.52),  and 3.35 percent total sulfur  (cr = 2.02).




 Crushing these coals to 1 1/2 inch top size provided 80 percent yield values




 of 6.5 percent ash  (cr = 3.2), 0.95 percent pyritic sulfur (cr  = 1.09), and




 2.02 percent total  sulfur (cr = 1.45).   Crushing to 3/8 inch top size pro-




 vided 80 percent yield values of 5 percent ash (cr = 2.1), 0.52 percent






                                       64

-------
 pyritic  sulfur (cr = 0.34), and 1.56 percent total sulfur (cr = 0.71).




 Further  crushing to 14 mesh top size proved to be of very limited values.




      4.4.1.7  Lower Kittanning Coal Bed.  Thirty-seven coal samples were




 collected from the following three states:




      1.   Maryland - 3 samples



      2.   Ohio - 5 samples




      3.   Pennsylvania - 29 samples.






The average characteristics of  the  raw samples collected from the Lower




Kittanning coal bed are 15.1 percent ash  (cr = 6.8), 2.31 percent pyritic




sulfur (
-------
     1.   Tennessee - 6 samples

     2.   Southern West Virginia - 3 samples

     3.   Virginia - 4 samples.

The average raw coal of the region contained 11.2 percent ash, 0.29 percent

pyritic sulfur, and 0.93 percent total sulfur.  These are generally low-

sulfur-content coals averaging less than 1 percent total sulfur content.

Because the pyritic sulfur is so low, crushing of these coals to release

sulfur would be of almost no benefit, although the pyritic sulfur reduction

owing to crushing and reduced yield is very good.  The sulfur reduction

of  these coals attained by washing is summarized below and in Figure 16.

     Summary data covering the 13 Southern Appalachian region samples
 evaluated by the Bureau of Mines are as follows:
                                               .(8)
Percent  No. of
 Yield   Samples  Average
                   Ash, Percent
                   (Raw Avg.: 11.2,
                    Sigma: 5.3)
         Pyritic Sulfur,
           Percent
         (Raw Avg.:  0.29,
           Sigma:  0.52)
 Total Sulfur,
    Percent
(Raw Avg.: 0.93,
  Sigma: 0.80)
Sigma    Average    Sigma

      1 1/2 Inch Top Size
Average
Sigma
60
70
80
90

60
70
80
90

60
70
80
90
6
12
12
8

5
10
12
8

9
13
12
8
4.0
4.0
4.3
4.8

4.1
3.9
3.8
3.5

2.8
3.2
3.9
4.5
1.6
1.7
2.2
2.1

0.9
1.7
2.2
2.0

1.3
1.6
1.9
1.9
0.15
0.10
0.10
0.14
3/8 Inch Top
0.14
0.09
0.08
0.12
14 Mesh Top
0.07
0.07
0.08
0.11
0.21
0.17
0.18
0.28
Size
0.19
0.16
0.13
0.25
Size
0.09
0.10
0.14
0.22
0.98
0.81
0.81
0.90

1.01
0.81
0.78
0.87

0.84
0.77
0.78
0.84
0.65
0.49
0.50
0.66

0.68
0.51
0.45
0.63

0.44
0.39
0.44
0.58
                                     66

-------
w
w
PU
W
B
(a)
(b)
(c)
(d)
                   90 PERCENT YIELD
                   i   i	i   i    i
                   70 PERCENT YIELD
 80 PERCENT YIELD
60 PERCENT YIELD
i    i    iii
345678

 SOURCE:  REFERENCE 8
       12345678012
                          SULFUR, PERCENT

RAW COAL TOTAL SULFUR CONTENT  CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT  COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1% INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                               FIGURE 16
         WASHABILITY OF SOUTHERN APPALACHIAN REGION COALS
                                 67

-------
     4.4.3  Alabama Region Coals




     Six samples were collected from the Alabama region.   The  average




characteristics of the raw samples are 14 percent ash  (cr = 3.7),  0.97  percent




pyritic sulfur (o- = 0.99), and 1.66 percent total sulfur  (
-------
 6.0 percent ash, 0.82 percent pyritic  sulfur,  and  2.61  percent total

 sulfur.  Crushing to 3/8  inch top  size did  not provide  significant im-

 provements in ash and sulfur values.

     Crushing these coals to 14  mesh  top  size  provided  90  percent yield

 values of 6.7 percent ash,  0.77  percent pyritic sulfur,  and  2.53 per-

 cent total sulfur.  The  70  percent yield  values were  5.1 percent ash,

 0.66 percent pyritic sulfur, and 2.38  percent  total sulfur.  At 60 per-

 cent yield the values were 4.4 percent ash, 0.58 percent pyritic sulfur

 and 2.29 percent total sulfur.


     Summary data covering the 82 Midwest region coal  samples evaluated

by the Bureau of Mines  are.as follows:
                    Ash, Percent
                   (Raw Avg.: 14.1,
 Pyritic Sulfur,
    Percent
(Raw Avg.: 2.29,
 Total Sulfur,
   Percent
(Raw Avg.:  3.92,
Percent
Yield

60
70
80
90

60
70
80
90

60
70
80
90
No. of
Samples

61
73
79
42

62
73
79
35

71
78
76
33
Sigma:
Average

5.4
6.0
7.0
7.5

4.7
5.3
6.4
6.9

4.4
5.1
6.2
6.7
4.8)
Sigma

1.2
1.6
1.9
1.6

1.1
1.4
1.7
1.6

1.2
1.5
1.8
1.5
Sigma:
Average
1 1/2 Inch
0.75
0.82
0.97
1.00
3/8 Inch
0.66
0.73
0.86
0.85
14 Mesh
0.58
0.66
0.77
0.77
1.00)
Sigma
Top Size
0.32
0.35
0.45
0.48
Top Size
0.25
0.30
0.37
0.34
Top Size
0.22
0.26
0.33
0.34
Sigma:
Average

2.49
2.61
2.72
2.76

2.42
2.47
2.60
2.59

2.29
2.38
2.48
2.53
1.26)
Sigma

0.70
0.69
0.78
0.97

0.70
0.74
0.78
0.86

0.73
0.73
0.75
0.83
                                  69

-------
     Figure 17 shows that 60 percent of the collected samples  contained  less




than 2 percent organic sulfur.  For top size crushing of  1  1/2 inch  and




less, over half of the pyritic sulfur is removed with 90  percent yield.




The reasonable range of total sulfur in the final product as indicated in




Figure 17 is 2-3 percent.




     The results of sampling the various coal beds of the Midwest region




are as follows:




     4.4.4.1  Kentucky No. 9 Coal Bed.  Thirteen samples  from  the Kentucky




No. 9 coal bed were collected from Western Kentucky.  The average composition




of the raw samples was 11.4 percent ash (
-------
w
en
H
(a)
(b)
(c)
(d)
                    90 PERCENT YIELD
                   70 PERCENT YIELD
       12345678012
                           SULFUR, PERCENT
RAW COAL TOTAL SULFUR CONTENT CURVE;
RAW COAL ORGANIC SULFUR CONTENT CURVE;
WASHED COAL TOTAL SULFUR CONTENT COAL CURVE
WHEN RAW COAL WAS CRUSHED TO MINUS 1>J INCHES;
AND,
WHEN RAW COAL WAS CRUSHED TO MINUS 14 MESH.
                              FIGURE 17
                WASHABILITY OF MIDWEST REGION COALS
345678


 SOURCE:  REFERENCE 8
                                  71

-------
     4.4.5  Illinois Geological Survey Studies





     In addition to the Bureau of Mines reported studies, washability




studies in two phases were conducted by the Illinois Geological Survey




on samples taken from Illinois coal mines.   During the first phase, 40




samples were taken from 35 Illinois coal mines located in most mining




areas in the state, the number of samples being greater than the number




of mines because several mines produced coal from more than one seam




and the different seams were sampled separately.




     During the second phase of the Illinois Geological Survey investi-




gation, washability tests were made on 27 coal samples taken from most




of the Illinois mines not sampled during the first phase.  The coal




samples (phases I and II) were obtained from the No. 1, No. 2, No. 4,




No. 5, No. 6, No. 7, DeKoven, and Davis seams.





      Float-sink tests indicated  that  only  in  those  Illinois  coals hav-




 ing relatively low-sulfur content,  as mined,  could  the total sulfur




 content be reduced to 1.5 percent  or  less  by  washing  techniques.   Most




 Illinois  coals,  as mined,  contain  3-5 percent sulfur.   Float-sink tests




 indicate  this level could be  reduced  to about 2.5 to  4 percent  total



 sulfur.





      In Phase I, only two of the 40 tested samples could be reduced to




 a total sulfur content of less than 1 percent at an 80 percent recovery.




 Five samples could be cleaned to less than 1.5 percent total sulfur




 with an 80 percent recovery.  These five samples were all naturally-




 occurring low-sulfur coals.   Of  the 40 coals tested during Phase  I, 10




                                   72

-------
samples could be cleaned to 2.5 percent  sulfur or  less  than an 80 per-


cent recovery.   The above was obtained with  top  size crushing of 1 1/2


inches.  Crushing to finer sizes did not provide additional significant


sulfur reductions.


     Due to the similarity of Phase I results between 11/2 inch and


3/8 inch top size testing and since 3/8  inch top size testing would


allow the use of a smaller quantity of coal  for  washing and chemical


tests, the following Phase II results are based  on testing at 3/8 inch


top size.


     In Phase II, 4 out of the 27  samples tested had less than one per-


cent total sulfur at recovery levels of  80,  60 or  40 percent.  Of these


four, one sample was obtained from a mine in current production and with


appreciable unmined reserves.  In  addition to the  above, one sample


obtained from a large mine had float coal with less than 1.5 percent


total sulfur content with an 80 percent recovery.  None of the other


samples could be washed, irrespective of yield,  to less than 1.5 percent


total sulfur.


                        ( 8)
     4.4.6  Western Coal


      The examination  of Western coals was initiated at  a later  date than


for  coals of the  other regions.   This is due to the preponderance of


steam coal traditionally supplied by states east of the Mississippi.  As


interest in the vast  reserves and the potential availability of Western


coal developed, washability examinations were performed, concentrating on


the  higher sulfur coals,  i.e.,  those coals  in which a  sulfur reduction

                                   (9)
potential would be most desirable.

                                      73

-------
     For this effort, twenty-six coal samples from the Western region




were collected from the following six states:




     1.   Iowa - 6 samples




     2.   Oklahoma - 4 samples




     3.   Kansas - 4 samples




     4.   Arkansas - 3 samples




     5.   Missouri - 4 samples




     6.   Colorado - 5 samples.




All of the Western coal samples, with the exception of those from Colo-




rado, are from the Western Interior region.  Colorado lies in the Rocky




Mountain region.



     The average composition of raw coal from the Western region was




14.5 percent  ash, 2.48 percent pyritic sulfur, and 3.72 percent total




sulfur.  Coals from the Western Interior region are characteristically




high in sulfur content, regardless of sulfur  treatment employed.  Coals



from the Rocky Mountain region conversely are characteristically of low




sulfur content, often less than one percent sulfur content, and range




in rank from  bituminous coal to lignite, with sub-bituminous predominating.




     4.4.7  Extension of Float-Sink Test to Finer Grinds^6>1Q^




     Washability studies were extended in a separate effort (ref. Figure




13) to cover  finer sizes of coal at a specific gravity of 1.60.  The coal




sizes studied were the 30 mesh x 0 size and the "as fired" or pulverized




coal (p.c.) grind.  All coal in the p.c. grind is minus 60 mesh with a




minimum of 80 percent of the coal minus 200 mesh.  The 30 mesh * 0 size




represented the lower limit in sizing that would contain a size range of




                                      74

-------
pyrite typical of a utility pulverizer's recycle load.  The coals "as




fired" (or p.c. grind) were of interest because potentially the maximum




pyrite liberation occurs, based on present utilization, with this de-




gree of pulverization.




     The results of the float-sink analysis of the coal samples are




discussed in terms of a first series of 70 samples and an additional




series of 20 samples.  The first series of 70 coals came from three geo-




graphical areas:  Western Pennsylvania, Eastern Ohio, and Illinois.  Max-




imum pyritic sulfur reduction obtained at the 30 x 0 mesh size was 93.7




percent with an Ohio No. 6 coal; the minimum pyritic sulfur reduction




obtained was 51.2 percent with an Illinois No. 6 coal.  At the p.c. grind,




95 percent of the pyritic sulfur was removable from a Pennsylvania Lower




Freeport coal while the minimum percentage of pyritic sulfur removal was




54.5 percent with a Pennsylvania Middle Kittanning coal which had a very




low R.O.M. pyritic sulfur content.  Total sulfur reductions covered a




much wider range  since  the  percentages  of organic  sulfur, which was not




removable, quite  significantly affected the percent reduction.




     The  second  series  of 20  coals came from  three geographical areas:




(1) the Southern Appalachian,  (2) Western Interior, and  (3) Rocky Mount-




ain regions.  The  total  sulfur in raw R.O.M. samples ranged from 0.32




to 6.37 percent by weight.  Pyritic  sulfur levels  ranged from 0.09 to




4.66 percent  by weight.  The  evaluation of the second  series of 20 coals




differed markedly from  the  initial series of  70 coals.   The majority of




the 20 coals were low in pyritic sulfur and little improvement could be






                                     75

-------
made in sulfur reduction regardless of top size crushing.   The  majority




of the group, high in pyritic sulfur, were also high  in  organic sulfur.




Consequently, total reductions were not overly impressive.




     The washability results of the first series of 70 coals  and the




second series of 20 coals are provided in Figures 18  and 19,  respectively.




These figures show the total sulfur reduction at 1.60 float for R.O.M.




coal crushed to the following sizes:  3/8-inch x 100  mesh,  14 mesh x 0,




30 mesh x 0, and p.c. grind.  Figure 18 shows that for the  initial 70-




coal series, the maximum total sulfur reduction ranged from 50  to 60




percent for 10 of the coals at the 1 1/2 inch top size to 80  to 90 per-




cent for one coal at the p.c. grind.  This figure indicates that the




largest incremental sulfur reduction is obtained when the coal  is re-




duced in size from a 1 1/2 inch top size to a 3/8 inch top  size.




     Figure 19, covering the second series of 20 coals,  shows that at




the  1 1/2  inch  top size 25 percent of the coals tested  (five  coals) could




be reduced  in total  sulfur by 20  to 30 percent when washed  at a 1.60




specific gravity.  In addition, five percent of the coals (i.e., one




coal) did not change in sulfur content when  its top size was  reduced




from 14 mesh  to 30 mesh.  The highest obtained total  sulfur reduction




was  69 percent with one coal at its p.c. grind; indicating  the  fineness




of the pyrite distribution  in this coal.




     4.4.8  Comparability of Core Samples and Face  Samples'  '




     One of  the specific objectives of the  (Phase  II) Illinois  Geologi-




cal  Survey  effort was to ascertain whether useful washability data could







                                    76

-------
    90-


    80-
 H
 8
 w
    60-
    40-
    30-
    20-
                              14 MESH x 0
                                                30 MESH x 0
3/8 INCH x 100 MESH
                                                   p.c. GRIND
         1 1/2 INCH x 100 MESH
                 I     I     1     I     1     I     I     I     I
               10-20      30-40      50-60     70-80     90-100

               TOTAL SULFUR REDUCTION LEVELS, PERCENT
                                          SOURCE:  REFERENCE 6
                          FIGURE 18
TOTAL SULFUR REDUCTION AT 1.60SPECIFIC GRAVITY AS RELATED TO
    SIZE FOR 70 W. PENNSYLVANIA, E. OHIO, AND ILLINOIS COALS
                             77

-------
  100


   90


   80


   70
o
g
W
PH
    30-


    20-


    10-


     0
           p.c.  GRIND


              30 MESH x 0


                14 MESH x 0
                                  3/8"  x 100 MESH
                                    1 1/2" x 100 MESH
           I      I     I     I     I     I
              10-20     30-40      50-60
                               I
                             70-80     90-100

TOTAL SULFUR REDUCTION LEVELS, PERCENT


                        SOURCE:   REFERENCE 10
                         FIGURE 19
 TOTAL SULFUR REDUCTION AT 1.60 SPECIFIC GRAVITY AS RELATED
  TO SIZE FOR 20 SOUTHERN, WESTERN, AND MID-WESTERN COALS
                            78

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be obtained from 2-inch-diameter core samples by examining the correla-




tions between this  size  sample and the normal size (i.e., large) sample.




Since these core samples usually weighed 10 pounds (approximately 6 foot




seam thickness), washability tests were made on both the 10-pound core




samples and the 100-pound fractions from normal face samples taken in



the same approximate  locations.




     Table IV lists the  percentages of total sulfur, pyritic sulfur, and




ash for 40, 60, and 80 percent recoveries for the 23 normal samples cover-




ing this effort.  Also shown are the corresponding values for the tests




made on the small  (core) samples (Suffix S).  The differences between




the values given for  the large and small samples are usually less than




those specified by  ASTM  for analytical tolerance between laboratories.




     Figures. 20 and 21 illustrate the similarity of results with large




and small  samples.   The curves are considered as .the best fit for the




data obtained  with the large samples.  The deviation from the curves




of the  data points for the small  sample are considered minor.
                                    79

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                                    TABLE IV




              COMPARISON OF WASHABILITIES OF SMALL AND LARGE SAMPLES
40 percent recovery
*
Sample
Sulfur (%)
Total
Pyritic
Ash
%
60 percent recovery
Sulfur (%)
Total
Pyritic
Ash
%
80 percent recovery
Sulfur (%)
Total
Pyritic
Ash
%
I
IS
2
2S
3
3S
4
4S
5
5S
6
6S
7
7S
8
8S
9
9S
10
10S
11
3.21
3.29
2.46
2.50
2.39
2.40
2.81
2.96
1.85
1.88
0.81
0.84
1.62
1.64
2.40
2.42
2.77
2.66
1.99
1.93
1.92
0.44
0.53
0.42
0.51
0.49
0.49
0.55
0.65
0.75
0.89
0.17
0.20
0.36
0.40
0.43
0.42
0.56
0.56
0.44
0.44
0.45
4.2
4.2
2.4
2.9
2.8
2.5
6.1
5.6
3.6
4.2
3.4
3.4
2.9
2.8
2.3
2.4
3.5
3.3
3.0
3.2
2.1
3.32
3.30
2.57
2.56
2.55
2.55
2.91
3.03
2.24
2.02
0.85
0.87
1.74
1.78
2.49
2.51
2.88
2.75
2.06
1.99
2.04
0.56
0.57
0.58
0.58
0.66
0.64
0.65
0.73
1.10
1.09
0.22
0.23
0.48
0.50
0.52
0.53
0.67
0.65
0.55
0.52
0.63
5.4
5.2
3.4
3.4
3.8
3.4
6.5
6.1
5.0
5.1
4.3
4.1
4.1
4.0
3.2
3.3
4.3
4.1
4.1
3.9
3.8
3.51
3.45
2.80
2.77
2.90
2.85
3.22
3.30
2.84
2.51
0.93
0.94
1.91
1.95
2.67
2.66
3.08
2.94
2.21
3.15
2.35
0.81
0.79
0.87
0.84
1.01
0.94
0.96
1.00
1.67
1.64
0.31
0.32
0.65
0.67
0.71
0.70
0.85
0.86
0,73
0.71
0.95
7.3
7.0
5.5
5.5
.6.1
5.4
7.5
7.0
6.9
6.9
5.5
.5.4
6.0
5.9
4.9
5.0
5.7
5.5
6.0
6.0
6.6
*  S = test run on small sample
                                       80

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                   TABLE IV   (con't)




COMPARISON OF WASHABILITIES OF SMALL AND LARGE SAMPLES
40 percent recovery
*
Sample ,
Sulfur (%)
Total 1 Pyritic
Ash
%
60 percent recovery
Sulfur (%)
Total
Pyritic
Ash
%
80 percent recovery
Sulfur (%)
Total
Pyritic
Ash
%
US
12
12S
13
13S
14
14S
15
15 S
16
16S
17
17S
18
18S
19
19S
20
20S
21
21 S
22
22S
23
23S
Source
2.08
1.76
1.78
2.59
2.75
0.71
0.70
0.53
0.57
2.07
2.20
3.14
3.38
2.49
2.77
2.56
2.66
1.37
1.25
2.21
2.26
3.39
3.30
3.81
3.82
0.47
0.72
0.76
0.33
0.60
0.15
0.12
0.02
0.08
0.45
0.54
0.48
0.46
0.71
0.89
0.51
0.63
0.41
0.33
0.32
0.34
1.57
1.61
0.38
0.43
3.3
4.5
4.8
2.9
3.9
3.5
3.5
3.0
3.2
4.5
4.6
4.1
4.0
3.0
4.1
3.1
4.2
3.1
2.4
6.0
7.0
8.4
8.0
3-7
4.1
2.13
1.86
1.82
2.75
2.80
0.71
0.70
0.53
0.57
2.24
2.34
3.16
3.43
2.68
2.91
2.71
2.71
1.41
1.32
2.23
2.26
3.68
3.57
3.85
3.82
0.56
0.84
0.83
0.48
0.66
0.17
0.12
0.02
0.08
0.67
0.67
0.53
0.52
0.87
1.02
0.69
0.70
0.43
0.38
0.36
0.34
1.87
1.92
0.54
0.52
4.5
5.5
5.6
4.4
4.6
4.1
4.0
3.6
3.8
5.9
6.0 .
4.7
4.7
4.3
5.1
4.5
4.8
3.9
3.3
7.0
7.2
10.2
9.9
4.9
5.1
2.39
2.07
1.97
2.93
3.01
0.72
0.70
0.57
0.58
2.59
2.63
3.36
3.62
2.93
• 3.08
2.95
2.91
1.48
1.39
2.26
2.29
4.07
3.94
4.07
4.02
0.87
1.08
1.04
0.66
0.92
0.19
0.15
0.07
0.08
1.04
1.02
0.79
0.76
1.13
1.22
1.02
0.97
0.50
0.47
0.42
0.41
2.31
2.33
0.90
0.86 '
6.8
6.9
6.9
6-. 8
7.4
4.7
4.6
4.6
4.7
7.6
7.7
6.3
6.2
6.6
7.0
6.8
6.9
5.5
5.3
8.6
8.6
12.6
12.3
6.8
7.0
: Reference 11.
                            81

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H
53
W
W
PM
ffi
CO
      6

      5

      4

      3
 0
26
24
22
20
18
16
14
12
10
 8
 6
 4
 2
 0
                                         SAMPLE  20
                                     D LARGE SAMPLE
                                     O SMALL SAMPLE
                                          TOTAL  SULFUR
               -D	30
                          cr
                                         PYRITIC SULFUR
                                  -D-
           10    20    30    40    50    60     70    80    90   100
                             RECOVERY,  PERCENT
                                              SOURCE:  REFERENCE  11
                            FIGURE 20
             WASHABILITY CHARACTERISTICS OF SAMPLE 20
                               82

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w
PL,
ac
            SAMPLE  22


            LARGE SAMPLE


          O SMALL SAMPLE
                                                              100
                            RECOVERY, PERCENT
                                          SOURCE:  REFERENCE 11
                             FIGURE 21 r

             WASHABILITY CHARACTERISTICS OF SAMPLE 22
                               83

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5.0  LABORATORY AND PILOT STUDIES EVALUATING PROCESSES FOR  PYRITE
     REMOVAL FROM FINE COALS

     This section describes the EPA-sponsored laboratory and  pilot study

projects conducted by the Bureau of Mines and Bituminous Coal Research,

Incorporated.  The objectives were (1) to determine the operating para-

meters for maximum pyrite separation, (2) to modify existing  techniques

and/or develop new techniques to separate pyrite from fine  coals, and

(3) to evaluate methods to process coal cleaning rejects so as to con-

centrate the pyrite and reclaim clean coal products.

     The equipment or processes were evaluated by the two contractor

organizations as indicated below.  The Bureau of Mines efforts concen-

trated on equipment operational parameters and the development of new

techniques while the Bituminous Coal Research efforts concentrated on

the applicability of equipment to various coals.

                                               Investigated by

                                       Bureau of         Bituminous
        Equipment/Process                Mines       Coal Research, Inc.

Wet Concentrating Table (Deister)          X                  X

Concentrating Spiral (Humphry)             X                  X

Hydrocyclones                              X                  X

Air Classifiers                                               X

Electrokinetic Techniques                  Y

Agglomo-Separation                         X,Y

Froth Flotation                            X,Y
                                    84

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              X designates pilot plant tests




              Y designates laboratory-scale tests




These processes are described briefly in  the following sections and re-




sults of their performance are summarized.




5.1  Wet Concentrating Table




     The wet table is a rectangular or rhomboid-shaped normally riffled




deck operated in essentially a horizontal plane.  A drive mechanism im-




parts a differential motion to the deck along  its long axis while water




flows by gravity along the short axis of  the table.   The rapid shaking




motion causes particles of different densities to migrate to different




zones on the table's periphery.




     Commercial tables have a deck approximately 16 feet long on the




clean coal side and 8 feet long on the refuse  side.   In these studies,




a quarter-size deck, 8 feet long on the clean  coal side and 4 feet long




on the refuse side, was used.  The direction of the feed coal mixture




and the reporting of the clean coal, middlings, and refuse to the var-




ious sections of the table are shown in Figure 22.  As the specific




gravity of the coarse particles increases,  the material deposits further




around the table toward the refuse end.




     In tests by the Bureau of Mines and  Bituminous Coal Research, In-




corporated, the wet concentrating table proved effective in separating




liberated pyrite and ash from coal.  Coals  with a high proportion of




pyritic sulfur relative to organic sulfur are  particularly amenable to




sulfur reduction by this process.
                                    85

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                DRESSING WATER
                                    FEED
©
COAL


MIDDLINGS

REFUSE


 SOURCE:  REFERENCE 12
                 FIGURE 22
 DISTRIBUTION OF CLEAN COAL, MIDDLINGS, AND
  REFUSE ON THE WET CONCENTRATING TABLE
                   86

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     Two series of wet concentrating  table tests  were performed  by  the




Bureau of Mines, one on a normal  size table feed  and the second  on  a




rather fine size feed.  The results of cleaning minus 1/4 inch coal are




shown in Table V.  The pyritic  sulfur content was reduced from 3.07




to 0.60 percent and the total sulfur  from 3.63 to 1.20 percent at a




clean coal recovery of 86.3 percent.




     Further analyses on the coal (first  series of tests) were made by




screening the minus 1/4 inch coal into four size  fractions as  indicated




by Table V.  The combined pyritic sulfur  reduction for the three larger




size fractions was approximately  84 percent each.  Also, the efficiency




of the separation deteriorated  in the minus 200 mesh size range  where




the pyritic sulfur reduction was  only 58  percent.




     For the Bureau's second series of tests (Table VI)  conducted on 35




mesh x 0 size coal, the 35 by 200 mesh fraction shows the pyritic sulfur




content reduced by 75 percent,  from 2.05  percent  in the feed to  0.50 per-




cent in the clean coal.  The pyritic  sulfur in the minus 200 mesh by




0 size fraction was reduced by  23 percent, or from 1.69 percent  in  the




feed to 1.30 in the clean coal.



     The results of the second  series of  wet concentrating table tests




are shown in Table VI.  When the  sample was broken down into the plus




and minus 200 mesh size fractions, the results showed that the efficiency




of the table for separating pyrite from coal deteriorated below  the 200




mesh size range.
                                    87

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                      TABLE V

      PRODUCT ANALYSIS OF A 1/4  INCH  BY  0  SIZE
      COAL WASHED  ON A WET  CONCENTRATING TABLE
                                Percent
  Products
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
                       Pyrltic
                       Sulfur
                         Total
                        Sulfur
2.6
36.9
7.0
0.56
19.19
2.92
1.13
19.60
3.47
                             14 by 48 mesh, 38.9 percent
              2.6
             40.9
              7.9
            .45
          17.15
           2.77
               1.08
              17.66
               3.38
                            48 by 200 mesh, 15.2 percent
                 Weight       Ash

                         1/4 inch by 14 mesh, 41.6 percent
 87.3
 12.7
100.0
 86.1
 13.9
100.0
 83.8
 16.2
100.0
 86.1
 13.9
100.0
 86.3
 13.7
100.0
 5.9
68.0
15.8
  .56
17.69
 3.32
                                      1.17
                                     17.79
                                      3.85
                           200 mesh by 0, 4.3 percent
28.4
71.9
34.6
 2.51
27.51
 6.00
                                      3.08
                                     27.64
                                      6.51
                           1/4 inch by 0, 100.0 percent
 4.2
45.6
 9.9
  .60
18.49
 3.07
                                      1.20
                                     18.86
                                      3.63
Source:  Reference 12.
                           88

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                        TABLE VI


         PRODUCT ANALYSIS OF A 35 MESH BY 0 SIZE
        COAL WASHED ON A WET CONCENTRATING TABLE
  Product
                                Percent
                 Weight
            Ash
              Pyritic
               sulfur
               Total
              sulfur
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
Clean coal
Refuse
Feed
 63.7
 36.3
100.0
 92.4
  7.6
100.0
 74.0
 26.0
100.0
                         35 by 200 mesh, 63.9 percent
     8,7
    53.2
    24.8
0.50
4.77
2.05
200 mesh by 0, 36.1 percent
    16.1         1.30
    27.6
    17.0
6.51
1.69
35 mesh by 0. 100.0 percent
    12.0          .87
    50.5         4.95
    22.0         1.92
1.25
5.18
2.67
1.98
7.08
2.36
               1.58
               5.39
               2.56
Source:  Reference 12.
                             89

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     In addition to the above, two-stage cleaning tests,  in which a




coarse sample (3/8 inch x 0) was tabled on a quarter sized unit  and the




clean fraction pulverized to a finer size (30 mesh x 0) which was re-




tabled, were performed by Bituminous Coal Research.  Equipment for




testing the coarse sample had a capacity of 2-1/2 to 3 tons per  hour,




and that for the fine sample of 1 to 1-1/4 tons per hour.  These tests




indicated that pyrite removal can be improved by use of the concentra-




tion table in two stages.  A total of eight coals, five eastern  and




three (mid)western, were subjected to two-stage tabling.  These  coals




are identified and their sulfur contents are shown in Table VII.   The




results are given in Table VIII which also shows feed rate during test-




ing, percent total sulfur in the feed, and percent sulfur in clean coal.




Reductions in total sulfur range from 29 percent to 68 percent.




5.2  Concentrating Spiral




     The concentrating spiral, although widely used for ore dressing, has




never been used for coal preparation even though it had been previously




considered for coal cleaning purposes.  It was evaluated because of its




low capital and operating costs.




     The concentrating spiral (see Figure 23) consists of a spiral




conduit of modified semicircular cross section.  In operation, pulp is




fed from the top of the spiral and as it flows downward centrifugal




force causes the heavier particles to concentrate in a band along the




inner side of the spiral.  They are removed through adjustable ports
                                   90

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                                              TABLE VII
                     ANALYSIS OF COALS SELECTED FOR CONCENTRATING TABLE TESTS
Coal Identification
Seam
County, State
Eastern Coals
No. 6-A
Harrison, Ohio
Upper Freeport
Westmoreland, Pa.
No. 8
Jefferson, Ohio
No. 6
Columbiana, Ohio
Lower Kittanning
Indiana, Pa.
Midwestern Coals
Lower Cherokee
Upper Spandra
Tebo Seam
BCR
Lot
No.

1735
1750

1768

1745
1755
2415
2416
2417
Weight
Total
Ash Sulfur

10.4 2.50
22.5 3.74

19.4 4.71

10.4 2.44
20.1 4.66
12.8 5.12
6.5 1.59
29.8 6.92
Percent , Dry
Sulfate
Sulfur

0.01
0.03

0.07

0.05
0.05
0.26
0.08
0.68
Basis
Pyritic
Sulfur

1.86
3.22

3.69

1.79
4.00
4.24
0.77
4.44

Organic
Sulfur

0.63
0.49

0.95

0.60
0.61
0.62
0.74
1.80
                                                                                        Organic Sulfur
                                                                                        as Percent
                                                                                        of Total Sulfur
                                                                                           25.2
                                                                                           13.1
                                                                                           20.2
                                                                                           24.6
                                                                                           13.1
Adapted  from References 6 and 10.

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                                                  TABLE VI11
                                          CONCENTRATING TABLE TESTS
                                         EFFECT OF TWO-STAGE CLEANING
Coal Identification
Seam
County State
Eastern Coals
No. 6-A
Harris on , Ohio
Upper Freeport
Westmoreland, Pa.
No. 8
Jefferson, Ohio
<, No. 6
r
-------
         FEED BOX
 WASH WATER
    MIDDLINGS
CENTRIFUGE
                     50'  LENGTH OF 1" FEED HOSE
                     INCREASES CIRCULATING TIME
                     TO 15  SECONDS
            PUMP
                                         HOSE SUPPORT
                                         REFUSE COLLECTING PIPE
                                         REFUSE PORT
                                        SPIRAL SECTION
SPLITTER BOX

CLEAN COAL,

REFUSE


MIXER


PUMP SUMP
                                    SOURCE;   REFERENCE 12
                         FIGURE 23
 HUMPHREYS SPIRAL CONCENTRATOR CLOSED CIRCUIT TEST UNIT
                            93

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located on each turn of the spiral at the lowest point  in  the  cross sec-




tion of the conduit.  As the spiral stream is discharged from  the lower




end of the spiral, an adjustable splitter divides  the stream into two




products:  a clean coal product  (outer coal) and a middling  product




 (inner coal).



     The Bureau of Mines evaluated spiraling on coals of top sizes rang-




ing from 4 mesh down to 35 mesh and on double sized fractions.   It was




found that the best separation occurred when the top size  of the spiral




feed was minus 14 mesh or less.  Surprisingly, the capacity  of  the




spiral remained about constant, regardless of the  feed  top size.   Con-




sequently, the capacity of the spiral for was-hing  fine-size  coal was




very high.




     The results of spiraling 35 mesh by 0 Middle  Kittanning bed coal




are shown in Table IX.  A feed coal having a total sulfur  content of 2.53




percent was reduced to 1.48 percent by spiraling at a clean  coal recovery




of 90.7 percent.  The final sulfur content of the  washed 35  by  200 mesh




coal was 0.92 percent sulfur, while the sulfur content  of  the washed




minus 200 mesh coal was 2.34 percent sulfur.  This rapid deterioration




of the efficiency of the washing technique with size reduction  is a nor-




mal characteristic of specific gravity separators. The excellent results




achieved by the Bureau of Mines with the spiral on fine-size coal sug-




gest it should be considered along with hydrocyclones and  the  wet con-




centrating tables as a "rougher" cleaning unit to  remove pyrite from




high sulfur coals prior to flotation.







                                   94

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                     TABLE IX

   PRODUCT ANALYSIS OF 35 MESH BY 0 MIDDLE KIT-
   TANNING BED COAL WASHED OVER THE COAL SPIRAL
Percent
Product Weight
Pyritic
. , Sulfur
Ash
Total
Sulfur
Clean coal
Refuse
Feed
                  35 by 200 mesh, 61.2 percent of feed
 88.3
 11.7
100.0
 7.2
42.8
11.4
 0.29
13.51
 1.85
 0.92
13.79
 2.43
Clean coal
Refuse
Feed
                  200 mesh by 0, 37.8 percent of feed
  94.7
   5.3
 100.0
 12.0
 21.4
 12.5
  1.71
  8.48
  2/07
 2.34
 8.96
 2.69
                Composite 35 mesh by 0, 100.0 percent of feed
Clean coal
Refuse
Feed
  90.7
   9.3
 100.0
  9.1
 38.2
 11.8
    .86
  12.43
   1.94
 1.48
12.75
 2.53
Source:  Reference 12.
                             95

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     Five different coals were used by Bituminous Coal Research,  Inc.,




in their evaluation of the concentrating spiral for cleaning  coal.




These coals were from the following seams:




     1.   No. 6-A seam, Harrison County, Ohio




     2.   Lower Kittanning seam, Indiana County, Pennsylvania




     3.   No. 6 seam, Columbiana County, Ohio




     4.   Upper Freeport seam, Westmoreland County, Pennsylvania




     5.   No. 8 seam, Jefferson County, Ohio.




Their sulfur contents are given in Table VII.  Coal from  the  No.  6^-A




Ohio seam was tested at the 30 mesh x 0 size, while the other four  were




precleaned on the wet concentrating table at the 3/8 inch x 0 size  and




the clean-coal fraction then crushed to 30 mesh x 0.  The fine coal was




then cleaned on the spiral,




     A 15.3 percent reduction in total sulfur, 94.8 percent recovery,




was obtained by single stage cleaning of the 30 mesh x 0, Ohio 6-A  seam




coal.  This result was obtained by combining the screen fractions of the




middling material and the clean coal.  For both the single and double-




stage cleaning, it was found that all the clean coal fractions contained




a significant quantity of high-ash, high-sulfur sink material.  Results




of the double-stage cleaning appear in Table X.  Comparison of these




sulfur reductions with those obtained by cleaning the same coals  with




the wet concentrating table (Table VIII) indicate that the spiral pro-




duces similar reductions and yields for two of the coals  tested and




somewhat lower reductions for the other two.
                                     96

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                                              TABLE X
                        CONCENTRATING TABLE AND SPIRAL CONCENTRATOR TESTS
                                   EFFECTS OF TWO-STAGE CLEANING
Coal Identification
 Lot         Seam
  Location
County,  State
Total Sulfur,
Feed to  Table*
   Percent
   Clean  Coal,      Total Sulfur Reduction,
Two-stage Cleaning    Two-stage Cleaning
    Percent                Percent


-o
VI

2031 Lower
Kit tanning
2026 No. 6
2012 Upper
Freeport
2013 No. 8
Indiana, 3.66
Pennsylvania
Columbiana, 2.90
Ohio
Westmoreland , 3 . 30
Pennsylvania
Jefferson, 3.98
Ohio
78.3
89.3
77.9
87.0
65.3
48.3
54.5
28.4
                       * Based  on Composite of Table Products, Rough Cleaning
Source:  Reference 6.

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5.3  Water Cyclone



     Water cyclone performance evaluation tjests were  conducted by the




Bureau of Mines on five units in commercial plants.   Preliminary results




of these tests showed excellent pyritic sulfur reductions were attain-




able.  The clean coal recoveries were highly dependent on the  size of




the material.  Clean coal recovery of the plus 48 mesh material was low,




while most of the minus 100 mesh material reported to the clean coal




product.  Final results of this work are planned to be published in a




Bureau of Mines report entitled Performance Characteristics of Coal-




Washing Equipment ;  Water-Only Cyclones.




     Water cyclone tests were also conducted by Bituminous Coal Research,




Inc.  '     Feed coals were pulverized to minus 30 mesh size prior to




test runs.  Ohio 6-A seam coal was used in the first  set of tests.   For




the remaining four tests, feed material was prepared  by pulverizing the




minus 3/8 inch clean fraction from the concentrating  table to  minus 30




mesh.  This approach is analogous to the two-stage cleaning with the



concentrating table.




     In two-stage cleaning of the minus 30 mesh Ohio  6-A coal,  the total




sulfur was reduced from 2.90 to 1.59 percent (ref. Table XI).   A com-




parison of the compound water cyclone run with the concentrating table




run is shown in Table XII.  This table indicates that the concentrating




table performed better than the compound water cyclone in the  cleaning




of this coal.  This finding is supported by the results of cyclone-
                                   98

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                                TABLE XI

               COMPARISON OF CONCENTRATING TABLE RUNS AND
                     COMPOUND WATER CYCLONE RUN WITH
                 30 MESH X 0, R.O.M., OHIO NO. 6-A SEAM
     Cleaning Unit
Compound Water Cyclone
  (Test No. 3, Run No. 6)

Compound Water Cyclone
  (Test No. 2, Run No. 2)

Concentrating Table Run
 Total Sulfur
   in Feed,
Weight Percent
     2.47


     2.39

     2.44
  Recovery,
Weight Percent
     91.4


     90.9

     92.0
 Total Sulfur
  Reduction,
Weight Percent
     21.1


     27.6

     36.5
Source:  Reference 6.
                                   99

-------
o
o
                                                          TABLE XII
                                  CONCENTRATING TABLE AND COMPOUND WATER CYCLONE TESTS
                                               EFFECTS OF TWO-STAGE CLEANING
                                                Run Ho. 2 Operating Conditions
                                                                                               Total Sulfur Reduction,
                                                                                                 Two—stage Cleaning
                                                                                               	Percent	


                                                                                                       57.9
                                                                                                       44.8
                                                                                                       62.7
                                                                                                       34.7
                 Based on Composite of Table Products, Rough Cleaning.

                Run No.  2 Operating Conditions:
                   Cone Type "M", Vortex Finder  Clearance:  1", Inlet Pressure: 8 psi, Feed  Solids Concentration:   8.C
Coal Identification
Lot Seam
2031 '
2026
2012
2013
Lower
Kit tanning
No. 6
Upper
Freeport
No. 8
Total Sulfur
Location Feed to Table*
County, State Percent
Indiana, 0 ,,
™ i * -5 . DO
Pennsylvania
Columbiana, „
Ohio
Westmoreland, _ „.
Pennsylvania
Jefferson, ., qa
Ohio y
Clean Coal
Two-stage Cleaning
Percent
73.2
80.3
69.9
78.8
                Source:  Reference 6.

-------
cleaning the other four coals  (at  30  mesh x 0 size)  which had been pre-




cleaned on the concentrating table.   Table XI gives  results under one




set of test conditions.  These  tests  show smaller  sulfur reductions for




three of the four coals tested  than were  achieved  by the wet concen-




trating table  (Table VIII).  Bituminous Coal Research,  Inc. believes




that improved results  in total  sulfur reduction could have been obtained




by using a closer-sized feed or feeds to  the compound water cyclone,




i.e., 30 mesh x 200 mesh and 200 mesh x 0^).




     A diagram of a McNally Visman Tricone of the  type evaluated by




Bituminous Coal Research,  Inc.,  is shown  in Figure 24.   It consists of




a cylindrical section, a compound  conical section  and a vortex finder.




In operation, coal/water tangentially enters near  the top of the cylin-




drical section, forming a  strong vertical flow.  Refuse moves along the




wall of the cyclone and is discharged through the  apex.  The washed coal




passes through the vortex  finder to the overflow chamber.   Washed coal




is discharged from this chamber  through the tangential  outlet.   This




particular design of the water-only cyclone has  three conical sections.




Particles of different sizes and specific gravities  form a hindered




settling bed in the first  conical  section.   Light  coarse particles are




removed from the first conical  section (A)  and light middlings are re-




moved from (B) the second  conical  section.   In the last conical section




(C), the bed is destroyed  and the  heavy fractions  pass  through the apex.




The central current of the departing  water  is  weak at this point and
                                    101

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          OVERFLOW
          CHAMBER
VORTEX
FINDER
        CONICAL
        SECTION
                                                   WASHED
                                                   COAL
                                                  CYLINDRICAL
                                                  SECTION
                                       ADAPTED FROM REFERENCE 6.
                         FIGURE 24
                 COMPOUND WATER CYCLONE
                            102

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only the fine, light particles are discharged  through  the  vortex




finder.




5.4  Air Classifier




     This is a two-stage process.  First  air is  used to  separate the




relatively coarse grind of pulverized  coal  into  a  fine fraction  and a




coarse, pyrite-rich fraction using the BCR-Majac and Alpine  zigzag air




classifiers.  Pyrite can then be removed  from  the  coarse fraction by




wet-coal preparation techniques.




     Float-and-sink analyses at 1.60 specific  gravity  were conducted on




both the coarse and fine fractions.  The  composite of  the  coarse and




fine clean coal fractions were also analyzed.




     Ten samples from the group of coals  used  for  float-sink washability




studies were selected for testing.  (Note that this group  is not from




the same sample lots as used for testing  other types of  cleaning equip-




ment; e.g., the spiral.)  The reduction of  total sulfur  by use of the




Majac unit ranged from 20.1 to 51.7 percent.   The  results  of the ten




coals are given in Table XIII.  One coal  was also  processed  on the Alpine




Zigzag unit (Table XIV).




5.5  Electrokinetics




     The electrokinetic process for the physical cleaning  of coal use




the technique of electrophoresis for separating  the pyrite from  the coal.




Electrophoresis is defined as the migration of electrokinetically




charged particles in a liquid toward an electrode  of opposite charge in
                                  103

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                                                          TABLE XIII
                                  PYRITIC SULFUR REDUCTION IN MAJAC AIR CLASSIFICATION TESTS
BCR
Lot
No.
1752

1750

1771

1745
1770

1735
1730
1747



1757
1733


Seam
Upper
Kittanning
Upper
Freeport
Lower
Freeport
No. 6
Thick
Freeport
No. 6-A
No. 6
Lower
Klttanning
and Lower
Freeport
Freeport
No. 8
Total Sulfur
in Raw Coal
Percent

2.71

3.74

2.54
2.44

2.08
2.50
4.72



2.42
2.52
4.58
Pyritic Sulfur
in Raw Coal,
Percent

2.31

3.22

1.89
1.79

1.68
1.86
3.70



1.84
2.16
2.84
Recovery
Majac Product
Percent

90.4

83.6

92.6
94.3

90.9
93.2
92.2



90.7
77.5
87.6
Total Sulfur
in Majac
Product Percent*

1.31

1.98

1.49
1.46

1.25
1.65
3.16



1.65
1.90
3.66
Total Sulfur
Reduction
Percent

51.7

47.1

41.3
40.2

39.1
34.0
33.1



31.8
24.6
20.1
Pyritic Sulfur
in Majac Product*
Percent

0.94

1.48

0.98
1.01

0.92
0.98
2.17



1.08
1.39
1.95
Pyritic Sulfur
Reduction,
Percent

59.3

54.0

48.1
43.6

45.2
47,3
41,4



41.3
35.6
31.3
* Majac product composed of raw fine  coal plus cleaned coarse fraction
  (1.60 specific gravity)

Source:  Reference 6.

-------
                                                   TABLE XIV
                              SULFUR REDUCTION IN ALPINE ZIGZAG CLASSIFIER TESTS

                                            A—Total Sulfur Reduction
      BCR
      Lot
      No.

      1733
Seam    Rank
No. 8    HVC
        Total  Sulfur
        in  Raw Coal,
           Percent

            4.58
                   Zigzag Product,
                      Percent

                        84.1
                      Total Sulfur in
                      Zigzag Product,*
                         Percent	

                            3.82
                     Total Sulfur
                      Reduction,
                       Percent

                         16.6
                              * Zigzag product  composed of raw fine coal plus cleaned
                                coarse fraction (1.60 specific gravity)
o
in
      BCR
      Lot
      No.

      1733
Seam    Rank
No.  8
HVC
                                            B—Pyritic  Sulfur Reduction
Pyritic Sulfur
 in Raw Coal,
    Percent

     2.84
Zigzag Product,
    Percent	

      84.1
Pyritie Sulfur in
Zigzag Product,**
	Percent	

       1.90
Pyritic Sulfur
  Reduction,
    Percent

    33.1
                              ** Zigzag product composed  of  raw fine coal plus cleaned
                                 coarse fraction (1.60  specific gravity)
       Source:  Reference 6.

-------
a d-c electrical field.  The speed of migration is directly  proportional




to the magnitude of the electrokinetic charge of the particles  and the




applied voltage and inversely proportional to the distance between the




electrodes.  The electrokinetic process was investigated  on  a laboratory




scale.




     The application of electrophoresis to physically wash coal was




based on earlier studies which showed that, while coal and pyrite  were




both negatively charged above a pH of 4, the coal was more negatively




charged than the pyrites.  In the use of the electrophoretic technique




for the separation of pyrites from coal, however, it was  found  that the




electrophoretic mobilities of coal and pyrite were never  sufficient to




overcome the effects of the specific gravity and the size variance in




particles.  Therefore, a modified cell was built to take  into account




not only the electrophoretic mobilities of coal and pyrite,  but also




their specific gravities (described in Reference 13).




     The electrophoretic cell consisted of a rectangular  plastic column




with inside dimensions of 3/8 inch by 3/8 inch by 24 inches. Platinum




electrode wires were used to produce a d-c field.  The column was  longi-




tudinally inclined at an angle of 45 degrees and laterally inclined at




angles varying from 4 to 11 degrees.  The anode was located  on  the high




side of the laterally inclined column and the cathode was on the lower




side.   During operation, the coal slurry was fed into the top of the




column and, as the slurry moved down the length of the column with an




applied d-c field, the heavier and less negatively charged pyrites







                                   106

-------
tended to slide toward the cathodic  side  and  the  coal was  drawn  toward




the anode.




     Initial tests were conducted with  the  electrophoresis column using




synthetic coal-pyrite mixtures.  Next,  a  series of  tests were  conducted




on a high-pyritic-sulfur coal.  Results of  three  test runs are given  in




Table XV.




     The laboratory-scale investigation indicated that  this was  an effec-




tive method to remove pyrite and other  impurities such  as  silica from




coal.  Economic assessments, unfortunately, indicated that the technique




would be too costly for commercial application.   Therefore further devel-




opment was not pursued.  The electrophoresis  column could  probably best




be used as a laboratory instrument for  investigating the physical de-




sulfurization of coal.




5.6  Agglomo-Separation  (Oil)




     The Agglomeration-Separation process developed by  the National Re-




search Council of Canada was investigated by  the  Bureau of Mines.   The




process was reported to recover a product low in  ash approaching the




clean coal product.  It was felt that a similar sulfur  reduction might




be obtained.  In addition, the process  had  the capability  to agglomerate




fine size coal to a larger size and  eventually to provide  for  pelleti-




zation.




     High energy mixing is employed  to  disperse kerosine or similar




light oils in a coal-water slurry.   The oil selectively coats  the coal




particles causing the particles to agglomerate and  then, with  an assist







                                   107

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                                                    TABLE XV



                               FRACTIONATION OF A SAMPLE OF 100  BY  325 MESH LOWER

                                 FREEPORT BED COAL IN  AN ELECTROPHORESIS COLUMN
o
oo
APPLIED
TEST VOLTAGE
VOLTS, DC
1 500
2 400
3 250
500
AVERAGE
CURRENT RECOVERY,
MILLIAMPS RECEPTACLE PERCENT
5.0 Coal
Reject
2.0 Coal
Reject
1.5 Coal 1st pass
5.0 Coal 2nd pass
Reject
94.3
5.7
55.6
44.4
13.8
77.3
8.9
ASH,
PERCENT
13.2
45.0
17.0
14.8
44.5
8.9
44.8
PYRITIC
SULFUR,
PERCENT
1.01
19.73
.34
4.63
.38
.62
21.00
TOTAL
SULFUR,
PERCENT
1.61
19.95
1.07
5.58
.61
1.38
22.65
       Source:  Reference 12.

-------
from entrained air, rise to the surface, while  the  impurities  remain  in




the water.  The investigation was conducted  on  both 35  mesh  x  0  and




325 mesh x 0 sized coals using kerosine as the  agglomerating oil in




slurries containing 10 percent of coal by weight.   Experiments were




conducted on both the laboratory and bench scale.   A blender-type mixer




was used in the laboratory experiments, and  a 4-gallon  cell  was  used  for




bench-scale testing.




     Four variables; kerosine dosage, retention time, slurry pH,  and




mixer speed were evaluated in the laboratory.   Kerosine dosage had the




most significant effect.  Generally, a concentration of 8 percent kero-




sine, based on the weight of dry coal in the slurry,  produced  the best




results.  At lower kerosine levels  the recovery of  clean coal  decreased,




while using larger amount of kerosine provided  minimal  increases in




recovery of clean coal.  Increasing the retention time  from  1  to 2 min-




utes increased recovery.  Beyond 2  minutes,  however,  there was no in-




crease in recovery.  Neither the pH of the slurry nor the speed  of mix-




ing had a significant effect on the product  recovery.




     Tables XVI and XVII show the results of two samples of  325  mesh  x.-, 0




size coals evaluated in the laboratory.  Reductions in  total sulfur range




from about 12 percent to 39 percent while yields of clean coal range




from 18 percent to 85 percent, depending on  test conditions  and  the




type of coal.  Under the same conditions ash reduction  ranges  from




25 percent to 60 percent.
                                  109

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                                 TABLE XVI

            EVALUATION OF THE AGGLOMO-SEPARATION PROCESS FOR THE
            LOWER FREEPORT BED COAL USING FOUR PROCESS VARIABLES
Coal Size
Total Sulfur, percent
Ash, percent
Agglomerating Oil
Slurry, percent solids

TEST
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
KEROSINE
DOSAGE,
PERCENT
2
4
8
2
4
8
2
4
3
2
4
8
2
4
8
2
4
8
2
4
8
2
4
8
AGITATOR
SPEED,
RPM
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
14,000
RETENTION
TIME,
MIN.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
Minus 325 mesh
2.5
19.3
Kerosine
10

SLURRY
PH
6.0
6.0
6.0
6.0
6.0
6.0
10.0
10.0
10.0
10.0
10.0
10.0
6.0
6.0
6.0
6.0
6.0
6.0
10.0
10.0
10.0
10.0
10.0
10.0

CLEAN
YIELD
58.5
70.5
81.8
60.4
75.0
82.5
68.5
78.5
82.1
77 .4
81.5
82.7
62.0
70.1
82.6
70.3
75.4
83.9
68.6
76.3
85.0
74.5
78.5
83.6


COAL PERCENT
SULFUR
1.9
2.2
2.1
2.0
1.9
2.2
1.9
1.9
2.1
1.8
2.0
2.2
1.8
1.9
2.1
1.8
1.9
2.0
1.7
2.0
2.1
1.8
1.9
2.1
ASH
12.8
11.2
11.2
12.8
11.2
10.5
12.1
12.0
10.1
10.0
8.7
9.2
11.6
11.6
10.6
10.6
12.3
9.2
10.7
11.9
9.3
10.2
8.8
8.5
Source:   Reference 14.
                                110

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                              TABLE XVII

         EVALUATION OF THE AGGLOMO-SEPARATION PROCESS FOR THE
           PITTSBURGH BED COAL USING FOUR PROCESS VARIABLES
Coal Size
Total Sulfur, percent
Ash, percent
Agglomerating Oil
Slurry, percent solids

Test
no.
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
Kerosine
dosage,
percent
2
4
8
2
4
8
2
4
8
2
4
8
2
4
8
2
4
8
2
4
8
2
4
8
Agitator
speed,
rpm
6,000
6,000
6,000
6,000
6,000
6,000
6,000
6,000
6,000
6,000
6,000
6,000
12,000
12,000
12,000
12,000
12,000
12,000
12,000
12 ,000
12,000
12,000
12 , 000
12,000
Retention
time,
min.
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
2
2
2
Minus 325 mesh
2.3
16.1
Kerosine
10

Slurry
PH
3.0
3.2
2.9
3.1
3.0
3.0
10.0
10.0
10.0
10.0
10.0
10.0
3.2
3.1
3.4
3.0
3.1
3.2
10.0
10.0
10.0
10.0
10.0
10.0



Clean Coal Percent
yield
18.1
54.1
60.4
17.1
49.5
63.5
39.8
54.5
65.8
36.3
53.3
60 , 6
35.9
52.9
68.1
24.4
48.8
64.7
40.1
53.4
62.6
42.3
56.3
67.5
sulfur
1.7
1.6
1.7
1.5
1.7
1.7
1.8
1.6
1.8
1.6
1.8
1.6
1.7
1.7
1.7
1.4
1.6
1.6
1.6
1.6
1.6
1.5
1.7
1.4
ash
10.9
11.7
9.9
8.8
10.5
10.0
12.0
11.0
10.6
10.7
10.5
9.0
9.7
9.8
10.1
8.0
9.7
10.3
10.8
10.2
9-0
10.3
10.7
9.0
Source:   Reference 14.
                                  Ill

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     The agglomo-separation process provided  only limited sulfur reduc-




tion but a substantial reduction in ash.   The oil coats the pyrite as




well as the coal particles, resulting  in agglomerates containing both




the clean coal and the pyrite.  There  is usually  some sulfur reduction




accompanying low recoveries of clean coal  due to  low concentrations of




agglomerating oil but, as the oil concentration is  Increased to obtain




maximum clean coal recovery, the percentage of sulfur in the product is




usually equal to or greater than that  of the  raw  coal.




     The laboratory work was scaled up to  a 500 pound per hour pilot




plant consisting of two 4-gallon capacity  cells equipped with turbine




blade impellers, a Bird dewatering screen  bowl centrifuge,  and a Dravo




39 inch pelletizing disc.  With this arrangement, a  10  percent slurry




of 35 mesh x 0 size coal was agglomerated  with 8  percent kerosine.   The




agglomerated clean coal was dewatered  to about 16 percent moisture  con-




tent in the centrifuge and then pelletized on the disc-pelletizer using




an asphalt binder.  This step was performed to study pelletization  as a




means of overcoming some of the problems encountered in drying and  handling




fine-sized coals.  Pellets made with approximately 5 percent asphalt




binder averaged 1/2 inch in diameter and contained about 16 percent




moisture.   The pellets were firm when wet  and had good  strength and




water resistance when dried.




     The quality of the clean coal produced by the pilot plant was  sim-




ilar to that obtained in the laboratory unit.  The sulfur reduction was




negligible,  but the recovery of low ash coal  was  good.







                                 112

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5.7  Froth Flotation




     "Froth flotation is a process for  separating  fine-size  particles  by




selective attachment of air bubbles  to  coal  particles,  causing  them to




be buoyed up into a froth while leaving the  refuse particles in the




water.  This process deals with fine particles  in  a  rather turbulent




and foamy aqueous system where specific gravity is not  as significant




as the surface properties of  the particles;  although much heavier  than




the coal, due to surface characteristics the pyrite  remains  with the




coal in the froth product11'    .




     The process consists of  thoroughly mixing  the fine raw  coal par-




ticles with water.  A frothing agent is added,  and air  is bubbled




through the mixture, causing  a froth to be produced  at  the surface.




This froth, containing primarily the hydrophobic components, is skimmed




away, thereby separating the  hydrophobic from the  hydrophilic fractions




which remain suspended in the bulk of water.  The  froth flotation  proc-




ess is reasonably new for coal processing, although  it  has long been




used in the mineral industry  to effect  separations between various




minerals often of a very complex nature.



     The research program to  determine  the pyrite  reduction  potential




of the froth flotation process pursued  two approaches.   These are  1)




the depression of coal, and 2) the depression of pyrite. The depression




of pyrite approach, involving a one-stage process, was  not encouraging.




The detailed procedures, results, and conclusions  are presented in




Reference 15.






                                   113

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     The second approach was concerned with a two-stage flotation process




for separating the pyrite remaining in the "initial" froth flotation




product.  This product from a conventional single-stage flotation proc-




ess is repulped in fresh water; treated with a coal flotation depressant,




a pyrite collector, and a frother; and is rewashed in a second bank of




froth flotation cells.  The pyrites are removed with the froth, leaving




a depressed fraction of clean coal containing less pyrites.  This two-




stage process can be reversed, i.e., the pyrite is floated (and the coal




is depressed) in the first stage and the coal is conventionally floated




in the second stage.  The two-stage froth flotation process was developed




because in the one-stage process the fine-sized pyrites reported with




the froth product.  Work on the two-stage flotation process in a half




ton per hour capacity pilot plant has been completed.




     Detailed results of the froth flotation research are presented in




Tables XVIII and XIX and in References 15 and 16.  A more complete




description of the process may be found in References 12 and 17.




     Of the innovative processes for pyrite separation investigated by




the Bureau of Mines under the EPA Clean Coal Program, the two-stage froth




flotation technique appears to show the greatest potential" for scale-up




to commercial operation.  The importance of this process results from




the fact that no other way has been identified to remove pyrite from




fine coals.
                                   114

-------
                                   TABLE  XVIII

          TWO-STAGE FLOTATION RESULTS WITH LOWER FREEPORT BED COAL  SLURRY
                        Analysis, percent        Distribution, percent
           Weight,           Total   Pyritic            Total   Pyritic
Product    percent   Ash    sulfur    sulfur    Ash    sulfur    sulfur
Test 1:   First stage; 40 g/ton MIBC
                       250 g/ton Aei
                       150 g/ton pot
                       40 g/ton MIBC
First stage; 40 g/ton MIBC
Second stage; 250 g/ton Aero Depressant 633,
              150 g/ton potassium amyl xanthate,
              Af\ rr /<-r«A MTUr1
64.2
9.1
73.3
26.7
100.0
10.0
15.5
10.7
79.8
28.9
1.11
7.06
1.85
3.57
2.31
0.51
6.54
1.26
3.51
1.60
22.2
4.9
27.1
72.9
100.0
30.8
27.8
58.6
41.4
100.0
20.5
37.2
57.7
42.3
100.0
Clean coal 2
Reject 2
Clean coal 1
Reject 1
Feed
Test 2:  First stage; 40 g/ton MIBC
         Second stage; 500 g/ton Aero Depressant  633,
                       200 g/ton potassium amyl xanthate,
                       40 g/ton MIBC
Clean coal 2
Reject 2
Clean coal 1
Reject 1
Feed
63.5
8.1
71.6
28.4
100.0
9.3
17.0
10.2
76.2
28.9
1.03
7.93
1.81
3.43
2.27
.46
7.35
1.24
3.22
1.80
20.4
4.8
25.2
74.8
100.0
28.8
28.3
57.1
42.9
100.0
16.2
33.1
49.3
50.7
100.0
Test 3:  First stage; 40 g/ton MIBC
         Second stage; 350 g/ton Aero Depressant  633,
                       250 g/ton potassium amyl xanthate,
                       40 g/ton MIBC
Clean coal 2
Reject 2
Clean coal 1
Reject 1
Feed
Source:   Reference 14.
59.7
12.7
72.4
27.6
100.0
9.8
13.4
10.4
77.2
28.7
.94
5.84
1.80
3.61
2.31
.32
5.06
1.15
3.60
1.83
20.4
5.9
26.3
73.7
100.0
24.3
32.1
56.4
43.6
100.0
10.4
35.1
45.5
54.5
100.0
                                       115

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                                     TABLE  XIX
        TWO-STAGE  FLOTATION RESULTS WITH MIDDLE  KITTANNING BED COAL SLURRY
                            Analysis, Percent
 Product
      Weight
      Percent
  Ash
Total
Sulfur
Pyritic
Sulfur
 Distribution, Percent
       Total     Pyritic
Ash    Sulfur    Sulfur
 Test  1:   First  stage;    300 g/ton kerosine,
                         80 g/ton MIBC
          Second stage;   250 g/ton Aero Depressant  633,
                         150 g/ton potassium amyl xanthate,
                         40 g/ton MIBC
 Clean  coal  2
 Reject 2
 Clean  coal  1
 Reject 1
 Feed
74.5
10.1
84.6
15.4
100.0
3.2
5.6
3.5
28.8
7.4
1.22
3.23
1.46
10.65
2.88
0.69
2.68
.93
10.18
2.35
32.2
7.6
39.8
60.2
100.0
31.6
11.3
42.9
57.1
100.0
21.9
11.5
33.4
66.6
100.0
 Test 2:
First stage;

Second stage;
Clean coal 2
Reject 2
Clean coal 1
Reject 1
Feed
300 g/ton kerosine,
80 g/ton MIBC
350 g/ton Aero Depressant 633,
250 g/ton potassium amyl xanthate,
40 g/ton MIBC
76.1
9.0
85.1
14.9
100.0
2.7
10.5
3.5
30.1
7.5
.95
6.22
1.51
10.68
2.87
.33
6.22
.95
10.53
2.38
27.4
12.6
40.0
60.0
100.0
25.2
19.5
44.7
55.3
100.0
10.6
23.5
34.1
65.9
100.0
Test 3:  First stage;

         Second stage;
Clean coal 2
Reject 2
Clean coal 1
Reject 1
Feed
               300  g/ton kerosine,
               80 g/ton  MIBC
               500  g/ton Aero  Depressant 633,
               350  g/ton potassium  amyl xanthate,
               40 g/ton  MIBC
78.8
9-9
88.7
11.3
100.0
2.6
12.2
3.7
31.7
6.8
.89
7.83
1.66
12.30
2.87
.34
7.23
1.11
12.13
2.35
30.1
17.8
47.9
52.1
100.0
24.4
27.0
51.4
48.6
100.0
11.4
30.5
41.9
58.1
100.0
                                         116
                                                  Source:  Reference 14

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5.8  Concentration of Pyrite from Refuse

     The laboratory and pilot studies discussed above have been con-

cerned primarily with removing sulfur, principally in the form of

pyrite, from coal.  Similar, though less extensive, studies were per-

formed by Bituminous Coal Research, Inc., to determine the potential

of fine-cleaning techniques for preparing a concentrated grade of py-

rite from the reject material^   .  These investigations were undertaken

because most of the major commercial processes for conversion of pyritic

sulfur to sulfuric acid or other usable forms require a pyritic feed-

stock considerably richer in pyrite than the reject material produced

by physically cleaning most U.S. bituminous coals.*

     Coals from six mines, with total sulfur content ranging from about

1.1 to 6.9 percent, were cleaned and the reject concentrated by staged

separation with wet concentrating tables and a hydraulic classifier.

For this effort, samples of each coal were crushed to 3/8 inch x 0, and

pre-cleaned on a wet concentrating table of the type normally Used for

coal preparation.  The fraction with the highest specific gravity  (pre-

sumably containing most of the pyrites) was crushed to 30 mesh x 0 and

cleaned on a metallurgical-type wet concentrating table with slime deck.
Conventional processes that burn pyrites and produce  sulfuric acid
 require ore with a minimum sulfur content of about 42 percent.   Total
 sulfur in the refuse from high-sulfur coals varies from  about 4  to  25
 percent.   Therefore, if this refuse is to be a  suitable  feed for acid
 production, it must be concentrated to a higher pyrite grade.  Also,
 see Section 7.2.
                                   117

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This was considered as concentrated pyrite.  The  fraction having the




next-to-highest specific gravity was crushed to 60 mesh x 0  and re-




cleaned on the metallurgical deck.  In some cases, an  intermediate




separation of the 60 mesh x 0 material was made with a hydraulic classi-




fier prior to the second cleaning on the metallurgical deck.   The hy-




draulic classifier was not used for all tests because  of  the  high per-




centage of fine pyrite lost during this operation.




     Results are summarized in Table XX.  These indicate  that pyrite




concentrates with sufficiently high total sulfur  content  for  conven-




tional acid-making processes can be achieved for  all coals tested,  but




sometimes at the expense of percentage of sulfur  recovered.   Total  sul-




fur in the pyrite concentrates range from 35.6 percent (corresponding




to a recovery of 46 percent of total sulfur in the ROM coal)  to 48.6




percent (corresponding to a 22.9 percent recovery).




     The effort verified that pyrite from refuse  can be concentrated




for use as a feedstock for the recovery of sulfur values  in either  the




form of elemental sulfur or sulfuric acid.  The processing of rejects




from various cleaning processes offers the capability  to  recover coal




values and to adjust the feedstock composition to the  requirements  of




a specific pyrite utilization process such as the High Sulfur Combustor




(covered in Section 8.0).
                                   118

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                                           TABLE XX
                        SULFUR RECOVERY IN PURITE CONCENTRATION TESTS
                                                  Percent of Sulfur in R.O.M.
Total Sulfur,
R.O.M. Coal,
Coal Identification Percent
2234 Ohio No. 6
2255 Upper Kittanning
2287 Indiana VII
2299 Lower Freeport
2415 Lower Cherokee
2417 Tebo
3.19
2.02
1.06
2.82
5.12
6.92
Pyritic Sulfur, Coal Reclaimed in Pyrite Total Sulfur, Ultimate
R.O.M. Coal, ' Concentrate Pyrite Concentrate Carbon,
Percent
2.56
1.72
0.39
2.07
4.24
4.44
Total Sulfur
22.9
46.0
3.8
18.1
13.1
12.3
Pyritic Sulfur
28.5
54.1
10.3
24.6
15.8
19.1
Percent
48.59
35.64
44.07
45.96
44.70
47.18
Percent
3.63
4.84
2.93
4.45
5.46
3.51
Averages                 3.52          2.57           19.4           25.4            44.36
 Source:   Reference 10.

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6.0  PROTOTYPE COAL CLEANING PLANTS



     The washability studies and pilot plant investigations previously




discussed indicated the amenability of a wide range of coals to physical




desulfurization under carefully controlled laboratory conditions.   Quite




different results could be obtained from the same types of coal clean-




ing equipment when operating in the laboratory than when operating  in




commercial-scale plants where conditions may be less carefully con-




trolled and where variability in the feed composition may be greater.




Although testing for pyrite removal could be conducted to a limited




degree in some existing preparation plants, the equipment and cleaning




circuits of such plants are not normally arranged to maximize sulfur




reduction but to meet ash and BTU specifications.  Commercial cleaning




plants are usually designed for maximum effectiveness in cleaning a




specific coal and do not have the flexibility of cleaning equipment and




circuits to maximize sulfur reduction of different coals having widely




varying washability characteristics.  For this reason, testing in exist-




ing plants would be difficult and generally unsatisfactory without  ex-




tensive modification to equipment and circuits.




     Ideally,  a plant to be used for investigating and demonstrating




desulfurization methods at high through-put capacities would provide




flexibility of equipment configurations, cleaning circuits, and operat-




ing conditions to permit adaptability to the desulfurization require-




ments of the various coals to be processed and to provide for maximum




pyrite recovery from the refuse.  The plant must have the proper sampling
                                    120

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and laboratory arrangements so that the coals and equipment can be properly




evaluated.  Such a plant would ideally be situated  in a location central




to the coals to be tested and the plant site should contain ground space




available for a possible future plant for processing the pyrite recov-




ered from the refuse.




     In order to determine the scope and cost of conducting investiga-




tions and demonstrations of pyrite removal using commercial cleaning




equipment on a scale approximating commercial capacity, EPA funded two




independent and competitive studies for designing a prototype coal clean-




Ing plant of 50-100 tons per hour capacity and for  estimating the capi-




tal and operating cost for the plant.   (Ref. 18, 19, 20, 21).  Testing




laboratories were addressed in the cost estimates.  Due to plant and re-




lated operational complexities and associated costs, two independent




and competitive studies were needed for EPA to identify the most accept-




able design/cost option.




     The study objectives were to produce a prototype plant design cap-




able of reducing the sulfur of various coals having widely variable




washability characteristics and other physical and  chemical properties




together with providing cost estimates for building and equipping the




plant and for performing appropriate studies on selected coals.  Specific




elements of the task were:




     •    To review and analyze the coal washability data furnished




          by EPA;




     •    To develop a ranking of the coals and select those most




          appropriate for evaluation in the prototype plant;




                                   121

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     •    To develop a design with circuits that could optimize




          sulfur reduction from a variety of coals;




     •    To select the most appropriate plant location;




     •    To develop detailed installed cost of the prototype  plant;




     •    To develop a test plan and schedule for evaluating each




          selected coal; and



     •    To develop detailed costs for operating the plant, conduct-




          ing the tests, and analyzing the generated data.




     The prototype plant design and cost studies were conducted by the




Roberts and Schaefer Company of Chicago and the McNally Pittsburg Manu-




facturing Corporation, Pittsburg, Kansas.  Each of these organizations




analyzed the washability data for some 200 coals, classified the coals




relative to amenability to physical desulfurization, designed  a proto-




type plant for sulfur removal, and developed the required test plans




and cost estimates.




     The major difference in the two studies was plant design; Roberts




and Schaefer's design was the more complex of the two, however, it




offered the maximum flexibility; the McNally design was the less com-




plex and provided reduced flexibility and greater ease of operation.




In view of the wide variation in coals to be tested, the provided maxi-




mum flexibility would more than off-set the probable resulting incre-




mental operating difficulties.  Results of the two independent studies




are summarized in the following sections.
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6.1  Classification and Selection of Coals




     Both study efforts (i.e., McNally Pittsburg and Roberts & Schaefer)




reviewed and analyzed the coal washability data provided by EPA.  Each




study effort examined the washability data on approximately 200 coals,




from various parts of the United States,  to  identify coals that poten-




tially would benefit from cleaning by achieving a significant reduction




in sulfur content.  Each study effort developed a coal grouping by size,




sulfur content of the washed  coal, coal recovery values, and coal type




with region of origin.




     The Robert and Schaefer  effort  considered as candidates those coals




for which cleaning could yield substantial benefits.  The criteria used




for selecting candidate coals were:




     •    Sulfur content in the raw  coal  should be  relatively high;




     •    The proportion of pyritic  sulfur in the raw coal should be




          relatively high;




     •    Significant reduction in total  sulfur should be possible at




          commercially feasible yields  (i.e., greater than 65 percent);




     •    Sulfur reduction should be judged  in relation to geographic




          area or coal field  considered;




     •    Substantial reserves of coal  should be available;




     •    Consideration should be given to coals which appear difficult




          to clean;




     •    Consideration should be given to selecting candidates from




          different geographic locations; and
                                   123

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     •    Candidates should be selected according  to  the  sulfur level




          in the clean coal and should cover the following  ranges:   less




          than 1 percent, 1.0-1.5 percent, 1.5-2.0 percent,  and 2.0-2.5




          percent total sulfur.




     Based on the above criteria, 32 coals were initially identified




with the decision to select four additional candidates at a  later date.




     The McNally Pittsburg effort identified 46 coals considered to  have




good or fair washability characteristics.  These 46 coals were  charac-




terized as being cleanable to less than 1.5 percent total sulfur and




deserving testing in the proposed coal cleaning plant.  These   were  com-




posed of 20 coals in excess of 1 percent sulfur that would wash to less




than 1 percent sulfur with a recovery in excess of 75 percent,  26 coals




that would either wash to less than 1 percent sulfur with a  50  to 75




percent recovery, or those that would wash to 1 to 1.5 percent  sulfur




with a 75 to 100 percent recovery.




     The differences in the numbers of coals selected by  the  two con-




tractors, i.e., Roberts and Schaefer and McNally Pittsburg is due to




differences in selection criteria and yields.  Roberts and Schaefer




limited their selections to coals providing commercial acceptable yields




of 65 percent or more whereas McNally Pittsburg considered yields down




to 50 percent.   In addition,  the two contractors had different  criteria




for acceptable total sulfur in the clean coal.
                                   124

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6.2  Design of Roberts and Schaefer Prototype Cleaning Plant, Test Plan,




     and Cost B CM. «• 20)




     6.2.1  Roberts and Schaefer Plant Design




     The Roberts and  Schaefer plant design  concept  is flexible with




alternate circuits and equipment choices which  can  be run  in various




combinations so as to handle coals of different sizes and  widely vary-




ing washability characteristics.  The Roberts and  Schaefer proposed




plant design comprises the following:




   :  1.   Heavy medium cyclone.  Two  stages of  heavy medium cyclones




          are provided in the prototype  plant.   The primary stage  is




          for low-gravity and is fed  by  gravity.   The  second  stage is




          for higher  gravities  and  is fed by pumping.




     2.   Hydrocyclones.   Two stages  of  20-inch-diameter hydrocyclones




          are used for cleaning 3/8  inch x  0 coal.   The  hydrocyclones




          are used for their  flexibility in varying the  specific  gravity




           (1.40 - 1.80).   In  addition,  fourteen-inch-diameter  hydro-




          cyclones will  be available to  clean 1/2  mm x 0 raw  coal.




     3.   Deister table.   The Deister table is  used for  3/8 inch x 0




          and 1/2 mm  x 100 mesh sized coal  cleaning.




The  equipment selection  is based not only  on the ability of each type to




clean coals  at low specific  gravities but  also the relative efficiency




of each.  The following  equipment  was excluded because of lack of ability




to clean  coal at low  specific gravities:  fine coal jig, air table,




hydrotator,  and the rheolaveur.
                                    125

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     In addition, the plant would contain a complete complement of  equip-




ment for receiving, storing, handling, crushing, sizing, sampling,  test-




ing, drying, and transporting of coal and reject material, plus utilities




and instrumentation.  The facility would also include office space, a




fully equipped chemical laboratory for analysis work, and data process-




ing equipment needed to interface with a leased computer.




     The test plant is designed for a maximum capacity of 75 TPH.   This




maximum capacity will be maintained while the heavy medium cyclones and




the 20-inch-diameter hydrocyclones are in use.  When the Deister tables




are in use using a raw feed of 1/4 or 3/8 inch top size, the plant  capac-




ity is reduced to 50 TPH.  The plant capacity is also limited to 50 TPH




when raw coal is pulverized to 14 mesh x 0.  For preparing the 14 mesh




x 0 size, the pulverizing and cleaning equipment for treating 1/2 mm x 0




are the limiting factors for plant feed capacity.




     Specifics concerning the plant and processes are as follows.   Two




heavy medium cyclone circuits are furnished; a primary heavy medium




cyclone circuit and a secondary heavy medium cyclone circuit.  Three




products are generated from these two circuits:  the low sulfur content




clean coal, the high sulfur content middlings, and the refuse.  The pri-




mary heavy medium reject is rinsed out on a reject screen.  The discharge




of the screen can be fed into the secondary circuit directly or be  crushed,




deslimed, and then fed to the secondary circuit.




     The raw coal feed to the heavy medium cyclone circuit will be  either




1-1/2 inch or 3/8 inch top size.  If the raw coal is 1-1/2 inch x 0 size,
                                    126

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it will by-pass the raw coal screen and will be  delivered with water via




raw coal pump to the desliming sieve bend and  screen  for removing  the




1/2 mm x 0 fines.  The plus 1/2 mm raw coal will be fed to  the primary




heavy medium cyclone, and the 1/2 mm x 0 will  be directed to  the 1/2 mm




x 0 sump for subsequent cleaning.  When the 1-1/2  inch x 0  raw coal




is to be crushed to 3/8 inch x 0 before desliming  and cleaning in  the




heavy medium cyclone, the 1-1/2 inch x 0 raw coal  will be fed to the




raw coal screen for separating at 3/8 inch.  The oversize (from the




screen) will be .crushed in a Cage-Paktor crusher to 3/8 inch x 0 size




which will be recycled to the screen for removing  plus 3/8  inch material.




The overall 3/8 inch x 0 material will then be deslimed.  Three by-




passes are provided in the heavy medium cyclone  circuits.   These are:




     1.   Primary heavy medium reject can report to the refuse if  its




          ash content is high and no further cleaning in the  secondary




          heavy medium circuit is warranted;




     2.   The primary heavy reject—crushed to 1/2 mm x 0—normally




          will be cleaned; however, it can be  rejected to the refuse




          thickener if the ash content is high and no further cleaning




          is warranted; and




     3.   The middling product can be loaded out as clean coal if




          warranted.




     All dilute medium slurries collected from drain-and-rise screens




used in the heavy medium circuits will be pumped to the Dutch State
                                    127

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Mines magnetite recovery circuit to reclaim the magnetite  for  reuse.




The recovery circuit consists of magnetite classifying cyclones,  a mag-




netic separator, and a magnetite thickener.




     The stages of 20-in-diameter cleaning hydrocyclones are furnished




to clean 3/8 inch x 0 raw coal to produce clean coal, middlings,  and




refuse.  The maximum top size of raw coal that can be cleaned  in  a




20-inch-diameter unit is 1 inch.  Raw coal and water are pumped to the




two primary cleaning hydrocyclones at a concentration of 150 gms  per




liter.  The reject from the primary unit is repulped and pumped to the




secondary unit for further cleaning.  The 1/2 mm x 0 in the 3/8 inch x  0




size will be cleaned to the degree practical for sulfur removal.   The




specific gravity of cleaning can be varied by changing the vortex finder




length in the cyclone.




     The Deister table circuit is fed with raw 3/8 inch x  0 coal  through




a cyclone classifier.  Three products are produced from the Deister




table circuit:  the clean coal, the middlings, and the refuse.  These




products will be dewatered in the same three vibrating screens provided




for the 20 inch diameter hydrocyclone cleaning circuit.  Each  product




will be automatically sampled in order to establish the performance of




each stage of the cleaning unit.




     Two stages of 14-inch-diameter cleaning hydrocyclones will be em-




ployed to clean 1/2 mm x 100 mesh raw coal down to 250 mesh.   The sec-




ond stage will be used to clean the primary reject and thereby will




provide for additional clean coal yield.
                                    128

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     The overflow from the combined  two-stage  14-inch-diameter hydro-




cyclone will be pumped to 14-inch-diameter  cyclone  classifiers for




classification at approximately 100  mesh.   The plus 100 mesh  clean  coal




will be separated on a two-stage rapped  sieve  bend  after  repulping.




The underflow  (containing the rejected material) will  report  to  the




refuse thickener.




     The 100 mesh x 0 raw coal from  the  14-inch-diameter  cyclone class-




ifiers along with the filtrate from  the  clean  coal  vacuum filter will




report to flotation cells.  The flotation cells (35 TPH capacity) are




used to reduce ash content of the  fine-sized raw coal.




     Both Deister tables and 20-inch-diameter  cleaning hydrocyclones




are to a degree able to clean 1/2  mm x 100  mesh coal.  If desirable, the




1/2 mm x 0 fraction from the above cleaning circuits can  be pumped  to




the 14-inch-diameter cyclone classifiers for separating at 100 mesh




prior to further processing.




     The 1/2 mm x 0 clean coal  (includes plus  100 mesh from the  rapped




sieve bend and minus 100 mesh from the flotation cells) will  be  de-




watered in a disc filter.  The filter cake  (1/2 mm  x 0 material) and




plus 1/2 mm clean coal from other  cleaning  circuits will  be combined




and conveyed out to the clean coal storage  pile prior  to  shipping.




     The flotation tailings and other rejectable 1/2 mm x 0 slurry  will




be combined and fed to a 90-foot-diameter refuse thickener.   The under-




flow from the refuse thickener will  be pumped  to a  head tank  in  the
                                   129

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preparation plant for re-use.  An emergency pond will be provided  for




draining the refuse thickener if required.




     6.2.2  Roberts and Schaefer Test-Program




     The purposes of the test program are:




     •    To evaluate cleanability of each coal selected for processing




          (e.g., best cleaning process, yield, refuse, compositions);




     •    To determine for each selected'coal the best cleaning plant




          configuration from both a technical and economic standpoint;




     •    To define for each coal tested the cost for one or more  levels




          of cleaning;




     •    To evaluate the performance of each major piece of equipment




          used in the plant; and




     •    To recommend additional experimental work as indicated by




          the cleaning program.




     This effort is composed of three phases:  pre-experimental, experi-




mental, and post-experimental.  Some elements of the pre-experimental




phase will take place during the construction of the plant.  Such  ele-




ments will include the detailed formulation of the experimental program




together with implementing arrangements for the purchase, shipment, and




receipt of test coals.  One coal should be on hand and in plant storage




prior to plant start-up and equipment debugging.  Two more coals should




be on hand before the experimental phase begins.  In addition, the pre-




experimental phase will include laboratory set-up, the training of plant
                                   130

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and laboratory personnel, and plant start-up with initial equipment




adjustments.




     The following comments apply to the pre-experimental phase.




     1.    It is assumed that by the time this phase commences, detailed




          washability data to be provided by other contractors will be




          available.




     2.    A schedule for testing the different coals will be developed.




          The schedule will be based on coal availabilities with asso-




          ciated washability data.




     3.    Sampling requirements, on-site laboratory capabilities, and




          data processing analysis requirements will be characterized




          so as to aid in planning overall testing sequences.




     4.    A determination will be made of the best way to process and




          to analyze the voluminous data that will be generated during




          the coal testing (experimental) phase of the program.




     5.    Capital cost data for the various processes that may be used




          will be collected.  These data will be used to define the




          economics of cleaning particular coals.




     6.    To insure that all process equipment and instrumentation is




          optimally maintained, a planned maintenance program will be




          established.




     7.    In order to expedite the laboratory work and to operate the




          laboratory at maximum efficiency, standardized routines for
                                   131

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          handling different samples will, insofar as possible, be




          developed.



     8.   A written safety program covering plant operations will be




          developed prior to scheduled plant "start-up".  During the




          plant start-up period, the safety program will be monitored




          and reviewed as to effectiveness.  Revisions will be made




          as warranted.




     9.   Arrangements will be made to sell processed clean coal and




          possible quantities of unprocessed raw coal.




     The experimental phase is the major and most important portion of




the entire project.  This phase will take about 38 months to complete




during which 36 coals will be tested in the prototype cleaning plant.




Actual testing is estimated to take 36 months, with data processing




and evaluation to continue for an additional two months.  In general,




it is planned that each coal will be tested under enough different con-




ditions to insure that sufficient data will be collected to accomplish




test objectives.




     In order to  insure that each coal (sample) to be tested has accept-




able characteristics, each coal test lot will be examined promptly upon




delivery to the plant and well in advance of actual testing.  Accordingly,




the plan is to have each test sample arrive at the plant at least 60




days prior to the start  of actual testing.  The testing schedule calls




for receipt (on the average) of a new coal test sample each month.
                                    132

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     For testing a particular coal,  the  first week of  testing  will most




likely be devoted to insuring the  test conditions  are  proper for  a test




run.  The second week would be  devoted to  a  test run.   For many coals,




test runs with different test conditions would  take place during  the




third and fourth weeks of a test period.




     During the washability studies,  samples will  be collected at 20  to




25 different locations with an  estimated 25  to  30  samples per  working-




day shift.  Samples may vary in size from  30 pounds to perhaps one ton.




     In addition to planned sampling, there  will be a  need for special




spot samples.  It is estimated  that  10 to  15 percent of the efforts of




laboratory and sample preparation  personnel  will be devoted to handling




these special samples.




     It is anticipated that automatic samplers  will be used to collect




these samples.  Plant personnel will collect, prepare, and perform the




required tests on these samples.




     For complete characterizations  and  selected in-process tests of  raw




coal, clean coal, and refuse, ASTM or other  recognized standard methods




will be used.  Total sulfur in-process testing  can be  provided using




the Leco combustion or equivalent  method.  For  in-process testing pur-




poses,  a rapid moisture test is believed acceptable.




     For each coal tested, the  plant operating  data and capital cost




data will be carefully documented  and evaluated and an individual report




will be prepared upon completion of  each coal investigated.  Each report




will include the estimated capital and operating cost  associated  with
                                    133

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cleaning the investigated coal to one or more sulfur levels.   In addi-




tion, each report will include supporting and analytical data  character-




izing the raw coal, clean coal, rejects, and where appropriate, the




middlings.  It is estimated that data processing, evaluation,  and report




preparation will require two months per tested coal.




     The post-experimental phase will commence upon completion of the




final coal washing experiment.  The first two months of the post-




experimental phase will overlap the last two months of the experimental




phase due to the fact that two months will be required to prepare a




report covering the final coal tested.  The post-experimental  phase




will consist of two principal activities.  These are:




     1.   Preparation of the final report, and




     2.   Closing the plant with auxiliary facilities to make  ready




          for subsequent disposal by the Government.




     Since an individual report will be prepared for each coal tested,




it is visualized that the final report will be an overall summary of




the contractual effort.  This report will also contain information on




coal cleanability based on coal characteristics, coal source area, rela-




tive merits of processing various coals, and the performance of differ-




ent processing techniques as applied to various coals.




     At this time, the ultimate disposition of the proposed cleaning




plant is not known.  It appears prudent that at the end of test program




the plant should be put in shape so as to prevent undue deterioration
                                   134

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in absence of usage.  Therefore a plant shut-down effort including




draining water lines and pumps, disconnecting electric service, apply-




ing appropriate lubricants and protective coatings, inventorying assets,




and providing physical security measures should be applied to the de-




activated plant.  It is estimated that four months will be required to




complete the post-experimental phase of this effort.




     6.2.3  Roberts and Schaefer Capital and Operating Costs




     Capital and operating cost estimates based on the design study




cover the prototype cleaning plant and are predicated on the following:




     •    The plant contains a fully equipped testing laboratory;




     •    The plant contains an analytical laboratory;




     •    Suitable office facilities are contained in the plant;




     •    Operating costs are based on a pre-experimental period of 12




          months, an experimental period of 38 months, and a post-




          experimental period of 4 months, there being a two month




          overlap of the experimental and post-experimental phases; and




     •    Test lots of 10,000 tons.




     The estimated program cost is $16,457,965.  Cost details are pro-




vided in Table XXI.  The above total does not include estimated credits




received from the sale of processed coal and credits from disposal of




plant equipment after program completion.  Total credits are estimated




to amount to $2,000,000.




     The initial Roberts and Schaefer overall program of work was re-




viewed to determine how the overall program might be modified to reduce
                                    135

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                                TABLE XXI

             COST ESTIMATES FOR FIFTY-TWO MONTH PROGRAM
A.  Plant Cost

    Design                                  $   175,000
    Equipment (machinery only)                1,500,000
    Construction (including                   1,525,000
      building)
    Test facilities for process                 698,000
      evaluation and quality control
                                                        $3,898,000
B.  Operating Costs

    Direct labor                                998,210
    Travel, relocating, report                  214,700
      reproduction, computer
      use fees
    Overhead and personnel services             569,205
    Utilities                                   323,000
    Test Coals                                3,600,000
    Expendable supplies                         724,920
    Plant and equipment maintenance             600,000
    General administration (e.g.,             1,169,962
      postage, telephone, office
      equipment)
                                                         8,199,997

C.  Laboratory services (via contract)

    Preliminary engineering                      20,000
    Laboratory work                           3,353,200
    Personnel service (1st year only)            56,400
                                                         3,429,600

D.  Fee (8% of B and C)                                    930,368

    Total                                              $16,457,965
                                136

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overall cost without unduly sacrificing program  objectives.  As a result




of this effort, an alternative program to be accomplished  in less time




and at lower cost was defined.  For the alternate lower cost program, the




overall program of work including the detailed design and  construction of




the prototype plant, development of the detailed experimental program and




in-plant testing of 36 coals is estimated to require 44 months.  The al-




ternative lower priced program is based on  the following:




     •    The amount of each of the 36 coals to  be  tested  in the proto-




          type plant will be 4,000 rather than the  initially recommended




          10,000 tons;




     •    The experimental work is programmed for 24 months  (rather than




          36 months);




     •    The overall effort of work covering the design and construction




          of the prototype coal cleaning plant and  the execution of the




          experimental work has been programmed  for 44 months  (rather than




          52 months); and




     •    The amount of on^site laboratory  work  and, consequently,  the




          equipment and personnel need have been reduced.




     Based on these changes, the cost for the modified program  concept




was estimated at $8,923,200; details are provided in Table XXII. The




modified program cost estimate does not include  credits received from the




sale of processed coal and credits from the disposal of plant  equipment




after program completion.  These credits are estimated to  amount to




$1,000,000.
                                   137

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                               TABLE XXII

               COST ESTIMATES FOR FORTY-FOUR MONTH PROGRAM

A.  Plant Cost

    Design                                $  175,000
    Equipment (machinery only)             1,500,000
    Construction (including                1,410,000
      building)
    Test facilities for process              323,500
      evaluation and quality control
                                                       $3,408,500

B.  Operating Costs

    Direct labor                           1,415,690
    Travel, relocating, report               179,700
      reproduction computer use
      fees
    Overhead and personnel services          788,550
    Test coals                             1,440,000
    Expendable supplies                      316,900
    Utilities                                201,300
    Plant equipment maintenance              400,000
    Contract testing                          30,000
    General administrative                   334,055
    Fee                                      408,505	
                                                       $5,514,700

    Total                                              $8,923,200
                                138

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6.3  Design of the McNally Pittsburg Prototype Cleaning Plant, Test Plan,


              (21)
     and Costs



     6.3.1  McNally Pittsburg Plant Design



     The design of the prototype plant  required  special considerations  to



ensure that it will suitably process a  wide variety  of coals  from which



satisfactory clean coals with acceptable  sulfur  content could be  pro-



duced.  The plant design provides  for flexibility through alternate



circuits and equipment choices  which can  be run  in any combination to



permit the handling of coals of different sizes  and  widely varying wash-



ability characteristics.   The recovery  and  concentration  of pyrite for



possible future commercial utilization  were also considered.   In  the



absence of established standard methods for the  recovery  of pyrite from



the  washery refuse, alternate circuits  as well as alternate equipment



items were deemed necessary to  enable  the determination of the most



suitable recovery processes.  All  of  these considerations were  taken



into account  in arriving  at the prototype plant  design concept.



     The recommended  plant has  a 50 TPH capacity, and contains a coarse



coal circuit  with a heavy media cyclone for cleaning the  various sizes



of 1-1/2 inch x 3/8 inch,  1-1/2 inch x 14 mesh,  3/4 inch x 3/8 inch,



3/4  inch x 14 mesh, and  3/8 inch x 14  mesh coals, and a fine coal cir-



cuit for treating  fractions 3/8 inch and less.  Coals which would be



crushed to 3/8 inch x 0  or 14 mesh x 0 would be washed in  the fine coal



circuits which has available primary and secondary McNally-Visman Tri-
                                     139

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cone.  The secondary Visman Tricone (unlike the primary  Tricone)  can be




used to treat high specific gravity material at a high cut  point.




     Besides the fine and coarse coal circuits, adequate arrangements




have been made for unloading, handling, and crushing the raw  coal  as




well as handling of clean coal and disposal of refuse.   A water clarifi-




cation system is included to provide for cleaning and subsequent reuse




of water, thereby substantially reducing the amount of water  required by




the plant.  An 8000-ton-capacity raw coal storage facility  has been  pro-




vided through two 4000-ton silos for storing raw coal sufficient for




one month's operation.




     In essence, the recommended prototype plant has been provided with




alternate circuits and equipment choices which can be run in  any combin-




ation so that it will be able to handle .coals of different  sizes and




widely varying washability characteristics.  In the absence of standard




methods for the recovery of pyrite from the washery refuse, alternate




circuits as well as alternate equipment are provided to  determine  the




most suitable process for pyrite recovery from any given coal.




     Although not included in the provided plant design, the  installa-




tion of a fluid bed type thermal dryer was recommended for  consideration.




The dryer could be used to treat fine coals with high moisture content




and would provide for obtaining valuable operating information.  The




collected data could be used to assist coal cleaning plant  and dust




collector designers and plant operators to meet air pollution restric-




tions in the supply and operation of full scale plants and  equipment.
                                  140

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     Specifics concerning  the  cleaning  plant  and  processes  are as  follows:




     The cleaning process  starts with raw coal  crushed  in a rotary breaker




and stored in one of two 4000-ton  steel silos.  The  two  silos  provide  the




storage capacity necessary for running  the plant  for 22  days at one shift




per day with an average feed rate  of  50 TPH.




     Although the overall  plant was designed  for  an  average capacity of




50 TPH, the raw coal crusher with  associated  conveyor belts, screens,




etc., was designed with excess capacity so as to  permit  an  increase in




load in the heavy media cyclone.   The raw coal  scalping  unit has inter-




changeable screens for 14  mesh or  3/8 inch.   The  14  mesh x  0 or 3/8 inch




x 0 size coal from the scalping screen  will normally be  conveyed to 8-inch




primary McNally Visman Tricones for washing.




     A crusher, provided after the heavy media  cyclone  sink screen,  will




crush the refuse to liberate interlocked pyrite particles prior to fur-




ther washing in McNally Visman Tricones.   Crushed refuse from  the  heavy




media cyclone or the coal  from the raw  coal scalping screen will be proc-




essed in eight 8-inch primary  Visman  Tricones in  order  to recover  low




sulfur coal.




     High sulfur refuse from the primary McNally  Visman  Tricones can be




washed in 8-inch secondary McNally Visman Tricones or in sequence




through secondary McNally  Visman Tricones and the Deister coal tables.




The coal table was specified to provide the means to determine the




feasibility as well as efficiency  of  recoverying  low sulfur coal from




pyrite rich refuse by employing a  tricone and/or  a coal  table.  Refuse
                                    141

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from the secondary McNally Visman Tricones can also be  fed  to  two ore




tables to treat the heavier pyrite/refuse fraction.




     Tailings from the magnetite separator and the minus  1/2 mm frac-




tion from the classifying cyclone underflow can be processed in the




flotation cells to recover low sulfur coal.  When recovery  is  not re-




quired, the flotation cells can be by-passed and the tailings  pumped




to the waste pond.




     The flotation concentrate, or coal, if found low in  sulfur,  will




be filtered and mixed with the coarse washed coal and conveyed to load-




ing.  If the coal concentrate from the flotation cell is  found high in




sulfur and not worthy of recovery, it will be diverted  to the  waste pond.




     Proper reagents to selectively float coal and depress  pyrite along




with other gangue materials present in the coal slurry  feed to the flota-




tion cell have not yet been developed for all the different coals. Work




is continuing in this field and the prototype plant will  provide an ex-




cellent test facility to carry out tests with the various types of coals




selected for processing.  Hopefully, it may be possible in  the operation




of this plant to find a suitable collector for the selective flotation




of coal.




     Adequate arrangements for the recovery of the magnetite from the




dilute medium have been provided.  The dilute medium will be thickened




in a thickener and the magnetite recovered by a double  drum magnetite




separator for system reuse.  As the washed coal is expected to have




high surface moisture, the recommendation was made that consideration
                                   142

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be given to the Installation of a fluid bed  type  thermal dryer for dry-




ing the fine coal.  Installation of such a dryer  will enable the col-




lection of valuable information on:




     •    Dryer fuel consumption versus dust loss as a function of




          operating conditions,




     •    Size distributions of solids and dust fraction within the




          processing system and those escaping to the atmosphere, and




     •    Selection of dust collecting equipment  required  to meet the




          dust emission code of the various  states.




     6.3.2  McNally Pittsburg Test-Program




     The purposes of the testing program are:




     •    To evaluate performances of each major  piece of  equipment




          used in the plant;




     •    To evaluate each coal selected for processing;




     •    To define the proper circuit for a given  coal;




     •    To evaluate overall performance of the  plant for cost analysis;




          and




     •    To make comprehensive plant studies including material balances,




          ash, total sulfur, and pyritic sulfur content for each coal.




     Approximately 8000 tons of coal will be required  (i.e., delivered




to the plant) for each coal tested.  For each test, a raw  coal sample




(1-1/2 inch x 0) will be collected one to two weeks prior  to test initia-




tion.  This sample will be collected by an automatic sampler and will be




based on sampling lots of 2800 tons in seven hours  at a 400 TPH feed.
                                   143

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The sampler will take nine cuts per hour at 55.6 pounds per  cut  for  a




total sample of 500 pounds per hour.  Samples will be sent to  two  bins,




set to receive alternate cuts, for a total of 250 pounds per hour  for




each bin.  This procedure will satisfy all conditions for ASTM D2234-65T




on mechanical sampling of coal and D492048 on sampling coals classified




according to ash content.  It will also provide the proper gross sample




with which to make the washability study from which plant settings will




be determined.




     The primary gross sample will be screened to produce the  following




sizes:




                              1-1/2 inch x 3/5 inch




                              3/4 inch x 3/8 inch




                              3/8 inch x 14 mesh




                              14 mesh x 28 mesh




                              28 mesh x 48 mesh




                              48 mesh x 0.




     Float and sink separations will be run on each size fraction  at the




following specific gravities:  1.30, 1.35, 1.40, 1.50, 1.60, 1.90, 2.20,




2.50, and 2.80.  The refuse will be visually examined to see if  heavier




gravities are required.  Laboratory tests will be performed  to define




dry ash, total sulfur, and pyritic sulfur contents of each size  gravity




fraction.  Related coal compositions will be calculated for  each coal
                                    144

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size which might be used as  feed  to  a  piece  of  equipment  in  the  cleaning




plant.  These coal sizes are:




                               1^1/2  inch j£ 3/8  inch




                               3/8 inch x 14  mesh




                               1-1/2  inch x 14 mesh




                               3/8 inch x 0




                               14  mesh  x  0.




     Based on the data, operating personnel  will  anticipate  an optimum




setting for each piece of  equipment.   As a new  coal  is  first fed to  the'




plant, samples will be collected  to  check the specific  gravity of opera-




tion.  When the various circuits  are set to  the operators' satisfaction,




daily runs can be started  to determine optimum  plant conditions  to pro-




vide for the maximum  sulfur  removal.   In some cases  it  is likely that




it will be necessary  to check more than  one  set of alternative condi-




tions to determine the point of optimum  sulfur  reduction. After the




equipment and the circuits are set for their best performance in sulfur




reduction, prolonged  test  runs will  be made  with  all the  sampling sta-




tions of all the circuits  in use  so  that a complete  plant evaluation can




be made for each coal washed.  The total plant  is specified  to contain




29 sampling points (i.e.,  27 automatic plus  2 manual).




     The plant feed and final  products for each coal will be analyzed




to determine compositions  and  the burning and slagging  characteristics




of the feed as well as the final  products.  Regular  checks will  also be
                                   145

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made on the plant effluent as well as on any pond water or  streams  which




might be affected by the plant operation.




     Cleaning and equipment performance data generated in pursuance of




this effort should be properly cataloged and stored for ready  access.




With this in view, microfilming arrangements together with  an  adequate




storage and retrieval system have been suggested.  Closed circuit TV




communication is also specified for confidential transmission  of data




to the plant and laboratory operations.




     The testing program design intent is to permit comprehensive cov-




erage of all sampling stations or only a few stations as may be dictated




by coals and circuits being tested.  Sufficient personnel and  equipment




are specified to permit completion of all necessary tests on a day's




run prior to the start of the next day's run.  In addition  to  the daily




tests, a washability test is required prior to each program for each




coal.  At the end of each month, one or more comprehensive  plant studies




including material balances and ash, sulfur, and pyritic sulfur balances




are specified.  This work will require substantial personnel and many




auxiliary tasks will have to be performed at off hours so as to not




interfere with the routine tests.




     The laboratory staff, in addition to maintaining the plant testing




program, will regularly collect samples of makeup and effluent water for




analyses.  Therefore, all water coming onto the property and leaving the




property will be checked.
                                    146

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     6.3.3  McNally Pittsburg Capital and Operating Costs

     Capital and operating cost estimates are based on the prototype

cleaning plant plus the following:

     •    The plant contains a fully equipped testing laboratory,

     •    The plant contains an analytical laboratory,

     •    Suitable office facilities are contained in the plant,

     •    One year is required for total plant installation time,

     •    Plant start up time is six months, and

     •    Plant operating time is three years.

     Estimated costs are;

                                    LABORATORY
                                      OFFICE        PLANT      TOTAL

     Estimated capital investment
     for equipment & installation   $1,078,191    $2,158,000   $3,236,191

     Six month start-up costs          911,514      253,335   1,164,849

     Operating costs for 3 years     5,430,000    1,520,010   6,950,010

     Insurance for 4-1/2 years          11.540       44,185      55,725

     Totals                         $7,431,245    $3,975,530 $11,406.775



     Depreciated value of the plant and laboratory equipment  at  the end

of 4-1/2 years has been assumed to be 10 percent  of the  capital  invest-

ment or $323,619.  The cost of 96,000 tons of raw coal  (for washing at

half the rated capacity during start-up and at 50 TPH for three  years)

was estimated to be $3,276,000.  The sale price of the washed coal was

estimated to be $995,163.
                                  147

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                    (22)
6.4  Data Evaluation


     The Roberts and Schaefer Company prototype plant design study was



judged the most appropriate in addressing the overall EPA program goal.


As a result, Roberts and Schaefer was given the responsibility to develop



a detailed test program for the prototype coal cleaning plant.  The re-


sulting program contained inputs from Roberts and Schaefer and the McNally



Pittsburg prototype plant design studies, the Bureau of Mines coal pre-


paration group, EPA technical personnel, and from Commercial Testing


and Engineering, Incorporated.


     A basic goal of the EPA coal cleaning program is to develop a cor-


relation of the cleanability of any coal with its raw coal physical



properties.  This would involve the identification and quantification


of those physical coal properties which correlate with cleanability in-


cluding the identification of the most appropriate process, process


parameters (e.g., coal size, specific gravity of separation), product


yield, and the sulfur and ash characteristics of the clean coal product.



     In general, the cleaning capabilities of operating preparation


plants are ascertained by sampling, analyses, and calculations.  The


same applies to the performance testing of an experimental prototype


coal cleaning plant.



     Since the calculations involved in predicting cleaning results and



in evaluating the test results are time-consuming, a computer is speci-


fied to perform the required calculations.  The design of the prototype


test program is based on the use of computer processing to provide for
                                    148

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timely and economical reduction of a voluminous amount  of data and  to


rapidly predict plant settings for subsequent runs on a given coal.


This quick response would be mandatory for completely evaluating a  given


coal in a one-week test period.

                                          (0\
     Four computer programs are availablev' and will be used to ulti-


mately provide one program which will be used for predicting the attain-


able sulfur and ash levels at selected yields from a given coal.  The


final computer program will basically evolve from a continuing examina-


tion and modification of an existing "Predicting Program."  The basic


"Predicting Program" and its modifications will be used to define the


plant flow scheme which best fits  the cleaning objectives.  The other


three referenced computer programs will aid in evaluating the validity


and accuracy of the prediction program and its successors.


     The four presently available  programs are:


Program No. 1 - The Predicting Program:


     The program for predicting the cleaning results of a plant or  for


     predicting the results of a piece of cleaning equipment in a plant


     using (1) performance data that is already known from experience


     on the various pieces of cleaning equipment, and  (2) the grainsize


     distribution and washabilities of the raw coal determined by suit-


     able laboratory test work;
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Program No. 2 - The Distribution Program:




     The program for establishing the distribution-curve data  of




     cleaning equipment from data acquired as a result of prototype




     plant operations.




Program No. 3 - The Classification Program:




     The program for establishing the classification curve of  classify-




     ing equipment from data acquired as a result of prototype plant




     operations.




Program No. 4 - The Solids Balance Program:




     The program for balancing the solids flow (tons) or the solids flow




     rate  (tons per hour) with the ash, pyritic sulfur, and total  sul-




     fur content of the solids through each line of the flow scheme.




     The programs will permit the calculations required to characterize




the sharpness and efficiency of a separation in any cleaning unit  in  the




plant.  As data become increasingly available, a running analysis  of




variance will delineate the sensitive variations in operating  conditions




or physical characteristics of the coals which affect cleaning perfor-




mance.  Factors to compensate for these variations will then be defined




and incorporated in the computer program.  Even though the initial pro-




grams do not cover sulfur content of the coal, inclusion of this para-




meter in the program will provide the ability to project the sulfur and




ash contents in the clean coal based on raw coal characteristics.




     It is anticipated that the final program will include raw coal data




obtained from the following:
                                   150

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     (1)  Sample crushed to three top sizes with  screen analyses for




          each with ash and sulfur determination  for  each  size  fraction.




     (2)  Washability relationships derived from  float-sink  tests  for




          each of the three size samples and  the  ash  and sulfur analyses




          for each specific gravity fraction.




     (3)  Hardgrove grindability index, BTU,  and  ultimate  and proximate




          analyses of each coal sample.




     6.4.1  Details of Presently Available Computer Programs




     The following presents information on each of the four  presently




available computer programs.




     a)   Program No. 1 - The Predicting Program:




          The inputs for the predicting program are the percent by




weight and the ash content for each specific  gravity  fraction (i.e., from




the washability), and an ashline relationship  (between specific gravity




and percent ash) of the raw coal.  The computer will  interpolate and




extrapolate the washability, calculate the yield, the specific  gravity




composition, and the ash content of the end products  for a separation by




employing distribution-curve data of  the desired  cleaning  equipment.  The




calculation will be based either on a given specific  gravity of separation




or a required ash content for the clean coal.




     Three systems of separation are available.   The  first is a separation




arrangement in which clean coal and refuse are separated and then  a




middling product is separated from the clean  coal.  The second  is  a re-




verse of this, the middling product being separated from the refuse.
                                    151

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The third arrangement involves middlings being separated from both  clean




coal and refuse after these two have been separated from each other.




     The program takes the washability data associated with each  size




fraction of the raw coal in the order provided by the data card set until




all size fractions are processed.  If more than one separation is to be




performed on any size fraction of the coal, the cleaning equipment  for




each separation will be specified.  The results of the program cleaning




calculations become data supplied to the program for calculation of the




results of the next separation in the system.




     b)   Program No. 2 - The Distribution Curve Program




     This program will be used to establish washing equipment distribu-




tion-curve data based on results obtained from the prototype plant  tests.




For the program, the input is the percent by weight from each specific




gravity fraction in each grain-size range of the feed and end products.




In the case of a cleaning unit making only one separation, three para-




meters are involved:  feed, clean coal, and refuse.  In the case of two




separations, four parameters are involved:  feed, clean coal, middlings,




and refuse.




     With this input the computer proceeds to calculate the percent




yield for clean coal, for middlings in the case of a two-separation pro-




cess, and for refuse.  Employing the yield calculation result, a  recon-




structed feed is determined and the distribution numbers calculated for




each piece of equipment.  The reconstructed  (or reconstituted) feed, as




opposed to the actual sampled feed, is used as a check on the accuracy
                                    152

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of both the analytical and the  sampling  procedures.   The  reconstructed




feed is determined by adding the  end products  together  on a weighted




basis for each size and specific  gravity composition, based on  the  cal-




culated yield percentages.




     c)   Program No. 3 - The Classification Program




     Program No. 3 is for establishing the  classification curve data  of




classifying cyclones and sieve  bends from data obtained from  prototype




plant testing.




     With the help of classification curves obtained by testing,  the




standard"classification curve already known from experience for classi-




fying cyclones and the classification curve known for sieve bends can be




checked and, if necessary, modified.  Using the standard  classification




curve, the grainsize composition  of the  end products of the classification




equipment can be predicted for  different grainsize compositions of  the




feed.




     A classifying cyclone or a sieve bend  component only is  not  always




used for classifying a product  (water plus  solids).   A  combination  of




such components can also be employed.  The  program is written in  such a




way that not only the test results of a  single component  but  also the




test results of a combination can be used as input.   In such  a  case the




computer calculates the classification-curve data for both pieces of  equip-




ment with less sampling and analytical test work than would be  the  case  if




both units were treated separately.
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     d)   Program No. 4 - The Solids Balance Program

     This program is to be used for balancing the solids flow  (tons),  or

the solids flow rate (tons per hour), with its ash, pyritic  sulfur,  and

total sulfur content through each line of the flow scheme.   The balancing

provides projections on the overall reduction of ash, pyritic  sulfur,  and

total sulfur in the clean coal obtainable on a full plant basis, and the

ash and sulfur reduction attributable to each piece of cleaning, sizing,

and classifying equipment.

     The computer program will allow the simulation of five  major and

thirty-three minor flow schemes.  By making use of balancing techniques,

the program usage will reduce the requirements for sampling  and analyt-

ical test work.

     6.4.2  Correlation of Coal Characteristics with Cleaning  Results
            (Multiple Regression Analysis)

     A continual analysis of the variations in the operating conditions

of the plant and in the physical characteristics of the coal that affect

cleaning equipment performance will be provided.  Data on the  perfor-

mance of each piece of cleaning equipment will be continuously collected,

through sampling and analysis, and the raw coals processed will be

analyzed with respect to certain major properties.  The examined proper-

ties include grindability, pyritic sulfur content, and the electrokinetic

potential.  The equipment parameters which will be varied include the  size

fraction of coal being cleaned and the tons per hour processed.  In  the

analysis of variations an attempt will be made to establish  whether  a

correlation can be made between pairs of observations or groups of ob-


                                    154

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servations.  The pairs of observations  will  be  in  the  form of  scattered




data in which an attempt will be made to  find functional  relationships.




These relationships may be  linear  or non-linear.   If they are  linear,  a




line of regression will be  determined taking each  variable in  turn as  the




independent variable by the method of least  squares, as used in a linear




regression analysis. If they are non-linear, an attempt will be made to




determine what sort of function is represented. For instance,  two vari-




ables may be parabolically  or  quadratically  related and perhaps an equa-




tion describing the relationship can be determined. In the case of a




correlation attempt on groups  of observations,  multiple correlations will




be attempted by a multiple  regression analysis.




     The purposes of the analysis  of variations are to determine which




coal properties and/or operating conditions  prove  to be significant par-




ameters and to determine,  if possible,  the relationship between these




parameters. Once this  is known to  any  substantial  degree, predictions




of greater confidence may  be provided.
                                     155

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7.0  PYRITE UTILIZATION ECONOMIC STUDY




7.1  Purposes of the Study; Overview and Approach




     Commercial coal cleaning plants are designed to remove non-carbon-




aceous materials from the coal. The composition of the reject material




varies with the type and source of the coal. It consists principally of




shale, sandstone, clayey substances, and pyrites (iron-sulfur compounds)




along with carbonaceous materials unavoidably lost.




     Several of the reject constituents have commercial value, but  the




low concentration of these materials and their relatively low market




price have in the past rendered their recovery and sale commercially un-




attractive. One apparent exception is pyritic and carbonaceous material,




which can serve as a source of sulfur, sulfur compounds, and energy. Con-




centrations of pyrites in the reject from cleaning certain coals appear




sufficient to make recovery of sulfur values economically feasible. This




would be more likely if the sulfur recovery can be combined with combus-




tion processes so that the energy from the combustion of pyrites, as well




as the coal fraction remaining in the rejects, can be utilized.




     The purposes of the Pyrite Utilization Economic Study portion  of




EPA's overall pyrite coal program are:




     (1)  To investigate the economics of utilizing the pyrites obtained




          from coal beneficiation by determining (a) the degree to  which




          it is possible to offset the increased costs involved in  maxi-




          mizing the reduction of sulfur content and (b) the ability to




          recover economic values in reject material;
                                    156

-------
     (2)   To evaluate the applicability of alternative commercial pro-




          cesses for recovering energy and chemical values from coal




          cleaning reject material; and




     (3)   To design, construct, and operate a plant that would demon-




          strate the technical and economic feasibility of the processes.




     Investigations concerned with the first two purposes listed above




were conducted concurrently.  In 1967, EPA awarded a contract to the




Bechtel'Corporation, assisted by Stanford Research Institute, to perform




a general review and evaluation of the technology and costs of available




commercial processes for utilizing pyrite-coal, and to investigate the




technical and economic feasibility of certain processes in greater de-




tail.  Also in 1967, EPA awarded a contract to Arthur D. Little, Inc.,




assisted by Dorr-Oliver, Inc., to determine the costs and benefits of




processing pyrites removed from coal.  The A. D. Little study concen-




trated on the technology and economics of fluidized bed roasting of




pyrite-coal, followed by conversion of sulfur dioxide to sulfuric acid




by the contact process.  A principal goal of the latter study was to




evaluate the acceptability of such processes to the industries involved




(coal, chemical, utilities, steel, etc.).  The results of these two




studies of various recovery  processes and the market potential for




recovered products and by-products are presented in the remaining por-




tions of  Section 7.




     The  Bechtel and A. D. Little studies lead to the general conclu-




sion that existing technology can readily be adapted to recovery of
                                    157

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sufficient quantities of energy and sulfur values from  the reject  mater-




ial from coal cleaning operation to be of commercial interest.   However,




the economics of such recovery operations are marginal, and  the  economic




viability of these operations is closely related to the supply and sell-




ing price of elemental sulfur.




     On the basis of technical and economic data developed in these  two




studies, EPA decided to look more closely at a system for burning  the




high-sulfur, high-ash reject materials produced by coal desulfurization.




This decision was based on the applicability of proven  technology  and




on economic analyses of various processing systems.  A  contract  was  sub"-




sequently awarded (in 1969) to Chemical Construction Company (Chemico)




to (1) select the most appropriate sulfur recovery process and design




a high-sulfur combustor system, (2) investigate combustion character-




istics of high-sulfur fuels, and (3) prepare a conceptual design and




cost estimate of a prototype plant employing the high sulfur combustor.




Chemico was assisted by the Foster Wheeler Corporation  in this under-




taking.  Results of the design and analysis effort are  presented in




Section 8 of this report.




7.2  Description of Candidate Recovery Processes




     Chemical and energy values can be recovered from pyrite-coal  by a




number of processes.  These employ markedly different approaches and




yield different combinations of products.  Certain processes accept  the




entire stream of reject material from a coal preparation plant while




others require additional concentration of the pyrite.
                                   158

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     Eight  separate  processes were selected for evaluation by Bechtel

Corp.  Three  of  the  eight (Fluid Bed,  Outokumpu,  and Orkla) were identi-

fied as being commercially available for the processing of pyrites for

metallurgical purposes,  but all three  have technical and economic limita-

tions for utilization  of the total refuse streams from coal cleaning op-

erations.   Thus,  evaluations were made of five processes that had not

reached commercial application.  These five additional processes accept

the total refuse  stream  from a conventional coal  preparation plant,  while

the presently available  commercial processes require additional  pyrite

concentration.  All  of the processes considered and their principal  pro-

ducts are identified in  Figure 25 with descriptions following.   The

marketing of  product sulfur and sulfuric acid is  discussed in Section

7.3, but it should be  mentioned at this point that recovery of sulfur

values in the form of  elemental sulfur is sometimes preferable to re-

covery in the form of  sulfuric acid because of the high shipping costs

for the acid.  This  consideration does not apply  when there is a market

for sulfuric  acid near the reject processing plant.

     7.2.1  Brief Description of Recovery Processes

     The eight recovery  processes evaluated are described briefly in the

following paragraphs.*  These descriptions include comments on the appli-

cability of each for processing pyrite-coal.   It  should be noted that

none of those processes  that  accept the entire refuse stream was in  com-
*More complete descriptions including process  flow  diagrams  are  given  in
 Reference 23.
                                  159

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     MINING
          RAW COAL
 COAL PREPARATION
     CLEAN COAL
REFUSE
    COMBUSTION-
    SULFUR OXIDES
    REMOVAL
   CARBONIZATION-
   DESULFURIZATION '
     SOLVENT
     EXTRACTION
     PREFERENTIAL
     OXIDATION
    TWO-STAGE
    GASIFICATION
 USULFURIC ACID
 |»ELECTRIC POWER
 •ELEMENTAL SULFUR
 •CHAR
 •PIPELINE GAS
 ^ELEMENTAL SULFUR
  LIGHT OIL
'{«COAL EXTRACT
    JBON DIOXIDE
       GAS
, KSULFURIC ACID
 WCHAR
, •ELEMENTAL SULFUR
 •ELECTRIC POWER
                                           PYRITE CONCENTRATION
REJECT
                                             PYRITE-
                                             COAL
             >rSULFURIC ACID
              ^ELEMENTAL SULFUR
              ksULFURIC ACID
              MRON OXIDES
              ^ELECTRIC POWER
               ELEMENTAL SULFUR
                                              SOURCE:  REFERENCE 23  (1968)
                                  FIJGURE 25
                              REFUSE PROCESSES
                                    160

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mercial operation at the  time  this  study was  conducted.   Processes  that

accept a concentrated pyrlte feed were in commercial use,  but  were  utiliz-

ing mined pyrites, not  pyrite-coal  reject materials.

              Combustion/Sulfur-Oxides-Removal

     The reject material  is burned  in a combustor designed for high-
     sulfur, high-ash feed.  Heat from the combustion is  used  to
     generate steam which is used in turn to  generate electric power.
     Sulfur  oxides produced in the  combustion are recovered from  the
     combustion gas and used to form sulfuric acid.   Several processes
     have been proposed for sulfur  dioxide recovery; the  Monsanto
     Catalytic Oxidation process was selected as a basis  for costing
     and evaluating the overall process.  In  the Cat-Ox process,  sulfur
     dioxide in the combustion gas  stream is  oxidized in  contact  with a
     catalyst to  form sulfur trioxide, which  is absorbed  in water to
     form marketable sulfuric  acid.

     Although the Cat'-Ox process was not in commercial use at  the time
     of this study, it  had been tested in a large-scale pilot  plant.


               Carbonization-Desulfurization

     This approach to material and  energy value recovery  involves a
     relatively complex set of reactions in which coal and pyrites  in
     the reject stream  are decomposed by heat.  Sulfur is removed from
     the decomposition  products to  form elemental sulfur; a high-
     BTU, low-sulfur combustible gas; low-sulfur char; and other  solid
     products.

     The carbonization-desulfurization approach can be illustrated by
     a highly abbreviated (and incomplete) description of a specific
     process.*  Volatile components are removed from coal in the  reject
     material by  contact with  a very hot char (produced by another
     step in the  process). Volatilized components are de-acidified by
     amine stripping, then passed  through a methanator where constituent
     carbon  monoxide and hydrogen react to form methane,  which is then
     compressed to'form a pipeline  gas.  The  solid components  of  the
     feed stream  are desulfurized by reaction with hydrogen to form
     hydrogen sulfide and a low-sulfur solid  char.  Sulfur is  removed
     from the hydrogen  sulfide by reaction with dolomite  to form a
 *The Consolidated  Coal  Company C02 Acceptor Process,
                                   161

-------
     solid sulfide, which is oxidized to remove sulfur as sulfur dioxide
     and to regenerate the dolomite for reuse.  The sulfur dioxide  is
     reduced by reaction with hydrogen sulfide or carbon monoxide  (from
     other process steps) to form elemental sulfur, water, and carbon
     dioxide.  The useful products are high-BTU, low-sulfur pipeline
     gas; low-sulfur char; and sulfur.

     This technically complex process would be further complicated  by
     the use of pyrite-coal instead of run-of-mine coal.  The effects
     of additional ash on the process and on the value of the char  are
     not well understood.  The process requires high capital investment.
     Preliminary economic studies are not encouraging.

                     Solvent Extraction*

     In this process, the coal in the refuse stream is dissolved in a  ,
     solvent.  A low sulfur, low ash solid coal extract is recovered
     from the solvent.  Depending on the specific processes used, other
     products may include light oil, fuel gas, and sulfur.

     This process is characterized by its technical complexity and  re-
     quirements for high capital investment.  It is still under develop-
     ment, using run-of-mine coal.  The effects of using pyrite-coal
     rejects for the feed material are not well known.  Prospects for
     processing coal-pyrite rejects, based on preliminary economic
     analysis and current developmental status, are not attractive but
     may become so through continued research and development.

                   Preferential Oxidation

     The reject stream is allowed to react with a limited quantity  of
     oxygen at a temperature range that promotes oxidation of pyritic
     sulfur in preference to carbon.  This temperature (around 800°F)
     must be carefully controlled to prevent excessive volatilization
     and oxidation of the coal.  Temperature control is a major tech-
     nical problem.  The sulfur dioxide formed by oxidation of pyrite
     is converted to sulfuric acid.

     The process has been studied on a laboratory scale.  Data are  not
     adequate for useful economic analysis.
*It should be recognized that the process termed "solvent extraction"
 here (and in Reference 23) involves dissolution of the carbonaceous com-
 ponents of coal, not the ash or pyritic components, and in this respect
 is similar to the Pittsburg-Midway "Solvent Refined Coal" process.
                                   162

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           Two  Stage Gasification Process

A  gasifier,  fired with coal refuse, operates in a system that
converts  the fuel value to electricity and recovers elemental sul-
fur  from  the gas.  Hot gases which contain most of the sulfur as
I^S  leave the  top of the gasification furnace, generate steam in
a  heat  recovery boiler, then preheat air for combustion of these
gases later  in the system.  Gas, now at 250°F, is scrubbed with
100  F water  to remove dust and condense water vapor.  Hydrogen
sulfide is removed from the gas by an absorbent solution and then
converted to elemental sulfur by a Glaus kiln or perhaps the
Giammarco-Vetrocoke process.  Clean gas from this system would
contain about  1.0 grain of hydrogen sulfide per cubic foot, and
sulfur  recovery would be about 98 percent of that absorbed.  The
sulfur  would probably be contaminated with small amounts of arsenic
from the  absorbent solution but purification with limewater would
be practical.   The clean gas from the sulfur recovery steps would
be burned with the preheated air from the heat exchange in a boiler
equipped  for preheating combustion air for the gasifier.  Waste
gas  at  about 450°F would pass to a stack.  Steam from this boiler
and  from  the heat recovery boiler would be available for electrical
power generation.

             Fluid-Bed Pyrite Roasting

Crushed pyrite (about 1/4 inch top size), on a grate or bed through
which an  upflow of air keeps the material turbulent, is oxidized
at high temperature to produce sulfur dioxide and iron oxide Cprin-
cipally hematite).  The sulfur dioxide in the gas stream is oxidized
catalytically  to produce concentrated sulfuric acid.  The solid.
residue can  be further processed to produce a material similar to a
high grade iron ore.  Since the oxidation of pyrite under these
conditions is  self sustaining and exothermic, the heat produced can
be used to generate steam which then can be used to generate
electric  power.  The products of this process are a marketable
grade of  sulfuric acid (93 to 98 percent ^504), electric power (or
steam), and  a  solid calcine material.  Iron from the pyrite may re-
.main in the  calcine as hematite (£6203), or it may be removed as a
separate  product, usually in the form of magnetite (£6304) suitable
for  steelmaking.

This process is widely used on a commercial scale for sulfuric acid
manufacture  from mined pyrites.  In at least one installation it
also produces  iron oxide pellets for steelmaking.  The process
usually requires pyrite containing 40 to 50 percent sulfur.  Since
the  pyrite-coal reject stream from a coal preparation plant typically
                               163

-------
contains 4 to 25 percent sulfur, a pyrite concentration step  is
required.

Preliminary economic analysis shows this process to be one of
the more promising for recovering energy and sulfur values from
coal-pyrite rejects.

                 Outokumpu Process

In this process, pyrites are flash smelted upon contact with hot
gases from an oil burner.  Labile sulfur in the pyrites volatilizes
in the form of elemental sulfur vapor, sulfur dioxide, and hydro-
gen sulfide.  The sulfur vapor is condensed and sulfur is recov-
ered from the sulfur dioxide and hydrogen sulfide in the form of
elemental sulfur.

Fixed sulfur in the pyrites remains as ferrous sulfide matte.  This
is roasted to produce iron-bearing calcine, from which iron can be
recovered, and sulfur dioxide, which is converted to sulfuric acid.
Heat produced at the smelting step and ferrous sulfide roasting
step of this process can be used to generate steam and electric
power.

This process is in commercial operation in Finland.  It appears
suited to a set of conditions existing there, where there is a mar-
ket for all of its principal products—sulfur, acid, iron oxide,
and electric power.  The economics of the process are not attrac-
tive for use in the U.S., where different market conditions exist
for its products, particularly for iron oxide.  If a pyrite-coal
feed is used, yields would be lower and the economic prospects
even less attractive.

                   Qrkla Process

This process is used in Norway to recover sulfur and metallic values
from copper-bearing pyrites.  It employs a furnace, similar to a
blast furnace, which is charged with lump pyrites, coke, sand, and
limestone.  Labile sulfur in the pyrites volatilizes initially with-
out oxidation as elemental sulfur in the upper part of the furnace
where no oxygen is present.  Fixed sulfur remains as metallic
sulfides,  which sink to the smelting zone of the furnace, where a
portion oxidizes to form sulfur dioxide and iron oxide, while the
remainder forms a matte of cupreous sulfide and iron sulfide, which
is resmelted to obtain copper.  The iron oxide reacts with silica
and limestone to form a slag, while a portion of the sulfur dioxide
is reduced by coke to form elemental sulfur.  The remaining sulfur
dioxide is reacted catalytically with gaseous sulfur compounds
formed at various processing steps to form elemental sulfur and
                                164

-------
     by-product gases.  Principal products are copper and elemental
     sulfur,  with a by-product slag of high iron content.

     While the Orkla process is the only one of the eight evaluated
     processes operating on a commercial scale that recovers most of
     the pyritic sulfur in elemental form, it has certain inherent
     disadvantages.  It requires that the pyrite feed be in lump form,
     which would necessitate briquetting of pyrite coal produced by a
     coal preparation plant.  Process economics, which are somewhat
     marginal using a cupriferous pyrite feed, are heavily dependent
     on recovery of copper, which, of course, would not be feasible
     from most pyrite coal feeds.  Although the process appears well
     suited to the situation in Norway, it does not appear economically
     attractive or readily adaptable technically to the processing of
     pyrite coal in the U.S.

     The eight processes described above are summarized in Table XXIII.

This table indicates the advantages, limitations, and economic character-

istics of each process, in addition to identifying the type of feedstock,

principal products, and major processing steps.

     7.2.2  Preliminary Economic Studies of Selected Processes

     To obtain a comparison of the economics of the above processes, five

were analyzed in a given scenario using a consistent set of assumptions

relative to size of operation, logistics, power and labor costs, product

market prices, etc.  The following processes were subjected to this type

of analysis:

     •  Refuse Combustion/Sulfur-Oxides-Removal;

     •  Fluid Bed Roasting;

     •  Outokumpu;

     •  Carbonization-Desulfurization;

     •  Solvent Extraction.

All of the above are either in commercial operation or reached the pilot

plant stage of development.  The remaining three processes were not

                                    165

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                                                                                      TABLE  XXIII




                                                                   SUMMARY OF PROCESSES FOR UTILIZING COAL REFUSE
PROCESS
Combustion- Sulfur
Oxides Removal











Carbonization-
Be s ul f ur i zat ion











Solvent Extraction
























Preferential
Oxidation







FEED
Entire refuse
stream











Entire refuse
stream











Entire refuse
stream























Entire refuse
stream







PRODUCTS
Sulfuric Acid
(78%)
Electricity










Sulfur
Pipeline gas
Char










Sulfur
Light oil
Coal extract
Carbon dioxide
Fuel gas




















Sulfuric acid








PROCESS DESCRIPTION
Coal refuse is burned in
a stream generator de-
signed for high ash and
sulfur fuel. Sulfur is
oxidized to sulfur diox-
ide which is catalyt-
ically converted to 803
followed by recovery of
sulfuric acid.
Process is in develop-
mental status


Coal refuse is dried,
devolatized, then de-
sulfurized in a fluid
bed with gas containing
about 50% H .
Sulfur forms H.S which
is removed by a dolomite
acceptor. Dolomite is
regenerated. H S is
converted to elemental
sulfur, process gas is
converted to fuel gas by
a methanation reaction.
Coal fraction of the re-
fuse is dissolved in
solvent derived from the
coal itself in the pre-
sence of hydrogen. So-
lution is filtered to
remove ash. Filtrate is
evaporated to recover
solvent, and liquid coal
extract is solidified.
The solvent is distilled
to yield light oil; the
heavier fraction is re-
cycled. Process gas
containing H2S, removed
along with solvent
vapor, is passed through
an amine treatment to
remove the acid gas.
Add gas is processed to
recover elemental sulfur
Process gas is steam re-
formed to give H2& for
recycle and C0« bypro-
duct.
Sulfur is oxidized pre-
ferentially without
burning excessive
amounts of coal. This
is done by carefully re-
gulating the quantity of
air and controlling the
temperature.

ADVANTAGES
Does not require pyrite
concentration
Based on relatively simple,
well-known technical
principles ~ -- -
Products are usually mar-
ketable






Requires no pyrite concen-
tration; uses entire re-
fuse stream
Recovers sulfur in ele-
mental form








Requires no pyrite con-
centration; uses entire
refuse stream
Produces high quality
products




















Simple process scheme
with few operational
steps






LIMITATIONS
Sulfuric acid product
is slightly discolored
and limited to about 78
percent concentration
Market radius is limited
by shipping cost of acid
(usually about 200 miles
maximum)
Final solution is required
to select economical
corrosion resistant ma-
terials of construction.
Pilot plant status
Complex, multioperation
process with many tech-
nical problems to solve
High-ash char may not be
marketable; this product
may retain sulfur
Pilot plant status






Complex process; it re-
quires further develop-
ment and solution of
technical problems
Economics favor very
large-scale operation
Pilot plant status


















treatment removes only a
small fraction of organic
sulfur and not all pyritic
sulfur.
Status of development is
bench-scale with very
limited data.
Temperature control problem
difficult to solve
ECONOMICS
Most promising
process











High capital and
net operating
costs










Highest capital
and net operating
costs of processes
evaluated





















No data because of
process status







er>

-------
                   TABLE  XXIII




SUMMARY. OF PROCESSES FOR UTILIZING COAL REFUSE  (CONT'D)
PROCESS
Two- Stage
Gasification



















Fluid Bed
Roasting











Outokumpu











Orkla






FEED
Entire refuse
stream



















Pyrlte concen^
t rat ion











Pyrite Concen-
tration



i,






Cupriferous
Pyrite





PRODUCTS
ulfur
lectricity



















Sulfur acid
!ron oxides
Electric power










Sulfur
Sulfuric acid
Iron oxide
Electricity








Sulfur






PROCESS DESCRIPTION
The gasifier is a spe-
cially designed vertical
cyclone furnace with two
burner ports, one above
the other. Refuse burns
at the upper port with
limited air to produce
an t^S rich gas and slag
containing FeS. The
slag runs down the walls
into the flame at the
lower port where refuse
is burned with excess
air, converting all sul-
fur compounds to 302-
Gases passing up through
furnace become H2S-rich.
Subsequent treatment
recovers sulfur and
yip.lds an-100 Rtu/cubic
foot fuel gac.
Pyrite concentrate is
roasted in a fluid-bed
furnace to produce S02
and a low-sulfur hemati-
tic calcine. S02 is
co verted o aci in a
plant. Iron ore may or
may not be recovered de-
pending upon quality and
market. Waste heat can
be recovered for process
or generation of electri
city.
Pyrite is flash smelted
by combustion gases
which remove the labile
sulfur for recovery in
elemental form. Other
gaseous compounds are
catalytically converted
to S. Liquid FeS matte
is granulated and
roasted to give an iron
oxide product and SO.
for conversion to acid.
rhe Orkla process smelts
pyrite in a specially
designed blast furnace
to produce elemental
sulfur . Iron , copper ,
and precious metals re-
port in the matte.
ADVANTAGES LIMITATIONS
Simple process with
efficient recovery of
fuel value
Produces valuable ele-
mental sulfur
















Relatively simple, well-
developed technology











Recovers about half of
the sulfur in elemental
form
Process developed to
commercial scale.







Produces elemental sulfur
Process developed to com-
mercial scale




The process is in the con-
cept stage only, no devel-
opment work has been done.


















Requires pyrite concen-
tration
Requires pilot plant de-
velopment for use with
coal refuse
Dilution of pyrite with
centration of SO- in gas
stream.
Degree of acid discolora-
tion is unknown.



Ash content of coal refuse
would cause technical
problems
Economy would suffer be^-
cause iron sinter would
not be marketable.
Requires very large-scale
operations




Limited to a lump pyrite
feed
Modification of technology
for feeding coal refuse
would be difficult.


ECONOMICS
No data because of
process status



















Low capi t al cos t
Net operating cost
is encouraging at
this stage of de-
velopment








Not as favorable
as conventional
fluid-bed process


-






No published data
It is generally be-
lieved to be eco-
nomic only with a
copper product.


                                                        Source:  Reference  23

-------
Included in the economic comparison because of  their  development status,

technical factors, or a combination of the two.  The  two-stage gasifica-

tion process was in the concept stage when this  study was  conducted.   The

preferential oxidation process had been studied  in  the  laboratory,  but

exhibited serious technical problems in the control of  reaction tempera-

ture.  The Orkla process was not analyzed further because  of  its depend-

ency on recovery of copper for overall economic  viability,  its require-

ment that finely-divided feed be briquetted, and the  technical and  eco-

nomic problems associated with the briquetting operation.

     Results of the preliminary analysis are summarized in  Table XXIV.

This table gives estimated costs and credits which  can be  presented on a

comparable basis for each process.  Of particular interest  are the

figures for "Change in Clean Coal Price," which  indicate the  effects  of

these processes on the cost of coal preparation  under the  assumption

that the total costs and credits for processing  the pyrite-coal rejects

are integrated with the costs of coal preparation.*  One of the processes

shows a small net credit while four show a net cost ranging from about

12 cents to $1.63 per ton of clean coal.

     The annual costs for each process reflect a 20-year depreciation

period.   Other assumptions relative to production,  logistics,  marketing,

etc., are detailed in Table XXV.
*The economic data presented in Table XXIV should be viewed  as  relative,
 not absolute, cost or credit information.
                                  168

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                             TABLE XXIV
                      COST EVALUATION SUMMARY














•. Capital Investment, $
Total Annual Cost,
$/Year
Credits for Products
(FOB Plant), $/Year
Credits for Fuel Value,
$/Year
Net Annual Cost,
$/Year



,H
0 >
•H O
•P S
W 0)
3 PH
-g
B CM
0 0
U CO


T!
0)

ni
, CO
.2 OT
** d)
"2 o
'S o
3 ^
h *




3
a
p 03
3 co
L^ QJ
O 0
•u o
3 M
O PH
i a
o
a -H
.3 ^
•P N
C8 -H
M H
•H 3
C M-i
O T-l
43 3
H 01
n) a)
0 O




a
o
•H
4J -W
Pi O
 ^
H -P
O !«!
W W
(figures in thousands except *)
8,300

2,201

1,160

1,230
-189

2,400^

1,077

826

36
215

5,000

1,695

867

60
768

14,000

4,006

2,432

—
1,574

19,500

7,420

4,368

—
3,052

Change in Clean Coal
Price, (2)$/ton* -0.10 +0.12 +0.41 +0',84 +1.63
.Cost of Transporting
Products to Market,
$/Year
Selling Cost of Products,
$/Year
Total Cost of Products
to Customer at Market,
$/Year


1,275

100


2,535


568

58


1,452


418

61


1,346


1,609

160


4,201


1,407

278


6,053
(1)  Facilities include waste heat boilers and acid plant.

(2)  Positive values indicated that  cost of process exceeds credits  from
     fuel value and products, which  results in an increase  in clean  coal
     price.  Negative values  indicate  that credits exceed costs, which
     results in a decrease in clean  coal price.

Source:   Reference 23 (1968).
                                 169

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                             TABLE XXV

          ASSUMPTIONS FOR PRELIMINARY ECONOMIC ESTIMATES
•  Coal Mine:  The coal mine produces 2,500,000 tons per year of ROM
   coal.  Mining cost is $3.50 per ton.

•  Coal Preparation Plant:  The coal preparation plant produces
   1,870,000 tons per year of clean coal (1.0% sulfur) at $0.50 per
   ton.  This quality is enough to fuel a 1000 Mw(e) electric power
   generator.

•  Clean Coal;  The clean coal has a heating value of 13,750 Btu
   per pound, a total sulfur content of 1 percent, and an ash content
   of 4 percent.

•  Pyrite-Coal Refuse;  A 630,000-ton-per-year stream of pyrite-coal '
   refuse is produced containing 33 percent mineral matter and 67 per-
   cent coal.  The total pyritic and organic sulfur content is 6.2
   percent, and the heating value-is 9700 Btu per pound.

•  ROM Coal;  The ROM coal has a heating value of 13,000 Btu per
   pound and contains 0.8 percent organic sulfur, 1.5 percent pyritic
   sulfur, and 10 percent ash.

•  Pyritic Concentration:  For the processes which require it, a
   pyritic concentration plant processes 1900 tons per day of pyrite-
   coal refuse, and produces 110 tons per day of pyrite containing
   90 percent FeS2, 5 percent coal, and 5 percent mineral matter with
   a pyrite recovery efficiency of 50 percent and a total operating
   cost of $3.00 per ton of concentrate.

•  Capital Costs;  Capital costs for the pyrite-coal utilization plant
   are the installed battery limit costs of the process equipment and
   auxiliary facilities.  The cost of land is not included in the
   estimate.  The installed costs are derived from estimates   published
   in nonproprietary sources using published scale factors to adjust
   for plant size.

•  Utilities;  The unit cost of utilities required for operating these
   processes are:

          Cooling Water                    $0.05/1000 gallons
          Boiler Feedwater                  0.50/1000 gallons
          Electric Power                    0.008/kwhr
                                 170

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                         TABLE XXV (con't)

          ASSUMPTIONS FOR PRELIMINARY ECONOMIC ESTIMATES
•  Raw Materials;  The unit cost of raw materials required for oper-
   ating these processes are:

         ROM Coal                         $3.85/ton-13,000 Btu/lb
                                           3.50/ton mining cost
         Clean Coal                        5.50/ton-13,750 Btu/lb
                                           75% recovery
         Pyrite Concentrate                3.00/ton-90% FeS
         Ash Disposal Cost                 0.75/ton

•  Labor;  Operating labor rates are averaged at $4.00/hr.

•  Supervision and Overhead;  The prorated cost of supervision,
   employee benefits, and administrative overhead is equal to oper-
   ating labor cost.

•  Maintenance, Labor, and Material;  An amount equal to six percent
   of plant capital cost is assumed for annual maintenance, labor,
   and material costs.

•  Fixed Capital Charges:  The annual fixed charge rate is 15 percent
   of the pyrite-coal utilization plant capital cost.  This includes
   20-year depreciation at 6.5 percent interest, property taxes, in-
   surance, and administrative expenses.

•  Transporation Costs:  The cost of shipping products to a market
   200 miles away, based on prevailing railroad point-to-point commod-
   ity shipping rates for the various products, is as follows:

          Clean Coal (unit train)              $1.44/ton
          Coal Extract                          2.90/ton
          Coal Char                             2.90/ton
          Iron Oxide                            6.25/ton
          Sulfur                                8.25/ton
          Sulfuric Acid                        11.00/ton
          Sulfur Dioxide                       12.00/ton
          Light Oil                             8.00/ton
          Carbon Dioxide                        8.00/ton
                                171

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                         TABLE XXV (con't)

           ASSUMPTIONS FOR PRELIMINARY ECONOMIC ESTIMATES
•  By-product Credits;   Credits for by-product sale.   FOB plant are
   derived from the prevailing market selling prices  for each by-
   product.  The credits are:
   Sulfuric Acid (98%)




   Sulfuric Acid (77.7%)



   Elemental Sulfur


   Coal Extract



   Char
   Fuel Value of
   Coal Refuse

   Pipeline Gas

   Light Oil

   Iron Oxide Pellets

   Liquid Carbon Dioxide


   Steam
$16.'00/ton       From 500 T/day plant
                 using elemental sulfur
                 at $38.00/ton produc-
                 ing 98% acid

 10.00/ton       From 98% acid at
                 $16.00/ton and dis-
                 count 20% for quality

 36.30/long ton  Liquid crude, dark
                 sulfur, midwest plant

  6.40/ton       15,800 Btu/lb based
                 on clean coal at $5.50/
                 ton

  1.10/ton       8600 Btu/lb based on
                 ROM coat at $3.50/
                 ton and discounted 50%
                 for quality
  1.95/ton       9700 Btu/lb

  0.26/1000 scf  975 Btu/scf
  0.10/gal

 13.00/ton

 15.00/ton


  0.50/1000 Ib
Pittsburgh-Midway

67% Fe

Pittsburgh-Midway
and Air Reduction Co.
   Source:   Reference  23 (1968).
                                172

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     7.2.3  Processes Selected for Detailed Cost Studies




     Two of the processes discussed above were selected for further anal-




ysis at a more detailed level.  The "Fluidized-Bed Pyrite Roasting Proc-




ess" was examined by A. D. Little, Inc., assisted by Dorr Oliver, and




the "Combustion/Sulfur-Oxides-Removal Process" was examined by Bechtel




Corporation.  Although the fluidized-bed process was an obvious candi-




date from the outset of the study by virtue of employing proven tech-




nology and having been in successful commercial use for roasting of




mined pyrites, it was nevertheless included in Bechtel's cost analysis




of candidate processes in order to provide a common point of reference




for economic comparison with other technically attractive processes.




Bechtel's preliminary cost analysis indicated that the Combustion/Sulfur-




Oxides-Removal Process and the Fluidized-Bed Pyrite Roasting Process




have the most favorable economic prospects in terms of their effect on




the price of clean coal.  (See Table XXIV.)




     These two processes will be discussed separately at greater length




later in this chapter.  For both, pyritic sulfur is oxidized initially




to sulfur dioxide, which is then converted to sulfuric acid.  Although




both processes produce by-product calcine and can produce a good grade




of iron oxide as well as electric power, the major product of both is




sulfuric acid.  Pertinent market characteristics of this commodity will




be discussed in the following section.




7.3  Sulfuric Acid Market Analysis




     Sulfuric acid, as an industrial chemical, is a relatively low-cost,




heavy commodity.  The principal commercial raw material in its manufacture




                                   173

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is elemental sulfur or some sulfur-bearing  compound  such as pyrite.  In




1970, over 85 percent of the sulfur consumed  in  the  United States was




used for making sulfuric acid.




     There are two features of the sulfuric acid market  that warrant




special note.  One is the large percentage of  the market that is captive




— that is, the consumer owns the acid production facilities needed to




fulfill his demand.  Second is the shipping characteristics of the acid




and its raw materials (elemental sulfur and pyrites).  Since a ton of




sulfur will yield about three tons of acid, it is usually advantageous




to ship the sulfur to an acid manufacturing plant near the point of acid




consumption rather than ship the acid a great  distance.




     A different trade-off exists when the source of raw material is




pyrite (FeS2), which in pure form contains about 58  percent sulfur by




weight.  One ton of pyrite could theoretically produce about 1-1/2 tons




of acid, although this theoretical conversion  efficiency would probably




not be obtained in commercial operation.  However, the total coal reject




stream is not pure pyrite and even pyrite concentrate from the reject




stream may contain significant amounts of other material.   This lowers




the weight ratio of acid-to-feed even further, and emphasizes the dis-




economy of shipping either acid or pyrite-coal over  any  appreciable




distance.   In general, shipment of the acid in quantity  is limited to




100-200 miles, although there are exceptions  to this generality.  An-




other consideration in the use of pyrite for acid manufacture is the
                                   174

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possibility of shipping the solid by-product  (iron-bearing calcines)  for




iron recovery or other disposition.




     The production and utilization  of  sulfuric  acid  were  examined  from




several points of view.  The production and disposition  on a  regional




basis are displayed in Table XXVI.   Deposits  of  coal  with  high  pyritic




sulfur content lie primarily in  the  Mid-Atlantic and  East  North Central




Regions, with additional deposits in Kansas and  Missouri (i.e.,  West




North Central Region).




     Nationwide consumption of sulfuric acid  by  end use  is indicated  in




Table XXVII.  Projected nationwide growth  rates  for six  major uses  are




given in Table XXVIII.




     In view of the costs of shipping either  sulfuric acid or pyrite-




coal, it appears that only a limited area  of  the U.S.  could provide a




market for acid made from pyrite-coal.   The sources of acid demand  must




be relatively near the sources of high-sulfur coal rejects so that  the




rejects can serve economically as a  raw material for  acid.  This condi-




tion exists to a greater or lesser degree  in  an  eight-state area con-




taining the Northern Appalachian and North Central coal  fields.   The




quantities of acid consumption by end use  are given for  each  of the




eight states in Table XXIX.  The estimated change in  annual rate of con-




sumption is also shown in this table.   From the  data  presented,  it  is




apparent that the use of sulfuric acid  for fertilizer manufacture in  this




geographic area represents the largest  end use,  about four times as great
                                   175

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                                             TABLE XXVI
               ESTIMATED REGIONAL PRODUCTION AND DISPOSITION OF SULFURIC ACID, 1966
                                     (thousands of short tons)
New England

Middle Atlantic

South Atlantic

East North Central

West North Central

East South Central

West South Central

Mountain

Pacific1

   Total
                                                 Production
                 Disposition
New
205
3770
9030
3372
1103
1877
4792
1834
1523
,506
Refortified
0
260
0
158
32
25
304
57
135
971
Total
205
4030
9030
3530
1135
1902
5096
1891
1658
28,477
In-Plant
95
1487
6791
1414
781
514
1632
1052
581
14,347
Shipments
110
2543
2239
2116
354
1388
3464
839
1077
14,130
Total
205
4030
9030
3530
1135
1902
5096
1891
1658
28,477
Capacity 1/1/67        34,652

% Operating Rate       82%

    Includes one plant in Hawaii
Source:  Reference 24 (1968)

-------
                                       TABLE XXVII
                        SULFURIC ACID DISTRIBUTION BY END USE
                           (thousands of tons, 100% H-SO,)
                                         1963    1964
 Phosphate  Fertilizers
 Ammonium Sulfate
 Titanium Dioxide
 Petroleum  -  Alkylate Refining
 Petroleum  -  Other uses
 Iron and Steel Pickling
 Hydrofluoric Acid
                    2
 Rayon and  Cellophane
 Alcohols
 Aluminum Sulfate
 Synthetic  Detergents
 Copper & Uranium Leaching & Processing   607
 Dyes and Intermediates
          3
 Explosives
 Other Chemicals
 Exports
 Miscellaneous
  Total

   ^Includes sulfonated petroleum lube oil  additives and other petroleum products.
   Includes other cellulose film, sheets,  or  products.
   Excludes mixed acid, which is included  in  other chemicals for 1963, 1964,  1965,

Source:  Reference 24 0968).
                                          177
1963
6906
1390
1951
1325
1130
1084
603
839
599
536
481
607
294
146
2697
7
1165
1,760
1964
7753
1759
1975
1375
1205
1190
630
885
631
574
500
576
312
118
2951
14
1302
23,750
1965
9275
1967
1900
1400
1260
1075
710
895
665
580
510
567
330
100
3099
7
1360
25,700
1966
11675
1885
1740
1435
1335
1000
785
836
700
592
530
550
350
198
3389
-
1500
28,500
7, of Total
41%
7
6
5
5
3
3
3
2
2
2
2
1
1
12

5
100%

-------
                                               TABLE XXVI11
                          GROWTH IN MAJOR SULFURIC ACID END USES, UNITED STATES
                                        (THOUSANDS OF TONS, H2SO4)
Phosphate Fertilizers

Titanium Dioxide

Ammonium Sulfate

Iron & Steel Pickling

Rayon & Cellophane

Petroleum Refining
*  Actual use declined in last few years
Source:   Reference  24  (1968).
J.33O
4825
1375
1325
750
650
n.a.
JLSOU
5575
1500
1200
900
700
n.a.
J.SOJ
6906
1951
1390
1084
839
2455
UQD
9275
1900
1967
1075
895
2660
1? DO
11,675
1740
1885
992
836
2770
Historical
12%
2-3%*
5%
0*
3%
4%
Projected to 1972
4-5%
0
5%
—
—
4%

-------
Fertilizers

Ammonium Sulfate

Synthetic Detergents

Titanium Dioxide

Aluminum Sulfate

Iron & Steel Pick-
  ling
Rayon & Cellophane

Refineries

Hydrofluoric Acid

Other Uses


           Total
                                        TABLE XXIX
              ESTIMATED SULFURIC ACID END-USE PATTERN IN SELECTED STATES, 1966
                            (THOUSANDS OF SHORT TONS 100% H2SO4)
             760
577
1814    416
308
130
338
797
5140
* Future growth will be in SO., sulfonation.

Source:   Reference 24 (1968).
                                                                                        Projected
Pa.
18
199
27
—
18
142
107
103
—
146
Ohio
93
69
75
—
28
80
—
50.
30
152
111.
1532
28
30
—
12
9
—
102
38
63
Ind.
47
88
50
—
—
105
—
103
~
23
W. Va. Ky. Tenn.
25 126
110 15
—
—
30
10
150 — 132
—
40 55
8 25 50
Mo.
284
—
39
410
30
—
—
17
—
17
Area
Total
2125
509
221
410
118
346
389
375
163
484
Average Annual
Growth Rate
8-10%
3
0*
0
4
0
0
2
4
5

-------
as the next largest, and also shows one of the largest  projected rates of




increase.



     The supply-demand situation for sulfuric acid  in the  states of pri-




mary interest is summarized in Table XXX.




7.4  Further Analysis of Two Selected Processes




     Two processes were selected from the eight described  in  Section 7.2




for additional technical and economic analyses.  These  are the  refuse-




combustion/sulfur-oxide-removal process and the fluidized  bed roasting




process.  The following discussion will augment the brief  description of




these processes given in Section 7.2.1.




     In the discussions that follow, the technical aspects are  discussed




separately from the economic aspects, with primary attention  given  the




latter.  These discussions present only the economic highlights of  each




process.  More detailed descriptions and analyses of the refuse-combus-




tion/sulfur-oxides-removal process can be found in Reference  23 and of




the fluidized bed roasting process in Reference 24.




     In conducting the economic studies, both contractors  utilized  com-




puterized models to investigate the complex relationships  among the




several variables considered, although somewhat different  approaches are




used for the two processes.  In modeling the refuse-combustion/sulfur-




oxides-removal process in which the entire reject stream is burned, the




reject stream is considered a source of energy that can be used to  meet




a given segment of a total (hypothetical) demand for electric power.  Re-




covery of sulfur values in the form of sulfuric acid is an ancillary step
                                     180

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                                  TABLE XXX




      SULFURIC ACID SUPPLY-DEMAND SITUATION  IN  SELECTED STATES, 1966




                       (thousands of tons, 100% ILSO,)
                                                                 Capacity to Produce
Pennsylvania




Ohio




Indiana




Illinois




West Virginia




Kentucky




Tennessee




Missouri




  Sub-total




Other States




  U.S. Total
Estimated
Production
966
689
677
1763
155
230
955
550
5,985
22,492
28,477
Estimated
Consumption
760
577
416
1814
308
130
338
797
5,140
23,330
28,470
Surplus
(Deficit)
206
112
261
(51)
(153)
100
617
(247)
845
(838)
7
New Acid
1/1/67
1040
865
695
1835
156
220
194
595
6,320
28,332
34,652
 Source:  Adapted from Reference 24 (1968)
                                      181

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whereby credits accrue to the overall process through the sale of by-




product acid.  Additional non-monetary benefit is realized from  the




attendent reduction in the sulfur oxide content of the combustion gases.




     In modeling the economics of the fluidized bed roasting of  pyrite




concentrate, emphasis was placed on improving the economics of acid pro-




duction.  Although this process can also yield electric power, this was




considered a subsidiary product and its production was not included in




all of the equipment configurations analyzed.




     7.4.1  Refuse-Combustion/Sulfur-Oxide-Removal (Technical Aspects)




     The basic steps of this process are:  combustion of the refuse




stream, steam generation, fly ash removed by an electrostatic precipita-




tor, catalytic oxidation of sulfur dioxide to sulfur trioxide, absorp-




tion of sulfur trioxide in water to form acid, concentration of  acid,




and demisting of stack gas.  A flow diagram is given in Figure 26.




     Three systems of refuse combustion were considered for use  in this




process:  pulverized refuse, cyclone furnace, and fluidized bed  com-




bustion.  In the economic analysis presented in Section 7.4.2, equip-




ment cost estimates were developed for a pulverized refuse combustor




and a cyclone furnace; the fluidized bed approach was not analyzed for




this process since it is treated in detail as a means of roasting pyrite




concentrate (Sections 7.4.3 and 7.4.4).




     The following processes were considered for processing the  sulfur




dioxide in the combustion gases:
                                   182

-------
                   STEAM
                    TO
           STEAM   TURBINE
           GENERATOR <
           FEED WATER
                                                        COMBUSTION   CLEAN GAS TO
                                                        AIR
                                         STACK, 250  F
   COAL  „
   REFUSE
00
u>
              i
          FLUE GAS
          900  F
CLEAN GAS
850° F
GAS
250° F
STEAM
GENERATOR
                     ASH
                      I
ELECTROSTATIC
PRECIPITATOR


CATALYTIC
CONVERTER
                    FLYIASH
GAS
850° F
                        ACID CONDENSER
                        AIR PREHEATER
                                                      PREHEATED AIR
                                                                       SULFU
                         MIST
                         ELIMINATOR
                                                                       SULFURIC ACID
                                                             IIC ACID
                                               1
                                                        TO WASTE DISPOSAL
                                                                         PRODUCT ACID
                                                                          (77% H2S04)
                                                                    SOURCE:  REFERENCE 23 (1968)
                                               FIGURE 26
                        REFUSE-COMBUSTION/SULFUR-OXIDES-REMOVAL FLOW CHART

-------
     •  the Topsoe process;




     •  the Reinluft process;




     •  the Wellman-Lord process; and




     •  the Monsanto catalytic oxidation  (Cat-Ox)  process.




     The Cat-Ox process was selected because of  its  advanced state of




development.




     7.4.2  Refuse-Combustion/Sulfur-Oxide-Removal (Economic Aspects)




     The economic analysis of the process was made in  terms  of a scen-




ario in which a given demand for electric power  was  satisfied in two




ways.  First, the demand is met conventionally by  a  single power plant




 (termed the "base plant") fueled by run-of-mine  (ROM)  coal.   Second, it




is met by two smaller plants:  one  (the "alternate plant") is a con-




ventional steam/electric plant fueled by ROM coal; the other (the "re-




fuse plant") is a combination plant fueled by reject material from a




coal preparation plant.  The combination plant produces both electric




power and sulfuric acid.  The nominal total power  demand is  750kw.




This dual scheme is depicted in Figure 27.




     In this analysis, the energy value and the  sulfur value of the re-




ject were determined separately.  This was done  because electric utility




companies and non-regulated companies handle their accounting differently




and have different views on profitability of investments.  These separate




components are not reported separately in this summary presentation but




are combined to determine total value which is reported as a function of




appropriate parameters.  For an indication of the  distribution of values




between these two components, see Figure 31 on page  196.




                                    184

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00
Ul


j ROM COAL AT 22$/MILLION BTU ._ BASE POWER PLANT P°WER AT 4.94 MILLS/Kwh _
1 * 750 Mw
1 SINGLE PLANT BASIS FOR POWER COST
j

*" CLEAN COAL SALES

ROM COAL^ rnAT PRRPA1}ATTnK COAL REFUSE ^
PLANT FUEL VALUE +
SULFUR VALUE
ROM COAL AT 22$ /MILLION BTU^
^DUAL PLANT SCHEME
SULFUR RECOVERY
PLANT
REFUSE-FIRED
POWER PLANT
A*Mw

ALTERNATE
POUFT? PT ANT
(750-A) Mw

l
SULFURIC ACID SALES^
POWER AT B* MILLS/Kwh
POWER AT
4.94
MILLS/Kwh
POWER AT C^MILLsTKwh
T— - , ^ J
       Refuse-Fired Plant Generating Capacity  (A)
       Cost of Poer From Refuae-Fired Plant (B), and
       Cost of Power From Alternate Plant (C)  are
       Variables to be Evaluated.
SOURCE:   ADAPTED FROM REFERENCE .23 (1968)
                                                 FIGURE 27
                                            DUAL PLANT SCHEME

-------
     Interrelations among the following parameters were considered in



determining reject value:


     •    Capacity of the refuse-fueled plant (in terms of electric



          power output)—shown as A Mw in Figure 27;



     •    Percent sulfur in reject material;



     •    Percent ash in refuse;


     •    Price of sulfuric acid  Cf.o.b. acid plant);



     •    Capital cost per kilowatt output capacity.



     Using typical ranges of values for the above parameters, Bechtel



worked backward to determine the  price that a utility using the dual-



plant scheme could afford to pay  for refuse as fuel.  The back-calculation



approach was used since it is the most direct, if not the only, method to



reflect the economic relationships for a dual-fuel plant with multiple



products.  By comparing the cost  of producing refuse having acceptable



energy and sulfur content with the estimated price that a utility could



afford to pay for such material,  an indication of the market acceptability



of refuse as fuel is thereby obtained.



     The determination of energy  value of the reject material involved

                     (23)
the following steps:



     1.   Establishing load requirement for electric utility  (base plant);



     2.   Estimating power cost for base plant;



     3.   Establishing capacity of refuse-fired power plant (refuse plant);



     4.   Establishing capacity factor of refuse plant;



     5.   Estimating power cost for power plant necessary to  supplement



         refuse plant (alternate  plant);


                                  186

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     6.   Estimating capital cost for refuse plant;




     7.   Estimating annual operating and maintenance costs for refuse



         plant;




     8.   Calculating annual fuel cost  for refuse plant;




     9.   Calculating refuse energy value.




The annual fuel cost for the refuse plant was determined by difference.




This procedure involves the premise that the cost of power from the two




smaller plants (the refuse plant and the alternate plant) must equal the




cost from the base plant.  The calculation is as follows:




     Base plant total annual cost  (including amortization) is equal to




     the total annual cost of the alternate plant plus the refuse plant.




where:




     Refuse plant total annual cost is equal to the annual fixed




     charges plus the annual operating, maintenance, and fuel costs.




All the above values except the annual fuel cost are calculated when plant




sizes and raw coal costs are established.  Note that total annual cost




includes amortization of capital investment plus all operation and main-




tenance costs.




     A summary of estimated costs for  the base plant is  given in Table




XXXI and for refuse plants of three capacities in Table XXXII.  For each




refuse plant capacity, separate cost estimates were made for a cyclone-




fired steam generator and for a pulverized-fuel-fired  steam generator.




The estimates for the two types of boilers were essentially the same ex-




cept those costs related to ash handling, where the differences were
                                   187

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                          TABLE  XXXI

                750-MW BASE POWER PLANT  SUMMARY
     Capacity factor  (percent)
     Annual  output  (billion kwh)

     Total capital  cost  (million  $)
                         ($/kw)

     Levelized Annual Cost
        Fixed charges  (millions  $)
        Operating  &  Maintenance  (millions  $)
        Fuel  (millions $)
        Total (millions $)
              (mllls/kwh)
 75
  4.93

 92.2
122.9
 13.0
  1.5
  9.8
 24.3
  4,94
      Source:   Reference  23 (1968).
                           TABLE XXXII

                   REFUSE POWER PLANT SUMMARY

Capacity factor (percent)
Annual output (billion kwh)
Total capital cost (millions $)
($/kw)
Levelized , annual
fixed charges (millions $)
Annual operating and
maintenance costs (millions $)
(percent of total annual cost)
Capacity (Mw)
200 300 500
85
1.49
37.8
188.8
5.3
0.7
11.7
85
2.24
51.1
170.3
7.2
0.9
10.4
85
3.72
74.3
148.8
10.5
1.4
8.9
Source:  Reference 23 (1968).
                              188

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minor, ranging between 1 percent and  3 percent.  An average figure for




estimated capital costs for each size unit was  therefore used for all




economic calculations.




     Sulfur value of  the refuse was determined  by a somewhat different




procedure which involved back-calculating the price an acid manufacturer




could afford to pay for various grades of reject material in order to




achieve a given return on  investment  for varying levels of manufacturing




expense, production capacity,  and  product acid  price.  The steps in this



                              (23)
procedure are outlined below:




     1.  Estimate capital  cost of  the sulfur recovery plant for a




         specific refuse plant capacity;




     2.  Establish method  of  financing;




     3.  Establish discounted  rate of return on equity investment and




         calculate discounted  equity  investment;




     4.  Establish refuse  type and sulfuric acid price (f.o.b. acid




         plant;




     5.  Calculate annual  revenue;




     6.  Estimate annual operating cost less price paid for refuse;




     7.  Establish depreciation method and calculate annual income tax,




         o.ther taxes, investment tax  credit, interest, and debt service




         payments;




     8.  Calculate refuse  sulfur value.




     Investment costs attributable to sulfur recovery are summarized




in Table XXXIII.  These cost  estimates were based upon a scaling down of
                                    189

-------
                              TABLE XXXIII

                   SULFUR RECOVERY PLANT INVESTMENT

Fixed capital cost (millions $)
Working capital (millions $)
Interest during
construction^ (millions $)
Total investment (millions $)
($/kw)
2
Loan (millions $)
Equity investment (millions $)
Discounted rate
of return (percent)
Discounted equity
investment (millions $)
Refuse power plant
net capacity (Mw)
200 300 500
8.3
0.4
0.5
9.2
45.9
2.6
6.5

12.5
5.1
11.4
0.6
0.7
12.7
42.3
3.6
9.0

12.5
7.1
17.2
0.9
1.0
19.1
38.2
5.4
13.6

12.5
10.6
   ^•6 percent interest for three years-
    period of construction

   ^ 30 percent of fixed and working capital
Source:  Reference 23 (1968).
                                   190

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more detailed cost estimates for applying  a  catalytic  oxidation  type  of
process to a 1000 megawatt conventional  coal-fired  plant.
     The operations of the refuse  power  plant  and the  sulfur  recovery
plant are, of course, not independent.   Certain  equipment  is  shared be-
tween the two operations; other equipment  (such  as  blowers and precipi-
tators) needed for either operation  must be  larger  to  meet the needs
of both.  Similarly, operational costs are mutually interdependent.   For
example, high sulfur concentrations  that are advantageous  for acid pro-
duction result in increased costs  for operating  the refuse-fired power
plant  (assuming a constant level of  power  output).   The  effects  of such
interdependences were taken into  account  in establishing  the values  of
energy and sulfur in the fuel.
     Total refuse value was determined by  combining the  values attribut-
able to energy content and sulfur  content.   This combined  value  is af-
fected by a variety of economic and  operating  conditions,  and is re-
ported as a function of:
     •   , capacity of refuse power plant;
     •    sulfur content of refuse;
     •    ash content;
     •    sulfuric acid sale price (7-7 percent 112804);
     •    plant investment per unit  of output;
     •    rate of return on investment.
When total value of the refuse is  determined on  a unit weight basis,  its
effect on the value of cleaned coal  can  be determined  from the percentage
yield of the coal preparation operation.
                                     191

-------
     Because of the number of variables affecting refuse value,  results




are presented in some 17 separate graphs.  These will not be  reproduced




in total, but the more important ones are presented here.  All dollar




figures shown reflect 1967-1968 costs, expenses, taxes, and dollar values.




It should be noted that the total reject (refuse) values presented here




represent the value of refuse at the refuse-fired power/acid  plant,  and




thus include any costs for transporting the refuse from the coal  pre-




paration plant to the refuse-fired power plant.




     Figure 28 shows refuse value as a function of plant capacity for




each of three levels of sulfur content and three levels of ash percentage.




All of these values assume an acid selling price of $12.50 per ton f.o.b.




plant.  Refuse values are seen to range from a negative value of  $1.00




per ton (meaning that a loss would be incurred in the power generating




and acid producing operations) under conditions of low sulfur content and




a very small (200 mw) refuse plant to a positive $4.50 per ton for a




high sulfur refuse being burned in a large (500 mw) plant.  The graph




also indicates that some reduction in coal preparation costs  can  be




achieved for any refuse (pyritic) sulfur content over 8.5 percent, irre-




spective of ash content in the refuse.




     For a 300 mw refuse power plant burning reject material  with 34




percent ash, Figures 29, 30, 31, and 32 respectively illustrate the




effects of the following parameters on both the reject (refuse) value




and the concentration of sulfur in the refuse:




     •    sulfuric acid price;
                                    192

-------
w
to
§
H

•OT-
pa
to
1
H
         200   250    300    350   400   450   500



              REFUSE POWER PLANT CAPACITY  (Mw)





                      PERCENTAGE OF

                      ASH CONCENTRATION
        NOTES:




        1.  BASE POWER PLANT CAPACITY = 750 Mw

        2.  BASE POWER PLANT CAPACITY FACTOR = 85%

        3.  SULFURIC ACID PRICE =  $12.50/TON

        4.  REFUSE MOISTURE = 15.0%
                                    SOURCE:  REFERENCE 23  (1968)
                         FIGURE 28


        TOTAL REFUSE VALUE-REFUSE POWER PLANT

              CAPACITY-REFUSE COMPOSITION
                            193

-------
      5.0
O
 •

Pn



§

EH
w
1
H
                                     8   9   10  11  12  13  14
-3.0



-4.0
                                  SOURCE:  REFERENCE 23  (1968)
                         FIGURE 29

    TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-

    SULFURIC ACID PRICE {REFUSE ASH CONCENTRATION, 34.0%)



                          194

-------
w
cr>
§
H
W
I
H
                                               53 ($/KW)

                                               70 ($/KW)

                                               187 ($/KW)
                                7  8  9  10  11 12  13  14
-2
    -3.0
    -A.O
                                   SOURCE:  REFERENCE 23  (1968)
                          FIGURE 30

  TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-REFUSE

    POWER PLANT CAPITAL COSTS (REFUSE ASH CONCENTRATION,

          34 PERCENT; SULFURIC ACID PRICE, $12.50/TON)




                            195

-------
     5.0
w
CO
§
H
•CO
W

1
                                                   $38/KW
           1   2  3   4   5  6   7  8   9  10  11. 12 13  14

                        SULFUR %, WET
                                  SOURCE:  REFERENCE 23  (1968)
                        FIGURE 31

     w      VALUE-REFUSE SULFUR CONCENTRATION-SULFUR
 RECOVERY PLANT INVESTMENT (REFUSE ASH CONCENTRATION
        34 PERCENT; SULFURIC ACID PRICE, $12.50 TON)
                          196

-------
    5.0
w
to
g
H
-co-
W

1


I
H
10% ROI
       01   2   34   5   6   7  8   9   10  11 12  13  14

                      SULFUR PERCENT, WET


                                 .SOURCE:  REFERENCE 23  (1968)
                         FIGURE 32
  TOTAL REFUSE VALUE-REFUSE SULFUR CONCENTRATION-RATE
   OF RETURN ON INVESTMENT (REFUSE ASH CONCENTRATION,
        34 PERCENT; SULFURIC ACID PRICE, $12.50/TON)

                           197

-------
     •    refuse power  plant  capital  cost;




     •    sulfur recovery plant investment;




     •    rate of return on investment.



     The distribution of total refuse value  between the energy component




and sulfur component for four levels  of  sulfur content is shown in




Figure 33 for a 300 mw refuse plant fired with a reject material con-




taining 34 percent ash.



     Figure 34 graphically illustrates the relative importance of the




variables that affect total refuse value.  The origin (0, 0 coordinates)




of this figure represents the specified  standard conditions given in Table




XXXIV, the abscissa represents the percent change in a single independent




variable; and the ordinate is the resulting incremental change in total




refuse value.  Although this chart was based on a 300 mw refuse-fired




power plant, the conclusions that may be drawn from this graph are gen-




erally true for other sizes.




     The chart shows that refuse value is most sensitive to change in




acid price and capital cost of the refuse-fired power plant.  For ex-




ample, a 10% increase in acid price nearly offsets a 10% increase in




refuse plant investment.




     7.4.3  Fluidized Bed Roasting of Pyrite, followed by Catalytic




            Oxidation of Sulfur Dioxide  - (Technical Aspects)




     This process requires a feed of  considerably  higher pyrite  content




than the reject  stream ordinarily produced by coal preparation.   Hence




an additional operation  is required  to concentrate the pyrite in the







                                    198

-------
+2.50 —


+2.00 - ^



^ SULFUR


^ ENERGY
+1.50-
£ SULFUR SULFU
S CONCENT. CONC
o -n.oo- 4-20% 6-38%
5 VALUE VALUE
£ -$0.364 4$0.51
3 +0.50 - pf
* 1*3
|/O/
-0.50 — 1$^
f^o -\
-1.00— ^^

j

'4w
fay,
t*£
ioi
'&££&
' -' - ^ ^ '
SULFUR
CONCENT.
10.26%
VALUE
+$2.30
SULFUR \
CONCENT.
8.50%
VALUE
+$1.403 |
^
ENT.
O

^v
\XNV-
>rs-.
xS>'
x05;
>NX-;
§^
'///
t$t
tot,
////,


P
I
1
w
lw
R
\//^-
m
¥/ *'*
Y*'-0'/,
I'////,



>* ' » «*
-0.081
SOURCE: REFERENCE 2:
                        FIGURE 33
TOTAL REFUSE VALUE COMPONENTS (300 M\N REFUSE POWER PLANT;
          REFUSE ASH CONCENTRATION, 34 PERCENT)

                          199

-------
                                +1.50
                   -10%
CHANGE IN INDEPENDENT
VARIABLE  (PERCENT)
PUNT O&M
  COST
                                      SOURCE:  REFERENCE 23  (1968)
                            FIGURE 34
         TOTAL REFUSE VALUE SENSITIVITY, 300-MW REFUSE
                         POWER PLANT
                              200

-------
                               TABLE XXXIV

                          STANDARD CONDITIONS

                      300-MW REFUSE POWER PLANTS
      Base Power Plant

      Net capacity
      Capacity factor
      Annual output
      First year fuel cost
      Fuel cost escalation
  750 Mw
   75 percent
 4.93 billion/kwh
 19-8 cents/million Btu
  1.5 percent/yr.
 II.   Alternate Power Plant

      Net capacity
      Capacity factor
      Annual output
      First  year fuel cost
      Fuel cost escalation
  450 Mw
   68 percent
 2.70 billion/kwh
 19.8 cents/million  Btu
  1.5 percent/yr.
III.   Cost Refuse Power Plant

      Net capacity
      Capacity factor
      Annual output
      Total capital cost
  300 Mw
   85 percent
 2.24 billion kwh
$51.1 million
170.3 $/kw
 IV.   Sulfur Recovery Plant

      Total investment

      Discounted rate of return
      Debt financing
$12.7 million
 42.3 $/kw
 12.5 percent
   30 percent
 Source:   Adapted from Reference 23  (1968).
                                  201

-------
reject component to be roasted.  The two cleaning and concentrating  op-r




erations are shown schematically in Figure 35.  The quantities  shown in




this figure indicate the approximate processing rates needed to produce




13,500 tons per day of clean coal and 1000 tons per day of 98 percent




sulfuric acid.



     The following comments on the fluidized bed roasting process  sup-




plement and expand upon the description of this process presented  in




Section 7.2. A flow diagram of the basic process yielding sulfuric acid




is shown in Figure 36.  The major processing steps are:




     • roasting the pyrite in a fluidized bed (where the crushed




       pyrite is "fluidized" by air blown through multiple openings




       in the floor of the bed and forced upward through the layer




       of crushed pyrite), to yield heat, combustion gases, and




       calcine;




     • generation of steam, then electric power, from heat produced




       in the roasting operation;




     • recovery of sulfur oxides from the combustion gases;




     • catalytic oxidation of sulfur dioxide to form sulfur trioxide;




     • absorption of sulfur trioxide in water to form sulfuric acid;




     • concentration of the sulfuric acid to commercial densities.




In some locations, an additional major step is added; the recovery of




iron oxides for use in steelmaking.  Preliminary analyses indicate




that recovery of iron values would not be economic in most geographic




areas of the U.S. where sulfuric acid is likely to be manufactured from







                                    202

-------
                            RAW COAL
                            15,000 TPD  (3.5ZS)

                            I	"
COAL
PREPARATION
PLANT        I
                            1 ___
                          PYRITE REFUSE
                          1,500 TPD (26.0%S)
                                                   CLEAN COAL  TO
                                                     UTILITIES
                                                       (3/8")
                                                 13,500 TPD (1.0%S)
             REFUSE
             CONCENTRATION
             PLANT
                                      '"I
                                   REFUSE TO WASTE
                                   725 TPD (5.4%S)
                            I	J
                         PYRITE-RICH REFUSE
                         775 TPD (85% PYRITE)
                         WILL MAKE 1000 TPD  98%
TPD = TONS PER DAY
                          SOURCE:  REFERENCE 24 (1968)
                              FIGURE 35
                      PYRITE-REMOVAL PROCESS
                                203

-------
N>
O
                                            FIGURE 36
                         FLOW DIAGRAM OF FLUOSOLIDS PYRITE-ROASTING/
                                     SULFURIC-ACID PLANT
                                        PLANT TYPE I-A
SOURCE:  REFERENCE 24 (1968)

-------
pyrites, hence credits for iron are not  claimed  in the economic analyses




that follow and the recovery of iron  is  not  included  in the  technical




description of the process.




     There are several options as  to  the type  of  ancillary equipment




that might be included with the basic  fluidized bed plant  for  pyrite




roasting and acid manufacture.  The steam/electric generator is ad-




vantageous in some cases, as when  the  acid plant  is integrated with




other types of chemical works or located in  an area with high  electric




power costs, but this is not generally the case.   Also,  cooling towers




can be used to reject waste heat to the  atmosphere rather  than to  a




nearby river, but this additional  item of equipment would  not  be re-




quired in some locations  (at least it  was not  in  1968,  when  this study




was completed).  Consequently, several alternative equipment configura-




tions can be assumed for the basic plant.  The following alternatives




were evaluated:




     •  plant with steam generator and cooling tower  (designated




        in the following tables as Type  I-A  plant);




     •  plant with steam generator but no cooling tower  (Type  I-B);




     •  plant with cooling tower but no  steam  generator  (Type  II-A);




     •  plant with neither steam generator nor cooling tower (Type II-B).




     Any of the above types of plants  could  be utilized  as a stand-alone




installation producing sulfuric acid and, in some cases, electric  power,




as the principal product(s).  Alternatively, they could  be integrated




with other chemical processes to make  quite  different  products,  one of






                                     205

-------
the more commercially attractive being phosphate fertilizer,   This  rep-

resents another type of option in plant configuration.  When  integrated

in this manner electric power produced by a steam generator heated

by the roaster can generally be utilized advantageously by various  steps

in the overall operation.

     One possible additional method is oxygen enrichment.  This approach

might be used for roasting low-grade (high coal content) pyrite to  pro-

duce high strength S(>2 gas for the manufacture of acid.  By virtue  of

less nitrogen dilution, oxygen enrichment would make it possible to pro-

duce a gas of higher S02 content.

     To evaluate the merits of oxygen enrichment a process and economic

study was performed as follows.  Consider a pyrite roasting-contact sul-

furic acid plant designed to process pyrite plant feed of a specified

composition (for example, composition No. 2* which contains 90 percent

pyrite, 5 percent coal, 5 percent inerts) .  By adding the appropriate

amount of oxygen to the air, lower-grade pyrite-feeds can be  processed

in this plant with no increase in gas volume or no decrease in sulfur

dioxide concentration in the gas.  Maintaining this level of  sulfur

dioxide concentration would permit utilization of conventional equip-

ment in the subsequent conversion of sulfur dioxide to sulfuric acid.

This is one of the real advantages of the use of pure oxygen.

     If the total processing costs for pyrite plant feed composition No.

2 are used as a basic standard and to these costs are added the oxygen



*See Tables XXXV and XXXVI for the ranges of feed compositions examined
 in the A.D. Little study.

                              206

-------
costs, the resultant total  should  represent  a reasonable approximation




of the total processing  costs  for  an oxygen  enrichment plant.   The re-




sulting cost total  indicates that  the use of oxygen to enrich  the  air  is




not an economical approach  to  reducing the processing costs.   A possible




reduction in processing  cost is  indicated only for  large tonnage,  1500-




2500 tons of acid per  day,  and for pyrite plant-feed composition numbers*




10 and 12.  However, for these low-grade pyrite feeds, the  total pro-




cessing costs  (with or without oxygen enrichment) make the  whole project




economically questionable.  Furthermore, a technical problem with  the




roaster heat balance and removal of excess heat for these lower-grade




feeds has not  been  resolved.




     In the roasting or  oxidation  of any particular pyrite-coal material




a certain amount of heat is generated over and above that required to




maintain the roasting  reaction at  the desired temperature level.   With




oxygen-enriched air, the volume  of product gas resulting from  oxidation




of the feed is less than with  air  only.   As  a result,  less  heat is re-




moved as sensible heat in the  product gas and, therefore, more of  the




excess heat must be removed by steam-generating bed coils or by water




injection.  As the  grade of pyrite feed  decreases  (less pyrite, more




coal) this generation  of excess  heat becomes more of a problem. At some




point along the line of  decreasing feed  grade it becomes no longer poss-




ible to place  a steam-generating coil with sufficient  heat-absorbing ca-




pacity in the  fluid bed.  Instead,  it becomes necessary to  increase
*See Tables XXXV and XXXVI  for composition of  the various  feeds





                                    207

-------
materially the number of lines of roasters required for a given  produc-




tion capacity.  This increases both capital costs and operating  costs.




For a plant that uses water or weak acid for removal of excess heat  and




for control of roasting temperature, the amount of additional water  or




weak acid required for a plant employing oxygen enrichment substantially




increases the roaster exit-gas volume.  This, in turn, requires  larger




and more expensive gas cooling and cleaning equipment.  For these  tech-




nical reasons the possible use of oxygen, even for large tonnages, is not




a solution for reducing processing costs.




     The use of oxygen instead of secondary air in the acid plant, to




supply the oxygen required for SC>2 oxidation, might be considered  as




an alternative to using oxygen-enriched air for the pyrite roaster.  This




approach would have the following effect upon the process: (1) the total




oxygen requirement would be less but this oxygen, because of the lower




demand, would be more expensive per pound; (2) the pyrite roasting plant




would not benefit by reduced equipment size, and (3) the acid plant




would benefit by the use of oxygen in place of secondary air from  the




standpoint of the acid-plant water balance and the heat balance.   With-




out going into detailed process calculations or plant cost data, it  is




believed quite likely that the use of oxygen in place of secondary air




would show less economic benefit than if oxygen were used to enrich  the



air to the pyrite roasters.




     A more practical approach might be to consider the possibility  of




adding both elemental sulfur and oxygen to the roaster as a means  of






                                    208

-------
decreasing the processing costs.  Additional  technical and economic

analysis would be required to determine the possible merits of  this

approach.

     7.4.4  riuidized Bed Roasting of Pyrite  Concentrate  (Economic
            Aspects)

     The economic analysis of this recovery system considered that each

of the following parameters could take on a range of values:

     •  Composition of the feed  (in  terms of  percent pyrite, percent

        coal, and percent gangue);

     •  Plant capacity  (tons of  sulfuric acid per day);

     •  Price of elemental sulfur;

     •  Market for sulfuric acid;

     •  Proximity of pyrite source to acid market;

     •  Rate of return on investment.

The analysis determined values of the following variables for various com-

binations of the above parameters  (not all parameters were used in each

economic determination):

     •  Battery limit costs and  total capital investment  for various

        acid plant types;

     •  Total processing costs for various plant types;

     •  Prices that could be paid for pyrites to keep manufacturing

        costs of sulfuric acid made  from pyrites competitive with acid

        made from elemental sulfur;
                                     209

-------
     •  Prices that could be paid for pyrites (f.o.b. coal preparation

        plant) to compete with elemental sulfur for manufacture of sul-

        fur Ic acid as part of an integrated operation to produce phos-

        phatic fertilizer.

Results from the above cost determinations are presented in the follow-

ing discussion.

     Capital costs for the various types and sizes of plants were esti-

mated on the basis of a complete plant being constructed from the ground

up.  Battery limit costs include purchase and erection of all processing

equipment including:^

      (1)  Calcine disposal and neutralized waste acid disposal equipment;*

      (2)  Liming station for neutralization of waste acid;

      (3)  Boiler-feed water-treatment equipment (for Plant Type I);

      (4)  Motor-control center, including switch gear and starters;

      (5)  Open (on the ground) storage for one month's supply of pyrite

          feed;

      (6)  Storage for seven days' production of acid in two or more tanks;

      (7)  Operating-control room and such other housing as required

          to protect such non-weatherproof equipment as instruments,

          motor-control center, etc. that are a part of the process

          facilities; and

      (8)  Water-cooling tower with air-circulation fans and water

          pumps (for Plant Type I-A and II-A).
*For the purposes of this report, the investment and operating costs
 of calcium disposal facilities were assumed to be the same as would
 be required if the calcines were sold as a sinter strandfeed material.
                                   210

-------
     Total plant costs were obtained by  increasing  the battery  limit




costs by a given percentage to cover offsite  facilities  such as  land,




power substation, water supply and  sewers, roads, fencing, etc.  This




percentage increase was 18 percent  for plants with  steam/electric gen-




erating equipment and 20 percent  for plants without  this equipment.




     Total capital investment was obtained by increasing the total plant




costs by 11 percent to cover construction and startup  (interest  on con-




struction money, taxes, insurance during construction, starting  personnel




training, etc.).




     For determining plant costs, the following  factors were treated as




parameters:





     •  plant capacity  (.tons per  day of  product  acid);




     •  plant type  (with or without steam generation equipment  or




        cooling  tower);




     •  pyrite  feed composition.




Estimated costs  of plants reflecting various  values  of these parameters




are given in Table XXXV.  The range of values considered for each para-




meter is shown  in the table.  Total capital investments  for plants meet-




ing this range  of parameter values  vary  from  $3.7 million  for a  Type II-B




plant of 258 tons/day capacity using No. 2 pyrite feed to  $35.5  million




for a Type I-A plant of 2500 tons/day capacity using No. 12 pyrite feed.




     Total operating costs were determined for plants  covering  the same




range of parameter values as used for capital cost  determination.
                                     211

-------
                                                                                       TABLE XXXV
                                                   BATTERY LIMIT COSTS AND TOTAL CAPITAL INVESTMENT VS. CAPACITY AND FEED CONSUMPTION
                                                                                  (MILLIONS OF DOLLARS)
o


Steam
Plant Type IA Cooling tower

TPD Capacity TPY (982) Acid
250 82500
500 165000
1000 330000
15CO 495000
2500 825000
Steam,
Plant TffiiL-IB So cooiins toBe
TPD Capacitv TPV (98%) Acid
250 82500
500 ' 165000
1000 330000
isno 495000
2510 825000
Cooline tower
Plant Type IIA 1]o t^n
TYP Capacity IPY (98%) Acid
"253 85000
517 170600
1033 340900
1550 511500
2583 852000
No cooling tow*
Plant^ype IIB Ko ^^ f .
TPD Capacity TPV (98SQ Acid
"^58 8500
517 170600
1033 340900
1550 511500
2583 852000

2
1.0

Bat Lim Tot Cao
Cost Invest.

3.16
4.19
6.97
9.21
14. 39

4.14
5.48
9.12
12.10
18.86

1

3.11
4.11
6.85
9.06
14.18

4.07
5.39
8.96
11.89
18.55



2.87
3.76
6.05
7.89
12.12

3.82
5.00
8.05
10.50
16.15
r

2.76
3.60
5.81
7.57
11. 71
3.67
4.80
7.73
10.08
15.65

4
0.897

••'lat L' T t C-
Cost Invest.

3.52
4.67
7.75
-0.26
.6.04
4.60
6.10
10.19
13.50
21.00



3.47
4.59
7.65
.0.10
.5.96

4.54
6.00
10.00
13.24
20.70



3.20
4.18
6.75
8.79
.3.50

4.27
5.58
8.98
11.70
17.98


3.07
4.01
6.48
8.44
.3.03
4.08
5.34
8.63-
11.20
17.37

6
0.833


a . ^ o . ap.

3.80
5.03
8.35
11.04
17.30
4.98
6.59
10.96
14.54
22.65



3.74
4.93
8.22
10.86
17.05

4.88
6.46
10.76
14.27
22.25



3.44
4.50
7.26
9.48
14.55

4.58
6.00
9.68
12.61
19.37


3.30
4. 32
6.95
9.09
14.05
4.39
5.75
9.25
12.10
18.73
oosition numbers
8
0.783


a . m. ^o . ^ap.

4.04
5.35
9.92
11.78
18. 37

5.29
7.00
11.66
15.42
24.10



4.06
5.26
8.75
11.56
14.21

5.20
6.87
11.46
15.18
23.70



3.66
4.78
7.73
10.10
15.49

4.88
6.38
10.30
13.45
20.60


3.52
4.59
7.42
9.66
14.95
4.68
6.10
9.87
12.88
19.90

10
0.673


r 't i
Approx.
4.69
6.21
10.30
13.67
21.40
6.14
8.15
13.53
17.95
28.00



4.61
6.11
10.16
13.46
21.00

6.05
8.00
13.31
17.65
27.55



4.26
5.56
8.98
11.70
18.00

5.67
7.51
11.94
15.60
24.00


4.09
5.35
8.60
11.22
17.35
5.44
7.12
11.45
14.99
23.12

12
0.530

B t LI

Order of Mas.
5.96
7.91
13.17
17.40
27.20
7.83
10.31
17.20
22.80
35.50



5.80
7.78
12.95
17.11
26.80

7.60
10.15
16.91
22.40
35.00



5.44
7.10
11.43
14.88
22.86

7.25
9.45
15.24
19.80
30.40


5.22
6.80
10.98
14.31
22.10
6.93
9.04
14.60
19.10
29.40
                                                        I-A   Cooling tower and steam generation equipment.
                                                        I-B   Steam generation equipment but no tower.
                                                       II-A   Cooling tower, no steam generation equipment.
                                                       II-B   No  cooling tower, no steam generation equipment.
                                             SOURCE:  REFERENCE 24  (1968)
                                                                                                                       Plant Peed Composition
No.
2
. 4
6
8
10
12
%Pyrite
90
80
85
70
70
65
%Coal
5
7
10
10
15
23
5
13
5
20
15
12

-------
Operating costs include direct costs  (power,  fuel, water,  chemicals,




maintenance supplies, operating  and maintenance  labor,  etc., but not




pyrite feedstock) and indirect costs  (managerial and  administrative




expense, office services and  supplies,  non-plant maintenance,  sales




expense, taxes, insurance, depreciation,  etc.)-   Total  operating cost




are presented in Table XXXVI.  The following  direct and  indirect costs




(and credits) were explicitly excluded:




     •  Cost of purchasing or processing  pyrite  feedstock;




     •  Cost of transporting  pyrite to  acid plant;




     •  Cost of shipping product acid;




     •  Credit for by-product steam,  electric power,  calcines, or iron




        oxide  (credits for these by-products  were estimated but not




        reflected in  this table  because of uncertain  markets for these




        items at the  probable locations of pyrite-coal  acid plants);




     •  Indirect credit for increased value of beneficiated coal or




        decreased disposal cost  of cleaning plant reject material.




It should be noted that operating cost  estimates for  plants using No. 10




and No. 12 feed (with low sulfur content  and  low sulfur-to-carbon ratios)




are of lower accuracy than the other  estimates in the table.   Considering




only the range of feedstocks  from No. 2 to No. 8 for  which firm esti-




mates are available,  the plant operating  costs vary from $5.51 to $20.81




per ton of product acid.  Some of these operating costs  for smaller plants




are expressed as costs per ton of product, and exceed the  estimated sell-




ing price of acid in the area under study in  the 1967-1968 time frame.







                                     213

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                                                                                   TABLE XXXVI
                                               TOTAL PROCESSING COSTS (DIRECT & INDIRECT COSTS) (DOLLAR* PER TON OF 98% PRODUCT ACID)
                                                               VS. PYRITE PLANT FEED COMPOSITION AND PLANT CAPACITY

                                                                   Pyrite riant Feed Composition and Plant  Capacity
                                             %Pyrite
                                             %Coal
                                             •^Inerts
                                             S/C Ratio
                                             S/H2 Ratio
             Plant Type
O
Plant Type I
250
500
1000
1500
2500
Plant Type
258
517
1033
1550
2583
II





               Plant Capacity - IPD  (98%) Acid
               Plant Type I
                250
                500
               1000
               1500
               2500
Plant Type II
 258
 517
1033
1550
2583
                        Source:  Reference 24 (1968).
2
90
5
5
13.8
182
IA
18.11
10.74
7.75
6.60
6.20
IB
18.64
11.33
8.34
7,20
6.80
IIA
15.63
9.47
6.92
5.92
5.51
IIB
16.62
10.44
7.91
6.93
6.56
4
80
7
13
8.7
116
IA
18.92
11.34
8.27
7.07
6.88
IB
19.54
11.97
8.91
7.72
7.54
IIA
16.57
10.08
7.43
6.38
6.20
IIB
17.54
11.14
8.55
7.51
7.36
6
85
10
5
6.5
86
IA
19.59
11.76
8.63
7.63
7.20
IB
20.21
12.47
9.34
8.34
7.92
IIA
17.17
10.52
7.82
7.00
6.53
IIB
18.23
11.67
9.00
8.21
7.78
8
70
10
20
5.36
71
IA
20.11
12.15
9.31
7.90
7.72
IB
20.81
12.88
10.07
8.68
8.49
IIA
17.73
10.90
8.46
7.32
7.03
IIB
18.84
12.11
9.70
8.58
8.34
10
70
15
15
3.58
47,5
IA
Approx
21.61
13.66
10.22
8.97
8.74
IB
Ap-proa
22.42
14.64
11. 1O
9.87
9.64
IIA
19.23
12.62
9.41
8.35
8.02
IIB
20.52
13.96
10.86
9.84
9.52
12
65
23
12
2.2
29
IA
Order c
24.53
15.74
12.29
11.53
11.14
IB
Order
25.40
16.86
13.42
12.65
12.29
IIA
f Mae.
22.21
14.65
11.62
10.76
10.32
IIB
of Mag.
23,80
16.45
13.49
12.70
12.23
                                                      Plant  Type   I-A

                                                                  I-B

                                                                 II-A

                                                                 II-B
Cooling tower and steam generation equipment.'

Steam generation equipment but no tower,.

Cooling tower no steam generation equipment.

No cooling tower, no steam generation equipment.

-------
     The determination of the price  that  a manufacturer  could  afford  to
pay for pyrite-coal reject material  was approached  in  two  ways.   The
first involves a comparison  total manufacturing  cost for making  98%
acid from elemental sulfur versus the  cost for making  it from  pyrite,
assuming both raw materials  are  delivered at  the plant site.   To  do this,
a functional relation was established  expressing acid manufacturing costs
as a function of price of elemental  sulfur f.o.b. the acid plant, assum-
ing plants of various capacities and 15 percent  return on  investment.
Acid manufacturing costs were determined  for  various prices of sulfur.
A second functional relation was developed expressing acid manufacturing
costs for the same type and  size of  plant and return on  investment as a
function of delivered price  of pyrite  feedstock  of  various grades.  The
prices that could be paid for pyrite to maintain acid manufacturing costs
equal to the costs corresponding to  various prices  of  sulfur was  thereby
determined.  Results are presented in  Table XXXVII.
     The second approach to  determining pyrite prices considered  the  case
where pyrite would be used to manufacture acid as part of  an integrated
operation to produce high analysis fertilizer (diammonium  phosphate).  A
brief analysis of the supply and demand for this type of fertilizer
revealed a high demand in the upper  midwestern U.S.  Production within the
region meets only about half of  the  demand, the  remainder  being  supplied
primarily by production in the southeastern and  Gulf states.
     Studies of the logistics of transporting pyrite rejects from coal
producing areas to an integrated fertilizer plant and  transporting ferti-
lizer from the plant to upper midwestern  market  areas  indicated  that  the
                                    215

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                                             TABLE XXXVII
                 THE PRICE THAT CAN BE PAID FOR PYRITES TO YIELD THE SAME SULFURIC ACID
                    MANUFACTURING COST AS WHEN USING BRIMSTONE AT VARIOUS PRICES
 Acid Plant Capacity
(Short Tons Per Day)
Pyrites Feed  Composition
Delivered Pyrites Price  ($ Per Short Ton) When the
Delivered Price of Brimston per Long Ton is:
       $35	$40     	$45
500
1000
1500
2500
500
„ 1000
°" 1500
2500
500
1000
1500
2500
4
4
4
4
6
6
6
6
8
8
8
8
1.49
4.00
5.24
5.50
0.46
3.37
4.48
5.10
-0.46
1.71
3.12
3.36
3.52
6.03
7.26
7.52
2.48
5.54
6.65
7.26
1.57
3.48
4.89
5.14
5.54
8.05
9.29
9.55
4.51
7.70
8.81
9.44
3.49
5.26
6.67
6.91
Feed Composition
Source:


Reference 24 (1968).


Number
4
6
8
—y ro 	 w 	
So A &
Pyrite Coal Gangue
80 7 13
85 10 5
70 10 20




-------
preferred location of  such a  plant  would be the Cairo,  Illinois - Paducah,




Kentucky area.  Cost studies  to  determine pyrite prices were based on a




plant in this location.




     The plant using pyrite as a source of sulfur was assumed to compete




with another diammonium phosphate fertilizer plant which could be in




either of two locations.   In  one case,  the competing plant would be lo-




cated in Cairo, and would  use elemental sulfur shipped  in from the Gulf




coast.  In the other case  the competing plant would be  in Baton Rouge,




Louisiana, a location  considered typical of new phosphate plants under




construction at the time of this study.  It would use Gulf coast sulfur




and its product fertilizer would be shipped to Cairo.  Functional rela-




tions for these two cases  (Case  A and Case B respectively) are shown in




Figure 37, which  indicates that  the more severe competition would be




imposed by the Baton Rouge-based plant.  The data in the figure are based




on a 10 percent return on  fixed  investment.  It is realistic to assume




that fertilizer production in the Gulf  coast area will, in fact, provide




the competition indicated  in  this example.  From the Case A (Baton Rouge)




curve, one sees that when  sulfur sells  for $38 per ton  f.o.b.  mine, the




fertilizer manufacturer could afford to pay $1 per ton  for 85 percent




pyrite delivered  to his plant and remain competitive.  If the sulfur price




rose to $48/ton,  he could  pay about $3.50/ton for pyrite, but if it fell




below $33 the price he could  pay for pyrite becomes negative,  and the




Cairo manufacturer could not  successfully compete, with regard to the




acid-making step  in his total operation.






                                   217

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oo
     CASE A - PYRITE-BASED PHOSPHATE PLANT AT  CAIIO MUST COMPETE WITH
              BRIMSTONE-BASED PHOSPHATE PLANT  AT  BATON ROUG E

     CASE B - PYRITE-BASED PHOSPHATE PLANT AT  CAI10 MUST COMPETE WITH
              BRIMSTONE-BASED PHOSPHATE PLANT  AT  CAIIO
       10
       ,-1
                                                        ACID COSTS INCLUDE 10%
                                                        PRE-TAX RETURN ON PLANT
                                                        INVESTMENT
                                             MOST LIKELY DOMESTIC PRICE RANGE FOR SULFUR
                                             BETWEEN 1963 -  1975  (f.o.b. MINE)
                34       36       38       40        42
               PRICE OF BRIMSTONE, DOLLARS (ELEMENTAL
               SULFUR) PER LONG TON, f.o.b. MINE IN
               SOUTHERN LOUISIANA
                              FIGURE 37
ESTIMATED VALUE OF PYRITE FOR SUPPLYING SULFURIC ACID TO PHOSPHATE
         FERTILIZER PLANT AT CAIRO, ILLINOIS AS A FUNCTION OF-
    1. Prevailing Price of Brimstone (Elemental Sulfur)
    2. Location of Brimstone—Based Phosphate Plant—Baton Rouge, La., or Cairo, III.
                                                                              SOURCE:  REFERENCE 24 (1968)

-------
     A different set of  functional relations similar to those of Figure




37 would apply if different  rates  of  return on investment were applied to




the plant using pyrite feed.   Table XXXVIII shows the effects of this




parameter on allowable price for pyrite,  when the return on investment




for the competing plants utilizing brimstone is held at 10 percent.




     It should be emphasized that  the pyrite prices  cited above and  in




Table XXXVIII are as delivered to  the acid production plant.   When the




cost of transportation from  the coal  preparation plant to the acid  (or




fertilizer) plant is considered, the  above prices must be adjusted by




deducting transportation costs.  If it is assumed that the cost of trans-




portation of pyrite reject from a  preparation plant  in western Kentucky or




southern Illinois is 50  cents per  ton, then the acid manufacturer could




afford to pay the prices tabulated in Table XXXVIII, less 50  cents,  for




pyrite at the preparation plant.   If  the  pyrite source Is the northern




Appalachian coal producing region, then the transportation costs are




grossly estimated as 50  cents per  ton from preparation plant  to dockside




in Pittsburgh, Pennsylvania,  plus  $2.00 per ton by barge from Pittsburgh




to Cairo, Illinois.  Thus, the prices in  Table XXXVIII must be reduced




by $2.50 per ton to arrive at the  estimated price allowable for pyrite




reject f.o.b. at a preparation plant  in the northern Appalachian region.




7.5  Findings



     The following conclusions jnay be drawn from the studies  performed




by Bechtel Corporation and Arthur  D.  Little,  Inc., on process costs  and




economics of pyrite coal  utilization:





                                      219

-------
                                           TABLE XXXVIII

                 ALLOWABLE PRICES FOR 85 PERCENT PYRITE DELIVERED TO CAIRO PLANT

                        UNDER VARIOUS RETURN-ON-INVESTMENT REQUIREMENTS*

                                           ($ Per Ton)
INVESTMENT CONDITION
  COMPETING WITH PLANTS USING
  ELEMENTAL SULFUR AT

Baton Rouge, La.	Cairo,  111.
Straight Manufacturing Costs with No Cost
For Capital Included
    2.42
                                                                                    5.65
10% Return on Fixed Investment  (ROI) for
both Pyrite-Fed Plants and Sulfur-Fed Plants
                                                       1.00
                                 4.23
15% ROI for Pyrite-Fed Plants and 10% ROI
for Sulfur-Fed Plants
   (0.14)
                                                                                    3.09
20% ROI for Pyrite-Fed Plant and 10% ROI
for Sulfur-Fed Plant
  (01.28)
                                                                                    1.95
*Assume:  Price of Elemental Sulfur is $38 per ton f.o.b.  Mine
Source:  Reference 24 (1968).

-------
•  The reject material from  large  coal  preparation  plants  that proc-




   ess pyrite-bearing coal contains  sufficient  quantities  of




   sulfur, sulfur compounds,  and coal  (in  addition  to ash)  to per-




   mit recovery of energy of  sulfur  values on a commercial  scale.




•  Adequate technology exists,  in  the  form of several commercially-




   used and proven processes, for  recovery of sulfur values of py-




   rite materials as elemental  sulfur  or sulfuric acid and  energy




   values as steam or electric  power.   These processes have been




   applied to mined pyrites  but have not yet been applied  to ut-




   ilizing the pyrite-bearing refuse from  coal  preparation plants




   as feedstock.




•  Preliminary studies indicate that several processes are  tech-




   nically capable of accepting such refuse as  feedstock, although




   certain of the processes  require  preliminary concentration of the




   refuse to increase its pyrite content.




•  All processes considered  require  some degree of  modification to




   accommodate the relatively low-pyrite,  high-ash  feedstock.  One




   reason is the low concentration of  sulfur dioxide in the com-




   bustion gases generated by burning  reject material rather than




   elemental sulfur or pyrites.  By  enriching the input air with




   pure oxygen, a higher concentration  of  sulfur dioxide in the




   combustion products may be obtained,  thereby minimizing  the re-




   quired modifications to existing  equipment and process  design.
                                221

-------
•  There is a large and relatively stable market for sulfuric acid.




   The competitive status of processes for converting the sulfur




   content of coal preparation plant refuse to sulfuric acid (for




   other salable products), compared with processes using elemental




   sulfur as a feedstock, is highly dependent on the availability




   and market value of elemental sulfur, which fluctuates greatly




   as some sources are exhausted and others are discovered.




•  Under conditions of the sulfur market at the time of the ref-




   erenced studies, two specific processes for recovering sulfur




   value and electric power from coal preparation refuse were found




   to be economically viable:  the refuse-combustion/sulfur-oxides-




   removal process (which accepts the entire refuse stream) and the




   fluid-bed roasting process (which require preliminary concentra-




   tion of the refuse).




•  The use of oxygen to enrich the input combustion air would be




   advantageous in permitting higher utilization of conventional




   process equipment,  but would not be economically advantageous




   because of oxygen costs and certain technical considerations re-




   lating to heat transfer.
                              222

-------
8.0  THE HIGH SULFUR COMBUSTOR — A  STUDY  OF  SYSTEMS FOR UTILIZATION




     OF COAL CLEANING REJECT MATERIAL




8.1  Objectives and Approach




     A study was performed  by the Chemical Construction Company  (Chemico)




during 1970 and 1971 to  identify a combustor  system for utilizing  reject




material produced  by the physical desulfurization of coal  and  to integrate




the combustor  into a system for  recovering the energy  and  sulfur values




of the reject  material.   Emphasis was  on equipment selection and design.




Specific tasks of  the  study were;




     •  To select/design an appropriate combustor;




     •  To select/design processes for recovery of sulfur  values as




        sulfur or  sulfuric  acid, with  emphasis on those processes




        in commercial  use Cor nearly so);




     •  To determine properties  of reject  material that influence




        combustor  design;




     •  To'establish procedures  to characterize reject material for




        use as fuel;



     •  To establish, specifications  for reject material for use as




        a fuel;



     •  To perform a conceptual  design of  a prototype  plant;




     •  To estimate costs of plant and of  the overall  operation,  in-




        cluding coal cleaning;




     •  To extrapolate  design to full-scale industrial and utility




        plants with energy  outputs in  the  range from 500,000 Ib/hr of






                                       223

-------
        industrial-quality steam to 500 megawatts electrical power,  with




        each design providing for recovery of sulfur values;




     •  To coordinate this study with other elements of EPA's Clean  Coal




        Program.



     These tasks were approached by first examining the characteristics




of raw coal in the geographic area of interest and capabilities of var-




ious methods of physical desulfurization.  This made it possible  to  de-




fine the ranges of reject characteristics for which recovery systems




would be designed, the characteristic of major interest being the sulfur-




to-carbon ratio (S/C ratio) in the reject material.




     Next, five "case studies" were developed consisting of very  general




performance specifications of various types of plants to extract  both




energy and sulfur values from rejects having sulfur-to-carbon ratios




across the range of interest.  Conceptual plant designs were developed




for the five case studies and estimates of capital and operating  costs




were developed for each design.  More detailed engineering designs,




equipment specifications, and cost estimates were prepared for a  proto-




type demonstration plant fitting one of the case studies.




     The study concludes that the reject material produced by the re-




moval of iron pyrites and ash from coal by conventional coal cleaning




operations can be blended to form a high sulfur fuel suitable for firing




an appropriately designed plant to generate electric power and recover




sulfur values.   The prototype plant design developed in the study would




provide the capability to demonstrate technical feasibility on a  reduced






                                   224

-------
scale (output: 50 megawatts  electric  and  100  tons/day  sulfur)  and  to




further investigate the  economics  of  such an  operation, which  appears




economically viable in preliminary analysis of  a  larger-scale  plant  (out-




put: 500 megawatts electric  and  770 tons/day  sulfur).




     The 50 megawatt plant design  selected for  more detailed analysis




and possible implementation  as a prototype plant  employs the same  basic




power generating system  and  technically-advanced  sulfur recovery process




as the 500 megawatt plant.   Although  not  of commercial scale,  it is of




sufficient size to permit investigation of the  effects of variations




in fuel characteristics  and  operating conditions  on power and  sulfur




output and to produce good estimates  of operating costs.  However, it




is not so large that disposal of sulfur and waste products is  likely




to present a major problem.  The production of  sulfur in its elemental




form helps to separate the basic problem  of sulfur recovery coupled




with power generation from the more complex problem of conversion  to




sulfuric acid.  Also, since  elemental sulfur  is easy to store  and  costs




less to ship than sulfuric acid, the  location of  a prototype plant




producing elemental sulfur would be less  critical, in terms of proximity




to acid-consuming industry,  than a plant  producing sulfuric acid.




8.2  Types of Coal and Effects of  Coal Cleaning




     A review of the effects of  various methods of physically  cleaning




and desulfurizing coals  produced in the six-state area of interest (Pennsyl-




vania, Ohio, West Virginia,  Kentucky,  Indiana and Illinois) led to the




following conclusion relating directly to  the design of combustor  systems:






                                    225

-------
     If, by size reduction and separation, it is feasible to  separate
     fractions to recover coal low in pyritic sulfur content  and  to  re-
     cover pyritic fractions low in coal content, then, by recombining
     these fractions, it is possible to produce high-sulfur fuel  hav-
     ing a controlled ratio of pyritic sulfur to coal.  The character-
     istics of such fuels can thus be tailored to the requirements of
     specific combustion-systems designed for the economic recovery  of
     energy and sulfur values.

     For the five case studies Foster-Wheeler did considerable work  on

determining feed compositions which were suitable.  Bituminous Coal

Research, Inc., (BCR) demonstrated that the compositions specified by

Foster-Wheeler could be produced through such means as blending,  etc.

BCR also performed work on the utilization of clean coal fractions.

Thus, the assumption is made that almost any run-of-mine coal contain-

int pyrites can, in general, be processed to yield low sulfur coal plus

a high-sulfur fuel.

     This conclusion permits establishing ranges of interest for  the

parameters characterizing high sulfur fuels, and selecting fuels  having

specific characteristics, upon which plant design can be based.

8.3  High Sulfur Fuel Characteristics

     Reject material from coal cleaned to reduce sulfur content ordin-

arily contains higher percentages of pyrites and non-pyritic ash  and

a lower percentage of carbon than run-of-mine coal.  The sulfur content

may range from a minimum of about one percent (assuming this one  percent

to be the nominal maximum for "desulfurized" coal) to a theoretical maxi-

mum of about 58 percent (corresponding to pure pyrite).

     The combustion in air of a known mixture of sulfur and carbon re-

sults in predictable sulfur dioxide concentration in the combustion  gas.

                                    226

-------
For practical purposes  this  is  also  true of  known sulfur-coal  and  iron-




pyrite mixtures when  the  conposition of  the  coal is  also  known.  Sulfur




dioxide concentrations  expected from combustion of sulfur-carbon mixtures




can be plotted according  to  S/C ratios.   The use of  the  S/C  ratio  for  this




purpose avoids the  ambiguity of "percent sulfur in coal"  which is  deter-




minant of total sulfur  but not  of  flue gas composition.   However,  coal




is not pure carbon  and  use of the  S/C ratio  results  in some  minor  incon-




sistencies.  The  S/C  ratio of high sulfur combustor  (HSC)  fuel must  be




held to narrow limits to  stabilize the heating value of  the  fuel and to




avoid penalizing  the  sulfur  recovery operation.




     The iron-pyritic ash content  must also  be controlled, partially




to maintain a specific  heating  value,  but more importantly to  avoid




an unpredictable  ash  fusion  temperature.  Failure to control ash




content can adversely affect the yield of cleaning operations  and  the




capability of the furnace designed to burn the HSC fuel.




     For recovery of  sulfur  values from  the  reject,  the percent sulfur




in the fuel is not  of as  much concern as the ratio of sulfur to carbon.




This sulfur-to-carbon ratio  bears  an almost  direct relation  to the per-




centage of sulfur dioxide in the gaseous products of combustion, from




which the sulfur  must be  recovered.   In  general, higher  concentrations




of sulfur dioxide promote efficiency of  recovery, at least in  currently




available technology.   The percentage of sulfur dioxide may  range  from




a small fraction  of a percent from burning a relatively  clean  fuel (say




one or two percent  sulfur) to about  13 percent from  burning  pure pyrite
                                   227

-------
(58 percent sulfur).  However, high sulfur fuels made from reject ma-

terials will not fall near the high or low end of the scale for either

percent sulfur or sulfur-to-carbon ratio, but within the mid-range.

     The following limits were selected to define the range of interest

for high-sulfur fuel composition:
                                          (25)
                                 HSC      V
                                     Lower                  Upper
Parameter                            Limit                  L^nit

Sulfur-to-carbon ratio                .08                     2

Percent S in fuel, (approximate)        7                    42

Equivalent percent pyrite              13                    79
in fuel,  (approximate)

Percent coal combustible               87                    21
(sulfur-free) in fuel, approximate)

Higher heating value                12600                  5300.
of fuel,  (approximate)

Although fuels of various compositions falling within this range were

selected for the various case-study process designs, the basic approach

is to design the process to fit the market, and to  tailor-make the

fuel to suit the process.

8.4  Performance Requirements for Recovery Systems—Base Parameters
     for Five Case Studies

     Three process systems utilizing currently available technology

appear capable of fully exploiting the full range of opportunities  for

recovering energy and sulfur values from high-sulfur coal-pyrites.   The

chemical processes selected for recovery of sulfur  values  or  the  standard

contact process, the Monsanto Cat-Ox process, and the magnesium sulfite/

                                     228

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oxide process.  Five case  studies  involving these  systems were  defined




as follows  (letter designations  are arranged to  group  similar processes




instead of  in alphabetical order):*




     CASE A;  Energy Product:    500,000  Ib/hour  industrial  steam




              Sulfur Product:    1800 tons/day 100% sulfuric acid




              Fuel S/C  Ratio:    2.0




     CASE A is  designed for firing a high sulfur fuel  having a  sulfur-




     to-carbon  ratio of about  2  to produce 500,000 Ibs/hr of industrial




     quality steam and  a flue  gas  of 6 percent  S02 concentration which




     is directly  converted to  some 1,800 tons/day  of commercial grade




     sulfuric acid.  These outputs would be secondary  coproducts of




     clean  coal produced at a  rate of 7  million  tons per year by wash-




     ing a  run-of-mine  coal containing 3 percent pyritic sulfur.   The




     actual clean coal  output  would, of  course,  depend on the actual




     run-of-mine  composition and washability.






     A system of  this  type is  conceived  to be of possible value as an




     addition to  an  existing coal-burning utility  complex,  or existing




     chemical or  steelmaking industry.






     CASE B;  Energy Product:    500,000  Ib/hour  industrial  steam




              Sulfur Product:    77% sulfuric acid  equivalent to 624




                                       tons/day  (100%  basis)




              Fuel S/C  Ratio:    0.4
*Adapted from Reference  25  (1971)




                                     229

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CASE B is designed to use the Monsanto Cat-Ox process  for  recovery




of sulfur as 77-80 percent sulfuric acid.  Since a lower sulfur-




carbon ratio fuel is used, a smaller quantity of acid  would  be  pro-




duced, the steam output rate remaining constant.









CASE E;   Energy Product:   500 megawatts electric power




          Sulfur Product:   77% sulfuric acid, equivalent  1420  tons/




                                   day (100% basis)




          Fuel S/C Ratio:   0.12









CASE E employs an 862 recovery technology (Monsanto Cat-Ox)  similar




to CASE B but this system is scaled to the 500 MW output level




(more than 10 times the energy capacity of CASE B) so  that the




combustion equipment is quite different.  The S02 recovery trains




operate on relatively weak gas of 0.7 percent SOo which is gener-




ated by a sulfur/carbon ratio of 0.12.








CASE D;  Energy Product:   500 megawatts electric




         Sulfur Product:   770 tons/day elemental sulfur




         Fuel S/C Ratio:   0.2









CASE D is also scaled to 500 MW energy output but the  S02 recovery




technology is quite versatile compared to processes mentioned




above.  The acid intermediates—liquid S02, magnesium  sulfite,  or
                               230

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      sulfur—can be produced for storage or shipment, or sulfur value




      can be converted directly to sulfuric acid, any of these by avail-




      able technology.  The main design theme of CASE D in this study is




      for output of sulfur at 770 net tons per day from a 1 percent S02




      flue gas that requires a sulfur/carbon ratio of 0.2






      CASE C:   Energy Product:   50 megawatts electric




               Sulfur Product:   102 tons/day elemental sulfur




               Fuel S/C Ratio:   0.2






      CASE C is the reduced-scale prototype or demonstration unit of




      CASE D,  designed to operate on the same HSC fuel composition but




      at  50 MW energy capacity and about 100 tons per day of sulfur.






      These cases cover sulfur-to-carbon ratios from 0.12 to 2.0.




Cases A  and B are primarily of industrial interest,  Cases D and  E are




of utility interest  with chemical co-products,  and  Case  C is for demon-




stration.   The plant design for Case C was carried  to much  greater de-




tail  than for the other case studies.




8.5   Selection of Equipment and Fuel Compositions




      8.5.1 High Sulfur Fuels




      Reject materials produced by coal cleaning operations  were  reviewed




with  respect  to  sulfur content,  coal content,  non-pyritic ash content,




heat value, and  other relevant  characteristics.  Fuel compositions for




each case  study were specified,  based  on  the  following ground rules:
                                    231

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     •    High sulfur fuel specifications must be compatible with




          optimum total yield of fuel value from the coal cleaning




          plant.




     •    Sulfur/carbon ratio must be controlled within narrow  limits




          to facilitate recovery operations.




     •    Non-pyritic ash content must be controlled to avoid unpre-




          dictable ash fusion temperature.




Fuels for each case study were specified in terms of proximate  and ulti-




mate analyses.  These will be presented in abbreviated form in  later ex-




hibits describing the processes employed in each case study (see Sec-




tion 8.5.6).




     Test procedures recommended for defining, preparing, and controll-




ing the quality of high sulfur fuels were:




     •    Ultimate Analysis;




     •    Proximate Analysis;




     •    Heating Value;




     •    Hardgrove Grindability;




     •    Reactivity (Ignition Index);




     •    Chemical Analysis of Ash;




     •    Ash Fusion, Reducing and Oxidizing Atmosphere;




     •    Size Analysis;




     •    Free Swelling Index.




     Only one of  the nine tests, reactivity, is not commonly accepted




in common practice.  It was included because it appears to be the best






                                     232

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indicator  of  combustion conditions over a wide range of fuel specifica-



tions.(25)




     8.5.2  Furnace Types




           The following types of furnace were considered:




                1.    Roasting Equipment




                     (a)  Kiln




                     (b)  Multiple Hearth




                     (c)  Flash Roasters




                2.    Fluidized Bed Combustors




                3.    Stoker Furnaces




                4.    Grate Furnaces




                5.    Crushed Coal-Fired




                     (a)  Cyclone Furnace




                6.    Pulverized-Fuel Fired




                     Ca)  Wet bottom furnace




                     (b)  Dry bottom furnace




                               Horizontally fired




                               Vertically fired.




     Types 1,  3, and 4  were eliminated from  consideration because they




cannot be fired at  sufficiently high temperatures to meet steam produc-




tion requirements.^     Type 2 (fluidized bed) was dropped because it is




not established commercially for this type of operation and because of




the uncertain  behavior  of  a coal-pyrite-ash  mixture in a fluidized bed
                                   233

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containing tubes.  Type 5(a) (Cyclone) was eliminated because of high




maintenance costs which could be aggravated by a high-iron, high sulfur




fuel.




     Pulverized-fuel fired systems were considered preferable to sus-




pension-fired ones on the basis of fuel characteristics, thus eliminat-




ing Type 4 (grate).  Wet bottom furnaces (Type 6(a)) were considered un-




suitable because of the high ash fusion temperatures resulting from high




iron content.




     Thus, by elimination, the dry-bottom, pulverized-fuel-fired type




of furnace was considered to be relatively risk-free, reliable, and most




generally suitable for all cases studied.




     8.5.3  Boilers, Burners, and Combustion Systems




     Specific types of combustion systems were selected for Cases A, C,




and D.  Combustor designs for Case B were not developed since funds were




not provided, but cost estimates for Case B equipment were made on the




basis of a modified Case A design.  The Case D combustor system is suit-




able for Case E with minor modifications.




     For Case A, an individual-type boiler fired by a special burner fir-




ing vertically downward, was selected to produce 500,000 Ib/hour of




steam at a pressure of 900 psig.




     For Case C, which requires a rate of steam production similar to




Case A but at a higher pressure for generating electric power, a utility-




type boiler fired horizontally with an intervane burner was selected




to produce some 500,000 Ib/hour of steam at 1450 psig.







                                    234

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      For  Case  D»  a utility-type boiler was selected to produce larger




quantities  of  higher quality steam which are fed to 500 MW turbo-gener-




ators.  As  in  Case C, a larger utility boiler fired horizontally with




intervane burners was selected.  It would produce some 3.5 million lb/




hour  of steam  at  2500 psig.




      The  Case  E equipment would be a modification of the Case D equip-




ment.




      8.5.4   Electric Generating Equipment




      Electric  generators driven by a conventional turbine drive cycle




were  selected  for both the 50 MW requirement  (Case A)  and the 500  MW




requirement (Cases D and E).




      The  500 MW size was fairly typical of U.S.  utility installations




ca.   1960.   More  recently this capacity (i.e.,  500 MW)  has been toward




the lower end  of  the range, with most installations falling between  600




and 850 MW. Capacities around 50 MW are still  in use  for some munici-




palities, industrial Installations,  etc.   Generating equipment of  much




lower capacities  is often considered as "special order" with much




higher cost per unit output.  Hence  the 50 MW size appeared about  right




for a prototype demonstration plant.




     8.5.5   Processes for Recovery of Sulfur  Values




     Sulfur values can be recovered  from the  gaseous products of pyrite




combustion  in  several forms, including sulfuric  acid,  elemental sulfur,




sulfur dioxide  (liquid),  and metallic sulfites.   Sulfuric acid is  usu-




ally the  salable  end-product,  and the other forms of recovered sulfur






                                   235

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may be considered intermediate materials for the production of acid.




As discussed in Section 7, there are advantages to shipping sulfur  in




forms other than sulfuric acid because of the acid's high specific  grav-




ity.  Hence, under some logistic situations, one of the intermediate




forms of sulfur may be the more desirable output of a recovery operation.




     The following processes for producing sulfuric acid or acid inter-




mediates were considered for use in the plant designs for the various




case studies:




     •  Processes Yielding Sulfuric Acid:




        •  the "Standard" contact process;




        •  the Monsanto Cat-Ox process (a modification of the basic




           contact process permitting use of sulfur dioxide concentra-




           tions in the range of 2 percent down to a few tenths of a




           percent);




        •  the Lurgi process;




        •  the Hitachi process;




     •  Processes for Concentrating Gas Mixtures Low in Sulfur Dioxide




        to Intermediate Levels:




        •  the Reinluft process (using char absorption);




        •  the Grillo process  (using metallic oxide absorption);



        •  the Magnesium Sulfite/Oxide process;




     •  Processes for Concentrating Weak Sulfur Dioxide Mixtures to



        High Levels (90-100 percent):
                                      236

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        •  aromatic  amine  absorption;




        •  basic aluminum  sulfate absorption;




        •  thermal cycle absorption (using water as solvent);




        •  alkali-metal sulfite/bisulfite absorption (Wellman-Lord



           process);




     •  Processes Yielding Elementary  Sulfur:




        •  reduction of high-concentration sulfur dioxide  by hot coke;




        •  reduction of dilute sulfur  dioxide  by produce gas  (a mix-




           ture of hydrogen and carbon monoxide);




        *  reduction of dilute sulfur  dioxide  by reformed  natural




           gas  (methane);




        •  reduction of sulfur dioxide by methane  (non-catalytic);




        •  reduction of sulfur dioxide by methane  (the West process);




        •  reduction  of sulfur dioxide by hydrogen  sulfide  (the Glaus




           process).




     Three processes  (or combinations)  from among  the above were se-




lected as adequate to exploit  the full range of  potentials for sulfur




value recovery presented by the  five case studies.   These were employed




as follows:




     Case A — "Standard"  Contact  Process;




     Case B — Monsanto Cat-Ox Process;




     Case C — Magnesium Sulfite/Oxide  Process;




     Case D — Magnesium Sulfite/Oxide  Process;




     Case E — Monsanto Cat-Ox Process.






                                    237

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     8.5.6  Process Description and Fuel Composition for Each  Case  Study^




     Summary descriptions of the processes, fuels, and products  for  each




case study are presented in Tables XXXIX, XL, XLI, XLII, and XLIII.




Process flow charts for each case study can be found in Reference 25,




Part VII; additional design detail is presented in Parts XIII  through




XVII of this reference.  The Case C prototype plant design is  accorded




special attention in Part XV.




     To facilitate comparison among the five case studies, the fuel  in-




put requirements and outputs of each are summarized in Table XLIV.   This




table shows the quantities of clean coal produced and the quantity of




high sulfur fuel derived from the coal-cleaning reject material.  It




also shows the resulting energy value and sulfur value obtained  from




utilizing the high sulfur fuel.  Equivalent quantities of sulfur pro-




ducts for each case study are shown for purposes of comparison; how-'




ever, the equipment specified in certain of the case studies is not




adapted to produce all of the sulfur products shown in this Table.   Com-




parison of the relative quantities of the various forms of sulfur pro-




ducts suggest that when the product is to be shipped over considerable




distances or when storage space is at a premium it may be highly ad-




vantageous to produce the sulfur in elemental form, or as another sul-




fur compound, instead of sulfuric acid.




8.6  Economic Analyses of the Five System Designs




     Capital costs and annual operating costs (less cost of high sulfur




fuels) for the processing system employed in each case study were







                                    238

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                         TABLE XXXIX
                      SUMMARY OF CASE A
PRODUCTS

     Energy Product:     500,000 Ib/hour at 825°F

     Sulfur Product:     gg% sulfuric  acid, equivalent to 1830 tons/day
                          C100% basis)

SUMMARY

      A run of mines bituminous  coal containing 3 to 4.5% sulfur,
washable to 1% sulfur, is assumed.  The reject is treated for
maximum yield of a high-sulfur  fuel of the CASE A specification.
This fuel is pulverized and  fired to raise 500,000 Ibs/hr of
industrial quality steam and a  flue gas containing 6% sulfur dioxide
and 4.3% oxygen.  The gas is wet cleaned in a packed tower,  dried
and converted catalytically  to  sulfur trioxide which is reacted
with water to make 98% sulfuric acid at the rate of 1,830 net tons
(100% basis) per day, 330 days  per year.  Sulfur emission equals
0.4% of sulfur charged.  Sulfur not emitted equals 93 pounds per
million Btu of heat recovered in the CASE A System, or 2,2 pounds
per million Btu of ROM coal  charged to the cleaning plant.

FUEL CHARACTERISTICS
                  „ n   „  .  4,*      Run of      Clean     High-Sulfur
Constituents (Wt. /. Dry Basis*)     fflne Coal    Coal         Fuel

     Iron Pyrite                                  1-0         61.6

     Organic Sulfur                               1-0          0.2
     Total Sulfur                   3 to 4.5                 (33.1)

     Coal Combustibles                                        18-2

     Non-Pyritic Ash                                          20-°

M Tons/Year                                                  64°'°
Tons/Hr:   Iron Pyrite                                        49.3
           Coal Combustibles                                 u-7

           Non-Pyritic Ash                                    16-°

Sulfur/Coal Ratio                                              1'8

BTU/LB                                                       442°

BTU/HR     .
* 6% Moisture  assumed  in high  sulfur fuel as fired

Source:  Adpated  from
         Reference 25  (1971).
                                    239

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                            TABLE XL
                      SUMMARY OF CASE B
PRODUCTS
     Energy Product:    500,000 Ib/hour at 825°F

     Sulfur Product:    77% sulfuric acid equivalent to 624 tons/day
                        (100% basis)
SUMMARY

      A run of mine bituminous coal containing 3 to 4.5% sulfur»
washable to 1% sulfur, is assumed.  The reject is treated for
maximum yield of a high sulfur fuel of the CASE B specification.
This fuel is pulverized and fired to raise 500,000 Ibs/hour of
industrial quality steam and a flue gas containing 2% sulfur
dioxide and 4.2% oxygen.  The gas is cleaned of particulates in an
electric precipitator at 805° F and is then converted catalytically
to sulfur trioxide which is reacted with water to make 77%-80% sulfuric
acid by the Cat-Ox process of Monsanto at the rate of 624 net tons
(100% basis) per day, 330 days per year.  Sulfur emission equals
0.5% of sulfur charged.  Sulfur not emitted equals 33 pounds per
million Btu of heat recovered in the CASE B System, or 2.0 pounds
per million Btu of ROM coal charged to the cleaning plant.
FUEL CHARACTERISTICS

Constituents (Wt. % Dry Basis*)     *un °f 1     Clean    High-Sulfur
                                   Mine Coal     Coal        Fuel
     Iron Pyrite                                              33.8

     Organic Sulfur                                           0.5

     Total Sulfur                  3 to 4.5                 (18f5)
     Coal Combustibles                                       45.7

     Non-Pyritic Ash                                         20.0

M Tons/Year                                                 406

Tons/Hr:   Iron Pyrite                                       17.1

           Coal Combustibles                                 23.4
           Non-Pyritic Ash                                   10.i

Sulfur/Coal Ratio                 .-..                           0.4

BTU/LB                                                     7400

BTU/HR                                                   750 x 1Q6
* 6% Moisture assumed in high sulfur fuel as fired
Source:  Adapted from
         Reference 25 (1971).
                             240

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                             TABLE XLI
                        SUMMARY OF CASE C
PRODUCTS

     Energy Product:     50  megawatts electric at 500° F

     Sulfur Product:     102 tons/day elemental sulfur


SUMMARY

      A run of mine bituminous  coal  containing 3 to 4.5% sulfur,
washable to 1% sulfur,  is assumed.   The reject is treated for
maximum yield of a high sulfur  fuel  of the CASE C and D specification.
This fuel is pulverized and  fired to raise 500,000 Ibs/hr of sub-
critical steam which is fed  to  a turbo-generator of 50 MW capacity.
The flue gas containing about 1% sulfur dioxide and 4.3% oxygen is
wet-cleaned in a venturi scrubber and led to a two-stage-venturi
absorber in which sulfur dioxide is.reacted, essentially with
magnesium oxide, to produce  magnesium sulfite.  This salt is
separated, dried, and calcined  to yield a 15% sulfur dioxide gas
concentrate and magnesium oxide which is recycled.   The 15% sulfur
dioxide is converted by catalytic reduction to sulfur at the rate
of about 100 net tons per day,  330 days per year.   Sulfur emission
equals 1.3% of sulfur charged.  Sulfur not emitted equals 16 pounds
per million Btu of heat recovered in the CASE C Prototype System,
or 2.2 pounds per million Btu of ROM coal charged to the cleaning
plant.
FUEL CHARACTERISTICS
                                    Run of       Clean    High-Sulfur
Constituents  (Wt.  % Dry Basis*)   Mine Coal     Coal        Fuel

      Iron Pyrite                                             20.8

     Organic  Sulfur                              1.0          0.6
     Total  Sulfur                  3 to 4.5                 (11.7)

     Coal Combustibles                                       58.6

     Non-Pyritic Ash                                         20.0

M Tons/Year                                                 298.0

Tons/Hr:  Iron Pyrite                                         7.7
          Coal Combustibles                                  22-°
          Non-Pyritic Ash                                     7-4

Sulfur/Coal Ratio                                             °-2

BTU/LB                                                     900°

BTU/HR                                                    67° x 10
* 6% Moisture assumed in high sulfur fuel as fired

Source:  Adapted  from
         Reference 25 (1971).
                              241

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                           TABLE XLII
                      SUMMARY OF CASED
PRODUCTS
     Ene
     Sulfur Product:     770 tons/day elemental sulfur
Energy Product:     500 megawatts electric at  500  F
SUMMARY
      A run of mine bituminous coal containing 3 to 4.5% sulfur,
washable to 1% sulfur, is assumed.   The reject is treated for
maximum yield of a high sulfur fuel of the CASE C and D specification.
The fuel is pulverized and fired to raise 3.5 million pounds per
hour of subcritical steam which is  fed to a turbo-generator of
500 MW capacity.  The flue gas composition is identical to that of
CASE C and is treated in an identical manner to yield 770 net tons
per day of sulfur.  Sulfur emission equals 0.8% of sulfur charged.
Sulfur not emitted equals 16 pounds per million Btu of heat recovered
in the CASE D System, or 2.3 pounds per million Btu of ROM coal
charged to the cleaning plant.
FUEL CHARACTERISTICS
Constituents (Wt. % Dry Basis*)       Run of       Clean    High-Sulfur
                                    Mine Coal     Coal        Fuel
     Iron Pyrite                                               20.8
     Organic Sulfur                                             0.6
     Total Sulfur                   3 to 4.5                  (11.7)
     Coal Combustibles                                         58.6
     Non-Pyritic Ash                                           20.0
M Tons/Year                                                  2280
Tons/Hr:   Iron Pyrite                                         59.3
           Coal Combustibles                                  338.0
           Non-Pyritic Ash                                     57.0
Sulfur/Coal Ratio                                               0.2
BTU/LB                                                       9000
BTU/HR                                                     5,128  x 1Q6
* 6% Moisture assumed in high sulfur fuel as fired

Source:  Adapted from
         Reference 25 (1971).
                                242

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                             TABLE XLIII
                        SUMMARY OF CASE E

PRODUCTS

      Energy Product:    500 megawatts electric power at 850° F
      Sulfur Product:    77% sulfuric acid, equivalent to 1420 tons/day
                          (100% basis)
SUMMARY

      A run of mine bituminous coal containing 3 to 4.5% sulfur,
washable to 1% sulfur, is assumed.  The reject is treated for
maximum yield of a high sulfur fuel of the CASE E specification.
This fuel is pulverized and fired to raise 3.5 million pounds per
hour of sub-critical steam which is fed to a turbo-generator of
500 MW capacity.  The flue gas containing 0.7% sulfur dioxide and
4.2% oxygen is treated by the Monsanto Cat-Ox process in a manner
similar to CASE B, but in multiple trains, to yield 1,420 net tons
(100% basis) of 77%-80% sulfuric acid per day.  Sulfur emission
equals 1.5% sulfur charged.  Sulfur not emitted equals 10 pounds
per million Btu recovered in the CASE E System, or 2.3 pounds per
million Btu of ROM coal charged to the cleaning plant.

FUEL CHARACTERISTICS
                                      Run of      Clean    High-Sulfur
Constituents (Wt. % Dry Basis*)      Mine Coal    Coal        Fuel

     Iron Pyrite                                               13.2

     Organic Sulfur                                            0.9
     Total Sulfur                     3 to 4.5                 (7.9)

     Coal Combustibles                                         65-9

     Non-Pyritic Ash                                           20-°

M Tons/Year                                                  2133
Tons/Hr:   Iron Pyrite                                         35.2
           Coal Combustibles                                  178.0

           Non-Pyritic Ash                                     53-3

Sulfur/Coal Ratio                                              °'12

BTU/LB                                                       966°     ,

BTU/HR
* 6% Moisture assumed in high sulfur fuel as fired
Source:  Adpated from
         Reference 25  (1971).
                                243

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                                                                                                TABLE XLIV
                                                                           SUMMARY OF INPUTS AMD OUTPUTS FOfl FIVE CASE STUDIES
IO
Case
D
A
E
B
C
Input
(Million Tons/Yr.)
Run-of-Mine
Coal
9.7
8.1
5.8
2.8
1.3
Output of Coal
Processing Operation
(Million Tons/Yr.)
Clean
Coal
7.1
7.1
3.5
2.3
0.9
High-Sulfur
Fuel
2.3
0.6
2.1
0.4
0.3
Output of Power and Sulfur Recovery Operations
Enerey
Electrical
(Hegasatts)
500

500

50
Steam
(Lb./Hour at 825 F)

500,000

500,000

Sulfur Values (Net Tons/Dav. Appro*.
Elenental
Sulfur
770*
640
510
230
102*
Sulfuric
Acid
Equivalent
2300
1830*
1420*
£24*
291
Magnesium
Sulfate
Equivalent
2500
1980
1580
710
310

Liquid
Sulfur Dioxide
Equivalent
1520
1220
970
440
190
                     Votes:  (1)  BOB:  1Z organic S,  3Z pyritic S, 13Z non-pyritic ash.
                             -(2)  Clean Coal:  12 organic S,  5Z non-pyritic ash
                             (3)  Clean Coal + HSC fuel - 95Z of ROM weight (dry basis)
                             (4)  Total cleaning losses = 5Z
                                                                                                                             * Design Basis for this Case Study
                     Source:  Adapted fro. Reference 25 C1971).

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determined.  Anticipated  income from sale of products was then estimated,

and the allowable cost  of high sulfur fuels was determined by difference.

     8.6.1  Method  for  Valuation of High-Sulfur Fuels

     The various systems  used to recover energy and sulfur values from

coal-pyrites may be considered salvage systems to improve the economics

of coal cleaning.   Sales  income, less all costs for energy and sulfur

value recovery and  other  expense, is a basis for valuation of high

sulfur fuels.  The  value  of .the high sulfur fuel is determined as

follows:

     High  Sulfur Fuel Value = Sales Value of Products (Electric power,

                               sulfuric acid, etc)

     less:  - Selling and Commercial Expense

            - Extraction  Costs

            - General Expense and Income Tax

            - High-sulfur Fuel Preparation, Transport and Handling
              Costs ("Precombustion Costs")

     plus:  Cost of Dumping Refuse (shown as a "plus" to  indicate
            a credit for  avoidance of dumping costs).

     The "precombustion cost" term has been estimated to  be  on the

order of 81 cents per ton of  high sulfur fuel delivered to the combustor;

this would increase for longer shipping distances.   The dumping cost

has been estimated  as lying between $1 and $2 per ton of  refuse.  (Each

of these estimates  is highly ""variable with local conditions  (land cost,

shipping distances,  etc.)).   For the present analysis, the assumption

is made that it is  as cheap to prepare and deliver  high sulfur fuel as


                                     245

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it is to handle and dump an equal tonnage of refuse; that is,  the  pre-

combustion costs and dumping costs cancel one another out in the above

formula.

     8.6.2  Capital Costs

     Capital costs are considered to include the costs of construction

labor, plant equipment, and material in 1971 or 1972.  Cost escalations,
               It
estimated as 10 percent/year for electrical equipment and 6 to 8 percent

for the chemical plant beyond 1972 are not included in the cost analysis.

Estimated capital costs for the five case-study systems are given  in

Table XLV.

     8.6.3  Operating Costs

     This category includes all costs for extraction of energy and

sulfur values except those for high-sulfur fuel, which will be determined

later by difference.  In addition to annual costs for utilities, labor

and supervision, maintenance, and general plant expense, operating costs

also include annualized capital costs to the extent that these are re-

flected by depreciation and interest.

     Operating cost estimates were prepared for each of the five case

studies using utilities prevalent in the six-state area of interest

(Pennsylvania, Ohio, West Virginia, Kentucky, Indiana, and Illinois)

during late 1970.  Detailed data for Case C  (the 50 MW prototype de-

sign) is shown in Table XLVI to illustrate the presentation format.

(Data for the other cases not included in this summary report  can  be

found in Reference 25, Part VIII.)


                                  246

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                               TABLE XLV

                        ESTIMATED CAPITAL COST
Combust or/Bo Her

Electric Equipment

Sulfur Recovery

Off-Sites

Land

     Fixed Capital
     Working Capital

     Total Capital
CASE A
 $M

 5,110



11,300

 1,550

   250

18,210
   130
 CASE B
  $M

 4,210
12,500

 1,550

   250

18,510
    90
18,340    18,600
 CASE C
  $M

 4,310

11,200

10,900

 2,550

   250

29,210
	60

29.270
 CASE D
  $M

 15,760

 56,200

 44,000

 10,100

  1.000

128,060
    460
 CASE E
  $M

 11,760

 56,200

 45,700

 10,500

  1.000

125,160
    410
                      128.520    125.570
Source:  Reference 25  (1971).
                                  247

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                           TABLE XLVI




            CASE C SYSTEM ESTIMATED OPERATING COST






                                   ELECTRICITY
SULFUR
Unit
Unit Value
Production
Energy MWH
Sulfur Value L.T.
Utilities, etc.
Electricity MWH $7.50
Cooling Water MMgal. 8.00
Boiler Feed Water Mgal. 0.60
Process Water Mgal. 0.40
Fuel Gas MMBtu 0.40
Chemicals
Waste Disposal N.T. 2.00
Labojr
Supervision Manhour 8.00
Operators and
Helpers Manhour 5.50
Maintenance
Plant General Expense
Factory
Overhead 80% of Direct
Taxes and
Insurance 2.5% of Total
Total Before Depreciation and Interest
Depreciation
Guideline Life 11 Years 9.1%
Guideline Life 28 Years 3.6%
Interest (Average)
Depreciable Capital 4.5%
Non-Depreciable Capital 9%
Cost Before HSC Fuel Charge (Rounded)
Units Annual
Per Year Cost

400,000
3,360 M$ 25
21,600 173
5 3
110,000 220

8,760 70
44,000 242
280
Labor 194
Capital 403
M$l,610
578

723
153
M$3,060
Units Annual
Per Year Cost

30,910
37,360 M$ 280
268 2
113,000 45
2,100,000 840
81
25,400 51

8,760 70
32,000 176
430
141
329
M$2,445
1,174

581
126
M$4,330

Source:  Reference 25  (1971),
                                 248

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     In these presentations, separate  costs  are  assigned to  the pro-

duction of energy and chemical values.   Ground rules  used in the in-

itial analysis assign all  costs for  "pollution control" to the  re-

covery of chemical values  rather  than  apportioning  it between the

two classes of products.   This leads to  an apparent low cost of energy

production and a high cost of chemical value recovery.   An adjustment

for this effect is indicated in the  following section on Operating

Economics.

     8.6.4  Operating Economics;   Cost of High-Sulfur Fuel

     The method for  estimating allowable prices  for high-sulfur reject

material is shown in Tables XLVTI and  XLVIII.  Here,  the expected  in-

come from selling products of the five case  study plants is  computed

on the basic prices  expected to prevail  in the six-state area,  based

on an analysis of price  trends.   Unit  price  assumptions  are  shown  in

Table XLVII.  Values of  energy products  and  chemical  products are

treated separately.

     The various categories of expense—costs of selling,  operation,
                         (
etc.—are then subtracted  from the income from sales.   The resulting

pre-tax income is adjusted for "pollution control" expense,  which  is

required because of  a computational  ground rule which assigned  all

pollution control costs  to the sulfur  recovery portion  of  the system.

Note that this adjustment  does not affect the combined  income,  but

merely shifts a part of  the expense  from one product  category to an-

other.  It should be noted that the  pollution control tariff reflected


                                   249

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                                                                          TABLE XLV1I
                                                      INCOME FROM SALES COSTS OF OPERATION AND PRODUCTS
                                                                 GAIN OR LOSS FROM OPERATION

                                                                           ANKUAL BASIS
Income From Sales

  Steam

  Electricity


  Sulfur


  Sulfuric Acid (100%)
Less:  Selling & Commercial
  Expense @  1% of Sales Value
          @  5% of Sales Valm

Operating Cost
General & Administrative
  @ 2Z of Sales
Adjustment for "Pollution Control"

  Add
  Deduct
Adjusted Cost of Energy Extraction
  Unit Cost of Energy Products:
    Per Net Ton of Steam
    Per Hegawatt Hour
  Unit Cost of Sulfur Products:
    Per Long Ton of Sulfur
    Per Set Ton of Sulfuric Acid

 Combined Sales Ttelue of Products
 All Costs Before U.S. Income Tax

Unit Annual
Unit Value Quantity
Sec Ton $ 1.30 2,000,000
MHH 7.50 400,000
4,000,000
Long Ton 25.0 30,910
233,300
Het Ton 12.75 610,000
208,000
473,300
1
alue
alue
ome Tax (Rounded)
Control"
[traction
ucts:

Value Recovery
ucts:
c Acid
oducts
Income Tax
CASE A
Sulfuric
Steam Acid
M$ 2,600


M$7,780
26
389
2,540 3,820
52 156
H$ 2,620 M$4,370
9,380
9,380
M$12,000
$ 6.00

(H$5,010)
H510.380
6,990
MS 3.390
CASE B
Sulfuric
Steam Acid
M$2,*00


MS2.650
26
132
1,880 3,910
52 53
M$l,960 M$4J100
4,520
4,520
MS6.4BO
$ 3.20

(H$ 420)
( 2.00)
H$ 5,250
6,060
01$ 810)
CASE C
Electricity Sulfur

MS30.000
M$ 770

30
39
3,060 4,330
60 15
MS3.150 M? 4,380
2,630
2,630
M55,780
$ 14.50

MS 1,750
MS 3,770
7,530
(MS 3,760)
CASK D
Electricity Sulfur

H$30.000
MS 5.830

300
292
12,600 20,630
600 117
HS13.500 MS 21, 000
14,450
14,450
MS28.000
$ 7.00

MS 6,550
S 28.00
M$ 35,830
34,500
HS 1,330
CASE E
Sulfuric
Electricity Acid

MS 30, 000

H$ 6.040
300
302
11,630 14,970
600 m
M$12,500 MS15.400
10,620
10.620
H$23,100
$ 5.80

M$ 4,780
MS 36,040
27,908
MS 8,140
                           Source:  Reference 25  U971)

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                                                TABLE XLVIII

                             VALUE  OF HSC FUELS,  OFFSET TO CLEANING COST,
                                         PAYOUT OF INVESTMENT


    Value  of HSC  Fuels;

    Taxable Gain  (or Loss)                  M$ 3,390    (M$    810)    (M$ 3,760)    M$ 1,330   M$ 8,140
    Gain  (or Loss)  After 48% Tax Effect    M$ 1,760    (M$    420)    (M$ 1,960)    M$   690   M$ 4,230

    HSC Fuel Consumed -  M Tons Per  Year         640           410          300       2,300      2,100
    Value  of HSC  Fuel -  Per Ton             $ 2.75     ( $  1.02     ( $ 6.53)     $ 0.30     $ 2.01

    Offset to  Coal Cleaning:

     Clean Coal Yield - M Tons  Per Year        7,100         2,300          920       7,100      3,500
to    Credit (or Debit) Per Ton  of Clean Coal $ 0.25     ( $  0.18)    ( $ 2.13)     $ 0.10     $ 1.21
Ol
\->
    Payout of  Investment:

     Gain (or Loss) After  48% Tax Effect     M$ 1,760    (M$    420)    (M$ 1,960)    M$   690   M$ 4,230
     Depreciation                              1,634         1,662        1,752       7,169      7,214

     Cash Flow                              M$ 3,394     M$  1,242    (M$   208)    M$ 7,859   M$ll,444

     Total Investment                         18,340        18,600       29,270     128,520    125,570

    Payout - Years                            5.4          15           —         16         11

          Source:   Reference 25 (1971).

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by the adjustment costs is much more severe than ordinarily required




in conventional coal-fired generators of comparable capacity.  This is




because of the high sulfur content and ash content of the reject ma-




terials used as fuel.




     Sales income from energy and chemical values, after adjustment




for pollution costs and other expenses, are then combined to form  the




total taxable income for each type of plant.  A 48 percent income  is




applied to yield the net yearly gain for the plant of each design  (Table




XLVIII).  Dividing this figure by the weight of high sulfur fuel con-




sumed per year yields an estimate of the cost that the manufacturer




could afford to. pay for these fuels.




     Table XLVIII indicates that three of the production plant designs




(Cases A, D, and E) show net gains (sales price less total costs)  rang-




ing from $0.30 to $2.75 per ton of high sulfur fuel derived from HSC




fuel utilization.  This corresponds to pre-sales credits ranging from




$0.10 to $1.21 per ton of the clean coal.  In other words, the HSC fuel




can be used for an economic advantage in addition to any profits gained




from selling the low sulfur coal.  Case B shows a net loss and there-




fore appears uneconomical.  The prototype plant design, Case C, also




shows a relatively high net loss and appears uneconomical as a production




process.   This is not surprising nor is it significant since Case  C




is a scaled-down version of Case D (which is economically feasible) and




is intended to serve as a research and demonstration unit.
                                    252

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     The economic analysis  summarized  in  Tables XLV,  XLVII,  and XLVIII.




does not present production costs  and  income  on a strictly comparable




basis, since Cases A, B, and  E  yield sulfuric acid as an end product,




while Case D (and the scaled  down  version in  Case C)  yields  elemental




sulfur as an end product.   The  analysis of Case D was extended  to




include the conversion  of sulfur to sulfuric  acid and the marketing




of the acid,  An analysis similar  to that of  Tables XLVII and XLVIII




shows that, under these conditions, the allowable price  for  high-




sulfur fuel for the Case D  plant would be about $2.00 per ton,  which




corresponds to a credit of  about $0.97 per ton of clean  coal.




     This extension of  the  analysis indicates that the plant  design




for Case D is much more competitive with  the  design for  Cases A and




E than is apparent from the figures presented in  Table XLVIII.   In




addition, the Case D design permits production of elemental  sulfur




or.other acid intermediates as  well as sulfuric acid,  thereby provid-




ing a flexibility for adapting  plant output to logistic  and market




conditions.




8.7  Findings




     The following conclusions  may be  drawn from  the  Chemico  study,




supported by the research on  high-sulfur  fuel composition conducted by




Bituminous Coal Research, Inc.  (BCR):




     •  Any run-of-mine coal  containing pyritic sulfur that  can be




        processed to yield  coal of lower  sulfur content  will  also




        yield a fuel of higher  sulfur  content.  The sulfur-to-coal






                                    253

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   ratio of the high sulfur fuel can be controlled to any specifi-




   cation within wide limits.




•  By using high-sulfur fuels of composition tailored to meet re-




   quirements of especially designed combustors and commercially




   available boilers, generators and sulfur-recovery processes,




   it appears possible to extract the energy and sulfur values




   of high-sulfur fuels on a commercially profitable basis.




•  By appropriate selection of processing equipment, energy values




   may be realized in the form of electric power or industrial-




   quality steam and sulfur values may be in the form of sulfuric




   acid, elemental sulfur, or other intermediate compounds.




•  In view of the high shipping costs resulting from the heavy




   weight of sulfuric acid, it is sometimes economically advanta-^




   geous to ship sulfur in elemental form or as other compounds




   instead of the acid.  The capability of a sulfur recovery plant




   to produce sulfur as several different compounds (or in elemental




   form) is therefore highly advantageous, especially in cases when




   the sulfur must be shipped to different points of consumption




•  Preliminary design and analysis indicate that construction of a




   reduced-scale prototype would be warranted for research and




   development efforts required to evaluate the promising, but as




   yet undemonstrated, approach typified by the Case D design—




   large scale (500 raw) electric power generating capacity, with
                               254

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versatile equipment for  recovering  sulfur  in  several  alterna-




tive forms  to meet various  market and logistic  situations.   The




need for demonstration of  the  capability to process high sulfur




fuels  in a  commercially  and environmentally acceptable manner




is underscored  by recent (1973)  shortages  of  low-sulfur fossil




fuels.
                              255

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                              REFERENCES


1.   W. E. Morrison, Disaggregated Energy Consumption by  Source, Form,
     and Sector, Office of Economics, Federal Power Commission, Feb-
     ruary 1973.

2.   Paul Weir Company, Inc., "An Economic Feasibility  Study of Coal
     Desulfurization", Volumes  I & II, A Study  for the  Division of Air
     Pollution, Public Health Service, U.S. Department  of Health, Edu-
     cation and Welfare, Contract No. PH 86-65-29, October 1965.

3.   "Report of Results of Washability Tests on Raw Run of Mine Coal
     Samples," for U.S. Public  Health Service,  National Center for Air
     Pollution Control, Cincinnati, Ohio, Commercial Testing and Engineer-
     ing Company, Contract No.  PH27-00079, December 1967.

4.   "Report of Results of Washability Tests on Raw Run of Mine Coal
     Samples," for U.S. Public  Health Service,  National Center for Air
     Pollution Control, Cincinnati, Ohio, Commercial Testing and Engi-
     neering Company, Contract  No. CPA-69-645,  November 1969.

5.   "Report of Results of Washability Tests on Raw Run of Mine Coal
     Samples," for U.S. Public  Health Service,  National Center for Air
     Pollution Control, Cincinnati, Ohio, Contract No.  CPA-69-530,
     April 1969.

6.   "An Evaluation  of Coal  Cleaning Processes  and Techniques for Re-
     moving Pyritic  Sulfur from Fine Coal," Bituminous  Coal Research,
     Inc., Public Health Service, for U.S. Department of Health. Edu-
     cation and Welfare, Contract No. PH-86-67-139, September 1969.

7.   R. J. Helfinstine, N. F. Shimp, and J. A.  Simon, "Sulfur Varieties
     in Illinois Coals, Float-Sink Tests," Report of Study Phase I,
     Supported in part by U.S.  Public Health Service, Department of
     Health, Education and Welfare, Contract No. PH 86-67-206, Illinois
     State Geological Survey, Urbana, Illinois, August  10, 1969.

8.   A. W. Deurbrouck, "Sulfur  Reduction Potential of the Coals of the
     United States," Report of Investigation 7633, Bureau of Mines,
     U.S. Department of Interior, 1972.

     Ibid, Appendix  I, "Sulfur  Concentration in Coal-A  Washability
     Study," November 1971,  in  Press.

     Ibid, Appendix  II, "A Statistical Evaluation of Ash and Sulfur
     Contents of U.S. Coals,"   November 1971, in Press.
                                    257

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     Ibid, Appendix III, "Graphical Summation of Appendices I and  II
     by Coalbeds and Regions," in Press.

9.   Hoffman, L., et al. "Survey of Coal Availabilities by Sulfur
     Content,"  MITRE Corporation Technical Report MTR-6086, May 1972

10.  "An Evaluation of Coal Cleaning Processes and Techniques for  Re-
     moving Pyritic Sulfur from Fine Coal,"  Bituminous Coal Research,
     Inc., Monroeville, Pennsylvania, February 1970.

11.  R. J. Helfinstine, N. F. Shimp, J. A. Simon, and M. E. Hopkins,
     "Sulfur Reduction in Illinois Coals - Washability Studies," Re-
     port of Study Phase II, supported in part by U.S. Public Health
     Service, Department of Health, Education and Welfare, Contract
     No. PH86-67-206, Illinois State Geological Survey, Urbana,
     Illinois, July 28, 1971.

12.  J. A. Cavallaro, A. W. Deurbrouck, and A. F. Baker, "Physical
     Desulfurization of Coal," Paper D28, Bureau of Mines, United
     States Department of the Interior.

13.  K. J. Miller and A. F. Baker, "Electrophoretic - Specific Gravity
     Separation of Pyrite from Coal,"  Bureau of Mines Report of
     Investigations, October 1970.

14.  A. W. Deurbrouck, Private Communication.

15.  A. F. Baker and K. J. Miller, "Hydrolyzed Metal Ions as Pyrite
     Depressants in Coal Flotation:  A Laboratory Study," Report of
     Bureau of Mines Investigations 7518, May 1971.

16.  K. J. Miller and A. F. Baker, "Flotation of Pyrite from Coal,"
     Bureau of Mines, Technical Progress Report«-51, February 1972.

17.  J. A. Cavallaro and A. W- Deurbrouck, "Froth Flotation Washability
     Data of Various Appalachian Coals Using Timed Release Analysis
     Technique,"  U.S. Bureau of Mines Report No. RI6652, 1965.

18.  Roberts and Schaefer Company, "Design and Cost Analysis for a
     Prototype Coal Cleaning Plant," Volume 1, July 15, 1969, Revised
     August 12, 1969.

19.  Roberts and Schaefer Company, "Design and Cost Analysis for a
     Prototype Coal Cleaning Plant,"  Volume 2, July 15, 1969,
     Revised August 12, 1969.

20.  Roberts and Schaefer Company, "Supplemental Report to Design  and
     Cost Analysis Study for a Prototype Coal Cleaning Plant," January
     7, 1970.
                                    258

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21.  'McNally, Pittsburg Mgf. Corp. "A Study on Design and Cost Analysis
     of a Prototype Coal Cleaning Plant," Prepared for National Air
     Pollution Control Administration Contract PH22-68-59, Parts I-VI,
     November 1969.

     Ibid., Part VII, "Coal Cleaning Plant:  Prototype Plant Specifi-
     cations"

     Ibid., Part VIII, "Coal Cleaning Plant:  Prototype Plant Design
     Drawings"

22.   Roberts and Schaefer Company, "Research Program for the Prototype
     Coal Cleaning Plant,"  Contract No. CPA 70-157, Program Element
     No. IA2013, January 1973.

23.   Bechtel Corporation, "Process Costs and Economics of Pyrite-Coal
     Utilization," A Report to National Air Pollution Control Adminis-
     tration, Contract No. PH86-27-224, December 1968.

24.   Arthur D. Little, Inc., "A  Study of Process Costs and Economics
     of Pyrite-Coal Utilization, A Report to Consumer Protection and
     Environmental Health Service, Contract No. PH86-27-258, March 1968.

25.   Chemico, "The High Sulfur Combustor," Final Report to Division of
     Process Control Engineering, National Air Pollution Control Adminis-
     tration, Contract No. CPA22-69-151, February 1971.

     Ibid., Volume II.

                         ADDITIONAL REFERENCES

     A. W. Deurbrouck and E. R.  Palowitch, "Performance Characteristics
     of Coal-Washing Equipment:  Concentrating Tables,"  Report of In-
     vestigations 6239, Bureau of Mines, United States Department of
     the Interior, 1963.

     Deurbrouck, Albert W., "Performance Characteristics of Coal-Washing
     Equipment:  Hydrocyclones," Report of Investigations 7891, Bureau of
     Mines, United States Department of the Interior, 1974.

     Joseph W. Leonard and David R. Mitchell, Eds., "Coal Preparation,"
     3rd ed,, The American Institute of Mining, Metallurgical, and
     Petroleum Engineers, Inc., New York, N.Y., 1968.

     R. J.  Helfinstine, N. F. Shrimp, J. A. Simon, and M. E. Hopkins,
     "Sulfur Reduction of Illinois Coals - Washability Studies Part 1,"
     Circular 462,  Illinois State Geological Survey, Urbana, Illinois,
     1971.
                                 259

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Miller, Kenneth J., "Flotation of Pyrite from Coal:   Pilot Plant Study,"
Report of Investigations 7822, Bureau of Mines, United States Department
of the Interior, 1973.
                               260

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                                 TECHNICAL REPORT DATA
                          (Please reaJ iHsiriictiuns on I/it- reverse before coii
 1. REPORT NO.
 EPA-650/2-74-030
                            2.
                                                       3. RECIPIENT'S ACCESSION-NO.
 . TITLE AND SUBTITLE
 An Interpretative Compilation of EPA Studies
      Related to Coal Quality and Cleanability
                                  G. REPORT DATE
                                  May 1974
                                  6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

 L.Hoffman, J. B. Truett, and S.J. Aresco
                                                       8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 The Mitre Corporation
 Westgate Research Park
 McLean, Virginia 22101
                                  10. PROGRAM ELEMENT NO.

                                  1AB013; ROAP 21AFJ-27
                                  11. CONTRACT/GRANT NO.
                                  68-02-1352
12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 NERC-RTP, Control Systems Laboratory
 Research Triangle Park, NC 27711
                                                        13»TYPJE OF REPORT AND PERIOD COVERED
                                                        Final
                                  14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
 The report provides an interpretative compilation of the overall EPA coal cleaning
 effort in the form of in-depth analysis, evaluation, and examination of the inter-
 relationships among elements comprising the EPA coal program.  The report
 basically addresses coal washability studies , sulfur reduction by cleaning processes
 including plant design and associated economics , and the utilization of reject sulfur
 and coal values from the cleaning processes.
17.
                              KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                           b.IDENTIFIERS/OPEN ENDED TERMS
                                               c.  COSATl l-'icld/Group
 Air Pollution
 Coal
 Coal Preparation
 Washing
 Desulfurization
 Sulfur
Design Criteria
Economic Analysis
Reclamation
Air Pollution Control
Stationary Sources
Reject Sulfur
Reject Coal Values
13B,  14A
21D
081
13H,  07A
07D
07B
13. DISTRIBUTION STATEMENT

 Unlimited
                      19. SECURITY CLASS (This Report)
                      Unclassified
                                               21. NO. OF PAGES
                             276
                                           20. SECURITY CLASS (Thispage)
                                           Unclassified
                                                                    22. PRICE
EPA Form 2220-1 (9-73)
             261

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