WATER POLLUTION CONTROL RESEARCH SERIES • 14050 EPU 08/71
Utilization of Phosphate Slimes
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL. RESEARCH SERIES
The '/later Pollution Control Research Series describes
the results and progress in the control and abatement
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Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Head, Project Reports
System, Office of Research and Development, Hater Quality
Office, Environmental Protection Agency, Room 1108,
Washington, 0. C. 20242.
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Utilization of Phosphate Slimes
International Minerals & Chemical Corporation
5401 Old Orchard Road
Skokie, Illinois 60075
for the
Environmental Protection Agency
Project 7?14050 EPU
August 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.25
Stock Number 5501-0097
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EPA Review Notice
This report has been reviewed by the
Water Quality Office, EPA, and approved
for publication. Approval does not
signify that the contents necessarily
reflect the views and policies of the
Environmental Protection Agency, nor
does mention of trade names or commercial
products constitute endorsement or recom-
mendation for use.
11
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ABSTRACT
Small scale tests were made to assess the feasibility
of producing materials economically for the building
industry from the clay slimes wastes of the Florida
phosphate industry. The objective was to find practical
means to utilize these clay materials in order to reduce
or eliminate the vast empoundment acreage devoted to
their storage and to make the water entrapped therein
available for re-use.
These studies showed that it is feasible to produce
a palletized lightweight aggregate and ultimately a
lightweight concrete from the slimes. It was estimated
that up to 6 - 8 million tons of clay solids can be so
used annually with the concurrent release of up to
5 billion gallons of water into the environment. Pro-
duction of ceramic materials was also explored.
The four major processing steps were investigated
batchwise on individual equipment types, and equipment
suitable for each was identified. These steps included:
pumping clay-slurries of 3 - 30% solids concentration;
drying of the slimes in a fluid-bed dryer; pelletizing
the dried product; and kilning it to a suitable light-
weight aggregate.
This report was submitted in fulfillment of grant
#14050 EPU, between the Federal Water Quality Adminis-
tration and International Minerals & Chemical Corporation
111
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CONTENTS
Page
Abstract iii
Table of Contents v
Figures vi
Tables vii
Appendices ix
Preface x
Conclusions 1
Recommendations 3
Introduction 5
Clay Slimes 7
Development of the Program 19
Preparation of Lightweight Aggregate 25
Lightweight Aggregate Product 41
Summary 59
Acknowledgments 61
References 63
Glossary 65
Appendices
Appendix A 71
Appendix B 83
Appendix C 87
Appendix D 109
Appendix E 119
Appendix F 125
v
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FIGURES
No. Page
1. Flowsheet of Florida Phosphate Mining Operations 8
2. Thermogram of Typical Phosphate Slime 12
3. Consolidation Rate of Typical Phosphate Slime 17
4. Preparation of Size-classified Pellets in a
Rotating-Disc Agglomerator 22
5. Sketch of Aggregate Pilot Plant 27
6. Flowsheet, Aggregate Pilot Plant 28
7. Conceptual Flowsheet of Agglomeration Plant 20
8. Schematic Diagram of Fluid-Bed Dryer 32
9. Flowsheet, 2 sq.ft. Fluid-Bed Dryer Circuit 33
10. Thruput-efficiency Relationship in a Fluid-Bed
Dryer 35
11. Fuel Costs of Drying Slimes 35
12. Theoretical Capacity of a 2 sq.ft. Fluid-Bed 36
Dryer
13. Heat imput to Dryer, Effect of Air Temperature 37
14. Effect of Recycle Ratio and Water Content on
Dryer Feed 33
15. Spectrum of Lightweight Concretes 49
16. Compressive Strengths of Concrete Made With
Phosphate Slime Coarse Aggregate 55
17. Thermal Conductivity of Insulating Concrete 55
18. Strength of Insulating Concrete 56
VI
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TABLES
No. Page
I. Phosphate Rock Production, 1950-1968 7
II. Approximate Mineralogical Composition of
Phosphate Slimes 9
III. Approximate Chemical Composition of Phosphate
Slimes 9
IV. Spectrographic Analysis of Phosphate Slimes H
V. Chemical Analyses of Phosphate Slimes 13
VI. Viscosity of Mixtures of Phosphate Slimes 15
VII. Settling Velocity, pH, and Color of Phosphate
Slimes 15
VIII. Crush Strength Requirements, Standard Strength
Clay Sewer Pipe 21
IX. Typical Performance of Direct-Heat Rotary Dryers 30
X. Economics of Spray Drying 31
XI. Summary of Test Results on Fluid-Bed Dryer 34
XII. Estimated Cost oi Dry7.ng in Fluid-Bed Dryer 39
XIIIo Analysis of Drying Experiments 40
XIV. Chemical Analyses of Fired Phosphate Slime
Bodies (Angular Aggregate) 42
XV. Physical Properties of Fired Phosphate
Slime Bodies (Angular Aggregate) 43
XVI. Density and Porosity of Expanded Phosphate
Slime Aggregates 44
XVII. Properties of Rotary Kiln Fired Expanded
Phosphate Slime Aggregates 45
VII
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TABLES
No. Page
XVIII. Properties of Blended Phosphate Slime
Aggregates 46
XIX. Specifications of Phosphate Slimes LWA,
ASTM C330 47
XX. Preparation & Properties of Plastic Concrete
Using Slimes LWA 52
XXI. Average Compressive Strength of 3 x 6 in.
Lightweight Concrete Cylinders Using Fired
Phosphate Slime as Coarse Aggregate 53
XXII. Size Distribution of Fine Aggregate Used
in Third Concrete Batch 54
Vlll
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APPENDICES
No.
A. An Appraisal to Management of the Project 71
B. Calculation of Recycle Ratio, Fluid-bed Dryer 83
C. Analysis of Fluid-Bed Drying of Phosphate
Slimes 87
D. Transportation Study, Lightweight Aggregate
E. Proximity of Lightweight Aggregate Producers
in Florida
F. Estimation of Concrete Strength from Aggregate 125
IX
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PREFACE
As this project approached conclusion, it was deemed
proper by the Grantee to obtain an objective assessment
of its nature, content, and potential value from an
authoritative and unbiased third-party. To this end,
the services of Dr. Donald F. Othmer, Consulting
Chemical Engineer, were obtained. As co-editor of
the Kirk-Othmer "Encyclopedia of Chemical Technology"
and one of the outstanding figures in Engineering,
Dr. Othmer brings to this context a vast experience
and knowledge so well known to the profession that
it need not be repeated here. Dr. OthmerTs incisive
evaluation of this program so clearly delineated
present values and future needs, that it is reproduced
here in its original form. (See Appendix A.)
Srini Vasan
Project Director
x
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CONCLUSIONS
This project has shown, in semi-batch tests of
individual pieces of equipment, that it is feasible
to produce. for a market of substantial size, light-
weight concrete with attractive properties using
dried, fired pellets of phosphate slimes as aggregate.
A fluid-bed dryer has been tested which is significantly
more efficient than drying systems previously proposed
for these slimes. A pelletizing technique has been
developed which can reliably be adapted to the new
drying and kiln systems.
Lightweight concrete produced from aggregate-from-
slimes showed good strength and density characteristics.
It met all the ASTM specifications (ASTM C330) for
Lightweight Aggregate.
Two alternate pumping systems have been developed
which could dependably remove pond-slimes from present
storage areas and deliver both these and slime-slurries
(concentrated up to 30% solids) to the dewatering and
drying facilities.
The feasibility of producing other potential products
such as ceramic tile, pipe; and brick was technically
confirmed (with a few technical hurdles yet to be
cleared) and our evaluation showed that further develop-
ment of these materials may not be warranted till the
cost-gap on these materials can be closed, especially
in view of their limited market in Florida.
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RECOMMENDATIONS
Successful batch-scale testing has proven that phosphate-
slimes can be dried efficiently and a superior aggregate
with strength, attractive for consumption in the Florida
building industry, has been developed in small-scale
equipment. It is therefore recommended that — an on-site
continuous Demonstration Project be conducted to develop
further these indicated benefits. It is recommended
that:
The Demonstration Project be devoted to the following
objectives:
(1) Production of aggregates-from-slimes at site
using fresh slimes as a continuous feed in a dryer-
agglomerator-kiln unit.
(2) Operation of this Pilot Unit at an optimum size
for scaleup purposes for a future commercial plant
(preferably a 5 ton per hour, or 100 tons per day
Dryer-Agglomerator-KiIn pilot unit).
(3) Product-quality assessment for determining
acceptability of aggregate in various lightweight
concrete formulations.
(4) Field-evaluation of product in select markets.
(5) Reassessment of potential in fines of dried-
slimes in pipe, bricks, and other products.
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INTRODUCTION
Disposal of wastes from Florida phosphate mining
operations is an enormous and continually increasing
problem. The major constituents of these wastes are
clay minerals, or slimes, whose retention of water
increases their volume six to ten times. As a result,
the volume of waste exceeds the original volume of rock
removed and requires above-grade storage. This is not
only costly in terms of useless land and storage dikes
but also is hazardous in terms of potential spillage,
pollution of streams, and damage to residential and
industrial property.
Many studies have been made, both by government and
industry, of various means to alleviate this problem.
These have included attempts to recover water for re-use,
to reclaim P2°5 values contained in these wastes, and
to make the clays themselves useful either for industrial
or land-fill purposes. None of these have so far been
fruitful due to the high costs of handling the vast
quantities of aqueous waste, and of energy required to
separate clay and water.
For this study, it was proposed that there are two
key elements in developing an economical method for
disposing of these wastes and alleviating the pollution
potential. First it is necessary to develop a more
efficient and less costly method of obtaining dry clay
from the waste stream. Second, it is necessary to
develop useful products which can be made from the
dewatered clay, the value of which can support the
processing costs, and the volume of which is sufficient
to utilize a significant portion of the wastes available.
In the course of this study, a drying system was
developed which is significantly more efficient and
less costly than the conventional drying methods which
previous investigators have used. This drying system
utilizes a fluidized-bed which has been shown to be
feasible for drying the phosphate slimes at an efficient
rate. The practicality of this dryer has been demonstrated
an pilot scale tests which have also proven the feasibility
of the peripheral pumping, agglomerating and handling
equipment.
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Also as a part of this study, the feasibility of
producing a number of commercially useful and desirable
products was demonstrated. Among these are: pressed
and tamped brick and tile, extruded products such as
ceramic pipe, and in particular, lightweight aggregate
for both bulk concrete and lightweight block. The
feasibility of producing lightweight aggregate con-
tinuously has been attempted. Concrete products of
high quality have been produced in sufficient quantity
in batch-wise steps, and these materials were obtained
in reproducible qualities.
6
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CLAY SLIMES
Florida phosphate deposits are strip-mined by first remov-
ing a sandy, generally unconsolidated over-burden and then
stripping the matrix for processing. According to the
Bureau of Mines (1), about nine million cubic yards of over-
burden must be removed to produce thirteen million cubic
yards of matrix per year. Figure (1) shews a typical flow
sheet of IMC mining operations.
Table I (2) shows the tonnages of phosphate rock mined and
product produced in the United States. Most of this pro-
duction is from Florida and approximately one-third of that
is produced by IMC.
TABLE I
PHOSPHATE ROCK - SUMMARY: 1950 to 1968
(QnintltlM In thousands of Abort tons]
ITEM
Value $1.000..
Per ton dollars..
Value . $1,000
Per ton dollars .
Value $1.000
Per ton _ dollars _
PiOi content-
Value -..$1,000.-
Per ton dollars-.
World production
1950
(NA)
(NA)
12, 478
3,994
63,334
8.08
11,484
3,736
89,028
6.14
97
« 1, 114
>11.48
1,971
861
10, 366
6.29
9,611
26,760
1955
44,432
6,582
13,737
4,363
76, 379
6.49
14,768
«,682
82,904
6.61
131
2,703
20.63
2,445
806
14,269
8.84
12.4&4
33,678
I960
60,868
9,276
19, 618
6,096
117, 041
8.97
19,268
8,994
116, 363
6.99
144
3,764
28.07
4,473
1,446
26,632
6.95
14,937
46,110
1965
84,305
14,320
29,482
9,132
193,323
6.66
29,039
9,015
188,6f>0
6.49
148
2,980
20.14
7,323
2,313
61,109
6.98
21,864
70,298
1966
112,960
18,644
39,044
12,112
281,092
6.69
36,443
11,367
246, 182
6.73
178
4.259
23.91
9,248
2,803
86, 952
7.18
27,873
83,194
1967
128,973
19,603
39,770
12,464
286,947
6.69
37,836
11,856
261, 163
6.64
139
3.261
23.49
10,072
3,290
89,479
6,90
27,902
86,133
1968
148.336
29,024
41,261
12,843
260,692
6.08
37,319
11, 694
228,347
6.12
116
2,679
23.09
12,099
8,871
76.663
8.26
28,336
'92,838
NA Not available. ' Data on PjOj content not available.
1 Market value (price) at port of shipment.
1 Amount sold or used plus Imports minus exports. < Preliminary.
According to the Bureau of Mines (1), "Slimes constitute
about one-third of the total matrix mined and amount to
approximately 4 million tons per year with an approximate
BPL value of 32%. About 30% of the BPL values of the
matrix remains with the slimes. The plus 150-mesh material
entrained in the slimes averages about 234,000 tons per
year.
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FIGURE 1. FLOW DIAGRAM OF FLORIDA PHOSPHATE ROCK MIUING OPERATIONS.
8
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"The mineral composition of the slimes varies because the
matrix is from different areas, depending on mining„ Con-
sequently, only a range of the composition can be estab-
lished, as shown in Table II, Slimes produced also vary
in chemical composition, as shown in Table III0 A typical
analysis and range is given as a guide rather than as a
standard. The maximum range is based on analyses over a
period of years."
TABLE II
APPROXIMATE MINERALOGICAL WEIGHT COMPOSITION OF PHOSPHATE
SLIMES
Mineral Percent
Carbonate fluorapatite . . . „ . ,
Quartz „„..„.,
Montmorilloni te .000.0.0,
Wavellite „ . „ . » . ,
Heavy minerals »..<>. ..<,„,
, . . . . 20-25
30-35
, . . . . 20-25
,.oo. 5-10
, o . . . 4-6
. . . . o 2-3
2-3
,00.0 1-2
0-1
TABLE III
CHEMICAL COMPOSITION OF PHOSPHATE SLIMES
Chemical Typical analyses, Range,
percent percent
P2O5 9.06 9-17
Si02 45.68 31-46
Fe203 3.98 3-7
Al20s 8.51 6-18
CaO 14.00 14-23
MgO 1.13 1-2
C02 80 0-1
F 87 0-1
LOI 10.60 9-16
BPL 19.88 19-37
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Spectographic analyses of slimes typical of those used
in these tests are shown in Table IV and a typical
thermogram is shown in Figure (2)„ Studies showed that
these slimes have properties comparable to many ceramic
clays, exhibiting plastic behavior at approximately
60 wt% solids content, and that they can be extruded at
about 70 wt% solids content„ In firing tests sintering
occurred over a reasonable temperature range of 1050° -
1150°C and color control can be achieved by controlling
firing temperature,, Slimes fired at the lower tempera-
ture are buff in color, progressing to deep red at the
higher temperature„ Initial experiments indicated
shrinkage during firing which may lead to surface check-
ing „ This may be alleviated by addition of a pre-
sintered material (grog) or sand,,
X-ray analysis as shown in Table IV was conducted on the
raw dried slimes. This investigation confirmed past
reports (3, 4) that variations in the mineralogy are to
be expected.
10
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TABLE IV
SPECTROGRAPHIC ANALYSIS OF PHOSPHATE SLIME
Metal
Amount(1)
Remarks
Iron
Silicon
Alumi num
Calcium
Phosphorus
Magnesium
Titanium
Chromium
Sodium
Manganese
Strontium
Barium
Zirconium
Nickel
Vanadium
Zinc
Copper
Berryllium
Potassium
Cerium
Yttrium
Lead
Tin
Lithium
Uranium
Boron
< 1
(.01)
(.01)
(.01)
(.001)
(.001)
Trace
Trace?
Trace?
9
9
Very strong
Strong
Strong
Strong
Definite
Weak
Weak
Definite
Definite
One line
One line
Much interference ''*'
Not detected
(1) Used a +_ 1% standard
(2) Less than 1%, greater than 0%
(3) Questionable
(4) Better separation can be obtained
by second order spectral analysis
11
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AT
N/*
\
DRIKD AT 200 C
WEIGHT
1
200 UOO 600 800
TEMPERATURE. DEGREES CENTIGRADE.
1000
AT
1
-
-
1
^/
x
_^~^~
1
— "-—v..
,
1
^^
1
-^
1
Arp
> L
1 1 '
DRIED AT 800° C
r\
WEIGHT
\^
\x
• — .
/
—
1
—
-
-
~ —
FIGURE 2. DIFFERENTIAL-THERMAL, GRAVIMETRIC ANALYSES OF DRIED
PHOSPHATE SLIMES. Note that endothermic reaction
and weignt loss read down-page.
12
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The results of chemical analysis are shown in Table V,
Previous analyses are also shown confirming the indications
above that the composition of these slimes are variable
and may require adjustment of composition during process-
ing of a ceramic body „
TABLE V
CHEMICAL ANALYSIS OF PHOSPHATE SLIMES, DRY BASIS
Constituent - —-^ (<) ~
Si02
A1203
CaO
P2°5
MgO
Fe203
MnO
Ti02
C
C02
Na20
K20
H20+
H20~
F
(1)
(2)
27.9
16.5
16.5
14.2
1.85
6.60
0.08
0.64
0.55
1.10
0.36
0.61
6.48
4.37
1.38
IITRI Analysis of
1 year old pond, "
32.6
16.2
18.4
11.8
2.3
4.8
-
-
1.3
1.4
-
12.8<6)
-
2.7
34.1
16.2
16.6
12.5
2.0
4.0
-
-
0.9
2.0
-
14.1
-
1.8
slime stored at
-14% solids, M.
41.8
7.2
11.7
9.8
1.8
3.3
-
-
-
-
-
(6) 12.6(6)
-
2.2
29.0
16.8
11.9
13.1
1.9
7.2
-
-
-
-
-
16. 3(6)
-
2.2
Noralyn, Florida.
H. Stanczyk and
I. L. Feld, "Electro-Dewatering Tests of Florida
Phosphate Eock Slime," Bureau of Mines RI 6451 (1964)
(3) Undetermined age; -*17% solids.
(4) Undetermined age, ^30% solids.
(5) 2 year old pond, 27% solids.
(6) Loss on ignition.
13
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Pyrometric Cone Equivalent tests (see Glossary) showed
that initial deformation occurred at about 1145°C0
Maximum deformation occurred at 1210°C and is equivalent
to a melting point. During firing, the color of the
ceramic body darkened progressively to a dark brown at
melting,. These tests also suggested the possibility that
some types of phosphate slimes may bloat or foam.
The Atterberg test (5), which determined the general
workability of a clay and the amount of water permissible
for plasticity to occur, was used to approximate the con-
ditions for handling unfired ceramics,. This indicated
that plasticity occurs in the range of 69-75 wt% water
added to the slime solids. Based on the total water-
solids slurry, this is equivalent to a solids content of
57-62.5 wt%.
The amount of solids in slurries obtained from the
Noralyn site ranged from 8 to 12% and initial tests were
carried out on both pond-stored and washer-discharged
slimeSo Subsequent slurries were pre-thickened by liquid
withdrawal to expedite dewatering and drying for pro-
cessing experimentso These slimes displayed a pH varia-
tion of 7.0 to 8.5.
Measurements of the rheological behavior were performed
to characterize handling characteristics,. These indi-
cated that grey pond-stored slimes are thixotropic,
whereas the fresh washer-discharged slimes are plastic
at low-shear and dilatent at higher shear rates. Thixo-
tropy is desirable for foaming because shear forces
increase fluidity. In contrast, dilatency is generally
undesirable because such stresses tend to make the material
less workable.
The viscosity of a 12.4% solids slurry was measured with
and without deflocculant. These limited results, shown
in Table VI, indicate that these slimes slurries can be
efficiently deflocculated.
14
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TABLE VI
VISCOSITY* OF PHOSPHATE
SLIME MIXTURES (12.4% SOLIDS)
Additive
CPS x 103*
None 63.2
0.2% Sodium Silicate 30.4
0.2% Na2CO3 82.4
*No. 3 spindle at 0.3 RPM
Brookfield Viscometer Model LVT
Additional characterization studies included settling and
thermal properties of these slimes. Table VII shows typi-
cal settling velocities and indicates that fluid-bed
drying increases settling velocities two orders of magni-
tude. It suggests that this drying may have altered
particle size or charge.
TABLE VII
PROPERTIES OF RAW AND DRIED SLIMES
DILUTED TO 5% SOLIDS SUSPENSIONS
Slime No.*
Settling Rate
i n./hr. pH
Observations
1
2
3
4
5
6
7
8
0.104
0.021
0.125
0.042
0.042
0.042
3.5
3.5
5
5
5
5-6
5
5
5
6
Buff
Grey
Light and dark buff
Brown
Light and dark buff
Light and dark buff
Coarse grain, buff
Coarse grain, buff
First six specimens were 35% solids raw slimes;
Nos. 7 and 8 were fluid-bed dried.
15
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Thermal conductivity for fluid-bed dried product was
measured as K - 1.13 BTU/hr/°F/ft^/in. at 70°F mean
temperature on material containing about 8% moisture
in particles less than 1/4 in. (unit weight 60 lb/ft3).
Specific teat of (mean temperature of 95°F) a -8+16
mesh fraction of fluid-bed dried slime measured 0.28
BTU/lb/°F giving a calculated value for bone dry slime
of 0.22 BTU/lb/°F. Fired pellets (-4+8 mesh fraction)
were found to have a specific heat of 0.24 BTU/lb/°F.
Commercial LWA (Materialite) had a specific heat of
0.25 BTU/lb/°F f°r "3/8+4 mesh particles. All of these
specific heat measurements compare normally with mixed
oxides.
Slime wastes are normally discharged into large settling
ponds from which some clear water can be recovered and
re-used in the processing plant. Since about 1.25 acre-
feet of wet slimes are produced per acre foot of matrix
mined, the settling ponds are located over mined-out
areas with above-grade dams around them. The Bureau of
Mines (1) estimated that the capital investment, for a
mine the size of IMC's Noralyn Operation, is about 1.66
million dollars and the net operating cost is about
$0.245 per ton.
From these settling ponds, only a fraction of the con-
tained water can be separated. Figure (3) shows that
even after 20 to 30 years of quiescent settling, only
about 15% of the water originally present separates and
the pond stabilizes at about 20% solids making land so
occupied useless.
16
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25
20
15
SOLIDS,
10
I _L_l
I 11
j i
0.01
0.1 1.0
TIME, YEARS.
10
FIGURE 3. RATE OF CONSOLIDATION OF PHOSPHATE SLIMES, TYPICAL
In addition, there is a continuing requirement for new
land for disposal-sites in a market of rapidly rising land-
values. There are increasing demands for water to replace
that which is tied up in these ponds in spite of potential
water shortages. Finally, there is the ever present
danger of dam failure which could result in severe pollu-
tion of rivers, streams, ground water resources, and
residential and recreational areas.
While costs of present disposal methods are increasing,
the phosphate industry is being subjected to other severe
economic pressures. Unless the phosphate rock industry
can be given relief in the form of an economic solution
to the disposal of these slimes, it will undoubtedly
suffer severe losses.
17
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DEVELOPMENT OF THE PROGRAM
The primary objective of the project was to demonstrate
that slimes could be removed from the slime ponds and dried
economically. A second objective of equal importance was
to show that these dry slimes could be utilized in building
products. A third objective, of lower priority, was to
review all literature and reports developed over the last
40 years and, with the aid of additional laboratory work,
fully characterize the phosphate slimes in terms of chemical,
physical and thermal properties.
The primary objective, the production of dry slime powders,
was demonstrated and is discussed in detail in a separate
section of this report. The properties of the clay slimes
was investigated and was discussed in the previous section.
Utilization of the dry slime powders will be discussed
in the section that follows. An underlying objective was
utilization of large volumes of the slimes in order to
eliminate storage of phosphate slimes, and this represents
the driving force and motivation for this project. Dry
slimes were utilized in a number of potential building
products. Concurrent with this, a preliminary market study
was made of all of the building products and the market
potential for phosphate slime was estimated for each
building application. The results of these concurrent
investigations are discussed below:
AGGREGATES
The production of lightweight aggregates was found to
be the most promising potential end-use for phosphate
slimes in building product applications. Lightweight
aggregates showed the highest potential for immediate
acceptance in lightweight structural concrete. In addition,
aggregates represented the largest market for building
products in the Florida area. This application could
consume nearly 8 million tons per year of dry slime solids.
This, in turn, would release nearly 20 million tons per
year (or nearly 5 billion gallons) of locked-up water
in the slime ponds for ultimate re-use.
In view of the large market potential for aggregates,
the possibility for immediate market acceptance and the
fact that aggregates could utilize over 20% of the industry's
19
-------
total annual production of slimes, it was decided to
apply maximum effort to this phase of the utilization
program. A detailed discussion of the aggregate
investigation is presented in separate sections of
this report.
BRICKS
Bricks were produced from dry phosphate slimes. In
initial tests heat requirement was excessive and dis-
tortion and surface imperfections of the test product
were observed. New formulations containing slimes plus
grog (i.e. sand) were tested indicating a substantial
reduction in firing time along with elimination of
distortion and a reduction in surface imperfections.
At this stage of the program the production of bricks
was screened, evaluated and rejected for the following
reasons:
(a) The total market for phosphate slime base red
bricks in the Florida market was very limited and did not
warrant added research efforts.
(b) Preliminary cost estimates placed the cost of
red bricks based on phosphate slimes at about 15£ per
brick. This was considered to be excessive or uneconomical
for sales in the limited Florida market.
(c) The surface and distortion problems could be
solved with additional research effort, but the cost to
blend an additive such as grog (i.e. sand) was found to
be unattractive.
When high volume markets for building products based
on slimes have been developed through other products,
it may be practical to reconsider brick as an application
for dry phosphate slimes.
PIPE
Pipe sections based on dry slimes were produced and
fired at 1100°C. The resultant test pipe exhibited
several disadvantages including excessive firing time,
dimensional instability and/or distortions. Efforts
were made to correct these problems by developing new
formulations containing grog (i.e. sand). As a result,
firing times were reduced and distortions were eliminated.
20
-------
Compression tests indicated that the pipe had a compressive
strength of nearly 1600 pounds per linear foot and indicates
that the pipe would pass the ASTM C330 specifications
shown in Table VIII below.
TABLE VIII
CRUSHING STRENGTH REQUIREMENTS FOR STANDARD STRENGTH CLAY PIPE
(ASTM CIS, "Standard Strength Clay Sewer Pipe")
Q. „ . , Minimum Strength',
Size, inches Ib/linear ft
4 1200
6 1200
8 1400
10 1600
12 1800
At this stage of the project, production of pipe was
re-evaluated and was rejected for the following reasons:
The total market for phosphate slime based pipe in the
Florida market was quite limited and would not warrant
added research effort at this time.
The various problems associated with pipe based on
phosphate slimes can probably be solved at reasonable
cost with added research. However, the limited markets
for pipe did not warrant this added research effort as
a part of this project in view of a substantially larger
market offered by aggregate made from phosphate slimes.
TILE
Samples of pressed tile were produced and fired in a
kiln. Technical problems such as shrinkage, distortion
and surface imperfections were apparent. No major efforts
were made to correct these problems in view of the limited
market potential in the Florida market and further research
on tile applications was abandoned.
21
-------
FOAMED BODIES
Foamed bodies made from slimes did not exhibit the
strength and drying characteristics of successfully foamed
red muds (4). In view of limited markets and low product
quality, no further work was conducted in this area.
FERTILIZER APPLICATIONS
Tests were made to determine the utilization of phosphate
slimes as a potential binder in the granulation or
agglomeration of fertilizer materials including: purified
potassium chloride, two grades of muriate of potash,
triple super-phosphate, and potassium sulfate. Each
was ground to -100 mesh, and then agglomerated in a
54 x 9 in. disc agglomerator, as shown in Figure 4.
Additional tests were performed using a 4-foot pan agglom-
erator in the Nitrin plant of IMC using commercial grades
of potassium sulfate and an undersize-standard white
muriate of potash product. Agglomerates were produced
with and without addition of slimes as a binder. These
agglomerates did not meet size specifications and were
in general unsatisfactory as a granular fertilizer product
WATER
FEED
ROTATION
DISCHARGE
Figue 4. AGGLOMERATION AND SIZE-CLASSIFICATION IN A
ROTATING IPISC ~"~
22
-------
LIGHTWEIGHT AGGREGATE (OR LWA)
Concurrent with the studies of alternatives described
above, considerable effort had already gone into investi-
gation of the possibilities of producing a lightweight
aggregate. About half-way through this project, it
became apparent that this would be the most likely candi-
date of all the alternatives under investigation to prove
feasible, profitable, and amenable to production at a
relatively early time.
Preliminary market studies showed that production of
lightweight aggregate may prove feasible and profitable
in the Florida area, especially considering volume of
intended usage. In 1969, consumption of LWA in Florida
was of the order of 3,000,000 to 4,000,000 tons. With
the projected boom in housing and construction industry
in Florida, this market for LWA should double in the
next decade. There are apparently few local competitors
and the geographical location of a future plant in The
Bone Valley area is within easy access to a large portion
of the State. In addition, the current sale price for
a variety of LWA is about $7.00/ton.
23
-------
PREPARATION OF LIGHTWEIGHT AGGREGATE
There are four major unit operations or processing steps
necessary for the production of lightweight aggregate
from phosphate slimes. These are defined as: material
handling, drying, agglomeration, and kilning.
The first problem to be solved was to develop a feasible
method of transferring wet phosphate slimes, with a
solids content ranging from 20 to 35%, to a process
unit for treatment including drying. The second step,
undoubtedly the most critical from an economic vie°wpoint,
was drying. Drying of partially dewatered slimes is the
area in which all previously proposed projects have
failed due to poor economics. Each of the unit operations
necessary for the production of lightweight aggregate
is discussed in greater detail below.
Material Handling
It was concluded early in the study that it would be
economically feasible to transfer wet slimes from the
slime pond to a processing plant located adjacent to
the slime pond by the use of conventional drag-line
equipment. However, additional methods of material
handling were also investigated and the possibility
of pumping slimes was investigated in detail. A number
of pumps of different types, such as gear, centrifugal
and positive displacement pumps were tested, most of
which proved impractical. However, two pumps (3) appeared
to be suitable for moving phosphate slimes of high solids
content.
A modified MOYNO* was found to be the most reliable
method of moving.slimes. A pump manufactured by the
Wilden Division of the Worthington Pump Corporation* was
also found to be equally reliable. This is a submersible
diaphragm pump originally designed for use as a drill
mud-pump in oil field operations. It is designed to be
placed into the mud (i.e. installed below the surface of
the mud) or in our case, slimes. Since the suction is
submerged, NPSH (Net Positive Suction Head) is always
positive.
* Mention of trade names of commercial products is for
identification only and does not constitute an endorsement
or recommendation by the Environmental Protection Agency.
25
-------
The drying, agglomeration and kilning of the dry slime
powders or pellets was carried out in three individual
unit operations.
Drying.
A Pilot Plant was built at Erie, Illinois for testing
these three unit operations, as shown schematically in
Figure 5. The equipment in this Pilot Plant included:
(1) Vibrating screens
(2) Crushers (2)
(3) Four-foot disc agglomerator
(4) Two rotary direct fired drying drums
(5) Large elevator
(6) Structural steel, platforms, railings, etc.
Added details are shown in Figure 6. Provision was made
in the Pilot Plant to permit later modification to produce
aggregates as shown in Figure 7.
Various methods of slime dewatering were investigated,
including leaching, leach-electrolysis, curing and baking,
ion exchange, electro-osmosis, filtration and drying in
various types of dryers. Investigation of dryers confirmed
the findings of past researches to the effect that the drying
problem was practically insurmountable in drying slimes
containing 20% to 35% solids. Rotary dryers were unable
to handle the semi-plastic slimes which tend to bridge and
clog the dryer, requiring frequent and costly maintenance.
Heat and mass transfer were hampered by the excess fluidity
of the feed. The major disadvantage of rotary dryers is
their low thermal efficiency (6) as illustrated in Table IX.
Spray drying was also considered. However, the costs (6)
as shown in Table X, were excessive due to the high fuel
cost of about $20.00 per ton of dry solids.
Attention was centered on a relatively new type of fluid-
bed dryer that has been in commercial development in
recent years. This dryer is shown schematically in
Figure 8. Hot gases are passed through the bottom of
the dryer into the bed of material to be dried, fluidizing
those materials. These hot gases remove the moisture and
carry it out through the overhead outlet. The unique
26
-------
FIGURE 5. GENERAL ARRANGEMENT, LIGHTWEIGHT AGGREGATE PILOT PLANT.
27
-------
FEED
WATER
AIR
GAS
BLENDER
AGGLOMERATOR
DRIER
VElMT
SCREEN
— OVERSIZE
->- SIZED PRODUCT
FIGURE 6. FLOW DIAGRAM, LIGHTWEIGHT AGGREGATE PILOT PLANT.
28
-------
DRY FEED
VENT
DRYER AND/OR KILN
IMDERSIZE
FLGURE 7. FLOW DIAGRAM FOR PROPOSED AGGREGATION PILOT PLANT.
29
-------
TABLE IX
TYPICAL PERFORMANCE OF DIRECT-HEAT ROTARY DRYERS
Material Dried
Moisture Content,%
(Wet Basis)
Initial Final
Heat Effi-
ciency, %
HIGH-TEMPERATURE
Sand 10
Stone .... o ..... 6
Fluorspar . 6
Sodium chloride ..... 3
(vacuum salt)
Sodium sulfate , 6
Ilmenite ore 6
MEDIUM-TEMPERATURE
Copperas ..... .... 7
Ammonium sulfate 3
Cellulose acetate .... 60
Sodium chloride 25
(grainer salt)
Cast iron borings .... 6
Styrene .„„.„..„. 5
LOW-TEMPERATURE
Oxalic acid ..<,.„.. 5
Vinyl resins .„„„... 30
Ammonium nitrate prills . 4
Urea prills . . „ . . . . 2
Urea crystals 3
0.5
0.5
0.5
0.04
0.1
0.2
61
65
59
70 to 80
60
60 to 65
1 (moles) 55
0.10 50 to 60
0.5 51
0.06 35
0.5
0.1
0.2
1
0.25
0.2
0.1
50 to 60
45
29
50 to 55
30 to 35
20 to 30
50 to 55
30
-------
TABLE X
ECONOMICS OF SPRAY DRYING
Operating temperature, °F
Evaporative capacity, Ib water/hr..
Heat requirement, BTU/hr
Power requirement , hp
Approximate equipment cost, $*
Typical operating cost ^i/lb^
Small
Typical
500
400
1,200 000 2,
20
36,000
1.2
Dryers,
High
1,000
1,000
200 000
30
38,000
0.6
Typic£fr
500
6,500
20,000,000
220
190,000
0.4
ge Dryegfgh
1,000
16,000
35,000,000
280
210,000
0.3
* Equipment costs are FOB shop.
f* Operating costs are 6/lb. of water evaporated, and include equipment,
power, labor, and fuel costs.
June 19, 1967 -
Chemical Engineering
100 Ibs . feed contains 75 Ibs . H20 and 25 Ibe . solids.
1 ton of feed contains 1500 Ibs. ^0 and 500 Ibs. solids.
If it costs 0.3£/lb. H20 evaporated, then 1500 x .003 = $4.50/ton feed
or $4.50 _ = $19.20/ton of dry solids.
500 Ibs. solids
-------
EXHAUST GAS AND FINES
WET
SOLIDS
FEED
FIGURE 8. SCHEMATIC DIAGRAM OF FLUID-BED DRYER..
(Fluid-bed dryer of Tailor & Company,* Bettendorf, Iowa
was used in all these tests.)
* Mention of trade names of commercial products is for
identification only and does not constitute an endorsement
or recommendation by the Environmental Protection Agency.
32
-------
feature of this dryer is that both the product and the
effluent gases leave the dryer at low temperature; thus,
most of the heat imput is consumed in the drying operation.
Low heat losses result in very high thermal efficiency
which can range as high as 80% to 90%. The development
of this dryer along with modifications installed by the
manufacturer to meet the special needs encountered in
drying phosphate slimes, was of great value. The high
efficiency of this dryer makes the drying of phosphate
slimes economically feasible.
Extensive tests were conducted on this dryer in the Erie,
Illinois test site. The layout of the dryer is shown
in Figure 9 and the results of these test runs are
summarized in Table XI.
WET
FEED
BLENDER
EXHAUST
BAG DUST
COLLECTOR
DRYER
SCREW PUMP
NATURAL
AIR SLIDE
->- DRY PRODUCT
FIGURE 9. ARRANGEMENT OF EXPERIMENTAL FLUID-BED DRYER
SYSTEM.
33
-------
TABLE XI
SUMMARY OF TEST RESULTS ON FLUID-BED DRYER MARCH - JUNE, 1970
Run
No.
2
3
4
5
Solids
in °F
65
66.3
55
83.8
Solids
Out °F
122
162
111
143.6
% H20
In Feed
25.7
29.5
21.2
23.3
% H20
Product
6.7
3.4
9.6
4.9
Dryi ng
Eff .%
52
62
72
70
Lbs/hr
Wet Feed
150
169
246
226
Oper .
Factor
75
80
90
82
In addition, dried agglomerated slimes product was
successfully made at the Erie Pilot Plant in October of
1970 using the 4-foot diameter pilot plant disc granulator.
Analysis of these data shows, as expected, that both
efficiency and capacity of this dryer increase as the
operating reliability increases. Also, as Figure 10 shows,
drying efficiency increases at higher throughput rates
because constant heat losses become a smaller part of the
total load. The data indicate that drying efficiencies of
80 - 90% can reasonably be expected in large scale equip-
ment .
Expected fuel costs were calculated assuming the 90%
thermal efficiency claimed by the manufacturer and the
cost and properties of fuel in Florida (37£ per million
BTU of fuel value). Figure 11 shows these calculated
fuel costs at various slimes-solids contents and indicates
that complete drying of 25% solids feed material would be
$3.20 per ton of dried slimes solids, for fuel cost alone.
The calculated theoretical maximum throughput for this
test dryer is shown in Figure 12. The pilot test dryer
was limited by its materials of construction to a maximum
temperature of 550°F whereas it would be expected that
a commercial dryer designed for these purposes would
operate at 1000° to 1500°F. It would therefore have
a capacity of as much as 2^ times th(
the present test unit on a Ibs/hr/ft"
rated capacity of
basis. An approximate
34
-------
8o
70
6o
DRYING
EFFICIENCY,
120
_L
_L
_L
160 180 200 220 2^0
POUNDS OF WET FEED PER HOUR
260
FIGURE 10. EFFECT OF THROUGH-PUT ON THE EFFICIENCY
OF DRYING .PHOSPHATE SLIMES IN THE FLUID-
BED DRYER.
VJ
5
k
ESTIMATED
FUEL COST,
3
DOLLARS PER
TON OF DRY
PRODUCT 2
1
0
\)
\
PRODU
\
\
V
\
CT
DRYFESS ,
{.<
\
^ \.
\
^
1 C\
"^^ -'-'-'
^
yjv soi
-^-^
-r-i^iQ
jJ-JJO
~--^.
0
20 ho 60 80
SOLIDS CONTENT OF DRYER FEED, %
100
FIGURE 11. ESTIMATED COST OF FUEL TO DRY PHOSPHATE SLIMES
IN A FLUID-BED DRYER.
(Calculated at 90% thermal efficiency,
140,000 BTU/gal. of fuel oil at 5.2$/gal.
35
-------
POIMDS
OF
DRY
PRODUCT
PER
HOUR
0 20 kO 60 80 100
SOLIDS CONTENT OF DRYER FEED, %
FIGURE 12. THEORETICAL CAPACITY OF 2 SQ,. FT. FLUID-BED DRYER.
Determined for the measured maximum heat input of
312,000 BTU/hr at 560 F inlet air temperature.
equation was developed showing the relationship between
hot air to the dryer and the heat content (and therefore
throughput) of the dryer. The basic relationship (6) is:
H = 0.24T + (1060.8 4- 0.48T) Y
Where H = BTU/lb of dry air,
Y = Ib water/lb dry air, and = 0.0173
T = Temperature °F.
For average ambient conditions in Florida, the relation-
ship is shown in Figure 13.
36
-------
1+00
300
HEAT INPUT,
BTU PER
POUND OF
DRY AIR
200
100
0
koo
600 800 1000 1200
DRYER INLET' AIR TEMPERARURE, PEG. F
ikOO
FIGURE 13. EFFECT OF AIR TEMPERATURE ON DRYER HEAT REQUIREMENT.
Estimated for ambient summer conditions in Florida.
The tests above have also shown that the recycle ratio,
(see Glossary) has a strong influence on the performance
of the system. Figure 14 shows that increasing recycle
ratios tend to reduce the amount of water in the dryer
feed, and therefore increase the potential capacity of
the dryer. On the other hand, this figure also shows that
increasing moisture content in the recycle stream increases
the amount of water in the dryer feed and therefore tends
to reduce its efficiency. Appendix B shows a typical
calculation of the recycle ratio and its effect on the
system operation. Most of the pilot tests on this dryer
were carried out with recycle ratios in the range of
7 to 10, wherein the blender discharge moisture content
was between 12 and 14%. Normally this would be considered
excessive in terms of equipment size, power requirements,
and heat loss. If it were possible to operate with a
more efficient blender which would produce a discharge
37
-------
10
RECYCLE
RATIO
0
10$ WATER IN RECYCLE
5 10 15 20 25 30
WATER CONTENT OF BLENDER DISCHARGE,%.
35
FIGURE 14. EFFECT OF MOISTURE ON RECYCLE RATIO TO
FLUID-BED DRYER.
Recycle Ratio is pounds of dry product
recycled per pound of fresh wet feed.
38
-------
material in the range of 20 to 25% moisture, it is
apparent from Appendix B that the recycle ratio would
be cut in half. The essential effect of this would be
to increase the overall capacity of the unit, and reduce
its costs .
From the above evaluation of the fluid-bed dryer,
estimates were made of the potential operating costs for
a commercial sized unit, as shown in Table XII. It is
estimated therein that for drying 100,000 tons per year
of slimes-solids, starting with 30% material, it is
reasonable to assume the net operating cost of $5.50
per ton of dried slimes-solids.
TABLE XII
ESTIMATED COST OF DRYING IN FLUID-BED DRYER
Basis: 30% slime-solids to dry slime at a rate of 100,000 TPY
Cost per ton
Cost of slimes into dryer $0.50
Fuel 2.50
Power .50
Depreciation 1.25
Labor and Maintenance 1.00
$5.75
Credit for ponding .25
Cost per ton dry slime-solids = $5.50
In order to verify these experimental results, inde-
pendent calculations were made by Professor D. T. Wasan
of Illinois Institute of Technology, as shown in Appendix C.
In this study, Dr. Wasan derived a mathematical model,
based on constant-rate drying, which was successful in
predicting experimental values of final moisture content
from the dryer. Data abstracted from Dr. Wasan's report
as shown in Table XIII, indicate that the controlling
mechanism in the dryer was heat transfer.
39
-------
TABLE XIII
ANALYSIS OF DRYING EXPERIMENTS
Run
No.
2
3
4
5
H20 Balance
Mi n. Air Rqd.
# feed
# air
# feed
9.46
2.00
15.50
4.65
Mi n. Fluid Air
# feed
# air
# feed
4.80
3.78
2.93
3.19
Air Needed
for Heat
# air
# feed
11.9
9.2
10.1
11.1
Actual Air
Used
# air
# feed
8.70
4.31
6.22
5.50
In the above Table, the underlined rate indicates
the controlling rate that is limiting on each run,
In all the runs (except Run 4), Heat Transfer was
shown to be the controlling rate.
Kilning
Slimes products from IMC drying tests were processed
through a pilot plant rotary kiln which was chosen be-
cause (1) the temperature can be accurately controlled,
(2) it produces a round shape, minimizing sticking,
(3) it is convenient to operate, (4) it produces a better
grade of concrete, (5) raw materials that show satisfactory
processing characteristics in the pilot plant unit, can
generally be handled in a commercial kiln.
The kilning operation was aimed chiefly at producing
products for evaluation rather than to produce design
data for equipment. Evaluation of the equipment is a
natural part of the Demonstration Project which should
follow this report. Evaluation of the product is covered
in the following sections of this report.
40
-------
LIGHTWEIGHT AGGREGATE PRODUCT
During the course of this project, two types of
aggregate were prepared. Initially, a somewhat angular
material was produced from air-dried and crushed raw
slimes and from fluid-bed-dried materials fired in a
rotary kiln. The second type of aggregate was a rounded
type produced by firing pelletized dried slimes.
Angular experimental lightweight aggregate was pro-
duced in trial quantities by firing dried, crushed
and screened slimes in a rotary kiln at about 1050°C.
Also, a +\ inch fraction of fluid-bed dried material
was fired in a similar manner. Typical chemical analyses
of these materials are shown in Table XIV and the physical
properties in Table XV. In firing these materials, there
was some difficulty with adherence of the fragments to
each other and to the wall of the kiln, and crush strength
was inadequate.
Slimes which had been dried in the fluid-bed dryer and
agglomerated in a disc-agglomerator prior to kilning
were also characterized. Table XVI shows the densities
and porosities of these materials, and Table XVII the
crush strength. For material having densities of 20 to
50 pounds per cubic foot, crush strength ranged between
634 and 2748 pounds per square inch, comparing very
favorably with the crush strength of competitive materials
These data, however, showed that the material thus pro-
duced was considerably lighter (20-50 pounds per cubic
foot) than conventional lightweight aggregate for
structural concrete, (usually in the range of 40-60
pounds per cubic foot) yet maintaining satisfactory
strength.
For ASTM tests (Specification Designation C330) these
aggregates were.blended to provide a coarse aggregate
as shown in Table XVIII. The steam test for iron oxide
revealed little staining, indicating the material is
satisfactory for use in concrete and organic material
was found either by chemical analyses or by soaking in
caustic soda. No friable particles (i.e. crushable with
the fingers) or lumps were found. The fineness modulous
(FM - See Glossary) for these materials was found to be
5.6, whereas the modulous less than 4 characterizes fine
aggregates and coarse aggregates may extend to about 7.
This test, which indicates the average surface area of
41
-------
TABLE XIV
CHEMICAL ANALYSES OF
FIRED PHOSPHATE SLIME BODIES
Pellets (1) Brick
Core (2)
5A (4)
IMD-5 (5)
With Without
Quartz Grog Grog (3)
SiO2
A1203
CaO
P2°5
MgO
Fe203
MnO
Ti02
Na20
K20
C
C02
H20-
H20+
S03
F
38.0%
17.6
18.1
13.4
3.08
5.56
.04
.62
1.14
0.78
0.05
0.22
0.05
0.01
0.18
1.33
56 . 0%
13.9
13.3
10.1
1.64
3.51
.03
.49
0.77
0.34
0.00
0.00
0.03
0.01
0.04
1.03
41.2%
18.9
18.1
13.7
2.23
4.77
0.04
0.67
1.05
0.46
0.00
0.00
0.03
0.01
0.05
1.40
39.5%
18.0
18.4
13.4
3.20
5.13
.03
.62
0.67
0.76
0.03
0.30
0.04
0.00
0.21
1.56
39.0%
17.8
18.4
14.0
3.08
5.15
.03
.61
0.18
0.75
0.07
0.24
0.03
0.07
0.18
1.38
(1) Air-Dried Slime HA
(2) Fluid-bed Dried Slime IMD-3
(3) Calculated
(4) Air-Dried Slime 5A
(5) Fluid-bed Dried Slime,
IMD-5 '
42
-------
TABLE XV
PROPERTIES OF ROTARY KILN FIRED AND
CRUSHED PHOSPHATE SLIME LIGHTWEIGHT AGGREGATE
CO
fn\
U.S. Screen Sizev
1)
2)
3)
5A*
a) + 1/2
-1
-1/2
-3/8
-4
b) -1/2
-1
-1/2
-3/8
-4
IMD-5*
(+1/4 in
-1
-1/2
-3/8
-4
IMD-3*
(+1/4 in
-1
-1/2
-3/8
—4
(3)
in. kiln feed:
+ 1/2
+3/8
+ 4
in. kiln feed:
+ 1/2
+ 3/8
+ 4
(4)
. kiln feed) :
+ 1/2
+3/8
+ 4
(4)
. kiln feed) :
+ 1/2
+ 3/8
+ 4
Cumula-
tive
Wt% Wt%
58.5
18.2
15.0
8.3
23.5
18.2
46.2
12.1
32.2
13.8
34.8
19.2
59.7
11.5
13.4
15.4
58.5
76.7
91.7
100.0
23.5
41.7
87.9
100.0
32.2
46.0
80.8
100.0
59.7
71.2
84.6
100.0
Unit Wt
Ib/ft
13
13
19
23
11
14
17
24
12
13
16
23
18
19
22
39
.54
.28
.85
.46
.50
.51
.10
.94
(5)
.01
.64
.44
.82
(5)
.85
.55
.80
.09
1 in.
41
37
96
83
41
78
73
73
37
37
39
119
92
87
119
128
Crush
, l| in
69
73
193
170
78
147
142
165
78
73
128
220
147
147
202
339
ing Strength
. 2 in
110
138
330
229
124
262
234
303
138
133
220
399
238
243
312
734
. 2^ in
184
243
665
642
225
486
431
596
229
248
440
729
468
463
546
1743
. 3 in.
298
422
1147
1083
431
1165
734
1101
376
413
734
1330
853
771
954
3762
TT) Nos. 1 and 2 fired to 1050^J ; No. 3 fired to 1150UC (over-fired) . (2) above line =
kiln feed; below line = product. (3) air-dried. (4) fluid-bed dried. (5) inaccurate
because of small amounts available. *Code identification shown in footnotes to Table XIV.
-------
TABLE XVI
DENSITY AND POROSITY OF EXPANDED PHOSPHATE
SLIME AGGREGATES (1) (2)
0
IS]
•H
W
d
0
0
in
0
CO
W
CD
1)
IMD-3
+ 1/2
-1/2+3/8
-3/8+4
-4+8
-8
2)
IMD-4
+ 1/2
-1/2+3/8
-3/8+4
-4+8
-8
True specific
gravity (3)
Apparent specific
gravity
Bulk
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
IMD-3 and IMD-4 —
(1) firing range
(2) pelletized in
1.58 0
1.40 0
1.64 0
1.71 0
1.45 0
1.67 0
1.54 0
1.49 0
1.47 0
1.49 0
Fluid-Bed
1100-1150°
rotating
Density
.81
.69
.79
.80
.65
.78
.66
.74
.78
.62
Apparent
Porosity, %
49.
50.
51.
51.
55.
53.
57.
50.
47.
58.
0
7
8
3
0
2
3
0
3
1
Sealed
Porosity, % (4)
19
22
17
17
20
16
17
21
22
18
/"-\
lO
\-s
co
b§. T3
•H
0 r-t
S 0
3 W
r-H
O «H
> 0
.8
.8
.8
.9
.0
.8
.3
.5
.7
.0
31,
26.
30.
30.
25.
30.
25.
28.
30.
23.
2
5
4
8
0
0
4
5
0
9
Measured Unit
Weight, Ib/ft3
20
26
30
32
50
19
21
25
27
40
(6)
.44
.97
.31
.52
.54(6)
/ s+ \
.65(6)
.68
.10
.28
.31(6)
Dried Slimes
C
inclined
disc
(3) approximation
(4) based
(5) based
on estimated true
on estimated true
(6) insufficient
specific
specific
material for
gravity
gravi
ty
accurate measurement
44
-------
TABLE XVII
PROPERTIES OF ROTARY KILN FIRED EXPANDED PHOSPHATE SLIME
AGGREGATES (1)(2)
U.S.
Screen Size wt'°
IMD-3
+ 1/2
-1/2+3/8
-3/8+4
-4+8
-8
IMD-4
+ 1/2
-1/2+3/8
-3/8+4
-4+8
-8
5.96
6.24
56.90
23.30
7.59
17.01
21.32
37.46
14.71
9.50
Cumulative Unit wt.
wt% lb/ft3
5.96
12.20
69.10
92.40
99.99
17.01
38.33
75.79
90.50
100.00
20.44
26.97
31.30
32.52
50.54
19.65
21.68
25.10
27.28
40.31
Crushing Strength, psi
1 in. 1^ in. 2 in. 2^ in-
3 in.
insufficient quantities
211
423
634
391
645
1015
740 1311
1078 2125
1797 3700
2167
—
—
insufficient quantities
insufficient quantities
222
529
825
370
899
1480
634 1226
1691
2748 6131
—
--
—
insufficient quantities
(1) firing range 1100-1150 C
(2) pelletized in rotating inclined disc
-------
the aggregate indicates that this material should result
in workable concrete mix. These tests are summarized
in Table XIX which shows that these materials satisfy
the requirements of ASTM C330.
TABLE XVIII
PROPERTIES OF BLENDED ' COARSE
PHOSPHATE SLIME LIGHTWEIGHT AGGREGATE
UoS,
Screen Size
-1/2 +3/8
-3/8 +4
-4 +8
-8 +16
-16 +30
-30 +50
-50 +100
Wt%
5,15
54,24
37,63
2,94
0.02
0,01
0,02
CuirioWt %
5,15
59,39
97,02
99096
99098
99,99
100,01
561.50,%FM=5,62
% Through
Sieve (2)
100
94,85
40,61
2.99
—
— —
,
ASTM (3)
100
80-100
5-40
0-20
—
—
—
Blended Unit Weight is 27,92 lb/ft3
(1) IMD-3 and IMD-4 (3) ASTM C330, wt% pass-
(2) Wt% passing through larger ing through larger
sieve indicated, sieve for \ in. to #4
aggregate,
(4) Fineness Modulus,
Fired pellets had a specific heat of 0.24 BTU/lb/°F,
compared with commercial lightweight aggregate (Materialite)
which has a specific heat of 0.25 BTU/lb/°F. It was deter-
mined by mercury porosimetry that the apparent density (See
Glossary) of these materials is 103 pounds/cubic foot, and
that the theoretical density of the basic material (See
Glossary) is 155 pounds/cubic foot.
Fired slime aggregates were also characterized according
to ASTM C127 (Specific Gravity in Absorption of Coarse
Aggregate), and ASTM C88 (Soundness of Aggregate by the
use of Sodium Sulfate or Magnesium Sulfate) as shown in
Table XIX. Water absorption for the slimes lightweight
aggregate is about 30%, while that for LWA made from clay
or slate processed in a rotary kiln is in the vicinity
of 20 to 25% absorption of water. Most normal weight
46
-------
TABLE XIX
SPECIFICATIONS OF PHOSPHATE SLIME LIGHTWEIGHT
AGGREGATE ACCORDING TO ASTM C330
(LIGHTWEIGHT AGGREGATES FOR STRUCTURAL CONCRETE)
Test
Method
Results
Staining
Loss on Ignition
Organic
Impurities
Grading
Friable Particles
in Aggregates
Clay Lumps
Fineness
Unit Weight
Bulk Specific
Gravity
Bulk Specific
Gravity (Sat-
urated Surface-
Dry Basis)
Apparent Specific
Gravi ty
Water Absorption
Soundness (Sodium
Sulfate)
ASTM C330
ASTM C114
ASTM C40
Stain intensity is light to
very light; Stain Index =
40 to 20
Chemical analysis indicates
<0.6% volatiles
No apparent organic materials
ASTM 136 & Not graded according to
ASTM C330 specifications (1)
ASTM C142
ASTM C330
ASTM C142
ASTM C29
0% friable
None discernible
5.62 (coarse aggregate) (2)
27.92 lb/ft3 (average) (3)
ASTM C127 0.845
ASTM C127 1.12
ASTM C127 1.16
ASTM C127 32.2%
ASTM C88 -"4.8% size reduction
(1) Quantities produced required economical use of all avail-
able aggregates, thus providing a somewhat non-specific
material.
(2) For information only, more applicable to fine aggregate.
(3) Conforms to specifications (dry-loose basis). Maximum
allowable unit weights range from 55 to 70 lb/ft , de-
pending on size of aggregate.
47
-------
aggregates, such as granite, dolomite, quartzite and schist
absorb less than 2% water- Although the larger sized aggre-
gate (-•| +3/8 in.) deteriorated in the saturated sodium
sulfate solution test after 20 cycles, the smaller size
(-3/8 -f8 mesh) showed no measurable deterioration.
Starting with 30% slimes-solids and based on estimated cost
of $4.50 per ton of dry slimes-solids (as per Table XII),
production cost of lightweight aggregate is estimated to be
of the order of $8.00 to $9.00 per ton. This works out to
be about $3.00 per cubic yard of this type of product (about
675 Ibs/cubic yard). In comparison, a variety of LWA is
sold in Florida at about $4.50/cubic yard (1300 Ibs/cubic
yard) or about $7.00 per ton. Since there are no competitive
producers of LWA (for structural concrete) in the immediate
area, as shown in Appendix E, LWA from slimes has a good
potential market within easy access to Tampa and Ocala areas.
A study of the transporation of light aggregates produced
from clay slimes was made as shown in Appendix D. This indi-
cates that the economic location for producing dried slimes
is at the slimes pond site. If the average density of the
product mix is light (less than 28 Ibs/cubic foot) and large
hopper cars are available, it would be most economical to
fire the slimes at a point near Bartow, Florida, and ship
the lightweight aggregate to the Tampa, Miami, and Jackson-
ville areas. If large cars are not available, it would be
economical to establish sattelite kiln operations at Miami
and/or Jacksonville. If the product mix had an average
density greater than 28 Ibs/cubic foot, the study shows that
it will always be cheaper to produce fired lightweight aggre-
gate in the Bartow area.
The final stage of the present project was preparation of
trial lots of lightweight concrete from phosphate slimes
expanded aggregate. Production of both insulating and
structural concretes were investigated and consideration
was given to the possibility of making concrete blocks.
The inter-relationship of these types of building materials
is shown in Figure 15, as developed by the Portland Cement
Association (8). Structural lightweight concrete is defined
as that which: (1) is made with lightweight aggregate and
conforms to ASTM C330, (2) has a compressive strength in
excess of 2500 Ibs/sq. foot at 28 days when tested according
to ASTM C330, (3) has an air-dry weight not exceeding
115 Ibs/cubic foot as determined by ASTM C567. Concrete in
which a portion of LWA is replaced by normal weight aggre-
gate (e.g. sand) and which meets the strength and weight
limitations is within the scope of ASTM C330. Since phosphate
slime LWA falls within the specifications as outlined, use
of structural lightweight concrete is desirable and was
tested accordingly.
48
-------
FIGURE 15. SPECTRUM OF LIGHTWEIGHT CONCRETES
At the low end of the scale we have the "super" lightweight
aggregates, vermiculite and perlite. They are capable of
producing a highly insulative concrete but with compressive
strengths ranging from 200 or 300 psi to a maximum of 1000 psi.
This concrete is used as an insulative roof fill over a
structural system or as fireproofing and is generally applied
by licensed applicators or subcontractors. The aggregate
also finds widespread use in making lightweight plaster.
At the high end of the scale we have structural concrete
ranging in unit weight from 85 to 120 pcf and capable of
developing compressive strengths from 2500 psi to 5000 and
6000 psi and even more. Note that all of the materials shown
here are not necessarily able to produce the high strength
concretes.
Between the two extremes, with strengths from 1000 to 2000
psi and unit weights between 50 and 85 pcf, are fill concretes,
that have some insulative value some inherent strength. De-
pending on the materials and the techniques of using them these
concretes may have properties of finishability or wearability
and at the high end of their range may be used in making small
precast products.
Concrete used in making lightweight concrete block falls in
the range of weight from 70 pcf to 110 pcf and includes all
of the materials shown except the "super" lightweight
aggregates.
49
-------
FIGURE 15. SPECTRUM OF LIGHTWEIGHT CONCRETES (Cont.)
Of the aggregates in the structural concrete range,
pumice, scoria and tuff are natural lightweight materials,
found in volcanic deposits in the West. They have gen-
erally poor concrete making properties and are primarily
used in making block or in fill concrete. With the use
of natural sands some deposits are capable of making a
fairly good concrete, but it is still difficult to obtain
high strengths.
Coal cinders are rapidly diminishing in availability
and that which is available is used principally in con-
crete block and to a limited extent in fill concrete.
It has poor and variable concrete making properties and
is not currently used as a structural lightweight aggregate,
Sintered expanded shale and expanded slag are primarily
block aggregates and have fair concrete making properties.
When used alone they have difficulty in achieving high
strength even with high cement factors; with natural
sand the unit weights tend to be high but the concrete
is quite satisfactory in other respects. Of the two,
the sintered expanded shales are used to a larger extent
in structural applications.
The rotary kiln expanded shales have good to excellent
concrete making properties and achieve high strength
with reasonable cement factors. In addition they have
all of the other desirable properties of quality concrete.
It is the principal aggregate used today in making
structural lightweight concrete with about 75 to 85%
of all structural lightweight concrete using this
aggregate. It is also used in making quality lightweight
concrete block.
All of these structural aggregates with increased air
contents are capable of producing fill concrete at lower
unit weight and with a corresponding reduction in
strength. Of course the spectrum becomes quite con-
fused when materials are blended with each other (rarely
done) or when mixed with natural sand (frequently done)
or when the air contents vary from low to excessive.
50
-------
Trial batches were prepared according to ACI 211.2-69
(Recommended Practice for Selecting Proportions for
Structural Lightweight Concrete) (9). Table XX shows
the proportions used in the concrete test trials and
lists the properties of the concretes produced in the
plastic state.
High-early-strength (Type III) cement was initially
used to expedite testing of hardened concrete. This
type of cement obtains almost the same strength in 7 days
as normal cement obtains in 28 days. Results obtained
on mixtures so made are shown in Table XXI, which indi-
cates that such a mixture compares quite favorably with
AST! Specification C330. This table also shows that a
3^ bag per cubic yard mix (87 Ibs/cubic foot) was not
satisfactory. This latter material had been made using
the initial angular aggregates which accounts for its
unsatisfactory performance. A third and lighter weight
batch was prepared as shown in Table XX. The properties
of this concrete compare very favorably with ASTM standards.
Table XXII shows the size distribution of the fine aggre-
gate used in this mix. The data of these three tests and
the appropriate ASTM Specifications are displayed in
Figure 16. In addition, a method was developed, as shown
in Appendix F, of estimating concrete strength from
aggregate crush strength results. The results of the
5th and 6th trial batches are shown also in Table XX
and data for these five trials are shown in comparison
in Table XXI.
A batch of lightweight concrete was made in the 50 Ib/cubic
foot range to determine if insulating concrete can be made.
Figures 17 and 18 show the inter-relationship of thermal
conductivity, density and compressive strength of light-
weight concrete after 28 days. It was noted while pre-
paring this mixture that the texture was quite harsh and
excess fines and water were added to produce a workable
mix. These adjustments, however, increased the water to
cement ratio to 1.49 causing excessive bleeding, segrega-
tion of aggregate and cement slurry, and low strength
(average 238 psi at 28 days). Although this was by no
means satisfactory, it gives encouragement for further
tests with the possibility that proper adjustment of the
mix will raise the strength of the material as contemplated.
51
-------
01
to
TABLE XX
PREPARATION AND PROPERTIES OF PLASTIC EXPANSIVE CONCRETES
USING PHOSPHATE SLIME COARSE LIGHTWEIGHT AGGREGATE
TRIAL BATCH NUMBER
Concrete Mix Proportions
Cement (Atlas), Type
Cement (Atlas), bags (94 Ib/bag)
Cement (Atlas), Ib/cu.yd.
(incl. mortar mix, Ib/cu.yd.
Coarse Aggregate, Phosphate Slimes
Ib/cu.yd.
Fine Aggregate, Ib/cu.yd.
Tap Water, room temp., Ib/cu.yd.
(incl. IMC additives, fl.oz/cu.yd.
Design total, Ib/cu.yd.
Plastic Concrete Properties
(Before Significant Expansion)
Slump (ASTM CMS) inches 2
Unit Wt. (ASTM C138) Ib/cu.ft. Ill
Vol. Cone. Prod. (ASTM C138)cu.ft. 26
Yield (ASTM C138) 5
cu.ft. concrete/bag cement
Relative Yeild (ASTM C138) 0.
Bags cement/cu . yd . cone. prod.
"Actual" Cement Factor (ASTM C138) 5
Air Content (ASTM C173) %
1
III
5
470
448
1560
450
2928
.75
.9
.17
.23
969
.16
3
III
5.5
517
496
880
421
2314
3 .0
93.88
24.65
4.48
0.913
6.03
5
I
5
470
356
1560
454
2480
2.75
103 .4
27.47
5.49
1.02
4.91
6
I
6
564
356
1560
513
2993
3.0
106.2
28.18
4.70
1.04
5.75
7
I
11.4
1069
(54)
240
1053
(5.4)
451
2813
5.
113.
24.
2.
0.
11.
8
I
6
564
356
1560
(3.0)
427
2907
5 3
8 106
73 27
29 4
916 1
79 5
9
I
11.4
1069
(54)
240
1053
(86.4)
459
2822
.75 5.
.8 103.
.22 27.
.54 2.
.01 1.
.95 10.
4.
10
I
6
564
356
1560
(48)
481
2961
25 7
3 104
24 28
52 4
01 1
70 5
0 5
.5
.0
.47
.74
.05
.7
.5
-------
TABLE XXI
AVERAGE COMPRESSIVE STRENGTH OF 3 x 6-in. LIGHTWEIGHT
CONCRETE CYLINDERS USING FIRED PHOSPHATE SLIME AS COARSE
AGGREGATE (1) (2)
3Unit Weight
Mix(bags/yd ) (Ib/ft ) Time of Cure (Days)
137 10 28
5 109 689v ' 1741 2107 2681 2933
3-1/2 87 — — — -- 1158
ASTM Specifications C330 (Lightweight Aggregates for
Structural Concrete)
105
110
115
2000
3000
4000
(1) Compared to concrete previously produced
(Quarterly Report No. 3) and ASTM C330
(2) This study compares Type III Cement with Type I Cement
used previously. Thus compressive strength of concrete
with Type III cement at 7 days is about equivalent to
concrete with Type I cement at 28 days.
(3) lb/in2
(4) Average 28 days compressive strength, min. psi.
53
-------
TABLE XXII
GRAIN SIZE DISTRIBUTION
OF FINE AGGREGATE (MATERIALITE)
USED IN THIRD CONCRETE BATCH
U.S.
Screen Size
3/8
4
8
16
30
50
100
pan
ASTM C33
% Through
100
95-100
80-100
50-85
25-60
10-30
2-10
— —
% on (1) (2)
Screen
0
2
6
19
30
25
14
4
Cumulative %
on Screen
0
2
8
27
57
82
96
100
(1) Custom blended to conform to ASTM C33
(2) Fineness Modulus =2.72
54
-------
^000
3000
2000
COMPRESSIVE
STRENGTH,
PS I
1000
0
70
o1
G
V
80 90 100 110 120
UNIT WEIGHT, POUNDS PER CUBIC FOOT
FIGURE 16. COMPRESSIVE STRENGTH OF CONCRETE MADE WITH PHOSPHATE SLIME
Symt
k
3
THERMAL
CONDUCTIVITY,
2
BTU PER HOUR
PER SO.. FT.
PER DEG. F
PER INCH i
THICKNESS
n
>ol: 7 da^
A
O
^
COARSE AGGREGATE.
r 28 day
V
A
0
^^
^^
{^^^
^
Fine Aggregate Cement Factor
Sand 3i
Sand 5
Materialite 6
^
^1
X
^
/
s\
x
/
r
0 20 kO 60 80 100
UNIT WEIGHT, OVM'i-DRIED, POUNDS PER CUBIC FOOT
FIGURE 17. APPROXIMATE THERMAL CONDUCTIVITY OF INSULATING CONCRETE.
Thermal conductivity of normal concrete generally ranges
55from 9.0 to 12.0.
-------
1000
10
20 30 UO 50 60 70
UNIT WEIGHT, OVEN-DRY, POUNDS PER CUBIC FOOT
FIGURE 18. APPROXIMATE 28-DAY COMPRESSIVE STRENGTHS OF INSULATING
CONCRETES.
Aggregates In the areas indicated are;
A...perlite,vermiculite, cellular neat cement, 1:3 -1:10
B...pummice, 1:5
C...expanded shale, 1:5 -1:14; expanded slag, 1:5 -1:9-
56
-------
Preliminary data showed that both concretes displayed
relatively high compressive strengths with somewhat lowered
water requirements. When compared to the strength-density
requirements of ASTM C330, indications are that both
concretes will conform to these specifications. The data
indicate that the admixture used is not detrimental to
the strength of the concrete as designed and, in fact,
appears to increase the strength. Moreover the use of
foam presents about 20% savings in weight over the light-
weight concrete normally produced in this study.
57
-------
SUMMARY
The objective of this project was to develop a means
of disposing economically of a significant portion of
the enormous volume of aqueous slimes generated as
waste from the Florida phosphate mining industry. To
that end, a potentially economical method of producing
fired lightweight aggregate for lightweight concrete
has been developed on a scale sufficient to show that
the data are reliable. In addition a drying process,
more economical than those previously studied, has been
developed which not only is suitable for lightweight
aggregate preparation but should reduce the cost of pro-
ducing other materials from slimes. The possibility of
producing other structural shapes in ceramic materials
including tile, pipe, and brick, was also investigated.
Emphasis was placed on the development of lightweight
aggregate as the key product of this project since this
was the largest volume product of those considered and
had the greatest possibility of rapid and economical
reduction to practice. The project has, at this time,
been carried to the point of having demonstrated each
piece of equipment (or unit-operation) on a small scale
(at the Erie Pilot Plant as part of this project) and
having produced reasonable quantities of dried-slimes,
fired-aggregate and concrete test-blocks to assure that
the data so far obtained — which are encouraging — are
valid. The lightweight aggregate produced from slimes
passed all the ASTM specifications (Lightweight Aggregates
for Structural Concrete - ASTM C330). The next step in
pursuing utilization of the results of this report will
be to produce on semi-works or demonstration plant scale,
sufficient product material from pond-slimes in a con-
tinuous manner and in sequential steps to verify the
encouraging economics developed herein. In addition
to and concurrent with such a study, further work should
be done to evaluate the potential of using these slimes
in producing other ceramic products.
59
-------
ACKNOWLEDGMENTS
The Project Director for IMC was Mr. Srini Vasan, Project
Director, Product Development Department, Agricultural
Division of IMC. The Project Manager under whom the
engineering work was carried out was Mr. John Senft,
Manager of Product Planning, Product Development, Agri-
cultural Division, IMC, and the work was carried out by
Messrs. Lester L. Cruse, Michael Mallary, and Charles E.
Miller, Operators of the IMC Pilot Plant. The laboratory
work subcontracted to Illinois Institute of Technology
Research Institute was carried out under the direction
of Mr. S. A. Bortz, Senior Engineer, Ceramics Research.
The work carried out under him was by Mr. Eugene Aleshin,
Associate Ceramist, Ceramics Research, and Mr. H. H. Naka-
mura, Associate Ceramist, Ceramics Research. Mr. M. Schwartz
and Dr. W. Crandall of IITRI provided general direction
on this project. The draft of the report was compiled
by Mr. H. P. Pursell, Manager of Process Development,
Product Development Department, Agricultural Division, IMC.
Support of the Project by the Federal Water Quality Admin-
istration and the help provided by Mr. Edmond Lomasney
and Dr. J. Shackelford of FWQA with their helpful comments
and advice, and the encouragement which Mr. A. Cywin and
Mr- E. Hall gave throughout this project, is acknowledged
with sincere thanks.
61
-------
REFERENCES
1. Boyle, J.R., "Waste Disposal Costs of a Florida
Phosphate Operation," Bureau of Mines Information
Circular 8404 (1969).
2. Lerner, W., ed,, "Statistical Abstract of the U.S.,
1970," 91st Annual Edition, USDC Bureau of Census,
USGPO, (1970), p.660.
3. Gart, J. Ho, I. L. Feld, and E. G. Davis, "Chemical
and Physical Beneficiation of Florida Phosphate
Slimes," Bureau of Mines, RI 6163 (1963).
4o Stanczyk, M.H., and I. L. Feld, "Chemical Processing
of Florida Phosphate Rock Slime," Bureau of Mines
RI 6844, (1966).
5. ASTM D423, "Method for Test for Liquid Limit of Soils."
6. Sloan, C. E., T. D. Wheelock, and G. T. Tsao, "Drying
Systems and Equipment," Chemical Engineering, 127-214,
(June 19, 1967) .
7. American Society of Heating & Air Conditioning
Engineers, "Heating, Ventilating, and Air Conditioning
Guide," p.170 (1959).
8. Portland Cement Association Bulletin ESCS1, 1-64/1-2
(1964) .
9. Waddell, J. J., "Concrete Construction Handbook,"
McGraw Hill Publishing Company, New York (1968).
63
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GLOSSARY
ACI - American Concrete Institute.
Apparent porosity - the volume of open pore space in a
material per unit total volume.
Apparent specific gravity - the ratio of weight in air of a
unit volume of material to the weight in air of equal density
of an equal volume of gas-free distilled water. In this
study, the volume is that portion impermeable to boiling water
ASTM - American Society of Testing Materials.
Bloating - excessive expansion of a ceramic body upon heating,
characterized by alteration of dimensions and dimensional
ratios. Sometimes accompanied by splitting and tearing at
the surface.
BPL - Bone phosphate of lime.
Core - formation in the center of a ceramic body characterized
by discoloration, separation from the outer layer (lamination)
and general weakness of the body. Caused by imperfect shaping
procedures, poor composition, or irregular firing.
Density - Theoretical - wt of particle/(vol of particle - vol
internal voids)
Apparent — wt of particle/ (vol of particle)
Bulk - gross wt of solids/gross volume
Differential thermal analysis (DTA) - measurement of gain or
loss in energy for a material, during controlled change in
temperature, as a result of vitrification, vaporization, phase
transitions, adsorption or desorption of gases, loss of water
(usually in several steps), decomposition, chemical reaction,
oxidation or reduction.
Pi latent - fluids have apparent viscosity, increase with
increasing shear rate.
Draw trial - a heating and firing test in which, at specific
temperatures, i.e. 100 or 50°C intervals, or at temperature
holds, a number of ceramic pieces are withdrawn from the
kiln and examined to detect and measure the effects of heat
and time on certain properties, such as shrinkage, weight
loss, density, porosity, warpage, etc.
65
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Drying Efficiency - Herein the drying efficiency is defined as:
HI + H2 + H3 x 100
Total BTU Input
Where: Hx = Heat req'd to heat up dry solids from ambient
to discharge conditions.
H£ = Heat req'd to heat up water content of solids
from ambient to discharge conditions.
H3 = Heat req'd to evaporate water content into
stream.
Throughput is defined as pounds per hour of wet
feed to the dryer.
Dust Loading - Typical Calculation of Dust Loading on Bag
Dust Collector
Assume
Given:
Moisture content of dryer discharge is the
same as dryer overhead to Dust Collector.
From previous calculation B - 2087 Ibs.
Star Valve discharges 0.15 cu.ft
Density dry product - 64 Ibs/ft
rev .
3
Then:
From Dryer
Discharge
3 RPM
From Dust
Collector
X
B =
2087 Ibs.
Expansion - increase in size of a ceramic body while retaining
general shape and dimensional ratios.
Fineness module (FM) - is an index of the coarseness or fineness
of a material, and is essentially 1/100 of the summation of
weights of aggregate retained on each of a specified series of
sieves.
66
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Green - wet-formed and weak, not hardened or fused.
Grog - a granular material generally produced from calcined
or fired refractories, added to a ceramic composition for the
purpose of reducing shrinkage, weight loss, and for increasing
strength.
Hydrophyllic - describes a substance which attracts water or
to which water adheres.
IITRI - Illinois Institute of Technology Research Institute.
LWA - Lightweigit aggregate.
Materialite - produced by Material Service Corporation.
Nitrin — a joint venture of IMC and Northern Natural Gas,
at Cordova, Illinois, now shutdown.
PCE - pyrometric cone equivalent (Cone Test) according to
ASTM C24 ; measurement of the effect of time and temperature
upon firing a ceramic. Also referred to but not synonymous
with fusion point, deformation point, and melting point.
Plastic - Bingham plastic fluids require a finite shear
stress to initiate flow.
temperature, generally quite suddenly,
'to extinguish a flame.
Quench -t6 lower
of ceramic ware, or
Recycle Ratio - Typical Calculation of Recycle Ratio for
2 sq. ft. Cross-Flow Dryer.
Assume: Moisture content of dryer discharge is the
same as dryer overhead product to Dust Collector,
Then: Moisture in Blender Discharge = 17% HgO
Star Valve delivers 0.15 cu oft/rev.
Feed Rate - 249 Ibs/hr.
Feed Moisture - 79%
B
b = 0.096
A = 250
a = 0.79
BLENDER
N
c
,c - (
67
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Recycle Ratio - Continued
Overall material balance around blender
A + B = C
Where: A = Wt . of Feed
B = Wt. of Recycle
C = Wt. of A & B
Moisture Balance
A(a) + B(b) = C(c)
Where: a = Fraction H20 in A
b = Fraction H2O in B
c = Fraction I^O in C
A = 250 Ibs.
a = 0.79
b = 0.096
c = 0.17
Rheology - science of the motion characteristics of fluids.
Thermal Efficiency - Herein thermal efficiency is defined as:
+ E + HQ + H x 100
Total BTU Input
Where: HI = Heat req'd to heat up dry solids from
ambient to discharge conditions.
H2 = Heat req'd to heat up water content of
solids from ambient to discharge conditions.
H3 = Heat req'd to evaporate water content into
stream.
H4 = Heat req'd to heat up air necessary for
mass transfer of water from slimes solids under
Florida design conditions.
Thermal gravimetric analysis (TGA) - measurement of gain or
loss in weight in a material, during controlled changes in
temperature, as a result of vaporization, adsorption or de-
sorption of gases, loss of water (usually in several steps)
decomposition, oxidation or reduction.
68
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Thixiotropic - fluids possess a structure which breaks
down with both shear rate and time. As it breaks down
with constant shear rate, shear stress decreases«
Ware - pertains to articles of the same class; especially,
manufactured articles. In this instance, pertains to ceramic
ware such as brick, pipe, tile, etc.
Water absorption - the relationship of the weight of water
absorbed to the weight of the dry material.
69
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APPENDIX A
AN APPRAISAL TO MANAGEMENT
OF THE PROJECT
By
Donald F. Othmer
Consulting Chemical Engineer
71
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DONALD F. OTHMER
CONSULTING CHEMICAL ENGINEER
TELEPHONE (2I£) MAIN S-I8XS
CA8LCS:OTHMEHDON NEW YORK
333 JAY STREET
BROOKLYN, NEW YORK naoi
October 21st, 1970
Dr. Srini Vasan
International Minerals & Chemical Corporation
Administrative Center
Skokie, Illinois 60076
Products from Phosphate Slimes
Dear Mr. Vasan:
It was a very real pleasure to review with you so thor-
oughly this development under your direction at International
Minerals & Chemical Corporation at Skokie and Libertyville,
Illinois, and with the help of Illinois Institute of
Technology Research Institute at Chicago.
The Problem and Its Background
The problem has been well defined and is well understood.
It is the basis of the development contract of International
Minerals and Chemical Corporation (IMC) for the handling of
slimes produced in beneficiating of phosphate rock mined
in the deposits near Bartow, Florida. These slimes are
now stored for indefinite periods in ponds with banks made
of dams which have to be artificially built up. The level
of the impounded material stands much above the level of
the surroundings. The dams which are built to enclose
an area and form the ponds break sometimes; and the slimes
released pollute considerable amounts of surface waters
and large areas of farm lands before the flood can be con-
trolled .
There is also a constant seepage from the ponds which may
present a problem to fresh water aquifers. Moreover,
this removal and storage above ground of considerable
amounts of ground water causes a lowering of the water
table; and in this low area only a few feet above tide
water level, there is the very real danger of encroach-
ment of sea water into the fresh water aquifers due to
this displacement.
72
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
The first part of the problem is the development of satis-
factory methods for dewatering the colloidal slimes; and
some attention has been paid to this. However, while the
solution of this problem has not been demonstrated on a
major scale, it is believed by this writer that it is
quite possible to decant satisfactorily by far the most
of the water substantially free of solids in a relatively
short space of minutes by the addition of very cheap
coagulants.
Methods which would probably accomplish this separation
and would thus free most of the water and thus most of the
storage volume now taken up by the slimes have been des-
cribed in U.S. Patents Nos. 3,338,828 and 3,388,828 to
Joseph R. Clark. This system utilizes as a coagulant
fly ash which is available from power stations at no cost
but that of carrying it away. After a special treatment
with acid, this fly ash, along with very minor amounts of
polyelectrolytes should give a very prompt and substantial
removal of most of the water to give a range of solids
between 25 and 30%, which is otherwise attained in the
storage ponds only after a period of years. It is prob-
able that similar results might be obtained with other
coagulation and sedimentation techniques, more or less
standard to those who are familiar with the best practices
in the treatment of sanitary and industrial wastes or
sewages. Thus, this part of the problem is not regarded
as of the most importance - at least from the standpoint
of its difficulty of solution.
One of the important aspects of this problem is the in-
creasing requirement of valuable land for utilization as
slime ponds, since there is required for each 2 cubic
feet of phosphate some 3 cubic feet of storage for slimes
in water. Once the dams are built for making such
storage, it is almost a complete condemnation of the land
for all future time for the removal of the waste which
stands there then for indefinite periods.
Alternatively, the removal of the slimes as fast as they
are formed would save future encroachment of this land,
which may be valued at probably $200 to $500 per acre
73
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
(and it is becoming less and less available at any price).
Some ponds which have been dried and dredged to give
lagoons and clay lands for farm use give excellent crops
and citrous orchards; others have been developed for
residential developments with a very high selling price
after the costs have been paid. The continuing pollution
or waste of land could thus be stopped with development
of methods of removing the water for reuse and for selling
the solids. If it were possible to develop markets for
more than the present production of solids in the slimes,
there would then be at least several hundred million tons
of solids available in present storage for use as raw
materials and for sale, and with the accompanying free-
ing of valuable space and the removal of the water for
reuse and ultimate transfer to the underground aquifer as
part of the future water resources.
The background of the industry involves the handling of
tremendous amounts of these slimes. IMC alone has to
dispose of some 10 million tons per year of the slime
solids in producing 8 million tons per year of phosphate
rock, 30% of the industry total. However, IMC's annual
capacity is larger, 12 million tons of phosphates; and
IMC, like the rest of the industry, is operating at a
lowered output. The cost to IMC of waste disposal by
ponding is about 25£ per ton of slime solids, which is
about 32£ per ton of phosphate rock produced, or $2.5
million per year on the present 8 million tons production.
One of the major problems of the phosphate rock industry
is that it has a vastly greater capacity than can be
utilized, with consequently considerable competition
and a price which has reduced in the last 5 years from
$6.00 per ton (f.o.b. mine) to $4.00 per ton in 1970.
Another point is that, from the standpoint of destruction
of land values and potential pollution of water, it is
distinctly an unattractive industry in Florida where the
tourist industry is at least 10 times the total value
of the phosphate industry which is destroying aesthetics,
land, and water values in the heartland of this great
tourist area. The recovery of the land finds a ready
74
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemicals Corp.
market for this area having such great and steady influx
of new settlers.
Of greatest importance is the program to find a commer-
cial way of utilizing the slimes to produce products of
large volume utilization and relatively low cost.. This
has been solved with eminent success by this project of
IMC by the use of the slimes for the production of
structural clay products, including bricks, sewer tiles,
roofing tiles, artificial light-weight aggregates for
use with cement in making concrete, etc. This area of
study has been the one pursued to the greatest extent in
your work and seems to have had major preliminary success
and major possibilities for realization of commercial
success within a couple of years of further engineering
design and commercial development on an industrial scale.
Still another industry which would also require large
volumes of material - also in the building field - would
be in making portland cement. The solids of these slimes
represent a possibility as one of the two basic feed
components in the manufacture of portland cement - the clay
or argillaceous constituent. Unfortunately, there is in
Florida no substantial amount of the other principal com-
ponent for portland cement production, calcareous or
lime materials. Not only in Florida, but most of the
southeastern seacoast of the United States and for some
distance inland, is substantially free of deposits of
limestone or other calcareous materials for this use in
cement making.
An engineering analysis might well be made, however, with
regard to the combination with these slimes solids of the
almost infinite supply of aragonite, a type of calcium
carbonate or limestone, which forms the basis of the
shoals surrounding and making up the Bahamian Islands.
There are relatively minor amounts of coral which tend
to form the backbone of some of these islands; however,
vast areas, both on the islands themselves and in the
shoals surrounding the islands, give a practically pure
aragonite when washed free of the salt water.
75
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— 5—
Dr. Srini Vasan October 21, 1970
International Minerals & Chemicals Corp.
The tremendous deposits of aragonite filling the sea to
make the shoals and thence of the islands come about due
to the interesting changes in the physical chemical
properties of calcium carbonate dissolved in sea water.
Above a critical point of temperature of about 25-30°C
there is a change in the solubility, also of the crystal-
line structure from the normal calcium carbonate, to give
aragonite. The very cold, lime-saturated waters at the
ocean depths come down from the Arctic regions, rise as
they are being warmed in the Torrid Zone, and then flow
back north in the Gulf Stream. Particularly noticeable
in this phenomenon in the Bahamian area - especially the
so-called "Tongue of the Ocean" - a deep of 5000+ feet
of cold water flowing south, warming, and rising at the
southern end. Here the calcium carbonate, in crystal-
lizing out slightly above 30°C, comes out as aragonite.
In other work known to this writer, the economics of
shipping tens of thousands of tons of this lime material
to the mainland coast has been studied for other reasons ;
and it might be desirable to consider this bringing in
of aragonite to use in conjunction with the clay and
related materials of the slimes in the production of
cement, presumably by a wet process at a point selected
as optimal from considerations of transportation. The
first costs of cement making are the preparation of raw
materials. Often this requires mining, crushing, and
grinding of hard rock. Here these expensive steps would
be eliminated due to the fact that both the materials
would be available in very fine form, with very low
initial preparation or processing cost. The distance
to such workable deposits of aragonite would be not more
than 250 miles by airline from the slimes, but probably
twice as much barging would be required, either for
aragonite from the Bahamas to Florida, or concentrated
slimes to the Bahamas. In the handling of the aragonite,
it would be possible to do this with a minimum of water
transport as compared to the semi-solid slimes freed of
as much water as possible by sedimentation.
76
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
The Contractor
The present program, currently being evaluated, seems
to have been developed under very particularly favorable
conditions because of the background of IMC, with its
several divisions, including the Phosphate Division pro-
ducing the slimes in question, and the great expertise
of this Division over many years in producing and handling
these slimes. Secondly, there is, of course, the expertise
of the Industrial Materials Division of IMC with its
experience in drilling muds, bentonite, and other similar
materials. Thirdly, and particularly the Lavino Division
of IMC has had long experience in production and sales of
bricks for special industrial purpose.
The contractual arrangement then developed with Illinois
Institute of Technology Research Institute (IITRI) brought
into the IMC team under your leadership the longtime back-
ground of this group in research in the development of
special materials in the ceramics and related industries.
Mechanical Operations
Practically all of the experience of IMC and other
phosphate rock producers is with the dilute slimes con-
taining only a few percent of solids and coming from the
flotation operations involved in the production of a
concentrate.
Pumps - Suitable pumps have had to be developed to handle
the slime solids in concentrates of up to slightly over
30%, which might be regarded as an almost equilibrium
value between solids and liquids in this system of a
practically permanent colloidal nature. Thus, if there
was used material from the storage pond of many years
accumulation, it might amount to about this concentration.
The development of a pumping system was thus an urgent
necessity and has been successfully accomplished.
Dryers - As a first requisite in handling the colloidal
material present in a maximum concentration of about
77
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
25-30%, there is the necessity before almost any use can
be made of the material of drying this to a low or
negligible water concentration. (One exception to this
requirement might be in its wet processing in the pro-
duction of portland cement.) A major program has been
carried on for the drying of the phosphate slimes
utilizing several different types of dryers which seemed
to have potentials for this purpose.
Pilot plant dryers have been built and very successfully
operated under this program on a basis which seems to
give reasonable costs for the production of large volumes
of low value material. Thermal efficiencies have been
achieved which are substantially equivalent to those of
the dryers of similar type in other industries working
with materials having much less difficult properties.
This part of the program can be regarded as adequately
solved.
Production of Ceramic Products
The Ceramic Laboratories of the IITRI have conducted a
thorough investigation which has been eminently success-
ful in producing bricks and sewer tile of satisfactory
qualities, to compete with those currently on the Florida
markets.
It should be noted that there are no other companies
producing clay products for building purposes in Florida,
and thus the materials now dominating the Florida market
come from Georgia, and have as an overhead charge the cost
of the major freight and related transportation costs. It
is obvious that these relatively high costs per unit of
value of such heavy materials would serve as an economic
umbrella over any Florida industry producing a clay
product, bricks, sewer pipe, floor or wall tile, roofing
tile, etc. Substantially, the early production is planned
to consist of bricks and sewer pipe. Other clay products
would be added as it became possible and profitable to
expand the line.
78
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
At this stage of the program which has been in progress
for something less than two years, there seems to be
complete success in the production of ceramic products
of acceptable and reproducible quality and at a competi-
tive price as to commercial usage. The various specifica-
tions of the American Society for Testing Materials (ASTM)
have been met in the products obtained as well as those
of the building codes of the various Florida cities which
would use the materials.
The cost of a clay products factory has been developed
in conjunction with engineers of the manufacturers of the
processing equipment which would be used, and others
familiar with such plant costs. The production costs have
also been evaluated with the help and experience in this
field of industrial engineers of IITRI and IMC, basing
their work on the costs which have been developed for
preparation and drying of the clay for use in clay
products.
It has been determined from various sources that Florida
utilizes about 100,000 tons per year of such products;
and a suitable plant for the phosphate industry slimes
would be at about the geographic center of the peninsula
part of Florida. The northern part of Florida (above
about 30° latitude) would probably fall within the ship-
ping and sales domain of clay products factories in
Georgia and Alabama.
A much bigger market for a less valuable material of
lower specification requirements would be obtained by the
production of lightweight aggregate. This would be used
in concrete construction and would compete in a market
for 2 million tons now available at a price of about
$4.50 per cubic yard or $7.00 per ton.
Here again the technology of production has been devel-
oped utilizing slightly modified equipment in the IITRI
laboratory and the IMC's pilot plant. A pan granulator
makes balls or pellets of the clay slimes of suitable
water content. These pellets or agglomerates of two to
79
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
six pellets each |" to 3/4" in diameter must have adequate
strength before firing to accommodate this further pro-
cessing. The very substantial strength of the finished
product after firing, which produces a porous, lightweight
material, meets the necessary building material specifica-
tions of both the ASTM and the building codes of the
several Florida cities which might offer the major market.
With the tremendous housing needs in Florida of even
the present population, and with the large increase in
population currently in progress and expected for the
predictable future, it is believed that there will be a
very major market developed for the slime solids in this
synthetic aggregate material for concrete construction,
as well as that to be readily sold in brick, pipe, tile,
and other related products. The sales should be excellent
in the rapidly growing housing and building construction
industry, and even a less than optimistic analysis indi-
cates that it would be possible to sell the solid products
of the slimes produced annually by the entire phosphate
industry of Florida.
The economics of such a venture are, of course, greatly
helped by the negative value of the starting material.
Very substantial by-products are the water values and
especially the land values obtained in the almost explo-
sive Florida real estate demand for plots for residences,
marinas, and related non-manufacturing uses.
Future Program
A further evaluation of the economics of the programs
operated to date is advisable to assure the correctness
of the very apparent markets for products which could be
developed from these slimes, with the larger markets
being in synthetic aggregate and a smaller market at a
higher price in specification grade bricks, sewer tile,
floor and wall tile, and other clay products.
A production plant for making both aggregate and bricks,
pipes, etc., should be built and operated to demonstrate
the application to the utilization of clay slimes of
80
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Dr. Srini Vasan October 21, 1970
International Minerals & Chemical Corp.
these methods and the industrial system of their manu-
facture and distribution.
The methods and conclusions developed by the contractual
work so far of IMC in the production of valuable materials
from polluting materials must be utilized on a large scale
These pollutants have a very substantial dollar cost of
disposal and have so far left a permanent scar on the
landscape, and a large cost of land thereby wasted in
their practically permanent storage. The promise of their
utilization to give increasing profits, as well, to a
depressed industry is an equally valuable aspect which
should be studied exhaustively to its conclusion with all
possible promptness and diligence.
Fortunately all of the expected markets are of a very
major tonnage size, commensurate with the hundreds of
millions of tons of back stock and tens of millions of
tons of annual production within a very short radius.
It is believed that the building industry, which must
develop greatly in Florida within the next years, can
use all of these slimes solids as fired clay products -
bricks, sewer and other tiles, and synthetic aggregates
for concrete. Even larger amounts may be used in com-
bination with aragonite from the Bahamian area for the
production of portland cement, if the transportation
problems can be solved.
I understand that this project is expected to continue
to demonstrate with commercial success the results so
far attained.
My investigation of its various aspects, and my knowledge
and experience in several of the related fields gives me
confidence that your work will indeed demonstrate within
another two or three years of operation on a larger
scale how this major pollution and waste of natural min-
eral resources, of land, and of water, may be stopped
with a profitable industry standing in its place.
81
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Dr. Srini
International Minerals & Chemical Corp.
October 21, 1970
Finally, and in closing, I would like to congratulate IMC,
and particularly you as the director of this project, as
well as also the Department of the Interior for its
substantial financial backing. Such success in the dem-
onstration of such profitable methods of solution of
pollution problems is not often encountered and must be
commended highly, particularly within such a short time
and at such a minor cost compared to the values demon-
strated.
Sincerely yours,
OTHMBR
82
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APPENDIX B
TYPICAL CALCULATIONS
FOR
FLUID-BED DRYER
83
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APPENDIX B
Wet Feed, Aa
DUST
COLLECTO:
II
Figure 1. FLOW DIAGRAM OF DRYING SYSTEM WITH
DRY RECYCLE
X = Dryer Discharge, Ib/hr
Y = Dust Loading, Ib/hr
TYPICAL CALCULATION OF RECYCLE RATIO FOR
2 SQ. FT, FLUID-BED DRYER
Assume
Then:
Moisture content of dryer discharge is the
same as dryer overhead product to Dust Collector,
c, Moisture in Blender Discharge = 17% H20
Star Valve delivers 0.15 cu.ft/rev.
A, Feed Rate = 249 Ibs/hr
a, Feed Moisture = 79%
84
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APPENDIX B (2)
Overall material balance around blender
A + B = C
Where: A = Wt. of Feed = 250 Ibs.
B = Wt. of Recycle
C = Wt. of A & B
Moisture Balance
A(a) + B(b) = C(c)
Where: a = Fraction H2O in A = 0.79
b = Fraction H2O in B = 0.096
c = Fraction H20 in C = 0.17
250 + B = C
0.79(250) + 0.096B = 0.17C
0.79(250) + 0.096B = 0.17 (250 + B)
197 + 0.096B = 42.5 + 0.17B
154.5 = .074B
154.5 =
0.074
2087 Ibs = B
Recycle Ratio = 2087 = 8.3 Ib Recycle
250 Ib Wet Feed
TYPICAL CALCULATION OF DUST LOADING
ON BAG DUST COLLECTOR
Assume: Moisture content of dryer discharge is the
same as dryer overhead to Dust Collector„
Given: From previous calculation B = 2087 Ibs
Star Valve discharges 0.15 cu.ft
rev .o
Density dry product - 64 Ibs/ft
85
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APPENDIX B (3)
Overall Material Balance Around Recycle System
X + Y = B
Where: X = Ibs Discharge from Dryer
Y = Ibs Discharge from Dust Collector
X = 3 Rev x 60 Min x 0.15 cu.ft. x 64 Ibs
Min Hr Rev cu0ft.
3(60) (64) (.15) = 1730 Ibs/hr
Y = Dust Loading = B = X
Y = 357 Ibs/hr
357 Ibs dust to collector = 1.43
250 Ibs wet feed
86
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APPENDIX C
ANALYSIS OF FLUID-BED DRYING
OF PHOSPHATE SLIMES
By
D. T. Wasan
Professor of Chemical Engineering
Illinois Institute of Technology
Chicago, Illinois 60616
87
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(1)
DATA SHEET #1
MASS BALANCE
Basis: 180 Ibs. of wet solids at 70°F
Water Removed = 124.2 - 1.5 = 122.7 Ib.
Air leaving at 160°F
Water content of satd. Air = 0.2990 Ib. H20
Ib. dry air
Minimum air required = 122.7 = 410 Ibs. of dry air
0.2990
HEAT BALANCE
1) Heat required to heat the Clay to 160°F
(55.8) (0.22) (160-70) = 1,110
2) Heat required to heat water to 160°F
(124.2) (1.0) (160-70) = 11,160
3) Heat required to evaporate 122.7 Ibs.
of water (122.7) (1000) = 122,700
134,970 BTU
Heat Supplied by Air
(530-160) (382) + (500-160) (324) + (328-160) (406) +
(260-160) (388) x 0.237 = 85,000 BTU
88
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(2)
GENERAL ANALYSIS
MASS AND ENERGY
BALANCES
Ti
Figure 1
' G2
tf
|Yx
= W-f = Ibs/hr of solids on dry basis
G = Ibs/hr of dry air = G, + GQ + GQ
J. £ o
= Ibs of water
Ib of dry air
= Ibs of water at inlet
Ibs of dry solids
Ibs of water at outlet
XJ
T
t
T,
Ibs of dry solids
Temperature of solid
Temperature of gas
Temperature of the dryer bed
Data: Specific heat of air
Specific heat of solids
Specific heat of water
89
= 0.237 BTU
Ib °F
= 0.22 BTU
Ib
= 1.00 BTU
Ib
-------
(3)
A) Minimum Air Requirement from Mass Balance:
Assume Tf = tf ; from the psychometric chart we can
find Yf from the saturation line
Water evaporated = xi wi ~ xf wf
- Gmin (Yf - YJ.)
Gmin = (Xj Wj - Xf Wf)
(Yf - Y±)
Where G = G^ + G2 + G3 + G4 yi can be estimated
by assuming that the inlet air was heated from room temperature
(70°F) at 60% Relative Humidity = Y± = 0.01 Ibs H20
Ib dry air
B) Minimum Heat Requirement:
Assume T, = Tf = tf
Minimum Heat Required = Heat required to raise temperature
of solids to Tf and heat required to raise temperature of
water to Tf + heat required to evaporate water at t^ + losses.
Heat Required = 0.22 (1 - X±) (W.) (Tf - 1^) + 1.0 (X±) (Wt)
(Tf - T±) + (1000) (X^ - XfWf) + losses
Heat Supplied = 0.237 l(t^ - tf) Gx + ( t2 - tf) G2 + ( t3 - tf)
G + (* ~ t) G
4
~|
C) Thermal Efficiency
+ Heat Reqd. _ x 100
Heat Supplied
90
-------
(4)
I. Estimation of Minimum Air Requirement for Mass Transfer
Run #2 (Typical calculation)
150 Ibs/hr of wet feed = (74.3% H20
(25.7% Solids
41.3 Ibs/hr of product = (6.7% H20
(93.3% Solids
108.7 Ibs HO evaporation
^
Minimum Air Required
Air leaving at 122°F
Saturated water content at 122°F = 0.08678 Ibs H20
Ib dry air
If inlet air 60% satd. at room temperature before
heating, its water content = 0.01 Ibs HgO
Ib dry air
108.7 Ibs H20 evaporated.
Minimum Air = 108.7 = 1420 # air
0.08678-0.01 hr.
Air Used = 1305 #/hr.
91
-------
(5)
II. Estimation of Actual Gas Flow Rates Used
The actual gas flow rates for each run was calculated
by averaging the inlet temperatures in the four compartments
and averaging the pressure drop in them. The calibration
curve supplied with the data sheets was used to calculate
gas flow rate in C.F.M. at 7° F and was converted to #/hr.
TABLE I - Gas Flow Rates Calculated from Operating Data
Run #2 (Typical calculation)
Compartment T, F
1 427
2 421
3 328
4 293
AP
(in.H20)
0.21
0.21
0.24
0.16
G (CFM )
(@ 7°F)
60
60
75
60
G (Ibs)
(hr.)
307
307
384
307
G = 1305 #/hr
92
-------
(6)
III. Calculations for Fluidization Air Required
The procedure recommended by Leva (Ref. 1) in
his book was used. (Page 67)
The average diameter D was calculated on wt.
fraction basis.
dpi
(Where X..^ is the wt. fraction of particles of size d . .)
The pressure drop in the packed bed can be found by
knowing the unit density and bed volume and area.
A P = Unit density x Volume (cuft)
Area (sq. ft)
The density of inlet air at a specified temperature
and at a pressure of P = P tm + AP was calculated. Using
this Pair ^p ~ ^aiP was calculated.
Viscosity of air at the inlet was estimated from
Perry's handbook.
The nomograph from Leva's book was used to estimate the
2
minimum fluidization gas flow rate in Ibm/hr ft .
93
-------
SCREEN ANALYSIS OF SLIMES (PRODUCT)
Tyler Mesh
5% 6
10% 8
18.7 9
61.5 14
81.5 20
95.5 35
99.7 100
100 -100
(7)
94
-------
(8)
TABLE II - Calculation of Average Diameter
Tyler
Mesh No
+ 6
8
9
14
20
35
100
- 100
L Xi.
1 dpi
Average
Opening
dia.
0.13 L_____
' .
0 . 093-^— — -~~~~~"
~~ • — — .
0.078<— — ' """
- — .
0.046 ^==r "
— — — _
0.0328<-r~- - "~~
• .
0.0164^-—- — "
- — — - — .
0 . 0058 — ""
= 0.05 +0.05 +
0.15 0.1120
+ 0.200 + 0.140
0.0394 0.0246
0.333
0.446
1.021
5.080
5.700
3.790
0.600
16.970
Diameter D_ =
p
d (inches)
Pi
0.1500
Z=- 0.1120
r=- 0.08505
~> 0.0620
^ 0.0394
— . 0.0246
_-
;=» 0.0111
0.0050
0.087 + 0.428
0.08505 0.0620
+ 0.042 + 0.003
0.0111 0.005
1 = 0.059
16.970
X
i
0.05
0.05
0.087
0.428
0.200
0.140
0.042
0.003
1.000
inch
95
-------
(9)
Fluidization Air Required
Run #2 (typical calculation)
Average temperature of 4 compartments = 367 F
Pair = 29 x 492 = 0.048 #
359 (367 + 460) eft
PS = 103#/cft
-------
(10)
TABLE III - Air Required for Heat Transfer
Heat Reqd.for t- ~£
Run # Vaporization, 1o f
BTU F °F
2 232,842 367 117
3 120,955 483 160
4 821,760 436 118
5 926,260 423 118
V. Heat Requirement for Water Vaporization and
of Thermal Efficiency
Air needed for
Heat Transfer
(Ib air/lb wet
feed)
11.9
9.2
10.1
11.1
Calculation
Run #2 (typical calculation)
Heat required to raise solid temperature to 122°F
= (122-65)(0.22)(78.4) = 983.1 BTU
Heat required to raise water temperature to 122°F
= (225.6)(1.)(57) = 12,859 BTU
Heat required to evaporate water at 122 F
= (218.9)(1,000) - 218,900 BTU
Total Heat Required = 232,842 BTU
Heat Supplied (Figure from John Senft) = 494,400 BTU
efficiency = 232,842 = 47.2%
494,400
97
-------
TABLE IV - AIR REQUIREMENTS/# FEED
*
d
^
«
2
3
4
5
»
0
-P
cj
« •
IH
73 45
0 43
PR rH
150
169
246
226
•
!H r(
O X!
SH \
45
• rH
73 -
0 0< 0
O P3 O
d d
C$ ^H Ctf
rH -H i-H
ctf
o
d
0
•H
O
•H
f,.
pq
i
ni
g
0
EH
47.2
55.5
79.2
62.4
00
-------
(12)
V. A Theoretical Model for Calculation of Dryer Performance
Let FI, Ff - Weight flow rates of wet solids at inlet
and outlet
T - Temperature of solids
t - Temperature of gas
x - Wt. fraction of water - Ibs
Ib of dry solids
y - Wt. fraction of water - Ibs water _
Ib of dry air
Tjj - Temperature of the bed
Tp - Temperature of the particle in the bed.
The model used here to analyze the dryer performance
is similar to the one discussed in Reference (2).
Consider a single wet porous particle d at temperature
Tp. The drying rate is given by
- COT dp3) ca dx =
T-d Kg (
-dp hp
Y - Yf ) dt
(Tfe - Tp) dt
A
The left hand size of Eqn. (1) represents the loss
of free moisture content. The first term on the right
hand side represents the mass transfer from the wet
particle to the gas and the second term represents the
heat transfer to the particle.
99
-------
(13)
Here 71 = latent heat of vaporization
v-
Y = equilibrium moisture content
hp = heat transfer coefficient
k™ = mass transfer coefficient
&
Therefore
-dX - 6hp (Tb - Tp)
fxdp A
For constant rate drying of wet porous particles,
the temperature of the particles remain close to the wet
bulb temperature of the gas in the bed, i.e. for constant
AT and for X = Xi at t = 0
X
Where ^ = PgdpXj /I
6 hp (tB- Tp)
1: has a dimension of time = time needed to completely
dry a feed particle. Now the residence time of particles
in each compartment is approximated by
"t. = wt. of bed in each compartment _ W
J Avg. flow rate of solids F- + F*
2
(4)
or the average residence time of particles is
"t = _W
Fi + Ff
2 (5)
100
-------
(14)
The distribution of residence time of particles
is given by
E (t) =
(Eqn n 3 in Ref
The residence time distribution as given by the
above equation is exponential in nature. This distribution
is sketched in Figure 2.
E(t)
Figure 2 - Residence time distribution of particles
in dryer.
Average moisture content is given by
X E(t) dt
X =
Therefore
X outlet = 1 -
X inlet '
or for each compartment
(6)
,
Xj outlet = 1 -
XJ i
(7)
101
-------
(15)
The final moisture content can be calculated by a
progressive procedure from one compartment to the next
with the exit moisture content of the solids leaving one
compartment as the inlet moisture content for the next
compartment. Equation (7) is used to calculate the moisture
content leaving a given compartment.
1. Estimation of Heat Transfer Coefficient
Using Ranz-Marshall correlation (Ref. 3)
(Nu)
1/3
= 2.0 + 0.6 (Pr) (Rep)
where
dp
= thermal conductivity of the gas
= 0.059"
= 0.22 BTU
&
(Pr)1/3
air
Rep
hr ftz
- (0.7)1/3«
dpU
1.0
Vft
I/ air
Av.Flow = 70CFM = >
Rep •£% 70
Therefore from Eqn. (7)
hp ^18.6 BTU
ft/sec.
f t"
o
F hr
2. Calculation of =
(103 x .059 x X. x 1000)/6 x 18.6(T - T )
.2 JB p
102
(8)
(9)
-------
(16)
3. Estimation of the weight of bed la each compartment
The volume of each compartment can be estimated from
the appropriate dimensions given.
Wt. of bed in each compartment
= volume of compartment x unit density of particles
x fraction of bed occupied by particles under
no fluidization condition
W = 4 ft3 x 64 Ib x 0.25 = 64 Ib
"Ft3
Run #2 (typical calculation)
Feed Rate = 150#/hr of wet solids = F±
Product Rate = 41.3 Ibs/hr = Ff
Residence time = t-: = _ W _ = 64
(150 + 41.3)
0.667 hr. in each
compartment
X± = 74.3 # water = 2.89
25.7 # dry solids
Water Evaporated = 108.7 Ib H20
Tp = 117°F
T1B = 120.8°F
T2B = 132.0°F
T3B = 135°F
T4B = 137°F
The mass flow rate of air G ^ 1420
103
-------
(17)
SUMMARY OF RESULTS AND CONCLUSIONS
1. The ratio of air used to air required for minimum
fluidization varied from 2.93 to 4.8.
2. The ratio pound of air needed for heat transfer to
pound of feed varied from 9.2 to 11.9.
3 . The ratio of pound of air used to pound of feed
varied from 4.31 to 8.70.
4. The ratio of air need for water vaporization to
pound of feed varied from 2.0 to 15.5.
5. The thermal efficiency varied from 47.2% to 79.2%.
6. With the possible exception of Run #4, the calculated
results as presented in Table IV, indicate that heat
transfer is controlling in the present runs.
7. A theoretical model based on the constant drying rate
period was devised and it successfully predicted the
experimental values for the final moisture content.
The agreement is better than should be expected. The
close agreement between the theoretical and experimental
values for Runs 2 and 3 verified the assumption that
the heat transfer is controlling.
8. The model clearly indicates that the drying time can
be reduced by increasing the difference between the
bed temperature and the particle temperature. This
can be conveniently achieved by increasing the inlet
gas temperature. Thus by decreasing the drying time
higher throughput can be achieved. The results of
Run #3 which employed a gas temperature of 483°F
verify this prediction.
9. The theoretical calculations using the proposed model
predict that comparing Runs 2 and 3, the better drying
is accomplished in Run #3. The experimental data
support this conclusion.
104
-------
(18)
10. Finally, it should be pointed out that the gas
flow rates were estimated from the calibration
curve and these values could be in error by at
least +_ 20% due to the nature of the calibration
chart. (See Figure 2.) For example, for Run #2,
an air flow rate of 1305 Ib/hr was estimated using
the calibration curve. The minimum air flow rate
required for water balance is 1420 Ib/hr. The
latter value differs from the former by less than
10%, and this deviation is considered to be within
the accuracy of the interpolation.
11. The data for most of the runs indicated an unsteady
state operation. Furthermore, the data on the bed
temperature was found to be inconsistent. For
example, for Runs 4 and 5, the bed temperature
was found to be lower than the temperature of the
particles which are assumed to be at the wet bulb
temperature of the exhaust stream. Therefore, no
attempt was made to calculate the theoretical moisture
concentration in the dryer for these two runs.
12. The inlet humidity content of the gas was unknown.
However, this value is needed to calculate theoretical
moisture content. Therefore, a value of 0.01 # water
which corresponds to 60% relative humidity # dry air
in room air at 70°F was assumed.
105
-------
(19)
RECOMMENDATIONS
It is stated that in order to develop a more
realistic procedure for the analysis of the dryer
data the following recommendations be considered:
1. The inlet and outlet humidity of all the
gaseous streams be recorded.
2. Gas flow rates be accurately recorded.
3. Amount of solids in each compartment be
determined.
4. Drying characteristics of the wet material
to be dried be determined in a separate
bench scale experiment.
5. The ratio of air used to air required for
minimum fluidization should be approximately
equal to 1.5 to 2.0.
With these additional data, a more thorough analysis
for the drying operation be carried out.
106
-------
REFERENCES
1. Leva, Max, "Fluidization," McGraw-Hill
Book Company, lac., N.Y., (1959),
page 67.
2. Kunii, Daizo and Octave Levenspiel,
"Fluidization Engineering,"
John Wiley, New York, (1969),
pages 443-446.
3. Ranz, W. E. and W. R. Marshall, Chem.
Eng. Progr., Vol. 48, 141, (1952)
(20)
107
-------
APPENDIX D
TRANSPORTATION STUDY
OF
LIGHTWEIGHT AGGREGATES
109
-------
APPENDIX D
TRANSPORTATION STUDY OF LIGHTWEIGHT AGGREGATES
PROBLEM (1) To determine the best distribution plan for
our lightweight aggregate product. Comparison
of shipping lightweight aggregate from Bartow
to consumer with shipping dried slimes to
satellite kilns.
PROBLEM (2) To determine transportation costs.
TABLE I
Given:
(1)
Freight Rates
from Bartow to:
Tampa
Jacksonville
Miami
Open Hopper*
Car Rates
$1.10/net ton
2.27/net ton
2.27/net ton
Closed Hopper*
Car Rates
$2.25/net ton
3.36/net ton
3.36/net ton
(2) Minimum car loading = 80,000 Ibs.
(3) Cars available = 1968 cu.ft. hoppers (50 ton)
3500 cu.ft. hoppers (100 ton)
(4) Lightweight aggregate can be shipped in open hoppers
(5) Dried slimes (64 Ibs/cu.ft.) must be shipped in
closed hoppers.
* Supplied by IMC's Transportation Dept.
110
-------
APPENDIX D (2)
Assume:
(1) Lightweight aggregate will be shipped under the
same tariff as expanded shale and slag.
(2) Dried slimes will be shipped under the same tariff
as expanded shale.
(3) Lightweight aggregate density may vary from
14 PCF to 40 PCF.
(4) 3500 cu.ft. hoppers have same minimum weight
restriction as 1968 cu.ft. hoppers.
SOLUTION:
To determine how much it will cost to ship a material
that weighs between 14 and 40 pounds per cu.ft. in a hopper
car that has a minimum weight specification of 80,000 Ibs
per car:
Two car sizes are available, 1968 cu.ft. cars and
3500 cu.ft. cars.
For the 1968 cu.ft. car case, locate point A (Figure 1)
as follows:
1968 cu.ft. x 14 Ibs x ton = 13.8 tons
car cu.ft. 2000 Ibs car
This point was plotted and a line drawn through the
origin. In a like manner, the line for the 3500 cu.ft.
car was determined.
Ill
-------
APPENDIX D (3)
Figure 1 shows that if the product-mix average
density is equal to or greater than 40 Ibs/cu.ft., the
1968 cu.ft. car is adequate. If, however, the product-
mix is less than 40 Ibs/cu.ft., there is a penalty since
the low weight requirement of 80,000 Ibs/car cannot be
met. In the case of the 3500 cu.ft. car, the break-even
point is at approximately 24 Ibs/cu.ft.
To evaluate shipment of dried slimes from Bartow to
a satellite kiln plant in Tampa, Miami or Jacksonville
in order to take advantage of the extra density (64 PCF)
and hence full hopper car criterion for this material
that is available to us, break-even was determined thus:
Figures 2 and 3 were constructed as follows:
Pt. D was picked from Table I. Open hopper rate to
the respective city.
Pto E was found as follows:
The minimum rate of 40 tons, or in the case of
Bartow to Tampa, is $1.10/ton. This amounts to
$44.00 per car load. However, the car only holds
13.8 tons making the actual cost $3.18/ton to ship.
This lightweight material, $3.18/ton, is plotted as
Point E. Other points were constructed in a similar
manner.
112
-------
APPENDIX D (4)
Tons
per
Car
100 -
80 -
60 -
40 .
20
3500 cu.ft.
hopper
car
1968 cu.ft
hopper
car
80,_OpO JLb
minimum car weight
0 0 20 40 60 80
Average Aggregate Density, Ib/cu.ft.
Figure 1. EFFECT OF AGGREGATE DENSITY ON CAR LOADING
113
-------
APPENDIX D (5)
Line AB = Freight Rate for LWA Using a
1968 cu.ft. Open Car.
Line ED = Freight Rate for LWA Using a
3500 cu.ft. Open Car.
Line CC = Operating Line Indicating Cost
of Shipping Dried Slimes Using
a Closed Car.
3 -
Freight
Cost,
Dollars
per
Ton
1 -
0
0 10 20 30 40 50
Average Density, Product Mix, Ib/cu.ft.
Figure 2. ESTIMATED BREAK-EVEN COST OF SHIPPING LIGHT-
WEIGHT AGGREGATE OR DRIED SLIMES FROM BARTOW
TO TAMPA, FLORIDA.
114
-------
APPENDIX D (6)
Freight
Cost,
Dollars
per
Ton
0
_L
_L
C"
_L
0 10 20 30 40 50
Average Density, Product-Mix, Ib/cu.ft.
Figure 3. ESTIMATE OF BREAK-EVEN COST OF SHIPPING LIGHT-
WEIGHT AGGREGATE OR DRIED SLIMES FROM BARTOW
TO MIAMI OR JACKSONVILLE, FLORIDA.
Line AB = Freight Rate for LWA Using a 3500
cu.ft. Open Car.
Line ED = Freight Rate for LWA Using a 1968
cu.ft. Open Car.
Line CC' = Operating Line Indicating Cost of
Shipping Dried Slimes Using a Closed Car.
115
-------
APPENDIX D (7)
CONCLUSIONS & RECOMMENDATIONS:
If Average Density of product-mix is light, i.e., less
than 28 Ibs/cu.ft.
lo If 3500 cubic foot hopper cars can be obtained
in sufficient quantity to meet production requirements,
it would be more economical to fire the slimes into
lightweight aggregate at the Bartow plant and ship
the lightweight aggregate to the customer in the Tampa,
Miami, and Jacksonville areas. Otherwise, use of
1968 cubic foot hopper cars suggests that satellite
kiln operations be established at Miami and Jacksonville.
2. The material produced for the Tampa market should
be produced at the Bartow plant.
3. The transportation difference in cost of firing
the lightweight aggregate at Miami and Jacksonville
location vs. firing it at the Bartow plant amounts to
$3.36 per ton, the Jacksonville and Miami satellites
being the cheaper alternative.
If Average Density of product-mix is heavy, i.e., greater than
28 Ibs/cu.ft.
4. It will always be cheaper to produce fired light-
weight aggregate at the Bartow plant.
Other Conclusions
5. It may be possible to negotiate a lower minimum
116
-------
APPENDIX D (8)
weight requirement for the cars in question, in which
case economics would have to be re-evaluated.
6. A product mix study of 14 PCF material and 40 PCF
material must be made.
7. The break even points shown in Figures 2 and 3
designate transportation costs only. Trade off values
between production costs and these transportation costs
must be made before a final evaluation as to the plant
configuration can be made.
117
-------
APPENDIX E
LOCATION OF
LIGHTWEIGHT AGGREGATE PRODUCERS
119
-------
APPENDIX E
MAP SHOWING LOCATION OF LIGHTWEIGHT AGGREGATE PRODUCERS
A map showing the location of Lightweight Aggregate
Producers together with an appropriate legend, is shown in
Figure 1 and Table I. Note that the primary producers in
the Florida area expand vermiculite or perlite. There is
only one manufacturer who expands clay which is used in
concrete block. Concrete block is one of the major building
materials in the Florida area. From the location of this
producer in the Jacksonville area, it is evident that a
producer further south would have a distinct advantage
since this is where most of the new construction activity
is located.
The map also shows that there are no major threats
to a central Florida producer anywhere in the neighboring
states.
Another factor that makes a lightweight aggregate plant
attractive in the mid-Florida area is that vermiculite and
perlite (the raw materials for competitive lightweight
aggregates), are shipped to Florida from other states like
New Mexico, South Carolina, and Montana. Any slimes light-
weight aggregate product that would compete with the current
suppliers would not have to bear the brunt of the raw material
transportation costs that is borne by vermiculite.
120
-------
200
300
Scale in Miles
Note:
Circles indicate pro-
ducers of expanded Clay
or Shale which could be
used in lightweight con-
crete block manufacture.
Uncircled producers make
Expanded Perlite or ex-
panded Vermiculite.
Figure !„
LIGHTWEIGHT AGGREGATE PRODUCING PLANTS IN
THE SOUTHEASTERN U-S,, COURTESY PIT & QUARRY
(1969)
121
-------
TABLE I
LIGHTWEIGHT AGGREGATE PRODUCING PLANTS
(Referred to in Figure 1)
SymboIs
Gin Cinders
D Diatomite
Ex Cl Expanded Clay
Ex Per Expanded Per lite
Ex Sh Expanded Shale
Ex SI Expanded Slag
Ex Slate Expanded Slate
Ex Ver Expanded Vermiculite
PFA Fly Ash
SFA Sintered Fly Ash
Pu Pumice
Tuff Tuff
V Ash . Volcanic Ash
V Cin Volcanic Cinders
V Sc Volcanic Scoria
FLORIDA
Air lite Processing
Bldg. #9 Air Base
Vero Beach, 32960
Brand: Permalite
Corp. ExPer
Chemrock Corp. ExPer
Box 39 Grand Crossing Sta.
Jacksonville 32205
Off: Osage St. P.O. Box 5685
Nashville, Tenn. 37204
Brand: Tensulate
Florida Solite Co. ExCl
P.O. Box 297
Green Cove Springs 32043
Off: 1114 SCL Railway Bldg.
Jacksonville 32202
Brand: Solite
Zonolite Div.
W. R. Grace & Co.
P.O. Box 67
Boca Raton 33432
Off: 62 Whittemore Ave.
Cambridge, Mass. 02140
Brand: Zonolite
ExVer
ExPer
FLORIDA
ExPer
Zonolite Div.
W. R. Grace & Co.
1050 S.E. 5th St.
Hialeah 33010
Off: 62 Whittemore Ave.
Cambridge, Mass. 02140
Brand: Zonolite
Zonolite Div. ExVer
W. R. Grace & Co.
1530 E. Adams St.
Jacksonville 32202
Off: 62 Whittemore Ave.
Cambridge, Mass. 02140
Brand: Zonolite
Zonolite Div. ExPer
W. R. Grace & Co. ExVer
P.O. Box 5047
Tampa 33605
Off: 62 Whittemore Ave.
Cambridge, Mass. 02140
Brand: Zonolite
122
-------
TABLE I
LIGHTWEIGHT AGGREGATE PRODUCING PLANTS
(Page 2)
ALABAMA
Tombigbee Ltwt Aggr.Co. ExCl
P.O. Box 2
Livingston 35470
Brand: Liv Lite
U.S. Pipe & Foundry Co. ExSl
4200 Huntsville Road
Birmingham 35207
Off: 3300 1st Ave.No.
Birmingham 35202
Vulcan Materials Co. ExSl
Southeast Div. ExSh
P.O. Box 7324-A
Birmingham 35223
Off: P.O. Box 7497
Birmingham 35223
Vulcan Materials Co. ExSl
Woodward
Off: P.O. Box 7324-A
Birmingham 35216
Brand: Expanslag
GEORGIA
Georgia Ltwt.Aggr.Co. ExSh
P.O. Box 188
Rockmart 30153
Off: P.O. Box 19781,Sta.N
Atlanta 30325
Brand: Galite
Zonolite Div. ExPer
W.R. Grace & Co. ExVer
P.O. Box 8127 Sta.F
Atlanta 30306
Office: 62 Whittemore Ave.
Cambridge, Mass. 02140
Brand: Zonolite
LOUISIANA
Big River Indus.,Inc. ExCl
U.S. Highway 190
Erwinville 70729
Off: P.O. Box 66377
Baton Rouge 70806
Brand: Gravelite
Filter Media Co. ExPer
Sycamore W 10th ExVer
Box 222 V Ash
Reserve 70084
Off: P.O. Box 19156
Houston, Texas 77024
Brands: Perlite King &
Micalite
Louisiana Indus.,Inc. ExCl
4600 Lee Street
P.O. Box 5427
Alexandria 71301
Brand: Haydite
Zonolite Div. ExVer
W.R. Grace & Co.
P.O. Box 10262
New Orleans 70121
Off: 62 Whittemore Ave.
Cambridge, Mass 02140
Brand: Zonolite
MISSISSIPPI
Delta Industries,Inc. ExCl
Cynthia
Off: P.O. Drawer 1292
Jackson 39205
Brand: Miss-Lite
123
-------
APPENDIX F
ESTIMATION OF CONCRETE STRENGTH FROM
AGGREGATE CRUSH STRENGTH RESULTS
125
-------
APPENDIX
ESTIMATION OF CONCRETE STRENGTH FROM
AGGREGATE CRUSH STRENGTH RESULTS
A chart produced from tests conducted by the National
Bureau of Standards showing the relationship between
various lightweight aggregate 1" compaction tests and
compressive strengths of concretes produced from them
after 28 days, is reproduced in Figure 1.
From Figure 1, Figure 2 was produced. Figure 2 dis-
plays data used to obtain the regression line together
with the limits of accuracy. This shows relative values
of concrete strengths from lightweight aggregate vs.
1" compaction tests.
The regression line used to estimate concrete strength
from lightweight aggregate 1" crush strengths can be
described by the equation:
Y = MX or Y = (2.75 + 0.4)X
Where Y = Concrete strength after 28 days
(Average for 5 & 7 bag mixes psi)
M = 2.75 ± 0.4
X = Lightweight aggregate crushing strengths
(1" compaction psi)
This equation will give us a crude tool for evaluating
concrete strengths from slimes lightweight aggregate crush
strength values.
126
-------
Expanded
Shale
Expanded
Slag
Scoria
Pumice
Perlite
Expanded
Vermiculite
|
Increasing Value
Figure 1.
Relative Crush Strength
COMPARISON OF AGGREGATE CRUSH STRENGTH
(1-IN. COMPACTION) WITH 28-DAY COMPRESSIVE
STRENGTHS OF CONCRETE
Comparison of crushing strength of
aggregate to compressive strengths
of concrete. From tests conducted
by National Bureau of Standards. The
solid block denotes the aggregate
average strength for 1-in. compaction;
the white area indicates the concrete
(average of 28-day strengths for five
and seven-bag mixes). Courtesy of
Rock Products.
127
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Relative crush strength of lightweight
aggregate
Figure 2. EFFECT OF AGGREGATE CRUSH STRENGTH ON
COMPRESSIVE STRENGTH OF CONCRETE
(CROSSOLOT OF FIGURE 1)
128
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Number
Subject Fn-ld & Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
International Minerals & Chemical Corporation
Skokie, Illinois
Title
Utilization of Phosphate 31imes
10
Vasan, Srini
16
Project Designation
EPU #14050
21
Note
22
Citation
23
Descriptors (Starred First)
*Lightweight aggregate, clays, slimes, phosphate
mining, slurry pumping, fluid-bed drying, pelletizing,
kilning, lightweight concrete, water re-use, land
rehabilitation.
or I Identifiers (Starred First)
*Lightweight aggregate, from waste phosphate slimes.
27
Abstract
Small scale tests were made to assess the feasibility of
producing materials economically for the building industry from the
clay slimes wastes of the Florida phosphate industry. The objective
was to find practical means to utilize these clay materials in order
to reduce or eliminate the vast empoundment acreage devoted to
their storage and to make the water entrapped therein available
for re-use.
These studies showed that it is feasible to produce a pelletized
lightweight aggregate and ultimately a lightweight concrete from
the slimes. It was estimated that up to 6 - 8 million tons of clay
solids can be so used annually with the concurrent release of up to
5 billion gallons of water into the environment. Production of
ceramic materials was also explored.
The four major processing steps were investigated batchwise on
individual equipment types, and equipment suitable for each was
identified. These steps included: pumping clay-slurries of 3 - 30%
solids concentration; drying of the slimes in a fluid-bed dryer;
pelletizing the dried product; and kilning it to a suitable light-
weight aggregate
Abstractor^
O]
*ini
Vasai
Institution
International
Mi
nerals
&
Chemical
Corpora
ti
on
WR:'<>2 (REV. JULY 1969)
WRSIC
SEND TO: V« A T E R RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C 20240
* GPO: 1969-359-339
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