DoE
EPA
United States
Department of Energy
Division of Solid Fuel
Mining and Preparation
Pittsburgh PA 15213
FE-9002-1
U.S. Environmental Protection Agency
Office of Research and Development
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-006
January 1979
Characterization of Solid
Constituents in
Blackwater Effluents
from Coal Preparation
Plants
Interagency
Energy/Environment
R&D Program Report
-------
-------
FE-9002-1
(EPA-600/7-79-006)
January 1979
Distribution Category UC-90b
Characterization of Solid Constituents
in Blackwater Effluents from Coal
Preparation Plants
by
F.F Apian and R. Hogg
Pennsylvania State University
University Park, Pennsylvania 16802
EPA/DoE Interagency Agreement No. DXE685AK
Program Element No. EHE623A
EPA Project Officer: David A. Kirchgessner DoE Project Officer: Richard E. Hucko
Industrial Environmental Research Laboratory Division of Solid Fuel Mining and Preparation
Research Triangle Park, NC 27711 Pittsburgh, PA 15213
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
and
U.S. DEPARTMENT OF ENERGY
Division of Solid Fuel Mining and Preparation
Pittsburgh, PA 15213
-------
Final Project Report, Part I
U.S. Department of Energy
Project No. ET-75-G-01-9002
Characterization of Solid Constituents from
Blackwater Effluents from Coal Preparation Plants
by
F. F. Apian
R. Hogg
Mineral Processing Section
Department of Material Sciences
The Pennsylvania State University
University Park, PA 16802
June 1977
-------
ACKNOWLEDGEMENTS
The authors wish to acknowledge Mr. Michael Placha, currently
with Birtley Engineering Corporation for his invaluable effort in
the development of the separation and sizing techniques and for
performing several of the size analyses described in this report.
Special thanks are also due to those companies who supplied
the black water samples.
11
-------
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
LIST OF TABLES vi
LIST OF FIGURES ix
I. INTRODUCTION 1
II. BACKGROUND AND THEORY 5
A. Introduction 5
B. Overview of Coal Preparation 6
C. Overview of Flocculation 11
D. Ash-Forming Minerals in Coal 16
III. EXPERIMENTAL MATERIALS AND METHODS 22
A. Samples 22
B. Identification and Quantification of the
Solid Constituents in Blackwater 25
1. Sample Preparation 25
2. Analysis of Carbonaceous Material 27
a. Introduction 27
b. Ash analysis 28
c. Sulfur analysis 28
3. Mineral Identification and Quantification . . 28
a. Introduction 28
b. Identification 29
c. Quantification 32
C. Particle Size Characterization 36
1. Sample Preparation 36
2. Sizing Method 37
D. Surface Properties of the Coal and Ash-Forming
Minerals 39
IV. EXPERIMENTAL RESULTS AND DISCUSSION OF
MINERALOGICAL CHARACTERIZATION . . 41
A. Identification and Quantification of the
Solid Material Present in Blackwater ....... 4]
111
-------
Page
1. Introduction 41
2. Carbonaceous Fraction 41
a. Introduction 41
b. Eastern samples 42
c. Western samples 46
d. Summary 47
3. Ash-Forming Mineral Matter 50
a. Introduction 50
b. Eastern samples 51
c. Western samples 66
d. Summary 70
B. Particle Size Analysis . 71
1. Evaluation of Sizing Methods . 71
2. Particle Size Distribution of Blackwater
Solids 75
3. Comparison of Size Distributions 86
4. Overall Size Distribution 89
C. Surface Properties of Mineral Matter and Coal
Contained in Blackwater 93
1. Introduction 93
2. Mineral Fraction 95
a. Illite 95
b. Chlorite 102
c. Other minerals ..... 104
d. Summary 104
3. Carbonaceous Material 107
4. Surface Properties of Blackwater Slurries . . 115
5. Summary 120
V- SUMMARY AND CONCLUSIONS 121
A. Mineralogical Composition 121
B. Particle Size Analysis 125
C. Surface Properties 126
D. Characterization of a Typical Eastern
Blackwater Sample 129
VI. RECOMMENDATIONS FOR FUTURE STUDY 131
REFERENCES 133
APPENDIX A
STANDARD X-RAY DIFFRACTION GRAPHS FOR QUANTIFICATION
OF THE MINERAL MATTER FRACTION FOUND IN BLACKWATER . • 137
iv
-------
Page
APPENDIX B
X-RAY DIFFRACTION ANALYSIS OF THE MINERAL MATTER
FRACTION FOUND IN BLACKWATER 145
APPENDIX C
POTASSIUM ANALYSIS OF THE MINERAL MATTER FRACTION
FOUND IN BLACKWATER FIRST ELEVEN SAMPLES 154
APPENDIX D
PARTICLE SIZE ANALYSIS 158
APPENDIX E
TABULATION OF THE MINERALOGICAL AND PARTICLE SIZE
CHARACTERISTICS OF EACH OF THE THIRTEEN
BLACKWATER SAMPLES 175
v
-------
LIST OF TABLES
Table PaSe
1 Water used in various coal cleaning operations .... 7
2 Possible methods of treating thickener underflow ... 10
3 Minerals found in coal 17
4 Mineralogical composition of anthracite refuse .... 18
5 Average mineralogical composition of ash forming
constituents in major U.S. coal seams 20
6 Blackwater samples tested 23
7 Principal x-ray diffraction spacings of minerals
commonly occurring with coal 30
8 Characteristic peaks used for quantitative analysis
of the principal minerals found in blackwater .... 34
9 Percentage of ash and sulfur in blackwater samples . . 43
10 Approximate illitic mineral content in the
mineral matter fraction from eastern blackwater
samples 58
11 Approximate composition of the mineral matter
fraction from eastern blackwater samples 61
12 Approximate mineral matter composition in U.S.
coal seams (weight percent) 62
13 Particle size analysis of blackwater 91
14 Relationship between colloid stability and
zeta potential 94
15 Point of zero charge for some minerals found in
blackwater 105
VI
-------
Table Page
16 Electrophoretic mobility of a blackwater sample
from a preparation plant treating Lower
119
17
A. 1
B. 1
B. 2
B. 3
B. 4
B. 5
B. 6
B. 7
B. 8
B. 9
B.10
B.ll
B.12
B.13
C. 1
D. 1
D. 2
D. 3
Characteristics of a typical eastern blackwater
sample
Characteristic peaks, source, and impurities found
Sample, Pi. W Pa 1
Sample, L.K. C Pa 2
Sample, L.K. C Pa 3
Sample, L.F. C Pa 4
Sample, Po. M WVa 5 .
Sample, Po. W WVa 6
Sample, Pi. /L.F. H Oh 7
Sample, El Ky 8
Sample, Pr. J Ala 9
Sample, 16/5 J 111 10
Sample, 16 W Ind 11
Sample, B.D. L Wa 12
Sample, S/L.S. Ut 13
Quantitative atomic absorption determination of K^O
Particle analysis of mineral matter fraction
cumulative percent finer
Particle analysis of carbonaceous fraction
cumulative percent finer
MSA sedimentation particle size analysis procedure
for mineral matter
130
144
147
147
148
148
149
149
150
150
151
151
152
152
153
157
162
165
168
-------
Table Page
D. 4 MSA sedimentation particle size analysis of
mineral matter fraction cumulative weight
percent finer 169
D. 5 MSA sedimentation particle size analysis
procedure for carbonaceous material 171
D. 6 MSA sedimentation particle size analysis of
carbonaceous fraction cumulative weight
percent finer 172
D. 7 Mean particle analysis of thickener underflow or
slurry and feed eastern samples (Nos. 1 to 11) .... 174
viii
-------
LIST OF FIGURES
Figure
1 Flowsheet for froth flotation of blackwater
samples 26
2 Shift of the 001 x-ray diffraction peak when clay
minerals are glycolated and heated 31
3 Comparison of subsieve size distribution of the
mineral matter from sample E L Ky 8 using the
Whitby Particle Size Analyzer and the Sedigraph ... 73
4 Comparison of subsieve size distribution of the
mineral matter from sample S/L.S. Ut 13 using the
Whitby Particle Size Analyzer and the Sedigraph ... 74
5 Particle size distribution of blackwater solids,
sample no. Pi W Pa 1 76
6 Particle size distribution of blackwater solids
from the Lower Kittanning samples, sample no.
L.K. C Pa 2 and L.K. C Pa 3 77
7 Particle size distribution of blackwater solids,
sample no. L.F. C Pa 4 78
8 Particle size distribution of blackwater solids
from the Pocahontas samples, sample no.
Po. M WVa 5 and Po. W WVa 6 79
9 Particle size distribution of blackwater solids,
sample no. Pi./L.F. H Oh 7 80
10 Particle size distribution of blackwater solids,
sample no. E L Ky 8 81
11 Particle size distribution of blackwater solids,
sample no. Pr. J Ala 9 82
-------
Figure
12 Particle size distribution of blackwater solids
from Indiana and Illinois samples, sample no.
16/5 J 111 10 and 16 W Ind 11 83
13 Particle size distribution of blackwater solids
from western samples, sample no. B.D. L Wa and
S/L.S. Ut 13 84
14 Mean particle size distribution of the mineral
matter in the eleven eastern blackwater samples ... 87
15 Mean particle size distribution of the
carbonaceous material in the eleven eastern
blackwater samples 88
16 Electrophoretic mobility of illite sample (A) from
Fithian, Illinois 96
17 Electrophoretic mobility of illite sample (B) from
Fithian, Illinois 97
18 Electrophoretic mobility of illite sample (C) from
Morris, Illinois 99
19 Electrophoretic mobility of illitic material from
the following blackwater samples 101
20 Electrophoretic mobility of the following minerals,
chlorite and limestone 103
21 Variation of zeta potential with pH for Pittsburgh
seam coal and its lithotypes 108
22 Effect of oxidation time on electrokinetic
behavior of HVA-bituminous vitrain 110
23 Electrophoretic mobility of coarse carbonaceous
material from the following blackwater samples . . . Ill
24 Electrophoretic mobility of coarse carbonaceous
material from the following blackwater samples . . . 112
25 Electrophoretic mobility of hand-picked coal
samples 114
x
-------
Figure Page
26 Zeta potential of blackwater slurries from
different seams
27 Electrophoretic mobility of an unf locculated
thickener feed from a plant treating Lower
Kittanning coal ................... 118
A. 1 Standard x-ray diffraction pattern for illite .... 139
A. 2 Standard x-ray diffraction pattern for kaolinite . . . 140
A. 3 Standard x-ray diffraction pattern for quartz .... 140
A. 4 Standard x-ray diffraction pattern for chlorite . . . 141
A. 5 Standard x-ray diffraction pattern for calcite .... 142
A. 6 Standard x-ray diffraction pattern for dolomite . . . 143
D. 1 Sedigraph particle size distribution, sample no.
E L Ky 8 ....................... 160
D. 2 Sedigraph particle size distribution, sample no.
S/L./S. Ut 13 .................... 161
XI
-------
I. INTRODUCTION
In 1973, 289 million tons of clean coal were produced by
mechanical cleaning from 398 million tons of raw coal in approxi-
mately 400 coal preparation plants throughout the United States (37).
The majority of these facilities is located in the Eastern coal
producing areas of the United Stafes, principally in the Appalachian
/
region. Assuming that 3 percent of the raw coal (2) processed in
coal preparation plants will report to some form of slurry or tailings
treatment, then approximately 12 million tons of slimes on a dry basis
were produced during the cleaning process in 1973. It is this fine
material which is suspended in the waste water - the "blackwater" of
coal preparation plants - that has to be treated in a manner that
meets environmental regulations.
In the past, blackwater usually was treated by flocculation
and thickening with the thickener underflow being pumped to slurry
ponds for final disposal, or, alternatively, the blackwater was sent
directly to the slurry pond without thickening or clarification.
The clarified or partially clarified water from the thickener and/or
slurry ponds was either recycled to the plant for additional use or
discharged to a stream. The new environmental regulations concerning
process water from coal preparation plants states: "There shall be no
discharge of pollutants from coal preparation plants" (10). The
-------
government is stressing the use of closed water circuits as a means
of achieving this "no discharge" regulation. These regulations make
it very difficult to obtain approval to use slurry ponds, and in most
cases the government insists on a closed water circuit that excludes
the use of slurry ponds to dewater thickener underflow (13).
Obtaining a closed water circuit for some preparation plants
may be expensive since this could involve modification or installation
of additional treatment processes such as froth flotation, floccula-
tion, clarification, filtration, centrifugation, etc. Furthermore,
in order to comply with the government regulations, a high degree of
reliability will have to be obtained in the water treatment system,
and this will undoubtedly involve additional capital and operating
expenditures.
One of the principal methods of concentrating fine solids in
the plant discharge water has been to allow the suspended particles
to settle in a thickener. The thickener overflow is then recycled
back to the plant water system. In order to achieve good thickener
efficiency, inorganic and organic flocculants have traditionally been
added to the feed slurry. This procedure not only increases the
settling rate of the fine particles, but the flocculants also serve
to clarify the thickener overflow to be recvcled. The effectiveness
of the different flocculants and their costs vary substantially from
plant to plant. Pritchard (31) in 1974 compared the cost of floccu-
lants at two different plants and found the following costs:
-------
Kentucky Mine Flocculant Cost
3-1/4 cents/ton of total cleaned coal
22 cents/ton of minus 28 mesh cleaned coal
Southern West Virginia Mine Flocculant Cost
27 cents/ton of total cleaned coal
$2.00/ton of minus 28 mesh cleaned coal
Thus, there can be a large variation in flocculant cost from
one plant to another, but, in any event, flocculation costs are by
no means a negligible part of the total preparation costs. There
are many possible explanations for this great variation in the costs
for flocculating blackwater from different sources, but mineralogical
and size differences most probably account for most of these differ-
ences. For example, in the cases cited, the run-of—mine coal from
the Kentucky mine had an ash content of 15 percent, while the West
Virginia coal contained an ash content of 45 percent in the run-of-mine
coal.
The purpose of this study is to characterize the fine solid
material in the waste water so that a better understanding of the
problems associated with treating "blackwater" may be obtained. The
three areas selected for investigation were: identification and
quantification of the solid constituents, size analysis of the partic-
ulate material, and an investigation of the surface properties of the
solid material. Thirteen samples of waste material from coal prepara-
tion planes throughout the United States were analyzed. The samples
-------
were so selected as to be representative of the discharge from
preparation plants treating coal from major coal seams in the
country. These samples were obtained from both surface and under-
ground mines and from plants with a wide variation in preparation
circuit complexity.
-------
II. BACKGROUND AND THEORY
A. Introduction
The purpose of this study was to characterize the fine solid
material in the primary effluent from coal preparation plants so
that a better understanding of the problems associated with treating
"blackwater" could be obtained. In this study "blackwater" is defined
as the aqueous, fine particle-containing, primary effluent from a
coal preparation plant. The composition of this effluent is highly
variable depending on the coal seam mined, the mining method, and
the preparation procedure employed. Due to differences in the nature
of the material mined and the extent of fine cleaning practices in
a particular plant, the fine particulates contained in the discharge
water may range anywhere from predominately coal to predominately
mineral matter. The size consistency of the particulates is generally
28 mesh or finer. Those older plants employing only crude preparation
processes may send all of the minus 28 mesh material to the refuse
slurry pond and this material will therefore contain a substantial
percentage of coal. On the other hand, modern preparation plants with
extensive fine cleaning circuitry, and employing froth flotation, may
discharge only a minimal amount of combustible material and the
blackwater effluent will contain largely high ash particles generally
less than 200 mesh in size. The composition of blackwater is thus
highly variable.
-------
The primary blackwater effluent is typically sent to a solid/
liquid separation unit such as a thickener or slurry pond and the
water is removed for recycling. Settlement of the solids is normally
assisted through the addition of a flocculant to improve clarity of
the recycled water, increase the settling rate of the particulates,
improve settled sludge density, and minimize the capital investment
of the solid/liquid separation unit. A basic understanding of the
particulate material being treated, its mineralogical composition,
size distribution, and surface properties is essential to the effec-
tive design of any flocculation process.
B. Overview of Coal Preparation
The type of coal preparation used at any particular site
depends on a number of factors, including such things as market
conditions, characteristics of the coal, and mining methods. Coal
is usually treated in stages with the coarse coal being cleaned in
a different manner than is the fine coal (20). The most commonly
employed coal cleaning methods are those using water, and the amount
of water used varies considerably from one method to another. This
is clearly shown in Table x. Generally, the fine cleaning methods
require more water per ton treated than do modern coarse cleaning
methods. Inherent in the type of material being treated, the
discharge water from the fine cleaning units tends to have more fine
solids suspended in it than does the waste water from coarse cleaning
units. Therefore, a plant which is treating a relatively high
-------
Table 1. Water used in various coal cleaning operations. (after Lucas, Maneval, and Foreman [21])
Coal
Cleaning
Unit
Baum Jig
Chance Cone
Hydroseparator
Menzies Cone
Belknap Washer
Rheolaveur
Sealed
Discharge
Hydro tator
DSM Cyclone
(as heavy media)
Size Range of Feed
Anthracite Bituminous
o ~" -L / o o""J,/o
o ~~ X / JL o o"""-L/j.o
5"-l/32" 5"-l/2"
5"-l/32" 5"-l/2"
None 6"-l/4"
4"-l/4" 4"-l/4"
2"-0" 2"-0"
3/4"-
20-48M l/4"-0"
Feed
Max tph
l-5tph/ft2
50tph/ft2
(425)
4tph/in.
(190)
Anth:160
Bit: 300
160
8-10tph/in
5tph/ft2
(320)
5-35
%
Solids
85-90
85-90
85-90
85-90
85-90
15-30
85-90
12-16
Cone
%
Solids
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Tails
%
Solids
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
Dewatered
GPH HO
tph Feed
3-5
(recycled)
7-12
media
14-18
14-18
5
(makeup)
6-12
12-16
20-30
media
-------
Table 1. Continued.
CO
Coal
Cleaning
Unit
Humphrey Spiral
Cone Table
Rheolaveur
Free
Discharge
Flotation Cell
Size Range of Feed
Anthracite Bituminous
l/4"-200M l/4"-200M
l/4"-0" l/4"-0"
1/4-0" l/4"-0"
28Mx200M 48Mx200M
Feed
Max tph
1.0-1.5
10-15
3-5 tph /in
2-4
%
Solids
15-20
15-25
15-30
20-30
Cone
%
Solids
12-25
10-20
Dewatered
35-60
Tails
%
Solids
15-40
20-35
Dewatered
10-20
GPH H
2°
tph Feed
30
12-16
3-4
13-16
-------
percentage of fine coal will most probably have a more difficult
water treatment problem.
Modern, efficiently designed and managed coal preparation
plants typically produce a water containing 35 mesh x 0 solids,
with the minus 325 mesh content, by weight, ranging from 35 to
80 percent, frequently tending toward the latter (2). The primary
blackwater effluent from coal preparation plants is usually treated
initially by flocculation techniques in conjunction with a thick-
ener. A typical thickener feed contains 1-5 percent solids by
weight and the thickener underflow will normally contain 20-35 percent
solids by weight (34).
The common types of flocculants used to treat blackwater
are inorganic electrolytes such as lime and alum, and organic
polymers such as starches and synthetic polymers (e.g., polyacryl-
amide). Thickening of coal refuse slurries is usually accomplished
by using high molecular weight organic flocculants that provide
rapid settling of most of the solids (6). The synthetic polymers
cost more per pound than do many of the natural polymers, but
their ability to produce comparative flocculation results at
relatively low concentrations makes them very economical.
The thickener underflow, consisting of the flocculated
and settled solids, can be treated by a number of different
methods such as those listed in Table 2.
-------
Table 2. Possible methods of treating thickener underflow.
(after Gregory [13])
Impoundment
Chemical mixing
Underground pumping
Spherical agglomeration
Mechanical dewatering
Pelletizing
Incineration
Thermal drying
10
-------
A preparation plant closed-water circuit is desirable in
order to comply with environmental regulations concerning the
quality and quantity of water discharge, and to achieve the economies,
which result from the efficient re-use of the large amount of water
required for coal preparation. In achieving a closed-water circuit
system for a coal preparation plant, operators strive to have no
discharge of blackwater, to minimize the build-up of solids in
the recirculated water, and to separate the solids from the primary
blackwater slurry in a form suitable for transport and disposal in
a stable, permanent form that is environmentally acceptable and
legal.
C. Overview of Flocculation
Solid particles suspended in water can be concentrated by
allowing the particles sufficient time to settle. Under relatively
quiescent conditions, fine particles will concentrate by settling
due to gravitational forces, but the rate at which particles settle
is dependent on a number of factors, one of which is particle size.
The rate of free settling for fine particles suspended in water is
described by Stokes' Law:
11
-------
V
_
m 18y t
V = maximum settling velocity
m
p = density of particle
p = density of liquid
Li
d = diameter of particle
g = gravitational acceleration constant
y = viscosity of liquid
s = distance
t = time
12
-------
Analysis of Stokes1 Law shows that the rate of settling
depends on the square of the particle diameter. Under the same
conditions, the time to settle a 1 urn particle will be 10,000 times
longer than the time to settle a 100 pro (150 mesh) particle of the
same density. Thus, for very fine particles, the use of settling
basins to concentrate the suspended solids becomes impractical for
commercial operations due to the enormous size of the basins that
would be necessary to obtain long retention times.
The fine particles, with their extremely slow settling rates,
can be settled at a much higher rate if the particles are agglomerated
to form large particles which settle at a much faster rate. Fine
particles can be agglomerated using established flocculation tech-
niques. Agglomeration of fine particles involves particle-particles
collisions of sufficient energy for van der Waals forces to take
effect and cause agglomeration.
The surface of suspended particles develop an electrical
charge due to imperfection in crystal structure and/or by the prefer-
ential adsorption of certain ions (38). In the formation of many
naturally-occurring minerals, especially alumina silicates, isomor-
+3 +4 +2 +3
phous substitutions (of Al for Si or Mg ~ for Al for example)
are common. These substitutions can lead to a net charge on the
crystal lattice. Fractured surfaces on particles produced by breakage
of larger fragments can also acquire an electrical charge. In this
case, the existence of unsatisfied valences at the surface causes thf
adsorption of various species from solution. If certain ions are
13
-------
adsorbed preferentially, a charge will be developed on the surface.
The charge on clay particles is a result of both of these effects:
crystal imperfection and broken bonds.
When the surface charge on a particle results from preferential
adsorption, its sign and magnitude can be varied by changing the
concentration of those ions in the solution. The ions responsible
for the charge development are known as the potential-determining
ions for that particular material (38). Since hydronium and hydroxyl
ions are potential determining for many insoluble oxide minerals and
coal (3,8), the sign and magnitude of the charges on the surface are
pH dependent. At a certain pH, the adsorption of hydronium and
hydroxyl ions is equal and the net charge on the surface is zero.
This condition is referred to as the pH of the "point of zero charge,"
(PZC) for that mineral.
As a result of the surface charge, a diffuse layer of ions,
of change opposite to that of the surface, accumulates in the liquid
near the particle surface creating an electrical double layer which
compensates for the surface charge of the particle. The thickness of
the double layer is inversely related to the ionic concentration of
the solution. If the ionic concentration is small then the thickness
of the double layer will be large and vice versa for concentrated
solutions. Thus, the thickness of the double layer of a charged
particle may be varied by varying the total ionic strength in the
suspending fluid.
14
-------
The magnitude and sign of the surface charge and the thickness
of the double layer will have a definite effect on the rate of
agglomeration of particles in a suspension. Particles of similar
sign will repel each other and as the magnitude of the charge
increases, the repulsion will increase making agglomeration more
difficult. The magnitude of the surface charge on an oxide mineral
or coal can be reduced by adjusting the pH of the solution in order
to decrease the surface potential and thus increase the ease with
which the suspension may be flocculated. The thickness of the
double layer also affects the rate of agglomeration. Particles
with thick double layers are held too far apart for van der Waals
forces to take effect during particle collision and flocculation
can only occur very slowly. The double layer thickness can be
reduced by increasing the ionic concentration in the suspension,
thus the rate of flocculation can be increased by adding inorganic
and/or organic electrolytes to a suspension (28).
Certain organic polymers are highly effective flocculants;
several mechanisms have been proposed to account for their action.
If the flocculant is a polyelectrolyte, charge neutralization,
double layer compression, etc., can occur as for inorganic electro-
lytes. A bridging mechanism was advanced by Healy and LaMer (15).
In this model, the polymer molecules are considered to adsorb
irreversibly on the surface of the particles. Each polymer mole-
cule adsorbs to two or more particles forming a "bridge" between
them. The floes produced by the polymer settle at a faster rate
15
-------
than the individual particles. Another proposed mechanism for the
action of polymeric flocculants is the "enmeshment" model advocated
by Vanderhoff (39). In this model the long chain polymer molecules
interlock in a sort of net and entrap particles either by attachment
or by enmeshment. These added features, bridging and enmeshment,
of organic polymers makes them a very effective means of flocculating
fine particles. Thickening of coal refuse slurries is usually
accomplished with high molecular weight organic flocculants that
provide rapid settling of most solids but, not infrequently, may
leave some of the finer particles still suspended (6) .
Characterization of the properties of a suspension to be
flocculated should be very helpful in optimizing fine particle
flocculation in that system. Particle size distribution, mineralog-
ical classification, and surface properties should be known to obtain
a basic understanding of the flocculation mechanisms taking place.
D. Ash-Forming Minerals in Coal
An estimation of the mineral matter contained in blackwater
may be obtained from the composition of the mineral matter found
within a coal seam. The identification of ash-forming minerals
commonly found in coal, as reported by Nelson (25) is shown in Table
3. The mineral constituents were not quantified in Nelson's report,
but certain minerals occurred more frequently and in larger quantities
than others. These important minerals, in the judgment of the author
of this thesis, have been underlined in Table 3.
16
-------
Table 3. Minerals found in coal. (after Nelson [25])
Shale Group:
Illite, Montmorillonite, Bravaisite,
Hydromuscovite, Muscovite
Kaolin Group:
Kaolinite, Levisite, Metahalloysite
Sulfide Group:
Pyrite, Marcasite
Carbonate Group:
Calcite, Siderite, Dolomite, Ankerite
Chloride Group:
Sylvite, Halite
Accessory Minerals Group:
Quartz, Gypsum, Chlorite, Rutile,
Hematite, Magnetite, Sphalerite,
Feldspar, Garnet, Hornblende, Apatite,
Zircon, Epidote, Biotite, Augite,
Prochlorite, Diaspore, Lepidocrocite,
Barite, Kyanite, Staurolite, Topaz,
Tourmaline, Pyrophyllite, Penninite
17
-------
Table 4. Mineralogical composition of anthracite refuse. (after Augenstein and Sun [5])
00
Sample
Von Storch
Powderly
Blue Coal
St. Nicholas
Oak Hill
Westwood
Hazelton Shaft
Illite
40.8
45.9
37.4
41.1
34.6
38.8
39.7
Mineral
Kaolinite
35.0
38.9
36.9
36.9
34.9
Constituents, % Mineral Matter
Pyrophyllite-
Kaolinite Quartz
20.8
12.4
22.4
44.3 9.9
51.6 10.6
21.6
22.6
Pyrite
1.7
0.7
1.7
3.3
1.8
1.2
1.1
Rutile
1.7
2.1
1.6
1.4
1.4
1.5
1.7
-------
Augenstein and Sun (5) studied the mineral composition of
Pennsylvania anthracite refuse and their data are shown in Table 4.
These data indicate that anthracite refuse is typically composed
of about 40 percent each of illite and kaolinite, or pyrophyllite-
kaolinite clays and 19-20 percent quartz, with smaller amounts of
pyrite and rutile.
More recently, 0'Gorman and Walker (27) have made a compre-
hensive study of the mineral matter contained in lithotypes from
major United States coal seams using x-ray diffraction and infra-red
spectroscopy. They also made a semi-quantative analysis of the
mineral matter of each of these coal samples. Table 5 is a
statistical summary of their findings adapted from their extensive
data. Note that while the variation between samples is great (range),
the principal mineral present, on the average, is kaolinite together
with lesser amounts of illite, quartz, and gypsum. It is interesting
to note that calcite did not occur in significant amounts in most
of the samples analyzed but gypsum did. It should be cautioned
that the 0'Gorman and Walker data were obtained mostly from hand-
picked lithotypes of coal containing but little ash. Their data
thus represent the mineral matter contained in coal, essentially the
inherent ash-forming minerals. Furthermore, because their study
represents the majority of United States coal seams presently being
mined, it is, in fact, largely a study of the mineral matter of coals
dating from the Pennsylvanian Period since this is the geologic period
in which the Appalachian and Mid-continent coal fields were formed.
19
-------
Table 5. Average raineralogical composition of ash forming constituents
in major U.S. coal seams. (modified after O'Gorman and
Walker [27])
Mineral
Kaolinite
Illite
Montmorillonite
Mixed Layer Illite -
Mont^orillonite
Chlorite
Quartz
Gypsum
Rutile
Mean
34.
7.
0.
3.
1.
10.
11.
2.
8
8
7
2
5
1
9
3
Standard
Deviation
23.6
8.5
1.3
2.3
1.5
10.1
13.0
1.3
Range
0-85
0-35
0-10
0-20
0-10
0-40
0-60
0-10
Others
Pyrite, siderite, dolomite, calcite, aragonite, ankerite, muscovite,
plagioclase, hematite, jarosite, thenardite
20
-------
Because the 0'Gorman and Walker study deals mainly with the
analysis of interspersed mineral matter in coal lithotypes, it may
not represent the mineral composition of run-of-mine coal. The
mineral matter in run-of-mine coal will be influenced by both the
inherent mineral matter of the coal and the more segregated mineral
matter which comprises the high ash constituents associated with
the coal, especially those near the edges of the seam. Thus, over-
break during mining, which may incorporate ash-forming minerals
from the adjacent strata into the coal coming from the mine, will
contribute in a major way to the material which eventually makes
up the black water. The composition of the blackwater is thus
not only a function of the mineral matter inherent in the coal
seam, but is influenced in a more important way by the mineralogical
composition of the adjacent strata when overbreak is substantial.
Then, too, there is a further complication in that the
mineral matter, either within the coal seam or adjacent to it,
will degrade in different ways during the preparation process. The
fine particulates contained in the blackwater will obviously come
largely from those ash-forming constituents that degrade most readily.
The need to obtain a mineral analysis of the actual blackwater
constituents is the reason for this study. The samples were selected
so as to be representative of the discharge from preparation plants
treating coal from major United States coal seams.
21
-------
III. EXPERIMENTAL MATERIALS AND METHODS
A. Samples
Thirteen samples of waste material from coal preparation
plants throughout the United States were selected for study (see
Table 6). The blackwater samples were classified into two main
groups—Eastern, Samples 1-11, and Western, Samples 12 and 13—
based on differences in the nature of the solid material as a
result of geologic genesis. Samples 1 through 11 were obtained
from thickener underflows, or slurry pond feed, with the first
nine samples received in slurry form and Samples 10 and 11 received
in dry form. Sample 12 was obtained from a settling pond and
Sample 13 from a refuse conveyor belt. In order that it correspond
approximately to the rest of the samples, the Sample 13 refuse was
wet screened over a 28 mesh sieve and only the minus 28 mesh frac-
tion retained for study. The majority of the samples were from
Appalachian coal fields since this area contains the majority of
preparation plants in the United States. An attempt was made to
obtain at least one sample from each of the major coal areas which
use wet preparation. Western sub-bituminous and lignite coal
samples were purposely excluded since they are not treated by wet
preparation methods.
22
-------
Table 6. Blackwater samples tested.
Identification
Identification Code3
Eastern
Pi. W Pa 1
L.K. C Pa 2
L.K. C Pa 3
L.F. C Pa 4
Po. M k'Va 5
Po. W WVa 6
Pi. /L.F. H Oh 7
E L Ky 8
Pr. J Ala 9
16/5 J 111 10
16 W Ind 11
Seam
Pittsburgh
Lower Kittanning
'B1 Lower Kittanning
"D" Lower Freeport
//3,4,5 Pocohontas
//3 Pocohontas
75% Pittsburgh
25% Lower Freeport
#2 Elkhorn
Pratt
#5,6 Illinois
//6 Indiana
County
Washington
Cambria
Cambria
Cambria
McDowell
Wyoming
Harrison
Letcher
Jefferson
Jackson
Worrick
State
Pennsylvania
Pennsylvania
Pennsylvania
Pennsylvania
West Virginia
West Virginia
Ohio
Kentucky
Alabama
Illinois
Indiana
-------
Table 6. Continued.
Identification Code'
Identification
Seam
County
State
Western
B.D. L Wa 12
S/L.S. Ut 13
Big Dirty
Somerset "B1, *C'
Lower Sunnyside
Lewis
Gunnison
Carbon
Washington
Colorado
Utah
Identification Code: Seam, county, state, sample number.
-------
B. Identification and Quantification of the Solid Constituents in
Blackwater
1. Sample Preparation
Particulate matter in blackwater consists of carbonaceous
material and mineral matter. Because of the substantial difference
in the properties between the mineral and carbonaceous particles,
it was decided to separate the solid material into a mineral frac-
tion and a carbonaceous fraction. Froth flotation (3,7) was used
to concentrate the blackwater samples into a froth containing the
coal and a tailings fraction composed mainly of the ash-forming
minerals. The flowsheet for this separation procedure is shown in
Figure 1. The efficiency of the separation was determined by
microscopic examination and by ash analysis of the two fractions.
Approximately 25 grams of solids from each blackwater sample
were separated using this procedure. The samples were dis-aggregated
in a Hamilton Beach, single-speed milkshake blender for five minutes,
and then transferred to a 100 gram Denver Flotation Cell. The
flotation unit consisted of a Hamilton Beach milkshake blender
that was converted into a flotation unit using a kit manufactured
by Denver Equipment Division, Joy Manufacturing Company, Denver,
Colorado. Air was incorporated into the pulp through the open
vortex caused by stirring, and so the speed of the impeller was
adjusted to give a sufficient air flow to produce the desired froth.
The propeller speed of the converted blender was varied using a
25
-------
Blackwater Sample * 30 Z Solids
I*- Tails
•Tails
•Tails
Blender
Flotation Rougher
i
Blender
Flotation Cleaner
1
Flotation Recleaner
Concentrate (coal)
5 minutes
1-2 Ib/ton MIBC;
fuel oil as
needed
5 minutes
Tails
(mineral
matter)
Figure 1. Flowsheet for froth flotation of blackwater samples.
26
-------
rheostat. The amount of time and reagents needed to obtain good
flotation results for each sample varied depending on the size of
the particles and the surface characteristics of the coal. The
flotation of coarse and oxidized coal particles was particularly
troublesome, and in some cases where large oxidized coal particles
were present, the efficiency of separation was not particularly
good. In those cases where unfloated coal particles were present
in the mineral matter fraction (in amounts never exceeding 10%),
the amount of coal was determined microscopically and the appropriate
adjustments were made in the analyses. The effectiveness of the
froth flotation step was not only estimated by microscopic examina-
tion, but also by an ash analysis of the two fractions.
The rougher concentrate was further cleaned by stirring it
for five minutes to insure maximum dis-aggregation of coal from the
high ash gangue and subjecting it to two more stages of flotation.
The final products consisted of a concentrate containing carbonaceous
material and a tailings containing the mineral matter.
2. Analysis of Carbonaceous Material
a. Introduction. As previously discussed, froth flotation
was used to separate the blackwater samples into separate fractions—
a mineral fraction and a carbonaceous fraction. The efficiency of
the separation of each blackwater sample was determined by micro-
scopic examination of the fractions and by ash analysis.
27
-------
b. Ash analysis. Ash analyses were performed on both
fractions—mineral and carbonaceous—of each sample. Ash deter-
minations were made using the ASTM D-271 method. A one gram, minus 65
mesh sample was measured into a weighed crucible, and the crucible
was then heated to 750°C in a laboratory muffle furnace. The sample
was stirred and allowed to remain at 750°C for 1-1/2 hours. After
cooling, the crucible and ash were weighed and the ash determined
by subtracting the crucible tare.
c. Sulfur analysis. The total sulfur in each sample was
determined using a LEGO Induction Furnace and Automatic Titration
Unit made by Laboratory Equipment Corporation, St. Joseph, Michigan.
In this procedure, the sample was ground to minus 65 mesh, heated
in a stream of oxygen, and the sulfur dioxide adsorbed into an
acidified starch-potassium iodide solution. The resulting solution
was titrated with a standard potassium iodate solution. The accuracy
of this method has been shown in previous studies (16,32). The
mineralogical sulfur source (e.g., pyrite, gypsum) in the mineral
fraction was identified by standard x-ray diffraction techniques.
3. Mineral Identification and Quantification
a. Introduction. The mineral matter in the blackwater sample
was separated from the carbonaceous material using the flotation
procedure previously outlined. Since the tailings product consisted
of a very dilute slurry containing the mineral matter, these solids
28
-------
were concentrated by centrifuging the entire suspension. Once the
material was concentrated, a representative sample of the mineral
matter was removed, dried, weighed, and analyzed by x-ray diffraction.
The mineral composition of each blackwater sample was deter-
mined in two ways. In the first method, an x-ray diffraction analysis
was made on the representative sample of the mineral matter of each
sample. In the second method, the minerals in the mineral fraction
were concentrated into different layers by centrifuging a dispersed
suspension of the material. The larger, heavier material concen-
trated at the bottom, while the smaller, lighter particles, which
settled more slowly, concentrated in the top layers. The material
was removed in separate layers which were then dried, weighed, and
their mineralogical composition quantified by x-ray analysis. From
the analysis of each layer, an overall mineralogical analysis was
calculated. The results of the two methods were used to obtain a
range and a mean percent for each mineral.
b. Identification. For identification of the mineral constit-
uents, the material was ground into a fine powder and dispersed with
water and spread onto a glass slide. The material was then scanned
over the appropriate 29 range (usually 5° to 40°) using a Philips
(Norelco) X-Ray Diffractometer with nickel-filtered copper K « radia-
tion at 40 Kv and 16 ma. The ash-forining minerals were identified
using JCPDS standard (19) characteristic values for the interplanar
spacing of each mineral. Table 7 lists the x-ray diffraction spacing
of each of the minerals which commonly occur with coal.
29
-------
Table 7. Principal x-ray diffraction spacings of minerals commonly
occurring with coal. (after 0'Gorman and Walker [27])
Mineral
Diffraction Spacing (A)
Kaolinite
Illite, Mica
Montmorillonite
Chlorite
Mixed Layer Illite-
Montmorillonite
Calcite
Dolomite
Siderite
Aragonite
Pyrite
Marcasite
Quartz
Gypsum
Rutile
Feldspar
7.15(100), 3.57(80), 2.38(25)
10.1(100), 4.98(60), 3.32(100)
12.0-15.0(100)
14.3(100), 7.18(40), 4.79(60), 3.53(60)
10.0-14.0(100)
3.04(100), 2.29(18), 2.10(18)
2.88(100), 2.19(30)
3.59(60), 2.79(100), 2.35(50), 2.13(60)
3.40(100), 3.27(52), 1.98(65)
3.13(35), 2.71(85), 2.42(65), 2.21(50)
3.44(40), 2.71(100), 2.41(25), 2.32(25)
4.26(35), 3.34(100), 1.82(17)
7.56(100), 4.27(50), 3.06(55)
3.26(100), 2.49(41)
3. .18-3. 24(100)
Relative intensities are shown in parentheses.
30
-------
X
0 7 10 14 17
Kaollnite A
}
Illite
Montmorlllonite
Chlorite
Mixed Layer
C
i
\
X
0 |
1
0
0
AA' AA
1
:
AA
0 I
X
1
AAAA
xxxlxxx
1
X
A Untreated
X Ethylene Glycol
0 550°C
Figure 2. Shift of the 001 x-ray diffraction peak when clay
minerals are glycolated and heated. (40)
31
-------
Expandable layer clays such as interstratifled illite-
montmorillonite and montmorillonite were identified by subjecting
the samples to an additional treatment with an organic swelling agent
and by heating (40). A drop of ethylene glycol was added to the
mounted sample, and covered to facilitate the adsorption of the
ethylene glycol. This treatment caused the basal spacing of the
montmorillonite-type structures to expand to their characteristic
spacing of 17 A, enabling a positive identification of these
minerals to be made. This technique is also useful for studying
randomly interstratified illite-montmorillonite mixed layer clays
(40). Heat treating the clays at 350°C makes it possible to
estimate the amount of mixed layer clay content relative to the
illite content (12). Figure 2 shows the shift of the 001 x-ray
diffraction peak when clay minerals are glycolated and heated.
c. Quantification. After the identification of the mineral
constitutents were made, x-ray diffraction was used to quantify the
predominant minerals present. As mentioned before, the quantifica-
tion of the mineral fraction was carried out by both a direct
determination of a representative sample of the composite tails
and by quantification and integration of each of the separate
layeered fractions. The individual values obtained by the two
methods were used to calculate a mean and a range for the minerals
present.
The important minerals were quantified using the height of
a characteristic x-ray diffraction peak of the particular mineral.
32
-------
A set of standard curves relating peak height to mineral content
(see Appendix A) was used to quantify the important minerals in
the blackwater samples. This standard curve was prepared for each
mineral by diluting a known standard mineral (see Table 8) with
varying amounts of glass (amorphous to x-rays) and plotting the
x-ray peak intensity versus the percentage of the standard mineral
present. The relevant peak height of an unknown quantity of a
mineral in a particular sample is then compared to this standard
curve to determine the amount of mineral present. The standard
curves for the dominant minerals are given in Appendix A.
Quantitative analysis was performed on powdered, dry-ground
material that was mounted so as to obtain random orientation. This
random orientation was achieved by mounting the powdered material
into the hole of a donut-shaped metal mount somewhat similar to a
washer. The mount was prepared by fastening one side of the ring
to a glass slide using masking tape while the open side was used
to fill the mount with the sample powder. Once the hole in the
mount was filled, a button-type back was taped on. The ring and
slide was flipped over, the glass slide was removed, and the
sample holder placed, open side up, in the x-ray diffractometer,
which rotates while the sample is being scanned. This type of
mounting helps to achieve a random sample orientation which in
turn produces a peak height that is not influenced by particle
orientation to any great extent.
33
-------
Table 8. Characteristic peaks used for quantitative analysis
of the principal minerals found in blackwater.
Mineral
Peak A (19) Source of Standard Reference Sample
Illite
Kaolinite
Chlorite
Calcite
Quartz
Dolomite
4.48, 2.57 API #34, Fithian, Illinois (Ward's)
3.57 API #9 Mesa Alta, New Mexico
(Ward's)
3.55 Calaveras Company, California
(Ward's)
3.04 Valentine, Center County, Pennsylvania
1.82 Castastone Products Company, Inc.
Raleigh, North Carolina
2.88 Thornwood, New York (Ward's)
34
-------
Table 8 shows the characteristic peaks used for quantifying
the predominant minerals. The peaks for kaolinite, chlorite, and
calcite were chosen because of their strong intensity and relatively
low interference from other minerals commonly found in coal. The
1.82 A* peak of quartz was used because the intensity of this peak
at concentration of 10-20 percent was similar to the intensities
of the peaks for the other minerals analyzed and therefore, the
need to change the sensitivity of the recorder was less, thus pro-
ducing more accurate results. The 4.48 A and 2.57 A peaks for
illite were chosen after an x-ray scan was performed on the Fithian,
Illinois, API #35, illite sample using a randomly oriented mount.
Although these peaks are not the two most prominent illite peaks
used in the slide identification scheme, they were found to be more
satisfactory for random orientation quantification.
The "illitic" material—illite, interstratified illite-
montmorillonite, and montmorillonite—were roughly quantified as a
group since our ability to analyze this material was somewhat limited.
X-ray diffraction and potassium analysis by atomic adsorption (23)
were two methods used to quantify the illitic material. Problems
associated with this quantification are discussed in Section IV.A.3.
When the only significant source of potassium in the mineral
material is illite, then a determination of potassium content can be
used as a means of quantifying the illitic clay if the stoichiometric
amount of potassium in illite is known (5). Weaver (40) suggests a
K_0 content of approximately 8.93 percent for most illites and a K_0
35
-------
content of 11.9 percent for mica. The K_0 content used for this
analysis was 5.12 percent which is the K_0 content of the illite
shale of Fithian, Illinois, after adjustment for contaminants. The
amount of quartz and calcite in the illite standard was determined
using the x-ray diffraction technique previously mentioned in this
section. The percentage of K_0 in the standard was then adjusted
to 100 percent illite, and this value was used to calculate the
amount of illite present in the different samples based on their
K_0 content. Atomic absorption was used to determine the amount of
potassium oxide present in each sample (23). Greater details of
this procedure are given in Appendix C.
C. Particle Size Characterization
1. Sample Preparation
Characterization of the particle size of blackwater involved
the initial separation of the solids into a mineral fraction and a
carbonaceous fraction using the froth flotation procedure outlined
in Section III.B.I. Each of these fractions was then divided, by
wet screening, at 400 mesh into a coarse and a fine fraction. The
use of a wetting agent, Aerosol OT, improved the efficiency of this
size separation. A drop, approximately 50 milligrams, of 75%
Aerosol OT was applied to the screening surface of the sieve to
help wet it, and another drop or two of the wetting agent was added
to each fraction in order to wet the particles. The carbonaceous
material tended to require more wetting agent than did the mineral
36
-------
matter, which would be expected since coal is naturally hydro-
phobic. The material was assumed to be wetted when skin flotation
was not observed. The plus 400 mesh material of each fraction was
drained, dried, and retained for further analysis. A 200 ml repre-
sentative sample of the minus 400 mesh fraction was removed for
analysis and the remaining slurry was filtered, dried, and weighed
to determine the percent solids.
2. Sizing Method
The size distributions of the carbonaceous material and the
mineral matter were determined separately. The plus 400 mesh frac-
tions were screened using a Ro-Tap shaking device, and laboratory
testing sieves (Tyler Standard Mesh). The minus 400 mesh fractions
were analyzed using gravitational and centrifugal sedimentation
methods. A Whitby Particle Size Analyzer, manufactured by Mine
Safety Appliances (MSA) Company, Pittsburgh, Pennsylvania, and a
Sedigraph, Model 5000 D, manufactured by Micromeritics Instrument
Corporation, Norcross, Georgia, were used for subsieve particle
analysis.
The MSA Particle Size Analyzer utilizes sedimentation, both
gravity settling for the coarse particles and centrifugation for
the fine, to determine particle size distribution (42). This
method utilizes a special centrifuge tube with a small capillary
at the bottom. The particle size distribution is calculated from
the ratio of the observed sediment height in the capillary at times
37
-------
corresponding to the desired particle sizes; to the height after
all particles have settled.
The Sedigraph employs a sedimentation method which uses an
x-ray beam as a means of measuring the settling rate of particles
(29). The application of the machine depends on the ability of the
material being analyzed to absorb x-rays, which is related to the
atomic number of the elements present in the material. Elements
with low atomic numbers such as carbon, atomic number 6, do not
absorb x-rays very well. Therefore, the Sedigraph could not be
used to analyze the carbonaceous material, but was used to analyze
the mineral matter since that material contained atoms of a high
enough atomic number for adsorbance to occur.
The 200 ml sample of the minus 400 mesh material was concen-
trated by allowing the suspension to stand for a number of days
so that all the material would settle, and the clear solution was ,
decanted. Approximately 5-10 ml of the concentrated slurry was
then transferred to a 35 ml bottle for dispersion treatment. The
slurry was dispersed using an ultrasonic bath and bleach (Bransonic
12, Branson Cleaning Equipment, Shelton, Connecticut), about 50
ppm NaOCl, which was added to oxidize any organic flocculants present
in the blackwater. A few drops of bleach were added to the 5-10 ml
slurry and it was then placed in an Ultrasonic Bath for a half hour.
The sample was then diluted to a total volume of approximately 25 ml
using a stabilizing solution, and the sample was returned to the
Ultrasonic Bath for another 15 minutes. The sample was then allowed
38
-------
to stand for an hour to determine the degree of dispersion. The
degree of dispersion was also determined by the visual appearance
of the material during the MSA analysis. If the material appeared
not to be dispersed, then a few more drops of bleach were added
to the slurry and it was subjected to additional ultrasonic treat-
ment. The mineral matter which contained a large amount of clay
was stablized using a 0.1 percent Calgon solution and sodium carbonate
to adjust the pH to 8.5. The carbonaceous fraction was stabilized
by the use of a few additional drops of bleach and distilled water.
About 5 rag of Aerosol OT were added to the slurry to wet the material
when it appeared to be sticking to the walls of the glass MSA tube
during the size analysis.
D. Surface Properties of the Coal and Ash-Forming Minerals
The surface properties of the coal and ash-forming minerals
were investigated using a Zeta Meter. The magnitude and sign of
the charged surfaces of the blackwater constituents were determined
as a function of pH in order to estimate the point of zero charge,
PZC, for the different constituents.
The Zeta Meter, manufactured by Zeta Meter, Inc., New York,
New York, was used to determine the electrophoretic mobility of
coals and minerals as a function of hydronium ion concentration.
Separate suspensions of coals and minerals were analyzed to determine
their characteristic surface properties.
39
-------
A dilute suspension of the material to be analyzed was placed
in a tubular cell between two electrodes and a known voltage was
applied across the ends of the cell. A microscope was used to
determine velocity and direction of the particles. This informa-
tion, together with the impressed potential, was used to determine
the sign and electrophoretic mobility of the particles. The use of
a microscope allows the operator to view the behavior ot the indi-
dual particles, and this is especially helpful in determining if
mineral species of different electrical properties are present.
40
-------
IV. EXPERIMENTAL RESULTS AND DISCUSSION OF
MINERALOGICAL CHARACTERIZATION
A. Identification and Quantification of the Solid Material Present
in Blackwater
1. Introduction
The solid material in blackwater consists essentially of
liberated mineral and carbonaceous matter. Because of the
differences in the physical and chemical properties of the two
different classes of material, it was necessary to analyze the
materials separately. After the material had been separated by
the flotation technique it was analyzed for the raineralogical
content, particle size distribution, and surface properties of the
solid material.
2. Carbonaceous Fraction
a. Introduction. The mineral matter and carbonaceous frac-
tions from each blackwater sample were analyzed for ash and sulfur
content using the procedure outlined in Section III.B.2. The total
ash and sulfur content in each original sample was calculated from
the ash and sulfur content of the fractions, determined experimentally,
and the weights of these two fractions. Results of these analyses
41
-------
for the thirteen blackwater samples tested are shown in Table 9.
The blackwater samples were separated into two groups—those from
the Eastern and Western halves of the United States—because of
differences in mineralogy due to geologic genesis. The 'Eastern'
samples, those from the Appalachian or Mid-continent coal fields,
were obtained from preparation plant thickener underflows or the
feed to the slurry pond. The two Western samples, B.D. L Wa 12
and S.L.S. Ut 13, were obtained from a preparation plant slurry
pond in the state of Washington and from the refuse conveyor from
a plant in the state of Utah, respectively.
b. Eastern samples. The ash content of the eleven samples
collected from coal preparation plants in the eastern half of the
United States ranged from 20.4 to 70.3 percent, with an average of
41.0 percent. Most of the ash-forming mineral in these blackwater
samples exist in a liberated form, and therefore the ash content
of the carbonaceous fraction was reduced drastically by the flota-
tion separation. The carbonaceous material has an ash content which
ranges from 8.4 to 14.4 percent, with an average of 10.9 percent.
At the same time, the percentage of ash in the mineral matter frac-
tion averages 84.3 percent with a range of 70.5 to 88.2 percent. The
ash content of the mineral matter will vary depending on the mineral
composition since the ash content of mineral matter will not neces-
sarily be equal to its original mass, but will generally be less than
100 percent . Upon heating to 750°C, minerals such as clays, carbon-
ates, and pyrite will lose weight as they release water, carbon
42
-------
Table 9. Percentage of ash and sulfur in blackwater samples.
Carbonaceous
Sample
Eastern Samples
Pi. W Pa 1
L.K. C Pa 2
L.K. C pa 3
L.F. C Pa 4
Po. M WVa 5
Po. W WVa 6
Pi. /L.F. H Oh 7
E L Ky 8
Pr. J Ala 9
16/5 J 111 10
16 W Ind 11
Average Eastern
Range Eastern
% Ash
10.2
9.2
11.9
14.4
12.6
12.1
10.9
10.8
9.2
10.7
8.4
10.9
8.4-
14.4
% S
1.14
1.75
1.06
1.30
0.94
0.76
2.26
0.71
1.12
2.92
2.67
1.51
0.71-
2.92
Wt %
55.5
64.2
66.0
80.4
70.9
63.9
84.1
47.9
72.3
19.0
28.9
59.4
19.0-
84.1
Ash-Forming Minerals
% Ash
86.1
79.3
81.8
87.9
87.5
86.2
70.5
87.1
88.0
84.3
88.2
84.3
70.5-
88.2
% S
1.11
2.36
1.46
1.40
0.70
0.56
5.23
0.56
0.59
4.54
3.14
1.97
0.56-
5.23
Wt %
44.5
35.8
34.0
19.6
29.1
36.1
15.9
52.1
27.7
81.0
71.1
40.6
15.9-
81.0
Total
% Ash
44.0
34.3
35.7
28.8
34.4
38.9
20.4
50.6
31.0
70.3
62.7
41.0
20.4-
70.3
% S
1.13
1.97
1.20
1.32
0.87
0.69
2.73
0.63
0.97
4.28
2.65
1.68
0.63-
4.28
-------
Table 9. Continued.
Carbonaceous
Sample
Western
B.D. L
S/L.S.
Average
Samples
Wa 12
Ut 13
Western
Range Western
% Ash
42.5
21.8
32.2
21.8-
42.5
%
1.
1.
1.
1.
1.
S
30
14
22
14-
30
Wt %
27.2
50.1
38.7
27.2-
50.1
Ash-Forming Minerals
% Ash
79.5
71.2
75.4
71.2-
79.5
% S
0.42
1.22
0.82
0.42-
1.22
Wt
72-.
49.
61.
49.
72.
1
8
9
3
9-
8
Total
% Ash
69.4
46.5
57.9
46.5-
69.4
% S
0.66
1.18
0.92
0.66-
1.18
-------
dioxide, and sulfur dioxide, respectively, while the mass of quartz
remains unchanged. Mineral matter that contains a high percentage
of clays (60-70 percent), some carbonates and quartz (10-20 percent
each), and a few percent of pyrite will have an ash content usually
ranging between 80 and 90 percent. Excluding three samples which
contained a small amount of carbonaceous material, Table 9 shows
the average ash content of an essentially pure mineral matter frac-
tion to be about 87 percent ash.
A microscopic examination was made of the mineral matter
fraction from each sample separated by flotation to determine the
amount of carbonaceous material, if any, that was not removed by
the flotation step. The following samples were seen to contain
a small amount of residual carbonaceous material:
Wt %
L.K. C Pa 2 3 %
L.K. C Pa 3 5 %
Pi./L.F. H Oh 7 10 %
The mineral matter fraction of the remaining eight Eastern
samples contained essentially no residual carbonaceous material.
The low ash value for the mineral matter from sample Pi./L.F. H Oh 7
resulted from the presence of 10 percent carbonaceous material and
11 percent pyrite which undergoes substantial weight loss upon
ashing. The carbonaceous material that was present in the mineral
matter fraction of samples L.K. C Pa 2 and L.K. C Pa 3 consisted of
45
-------
large particles containing locked mineral and carbonaceous compon-
ents. The difficulty in obtaining an efficient separation for
these two samples may be due to the presence of some carbonaceous
material of high ash content and large particle size. Sample
Pi./L.F. H Oh 7 contained large carbonaceous particles, about 48
mesh, of relatively low ash content. The large particle size of
this material and the possibility that the coal had become oxidized
would make for a difficult flotation separation. Since the efficiency
of the froth flotation separation method depends on the surface
characteristics of the material, locking, and particle size, it is
understandable why these three samples were not separated as
efficiently as were the other eight.
The sulfur content of the Eastern samples ranged from 0.63
to A.28 percent, with an average of 1.68 percent. The sulfur content
of most of the mineral and carbonaceous fractions obtained by the
flotation separation did not differ appreciably from that of the
whole sample, and the sulfur content of the carbonaceous fraction
ranged from 0.71 to 2.92 percent, with an average of 1.51 percent.
A few of the samples, containing a significant amount of larger,
liberated pyrite particles, showed a decrease in sulfur content of
the carbonaceous material as compared to the total sample.
c. Western samples. The ash content of the two Western
samples, B.D. L Wa 12 and S/L.S. Ut 13, as received, was 69.4 and
46.5 percent, respectively. The samples contained a carbonaceous
material that was exceptionally difficult to separate from the
46
-------
mineral matter. Large amounts of fuel oil, about 10 Ib/ton, were
used during the froth flotation process to improve the floatability
of the oxidized coal, but unfortunately, this also increased the
floatability of the mineral matter as well. The separation process
was further complicated by the presence of a small percentage of
locked coal-gangue particles in Sample 12 and rather large locked
particles in Sample 13. The efficiency of separation for these
two samples was low as a result of these problems, and this inef-
ficiency is indicated by the ash analysis of the carbonaceous
material from these two samples. Microscopic examination of the
mineral fraction of the samples shows that B.D. L Wa 12 contains
5 percent, and S/L.S. Ut 13 10 percent of carbonaceous material.
Sample 13 also contains a large quantity of carbonate minerals which
have a high weight loss due to the release of carbon dioxide on
ashing, and this would produce a lower percentage of ash for the
mineral matter fraction. The sulfur content of S/L.S. Ut 13 was
low and, as with the Eastern samples, was relatively constant
between the carbonaceous and mineral matter fractions, while
B.D. L Wa 12 contains mineral matter that is much lower in sulfur
than the carbonaceous material.
d. Summary. Quantification of pyrite and/or marcasite
in the mineral fraction was determined by a chemical method which is
discussed in the section on sulfur analysis. The amount of sulfur
in the mineral fraction was accredited as pyrite since this was the
most common form of sulfur identified in the mineral fraction. No
47
-------
gypsum was detected by x-ray diffraction analysis though some may
have been present in quantities below the detection limit of the
x-ray method (a few percent). One percent of gypsum contained in
a mineral matter sample would produce 0.19 percent sulfur in the
overall sulfur analysis. Since the sulfur content of the mineral
matter was greater than 0.42 percent for all of the samples and was
usually greater than 1.0 percent, if any significant portion of
this sulfur were due to gypsum, the gypsum content would be great
enough to be readily identified by x-ray methods. In this way,
absence of all but a percent or two of gypsum is confirmed.
Overall, the quality of the carbonaceous fraction was close
to that expected of a clean coal product from the various mines
with the exception of samples B.D. L Wa 12 and S/L.S. Ut 13. The
sulfur and ash content of the various carbonaceous fractions was
slightly high if the material is considered to be the only component
of a high quality, clean coal product, but is sufficiently low for
the material to be blended with the normal, coarser clean coal product
without lowering the quality of the total product significantly. The
largest difference between the quality of the carbonaceous material
and that of the total sample was in ash content. Furthermore, it
must be remembered that the blackwater from several of these plants
had already passed through a flotation circuit so the easy-to-float,
low ash fraction had already been removed ahead of the thickener or
slurry pond.
In spite of the shortcomings of the flotation process, the
ash content of the carbonaceous material was reduced drastically.
48
-------
For most of the samples the ash content decreased by an average
of 73 percent. The change of sulfur content of the carbonaceous
material from that of the original solids contained in the black-
water samples was slight in most cases, some carbonaceous material
decreased while others increased slightly in sulfur content.
This effective use of flotation to remove coal from the
blackwater, and the relatively high percentages of carbonaceous
material contained in the as-received blackwater samples (59.4
percent average, by weight of the Eastern samples and 38.7 percent
average, by weight for the Western samples) indicate the advantage
of an increased use of the flotation process to remove additional
clean coal from current blackwater discharge streams. Not only
would this result in an increased production of clean coal but
would also lower the loading on the water clarification and recycle
circuit, and increase the expected life of the fine refuse disposal
area.
The difference in carbonaceous material content for the thir-
teen blackwater samples was more than likely due to a difference in
mining and preparation methods employed at the different mines
rather than to a difference in the type of coal being mined. Some
of the samples were obtained from surface mines, though most of
the samples were from underground mines. The complexity of the
preparation plants varied widely, with some plants treating only
the coarse coal while others cleaned both coarse and fine.
49
-------
3. Ash-Forming Mineral Matter
a. Introduction. The ash-forming mineral matter (hereafter
simply called "mineral matter") in each sample was identified and
quantified using the x-ray diffraction procedure outlined in
Section III.B.3. An exception was the determination of the amount
of pyrite present, which was determined by the chemical method
discussed in Section III.B.2c. Because of mineralogical differences
in the solid material resulting from differences in geologic genesis,
the blackwater samples were separated into two distinct groups,
Eastern and Western.
The following minerals found in the blackwater samples were
quantified using the x-ray diffraction procedure previously mentioned:
kaolinite, chlorite, calcite, quartz, and dolomite. The mineral
content of each sample was determined by comparing the height of
the characteristic x-ray diffraction peak(s) of a given mineral to
a standard curve of peak height versus percent of a particular mineral
present.
For the "illitic" minerals—illite, montmorillonite, and inter-
stratified illite-montmorillonite—this procedure was not uniformly
successful because of structural irregularities and a modified tech-
nique had to be adopted. Some of the main types of structural
irregularities which occur in these clay types are (22):
50
-------
1. Random piling of layers.
2. Bending of layers.
3. Variation of composition within the layers.
4. Variation of composition from layer to layer.
Structural irregularities in these clays may be determined
from their x-ray diffraction pattern. Random piling of layers of
illite with montmorillonite is determined by the shape of the
10 A peak (12,22) by mounting the clay on a glass slide and
treating it with ethylene glycol to expand the layers from 9 A
to 17 A. The glycolated clay is then scanned by x-ray diffraction
to identify this expansion. An interstratified illite-montmorillonite
clay is identified by the skewed shape of the 10 A peak, and the
amount of broadening of the 10 A peak on the low angle side is
used to estimate the degree of interstratification of the illite-
montmorillonite. Well-crystallized mica can be distinguished from
the "illitic" material by the presence of a sharp, narrow peak at
10 X (33).
b. Eastern samples. The mineral matter in the eleven black-
water samples obtained from operatons in the Midwestern and
Appalachian coal fields was found to be similar. This is not unex-
pected since they all date from the Pennsylvanian Period. Each
sample contained a large amount of "illitic" material, with most of
the samples containing lesser amounts of kaolinite, chlorite, calcite,
51
-------
quartz, and pyrite. The illitic material in each sample was
characterized by these methods:
a. Identification of the type of illitic clays present.
o
b. Description of the shape of the 10 A peak.
c. Identification of the dominant, 15% or greater,
illitic clays.
Using this system the following results were obtained for
each sample:
Pi. W Pa 1
a. Illite, interstratified illite-montmorillonite,
montmorillonite.
b. Very broad at the low angle side.
c. Moderately interstratified illite-montmorillonite.
L.K. C Pa 2
a. Illite, interstratified illite-montmorillonite,
montmorillonite.
b. Slightly broad at the low angle side.
c. Illite, slightly interstratified illite-montmorillonite
52
-------
L.K. C Pa 3
a. Illite, interstratifled illite-montmorillonite,
montmorillonite.
b. Very slight broadening at the low angle side.
c. Illite.
L.F. C Pa 4
a. Illite, interstratified illite-montmorillonite,
montmorillonite.
b. Very broad peak at the low angle side.
c. Highly interstratified illite-montmorillonite.
Po. M WVa5
a. Illite, muscovite.
b. Very sharp peak with no broadening at the low angle
side.
c. Illite.
Po. W WVa 6
a. Illite, interstratified illite-montmorillonite,
montmorillonite, muscovite.
b. Sharp peak with some broadening at the low angle side
c. Illite.
53
-------
Pi./L.F. H Oh 7
a. Illite, interstratified illite-montmorillonite,
montmorillonite, hydromuscovite.
b. Broad peak at the low angle side.
c. Moderately stratified illite-montmorillonite.
E L Ky 8
a. Illite, interstratified illite-montmorillonite,
raontraorillonite, muscovite.
b. Slight broadening of the low angle side.
c. Illite.
Pr. J Ala 9
a. Illite, interstratified illite-montmorillonite,
montmorillonite, muscovite.
b. Slight broadening at the low angle side.
c. Illite.
16/5 J 111 10
a. Illite, interstratified illite-montmorillonite, muscovite.
b. Very broad at the low angle side.
c. Highly interstratified illite-montmorillonite.
54
-------
16 W Ind 11
a. Illite, interstratifled illite-montmorillonite,
montmorillonite, muscovite.
b. Very broad at the bottom half of the peak at the low
angle side.
c. Illite, highly interstratified illite-montmorillonite.
The type of "illitic" material present in these samples was
sometimes seen to vary substantially in crystallinity. For example,
sample L.F. C Pa 4 contains an illitic material of poor crystallinity
composed of a highly interstratified illite-montmorillonite with
significant amounts of illite and montmorillinite present, while
sample Po. M WVa 5 contained an illitic material, of good crystal-
linity, composed mainly of illite and some muscovite. The samples
studied from West Virginia, Kentucky, and Alabama contained an
"illitic" material of relatively good crystallinity with very little
or no interstratification of raontmorillonite with the illite, while
the samples from Pennsylvania, Ohio, Indiana, and Illinois contained
an illitic material of varying crystallinity and interstratification.
Quantifying the illitic material by x-ray diffraction using
peak height has many limitations, and the structural irregularities
in illitic clays limits the use of x-ray diffraction as a means of
quantifying these clay minerals. Because of these difficulties in
quantification, three different methods were used in order to estimate
the percentage of illite present.
55
-------
Method 1, Direct X-Ray Quantification
X-ray diffraction was used to quantify the illitic material
0 °
directly. The peak heights at 4.48 A and the 2.57 A were used
for quantification. A standard curve was prepared by diluting a
known standard illitic clay (Fithian, Illinois, APL #35) with
varying amounts of glass and plotting the x-ray peak intensity
versus the percentage of the standard illite present. The height
of the relevant peak of an unknown is then compared to this standard
curve to determine the amount of illite present.
Method 2, Potassium Analysis
Assuming that illite is the only mineral present containing
a significant percentage of potassium and, furthermore, that the
potassium content of all of the illitic material studied remains
essentially constant, the amount of illite present in a given
sample may be approximated by comparing the percentage of K_0
present in a given sample to the K_0 content in a standard sample
(in this case: Fithian, Illinois shale, Appendix C).
Method 3, Difference Method
The difference method consisted of quantifying the amount
of all of the other minerals present (kaolinite, chlorite, calcite,
quartz, and pyrite) and crediting the balance of the mineral matter,
not previously quantified, to the illitic group of minerals.
56
-------
The results of the illitic clay mineral analysis by the
three methods are shown in Table 10. The "best" value was usually
an average of the direct and difference methods, though in four
cases the K«0 method was also used in arriving at the "best" value.
In the one case where the mineralogical analysis as determined by
direct x-ray quantification did not total near 100 percent, the
value obtained by the difference method was assumed to be more
accurate than the other two methods. This is a reasonable assump-
tion because the difference values are not influenced by the
structural irregularities of the illitic material. The difference
average was obtained by averaging the two difference values obtained
by analyzing the mineral matter that was separated into layers using
the centrifuging technique discussed in Section III.B.3. and by
analyzing a representative sample of the composite mineral matter.
The potassium analysis generally produced values that were not in
complete agreement with the other two methods, but the method
served as a guide. The reason for the poor agreement of the potas-
sium results may be due to the large variation in the amount of
montmorillonite and mica present in the different blackwater samples.
Four samples (Nos. 7, 9, 10, and 11) show fairly good agree-
ment using all three methods, while all but one of the samples
(L.F. C Pa 4) show reasonable agreement between the difference
method and the direct x-ray method. The poor agreement for this
sample was due to the presence of a large amount of highly inter-
stratified illite-montmorillonite and its poor crystallinity. For
57
-------
Table 10. Approximate illitic mineral content in the mineral matter fraction from eastern
blackwater samples.
CO
Thickener
Underflow
Sample
(1) (2)
Based on Based on
Direct X-ray ^0
Quantification Analysis
(3)
Based on
Difference "Best"
Method Average Value
Source of
"Best" Value
Technique
Weight Percent
Pi.
L.K
L.K
L.F
Po.
Po.
Pi.
W Pa 1
. C Pa
. C Pa
. C Pa
M WVa
W WVa
/L.F.
2b
3b
4
5
6
H Oh 7b
E L Ky 8
Pr.
J Ala
9
16/5 J 111 10
16
W Ind
11
48
45
48
26
53
45
43
55
56
48
60
37
34
34
39
71
68
37
80
67
47
60
51
50
53
59
59
50
45
69
70
44
48
50
48
51
59
56
48
42
62
64
46
56
1,
1,
1,
3
1,
1,
1,
1,
1,
1,
1,
3
3
3
3
3
2,
3
2,
2,
2,
3
3
3
3
-------
Table 10. Continued.
tn
CO
Thickener
Underflow
Sample
Weight Percent
Average
Range
(1)
Based on
Direct X-ray
Quantification
48
26-60
(2)
Based on
K20
Analysis
52
34-80
(3)
Based on
Difference
Method Average
54
45-70
"Best"
Value
53
46-64
Source of
"Best" Value
Technique
, Illitic material: Illite, interstratified illite-montmorillonite, raontmorillonite, clays,
Values have been adjusted for carbonaceous content.
-------
those samples showing general agreement between these two methods,
the largest difference between methods is only 14 percent (Samples
E L Ky 8, Pr. J Ala 9) while 6 of the 11 samples show a difference
of 5 percent or less. Differences in structural irregularities in
the illitic minerals contained in these samples undoubtedly was the
cause of the variation between the three methods of analysis.
A summary of the mineral matter content of all these Eastern
blackwater samples is given in Table 11. Illitic material is seen
to be the dominant constituent in each sample tested, together with
varying and lesser amounts of quartz, calcite, and kaolinite, and
much smaller amounts of chlorite and pyrite. These minerals
accounted for essentially all of the mineral matter present in
most of the samples, though some samples also showed small amounts
of dolomite, feldspar, rutile, and siderite. These minor minerals
are also shown in Table 11.
Because of the method used to obtain, especially, the "best"
value for illitic material, the mineral composition of each sample
does not necessarily total exactly 100% but range from 94 to 106.
A comparison of, data from the 0'Gorman and Walker study on
the mineral constitutents in coal (27) with the data from the present
study on the mineral constituents in the blackwater effluent from coal
preparation plants was made. Table 12 shows the results of O'Gorman
and Walker's analytical results for some of the same coal seams as
were examined in the present study. As may be seen from Table 12,
the dominant mineral in most of these ccals is kaolinite, together
60
-------
Table 11. Approximate composition of the mineral natter fraction from eastern blackvater samples (veight percent).
Illltlc Material
Staple
PI. W P» 1
L.K. C Pa 2b
L.K. C Pa 3b
L.F. C Pa 4
Po. M WVa J
Po. U WVa 6
Pi. /L.F. H Oh 7b
E L Ky 8
Pr. J Ala 9
16/5 J 111 10
U U Ind 11
Average
tange of Average
"Best"*
Value
50
48
51
59
56
48
42
62
64
46
56
53
46-64
Illite
• tg.
doa.
doa.
• Ig.
doa.
don.
• ig.
doa.
doa.
•ig.
don.
Illite-
Mont.
doo.
don.
•ig.
• Ig.
•ig.
• Ig.
doa.
•ig-
• ig.
doa.
doa.
Mont.
• ig.
»ig-
•Ig-
•Ig.
• ig.
•Ig.
• ig.
• Ig.
•ig-
Kaolinite
Ave . Range
12
17
22
7
11
15
8
8
7
6
14
11
6-22
10-14
15-19
20-23
5- 8
9-13
13-17
7- 8
6 -9
6- 7
3- 8
10-17
Quartz
Ave.
18
14
9
8
17
15
16
13
14
21
22
15
8-22
Range
14-21
11-16
6-11
7- 9
16-18
14-16
13-19
12-14
13-14
19-22
21-22
Calcite
Ave.
19
12
14
21
6
17
13
0
0
22
4
12
0-22
Range
18-20
11-13
12-16
19-23
5- 7
15-18
12-14
17-26
1- 7
Chlorite
Ave.
3
4
4
3
6
5
3
7
4
0
4
4
0- 7
Range
2-3
3-4
3-5
2-3
6-6
3-6
2-3
6-7
3-5
—
3-5
Other
Pyrite Mineral*
2
4 K
3
3
1 0, ». S
1 ». S
11 I
1 ». «. S
1 0
9
6
4
1-11
?Proa Table 10.
Values have been adjusted for carbonaceous content.
Significant: 5-15Z
Doainate: Greater than 15Z
D--Dolomite; F~Feldapar; R--Rutile; S~Siderlte
-------
Table 12. Approximate mineral natter composition In G.S. coal seams (weight percent), (modified after O'Gorman and Walker)(27)
Oi
to
PSOC
Sample
"umber
Eastern
2
3
4
6
22
26
mi
AU J
103A
108
109
110
111
113
114
116
125
126
127
Seam
Samples
13 Elkhorn
13 Elkhorn
f3 Elkhorn
n Elkhorn
16 Illinois
16 Illinois
Pittsburgh
Pittsburgh
Plttaourgh
Pittsburgh
Pittsburgh
Pittsburgh
Lr. Kittannlng
Lr. Kittannlng
Lr. Freeport
Lr. Freeport
Lr. Kittannlng
Lr. Kittannlng
Locality
Diane, Ky.
Deane, Ky.
Deane, Ky.
Deane, Ky.
Victoria, 111.
Carrier Mills. 111.
tfishififtton Co • PA*
Washington Co. . Pa
Marianna, Pa.
Marianna, Pa.
Marianna, Pa.
Marianna, Pa.
Tire Hill'. Pa.
Tire Hill. Pa.
Ehrenf eld , Pa •
Hastings, Pa.
Ebensburg, Pa.
Ebensburg, Pa.
Kaol.
40-50
30-40
1-10
40-50
20-30
trace
50-60
>70
20-30
30-40
40-50
30-40
40-50
50-60
30-40
30-40
50-60
60-70
111.
trace
trace
1-10
1-10
10-20
1-10
10-20
1-10
1-10
10-20
10-20
30-40
1-10
10-20
1-10
10-20
n.d.
10-20
Mus.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n d.
n.d.
n.d.
n.d.
n d
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Chi.
n.d.
trace
1-10
1-10
trace
1-10
n d
n.d.
n.d.
n.d.
n d
n.d.
n.d.
trace
n.d.
n.d.
n.d.
n.d.
Mont.
n.d.
n.d.
trace
n.d.
n.d.
trace
n d
n.d.
,n.d.
n.d.
*n d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Mix.
1-10
trace
1-10
n.d.
1-10
1-10
n.d.
1-10
1-10
n.d.
n.d.
1-10
1-10
1-10
1-10
1-10
1-10
1-10
Cal.
n.d.
n.d.
n,d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
trace
n.d.
n.d.
n.d.
trace
1-10
Dol.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Qt«.
30-40
40-50
1-10
10-20
10-20
1-10
10-20
1-10
1-10
10-20
1-10
10-20
1-10
10-20
1-10
10-20
1-10
1-10
Gyp.
1-10
1-10
10-20
1-10
1-10
1-10
1-10
1-10
n.d.
10-20
trace
1-10
1-10
1-10
1-10
1-10
1-10
1-10
Pyr.
1-10
1-10
10-20
1-10
10-20
60-70
1-10
1-10
30-40
1-10
20-30
10-20
30-40
trace
30-40
10-20
10-20
1-10
-------
Tabl« 12. Continued.
CT>
PSOC
Sample
•unber
128
12*
132
133
135
U6
137
Heitern
67
Sum
Lr. lie tanning
Lr. Kit canning
Pocahontas 13
Pocahontas M
Prate
Pratt
Pratt
Sample*
Lower Suimyalde
Locality
Ebensburg, Pa.
Ebcnsburg, Pa.
Gary, W.Va.
Gary, W.Va.
Huaytown. Ala.
Rueytovn, Ala.
Ron* Canyon, Ut.
Kaol.
50-60
>70
10-20
30-40
50-60
60-70
20-30
10-20
111.
1-10
n.d.
n.d.
n.d.
10-20
1-10
n.d.
1-10
Mus.
n.d.
n.d.
n.d.
n.d.
10-20
1-10
n.d
n.d.
Chi.
n.d.
n.d.
1-10
1-10
trac*
n.d.
n.d.
n.d.
Mont.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Mix.
1-10
1-10
trace
1-10
n.d.
n.d.
1-10
1-10
Cal.
trace
1-10
trace
1-10
n.d.
n.d.
n.d.
n.d.
Dol.
n.d.
n.d.
10-20
n.d.
n.d.
n.d.
n.d.
n.d.
Qti.
1-10
1-10
10-20
1-10
10-20
1-10
1-10
1-10
Gyp.
trace
1-10
10-20
10-20
1-10
1-10
1-10
20-30
Pyr.
20-30
1-10
1-10
trace
1-10
1-10
50-60
20-30
Kaol.—Kaollnlte
111.—mite
HIM . — Muscovite
Chi.—Chlorite
Moot.—MontBorlllonite
Mix.—Mixed Layered Illlce-Honcnorlllonlte
C*l.~Calclta
Dol.— Doloalte
Qt*.—Quartz
Cyp.—Gypsum
Pry.—*yrite
Trace • < l.OZ
n.d. • not detected
-------
with lesser amounts of illite, interstratifled (mixed layer)
illite-montmorillonite, quartz, gypsum, and pyrite. It is worth
noting that chlorite and calcite were not usually detected in their
study.
Table 11 and 12 show that the commonly reported minerals in
both studies were kaolinite, illite, interstratified illite-
montmorillonite, quartz, and pyrite. Thus, although both studies
indicate the presence of the same types of minerals, the quantity
of some of them is strikingly different. O'Gorman and Walker show
kaolinite to be the dominant mineral in most of their samples,
while this study consistently shows the illitic material to be
dominant. The two studies also disagree sharply in the type of
minerals that show up in lesser amounts. Table 12 shows gypsum to
be a mineral commonly found in the coal samples studied by O'Gorman
and Walker, while chlorite and calcite were rarely found in their
samples. In contrast to this, Table 11 shows that chlorite and
calcite were common in most of the blackwater samples studied,
while gypsum was not detected in any of the samples. The differ-
ences in mineral composition found in the two studies strongly
indicate that the composition of the mineral matter contained in the
blackwater was influenced by some source other than the minerals
inherent in the coal seam.
The high illitic clay content in the blackwater samples
indicates that a large amount of the mineral material in the black-
water is of a shale origin. It is well known that the clay fraction
64
-------
of most Pennsylvania!! shales contains a large illitic clay fraction,
^80 percent (40), together with ^17 percent kaolinite and ^3 percent
chlorite. Some of the other minerals commonly found in shales are
quartz and carbonates. The clay content of shales, in general, is
usually about 60 percent, with illite the most abundant clay mineral,
montmorillonite and mixed-layer illite-raontmorillonite next, followed
by kaolinite, chlorite, and mixed-layer chlorite-montmorillonite
(40). Other clay minerals are relatively rare in normal sediments
(40). Furthermore, the presence of chlorite in all but one of the
Eastern blackwaters reinforces the conclusion as to the presence of
shale constituents material in the blackwater. Chlorite is commonly
found in roof shales of Pennsylvania coals but is rarely found within
the coal seam (12).
Most run-of-mine coal contains roof and floor material that
has become mixed with the coal during the mining operations, and it
is common for run-of-mine coal to have an ash content of 15 percent
or greater. This ash content may go as high as 40 percent for some
operations. Since this is substantially higher than the 5-10 percent
ash inherent in a coal seam, the balance of the ash must come from
overbreak during the mining operation. As an ever greater amount of
mechanization is introduced, such as the continuous miner and the
longwall, such overbreak material from floor and/or roof may be
expected in all run-of-mine coal in increasing amounts. Since part
of this shaley material is quite soft, and would decompose easily
during processing, its presence in the blackwater effluent from a
coal preparation plant is virtually assured.
65
-------
The composition of the mineral material in the eleven thick-
ener underflow blackwater samples thus bear a much more striking
similarity to the composition of the Pennsylvanian shales than to
the mineral composition of Pennsylvanian coals. Hence, the mineral
composition of the coal appears to have little influence on the
composition of the mineral matter in the blackwater, but is largely
determined by the nature of the adjacent roof and floor horizons
which are introduced into the run-of-mine coal by overbreak during
the mining operation.
c. Western samples. Two samples of waste material from coal
operations in the western part of the United States were also tested.
The mineralogical composition of these two samples is very different
from that of the other samples, and therefore is discussed separately.
Sample B.D. L Wa 12 was obtained from a slurry pond of an
operation in Washington state. Because the sample was obtained from
a settling pond rather than from a thickener underflow, as was true
for most of the other samples, the mineral matter may be expected
to be substantially finer in particle size than that of the other
samples. The sample was analyzed in the same manner as were the
other samples, except that the lack of illite as a major constituent
allowed quantification to be made using x-ray diffraction analysis
alone. The separated mineral matter fraction from flotation was
concentrated into layers by centrifuging the slurry and removing
each layer separately for quantification.
66
-------
Identification of the major minerals in each layer was
determined using the x-ray diffraction procedure outlined previously.
Section III.B.3. The mineral matter in this sample was found to
consist of a large clay fraction, mainly a montmorillonite, together
with plagioclase feldspars. The mineral material in the top layer
which consisted exclusively of the finest particles, was found to
be mostly montmorillonite. Thus, this layer was used as a standard
to estimate the amount of montmorillonite in the other layers and
in the total sample. Since no other minerals were found, and because
of the prominence of the characteristic x-ray diffraction peaks for
feldspar, the balance of the material was accredited to feldspar.
The presence of about 5 percent coal in the mineral matter was
quantified by microscopic examination and corrected from volume to
weight percent using the appropriate density.
The mineral composition of this sample is thus substantially
different from the other twelve samples in that this sample contained
a large amount of feldspar minerals. Montmorillonite was the only
clay constituent detected in the sample, which is also unusual.
Approximate Mineral Composition of Sample B.D. L Wa 12
Mineral Percentage
Montraorillonite 70
Feldspar 30
67
-------
Sample S/L.S. Ut 13 was a refuse sample obtained from a coal
preparation plant in Utah that treats coal rained in both Utah and
Colorado. Mineral analyses were performed on the minus 28 mesh
material obtained by screening the coarse refuse product.
The sample was separated into carbonaceous and mineral frac-
tions using the same froth flotation procedure as was used with
the other samples. The mineral fraction was then split at 400 mesh
and the coarse and fine fractions were analyzed separately using x-ray
diffraction. The minerals present in this sample were similar to
those found in the Pennsylvanian samples except for both a higher
dolomite content and a higher montmorillonite content. The mont-
morillonite was identified using the oriented mount technique
described in Section III.B.3. and quantified by the difference
method.
Approximate Mineral Composition of Sample S/L.S. Ut 13
Mineral Percentage
Montmorillonite 31
Kaolinite 24
Quartz 12
Calcite 17
Dolomite 14
Feldspar < 1
Pyrite 2
68
-------
As may be seen from Table 12, the mineral matter inherent in
the Lower Sunnyside seam contains about 20-30 percent gypsum, whereas
no gypsum was detected in the refuse material from the coal prepara-
tion plant treating coal from the Lower Sunnyside seam. The lack of
gypsum in the refuse sample suggests the possibility that the mineral
composition of the refuse had been influenced by some source other
than the coal itself. Again, the most likely source of this mineral
matter is the material bordering the coal seam. The fact that the
coal fed to this plant is produced by underground mining, where
overbreak is much more difficult to control than in surface mining,
supports the idea that the bordering material has a major influence
on the mineral composition of the refuse. Other possibilities may
be variation of mineral composition within the mining area, or that
coal from the Lower Sunnyside seam was not being treated at the
time this refuse sample was taken. The high clay content of this
sample was similar to that of the Eastern samples, although the high
montmorillonite content of this sample is certainly not like the
Pennsylvanian samples, but is more typical of the other Western
sample.
Summary Samples B.D. L Wa 12 and S/L.S. Ut 13 were from
Western coal seams that belong to the Tertiary and Cretaceous
geological periods, respectively, while the eleven Eastern samples,
discussed previously, belong to the Pennsvlvanian period. The
mineral composition of the two Western samples differs from the
other eleven samples in that the Western samples contain a
69
-------
significant amount of montmorillonite clay and essentially no
illite clay. Sample S/L.S. Ut 13 contains some of the typical
minerals found in the Eastern, or Pennsylvanian period, samples
such as kaolinite, quartz, and calcite. Again, the mineralogical
composition of the mineral matter from these two samples was
probably determined by the mineralogical nature of the adjacent
strata.
d. Summary. It appears that the composition of the mineral
matter in the effluent from a coal preparation plant will more than
likely resemble the mineral composition of the adjacent strata
rather than the mineral composition inherent in the coal seam
itself. The evidence for this is especially strong since the
mineralogical composition of the samples, and most especially the
high illite content, is much more characteristic of the adjacent
Pennsylvanian shales than of the mineral matter inherent in the
coal seam. The amount of clay in the blackwater of a coal prepara-
tion plant may be an indication of the degree of difficulty expected
when treating a "blackwater." Clay minerals consist of very small
platelet-shaped particles often with a mean size of a few micro-
meters or smaller. Because of their very slow settling rate, these
particles in a blackwater can be expensive and difficult to remove.
Montmorillonite clays, such as those found in the two Western samples,
are often even more difficult to flocculate efficiently and higher
turbidities in the recycled water are to be expected.
70
-------
B. Particle Size Analysis
1. Evaluation of Sizing Methods
Each blackwater sample after being separated into carbo-
naceous and mineral fractions by flotation, was then split at
400 mesh. The coarse fraction was analyzed using sieving tech-
niques and the fine fraction was analyzed using the MSA Whitby
Particle Size Analyzer. A comparison of some subsieve results was
made between those of the MSA Whitby Analyzer with those obtained
from the Sedigraph, manufactured by Micromeritics Instrument Corp-
oration, Norcross, Georgia.
A comparison between these two instruments was made to
determine the reliability of the MSA results. Allen (1) points
out some of the disadvantages of the MSA apparatus. These include:
possible compression of the sediment column with increasing speed
during centrifuging; the glass tube is the wrong shape to prevent
wall effects during settling; hindered settling in the neck of the
capillary eliminating the analysis of materials with a narrow size
range, which will settle at about the same time; and the loss of
sedimentation height as material builds up in the capillary. How-
ever, the results noted in this study are so reproducible that
these effects are probably not of major importance. The main
advantage of the method is that it is suited to both the gravita-
tional and centrifugal range, hence, a size range from about 0.2 to
80 urn may be analyzed. In this particular study the MSA was
71
-------
especially suitable since it offered a relatively fast method of
analysis for both the mineral and the carbonaceous sub-sieve
fractions.
Figures 3 and 4 show the results obtained when the mineral
fractions of two of the thirteen samples were analyzed by these
two different methods. The results of both analyses agree rela-
tively well, especially above 1 ym. This agreement indicates that
the sub-sieve analysis performed with the MSA Whitby Particle Size
Analyzer is quite reliable. The carbonaceous material in blackwater
made the Sedigraph impractical for the analysis of both the mineral
and the carbonaceous fractions and therefore, it was not used as the
main method of sub-sieve size analysis.
Two MSA analyses were used to determine the sub-sieve size
distribution of the minus AGO material in each sample. The values
of the two tests were plotted on Rosin-Rammler paper, and a smooth
curve was drawn through the points to produce the sub-sieve size
distribution for that particular sample. The values of the sub-sieve
size distribution were then combined with the sieve analysis by
multiplying the sub-sieve values by the value for the fraction of
material in that particular sample that was finer than 400 mesh.
There appeared to be no need to use a shape factor to incorporate
the sieve and sub-sieve results since most of the results produced
a relatively smooth curve. The size analysis data of the sieve and
sub-sieve material for the thirteen blackwater samples is in
Appendix D.
72
-------
-J
00
o
CC
111
a.
t
99.9
99.0
95
90
70
50
30
o
10
O.I
1.0 10
LOG PARTICLE SIZE (ftm)
100
Figure 3. Comparison of subsieve size distribution of the mineral matter from sample E L Ky 8
using the Whitby Particle Size Analyzer and the Sedigraph.
O Whitby Particle Size Analyzer
n Sedigraph
-------
z
UJ
o
oc
UJ
Q.
2
UJ
UJ
2
o
99.9
99.0
95
90
70
50
30
10
5-
2
0.1
1.0 10
LOG PARTICLE SIZE
100
Figure 4. Comparison of subsieve size distribution of the mineral matter from sample S/L.S. Ut 13
using the Whitby Particle Size Analyzer and the Sedigraph.
OWhitby Particle Size Analyzer
Q Sedigraph
-------
2. Particle Size Distribution of Blackwater Solids
Size distributions for all thirteen samples are shown in
Figures 5 through 13. The size distribution of the mineral frac-
tion was significantly finer than that of the carbonaceous fraction
for each sample analyzed. The difference in size distribution
between the two fractions is presumably due to the high clay content
in the mineral fraction. Clay minerals have layer structures with
very weak bonding between layers (14). Since water can penetrate
between the layers, the particles readily break down in suspension
and their size tends to be somewhat limited. X-ray diffraction
results show an extremely high clay content in the mineral matter,
especially in the finer material.
In addition to differences in relative fineness, the distribu-
tions for the coal and mineral fractions have quite different shapes.
The shape of the distribution curves for the mineral material of
the different samples are similar and somewhat unusual. The mineral
distribution curves have a flat portion starting at about 74 ym and
ending at about 20 urn, indicating the presence of very few particles
within that range. This plateau is a result of a decrease in the
amount of "coarse minerals" such as quartz, calcite, and pyrite at
about 74 urn and an increase in the clay minerals at about 20 ym or
less. To verify that this plateau was real and not simply an arti-
fact of the measurement technique, additional sedimentation analyses
were carried out. In these tests, MSA determinations were made on
the minus 200 mesh (74 ym), mineral matter rather than on the minus
75
-------
I 0 100
LOG PARTICLE SIZE
IOOO
Figure 5. Particle size distribution of blackwater solids, sample no. Pi W Pa 1.
Washington County, Pennsylvania, 55.5 Wt % Coal)
O Carbonaceous
CJ Mineral matter MSA used for minus 37 ym
B Mineral matter MSA used for minus 74 ym
(Pittsburgh Seam,
-------
I 0 100
LOG PARTICLE SIZE
1000
Figure 6. Particle size distribution of blackwater solids from the Lower Kittanning samples,
sample no. L.K. C Pa 2 and L.K. C Pa 3. (L.K. C Pa 2—Lower Kittanning Seam, Cambria
County, Pennsylvania, 64.2 Wt % coal; L.K. C Pa 3—Lower Kittanning Seam, Cambria
County, Pennsylvania, 66.0 Wt % coal)
Sample No. L.K. C Pa
O Carbonaceous
Q Mineral matter
Sample No. L.K. C Pa 3
% Carbonaceous
• Mineral matter
-------
oo
10 100
LOG PARTICLE SIZE (pm)
1000
Figure 7. Particle size distribution of blackwater solids, sample no. L.F. C Pa 4.
Seam, Cambria County, Pennsylvania, 80.A Wt % coal)
O Carbonaceous
D Mineral matter
(Lower Freeport
-------
IT
HI
Z
liJ
o
(E
UJ
a
UJ
>
o
100
1000
LOG PARTICLE SIZE
Figure 8. Particle size distribution of blackwater solids from the Pocahontas samples, sample
no. Po. M WVa 5 and Po. W WVa 6. (Po. M WVa 5—#3, #4, #5, Pocahontas Seam, McDowell
County, West Virginia, 70.9 Wt % coal; Po. W WVa 6—#3 Pocahontas Seam, Wyoming County,
West Virginia, 63.9 Wt % coal)
Sample No. Po. M WVa 5
Q Carbonaceous
DMineral matter
Sample No. Po. W WVa 6
•Carbonaceous
^Mineral matter
-------
00
o
cc
UJ
iZ
I-
UJ
o
£C
UJ
a.
i-
i
S2
ui
UJ
>
ID
O
10 100
LOG PARTICLE SIZE
1000
Figure 9. Particle size distribution of blackwater solids, sample no. Pi./L.F. H Oh 7. (75%
Pittsburgh Seam/25% Lower Freeport Seam, Harrison County, Ohio, 84.1 Wt % coal)
O Carbonaceous
DMineral matter
-------
oo
I 0 100
LOG PARTICLE SIZE (ft.m)
1000
Figure 10. Particle size distribution of blackwater solids, sample no. E L Ky 8.
Seam, Letcher County, Kentucky, 47.9 Wt % coal)
O Carbonaceous
Q Mineral matter
(#2 Elkhorn
-------
10 100
LOG PARTICLE SIZE
1000
Figure 11. Particle size distribution of blackwater solids, sample no. Pr. J Ala 9.
Jefferson County, Alabama, 72.3 Wt % coal)
O Carbonaceous
Q Mineral matter
(Pratt Seam,
-------
CO
CO
OL
UJ
z
UJ
o
cr
z
o
UJ
>
<
_l
u
2
3
O
I 0
LOG PARTICLE SIZE
100
1000
Figure 12. Particle size distribution of blackwater solids from Indiana and Illinois samples, sample
no. 16/5 J 111 10 and 16 W Ind 11. (16/5 J 111 10—#5, //6, Illinois Seam, Jackson County,
Illinois [30], 19.0 Wt % coal; 16 W Ind 11—#6 Indiana Seam, Warrick County, Indiana [30],
f\ f\ f\ r f . at -i\
28.9 Wt % coal)
Sample No. 16/5 J 111 10
O Carbonaceous
Q Mineral matter
Sample No. 16 W Ind 11
• Carbonaceous
M Mineral matter
-------
10 100
LOG PARTICLE SIZE (ptn)
1000
Figure 13. Particle size distribution of blackwater solids from western samples, sample no.
B.D. L Wa and S/L.S. Ut 13. (B.D. L Wa—Big Dirty Seam, Lewis County, Washington
[30], 27.2 Wt % coal; S/L.S. Ut 13—Somerset 'B1, 'C1, Colorado/Lower Sunnyside,
Utah, 50.1 Wt % coal)
Sample No. B.D. L Wa 12
0 Carbonaceous
fH Mineral matter
Sample No. S/L.S. Ut 13
O Carbonaceous
Q Mineral matter
-------
400 mesh (37 ym) material. In this way, a region of overlap (37 to 74
ym) between the sieving and sedimentation results was obtained. As
shown in Figure 5, the distributions obtained from both methods are
in very good agreement.
The size distributions of the carbonaceous material from the
different samples are also quite similar to each other. The carbo-
naceous material is somewhat more uniform than the mineral matter and
the distributions therefore tend to have a smoother shape than those
of the mineral material.
The shape of any size distribution is dependent upon the history
of the sample, and this may explain the atypical nature of some of
the samples, especially samples B.D. L Wa 12 and S/LS Ut 13. Sample
B.D. L Wa 12 was from a settling pond and S/LS Ut 13 was minus 28
mesh refuse obtained from the refuse product. The other eleven
samples were typically from thickener underflows from different
preparation plants. Sample B.D. L Wa 12 contains finer material
than any of the other samples. Thirty-one percent of its material
was found to be less than 1 ym, while the next finest material was
19% minus 1 ym. The extreme fineness of this sample may be due to
the fact that the sample came from a slurry pond where the solids
may have had a long period of time to settle. In addition, this
sample contained a large amount of montmorillonite clay which tends
to be extremely fine.
Sample S/LS Ut 13 contains a mineral fraction that was some-
what coarser than the other samples. Only 51% of its mineral material
85
-------
was less than 45 um while Che next coarsest sample contained 70%
less than 45 ym. The relative coarseness of this sample may have
been a result of the method used to obtain the sample, i.e., by
removing the minus 28 mesh fraction from the plant refuse by
screening.
The size analysis for Samples 16/5 J 111 10; 16 W Ind 11;
and B.D. L Wa 12 were determined by Michael F. Placha (30). He
used the same procedure that was previously outlined in Section
III.C.
3. Comparison of Size Distributions
A notable feature of this particle size characterization work
is the rather surprising similarity of the size distributions
obtained from seemingly quite different samples. This similarity
can be seen clearly in Figures 14 and 15 in which the mean size
distribution of the first eleven blackwater samples was calculated
for the mineral matter and the carbonaceous fractions, respectively.
Samples 12 and 13 were not included because of their differences
in their mineral composition and the method of sampling used. The
first eleven samples are from preparation plants, in the East and
Midwest, treating coal from seams belonging the the Pennsylvanian
Period.
The dashed lines in Figures 14 and 15 correspond to one
standard deviation about the mean, which indicates that the size
distribution of the eleven samples falls into a relatively narrow
band. This similarity Jas unexpected since the samples come froci a
86
-------
oo
I 0 100
LOG PARTICLE SIZE
1000
Figure 14. Mean particle size distribution of the mineral matter in the eleven eastern blackwater
samples.
O Mean
Q One standard deviation
-------
CO
00
CC
Ul
y soh
UJ
a
UJ
£
UJ
>
t-
<
:D
o
1.0
10 100
LOG PARTICLE SIZE
IOOO
Figure 15. Mean particle size distribution of the carbonaceous material in the eleven eastern
blackwater samples.
O Mean
Q One standard deviation
-------
variety of coal seams, mining operations, and preparation methods.
Although all eleven samples are from coal seams of the same geolog-
ical period, their geographical area covers most of the Appalachian
and some of the Mid-western states. Samples were obtained from
both surface and underground mining operations with the majority
of the samples coming from underground operations. A large variety
of treatment methods were employed at the different preparation
plants. Some of the plants have very simple circuitry in which
only coarse coal was being cleaned while many of the plants were
preparing metallurgical coal and therefore tend to have a more
complex circuit in which fine coal is cleaned. The shape of the
two mean size distributions are very different, with the mineral
fraction consisting of a finer material than the carbonaceous
material. The fineness of the mineral material was mainly due to
the presence of a lot of clay, while the carbonaceous material
contained essentially all coal and thus had a somewhat coarser size
distribution.
4. Overall Size Distribution
For each sample an overall size distribution can be calculated
from the separate size distributions of the mineral and carbonaceous
material (given in Appendix D) and from their weight percent (given
in Table 9). The combined size distribution for a sample can be
calculated using the following procedure:
89
-------
Example: Sample Pi W Pa 1
Data
Material -400 Mesh Wt% of Solids
Mineral
Carbonaceous
92.
64.
6
6
44.
55.
5
5
Percent of -400 mesh = (0.926 x 44.5) + (0.646 x 55.5) material in
sample = 77.1 percent
This method was used to generate the data given in Table 13,
except that the minus 44 pm (325 mesh) values were determined by
interpolation from the size distribution plots since this value
was not measured experimentally. Table 13 contains values for the
amount of material that is less than 44 pm and 1 urn for each frac-
tion and the total amount in each sample.
The overall size distribution for most of the thirteen black-
water samples is similar, especially for the eleven Eastern samples.
There are a few samples that are finer or coarser than the others,
but the majority of the samples show an unexpected similarity. The
range of the minus 44 ym material in the thirteen blackwater samples
is 28-86 percent, a 58 percent difference. If the two extreme samples
are not considered, a range of 40-77 percent, a 37 percent difference,
exists. Six of the thirteen samples have a range of 64-70 percent,
only a 6 percent difference. It is interesting to note that the
90
-------
Table 13. Particle size analysis of blackwater. (Weight percent
less than 44 yma and 1 ym)
Sample
Pi W Pa 1
L.K.C. Pa 2
L.K.C. Pa 3
L.F.C. Pa 4
PoM WVa 5
PoW WVa 6
Pi/LFH Oh 7
EL Ky 8
PrJ Ala 9
I6/5J 111.10
I6W Ind.ll
BDL Wa 12
S/LS Ut 13
Mean
Range
Coal
4 ym
66
43
35
44
62
52
16
47
54
30
32
16
40
41
16-66
Fraction
1 ym
6.1
2.5
2.5
4.2
5.0
2.3
1.1
3.0
2.8
0.8
5.2
2.3
3.1
0.8-6.
Mineral
4 ym
93
84
70
76
89
84
90
93
93
80
91
91
51
83
1 51-93
Fraction
1 yra
33
27
15
18
18
17
19
25
43
28
12
31
14
23
12-43
Total
4 ym
77
58
40
50
70
64
28
69
65
64
66
86
45
60
28-86
Sample
1 ym
17
11
4
7
9
8
4
14
14
19
9
31
9
12
4-31
a
44 ym equals 325 mesh.
91
-------
two samples that have extreme values for the minus 44 urn, total
material, are the two samples from the West. The reason for their
difference is most likely due to the source of the samples and to
the method of sampling.
A sub-sieve size distribution of the carbonaceous material
in sample B.D. L Wa 12 was not determined since this material com-
prised less than 3.0 percent of the total material. A size analysis
was made on the total sample, assuming the presence of such a small
amount of carbonaceous material would not have any significant effect
on the outcome of the analysis. This sample contained carbonaceous
material that appeared to be highly oxidized, resulting in poor
separation during froth flotation.
In most of the samples, the high clay content dominated the
size characterization of the mineral material and influenced the
overall size characteristics of the waste material. The thirteen
samples produce a total mean size distribution of 60 and 12 weight
percent minus 44 pm and 1 yra, respectively. The high percentage
of fine material in the waste water may be an indication of the
difficulty expected when treating the waste water. The mineralog-
ical and size characteristics for each specific sample has been
tabulated and given in Appendix E.
92
-------
C. Surface Properties of Mineral Matter and Coal Contained in
Blackwater
1. Introduction
The surface properties of the ash-forming minerals and the
coal fractions from the blackwater samples were investigated using
a Zeta Meter. The magnitude and sign of the surface charge of the
blackwater constituents were determined as a function of pH in
order to estimate the point of zero charge (PZC) for the different
constituents. The zeta potential of the particles composing a
suspension has an effect on the stability of that suspension, and
an approximation of this effect is shown in Table 14. This approxi-
mation ignores the effects of particle size and ionic strength of
the suspension, and assumes that all the particles are of the
same surface polarity.
According to Table 14, a zeta potential of 5 to 10 mv offers
fair agglomeration for material of similar surface polarity, with
excellent agglomeration occuring at about 5 mv or less. Of course,
it is the goal in the treatment of blackwater to destabilize the
suspension, i.e., to agglomerate or flocculate the particles. One
way to achieve this is to reduce the potential to near zero. Thus,
a knowledge of the potential of the bulk suspension and the individual
particles contained in the suspension is of great importance. For
this study the mineral matter and carbonaceous fractions were
initially studied separately. The fractionation procedure has
previously been outlined in Section III.B.3a.
93
-------
Table 14. Relationship between colloid stability and zeta
potential. (after Riddick [43])
Stability Zeta Potential3, mv
Excellent agglomeration 5 mv
Fair agglomeration 5 to 10 mv
Threshold for agglomeration 10 to 20 mv
Moderate stability 30 to 40 mv
Good stability 40 to 60 mv
Excellent stability 60 mv and higher
Helmholtz-Smoluchowski formula (43).
94
-------
2. Mineral Fraction
Once the mineral constituents in the blackwater samples
were identified, quantified, and their size distribution deter-
mined, the surface properties of the principal minerals were then
characterized. The surface properties of some of the principal
constituent minerals found in the blackwater, such as kaolinite,
have been investigated in the past and are well known, and there-
fore were not investigated in detail here. However, the surface
properties of especially the illites and chlorites are not avail-
able from the literature, and so these minerals were emphasized
in this study.
a. Illite. The surface properties of illite clays from
both illitic shales and from various blackwater samples were
determined and compared. The illitic shales that were investigated
were two samples from Fithian, Illinois: A. API Standard Clay
#35; and B. 25-lb bulk sample; and C. One sample from Morris,
Illinois, API Standard Clay #36.
The surface properties of the three illitic shales were
investigated to establish the general behavior of illites. The
pH-potential curves for the 'as-is1 illite samples A and B, from
Fithian, Illinois, were determined using distilled water (with HC1
and NaOH as pH regulating agents) and the results of this study
are shown in Figures 16 and 17. Note the similarity of these two
curves which show a zeta potential of about -5 to -10 mv over the
pH range of 3 to 8. Illite sample C from Morris, Illinois shows a
95
-------
3.0-
CD
--10
--20
--30
UJ
o
CL
u
M
Figure 16. Electrophoretic mobility of illite sample (A) from Fithian, Illinois. The surface
properties of the sample were investigated under the following conditions:
O As is distilled water
• As is 1 x 10~2M NaCl
Q Acid washed
A Acid washed 1 x 10~3M NaCl
Acid washed 1 x 10~2M NaCl
-------
<£>
3.0
o
^ 2.0
1.0
ffi
O
O
UJ
tr.
-1.0
a.
o
a:
-2.0
-3.0
6 7
pH
-30
20
10
>
E
-10
-20
-30
ui
&
£L
K
UJ
N
10 II
Figure 17. Electrophoretic mobility of illite sample (B) from Fithian, Illinois. The surface
properties of the sample were investigated under the following conditions:
O As is distilled water
LJ Acxd washed
Acid washed 1 x 10~3M NaCl
-------
somewhat different pattern (Figure 18). The change in surface
potential with pH for this sample is much more pronounced than
was found for the other two illite samples, not only was an
isoelectric point found at approximately pH 2.2, but the zeta
potential becomes more negative (-20 mv) in alkaline solutions
than was observed with the other two samples (-10 mv).
Because of the well-known ion exchange properties of clays
(14) the samples were given an acid wash to remove any cations
that might influence the behavior of the minerals in suspension.
The clays were washed with a 1:5 HC1 and water solution, stirred
for 5-10 minutes and then centrifuged. The acid solution was then
poured off and the solid material washed with distilled water and
centrifuged again. The washing step was repeated once and the
illitic material then dispersed by vigorous stirring before surface
analysis. This acid wash made the illite samples more negative
in each case, increasingly so at higher pH values (see Figures
16-18).
In order to evaluate the effect of ionic strength and to
determine if a better estimation of the PZC of these samples could
be made, both the 'as is1 and the acid washed samples were run in
-3 -2
10 or 10 M/L salt solution. Outside of reducing the potential,
as would be expected, this technique did not help as may be seen in
Figures 16-18.
A sample of illitic material from different blackwater
mineral matter fractions was obtained from the material used in the
98
-------
CD
CD
H-io
--20
--30
O
a.
UJ
N
Figure 18. Electrophoretlc mobility of illite sample (C) from Morris, Illinois. The surface
properties of the sample were investigated under the following conditions:
O As Is distilled water
Q Acid washed
A Acid washed 1 x 10~3M NaC1
Acid washed 1 x 10~2M NaCl
-------
identification and quantification process. X-ray analysis provided
both a careful identification and a quantification of this illitic
material, and the use of the centrifuge layering technique allows
the selection of a well-characterized material to be used for these
surface studies. A fraction of mineral matter that contained
essentially all illitic material was chosen for use in these surface
studies. The three samples used in these surface studies were
samples numbered Pi. W Pa 1; Po. M WVa 5; and 16/5 J 111 10, which
have the following characteristics:
Sample
Pi. W Pa 1
Po. M WVa 5
16/5 J 111 10
Illitic
Mineral
Present
Slightly
interstratified
illite-
montmorillonite
Illite
Highly
interstratified
illite-
montmorillonite
Approximate
Mineral
% Illitic
Minerals
65
80
90
Composition
% Other
Minerals
33
21
7
These particular samples were selected because each sample
contained a different type of illitic material. The results of
these studies of the surface properties of the three blackwater
illites are shown in Figure 19. The surface charge of the three
materials remains negative until pH 2.5 where the PZC for Po. M WVa 5
100
-------
3.0
2.0
1.0
_t
CD
i
o
h-
UJ
-1.0
(E
K
uj
_j
UJ
-2.0
-3.0
D-D
6 7
pH
30
20
10
>
E
-.0
-20
I
UJ
N
-30
10 II
Figure 19.
Electrophoretic mobility of illitic material from the following blackwater samples.
O Pi. W Pa 1
Q Po. M WVa 5
16/5 J 111 10
-------
occurred. The curves for samples Pi. W Pa 1 and 16/5 J 111 10
are seen to generally follow the pattern of the standard illite
samples from Fithian and Morris, Illinois, and show zeta-potentials
of about -15 to -10 mv over the pH range 3 to 7. As was true for
the standard illite samples, there is no indication that the PZC
is being approached for these latter two samples.
The difference in surface properties of these illitic
minerals is not unusual since illitic clays can vary in crystal
structure, ionic substitution, and chemical composition. All of
the illites developed a negative zeta potential of about -10 rav
or higher at neutral pH and this increases to about -20 mv at pH 9.
Agglomeration of illitic material is favored at low pH values, while
stability is favored at high pH values.
b. Chlorite. Due to the low concentration of chlorite in
the blackwater samples, it was not possible to produce a chlorite-
rich fraction from this source. However, the surface properties
of chlorite samples from Ishpemig, Michigan, and Calaveras, Cali-
fornia were investigated. The results of this study are shown in
Figure 20. The PZC for the two samples is quite different—pH 5.7
for the Michigan sample and pH 2.5 for the California sample.
Differences in the surface electrical properties of these two
samples is not unexpected in view of the wide variation in compo-
sition and cyrstallinity of chlorite (14).
102
-------
o
03
Figure 20. Electrophoretic mobility of the following minerals, chlorite and limestone.
O Chlorite, Ishpeming, Michigan
Q Chlorite, Calaveras, California
/\ Valentine Limestone, Centre County, Pennsylvania
-------
c. Other minerals. The surface properties of limestone in
alkaline solution were also investigated and the data are shown
in Figure 20. Calcite is a slightly soluble mineral whose potential
I | — _!_
determining ions (A) are Ca , CO . Although H and OH ions are
not preferentially adsorbed at the calcite surface, the pH of a
calcite suspension will influence its surface properties by
I L
effecting the concentration of the potential determining ions, Ca
and C0_, since these ions react with H and OH ions to form other
_ +
chemical species such as CO , HCO , H2CO , CaOH , and Ca(OH)2- The
limestone acquired a negative zeta potential of less than 5 mv
from pH 8 to 9.5, which indicates a good pH range for agglomeration.
The other principal minerals in the Eastern blackwater samples
are kaolinite, quartz, and small amounts of pyrite. In addition,
the two Western samples were found to contain a large amount of
montmorillonite (bentonite), dolomite, and feldspar. The PZC values
for these minerals are shown in Table 15, with the exception of
pyrite. Only once did feldspar and dolomite occur in the blackwater
samples in any significant amount and that was in Sample B.D. L Wa 12
and S/L.S. Ut 13, respectively. Although pyrite was detected in most
of the samples, its level was usually less than 5 percent.
d. Summary. The mineral matter in these blackwater samples
consists of two types of minerals; silicates and non-silicates. The
silicate minerals, in turn, consist of two subgroups:
104
-------
Table 15. Point of zero charge for some minerals found in blackwater.
(Literature values) (Potential determining ions are
H+ and OH~)
Mineral PZC
Kaolinite (18) pH 3.4
Quartz (11,28) pH 2 to 3.7
Montmorillonite (18) pH 8 + 10 mv or higher
Feldspar
Albite (9) pH 2.0
Oligoclase (26) pH 1.0
Microcline (9) pH 2.4
Orthoclase (26) pH 1.0
105
-------
1. Layer Structure Silicates—
illitic, kaolinite, montmorillonite clays and chlorite.
2. Framework Silicates—
quartz and feldspar -
Calcite is the most dominant mineral in the non-silicate
group with lesser amounts of dolomite and pyrite. The surface
properties of all the silicate minerals present are somewhat similar
in that the potential determining ions for these minerals are H
and OH , and their indicated point of zero charge occurs below pH 4.
The minerals in the non-silicate group are indirectly affected by
the concentration of H and OH ions because of the effect of pH
on their potential determining ions through the CO?-HCO -CO and
H~S-SH -S equilibria and through precipitation of metal ions by
hydroxyl ions.
Since the bulk of the mineral matter in the blackwater
samples is the clay mineral group, the surface properties of these
clay minerals will greatly affect the surface properties of the
suspension as a whole. This effect is further magnified because of
the small particle size and high surface area of the clays. Manipu-
lation of the pH of blackwater suspensions will thus have a strong
influence on the zeta potential of the contained mineral matter,
and therefore offers a means of controlling the agglomeration of
this mineral matter. Alkaline suspensions tend to develop large
negative zeta potentials for most silicate minerals which, in turn,
106
-------
would tend to decrease the agglomeration for these minerals. This
would leave slow settling fine particles suspended in the water
and result in a high turbidity of the water to be recycled. The
agglomeration of most of the mineral matter found in blackwater,
the silicates, should be enhanced as the pH of the suspension is
lowered.
3. Carbonaceous Material
The large carbonaceous content of most of the blackwater
samples suggests that the surface properties of this material will
exert an important influence on any blackwater treatment processes.
The surface properties of a material as heterogeneous as coal vary
depending on rank (41) , lithotypes (8), and mineral matter content
of the coal (3).
Campbell and Sun studied the effect of pH on the electrical
properties of coal surfaces and concluded that hydronium and hydroxyl
ions behave as potential determining ions (8). The effects of these
ions on different lithotypes produced a variety of results, as is
shown in Figure 21. The PZC for the whole coal sample, Pittsburgh
seam, Ellsworth, Pennsylvania, is pH 4.6. The zeta potential of
the whole coal sample is negative for pH values above 4.6 with
the magnitude of the potential increasing significantly as the pH
becomes alkaline. Not only do the surface properties of coal depend
on its rank and lithotype, but also on the degree of oxidation of
its surface (41). The effects of oxidation on surface properties
107
-------
o
oo
UJ
-30
--10
-20
-30
UJ
H
O
Q.
UJ
N
Figure 21. Variation of zeta potential with pH for Pittsburgh seam coal and its lithotypes.
(after Campbell and Sun) (8)
1
2
3
4
5
Fusain
Gangue
Durain
Whole coal
Vitrain
-------
of a high volatile A bituminous vitrain can be seen in Figure 22.
These results indicate that increases in the degree of oxidation
of coals increase the negative value of the zeta potential and
lower the PZC.
The surface properties of carbonaceous material taken from
several of the blackwater samples studied in this report were
investigated. A direct measurement of the surface properties of
the carbonaceous material was not performed since the samples were
obtained from a flocculated thickener underflow. The effect of
any flocculants that may have contaminated the coal surface was
minimized by taking only the plus 400 mesh carbonaceous fraction
and grinding it to near colloidal size to achieve a relatively
clean surface. The surface properties of this material from six
different blackwater samples were then investigated as a function
of pH. The results are shown in Figures 23 and 24.
The results for all of these samples are roughly similar
with an indicated PZC at pH 2.5 to 4.0 for all of the samples
except for that from the Lower Kittanning seam (L.K. C Pa 2).
They thus follow the general pattern established by Sun and
co-workers (8,41) for fresh and oxidized coal. In actual prac-
tice one might expect the particles contained in blackwater to
have surface properties more closely approximating those of
oxidized coal (Figure 22).
In order to characterize, more thoroughly, the nature of
the carbonaceous material contained in blackwater, the pH-zeta
109
-------
E
o
4.0
2.0h
m
o
UJ
cc
o
z
Q.
O
(T
o -4.0h
-6.0
7 8
pH
10 II 12
-60
Figure 22. Effect of oxidation time on electrokinetic behavior of HVA-bituminous vitrain.
(after Wen and Sun) (41)
HVA bituminous vitrain oxidation time at 125°C, Hr
• 0
C 24
Q 48
A 120
4 380
-------
3.0-
2.0-
1.0
oo
o
a.
o
a:
o
-1.0
-2.0
-3.0
30
20
10
UJ
o
Q.
-10
UJ
N
-20
-30
6 7
PH
8
10 II
Figure 23. Electrophoretlc mobility of coarse carbonaceous material from the following
blackwater samples.
O Pi. W Pa 1
A L.K. C Pa 2
O Pi./L.F. H Oh 7
-------
3.0
E
i: 2.0
^
u
I
* ,.o
ffl
O
O
a:
$ "
a.
o
a:
-2.0
UJ
-3.0
10
30
20
10
i
O
a.
-10
-20
-30
II
PH
Figure 24. Electrophoretic mobility of coarse carbonaceous material from the following
blackwater samples.
A Po. W WVa 6
Q E L Ky 8
16 W Ind 11
-------
potential curves were determined for coal selected from three of
the seams from whence came the blackwater. These seams are the
Pittsburgh (Pi. W Pa 1) , Lower Kittanning (L.K. C Pa 2), and Lower
Freeport (L.F. C Pa 4). The results shown in Figure 25 indicate
a pattern for fresh coal substantially different than that shown
in the other figures. It definitely indicates that the coal taken
from the blackwater samples was oxidized. Oxidized coal in a froth
flotation circuit will tend to report to the tails and thus end up
in the primary effluent of a preparation plant. The flotability
of coal decreases as it becomes oxidized by weathering (36).
The surface properties of the carbonaceous materials con-
tained in blackwater depend on a number of factors such as the rank,
lithotype, and degree of oxidation of the particular coal sample.
The zeta potential of most coals is negative in alkaline solution
and the potential decreases as the pH is lowered. The PZC of a
particular coal will depend on the composition of the coal and
the degree of oxidation of the surface has acquired, with the PZC
becoming lower as the degree of oxidation increases. Therefore,
in the absence of specific flocculating agents such as alum, lime,
starch, synthetic polymers, the agglomeration of most coal suspen-
sions will be enhanced as the pH of the coal slurry becomes
moderately acidic because of the lower zeta potential. The optimum
pH range for agglomeration to occur for a particular coal will
depend on the specific properties of that material, most especially
its degree of surface oxidation. However, it appears that an
113
-------
Figure 25. Electrophoretic mobility of hand-picked coal samples.
O Pittsburgh seam
Q Lower Kittanning
/\ Lower Freeport
-------
alkaline pH for most coals results in a high negative zeta poten-
tial and thus a decrease in the ability to agglomerate. The best
pH for flocculation of coal by pH control alone would be pH 5 to 7
for fresh coal and pH 2 to 4 for oxidized coal. The PZC value for
fresh coal is substantially different from that of the mineral
matter, whereas for the oxidized coal the optimum pH for floccu-
lation, about pH 2, is similar to that of the mineral matter.
4. Surface Properties of Blackwater Slurries
Miller and Deurbrouck (24) analyzed the surface properties
of blackwater slurries from four different coal seams—Upper Free-
port, Hernshaw, Pocohontas No. 3, and Pittsburgh. The slurries
were obtained from refuse thickener feed and did not contain any
flocculants, but some of the samples did contain flotation reagents.
The samples were dried to prevent disintegration of the solids
during storage. The results of this study are shown in Figure 26.
The surface properties of the four slurries are roughly
similar for pH values below 10. The PZC for the four samples
occurs near pH2 and are similar to those of an oxidized coal in
the region below pH 10. The ash content of the slurries ranged
from 16.7 to 54.2 percent, indicating that the slurries contained
much carbonaceous material. If oxidized, this carbonaceous material
would produce a zeta potential curve similar to those obtained in
the present study.
The surface properties of an unflocculated thickener feed,
obtained from the same preparation plant as was blackwater sample
115
-------
3.0
2.0
1.0
E
o
o
«
•>
CD
O
O
H
UJ
o -1.0
i
0.
o
-------
L.K. C Pa 2, were studied, and the results of this analysis are
shown in Figure 27. About 60 percent of the solid material in
this sample was carbonaceous, and the balance was mineral matter.
A total of 30 randomly picked particles were measured, and the
data obtained were used to calculate the mean zeta potential at
a particular pH range. Table 16 gives a tabulation of the varia-
tion in electrophoretic mobility for the various particles measured.
Note that electrophoretic mobilities of most of the particles are
similar, suggesting that the surface properties of most of the
material are similar.
The zeta potential of the material was not significantly
effected by varying the pH of the suspension. Since the zeta
potential of this slurry did not vary significantly from -10 mv
as the pH was varied from pH 2.2 to pH 9 (see Figure 27).
This insensitivity of the surface potential of this material
may be real or may be due to adsorbed compound such as flotation
reagents, e.g., frother. Flotation reagents would tend to contami-
nate the surface of the particles and modify the surface properties.
In this regard, one possible explanation for the differences
between the present results and those of the Miller and Deurbrouck
study may be the manner in which the slurries were stored. In the
Miller-Deurbrouck study, the four slurries were stored in a dry
form, while in the present study, the sample was stored in a
slurry form. Drying the slurries may have caused the organic
117
-------
CO
3.0
2.0
,.o
o
o
0
M
S
UJ
o -i.o
x
CL
O
5 -2.0-
UJ
-3.0-
2
pH
30
20
,0
-10
UJ
2
UJ
Nl
-20
-30
10 II
Figure 27,
Electrophoretic mobility of an unflocculated thickener feed from a plant treating
Lower Kittanning coal.
L.K. C Pa 2
-------
Table 16. Electrophoretic mobility of a blackwater sample from a
preparation plant treating Lower Kittanning coal.
(Percentage of the 30 particles counted versus
electrophoretic mobility)
Electrophoretic
Mobility
(Negative)
0.50
0.58
0.66
0.80
1.00
1.33
- 0
- 0
- 0
- 1
- 1
- 2
.58
.66
.80
.00
.33
.00
Percent of
PH
3.0
16.
30.
23.
10.
6.
0.
pH
3.9-4.3
7
0
3
0
7
0
10.
33.
26.
13.
10.
0.
0
3
7
3
0
0
Particles
PH
5.5-6.2
23.
36.
20.
13.
6.
3
7
0
3
7
PH
6.8-7.2
10.
3.
26.
13-
20.
16.
0
3
7
3
0
7
pH
9.3-9.4
3.3
20.0
36.7
26.7
13.3
Mean
Electrophoretic
Mobility
(Negative) 0.64 0.70 0.80 0.95 0.97
Equivalent
Zeta
Potential
mv
(Negative) 2.5 9.3 10.6 12.6 13.0
119
-------
flotation reagents to be destroyed or modified whereas this would
be very unlikely to occur when the sample is stored in slurry form.
5. Summary
Generally blackwater consists of a large amount of carbo-
naceous material together with mineral matter that is predominantly
silicates such as clays and quartz. The potential determining ions
for most of this material are hydronium and hydroxyl ions. While
the PZC for the different coals and silicate minerals are not the
same, still most of the materials present in blackwater, except
carbonates, have a PZC below pH 5. Generally, the zeta potential
for most constituents found in blackwater is decreased as the pH is
lowered, thus favoring agglomeration. This, of course, applies only
to those systems where specific inorganic or organic flocculants
are not added.
120
-------
V- SUMMARY AND CONCLUSIONS
Characterization of the fine solid material in the primary
effluent from coal preparation plants provides the basis for a
better understanding of the problems associated with treating
"blackwater." The present study was made to obtain a comprehen-
sive characterization of the blackwater solids from coal preparation
plants. The suspended solids from thirteen blackwater samples,
representative of the major United States coal seams where wet
preparation methods are used, were characterized by mineralogical
content, particle size distribution, and surface properties.
The conclusions from this work are as follows:
A. Mineralogical Composition
1. Blackwater solids consist of two types of material—
carbonaceous and mineral—of distinctly different chemical and
physical properties.
2. Based on mineralogical similarities, the samples were
divided into two groups: those from the Eastern half of the
United States (Appalachian and Midwestern coal fields) and those
from the Western half. The mineralogical content of the eleven
Eastern samples was similar, while the two Western samples were
121
-------
different from the Eastern ones, as well as from each other. The
Eastern samples show marked similarities since they are all derived
from coals of the Pennsylvanian period.
3. For all eleven Eastern blackwater samples tested, the
carbonaceous content amounted to approximately 60% of the total
weight of the blackwater solids. These studies showed that it
is possible to remove, by froth flotation, essentially all of this
carbonaceous (coal) fraction from the blackwater, and that the
quality of this coal is such that it could be blended with the
coarse clean coal without significantly altering the quality of
the total product.
4. Additional clean coal may be recovered from current
blackwater discharges from preparation plants by a more extensive
use of the flotation process.
5. The average ash content of the carbonaceous fraction
removed by froth flotation was 11 percent, as compared to an average
of 41 percent ash in the as received blackwater samples.
6. The mineral fraction of the blackwater solids from
Eastern and Midwestern coal fields contains largely illitic clays
together with lesser amounts of kaolinite, quartz, calcite, chlorite,
and pyrite. Minor amounts of dolomite, feldspar, rutile, or siderite
were found in some of the samples.
122
-------
7- The average mineralogical composition of the mineral
matter fraction from blackwater solids of the eleven samples
representative of the 'Eastern' coal fields can be summarized
as follows:
Principal Minerals, Percent
Illitic Kaolinite Chlorite Calcite Quartz Pyrite
Average 55 11 4 12 15 4
Range of
Average 47-65 6-22 0-7 0-22 8-22 1-10
Blackwater from plants treating coals dating from the
Pennsylvanian period may be expected to have a mineral composition
similar to this.
8. The high illitic clay content in the Eastern blackwater
samples indicates that a large amount of the mineral material in
the blackwater is of shale origin. Since shaley material is usually
soft, and would decompose easily during processing, its presence in
the blackwater effluent from a coal preparation plant is virtually
assured.
9. The samples studied from West Virginia, Kentucky, and
Alabama contained an "illitic" material of relatively good crystal-
linity with very little or no interstratification of montmorillonite
123
-------
with the illite, whereas the samples tested from Pennsylvania,
Ohio, Indiana, and Illinois contained an illitic material of
varying crystallinity and interstratification.
10. The two Western samples have a different mineralogy
than do the eleven Eastern samples studied. Both Western samples
contain a large amount of montmorillonite clay. The unique
mineral content of these two samples may be attributed to the
fact that these coal seams belong to two different geological
periods—the Washington sample (B.D. L Wa 12) from the Tertiary
and the Colorado/Utah sample (S/L.S. Ut 13) from the Cretaceous.
11. Montmorillonite clay, such as that found in the Western
samples, is often more difficult to flocculate efficiently than
are illitic and kaolin clays, and a higher turbidity in the
recycled water from plants treating these Western coals is to be
expected.
12. The primary control on the composition of the mineral
matter contained in blackwater is shown to be the composition of
the adjacent strata which becomes incorporated into the run-of-mine
coal during mining.
13. The differences in the carbonaceous content from sample
to sample in the thirteen blackwater samples is more than likely
due to differences in the mining and preparation methods employed
at the different mines rather than to a difference in the type of
coal being mined.
124
-------
14. The average ash content of pure mineral matter of a
typical Eastern sample is about 87 percent. The remaining 13
percent loss is due to the formation of H~0, CO , SO , etc. upon
heating.
B. Particle Size Analysis
1. Carbonaceous (coal) and mineral fractions from the
different blackwater samples produce two distinct size distribu-
tions. The carbonaceous fraction is consistently coarser than
the mineral matter fraction. On the average, 41 percent of the
carbonaceous particles are less than 44 yra, whereas 83 percent, on
average, of the mineral matter particles are less than 44 ym.
2. A considerable similarity in particle size distribution
was found among the eleven Eastern samples. The two Western
samples, however, were found to have quite different size distribu-
tions, probably due to differences in the mineralogy and in the
sampling procedures.
3. Typically, the size distributions for the mineral matter
tend to be bimodel, probably due to the presence of mixtures of
"coarse" minerals (quartz, calcite, pyrite, etc.) and "fine"
minerals (clays).
4. The size distributions of the mineral matter in the
Eastern samples were found to be remarkably similar presumably
125
-------
because of the similarity in their mineral content. The particle
size distributions of the mineral matter from all eleven of these
Eastern samples could be plotted as a narrow band with a standard
deviation ranging from +2.2 to +9.7 percent depending on size.
A composite size distribution shows that, on the average, 70, +9.7
percent of the mineral matter is finer than 10 microns. The fine-
ness of these materials is no doubt due to the presence of large
amounts of clay minerals.
5. Similar composite size distributions for the carbonaceous
fractions produced a standard deviation ranging from +0.8 to +15.9
percent. The average size distribution of the carbonaceous fraction
indicates this material to be much coarser than is the mineral
matter fraction. By comparison with the mineral matter fraction,
the carbonaceous material averages only 21.2, +7.3 percent finer
than 10 microns.
6. For most of the samples, the high clay content completely
dominated the size characteristics of the mineral matter fraction
and strongly influenced the overall size characteristics of the
blackwater solids.
C. Surface Properties
The third area of investigation was a study of the surface
properties of the principal mineral and carbonaceous constituents.
126
-------
A Zeta Meter was used to determine the electrophoretic mobility of
these constituents as a function of pH.
1. Hydroniura and hydroxyl ions are potential determining
ions for coal and the silicate mineral constituents in blackwater.
These two mineral categories (coal and silicates) typically account
for about 90% of the particulate matter found in blackwater.
2. Pyrite and the carbonate minerals, mostly calcite, are
the only important constituents found in blackwater for which these
ions are not directly the potential determining ions. These minerals
are indirectly affected by the concentration of H and OH ions,
however, because of the effect of pH on their potential determining
ions through the CO -HCO_,CO* and H2S-SH~-S~ equilibria and through
precipitation of metal ions by hydroxyl ions.
3. The point of zero charge, PZC, for the silicate minerals
is usually below a pH of 4.
4. The surface properties of the illitic group of clay
minerals was highly variable reflecting the high degree of structural
and compositional variation in this class of clay minerals. For
some illites the PZC occurred at pH 2-3 while for others no PZC
was found and the particles maintained a negative potential over
the entire range studied, pH 2-10.
127
-------
5. Manipulation of the pH of blackwater suspensions will
have a strong influence on the zeta potential of the contained
mineral matter, and offers a means of controlling the agglomeration
of this mineral matter. The agglomeration of most of the mineral
matter in blackwater, the silicates, should be favored as the pH
of the suspension is lowered.
It is not to be inferred that pH control would be the only
means, or even the preferred means, of achieving flocculation of
the particulate matter in blackwater. In practice, the use of
inorganic and organic flocculating agents such as lime, alum, starch,
and polyacrylamides would usually be the preferred method of floccu-
lation.
6. Since most of the mineral matter in blackwater is clays,
the surface properties of these clay minerals will exert a major
influence on the surface properties of the suspension as a whole.
This effect is further magnified because of the small particle size
and high surface area of the clays.
7. The large carbonaceous (coal) content in most of the
blackwater samples suggests that the surface properties of this coal
will also be an important factor in determining the bulk properties
of the suspension and the blackwater treatment process.
8. The fresh coal samples tested have a PZC between pH 3
and 7, with the PZC decreasing to pH 2 or below as the surface of the
128
-------
coal becomes oxidized. The zeta potential of most coals is negative
for alkaline solutions and decreases in magnitude as the pH is
lowered.
The surface properties of the carbonaceous constituents of
blackwater will depend on a number of factors such as rank, litho-
type, degree of oxidation, and the chemistry of the blackwater
solution.
9. In actual practice one would expect the carbonaceous
particles contained in blackwater to have surface properties much
closer to those of oxidized coal than to the fresh coal.
D. Characterization of a Typical Eastern Blackwater Sample
The characteristics of an average Eastern blackwater sample
are shown in Table 17.
129
-------
Table 17. Characteristics of a typical eastern blackwater sample.
Solid Material
Mineral Carbonaceous
Weight, Percent 40.6 59.4
Ash, Percent 84.3 10.9
Sulfur, Percent 1.97 1.51
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite Chlorite
55 11 15 12 4
Particle Size Analysis (weight percent less than)
Size (yra) Mineral Carbonaceous
44 86 44
1 22 3
Surface Properties of the Principal Constituents (coal
Potential Determining Ions H OH
Point of Zero Charge Less than pH 5
Total
100.0
41.0
1.68
Pyrite
4
Total
59
11
and silicates)
130
-------
VI. RECOMMENDATIONS FOR FUTURE STUDY
This work, while accomplishing much in the area of character-
izing blackwater, opened up several new areas worthy of future study.
The following suggestions are given for the extension of this
research:
1. Characterization of effluent from different unit opera-
tions, especially jigs, heavy media vessels, cyclones, tables, and
froth flotation.
2. An analysis of the fine particulate material that tends
to remain suspended in the thickener overflow at different coal
preparation plants.
3. Comparison of the surface properties of solid material
in the primary effluent from plants having froth flotation with
that of plants not having flotation.
4. Analyses of the particle size of thickener underflow
from preparation plants using similar treatment methods but treating
coal from different seams.
5. Determination of the mineral composition of the strata
bordering different coal seams for purposes of making a direct
131
-------
comparison with the mineral composition of their respective
blackwaters.
6. Investigate how the information obtained in this study
relates to obtaining a more efficient method of treating blackwater,
especially in the areas of flocculation and filtration.
132
-------
REFERENCES
1. Allen, T., Particle Size Measurement, London: Chapman and
Hall, Ltd., 1975.
2. Anderson, J. C., "Coal Waste Disposal to Eliminate Tailings
Ponds," Mining Congress Journal, July, 1975, pp. 42-45.
3. Apian, F. F., "Coal Flotation" in Flotation - A. M. Gaudin
Memorial Volume, ed. by M. C. Fuerstenau, New York: AIME,
1976, pp. 1235-1261.
4. Apian, F. F. and Fuerstenau, D. W., "Principles of Nonmetallic
Mineral Flotation," Froth Flotation - 50th Anniversary Volume,
ed. by D. W. Fuerstenau, New York: AIME, 1962, pp, 170-214.
5. Augenstein, D. A. and Sun, S. C., "Characterization of Coal
Refuse by Low Temperature Ashing," Trans. AIME, Vol. 256,
pp. 161-166 (1974).
6. Baker, A. F. and Miller, K. J., "Zeta Potential Control: Its
Application in Coal Preparation," Mining Congress Journal,
January, 1968, pp. 43-44.
7. Brown, D. J., "Coal Flotation," Froth Flotation - 50th Anniver-
sary Volume, ed. by D. W. Fuerstenau, New York: AIME, 1962,
pp. 518-539.
8. Campbell, J. A. and Sun, S. C., "Bituminous Coal Electrokinetics,"
Trans. AIME, Vol. 247, pp. 111-114 (1970).
9. Deju, R. A. and Bhappu, R. B., "A Chemical Interpretation of
Surface Phenomena in Silicate Minerals," Trans. AIME, Vol.
235, pp. 329,332 (1966).
10. Environmental Protection Agency, "Coal Mining Effluent Guide-
lines and Standards," Federal Register, May 13, 1976,
p. 19838.
11. Gaudin, A. M. and Fuerstenau, D. W., "Quartz Flotation with
Anionic Collectors," Trans. AIME, Vol. 202, p. 66 (1955).
133
-------
12. Gluskoter, H. J., "Clay Minerals in Illinois Coals," Journal
of Sedimentary Petrology..Vol. 37, No. 1, pp. 205-214, March,
1967.
13. Gregory, M. J., "Problems Associated with Closing Plant Water
Circuits," Mining Congress Journal, November, 1975, pp.
52-55.
14. Grim, R. E. , Clay Mineralogy, New York: McGraw-Hill, 1968.
15. Healy, T. W. and LaMer, V. K., "Flocculation of Mineral Dis-
persions by Polymers," Proceedings VII International Mineral
Processing Congress, ed. by Nathaniel Arbiter, Gordon and
Breach Science Publishers, September, 1964, pp. 359-366.
16. Hirt, W. C. , M.S. Thesis, Mineral Processing Section, The
Pennsylvania State University, 1973.
17- Iwasaki, I., Cooke, S. R. B., and Choi, H. S., "Flotation of
Cummingtonite," Trans. AIME, Vol. 220, p. 394 (1961).
18. Iwasaki, I., Cooke, S. R. B., Harraway, D. H., and Choi, H. S. ,
"Iron Wash Ore Slimes - Some Mineralogical and Flotation
Characteristics," Trans. AIME, Vol. 223, p. 97 (1962).
19. Joint Committee of Powder Diffraction Standards, Search Manual,
1974.
20. Leonard, J. H. and Mitchell, D. R., Coal Preparation, 3rd
Edition, New York: AIME, 1968.
21. Lucas, R. J., Maneval, D. R., and Foreman, W. E., "Plant Waste
Contaminants," Coal Preparation, 3rd Edition, New York:
AIME, 1968, p. 17-1.
22. MacEwan, D. M. G., "Effects of Structural Irregularities on
the Quantative Determination of Clay Minerals by X-Rays,"
Acta Universitatis Carolinae - Geoligica Supplementum I, 1961,
pp. 83-90.
23. Medlin, J. H. , Suhr, N. H., and Bodkin, J. B., Atomic Absorption
Newsletter, Vol. 8, No. 2, p. 25 (1969).
24. Miller, K. J. and Deurbrouck, A. W., "Evaluation of Synthetic
Organic Flocculants in the Treatment of Coal Refuse," United
States Bureau of Mines RI 7102 (1968).
25. Nelson, J. B., "Assessment of Mineral Species Associated with
Coal," British Coal Utilization Research Association Monthly
Bulletin. Vol. 17, No. 2, pp. 41-45 (1953).
134
-------
26. Ney, P., Zeta-Potentiale und Flotierbarkeit Von Mineralen,
New York: Springer-Verlag Wien, 1973.
27. O'Gorman, J. V. and Walker, P- L., Jr., "Mineral Matter and
Trace Elements in U.S. Coals," United States Department of
Interior, Office of Coal Research, Report No. 61, Interim
Report No. 2 (1972).
28. O'Melia, C. R., "A Review of the Coagulation Process," Public
Works, May. 1969, pp. 87-98.
29. Oliver, J. P., Hickin, G. K. and Orr, C. , Jr., "Rapid Automatic
Particle Size Analysis in the Subsieve Range," Powder Tech-
nology, Vol. 4, pp. 257-263 (1970/71).
30. Placha, F. M. , Senior Research Project, Metallurgy Section, The
Pennsylvania State University, 1976.
31. Pritchard, D. T., "Closed Circuit Preparation Plants and Silt
Ponds," Mining Congress Journal, November, 1974, p. 30.
32. Rastogi, R. C., M.S. Thesis, Mineral Processing Section, The
Pennsylvania State University, 1970.
33. Roy, R. and Warshaw, G. M., "Classification and a Scheme for
the Identification of Layer Silicates," Geological Society
of American Bulletin. Vol. 72, pp. 1455-1492 (1961).
34. Sandy, E. J., "Mechanical Dewatering," Coal Preparation, 3rd
Edition, ed. by J. W. Leonard and D. R. Mitchell, New York:
AIME, 1968, pp. 12-1.
35. Somasundaran, F- and Agar, G. E., "The Zero Point of Charge of
Calcite," Journal of Colloid Interface Science, Vol. 24,
pp. 433-440 (1967).
36. Sun, S. C., "Effects of Oxidation of Coals on Their Flotation
Properties," Trans. AIME. Vol. 199, pp. 396-401 (1954).
37. United States Bureau of Mines, Minerals Yearbook 1973, Vol. 1,
1973.
38. Van r.iphen, H. , An Introduction to Clay Colloid Chemistry, New
York: Interscience Publishers, 1963.
39. /anderhoff, J. W., "Mechanism of Flocculation of Colloidal
Suspensions," in Proceedings of the Chemical Institute of
Canada, Flocculation and Dispersion Symposium, November,
1974, p. 173.
135
-------
40. Weaver, C. E., "The Significance of Clay Minerals in Sediments,"
Fundamental Aspects of Petroleum Geochemistry, ed. by
Bartholomew Nagy and Umberto Colombo, Amsterdam: Else-
vier Publishing Company, 1967, p. 41.
41. Wen, W. W. and Sun, S. C. , "An Electrokinetic Study of the
Araine Flotation of Oxidized Coal," Preprint 76-F-343, Fall
Meeting, Denver, September 1-3, 1976.
42. Whitby, K. T., "A Rapid General Purpose Centrifuge Sedimen-
tation Method for Measurement of Size Distribution of Small
Particles," Heating, Piping, and Air-Conditioning, June, 1955,
pp. 69-71.
43. Zeta Meter Manual. 2nd Edition, New York: Zeta-Meter, Inc., 1968.
136
-------
APPENDIX A
STANDARD X-RAY DIFFRACTION GRAPHS FOR QUANTIFICATION OF THE
MINERAL MATTER FRACTION FOUND IN BLACKWATER
137
-------
Several of the important minerals were quantified using peak
height of a characteristic x-ray diffraction peak of that particular
mineral. A set of graphs (Figures A.1-A.6) relating peak height to
the mineral content was used for this quantification. The mineral
content was varied by adding known amounts of powdered glass, an
amorphous substance which serves as a diluent. The mixtures were
mounted and x-rayed using the procedure outlined in Section III.B.3.
The characteristic peak, source, and impurities of each standard
are listed in Table A.I.
138
-------
0.0
10 20 30 40
PERCENT ILLITE
Figure A.I. Standard x-ray diffraction pattern for illite.
2.57 X Peak
4.48 X Peak
139
-------
15
. 10
o
ui
Ui
a.
10 20 30
PERCENT KAOLINITE
40
50
10 ZO 30
PERCENT QUARTZ
Figure A.2. Standard x-ray diffraction
pattern for kaolinite.
3.57 X Peak
Figure A. 3. Standard x-ray diffraction
pattern for quartz.
1.82 & Peak
-------
5 10 15 20
PERCENT CHLORITE
Figure A.4. Standard x-ray diffraction pattern for chlorite.
3.55 8 Peak
141
-------
10
20 30 40
PERCENT CALCITE
50
Figure A.5. Standard x-ray diffraction pattern for calcite.
3.04 X Peak
142
-------
5 10 15
PERCENT DOLOMITE
20
Figure A.6. Standard x-ray diffraction pattern for dolomite.
2.88 X Peak
143
-------
Table A.I. Characteristic peaks, source, and impurities found in
the blackwater samples.
Mineral
Peak A (19) Source
Impurities
Illite 4.48, 2.57 API #35 Fithian, Illinois 17% quartz
8% calcite
Kaolinite 3.57 API #9 Mesa Alta,
New Mexico
Chlorite 3.55 Calaveras County,
California
Calcite 3.04 Valentine, Centre County
Pennsylvania
Quartz 1.82 Castastone Products Company,
Inc., Raleigh, North
Carolina
Dolomite 2.88 Thornwood, New York
API, American Petroleum Institute Clay Mineral Standards,
Project No. 49.
144
-------
APPENDIX B
X-RAY DIFFRACTION ANALYSIS OF THE MINERAL MATTER FRACTION
FOUND IN BLACKWATER
145
-------
Following separation of the solids found in blackwater into
a carbonaceous and a mineral matter fraction, the mineral composi-
tion of this latter fraction was determined for each sample by
x-ray diffraction using two different techniques.
In the first method the mineral composition of each black-
water sample was determined by performing x-ray diffraction analysis
on a representative sample of the mineral matter from each sample.
This sample is called the composite sample.
In the second method the mineral matter was separated into
layers by centrifuging and each layer was weighed and analyzed by
the x-ray method. From these data the total mineral composition
could be calculated. Specific details of the procedure are given
in Section III.B.3.
The following tables give the primary mineralogical analysis
of each layer, as determined by x-ray techniques, used to calculate
the mineral content of each sample shown in Tables 9-11.
146
-------
Table B.I. Sample, Pi. W Pa 1.
Layers
Weight %
Illitic3 4.48 X
2.57 8
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
6
65
63
24
5
3
1
2nd
17
82
63
18
4
4
5
3rd
33
66
58
15
3
10
17
4th
44
40
33
11
4
14
30
Total
100
57
48
14
4
10
20
3
Composite
___
45
43
11
3
18
14
2
a
Dominate: Slightly interstratified illite-montmorillonite.
Significant: Illite
Table B.2. Sample, L.K. C Pa 2.
Layers
Top
Bottom
Total
Composite
Weight %
Illitic3 4.48 R
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
32
56
61
30
4
11
15
68
44
33
14
4
14
16
100
48
42
19
4
13
16
4
41
39
15
3
11
11
4
Identification:
Dominate: Illite, moderately interstratified illite-montmorillonite.
Significant: Montmorillonite.
Carbonaceous: ^3%.
Other Minerals: Rutile ^1%.
147
-------
Table B.3. Sample, L.K. C Pa 3.
Layers
Weight %
Illitic3 4.48 g
2.57 A
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
69
54
57
20
2
5
12
Bottom
31
49
27
19
4
8
15
Total
100
52
48
20
3
6
13
3
Composite
__-
44
47
20
4
12
10
3
aldentification:
Dominate: lllite.
Significant: Slightly interstratified illite-raontmorillonite.
Carbonaceous: ^5%.
Table B.4. Sample, L.F. C Pa 4.
Layers
Weight %
Illitic3 4.48 &
2.57 %
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
15
66
39
10
4
5
0
2nd
20
40
34
11
3
10
11
3rd
36
25
2
1
3
28
10
4th
29
25
12
5
2
22
5
Total
100
34
18
6
3
19
7
3
Composite
28
23
8
2
23
9
3
Identification:
Dominate: Highly interstratified illite-montmcrillonite.
Significant: lllite, montraorillonite.
148
-------
Table B.5. Sample, Po. M WVa 5.
Layers
Weight I
Illitic3 4.48 X
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
23
50
48
8
5
3
5
2nd
29
42
42
5
5
5
11
3rd
30
53
64
11
6
11
26
4th
18
75
75
11
6
9
20
Total
100
53
56
9
6
7
16
1
Composite
___
46
55
13
6
5
18
1
Identification:
Dominate: Illite.
Other Minerals: Dolomite, rutile, siderite, all
Table B.6. Sample, Po. W WVa 6.
Layers
Weight %
Illitic3 4.48 X
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
27
60
58
15
6
8
6
Bottom
73
38
42
18
6
17
20
Total
100
44
46
17
6
15
16
1
Composite
46
49
13
4
16
11
1
Identification:
Dominate: Illite.
Significant: Slightly interstratified illite-montmorillonite,
montmorillonite.
Other Minerals: Rutile, siderite, all VL%.
149
-------
Table B.7. Sample, Pi./L.F. H Oh 7-
Layers
Weight %
Illitic3 4.48 X
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
26
57
51
12
3
8
18
Bottom
74
29
32
5
2
15
16
Total
100
36
37
7
2
13
17
10
Composite
49
34
6
3
11
12
10
Identification:
Dominate: Moderately interstratified illite-montmorillonite.
Significant: Illite, montmorillonite.
Carbonaceous: ^10%.
Other Minerals: Rutile.
Table B.8. Sample, E L Ky 8.
Layers
Weight %
Illitic3 4.48 X
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
9
58
65
9
6
2
2
Bottom
91
51
58
9
7
0
15
Total
100
52
59
9
7
0
14
1
Composite
48
62
6
6
0
12
1
Identification:
Dominate: Illite.
Significant: Interstratified illite-montraorillonite,
montmorillonite.
Other Minerals: Feldspar, rutile, siderite, all
150
-------
Table B.9. Sample, Pr. J Ala 9.
Layers
Weight %
Illitic3 4.48 X
2.57 X
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
62
66
62
7
5
0
9
Bottom
38
50
56
6
4
0
20
Total
100
60
60
7
5
0
13
1
Composite
___
59
61
6
3
0
14
1
Identification:
Dominate: Illite.
Significant: Slightly interstratified illite-montmorillonite,
montmorillonite.
Other Minerals: Dolomite,
Table B.10. Sample, 16/5 J 111 10.
Layers
Weight %
Illitic3 4.48 8
2.57 8
Kaolinite
Chlorite
Calcite
Quartz
Pyrite
Top
7
75
69
5
0
2
0
2nd
17
72
66
6
0
2
1
3rd
33
56
56
6
0
10
26
4th
43
23
23
10
0
31
24
Total
100
46
44
8
0
17
19
4
Composite
60
42
3
0
26
22
9
Identification:
Dominate: Highly interstratified illite-montmorillonite.
Significant: Illite.
151
-------
Table B.ll. Sample, 16 W Ind 11.
Layers
Weight %
Illitic3 4.48 X
2.57 X
Kaollnite
Chlorite
Calcite
Quartz
Pyrite
Top
3
57
62
17
4
3
9
2nd
12
62
48
11
3
2
0
3rd
44
60
78
19
5
3
20
4th
40
57
60
19
5
9
30
Total
100
58
66
17
5
7
21
6
Composite
65
52
10
3
7
22
6
Table B.12. Sample, B.D. L Wa 12.
Layers
Weight %
Montmorillonite
Feldspar
Top
7
100
0
2nd
20
90
10
3rd
31
80
20
4th
42
50
50
Total
100
70
30
Carbonaceous:
152
-------
Table B.13. Sample, S/L.S. Ut 13.
Layers
Weight %
Montmorillonite
Kaolinite
Quartz
Calcite
Dolomite
Pyrite
-400 Mesh
50
48
16
9
15
12
+400 Mesh
50
15
32
15
19
17
Total
100
31
24
12
17
14
2
Carbonaceous: ^10 %.
Other Minerals: Feldspar
153
-------
APPENDIX C
POTASSIUM ANALYSIS OF THE MINERAL MATTER FRACTION FOUND IN BLACKWATER
FIRST ELEVEN SAMPLES
154
-------
The potassium content of the mineral matter fraction from
the Eastern blackwater samples was used as one method of quanti-
fying the illite content. The potassium content of the samples was
determined using atomic absorption (22). The average K-0 content
of the two Fithian, Illinois samples was used as a standard value
to estimate the illite content in the mineral matter fraction of
the various blackwater samples. These standard illite samples
were purchased from Ward's Natural Science Establishment, Inc.,
Rochester, New York, at different times, and they are listed as
the API #35 sample and the 25 pound sample. The purity of the
two samples was determined using the x-ray diffraction procedure
outlined in Section III.B.3 and the "difference" method. The
mineral composition of the two illite standards was as follows:
API #35-75% illite, 17% quartz, and 8% calcite; 25 Ib material-80%
illite, and 20% quartz. From this average K 0 content of standard
illite, 5.12%, the illite content of the mineral matter fraction
from each of the blackwater samples was calculated. The K?0
analytical data and the calculated percentage of illite in each
sample is shown in Table C.I.
The K?0 content of the two standards was corrected for
contamination by other minerals using the following procedure:
155
-------
API #35 contained 75% illite and 3.95% K00
3.95% K 0
100% illite = -— = 5.26%
25 Ib sample contained 80% illite and 3.98%
3.98% K 0
100% illite = . Qr. = 4.98% K.O
U. oU /
The average K?0 content of the illite clay in these two
standard samples is 5.12% which was used to determine the illite
content in the mineral matter fraction from the blackwater samples.
Percent illite in mineral matter
Percent K^O in sample -f- (5.12) x 100
These samples had been collected in the field by Ward's from
the same location but the two samples were taken several years
apart. Thus, some sample variability is to be expected.
156
-------
Table C.I. Quantitative atomic absorption determination of K_0.
Sample
Pi. W Pa 1
L.K. C Pa 2
L.K. C Pa 3
L.F. C Pa 4
Po. M. WVa 5
Po. W. WVa 6
Pi. /L.F. H Oh 7
E L Ky 8
Pr. J Ala 9
16/5 J 111 10
16 W Ind 11
API #35 Illite
25 Ib Sample Illite
*K2o
1.90
1.70
1.75
2.02
3.62
3.45
1.75
4.12
3.44
2.44
3.05
3.95
3.98
% Illite3
37
34
34
39
71
68
37
80
67
47
60
Standard
Standard
Based on 100% illite =• 5.12%
157
-------
APPENDIX D
PARTICLE SIZE .ANALYSES
158
-------
The size analysis of the blackwater samples was determined
using the procedure outlined in Section III.C. The separate
analyses of each minus 400 material using the MSA-Whitby device
were used to determine the size distribution of that material. The
values from these two tests were then plotted on Rosin-Rammler
paper and a smooth curve was drawn through the points. This size
distribution was then adjusted from a base of 100 percent to a
percentage that equaled the minus 400 mesh material contained in the
sample. These values and the sieve values were then used to produce
the combined size distribution of that material shown in Figures
5-15. Two samples were also analyzed using the Micromeritics
Sedigraph (Figures D.I and D.2) in which only the mineral matter
portion was examined. Tables D.I to D.6 give particle size data
for both mineral matter and carbonaceous material for all the black-
water samples examined while Table D.7 gives mean particle size data
of eleven eastern blackwater samples.
159
-------
100
as
o
o
-------
too
10 I
EQUIVALENT SPHERICAL DIAMETER,^.™
Figure D.2. Sedigraph particle size distribution, sample no. S/L./S. Ut 13.
Sample Identification: Mineral matter (-400 mesh)
Density: 2.7 g/cc
Liquid: Water
Temperature: 33°C
Rate: 465
Start Diameter: 50 ym
-------
Table D. 1. Particle analysis of mineral matter fraction cumulative percent finer.
01
Size, Sieve
14
14 x 20
20 x 28
28 x 35
35 x 48
48 x 65
65 x 100
100 x 150
150 x 200
200 x 270
270 x -400
Subsieve (MDI)
20
10
5
3
2
1
0.5
0.3
0.2
Pi WPa 1
100.0
100.0
100.0
99.9
99.9
99.7
99.1
98.1
95.8
94.4
92.6
91.3
82.5
68.9
55.6
47.8
29.1
18.6
12.2
7.6
L.K.C. Pa 2
100.0
99.9
99.7
99.5
99.2
98.6
97.1
95.3
90.0
86.6
81.7
80.6
74.0
61.9
50.1
44.7
27.4
17.5
9.8
4.0
L.K.C. Pa 3
100.0
99.2
97.4
93.5
88.5
85.2
82.3
80.2
75.9
73.5
69,9
64.7
55.7
40.5
32.0
27.4
15.7
8.7
4.6
1.7
L.F.C. Pa 4
100.0
99.9
99.6
99.1
97.5
94.8
90.6
87.2
80.9
77.9
73.8
65.6
50.9
45.2
34.8
29.4
18.5
11.7
7.3
3.0
Po MWVa 5
100.0
100.0
99.8
99.6
99.2
98.4
96.5
94.5
90.8
89.1
87.1
83.0
69.9
52.7
41.3
31.7
18.3
10.3
5.4
3.4
Po WWVa 6
100.0
99.8
99.7
99.3
98.3
96.3
93.4
91.4
87.6
85.4
82.2
78.2
69.9
51.8
36.9
28.2
16.2
8.3
6.9
3.8
-------
03
GO
Table D.I. Continued.
Size, Sieve
14
14 x 20
20 x 28
28 x 35
35 x 48
48 x 65
65 x 100
100 x 150
150 x 200
200 x 270
270 x 400
Subsieve (pro)
20
10
5
3
2
1
0.5
0.3
0.2
Pi/LFHOh 7
100.0
99.4
99.0
98.6
98.1
97.4
96.7
96.2
94.5
92.7
88.3
80.2
69.5
50.7
38.8
30.1
19.2
11.5
6.6
3.1
ELKy 8
100.0
90.7
99.4
99.3
99.1
98.8
98.3
97.8
96.1
94.9
92.8
91.5
83.6
68.5
51.1
40.8
25.0
12.2
7.9
5.3
PrJala 9
100.0
99.9
99.8
99.7
99.5
99.2
98.4
97.5
95.1
94.1
92.0
83.0
69.9
52.7
41.3
31.7
18.3
10.3
5.4
3.4
I6/5JI11 10a
99.5
98.2
96.1
93.1
88.9
84.6
82.2
78.2
76.1
69.2
60.1
50.9
41.7
28.0
17.5
0.5
— — —
I6WInd lla
99.4
97.9
95.8
94.2
93.1
92.6
90.8
86.9
75.4
56.0
40.0
34.2
22.6
3.9
— — —
Size analysis by Michael F. Placha (30).
-------
Table D.I, Continued.
Size, Sieve
14
14 x 20
20 x 28
28 x 35
35 x 48
48 x 65
65 x 100
100 x 150
150 x 200
200 x 270
270 x 400
Subsieve (pro)
20
10
5
3
2
1
0.5
0.3
0.2
B.D.L.Wa 12a
___
99.4
98.7
97.7
96.2
93.7
92.3
90.5
89.7
82.5
65.1
57.4
51.9
31.4
20.5
12.9
6.6
S/LS Ut 13
.._
99.6
83.9
67.8
60.1
55.9
53.7
51.6
50.8
50.0
47.9
41.8
33.0
26.2
22.5
14.3
9.9
6.9
4.7
Size analysis by Michael F. Placha (30)
-------
Table D.2. Particle analysis of carbonaceous fraction cumulative percent finer.
Size,
+ 14
14 x
20 x
28 x
35 x
48 x
65 x
100 x
150 x
200 x
270 x
Sieve
20
28
35
48
65
100
150
200
270
400
Pi
— — —
98.
97.
93.
89.
85.
82.
75.
70.
64.
WPa 1
4
5
5
5
8
4
9
7
6
L.
__
99
98
94
88
81
72
62
53
48
40
K.C. Pa 2
_
.8
.3
.5
.6
.3
.3
.8
.8
.3
.3
L.
99
93
83
72
96
57
49
42
37
32
K.C. Pa 3
.3
.9
.3
.7
.3
.6
.0
.7
.7
.9
L.
99
99
96
88
81
74
67
59
47
43
F.C. Pa 4
.8
.2
.1
.7
.4
.3
.1
.3
.9
.3
Po
99.
96.
92.
89.
84.
79.
71.
61.
56.
MWVa 5
1
7
8
2
6
8
9
5
1
Subsieve (pm)
20
10
5
3
2
1
0.5
50.
33.
22.
17.
13.
6.
2.
8
7
4
1
3
4
4
32
19
12
8
5
2
0
.5
.6
.8
.4
.6
.6
.3
27
16
11
7
5
2
0
.0
.7
.0
.1
.3
.5
.6
37
24
15
12
9
4
2
.8
.8
.8
.7
.7
.9
.4
46.
29.
19.
13.
10.
5.
1.
1
1
6
3
1
0
4
-------
Table D.2. Continued,
O)
en
Size, Sieve
+ 14
14 x 20
20 x 28
28 x 35
35 x 48
48 x 65
65 x 100
100 x 150
150 x 200
200 x 270
270 x 400
Subsieve (urn)
20
10
5
3
2
1
0.5
Po WWVa 6
99.8
99.5
98.1
94.6
88.7
82.6
75.6
68.3
61.2
56.6
49.2
38.9
24.2
14.2
8.5
5.3
2.3
0.0
Pi/LFHOh 7
99.9
99.7
98.9
96.6
86.6
66.8
44.6
29.8
21.8
18.7
15.4
12.9
8.4
5.1
3.6
2.4
1.1
0.4
ELKy 8
99.8
99.2
97.7
95.9
91.8
84.1
73.6
64.0
56.0
51.4
44.5
36.9
22.9
13.6
10.0
7.2
2.9
1.1
PrJAla 9
99.8
99.7
99.4
98.3
95.3
91.1
85.5
77.8
68.0
60.0
49.9
35.3
22.9
13.5
9.4
6.7
2.6
1.2
I6/5JI11 10a
u_ iHf _^_
99.9
99.8
99.6
96.3
84.9
67.8
54.2
48.6
38.1
26.2
20.6
11.1
6.8
6.0
5.7
0.7
0.1
Size analysis by Michael F. Placha (30).
-------
Table D.2. Continued.
Size,
+ 14
14
20
28
35
48
65
100
150
200
270
X
X
X
X
X
X
X
X
X
X
Sieve
20
28
35
48
65
100
150
200
270
400
I6WInd lla
_„
99.
96.
87.
74.
63.
54.
46.
39.
35.
30.
5
4
5
2
7
6
8
7
6
3
B.
—
—
90
71
64
56
44
31
24
11
D.L.Wa 12a
-
-
.0
.0
.0
.0
.0
.0
.0
.0
S/LS Ut 13
—
99
98
92
84
49
48
44
42
40
-
.9
.4
.9
.4
.5
.3
.4
.0
.1
Subsieve (ym)
20
10
5
3
2
1
0.
5
25.
19.
10.
7.
5.
2.
0.
1
6
7
2
3
7
9
._
—
—
—
—
—
«
.
-
-
-
-
-
~"
27
16
9
6
4
2
1
.0
.0
.7
.5
.7
.3
.5
Size analysis by Michael F. Placha (30).
-------
Table D.3. MSA sedimentation particle size analysis procedure for
mineral matter.
Sample Material—mineral
Sample Density—2.7 (tails)
Feeding Liquid—distilled water
Dispersing Agent—0.15 calgon, 50 ppm bleach
Room Temperature—23°C
Tube Size—0.75 mm
Sedimentation Liquid—distilled water
Wetting Agent—Aerosol OT
R = 3.3 cm
o
R2 = 13.3 cm
K - 9.31 x 104
g
d
40
20
10
5
3
2
1
0.5
0.3
0.2
RPM
Gravity
Gravity
Gravity
600
1200
1200
3600
3600
3600
3600
Time
(sec)
58
233
931
77
55
111
67
267
637
1235
Corr. Time
(sec)
58
233
931
86
65
121
106
306
676
1274
Note:
After the 0.2 urn value was determined, the sample was repeatedly
centrifuged at 3600 RPM for 20 minutes until a final height was
obtained.
168
-------
Table D.4. MSA sedimentation particle size analysis of mineral matter fraction cumulative weight percent
finer.
OS
CO
PiWPa 1
Sample
Size
(urn)
40
20
10
5
3
2
1
0.5
0.3
0.2
Test
1
98.9
90.7
73.4
59.4
51.5
35.9
20.3
11.7
6.8
2
98.6
89.0
74.4
60.0
51.6
31.5
20.1
13.2
8.2
L.K.C
.Pa 2
Test
1
97.2
90.6
73.6
64.2
52.4
35.8
24.0
15.7
5.9
2
98.7
90.6
75.8
61.4
54.7
33.6
21.5
12.1
5.0
L.K.C
.Pa 3
Test
1
92.5
71.7
57.9
45.8
39.2
22.5
12.5
6.7
2.5
2
93.3
79.6
61.3
48.4
40.0
23.1
12.0
5.3
0.4
L.K.C
.Pa 4
Test
1
99.6
88.9
69.0
61.3
47.2
39.9
25.1
15.9
10.0
4.1
2
90.9
77.2
64.6
52.8
42.9
26.0
16.5
9.4
5.1
PoMWVA 5
Test
1
— _
95.3
80.2
60.5
47.4
36.4
21.0
11.9
6.3
4.0
2
96.4
81.0
60.5
47.0
36.4
20.6
10.3
7.1
3.6
PoWWVa 6
Test
1
95.2
85.0
63.1
44.9
36.9
18.2
10.2
4.8
1.0
2
___
97.1
88.8
66.3
52.2
44.3
23.1
14.3
8.4
4.7
Pi/LFHOh 7
Test
1
90.9
72.6
57.5
44.0
34.1
21.8
13.1
7.5
3.6
2
_— _
95.4
78.7
59.2
46.5
35.5
22.0
12.1
6.7
2.8
-------
Table D.4. Continued.
ELKy 8
Sample
Size
(um)
40
20
10
5
3
2
1
0.5
0.3
0.2
Test
1
98.6
90.1
73.8
55.1
46.3
23.4
13.2
6.3
2.2
2
99.0
95.3
79.1
66.3
57.3
29.4
18.0
10.4
5.8
PrJAla 9
Test
1
93.4
87.5
72.0
60.7
50.7
37.4
23.8
12.5
6.6
2
88.9
81.8
68.5
56.5
48.5
32.5
20.9
12.9
7.1
I6/5JI11 10a
Test
1 2
97.1
88.3
76.3
64.9
53.2
35.7
22.3
0.6
0.0
16WInd lla
1
—
95
83
61
44
37
24
4
0
0
Test
2
_
.7
.0
.7
.7
.7
.9
.3
.0
.0
BDLWa
12a
Test
1
99.2
92.9
73.3
60.8
54.4
33.3
22.3
14.2
7.3
2
99.0
89.4
70.4
65.9
60.3
36.0
22.8
14.2
— — —
S/LS Ut 13
Test
1
95.9
83.7
66.0
52.5
45.0
28.6
19.8
13.8
9.4
2
96.4
84.9
64.1
51.0
39.5
22.4
13.5
7.6
3.3
Size analysis by Michael F. Placha (30).
-------
Table D.5. MSA sedimentation particle size analysis procedure for
carbonaceous material.
Sample Material—carbonaceous
Sample Density—1.5
Feeding Liquid—distilled water
Dispersing Agent—100 ppm bleach
Room Temperature—23°C
Tube Size—0.75 mm
Sedimentation Liquid—distilled water
Wetting Agent—aerosol OT
R = 3.3 cm
o
R2 = 13.3 cm
K = 3.15 x 105
g
d
40
30
25
20
10
8
5
3
2
1
0.5
0.3
RPM
Gravity
Gravity
Gravity
Gravity
600
600
1200
1200
1200
3600
3600
3600
Time
(sec)
197
257
504
788
65
57
65
194
377
227
908
2160
Corr. Time
(sec)
197
257
504
788
74
66
75
204
387
266
947
2199
Note:
After the 0.3 um value was determined, the sample was repeatedly
centrifuged at 3600 RPM for 20 minutes until a final height was
obtained.
171
-------
Table D.6. MSA sedimentation particle size analysis of carbonaceous fraction cumulative weight percent
finer.
CO
PiWPa 1
Sample
Size
(urn)
40
30
25
20
10
8
5
3
2
1
0.5
0.3
Test
1
___
99.0
86.3
78.7
52,2
45.7
34.7
26.5
20.6
10.0
3.8
0.7
2
98.7
95.5
81.4
74.8
47.5
38.7
34.8
24.9
18.3
10.6
3.7
0.5
L.K.C.Pa 2
Test
1
— — —
60.5
56.6
30.1
22.6
16.8
6.6
0.4
0.0
2
99.6
80.7
48.7
31.9
20.8
13.9
6.6
0.9
0.0
L.K.C
.Pa 3
Test
1
99.2
97.1
90.1
84.5
52.4
48.9
34.5
22.2
16.8
8.0
1.9
0.3
2
99.6
98.3
91.4
85.3
54.3
48.3
33.2
25.4
19.8
7.8
1.3
0.0
L.F.C
.Pa 4
Test
1
99.0
98.0
92.6
85.5
59.5
54.4
40.2
32.4
24.0
7.4
5.7
0.7
2
99.7
98.5
93.3
87.4
57.3
50.9
36.6
29.5
22.5
6.4
2.6
0.3
PoMWVa 5
Test
1
98.6
97.3
90.4
82.6
54.1
45.0
34.9
24.8
17.4
11.0
3.2
0.0
2
___
98.9
89.2
82.3
52.0
45.1
32.5
23.8
22.4
9.0
2.5
1.1
PoWWVa 6
Test
1
.»_ —
79.2
49.3
33.5
20.5
10.8
3.2
0.0
0.0
2
99.6
97.0
87.0
70.4
45.2
42.6
24.8
17.4
11.7
4.8
0.8
0.0
Pi/LFHOh 7
Test
1
___
98.8
91.1
83.8
54.4
46.7
33.2
23.6
18.2
7.7
2.7
0.3
2
99.7
99.2
92.3
87.2
55.8
48.7
39.6
27.4
21.9
10.8
6.6
4.3
-------
Table D.6. Continued.
Sample
Size
(lam)
40
30
25
20
10
8
5
3
2
1
0.5
0.3
ELKy 8
Test
1 2
99
89
85.5 83
53.8 51
45
30.9 30
20.6 22
17.7 16
6.3 6
2.6 2
—
PrJAla
9
Test
.7
-
.1
.0
.6
.2
.7
.6
.3
.7
.4
—
1
97.2
70.8
42.7
27.1
18.9
13.5
5.3
2.5
1.4
2
99
—
—
75
46
—
27
18
13
5
2
0
.6
-
-
.7
.0
-
.2
.8
.4
.0
.5
.8
I6/5JI11 10a
15WInd II3
Test
1
98.5
97.0
90.9
81.8
45.8
43.2
28.8
24.6
24.2
3.0
0.0
0.0
2
97.6
95.5
85.0
76.1
39.4
36.0
23.6
21.2
19.8
2.9
1.4
0.0
1
91
—
—
82
64
__
35
23
17
8
2
0
Test
2
.2
.8 —
.7
.3
q
.6
.8
.9
.0
S/LS
Ut 13
Test
1
96.3
91.1
78.0
67.5
39.9
33.9
24.4
20.2
16.3
5.8
3.9
1.8
2
95.9
91.0
77.6
69.0
39.9
33.6
23.9
16.4
11.9
3.7
1.9
0.0
aSize analysis by Michael F. Placha (30).
Note:
Sample BDLW 12 carboniferous material was not analyzed due to the small percentage, <11%, that was
present as minus 400 mesh material.
-------
Table D.7. Mean particle analysis of thickener underflow or slurry
and feed eastern samples (Nos. 1 to 11).
Cumulative Weight % Finer
Size, Sieve
14
14 x 20
20 x 28
28 x 35
35 x 48
48 x 65
65 x 100
100 x 150
150 x 200
200 x 270
270 x 400
Subsieve (ym)
20
10
5
3
2
1
0.5
0.3
0.2
Mineral
Mean
___
97.9
96.6
94.7
92.8
89.5
87.6
84.5
80.1
70.0
55.4
43.0
35.2
21.7
11.9
6.1
3.2
Material
Std.Dev.
___
— =
3.2
4.0
4.8
5.5
6.6
7.2
7.9
8.8
9.7
8.9
7.7
7.1
4.9
4.4
3.6
2.2
Carboniferous Material
Mean
— _
94.6
88.1
80.1
70.6
62.0
54.4
47.9
41.1
33.1
21.2
13.2
9.4
7.0
3.1
1.0
_ __
Std.Dev.
___
— _
4.8
7.8
9.9
13.4
15.9
15.7
14.6
14.1
11.0
7.3
5.0
3.7
2.9
1.7
0.8
«•_
174
-------
APPENDIX E
TABULATION OF THE MINERALOGICAL AND PARTICLE SIZE CHARACTERISTICS
OF EACH OF THE THIRTEEN BLACKWATER SAMPLES
175
-------
Sample No. Pi W Pa 1
Solid Material
Wt %
Ash %
S %
Mineral
44.5
86.1
1.11
Carbonaceous
55.5
10.2
1.14
Total
100
44.0
1.13
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
51
12
18
19
Chlorite
Pyrite
2
Particle Size Analysis (weight percent less than)
Size (pm) Mineral Carbonaceous
44 93 66
1 33 6.1
Total
77
17
176
-------
Sample No. LK C Pa 2
Solid Material
wt %
Ash %
S %
Mineral
35.8
79.3
2.36
Carbonaceous
64.2
9.2
1.75
Total
100
34.3
1.97
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
46 17 14 12
Chlorite
Pyrite
4
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 84 43
1 27 2.5
Total
58
11
177
-------
Sample No. LK C Pa 3
Solid Material
Wt %
Ash %
S %
Mineral
34.0
81.8
1.4.6
Carbonaceous
66.0
11.9
1.06
Total
100
35.7
1.20
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
48 22 9 14
Chlorite
Pyrite
3
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 70 35
1 15 2.5
Total
40
4
178
-------
Sample No. LF C Pa 4
Solid Material
wt %
Ash %
S %
Mineral
19.6
87.9
1.40
Carbonaceous
80.4
14.4
1.30
Mineral Composition (weight percent)
Illitic Kaolinite Ouartz Calcite
65
8
21
Chlorite
Pyrite
3
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 76 44
1 18 4.2
179
-------
Sample No. Po M W Va 5
Solid Material
Wt %
Ash %
S %
Mineral
29.1
87.5
0.70
Carbonaceous
70.9
12.6
0.94
Total
100
34.4
0.87
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite Chlorite Pyrite
57 11 17 6 6 1
Particle Size Analysis (weight percent less than)
Size (yim) Mineral Carbonaceous
44 89 62
1 18 5.0
Total
70
9
180
-------
Sample No. Po W WVa 6
Solid Material
Wt %
Ash %
S %
Mineral
36.1
86.2
0.56
Carbonaceous
63.9
12.1
0.76
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Galcite
47 15 15 17
Chlorite
Pyrite
1
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 84 52
1 17 2.3
Total
64
8
181
-------
Sample No. Pi/LF. H Oh 7
Solid Material
Wt Z
Ash Z
S %
Mineral
15.9
70.5
5.23
Carbonaceous
84.1
10.9
2.26
Total
100
20.4
2.73
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
37 7 15 12
Chlorite
Pyrite
10
Particle Size Analysis (weight percent less than)
Size (yim) Mineral Carbonaceous
44 90 16
1 19 1.1
182
-------
Sample No. E L Ky 8
Solid Material
Wt %
Ash %
S %
Mineral
52.1
87.1
0.56
Carbonaceous
47.9
10.8
0.71
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
62 8 13 0
Chlorite
Pyrite
1
Particle Size Analysis (weight percent less than)
Size (um) Mineral Carbonaceous
44 93 47
1 25 3.0
Total
69
14
183
-------
Sample No. Pr J Ala 9
Solid Material
Mineral
Wt % 27.7
Ash % 88.0
S % 0.59
Carbonaceous
72.3
9.2
1.12
Total
100
31.0
0.97
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
64 7 1A 0
Chlorite
Pyrite
1
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 93 54
1 43 2.8
Total
65
14
184
-------
Sample No. I 6/5 J 111 10
Solid Material
Mineral
Wt % 81.0
Ash % 84.3
S % 4.54
Carbonaceous
19.0
10.7
2.92
Total
100
70.3
4.28
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite
49 6 21 22
Chlorite
Pyrite
9
Particle Size Analysis (weight percent less than)
Size (urn) Mineral Carbonaceous
44 80 30
1 28 0.8
185
-------
Sample No. 16 W Ind 11
Solid Material
Wt %
Ash %
S %
Mineral
71.1
88.2
3.14
Carbonaceous
28.9
8.4
2.67
Mineral Composition (weight percent)
Illitic Kaolinite Quartz Calcite Chlorite Pyrite
61 14 22 4 4 6
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 91 32
1 12 5.2
186
-------
Sample No. BD L Wa 12
Solid Material
Mineral Carbonaceous Total
Wt % 72.8 27.2 100
Ash % 79.5 42.5 69.4
S % 0.42 1.30 0.66
Mineral Composition (weight percent)
Montmorillonite Feldspar
70 30
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 91 16
1 31
187
-------
Sample No. S/LS UT 13
Solid Material
Wt %
Ash %
S %
Mineral
49.9
71.2
1.22
Carbonaceous
50.1
21.8
1.14
Total
100
46.5
1.18
Mineral Composition (weight percent)
Montmorillonite Kaolinite Quartz Calcite Chlorite Pyrite
31 24 12 17 14 2
Particle Size Analysis (weight percent less than)
Size (ym) Mineral Carbonaceous
44 51 40
1 14 2.3
Total
45
9
188
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
F E-9002-1 (EPA-600/7-79-006)
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE CharacterizaUon Qf
in Blackwater Effluents from Coal Preparation Plants
6. REPORT DATE
January 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
F. F. Apian and R. Hogg
DoE FE-9002-1
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Pennsylvania State University
University Park, Pennsylvania 16802
10. PROGRAM ELEMENT NO.
EHE623A
11. CONTRACT/GRANT NO.
EPA Inter agency Agreement
DXE685AK
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 7/75 - 10/77
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES T£RL-RTP project officer: D.A.Kirchgessner, MD-61,919/541-
2851. DoE project officer: R.E.Hucko, Div. of Solid Fuel Mining and Preparation,
Pittsburgh PA 15213.
16. ABSTRAC
The report gives results of a characterization of the fine solid constituents
of coal preparation plant waste water, to provide a better understanding of how to
treat the water for recycle or discharge. Thirteen waste water samples , obtained
from coal preparation plants throughout the U.S. , were analyzed for: identification
and quantification of solid constituents, size analysis of solids, and surface proper-
ties of the solids. The study concluded that: (1) Eastern and Western coal region
samples can be distinguished on the basis of mineralogy and size distribution of the
solid particles; (2) the carbonaceous material of Eastern coals averages 60% of the
blackwater solids, and the remaining 40% consists of clay minerals, quartz, calcite,
and pyrite; and (3) virtually all of the carbonaceous material in Eastern plant waste
waters can be removed by froth flotation, with the product containing 11% mineral
matter.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Quartz
Coal Preparation Calcite
Waste Water Pyrite
Particle Size Distribution
Carbon Flotation
Clay Minerals Froth
Pollution Control
Stationary Sources
Blackwater
Mineralogy
Particulate
13 B
081
07B
08G
07A,13H
11G
IS. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
203
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
$9.25
EPA Form 2220-1 (9-73)
189
n U.S. GOVERNMENT PRINTING OFFICE: 1979-640-092/ 474
------- |