United States
           Environmental Protection
           Agency
           Office of Air Quality
           Planning and Standards
           Research Triangle Park NC 27711
EPA-450/3-79-003
January 1979
           Air
&ER&
A Review of Standards
of Performance for New
Stationary Sources -
          Acid Plants

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                                          EPA-450/3-79-003
A  Review of Standards of Performance
       for  New  Stationary  Sources  -
              Sulfuric Acid  Plants
                             by

                  Marvin Drabkin and Kathryn J. Brooks

                 Metrek Division of the MITRE Corporation
                    1820 Dolley Madison Boulevard
                      McLean. Virginia 22102
                      Contract No.68-02-2526



                   EPA Project Officer. Thomas Bibb

                Emission Standards and Engineering Division



                          Prepared for

                U S ENVIRONMENTAL PROTECTION AGENCY
                   Office of Air, Noise, and Radiation
                Office of Air Quality Planning and Standards
                Research Triangle Park, North Carolina 27711

                         January 1979

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This report hasbeen reviewed by the Emission Standardsand Engineering Division of the Office of Air
Quality Planning and Standards, EPA, and approved for publication  Mention of trade names or
commercial products is not intended to constitute endorsement or recommendation for use Copies of
this report are available through the Library Services Office (MD-35), U.S Environmental Protection
Agency, Research Triangle Park, N.C  27711; or, for a fee, from the National Technical Information
Services, 5285 Port Royal Road, Springfield, Virginia 22161
                             Publication No EPA-450/3-79-003

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                          TABLE OF CONTENTS

                                                                 Page

LIST OF ILLUSTRATIONS                                            viii
LIST OF TABLES                                                   ix

1.0  EXECUTIVE SUMMARY                                           1-1

1.1  Best Demonstrated Control Technology                        1-1
1.2  Current S02 NSPS Levels Achievable With Best
     Demonstrated Control Technology                             1-2
1.3  Economic Considerations Affecting the S02 NSPS              1-3
1.4  Current Acid Mist Levels (and Related Opacity Levels)
     Achievable With Best Demonstrated Control Technology        1-4

2.0  INTRODUCTION                                                2-1

3.0  CURRENT STANDARDS FOR SULFURIC ACID PLANTS                  3-1

3.1  Background Information                                      3-1
3.2  Facilities Affected                                         3-2
3.3  Controlled Pollutants and Emission Levels                   3-3
3.4  Testing and Monitoring Requirements                         3-5

     3.4.1  Testing Requirements                                 3-5
     3.4.2  Monitoring Requirements                              3-6

4.0  STATUS OF CONTROL TECHNOLOGY                                4-1

4.1  Status of Sulfuric Acid Manufacturing Industry
     Since the Promulgation of the NSPS                          4-1

     4.1.1  Geographic Distribution                              '4-1
     4.1.2  Production                                           4-1
     4.1.3  Industrial Trends                                    4-10

4.2  Contact Process for Sulfuric Acid Production                4-11

     4.2.1  Elemental Sulfur Burning Plants                      4-11
     4.2.2  Spent Acid and Other By-Product Plants               4-13

4.3  Emissions from Contact Process Sulfuric Acid Plants         4-15

     4.3.1  Sulfur Dioxide                                       4-15
     4.3.2  Acid Mist Formation                                  4-17
     4.3.3  Visible Emissions (Opacity)                          4-21
     4.3.4  Oxides of Nitrogen                                   4-23

                                 iii

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                          TABLE OF CONTENTS (cont.)

                                                                 Page

4.4  Control Technology Applicable to the NSPS Control of
     S02 Emissions from Contact Process Sulfuric Acid Plants     4-24

     4.4.1  Dual Absorption Process                              4-24
     4.4.2  Sodium Sulfite - Bisulfite Scrubbing                 4-28
     4.4.3  Ammonia Scrubbing                                    4-29
     4.4.4  Molecular Sieves                                     4-30

4.5  Control Technology Applicable to the NSPS for Acid Mist
     Emissions from Contact Process Sulfuric Acid Plants         4-30

     4.5.1  Vertical Tube Mist Eliminators                       4-31
     4.5.2  Vertical Panel Mist Eliminators                      4-34
     4.5.3  Horizontal Dual Pad Mist Eliminators                 4-37

5.0  INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS               5-1

5.1  Test Results EPA Regional Sources                           5-1
5.2  Analysis of NSPS Test Results                               5-1

     5.2.1  Control Technology Used to Achieve Compliance        5-6
     5.2.2  Statistical Analysis  of NSPS Compliance Test Data    5-7
     5.2.3  Validity of NSPS Test Data                           5-7
     5.2.4  Comparison of NSPS Compliance Test Data with Day-
            to-Day Emission Control Performance                  5-9
     5.2.5  Emission Control Performance Based on  Excess
            Emissions Reports                                    5-11

5.3  (Indications  of  the Need  for  a Revised Standard              5-11
     *• *"

     5.3.1  S02  Standard                                         5-11
     5.3.2  Acid  Mist NSPS  (and  Related Opacity  Standard)        5-13

6.0  ANALYSIS OF  POSSIBLE REVISIONS TO THE STANDARD              6-1

6.1  Effect of NSPS  Revision  on  Sulfuric Acid Production
     Economics                                                   6-1
6.2  Effects  of  New  Sulfuric  Acid Plant Construction  on the
     NSPS                                                       6-5
                                  iv

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                    TABLE OF CONTENTS (Concluded)

                                                                Page

7.0  FINDINGS AND RECOMMENDATIONS                               7-1

7.1  Findings                                                   7-1

     7.1.1  S02 NSPS                                            7-1
     7.1.2  Acid Mist NSPS (and Related Opacity Standard)        7-2

7.2  Recommendations                                            7-3

     7.2.1  S02 NSPS                                            7-3
     7.2.2  Acid Mist NSPS (and Related Opacity Standard)        7-4

8.0  REFERENCES                                                 8-1

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                        LIST OF ILLUSTRATIONS

Figure Number                                                    Page

     4-1       Contact Process Sulfuric Acid Plants
               Completed in the U.S. Since 1971                  4-4

     4-2       Gross Total Production of Sulfuric Acid:
               1971 to 1977                                      4-6

     4-3       Sulfuric Acid End Uses                            4-8

     4-4       Percent of Total Production of Sulfuric
               Acid in Captive Use                               4-9

     4-5       Contact-Process Sulfuric Acid Plant
               Burning Elemental Sulfur                          4-12

     4-6       Contact-Process Sulfuric Acid Plant
               Burning Spent Acid                                4-14

     4-7       Sulfuric Acid Plant Feedstock Sulfur
               Conversion vs. Volumetric and Mass S0£
               Emissions at Various  Inlet SC>2 Concentrations
               by Volume                                         4-18

     4-8       Sulfuric Acid Plant Concentrations of Mist
               for Mass Stack Emissions Per Unit of Production
               at Inlet S02 Volume Concentrations                4-22

     4-9       Dual Absorption Sulfuric Acid Plant Flow
               Diagram                                           4-27

     4-10      Vertical Tube Mist Eliminator Installation        4-32

     4-11      Vertical Panel Mist Eliminator  Installation       4-36

     4-12      Horizontal Dual Pad Mist Eliminator               4-38

     5-1       Contact  Process Sulfuric Acid Plant NSPS
               Compliance Test Results - S0_ Emissions           5-3

     5-2       Contact  Process Sulfuric Acid Plants NSPS
               Compliance Test Results - Acid  Mist Emissions     5-4
                                   vi

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                           LIST OF TABLES

Table Number                                                     Page

     4-1       Summary of New Sulfuric Acid Plant
               Completions Since the Promulgation of
               the NSPS                                          4-2

     4-2       Sulfuric Acid Plants Planned or Under
               Construction                                      4-3

     4-3       Sulfuric Acid Production (Mg of 100%
               H2S04)                                            4-5

     4-4       Sulfur Dioxide Conversion Efficiencies and
               Emissions for Four-Stage Converters               4-16

     4-5       Contact Process Sulfuric Acid Plant Built
               Since Promulgation of the NSPS                    4-25

     5-1       NSPS Compliance Test Results for Sulfuric
               Acid Plants                                       5-2

     5-2       NSPS Compliance Test Results for New
               Sulfuric Acid Plants Breakdown by Emissions
               Level                                             5-5

     5-3       Effect of Plant and Catalyst Age on S02
               Emission Level                                    5-10

     6-1       Basic Data Used in Catalyst Replacement
               Cost Calculations                                 6-3

     6-2       Effect of Catalyst Replacement on Cost of
               Production of Sulfuric Acid in a Dual
               Absorption Plant                                  6-4

     6-3       Projected Cumulative S(>2 Emissions from
               New Contact Sulfuric Acid Plants Added
               Between 1981 and 1984                             6-7

     6-4       Projected Cumulative Acid Mist Emissions
               From New Contact Sulfuric Acid Plants Added
               Between 1981 and 1984                             6-8
                                  vii

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1.0  EXECUTIVE SUMMARY




     The objective of this report is to review the New Source




Performance Standard (NSPS) for the sulfuric acid plant production




unit in terms of developments in control technology, economics and




new issues that have evolved since the original standard was




promulgated in 1971.  Possible revisions to the standard are analyzed




in the light of compliance test data available for plants built since




the promulgation of the NSPS.  The NSPS review includes the S(>2




emission and acid mist emission standards.  The opacity standard,




while included in the sulfuric acid plant NSPS, is not reviewed




separately since it is directly related to the acid mist emission




standard.  The following paragraphs summarize the results and




conclusions of the analysis, as well as recommendations for future




action.




1.1  Best Demonstrated Control Technology




     Sulfur dioxide and acid mist are present in the tail gas from




the contact process sulfuric acid production unit.  In modern




four-stage converter contact process plants burning sulfur with




approximately 8 percent S(>2 in the converter feed, and producing




98 percent acid, SO2 and acid mist emissions are generated at




the rate of 13 to 28 kg/Mg of 100 percent acid (26 to 56 Ib/ton)




and 0.2 to 2 kg/Mg of 100 percent acid (0.4 to 4 Ib/ton), respec-




tively.  The dual absorption process is the best demonstrated control
                                 1-1

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technology* for S(>2 emissions from sulfuric acid plants, while

the high efficiency acid mist eliminator is the best demonstrated

control technology for acid mist emissions.  These two emission

control systems have become the systems of choice for sulfuric acid

plants built or modified since the promulation of the NSPS.  Twenty-

eight of the 32 new or modified sulfuric acid production plants built

since 1971 and subject to NSPS incorporate the dual absorption pro-

cess; and all 32 plants use the high efficiency acid mist eliminator.

1.2  Current SO? NSPS Levels Achievable With Best Demonstrated
     Control Technology

     All 32 sulfuric acid production units subject to NSPS showed

compliance with the current S02 NSPS control level of 2 kg/Mg (4

Ib/ton).  The 26 compliance test results for dual absorption plants

showed a considerable range from a low of 0.16 kg/Mg (0.32 Ib/ton) to

a high of 1.9 kg/Mg (3.7 Ib/ton) with an average of 0.09 kg/Mg (1.8

Ib/ton).  The average S02 emission level obtained in the NSPS com-

pliance tests for dual absorption plants is about one order of magni-

tude lower than the S(>2 emission level obtained from uncontrolled

single absorption plants.   Information received on the  performance of

several sulfuric acid plants  indicates that low S02 emission
 It should be  noted  that  standards  of  performance  for new sources
 established under Section 111  of  the  Clean  Air Act  reflect emission
 limits achievable with  the best adequately  demonstrated technolog-
 ical system of  continuous emission reduction  (taking into considera-
 tion the cost of achieving such emission  reduction, as well as any
 nonair quality  health and environmental impacts and energy require-
 ments) .


                                  1-2

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results achieved in NSPS compliance tests apparently do not reflect




day-to-day S(>2 emission levels.  These levels appear to rise toward




the standard as the conversion catalyst ages and its activity drops.




Additionally, there may be some question about the validity of low




S02 NSPS values, i.e. less than 1 kg/Mg (2 Ib/ton), due to defects




in the original EPA Method 8.  Based on all of these considerations,




it is recommended that the level of SC>2 emissions as specified in




the current NSPS not be changed at this time.




1.3  Economic Considerations Affecting the S02 NSPS




     The cost of more frequent conversion catalyst replacement as a




method of maintaining low SC>2 emission values, i.e., below 1 kg/Mg




(2 lb/ ton), was estimated in this study.  Complete replacement of




catalyst in  the first three beds of the four-bed catalytic converter,




approximately three times as frequently as is normally practiced, was




estimated to result in an increase in operating cost of 55 cents/Mg




of 100 percent acid.  From an economic standpoint, this method would




not be feasible since pretax profits could be reduced by  20 percent




or more.




     Based on an estimated sulfuric acid plant growth rate of four




new production  lines per year between 1981 and 1984, a 50 percent re-




duction of the present S02 NSPS  level—from 2 kg/Mg  (4 Ib/ton) to 1




kg/Mg  (2 Ib/ton)—would result in a drop in the estimated percentage




SC>2 contribution of these new sulfuric acid plants to the total na-




tional SC>2 emissions, from 0.04  percent to 0.02 percent.  The




national impact of a more stringent SC>2 NSPS would be marginal due



                                 1-3

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to the very small decrease in 802 emissions (resulting from a

tighter standard) from the sulfuric acid plants projected to be built

during the 1981 through 1984 period.

1.4  Current Acid Mist Levels (and Related Opacity Levels)
     Achievable With Best Demonstrated Control Technology

     All 32 sulfuric acid production units subject to NSPS showed

compliance with the current acid mist NSPS control level of 0.075

kg/Mg of 100 percent acid (0.15 Ib/ton).  The NSPS compliance test

data are all from plants with acid mist emission control provided by

the high efficiency acid mist eliminator.  The data showed a wide

range with a low of 0.008 kg/Mg (0.016 lb//ton) to a high of 0.071

kg/Mg (0.141 Ib/ton), and an overall average value of 0.04 kg/Mg

(0.081 Ib/ton).  Acid mist emission  (and related opacity) levels are

unaffected by  factors affecting S02  emissions, i.e., conversion

catalyst aging.  Rather, acid mist emissions are primarily a function

of moisture levels  in the sulfur  feedstock and air fed to the sulfur

burner, and the efficiency of  final  absorber operation.  The order-

of-magnitude spread observed in NSPS compliance test values is prob-

ably a result  of variation in  these  factors.  Additionally, variabil-

ity in the original EPA  Method 8  may have contributed to this spread.

Making the acid mist  standard more  stringent  is not believed to be

practicable at this  time because  of  the need  to provide a margin of

safety due  to  in-plant  operating  fluctuations, which  introduce vari-

able quantities  of  moisture  into  the sulfuric acid production  line.
                                  1-4

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2.0  INTRODUCTION

     In Section 111 of the Clean Air Act, "Standards of Performance

for New Stationary Sources," a provision is set forth which requires

that "The Administrator shall, at least every four years,  review and,

if appropriate, revise such standards following the procedure

required by this subsection for promulgation of such standards."

Pursuant to this requirement, the MITRE Corporation, under EPA

Contract No. 68-02-2526, is to review 10 of the promulgated NSPS

including the sulfuric acid plant production unit.

     The main purpose of this report is to review the current

sulfuric acid standards for S02, acid mist and opacity and to

assess the need for revision on the basis of developments  that have

occurred or are expected to occur in the near future.  This report

addresses the following issues:

     1.  A review of the definition of the present standards
         and the NSPS monitoring requirements.

     2.  A discussion of the status of the sulfuric acid
         industry and the status of applicable control
         technology.

     3.  An analysis of SC>2, acid mist and opacity test results
         and review of level of performance of best demons-
         trated control technology for emission control.

     4.  A review of the impact of NSPS revision on sulfuric
         acid production economics, and the effect of new
         sulfuric acid plant construction on the NSPS.

    Based on the information contained in this report, conclusions

are presented and specific recommendations are made with respect to

changes in the NSPS.

                                 2-1

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3.0  CURRENT STANDARDS FOR SULFURIC ACID PLANTS




3.1  Background Information




     Prior to the promulgation of the NSPS in 1971, almost all




existing contact process sulfuric acid plants were of the single-




absorption design and had no S(>2 emission controls.  Emissions from




these plants ranged from 1500 to 6000 ppra SC<2 by volume, or from




10.8 kg of S02/Mg of 100 percent acid produced (21.5 Ib/ton) to




42.5 kg of S02/Mg of 100 percent acid produced (85 Ib/ton).




Several state and local agencies limited S02 emissions to 500 ppm




from new sulfuric acid plants, but few such facilities had been put




into operation (EPA, 1971).




     Many sulfuric acid plants utilized some type of acid mist con-




trol prior to 1971, but several had no controls whatsoever.  Uncon-




trolled acid mist emissions varied between 2 and 50 mg/scf, or from




0.4 to 9 Ib of H2S04/ton of 100 percent acid produced, the lower




figure representing emissions from a plant burning high-purity sul-




fur.  State and local regulatory agencies had only begun to limit




acid mist emissions to more stringent levels; i.e., some agencies had




adopted limits of 1 and 2 mg/scf, respectively, for new and existing




plants (EPA, 1971).




     It is estimated that S(>2 emissions from sulfuric acid plants




totalled 528,000 Mg (580,000 tons) in 1971 and 245,000 Mg (269,000




tons) in 1976 (Mann, 1978).  This represents a 54 percent drop in




S02 emissions from this industry in the first 5 years after the
                                 3-1

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promulgation of the NSPS for this pollutant.*  By 1976 sulfuric acid

plants, in compliance with the NSPS, represented 31 percent of the

sulfuric acid industry capacity (Stanford Research Institute, 1977).

     No corresponding data are available for the effect of the NSPS

on total acid mist emissions from the industry.

3.2  Facilities Affected

     The NSPS regulates sulfuric acid plants that were planned or

under construction or modification as of August 17, 1971.  Each sul-

furic acid production unit (or "train") is  the affected facility.

The standards of performance apply to contact-process sulfuric acid

and oleum facilities that burn elemental sulfur, alkylation acid,

hydrogen sulfide, metallic sulfides, organic sulfides, mercaptans or

acid sludge.  The NSPS does not apply to metallurgical plants that

use acid plants as control systems, or  to chamber process plants or

acid concentrators.

     An existing sulfuric acid plant  is subject to the promulgated

NSPS if:   (1) a physical  or operational change  in an  existing facil-

ity causes an increase  in the  emission  rate to  the atmosphere of any

pollutant  to which  the  standard applies, or (2) if in the  course of

reconstruction  of  the  facility, the  fixed capital cost of  the new

components exceeds  50  percent  of  the  fixed  capital cost  that would  be

required  to construct  a  comparable  entire new  facility that meets the

NSPS.
 *It  is not known what portion of this drop in SC>2 emissions  is  due
  to  NSPS-controlled plants or to existing plants  covered  by  State
  Implementation Plans (SIP).
                                  3-2

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3.3  Controlled Pollutants and Emission Levels

     The pollutants to be controlled at sulfuric acid plants by the

NSPS are defined by 40 CFR 60, Subpart H (as originally promulgated

in 36 FR 24881 with subsequent modifications in 39 FR 20794) as fol-

lows :

     1.  Standard for sulfur dioxide

         (a)  "On and after the date. . . no owner or operator sub-
         ject to the provisions of this subpart shall cause to be
         discharged into the atmosphere from any affected facility
         any gases which contain sulfur dioxide in excess of 2 kg per
         metric ton of acid produced (4 Ib per ton), the production
         being expressed as 100 percent 112804."

     2.  Standard for acid mist

         (a)  "On and after the date. . . no owner or operator sub-
         ject to the provisions of this subpart shall cause to be
         discharged into the atmosphere from any affected facility
         any gases which:

              (1)  Contain acid mist, expressed as 1^804, in
              excess of 0.075 kg per metric ton of acid produced
              (0.15 Ib per ton), the production being expressed as
              100 percent ^804.

              (2)  Exhibit 10 percent opacity, or greater.  Where the
              presence of uncombined water is the only reason for
              failure to meet the requirements of this paragraph,
              such failure will not be a violation of this section."

     The values of these standards were derived from the following

data sources:

      1.  A literature search revealed that over 20 dual-absorption
          plants had been operating successfully in Europe for
          several years using both elemental sulfur and roaster gas
          as feed and that three of these plants produced maximum
          S(>2 emissions ranging from 91 to 260 ppm 862 by volume,
          or from 0.6 kg of 802 per M8 of acid produced (1.2
          Ib/ton) to 1.6 kg of 802 Per M8 of acid produced (3.1
          Ib/ton).

                                 3-3

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     2.  The two plants  tested and evaluated by EPA engineers were
         a plant of typical dual-absorption design and a single-
         absorption spent-acid burning plant that used a sodium
         sulfite-bisulfite scrubbing process to recover SC>2 from
         tail gas.

     The dual-absorption sulfuric acid plant was the first of its

kind in the U.S. and was used by EPA as part of the best demonstrated

control technology rationale for the NSPS  for S02 emissions.  Since

1971,  17 dual-absorption plants have been  built in the U.S. with a

total  of 32 individual sulfuric acid units (or trains).  This process

has become the best demonstrated control technology for S(>2 control

in the industry.  No new sodium sulfite-bisulfite scrubbing units for

S(>2 abatement have been  installed on sulfuric acid plants built in

the U.S.

     Emission tests from both the original dual-absorption sulfuric

acid plant and the single  absorption plant with sodium sulfite-sodium

bisulfite scrubbing,  indicated  that both operations were capable of

maintaining SC>2 and acid mist emissions below 2.0 kg/Mg (4 Ib/ton)

and 0.075 kg/Mg (0.15  Ib/ton),  respectively, at full  load operations.

Additionally, control  of acid mist below 0.075 kg/Mg  (0.15 Ib/ton) at

these  plants, resulted in  no visible emissions  from the stack,  i.e.,

opacity was below  10  percent.   Continuous  stack monitoring at these

plants indicated  that  at full  load,  the  plants  could  be consistently

operated  so  that  S(>2  emissions  would be  kept within the limits  of

the  performance standard (EPA,  1971).   In  Section 5.0 of  this report,

NSPS emission test results for  SC>2 and  acid mist are  presented  for
                                   3-4

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all the new sulfuric acid units completed since the promulgation of




the standard.




3.4  Testing and Monitoring Requirements




     3.4.1  Testing Requirements




     Performance tests to verify compliance with 802, acid mist and




opacity standards for sulfuric acid plants must be conducted within




60 days after the plant has reached its full capacity production




rate, but not later than 180 days after the initial start-up of the




facility (40 CFR 60.8).  The EPA reference methods to be used in




connection with sulfuric acid plant testing include:




     1.  Method 8 for the concentrations of S02 and acid mist




     2.  Method 1 for sample and velocity traverses




     3.  Method 2 for velocity and volumetric flow rate




     4.  Method 3 for gas analysis.




     For Method 8, each performance test consists of three separate




runs each at least 60 minutes with a minimum sample volume of 1.15




dscm (40.6 dscf).  The arithmetic mean of the three runs taken is the




test result to which compliance with the standard applies (40 CFR




60.8).




     The sulfuric acid production rate, expressed as Mg/hr of 100




percent 112804, is to be determined during each testing period by




suitable methods and confirmed by a material balance over the




production system.  Sulfur dioxide and acid mist emissions in kg/Mg
                                 3-5

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of 100 percent H2S04 are determined by dividing the emission rate




in kg/hr by the hourly 100 percent acid production rate.




     3.4.2  Monitoring Requirements




     SC>2 emissions in the tail gas from sulfuric acid plants are




required to be continuously monitored.  Continuous S02 monitoring




instrumentation should be able to:  (1) provide a record of




performance and (2)  provide intelligence  to plant operating personnel




such that suitable corrections can be made when the system is shown




to be out of adjustment.  Plant  operators are required to maintain




the monitoring equipment  in calibration and to furnish records of




SOo excess emission  values  to  the Administrator of EPA or to the




responsible State  agency.




     Measurement  principles used in the gas analysis  instruments




are:




     1.   Infrared  absorption




     2.   Colorimetric  titration  of  iodine




     3.   Selective permeation  of SC>2  through  a membrane




     4.   Flame photometric  measurement




     5.   Chromatographic measurement




     6.   Ultraviolet absorption.




The  ultraviolet  absorption  system and the iodine  titration method




have received  widespread application  for  SC>2  measurement  in  sul-




furic  acid  plants subject to  NSPS (Calvin and Kodras, 1976).
                                   3-6

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     The continuous monitoring system is calibrated using a gas




mixture of known 862 concentration as a calibration standard.




Performance evaluation of the monitoring system is conducted using




the S02 portion of EPA Method 8.




     Excess S02 emissions are required to be reported to EPA (or




appropriate state regulatory agencies) for all 3-hour periods  of such




emissions (or the arithmetic average of three consecutive 1-hour




periods).  Periods of excess emission are considered to occur when




the integrated (or arithmetic average) plant stack S02 emission




exceeds the standard of 2 kg/Mg (4 Ib/ton) of 100 percent




produced.
                                 3-7

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4.0  STATUS OF CONTROL TECHNOLOGY

4.1  Status of Sulfuric Acid Manufacturing Industry Since
     the Promulgation of the NSPS

     4.1.1  Geographic Distribution

     In 1971 there were 167 contact process sulfuric acid and oleum

plants in the U.S.  By 1977 the number of plants had decreased to

150.  Thirty-two sulfuric acid units subject to NSPS are included in

these 150 plants.  Table 4-1 provides a summary by EPA region of the

number of units subject to NSPS and their design tonnage.  Table 4-2

is a tabulation of the eight new units planned or under construction

which will be coming on-line by 1980.

     Figure 4-1 shows the geographical distribution of contact pro-

cess sulfuric acid units completed since 1971.  The heaviest concen-

tration of new units is in Region IV (Southeast).  The high concen-

tration of sulfuric acid units constructed in Florida since 1971 can

be explained by the presence of rich phosphate rock deposits.  Eighty

percent of the phosphate rock mined goes into the manufacture of

phosphatic fertilizers, which is also the end use of 60 percent of

the total U.S. sulfuric acid production (Bureau of Mines, 1975;

1978).  Since most sulfuric acid is consumed near its point of manu-

facture, units with production dedicated for phosphate fertilizer

manufacture will, usually, be located near phosphate rock deposits.

     4.1.2  Production

     U.S. production of sulfuric acid in 1977 totalled approximately

30.9 million Mg (34 million short tons), representing an average


                                 4-1

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                                    TABLE 4-1

                  SUMMARY OF NEW SULFURIC ACID PLANT COMPLETIONS
                        SINCE THE PROMULGATION OF THE NSPS
EPA Region
II
IV
V
VI
IX
X

Units
In Production
(1971-1977)
2
18
1
4
1
6
Total 32
Average
Plant
Design Capacity3
(100% H2S04)
Mg/day (TPD)
1,820 (2000)
28,670 (31,500)
230 (250)
5,370 (5900)
1,640 (1800)
1,890 (2080)
39,610 (43,530)
1200 (1300)
Percent of Total
New Design
Capacity
4.6
72.3
0.6
13.6
4.1
4.8
100.0

aThese units all use the double absorption process except one plant (one
 new unit and two existing units) in Region VI and one plant (two new units)
 in Region X which use a single absorption process with ammonia scrubbing.
 One new plant in Region V is currently retrofitting from single to double
 absorption.

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4S>
I
                                                       TABLE 4-2


                                   SULFURIC ACID PLANTS PLANNED OR UNDER CONSTRUCTION
Region
III
IV

V
VI
VII

Company
Getty Oil
Occidental
Chemical Co.
Royster Co.
Shell Chemical
American
Cyanamid Co.
U.S. Army
Sunflower Arsenal

Plant Location
Delaware City,
Del.
White Springs,
Fla.
Mulberry, Fla.
Wood River,
111.
Fortier, La.
Lawrence, Kan.
TOTAL
No. of
Units
2
2
1
1
1
1
8
Plant Capacity
Mg/day (TPD)
540 (600) a
3640 (4000)b
720 (800)
230 (250)
1460 (1600)
270 (300)
6860 (7500)
Anticipated
Startup Date
1980
Late 1979
Late 1979
Fall, 1979
Fall, 1978
1980

Source
Hansen ,
1978
Hansen,
1978
Hansen,
1978
Williams,
1977
Chem. Eng. ,
1977
Hansen,
1978

     a2 - 270 Mg/day  (300 TPD)  units.


     3 2 - 1820 Mg/day  (2000 TPD)  units.
     'Retrofit of  dual absorption system.

-------
LEGEND
 • Units in operation
 O Units planned or under
   construction as of 1978
                                      FIGURE 4-1
                      CONTACT PROCESS SULFURIC ACID PLANTS
                          COMPLETED IN THE U.S. SINCE 1971

-------
yearly increase of 1.9 percent (575,000 Mg) since 1971  (Department of

Commerce, 1976; Chemical and Engineering News, 1978).   Figure 4-2

shows total annual production of sulfuric acid for 1971 to 1977,

including production by the lead chamber process, which has almost

been phased out of the industry (EPA, 1976).  Production by the con-

tact process alone represented 99.3 percent of total production in

1971 and increased to 99.8 percent in 1976 (Chemical and Engineering

News, 1978).  Table 4-3 shows the increase in sulfuric  acid produc-

tion by region from 1975 to 1976.  Production in the South represen-

ted 70 percent of the U.S. total in 1976 (Department of Commerce,

1976).

                              TABLE 4-3

                      SULFURIC ACID PRODUCTION
                         (Mg of 100% H2S04)
Region
Northeast
North Central
West
South
1975
1,728.2
2,804.4
4,110.7
19,640.9
1976
1,527.2
2,636.9
4,445.5
20,667.9
Change
(%)
-12
-6
+8
+5
Total Production
1976(%)
5
9
16
70
Source:  Department of Commerce, 1976.


     The growth of the sulfuric acid industry since the promulgation

of the NSPS has been largely dominated by the growth in the phosphate

fertilizer industry in the early and mid-seventies.  Of the 32

                                 4-5

-------
fi
o
CO
CO
c
5
r-l
             1971  1972   1973   1974   1975   1976   1977
                                YEAR

                SOURCE:  Department of Commerce,  1976; 1977.
                         FIGURE 4-2
        GROSS TOTAL PRODUCTION OFSULFURIC ACID:
                        1971 TO 1977
                            4-6

-------
contact process sulfuric acid units subject  to NSPS,  the  output  of at




least 24 units is dedicated to the acidulation of  phosphate  rock as




the first step in the manufacture of wet process phosphate and acid




superphosphate fertilizers.




     About 68 percent of the contact process sulfuric acid is  pro-




duced from elemental sulfur, representing approximately 85 percent of




the total sulfur consumption in the U.S.  The remaining acid is  made




from iron pyrites (4.5 percent);  tail gas from smelters (9 percent);




and hydrogen sulfide, spent alkylation acid, and acid sludge from




petroleum refineries (18.5 percent).




     Sulfuric acid is produced in various concentrations  and in  four




grades:  commercial, electrolyte  or high purity, textile  (having low




organic content), and chemically  pure (C.P.) or reagent grade.  The




various end uses of sulfuric acid are shown  in Figure 4-3.   In addi-




tion to the manufacturing of fertilizer, other major uses are  petro-




leum refining (7 percent), other  inorganic chemicals (6 percent), and




copper ores (5 percent).




     An increasing number of sulfuric acid consumers, specifically




fertilizer manufacturers, produce their own  sulfuric acid for captive




use.  The ratio of production for merchant sales  (or shipments)  to




production for captive use decreased from 2:1 in 1939 and 1:1  in 1966




to 0.7:1 in 1973.  This relationship is shown in Figure 4-4.
                                 4-7

-------
                                                    Phosphatic fertilizer
                                                    Petroleum refining
                                                    Other  inorganic chemicals
                                                    Copper ores
                                                    Unidentified
                                                    Other  chemical products
                                                    Industrial organic chemicals
                                                    Nitrogenous fertilizers
                                                    Inorganic pigments 4 paints
                                                    Synthetic rubber & other plastic
                                                    Pulp mills
                                                    Cellulosic fibers
                                                    Detergents
                                                    Steel  pickling
        Uses  under 1% are:  uranium & vanadium ore,
        other ore, other paper products, drugs,
        pesticides, other agricultural chemicals,
        explosives, water treating compounds,
        rubber  & miscellaneous plastic products,
        nonferrous metals, other primary metals,
        and  storage batteries (acid).  There were
        no sulfuric acid exports in 1977.
SOURCE:   Bureau  of  Mines,  1978.
                                        FIGURE 4-3
                                SULFURIC ACID END USES
                                          4-8

-------
I
SO
          100
          90 -
           80 -
           70 -
           60 -
B
w
   50 -
           40 -
           30 -
           20 -
           10 -
                 SOURCE:  EPA,  1977; Chemical and Engineering News,  1978.
         1939                      1966       1972   1973   1974
                                      YEAR •
                                 FIGURE 4-4
             PERCENT OF TOTAL PRODUCTION OF SULFURIC ACID IN
                                CAPTIVE USE
                                                                        1975   1976

-------
     4.1.3  Industrial Trends




     U.S. sulfuric acid production in 1968 was 25.9 million metric




tons, and approximately 30.9 million metric tons in 1977.  Production




is expected to increase to 49 and 80 million metric tons by the years




1980 and 1990, respectively.




     Tables 4-1, 4-2, 4-3 and Figure 4-1 show the strong trend




towards siting sulfuric acid plants in the southern states.  Over 86




percent of the new sulfuric acid design capacity is located in EPA




Regions IV and VI.   In 1971 EPA projected two new units to be coming




on-line each year for the next several years (EPA, 1971). On the




average, six new units have actually been completed each year since




1971.  Of the total  of 32 new units, 15 are located in Florida. Most




of the sulfuric acid production units in the South are captive in




nature with the output going into phosphate fertilizer production at




the  same plant complex.   In 1976, over 70 percent of the total




national production  of new sulfuric acid was in  the South.  There-




fore, based on  the high  phosphate rock concentrations  (Department of




the  Interior, 1973)  on  the new construction in Region  IV, and on the




production  trends of sulfuric acid  (Figure 4-4),  three of  the four




units projected to be coming on-line each year will most probably be




located  in  the  South.




     The  location of sulfuric acid  plants is not dependent on the




location of  sources  of  sulfur, but  rather on  the location  of various




industries  associated with  the use  of sulfuric  acid,  i.e.  the
                                  4-10

-------
fertilizer and petroleum refining industries.  The future supply of
sulfur for new acid will lean more heavily on recovered sulfur from
petroleum production and sulfur dioxide abatement and less on mined
(Frasch) sulfur.
4.2  Contact Process for Sulfuric Acid Production
     All contact sulfuric acid manufacturing processes incorporate
three basic operations:  (1) burning of sulfur or sulfur-bearing
feedstocks to form 802, (2) catalytic oxidation of S02 to 863,
and (3) absorption of 803 in a strong acid stream.  The several
variations in the process are due principally to differences in feed-
stocks.  The least complicated systems are those that burn elemental
sulfur.  Where there are appreciable organics and moisture as in
spent acid and acid sludge, additional operations are required to
remove moisture and particulates prior to catalysis and absorption.
The composition of feedstock can affect the sulfur conversion ratio,
the volume of exhaust gases and the character and rate of pollutant
releases.
     4.2.1  Elemental Sulfur Burning Plants
     Figure 4-5 is a schematic diagram of a contact sulfuric plant
burning elemental sulfur.  Sulfur is burned to form a gas mixture
which is approximately 8 to 10 percent sulfur dioxide, 11 to 13
percent oxygen, and 79 percent nitrogen.  Combustion air is predried
by passing through a packed tower circulating 98 percent sulfuric
acid.  Air drying minimizes acid mist formation and resultant corro-
sion throughout the system.
                                 4-11

-------
I
M
NJ
      RYING
     TOWER
      AIR
BLOWER
 LIQUID
 SULFUR
                    STEAM DRUM


                SLOWDOWN •*•
                                  ACID
                                 COOLER
              SULFUR
               PUMP
    STORAGE


SOURCE:  EPA, 1971.
                                                                          STEAM  TO
                                                                            •ATMOSPHERE
                                  FURNACE     BOILER    BOILER   CONVERTER

                                                      BOILER FEED WATER	'
                                                                 1
          ECONOMIZER
              ABSORPTION
               TOWER
_T
-*„
                                WATER
 ACID
COOLER
                                                     TTI  ACID PUMP
                                                     Lcb|   TANK
                                                    	> PRODUCT
                              FIGURE 4-5
          CONTACT-PROCESS SULFURIC ACID PLANT BURNING
                          ELEMENTAL SULFUR

-------
     802 i-s oxidized to 803 in the presence of a catalyst con-




taining approximately 5 percent vanadium pentoxide.  The temperature




of the reacting gas mixture increases as the composition approaches




equilibrium.  Maximum conversion to 803 requires several conversion




stages with intermediate gas cooling.  The gas exiting the converter




is cooled in an economizer to temperatures between 230° and




260°C, and 803 is absorbed in 98 percent sulfuric acid circulat-




ing in a packed tower.  The acid content and temperature must be




carefully controlled to prevent excessive 863 release.




     If fuming sulfuric acid (oleum) is produced, the 803 contain-




ing gases are first passed through an oleum tower which is fed with




acid from the 98 percent absorption system.  The gas stream from the




oleum tower is passed through the 98 percent acid absorber for recov-




ery of residual sulfur trioxide.




     4.2.2  Spent Acid and Other By-Product Plants




     Where spent acid, sludge, and similar feedstocks are employed,




the processes are more elaborate and expensive than sulfur-burning




plants due to the fact that the sulfur dioxide containing gas stream




is contaminated.  Gases must be cleaned if high-quality acid is to




be produced.  This requires additional gas cleaning and cooling




equipment to remove dust, acid mist, and gaseous impurities, along




with excessive amounts of water vapor.  Purification equipment con-




sists of cyclones, electrostatic dust and mist precipitators, plus




scrubbers and gas-cooling towers in various combinations.  Figure 4-6
                                 4-13

-------
•e-
                     i—SPENT ACID
                      -SULFUR
                      - FUEL OIL
         WATER
                        FURNACE
  DUST   WASTE HEAT   GAS      GAS     ELECTROSTATIC
COLLECTOR BOILER   SCRUBBER  COOLER   PRECIPITATORS
                                                                                      STRIPPER
                                                                                      .  TO
                                                                                     ATMOSPHERE
                                            *>  ACID TRANSFER «
               DRYING
               TOWER
                                                  ABSORPTION
                                                    TOWER
                93% ACID PUHP TANK  COOLER
                         ACID COOLERS    98% ACID PUMP TANK
              SOURCE:   EPA, 1971.
                                                 FIGURE 4-6
                                 CONTACT-PROCESS SULFURIC ACID PLANT
                                           BURNING SPENT ACID

-------
shows one possible configuration of a spent acid plant.   The balance




of the process following the drying tower is essentially the same as




an elemental sulfur-burning plant.




     A few plants burning only hydrogen sulfide or hydrogen sulfide




plus elemental sulfur use a simplified version of the above process.




Wet gases from the combustion chamber and waste heat boiler are




charged directly to the converter with no intermediate treatment.




Gases from the converter flow to the absorber, through which 70 to 93




percent sulfuric acid is circulating.  In such a "wet gas" plant much




of the sulfur trioxide from the converter is in the form of acid mist




which is not absorbed in the absorption tower.  High efficiency mist




collectors are utilized both to recover product and to prevent exces-




sive air pollution.




4.3  Emissions from Contact Process Sulfuric Acid Plants




     4.3.1  Sulfur Dioxide




     Mass S02 emissions vary inversely as a function of the sulfur




conversion efficiency (i.e., fraction of SC>2 oxidized to 803).




For sulfur burning plants, the inlet SC>2 concentration to the cata-




lytic converters normally ranges between 7.5 and 8.5 percent but can




be as high as 10.5 percent.  Conversion efficiency depends upon the




number of stages in the catalytic converter and, to a lesser extent,




on the amount of catalyst.




     Most plants built prior to 1960 had only three catalyst stages,




and overall conversion efficiencies were approximately 95 to 96
                                 4-15

-------
percent.  Sulfur burning plants built since 1960 generally have  four

stages* and efficiencies normally range between 96 and 98 percent.

For three-stage plants, S02 release ranges between 28 and 35 kg/Mg

and for four-stage plants, between 13 and 28 kg/Mg.

     Spent acid plants followed the same design trend.  Most three-

stage plants were built prior to 1960 and four-stage plants have

usually been built after 1960.  Typical S02 concentrations in the

converter feed, conversion efficiencies, and resultant emissions for

plants burning sulfur, l^S or primarily acid sludge are given in

Table 4-4.

                              TABLE 4-4

        SULFUR DIOXIDE CONVERSION EFFICIENCIES AND EMISSIONS
                      FOR FOUR-STAGE CONVERTERS

                                       Hydrogen Sulfide
                                        (with some other     Acid
    Feedstock	Sulfur    sulfur compounds)   Sludge
S02 in converter feed,     7.5  to 8.5          7           6 to 8
  % by volume

Sulfur  conversion  to  803,   96  to 98
  % by weight

S02 emissions,              13  to 28        25 to 43       15 to 56
  kg/Mg 100% acid

S02 emissions,              1500  to         1500  to         1500 to
  ppm by  volume	4000	4000	4000

Source:   EPA,  1971.
 *There  have  been a  number of  five-stage  converters included in dual
  absorption  plants  built since 1971  (see Section 5.2.1).
                                  4-16

-------
     Exit S02 concentrations from contact plants vary as a func-




tion of the SO2 content of dry gases fed to the converter.  Where




SC>2 strength is relatively low, there is a significantly greater




volume of gases handled per ton of acid produced.




     A plant with 4.0 percent SC>2 in the dry gases to the converter




will exhaust over two and one-half times the gas volume of a plant




operating on a 10.0 percent S(>2 stream, i.e., 4600 sm^/Mg* vs.




1700 sm3/Mg.




     The relationship between mass emission rate, sulfur conversion




and SC>2 exit concentrations has been plotted in Figure 4-7 for




plants of various S(>2 strengths.  The curve can be used for uncon-




trolled single absorption plants and for those plants equipped with




tail gas removal systems or with the dual absorption process.  It can




be seen that the NSPS of 4.0 Ib per ton of acid requires 99.7 percent




sulfur conversion (dual absorption) or an equivalent 802 exit gas




concentration of 380 ppm.  This conversion is achieved by the dual




absorption  technique.  At 98 percent conversion, which is optimum for




most single absorption contact plants, exit SC>2 concentrations can




vary from 900 to 2500 ppm as the inlet SC^ content varies from 4.0




to 10.0 percent.




     4.3.2  Acid Mist Formation




     The sulfuric acid liquid  loading in the tail gas from the




absorber in a contact process  plant is classified into two broad




areas based on the acid particle size:   (1)  spray, which is defined
*Standard cubic meter per metric ton.




                                  4-17

-------
                             Sulfur Conversion - Percent of Feedstock Sulfur
   10,000
     5000
1
     100
                                               10.0    15   20     30       50
                          S02 Emissions  - Lb Per Ton of 100% HjSO^ Produced
        Source:  EPA, 1976
                                       FIGURE 4-7
                   SULFURIC ACID PLANT FEEDSTOCK SULFUR CONVERSION
                    VS. VOLUMETRIC AND MASS SO. EMISSIONS AT VARIOUS
                          INLET SO. CONCENTRATIONS BY VOLUME
                                         4-11

-------
as acid particles larger than 10 microns,  and (2) mist,  which is

defined as acid particles smaller than 10 microns (Duros and Kennedy,

1978).*

     Spray is primarily formed by mechanical generation  of particles

that are formed when a gas and liquid are mixed together.  Examples

of spray formation are liquid droplets formed by nozzles and liquid

entrainment leaving a packed tower.  A typical tower design in a

modern acid plant will have a spray loading of 175 to 350 milligrams

per actual cubic meter (mg/AM^) under normal operating conditions.

     Acid mist formation is more complex to define than  spray.  There

are two primary mechanisms of acid mist formation.  The  first mechan-

ism is the reaction between two vapors forming a liquid  or solid

(i.e., change of state where volume reactants is much greater than

volume products).  This is best exemplified by the reaction of sulfur

trioxide and water vapors to form submicronic sulfuric acid mist.

                 H2°(g)  +  S°3(g)	 H2S04(£)

     The second mechanism of mist formation is vapor condensation in

the bulk gas phase by lowering the gas stream temperature beyond the

liquid dew point.  The dew point of a sulfuric acid under typical

conditions is about 300° to 350°F.  However, because of  the uncer-

tainties of bulk phase temperature differences, nonideal conditions

and wall effects, the gas stream temperature is normally maintained

between 375° to 425°F.  This is done to insure that acid mist is not

present to attack metal equipment.
*The EPA definition of acid mist (Method 8) includes both liquid
sulfuric acid particles and 803 gas.

                                  4-19

-------
     The formation of sulfuric acid mist in an acid plant is due to a




combination of these mechanisms.  When a gas stream containing 803,




H2S04 and 1^0 vapor is cooled below the liquid dew point, the




H2&04 vapor condenses and the 803 vapor and t^O vapor combine




to form H2S04, which also condenses.  Submicronic mist particles




will be formed when the gas is cooled faster than the condensable




vapor can be removed by mass transfer (i.e., "shock cooling").  The




conditions for "shock cooling" are present in the absorbing towers of




an acid plant.




     The practical key to controlling mist formation is to keep the




H20 content in a gas stream as low as possible.  As an example of




mist forming capability of extraneous water, 1 mg of water vapor




carried through the plant has the potential to produce 190 mg/m^ of




submicronic acid mist (Duros and Kennedy,  1978).  The water content




of the gas stream can be  increased by:




     1.  High organic content of contaminated elemental sulfur




         (sulfur burning  plants only),




     2.  Acid mist carryover from upstream equipment,




     3.  Inadequate drying of the process  air stream, and




     4.  Low absorbing tower acid strengths




At acid strengths below 98.5 percent, the  acid begins to exert a mea-




surable water vapor pressure.  The optimum absorbing tower acid has




the minimum vapor pressure of both water  (minimizing mist  formation




problems) and sulfur trioxide (minimizing  803 slippage).
                                  4-20

-------
     In oleum producing plants, greater quantities and a much finer




mist are produced.  From 85 to 95 weight percent of the particles are




less than 2 microns in diameter as compared with about 30 percent




less than 2 microns for 98 percent acid production.  Acid mist emis-




sions prior to control equipment range between 0.2 to 2 kg/Mg for




sulfur burning contact plants producing no oleum to about 0.5 to 5




kg/Mg for spent acid burning plants producing oleum, based on an 8




percent S(>2 feed to the converter.




     Spent acid plants characteristically form acid mist in the early




stages of the process.  This requires mist removal prior to drying




and oxidation as well as  from  the tail gas after absorption.




     "Wet gas" plants burning  hydrogen sulfide deliberately form acid




mist by not drying the process  gas.  Much of  this mist  is recovered




as product acid with gas  cooling equipment and high efficiency mist




eliminators or electrostatic precipitators.




     For a given  mass emission rate, acid mist concentrations vary as




a  function of  the exhaust gas  volume and, thus,  the S02 control  of




the  gases  fed  to  the converter.  Figure  4-8  shows  a relationship




between mass  emission  rates  and concentrations  over a range  of S(>2




strengths.  The curves  can be  used with  any  gas  stream before or




after  mist eliminators,  provided  there  is no dilution.




     4.3.3  Visible Emissions  (Opacity)




     Acid  mist in exhaust gases creates  visible  emissions  ranging




 from white  to blue depending on particle size,  concentration and






                                  4-21

-------
0.10
 0.01
   SOURCE:
0.02    0.03  0.04           0.10       0.20   0.30    0.50

 ACID MIST EMISSIONS, Ib H2S04/T OF 100 PERCENT H2 S04 PRODUCED

EPA,  1977.
                            FIGURE 4-8
          SULFURIC ACID PLANT CONCENTRATIONS OF MIST
              FOR MASS STACK EMISSIONS PER UNIT OF
        PRODUCTION AT INLET SO2 VOLUME CONCENTRATIONS
                               4-22

-------
background.  Where there is no control of mist, opacities generally




range from 80 to 100 percent.




     The effect of acid mist on opacity is more dependent on the size




of the mist particle than on the quantity of mist.  The smaller par-




ticles scatter light more, producing a denser plume.  Nevertheless,




it has been demonstrated that opacity of the plume from an efficient




863 absorber a function of acid mist concentration and that visible




emissions can be eliminated by minimizing acid mist levels in the




acid plant tail gas, through the use of a good mist eliminator.  At




the current NSPS acid mist control level, there are essentially no




visible emissions.




     4.3.4  Oxides of Nitrogen




     Nitrogen oxides present in the converter gas also cause acid




mist emissions, since they reduce the efficiency of the absorption




tower.  Nitrogen oxides may result from the fixation of atmospheric




nitrogen in high temperature sulfur furnaces, or may be formed from




nitrogen compounds in the feedstocks.  Nitrogen oxides can be held




to a reasonable minimum by using the same techniques which have




been applied to steam generators.  For instance, in the decompo-




sition of spent acid containing nitrogen compounds, operation at




furnace temperatures less than about 2000°F and a low oxygen con-




tent will generally keep nitrogen oxides concentrations below 100




ppm.
                                  4-23

-------
4.4  Control Technology Applicable to the NSPS Control of S02
     Emissions from Contact Process Sulfuric Acid Plants

     There are a few physical mechanisms and many chemical means of

removing SO2 from gas streams.  Almost any soluble alkaline materi-

al will absorb a significant fraction of 802 even in a crude scrub-

ber.  For years, sulfur dioxide has been removed from many process

gases where the 802 adversely affected the product.  The problems

of removing 802 from acid plant gases are principally that of find-

ing the least expensive mechanism consistent with minimal formation

of undesirable by-products.  The control processes in use by the sul-

furic acid industry (in those units installed since the promulgation

of the NSPS), are reviewed below.

     4.4.1  Dual Absorption Process

     The dual absorption process (used partially as the basis of the

rationale for the SC>2 NSPS) has become the SC>2 control system of

choice by the sulfuric acid industry since the promulgation of the

NSPS.  This can be seen by examination of Table 4-5, which presents a

tabulation of the new sulfuric acid units built since the promulga-

tion of the NSPS together with their locations, design capacities,

basic process design, and 502 and ac:"-d mist control technologies.

Out of 32 new units built since the promulgation of the NSPS, 28 have

employed the dual absorption process for S02 control.  This process

offers the following advantages over other SC>2 control processes:

     •  As opposed to single absorption with scrubbing, a greater
        fraction of the sulfur in the feed is converted to sulfuric
        acid.


                                 4-24

-------
                                                                    TABU »-5



                                      CO.TTACT PROCESS  1UIHJ8R ACI1) PLANTS BUILI SINCF PKOHUU.AriON 01 THh SSPS
EPA Region
11

IV












V

VI



IX


I




Company

NL Industries. Inc

Cardliler. Ine
Agrlco Chemical
Inc
CF Chemlcele. Inc
CF Chemicals. Inc
H R Grace I Co
International Hlner
i Chemical Corp
Occidental Petro-
leum Corp
American Cyanamld C

Hlsslsslppl Cheml-
cel Carp


Texas Gulf. Inc


Anlln Chemical
Corp»

Agrlco Chcm Co
reeport Chen Co
ota 4 Uses

alley Nitrogen
Frod . Inc


eker Industries
R Slmplot Co


llled Chen Corp
State and Locallt
Hotf Jersey
Sayrevllle
Florida
Taapa
So Pierce
Bartw
Plant City
Bartotf
Now Kales
White Springe
ieorttle
Savannah
HlsslsalDDl
Paacsgoula

to Carolina
Lee Creek

Illinois
Hood River
•ouislana
Donaldsonvllle
ncle Sam
exae
eer Park
allfornla
aim

lano
onda
ocatello

Mhlns-ton


rear
CoBpleiei

1973

1976
1975
1975
1974
1976.1977
1975
1975
19-5

1975


1975


1974

1974
1974


1975


1974
1976



TOTALS
AVERAGE
No o
Unit

2

1
2
1
2
3
3
2
1

1


2


1

2
1
1

1


1
2


3
32
Plant
Doalgn Capaclt
(1001 HjSOj)
IS /day (TPD)

1.820 (2.000)

2.370 (2.600)
3.800
3 280 (2.000)
2,910 (3.200)
4.370 (4,800)
5.460 (6.000)
3.280 (3.600)
720 (800)

1.370 (1,500)


2.7W (3.000)


230 (250)

3,090 (3,600)
1.46C (1.600)
640 ( 700)

1.640 (1,800)


770 ( 850)
820 ( 900)


300 ( 330)
39,610 (43,530)
1.740 ( 1.1«)
Procaas Design
Single
















X



K




X




Dual

X

,"
X
X
It
."
X

ft


X




,b
X


b
X


X


xe

Emissions Control System
S02

Process

Procees
Procsss
Process
Process
Frocees
Process
Process
Process

Procaas


Process


Holeeulsr Sieve

Process
Process
Amnonla
Scrubbing
recess


'roeeas
Scrubbing

rocess



Hist Eliminator

Fiber Hist Lllmlutor
York "S" Hist
Eliminator
Brink Fiber n-v
Hist Rlimlnator
Brink Fiber H-V
Hist Eliminator
Fiber Hist Eliminator
Brink Fiber Met
Ellalnator
Parsan-York Doub la Con-
tact Hlat Eliminator
Hist Ellmlnstor

Bayer/Lurgl Hist
Ellmlnstor

Brink Fiber Hist
Ellmlnstor

Fiber Hist Eliminator

York "S" 2 Stags Hash
Hist Eliminator
Fiber Hlat Eliminator
Fiber lilst Eliminator

Brink Fiber Hist
Eliminator

rink Fiber Hist
Eliminator
Brink Fiber Hist
Eliminator

Fiber Hlat Ellainator



CDS'. 1978

CDS. 197.-
CD5, 1978
CD* 1478
CDS. 1"7S
CDS. 1978
CDS. 19-8
CDS. 147B
FCDCo . 1977

CDS. 1978


CDS, 1978


Ullllams. 1977

Sprulell, 1978
Sprulell 19)8
Sprulell. 1978

Reynolds 1977


Prouder. 197B
Pleader. 1978


Hooper, 1978

 One of these units  is of 1



Source   MITRE Corp  . 1978. PEDCO.  Inc  .  1977

-------
     •  There are no by-products.

     •  Contact acid plant operators are familiar with the operations
        involved.

     Figure 4-9 is a process flowsheet of the dual absorption

process.  The SO-j formed in the first three converter stages is

removed in a primary absorption tower and the remainder of the gas  is

returned to the final conversion stage(s).  Removal of a product of a

reversible reaction

                     S02 + 1/2 02 -*S03

drives the oxidation further toward completion approaching the

reaction equilibrium expressed by:
                        K =           1/2
                             (S02)  (02)

where K is the reaction equilibrium constant peculiar to the tem-

perature of the reaction and the parenthetical entities are the molar

quantities of the gases involved.  The resulting 803 is absorbed in

a secondary absorption tower obtaining at  least 99.7 percent overall

conversion of the sulfur to  sulfuric acid.

     The dual absorption process permits higher inlet S02 concen-

trations than normally used  in  single absorption plants since the

second conversion step effectively handles  the residual S02 from

the first conversion  step.   Higher inlet S02 concentrations permit

a reduction in equipment size which partially offset the cost of the

additional equipment  required for  a dual absorption plant.  The dual

absorption equipment  occupies little more  space than a conventional

plant, even though  an additional absorber  is required.

                                   4-26

-------
I
CO
                  98% ACID   PRIMARY    HEAT     CONVERTER    ECONOMIZER  SECONDARY  98% ACID
                          ABSORBER EXCHANGER                        ABSORBER
             SOURCE:   EPA,  1971.
                                              FIGURE 4-9
                               DUAL ABSORPTION SULFURIC ACID PLANT
                                           FLOW DIAGRAM

-------
     Spent acid or H2S may be used as feedstock in a dual absorp-
tion process with appropriate conventional process gas pretreatment,
i.e., particulate removal.  The dual absorption process requires the

same types of equipment as the conventional single absorber design.
Although additional equipment is required, the on-stream production

factor and manpower requirement are the same.
     4.4.2  Sodium Sulfite - Bisulfite Scrubbing
     Tail gas scrubbing systems are generally applicable to all
classes of contact acid plants.  They can provide simultaneous
control of S02 and to some extent 803 and acid mist.  To date
only the sodium sulfite-bisulfite scrubbing process has been demon-

strated to  be capable of meeting the SC>2 limit in the most cost
effective manner.  Other control processes such as ammonia scrubbing
can meet the standard, but costs are relatively highly dependent on

the marketability of by-products, i.e., ammonium sulfate, for which
there may be little demand.
     In the Wellman-Power Gas process, the tail gases are first

passed through a mist eliminator to reduce acid mist.  Following mist
removal, the SC^ is absorbed  in a three-stage absorber with a

sodium sulfite solution.  A sodium bisulfite solution results and  is
fed  to a heated crystallizer  where sodium sulfite crystals are  formed

and  SC>2 gas and water vapor are released.  The crystals are sepa-
rated from the mother  liquor  and dissolved in the recovered conden-

sate for recycle to the absorber.  The recovered wet S(>2 is sent
back to the acid plant.
                                 4-28

-------
     In all processes employing sulfite-bisulfite absorption even

without regeneration, some portion of the sulfite is oxidized to sul-

fate, from which the sulfur dioxide cannot be regenerated in the

heating sequence.  This sulfate must be purged from the system.  In

the Wellman-Power Gas process, some thiosulfate is also formed.

Apparently the extent of oxidation is dependent on several factors

such as the oxygen content of the gas stream, the temperature and

residence time of the liquor in the recovery sections, and the pres-

ence of contaminants that may act as oxidation catalysts.  Despite

the effectiveness of the sodium sulfite-bisulfite scrubbing process,

none of the sulfuric acid plants installed since the promulgation of

the NSPS have employed this process for tail gas 802 control.

     4.4.3  Ammonia Scrubbing

     The ammonia scrubbing process uses anhydrous ammonia (NH3) and

water make-up in a two-stage scrubbing system to remove SC>2 from

acid plant tail gas.  Excess ammonium sulfite-bisulfite solution is

reacted with sulfuric acid in a stripper to evolve SC>2 gas and pro-

duce an ammonium sulfate byproduct solution.  The 802 ^s returned

to the acid plant while the solution is treated for the production of

fertilizer grade ammonium sulfate.  The process is dependent on a

suitable market for ammonium sulfate.

     Since the promulgation of the NSPS for sulfuric acid plants, one

new plant (two units) and a new unit added to an existing plant, are

employing an ammonia scrubbing system for tail gas S02 emissions

control.
                                  4-29

-------
   4.4.4  Molecular Sieves


     This process utilizes a  proprietary molecular sieve system in


which S(>2 is adsorbed  on  synthetic  zeolites.  The adsorbed material


is desorbed by purified hot tail gas  from  the operating system and


sent back to the acid  plant.


     Since the promulgation of  the  sulfuric acid plant NSPS, one new


unit has incorporated  a molecular sieve system  for S(>2 control in


the original design.   However,  extensive operational difficulties


with this system have  caused  this plant to be retrofitted with a dual


absorption system for  SC>2 control.


4.5  Control Technology Applicable  to the  NSPS  for Acid Mist
     Emissions from Contact Process Sulfuric Acid Plants
                                                     i

     Effective control of stack gas acid mist emissions can be


achieved by fiber mist eliminators  and electrostatic precipitators


(ESPs).  Although ESPs are frequently used in the purification sec-


tion of spent acid plants, there is no evidence that any have been


installed to treat the stack  gas of any new sulfuric acid plants.


Even though ESPs do have  the  advantage of  operating with a lower


pressure drop than fiber  mist eliminators  (normally less than 1 inch


of H£0), lack of application  of this  equipment  to new sulfuric acid


units is probably due  primarily to  its relatively large size and re-


sultant high installation cost  compared to fiber mist eliminators and


to the high maintenance  cost  required to keep the ESPs operating
                                   4-30

-------
within proper tolerances in the acid environment which is corrosive




to the mild steel equipment.




      Fiber mist eliminators utilize the mechanisms of impaction and




interception to capture large to intermediate size acid mist parti-




cles and of Brownian movement to effectively collect micron to




submicron size particles.  Fibers used may be chemically resistant




glass or fluorocarbon.  Fiber mist eliminators are available in three




different configurations covering a range of efficiencies required




for various plants having low to high acid mist loadings and coarse




to




fine mist particle sizes, respectively.  The three fiber mist elimi-




nator configurations are:




     1.  Vertical tube




     2.  Vertical panels




     3.  Horizontal dual pads.




     4.5.1  Vertical Tube Mist Eliminators




     Tubular mist eliminators consist of a number of vertically




oriented tubular fiber elements installed in parallel in the top of




the absorber on new acid plants and usually installed in a separate




tank above or beside the absorber on existing plants.  Each element




consists of glass fibers packed between two concentric 316 stainless




steel screens.  In an absorber installation (see Figure 4-10) the




bottom end cover of the element is equipped with a liquid seal pot to




prevent gas bypassing.  A pool of acid provides the seal in the sepa-




rate tank design.  Mist particles collected on the surface of the



                                 4-31

-------
               ACCESS
               MANHOLE
MISTY
GAS IN
                                                 CYLINDRICAL
                                               ^SCREENS
                                               RECOVERED
                                               LIQUID (MIST)
                                               , FIBER ELEMENTS
     SOURCE:   EPA, 1977.
LIQUID &
SOLIDS OUT
                         FIGURE 4-10
      VERTICAL TUBE MIST ELIMINATOR INSTALLATION
                            4-32

-------
fibers become a part of the liquid film which wets the fibers.  The




liquid film is moved horizontally through the fiber beds by the gas




drag and is moved downward by gravity.  The liquid overflows the seal




pot continuously, returning to the process.




      Tubular mist eliminators use inertial impaction to collect




larger particles (normally greater than 3 microns) and use direct




interception and Brownian movement to collect smaller particles.  The




low superficial velocity of gas passing through the fiber bed—6 to




12 meters/minute—provides sufficient residence time for nearly all




of the small particles with random Brownian movement to contact the




wet fibers, effecting removal from the gas stream.  The probability




that such a particle could pass through the bed following the resul-




tant greatly lengthened travel path is very low.




     Design volumetric flow rate through an element is about 28.3




sm-Vmin, and the number of elements required for a given plant size




can be determined from the standard cubic meters per minute handled




at capacity.  Depending on the size of the sulfuric acid plant,




anywhere from 10 to 100 elements may be used; each element is




normally 0.6 meters in diameter and 3 meters high.




     Pressure drop across the element varies from 13 to 38 cm. of




H20 with a higher pressure drop required for a higher removal




efficiency on particles smaller than 3 microns.  The manufacturer of




these elements guarantees a mist removal efficiency of 100 percent on




particles larger than 3 microns and 90 to 99.8 percent on particles







                                 4-33

-------
smaller than 3 microns with 99.3 percent being most common.   These




efficiencies can be achieved on the stack gas of sulfuric acid plants




burning elemental sulfur or bound-sulfur feedstocks (spent acid,  wet




gas, etc.) and producing acid or oleum.




      Because the vertical tube mist eliminator does not depend only




upon impaction for mist removal, it can be turned down (operated  at a




volumetric flow rate considerably below design) with no loss in effi-




ciency.




     Available information indicates that the vertical tube mist




eliminator is used in the great majority of new sulfuric acid units




for acid mist control.




     4.5.2  Vertical Panel Mist Eliminators




     Panel mist eliminators use fiber panel elements mounted in a




polygon framework closed at the bottom by a slightly conical drain




pan equipped with an acid seal pot  to prevent gas bypassing.  The




polygon top is surmounted by a circular ring which is usually




installed in the absorption tower and welded to the inside of the




absorption tower head.  Each panel  element consists of glass fibers




packed between two flat parallel 316 stainless steel screens.  In




large high velocity towers, recent  designs have incorporated double




polygons, one inside the other, to  obtain more bed area in a given




tower cross section.




     As in the high efficiency  tubular mist eliminator above, the gas




flows horizontally through the bed, but at a much higher superficial






                                 4-34

-------
velocity (120 to 150 m/min) using the impaction mechanism for collec-




tion of the mist particles.  Gas leaving the bed flows upward to the




exit port, while the collected liquid drains downward across the pan




and out through the seal pot back into the tower or to a separate




drain system (see Figure 4-11).




     The polygon may contain 10 to 48 vertical sides, each side norm-




ally consisting of an 18 1/2" x 53" panel.  A smaller 18 1/2" x 26"




panel is available for small plants, e.g., 32 Mg per day.




     Pressure drop across the panel is usually about 8 inches of




H20.  The manufacturer of panel mist eliminators will usually




guarantee an emission no higher than 2 rag/ft-* (equivalent to 0.375




Ib/ton of 100 percent H2S04 produced) for a sulfur-burning plant




producing oleum up to 20 percent in strength and/or acid.




     Because of the large percentage of submicron (below 1 micron)




mist present in the stack gas of a spent acid plant and of a plant




producing oleum stronger than 20 percent, the vertical panel mist




eliminator will usually give unsatisfactory performance for these




plants when used for acid mist control in the tail gas.  These units




find application in new dual absorption plants for acid mist removal




from the intermediate absorber in order to afford corrosion protec-




tion for downstream equipment.




     Vertical panel mist eliminators normally operate with a liquid




level in the acid seal pot below the conical drain pan.  Although the




velocity through the panels could be increased at lower throughputs
                                  4-35

-------
                   CLEAN GASES OUT
ACCESS MANHOLE
                         SEAL POT

          DISTRIBUTOR PAN OF TOWER
                                    FIELD WELD
                                        STRUCTURAL
                                        SUPPORT
                                        CYLINDER
                                         ELEMENTS
                                         IN POLYGON
                                         FRAME
                                         RECOVERED
                                         LIQUID
SOURCE:  EPA,  1977.
                     FIGURE 4-11
  VERTICAL PANEL MIST ELIMINATOR INSTALLATION
                        4-36

-------
by raising Che liquid level to cover the lower part of each panel,




this would not be good practice since it would cause reentrainment of




spray by the gas passing over the liquid level in the basket.




     4.5.3  Horizontal Dual Pad Mist Eliminators




     Two circular fluorocarbon fiber beds held by stainless steel




screens are oriented horizontally in a vertical cylindrical vessel




one above the other, so that the coarse fraction of the acid mist is




removed by the first pad (bottom contactor) and the fine fraction by




the other (top contactor), as shown in Figure 4-12.  The bottom




contactor consists of two plane segmented sections installed at an




angle to the horizontal to facilitate drainage and give additional




area for gas contact.  The assembly may be located adjacent to—or




positioned on—an absorption tower.




     This unit uses the high velocity impaction mist collection




mechanism, as does the panel mist eliminator; however, the collected




acid drains downward through the pads countercurrent to the gas flow




producing a scrubbing action as well.  Collected acid may be drained




from external connections or returned directly to the absorber




through liquid seal traps.




     Total pressure drop across both pads is usually about 23 cm. of




H20.  The superficial velocity through the unit is 2.7 to 3.0 m/s.




Hence, the diameter of the cylindrical shell and the pads is deter-




mined from the volume of gas handled.  Height requirements for the




unit depend upon whether it is located adjacent to or positioned  on
                                  4-37

-------
               XVI
           \
            I —-^   \ j CLEAN GAS
            \   ^-.  VI TO ATMOSPHERE
      I
      I

  DRAIN;
  it*1
           TOP CONTACTOR.
r BOTTOM CONTACTOR-^ L DRA|N


                 Is

        i
                 •ABSORBER
             MIST-ADEN
               GAS IN

               (COURTESY OF YORK SEPARATORS, INC.)
SOURCE:  EPA, 1977.
               FIGURE 4-12

  HORIZONTAL DUAL PAD MIST ELIMINATOR
                  4-38

-------
the absorber, but are roughly 1.5 to 2 times the diameter of the




unit.




     As with the panel mist eliminator, the dual pad unit will reduce




acid mist emissions to 2 rag/ft^ (0.375 Ib/ton of 100 percent




112804) or less, provided the plant burns sulfur and does not pro-




duce oleum stronger than 20 percent, and provided that a particle




size distribution curve shows that this level can be met.
                                 4-39

-------
5.0   INDICATIONS FROM NSPS COMPLIANCE TEST RESULTS




5.1   Test Results  from EPA Regional Sources




      The Mefrek Division of The MITRE Corporation conducted a survey




of all 10 EPA regions to gather available NSPS compliance test data




for each of the 10 industries under review (MITRE Corporation, 1978).




This  survey yielded test data on 20 new sulfuric acid units.  Data




included average S02 and acid mist emissions and 100 percent




sulfuric acid production rates for these units.  In all cases, the




sulfuric acid production rate was at the unit design maximum (the




actual production rates usually exceeded the nominal design rates by




5 to  10 percent).  Only a few values of opacity readings were




reported as compared with the total number of tests.




      Telephone contacts with EPA regional personnel and, in some




cases, with sulfuric acid plant operators yielded NSPS compliance




test  data on an additional 12 new sulfuric acid units.  In all,  29




sets  of data were obtained representing 32 new sulfuric acid units




(in two cases, the NSPS tests were run on two or more new units




combined).  Insofar as is known,  the test data obtained represent all




of the sulfuric acid units completed from 1971 through 1977, and




subject to NSPS.




5.2  Analysis of NSPS Test Results




     The results of the NSPS compliance tests for the 32 new sulfuric




acid units are tabulated in Table 5-1  and displayed in Figures 5-1




and 5-2 for S02 and acid mist emissions,  respectively.  Table 5-2






                                  5-1

-------
                                                                                                            TABU J-l

                                                                                        NSPS COMPLIANCE TEST RESULTS  FOB SULPURIC »CtD PUOTS
Cn
to


I.
IV







V
VI
IX
I



BL lodultriea. Inc
Air ICO Cheolcal. Inc
CF ChcalcalB. Inc
CP cnaalcals. Inc
Cardlaler. Inc.
b B Grai-e Co

IXC Chealcal Corp

Occidental Petroleua Corp
An C/anaold Co
Hlaalaalppl Clerical Corp
Teuagulf Inc

Anlln Corp*
Agrlco Chenical Inc
Agrleo Chenical, Inc
Preeport Chooleal Co
Bohn 6 Haaa. Inc
Valley Mtrogen Producera, Inc
Baker InduBlrlee. Inc
J B Sleplot Co
Allied ChCBlcal Corp

Monlnal
Unit SHO
(1001 B2S04)
Plant location H«/oay/TPD
Sayravllle, II J 910 (1000)
910 (1000)
So Pierce. Pla 16*0 (1800)
Bartov. Pla 1800 (2000)
Plant City. Plo 1*60 (1600)
1*60 (1600)
Tampa, Pla 2370 (2600)
1*60 (1600)
larto.. Pla 1*60 (1600)
1*60 (1600)
1*60 (1600)
Mulberry Pla 1800 (2000)
1800 (2000)
1800 (2009)
Uhlla Sprlnga. 1640 (1800!
n' 1640 (1809)
Savannah. Ca 730 (800)
Paeeacoula. HUB 1370 (1500)
Lee Crock, n C 1170 (1500)
1370 (1500)
Wood Hlver. Ill 230 (250)
Donaldarnvlllc. 1640 (1800)
u 16*0 (1800)
Convent. La 1*60 (1600)
Deer Park, T> 640 (700)
Heine. Calif 16*0 (1800)
Conda, Idaho 770 (850)
Pocatello, Idaho 810 (900) b
Anecortca, Uaah WO (330)

Average SOj
Emlaalona
kg/Kg of 1001
a2SO* (Ib/ton)
0 71 (1 42)
19 (37)
I
1 11 (2 22)
0 56 (1 12)
0 76 (1 32)
1 26 (2 52)
0 97 (1 94)
0 87 (1.71)
0 16 (0 32)
1 03 (2 16)
12 (21)
0 73 (1 45)
0 79 (1 58)
0 65 (1 10)
1.62 (3 23)
0 47 (0 93)
1 17 (2 33)
0 48 (0 95)
0 85 (1 70)
0 91 (1 82)
1 85 (3 69)
0 55 (1 10)
0 55 (1 11)
1 0 (1 99)
1 16 (2 12)
0 *0 (0 79)
1 56 (3.02)
0 33 (1 05) b
1 70 (3 41) c
__^ — — —
Avorago Acid Mlal
EmUalonB kn/Hg
of lOOt B2S04
(Ib/ton)
0 018 ( 035)
0 062 ( 123)
0 053 (0 109)
0 010 (0 021)
0 038 (0 116)
0 026 (0 052)
0 036 (0 071)
0 030 (0 061)
0 03 (0 06)
0 02 ( 0*)
0 07 (0 13)
0 008 (0 016)
0 008 (0 016)
0 Oil (0 022)
0 071 (0 1*2)
0 06* (0.127)
0 OV (0 039)
0 06* (0 128)
0 023 (0 046)
0 017 (0 073)
0 072 (0 144)
0 037 ( 073)
0 0*2 (0 083)
0 08 (0 15)
0.0*1 (0 082)
00* (07)
0 053 (0 105)
0 0*6 (0 092) b
0 0* (0 07)=

Actual Plant Meaaured
Produ.t Kalr Opacity
During SSPS During
Ten Kg/day Teal
1001 «ZSO» (TPll) (Percent)
84S (929) 0
808 (888) 0
1629 (1790)
1781 (1957)
1562 (1717)
1277 (1*03)
2424 (266*) 0:3
1616 (1771) C 3
15*7 (1700)
1535 (1687)
16*1 (1805)
2*37 (2700)
2166 (2600)
2503 (2750)
1756 (1930)
1641 (1803)
779 (836)
1387 (132*)
1474 (1620)
1113 (14*3)
219 (2*1)
1830 (2011) <10
1677 (18*3) <10
1694 (1862)
716 (787) 9 2
<3
1001 (1100)
853 (918) b
222 (244) S

Reference
W* " " •
CDS. 1978
CDS. 1978
CDS. 1978
CDS. 1978
Carrett. 1978
Carroll. 1978
CE6 , 1971
Vu. 1978
Wu, 1978
CDS, 1978
CD8. 1978
Q1S , 1976
CDS. 1978
CDS, 1978
Gardner. 1978
CDS. 1978
CDS. 1978
CDS, 1978
Cohen. 1978
Shonk. 1978
Shook. 1978
Spruloll. 1978
Sprulell. 1978
Reynold! . 1978
Pfandrr. 1978
Pfandir, 19 "9
Sntvdcn a Alifard.
1976
                                                acy w.  pu
                                         bTotal output of two unlti
                                         Stvcrage of three unit*

-------
N
O
O
I
 CN
O

a)
   4.0
   3.5
   3.0
   2.5
   2.0
   1.5
   1.0
          ±
            rf
                               :r
           Current EPA NSPS - Sulfuric Acid Pla
                                            	h
      ffl
      m

              t:
            tit:
                   f-
                 t-t-t--
                 Ttt:
                   t--
                          -i	1-
                         tt
                             :r
                            ffl
                                 +rt
                                 ^+t
                                  : rr
                                       I I i I I l-l-i.
                                       dPlantsi
                                       rrnrrrs
                                       fh-
-r"
                                            tti
                                            fr • r

                                          ffS
          ;m
                                                        Legend:

                                                       O - Region 2

                                                       • - Region 4

                                                       • - Region 5

                                                       ,D - Region 6

                                                       A - Region 9

                                                          - Region 10
                                                       tfl
                                                            -rt
                                                            .ft
                                                                TTT
                                                                 TO
                          rTi
                          t H
                                                                 ill
                         1000        L500       2000
                         Plant Production Rate,  TPD

                               FIGURE 5-1
                 CONTACT PROCESS SULFURIC ACID PLANTS
                     NSPS COMPLIANCE TEST RESULTS
                             S02 EMISSIONS
                                                         2500
                                                                   3000
                                 5-3

-------
§
,-H

§
H
c
o
•H
 01
-H
X

"O
•H
 u




 03

 0)
                                                                   i
               mmmmrmttt-m.t'
. JCurrent EPA NSPS - Sulfuric Acid Plants
                                                   Legend:


                                                   O - Region 2


                                                   • - Region 4


                                                     - Region 5


                                                     - Region 6


                                                   A - Region 9


                                                   A - Region 10
      •I--: 4-Uj.
  .02
                500
                    1000        1500       2000

                     Plant Production Rate, TPD
                                                           2500
                                                                       3000
                                 FIGURE 5-2
                   CONTACT PROCESS SULFURIC ACID PLANTS
                       NSPS COMPLIANCE TEST RESULTS
                            ACID MIST EMISSIONS
                                     5-4

-------
                                                  TABLE  5-2
in
I
Ui
                                        NSPS  COMPLIANCE  TEST RESULTS

                                        FOR NEW  SULFURIC ACID PLANTS

                                        BREAKDOWN BY  EMISSIONS LEVEL

NSPS Test Results
(Ib/ton)
3.0 to 4.0
2.0 to 3.0
1.0 to 2.0
0 to 1.0




S02
No. of
Results
5
6
14
4
29




% of
Total
17
21
48
14
100




NSPS Test Results
(Ib/ton)
0.13 to 0.15
0.11 to 0.13
0.09 to 0.11
0.07 to 0.09
0.05 to 0.07
0.03 to 0.05
0.01 to 0.03

Acid Mist
No. of
Results
3
5
2
6
6
3
4
29

% of
Total
10
17
7
21
21
10
14
100

-------
presents a percentage breakdown of NSPS S02 and acid mist emis-

sion results at various  levels below the respective control levels.

     5.2.1  Control Technology Used to Achieve Compliance

     All 32 units tested showed compliance with the NSPS S02 and

acid mist control levels.  Of the 32 units tested, 28 achieved com-

pliance with the SC>2 standard through use of the dual absorption

process.  Of the remaining four units, three use ammonia scrubbing

and one employs a molecular  sieve process* to meet the standard.  All

of the new units use mist eliminators to achieve acid mist control.

The bulk of these control units are vertical tube mist eliminators.

Only nine values of opacity  were reported  (all meeting the NSPS stan-

dard).  It is assumed that all of the new plants were meeting the

opacity standard during  the  compliance tests since opacity is direct-

ly related to acid mist  concentration.

     In one vendor's modification of the dual absorption process (the

R.M. Parsons Co., Pasadena,  California), the usual four-bed catalytic

converter was replaced with  a five-bed unit, i.e. , three beds are

used for SC>2 conversion  prior to the interpass or primary absorp-

tion tower, followed by  two  beds being utilized for further S02

conversion before the  final  absorber.  This method is intended  to

achieve 99.8 to  99.9 percent conversion  to SO^ equivalent to

approximately 0.5 kg/Mg  (1.0 Ib/ton) SO2 emission level in the  tail

gas.  Eight new  dual absorption units  incorporating this design have
*Due  to  operational difficulties,  the molecular sieve  operation  is
 currently  being replaced by a dual absorption plant.

                                  5-6

-------
been installed (Field, 1978).  The Parsons units are identified in




Table 4-5.  Inspection of Table 5-1 indicates that the Parsons units




show a range of S(>2 emissions from 0.4 kg/Mg (0.8 Ib/ton) to 1.7




kg/Mg (3.4 Ib/ton), with the average being approximately 1.0 kg/Mg




(2.0 Ib/ton).  Based on NSPS compliance test results, it appears that




the SC>2 emission levels obtained from these five-bed units have not




been able to reach the original design levels.




      5.2.2  Statistical Analysis of NSPS Compliance Test Data




     The arithmetic mean and 95 percent confidence interval has been




calculated for the dual absorption plant NSPS test results.  The




arithmetic mean for SC>2 is 0.9 kg/Mg (1.8 Ib/ton) with a 95 percent




confidence interval of ^0.15 kg/Mg (+0.3 Ib/ton).  The arithmetic




mean for acid mist emissions is 0.04 kg/Mg (0.08 Ib/ton) with a 95




percent confidence interval of +0.01 kg/Mg (+0.02 Ib/ton).  The wider




95 percent confidence limits for acid mist emissions are indicative




of a greater spread in acid mist emission results (as can be seen by




comparing Figures 5-1 and 5-2).




     5.2.3  Validity of NSPS Test Data




     The 26 data points obtained for dual absorption plants equipped




with high efficiency acid mist eliminators show a rather large spread




for S02 control levels, i.e., SC>2 emission values range from a




low of 0.16 kg/Mg (0.32 Ib/ton) to a high of 1.9 kg/Mg (3.7 Ib/ton).




Additionally, the corresponding acid mist emission values range from




a low of 0.008 kg/Mg (0.016 Ib/ton) to a high of 0.071 kg/Mg (0.14




Ib/ton).  All data were obtained using the standard EPA Method 8.




                                 5-7

-------
It is not clear why the use of  this  test method should have produced




such a wide variation  in  the test results  for plants with identical




control technologies.  Region IV believes  that at least part of the




observed variation may be due to differences in test contractor's




techniques (Rom, 1978).   In this regard, discussion with EPA person-




nel in the Quality Assurance Branch  (QAB)  of the Environmental




Monitoring and Support Laboratory indicate areas where the original




Method 8* (used in testing all  of new sulfuric acid units subject to




NSPS) could yield misleading SC>2 and acid  mist results.  Detailed




studies of the original Method  8 by  QAB indicated that the isopro-




panol (IPA) used in the test could contain trace quantities of




peroxide, which, if present, would react with S02 during the test




procedure to  form 803, yielding lower S(>2  and higher acid mist




values in the tail gas.   Additionally, when the test contractor




performed the impinger train leak check, upon release of the applied




vacuum, a fine spray  of hydrogen peroxide  solution could deposit on




the filter, causing the 862 —^803 conversion mechanism to be set




into motion during the tail gas sampling period.  This again could




result in misleading  levels of  802 and acid mist in the tail gas




(Midgett, 1978).




     The revised Method 8 has  attempted  to remedy these defects  in




the original  test.*   This method requires  that the IPA be  tested for
*Method  8  was  revised effective August 18,  1977.
                                  5-8

-------
peroxides.  If the latter are found, the IPA batch must either be

discarded or treated to remove the peroxide.  Since operator tech-

nique is the controlling factor in minimizing errors due to the leak

check, the revised Method 8 provides a warning to the test equipment

operator to avoid this pitfall by careful manipulation of the equip-

ment.

     In summary, it would seem reasonable to have some question about

the validity of the S(>2 and acid mist results obtained from the

NSPS compliance tests made prior to August 1977 on the grounds of the

reliability of the test method itself.

     5.2.4  Comparison of NSPS Compliance Test Data with Day-to-Day
            Emission Control Performance

     MITRE has made a number of inquiries of sulfuric acid plants

that are operating units subject to NSPS to ascertain whether the

compliance test data for these units represent the current day-to-

day emission control levels.  A literature search had indicated that

NSPS emission controlled plants (dual absorption) could be expected

to operate (after an initial startup period with fresh catalyst) with

SC>2 emissions in the 1 to 1.5 kg/Mg (2 to 3 Ib/ton) range.  One

recent literature reference indicated that a new sulfuric acid unit

with an NSPS S02 test value of 0.56 kg/Mg (1.12 Ib/ton) in 1975,

was currently averaging 1.5 kg/Mg (3.0 Ib/ton) SC>2 emissions

(PEDCo, 1977).  Another reference indicated that a typical dual

absorption plant with an average S02 NSPS compliance test result of

0.85 kg/Mg (1.70 Ib/ton) was operating at an average S02 emission

level of 1.15 kg/Mg (2.3 Ib/ton) (EPA, 1976).


                                 5-9

-------
      Data  obtained  from one new dual  absorption sulfuric acid unit

points  up  the  effect  of plant  and  catalyst  aging on the S02 emis-

sion  level.  These  data are tabulated in  Table 5-3.

                               TABLE 5-3

      EFFECT  OF PLANT  AND CATALYST  AGE ON  S02 EMISSION LEVEL3


                                                    S02 Emissions
 Date                 Source of Data                 kg/Mg (Ib/ton)

9/17/75      NSPS  Compliance Test (EPA Method 8)     0.47 (0.93)

10/22/76     Dupont  Continuous  S02  Monitorb          1.30 (2.59)

4/4/77       Dupont  Continuous  S02  Monitorb          1.43 (2.85)

3/28/78      Dupont  Continuous  SO?  Monitorb	1.6  (3.2)


aThis is an  1800  ton/day (100  percent H2S04) plant.
"Results of  Dupont  continuous  monitor checked concentrations,  when
 converted to  kg/Mg of  100  percent acid,  checked to within 1 percent
 of EPA Method  8.

Source:  Mullins, 1978.

     This plant (a  total  of  two units  subject to NSPS) is stated to

operate at an  S02 emission  level of 1.25  to 1.50 kg/Mg (2.5  to 3.0

Ib/ton) on a day-to-day  basis  (Mullins, 1978).

     Another plant  which  had an S02 NSPS  test result of 0.48 kg/Mg

(0.95 Ib/ton)  indicated  that this  result  was obtained with fresh

catalyst and that the day-to-day operating value of S02 emissions

averaged 0.5 to 1.0 kg/Mg (1 to 2  Ib/ton) (Stark,  1978).

      In summary, indications  from the literature and from contacts

with sulfuric  acid  plant  operators are that low NSPS compliance test


                                 5-10

-------
SC>2 emission values do not necessarily reflect day-to-day plant

operating levels.  These levels appear to realistically lie in the 1

to 1.5 kg/Mg (2 to 3 Ib/ton) range for dual absorption units.  There

is a definite trend towards increased 502 emission values as the

conversion catalyst ages and its activity correspondingly decreases.

Thus, even though a large percentage of the compliance test results

are significantly less than the NSPS of 2 kg/Mg (4 Ib/ton), it

appears that S02 emissions tend to rise towards the control limit

as the plant and catalyst age.

     Acid mist emission (and related opacity) levels are unaffected

by conversion catalyst aging, being primarily a function of moisture

levels in the sulfur feedstock and air fed to the sulfur burner, and

the efficiency of final absorber operation.  The wide spread observed

in NSPS compliance test values is probably a result of variations in

these factors or quite possibly errors in the test method itself (as

discussed in Section 5.2.3).

     5.2.5  Emission Control Performance Based on Excess Emissions
            Reports

     It was not possible to evaluate excess emissions reports with

regard to sulfuric acid plant SC>2 and acid mist control perfor-

mance, since a very limited number of reports were available.

5.3  Indications of the Need for a Revised Standard

     5.3.1  SO? Standard

     At this time, there is not sufficient justification for revision

of the present SC>2 NSPS, based on the following considerations:

                                  5-11

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    •  The  current  best  demonstrated  control  technology  (the
       dual absorption  process)  is  identical  in  basic  design  to
       that used  as the  rationale  for the original  S02 standard.

    •  While  the  S02 NSPS compliance  test data averages  close to  1
       kg/Mg  (2  Ib/ton)  with a number of values  in  the 0.5  kg/Mg  (1
       Ib/ton)  to 1 kg/Mg (2 Ib/ton)  range,  an analysis  of  these
       data indicates that:

       1.   There  may be  some question about  the validity of the  low
            values of S02 emissions  based on  defects in the  origi-
            nal  EPA Method 8.

       2.   Actual plant  experience  shows that the low NSPS  values do
            not  necessarily reflect  the day-to-day operating S02
            emission levels which tend to rise toward the standard as
            the  conversion catalyst  ages.

    •  According to a prime manufacturer of  dual absorption plants,
       in  order to guarantee performance at  the present  level, a
       margin of safety is built into the unit design to compen-
       sate for the effects of plant  and catalyst aging, fluctuating
        feed rates and other deviations from ideal operating condi-
       tions.  Construction of new plants to meet an appreciably
        lower  S02 NSPS involves greatly increased capital costs,
       since  a  margin of safety would have to be built into the
       new plant to meet performance guarantees (Donovan et al.
        1977).

    •  A trend  toward higher  levels of S(>2 in the gas feed to the
        converter,  i.e., 12 percent S(>2 or higher may develop  in
        the industry, since there is appreciable energy savings due
        to the additional heat recovery available from the highly
        exothermic  conversion  reaction.  Meeting an S02 emission
        standard appreciably lower  than 2 kg/Mg  (4 Ib/ton)  in  this
        situation would  be extremely difficult without extensive  (and
        expensive)  equipment additions to the  plant.

     Other considerations, including economic  factors, that militate

against a change  in the  present  S(>2 NSPS  are  discussed in Section

6.0.
                                 5-12

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     5.3.2  Acid Mist NSPS (and Related Opacity Standard)

     At this time,  there is not sufficient justification for revision

of the present acid mist (and opacity) NSPS, based on the following

considerations:

     •  The current best demonstrated control technology (the high
        efficiency  acid mist eliminator) is identical to that used
        as the rationale for the original acid mist standard.

     •  The NSPS compliance test data showed a wide scatter, with an
        appreciable number of the acid mist emission values close to
        the control limit.  The scatter observed in these values may
        be due to the defects in the original EPA Method 8 which
        tended to introduce variability in the acid mist levels
        obtained.

     •  Making the  acid mist standard more stringent is not believed
        to be practicable because of the need to provide a margin of
        safety due  to in-plant operating fluctuations.  Variation in
        the sulfur  feedstock, leaks, or improper inlet air drying
        tower operation can introduce moisture (the controlling
        factor in the production of acid mist) into the system,
        increasing  the production of acid mist.  It should be noted
        that acid mist control is far more vulnerable to operating
        fluctuations which deviate from standard plant operating con-
        ditions  than sulfur dioxide control.

     a  Manufacturers of acid mist eliminators guarantee maximum
        stack emission of  1 mg/scf ( 0.15 Ib/ton) for high-
        efficiency  units. These manufacturers do not guarantee any
        form of  visible emission limitation, but acid mist emissions
        of 1 mg/scf normally result in stack plumes of less than 10
        percent  opacity (Serne and Weisenberg, 1976).
                                 5-13

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6.0  ANALYSIS OF POSSIBLE REVISIONS TO THE STANDARD




6«1  Effect of NSPS Revision on Sulfuric Acid Production Economics




     The S02 emissions in a dual absorption plant are primarily




determined by the efficiency of the catalytic converter system.  Acid




mist emissions are controlled by plant operators' attention to con-




trol of residual moisture in the S02~laden inlet gas to the system




and to efficient absorber and acid mist eliminator operation.  NSPS




compliance test values of these emissions, which are appreciably




below the present control levels, are, as has been shown in Sections




5.2 and 5.3, not necessarily representative of the levels achievable




by a particular plant on a day-to-day basis.  Additional capital and/




or operating expense would be entailed by plants using the present




best demonstrated control technology in order to reduce NSPS control




levels appreciably below the present values.




     Additional capital expense required to control emissions below




the present NSPS levels would be involved for a scrubber installation




to further reduce S02 in the tail gas from the dual absorption




system or an additional acid mist eliminator in series with the




present unit to further reduce acid mist.




     As shown in Section 5.0, NSPS S02 levels for new plants tested




predominantly in the 1 to 1.25 kg/Mg (2 to 2.5 Ib/ton) range.  Making




the standard more stringent in order to accomplish reduction of S02




emissions appreciably below the present NSPS control level on a day-




to-day basis,  can probably be achieved by increasing sulfuric acid







                                 6-1

-------
plant operating expense significantly.  Since SO2 emissions are




directly affected by the level of catalyst activity, the former




should be able to be maintained at  levels comparable to the observed




NSPS compliance test values, if fresh catalyst with the maximum




activity were to arbitrarily replace older material in the converter




beds at frequent intervals.  The economics of a catalyst replacement




program have been developed and applied to the cost of producing




sulfuric acid in a dual absorption  plant, as described below.




     In the four-bed catalytic converter  system in a typical dual




absorption plant, the  first bed exposed to the inlet gas experiences




the greatest rate of activity decrease due to dirt and traces of




catalyst poisons, with beds two and three suffering progressively




less loss of activity  due  to these  contaminants.  These beds have an




average service life of 3  to 5 years.  The final catalyst bed, which




treats  the S02-laden gas  from  the  first absorption  tower, can have




a service life of 10 to 15 years.  Normal  plant practice is to




progressively elevate  these catalyst  beds during the plant turnaround




periods so that the overall average bed  life is 5 to 7 years.




     The basic  information used  in the catalyst replacement  cost cal-




culations is summarized in Table  6-1, and the results of the calcula-




tions  are shown  in  Table  6-2.




     Based on a sulfuric  acid  manufacturing  cost of $36/Mg,  the




incremental  increase  of 55 cents/Mg for  the  catalyst replacement pro-




gram outlined above,  represents  only  a  1.4  percent  increase.  With
                                  6-2

-------
                              TABLE 6-1

     BASIC DATA USED IN CATALYST REPLACEMENT COST CALCULATIONS
                 Items
          Source
• 1000 Mg/day dual absorption plant

• 4 Bed Converter

• First three beds (Beds 1, 2 and 3) -
   Average life of 3-5 years, Final bed
   (Bed 4) - Average life of 10-15 years

• Average catalyst makeup rate (first
   bed) is 10 percent per year due to
   screening and attrition losses

• Catalyst loading of 140 liters/daily
   Mg of acid at 10.5% SC>2 in inlet gas
   to converter

• Total catalyst replacement cost is
   $3/liter installed

• Total sulfuric acid manufacturing
   cost is $36/Mg (direct and fixed
   costs)

• Average pretax profit for merchant
   sulfuric acid is $3/Mg
Design Basis

Design Basis

Sheputis, 1978



Sheputis, 1978



Monsanto Enviro-Chem, 1974



Sheputis, 1978


Hansen, 1978



EPA, 1977
                                  6-3

-------
                              TABLE 6-2

       EFFECT OF CATALYST REPLACEMENT ON COST OF PRODUCTION OF
               SULFURIC ACID IN A DUAL ABSORPTION PLANT
ASSUMPTIONS

•  In order to maintain overall catalyst activity at a level to obtain
   S02 conversion equivalent to emission of 1 to 1.25 kg/Mg of 100
   percent acid (2 to 2.5 Ib/ton), replace catalyst beds on the fol-
   lowing schedule:

   Bed 1:  Complete replacement once a year (a net replacement of 90
           percent of the original bed).

   Bed 2:  Complete replacement once every 2 years.

   Bed 3:  Complete replacement once every 3 years.

   Bed 4:  Complete replacement once every 10 years.

•  Each bed holds 25 percent of the total catalyst loading.

•  Plant operates 350 days per year.
Bed
No.
1
2
3
4
Totals
Annual Catalyst
Volume Replaced
(liters)
31,500
17,500
11,700
3,500
Annual Catalyst
Replacement
Cost, $
94,500
52,500
35,100
10,500
192,600
Mg/Yr of 100%
Acid Produced
350,000
350,000
350,000
350,000
Annual Catalyst
Replacement Cost
$/Mg of
Acid Produced
0.27
0.15
0.10
0.03
0.55
                                 6-4

-------
a present FOB plant selling price for 100 percent merchant acid of




approximately $50/Mg (Gulf Coast area) (Chemical Marketing Reporter,




1978), an incremental increase of 55 cents/Mg for catalyst replace-




ment represents only 1 percent of the selling price.  However,  the




effect of this cost on pretax profit, based on an average pretax




profit of $3/Mg, is much more drastic, i.e.,  55 cents/Mg for annual




catalyst replacement represents an approximate 20 percent reduction




in pretax profit.  An adverse economic penalty to the sulfuric  acid




industry would seem to be indicated by this approach.




     A serious problem raised by the catalyst replacement program




outlined above would be the need to dispose of the highly toxic spent




vanadium pentoxide catalyst waste generated.   This material is  not




considered valuable enough to rework by the major processors.  Some




of the catalyst disposed of at present is reworked by several mar-




ginal processors (Sheputis, 1978).




6.2  Effect of New Sulfuric Acid Plant Construction on the NSPS




     As mentioned in Section 4.2, the rate of completion of new sul-




furic acid units during the 1971-1977 period was approximately 5 per




year.  During the 1978-1980 period, the number of new sulfuric  acid




units announced or under construction has slowed to approximately 3




per year.  This slowdown in new growth is due primarily to the  pre-




sent imbalance in the demand-supply situation in the phosphate  ferti-




lizer industry.  Based on anticipated growth in the phosphate ferti-




lizer industry, an estimate for the 1981 to 1984 period of four new




sulfuric acid units completed per year has been used as a basis




                                 6-5

-------
for calculating Che total S02 and acid mist emissions at various




emission levels for the  16 new units projected to be completed during




this period.  The results of these calculations are shown in Tables




6-3 and 6-4.




     A study of Table 6-3 indicates that reducing the NSPS control




level for S02 emissions  from the present 2 kg/Mg (4 Ib/ton) to 1




kg/Mg (2 Ib/ton), a 50 percent reduction, would reduce the total




S02 emissions for sulfuric acid plants regulated by the NSPS by




approximately 6000 Mg/yr (7000 tons/yr)  in 1984.  Correspondingly, a




study of Table 6-4 indicates that reduction of the NSPS acid mist




control levels from the  present 0.075 kg/Mg (0.15 Ib/ton) to 0.05




kg/Mg (0.10 Ib/ton), a 33 1/3 percent reduction, would reduce the




total acid emissions for these sulfuric  acid  plants by approximately




150 Mg/yr (170 tons/yr)  in 1984.




     As a further comparison of  the potential impact of SC>2 emis-




sions from sulfuric acid units projected to be built between 1981 and




1984, data  from projections of S02 emissions  from all stationary




sources in  1984 were used to calculate  the effect of sulfuric acid




plant S(>2 NSPS reduction.  Total  S02  emissions  from stationary




sources in  1984  (based  on all existing  NSPS and  state standards in




effect  in 1975)  are  indicated  to  be  approximately 33 x  10^ Mg/yr




(EPA, 1976).  With  the  present sulfuric  acid  NSPS of 2  kg/Mg (4 lb/




ton), the percent  SC>2  emission contribution  of  the  projected 16 new




units in  1984 would  be  0.04  percent.   Correspondingly,  with an NSPS
                                   6-6

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                                                 TABLE 6-3

                       PROJECTED CUMULATIVE S02 EMISSIONS FROM NEW CONTACT SULFURIC
                                 ACID PLANTS ADDED BETWEEN 1981 AND 1984a
Control Level
kg/Mg (Ib/ton)
Projected Emissions
Mg/yr (ton/yr)b
1981
2.0
1.75
1.5
1.25
1.0
(4.0)
(3.5)
(3.0)
(2.5)
(2.0)
3,060(3
2,680(2
2,290(2
1,910(2
1,530(1
,360)
,940)
,520)
,100)
,680)
1982
6,120(6
5,350(5
4,590(5
3,820(4
3,060(3
,720)
,880)
,040)
,200)
,360)
1983
9,180(10
8,030(8,
6,880(7,
5,730(6,
4,590(5,

,080)
820)
560)
300)
040)
1984
12,230(13
10,700(11
9,170(10
7,640(8,
6,120(6,
Percent of Total Annual
S02 Emissions of
NSPS Plants in 1984C

,440)
,760)
,080)
400)
720)

27
25
22
18
16

.6
.0
.2
.8
.0
aFour contact process double-absorption sulfuric acid plants (average production capacity  of
 1100 Mg/day (1200 tons/day) of 100% l^SO^ each) are projected to be installed per year from
 1981-1984, inclusive.
"Calculations based on a 350-day work year.
cTotal annual S02 emissions of 42 existing NSPS H2S04 units in 1984 (at  present 4.0 Ib/ton
 control level) is 33,000 Mg/yr2 (35,300 tons/yr).

-------
                                                 TABLE 6-4

                     PROJECTED CUMULATIVE ACID MIST EMISSIONS FROM NEW CONTACT  SULFURIC
                                 ACID PLANTS ADDED BETWEEN 1981  and 1984a
Control Level
kg/Mg (Ib/ton)


CT>
CO



0
0
0
0
0
0
.075
.07
.065
.06
.055
.05
(0.
(0.
(0.
(0.
(0.
(0.
15)
14)
13)
12)
11)
10)
Projected Emissions
Mg/yr (ton/yr)b
1981
115(126)
108(119)
99(109)
93(102)
"83(91)
76(84)
1982
229(252)
217(238)
197(217)
185(203)
166(182)
153(168)
1983
344(378)
325(357)
297(326)
278(305)
248(273)
229(252)
Percent of Total Annual
Acid Mist Emissions of
NSPS Plants in 1984C
1984
459(504)
433(476)
395(434)
369(406)
331(364)
306(336)

27
26
24
23
21
20

.6
.4
.7
.5
.6
.3
aFour contact process double-absorption sulfuric acid plants (average production capacity  of
 1100 Mg/day (1200 tons/yr) of 100% R2SOU each) are projected to be installed per year from
 1981-1984, inclusive.
bCalculations based on a 350-day work year.
cTotal annual acid mist emissions of 42 existing NSPS units in 1984 (at present 0.15  Ib/ton control
 level) is 1200 Mg/yr (1325 tons/yr).

-------
of 1 kg/Mg (2 Ib/ton), the percent S(>2 emission contribution of the




projected 16 new units in 1984 would be 0.02 percent.  The national




impact of a more stringent SC>2 NSPS would be marginal due to the




very small decrease in 862 emissions (resulting from a tighter




standard) from the sulfuric acid plants projected to be built during




the 1981 through 1984 period.
                                 6-9

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7.0  FINDINGS AND RECOMMENDATIONS

     The primary objective of this report has been to assess the need

for revision of the existing NSPS for sulfuric acid plants, including

review of the S02 and acid mist standards.  The existing opacity

standard is directly related to the acid mist standard and is not

reviewed separately.  The findings and recommendations developed in

these two areas are presented below.

7.1  Findings

     7.1.1  SO-? NSPS

     7.1.1.1  Process Emission Control Technology.

      •  The current best demonstrated control technology, the dual
         absorption process, is identical in basic design to that
         used as the rationale for the original S02 standard.  The
         dual absorption process is in use in over 90 percent of all
         sulfuric acid production units installed since the promulga-
         tion of the S02 NSPS for sulfuric acid plants and will be
         installed in all new plants built through 1980.

      •  While the overall average S02 emission obtained  in the
         NSPS compliance test results is 0.9 kg/Mg (1.8 Ib/ton), the
         wide range shown in this data, from a low of 0.16 kg/Mg
         (0.32 Ib/ton) to a high of 1.9 kg/Mg (3.7 Ib/ton) for dual
         absorption plants, may be partially due to defects in the
         original Test Method 8 or to variations in test  operator
         technique.  The average S02 emission level obtained in the
         NSPS compliance tests for dual absorption plants is about
         one order of magnitude lower than the emission level
         obtained from uncontrolled single absorption plants.

      •  The dual absorption process, while yielding low  NSPS compli-
         ance test S02 emission levels,  can not maintain  these
         levels on a day-to-day basis.   The S02 emission  level is a
         function of catalyst conversion efficiency which drops as
         the catalyst ages.
                                 7-1

-------
 7.1.1.2  Economic Considerations.

 •  In order to guarantee SC>2 emission control performance at
    the present NSPS level, vendors of the dual absorption
    process plants incorporate a sufficient margin of safety in
    the plant design, consistent with reasonable investment
    cost, to compensate for the effects of plant and catalyst
    aging, fluctuating feed rates and other deviations from
    ideal operating conditions.  Making the present SC>2 NSPS
    more stringent would involve greatly increased capital costs
    since sulfuric acid plant vendors would have to redesign
    for lower S02 emission rates in order to retain this
    margin of safety.

 •  More frequent conversion catalyst replacement (as compared
    with present practice) in order to maintain a more stringent
    S02 control level than the present standard in sulfuric
    acid plants subject to NSPS would represent a substantial
    drop in pretax profits (20 percent or more).

 •  Projections over the 4-year period, 1981 through 1984, for
    the 16 new sulfuric acid plants expected to be built during
    this period indicate that there would be only a 0.02 percent
    drop in SC>2 emission contribution from these plants to the
    total U.S. annual S02 emissions if the present S02
    standard were dropped from 2 kg/Mg (4 Ib/ton) to 1 kg/Mg (2
    Ib/ton).

7.1.2  Acid Mist NSPS (and Related Opacity Standard)

 •  The current best demonstrated control technology, the high
    efficiency acid mist eliminator, is identical to that used
    as the rationale for the original acid mist standard.  This
    technology is in use in all sulfuric acid plants built since
    the promulgation of the acid mist NSPS for sulfuric acid
    plants.

 •  While the average acid mist emission obtained in the NSPS
    compliance test results is 0.04 kg/Mg (0.08 Ib/ton), the
    wide range shown in this data, from a low of 0.008 kg/Mg
    (0.016 Ib/ton) to a high of 0.071 kg/Mg (0.14 Ib/ton) for
    high efficiency acid mist eliminator control, may be
    partially due to defects in the original EPA Method 8 which
    tended to introduce variability in the acid mist levels
    obtained.
                             7-2

-------
     •  An appreciable number (approximately 25 percent) of the NSPS
        compliance test results obtained for acid mist emissions are
        within 75 to 100 percent of the present NSPS acid mist
        control level.  This may be indicative of the vulnerability
        of sulfuric acid plants to in-plant operating fluctuations
        such as variation in the sulfur feedstock, leaks, or improper
        inlet air drying tower operations,  all of which introduce
        moisture (the controlling factor in the formation of acid
        mist) into the system, thus increasing the acid mist
        emissions.

     •  Manufacturers of acid mist eliminators guarantee maximum
        stack emissions of 1 mg/scf (~0.15 Ib/ton) for high
        efficiency units under normal operating conditions. While
        there is a 10-percent opacity limitation for stack plumes
        under the present NSPS, no guarantee is provided for any
        form of visible emission limitation.  However, available
        data indicate that acid mist emissions of 1 mg/scf will
        result in stack plumes of less than 10 percent opacity.

7.2  Recommendations

      7.2.1  SO? NSPS

     At this time there is not sufficient justification for revision

of the S02 NSPS for sulfuric acid plants, based on the following

considerations:

     •  The best demonstrated control technology, the dual
        absorption process, is in use in all new sulfuric acid
        plants.

     •  SC>2 emission levels achieved in the NSPS compliance tests
        which were significantly lower than the standard are not
        representative of day-to-day plant operations. These levels
        tend to rise toward the standard as the conversion catalyst
        ages.  The dual absorption process can not adjust the SC>2
        emission levels to compensate for the loss of catalyst
        activity.

     •  The national impact of a more stringent SC>2 NSPS would be
        marginal due to the very small decrease in S(>2 emissions
        (resulting from a tighter standard) from the sulfuric acid
        plants projected to be built during the 1981 through 1989
        period.
                                 7-3

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     7.2.2  Acid Mist NSPS (and Related Opacity Standard)

     At this time there is not sufficient justification for revision

of the acid mist (and opacity) NSPS based on the following

considerations:

      •  The best demonstrated control technology (the high
         efficiency acid mist eliminator) is in use in all new
         sulfuric acid plants.

      •  The need exists to  retain a margin of safety for maintenance
         of the present acid mist NSPS control level since there is
         always a possibility of in-plant operating fluctuations
         which deviate from  standard sulfuric acid plant operations
         and introduce unexpected amounts of moisture into the
         system.

      •  Control of acid mist emissions  at  the present NSPS level,
         results in essentially no visible  emissions, i.e., less than
         10 percent opacity.
                                  7-4

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8.0 REFERENCES

     Calvin, E.L. and F. D. Kodras, 1976.  Inspection Manual for the
Enforcement of New Source Performance Standards as Applied to Contact
Catalyst Sulfuric Acid Plants.  Catalytic, Inc., Charlotte, N.C.

     CE Construction Alert, 1977.  Chemical Engineering, Vol. 84,
No.6.

     Chemical and Engineering News, 1978.  Facts and Figures for the
Chemical Industry.  Vol. 56, No. 24.

     Cohen, E., 1978.  Personal Communication.  EPA Region V,
Chicago, 111.

     Donovan, J. R. et al., 1977.  Analysis and Control of Sulfuric
Acid Plant Emissions, Chemical Engineering Progress, Vol. 73, No. 6.

     Duros, D.R. and E.D. Kennedy, 1978.  Acid Mist Control.
Chemical Engineering Progress, Vol. 74, No. 9, 1978.

     Field, D., 1978.  Personal Communication.  R. M. Parsons
Company, Pasadena, Calif.

     Gardner, R., 1978.  Personal Communication.  Georgia Department
of Natural Resources, Atlanta, Ga.

     Garrett, W., 1978.  Personal Communication.  Florida Department
of Environmental Regulation, Winterhaven, Fla.

     Hansen, D. R., 1978.  Personal Communication.  Monsanto
Enviro-Chemical, St. Louis, Mo.

     Hooper, M. H., 1978.  Personal Communication.  EPA Region X,
Seattle, Wash.

     Mann, C., 1978.  Personal Communication.  Requests and
Information Section, National Air Data Branch, U.S. Environmental
Protection Agency, Research Triangle Park, N.C.

     Midgett, M. R. , 1978.  Personal Communication.  Quality Assur-
ance Branch, National Air Data Branch, U.S. Environmental Protection
Agency, Research Triangle Park, N.C.

     Mistry, M. T. et al., 1975.  Personal Communication to EPA
Region II.  Betz Environmental Engineers, Newark, N.J.
                                 8-1

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     MITRE Corporation, 1978.  Regional Views on NSPS for Selected
Categories.  Metrek Division, McLean, Va.

     Monsanto Enviro-Chemical, 1974.  Vanadium Catalysts for Contact
Sulfuric Acid Plants.  St. Louis, Mo.

     Mullins, F., 1978.  Personal Communication.  Occidental
Petroleum Corporation, White  Springs, Fla.

     PEDCo Environmental Inc., 1977.  Summary Report on S02 Control
Systems for Industrial Combustion and Process Sources, Vol. IV
Sulfuric Acid Plants.  Cincinnati, Ohio.

     Reynolds, W. ,  1977.   Personal Communication to EPA Region IX,
Valley Nitrogen Producers, Inc., Helm,  Calif.

     Pfander, J., 1978.  Personal Communication.  EPA Region X,
Boise, Idaho.

     Rom, J., 1978.   Personal Communication.  EPA Region IV, Atlanta,
Ga.

     Serne, J.  C. and I. J.  Weinsenberg,  1976.  Engineering Evalua-
tion of Cities  Service Smelter,  Copperhill  Tennessee  for S02
Emission Control.   Pacific Environmental  Services,  Inc., Santa
Monica, Calif.

     Sheputis,  J. ,  1978.   Personal  Communication.   Monsanto
Environ-Chemical,  St. Louis,  Mo.

     Shonk,  R.  D. ,  1978.   Personal  Communication.   Agrico  Chemical
Co., Donaldsonville,  La.

     Snowden, W.  D. and D. A. Alguard,  1976.   Personal  Communication
 to EPA Region X,  Alsid,  Snowden & Assoc., Believe,  Wash.

      Spruiell,  S. ,  1978.   Personal  Communication.   EPA  Region VI,
 Dallas, Tex.

      Stanford Research Institute, 1977.  Directory  of Chemical
 Producers,  Palo Alto, Calif.

      Stark,  C. , 1978.  Personal Communication.   Mississippi Chemical
 Corporation,  Yazoo City,  Miss.

      U.S.  Department of Commerce, 1976.  Sulfuric Acid  1976,  Current
 Industrial Reports.  M28A(76)-14 Supplement 1.   Bureau  of  the Census,
 Washington,  D.C.

                                  8-2

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     U.S. Department of Commerce, 1977.   Sulfuric Acid 1977 Current
Industrial Reports.   M28A(77)-14 Supplement 1.   Bureau of the Census,
Washington, O.C.

     U.S. Department of the Interior, Bureau of Mines, 1975.   Miner-
als Yearbook 1975,  Metals,  Minerals, and Fuels.  Vol. 1.   U.S.
Department of the Interior, Washington,  D.C.

     U.S. Department of the Interior, Bureau of Mines, 1978.   Mineral
Industry Surveys.  U.S. Department of the Interior,  Washington, D.C.

     U.S. Environmental Protection Agency, 1971.  Background Informa-
tion for Proposed New Source Performance Standards.   Office of Air
Programs, Research Triangle Park, N.C.

     U.S. Environmental Protection Agency, 1971a.  Control of Air
Pollution from Sulfuric Acid Plants.  Emission Standards  and En-
gineering Division,  Durham, N.C.

     U.S. Environmental Protection Agency, 1976.  Sulfuric Acid Plant
Emissions During Start-up,  Shutdown, and Malfunctions.  EPA-600/
2-76-010.  Industrial Environmental Research Laboratory,  Research
Triangle Park, N.C.

     U.S. Environmental Protection Agency, 1977.  Final Guideline
Document:  Control of Sulfuric Acid Mist Emissions from Existing
Sulfuric Acid Production Units.  EPA-450/2-77-019.  Office of Air
Quality Planning and Standards, Research Triangle Park, N.C.

     U.S. Environmental Protection Agency, 1976.  Priorities and
Procedures for Development of Standards of Performance for New
Stationary Sources of Atmospheric Emissions.  EPA-450/3-76-020.  Of-
fice of Air Quality Planning and Standards.  Research Triangle Park,
N.C.

     U.S. Environmental Protection Agency, 1978.  Compliance Data
System Source Data Reports.

     Williams, A. R., 1977.  Personal Communication  to EPA Region V,
Shell Oil Company,  Wood River, 111.

     Wu, J. , 1978.   Personal Communication.  EPA Region IV, Atlanta,
Ga.
                                  8-3

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                                   TECHNICAL REPORT DATA
                            (Pirase read Instructions on the ret crsc before completing)
 REPORT NO
 PA-450/3-79-003
                                                            3 RECIPIENT'S ACCESSION NO
 TITLE AND SUBTITLE
A Review of Standards  of Performance for New  Stationary
Sources-Sulfuric Acid  Plants
                                                             REPORT DATE
              January  1979
            6 PERFORMING ORGANIZATION CODF
Marvin Drabkin and  Kathryn J. Brooks
            8 PERFORMING ORGANi.-Alll'N HUOrll
              MTR-7S72
 PERFORMING ORGANIZATION NAME AND ADDRESS
Metrek Division of  the  MITRE Corporation
1820 Dolley Madison Boulevard
McLean, Virginia  22102
                                                            1O PROGRAM ELEMENT NO
            11  CONTRACT/GRANT NO

               68-02-2526
 2 SPONSORING AGENCY NAME AND ADDRESS
                                                            13 TYPE OF REPORT AND PERIOD COVERED
DAA  for Air Quality Planning and  Standards
Office of Air,  Noise and Radiation
U.  S.  Environmental  Protection Agency
Research Triangle  Park, North Carolina   27711
            14 SPONSORING AGENCY CODE
               EPA 200/04
 5 SUPPLEMENTARY NOTES
 6 ABSTRACT
 This report reviews the current  Standards of Performance  for  New Stationary Sources:
 Subpart H.  It  includes a summary of the current standards, the status of current
 applicable control  technology, and the ability of plants  to meet the current standards,
 Recommendations are made for  future studies needed of unresolved issues.
17.
                                 KEY WORDS AND DOCUMENT ANALYSIS
                   DESCRIPTORS
                                               b IDENTIFIERS/OPEN ENDED TERMS
                                                                             COSATI I Icld/Group
 sulfuric  acid
 manufacturing
 process
 performance standards
 regulations
                              13B
 18 DISTRIBUTION STATEMENT
 Release  Unlimited
19 SECURITY CLASS (This Report)
 Unclassified
21 NO OF PAGES

     87
                                                20 SECURITY CLASS (This page)

                                                 Unclassified
                                                                          22 PRICE
 EPA Form 2220-1 (Rev 4-77)   PREVIOUS EDITION is OBSOLETE

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