PB84-133347
    Process Modifications Towards Minimization of
    Environmental Pollutants in the
    Chemical Processing Industry
    Illinois Inst. of Tech., Chicago
    Prepared for

    Industrial Environmental Research
    Lab.-Cincinnati, OR
    Nov 83
U.S. Department of Corererw
National Ta&tol fe&mntkn Serin

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                                              EPA-COO/2-83-120
                                              November 1983
       PROCESS MODIFICATIONS TOWARDS
  MINIMIZATION OF ENVIRONMENTAL POLLUTANTS
    IN THE CHEMICAL PROCESSING INDUSTRY
          Professor L. L. Tavlarldes
     Department of Chemical Engineering
       Illinois Institute of Technology
           Chicago, Illinois  60616
            EPA Cooperative Agreement
                 CF. 80G819-01
               EPA Project Officer
                William A. Cawley
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORf
     OFFICE OF RESEARCH AJD DEVET-OPHENT
    U.S.  ENVIRONMENTAL P;«07ECTIOH AGENCY
           CINCINNATI, Oil  45268

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                                  TECHNICAL REPORT DATA
                           IPteast read Initrucnons on tht reverse be'ore completing)
 REPORT NO.
 EPA-600/2-83-120
3 RECIPIENT'S ACCES'. ION NO.
     P88  k   13334?
 TITLE AND SUBTITLE
 Process Modifications Towards  Minimization of
 Environmental Pollutants in  the Chemical Processing
 Industry                          	^	
6. fERFORMINC ORGANIZATION CODE
 AUTHOR'S)
 Professor L.I.  Tavlarides
                                                            I. PERFORMING ORGANIZATION REPORT NO.
  REPORT DATE
  November 1983
                                                            10. PROGRAM ELEMENT NO.
 PERFORMING ORGANIZATION NAME AND ADDRESS
 Illinois Institute of Technology
 Chicago, Illinois  60616
11. CONTRACT/GRANT NO.

    CR80G819-01
2. SPONSORING AGENCY NAME AND ADDRESS
  USEPA  Industrial Environmental Research Laboratory
  26 West St.  CJair St.
  Cincinnati,  Ohio  45268
                                                            13. TYPE OF REPORT AND PERIOD COVERED
 14. SPONSORING AGENCY CCDE

   EPA 600/12
 S SUPPLEMENTARY NOTES
 6. ABSTRACT
The report covers the development of a matrix of  significant pollution problems and
attendant process modifications which would have  impact on the reduction or elimination
of pollutants inherent in these processes.  Industries covered are:   (1)  Refining of
Nonferrous Metals; (2) The Electroplating Industry;  (3) Coal Conversion  Processes;
 (4) Specialty Chemicals;(5)  The Paper & Pulp Industry; (6) Iron and Steel Industry;
 (7) The Primary Aluminum Industry; and (8) Phosphate Fertilizer Industry.

The matrix for each of the industries noted covers the individual process; the
pollutants .ind their sources in the process; the  nature of the pollutant and the
control strategy for mitigation or reduction of the pollutant.
17.
                                KEY WO PI OS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                               D.IDENTIFIERS/OPEN ENDED TERMS  C. COSATI Field/Group
18. DISTRIBUTIONS' VTEMENT
                                               19 SECURITY CLASb ,'77iuReport)
                                                                          21 NO. OF PAGES
                                               20 SECURITY CLASS (Thu pagel
                                                                          22 PRI
EPA Pofm 2220-1 (R«y. 4-77)   PREVIOUS EDITION is OBSOLETE

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                               DISCLAIMER

     This document has been reviewed by the U.S. Environmental
Protection Agency and approved for publication. It 1s 1n partial
fulfillment of Cooperative Agreement No. CR  806819-01 between the
Illinois Institute of Technology and the U.S. Environmental Protection
Agency and teas developed as part of the first year of the Industrial
Waste Elimination Research Center. Mention of trade names o.  commercial
products does not constitute endorsement or recommendation for use.
                                    11

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                              TABLE OF CONTENTS
LIST OF FIGURES .	      v

LIST OF TABLES	v111

LIST OF ABBREVIATIONS 	

INTRODUCTION  	     X1

CHAPTER                                                                Page

     I.   REFINING OF NONFERROUS METALS	1.1

          Introduction  	 1*1
          Copper Production by Pyrometallurgical Processes  	 1.1
               Comminution and Froth Flotation
               Roasting of Copper Concentrate
               Smelting
               Electroreflnlng
               Recommended Areas for Process Modification
          Copper Production by Hydrometallurgical
               Processes  ...... 	 1.11
               Leaching
               Cementation
               Solvent Extraction
               Recommended Areas of Process Modification
          Uranium Production by Hydrometallurgy Processes   	 1.16
               LeachlnR
               Solution Purification and Concentration
               Recommended Areas of Process Modification
          Bibliography  	 1.21

    II.   ELECTROPLATING	2.1

          Electroplating of Common Metals	2.1
               Recommendations for Process Modifications
               Bibliography 	 .......... 	 2.5
                                     111

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III.    COAL CONVERSION PROCESSES	3.1

        Introduction	3.1
        Liquefaction	3.1
             Solvent Refined Coal Liquefaction
               Particulate Emissions
               Coal Pile Drainage
               Gas Slag and Fly Ash
               Residue from Solids/Liquids Separation
               Spent Catalyst
               Tail Gas From Acid Gas Removal
               NOz Removal
               Recommended Areas for Pollution Control P< search:
                 SRC-Coal
                 Liquefaction Process
        Gaslfica:ion  	  3.11
             Lurgi Coal Gasification
               Coal Preparation
               Coal Gasification
               2as Purification
               Gas Upgrading
               Gasifi'jr and Boiler Ash
               'Spent Guard Catalyst
               Spent Shlft/Methanation Catalysts
               Ash Quench Slurry
               Removal of Sulfur Compounds from
                 'xectlsol Process
             Riicora&ended Areas for Pollution Control
               Research: Lurgi Coal Gasification Process
        Blbllorraphy  	  3.23

  IV.   EXPLOSIVES INDUSTRY 	  4.1

        Introduction	4.1
        Nitric Acid Production  	  4.1
             Ammonia Oxidation Process
             Nitric Acid Concentration
             Spent Acid Recovery
        TNT Production	4.9
             Nitration
             Purification
             Finishing
             Recommendea Areas for Pollution Control Research
               in TNT Production
                                     1v

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         Nitrocellulose Production 	 .4.14
              Nitration
              Purification
              Recommended Areas for Pollution Control Research in
                Nitrocellulose Production
         Bibliography	•	4.23

    V.   IRON AND STEEL INDUSTRY	5.1

         Introduction  	 5.1
         Coke Making	.	5.4
         Coke By-Product Recovery	5.9
         Iron Making	5.12
         Steel Making	5.21
         Acid Pickling	5.27
         Recommended Areas far Process Modifications Research  .... 5.29
         Bibliography	5.34

   VI.   PAPER AND PULP INDUSTRY	6.1

         Introduction  	 .6.1
         Kraft Pulping	6.1
              Digester System
              Brown Stock Washer System
              Multiple Effect Evaporator System
         Recovery Furnace System	 ^	6.10
              Smelt Dissolving Tank
         Lime Kiln	6.17
         Recommended Areas for Process Modification
           Research	6.19
         Bibliography  	 6.22

 VII.    THE PRIMARY ALUMINIUM INDUSTRY	7.1

         Introduction  	 7.1
         Bauxite Processing  .. 	 7.1
         Primary Aluminium Smelting	7.6
         Recommended Research Studies For Pollution Control In The
           Primary Aluminium Industry  	 .........7.15
         Bibliography	7.19

VIII.    FROSPHATE FERTILIZER INDUSTRY 	 8.1

         Introduction  	 .........8.1
         Wet Process Phosphoric Acid Production  	  8.2
         Reccnaended Areas For Pollution Coatrol Research:  Wet
           Process Phosphoric Acid Productioa  	  8.7
         Normal Superphosphate Production  	  8.8

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      Recommended Areas For Pollution Control Research:  Normal
        Superphosphate Production	  8.11
      Ammonium Phosphate Production .		8. II
      Recommended Areas For Pollution Control
        Research: Ammonium Phosphate Production 	  8.17
      Bibliography  	  8.18

IX.   CONCLUSIONS AND RECOMMENDATIONS	9.1

      Introduction  	  9.1
      Solvent Extraction  	  ......  9.1
      Catalyst Deactlv&cion 	  9.1
      Leaching Process	9.2
      Gas Absorption	9.2
      Gas-Llquid-Solld Reactions  	  	  9.3
                                   vl

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                              LIST OF FIGURES

Figure                                                               Page

 1.1      Flow Chart Showing the Principal Process Steps
          For Extracting Copper From  Sulphide Ores 	 1.3

 1.2      Conalnution and Froth Flotation	1.4

 1.3      Flow Chart For Electrorefining  Process	1.8

 1.4      Flow Chart For Solvent Extraction Process	1.14

 1.5      Process Schematic For Uranium Recover;  . 	 1.18

 2.1      Flow Chart For Water Flow in Chromium
          Plating Zinc Die Castings,  Decorative	2,2

 3.1      Flow Sheet For An Integrated Liquefectlcn
          Process  	  .....3.3

 3.2      lurgi SNG Process	3.13

 4.1      Processes In The Explosive  Industry   	 4.2

 4.2      How Chart For Nitric Acid  1 reduction	4.3

 4.3      Flow Chart For TNT Production   ........  	 4.11

 4.4      Flow Chart For Nitrocellulos Production	4.17

 5.1      Overview of Iron and Steel  Manufacturing Process ...... 5.2

 5.2      Coke Maklne	5.5

 5.3      Coke By-Products Recovery	5.10

 6.1      Flow Chart of Kraft Pulping Process   ...  	 6.2

 7.1      Bauxite Processing	7.2

 7.2      Primary Aluminium Production 	  ....... 7.8

 8.1      Wet Process Phosphoric Acid Production  	 8.3

 8.2      Flow Chart of Normal Superphosphate
          Production Process 	 .......... 8.9

 8.3      Flow Diagram For TVA Ammonium Phosphate Process  	 8.13

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                                LIST OF TABLES

Table                                                           Page

 1.1      Flow Rates of Metals In Process Streams  ........1.6

 1.2      Concentration Ranges in Effluent Streams
          Froa Electroreflnlng Process  	 1.9

 1.3      Pollutants and Suggested Control Strategy
          for Copper Production by Pyrometallurglcal
          Processes	J.JO

 1.*      Pollutants and Suggested Control Strategy for
          Copper Production by Hydrometallurgical
          Processes	1.15

 2.1      Composition of Raw Waste Streams Prom
          Conncn Metals Plating	 2.3

 3.1      Approximate Trace Element Analysis of Coal
          Pretreatment Dust After Scrubbing	3.5

 3.2      Estimated Trace Elements Composition of
          the SSC Liquefaction Residue	3.7

 3.3      Pollutants and Control Options in SRC
          Liquefaction Process  	 3.10

 3.4      Laboratory Leaching Results of Chen-Fixed
          Refinory Wastes	3.15

 3.5      Spent Harshaw Nickel Catalyst Analysis	3.16

 3.6      Distribution Coefficients for Various Phenols
          in Butyl Acetate at 300°K	3.19

 3.7      Control Options for the Concentration Wastes  ..... 3.20

 3.8      Pollutants and Control Options in Lurgi  SNG
          Process	3.22

 4.1      Pollutants and Control Options in Nitric
          Acid Production Process	4.8

 4.2      Pollutants and Control Options in TNT
          Production	4.15

 4.3      Pollutants and Control Options in NC
          Production	4.21

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Table                                                            Page

 5.1      Average Analysis Of  Quench Water  Samples   	 5.7

 5.2      Coke Oven Gasea	5.11

 5.3      Analysis Of Blast  Furnace Scrubber Wastewaters
          Flow Rate	  . 5.13

 5.4      Vastevater Thickener Under Flow	5.14

 5.5      Raw Uastewaters From Steel Making
          Operations	5.24

 5.6      Pollutants and Suggested  Control  Strategy,  Iron
          and Steel Industry	 5.30

 6.1      Typical Emissions  Bates From Batch Digester 	 6.4

 6.2      Emission Rates From  Vacuum Washer	6.6

 .6.3      Emission Rates From  HEE	6.8

 6.4      Emission Rates >rom  Recovery Furnace   	 6.10

 6.5      Participate Emission Rates From the
          Recovery Furnace   	 6*11

 6.6      Emission Rates From  Smelt Dissolve Tank	6.16

 6.7      Lime Kiln Emission Rates   .......... 	 6.18

 6.8      Pollutants and Control Options  in Kr^ft
          Pulping Process 	 6.20

 7.1      Chemical Analysis  of Red  Muds ............. 7.3

 7.2      Emissions From Solderberg Cell	7.1C

 7.3      Effect of Cell Operating  Parameters as
          Flourlde Effluent  ... 	 7.13

 7.4      Suggested Process  Modifications for Pollution
          Control in the Primary Aluminium  Industry	7.16

 8.1      Pollutants and Suggested  Strategy for Selected
          Phosphate Rock Fertilizer 	 8.16
                                       1x

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                            LISI OF ABBREVIATIONS

Abbreviation                                      Terms
     cfn                                cubic feet per minute
     ft3                                cubic feot
     g/1                                grams per liter
     K.W.H.                             kilowatt hours
     m3                                 cubic meters
     am                                 millmeters
     MG                                 million gallons
     N-K-P                              nitrogen, potassium, phosphorous ratio
     ppn                                parts per million
     scf                                standard cubic feet
     SNG                                synthesized natural gas
      n                                 microns

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                             INTRODUCTION






      The objective of  this  planning  project  on Process Modifi-



 cation Towards Minimization of Environmental Pollutants  in  the



 chemical process  industry is to suggest fundamental research



 studies  which will have  significant  Impact in the minimization of



 industrial pollutants.   Towards this end, eight  industries  are



 surveyed to develop a  matrix of significant  pollution problems



 and attendant process  modifications which would  have impact on



 the reduction or  elimination of pollutants inherent in these



 processes.  The industries  surveyed are as folJows:



      1.   Refining of  Nonferrous Metals



      2.   The Electroplating Industry



      3.   Coal Conversion Processes



      4.   Specialty Chemicals



      5.   The Iron and Steel Industry



      6.   The Paper and Pulp Industry



      7.   The Primary Aluminum Industry



      S.   Phosphate Fertilizer Industry



     Although these industries are diverse, it is apparent  that



generic pollution problems cut across most of these and other



industries not covered in the survey.  Accordingly, various



process modification strategies and attendant research programs



which would minimize these pollution problems and are generic



in nature, are indentified.
                                   XI

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                             CHAPTER 1                                 1.1



                   REFINING OF 1,ONFERROUS METALS








1.1  INTRODUCTION



     This chapter will concentrate on the refining of non-



ferrous metals from mineral oze.  The sections of this chapter



are divided as follows:



     1.   Copper Production by Pyrometallurgical Processes



     2.   Copper Production by Hydronetallurgical Processes



     3.   Uranium Production by Hydrometallurglcal Processes.



1.2  COPPER PRODUCTION BY PYROMETALLURGICAL PROCESSES



     Ninety percent of the world's primary copper originates



in the sulphide form.  A vast majority of this copper is



extracted by pyrometallurgical techniques because sulphide



ores are not easily leached.  Typical copper deposits con-



tain only 1 to 21 copper, therefore, the ore must undergo



several process steps to concentrate the copper before smelting.



This method of copper extraction includes the following steps



(Biswas and Davenport, 1980):



     1.   Concentration by Froth Flotation



     2.   Roasting



     3.   Matte Smelting



     4.   Converting to blister copper



     5.   Electroreflnlng

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      The pollutants  of primary concern  include  SO-, partlcu-



 lates,  slag,  and  dissolved metal salts  in various  effluent



 streams (Barbour,  1980).  Figure 1.1  is a flow  chart of this



 process, indicating  the numerous ways in which  copper concen-



 trate can be  smelted to produce blister copper.



      Other  sources of waste water  Include acid  plant blow-



 down, slag  granulation, and cooling of  the hoc  metal anodes.



 Electroreflning also generates waste  through spent electrolyte,



 washing cathodes,  and the recovery of slime (U.S.  EPA, Feb. 1975).



 1.2.1   Comminution and Froth Flotation



     A  copper concentrate is produced by a series  of flota-



 tion  cells  which  selectively float copper sulphide to the



 surface of  the bath  so the concentrate  can be skimmed off



 the top.  Thlt process is depicted In Figure 1.2.  The tail-



 Ings  taken  from the  tank are piped to evaporation  ponds where



 the water is  clarified and recycled (Biswas and Davenport, 1980).



     The tailings  require pH adjustments and extraction of



 arsenic, cyanide,  and some metals.  The  amount of water con-



 sumed for this process step can be reduced if Improvements



are made to the grinding efficiency of the dry ore.



 1.2.2  Roasting of Copper Concentrate



     The copper concentrate can be refined by several different



methods of roasting and/or smelting as shown in Figure 1.1.



Roasting of sulphide concentrates produce calcines for leach-



Ing or for reverbatory (or electric)  furnace smelting.   The

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                                ou
                                                                           1.3
1




COtMIHUTIOH
i
FUJTAnOS
CELLS
i
1 \»> 1
DRYING
I

ROASTING
DRYING
|S02 ) I90! \ fM2
ELECTRIC
FURNACE

REVERBATORY
FURNACE
FLASH
FURNACE

1
SINTERING
1 I"2
BLAST
FURNACE
SLAG
                                                             SLAG
                      SLIME
                                         SPEHT ELECTROLYTE
    Figuri 1.1.  Flow Chmrt Showing th« ?rlnclp«l Proeisa Sc«pi
                 For Extracting Copper from Sulphide OTM.
                 (Bim*  ad Dwtnport. 1980).

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                           GRINDING
                          SCREENING
                              1
                            HILLING
   HYDROCYCLONE
H
FLOTATION
  CELLS
H
TAILINGS
  POND
                  Cu Concentrate (24Z Cu)

Figure 1.2.  Comminution and Froth Flotation
             (Biswas and Davenport, 1980).

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fluid-bed  roaster  la  the best device Cor uulphide roasting



since it has  a high production rate ant produces 5-152 by



volume SO.  in the  flue gases which can be easily converted



into usable forma  of  sulfur (Gill, 1980).



1.2.3  Smelting



     The process of sicelting and converting vary widely in



equipment design •but  the pollutants are essentially the same:



SO., parclculates, and slag.  There are several reasons for



cleaning gases  from metallurgical processing, the most Import-



tant of these are  (6111, 1980):



     1.   To  recover value-bearing participate material



          which can be returned to the plant for



          reprocessing.



     2.   Environmental pollution, from the viewpoint of



          employees exposed to harmful gases and, SO, com-



          bining with atmospheric water vapor to form acid



          rain, damaging plants and injuring animals.



     3    To remove value-bearing gaseous by-products such



          as S02, which can be used as the feed material



          for the production of marketable sulfurlc acid



          or elemental sulfur.



     4.    To recover fuel value of gaseous by-products



          like combustible CO.



     5.    To reclaim the sensible heat to the flae gases



          In waste heat boilers.

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     Optimization of the smelter design can reduce the amount of



environmental pollution or alter the effluent streams so that



the pollutants can be easily removed.  If the S02 concentration



is greater than 4Z by volume, it cen bfc converted into sulphuric



acid without much difficulty.  Typically S02 is converted into



sulphuric acid, sulfur, or ammonium sulfate.



     A survey of metals in various process streams was tak^n



at a smelting plant owned by the Radian Corporation in Austin,



Texas.  Table 1.1 is a compilation cf the flow rates



(Sclwltzebel, e£ al. 1978).  Some of the streams were not



measured or recorded but the chart does Illustrate the number



of different elements present in the effluent streams.



TABLE 1.1.  FLOW RATES OF METALS IN PROCESS STREAMS
1.6
Flow Rat- Ib/hr
Element
Al
As
Ba
Be
Ca
Cd
Cr
Cu
F
Fe
Hg
Mo
Ni
Pb
Sb
Se
Si
V
Zn
Feed
400
190
3i
0.072
770
59
0.076
16000
3.4
10000
0.018
79
0.70
49
6.0
10
1100
0.92
42
Matte
17
48
33 .
4.1x10
12
37
0.64
18000
0.012
Flue
Slag Outlet
700
48
43
0.032
1900
0.33
3.8
220
2.2
11000 12000
0.020
8.5
2.0
84
4.6
0.17
42
0.33
31
0.0091
89
0.76
13
3.4
5.5
4800
0.86
30
0.10
76
0.64
0.0034
0.011
0.076
0.044
1.8
9.4
0.55
0.033
0.17
0.011
0.38
0.030
0.65
1.7
0.027
0.22
ESP
Catch
1.1
30
0.023
0.0004
2.1
0.74
0.018
62
0.032
42.6
0.00015
6.6
0.059
«.3
1.3
0.16
1.7
0.011
4.6

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     To recover the metals from the captured participates,               1*7



it may be possible to use acid leaching and solvent extraction



to selectively remove metals from low concentration leach



solutions.



1.2.4  Sleetrorefining



     Electrorefinlro is the final step rf purifying blister



copper to 99.99Z Cu which can be used for most Industrial



applications.  The spent electrolyte is recycled, but some of



the acid must be treated to remove excess nickel and unclaim-



ed copper as well as other trace metals.  Slime develops from



the participates and precipitates and must be treated to re-



cover cupper and/or precious metals.  Figure 1.3 is a flow



chart illustrating the representative steps of the electro-



refining process (U.S. EPA, Feb. 1975).



     Table 1.2 lists the concentration ranges of oeveral prio-



rity pollutants contained in the designated process streams.



Slime is either discarded or undergoes further treatment for



recovery of trace metals.  A bleed from the electrolyte,



water used to wash the anodes during preparation, and stllae ara



the primary sources of water contamination from the electro-



refining process.



     Table 1.3 surmarlzes the pollutants and suggested control



strategy for copper production by pyrometallurgical processes.

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         BLISTER
         COFFER
           ANODE
       PREPARATION
•HASH WATER
       ELECTROLTTIC
           CELLS
   ACID
 STORAGE
                   SI DIE
99.991
COFPFR
    Cu
 LIBERATOR
                             •ISO..
                             •te.
                                             COFFER
rigur* 1.3.  Flow Chart (or El«etror«flnlng PTOCMS
             (U.S. EFA. F«h. 1975).

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     Table 1.2.  Concentration Ranges in Effluent Screams
POLLUTANT
Astinony
Arsenic
Copper
Lead
Nickel
Selenium
Silver
ELECTROLYTE (g/L)
0.2 to 0.7
0.5 to 12.0
45.0 to 50.0

2.0 to 20.0


SLIME (Z)
0.5 to 5.0
0.5 to 4.0
20.0 to 40.0
2.0 to 15.0
0.1 to 2.0
J..O to 20.0
3.4 to 27.4
     Table 1.3 sunmarizes tht pollutants and suggested control
strategy for copper production by pyrometallurgical processes.
1.2.5  Recommended Areas for Process Modifications Research
     After evaluating the available lit*, -ature, the following
areas are recommended for further research by the study:
          Optimization of the communition of dry mineral
          ore to reduce the amount of water used in froth
          flotation.
          Recover value-bearing products by dissolving the
          metals from participates collected in the electro-
          static preclpltators and use solvent extraction
          procedures to extract the desired products.
          Use solvent extraction  to recover copper or other
          metals from effluent streams before  the water is
          sent  to  the tailing ponds.
          Improve  smelter design  to contain and eliminate
          the release of  SO. and  other hazardous flue gases
          into  the atmosphere.

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Table 1.9. Pollutant*  and Suggested Control Strategy for Copper Production
           by Pyro»aiallurglcal Proceaaaa
Ptoceae
Ore grinding
froth
flotation
Suiting
(•) Reverb
(b) Electric
(c) rieeb
(41 Blaat
Convert lot
•node
preparat loo
electro-
refining
Pollutant
hrtlnletee
Metele. Dleaolved
•ludya. cyanide,
pH etc.
»-. .l«g
and partleulaica
SO. alag and
pafdculatfla
Dlaaolwd
•etala. HjSO4
Dlaaolved
netal. BjSO^
Source la
Procesi
CniBbere
grlndera.
ball Mill etc.
Tall Inge
Plue geeea.
•lag diap
PliH gaaaa,
•lag diaip
Anode waah
Electrolyte.
cathode cool-
Ing etc.
Mature of
Pollutant
Inorganic
Inorganic and
organic addlclvea
Inorganic and
Caeeoua SO.
Inorganic and
gaacoua SOj
Inorganic
Inorganic
Pollutant Coetrol Strategy
Elactroatatlc preclpltator
Solvent eatrectlon, evaporation,
tailing* pond
Acid plant for SO.. ESP.
oolvent eatractlon
acid plant, ESP, solvent
extraction
Solvent Imtractlon
Solvent extraction

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1.3  COPPER PRODUCTION BY HYDROMETALLURGICAL PROCESSES                1.11



     Hydrometallurgy has three advantages over the smelting



and converting processes that are traditionally used for the



manufacture of copper.  First* leachiug is a more economical



method of extraction when the ore has a low concentration of



copper.  Second, increasing energy costs of the furnaces is



making pyrometallurgy less economical.  Third, it Is becoming



increasingly difficult for smelters to meet stringent environ*



mental regulations (Harbour, 1980).



     The hydrometallurg-lcal process entails three major steps;



leaching, cementation (or solvent extraction), and electro-



vixmlng.  This method of extracting copper from mineral ore



has not been extensively applied to sulflde ores which are



not readily leached.  Due to the environmental problems



associated with SO,, hydrometallurgy is becoming a more



acceptable method of producing copper (Biswas and Davenport,



1980).



1.3.1  Leaching



     There are numerous methods of leaching and several types



of leaching solutions.  Sulfurlc acid is commonly used as a



leaching medium, but new technology has introduced other forms



of leaching solutions such as ammonlacal and ferric chloride



solutions.  Leaching of sulflde ores can be Improved by



bacterial enhancement as well.  The pregnant leach solution



can undergo either solvent extraction, ion exchange or cemen-



tation to recover the copper while leaving the remaining

-------
trace metals in the leach solution (Wadsvorth, 1980).                 1.12
There are four methods of leaching (Wadsvorth, 1979):
     1.   In altu leaching
     2.   Dump and heap leaching
     3.   Vat leaching
     4.   Agitated leaching
     In situ and dump leaching are long term processes which
can leach the ore with acid solution for several years.  Due
to this long period of exposure, significant quantities of
the sulfide minerals will dissolve into the leach solution.
Contamination of ground water may occur and could produce
serious detrimental effects to the surrounding environment.
     Vat leaching and agitated leaching are lone with such
smaller volumes of crushed ore at much shorter periods of
exposure.  These short term processes are useful for ores
containing copper in the oxide form which dissolve easily
in acid solutions.  The pregnant leach solution is taken to
refining process, while the remaining sludge is either dumped
or recycled for additional processing to recover other metals
that were not extracted.
     If the leach solution has a high concentration of coppar
(40 r.o 60 g/lj, it can be sent directly to the electrowiming
circuit (Flett, 1974).  When the solution has a low concen-
tration, making direct electrowinning uneconomical, then a
process step must be taken to separate the copper from the
rest of the leach solution and redlssolve the copper at a

-------
higher concentration into an electrolyte.  Three commercially         1.13



available processes chat accomplish this cask are cementation



solvent extraction, and ion exchange.



1.3.1.1  Cementation



     Cementation is a reaction where copper precipitates



directly onto the surface of the scrap iron.  The effluents



contain very large quantities of iron salts and are generally



sent to the tailings pond for vaste treatment.



1.3.1.2  Solvent Extraction



     Solvent extraction is a process having several circula-



tion loops where copper lens are selectively extracted from



a leach solution by a specific solvent.  The extracted copper



is stripped from the solvent which is then recirculated int



the extraction circuit.  The flow chart shown in Figure 1.4



illustrates the multiple circuits of the solvent extraction



process.



     Some of the pollution problems that exist in this process



are the build up of trace metals in the leach solution and



entrained solvent in the extraction and stripping sections.



Problems associated with entrainment are complicated by the



unavoidable degradation of the solvent.  This reduces the



extraction activity of the organic material and some make up



must be added to che recycle.



     Table 1.4 summarizes the pollutants and suggested control



strategy for copper production by hydrometallurglcal processes.

-------
                                                                 1.14

Loaded
Solvent
Regenerated
Organ ie
LZACHISG
I
SOLVENT
OCTRACriON
1 1
*
STHimNS

I C«1u»«
ELECTKOVUHtNC





1
RAPntUTE
SPOT
ELECTROLYTE
                  JO.

rigur* 1.4.  now dart of Solvent Extraction Procesa.
            (6111. 1980).

-------
Table 1.4  Pollutants and  SuggMted Control Strategy for
           Copper Production by Hydrome^allurglcal Processea
Process
Leaching In
situ, ho*n,
vat,
ajltated
Cementation
Solvent
extraction
Electro-
winning
Pollutant
Dissolved
metal salts,
aulfurle jetd
organic additives
(wetting agenta)
Dissolved
metal salts
Dissolved
iwtala, entrained
solvents
Dissolved
metals,
acid,
cyanide
Source in
Process
Leech
solution
Iron ion fro*
screp Iron
Excess from
process at reams
solvent degra-
dation
Bxcesu from
process
at reams,
cathode wash
and cooling
Nature of
Pollutant
Inorganic,
metals and acid
Inorganic
Inarganlc metals
and organic
solvents
Inorganic metals
and acid
Pollutant Control Strategy
Recycle Leach solution
after solvent extraction
of excess metals, watch
for seepage of natal* Into
the ground water
Solvent extraction of
effluents
Improve mixer-settlers,
study methods for regeneration
of aolventa
Solvent extraction
of effluenta

-------
1.3.2  Recommended Areas of Process Modification Research              1.16



     After evaluating the available literature, the following



areas are recommended for further research by the study:



     .    Recover trace metals in the effluent streams by



          using solvent extraction.  Conduct research in



          the area of simultaneous extraction of several



          metals that are considered hazardous pollutants.



          Recover entrained solvents by filtration, flota-



          tion, centrifugal separation, etc.  Study the various



          methods of separating liquid-liquid mixtures and



          determine the best process to use.



     .    Solvents tend to degrade due to temperature, pH,



          or radiation extremes.  Analyze the by-products



          of this degradation and determine the best way to



          eliminate these by-products either in the recycle



          stream or the exit stream.



          Evaluate new techniques for leaching sulphide ores



          ot develop new techniques to improve selectivity



          in leaching mineral ores.



1.4  URANIUM PRODUCTION BY HYDROMETALLURCY PROCESSES



     Uranium is becoming an important energy source since pro-



jected energy demands will greatly increase in the near fu*nre.



Uranium content of a typical ore is in the order of 0.2 to



0.3 percent U.Og.  For this reason, large quantities of



material must be handled to mine and extract uranium.   The

-------
conventional recovery processes include acid or alkaline              1.17



leaching, solution purification, and product precipitatioa



into yellow cake  (U.O.).  Solvent extraction and ion exchange



have become the primary methods for solution purification



and concentration of uranium values (Reed, et al. 1979).



Figure l.S is a representation of a process flow chart for



the refining of uranium ore.



1.4.1  Leaching



     As mentioned in Section 1.3, there are numerous methods



of leaching with  varying degrees of ore preparation.  Interest



has increased in  the use of in-sltu leaching of underground



deposits for uranium mining.  The advantages of in-situ



leaching are the  significant reduction of processing costs and



the minimal disturbance to the surface conditions.  The



subsurface deposit is flooded with leach solution and then



pumped to the surface ready for uranium recovery.  With in-situ



leaching, the ore body remains intact and only the metal is



removed, therefore a relatively small volume of waste requires



disposal.



     This method  of leaching can only be done when the ore



body is contained within a rock formation which is relatively



impermeable, otherwise the ground water may become contaminated.



The possibility of polluting fresh-water aquifers is present,



particularly when a deposit is contained within an aquifer.



Regulatory authorities require a "cleanup" of the deposit



subsequent to the leaching operations.  With proper design,

-------
                                                                                  1.18









>

>
>

REACENT >
\
1
\



POR
0







•



h
I

\ Jt,




.
\
t
nJEED
WPURITY
9KTRUL


f
UACB HELD


sourrios •— LIZIYIART
PRETBEATHERT RECERERATIOH

EVAPORATION
t
108 EZCBANCE \ B LESD\ TAttlHCS
T\ 'T
»au«- / l
1 X\^->»»-, , m BISWSAL
JLVEHT ^ ; ^ISSfT
ucrimi > ' COHTROL


PRECIPITATION ^^|^_____ STEAM AND/OR REACEHTS
»

UEWATEKINC
1 .'

DRTIRC AND
PACICTNC
\
TEUOU CAKE
PRODDCT
CIRCUIT
Flgur* 1.5.   Proe**s SctMoatle (or Urntua Racovery

-------
Dp-.ration, monitoring, and cleanup, in-situ leaching can be           1.19



Che most environmentally acceptable method of extracting



metals from subsurface deposits.



     Other methods of leaching can be used, but the damage



to the surface, the amount of waste produced, and the costs



for processing the ore will Increase.



     Uranium can also be recovered from leach solutions used



for the extraction of other non-ferrous metals like copper,



zinc, nickel, etc.  Once the uranium is reclaimed from the



leach solution it can be recycled Into the leaching process



after some "make-up" is added.  A tailings pond is used



to store the spent solution so that suspended particals



are allowed to settle and the effluents can be contained



without affecting the surrounding environment.



1.4.2.  Solution Purification and Concentration



     Leach solutions generally contain a large amount of im-



purities such as molybdenum, vanadium, selenium, iron, copper,



etc.  The concentration of pregnant solutions may range between



.6 and 2.0 g/1 U.O-.  Solvent extraction techniques, and in



soroe cases ion exchange are used to purify and concentrate



the U,0Q in the solution.  The final solution, after solvent
     J O


extraction can be made to be 30 to SO g/1.  Ion exchange of



clarified leach solution usually results in an elluant con-



taining 10 to 12 g/1 U30g (Reed, et al. 1979).

-------
     By using an ion exchange unit first and then a solvent           1.20



extraction process, the amount of solvent required to recover



the uraniua nay be greatly reduced.  This modification has a .



tremendous economic advantage by reducing solvent inventory



but may also lessen the pollution effects due to solvent



entrainment and degradation.



1.4.3  Recommended Areas of Process Modification Research



     After evaluating the available literature, the following



areas are recommended for further research by the study:



     .    Evaluate new leaching solutions that may offer



          improvement in leaching selectivity and/or efficiency.



     .    Determine the best solvent for solvent extraction



          of uranium salts with minimal degradation.



          Divert recycle streams into additional process



          circuits to remove trace metals.

-------
                            BIBLIOGRAPHY                              1.21
Barbour, A.K.  "The Environmental Pressures on Nonferrous
     Metal Production", Metals and Materials. Vol. Mo. 1980,
     pp. 42-46.

Biswas, A.K. and Davenport, W.G.  Extractive Metallurgy of
     Copper. 2nd edition, Pergamon Press 1980.

"Cyprus Bagdad: 'State of the Art1 Copper-Molybdenum
     Production", Engineering and Mining- Journal. Vol. 181,
     No. 8,  1980, pp. 56-63.

Flett, D.S.  "Solvent Extraction in Copper HydroBetallurgy"
     Traau.  Inatn. Mia. Me tall., Section C, Vol. 83, March,
     1974, pp. 30-3.

Gill, C.I.   Nonferrous Extractive Metallurgy. John Wiley &
     Sonn, Inc., 19807

Reed, A.K.,  Meeks, B.C., Pomeroy, S.E., and Hale, V.}.
     Assessment of Environmental Aspects of Uranium Mining
     and Milling. EPA-600/7-76/036, Dec. 1979.

Schvltzebel, K., £t al.  Trace Elements Study at a_ Primary
     Copper  Smelter. Volume I.. EPA/600/2-78/065a7 March,
     1978.

U.S. ZPA.  Development Document for Interim Final Effluent
     Limitations Guidelines and Proposed New Source Performance
     Standards for the Primary Copper Smelting Subcatbgory and
     the Primary Copper Refining Subcategory of the Copper
     Segment of the Nor*errous Metals Manufacturing Point
     Source  Category. EPA 440/1-75/032-b, February, 19/5.

Wadsworth, M.E.  "Review of Developments in Hydrometallurgy
     in 1978", Journal of Metals. Vol. 31, no.5, 1979,
     pp. 12.

Wadsworth, M.E.  "Review of Developments in Hydrometallurgy
     in 1979", Journal of Metals. Vol. 32, no. 4, 1980,
     pp. 27-31.

-------
                       SUPPLEMENTAL REFERENCES
 Agera, D.W.  and DeMent, E.R.  "The Evaluation of New LIZ
     Reagents  for  the Extraction of Copper and Suggestions
     for  the Design of Commercial Mixer-Settler Plants."
     Ingenleursblad, 41, 1972, pp. 433-4.

 .aderson, S.O.S. and Reinhardt, B.  "MAR-Bydronetallurgical
     Recovery  Processes.", Paper given for the ISEC 77,
     Sept. 1977, pp 798-804 oC the CIM Special Vol. 21, 1979.

 Ansden, M.,  Swietin, R., and Treilhard, 0.  "Selection and
     Design  of Texas Gulf Canadian Copper Smelters and
     Refinery", Journal of Metala. Vol. 30, Mo. 7, 1978,
     pp. 16-26.

 "Arizona's Copper Producers Rally to Fight the E.P.A. Smelters
     Regulations",  Engineering and Mining Journal. Vol. 179,
     No. 4,  1978, pg. 33.

 Ashbrook, A.W. , Itykovich, I.J.. and Sova, V.  "Losaes of
     Organic Compounds in Solvent Extraction Procesuas"
     Paper given for the ISEC 77, Sept. 1979, pp 781-790 of
     CZM Special Vol. 21, 1979.

 Baxner, B.E., Hulbred, G.L. , and Kilumpar, Z.V.  "Sensitivity
     of LIZ Plant Costs to Variations of Process Parameters",
     Paper given for the ISEC 77, Sept. 1977, pp 552-560 of
     CIM Special Vol. 21, 1979.

Barthel, G.  "Solvent Extraction Recovery of Copper frou
     Mine and Smelter Waters",  Journal of Metala. Vol. 30,
     Bo. 7, 1978, pp. 7-12.

"Clarksville Zinc Plant First in the D.S.  for 37 Years",
     Mining Magazine. Vol.  140, No.  12, 1979. pg. 551.

Cogut,  B.   "Morenci Clear-Air Prediction System Bas Unique
     Potential for Controlling Air Quality",   Engineering
     and Mining Journal.  Vol.  179, No.  4,  1978,  pp. 65-70.

Collins, G.,  Cooper,  J.B.,  and Brandy,  M.R.   "Designing
     Solvent  Extraction Plants to Cut the Risk of Fires",
     Engineering and Mining Journal.  Vol.  179,  No.  12,
     1978, pp 56-62.

-------
 Costle,  G.M.  "Environmental Regulation of  the Metals                 1.22
      Industry",  Journal of Metals. Vol.  30, No.  1,  19^3,
      pp  30-32.

 Davidson,  D.H.  "In-Situ Leaching of Nonferrous Metals"
      Mining Congress Journal. Vol. 66,  No.  7, 1980,  pp 52-57.

 Finney,  S.A.  "A Review of Progress in  the  Application of
      Solvent Extraction for the Recovery  of Uranium  from
      Ores  Treated by the South African  Gold Mining Znd."
      Paper given to the ISEC 77,  Sept 77, pp 567  to  576 of
      the Canadian Institute of Mining and Metallurgy,
      Special Volume 21, 1979.

 Henrle,  F.   "Gearing up to Control Trace  Elements During
      Mineral Processing",   Mictog Congress  Journal.  Vol. 66,
      No. 4,  I960,  pp.  18-20.

 Huff, R.V.,  Davidson,  D.A., Boughoan, D., and Axen.  S.
      "Technology for In-Situ Uranium Leaching",  Mining
      Engineering.  Vol.  32,  No.  2, 1980, pp. 163-164.

 "Bydrometallurgy Review,  1978",  Mining Engineering. Vol. 31,
      No. 5,  1979,  pp.  527-529.

 "Hydroaetallurgy Review,  1979",  Mining. Engineering. Vol. 32,
      No. 5,  1980,  pp.  540-542.

 Isenberg, E.   "Alternatives for Hazardous Waste Management
      in  the  Metals Smelting and Refitting  Industries. EPA/
      5307sW-153c.

 "Jersey  Mines Zinc:  Plant Design and Startup",  Engineering
      and Mining Journal. Vol.  181, No.  7, 1980, pp 65-88.

 Jones, H.R.   Pollution  Control  in the Nonferrous Metals
      Industry.  1972, Noyes  Data Corp.,  1972.

 Kordoalty, G.A.,  MacKay, R.D., and Vlrnlg, M.J.  "A New
     Generation of Copper Extractant".  Paper presented
      for Metallurgy Society of AIKE, 1976.

MacDonald, B.J.  and Weiss,  M.  "Impact of Environmental
     Control  Expenditures of U.S. Cu, Pb, and Zn Mining
     and Smelting",  Journal  of Metals. Vol. 30,  No.  1,
     1978, pp 24-29.

-------
Mackay. D.,  and Medir, M.  "The Applicability of Solvent              1.24
     Extraction to Waste Water Treatment",  Paper given to
     Che  ISEC  77, Sept. 1977. pp. 791 to 797 of the CIM
     Special Vol. 21, 1979.

Macklv, V.V.   "Current Trends in Chemical Met.-lurgy",
     The  Canadian Journal of Chemical Engineering. Vol. 46,
     Ho.  2,  1968, pp. 3-15.

IfcGarr, H.J.   "Solvent Extraction Stars in Making Ultra-
     pure Copper",  Chemical Engineering. Vol. 77, No. 17,
     Aug. 10,  1970, pp. 82-84,

Mlzrahl, J., Barnes, E., and Meyer, D.  "The Development
     of Efficient Industrial Mixer-Settlers",  Paper
     Presented to the International Solvent Extraction
     Conference W4 (ISEC 74), Sept. 1974.

Renzoni, L.S.  "Extractive Metallurgy at International Nickel —
     A Half  Century of Progress",  The Canadian Journal of
     Ct.eai.eal  Engineering. Vol. 47,~No. 2, 1969, pp. 3-11.

Schultz, D.A.  "Pollution Control and Energy Consumption at
     U.S. Copper Smelters".  Journal of Metals. Vol. 30, No. 1,
     1978, pp. 14-20.

Stelllng  III,  J.H.E.  "Source Category Survey; Uranium Refining
     Industry". EPA-450/3-80/010, May 80.

U.S. EPA.  Solution Mining of Uranium; Administrator'a Guide.
     PB-301  173. May 79.

U.S. EPA.  Heavy Metal Pollution From Spillage at Ore Smelters
     and Mills. EPA/600/2-77/171, Aug. 1971.

U.S. EPA.  Economic Impact of Environmental Regulation on the
     U.S. Copper Industry. EPA/230/3-78/002, Jan. 1978.

Virnig, M.J.   "Synthetic Structure, and Bydrometallurgical
     Properties of LIX 34",  Paper given for the International
     Solvent Extraction Conference in 1977 (ISEC 77), Sept.
     1977, pp. J35-541.

Veisenberg,  I.  "Design and Operating Parameters fot Emission
     Control Studies; Kennecoct, Hurley", EPA/600/2-76/036d,
     Feb. 1976.

Veisenberg,  I. "Design and Operating Parameters for Emission
     Control Studies; Phelps Dodge, Morenel", EPA/600/2-76/036g.
     Feb. 1976.

-------
                             CHAPTER 2                               2<1
                          ELECTROPLATING

2.1  ELECTROPLATING OF COMMON METALS
     Electroplating is a series of process steps that involves
the preparation of the part in addition to the plating opera-
tion.  Figure 2.1 is a flow chart of a chromium plating opera-
tion of zinc die castings.  The sequence and/or the process
steps may vary from plant to plant because of the many
variables involved with electroplating.  Table 2.1 is * list
of pollutants that typically exist In the waste streams and
their respective concentration ranges.
     There are numerous methods of treatment for dissolved
materials that exist in effluent streams.  They are (U.S. EPA,
April 1975):
               .    Ion Exchange
                    Reverse Osmosis
                    Electrodlalysld
                .    Chemical Precipitation
                .    Ion Flotation
                .    Carbon Absorbtion
                .    liquid-Liquid  Extraction
     Each method has  advantages  and  lisadvantages  that must be
 considered with respect  to  the specific electroplating industry.

-------
                                                                          2.2
          woa*
               run















CLEAN I
MAJUI |


•
















H





_







^M



•m



CLEAN
1
RIHSZ

I
AC ID
DIP
I
RINSE

CYANIDE
(.urrui
STRIKE
t

»«„
RINSE
1
ACID

I
ACID
COFFER
PT*Tr
*
RINSE
I
I RIOEL
| PLATE
L I
\ RIRSE

1 caxcniun
L ft «T»
[RINSE ARD







-1

I
1










h

]

h

J
I-





















I

L
r




























••M
^•M

i^—





ramuaizi AND
PRECIPITATE





OXIDIZE
CTANIDE
I
PRECIPITATE
COPPER



J


1
SLUDGE

1 PRECIPITATE
Niaax AND
1 ^flDWV

1EOBCE
CHltOHlim
»
PRECIPITATE
nramTiTM














n

1

ETTL





^^



^^H


















E



























^"1
H
.— n

i
rREATED )IATER







             KIT
Plfurt 2.1.  Flow Chart (or W«t«r ?' M In Oiraolua Plating
            Zinc 01* CMtloM, »«eor«tiv«  (U.S. EPA, April 1973).

-------
Since these recovery methods are readily available, similar         2.3

methods caa be adopted as additional process steps to remove

trace metals before the water la recycled back Into the process.

TABLE 2.1.  COMPOSITION OF RAW WASTE STREAMS FROM COMMON
	METALS PLATING (U.S. EPA. August 1979)


                                             (ng/D


Copper                                  0.032 - 272.5

Mickel                                  0.019 - 2954

Chromium. Total                         0.088 - 525.9

Chromium, Hexavalent                    0.005 - 334.5

Zinc                                    0.112 - 252.0

Cyanide, Total                          0.005 - 150.0

Cyanide, Amenable to  Chlorination       0.003 - 130.0

Fluoride                                0.022 - 141.7

Cadmium                                0.007 - 21.60

Lead                                    0.663 - 25.39

 Iron                                    0.410 - 1482

Tin                                    0.060 - 103.4

Phosphorus                             0.020 - 144.0

Total Suspended Solids                 0.100 - 9970



 2.1.1  Recommendations for Process Modifications

      The best way to reduce the amount of water needed in an

 electroplating process is to maintain good "housekeeping"

 practices to avoid spillage or "dragout"  of treating solutions

 into rinse waters.  Other recommendations include:

-------
     Substitute low concentration solutions in place            2.4



     of high concentration baths.



     Use non-cyanide solutions in place of the cyanide



     treatments.



.     Use counter-flow rinses.



     Add a wetting agent to rinse wateis.



     Install air or ultransonic agitation.



     Recover und reuse metals that are in effluent



     streams by solvent extraction.



     Recycle used rinse waters into the make-up



     solutions of their respective treating baths.

-------
                           BIBLIOGRAPHY                             2.5
O.S. EPA.  Development Document for Interim Final Effluent
     Limitations Guidelines and Proposed New Source Per-
     formance Standards for the Common and Precious Metals
     Segment of the Electroplating Point Source Category.
     EPA/440/1-75/040, April 1975.

U.S. EPA.  Development Docunent For Existing Source Pretreat-
     ment Standards for the Electroplating Point Source
     Category. EPA/4407l-79/003, Aug. 1979.
                      SUPPLEMENTAL REFERENCES

Belnont, T.V. and Cuxmiff, J.G.  "Plating Waste Treatment",
     Industrial Wastes. Vol. 26, No. 6, 1980, pp. 14 & 27.

Elicker, L.N.  Evaporative Recovery of Chromium Plating
     Rinse Water.  EVA/600/2-78/127, June 1975.

Hallovell, J.B.  Aasesmcent of Industrial Hazardous Waste
     Practices. Electroplating and Metal Finishing. Job
     Shops.  ZPA/530/SW-136C, Sept. 1976.

Landrigan, R.B. end Hollnwell, J.B.  HemovtJ. of Chromium
     from Plating Rinse Water Using Activated Carbon.
     EPA/670/2-75/055, June 1975.

McDonald, C.W.  Renoval ot. Toxic Metals from Finishing
     Waatewater by. Solvent Extraction. EPA/600/2-78/011,
     February, 1J»78.

Petersen, R.J.  and Cobian, K.E.  New Membranes for Treating
     Metal Finishing Effluents by Reverse Osmosis. EPA/600/2-76/
     197.

Poon, C.  "Electrochemical Treatment of Plating Rinse Water",
     Effluent and Water Treatment Journal. July 1979, pp. 351-
     355.

Pozlelle, L.T., Kopp Jr., C.V., and Gobian, K.E.  New Membranes
     for Reverse Osmosis Treatment of Metal Finishing Effluents,
     EPA/660/2-73/033.

U.S. EPA.  Control of Volatile Organic Emissions from Solvent
     Metal Cleaning.  EPA/450/2-77/022.

-------
U.S. EPA.  Copper, Nickel. Chromium and Zinc Segment of Electro-    2.6
     plating Development Document for Effluent Limitations
     Guidelines ma New Source Performance Standards. EPA/440/
     1-74/— 3a.
U.S. EPA.  Innovative Rlnse-and-Recovery System for Metal
     Finishing Process. EPA/600/2-77-099.

O.S. EPA.  Second Conference on Advanced Pollution Control for
     Metal Finishing Industry. EPA/8-79/014.

U.S. EPA.  Source Assessment; Solvent Evaporation-Degreaaing
     Operations. EPA/600/2-79/019f.

O.S. EPA.  Haste Water Treatment acd Reuse in a Metal Finishing
     Job Shop. EPA/ 670/2-74/042.

Tost. K.J. and Scarf i, A.  "Factors Affecting Zinc Solubility In
     Electroplating Waste",  Journal £f the Water Pollution
     Control Federation. Vol. 51, No. 7, 1979, pp. 1878-1887.

-------
                             CHAPTER 3                              3.1



                     COAL CONVERSION PROCESSES








3.1  INTRODUCTION



     The unpredictability of the international energy market



and the very danger of global oil shortages in the next few



decades.have necessitated a rapid expansion in the dooestlc



energy base in the U.S.  Consequently, the commercial produc-



tion of synthetic fuels  from the abundant reserves of coal is



a major objective of the nation's energy research and develop-



ment programs.  Coal liquefaction and coal gasification



technologies have received renewed interest in this regard.



Economic viability and environmental Impact will be the limit-



ing factors in the commercialization of such processes.



3.2  LIQUEFACTION



     All coal liquefaction processes produce liquids from coal



by yitiding a material having a higher hydrogen content than



coal.  Fuel oils contain about 9Z hydrogen and 14Z gasoline as



compared to roughly 5Z hydrogen In raw coal.  Currently, some



twenty-odd liquefaction processes are in various stages of



development by industry and federal agencies.  Coal liquefaction



technologies can be categorized under hydrogenatlon, pyrolysis

-------
and hydrocarbonlzation, and catalytic synthesis.  Of these,         3.2



Bydrogenation is the most advanced (Koradek and Fatel, 1976).



     In this chapter, the environmental problems associated vith



the following four coal liquefaction technologies vill be dis-



cussed:



          1.   Solvent Refined Coal, CSRC)



          2.   Synthoil



          3.   B-Coal



         . 4.   Bacon Donor Solvent



     The following section will discuss the pollutant streams



from and suggested control methods foi the SRC process.



3.2.1     Solvent Refined Coal Liquefaction



     A fully integrated SRC liquefaction system flow scheme



(Shield, .££ al. 1979) is shown in Figure 3.1.  Raw coal from



the coal storage facilities is sent to the coal pretreatment



operation where it is sized, dried and mixed with reactor



product slurry recycled from the gas separation processes.



The resulting feed slurry is combined with recycled hydrogen



from the hydrogen/hydrocarbon recovery process and makeup



hydrogen.  This hydrogen-rich slurry is pumped through a



preheater to the liquefaction reactor, or dlssolver.  Exothermic



hydrogenation reactions initiated in the preheater continue la



the dissolver which typically operates between 435°C - 470°C.



The reactor product slurry is sent to the gas separation pro-



cesses where the gaseous products are removed.  Auadlary pro-



cesses separate these gases including recyled hydrogen, SNG,

-------
 MAJOR INPUTS
   RAW GOAL  RAH WATER
     \         I
 AUXILIARY
  PROCESS
 FACILITIES:

 COAL RECEIVING/STORAGE
 STEAM/POWER GENERATION
 HTDROCEH GENERATION
 OXYGEN GENERATION
 ACID GAS REMOVAL
 HYDROGEN/HYDROCARBON
    RECOVER?
 SULFUR RECOVERY
 AMMONIA RECOVERY
 PHENOL RECOVERY
    COAL FROM STORAGE
                                      COAL
                                  PRETREATHENT
                                FEED
                                SLURRY
    MAKED? AND RECYCLE
       HTDROCEH
                                  .iqUEFACTWN
                               REACTOR
                               PRODUCT
                               SLURRY
         UKTFUATnt
         FLASHED CASES
    . WASTEWATER
    CAS
SEPARATION
                         FLASHED CASES
                                        fYDr.oTREAT7.NG
                                  Oil.
                       J
RECYCLE
SOLVENT
                               FILTER CAKE
                                                         SOLIDS/LIOjl
                                          WASH
                                          SOLVENT
                           SOLID SHC
                                                           SEPA1
                             FILTERED
                             PRODUCT
                             LIQUIDS
                                                               1ATIOH
                                                      iFRACTIONAtlOB
                   AMIONIA
               SULFUR
           SOLID SRC
       FUEL OIL
    NAPHTHAS
LIGHT OILS
MAJOR PRODUCTS
AND BY-PRODUCTS
                 Flgur* 3.1.  Flov Shan for An Integrated
                              Uqutfaction Precasi

-------
LNG and sulfur species.  The sulfur specijs are further coc-        3.4



verted to by-product elemental sulfur.  Part of the separated



slurry from gas separation is recycled to the coal pretreaonent



operation.  The remainder of the slurry is sent to the frac-



tlonator.  The fractionator generates three streams:  a light



distillate which is hydrotreated to form naphtha and fuel oil



products; liquid SRC, the primary product; and a bottom stream



which is sent to solids/liquids separation processes.  The



vacuum distillation unit in the solids/liquids separation recovers



additional SRC liquid from the fractionator bottoms, yielding



a residue of high mineral matter content.  Part of this



residue is gasified to produce makeup hydrogen.



3.2.1.1   Participate Emissions



     Fugitive emissions (i.e., partlculates) will be emitted



from the following sources:  coal storage piles, coal reclaim-



ing and crushing, coal receiving, dryer stack gas, and ash



from stream generation.  Trace elements of fugitive emissions



from coal preparation have a potential health hazard consist-



ing .predominantly of aluminum, chromium and nickel (Hupkins,



et al. 1978).  Trace element concentrations In partlculates



escaping from treated stack gas are enriched in zinc, copper,



zicronlum, molybdenum and selenium.  The trace element concen-



tration of coal dust is expected to be similar to that of



the parent coal, although certain trace elements may concentrate



in the smaller size range.  Dust (typically 1 to 100 p in size)



generated from coal receiving, storage, reclaiming and crushing

-------
is estimated to be about 24 tons/day fox a 20,000 ton/day SRC       i.3

II plant (Rogoahewskl, £t al. 1978).  Table 3.1 lists analysis

of some trace elements in dust from coal preparation after

treatment with a vet scrubber (Hopkins, et al. 1978).

     Suggested control alternatives for coal dust include

polymer spraying, enclosed storage and water spraying.  Of

these, enclosed storage involves $6-8 million capital Invest-

ment for a 10,000 tou csal pile (Rogoahewski, et al. 1978).

Cyclone and baghouse filters are probably the most effective

methods for controlling coal dust.  Due to the small particle

range, magnetic and electrostatic filters will be needed.
Table 3.1 Approximate Trace Element Analysis of Coal
          Pretreatment Puat after Wet Scrubbing
Element
Aluminum
Arsenic
Chromium
Nickel
g/day
8,910
3.9
13.0
15.0
Degree of Bealt!
Hazard*
2.21
2. SO
17.0
1.3
*De*ree of health hazard • Concentration

-------
 3.2.1.2    Coal Pile Drainage                                       3.6



      Coal  pile runoff  resulting f. on rainfall and such,  nay



 contain oxidation products of metallic  sulfldea.   This run-



 off nay also be  acidic with relatively  high concentrations of



 suspended  and dissolved  solids  (Rogoshewski,  et al.  1978).  The



 elements in this runoff  Include calcium,  iron, «T»«m
-------
in dilute  acid did not produce  any leacheate.  Table 3.2            - -

given the  composition of some of  the elements in this

mineral residue  (Hopkins, _e£ al.  1978) which totals about

3(700 Kg/day for a SRC-XI liquefaction plant producing

10,000 ton/day liquids.
Table 3.2  Estimated Trace Elements Composition of the SRC
           Liquefaction Residue
Element
Arsenic
Barium
Calcium
Iron
Luterlum
Nickel
Sodium
Zinc
Concentration ppa
24.9
579
33,323
116,760
2,050
126
1.155
1,938
The extraction of metals from this residue is another area

that requires further research.

3.2.1.5   Spent Catalyst

     Catalyst used in the shift reaction in hydrogen genera-

tion has been estimated at about 135 m  (Hopkins, _et_ al. 1978).

Trace elements, sulfur compounds and heavy hydrocarbons may

be adsorbed on the catalyst.  The estimated life time ot a

-------
cobalt molybdate catalyst is three years.  Regeneration of         3.8



spent catalyst may not be possible due to the presence of



trace metals and sulfur as well as possible sintering of



the catalyst.  It is suggested that valuable metals be



extracted from the spent catalyst at an off-site facility.



Similar facilities may be needed for spent sulfur guard and



methanatlon catalysts.



3.2.1.6   Tail Gas From Acid Gas Removal



     Acid gas from the gas purification module and ga_ from



hydrogen production axe routed to a Stratford Unit where



H2S (472 Mg/iay) (Hopkins, et al. 1978) is recovered as



elemental sulfur.  The Stretford process has an efficiency



greater than 99.SZ in sulfur recovery and can reduce H_S



concentrations to less than lOppm.  However tall gas treat-



ment may be needed before the spent gas can be vented.  The



Stretford solution consists of mainly sodium metavanadate,



sodium anthraqulnone dlsulfonate (ADA), sodium carbonate and



sodium bicarbonate In water.  The Stretford solution purge



stream has a total salt concentration of 10-25Z.  Using a



high temperature hydrolysis technique, vanadium (as solid)



and sodium carbonate, sulfate and sulfite can be recovered



as solidJ.  HCN Is completely converted to CO., H.O and N.



(Rogoshevskl, e± a^. 1978).  The Stretford tall ga« contains



about 42.7Z CO. and 5,500 ppm hydrocarbons (as C,Hfi).



Direct flame incineration and carbon adsorption with incln-

-------
eration (Ad Sox) is recommended as call gas treatment for               3.9



hydrocarbons.  Further scrubbing might be needed to reaove



CO. in the tail gas.  It is suggested that the Stretford



solution be modified to reduce CO. emissions In the tail



gas.  This is one area which necessitates further research



on adsorption phenomena of SOL and CO. in various solvents.



3.2.1.7   NO  Removal
     The reported sources of N0_ emissions within the SRC



plant include (Hopkins, et al . 1978):



          Steam generation         8.4 Mg/day



          Stretford effluent gas   0.003 Mg/day



The 
-------

Process
Coal
Pretreatment
Coal
Pretreatment
Caalfler
Solids/
Liquids
Separation
Hydrogen
Gene ratios
Acid gas
Removal
Stean
Generation
Pollutants
Coal Dust
Thickener
Underflow
Slag. Fly
ash
Mineral
Residue
Spent
Catalyst
Tail gaa
NO,
Emissions
Sources in Procesi
Storage, handling
SUing
Coal Pile Run Off
—
Pract lonator
Bottoms
Reactor
Stretford Process
—
Nature of
Pollutants
Similar Original
Coal
Minerals and
Suspended Solids
Inorganics,
Uetals and
Organ ica
Inorganics.
Metals and
Organ ica
—
Hydrocarbons
and COa {'43%)
MO^ gases
Pollutant Control Strategy
Cyclone, vet scrubbing, polymer
Coating, Electrostatic and
Magnetic Filters
Extraction and Disposal of
Tailings.
Leaching of Metals and Strip
Mining.
Extraction of (Toxic) Metals
Extraction of Co, Mo. Hi
Direct Flame Incineration. Modifi-
cation of Stretford process to
remove CO.
Substolchlometrlc supply of air,
Reclrculatlon of Flue Gas
III
•
t"
o

-------
           The applicability of electrostatic  and magnetic           3.11
           filters  to control emissions of  coal dust particles
           in the submJcron range.
           teachability of gasifier slag and fly ash to
           determine  treatment and/or disposal methods.
           Extraction of possibly toxic and/or valuable
           metals from solids/liquids separation residue.
           Extraction of valuable metals (Ni,  Co, Ho, etc.)
           from spent shift and hydrogen generation
           catalysts.
      .     Studies  on the absorption of SOL and.CO, In
           Stretford  process leading to process modifica-
           tion Co  reduce CO, emissions in  tail gas.
      .     Modification of steam generation operation to
           reduce N0_  emissions.
3.3  GASIFICATION
     In this section,  the pollution problems  and control alter-
natives for  the following four High-Btu coal  gasification
technologies will  be  discussed.
           1.   Lurgi
           2.   Hy  Gas
           3.   Bl  Gas
           4.   Koppers-Totzek
In the following section,  the Lurgi coal gasification process
is discussed.

-------
3.3.1     Lurgi Coal Gasification                                      3'12

     The conversion of coal to SNG involves the reaction of

coal with steam and oxygen in a gaslfier with subsequent

gas processing to (a) adjust the H.:CO ratio by vater-gas

shift reaction, (b) remove acidic components, and (c) cata-

lytic methanation.  The corresponding chemical reactions

are:

     6(C4fl) + 4 0, + 3H-0 •» 4H, + 2CO + 3CO. + CH.
      coal    *  *     L
                                   Lurgi gasification  (3.1)

          CO + BjO •»• C02 + B2      Water-gas shift     (3.2)
                                           •
          SHj + CO * CH4 +• HjO     Methanation         (3.3)

     The four major processes in the Lurgi gasification are

discussed below.  A flow sheet of the process is given in

Figure 3.2.

3.3.1.1  Coal Preparation

     Coal pretreatment in the Lurgi System generally consists

of only crushing and screening the coal to produce 3-35 mn

particles.  This larger size range, compared to certain other

gasification processes, decreases fugitive emissions.

3.3.1.2  Coal Gasification

     The coal gasifier is operated at a pressure of about

25 to 35 atm and receives coal through a feed hopper at the

top and discharges ash through the bottom.  Oxygsn and steau

enter at the bottom of the gasifier and the product gas exits

near the top.  On a dry basis the product gas contains about

4Z Hj, 32 C02, 18Z CO and 10Z CB^ as well as higher molecular

-------
COAL
ML PREPARATION
OPERATION
CRUSHING
AND
SCRESHIHG


COAL PINES
(TO BOILER)
COM
C

. GASIFICATION |
VERATIOH

GASIFICATION
1
ASH
(TO DISPOSAL)



GAS PURIFICATION
OPERATION

RAW CAS
IDQUOR
(TO
TAR/OIL
SEPARA-
TION)
CONCENT!
TED ACID

^»
-•
IA-
CASES
(TO SULFUR
PRIHARY
COOLIHT.


SECONDARY
COOLING


RECTISOL
ACID
CAS
REMOVAL
RECOVERY)



TRACE
SULFUR AND
ORCANICS
REMOVAL







CA1
«
'



1 UPGRADING
IPERATION
SHIFT
CCNVERSION



METHAHATIOM.
DRV INC AND
COMPRESSION


\


                                                                                                          NCI
                                                                                     (TO BOILER)
                              Figure  1.2.   Lurgt  SNC Process.
                                                                                                                                       o
                                                                                                                                       •

                                                                                                                                       t-

-------
weight hydrocarbons, reduced sulfur and nitrogen compounds.        3.J4
3.3.1.3  Gas Purification
     Gas purification consists of the removal of ccmdensables
by cooling, Rectisol treatment for the removal of bulk CO^
and reduced sulfur compounds, and removal of trace sulfur
using "methanatlon guards".  The condensates produced are
sent to tar/oil separation units and by-product recovery.
The Rectisol process uses cold methanol to absorb acid gases
under pressure.  The used solvent is regenerated by stepvlse
depressurlzatlon and heating.  Methanation guards are beds
of solid adsorbent  (e.g. ZnO).  The exhausted beds are
usually discarded rather than regenerated.
3.3.1.4  Gas Upgrading
     Cobalt molybdate is used as shift catalyst to obtain a 3:1
E.:CO ratio.  Nickel based materials are usually used as
methanation catalysts.  Both the spent shift and methanatlon
catalysts  are solid wastes requiring treatment for metal
recovery and/or disposal.
3.3.1.5  Gaslfler and Boiler Ash
     Wet ash from the gasifler and boiler ash quench systems
is the largest volume solid  waste stream in an 5NG plant
 (Ghasseml, et al. 1979).  A  250 x 106 Scf/day Lurgi SNG
plant using a coal  containing 152 ash is expected to generate
about 5400 ton/day  wet  ash having «« 2Z moisture content.  This
ash  contains leachable  inorganic and organic materials.  These
constituents can be possible sources of groundwater contamlna-

-------
tion.  An alternative disposal scheme would Involve stabilize-    3.15

cicn to convert the wastes into a chemical form that is more

resistant to leaching in the ultimate disposal site.  Table 3.4

presents typical leaching study results for wastes stabilized

by the Chemflx process (Connor, 1974).
   Table 3.4  Laboratory Leaching Results of Chem-Flzed
              Refinery Wastes

Element           Concentration in   Concentration in approx.
                  Raw Sludgpvn       200 ml Leachate water
                                     after Chem Fix ppm
Total Chromium
Iron
Zinc
Nickel
43.5
1310
88.0
8.9
< 0.1
< 0.1
< 0.1
< 0.1
The leachability of the ash produced in Lurgi SNG is an area

which requires further investigation.

3.3.1.6  Spent Guard Catalyst

     Zinc oxide beds are used for removing the last traces

of sulfur after gas removal has removed all but a few parts

per million.  Water vapor content is critical in that liquid

water can possibly degrade the ZnO bed completely (Ghassemi,

et al. 1979).  The sulfur loading capacity of the ZnO

catalyst increases from 35 wtZ at 273°K to = 20 wtZ at 673°K.

-------
However, Che maximum recommended loading la only 3 vtZ when       3.16



the desired exit gae specification is 0.02 ppm HjS (Drano



Corp., 1978).  Spent metharation guard material will consist



primarily of zinc sulfide and unreacted sine oxide.  Operating



data on the quantity and composition of spent methanation



guard catalyst are needed to evaluate the disposal and/or



reclamation of the spent catalyst (Ghassemi, «. al. 1979).



3.3.1.7  Spent Shlft/Methanatlon Catalysts



     Catalysts used for shift and methanation require



periodic replacement; the spent catalysts constitute a



solid waste.  Gross composition of spent catalyst is not



expected to be dramatically different from that of fresh



catalyst, although accumulation of carbon, sulfur, and



metallic elements is to be expected.  Data is needed on the



characteristics of spent Lurgi SNG catalysts.  Cobalt-



Molybdate la used as a shift catalyst.  Table 3.5 presents



pilot plant data on spent Barshaw N1-0104-T-1/4 catalyst



(Leppln, 1977).







     Table 3.5  Spent Harshaw Nickel Catalyst Analysis
Typical Fresh
Catalyst
Sulfur, Z wt. 0.15
Carbon, Z 3.4
Nickel, Z 60.0
Bottom of First
Stage Methanator
3.7
3.4
52.0
Top of Second
Stage Hethaaator
0.16
4.5
61.0

-------
Spent nickel methanation catalyst is as active as zinc for        3.17



trace sulfur removal and can be used as sulfur guard catalyst



(Ghassemi, et. al. 1978).  Sequential interchange of the first



and second stage methanators is also recommended, as it is



apparent from Table 3.5 that the catalyst at the top of



second stage methanator is almost fresh.  In the end,



however, spent methanation catalyst constitutes a solid



waste.  The large weight percent of Ni on the catalyst would be



an economic incentive for reclaiming metal from the spent



catalyst.  Data on the properties of spen.. nickel



methanation catalysts and the applicability of metal



extraction for reclamation are two areas that need



further investigation.  Further, the spent catalysts, al-



though of small quantity, are of special concern due to



their content of potentially toxic metals (Ni, Co, Mb)



and coal-derived organlcs (metal carbonyls for example)



and trace elements.  Fixed-bed methanation/shlft reactor



system Is reported to have '.he advantages of (1) operation



at conditions removed from carbon formation, thereby



increasing catalyst life, (2) reduction in catalyst



sensitivity to sulfur, and (3) need C02 removal from a



reduced volume of gas.  However, this has not been



commercially demonstrated yet  (Gassaeml, e_t_ jl. 1978).

-------
3.3.1.8  Ash Quench Slurry                                         3.18


     An ash quench slurry results when process waters are


used to cool and transport gasifler ash to a settling unit


or disposal site.  No operating data are available for ash


qunch slurry characteristics (Ghasseml, et al. 1979).


Laboratory data indicates that this slurry can contain


up to 20 g/L of dissolved solids with the dominant ions


being Ca+2, S0~? K* and Ha* (Griffin, et al. 1977).  An


increase in the solubility of Fe, Mn, Cd and A£ is also


expected with decreasing pH.  In addition, the concen-


tration of certain hatardous elements (e.g. As, Hi, Cr


and Cu) can reach levels which warrant control of the


aah slur.-y discharge.  Characterization of ash slurry tracer


la needed to evaluate pollution control alternative.* such


as coagulation and flocculation of solubles.


3.3.1.9  Phenol Recov..*y


     Gas liquor from tar-oil recovery contains a high


concentration of phenol:., up to 4200 mg/L (Ghasseml, e£


al. 1979).  The Fhenosolvan process using butyl acetate


as solvent is used to extract these phenola.  Most of the


available data on the performance of this solvent extrac-


tion process are for the unit in Salsbury, South Africa.


Solvents suggested for the Phenosolvan process Include butyl


acetate, Isopropyl ether and light aromatic oil (Wurm,
                     •

1969; Earhart, et, al. 1977).  For butyl acetate the


following distribution coefiicients for various phenolic

-------
compounds have been reported (Earhart. et al. 1977).              3.19
Table 3.6 Distribution Coefficients for Various Phenols in
Butyl Acetate at 300°K
                    Compound            Kg

                    Phenol              65
                    3,5 Xylenol        540
                    Pyrocatechol        13
                    Resorcinol          10
**» •
The solverts can remove only limited amounts of non-phenolic
organlcs.  A better characterization of the available
solvents for phenol extraction and their removal efficiencies
for various phenols are needed.  Further development of
solvent extraction systems to remove non-phenolic organlcs is
also suggested.
3.3.1.10  Removal of Sulfur Compounds from Rectlsol Process
     In terms of total volume acd content of B.S and other
reduced sulfur compounds, concentrated acid gas from the
Rectisol process Is the most important gaseous vaate stream
in a Lurgi SNJ facility.  Some of the control options for
concentrated acid gas stream (Ghassemi, et_ al. 2979) are
shown in Table 3.7.

-------
Table 3.7 Control Options for the Concentrated Acid Gas
          Stream                       	
                               3.20
     Control Opeions
1. Claus Plant Sulfur Recovery
2. Claus Plant Stucur Racovery
   and tall gas treatment
3. Claus Plant Sulfur recovery
   and SO. control/recovery


4. Stretford Sulfur Recovery
High Concentration of H.S
In tall gaa; feed gas H.S
enrichment sod Hydrocarbon
removal are needed

Net highly effective at high
levels of CO. In feed, appli-
cable only for streams con-
taining 5-15Z B2S

Reasonable option when feed
gases contain more than
5-15J
Inapplicable to waste gases
containing greater than 152
B.S; not economical at high
CO. levels; discharge may
contain high COS and HC
levels
     The determination of the best option for the management of

a specific sulfur bearing gas stream must be made on a case

by case basis due to the restrictions on feed compositions

and economics for different processes.  Some of the above

options have not appeared in commerical design (Ghassemi,

et al. 1979) due to the lack of engineering data.  It is

suggested that research be organized to provide operational

data for various sulfur recovery, SO. and tall gas treatment

processes.

-------
     Table 3.8 auauarlzes some of the pollution problems              3.21
associated with the Luzgi SSG process and suggested control
alternatives.
3.3.2  Recommended Arena for Pollution Control Research:
       Lurgi Coal Gasification Process
     After Evaluating  .he available literature, the following
areas are reconmended  for further research by the study:
          Stabilization of gasif ier and boiler ash to
          decrease or  prevent leachability.
          Opurating data and compos! .ion on spent
          methanation  guard, shift and nethination catalyst
          to  determine possible extraction of valuable  ar.d
          toxic metals.
      .    Studies on the use of spent methanation catalyst
          as  sulfur guard.
          Development  of  solvent  extraction  systems  to
           remove  non-phenolic  organics  and determination of
          distribution coefficients for existing solvents.
           Engineering data on  various sulfur recovery,
           and tail gas yratreatment processes.
,

-------
TafcU   J-8.    Follutaata and Control Option* In Lurgl SHB Proeaae
Pvfecaee
Coal Kaelfl-
citlon
Rae Upgrading
bKft/Metha-
•atijB
Coal
CMirfccciM
Tar/oil
•*M rat too
A*ld gae
T novel
rallutat*
Mh
Sp«ac Mtto-
nation guard
caMlyat
Spmt
catklysti
aan quench
•lurry
Vtiaaola In
M* llquni
Sulfur
cenDouad*
Soor<-c« in
pr6k.:a«
~
Hathanatlon
guard r*acc«r
Rtactor*
Ttitck*n»r
ovcrflov
—
Rncttael
fall pa*
Nature of
Tollutant
laaehabla lo-
orpanlc.
oritanle
•aurlala
ZaO with
craca orian-
lca( aulfur
and Batalfl
Co, Ho, HI.
with ttaca
ornanlca.
aulfur
Dlcanlvad !o-
organlca,
hacardoua
•acala (a*. Nl)
NonnlMiuillc
organlca
S*»ji H j*. W*2
Pollutant control StrattRv
atabllltatloa of aih to da-
eroana or pravant leach
ability
laelautloa by axtractloo
Spent •ethanatlon catalvet ee
•ethaaatton guard, eitractlon
of toxic aatala (COB apant
cacalyat
Coagulation and rioceulatlon
to ranova dlaaolvad aalta
Batter eharaetarlaattoa of
aol(r«ta Ce •odtfr/davalop
eicractlon eyateaa
Clana oulfur reeevarv and SO
tall aaa treatnent, StretfoiB
•ulfur vacovarr

-------
                         BIBLIOGRAPHY                            3.23
Connor, J.R.  Disposal of Liquid Wastes by Chemical Fixation.
     Waste Age, Sept. 1974, pp. 26-45.

Dram) Corp.  Handbook of_ Gasiflers and Caa Treatment Systems,
     EFDA No. FE-1772-11. Pittsburgh, PA, 1976.

Earbart, J.P»,£tal.  Recovery of Organic Pollutant a Via
     Solvent Extraction.  Chen. Eng. Frogr.,  Kay 1977, p.  67.

Ghaaaeai, M., _« al.  Environmental Assessment Data Base for
     Hlgh-Btu Gasification Technology; Volume II. Appendices
     A, j», and C,  EPA-600/7-7&-186b, Prepared for U.S. EPA
    • by TRW Environmental Eng. Olv., Redondo, Beach, CA, Sept.
     1978.

Chaaseml, H., «£ aJ..  Environmental Assessment Report; Lurgl
     Coal Gasification Systems for SNG.  EPA-600/7-79-120,
     Prepared for U.S. EPA by TRW Environmental Eng. Olv.,
     Redondo Beach, CA, Hay 1979.

Griffin, R.A., £t al.  Solubility and Torlelty ojf Potential
     Pollutants in Solid Coal Waste.  Presented at EPA
     Symposium on the Environmental Aspects of Fuel Conversion
     Technology, Sept. 1977.

Hopkins, H.T., £t ^1.  SRC-Sit-Specific Pollutant Evaluation!
     Vol. I, Discussion.  EPA~600/7-78-223a, Prepared for U.S.
     EPA. by Hittmann Associates, Inc., Columbia, Md., Nov.
     1978.

Koradek, C.S. and Patel, b.s.  Environmental Assessment Data
     Base for Coal Liquefaction Technology; Vol. _!. Systems
     for 1A Liquefaction Processes.  EPA-600/7-7«M.84a,
     Prepared for U.S. EPA. by Hittmann Associates, Inc.,
     Columbia, Md., Sept. 1978.

Leppln, 9.  Slnth Synthetic Pipeline Caa Symposium. Chicago,
     IT,, Oct. 31 - Nov. 2, 1977.

Rogoshewskl, P. J., et al.  Standards of Practice Manual for
     the Solvent Refined Coal Processes.  EPA-600/7-78-091,
     Prepared for U.S. EPA. by Hittmann Associates, Inc.,
     Columbia, Md., June, 1978.

-------
Shields, K.J., .etal.  Environmental Assessment Report; Solvent  3.24
     Refined Coal (SRC) Systems.  EPA-600/7-79-146, Prepared
     for U.S. EPA. by Hlttaann Associates, Inc., Columbia, Md.,
     June 1979.

Wuzm, H.J.  Treatment £f Phenolic Wastes. Eng. Bull. Purdue
     Univ.. Eng. Ext. Serv., 132'(II), 1054-73. 1969.
                      SUPPLEMENTAL REFERENCES
U.S. EPA.  Saaol; South Africa's Oil to Coal Story—Back-
     ground for Environmental Assessment. EPA-600/8-80-002,
     Jan. 1980.

U.S. EPA.  Air Emissions from Combustion of Solvent Refined
     Coal. EPA-600/7-79-004, Jan. 1979.

U.S. EPA.  Coal Processing Technology: Environmental Impact
     of Synthetic Fuels Development. Chem. Eng. Progr., 1975,
     6.

U.S. EPA.  Control Technologies for Particulate and Tar
     Emissions from Coal Converters. EPA-600/7-79-170, July
     1979.

U.S. EPA.  Effects of Combustion Modifications for NO
           ""^^^^™™^^™™                                   3fc
     Control on Utility Boiler Efficiency and Combustion
     Stability. EPA-600/2-79-190, Sept. 1977.

U.S. EPA.  Engineering Evaluation of Control Technology for
     the H-Coal and Exxon Donor Solvent Procesaea. EPA-600/7-
     79-168, July 1979.

U.S. EPA.  Environmental Assessment of Coal Liquefaction!
     Annual Report. EPA-600/7-78-019, Feb. 1978.

U.S. EPA.  Environmental Assessment of High-Btu Gasification!
     Annual Report. EPA-600/7-78-025, Feb. 1978.

U.S. EPA.  Environmental Assessment Data Base Ccal Liquefac-
     tion Technology! Vol. _!_!. Syntholl. H-Coal. and Eaccon
     Donor Solvent Processes. EPA-600/7-78-184B, Sept. 1978.

-------
U.S. EPA.   Environmental Assessment Data Base for High-Btu       3.25
     Gasification  Technology: Volume I. Technical Discussion.
     EPA-600/7-78-186A, Sept.. 1978.

U.S. EPA.   Evaluation of Background Data Relating to Nev
     Source Performance Standards for LURGI Gasification.
     EPA-600/7-77-057, June 1977.

U.S. EPA.   Evaluation of Pollution Control in Fossil Fuel
     Conversion  Processes — Liquefaction; SectiOw 2 - SRC
     Process. EPA-650/2-74-009P.

U.S. EPA.   Evaluation of Pollution Control in Fossil Fuel
     Conversion  Processes — Gasification.
     Section 1 - Koppers-Totzek Process-EPA-650/2-74-009A
     Section 3 - Lurgi Process - EPA-650/2-74-009C
     Section 5 - Bl  gas Process - EPA-650/2-74-009G
     Section 6 - Hygas Process - EPA-650/2-74-009H

U.S. EPA.   Mechanism and Kinetics of the Formation of NO
     and other Combustion Products — Pfr.sae J[I Modified
     Combustion. EPA-600/7-76-009B, Aug. 1976.
U.S. EPA.  Pollutants from Synthetic Fuels Production;
     Sampling and Analysis Method
     EPA-600/7-79-201, Aug. 1979.
Sampling and Analysis Methods for Coal Gasification.
       /7-7
U.S. EPA.  Sulfur and Nitrogen Balances in The Solvent
     Refined Coal Processes  (Task I). EPA-650/2-75-011. Jan.
     1975.

U.S. EPA.  Sulfur Retention  in Coal Ash. EPA-600/7-78-1538,
     Nov. 1978.

U.S. EPA. Symposium Proceedings; Environmental Aspects of
     Fuel Conversion Technology. II, Dec. 1975, EPA-600/2-76-
     149, June 1976.

U.S. EPA-  Symposium Proceedings; Environmental Aspects of
     Fuel Conversion Technology. III. Sept. 1977, EPA-600/7-
     78-043, April 1978.

U.S. EPA.  Symposium Proceedings; environmental Aspects of
     Fuel Conversion Technology. VI. April 1979, EPA-600/7-
     79-217, Sept. 1979.

U.S. EPA.  The Solubility of Acid Cases. In Methanol. EPA-
     600/7-79-097, April 1979.

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                              CHAPTER 4                                4.1



                         EXPLOSIVES INDUSTRY



4.1  INTRODUCTION



     The processes involved in manufacturing of high explosives



are discussed In this chapter.  The purpose of this chapter



Is to provide an Insight In reducing the pollutants arising



from these processes by means of process modification.  This



chapter Includes the two most produced high explosives;



trinitrotoluene and nitrocellulose.  Both explosives are



generated by nitration processes to yield nltrocompounds.



     The explosive Industry as a whole has been grouped Into



four categories:



     1.   Manufacturing of explosives



     2.   Manufacturing of propellents



     3.   Formulation [load, assemble and pack (LAP)l



     4.   Manufacturing of Initiating compounds



     Since both of the compo"ads discussed in this chapter



require large amounts of nitric acid for production, the



process for producing nitric add is also presented.  Process



descriptions given here do not include actual formulation



(load, assemble, and pack).  Figure 4.1 is an overview flow



chart of the explosive industry.



4.2  NITRIC ACID PRODUCTION



     Figure 4.2 demonstrates the role of nitric acid in the



explosive industry.  The process given here is not the only

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CHEMICAL
  MATERIAL
 NITRATION
PROCESSING
                                                                INDUSTRY
                                                                PRODUCTS
EXPLOSIVE
ORGANIC
NITKATION
PRODUCTS
rOUULATlOM
                                                                            OTHER PORMIUTIOH
                                                                                 INGREDIENTS
                       rigur* 4.1.   ProceiM>  In Iha bploelv* In'ustry (Koradak and Pitcl. 1976).
                                                                                                                                  K)

-------
                                                                4.3
                 ri_W
                 st

SKBT ACID
ttCOTERT
T

L
^^^ TO RECTCLE
AID/OR
rijur. 4.2.  Flow Chart for nitric Acid Production
           (Hudok nd ParMBC.  1977).

-------
 process available for nlcrie acid production.   Aa it ia sug-          4.4



 gested ia this section, other systems for this process must be



 closely ex2Blned«



 4.2.1  Ammonia Oxidation Process



      Za this process anhydrous ammonia is vaporized and mlsed



 with preheated air and combusted under pressure in the pre-



 sence of a catalyst tt: produce nitric oxide.   Nitric oxide



 is further oxidized by excess air to nitrogen  dioxide and Its



 dioer (NjO^).   Typically the catalyst is platlnum-rhubidlum



 or platinura-palladiura-mercury.  The bed operates at 800-919°C



 and 120 psla.   The equilibrium mixture of NO.  and its dlmer



 are adsorbed in a water cooled absorption tower to fora weak



 nitric acid (60-65Z HNOj)  (Hudak and Parsons,  1977;  Patterson,



 et al.  1976).



      The main  source of pollution from the ammonia oxidation



 process (AOP)  is the tail  gas from the absorption tower which



 produces approximately 2.5 g NO^/kg ENO^ for the high pressure



 process.   The  conversion is at least 95Z of theoretical with an



 ammonia consumption of 0.4 kg/kg HN03 (Hudak and Parsons,  1977).



 In addition, the tall gas  contains NZ (Patterson,  et  al.  1976).



     Quantitative reduction in pollutants can be achieved  as



 a  direct  result of as. increase in HMO.  production.  The  first



 strategy  in  increasing HNO^ output is a more efficient design



 for the  catalytic bed.   Ma^mum yield of nitrogen oxides can



be attained by  mixing the  gases via a filter near  the inlet

-------
 before contactIng the guaze and by  selection of  an optimal             4.5



 operating temperature (Smith and Lockyer,  1979;  Dorfman,



,££.81.  1978).  On the other hand, the mechanism  of the



 surface catalysis plays an Important role  In NO  generation.



 For small concentrations of NH_ on  the catalyst  surface,



 the conversion of MH^ Into NO Is almost complete.  The yield



 of NO  tends  to decrease, since NO Is decomposed  to N.   .



 (Atroschenko, et, al.  1979).  This decrease Is a  result of



 poor exchange between catalyst surface and the gas bulk, and



 subsequent accumulation of NO on the catalyst surface.



 Based  en this argument, the yield of NO In the bed can be



optimized by increasing the rate of mass transfer from the



bulk gas to  the  catalyst surface.  Furthermore,  the degree of



dissociation of NO increases linearly with time  {Zhidkov,



e£ al.  1979).  Thus knowledge of the NO dissociation reaction



and NO production rate will be needed In maximizing NO output.



     It  is also of value to examine the operating parameters



for the  absorption tower.  The rate of nitric acid production



can be Improved by controlling the temperature of the absorber.



Dorfman,  et al.   (1978) accomplished a 4Z increase In BNO. out-



put by adjusting  the EjO consumption, thus controlling the



temperature.



4.2.2  Nitric Acid Concentration



     The nitric acid concentration process Is a continuous



operation in which nitric acid from the AOP is mixed with

-------
concentrated H.SO,  and  fed  to  the distillation tower with             4.6



steam.  The sulfuric  acid combines with free water while HKO.



vapors  (98-99Z)  (Hudak  and  Parson, 1977) form an overhead



stream.  The nitric acid vapors, contaminated with small



amounts of  NO  and  0. Iron  HNO, dissociation, pass to a



bleacher and condensor.  The HNO.. vapors condense as 95-99Z



HNO_, while NO   and 0.  pass to the absorber column 'for conversion



to and recovery  of  additional  weak nitric acid.  This weak



nitric acid is recycled to  the dehydrating unit.  The bottom



product, consisting of  approximately 68Z H.SO, (Hudak and



Parsons, 1977),  Is  recovered and sent to a concentration unit



fox reprocessing.



     The principle  source of emissions, 0.1 - 2.5 5 SO /Kg



HN03 produced (Hudak  and Parsons, 1977), is from the absorber



tall gas.   The NO^  content  of  the tail gas is affected by



several variables:  insufficient air supply to the absorber,



high temperatures In  the absorber, and Internal leakage



which permits gases from the AOP to enter the absorber (Hudak



and Parseme, 1977).



     In search of process modifications which may lead to



abatement of pollutants, it is advantageous to consider



other processes  for producticn of nitric acid.  One such newly



developed process is  concentrating nitric acid by surpassing



the azeotrope.   In  this process k-he gases leaving the oxida-



tion step of AOP are  enriched  in NO- and then absorbed

-------
in azeotropic acid to produce a super azeotrope mixture C60Z

HNO-).  This mixture is then easily distilled.  The exiting

gases from this particular process contain 300 ppa o£ HO

(Harzo and Harzo, 1980).  The advantage of this process as

opposed to the conventional, oxidation absorption operation,

should be considered.

4.2.3  Spent Acid Recovery

     Spent acid from the various nitration processes flow into

the top of a denitrating tower.  The HNO, and NO  are stripped

from the spent acid by steam.  The bottom product contains

H.SO, which is sent to a H.SO. concentrator.  Sulfurlc acid

(93Z) from the concentrator is a by-product of most nitration

processes (Patterson, et al. 1976).
                              i
     Waste waters from the spent acid recovery unit are

characterized by high concentrations of suspended solids and

small quantities of nitrogen salts.  The solids from these

processes, called nltrobodies, must be removed from the

spent acid for pollution control.

     Table 4.1 summarizes some of the pollution problems

associated with nitric acid production and suggests the

control alternatives.

4.2.4  Recommended Areas for Pollution Control Research in

       Nitric Acid Production

     After evaluating the available literature, the following

areas are recommended for further research by the study:

-------
Table IV-1  Pollutants and Control Options in Nitric Acid Production Process
Process
Ammonia
Oxydation
Procass

Nitric
acid
concentra-
tion
ttpent
acid
recovery
Pollutants
«V N2

N0x
Nitrogen
salts
nitrobodies
Source in
Process
Tail gas
from
absorption
tower

Absorption
tail gas
From nitra-
tion
processes.
Nature of
Pollutants
Inorganic gases

Inorganic gases
Organic and
inorganic
Pollutant Control Strategy
Adjustment of operating
temperature for maximum
HNO, output.
Mixing of gases at the
inlet cf catalytic bed.
Improvement of mass trans-
fer rate between the cata-
lyst and the bulk gas.
Provide sufficient air
supply .
Prevention of leakage
from AGP.
Removal of suspended solid

-------
          Studies on kinetics and mass transfer process               4.9



          for heterogeneous catalysis to improve the



          catalytic bed design which wUi reduce NO dis-



          sociation and Increase NH. consumption.



          Studies on heat and mass transfer with reaction in



          absorption towers to optimize HNO- production by



          finding the optimal parameters for adsorption



          tower operation.



     .    Consideration of nitric acid production by means



          of a super azeotropic mixture which ma? be use -



          ful In modification of the present process.



4.3  TNT PRODUCTION



     Trinitrotoluene is the most extensively produced military



high explosive.  Production of TNT during 1969-71 exceeded



22,000 tons/month, more than any other high explosive compound



(Patterson, et a.l. 1976).  Trinitrotoluene production Involves



three distinct processes, nitration, purification and finishing.



Schematically, TNT production is shown in Figure 4.3.



4.3.1  Nitration



     Nitration cf toluene is performed in a series of reactors



with a mixed acid stream flowing countercurrently to the flow



of the organic stream.  The oleum fad to the last reactor



emerges as the spent acid from the first reactor.  The acid



stream to second and third reactors are fortified with 60Z

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                                                              SELLITE
                                                           Na,CO,
TO HIHD ACID
 PREPAMTU
                      NITRIC ACID
                     CONCENTBATIOH
                                                                                    TO STORACB
                                                                                    FflkMJLATUM
                                                                                      OR UP
         Ptgur* 4.J.  Mov Chart  for TNT Production (Budak and Parson. 1977).

-------
HNO-.  "Yellow water" is added to the second reactor.  Approxl-



mately SZ (Hudak and Parsons, 1977; Patterson, et al. 1976)



of the TNT from the third reactor is 6 or 2,3,4 and Y or 3,4,6



isomers (the favorable product is a or the 2,4,6 isoner).



     The gases from the nltrator-separator step contain CO, C02>



NO, NO., N20 and trlnitromethane (TNM).  These gases are passed



through a fume recovery system, for recovery of NO^ as nitric



acid, and are then vented through a scrubber to the atmosphere.



Final emissions contain unabsorbed NO^ as well as TNM.



Rated capacity for a typical fume recovery system operation



for the continuous process is indicated to be 272 Kg HNO^/houv



(Hudak and Parsons, 1977).  Approximately 245 Kg NO^/Mg TNT are



generated by the nitratovs of which 9.6 Kg NO^/Mg TNT are vented



to the atmosphere (Hudak and Parsons, 1977).  In addition un-



syonetrlcal "meta" isomers as well as oxidation products are



generated.  "Red Wat«sr", the main source of pollution, is the



by-product of the creaunenc of "meta" isomers in the purification



step.



     The pollutants from TNT production can c« alleviated by



improving the chemical reaction  that would decrease  the decom-



position of nitric acid, the oxldative side reactions, and



the  formation of unsymmetrlcal Isomers.  For  this purpose a



low  temperature  (-10°C) nitration, dlnitrate  toluene,



followed by a high temperature (90°C) trlnltratlon is recom-



mended  (Hill, et al.  1976; Haas, ,et al. 	).  The major

-------
 changes from the existing process occur in Che dlnlcration            4.12
 step.   It was shown that lowering the temperature from 33°C
 to -8°C In the dlnltrator step results In reduction of "mata"
 Isomers concentration In the product from 2.4Z to 1.8Z (Baas,
 et, al.      ).
     The fume recovery system for gaseous emissions in the
 nitration separation step trust be designed to operate
 efficiently at the nu"Hm.mi production level of TNT.
 4.3.2   Purification
     The crude TNT from the nitration step is washed with
 water to remove free ncids.  This step is accomplished by
 using a countercurrent flow of water.  The TNT is then
 neutralized with soda ash and treated with a 16Z aqueous
 sodium  sulfite (sellite)  solution to remove the nltro group
 in  the  meta position is a and Y - TNT by a sodium sulfonate
 group,  forming highly soluble sodium salts of the corres-
 ponding dinitrotoluene sulfonlc acid.  The TNT is then
 treated in a series of countercurrent extractors with H.O
 and is  then transferred to the finishing process as a slurry.
     The waste stream from the purifications are "yellow
water",  "red water" and "pink water".  "Yellyw water" is
 generated  as a result of  the first water w*.sh.   Some of this
 acidic  effluent is  returned to the dln-i.tration step and the
 rest is combined with other process  waste waters for treat-
ment.   "Red water",  the effluent  of  sellite treatment and

-------
subsequent washing of TNT, is composed of 27.6Z vacer, 17.3%          4.13



organics, 5.2% NaNO^, and 2.9Z NajSO^ (Hudak and Parsons,



1977).  The generation of "red water" amounts to 0.34 kg/kg



TNT produced and consists of 0.26 kg process water, 0.06 kg



organics (nltrotoluenes and nitrotoluene - sulfonlc acid



salt), and .02 kg dissolved organics (NaNO^  and NaSO^)



(Hudak and Parsons, 1977).  "Pink water" is the waste



stream generated from TNT manufacturing as well as LAP opera-



tion.  "Pink water" arises from the nitration fume scrubber



discharge, "red water" concentration distillate, finishing



operation hood scrubber and wash down effluent, and possibly



spent acid recovery waates.



     Control strategy for reduction of "red water" has been



discussed in the nitration section.



     The traces of TNT in "pink water" and "yellow water"



should be recovered.  It is possible to purify these streams



by treating the waste waterr with surfactant, thus forming a



precipitate with TNT which can easily be removed by filtration



(Okamota, _et al. 1979).  The "pink water" resulting from TNT



spent acid recovery contains 15-118 kg/day of TNT for a



typical plant (Hudak and Parsons, 1977).  In addition "pink



water" contains DNT which, by imporving the nitration process,



should be reduced to a tolerable level.



4.3.3  Finishing



     In this process TNT is solidified on a water-cooled



flaker drum or belt and is then scrapped with a blade.

-------
     The vaace streaa from che finishing process la mainly
waste from spillage, floor drainage, and washings from Che
finishing area.
     The recovery of TNT from these vaste streams should be
considered If TNT appears In any large quantities in these
streams.
     Table 4.2 is che summary of the pollution problems
associated with TKT production and suggested control alterna-
tives.
4.3.4  Recommended Areas for Pollution Control Research In
       TNT Production
     After evaluating the available literature, the following
areaa are recommended for further research by the study:
     .    Research on kinetics of the nitration reactions
          which will permit alleviation of pollutants by
          adoption of a low temperature danltration stage.
     .    Material balances to find the optimal design for the
          fume recovery system in the nitration-separation
          procesj.
     .    Recovery at TUT in the "pink water" by application
          of f&sn seoarptlcn to an aqueous solution.
4.4  HirBOCEU.OT.OSE PRODUCTION
     nitrocellulose (ST.) is the second largest product from
the military sector of the C.S. explosive industry, with a
1969-71 production level ox pearly .2,400 tens/month (Patterson,

-------
Table  4-1   Pollutanta and Control Ope Ion* In TNT Production
Procaia




Nitration









Purification








rtnlahlng
Pollutanta

CO, CO ,NO,KO
y A lin TMM
HjO, mjm

unaynnetrlcal
"hata" laoura
of TNT



"Yellow water"
acidic efflu-
ent trecea of
TUT


•Red «ater"
NaHO , Na.SO
nltrotoluenea
and nltrotolu-
•noa aulfurlc
acid
"Pink water"
DNT. TOT, all
pollutanta pre-
•ent In red
water




Spillage,
Sourcee in
proceaa
Nltratnr-
Beparator



Pune recovery
ayaten

PI ret water
waah



Selllte vaeh



Nitration fuaw
acrubber
dtecharge "led
water" concen-
tration
diatlUatea.
Plnleblng
operation
hard acrubber
UgHh down
effluent

Nature of
pollutant*
InorRanlc and
organic, gaaea



Inorganic and
organic g*aea
-
Inornanlc and
organic liquid
-


tnornanlc and
Organic liquids


Inorganic and
organic liquid






Pollutant control strategy

Low temperature dinltratloa
atage to reduce "r:ta'' Isoneri
and oildea of nitrogen and
carbon.

Change the dealfu- aa to
operate at eiastBii* TNT
prnttuetlon capaclt*
Removal of TNT from all
waate watare by application
of foa« aaparatloe. "Red water"
generation will be conaldarably
lower when "neta" laonera
forvatloa ie decreaeed.













-------
ec al. 1976).  MC is Che fundamental ingredient used in the



production of all gun propellants and many rocket propellents.



Cellulose nononitrate, dlnitratc and trlnltrate have nitrogen



contents of 6.75, 11.11, and 14.4Z respectively, representing



progreosive replacements of the -OB groups in the cellulose



unit by ON02 groups.  Typically there are three grades of NC;



proxylln, pyrocellulose, and guncotton with 8-12Z, 12.SZ, and



13Z minimum nitrogen content respectively.  The preparation



of all grades of NC require the sane procedure with the excep-



tion of the acid nix used In thb nitration process (Mark, 1966).



Manufacturing of NC consist of two processes, nltratioa and



purification.  An overall flow chart of NC production is



depicted in Figure 4.4.



4.4.1  Nitration



     In this process, pre-purlfied pulp is added to a mixture of



nitric acid and sulfurlc acid In "dipping pots".  Since the



nitration reaction is exothermic the vessel is cooled, the



operating temperatures vary from 30 to 34 C as veil as 37 to



40 C.  In a continuous process approximately 68 to 70 kg/nln



of crude NC is produced.



     The nitration is followed by centrlfuglng the crude NC



to remove spent nitrating acids.  The wrung NC is then dumped



into "drowning tubs" filled with water to stop the reaction.



The nitrogen content of NC is held between 10. SZ to 13.8Z



nitrogen (Hudak and Parsons, 1977).

-------
                                                                             4.17
H,S04OI
     "_i
                       TO MIXED
                         ACID
                          'ARATIOT
(""   ](°
1.   t   J        l
                                                        CELLULOSE
         nnic ACID

        CIMLUirUTlOB
-£_
Y
PCHOTCATIOH


          TO BECTCLE
               OR
          DISPOSAL
                                                         TO
                                                      PIOPELLAIIT
                                                      POWDUTIOB
            Fipin 4.4.   Plow Chart for MtreealluloM Production.
                         (Bud«k nd Panoiw. 1977).

-------
     The pollutants emitted from the nitration process are             4.18



0.65g  SO  and  l.OSg NO   per kg NC from  the reactor pots and J2.5g



SO  and  14.Sg  NO  per kg NC from the acid concentrators.  The NO



from the reactors  and centrifuge are vented  to an absorber where



N0x is oxidized  and absorbed in  the water generated weak nitric



acid.  Most  of the waste water from nitration process is due to



clean ups.   Thus,  waste  waters may be expected to have a low pH,



relatively high  levels of NO., and suspended solids.



     Nitration of  cellulose in the "dipping  pots" can be formed



at 17 to 45°C  (Miles, 1955),  depending on the nature of the



desired  product.   Julian Linares (1966) carried out this



nitration at 29°C  producing cellulose nitrate of 13.35Z N



content.  Thus,  it is evident that the nitration temperatures



are flexible and can result in an end-product of comparable



quality.  The  optimal operating  temperature must be considered



for reduction  of SO^ and NO^ emissions.  Furthermore, the



possibility  of converting the waste acid from the nitration



process  to aulfuric acid must be considered.  Such a process



involves  the reaction of roasting gases containing SO. at



temperatures exceeding 250°C with the acid waste (mostly H.SO,



and HN03) and  water spray to  form sulfurlc acid



(Rensh and Jenthe,  1967).  Absorption of NO  from the acid



concentrator also  may prove beneficial.



4.4.2  Purification



     The  purification of NC invloves five processes:  boiling



tub house, beater  house, poacher house, blender house, and

-------
final wringer house.  In the boiling tub house, unstable
sul£ate esters and nitrates of partially oxidized cellulose
are destroyed by acid hydrolysis.  In the beater house, the
HC is reduced to a physical state more amenable to purifica-
tion by Jordan beaters.  In the poacher house the NC is
treated with soda ash and unpulped fibers are removed.  The
function of the bleacher house is to sample and regulate the
quality of the final product.  In the final wringer house,
the KC slurry is centrifuged to approximately 30Z moisture
content.
     Due to large quantities of process water used during the
manufacturing of HC, the treatment and disposal of waste
water is a formidable problem.  Presently, overflow from the
settling pits flows to the waste add neutralization facilities
where CaCO. is added to neutralize the acid.  After neutralization,
the material is either discharged directly or transferred to
settling lagoons.  Approximately 13.6 x 10 kg CaSO^ sludge
is generated yearly, as a result of waste acid neutralization,
at one NC production plant (Eudak and Parsons, 1977).
     Vaste waters from the beater, poacher and blender houses
flew to another pit area where NC fines settle out.  Effluent
from the pit is either recycled  to the wash lines or is
discharged.  The major portion of total suspended solids in
the waste water discharged, is NC fines.  One source lists

-------
the following losses during NC purification (Jludak and               4-20
Parsons, 1977):
          Boiling tub house        68.2 kg/day
          Jordan beater house      295 kg/day
          Poacher house            295 kg/day
     Nitrocellulose fines lost during the boiling tub, Jordan
beater, and poacher house operations constitute inefficiencies
in NC Purification.  NC fines can be recovered from waste
waters by simple filtration, thus reducing the suspended solid
content as well as improving the efficiency of the process.
     It is perhaps, not possible to recycle all the water used
in the purification of NC, but it nay be possible to reduce
the volume of  the waste water.  For this purpose an In-de^th
study of NC purification is necessary.  Such studies must
concentrate on methods of purification with minimum water
usage.  Thus,  an overall material balance of the purification
step will be useful.
     Table 4.3 is  a summary of the pollution problems
associated with NC production and suggested control
alternatives.
4.4.3   Recommended Areas  for Pollution Control Research in
        Nitrocellulose Production
     After evaluating the available literature, the following
areas  are  recommended for further  research by the study:
           Better  understanding  of  the kinetics of the
           cellulose nitration will  indicate methods of

-------
Table 4-1.  Pollutant* and Control Option* In HC Production
Proceaa
Nitration
Purification




Pollutant*
SO., »,. HO,
suspended eolld
Waste acid
HMO,. «,»,
NC rtna*



Froceee uater,
acidic.
Source In
process
Raactore.
nitration
vessel.
Centrifuge
tolling Tub
houee
Jordan better
houae
poacher houaa


Mature of
pollutant
Inorganic gaaea
Mid solid.
IP. irganlc aclda
Organic, •uipended
•olida



Inorganic aclda

Pollutant Control Strategy
Improve reaction by te«peratura
adjuatncnt to reduce
generation of oildea.
Conversion to aulfurlc acid bjr
apraylng acid Haste by mter
In preaence of rotating gaaea
containing SO..
Reaoval by filtration from
waste atreaaa.



•eduction of process water.


-------
operation Co minimize NO  and SO   formation.                 4.22



Better understanding of absorption of SO  and



addition of an absorption Cower to the acid



concentrator to recover HO .



Research on filtration operations  and filtration



units for effective recovery of NC fines from



boiling tub, Jordan beater and poacher houses.



Reexamlne and modify flow streams  to optimize



water usage by recycle and other techniques la the



purification process.

-------
                           BIBLIOGRAPHY                              4.23
Atroshchenko, V., Q al. Simulation of Process and Ammonia
     Oxidation Reactor. E. A. Int. Congr. Chen. Eng. Chen.
     Equip. Des.. Autom. 1979.

Dorf man, A.D., et al., Methods of Anmania OBcidation Control.
     Artom. Khia. Proizvod. (Moscow), 1973.

Baas, R., _et al. Lov Temperature Proceas for TOT Manufacture
     Part ji Pilot Plant Development. Industrial and Laboratory
     NitraTion. ACS-Symposium Series 22, American Chemlcrl
     Society pp. 272.

Hill, M., et al., Lov Temperature Process for TOT Manufacture
      Part_! Laboratory Development. Industrial and Labora-
     tory Nitration. ACS-Symposium Series 22, American
     Chemical Society, 1976, pp. 253.

Hudak, C. and Parsons, T.  Industrial Process :*rofiles for
     Environmental Use; Chapter 12. The Explosive Industry.
     EPA 600/277/023L, Feb. 1977.

Julien Linares, French Patent 87097 <19€5).

Klrk-Othner Encyclopedia of Chemical Technology. Vol. 8,
     H.F. Hark, N.T., Wiley 1966.

Karzo, L. and Marzo, J.  'incentratlng Nitric Acid by
     Surpassing an Azeotr^pe.  Chemical Engineering.
     Nov. 3, 1980.

Miles, F., Cellulose Sitrate. Mew York: Interscience
     Publishers Inc. 1955.

Okamota, e£ al. Application of Foam Separation t£ Aqueous
     Solutions of TNT. Part jl Removal of Organic Explosives
     With Surfactant. Order no. AD-A066118, Avail. NTIS.
     froaGcv. Rep. Annoce. Index (U.S.) 1979, 79 (15), 239.
Patterson, J.V., et al. St«te of the Art: Military Btploatves
     end Propellanta Production Industry Vol. Ill Waste
     Water Treatment.  EPA/600/2-76/213C, Feb. 1976.

Rensh, Werner, Jenthe, Borst, Ger (East) Patent 58293
     (1967).

-------
Smith, Norman, and Loclcyer, John, British Patent 1538198              4.24
     (1979).

Zhidkov, B.(
-------
                             CHAPTER 5                                5<1
                      IRON AMD STEEL INDUSTRY

5.1  INTRODUCTION
     The manufacture of steel involves many processes Which
require large quantities of raw materials and other resources.
Due to the vide variety of products and processes, operations
vary from plant to plant.  However, the steel industry can
be segregated into two major components; raw steel making, and,
forming and finishing operations.  An overview of the iron and
steel process Is given in Figure 5.1 (U.S. EPA, Dec. 1980a).
     la the first major process, coal is converted to coke.
dearly all active coke plants are by-product plants which
produce, in addition to coke, usable by-products such as
coke oven gas, coal tar, crude or refined light oils,
ammonium sulfate or anhydrous ammonia, and uapthalene.
Less than 1Z of domestic coke is produced in behive coke
making.
     The coke from coke making operations is then supplied
to the blast furnace process where molten iron is produced.
In the blast furnaces, iron ore, limestone and coke are placed
into the top of the furnace and air is blown countercurrently
from the bottom.  The combustion of coke provides heat which
produces metallurgical reactions.  The limestone  forms a
fluid slag which combines  with unwanted Impurities in the ore.
Molten iron  from <-.he bottom of the  furnace and molten slag,
which floats on top of the irou, are  periodically withdrawn.

-------
                          AIR
         BEEHIVE  | COAL F1KPS
          OVEN
  COKE
   CMS
              SINTER
              VLANT
                            COKE
                 coo
                                                                 OXYCEN
                                                                 PUNT
                                                 SINTER
                                                   HOT
                                                 ICETAL
     CAS
      4
  LinuiD
                                       SLAG
        COAt
      CHEMICAL
                                                          SCRAf
                                                          STONj
                                                           IHO
                                                       iLECTHOpf S
COAL DISTILLATION
     PRODUCTS
                                        ELECTRIC   i.
                                 ..      FURNACE    LiqUID
                                 TOSIP1           I STEEL


                                          Sllfl
figure S.I.  Overview of Iron aiut Steel Hanufactiirlag Proceaa
                                                                       OXYGEN
                                           BOP
                                                                   SIAC
                                                                   OPEN
                                                                  DEARTH
                                                                   I
                                                          LIQUID
                                                          STEEL
                                                                                               IHCOT2
                                                            Liquu
                                                           *STEE1.
 CAST STEEL
INTERMEDIATES
                                                                 riHlSHED
                                                                 CAST STEEL
                                                                  PRODUCTS
                                                                                                                                    M

-------
The blast  furnace flue gas. which has  considerable heating             3*3



value,  is  cleaned and then burned in stoves  to preheat  the



incoming air blast to tbe furnace.



     Steel is an alloy of iron containing less than 1Z



carbon.  Steel making consists essentially of oxidizing



constituents (particularly carbon) at  specified low levels,



and Chen adding various alloying elements according to  the



grade of steel to be produced.  The basic raw materials for



steel making are hot metal SV pig iron, steel scrap, lime-



stone, burned lime, dolomite, fluorspar, iron ores, and



iron-bearing materials such as pellets or mill scale.   The



principle  steel making processes in use today are the Basic



Oxygen Furnace (BOP), the Open Hearth  (OH) Furnace, and,



the Electric Arc Furnace (EAF).



     The hot forming (including continuous casting) and cold



finishing  operations follow the steel  making procesj.   These



operations are so varied that simple classification and



description is difficult.  In general, hut forming primary



mills reduce ingots to slabs or blooms and secondary hoc



forming mills reduce slabs or blooms to billets, plates,



etc.  Steel finishing operations Involve a number of operations



that basically icpart desirable surface or mechanical



properties r.o the steel.  Correct surface preparation is the



most Important requirement for satisfactory application of



protective coatings to the steel surface.  The steeJ surface



must be cleaned at various production  stages to Insure  that

-------
the oxides which form on the surface are not worked into the         5.4



finished product.  The pickling process, chemically removes



oxides and scale from the surface of the steel by the action



of Inorganic acids.  This method ia the. most widely used due



to comparatively low operating costs and ease of operation.



Pickling win be the only finishing operation considered in



thi* report.



5.2  COKE MAKING



     Figure 5.2 provides a flow diagram of a coke plant, the



processes required include:



     1.   Coal Mining and Transportation



     2.   Coal Preparation



     3.   Charging of Coal



     A.   Coking



     5.   Pushing and Quenching



     6.   Coke Handling and Tar Condensation



     Coal dust is emitted during size reduction and trans-



portation of the coal.  Emissions are estimated to be 5 kg/yr/tor



of coal.  Particles are generally less than 0.1 ma In size with



suspended fractlone in the range of 1 to 10 u (Barnes, et al.



1970).  The wastewaters produced from coal preparation may



contain up to 200 g/1 of suspended particles (28 mesh to



colloidal dimensions) and most can be eliminated by thickener/,



cyclones and filters (Keystone Coal Industry Manual, 1974).



Some trace elements contained in the wastovater include arsenic,



cadmium and lead.

-------
                                                               3.3
                      111
                 MINING
                   AMD
                TMRSFORTATIOM
                         11
HATH
                   COM.
                 nCPAAATIO*
  AIR
FUEL
HATER
          BEMI7ACTED
            COAL.
                COAL CHARGING
                 TO  OVEN
                 COXINC
                con
                 PUSHING ARD
               WET QUEHCHING
                    con
                HAHDLIHG
                                    COU OVER CAS POR
                                   ^BT-PRODUCT RECOVERY
                                    AND COMBUSTION
                         11      I
                                     T
                                     t
                                         CASEOUS HASTES
                                        LIQUID HASTES
                                        SOLID UASTSS
               COKE TO BLAST FUMUCE


Figure S.2.  Cok« (taking

-------
     Coke  is  the  residue  Croa  Che deacruccive disCillaclon of         5.6



cool.  Coal is heaced  in  the coke ovens (with no air in the



oven) by adjacent chambers or  flues using; 1) some of the



gas recovered from coking operations, 2) cleaned blast



furnace gas,  or,  3) a  mixture  of coke oven and blast furnace



gases.  During carbonization about 2QZ to 3SZ by weight of



the initial coal  charge is evolved as mixed gases and vapors



which are  collected through an opening at the cop of the oven.



Froa one ton  of coke about 544-636 kg blast furnace coke,



45-91 kg coke breeze,  270-325  m  coke oven gas, 30-45 kg tar,



9-13 kg (NBA)^S04, 54-312 kg ammonia liquor and 9-15 kg light oil



are produced  (Keystone Coal Industry Manual, 1974).



Potentially hazardous  emissions trom a coke plant Include



CO, amines, organometallies, tar and soot, carbonyls, hydrogen



cyanide, sulfur compounds, etc. (Cavanaugh, et al. 1974).



The use of refined or  cleaned  coal as a raw material and



better knowledge  of coking reactions can eliminate or reduce



some of these pollutants.



     Most  of  the  participates  generated in hot coke quenching



operations are collected  and reused within the plant and do



not constitute a  significant pollution problem.  However,



wastevaters from  wet coke quenching operations contain high



concentrations of ammonia, oil and grease, and phenol (all



of the three  exert a biochemical oxygen demand), plus cyanide,



sulfide and suspended  solids.  Table 5.1 gives an analysis



of quench wastewater samples (U.S. EPA, Feb. 1977).

-------
TABLE 5.1  AVERAGE ANALYSIS OF QUENCH WATER SAMPLES	          5'7
Contaminants
Phenols
Sulfates
Chlorides
Total Ammonia
Cyanides
Total Solida
Concentration
(pen)
776
1,066
1,954
2,517
98
5,214
     Some of the treatment technologies used for control of

nnllutlon from the quench waters are (U.S.  EPA,  Jan.  1974):

     1.   Distillation With Ammonia Recovery of  Waste
          Ammonia Liquor

     2.   Alkaline Ammonia Stripping

     3.   Neutralization

     4.   Settling

     5.   Air Flotation

     6.   Clarification With Vacuum Filtration of Sludge

     7.   Filtration

     8.   Carbon Adsorption

     Conversion of hot coke quenching from  the vet to the dry

process would: 1} eliminate air and wastewater emissions from

the wet quenching process, 2) provide additional potential

for participate emission since control of these  emissions

-------
are pare of  the the dry quenching design (U.S. EPA, July 1976).       5.8



Pollution  control costs are not  significant for the dry



process.   The hoc quench gases can be cooled recovering



useful energy.  Capital and operating costs are significantly



higher than  vet quenching operations by up to 10.7 dollars



per ton of coke.  Dry coke quenching is claimed to produce



a higher-grade coke by Russian authors, thus reducing the



coke rate  in the blast furnace.  However, this claim needs



to be demonstrated for U.S. coals.



     A detailed description of the dry coke quenching process



is given in  "Environmental Considerations of Selected Energy



Conserving Manufacturing Process Options."  In dry quenching



of coke, the hot coke pushed from the ovens is cooled in a



closed system.  Dry quenching uses "inert" gases to extract



heat from  the incandescent coke by direct contact.  The heat



is then recovered in waste heat boilers or by other techniques.



The "inert"  gases can be generated from an initial intake of



air which  reacts with the hot coke to form a quenching gas



containing 14.SZ C02> 0.4Z 02> 10.6Z CO, 2Z Hj and 72.5Z Nj.



After cooling, the gases pass through two dust recovery



cyclones (where participates are collected at -400-600 Ib/hr.)



before being recycled.  The partlculates consist mainly of



carbon dust  and is bunt as solid fuel.  Part of the gases



after participate removal may be sent for removal of evaporated



cyanides and SO , to prevent accumulation.   Additional



research is  needed to study the applicability of dry quenching

-------
of U.S. cools and the cleaning of recycle gases using systems         5.9



similar to those used in by-product coke recovery operations,



as discussed below.



5.3  COKE BY-PRODUCT RECOVERY



     Figure 5.3 shows the various coke by-product recovery



operations (U.S. EPA, Feb. 1977).



     The condensace from the cooled coke oven gases contains



tar and ammonia liquor which are decanted.  The uncondensed



gases are reheated and passed on to the ammonia scrubber.



Some of the tar derivatives recovered Include creosote oil,



cresols, naphthalene, phenol and medium and hard pitch.



Phenol is recovered from the weak ammonia liquor by scrubbing



with benzene or light oil.  The phenollzed benzene or light



oil is contacted with caustic soda to extract sodium pheno-



late.  The sodium phenolate is neutralized with CO. to



liberate crude phenols.



     The weak ammonia liquor is heated to remove "free"



ammonia and is then contacted with Ca(OH). solution to
remove and strip HH_ as vapor.  These vapor* are sent to the



ammonia absorption process.  The waste liquor generated In



the ammonia still contains 0.75 of sulfide as 3.3.  The



total amount of waste produced ranges between 80-340 tons of



coal carbonized.  These wastes may contain up to 20Z by



volume of Ca(OB)2 (U.S. EPA, Feb. 2977).  It is suggested



that Ca(OH)2 be recovered from the waste liquids and



recycled to the ammonia still.

-------
COKE
f
                       ABSORPTION
                SULFUR1C
                                                                            SODIUM PHESOLATE
                                                                                I3 RECOVLRED
                                                                                FROM STILL
CRYSTALLIZA-
TION AND
 DRYING
                                  WATER IN
                              0 a
                                           LIGHT OIL
                                           RECOVERY
                                                       H
                                           'HATER OUT
                                                H OIL  —
                                            EC1RCULATED
                                                it
                                          FRACT10NATIOI
                                              AND
                                            RECOVERY
                                                                                                      0 CASEOUS
                                                                                                      1 HASTES
                                        I
SOLID
HASTES
                             FIGURE 5.3.  Coke By-ProductB Recovery (U.S.  EPA. Feb.  1977).

-------
     Ammonia vapors from the primary cooling and heating opera-      5.11

tions and the ammonia still are absorbed in a dll.   HjSO^

solution, the (NH^SO^ product is crystallized from the

resulting slurry.  Gases leaving the ammonia absorber are

scrubbed with recycled wash oil to remove light oil.  The

light oil is refined to produce benzene, toluene and xylene.

The uncondensed "coke oven gases" are sent to a gas holder

and contain mainly CO., CO, N.,^, 0. and H.S.  The composi-

tions are given in Table 5.2.

TABLE 5.2.  COKE OVEN GASES (AFTER BY-PRODUCT RECOVERY)
            (Ess, 1948; Wilson, et al. 1980)

Component
co2
CO
H2
N2
0,
2
H,S
2
It is suggested that H.
Kg/ton of Coal
10.42
31.54
13.66
3.85
7.17

3.25

,S be removed prior to ammonia
absorption using the Glaus or Stretford process (Dunlap, et

al. 1973).

     One of the major pollutants from light oil recovery Is

cyanide (Alien, 1979).  HCN contained in the gas leaving the

cooling tower at one site amounted to 0.56 Ib/ton of coke.

-------
It is suggested that cyanide be removed by adsorption or other



suitable methods.  About the same amount of cyanide is expected



to be in the cooler wastewaters.  Biological systems followed by



nutrient addition In the form of phosphoric acid have been



reported to produce a reduction of cyanide of up to 95Z



(Hofstein and Kohlmann, 1980).



5.4  IRON MAKING



     Blast furnaces are large cylindrical structures in



which molten iron is produced by the reduction of the iron



bearing ores with coke and limes rone.  Reduction is promoted



by blowing heaeed air Into the lower part of the furnace.



As the raw materials melt and decrease in volume, the entire



mass of the furnace charge descends.  Additional raw materials



are added (charged) at the top of  the lurnace to keep the



amount of raw materials within the furnace at a constant




level.



     Iron oxides react with  the hot CO from the burning coke,



and the limestone reacts with Impurities  in the Iron ore and



coke to form molten slag.  These reactions start at the top



of the furnace  and proceed to completion  as the charge passes



to the bottom of the  furnace.  The molten slag, which floats



on top of the molten  iron, is drawn off  (tapped) by way of



a "tapping hole."  Blast  furnace operations within the U.S.



produce greater than  99%  of  the basic  iron.  The total rated



capacity of all U.S.  plants  is 321,8.'»7  tons/day.

-------
     Ti-e ^ases which are produced In the furnace are exhausted       5.13

through the top of the furnace.   These gases are cleaned,

cooled, and then burned to preheat the incoming air to the

furnace.  Generally, gas cleaning involves the removal of

the larger participates by a dry dust collector, followed by

a variety of wet scrubbers for finer particle removal.  Many

of the same pollutants found in coke plant wastewaters are

also found in iron making wastewaters.  The phenolic pollu-

tants found In iron making wastewaters are attributable to' the

coke used in the iron making process.  Cyanide and ammonia

(reaction products formed within the furnace or transferred

from the coke charge to the furnace gases) are carried over

with the gas stream and transferred to scrubbing waters.

Table 5.3 lists some of the pollutants in these scrubbing

waters  (U.S. EPA, Dec. 1980b).


TABLE 5.3.  ANALYSIS OF BLAST FURNACE SCRUBBER WASTEWATERS
	FLOW RATE. GALLON/TON IRON 2057	


          Pollutant                  Concentration
                                        mg/1


                                        63.2
          Cyanide                       16.9

          Phenols                        2.77

          Flouride                      23

          Suspended Solids             693

          pB                             7.1 - 8.3

-------
The  cleaned gases  are  then cooled with direct contact sprays        5.14

In large  gas cooling vessels before being burned.

     About  901 of  the  present blast furnace wastewater

treatment systems  include recycle (after thickening) and

discharge only about 52  to 10Z of the process flow.  The

dewatered solids from  thickener are either sent to the sintering

operations  or to off-site disposal.  These solids contain

Zn, Ag, Ni,  Cu, Pb, etc.  The effluent concentrations are

listed in Table 5.4.
TABLE 5.4.  WAGTEWATER THICKENER UNDERFLOW (U.S. EPA. DEC. 1980b)
            FLOW RATE 87 GALLONS/TON IRON

Pollutant
Cu
Pb
Nl
Ag
Zn
Concentration
mg/1
0.19
2.11
0.10
0.023
27.5
It is suggested that the gas cleaning system be modified to

use few and  if possible no wet scrubbers.  For fine particle

collection the possibility of using electrostatic filters or

magnetic filters should be studied.  The cleaned gases are

generally cooled in spray towers  (before being burnt) thus

-------
producing more vascevaters.  Inscead It is suggested that  1)         5.15



cleaned gases be burnt directly, or  2) be cooled by heat ex-



change with air fesd to the blast furnace and then burnt.



     It was suggested for the coke by-product recovery process



that organic compounds be removed by adsorption on activated



carbon.  Similar systems are proposed for removal of organlcs



from the blast furnace wastewaters.  The use of biological



oxidation and alkaline chlorinatlon systems for treatment of



these wastewaters to remove HCN is also suggested.



     Hofstein and Kohlman  (1979) report that one of the non-



11. S. plants they visited uses Caros Acid (per-monosulfurlc



acid - H.SOe) to reduce cyanide and phenol levels in the



blast furnace wastewaters  to 0.2 mg/1 HCN and 0.5 mg/1



phenol.  The normal influent level of phenol at that plant



was 2 mg/1.  The addition  of polyphosphate in the cooling



towers had been reported to aid in CM removal but at CN



levels above 10 mg/1 it was not effective.  Another plant



theorized, based on operating experience, that the formation



oS metallo-cyanlde complexes adsorbed in the sludge reduced



cyanide  levels from 0.2 mg/1 to 0.1 mg/1.  Another plant in



West Germany uses aeration prior  to discharge to  the clari-



fiers as an Integral part  of the  gas cleaning water recircu-



lation system.  The purpose of  aeration is to strip CO and C02



from the water and to  precipitate CaCO..  A portion of the



clarifler  sludge  is recycled to act as  a seed and enhance



precipitation and sedimentation.

-------
     Osantowski and Gienopolos (1979) obtained pilot plan1:            5.16



data on the applicability of advanced waste treatment methods



for upgrading blase furnace wastewaters.  The treatment



methods investigated included:  alkaline chlcrination, clarifi-



cation, filtration (dual media and magnetic), ozonation,



activated carbon and reverse osmosis.  Alkaline chlorination



consisted of elevating the pB of the oncoming vastevaters to



11.0-11.5 with addition of sodium hypocblorlte for oxidation



of cyanide; followed by neutralization for ammonia removal.



The settled effluent was dechlorlnated by activated carbon.



These studies showed that above a C12:UH3 ratio of 7.3:1,



NH. levels dropped sharply to as low as 0.48 mg/L, NB3 removal



was high and all other ozidizable contaminants were also rencved.



Further research is needed to optiolze  the CljtN^ ratio to



obtain the best ammonia removal.  Ozonation was determined to



be effective in meeting discharge levels.  Prefiltered waste-



water was elevated  to a pH of  10.5  prior  to ozonation.  The  ozone



dosage varied  from 0-1, 500  mg/1 of wastewater treated and



contact  times  from 60-240 minutes.   NH, and cyanide levels of



3.1 and  0.001  mg/1  were achieved.   Research  is required to



find  the optimal  pB and contact time.



     Metals  in the raw wastewaters  may  be better  removed by



sulfide  precipitation.  The use of  excess sulfide in  a  treated



effluent may cause an objectionable odor  problem.  A  decrease



in pH might  affect personnel If the wasteweter becomes  acidic.



 In view of  these objections, a ferrous sulfide slurry may  be

-------
• good choice since it does not dissociate readily, thus,



controlling the pressence of excess sulfide.  To this date,



there are no furnace vastevater systems currently using



sulfide precipitation (U.S. EPA, Dec.l980b), even though this



technology has been demonstrated in the metal finishing



industry.  Zt is suggested that applicability of sulfide



precipitation to remove metals from blast furnace vastevaters



be investigated.



     There are two types of dust materials collected from the



blast furnace operations;  1) dry-collected dusts are ob-



tained from cyclone dust collectors, and ,  2) vet-collected



dusts are obtained from vet scrubbers after reducing the



vater content by thickners and filters.  The bulk of this



material Is used as landfill even though some is utilised



In the sintering operations.  Coke, pellet, and BOP slag



fragments are the predominant components of the dry dust



materials and include significant quantities of hematite,



magnetite, graphite, calcium carbonate, vusite and silica.



The size distribution of these dusts ranges from 2.3 mm



to 0.014 mm.  Vet-collected dusts are similar to dry-



collected dusts and average 24Z by velght Fe and 451 by



weight C, with about 68Z of the material less than 60.5 pn



in size.  The high and variable carbon content of this



material makes it difficult to use in the sintering operations.



Furthermore, the high amounts of zinc in the vet-collected

-------
dusts can  impede  Che blast furnace operations if recycled.            5.18



A briquetting method for dezlncing these dusts has been de-



veloped  (Allen, 1979).  Typical analysis of salable cine



oxide dust is 63.31 Zn, 6.9Z Pb, and 1.2Z Fe.  Another possible



alternative dezincing process may be extracting the zinc from



collected  dusts.



     The Waelz process is a direct reduction technique that



has been used for 20 years to refine low grade zinc ores.



The Berzelium and Lurgi companies conducted a large scale



experiment in Dinsburg, Germany that used iron and steel



material dusts (Rausch and Serbert, 1948).  They observed



that dezlncificatlon vaa possible with a continuous process,



9SZ of the zinc and SOZ of the alkalis were removed and 95Z



of iron was metallized.  This process was found to operate



more economically on a lover throughput (10  tons/year) than



other direct reduction processes (U.S. EPA, April 1979) and it



Is less sophisticated since it does not require peUetizing



before reduction.



     Advances in technologies such as auxiliary fuel injection,



higher hot blast temperatures, moisture injection, and oxygen



enrichment have been major factors in increasing the effi-



ciency of  the blast furnace process.  Based on a statistical



analysis technique of certain operating parameters, Quigley



and Sayles (1974) concluded that as the coke stability is



improved by increasing bulk density and coking time, and



Improving  coal grinding.  They also found that an Increase

-------
of l.SZ in ash content of the coke resulted in over 50Z off-         5.19



quality iron over a two day period.  Thus, a study aimed at



improving blast furnace performance by improving the coking



process is suggested.



     Slags from the blast furnace usually come into contact



with water immediately after their removal from the blast



furnace.  The reaction between slag and water produces E^S



and SO. among other gases, which even though small in quantity



can cause odor problems.  Knowledge on the mechanism of HjS



and SO, formation is limiting.  It Is believed that SOj result?



primarily from the oxidation of HjS.  It is desirable to



suppress the formation of sulfurous gases, primarily HjS.  In



laboratory experiments Kaplan and Rengstroff (1973) showed



that treatment of the slag with the oxidizing materials Fe2°3*



CO., CaCO., open-hearth slag or steam decreased the emission



of H.S.  In-plant trials where commercial batches of blast



furnace slag was treated with steam prior to water quenching



the hot solid slag and molten slag, the steam treatment resulted



in an  Increase in the emission of E^S.



     One important process modification then, would be, to



optimize slag quenching methods to decrease H-S emissions.



This would require a better understanding of H^S and S02



formation during slag quenching and the effect of various



additives.

-------
     Another option  is  to  produce elemental sulfur from B.S          5.2''



by Che Claus or  Stretford  Process.   If BCN is found to cause



fouling of  the Claus catalyst  beds or decrease the life of



Stretford absorption solution, ECU may have to be removed



from the feed gases  by  the polysulflde process which is



known to have removal effJciences of up  to 90% of HCN (Hill,



1945).



     Cyanides are  thought  to form in the blast furnace



according to the following reaction:





     K20 +  3C +  H2   *   2KCN •«• CO                      (5.1)



This reaction is favored at high temperatures and in the



absence of  CO.   The  oxidation  of cyanides takes place accord-



Ing to the  following reaction:






     2KCN + 4C02    ?  K2C03 + NZ +  5CO                (5.2)






It would appear  that conditions favorable for the formation



of cyanides,  i.e., Che  coexistence of coke, alkali oxides,



and N. at high temperatures and in a reducing atmosphere are



Inherent in the  operation  of the iron blast furnace.  In



contrast. It may be  possible,  at least in principle, to



modify the  conditions In the stack region, so that oxidation



of cyanides is promoted.   Very little work has jeen done,



however, on the  kinetics of the reactions in the formation



and oxidation of cyanides  In the blast furnace.  Sohn and



Szekely (1943) assumed  mass transfer to  the KCN particle to

-------
be race controlling and concluded Chat there may be a real             5.21



possibility of reducing the net emission of cyanides from the blast



furnace by the appropriate manipulation of the temperature



and CO/CO, profiles within the stack.  It is suggested that



research efforts be directed at obtaining kinetic information



on the formation and oxidation of cyanides In the blast furnace



and at optimizing stack design and operation to reduce the total



cYanJue in the effluent gases.



5.5  STEEL MAKING



   Steel is an alloy of iron containing less than l.OZ carbon.



Steel making is basically a process in which carbon, silicon,



phosphorous, manganese, and other impurities present in the



raw hot metal or steel scrap, are oxidized to specific mini-



mum levels.  The hot steel is then either teemed into ingots



or transferred to a continuous casting or pressure casting



operation for direct conversion into a semi-finished product.



   The basic raw materials for the stee?. making processes



are hot metal or pig iron, steel scrap, limestone, burned



lime, dolomite, fluorspar, iron ores and iron bearing minerals



such as nellets, mill scale and waste solids from  the lurnaces.



Various types of steel are manufactured by adding  alloying



agents either to the hot charge in the furnace or  to the



ladle of steel after the hot steel is "tapped" from the



furnace.  The three types of steel making processes are:



   1.     Basic Oxygen Furnace  (BOF)

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      2.    Open Hearth Furnace (OH)



      3.    Electric Arc Furnace (EAF),



A comprehensive discussion of the various  operations  that



constitute each of these processes  is  given by McGannon (1964).



      The large quantities of airborne  gases, dusts, smoke,



and  iron oxide fumes generated in the  steel making processes



are  collected  and  contained by various gas cleaning systems.



Depending on the type of gas cleaning  system used, waste-



waters discharges  or sludge generation can result.  The



basic gas treatment systems used  are:



                BOF  Semi-wet



                     Wet-Suppressed Combustion



                     Wet-Open Combustion



                     Semi-vet



                OH    Wet



                EAF  Semi-wet



                     Wet



The  semi-wet air pollution control systems use water to part-



ially cool and  condition the waste gases and fumes prior to



final particulate  removal in dry  collectors such as precipi-



tators or baghouses.  Wet air pollution control systems use



water not only  to  cool  the waste  gases  but also to scrub the



fume  particles  from the waste gases.  BOF uses combustion



systems,  suppressed or  open,  to control CO emissions.

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     The  two variations  of  the BOF process  are  the  Ka\do pro-     5.23



 cess and  the Q-BOP furnace.  At present,  there  is only  one



 Kaldo  installation and only three Q-BOF installations in the



 United States.  The waste products from the BOF steel making



 process include airborne fluxes, slag, carbon monoxide  and




 dioxide,  and oxides of iron (FeO, ^2°3'  Fe3°4^ «**-tted as



 submicron dust.  Also, when hot metal  (iron) is poured  into



 ladles or the furnace, submicron iron  oxide fumes are released



 and some  of the carbon in the iron is  precipitated  as



 graphite, commonly called "kish".  Approximately 1Z to  2Z



 of the ingot steel is ejected as dust.  The primary gas



 constituent emitted from the BOF during the oxygen  blowing



 cycle is CO.  CO will burn  outside of  the BOF,  if allowed to



 come in contact with outside air (open combustion).  If



 outside air is prevented from coming in contact with the CO



 gas, combustion Is retarded  (suppressed combustion).



     In the Open Hearth  (OH) process,  steel is produced in



 a shallow rectangular refractory basin, or hearth,  enclosed



 by refractory lined walls and roof.  OH furnaces can use



 all scrap steel charge;  however, a SOZ scrap/SOZ hot metal



 charge is typical.  Fuel oil, coke oven gas, natural gas  etc.



are burned as fuel and the hot gases are circulated above



 the raw material charge.   The waste gases are water cooled,



scrubbed with recycled water and sent through a electrostatic



precipltatir before being vented.   The waste products resulting



from the OH process are  slag, iron oxides as submicroa dust,

-------
waste gases  (consisting of  air, C02 and water vapor), SO^ and        5.24

NO   (due  to  the nature of certain  fuels being burned) and

oxides of zinc.

     The  Electric Arc Furnace  (EA?) steel making process pro-

duces high quality alloy steels in refractory lined cylindri-

cal  furn&ces using a cold steel scrap charge and fluxes.  The

waste products from EAF process are smoke, slag, CO. CO., metal

oxides (mainly iron) emitted as submicron particles and zinc

oxides.

     Raw  wastewater characteristics are given in Table 5.5

(U.S. EPA, Dec. 1980b).


TABLE 5.5.   RAW WASTEWATERS FROM STEEL MAKING OPERATIONS
	CONCENTRATION  (mg/1)	


I.   Basic Oxygen Furnace

     a.    Semi-wet (Flrvrate - 429 gal/ton)

           Suspended Solids                          345.0

           Cu                                         0.004

           Pb                                         1.5

           Zn                                         1.0

     b.    Wet-Suppressed Combustion (Flowrate •
           982 gal/ton

           Suspended Solids                         1500.0

           Cr                                         0.5

           Cu                                         0.25

           Pb                                        15.0

           Ni                                         0.5

           Zn                                         5.0

-------
TA2LE 5.5.  Continued	        5.25


     c.   Wet-Open Combustion (Flowrate -
          446 gal/ton)

          Suspended Solids                         4200.0

          Cd                                          0.5

          Cr                                          5.0

          Pb                                          1.0

          Zn                                          5.0

XI.  Open Hearth Furnace

     a.   Semi-Wet (Flowrate - 1163 gal/ton)

          Suspended Solids                          500.0

          Cr                                          0.8

          Cu                                          0.8

          Cyanide                                     0.04

          Zn                                          0.5

     b.   Wet (Flowrate - 554 gal/ton)

          Suspended Solids                         1100.0

          Cu                                          2.0

          Pb                                          0.6

          Zn                                        200.0

III.  Electric Arc Furnace

     a.   Semi-Wet (Flowrate - 60.4 gal/ton)

          Suspended Solids                         2200.0

          Cu                                          2.0

          Pb                                        30.0

          Zn                                        125.0

-------
TABLE 5.5.  Continued	         5.26





III. Electric Arc Furnace ".ont'd



     b.   Wet (Flcwrate - 3060 gal/ton



          Suspended Solids                         3400.0



          Arsenic                                     2.0



          Cd                                          4.0



          Cr                                          5.0



          Cu                                          2.0



          Pb                                         30.0



          Zn                                        125.0
     The zreatmenc methods presently used do not attempt to



remove these toxic metals exclusively (U.S. EPA, Dec. 1980b).



Sulfide precipitation to enhance the precipitation of metals from



wastevaters before recycle is a suggested pollution control



approach.  There is a need to develop extraction and ion



exchange systems to remove toxic metals formed in the steel



furnace wastevaters.



     Suspended solids in steel making wastevaters are very



fine, red in color, and are principally iron oxide.  Magnetic



separation can decrease the level of suspended solids to



25-30 mg/1 (Centl, 1973).

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5.6  ACID PICKLING                                                   5'2?



     Acid pickling is the sceel finishing process In which



steel products are immersed in heated acid solutions to re-



move surface scale.  Based on the type of pickling acid used,



this process can be subdivided into:



     1.   Selfuric Acid Pickling



     2.   Hydrochloric Acid Pickling



     3.   Combination Acid Pickling



     Wastewaters are generated by three sources in the pick-



ling process.  The largest source is the rlnsewatcr used to



clean  the acid solution from the product after it has been



immersed in the pickling solution.  The second source is the



spent  pickling acid liquor which is used to treat the steel



product.  The spent pickle liquor is a small volume waste,



containing high concentrations of iron and toxic metal



pollutants.  Vastewater from the wet acid fume scrubbers is




the  third source.



     Rinse water  discharge flows can be minimized with a



cascade of countercurrent rinse systems.  These  systems



reduce water  flow, concentrate the  pollutants  In the last



rinsing chamber,  and  achieve more  thorough rinsing  (D.S. EPA,




Dec.  1980c).



     The most common  method  of recovering spent  sulfuric acid



is acid recovery  by  removing  ferrous  sulfate  through crystal-



lization and  rinsing the concentrated acid  (U.S.  EPA, Dec.  1980c).

-------
The spent liquor from hydrochloric acid pickling contains free        5.28



hydrochloric acid, ferrous chloride, and water.  This liquor



is heated to 1,050°C, at this temperature the water is complete-



ly evaporated and Fed. decomposes completely into Fe.O. and



HC1 gas.  The iron oxide is separated and removed and HC1



gas is.reabscrbed in the water.



     Recycle systems, with recycle rates as high as 90Z-95Z



of the total wastewater flow are used to control pollutants



ger.srated during the scrubbing of acid fumes.  Recycle rates



are limited by the build-up of solids.  Lime and sulfide



precipitation are suggested to Improve precipitation of



metals in the wastewaters.



     Temperature and agitation are Important operating factors



in the pickling process.  The temperature of pickling drama-



tically effects the reaction rate.  Agitation is probably



the most ignored aid to good pickling.  The speed of pickling



can be increased significantly by properly agitating the acid



bath cr using the steel product during the pickling opera-



tion.  One method of agitation is an air-operated, mechanical



agitation system.  An added benefit of this system is that



the evaporation caused by air agitation concentrates, rather



than dilutes, the acid bath.  It is suggested that process



improvements be aimed at decreasing pickling time and main-



taining good agitation and high enough acid concentration



levels during pickling.

-------
     Table 5.6 lists the various process modifications 3ug-           5.29



gested for control of pollution from the iron and steel industry.



5.7  RECOMMENDED AREAS FOR PROCESS MODIFICATIONS RESEARCH



     After careful evaluation of the available literature, the



following areas are recommended for further research:



          Use of refined or cleaned coal in coke making



          Study of the formation of cyanides and carbonyls



          during coking in order to prevent or reduce



          pollutant formation.



     .    Dry coke quenching of U.S.  Coals to eliminate



          quench water contamination.



          The effect of process variables such as coal



          grinding and coking time on coke produced.   This



          would be used to improve the quality of coke



          stability in order to enhance blast furnace



          performance.



          Development of biological oxidation systems to



          remove HCN from by-product  coke making vastewaters.



     .    Absorption of H.S from coke oven gases by Glaus



          or  Stretford  process.



     .    Development of better CN removal systems from



          blast furnace vastewaters by using additives



          such as Caros acid (HjSO.) and  polyphosphate,



          and by aeration.

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Table 5-6.  Pollutants and Suggested Control Strategy Iron and Steel Industry
Pri-cesa
Coke
Making
Coke
By-Prnduct
Reciwery
Iron
Making
Pollutant
OrganoBatalllcs,
Carbonyls,
HCM. SO^. H2S
Phenols, Sulfatee,
Chlorides, Aononla,
Cyanides
H,S
HCH
Metals
(Zn. Pb. etc.)
Source In Process
Enlaslons froa
coke ovens
Uastewatera froa
coke quenching
Coke oven gases
having by-product
recovery
Cooler Uastewsters
Blast Furnece
wastewsters
Nature of Pollutant
Toxic gases
Dissolved and
suspended solids
	


Suspended
solids
Pollutant Control
Strstegy
Use of refined
coal, better control
of coking operations.
C -version to dry
coke quenching with
psrtlcalste removal
Removal of H.S by
Claus or StrCtford
Process
Removal of KCH
by biological
oxidation syateos
Conversion irom
wet to dry gas
cleaning aystcBs -
electrostatic.
•agnetic filter*

-------
Table 1-6.  Pollutant* aad SuMeeled Control Siraief, for Iron and Steal laduatry (Conl'd)
Proceaa
Iron
Naktnf
Pollutant
C]TMld*
Hoc
"2S- W*
CyMldm
Sourca la Froc**«
•!••( Pur»*c«
lta*t«Mt«r*
•IMI rar«*t«
Oust*
Blast PurMc*
•!•• O"*"11!"*
BUit Vunac*
•aiur* of Pollniut


Inorganic (••••
laoriaatc
patilculatta
rollutanl Control
Strategy
OptlaJtatlon al pa
lad contact lla» to
laprova alkalloo
chlorlnalloo. ua«
of addltlraa aucn M
HjSO. aod B«t])pho«phalae
3ol*mt ••traction
ol.In or t«oa«al by
Ualai proeaaa. racket*
treated dual a to
alnterlna, plant
uao of addillvaa to
••prove oaldalloa of
V
Improved atack de»l|»
and opera! loo to
opllBlia oildalloo of
cyenloae

-------
Table V6. Pollutant* and Suggeeted Control Stratopy for Iron and Staal laduatry (Coat'd)
Procaaa
Staal
Acid
Pickling
Pollutant
Zn. Cr. Pb. Co.
Iron oilda
Spant Plckl*
Liquor (S?L)
•Inaa Hatara
Source In Procaaa
Waatavatara froa cooling
and conditioning of
gaaaa from •(••! auklng
.__-._
product aftar pickling
Nature of Pollutant
Suapended. diaaolvad
aollda
Inorganic aclda.
auepended toalc
etetele. Iron
Inorganic acid*.
•ucpendad toilc
Belale. Iron
Pollutant Control
Stracagy
Sulflda precipitation
of loilc oalala 4
recycle of treated
uaatavatara m*gn«ilc
eeperecloa ef H'lneadet
Iron aildaa.
•olvaut aa tract Ion of
Improved plckllne
procaaa by temperature
control and good
agitation to dacraaaa
SPL. recovery of acid
Hlnlnlilng rlnaauater
dlachargea by uilng
caacada or counter-
currant rlnee eyetaaa
10

-------
Optimization of pH acd contact tine to improve             5.33
Alkaline chlorination and ozonation to upgrade
blast furnace vasteuaters.
Solvent extraction of Zinc or derinciflcatlon by
ttalez process to remove zinc from blast furnace
duata.  Such zinc removal can facilitate the use
of treated duats in the sintering process.
Study of kinetics of B.S and SO^ formation during
blast furnace slag quenching to develop methods by
which ELS formation can be decreased.
Study the kinetics of formation and oxidation of
cyanides in the blast furnace to optimize the
design  and operation of the stack in  order to
oxidize the cyanide.
Development of solvent extraction and sulfide
precipitation methods to  remove toxic metals from
the  recycled steel plant vastevaters.
Study the effect  of  temperature and agitation
in order to optimize pickling operations.

-------
                           BIBLIOGRAPHY                              5.34
Allen, E.J.  International Mineral Recovery T.td. Dezinclng
     Process.  Proc. of Che First Symp. on Iron and Steel
     Pollution Abatement Technology, Chicago (1979),
     EPA-600/9-80-12, PB80-146258.

Allen, G.C., Jr.  Environmental Assessment of Coke By
     Product Recovery Plant.  Proc. of the First Symp.
     on Iron and Steel Pollution Abatement Technology,
     Chicago. (1979), EPA-600/9-80-012, PB 80-176258.

Barnes, T.M., j£jil.  Evaluation of Process Alternatives
     to Improve Control of Air Pollutioi  from Production
     of Coke.  Battelle Memorial Institute, Columbus, OH,
     Jan. 1970.

Cavanaugh, et al.  Potentially Hazardous Emissions from
     the Extraction and Processing of Coal and Oil,  EPA-
     650/2-75-038. April. 1974.

Centi, T.J.  A Survey of Wastevater Treatment Techniques
     for Steel Mill Effluents, in "The Steel Industry and
     The Environment", ed. by, Szekely, J., Marcel Delcker,
     Inc., New York, (1973).

Dunlap, R.W., e£ al.  Desulfurization of Coke Oven Gas;
     Technology, Economics and Regulation Activity, in "The
     Steel Industry and The Environment", Szekely, J., (ed.);
     Marcel Delcker, Inc., New Tork, (1973).

Ess, T.J.  The Modern Coke Plant.  Iron and Steel Engineer,
     C3-C36, Jan. 1948.

Hill, W.  Recovery of Ammonia. Cyanogen. Pyridine. and
     other Nitrogenous Compounds from Industrial Gases.
     in "Chemistry of Coal Utilization, Vol. II", ed. by,
     Lowry, H.H.; Wiley, New York, (1945).

Hofstein, R. and Kohlmann, H.J.  Study of Non-U.S. Waste-
     water Treatment Technology at Blast Furnace and
     Coke Plants.  Proc. of the First Symp. on Iron and
     Steel Pollution Abatement Technology, Chicago, (1979),
     EP4-600/9-80-012, PB 80-176258.

-------
Kaplan, R.S. and Rcngstroff, G.U.P.  Emission of Sulfuroua            5.35
     Gases from Blast Furnace Slags. In "The Steel Industry
     and Che Environment, ed. by Szekely, J.; Marcel Dekker,
     Inc., New York, (1973).

Keystone Coal Industry Manual. Mining Information Services
     of the McGraw Hill Publishing, 1974.

McGannon, E.H.,  The Making. Shaping, and Treating of Steel.
     United States Steel Corporation, Eighth ed., 1964),
     Pittsburgh, Pa.

Osantowski, R. and Geinopolos, A.  Physical-Chemical Treat-
     ment of_ Steel Plant Wastewaters Using Mobile Plant
     UnitTs.  Proc. of the First Symp. on Iron and Steel
     Pollution Abatement Technology, Chicago, (1979),
     ET-A-60079-80-012, PB80-176258.

Qulgley, J.J. and Sayles, N.  An Analysis of the Effect
     of Coke Characteristics and Other Operating Variables
     Upon Blast Furnace Performance. 33rd Iron Making
     Conference Proc., Vol. 33, Atlantic City Meeting,
     April 28 - May 1, (1974).

Rausch, H. and Serbert, H.  Benefaction of_ Steel Plant
     Waste Oxides by_ Rotary Kiln Processes.  Paper
     Presented at Sixth Mineral Waste Utilization Symp.,
     Chicago, May 2-3 (1948).

Sohn, H.Y. and Szekely, J.  On the Oxidation of Cyanides
     in the Stack Region £f_ the Blast Furnace, ed. by,
     Szekely, J., Marcel DeJtker, Inc., New York, (1943).

U.S. EPA.  Development Document for  Effluent Limitations
     Guidelines and Standards for  the Iron and Steel
     Manufacturing Proposed.  Point Source Category. Vol. ,1,
     EPA-440/l-8C/024-b, December  1980a.

U.S. EPA.  Development Document for  Effluent Limitations
     Guidelines and Standards for  the Iron and Steel
     Manufacturing — Proposed. Point Scarce Category
     Vol. II, Coke Making.  Sintering. Iron Making Sub-
     categories. EPA-400/l-"0/024-b, December 1980b.

U.S. EPA.  Development Document for  p*fluent Limitations
     Guidelines and Standards for  the Iron and Steel
     Manufacturing — Point Sourr.e Category. Vol. III.
     Proposed, Steel Making Subcatat.ory. Vacuum Degassing
     Subcategory. Continuous  Casting Subcategory.
     EPA—»40/l-80/024-b, December,  1980c.

-------
U.S. EPA.  Development Dov-ument for Effluent Limitations              5.36
     Guidelines and Standards for the Iron and Steel
     Manufacturing — Point Source Category Proposed.
     Vol. J7, Scale Removal Subcategoi-y Acid Pickling
     Subcategory.  EPA-440/l-80/024-b, December, 1980d.

U.S. EPA.  Environmental and Resource Conservation Considera-
     tions of Steel Industry Solid Waste.  EPA-600/2-79/074,
     PB-299919, April, 1979.

U.S. EPA.  Industrial Process Profiles for Environmental
     Use; Chapter 24.  The Iron and Steel Industry.
     EPA-600/2-77-023X, PB266226.

U.S. EPA.  Environmental Considerations of Selected Energy
     Conserving Manufacturing Process Options - Vol. Ill -
     Iron and Steel Industry Report.  EPA-600/7-76-034C,
     PB-264269.

U.S. EPA.  Development Document for Proposed Effluent
     Guidelines and New Source Performance Standards for
     Steel Making Segment of the Iron and Steel Point
     Source Manufacturing Category.  EPA, January, 1974.
Wilson, Jr., P.J. and Wells, J.H. (ed.)  Coal. Coke Chemicals
     Chap. II. Chen. Eng. Series. McGrav Hill Book Co.,
     (1950).

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                             CHAPTER 6



                      PAPER AND PULP INDUSTRY




6.1  INTRODUCTION



     The pulping process, kraft (or sulfate)  pulping in



particular, la discussed in this chapter.  Pulping wood is



Che initial process in the manufacture of paper and paper



products.  The pulping process is the conversion of fibrous



raw material, wood, into a material suitable for use in



paper, paperboard, and building materials.  Pulp is the



fibrous material ready to be made into paper.



     There are four major chemical pulping techniques:



(1) kraft or sulfate, (2) sulfite, (3) semichemieal, and (4)



soda.  Of the major pulping techniques,  the kraft or sulfate



process produces over SOX of the chemical pulp produced



annually in the United States.  In 1970, there wt-e 116



mills producing 29.6 million tons of pulp by the kraft



process.  During the same year the pitlp  and paper board



consumption was 56.8 million tons (U.S.  EPA, Sept. 1973).



6.2  KRAFT PULPING



     The two basic components of the pulp wood are cellulose



and llgnln.  The cellulose fibers, which constitute the pulp,



are bound together by lignin, thus, any  process manufacturing



pulp must remove the lignin.  The Kraft  process employs



chemical dissolution of  the lignin.  The flow chart of the



kraft process is depicted in Figure 6.1.

-------
        Evaporator
           Gaaaa
Strong
Black
Liquor
                                                                Piilp
                       CM
          Condtnsatea


I
»
Cuuatlcizi
Tank


{ . Sattllng
\^ Tank
(CaO) (

                                    Llaa Kiln
                                                              Flltar
  Mud
(CaCO,)
                                                                    Kiln
                                                                    Caaeti
               Figure  6.1.   Flow Chart of Kraft Pulping Procaaa
                             (U.S. EPA. Sept.  1973).

-------
      The typical pollutants from the kraft pulping  process           6.3,



 are hydrogen sulfate,  methyl mercaptant,  dimethyl sulfate,



 and dimethyl disulfide.  The pollutants  containing sulfur are



 collectively called total reduced sulfur  (TRS).  Hydrogen



 sulfite  emissions are  a  direct  result of  sodium  sulflde



 breakdown in the kraft cooking  liquor.  Methyl mercaptant



 and dimethyl sulflde are formed in the  reactions with  llgnln.



 Dimethyl sulflde is formed thorugh the  oxidation of mercaptant



 groups derived from the  thiollgnin.



      The kraft process as a whole can be  subcategorized  into



 two parts; actual pulping,  and  recovery.   The pulping  occurs



 in  the digester  system followed by the  pulp wash.   The



 recovery refers  to multiple effect evaporators (MEE),  recovery



 furnace,  smelt dissolver,  and lime kiln,  all of which  serve



 to  recover the white liquor and heat.



 6.2.1  Digester  System



     There are two types  of  digesters,  continuous and batch



 digesters.  The  composition  and quality ox digester gases



 will differ between the  two  digester  types.  Baech digesters



 often present air  pollution  problems because of gas surges



 produced during blowing.  Continuous digesters,  however,



 present much smaller pollution problems than batch digesters



 because contaminated condensates and odorous gases flow at a



 regular rate. Most of  the kraft pulping is currently done in



batch digesters  (Goodwin, 1978). The following discussion



entails only the batch digester system.

-------
     The digestion process is a delignlfication process in            6.4

which white liquor and wood chips are heated to 170-1?5°C.

White liquor is composed of sodium sulfide (Na.S) end

sodium hydroxide  (NaOH).

     Emissions from the digester are caused by two streams;

the relief gases  and blow gases.  The relief gases are the

ventilation gases which maintain the digester at the proper

pressures (100-135 psig).  The blow gases, steam and other

gases, are from the blow tank where the cooking liquor is

drained from the  pulp.  Both the relief and blow gases are

condensed for heat recovery.  Table 6.1 gives the pollutant

emission rates for the digester system.
TABLE 6.1.  TYPICAL EMISSION RATES FROM BATCH DIGESTER
            IN kg SULFUR/TON OF ADP*  (U.S. EPA. JAN. 1978)
Pollutant
H2S
CH3SH
C3-SCH-
CH-SSCH.
Blow Gases
0-0.1
0-1.0
0-0.25
0-0.1
Relief Gases
0-0.5
0-0.3
0.05-0.8
0.05-1.0
* ADP - Air Dried Pulp

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     Mercaptants and methyl sulflde are unavoidable by-              6'-5
products of kraft pulping, however, there are few measures
which can limit their production.  Generally, h' -h tempera-
tures, high sulfidity and long reaction tines favor »-he
production of the sulfur compounds (Douglas, 1966).  Thus,
if the sulfidity of the white liquor is kept at a minimum,
the formation of gaseous sulfur compounds will be reduced.
Sarkanen, .§£ al. (1970), suggests a 20Z sulfidity for most
paper mills.
     Final emissions of the digester system is determined by
the effective operation of the condenser  (heat exchanger)
units.  Experience shows that the surface area of the heat
exchanger, thought originally to be sufficient may later
prove  to  be too  small  (U.S. EPA, Oct.  1976).  This is due  to
fiber  carryover  by the blow gases  and  :onsequent fouling of
the heat  transfer surfaces.  The fiber carryover is  caused
by excessive  gas velocities at  the entrance of  the flow
exhaust pipe.  The minimum velocity to suspend  solid particles
is 18 fps, and  the actual velocity in  the blow  tank
reached 46 fps  (Martin,  1969).   The recommendations  to
reduce fiber  carryover are: decrease the digester wood to
 liquor ratio, relieve the digester to  a lower pressure
before blowing and/or blowing for a longer time period,
 installation  of a cyclone separator,  and initially providing
more heat exchange surface.

-------
6.2.2  Brown  Stock Washer  System                                      6.6

     The washing process is  a minor  source of air pollution

as compared to  digestion,  evaporation, and combustion.  The

emission of air contaminated with organic sulfur compounds

is due primarily to  the contact of air with black liquor.

The amount of air and sulfur compounds ventilation depends

mainly on the type of washing process and equipment.  The

two main washing processes are displacement and diffusion

washing (U.S. EPA, Oct. 1976).

     Categorically,  displacement washers include vacuum

washers and pressure washers.  Of the two, the pressure

washers' hood vent and foaa  tank vent will have smaller flow

rates and total reduced sulfur (TRS) emissions.

     Typical  emission rates  from the vacuum washers' hood

vent and the  foam tank are shown in Trble 6.2.
TABLE 6.2.  EMISSION RATES FROM VACUUM WASHER IN kg
            SULFUR/Ton ADP (U.S. EPA. October 1976)
Pollutant
H2S
CHjSH
CH^CILj
CH.SSCH.
Washer Hood Vent
0-0.1
0.05-1.0
0.05-0.5
0.05-0.4
Washer Foam Tank
0-0.01
0-0.01
0-0.05
0-0.03

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Diffusion washing Is superior to displacement washing,  since



the washing takes place in a closed reactor.  In diffusion



washing, ideally, there Is no air Involved, thus, black



liquor oxidation and odor release are very small compared to




displacement washing.



     Some mills employ contaminated condensates for washing.



A study of 17 washing systems irdicated an emission rate of



0.014 Ib/ton ADP as HjS using H20, ami 0.35 Ib/ton ADP



treating with eondeneate (U.S. EPA, Sept. 1973). In view of



pollution abatement, water is a better washing medium than



the condenaates.  Another possibility is to reduce sulfur



contents of tlie condensate by stripping.



6.2.3  Multiple Effect Evaporator System



     Multiple effect evaporators (MZE) are utilized to concen-



trate weak black liquor from 12-18Z solids  to 40-55Z solids



(Goodwin, 1978).  The weak black liquor is a mixture of



digester spent cooking liquor and stock washer discharge.



Basically each effect consists of a heating element and a



vapor head.  The hot vapors from the vapor heat of a previous



effect pass to the heating element of 'lie following effect.



The vacuum Is maintained by means of rapid  condensation of



the vapor from the  final effect.



     This section includes only the most important indirect



steam evaporation system from the view point of pollution.



Thus, the following discussion is for Vacuum MEE.  However,

-------
Che pollution control strr-.egies can be readily applied to          6<8

other evaporation techniques.  Typical emission rates for

MEE are shown in Table 5.3.
TABLE 6.3.  EMISSION RATES FROM MEE  IN kg SULFUR/TON
            ADP  (U.S. EPA, OCT. 1973).	
      Pollutant                   Emission Rate
                                kg Sulfur/ton ADP
*2S
CBjSB
CB_SCH3
CB-jSSCBj
0.05-1.5
0.05-0.8
0.05-1.0
0.05-1.0
     The most  effective method  of  reduction of pollution in

MEE is  to  steam atrip  the  condensate  and  to Incinerate the so

called  noncondensable  gases  (H.,S,  CH^B,  CE^CB^, and CH3SSCB3).

Matteson,  e_£ al.  (1967) successfully  stripped the condensate

generating overhead vapor  of more  than  95Z hydrogen sulfide,

mercaptants, and dimethyl  disulflde.  Steam stripping vas

performed  in a conventional  bubble cap  tray stripper result-

ing in  a bottom product of nearly  pure  and reusable water.

The stripped gases  and other gases from the MEE can be

incinerated in the  lime kiln (Walther and Amberg, 1970).

     The liberation of B,S and  to  a lesser extent CH.SH

depends on the pH of  the black  liquor.  This is due to the

acidic  nature  of both gases. Furthermore, these gases

-------
                                                                     «  Q
dissociate more readily in an aqueous solution of higher pH.          "•'.


Addition of caustic soda to the weak black liquor can be


beneficial in alleviating BjS and CB^SB.


     The emissions of H.S and CH^SH arc dependent on the


sulfide concentration of the weak black liquor.  Oxidation


of this weak black liquor can convert sulfide to thlosulfate


and CH.SB to CB.SSCB-.  These conversions will facilitate


the reduction of R,S and CB^SB emission from MEZ.  The


condensata from the HEE processing of oxidize weak black


liquor will require little, if any. treatment for odor


abatement (ZPA, 1976).


     Furthermore, Caleno and Amsolen (1970) observed several


benefits of weak black liquor oxidation with 02 a« compared


to lack of oxidation.  The oxidation uitllzing 02 resulted


in lower emlsisons of H.S from the MZE, and improved the


evaporator condensate water quality.


     There are two major factors which should be considered


in the effectiveness of weak black liquor oxidation to


prevent TRS emission.  First, a high degree of oxidation is


required.  Second, oxidized sulfur compounds havf tendencies


to revert to sulfide during MEE as well as during extended


ctcrage. Long  storage periods after black liquor oxidation


should be avoided.

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6.3  RECOVERY  FURNACE  SYSTEM

     The  recover?  furnace  functions include:  (1) recovery

of Kodlua and  sulfur.  (2)  production of steaa and, (3)

disposition of unwanted components of the dissolved wood.

The recovery furnace system generally includes the following

units:  recovery furnace,  flue gas direct contact evapora-

tor, primery particulate control device, and  secondary

participate control device.   In some cases the direct

contact evaporators have been used to contain the partlculate

emissions er eliminated all together (U.S. EPA, March 1970).

Table 6.4 is a listing of  emission rates from the recovery

furnace.
TABLE 6.4.  EMISSION RATES FROM RECOVERY FURNACE (U.S. EPA,
            OCT. 1976).
Pollutants
V
CH-jSH
CHjSCH^
CH-SSCH-
^2
S°3
NO,
Emission Rate kg/ton ADP
0-25
0-2
0-1
0-0.3
0-40
0-4
0.7-5
The partlculate emission rates are listed In Table 6.5.

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TABLE 6.5.  PARTICULATE EMISSION RATES FROM THE RECOVERY            6.11
	FURNACE (U.S. EPA. OCT. 1976)	


Emission Source                    Emission Rage kg/ton
                                            ADP
Recovery System after
  Electrostatic Precipitator            0.5-12

After Venturi Evaporator                 14-50

Flue Gas Dust Load                       40-75
     The  three direct evaporators used in the kraft pulping

mills are cascade evaporators, cyclone evaporators, and the

venturi recovery unit.  The difference between a venturi and

the  other two evaporators  is its efficiency  in removing

particulatea.  While cyclone and cascade evaporators remove

only 40-50Z  of the partlculate matter, the venturi recovery

units can be designed to capture better than 90Z of the

participates (U.S. EPA, Sept. 1973).  The direct contact

evaporator serves as an adsorption  unit for  SO. and nearly

all  SO-.   Furthermore, it  absorbes  HjS emitted from the

recovery  furnace under conditions of  high black liquor pH

and  low sodium sulfide concentrations in the strong black

liquor.

     The  direct evaporation unit is also a potential source

of TRS.   However,  the emission of TRS depends heavily  on the

residual  sulfide  in the black liquor  from MEE.  For this

-------
purpose, some mills employ strong black liquor oxidation.  A        6.11



survey of 32 recovery furnace systems where black liquor



oxidation is not used showed sulfur emission ranging team



0.75-31g/Kg ADP, with an average of 7.7g/Kg ADF.  Conversely,



a survey of 17 units that utilized black liquor oxidation



indicated emission ranges of 0.113g/Kg ADF. with an average



of 3.7g/Kg ADP (Goodwin, 1978).



     It is possible to eliminate the direct contact evapora-



tor in favor of a non-contact design.  This change will



cause an increase in particulate emissions which would then



require installation of a more  efficient particulate control



device.



     The emission of sulfur compounds from the recovery



furnace is also dependent on the design of the furnace.  The



recovery furnace has two functions; recovery of the chemicals



in their reduced state (i.e. sulfur should be present as



sulfide and not sulfate), and recovery of heat to generate



steam for the processes.



     Combustion within the recovery furnace la separated



into two zones.  The first zone must be maintained under



reducing conditions* less than  the required stolchlometric



amounts of air.  The products of this zone discharge chemicals



in the molten state with the sulfur present mainly as sulfide



and organic matter as a  gas having considerable heat value.



The second zone of combustion starts with the addition of

-------
secondary air.  The secondary air should be supplied in 10-          6.13



20Z excess of the amount required for complete combustion.



     The release of sodium from the burning char of black



liquor depends on the temperature and the gas conditions in



the border zone between the bed and the flue gas.  The TRS



release to the flue gas is affected by the total sulfur



concentration and the sodium to sulfur ratio. Since the



sodium/sulfur ratio in the smelt bed depends on temperature,



the release of sulfur to the flue gas is also a function of



temperature.  Hydrogen sulfide may be present in the flue



gas in the pr. -nary air combustion zone at 50-100ppm if the



zone between the bed and the flue gas are kept at the optimal



temperature.  Hydrogen sulfide concentrations of 15,000 ppm



have been observed in this region when black out conditions



are present (black out conditions refers to insufficient



rate of combustion in the hearth).  Typically, a low tempera-



ture favors the presence of S and H2S (U.S. EPA, Oct. 1976).



     There are several advantages In raising the primary air



temperature.  The velocity for the same flow of air will



increase and Improve the sodium evaporation from the bed.



Also, the release of sulfur from the bed decreases.



     Immediately after introduction of secondary air, the



final combustion starts.  The amount of primary air for most



furnaces must be more than 1102 and less than 125Z of the



theoretical air to avoid formation of stick dust.  Stick



dust has a tendency to foul the heating svrfaces.  The

-------
secondary air should be supplied to the furnace such that it         6.14



mixes with the gas cooing from the primary air combustion



zone.  Therefore, efficient regulation and method of intro-



duction of secondary air Is important in the generation of



scick dust.



     The variable tffeeting the TRS emissions from the



recovery furnace are as follows: quantity and method of



introduction of combusted air, the rate of black liquor



feed, the degree of turbulance in the oxidation zone,



the 0. content of flow gas, the spray pattern and droplet



size of the liquor fed to the furnace, and the degree of



disturbance In the smelt bed.  These variables are Inde-



pendent of the presence or absence of a direct contact



evaporator 'Theon, et al. 1968).



     Teller and Amberg (1975) have developed a control



technique for use in the recovery furnace which utilizes



alkaline adsorption with carbon activated cxidatlon of the



scrubbing solution.  Pilot plant studies shoved this technique



Is capable of reducing TRS emissions from 20-1500 ppm to



1 to 10 ppm.  This method would alno alleviate particulate and



SO. emissions (Teller and Amberg, 1975).  Another effective



adsorption method is the TRS system potential by the



Weyerhaeuser Company.  The TRS scrubber adsorbs up to 99%



of H-S and collects about 85Z of the particulate matter.

-------
     Nitrogen oxides are generated in the recovery furnace          6.15



at a rate of 0.7-5 kg/ton ADP (U.S. EPA, Oct. 1976).  The



reduction of NO  production lies in provisions for facillta-
               3*


tion of a heat sink in the recovery furnace.  The endothemic



reaction of Sa_SO, to Na-S in the smelt bed also acts as a



heat sink to inhibit excessive flame temperatures.  A reducing



atmosphere above the smelt bed will also reduce NO  formation.



The supply of air can be arranged to spread out the flame



front, and in that way, inhibit the increase in gas tempera-



ture.



6.3.1  Smelt Dissolving Tank



     The molten smelt accumulated in the recovery furnace,



as a result of combustion, is dissolved in water in the



smelt dissolving tank.  Dissolution of the molten smelt



(sodium carbonate and sodivan sulfide) in water forms a green



liquor.  The dissolution is aided by agitators and steam,



or a liquid shatterjet system, to break up the smelt stream



before it enters the solution.  The large volume of steam



generated by the contact of smelt with water is vented.



Table 6.6 depicts the emission rates from the smelt dissolving



tank.

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TABLE 6.6.   EMISSION RATES FROM SMELT DISSOLVE TANK                  6.16
	(U.S.  EPA. OCT. 1976)	


         Pollutants                  Kg Sulfur/ton ADP


                                        0-1.0

                                        0-0.8

                                        0-0.5

          CB3SSCH3                     0-0.3

                                        Kg/ton ADP

     Particulate Emission
     (After Control Device)             0.01-0.5

          S02                           0-0.2
     Particulate  matter contains  dissolved  and undlssolved

NaOE, Na.CO.,  and Na.S.   The particulate  emissions are cap-

tured from escaping vent gases  by mist  eliminator pads.

Typical  efficiency of the pads  for particulate removal is

70-90Z,  however*  higher efficiencies  can  be achieved by

facilitating the  smelt tank with  a spray  or packed scrubber

in addition to mist eliminator  pads.  Combinations of this

type can be 98Z efficient in removing particulate matter

(U.S. EPA, Oct. 1976).  Another alternative is to combine

vent gases from the smelt tank  with  flue  gases from the recovery

furnace  prior to  entering the particulate collection de-rice.

However, the effectiveness of a electrostatic preclpitator

is reduced due to the water vapor content of the smelt

-------
 tank vent  gases.   Furthermore,  the  Na.S  entrained  in  the             6.17



 smelt tank vent gases  coming  Into contact with CO,  from the



 recovery furnace may promote  formation of H.S.   It  is evident



 that the best  particulate  control device for  the smelt tank is



 a  combination  of mist  eliminator pads  and a scrubber.



      The TRS emissions depend on the aulfide  content  of p*srtl-



 culate matter, the turbulence in the dissolving tank,  the



 type of solution used  In a scrubber, if  present, and  pH of  the



 scrubber liquor.   Fresh water is the best solution  for scrub-



 bing and is capable of producing 0.001 Ib sulfur/ton ADP



 (Martin, 1969).



 6.4   LIME  KILN




      The green liquor  is converted  to  white liquor  in  the



 lime  kiln.  This unit  is an essential  element of the closed-



 loop  system.  The  kiln calcines the calcium carbonate  which



 precipitate from the causticlzer to produce quicklime  (CaO).



 The calcined calcium carbonate precipitate is also  called



 lime mud.  The quicklime is wetted  (slacked) by the water



 in the green liquor solution  to form calcium hydroxide for  the



 causticlzlng reaction.




     The mud is contacted by  the hot gases produced by  the



combustion of natural gas or  fuel oil and proceeds  through  the



kiln in the opposite direction of the gas flow.  The lime mud



is a 55-60Z solid-water slurry and is fed at elevation  to



the kiln.   In the upper part of the kiln the mud dries while

-------
at Che lover end, Che high temperature zone (1800-2000°F),          6.18



1C agglomerates Into snail pellets and is calcined to CaO.



Typical emission races from lime, kiln are given in Table 6.7.



TABLE 6.7.  LIME KILN EMISSION RATES (U.S. EPA. OCT. 1976)
Pollutants
V
CH3SH
CH3SCH
CH3SSCH3

S°2
N°x
Lime Kiln Exhaust &
kg Sulfur/ton AOP
0-0.5
0-0.2
0-0.1
0-0.05
kg/ ton ADP
0-1.4
10-25
Line Slaker Vent
kg Sulfur/ ton ADP
0-0.01
0-0.01
0-0.01
0-0.01
kg/ton ADP
—
^•^
     Variables affecting  the TRS emission of Che lime kiln



are the temperature at  Che cold end of Che kiln, Che 0.



content of Che gases leaving Che kiln, the sulflde concent of



the lime mud, and  the pH  and sulflde  content of Che water



used in the participate scrubber (NCASI, 1971).  If contami-



nated condensate is used  as Che scrubbing solution, Che



exhaust gases could strip out  the dissolved TRS and increase



the TRS emission from the lime kiln.



     The two most  important preventive measures in view of



TRS emission are;  maintenance  of the  proper process conditions,



and scrubbing the  exhaust gases with  caustic solution.  For

-------
example, TRS emission can be reduced by a sufficient supply of       6.19



0. and a reduction in sulfide content of the mud.



     The lime kiln is operated with excess air and high tem-



perature, both conditions favor the production of NO^,  there-



fore, any measure to reduce TRS may promote generation of



NO .  Thus, oxides of nitrogen are unavoidable by-products



of the lime kiln and any measure to control their release



should occur after the kiln.



     Table 6.8 summarizes some of the pollution problems



associated with the kraft pulping process and suggests con-



trol alternatives.



6.5  RECOMMENDED AREAS FOR PROCESS MODIFICATION RESEARCH



     After evaluating the available literature, the following



areas are reconmendsd for further research by the study:



          Research on digestion of wood chips to determine



          optimal sulfidity, pH, and temperature to reduce



          pollution.



          Studies on control of fiber carryover from the blow



          tank by cyclone and/or by reduction of relief



          pressure and selection of wood to liquor ratio to



          prevent TRS emission.



     .    Comparative studies on design and application of



          diffusion and displacement washers to minimize TRS.



          Effect of black liquor oxidation and pH control



          on weak and strong black liquor to reduce TRS



          emission.

-------
Table 6-8.  Pollutant* end Control Optima In Kraft Pulping Proccaa
Process
Digester
Broun Stock
Kosher
Multiple
Effect
Evaporators
Recovery
Furnace
Systes)
Snlt Otss'lve
Tank
Lin Kiln
Pollutants
TRS. relief i
blow gases
TRS. noncondena-
ablea
TRS. noncendens-
ables
TRS. SOj SOj,
HO^ Partlculatao
TRS. S02.
Partlculatea
TRS. S02.
HO
Sources In
Process
Digester Tank
blow tank
Vacuusi vainer
Evaporators
Recovery furnace
direct contact
evaporator
Soelt Tank
Kiln
Nature of
Pollutants
Organic, gases
Organic, gaaea
Organic, gaaee
Organic and
Inorganic gases
and solids
Orfanic and
Inorganic gases
=r~i solids
Organic and
Inorganic gases
Pollutant Control Strategy
Lower aulfldlty. lower blow
pressure, reduce fiber
carryover by cyclone or
other aw thuds.
Use water aa washing
fluid, employ diffusion
washers.
Treatment of week black
liquor by oxidation Mt
vUh caustic sods. Effective
stripping of condensate frooi the
condenser unit.
Strong blsck liquor oxidation.
Use direct contact evaporator,
venturl type. Improve design.
Alkaline sdsorptlon with
carbon-activated oxidation of
the scrubbing solution.
Combination cf alst ellatlnstor
pad and scrubber unit. Use fresh
water for scrubbing.
Bslntsln proper process
conditions. Sufficient
supply of O and reduction
In sulfur content of the mud.

-------
Studies on the direct and non-contact evaporation          6.21



in the recovery furnace system to determine capabi-



lity and merits of each unit in reducing the TRS



emission.



Research on combustion of strong black liquor to



prevent black out conditions and stick dust forma-



tion by optimizing the design and operating condi-



tions In the recovery furnace.



Research and application of scrubbing techniques to



reduce TRS emission.

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                             BIBLIOGRAPHY                              6.22
 Douglas,  I.B.,   "The Chemistry of Pollutant Formation in
      Kraft  Pulping." In proceedings of  International confer-
      ence on Atmospheric Emissions from Sulfate Pulping,
      April  28,  1966.  E.O.  Painter Printing Co., 1966.

 Galeano,  S.F. and Amsden, C.D.  "Oxidation of Weak Black
      Liquor with Molecular  Oxygen". TAPPI. Vol. 53, November
      1970,  pp.  2142-2146.

 Goodwin,  D.R.   "Draft Guideline Document: Control of TRS
      Emissions  from Existing Kraft Pulp Mills", EPA 450/2-
      78/003A.   January 1978.

 Martin, G.C.  "Fiber Carryover With Blow Tank Exhaust",
      TAPPI.  Vol.  52, No.  12, December 1969.

 Matl,.son, M.J.,  et  al.   "Sekor II: Steam Stripping of
      Volatile Substances from Kraft Pulping Mill
      Affluent Stream".   TAPPI. Vol. 50, No. 2,
      February 1967.

 Sarlr.Jien, K.V.,  et  al.,   "Kraft Odor", TAPPI. Vol. 53,
      No.  5.  May 1970.

 Suggested Procedure for  the Conduct of Lime Kiln
      Studies to Define Emissions of Reduced Sulfur
      Through Control of  Kiln and Scrubber Operating
      Variable." NCASI Special Report No. 70-71,
      January 1971.

Teller, A.J. and Amberg, H.R. "Considerations in the
      Design  for TRS and  Particulate Recovery from
      Effluents  of Kraft  Recovery Furnaces." TAPPI
      Environmental  Conference. May 1975.

Theon, G.N., e_t al.   "The Affect of Combustion
      Variable on the Release of Odorous Sulfur
      Compounds  from a Kraft Recovery Furnace,  TAPPI.
      Vol. 51, No. 8, August 1968,  pp.  324-333.

-------
"Factors Affecting Emission of Odoroua Reduced  Sulfur                 6.23
     Compound* from Miscellaneous Kraft Proceaa Sourcea",
     HCASI Technical Bulletin. So. 60, March  1972.

Bansen. S.P.  and Burgesa. P.I.  "Carbon Treataent of Kraft
     Condeoaatei Vaatea." TA?P1. Vol. SI.  June  1966.
     pp. 241-245.

Prakaah, C.B. and Hurry, 7.E.   "Studies oo H-S  Emiaaiooa
     during Calcining1*. Pulp and Paper Maaaalne of Canada.
     Vol. 74, Hay 1973, pp. 99-102.

Teller, A.J.  and Aaberg, H.ft.   "Considerations  in the Design
     for TRS  and Partieulate Recovery froa the  Effluents of
     Kraft Recovery Furnace." Preprint TAPPI  Environmental
     Conference. May *975.

Ualther, J.E. and Aaberg, B.R.  "The Role  of  Che Direct
     Contact  Evaporator in Controlling Kraft  Recovery.
     Furnace Eaisaiona". Pulp and Paper Magatine of Canada.
     Vol. 72, October 1471. pp. 65-67.

-------
D.S. EPA.  "Control of Atmospheric Emissions la the Wood
     Pulping Industry", Environmental Engineering Inc., and
     J.E. Sirrlne Company. Final Keport, EPA Contract So.
     CPA-22-49-18, March IS, 1970.

O.S. EJA.  "Atmospheric Emissions Proa the Pulp and Paper
     Manufacture Industry." Environmental Protection Agency.
     •Research Park H.C. Office of Air Quality Planning and
     Standards.  EPA 459/1-73/002, September 1973.

O.S. EPA.  "Environmental Pollution Contrcl Pulp and Paper
     Industry: Part 1  Air", EPA 625/7-76-001. October 1976.

Ualther. J.E. and Amberg, B.R.  "A Positive Air Quality
     Program at  a New  Kraft Mill", Journal of Air Pollution
     Control Aasoe.. Vol. 20, No. 2, January 1970.


                        SUPPLEMENTAL  REFERENCES


Anderson.  H.K.  and  Ryan,  J.   "Improved Air  Pollution Control
      for a Kraft Recovery Boiler: Modified  Recovery Border
      No. 3", EPA 650/2-74-071-a.  August, 1974.

 Bhati*. S.P., £t al.,   "Removal of  Sulfur Compounds from
      Kraft Rucuvery Stack with Alkaline Suspension of
      Activated Carbon", TAPTI.  Vol.  56, Deceabei  1973, pp.
      164-167.

 Clement, J.L. and Eliot. J.S.  "Kraft Recovery Boiler
      Design for Odor Control".  Pulp and Paper Magazine
      of Canada. Vol.  78, NO. 8, February 7, 1969, pp. 47-52.

 Cooper. H.B.E. and Roasano. A.T., Jr.  "Black Liquor
      Oxidation with Koleculor Oxygen in Plug Flov Reactor ,
      TAPPI. Vol. 56, June 1973, pp. 100-103.

 Douglas.  I.B.  "Sources of Odor in the Kraft Process:
      Odor formation in Black Liquor Multiple Effect
      Evaporators."  TAPPI. Vol. 52, September 1969.
      pp.  1738-1741.

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                             CHAPTER 7                              7.1
                  THE PRIMARY ALUMINIUM INDUSTRY
7.1  INTRODUCTION
     The primary alunlnlun Industry consists of processing
bauxite ore to produce alumina (and occasionally aluminium
hydroxide) and processing the alumina » produce aluminium.
Approximately, 7.6 x 106 tons of alumina were oroduced in U.S.
from processing about 15.4 x 106 tons of bauxite in 1972,
942 of the alumina was utilized to make aluminium  (Saxton and
Kramer,  1975).
7.2  BAUXITE PROCESSING
     Bauxite is composed mainly of met  . —c  oxides with
aluminium oxide comprising  from 20Z  to  60Z of  the  ore  as
mined.   Approximately 87Z of th* bauxite  ore la Imported,
mainly from Jamaica and Surinam.  The many  environmental
problems associated with bauxite mining and shipping are
caused by fugitive dust and water  runoff.   Bauxite ore may
 contain up to 301 moisture and should be dried at 110°C before
 shipping.
      An overview of the Bauxite processing Is shown In
 Figure 7.1.
      The raw bauxite ore la benefacted by grinding to about
 100 mesh, digested in caustic at elevated temperatures and
 pressures (145CC and 60 psig), and then filtered  or thickened
 in the presence of flocculants.  These operations yield a

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                                                                  7.2
 MIHZD BMJXRE ORE


NAKED?
IUOH ^^
—


GRINDING
9IGEST10K AND
THICKHISC



c*o.
HoOB
AUKINATE
LJOOOB

• "•- FLOCCUURT

RED MUD
C«CO f 0 '
1 * ^ffl o—
1 Dlg«*tlon. "
^^ Sintering 7
md
Washing ™| Vi

T
BROWN HUD


PRICIPITATI01I.
TO.TRATIOB.
CALCIHIHG

_, 1 23 9
Handling
•nd
Shipping

1
Lltrrlng
•nd
uhlng
\
ut««
ICM
1 Solid HMCM
Flgun 7.1.  Btuxltt  ProecMlng

-------
sodium aluminate liquor and a waste stream of "red mud" which      7.3



contains the impurities found In the bauxite ore.



     The aluminate liquor is diluted and cooled to hydrolyze



the sodium aluminate, forming a precipitate of aluminium



hydroxide which is filtered and calcined to alumina.  The



alumina is then shipped to aluminium smelting if so desired.



Depending on the type of Bauxite processed, 1/3 to 2 kg of



red mud is produced per each kilogram of alumina product.



Table 7.1 gives the chemical analysis of red mud slurries



from different bauxite ores  (U.S. EPA, Oct. 1974).  The pH



of this slurry is approximately 12.5.





     TABLE 7.1.  CHEMICAL ANALYSIS OF RED MUDS
Weight Z
Component
Fe203
Ai2°3
sio2
T102
CaO
Ha20
Arkansas
55-60
12-15
4- 5
4- 5
5-10
2
Surinam
30-40
16-20
11-14
10-11
5- 6
6- 8
Jamaica
50.54
11-13
2.5-6
—
6.5-8.5
1.5-5.0
      In the combination process, bauxite ores with high



 silica content, such as those from Arkansas,  the red mud



 residue is treated to extract additional amounts of almlna

-------
and to recover sodium values.  This additional extraction            7.4



step is  accomplished by mixing red mud with limestone and



(Na)2CO.,  and then sintering  this mixture at 1100 to 1200°C.



The important reactions are the conversion of silica to cal-



cium silicate and residual alumina to sodium aluminate.  The



sintered products are leached to produce additional sodium



alumlnate  solution, which is  either filtered and added to the



main stream for precipitation or is precipitated separately.



By the addition of seed material and by careful control of com-



position and agitation, alumina trihydrate is precipitated in



a controlled form.



     The ideal solution to the red mud problem would be to



develop  a.  use for it.  A possible application utilizes the



high iron  content of the red  mud (Table 7.1).  Fursman,



£t al. (1970) described a process based on sintering the



red mud  with carbon and limestone and melting the sinter in



an electric ore furnace to produce a low priority iron



which could be further processed into steel.  This process



was further developed (Guccione, 1971) but has not yet



found commercial application.  Other investigators have



examined the applicability of red mud to manufacture port-



land cement, bricks, and road construction (Fursman, et



al. 1970;  Solyman and Briudnso, 1973).



     There is a need to develop an economically viable



leaching and extraction process for the recovery of mineral



values from red mud wastes.

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     During Che handling and shipping of alumina, dust is            7.5



formed.  The tendency of aluminas to form dust during handling



depends on the degres of calcination and on the particle size



distribution.  The size distribution and adsorption capability



of calcined alumina are important in the reduction and dry



gas cleaning stages of aluminium manufacture, as will be



discussed later.



     With highly calcined, flowing aluminas, the formation



of dust is prevented by the surface roughness, which increases



as the a-alumlna content rises.  If fine grained hydroxide is



calcined to a lower degree, it will start developing dust.



The tendency of weakly calcined aluminas to cause dusting



is counteracted by minimizing the amount of fines.  This is



normally done in the precipitation area of the Bayer process,



where the particle size distribution of the hydroxide is



controlled.



     Decisive for the mechanical strength acquired by the



individual hydroxide particles are (Schmidt, 1980):



          The basic principle applied for crystallization,



          i.e., nucleation, crystal growth, or agglomera-



          tion conditions



          Influence of liquor impurities such as CaCo.



          oxalates etc.



          The mechanical stresses to which the hydroxides



          are exposed during precipitation.

-------
     Schmidt, £t al. (1980) reported that the gas/solid              7.6



velocities and thermal stresses in the fluid bed calciner



and in the rotary kiln have a strong Influence on the



particle size distribution of the calcined alumina.



     Thus a detailed research program to improve the mechani-



cal strength, adsorption capability and particle size distri-



bution of calcined alumina by modifying the precipitation



and calcining of alumina IB suggested.



     Studies conducted in the USSR and elsewhere indicate



the possibility of using nitric acid stripping for the



extraction of alumina from ores containing high amounts of



silica.  Sutyrln and Zverev (1976) reported that stripping



at 160°C lowered acid usage and produced solutions less



contaminated by Iron.  Acid stripping of domestic D.S. ores



which contain high amounts of silica should be optimized by



proper control of the stripping temperature.



     The enrichment of high silica bauxite ores using



heterotrophlc bacteria is  reported by Andreev, et^ al.  (1976).



It was possible to produce a concentrate with 48.4* A&2°3



content at  a recovery of 74Z.  Thus, additional research is



needed to develop acid stripping  and bacterial enrichment of



domestic bauxite ores.



7.3  PRIMARY ALUMINIUM SMELTING



     The large  scale,  economic production of  primary alumi-



nium became possible when,  in  1886, C.M. Ball and P. Heroult



independently developed  the electrolytic process which has

-------
remained essentially unchanged, except for improvements in           7.7



equipment design and operating practices, it is used in all



the commercial processes in U.S. producing primary aluminium.



There are 31 aluminium reduction plants In the U.S. with



a totax annual capacity of about 4.5 x 10  tons.  The energy



consumed annually at full production is estimated to be in



the range of 80 to 100 billion K.W.H.



     The basic process for reducing alumina to aluminium is



shown schematically In Figure 7.2.



     The raw materials used In the aluminium production



include alumina, cryolite (a double flourlde of Na and A£),



pitch, petroleum coke, and aluminium flourlde.  For every kg



of aluminium produced, about 2 kg alumina, 0.25 kg pitch,



0.05 kg cryolite, 0.5 kg petroleum coke, 0.04 kg aluminium



flourlde, 0.6 kg baked carbon and 22 K.W.H. of electrical



energy are needed.



     The heart of the aluminium plant  is the electrolytic



cell, which consists of a steel container lined with re-



fractory brick with an inner lining of carbon.  The cells



are arranged in rows, in an operating  unit  (potline) as



many as 100 to 250 cells are electrically connected in series.



The electrical supply is direct current  and is on  the order



of several hundred volts and 60,000 -  100,000 amperes. The



carbon lining at the bottom of  the cell  acts as a  cathode



when covered with molten gl"m-»n
-------
                                                                                   7.8
       PETROLEUM COKE
        CRUSHING
          AND
      CLASSIFYING
                 PITCH
      ANODE   PASTE

       HOT - BLENDING
I COOLING
       PRESSING
                                          SOUERBCRG
                                            ANODE
                                          BRIQUETTES
         BAKING
                       ELECTRICAL  POWER
                        SUPPLT  ~""
                         (D.C.)
                         ANODES
                    CATHODES
                                                   •ALUMINA
                     CRYOLITE
                    -CALCIUM rLOURlDE
                     ALUMINUM PLODRIDE
                                      FUSED SALT
                                    ELECTROLYTIC
                                        CELL
                      CASES,
                       DUST
                      FUMES
             CAS
          SCRUBBING
         BLEHDINC
  MOLTEN Al.
 TO  DEGASSING
 AND CASTING
Anthracite
               Pitch
                                      AlunloluB
                                   (pig. billet. Ingot.
                                         rod)
DRY PROCESS
SOLIDS TO
CELL
                                                                             BET
                                                                          SCRUBBER
                                                                          LIQUOR
                                                                            TO
                                                                        TREATMENT
                     Spent  Potllnere
               Figure 7.2.  Primer? Aluminium Production.

-------
cryolite (80-85Z by wt.), calcium flourida (5-72), and                7-9



alumina (2-8Z).  Alumina la added to the bath intermittently



to maintain the concentration of dissolved elumina within the



desired range.  The fused salt bath is usually at a tempera-



ture of 900°C.



     The reaction In the aluminium reduction cell is not



completely understood (Kirk-Othmer, 1963).  Apparently alumi-



nium is reduced from the trlvalent state assuming ionlzation



in the molten salt, to the liquid metal state at the cathode.



Oxygen, assumed present in the bath in the divalent state



appears at the carbon anode and Limediately reacts with the



anode and forms a mixture of C02 (=75Z) and CO (=252).



     Thus, the operation of the elsctrolytic aluminium re-



duction cell results in the continuous consumption of alumina



and the carbon cnode, and the evolui.'on of gaseous reaction



products.  The aluminium is withdrawn intermittently from



the bottom of the molten bath and is collected in ladles and



cast into Ingots.



     The various anode making operations are conducted in



the anode paste plant.  The anode paste consists mainly of



high grade coke (petroleum and pitch coke) and pitch, with



a mjfg-tmmn of 0.7Z ash, 0.72 sulfur, 82 volatiles, 0.5Z alkali



and 22 moisture.  The two types of pitch handling systems



are, solid pitch handling and liquid pitch handling  (using



organic liquids as a heat transfer medium).  Dust and



toxic emissions are the main pollutants from these systems.

-------
     The two different anode systems ur-.d differ in the

replacement of the anode.

     1.   Prebaked system - the anode is replaced inter-

          mittently,

     2.   Solderberg system - the anode is replaced continu-

          ously by the anode paste descending from the anode

          shell suspended above the electrolytic cell.

     The carbon cathode has an average life of between 2-3

years.  The spent cathode lining is removed by drilling and/or

soaking In water.  About 1200 m  of shell vasts is generated

each year in the U.S.

     The major pollutants generated during the smelting of

alumina Include particulate emissions, inorganic flourides,

oxides of sulfur, H,S, carbon disulfide, carbonyl sulphide,

CO and CO,, and spent carbon cathode.

     Emissions from the horizontal-stud Solderberg cell

and vertical-stud Solderberg cell (Rotari, jet al. 1974)

are shown in Table 7.2.

     TABLE 7.2  EMISSIONS FROM SOLDERBERG CELL	

   Cell Type             Emissions           Ib. per ton of
Vertical-stud            Participates             98.4
Solderberg               Gaseous Flourldes (HP)   26.6
                         Particulate Flouride     15.6
Horizontal-stud          Partlculates             78.6
Sblderberg               Gaseous Flourides(HF)    30.4
                         Particulate Flouride     10.6

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The partlculatea contain A£.0.f Na.CO. and carbon duac.              7.11
Approximately 60Z of the particulates are leas than 5 ym
In size.  Increasing the mechanical strength of AA.O.
by modifying precipitation and calcination operatlona (aa
discussed earlier in this section) may lead to a reduction
of particulace A£_0. emi38ions*
     The emissions of both particulate and flourine compounds
from the bath increase with increasing temperature, decreasing
alumina content, and decreasing bath ratio of NaF/A&F. (Kotarl,
et_ al. 1974).  The hydrogen flouride emissions are generated
primarily as a result of moisture treating with AW. containing
materials.  The HF emissions Increase directly with the water
(Bell and Dawson, 1971).  The sources of moisture are from the
atmosphere, the moisture content ?f A£.0_.
     The flourid- particulates range in size froa about 0.05 -
0.75 urn with the majority of the particles smaller than 0.25 ym
(McCabe, 1975).  The flourine content of the total gases,
withdrawn from the pots or pot rooms may vary from 2 to 40 mg/ft ,
or between 18.97 - 25.63 kg/ton of the raw material (Kotari,
et al. 1974).  Cooling the process by 5°C will reduce flourine
consumption by 0.2 kg/ton of raw material (Kotari, £t, al. 1974).
An optimization of the operative temperature of the electrolytic
cell is needed to minimize the generation of hydrogen flouride.
Fifteen percent of the flouride present in the emissions from
prebaked pots occurs as HF, while 90Z of the flouride in Solder-
berg pot emissions occurs as HF (Less and Waddingtern, 1971).

-------
 found  that  the maximum adsorption capacity determined  in  the          7.12



 laboratory  is roughly twice that  determined under  production



 conditions.   Research efforts are needed  to explain  this



 discrepancy  between laboratory and production  tests  and there-



 by  improve  the adsorption of HF on A&.0.  in industrial pollu-



 tion control devices.  Any increase In  the surface area of



 M 2°3  per unit weight would Increase its  HF adsorption capacity.



     Sulfur  oxides  in the fumes from electrolytic  cells are



 generally removed by wet  scrubbing (in  lime scrubbers) and/or



 by  dry scrubbing (by adsorption on A&20.).  It  is  reported



 (U.S.  EPA, Dec. 1973) that a venturi type line  scrubbing  system



 at  the Mitsui Aluminium Company,  Ltd. has operated at  SO. removal



 efficiencies of 86Z-93Z for more  Chan a year.   It  may  be  necessary



 to  improve on the venturi contacting device to  improve SO.



 removal efficiencies or to use additional dry scrubbing units



 to  further remove SO..



     The low equilibrium  value of SO- adsorption. Jn  smelter



 grade A£203  is a limiting factor  in the removal of SOj from



cell gases in a dry scrubber.   It was shown by Lamb  (1979)



that the presence of adsorbed flourlde  from cell gas would



reduce equilibrium  adsorption of  SO. even further.   This



effect will  be most important with vertical stud Solderberg



cells where  HF loading  and concentration  is higher than the



horizontal stud Solderberg or prebaked  electrolytic  cells.



It is necessary to  understand the interaction of SO, and



HF on A&.0.  to develop  dry scrubber systems to remove SO..

-------
     Benry (1963) reported on experiaental work vhlch established  7.13
correlations between three cell operating paranetara  and effluent
production.  The reaulta of theae ezperiaenta are aunnarlsed in
Table 7.3.
TABLE 7.:.  EFFECT Of CELL OPERATING PARAMETERS AS FLOURIDB
            EFFLUENT
Range of Variables
Cryolite Bath
Ratio (SaF/AiF3)
1.44 to 1.S4
1.30
l.SO
Alumina
Content
4Z
32 to 3Z
4Z
Jeop.
9.73°C
973°C
982°C
Effect on
Flourlde
Effluent
31Z decrease
20Z decrease
24Z decrease
It waa thus shown that by increasing tha bath ratio
the alualna content of tha bath, and decreasing the call tanpera-
tun, a decreaaa waa seen in tha flouride content of tha call
effluent.  Rettarch efforta should be directed to aodlfy these
call operational variablea in ordar to minlalza f ourlde production.
     There haa been several research afforta directed at tha
reduction of  fune troataant by adsorbing B7 on alumina.  Xavesti-
gationa carried under production conditions CColpitta, 1972;
Chavinaan and Muhlrad. 1973; Cochran, 1974) show that tha effi-
ciency of the adsorption process falla off once a certain
quantity of gaseous fxourine has been adsorbed, and that this
quantity la directly proportional  to tha specific surface area
of Ai-0..  In a recent study, Baverrx and Deltarco (1950) shoved
that BF is adsorbed oc A*2°J ** tvc blaolecular 1«7«".  They

-------
     The possibility of the uce of chemical additives to



remove sulfur in the coal aa slag ia another research area



Chat la being investigated by Alcoa (West. 1980) under a con-



tract with the DOE.  Alkali additives and K^CO^ are known to



achieve high efficiencies in removing S02<



     Tschopp. Franke and Bernhauser (1979) report that additions



of Lithiun reduced the operating temperature of the electrolytic



cell by 14°C and reduced flourine evolution by 251. based on



their studies at a Sviaa aluminium plant at Essen.



     The used cell linings consist largely of carbon (the cathode),



but also contain cryolite, aluminium carbide, and aluminium nitride.



RaOH and sodium cyanide also appear In waters resulting from



leaching of cell linings.  The carbides react with water vapor



in the air to produce methane  (CH^), hydrogen, C2H2 and other



hydrocarbons.  The nitride yields ammonia.  This cathode



material. In the past, has been dumped or used aa landfill.



However, environmental concerns now consider the flouride



content to pose a possible pollution hazard.  Over 30Z of the



flouride in  scrapped cell linings is water  soluble.  Lu and



Shelley (1970) describe  eleven treatment methods to  treat cell



linings.  They concluded that  apart  from  the two methods,



sodium hydroxide  leaching and  steam hydrolysis, already in



commercial use,  the most promising  approach seems  to be the



use of hot water  hydrolysis  and  recycle of  treated cathode



material.  However, it is unlikely  that all the cathode carbon



con be recycled,  the problem of  flourldes and  cyanides  in

-------
unused cathode still remains.  It is necessary to develop            7-15
leaching methods to reaove flourides oad cyanides to
facilitate dlsp. .al of cathode linings.
     Table 7.4 gives the major pollution problems associated
with the Primary Aluminium Industry.
7.4  RECOMMENDED RESEARCH STUDIES FOR POLLUTION CONTROL Hi THE
     PRIMARY ALUMINIUM INDUSTRY
     After evaluating the available literature, the following
areas are recommended for further research by the study:
     .    Leaching and extraction of red mud to recover
          mineral values.
     .    Improving the mechanical strength, adsorption
          capacity and particle size distribution of cal-
          cined alumina by optimizing  precipitation and
          calcination of alumina.
     .    Optimizing the temperature for and stripping of
          high silica U.S. Bauxite ores.
          Enrichment of high silica U.S. Bauxite using
          bacterial action.
          Improving calcination of f^2°3 to reduce lta
          moisture content thereby  reducing formation of
          HF from electrolytic cells.
          Optimization of the cryolite bath QiaF/AiF^)
          ratio,  alumina content  and temperature of cell
          •;o reduce  flourlde emissions.
          Increanlng  the adsorption capacity  of AJO-  to

-------
Table 1-1.  Surfeited Process Modification  for Pollution Control In the Primary Alumlnluc Industry.
Proceas
Bauilte
Processing.
Handling and
Shipping



Primary*
Aluminium
Smelting


Prlvary
Alu-Mnlum
Sncltlng





Pollutants

Red Mud

Alumina




Alumina





Plourlde*





Source In
Prn*»0aa
Ore DlpesUnn

_w_v_ *_..—*




Electrolytic
Cell



Electrolytic
Cell






Nature of
FollutantB
Pe 0 . AtjO..
• J * J "
etc. oildei
Fartlculatea




Parttculatea




HP







SuMeated Proceaa
Hodiricatloni
Recovery of mineral valuea,
Developing alternative
Ueea for red mud.
Opt tailing precipitation
and calcination to improve
ccchanlcal strength and
particle aiie distribution
of alumina.
Optimising precipitation
and calcination to improve
mechanical strength and
particle else distribution
of alumina.
Improvlnf calcination of At.O.
to decrease rolsture content;
optlmlslne cryolite bath
ratio, alumina content and
temperature of cell; use of
lithium as additive; and.
increasing adsorption capacity
of Al20j.

-------
Table 7-4.  Surgeated Proceee Modification for Pollution Control in the Primary Alualnlus Induetry.  (Cont'd)
Procete
Prlnary
AluMlnluai
SnelLtng

Prlaiary
AliwInluB
Sneltlng


Pollutant!


*>*

Spent Cathode
Lining*


Source In

Electrolytic
Cell

electrolytic
Cell



Nature of


— — -------

Carbon, cryolite.
aluainlua carbide
aluailnliui nitride.
cyanidca and
flour Ides
Suggested Procaaa
[•proving adsorption of SO
an Al ,Oj In the preaence
IF; Use of additives to reanve
aulfur In coal as alag.
Leaching to reaove cyanldea
and flourldea; and hot-water/
steaa hydrolyala and aodluai
hydroxide leaching to recycle
apcnt cathode.

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remove HF in Che fumes from electrolysis.                 7.18



Understanding the interaction of HF and SO  on



A£2°3 to Improve dry scrubbing of SO  gases from



the electrolytic cell.



The effect of various additives in removing



sulfur In coal as slag.



Effect of adding Lithium on cell operating tempera-



ture and HF emissions.



Leaching of cathode linings to remove flourides



and cyanides.

-------
                           BIBLIOGRAPHY                               7.19
Andreev, P.I., .et al. Light Metal Age, 34 (3-4), 5-6, April,
     (1976).

Ball. D.F. and Dawson, P.R. Air Pollution from Aluminium
     Smeltera. £hem. Proc. Eng., 52, (1971).

Saverez, M. aad Demarco, R.  J. of Metala. 32(1), p. 10-14,
     Jan. (1980).

Chavinean. A. end Muhlrad, W.  Dry Proc  
-------
Lamb., W.D.  J. of Metals. 31(9), pp. 32-37, Sept.,                  7.20
     (1979). ~

Less, L.N. and Waddington, J.  The Characterization of
     Aluminium Reduction Cell Fume. AIME, New York,
     (1971).

McCabe, L.C.  Atmospheric Pollution. I&EC, 47(8),
     August, (1955).

Saxtoa, J. and Kramer, M.  EPA Finding on Solid Wastes
     from Industrial Chemicals. April 28, (1975).

Schmidt, H.W., et al.  J. £f Metals, Vol. 32(2). 31-39,
     Feb., (1980).     ~~

Solyman, K., and Brijdoso, E.  Properties of Red Mud in
     the Bayer Process and Its Utilization.  Paper No. A73-
     56, Metallurgical Society of AIME, Feb. 28 - Mar. 1,
     (1973), Chicago, Illinois.

Sutyrin, Yu. E. and Zerev, L.V.  Light Metal Age. 34 (1-2),
     9-10. Feb., (1976).

Tschopp, Th., Franke, A. and Bemhauser, E. J.- of Metals.
     ,31  (6), pp. 133-135, June,  (1979).

U.S. EPA.  Operation and Performance of the Lime Scrubbing
     System a£ Mitsui Aluminium  Co., Ltd.  U.S. ETA 450/2-
     73-007, Dec.,  (1973).

U.S. EPA.  Trace Pollutant Emission from the Processing
     of Metallic Ores. EPA 650/2-74-115. Oct.,  (1974).

West, C.E.  Light Metal Age. 38  (9-10), pp. 16-18, October
     (1980).

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                             CHAPTER 8
                   PHOSPHATE FERTILIZER INDUSTRY
8.1  INTRODUCTION
     Fertilizers in general can be categorized by their composi-
tion of plant nutrients.  The fertilizers differ in their composi-
tion of plant nutrients of nitrogen, phosphorous, and potassium.
Normal superphosphate contains only one nutrient, phosphorous.
Ammonium phosphate contains phosphorous and nitrogen.  Generally,
the aolid and liquid mix fertilizers contain all three nutrients
in varying amounts.
     Over 44 million metric tons of phosphate rock were mined
in the United States during 1975.  Approximately 22.7j million
metric tons were consumed by the fertilizer industry during
the same period (Nyers, et al. 1979).
     The phosphate based fertilizers are produced by conver-
sion of insoluble phosphate ore into the soluble form necessary
for plant consumption.  The phosphoric acid, backbone of
phosphate fertilizer, is formed by mixing phosphate rock with
sulfuric acid.
     This chapter  concentrates on the production of phosphoric
acid, normal  superphosphate, and ammonium phosphate.  The
preparation of  phosphate rock  is not discussed in  this chapter.

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8.2  VET PROCESS PHOSPHORIC ACID PRODUCTION                            8>2
     Most of the phosphoric acid in the fertilizer industry is
prepared by the wet process.  In this process phosphate rock
reacts with sulfuric acid to fora phosphoric acid and gypsum.
The overall chemistry of this reaction is shown In equation 8.1
(Corbridge, 1978):


     Ca10(PW2 * 10 H2S04 * 20H2  *
        (Flourapatite)
          6H3P04 + 2HF + 10CaS04 + 2H2                 (8.1)
            (gypsum)


Phosphoric acid is the most important intermediate in the
production of phosphate fertilizer.  In addition to its use
in the production of ammonium phosphates and concentrated
superphosphate, It is an intermediate for mixed fertilizer,
both liquid and solid (Nyers, et al. 2979).
     A simplified flow diagram of the wet process for phosphoric
acid production is given in Figure 8.1.  The process consists
of three steps:   (1) reaction of phosphate rock, (2) separation
o£ acid from  the  sulfate, and (3) concentration of the acid.
Important variables for a successful operation are type of
phosphate rock used,  the temperature of the reaction, and
the slurry density controlled by recycling weak acid to tLe
digester step.

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                                                                                8.3
PHOSPHATE
  ROCK
SUUORIC
  ACID
                                                  SUUVRIC
                                                    ACID
                                               DILUTION WATER
                          ATTACK
                          VESSEL
                                                 SCRUBBER
                         FILTRATION
                                                   CYTSUH
                                                    POHD
                        CVAFOKAriQfF
                                                  CTPSim
                                                 BT-PROOUCT
                        nomicr ACID
          Figure R.I.  Vet Proccat
                       (Hyvra, «£..«£
                    id Production Ptoe««s

-------
     Most vet process plants employ the crystallzatior of              8><*



calcium sulfate in the dehydrated state as opposed to heml-



hydrate or anhydrate.  This is due to the fact that the de-



hydrate process dees not impose as many operating problems



as the hemi-hydrate or anhydrate process.  Acid produced by



the dehydrate process contains about 13% Phosphorus (P) (30Z



P20.) and is generally concentrated to 17 to 24S P (43 to



54Z P2°s) before use.  The concentration of phosphoric acid



is facilitated by continuous heated vacuum evaporators



(Olson, et al. 1971).



     There is a substantial amount of pollutants evolved by



the wet process.  A large portion of reactants become by-



products contributing to the pollution.  The main by-product



of the dehydrate process is the  impure gypsum of little



practical use.  Phosphate roc'.-: is compoied of 2/3 gypsum,



thus making  the disposal of the  by-products a formidable



problem.  The other by-product is flourlde, which evolves



during digestion of phosphate  rock  and can be recovered



with water by a relatively simple scrubbing procedure.



     The  evolution of gaseous  flouride is caused by any



flourlde  containing  liquid due to  tne vapor przsaure  of



flrurlde.  The emission rate varies with temp mature,  concen-



tration,  absolute  pressure,  and  exposed  area of  the  liquid



surface on the digester.  Gaseous  flouride emissions  contain



silicon tetraflourlde,  which is  formed by the  reaction of

-------
hydrogen flourlde in the reactor.  Tetraflouride formation              8.5



is favored at temperatures below 100°C (Nyers, £t, al. 1979).



     Poorly controlled wet process phosphoric acid (WPPA)



plants may have emissions as high as .07 pound of flouride/ton



of P.O. fuel.  On the other hand, well controlled plants using



packed scrubbers or other equally effective control devices



can achieve flourlde emissions below .02 pound/ton of P.O.



input (U.S. EPA, Oct. 1974).  The data indicates that the



emission factors for plants that use flouride recovery is p- •



significantly different from those plants that employ the



recovery.  The recovery refers to flourlne recovered as



fluosilicic acid, flourides, flousillcates, or other by-



products (Nyers, _e£ jd. 1979).



     The final flourlne emission Is strongly dependent on the



type of scrubber used, scrubber operation, and use of fresh



water tail gas scrubbers.  Plant? that use flourine recovery



may dispose less volatile flourlne to their pond system, thus



having fewer emissions from the ponds.



     The most Important emission source in the typical WPPA



process is the ventilating air from the digester.  The



digester vent gases contain water vapor, participate dust,



and S1F..  The removal of flourine can be accomplished by



the wet process or adsorption (solid reagent or adsorption



system) of the ventilating air.  The wet process has been



used exclusively, however, the advantages and capabilities

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of Che adsorption process should be studied (U.S. IP A, Hatch 1973).    8.6



     The design of the scrubbing equipment is Limited by the



cheoistry of the reactions between the gypsum pond water and



tae flourine containing gases discharged from the WPPA plant



reactor.  The folloving reactions occur In the reactor:
     CaF2 •»• HjSO^  * CaS04 + 2HF                  (6.2)




or



     2HF + S1F,   *   H.SiPt                       (8.3)
Furthermore,  hydrolysis of  SiF^  can occur at  high  concentra-



tions  (i.e. higher than equilibrium concentration)  as  follows:
      3S1F4  + WjO  *    Si 
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flow scrubber la v compromise between the counter and co-              8.7



current scrubbers, ic employs the efficiency of the former



with the nechanicel advantages of the latter.  The crosa-



f)->- sci-ibbar has been used in combination with spray towers,



venter!. or wet cyclones in pl-.osphorlc acid plants (U.S. EPA,



March 1973).



     The efficiency of the scrubber is dependent on the



temperature and rtnooc'tlon of the scrubber nudlum.  The



gypaun pond water >iaeo In the ^crvl^er contains 30C9 ppm



to 10,000 ppa of flourine (Nyezs, .ct ;-l.  !<)". O.  Efficient



renoval of flourine C.-cn the gaa stream  is reduced, ^ue to



the high partial pressure of hydrogen flourid   In  the pond



water.  The tnaaa transfer rate alao decreases as temperature



increases, thus, fresh water should be used  as  the scrubolng



medium in the last stage of scrubbing.



     Oxides of sulfur are alao emitted in the WPPA procc*-.



Their production ranges from 0.0077 to O.OS8g/kg P2°s'



However, the origin of SO  formation la  not  clear  in tlc



WPPA proceas (Nyera. £££!.• 1979).  The  cause of its



emlaaion must firat be determined before any measure



regarding Its reduction wit Lin the process la taken.



8.3  RECOMMENDED AREAS FOR FOU.UTIOS CONTROL RESEARCH:



     VET PROCESS PHOSPHORIC ACID PRODUCTION



     After evaluating the avallab.'c literature, tha following



areaa are recooBended for further research by the  study:

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     .    Studies on purification of phosphate feed to



          reactor to reduce impurities which cause



          by-produce formation.



     .    Cooper a Live studies on adsorption and absorption



          of flourine to determine the most efficient



          technique to alleviate flourine emission.



     .    Research on the design and operating parameters of



          the scrubber to reduce plugging and Increase the



          rate of flourine transfer from the vent gases to



          scrubbing medium.



8.4  UORMAX. SUPERPHOSPHATE PRODUCTION



     Normal superphojpoate (RS) Is produced by the reaction of



phosphate rock with aulfuric acid.  The phosphate, rock and



ILSO. are nixed In a cone mixer (reactor vessel), the acidulate



la then transfered to an enclosed area (den) to solidify.



The solidified product is then stored for curing.  The schematic



diagram of this- process la shown In Figure 8.2.



     The HS production csa be accomplished by both continuous



and batch processes.  ?or th* batch process, a pan miser



(Instead of cone mixer for the continuous process is used.  However,



both processes convert fluorapatlte in the rock to soluble



monecalciuE phosphate.  The major reaction la this process is:
          3CCaH4  (P04)2 By)! + 7CaS06 * 2HP            (8.5)

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StrutiHC
  ACID
                                                                                          nissiOM
                                                                                         IKTCUD
                                                                            TO CtmiMC
                     1.1.  flew Chan of HDIM! SupcrphoiphaU Product la*

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     The  source  of  pollution  emissions  for  a NS plane are the          8.i«x



mixers, den,  and curing  building.  Between  1.5 kg  and 9.0 kg



of  flouridea/metrle ton  of NS are released  during  production



and the curing process (Myers,  et. al. 1979).  The  flouride emis-



sions occur in form of flouride vapor evolving as  hydrogen



flouride  and  silicon tetraflouride.  The flouride  emissions



range from 0.07  g F/kg PjOj to  0,45  g F/kg  PjO^.   Individual



emission  rates from each unit is hard to find since all gases



are vented to the same stack.



     As previously  discussed, tha scrubbing is inhibited by



the formation of  a  gelatinous mass,  generated by the reaction



of  tetraflouride  and water.   Thus, the  use  of conventional



scrubbing,  for pollution abato-neat,  is  greatly influenced



by  this reaction.   The effectiveness of the flouride reduc-



tion by a scrubber  is determined by  Inlet flourine concentra-



tion, outlet  saturation  temperature, composition and tempera-



ture of the scrubbing liquid, scrubber  type and transfer



units, and  effectiveness of entrainmenc separation (Heller,



et al. 1968).



     The  best strategy for pollution control is to use a cross-



flow scrubber.  Furthermore,  flcurine removal is enhanced by



use of fresh  water  in the last  stage and increasing the number



of  stages in  the  scrubber (Myers, j£ al. 1979).

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8.3  RECOMMENDED AREAS FOR POLLUTION CONTROL RESEARCH:  NORMAL      8.11



     SUPERPHOSPHATE PRODUCTION



     After evaluating the available literature, the following



areas are reconnended for further research by the study:



          Studies on the scrubber design and optical operating



          paraaeters to reduce flourlne emissions.



8.6  AMMONIUM PHOSPHATE PRODUCTION



     The production of ammonium phosphate (AP), mostly



dlanmonlum phosphate (DA?), has increased rapidly in the past



3 decades.  The total of ammonium phosphate produced in the



U.S. reached nearly 3.7 million tons ^S* vhicn ls 63.4Z



of all phosphate fertilizers produced in the U.S. (Kirk-



Othmer, 1980).  Approximately 99Z of AP are used as fertilizer



(Nyers, et al. 1979).



     The discussion to follow includes the granulation of



phosphoric acid with anhydrous ammoniation-granulation to



produce granular fertilizer.  Ammonium phasphate is produced



by the reaction of phosphoric acid with anhydrous ammonia.



In 1975, 84Z of AP produced in the U.S. was of DAP grade



(i.e. percentage of available N-K-P is 16-0-48 (Myers, et.



al.  1979).



     Ammonium phosphate C(NH.j.HPO.3 is produced by the



reaction of 1 mole of phosphoric acid with 2 moles of ammonia



forming a product with 21.1Z nitrogen and 5AZ available



phosphorous.  Monoammoaium phosphate (MAP) can also react

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with amnonla to yield DAP.  The DAP production eaa be                  8.12



performed in either a pugmill or rotary drum ammonia tor.



Approximately 95Z of aononiatlon granulation plants in the



U.S. use rotary drum-mixer developed by TVA (Ravlirgs and



Reznik, 1976).



     The pollution sources arise from four operations in



tht ammonium production process:  (1) reactor, (2) ammonlator,



(3) dryer, and (4) cooliug.  Typical emissions include,



ammonia, flouride, particulates, and negligible amount of



combustion gases.  The following discussion is for the TVA



process depicted in Figure 8.3.



     The reactor or preneutralizer is a vessel into which



70S of ammonia and all of the phosphoric acid is introduced.



The reactor operates at atmospheric pressure and 100-120°C.



The NH.:H.POA ratio Is maintained at 1.3:1 to 1.5:1 for



ma-rim,,m soliblllty of MAP, which is the main product of the



reactor (Nyers, e£ _•!. 1979).



     The emissions from the reactor contain ammonia and



flourldes In form of gaseous emissions.  The emissions are



caused by volatilization due to incomplete chemical reactions



and excess free ammonia.  Collective emissions for reactor



tad ammonlator-granulator are as follows:



     Flourldes (as F)                   0.023g/kg P^



     Particulars                        0.076g/kg P20j



Ammonia emission data is available for the AP production



as a whole (Nyers, et al. 1979/.

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   CypaiM
fond Water
                                                                                   Cypaua
                                                                                    Pond Water
                                                                                                                    Product to
                                                                                                                    Storage
                                                                                                                    Bagging.
                                                                                                                    or Bulk
                                                                                                                    ShlpMni
                          rtgure 8.1.   Plow Dlagraa for TVA AMonltw Phosphate Proceaa.
                                       (Nyera. tl rl.  1979).

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     The reactor emissions can be controlled with a taore               8.14
efficient design of the reactor.  Zn theory, the reactor
can be designed without any ventilation, but in practice
they are operated at a 57 - 76 cfa ventilation rate (U.S. EPA,
March 1973).
     The reactor design can be modified to reduce the venti-
lation rate and thus the atmospheric emissions.  Furthermore,
the excess ammonia should be avoided in the reactor vessel.
The rate of reaction should be increased catalytical.V/ by
changing the process conditions, and/or the residence time
should be Increased in order to achieve complete reaction.
     The granulation by agglomeration  and by coating particles
with slurry from the reactor takes  place in the rotating
drum.  Ammonia is supplied by a sparging action underneath
the bed  to bring the NH^H^C^  ratio to 1.8:1.0 to 2.0:2.0
(U.S. EPA, March 1973).  The granulation can,  theoretically,  be
performed with no ventilation.  The ventilation is mainly
a function of  design of  the  granuletor, thus design considera-
tions  play an  Imprrtabt  role in the final emissions of
ammonia.
     The emission  from the reactor and granulator  are scrubbed
 for pollution reductions.  Anyone of  the various scrubbing
 techniques  can be  applied to these off gases.  However,  packed
 scrubbers should be avoided due to the formation of gelatinous
 silicon or DAP,  which tend to plug the scrubber.   The best

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scrubbing technique for pru^ry scrubbing is a venturi cyclone         8-15
scrubber which has good capabilities for absorption of
ammonia and particulate matter.
     Moist granules of DAP are dried to 2Z moisture in a
counter-current gas or oil fired dryer unit.  The controlled
emissions from the dryer and cooler are 0.015g/kg PjO^
flouride and 0.75g/kg PjOj particulate emissions (Nyers, et
al. 1979).
     The flouride emissions are due to ch« dissociation of the
fertilizer -product and particulate emissions are caused by
entrainment of DAP and MAP dusts in the ventilation air
streams.  The particulate emissions may contain both
ammonium flouride and ammonium phosllicates  (U.S. EPA, March  1973).
Typically, the primary scrubbers are designed  to capture the
participates.  Thus  the  design of  the  primary  scrubbers must
account for  the  particulate  as veil as removal of off gases from
the ventilation  streams.  Furthermore,  the scrubbing  medium,
in the primary scrubber,  should be acidic enough  to absorb  the
ammonium discharge.   For this pruoose  30Z phosphoric  acid
solution is  used for the primary  scrubbing medium to  recover
ammonia (U.S.  EPA, March 1973).
      Whenever the use of only one scrubber is not sufficient
 to remove particulares and gases,  combination of  scrubbers
 must be considered.
      Table 8.1 contains the summary of pollution problems
 associated with the phosphate rock industry and the suggested

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Table 8-1.  Pollutant* and Suggested Strategy for Selected Phosphite Rock  Fertiliser
Industry
Wet process
phosphoric
acid
Normal
Super-
phosphate
Product Ion
Anon 1 urn
Phoephste
Production
Process
Phosphate
Roc* Processing
Phosphste
Rock
Processing
DlammonluB
Phosphate
Production
Pollutanta
Flourldes
Partlculatea,
SOg, k Gypsum.
Flourldes.
Participates
Aanonla. -
Flourldea,
and
Partleul.cea
Source* In
Process
Reactor vessel.
rilteratlon.
vapors t Ion. &
gypsum pond
Nliera. den,
end curing.
Reactor, ~
at.monlator.
fryer, and
cooler.
Nature of
Pollutanta
Inorganic
gases, and
solids
Inorganic
gases, and
solids
Inorganic
gsses, and
solids
Pollutant Control
Cross flow scrubbing with
'fresh water In the Isst
stage, a-.id/or use combi-
nation of scrubbers.
Scrubbing the offgases.
cross flow scrubbing,
and/or use combination
scrubbing
Use combination primary
and secondary acrubblng
Improve the design on
the reactor end smaonlator
to reduce ventilation rate.
                                                                                                                                  CO
                                                                                                                                  •

                                                                                                                                  fr»
                                                                                                                                  o>

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strategy.                                                          8.17



8.7  RECOMMENDED AREAS FOR POLLUTION CONTROL RESEARCH:



     AMMONIUM PHOSPHATE PRODUCTION



     After evaluating the available literature, the following



areas are recommended for further research by the study:



     .    Research on kinetics of reaction of ammonia



          with phosphoric acid to enhance this reaction,



          either catalytically or by increasing the resi-



          dence time in the reactor vessel, which would



          reduce the emission.



          Studies on design of the reactor vessel and



          granulators to minimize the ventilation rate



          which would lead to smaller volumes of gaseous



          emission.



          Research on the design and selection of optimal



          operating parameters for the scrubbing unit to



          reduce the ammonia, flourlde, and particulate



          emissions.

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                              BIBLIOGRAPHY                             8.18
Chemistry and Technology of Fertilizer.  V. Sauchelli, ed.
     Rlenhold Publishing Corp., New York, New York 1960.

Corbridge, D.  Phosphorous. Elsevlor Scientific Publishing
     Company, New York, 1978.

Heller, A.N., Cuffi, S.T. and Goodwin, D.R.  Inorganic
     Chemical Industry. Air Pollution. Vol. Ill: Source
     of Air Pollution and Their Control.  A.C. Stern, ed.,
     Academic Press, New York, New York, 1968.

Lutz, W.A. and Pratt, C.J.  Principles of Design and Ope-ation
     in: Phosphoric Acid. No. 1, A.V. Slack, ed. Marcel
     Dekker, Inc., New York, New York, 1968..

Nyers, J., ££aJL.  Source Assessment; Phosphate Fertilizer
     Industry.  EPA-600/2-79-019C, May 1979.

Olson, R.j.ejtal^  Fertilizer Technology & Use.  Soil
     Science Society of America, Inc., Wisconsin, 1971.

Rawlings, G T. and Reznik, R.B.  Source Assessment! Fertilizer
     MixinK Plants.  EPA-600/2-76-032C.  March 1976.

Slack, A.V.  Chemistry and Technology of Fertilizers.  John
     Wiley and Sons, Inc., New York, New York 196/.

U.S. EPA.  Air Pollution Control Technology and Costs in
     Seven Selected Areas.  Industrial Gas Cleaning Inst.,
     Inc.. Stanford, CT, EPA-450/3-73-010, March, 1973.

U.S. EPA.  Background Information for Standards of Performance;
     Phosphate Fertilizer Industry. Environmental Protection
     Agency, Research TriavgjL* Park, N.S. Office of Air
     Quality Planning and Standards.  EPA-450/2-74-019A, Oct.
     1974.

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                                                                      8.19
                      SUPPLEMENTAL REFERENCES
Gartrell, F.E. and Barber, J.C.  Pollution Control Inter-
     relationships, Chemical Engineering Progress. 62(10):
     44-77, 1966.

Huffstufler, K.K.  Pollution Problems in Phosphoric Acid
     Production in; Phosphoric Acid. Vol. I, A.V. Slack,
     ed., Marcel Dekker, Inc., New York, New York, 1968.

Illarionov, N.V., et al.  Zh. Prikl-Khin. Vol. 36, 1963.

Kirk-Othmer Encyclopedia of Chemical Technology, Third
     Edition, Volume 101, John Wiley and Sons, New York,
     1980.

Lehr, J.R.  Purification of_ Wet Process Acid In: Phosphoric
     Acid. Volume I, A.V. Slack, ed. Marcel Dekker, Inc.,
     New York, 196?.

Muehberg, P.E., Reding, J.T. and Shepherd, B.P.  Draft
     Report: The Phosphate Rock and Basic Fertilizer
     Materials Industry.  Contract 68-02-1324, Task 8, EPA,
     Research Triangle Park, North Carolina, May 1976.

Shreve, R.N.  Chemical Process Industries. Third Edition.
     McGraw-Hill Book Company, New York, 1967.

U.S. EPA.  Atmospheric Emissions from Wf.t Process Phosphoric
     Acid Manufacture. U.S. Department of Health, Education
     and Welfare, NAPLA. No. AP-S7, April 1970.

U.S. EPA.  Final Guideline Documei.t; Control of Flouride
     Emissions from Existing Phosphate Fertilizer Plants.
     EPA 450/2-77-0051 March 1977.

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                             CHAPTER 9



                  CONCLUSIONS AND RECOMMENDATIONS








9.1  INTRODUCTION



     Based on Che preparation of the reports submitted for the



eight industries, it is concluded that research programs in the



following areas should yield results encompassed in the objectives




of this program.



9.2  SOLVENT EXTRACTION



     Modification of solvent extractor design and operation would



minimize metal ions or non phenolic organlcs in process streams



leaving extractor batteries in hydromet&llurgical and coal lique-



faction processes respectively.   Studies could include modelling



of selective ion extraction in multiple metal systems, characteri-



zation of liquid dispersion properties such &3 surface area and



droplet mixing as a  function of  power consumption, extraction



kinetics, and  separation of liquid-liquid dispersions.




9.3  CATALYST  DEACTIVATION



     Modification of  catalyst  reactor bed operation  and studies



on catalyst deactivation will  increase  catalyst,  life and  reduce



the volume  of spent  catalyst  from coal  gasification  operations.



Studies  could Include modelling catalyst deactivation  phenomena



as affected by temperature,  pressure, feed  gas  composition,



catalyst structure,  and catalyst type.   Optimal reactor



operation studies for sulfur guard catalysts (ZnO),  shift

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                                                                         9.2
 catalysts (cobalc-molybdate), and oethanation catalysts (nickel)
 can be conducted.
 9.4  LEACHING PROCESSES
      Modification and improvement of leaching processes for
 aulfide or oxide ores will reduce ground vater contamination
 and dissolved metal salts In process streams in' hydrometallur-
 gical processes.  These results also apply to recovery of metals
 from particulates (smelting dust),  coal liquefaction ash,  spent
 catalysts in coal gasification, and coal liquefaction residues.
 Studies could Include vat leaching  using ammonlal or in organic
 acid solutions.   Characterization of kinetics of leaching  as
 affected by  particle size,  temperature,  concentrations and
 particle structure can be explored.   Minimum power requirements
 to  suspend particles and  maximize particle-liquid mass transfer
 ran be  studied.
 9.5  GAS  ABSORPTION
     Modification and Improvement of  gas absorption processes
 such as  the Stretford absorption  process will reduce emissions
 of H2, HCN, and COj  in tail gases from coal liquefaction pro-
 cesses and H2S and S02 for smelter off gas recovery  operations.
 Studies could Include  gas-liquid mass transfer and gas-liquid
 reactions in absorption liquids (sodium metavanedate, sodium
carbonate, sodium bicarbonate, and ADA) as affected by tempera-
ture, pressure, and gas-liquid contacting.

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                                                                        9.3
9.~6  GAS-LIQUID-SOLID REACTIONS
     Modification and improvement cf reactors for contacting
•ad reacting gas-liquid-solid dispersions vould minimize
partlculate emissions in coal liquefaction reactions as well
as vat leaching processes.  Studies could include coal dissolu-
tion rates, gas dispersion, participate agglomeration, dissol-
ved gat-particle reactions, and determination of the rate
limiting  steps as  affected by mechanical imitation, temperature,
pressure  and compositions.

-------