EPA-670/2-75-043
May 1975
Environmental Protection Technology Series
DISPOSAL AND UTILIZATION OF
WASTE KILN DUST FROM CEMENT INDUSTRY
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-670/2-75-043
May 1975
DISPOSAL AND UTILIZATION OF WASTE KILN
DUST FROM CEMENT INDUSTRY
BY
Thomas A. Davis
Don B. Hooks
Southern Research Institute
Birmingham, Alabama 35205
Project No. R-801872
Program Element No. 1BB036
Project Officer
Edmond Lomasney
U.S. Environmental Protection Agency
Region IV
Atlanta, Georgia 30309
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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REVIEW NOTICE
The National Environmental Research Center—
Cincinnati has reviewed this report and approved its
publication. Approval does not signify that the
contents necessarily reflect the views and policies
of the U. S. Environmental Protection Agency, nor
does mention of trade names or commercial products
constitute endorsement or recommendation for use.
11
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FOREWORD
Man and his environment must be protected from the
adverse effects of pesticides, radiation, noise and other
forms of pollution, and the unwise management of solid
waste. Efforts to protect the environment require a
focus that recognizes the interplay between the components
of our physical environment—air, water, and land. The
National Environmental Research Centers provide this
multidisciplinary focus through programs engaged in
studies on the effects of environmental
contaminants on man and the biosphere, and
a search for ways to prevent contamination
and to recycle valuable sources.
The studies for this report were undertaken to
determine the nature, quantity and fate of dust collected
from the effluent gases of cement kilns, to identify and
describe potential uses for the dust, and to identify
specific areas where the Agency's participation in the
development of new technology could have maximum effect
on the cement industry's efforts to protect our Nation's
environment.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center, Cincinnati
111
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ABSTRACT
A survey that included 60% of the cement manufacturing plants
in the United States was made to determine the fate of dust
collected from the gases emanating from cement kilns. Because
of high alkali content, large quantities of the dust cannot be
returned to the cement-making process. A survey was made of the
literature in the United States and Europe pertaining to handling,
reclaiming, and utilizing the collected dust. Abstracts of 71
references are included in the Appendix. Acid neutralization
capacity and potash content make the dust valuable for appli-
cation to farmland, and the potential market for agricultural
use alone could consume all of the waste dust that is now being
discarded.
This report was submitted by Southern Research Institute in
fulfillment of Project No. R-801872 under the sponsorship of
the Environmental Protection Agency.
IV
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CONTENTS
Page
Abstract iv
List of Figures vi
List of Tables vii
Acknowledgments viii
Sections
I Conclusions 1
II Recommendations 2
III Introduction 3
IV The Industry 6
V Dust Collection 10
VI Characteristics of Kiln Dust 14
VII The Alkali Problem 17
VIII Dust Disposal 19
IX Dust Reclamation 21
X Dust Utilization 29
XI List of Publications 36
XII Appendix 37
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FIGURES
No. Pages
1 Sample Form Used to Record Survey Data 5
2 System for Containment and Treatment of
Runoff from Kiln Dust Disposal Pile 20
3 Flow Diagram Showing Steps in Electrodialytic
Concentration of Leachate 23
4 Diagram of Electrodialytic Concentration Stack 25
5 Fuller-Pyzel Fluidized Bed Process for Produc-
tion of Clinker and By-Product Alkalies 27
6 Rotary Unloader for Nodulizing Waste Kiln Dust 30
7 Agricultural Lime and Limestone Usage in the
Contiguous United States, and Locations of
Plants Known to be Discarding Kiln Dust 33
vi
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TABLES
No. Page
1 Plant Production Costs 9
2 Distribution of Kiln Dust Collection Systems
in Wet and Dry Process Cement Plants 11
3 Particle Size Analysis and Distribution of
Alkalies in a Specimen Kiln Dust from an
Electrostatic Precipitator 14
4 Composition of Dried Kiln Dust 16
5 Withdrawal of Potassium by Agricultural Crops 34
vii
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ACKNOWLEDGMENTS
The authors gratefully acknowledge the assistance of the Portland
Cement Association in our literature survey and in establishing
contact with appropriate individuals in the cement industry. We
express appreciation to the managers of the individual plants who
generously provided data and insights concerning problems of dust
handling. We especially appreciate the assistance of Mr. Bruce E.
Kester, Vice President, Environmental Systems, Missouri Portland
Cement Company, who contributed greatly to our understanding of
the industry and who verified the technical descriptions presented
in this report.
We acknowledge the aid of Mr. George A. Wieczorek of the Division
of Chemical Development, Tennessee Valley Authority, in providing
considerable information concerning the use of cement dust for
fertilizer, and of Dr. Robert C. Rund, Secretary of the Association
of American Plant Food Control Officers, for providing information
on specifications for fertilizer materials.
Dr. Charles E. Feazel, Senior Research Advisor, Southern Research
Institute, assisted in our literature survey by translating a
number of patents and journal articles that were available only
in German or Russian. He also assisted in editing this report.
Vlll
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SECTION I.
CONCLUSIONS
The exhaust gases from portland cement kilns carry away an aver-
age of 12.2% of the kiln feed. To reduce particulate emissions,
an average of 96% of this material is removed from the exhaust
gases by dust collectors. Since the dust has an estimated value
of $2 per ton, it is returned to the kiln whenever possible. Of
the 16.4 million tons of dust collected annually from cement kiln
exhausts, 11.9 million tons are returned to the cement-making
process, and 4.5 million tons are discarded.
The major factor preventing return of more dust to the kilns is
that the high concentration of alkalies in the dust would cause
the alkali content of the clinker to exceed the limit of 0.6%.
Seven plants employ a leaching process to remove the alkalies so
that the dust can be returned, but the alkalies in the leachate
pose a serious water pollution problem. Several other techniques
for removing alkalies are described in the literature, but none
is presently used in the United States.
Most waste kiln dust is stored in open piles on the ground or in
abandoned cjuarries. The highly alkaline runoff of rainwater from
disposal sites can cause pollution of streams or ground water
unless it is contained and treated. The combined costs of hauling
the dust and controlling runoff appear to make dust disposal
economically and ecologically unattractive. In most cases cement
manufacturers would give away their waste dust if someone would
take it.
The markets for agricultural lime and potash fertilizer materials
are large enough to consume all of the waste kiln dust that is
currently being discarded. Moreover, on the basis of numerous
studies cited in this report, the chemical composition of kiln
dust appears suitable for the dust to be applied to acidic soils
and to soils that require additional potassium. However, only
small amounts of the dust are being used for this purpose in the
United States.
Other uses for waste dust from cement kilns include landfill,
soil stabilization, neutralization of acidic wastes (e_.g_. mine
drainage and pickle liquor), absorption of S02 from stack gases,
water treatment, glass making, and production of light-weight
aggregate.
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SECTION II
RECOMMENDATIONS
This state-of-the-art study was limited to a survey of the
industry to determine present practice of dust disposal and
utilization and a survey of the literature to identify
potential alternatives to wasting high-alkali kiln dust.
It was not within the scope of 'the program to perform demon-
stration experiments or to establish the economic feasibility
of various alternatives for dust utilization.
Since agricultural uses appear to be the most promising appli-
cations of dust that cannot be returned to the cement-making
process, we recommend that action be initiated with the
Association of American Plant Food Control Officials (AAPFCO)
to have cement dust specified as an agricultural liming mate-
rial and as a potassium fertilizer material. The data
obtained in our survey concerning the quality and quantity
of dust available from cement plants could be used by the
AAPFCO to establish specifications that might allow the dust
to be applied to farmlands without any modifications of its
properties. Specifications that require little or no monitor-
ing and control of the composition of the material would
facilitate distribution and marketing of the dust by the
cement manufacturers. On the other hand, AAPFCO may deter-
mine that modifications of the chemical composition and
physical form of the dust would make it more suitable as a
fertilizer material. This may require a research program to
develop methods of treating the dust from various cement
plants to meet the specifications.
The dust leaching systems presently in operation at seven
plants appear to be economically attractive; however, sub-
stantial modifications to the leaching process will be re-
quired to meet water pollution control regulations. We
recommend that studies be undertaken to determine the
economic feasibility of recovering alkalies from the leach-
ate so that they are not discharged to the environment. If
alkali recovery appears justified, we recommend that pilot
plant facilities be set up and operated with an existing
leaching operation to demonstrate technical feasibility.
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SECTION III
INTRODUCTION
The manufacture of portland cement is accompanied by the genera-
tion of large quantities of dust. Grinding and conveying raw
materials, heating them in a rotary kiln, and grinding the result-
ing clinker are all dust-producing operations, and the dust
escaping from these operations must be collected to prevent air
pollution.1 Dust collected in raw material processing operations
can be returned to the process, and dust from clinker grinding
can be sold as cement. Since the manufacturer has economic in-
centive to collect and reuse these dusts,2 their disposal is
seldom a problem, and they will not be discussed further in this
report.
The dust generated in the rotary kiln is difficult to collect
because it is entrained in large volumes of hot exhaust gases.
Moreover, it often contains unacceptably high concentrations of
alkalies (sodium and potassium) which make it unsuitable for re-
turn to the cement-making process. Disposal of the dust is com-
plicated by the presence of soluble alkalies in the dust; when
these are leached out by rainwater, they can cause pollution of
surface or ground waters. This study was undertaken to assess
the problems associated with kiln-dust disposal and to find and
evaluate possible solutions to these problems with an emphasis
on utilization of waste dust rather than development and
maintenance of expensive and wasteful disposal systems.
A successful assessment of the state of the art of collection,
disposal and utilization of waste kiln dust required a review of
pertinent technical literature. Chemical Abstracts, the reference
files of the Portland Cement Association and a bibliography from
the Tennessee Valley Authority were used to gain initial access
to the literature. The literature search yielded numerous refer-
ences, both foreign and domestic, which were screened for their
applicability to the purpose of the study. Polish, Russian, and
German articles made up the bulk of the pertinent foreign liter-
ature. Whenever the title or published abstract of an article
appeared relevant, the original article was copied and read. In
several cases we corresponded with the author to update or
elaborate on the information published in his article or patent.
Many articles in foreign languages were translated by members
of the staff of Southern Research Institute. Abstracts for
references cited in this report are given in the Appendix.
Concurrent with this study, we were also engaged in a survey to
obtain the background data necessary to establish the Effluent
Limitation Guidelines for the Cement Industry. The data forms
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used to record information from phone calls and plant visits for
that study also had space for data on collection, disposal, and
utilization of kiln dust. Later another data form shown in
Figure 1 was used for further contacts with cement manufacturers.
Date from about 60% of the active cement plants in the United
States were processed by computer to provide a basis for estimating
the amounts of kiln dust collected, discarded, and utilized by the
entire industry.
In addition to contacts with plant personnel for acquisition of
operating data, we contacted corporate environmental and managerial
personnel of several cement companies, consultants, equipment
manufacturers, EPA personnel, potential consumers of waste dust,
and suppliers of materials for which kiln dust may be a substitute.
These contacts were made to solicit opinions and facts on problems
attendant to utilization of dust in particular applications and to
seek additional potential applications.
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CEMENT KILN-DUST WORKSHEET SRI ID
Company name
Plant name and location
Contact Ph:
1. Kiln-dust collection
a. Collection equipment (check one or more)
Cyclones or multiclones Q
Baghouse Q
Electrostatic precipitator...... p
Wet scrubber Q
Other (specify) p
None O
b. Estimated collection efficiency (%)
2. Kiln-dust disposition
a. Total collected (tons/day)
Alkali content - K20(%)
- Na20(%)
- Na2O equivalent(%)
b. Total returned to kiln (tons/day)
Alkali content - K->O(%)
- Na20(%)
- Na~O equivalent(%)
Method of return
insufflation Q
mixed with feed Q
leached Q
c. Total discarded (tons/day)
Alkali content - K-0(%)
- N32O(%)
- Na20 equivalent(%)
Method of disposal
Surface piling O
Quarry piling O
Slurry to quarry a
Slurry to pond a
Other (describe) a
Utilization (describe) a
c. Does this company have plans for future utilization
of cement dust? If yes, how?
3. Additional remarks (novel practices, special problems/ etc)
Figure 1. Sample form used to record survey data.
5
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SECTION IV
THE INDUSTRY
Portland cement is composed of the oxides of calcium, silicon,
aluminum, and iron, bound in a complex mineralogical matrix, with
the ability to hydrate and harden into a stone-like material.
The raw materials generally include a calcium carbonate source
such as limestone, cement rock, marl, chalk or oyster shell, a
silica source such as sand, quartzite or Fuller's earth, an
alumina source such as clay, shale, slag, aluminum ore tailings
or fly ash, and an iron source such as iron ore, iron oxide,
blast furnace flue dust or iron pyrites.3 Some raw materials
contain several of the necessary constituents and thereby reduce
the number of materials that must be handled by a manufacturer.
The most common combinations of materials are: cement rock;
limestone and clay; limestone and shale; and limestone, clay,
and iron ore. Naturally occurring raw materials contain un-
necessary or undesirable elements such as magnesium, potassium,
sodium, sulfur, chloride, fluoride, phosphate, and heavy metals;
however, when these are present in only trace amounts, they are
not deleterious to the manufacturing process or to the product.
The principal steps in the manufacture of portland cement are
quarrying (or dredging of shells), crushing, grinding, blending,
firing, and finish grinding. The quarrying and crushing opera-
tions are not unique to the cement industry, in fact, almost all
mineral quarrying and crushing operations use the same techniques
and equipment. Raw grinding of the sized materials reduces them
to a fineness of about 200 mesh. Most plants employ ball mills
for raw grinding and some add water to the material being ground.
Those plants grinding raw material as a water slurry usually keep
the material wet until it is dried in the kiln, thus the term
"wet process". In those plants grinding raw material dry the
term "dry process" has been adopted. Wet process plants pump
the ground material to large stirred tanks, called slurry tanks,
where the composition is adjusted as necessary and the batch is
stirred to assure uniformity. The analogous dry process equip-
ment is a homogenizing or blending silo stirred by introduction
of compressed air at the base. Factors that determine whether
wet or dry grinding will be used include: moisture content of
the raw materials, availability of water, and the price of fuel.
(Wet-process plants require additional fuel to evaporate the
moisture in the kiln feed.)
Quarrying, crushing, grinding, and blending prepare raw material
for the most important step in processing, burning in the kiln.
The kiln feed (also called raw meal or raw mix) is continuously
metered into the upper end of the kiln to begin its transit of one
6
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to four hours through the kiln. A burner maintains the tempera-
ture at the lower end of the kiln at about 1500°C and the feed
temperature approaches this value as it traverses the kiln. Dur-
ing the movement of feed through the kiln, three thermally induced
events occur: moisture is driven off, the calcium carbonate
calcines to calcium oxide, and then the entire mass fuses into
semi-liquid, marble-size balls called clinker. The fusion step
involves several complex chemical reactions resulting in a new
mineralogical material, portland cement clinker.
Clinker discharged from the kiln, usually onto a moving grate
clinker cooler, is cooled by a stream of air passing up through
the grate. Usually a portion of the hot air from the clinker
cooler is used as combustion air for the burner. Water spray
cooling is the only other significant clinker cooling method in
the industry. After cooling, gypsum (usually about 5% by weight)
is added to the clinker to retard hydration. Then the mixture is
finely ground (325 mesh) prior to bagging or bulk shipment.
The various standard grades of cement available are all produced
with the same equipment and essentially the same raw materials.
The differences between cement grades are achieved by variations
in kiln operating conditions and ratios of raw materials.
The cement industry is now in a period of growth in production
capacity. During the period 1965-70 the cement industry suffered
from excess capacity. There were 177 active plants in 1964,l and
several of these were shut down due to reduced profits and air
pollution regulations that required expensive additions of
emission control devices. During the 1970's the number of plants
has remained in the range of 165 to 170 as new plants come on
stream and older plants are closed. However, the larger capacity
of newer plants and the expansion of some existing plants resulted
in a steady increase of cement shipments in the United States
from 75.3 million tons* in 1970 to 87 million tons in 1973.* The
value of the 1972 cement shipments was about $1654 million, pro-
ducing a profit of about 9% return on net worth.5
Locations of portland cement plants are dictated normally by
distance to market, availability of transportation and availability
of raw materials. Typically, the market area is considered to be
within 100-200 miles from the plant along transportation routes.
Low cost transportation such as rail or water is usually required
to profitably ship cement further than the 10-50 mile radius of
the local market. Similarly, proximity of raw materials is im-
perative if a plant is to compete economically. Most plants utilize
*The cement industry has adopted the short ton, 907 kg, as its
standard unit of weight. Therefore, all production figures in
this report will be expressed in short tons.
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stone quarries adjacent to the plant so that raw material trans-
portation costs are kept low. Some plants, however, are located
so as to minimize distribution problems and must transport raw
materials several miles from quarry to plant site. Still other
plants purchase shell or stone from other suppliers.
The costs of cement production do not depend as much on materials
as on labor, which accounts for roughly one-third of the total
inplant cost for producing cement. Examples of major costs for
14 plants are given in Table 1.
The future of portland cement is good despite the more stringent
pollution control laws. Demand is increasing due to increased
construction and increased use of prestressed concrete products.
The average annual increase in shipments of portland cement is
predicted to be about 3.4%.** Factors which could adversely affect
the cement industry are as yet speculative. The greatest threat
to the industry is the fuel shortage, which is likely to result in
significant process modifications to improve thermal efficiency.
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Table 1. PLANT PRODUCTION COSTS
(1973 dollars per short ton)
Plant ABCDEFGHIJKLMN Avg.
Purchased
Raw Material
Freight on
Limestone
Haste Dust
Disposal
Labor
Fuel
Power
Operating
and Repair
Supplies
Taxes and
Insurance
Miscell-
aneous
Depreciation
& Depletion
Total Plant
Cost
0.69 1.82
0.16
5.85 5.00
2.18 2.39
1.17 1.92
1.92 2.07
0.37 0.32
0.05 0.05
1.49 2.55
13.72 16.28
1.13
1.06
6.40
2.83
1.17
2.12
0.53
0.05
1.59
16.86
0.76 4.22 5.25 0.76 0.59
1.01
7.23 5.75 4.52 8.40 6.80
2.39 2.39 1.76 3.46 3.40
1.55 1.86 1.70 1.17 0.75
2.44 1.92 1.23 1.27 1.75
0.21 1.59 0.59 0.11 0.80
0.05 0.50 0.50 0.05 0.05
1.81 1.59 2.39 0.59 1.27
16.33 19.25 17.45 15.80 16.44
0.76 0.85 0.91 4.17 0.65 0.59
1.38
7.08 5.48 4.00 3.84 5.59 5.96
2.29 1.80 3.09 2.13 2.08 2.66
1.27 1.54 1.59 1.27 1.13 0.75
1.38 1.97 2.44 1.81 2.24 2.92
0.48 0.64 0.37 0.53 0.32 0.69
0.05 0.16 0.05 0.05 0.05 0.05
1.59 1.70 1.92 1.59 3.03 1.86
14.89 14.15 14.36 15.37 15.05 16.86
1.65
0.25
0.01
5.35
2.49
1.34
1.96
0.54
0.06
1.78
15.91
Source: J.D. Wilson/ Bendy Engineering Company, St. Louis, Missouri.
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SECTION V
DUST COLLECTION
The Environmental Protection Agency and most state air pollution
control agencies have set standards for particulate emissions
from cement manufacturing processes. United States Environmental
Protection Agency guidelines call for a maximum dust emission from
the stack of 0.3 Ib of particulates per ton of dry raw feed, and
a maximum dust emission from the clinker cooler of 0.1 Ib per ton
of dry raw feed to the kiln.2'6 Because it is almost always
relatively coarse and low in alkalies, clinker cooler dust can be
collected and returned to the process without any problems. Since
clinker cooler dust is seldom discarded it was not covered in this
study.
An example of the level of control represented by the EPA guide-
lines can be demonstrated by the following calculations:
• The average production of a portland cement plant in
the United States is about 1670 tons per day.
• Approximately 1.6 tons of raw material are required to
produce one ton of clinker resulting in an average feed
of about 2672 tons per day.
• The average amount of dust collected (not emitted) is
312 tons per day.
• The average collection efficiency of 101 plants studied
is about 96%, so total dust generated is about 325 tons/day.
• The average amount of dust generated per ton of feed is
325/2672 or 0.122 tons (244 Ib) of dust per ton of feed.
• To reduce emission to 0.3 Ib of dust per ton of feed,
243.7 Ib of dust must be collected which is (243.7/244)
x 100% or 99.88% removal.
This example is consistent with actual requirements faced by the
industry. Most modern dust collection equipment is certified above
98% for normal operating conditions and some collectors have tested
as high as 99.98%. The amount of dust that must be removed from
exhaust gases depends, naturally, on the total amount of dust in
the gases and this can vary tremendously. Dust generation depends
on almost every factor that affects cement making. Some of the
more noticeable causes of high dust generation are non-uniformity
of feed particle size and operation of kilns above the design
production rate.
10
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The most important step in preventing air pollution is preventing
escape of kiln dust to the atmosphere. To prevent kiln dust escape,
many types of collectors have been utilized by cement manufacturers.
The types of dust collectors used in the 101 plants surveyed are
shown in Table 2.
Table 2. DISTRIBUTION OF KILN DUST COLLECTION SYSTEMS
IN WET AND DRY PROCESS CEMENT PLANTS
Kiln-dust collection system
Single dust collector
Cyclones
Precipitators
Baghouses
Wet scrubbers
Settling chamber
Combinations of dust collectors
Precipitators and wet scrubbers
Cyclones and wet scrubbers
Cyclones and precipitators
Cyclones and baghouses
Cyclones, baghouses, and precipitators
Baghouses and precipitators
Baghouses and wet scrubbers
Type of Process
and
Number of Plants
Wet
2
31
3
1
1
1
1
14
4
2
1
0
Dry
2
3
3
0
0
0
0
12
16
2
1
1
The earliest and least expensive dust collector is the settling
chamber. A settling chamber is typically a large box in the duct
between a kiln and the exhaust stack or chimney. Exhaust gases
passing through the chamber experience a reduction in velocity
due to the larger cross sectional area of the chamber compared to
that of the kiln. Reduced velocity allows large dust particles
to settle to the bottom of the chamber. Such "dense" particles
are usually 20 to 30% of the dust emanating from a cement kiln.
The settled dust is removed from the chamber and usually added
to the kiln feed. Only one plant contacted in our survey used
a settling chamber as its only dust collector, and this plant is
in the process of upgrading its collection system. Although not
reported, it is likely that many plants still use settling chambers
ahead of more efficient dust collectors.
11
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Cyclones produce better separation results than settling chambers
and are utilized extensively in the cement industry. Over half
of the plants surveyed use cyclones for kiln dust collection, but
only four plants still use them as the only dust collectors. The
operating principle of the cyclone is the application of centri-
petal force to a moving gas stream by introducing the gas tangen-
tially to the inner surface of a cylinder thus forcing the gas in
a circular path. The radial acceleration experienced by the dust
particles concentrates them against the wall of the cylinder while
gases depleted of dust are removed from along the axis of the
cylinder. Both cyclones and settling chambers use a force directed
at right angles to the stream flow to remove dust particles but in
a cyclone the percentage of dust removed is greater because the
radial acceleration is much greater than the acceleration of gravity
employed in a settling chamber.
Electrostatic precipitators have been in use in the cement in-
dustry for many years. Early installations were generally only
slightly better than cyclones but continuing research in construc-
tion and materials have made precipitators extremely efficient
and have improved economy. The principle of electrostatic pre-
cipitation involves the attraction of electrically charged par-
ticles to an electrode of opposite charge. As dust laden gas passes
through a precipitator, the dust particles are exposed to a corona
discharge in an electric field and acquire static electrical
charges. Under the influence of the electric field, the charged
particles are attracted to electrodes bearing a charge opposite
to that imparted to the particles, and are deposited on these elec-
trodes, from which they fall to hoppers below. Usually, electro-
static precipitators comprise two, three, or four stages
pneumatically in series.
Electrostatic precipitators are used in 67 of the 101 plants
surveyed. As shown in Table 2, they are the preferred dust col-
lector for wet process plants (49 of the 61 plants). The moisture
content of the exhaust gases helps in the conditioning of the dust
particles that results in electrical conductivity properties of
collected dust that are desirable for electrostatic precipitation.
The fabric filters most commonly used to collect cement kiln dust
are baghouses. They consist of hundreds of siliconized-glass fab-
ric tubes through which the dust laden gases flow, leaving the
dust particles on the inside walls of the vertically hanging bags.
The bags are shaken to dislodge the dust which falls into a hopper.
The maximum temperature tolerated by the glass bags is somewhat
less than 300°C.7
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Wet scrubbers are employed by only two of the plants in our survey.
Only one scrubber is actually used as the primary dust collector,
and it has a history of mechanical problems. The dust laden exhaust
gases are brought into contact with a high-velocity water spray
that entraps the dust particles. The droplets are collected in
cyclones and sent to a settling pond. The sludge from the settling
pond is usable as kiln feed, but the overflow is a potential water
pollution problem.8
Combination systems utilizing the best features of two or more
collectors are quite common in the cement industry. The most
common multiple systems are cyclones with precipitators and
cyclones with baghouses. Cyclones are used ahead of the other
collectors to remove coarser particles inexpensively and the second
system then collects the finer particles. Usually, when alkali
problems are encountered with the dust collected in a combination
system, only the fine fraction from the final dust collector needs
to be discarded.
13
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SECTION VI
CHARACTERISTICS OF KILN DUST
In the process of grinding the raw materials to a fineness of
minus 200 mesh, a significant amount of extremely fine particulate
matter is produced. When the raw materials are subjected to the
tumbling action of the kiln, these fine particles become airborne
and are swept away by the hot combustion gases.
Dust collected in an efficient U.e_ 98-99.9%) collector shows a
wide range of particle sizes depending upon the type and extent of
grinding, the type of kiln, and the type of dust collection system
employed. The dust sample in Table 3 was extremely fine; most of
the particles were less than 6 microns in diameter.9 Other studies
of particle size analysis reported substantial fractions of the dust
with particle sizes as large as 100 microns.10
Table 3. PARTICLE SIZE ANALYSIS AND DISTRIBUTION OF ALKALIES IN
A SPECIMEN KILN DUST FROM AN ELECTROSTATIC PRECIPITATOR9
Particle Size
Range (Microns)
Total Alkalies Water Soluble
Weight % Alkalies, %
Percent Na20 K20 Na2O K20
Water
Insoluble
K20, %
+68
-68+48
-48+34
-34+24
-24+17
-17+12
-12+6
-6
0
0.3
0.4
0.7
1.8
5.1
27.3
64.4
0.30
0.31
0.35
0.38
0.40
0.33
0.42
3.62
3.46
4.51
5.08
5.15
5.35
10.72
*
*
0.094
0.117
0.134
0.134
0.242
it
*
1.927
2.560
3.072
3.252
8.191
2.58
2.52
2.08
2.10
2.53
*Insufficient sample for analysis,
An important factor associated with dust particle size is the dis-
tribution of alkalies in the dust. Sodium and potassium sulfates,
chlorides, and carbonates exhibit a strong tendency to concentrate
in the finer fractions of collected dust because the specific surface
area of the particles increases dramatically as effective diameter
decreases. This relationship is best shown by the data in Table 3.
The relationship of alkali content to surface area is explained by
the following sequence of events. First, as the raw materials
proceed down the kiln and increase in temperature, sodium and potas-
sium compounds reach their boiling or subliming temperature and
vaporize; then, as the gases containing airborne raw material and
vaporized alkalies leave the hot part of the kiln, the alkalies
14
-------
cool and begin to condense both as a fume and onto particles in the
gas stream. The fume produced is composed of extremely fine par-
ticles and apparently accounts for only a small part of the volatil-
ized alkali. Most of the alkali present in the gases condenses on
entrained dust particles, and since the finer particles have more
surface per unit of weight to be coated, they contain more alkali
per unit of weight, i.-e_. , higher concentration of alkalies than
the larger particles. ~"
The chemical composition of kiln dust is determined by the composi-
tion of the raw materials and the conditions the dust particles
have encountered in the kiln. Published data on the proportions
of major constituents, Ca, Mg, Si, K, Na, S, C, etc. vary so widely
that no really typical dust composition can be assumed. Careful
analysis of a dust sample would reveal a variety of elements, some
present in only trace concentrations as shown in Table 4. This
particular sample had a high concentration of the usual alkali
metals Na and K and smaller concentrations of the others in that
group*Li, Rb, and Cs.11 Most of the cations are associated with
C0a~ and SO4—, but halide anions are also present. Volatile
heavy metals such as Zn and Pb are likely to be present in con-
centrations significantly higher than those found in the raw
materials.
The collected kiln dust has experienced some degree of calcination
and thus has a lower content of CO3than the raw materials. The
"loss on ignition" value of the dust may range from 10 to 35% com-
pared to a typical value of about 36% for raw materials. The
degree of CO3depletion is an indication of how hot the dust be-
came and, therefore, how far down the kiln it traveled before
becoming airborne and escaping with the gases. Since the dust is
partially calcined it has the ability to harden somewhat upon
exposure to moisture.
15
-------
Table 4. COMPOSITION OF DRIED KILN DUST11
Clay (HC1 insoluble, fired at 800°)
Organic substance
Cations
Lithium
Sodium
Potassium
Rubidum
Cesium
Magnesium
Calcium
Strontium
Li*
Na+
K +
Cs'
Mg"
Ca'
Sr
Sum of Cations
"1"1"
Weight, %
4.61
2.06
0.0064
12.25
24.50
0.475
0.0074
Trace
9.26
0.015
Meg/10Q q
0.92
523
627
5.56
0.06
462
0.34
1,618.88
Anions
Fluoride F ~
Chloride Cl~
Bromide Br~
Iodide I ~
Carbonate CO3
Sulfate SO i,
Sulfide
Borate
Phosphate
Sum of Anions
S —
B03-
Heavy Metals
Chromium
Manganese
Iron
Zinc
Lead
Cr
Mn
Fe
Zn
Pb
0.011
0.013
0.84
1.62
0.562
Sum of all determinations
Oxygen (from CaO not bound in carbonate)
Sum of all constituents
0.46
1.43
0.040
0.0552
29.59
9.06
Trace
0.152
Not detectable
Heavy Metal
Cr203
Mn02
Fe2O3
ZnO
PbO
bonate )
24.2
40.3
0.5
0.44
987
189
2.58
1,244.02
Oxides
0.016
0.021
1.19
2.02
0.607
97.825
2.98
100.805
16
-------
SECTION VII
THE ALKALI PROBLEM
The major sources of alkalies in the raw materials for cement
manufacture are the argillaceous and siliceous components rather
than the limestone or the fuel. Fixed alkali cations in the raw
materials are not susceptible to removal by direct water leaching
or ion-exchange methods. The only practical way of removing them
is through decomposition of the clay structure by heating a lime-
clay mix at ratios approaching the formulation of portland cement.12
Under these conditions changes in mineralogical structure of the
clay allow the alkalies to escape as vapors that subsequently
condense on the surfaces of cool dust particles in the kiln.
When necessary, CaCl2 can be added to the kiln feed to further
volatilize the alkalies.
The alkali content of collected kiln dust is the most important
characteristic determining whether the dust can be reused in
the manufacture of cement. If the total alkali content of the dust
(expressed as NaaO equivalent) is below about 1%, usually most or
all of the dust can be returned to the kiln. Alkalies in the dust
upset kiln operation by lowering the fusion temperature of the other
materials and thereby increasing the fluidity of the kiln load.
This causes a* reduction in the thickness of the layer of material
coating and protecting the refractory lining of the kiln. Also,
the presence of substantial quantities of free alkalies in the kiln
material during the burning process results in the formation of
free lime, as an equilibrium product.13 Moreover, since most of
the alkali returned to the kiln eventually finds its way into the
clinker, return of high-alkali dust can result in the production
of clinker with an alkali content above the limit of 0.6% specified
for low-alkali cement. This specification is an effort to avoid
problems with the well known "alkali-aggregate reaction".
When the aggregate in concrete contains amorphous silica, alkalies
in the cement can react with the silica to cause swelling of the
concrete.11*'15 This slow, insidious deterioration of concrete can
be a serious problem in construction of a dam or the foundation
of a building, but it would be of no consequence in a sidewalk or
driveway. High alkali content of the cement also has an adverse
effect on the rate at which concrete gains strength.16
Many construction contracts and codes routinely specify low-alkali
cement, even when non-reactive aggregate is to be used. This trend
has forced many cement manufacturers to supply low-alkali cement
17
-------
when normal cement would be quite adequate. If the manufacturer
is fortunate enough to have raw materials with low alkali content
he can make low-alkali clinker with no problem. However, if the
raw materials contain more alkali than can be tolerated in the
clinker, some of the alkali must be removed and discarded. Since
alkalies tend to accumulate in the fine dust entrained in the
exhaust gases of the kiln, discarding dust is the easiest way to
reduce the alkali content of clinker. As dust collection
efficiencies for cement kiln effluent gases are improved from
the average of 96% presently achieved to the 99.88% required by the
New Source Performance Standards, the amount of high-alkali dust
collected will increase substantially.
18
-------
SECTION VIII
DUST DISPOSAL
Kiln dust with a high alkali content or other property making it
unsuitable for return to the process is usually discarded. Of
the 101 plants surveyed, 16 discard all of the dust they collect,
and 57 discard a portion of their dust. The most common method
of disposal is piling on plant property. Most often these piles
are begun on an unused, fairly level location, convenient to the
collection equipment and downwind of the plant proper. Another
common practice is to dump the waste dust into an abandoned quarry
near the plant. In either case, water pollution problems are
encountered due to the solubility of the alkalies in kiln dust.
Typically, 30 to 60% of the alkalies present in kiln dust are
water soluble and can be leached out as water percolates through
the dust piles. The runoff from a dust pile usually has a pH of
12 to 13 and will kill most vegetation. One dust pile containing
discarded cyclone dust at least 5 years old produced a leachate
solution with a pH of 12.5 while a nearby pile of freshly deposited
dust collected in an electrostatic precipitator produced a leachate
solution with a pH of 12.9. Thus, the alkalies leached from a dust
pile in this instance decreased very little over a period of 5 years
A considerable retention time must be assured before runoff from a
dust pile can be released untreated to the environment.
Effluent guidelines for the cement industry require containment
of a rainwater runoff from materials storage piles including waste
kiln dust piles.17 In many cases this will require construction of
a dike around the dust piles as illustrated in Figure 2. Facilities
will be needed for adding acid to obtain a pH in the range of 6 to
9 for the runoff water that percolates through the pile into the
containment pond before it is released to the receiving stream.
Water slurries of dust occur when wet scrubbers are used for dust
collection as in two plants of the 101 surveyed. Another situation
resulting in water slurries of dust arises when plants mix dust
with water and pump the slurry to a disposal pond or lagoon.18
Some plants use abandoned quarries as the disposal site for dust-
water slurries. Others construct ponds or lagoons where the water
slurry can settle, concentrating the suspending solids as a sludge
in the lagoon. Most plants that dispose of dust as a slurry use
waste water from the plant and discharge the supernatant liquid
from the settling pond to surface waters. Naturally, the waste
water must be retained or treated before discharge just as rainfall
runoff from a dry disposal pile. One alternative to treating water
before discharge is to maintain a closed water system by recycling
the supernatant liquid back to slurry more dust. In areas where
the mean annual evaporation exceeds the rainfall, large evapora-
tion ponds could be used to dispose of alkaline wastewater.
19
-------
Figure 2. System for containment and treatment of
runoff from kiln dust disposal pile.
20
-------
SECTION IX
DUST RECLAMATION
Presently, 28 out of the 101 plants surveyed return all of the
dust they collect to the process, while 16 discard all of the
dust they collect. The remainder of the plants, well over half
of those surveyed, recycle as much dust as they can without
exceeding the limits for alkali content in their clinker, and
they waste the remaining dust. On an industry-wide basis, our
survey of the amounts of dust collected and discarded indicated
that about 73% of the collected dust is reprocessed to make
cement. A variety of methods are employed for recycling dust
to the kiln. Dust can be introduced to the kiln by insufflation
through the burner pipe or a pipe parallel to the burner pipe so
that the dust reaches reaction temperature very rapidly. '
One disadvantage of insufflation is the tendency of the dust to
remain airborne due to its fineness, thus establishing a recircu-
lating dust load and wasting energy for collection and reheating.
Also, in insufflation the dust cloud in and around the burner
causes difficulty in measuring flame temperatures by optical
methods.
A second method of dust return employs scoops located about mid-
length of the kiln which feed dust from a collar around the kiln
to the interior. Scoops appear to be decreasing in popularity
as a means of dust return.
Probably the most popular method of dust return to dry process
kilns is by blending with the raw feed to obtain a uniform mix so
that a more consistent product is obtained. In wet process plants
blending of dust with kiln feed is difficult because the partially
calcined dust tends to harden when exposed to moisture. Some wet
process plants have solved their dust return problems by carefully
adding dry dust to the feed slurry just before it enters the kiln.
A Russian plant made a slurry of the dust and mixed it with the
feed slurry.21 Other plants use additives such as molasses or
lignosulfonates from pulpwood mills to retard the setting of the
dust when it is hydrated.22
As mentioned previously, most manufacturers discard dust that has
too much alkali to allow it to be returned directly to the kiln.
The dust has an estimated value of $2 per ton as a cement raw mate-
rial because it has already been mined, crushed, and ground. The
4.5 million tons of dust discarded in the United States in 1972
would have been worth $9 million if it had been used to make
cement. Although a variety of methods for reclaiming high alkali
dust have been investigated, only one process, leaching, is in use
in the United States, and this process is now practiced in only
seven plants, six of which are wet-process plants. All of the
leaching plants use electrostatic precipitators to collect the
dust.
21
-------
In the leaching process, collected dust is thoroughly mixed with
water in a pugmill or mixing tank. This slurry which contains
about 10% solids is pumped to a clarifier or thickener where the
solids settle to the bottom and excess water overflows.23 The
underflow from the clarifier, a slurry containing about 50% solids
is returned to the kiln and burned to clinker. In the single dry-
process leaching plant this slurry is injected through a pipe
extending down from the feed end of the kiln into a region where
the temperature is high enough to flash off the water. In wet
process leaching plants the underflow is either mixed with the
feed slurry or pumped into the kiln through a pipe parallel to the
kiln ^1*
Disposal of the alkaline wastewater from the leaching process is
a serious problem faced by cement manufacturers . Two leaching
plants discharge their wastes to municipal sewage treatment systems
where they claim it is beneficial in neutralizing the acidic wastes
in the sewage. Presumably they will be allowed to continue this
practice in the foreseeable future. One plant adds acid to the
leachate to lower the pH to acceptable levels and one plant
carbonates the leachate with stack gas. The other plants dis-
charge the alkaline wastewater directly to rivers, a practice that
will be prohibited by the Effluent Limitation Guidelines recently
promulgated by the Environmental Protection Agency.17 By 1977 the
levels of pH and suspended solids of the discharge must be con-
trolled, and by 1983 discharge of dissolved solids must be curtailed
This gives manufacturers almost ten years to find a way to recycle
leachate or face shutdown of their leaching operations.
The diagram in Figure 3 shows a scheme for eliminating discharge
of pollutants from a dust leaching operation. The overflow from
the primary clarifier, the water that is now being discharged by
most leaching plants, is saturated in lime, has a pH of 13, and
contains 10,000 ppm of dissolved solids. In the first carbonator
C02 from_the stack gas reacts with OH~ ions in the leachate to
form C03 ions. If the alkalinity of the leachate exceeds the
hardness, almost all of the calcium is precipitated as CaCOs
which has its minimum solubility, 16 ppm, at pH 9.5.25 This pre-
cipitate settles to the bottom of the secondary clarifier and is
ultimately returned to the kiln. Residual suspended CaC03 in the
overflow from the secondary clarifier redissolves as the pH
decreases in the secondary carbonator.26 This overflow would
be within the limits of pH and suspended solids required by 1977.
Electrodialysis appears to be the process of choice to remove
alkali salts from the leachate and concentrate them in a solution
for recovery of valuable by-products by evaporation and fractional
crystallization. The operation of an electrodialysis stack is
22
-------
to
CJ
Stack
gas
Primary
clarifier
pH=13.0
Underflow returned
to kiln feed
I
Stack
gas
First
carbonator
PH=9.5>
Secondary
clarifier
pH=9.5.
Underflow returned
to primary clarifier
Kiln dust
Mixerl
T
Partially desalted
water returned
for reuse in .«
slurrying dust
Electrodialysis
units
(detailed in Fig.4)
Make-up
water
1
Concentrated brine
(ca. 20% solids) to
evaporation
1
Second
carbonator
pH=8.0
Sand filter
Figure 3. Flow diagram showing steps in electrodialytic
concentration of leachate.
-------
shown in Figure 4. An electric potential forces ions through
semipermeable membranes into a concentrated brine. Water enters
the brine by osmosis and carries away the concentrated salts. The
partially desalted water is reused to leach alkalies from collected
dust, and no water is discharged.
In electrodialysis of water containing appreciable concentrations
of calcium, problems are encountered with precipitations of CaSOi,
and CaCOa from the concentrated brine. These precipitates damage
membranes and block the flow of solutions in the electrodialysis
stack. Therefore, it is important that the calcium content of the
water be reduced to a very low level by the carbonation procedure
described above. Univalent cation-selective membranes that prevent
the passage of calcium ions can be used if the alkalinity (OH" ion
content) of a particular leachate is insufficient to allow nearly
complete removal of calcium upon carbonation.27 However, this
problem would be expected to occur only in plants that use fuel
with very high sulfur content.
The concentrated brine from the electrodialysis stack would contain
about 20% dissolved solids, mainly K+, Na+, C03 , and SOi, . Since
the ratio of K to Na in the solution is likely to be greater than
10:1, the concentrated leachate may be suitable as a liquid
fertilizer. Further purification and concentration of the K, which
is the more valuable of the two alkalies, could be achieved by
fractional crystallization and evaporation.
Other processes for leaching alkalies from dust have been reported
but none is presently being used commercially. During World War I
potassium was produced by the Riverside Cement Company.28 CaF2 was
added to the kiln feed to volatilize the K which was subsequently
converted to K2SOi» in the combustion gases. Collected dust was
leached, the leachate was filtered and evaporated, and a precipitate
of KaSOit was collected.
A process described in a British patent by Singleton and Bruce
utilizes a strong solution of potassium chloride to selectively
remove Na from the dust.29 Then l^SOi* is removed from the dust by
a second extraction. The leached dust is suitable for return to
the kiln and the separated K2SOi* is a valuable by-product.
Leaching with hot water is reported to be more effective than leach
ing at ambient conditions. Patzias found that a larger portion of
the total alkali in the dust was soluble when the dust-water slurry
was heated.90'31 Palonen and Kaiser found that high concentrations
of alkalies in the leachate could be achieved by countercurrent
extraction with hot water.15
24
-------
Partially
desalted
water
Cathode
i
^-^
-*• Concentrated
brine
rs///s,
A C A
K+
Y///S*
C A C
C - represents cation-exchange
membranes
A - represents onion-exchange
membranes
T
Solution to be
treated
x\ Anode
1
Figure 4. Diagram of electrodialytic concentration stack,
25
-------
One reason that electrostatic precipitators have found wide
acceptance as kiln dust collectors is their ability to separate
coarse and fine dust particles. Coarse particles are more easily
collected and they tend to predominate in the fraction of dust
collected in the first section of the precipitator. The finest
particles/ which because of their large surface-to-mass ratio have
high alkali content, predominate in the fraction of dust collected
in the last section of the precipitator. Discarding this fine,
high-alkali fraction allows the manufacturer to discard the minimum
amount of dust while maintaining acceptably low alkali content in
the clinker. Heilmann patented a process in which dust collected
in intermediate sections of the precipitator is subjected to further
size classification to achieve greater fractionation of alkalies.32
In a process developed by Bade, hot gases from the kiln with
alkalies still in vapor form are cleared of coarse dust particles
by a cyclone.33 Then cool fine dust particles are mixed with the
hot gases to condense the alkalies which are subsequently removed
with the dust in a second cyclone. Then the hot gases are used to
preheat raw materials in a turbulence stack. Cool exhaust gases
from the turbulence stack are cleaned by an electrostatic pre-
cipitator and the collected dust is recycled to condense alkalies.
A process developed and tested in Russia used cyclone heat exchangers
to recover heat and large particles of dust from hot exhaust gases.
Then the gases were cooled with finely dispersed water spray to
condense the alkalies so they could be subsequently removed in a
second dust collector as a powder with 70 to 80% alkali carbonates
and sulfates. 31f
When cement is made in a fluidized bed, the hot exit gases carry
away the volatile alkalies. When these gases are cooled either by
heat exchangers or by water sprays, the alkalies condense in a form
that can be used as a high-grade by-product.35'36'37 Fluidized-
bed reactors emit very low levels of particulates and they can use
low-grade fuels such as kerogen-rich shale. However, since they,
unlike rotary kilns, do not employ countercurrent flow of gases and
raw materials, expensive heat exchangers are required to achieve
reasonable utilization of heat in the system. Figure 5 shows
schematically how such a system operates. A fluidized bed pilot
plant was operated by the Fuller Company several years ago, but
no commercial operation is in existence.
Flame volatilization for alkali recovery utilizes the high tempera-
ture of a flame to volatilize the alkalies from the surface of dust
particles. The alkali vapors are removed from the hot gases by
condensation on a cool surface.9 Although flame volatilization
actually occurs during insufflation, the alkalies recondense on
the dust particles in the kiln, and useful separation of alkalies
is not achieved.
26
-------
to
RECYCLE CLINKER
COOLER
SCREEN
CLINKER
PRODUCT
REACTOR
RAW MATERIAL
FAN
PREHEATED AIR
STACK
t
ALKALI
COLLECTOR
HEAT
EXCHANGER
-*• AIR
FUEL
BLOWER
Figure 5. Fuller-Pyzel fluidized bed process for production
of clinker and by-product alkalies.
-------
Preheater kilns are commonly used in Europe for fuel economy, and
their use is likely to increase in the United States as the fuel
shortage worsens. Hot gases from the kiln are brought into direct
contact with raw materials in cyclonic-, grate-, or hearth-type
preheater. Since alkali vapors in these hot gases will condense
on the cool feed materials, preheaters cannot be used with high-
alkali raw materials unless the alkalies can be removed from the
kiln gases.
Several processes for removing alkalies from preheater kilns are
described in the European literature. Polysius developed a
process for removing alkali-laden gases from the Lepol preheater
collecting the dust, leaching the alkalies, and evaporating the
leachate to dryness in a thin film evaporator.38 In a process
developed in France, alkalies are condensed from hot kiln gases
onto a curtain of moving endless chains.39 The chains are then
drawn through a water bath where the alkalies on their surfaces are
dissolved and the chains are cooled. In a similar process for re-
moving alkalies from a preheater kiln, the hot, alkali-laden gases
pass over cool tubes. "° The alkalies that condense on the tube
surfaces are scraped off and recovered.
Alkalies can also be removed from preheater kilns via bypass of a
portion of the kiln gas that would ordinarily enter the preheater.
Nordquist and Heian reported substantial alkali reduction in the
clinker produced in a traveling grate preheater (Lepol) kiln when
30% of the 870°C gas was bypassed, cooled to 315°C by mixing with
ambient air. cleaned by a cyclone and returned to dry the raw
materials." Weber found that considerable alkali reduction could
be achieved in a Lepol preheater, but very little alkali was lost
from a suspension preheater."2 However, his study showed that the
alkali content of the clinker could be reduced by adding CaCl2 to
the kiln feed to increase the alkali volatility. Brachthauser
patented a process for converting alkalies to the more volatile
hydroxide form by vaporizing water in the clinker cooler and
blowing this hot moist air into the burner section of the kiln.1*3
A process for making low alkali clinker from feed materials which
may have high alkali content has been patented by Union Carbide.""
In this process, the kiln is replaced by a much smaller, stationary,
vortex reactor in which clinkering occurs. Alkalies are removed
in the gas stream from the clinker reactor. A separate burner and
off-gas system are used for suspension preheating the feed prior
to clinkering. The process seems particularly useful for convert-
ing high alkali dust into clinker and fertilizer.
28
-------
SECTION X
DUST UTILIZATION
In our survey we found that of the 73 plants that discard some
or all of their collected kiln dust/ only 13 reported any utiliza-
tion of the discarded dust. From the figures they reported we
estimated that about 1.5% of the 4.5 million tons of waste kiln
dust discarded annually is actually being used constructively, and
over half of that usage is for landfills. In our review of the
literature we found many documented uses of cement dust and in
our discussions with industry personnel we received many sugges-
tions for potential uses.
The largest single use of waste dust in the United States is for
landfill. In many cases it is difficult to ascertain whether
the purpose of the landfill is to dispose of dust or to increase
the value of the land. In the former case the cement manufacturer
may pay to have his dust hauled to the landfill; whereas, in the
latter case-he may be able to sell the dust. Both cases were
found in our survey. The high temperature when collected and the
extreme fineness of the waste dust make it difficult to handle. **s
Windblown fugitive dust from waste piles or landfills is a signi-
ficant source of air pollution. Spraying the dust with water is
helpful in alleviating this problem.
Some manufacturers employ a rotary unloader like the one shown
in Figure 6 to agglomerate the dust before loading it into trucks.
The device consists of a rotating inclined drum with water sprays
inside. As the hot, dry dust tumbles through the drum it becomes
moist and forms nodules that are easy to handle and can be hauled
in open trucks to disposal sites. The moisture in the nodules
hydrates the cement to some extent so that the nodules do not
disintegrate as they dry. Thus, compared to loose dust, the
nodulized dust is not as subject to wind erosion or flowing down
the pile when it is dumped.
The ability of waste kiln dust to harden after exposure to mois-
ture makes it useful for soil stabilization. One plant in our
survey reported that their waste dust was mixed with shells and
used as a sub-base for roads. Another reported that they dump
their dust in strip mines where it neutralizes acid mine drainage
and precipitates iron from the runoff water. Such an application
could potentially use large quantities of waste dust.
Kiln dust has also been used as a mineral filler for bituminous
paving materials and asphaltic roofing materials. It has also
been suggested as a filler for plastics and for asphaltic products
29
-------
Figure 6.
Rotary unloader for nodulizing waste kiln dust
(photograph courtesy of United Conveyor Corp.)
-------
such as insulating board, concrete expansion strips and sound
deadening material. There is at least one process under develop-
ment to use waste kiln dust in the manufacture of lightweight
aggregate.
The lime content of the dust makes it useful as a neutralizing
agent for acidic bogs, lakes and streams. In a study carried out
in 1957, waste kiln dust was used to kill vegetation in an acidic
bog."16 Considerable interest has been expressed in the possible
use of waste kiln dust to treat acid mine drainage. Since fresh
dry dust flows so easily, it might be pumped into abandoned mines
to neutralize acid, precipitate dissolved iron, and possibly re-
duce seepage of water from the mine. Industrial acidic wastes
that might be neutralized by kiln dust include spent pickle liquor
and wastes from leather tanning and cotton seed delinting processes
Kiln dust has been successfully substituted for lime in coagula-
tion processes. In Oregon, kiln dust was used as a partial and
total replacement for lime in the preparation of alum flock for
removal of turbidity from water.1*7 The dust successfully neu-
tralized the water and in addition improved flocculation,
apparently because the small residual insoluble dust particles
provided dense nucleation sites for the alum floe.
In the adsorption of SOa from stack gases by wet scrubber slurry,
cement kiln dust was found to be better than limestone and almost
as good as lime.1*8 Surprisingly, problems of scaling in the
scrubber system were less severe with kiln dust than with lime
in the slurry.
In the manufacture of glass large amounts of soda are used. Emer
found that kiln dust could be used beneficially as a partial
replacement for soda in making green glass, because it increased
the rate of decomposition of sulfates which is the main cause of
foaming in glass baths.1*9 Gregor and Hives reported similar
success in the use of kiln dust to make glass where color and
high chemical stability are not essential considerations.10
Agricultural use of kiln dust promises to be a way of converting
a waste material into a valuable by-product. Two properties
of the dust that make it useful for agricultural purposes are
its acid neutralizing capacity and its potassium content. Re-
searchers at the United States Department of Agriculture station
at Beltsville, Md., found that cement dust had about 80% of the
soil neutralizing capacity of lime and about the same liming
qualities as pulverized limestone.50'51 Studies carried out in
Latvia showed that cement dust could fully replace lime for treat-
31
-------
ment of acidic soils to grow sugar beets or corn, and the dust
could partially replace lime for growing potatoes and rye.52 A
study in Hungary indicated that in addition to its stimulation of
plant growth, it also had insecticidal properties.53
In Russia and Poland several studies have demonstrated the utility
of cement dust application on potato crops. One group found that,
whereas most inexpensive potassium fertilizers contain appreciable
amounts of chloride which is bad for potatoes, the high alkali
fraction of kiln dust had essentially no chloride and was an
acceptable, inexpensive substitute fertilizer for potatoes. 5I*
Rogalov found that application of cement dust increased the starch
content of potato tubers but had no greater affect on the yield of
potatoes than other fertilizers.55 Litynski explained that the
sulfate in kiln dust was responsible for the increased starch con-
tent of potatoes fertilized with the dust.56 He also suggested
that the presence of calcium in fertilizer favorably influenced
the uptake of potassium in acidic soils.57
A Dutch study indicated that comparable yields of oats were achieved
when cement dust or limestone and KaSOi, were used for fertilizer.58
Litynski found that mixed peas-and-oats crops fertilized with kiln
dust contained about 2% more protein than crops grown with KC1
fertilizer.59 He also found that the dust produced more starch
in fodder and more sugar in sugar beets.6 °
The size of the market for agricultural lime and limestone makes
it potentially a very good route for disposal of waste kiln dust.
More than 20 million tons of lime and limestone are sold each year
for agricultural purposes.61 This single market if properly
developed could use most of the 4.5 million tons of kiln dust being
discarded in the United States each year. Figure 7 shows the
usage of agricultural lime in the United States on a statewide
average basis. Also shown are the locations of plants that our
survey revealed to be discarding major amounts of dust. Most of
these plants appear to be located in or near states where sub-
stantial amounts of agricultural lime are used.
Approximately 94% of the potash consumed in the United States is
used in fertilizer.62 Of the 14 chemical elements essential to
plant growth, nitrogen, phosphorus, and potassium are the most
rapidly exhausted from the soil and must be replaced by the addi-
tion of fertilizers to assure optimum plant growth.6 3 »*** Examples
of amounts of potassium withdrawn by various crops are presented
in Table 5.
32
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uo
U)
2-20lb/acre
20-501 b/acre
50 -100 I b/acre
>IOOIb/acre
Figure 7. Agricultural lime and limestone usage in the
contiguous United States,6 and locations of
plants known to be discarding kiln dust.
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TABLE 5. WITHDRAWAL OF POTASSIUM BY
AGRICULTURAL CROPS65
Good Acre K2O Removed,
Crop Yield Ib/acre
Soybean 50 bu 120
Clover grass 9000 Ib 175
Peanuts 3000 Ib 120
Alfalfa 6 tons 270
Coastal Bermuda
grass 10 tons 400
Cabbage 25 tons 210
Irish potatoes 20 tons 310
Tomatoes 30 tons 480
Sugar beets 30 tons 550
Sugar cane 100 tons 590
Rice 4500 Ib 110
Corn, ears 150 bu 195
Corn, silage 30 tons 245
Wheat 60 bu 110
Cotton 1250 Ib 90
Tobacco 2800 Ib 190
Apples 600 bu 135
Peaches 600 bu 120
Grapes 10 tons 80
Oranges 800 boxes 175
Many of the cement manufacturers contacted in our survey reported
that local farmers occasionally visit their plants and haul away
truck loads of waste kiln dust to spread on their fields. Although
the farmers and cement manufacturers alike recognize the value of
the dust as a fertilizer material, apparently no great effort has
been made to exploit this resource. One hindrance to its exploita-
tion appears to be fertilizer specifications.
Fertilizer is sold on the basis of its nutrient content. The
three nutrients mentioned earlier (nitrogen, phosphorus, and
potassium) are measured in "units", each unit representing one
percent of an available nutrient. A 6-8-4 fertilizer, for example,
is guaranteed to contain at least 6 percent of available nitrogen,
8 percent of available phosphoric acid, and 4 percent of available
potash (K2O). There are at least 33 cement plants discarding dust
with an average potash content greater than 7 percent. With addi-
tions of phosphorus and nitrogen compounds a commercially acceptable
fertilizer could be produced using kiln dust without further con-
centration of the potassium present. Under regulations set by the
Alabama Department of Agriculture and Industry, fertilizers offered
for sale must meet certain minimum standards for available nutrient
34
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content. There is a regulation which, while not written to cover
the sale of cement dust, allows the sale of cement dust without
major modifications. Under section 3(b)(1), Act 434, a material
which "... contains important quantities of no more than one of
the primary plant nutrients (nitrogen, phosphorus, and potassium)"
is defined as a "fertilizer material."6* Cement dust satisfies
this definition if the potassium content is considered. Other
regulations which might be met by cement dust are in the areas of
a soil-conditioning material and a fortified liming material.
Most of the states adhere to the Uniform State Fertilizer Bill
suggested by the Association of American Plant Food Control
Officers. This bill cites definitions in the AAPFCO annual
publication. Cement dust easily meets fertilizer material defini-
tion C-13.67 Thus cement dust can meet commercial content re-
quirements.
Once the question of the legality of sale and use of kiln dust for
fertilizer is settled, the next question is how can it be applied.
One serious problem is the handling of the fine dust. When dry,
it flows readily and is easily carried away by the wind. A
Russian patent suggests the preparation of granules by rolling the
dust in water.68 A device like the rotary unloader shown in
Figure 6 can be used for this purpose. Then the granules are
treated with C02 to make them non-hygroscopic and mechanically
strong.
If fertilizer markets for kiln dust are developed, it is likely
that the manufacturer will want to modify the composition of the
fertilizer to meet specific soil and crop needs. Chlorination
roasting was used by a Russian group to raise the KaO content
of kiln dust to over 20%.69 A Russian patent describes a process
in which kiln dust is mixed with a nitric acid-phosphate extract
to yield a ternary N-P-K fertilizer.70
Fortunately there are abundant supplies of potash in North America
so that there is no danger of long-term shortage. However, the
potash fertilizer consumption in the United States is over 5 million
tons per year,62 and there is a general shortage of other fertil-
izer materials.71 Cement manufacturers with waste dust problems
would be well advised to contact their State Fertilizer Control
Officers for a first-hand opinion of the possibilities of using
the dust as a fertilizer material.
35
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SECTION XI
LIST OF PUBLICATIONS
1. Davis, T. A., and D. B. Hooks. Utilization of waste kiln
Dust from the Cement Industry. In: Proceedings of the
Fourth Mineral Waste Utilization Symposium, Aleshin, E.
(ed.). Chicago, IIT Research Institute, 1974. p. 354-363.
2. Davis, T. A. Disposal of Waste Dust From Cement Kilns.
Record of the 1974 IEEE Cement Industry Technical Conference,
Library of Congress Catalog Number 75-28930. IEEE Catalog
Number 74CH0785-6 IA.
36
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SECTION XII
APPENDIX
1. Kreichelt T. E., D. A. Kemnitz, and S. T. Cuffe. Atmospheric
Emissions From the Manufacture of Portland Cement. Bureau
of Disease Prevention and Environmental Control, Cincinnati,
Ohio. PHS No. 999-AP-17. 1967.
Abstract: Air pollution control in cement manufacturing was
studied in detail. This report gives descriptions of raw
materials, processes, equipment, volumes of dust, and methods
of dust control employed.
2. Anonymous. Background Information for Proposed New-Source
Performance Standards: Portland Cement Plants. NTIS
Publication PB-202 459, Technical Report 3, August 1971.
Abstract: Proposed standards for particulate emission of
0.3 Ib from the kiln and 0.1 Ib from the clinker cooler
per ton of kiln feed (dry basis) are justified. The economic
impact of the proposed standards is also presented.
3. Anonymous. Concrete Information. Portland Cements (IS 004.
04T), Portland Cement Association, Skokie, Illinois, 1971.
Abstract: Raw materials, processes, types, chemical compo-
sitions, physical properties and handling requirements of
Portland Cement are discussed.
4. Levine, S. and E. W. Stearn. The Year Ahead—1974. Rock
Products, 39-43, December 1973.
Abstract: Construction minerals shipments and values for past
years and estimates for 1974 are tabulated. Included is a list
of cement plants, capacities, and process types.
5. Grancher, R. A. Cement's Second Look at Capacity. Rock
Products. 50-53, 74, December 1973.
Abstract: Cement plant capacity increases, especially in
the Southeastern U.S., are forecast through 1978.
6. Anonymous. Standards of Performance for New Stationary
Sources. Federal Register 36(159): 15707, August 17, 1971.
Abstract: Standards of performance for portland cement
plants are specified for new sources, including plant
expansions. Particulate emissions are set at 0.3 Ib per ton
of feed and 10% opacity (1/2 on Ringleman scale) for the kiln
gas effluent. For the clinker cooler these values are 0.1 Ib
per ton of feed and 1/4 on the Ringleman scale.
37
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7. McCubbin, T. L. Dust Control Techniques for a Portland
Cement Plant. Minerals Processing. 24-25, 35, May 1969.
Abstract: Generation, composition, and return of kiln
dust are discussed. Design and operation of glass-fabric
bag collectors are described.
8. Goldberger, R. H. Rx for Cement Dust. Rock Products. 55
76, 78, August 1973.
Abstract: The wet scrubber used for kiln dust collection
at National Portland Cement Company's plant in Bethlehem,
Pennsylvania, is described in detail. Water that accumulates
in the quarry is pumped through venturi scrubbers where it
washes out particles of dust from the exit gases of the kilns
with 97.7% efficiency. The C02 and SO2 in the gases neutral-
ize the alkalies leached from the dust. The water is then
treated in an 80-ft-diameter clarifier where the suspended
dust particles are removed for return to the kiln feed.
After treatment to oxidize dissolved H2S, the scrubber
water is diluted with quarry water and discharged to a nearby
C1T66JC •
9. Greening, N. R., R. j. Hinchey, and H. Nagao. Elimination of
Water Pollution by Recycling Cement Plant Dust. Progress
Report No. 2, Contract No. 802196, Project CR-7050, Basic
Research Department, Portland Cement Association, Skokie, 111
for Office of Research and Monitoring, U. S. Environmental *'
Protection Agency. October 1973.
Abstract: A system for flame volatilization of
alkalies is described. Particle size analysis, chemical
analysis, alkali distribution, and results of experiments
are presented.
10. Gregor, M., and L. Hives. Potash Balance of Cement
Shaft Kilns with Special Regard to Possibilities of
Potash Recovery. Proc. 6th Conf. Silicate Ind.,
Budapest 1961. 177-89, Pub. (in English) 1963.
Abstract: Flue dust samples from shaft kilns at a
cement plant were analyzed over a period of 12 weeks.
The raw material was lime marl which had a K20 content
of 1.2%. The K20 content of the flue dust averaged
34%. The quantity of dust collected was 1.7% of the
weight of clinker produced. The clinker contained
0.86% K20. In addition to its value as an agriculture
material, tests showed the flue dust to be a satis-
factory substitute for potash in making glass where
color and high chemical stability are not essential
considerations.
38
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11. Kasz, W. Chemical Investigation of the Dust Collected in an
Electrostatic Precipitator at a Portland Cement Plant in
Blaubeuren. Jahresber. Mitt. Oberrhein. Geol. Ver. (Stuttgart).
46:1-8, January 12, 1964.
Abstract: The dust was analyzed by chemical methods and x-ray
fluorescence spectroscopy, and the composition of the dust
was compared with that of the Upper Weissjura marl and chalk,
which is the raw material. The dust was enriched in the
elements from the raw material that were volatilized in the
kiln, specifically, rubidium (0.475% of dust by weight),
cesium (0.0074%), iodine (0.0552%), zinc (1.62%), and
lead (0.562%).
12. Kester, B. E. Development of Low Alkali Processes in Port-
land Cement. Preprint No. 63H43, a paper presented at the
Annual Meeting of the American Institute of Mining, Metallur-
gical, and Petroleum Engineers Inc., Dallas, Texas,
February 24-28, 1963.
Abstract: The source and nature of alkalies in cement and
their effects on certain aggregates are discussed. Leaching
systems for wet and dry process plants are described. Steam
treatment was studied as a method for destroying hydraulic
set properties of dust. The use of CaCl2 to volatilize
alkalies was found to be effective but was more expensive
than leaching.
13. Palonen, C. V. and E. W. Kaiser. Inorganic Dust Treatment
Process. U. S. Patent No. 2,871,133, January 27, 1959.
Abstract: Kiln dust is pelletized and heated to about 950°C
and then leached. The normal 10 to 60% water-soluble content
is raised to 94 to 96%.
14. Kryzhanovskaya, I. A., et al. The Effect of Alkalies
on the Behavior of Cement. Tsement (Moscow), April 1969.
Translation by R. Keen. Cement and Lime Manufacture (London).
97-100, September 1969.
Abstract: Data are presented on cure rates and strengths
of cements containing varying amounts of added alkali.
The investigations established that, in the presence of
0.6% alkali, the activity of portland cement is reduced
irrespective of the kind of alkali compounds present.
An increase in the alkali content reduces the activity
both at early and late ages due to suppression of the
hydration of the clinker materials by the alkalies in
the liquid phase.
39
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15. DePuy, G. W. Experiments with Alkali-silica Re-
active Constituents of Sand-gravel Aggregate. National
Academy of Science - National Research Council, Publ. No.
1367. 41-9, 1966.
Abstract: A pilot study investigated the effect of
alkali-silica reactive constituents in a sand-gravel
aggregate in the sealed moist-storage and the Con-
row cycle mortar bar expansion tests. A highly
.alkali-silica reactive sand-gravel from the Republican
River was tested against South Platte River aggregate
as control. It produced deleterious expansion in
both the sealed moist-storage test and the Conrow
cycle mortar tests. The removal of the alkali-
silica reactive particles reduced expansion in the
sealed moist-storage test to within safe limits, but
in the Conrow cycle test, expansion was reduced but
a significant amount of expansion remained. The re-
maining expansion appeared to be due to the character-
istic cement-aggregate reaction of sand-gravel aggregates.
The tests indicate that the alkali-silica reaction is
a major factor in the cement-aggregate reaction with
alkali-silica reactive sand-gravel aggregates. The
tests also indicate that the Conrow cycle mortar bar
expansion test is sensitive to alkali-silica reaction.
16. McCoy, W. J. and O. L. Eshenour. Significance of Total and
Water Soluble Alkali Contents of Portland Cement. Journal of
Materials, JMLSA. 3(3):684-45, September 1968.
Abstract: The amount of alkali in cement clinker depends on
the raw materials, the burning temperature, and the presence
of SO3. The ratio of water-soluble to non-soluble alkali
can vary from 1:9 to 6:4 (10% to 60%). Relation of Na2O
volatilization to K20 volatilization: Na20 volatilizes
until about 30% of the K20 present has volatilized and
after that point K20 volatilizes about 50% faster than
Na20. Tests reveal that early strengths of cements are
higher with some alkali than with none. The amount of
soluble alkali has little effect on the pH of aqueous
extracts of cement.
40
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17. Anonymous. Effluent Guidelines and Standards - Cement Manu-
facturing Point Source Category. Federal Register 39(35):
6590, February 20, 1974.
Abstract: Plants in which kiln dust is not contacted with
water as an integral part of the process are in the nonleaching
subcategory. Effluent limitations (maximum for any one day)
for these plants are 0.005 kg of suspended solids per kkg
of product, temperature not to exceed 3°C rise above inlet
temperature, and pH within the range 6.0 to 9.0. These
standards apply to both existing sources and new sources.
Plants in which kiln dust is contacted with water (leaching
for dust reuse, slurrying for dust disposal, and wet
scrubbing for dust collection or gas conditioning) are in
the leaching subcategory. By 1977 new or existing leaching
plants must meet effluent limitations of 0.4 kg suspended
solids per kkg of dust leached, temperature not to exceed
3°C rise above inlet temperature, and pH within the range
of 6.0 to 9.0. By 1983 leaching plants must meet the same
standards as nonleaching plants. For all existing cement
manufacturing plants, the runoff of rainfall which derives
from the storage of materials, including raw materials,
intermediate products, finished products, and waste materials,
must meet effluent limitations of 50 mg/1 and pH within the
range at 6.0 to 9.0 except when the flow exceeds the 10
year, 24 hour rainfall event.
18. Cohrs, F.W. How the Newer Plants Handle Kiln Dust Dis-
posal. Rock Products. 58-59, 80-82, November 1971.
Abstract: An overview is given of dust collection, return
and wasting, with results of a questionnaire sent to 30
plants built after 1960 detailing the trend of -thinking
about dust and the dust handling methods employed. A
description is given of the wet dust disposal system at
Charlevoix, Michigan, giving the particulars of the system:
alkali reduction in the dust, neutralization of the
disposal (leachate) water, and suspended solids content
of the water (15 ppm). Reuse of the leached and dried dust
as a raw material for dry plants is suggested.
19. Rygaard, O. F. Utilization of Cement-kiln Dust. U.S.
Patent No. 3,206,526, September 14, 1965.
Abstract: Insufflation of dust as a cloud above the burner
pipe avoids obscuring optical pyrometry measurements of flame
and clinker. The cloud also helps insulate the upper side
of the kiln from radiated heat. Further, a uniform clinker
is produced because the dust is mixed with the clinkering
mass before its temperature reaches the reaction point.
41
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20. Siegert, L. D. Kilns Reuse Dust the Insufflation Way.
Rock Products. 52-54, 81, 84, February 1974.
Abstract: This is a discussion of methods of insufflation
of dust and parameters affecting or affected by insuffla-
tion, including fuel, flame emissivity, flame propagation,
exhaust gas velocity, dust loading, particle size, position
of insufflation pipe, and coating of refractories.
21. Dyatlov, I. P. Utilization of Dust Collected in
Electrostatic Precipitators. Tsement (Moscow).
28(3):18-19, 1962.
Abstract: The Kuvasaisk cement combine in Russia experi-
mented with techniques for returning collected dust to
their wet-process kiln. With 97% collection efficiency
in an electrostatic precipitator, the dust represented
10 to 20% of the dry mass of kiln feed. Adding dry dust
to the feed slurry containing 31-35% moisture resulted in
the formation of hard rings that interfered with the move-
ment of the charge through the kiln. The problem was
solved by making a slurry of the dust with 45 to 48% water.
The dust slurry and the normal slurry were mixed in a
scoop slurry feeder and introduced to the kiln via a batch
feeder.
22. Dersnah, W. R. and C. F. Clausen. Can That Dust be Used
Again? Pit and Quarry. 84-85, 88-91, September 1958.
Abstract: Problems associated with return of dust to
wet-process kilns are discussed. Methods of return
include hydration and regrinding, leaching, insuffla-
tion, and addition via scoops, feed pipes, vortex
feeders, and pug mills. Addition of molasses to inhibit
hardening is also discussed.
23. Goller, C. H., Jr. Is Dust Leaching Worthwhile? Pit
and Quarry, 122-123, August 1966.
Abstract: The four most popular ways to produce low-
alkali cement are: use low-alkali raw materials, waste
the dust, increase the amount of alkali in the dust and
gas, and leach alkalies from the dust to be returned to
the kiln. In comparison with the first three ways, the
disadvantages of leaching are: higher capital investment,
lower reliability, large water consumption, and water
pollution.
42
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24. Lindsay/ G. C. Don't Throw Away Dust. Rock Products.
65:87-89, 125, July 1962.
Abstract: Missouri Portland's reprocessing of kiln-dust
is described. Plant operating advantages are cited: less
mud-ring buildup, more uniform product allowing uniform
gypsum addition, reduction of alkali sulfate buildup on
electrostatic precipitator electrodes, and better control
of dust addition to kiln.
25. Quinn, E. L. and C. L. Jones. Carbon Dioxide. American
Chemical Society Monograph Series No. 72, 1936. p. 121-125.
Abstract: The action of carbonic acid on calcium compounds,
solubility of CaCO3 in water solutions of CO2, and relation-
ship of CO2 and pH in natural waters are explained.
26. Wilson, J. B. Controls Spark Waste Water Dilemma. Rock
Products. 75-76, 92, March 1973.
Abstract: The major water discharges from cement plants are
cooling water and water that has been in contact with kiln
dust containing soluble alkalies. Leaching of alkalies
may occur from runoff of rainwater from waste dust piles,
from dust-slurry disposal ponds, or from dust leaching
facilities. Leachate may be used to adjust the pH of sewage
plants or acid mine drainage. Carbonation of leachate reduces
its pH to levels acceptable for discharge.
27. Nishiwaki, T. Concentration of Electrolytes Prior to
Evaporation with an Electromembrane Process. In:
Industrial Processing with Membranes, Lacey, R. E., and
S. Loeb (ed.). New York, Wiley-Interscience, 1972.
p. 83-106.
Abstract: This book was written for engineers who wish
to determine whether membrane processes should be consider-
ed for a given situation and, if so, which process should be
used. It also offers theoretical and practical information
for the design and operation of membrane processing plants.
The use of electrodialysis to recover NaCl from sea water
is described in detail. From an initial concentration of
3%, the concentration of salt in the brine is raised to
about 20% with an expenditure of about 250 KW-hr per ton of
salt concentrated.
43
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28. Anonymous. Potash from Cement at the Riverside Portland Cement
Company. Metallurgical and Chemical Engineering. 16(12):701-
703, June 15, 1917.
Abstract: A process to recover 6 Ib of K2SOi* per bbl of clinker
manufactured for each 1% K20 in the raw mixture (theoretical
yield) gave, in fact, 2/3 of this amount. KF is formed when
CaF2 is added to the raw material and the temperature reaches
1100°C; this is above the KF boiling point and about 90%
volatilizes. The combustion gases convert this to K2SOi» and
the fluoride recombines with calcium in the dust. The dust is
leached and the leachate is filtered and evaporated to satur-
ation to precipitate KaSOi*. The CaF2 in the filter cake is
returned to the kiln feed.
29. Singleton, F. H. and J. W. Bruce. Improvements re-
lating to the Treatment of Inorganic Dust. British
Patent No. 1,131,354, October 23, 1968.
Abstract: A solvent extraction method for removing alkali
metals from cement-kiln dust as sulfates and chlorides is
described. The process relies on the solubilities of the
alkali sulfates and chlorides in various chloride and
sulfate solutions. Batch and continuous schemes use
compounds recovered in one step to prepare the solvent in
the next.
30. Patzias, T. Extraction of Potassium Oxide From Cement Kiln
Flue Dust. M.S.C.E. Thesis, Wayne State University, Detroit,
Michigan. 1959.
Abstract: Kiln dust is leached with hot water to increase
solubility of alkalies. Leached dust is suitable for return
to the kiln. K2SO«, is recovered from the leachate by cry-
stallization, and the supernatant is recycled to the leach-
ing system.
31. Patzias, T. Recovery of Potassium Sulfate from
Cement-kiln Flue Dust. U.S. Patent 2,991,154,
July 4, 1961.
Abstract: Cement rotary-kiln flue dusts are leached for
extraction and recovery of K2SOi». For example, cement
dust is drawn from bins under an electrostatic precipitator
and mixed with H2O in closed tanks. The steam pressure
is kept at 150 Ib/sq in. absolute, and the extraction is
completed in 30 min. The mixture is then filtered, and
the solution containing 4.5% K2SOi» is evaporated to 19.4%.
This solution is neutralized with H2SOi» and crystallized.
The K salt is centrifuged, and the mother liquor is
recycled to the evaporator. When 200 tons of flue dust
is extracted with a water-dust ratio of 3:1, 85% of the
K2SOU is recovered. The K salts can be worked up for use
in fertilizers.
44
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32. Heilmann, T. Treatment of Dust from Cement Kilns. British
Patent No. 1,145,827, March 19, 1969.
Abstract: Fractionation of dust in multistage electrostatic
precipitators is a method of removing the high-alkali dust
for use as a potash fertilizer and returning the coarse,
low-alkali dust to the kiln. Data on percentages of
potassium, sodium, sulfate and chloride vs_ particle size
are given.
33. Bade, E. Method of and Apparatus for Recovering Substances
with a High Alkali Percentage from the Flue Gases of Cement
Kilns. U. S. Patent No. 3,288,450, assigned to Polysius G.
M. B. H., November 29, 1966.
Abstract: Large particles of dust are recovered from flue
gases by cyclones and small particles by an electrostatic pre-
cipitator. The large, low-alkali particles collected in the
first cyclone are returned directly to the kiln with the feed,
The fine precipitator dust is then added to the still hot
flue gases where the volatile alkalies condense on the cooler
dust particles, increasing their size and weight. The alkali-
coated particles are collected in a second cyclone, and the
cooler gas with its uncoated dust passes through the preci-
pitator where the dust is collected for recycle to the hot
flue gases.
34. Kravchenko, I. V. and I. A. Fridman. Process of Removing
Volatile Compounds. Russian Patent 258,906, June 29, 1970.
Abstract: Volatile compounds, e.g., alkalies, are removed
from the gaseous effluent of cement kilns by preliminary
dedusting followed by cooling with finely dispersed water.
The gas stream is cooled to the temperature of condensation
of the volatile compounds — alkali sulfates 900-950°C,
carbonates 800-850°C, etc. The consumption of water for re-
moving the volatile alkalies is 0.08-0.09 kg water per kg
calcined charge. Full-scale experiments carried out in a
dry-process kiln produced a powder containing 70-80% alkali
carbonates and sulfates suitable for use in fertilizer.
35. Van Dornick, E. New Cement Process Offers many "Pluses".
Rock Products. 57, 89, August 1972.
Abstract: A heat exchanger is proposed to preheat incoming
gases above (1100°C), thus preventing condensation of vola-
tilized alkali within the kiln but allowing condensation and
recovery from the self-scouring heat exchanger outside the
kiln.
45
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36. Van Dornick, E. Will Kilns Give Way to Fluo-Solid Reactors?
Rock Products. 116, 138, September 1969.
Abstract: The Fluo-solid reactor is compared with rotary
kiln. No specific data are given because of the status of
a patent application.
37. Pyzel, R. Hydraulic Cement Process. U.S. Patent No. 3,013,786,
December 19, 1961.
Abstract: A process is claimed for production of portland
cement by maintaining reaction temperature in a fluidized
bed of raw materials in contact with the burning fuel. The
fuel can be pulverized coal suspended in the bed, carbonaceous
raw materials, or gas mixed with the fluidizing air stream.
Advantages claimed include lower capital cost due to smaller
equipment necessary, elution of volatilized alkalies away
from reacting mass, and small clinker size.
38. Polysius, G. M. B. H. Method of Recovering the Content of
Alkali Metal Compounds from Alkali-Rich Dust Obtained when
Producing Cement Clinker and Apparatus for Performing the
Same. British Patent No. 1,000,984, August 11, 1965.
Abstract: Dust collected from preheater gases at 100 to 300°C
is leached with water. The leachate is evaporated in a heat
exchanger and dried in a thin film evaporator. Heat for
evaporation comes from steam generated by exhaust gases from
the clinker cooler. Evaporation is carried out under partial
vacuum.
39. Deynat, G. Device for Continuous Extraction of Alkalies from
the Escape Gases of a Cement Kiln. U.S. Patent 3,503,187,
March 31, 1970.
Abstract: An array of endless chains is exposed to the
exhaust gases of a cement kiln, and alkali metal compounds
condense on the cool chains. The chains coated with alka-
lies are revolved out of the gas stream, and the alkalies
collected thereon are removed by immersion in a tank of water
which dissolves the compounds and cools the chain.
40. Schlauch, R. G. Method for the Production of Hydraulic Cement.
U.S. Patent No. 3,043,703, July 10, 1962.
Abstract: A means of condensing alkali vapors on cooled
tubes and recovering the alkalies is described. Alkalies
in the gases emanating from the reaction zone of a cement
kiln condense as a solid on tubes cooled with air or water.
The condensed alkalies are scraped from the surfaces of the
tubes and collected in a bin.
46
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41. Nordquist, E. A. and G. A. Heian. Alkali Removal via the
Grate-kiln System. Rock Products 7th International Cement
Industry Seminar. 17-27, 1971.
Abstract: Portions of kiln exhaust gases are cooled to 230°C
to solidify gaseous alkalies. Then the warm gases are used to
dry the pelletized feed. Alkalies in the clinker and recir-
culating in the kiln are reduced. Various configurations of
the traveling-grate preheater kiln with and without by-
pass and cooling of portions of gas stream are described.
42. Weber, P. Alkali Problems and Alkali Elimination
in Heat-Economizing Dry-Process Kilns. Zement-
Kalk-Gips (Wiesbaden, Germany). 17:335-44, August
1964.
Abstract: Investigation of alkali conditions in
11 Lepol kilns and 7 suspension-preheater kilns
showed that suspension preheaters allow very little
alkali (3 to 19%) to escape from the kiln system
into the dust collectors or the atmosphere. Lepol
kilns allow more alkali (34 to 100%) to escape so
that alkali content of the clinker is lower. Mater-
ial balance is used to develop an alkali cycle
factor that is a function of the volatility and
content of raw material alkalies and the amount
of residual alkali in the clinker.
43. Brachthauser, K. Process for Producing Substantially Alkali-
free Kiln Output when Burning Minerals Containing Difficult-
to-volatilize Alkali. U.S. Patent 3,365,521, January 23, 1968,
Abstract: A process is described for converting alkalies
to the more volatile hydroxide form by reaction with vaporized
water in the kiln.
44. Kiyonaga, K. and P. Wrampe. Method and Apparatus for Pro-
ducing Cement Clinker. U. S. Patent No. 3,584,848,
June 15, 1971.
Abstract: Cement-forming raw materials are introduced into
a swirling stream of hot gas in a cylindrical reaction
zone where the raw materials react to form clinkers and
where the gas stream holds the clinker particles in sus-
pension until the particles grow heavy enough to drop to
the lower portion of the reaction zone. Apparatus suitable
for carrying out the process is also described.
45. Wolfe, J. M. Kiln Dust - Properties and Handling. Pit
and Quarry. 136-7, 140-2, 145, March 1964.
Abstract: Kiln dust is difficult to handle because of its
fineness, excessive heat, aeration, stickiness, lumpiness,
and alkali content. Flow sheets are presented for a variety
of methods for discarding dust or returning it to the kiln.
47
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46. Trembly, F. J., J. A. Mihursky, and E. W. Hertz. Use of
Cement Plant Stack Dust as a Neutralizing Agent in Acid
Water Lakes. Trans. Northeast Wildlife Conf. 1:55-60,
1958.
Abstract: Cement dust, applied at 40 tons per acre, suc-
cessfully killed off the acidophilic vegetation in a bog
that was to become the bottom of a new lake. A study was
begun in 1958 on long term cement kiln dust neutralization
of some acidic lakes and ponds in Pennsylvania.
47. Farnham, W. Process of Clarifying Turbid Water Using
Cottrell Flour and Acidifying Coagulant. U.S. Patent 2,964,466,
December 13, 1960.
Abstract: Kiln-dust from the Oswego plant of Oregon Port-
land Cement, used as a partial of total replacement for lime as
a co-coagulant with alum, improved floe formation so that
three test waters were substantially clearer than when
treated with alum and lime. The dust successfully neu-
tralized the water to the required range of pH 6.1 to 6.9
and apparantly provided floe nucleation sites by virtue of
the very small insoluble particles in the dust.
48. Gorman, P. G. Cement Dust as an Absorbent for S02 Removal
from Stack Gases. Master of Science in Engineering Thesis-
Graduate School of University of Missouri. 1972.
Abstract: Cement dust was compared with lime and crushed lime-
stone as a sorbent for S02 from stack gases in a wet scrubber
slurry. The dust was found to be better than limestone and
almost as good as lime for sorption of S02 and even better
than lime when scaling problems are considered.
49. Emer, P. Formation of Foam on the Surface of Molten Glass
Baths. Glastech. Ber. (Frankfurt, Germany). 42:30, June 1969.
Abstract: Kiln dust can serve as a partial replacement for
the soda used in glass making. Decomposition of sulfate in
the melt is responsible for foaming problems, and the potassium
in cement kiln dust accelerates the decomposition, allowing
more rapid degassing.
50. C. W. Whittaker, C. J. Erickson, K. S. Love, and D. M. Carroll.
Liming Qualities of Three Cement Kiln Flue Dusts and a Lime-
stone in a Greenhouse Comparison. Agronomy Journal.
51:280-2, 1959.
Abstract: Three cement kiln flue dusts had about the same
soil liming qualities as pulverized limestone. In cultures
all receiving the same total amount of soluble potash, the
dusts produced alfalfa yields on initially acid soils equal
to or exceeding those produced by the limestone and had
similar effects on soil pH, potassium and calcium contents
of the crop, and on crop reduction through overliming.
48
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51. Carroll, D. M., C. J. Erickson, and C. W. Whittaker. Agronony
Journal. 56:373-76, 1964.
Abstract: Researchers in Beltsville, Md. evaluated kiln
dust from 21 cement plants as a substitute for agricultural
lime and found that it had about 80% of the soil neutrali-
zation power of lime. Kiln dust was found to be superior
to crushed limestone for some applications.
52. Bambergs, K. and R. Apenite. Cement Dust as a Lime
Fertilizer. Tr. Latv. Sel'skokhoz. Akad. (Latvia).
18:151-63, 1967.
Abstract: Cement dust containing 42-47% CaO (of which
44-59% was CaCO3, the rest Ca silicates), 2.57-2.64%
MgO and 1.3% available K20 was rotary-hoed into acidic
soils in the month of May. It was applied at 2-10
tons/ha, and supplemented with lime. If soil with
pH above 4.5 was used for neutral-soil plants, e.g_., sugar-
beets or corn, cement dust could fully replace lime,
but for plants growing in slightly more acidic soils,
e.g., potatoes or rye, cement dust addition could
be 50-60% of total lime.
53. Simakin, A. I. Agrochemical Properties of Slime Dust
of Cement Plants. Vestn. Sel'skokhoz. Nauk. Ves.
Akad. Sel'skokhoz. Nauk (Budapest). 8 (5):62-4, 1963.
Abstract: Slime dust of cement plants proved useful
as a fertilizer on acidic soils. A typical composition
on air-dry basis is N 0.2, P205 0.1, and K20 15.4%.
Trace elements include Mg 1, Mn 0.03, Pb 0.03-0.1,
Ag 0.001, Ba 0.01-0.03, Be 0.001, Cr 0.003, Ti 0.1-0.3,
V 0.003, Zr 0.001 and Sr 0.1%. It also had insecticidal
properties.
54. Kobeleva, E. N., N. N. Popova, and L. G. Shvetsova, Cement
Dust - A Valuable Potassium Fertilizer for Potatoes. Trudy
Sverdlovsk. Sel'skokhoz. Inst. (Sverdlovsk, USSR).
15:59-68, 1969.
Abstract: Cheap potassium fertilizer usually contains an
appreciable amount of chloride which can markedly interfere
with the development and yield of potatoes, and better grades
are too expensive for use on potatoes. The high-alkali fraction
of cement dust, which has essentially no chloride, was found
to be an inexpensive and acceptable substitute fertilizer.
49
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55. Rogalev, I. E. Improved Forms of Potassium-Ceinent Dust
and its Effect on Potato, Peas, Flax, and some other
Crop Yields. Agrokhimiya (Moscow). 56-9, January, 1966
Abstract: Three forms of K-cement dust
were used to fertilize a heavy loam podzol
soil growing potatoes, peas, and flax and a light
sandy soil growing corn. The content of K2O in
the three K-cement dusts were 34.9% (in the sulfate
form), 40.3% (in the carbonate and sulfate forms),
and 41.0% (in a reduced-carbonate and sulfate forms),
respectively. It was established that these forms
of dusts had no greater effect on yield than ordin-
ary mineral fertilizers. In their effect on the
quality of the crops, these K-cement dusts have
proven to be superior to KC1. As a result of dust
applications, the content of starch in the potato
tubers increased 1.3-1.6% compared to results ob-
tained from an application of KC1. The same differ-
ences were found for peas (an increase in weight of
grains) and flax (an increase in fiber and straw).
The intensity of absorption of K in the growth phase
from the K-cement dust does not substantially differ
from that obtained by the application of ordinary
mineral K fertilizers.
56. Litynski, T., K. Mazur, and A. Siekanski. Fer-
tilization of Potato Fields with Cement-kiln Dust.
Zesz. Nauk. Wyzszej Szkoly Rolniczej, Krakow,
Rolnictwo (Warsaw, Poland) 5:85-95, 1958.
Abstract: Crops of potatoes exactly similar in
quantitative respects were obtained by using cement-
kiln dust or 40% K salts as a K fertilizer. Starch
content in potato tubers was higher in the case of
cement-kiln dust. The favorable effect on starch
content is probably due to K being present in the
sulfate form. Sulfate ions, unlike chloride ions,
have a contracting effect on the colloids of the plasma;
this causes a rise in starch content of potatoes.
57. Litynski, T., and K. Gorlach. Fertilizing Value of
Cement Plant Flue Dust Dependent on Soil Reaction.
Roczniki Nauk Ronlniczych, Ser. A. (Warsaw, Poland).
90 (1):113-30, 1965.
Abstract: Two problems were investigated: (1) whether
and to what extent the presence of Ca in cement plant
flue dust influences its K fertilizing properties, and
(2) to what extent the fertilizing value of the flue
50
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dust changes in relation to the pH value of the soil.
The experiments were carried out under strictly con-
tolled conditions by a pot culture of sunflower/ oats,
white mustard, and buckwheat. It has been ascertained
that Ca present in cement plant flue dust favorably
influences the uptake of K from it, and at the same time
it creates more favorable conditions for plant develop-
ment by reducing the soil acidity. On acidic soils the
fertilizing value of flue dust vastly exceeds that of the
40% K salt fertilizer. If however, the pH of the soil
is raised by liming, the uptake of K from the flue dust
remains practically unchanged while the uptake of K from
the K salt fertilizer increases. The reason for this
phenomenon may be attributed to different solubility of K
in both types of fertilizer and (or) to the antagonism
between Ca and K. In general, the raising of the soil
pH by liming increases the availability of K in it.
58. Hudig, J., and J. P. Planje. The Cement Dust of the Cement
Industry as Fertilizer. Landbouwkund. Tijdschr. (Wageningen,
Netherlands). 48:593-624, 1936.
Abstract: Comparative yields of oats fertilized with cement
dust, CaCOa, R^SOi, and K2CO3 separately and in various com-
binations are given. The cement dust contained about 4% K
in one case and 10% in another. The content of Ca in the
form of silicate and carbonate was about 40%. Both Products
had about the same effect as combinations of limestone and
K2SOi». The cement dust does not add superfluos mate-
rial to the soil, as most artificial fertilizers do. The
authors consider the application of this material as an
advantage in cases where K- and Ca- poor soils are to be
brought back to profitable production.
59. Litynski, T. Cement-kiln Dusts and their Value for Agri-
culture. Zesz. Nuak. Wyzszej Szkoly Rolniczej. Krakow,
Rolnictwo (Wroclaw, Poland). 4:3-27, 1958.
Abstract: Cement-kiln dusts from rotary kilns in the
production of portland cement may be an important source
of K for plants. The dusts contain approximately 9% K2O
(70% soluble in HjO, the rest soluble in 2% citric acid)
and can be enriched by adding aluminosilicates to the crude
mixture. K in these dusts occurs as K2SCK, which by some
plants is preferred to KC1. The important other compo-
nents of the dust are sulfates, CaCOj, and colloidal silica.
Thus, the dust is a low-percentage K-Ca fertilizer good
for acid soils with weak structure. Pot and field experi-
ments showed it equal to, or better than, KC1 and 40% K
salts as a source of K. Mixed peas-and-oats crops con-
51
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tained more proteins (about 2% more than crops grown on the
latter mixture). The cement dust increased especially the
content of starch in potato tubers. It was a good K fer-
tilizer for meadows, where in two experiments protein
synthesis was enhanced.
60. Litynski, T. Flue Dusts from Cement Rotary Kilns as
Chemical Fertilizers. Przemysl Chem. (Warsaw, Poland).
40:260-2, 1961.
Abstract: The potential use of flue dust from cement
rotary kilns containing SiO2, A1203, CaO, and KjO was
investigated in Poland. Potassium compounds in dusts
are partly soluble in H2O and about 80% soluble in 2%
citric acid. Field and pot tests showed good fertilizing
properties for clinker dusts which contained SiO2 24.16,
CaO 19.94, and K20 13.36%. Fertilizing action of this dust
compared favorably with that of equivalent quantities of
40% H2O-soluble standard K fertilizer. It produced more
proteins in fodder, starch in potatoes, and sugar in sugar
beet roots. Cement dust can be used as chemical ferti-
lizer, preferably in a granulated form as a low grade K
fertilizer.
61. Hargett, N. L. 1972 Fertilizer Summary Data. National Fer-
tilizer Development Center, Tennessee Valley Authority,
Muscle Shoals, Alabama. 1972.
Abstract: Agricultural materials (limestone, potash, etc) are
listed by region and State with consumption from 1950
through 1971.
62. Anonymous. Commodity Data Summaries. Bureau of Mines,
Department of Interior. January 1974.
Abstract: Data on production, consumption, and value and
forecasts for 95 minerals, metals, and fuels, including
cement, lime, potash, phosphate rock and nitrogen compounds.
63. Lodge, F. S. Potash in the Fertilizer Industry. Ind Eng
Chem, 30:878-882, August 1938.
Abstract: Sources of potash that have been used in the manu-
facture of fertilizer are described.
64. Rouse, R. D. Potassium Requirements of Crops on Alabama Soils.
Bulletin 324, Agricultural Research Station, Auburn Univer-
sity, March 1960.
Abstract: An analysis of 50,000 Alabama soil samples shows
that 75% need a fertilizer with equal amounts of P and K and
18% need more K than P. Sources of K are listed and crop
requirments of and response to K are discussed.
52
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65. Anonymous. Potassium for Agriculture. American Potash Institute,
Revised January 1965.
Abstract: History of potassium in agriculture, function in
plants and animals, and relationship to other nutrients are
given as introduction. Description of various potassium
fertilizer materials, production methods, application methods,
and crop responses to potassium are given.
66. Alabama Legislature (Young and Smith), Alabama Fertilizer Law
of 1969. Act 434, Regular Session, 1969.
Abstract: This act of the Alabama Legislature sets forth the
regulations applicable to the manufacture and sale of ferti-
lizer, fertilizer materials, and other plant food and soil
conditioning materials. The regulations follow the recommen-
dations of the Association of American Plant Food Control
Officials.
67. Association of American Plant Food Control Officials.
Official Publication No.27 Lafayette, Indiana, 1974.
p. 37.
Abstract: Officially adopted documents of the Association
included in the Uniform State Fertilizer Bill are; Rules
and Regulations, Statement of Uniform Interpretation and
Policy, Official Fertilizer Terms, and Definitions of
Fertilizer Materials. Definition C-13 reads in part,
"Waste lime, by-product lime is any industrial waste or
by-product containing calcium or calcium and magnesium
in forms that will neutralize acids."
68. Dymshits, R. A., N. N. Tikhomirova, E. Ya. Gryazina,
E. N. Ostapenko, and L. V. Nelidova. Granular Fertilizers
from Cement Dust. Russian Patent 220, 277, June 28, 1968.
Abstract: Granular fertilizers are prepared from cement
dust with a high K2CO3 content by rolling the dust with
an additive of water or a solution of this dust. To pre-
pare non-hygroscopic, mechanically strong granules, the
granules are treated with C02 or gases containing C02.
69. Nudel'man, B. I., S. Tokhtakhodzhaev, and M. N.
Nabiev. Preparation of Quality Standardized
Potassium Fertilizers During the Production of
a Portland Cement Clinker by Means of Chlorina-
tion Roasting. Dokl. Akad. Nauk. Uzb. SSR (Tash-
kent, 24(10):30-1, 1967.
Abstract: K from the cement kiln charge can be
almost fully recovered in the dust collected by
electrostatic precipitators when 0.61-1% of
NaCl or CaCl2 is added to the charge. K, present
in various compounds and minerals, is converted
53
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into KC1 by their interaction with the added Cl
and sublimed off. The K20 content of the flue
dust of the Kuvasai and Dushanbe plants is thus
increased from 6.0 and 7.1 to 13.81 and 20.72%,
respectively. The dust can be used efficiently
as K20- and CaO-bearing raw material by the local
fertilizer industry.
70. Tokhtakhodzhaev, S. T., M. N. Nabiev, and B. I. Nudel'man,
Process For Munufacturing Fertilizer. Russian Patent No.
176,595, November 17, 1965.
Abstract: The familiar process for manufacturing fertilizer
from cement dust consists of recovering the dust obtained
from calcining the cement slurry, mixing it with water and
neutralizing the alkaline content with phosphoric acid in
a mixture of mineral acids. With the goal of manufacturing
a fertilizer with a high content of soluble potassium salts,
NaCl is added to the cement slurry before it is calcined.
The cement dust is recovered in an electrostatic precipitator
and mixed with water. The solution obtained is freed from
insoluble particles and is mixed with a nitric acid-
phosphate extract. The solution may be applied as a liquid
ternary N-P-K fertilizer or converted to a solid fertilizer.
71. Anonymous, Potassium Phosphate Fertilizer Use Expands. Chem.
Eng. News. 17-18, September 10, 1973.
Abstract: Pennzoil's plant in Hanford, Calif, is doubling
its production of ?20s to 60 tons/day with plans to produce
a 0-50-40 fertilizer by next year. Rising production costs
have stimulated the replacement or augmentation of organic
and nitrogen fertilizers with potassium-phosphorus fertilizers,
Some production costs and material values are given.
54
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-670/2-75-043
3. RECIPIENT'S ACCESSIOf*INO.
4. TITLE AND SUBTITLE
DISPOSAL AND UTILIZATION OF WASTE KILN DUST
FROM CEMENT INDUSTRY
5. REPORT DATE
May 1975; Issuing Date
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
Thomas A. Davis and Don B. Hooks
8. PERFORMING ORGANIZATION REPORT NO.
SORI-EAS-74-237
I. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
2000 9th Avenue, South
Birmingham, Alabama 35205
10. PROGRAM ELEMENT NO.
1BB036; ROAP 21BET; Task 11
11. CONTRACT/GRANT NO.
R-801872
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A survey that included 60% of the cement-manufacturing plants in the
United States was made to determine the fate of dust collected from the
gases emanating from cement kilns. Because of high alkali content,
large quantities of the dust cannot be returned to the cement-making
process. A survey was made of the literature in the United States and
Europe pertaining to handling, reclaiming, and utilizing the collected
dust. Abstracts of 71 references are included in the Appendix. Acid
neutralization capacity and potash content make the dust valuable for
application to farmland, and the potential market for agricultural use
alone could consume all of the waste dust that is now being discarded.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
*Portland cements
*Dust control
Alkali aggregate reactions
Fertilizers
Potassium inorganic compounds
13B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
63
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
55
U.S. GOVERNMENT PRINTING OfFICE: 1975-657-593/5375 Region No. 5-11
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