United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-88/012 Nov. 1988
c/EPA Project Summary
Cost of Controlling Directly
Emitted Acidic Emissions from
Major Industrial Sources
T.E. Emmel, J.T. Waddell, and R.C. Adams
Stationary U.S. sources, each of which
as a group emits over 4,500 Mg (5000
tons) or more of acidic material (e.g.,
acid sulfates, HCI, HF) per year, include:
utility and industrial boilers, Glaus sulfur
recovery plants, catalytic cracking units,
primary copper smelters, coke oven
plants, primary aluminum smelters, and
municipal solid waste incinerators. Utility
and industrial boilers are by far the
largest sources, emitting about 760,000
Mg (830,000 tons) and 180,000-250,000
Mg (200,000-275,000 tons) of acidic
material per year, respectively. Using a
model plant approach, estimates were
made of costs for retrofitting selected
control systems to these plants. Cost-
effectiveness (defined as the unit annual
cost for removal of the acidic materials)
of each control system was calculated
based on the anticipated performance of
the system. If SO2 is simultaneously
emitted with the acidic materials, con-
trols were selected which removed both
SO2 and the acidic materials. Cost-
effectiveness was considerably better for
the combined (SO2 + acidic material)
removal systems. For example, a
limestone wet scrubber on a 600 MW,
high-sulfur-coal-fired utility boiler was
estimated to have a cost-effectiveness of
$65,000/Mg ($59,000/ton) for acid
sulfates, HCI, and HF, but a combined
(SO2 + acidic material) cost effec-
tiveness of $1100/Mg ($1000/ton). Be-
cause of a need for performance data on
acidic emissions control systems, it
would be desirable if research could be
conducted on removal of acid sulfates
and nitrates by existing gaseous and par-
ticulate control systems.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of the
research project that is fully documented
in a separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Acid Precipitation Act of 1980
established an Interagency Task Force to
develop a comprehensive research pro-
gram for investigation of acid precipitation
issues. The National Acid Precipitation
Assessment Program (NAPAP) was subse-
quently established to develop the
necessary data and provide a framework
for policy recommendations in regard to
acid precipitation. One aspect of the overall
acid deposition issue is to understand the
role and significance of direct emissions of
acidic materials. As such, it is necessary
to identify the major industrial sources of
direct emissions of acidic material (e.g.,
sulfates, chlorides) and to evaluate the con-
trol of these materials. In addition, it is im-
portant to know if the most cost-effective
methods for reducing acidic emissions dif-
fer from those for controlling acid deposi-
tion precursors (SO2> NOX, and VOC).
Accordingly, the objectives of this study
were: 1) to identify and characterize sta-
tionary combustion and industrial sources
of directly emitted acidic materials in the
U.S.; 2) to evaluate the technical feasibility
of control techniques for these sources; and
3) to estimate the costs of applying these
control technologies. This assessment was
conducted by reviewing and analyzing ex-
isting data, including the preliminary
control strategies evaluated by the In-
teragency Task Force. The potential for
emissions from transportation sources was
not examined in this study.
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Results of the study can be used to
evaluate the merits of controlling directly
emitted acidic materials as part of a policy
evaluation of overall acid deposition con-
trol strategies. For example, if it were deter-
mined that (for a region) local emissions of
directly emitted acid materials were more
significant than long range precursor emit-
ters, the information in this report could be
used to evaluate the cost-effectiveness of
controlling local sources of directly emitted
acidic materials versus sources of long
range precursor emissions.
Methodology
To identify and characterize sources of
directly emitted acidic materials, national
acidic materials emissions of all stationary
combustion and industrial sources were
identiied by means of a literature search.
Model units were then developed for
sources that emit 4,500 Mg (5,000 tons) or
more of acidic material per year. The model
units were used as bases for establishing
control techniques and for determining the
technical feasibility of candidate conven-
tional control techniques. The cost of retrofit
controls for the model units was estimated,
and cost-effectiveness values were deter-
mined. The cost-effectiveness of acidic
materials control was compared with the
cost-effectiveness where applicable of SO2
which is co-emitted with acidic materials.
Additionally, promising research and
development activities relevant to acid
materials control were also examined.
Results and Recommendations
The major combustion and industrial
sources of directly emitted acidic materials
that were identified during this study are
presented in Table 1. For most source
categories, emissions were estimated
using emissions factors and combustion
and process capacities found in the litera-
ture. Utility and industrial boilers are by
far the largest acidic emissions sources
in the U.S., producing about 760,000 Mg
(830,000 tons) and 180,000-250,000 Mg
(200,000-275,000 tons) of acidic material
emissions per year, respectively. It was also
estimated that emissions of directly emit-
ted acidic materials represent only 2% of
the annual emissions of SO2, NOX, and
VOC (which are acid precipitation precur-
sors) from stationary sources.
Based on information obtained in the
literature, model plants, including the most
applicable acidic material controls, were
developed for sources that emit over 4,500
Mg (5,000 tons) of acidic material per year.
This cutoff point allowed the project to focus
on source categories with the greatest
emissions. The major sources considered
include utility and industrial boilers, Claus
sulfur recovery plants, catalytic cracking
units, primary copper smelters, coke oven
plants, primary aluminum smelters, and
municipal solid waste incinerators.
Although Kraft pulp mills, gypsum plants,
and cement plants are large sulfate emis-
sions sources, they were not analyzed fur-
ther because the compounds emitted are
alkaline or pH neutral. In addition, gypsum
ponds were identified as a source category
emitting large amounts of HF. However, HF
emissions from gypsum ponds are reduced
by water treatment methods, whereas this
study focused primarily on controls which
treat acidic gases. Thus, no further analysis
was attempted.
Little performance data is available con-
cerning the control of acidic emissions by
currently operating control systems.
Therefore, the systems chosen for model
unit development are generally those which
are demonstrated for control of SO2 and
NOX and provide the greatest potential for
control of acidic material emissions.
Cost analyses were performed to
estimate the costs required for retrofitting
the selected control systems to model
plants. Table 2 summarizes the control
systems analyzed for each significant
source category and their respective cost-
effectiveness. Cost-effectivenes is defined
as the unit annual cost for removing the
acidic materials. If SO2 is present in the
emission stream, controls were selected for
concurrent removal of SO2 and the acidic
materials. Typically, the volume of SO2 is
quite large compared to that of acidic
materials. Therefore, cost-effectiveness is
considerably improved if calculated for the
combined removal of acidic materials and
SO2. The combined cost-effectiveness
values are included in Table. 2.
The greatest obstacle in this study was
the lack of available performance data for
acidic emissions control systems. No infor-
mation was available concerning the con-
trol of acid nitrates. All test data for remov-
ing acid sulfates were presented in terms
of H2SO4 mist control and show a wide
range of removal efficiencies. Therefore, it
would be desirable if research could be
directed toward quantitating the acid sulfate
and acid nitrate control performances of ex-
isting applicable gaseous and paniculate
controls. While data for HCI and HF
removal are also lacking, the need for
research in this area is not urgent, because
HCI and HF have high affinities to the
alkaline solutions commonly used by FGD
systems and, as indicated by the limited
test data, removal is expected to be high.
The technologies identified as being
most applicable to reducing directly emit-
ted acidic materials are wet/dry scrubbing
techniques. Conventional electrostatic
precipitators and fabric filters are not as ef-
fective because acidic material frequently
forms downstream of where these devices
are typically located. For this reason, the
most cost-effective control devices for
sulfates, fluorides, and chloride are the
same as would be employed for SO2. Con-
ventional combustion modification techni-
ques, used to control NOX emissions from
boilers, were identified as the best commer-
cially available methods for reducing nitrate
emissions.
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Table 1. National Emissions
Source Category
Utility Boilers
Coal
Residual Oil
Distillate Oil
Industrial Boilers
Coal
Residual Oil
Distillate Oil
Municipal Solid Waste
Catalytic Cracking
Primary Copper
Primary Aluminum
Gypsum Ponds
Claus Plants
Coke Ovens
Proplyene Oxide
Manufacturing
Residential Boilers
Sulfuric Acid Plants
Phosphoric Acid Plants
Triple Superphosphate
Manufacturing
Primary Zinc
Diammonium Phosphate
Manufacturing
HF Manufacturing
Estimates for Identified Source Categories
Acid Sulfate Emissions Nitrate Emissions
(703 Mg/yr) (103 Mg/yr
103 tons/yr) 103 tons/yr)
107(117) 64(70)
25 (28)
3.6 (4)
20-81 (25-89) 32 (35)
5-10.4 (5.5-11.5)
27 (30)
11.3(12.5)
8.6-10.4 (9.5-11.5)
0.18-0.41 (0.2-0.45)
5.4 (6)
5 (5.5)
1.8 (2)
0.2 (0.25)
Tattle 2. Summary of Controls Analyzed and Cost-Effectiveness
Source Category/ Fuel
Process Capacity Type" Control
Industrial Boilers''
30 5 GJ/hr (3O MMBtu/hr)
HCI Emissions HF Emissions Total Emissions Year
(103 Mg/yr) (10* Mg/yr) (103 Mg/yr) Data
103 tons/yr) 103 tons/yr) 103 tons/yr) Reported
496(546) 60(66) 756(831) 1980/1982
88 (96) 10.6(11.5) 182-248(203-273) 1980/1982
20 (22) 20 (22) —
11.3(12.5) 1983
8.6-10.4 (9.5-11.5) 1984
5.9(6.5) 6.1-6.3(6.7-7) 1983
5.9 (6.5) 5.9 (6.5) 1980
5.4 (6) 1980
5 (5.5) 1983
2.7-4.1(3-4.5) 2.7-4.1(3-4.5) 1980
2.7(3) 0.2(0.25) 2.9(3.25) 1974
1.8 (2) 1982
0.14(0.15) 0.14(0.15) 1980
0.18(0.2) 0.18(0.2) 1980
0.2 (0.25) 1983
0.2 (0.25) 0.2 (0.25) 1980
0.01-1.2 (0.01-1.35) 0.01-1.2 (0.01-1.35) 1980
Cost-Effectiveness of Removal
Acidic Species Acidic Material Acidic Material + SO2
Controlled $/Mg ($/ton) $/Mg ($/ton)
HSC Sodium-Based Scrubber SuHates, HCI, HF 39,300 (35,700) 810 (740)
LSC 24,400 (22,200) 2,640 (2,400)
DO Sulfates 359,000 (327,000) 4,890 (4,440)
RO 492,800 (448,000) 1,110 (1,010)
HSC Dual Alkali Scrubber
LSC
DO
RO
HSC Lime Spray Dryer
LSC
DO
RO
Sulfates, HCI, HF 86,100 (78,300) 1,770 (1.610)
66,000 (60,000) 7,130 (6,480)
Sulfates 999,000 (908,000) 13,600 (12,360)
1,200,000 (1,090,000) 2,720 (2,470)
SuHates, HCI, HF 72,600 (66,000) 1,910 (1,730)
59,900 (54,400) 7,930 (7,210)
Sulfates 626,000 (569,000) 15,400 (14,000)
704,000 (640,000) 2,920 (2,660)
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Table 2. (Continued)
Source Category/
Process Capacity
406 GJ/hr (400 MMBtu/hr)
Utility Boiler"
2,0311 GJ/hr (2,000 MMBtu/hr)
5,078 GJ/hr (5,000 MMBtu/hr)
Cost-Effectiveness of Removal
Fuel
Typ^
HSC
LSC
DO
RO
HSC
LSC
DO
RO
HSC
LSC
DO
RO
HSC
LSC
Coal
HSC
LSC
RO
HSC
LSC
HSC
LSC
Coal
Coal
Oil
Coal
Oil
HSC
LSC
RO
HSC
LSC
HSC
LSC
Coal
Coal
Oil
Coal
Oil
Control
Sodium-Based Scrubber
Dual Alkali Scrubber
Lime Spray Dryer
Low Excess Air
Overfire Air
Limestone Wet Scrubber
Wellman-Lord System
Lime Spray Dryer
Low A/0* Burners
Low Excess Air
Overfire Air
Limestone Wet Scrubber
Wellman-Lord System
Lime Spray Dryer
Low A/Ox Burners
Low Excess Air
Overfire Air
Acidic Species
Controlled
Sulfates, HCI, HF
Sulfates
Sulfates, HCI, HF
Sulfates
Sulfates, HCI, HF
Sulfates
A/O/
A/0/
Sulfates, HCI, HF
Sulfates
Sulfates, HCI, HF
Sulfates, HCI, HF
A/0/
A/0/
A/O/
Sulfates, HCI, HF
Sulfates
Sulfates, HCI, HF
Sulfates, HCI, HF
WO/
A/0/
A/O/
Acidic Material Acidic Material + SO2
$/Mg ($fton) $/Mg (Won)
18,900
7,000
89,000
200,000
20,600
11,400
156,000
249,000
21,700
14,300
119,000
172,000
132
9
112
64,700
52,600
291,000
94,600
62,800
62,100
47,300
123
7
2
96
131
45,700
37,600
229,000
74,300
49,400
48,000
35,300
71
3
1
56
83
(17,200)
(6,300)
(81,000)
(182,000)
(18,700)
(10,300)
(142,000)
(226,000)
(19,800)
(13,000)
(108,000)
(156,000)
(120)
(8)
(102)
(58,800)
(47,800)
(264,600)
(86,000)
(57, 100)
(56,500)
(43,000)
(112)
(6)
(2)
(87)
(119)
(41,600)
(34,200)
(208,000)
(67,600)
(44,900)
(43,600)
(32,000)
(64)
(3)
(1)
(51)
(75)
390
750
1,180
450
420
1,220
2,060
560
560
1,810
2,870
710
1,130
4,960
2,350
1,660
5,930
1,140
4,650
800
3,550
1,850
1,300
4,670
880
3,460
(350)
(680)
(1,070)
(410)
(380)
(1,110)
(1,870)
(510)
(510)
(1,650)
(2,610)
(640)
(1,030)
(4,510)
(2,140)
(1,510)
(5,390)
(1,040)
(4,230)
(730)
(3,230)
(1,680)
(1, 190)
(4,240)
(800)
(3,150)
C/aus Plants
10 Mg/day (11 tons/day)
100 Mg/day (110 tons/day)
250 Mg/day (275 tons/day)
Amine Tail Gas Treatment
Sulfates 242,800 (220,300) 2,420 (2,200)
77,200 (70,000) 770 (700)
54,900 (49,800) 550 (500)
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Table 2. (Continued)
Cost-Effectiveness of Removal
Source Category/
Process Capacity
Fluid Catalytic
Cracking Units
2,500 mVsd (15,725 bbl/sdf
8,000 m3/sd (50,320 bbl/sdjf
Primary Copper Smelters
115,000 Mg/yr (127,000 tons/yr)
Coke Oven Plants
2000 Mg/day (220 tons/day)
6000 Mg/day (6600 tons/day)
Municipal Solid Waste (MSW)
380 Mg/day (420 tons/day)
730 Mg/day (800 tons/day)
Fuel Acidic Species Acidic Material Acidic Material + SOj
Type3 Control Controlled $/Mg ($/ton) $/Mg ($/ton)
ISF" Sodium-Based Scrubber9 Sutfates 93,640
HSP* 63,450
ISFd 62,580
HSP* 47,830
Sulfuric Acid Plant Sulfates 9,800
Vacuum Carbonate System Sulfates 11,700
6,900
MSW Sodium-Based Scrubbed HCL 1,900
MSW 1,480
(84,950)
(57,560)
(56,770)
(43,390)
(8,900)
(10,600)
(6,300)
(1,730)
(1,340)
1,090
740
730
560
130
950
570
1,020
970
(990)
(670)
(660)
(510)
(120)
(870)
(520)
(1,120)
(880)
*HSC = high-sulfur coal; LSC = low-sulfur coal; DO = distillate oil; RO = residual oil.
"Boiler capacities presented in terms of heat input.
°No emissions data, specifically in terms of acid nitrate emissions, were available. Thus, all cost-effectiveness results are given in terms of controlling NOX emissions.
"Catalytic cracking unit feed rather than fuel. ISF = intermediate-sulfur feed (1.5 wt. % S); HSF = high-sulfur feed (3.5 wt. % S).
"High energy venturi scrubber using soda-ash-based scrubbing liquor.
'Single stage acid plant.
^Employs caustic-soda-based scrubbing liquor.
hExcludes benefits of concurrent SO2 reductions.
'm3/sd: cubic meter per stream day
bbl/sd: barrel per stream day.
T. £. Emmel, J. T. Waddell, and R. C. Adams are with Radian Corporation,
Research Triangle Park. NC 27709.
Julian W. Jones is the EPA Project Officer (see below).
The complete report, entitled "Cost of Controllling Directly Emitted Acidic
Emissions from Major Industrial Sources," (Order No. PB 88-234 190/AS;
Cost: $19.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
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