United States
        Environmental Protection
         Industrial Environmental Research
EPA-600/7-80-01 2d
March 1980
         Research Triangle, Park NC 2771 1
Waste and Water
Management for
Conventional Coal
Combustion: Assessment
Volume IV.
Utilization of FGC Wastes

R&D Program Report


Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology  Elimination of traditional  grouping was  consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

    1. Environmental Health Effects Research

    2. Environmental Protection Technology

    3. Ecological Research

    4. Environmental Monitoring

    5. Socioeconomic Environmental Studies

    6. Scientific and Technical Assessment Reports (STAR)

    7. Interagency Energy-Environment Research and Development

    8. "Special" Reports

    9. Miscellaneous Reports

This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded  under the 17-agency Federal Energy/Environment Research  and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects;  assessments of, and development of,  control technologies for energy
systems; and integrated assessments of a wide-range of energy-related environ-
mental issues.

                        EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.

This document is available to the public through the National Technical  Informa-
tion Service, Springfield, Virginia  22161.


                                          March 1980
     Waste and Water Management
  for Conventional Coal Combustion
        Assessment Report-1979
Volume  IV. Utilization of FGC Wastes

               C.J. Santhanam, R.R. Lunt, C.B. Cooper,
            D.E. Klimschmidt, I. Bodek, and W.A. Tucker (ADL);
               and C.R. Ullrich (University of Louisville)
                    Arthur D. Little, Inc.
                      20 Acorn Park
                Cambridge, Massachusetts 02140
                   Contract No. 68-02-2654
                 Program Element No. EHE624A
                EPA Project Officer. Julian W. Jones

             Industrial Environmental Research Laboratory
           Office of Environmental Engineering and Technology
                Research Triangle Park, NC 27711
                      Prepared for

                Office of Research and Development
                   Washington, DC 20460

                       PARTICIPANTS IN THIS STUDY

     This First Annual R&D Report is submitted by Arthur D.  Little, Inc.
to the U. S. Environmental Protection Agency (EPA) under Contract No.

68-02-2654.  The Report reflects the work of many members of the

Arthur D. Little staff, subcontractors and consultants.  Those partici-

pating in the study are listed below.

Principal Investigators

     Chakra J. Santhanam
     Richard R. Lunt
     Charles B. Cooper
     David E. Kleinschmidt
     Itamar Bodek
     William A. Tucker

Contributing Staff
     Armand A. Balasco                        Warren J. Lyman
     James D. Birkett                         Shashank S. Nadgauda
     Sara E. Bysshe                           James E. Oberholtzer
     Diane E. Gilbert                         James I. Stevens
     Sandra L. Johnson                        James R. Valentine

Sub contractors
     D. Joseph Hagerty                        University of Louisville
     C. Robert Ullrich                        University of Louisville

     We would like to note the helpful views offered by and discussions

with Michael Osborne of EPA-IERL in Research Triangle Park, N. C., and

John Lum of EPA-Effluent Guidelines Division in Washington, D. C.

     Above all, we thank Julian W. Jones,  the EPA Project Officer, for

his guidance  throughout the course of this work and in the preparation

of this report.


     Many other individuals and organizations helped by discussions with
the principal investigators.  In particular, grateful appreciation is
expressed to:
     Aerospace Corporation - Paul Leo, Jerome Rossoff
     Auburn University - Ray Tarrer and others
     Department of Energy - Val E.  Weaver
     Dravo Corporation - Carl Gilbert, Carl Labovitz, Earl Rothfuss
          and others
     Electric Power Research Institute (EPRI)  - John Maulbetsch,
          Thomas Moraski and Dean Golden
     Environmental Protection Agency,  Municipal Environmental Research
          Laboratory - Robert Landreth,  Michael Roulier,  and Don  Sanning
     Federal Highway Authority - W.  Clayton Ormsby
     IU Conversion Systems (IUCS)  -  Ron  Bacskai,  Hugh Mullen
          Beverly  Roberts,  and others
     Louisville  Gas  and Electric Company  -  Robert P.  Van  Ness
     National Ash  Association - John Faber
     National Bureau of Standards -  Paul  Brown
     Southern Services - Reed Edwards, Lament  Larrimore,  and Randall  Rush
     Tennessee Valley Authority  (TVA)  -  James  Crowe,  T-Y.  J.  Chu,
          H.  William Elder,  Hollis B.  Flora, R. Janes  Ruane,
          Steven K.  Seale,  and others

                            CONVERSION FACTORS
     English/American Units
     1 inch
     1 foot
     1 fathom
     1 mile (statute)
     1 mile (nautical)
     1 square foot
     1 acre
     1 cubic foot
     1 cubic yard
     1 gallon
     1 barrel (42 gals)
     1 pound
     1 ton  (short)
     1 atmosphere (Normal)
     1 pound per square inch
     1 pound per square inch
     1 part per million (weight)
     1 knot
     1 British Thermal Unit
     1 megawatt
     1 kilowatt hour
     1 degree Fahrenheit
     Metric Equivalent

  2.540  centimeters
  0.3048 meters
  1.829  meters
  1.609  kilometers
  1.852  kilometers

  0.0929 square  meters
  4,047  square meters

 28.316  liters
  0.7641 cubic meters
  3.785  liters
  0.1589 cu. meters

  0.4536 kilograms
  0.9072 metric  tons

101,325  pascal
  0.07031 kilograms  per square centimeter
    6894 pascal

  1 milligram per liter

  1.853  kilometers per hour

  1,054.8 joules
  3.600 x 10* joules per hour
  3.60 x 106 joules

  5/9 degree Centigrade

Cementitious:  A chemically precipitated binding of particles
resulting in the formation of a solid mass.

Fixation;  The process of putting into a stable or unalterable

Impoundment:  Reservoir, pond, or area used to retain, confine,
or accumulate a fluid material.

Leachate:  Soluble constituents removed from a substance by the
action of a percolating liquid.

Leaching Agent:  A material used to percolate through something
that results in the leaching of soluble constituents.

Pozzolan:  A siliceous or alundnosiliceous material that in
itself possess little or no cementitious value but that in
finely divided form and in the presence of moisture will react
with alkali or alkaline earth hydroxide to form compounds possessing
cementitious properties.

Pozzolanic Reaction:   A reaction producing a pozzolanic product.

Stabilization;   Making stable by physical or chemical treatment.

S, or lit
biochemical oxygen demand
British thermal unit
cubic centimeter
chemical oxygen demand
degrees Centigrade (Celcius)
degrees Fahrenheit
electrostatic precipitator
flue gas cleaning
flue gas desulfurization
gallons per day
gallons per minute
joule per second
square meter
cubic meter
million gallons per  day
megawatt electric
megawatt hour
parts per million
pounds per square inch
pounds per square inch absolute
standard cubic  feet  per minute
total dissolved solids
total oxidizable sulfur
total suspended solids
tons per year

                           TAU [" OF CON'J KN'l S


ACKNOWLEDGEMENTS                                               iii

CONVERSION FACTORS                                              iv

GLOSSARY                                                         v

ABBREVIATIONS                                                   vi

LIST OF TABLES                                                  ix

LIST OF FIGURES                                                 ix

1.0  INTRODUCTION                                              1_1

     I.I  Purpose and Content:                                  l_i
     1.2  Report of Organization                               ~L-2

2.0  UTILIZATION OF COAL ASh                                   2-1

     2.1  Introduction                                         2-1
     2.2  Current Utilization                                  2-2

          2.2.1  Characteristics  of Coal Ash                   2-2
          2.2.2  Current Utilization                            2-5

     2.3  Ash Utilization as Fill Material                     2-10

          2.3.1  Borrow Substitute                              2-10
          2.3.2  Soil Stabilization                            2-14
          2.3.3  Market Characteristics  and Economics           2-16
     2.4  Ash in Cement and  Concrete                            2-16

          2.4.1  Ash in Cement                                  2-17

         Cement  Production                    2-17
         Ash as  Cement  Raw Material            2-17
         Ash as  Cement  Additive                2-20

          2.4.2  Ash in Contrete                                2-20
          2.4.3  Lime/Fly Ash/Aggregate  Basic  Courses           2-24
          2.4.4  Ash as Aggregate Substitute                    2-25
          2.4.5  Market Characteristics  and Economics           2-25

     2.5  Ash in Miscellaneous  Use                              2-27

     2.6  Ash as a Mineral Resource                           2-29

     2.7  R&D Programs  - Ash  Utilization                       2-30

          2.7.1  U.  S.  Army Corps of Engineers                 2-31
          2.7.2  Bureau of Reclamation                         2-35
          2.7.3  Coal Research  Bureau - West Virginia U        2-35
          2.7.4  Department of  Energy - Gordian Associates     2-37
          2.7.5  Federal Highway Administration                2-38
          2.7.6  National Bureau of Standards                  2-39
          2.7.7  Tennessee Valley Authority                    2-41
          2.7.8  GM  - Plastic Filler                           2-42
          2.7.9  Other  R&D                                    2-43


                          TABLE OF CONTENTS


     3.1  Introduction                                         3-1
     3.2  Utilization of Nonrecovery FGD Wastes                3-1

          3.2.1  Description of Wastes                         3-1

         Solid Wastes                         3-2
         Liquid Wastes                        3-5

          3.2.2  Current Utilization Practices                  3-6
          3.2.3  Potential Utilization Alternatives            3-6

         Structural Landfill                  3-7
         Gypsum                               3-7
         Aggregate                            3-10
         Agricultural Uses                    3-11
         Building Brick                       3-13
         Recovery of Chemicals                3-13

          3.2.4  R&D Programs - Nonrecovery FGD Wastes         3-13

         Pullman Kellogg                      3-17
         TVA                                  3-17
         TRW                                  3-20
         Texas A&M University                 3-23

      3.3  Utilization  of Wastes and By-products
          from Recovery FGD  Systems                            3-25

          3.3.1 Introduction                                 3-25
          3.3.2 Waste Streams  from Recovery Processes         3-26
          3.3.3 Marketability  of Sulfur or Sulfuric Acid      3-27
          3.3.4 Stockpiling                                  3-28
          3.3.5 Energy Demands                               3-29

      3.4  FGD Waste and By-product Marketing                   3-29

 4.0  REGULATORY CONSIDERATIONS                                4-1


      5.1  Assessment of Utilization                           5-1

           5.1.1  Technical Considerations                      5-1
           5.1.2  Institutional Barriers                        5-2
           5.1.3  Other Factors                                 5-2

      5.2  R&D Assessment                                       5-3
      5.3  Future Utilization Considerations and Data Gaps      5-5
      5.4  Emerging Technologies                                5-8

 REFERENCES                                                     R-l
 INDEX                                                          R~7


                             LIST  OF TABLES

Table No.
   2.1     Range  of  Coal Ash  Compositions                       2-3
   2.2     Commercial Utilization  of  Coal Ash in  the
          United States                                        2-6
   2.3     Ash Utilization                                      2-8
   2.4     Total  Ash Utilized                                  2-9
   2.5     Ash Utilization as Fill                             2-11
   2.6     ASTM C 593 Requirements Pertaining to  Fly
          Ash for Use with Lime/Soil Mixtures                  2-15
   2.7     Ash Utilization in Cement and Concrete               2-19
   2.8     Ash Utilization in Miscellaneous Uses                2-28
   2.9     Current Research in Fly Ash Utilization              2-32
   3.1     Current Research in FGD Waste Utilization            3-15
   3.2     TRW:   Sensitivity  Analysis                           3-24
   3.3     Summary of TVA Gypsum Marketing Results              3-32
                            LIST OF FIGURES

Figure No.
  2.1     Coal Ash/Utilization in Concrete Products            2-18
  3.1     Process Flowsheet for Producing Solid Granular
          Fertilizer Material from Scrubber Waste              3-18
  3.2     TRW Process Flowsheet                                3-21
  5.1     Product Development Logic                            5-7

 1.1  Purpose and Content
      With increasing coal utilization in industrial and utility boilers,
 generation of coal ash (fly ash and bottom ash)  and flue gas  desulfuriza-
 tion  (FGD) wastes, which together comprise flue  gas cleaning  (FGC)  wastes,
 is  expected to increase  dramatically in  the next twenty (20)  years.
 Utilization will constitute a valuable element of an integrated FGC waste
 management program.  Against the background of developing regulatory
 constraints pertaining to air and water  pollution control and the  rising
 cost  of disposal,  utilization may offer  an attractive waste management
 alternative to disposal.   Furthermore, with a large anticipated mineral
 deficit in the United States in  the future,  FGC  wastes  may present  a
 potential  source of minerals in  the future.
      This  is  the fourth volume in a five-volume  report  assessing
 technology for the control of waste and  water pollution from  combustion
 sources.   This volume reports on  the status  of FGC  waste  utilization
 including  both current commercial  practice  and ongoing  resource  and
 development programs.
      The focus of  this volume on  utilization is  the evaluation  of the
 technical, economic,  regulatory,  and environmental  aspects of ongoing
 technology development and commercialization of  FGC waste utilization.
 FGD wastes considered in  this report are primarily  those  from nonrecovery
      At present, utilization  of FGC wastes in the United States is modest
 but growing.   Many  European  countries and Japan utilize a higher proportion
 of the coal ash and FGD waste produced in these countries than does the
United States.  There are, of course, inherent differences in availability
 of raw materials and marketability which account  for some of the differ-
 ences.  For some specific end-uses,  there may be some technological ad-
vantages favoring higher  levels of utilization abroad.  However, in gen-
eral,  there are significant  institutional factors which favor increased
utilization abroad  and hinder expansion of domestic utilization.

     The review and assessment has involved two separate efforts as
described below:
     (1)  Review of the data and information available as of
          December 1978 on the utilization of FGC wastes.  The
          review is based upon published reports and documents
          as well as contacts with private companies and other
          organizations engaged in FGC utilization technology
          development.  Much of the information has been drawn
          from the FGC waste utilization studies and technology
          development/demonstration programs sponsored by various
          agencies of the U.S. government including, the Federal
          Highway Administration, the Army Corps of Engineers,
          the Department of Energy (DOE), the Bureau of Mines, the
          Environmental Protection Agency (EPA)  and the Electric
          Power Research Institute (EPRI) .
     (2)  An assessment of ongoing work in  waste charac-
          terization,  identification of data and infor-
          mation gaps  relating to waste utilization, and
          development  of recommendations for potential
          initiatives  to assist in closing  these gaps.
Throughout this work,  emphasis has been placed upon waste utilization
by commercially demonstrated technologies and, where data are available,
by technologies in advanced stages of development that are potentially
capable of achieving commercialization in the United States in the near
1.2  Report Organization
     This report:
     •  Presents an overview on coal ash (.fly ash and bottom ash)
        utilization in commercial practice  at present,
     •  Assesses R&D programs for coal ash  and FGD waste
     •  Identifies some of the constraints  on FGC waste utilization,
     •  Presents an outline of related data and information gaps.

2.1  Introduction
     Coal-fired utility and industrial boilers generate two types of
coal ash—fly ash and bottom ash.  (Economizer ash and mill rejects  are
lumped into the two major categories here.)  Both constitute the non-
combustible (mineral) fraction of the coal and the unburned residuals.
Fly ash, which accounts for the majority of the ash generated,  is the
fine ash fraction carried out of the boiler in the flue gas.  Bottom
ash is that material which drops to the bottom of the boiler and is
collected either as boiler slag or dry bottom ash, depending upon the
type of boiler.
     The total amount of coal ash produced is directly a function of
the ash content of the coal fired.  Thus, the total quantity of ash
produced can range from a few percent of the weight of the coal fired
to as much as 35%.  The partitioning of ash between fly ash and bottom
ash usually depends upon the type of boiler.  Standard pulverized coal-
fired boilers typically produce 80-90% of the ash as fly ash.  In cyclone-
fired boilers, the fly ash fraction is usually less.  In some cases,
bottom ash constitutes the majority of the total ash.
     The technology of ash collection, the characteristics of the ash
produced, and projection of waste generation are discussed in Volume 3.
This volume provides a review of ash utilization, both current practices
as well as potential utilization alternatives that have been or are  being
     Fly ash  is the major source of particulate  emissions from utilities
and with increasing regulatory  stringency has required major collection
systems.  Control of particulate emissions  from  pulverized-coal-fired
steam generators  is rapidly becoming  a  significant  factor  in the  siting
and public acceptability of coal-burning power plants.  The particulate
emission limit  set by  the EPA for  large, new coal-fired boilers  is  0.043
grams/106 joules  (0.1  lb/106  Btu).   Some states  have  requirements more
restrictive  than  this.

      Fly  ash  carried  in  the  flue  gas stream can be collected in a number
 of ways to meet  the current  particulate emission control limitations as
 noted above.  Typical methods historically employed include mechanical
 collection, electrostatic precipitation, fabric filtration and wet
 scrubbing.  However,  the tightening regulatory requirements support two
 criteria  for  fly ash  collection systems:
      • The collector must be efficient in removing sub-micron size
        particulate matter.  This  criterion eliminates from con-
        sideration all mechanical  collectors and many wet scrubber
        systems  (if they are used  alone).  Mechanical collectors
        may,  however, function as  a first unit followed by a more
        efficient collector.
      • The collector must be available commercially and be proven
        in a  utility  boiler  application.  This constraint eliminates,
        for the  immediate future,  many hybrid wet scrubber systems
        and novel collectors that  are now under development.  In the
        long  run, however, it is conceivable that such advanced
        systems  may be used  at least in some instances.
      Collection  of bottom ash (or  boiler slag) does not involve systems
 outside the boiler.   The technology of bottom ash handling is discussed
 in Volume 2.
 2.2   Current  Utilization
 2.2.1  Characteristics of Coal Ash
      Detailed discussions and data on the physical and chemical charac-
 teristics of  coal ash are presented in Volume 3.  In this section, some
 of the salient characteristics affecting ash utilization are outlined.
     The chemical composition of coal ash (bottom ash, fly ash, and slag)
varies widely, in concentrations of both major and minor constituents.
Table  2.1 shows  a compilation of chemical composition of both fly ash and
bottom ash from  the firing of a wide range of different coals.   The
principal factor  affecting the variation in the composition is the vari-
ability in the mineralogy of the coal.   However,  differences in compo-
sition can exist between fly ash and bottom ash (or boiler slag)  generated

                     Table 2.1
           Range of Coal Ash Compositions
Major Constituents (wt %)
     Silica (as Si02)                        25 - 60
     Alumina (as A^O-)                      10 - 30
     Ferric Oxide (as Fe^OO                  5-40
     Lime (as CaO)                          0.5-25
     Magnesia (as MgO)                      0.2 - 8.0
     Potassium Oxide  (as K20)               0.1 - 4.0
     Sodium Oxide (as No20)                 0.1 - 4.0
     Titanium Dioxide  (as Ti02)             0.5 - 2.5
     Sulfur Trioxide  (as S03)               0.2-20
     Carbon and Volatiles                    ND - 2
Source:   [1,  2]

 from  the same coal due to differences in the degree of pulverization of
 the coal prior to firing, the type of boiler in which the coal is fired,
 and the boiler operating parameters and combustion efficiency.  Regard-
 less  of the type of ash (either fly ash or bottom ash), more than 80%
 of the total weight of the ash is usually made up of silica, alumina,
 iron  oxide, and lime.  It should be noted that the compositional break-
 down  shown in Table 2.1 reflects only the elemental breakdown of the con-
 stituents reported as their oxides and not necessarily the actual compounds
      The physical properties of fly ash vary with the type of coal fired,
 the boiler operating conditions, and the type of fly ash collector em-
 ployed.  A mechanical collector, which generally removes only the heaviest
 fly ash fraction, produces a relatively coarse material with the con-
 sistency of a fine sand.  In contrast, the ash removed in an electro-
 static precipitator is usually finer, with silt-like grading.  The range
 of specific gravities of fly ash depends upon particle size distribution
 and fly ash composition; however, specific gravities typically range from
 approximately 1.9 to 2.7.  A small portion of the fly ash (<4%) consists
 of cenospheres (hollow spheres) which have an apparent density less than
 water.  Bulk densities of fly ash, because of the variations in specific
 gravity and particle size distribution, var> greatly.  Bulk densities of
 fly ash, therefore, vary greatly, although the typical range for fly ash
 compacted at optimum bulk density would be 110-135 Ib/ft .
     An important property of coal fly ash is its pozzolanic activity.
 Pozzolanic activity in fly ash, either due to contained lime or through
 the addition of lime, causes the fly ash to aggregate and harden when moist-
 ened and compacted.  Because of the presence of pozzolanic activity in some
 fly ashes,  the engineering properties of fly ash vary greatly.  In
 general, untreated fly ash (that to which lime has not been intentionally
 added) exhibits engineering properties similar to soils of equivalent
particle size distributions.   Permeabilities of compacted fly ash samples
generally range from 5 x 10   cm/sec to 5 x 10   cm/sec.   Treatment
of pozzolanic fly ashes with lime can result in significant increases in
 compressive strength and increases in permeability (depending upon the

amount of lime, the water content, curing time, and degree of compaction).
     Bottom ash can be collected either dry or in a molten state, in
which case it is generally referred to as boiler slag.  Dry-collected
bottom ash is heavier than fly ash, with a larger particle size dis-
tribution.  Since it has a similar chemical composition to that of fly
ash, it behaves similarly, although pozzolanic activity is usually some-
what less in bottom ash.
     Boiler slag is a black glassy substance composed chiefly of angular
or rod-like particles, with a particle size distribution ranging from
fine gravel to sand.  Boiler slag is porous, although not of so great a
porosity as dry bottom ash.  It is generally less reactive in terms of
its pozzolanic properties than either dry bottom ash or fly ash.
2.2.2  Current Utilization
     Numerous uses for coal ash have been developed, both here in the
United States and abroad.  In 1977, total U.S. generation of coal ash
was 61.6 million metric tons, of which 12.7 million metric tons were
utilized* [3].  Data on utilization of coal ash for some selected years
are presented in Table 2.2  Although the three types of coal ash (fly ash,
bottom ash, and boiler slag) are interchangeable in some circumstances,
they have historically served different markets.
     Commercial utilization of coal ash is expected to increase in the
United States, continuing the trend presented in Table 2.2.  The increas-
ing reliance on coal as a utility fuel with attendant increases in ash
production may result in the percent of utilization being unchanged or
even decreasing despite efforts to promote ash utilization through in-
creased market visibility and technological development.  Preliminary
projections on generation of coal ash and FGD wastes are presented in
Volume 3.  Tightening environmental control regulations concerning disposal
*"Utilized" in this sense refers to fly ash which is used as a substitute
 for some other material.  Particularly in landfill applications  (e.g.,
 mine subsidence,  fill, etc.) the distinction between utilization and
 disposal is often unclear.  National Ash Association (NAA) statistics
 on utilization include material which is removed at no  cost  (or  credit)
 to the utility and material which  is removed from  the utility disposal
 site.  Federal Power  Commission  (FPC), on the other hand,  includes only
 that material which is sold.

                                             Table 2.2

                      Commercial Utilization of Coal Ash in the United States

                         Millions of Metric Tons (Millions of Short Tons)

                                   19663           1974            1975           1976           1977
Ash Collected
Fly Ash
Bottom Ash
Boiler Slag
Total Ash Collected (Tons
Ash Utilized
£ Fly Ash
Bottom Ash
Boiler Slag
Total Ash Utilized (Tons
Percent of Ash Utilized
% Fly Ash
% Bottom Ash
% Boiler Slag

15.5 (17.
7.4 ( 8.
x 10 )229(25.

1.3 ( 1.
1.5 ( 1.
x 10fc)2.8 ( 3.


Percent of Total Ash Utilized 12.









( 4.8)

( 3.4)
( 2.9)
( 2.4)
( 8.7)






( 4.6)

( 4.5)
( 3.5)
( 1.8)
( 9.8)




( 4.8)

( 5.7)
( 4.5)
( 2.2)




( 5.2)

( 6.3)
( 4.6)
( 3.1)

a  First year that data were taken.
Source:  [3]

of wastes and constraints on land availability in some areas,  however,
would continue to impact utilization or disposal of FGC wastes.   In
particular, as regulations under the Resource Conservation and Recovery
Act of 1976 (RCRA) become clearer, the impact of this key legislation
on utilization would become better defined.  At present, the utility
by-product utilization industry is concerned about potential negative
impact on utilization due to:
     •  Special waste category, and
     •  The effect of "use constituting disposal"
     A comparison of utilization data for 1971, 1976, and 1977 is pre-
sented in Table 2.3.  Annual total ash utilization is presented in
Table 2.4.  Total ash utilization historically has been increasing from
a low of 2.8 million metric tons in 1966 to a high of 12.7 million metric
tons in 1977.  However, it is difficult to draw conclusions about the
trends in individual end-use categories; survey coverage has been in-
creasing over the years, the end-use markets listed have been expanded,
and about 35% of total consumption is in poorly defined or unknown
     Based on the available data, the following conclusions can be reached,
Fly ash and bottom ash utilization has been increasing, from 2.8 million
metric tons in 1966 to 4.4 million metric tons in 1971, to 9.9 million
metric tons in 1977.  Utilization of boiler slag has fluctuated but has
not shown a discernible trend, staying around  2.7 million metric tons per
year.  A possible explanation  for some of  the  variation is that boiler
slag (and sometimes bottom ash) is normally sold out of stockpile; there-
fore, sales in any given year have little  relation to production.  Fill
usage, the largest single end-use market, has  been relatively constant
over the years.  Usage  in cement  and cement products has been increasing
gradually as has  the use of  slag  in blast  grit/roofing.

                                                    Table 2.3
                                                 Ash Utilization
                                Millions of Metric Tons (Millions of Short Tons)
A. Commercial Utilization
1. Mixed with raw mat-
erial before forming
cement clinker
2. Mixed with cement
clinker or mixed with
pozzolan cement (I-P)
3. Cement replacement
^ 4. Lightweight aggregate
00 5. Fill material for roads,
construction sites, etc.
6. Stabilizer for road bases
parking areas, etc.
7. Asphalt filler
8. Ice control
9. Blast grit/roofing
10. Miscellaneous
B. Ash Removed from Plant
Site (at no cost to utility
but not covered in catego-
ries listed above)
C. Ash Removed to Disposal
Areas fat company expense)



Fly Ash


Bottom Ash






















Source:  [3, 4, 5]

                                             Table 2.4
                                        Total Ash Utilized
                         Millions of Metric Tons (Millions of Short Tons)
Fly Ash
1.3 (1.4)
1.3 (1.4)
1.7 (1.9)
1.7 (1.9)
2.0 (2.2)
3.0 (3.3)
3.3 (3.6)
3.5 (3.9)
3.1 (3.4)
4.1 (4.5)
5.2 (5.7)
5.7 (6.3)
Bottom Ash
1.5 (1.7)
2.1 (2.3)
1.6 (1.8)
1.8 (2.0)
1.6 (1.8)
1.5 (1.6)
2.4 (2.6)
2.1 (2.3)
2.6 (2.9)
3.2 (3.5)
4.1 (4.5)
4.2 (4.6)
Boiler Slag
- (-)
- (-)
1.4 (1.5)
0.9 (1.0)
1.0 (1.1)
3.4 (3.7)
1.2 (1.3)
1.6 (1.8)
2.2 (2.4)
1.6 (1.8)
2.0 (2.2)
2.8 (3.1)
2.8 (3.1)
3.4 (3.7)
4.7 (5.2,)
4.4 (4.9)
4.6 (5.1)
7.9 (8.6?
6.9 (7.5;
7.2 (8.0)
7.9 (8.7)
8.9 (9.8)
11.3 (12.1',)
12.7 (14. (>)
Source:  [6]

      Important commercial markets for coal ash in the United  States  in-
 clude the manufacture of cement and concrete,  use as landfill and soil
 stabilizer,  use in blasting (abrasion)  compound,  and for ice  control.
 For the purposes of this discussion,  utilization  of coal ash  has  been
 broadly broken down into three end-use  categories:
      •  Fill material,
      t  Manufacture of  cement, concrete,  and pavements,  and
      •  Miscellaneous.
      Each of these categories  is discussed in  the following section.
 2.3  Ash Utilization as Fill Material
      The largest use of coal ash historically  has been as fill material
 in construction,  either as a replacement  for common borrow, or to stabi-
 lize poor soils in fly  ash/soil mixtures  or lime/fly ash/soil mixtures.
 Ash and ash/soil  mixtures can  be more economical  than common  borrow where
 the hauling  distance is relatively  short,  if there  is a  lack  of suitable
 borrow material near the construction site,  or if other  material  is not
 available locally for environmental reasons.
 2.3.1  Borrow Substitute
      Coal ash can offer distinct  technical  advantages as  a fill material
 because of its  low density and significant  strength  (Table 2.5).   In
 situations where  filling is necessary on  relatively weak subsoils,
 natural  materials  can produce  excessive settlement.   Traditional  materials
 are  available  for  use as  a fill  in  these  situations,  but because  of its
 low  density,  fly ash  can represent  a  more economical  solution since it
 reduces  the overburden weight.
     A significant  characteristic of  fly ash is its strength.  Well-
 compacted fly ash has been shown to exhibit strengths  comparable  to those
 for  soils normally  used  in earthfill  operations.  Tests  indicate  that
most fly ashes have shear strength parameters which would make them stable
and  strong construction materials for highway embankments and other light
load-bearing fills  [7],   In addition, many fly ashes possess self-hardening
properties in the presence of moisture,  which can result in the development
of shear strengths in excess of those encountered in many soils.   The ad-
dition of lime or cement can induce hardening in fly ashes which may not
self-harden alone.  Significant increases in shear strength parameters can

                               Table 2.5

                         Ash Utilization as Fill

Fill Supplier
a) Particle size dis—   a) Particle size distribution
   tribution important     important
b) Fly, bottom, or      b) Must be <10% water soluble
   slag                 c) Fly,  bottom,  or  slag
a) Lighter than
   common fill
b) Erosion can be
c) Dusting can be
d) Water slippage
   can be problem
a) Can be stronger than
   common fill
   Site specific
   Site specific
   Ash  fill  can be
   useful  to reduce
   load on base
   Stabilized fill can
   be stronger
    Site specific
    Site  specific
    Source:   Arthur D.  Little,  Inc.

be realized in relatively short periods of time and, if taken into con-
sideration in design,  can represent a distinct technical advantage over
other construction fill  materials.  Addition  of lime  (or alternatives
allowing the  self-hardening process in  some fly ashes  to proceed) is
called stabilization.
      Coal ash,  if  not  properly  stabilized, is subject  to freeze/thaw
failure,  erosion,.and  leaching  problems (if not properly applied).
      •  The grain-size distribution of  most fly ashes  makes  them
         similar to frost susceptible soils.   Frost  susceptibility
         is influenced  by particle size  distribution, size, min-
         eralogical composition, strength, and permeability [7] but
         cannot be  satisfactorily correlated with a  single parameter
         of strength or permeability and no specifications have been
         developed  for  this  use.  Testing is required for each indi-
         vidual  fly ash if the ash is to be used in  regions where it
         is exposed to  freezing  temperatures.
      •  Unprotected, compacted  slopes of fly  ash are subject to
         erosion  by surface  runoff or wind.  It is necessary  to pro-
         tect these surfaces by  pavement, topsoil and seeding,
         asphalt  emulsion, or stabilization with cement.
      •  Fly ash  contains water  soluble  components in the range of
         1-7% by weight [8, 9, 10].  Leaching  of these  components
         can occur  by surface runoff or  infiltration (percolation).
        Leachates  from fly ashes are of environmental  concern par-
         ticularly  if the leachate contains trace metals.  Potential
        pollution  of ground and surface water from  such leachates
        can be minimized by pavement or liners^ topsoil, vegetative
        cover, or drains.
     Fly ash, bottom ash, and boiler slag can all be utilized as borrow
material.  However, fly ash and bottom ash are used in this duty more
frequently;  boiler  slag often can be used in more valuable ways.  When
used by itself,  ash can offer an economic advantage in areas where
borrow materials are not easily available.   However, except for this

be realized in relatively short periods of time and,  if taken into con-
sideration in design, can represent a distinct technical advantage over
other construction fill materials.   Addition of lime  (or alternatives
allowing the self-hardening process in some fly ashes to proceed)  is
called stabilization.
     Coal ash, if not properly stabilized, is subject to freeze/thaw
failure, erosion, and leaching problems (if not properly applied).  The
grain-size distribution of most fly ashes makes them similar to frost
susceptible soils.  Frost susceptibility is influenced by particle size
distribution, mineralogical composition, strength,  and permeability
[7] but cannot be satisfactorily correlated with a single parameter of
strength or permeability, and no specifications have been developed for
this use.  Testing is required for each
     •  individual fly ash if the ash is to be used in
        regions where it is exposed to freezing temperatures.
     •  site where unprotected, compacted slopes of fly ash
        are  subject  to erosion by surface runoff or wind.  It
        is necessary to  protect these surfaces by pavement,
        topsoil  and  seeding, asphalt emulsion, or stabilization
        with  cement.
     •  fly  ash  containing water soluble  components  in the range
        of 1-7% by weight  [8, 9, 10].  Leaching of these com-
        ponents  can occur by surface runoff or infiltration
        (percolation), particularly if the leachate contains
        trace metals.  Leachates from fly ashes are of en-
        vironmental  concern.  Potential pollution of ground
        and  surface water  from such leachates can be mini-
        mized by pavement or liners, topsoil, vegetative
        cover, or drains.
     Fly ash, bottom ash, and boiler slag can all be utilized  as borrow
material.  However,  fly  ash and bottom ash are used in this  duty more
frequently;  boiler slag  often can be used in more valuable ways.   When
used by itself,  ash  can  offer an economic advantage  in areas where
borrow materials are not easily available.  However,  except  for this


 special  circumstance,  and  those  instances where it offers a distinct
 technical  advantage, ash is not  generally used for landfill because of
 the wide availability  of natural fill materials.
 2.3.2  Soil Stabilization
     Some  of  the problems  associated with unstabilized ash fill can be
 overcome (or  at least  lessened)  if the fly ash is used with soil in a
 stabilized mixture.  These types of mixtures have been used commercially,
 especially in England  but  have not been used extensively in the United
     Soil  stabilization generally refers to the physical and/or chemical
 methods  used  to improve natural soils or soil-aggregates for use in some
 engineering applications.  Soil stabilization is used predominantly in
 the construction of roadways, parking areas, runways, and foundations.
 Soil stabilization can eliminate the need for expensive borrow materials,
 expedite construction  by improving particularly wet or unstable subgrade,
 effect savings in pavement thicknesses by improving subgrade conditions,
 and permit the substitution in the pavement cross-section of low-cost
 materials  for conventional and less economical materials.
     The low  cost of fly ash and its excellent pozzolanic properties make
 lime/fly ash  stabilization more advantageous than lime or cement stabiliza-
 tion in  many  cases.  Depending on the soil type, lime/fly ash stabilization
 can produce greater strengths and improved durability compared with lime
 stabilization.  In locations where lime is cheaper than cement, lime/fly
 ash stabilization can  often produce material of comparable long-term
 strength and durability at a reduced cost when compared to cement
     The suitability of a particular fly ash for stabilization can be
 determined by subjecting various mixtures of the fly ash and the soil to
be stabilized to a suitable laboratory testing program.   The American
 Society  for Testing and Materials (ASTM)  Specification C 593 places two
 constraints on fly ash to be used in lime/soil mixtures.   The require-
ments,  which pertain to maximum allowable water soluble  fraction and to
gradation,  are outlined in Table 2.6.

                  Table 2.6
    ASTM C 593 Requirements Pertaining to Fly Ash
           for Use With Lime/Soil Mixtures
     Item                         Criteria %
Water Soluble Fraction              Max. 10
Fineness-amount retained
  when wet sieved:
  No. 30 (595 y) sieve              Max. 2.0
  No. 200 (74 y) sieve              Min. 30.0
Source:   [14]

      An  important  physical  indicator  of  stabilization potential  is  the
 fineness,  or specific  surface,  as  determined  in  accordance with  ASTM C
 311-68.  The finer the fly  ash  particles,  the greater the rate of poz-
 zolanic  reaction.   High carbon  content (measured as a loss-on-ignition
 in accordance with ASTM C 311-68)  tends  to inhibit the pozzolanic re-
 activity of  a fly  ash  as well as decrease  its density.  High calcium
 oxide (CaO)  is usually indicative  of  the presence of substantial amounts
 of free  lime, which not only may have a  beneficial effect on a soil's
 physical properties but which reacts  with  the siliceous and aluminous
 compounds  in the fly ash to produce cementation.
      Stabilization of  soils with fly  ash alone is still in the develop-
 mental stage.  This method is most successful when fly ash with  self-
 hardening  properties is used.   In  general,  fly ash of this type  has a high
 free  lime  content  and  low carbon content,  as  measured by loss-on-ignition.
 2.3.3 Market Characteristics and Economics
      The available  literature indicates  that,  to date, there have been
 no significant problems with lime/fly ash/soil mixtures when properly
 placed [7, 11, 12].  The Federal Highway Administration (FHWA) has  done
 extensive  research  in  this end-use application and has approved  its use
 in highway construction in a variety  of  ways  [13].
      The market size for fill material is  quite  large.  However, the use
 of coal  ash  in this application is limited.   Borrow material usually is
 available and costs about $2 to $3 per ton at  the borrow site ;
 cost  of  transportation  is added to this  base  cost.  The latter usually
 is  the limiting factor  in the cost of borrow material.  Since,  borrow
 sites usually can be developed in reasonable proximity to point  of use
 (as a fill),  the use of coal ash in this  application is  normally
 limited  to specific cases where the characteristics of the ash merit such
 consideration or where borrow material is  not  readily available.
 2.4  Ash in Cement and Concrete
     The use of coal ash in cement and concrete products is the  second
largest and one of the more visible uses for ash.  Ash can be used in a
variety of ways in this end-use.  Some options on using ash in concrete


products are presented in Figure 2.1.   It can be added to the raw mate-
rials and processed with the cement;  it can be added to the finished
cement and blended, either at the production facility, at a readymix
plant, or at the construction site; or lime can be added to coal ash to
take advantage of the inherent pozzolanic properties of the ash.  Each
use has advantages and disadvantages  some of which are summarized in Table
2.4.1  Ash in Cement  Cement Production
     Cement manufacture involves burning lime, silica, alumina, iron, and
magnesia in a kiln and pulverizing the product.  The cement reacts with
water to bond rock or sand and gravel into concrete.  The key material is
lime  (CaO); important sources include cement rock (impure limestone),
limestone, marl, and shell.  When alumina and silica are not present with
the lime in sufficient amounts, secondary raw materials are needed  to
supply the balance.  Natural sources of silica include sand and quartz;
alumina sources include shales, mud, clay, and wastes, such as  fly  ash,
slag, and red muds from bauxite processing.  Iron is sometimes  added  in
small amounts to adjust the composition of the cement mix.  Although
composition varies between different types of cement, the raw material
blend is generally 73-78% CaC03, 12-17% Si02, 2-5% A1203, 1-3%  Fe03,
1-5% MgC03, and less than 1% alkalis.  For a detailed review of cement
production processes, the reader is referred to  [15, 54].  Ash As A Cement Raw Material
      Ash can substitute for other  sources of alumina, silica, or  iron in
cement production.   Coal ash  compares  favorably  with  other raw  material
sources  for blending with limestone as  feed  to  the kiln.  A  uniform
quality  fly ash is an important  chemical  requirement  in  order  to  avoid
frequent costly and  time-consuming checks and  adjustments  of the raw
mixture  to maintain  proper kiln  feed  composition.
      The use of fly  ash as a  raw material eliminates  the mining,  crushing,
and pulverizing process that  is  required for use of clay and shale.  An
additional  advantage of  fly  ash  results from the presence of carbon which

To kiln for   i
chemical balance
and fuel content

  Raw         .
Materials	*—
                                                             To concrete plants
                                                                as extender
                           To grinding
                           as extender
                        To mixing
                        as extender
                                 Cement Producer

• -ii^ ^ ••^. '


. Concrete
' Products
                     Source:   Arthur D.  Little, Inc.
                                Figure 2.1   Coal Ash Utilization in Concrete Products

                                                    Table 2.7

                                    'Ash Utilization in Cement and Concrete
     I. Cement
    II. Cement
     III. Cement
IV. Readymix  Supplier,
   Concrete  User
 To User
a) High carbon okay
b) Particle size
a) Reduces raw
   material consump-
 Slight—some second-
 ary raw material
a) Low carbon required
b) Particle size unim-
c) Fly, bottom, or slag
a) Reduces kiln energy
b) Reduces raw mater-
 Portion of kiln
                           %  of  cement
                           manufacturing  cost
a) Low carbon required
b) Particle size impor-
c) Must meet ASTM cement
d) Fly ash only

a) Reduces kiln energy
b) Reduces raw material
c) Reduces grinding

"Portion of kiln and
 grinding energy
 a) Low  carbon  required
 b) Must meet end-use
 c) Particle size importan
 d) Fly ash only

    Reduces portland
    cement consumption
  Approximately 45 kg
  (100 Ib) of cement
  per m  concrete
                                                     a) Improved workability
                                                     b) Decreased heat of hydration
                                                     c) Improved surface finish
                                                     d) Increased long-term strength
                                                     e) Increased resistance to sulfate
                              %  of  cement
                              manufacturing  cost
                            % of concrete
                            selling price
 Source:   Arthur D.  Little,  Inc.

 can supply fuel  for firing in the kiln,  and,  since it  contains no water
 or crystallization which  must be driven  off as  do  clay and  shale, the
 heating requirements are  reduced.   However, apart  from the  potential
 economic advantage, coal  ash has no technical advantage over  other  raw
 materials in this  use.  Ash As  A  Cement  Additive
      Fly ash can be mixed with finished  cement  or  interground with  cement
 clinker.  Fly ash  added at either of these  two  points  in the  manufacturing
 process remains  as fly  ash and is thoroughly  blended into the portland
 cement.  The resulting  material has essentially the same advantages in
 use as  those obtained by  adding fly ash  to  concrete mix (see-  Section
      Cement  with fly ash  additive must be marketed as  a separate product
 and as  such,  separate handling,  storage, stocking,  etc.,  are  involved.
 Unless  the volume  of such fly ash cement is adequate,  this  utilization
 of fly  ash would have economic demerits.  Also,  the blending  of the two
 materials  requires  careful control to ensure  uniformity of  the cement.
      It should be  noted that  the product specifications for the use of
 ash in  concrete  are quite different from that for  the  use of  ash in
 cement.   It  is possible to use different clinkers  for  these two different
 2.4.2   Ash in  Concrete
     The ingredients  used to  produce conventional  portland  cement concrete
 are portland cement, water, gravel or stone, sand,  and  a  variety of chemi-
 cals to  either increase the air  content of the  concrete or  reduce the
 amount of water  required  for  the proportioning  of  the concrete mixture,
 or modify the  settling characteristics of the cement.   The  amounts of
 each of  the ingredients affect the  concrete properties.   ASTM Specifica-
 tion C 618-77  [19]  for  the use of  fly ash as a  pozzolan in  concrete manu-
 facture  classifies  fly ash as  derived from: 1)  anthracite or bituminous coal or
 2)  lignite or  subbituminous coal.   The specifications cover combined per-
 centages of silica  (Si02), alumina  (A120,), and ferric  oxide  (Fe-O-), maxi-
mum SO-, maximum moisture  content, maximum loss-on-ignition, maximum
magnesium oxide  (MgO) content, maximum sodium oxide (Na^O)  content, required
particle fineness,  pozzolanic activity index,  soundness, and uniformity.


     The use of fly ash as a raw material  in the production  of  concrete
serves two primary purposes:
     •  To supplement or replace fine aggregate and cement,
     •  To improve properties of the concrete.
     Coal ash is useful as aggregate replacement because of  its pozzolanic
nature.  A pozzolan is a siliceous or alumino-siliceous material which
is not cementitious in itself but which,  in finely divided form and in  the
presence of moisture, reacts with alkali  and alkaline earth  products to
produce cementitious products [16].  The pozzolanic reaction  between fly
ash and lime (cements) results in a material of substantial  strength.
     Among the improvements attributed to fly ash/concrete are improved
pumpability, higher compressive strength (and long-term strength), better
workability and finishability, and higher resistance to sulfates and
alkali/aggregate reaction: use of fly ash in concrete decreases the heat
of hydration, drying shrinkage, particle segregation, bleeding, permea-
bility, and leaching  [16, 17, 18].
Sulfate Resistance
     There is strong evidence that blended cements tend to show higher
resistance to sulfate attack than do portland cements  [20].   Sulfate
attack on concrete can lead to expansion of the cement with resultant
catastrophic cracking/crumbling of the concrete.  Concrete can be exposed
to sulfate conditions from  drainage water, groundwater, and seawater.
While  the actual mechanism  is not fully understood, attack may result
from reaction of soluble  sulfates (e.g., from groundwater) with  the  cal-
cium hydroxide and hydrated alumina  in the cement  to  form gypsum and
highly hydrated calcium aluminosulfate compounds having large  specific
volumes.  Susceptibility  to these reactions appears  to be reduced  in
blended  cements, possibly because of reactions between the  calcium hy-
droxide  and  fly ash  [17,  18,  20].

 Alkali/Aggregate Reaction
      The reaction between alkalis present in cement  and certain types  of
 stone aggregate used in concrete sometimes leads  to  the formation of
 highly hydrated alkali silicates [20].  The formation of these com-
 pounds can result in disruptive expansion of concrete.   The  mechanisms
 and kinetics  of these reactions are  not well understood and, depending
 on the nature of the aggregate  and the exposure conditions,  expansion
 may manifest  itself  at an early age  or only after several years.   Addi-
 tions of fly  ash to  a cement  or concrete  can reduce  the expansion due  to
 this reaction but low alkali  portland  cements are more  commonly used.
 Improved Workability
      Fly ash  improves the workability  of  concrete by making  it  more
 plastic,  decreasing  particle  segregation,  and decreasing bleeding [16].
 Normally,  more water is  required for making concrete when pozzolans have
 been added to the mix.   Fly ash differs from most pozzolans  in  this re-
 spect.   Concrete containing low-carbon (2%)  fly ash generally requires
 less water than portland cement concrete  [21].  However,  work by  ASTM
 Section C09.03.08 suggests that both carbon content and fineness  influence
 the water  requirements  [22]; high  carbon  content  does not raise water  re-
 quirements, per se.   Concretes  with  fly ashes  containing an  excess  of
 about  2% carbon require  proportionately more water than does standard
Heat of Hydration
     Concretes  containing  fly ash have a lower heat of hydration than
portland cement  concrete.  Consequently,  they do not get  as warm as
equal amounts of portland  cement concrete.   For this reason, fly ash is
used in much of  the mass concrete construction in  dams and spillways
 [18, 23].  Specifications exist for this use, and  fly ash is proportioned
according  to the heat of hydration desired.
     When ash is substituted for portland cement in concrete, the two
products have different rates of strength gain and differences in the
effects of curing temperature on strength gain may be substantial.  The

addition of small amounts (5-10%) of fly ash to Type 1 portland cement
may improve the early strength of the concrete.  Concrete containing
greater amounts of fly ash may show less rapid gains in strength but
higher ultimate strengths [20],  Mixes in which fly ash is substituted
for cement on a one-for-one basis (to conform to water-cement ratio
specifications) usually produce concrete that is weaker than no-ash
concretes at ages up to 28 days.*  Properly proportioned fly ash con-
crete mixes usually will produce concretes with 28-day strengths com-
parable to concrete without fly ash.
Freeze/Thaw Durability
     In much of the country, concrete is subject to damage from repeated
freezing/thawing cycles.  When fly ash concrete is tested for freeze/
thaw durability, inferior resistance has been observed, probably because
the test is begun after a short curing period (i.e., less than 28 days)
and does not allow for the lower rate of strength development of ash
concrete.  Freeze/thaw studies, when initiated after longer curing periods,
have indicated that fly ash concrete develop strengths equivalent or
superior to those of portland cement concrete and develop superior re-
sistance to freezing and thawing [20].  Another factor involved in freeze/
thaw durability is the air content.  When fly ash concrete with an air
content equal to that of conventional portland cement concrete is tested,
it appears to have good freeze/thaw durability [24].
     Adequate quality control of the fly ash and proper system design are
essential for effective utilization of ash in concrete.  Lack of proper
attention to quality control has been the cause of  some problems.
     The properties that make ash utilization in  concrete desirable  can
also make handling difficult; easy  flowability may  cause problems in
feeding  and weighing the fly ash, and the fineness  of  fly ash  can cause
air pollution  and other problems.   Control of  the fineness  and other
properties of  the fly ash can pose  problems.  Uniformity of performance
*Much readymixed concrete is required to meet 28-day minimum strength

 of a fly ash/cement depends on both  the cement  and  the  fineness and
 composition of the fly ash.  Determination of the proportions  for  fly
 ash concrete is system-specific due  to  the variation  in the physical and
 chemical properties of different ash materials.
      Much of the concrete  placed in  the United  States contains chemical
 admixtures which are used  to regulate set  times, entrain air or reduce
 water requirements:[20].   Set regulation is used to extend the time
 available for  finishing; air entrainment (production  of small  air  bubbles
 in the cement)  is  used to  improve resistance to freeze/thaw damage;
 decreased water requirements  lead to a  reduction in the porosity of the.
 concrete which  increases strength and chemical  resistance.  Cements con-
 taining fly ash contain variable amounts of carbon from incomplete com-
 bustion of the  coal.   Carbon  adsorbs chemical admixtures  and tends to
 diminish their  effectiveness  as  well as  making  them difficult  to predict.
 2.4.3  Lime/Fly Ash/Aggregate  Basic  Courses
      Lime/fly ash/aggregate (LFA)  mixtures  are blends of mineral aggregate,
 lime,  fly ash and water.  When combined  in  proper proportions and  com-
 pacted to  a high relative density with reasonable curing conditions, they
 gradually harden to produce high quality paving materials.  A wearing
 surface  is  applied  to  the base course to protect the  material  from the
 abrasive effects of traffic,  from weathering, and from water infiltration.
      In  addition to lime, stabilization  (that is, pozzolanic reaction)
 of  fly ash  can be produced  in  a  number of ways.  In lime  stabilization,
 lime  is  added directly  to the  fly  ash, moisture is introduced, and the
 mixture  is  then compacted to  facilitate  the pozzolanic  reaction.    In
 cement stabilization, cement  is  added to the fly ash  instead of lime;
 the cement  hardens as well  as  releasing  certain amounts of lime which
 react with  the fly ash  in a pozzolanic manner.   Certain types of fly ash
 also contain substantial quantities of free lime which can harden  fly
 ash without the external addition  of lime or cement.  This third process
 is known as self-hardening of  the  fly ash.
     LFA mixtures have been used extensively abroad.  To a lesser  extent,
LFA mixtures have been used in the United States.   Approximately 500,000

to 1,000,000 tons per year are typical quantities  placed for  the  last
10 or more years of lUCS's "Poz-0-Pac" roadbase, and considerable quan-
tities of similar materials have been placed by others  [25].   Against
the background of total roadbase construction,  these are not  large;
however, the potential use is significant.
2.4.A  Ash As Aggregate Substitute
     Aggregates are the largest single mined commodity  in the United
States.  However, the supply is decreasing  and in  certain areas of the
country (particularly some industrial or metropolitan areas)  demand for
natural mineral aggregates for construction purposes exceeds  locally
available supplies.  With increasing energy costs  and consequent  cost
increase for transportation, there is an economic  incentive to find
suitable replacement aggregates in the local area  rather than transport
them over large distances.  Utilization of  fly ash as a lightweight ag-
gregate is feasible, particularly in many parts of the  country where there
are shortages and coal-fired generating plants in  the same area.   There
are few significant technical limitations to the use of fly ash for light-
weight aggrgate.
     Bottom ash has also found use as a lightweight aggregate in con-
struction and as aggregate in roadbase construction.  Extensive testing
has been done on the physical and structural characteristics of bottom
ash and boiler slag for various purposes in road construction  [26].
     The increasing acceptance of coal ash as aggregate materials and the
development of appropriate specification for its use may provide an
outlet in those areas of the country where large amounts of coal-fired
wastes will be generated.
2.4.5  Market Characteristics and Economics
     While a large body of data has been accumulated on specific uses of
fly ash in cement, concrete, and in roadbase construction, generic eco-
nomic  data are not available.  Economics of ash utilization in this cate-
gory are very site- and system-specific; a  case-by-case evaluation is

      The profitability  of  using  fly  ash  depends upon where in the cement
 production process  it is substituted,  its  quality, its cost relative to
 cement,  the transportation distance  involved, the value accrued from any
 technical advantages, e.g., less pouring time and less finishing time
 than  for standard concrete, and  the  expense  for additional equipment to
 handle fly ash at the cement  plant.
      Ash can be substituted as a raw material in the cement kiln feed,
 as  an additive with clinker in the grinder feed, as an additive with
 cement at a mixing plant (sold as cement), or as an additive in concrete
 at  a  readymix plant.  The  profitability  of using ash at the cement pro-
 ducer is probably minimal  except in  special  cases.  As a raw material
 additive,  ash imparts few  technical  advantages and has no significant
 cost  advantages except  in  cases where other  materials are not available.
 As  an additive to clinker  for grinder feed,  ash would save a propor-
 tional fraction of the  kiln energy.  Technical advantages may result from
 ash use  in this application,  however the cost savings would probably not
 offset the increased capital  expenditure for ash-handling equipment.
      Ash utilization as an additive  to cement or concrete can poten-
 tially result in significant  cost advantages.  Previous work has in-
 dicated  that the cost advantage to using ash is related to the trans-
 portation  distance for a given set of conditions (e.g., plant size,
 cement cost, transportation cost).   This impact will be very site-
 specific and vary from location to location.  For example, in the west
where there is a lack of natural pozzolans,  ash could be transported
 great distances and still  be  an economically usable pozzolan.  Conversely,
 in  the east, transportation costs can offset any cost advantages quite
 rapidly.   Work just being  completed  (see R&D-DOE) indicates that ash
 utilization usually has an economic  advantage but that institutional
 factors  have hindered further utilization  of ash.  The latter are dis-
 cussed later in Section 5  of  this volume.
     The profitable marketing of ash in cement/concrete cannot be based
 on  cost  considerations alone.  The marketplace is significantly influenced
 by a variety of non-economic  factors which can easily outweigh any per-
 ceived cost advantages.


     In order to use fly ash in cement economically,  it  may be  necessary
for the cement plant to be located near a coal-burning utility.   For
example, clay or shale is stripped to obtain underlying  limestone for a
cement plant.  That clay or shale will often be used  in  the raw batch
even if fly ash is available nearby.   The fineness  and flow characteris-
tics of fly ash require handling, transportation, and dust collection
equipment different from those for the stripped clay  or  shale.   If fly
ash is to be used, considerable capital investment  in cement plant de-
sign and equipment must be committed to a fly ash  raw material source.
Guarantees as to quantity and quality of fly ash that will be available
for future use will be essential for a cement manufacturer to commit
himself to fly ash.  Quality control and long-term guarantees are key
requirements to increase utilization of ash in any  premium use.
2.5  Ash in Miscellaneous Uses
     Coal ash has been used in a variety of other applications in the
United States, but these are generally on a smaller scale than the uses
described earlier.  However, three specialized uses are important and
presented in Table 2.8.
     A significant amount of bottom ash  (0.92 M  tons in 1977) and boiler
slag (0.36 M  tons) are used for ice  control on winter roads.  Such mate-
rials are often provided at no cost or at nominal cost to the user by  the
utilities.  Little generic  information is available on this, but  it would
seem to be inherently site-specific.  Broadly, there are some environmental
advantages in using ash  in  preference to salt  in this use in addition  to
technical and economic benefits.   (See Table 2.8.)
     Almost half  (1.35 K tons in  1977)  of  all boiler slag  is  consumed as
blast  grit or roofing  granules.  Again,  it  would appear to  be  a  site-
specific  use  depending upon the  availability of alternative materials.
     A potential  end-use for fly ash  which  could consume  significant
quantities of ash in  the future,  is  in production  and/or  fixation/
stabilization of  FGD waste. The amount  and type of  ash in FGD waste can
influence both  the scrubber operation and  the disposal  operation.  In
certain instances, especially  with high  CaO western  coals,  the alkalinity

                               Table 2.8

                   Ash Utilization in Miscellaneous Uses
Blast Grit/


Highway Department
a) Only boiler slag

b) Size restriction
a) Bottom ash or boiler
   Low solubility
   Equal to cost
   Equal to cost
  Source:   Arthur D.  Little,  Inc.

in the ash can be substituted for some or all  of the scrubber  reagent.
Fly ash also can aid in disposal because dewaterability is  improved,  the
fly ash acts as a pozzolan to help "fix" the waste (especially when there
is free lime), and fly ash oxidizes calcium sulfite to sulfate.  Proc-
esses are currently being commercially marketed for the fixation of FGD
waste which utilize fly ash; these are discussed in Volumes 3  and 5.
Fixation of FGD wastes by fly ash and lime usually results  in  a soil-like
material subj ect to less leaching due to lower permeability and occupying
less volume due to increase in final bulk density compared to  separate
disposal of these materials.
2.6  Ash As A Mineral Resource
     In addition to the uses discussed above,  a variety of potential uses
for coal ash have been proposed  [6, 11, 16, 71].  These have included:
     •  Mineral recovery (alumina, iron, magnetite),
     •  Mineral wool,
     •  Mineral aggregate,  and
     •  Filler  (for plastics, rubber, etc.) and many others.
     Some of  these uses are currently being commercialized in  the United
States; others have been or are being used abroad,  and some are still
under development.  However, these applications require technical break-
throughs or  fundamental institutional or  economic  changes.  An example
of a  future  potential  use  requiring  technological  breakthrough for eco-
nomic competitiveness  is mineral recovery from fly ash.  Some  research
has been done and methods  for extracting alumina,  magnetite or other min-
 erals do  exist.   However,  at present,  these processes are  either not
 capable of competing with more  established processes or the market does not
 exist because of a readily available alternate supply of  the  mineral.
      To provide some perspective on the potential mineral  recovery poten-
 tial from coal ash,  it may be noted that a 2,600 MW power plant typically
 produces 1.1 million tons of coal ash annually containing silicon oxide,
 aluminum oxide, iron oxide, and a host of other raw materials [27].  It
 is reported that by the year 2000 the minerals deficit in the United States
 will exceed the energy deficit; the trade deficit in minerals may be
 as high as $100 billion within 25 years  [28].  Currently, United States


 requirements  for 22 of  the  74 non-energy essential minerals are
 met  principally from  foreign sources.   Hence, over the long-term, the use
 of coal  ash as a mineral  resource may  be a  possibility.  For example, ex-
 traction of the aluminum  content  of  the fly ash  can  completely offset
 bauxite  imports currently [29].   Zinc  concentrations in  the fly ash are
 equivalent  to zinc concentrations in commercial  ores.  It appears that
 continuation  of R&D on  such uses  is  essential in the light of a potential
 mineral  crisis in the future.
 2.7   R&D Programs - Ash Utilization
      Current  R&D projects in coal ash  utilization are being carried on
 both in  further refinement/understanding of existing uses, and develop-
 ment of  new uses.
      The manner in which  ash is  collected can affect its potential
 for  utilization.  Ash can be collected either in dry or  wet systems.  In
 dry  collection systems, fly ash is collected in  electrostatic precipita-
 tors and stored in large  silos.   Bottom ash is collected from the boilers
 in sluice ducts, dewatered,  and is stored separately.  In wet systems,
 fly  ash  and bottom ash  are  slurried  (either separately or in a common
 pipe) and pumped to holding ponds.  Water is recycled from the ponds back
 into the  system when  possible.
      From a utilization point of  view,  dry  ash or ash slightly wetted
 (for dust control) is more  advantageous in  most  situations than wet ash.
 Principal advantages  are:
      •  The ash does not  need to  be dried for certain uses,
        saving energy costs.
      •   If  the ash contains  CaO and is wet,  it may harden
         upon  standing.  Dry ash is easier to recover from stockpile.
      •  Dry ash may be more uniform than wet ash if leaching,
        agglomeration, and  cementation have occurred in  the latter.
      Currently,  the split between wet and dry collection is fairly even
 [3,  24]  although there has been a shift toward dry collection for a variety
of reasons.

     The U.S.  Army Corps of Engineers,  the National  Bureau  of  Standards
(NBS),  the Department of Energy,  and the Bureau of Reclamation all  are
carrying on programs on the influence of coal ash on concrete/cement
properties.  A particularly active area at present is research in  the
increased sulfate resistance developed by fly ash concrete.  Strength
gain, alkali-aggregate reaction,  and dimensional stability  also are being
studied.  In addition, numerous small, specific studies  are being  carried
on both by industry and by universities on various  fly ash  properties in
specific situations.  The Department of Energy is just completing  an
evaluation of the use of ash as a cement replacement in concrete.   This
work focused on the factors affecting increased utilization of ash.  DOE
is also funding research at Iowa State University on recovery of metal
values from fly ash.  Programs on development of new uses are being carried
on by the TVA and the Coal Research Bureau (CRB) at  West Virginia Univer-
sity (WVU).  The TVA currently has a pilot scale development program under-
way using mineral wool technology developed at WVU.   Additionally, the
TVA, by itself and with outside contractors and sponsors, is looking at
extraction of alumina, magnetite, iron, etc.  The CRB, in addition to
working with TVA on mineral wool, has developed technology for the com-
mercial production of brick from fly ash and bottom  ash.  The Federal
Highway Administration  (FHWA) is completing an extensive program
on the use of coal ash  in road construction.  Their  results favor use and
the  Implementation Division is funding projects to demonstrate developed
construction technology  [12].  The NBS is not currently looking at new
areas for ash utilization but anticipates reactivating a currently dor-
mant program in this  area  [30].
     Specific R&D programs  in these  areas are summarized in Table  2.9
and  detailed in the  following section.   In addition,  numerous  small  R&D
projects  are being  carried  on in  a variety of organizations.
2.7.1   U.S. Army  Corps  of  Engineers
     The  Corps of Engineers has been using pozzolans (primarily fly  ash)
for  over  20 years  [31].   Generally,  25-35% by weight fly ash  is added
to  concrete  (about  45 kg per nr  or  100  Ib/m^)  because it reduces  the heat
of hydration of  the concrete  during setting.

                                                       Table 2.9
     Primary Sponsor
 Current  Research  in  Fly  Ash  Utilization

	Project Focus/Status
     U.S.  Army Corps of Engineers
     Bureau of Reclamation
Coal Research Bureau
West Virginia University
     Dept.  of Energy  -  Gordian Associates
     Dept. of Energy - Iowa State University
          Effect of fly ash on properties of concrete.
          Laboratory work on sulfate resistance, strength,
          alkali-silicate reaction.  Much of the research
          work has been completed, reports will be
          prepared within next 1-2 years.

          Effect of fly ash on properties of concrete.
          Laboratory work on effect of ash on sulfate

          Development of new and expanded uses for ash.
          Laboratory, pilot scale, and demonstration work
          in a variety of end-uses.  Extensive work has
          been/is being done on a process to produce
          bricks from fly ahd bottom ash and a process to
          produce mineral wool from bottom ash.

          Overview of use of fly ash for replacement
          of cement in concrete.  Considered supply
          constraints, economics, technical issues,
          institutional factors.
                          (Draft Report - December  1978)

          Recovery of metals from fly ash. (ongoing)
           that this summary specifically excludes research on the use of ash as at soil amendment.

      Source:   Arthur D.  Little,  Inc.

                                                        Table 2.9 (Continued)

                                         Current Research in Fly Ash Utilization
      Primary Sponsor
Project Focus/Status
      Federal Highway Administration
     National  Bureau  of  Standards
                     Use of sulfate waste (including FGD sludge) in
                     road construction.  Laboratory investigations
                     of lime-fly astv-sulfate waste mixtures for
                     strength-compositional relationship.  Engineering
                     investigation of most promising mixtures.
                                   (Completed - 1975)

                     Use of coal ash as a highway construction material.
                     Assessment of available information, some
                     laboratory work.  Implementation.  Division has
                     sponsored demonstration work.
                          (Most research is complete-published 1976)

                     Effects of ash on engineering properties of concrete.
                     Laboratory work on sulfate resistance, alkali-
                     aggregate reaction.   Sets  guidelines for use in
                     specifications by other agency.

                     Waste Utilization Program  currently inactive.
                     Anticipate reactivation within 1-2 years.
                               (Currently inactive)

                     Production of mineral wool from boiler slag.  Using
                     Coal  Research Bureau, W. Va.  Univ.  process,  pilot
                     plant under construction (about  1 tph) will be
                     started up about  December  1979.
                                                  12,  34
                                                                                                            7,  12
                                                 36,  37
                     Several other  smaller projects  on  alumina  extraction,
                     mineral extraction, cenospheres, magnetite.  All
                     projects in preliminary economics  -  technical feasibility -
                     process development phase.
     Source:  Arthur D. Little, Inc.

      The Corps of Engineers reports good results with the material poured
 to date, but control of fly ash quality is important.  They suggest a
 specification of 6% maximum loss-on-ignition versus the 12% in ASTM
 specifications; the higher carbon content causes problems with excess
 air entraining agent to obtain desired air content.  Tie-form failures
 have also occurred due to the slow early strength rise of the fly ash
 concrete [31].
      The Corps of Engineers is currently conducting a multi-faceted
 program on fly ash and its use in concrete at its Waterways Experiment
 Station [18].  One area of study is a general analysis of the effect of
 fly ash on concrete.  They are using various kinds of subbituminous and
 lignite fly ashes blended with Type I and Type II cements; specimens are
 analyzed for strength.  They also have looked at the physical and chemi-
 cal tests made in acceptance of the cement and ash in these various uses
 and their appropriateness.
      A second area of interest to the Corps is sulfate resistance of
 concrete.   The Corps generally prefers to use Type II* cement in their
 work because of the lower heat of hydration,  the increased sulfate resis-
 tance and the increased long-term strength.  Type I-P** cement (inter-
 blended with fly ash)  is being evaluated as a potential substitute for
 Type II in times of shortages.  In this laboratory program, fly ash has
 been interblended and interground in a Type I-P** cement (22% maximum)
 and the effects on sulfate resistance are being analyzed.   Indications
 are that the ash increases the sulfate resistance sufficiently to make
 Type I  cement equivalent to Type  II*  The Corps of Engineers  is also
 reviewing whether the  new type of cement manufacturing equipment will
 significantly change cement characteristics.
 Type  II  cement  is portland  cement  for  use  in  general  concrete  construc-
  tion  exposed to moderate sulfate action or where  moderate sulfate action
  or where moderate heat  of hydration is required.
 Type  I cement is portland cement for use in general concrete construc-
  tion.  Type  I-P is  the  same as  Type I  with the  addition of a pozzolan.

     A third research topic has been the minimization of alkali-silicate
reaction.  Laboratory work has been done with subbituminous  and  lignite
fly ash, as well as other pozzolans.  Test samples were made with  high
alkali cement and the ability of the ashes to quench or minimize the
reaction were measured.
     Much of the experimental work in all three of these program areas
has been completed.  Reports will be prepared within the next  year or
two [18].  Preliminary conclusions are that fly ash increases  sulfate
resistance, decreases susceptibility to alkali-aggregate reaction, and
increases resistance to sulfate expansion.  The Corps also has obtained
substantive data on the fly ash cement chemistry and its behavior.  Over
the next five years, much of the research will be aimed at maintenance
and rehabilitation on existing structures.  However, some work,  on a
smaller scale, may continue on alkali-silica reaction and the mechanisms
2.7.2  Bureau of Reclamation
     The Bureau of Reclamation uses fly ash extensively as a pozzolan
in concrete, primarily in massive structures, dams, canals, etc.  Use
is predicated on technical reasons; fly ash decreases the heat of
hydration in setting cement, fly ash increases the ultimate strength
of the cement, and, fly ash is the cheapest pozzolan readily
     The Bureau has an ongoing research program providing support to
fly ash use  [23].  The primary focus of this program  is currently on the
sulfate resistance of fly ash concrete when using  "soft" coal ash  (i.e.,
sub-bituminous, lignite).  Their  laboratory program  is  concentrating
on what causes sulfate resistance in concrete and  why some  ashes  give
good resistance and others not.   They  also have been  looking  to a lesser
degree of heat of hydration reduction by fly ash, and the freeze/thaw
durability of fly ash concretes.
2.7.3   CRB-WVU
     The Coal Research Bureau of West Virginia University has been
studying new and expanded uses for  ash.  Although  many  uses have  been

 studied [32,  38,  39]  including use  as  soil  amendment,  in concrete, and
 for trace metal recovery,  major emphasis  has been placed in two areas:
 a patented process for producing structural materials  from fly ash
 [40,  41,  42,  43,  44]  and a process  being  developed with the TVA for the
 production of mineral wool from boiler slag (see TVA for discussion).
      The  process  for  structural materials was developed to produce high-
 quality,  dry-pressed,  fly  ash-based brick utilizing most fly ashes;
 physical  and  chemical property variations in the fly ash were not found
 to cause  serious  problems.  Bench-scale studies and pilot plant opera-
tions were conducted  and process economics  were analyzed.  A raw mate- -
 rials mix consisting  of  72.0%  fly ash,  25.2% slag, and 2.8% sodium sili-
 cate  (as  a bonding agent)  on a dry  basis  was used.  These brick were
 much  lighter  than clay brick and met or surpassed all ASTM standards for
 clay  brick.
      In subsequent work, the sand was  replaced with bottom ash and slag
 significantly improving  product quality.  With improved mixing tech-
 niques, a product containing over 97%  coal-derived ash has been produced.
      A pilot  plant was designed and constructed at Morgantown, West
 Virginia,  to  produce  fly ash-based  brick  in sufficiently large quantities
 to  permit projection  of  technical factors and economic data to a com-
 mercial scale.  Raw materials  used  were fly ash, bottom ash, and boiler
 slag  obtained from eastern, central, and  western coal areas.  The work
 has demonstrated  that  most, if not  all, types of ash produced from
American  coals  can be  made  into construction products meeting or exceeding
ASTM  standards  for superior-grade face brick.
      The pilot  plant was designed with a  productive capacity of up to
3,000  green (unfired) brick per hour and  1,000 fired brick per day and
was successfully operated for  several years.  It was demonstrated con-
clusively that  the process, with slight modifications,  could be applied
 to virtually  any  fly ash and that a wide variety of structural products
 (brick, block,  tile, etc.)  could be produced.  Economics of the process
were shown to be highly attractive with a high probability of commercial
success.  Full-scale design information was developed.

     Fly ash brick differ from their clay  counterparts  in  three
significant ways:
     •  Being lighter,  they cost less to transport,  have
        and improved market potential for  high-rise  con-
        struction, and  are easier for masons  to  handle.
     •  Fly ash structural forms are dimensionally pre-
        cise and are therefore replaceable without change
        of shape or color.
     •  Fly ash structural forms can be expanded in  size
        and shape without warpage,  size variation or
        surface defects.
     Based upon a detailed economic analysis, the WVU-OCR investigation
concluded that fly ash-based brick and other structural materials have
significant potential for economic success.   This analysis (1973 costs,
M&S-345) indicated that total production costs for standard 8-inch facing
brick would be $30 to $40 per 1,000 standard brick equivalents [45].  In
some cases, costs as low as $24 to $30 per 1,000 may be attainable de-
pending on local market conditions, labor factors, etc.  These figures
represent total cost FOB the plant including equipment write-off and all
overhead costs, such as general and administrative expense.
     An attempt to commercialize this process has not been successful
to date.
2.7.4  DOE - Gordian Associates
     Gordian Associates has completed a study for the Department of
Energy looking at  the use of fly ash and  granulated blast furnace slag
as a cement replacement  in concrete  [33].  This overview study was con-
cerned with supply considerations, availability,  cost structure of the
market, other  economic considerations, technical  considerations, and
institutional  issues.  The study concluded that  although  technical con-
cerns may  in many cases  be valid  (e.g., composition variations,  carbon
content)  they  can be handled  through proper  engineering and  still leave
a positive cost  advantage to  the use of ash.  Rather,  institutional
factors have  created a bias against  the use  of  ash  in  concrete  and  thus

hinder  its use.  If this bias can be corrected through a sufficiently
large commercialization program, fly ash use will increase.  This report
is currently  (January 1979) in a draft form and should be released for
publication soon.
2.7.5   Federal Highway Administration
     The FHWA initiated a comprehensive research program in waste uti-
lization in 1972 and focused on utilization of a variety of wastes in
highway construction.  Research has been done in two major areas:
Category 4C - Use of Waste as Material for Highways; and Category 4D -
Remedial Treatment of Soil Materials for Earth Structures and Foundations
[46, 47].  Much of this work concerning fly ash and FGD waste has been
completed and has been, or is being, reported in the literature.
     Results of the major research work on ash utilization are summarized
in a report on the use of fly ash in highway construction [7].  The tech-
nical information necessary for the use of ash in highway construction
has been developed.  These uses include:
     •  Base and sub-base courses,
     •  Subgrade modifications,
     •  Embankments,
     •  Structural backfill, and
     •  Grouting.
     The FHWA has not put a major emphasis in its research program on
the use of ash in concrete* although some specific studies have been
done in this area [12].
     Information has been assembled on production, handling,  and physical
and chemical properties of fly ash which influences its use in highway
applications.   The FHWA has considered various factors which affect uti-
lization, case histories,  design criteria, testing procedures, and con-
struction procedures.   The pozzolanic properties of fly ash make it a
good quality base or sub-base course material when used with  lime or
cement to stabilize aggregates and soils,  or when used alone with lime
or cement.   Strength and durability criteria have been established for
this application, and appropriate testing procedures have been developed.


Construction procedures utilize standard equipment and techniques for central
mixing or mix in-place operations.   Fly ash is used as embankment or struc-
tural backfill material over weak or compressible soils because of  the
reduced surcharge that results from its light unit weight.   In addition,
it has low compressibility and good stability characteristics, if placed
properly.   Economies can be realized in the design of  retaining structures
backfilled with lightweight fly ash.  Fly ash improves the flow properties
and strength characteristics of grouts.  It can be used alone for void-filling
or used in conjunction with portland cement, lime, clay, sand, and gravel to
develop grouts for applications related to highway structures.
     Potential application of FGD waste in road construction has been
discussed in a report on sulfate waste use [34],  Mixtures of fly  ash,
lime, and sulfate waste were evaluated based on fly ash source, form of
calcium sulfate, lime type, mixture consistency, curing temperature, ad-
mixtures, and impurities.  Studies of compound development in selected
mixtures were performed.  In the second phase of the study, strength-
compositional relationships for samples prepared with actual waste
sulfates were obtained.  Results of this phase were used for the selec-
tion of mixtures for engineering evaluation.  These mixtures were
examined for compressive and tensile strength, freeze/thaw resistance,
wet/dry stability, California Bearing Ratio, permeability, and leachability.
     While the mixtures were found to have acceptable strength properties,
high California Bearing Ratio and low permeability, the durability prop- x
erties were judged to be marginal.  This requires that care and proper
precautions be taken in using these mixtures for construction purposes.
Laboratory test procedures  for mix design and typical specifications which
might be used were also suggested.
     A third area of research was  concerned with use of sulfate waste as
a soil conditioner  [48, 49].  This work  is discussed elsewhere.
2.7.6  National Bureau of  Standards
     The NBS has been  doing research  on  fly  ash  for several  years.   Its
resource  recovery program  has been dormant  for  several  years  but  is now
being  revitalized and  the  Bureau  plans  to  look  at new uses for coal ash
and FGD waste  [30].


      Most of the NBS work is aimed at establishing tests which  can be
 referenced by other organizations in establishing  standards and speci-
 fications for use.
      Most of the past and current research  has  been focused on  the effects
 of bituminous coal  ash addition on the durability  of concrete  [35],
 NBS is just beginning work on lignite ashes;  current plans are  to look
 at the same areas as have been studied with bituminous.  Three  specific
 areas have been looked at and test data are being  developed to  assess
 the effect of fly ash on:
      •  Alkali-aggregate reaction,
      •  Sulfate attack,  and
      •  Dimensional stability.
      Alkali  present  in the  feed materials to  cement kilns tends to volatilize
 and is  collected  as  dust.   Cement producers would like to recycle
 the dust for its  lime value.  However,  as the recycle rate increases,
 the alkali content of the cement  increases.   Reaction of alkali present
 in cement with  certain types  of aggregate can result  in disruptive ex-
 pansion of the  concrete.   Fly ash  addition  tends to  quench the  reaction.
 However,  current  specification for 'cements  to be used with reactive ag-
 gregates  requires the use of  low alkaline cement.  If performance speci-
 fication  for blended  fly  ash-cement could be  developed to account for
 the alkali absorptive capacity of the fly ash, the amount of kiln dust
 recycled  could be increased significantly and higher alkali raw materials
 could be  used.
     Concrete is subject  to disruptive  expansion when exposed to sulfate
 compounds; sulfates can exist in groundwater, seawater, or other sources.
 Ash may reduce this susceptibility by quenching the sulfate-cement
 reaction.  However,  ash-cement blends are seldom used at present when
 the concrete may be subject to interaction with sulfates because there
 are not standard tests for establishing sulfate resistance.  The avail-
 ability of a test which would simulate sulfate attack under field con-
ditions would allow the selection of an appropriate cement (blended or

     Hydration of MgO and CaO during setting causes  concrete to  expand.
Current ASTM specifications (ASTM C595-74)  limit MgO to 5% of the cement
clinker.  There are indications that the presence of fly ash greatly
diminishes the MgO-hydration expansion.   Current work is aimed at
developing necessary data to support or  refute these indications and also
to develop more appropriate tests to measure expansion.
     The NBS will assist in a potential  demonstration project in Mercer
County, North Dakota.  Several coal-burning power plants are being built
in the area, and a plant has been proposed to produce bricks from the
fly ash.  The NBS will be responsible for developing the necessary standard
tests for durability and strength of the bricks.  The project is being
sponsored by the Mercer County Development  Board and is at least two to
three years from production.
2.7.7   Tennessee Valley Authority
     The TVA is conducting a large-scale feasibility test for the pro-
duction of mineral wool for insulation from boiler slag  [36, 37].  The
mineral wool process was developed at the Coal Research Bureau  at West
Virginia University  under a grant from the Bureau of Mines.  Tests will
be run to determine  the financial feasibility of the process at the
Thomas  Allen Station, Memphis, Tennessee.  The TVA prototype will be  semi-
commercial size and  use four tons per hour of slag on  a  single  eight-hour
shift.  The slag is  from a  single 300-MW unit, with  a  wet bottom col-
lection system.  Slag will be  ejected from  the boiler  at  about  1100°C
(2000°F), limestone  is  added as  flux and the  temperature will be raised
to 1370°-1540°C  (2500°-2800°F);  the  fibers  are  spun  conventionally.   The
;> roc ess i<3  only  applicable  to  wet bottom units.  TVA currently  is working
on the design  for  the  unit  and expects  to have  the  unit operational by
late 1979   [37].   They have run the  process  in  a cupola-type unit.  Lime-
stone is  added to  drop the  slag viscosity.   Preliminary estimates  are that
the  process  has  an approximate payout period of five years.
      The  TVA staff is  currently working in conjunction with an  aluminum
company to  determine the economic feasibility of extracting alumina from
boiler fly ash.   Preliminary economics  indicate that extracting alumina

from fly ash might well be competitive with conventional technologies
for the extraction of alumina from Georgia clay (kaolin clay).   The TVA
is presently considering a 2 ton/hour pilot plant facility to investigate
the feasibility of extracting and recovering certain minerals (alumina,
iron, etc.) from boiler fly ash.
     TVA is also working in conjunction with some commercial interests
based in St. Paul, Minnesota, on the development of a process for ex-
tracting magnetite from boiler fly ash.  Magnetite is a major constituent
of the heavy medium slurry used in coal cleaning plants, and TVA believes
that the fly ash produced at its 1,700-MW Kingston plant contains suffi-
cient magnetite to feed the TVA Paradise coal cleaning plant.
     A TVA program currently is underway by the TVA to study the pos-
sibility of using fluidized bed combustion wastes as soil additives to
stabilize load-bearing fill/sub-base for small airport runways, high-
ways, etc.
     One other project in progress, being done with P&W Industries, in-
volves determining the feasibility of separating and collecting ceno-
spheres (hollow glass balls) from dry fly ash and marketing them com-
mercially for application as fillers for plastics, paint extenders, etc.
2.7.8  CM - Plastic Filler
     The Polymers Department of General Motors Research Laboratories has
been studying the use of fly ash as a filler in polypropylene [72, 73].
Mineral fillers currently used in plastics consist largely of silica,
alumina, and other oxides in the form of kaolin or talc.
     GM obtained fly ash from several sources and in a laboratory program
characterized the particle size, density, and chemical composition.  Samples
of filled polypropylene were prepared with appropriate antioxidants on a
roll mill at 190°C (400°F) and by extrusion at 205°C (425°F).  The material
was granulated for use in injection molding.
     Results indicated that fly ash particle size was important in some
applications.  Smaller particles tend to give products with greater impact
strength and better elongation properties than do larger particles.

However, particle size apparently had no measurable effect on yield
strength or modulus.  Tensile strengths were reported to be 2.07 to
2.48 x 107 Pa  (3000 to 3600 psi) and tensile moduli were 2.07 x 107
to 2.76 x 109 Pa (300,000 to 400,000 psi) for the filled plastics.
     GM postulates that the fly ash-filled material is low in strength
and stiffness because of the particle shape — irregular and jagged
versus platelike talc.  The higher length/thickness ratio of talc pro-
vides more reinforcement to the polypropylene matrix.
2.7.9  Other R&D
     Some limited information is available on the following:
     •  The Fossil Energy Division of DOE has funded research at Iowa
        State University on the recovery of metals from fly ash.  The
        objective of the program is to investigate the chlorination
        of coal fly ash as a method for recovering the aluminum and to
        develop a process for the large-scale recovery of aluminum and
        iron from fly ash by this method.  Previous work here has achieved
        80% recovery of aluminum as aluminum trichloride  (A10C1 ).
                                                             2.   6
     •  The Federal Energy Administration has funded  research at
        Southwest Research Institute  for the evaluation  of  utilization
        of slag, fly ash and kiln dust as additions  to portland cement
        by intergrinding with clinker or blending.   Fly  ash was added
        at 0-15% and blends were  tested  at  ages  up  to one year  for
        physical and  other characteristics.
     •  The American  Electric Power Service Corp.  is  funding a  field
        study  of fly  ash construction at West Virginia  University.  The
        aim of the  research  is  to study  the field  behavior  of  fly  ash
        embankments and stabilized  fly  ash  base  courses  to  provide
        engineering design  data.  Laboratory and field  studies  included
         (1) placement and  compaction techniques; (2)  properties of
        the  in-place  material  as a  function of  time and location in the
        embankment  and/or  base; (3) effects of  frost action on material

properties; (4) moisture retention by fly ash and its effect
on strength; (5) effects of traffic on material properties;
(6) corrosion of metals embedded in fly ash: (7) permeability
of fly ash; and (8) immediate and long-term compressibility
of fly ash.

3.1  Introduction
     FGD systems are generally  categorized  into  two  groups:
     •  Nonrecovery—or throwaway—systems,  which  produce a  solid  or
        liquid waste with little market  value, and
     •  Recovery systems, which produce  primarily  purified,  concentrated
        S0~ elemental sulfur or sulfuric acid  as a byproduct for sale.
At present, the overwhelming majority of FGD systems for controlling
emissions from utility and industrial boilers  utilize some  form of non-
recovery technology.  Over 90%  of the more  than  50,000 MW of utility
boiler capacity now committed to flue gas desulfurization  involve  non-
recovery processes.  This dominance of nonrecovery systems  is expected
to continue for the near future.  Except in site-specific  cases with
favorable local market conditions for the by-products (sulfur or sulfuric
acid), recovery processes are more expensive.
     The technology of recovery and nonrecovery systems, the character-
istics of the wastes produced,  and projection of waste generation are
discussed in Volume 3.  This chapter provides a review of waste utiliza-
tion, both current practices and potential utilization alternatives
that have been or are being investigated.  Emphasis is placed upon wastes
from nonrecovery processes, since nonrecovery technology will be  the
principal approach to the desulfurization of flue gases from fossil fuel
combustion, at least over the next 10 to 15 years.  Furthermore,  the
primary byproduct of recovery systems will be sulfur or sulfuric  acid,
conventional products for which markets are already established.
3.2  Utilization of Nonrecovery FGD Wastes
3.2.1  Description of Wastes
      Commercially available nonrecovery processes can be conveniently
subdivided into  two  groups according  to the form of the waste material
produced—those  which convert the  S0~ into  a solid waste and those which
produce a  liquid waste.   Nonrecovery  systems can  also be classified
according  to  the manner in which  the  flue  gas is  contacted  with the S02
sorbent—i.e.,  wet  scrubbing processes  versus dry processes.

     All nonrecovery systems now in commercial operation on utility and
industrial boilers are wet processes involving contact of the gases with
aqueous slurries or solutions of absorbents.  Although most nonrecovery
wet systems can withstand relatively high levels of particulate and trace
contaminants and many in the past have been designed for simultaneous SO-
and particulate control, most wet systems being installed today on utility
boilers are downstream from high efficiency electrostatic precipitators
in order to ensure more reliable service.  The notable exceptions are
systems designed to utilize alkalinity in the fly ash for all or part of
the SOo removal.  These frequently incorporate simultaneous fly ash and
S02 control.
     Dry non-recovery processes have not yet been commercially demonstrated
on a utility scale in the United States.  However, a number of different
approaches have been investigated, including dry injection of sorbents
into the boiler and flue gas and the use of spray dryers.  All of these
involve simultaneous S(>2 and particulate control, and all produce a dry
waste material.  The most promising approach at present employs spray
dryers for contacting the flue gas with slurries (or solutions) of
calcium hydroxide or sodium carbonate/bicarbonate.  Three such systems
have been contracted for application to utility-scale boilers.  Solid Wastes
     The four basic types of nonrecovery systems producing solid wastes
     •  Direct lime scrubbing,
     •  Direct limestone scrubbing,
     •  Alkaline fly ash scrubbing, and
     •  Double (dual) alkali.
     The first three of these utilize slurries of lime, limestone, or
ash to contact the flue gases and produce slurries containing 5-20 wt%
solids which are either discharged directly or partially dewatered and
possibly further processed prior to discharge.  All three of these are
commercially demonstrated technologies.  The fourth, the double alkali

process, is a second generation technology  which  has' been applied  suc-
cessfully to industrial-scale boilers but is only now  reaching  commercial
demonstration on utility boilers.   Double alkali  processes utilize
solutions of sodium salts for S02  removal which are then regenerated
using lime to produce a waste solid that is discharged as a filter cake.
     In addition, dry sorbent based FGD systems are also likely to be
in commercial use by the early 1980*s.  These will be  based on lime,
sodium salts or other sorbents and will produce dry solid wastes.   To
date, the extent of focus on utilization of such  dry sorbent wastes has
been minimal.  EPA is planning some pilot studies on dry sorbent processes
and dry surbent wastes in 1979 [50].
     The quantity and composition of ash-free FGD wastes are dependent
upon a number of factors including:  coal characteristics (most impor-
tantly, its sulfur content and heating value); S0~ emission regulations;
the type of boiler and its operating conditions;  and the type of FGD
system and its operating conditions.  In general, the quantity of dry,
ash-free FGD waste produced varies from about 2.0 to about 3.5 times the
quantity of 862 removed from the flue gas.  Hence, a typical utility
boiler operating at a 70% load factor could produce anywhere from 50 to
500 tons of dry, ash-free solids annually per megawatt  of boiler capacity.
     The principal substances making up the solid phase of FGD wastes  are
calcium-sulfur salts  (calcium sulfite and/or calcium sulfate) along with
varying amounts of calcium carbonate, unreacted  lime,  inerts and/or fly\
ash.  In wet processes the ratio of calcium sulfite to  calcium  sulfate
is a key design and operating parameter, especially for direct  scrubbing
systems since it can affect not only  the scale potential of  the system
but also the waste solids properties.   The  relative amounts  of  calcium
sulfite and  sulfate present depend principally upon the extent  to which
oxidation  occurs within  the system.   Oxidation is  generally  highest in
systems  installed on boilers burning  low sulfur  coal or in  systems  where
oxidation  is  intentionally promoted.   In most  medium  to high sulfur coal
applications, oxidation  of sulfite to sulfate  in the  scrubber  system
amounts  to only  10-30%,  and  calcium sulfite is the predominant  material

in the waste.  When the sulfate content of the waste solids is low,  calcium
sulfate can exist with calcium sulfite as a solid solution of the hemi-
hydrate crystals (CaSO • 1/2H70).  At higher calcium sulfate levels,
gypsum (CaS04 • 2H20) becomes the predominant form of calcium sulfate.
At very high levels of oxidation (greater than 90% oxidation of the  S02
removed) all of the calcium sulfate usually will be present as gypsum.
      Because the differences in the crystalline morphology of hemihydrate
and dihydrate solids not only reflect the chemical composition but also
can affect the physical and engineering properties, it is convenient  to
classify FGC wastes on the basis of the ratio of calcium sulfate to
total calcium-sulfur salts.  The three categories are as follows:
      •  Sulfate rich (CaSO,/CaSO  > 0.90),
                          *fr     X
      •  Mixed (0.25 < CaSO,/CaSO  < 0.90), and
                          ^     •*»
      •  Sulfite rich (CaSO,/CaSO  < 0.25),
                          ™T     X
where CaSO  is the total calcium-sulfur salts.
      Calcium sulfite wastes present a problem because of difficulty in
dewatering.  However, calcium sulfite wastes can be oxidized to calcium
sulfate, either intentionally in the scrubber or in an external oxidation
reactor.  From the viewpoint of utilization, calcium sulfate is the
desirable FGD by-product.
      EPA studies at the Industrial Environmental Research Laboratory
(Research Triangle Park, North Carolina)  have shown that calcium sulfite
can be readily oxidized to gypsum by simple air/slurry contact in the
hold  tank of the scrubber recirculation loop.  Although the rate of
oxidation reaches a maximum at a pH of 4.5 and then declines at higher
pH, it was found that oxidation could be accomplished at a practical
rate  up to a pH of about 6.0 [69].
      In Japan, where natural gypsum is not available, forred oxidation
in scrubber systems has been employed extensively to produce a high-
quality gypsum raw material for the cement and wallboard industries.
Japanese FGD units are primarily used on oil-fired boilers and do not
have  to contend with fly ash admixtures with gypsum.   In the United States,
FGD systems are mainly on coal-fired boilers and usually supplement fly

ash collection units;  gypsum admixture with  fly  ash  is  possible  in poorly
designed or operated systems.  Furthermore,  scrubber gypsum may  be unable
to compete extensively with the widely available natural gypsum  except
in some specific areas.  Thus,  the incentive in  the  United States has
been to develop simplified forced oxidation  procedures  and has been
directed only toward improving  waste solids  handling and disposal prop-
erties and not towards the production of gypsum  with minimum  fly ash
content; moreover, the oxidation reaction need be carried only  to about
95% completion if one is only aiming towards relatively good  dewatering
characteris tics.
     There is little information currently available on the composition
of wastes from dry scrubbing systems utilizing spray dryers.  However,
while all of these wastes would contain fly ash, the fraction of the waste
resulting from SO^ control would be expected to  be similar in chemical
composition to those produced by wet processes using the same sorbents.
For lime-based dry scrubbing, the FGD wastes should consist primarily of
a mixture of calcium sulfite, sulfate, and unreacted lime.  The quantity
of unreacted lime, however, may be somewhat higher than in wet scrubbing
wastes owing to the higher stoichiometries that would probably be
required.  The mix of calcium sulfate and sulfite solids may also be
somewhat different, both in terms of their relative quantities as well
as the crystalline forms present.
     For dry systems utilizing alkaline sodium salts (e.g., nahcolite
or sodium bicarbonate) the waste solids would be expected  to contain in
addition to fly ash a mixture of principally sodium sulfate, sulfite,
chloride, and unreacted carbonate.  These would be similar  in
composition to the wastes produced from once-through sodium solution
scrubbing except  that  the solids would be discharged as a  dry material
rathe"r than as a  liquid.  Liquid Wastes
     There are two different liquid waste-producing FGD processes that
are in commercial operation  on combustion boilers—(1) once-through-scrubbing
using solutions of alkaline  sodium salts and (2) scrubbing using ammonia-laden
water.   Of  the  two, once-through sodium scrubbing has  achieved  the  widest
acceptance, having  been applied  to many industrial  steam plants and a  few
utility  boilers.  Once-through sodium scrubbing produces a waste liquor
containing primarily  sodium sulfate,  sulfite, and  chloride at  total
dissolved  solids  concentrations  generally in the range of 15-30 wt%.


Most  of  these waste  liquors  also  contain  significant  levels since the
systems  are  used  for combined  participate and  SO™  control.  Frequently,
the waste  liquors are air-sparged to  oxidize any residual sulfite to
sulfate, especially  where wastes  are  discharged for disposal.
3.2.2  Current Utilization Practices
     The available data on industrial and utility  boiler FGD systems
indicate that there  is very  little commercial  utilization of FGD wastes
in the United States.  In fact, the only  commercial utilization reported
for nonrecovery wastes is the  reuse of once-through sodium scrubbing
liquors at pulp and  paper plants  [51]. There are two  such plants where
the scrubber discharge liquor  is  recycled for  use  in  pulping operations.
3.2.3  Potential Utilization Alternatives
     A variety of potential  uses  for  stabilized and unstabilized calcium
sulfite/sulfate wastes from  lime- and limestone-based scrubbing have
been proposed including:
     •  Road construction base,
     •  Cement and concrete  manufacture,
     •  Filler in glass,
     •  Fertilizer and fertilizer base,
     •  Fill material  (structural or landfill),
     •  Brick manufacture,
     •  Commercial gypsum substitute  (in wallboard and cement) either
        as a direct waste or converted sulfite-rich material,
     •  Aggregate,
     •  Recovery/reuse of chemical values  (including  beneficiation), and
     •  Artificial reef constructions (although this  is generally con-
        sidered to be disposal and is discussed in Volume 5).
Recent studies [7, 43] have  indicated the  feasibility for use as struc-
tural fill, brick manufacture, and highway construction, although the
current level of development is low at this time.   The technical feasi-
bility of most of these product uses has been evaluated on only a limited
scale; and even for those which have been  shown to be technically feasible,
the economic viability is still uncertain.  Also,  for some of the po-
tential uses that have been proposed, coal ash can also be used (as
mentioned earlier),  and in many cases, coal ash will be the preferred

     A brief discussion of some of the more viable  options  is  presented
below prior to the discussion of research and development programs  in
waste utilization.  Structural Landfill
     Unstabilized FGD waste typically has poor structural properties.
Sulfite-rich materials are usually difficult to dewater and can be
structurally unstable (tendency to liquefy and flow).   As a result,
unstabilized waste probably will not be useful for  fill.
     Stabilized waste may provide viable fill materials.  On a demonstra-
tion basis, stabilized FGD waste has been used for  road base,  road  fill,
lightweight aggregate, and artificial reefs [52].  Its use also has been
suggested for mine reclamation, subsidence control, acid mine drainage
control, etc. [11].  The stabilization processes are discussed in more
detail in Volume 3.
     As more FGD systems begin to utilize stabilization procedures with
landfill of wastes, the modified and stabilized waste might find an
outlet for use in structural fills and enbankments.  The stabilized
waste usually contains significant amounts of fly ash as a result  of the
stabilization process.  The structural properties of stabilized waste
may make it advantageous for landfill or strip mine reclamation.  Gypsuro
     Forced oxidation of FGD waste can yield  gypsum as  an end-product.
Gypsum so produced may be  useful  for wallboard manufacture, cement pro-  r-
duction  (as a set retarder), and  as a soil additive; wallboard has the
potential for being the largest end-use market.
     The technical differences between by-product gypsum and natural
gypsum are somewhat uncertain, and conflicting information exists.   By-
product  gypsum has a smaller particle size  and contains more  free  moisture
 (20% versus  3% in natural)  than natural  gypsum.  It is  up to  96% pure
 calcium  sulfate,  with  the  primary impurity  calcium carbonate  and less
 than  .05%  solubles  [67].   Some by-product  gypsum is purer  than natural
 gypsum;  in  one  test,  Chiyoda process  gypsum was  about  90%  calcium  sulfate
 versus  80%  purity for  natural  gypsum being imported from Canada [69].


Industry  (wallboard) manufacturers have expressed concern over the pos-
sible effect of contaminants (e.g., fly ash, reagents, calcium sulfite,
and soluble salts) on product quality and economics, and the effect of
variations in sludge (gypsum) quality and composition on product quantity
and economics [35].  Wallboard or cement gypsum can contain up to 15%
CaCOo, with the nominal grade containing 8-15% CaCO-j.  Sulfuric acid may
be added  to convert excess CaC03 to gypsym and also to lower the pH to
enhance oxidation of sulfite to gypsum.  The effect of entrained trace
metals and elements on gypsum is unknown.
     Wallboard is currently produced from natural gypsum which is either
mined domestically or imported.  Production is generally from a captive
source, as the industry is vertically integrated and most companies own
or control their own mines either here or abroad.  This could make market
entry for by-product gypsum very difficult.   The degree and amount of im-
purities  that can be tolerated in gypsum depend upon intended use.  In
wallboard manufacture, impurities in gypsum reduce the strength of the
product and more pounds of gypsum are required to achieve a given strength
of finished wallboard.
     Entrained coal fly ash apparently has little effect on the quality
of the wallboard produced, although it does produce a dark-colored gypsum
which may have some associated sales resistance [35].  Chloride, which
occurs at higher concentrations in scrubbers on coal-fired versus oil-
fired utilities,  may cause corrosion problems in wallboard installations
[52].   Chloride also affects calcining temperature, set time, and stucco
slurry consistency.  Soluble chlorides are usually limited to 0.02% to
0.03% if  the gypsum is used in wallboard.  The hydrous sulfate salts affect
moisture  pickup and bonding characteristics of the wallboard and are also
limited to 0.02% to 0.03%.  Hydrous clays of up to 1.0% to 2.0% may be
tolerated [54].   Gypsum is also used as a soil conditioner; this use is
discussed later in this section.
     In Japan, by-product gypsum is widely produced, as most utilities
equipped with lime/limestone scrubbing convert the sludge produced to
gypsum through intentional forced oxidation.  However, a distinct set of

circumstances exists which tend to encourage this  practice:
     •  Regulatory agencies frown on throwaway or  unoxidized waste.
     •  There is a scarcity of suitable land for waste disposal,
     •  Since there are no natural sources of gypsum,  market demand
        is high.
     •  Boilers are generally oil fired rather than coal fired.
     Japan has little or no natural gypsum and,  therefore, must  depend on
imports and byproduct gypsum from chemical processes (e.g.,  production
of phosphoric acid).  When lime/limestone scrubbing was introduced,  this
ready market for gypsum led most system suppliers  to develop oxidation
units.  Most Japanese power plants burn oil; the ratio of power  produced
from oil to that from coal is about 10 to 1 [70].  The gypsum from scrub-
bing coal-fired boilers may be less acceptable becasue of the higher
impurity content from entrained fly ash, chlorides, etc. [52, 70]-
     Most of the FGD gypsum made in Japan goes to the wallboard industry
where it commands a higher price than in the cement industry where higher
fly ash content can be tolerated.  The market for FGD gypsum in Japan has
held up well, considering the large amounts being produced as a scrubbing
byproduct and as a byproduct of phosphoric acid manufacture.  However,
recently supply has exceeded demand, and this may affect the overall
     The potential for utilization of gypsum in the United States is
probably not as favorable  as that  in Japan.  The United States has more
open  land available  for sludge disposal  and hence,  disposal costs are less
than  in Japan.  Moreover,  natural  gypsum sources are available to satisfy
the market  at reasonable  cost.   Furthermore, FGD systems in the United
States are  and will  continue to  be installed on coal-fired boilers; po-
tential admixture with  coal ash  would  impact quality control requirements.
Market studies  by the TVA and others  [55,56,67] indicate that the pro-
duction and marketing of  abatement gypsum may offer substantial economic
advantages  over FGD  waste  disposal but  that abatement  gypsum probably  can-
not  compete with  natural  gypsum  except  in specific situations.   (See  Section
2.3.) Successful entry of abatement  gypsum into  the wallboard  industry as

a replacement and competitor of naturally mined gypsum seems uncertain.
The wallboard industry is proceeding with caution in accepting abatement
gypsum as a substitute despite some advantageous properties of abatement
gypsum and several successful demonstrations.
     Gypsum could be utilized also in the manufacture of portland cement
[67].  This is practiced in Japan and does not require as high a grade of
gypsum as wallboard manufacture.  However, little information exists on
the technical requirements for gypsum in this application.  This market
segment is not generally integrated into natural gypsum production and
marketing so that market penetration may be easier here than in the wall-
board industry.  Gypsum is used in the cement industry as a set retarder;
it is added to clinker and ground into the final product.  The sulfite
content of the by-product gypsum may limit its use.  In general, the
specifications for use in cement are not as stringent as those for use in
     The use of by-product gypsum in agriculture, although representing
a smaller market than either of the above uses, looks promising.  At least
one source indicates current commercial utilization in this capacity [67].
The use of by-product gypsum is discussed more fully in Section  Aggregate
     Production of aggregate from FGD waste is a potential large volume
market because of increasingly more expensive naturally occurring
     A mineral aggregate containing sludge was developed by I.U. Conversion
Systems and has been satisfactorily used in a demonstration project [57].
Mineral aggregate also has been produced using an autoclave process where
pelletized sludge is hydrothermally agglomerated by curing with saturated
steam at 300 psi.  This process would be faster than that proposed by the
Corson Company but more expensive because of the energy requirements.
     Manufacture of lightweight aggregate has also been proposed as a
potential use for FGD wastes.  Lightweight aggregate currently is produced
by expanding shale,  slate,  or clay.   The growth in use of lightweight
aggregates (a doubling of use is expected in the next 20 years)  and the

shortages expected to occur in certain urban areas  are likely to favor
such potential utilization of FGD wastes.   A number of plants have been
constructed that sinter fly ash into a lightweight  aggregate and in some
areas this sintered fly ash has been found to be economically competitive
[58].  Fusion tests indicate that control  of the process with FGD waste
might be difficult because of the variability of the sludge and the narrow
softening - fusion temperature band.
     Mineral aggregate shows considerable  promise for large volume utili-
zation of by-product sludge, but technical  and economic problems must be
solved before this use is commercialized.  Agricultural Uses
     FGD scrubber waste may be useful as a soil amendment, a gypsum
substitute, or in fertilizer.  Such use will be possible in some areas,
for example, California and the southeastern states [52], but will probably
be limited to local markets which may coincidentally be available to a
     Research efforts directed toward the use of FGD waste as a fertilizer
base or additive range from simple studies of the effects of directly adding
unstabilized waste to soil to more sophisticated conversion process
technologies related to fertilizer production.
     As a direct soil additive, FGD waste has potential benefits  including
its neutralization capability and its use as a  source of  sulfur,  calcium,
magnesium, and certain necessary trace metals that may participate  in
plant growth.  However, FGD waste has little or no nitrogen, phosphorous,
or potassium value,  and the presence of high levels of IDS  (particularly
sodium  and chlorides) as well as some potentially  toxic trace metals may
present problems in  agricultural uses in  any large quantities.
     Oxidized FGD waste may be  useful as  a  gypsum  substitute.   Gypsum is
used in the  following ways:
     •   As a  soil  amendment  on  high-alkali  soils,
     •   As a  neutral source  of  calcium, and
     •   To provide sulfur  on sulfur-deficient  soils.

      Soil  amendments may be of  three  types:  soluble calcium salts (calcium
 chloride and gypsum); low  solubility  calcium salts (limestone); and acid
 or acid-forming  compounds  such  as sulfur, sulfuric acid, iron, and
 aluminum sulfate [5].  Because  of their low cost and suitability, gypsum
 and sulfur are the most widely  used.
      Peanuts require large amounts of soluble calcium in the soil surface
 to facilitate pegging and  nut formation.  Gypsum use is recommended when
 soil pH is already satisfactory but additional calcium is needed (gypsum
 is a non-alkaline source of calcium).
x     Where soils are deficient in sulfur, gypsum can be used as a source
 of this nutrient.  However, since the requirement per acre is usually
 small (VLO Ib/acre), it is usually easier to simply add the sulfur to.
 fertilizer and apply both  in a single application.
      A process to produce  granular fertilizer from scrubber waste has
 been proposed in the literature and currently is being developed [59].
 Research is being conducted by the TVA as part of an Interagency Agreement
 involving  the use of lime/limestone scrubbing wastes in agricultural
 applications.  This portion of the work involves use of direct lime and
 limestone  scrubbing system wastes as  a filler material in and as a source
 of sulfur  for fertilizer.  The work includes pilot testing of the fertil-
 izer inclusion/production  process, testing of field plots using wastes/
 fertilizer mixtures, and studies of the costs associated with producing
 such a fertilizer and its market potential.  To date, initial pilot plant
 tests have shown some problems in introducing waste into standard fertil-
 izer production units. (See Section 2.3, R&D - TVA.)  Waste also may be
useful for its liming value [59].  The liming value will probably vary
with the unreacted lime and the amount and basicity of the fly ash con-
tained in the waste.  Gypsum and sulfite have little or no liming value
but  provide soluble calcium and sulfur.  Fixation additives may affect
the  value of sludge as fertilizer.  Little information is available on
 this  end-use, and it probably would be economical within a limited
distance from the waste source.

-------  Building Brick
     Brick production by the conventional sintering process  as used  for
fly ash or clay brick is not technically  feasible  for FGD waste raw
materials at this time.  S(>2 is  evolved during the sintering process,
and control of the level of softening during sintering  is difficult  (see
lightweight aggregate).  Calcium silicate brick has been made from FGD
waste  [38].  The brick is a mixture of scrubber waste,  silica sand,  and
lime, which is pressed into shape and then autoclaved.   The  bricks are
of good quality and meet the ASTM specification for calcium-silicate brick
[38].  Calcium silicate brick is not a common building  material in the
United States, and major market changes would have to take place  before
this method of utilization would become practical.  Recovery of Chemicals
     Various investigators have suggested and explored  the  concept of
the recovery of useful chemicals from scrubber wastes (FGD or FGC).
Furthermore, recovery FGD systems produce sulfur or sulfuric acid as
by-products.  At present, two [2] utility plants employ recovery  FGD
systems.  Thus, the list of possible by-product chemicals  from scrubbing
the sulfur contained in flue gases includes calcium oxide,  magnesium oxide,
elemental sulfur, sulfuric acid, sodium sulfate, sodium sulfite,  and
ammonium sulfate.  Some of these chemicals can be obtained from scrubbers
using  recovery systems but may not be practicably obtainable from lime/
limestone sludge because of the extensive reprocessing necessary to  ex-
tract  these materials.  The one potential exception is production of ele-
mental sulfur.  A variety of processes have been suggested for the pro-
duction of elemental  sulfur from FGD waste  [56, 60, 61].  None of these
processes have been implemented on a full-scale basis.
3.2.4  R&D Programs -  Nonrecovery FGD Wastes
     The largest ongoing research program on FGD waste utilization is
that sponsored by the EPA.  The EPA  is currently  sponsoring  four  projects
connected with  utilization  of nonrecovery FGD wastes:
     1.  Converting  FGD waste to sulfur  (Pullman-Kellogg),
     2.  Converting  FGD waste to fertilizer (TVA),

      3.  Utilizing FGD waste  to extract alumina from kaolin clay
         (TRW), and
      4.  Marketing of FGD waste as gypsum  (TVA).
      A fifth project has been discussed on utilization of FGD waste in
 cement manufacture, but no projects are reported.  The overall objectives
 of  the projects are shown in  Table 3.1.  The current status is as
      •  The Pullman-Kellogg sulfur project has proceeded through
        pilot plant testing of the critical process units.
        Evaluation of process economics is necessary before further
        work proceeds.
      •  Fertilizer production from waste, being studied by TVA,
        is currently on hold, partly because of uncertainties over
        regulatory requirements in the future.  A pilot plant
        program has been developed, but further work is unlikely
        until resolution of these requirements [37].
      •  The TRW study of alumina production with FGD has been
        completed and a final report published.  This economic
        study concluded that FGD waste utilization for alumina
        production from kaolin clays, coupled with an adjacent
        cement plant to utilize by-product dicalcium silicate,
        may be feasible in the future depending on alumina prices.
        A future series of laboratory projects is suggested in
        the report.
     •  The TVA has recently completed a study of by-product
        marketing of sulfuric acid, sulfur, and gypsum [ 67].
        A linear programming model was used to determine the
        potential marketability (based on low-cost constraints)
        of the three by-product wastes.  This study is dis-
        cussed in more detail in Section 3.4.
     Northern States Power Corporation and Texas  A&M University have an
ongoing program to demonstrate the technical feasibility of lightweight
aggregate production from FGD waste and clay.  Bench-scale work has been

                                                        Table 3.1

                                        Current Research in FGD Waste Utilization
     Primary Sponsor
       Project  Focus/Status
     Northern States Power   Texas A&M
 Demonstration  of  process  for  conversion  of
 FGC  scrubbing  waste  to  sulfur and calcium
 carbonate.  Pilot plant work  demonstrating
 technical  feasibility of  major units has been
 completed.  Economics need  to be evaluated
 before  further scale-up.

 Assessment  of  FGC waste for conversion
 fertilizer.  Some pilot plant work has been
 completed.  Project  is  currently on hold
 awaiting decision vis-a-vis RCRA regulations.
            (On Hold)

Marketing of byproducts from  FGC waste.
Marketability  study of  byproduct sulfur,
 sulfuric acid, and gypsum using least-cost
 linear programming mode.  The study has
been completed and reported.
 (Completed Final  Report,  October 1978)

Process design and economic evaluation of proposed
process to use FGC waste  was  for the extrac-
tion of alumina from kaolin clay with calcium
disilicate byproduct recovery.
            (Draft Report)

Assessment of use  of FGD waste for production
of lightweight aggregate.   Bench scale work
completed.   Pilot  scale work under development.
60, 61
                                                                              60, 61
                                                                              60, 61
                                                                              60, 61
     Source:   Arthur D.  Little, Inc.

completed, and work is proceeding on a pilot level.   These  projects are
discussed in detail in the following section.
     In addition to these programs,  several other R&D projects  are
    a.   Southern Services has contracted with the U.S.  Gypsum
        Company for test runs of wallboard production utilizing
        abatement:gypsum generated from the Chiyoda  Thoroughbred
        101 dilute  acid scrubber at  the coal-fired Scholz Plant
        of Gulf Power.  These production runs  were conducted  in
        June and December 1976.   The full results of these  tests
        are not yet available, but indications are that the tests
        were reasonably successful [69].
    b.   Southern California Edison (SCE)  has been experimenting
        with gypsum production from  its Highgrove Station Unit
        No.  4.   This is a 10-MW  oil-fired facility.   A 50-ton
        full-scale  wallboard production run has been completed, but
        test results were not available.
    c.   The Purity  Corporation is pursuing the development  of
        a patented  process for using waste as  a fertilizer.   The
        process makes use of the sulfur and calcium  in the wastes
        with the addition of phosphorous  and ammonia to produce
        a granulated fertilizer.
    d.   The University of Florida Agricultural Research Center  in
        Quincy, Florida,  is  testing  for the Southern Company  the
        use of  two  different wastes  as  soil amendments.  The  two
        wastes  being tested  are  the  dual  alkali filter  cake and
        gypsum  from the ADL/CEA  and  Chiyoda prototype  systems,
        respectively,  at  the Scholz  Steam Plant in Sneads, Florida.
        Testing is  directed  toward determining the effectr of
        different concentrations  of  the wastes on soil  pH and the
        availability of calcium,  magnesium,  potassium,  and phos-
        phorous.  Tests are  also  being  conducted  to  project the
        effects of  these wastes on the dry matter yield of soybeans
        and  peanuts.

-------  Pullman Kellogg [61,63]
     The M. W.  Kellogg Company developed the "KEL-S"  process  for conver-
sion of lime/limestone scrubbing  wastes to elemental  sulfur with recovery
of calcium in the waste as calcium carbonate.
     As conceived, the process will reduce CaSO- and  CaSO/  in FGD waste
to calcium sulfide (CaS) in a rotating kiln with coal.   The CaS is
reacted with hydrogen sulfide (H2S) producing calcium hydrosulfide, i.e.,
(Ca(HS)2).  The Ca(HS)2 is dissolved in water; the solution is filtered
and reacted with CO^-rich gas from the kiln.  The Ca(HS)2 reacts with
the CO- to form ELS gas and calcium carbonate (CaCCO which precipitates.
Some of the H2S is recycled for reaction with the CaS; the remainder is
converted to sulfur in a Glaus unit.  The precipitated calcium carbonate
is recycled to the scrubber system.
     Pilot-scale work has been conducted to evaluate the technical feasi-
bility of various process steps.   The production step (reduction  to CaS
and dissolution) has been demonstrated to be technically feasible, and
the calcium regeneration step has been proven satisfactory.   The  economics
of the process need to be evaluated before any  further decision on the
process is made.  Design data need to be generated before  scaleup to a
larger prototype test unit could be made.  TVA [61, 63]
     The TVA is assessing the use of lime/limestone FGD waste as  a filler
material in and a source of sulfur  for  fertilizer.  The work  is being
performed by TVA, Office of Agricultural  and  Chemical Development, Muscle
Shoals, Alabama,  as part of an interagency  agreement on the evaluation
of FGD waste utilization.
     The process  (see  Figure  3.1)  mixes phosphoric acid  (HJPO.)  and ammonia
with dewatered  FGD waste at approximately  93°C  (200°F)  in  a preneutralizer.
The hot mixture is transferred to  an  ammoniator-granulator where  the slurry
solidifies  as  it  is ammoniated,  forming a granular material.   This material
is dried,  cooled,  and  screened to  obtain  a fertilizer product.

                                                                                  TO STACK
                                                           TO STACK
                                                               EXHAUST FAN
                                                               r«     —i
                                                           EXHAUST GAS
Source:  [61]
                  Figure 3.1   Process Flowsheet for Producing Solid Granular
                               Fertilizer Material from Scrubber Waste

     The tests used waste produced at the 1-MW  limestone  pilot  unit  located
at the TVA Colbert Steam Plant.  Severe foaming occurred  during the intro-
duction of waste, phosphoric acid, and ammonia  into the preneutralizer.
A specially designed preneutralizer was constructed to  eliminate the
problems encountered.  Alternative methods and locations  for adding the
waste, acid, and ammonia, improved agitation, foam breaking methods, and
insulation were tested.   Initial testing with the modified preneutral-
izer resulted in sulfur  losses  ranging from 78  to 90 wt%  and an ammonia
loss of 34 to 61 wt% based on input quantities.
     The losses are suspected to result from a reaction between calcium
sulfite in the waste and phosphoric acid:
     3CaS0  + 2HP0  -> Ca
Laboratory tests and past pilot plant experience indicate that these
reactions are possible.
     It  is expected that these unwanted reactions can be prevented by
either neutralizing the phosphoric acid before it comes into  contact with
the waste or by oxidizing the calcium sulfite to calcium sulfate before
feeding  to the preneutralizer.  Therefore, tests are being planned to
determine the feasibility of using oxidized sludge  in the preneutralizer.
     Additional tests were  conducted to define preneutralizer operating
conditions.  These included the effect on ammonia-to-phosphoric acid
ratios and the location of  the waste feed and its flow rate.  Problems,
including release of SC^, sparger plugging, and  temperature and fluidity
control, were encountered under the conditions tested.  Indications are
that pH  may  control the fluidity and SC^ release problem.
     Plans and  cost estimates  for pilot plant development of  a cross-
pipe reactor to possibly overcome these problems have been developed.
This program is  currently on hold.  A key  factor that will impact uti-
 lization in  this  and  other  applications is  the emerging regulations under
 the Resource Conservation  and  Recovery  Act  (RCRA) of  1976.   Restarting of
 this  and possibly other projects  depends on future  RCRA implications  [37].

-------  TSW  [61, 63, 64]
     TRW Systems has completed a preliminary process design and economic
 evaluation of a process to use lime/limestone FGD waste for the extraction
 of alumina from low-grade kaolin clays.  Byproduct dicalcium silicate and
 elemental sulfur are produced, thereby completely utilizing the waste.
     In the conceived process (see Figure 3.2) raw kaolin clay, lime/
 limestone scrubber;waste, sodium carbonate solution, and recycled desili-
 cation residue are ground and mixed in tube mills.  The mixture is dried,
 sintered at 780°C (1436°F), and reduced with carbon monoxide (CO) at 1200°C
X(2192°F) to produce soluble sodium aluminate (Na20 • Al20g) and insoluble
 dicalcium silicate (2Si02 • 2CaO) plus hydrogen sulfide gas (H2S), sulfur
 dioxide (S02), and combustion gases.  Most of the H^S and S02 are fed to
 a conventional Glaus unit producing elemental sulfur and a Beavon tailgas
     The cooled solids are leached with sodium carbonate (to dissolve the
 alumina) and filtered to remove the dicalcium silicate; residual dicalcium
 silicate is precipitated from solution with lime.  The alumina trihydrate
 is precipitated from the pregnant solution by adjusting the pH with
 combustion offgases (CO- carbonation), filtered, washed, dried, and
 calcined at 1093°C (2000°F) to alumina.  The remaining solution is
 concentrated and recycled.  Dicalcium silicate is washed, filtered, and
 sent to an adjacent cement plant where it substitutes for lime and silica
     The process is predicated on several technical assumptions, the
 validity of which need to be demonstrated before the process could be
 considered technically feasible.  These assumptions include:
     •  One ton of waste requires 0.012 ton of soda ash, 0.30 ton of
        clay, and 0.273 ton of coal, and will produce 0.07 ton of alumina
        0.156 ton of sulfur, and 0.625 ton of dicalcium silicate.
     •  The sintering-reduction reactions proceed in the proper sequence
        and produce a given offgas composition; otherwise, an absorption
        plant may be needed for the Claus unit.


Na C0_


           Dicalcium   I
                                                                                                   >- Stack  Gas
                                                                                                   >- Sulfur
 Source:   [61, 64]

                                    Figure 3.2   TRW Process Flowsheet

      •  The reactions of soda,  alumina,  calcium,  and silica to form
         dicalcium silicate and  sodium aluminate will proceed in a
         reducing atmosphere to  a high percentage  completion.
      •  The reaction rates are  sufficiently fast  to be practical.
      •  Side reactions do not occur which inhibit the formation of soluble
         sodium aluminate and thus negate the output of alumina.
      •  Coal can be used to produce a reducing atmosphere in the proper
         amounts in this processing scheme.   The process may require a
         coal gasification reactor for some or all of the coal required.
      •  The dicalcium silicate  byproduct possesses the necessary mechan-
         ical properties for compatibility with standard cement manufacture.
      TRW noted that an alternative processing scheme in which the principal
 product is cement (tricalcium silicate)  may have  the potential for increased
 economic leverage.   This latter scheme would use  sand and lime/limestone
 scrubber waste as primary feedstocks.  Physically, the design of such a
 process need not extend beyond  grinding of the kiln sinter and, hence,
 would require significantly less capital than the alumina extraction pro-
 cess.  Such a process would also be less energy intensive.
      The  study  concluded  that the alumina extraction process was  commer-
 cially  feasible  based on  existing economic  conditions,  provided that  the
 process complex  includes  a  cement plant  to  utilize the  dicalcium  silicate
 byproduct.   Investment  costs were based  on  1975 costs  (M&S  index  *  444.3).
 Interest  rate during construction was  taken as 9%  with  a  two-year con-
 struction period.  Total  investment  for  a plant capable of handling waste
 from  a 1000-MW power plant was estimated to be $51.5 million using  the
 Bureau of Mines  "study  estimate" method; using a standard estimating method,
 capital costs are calculated to be $52.2 million.    Standard  techniques
were  used to ratio purchased equipment costs to installed costs.  Major
process equipment was sized and estimated.  Raw materials were  estimated
as of July 1976.  These costs were used with various assumed discounted
cash  flow (DCF) rate of return on investment to calculate minimum required
alumina prices, both with and without a combined cement plant.

     A parametric evaluation of cost sensitivity was  done to  assess  the
affect of raw material costs,  by-product credits, energy  costs,  and  DCF
rate on either alumina price or required sludge credit  for a  given alumina
price.  Some of the salient results are presented below.   (See Table 3.2.)
For comparison, the current market price of alumina is  about  $140/ton
[65].  Note that the bulk of the analysis was done without a  combined
cement plant, but the results still are generally applicable.  A definite
economic advantage exists for the combined alumina/cement plant.
     The required price for alumina is sensitive to  the rate of  return,
sulfur credit, sludge credit, and coal cost.  Depending upon what values
are chosen for these variables, the alumina produced may or may  not  be
economically marketable.  TRW used a discounted  cash flow rate of return
of 10-15%.  This appears low considering the level of risk inherent  in
this type of project.  A higher rate of return would increase the required
alumina prices even more than the values indicated here.
     The study recommended that any further work concentrate on  (1)  veri-
fying the technical assumptions, and (2) considering production  of  cement
as the principal product.  Texas A&M University  [62]
     Northern  States Power Corporation  (NSPC)  is sponsoring a study at
Texas A&M which is looking at  the  feasibility  of using FGC waste for the
production of  lightweight aggregate.  NSPC uses  aqueous  limestone and  fly
ash  for scrubbing and produces  FGC waste.   Texas A&M has  produced light-
weight aggregate from this waste  in a muffle furnace.  Investigations  are
cu-rently underway on a pilot  plant unit which will utilize a rotary kiln.
The  aggregate  is produced by mixing clay and sludge, agglomerating,  and
firing in the  kiln.
      This portion of  the study is focusing on  a  technical assessment of
the  pilot unit.  If  the process proves  technically feasible,  market and
economic studies will be conducted.

                                                    Table 3.2

                                           TRW:  Sensitivity Analysis

         Combined Cement     Coal     Clay   Capital    Sludge     Cement     Sulfur         Estimated Alumina Cost	
Case          Plant          Cost     Cost     Cost     Credit     Credit     Credit     10% DCF     12% DCF     15% DCF

Sludge          No            $20      $6     $52M        $1         -         $10      .. $370         $404        $461
Credit                                                    $5                              $292         $327        $383
$1-$10                                                    $10                             $195         $229        $286

Capital         No            $20      $6     $52M        $5         -         $10        $292         $327        $383
Cost                                           xO.5                                       $193         $210        $237
±50%                                           xl.5                                       $392         $444        $529 ,

Clay Cost      No             $20      $1     $52M        $5         -         $10        $270         $304        $360
$1-$10                                 $6                                                 $292         $327        $383
Coal Cost                              $10                                                $310         $385        $401
@ $40                         $40      $6                                                              $468

Sulfur          No            $20      $6     $52M        $5         -         $0         $315         $349        $405
Credit                                                                         $10        $292         $327        $383
$0-$25                                                                         $25        $259         $293        $350

With Cement     Yes           $20      $6     $87M        $0         $50       $10        $221         $279        $369
Plant-Sludge                                              $5                              $124         $182        $272
Credit $0-$10                                             $10                             $27          $85         $174
  Source:  [64]

3• 3  Utilization of Wastes and By-products from Recovery FGD Systems
3.3.1  Introduction
     As a category,  recovery processes differ from nonrecovery processes
in that they are designed to produce a high  purity by-product  sulfur
compound with an existing,  established market.  At present,  only systems
producing elemental  sulfur,  concentrated sulfuric acid and/or  concentrated
SO- are considered to be recovery systems in the United States.  In a sense,
processes producing  a high quality gypsum by-product could also be con-
sidered recovery systems as they are in Japan; however, in the United
States, there are no commercial FGD systems designed for the production
of relatively high quality gypsum intended for sale.  Most processes
now being considered are geared more toward the improvement of system
performance (e.g., minimization of scale prevention, improved  limestone
utilization, etc.) and enhancement of waste properties for disposal
operations, rather than manufacturing a product.  Present gypsum-producing
processes are therefore thought of in the United  States as nonrecovery
systems, and the utilization of FGD gypsum has been discussod  along with
other wastes from nonrecovery systems.
     Recovery processes  (those producing sulfur,  sulfuric acid or
concentrated S0?) can offer potential advantages  over nonrecovery  systems
in that they simultaneously produce a by-product  chemical where there
is an  existing market and reduce  the volume  of FGC wastes that may have
to be  discarded.  However,  the total volume  of FGC wastes produced will
still  be high,  since coal ash will  still be  generated and the  recovery
systems themselves also  produce  a small  amount of waste.
     There  are  a number  of  factors, however,  which may tend to offset
 the  advantages  of a  saleable by-product  and the  reduction in  waste
volume and  which may ultimately  impact  the  viability  of producing
 sulfuric  acid  and/or sulfur in many cases.   The most  important of  these
 factors are as  follows:
      •  Production  of waste streams which require treatment
         and disposal,

     •  Immediate and longer-range marketability of by-product
        sulfur and sulfuric acid,
     •  Feasibility of stockpiling by-products such as sulfur
        in anticipation of a future market, and
     •  Increased energy demands of many recovery systems,
        especially those producing sulfur.               ^
3.3.2  Waste Streams from Recovery Processes
     Recovery processes require separate removal of fly ash.  Consequently,
fly ash and bottom ash are collected separately and may be maintained
as separate products from the by-product of recovery.  Therefore, all
products are potentially marketable on a segregated basis; this may be
an advantage.  In addition, since FGD waste essentially is reduced or
eliminated, fly ash which might be needed to stabilize waste can now be
marketed.  In the future, nonrecovery processes may require greater and
greater amounts of potentially saleable fly ash to stabilize FGD wastes.
Therefore, one potential advantage of recovery processes would be that
more fly ash could be utilized in a direct fashion rather than being
used to stabilize FGD scrubber waste.
     On the other hand, no recovery system is likely to be waste free.
All of the commercially available recovery processes as well as those
now being demonstrated on a utility scale boiler produce some form of
waste in addition to the by-products.  The most highly developed
recovery systems (Wellman-Lord process, magnesium oxide scrubbing,
citrate process, and aqueous carbonate scrubbing) are wet processes and
involve contacting the flue gas with absorbent solutions or slurries
analogous to nonrecovery systems.   These systems cannot tolerate any sig-
nificant contamination of the absorbent liquors with fly ash,  chlorides, or
possibly other trace species present in the flue gas.   These impurities can
interfere with the system chemistry and/or contaminate the by-product.
Hence,  application of these wet processes to combustion boilers, particularly
coal-fired boilers, would normally require incorporation of a prescrubber
ahead of the SO- absorber, even where a high-efficiency precipitator
is used for particulate control.

     In addition to removing chlorides,  residual fly ash,  and some
trace species which would otherwise be trapped in the absorber,  such
prescrubbers also can remove significant quantities of S0_.   The blow-
down from these prescrubbers is therefore acidic and can contain appre-
ciable levels of suspended solids as well as potentially higher  levels
of soluble species than present in many nonrecovery wastes.   Treatment
of the blowdown prior to discharge can result in waste quantities equiva-
lent to as much as 15% of that produced by nonrecovery systems.
     Some of the processes such as the Wellman-Lord process and
magnesium oxide scrubbing produce secondary waste streams.  In the case
of the Wellman-Lord system, it is an impure sodium sulfate waste cake.
Sodium sulfate is formed by oxidation of the sulfite absorbent.   Since
it cannot be readily regenerated to an active alkali, it must be purged
from the system.  If there is no ready market (e.g., local sodium-based
pulp and paper mill) it must be disposed of.
     In the case of magnesium oxide scrubbing, magnesium sulfate may
need to be purged if oxidation levels exceed steady-state levels
consistent with the ability to convert it to magnesium oxide.
3.3.3  Marketability of Sulfur or Sulfuric Acid
    A key market-related constraint on recovery FGD systems is the
geographic limitation of the market for elemental sulfur and sulfuric
acid.  Transportation costs limit the marketing radius for sulfur or
sulfuric acid.  Sulfur or  sulfuric acid from recovery FGD systems would x
have to potentially compete against sulfur  from other sources including
Frasch sulfur,  sulfur from smelters, and sulfur from sour-gas sweetening.
In  certain  specific locations, a local market may exist with these  con-
straints.   However,  there  does not appear to be a sufficient market on the
large  scale in the immediate  future for  the sulfur  or sulfuric  acid that
would be  produced if  a  significant percentage of power  plants produce
by-product  sulfur or  acid.

      Furthermore, markets for these products are currently constrained
 by oversupply in some areas;  and the cost for producing the by-product
 with FGD systems is high.  Therefore,  the market potential for  these
 types of utilization products is probably limited,  except  in special
 cases.  By-products from recovery processes can probably be successfully
      •  In specific locations where a  market for the  products exists
         because of limited supply from other sources  (e.g.,  trans-
         portation constraints),  or
      •  In areas where availability of disposal options for
         nonrecovery processes is so constrained that  the
         cost  of disposal of wastes is  higher than the marketing
         costs for these by-products.
 This potential for utilization of nonrecovery processes will be very
 3.3.4  Stockpiling
      Since about  80%  of sulfuric acid  is  produced from  elemental sulfur,
 these chemicals  are highly interrelated.   Sulfur has  a  number of other
 uses including hydrotreating,  fertilizer,  insecticides  and vulcanization;
 and  research  activities continue to develop  new uses  for sulfur (e.g.,
 road construction).  While most  current demand  is met by the Frasch
 (from the  Gulf coast) process, at  some future date these sources may be
 depleted.   Further, energy requirements may  limit recovery of low-grade
Frasch  deposits.   TVA  [56] concludes that over  the long-term a greater
portion of  the sulfur will have  to come from other than natural sources.
Beyond  the year 2000, demand for sulfur is projected to exceed supply
[66].  Then alternative sources could be important.   In fact, stockpiling
might be one alternative for utilities which could not find an immediate
market outlet for by-product sulfur.  Stockpiling of sulfuric acid is not
practical due to technical difficulties.  Stockpiling of elemental sulfur
however, would be feasible if sufficient incentives  existed.  Stockpiling
could be considered a special type of future utilization.  At present, the
full implications—technical,  financial and institutional—of stockpiling
are not known.

3.3.5  Energy Demands
     The production of elemental sulfur from recovery  processes  requires
the use of some form of reductant such as natural  gas,  hydrogen,  carbon
monoxide or coke.  Those processes which produce an intermediate stream
of concentrated S02 for conversion to sulfur (Wellman-Lord,  magnesium
oxide) can utilize natural gas directly (the Allied Chemical process)
or lUS (conventional Claus).   The citrate process  also utilizes  H~S
to produce sulfur by reaction with the sulfur-laden absorbent solution.
The hydrogen required can be produced by steam reforming a suitable
feedstock such as naphtha or possibly by coal gasification.   However,
coal gasification technology is not as advanced as the recovery systems
and adds another level of complexity to FGD systems.  Hence, the principal
source of reductant for conversion to sulfur, at least for the next
few years, would probably be natural gas or naphtha.  Aside from the
economics, the uncertainties in supply and the potential constraints
on natural gas and naphtha consumption could be problematic.
     In addition to coal gasification, there are other alternatives
now being researched which could avoid the need for natural gas or naphtha.
These include:  the Foster Wheeler RESOX process in which S02 is reduced
by passage of the gas through a bed of anthracite  coal (a development
program is now being sponsored by EPRI in West Germany); and the aqueous
carbonate FGD process which utilized petroleum coke or coal for direct
reduction of spent scrubbing liquors  (a  demonstration process is now being
funded by EPA).  Allied Chemical also has a  coal reduction process.
However, these processes are many years  from commercialization  and the
current potential shortages of  natural gas and oil could impact the im-
plementation of  recovery systems.
3.4   FGD Waste and By-product Marketing
      Previous work  [11,  38] has indicated a  variety of potential uses and
markets, but the work devoted  to definitive  market assessment studies or
utilization  economics  has  been  limited.   In  part,  this has  been due  to
variability  in FGC wastes  and  uncertainties  in waste  processing and  con-
version costs.   Unknowns  regarding waste properties affecting  utilization
coupled with institutional constraints can  also act as dissentives to

utilization where FGC wastes would be a substitute for existing materials
Examples include the use of FGD gypsum as a substitute for natural gypsum
in the manufacture of construction materials (e.g., use in wallboard and
cement) and the use of stabilized wastes as fill materials.  However,
future shortages of chemicals, mineral products and construction mate-
rials may alter the incentives for utilization of FGC wastes (both fly
ash and FGD wastes).
     TVA has recently completed a series of studies for the EPA [37, 56,
67] assessing the potential marketability of wastes and by-products for
which conventional markets exist—sulfur, sulfuric acid and gypsum.
Generalized cost models were developed comparing a clean fuel strategy
with nonrecovery scrubbing, and scrubbing systems producing the desired
by-product (gypsum, sulfur, or acid).  In all cases, the SO* control
strategy was selected on the basis of minimum cost for compliance where
compliance was based on NSPS regulations for new boilers or the applicable
state implementation plan (SIP) for existing boilers as of 1976.  Non-
recovery scrubbing was based on the conventional limestone slurry process
producing sulfite or sulfate-rich material.  Sulfuric acid production
utilized the MgO scrubbing process and sulfur production was based on
Wellman-Lord/Allied technology.  Production of gypsum was assessed for
three gypsum-producing FGD systems—limestone-gypsum, Chiyoda Thorough-
bred 101 (Japanese technology), and the Dowa process (aluminum sulfate
absorption)—and the limestone-gypsum process was chosen for the market
cost comparison.  The analysis was carried out under the assumption that
abatement gypsum would be interchangeable with natural gypsum and the
supply price of natural gypsum would be $3-$6/ton.
     For those plants where production of sulfur, gypsum or acid was the
low-cost control strategy, a market simulation model was used to evaluate
the distribution of by-products in competition with existing markets.
A production cost module was used to predict market costs for elemental
sulfur producers, sulfur-burning sulfuric acid producers, by-product
sulfuric acid producers (associated with smelters), and gypsum supplied
to wallboard plants and cement plants.  A linear programming costing
model was developed which minimized the total cost to both the acid and
the utility industry subject to acid and gypsum demands being met either

from traditional sources or from substitution of  abatement by-products^
given production costs for each sulfuric acid plant,  each wallboard plant
and cement plant, and the cost of producing and transporting abatement
acid, sulfur, or gypsum at each U.S.  utility.
     The entire U.S.  utility industry was characterized from Federal
Power Commission data with respect to plant age,  fuel type capacity,
load factors, and SO  emission rates for 1978 (projected).  Out of a
total 3382 boilers at 800 power stations, 833 boilers at 187 stations
were projected to be out of compliance and were the subject of this
     In general, the results of the study indicated that  taking into
account the credit for sales of the by-products, production of sulfur,
acid, or gypsum can be competitive with conventional direct limestone
scrubbing producing waste for disposal.  Gypsum was found  to be marketable
in isolated instances and sulfuric acid was marketable in  areas near
utilities  but remote from traditional sources of supply;  however,  sulfur
was  generally not competitive with other sources of sulfur.
     Specific conclusions regarding the marketability of by-product acid
and  sulfur,  and  gypsum  that were  reached are:
     Acid and Sulfur;   For the  alternatives and  technologies
     considered, acid production  was  a  less  costly alternative
     than sulfur production in  all cases.  At  $60 per ton sulfur,
     and  $.70/MBtu increment for compliance fuel, the amount of
     acid produced and  marketed would be approximately six million
     tons from  29 plants; an  additional five million tons would
     be available as  a  low  cost alternative but  was not  competitive
     with acid  produced from  sulfur.   The  amount of  substitution
     is very sensitive  to the assumed price  of sulfur.   Generally,
      (as  could be  expected)  the by-product acid  was  competitive  in
     markets supplied by smaller, older,  remotely  located conven-
      tional acid plants.
      Gypsum:  Table 3.3 summarizes the results of  the study re-
      garding gypsum marketability.   For the conditions and

                                Table 3.3

                 Summary of TVA Gypsum Marketing Results
Total number of plants out of  compliance                           187
Lowest-cost strategy
  Clean fuel, number of plants                                     71
  Limestone slurry process, number of plants                        86
  Gypsum production and marketing, number of plants                 30
Total gypsum produced, tons                                  2,400,000
Average production per steam plant, tons                        80,000
Smallest gypsum supplier, tons                                   6,700
•^Largest gypsum supplier, tons                                  171,000
Total gypsum sold, tons                                      2,230,000
Total gypsum stockpiled, tons                                  171,000
No. of plants where part of production was stockpiled                5
Wallboard plants served                                              1
Cement plants served                                                92
Sold to wallboard plants, tons                                 95,000
Sold to cement plants, tons                                  2,135,000
Total net revenue to utilities, $                           11,076,000
Total savings to gypsum industry, $                          1,900,000
Savings to gypsum industry, %  of total cost                        1.5
Average savings per ton of gypsum purchased, $       „            0.86
Total first-year compliance cost for 113 plants using
  the limestone slurry process, $                        2,038,000,000
Reduction by marketing gypsum, $                            11,076,000
Cost reduction, %                                                  0.5
Required sulfur removal, tons                                4,109,000
Sulfur removed by gypsum process, %                                8.7
Reduction in sludge disposal by limestone slurry, %                8.0
Imported gypsum displaced, tons                                856,000
Domestic gypsum displaced, tons                              1,372,000
1978 calcining market served with abatement gypsum, %              0.8
1978 cement market served with abatement-gypsum, %                67.0
Source:   [67]

alternatives considered,  it was  found that 15  plants  could
produce gypsum from flue  gas desulfurization at  a lower  cost
than that of conventional direct limestone scrubbing  generat-
ing waste for disposal.   These 15 plants would produce
863,000 tons of gypsum annually.  An additional  25 plants
could meet compliance using gypsum producing FGD technology
at an incremental cost over conventional direct  limestone
scrubbing of less than $3/ton (the crude gypsum mining cost).
These additional 25 plants could produce another 3.4  million
tons of gypsum annually.
Of these 40 potential plants, 30 plants could produce and
market about 2.4 million tons of gypsum in competition with
the natural material.  These 30 plants would serve a total
of 93 demand points.  Only one wallboard plant would purchase
abatement gypsum, while 92 cement plants would utilize the
remainder (partly because of the higher price offered by
cement plants).
The utilization of abatement gypsum at  92  cement  plants
represents substitution for about 67% of  the projected use
of natural gypsum in cement production.   Of the  total gypsum
used by cement plants, approximately 1.1  million  tons were
projected to be imported.  Abatement gypsum was  estimated to
replace about  74% of this  imported gypsum.
Use of gypsum-producing  technology at the 30  power plants
would solve only 8.7% of  the electric utility sulfur oxides
compliance problem  and reduce the required ponding of calcium
solids by 8.0%.
In  general, production and marketing of abatement gypsum to
the  cement  industry appears to  offer an opportunity  for  steam
plants with low annual volumes  of sulfur removal to  lower their
cost  of  compliance.  There appears  to be little opportunity
to  lower  compliance cost by marketing abatement gypsum to

     the existing wallboard products industry.  The gypsum pro-
     duction alternative appears to offer only a limited potential
     to solve the utility compliance problems; however, in terms
     of a total program of waste utilization, the gypsum production
     alternative may fill a specific role in that it appears to
     meet the needs of small plants when other by-products may be
     better suited to large plants.
     Locational considerations were shown to play a major role in
     determining the feasibility of marketing of abatement gypsum.
     Specific location studies for each plant where gypsum offered
     an economic advantage, were recommended.  This could also include
     the feasibility/marketability of new wallboard producing plants.
     This study by TVA as well as most all other studies performed to
date on the utilization of FGC wastes and by-products are generally
based upon conventional uses and existing market structures.  A number
of factors could impact the future potential for waste and by-product
utilization, indtrfflng:
     •  Regulatory incentives or disincentives for utilization,
     •  Changes in institutional constraints,
     •  Depletion of existing sources of equivalent raw mate-
        rials or chemicals that can be derived from flue gas
     •  Development of new, more cost-effective FGD
        technologies, and
     •  Development of new uses for wastes and by-product

     Utilization of FGC wastes is not expected to be significantly  en-
couraged or restrained by recent environmental legislation.   Implementa-
tion of the Toxic Substances Control Act (TSCA)  conceivably  could impact
new uses; while the Resource Conservation and Recovery Act (RCRA)
ultimately could have major impact on utilization.  The regulations
under these laws are still emerging.
     The utility industry is concerned that RCRA, at least in its present
form, may not encourage utilization.  The National Ash Association has
expressed this concern [24].  These organizations are concerned that [24]:
     •  The emphasis of RCRA may be on disposal, at
        least over the near-term, and
     •  The "use constituting disposal" issue may impede
Over a long term, RCRA is clearly intended to enhance recycle of
     The TSCA established within the EPA the Office of Toxic Substances
(OTS), with broad authority to regulate the entry of  chemicals into the
environment.  With an estimated 43,000 chemicals already  in commerce,
and new ones coining into use at a rate of about 1,000 per year  [68],  it
will be necessary for the OTS to set priorities for determining  which
chemicals to test and regulate.  Because many of  these thousands of chemi-
cals are known to be far more important in terms of toxicity than FGC
wastes, it is anticipated that the  OTS will not regulate  utilization of
these wastes.  The necessity of prioritizing chemicals for testing was
recognized in the Act in Section 4(e), which established  the Interagency
Toxic Substances Testing Committee  which advises the  EPA  of priority
chemicals for testing.  To  date, the committee has listed 21 chemicals—
FGC wastes are not listed.  Unless  important  toxic effects from  FGC waste
utilization are  observed, it  is highly unlikely that  the  OTS will regulate
them in the next 5-10 years.
     The  OTS has concentrated on two  sections of  the  law  to  date,  those
calling  for an  inventory of chemicals  already in  production  and use,  and

 the development of procedures  for  premanufacturing  notification by in-
 dustry of its intent  to market a new chemical.
      The  publication of the inventory has been delayed by over a year
 from its  mandated deadline  [68].   The questionnaire was  distributed to
 electric  utilities, and FGC wastes were  reported as existing chemicals
 already in use.   This would exempt them  from the premanufacturing noti-
 fication  requirements in the future,  unless  they were being marketed
 for a significant new use.
      Procedures for premanufacturing notification have not yet been
^established;  these rules were  only proposed  in January 1979.  They are -
 unlikely  to significantly restrain utilization and  hence will not be dis-
 cussed further here.
      The  objectives of  the RCRA include  (Section 1003)  the conservation
 of  valuable material by:
      • Providing technical and financial assistance to  the states
        and local government bodies which will promote new and
        improved methods  of recovery  of  solid waste,
      • Providing for establishment  of guidelines for the recovery of
        solid wastes,
      • Promoting research and development for recovery  and recycling
        of  solid wastes,
      • Promoting the demonstration,  construction,  and application of
        resource recovery systems, and
      • Establishing a  cooperative effort among federal, state, and
        local governments and private enterprise in order to recover
        valuable materials from solid wastes.
      Based  on these objectives the Act would be expected to encourage the
 utilization of FGC wastes.  However,  there are few substantive provisions
 of  the Act which will encourage use of FGC wastes.  The strength of the
 Act is in the solid waste and hazardous waste management plans, which
 provide for the  environmentally sound disposal of wastes.

     Section 2003 provides for the establishment  of  "Resource  Conserva-
tion & Recovery Panels" - teams of personnel  to provide  technical  assis-
tance to states and local governments on solid waste management, resource
recovery, and conservation.  Funding for this program is $7-8  million
per year.
     State solid waste management plans established  in Subtitle D  are
prohibited from hindering resource recovery,  but  only limited  incentives
for resource recovery are provided at present.
     In Subtitle E, the Department of Commerce "shall encourage com-
mercialization of proven resource recovery technology by providing:
     (1)  Accurate specifications for recovered materials, and
     (2)  Stimulation of development of markets for recovered
     The specifications pertain to chemical and physical properties of
such materials with regard to their viability in replacing virgin mate-
rials in various uses.
     In Subtitle F, federal agencies are required to use recycled materials
to the greatest extent practicable.  Government specifications for procure-
ment of materials must not exclude recovered material.  EPA is responsible
for setting guidelines for federal procurement of recovered materials.
Section 6002(e) of RCRA  focuses on the  setting of guidelines  for  the
federal procurement of recovered  materials.  Ultimately,  this  could have a
significant impact on  the extent  of  utilization of  FGC  wastes.  Finally,
Subtitle H provides funding for research into  resource  recovery.
     In  addition,  another significant  support  for FGC waste utilization
is the  requirement that  the Department  of  Commerce  provide adequate
specifications  for recovered  materials  pertaining to their use in replac-
ing virgin materials.

5.1  Assessment of Utilization
     In 1977 total U.S. production of coal ash (fly  ash,  bottom ash,  and
boiler slag) was 61.6 million tons with 12.7  million tons successfully
recovered and utilized [3].   This is more than three times that used  by
any other nation during the  same time period.  On a  percentage basis,
21% of the ash produced was  thus utilized.  In contrast,  Western Europe
uses a much higher percentage of their coal ash and  Japan uses a much
greater percentage of their  production of FGD wastes.   A variety of ex-
planations have been given for this fact, usually in some way related
to the research perspective  of the organization doing the assessment.
Specifications, quality control, lack of markets, consumer bias, lack of
technical development, and many other reasons have been put forward and
are hindering increased utilization of ash and sludge in the United
States.  All of these reasons are valid in at least  some instances, and  some
are universally valid.  On balance, a combination of three types of
factors constrain FGC waste  utilization:
     •  Technical considerations, particularly in comparison with
        alternative materials,
     •  Institutional barriers related to poor understanding of
        the by-products and failure to develop markets by either
        the utility industry or user industries, and
     •  Possible environmental concerns related to some uses.
5.1.1  Technical Considerations
     Since coal ash and FGD wastes are by-products,  quality control in
the production of these materials is a major factor.  Utilities are in
the business of producing power; ash and FGD wastes  are simply by-products
of their operation.   Since ash and FGD waste characteristics are influenced
by coal properties, system design, and operating conditions, quality
control at the utility can be a problem.  Some progress has been made in
setting appropriate standards for quality in FGC wastes  for utilization
purposes.  In some instances, uncertainty exists as to what waste  proper-
ties are important for a particular use.  Additional standards and accep-
tance  by users are needed to make utilization more  attractive.

      Transportation of the FGC wastes is another constraint.  Since most
proposed uses are in low value applications, the economic radius of the
market is often small.  Virgin materials may also have a more desirable
transportation rate structure.  The economic margin in favor of FGC waste
use in preference to an alternative material is usually not large.
5.1.2  Institutional Barriers
     Perhaps the largest institutional barrier has been that the potential
consumer industries for FGC waste utilization are conservative, traditional
industries.  Such an industrial sector is reluctant to consider new ap-
proaches that would be required if FGC wastes are to be used.  Furthermore,
fVom the utility viewpoint, it is preferable to have all FGC wastes
handled through a single source as opposed to many small consumers buying
from them.  Since most users cannot accommodate the entire output of a
large utility, brokers can enter the picture (as well as for other
reasons) which adds another variable.  Tax and transportation rate struc-
tures also disfavor by-product use.  Basic changes would have to occur
in all of the above factors if FGC by-product utilization is to be
5.1.3  Other Factors
     A variety of less obvious issues also plague utilization.  The poten-
tial effect of RCRA regulation is of concern vis-a-vis disposal.  There
also is concern over whether fly ash could be declared toxic or radioactive.
Product liability concerns may have an effect on utilization.  The high
rate of inflation and the rapid rise in energy and raw material costs
make the task of assessing the economic viability of new utilization
schemes in the future somewhat arbitrary.  An issue requiring clarification
to enhance FGC waste utilization is that related to short and long-term
liability.   There is some hesitancy on the part of some sectors of the in-
dustry to sell FGC wastes for use in otherproducts such as wallboard or
cement.  If at a future date a product made with FGC wastes as one of the

raw materials is found hazardous or harmful,  what  will  be  the  liability
to the generator of FGC wastes?  All of these concerns, as well  as  others,
both by themselves and in combination tend to hinder increased utilization
of FGC wastes.
     Considering the anticipated growth in the generation  of FGC wastes,
removal of, or reduction in, barriers to FGC waste utilization becomes
important.  In some cases, technical problems preclude  successful large-
scale utilization.  The more serious impediments are apparently  insti-
tutional in nature but can potentially be overcome by concerted  efforts.
Utility companies previously have been concerned primarily with  the pro-
duction of electricity:  marketing of waste by-products has been secondary.
Wastes have been viewed as a nuisance and liability rather than  as a
potential asset to be sold and produced along with electricity.   The
utility companies not only need to envision the importance of marketing
their FGC wastes as by-products, but also must aggressively develop mar-
kets with education being a key factor in overcoming the reluctance on the
part of many industries to utilize FGC wastes.  Potential users are
concerned about chemical and physical variability of the material, lack
of existing specifications for use in manufacturing processes, and fear
of a lack of constant supply depending upon the vagaries of plant opera-
tion.  Furthermore, in those uses where environmental  or other regulatory
concerns exist, policy decisions are needed to remove  elements of uncertainty.
5.2  R&D Assessment
     The use of fly ash in construction (e.g., cement, concrete, aggre-
gate, fill) is a relatively highly developed end-use.  These materials are
in widespread full-scale  commercial use on a routine basis.  Little research
is currently being done on new end-uses within the construction sector
because of this development.   However, several organizations either have
been or currently are  sponsoring a variety of technical programs aimed
at identifying and quantifying the effect of fly  ash on these materials.
Much of this work is aimed  at  concrete  (NBS, Bureau of Reclamation, Corps
of Engineers) although work has been  done by the  FHWA  on  use  in road con-
struction.   It appears  that any additional EPA research activity  in tech-
nical areas beyond what is  currently  ongoing is not warranted.

     Stabilization of FGD waste represents a significant potential for
using fly ash.  However, this is probably more appropriately considered
a disposal option.  Any additional research sponsored by the EPA on the
utilization aspects of this end-use is probably not warranted.
     A variety of new uses for fly ash currently are being investigated,
mostly at the research or bench scale level.  Some of these processes may
prove viable in a longer time frame; some (e.g., vanadium recovery) are
currently being practiced on a small scale.  It is desirable that this
type of research continue, but additional funding by the EPA is probably
not warranted at present.
     The use of bottom ash and boiler slag is quite extensive, about 60%
of the boiler slag is consumed.  The markets served are fairly well de-
veloped, and use has been relatively constant over the past several years.
Additional research is probably not required in this area.
     FGD wastes currently are being utilized abroad (notably in Japan)
where they are generally oxidized to produce gypsum for sale to the cement
or wallboard industry.  There currently is no utilization of FGD wastes
in the United States, principally because FGD wastes have not been pro-
duced in significant quantities until recently (i.e., full-scale lime/
limestone scrubbing is relatively new in the United States).  The poten-
tial utilization of FGD wastes is dependent upon successful solutions of
a variety of technical and non-technical problems in addition to those
mentioned earlier.
     Gypsum production is the only utilization option which is near full-
scale commercial development in the United States.  The EPA is sponsoring
a number of programs which will demonstrate oxidation of FGD waste to
gypsum, but these have been aimed primarily at enhancing the disposal
properties of the waste.  (See Volume 5.)  If gypsum production does become
a commercial reality, some market penetration can be expected.  However,
this will still be only a small fraction of total FGD waste generation,
estimated to be about 38 to 57 million tons per year by 2000  [1J.  The
TVA has done some work on the potential market size for abatement gypsum
using a least-cost LP model.  A continuation of this work on a more general
market-institutional level may be useful.

     Several other end-uses are being considered by  various organizations,
but are not at the same level of development as  gypsum.   TRW has  proposed
a process whereby FGD waste is used as a reagent for the extraction of
alumina from kaolin clay and by-product dicalcium silicate is  produced.
A sulfur byproduct is produced.  Based on the economic analysis,  it is
unclear whether the process is viable at present.
     Two projects are being sponsored by EPA on the development of a
sulfur production process, and a fertilizer production process by Pullman-
Kellogg and the TVA, respectively.  The economics of both processes are
uncertain at this time and should be investigated further.
5.3  Future Utilization Considerations and Data Gaps
     By the year 2000, the U.S. minerals deficit will exceed the energy
deficit, possibly approaching  $100 billion dollars  [28].  The United
States is currently  dependent  on foreign sources  for 22  of the 74 non-
energy essential minerals.  Of the 12  crucial elements,  seven are  imported
in quantities  greater  than 50% of consumption [28, 53].  Utilization of FGC
wastes can  potentially help offset this deficit and provide an alternative
domestic source  for  a  variety  of minerals,  thereby  reducing dependence  on
imports.  The  presence  of  these minerals in  coal  ash  and FGD waste,  and
the  large amounts  of FGC wastes available,  are  incentives for basic  R&D
on conversion  and/or extraction processes.
     Much research has  already been  done on  extracting alumina,  magnetite,
and  other minerals  from ash  and FGD.   However,  these  processes are not  v.
currently  capable of competing generally with more  established processes,
and  in some cases the  market does  not exist because of more readily  avail-
able alternate sources of  minerals.   However,  utilization R&D is really
just one  facet of a long-term product development program with FGC as the
 raw  material.   As such, commercial marketability  should be thought of in
a long-term (e.g.,  10  years  or more)  time  frame and FGC wastes should
be considered an eventual  source  of  minerals or other raw materials.
This is  not to say that some processes might not  be viable sooner; only
 that R&D should not be discontinued because a process does not appear
 to be economic in the near term.

     Additionally, depending upon the current market situation, the
abolishment of disincentives or the establishment of incentives may be
necessary at the state or national level for the effective promotion of
the use of FGC waste as a resource.  Ultimately, utilization of FGC waste
should be viewed as an alternative source of minerals, not a disposal
option, although the promotion of utilization may help to alleviate dis-
posal problems.
     An overall product development program may be thought of as a
series of steps (see Figure 5.1) which lead to introduction and (hopefully)
acceptance of the product in the marketplace.   The steps generally follow
three distinct lines representing the following criteria:
     •  Technical feasibility,
     •  Economic attractiveness, and
     •  Marketability.
     The initial step of identifying the potential products may be quite
involved as it ideally looks at all possible products, and considers such
things as technical complexity, commercialization requirements, etc., in
an evaluation of which products have the greatest probability of success
in the largest market.  For each product chosen, a technical, economic
and market evaluation must be conducted.  If all three yield positive
results, commercialization (implementation) may begin.
     Even if the product is technically, economically and marketably
qualified, it may not be accepted in the marketplace for a variety of
reasons beyond the direct control of the market (externalities).  It is
desirable to identify all external influences which may affect market
acceptance of the product at the earliest possible date, and to either
correct them or adjust for them in the product.
     Three areas could benefit from additional research.
     Product Evaluation
     From a general point of view, which of many products suggested for
FGC wastes are the most attractive technically, economically, and in the
marketplace, in a 10-20 year time frame?

Economic (Cost)
Economic (Cost)
                    Demons t rat ion
             Source:   Arthur D.  Little,  Inc.
                                     Figure 5.1   Product  Development  Logic

      Commercialization Requirements
      The  issue of quality control is a technical area which is still
 cloudy.   From the production point of view, the utility has some control
 over  the  carbon  content of  fly ash, and the characteristics of FGD waste.
 Which characteristics are important for utilization?  How do various
 properties affect, for example, concrete?  What effects do storage and
 transportation have on utilization?  How do ash characteristics vary
 across the country?  How does this affect utilization?  Can blending be
 useful for quality control?
     A better understanding of the various institutional constraints which
affect FGC waste utilization would be very useful.  What constraints
exist?  How are the constraints interrelated?  How can they be overcome?
Which should be overcome?  How are institutional factors different abroad?
5.4  Emerging Technologies
     This report has been focused on analysis and utilization of FGC wastes
produced by conventional combustion of coal.  This will continue to be
the most important method to utilize coal for the next twenty (20) years.
However, a number of other methods of utilization of coal are emerging
and will reach significant commercialization in the next twenty (20)
years.  These include:
     •  FLuidized bed combustion (FBC) of coal,
     •  Coal preparation processes,
     •  Coal liquefaction,
     •  Low Btu gasification and combined cycle
        generation of power, and
     •  Magnetohydrodynamics (MKD).
     These have been largely discussed in Volume 1, Section 4.8.   All
these technologies will generate wastes; however,  the quantity,  the
physical and chemical characteristics, and the point of generation (mine
end, utility end or other) of the wastes would be  different from those
associated with conventional coal combustion.

     Additional focus on the waste  generated by such  technologies and
exploration of potential utilization  of  such wastes should be an essential
part of the development of these emerging  technologies.

 1.   "Health and Environmental  Impacts of Increased Generation of Coal
     Ash  and FGD Sludges," Office of Research and Development, Environ-
     mental Protection Agency,  Washington, B.C., December 1977.

 2.   Arthur D.  Little, Inc.,  "An Evaluation  of  the Disposal of FGD Waste
     in Mines  and  the Ocean  —  Initial Assessment."   EPA-600/7-77-051,
     Environmental Protection Agency, Washington, D.C., May 1977.

 3.   National  Ash  Association,  Ash  at Work,  Vol. X, No. 4, Washington, D.C.

 4.   Browning,  J.  E., Ash -  The Usable Waste, Chemical Engineering,
     April  16,  1973, pages 68-70.

 5.   National  Ash  Association,  Ash  at Work,  Vol.  IX,  No.  6,  1977.

 6.   Faber,  J.  H., Disposal  and Potential Uses  of  Fly-ash,  presented at
     The  International  Coal  Utilization  Convention,  Houston,  Texas,
     October 17-19, 1978, pages 319-335.

 7.   Mayers,  J. F., R.  Pichumani,  and  B. S.  Kappies,  Fly Ash as a Con-
     struction Material for  Highways,  FHWA-IP-76-16,  Federal Highway
     Administration.  U.S. Department  of Transportation,  May 1976,
     Contract  #DOT-FG-11-8801.

 8.   Barber,  E.G., The  Utilization of  Pulverized Fuel Ash,  Journal of
     the  Institute of  Fuels. Vol.  43,  No.  348,  January 1970.

 9.   Gray,  D.H.,  and Y.K. Lin,  Engineering Properties of Compacted Fly-
     ash, Journal of the Soil Mechanics and Foundation Division, ASCE,
     Vol. 98,  No.  SM4,  Paper 8840, April 1972.

10.   Rohrman,  F.A., Analyzing  the Effect of Fly-ash on Water Pollution,
     Power, August 1971.

11.   Technical and Economic Factors Associated with Fly Ash Utilization,
     Final Report, PB-204 408, Environmental Protection Agency, Washington,
     D.C., prepared under EPA  Contract No.  F04701-70-C-0059 by Aerospace
     Corporation,  El Segundo,  California, July  26, 1971.

12.   Ormsby,  C., U. S.  Department of Transportation,  Federal  Highway
     Administration,  McLean, Virginia,  personal communication with
     D.  E.  Kleinschmidt of Arthur D. Little, Inc. ,  1978.

13.  Lindberg, H.A., Use of Fly Ash in Portland Cement Concrete and
     Stabilized Base Construction, FHWA Notice N-5080.4, Federal Highway
     Administration, Washington, D.C., January 17, 1974.

14.  ASTM Specification C-593, American Society for Testing and Materials,
     Philadelphia, Pennsylvania, 19103.

15.  Arthur D. Little, Inc., Environmental Consideration of Selected
     Energy Conserving Manufacturing Process Options, Vol. X, Cement
     Industry Report, EPA-600/7-76-034J, Industrial Pollution Control
     Division, IERL, Environmental Protection Agency, Cincinnati,  Ohio,
     December, 1976.

16.  Capp, John P. and Spencer, John D., Fly Ash Utilization - A Summary
     of Applications and Technology, U.S. Bureau of Mines, Washington, D.C.,
     Information Circular 8483, 1970.

17.  Brown,  P. W.,  et al,  Limitations to Fly Ash Use in Blended Cements,
     National Bureau of Standards, Washington, D. C.

18.  Mather,  K.,  U. S.  Army Corps of Engineers, Waterways Experiment
     Station, Vicksburg,  Mississippi, personal communication with
     D. E.  Kleinschmidt of Arthur D. Little, Inc., 1978.

19.  ASTM Specification C618-77, American Society for Testing and Materials,
     Philadelphia, Pennsylvania, 19103.

20.  Brown, P.W.,  eit al, The Utilization of Industrial Byproducts in Blended
     Cements, Proceedings of the Fifth Mineral Waste Utilization Symposium,
     Chicago, Illinois, April 13-14, 1976, pages 278-284.

21.  Davis, R.E.,  e£ al, Weathering Resistance of Concretes Containing Fly-
     ash Cements, Journal of the American Concrete Institute, January 1941.

22.  ASTM Committee C-9 on Concrete and Concrete Aggregates, American Society
     for Testing and Materials, Philadelphia, Pennsylvania, 19103.

23.  Harboe,  E.,  Department of the Interior, Bureau of Reclamation, Denver,
     Colorado, personal communication with D. E. Kleinschmidt of Arthur D.
     Little,  Inc.,  1978.

24.  Faber,  John,  National Ash Association,  Washington, D. C., personal
     communication with Chakra J.  Santhanam of Arthur D. Little, Inc.,  1979.

25.  Weaver,  Val E.,  Division of Fossil Fuel Utilization, Department of
     Energy,  Germantown, Maryland, personal communication with Chakra J.
     Santhanam of Arthur D.  Little, Inc., 1979.

26.  Moulton, Lyle, K., Bottom Ash and Boiler Slag,  Proceedings, Third
     International Ash Utilization Symposium, March 13-14, 1973, pp 148-169.

27.  Morrison,  R.  E.,  "Power Plant  Ash  -  A New Mineral  Resource,"
     Proceedings of the Fourth International Ash  Utilization Symposium,
     St.  Louis, Mo.,  March 24-25,  1976, pp 204-210.

28.  Canon, R.  M., et^ al_. , Removal and  Recovery of Metals  from Fly Ash,
     presented  at the Conference on Ash Technology and  Marketing,  London,
     October 1978.  Oak Ridge National  Laboratory, Chemical Technology
     Division,  Oak Ridge,  TN.

29.  Murtha, M. J. and G.  Burnet,  Extraction of Alumina from Bituminous
     Coal Fly Ash by the Lime-Soda Sinter Process.  Presented at the
     Conference on Ash Technology and Marketing,  London, 1978.
     Ames Laboratory and Department of  Chemical Engineering, Iowa  State
     University, Ames, la.

30.  Berke, J.  National Bureau of Standards, Washington, D. C.,
     personal communications with D. E. Kleinschmidt of Arthur D.  Little,
     Inc, 1978.

31.  Philleo, R. Army Corps of Engineers, Concrete Branch, Washington,
     D. C., personal communications with D. E. Kleinschmidt of Arthur D.
     Little, Inc., 1978.

32.  Humphreys, K., Coal Research Bureau, West Virginia University,
     Morgantown, W. Va., personal communication with D. E. Kleinschmidt
     of Arthur D. Little, Inc., 1978.

33.  Natof, S., Department of Energy, Washington, D. C., personal
     communication with D. E. Kleinschmidt  of Arthur D. Little, Inc.,

34.  Smith, L. M., et_ al.. , Technology for Using  Sulfate Waste  in
     Highway Construction, PB-254-815/4ST,  Federal Highway Administration,
     Washington,  D. C., December 1975.

35.  Brown, P. W., National  Bureau  of Standards,  Washington, D. C.,
     personal  communication  with D.  E. Kleinschmidt of  Arthur  D.  Little,
     Inc.,  1978.

36.  Anon,  TVA to Produce Mineral Wool from Coal Ash Slag,  Skillings
     Mining Review. July  15, 1978,  page  15.

37.  Parker, F.,  Tennessee  Valley Authority, Chattanooga, Tn.,  personal
     communication with D.  E. Kleinschmidt  of Arthur D. Little, Inc.,

 38.  Condry, L.  Z.,  et al:   Potential  Utilization of Solid Waste  from
     Lime/Limestone  Wet-Scrubbing of Flue Gases, presented at the
     Second International Lime/Limestone Wet-Scrubbing Symposium,
     New Orleans, November  1971,  work  performed  under  EPA contract
     CPA 70-66 at West Virginia University, Morgantown, W. Va.

 39.  Humphreys, K. K.,  Fifteen Years  of  Service  to  the  State of West
     Virginia, A Key Word  Index  of  Coal  Research Bureau Reports,
     Report No. 140, Coal  Research  Bureau, West  Virginia University,
     Morgantown, W. Va., January 1977.

 40.  Humphreys, K. K.,  Operating and  Capital  Costs  of Producing Fired
     Structural Products from Waste Coal Ash, Report No. 98, Coal
     Research Bureau, West Virginia University,  Morgantown, W. Va.,
     July  1974.

 41.  Slonaker, J. F., The  Role of Fly Ash Brick  Manufacture in Energy
     Conservation, Report  No. 149,  Coal  Research Bureau, West Virginia
     University, Morgantown, W.  Va.,  November 1977.

 42.  Slonaker, J. F., Production of Forty Percent Core  Area Fly Ash
     Brick using a Southern West Virginia Fly Ash,  Report No. Ill,
     Coal  Research Bureau, West  Virginia University, Morgantown, W. Va.,
     October 1975.

 43.  Slonaker, J. F., A New Method  for Increasing the Durability of
     Fly-ash Structural Products, Report No.  141, Coal  Research Bureau,
     West  Virginia University, Morgantown, W. Va.,  June 1977.

 44.  Slonaker, J. F., A Study of the  Effect of Firing Conditions Upon
     Fly-ash Structural Products, Report No.  128, Coal  Research Bureau,
     West  Virginia University, Morgantown, W. Va.,  November 1976..

 45.  Slonaker, J. F., Coal Research Bureau, West Virginia University,
     Morgantown, W. Va., personal communication  with D. E. Kleinschmidt
     of Arthur D. Little,  Inc.,  1978.

 46.  1977  Federally Coordinated  Program  of Highway  Research and Develop-
     ment, U.S. Department of Transportation, Federal Highway Administration,
     Washington, D. C.

 47.  FCP Annual Progress Report  Year  Ending September 30, 1978.  Project
     No. 4C, "Use of Waste as Material for Highways," U.S. Department of
     Transportation, Federal Highway  Administration, Washington, D. C.

 48.  Use of Waste Sulfate  for Remedial Treatment of  Soils,  Vol. II,
     Appendices, Final  Report No. FHWA-RD-76-144, U.S.  Department of
     Transportation, Federal Highway  Administration, Washington, D. C.,
     by Midwest Research,  August 1976.

 49.  Use of Waste Sulfate  for Remedial Treatment of Soils, Vol.  I,
     Discussion of Results, Final Report No.  FHWA-RD-143, U.S. Depart-
     ment of Transportation, Federal Highway Administration, Washington,
     D. C., August 1976.

50.  Osborne,  M.,  EPA-IERL, Research Triangle Park,  N.  C., personal
     communication with C.  J.  Santhanam of Arthur D. Little, Inc.,  1979.

51.  Tuttle, J., et al_._, EPA Industrial Boiler FGD Survey:  First
     Quarter 1979, EPA-600/7-79-067b, IERL, U.S. Environmental
     Protection Agency, Washington, D. C., April 1979.

52.  Duval, W. A., et^ al^, State of the Art of FGD Sludge Fixation,
     Final Report, EPRI-FP-671, EPRI RP 786-1, Michael Baker Associates,
     Beaver, Pa., January 1978.

53.  Morgan, J. D., "Supply and Demand of Corrosion Resistant Minerals,"
     Chem. Eng. Progress, March 1978, pp 25-31.

54.  Lefond, S. J., editor, Industrial Minerals and Rocks, 4th edition,
     American Institute of Mining, Metallurgical and Petroleum Engineers,
     1975, pp 710, ff.

55.  Corrigan, P. A., Preliminary Feasibility Study of Calcium Sulfur
     Sludge Utilization in the Wallboard Industry, prepared by TVA under
     Interagency Agreement No. EPA-IAG-D4-0527 for Control Systems Lab,
     Research Triangle Park, N. C., June 21, 1974.

56.  Bucy, J. I. and J. M. Ransom, Potential Markets  for  Sulfur  Dioxide
     Abatement Products, Paper presented at Flue Gas  Desulfurization
     Symposium, Hollywood, Florida, November 8-11, 1977.

57.  Proceedings, Fourth International Ash Utilization Symposium,
     St. Louis, Mo., sponsored by the National Coal Association  et al.,
     compiled by John H. Faber et^ al., March 24-25, 1976.

58.  Taylor, W. C. and J. C. Haas, Potential Uses of  the  Byproduct from
     the Lime/Limestone Scrubbing of  S02 from Flue Gases, Paper  presented
     at the AIME meeting, Dallas, Texas, February 23-28,  1974; Preprint
     No. 74-H-47.

59.  Terman, G. L., Solid Wastes from Coal-Fired Power Plants:   Use or
     Disposal on Agricultural  Lands,  Bulletin Y-129,  National Fertilizer
     Development Center, Tennessee Valley  Authority,  Muscle  Shoals, Ala.,
     June  1978.

60.  Leo,  P.  P.  and J.  Rossoff,  Treatment  and  Disposal of Flue  Gas
     Cleaning Wastes  from Utility  Power  Plants:   R&D  Status,  Draft
     Aerospace  Report No.  ATR-76 (72-97-01),  Aerospace Corporation,
     Los Angeles, Ca.,  March  1976.

61.  Leo,  P.  P.  and J.  Rossoff,  Control  of Waste  and  Water  Pollution
     from  Coal-Fired  Power  Plants:   Second R&D Report, EPA-600/7-78-224,
     U.S.  Environmental Protection Agency, Washington, D. C.,  prepared
     under Contract 68-02-1010 by  Aerospace Corporation,  Los Angeles,  Ca.,
     November 1978.

62.  Leadbetter,  W. B., Texas Transportation Institute,  Texas A&M University,
     College Station, TX,  personal communication with D.  E.  Kleinschmidt of
     Arthur D.  Little, Inc.,  1978.


63.  Jones, J. W., IERL, U.S. Environmental Protection Agency, Washington,
     D. C., personal communication with D. E. Kleinschmidt of Arthur D.
     Little, Inc., 1978.

64.  Cosgrove, T. H. and E. P. Motley, Utilization of Lime/Limestone
     Waste in a New Alumina Extraction Process, Draft TRW Report No.
     29670-6008-RU-01, U.S. Environmental Protection Agency, Washington,
     D. C., EPA Contract No. 68-01-3152, June 1978.

65.  Arthur D. Little, Inc., Estimates.

66.  Pearse, G. H. K., "Sulfur Economics and New Uses," Presented at
     the Canadian Sulfur Symposium, Ottawa, Ontario, Canada, May 30 -
     June 1, 1974.

67.  Ransom, J. M. et^ al., Feasibility of Producing and Marketing Byproduct
     Gypsum from S02 Emission Control at Fossil-Fuel-Fired Power Plants,
     EPA Report EPA-600/7-78-192, TVA Bulletin Y-137, U.S. Environmental
     Protection Agency, Washington, D. C., October 1978.

68.  Science. Vol. 202, November 10, 1978, p 598.

69.  Rush, R. E. and R. A. Edwards, Evaluation of Three 20MW Prototype
     Flue Gas Desulfurization Processes, EPRI-FD-713, Electric Power
     Research Institute, Palo Alto, Ca., March 1978.

70.  Maxwell, M. A. et al., Sulfur Oxides Control Technology in Japan,
     Interagency Task Force Report to Senate Committee on Energy and
     Natural Resources, June 30, 1978.

71.  Clifton, J. R., P. W. Brown and G. Frohndorff, Survey of Uses of
     Waste Materials in Construction in the United States, NBSIR 77-1244,
     National Bureau of Standards, Washington, D. C., July 1977.

72.  National Ash Association, Ash at Work, Vol.  X, No. 5, Washington,
     D. C., 1978.

73.  Anon, Fly Ash Shows Promise as Plastics Filler, Chemical and
     Engineering News, May 8, 1978, p 29-30,

Army Corps of Engineers, current ash utilization research  2-31

     production from ash, research  2-36
     production from FGD wastes     3-13
Boiler slag
     physical properties  2-5
     utilization - see Utilization of ash
Bottom ash, physical properties  2-5    (see  also Vol.  Ill)
Bureau of Reclamation, current ash utilization research  2-35

     bulk density  2-4
     research on use as plastic filler  2-42
Chemical recovery, from FGD wastes  3-13
Coal ash  2-1
     chemical composition  2-2, 2-3    (see also Vol.  Ill)
     research on fly ash in  2-34, 2-35, 2-37,  2-38, 2-40, 2-43
     use of fly ash in, See - Utilization  of ash

Department of Energy  (DOE), ash utilization  study, 2-37
Dry scrubbing wastes  3-2
     chemical composition  3-5    (see also Vol. Ill)

Environmental Protection Agency  (EPA)
     FGD waste utilization research   3-17, 3-20
     regulation affecting utilization   4-1 to  4-3

Federal Highway Administration  (FHA),  ash  utilization  research  2-38
Fertilizer, from FGD wastes  3-12,  3-17
FGD stabilization, with  fly ash   2-27
FGD wastes
     nonrecovery systems  3-1 to  3-5
     recovery systems     3-25  to 3-29
     research and development programs  3-14,  3-16
             see also -  Research  and  development, FGD
     utilization  3-6    see also Utilization  of FGD wastes
Fly ash
     collection systems  2-2
     emission standards  2-1
     physical properties 2-4
     pozzolanic properties, affect  on physical properties   2-4
     research and development programs  2-31
           (see also  research and  development,  Ash)
     utilization  2-5      (see  also Utilization of ash)
     wet  vs. dry  collection systems  2-30

 General Motors,  research  on  ash  as plastic filler   2-42
 Gypsum, from FGD wastes
      impurities  in  3-8
      in Japan       3-8
      marketing      3-30
      potential use  in U.  S.   3-9
      research on 3-16, 3-30
      as soil additive  3-11
      wallboard   3-7

 Insulation,  production from  ash  2-41

 Lightweight  aggregate, production from ash  2-25

 Mineral recovery from ash 2-29
      research on 2-41, 2-43

 National Bureau  of  Standards (NBS), current ash research  2-39
 Nonrecovery  FGD  systems
      chemical composition of waste  3-3, 3-5
      classification of wastes       2-1
      forced  oxidation of  3-4
      gypsum  production from  3-4, 3-7 to 3-9, 3-11
      utilization of wastes from  3-6 to 3-12

 Recovery FGD systems  3-25
      energy use  in    3-29
      marketing wastes from   3-29
      sulfur  and  sulfuric  acid from  3-27, 3-28
      wastes  from 3-29

 Regulations affecting FGC utilization
      Resource Conservation and Recovery Act (RCRA)   4-1
      Toxic Substances Control Act (TSCA)             4-2
 Research and development, ash utilization related
         (see also  specific  organization)
      alkali-silicate reaction in concrete,  2-35, 2-40
      brick from  ash  2-36
      cement additive  2-43
      concrete, use of ash in  2-34, 2-35, 2-37
      highway construction, use of ash in  2-39
      insulation,  from boiler slag  2-41
     mineral recovery  2-41,  2-43
     plastic filler, ash as  2-42
      sulfate resistance of concrete  2-34, 2-35, 2-40
Research and development,  FGD utilization related,
         (see also  specific  organization)
     alumina production from clay,  with FGD waste  3-20
     fertilizer production  3-17
     lightweight  aggregate from  3-23

     marketing; sulfur,  sulfuric acid,  gypsum  3-30
     road construction  2-49
     sulfur production  3-17

Stabilization of FGD with fly ash  2-27

Tennessee Valley Authority (TVA)
     ash related research  2-41
     FGD related research  3-17, 3-30

Texas A&M University, FGD related research  3-23

Utilization of ash
     as aggregate substitute, 2-25
     as blast grit, 2-27
          as blending agent  2-20
          cement production technology  2-17
          as raw material in, 2-17
          advantages of, 2-21
          alkali/aggregate reaction, 2-22
          disadvantages of, 2-23
          freeze/thaw durability, 2-23
          heat of hydration effects, 2-22
          specifications for use, 2-20
          strength effects, 2-22
          sulfate resistance, 2-21
          workability, 2-22
     constraints to increased usage,  5-2
     current usage  2-5, 2-6
     economic considerations, 2-25 to 2-27
     fill material  2-10
          limitations  2-12
          physical properties   2-10
          types of ash used for   2-13
     for FGD stabilization  2-27
     ice control  2-27
     institutional barriers to use   5-2
     in lime/fly ash/aggregate mixtures   2-24
     market considerations  2-25  to  2-27
     mineral recovery  2-29
     regulations affecting  4-1
     research assessment  5-2
     research and development programs  2-31
     roofing granules  2-27
     soil stabilizer  2-13
          economics   2-16
          fineness as indicator for  usefullness   2-16
          suitability of  ash  2-13
     trends  2-5,  2-6

Utilization of FGD wastes  2-6
     aggregate substitute  3-10
     brick production      3-13
     chemical recovery  3-13
     fertilizer production  3-12
     gypsum production, for wallboard  3-7
          impurities in  3-8
          notential in U. S.  3-9
          use in Japan  3-8
     research on  3-14, 3-16
     soil additive  3-11
     structural fill  3-7

West Virginia University, current ash utilization research  2-35

(Please read Instructions on the reverse before cot Dieting)
1. REPORT NO. 2.
4. TITLE AND SUBTITLE Waste and Water Management for
Conventional Coal Combustion Assessment Report —
1979; Volume IV. Utilization of FGC Wastes
7 AUTHORISE ^ j Santhanam , R. R. Lunt , C. B. Cooper ,
D.E.Klimschmidt.I.Bodek, and W. A. Tucker (ADL);
and C.R.Ullrich (Univ of Louisville)
Arthur D. Little, Inc.
20 Acorn Park
Cambridge, Massachusetts 02140
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
March 1980
Final; 9/77-8/79
is. SUPPLEMENTARY NOTES IERL-RTP project officer is Julian W. Jones, Mail Drop 61, 919/
The report, the fourth of five volumes , focuses on utilization of coal ash
                -   '                           7
 and FGD wastes. With increasing utilization of coal, generation of these wastes is
 expected to grow, but at a slower rate than generation, thus increasing the volume
 of wastes sent to disposal.  Many uses for coal ash have been developed in three
 categories: as fill material; in the manufacture of cement,  concrete, and pave-
 ments; and in miscellaneous uses such as ice  control and blasting grit. In 1977,
 about 21% of the 61. 6 million tons of coal ash generated was utilized. Current R and
 D projects on ash focus on  understanding existing uses and developing new uses
 including mineral recovery. FGD wastes are not presently used in the U.S.  Poten-
 tial FGD utilization options may include use as gypsum substitutes, as fillers and
 soil conditioners, in cement and concrete manufacture, and construction of artifi-
 cial reefs.  Technical, environmental, and institutional barriers  (the last being the
 most important) constrain utilization.  Data gaps remain in quality requirements
 for using coal ash and FGD wastes in specific applications and understanding the
 instiutional constraints to utilization.
                            KEY WORDS AND DOCUMENT ANALYSIS
Flue Gases
Release to Public
Pollution Control
Stationary Sources
Flue Gas Cleaning
Waste Utilization
19. SECURITY CLASS (This Report)
20. SECURITY CLASS (This page)
c. COSATI Field/Group |
13B 07B
2 IB 13H
EPA Form 2220-1 <»-73)