&EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-79-012
March 1979
Air
A Review of Standards
of Performance for New
Stationary Sources -
Portland Cement Industry
-------
EPA-450/3-79-012
A Review of Standards
of Performance for New
Stationary Sources -
Portland Cement Industry
by
Kris W. Barrett
Metrek Division of the MITRE Corporation
1820 Dolley Madison Boulevard
McLean, Virginia 22102
Contract No. 68-02-2526
EPA Project Officer: Thomas Bibb
Emission Standards and Engineering Division
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1979
-------
This report has been reviewed by the Emission Standards and Engineering
Division, Office of Air Quality Planning and Standards, Office of Air, Noise
and Radiation, Environmental Protection Agency, and approved for publica-
tion . Mention of company or product names does not constitute endorsement
by EPA. Copies are available free of charge to Federal employees, current
contractors and grantees, and non-profit organizations - as supplies permit
from the Library Services Office, MD-35, Environmental Protection Agency,
Research Triangle Park, NC 27711; or may be obtained, for a fee, from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
VA 22161.
Publication No. EPA-450/3-79-012
ii
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ABSTRACT
This report reviews the current Standards of Performance for New
Stationary Sources: Subpart F - Portland Cement Plants. It includes
a summary of the current particulate matter standard, the status of
current applicable control technology, and the ability of plants to
meet the current particulate matter standard. No changes to the
existing standard are recommended, but EPA should continue evaluation
of sulfur oxide and nitrogen oxide controls with a view toward incor-
porating these emissions under the scope of the standard at a later
date.
iii
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TABLE OF CONTENTS
Page
1.0 EXECUTIVE SUMMARY 1-1
1.1 Best Demonstrated Control Technology 1-1
1.2 Current Particulate Matter Emission Levels
Achievable with Best Demonstrated Control Technology 1-2
1.3 Economic Considerations Affecting the NSPS 1-3
1.4 Future Additions to the Standard 1-3
2.0 INTRODUCTION 2-1
3.0 CURRENT STANDARDS FOR PORTLAND CEMENT PLANTS 3-1
3.1 Affected Facilities 3-2
3.2 Controlled Pollutants and Emission Levels 3-2
3.3 Testing and Monitoring Requirements 3-3
3.4 Regulatory Basis for Any Waivers, Exemptions, or
Other Tolerances 3-4
4.0 STATUS OF CONTROL TECHNOLOGY 4-1
4.1 Scope of Portland Cement Operations 4-1
4.1.1 Geographic Distribution 4-1
4.1.2 Technological Trends in Production 4-4
4.2 Production of Portland Cement 4-6
4.3 Particulate Matter Characterization 4-10
4.4 Control Technology Applicable to the NSPS for
Portland Cement Plants 4-17
4.4.1 Cyclones 4-17
4.4.2 Electrostatic Precipitators 4-19
4.4.3 Fabric Filters 4-21
4.4.4 Gravel Bed Filters 4-22
4.4.5 Wet Scrubbers 4-25
4.5 Comparison of Levels Achievable with Best
Demonstrated Control Technology Under the Present NSPS 4-25
5.0 INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS 5-1
5.1 Test Coverage in the EPA Regions 5-1
5.2 Analysis of the NSPS Test Results 5-1
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TABLE OF CONTENTS (Concluded)
Page
5.2.1 Control Technology Used to Achieve Compliance 5-7
5.2.2 Analysis of Compliance Test Data 5-9
5.3 Indications of the Need for a Revised Standard 5-11
5.3.1 Particulate Matter Standard for Portland
Cement Kilns 5-11
5.3.2 Particulate Matter Standard for Portland
Cement Clinker Coolers 5-12
5.3.3 Opacity Standards 5-12
6.0 ANALYSIS OF THE IMPACTS OF OTHER ISSUES ON NSPS 6-1
6.1 Industry Economics and New Construction 6-1
6.2 Excessive Emissions During Cement Kiln Startup 6-14
6.3 Raw-Mill Bypass 6-15
6.4 Use of Alternate Fuels 6-16
6.5 Gaseous Emissions 6-17
6.5.1 Carbon Monoxide 6-17
6.5.2 Fluorine 6-17
6.5.3 Hydrocarbons 6-17
6.5.4 Hydrogen Sulfide 6-18
6.5.5 Nitrogen Oxides 6-18
6.5.6 Sulfur Oxides 6-19
7.0 FINDINGS AND RECOMMENDATIONS 7-1
7.1 Findings 7-1
7.1.1 Process Emission Control Technology 7-1
7.1.2 Economic Considerations 7-1
7.1.3 Gaseous Emissions 7-2
7.2 Recommendations 7-2
7.2.1 Opacity NSPS 7-2
7.2.2 Particulate Matter NSPS 7-2
7.2.3 Gaseous Emissions 7-3
8.0 REFERENCES 8-1
vi
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LIST OF ILLUSTRATIONS
Figure Number Page
4-1 Geographic Distribution of Portland
Cement Plants (November 1978) 4-2
4-2 Production of Portland Cement 4-7
4-3 Particle Size Distribution of Cement Dust 4-16
4-4 Resistivity of Dust from Portland Cement
Kilns and Coolers 4-18
4-5 Rexnord, Inc. Gravel Bed Filter 4-24
5-1 Portland Cement Plants NSPS Compliance
Test Results Kiln Particulate Matter
Emissions 5-5
5-2 Portland Cement Plants NSPS Compliance
Test Results Clinker Cooler Particulate
Matter Emissions 5-6
6-1 Construction Spending and Cement Output 6-2
6-2 U.S. Portland Cement Capacity and
Production 6-3
6-3 Cement Plant Clinker Capacity by Age
of Kiln 6-5
6-4 Cement Plant Kiln Age 6-7
vii
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LIST OF TABLES
Table Number Page
4-1 Portland Cement Clinker Production
Capacity 4-3
4-2 Energy Consumption of Portland Cement
Manufacturing Processes 4-5
4-3 Summary of Major Sources of Cement
Dust Emissions 4-11
4-4 Typical Composition of Dried Kiln Dust 4-13
4-5 Particle Size Distribution of Alkalies
in Kiln Dust 4-14
^ 4-6 Ranges of Dust Emission from Control
Systems Serving NSPS Portland Cement Plants 4-27
^ 5-1 NSPS Compliance Test Results for
Portland Cement Plants 5-2
t- 5-2 Results of Using Various Particulate
Matter Control Technologies at Portland
Cement Plants 5-8
5-3 Analysis of Portland Cement Plant
Compliance Test Data 5-10
6-1 Portland Cement Clinker Production
Capacity 6-10
6-2 Announced Cement/Clinker Capacity
Changes as of November 15, 1978 6-11
viii
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1.0 EXECUTIVE SUMMARY
The objective of this report is to review the New Source Per-
formance Standards (NSPS) for portland cement plants in terms of
developments in control technology, economics, and new issues that
have evolved since the original standard was promulgated in 1971.
Possible revisions to the standard are analyzed in the light of com-
pliance test data available for NSPS-affected facilities. The review
includes the particulate matter mass emission limit for cement kilns
and clinker coolers, as well as the opacity standard for these and
other sources within the cement plant. The following paragraphs sum-
marize the results and conclusions of the analysis, as well as recom-
mendations for future action.
1.1 Best Demonstrated Control Technology
The portland cement industry was one of the first industries to
have a NSPS promulgated to control their emissions due to the large
quantity of particulate matter emitted. The cement kiln and clinker
cooler are the primary sources of those emissions. The original
standard was based on greater than 99 percent removal of particulate
matter from the exhaust streams of the kiln and cooler by fabric
filter baghouses. Electrostatic precipitators (ESPs) used at that
time were incapable of meeting the new standard. Since that time,
ESPs have been improved to the point where they also are capable of
*This report is based on data that were available in November 1978.
1-1
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controlling emissions from cement kilns to satisfy NSPS requirements.
Gravel bed filters and one wet scrubber have been used successfully,
in addition to the baghouse, to control emissions from clinker
coolers.
There are 49 NSPS affected cement kilns and clinker coolers
operating. Data were available on 29 kilns and 20 coolers, all of
which were in compliance. Electrostatic precipitators were installed
on 12 kilns, baghouses on 16 kilns and 16 coolers, gravel bed filters
on 3 coolers, and a wet scrubber was installed on 1 cooler (Data for
one kiln compliance test did not include the type of control.)
1.2 Current Particulate Matter Emission Levels Achievable with Best
Demonstrated Control Technology
Of the 49 known NSPS-affected cement kilns and clinker coolers,
47 are in compliance with the 0.15 kg/Mg kiln feed (kiln) and 0.05
kg/Mg kiln feed (cooler) emission limits. One completed kiln has
only recently been tested and data are not available; and one fa-
cility has notified its state authority that it cannot meet the stan-
dard. The number of sources with other NSPS-affected facilities is
unknown, although there are none that are not in compliance with the
applicable 10 percent opacity standard.
The mean emission rate for 29 cement kilns was 0.073 kg/Mg dry
kiln feed (range 0.013 to 0.142). There was a random spread of test
results within the range of values, indicating that no control or
process technology was consistently better at reducing emissions.
1-2
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The mean emission rate for 20 clinker coolers was 0.024 kg/Mg
dry kiln feed (range 0.005 to 0.061). Again, there was no correla-
tion among control, process, and emission level.
There are no data to indicate the effect of time on the emission
levels measured. It can be assumed that emissions increase as con-
trol equipment deteriorates with age.
1.3 Economic Considerations Affecting the NSPS
The cement industry has been thoroughly investigated by the
Council on Price and Wage Control because of its influence on the
construction industry. Although the Council concluded that pollution
controls are not the most important factor in cement plant closings,
it did state that a large increase in pollution abatement costs could
influence new construction. This is very important in a period when
regions of the U.S. are experiencing a shortage of cement production
capacity.
Because of the maximum capabilities of the control technologies
and the closeness of many of the compliance tests to the standard, it
is recommended that the present level of emissions specified in the
current NSPS not be changed.
1.4 Future Additions to the Standard
The portland cement industry generates large quantities of
gaseous pollutants, primarily NOX and S02. The sulfur dioxide
emissions are reduced approximately 70 percent by sorption in the
1-3
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process and are incorporated in the clinker, or removed with the col-
lected dust.
Nitrogen oxides, however, are emitted to the atmosphere with-
out control. Using EPA NOX emission factors, it is estimated that
as much as 93,000 metric tons (Mg) of NOX were emitted by cement
plants in 1977. Presently, there are no economically feasible con-
trols for these emissions.
It is recommended that research be conducted to determine the
actual cement kiln 802 an<* N0x emission levels and that the effect
of process changes, such as flash calciners, on NOX generation be
determined.
1-4
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2.0 INTRODUCTION
Section 111 of the Clean Air Act, "Standards of Performance
for New Stationary Sources," requires that "The Administrator shall,
at least every four years, review and, if appropriate, revise such
standards following the procedure required by this subsection for
promulgation of such standards." Pursuant to this requirement, the
MITRE Corporation, under EPA Contract No. 68-02-2526, is to review
10 of the promulgated NSPS including portland cement plants.
The purpose of this report is to review the current portland ce-
ment plant standards and to assess the need for revision on the basis
of developments that have occurred or are expected to occur in the
near future. This report addresses the following issues:
1. Review of the definition of the present standard.
2. Review of the portland cement industry and the status of
applicable control technology.
3. Analysis of the cement plant particulate matter emission
test results and a review of the level of performance of
best demonstrated control technology for emission control.
4. Review of the portland cement industry economics and pro-
jections of new kiln construction.
5. Discussion of cement plant gaseous emissions and control
technology presently available.
Based on the information contained in this report, a set of
findings is presented and specific recommendations are made for
changes in the NSPS. In addition, recommendations are made for R&D
studies on gaseous emissions.*
This report is based on data that were available in November 1978.
2-1
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3.0 CURRENT STANDARDS FOR PORTLAND CEMENT PLANTS
In accordance with the Clean Air Act of 1973, New Source Per-
formance Standards (NSPS) were promulgated that specified allowable
levels of particulate matter emissions from portland cement plants.
Any portland cement plant which commenced construction on or after
August 17, 1971, became subject to the NSPS.
The NSPS for portland cement plants were originally promulgated
on December 23, 1971. On June 29, 1973, the U.S. Court of Appeals
for the District of Columbia remanded the NSPS for portland cement
plants to the Environmental Protection Agency as a result of ques-
tions regarding the standards, in particular opacity standards (40
CFR 60.60). Petitioned by the Portland Cement Association with re-
spect to the opacity standards, the Court of Appeals identified two
aspects of the standards as bases for concern: (1) the inherent
reliability of opacity standards, i.e. whether measurements of opac-
ity can be made with reasonable accuracy, and (2) the achievability
of the opacity standard set for portland cement plants. EPA's re-
sponse to the remand concluded that the opacity standard is a reli-
able, valid and necessary standard that meets the requirements of
Section 111 of the Clean Air Act, and that the standards other than
the opacity standard should not be changed (EPA, 1974). However,
EPA did conclude that the opacity standard should be revised. Where
the opacity standard had originally been 10 percent for all affected
facilities, it was subsequently modified on June 14, 1974, to 20
3-1
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percent for cement kilns and 10 percent for all other affected fa-
cilities (EPA, 1974). EPA's position was supported by the Court.
3.1 Affected Facilities
The facilities of a portland cement plant that are subject to
NSPS are the: kiln, clinker cooler, raw mill system, finish mill
system, raw mill dryer, raw material storage, clinker storage, fin-
ished product storage, conveyer transfer points, bagging, and bulk
loading and unloading systems. Also affected by NSPS are modified
Portland cement plants (a plant that has undergone a physical or
operational change that increases the emission rate of any pollutant
regulated by the standard) and reconstructed portland cement plants
(those in which the cost of replacement components exceeds 50 percent
of the cost of building a comparable new facility).
3.2 Controlled Pollutants and Emission Levels
The NSPS for portland cement plants require the control of par-
ticulate matter emissions. As stated in 40 CFR 60.62, no owner or
operator of a portland cement plant under construction on or after
August 17, 1971, shall discharge or cause the discharge into the
atmosphere from any kiln any gases which:
1. Contain particulate matter in excess of 0.15 kg/Mg
(0.30 Ib/ton) of feed to the kiln, or
2. Exhibit 20 percent opacity or greater;
t
or discharge to the atmosphere from any clinker cooler any gases
wh i ch:
1. Contain particulate matter in excess of 0.050 kg/Mg
(0.10 Ib/ton) of feed (dry basis) to the kiln, or
3-2
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2. Exhibit 10 percent opacity or greater;
or discharge to the atmosphere from any affected facility other than
the kiln and clinker cooler any gases which exhibit 10 percent opac-
ity, or greater.
3.3 Testing and Monitoring Requirements
A performance test of a portland cement plant must be conducted
within 60 days after the facility has achieved its maximum production
rate and not later than 180 days after its initial startup. Such a
test consists of three separate runs of which the arithmetic mean is
the result for determining compliance with NSPS. If one of the runs
is lost due to forced shutdown, failure of an irreplaceable portion
of the sample train, extreme meteorological condition, or other
circumstances beyond the operator's control, the arithmetic mean of
the remaining two runs may suffice as the performance test result,
upon approval by the Administrator.
Test methods to be used to determine compliance with NSPS are:
1. Method 5 for the concentration of particulate matter and the
associated moisture content, with minimum sampling times of
1 hour and minimum volumes of 0.85 dscm (kiln) and 1.15
dscm (cooler)
2. Method 1 for sample and velocity traverses
3. Method 2 for velocity and volumetric flow rate
4. Method 3 for gas analysis.
The owner or operator of a portland cement plant subject to NSPS
is also required to record the daily production rates and kiln feed
rates. •
3-3
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3.4 Regulatory Basis for Any Waivers, Exemptions, or Other
Tolerances
Compliance with the mass emission standard is determined by the
results of performance tests (Reference Method 5). These tests are
conducted only on an affected facility that is operating at a level
representing normal operations. Operations during periods of start-
up, shutdown, and malfunction are specifically exempted as nonrepre-
sentative operations.
The opacity standard applies at all times except during periods
of startup, shutdown, and malfunction. Opacity readings of portions
of plumes that contain condensed, uncombined water vapor are not used
to determine compliance. Although these exemptions apply to all
affected facilities, owners and operators are required to maintain
and operate their facilities in a manner consistent with good air
pollution control practice for minimizing emissions, even during the
exempt periods.
3-4
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4.0 STATUS OF CONTROL TECHNOLOGY
4.1 Scope of Portland Cement Operations
4.1.1 Geographic Distribution
There are currently 53 cement companies producing portland
cement in the U.S. The largest producers are Ideal (6.5% of total
capacity), Lone Star (6.2%), Martin Marietta (5.1%), and General
(5.0%). The 53 companies operate 158 cement plants throughout the
U.S. with the largest single plant having a total cement capacity
of 2,161,000 Mg per year. The smallest plant has an annual cement
capacity of 50,000 Mg (Portland Cement Association, 1978).
The industry also operates plants solely with clinker grinding
facilities. These plants (eight in all with a total annual cement
capacity of 2,614,000 Mg) use either imported or domestic clinker as
feed material and are very important during periods of high demand
when imports increase to make up for a lack of domestic clinker
producing capacity.
The geographic distribution of the cement plants is shown in
Figure 4-1. Cement plants are found in nearly every state because
of the high cost of transportation. The actual clinker capacity of
these plants is also distributed throughout the U.S., although some
regions have little capacity due to a lack of demand. Table 4-1
shows the distribution of clinker production capacity in each EPA
Region. The clinker capacity in New England, the Northwest, and
Midwest is dwarfed by the capacity of the rest of the country.
4-1
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• Portland Mmmt piMt
• Grinding only ptanU
Rt +L QBOalUPHtC MSTMIUTION 0^ POATLANO CEMENT PUINTS
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TABLE 4-1
PORTLAND CEMENT CLINKER PRODUCTION CAPACITY
to
EPA
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
TOTAL
Clinker,
Capacity
(103 Mg/yr)
None
4,248
12,159
14,852
13,337
11,889
10,431
3,942
11,789
2,333
84,980
New
No.
None
1 Dry
3 Dry
7 Dry
4 Wet
9 Dry
2 Dry
3 Wet
4 Dry
1 Dry
3 Wet
2 Dry
1 Wet
None
29 Dry
11 Wet
Kilns 1972-19783
Capacity (103 Mg/yr)b
490
1,602
3,883
1,744
4,215
753
785
1,123
509
863
720
441
-
13,295
3,833
No.
None
None
None
1 Dry
1 Dryd
1 Dry
1 Dryd
2 Dry
1 Dryd
1 Dry
1 Dryd
1 Dry
1 Dry
1 Dry
1 Wet
3 Dry
3 Dry
1 Dryd
19 Dry
1 Wet
£
Announced Growth
Capacity (103 Mg/yr)
-
-
100
1,361
518
499
236
726
205
907
131
603
122
81
483
1,406
454
7,751
81
Yeara
-
-
79
81
80
79
79
80
80
NA
78
80
79
79
79
NA
79
NA = Not Announced
^Completion Year
As of December 31, 1977
JjAs of November 15, 1978
New plant
Source: Portland Cement Assn., 1978.
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Although many areas of the country are presently experiencing cement
shortages and delays, announced capacity increases in these areas are
still small. Table 4-1 also shows the trend toward new construction
of dry process kilns. During the last 7 years, nearly three times as
many dry process kilns as wet process kilns have been built (29 dry
vs. 11 wet), for an increase in clinker capacity of 17,128,000 Mg/yr
(13,295,000 dry vs. 3,833,000 wet).
4.1.2 Technological Trends in Production
The portland cement industry is very energy intensive with
energy costs accounting for approximately 40 percent of the cost of
cement. A number of new innovations have been made in the production
process to increase energy efficiency. The dry process can be twice
as energy efficient as the wet process. The dry process uses driers
or combined drying/grinding units to reduce the raw material free
moisture content to less than 1 percent. The wet process is very
similar to the dry process except that water is added to the raw
materials before or during grinding so that the kiln feed material is
a slurry. Energy savings are realized immediately because there is
no water to evaporate from the feed material. For this reason,
almost all new and planned construction will use the dry process.
Additional large savings can be realized by using preheatero, espe-
cially suspension preheaters. Table 4-2 shows the energy savings
attributable to the various new technologies.
These process changes have both positive and negative effects on
particulate emissions. The replacement of wet process units with dry
4-4
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TABLE 4-2
ENERGY CONSUMPTION OF PORTLAND CEMENT MANUFACTURING PROCESSES
Energy Energy Reduction
Consumption Over Average
Process (lO^ BTU/ton) Current Practice (%)
Wet Process
Long Kiln (average current practice) 5.94
Calcinator and short kiln 4.68 26.9
Preheater and short kiln 3.60 43.8
Dry Process
Long Kiln (average current practice) 4.68
Suspension preheater and short kiln 3.15 50.8
Grate preheater and short kiln 3.42 46.6
SOURCE: Ketels et al., 1976.
4-5
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process units increases emissions, particularly in the grinding, mix-
ing, blending, storage, and feeding of raw materials to the kiln.
The suspension preheater, on the other hand, tends to decrease
particulate emissions due to its multicyclone construction. It also
ensures more thorough contact of the kiln exhaust gases with the feed
material which may increase sorption of sulfur oxide from the exhaust
on the feed.
4.2 Production of Portland Cement
There are four distinctive steps in the production of portland
cement:
• Quarrying and crushing of raw materials
• Grinding and blending raw materials
• Clinker production
• Finish grinding and packaging.
These four steps are depicted in Figure 4-2. The production of port-
land cement begins with the quarrying of raw materials. In the
initial step, cement rock, limestone, clay, and shale are generally
mined from open pit quarries at or near the cement plant. The large
rocks are crushed to a final size of 2 to 2.5 cm and stored for
future use in piles or compartments.
The second production step is the preparation of raw materials
for feeding to the kiln (pronounced "kill"). The raw materials are
ground to approximately 200 mesh either before, during, or after
blending. Either the dry process or the wet process is used. In the
dry process, heat for drying is provided by direct dryer firing of
4-6
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/\ ...«y_
QUARRYING AND CMMHUtO OPERATION
-^^..jni'i'iniiKij
i
—^ ^ iy'r—i—
iww«23/n -' '—'"*"*. •.
U TDMHIIOMpfP^-'
RAW MATERIALS ARE GROUND TO POWDER AND BLENDED
U-Sf-—*^
rrrrL-1 I
safeajir^ ^
/crrmTK
Figure 4-2B
GRINDING WO BLENDING OPERATIONS
FMUHE44C.
KILN DURATION
0
Ml
UA DMUIiMnl ol HtMh. Uuullon. and Wdlin. 1 Mr.
FINE aMNonra AND PACKAOINQ OPERATION
FIGURE «. PRODUCTION OF PORTLAND CEMENT
4-7
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coal, oil or gas, separately fired furnaces, or hot kiln exhaust
gases. The finished finely ground raw material is then conveyed to
blending, homogenizing, and/or storage silos. Kiln feed is then
withdrawn from the silos.
In the wet process, the raw materials may be proportioned prior
to grinding or individual raw material slurries may be blended after
grinding. The finished slurry used as kiln feed may be 30 to 40
percent water or it may be dewatered to approximately 20 percent
water and fed as a filter cake.
The third step, clinker production, is the heart of the opera-
tion. Proper firing of the kiln will determine the quality of the
final product. Cement kilns range in size from 60 feet in length and
6 feet in diameter to 760 feet in length and 25 feet in diameter.
The kiln is placed in a near-horizontal position with a slope of 0.03
to 0.06 cm/m of length and rotates on its longitudinal axis. The
blended feed material (wet "slurry" or dry "raw meal") is fed into
the upper (highest) end of the kiln. Firing is done from the lower
end of the kiln using coal, oil or gas fuel so that the exhaust gases
flow countercurrent to the feed material. As the feed flows slowly
down the kiln, it is exposed to higher temperatures which first cause
heating, then drying, calcining, and sintering. Finally, the feed is
heated to the point of fusion, resulting in clinker. Clinker, a
round, marble-sized particle, is formed at approximately 1595°C.
This requires process temperatures of up to 1650° at the lower end of
4-8
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the kiln. The clinker is cooled in a clinker cooler and stored for
finish grinding and packaging.
Older kilns use suspended chains in the drying zone to assist
in moving the feed material down the kiln and to increase heat
absorption from the exhaust gases. Many new dry process kilns use
pre-heaters which increase energy efficiency and permit shorter kilns
since heating, drying, and even calcining of the feed material can be
accomplished prior to entering the kiln. Two types of preheaters are
presently in use: grate and suspension preheaters. The grate pre-
heater uses a slow moving grate which kiln exhaust gases pass through
to dry and heat pelletized feed. The pellets are formed by mixing
the raw feed material with 10 to 12 percent water and forming pellets
approximately 2.5 cm in diameter. The hot pellets are then fed di-
rectly to the kiln.
The suspension preheater uses a multistage eyelone/suspension
system to ensure direct contact of the kiln exhaust and the dry raw
meal feed. The kiln exhaust gases flow counter-current to the raw
meal feed through a series of staged cyclones. This system is used
on dry process units only. (A state-of-the-art discussion of the re-
inforced suspension preheater (RSP) process can be found in
Kohanowski and Shy, 1978.)
The final step of cement production is the finish grinding and
packaging. Clinker is finely ground (approximately -325 mesh) in a
ball mill or tube mill in one or two stages. Ground with the clinker
4-9
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is a small amount of gypsum (4 to 6 percent) which controls the set-
ting time of the cement. The portland cement is then stored, bagged,
or shipped in bulk by truck, rail, barge, or ship.
4.3 Particulate Matter Characterization
Dust is generated throughout a cement plant with the largest
quantities coming from the kiln and clinker cooler. Table 4-3 is
a summary of the major sources of particulate matter emissions at a
cement plant. The dust from burning is a mixture of substances that
are nearly identical to the kiln feed with two exceptions: (1) some
of the dust has been partially calcined, and (2) the dust has a high
alkaline content. Partial calcination prevents recycling the dust to
the feed end of a wet process kiln, since it will harden on contact
with water. This problem does not occur in dry process kilns. In-
sufflation,, adding the dust at the burner, is also used to recycle
the dust if the alkalinity is not excessive. Insufflation can be
used in either wet or dry process kilns.
Most kiln dust is too alkaline for recycling, however, and must
be either leached with water prior to recycling (generally wet pro-
cess) or disposed of, usually into settling ponds or landfills*
These disposal practices lead to fugitive air emissions during trans-
port and water pollution from leachate.
The reasons that make waste kiln dust unacceptable for recycling
in the kiln also make it a potential resource (although this poten-
tial is inhibited due to the heavy metal content). The characteris-
tics of kiln dust that make it potentially useful as a resource are
4-10
-------
TABLE 4-3
SUMMARY OF MAJOR SOURCES
OF CEMENT DUST EMISSIONS
Process
Burning
(kiln)
Clinker Cooler
Finish Grinding
(mill)
Bagging
Emission Dust
Concentration Mean Size
(g/m3) (nm)
100 - 400 20a
(83.5 g/kg (7 - 40)
of cement)
50 50
25 - 1000 30
(15 - 40)
10 - 40 30
Specific
Gravity Control
(g/cm3)
2.3 - 2.9 ESP (wet)
Fabric
Filter (dry)
ESP or bag-
house pre-
ceded by
cyclone
2.7 - 3,1 Fabric fil-
ter preceded
by separator
Bag filters
After control by ESP, the mean size emitted to the atmosphere is
about 1
Source: Davis and Hooks, 1975.
4-11
-------
its potassium and lime content, acid-neutralizing capacity, and abil-
ity to harden upon hydration. The dust can be used as a fertilizer
or soil conditioning agent. It can neutralize acid soils and sweeten
acidic lakes, bogs, or acid mine drainage. There are numerous other
potential uses for kiln dust ranging from use as a water treatment
flocculating agent to a source of potash.
The composition of kiln dust varies as widely as the feed mater-
ial and the firing process used. Depending on chemical compound
volatilities and vapor pressures, varying quantities of these com-
pounds will end up in the kiln dust rather than in the clinker. A
typical elemental composition of dried kiln dust is shown in Table
4-4. As expected, carbonate from uncalcined limestone, potassium,
sodium, and calcium are the major components of kiln dust.
Under the oxidizing conditions in the high temperature clinker
forming zone of the rotary kiln numerous oxides will form. Due to
their high vapor pressure, some of these will volatilize and travel
to the cooler portions of the kiln with the kiln exhaust. Upon cool-
ing, these oxides will condense as a fume. The very small fume
particles will exit with the kiln exhaust and be captured in the
baghouse or electrostatic precipitator. Because of their very small
size, the alkaline salts which form a fume will be precipitated in
the last chambers of a precipitator, but will be dispersed throughout
a baghouse. Table 4-5 shows an analysis of the distribution of alka-
lies from a kiln dust electrostatic precipitator based on particle
4-12
-------
TABLE 4-4
TYPICAL COMPOSITION OF
DRIED KILN DUST
Component
Weight %
Clay (HC1 insoluble, fired at 800°C)
Organic substance
Cations
4.61
2.06
Lithium
Sodium
Potassium
Rubidium
Cesium
Magnesium
Calcium
Strontium
K
Kb]
Cs
Mg
Ca
Sr
0.0064
12.25
24.50
0.475
0.0074
Trace
9.26
0.015
Anions
Fluoride
Chloride
Bromide
Iodide
Carbonate
Sulfate
Sulfide
Borate
Phosphate
F
Cl"
Br"
I "
CO.
SO
S
BO
4__
0.46
1.43
0.040
0.0552
29.59
9.06
Trace
0.152
Not detectable
Heavy Metals (Weight %)
Heavy Metal Oxides (Weight %)
Chromium Cr 0.011 Cr203
Manganese Mn 0.013 Mn02
Iron Fe 0.84 Fe2C*3
Zinc Zn 1.62 ZnO
Lead Pb 0.562 PbO
Sum of all determinations
Oxygen (from CaO not bound in carbonate)
Sum of all constituents
0.016
0.021
1.19
2.02
0.607
97.825
2.98
100.805
Source: Davis and Hooks, 1975.
4-13
-------
TABLE 4-5
PARTICLE SIZE DISTRIBUTION
OF ALKALIES IN KILN DUST
Particle
Size
Range (urn)
>68
<68>48
<48>34
<34>24
<24>17
<17>12
<12>6
<6
Weight
Total Alkalies
(Percent)
(Percent) ys o v n
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
Water Soluble
Alkalies (percent)
Na20
—
a
a
0.094
0.117
0.134
0.134
0.242
K20
—
a
a
1.927
2.560
3.072
3.252
8.191
Insufficient sample for analysis.
Source: Davis and Hooks, 1975
4-14
-------
size. Over half (64.4 percent) of the alkali particles are less than
6 microns in diameter. As shown in Table 4-4, the alkalies (potas-
sium, sodium, rubidium, etc.) form most of the kiln dust. From these
analyses, one would expect the majority of kiln dust to be made up of
very small particles.
Over half the particles in cement kiln dust are, in fact, less
than 10 microns in diameter. This varies by process and feed mate-
rial, but a particle size distribution curve showing ranges of par-
ticle sizes can be drawn (Figure 4-3). This figure also shows the
particle distribution for clinker cooler dust.
Figure 4-3 shows the differences in the particle size distri-
bution of cement dust from a preheater kiln, wet process kiln, and
clinker grate cooler. In this presentation it is obvious that the
particles are smallest from a preheater kiln and largest from a
clinker grate cooler. This is probably due to the multicyclone con-
figuration of the preheater which will capture the larger particles
and return them to the kiln. Although data are not available, one
would expect that the dust from the preheater kiln would be very high
in alkaline salts, especially with 15 to 40 percent of the particles
less than 1 micron in diameter.
Another characteristic of the kiln dust that is of importance to
the control of emissions is resistivity. The resistivity of the dust
is a factor indicating the ease of applying a negative charge to a
4-15
-------
Preheater Kiln
2 345
Source: Lind, 1978.
10
20 30 50 100 200
500
FIGURE 4-3
PARTICLE SIZE DISTRIBUTION OF CEMENT DUST
4-16
-------
particle and determines the effectiveness of an electrostatic precip-
itator. From the dust resistivity data shown in Figure 4-4, it is
apparent why ESPs are not used to control the particulate emissions
from clinker grate coolers. On the other hand, the emissions from a
wet process rotary kiln are particularly suitable for control by an
ESP due to their low resistivity. Figure 4-4 also shows the effect
of temperature on dust resistivity. Resistivity increases with
temperature up to 200° to 250°C, above which it decreases as the
temperature continues to rise.
4.4 Control Technology Applicable to the NSPS for Portland Cement
Plants
Particulate matter emissions from portland cement plants are
generally controlled with dry mechanical collectors of three types:
cyclones, ESPs and fabric filters. However, in some cases, gravel
bed filters and wet scrubbers are used. In most instances, the cy-
clones are used in conjunction with either a precipitator or fabric
filter. Although the NSPS was based on the use of a fabric filter
baghouse, other control technologies are capable of reducing emis-
sions to meet the NSPS. These control technologies will be discussed
individually in the following sections.
4.4.1 Cyclones
Cyclones are the most basic and elementary of the three types
of particulate matter collectors. They are the least expensive,
easiest to maintain, and have the lowest pressure drop, but are the
least efficient. If an emission source is to meet the stringent air
4-17
-------
Qcm
Clinker Grate Cooler
'Alkali By-Pass
4 Stage
Preheater
Kiln
1 Stage
Preheater
Kiln
Long Dry Kiln
Wet Kiln
100
Source: Lind, 1978.
200
300
400 °C
FIGURE 4-4
RESISTIVITY OF DUST FROM PORTLAND CEMENT KILNS AND COOLERS
4-18
-------
pollution standards, a cyclone must be followed by either an ESP or
a fabric filter* Collection efficiencies of a cyclone are 60 to 80
percent depending on the particle size. The efficiency begins to
drop off when the particles reach the range of 20 to 40 microns in
diameter (Research Triangle Institute, 1970). Since over half the
cement dust is less than 10 microns in diameter, the cyclone cannot
reduce emissions sufficiently to meet the NSPS. Used in conjunction
with an ESP or fabric filter, however, removal efficiencies greater
than 99 percent are achievable while reducing the abrasion caused by
larger particles.
4.4.2 Electrostatic Precipitators
Electrostatic precipitators operate by maintaining a corona
discharge between a negatively charged electrode and a grounding
plate. The exhaust gas stream passes through the corona discharge,
and entrained particles pick up a charge. The charged particles
are attracted to the grounding plates where they agglomerate. The
cleaned gas stream continues on to the stack, while the agglomerated
particles are removed from the plates by frequent "rapping" and fall
into dust hoppers for future removal and disposal.
A number of variables influence the efficiency of an ESP: gas
velocity, moisture content and temperature, and dust quantity, parti-
cle size, resistivity and physical characteristics. Although all of
these variables are important to the designer, dust particle resisti-
vity is the most important. Particles with a high resistivity will
4-19
-------
not acquire a charge when they pass through the corona discharge.
Kiln dust from a preheater kiln has a resistivity which makes an ESP
unsuitable. The resistivity can be reduced, however, by treating the
exhaust gas prior to its entry into the ESP. Moisture control is the
easiest method of pretreatment. As the moisture content of the dust
is raised, the resistivity is reduced. This is a primary reason for
the reduced resistivity of dust from a wet process kiln.
Chemical exhaust gas conditioning is growing in use. Polar
compounds adsorbed on the surface of particles can reduce resistiv-
ity and increase the ESP collection efficiency. This has been dem-
onstrated as a viable method of reducing particulate emissions from
power plants converting to coal fuel. Chemical conditioning has the
advantages of rapid installation (4 to 6 weeks) and cost (capital:
10 to 25 cents/kW capacity, and operation: 0.2 mil/kWh) (Chemical &
Engineering News, 1978).
The advantages of an ESP are:
1. The ability to handle large volumes of gas with very little
pressure drop.
2. Relatively lower power requirements (compared to fabric fil-
ters) due to the low pressure drop.
3. The ability to handle high temperature gases and corrosives.
These advantages must be weighed against the disadvantages of using
an electrostatic precipitator at a cement plant:
1. The entire ESP must be shut down and bypassed for mainte-
nance or repairs when required.
4-20
-------
2. Sulfur oxides in the exhaust gas corrode the metal parts
causing reduced efficiency.
3. Sulfur acids can diffuse into concrete casings and eventu-
ally destroy them.
4. Alkalies can coat high-voltage components and cause short
circuits.
Also, an ESP must be bypassed during startup due to a fire and
explosion hazard from unburned fuel in a chamber with electrical
arcing.
4.4.3 Fabric Filters
Fabric filters are one of the oldest methods of removing dust
from a gas stream. The cement industry uses glass fiber filters
because they are reliable, efficient in removing particles in the
size range of concern, and capable of withstanding high tempera-
tures. Fabric filters are capable of greater than 99.5 percent
removal of cement dust from cement plant exhaust streams.
The advantages of fabric filters are:
1. Reliability
2. Lower cost due to simplicity
3. Very high removal efficiencies
4. Rapid repairs and the opportunity to isolate areas for
repair and maintenance without bypassing the entire
bag-house.
Baghouses have disadvantages also:
1. Increased pressure drop (relative to ESP) which must be
overcome by induced draft.
2. Increased cost of draft equipment may overcome the other
cost advantages.
4-21
-------
3. Susceptibility to clogging from moisture.
4. Bag-life is very dependent on temperatures and is limited
to less than 315°C (600°F).
In general, it appears that the glass-fabric baghouse would be
used for collecting particulate matter from the dry-process kiln and
clinker cooler gases and electrostatic precipitators would be the
choice for wet-process kilns. However, it has been reported that a
higher collection efficiency can be maintained with the baghouse than
the precipitators (Research Triangle Institute, 1970) and, in fact,
the baghouse is used on both wet and dry process kilns.
A survey of NSPS affected facilities shows 12 kilns with precip-
itators and 16 with baghouses. Eighteen out of 22 clinker coolers
at these NSPS sites use baghouses to control particulate emissions.
Additional details on this data are discussed in Section 4.5.
4.4.4 Gravel Bed Filters
Gravel bed filters have been in use since 1957, primarily in
Europe. Recently they have been used for particulate matter control
in the domestic cement industry. In the period 1972-1978, Rexnord,
Inc., installed 24 gravel bed filters on domestic clinker coolers.
The available data show only two of these on sources subject to
NSPS—National Cement Company, Ragland, Alabama; and U.S. Steel,
Leeds, Alabama. The compliance test results show both these units
as in compliance with 74 percent and 91 percent of allowable emis-
sions, respectively.
4-22
-------
Figure 4-5 shows a cutaway drawing of a Rexnord, Inc. gravel bed
filter. The particle-laden gases from a clinker cooler or kiln
preheater enter the module at the raw gas inlet (A) and enter the
cyclone. The cyclone (B) removes the larger particles and the gas
stream moves up the vortex tube (C) and into the raw gas chamber (D),
while the large dust particles are removed through a double tipping
gate (E) at the bottom of the cyclone. The raw gas is directed
through the filter medium (F) where the remaining dust is removed.
The gas stream passes through the media support screen (G), into the
clean gas chamber (H), and out of the module through the clean gas
outlet duct (I). When the filter media becomes clogged, the module
is backflushed by opening the backflush control valve (J) and forcing
clean air through the backflush duct (R). This air passes up through
the tilter medium (F), while stirring rakers (L) agitate the medium.
The dust, which had been trapped in the filter medium, is removed and
directed back down the vortex tube (C) and either out the double tip-
ping gate or out the raw gas intake and to another module's cyclone.
Only one module is backflushed at a time so that particulate matter
control is in operation at all times.
Advantages of the gravel bed filter, as reported by Shumway et
al. (1978), include:
1. Rapid construction (approximately 4 months)
2. . Low maintenance costs (average $2,000/year)
3. Handling of increased gas flow during upset conditions
4-23
-------
Raw Gas Dust
0
MM Primary Collector (Cyclone)
Ccj Vortex Tube
flO Raw Gaa Chamber
M Double Tipping Gate (Dust Discharge)
Gravel Bed Filter Medium
Source: Shumvay et al. , 1978.
Screen Support for Bed
M Clean Gas Chamber
Exhaust Fort
Backf lush Control Valve
Backflush Duct
LJ Stirring Raker
FIGURE 4-S
REXNORD, INC. GRAVEL BED FILTER
4-24
-------
4. Continuous particulate matter control during periods of
maintenance or repair
5. Handling of high temperature gases (>371°C (>700°F) at
Missouri Portland, Joppa, Illinois).
4.4.5 Wet Scrubbers
Wet scrubbers are not used very much in the portland cement
industry. Only one unit is in operation on a NSPS-affected facility
(clinker cooler). The principle of operation of a wet scrubber is
simply to trap a small dust particle in or on a larger water droplet
and then remove the droplet in a cyclone.
Wet scrubbers are used in areas where elevated gas temperatures,
or sticky or hygroscopic dust is encountered. They are also suitable
in areas where there is a preference for collected dust in a slurry
form. They are not suitable for dust particles of submicron diame-
ter, dust which becomes corrosive when wet, or when there is a pre-
ference for collected dust in a dry form.
These attributes and shortcomings make wet scrubbers suitable
for particulate matter control on clay dryers and in primary
crushing, screening and secondary rock crushing. In each of these
situations, there may be sufficient moisture in the gas stream to
cause condensation problems in dry collectors.
4.5 Comparison of Levels Achievable with Best Demonstrated Control
Technology Under the Present NSPS
The available data on control technologies for the removal of
particulate matter from exhuast gas streams at portland cement plants
show that a number of controls are suitable for reducing emissions
4-25
-------
below the level required by the NSPS. The technologies are described
in Section 4.4. Table 4-6 summarizes the ranges of emissions from
control systems in use on NSPS-affected facilities. Since the NSPS
for portland cement plants do not specify a mass emission limit for
sources other than kilns and clinker coolers, there are no data to
show the effectiveness of controls used for fugitive emissions or
emissions from grinding, drying, blending, packaging, etc., opera-
tions.
As discussed in Section 4.4, there is no single best demon-
strated control technology for particulate matter emissions from
Portland cement plants. Rather, there are four technologies that
are preferable under different circumstances within a plant and at
different plants. Most portland cement plants use some combination
of cyclone, ESP, baghouse, and gravel filter to reduce the emission
of particulate matter.
4-26
-------
TABLE 4-6
RANGES OF DUST EMISSION FROM CONTROL SYSTEMS SERVING
NSPS PORTLAND CEMENT PLANTS
Range of Dust Emissions
Type of From Collector
Source Dust Collector (kg/Mg)a
Kiln - dry ESP 0.021-0.125
Baghouse 0.013-0.124
Gravel Bed NAb
Kiln - wet ESP 0.020-0.142
Baghouse 0.049-0.132
Gravel Bed NA
Clinker Cooler ESP NA
Baghouse 0.005-0.061
Gravel Bed 0.023-0.045
Wet Scrubber 0.022-c
aKilograms of particulate matter per metric ton of kiln feed.
^NA « No compliance test data.
cSingle compliance test result.
Source: MITRE Corporation, 1978.
4-27
-------
5.0 INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS
5.1 Test Coverage in the EPA Regions
The Metrek Division of the MITRE Corporation conducted a survey
of all 10 EPA Regional Offices to gather available NSPS compliance
test data for each of the 10 industries under review (Watson et al.,
1978). This survey yielded test data on 28 new portland cement
kilns/clinker coolers. The data included average particulate mat-
ter emissions and opacity measurements for these units. Only a few
opacity readings were reported, as compared with the total number of
tests.
Information received from the Portland Cement Association in-
dicated that numerous additional NSPS-affected facilities existed.
Telephone contacts with EPA Regional personnel, State Air Pollution
Control Agencies, and, in some cases, with portland cement plant
operators yielded NSPS compliance test data on an additional 21
facilities. Data were not obtained for seven other possible NSPS
cement kilns. According to industry reports, this information
represents all of the portland cement plants completed from 1971
through 1978, and subject to the NSPS (MITRE Corporation, 1978).
5.2 Analysis of the NSPS Test Results
The results of the NSPS compliance tests for 49 portland cement
NSPS-affected facilities are tabulated in Table 5-1 and displayed
in Figures 5-1 (cement kilns) and 5-2 (clinker coolers). Only one
cement kiln subject to the NSPS is unable to pass a NSPS compliance
5-1
-------
TABLE 3-1
HSPS CCHFLUNCE TEST USOLTS FOK fOKTLAKD CEMENT PUHTS
f ••
Wl
1
ro
Plant Kilo
ueitm I
Menu n
Pllntkot* Caanaay 1
Claoa Palla Portland
Dlv. . Clan Palla. M.T.
Ban Joan Caawnt 3
Dorado. P.B.
Cop lay. Batarath. Pa. 1
Una Sear, Cltadal Ca-
•ant Corp.. Boaaoka, Va. 5
Hhltahall 3
Cananron, Pa.
BBCIOI IV
Cltadal faaanr Corp. 1
DaaopoUi, Ala.
Rational CaMnt Co. 1
Bag land, Ala.
Onlvaraal Atlaa Caaant 1
DU. of D.B. Btaal Coxy.
Laada, Ala.
Florida Mining t Hatarlala
Brookarllla. Via. 1
HlM} 10 IttafaUtTaLtM • IlfcCa 3
Tfluf»Mt^t yi«j.
Milan ran ant Co. 1
Cllnehflald. Ca.
Pllntkota 1
Taxaa Indoatrtaa 1
Artaala, Mlai.
Taar
Coapl'd
1973
1976
1978
1976
1973
1977
1976
1976
1973
197S
1974
1974
1974
Coapllane* Ta*t Data
rfflmj TrVr'lT Kll° Cllnkar Coolar
Capacity Pra- Kiln Cllnkar Fart Opacity Part Opacity
(Kg/day) haatar Procaaa Fual Coolar (kg/Mg) (I) (kg/Hg) (1)
1484£0.' X Dry Oil BBP Bag 0 :>"> 0.021 0 .' ---.i 0.017 1C
(0.088)
113*4), J Hat Oil Bag Bag 0.0 1C
2819 ; ' > X Dry Coal -- 1C
1*88 t!( J- X Dry Coal Bag „ 0)1, 0.013 0
619?^* X Dry Coal Bag 0,11$ 0.089 0-20
2132 T; Y X Dry Coal
1996 'r/. 7 X Dry Coal/ SSP Oraval f.il 0.035 <10 0.0~> 0.035 <10
Oil Bad
1619 7.iAV 0.062 3 0.10 0.45 5
Bad
1342 '" S X Dry Coal Bag Bag „ at(, 0.033 1C JO-'O 0.015 1C
1930 81 <• Hat Oaa ESP Bag 0 owi 0.01 1C O. o~"> 0.0)3 1C
1304 bl , 1 x Dry Coal Bag Bag ,] ivf 0.104 1C a . ^^0.028 ic
1733 50 fa X Dry Coal EBP Bag <,.( 0^0.031 1C 0 . *"/ 0.039 1C
103*^'. i/ Hat Caa BBP Hat g 1 '^ 0.103 1C
-------
TABU 5-1 (Continued)
«srs coiruMCB HST USULTS FOB NBTLMD CBMZMT nans
Cn
Plant
Glut Portland Coaant
Barlayrllla. S.C.
Clfford-Hlll Camant
Barlayvllla, S.C.
Santaa Portland Canant
Belly Rill. S.C.
n|ffini v
Mlaaourl Portland
Joppa. 111.
Cantax
LaSalla. 111.
Loalavllla CaMnt
Spaad. Ind.
Rational Gypaiai
Alpana, Mich.
Sontbwaatarn Portland
CaMnt, Falrborn, Ohio
Uhlgh, Hltchall, Ind.
Cantax, Auatln Canvnt
Co., Buda, Tax.
Clfford-Blll Caawnt
Midlothian, Tax.
Kalaar, San Antonio, Tax
OKC, Raw Orlaana, U.
Kiln
4
1
2
2
1
1
2
22
23
2
3
1
3
. 4
2
Taar
COBBl'd
1974
1974
1974
1975
1974
1973
1977
1975
1975
1974
1976
1978
1972
1975
1974
Capacity Pra-
(Mg/day) haatar
S90;7,0.3
1488
1665 7foV x
653 $O.O x
1500 lf& f
753 W. *
1052 40. ? X
880 <-fO- •/
Procaaa
Hat
Dry
Hat
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Hat
Dry
Hat
Control Taehaoloiy
Kiln Cllnkar
Pual Coolar
Gai Bag Bag
Caa Bag Bag
Caa ESP Bag
Coal ESP
Coal
Coal
Coal GBO'1
Coal Bag
Coal **B
Coal Bag Bag
Coal
Bag Bag
Coal/ ESP
Caa
Coal Bag Bag
Coal Bag
CoBBlUnea Taat Data
Kiln Cllnkar Coolar
Part Opacity Part Opacity
(kg/Mg) (I) (kg/Mg) (I) R«arka
0 ivb 0.123 5 0.08C 0.043 5
,
. IOL/ 0.052 20 &.6 0.017 1C
'
j v v-S 0.129 1C 0' 0~> ° 0.035 1C
Q.tOO o.OSO 1C
Quaetlonabla atatua aa naw
aource.
.. .. ..
a. j-ru 8: Oil" 1C O. "VM).023 1C Two eonpllanea taata on kiln with
o.t'" avaraga of 0.1 kg/Mg.
Both kllna vantad to ciaainu
0 IfO 0.070 0 -- — baghouaa & itack. Stata taat
dona on atack In kg/Mg product.
O.t^le 0.123 0 fl.O"/ 0.007 0
Out of coaellanca. Mo taat
data tubalttad.
0.0(rb 0.033 Ic 5,31^0.012 Ic
0,iO 5"4 0.028 Ic
fl-dV 0.017 1C •> CIO 0.005 1C
0. 0$& 0.049 1C — — Taatad In coBpllanca, latar found
out of coaplUnc* & r«tMt»d.
frvccntly In
-------
TaBU 5-1 (Concluded)
mn cofPUMct TUT utian FOB NKTUJD cwnrr rum
o»
Plant
tMSKM Til
aah Crave Cenant Co.
LoulavlUe, Bob.
Borthmatern Sutaa
Haaon City. lora
Monmrch Cement Co.
HoBboUt. ba.
Vim TIT1
Utah Portland CaBent Co.
Bait Lake City. Utah
Meal, Portland, Col.
Uaal. Trident. Mont.
Soeth Dakota fanenf
Bapld City, S.D.
MBK1 H
Monolith Portland
Monolith. Cal.
mmaat »
Kiln
4
3
3
*
3
1
4
1
Tear
COBBl'd
1973
1976
1973
1973
1974
1973
1977
197*
Capacity Pre-
(Hg/day) heater Proceaa
1170 5 i .? x Dry
771 ^V Dry
'« 1^ I Dry
43* J ".1 Hat
1270 i * ^ Het
S34 ~'«.3 n,t
1342 ?"•/ x Dry
1315 ^'U Het
Blln Clinker Cooler
Kiln Clinker Part Opacity Pert Opacity
Puel Cooler (kg/*.) (V (kgTMg) (t) Unark.
Coal/ BBP Bag i7 . , ', ' 0.123 3-15 0 /:/O.Ml 5-10
CM
Coal Bag Bag <;"''- °-073 1C <^ ° - 0.011 1C
CM Bag Bag <9 > '•'- 0.123 5 ;.\ £' ^0.009 0
Coal/011/ Blgh efficiency cyclone -- — — _
CM follomd by baghouao BO til. at Beglon
Coal DP Bag r.'v"' °-077 M r "^ 0.014
Coal IBP o -Ll
-------
Current NSPS
U.1J
? 0.13
-------
"O
0)
-------
test—Lehigh Cement, Mitchell, Indiana—and the company has not sub-
mitted to state air pollution officials any test data to indicate how
much their emission level exceeds the NSPS limit. All clinker cool-
ers and other affected facilities are reported to be in compliance.
5.2.1 Control Technology Used to Achieve Compliance
Data received show that all 29 cement kilns and 20 clinker
coolers are in compliance with the NSPS. Of the remaining 7 NSPS-
affacted cement kilns, five are known to be in compliance, one is
known to be out of compliance, and one has just recently been tested
and the results have not yet been analyzed.
The particulate matter emissions from the portland cement plants
are controlled by ESPs, fabric filter baghouses, gravel bed filters,
and wet scrubbers. Table 5-2 summarizes results of using these dif-
ferent control technologies on cement plant exhaust streams.
Cement kilns have been tested at emission levels ranging from a
high of 0.142 kg/Mg feed and a low of 0.013 kg/Mg feed. The range
for kilns with emissions controlled by ESP is 0.142 to 0.020 kg/Mg,
and for kilns with fabric filter baghouses the range is 0.132 to
0.013 kg/Mg dry kiln feed. The data indicate that neither the ESP
nor the baghouse is significantly better at controlling cement kiln
particulate matter emissions.
Cement plant clinker coolers have been tested at emission levels
ranging from a high of 0.061 kg/Mg and a low of 0.005 kg/Mg dry kiln
5-7
-------
Ul
oo
TABLE 5-2
RESULTS OF USING VARIOUS PARTICULATE MATTER
CONTROL TECHNOLOGIES AT PORTLAND CEMENT PLANTS
Electrostatic
Affected Facility Precipitator
Kiln Emissions (kg/Mg feed)
//Units
Maximum
Minimum
Clinker Cooler Emissions (kg/Mg feed)
#Units
Maximum
Minimum
12a
0.142
0.020
0
— —
Fabric Filter Gravel Bed
Baghouse Filter
16a
0.132
0.013
16a
0.043b
0.005
0
—
—
3a
0.045
0.023
Wet
Scrubber
0
—
—
la
0.022
0.022
fNumber of units with available test data.
A single compliance test shows 0.061 kg/Mg. The EPA Region states that the source is in
compliance
Source: MITRE Corporation, 1978.
-------
feed (mean 0.024 kg/Mg). Compliance test data on a single wet scrub-
ber show emissions near the mean emission level for fabric filter
baghouse controls (0.022 kg/Mg). Data for affected facilities using
gravel bed filters indicate a mean emission level of 0.034 kg/Mg dry
feed (0.023-0.045 kg/Mg).
5.2.2 Analysis of Compliance Test Data
The compliance test data shown in Table 5-1 were analyzed to
determine if any of the following variables affected the ability to
control the emission of particulate matter from portland cement kilns
or clinker coolers:
• Kiln control technology - ESP or baghouse
• Kiln control technology as a function of production process -
wet or dry
• Kiln production process - wet or dry
• Clinker cooler control technology - baghouse, gravel bed
filter, or wet scrubber.
The results of this analysis are summarized in Table 5-3. The
compliance test data were grouped into sets corresponding to the
previously mentioned variables, which facilitate comparisons of the
effectiveness of any single control technology, if a control was more
effective on a particular process, or if the effect of available con-
trols was more pronounced on a specific process. The table shows the
number of compliance tests, the range and the mean of the test re-
sults, and the standard deviation and standard error of each set of
data.
5-9
-------
TABLE 5-3 ;
\
ANALYSIS OF PORTLAND CEMENT PLANT COMPLIANCE TEST DATA
Statistic '
Variable
Dry Process
ESP
Baghouse
Wet Process
ESP
Baghouse
All Processes
ESP
Baghouse
All Controls
Dry Process
Wet Process
All Kiln Data
Clinker Cooler
Baghouse
Gravel Bed
Wet Scrubber
All Controls
Number
Values*
8
10
6
4
14
14
18
10
28
16
3
1
20
Mlnlaumb
0.021
0.013
0.020
0.049
0.020
0.013
.
0.013
0.020
0.013
0.005
0.023
0.022
0.005
Maximum1*
0.125
0.123
0.142
0.132
0.142
0.132
0.125
0.142
0.142
0.061C
0.045
0.022
0.061
Mean
0.061
0.070
0.084
0.091
0.070
0.076
0.066
0.087
0.073
0.022
0.034
0.024
Standard
Error
0.012
0.013
0.021
0.021
0.011
0.011
0.009
0.014
0.008
0.004
0.006
0.003
Standard
Deviation NSPS
0.033 0.15
0.041
0.051
0.043
0.041
0.041
0.037
0.046
0.040
0.016 0.05
0.011
0.015
\
aNumber of compliance tests.
Particulate emissions in kg/Mg feed.
CA single compliance test shows 0.061 kg/Mg. The EPA Region
states that the source is in compliance.
Source: MITRE Corporation, 1978.
^ * Fx /r
5-10
-------
A comparison of the mean values for each set of compliance test
data indicates that no control technology in use today is more
effective for controlling particulate matter emissions. The mean
values also indicate that there is a possibility that emissions from
dry process kilns are controlled slightly more effectively than wet
process kilns. Further analysis shows that this is not, in fact, a
statistically significant difference. The standard deviation, a
measure of the variability of the test results, indicates that the
current NSPS is set at a level that ensures continuous compliance
with an adequate margin of safety.
5.3 Indications of the Need for a Revised Standard
5.3.1 Particulate Matter Standard for Portland Cement Kilns
There is not sufficient justification for revision of the pre-
sent standard for cement kilns based on the following considerations:
• The current best demonstrated control technology is either
fabric filter or ESP. However, the original background study
used fabric filter technology as the basis for the standard.
This technology has not changed during the past 8 years.
Although the ESP has improved, test results ate that it is
not capable of significantly better performance than fabric
filters.
• Although the mean emission rate for the 28 compliance tests
analyzed was 0.073 kg/Mg dry kiln feed, the range was from
0.142 to 0.013 kg/Mg dry kiln feed with 16 kilns tested above
and 13 below the mean. There was a random spread of test
results throughout the range of values, indicating that there
is no control or process technology that is consistently bet-
ter at reducing emissions or having emissions reduced.
• Although no data are available, it is generally accepted
knowledge that control technologies being used at cement
plants deteriorate with age. Baghouses, ESPs, and cyclones
5-11
-------
are all subject to erosion, clogging, tearing, shorting,
or similar problems with time. As the controls deteriorate,
the level of emissions is expected to increase.
5.3.2 Participate Matter Standard for Portland Cement Clinker
Coolers
There is not sufficient justification for revision of the pre-
sent standard for clinker coolers based on the following considera-
t ions:
• Fabric filters remain the primary control technology for
removing particulate matter from clinker cooler exhaust gases
and are identical to those used as the rationale for setting
the standard in 1971.
• The same problems with deterioration apply to both clinker
cooler and kiln emission control.
• An analysis of the compliance test data indicates that the
current NSPS is set at a level that ensures continuous com-
pliance with an adequate margin of safety.
5.3.3 Opacity Standards
The opacity standard has been studied thoroughly in answer to
a Court remand in 1973. No changes have occurred in the industry to
invalidate the conclusions of that study.
5-12
-------
6.0 ANALYSIS OF THE IMPACTS OF OTHER ISSUES ON NSPS
6.1 Industry Economics and New Construction
The historical growth pattern of the cement industry shows its
close ties with the construction industry. Figure 6-1 displays how
the production of cement has paralleled construction spending in
the U.S. for the period 1966-1977. It is estimated that cement is
a necessary input to 90 percent of all construction projects and
99 percent of all cement is used in construction (Bureau of Mines,
1976). The clinker capacity of the industry however has not fol-
lowed this pattern very closely. Figure 6-2 shows the comparison
of clinker capacity and production for the period 1945 through 1977.
Future capacity and production growth estimates are also shown. From
this graph, it is obvious that although cement production and con-
struction are closely related, clinker capacity and construction are
not. A number of external events can be noted which preceded the
wide fluctuations between clinker capacity and production. These
include a post war housing boom in the late 1940s and early 1950s,
another construction boom in the early 1970s, the Clean Air Act of
1970, New Source Performance Standards in 1971, price and wage con-
trols in 1971, the Clean Air Act Amendments of 1972 and an economic
recession in 1973-1975.
The cement industry built no "greenfield" plants (plants
constructed at a new site location) during the period 1931 to 1945
(Mongoven, 1977). During the post-World War II era, the immediate
6-1
-------
to
Index of Cement Output
47-49-100<
250
240
230
220
210
200
190
180
$ Bil
New Construction
Put in Place
Constant 1967
95
90
85
80
75
70
65
60
1966 67 68 69
Source: Mongoven, 1977.
70 71 72 73 74 75 76 77
FIGURE 6-1
CONSTRUCTION SPENDING AND CEMENT OUTPUT
-------
100
90-
8 do
o
70
60
5
50
40
30
Clinker Capacity
Production
Projection
1948 50
55
60
65
70
75
80
85
Source: Bureau of Mines, 1978.
FIGURE 6-2
U.S. PORTLAND CEMENT CAPACITY AND PRODUCTION
-------
demand for cement by the construction industry was met by capacity
released from war production. In 1947 the industry utilization of
capacity was 75 percent (Bureau of Mines, 1973). This steadily
increased to greater than 90 percent utilization during 1953-1956
with the post-war housing boom and peaked in 1955 at 94.3 percent
(Bureau of Mines, 1973). Due to the regional nature of the industry,
regional shortages were encountered while the industry was realizing
greater than 15 percent return on sales (Mongoven, 1977).
During the period 1955-1967, cement production capacity in-
creased 61.4 percent, approximately two-thirds of the total post war
increase occurring in this 12-year period (Bureau of Mines, 1973).
Figure 6-3 shows that although a relatively large number of kilns
built prior to 1946 (20 percent) are still operating, these kilns
account for only 10 percent of clinker capacity. In the early 1960s,
the industry was faced with overcapacity. The utilization of pro-
duction capacity dropped to less than 80 percent (Bureau of Mines,
1973). Where production had increased 50 percent during the 1950s,
production increased only 15 percent during the 1960s (Bureau of
Mines, 1973).
In the late 1960s and early 1970s, utilization of production
capacity slowly climbed once again to greater than 90 percent in
1972-1973 (Bureau of Mines, 1973). At the time, little new capacity
was built, while older plants were closed due to age and the new
pollution control standards. Several existing cement plants closed
because industry did not feel that the additional capital cost for
6-4
-------
Ui
*v
'
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Wet Process
Dry Process
Total
••
MH
^
^
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i ;.;.
-J\
^*
ft: ;i
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^^^ T'si ^^
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Prior to 1931- 1936- 1941-
X
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1931 1935 1940 1945 1950
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1951- 1956- 19
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^
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.-
^
x
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s
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ss
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i
i
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^
'*
7
5.5
0.0
L96 - 1971- 1976-
1955 1960 1965 1970 1975 1977
Source: Portland Cement Assn, 1978.
FIGURE 6-3
CEMENT PLANT CLINKER CAPACITY
BY AGE OF KILN
-------
pollution control equipment could be justified at obsolete plants.
According to Daugherty and Wist (1974) 15 plants had closed due
chiefly to environmental pressures. Figure 6-4 shows the age and
number of kilns presently operating in the U.S. A total of 14 per-
cent of these kilns were built prior to 1931 and over 20 percent
prior to 1946. Rarely are these older facilities closed solely
because of pollution abatement requirements. The Bureau of Economic
Analysis (Department of Commerce) surveyed 131 industrial closings
over the period 1974-1977 that involved pollution abatement require-
ments. The hypotheses that they suggested from their survey results
were that:
• First, most permanent closings involving pollution problems
did not occur solely because of pollution abatement
requirements.
• Second, the number of permanent closings fell after 1975 when
general economic conditions improved.
• Third, air pollution requirements contributed to more per-
manent closings than water pollution requirements, possibly
because of a combination of the Clean Air Act of 1970 dead-
line of 1975 and the slack economic conditions in 1974 and
early 1975 (Rutledge et al., 1978).
The closings may have been a contributing factor in the regional
lack of capacity in 1972-1973. It is more likely, however, that this
shortage was a result of the price and wage controls imposed in 1971
which held the price of portland cement at a level that ensured the
industry its lowest profit margin since the Depression in the 1930s
(Frondistun-Yannas, 1976).
6-6
-------
a
ti
M
0)
50
45
40
35
30
25
20
15
10
5
Wet Process
Dry Process
I
33
20
48
24.
24
20
14
10
Prior to
1931
1931-
1935
1936-
1940
1941
1945
1946
1950
1951-
1955
1956-
1960
1961- 1966- 1971- 1976-
1965 1970 1975 1977
Source: Portland Cement Assn, 1978.
FIGURE 6-4
CEMENT PLANT KILN AGE
-------
Decreased capacity and increased demand resulted in high capac-
ity utilization and regional shortages. This time, however, the
margin on sales, which had slowly climbed to 4 to 5 percent was
restrained by price controls (Mongoven, 1977). The price controls
put into effect in 1971 used the late 1960s as a base period. This
period was particularly poor financially for the industry and the
effect was to postpone new construction during what should have been
a particularly profitable period. The cement industry was one of the
first industries to have controls removed in 1973. When the controls
were removed, the price of cement jumped 14 percent and new capacity
construction was initiated. Shortly thereafter, the U.S. entered a
severe recession which left the cement industry with excess capacity.
By 1975, production had fallen to 64.5 million Mg while capacity
had grown to 92.3 million Mg for a net of 70 percent utilization of
clinker production capacity (Bureau of Mines, 1975). With excess
capacity came low profit margins again and a lack of investment
capital. Recent expansion has accompanied the rapid growth in the
construction industry, but the construction industry can increase
demand for cement much faster than the cement industry can increase
capacity. Parts of the U.S. are already seeing cement shortages,
particularly in the West. The cement industry, however, is wary of
increasing capacity as it has done in the past, only to discover that
the excessive demand for cement was a short-term phenomenon.
6-8
-------
As shown in Figure 6-2, the Bureau of Mines projections for the
early 1980s indicate a possibility of high capacity utilization and
possibly regional shortages that usually accompany this trend. Some
of this effect is already being felt, i.e., East Coast cement plants
are operating at 60 to 65 percent capacity while some West Coast
plants are operating at 100 percent capacity (Business Week, 1977).
Two interesting details are that East Coast manufacturers are
receiving as low as $28/ton while West Coast manufacturers are
receiving as much as $53/ton for an identical product (Business Week,
1977). Secondly, although the demand is greater in EPA Region IX,
over 50 percent of the capacity completed between 1972 and 1978 was
in EPA Regions IV and V (7.4 percent in Region IX) (Portland Cement
Association, 1978). Also, the projected future growth announced by
the cement industry for 1978 through 1981 indicates less than 30
percent of new kiln capacity will be built in EPA Regions IX and X.
Table 6-1 shows the current and projected distribution of cement
production capacity in the U.S. as of November 15, 1978. According
to the Portland Cement Association figures, five new plants will be
completed by 1981, with a combined capacity of 39 million Mg per
year. Table 6-2 shows all the changes in future cement plant capac-
ity changes announced by the cement industry. These announcements
indicate an anticipated capacity increase of 2.3 million Mg/year in
EPA Regions IX and X. This is 30 percent of the total capacity in-
crease of 7.8 million Mg/year of clinker expected by year-end 1981.
6-9
-------
TABLE 6-1
PORTLAND CEMENT CLINKER PRODUCTION CAPACITY
ON
I
EPA
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
TOTAL
Clinker
Capacity^*
(HHMg/yr)
None
4,248
12,159
14,852
13,337
11,889
10,431
3,942
11,789
2,333
84,980
New
No.
None
1 Dry
3 Dry
7 Dry
4 Wet
9 Dry
2 Dry
3 Wet
4 Dry
1 Dry
3 Wet
2 Dry
1 Wet
None
29 Dry
11 Wet
Kilns 1972-1978a
Capacity (103 Mg/yr)b
490
1,602
3,883
1,744
4,215
753
785
1,123
509
863
720
441
—
13,295
3,833
No.
None
None
None
lDryd
1 Dry
1 Dry
1 Dry
2 Dry
1 Dry
IDry
1 Dry
1 Dry
1 Dry
1 Dry
1 Wet
3 Dry
3 Dry
1 Dry
19 Dry
1 Wet
Announced Growth0
Capacity (10J Mg/yr)
__
-
-
100
1,361
518
499
236
726
205
907
131
603
122
81
483
1,406
454
7,751
81
Year*
-
-
79
81
80
79
79
80
80
NA
78
80
79
79
79
NA
79
NA = Not Announced
Q
.Completion Year
As of December 31, 1977
^As of November 15, 1978
New plant
Source: Portland Cement Assn., 1978.
-------
TABLE 6-2
ANNOUNCED CEMENT/CLINKER CAPACITY CHANGES
AS OF NOVEMBER 15, 1978
Year
Plant Name
Location
Process
Capacity (10 Mg/yr)
From
To
Difference
1978
1979
1980
1981
No Date
Given
Lehigh
Oregon Portland
Texas Industries
Amcord
Ideal
Ideal
Kaiser
Lone Star
OKC
Utah Portland
General Portland
Kaiser
Marquette
Medusa
Southwestern
Ideal
Lonestar
California
Portland
Flintkote
Kaiser
Mason City, IA
Durkee, OR
Hunter, TX
Oro Grande, CA
Boettcher, CO
Knoxville, TN
San Antonio, TX
Davenport, CA
Pryor, OK
Salt Lake City,
UT
New Braunfels, TX
Permanente, CA
Cape Girardeau, MO
Charlevoix, MI
Odessa, TX
Theodore, AL
Georgetown, TX
Mojave, CA
Redding & San
Andreas, CA
Lucerne Valley, CA
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Wet
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Dry
D-W
Wet
549 680 131
SUBTOTAL 1978 +131
1041
295
426
713
358
390
318
454
499
1247
417
526
713
635
626
399
454
499
206
122
100
0
277
236
81
SUBTOTAL 1979 +1975
1450
304
698
249
726
1450
907
1216
454
726
0
603
518
205
SUBTOTAL 1980 +2052
— 1361 1361
SUBTOTAL 1981 +1361
907
1043 1996
816
907
1270
907
SUBTOTAL
TOTAL CHANGE IN DRY PROCESS
TOTAL CHANGE IN WET PROCESS
GRAND TOTAL PROCESS CHANGE THROUGH 1981
907
953
453
0
+2313
+7751
81
+7832
Source: Portland Cement Association, 1978a.
6-11
-------
The effects of pollution abatement requirements on the cement
industry have been mentioned previously. Rutledge et al. (1978) hypo-
thesized that air pollution regulations contribute to more industrial
closings than water pollution requirements. In their survey, they
found that air pollution problems were cited as a contributory factor
in permanent closings almost twice as often as water pollution prob-
lems. Daugherty and Wist (1974) reported that in the years prior to
1974, 15 cement plants were shut down chiefly due to environmental
pressures. Plant closures are expected to continue as new, energy-
efficient, cement plants are built. These new plants will often
replace older, obsolete equipment in an air pollution and cost mini-
mizing trade-off situation.
Capital expenditures for air pollution abatement equipment in
the U.S. decreased in 1977 (Rutledge et al., 1978). In the portland
cement industry, pollution control expenditures average about 10
percent of the total construction costs for a new plant (Mongoven,
1977). This is a decrease from the estimated 13 percent that EPA
indicated in 1971 in the original background study for the proposed
new-source performance standards.
The Council on Wage and Price Control (Mongoven, 1977) came to
the following conclusion concerning the effect of pollution abatement
on the cement industry:
A reduction in the rate of increase in operating costs from 6
percent to 5 percent will do more to encourage the building of
new cement capacity than would the reduction in the cost of a
6-12
-------
new plant (by eliminating the need for pollution control de-
vices). This result suggests that an effective macroeconomic
stabilization policy could be the most important step in re-
ducing the possibility of long run material shortages.
Have the NSPS for Portland Cement Plants stifled new capital
investment? The Council on Wage and Price Stability (Mongoven, 1977)
concluded that:
...These figures indicate that the added pollution control costs
do change the way a firm would consider a new investment deci-
sion by making larger price increases necessary for the expendi-
tures to be committed. This does not mean that the imposition
of these controls has necessarily caused any reduction in new
capacity expenditures in the cement industry. However, this
analysis does leave open the possibility that an investment de-
cision could be changed for a marginal plant because of pollu-
tion control costs. (Particularly a plant selling cement for
$40 per ton and using a 12 percent rate of return).
Since cement is already selling for as high as $53 per ton on the
West Coast, it is very likely that capital investment will not be
stifled by pollution control expenditures.
In conclusion, the following remarks summarize the status of the
cement industry:
• Cement production is a regional industry caused by the high-
volume/low-value nature of the product and high transporta-
tion costs.
• The industry has suffered high excess capacity periods and
low profits that have stifled capital investment.
• Pollution abatement requirements may affect capital invest-
ment decisions, however, minor changes in future operating
costs will have a more significant effect.
• The current price of cement is sufficient to stimulate new
capacity construction, regardless of the effect of present
pollution abatement requirements.
6-13
-------
6.2 Excessive Emissions During Cement Kiln Startup
The NSPS specifically exempt affected facilities from the stan-
dard during periods of startup, shutdown, or malfunction. If a
cement kiln is permitted to operate uncontrolled during the start-up
period, emissions may be estimated as 122 kg/Mg feed (dry process)
and 114 kg/Mg feed (wet process) (EPA, 1977) and greater than 60 per-
cent opacity (PEDCo Environmental, Inc. 1978) for 4-24 hours.
Although startup periods are estimated to be only 2 percent of total
operating time, controlled emissions are so low that startup emis-
sions are a significant -amount of the total kiln emissions.
During kiln startup, the temperature of the kiln is raised
slowly to reduce the loss of refractory lining. While it is warming
up, a number of combustible materials will be present in the exhaust
stream. These include carbon monoxide as well as unburned fuel.
Under normal conditions, the emission controls are not bypassed dur-
ing periods of startup and shutdown and cyclones and fabric filters
are not affected by the exhaust stream composition during these peri-
ods. However, due to the nature of electrostatic precipitator oper-
ations, the internal arcing presents a fire and explosion hazard in
the presence of combustibles. For this reason ESPs are generally
shut down during kiln startup and provide only settling chamber con-
trol of particulate emissions. Approximately 40 percent of present
NSPS affected facilities use ESPs for kiln emission control.
A common operating practice during startup is to gradually en-
ergize the ESP once the inlet gas temperature reaches 177°C (350°F).
6-14
-------
The ESP is energized gradually to prevent damage to insulators. In
the case of shutdown, the ESP is left energized so that excessive
emissions are not a problem.
There is little that can be done to reduce emissions during
cement kiln startup and shutdown when an ESP is used as the control.
The excessive emissions are a result of the limitations of the kiln
and ESP in that the kiln cannot be heated rapidly and the ESP cannot
be activated in the presence of combustibles. The following sugges-
tions were made by PEDCo Environmental, Inc. (1978) as means of mini-
mizing the excessive emissions:
1. Use oil or gas fired preheating on coal fired kilns, then
switch to coal after the ESP has been energized.
2. Use sensors to monitor the ESP inlet gas stream for combus-
tible gases. As soon as the gas stream is safe, energize
the ESP.
3. Use a cyclone before the ESP.
6.3 Raw-Mill Bypass
An issue was raised by EPA Region IV personnel about compliance
during periods of excessive emissions caused by bypassing the raw-
mill on a dry process kiln. Usually the raw-mill feeds raw meal (dry
kiln feed material) to storage from which the kiln is fed. Kiln ex-
haust passes through the storage and raw-mill to conserve energy by
preheating the feed. A side benefit of doing this is a reduction in
particulate matter loading in the inlet gas stream to the emission
control device.
6-15
-------
However, when the raw-mill produces raw meal at a faster rate
than the kiln is being fed, it must be shut down until the kiln
catches up. At this time, the kiln exhaust stream bypasses the raw-
mill and goes directly to the emission control device. The increased
loading to the control device yields increased emissions to the
atmosphere which in turn may make the facility out of compliance.
The issue was resolved in that raw-mill bypass is considered a
normally accepted operating procedure in the industry and would not
constitute an upset or malfunction operation, thereby qualifying for
an exemption from the NSPS.
6.4 Use of Alternate Fuels
Most of the NSPS affected facilities use coal as fuel to fire
the kiln and were tested for compliance while using coal. All but
one kiln was found to be in compliance with the standard.
Although one would expect the burning of coal to increase par-
ticulate matter loading in the exhaust stream, the fly ash that does
not become incorporated into the clinker is not expected to raise
emissions to the point that they exceed the standard. It is expected
that the environmental effects of converting from oil or gas to coal
will be primarily the fugitive dust emissions from the handling and
storage of coal (Arthur D. Little, Inc., 1976). Water pollution
resulting from rainwater runoff from outdoor coal storage piles must
also be controlled.
No major air pollution effects are anticipated from the conver-
sion to coal from oil and gas.
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6.5 Gaseous Emissions
The exhaust streams from cement kilns and clinker coolers con-
tain a number of gaseous species in addition to the particulate mat-
ter. The vaporized alkaline salts that condense to a fume and are
removed with mineral dust particles have already been discussed.
The following paragraphs discuss those emissions of carbon monoxide,
sulfur oxides and nitrogen oxides which remain in a gaseous state and
are therefore uncontrolled. Fluorides, hydrocarbons and hydrogen
sulfide may also be emitted.
6.5.1 Carbon Monoxide
Carbon monoxide emissions are generally negligible due to the
excess air present in the kiln. A typical analysis of the kiln ex-
haust gas would have 0 to 2 volume percent carbon monoxide (Daugherty
and Wist, 1974).
6.5.2 Fluorine
Fluorine can be released in the kiln from the raw materials and
fuel during the formation of clinker. Tests performed on the cleaned
gas from 11 cement kilns found no gaseous fluorides (Daugherty and
Wist, 1974). This was expected since calcium fluoride is produced in
the presence of excess calcium oxide and the ESP or baghouse is capa-
ble of removing the solid calcium fluoride.
6.5.3 Hydrocarbons
Hydrocarbons, principally aldehydes, can result from the dis-
charge of the products of incomplete fuel combustion. This would
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ordinarily only occur during startup or malfunction. Data collected
by Daugherty and Wist (1974) indicate an annual emission of 54 Mg of
hydrocarbons from a 444,000 Mg per year dry process plant and only 34
Mg from a 298,000 Mg/yr wet process plant.
6.5.4 Hydrogen Sulfide
Hydrogen sulfide and other odiferous sulfides can be emitted
from a cement plant if certain raw materials such as marl, clay,
shale, and marine shells are used in a wet process kiln. It is also
possible that a kiln operated under reducing conditions, rather than
the usual excess air conditions, can reduce sulfur oxides to poly-
sulfides and hydrogen sulfide (Daugherty and Wist, 1.974). Establish-
ing excess air conditions by reducing the fuel supply and increasing
the air supply will control this.
6.5.5 Nitrogen Oxides
Cement kilns are a very large source of nitrogen oxides (NOX)
emissions. The EPA (1974) estimates NOX emissions as 1.3 kg/Mg
of cement produced. Since 71.4 million Mg of portland cement were
produced in 1977 (Bureau of Mines, 1978), an estimated 93,000 Mg of
NOX were emitted by portland cement plants that year. According to
the 1975 National Emissions Report, Mineral Products is the second
largest industrial process source of NOX emissions. In addition,
data presented by Daugherty and Wist (1974) show NOX emissions
ranging from 150 to 1050 ppm.
6-18
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Nitrogen oxides are formed in the high temperature burning zone
of the cement kiln. This portion of the kiln is maintained at tem-
peratures up to 1650°C and under oxidative conditions. The gener-
ation of NOX in the kiln cannot be avoided because use of any other
nonnitrogen containing oxidizing gas would be prohibitively expen-
sive.
The main factors that result in the production of NOX are the
flame and kiln temperature, the residence time that combustion gases
remain at this temperature, the rate of cooling of these gases, and
the quantity of excess air in the flame. Control of these factors
may permit the operator to sharply reduce the emission of NOX, but
at the present time there is no control equipment in cement plants
for NOX emissions.
It is reported that use of a flash calciner in a suspension pre-
heater will reduce the NOX emitted per ton of cement. This occurs
because the fuel burned in the calciner is at a lower temperature
that does not favor NOX formation. The fuel burned in the calciner
reduces the quantity of fuel that must be burned in the kiln as well
as reducing the length of the kiln (shortening residence time)
required for clinker formation, thus reducing NOX formation.
6.5.6 Sulfur Oxides
Sulfur oxide (SOX) emissions from cement kilns are essentially
all sulfur dioxide (802) from burning raw meal in the kiln. The
burned fuel and the raw meal both contribute to the total S02
6-19
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generated. However, very little of the S(>2 generated is actually
emitted into the atmosphere. As the S02 is generated, it comes
into direct contact with calcium oxide and alkaline oxides already
formed in the kiln. Approximately 75 percent of the S02 is sorbed
on the oxide particles and eventually is incorporated in the clinker
(Ketels et al., 1976). In addition, 50 percent of the remaining
SC>2 is removed by sorption in a fabric filter baghouse by the same
mechanism.
The uncontrolled emission of SC>2 is estimated by EPA (1977) as
5.1 kg/Mg of cement produced plus the S02 contributed by the fuel:
2.15 kg/Mg for oil and 3.45 kg/Mg for coal. If all cement plants
were converted to use 3 percent sulfur coal, in a kiln controlled by
a baghouse, then an estimated 186,000 Mg of 862 would have been em-
itted during 1977. This is a very high estimate and does not take
into consideration the following factors:
1. Sulfur content of the kiln feed can vary widely
2. Sorption of S02 will be affected by the availability of
calcium and alkaline oxides which will vary with the kiln
feed
3. The type of process—the mechanism of a suspension
preheater—should permit greater sorption of S02-
Only one NSPS cement plant was tested for S02 emissions. The
Louisville Cement Plant at Speed, Indiana, showed S02 emissions of
0.716 kg/Mg feed with the mill on and 1.517 kg/Mg feed with the mill
off. These measurements are substantially less than the EPA estimate
of uncontrolled emissions mentioned above.
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7.0 FINDINGS AND RECOMMENDATIONS
The primary objective of this report has been to assess the need
for revision of the existing NSPS for portland cement plants. The
particulate matter standard is reviewed below. The existing opacity
standard was thoroughly reviewed in the report to the U.S. District
Court of Appeals for the District of Columbia in answer to their
remand of the standard to EPA.
7.1 Findings
7.1.1 Process Emission Control Technology
• The current best demonstrated control technology for partic-
ulate matter emissions has changed since the original stan-
dard was promulgated only in that kilns equipped with ESPs
are capable of meeting the standard. Fabric filter baghouses
continue to share the position as a best control technology
since the original standard was based on this type of con-
trol. No new developments have occurred in either of these
technologies to substantiate a reduction in the allowable
emissions from either kilns or clinker coolers.
• Although the measured kiln emissions were as low as 0.013
kg/Mg feed, there was no indication that this level could
be maintained or that other units testing as high as 0.142
kg/Mg feed could emit less. There was no correlation between
kiln size, control technology, wet or dry process, and emis-
sion rate.
• The range of emission rates for clinker coolers (0.005 kg/Mg
to 0.43 kg/Mg feed) also showed no correlation with known
variables or that these levels could be maintained with age.
• Both the kiln and clinker coolers are presently required to
reduce emissions greater than 99 percent.
7.1.2 Economic Considerations
The cement industry is a capital and energy intensive indus-
try that has had difficulty attracting capital investment due
to low profitability in past years.
7-1
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• The cost of pollution controls to the cement industry is
approximately 10 percent of capital investment at the pre-
sent time.
• The U.S. is currently entering a period of cement capacity
shortage and increased pollution abatement costs will have
an effect on investment decisions.
7.1.3 Gaseous Emissions
• The emissions of carbon monoxide, hydrocarbons, fluorides,
and hydrogen sulfide are not significant.
• Sulfur dioxide emissions are controlled substantially (nearly
90 percent) already, without a standard. It is not known if
emissions can be reduced beyond that level.
• Nitrogen oxides are emitted from cement kilns in large quan-
tities. There are no known controls for these emissions.
Possible methods of reducing the quantity of NOX emitted
have not been tested.
7.2 Recommendations
7.2.1 Opacity NSPS
There is no justification for changing the opacity standard for
any portion of the portland cement plant.
7.2.2 Particulate Matter NSPS
There is no justification for changing the particulate matter
standard for either the kiln or clinker cooler because:
• The best demonstrated control technologies, ESP and/or bag-
house, are currently in use at all new portland cement
plants.
• The current standard requires greater than 99 percent reduc-
tion in emissions, which is the maximum for these control
technologies.
7-2
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7.2.3 Gaseous Emissions
It is recommended that a monitoring program be initiated to
determine the actual emission rate of 802 an<* N0x from port land
cement kilns.
It is further recommended that research and development be
conducted to find means for reducing NOX emissions.
7-3
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8.0 REFERENCES
Arthur D. Little, Inc., 1976. Environmental Considerations of
Selected Energy Conserving Manufacturing Process Options:
Volume X. Cement Industry Report. PB-264 276. NTIS,
Springfield, Va.
Bowker, A.H. and G.J. Lieberman, 1963. Engineering Statistics
(Fifth Printing), Prentice-Hall, Inc., Englewood Cliffs, N.J.
Business Week, 1977. Cement's Bad Case of Regional Softness.
November 14. p. 41.
Chemical and Engineering News, 1978. Chemical Flue Gas Conditioning
Growing In Use. October 9. p. 14.
Daugherty, K.E. and A.O. Wist, 1974. Air Pollution in the Cement
Industry. In Recent Advances in Air Pollution Control. AIChE
Symposium Service, 70 (137):50-55.
Davis, T.A. and D.B. Hooks, 1975. Disposal and Utilization of Waste
Kiln Dust from the Cement Industry. EPA-670/2-75-043. NTIS,
Springfield, Va.
Frondistou-Yannas, S.A., 1976. The Hydraulic Cement Industry in
the United States, A State-of-the-Art Review. Massachusetts
Institute of Technology. PB-265 874. NTIS, Springfield, Va.
Gieseke, J.A. and E.W. Schmidt, 1978. Characteristics of Dust in
Collector Selection. Battelle Columbus Laboratories. In
Pollution Control Short Course, Apr. 24-28, 1978, Portland
Cement Association, Skokie, 111.
Retels, P.A., J.D. Nesbitt, and R.D. Oberle, 1976. Survey of Emis-
sions Control and Combustion Equipment Data in Industrial
Process Heating. Institute of Gas Technology. PB-263 453.
NTIS, Springfield, Va.
Rohanowski, F.I. and J.L. Shy, 1978. Second-generation Precalcining
with By-pass Alternatives for Alkali Control. Allis-Chalmers
Corp. In Proceedings of the International 13th Cement Seminar.
Maclean-Hunter Publishing Corporation, Chicago, 111.
Lind, J.H. Electrostatic Precipitators. F.L. Smith & Co. In
Pollution Control Short Course, Apr. 24-28, 1978, Portland
Cement Association, Skokie, 111.
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MITRE Corporation, 1978. Follow-up communications to Watson et al.,
1978, with EPA Regional Offices, State Air Pollution Control
Offices, and cement plant representatives.
Mongoven, J., 1977. Prices and Capacity Expansion in the Cement
Industry. Executive Office of the President, Council on Wage
and Price Stability, Washington, D.C.
PEDCo Environmental, Inc., 1978. A Review of Particulate Emission
Problems During Cement Kiln Start-up. (Preliminary Draft).
Cincinnati, Ohio.
Portland Cement Association, 1978. U.S. Portland Cement Industry:
Plant Information Summary. December 31, 1977. Skokie, 111.
Portland Cement Association, 1978a. Announced Cement/Clinker Capac-
ity Changes as of November 15, 1978. Personal communication
with T.R. O'Connor, Director, Economic Research Department,
Skokie, 111.
Research Triangle Institute, 1970. Establishment of National Emis-
sion Standards for Stationary Sources, Volume VI, Portland
Cement Manufacturing Plants. Research Triangle Park, N.C.
Rutledge, G.L., F.J. Dreiling, and B.C. Dunlap, 1978. Capital Expen-
ditures by Business for Pollution Abatement, 1973-77 and Planned
1978. In. Survey of Current Business, June 1978. U.S.
Department of Commerce, Washington, D.C.
Schumway, R.E, , D.W. Janocik, and C.U. Pierson, 1978. The Applica-
tion of Gravel Bed Filters on Clinker Cooler Vents. Rexnord
Inc. In_ Pollution Control Short Course, Apr. 24-28, 1978,
Portland Cement Association, Skokie, 111.
U.S. Department of Health, Education, and Welfare, 1967. Atmospheric
Emissions from the Manufacture of Portland Cement. Cincinnati,
Ohio.
U.S. Department of Interior, Bureau of Mines, 1973. Cement. Miner-
als Yearbook, 1972. Washington, D.C.
U.S. Department of Interior, Bureau of Mines, 1975. Cement. Miner-
als Yearbook, 1974. Washington, D.C.
U.S. Department of Interior, Bureau of Mines, 1976. Cement. Miner-
als Yearbook, 1975. Washington, D.C.
8-2
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U.S. Department of Interior, Bureau of Mines, 1978. Cement.
December 1977. Mineral Industry Surveys. Washington, D.C.
U.S. Environmental Protection Agency, 1974. EPA Response to Remand
Ordered by U.S. Court of Appeals for the District of Columbia in
Portland Cement Association v. Ruckelshaus. EPA-450/2-74-023.
Research Triangle Park, N.C.
U.S. Environmental Protection Agency, 1977. Compilation of Air Pol-
lutant Emission Factors, Third Edition, AP-42. Office of Air
Quality Planning and Standards, Research Triangle Park, N.C.
U.S. Environmental Protection Agency, 1978. 1975 National Emissions
Report. National Emissions Data System of the Aerometric and
Emissions Reporting System. EPA-450/2-78-020. Office of Air
Planning and Standards, Research Triangle Park, N.C.
Watson, J.W., L.J. Duncan, E.L. Keitz, and K.J. Brooks, 1978.
Regional Views on NSPS for Selected Categories. MTR-7772.
MITRE Corporation, McLean, Va.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/3-79-012
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE ANDSUBTITLE
A Review of Standards of Performance for New
Stationary Sources - Portland Cement Industry
5. REPORT DAT6
October 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Kris W. Barrett
8. PERFORMING ORGANIZATION REPORT NO.
MTR-7982
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Metrek Division of the MITRE Corporation
1820 Do!ley Madison Boulevard
Me Lean, VA 22102
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-2526
12. SPONSORING AGENCY NAME AND ADDRESS
DAA for Air Quality Planning and Standards
Office of Air, Noise, and Radiation
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA 200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report reviews the current Standards of Performance for New Stationary
Sources: Subpart F - Portland Cement Plants. It includes a summary of the
current standards, the status of current applicable control technology, and
the ability of plants to meet the current standards. No changes to the existing
standard are recommended, but EPA should continue evaluation of sulfur oxide
and nitrogen oxide controls with a view toward incorporating these emissions
under the scope of the standard at a later date.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
83
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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