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A few plants burning only hydrogen sulfide or hydrogen sulfide
plus elemental sulfur use a simplified version of the above pro-
cess. 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 a plant
burning only hydrogen sulfide, all of the sulfur trioxide from
the converter is in the form of acid mist, much of which is not
absorbed in the absorption tower. High efficiency mist collectors
both recover product acid and prevent excessive air pollution.
3.1.3 Dual Absorption Plants
In the dual absorption process, Figure 3.3, a greater fraction of
the sulfur 1n the feedstock 1s converted to sulfuric add than
1n the single absorption process. The SO. formed 1n the primary
conversion stages 1s removed 1n a primary absorption tower and
the remainder of the gas 1s returned to the final conversion
stage(s). Removal of a product of a reversible reaction such
as:
S09 + 1/2 0, - SO, (3.1)
£ £ O
drives the oxidation further toward completion* approaching
the reaction equilibrium expressed by:
(so3)
(3,2)
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where K 1s the reaction equilibrium constant peculiar to the
temperature of the reaction and to the units of the parenthetical
entitles, which are usually taken as the molar concentrations of the
gases involved.
The resulting SO, Is absorbed In a secondary absorption tower
obtaining at least 99.7 percent overall conversion of the sulfur
to sulfurlc acfd.
Figure 3.3 depicts primary absorption after the third conversion
stage with one final conversion stage. Dual absorption plants are
also designed with primary absorption after the second conversion
stage and two final conversion stages.
The dual absorption process penults higher Inlet StL
concentrations than normally used in single absorption plants
since the final conversion stage(s) effectively handles the
residual S02 from the first conversion stages. Higher inlet SCL
concentrations permit a reduction in equipment size which
partially offsets 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.
As shown in Table 2.1, the dual absorption process has been
applied to sulfuric acid plants burning sulfur, spent acid and
hydrogen sulfide; to metallurgical plants; and to plants producing
acid and oleum. However, most applications have been for sul^ur-
burning and metallurgical plants producing acid only.
3-8
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The 99.7 percent overall conversion efficiency of the dual
absorption process corresponds to a stack emission of 4.0 pounds
of SCL per ton of acid produced. This same low Sf^ emission level
I can be achieved in a single absorption plant by the use of a tail
gas recovery system. In the United States, three such systems which
I have been commercially demonstrated to achieve this level or below
. are sodium sulfite scrubbing, ammonia solution scrubbing, and
molecular sieve separation.
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The sodium sulfite scrubbing system scrubs Sn« from the tail
gas yielding various percentages of sodium sulfite, bisulfite
and sulfate in the spent scrubbing liquor (2). The bisulfite is
then thermally decomposed to yield sodium sulfite crystals, $0
and water vapor. Most of the water vapor is condensed and the
| wet S0? is sent back to the acid plant. The crystals are separated
from the mother liquor and are either dissolved in recovered con-
densate and recycled to the absorber or are consumed in the manu-
Ifacture of other products. The mother liquor or spent scrubbing
liquor must be purged to prevent sulfate buildup, and this purge
I
stream is usually treated to reduce water pollution or may be dried
for sale.
I
The ammonia solution scrubbing system scrubs S^2 from the tail
| gas yielding various percentages of ammonium sulfite, bisulfite
_ and sulfate (5). The spent scrubbing liquor can be converted
* to ammonium sulfate, if a market exists, or can be thermally
decomposed to produce S0?, nitrogen, and water vapor, the S0?
beino sent back to the acid plant. In the TVA "ABS" process, the
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ammonium sulfate is melted and decomposed to form ammonium
bisulfate and ammonia gas which are both recycled.
The molecular sieve separation system removes SO^ from the tail
gas on an adsorbent bed (6). Just before the bed becomes
completely saturated with Sf^. the feed gas is switched to an
alternate bed and the saturated bed is regenerated with a purge
of hot, dry air. The effluent purge stream, rich in SOp, is
fed back to the acid plant. The entire adsorption/regeneration
cycle operates continuously on an automatically timed basis.
Relative acid mist production in dual vs. single absorption
plants and the location of mist eliminators in the dual absorption
process and in tail gas recovery systems is discussed in Section
4.3.
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I
3.2 REFERENCES FOR SECTION 3.
1. Establishment of National Emission Standards for
I Stationary Sources. Vol. IV. Sulf uric Add Plants.
_ Research Triangle Institute and PEDCO - Environmental
Specialists, Inc. Final Report. Contract CPA 70 - 164,
Task Order No. 3, National Air Pollution Control
Administration. Research Triangle Park, North Carolina.
| September 30, 1970. 43 p.
2. Engineering Analysis of Emissions Control Technology
for Sulf uric Add Manufacturing Processes. Chemical
I Construction Corporation. Final Report. Contract 22-69-81 ,
_ National Air Pollution Control Administration, PHS, U. S.
" DHEW. New York, N.Y. Publication No. PB-190-393. March
1970. Vol. 1.
3. Shreve, R. N. Chemical Process Industries. 3rd
Edition. New York, McGraw-Hill Book Company, 1967. pp.
I
322-342.
4. Cuffe, S. T., and C. M. Dean. Atmospheric Emissions
from Sulfuric Acid Manufacturing Processes. National Air
M Pollution Control Administration. Durham, North Carolina.
Publication No. 999-AP-13. 1965. 127 p.
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5. Horlacher, W.R. et. al. Four SOp Removal Systems.
Chemical Engineering Progress. 68.: 43 - 50, August 1972.
o
6. The Pura Siv Process for SOp Removal and Recovery:
A New Molecular Sieve Process for SCL Removal and Recovery
from Sulfuric Acid Plant Vent Gas. Union Carbide Corporation,
Materials Systems Division, New York, N.Y.
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4. ACID MIST EMISSIONS (1,2,3)
4.1 POINTS OF EMISSION.
_ The principal point of acid mist emission in a sulfuric acid
plant is the exit gas from the final absorber, more commonlv
referred to as "stack gas" or "tail gas".
m 4.2 FORMATION AND CHARACTERISTICS.
Hexavalent sulfur is present in the stack gas as sulfuric acid
vapor, gaseous sulfur trioxide (S03), and particulate acid mist.
-1.2.1 Sulfuric /^cid Vapor
The stack gas leaving the final absorber always contains sulfuric
acid vapor. This vapor is in equilibrium with the acid in the
absorber at its operating acid concentration and temperature ,
and on cooling may condense in long ducts leading to the stack
or in the stack itself. If no mist controls are employed or
if the cooling occurs after the mist eliminator, the condensed
vapor can be carried out of the stack as relatively large droplets
which fall in the vicinity of the plant. Acid vapor may be reduced
M by operating the absorber at lower temperatures where H-SO. vapor
pressure is lower; however, this may increase acid mist formation.
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Table 4.1 shows that the H^SO, vapor pressure is dependent upon
temperature and, to some extent, upon acid concentration (4). To
reduce acid vapor emissions from a specific absorber, the lowest
operating temperature consistent with good operation must be
found. This generally lies in the range 170 - 185°F.
4.2.2 Sulfur Trioxide Vapor
If significant gaseous S03 is present in the stack gas as a
result of poor absorber operation, it will combine with water
vapor in the atmosphere to produce a visible acid mist. The
only way to prevent this mist formation is through proper
absorber operation and design (5).
Table 4.1 shows that the vapor pressure of S(L increases
rapidly above 99 percent acid concentration (4). Since SCL
absorption efficiency drops off below 98 percent acid concentration,
control of concentration in the range 98 - 99 percent is generally
good practice.
Concentrations of SO., in the absorber exit aas vill of necessity
exceed the equilibrium concentrations given in Table 4.1. This
is because no absorber of finite heiqht can achieve S03 equilibrium
between the acid entering the top of the tower and the tower top
exit gas.
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4.2.3 Particulate Add H1st
Acid mist is formed anywhere in a sulfuric acid plant where
sulfuric acid vapor is cooled below the dewpoint corresponding
to that particular acid vapor concentration; the original
H-SO. vapor can arise from acid vapor pressure, or from reaction
of SCL with water vapor in the carrier gas stream. Once formed,
this mist is extremely stable, is not readily separated or
absorbed, and much of it passes through the absorber. The
quantity and particle size distribution of acid mist are functions
of the sulfur feedstock and the strength of the acid produced.
For a bright elemental sulfur plant, the only sources of water
vapor are moisture in the sulfur and in the inlet air to the
drying tower. The drying towers in most contact plants are
able to dry the process gas to a moisture content of about
3 milligrams per standard cubic foot (mg/scf) (6). Theoretically,
the 3 mg/scf of water vapor will form 16 mg/scf of sulfuric
acid mist. Part of the mist is probably removed in the absorber,
however.
When dark or contaminated sulfur is burned, hydrocarbon impurities
present in the sulfur burn to produce water vapor. This in turn
combines with SCL to form acid mist as the gas cools in the
4-4
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economizer or absorption tower. This mist formation may be
M accentuated by sudden chilling of the gas on cold surfaces,
an effect sometimes produced by rain on the gas duct. Existing
information indicates that this mist consists of 1 to 5 micron
particles (7).
Another cause of mist formation is the presence of nitrogen
oxides in the converted gas. Although the nitrogen oxides may
result from fixation of atmospheric nitrogen in high temperature
furnaces or from arcing of electrostatic precipitators in the
« purification section upstream of the drying tower in non-sulfur
burning plants, they more commonly result from nitrogen compounds
I in the raw material used. Spent acids recycled from organic
reactions are most likely to produce nitrogen oxides. Part of
| the mist formation undoubtedly results from oxidation of S0? by
these nitrogen oxides (the chamber plant reactions) (8). It is
* also believed that nitric oxide (NO) reacts with S03 to form
nitrosyl pyrosulfate, (N0)2 S-j07; and that nitrosyl pyrosulfate
reacts with atmospheric moisture to form nitrosyl bisulfate,
p NOHSO,. Nitrosyl pyrosulfate will pass through the final absorber
_ and any mist eliminator in gaseous form at normal exit gas
temperatures, and both nitrosyl pyrosulfate and nitrosyl bisulfate
can exist in the stack gas as very fine mist. (9). These mist
emissions can be minimized through use of high efficiency mist
eliminators and/or electrostatic precipitators in the purification
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section and in the stack gas, and by proper furnace operation. |
As an example of the latter, one report claims that furnace g
operation below 2000°F with low oxygen content will insure that
the decomposition products contain no more than 100 ppm of I
nitrogen oxides (8).
In ''wet gas" plants burning hydrogen sulfide, no attempt is made
to remove water vapor either from the combustion air or from the W
gas resulting from combustion of the hydrogen sulfide. Hence,
the amount of water vapor in the gas entering the converter is
more than enough to combine with all of the sulfur trioxide M
produced, and the entire output of the plant initially is in the
form of acid mist. Most of this mist is recovered as product I
acid with gas cooling equipment and high efficiency mist eliminators.
In oleum producing plants, a greater quantity of mist and a much
finer mist is produced. In these plants, oleum (i.e. sulfuric
acid containing excess SO- in solution) is produced in a pre-
liminary absorption step before the final absorption tower. Only
part of the S03 is absorbed and the gas leaving the oleum tower m
still contains SOs which is absorbed in the final absorption
tower. In spite of this preliminary absorption, the stack gas
always contains more mist than when the oleum tower is bypassed.
The quantity of mist appears to be proportional to the oleum/
acid production ratio and to the strength of the oleum produced (10). m
The mechanism is not clearly understood but it has been established
4-6
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1
that the mist is formed i
the oleum tower (7).
Table 4.2 gives a partial
mist emissions at plants
and 32 percent oleum (11
using a cascade impactor
Table 4.2 indicates that
n the final absorption tower, not in
e size distribution for sulfuric acid
producing strong acid, 20 percent oleum
»12)- These distributions were obtained
(See Section 6.2.1.2 for a description).
oleum production results in a finer
particle size distribution than acid production alone, and that
the distribution becomes
finer with increasing oleum concentration.
TABLE 4.2
PARTICLE SIZE DISTRIBUTIONS IN SELECTED SULFURIC ACID PLANT ABSORBER
1
1
1
1
1
t
1
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EFFLUENTS
Cumulative weight percent smaller than
Particle diameter Acid production 20% oleum 32% oleum
(microns)
0.2
0.4
0.6
0.8
1.0
1.5
2.0
only production production
0.4 3.6
2 16
1 4.8 30
7 8 42
12 11.6 53
21 48 86.5
40 84.5 97
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4.3 TYPICAL PLANT MIST EMISSIONS. "
Figure 4.1 shows the relationship between mist concentration
and pounds of mist per ton of acid produced. For a given mass
emission rate, acid mist concentration (in milligrams of H2SO.
per standard cubic foot) is a function of the volume of air I
fed to the process. The air volume in turn depends on the SCL _
concentration in the gas stream fed to the converters. The
curves can be used for any gas stream before or after mist elimina-
torss provided there is no air dilution.
Stack gas acid mist emissions range from 2 to 20 milligrams
per standard cubic foot (mg/scf) for a plant producing no fl
oleum to 5 to 50 mg/scf for an oleum plant (13). For a typical
sulfur-burning system feeding 8 percent S02 to the converter, £
these stack gas emissions are equivalent to 0.4 to 4 pounds per _
ton (Ib/ton) of 100 percent H^SO. produced for an acid plant *
and 1 to 10 Ib/ton of 100 percent HpSO* produced for an
oleum plant (refer to Figure 4.1). The lower mist limit in each
range requires some form of mist control device while the upper £
limit is typical of no control. _
Generally speaking, the dual absorption process does not reduce
the acid mist emission, and a dual absorption plant will require f
the same type of mist control device as a conventional plant
I
An additional mist eliminator is required on the primary absorption
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0.10
0.01
0.02 0.03 0.04 0.10 0.20 0.30 0.50
ACID MIST EMISSIONS, Ib H2S04/T OF 100 PERCENT H2S04 PRODUCED
Figure 4.1 Sulfuric acid plant concentrations of mist for mass stack
emissions per unit of production at inlet SO,, volume concentrations.
4-9
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tower (see Section 3,1.3) to protect the downstream heat exchangers I
from corrosion. This additional mist eliminator will often allow
. ...... .. ,. ._
6.2.1.3) to do an adequate final cleanup on the secondary
absorption tower, whereas a high efficiency mist eliminator
(Section 6.2.1.1) might otherwise have been required.
The use of a tail gas scrubbing system, for removal of S0?, g
such as sodium sulfite or ammonia scrubbing, does not reduce ^
the need for a mist eliminator since - as mentioned in Section
4.2 - acid mist is not readily absorbed.
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With the sodium sulfite system, it is best to locate the
mist eliminator upstream of the scrubber to minimize the
formation of sulfates which must be purged from the system. |
It may even be desirable to have two high-efficiency mist
eliminators: one installed in the absorber and the other *
"at grade", downstream of the absorber and upstream of the
scrubber. ("At grade" and "piggyback" installations are discussed
in Section 6.2.2). The scrubber exit gas does not normally f
require mist removal.
The ammonia solution scrubbing process requires a pH of
6.0 or greater for effective S(L control. However, as the pH £
of the liquor increases, ammonia losses increase and the ammonia
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combines with the SCL to form a highly visible plume of ammonium
sulfite, bisulfite, and sulfate. A high efficiency mist
eliminator must be installed downstream of the scrubber to
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- control these emissions. Further information on the use of mist
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eliminators in ammonia solution scrubbing systems can be found
in reference (15).
J The use of a molecular sieve requires removal of all H^SCL mist,
H2S04 vapor» and 9aseous S03 upstream of the sieve, as H2SO.
cannot be regenerated from the sieve. This, and the fact that
A the sieve has a higher capacity at lower temperatures, requires
that the absorber tail gas first be cooled by passage through a
J refrigeration system before passage through a high efficiency mist
eliminator. This cooling cannot be achieved by water Injection
since the sieve absorbs water vapor. It cannot be achieved by
H lowering the acid temperature to the absorber as this may
increase acid mist formation. A plant may choose to install
fl another mist eliminator.upstream of the cooler to reduce the
load on the second mist eliminator. This mist eliminator would
8 usually be installed in the absorber in new plants and "piggyback"
£ or "at grade" in existing plants. Due to the extensive preliminary
treatment, sieve stack gas should contain virtually no acid
|
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4.4 REFERENCES FOR SECTION 4.
1. Establishment of National Emission Standards for Stationary
Sources. Vol. IV. Sulfuric Acid Plants. Research *
Triangle Institute and PEDCO - Environmental Specialists, ft
Inc. Final Report. Contract CPA 70 - 164, Task Order No.
3, National Air Pollution Control Administration. Research p
Triangle Park, North Carolina. September 30, 1970. 43 p. ,_
2. Engineering Analysis of Emissions Control Technology for
Sulfuric Acid Manufacturing Processes. Chemical Construction |
Corporation. Final Report. Contract 22-69-81, National .
Air Pollution Control Administration, PHS, U. S. OHEW. *
New York, N.Y. Publication No. PB - 190-393. March 1970.
Vol. 1.
3. Cuffe, S. T. and C. M. Dean. Atmospheric Emissions from
Sulfuric Acid Manufacturing Processes. National Air Pollution
Control Administration. Durham, North Carolina. Publication
No. 999-AP-13. 1965. 127 p. 1
4. Gmitro, J. I. and T. Vermeulen. Vapor-Liquid Equilibria p
for Aqueous Sulfuric Acid. Lawrence Radiation Laboratory,
Berkeley, Calif. Contract No. W-7405-eng-48. June 24, 1963.
5. Reference 2, above, p. 111-11.
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6. Reference 3, above, p. 30.
m 7. Reference 2, above, p. I I 1-9.
8. Reference 2, above, p. 111-10.
9. Kurek, R.W. Special Report on EPA Guidelines for State
Emission Standards for Sulfuric Acid Plant Mist dated
m June 1974. E.I. du Pont de Nemours & Co., Inc., Industrial
Chemicals Department. Wilmington, Delaware. Prepared for
I U.S. Environmental Protection Agency , Office of Air
Quality Planning & Standards. October 4, 1974. Exhibit 15.
t
10. Reference 3, above, p. 32.
11. Brink, J.A., Jr. Cascade Impactor for Adiabatic fteasure-
H ments. Industrial & Engineering Chemistry. 50: 647,
April 1958.
12. Reference 9, above, Exhibit 12.
13, Reference 2, above, pp. 111-14, 15 and 22.
* 14. Reference 2, above, p. IV-15.
j[ 15. Brink, J.A., Jr. and C.N. Dougald. Particulate Removal
from Process Exhaust Gases. Proceedings of International
* Sulfite Conference, TAPPI and CPPA, Boston, Mass., October
30 - November 1, 1972. October 30, 1972. pp. 377-389.
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5. HEALTH ANN WELFARE EFFECTS OF ACIP MIST
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5.1 INTRODUCTION
I
In accordance with 40 CFR 60.22(b), promulgated on November 17, 1975
(40 FR 53340), this chapter presents a summary of the available
information on the potential health and welfare effects of sulfuric
£ acid mist and the rationale for the Administrator's determination
. that it is a health-related pollutant for purposes of section lll(d)
of the Clean Air Act.
m The Administrator first considers potential health and welfare
« effects of a designated pollutant in connection with the establishment
of standards of performance for new sources of that pollutant under
fl section lll(b) of the Act. Before such standards may be established,
the Administrator must find that the pollutant in question "may contribute
jjf significantly to air pollution which causes or contributes to the
endangerment of public health or welfare"(see section 111 (b)(l )(A)).
* Because this finding is, in effect, a prerequisite to the same
flj pollutant being identified as a desiqnated pollutant under section lll(d),
all designated pollutants wtll have been found to have potential adverse
| effects on public health, public welfare, or both.
W As discussed in section 1.1 above, Subpart B of Part 60 distinguishes >
between designated pollutants that may cause or contribute to endangerment
| of public health (referred to as "health-related pollutants") and those
for which adverse effects on public health have not been demonstrated
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("welfare-related pollutants"). In general, the sionificance £
of the distinction is that States have more flexibility in
establishing plans for the control of welfare-related pollutants w
than is provided for plans involving health-related pollutants.
In determining whether a designated pollutant is health-related
or welfare-related for purposes of section lll(d), the Administrator *
considers such factors as: (1) Knov/n and suspected effects of the
pollutant on nublic health and welfare; (2) potential ambient
concentrations of the pollutant; (3) generation of any secondary ||
pollutants for which the designated pollutant may be a precursor;
(4) any synergistic effect with other pollutants; and (5) potential <
effects from accumulation in the environment (e.g., soil, water
and food chains).
It should be noted that the Administrator's determination whether *
a designated pollutant is health-related or welfare-related for ff
purposes of section lll(d) does not affect the degree of control
represented by EPA's emission guidelines. For reasons discussed J[
in the preamble to Subpart B, EPA's emission guidelines (like ^
standards of performance for new sources under section lll(b) are *
based on the degree of control achievable with the best adequately
demonstrated control systems (considering costs), rather than on
direct protection of public health or welfare. This is true whether p
a particular designated pollutant has been found to be health-related
or welfare-related. Thus, the only consequence of that finding is
the degree of flexibility that will be available to the States in
establishing plans for control of the pollutant, as indicated above.
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5.2 HEALTH EFFECTS
I Short-term human exposure to sulfuric acid mist can cause temporary
and permanent damage to the lungs and bronchial tubes. Long-term
w exposure can cause skin damage, inflamation of the eyes, mouth and
m stomach, and permanent tooth damage, the latter being the most
serious (1 ,2).
* One hour exposure to a. concentration of 39,000 micrograms per cubic
meter (|ig/m3) of dry mist has produced persistent wheezing for up
to 4 days after exposure, an increase in airway flow resistance of
35.5 to 100 percent above normal, and long-lastinq bronchial
irritation (3,4). A deep breath at a concentration of 5000 yg/m3
will usually produce coughing. A concentration of 3000
A produces a noticeable odor, although concentrations below 600 yg/m3
usually cannot be detected(l). Occupational exposure to 1000 ya/m3
is unlikely to result in lung injury (2,5).
A Workers exposed to long-term concentrations of 3000 to 16000 yg/m
evidenced severe corrosion of dental enamel (2,6), but no damage
£ was noted after occupational exposure to 1000 yg/m3 £2»«5).
w A threshold limit value of 1000 yg/m3 for 8-hour workday exposure
has been set by the American Conference of Governmental Industrial
Hygienists, a level which should not cause irritation of respiratory
» passages and tooth injury (2). This same level was recommended by
the National Institute for Occupational Safety and Health for
occupational exposure to sulfuric acid mist as a time-weighted
average exposure for up to 10 hours per day, 40 hour work week (10).
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The effects of sulfuric acid mist on the lungs are aggravated by *
high humidity. In terms of sulfur equivalent, sulfuric acid is
considerably more of an irritant to humans than is sulfur dioxide (2,4,39).
Emissions of the acids and oxides of sulfur contribute to the total
sulfate concentration in the air. A method for measuring atmospheric V
H2S04 is not available. A comparison of measured atmospheric sulfate
with atmospheric metals and ammonium ions indicates that about half
of the atmospheric sulfate could be in the form of ^804 (38). In 1970, ^
the national average sulfate concentration at urban locations was 10.1
The nonurban average was 6.3 yg/m^ (37). Acid mist emissions add to the ft
total background, but reliable no-effect threshold levels have not been
established. ft
i"
A recent investigation in guinea pigs demonstrated that the total ft
respiratory deposition rate of inhaled particles and the pattern of
regional respiratory deposition of these particles was altered by ft
sulfuric acid mist inhalation. These effects were noted at acid mist ^
concentrations as low as 30 yg/nr*, particle size < 1 ym, for 1 hour.
This response was probably associated with increased pulmonary airflow- ft
resistance. Increased pulmonary airflow resistance is the principal
physiologic response in uncomplicated asthma. It has been hypothesized, p
therefore, that sulfuric acid mist inhalation may act to increase the . ^
incidence of asthma attacks through increased deposition of inhaled ' *
particles and/or a shift in the principal site of desposition of '
inhaled particles to airway reaions where asthma can be triggered (8).
Another recent animal study examined respiratory physiologic responses
to a variety of sul fates of similar aerosol size and mass concentrations (9). ft
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Sulfuric acid was found to be the greatest respiratory irritant. The
differences in the inhalation response of some of these sul fates was
small. Although these data do not constitute an adequate basis for a
determination of the comparative toxicity for specific inorganic sul fates,
J the data do suggest that the toxicological evaluation of parti cul ate
_ sulfur oxides must consider the cation as well as the an ion of the molecule,
* and that aerosol acidity is of great importance. These studies were
jtt based upon a sensitive respiratory physiologic response, primarily
increased pulmonary airflow resistance in guinea pigs. This response
g results from narrowing of the airways within the respiratory system.
A similar response has been observed in men exposed to sulfur dioxide
and H2S04 aerosol. This physiological response is a generally accepted,
sensitive measure of airway irritation.
^ Data on sulfuric acid mist toxicity in humans are limited, but there
* is some information on short-term exposures. One study reported
an increase in pulmonary flow resistance in humans of 18 percent at
H2S04 aerosol levels (particle size 1.8 iom, count median diameter)
p as low as 10 - 100 ug/m^ (40), although the experimental techniques
used in this study have been faulted by independent reviews.
In another study, respiratory rate has been reported to increase by
g about 30 percent, tidal volume to increase by about 28 percent, and
_. maximum inspiratory-expiratory flow rates to decrease by about 20
* percent at exposure levels of 350-500 ng/m3, concentrations below
subjectively detectable levels (5). These changes occurred during
the first three minutes of exposure, were maintained throughout the
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15 minute exposure period, and returned to pre-exposure levels within
15 minutes after the exposure ended. At higher levels, bronchospasm,
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increased upper respiratory tract secretions, increased flow I
resistance and increased respiratory rate have been consistently
found. It thus appears that as hUSO, concentration increases, Q
so do respiratory rate and pulmonary air flow resistance. All
of the subjects involved in the clinical studies were healthy, *
young adults who could easily compensate for the increased
resistance imposed upon their breathing. Effects on persons
with pre-existing disease have not been determined. |
Visibility decreases with increasing acid mist concentration and
increasing relative humidity, and is particularly important in
1
5.3 WELFARE EFFECTS
In addition to its effect on the bronchial tubes, another annoying |
property of sulfuric acid mist is the ability of the aerosol particles _
to reduce visibility. They do this by scattering and absorbing the
light passing from object to observer thus reducing the eye's ability A
to distinguish objects from their background, and by scattering light
from the sky and sun into the line of sight of an observer (12). |
The most serious sulfuric mist visibility reduction is caused by I
small particles from 0.2 to 2 microns in diameter. About 5 to 20
percent of the particles in urban air are sulfuric acid and other |
sulfates, and 80 weight percent or more of these sulfate particles ^
are smaller than 2 microns in diameter (13).
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aircraft operations. At a visual range of less than 5 miles,
operations are slowed at airports because of the need to maintain
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5-6
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larger distances between aircraft (13). Sulfuric acid mist can
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limit visibility to 5 miles at 98 percent relative humidity and
3
an acid mist concentration of 200 yg/m , at 90 percent relative
3
m humidity, and 60 yg/m and at 50 percent relative humidity and
* 200 yg/m3 (14).
*
In atmospheres containing sulfur dioxide 'and sulfuric acid, an
|B increase in humidity increases the ratio of sulfuric acid to sulfur
dioxide and this results in an increase of sulfuric acid concentration
in the size range characteristic of acid fogs (15).
| Sulfuric acid mist exerts a negative economic effect by damaging
materials and vegetation. Acid mist accelerates the corrosion of
* most metals, in particular iron, steel, and zinc. The damage increases
with increasing relative humidity and temperature. In addition,
atmospheric sulfuric acid can react with some suspended parti culates
£ to form sulfate salts which further accelerate the corrosion (16,17,
18,19,20).
Sulfuric acid will attack building materials and deface monuments.
I The attack is very severe if the building material contains calcium
JB carbonate, as do limestone, marble, roofing slate, and mortar. The
carbonate is converted to relatively soluble sulfates and then leached
V away by rainwater (21,22,23,24). Dolomites, which contain both calcium
and magnesium carbonates, are particularly vulnerable as magnesium
carbonate is readily soluble in an acid environment (21,25,26,27).
Granite, gneiss, and many sandstones, which do not contain carbonates,
and well-baked bricks, glazed bricks and glazed tile are less readily
attacked by sulfuric acid. Sulfuric acid can also disintegrate
stone structures by corroding iron tie rods (21,25).
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Textile fabrics made of cellulosic vegetable fibers, such as cotton,
linen, hemp, jute, rayons and synthetic nylons, are particularly
vulnerable to sulfuric acid. After exposure, these fibers lose
tensile strength (21,28). Animal fibers, such as wool and furs,
are more resistant to acid damage (21,27). Certain classes of fabric
dyes are attacked by sulfuric acid which is often absorbed or adsorbed
on atmospheric particles. The dye coloring is reduced or sometimes
destroyed entirely (21,29,30).
Sulfuric acid also causes discoloration, embrittlement, and a
decrease in folding resistance of both book and writing paper (25,31,32)
Sulfuric acid droplets have settled on dry leaves without causing
injury but when the leaf surface was wet, as may occur during
polluted fogs, a spotted injury has developed. The injury consists
of progressive cellular collapse from the exposed Surface through
the leaf leaving scorched areas (33,34,35). Injury may occur at
concentrations of 100 yg/m (36). Injury has occured on Swiss chard,
beets, alfalfa and spinach, the latter showing a more diffuse type of
injury (33).
5.4 RATIONALE
Based on the information in sections 5.2 and 5.3, it is clear that
sulfuric acid mist has significant health and welfare effects. To
be classified as a health related pollutant, the health effects
of acid mist must be present at reasonably expected ambient con-
centrations. Results of diffusion modeling presented 1n section
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8.1.1.2 indicate that expected maximum ground-level concentrations
m from uncontrolled acid and oleum plants are in the range of 0.6 to
12 vg/m3 on an annual average, 3 to 60 yg/m3 on a 24-hour average,
I 40 to 300 -pg/m3 on a one hour average, and 640 to 4700 yg/m3 on a
ten second average. (See Table 8.1 for complete results.)
I
The predicted short-term concentrations are in the range where
health effects have been observed in healthy, young subjects (see
section 5.2). It is a reasonable conclusion that potentially more
sensitive individuals (e.g., infants and others of great susceptability
such as persons whose health is already compromised by pre-existing
disease conditions and whose physiologic reserves are, therefore,
reduced) would exhibit adverse effects at even lower concentrations
I
than the clinical studies indicated, or more serious adverse effects
at the levels studied.
" Therefore, the Administrator concludes that sulfuric acid mist
contributes to endangerment of public health and may in fact cause
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that endangerment. Thus, sulfuric acid mist will be considered a
health-related pollutant for purposes of section lll(d) and Subpart B
of Part 60.
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5.5 REFERENCES FOR SECTION 5.
1. Air Quality Criteria for Sulfur Oxides. National Air *
Pollution Control Administration. Washington, D. C.
Publication No. AP - 50. April 1970.
2. Documentation of the Threshold Limit Values for Substances
in Workroom Air. Cincinnati, Ohio, American Conference of w
Governmental Industrial Hygienists, 1971. pp. 239 - 240.
I
3. Reference 1, above, p. 95.
4. Sim, V. M. and R. E. Pattle. Effect of Possible Smog *
Irritants on Human Subjects. Journal of the American I
Medical Association. 165; 1908 - 1913, December 14, 1957.
5. Amdur, M. 0., L. Silverman, and P. Drinker. Inhalation of H2S04 Mist
by Human Subjects. Archives of Industrial Hygiene and Occupational
Medicine. 6: 305, October 1952.
6. Malcolm. D. and E. Paul. British Journal of Industrial
Medicine. 1_8: 63, 1961.
7. Paule, A. Med. d. Lavoro 45; 59, 1954. Abstract in American
Industrial Hygiene Association Quarterly. 1_6_: 153, 1955 (abstract). ff
8. Fairchild, G. A., S. Stultz, and D. L. Coffin. Sulfuric Acid Effect on
Deoosition of Radioactive Aerosol in Respiratory Tract of Guinea Pigs.
J. Am. Ind. Hyg. Assoc. (In Press) 1975. m
9. Amdur, M. 0., J. Bayles, V. Aqro, M. Dubriel, and D. W. Underbill,
Respiratory Response of Guinea Pigs to Sulfuric Acid and Sulfate Salts, *
presented at Symposium: Sulfur Pollution and Research Approaches, Duke
University, May 27-29, 1975.
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10. Criteria for a Recommended Standard . . . Occupational Exposure to
M Sulfuric Acid, U. S. Department of Health, Education and Welfare,
m National Institute for Occupational Safety and Health, 1974.
11. Reference 1, above, p. 111.
' 12. Reference 1, above, p. 10.
m 13. Reference 1, above, p. 14.
| 14. Reference 1, above p. 13.
15. Reference 1, above, p. 15.
16. Reference 1, above, p. 51.
17. Serada, P. J. Atmospheric Factors Affecting the Corrosion
of Steel. Industrial and Engineering Chemistry. 52;
157-160, February 1960.
18. Greenblatt, J. H. and R. Pearlman. The Influence of
Atmospheric Contaminants on the Corrosion of Steel.
fl Chemistry in Canada. J£: 21 - 23, November 1962.
19. Vernon, W. H. J. The Corrosion of Metals, Lecture I.
I Journal of the Royal Society of the Arts. pp. 578 - 610,
m July 1, 1949.
20. Sanyal , B. and D. V. Bhardwar, The Corrosion of Metals
in Synthetic Atmospheres Containing Sulphur Dioxide.
m J. Sci. Ind. Res. (New Delhi). 18A; 69-74, February 1959.
. 21. Reference 1, above, p. 54.
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22, Yocum, J. E, The Deterioration of Materials in Polluted
Atmospheres. Journal of the Air Pollution Control Association,
8_ (4): 203 - 208, November 1958.
23. Benner, R. C. The Effect of Smoke on Stone, In: Papers
on the Effect of Smoke on Building Materials, University
of Pittsburgh, Mellon Institute cf Industrial Research
and School of Specific Industries, Bulletin 6, 1913.
24. Turner, T. H. Damage to Structures by Atmospheric
Pollution. Smokeless Air. 23: 22 - 26, Autumn 1952.
25. Parker, A. The Destructive Effects of Air Pollution on
Materials. In: Proceedings, 1955 Annual Conference,
National Smoke Abatement Society, London, 1955. pp. 3 - 15.
(Presented at Sixth Des Voeux Memorial Lecture).
26. Regan, C. J. A Chadwick Lecture on Air Pollution. Smokeless
Air. 88_: 67 - 76, 1953.
27. Petrie, T. C. Smoke and the Curtains. Smokeless
Air. J8_: 62 - 64, Summer 1948.
28. Waller, R. E. Acid Droplets in Urban Air. International
Journal of Air and Mater Pollution. 7_: 773 - 778, 1963.
29. Salvin, V. S. Effect of Air Pollutants on Dyed Fabrics.
Journal of the Air Pollution Control Association. 13;
416 - 422, September 1963.
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30. Salvin, V. S. Relation of Atmospheric Contaminants and
I Ozone to Lightfastness. American Dyestuff Reporter, 53;
33-41, January 6, 1964.
31. Reference 1, above, pp. 55.
* 32. Burdick, L. R. and 0. F. Barkley. Effect of Sulfur
A Compounds in the Air on Various Materials. U. S. Bureau
of Mines, Information Circular 7064, April 1939.
33. Reference 1, above, pp. 66 - 67.
34. Thomas, M. D., R. H. Hendricks, and G. R. Hill.
Some Impurities in the Air and Their Effects on Plants.
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In; Air Pollution, McCabe, L. C. (ed). New York, McGraw
Hill, 1952. pp. 41 - 47.
35. Middleton, J. T. , E. F. Darley, and R. F. Brewer.
Damage to Vegetation from Polluted Atmospheres. Journal
of the Air Pollution Control Association. 8; 9 - 15, 1958.
" 36. Reference 1, above, p. 68.
9 37. Summary Report on Suspended Sul fates and Sulfuric Acid
g Aerosols. U.S. Environmental Protection Agency, NERC,
* Research Triangle Park, North Carolina. EPA 650/3-74-000.
March 1974.
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38. Altshuller, A.P. Atmospheric Sulfur Dioxide and Sulfate: _
Distribution of Concentration at Urban and Nonurban Sites *
in United States. Environ. Sci. Techno!. 7: 709-712,
August 1973.
39. Amdur, M. 0. Toxicologic Appraisal of Particulate Matter,
Oxides of Sulfur, and Sulfuric Acid, Journal of the Air tt
Pollution Control Association. 19_: 642, September 1969.
40. Toyama, T. and K. Nakamura, Synergistic Response of Hydrogen Perioxide
Aerosols and S02 to Pulmonary Airway Resistance, Ind. Health 2:34-45, I
March 1964.
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5-14
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* 6. CONTROL TECHNIQUES FOR ACID MIST
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As mentioned in Section 1, the intent of the acid mist new source
performance standard and these guidelines for existing facilities
is to limit the ^$04 concentrations in the atmosphere resulting
from particulate acid mist, ^$04 vapor, and gaseous $03. Acid mist
is defined by EPA Method 8 which measures virtually all of the parti -
culate acid mist, but only a fraction of the 503 and ^$04 vapor.
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Effective control of acid mist as defined in the standard thus
requires more than control of particulate acid mist alone. As
mentioned in Section 4.2, it also requires control of ^$04 vapor
I and 503 through proper absorber operation. Consequently, Section 6.1
deals with absorber operating parameters that can affect the emission
| of H2S04 vapor and $03; and Section 6.2 deals with control techniques
for particulate acid mist.
Section 6.3 presents the results of EPA source tests to support the
standard of performance for new stationary sources (SPNSS) for acid
mist, EPA source tests to support this lll(d) document dealing with
retrofit plants, and miscellaneous company-run source tests. All of
the plants for which data are given were tested using EPA Method 8.
Section 6.4 presents EPA's emission guideline for existing sources
based on applying the best system of emission reductionconsidering
I costthat is available to existing plants. This guideline reflects
_ the application of the vertical panel or horizontal dual pad mist
* eliminators, as a minimum, to sulfur burning plants producing acid
or low strength oleum, and generally require the application of
vertical tube mist eliminators to other non-metallurgical sulfuric
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acid plants.
Section 6.5 deals with good plant operating practices that can
reduce the generation of particulate acid mist upstream of the
absorber.
6-2
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. 6.1 ABSORBER OPERATION. (1,2)
In an absorption process, a soluble component of a gas
w mixture is dissolved into a relatively nonvolatile liquid.
As the component is dissolved, it may react chemically with the
liquid, with evolution or absorption of heat. Furthermore, if
I the gas and liquid enter the absorber at different temperatures,
ordinary heat transfer will also occur from one stream to the
other.
| The final operation in a contact process sulfuric acid unit
is the absorption of gaseous SO, into a liquid stream of strong
I
HpSO.. ^e ^3 ^s absorbec* fforo a gas stream which also
contains nitrogen, oxygen, SO^, and particulate acid mist.
Absorption is carried out by passing the liquid H^SO^ and the
gas streams countercurrent to each other in a vertical packed
cylindrical tower known as an absorber. The liquid JLSO. drains
down the packing by gravity and the gas flows upward through the
tower, coming into intimate contact with the liquid on the surface
of the packing. The gaseous SO., diffuses out of the gas stream
into the liquid H2$0., reacts with the water in the acid stream
to form more H-SO^, and releases heat. Water make-up is necessary
to maintain constant acid concentration to the absorber. The
m operation of the absorber also involves the physical transfer of
heat from the gas to the liquid. In a typical absorber, acid
enters the tower at 180°F and cools the gas stream nearly to its
own inlet temperature, from about 450°F. The heat generated
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in the absorber leaves with the acid stream, thus requiring acid _
cooling external to the absorber.
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In a well-designed and operated absorber, sufficient contact
time is provided between the gas and the liquid streams so that
the gas leaving the absorber contains equilibrium vapor con-
centrations of the liquid and of the component being dissolved.
These equilibrium concentrations are characterized by the vapor
pressures of the liquid and the component at the liquid concentration |
and temperature entering the absorber. _
Table 4.1 (Section 4.2) gives H0SO. and SO- vapor pressures at
C. "t J
selected acid temperatures and concentrations. The table shows I
a distinct increase in H-SO. vapor pressure (acid volatility) with an M
increase in temperature, and emphasizes the importance of control!inn
the acid temperature to the absorber. As mentioned in Section 4.2, I
a good operating range is generally 170 - 185°F. The table
also shows a rapid increase in the vapor pressure of SO, as jj
the acid concentration exceeds 99 percent, and emphasizes the g
importance of controlling the acid strength so that the concentration
does not approach that of an oleum (greater than 100 percent acid). ft
Although not shown in the table, the vapor pressure of SO-
over oleum is even higher than its vapor pressure over 100 percent p
HpSO.. Since SO., absorption efficiency drops off below 98 percent
acid concentration, a good operating range is generally 98-99 *
percent.
6-4
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Proper absorber operation requires limiting the liquid temperature
and concentration rises across the tower, and this requires that
the liquid flow be maintained above a minimum level. Ideas on
V proper absorber acid flowrate have changed over the years, but
m it appears that the minimum flow required is about 2 gallons
per minute of acid per ton per day of 109 percent H^SO^
ft produced. Installation of a flowmeter indicating acid flowrate
to the absorber is good operating practice.
I
Proper absorber operation also requires even cross-sectional
distribution of the liquid from the top to the bottom of the
tower packing so that the gas receives maximum contact time
I on the surface of the packing and does not channel past the
m liquid. This even distribution requires proper arrangement of
the packing and proper liquid distribution at the top of the
packing. A detailed discussion of tower internals can be found in
references (3,4).
I
The condition of the distributor and the packing should be
checked during scheduled downtimes. The acid distribution can
be checked by running acid over the tower with no gas flow.
Also, if the packing is dirty, the tower should be washed out
M with clean eicid during the downtime.
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| 6-5
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6.2 FIBER MIST ELIMINATORS
Effective control of stack gas acid mist emissions can be1 achieved
by fiber mist eliminators and by electrostatic precipitators.
Although electrostatic precipitators are frequently used in
the purification section of spent acid plants, there is no
evidence that any have been installed to treat the stack gas of
sulfuric acid plants in the last two years (5,6). This disuse
is probably due primarily to their relatively large size and
resultant high installation cost compared to fiber mist eliminators
and to the high maintenance cost required to keep the units
operating within properrtolerances in the acid environment which
is corrosive to the mild steel equipment. Hence, although electro-
static precipitators do have the advantage of operating with a lower
pressure drop than fiber mist eliminators (normally less than 1 inch
of H20), attention in this document is concentrated on fiber mist
eliminators.
Fiber mist eliminators utilize the mechanisms of impaction and
interception to capture large to intermediate size acid mist
particles and of Brownian movement to effectively collect low
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 eliminator configurations are:
6-6
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(a) Vertical tubes
(b) Vertical panels
(c) Horizontal dual pads
6.2.1 Description
6.2.1.1 Vertical tubes (7,8,9,10)
| 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
(see Figure 6.1) consists of glass fibers packed between two
jj concentric 316 stainless steel screens. In an absorber installation,
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 separate tank design. Mist particles collected on the surface
of the 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.
g Tubular mist eliminators use inertia! impaction to collect larger
_ particles (normally greater than 3 microns) and use direct inter-
ception and Brownian movement to collect smaller particles. The
low superficial velocity of gas passing through the fiber bed--
20 to 40 feet per minuteprovides sufficient residence time for
I nearly all of the small particles with random Brownian movement
to contact the wet fibers, effecting removal from the gas stream.
I
The probability that such a particle could pass through the bed
6-7
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CLEAN GAS TO
ATMOSPHERE
MIST-LADE
GAS IN
(COURTESY OF MONSANTO
ENVIRO-CHEM SYSTEMS, INC.)
Figure 6.1. Vertical tube mist eliminator element.
6-8
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following the resultant greatly lengthened travel path is
very low.
« Design volumetric flow rate through an element is about 1000
standard cubic feet per minute (scfm) (11) and the number of
fl elements required for a given plant size can be determined
from the scfm 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 2 feet in diameter and
10 feet high (11).
| Pressure drop across the element varies from 5 to 15 inches of
HpO with a higher pressure drop required for a higher removal
efficiency on particles smaller than 3 microns. The manufacturer
I 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 smaller than 3 microns with 99.3 percent being
most common (11). 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 efficiency.
6.2.1.2 Vertical panels (7,8,9,10,12)
polygon framework closed at the bottom by a slightly conical
6-9
Panel mist eliminators use fiber panel elements mounted in a
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drain pan equipped with an acid seal pot to prevtnt gas bypassing. I
The polygon top is surmounted by a circular ring which is usually
installed in the absorption tower and welded to the inside of the m
absorption tower head. Each panel element consists of glass fibers
packed between two flat parallel 316 stainless steel screens (see
Figure 6.2). 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 I
flows horizontally through the bed, but at a much higher superficial
velocity (400 to 500 feet per minute) using the impaction mechanism
for collection of the mist particles. Gas leaving the bed flows
upward to the exit port while the collected liquid drains down-
ward across the pan and out through the seal pot back into the
tower or to a separate drain system.
I
The polygon may contain 10 to 48 vertical sides, each side normally
consisting of an 18 1/2" x 53" panel. A smaller 18 1/2" x 26" panel I
is available for small plants, e.g., 35 tons per day (11).
Pressure drop across the panel is usually about 8 inches of H^O.
The manufacturer of panel mist eliminators will usutlly guarantee |
an emission no higher than 2 milligrams per cubic foot (equivalent
to 0.375 pounds per ton of 100 percent HgSO. produced -- see I
Figure 4.1) for a sulfur-burning plant producing oleum up to 20
percent in strength and/or acid (9,11). For an inlet loading of 20
milligrams per cubic foot which is typical of a plant not producing I
oleum (refer to Section 4.3), 2 milligrams per cubic foot outlet
loading corresponds to a 90 percent removal efficiency. I
6-10
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CLEAN GAS TO
ATMOSPHERE
MIST-LADEN
GAS IN
(COURTESY OF MONSANTO
ENVIRO-CHEM SYSTEMS, INC.)
Figure 6.2. Vertical panel mist eliminator.
6-11
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Before guaranteeing that the above emission level will be met,
it is necessary to obtain an acid mist particle size distribution
curve on the absorber tail gas. This is done by sampling with
a cascade impactor. Use of one such impactor available on the
market is described in Industrial and Engineering Chemistry (13).
The impactor separates the mist particles into several size
fractions by passage in series through several impaction jets
designed to collect progressively smaller particles. From these
fractions, a particle size distribution curve can be constructed.
The collection efficiency of the panel mist eliminator falls off
below 1 micron. From the particle size distribution curve, the
mist eliminator removal efficiency curve, and the acid mist loading,
the expected acid mist emission from the panel mist eliminator can
be calculated. Sampling with an impactor and calculating the particle
size distributions can be time-consuming operations. However, the
problem of guaranteeing an emission level is of more concern to a
vendor than it is to EPA or to a State agency.
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.
(See Table 4.2 for oleum plant particle size distributions.)
Removal efficiency decreases as the gas velocity through the vertical
panel mist eliminator drops below the lower design limit. This limit
varies from unit to unit, the design limit being dependent upon many
factors including local ordinances. As the velocity is lowered below
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this limit, acid mist emissions and the stack opacity increase. Hence,
to properly enforce a standard, a State agency should measure the
stack gas acid mist loading with the unit running at or near rated
capacity, and not during unit startup or shutdown.
Vertical panel mist eliminators normally operate with a liquid
level in the acid seal pot below the conical drain pan. Although
I the velocity through the panels could be increased at lower
throughputs by raising the liquid level to cover the lower part
of each panel, this would not be good practice since it would cause
re-entrainment of spray by the gas passing over the liquid level in
the basket.
Vertical panel mist eliminators also have an upper velocity design
limit above which acid spray re-entrains from the inner surface
of the polygon. This spray may or may not reach the atmosphere,
| depending upon the configuration of the ductwork. If it does, it
normally will not cause an increase in stack opacity and will fall
out on the plant equipment. Hence, operating above the upper limit
should be of more concern to the plant operator than to EPA or a
State agency. Further information on removal efficiency is contained
in references (10,12).
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6.2.1.3 Horizontal dual pads (7,14)
Two circular fluorocarbon fiber beds held by stainless steel
screens are oriented horizontally in a vertical cylindrical vessel
I one above the other, so that the coarse fraction of the acid mist
is removed by the first pad (bottom contactorsee Figure 6.3) and
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\ [CLEAN GAS
1 TO ATMOSPHERE
DRAIN:
TOP CDWTACTOR.
f BOTTOM CONTACTOR-
i
DRAIN
MIST-LADEN
GAS IN
(COURTESY OF YORK SEPARATORS, INC.)
Figure 6.3. Horizontal dual pad mist eliminator.
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_ the fine fraction by the other (top contactor). The bottom
contactor consists of two plane segmented sections installed at an angle
I to the horizontal to facilitate drainage and give additional area
for gas contact. The assembly may be located adjacent toor
0 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
I drains downward through the pads countercurrent to the gas flow
j 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 9 inches of
HpO. The superficial velocity through the unit is 9 to 10
feet per second. Hence, the diameter of the cylindrical shell
and the pads is determined from the volume of gas handled. In
one application, a 9-foot diameter unit was installed to handle
34,000 actual cubic feet per minute (acfm) at 160°F, and in
another application an 11-foot diameter unit was installed to
I handle 51,000 acfm at 175°F. Height requirements for the unit
depend upon whether it is located adjacent to or positioned on the
I absorber, but are roughly 1 1/2 to 2 times the diameter nf the unit.
I As with the panel mist eliminator, the dual pad unit will reduce
_ acid mist emissions to 2 milligrams per cubic foot (0.375 pounds
per ton of 100 percent HpSO^) or less, provided the plant burns
sulfur and does not produce oleum stronner than 20 percent 0A)
I 6-15
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and provided that a particle size distribution curve shows
that this level can be met. (See Section 6.2.1.2 for a dis-
cussion of how a particle size distribution curve is obtained).
The removal efficiency of the horizontal dual pad mist eliminator
decreases below the lower velocity design limit as it does for
the vertical panel mist eliminator. When properly designed and
installed, no increase in visible emissions should result from
reducing the superficial velocity to 5 feet per second. However,
just as with the vertical panel mist eliminator, it would be
desirable for a State agency to measure the acid mist loading
with the unit running near rated capacity, and not during unit
startup or shutdown.
If a plant plans to run considerably below capacity for an extended
period of time, it is possible to blank off some of the segments
of the bottom contactor to maintain the desired removal efficiency.
Above a superficial velocity of 12 feet per second, the top
contactor will not drain properly and the result is the same as
for the vertical panel mist eliminator. Further information on
rental efficiency is contained in reference (14).
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6.2.2 Installation and Maintenance
| 6.2.2.1 Vertical tubes (11)
I Figure 6.4 shows the installation of vertical tube elements in
a separate tank ("at grade") which is the usual case for
existing plants. The elements are bolted into a tube sheet
supported by I-beam stiffeners and provided with a liquid seal
to prevent gas bypassing. The tube sheet is one-inch carbon
steel, and the tank is carbon steel above the tube sheet and
carbon steel lined with acid-proof brick below the tube sheet.
| The vessel must have both sufficient space above the tube
m sheet and a large enough manway to allow positioning the ele'ments.
* Representative tank sizes are 10'9" diameter x 23'5" for a 250
ton per day plant and 21'6" diameter x 25'3" for a 1000 ton per
day plant.
I
The weight of the internals is determined by calculating the number
of elements required and using a factor of 850-900 pounds for the
unit weight of one element and its associated tube sheet when wetted
with acid. The ducts leading to and from the tank are carbon steel,
m the inlet duct being sized for an average velocity of 1500-2000 fpm
and the stack for 2000-4000 fpm. A new sump and pump is usually
required to transport the collected acid to a storage tank.
If space is available, the elements can be installed in the final
absorber. It is more common to install them in a "piggyback" unit
mounted above the absorber on separate footings (10). These
arrangements eliminate the sump and pump and minimize the ductwork.
6-17
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ACCESS
MANHOLE
MISTY
GAS IN
CLEAN GAS OUT
TUBE PLATE
CYLINDRICAL
SCREENS
, FIBER! ELEMENTS
RECOVERED
LIQUID (MIST)
SEAL PIPES
LIQUID SEAL
(COURTESY OF MONSANTO ENVIRO-CHEM SYSTEMS, INC.) Lj QUID
Figure 6.4. Vertical tube mist eliminator
installation.
6-18
-------
According to the manufacturer, tubular mist eliminators have
been operating maintenance-free.
Acid plants' are usually designed with 20-30 inches of H20 unused
pressure drop out of a total of about 140 inches of HgO plant
pressure drop. However, as the unit becomes dirty this safety
I factor is used up. In order to insure no drop in production
in a controlled plant, an additional fan to pull 25 inches of
I hLO should be installed in series with the existing blower,
M unless a sufficient design allowance has been included in the
total plant drop.
I
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6.2.2.2 Vertical panels (11)
Figure 6.5 shows the installation of a vertical panel polygon
I in the top of the absorber, which is the usual case for existing
plants. The polygon is constructed of 316 stainless steel and
the top of the carbon steel tower is lined with acid-proof brick
I up to the dished head. About eight feet of vessel height are
required to install the polygon. It is normally installed by
| putting a new top on the existing absorber or by cutting slits
« in the top of the existing absorber, lowering the panels through
the slits, and assembling the cone inside the vessel. If the
fl vertical panel unit was installed in a separate vessel, representative
tank sizes would be 8'0" diameter x 10'7" for a 250 ton per day
| plant and 19' 0" diameter x 13' 7" for a 1000 ton per day plant.
Comments on stack velocity and on pressure drop in Section 6.2.2.1
also apply to the vertical panel installation.
6-19
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CLEAN GASES OUT
ACCESS MANHOLE
DISTRIBUTOR PAN OF TOWER
FIELD WELD
STRUCTURAL
SUPPORT
CYLINDER
ELEMENTS
IN POLYGON
FRAME
RECOVERED
LIQUID
(COURTESY OF MONSANTO ENVIRO-CHEM SYSTEMS, INC.)
Figure 6.5. Vertical panel mist eliminator
installation.
6-20
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Vertical panel mist eliminators are subject to corrosion of the
wires holding the fibers in place in the panel by the high
velocity acid flow. The panels have to be rescreened every
six to seven years at a cost of 15-20 percent of the original
equipment price of the unit. The corrosion is particularly
I severe on the bottom of the inside of the polygon. &-
I
6.2.2.3 Horizontal dual pads
I Figure 6.6 shows a specific retrofit installation of a horizontal
dual pad unit handling 34,000 acfm in the^tail gas of an existing
| plant producing about 400 tons per day of 100 percent H,,S04. In
_ this case (the 9-foot diameter unit discussed in Section 6.2.1.3)
the unit is offset from the stack on the final absorber to prevent
sulfate fouling of the pads by corrosion products formed in the
stack (primarily iron sulfate). The unit is positioned on top of
| the adjacent drying tower (no process connection) and acid collected
_ on the pad is drained through two one-inch drains to the drying tower
The internal structural supports and ductwork for this installation
I are 304 low carbon stainless steel, as are the screens for the fiber
M beds. Stack and duct sizes for this installation are shown in
Figure 6.6.
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_ As mentioned above, dual pad mist eliminators are vulnerable to
sulfate fouling. This fouling can be particularly severe when
the plant is shutdown. When the process gas flow is turned off,
sulfate which has been held up in the stack can drain onto the
b-zl
The comment on pressure drop in Section 6.2.2.1 also generally applies
to a dual pad installation.
-------
60 INCHES
54
INCHES
STACK
DRAIN
BLANK
TOP CONTACTOR-
DUAL PAD-
UNIT
SCRUBBER
DRAIN
«9 FEET-
iTTOSTcONtACTOR
£ 1
J
54 \
'"CHES BUNK^
\
PLATFORM
_£,'
I ri
SCRUBBER
DRAIN
ELEVATION 6ft
FEET
ABSORBING TOWER
48 (NCI
DRYING TOWER
*ES
Figure 6.6. Retrofit horizontal dual pad mist eliminator installation.
6-22
-------
* pads. Dual pad mist eliminators are also subject to corrosion
of the wires holding the fibers in place.
6.2.3 Design, Installation and Start-up Times
_ Table 6.1 presents manufacturers' May 1974 estimates of the
normal length of time required to design and install fiber mist
eliminators and bring the retrofitted unit back to normal opera-
tion (15,16). It shows that the total lead time required can
I vary from seven or eight months up to a year and a half.
I The two items in Table 6.1 with the longest and most widely
varying lead times are "Initial Design and Approval" and
| "Fabrication". Initial Design and Approval includes (15):
_ 1) Engineering design of the overall layout including
general specifications and drawings of the mist eliminator,
tank and ductwork.
2) Project fund approval.
J 3) Control agency approval.
4) Order placement.
The above are all items over which the mist eliminator manufacturer
has little control.
_ The lead time for fabricating vertical tube and vertical panel
mist eliminators depends greatly upon the size of the order,
the manufacturer's shop backlog, and the availability of steel for
tank fabrication. The fabrication lead times shown in Table 6.1
I are for tank fabrication; mist eliminator fabrication lead times
I 6-23
I
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TABLE 6.1
MIST ELIMINATOR LEAD
(weeks)
Initial Design and Approval
Preparation of Drawings
Plant Approval
Fabrication
Shipment
Installation
Startup
Totals
TIMES
Vertical
Vertical
8 -
4 -
13 -
1 -
32 -
Tube and
Panel
26
8
3
35
2
3
1
78
Horizontal
Dual Pad
4-20
2-6
3
30 - 45
2
1
1
43 - 78
6-24
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I
vary from 3-6 months (13-26 weeks). Tank fabrication lead times
I were no longer than 5 months (22 weeks) from 1960 to 1972, but
increased dramatically from 1972 to 1974. Although 316 staln-
less steel is the normal material of contruction for vertical
tube and vertical panel mist eliminators, a plant may occasion-
ally require alloy 20 construction. In this case, the long
J delivery times on alloy 20 can make the mist eliminator fabrica-
tion lead time as long as a year (15). The long lead time for
fabricating horizontal dual pad mist eliminators is due to long
delivery times on steel. In 1973, fabrication took but 16-20
weeks (.16).
The installation lead times in Table 6.1 assume that the mist
eliminator can be tied-in as soon as it is delivered to the plant.
To minimize production downtime, this delivery is generally
I scheduled to coincide with a planned unit shutdown (16).
I Startup after a planned shutdown or after a shutdown specifically
for tie-in usually takes a week or less. This does not include
| the time to test for compliance which usually adds another week
_ to the total lead time. It is desirable to test for compliance
with the acid unit running at capacity.
I
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6-25
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I
6.2.4 Costs _
Table 6.2 summarizes the estimated costs for control of acid
mist from existing acid plants. For each control unit and each I
type of installation, the installed capital cost, the net annual
cost, and the net annual cost per ton of production (unit cost)
are qiven for several sizes of acid plants as of November 1974.
Depending on the physical considerations of a particular plant,
the control unit may be installed on top of the existing absorber
or on the ground in an available space and connected by ducts to I
the absorber and the stack. The former is termed the "piggyback"
installation, and the latter the "at grade" installation. I
For cost estimation purposes, the piggyback horizontal dual pad J
installation is assumed to consist of dual pads pre-mounted inside
a stainless steel vessel, which is installed on top of the
existing absorber. The other two mist eliminator piggyback
installations involve an extension of the acid-resistant brick-
lined carbon steel absorber with the appropriate mist eliminator
mounted inside. It is assumed that the piggyback installations
require no additional supporting structure and that no additional
fan capacity is added in order to arrive at a least-cost case.
The at grade installation houses the same type of control
equipment mounted on a new foundation on the ground near the
absorber. The cost of these installations is based on a new
foundation, an acid return pump, additional ducting, and 25 inches
of H20 additional fan capacity.
6-26
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6-27
-------
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The installed cost range between these two types of installations
should be representative of the costs for most acid plants.
However, there may be certain plants which could experience
I costs outside the range due to the variability in factors
such as: additional structural support.requirements, fan
requirements, congestion at the plant site with difficulties
m in ducting, and design allowances built into the existing
absorber for future installation of the control elements.
The installed cost for the horizontal dual pad installation
shown in Figure 6.6 was $57,000 in early 1970. Multiplying
by a cost index ratio of 1.5 gives an installed cost of $85,000
for November 1974. The unit handles 34,000 acfm and by linear
interpolation of Table 6.2 would be expected to cost about $46,000
| (in November 1974 dollars). The additional cost is at least
_ partially due to the ductwork to and from the unit, the inclusion
I
of three access platforms, added structural support, and labor
costs above the national averige.
I The installed capital costs (Table 6.2) for the vertical tube
unit are based on element capital costs for 99.3 percent removal
efficiency on particles 3 microns and smaller in diameter at 12
inches of H20 pressure drop. Figure 6.7 shows the relative
element capital costs for designs at other combinations of removal
efficiency and pressure drop.
I
- 6-2P
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1.0
0.9
0.8
0.7
cc
o
§0.6
s
o
<0.5
El
o
0.4
0.3
0.2
0.1
1
68 10 12 14
ELEMENT PRESSURE DROP, inches of water
(COURTESY OF MONSANTO
ENVIRO-CHEM SYSTEMS, INC.)
Figure 6.7. Relative changes in capital costs for vertical tube
mist eliminator elements at different removal effi-
ciencies and pressure drops.
6-30
-------
The gross annual cost consists of: capital related charges such
as depreciation, interest on borrowed capital, property tax,
(insurance, and overhead which add up to 26 percent of the installed
I capital cost; operating cost which is totally made up of power cost
for the pressure' drop caused by the control unit; and maintenance
cost which is based on information supplied by the equipment
m manufacturers. In order to determine the net annual cost, the
credits for recovered acid are subtracted from the gross annual
I
I
cost.
The wide range of reported emission rates for acid mist results
in a range of cost credits and a range of net annual costs.
£ The higher the pre-control emission rate, the hiaher the credit
for recovered product would be. The value of the acid recovered
is based on the production cost (see Table 6.4) rather than
on the market sales price. The final figures shown in Table
6.2 are the net annual cost. per ton of production. An operating
I ratio (production/capacity) of 90 percent is assumed for this
calculation.
I
Table 6.3 shows the approximate installed capital cost_for
control of acid mist in new acid plants as of November 1^74.
They were obtained by multiplying the costs in Table 15,
reference (7), by a cost index ratio of 1.58. The cost for a
new plant should always be less than the cost for retrofit since
the control unit can be designed in from the beginning (usually
as an expanded section at the top of the absorber). The fact
6-31
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TABLE 6.3
INSTALLED CAPITAL COSTS FOR ACID MIST CONTROL IN NEW PLANTS
Horizontal Dual Pad ($)
Vertical Tube ($)
Vertical Panel ($)
Size (TPD of 100% H2S04)
50
15,800
87,400
22,000
250
31 ,600
111,000
36,400
750
44,200
166,000
87,000
1500
60,000 '
269,000
151,000
that this does not appear to be the case for the 50 TPD vertical
tube piggyback installation is probably due to differences in cost
estimating procedures.
To facilitate comparison of the above acid mist control costs to
the total costs of installing and operating a sulfuric acid unit,
Table 6.4 shows estimated capital cost and production cost for a
new sulfur burning dual absorption unit as of November 1974.
Accurate cost figures are not available to allow comparison with
an existing unit. Costs are given for a dual absorption unit
since all new units will have to be dual absorption or employ tail
gas scrubbing systems to control S02 emissions to the level re-
quired in the EPA standard of performance for new sulfuric acid
plants. Table 6.4 is based on information (17) used to support
this new source standard. This information source cites capital
6-32
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TABLE 6.4
ESTIMATED COSTS FOR NEW SULFUR BURNING DUAL ABSORPTION SULFURIC ACID UNIT
Capital Cost ($)
Production Cost ($/Ton)
Size
50
903,000
30.68
(TPD of 100% H2S04)
250
2,650,000
23.34
750
5,539,000
20.18
1500
8,810,000
18.7
and production costs for a 1000 TPD acid plant. The capital
costs for the sizes given in the table are extrapolated using an
exponent of 0.67 from the Chemical Engineering cost file (18).
The production costs for the sizes given were determined from
utility, raw material and labor requirements and capital charges
for the same 1000 TPD plant cited above (17).
6-33
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6.3 EMISSION REDUCTION
6.3.1 SPNSS Source Testing
Table 6.5 presents the results of testing performed during 1971 by EPA
in developing the acid mist standard of performance for new stationary
sources (SPNSS). All three plants tested employed vertical tube
mist eliminators. All runs were made using EPA Method 8. All of
the test results are equal to or less than the acid mist standard
of performance for new sulfuric acid plants of 0.15 pounds per
ton of 100 percent H^SO* produced.
Unit A had a capacity of 700 tons per day (TPD) of TOO percent
fLSO. and burned only dark sulfur at the time of the test. It
produced 35 percent oleum on February 17, and 30 percent oleum on
February 18, but the oleum/acid oroduction ratios are unknown.
The unit was less than a vear old at the time of this test, the
mist eliminator being installed when the unit was built.
Unit B had a capacity of 750 TPD at the time of the test. On
March 27, it burned 250 TPD of spent acid (on a 100 percent H^O^
basis) and the balance was elemental sulfur. On that same dav, it nro-
duced 70 TPD of 93 percent acid, 460 TPD of 98 percent acid, and
200 TPD of 20 percent oleum (all on a 100 percent H2S04 basis).
Unit B is an older unit whose mist eliminator had been retrofitted.
Subsequent to this retrofit but prior to the EPA tests, a sodium
sulfite scrubbing tower for SCL control was installed downstream
of the mist eliminator. The tests were conducted downstream of
this scrubbing tower.
6-34
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6-35
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I
Unit C had a capacity of 450 TPD at the time of the test. Durina
the period August 31 - September 2, 1t burned spent acid and sulfur
and produced 20 percent oleum and 99 percent acid. The spent
acid/sulfur feedstock ratios and the acid/oleum production ratios
are unknown. However, average consumption for the months of
August and September combined are 266 TPD of spent acid and 204
TPD of sulfur. For the same two-month period, average production
was 242 TPD of acid and 210 TPD of oleum (all grades). All of the
above rates are on a 100 percent H^SO. basis. The total production
and consumption rates of 452 and 470 TPD, respectively, indicate a
unit conversion efficiency of about 96 percent. Unit C is an
older unit with a very unusual design. The converter exit gas
is split in half and fed to two equivalently-sized final absorbers.
Each absorber is followed by a booster blower, a mist eliminator,
and a stack. Both mist eliminators are retrofits. EPA tested one
stack. The equivalent capacity for this one stack is thus 2?5TPD.
The production rates shown in Table 6.5 (185, 175, 193 TPD) also apolv
only to this stack and are one-half of the total unit production rates.
6.3.2 Section lll(d) Source Testing
Table 6.6 presents the results of additional testing performed under
EPA supervision by a contractor. The purpose of these two tests
was to define the performance of the vertical panel and the horizontal
dual pad mist eliminators covered in this document, and to compare
6-36
-------
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EPA Method 8 with the Monsanto Method by simultaneous runs with
both methods^ . The latter is important because considerable
data based on the Monsanto Method exists.
I Unit D had a capacity of 1100 TPD, burned moderately dark sulfur
and produced 93 percent acid (no oleum) at the time of the test.
I The unit was then only about a year old, the vertical panel
_ mist eliminator being Installed when the unit was built. It
would have been desirable to test an older unit that had been
recently retrofitted with a vertical panel mist eliminator, but
no assistance was obtained from the vendor in locating a suitable
I unit, and the unit tested was the most suitable one that could be
found within the time available. The vertical panel mist elimina-
tor tested was of the double polygon design. Further information
on double polygons is contained in Section 6.2.1.2 and in reference
(10). Gas leaving the absorber flowed through the two polygons
| in parallel, not in series, so that the performance of this desicm
« at Unit D should be identical to that which would have been ob-
tained had the unit been equipped with a single polygon of equal
cross-sectional bed area.
Unit E had a capacity of 350 TPD and also burned moderately dark
sulfur and produced 93 percent acid (no oleum) at the time of the test.
I
I (a) Mention of 9 trademarked product or company name is not
intended to constitute endorsement by the Environmental
Protection Agency.
6-39
I
-------
It is an older unit that had been retrofitted with a horizontal
dual pad mist eliminator in early 1970.
Testing of Units D and E with the EPA and Monsanto trains was
done simultaneously so that, for instance, Unit P, Pun Number 1,
EPA Method was run at the same time as Unit D, Run Number 1,
Monsanto Method. At Unit D, only one sampling port was avail-
able and consequently sampling was done across one diameter with
the probes of the two trains adjacent. A velocity check across
the diameter perpendicular to the test diameter indicated a
similar flow pattern to that of the test diameter. At Unit E,
sampling was conducted through two ports on perpendicular diameters.
The probe of one train traversed the horizontal diameter for the
first half of a run and the vertical diameter for the second half,
while the probe of the other train traversed the vertical for the
first half and the horizontal for the second half. The oas flows
as measured are not identical for the individual EPA and Monsanto
runs (Run 1 vs. Run 1) because separate velocity traverses were
made for each train.
The EPA catch consisted of the probe, first impinger and filter.
The Monsanto method used was as specified in references O0*^)
was not the modified Monsanto method. The Monsanto catch included
6-40
-------
the probe, cyclone, and filter. Inclusion of the probe catch is
particularly important as it represented a significant fraction of the
total catch for all the runs. Further process, sampling and
J analytical information on these two tests is contained in the source
test reports (21, 22).
The EPA Method results averaged higher than the Monsanto Method
results for Unit D, while for Unit E, the reverse was true.
M However, linear regression analysis of the data in Table 6.6,
shows that the EPA and Monsanto methods are related by the equation:
| Conc-Monsanto = °'63 Conc'EPA + °'19
The coefficient of correlation is 0.97. Thus, although the two
methods do not give identical results, the results of one method
can be predicted from the results of the other method with a
reasonable degree of accuracy for these particular sulfur burning plants
M controlled with pads or panels. It should be emphasized that these
results were obtained from only two tests and that they do not mean
that the two test methods used are necessarily equivalent for all
« acid plants.
It is important that the performance of both mist eliminators
using both test methods was well below the 2.0 milligrams per cubic
foot, actual or standard, that the manufacturers of these mist
eliminators will guarantee. The results do not mean that the
horizontal dual pad mist eliminator's performance is superior to
the vertical panel's performance since the two mist eliminators
6-41
I
I
-------
were not tested under identical conditions. The results also do
not mean that a sulfur-burning acid unit with a horizontal dual
pad mist eliminator can consistently meet the new source performance
standard of 0.15 pound per ton of 100 percent H,,S04 as it did in
this test.
6.3.3 Miscellaneous Source Test Data
Table 6.7 presents the results of EPA Method 8 testing performed by
companies and submitted to EPA and State air pollution control
agencies. The data in Table 6.7 for plants A, I and J were volun-
tarily submitted in 1972 (plant A) and in October 1974 (plants I
& J) to the EPA Research Triangle Park, N.C. offices by the
respective companies. A considerable effort was made to obtain
other EPA Method 8 test data. In October 1974, six EPA regional
offices and 10 State agencies were contacted, and data were ob-
tained for only three plants (F, G and H). There is no trade
association specific to the sulfuric acid industry, and the Manu-
facturing Chemists Association had no data.
Unit A is the same Unit A that EPA tested (Section 6.3.1). It had
a capacity of 700 TPD, burned elemental sulfur, and produced add
and oleum at the time of the company-run test. Oleum/acid produc-
tion ratios and known oleum strengths are given in Table 6.7, The
unit produced 30 percent oleum on December 9, 1971. Runs were made
6-42
-------
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using other test methods besides EPA Method 8 during the company-
run test at Unit A, but no simultaneous runs involving EPA
Method 8 and another test method were made.
Unit F had a capacity of 1525 TPD, burned elemental sulfur and
did not produce oleum at the time of the test. Unit F was new at
the time of the test, the mist eliminators having been installed
| when the unit was built.
Unit G had a capacity of 240 TPD, burned only hydrogen sulfide and
did not produce oleum at the time of the test. This unit was
| also new at the time of testing, the mist eliminator having been
M installed when the unit was built.
Units H, I, and J all produced oleum during testing. Unit H
burned sulfur; Unit I burned sulfur and spent acid; and unit J
burned sulfur and waste acid containing ammonium sulfate. Bound
sulfur/total sulfur feedstock ratios, operating ratios (production/
capacity), oleum strengths and oleum/total acid production ratios
are given in Table 6.7. For unit H, the mist eliminator was a
retrofit installed upstream of an Sf^ tail gas scrubber. For unit I,
m the horizontal dual pad mist eliminator was replaced in 1973 with
a vertical tube mist eliminator.
It is important that all of the data in Table 6.7 are below 0.5
pounds of mist per ton of 100 percent H,,SO. produced.
I
_ 6-45
I
-------
Table 6.8 gives particle size distributions in the gas streams
entering and leaving a horizontal dual pad mist eliminator at one
specific spent acid plant producing strongs-oleum (23). Each set
of data is an average of five individual runs taken over the period
February 10-25, 1972. The plant burned spent acid and sulfur
during one of the five inlet sampling runs and three of the five
exit sampling runs, and burned only elemental sulfur for the rest.
It produced oleum during all the runs, in strengths varying from
23.4 to 27.5 percent free SO,. Production of oleum approached 60
percent of total acid production.
The particle size distribution in Table 6.8 was determined using
a cascade impactor. Further information on the cascade impactor
is contained in Section 6.2.1.2 and reference (13). The average
acid mist inlet loading for the five inlet runs was 3.81 mg/scf,
and the average exit loading was 2.11 mg/scf corresponding to
0.37 Ib/ton. This data was obtained using the Monsanto test method.
Table 5.8 shows that a significant percentage of the acid mist
in the absorber effluent is submicron. The above inlet and exit
loadings shows that impaction devices, such as the horizontal dual
pad mist eliminator, do not effectively remove such mist.
6.3.4 Extent of Acid Mist Control
Accurate information on the number of units with controlled and
uncontrolled stack gas is most difficult to obtain. The best
6-46
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at
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information available to EPA is late 1972 data which show that about 40
percent of the sulfuric acid units in the United States employ vertical
tube and vertical panel mist eliminators for stack gas mist
control, 10 percent employ electrostatic precipitators, and
45 percent employ horizontal dual pad mist eliminators. Of the
latter, not all employ the scrubbing action described in Section
6.2.1.3, not all operate with a pressure drop as high as 9 inches
of HpO, and not all are necessarily able to reduce emissions to
2.0 milligrams per cubic foot or less. It is known that at least
15 percent of the total sulfuric acid units in the United States
employ horizontal dual pad mist eliminators which do meet these
requirements. If the above percentages are accurate, they mean
that about 5 percent of the sulfuric acid units in the United
States do not have stack gas acid mist controls.
In 1971 about 70 non-metallurgical contact-process sulfuric acid
plants were not covered by enforceable state regulations. Table 6.9
gives state regulations for acid mist emissions from existing
plants as of July 1972 (24). Eighteen of the 41 states with
sulfuric acid plants had enforceable regulations for existing
plants. In addition, East Chicago, Indiana had a regulation of
0.5 Ib mist/ton acid; and Wayne County, Michigan a regulation of
0.7 Ib mist/ton acid. Eight states had a regulation of 0.15 Ib
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mist/ton acid for new plants. All new plants must now meet the
EPA new source performance standard of 0.15 Ib mist/ton acid;
states may adopt or enforce standards that are at least as strin-
gent as the EPA standard.
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TABLE 6.9
STATE REGULATIONS FOR ACID MIST EMISSIONS FROM EXISTING
SULFURIC ACID PLANTS (24)
Lb H2S04 Mist Per
States Ton of 100% H2S04 Produced
Georgia, Illinois,
Wyoming 0.15
| New Hampshire 0.18
Alabama, Iowa, Kansas,
Mississippi, Missouri,
North Carolina, Ohio, >- 0.5
Pennsylvania, South
ft Carolina, Tennessee
Kentucky, Virginia 0.9
| Minnesota 1.7
^ New Jersey 1.88
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6.4 EMISSION GUIDELINE FOR EXISTING SULFURIC ACID PLANTS
Enission guidelines for existing sources must be based on applying
the best available system of emission reduction, considering I
cost. For sulfuric acid plants, these guidelines apply to exist-
ing contact-process sulfuric acid and oleum facilities that burn
elemental sulfur and chemically bound sulfur feedstocks such as A
alkylation acid, hydrogen sulfide, organic sulfides, mercaptans
or acid sludge. These emission guidelines do not apply to acid plants ft
used as S02 control systems, to chamber process plants, to acid
concentrators, or to oleum storage and transfer facilities. |
Based upon the rationale in Section 7 and the source test data in
Section 6.3, the acid mist emission guideline for existing sulfuric
acid plants that reflects the application of the best system of
emission reduction considering cost is:
No more than 0.25 p (measured as ^$04) ner Ka of
acid (as 100 nercent I^SO^) produced, or 0.5 Ib
per ton.
The reference method for determining acid mist emissions is EPA
Method 8 of Appendix A to 40 CFR Part 60.
The emission guideline reflects the application of vertical
panel or horizontal dual pad mist eliminators, as a minimum, to
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I sulfur burning plants producing acid or low strength oleum.
For plants burning bound sulfur feedstocks and/or producing
m strong oleum, the guideline reflects the application of vertical
tube mist eliminators. However, there may be some bound sulfur
feedstock or oleum plants capable of meeting the emission guide-
line vrith vertical panel or horizontal dual pad mist eliminators,
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6.5 GOOD PRACTICES. (1)
The greater the acid mist loading to fiber mist eliminators,
the greater the acid mist emissions from them to the atmosphere
is likely to be. Hence to minimize acid mist emissions it is
important to minimize acid mist formation in the acid production
un i t.
Good practices which minimize mist formation fall irto three
classes: those that apply to all units, those that apply to
sulfur burning units only, and those that apply to units burning
spent acid and other by-products. Good practices which apply
to all units include those which minimize moisture to the converter,
those which minimize acid spray to the converter, and those which
minimize mist formation between the converter and the absorber.
To minimize moisture to the converter, make sure that:
1 1. The acid to the drving tower is at the prooer strength.
It should be between 93 and 99 percent H?SO..
2. The acid to the drying tower is at the proper temperature.
It should be below 120°F for a unit drying with 93
percent acid and below 170°F for a unit drying with
98 percent acid.
3. There is sufficient acid flow to the drying tower. A
minimum acid flow is about 1.5 gallons per minute
per ton of 100 percent ^SO. produced.
4. The acid is properly distributed on the top of the
oacking in the drying tower.
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5. The packing in the drying tower is clean.
6. If the blower is located after the drying tower,
that atmospheric moisture is not drawn in the
suction duct or connections of the blower.
To minimize acid spray to the converter which can cause
Q moisture in the SCL gas leaving the converter make sure that:
1. Splashing is not occurring in the acid distribution
system on the top of the drying tower.
2. Failure has not occurred in the drying tower
I entrainment separator.
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3. Flooding has not occurred in the drying tower.
To minimize mist formation between the converter and the
absorber, make sure that:
* 1. Cooling in the economizer is not too great, too
fast, or localized.
2. Rainstorms or sudden changes in temperature and wind
velocity have not caused duct cooling and subsequent
fl mist formation. If atmospheric conditions appear to
affect mist formation, duct shielding may be required.
3. If the unit is producing oleum, that leakage is not
occurring in the S(L gas line bypassing the oleum tower,
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The subsequent mixing of hot and cooled gas streams
can generate mist.
Good practices which apply to sulfur burning units only include
those which minimize nitrogen oxides in the burner, those which fl
minimize steam or water leaks in the unit, and those which m
improve quality control of the sulfur.
To minimize nitrogen oxides, make sure that the sulfur burner
temperature is below 2000° F. Very high burner temperature
causes nitrogen to combine with oxygen and form nitrogen oxides.
The primary places where steam or water leaks can occur are in the *
sulfur line to the burner and in the process boilers and economizer.
To minimize acid mist formation stemming from the sulfur, it is m
important to have a suitable analytical quality control program.
The two most important analyses to consider are hydrocarbon and
moisture. Cood sulfur filtering can sometimes help to reduce
hydrocarbons, and proper storage and handling practices can |
help to reduce moisture.
Good practices which apply to units burning spent acid and
other by-products include those which minimize mist carryover
from the gas purification section and those which minimize
nitrogen oxide formation.
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To minimize mist carryover it is important that the
dust and mist removal device in the pas purification section
(usually an electrostatic precipitator) be operating
* efficiently.
To minimize nitrogen oxide formation, make sure that:
m 1- The burner temperature is below 2000°F.
2. Arcing is not occurring in the electrostatic
precipitator which is in the gas purification
section.
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G.6 REFERENCES FOR SECTION 6.
1. Cuffe, S. T. and C. M. Dean. Atmospheric Emissions
from Sulfuric Acid Manufacturing Processes. National
Air Pollution Control Administration. Durham, North
Carolina. Publication No. 999-AP-13. 1965. 127 p.
2. Control Techniques for Hydrocarbon and Organic Solvent
Emissions from Stationary Sources. National Air Pollution
Control Administration. Washington, 0. C. Publication
No. AP-68. March 1970. pp. 3-14 to 3-19.
3. Leva, M. Tower Packings and Packed Tower Design. Akron,
Ohio, The United States Stoneware Company, 1953, 214 p.
4. Zenz, F. A. Designing Gas - Absorption Towers. Chemical
Engineering. 79. (25): 120 - 138, November 13, 1972.
5. Personal communication, H. Haaland, Joy Manufacturing
Company, Western Precipitation Division, Los Angeles,
California, to B. A. Varner, Emission Standards and
Engineering Division, OAQPS, OAWP, EPA, September 19, 1972.
6. Personal communication, E. P. Stastny, Koppers Co., Inc.,
Industrial Gas Cleaning Division, Baltimore, Maryland,
to B. A. Varner, Emission Standards and Engineering Division,
OAQPS, OAWP, EPA, September 19, 1972.
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7. Engineering Analysis of Emissions Control Technology
| for Sulfuric Acid Manufacturing Processes. Chemical
Construction Corporation. Final Report. Contract
" 22-69-81, National Air Pollution Control Administration,
PHS, U. S. DREW. New York, N. Y. Publication No. PB-
190-393. March 1970. Vol. 1.
I
8. Brink Fact Guide. Brochure RSA-8. Monsanto Enviro-
Chem Systems, Inc., St. Louis, Missouri.
P
9. Brink Fibre Bed Equipment for Sulphuric Acid Plants.
Technical Bulletin BSE - 2/ME. Monsanto Enviro-Chem
I Systems, Inc., St. Louis, Missouri. February 1971.
10. Brink, J. A., Jr., W. F. Burggrabe, and L. E. Greenwell.
Mist Eliminators for Sulfuric Acid Plants. Chemical
Q Engineering Progress. 6£; 82-86, November 1968.
11. Varner, B. A., Trip Report: Monsanto Enviro-Chem Systems.
Emission Standards and Engineering Division, OAOPS, OAWP,
I EPA. October 4. 1972.
12. Brink, J. A., Jr., W. F. Burggrabe, and J. A. Rauscher.
Fiber Mist Eliminators for Higher Velocities. Chemical
Engineering Progress. 60; 68 - 73, November 1964.
| 13. Brink, J. A., »V. Cascade Impactor for Adiabatic Measure-
g ments. Industrial & Engineering Chemistry. 50; 645 - 648,
April 1958.
I 6-57
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14. York, O.H. and E.W. Poppele. Two-Stage Mist Eliminators
for Sulfuric Acid Plants. Chemical Engineering Progress.
66: 67-72, November 1970.
15. Personal communication, Dr. J.A. Brink, and I.E. Greenwell,
Monsanto Enviro-Chem Systems, Inc., St. Louis, Missouri, to
B. A. Varner, Emission Standards and Engineering Division,
OAQPS, OAWP, EPA, October 18, 1972, July 30, 1973, and May 20,
1974.
16. Personal communication, E.W. Poppele, York Separators,
Inc., Parsippany, New Jersey, to B. A. Varner, Emission
Standards and Engineering Division, OAQPS, OAWP, EPA,
October 19, 1972, July 30, 1973, and May 21, 1974.
17. Letter, J. T. Middleton, EPA, Office of Air Programs,
to W. A. Bours, DuPont, Industrial and Biochemicals
Department, dated December 29, 1971.
18. Chemical Engineering Cost File. Chemical Engineering.
74_: 215, December 4, 1967.
19. Patton, W.F. and J.A. Brink, Jr. New Equipment and
Techniques for Sampling Chemical Process Gases. Presented
at the 55th Annual Meeting of APCA. Sheraton - Chicago
Hotel, Chicago, Illinois, May 20-24, 1962.
20. BrinkR Mist Sampler Model EMS - 10 Users Manual. Monsanto
Enviro - Chem Systems, Inc., St. Louis, Missouri.
(Preliminary Draft Copy).
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21. Source Test Report on Measurement of Emissions.
Test No. 73-SFA-l . Environmental Science and Enciineerinci,
_
Inc., Gainesville, Florida. Prepared for Environmental
Protection Aoencv under Contract Number 68-02-0232.
. 22. Source Test Report on Measurement of Emissions.
Test No. 73-SFA-2. Environmental Science and Enaineerin".
Inc., Gainesville, Florida. Prepared for Environmental
Protection Aqencv under Contract Number 68-02-0232.
I
23. Kurek, R.W. Special Report on EPA Guidelines for State
Emission Standards for Sulfuric Acid Plant Mist dated
June 1974. E.I. duPont de Nemours & Co., Inc.,
Industrial Chemicals Department, Wilmington, Delaware.
Prepared for U.S. Environmental Protection Agency, Office
of Air Quality Planning and Standards. October 4, 1974.
I
Exhibit 8.
24. Analysis of Final State Implementation Plans - Rules
and Regulations. SSPCP, OAP, EPA. Research Triangle
| Park, N.C. Contract No. 68-02-0248. Publication No.
APTD-1334. July 1972. pp. 55-57.
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7. ECONOMIC IMPACT
_ 7.1 INTRODUCTION
This section develops the rationale for the selection of the
emission guideline. The economic impact is analyzed for both
| captive and open market producers. The analysis is specific
to the following industry categories: plants burning elemental
I sulfur and producing no oleum, plants burning bound sulfur
feedstocks, and oleum producers burning any raw materials.
The emission guideline is a level not to exceed 0.5 Ib of
acid mist per ton of acid produced, when measured by EPA
Method 8. This level will allow low-cost mist eliminators
for the sulfur burning, f^SO^-producing plants. The remainder
of the industry will be expected to install the more expensive
vertical tube device.
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Profits in general are currently high in the industry and will
be sufficient to absorb any of the control costs for those plants
needing retrofits wherever competitive forces may prevent price in-
creases. The only adverse impact foreseen may occur for the sludge
processing plants that sell much of their acid on the open market
I in competition with acid producers incurring lower production and con-
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trol costs. Oleum producers, on the other hand, will be expected
to pass on most of the costs.
7.2 INDUSTRY STRUCTURE
Over fifty percent of the sulfuric acid produced is consumed for
phosphate fertilizers and ammonium sulfate fertilizers. Most of
the acid produced for these uses is captive to the firms that
manufacture fertilizers and is mainly derived from elemental sulfur.
The second largest use for sulfuric acid is alkylation in petroleum
refining. Acid plants producing this acid use spent sludge acid
from the refineries. These acid plants may either be captive or
owned by chemical companies that specialize in processing such
material. About eight percent of all sulfuric acid production is con-
sumed by refineries.
The balance of sulfuric acid production and oleum is spread among
many chemical manufacturing activities such as explosives, fibers
(rayon, cellulose/acetate), pigments, batteries, aluminum sulfate,
alcohols, phenol, and sulfonates. Acid produced for this segment
of the industry is sold on the open market, hence the term merchant
acid. Most oleum is sold as merchant acid for consumption in
many of the above activities.
Pricing for sulfuric acid is sensitive to shipping volume and
transportation costs. Concise information for a particular locale
7-2
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can only be obtained by contacting local suppliers or buyers. A
I wide range of prices exists 1n the Industry, as demonstrated by
the following information. Current quotes by the Chemical Market-
1ng Reporter (Nov. 4, 1974) price acid at $43 to $50 per ton (at
the acid plant). According to several contacts in the industry,
these prices are what a customer pays for a small, one-time trans-
action. Contact with one large consumer (Gulf Coast) (1) and one
large merchant acid seller (2), indicates prices ranging from $23
I to $30 per ton delivered, for larger shipments. These lower prices
represent long term contracts (consistent with large volume pro-
duction) with escalation clauses protecting both acid producer and
I consumer against fluctuation in sulfur prices. Transportation is
such an important factor that plants ideally located (with low
| transportation costs to the consumer) can favorably compete against
« lower cost producers that are remote.
Prices for oleum are difficult to establish. One seller (2)
indicated that oleum carries a market premium over 100 percent
acid on an equivalent weight basis (^SO^ content). This premium
or price spread increases with the percentage of S03> Contact
I with a buyer (1) revealed no existence of premiums. The con-
clusion from these contacts is that oleum and sulfuric acid are not
always priced equally. Two factors that might reduce current premiums
H for oleum would be: more sulfuric acid producers converting to
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oleum production, or a decline in demand for oleum relative to acid. I
Air pollution control costs (specifically acid mist control costs),
on the other hand, might be expected to prevent convergence of 9
prices for oleum and sulfuric acid.
7.3 IMPACT ON MODEL PLANTS
The sulfuric acid industry consists of plants using different
raw materials and selling sulfuric acid and various grades of |
oleum. Production costs will differ according to requirements for .
purification, feed stream drying, and pollution control. The cost
structure of the industry is dependent upon many important production
variables, notably: plant size, raw materials, plant design, and
products. |
Table 7.1 exhibits production costs for an elemental sulfur burning
plant and a spent acid burning plant, both producing 1000 tons per
day, 100 percent H^SO.. An acid price of $30 per ton delivered was I
arbitrarily set to represent a typical long-term contract. Freight m
costs were also arbitrarily set. According to one source (3),
profits before taxes average about $2.40 per ton of acid for a I
utilization of 75 percent of capacity.
Pre-tax profits for the industry with the same utilization rate
were estimated to vary from $1.00 per ton to $4.00 per ton, according
to plant size. Table 7.1 shows significantly higher profits for
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TABLE 7.1
____ nnr\m ir*TT AH r*Af*T
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(a) Sulfur credit to refinery
| (b) Includes air + water abatement costs to meet SIP's (S02 only)
and water effluent guidelines, respectively. These costs
are as follows :
Elemental sulfur burning plant - air costs, $1.50 per
ton; water costs, $0.50 per ton. Spent acid burning plants -
air costs, $2.50 per ton; water costs, $1.00 per ton.
(c) Freight based on 150 miles via rail @ 2$ per ton-mile one
direction.
(d) Freight based on 100 miles round trip via rail @ 2$ per- ton mile.
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PRODUCTION COSTS FOR EXISTING
(Built in period from 1968
Original Plant Capital ($1000)
Capacity, TPD
Production, TPY
Sales ($/T), Delivered
Sulfur Cost ($/T)
Other Product Costs ($/T)^
Total Mfg. Costs ($/T)
Selling Expense, Administrative,
Corporate Overhead ($/T)
Freight ($/T)
Operating Profit ($/T)
Income Taxes ($/T)
Profit After Taxes ($/T)
ACID PLANTS
to 1972)
Elemental Sulfur
3000
1000
328,000
30
13.50
3.52
17.02
2.50
3.00(c)
7.48
3.74
3.74
Spent Aci
5400
1000
328,000
30
13.50(a)
7.72
21.22
2.50
2.00(d)
4.28
2.14
2.14
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the case of the sulfur burning plant. This is expected due to I
the plant's large size (average plant size is 500 TPD). Also,
rate of utilization of capacity is assumed to be 90 percent. In |
general, with high utilization today (at 90 percent) and high g
product demands, profits can be conservatively estimated to be
approximately double the above estimate of $1.00-$4.00 per ton (3).
The profit depicted for the spent acid plant ($2.14) is somewhat
above the profit of the average-sized plant (500 TPD). However, |
a new sludge processing plant (for 1000 TPD production) would cost _
nearly $10 million in 1974, or $30 per annual ton capacity. The $2.14
profit thus amounts to a return on equity of approximately 7 percent.
This is unattractive when compared with today's corporate borrowing
cost of 10 percent. This is important to the refinery that may I
consider building its own captive sludge plant in lieu of paying
the sludge processor for his controls. Environmental costs for
abatement of SOp and for neutralization and settling of suspended
solids for waste water discharges have been incorporated into the
cost structures exhibited in Table 7.1. The costs for meeting SIP I
requirements on abatement of S02 are approximately $1.50 per ton of
product for the elemental sulfur burning plant and $2.50 per ton for I
the sludge burning plant (4). However, the requirements for SOp
abatement in SIP's are not the same in all states. Stage I water
treatment guidelines costs (3) are $0.50 per ton and $1.00 per
ton for the elemental sulfur and sludqe burninq plants respectively.
Total environmental control costs before mist controls are thus |
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approximately $2.00 per ton for the elemental sulfur plant
and $3.50 for the sludge acid plant.
For a 1000 TPD elemental sulfur-burning acid plant, the
least cost option of achieving the acid mist guideline will
range from $0.04 to $0.11 per ton (interpolated from Table 6.2).
I For a spent acid-burning plant or a plant producing strong
oleum operating at 1000 TPD acid, the cost of achieving
the guideline would ranae from $0.34 to $0.65 per ton, the
low end of the range representing "piggyback" installation
and the high end representing "at grade" installation.
I These costs will be higher for the elemental sulfur-burning
plant that may convert only a small portion of its acid to
I heavier grades of oleum. For such a plant producing 1000 TPD,
m the marainal cost to control acid mist ner ton of oleum with
a high efficiency vertical tube collector could be significantly
more than $1.00 per ton. However, the average cost remains
the same as for the acid sludge-burning plant and the full
| time oleum producer. The impact of this situation for the
m occasional oleum producer will be discussed in the next section.
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7.4 RATIONALE FOR SELECTION OF GUIDELINES
Emission guidelines for existing sources must be based on
applying the best available system of emission reduction
considering costs. For §ulfuric acid plants, the guideline
applies to existing contact-process sulfuric acid and oleum
facilities that burn elemental sulfur and chemically bound sulfur
feedstocks such as alkylation acid, hydrogen sulfide, organic
sulfides, mercaptans, or acid sludge. Practicable retrofits for
controlling acid mist emissions from these plants include vertical
tube, vertical panel and horizontal dual pad mist eliminators.
Ti.e emission guideline does not apply to metallurqical acid plants,
to chamber process plants, to acid concentrators, or to oleum
storage and transfer facilities.
Based upon equipment capabilities, existing State standards,
emission test data, and best demonstrated control technology for
new plants (the EPA acid mist standard of performance for new
sulfuric acid plants), four alternative control levels could be
proposed as candidates for the emission guideline. Table 7.2
lists these levels and the corresponding control equipment required.
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TABLE 7.2
ALTERNATIVE ACID MIST CONTROL LEVELS AND CORRESPONDING CONTROL EQUIPMENT
Required Control Equipment
Oleum Plants
Candidate Control Level and Bound Sulfur Sulfur Burning
(Ib mist/ton 100% H,,S04) Feedstock Acid Plants Acid Plants
2.0 Vertical panel and Vertical panel
horizontal dual pad and horizontal
dual pad
0.5 Vertical tube Vertical parrel
(commonly) and horizontal
dual pad
0.3 Vertical tube Vertical tube
0.15 Vertical tube Vertical tube
The 2.0 pound control level is based upon the capabilities of the
vertical panel and horizontal dual pad mist eliminators applied
to oleum plants and bound sulfur feedstock acid plants, and
the fact that not one of the 18 state standards for existing
plants is higher than this level (see Table 6.9, Section 6.3.4).
The 0.5 pound control level is based upon the capabilities of the
vertical panel and horizontal dual pad mist eliminators applied to
sulfur burning acid plants, and the fact that 14 of the 18
states with standards for existing plants have standards at or
below this level. For oleum plants and for bound sulfur feedstock
acid plants, the vertical tube mist eliminator is usually required
to achieve the 0.5 pound control level.
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The 0.3 Ib/ton level is based on the test data in Tables 6.5, 6.6, and 6.7.
Most of those data are well below 0.3 Ib/ton, and only two individual
runs exceeded 0.3 Ibs/ton. Assuminq the two high runs are valid, when
averaged with other runs as is done for a performance test, the plant
would be in comnliance with a 0.3 Ib/ton standard. This level of
control would require vertical tube mist eliminators on most sulfuric
acid plants.
The 0.15 pound control level is based upon best demonstrated
control technology for new plants as specified in the EPA standard
of performance for new plants. This standard is based on source
tests at plants producing oleum as well as acid, and burning
elemental sulfur and other feedstocks. Of the types of devices
considered, the vertical tube mist eliminator is the only one
that will allow any type of sulfuric acid plant to achieve the
0.15 pound control level.
The following discussion deals with the economic impact and
other issues associated with each of the candidate levels.
The 2.0 Ib. level of control corresponds to control which v/culd be achieved
by application of the vertical panel or horizontal dual pad across the
board. All states with regulations for acid mist had levels lower than
the 2.0 Ib guideline, and thus, this candidate level was dismissed since
it does not represent application of best control technology, considering
cost.
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I 0.5 Ib/ton
The 0.5 Ib. level of control can be achieved on sulfur burning acid plants
I with vertical panel and horizontal nad mist eliminators. For the plants
m considered in Table 6.2, the least cost option of control will range from
$0.03 to $0.42 per ton of acid, over the 50 TPD to 1500 TPD plant sizes,
with lower costs favoring the larger plants. This level of control
will generally require the use of the more expensive vertical tube mist
| eliminator on oleum plants producing the higher grades of oleum, and
M on bound sulfur feedstock acid plants. The tube mist eliminator will
cost from $0.49 to $1.69 per ton for the 50 TPD to 1500 TPD plant for
the at-grade retrofit (see Table 6.2).
It should be noted that industry feels that the pad type mist eliminators
will meet acid mist standards of 0.5 Ib/ton in plants burning bound sulfur
feedstocks and making strong oleum. Data for plants A, H and I in
Table 6.7 indicate this may be true in many cases; however, EPA doubts
I that it is universally true because vendors of the two kinds of pad
M mist eliminators will not guarantee their products for the 0.5 Ib/ton
level for oleum plants.
B In addition, a comparison of superficial gas velocities through the
pad and the tubular mist eliminators shows 400-600 ft/mint for
the pads and only 20-40 ft/mi n for the tubular. Thus, the pad removes
I mist particles by the single mechanism of inertia! impaction; the
tubular mist eliminator removes mist by the three mechanisms of inertia!
impaction for large particles, direct interception for smaller particles,
and Brownian movement for sub-micron particles.
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As indicated in Table 4.2, oleum production results in a finer particle
size distribution than acid production and the mist becomes finer with
increasing oleum strength. Consequently, oleum mist is best removed
by the tubular mist eliminator because its performance is not much
affected by changes in plant production rate and has a good turndown
ratio.
In this case where the guideline will likely require different control
equipment for oleum plants, EPA feels that the guideline is justified
because: (1) oleum is a different product from acid; (2) oleum
production is a different process from acid production and requires
more complex plants, and (3) oleum has different markets and end uses
than acid. Thus, oleum plants may be considered a subcategory of acid
production units requiring different controls than acid plants do and
it is economically reasonable for oleum plants to spend more for
controls.
A State standard of 0.5 Ib per ton would be expected to create no
adverse impact for sulfur burning acid plants and minimal adverse
impact for the oleum producers and spent acid processors. Control
costs could be passed on or readily absorbed at the present high
profitability in the industry. Only the sludge plant that operates
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I extensively in open markets may find difficulty in absorbing the
control costs or passing them on to its merchant acid customers.
In comparison with sulfur burning acid producers, this sludge
I processor will have relatively higher control costs and lower profit
margins before implementation of mist controls. The only outlet
| for sharing the cost burden of the sludge processor is the source
of the sludge the refinery. The refiner will either have to build
his own acid plant or assist 1n paying for the portion of the control
| costs that cannot be transferred to the merchant acid market or
absorbed by the sludge processor. In the short run, the refiner
will be expected to prefer paying the mist control costs because,
as stated in section 7.3, he would find that the alternative of
building an acid plant would be an unattractive proposition.
The producers of oleum would handle their control costs in much
the same way as would the sludge processing acid plant engaged in
significant merchant acid sales. The costs for the control device
| can be partially passed on to the oleum consumer to the extent
allowed by the price elasticity of demand on the part of oleum con-
_
sumers. Whenever the consumer needs the S03 content of oleum as a
carrier for reactions, drying, etc., he will be willing to pay a
little more than the current sulfuric acid price. By contrast, the
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consumer buying oleum strictly for the freight savings will not be
willing to pay additional control costs.
7-13
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The occasional oleum producer would probably be forced to absorb
more of his control costs than his competitors who sell sulfuric
acid or oleum as their only product. Since the size and total in-
vestment of a mist eliminator are based upon the entire plant's
oleum and acid production, the incremental costs for the tube over
the panel or pad are too large to be borne by the oleum consumers
alone. Attempts to pass costs on to the acid consumers will be
limited by competition from acid producers incurring both lower
production and control costs. As a result, the occasional oleum pro-
ducer will have to absorb those costs that cannot be passed on to his
consumers. Since most oleum producers generally sell both acid and
oleum, there doesn't appear to be any individual producers in an un-
favorable trade position who would suffer an adverse impact from the
recommended emission limitation. Vendors refuse to guarantee the
performance of panels and pads on oleum plants, and most State stan-
dards are 0.5 Ib/ton or lower. For these reasons, occasional oleum
producers would have installed vertical tubes and/or adjusted their
market position.
0.15 Ib/ton
The 0.15 Ib level of control can be achieved only by installation
of the vertical tube mist eliminator on all acid olants. Such a
level would create adverse economic impact for smaller, older plants
that are faced with both acid mist and S02 abatement. On the
7-14
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other hand, high costs of achieving the 0.15 Ib. limitation can be
more easily absorbed by plants that do not require a strict level
| of S02 abatement (such as that associated with dual absorption
_ or tail gas scrubbing). With the uncertainty in establishing SO,
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controls, the problem of quantifying the impact is difficult.
An important element that would contribute to the adverse economic impact
on the industry is the resultant double retrofitting of controls
that would be required by the 0.15 level. It is estimated that
I 40 percent of all sulfuric acid units in the United States have
vertical tube or vertical panel mist eliminators and 15 percent
have horizontal dual pad mist eliminators capable of meeting the
0.5 pound control level. If one-half of the vertical mist elimina-
tors are panels, then it follows that 35 percent of all sulfuric
I acid units (20 percent, vertical panels; 15 percent, pads) are
exceeding the 0.15 pound level, but meeting the 0.5 pound level.
If the above acid unit percentages are comparable on an acid plant
basis, and if all the vertical panel and horizontal dual pad mist
eliminators are installed on the 45 percent of the U.S. plants
I that burn sulfur and do not produce oleum, then 78 percent (35 of
45) of these would be forced to retrofit. If only 10 percent of
I all acid plants can be assumed to have vertical panels, then 56
_ percent (25 of 45) of the sulfur burning, H2S04-producing plints
would still be forced to double retrofit.
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To undergo double retrofit expenditures at a time when ferti-
lizer production capacity is tightly constrained (over fifty
percent of the sulfuric acid produced goes into fertilizers)
would further aggravate contemporary world food shortage problems.
In addition, many of the fertilizer industry's sulfuric acid plants
have been compelled to undergo major expenditures to limit S0?
emissions to a level equivalent with performance of dual absorption
acid plants.
0.3 Ib/ton
Since for most acid plants 0.3 Ib/ton can be achieved only with a
vertical tube mist eliminator, the problems of double retrofittina
discussed for the 0.15 Ib/ton level also apply. While the data in
Tables 6.5, 6.6, and 6.7 are almost all below 0.3 Ib/ton, the data
base is limited, since two of the plants in Table 6.5 operated
substantially below capacity, plants in Table 6.6 produced no oleum,
and the data in Table 6.7 are from sources other than EPA tests.
Another consideration is the vendor quarantee's of 2.0 ma/scf for a
vertical panel or horizontal dual pad mist eliminator. Plant E
(Table 6.6) has a converter inlet concentration of seven percent SO^.
From Figure 4.1, 2.0 mq/scf is equivalent to 0.45 Ib/ton of acid mist,
Thus, the vendor guarantee might prohibit installation of a vertical
panel or horizontal pad mist eliminator to comnlv with a 0.3 Ib/ton
emission standard.
Finally, the emission guideline requires more than control of
particulate acid mist; it also requires control of S^. vaoor and
7-16
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SO, through proper absorber operation and desiqn. Even in proper!v
operated plants the theoretical amount of H,,S04 and S03 vapor, measured
I as H2S04, can amount to over 1 Ib/ton acid produced. To further
reduce the vapor emissions would require increased absorber heiqht and
power costs. Since EPA Method 8 measures a small fraction of the
vapor emissions, the mist eliminator, which controls only the
particulate acid mist}must be capable of reducina mist emissions to
I a level of the EPA guideline minus the fraction of H^O^ and S03
vapors measured by Method 8. Thus because of the uncertainty of the
amount of vapor measured, a plant owner miqht be compelled to install
M a vertical tube mist eliminator to insure compliance with a standard
of 0.3 Ib/ton.
Because Reference Method 8 does measure an unknown fraction of
the S03 and H2S04 vapor, there has been some question regarding the
precision and accuracy of the method. Results of a collaborative test
I performed in 1974 showed poor precision for the method (5). Recent
review of this study indicates that the problem may be due to the
I collaborative test procedure and not due to Method 8. Specifically,
because the high values of acid mist collected on any run were
accompanied by comparatively low results for S02, it is likely that
contamination of the isopropanol solution occurred prior to the test,
either through poor preparation or by back flushing hydrogen
I peroxide solution during the leak check. This contamination would
cause some of the S02 to be counted as acid mist. As a result of
the apparent problems with this study, EPA is commencing a study to
further investigate the isopropanol contamination problem and to
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7-18
I
establish the precision of the method. If these studies indicate
a problem, EPA will make appropriate revisions to Reference Method I
8 and the emission guideline. As pointed out in section 6.3.2, for
sulfur burning acid plants the EPA and Monsanto methods have shown I
a good correlation, and thus major problems with the method are not
expected.
EPA's position regarding the accuracy of the method is that I
as long as the compliance test method is consistent with the method
used to develop the emission guideline (Method 8), it is not |
necessary to know the absolute concentration of acid mist in the _
stack. Thus in compliance testing, the repeatability (precision)
is more critical than the accuracy. I
Dual Guideline
I
During the course of t'ne development of the guideline sone con-
sideration was given to setting a 0.15 lb guideline for plants
producing oleum and/or burning bound sulfur feedstocks, and a
0.50 lb. guideline for sulfur burning, HgSO^-producing plants. J
The approach was rejected due to a lack of supportive emission
data over a wide enough range of operating conditions for plants
producing oleum and/or burning bound sulfur feedstocks. Furthermore,
many plants make oleum on a part-time basis, based on market
Thus, these plants could be required to install the most expensive I
control for a few runs per vear if EPA promulgated a dual guideline
(relief under §60.24(f) could possibly mitigate this problem). |
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I Summary
In summary, Industry-wide adverse Impacts are not expected
for the recommended emissions guideline of 0.5 lb/ton.
I However, there may be a few isolated cases where a sludge
processing plant may have difficulty if the plant is not
I captive to a petroleum rpfinery. Depending on their product
« mix or sulfuric acid and oleum, oleum producers will pass
on to a greater or lesser extent their control costs. No
I problems are foreseen for any individual oleum producer that
may sell oleum only in snail quantity.
The cost analysis which resulted in a guideline of 0.5 Ib/ton
I was influenced by the double retrofitting involved with a
guideline less than 0.5 lb/ton. However, where double retrofitting
I is not a problem (i.e., in States with plants in compliance
_ with existing standards more stringent than the guideline, or
for presently uncontrolled plants), State standards as low as
I the standard of performance for new sources (0.15 lb/ton) may be
justified.
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' 7-19
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7.5 REFERENCES FOR SECTION 7.
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1. Personal communication from R. C. Lamos, Dow Badische Co., I
Williamsburg, Virginia, to F. L. Bunyard, Strategies and
Air Standards Division, OAQPS. Environmental Protection
Agency, Research Triangle Park, N.C. November 19, 1974.
2. Personal communication from F. Koontz, Cities Service Co., _
Industrial Chemicals Division, Atlanta, Georgia, to F. L.
Bunyard, Strategies and Air Standards Division, OAQPS,
Environmental Protection Agency, Research Triangle Park,
N.C. November 18, 1974. J
3. Study of the Economic Impact of the Cost of Alternative I
Federal Water Duality Standards on Ten Inorganic Chemicals.
Booz-Allen ?* Hamilton. Washington, D.C. Prepared for |
Environmental Protection Agency. December 4, 1972.
4. LeSourd, D.A. and F.L. Bunyard. Comprehensive Study of
Specified Air Pollution Sources to Assess the Economic
Impact of Air Quality Standards. Research Triangle Institute.
Research Triangle Park, N.C. Prepared for Environmental
Protection Agency under Contract No. 68-02-0088. Report I
No. FR-41U-649. August 1972.
5. Hamil, H. F., D. E. Camann, R. E. Thomas. Collaborative Study
of Method for the Determination of Sulfuric Acid Mist and |
Sulfur Dioxide Emissions from Stationary Sources. Southwest
7-20
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Research Institute. San Antonio, Texas. Prepared for
Environmental Protection Agency under Contract No. 68-02-0626,
EPA 650/4-75-003. November 1974.
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7-21
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8. ENVIRONMENTAL IMPACT
I 8.1 ENVIRONMENTAL IMPACT OF THE EMISSION GUIDELINE
| The assessment of the environmental impact of the emission
guideline is based on the incremental impact above that normally
imposed on the environment by the affected sources or process
controlled to meet other pollution regulations such as State
Implementation Plans (SIP) or local regulations. The environmental
impact is therefore a function of incremental effects, or a
comparison of two degrees of control, and is not the total effect
I of the pollution control itself.
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8.1.1 Air Impacts
8.1.1.1 Changes in mass emission rates
In Section 6.3.4, it was estimated that 95 percent of the sulfuric
I acid units in the United States have acid mist controls. Stack
gas control equipment capable of meeting the emission guideline of
0.5 Ib acid mist/ton H2S04 produced (Ib/ton) includes vertical tube,
I vertical panel and horizontal dual pad fiber mist eliminators; and
electrostatic precipitators. According to Section 6.3.4, at least
I 65 percent (40-tube and panel; 15-dual pad; 10-ESP) of all acid
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8-1
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units have such controls. The most common State acid mist regula- «
tion is 0.5 Ib/ton, a level adopted by 10 of the 18 states with *
enforceable regulations, listed in Table 6.9. Four states have
higher standards; four have lower ones. Hence, the greatest impact
will be around the 35 percent of acid plants which presently do not I
have adequate mist eliminators. In addition, State standards will
require those plants which have mist eliminators to maintain and
operate the control systems properly, which will yield a beneficial, I
but unquantifiable air impact.
I
An average-sized sulfuric acid plant has a capacity of about 500
TPD. For a 500 TPD acid (vs. oleum) plant operating 350 days per I
year, an uncontrolled emission rate of 4.0 Ib/ton (see Section 4.3)
is equivalent to an emission of 350 tons/year. For a 500 TPD oleum
plant, an uncontrolled emission rate of 10.0 Ib/ton is equivalent
to an emission of 875 tons/year. If either the acid or the oleum
plant is controlled to the level of the emission guideline and most I
State regulations (0.5 Ib/ton), the emission for the plant is
reduced to 44 tons/yr. For a 500 TPD plant, each emission incre~ I
ment of 0.1 Ib/ton is equivalent to a difference in emission of
8.75 tons/yr.
About one third of the U.S. sulfuric acid plants produce oleum while
two-thirds do not (see Table 2.3). Hence, on a national basis, an I
average uncontrolled emission rate is about 6.0 lb/ton--[2 (4) + 1
1
8-2 I
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I
(10)] / 3. This rate is equivalent to an emission of 95,000 tons/
year at the 1973 sulfuric acid production level of 31.7 million
tons per year. Control at the 0.5 Ib/ton level reduces this
I emission to 7925 tons/year. Each emission increment of 0.1 Ib/ton
is equivalent to a difference of 1585 ton/year.
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M 8.1.1.2 Atmospheric dispersion
A dispersion analysis was made for several plant sizes, types, and
averaging times. Ground level concentrations were calculated for
both controlled and uncontrolled plants. The methodology and assump-
| tions used are summarized in Appendix A. Results of this analysis
Q are presented in Table 8.1. As can be seen from the results,
* controlling plants to a level of 0.5 Ibs per ton of acid has a
tremendous impact on ground-level concentrations compared to the
uncontrolled plants.
Estimates presented in Section 6.3.4 indicate that 5 percent of the
sulfuric acid plants in the U.S. do not have acid mist control systems,
Since 27 states either have no regulations or regulations less
I stringent than the emission guideline, it may be assumed that the
ground-level concentrations in Table 8.1 from the uncontrolled plants
are an upper bound to the concentrations actually observed in those
states. Application of state standards at least as stringent as the
emission guideline will result in significant reductions in ground-
| level concentrations.
I 8-3
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8-4
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8.1.1.3 Effects on other air pollutants
Sulfur dioxide (SO,,) is the air pollutant emitted in greatest
quantity from sulfuric acid plants. Like acid mist, its principal
| emission point is the stack gas from the final absorber. Instal-
lation of stack gas acid mist control devices will not change
the quantity of SO 2 emitted. Furthermore, their installation
I will not generate any additional secondary air pollutants.
I Nitrogen oxides may be present in the converter exit gas stream,
especially in spent acid plants. As discussed in Section 4.2.3,
| they react with SOp and sulfur trioxide (SO-) to form very fine
mists. These mists will pass through the final absorber and through
impaction mist control devices like vertical panel and horizontal
dual pad mist eliminators. High efficiency vertical tube mist
eliminators will remove most of this mist from the stack gas.
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8.1.2 Water Pollution Impact
The sulfuric acid collected by acid mist controls is returned to
the process. Hence there is no effluent discharge at any acid
mist air pollution control level. However, some of the acid mist
discharged 'rorc the stack will fall out in tte vicinity of the plant
anri may be washed out by rainfall. Ground runoff r»" cause sone of this
acid fallout to eventually reach local watercourses-, however, it
is more likely to react with the calcium carbonate or other acid-
consuming constituents of the soil and so lose its acid character.
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8.1.3 Solid Waste Disposal Impact
Because acid mist controls do not generate or recover solid waste
there is no solid waste disposal impact.
8.1.4 Energy Impact
The guideline has little energy impact because the electrical
energy requirements associated with fiber mist eliminators are
small and most plants already have some type of fiber mist
eliminator. For example, an energy penalty of 3.6 kilowatt-hours (KWH)
per ton of acid produced can be calculated based upon a fiber mist
eliminator pressure drop of 10 inches of FLO, a fan efficiency of
55 percent and an acid plant process air requirement of 71 acfm
per ton of acid produced.
The reduction in emissions from installation of fiber mist
eliminators far outweighs the additional pollution emitted by a
power plant in generating the mist eliminator's attendant electrical
requirement. For example, such an installation will reduce the
acid mist emission rate from a typical acid (vs. oleum) plant from J
4.0 to 0.5 Ib/ton, a reduction of 3.5 Ib/ton. From the preceding
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paragraph, a typical attendant energy penalty is 3.6 KWH/ton. This
is equivalent to 37,800 BTU heat input per ton of acid produced,
assuming a power plant heat input requirement of 10,500 BTU/KWH.
I If the electricity is generated in a coal -fired plant complying with
the EPA standards of performance for new stationary sources, then
B parti cul ate, SO,,, and nitrogen oxide (NO ) emissions are restricted
t~ A
to 0.2, 1.2 and 0.7 Ib per million BTU heat input, respectively.
For a heat input of 37,800 BTU, corresponding emissions of parti-
cul ate, S02 and NOX are 0.008, 0.045 and 0.027 Ib per ton of acid,
respectively, or a total of 0.08 Ib/ton. Thus in this example,
I the electrical energy associated with one pound of air pollution
at the power plant will help eliminate 44 pounds (3.5/0.08) of
air pollution when delivered to a fan supplying an acid plant mist
I eliminator pressure drop requirement of 10 inches of H^O.
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8.1.R Noise effects
The emission guideline has no noise impact because fiber mist eliminators
and final absorbers operate with no detectable noise. When retrofitting
fiber mist eliminators, an additional fan may be needed to handle the
increased pressure drop (See Section 6.2.2.1). This fan may sliqhtly
| increase the plant's noise level.
G.I. C Gtlier environmental Concerns
M Tin re arc no other environmental concerns - such as an incrrasr i",
radiative heat or in dissipated static electrical energy - related
to the level of the emission nuideliie.
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8.2 ENVIRONMENTAL IMPACT UNDER ALTERNATIVE EMISSION CONTROL SYSTEMS
The emission guideline15 based upon the capabilities of fiber
mist eliminators. No alternative emission control system meets
the requirements of best demonstrated control technology considering
cost. Although mild steel electrostatic precipitators effectively
control acid mist, their large size makes retrofit installation
costs high, and they are expensive to maintain in a corrosive acid
environment.
8.3 SOCIO-ECONOMIC IMPACTS
Minimal adverse socio-economic impact should result from the |
emission guideline. The only adverse economic impact foreseen _
may occur for the sludge processing plants competing on the open
I
market (See Section 7). In 1967, the sulfuric acid industry employed
4,500 persons. Hence closure of an average-sized plant would mean
employment loss for about 20 people. However, no plant I
closures or loss of employment are anticipated.
8.4 OTHER CONCERNS OF THE EMISSION GUIDELINE
The emission guideline should not have any other adverse or beneficial
environmental effects. It will not create short-term environmental I
gains at the expense of long-term environmental losses or vice
versa, and will not result in irreversible and irretrievable
commitment of resources. It will not foreclose future control I
options or curtail the diversity and range of beneficial uses of
the environment. |
8-8
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I 8.5 REFERENCE FOR SECTION 8
1. 1967 Census of Manufacturers. Bureau of the Census, U. S. Dept.
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of Commerce, Washington, D. C. Vol, II, Industry Statistics,
Part 2. January 1971. p. M28A-43.
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APPENDIX A - DISPERSION ANALYSIS
_ METHODOLOGY AND ASSUMPTIONS
The diffusion analysis results of Table 8.1 were generated by the
Source Receptor Analysis Branch, EPA using the Single Source Model
developed by the Meteorology Laboratory, EPA. The model is designed to
estimate concentrations due to sources at a single location for
averaging times from one hour to one year.
This model is a Gaussian plume model using diffusion coefficients
I
suggested by Turner (1970). Concentrations are calculated for each
hour of the year, from observations of wind direction (in increments
of 10 degrees), wind speed, mixing height, and atmospheric stability.
The atmospheric stability is derived by the Pasquill classification
method as described by Turner (1970). In the application of this model,
| all pollutants are considered to display the dispersion behavior of
» non-reactive gases.
The 10-second concentrations in Table 8.1 were calculated manually
from the one-hour concentrations, using Eq 5.12 (p. 38) of Turner's
"Workbook of Atmospheric Dispersions Estimates." Based on the advice
I of Mr. Turner, a strong dependence on stability class was incorporated
into the equation. Specifically, the exponent "p" varies from about
0.67 to about 0.17 as stability class varies from A to F. The plants in
this study exert their greatest impact under very unstabled ("A")
conditions, and therefore an exponent of 0.67 was used.
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Meteorological data for 1964 are used as input to the model. The I
reasons for this choice are: (1) data from earlier years did not have
sufficient resolution in the wind direction; and (2) data from subsequent |
years are readily available on magnetic tape only for every third hour. _
Mixing height data are obtained from the twice-a-day upper air
observations made at the most representative upper air station. Hourly
mixing heights are estimated by the model using an objective interpola-
tion scheme.
A feature of this model is the modification of plume behavior to
account for aerodynamic effects for plants in which the design is not
optimal. These effects result from the interaction of the wind with the
physical structure of the plant. The extreme case is commonly referred
to as "downwash." With downwash, the effluent is brought downward into I
the wake of the plant, from which point it diffuses as though emitted
very close to the ground. In the retardation case, some of the I
dispersive benefits of plume rise are lost; while in the downwash case,
all of the benefits of plume rise are lost, along with most of the
benefits of stack elevation. Both phenomena - but especially downwash - I
can seriously increase the resulting ambient air impact.
The aerodynamic-effects modification then, is an attempt to include |
these effects in a predictive model. It was developed within EPA, and
while not yet validated, is the best known operational approach. Basic-
ally, it enables the model to make an hour-by-hour, stack-by-stack I
assessment of the extent (if any) of aerodynamic complications. The
parameters used in making the assessment are wind speed, stack-gas exit |
velocity, stack height, stack diameter, and building height. If a .
particular assessment indicates no aerodynamic effect, then for that '
A-2 '
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stack (for that hour) the model behaves just as the unmodified version.
If there are aerodynamic effects, the modified version contains equations
by which the impact of these effects on ground-level concentrations is
estimated. Aerodynamic effects were not a factor in this study due to
favorable stack heights assumed.
Calculations are made for 180 receptors (at 36 azimuths and five
selectable distances from the source). The model used can consider
both diurnal and seasonal variations in the source. Separate variation
factors can be applied on a monthly basis to account for seasonal
fluctuations and on an hourly basis to account for diurnal variations.
Another feature of the model is the ability to compute frequency
distributions for concentrations of any averaging period over the course
of a year. Percentages of various ranges in pollutant concentrations
are calculated.
The following assumptions were applied in the analytic approach:
1. Mist was considered to behave as a non-reactive gas.
2. The plant is located in flat or gently rolling terrain with a
meteoroligical regime which is unfavorable to the dispersion
of pollutants. The effect of the latter is to introduce an
element of conservatism into the analysis. In a restrictive
terrain, the dispersion of pollutants could be even more
impaired resulting in higher ambient concentration levels.
3. There are no significant seasonal or hourly variations in
emission rates for this plant.
4. Source characteristics assumed are in Table A-l.
A-3
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Table A-l
Plant size (TPD)
Stack ht (m)
Stack diam. (m)
Stack Temp. (K)
Exhaust gas volume
nr/sec
Exhaust gas velocity
(m/sec)
Emission rate
(g/sec)
Controlled to 0.5
Ib/ton
Uncontrolled
50
46 (150 ft)
0.6 <2 ft>
344
1.64
5.8
0.13
1.0 acid
2.6 oleum
250
46 (15° ft)
0.9 <3 ft>
344
8.2
12.9
0.66
5.3 acid
13.2 oleum
750
61 (200 ft)
1.5 <5ft)
344
25.1
14.2
1.97
15.8 acid
39.4 oleum
1500
76 (250 ft)
2.1 <7 ft>
344
50.6
14.6
3.94
31 .5 acid
78.3 oleum
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Reference
1. Turner, D. B., "Workbook of Atmospheric Dispersion Estimates," U. S.
Department of H.E.W., PHS Publication No. 999-AP-24 (Revised 1970).
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A-5
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REP
E&-£?0/2-77-019
4 "ITLE AND SUBTITLE
Final Guideline Document: Control of Sulfuric Acid
'iist Emissions from Existing Sulfuric Acid Production
JJnitjL
5. REPORTJ1ATE _-
September, 1977
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION" NO.
7 AUTHOR(S)
U. S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, RTP, NC 27711
8. PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Standarus Development Branch
Emission Standards and Engineering Division
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY .NAMEAND ADDRESS . _. , ,
DAA for Air Qua!ity Planning and Standards
Office of Air and Waste Management
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The U. S. Environmental Protection Agency is required under 40 CFR Part 60 to publish
a guideline document for development of State emission standards after promulgating
any standard of performance for a designated pollutant. Standards of performance
limiting emissions of such a designated pollutantsulfuric acid mistfrom new and
modified sulfuric acid production units were promulgated on December 23, 1971,
necessitating the development of this document. The document includes the following
information: (1) Emission guidelines and times for compliance; (2) A brief
description of the sulfuric acid industry, and the nature and source of acid mist
emissions; (3) Information regarding the effects of acid mist on health and
welfare; and (4) Assessments of the environmental, economic, and energy impacts of
the emission guideline.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Sulfuric Acid
Sulfuric Acid Hist
Uemisters
Air Pollution Control Equipment
Standards of Performance
Air Pollution Control
18. DISTRIBUTION STATEMENT
Unlimited - Available to the public free
of charge from: Public Information
Center (PM-215), EPA, Washington. DC 20460
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
185
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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