United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-79-003
January 1979
Air
&ER&
A Review of Standards
of Performance for New
Stationary Sources -
Acid Plants
-------
EPA-450/3-79-003
A Review of Standards of Performance
for New Stationary Sources -
Sulfuric Acid Plants
by
Marvin Drabkin and Kathryn J. Brooks
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
January 1979
-------
This report hasbeen reviewed by the Emission Standardsand Engineering Division of the Office of Air
Quality Planning and Standards, EPA, and approved for publication Mention of trade names or
commercial products is not intended to constitute endorsement or recommendation for use Copies of
this report are available through the Library Services Office (MD-35), U.S Environmental Protection
Agency, Research Triangle Park, N.C 27711; or, for a fee, from the National Technical Information
Services, 5285 Port Royal Road, Springfield, Virginia 22161
Publication No EPA-450/3-79-003
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TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS viii
LIST OF TABLES ix
1.0 EXECUTIVE SUMMARY 1-1
1.1 Best Demonstrated Control Technology 1-1
1.2 Current S02 NSPS Levels Achievable With Best
Demonstrated Control Technology 1-2
1.3 Economic Considerations Affecting the S02 NSPS 1-3
1.4 Current Acid Mist Levels (and Related Opacity Levels)
Achievable With Best Demonstrated Control Technology 1-4
2.0 INTRODUCTION 2-1
3.0 CURRENT STANDARDS FOR SULFURIC ACID PLANTS 3-1
3.1 Background Information 3-1
3.2 Facilities Affected 3-2
3.3 Controlled Pollutants and Emission Levels 3-3
3.4 Testing and Monitoring Requirements 3-5
3.4.1 Testing Requirements 3-5
3.4.2 Monitoring Requirements 3-6
4.0 STATUS OF CONTROL TECHNOLOGY 4-1
4.1 Status of Sulfuric Acid Manufacturing Industry
Since the Promulgation of the NSPS 4-1
4.1.1 Geographic Distribution '4-1
4.1.2 Production 4-1
4.1.3 Industrial Trends 4-10
4.2 Contact Process for Sulfuric Acid Production 4-11
4.2.1 Elemental Sulfur Burning Plants 4-11
4.2.2 Spent Acid and Other By-Product Plants 4-13
4.3 Emissions from Contact Process Sulfuric Acid Plants 4-15
4.3.1 Sulfur Dioxide 4-15
4.3.2 Acid Mist Formation 4-17
4.3.3 Visible Emissions (Opacity) 4-21
4.3.4 Oxides of Nitrogen 4-23
iii
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TABLE OF CONTENTS (cont.)
Page
4.4 Control Technology Applicable to the NSPS Control of
S02 Emissions from Contact Process Sulfuric Acid Plants 4-24
4.4.1 Dual Absorption Process 4-24
4.4.2 Sodium Sulfite - Bisulfite Scrubbing 4-28
4.4.3 Ammonia Scrubbing 4-29
4.4.4 Molecular Sieves 4-30
4.5 Control Technology Applicable to the NSPS for Acid Mist
Emissions from Contact Process Sulfuric Acid Plants 4-30
4.5.1 Vertical Tube Mist Eliminators 4-31
4.5.2 Vertical Panel Mist Eliminators 4-34
4.5.3 Horizontal Dual Pad Mist Eliminators 4-37
5.0 INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS 5-1
5.1 Test Results EPA Regional Sources 5-1
5.2 Analysis of NSPS Test Results 5-1
5.2.1 Control Technology Used to Achieve Compliance 5-6
5.2.2 Statistical Analysis of NSPS Compliance Test Data 5-7
5.2.3 Validity of NSPS Test Data 5-7
5.2.4 Comparison of NSPS Compliance Test Data with Day-
to-Day Emission Control Performance 5-9
5.2.5 Emission Control Performance Based on Excess
Emissions Reports 5-11
5.3 (Indications of the Need for a Revised Standard 5-11
*• *"
5.3.1 S02 Standard 5-11
5.3.2 Acid Mist NSPS (and Related Opacity Standard) 5-13
6.0 ANALYSIS OF POSSIBLE REVISIONS TO THE STANDARD 6-1
6.1 Effect of NSPS Revision on Sulfuric Acid Production
Economics 6-1
6.2 Effects of New Sulfuric Acid Plant Construction on the
NSPS 6-5
iv
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TABLE OF CONTENTS (Concluded)
Page
7.0 FINDINGS AND RECOMMENDATIONS 7-1
7.1 Findings 7-1
7.1.1 S02 NSPS 7-1
7.1.2 Acid Mist NSPS (and Related Opacity Standard) 7-2
7.2 Recommendations 7-3
7.2.1 S02 NSPS 7-3
7.2.2 Acid Mist NSPS (and Related Opacity Standard) 7-4
8.0 REFERENCES 8-1
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LIST OF ILLUSTRATIONS
Figure Number Page
4-1 Contact Process Sulfuric Acid Plants
Completed in the U.S. Since 1971 4-4
4-2 Gross Total Production of Sulfuric Acid:
1971 to 1977 4-6
4-3 Sulfuric Acid End Uses 4-8
4-4 Percent of Total Production of Sulfuric
Acid in Captive Use 4-9
4-5 Contact-Process Sulfuric Acid Plant
Burning Elemental Sulfur 4-12
4-6 Contact-Process Sulfuric Acid Plant
Burning Spent Acid 4-14
4-7 Sulfuric Acid Plant Feedstock Sulfur
Conversion vs. Volumetric and Mass S0£
Emissions at Various Inlet SC>2 Concentrations
by Volume 4-18
4-8 Sulfuric Acid Plant Concentrations of Mist
for Mass Stack Emissions Per Unit of Production
at Inlet S02 Volume Concentrations 4-22
4-9 Dual Absorption Sulfuric Acid Plant Flow
Diagram 4-27
4-10 Vertical Tube Mist Eliminator Installation 4-32
4-11 Vertical Panel Mist Eliminator Installation 4-36
4-12 Horizontal Dual Pad Mist Eliminator 4-38
5-1 Contact Process Sulfuric Acid Plant NSPS
Compliance Test Results - S0_ Emissions 5-3
5-2 Contact Process Sulfuric Acid Plants NSPS
Compliance Test Results - Acid Mist Emissions 5-4
vi
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LIST OF TABLES
Table Number Page
4-1 Summary of New Sulfuric Acid Plant
Completions Since the Promulgation of
the NSPS 4-2
4-2 Sulfuric Acid Plants Planned or Under
Construction 4-3
4-3 Sulfuric Acid Production (Mg of 100%
H2S04) 4-5
4-4 Sulfur Dioxide Conversion Efficiencies and
Emissions for Four-Stage Converters 4-16
4-5 Contact Process Sulfuric Acid Plant Built
Since Promulgation of the NSPS 4-25
5-1 NSPS Compliance Test Results for Sulfuric
Acid Plants 5-2
5-2 NSPS Compliance Test Results for New
Sulfuric Acid Plants Breakdown by Emissions
Level 5-5
5-3 Effect of Plant and Catalyst Age on S02
Emission Level 5-10
6-1 Basic Data Used in Catalyst Replacement
Cost Calculations 6-3
6-2 Effect of Catalyst Replacement on Cost of
Production of Sulfuric Acid in a Dual
Absorption Plant 6-4
6-3 Projected Cumulative S(>2 Emissions from
New Contact Sulfuric Acid Plants Added
Between 1981 and 1984 6-7
6-4 Projected Cumulative Acid Mist Emissions
From New Contact Sulfuric Acid Plants Added
Between 1981 and 1984 6-8
vii
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1.0 EXECUTIVE SUMMARY
The objective of this report is to review the New Source
Performance Standard (NSPS) for the sulfuric acid plant production
unit 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 compliance test data available for plants built since
the promulgation of the NSPS. The NSPS review includes the S(>2
emission and acid mist emission standards. The opacity standard,
while included in the sulfuric acid plant NSPS, is not reviewed
separately since it is directly related to the acid mist emission
standard. The following paragraphs summarize the results and
conclusions of the analysis, as well as recommendations for future
action.
1.1 Best Demonstrated Control Technology
Sulfur dioxide and acid mist are present in the tail gas from
the contact process sulfuric acid production unit. In modern
four-stage converter contact process plants burning sulfur with
approximately 8 percent S(>2 in the converter feed, and producing
98 percent acid, SO2 and acid mist emissions are generated at
the rate of 13 to 28 kg/Mg of 100 percent acid (26 to 56 Ib/ton)
and 0.2 to 2 kg/Mg of 100 percent acid (0.4 to 4 Ib/ton), respec-
tively. The dual absorption process is the best demonstrated control
1-1
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technology* for S(>2 emissions from sulfuric acid plants, while
the high efficiency acid mist eliminator is the best demonstrated
control technology for acid mist emissions. These two emission
control systems have become the systems of choice for sulfuric acid
plants built or modified since the promulation of the NSPS. Twenty-
eight of the 32 new or modified sulfuric acid production plants built
since 1971 and subject to NSPS incorporate the dual absorption pro-
cess; and all 32 plants use the high efficiency acid mist eliminator.
1.2 Current SO? NSPS Levels Achievable With Best Demonstrated
Control Technology
All 32 sulfuric acid production units subject to NSPS showed
compliance with the current S02 NSPS control level of 2 kg/Mg (4
Ib/ton). The 26 compliance test results for dual absorption plants
showed a considerable range from a low of 0.16 kg/Mg (0.32 Ib/ton) to
a high of 1.9 kg/Mg (3.7 Ib/ton) with an average of 0.09 kg/Mg (1.8
Ib/ton). The average S02 emission level obtained in the NSPS com-
pliance tests for dual absorption plants is about one order of magni-
tude lower than the S(>2 emission level obtained from uncontrolled
single absorption plants. Information received on the performance of
several sulfuric acid plants indicates that low S02 emission
It should be noted that standards of performance for new sources
established under Section 111 of the Clean Air Act reflect emission
limits achievable with the best adequately demonstrated technolog-
ical system of continuous emission reduction (taking into considera-
tion the cost of achieving such emission reduction, as well as any
nonair quality health and environmental impacts and energy require-
ments) .
1-2
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results achieved in NSPS compliance tests apparently do not reflect
day-to-day S(>2 emission levels. These levels appear to rise toward
the standard as the conversion catalyst ages and its activity drops.
Additionally, there may be some question about the validity of low
S02 NSPS values, i.e. less than 1 kg/Mg (2 Ib/ton), due to defects
in the original EPA Method 8. Based on all of these considerations,
it is recommended that the level of SC>2 emissions as specified in
the current NSPS not be changed at this time.
1.3 Economic Considerations Affecting the S02 NSPS
The cost of more frequent conversion catalyst replacement as a
method of maintaining low SC>2 emission values, i.e., below 1 kg/Mg
(2 lb/ ton), was estimated in this study. Complete replacement of
catalyst in the first three beds of the four-bed catalytic converter,
approximately three times as frequently as is normally practiced, was
estimated to result in an increase in operating cost of 55 cents/Mg
of 100 percent acid. From an economic standpoint, this method would
not be feasible since pretax profits could be reduced by 20 percent
or more.
Based on an estimated sulfuric acid plant growth rate of four
new production lines per year between 1981 and 1984, a 50 percent re-
duction of the present S02 NSPS level—from 2 kg/Mg (4 Ib/ton) to 1
kg/Mg (2 Ib/ton)—would result in a drop in the estimated percentage
SC>2 contribution of these new sulfuric acid plants to the total na-
tional SC>2 emissions, from 0.04 percent to 0.02 percent. The
national impact of a more stringent SC>2 NSPS would be marginal due
1-3
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to the very small decrease in 802 emissions (resulting from a
tighter standard) from the sulfuric acid plants projected to be built
during the 1981 through 1984 period.
1.4 Current Acid Mist Levels (and Related Opacity Levels)
Achievable With Best Demonstrated Control Technology
All 32 sulfuric acid production units subject to NSPS showed
compliance with the current acid mist NSPS control level of 0.075
kg/Mg of 100 percent acid (0.15 Ib/ton). The NSPS compliance test
data are all from plants with acid mist emission control provided by
the high efficiency acid mist eliminator. The data showed a wide
range with a low of 0.008 kg/Mg (0.016 lb//ton) to a high of 0.071
kg/Mg (0.141 Ib/ton), and an overall average value of 0.04 kg/Mg
(0.081 Ib/ton). Acid mist emission (and related opacity) levels are
unaffected by factors affecting S02 emissions, i.e., conversion
catalyst aging. Rather, acid mist emissions are primarily a function
of moisture levels in the sulfur feedstock and air fed to the sulfur
burner, and the efficiency of final absorber operation. The order-
of-magnitude spread observed in NSPS compliance test values is prob-
ably a result of variation in these factors. Additionally, variabil-
ity in the original EPA Method 8 may have contributed to this spread.
Making the acid mist standard more stringent is not believed to be
practicable at this time because of the need to provide a margin of
safety due to in-plant operating fluctuations, which introduce vari-
able quantities of moisture into the sulfuric acid production line.
1-4
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2.0 INTRODUCTION
In Section 111 of the Clean Air Act, "Standards of Performance
for New Stationary Sources," a provision is set forth which 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 the sulfuric acid plant production unit.
The main purpose of this report is to review the current
sulfuric acid standards for S02, acid mist and opacity 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. A review of the definition of the present standards
and the NSPS monitoring requirements.
2. A discussion of the status of the sulfuric acid
industry and the status of applicable control
technology.
3. An analysis of SC>2, acid mist and opacity test results
and review of level of performance of best demons-
trated control technology for emission control.
4. A review of the impact of NSPS revision on sulfuric
acid production economics, and the effect of new
sulfuric acid plant construction on the NSPS.
Based on the information contained in this report, conclusions
are presented and specific recommendations are made with respect to
changes in the NSPS.
2-1
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3.0 CURRENT STANDARDS FOR SULFURIC ACID PLANTS
3.1 Background Information
Prior to the promulgation of the NSPS in 1971, almost all
existing contact process sulfuric acid plants were of the single-
absorption design and had no S(>2 emission controls. Emissions from
these plants ranged from 1500 to 6000 ppra SC<2 by volume, or from
10.8 kg of S02/Mg of 100 percent acid produced (21.5 Ib/ton) to
42.5 kg of S02/Mg of 100 percent acid produced (85 Ib/ton).
Several state and local agencies limited S02 emissions to 500 ppm
from new sulfuric acid plants, but few such facilities had been put
into operation (EPA, 1971).
Many sulfuric acid plants utilized some type of acid mist con-
trol prior to 1971, but several had no controls whatsoever. Uncon-
trolled acid mist emissions varied between 2 and 50 mg/scf, or from
0.4 to 9 Ib of H2S04/ton of 100 percent acid produced, the lower
figure representing emissions from a plant burning high-purity sul-
fur. State and local regulatory agencies had only begun to limit
acid mist emissions to more stringent levels; i.e., some agencies had
adopted limits of 1 and 2 mg/scf, respectively, for new and existing
plants (EPA, 1971).
It is estimated that S(>2 emissions from sulfuric acid plants
totalled 528,000 Mg (580,000 tons) in 1971 and 245,000 Mg (269,000
tons) in 1976 (Mann, 1978). This represents a 54 percent drop in
S02 emissions from this industry in the first 5 years after the
3-1
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promulgation of the NSPS for this pollutant.* By 1976 sulfuric acid
plants, in compliance with the NSPS, represented 31 percent of the
sulfuric acid industry capacity (Stanford Research Institute, 1977).
No corresponding data are available for the effect of the NSPS
on total acid mist emissions from the industry.
3.2 Facilities Affected
The NSPS regulates sulfuric acid plants that were planned or
under construction or modification as of August 17, 1971. Each sul-
furic acid production unit (or "train") is the affected facility.
The standards of performance apply to contact-process sulfuric acid
and oleum facilities that burn elemental sulfur, alkylation acid,
hydrogen sulfide, metallic sulfides, organic sulfides, mercaptans or
acid sludge. The NSPS does not apply to metallurgical plants that
use acid plants as control systems, or to chamber process plants or
acid concentrators.
An existing sulfuric acid plant is subject to the promulgated
NSPS if: (1) a physical or operational change in an existing facil-
ity causes an increase in the emission rate to the atmosphere of any
pollutant to which the standard applies, or (2) if in the course of
reconstruction of the facility, the fixed capital cost of the new
components exceeds 50 percent of the fixed capital cost that would be
required to construct a comparable entire new facility that meets the
NSPS.
*It is not known what portion of this drop in SC>2 emissions is due
to NSPS-controlled plants or to existing plants covered by State
Implementation Plans (SIP).
3-2
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3.3 Controlled Pollutants and Emission Levels
The pollutants to be controlled at sulfuric acid plants by the
NSPS are defined by 40 CFR 60, Subpart H (as originally promulgated
in 36 FR 24881 with subsequent modifications in 39 FR 20794) as fol-
lows :
1. Standard for sulfur dioxide
(a) "On and after the date. . . no owner or operator sub-
ject to the provisions of this subpart shall cause to be
discharged into the atmosphere from any affected facility
any gases which contain sulfur dioxide in excess of 2 kg per
metric ton of acid produced (4 Ib per ton), the production
being expressed as 100 percent 112804."
2. Standard for acid mist
(a) "On and after the date. . . no owner or operator sub-
ject to the provisions of this subpart shall cause to be
discharged into the atmosphere from any affected facility
any gases which:
(1) Contain acid mist, expressed as 1^804, in
excess of 0.075 kg per metric ton of acid produced
(0.15 Ib per ton), the production being expressed as
100 percent ^804.
(2) Exhibit 10 percent opacity, or greater. Where the
presence of uncombined water is the only reason for
failure to meet the requirements of this paragraph,
such failure will not be a violation of this section."
The values of these standards were derived from the following
data sources:
1. A literature search revealed that over 20 dual-absorption
plants had been operating successfully in Europe for
several years using both elemental sulfur and roaster gas
as feed and that three of these plants produced maximum
S(>2 emissions ranging from 91 to 260 ppm 862 by volume,
or from 0.6 kg of 802 per M8 of acid produced (1.2
Ib/ton) to 1.6 kg of 802 Per M8 of acid produced (3.1
Ib/ton).
3-3
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2. The two plants tested and evaluated by EPA engineers were
a plant of typical dual-absorption design and a single-
absorption spent-acid burning plant that used a sodium
sulfite-bisulfite scrubbing process to recover SC>2 from
tail gas.
The dual-absorption sulfuric acid plant was the first of its
kind in the U.S. and was used by EPA as part of the best demonstrated
control technology rationale for the NSPS for S02 emissions. Since
1971, 17 dual-absorption plants have been built in the U.S. with a
total of 32 individual sulfuric acid units (or trains). This process
has become the best demonstrated control technology for S(>2 control
in the industry. No new sodium sulfite-bisulfite scrubbing units for
S(>2 abatement have been installed on sulfuric acid plants built in
the U.S.
Emission tests from both the original dual-absorption sulfuric
acid plant and the single absorption plant with sodium sulfite-sodium
bisulfite scrubbing, indicated that both operations were capable of
maintaining SC>2 and acid mist emissions below 2.0 kg/Mg (4 Ib/ton)
and 0.075 kg/Mg (0.15 Ib/ton), respectively, at full load operations.
Additionally, control of acid mist below 0.075 kg/Mg (0.15 Ib/ton) at
these plants, resulted in no visible emissions from the stack, i.e.,
opacity was below 10 percent. Continuous stack monitoring at these
plants indicated that at full load, the plants could be consistently
operated so that S(>2 emissions would be kept within the limits of
the performance standard (EPA, 1971). In Section 5.0 of this report,
NSPS emission test results for SC>2 and acid mist are presented for
3-4
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all the new sulfuric acid units completed since the promulgation of
the standard.
3.4 Testing and Monitoring Requirements
3.4.1 Testing Requirements
Performance tests to verify compliance with 802, acid mist and
opacity standards for sulfuric acid plants must be conducted within
60 days after the plant has reached its full capacity production
rate, but not later than 180 days after the initial start-up of the
facility (40 CFR 60.8). The EPA reference methods to be used in
connection with sulfuric acid plant testing include:
1. Method 8 for the concentrations of S02 and acid mist
2. Method 1 for sample and velocity traverses
3. Method 2 for velocity and volumetric flow rate
4. Method 3 for gas analysis.
For Method 8, each performance test consists of three separate
runs each at least 60 minutes with a minimum sample volume of 1.15
dscm (40.6 dscf). The arithmetic mean of the three runs taken is the
test result to which compliance with the standard applies (40 CFR
60.8).
The sulfuric acid production rate, expressed as Mg/hr of 100
percent 112804, is to be determined during each testing period by
suitable methods and confirmed by a material balance over the
production system. Sulfur dioxide and acid mist emissions in kg/Mg
3-5
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of 100 percent H2S04 are determined by dividing the emission rate
in kg/hr by the hourly 100 percent acid production rate.
3.4.2 Monitoring Requirements
SC>2 emissions in the tail gas from sulfuric acid plants are
required to be continuously monitored. Continuous S02 monitoring
instrumentation should be able to: (1) provide a record of
performance and (2) provide intelligence to plant operating personnel
such that suitable corrections can be made when the system is shown
to be out of adjustment. Plant operators are required to maintain
the monitoring equipment in calibration and to furnish records of
SOo excess emission values to the Administrator of EPA or to the
responsible State agency.
Measurement principles used in the gas analysis instruments
are:
1. Infrared absorption
2. Colorimetric titration of iodine
3. Selective permeation of SC>2 through a membrane
4. Flame photometric measurement
5. Chromatographic measurement
6. Ultraviolet absorption.
The ultraviolet absorption system and the iodine titration method
have received widespread application for SC>2 measurement in sul-
furic acid plants subject to NSPS (Calvin and Kodras, 1976).
3-6
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The continuous monitoring system is calibrated using a gas
mixture of known 862 concentration as a calibration standard.
Performance evaluation of the monitoring system is conducted using
the S02 portion of EPA Method 8.
Excess S02 emissions are required to be reported to EPA (or
appropriate state regulatory agencies) for all 3-hour periods of such
emissions (or the arithmetic average of three consecutive 1-hour
periods). Periods of excess emission are considered to occur when
the integrated (or arithmetic average) plant stack S02 emission
exceeds the standard of 2 kg/Mg (4 Ib/ton) of 100 percent
produced.
3-7
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4.0 STATUS OF CONTROL TECHNOLOGY
4.1 Status of Sulfuric Acid Manufacturing Industry Since
the Promulgation of the NSPS
4.1.1 Geographic Distribution
In 1971 there were 167 contact process sulfuric acid and oleum
plants in the U.S. By 1977 the number of plants had decreased to
150. Thirty-two sulfuric acid units subject to NSPS are included in
these 150 plants. Table 4-1 provides a summary by EPA region of the
number of units subject to NSPS and their design tonnage. Table 4-2
is a tabulation of the eight new units planned or under construction
which will be coming on-line by 1980.
Figure 4-1 shows the geographical distribution of contact pro-
cess sulfuric acid units completed since 1971. The heaviest concen-
tration of new units is in Region IV (Southeast). The high concen-
tration of sulfuric acid units constructed in Florida since 1971 can
be explained by the presence of rich phosphate rock deposits. Eighty
percent of the phosphate rock mined goes into the manufacture of
phosphatic fertilizers, which is also the end use of 60 percent of
the total U.S. sulfuric acid production (Bureau of Mines, 1975;
1978). Since most sulfuric acid is consumed near its point of manu-
facture, units with production dedicated for phosphate fertilizer
manufacture will, usually, be located near phosphate rock deposits.
4.1.2 Production
U.S. production of sulfuric acid in 1977 totalled approximately
30.9 million Mg (34 million short tons), representing an average
4-1
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TABLE 4-1
SUMMARY OF NEW SULFURIC ACID PLANT COMPLETIONS
SINCE THE PROMULGATION OF THE NSPS
EPA Region
II
IV
V
VI
IX
X
Units
In Production
(1971-1977)
2
18
1
4
1
6
Total 32
Average
Plant
Design Capacity3
(100% H2S04)
Mg/day (TPD)
1,820 (2000)
28,670 (31,500)
230 (250)
5,370 (5900)
1,640 (1800)
1,890 (2080)
39,610 (43,530)
1200 (1300)
Percent of Total
New Design
Capacity
4.6
72.3
0.6
13.6
4.1
4.8
100.0
aThese units all use the double absorption process except one plant (one
new unit and two existing units) in Region VI and one plant (two new units)
in Region X which use a single absorption process with ammonia scrubbing.
One new plant in Region V is currently retrofitting from single to double
absorption.
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4S>
I
TABLE 4-2
SULFURIC ACID PLANTS PLANNED OR UNDER CONSTRUCTION
Region
III
IV
V
VI
VII
Company
Getty Oil
Occidental
Chemical Co.
Royster Co.
Shell Chemical
American
Cyanamid Co.
U.S. Army
Sunflower Arsenal
Plant Location
Delaware City,
Del.
White Springs,
Fla.
Mulberry, Fla.
Wood River,
111.
Fortier, La.
Lawrence, Kan.
TOTAL
No. of
Units
2
2
1
1
1
1
8
Plant Capacity
Mg/day (TPD)
540 (600) a
3640 (4000)b
720 (800)
230 (250)
1460 (1600)
270 (300)
6860 (7500)
Anticipated
Startup Date
1980
Late 1979
Late 1979
Fall, 1979
Fall, 1978
1980
Source
Hansen ,
1978
Hansen,
1978
Hansen,
1978
Williams,
1977
Chem. Eng. ,
1977
Hansen,
1978
a2 - 270 Mg/day (300 TPD) units.
3 2 - 1820 Mg/day (2000 TPD) units.
'Retrofit of dual absorption system.
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LEGEND
• Units in operation
O Units planned or under
construction as of 1978
FIGURE 4-1
CONTACT PROCESS SULFURIC ACID PLANTS
COMPLETED IN THE U.S. SINCE 1971
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yearly increase of 1.9 percent (575,000 Mg) since 1971 (Department of
Commerce, 1976; Chemical and Engineering News, 1978). Figure 4-2
shows total annual production of sulfuric acid for 1971 to 1977,
including production by the lead chamber process, which has almost
been phased out of the industry (EPA, 1976). Production by the con-
tact process alone represented 99.3 percent of total production in
1971 and increased to 99.8 percent in 1976 (Chemical and Engineering
News, 1978). Table 4-3 shows the increase in sulfuric acid produc-
tion by region from 1975 to 1976. Production in the South represen-
ted 70 percent of the U.S. total in 1976 (Department of Commerce,
1976).
TABLE 4-3
SULFURIC ACID PRODUCTION
(Mg of 100% H2S04)
Region
Northeast
North Central
West
South
1975
1,728.2
2,804.4
4,110.7
19,640.9
1976
1,527.2
2,636.9
4,445.5
20,667.9
Change
(%)
-12
-6
+8
+5
Total Production
1976(%)
5
9
16
70
Source: Department of Commerce, 1976.
The growth of the sulfuric acid industry since the promulgation
of the NSPS has been largely dominated by the growth in the phosphate
fertilizer industry in the early and mid-seventies. Of the 32
4-5
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fi
o
CO
CO
c
5
r-l
1971 1972 1973 1974 1975 1976 1977
YEAR
SOURCE: Department of Commerce, 1976; 1977.
FIGURE 4-2
GROSS TOTAL PRODUCTION OFSULFURIC ACID:
1971 TO 1977
4-6
-------
contact process sulfuric acid units subject to NSPS, the output of at
least 24 units is dedicated to the acidulation of phosphate rock as
the first step in the manufacture of wet process phosphate and acid
superphosphate fertilizers.
About 68 percent of the contact process sulfuric acid is pro-
duced from elemental sulfur, representing approximately 85 percent of
the total sulfur consumption in the U.S. The remaining acid is made
from iron pyrites (4.5 percent); tail gas from smelters (9 percent);
and hydrogen sulfide, spent alkylation acid, and acid sludge from
petroleum refineries (18.5 percent).
Sulfuric acid is produced in various concentrations and in four
grades: commercial, electrolyte or high purity, textile (having low
organic content), and chemically pure (C.P.) or reagent grade. The
various end uses of sulfuric acid are shown in Figure 4-3. In addi-
tion to the manufacturing of fertilizer, other major uses are petro-
leum refining (7 percent), other inorganic chemicals (6 percent), and
copper ores (5 percent).
An increasing number of sulfuric acid consumers, specifically
fertilizer manufacturers, produce their own sulfuric acid for captive
use. The ratio of production for merchant sales (or shipments) to
production for captive use decreased from 2:1 in 1939 and 1:1 in 1966
to 0.7:1 in 1973. This relationship is shown in Figure 4-4.
4-7
-------
Phosphatic fertilizer
Petroleum refining
Other inorganic chemicals
Copper ores
Unidentified
Other chemical products
Industrial organic chemicals
Nitrogenous fertilizers
Inorganic pigments 4 paints
Synthetic rubber & other plastic
Pulp mills
Cellulosic fibers
Detergents
Steel pickling
Uses under 1% are: uranium & vanadium ore,
other ore, other paper products, drugs,
pesticides, other agricultural chemicals,
explosives, water treating compounds,
rubber & miscellaneous plastic products,
nonferrous metals, other primary metals,
and storage batteries (acid). There were
no sulfuric acid exports in 1977.
SOURCE: Bureau of Mines, 1978.
FIGURE 4-3
SULFURIC ACID END USES
4-8
-------
I
SO
100
90 -
80 -
70 -
60 -
B
w
50 -
40 -
30 -
20 -
10 -
SOURCE: EPA, 1977; Chemical and Engineering News, 1978.
1939 1966 1972 1973 1974
YEAR •
FIGURE 4-4
PERCENT OF TOTAL PRODUCTION OF SULFURIC ACID IN
CAPTIVE USE
1975 1976
-------
4.1.3 Industrial Trends
U.S. sulfuric acid production in 1968 was 25.9 million metric
tons, and approximately 30.9 million metric tons in 1977. Production
is expected to increase to 49 and 80 million metric tons by the years
1980 and 1990, respectively.
Tables 4-1, 4-2, 4-3 and Figure 4-1 show the strong trend
towards siting sulfuric acid plants in the southern states. Over 86
percent of the new sulfuric acid design capacity is located in EPA
Regions IV and VI. In 1971 EPA projected two new units to be coming
on-line each year for the next several years (EPA, 1971). On the
average, six new units have actually been completed each year since
1971. Of the total of 32 new units, 15 are located in Florida. Most
of the sulfuric acid production units in the South are captive in
nature with the output going into phosphate fertilizer production at
the same plant complex. In 1976, over 70 percent of the total
national production of new sulfuric acid was in the South. There-
fore, based on the high phosphate rock concentrations (Department of
the Interior, 1973) on the new construction in Region IV, and on the
production trends of sulfuric acid (Figure 4-4), three of the four
units projected to be coming on-line each year will most probably be
located in the South.
The location of sulfuric acid plants is not dependent on the
location of sources of sulfur, but rather on the location of various
industries associated with the use of sulfuric acid, i.e. the
4-10
-------
fertilizer and petroleum refining industries. The future supply of
sulfur for new acid will lean more heavily on recovered sulfur from
petroleum production and sulfur dioxide abatement and less on mined
(Frasch) sulfur.
4.2 Contact Process for Sulfuric Acid Production
All contact sulfuric acid manufacturing processes incorporate
three basic operations: (1) burning of sulfur or sulfur-bearing
feedstocks to form 802, (2) catalytic oxidation of S02 to 863,
and (3) absorption of 803 in a strong acid stream. The several
variations in the process are due principally to differences in feed-
stocks. The least complicated systems are those that burn elemental
sulfur. Where there are appreciable organics and moisture as in
spent acid and acid sludge, additional operations are required to
remove moisture and particulates prior to catalysis and absorption.
The composition of feedstock can affect the sulfur conversion ratio,
the volume of exhaust gases and the character and rate of pollutant
releases.
4.2.1 Elemental Sulfur Burning Plants
Figure 4-5 is a schematic diagram of a contact sulfuric plant
burning elemental sulfur. Sulfur is burned to form a gas mixture
which is approximately 8 to 10 percent sulfur dioxide, 11 to 13
percent oxygen, and 79 percent nitrogen. Combustion air is predried
by passing through a packed tower circulating 98 percent sulfuric
acid. Air drying minimizes acid mist formation and resultant corro-
sion throughout the system.
4-11
-------
I
M
NJ
RYING
TOWER
AIR
BLOWER
LIQUID
SULFUR
STEAM DRUM
SLOWDOWN •*•
ACID
COOLER
SULFUR
PUMP
STORAGE
SOURCE: EPA, 1971.
STEAM TO
•ATMOSPHERE
FURNACE BOILER BOILER CONVERTER
BOILER FEED WATER '
1
ECONOMIZER
ABSORPTION
TOWER
_T
-*„
WATER
ACID
COOLER
TTI ACID PUMP
Lcb| TANK
> PRODUCT
FIGURE 4-5
CONTACT-PROCESS SULFURIC ACID PLANT BURNING
ELEMENTAL SULFUR
-------
802 i-s oxidized to 803 in the presence of a catalyst con-
taining approximately 5 percent vanadium pentoxide. The temperature
of the reacting gas mixture increases as the composition approaches
equilibrium. Maximum conversion to 803 requires several conversion
stages with intermediate gas cooling. The gas exiting the converter
is cooled in an economizer to temperatures between 230° and
260°C, and 803 is absorbed in 98 percent sulfuric acid circulat-
ing in a packed tower. The acid content and temperature must be
carefully controlled to prevent excessive 863 release.
If fuming sulfuric acid (oleum) is produced, the 803 contain-
ing gases are first passed through an oleum tower which is fed with
acid from the 98 percent absorption system. The gas stream from the
oleum tower is passed through the 98 percent acid absorber for recov-
ery of residual sulfur trioxide.
4.2.2 Spent Acid and Other By-Product Plants
Where spent acid, sludge, and similar feedstocks are employed,
the processes are more elaborate and expensive than sulfur-burning
plants due to the fact that the sulfur dioxide containing gas stream
is contaminated. Gases must be cleaned if high-quality acid is to
be produced. This requires additional gas cleaning and cooling
equipment to remove dust, acid mist, and gaseous impurities, along
with excessive amounts of water vapor. Purification equipment con-
sists of cyclones, electrostatic dust and mist precipitators, plus
scrubbers and gas-cooling towers in various combinations. Figure 4-6
4-13
-------
•e-
i—SPENT ACID
-SULFUR
- FUEL OIL
WATER
FURNACE
DUST WASTE HEAT GAS GAS ELECTROSTATIC
COLLECTOR BOILER SCRUBBER COOLER PRECIPITATORS
STRIPPER
. TO
ATMOSPHERE
*> ACID TRANSFER «
DRYING
TOWER
ABSORPTION
TOWER
93% ACID PUHP TANK COOLER
ACID COOLERS 98% ACID PUMP TANK
SOURCE: EPA, 1971.
FIGURE 4-6
CONTACT-PROCESS SULFURIC ACID PLANT
BURNING SPENT ACID
-------
shows one possible configuration of a spent acid plant. The balance
of the process following the drying tower is essentially the same as
an elemental sulfur-burning plant.
A few plants burning only hydrogen sulfide or hydrogen sulfide
plus elemental sulfur use a simplified version of the above process.
Wet gases from the combustion chamber and waste heat boiler are
charged directly to the converter with no intermediate treatment.
Gases from the converter flow to the absorber, through which 70 to 93
percent sulfuric acid is circulating. In such a "wet gas" plant much
of the sulfur trioxide from the converter is in the form of acid mist
which is not absorbed in the absorption tower. High efficiency mist
collectors are utilized both to recover product and to prevent exces-
sive air pollution.
4.3 Emissions from Contact Process Sulfuric Acid Plants
4.3.1 Sulfur Dioxide
Mass S02 emissions vary inversely as a function of the sulfur
conversion efficiency (i.e., fraction of SC>2 oxidized to 803).
For sulfur burning plants, the inlet SC>2 concentration to the cata-
lytic converters normally ranges between 7.5 and 8.5 percent but can
be as high as 10.5 percent. Conversion efficiency depends upon the
number of stages in the catalytic converter and, to a lesser extent,
on the amount of catalyst.
Most plants built prior to 1960 had only three catalyst stages,
and overall conversion efficiencies were approximately 95 to 96
4-15
-------
percent. Sulfur burning plants built since 1960 generally have four
stages* and efficiencies normally range between 96 and 98 percent.
For three-stage plants, S02 release ranges between 28 and 35 kg/Mg
and for four-stage plants, between 13 and 28 kg/Mg.
Spent acid plants followed the same design trend. Most three-
stage plants were built prior to 1960 and four-stage plants have
usually been built after 1960. Typical S02 concentrations in the
converter feed, conversion efficiencies, and resultant emissions for
plants burning sulfur, l^S or primarily acid sludge are given in
Table 4-4.
TABLE 4-4
SULFUR DIOXIDE CONVERSION EFFICIENCIES AND EMISSIONS
FOR FOUR-STAGE CONVERTERS
Hydrogen Sulfide
(with some other Acid
Feedstock Sulfur sulfur compounds) Sludge
S02 in converter feed, 7.5 to 8.5 7 6 to 8
% by volume
Sulfur conversion to 803, 96 to 98
% by weight
S02 emissions, 13 to 28 25 to 43 15 to 56
kg/Mg 100% acid
S02 emissions, 1500 to 1500 to 1500 to
ppm by volume 4000 4000 4000
Source: EPA, 1971.
*There have been a number of five-stage converters included in dual
absorption plants built since 1971 (see Section 5.2.1).
4-16
-------
Exit S02 concentrations from contact plants vary as a func-
tion of the SO2 content of dry gases fed to the converter. Where
SC>2 strength is relatively low, there is a significantly greater
volume of gases handled per ton of acid produced.
A plant with 4.0 percent SC>2 in the dry gases to the converter
will exhaust over two and one-half times the gas volume of a plant
operating on a 10.0 percent S(>2 stream, i.e., 4600 sm^/Mg* vs.
1700 sm3/Mg.
The relationship between mass emission rate, sulfur conversion
and SC>2 exit concentrations has been plotted in Figure 4-7 for
plants of various S(>2 strengths. The curve can be used for uncon-
trolled single absorption plants and for those plants equipped with
tail gas removal systems or with the dual absorption process. It can
be seen that the NSPS of 4.0 Ib per ton of acid requires 99.7 percent
sulfur conversion (dual absorption) or an equivalent 802 exit gas
concentration of 380 ppm. This conversion is achieved by the dual
absorption technique. At 98 percent conversion, which is optimum for
most single absorption contact plants, exit SC>2 concentrations can
vary from 900 to 2500 ppm as the inlet SC^ content varies from 4.0
to 10.0 percent.
4.3.2 Acid Mist Formation
The sulfuric acid liquid loading in the tail gas from the
absorber in a contact process plant is classified into two broad
areas based on the acid particle size: (1) spray, which is defined
*Standard cubic meter per metric ton.
4-17
-------
Sulfur Conversion - Percent of Feedstock Sulfur
10,000
5000
1
100
10.0 15 20 30 50
S02 Emissions - Lb Per Ton of 100% HjSO^ Produced
Source: EPA, 1976
FIGURE 4-7
SULFURIC ACID PLANT FEEDSTOCK SULFUR CONVERSION
VS. VOLUMETRIC AND MASS SO. EMISSIONS AT VARIOUS
INLET SO. CONCENTRATIONS BY VOLUME
4-11
-------
as acid particles larger than 10 microns, and (2) mist, which is
defined as acid particles smaller than 10 microns (Duros and Kennedy,
1978).*
Spray is primarily formed by mechanical generation of particles
that are formed when a gas and liquid are mixed together. Examples
of spray formation are liquid droplets formed by nozzles and liquid
entrainment leaving a packed tower. A typical tower design in a
modern acid plant will have a spray loading of 175 to 350 milligrams
per actual cubic meter (mg/AM^) under normal operating conditions.
Acid mist formation is more complex to define than spray. There
are two primary mechanisms of acid mist formation. The first mechan-
ism is the reaction between two vapors forming a liquid or solid
(i.e., change of state where volume reactants is much greater than
volume products). This is best exemplified by the reaction of sulfur
trioxide and water vapors to form submicronic sulfuric acid mist.
H2°(g) + S°3(g) H2S04(£)
The second mechanism of mist formation is vapor condensation in
the bulk gas phase by lowering the gas stream temperature beyond the
liquid dew point. The dew point of a sulfuric acid under typical
conditions is about 300° to 350°F. However, because of the uncer-
tainties of bulk phase temperature differences, nonideal conditions
and wall effects, the gas stream temperature is normally maintained
between 375° to 425°F. This is done to insure that acid mist is not
present to attack metal equipment.
*The EPA definition of acid mist (Method 8) includes both liquid
sulfuric acid particles and 803 gas.
4-19
-------
The formation of sulfuric acid mist in an acid plant is due to a
combination of these mechanisms. When a gas stream containing 803,
H2S04 and 1^0 vapor is cooled below the liquid dew point, the
H2&04 vapor condenses and the 803 vapor and t^O vapor combine
to form H2S04, which also condenses. Submicronic mist particles
will be formed when the gas is cooled faster than the condensable
vapor can be removed by mass transfer (i.e., "shock cooling"). The
conditions for "shock cooling" are present in the absorbing towers of
an acid plant.
The practical key to controlling mist formation is to keep the
H20 content in a gas stream as low as possible. As an example of
mist forming capability of extraneous water, 1 mg of water vapor
carried through the plant has the potential to produce 190 mg/m^ of
submicronic acid mist (Duros and Kennedy, 1978). The water content
of the gas stream can be increased by:
1. High organic content of contaminated elemental sulfur
(sulfur burning plants only),
2. Acid mist carryover from upstream equipment,
3. Inadequate drying of the process air stream, and
4. Low absorbing tower acid strengths
At acid strengths below 98.5 percent, the acid begins to exert a mea-
surable water vapor pressure. The optimum absorbing tower acid has
the minimum vapor pressure of both water (minimizing mist formation
problems) and sulfur trioxide (minimizing 803 slippage).
4-20
-------
In oleum producing plants, greater quantities and a much finer
mist are produced. From 85 to 95 weight percent of the particles are
less than 2 microns in diameter as compared with about 30 percent
less than 2 microns for 98 percent acid production. Acid mist emis-
sions prior to control equipment range between 0.2 to 2 kg/Mg for
sulfur burning contact plants producing no oleum to about 0.5 to 5
kg/Mg for spent acid burning plants producing oleum, based on an 8
percent S(>2 feed to the converter.
Spent acid plants characteristically form acid mist in the early
stages of the process. This requires mist removal prior to drying
and oxidation as well as from the tail gas after absorption.
"Wet gas" plants burning hydrogen sulfide deliberately form acid
mist by not drying the process gas. Much of this mist is recovered
as product acid with gas cooling equipment and high efficiency mist
eliminators or electrostatic precipitators.
For a given mass emission rate, acid mist concentrations vary as
a function of the exhaust gas volume and, thus, the S02 control of
the gases fed to the converter. Figure 4-8 shows a relationship
between mass emission rates and concentrations over a range of S(>2
strengths. The curves can be used with any gas stream before or
after mist eliminators, provided there is no dilution.
4.3.3 Visible Emissions (Opacity)
Acid mist in exhaust gases creates visible emissions ranging
from white to blue depending on particle size, concentration and
4-21
-------
0.10
0.01
SOURCE:
0.02 0.03 0.04 0.10 0.20 0.30 0.50
ACID MIST EMISSIONS, Ib H2S04/T OF 100 PERCENT H2 S04 PRODUCED
EPA, 1977.
FIGURE 4-8
SULFURIC ACID PLANT CONCENTRATIONS OF MIST
FOR MASS STACK EMISSIONS PER UNIT OF
PRODUCTION AT INLET SO2 VOLUME CONCENTRATIONS
4-22
-------
background. Where there is no control of mist, opacities generally
range from 80 to 100 percent.
The effect of acid mist on opacity is more dependent on the size
of the mist particle than on the quantity of mist. The smaller par-
ticles scatter light more, producing a denser plume. Nevertheless,
it has been demonstrated that opacity of the plume from an efficient
863 absorber a function of acid mist concentration and that visible
emissions can be eliminated by minimizing acid mist levels in the
acid plant tail gas, through the use of a good mist eliminator. At
the current NSPS acid mist control level, there are essentially no
visible emissions.
4.3.4 Oxides of Nitrogen
Nitrogen oxides present in the converter gas also cause acid
mist emissions, since they reduce the efficiency of the absorption
tower. Nitrogen oxides may result from the fixation of atmospheric
nitrogen in high temperature sulfur furnaces, or may be formed from
nitrogen compounds in the feedstocks. Nitrogen oxides can be held
to a reasonable minimum by using the same techniques which have
been applied to steam generators. For instance, in the decompo-
sition of spent acid containing nitrogen compounds, operation at
furnace temperatures less than about 2000°F and a low oxygen con-
tent will generally keep nitrogen oxides concentrations below 100
ppm.
4-23
-------
4.4 Control Technology Applicable to the NSPS Control of S02
Emissions from Contact Process Sulfuric Acid Plants
There are a few physical mechanisms and many chemical means of
removing SO2 from gas streams. Almost any soluble alkaline materi-
al will absorb a significant fraction of 802 even in a crude scrub-
ber. For years, sulfur dioxide has been removed from many process
gases where the 802 adversely affected the product. The problems
of removing 802 from acid plant gases are principally that of find-
ing the least expensive mechanism consistent with minimal formation
of undesirable by-products. The control processes in use by the sul-
furic acid industry (in those units installed since the promulgation
of the NSPS), are reviewed below.
4.4.1 Dual Absorption Process
The dual absorption process (used partially as the basis of the
rationale for the SC>2 NSPS) has become the SC>2 control system of
choice by the sulfuric acid industry since the promulgation of the
NSPS. This can be seen by examination of Table 4-5, which presents a
tabulation of the new sulfuric acid units built since the promulga-
tion of the NSPS together with their locations, design capacities,
basic process design, and 502 and ac:"-d mist control technologies.
Out of 32 new units built since the promulgation of the NSPS, 28 have
employed the dual absorption process for S02 control. This process
offers the following advantages over other SC>2 control processes:
• As opposed to single absorption with scrubbing, a greater
fraction of the sulfur in the feed is converted to sulfuric
acid.
4-24
-------
TABU »-5
CO.TTACT PROCESS 1UIHJ8R ACI1) PLANTS BUILI SINCF PKOHUU.AriON 01 THh SSPS
EPA Region
11
IV
V
VI
IX
I
Company
NL Industries. Inc
Cardliler. Ine
Agrlco Chemical
Inc
CF Chemlcele. Inc
CF Chemicals. Inc
H R Grace I Co
International Hlner
i Chemical Corp
Occidental Petro-
leum Corp
American Cyanamld C
Hlsslsslppl Cheml-
cel Carp
Texas Gulf. Inc
Anlln Chemical
Corp»
Agrlco Chcm Co
reeport Chen Co
ota 4 Uses
alley Nitrogen
Frod . Inc
eker Industries
R Slmplot Co
llled Chen Corp
State and Locallt
Hotf Jersey
Sayrevllle
Florida
Taapa
So Pierce
Bartw
Plant City
Bartotf
Now Kales
White Springe
ieorttle
Savannah
HlsslsalDDl
Paacsgoula
to Carolina
Lee Creek
Illinois
Hood River
•ouislana
Donaldsonvllle
ncle Sam
exae
eer Park
allfornla
aim
lano
onda
ocatello
Mhlns-ton
rear
CoBpleiei
1973
1976
1975
1975
1974
1976.1977
1975
1975
19-5
1975
1975
1974
1974
1974
1975
1974
1976
TOTALS
AVERAGE
No o
Unit
2
1
2
1
2
3
3
2
1
1
2
1
2
1
1
1
1
2
3
32
Plant
Doalgn Capaclt
(1001 HjSOj)
IS /day (TPD)
1.820 (2.000)
2.370 (2.600)
3.800
3 280 (2.000)
2,910 (3.200)
4.370 (4,800)
5.460 (6.000)
3.280 (3.600)
720 (800)
1.370 (1,500)
2.7W (3.000)
230 (250)
3,090 (3,600)
1.46C (1.600)
640 ( 700)
1.640 (1,800)
770 ( 850)
820 ( 900)
300 ( 330)
39,610 (43,530)
1.740 ( 1.1«)
Procaas Design
Single
X
K
X
Dual
X
,"
X
X
It
."
X
ft
X
,b
X
b
X
X
xe
Emissions Control System
S02
Process
Procees
Procsss
Process
Process
Frocees
Process
Process
Process
Procaas
Process
Holeeulsr Sieve
Process
Process
Amnonla
Scrubbing
recess
'roeeas
Scrubbing
rocess
Hist Eliminator
Fiber Hist Lllmlutor
York "S" Hist
Eliminator
Brink Fiber n-v
Hist Rlimlnator
Brink Fiber H-V
Hist Eliminator
Fiber Hist Eliminator
Brink Fiber Met
Ellalnator
Parsan-York Doub la Con-
tact Hlat Eliminator
Hist Ellmlnstor
Bayer/Lurgl Hist
Ellmlnstor
Brink Fiber Hist
Ellmlnstor
Fiber Hist Eliminator
York "S" 2 Stags Hash
Hist Eliminator
Fiber Hlat Eliminator
Fiber lilst Eliminator
Brink Fiber Hist
Eliminator
rink Fiber Hist
Eliminator
Brink Fiber Hist
Eliminator
Fiber Hlat Ellainator
CDS'. 1978
CDS. 197.-
CD5, 1978
CD* 1478
CDS. 1"7S
CDS. 1978
CDS. 19-8
CDS. 147B
FCDCo . 1977
CDS. 1978
CDS, 1978
Ullllams. 1977
Sprulell, 1978
Sprulell 19)8
Sprulell. 1978
Reynolds 1977
Prouder. 197B
Pleader. 1978
Hooper, 1978
One of these units is of 1
Source MITRE Corp . 1978. PEDCO. Inc . 1977
-------
• There are no by-products.
• Contact acid plant operators are familiar with the operations
involved.
Figure 4-9 is a process flowsheet of the dual absorption
process. The SO-j formed in the first three converter stages is
removed in a primary absorption tower and the remainder of the gas is
returned to the final conversion stage(s). Removal of a product of a
reversible reaction
S02 + 1/2 02 -*S03
drives the oxidation further toward completion approaching the
reaction equilibrium expressed by:
K = 1/2
(S02) (02)
where K is the reaction equilibrium constant peculiar to the tem-
perature of the reaction and the parenthetical entities are the molar
quantities of the gases involved. The resulting 803 is absorbed in
a secondary absorption tower obtaining at least 99.7 percent overall
conversion of the sulfur to sulfuric acid.
The dual absorption process permits higher inlet S02 concen-
trations than normally used in single absorption plants since the
second conversion step effectively handles the residual S02 from
the first conversion step. Higher inlet S02 concentrations permit
a reduction in equipment size which partially offset the cost of the
additional equipment required for a dual absorption plant. The dual
absorption equipment occupies little more space than a conventional
plant, even though an additional absorber is required.
4-26
-------
I
CO
98% ACID PRIMARY HEAT CONVERTER ECONOMIZER SECONDARY 98% ACID
ABSORBER EXCHANGER ABSORBER
SOURCE: EPA, 1971.
FIGURE 4-9
DUAL ABSORPTION SULFURIC ACID PLANT
FLOW DIAGRAM
-------
Spent acid or H2S may be used as feedstock in a dual absorp-
tion process with appropriate conventional process gas pretreatment,
i.e., particulate removal. The dual absorption process requires the
same types of equipment as the conventional single absorber design.
Although additional equipment is required, the on-stream production
factor and manpower requirement are the same.
4.4.2 Sodium Sulfite - Bisulfite Scrubbing
Tail gas scrubbing systems are generally applicable to all
classes of contact acid plants. They can provide simultaneous
control of S02 and to some extent 803 and acid mist. To date
only the sodium sulfite-bisulfite scrubbing process has been demon-
strated to be capable of meeting the SC>2 limit in the most cost
effective manner. Other control processes such as ammonia scrubbing
can meet the standard, but costs are relatively highly dependent on
the marketability of by-products, i.e., ammonium sulfate, for which
there may be little demand.
In the Wellman-Power Gas process, the tail gases are first
passed through a mist eliminator to reduce acid mist. Following mist
removal, the SC^ is absorbed in a three-stage absorber with a
sodium sulfite solution. A sodium bisulfite solution results and is
fed to a heated crystallizer where sodium sulfite crystals are formed
and SC>2 gas and water vapor are released. The crystals are sepa-
rated from the mother liquor and dissolved in the recovered conden-
sate for recycle to the absorber. The recovered wet S(>2 is sent
back to the acid plant.
4-28
-------
In all processes employing sulfite-bisulfite absorption even
without regeneration, some portion of the sulfite is oxidized to sul-
fate, from which the sulfur dioxide cannot be regenerated in the
heating sequence. This sulfate must be purged from the system. In
the Wellman-Power Gas process, some thiosulfate is also formed.
Apparently the extent of oxidation is dependent on several factors
such as the oxygen content of the gas stream, the temperature and
residence time of the liquor in the recovery sections, and the pres-
ence of contaminants that may act as oxidation catalysts. Despite
the effectiveness of the sodium sulfite-bisulfite scrubbing process,
none of the sulfuric acid plants installed since the promulgation of
the NSPS have employed this process for tail gas 802 control.
4.4.3 Ammonia Scrubbing
The ammonia scrubbing process uses anhydrous ammonia (NH3) and
water make-up in a two-stage scrubbing system to remove SC>2 from
acid plant tail gas. Excess ammonium sulfite-bisulfite solution is
reacted with sulfuric acid in a stripper to evolve SC>2 gas and pro-
duce an ammonium sulfate byproduct solution. The 802 ^s returned
to the acid plant while the solution is treated for the production of
fertilizer grade ammonium sulfate. The process is dependent on a
suitable market for ammonium sulfate.
Since the promulgation of the NSPS for sulfuric acid plants, one
new plant (two units) and a new unit added to an existing plant, are
employing an ammonia scrubbing system for tail gas S02 emissions
control.
4-29
-------
4.4.4 Molecular Sieves
This process utilizes a proprietary molecular sieve system in
which S(>2 is adsorbed on synthetic zeolites. The adsorbed material
is desorbed by purified hot tail gas from the operating system and
sent back to the acid plant.
Since the promulgation of the sulfuric acid plant NSPS, one new
unit has incorporated a molecular sieve system for S(>2 control in
the original design. However, extensive operational difficulties
with this system have caused this plant to be retrofitted with a dual
absorption system for SC>2 control.
4.5 Control Technology Applicable to the NSPS for Acid Mist
Emissions from Contact Process Sulfuric Acid Plants
i
Effective control of stack gas acid mist emissions can be
achieved by fiber mist eliminators and electrostatic precipitators
(ESPs). Although ESPs are frequently used in the purification sec-
tion of spent acid plants, there is no evidence that any have been
installed to treat the stack gas of any new sulfuric acid plants.
Even though ESPs do have the advantage of operating with a lower
pressure drop than fiber mist eliminators (normally less than 1 inch
of H£0), lack of application of this equipment to new sulfuric acid
units is probably due primarily to its relatively large size and re-
sultant high installation cost compared to fiber mist eliminators and
to the high maintenance cost required to keep the ESPs operating
4-30
-------
within proper tolerances in the acid environment which is corrosive
to the mild steel equipment.
Fiber mist eliminators utilize the mechanisms of impaction and
interception to capture large to intermediate size acid mist parti-
cles and of Brownian movement to effectively collect micron to
submicron size particles. Fibers used may be chemically resistant
glass or fluorocarbon. Fiber mist eliminators are available in three
different configurations covering a range of efficiencies required
for various plants having low to high acid mist loadings and coarse
to
fine mist particle sizes, respectively. The three fiber mist elimi-
nator configurations are:
1. Vertical tube
2. Vertical panels
3. Horizontal dual pads.
4.5.1 Vertical Tube Mist Eliminators
Tubular mist eliminators consist of a number of vertically
oriented tubular fiber elements installed in parallel in the top of
the absorber on new acid plants and usually installed in a separate
tank above or beside the absorber on existing plants. Each element
consists of glass fibers packed between two concentric 316 stainless
steel screens. In an absorber installation (see Figure 4-10) the
bottom end cover of the element is equipped with a liquid seal pot to
prevent gas bypassing. A pool of acid provides the seal in the sepa-
rate tank design. Mist particles collected on the surface of the
4-31
-------
ACCESS
MANHOLE
MISTY
GAS IN
CYLINDRICAL
^SCREENS
RECOVERED
LIQUID (MIST)
, FIBER ELEMENTS
SOURCE: EPA, 1977.
LIQUID &
SOLIDS OUT
FIGURE 4-10
VERTICAL TUBE MIST ELIMINATOR INSTALLATION
4-32
-------
fibers become a part of the liquid film which wets the fibers. The
liquid film is moved horizontally through the fiber beds by the gas
drag and is moved downward by gravity. The liquid overflows the seal
pot continuously, returning to the process.
Tubular mist eliminators use inertial impaction to collect
larger particles (normally greater than 3 microns) and use direct
interception and Brownian movement to collect smaller particles. The
low superficial velocity of gas passing through the fiber bed—6 to
12 meters/minute—provides sufficient residence time for nearly all
of the small particles with random Brownian movement to contact the
wet fibers, effecting removal from the gas stream. The probability
that such a particle could pass through the bed following the resul-
tant greatly lengthened travel path is very low.
Design volumetric flow rate through an element is about 28.3
sm-Vmin, and the number of elements required for a given plant size
can be determined from the standard cubic meters per minute handled
at capacity. Depending on the size of the sulfuric acid plant,
anywhere from 10 to 100 elements may be used; each element is
normally 0.6 meters in diameter and 3 meters high.
Pressure drop across the element varies from 13 to 38 cm. of
H20 with a higher pressure drop required for a higher removal
efficiency on particles smaller than 3 microns. The manufacturer of
these elements guarantees a mist removal efficiency of 100 percent on
particles larger than 3 microns and 90 to 99.8 percent on particles
4-33
-------
smaller than 3 microns with 99.3 percent being most common. These
efficiencies can be achieved on the stack gas of sulfuric acid plants
burning elemental sulfur or bound-sulfur feedstocks (spent acid, wet
gas, etc.) and producing acid or oleum.
Because the vertical tube mist eliminator does not depend only
upon impaction for mist removal, it can be turned down (operated at a
volumetric flow rate considerably below design) with no loss in effi-
ciency.
Available information indicates that the vertical tube mist
eliminator is used in the great majority of new sulfuric acid units
for acid mist control.
4.5.2 Vertical Panel Mist Eliminators
Panel mist eliminators use fiber panel elements mounted in a
polygon framework closed at the bottom by a slightly conical drain
pan equipped with an acid seal pot to prevent gas bypassing. The
polygon top is surmounted by a circular ring which is usually
installed in the absorption tower and welded to the inside of the
absorption tower head. Each panel element consists of glass fibers
packed between two flat parallel 316 stainless steel screens. In
large high velocity towers, recent designs have incorporated double
polygons, one inside the other, to obtain more bed area in a given
tower cross section.
As in the high efficiency tubular mist eliminator above, the gas
flows horizontally through the bed, but at a much higher superficial
4-34
-------
velocity (120 to 150 m/min) using the impaction mechanism for collec-
tion of the mist particles. Gas leaving the bed flows upward to the
exit port, while the collected liquid drains downward across the pan
and out through the seal pot back into the tower or to a separate
drain system (see Figure 4-11).
The polygon may contain 10 to 48 vertical sides, each side norm-
ally consisting of an 18 1/2" x 53" panel. A smaller 18 1/2" x 26"
panel is available for small plants, e.g., 32 Mg per day.
Pressure drop across the panel is usually about 8 inches of
H20. The manufacturer of panel mist eliminators will usually
guarantee an emission no higher than 2 rag/ft-* (equivalent to 0.375
Ib/ton of 100 percent H2S04 produced) for a sulfur-burning plant
producing oleum up to 20 percent in strength and/or acid.
Because of the large percentage of submicron (below 1 micron)
mist present in the stack gas of a spent acid plant and of a plant
producing oleum stronger than 20 percent, the vertical panel mist
eliminator will usually give unsatisfactory performance for these
plants when used for acid mist control in the tail gas. These units
find application in new dual absorption plants for acid mist removal
from the intermediate absorber in order to afford corrosion protec-
tion for downstream equipment.
Vertical panel mist eliminators normally operate with a liquid
level in the acid seal pot below the conical drain pan. Although the
velocity through the panels could be increased at lower throughputs
4-35
-------
CLEAN GASES OUT
ACCESS MANHOLE
SEAL POT
DISTRIBUTOR PAN OF TOWER
FIELD WELD
STRUCTURAL
SUPPORT
CYLINDER
ELEMENTS
IN POLYGON
FRAME
RECOVERED
LIQUID
SOURCE: EPA, 1977.
FIGURE 4-11
VERTICAL PANEL MIST ELIMINATOR INSTALLATION
4-36
-------
by raising Che liquid level to cover the lower part of each panel,
this would not be good practice since it would cause reentrainment of
spray by the gas passing over the liquid level in the basket.
4.5.3 Horizontal Dual Pad Mist Eliminators
Two circular fluorocarbon fiber beds held by stainless steel
screens are oriented horizontally in a vertical cylindrical vessel
one above the other, so that the coarse fraction of the acid mist is
removed by the first pad (bottom contactor) and the fine fraction by
the other (top contactor), as shown in Figure 4-12. The bottom
contactor consists of two plane segmented sections installed at an
angle to the horizontal to facilitate drainage and give additional
area for gas contact. The assembly may be located adjacent to—or
positioned on—an absorption tower.
This unit uses the high velocity impaction mist collection
mechanism, as does the panel mist eliminator; however, the collected
acid drains downward through the pads countercurrent to the gas flow
producing a scrubbing action as well. Collected acid may be drained
from external connections or returned directly to the absorber
through liquid seal traps.
Total pressure drop across both pads is usually about 23 cm. of
H20. The superficial velocity through the unit is 2.7 to 3.0 m/s.
Hence, the diameter of the cylindrical shell and the pads is deter-
mined from the volume of gas handled. Height requirements for the
unit depend upon whether it is located adjacent to or positioned on
4-37
-------
XVI
\
I —-^ \ j CLEAN GAS
\ ^-. VI TO ATMOSPHERE
I
I
DRAIN;
it*1
TOP CONTACTOR.
r BOTTOM CONTACTOR-^ L DRA|N
Is
i
•ABSORBER
MIST-ADEN
GAS IN
(COURTESY OF YORK SEPARATORS, INC.)
SOURCE: EPA, 1977.
FIGURE 4-12
HORIZONTAL DUAL PAD MIST ELIMINATOR
4-38
-------
the absorber, but are roughly 1.5 to 2 times the diameter of the
unit.
As with the panel mist eliminator, the dual pad unit will reduce
acid mist emissions to 2 rag/ft^ (0.375 Ib/ton of 100 percent
112804) or less, provided the plant burns sulfur and does not pro-
duce oleum stronger than 20 percent, and provided that a particle
size distribution curve shows that this level can be met.
4-39
-------
5.0 INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS
5.1 Test Results from EPA Regional Sources
The Mefrek Division of The MITRE Corporation conducted a survey
of all 10 EPA regions to gather available NSPS compliance test data
for each of the 10 industries under review (MITRE Corporation, 1978).
This survey yielded test data on 20 new sulfuric acid units. Data
included average S02 and acid mist emissions and 100 percent
sulfuric acid production rates for these units. In all cases, the
sulfuric acid production rate was at the unit design maximum (the
actual production rates usually exceeded the nominal design rates by
5 to 10 percent). Only a few values of opacity readings were
reported as compared with the total number of tests.
Telephone contacts with EPA regional personnel and, in some
cases, with sulfuric acid plant operators yielded NSPS compliance
test data on an additional 12 new sulfuric acid units. In all, 29
sets of data were obtained representing 32 new sulfuric acid units
(in two cases, the NSPS tests were run on two or more new units
combined). Insofar as is known, the test data obtained represent all
of the sulfuric acid units completed from 1971 through 1977, and
subject to NSPS.
5.2 Analysis of NSPS Test Results
The results of the NSPS compliance tests for the 32 new sulfuric
acid units are tabulated in Table 5-1 and displayed in Figures 5-1
and 5-2 for S02 and acid mist emissions, respectively. Table 5-2
5-1
-------
TABU J-l
NSPS COMPLIANCE TEST RESULTS FOB SULPURIC »CtD PUOTS
Cn
to
I.
IV
V
VI
IX
I
BL lodultriea. Inc
Air ICO Cheolcal. Inc
CF ChcalcalB. Inc
CP cnaalcals. Inc
Cardlaler. Inc.
b B Grai-e Co
IXC Chealcal Corp
Occidental Petroleua Corp
An C/anaold Co
Hlaalaalppl Clerical Corp
Teuagulf Inc
Anlln Corp*
Agrlco Chenical Inc
Agrleo Chenical, Inc
Preeport Chooleal Co
Bohn 6 Haaa. Inc
Valley Mtrogen Producera, Inc
Baker InduBlrlee. Inc
J B Sleplot Co
Allied ChCBlcal Corp
Monlnal
Unit SHO
(1001 B2S04)
Plant location H«/oay/TPD
Sayravllle, II J 910 (1000)
910 (1000)
So Pierce. Pla 16*0 (1800)
Bartov. Pla 1800 (2000)
Plant City. Plo 1*60 (1600)
1*60 (1600)
Tampa, Pla 2370 (2600)
1*60 (1600)
larto.. Pla 1*60 (1600)
1*60 (1600)
1*60 (1600)
Mulberry Pla 1800 (2000)
1800 (2000)
1800 (2009)
Uhlla Sprlnga. 1640 (1800!
n' 1640 (1809)
Savannah. Ca 730 (800)
Paeeacoula. HUB 1370 (1500)
Lee Crock, n C 1170 (1500)
1370 (1500)
Wood Hlver. Ill 230 (250)
Donaldarnvlllc. 1640 (1800)
u 16*0 (1800)
Convent. La 1*60 (1600)
Deer Park, T> 640 (700)
Heine. Calif 16*0 (1800)
Conda, Idaho 770 (850)
Pocatello, Idaho 810 (900) b
Anecortca, Uaah WO (330)
Average SOj
Emlaalona
kg/Kg of 1001
a2SO* (Ib/ton)
0 71 (1 42)
19 (37)
I
1 11 (2 22)
0 56 (1 12)
0 76 (1 32)
1 26 (2 52)
0 97 (1 94)
0 87 (1.71)
0 16 (0 32)
1 03 (2 16)
12 (21)
0 73 (1 45)
0 79 (1 58)
0 65 (1 10)
1.62 (3 23)
0 47 (0 93)
1 17 (2 33)
0 48 (0 95)
0 85 (1 70)
0 91 (1 82)
1 85 (3 69)
0 55 (1 10)
0 55 (1 11)
1 0 (1 99)
1 16 (2 12)
0 *0 (0 79)
1 56 (3.02)
0 33 (1 05) b
1 70 (3 41) c
__^ — — —
Avorago Acid Mlal
EmUalonB kn/Hg
of lOOt B2S04
(Ib/ton)
0 018 ( 035)
0 062 ( 123)
0 053 (0 109)
0 010 (0 021)
0 038 (0 116)
0 026 (0 052)
0 036 (0 071)
0 030 (0 061)
0 03 (0 06)
0 02 ( 0*)
0 07 (0 13)
0 008 (0 016)
0 008 (0 016)
0 Oil (0 022)
0 071 (0 1*2)
0 06* (0.127)
0 OV (0 039)
0 06* (0 128)
0 023 (0 046)
0 017 (0 073)
0 072 (0 144)
0 037 ( 073)
0 0*2 (0 083)
0 08 (0 15)
0.0*1 (0 082)
00* (07)
0 053 (0 105)
0 0*6 (0 092) b
0 0* (0 07)=
Actual Plant Meaaured
Produ.t Kalr Opacity
During SSPS During
Ten Kg/day Teal
1001 «ZSO» (TPll) (Percent)
84S (929) 0
808 (888) 0
1629 (1790)
1781 (1957)
1562 (1717)
1277 (1*03)
2424 (266*) 0:3
1616 (1771) C 3
15*7 (1700)
1535 (1687)
16*1 (1805)
2*37 (2700)
2166 (2600)
2503 (2750)
1756 (1930)
1641 (1803)
779 (836)
1387 (132*)
1474 (1620)
1113 (14*3)
219 (2*1)
1830 (2011) <10
1677 (18*3) <10
1694 (1862)
716 (787) 9 2
<3
1001 (1100)
853 (918) b
222 (244) S
Reference
W* " " •
CDS. 1978
CDS. 1978
CDS. 1978
CDS. 1978
Carrett. 1978
Carroll. 1978
CE6 , 1971
Vu. 1978
Wu, 1978
CDS, 1978
CD8. 1978
Q1S , 1976
CDS. 1978
CDS, 1978
Gardner. 1978
CDS. 1978
CDS. 1978
CDS, 1978
Cohen. 1978
Shonk. 1978
Shook. 1978
Spruloll. 1978
Sprulell. 1978
Reynold! . 1978
Pfandrr. 1978
Pfandir, 19 "9
Sntvdcn a Alifard.
1976
acy w. pu
bTotal output of two unlti
Stvcrage of three unit*
-------
N
O
O
I
CN
O
a)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
±
rf
:r
Current EPA NSPS - Sulfuric Acid Pla
h
ffl
m
t:
tit:
f-
t-t-t--
Ttt:
t--
-i 1-
tt
:r
ffl
+rt
^+t
: rr
I I i I I l-l-i.
dPlantsi
rrnrrrs
fh-
-r"
tti
fr • r
ffS
;m
Legend:
O - Region 2
• - Region 4
• - Region 5
,D - Region 6
A - Region 9
- Region 10
tfl
-rt
.ft
TTT
TO
rTi
t H
ill
1000 L500 2000
Plant Production Rate, TPD
FIGURE 5-1
CONTACT PROCESS SULFURIC ACID PLANTS
NSPS COMPLIANCE TEST RESULTS
S02 EMISSIONS
2500
3000
5-3
-------
§
,-H
§
H
c
o
•H
01
-H
X
"O
•H
u
03
0)
i
mmmmrmttt-m.t'
. JCurrent EPA NSPS - Sulfuric Acid Plants
Legend:
O - Region 2
• - Region 4
- Region 5
- Region 6
A - Region 9
A - Region 10
•I--: 4-Uj.
.02
500
1000 1500 2000
Plant Production Rate, TPD
2500
3000
FIGURE 5-2
CONTACT PROCESS SULFURIC ACID PLANTS
NSPS COMPLIANCE TEST RESULTS
ACID MIST EMISSIONS
5-4
-------
TABLE 5-2
in
I
Ui
NSPS COMPLIANCE TEST RESULTS
FOR NEW SULFURIC ACID PLANTS
BREAKDOWN BY EMISSIONS LEVEL
NSPS Test Results
(Ib/ton)
3.0 to 4.0
2.0 to 3.0
1.0 to 2.0
0 to 1.0
S02
No. of
Results
5
6
14
4
29
% of
Total
17
21
48
14
100
NSPS Test Results
(Ib/ton)
0.13 to 0.15
0.11 to 0.13
0.09 to 0.11
0.07 to 0.09
0.05 to 0.07
0.03 to 0.05
0.01 to 0.03
Acid Mist
No. of
Results
3
5
2
6
6
3
4
29
% of
Total
10
17
7
21
21
10
14
100
-------
presents a percentage breakdown of NSPS S02 and acid mist emis-
sion results at various levels below the respective control levels.
5.2.1 Control Technology Used to Achieve Compliance
All 32 units tested showed compliance with the NSPS S02 and
acid mist control levels. Of the 32 units tested, 28 achieved com-
pliance with the SC>2 standard through use of the dual absorption
process. Of the remaining four units, three use ammonia scrubbing
and one employs a molecular sieve process* to meet the standard. All
of the new units use mist eliminators to achieve acid mist control.
The bulk of these control units are vertical tube mist eliminators.
Only nine values of opacity were reported (all meeting the NSPS stan-
dard). It is assumed that all of the new plants were meeting the
opacity standard during the compliance tests since opacity is direct-
ly related to acid mist concentration.
In one vendor's modification of the dual absorption process (the
R.M. Parsons Co., Pasadena, California), the usual four-bed catalytic
converter was replaced with a five-bed unit, i.e. , three beds are
used for SC>2 conversion prior to the interpass or primary absorp-
tion tower, followed by two beds being utilized for further S02
conversion before the final absorber. This method is intended to
achieve 99.8 to 99.9 percent conversion to SO^ equivalent to
approximately 0.5 kg/Mg (1.0 Ib/ton) SO2 emission level in the tail
gas. Eight new dual absorption units incorporating this design have
*Due to operational difficulties, the molecular sieve operation is
currently being replaced by a dual absorption plant.
5-6
-------
been installed (Field, 1978). The Parsons units are identified in
Table 4-5. Inspection of Table 5-1 indicates that the Parsons units
show a range of S(>2 emissions from 0.4 kg/Mg (0.8 Ib/ton) to 1.7
kg/Mg (3.4 Ib/ton), with the average being approximately 1.0 kg/Mg
(2.0 Ib/ton). Based on NSPS compliance test results, it appears that
the SC>2 emission levels obtained from these five-bed units have not
been able to reach the original design levels.
5.2.2 Statistical Analysis of NSPS Compliance Test Data
The arithmetic mean and 95 percent confidence interval has been
calculated for the dual absorption plant NSPS test results. The
arithmetic mean for SC>2 is 0.9 kg/Mg (1.8 Ib/ton) with a 95 percent
confidence interval of ^0.15 kg/Mg (+0.3 Ib/ton). The arithmetic
mean for acid mist emissions is 0.04 kg/Mg (0.08 Ib/ton) with a 95
percent confidence interval of +0.01 kg/Mg (+0.02 Ib/ton). The wider
95 percent confidence limits for acid mist emissions are indicative
of a greater spread in acid mist emission results (as can be seen by
comparing Figures 5-1 and 5-2).
5.2.3 Validity of NSPS Test Data
The 26 data points obtained for dual absorption plants equipped
with high efficiency acid mist eliminators show a rather large spread
for S02 control levels, i.e., SC>2 emission values range from a
low of 0.16 kg/Mg (0.32 Ib/ton) to a high of 1.9 kg/Mg (3.7 Ib/ton).
Additionally, the corresponding acid mist emission values range from
a low of 0.008 kg/Mg (0.016 Ib/ton) to a high of 0.071 kg/Mg (0.14
Ib/ton). All data were obtained using the standard EPA Method 8.
5-7
-------
It is not clear why the use of this test method should have produced
such a wide variation in the test results for plants with identical
control technologies. Region IV believes that at least part of the
observed variation may be due to differences in test contractor's
techniques (Rom, 1978). In this regard, discussion with EPA person-
nel in the Quality Assurance Branch (QAB) of the Environmental
Monitoring and Support Laboratory indicate areas where the original
Method 8* (used in testing all of new sulfuric acid units subject to
NSPS) could yield misleading SC>2 and acid mist results. Detailed
studies of the original Method 8 by QAB indicated that the isopro-
panol (IPA) used in the test could contain trace quantities of
peroxide, which, if present, would react with S02 during the test
procedure to form 803, yielding lower S(>2 and higher acid mist
values in the tail gas. Additionally, when the test contractor
performed the impinger train leak check, upon release of the applied
vacuum, a fine spray of hydrogen peroxide solution could deposit on
the filter, causing the 862 —^803 conversion mechanism to be set
into motion during the tail gas sampling period. This again could
result in misleading levels of 802 and acid mist in the tail gas
(Midgett, 1978).
The revised Method 8 has attempted to remedy these defects in
the original test.* This method requires that the IPA be tested for
*Method 8 was revised effective August 18, 1977.
5-8
-------
peroxides. If the latter are found, the IPA batch must either be
discarded or treated to remove the peroxide. Since operator tech-
nique is the controlling factor in minimizing errors due to the leak
check, the revised Method 8 provides a warning to the test equipment
operator to avoid this pitfall by careful manipulation of the equip-
ment.
In summary, it would seem reasonable to have some question about
the validity of the S(>2 and acid mist results obtained from the
NSPS compliance tests made prior to August 1977 on the grounds of the
reliability of the test method itself.
5.2.4 Comparison of NSPS Compliance Test Data with Day-to-Day
Emission Control Performance
MITRE has made a number of inquiries of sulfuric acid plants
that are operating units subject to NSPS to ascertain whether the
compliance test data for these units represent the current day-to-
day emission control levels. A literature search had indicated that
NSPS emission controlled plants (dual absorption) could be expected
to operate (after an initial startup period with fresh catalyst) with
SC>2 emissions in the 1 to 1.5 kg/Mg (2 to 3 Ib/ton) range. One
recent literature reference indicated that a new sulfuric acid unit
with an NSPS S02 test value of 0.56 kg/Mg (1.12 Ib/ton) in 1975,
was currently averaging 1.5 kg/Mg (3.0 Ib/ton) SC>2 emissions
(PEDCo, 1977). Another reference indicated that a typical dual
absorption plant with an average S02 NSPS compliance test result of
0.85 kg/Mg (1.70 Ib/ton) was operating at an average S02 emission
level of 1.15 kg/Mg (2.3 Ib/ton) (EPA, 1976).
5-9
-------
Data obtained from one new dual absorption sulfuric acid unit
points up the effect of plant and catalyst aging on the S02 emis-
sion level. These data are tabulated in Table 5-3.
TABLE 5-3
EFFECT OF PLANT AND CATALYST AGE ON S02 EMISSION LEVEL3
S02 Emissions
Date Source of Data kg/Mg (Ib/ton)
9/17/75 NSPS Compliance Test (EPA Method 8) 0.47 (0.93)
10/22/76 Dupont Continuous S02 Monitorb 1.30 (2.59)
4/4/77 Dupont Continuous S02 Monitorb 1.43 (2.85)
3/28/78 Dupont Continuous SO? Monitorb 1.6 (3.2)
aThis is an 1800 ton/day (100 percent H2S04) plant.
"Results of Dupont continuous monitor checked concentrations, when
converted to kg/Mg of 100 percent acid, checked to within 1 percent
of EPA Method 8.
Source: Mullins, 1978.
This plant (a total of two units subject to NSPS) is stated to
operate at an S02 emission level of 1.25 to 1.50 kg/Mg (2.5 to 3.0
Ib/ton) on a day-to-day basis (Mullins, 1978).
Another plant which had an S02 NSPS test result of 0.48 kg/Mg
(0.95 Ib/ton) indicated that this result was obtained with fresh
catalyst and that the day-to-day operating value of S02 emissions
averaged 0.5 to 1.0 kg/Mg (1 to 2 Ib/ton) (Stark, 1978).
In summary, indications from the literature and from contacts
with sulfuric acid plant operators are that low NSPS compliance test
5-10
-------
SC>2 emission values do not necessarily reflect day-to-day plant
operating levels. These levels appear to realistically lie in the 1
to 1.5 kg/Mg (2 to 3 Ib/ton) range for dual absorption units. There
is a definite trend towards increased 502 emission values as the
conversion catalyst ages and its activity correspondingly decreases.
Thus, even though a large percentage of the compliance test results
are significantly less than the NSPS of 2 kg/Mg (4 Ib/ton), it
appears that S02 emissions tend to rise towards the control limit
as the plant and catalyst age.
Acid mist emission (and related opacity) levels are unaffected
by conversion catalyst aging, being primarily a function of moisture
levels in the sulfur feedstock and air fed to the sulfur burner, and
the efficiency of final absorber operation. The wide spread observed
in NSPS compliance test values is probably a result of variations in
these factors or quite possibly errors in the test method itself (as
discussed in Section 5.2.3).
5.2.5 Emission Control Performance Based on Excess Emissions
Reports
It was not possible to evaluate excess emissions reports with
regard to sulfuric acid plant SC>2 and acid mist control perfor-
mance, since a very limited number of reports were available.
5.3 Indications of the Need for a Revised Standard
5.3.1 SO? Standard
At this time, there is not sufficient justification for revision
of the present SC>2 NSPS, based on the following considerations:
5-11
-------
• The current best demonstrated control technology (the
dual absorption process) is identical in basic design to
that used as the rationale for the original S02 standard.
• While the S02 NSPS compliance test data averages close to 1
kg/Mg (2 Ib/ton) with a number of values in the 0.5 kg/Mg (1
Ib/ton) to 1 kg/Mg (2 Ib/ton) range, an analysis of these
data indicates that:
1. There may be some question about the validity of the low
values of S02 emissions based on defects in the origi-
nal EPA Method 8.
2. Actual plant experience shows that the low NSPS values do
not necessarily reflect the day-to-day operating S02
emission levels which tend to rise toward the standard as
the conversion catalyst ages.
• According to a prime manufacturer of dual absorption plants,
in order to guarantee performance at the present level, a
margin of safety is built into the unit design to compen-
sate for the effects of plant and catalyst aging, fluctuating
feed rates and other deviations from ideal operating condi-
tions. Construction of new plants to meet an appreciably
lower S02 NSPS involves greatly increased capital costs,
since a margin of safety would have to be built into the
new plant to meet performance guarantees (Donovan et al.
1977).
• A trend toward higher levels of S(>2 in the gas feed to the
converter, i.e., 12 percent S(>2 or higher may develop in
the industry, since there is appreciable energy savings due
to the additional heat recovery available from the highly
exothermic conversion reaction. Meeting an S02 emission
standard appreciably lower than 2 kg/Mg (4 Ib/ton) in this
situation would be extremely difficult without extensive (and
expensive) equipment additions to the plant.
Other considerations, including economic factors, that militate
against a change in the present S(>2 NSPS are discussed in Section
6.0.
5-12
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5.3.2 Acid Mist NSPS (and Related Opacity Standard)
At this time, there is not sufficient justification for revision
of the present acid mist (and opacity) NSPS, based on the following
considerations:
• The current best demonstrated control technology (the high
efficiency acid mist eliminator) is identical to that used
as the rationale for the original acid mist standard.
• The NSPS compliance test data showed a wide scatter, with an
appreciable number of the acid mist emission values close to
the control limit. The scatter observed in these values may
be due to the defects in the original EPA Method 8 which
tended to introduce variability in the acid mist levels
obtained.
• Making the acid mist standard more stringent is not believed
to be practicable because of the need to provide a margin of
safety due to in-plant operating fluctuations. Variation in
the sulfur feedstock, leaks, or improper inlet air drying
tower operation can introduce moisture (the controlling
factor in the production of acid mist) into the system,
increasing the production of acid mist. It should be noted
that acid mist control is far more vulnerable to operating
fluctuations which deviate from standard plant operating con-
ditions than sulfur dioxide control.
a Manufacturers of acid mist eliminators guarantee maximum
stack emission of 1 mg/scf ( 0.15 Ib/ton) for high-
efficiency units. These manufacturers do not guarantee any
form of visible emission limitation, but acid mist emissions
of 1 mg/scf normally result in stack plumes of less than 10
percent opacity (Serne and Weisenberg, 1976).
5-13
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6.0 ANALYSIS OF POSSIBLE REVISIONS TO THE STANDARD
6«1 Effect of NSPS Revision on Sulfuric Acid Production Economics
The S02 emissions in a dual absorption plant are primarily
determined by the efficiency of the catalytic converter system. Acid
mist emissions are controlled by plant operators' attention to con-
trol of residual moisture in the S02~laden inlet gas to the system
and to efficient absorber and acid mist eliminator operation. NSPS
compliance test values of these emissions, which are appreciably
below the present control levels, are, as has been shown in Sections
5.2 and 5.3, not necessarily representative of the levels achievable
by a particular plant on a day-to-day basis. Additional capital and/
or operating expense would be entailed by plants using the present
best demonstrated control technology in order to reduce NSPS control
levels appreciably below the present values.
Additional capital expense required to control emissions below
the present NSPS levels would be involved for a scrubber installation
to further reduce S02 in the tail gas from the dual absorption
system or an additional acid mist eliminator in series with the
present unit to further reduce acid mist.
As shown in Section 5.0, NSPS S02 levels for new plants tested
predominantly in the 1 to 1.25 kg/Mg (2 to 2.5 Ib/ton) range. Making
the standard more stringent in order to accomplish reduction of S02
emissions appreciably below the present NSPS control level on a day-
to-day basis, can probably be achieved by increasing sulfuric acid
6-1
-------
plant operating expense significantly. Since SO2 emissions are
directly affected by the level of catalyst activity, the former
should be able to be maintained at levels comparable to the observed
NSPS compliance test values, if fresh catalyst with the maximum
activity were to arbitrarily replace older material in the converter
beds at frequent intervals. The economics of a catalyst replacement
program have been developed and applied to the cost of producing
sulfuric acid in a dual absorption plant, as described below.
In the four-bed catalytic converter system in a typical dual
absorption plant, the first bed exposed to the inlet gas experiences
the greatest rate of activity decrease due to dirt and traces of
catalyst poisons, with beds two and three suffering progressively
less loss of activity due to these contaminants. These beds have an
average service life of 3 to 5 years. The final catalyst bed, which
treats the S02-laden gas from the first absorption tower, can have
a service life of 10 to 15 years. Normal plant practice is to
progressively elevate these catalyst beds during the plant turnaround
periods so that the overall average bed life is 5 to 7 years.
The basic information used in the catalyst replacement cost cal-
culations is summarized in Table 6-1, and the results of the calcula-
tions are shown in Table 6-2.
Based on a sulfuric acid manufacturing cost of $36/Mg, the
incremental increase of 55 cents/Mg for the catalyst replacement pro-
gram outlined above, represents only a 1.4 percent increase. With
6-2
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TABLE 6-1
BASIC DATA USED IN CATALYST REPLACEMENT COST CALCULATIONS
Items
Source
• 1000 Mg/day dual absorption plant
• 4 Bed Converter
• First three beds (Beds 1, 2 and 3) -
Average life of 3-5 years, Final bed
(Bed 4) - Average life of 10-15 years
• Average catalyst makeup rate (first
bed) is 10 percent per year due to
screening and attrition losses
• Catalyst loading of 140 liters/daily
Mg of acid at 10.5% SC>2 in inlet gas
to converter
• Total catalyst replacement cost is
$3/liter installed
• Total sulfuric acid manufacturing
cost is $36/Mg (direct and fixed
costs)
• Average pretax profit for merchant
sulfuric acid is $3/Mg
Design Basis
Design Basis
Sheputis, 1978
Sheputis, 1978
Monsanto Enviro-Chem, 1974
Sheputis, 1978
Hansen, 1978
EPA, 1977
6-3
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TABLE 6-2
EFFECT OF CATALYST REPLACEMENT ON COST OF PRODUCTION OF
SULFURIC ACID IN A DUAL ABSORPTION PLANT
ASSUMPTIONS
• In order to maintain overall catalyst activity at a level to obtain
S02 conversion equivalent to emission of 1 to 1.25 kg/Mg of 100
percent acid (2 to 2.5 Ib/ton), replace catalyst beds on the fol-
lowing schedule:
Bed 1: Complete replacement once a year (a net replacement of 90
percent of the original bed).
Bed 2: Complete replacement once every 2 years.
Bed 3: Complete replacement once every 3 years.
Bed 4: Complete replacement once every 10 years.
• Each bed holds 25 percent of the total catalyst loading.
• Plant operates 350 days per year.
Bed
No.
1
2
3
4
Totals
Annual Catalyst
Volume Replaced
(liters)
31,500
17,500
11,700
3,500
Annual Catalyst
Replacement
Cost, $
94,500
52,500
35,100
10,500
192,600
Mg/Yr of 100%
Acid Produced
350,000
350,000
350,000
350,000
Annual Catalyst
Replacement Cost
$/Mg of
Acid Produced
0.27
0.15
0.10
0.03
0.55
6-4
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a present FOB plant selling price for 100 percent merchant acid of
approximately $50/Mg (Gulf Coast area) (Chemical Marketing Reporter,
1978), an incremental increase of 55 cents/Mg for catalyst replace-
ment represents only 1 percent of the selling price. However, the
effect of this cost on pretax profit, based on an average pretax
profit of $3/Mg, is much more drastic, i.e., 55 cents/Mg for annual
catalyst replacement represents an approximate 20 percent reduction
in pretax profit. An adverse economic penalty to the sulfuric acid
industry would seem to be indicated by this approach.
A serious problem raised by the catalyst replacement program
outlined above would be the need to dispose of the highly toxic spent
vanadium pentoxide catalyst waste generated. This material is not
considered valuable enough to rework by the major processors. Some
of the catalyst disposed of at present is reworked by several mar-
ginal processors (Sheputis, 1978).
6.2 Effect of New Sulfuric Acid Plant Construction on the NSPS
As mentioned in Section 4.2, the rate of completion of new sul-
furic acid units during the 1971-1977 period was approximately 5 per
year. During the 1978-1980 period, the number of new sulfuric acid
units announced or under construction has slowed to approximately 3
per year. This slowdown in new growth is due primarily to the pre-
sent imbalance in the demand-supply situation in the phosphate ferti-
lizer industry. Based on anticipated growth in the phosphate ferti-
lizer industry, an estimate for the 1981 to 1984 period of four new
sulfuric acid units completed per year has been used as a basis
6-5
-------
for calculating Che total S02 and acid mist emissions at various
emission levels for the 16 new units projected to be completed during
this period. The results of these calculations are shown in Tables
6-3 and 6-4.
A study of Table 6-3 indicates that reducing the NSPS control
level for S02 emissions from the present 2 kg/Mg (4 Ib/ton) to 1
kg/Mg (2 Ib/ton), a 50 percent reduction, would reduce the total
S02 emissions for sulfuric acid plants regulated by the NSPS by
approximately 6000 Mg/yr (7000 tons/yr) in 1984. Correspondingly, a
study of Table 6-4 indicates that reduction of the NSPS acid mist
control levels from the present 0.075 kg/Mg (0.15 Ib/ton) to 0.05
kg/Mg (0.10 Ib/ton), a 33 1/3 percent reduction, would reduce the
total acid emissions for these sulfuric acid plants by approximately
150 Mg/yr (170 tons/yr) in 1984.
As a further comparison of the potential impact of SC>2 emis-
sions from sulfuric acid units projected to be built between 1981 and
1984, data from projections of S02 emissions from all stationary
sources in 1984 were used to calculate the effect of sulfuric acid
plant S(>2 NSPS reduction. Total S02 emissions from stationary
sources in 1984 (based on all existing NSPS and state standards in
effect in 1975) are indicated to be approximately 33 x 10^ Mg/yr
(EPA, 1976). With the present sulfuric acid NSPS of 2 kg/Mg (4 lb/
ton), the percent SC>2 emission contribution of the projected 16 new
units in 1984 would be 0.04 percent. Correspondingly, with an NSPS
6-6
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TABLE 6-3
PROJECTED CUMULATIVE S02 EMISSIONS FROM NEW CONTACT SULFURIC
ACID PLANTS ADDED BETWEEN 1981 AND 1984a
Control Level
kg/Mg (Ib/ton)
Projected Emissions
Mg/yr (ton/yr)b
1981
2.0
1.75
1.5
1.25
1.0
(4.0)
(3.5)
(3.0)
(2.5)
(2.0)
3,060(3
2,680(2
2,290(2
1,910(2
1,530(1
,360)
,940)
,520)
,100)
,680)
1982
6,120(6
5,350(5
4,590(5
3,820(4
3,060(3
,720)
,880)
,040)
,200)
,360)
1983
9,180(10
8,030(8,
6,880(7,
5,730(6,
4,590(5,
,080)
820)
560)
300)
040)
1984
12,230(13
10,700(11
9,170(10
7,640(8,
6,120(6,
Percent of Total Annual
S02 Emissions of
NSPS Plants in 1984C
,440)
,760)
,080)
400)
720)
27
25
22
18
16
.6
.0
.2
.8
.0
aFour contact process double-absorption sulfuric acid plants (average production capacity of
1100 Mg/day (1200 tons/day) of 100% l^SO^ each) are projected to be installed per year from
1981-1984, inclusive.
"Calculations based on a 350-day work year.
cTotal annual S02 emissions of 42 existing NSPS H2S04 units in 1984 (at present 4.0 Ib/ton
control level) is 33,000 Mg/yr2 (35,300 tons/yr).
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TABLE 6-4
PROJECTED CUMULATIVE ACID MIST EMISSIONS FROM NEW CONTACT SULFURIC
ACID PLANTS ADDED BETWEEN 1981 and 1984a
Control Level
kg/Mg (Ib/ton)
CT>
CO
0
0
0
0
0
0
.075
.07
.065
.06
.055
.05
(0.
(0.
(0.
(0.
(0.
(0.
15)
14)
13)
12)
11)
10)
Projected Emissions
Mg/yr (ton/yr)b
1981
115(126)
108(119)
99(109)
93(102)
"83(91)
76(84)
1982
229(252)
217(238)
197(217)
185(203)
166(182)
153(168)
1983
344(378)
325(357)
297(326)
278(305)
248(273)
229(252)
Percent of Total Annual
Acid Mist Emissions of
NSPS Plants in 1984C
1984
459(504)
433(476)
395(434)
369(406)
331(364)
306(336)
27
26
24
23
21
20
.6
.4
.7
.5
.6
.3
aFour contact process double-absorption sulfuric acid plants (average production capacity of
1100 Mg/day (1200 tons/yr) of 100% R2SOU each) are projected to be installed per year from
1981-1984, inclusive.
bCalculations based on a 350-day work year.
cTotal annual acid mist emissions of 42 existing NSPS units in 1984 (at present 0.15 Ib/ton control
level) is 1200 Mg/yr (1325 tons/yr).
-------
of 1 kg/Mg (2 Ib/ton), the percent S(>2 emission contribution of the
projected 16 new units in 1984 would be 0.02 percent. The national
impact of a more stringent SC>2 NSPS would be marginal due to the
very small decrease in 862 emissions (resulting from a tighter
standard) from the sulfuric acid plants projected to be built during
the 1981 through 1984 period.
6-9
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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 sulfuric acid plants, including
review of the S02 and acid mist standards. The existing opacity
standard is directly related to the acid mist standard and is not
reviewed separately. The findings and recommendations developed in
these two areas are presented below.
7.1 Findings
7.1.1 SO-? NSPS
7.1.1.1 Process Emission Control Technology.
• The current best demonstrated control technology, the dual
absorption process, is identical in basic design to that
used as the rationale for the original S02 standard. The
dual absorption process is in use in over 90 percent of all
sulfuric acid production units installed since the promulga-
tion of the S02 NSPS for sulfuric acid plants and will be
installed in all new plants built through 1980.
• While the overall average S02 emission obtained in the
NSPS compliance test results is 0.9 kg/Mg (1.8 Ib/ton), the
wide range shown in this data, from a low of 0.16 kg/Mg
(0.32 Ib/ton) to a high of 1.9 kg/Mg (3.7 Ib/ton) for dual
absorption plants, may be partially due to defects in the
original Test Method 8 or to variations in test operator
technique. The average S02 emission level obtained in the
NSPS compliance tests for dual absorption plants is about
one order of magnitude lower than the emission level
obtained from uncontrolled single absorption plants.
• The dual absorption process, while yielding low NSPS compli-
ance test S02 emission levels, can not maintain these
levels on a day-to-day basis. The S02 emission level is a
function of catalyst conversion efficiency which drops as
the catalyst ages.
7-1
-------
7.1.1.2 Economic Considerations.
• In order to guarantee SC>2 emission control performance at
the present NSPS level, vendors of the dual absorption
process plants incorporate a sufficient margin of safety in
the plant design, consistent with reasonable investment
cost, to compensate for the effects of plant and catalyst
aging, fluctuating feed rates and other deviations from
ideal operating conditions. Making the present SC>2 NSPS
more stringent would involve greatly increased capital costs
since sulfuric acid plant vendors would have to redesign
for lower S02 emission rates in order to retain this
margin of safety.
• More frequent conversion catalyst replacement (as compared
with present practice) in order to maintain a more stringent
S02 control level than the present standard in sulfuric
acid plants subject to NSPS would represent a substantial
drop in pretax profits (20 percent or more).
• Projections over the 4-year period, 1981 through 1984, for
the 16 new sulfuric acid plants expected to be built during
this period indicate that there would be only a 0.02 percent
drop in SC>2 emission contribution from these plants to the
total U.S. annual S02 emissions if the present S02
standard were dropped from 2 kg/Mg (4 Ib/ton) to 1 kg/Mg (2
Ib/ton).
7.1.2 Acid Mist NSPS (and Related Opacity Standard)
• The current best demonstrated control technology, the high
efficiency acid mist eliminator, is identical to that used
as the rationale for the original acid mist standard. This
technology is in use in all sulfuric acid plants built since
the promulgation of the acid mist NSPS for sulfuric acid
plants.
• While the average acid mist emission obtained in the NSPS
compliance test results is 0.04 kg/Mg (0.08 Ib/ton), the
wide range shown in this data, from a low of 0.008 kg/Mg
(0.016 Ib/ton) to a high of 0.071 kg/Mg (0.14 Ib/ton) for
high efficiency acid mist eliminator control, may be
partially due to defects in the original EPA Method 8 which
tended to introduce variability in the acid mist levels
obtained.
7-2
-------
• An appreciable number (approximately 25 percent) of the NSPS
compliance test results obtained for acid mist emissions are
within 75 to 100 percent of the present NSPS acid mist
control level. This may be indicative of the vulnerability
of sulfuric acid plants to in-plant operating fluctuations
such as variation in the sulfur feedstock, leaks, or improper
inlet air drying tower operations, all of which introduce
moisture (the controlling factor in the formation of acid
mist) into the system, thus increasing the acid mist
emissions.
• Manufacturers of acid mist eliminators guarantee maximum
stack emissions of 1 mg/scf (~0.15 Ib/ton) for high
efficiency units under normal operating conditions. While
there is a 10-percent opacity limitation for stack plumes
under the present NSPS, no guarantee is provided for any
form of visible emission limitation. However, available
data indicate that acid mist emissions of 1 mg/scf will
result in stack plumes of less than 10 percent opacity.
7.2 Recommendations
7.2.1 SO? NSPS
At this time there is not sufficient justification for revision
of the S02 NSPS for sulfuric acid plants, based on the following
considerations:
• The best demonstrated control technology, the dual
absorption process, is in use in all new sulfuric acid
plants.
• SC>2 emission levels achieved in the NSPS compliance tests
which were significantly lower than the standard are not
representative of day-to-day plant operations. These levels
tend to rise toward the standard as the conversion catalyst
ages. The dual absorption process can not adjust the SC>2
emission levels to compensate for the loss of catalyst
activity.
• The national impact of a more stringent SC>2 NSPS would be
marginal due to the very small decrease in S(>2 emissions
(resulting from a tighter standard) from the sulfuric acid
plants projected to be built during the 1981 through 1989
period.
7-3
-------
7.2.2 Acid Mist NSPS (and Related Opacity Standard)
At this time there is not sufficient justification for revision
of the acid mist (and opacity) NSPS based on the following
considerations:
• The best demonstrated control technology (the high
efficiency acid mist eliminator) is in use in all new
sulfuric acid plants.
• The need exists to retain a margin of safety for maintenance
of the present acid mist NSPS control level since there is
always a possibility of in-plant operating fluctuations
which deviate from standard sulfuric acid plant operations
and introduce unexpected amounts of moisture into the
system.
• Control of acid mist emissions at the present NSPS level,
results in essentially no visible emissions, i.e., less than
10 percent opacity.
7-4
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8.0 REFERENCES
Calvin, E.L. and F. D. Kodras, 1976. Inspection Manual for the
Enforcement of New Source Performance Standards as Applied to Contact
Catalyst Sulfuric Acid Plants. Catalytic, Inc., Charlotte, N.C.
CE Construction Alert, 1977. Chemical Engineering, Vol. 84,
No.6.
Chemical and Engineering News, 1978. Facts and Figures for the
Chemical Industry. Vol. 56, No. 24.
Cohen, E., 1978. Personal Communication. EPA Region V,
Chicago, 111.
Donovan, J. R. et al., 1977. Analysis and Control of Sulfuric
Acid Plant Emissions, Chemical Engineering Progress, Vol. 73, No. 6.
Duros, D.R. and E.D. Kennedy, 1978. Acid Mist Control.
Chemical Engineering Progress, Vol. 74, No. 9, 1978.
Field, D., 1978. Personal Communication. R. M. Parsons
Company, Pasadena, Calif.
Gardner, R., 1978. Personal Communication. Georgia Department
of Natural Resources, Atlanta, Ga.
Garrett, W., 1978. Personal Communication. Florida Department
of Environmental Regulation, Winterhaven, Fla.
Hansen, D. R., 1978. Personal Communication. Monsanto
Enviro-Chemical, St. Louis, Mo.
Hooper, M. H., 1978. Personal Communication. EPA Region X,
Seattle, Wash.
Mann, C., 1978. Personal Communication. Requests and
Information Section, National Air Data Branch, U.S. Environmental
Protection Agency, Research Triangle Park, N.C.
Midgett, M. R. , 1978. Personal Communication. Quality Assur-
ance Branch, National Air Data Branch, U.S. Environmental Protection
Agency, Research Triangle Park, N.C.
Mistry, M. T. et al., 1975. Personal Communication to EPA
Region II. Betz Environmental Engineers, Newark, N.J.
8-1
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MITRE Corporation, 1978. Regional Views on NSPS for Selected
Categories. Metrek Division, McLean, Va.
Monsanto Enviro-Chemical, 1974. Vanadium Catalysts for Contact
Sulfuric Acid Plants. St. Louis, Mo.
Mullins, F., 1978. Personal Communication. Occidental
Petroleum Corporation, White Springs, Fla.
PEDCo Environmental Inc., 1977. Summary Report on S02 Control
Systems for Industrial Combustion and Process Sources, Vol. IV
Sulfuric Acid Plants. Cincinnati, Ohio.
Reynolds, W. , 1977. Personal Communication to EPA Region IX,
Valley Nitrogen Producers, Inc., Helm, Calif.
Pfander, J., 1978. Personal Communication. EPA Region X,
Boise, Idaho.
Rom, J., 1978. Personal Communication. EPA Region IV, Atlanta,
Ga.
Serne, J. C. and I. J. Weinsenberg, 1976. Engineering Evalua-
tion of Cities Service Smelter, Copperhill Tennessee for S02
Emission Control. Pacific Environmental Services, Inc., Santa
Monica, Calif.
Sheputis, J. , 1978. Personal Communication. Monsanto
Environ-Chemical, St. Louis, Mo.
Shonk, R. D. , 1978. Personal Communication. Agrico Chemical
Co., Donaldsonville, La.
Snowden, W. D. and D. A. Alguard, 1976. Personal Communication
to EPA Region X, Alsid, Snowden & Assoc., Believe, Wash.
Spruiell, S. , 1978. Personal Communication. EPA Region VI,
Dallas, Tex.
Stanford Research Institute, 1977. Directory of Chemical
Producers, Palo Alto, Calif.
Stark, C. , 1978. Personal Communication. Mississippi Chemical
Corporation, Yazoo City, Miss.
U.S. Department of Commerce, 1976. Sulfuric Acid 1976, Current
Industrial Reports. M28A(76)-14 Supplement 1. Bureau of the Census,
Washington, D.C.
8-2
-------
U.S. Department of Commerce, 1977. Sulfuric Acid 1977 Current
Industrial Reports. M28A(77)-14 Supplement 1. Bureau of the Census,
Washington, O.C.
U.S. Department of the Interior, Bureau of Mines, 1975. Miner-
als Yearbook 1975, Metals, Minerals, and Fuels. Vol. 1. U.S.
Department of the Interior, Washington, D.C.
U.S. Department of the Interior, Bureau of Mines, 1978. Mineral
Industry Surveys. U.S. Department of the Interior, Washington, D.C.
U.S. Environmental Protection Agency, 1971. Background Informa-
tion for Proposed New Source Performance Standards. Office of Air
Programs, Research Triangle Park, N.C.
U.S. Environmental Protection Agency, 1971a. Control of Air
Pollution from Sulfuric Acid Plants. Emission Standards and En-
gineering Division, Durham, N.C.
U.S. Environmental Protection Agency, 1976. Sulfuric Acid Plant
Emissions During Start-up, Shutdown, and Malfunctions. EPA-600/
2-76-010. Industrial Environmental Research Laboratory, Research
Triangle Park, N.C.
U.S. Environmental Protection Agency, 1977. Final Guideline
Document: Control of Sulfuric Acid Mist Emissions from Existing
Sulfuric Acid Production Units. EPA-450/2-77-019. Office of Air
Quality Planning and Standards, Research Triangle Park, N.C.
U.S. Environmental Protection Agency, 1976. Priorities and
Procedures for Development of Standards of Performance for New
Stationary Sources of Atmospheric Emissions. EPA-450/3-76-020. Of-
fice of Air Quality Planning and Standards. Research Triangle Park,
N.C.
U.S. Environmental Protection Agency, 1978. Compliance Data
System Source Data Reports.
Williams, A. R., 1977. Personal Communication to EPA Region V,
Shell Oil Company, Wood River, 111.
Wu, J. , 1978. Personal Communication. EPA Region IV, Atlanta,
Ga.
8-3
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TECHNICAL REPORT DATA
(Pirase read Instructions on the ret crsc before completing)
REPORT NO
PA-450/3-79-003
3 RECIPIENT'S ACCESSION NO
TITLE AND SUBTITLE
A Review of Standards of Performance for New Stationary
Sources-Sulfuric Acid Plants
REPORT DATE
January 1979
6 PERFORMING ORGANIZATION CODF
Marvin Drabkin and Kathryn J. Brooks
8 PERFORMING ORGANi.-Alll'N HUOrll
MTR-7S72
PERFORMING ORGANIZATION NAME AND ADDRESS
Metrek Division of the MITRE Corporation
1820 Dolley Madison Boulevard
McLean, Virginia 22102
1O PROGRAM ELEMENT NO
11 CONTRACT/GRANT NO
68-02-2526
2 SPONSORING AGENCY NAME AND ADDRESS
13 TYPE OF REPORT AND PERIOD COVERED
DAA for Air Quality Planning and Standards
Office of Air, Noise and Radiation
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
14 SPONSORING AGENCY CODE
EPA 200/04
5 SUPPLEMENTARY NOTES
6 ABSTRACT
This report reviews the current Standards of Performance for New Stationary Sources:
Subpart H. 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,
Recommendations are made for future studies needed of unresolved issues.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
COSATI I Icld/Group
sulfuric acid
manufacturing
process
performance standards
regulations
13B
18 DISTRIBUTION STATEMENT
Release Unlimited
19 SECURITY CLASS (This Report)
Unclassified
21 NO OF PAGES
87
20 SECURITY CLASS (This page)
Unclassified
22 PRICE
EPA Form 2220-1 (Rev 4-77) PREVIOUS EDITION is OBSOLETE
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