United States
 Environmental Protection
 Agency
Research and
Development
EPA--600/8- 87-0341

September 1987
PREVENTION REFERENCE MANUAL:

CHEMICAL SPECIFIC

VOLUME 12: CONTROL OF

ACCIDENTAL RELEASES

OF SULFUR DIOXIDE
Prepared for
Office of Air Quality Planning and Standards
Prepared by
Air and Energy Engineering Research
Laboratory
Research Triangle Park NC 27711

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                 RESEARCH REPORTING SERIES


Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories  were established to facilitate  further development and  application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

     1.  Environmental Health Effects Research

     2.  Environmental Protection Technology

     3.  Ecological Research

     4.  Environmental Monitoring

     5.  Socioeconomic Environmental Studies

     6.  Scientific and Technical Assessment Reports (STAR)

     7.  Interagency Energy-Environment Research and Development

     8.  "Special" Reports

     9.  Miscellaneous Reports

This report has been assigned to the SPECIAL REPORTS series. This series is
reserved for reports which are intended to meet the technical  information needs
of specifically targeted user groups. Reports in this series include Problem Orient-
ed Reports, Research Application Reports, and Executive Summary Documents.
Typical of these reports include state-of-the-art analyses, technology assess-
ments, reports on the results of major research and development efforts, design
manuals, and user manuals.



                        EPA REVIEW NOTICE

This report has been reviewed  by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161.

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                                   ABSTRACT

     Recent headlines of accidental releases of toxic chemicals at Bhopal and
Chernobyl have created the current public awareness of toxic release problems.
As a result of other, perhaps less dramatic incidents in the past, portions of
the chemical industry were aware of this problem long before these events.
These same portions of the industry have made advances in this area.  Interest
in reducing the probability and consequences of accidental toxic chemical
releases that might harm workers within a process facility and people in the
surrounding community prompted the preparation of this manual and a planned
series of companion manuals addressing accidental releases of toxic chemicals.

     Sulfur dioxide has an IDLE (Immediately Dangerous to Life and Health)
concentration of 100 ppm, which makes it an acute toxic hazard.

     Reducing the risk associated with an accidental release of sulfur dioxide
involves identifying some of the potential causes of accidental releases that
apply to the processes that use sulfur dioxide.  In this manual, examples of
potential causes are identified as are specific measures that may be taken to
reduce the accidental release risk.  Such measures include recommendations on
plant design practices, prevention, protection and mitigation technologies,
and operation and maintenance practices.  Conceptual cost estimates of possi-
ble prevention, protection, and mitigation measures are provided.
                                     11

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                               ACKNOWLEDGEMENTS

     This manual was prepared under the overall guidance and direction  of T.
Kelly Janes. Project Officer, with the active participation of Robert  P.
Hangebrauck. William J. Rhodes, and Jane M. Crum. all of U. S. EPA.   In
addition, other EPA personnel served as reviewers.  Radian Corporation
principal contributors involved in preparing the manual were Graham  E.  Harris
(Program Manager). Glenn B. DeWolf (Project Director), Daniel S.  Davis,
Jeffrey D. Quass, Miriam Stohs, and Sharon L. Wevill.  Contributions were also
provided by other staff members.  Secretarial support was provided by Roberta
J. Brouwer and others.  A  special thanks is given to many other  people, both
in government and industry, who served on  the Technical Advisory Group  and  as
peer reviewers.
                                       111

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                               TABLE OF CONTENTS
Section

  ABSTRACT
  ACKNOWLEDGEMENTS
  FIGURES	    v
  TABLES	   vi

  1       INTRODUCTION	    1

          1.1  Background	    1
          1.2  Purpose of This Manual	    2
          1.3  Uses of Sulfur Dioxide	    2
          1.4  Contents of this Manual   	    3

  2       CHEMICAL CHARACTERISTICS	    4

          2.1  Physical Properties 	    4
          2.2  Chemical Properties and Reactivity  	    7
          2.3  Toxicological and Health Effects  	    8

  3       FACILITY DESCRIPTIONS AND PROCESS HAZARDS  	   11

          3.1  Manufacture	   11
          3.2  Processing and Consumption  	   13
               3.2.1  Manufacture of Sulfuric Acid	   14
               3.2.2  Sulfonation of Alkanes	   17
               3.2.3  Sulfur Dioxide in the Pulp and Paper Industry   .  .   21
               3.2.4  Water and Wastewater Treatment 	   28
               3.2.5  Sulfur Dioxide in the Petroleum Industry  	   30
          3.3  Repackaging Sulfur Dioxide  	   35
          3.4  Storage and Transfer	   36
               3.4.1  Storage	   37
               3.4.2  Transfer from Tank Cars and Trucks	   38
               3.4.3  Transfer from Storage Vessels  	   39
               3.4.4  Transporting Sulfur Dioxide Storage Containers  .  .   41

  4       POTENTIAL CAUSES OF RELEASES 	   42

          4.1  Process Causes	   42
          4.2  Equipment Causes  	   43
          4.3  Operational Causes	   45

  5       HAZARD  PREVENTION AND CONTROL  	   46

          5.1  General Considerations  	   46
          5.2  Process Design	   47
          5.3  Physical Plant Design 	   48
               5,3.1  Equipment	   49
               5.3.2  Plant Siting and Layout	   65
               5.3.3  Transfer and Transport Facilities   	   67


                                       iv

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                         TABLE OF CONTENTS  (Continued)
Section                                                                   Page

          5.4  Protection Technologies 	   68
               5.4.1  Enclosures	   68
               5.4.2  Scrubbers	   70
          5.5  Mitigation Technologies	   73
               5.5.1  Secondary Containment Systems  	   74
               5.5.2  Flotation Devices and Foams	   79
               5.5.3  Mitigation Techniques for Sulfur Dioxide Vapor .  .   81
          5.6  Operation and Maintenance Practices 	   82
               5.6.1  Management Policy  	   83
               5.6.2  Operator Training  	   85
               5.6.3  Maintenance and Modification Practices 	   87
          5.7  Control Effectiveness 	   91
          5.8  Illustrative Cost Estimates for Controls  	   92
               5.8.1  Prevention and Protection Measures 	   92
               5.8.2  Levels of Control	   92
               5.8.3  Summary of Levels of Control	   96
               5.8.4  Equipment Specifications and Detailed Costs  ...   96
               5.8.5  Methodology	   96

  6       REFERENCES	137

  APPENDIX A - GLOSSARY	142
  APPENDIX B - METRIC (SI) CONVERSION FACTORS	145

                                    FIGURES
Number                                                                   Page

3-1  Conceptual diagram of typical sulfur dioxide extraction process .  .   12

3-2  Conceptual diagram of typical double-absorption sulfuric acid
     process	   16

3-3  Conceptual diagram of typical sulfurization process 	   19

3-4  Conceptual diagram of sulfite cooking liquor preparation and sulfur
     recovery process  	   23

3-5  Conceptual diagram of typical chlorine dioxide manufacturing
     process	   25

3-6  Conceptual diagram of water dechlorination with sulfur dioxide  .  .   27

3-7  Conceptual diagram of typical batch chromium waste treatment
     process	   29

3-8  Conceptual diagram of typical sulfur dioxide extraction process .  .   31

5-1  Computer model simulation showing the  effect of diking on  the
     vapor cloud generated from a release of liquified sulfur dioxide   .   78

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                                    TABLES

Number                                                                   Page

2-1  Physical Properties of Sulfur Dioxide	'	•    5

2-2  Exposure Limits for Sulfur Dioxide  	    9

2-3  Predicted Human Health Effects of Exposure to Various Concentrations
     of Sulfur Dioxide	   10

3-1  Sulfur Dioxide Reaction Products  	   15

5-1  Example Process Design Considerations for Processes Involving
     Sulfur Dioxide  	   43

5-2  Materials of Construction for Sulfur Dioxide Service  	   50

5-3  Maximum Safe Volume of Liquid Sulfur Dioxide in a Storage Tank at
     Various Temperatures  	   53

5-4  Example of Performance Characteristics for an Emergency Packed Bed
     Scrubber for Sulfur Dioxide	   72

5-5  Examples of Major Prevention and Protection Measures for Sulfur
     Dioxide Releases  	   93

5-6  Estimated Typical Costs of Major Prevention and Protection Measures
     for Sulfur Dioxide Releases 	   94

5-7  Summary Cost Estimates of Potential Levels of Controls for Sulfur
     Dioxide Storage Tank and Extraction Tower 	   97

5-8  Example of Levels of Control for Sulfur Dioxide Storage Tank  ...   98

5-9  Example of Levels of Control for Sulfur Dioxide Extraction Tower  .  100

5-10 Estimated Typical Capital and Annual Costs Associated with Baseline
     Sulfur Dioxide Storage System 	  102

5-11 Estimated Typical Capital and Annual Costs Associated with Level 1
     Sulfur Dioxide Storage System 	  103

5-12 Estimated Typical Capital and Annual Costs Associated with Level
     2  Sulfur Dioxide Storage System 	  105

5-13 Estimated Typical Capital and Annual Costs Associated with Baseline
     Sulfur Dioxide Extraction Tower System  	  107

5-14 Estimated Typical Capital and Annual Costs Associated with Level 1
     Sulfur Dioxide Extraction Tower System  	  108

                                      vi

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                              TABLES (Continued)

Number                                                                    Page

5-15 Estimated Typical Capital and Annual Costs Associated with Level 2
     Sulfur Dioxide Extraction Tower System  	    110

5-16 Equipment Specifications Associated with Sulfur Dioxide Storage
     System	    112

5-17 Details of Material and Labor Costs Associated with Baseline
     Sulfur Dioxide Storage System 	    115

5-18 Details of Material and Labor Costs Associated with Level 1 Sulfur
     Dioxide Storage System  	    116

5-19 Details of Material and Labor Costs Associated with Level 2 Sulfur
     Dioxide Storage System  	    118

5-20 Equipment Specifications Associated with Sulfur Dioxide' Extraction
     Tower System	    120

5-21 Details of Material and Labor Costs Associated with Baseline Sulfur
     Dioxide Extraction Tower System 	    123

5-22 Details of Material and Labor Costs Associated with Level 1 Sulfur
     Dioxide Extraction tower System 	    124

5-23 Details of Material and Labor Costs Associated with Level 2 Sulfur
     Dioxide Extraction Tower System 	    126

5-24 Format for Total Fixed Capital Cost	    129

5-25 Format for Total Annual Cost	    131

5-26 Format for Installation Costs 	    136
                                     vii

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                                   SECTION 1
                                 INTRODUCTION

1.1  BACKGROUND

     The consequences of a large release of a toxic chemical can be
devastating.  This was clearly evidenced by the release of a cloud of toxic
methyl isocyanate in Bhopal. India on December 3. 1984. which killed
approximately 2,000 people and injured thousands more.  Prior to this event.
there had been other, perhaps less dramatic, releases of toxic chemicals, but
the Bhopal incident precipitated the recent public concern for the integrity
of process facilities which handle hazardous materials.
                                   •
     Recognizing the fact that no chemical plant is free of all release
hazards and risks, a number of concerned individuals and organizations have
contributed to the development of loss prevention as' a recognized specialty
area within the general realm of engineering science.  Interest in reducing
the probability and consequences of an accidental release of sulfur dioxide
prompted the preparation of this manual.  Furthermore, a series of manuals is
planned which will address the prevention and control of a large release of
any toxic chemical.  The subjects of the other manuals planned for the series
include:

     •    A user's guide.
     •    Prevention and protection technologies,
     •    Mitigation technologies, and
     •    Other chemical specific manuals such as this one.

The manuals are based on current and historical technical literature, and they
address the design, construction, and operation of chemical process facilities
where accidental releases of toxic chemicals could occur.  Specifically, the

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user's guide is intended as a general introduction to the subject of toxic
chemical releases and to the concepts which are discussed in more detail in
the other manuals.  Prevention technologies are applied to the design and
operation of a process to ensure that primary containment is not breached.
Protection technologies capture or destroy a toxic chemical involved in an
incipient release after primary containment has been breached but before an
uncontrolled release occurs, while mitigation technologies reduce the
consequences of a release once it has occurred.

     Historically, there do not appear to have been any significant releases
of sulfur dioxide in the United States.  Major incidents elsewhere involving
sulfur dioxide also do not appear to have been common.

1.2  PURPOSE OF THIS MANUAL

     The purpose of this.manual is to provide technical information about
sulfur dioxide with specific emphasis placed on the prevention of accidental
releases of this chemical.  This manual addresses technological and procedural
issues, related to release prevention, associated with the storage, handling,
and process operations involving sulfur dioxide.

     This manual is intended as a summary manual for persons charged with
reviewing and evaluating the potential for releases at facilities that use,
store, handle, or generate sulfur dioxide.  It is not intended as a
specification manual, and the reader is often referred to additional technical
manuals and other information sources for more complete information on the
topics discussed.  Other sources of information include manufacturers and
distributors of sulfur dioxide in addition to technical literature on design.
operation, and loss prevention in facilities which handle toxic chemicals.

 1.3   USES OF SULFUR DIOXIDE

      Sulfur dioxide is a significant commodity chemical, produced by burning
sulfur bearing ores or elemental sulfur in air, or by recovery from stack

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gases to meet clean air requirements.  Numerous references in  the  technical
literature provide information on both the manufacture and uses  of  sulfur
dioxide.

     The dominant use of sulfur dioxide is as a captive  intermediate  in  the
production of sulfuric acid.  Its other major uses  include chemical
manufacture  (primarily sulfites). food processing  (primarily corn), pulp and
paper manufacture, water and waste water treatment, and  metallurgical
applications.  Minor uses are found  in a variety of industries including the
refrigeration, food preservation, bleaching, fumigating, and petroleum
industries.

1.4  CONTENTS OF THIS MANUAL

     Following this introductory section, the remainder  of this  manual
presents technical information on specific hazards  and categories  of  hazards
for sulfur dioxide releases and  their control.  As  stated previously, these
are examples only and are representative of  9nly some of the hazards  that  may
be related to accidental releases.   The physical,  chemical, and  toxicological
properties of sulfur dioxide which create or enhance the hazards of an
accidental release are presented in  Section  2.  In Section 3.  the  manufacture,
consumption, and storage of sulfur dioxide are  discussed, and  the  release
hazards associated with these operations are identified.  Potential causes of
releases, including those identified in Section 3.  are summarized  in  Section
4.  Section 5 contains detailed  information  about  hazards prevention  and
control.  Topics included in this section are process and physical  plant
designs, protection and mitigation technologies, operating and maintenance
practices, and illustrative costs.

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                                  SECTION 2
                           CHEMICAL CHARACTERISTICS

     This section describes the physical, chemical, and toxicological proper-
ties of sulfur dioxide as they relate to accidental release hazards.

2.1  PHYSICAL PROPERTIES

     Sulfur dioxide (SO.) is a colorless gas  with a characteristic pungent
odor and taste.  Although the gas is relatively inert  and stable,  it  is toxic
and highly irritating.  Its more important physical and chemical properties
are presented in Table 2-1.

     The solubility of sulfur dioxide gas in  water is  36 volumes per  volume of
water at 68 °F.  It is also very soluble (several hundred volumes per volume
of solvent) in a number of organip solvents such as acetone, other ketones.
and formic acid (1).

     Because of the low boiling point, and because the gas is considerably
heavier than air. spills and leaks of liquid  sulfur dioxide could result in a
vapor cloud or plume that will remain close to the ground, posing a threat to
workers and surrounding communities.

     Pure liquid sulfur dioxide is a poor conductor of electricity and is only
slightly miscible with water (1).  The liquid also has a high coefficient of
expansion, expanding approximately 10% when warmed from 68 °F to 140  °F (1).
Hence, an overpressurization hazard exists if storage  vessels have insuffi-
cient expansion space or if liquid sulfur dioxide pipelines may be blocked in.

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               TABLE 2-1.  PHYSICAL PROPERTIES OF SULFUR DIOXIDE
                                                                    Reference
CAS Registry Number
Chemical Formula
Molecular Weight
Normal Boiling Point
Melting Point
Liquid Specific Gravity (H 0=1)
Vapor Specific Gravity (air=l)
Vapor Pressure
Vapor Pressure Equation


                         where:
    7446-09-5
    so2
    64.06
    14.0 °F ® 14.7  psia
    -98.9 °F
    1.436 ® 32 °F
    2.263 ® 32 °F
    49.1 psia ® 70  °F


log Pv = A - rjp
Liquid Viscosity
Solubility in Water at 1 atm,
g/lOOg H0
                                                                           1
                                                                           1
                                                                           2
                                                                           1
                                                                           2
                                                                           3
    Pv = vapor pressure,  mm Hg
     T = temperature,  °C
     A = 7.28228,  a constant
     B = 999.900,  a constant
     C = 237.190,  a constant

    0.49 centipoise @ -4  °F and 14.22 psia  4
                                            1
32 °F
50 °F
68 "F
86 °F
104 °F
22.971
16.413
11.577
8.247
5.881
                                                                  (Continued)

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                             TABLE 2-1 (Continued)
                                                                     Reference
Specific Heat at Constant
Pressure (vapor)

Specific Heat at Constant
Pressure (liquid)

Latent Heat of Vaporization

Liquid Surface Tension
0.149 Btu/(lb-°F) @ 77 «F


0.327 Btu/(lb-°F) @ 68 °F

167.24 Btu/lb ® 14.0 °F

28.59 dynes/cm @ 14 °F
4

1

4
Additional properties useful in determining other properties from physical
property correlations:
Critical Temperature               315.7 °F

Critical Pressure                  1,147 psia
                                             3
Critical Density                   0.51 Ib/ft

Energy of Molecular Interaction    252 K

Effective Molecular Diameter       4.29 Angstroms
                                        1

                                        1

                                        1

                                        5

                                        5

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2.2  CHEMICAL'PROPERTIES AND REACTIVITY

     Sulfur dioxide is extremely stable to heat, even up to 3600 °F (1).  It
does not form flammable or explosive mixtures with air.  It will, however,
react with water or steam to produce toxic and corrosive fumes (6).  When the
gas dissolves in water it forms a weak acid solution of sulfurous acid (H-SO.)
which is corrosive and unstable when exposed to heat (7).  Sulfurous acid does
not exist in the free state, dissociating to the sulfite and bisulfite ions,
S03~ and HS03~.  The deleterious effect of sulfur dioxide and sulfites in
domestic water is the increased corrosivity owing to the lowered pH.  However,
oxidation of sulfite to sulfate in aqueous solutions uses dissolved oxygen,
and this may retard corrosion  (6).  While the oxidation of sulfite and
sulfurous acid to sulfate and  sulfuric acid in the atmosphere is an
environmental concern, this reaction is too slow to significantly reduce the
concentration of sulfur dioxide in a short time period in the event of a large
release.

     Sulfur dioxide can be reduced by hydrogen to hydrogen sulfide.  It also
reacts with chlorine to form sulfuryl chloride.  Both of these gaseous pro-
ducts are toxic.  The reduction of sulfur dioxide to sulfur can be accomplish-
ed with H_S, methane, carbon (coal), and CO (1).  The reaction with H.S will
occur at ambient temperatures  in the presence of water, but requires high
temperatures or a catalyst when sulfur dioxide is in the dry state.  Sulfur
dioxide is reported to react violently with a number of compounds of which
several may be present in facilities which also use sulfur dioxide, e.g..
chlorates, Al, and Cr compounds (6,8).  The reaction with chlorates produces
chlorine, and this has the potential to become an explosive reaction at
elevated temperatures (8).

     Most metals are resistant to commercial dry liquid sulfur dioxide, dry
gaseous sulfur dioxide, and hot gaseous sulfur dioxide containing water vapors
above the dew point (1).  These include iron, steel, copper, aluminum, and
brass.  However, these materials are readily corroded by wet sulfur dioxide

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gas below the dew point. Zinc is also readily oxidized by sulfur dioxide to
form
2.3  TOXICOLOGICAL AND HEALTH EFFECTS

     Sulfur dioxide is a toxic, highly irritating gas which can have immediate
effects on the eyes, throat, lungs, and skin.  The toxicology of sulfur
dioxide has been studied through accidental human exposure and through animal
studies (9) .  A concentration of 100 ppm has been designated as the IDLH limit
(Immediately Dangerous to Life and Health), which is based on a 30-minute
exposure (10) .  Table 2-2 presents a summary of some of the relevant exposure
limits for sulfur dioxide.

     The primary health effects from exposure to sulfur dioxide occur in the
upper respiratory tract and the bronchi.  Chronic exposure may result in
nas ©pharyngitis, fatigue, altered sense of smell, and chronic bronchitis
symptoms such as dyspnea on exertion, cough, and increased mucous excretion
(10) .  It may cause edema of the lungs or glottis and can produce respiratory
paralysis  (6) .  In concentrations greater than 20 ppm, sulfur dioxide is
irritating to the eye and will cause pain, tearing, inflammation, swelling of
tissue and possible destruction of the eye (7,8).  Acclimation to the effects
of sulfur dioxide has been reported to develop quickly as a result of the
depression of the tracheobronchial nerve reflexes; this adjustment is not
considered to be a beneficial effect because of the possibility that the
absence of discomfort merely removes one measure of protection (9) .  The
physical effects of increasing levels of gas concentrations on humans are
summarized in Table 2-3  (11).

     Sulfur dioxide is not listed in the National Toxicology Program, the
International Agency for Research on Cancer, nor the Registry of Toxic Effects
of Chemical Substances (1981-82) as a carcinogen or potential carcinogen (12).
However, sulfur dioxide has been implicated as a cocarcinogen (promoter) with
arsenic (9) .

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     Contact with liquid sulfur dioxide may  cause  cryogenic  burns  to  the  skin

in addition to conjunctivitis, corneal burns, and  corneal  opacity  of  the  eye
(7.8.10).  It is also reported that high  concentrations  of sulfite ion in
water may cause eczema  (6).


                TABLE 2-2.  EXPOSURE LIMITS  FOR  SULFUR DIOXIDE

Exposure      Concentration
 Limit           (ppm)                    Description                      Ref.


IDLH              100         The  concentration  defined  as posing           10
                              an immediate danger  to life  and health
                               (i.e.. causes  irreversible toxic  effects
                              for  a 30-minute exposure).

PEL                 5         This concentration was determined by         10
                              the  Occupational Safety and  Health
                              Administration (OSHA) to be  the time-
                              weighted 8-hour exposure limit which
                              should result  in no  adverse  effects  for
                              the  average worker.

LC--.              400         This concentration is the  lowest               6
                              published  lethal concentration for a
                              human over  a 5-minute exposure.

TCL.                4         This concentration is the  lowest               6
                              published  concentration  causing toxic
                              effects  (irritation).
 *PEL stands for  the  "permissable exposure limit."

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  TABLE 2-3.  PREDICTED HUMAN HEALTH EFFECTS OF EXPOSURE TO VARIOUS
              CONCENTRATIONS OF SULFUR DIOXIDE (7)

  ppm                       Predicted Effect
 0.3-1              Can be detected by taste and smell

     3              Easily noticeable odor

  6-12              Immediate irritation of nose and throat

    20              Eye irritation - ill effects if exposure is
                    prolonged

50-100              Maximum permissible concentration for 30 to
                    60 minutes exposure

   200              Severe toxic effects after one minute

  >400              Immediately dangerous to life
                              10

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                                   SECTION 3
                   FACILITY DESCRIPTIONS AND PROCESS HAZARDS

     This section contains brief descriptions of the processes and facilities
for the manufacture, consumption, and storage of sulfur dioxide in the United
States.  The purpose of this section is to identify major hazards associated
with these facilities which may directly or indirectly cause accidental
releases.  Measures taken for the prevention of these hazards are discussed in
Section 5.

3.1  MANUFACTURE  (1.2.13)

     Sulfur dioxide gas is produced in the United States by several methods
which include the combustion of sulfur or pyrites, as a by-product of smelter
operations, and as a by-product of other chemical operations.  For many of the
chemical process applications which require sulfur dioxide gas or sulfurous
acid, sulfur dioxide is captively produced by the burning of sulfur or pyrite,
FeS., and the gas is immediately consumed in the process.  The manufacture of
liquid sulfur dioxide for commercial sale involves passing the combustion gas
into water which dissolves it and certain impurities.  This liquor is then
heated to drive off the sulfur dioxide, and the liberated gas is dried and
liquefied.

     Figure 3-1 is a typical flow diagram for the preparation of liquid sulfur
dioxide.  The sulfur-bearing raw material is fed to the burner where it is
combusted with air.  The type of burner used is primarily determined by the
rate and concentration of sulfur dioxide to be produced and the quality of
sulfur to be burned.  The sulfur dioxide content of the burner gas is depen-
dent on the equilibrium adiabatic flame temperature and varies from about 6.5%
at 1470 °F to about 20% at 3180 °F when the raw material is elemental sulfur
(13).  After leaving the burner, the heat of combustion is recovered in a
                                      11

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                                               STEAM
                                        BOILER
                                      FEED WATER  I
                                        I
WATER
 I
SULFUR BEARING
 RAW MATERIAL
BURNER


WASTE
HEAT
BOILER


ARQnnnpR



EVAPORATOR
CONDENSER


mMPRPQQnn



SCRUBBER
                                      LIQUID SULFUR DIOXIDE
                                           TO STORAGE
         Figure 3-1.   Conceptual  diagram of  typical sulfur  dioxide manufacturing process.

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waste-heat boiler, after which the combustion gas is further cooled prior to
absorption in water.  Lead pipes in flowing water are commonly used for cool-
ing the gas.  The combustion gas then passes through one or more absorption
towers in which the sulfur dioxide and certain impurites are absorbed into
water.  The resulting liquor is then heated to drive off sulfur dioxide gas.
The gas is cleaned and dried with concentrated acid, cooled, compressed, and
finally condensed to pure liquid product.

     The primary hazard areas in the production of liquid sulfur dioxide are
at the latter end of the process where sulfur dioxide is present in pure form.
The following potential release hazards may be identified in this portion of
the process (excluding the bulk storage system which is discussed in Section
3.4):

     •    The leakage of moisture into any equipment which handles a
          large amount of sulfur dioxide with the consequent forma-
          tion of corrosive -sulfurous acid;

     •    Failure of the sulfur dioxide compressor possibly
          resulting from a power failure, rotor failure, or
          excessive stress caused by severe vibrations; and

     •    A loss of cooling to the sulfur dioxide condenser which
          results in a pressure buildup and possible equipment
          failure.

Other release hazards, or possible causes of release, which are general to all
sulfur dioxide processing facilities are summarized in Section 4.

3.2  PROCESSING AND CONSUMPTION

     The example processes discussed in this section represent many of the
primary uses of sulfur dioxide and include the production of sulfuric acid,
                                      13

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the sulfonation of alkanes.  pulp and paper manufacture, water and waste
treatment, and solvent extraction.  Sulfur dioxide is also used in the
manufacture of a variety of important industrial chemicals which are too
numerous to discuss individually.  Many of these products are listed in Table
3-1.

3.2.1  Manufacture of Sulfuric Acid (1)

     Sulfuric acid is produced by the contact process.  Different variations
of this process use a wide range of sulfur-bearing raw materials.  The most
common raw material is elemental sulfur.  The process produces gaseous sulfur
dioxide by sulfur combustion, followed by catalytic conversion of the sulfur
dioxide to sulfur trioxide (S0g). and absorption of the SO, into concentrated
sulfuric acid.

     Regardless of the source of sulfur, the first step in the contact process
produces a continuous, contaminant-free gas stream containing appreciable
sulfur dioxide and some oxygen.  A dry gas stream entering the catalytic
converters is desirable; the air used for burning elemental sulfur is general-
ly predried, while other processes dry the sulfur dioxide stream after it
leaves the combustion chamber.  Sulfur trioxide is produced from the sulfur
dioxide by catalytic conversion, and it is subsequently absorbed into a
circulating stream of 98-99% H2so4 at approximately 158-176 °F.

     Figure 3-2 illustrates the contact process for a double-absorption
sulfur-burning plant.  Single-absorption plants used to be the industry norm,
but  stricter controls on residual sulfur dioxide emissions necessitated an
intermediate absorption step to effect overall sulfur dioxide conversions of
99.5-99.8% in the newer plants.  However, most existing facilities chose to
add  a tail-gas unit instead of modifying the process with an additional
absorption step.
                                       14

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TABLE 3-1.  SULFUR DIOXIDE REACTION PRODUCTS (14)
          sulfur dioxide
          ammonium sulfite
          ammonium thiosulfate
          hydroxylamine sulfate
          potassium bisulfite
          potassium sulfate
          potassium thiosulfate
          sodium bisulfite
          sodium persulfate
          sodium sulfite
          sodium bisulfate
          sodium thiosulfate
          sodium hydrosulfite
          sulfurous acid
          sulfuryl chloride
          pyrosulfuryl chloride
          zinc sulfide
          zinc hydrosulfite
          zinc formaldehyde sulfoxylate
          sulfonamides:
            sulfadiazine
            sulfanilimide
            sulfapyridine
            sulfathiazole
            sulfolane
                        15

-------
Molten
Sullur
i
t •

t 	 *
Dilution Water
Boiler T
Feed 1
Water J
Sulfur
Burner
Dry
Air

Drying
Tower
SO2 Gas

(Acid)
(Acid)

Sleam
Waste
Heat
Boiler





Concentrated
Acid
1





SC
Ga


Acid
Coolers

Boiler Y
Feed 1
Water 1
Converter
And Heal
Exchange
Equipment
'3
s
Inli
Abs
Ti




urpass
orptlon
iwer




Cooled Acid

Concentrated Acid
Steam
Economizer
S03
Gas

Final
Absorption
Tower
1

                                                                                         Gas
                                                                                          lo
                                                                                         Slack
   As Required
                                 Product Acid
Figure  3-2.   Conceptual diagram of typical  double-absorption  sulfuric acid  process.

-------
     The maximum concentration of sulfur dioxide present at any point in the
process is in the gas stream exiting the sulfur combustion chamber.  Typical
sulfur dioxide concentrations range from 4-11 vol%.  Since sulfur dioxide is
only present at this concentration between the sulfur burner and the catalytic
converters, the pieces of equipment in this part of the process are the only
potential sources of a hazardous release of sulfur dioxide under normal
operating conditions.  Some general causes of equipment failure which may lead
to a large release of sulfur dioxide are discussed in Section 4.

     If a process upset were to occur such that the conversion level of sulfur
dioxide to SO. was greatly reduced, the process stream beyond the catalytic
converters would contain a considerable quantity of sulfur dioxide.  One
possible upset is a loss of temperature control in the converters resulting in
a significant temperature increase which would cause the equilibrium in the
oxidation reaction to become less favorable toward SO. formation.

     Because of the exothermic nature of the oxidation of sulfur dioxide to
SO,, overheating resulting in overpressure is also a potential hazard in the
catalytic converters with the consequent possibility of leaks developing of,
in the worst case, equipment failure and loss of containment.

3.2.2  Sulfonation of Alkanes (15)

     Sulfur dioxide is used as a reagent in several sulfation and sulfonation
processes which chemically introduce the SO, group into organic molecules.
Sulfonated and sulfated organics have many "surface-active" applications,
e.g., detergents, dyes, and medicinals, because of their unique properties of
solubility, emulsification, wetting, and foaming.

     In most sulfation and sulfonation processes, the actual sulfonating agent
is either oleum, sulfuric acid, or sulfur trioxide.  The use of sulfur dioxide
in these processes is not widespread in industry.  However, one sulfonation
process employed in the U.S. does use significant quantities of liquid sulfur
                                       17

-------
dioxide.  The"sulfur dioxide in this process serves as a diluent for oleum
(fuming sulfuric acid)  which contains 60-75% free sulfur trioxide.  It is
necessary to dilute the sulfur trioxide, because acid of this strength will
severely char and degrade the alkane being sulfonated.  As the reaction is
highly exothermic, cooling requirements also become very important at high
sulfur trioxide concentrations.  If the sulfur dioxide is supplied in
sufficient quantities it will serve as the cooling medium for the process.
Because the sulfur dioxide does not participate as a reactant in the
sulfonation. it is separated from the reaction products and recycled to the
process.

     Figure 3-3 is a flow diagram of a typical sulfonation process which uses
sulfur dioxide as a diluent and a refrigerant.  The sulfur dioxide and oleum
are pumped from storage to an agitated weigh tank.  The weight ratio of sulfur
dioxide to oleum is approximately 7 to 1, and the quantity of sulfur dioxide
used corresponds to a weight ratio of about 2 to 4 parts of sulfur dioxide to
one part of the alkane subsequently added.  The process may be adapted for
continuous or batch-sulfonation depending on the way the reactants are fed to
the sulfonator.  For batch operation, the alkane is charged to the reactor.
and the diluted oleum charge is fed to the agitated sulfonator at a controlled
rate to avoid overheating.  For continuous operation, both the alkane and the
oleum are pumped continuously at controlled rates to the sulfonator, and the
sulfonated product is continuously withdrawn.  The flow rates of the reactants
may be  regulated by a valve which is controlled by the temperature of the
reactants in the sulfonator.  This is done to maintain a reaction temperature
of about 20-65 °F.  The heat of reaction is continuously removed from the
reactor by the vaporization and release of sulfur dioxide.  The vented sulfur
dioxide passes through a liquid trap where any liquid materials are separated
and allowed to drain back to the sulfonator.  The gas stream is then scrubbed
in a solution of 93-100% sulfuric acid before passing to one or more compres-
sors.  After compression and condensation, the sulfur dioxide is returned to
storage for reuse in the process.
                                      18

-------
Condenser
    SO,
Compressors
                                             H2 S04
                                            Scrubber
   so2
  Storage
  Oleum
  Storage
                      Oleum
                      Weigh
                       Tank
                                            Knockout
                                              Pol
                  so2
                  gas
                               SO..
Liquid
Return
                       Sulfonator
              Alkane
              Weigh
               Tank
Alkane
Storage
                                            Vacuum
                                           Distillation
                                              Sulfonated Product
                                                  to Storage
         Figure 3-3.   Conceptual diagram of typical sulfonation process.

-------
     There are a number of areas in this process where the sulfur dioxide is
present in high concentrations or nearly pure form.  Because the sulfur
dioxide is not consumed in the sulfonation reaction, the possibility of a
large release of this chemical is greater than what might exist in a process
where the sulfur dioxide is consumed as a reactant.  From a sulfur dioxide
release perspective, critical areas of the process include the sulfur dioxide
storage and feed systems, the sulfonator. and the sulfur dioxide recovery
section (including the sulfur dioxide compressors, condenser and storage
tank).  Examples of possible causes of a large release include the fallowing:

     •    If moisture leaks into the system, equipment which handles
          a large amount of sulfur dioxide may be corroded by the
          sulfurous acid formed and be weakened to the point of
          sudden rupture;

     4    If there is a failure in the feed control system, a
          runaway reaction may result which causes a buildup of
          pressure exceeding the design pressure of the sulfonator;
          and

     •    A loss of cooling to the sulfur dioxide condenser may also
          result in a pressure buildup and equipment failure.

     If the oleum feed is too concentrated, the exothermic sulfonation reac-
tion will proceed too quickly, resulting in a temperature rise in the reactor
and a consequent increase in pressure.  Because the sulfur dioxide recovery
section involves relatively pure streams of sulfur dioxide, this section of
the process represents a potential hazard area.  Overpressurization of a con-
denser may occur if the cooling system fails.  Although this may not lead to
catastrophic equipment failure, leaks of sulfur dioxide into the plant cooling
water could result in the formation of corrosive levels of sulfurous acid.
                                      20

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3.2.3  Sulfur Dioxide in the Pulp and Paper Industry

Sulfite Pulping (16.17.18)--
     One of the primary uses of sulfur dioxide is in the manufacture of
chemicals (see Table 3-1) of which sulfites represent a majority of the sulfur
dioxide consumed.  One major application of sulfite solutions is the sulfite
pulping process used in the manufacture of paper.  There are a number of
variations of the sulfite pulping process, and there are also many other
pulping processes, encompassing both mechanical and chemical methods, which do
not require the use of sulfur dioxide.

     The purpose of pulping is to separate the cellulose fibers from the
matrix of lignin which cements them together.  The usual sulfite process is a
chemical method which consists of digesting the wood by "cooking" it in an
aqueous bisulfite solution (usually Ca, Mg. Na. or NH_) and an excess of
sulfur dioxide.  Recently, multi-stage pulping processes have been introduced
in which the stages differ from each other in the cooking liquor used.  Liquid
sulfur dioxide is used in some of these processes as the cooking liquor in the
second stage (16).

     In the preparation of the sulfite solution, gaseous sulfur dioxide is
typically generated by burning molten sulfur in either rotary or spray burn-
ers.  The gas exiting the burner usually contains about 17% sulfur dioxide
with the remainder of the gas consisting mostly of nitrogen and a small amount
of oxygen.  This gas is cooled from a temperature of about 1800 °F to between
77 °F and 158 °F depending on the desired pH of the sulfite liquor.  The
cooling process generally involves a horizontal, vertical, or pond cooler
consisting of a system of pipes surrounded by water.

     The sulfite "cooking acid" is prepared by the absorption of the gaseous
sulfur dioxide in aqueous solutions containing calcium, magnesium, sodium, or
ammonium compounds.  This is accomplished in a series of two or more absorp-
tion towers or acid-making tanks for Mg(HSO,)-.  Sulfur dioxide solubility is
                                      21

-------
a function of the temperature,  pressure,  and  pH during  absorption.   System
absorption efficiencies  for the different absorption systems  used in industry
range from 97% to greater than  99%  (18).

     The portions of the sulfite pulping  process which  involve significant
quantities of sulfur dioxide include  the  gas  exiting the sulfur burners and
the recovery of sulfur dioxide  from the spent cooking liquor.  Potential
hazards associated with  the process gas stream involve  the piping between the
sulfur burners and the absorption towers  including  the  gas cooling section.
Because water is used as the cooling  medium,  a release  of sulfur dioxide gas
would result in the formation of corrosive sulfurous acid. Some general
causes of equipment failure (including piping systems)  are discussed in
Section 4.

     A number of sulfur  recovery procedures are employed in the pulping
industry.  Some of these processes  include a  sulfur dioxide stripping opera-
tion which produces a nearly pure stream  of gaseous sulfur dioxide.  While the
recovered sulfur dioxide is generally fed back to the sulfur  dioxide absorp-
tion towers, it may also be combined  with H.S and fed to a Glaus unit or used
                                           ft
to make liquid sulfur dioxide for use in  a multi-stage  pulping process (16).
This type of system is illustrated  in Figure  3-4 which  shows  the preparation
of the cooking acid and  recovery of the sulfur from the spent solution.
Potential hazards associated with the sulfur  dioxide recovery section depend
on the process employed  by the  particular pulping operation.   Some possible
causes of release general to many sulfur  dioxide applications are discussed in
Section 4.

     For multi-stage processes  which  use  liquid sulfur  dioxide, the storage
system constitutes one of the potential sources of  a hazardous release.  The
general hazards associated with the storage of sulfur dioxide are discussed in
Section 3.4.
                                      22

-------
"Green Liquor"
Na2S + Na2C03
I w.
(from Incinerator)
SO2conlalning
flue gas
> fc

:
H2S * C02

Cartaonalkm
lower
1
Steam
*— I "2"
co2
Glaus
Unit

Sulfur
Make-up
Na2S03 Sulluf ••
Flue Gas
Scrubber
Na2S03
NaHSO3





Bisulfite
Tower
Sullur
Burner
IfTB OVf-.
N2.02

„ SOj S02
" Comprossor " Condenser
100% SO, 1 Liquid SO,


so2
Stripper _ „ ^


Abi
1
SO. containing gas



S02 + H20
so2
•nrnttVkn -*- - -- - — H O
tower

I
NaHSO3(cooklng acid) ^
Figure 3-4.  Conceptual diagram of sulfite cooking liquor preparation and sulfur
             recovery process.

-------
Preparation of Chlorine Dioxide (16.19.20.21)—
     Chlorine dioxide is used in the pulp bleaching process, not only to
increase the brightness, but also to improve pulp strength, decrease color
reversion, and to make possible the recovery of bleach plant effluents.
Because this chemical is explosive at higher concentrations, it cannot be
transported in any concentrated form; thus, it is generally produced at the
pulp mill immediately before use.

     Chlorine dioxide is manufactured from sodium chlorate in strong acid
solution, usually sulfuric.  A reducing agent is required to reduce the
chlorate ion to chlorine dioxide.  Three reducing agents are used for this
purpose in industry, one of which is sulfur dioxide.  Figure 3-5 is a flow
diagram for a typical process which uses sulfur dioxide as the reducing agent.

     The reaction is carried out in a cylindrical vessel which contains a
     i
solution of sodium chlorate, sulfuric acid, and chloride ions.  Sulfur dioxide
and chlorine are pumped from their respective liquid storage vessels to the
evaporators.  The two gas streams are diluted with nitrogen (air is also
sometimes used) and mixed prior to entering the reactor through a sparger.
The effluent gas exiting the reactor contains chlorine dioxide, chlorine gas.
and nitrogen.  Sodium chlorate and sulfuric acid are recovered from the
effluent solution and recycled back to the reactor.

     The reaction of sulfur dioxide with chlorate is highly exothermic.  The
temperature of the reaction must be carefully controlled to avoid a runaway
reaction.  For this reason, the volume percent of sulfur dioxide in the gas
mixture must be maintained below 18% to avoid an excessive heat of reaction.
The metering of reagents and the flow of dilution gas have to be accurate.
The process hazard from an excess of sulfur dioxide in the feed or the loss of
cooling to the reactor is the production of too much chlorine dioxide.  At
higher concentrations this chemical quickly decomposes to chlorine gas and
                                       24

-------
                                                              •*• QO2, CI2. and N2 to Recovery
                                                           Recovered H2SO4 with NaOO
                           Nad03(dry)	„


                        NaOH (solution)	»
Neutralization
    and
Crystallization
Centrifuge
                  by-product
Figure 3-5.   Conceptual diagram of  typical chlorine dioxide manufacturing process.

-------
oxygen with explosive force.   Therefore,  most operations incorporate a temper-
ature shutdown switch into the control system which shuts off the feed in the
event of an unacceptable rise in reaction temperature.

     The prevention of an explosive concentration of chlorine dipxide gas is
the major process concern in the production of this chemical* but the release
of a large amount of sulfur dioxide is not the primary hazard of such an
explosion.  This is because the release of a large quantity of chlorine
dioxide and chlorine gas would be a greater danger to workers and the sur-
rounding community.  However* the ratio of sulfur dioxide to chlorine gas in
the feed may be as high as 10 to 20:1 (20).  Hence, if the feed system is not
shut off at the time of a reactor explosion, the sulfur dioxide released from
a venting feed line could, in this case,  pose a serious hazard in itself.

     As liquid sulfur dioxide is used as the source of the gaseous sulfur
dioxide feed, potential hazards which may result in a large release of sulfur
dioxide involve the storage facilities, the evaporator, and the feed system to
the reactor.  Hazards associated with the storage of liquid sulfur dioxide are
discussed in Section 3.4.  Other general equipment hazards are discussed in
Section 4.

Preparation of Sodium Dithionate (18)—
     Sodium dithionate is also used in the pulp bleaching process.  It is
produced at the mill site by the reaction of sulfur dioxide or bisulfite with
sodium borohydride in an alkaline medium.  As the sulfur dioxide is consumed
in the reaction, the hazards which may lead to a large release of sulfur
dioxide are the hazards associated with the storage and feed systems for this
chemical.  General hazards pertaining to these areas are discussed in Sections
3.4 and 4.
                                      26

-------
CHLORINATED
  WATER
                        INJECTOR
                         PUMP
I—t
                                       SULFUR
                                       DIOXIDE
                                       STORAGE
                            INJECTOR
                                                    WEAK
                                                  SULFUROUS
                                                    ACID
DECHLORINATED
   WATER
        Figure 3-6.   Conceptual diagram of water dechlorination with sulfur  dioxide.

-------
3.2.4  Water and Wastewater Treatment

Water Dechlorination (22)—
     Dechlorination is a process for partially or completely removing residual
chlorine from chlorinated water.  Sulfur dioxide is often used as the dechlor-
inating agent, because it reacts with residual chlorine very quickly with
little mixing, and the process is relatively simple compared to other methods
for dechlorination.  The process involves absorbing gaseous sulfur dioxide
into water which results in the formation of sulfite ions.  The sulfite ions
then react with the residual chlorine reducing it to chloride.

     Figure 3-6 is a flow diagram of a typical dechlorination process using
sulfur dioxide.  The injector prepares a weak sulfurous acid solution by
contacting sulfur dioxide gas with a small water stream.  The weak sulfurous
acid is intimately mixed with the chlorinated water in the diffusor.  No
further mixing is required for dechlorination with sulfur dioxide since the
reaction with the residual chlorine is virtually instantaneous.  Feed forward
control is the most common method of controlling the addition of sulfur
dioxide.  An effluent flow rate signal is combined with a residual chlorine
signal to produce a control signal to the sulfur dioxide metering equipment.
The sulfur dioxide injection rate will automatically increase or decrease with
changes in water flow rate and/or residual chlorine.

     The release hazards associated with the dechlorination process are
associated with the sulfur dioxide feed and storage systems.  These hazards,
which are general to all sulfur dioxide processes, are discussed in Sections
3.4 and 4.

Treatment of Chromium Waste (23)—
     Sulfur dioxide is often used to treat industrial waste water which
contains toxic, hexavalent chromium by reducing it to the trivalent state.
Following reduction, the pH of the solution is adjusted, and the trivalent
chromium precipitates as the insoluble hydroxide.
                                       23

-------
WASTE CHROME
   LIQUOR
                                                                  HYDRATED
                                                                    LIME
                                                                                   WATER
SULFUR
DIOXIDE
STORAGE
                                            TO SLUDGE
                                            SEPARATOR
       Figure 3-7.   Conceptual diagram of typical batch chromium waste treatment process.

-------
     Figure 3-7 is a flow diagram of a typical chromium reduction process.
Waste liquors are collected in storage tanks and treated in a series of
batches.  Liquid sulfur dioxide is injected through an "L" shaped diffuser
located near the bottom of the reduction tank.  The reduced chrome is trans-
ferred to the liming tank and treated with sufficient hydrated lime to adjust
the pH to 8.0-8.6. causing the chromium to precipitate.

     As with the dechlorination process, the primary release hazards of the
chrome reduction process involve the sulfur dioxide feed and storage systems.
However, because the sulfur dioxide is fed as a liquid to the reduction tank.
there is the additional hazard of isolating liquid sulfur dioxide between
closed valves when the unit is not operational.  Were this to occur, the
pressure in the piping would rapidly rise as the sulfur dioxide warms, and
overpressurization could result in pipe failure and an uncontrolled release of
sulfur dioxide.

3.2.5  Sulfur Dioxide in the Petroleum Industry

Modified Sulfur Dioxide Extraction (24,25.26) —
     Liquid sulfur dioxide is used as a solvent in the Edeleanu process in
which aromatic hydrocarbons and sulfur-bearing compounds are extracted from
paraffins and naphthenic hydrocarbons.  A modification of the original process
involves washing the extract with a washoil to further concentrate the aroma-
tics which are often equal in value to the paraffinic raffinate.

     The washoil used in the modified process is dependent on the charge.  For
the recovery of aromatics from naphtha fractions, a kerosine cut is used.
Other washoils include a gasoil cut, such as a sulfur dioxide raffinate, for
the recovery of a relatively pure aromatic stream from a petroleum fraction,
or a light paraffinic hydrocarbon, such as hexane or heptane, for use with a
gasoil feedstock.

     Figure 3-8 is a typical flow diagram for the recovery of aromatics from a
naphtha refonnate.  The feed is dried, deaereated, and chilled before entering
                                       30

-------
                                                             Liquid SO,
                                                                                        Rafflnate
Feed
           Deaeralor
Dryer
                                              Chillers
                                                              Feed
                                                             Washoll
                                                              soa
                                                             Drying
                                                            Column
Extraction
  Tower
                                                                         Extract
                                                 Extract
                                                 Stripper
                                              (Evaporators)
                                                                              S02
                                                                           Condensers
                                                                         Washoll Recycle
  Rafflnate
  Stripper
(Evaporators)
 Ralllnate/
  Washoll
Fracllonalor
                                                                           Aromatlcs to
                                                                          Extract Splitter
                             Extract/
                             Washoll
                           Fractlonator
             Figure 3-8.   Conceptual  diagram of typical  sulfur dioxide extraction  process.

-------
 the  extraction tower.  Sulfur dioxide is used as the refrigerant  to  permit the
 use  of common condensers, collecting equipment, and pumps  for  the refrigerant
 and  the  extraction solvent.  The tower shown in Figure 3-8 is  used for both
'the  sulfur dioxide extraction and the stripping of the extract.   The two
 product  streams go to evaporators where the sulfur dioxide is  taken  overhead
 to be condensed in water-cooled tubular equipment.  Part of the recovered
 sulfur dioxide is then used to cool the charge stock and the washoil to
 extraction temperature by flash vaporization, after which  the  vapor  is com-
 pressed  and  returned to the water-cooled condensers.  The  water content of the
 circulating  sulfur dioxide is controlled by sending a slip stream of vapor
 from the extract evaporator to a sulfur dioxide drying column. Provision is
 also made for removal of inert gas from the circulating sulfur dioxide.

     Operating temperatures for the sulfur dioxide extraction  process range
 from -20 °F  for naphthas and kerosines to 60 °F for high-pour-point  stocks
 (25) . ' To maintain the sulfur dioxide as a liquid at these temperatures,
 required operating pressures range from less than 1 atm to 3 atm. The solvent
 to feed  ratios range from 0.5:1 to 3:1, with the heavier charge material
 requiring higher solvent to oil ratios (25).

     From a  sulfur dioxide release perspective, a fundamental  characteristic
 of the extraction process is the use of sulfur dioxide as  a solvent  rather
 than a reactant.  Because recovery and recycle of the solvent  involves a
 number of critical areas where sulfur dioxide is present in high  concentra-
 tions or nearly pure form, the possibility for a release may be greater than
 what might exist in a process where it is consumed as a reactant.

     High hazard areas specific to this process, excluding bulk storage and
 transfer (discussed in Section 3.4), include the following:

      •    Feed treatment to remove water from the hydrocarbon  charge;
      •    The treating tower;
      •    Heat exchange equipment; and
      •    Sulfur dioxide drier.
                                       32

-------
     Removal of water from the feed is important, because sulfur dioxide
combines with water to form sulfurous acid which is corrosive to common
materials of construction such as carbon steel.  The feed does not contain any
sulfur dioxide, but water introduced with the feed will mix with sulfur
dioxide downstream.  While a properly designed system should use materials
which are sufficiently corrosion resistant, the materials selection will have
been based on a certain feed moisture concentration.  Therefore, failure of
the water removal system to maintain the design moisture concentration may
result in a protracted corrosion problem leading eventually to an equipment
failure.

     The primary concern in the treating tower is temperature control.  If a
process upset were to occur which resulted in a substantial temperature
increase in the tower, significant expansion and vaporization of the liquid
sulfur dioxide may occur resulting in a number of process problems.  Further-
more, the liquid phases in the column become more miscible at higher tempera-
tures, and a single liquid phase may result if the treating temperature is too
high (26) .  No separation would take place in this situation, and the
raffinate recovery section could become overloaded with the excess sulfur
dioxide in the overhead product.

     The use of sulfur dioxide as a refrigerant as well as the solvent means
that it will be present in a number of heat exchange vessels in pure form.
The circulating sulfur dioxide will require auxiliary equipment (pumps and
compressors) as well as a considerable amount of piping in the system.  A
large amount of process equipment handling pure sulfur dioxide increases the
chances of leaks developing in the system.  Some possible causes of leaks
include a loss of temperature control resulting in overpressure, corrosion, or
defective or worn-out equipment.  The use of water-cooled sulfur dioxide
condensers also presents the possibility of a leak into the cooling water
system leading to the formation of sulfurous acid and the associated corrosion
hazard that this would create.
                                       33

-------
     Despite precautions taken to dry the charge oil stream, small amounts of
water enter the circulating sulfur dioxide stream from this source.  This
moisture must be continuously removed to prevent accumulation in the recycle
and corrosive levels of sulfurous acid from forming.  A common process used
for drying the sulfur dioxide is sending a slip stream of sulfur dioxide vapor
to a fractionating tower.  Since a level of water collects in the reboiler. it
is necessary to maintain the temperature of the reboiler sufficiently low to
minimize water vaporization.  The possibility of overheating the reboiler
presents a potential hazard which would result in water vapor entering the
sulfur dioxide stream and forming a corrosive mixture.

Liquid Sulfur Dioxide-Benzene Extraction (25) —
     Two extraction processes which employ liquid sulfur dioxide as a
co-solvent with benzene are the removal of low-viscosity-index constituents
and the removal of wax from lube oils.  These extraction processes can be
advantageously arranged in series by adjusting the solvent composition.  The
solvent composition varies according to process requirements, ranging from
15-30% sulfur dioxide by volume for dewaxing to greater than 50% by volume for
lube refining.  In the dewaxing process, sulfur dioxide evaporation furnishes
internal refrigeration for the precipitation of wax before its removal with
closed continuous rotary filters.  The extraction temperature used in the lube
refining process is about 25 °F with a mixed solvent to oil ratio of about
2:1.

     Process hazards associated with these two extraction processes are
similar to  those of the modified sulfur dioxide extraction described above.
However, since the sulfur dioxide is not in pure form, the hazardous effects
of this chemical resulting from a release of solvent may be less severe.

Glaus Process—
     The Glaus process is a method of treating refinery off-gases by convert-
ing hydrogen sulfide to elemental sulfur.  Although appreciable amounts of
gaseous sulfur dioxide are present in the process gas stream, this stream
contains an even greater concentration of hydrogen sulfide.  Hence, the
                                      34

-------
primary hazard in the event of a process stream release is the toxicity of the
H2S. while the adverse effects of the released sulfur dioxide would be less
urgent relative to those of the released H,S.

3.3  REPACKAGING SULFUR DIOXIDE (4.27.28)

     Liquid sulfur dioxide is repackaged at several locations throughout the
U.S.  This process involves a number of procedures, the use of which depends
on whether the transfer is from tank cars into tank trucks, or from tank cars,
trucks, or other bulk storage containers into cylinders or one-ton steel
drums.

     When a bulk quantity of liquid sulfur dioxide arrives at a repackaging
facility, filling operations may be carried out by transferring sulfur dioxide
directly from the tank car or truck to the receiving container(s).  However,
most repackagers firs*t transfer the sulfur dioxide to bulk storage before
filling smaller containers.  Tank cars and trucks are unloaded with the use of
a gas compressor or transfer unit; the suction side draws gas from the top of
a storage tank, while the discharge is connected to a valve on the tank car or
truck which allows flow through a dip pipe terminating in the vapor phase
within the tank.  Thus, the liquid sulfur dioxide flows to the bulk storage
vessel as the pressure in this vessel is lowered and the pressure in the tank
is increased.  Tank cars may alternatively be unloaded with the use of
compressed air as the padding medium in the car which causes the liquid to
flow into the bulk storage vessel.  As tank trucks are equipped with self-pow-
ered compressors, they are always unloaded by the former procedure.  The
potential hazards associated with the transfer of liquid sulfur dioxide from
tank cars and trucks are discussed in Section 3.4.2.

     Transfer to cylinders or drums is accomplished with the use of compressed
air to pad the storage vessel, causing the liquid sulfur dioxide to flow out
of the vessel.  The compressed air line should be equipped with a moisture
and/or oil separator, followed by a drier.  The dew point of the dried,
compressed air should not exceed 20 °F (4).  During the filling operation,  the
                                      35

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receiving vessels are mounted on scales to determine when they have been
filled with the correct amount of sulfur dioxide.  Some repackagers reweigh
the vessels on a second scale to verify that the measurements made with the
first scale were accurate.

     Equipment for the refilling process usually consists of a reciprocating
compressor, adapters for the cylinder and storage tank valves, and associated
piping.  Equipment used in  repackaging operations should be constructed from
materials compatible with sulfur dioxide.  Suitable materials of construction
for sulfur dioxide service  are discussed in Section 5.

     Examples of potential  hazards in repackaging operations include the
following:

     •    Equipment corrosion from sulfurous acid formed by moisture
          'leaking into the  system;

     •    Overpressurization of the storage vessel; and

     •    Overfilling of the receiving vessel.

     Accidental overpressure of the storage tank could result in a release of
sulfur dioxide to the atmosphere through a relief valve (if the valve is not
vented to a closed system.)  Overfilling could cause a release from a rupture
in the piping or the receiving vessel from a pressure buildup.  A latent
hazard also exists in an. overfilled vessel which goes undetected and leaves
the repackaging facility.  Other potential sources of release include leaks in
the connecting piping as a  result of corrosion, loose joint-pipe connections.
cloggings of vapor pipes resulting in overpressure, and human error.

3.4  STORAGE AND TRANSFER

     All industries which use or handle sulfur dioxide in bulk quantities must
have appropriate facilities and procedures for the safe storage and transfer
                                      36

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of this material.  In this section, potential hazards associated with the
storage and transfer of sulfur dioxide common to all installations are identi-
fied.  Proper procedures and safety precautions for the control of these
hazards for release prevention are discussed in Section 5.

3.4.1  Storage

     Large quantities of liquid sulfur dioxide are stored in pressure vessels.
because sulfur dioxide has a relatively low boiling point and a high vapor
pressure at ambient temperatures.  These vessels are generally constructed of
carbon steel according to the latest edition of the American Society of
Mechanical Engineers (ASMS) Code for Unfired Pressure Vessels. Section Till,
Division I, and with the American National Standards Institute (ANSI)
Standards for Piping and Fittings (29.30.31.32).  The maximum amount of sulfur
dioxide that may be stored in a container is equal to 1.25 times the water
weight capacity of the container at 60 °F (2).

     The primary hazard associated with the storage of liquid sulfur dioxide
is failure of a pressurized storage vessel or its associated piping.  There
are several ways this might occur:

     •    Overheating;
     •    Overfilling; and
     •    Failure of safety relief devices.

     A liquid-full container may result from a temperature increase of the
vessel.  If the vessel was overfilled to begin with, the temperature at which
it will become liquid-full is lowered.  Denting or other deformations of a
storage container also effectively lowers the temperature at which it will
become liquid-full.  The maximum recommended temperature to which a vessel may
be safely heated is 125 °F.  Cylinders and drums are equipped with fusible
safety plugs designed to melt at 165 °F to prevent rupture of the container
because of overpressure, but the possibility also exists that the plug is
defective and will fail to melt at the correct temperature.  Furthermore,
                                       37

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although a fusible plug will prevent a rupture of explosive force, a melted
plug will still allow a. complete release of the contents of the container.
Larger storage vessels are generally equipped with pressure relief valves
which discharge to a pressure relief vessel or vent gas scrubber.

     A potential hazard exists if sulfur dioxide is stored in an area which is
located near flammable or incompatible materials, especially if the area is
congested or not well ventilated.  Cylinders or other storage vessels kept in
an area in which they are exposed to direct sunlight are also susceptible to
overheating.  Storage vessels in constant contact with, dampness or standing
water are susceptible to corrosion with the consequent development of leaks.
Since the density of sulfur dioxide vapor is greater than that of air.
sub-surface storage of this material is potentially hazardous, because leaking
vapor will remain close to the ground and will not be readily dispersed in the
atmosphere.

3.4.2  Transfer from. Tank Cars and Trucks

     Shipments of liquid sulfur dioxide are made in tank cars, tank trucks.
2.000-pound drums, and 150-pound cylinders.  Tank cars are lagged with insula-
tion to minimize variations in pressure with ambient temperature, and they are
equipped with spring-loaded pressure-relief valves which are set to discharge
at 225 psig (4).  Purchasers of tank-car quantities are required to have
adequate storage facilities to allow the prompt transfer of the sulfur dioxide
upon arrival.

     Appropriate procedures must be followed when transferring sulfur dioxide
from tank cars and trucks to storage vessels to reduce the risk of a hazardous
chemical release.  Tank cars are unloaded by one of the two methods described
in Section 3.3.  (One method involves the use of a gas compressor, and the
other uses compressed air as a padding medium in the tank.)  Tank trucks are
unloaded with the use of a self-powered compressor.  Examples of potential
hazards associated with the unloading of tank cars and trucks include the
following:
                                      38

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     •    The pressure in the tank car or truck attains the pressure
          setting of its relief valve, and sulfur dioxide vapor is
          vented to the atmosphere;

     •    Moisture enters the system with the compressed air.
          because the pre-drying system is not functioning at design
          conditions, resulting in the formation of sulfurous acid
          which is highly corrosive to the tank car, transfer lines,
          and storage tank;

     •    Leakage resulting from pipe corrosion or loose joint-pipe
          connections; and

     •    Human error.

3.4.3  Transfer from Storage Vessels

     Another aspect of the transfer of liquid or vapor sulfur dioxide to
consider is the discharge of sulfur dioxide from a storage container for its
designated use in the plant.  This is generally accomplished by creating a
pressure differential between the container and the receiving vessel or
process to which it is flowing.

Cylinders and Drums—-
     At room temperature, a 150 Ib cylinder or one-ton drum will discharge
sulfur dioxide liquid at a rate of about 5 Ibs per minute or vapor at a rate
of 0.4 Ib per minute against a discharge pressure of 10 psig (4) .  When higher
rates are desired, the cylinder may be warmed to promote discharge of gaseous
or liquid sulfur dioxide.  There are several safe methods of heating the
cylinder or drum including the use of a blanket type heater or electric strip.
which may be controlled with a thermostat, or use of a warm bath or heated
room not exceeding 125 °F.  A potential hazard exists if an improper method of
heating a cylinder or drum is employed, such as using a blow torch or flame,
because of the danger of local overheating which may draw the temper of the
                                       39

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steel or cause the fusible plug to melt thereby releasing the contents of the
cylinder.  Small,  well-insulated wooden structures may be constructed in which
one or two drums are heated with careful temperature control, but care must be
taken to protect the fusible plugs from overheating from exposure to radiant
heat.

     It is possible that the evaporation of sulfur dioxide in a drum during
discharge will cause the contents of the drum to be refrigerated to a point
where there is little or no flow of gas.  To avoid such a condition from
developing, drums are often manifolded together in parallel to increase the
total withdrawal rate while reducing the withdrawal rate from individual
drums.  A potential hazard exists in such an arrangement if there is a gaseous
transfer between drums at different temperatures with subsequent reliquefac-
tion.  If this should happen, the normal filling ratio of a drum may be
exceeded because of an increase in the ambient temperature.  This condition
could result in distortion or rupture of the drum with a consequent hazardous
release of sulfur dioxide.

     Another method of achieving higher flowrates of gaseous sulfur dioxide is
rapidly withdrawing and vaporizing liquid sulfur dioxide in a steam or elec-
trically heated vaporizer.  A potential hazard of this process is an improper
piping arrangement which allows more than one drum to be connected to the
evaporator at a time.  Transfer of liquid sulfur dioxide between two drums
connected in parallel at even slightly different temperatures takes place
rapidly and will not cease until the cooler drum is completely filled.  The
hazard potential is heightened if reliance is placed on manually operated
isolation valves alone.

     The use of nitrogen or air padding to promote the flow of sulfur dioxide
from cylinders or drums is also potentially hazardous, as dangerous pressures
may develop as a result of an increase in the ambient temperature, and
moisture or other forms of contamination may be introduced with the gas.

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     Other example potential hazards include:

     •    The possibility of hazardous backflow into the cylinder or
          into the upper valve chambers when the feed valve is shut
          off at the drum;

     •    Contamination by moisture which could lead to a build-up
          of hydrogen pressure in closed equipment and cause an
          explosion of equipment with violent force;

     •    The possibility of isolating liquid sulfur dioxide in
          piping between closed valves which could lead to bursting
          of the line from a build-up in hydrostatic pressure; and

     •    The possible failure of piping connections from corrosion,
          improper materials of construction, or work hardening or
          fatigue.
                                                  t
Bulk Storage Containers—
     Potential hazards associated with the transfer of sulfur dioxide from
bulk storage containers include most of those already mentioned for cylinders
and drums.  The primary possibilities are overpressure as a result of over-
heating, corrosion from exposure to moisture or from moisture entering the
piping system, isolation of liquid sulfur dioxide between closed valves, and
failure to follow proper operating and maintenance procedures.

3.4.4  Transporting Sulfur Dioxide Storage Containers

     Unloading containers of sulfur dioxide from a delivery vehicle or moving
them within the plant is another aspect of the storage and transfer of this
material.  In general, potential hazards associated with the transport of
sulfur dioxide within a closed vessel arise from failure to follow the proper
operating procedures.  Prevention of a hazardous release resulting from human
error is discussed in Section 5.
                                      41

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                                   SECTION 4
                         POTENTIAL  CAUSES  OF RELEASES

     The potential for a hazardous  release of liquid or gaseous sulfur dioxide
exists in any type of chemical  plant which handles  this material.   The possi-
ble sources of such a release are numerous.   Large-scale releases  may result
from leaks or ruptures of large storage vessels  (including tank cars on-site)
or failure of process machinery (e.g., pumps or  compressors)  which maintain a
large throughput of sulfur dioxide  gas or  liquid.   Smaller releases may occur
as a result of ruptured lines,  broken gauge glasses, or leaking valves, fit-
tings, flanges, valve packing,  or gaskets.

     The properties of sulfur dioxide which can  promote equipment  failure are
a high'coefficient of expansion and the corrosiveness  of sulfurous acid which
is formed when dry sulfur dioxide comes into contact with moisture.
                                        *
     In Section 3, specific release hazards associated with the manufacture,
consumption, and storage of sulfur  dioxide were  identified.  In addition to
those discussed, there are also numerous general hazards which, if realized,
could lead to an accidental release.  Both the specific and general hazards in
sulfur dioxide facilities may be broadly classified as having process,
equipment, or operational causes.   This classification is for convenience
only.  Causes discussed below are intended to be illustrative, not exhaustive.
More detailed discussions of possible causes of  accidental releases are
planned for other parts of the  prevention  reference manual series.

4.1  PROCESS CAUSES

     Process causes are related to  the  fundamentals of process chemistry,
control, and general operation. Example process causes of a sulfur dioxide
release include:
                                      42'

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     •    Excess  sulfur dioxide feed to a chlorine  dioxide  reactor
          leading to excessive exothermic reaction,  combined with
          failure of the cooling system;

     •    Backflow of process reactants to a sulfur dioxide feed
          tank resulting in the formation of corrosive  sulfurous
          acid or explosive reactions with incompatible materials;

     •    Inadequate water removal from hydrocarbon feeds in a
          sulfur  dioxide extraction process over a  long period  of
          time leading to progressive corrosion;

     •    Excess  feeds in any part of a process leading to  over-
          filling or overpressuring equipment;

     •    Loss of condenser cooling to distillation units;  and
                                                         •
     •    Overpressure in sulfur dioxide storage vessels  from
          overheating or overfilling.

4.2  EQUIPMENT CAUSES

     Equipment causes of accidental releases result from  hardware  failures.
Some possible causes include:

     •    Excessive stress on materials of construction owing to
          improper fabrication, construction, or installation;

     •    Failure of vessels at normal operating conditions as  a
          result  of weakening of equipment from excessive external
          loadings or thermal cycling;
                                      43

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Mechanical fatigue and/or shock in any equipment
(mechanical fatigue could result from age, vibration, or
stress cycling, for example; shock could occur from
collisions with moving equipment such as cranes or.other
equipment in process or storage areas);

Thermal fatigue and/or shock in reaction vessels, heat
exchangers, and distillation columns;

Brittle fracture in any equipment, especially in carbon
steel equipment subjected to extensive corrosion where
hydrogen embrittlement may have occurred (equipment
constructed of high alloys, especially high strength
alloys selected to reduce the weight of major process
equipment, might be especially sensitive where some
corrosion has occurred or severe operating conditions are
encountered);                       . •

Creep failure in high temperature equipment subjected to
extreme operational upsets, especially excess temperatures
(this can occur in equipment subjected to a fire that may
have caused damage before being brought under control);
and

All forms of corrosion, including external corrosion from
fugitive emissions of sulfur dioxide, pipe connections
which have slowly corroded as a result of moisture
entering the tubing when cylinders are switched, and
stress corrosion cracking.

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4.3  OPERATIONAL CAUSES

     Operational causes of accidental releases are a result of incorrect
procedures or human errors.  Examples of these causes include the following:

     •    Overfilled storage vessels;

     •    Improper process control system operation;

     •    Errors in loading and unloading operations;

     •    Poor quality control resulting in replacement parts which
          do not meet system specifications;

     •    Inadequate maintenance in general, but especially on water
          removal unit operations, pressure relief systems, and
          other preventive and protective systems; and
       9
     •    Lack of inspection and non-destructive testing of vessels
          and piping to detect corrosion weakening.
                                      45

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                                   SECTION 5
                        HAZARD  PREVENTION AND  CONTROL
5.1  GENERAL CONSIDERATIONS

     Prevention of accidental releases  relies on a combination of technologi-
cal, administrative,  and operational practices.   These practices apply to the
design, construction, and operation of  facilities where sulfur dioxide is
stored and used.  When developing a thorough release prevention and control
plan, considerations  must be made in the following areas:

     •    Process design,
     •    Physical plant design,
     •    Protective  systems, and
     •    Operating and maintenance practices.

     Hazards prevention and control first involves identification of specific
factors in each of these areas which could directly or indirectly cause a
hazardous release of  sulfur dioxide.  A number of these factors or potential
causes of release were discussed in Sections 3 and 4.  Equipment and proce-
dures should then be  examined to ensure that they are in accordance with
applicable codes, standards, and regulations as a minimum.  Further evalua-
tions should then be  made to determine where extra protection against a
release is appropriate so that stricter equipment and procedural specifi-
cations may be developed.

     The following subsections discuss specific measures for hazards preven-
tion and control in chemical plants which maintain a significant inventory
                                       46

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of sulfur dioxide; more detailed discussions may be found in a manual on
control technologies, part of this manual series.

5.2  PROCESS DESIGN

     Process design considerations involve the fundamental characteristics of
the processes which use sulfur dioxide.  These include the hasic chemistry
involved and how this chemistry is affected by the variables of flow, pres-
sure, temperature, and composition.  These characteristics are the basis for
the overall process design which includes the sequence of unit operations
along with equipment selection (process equipment, measuring systems, mixing
systems, instrumentation, emergency equipment, etc.)

     Of primary concern in process design is determining how deviations from
expected conditions might initiate a series of events that could result in an
accidental release.  A sensitivity analysis for the purpose of assessing the
potential hazards of a given design may result in process modifications which
would enhance the integrity of the system.  Changes may involve any aspect of
the process.  Possibilities include changes in the quantities of materials
used, the pressure and temperature conditions, the type and sequence of unit
operations, control strategies, and instrumentation.

     In the context of the processes discussed in Section 3. primary consider-
ation should be given to the items listed in Table 5-1.  For each item, the
specific process or unit operation for which the item is of greatest concern
is given.  This list is not intended to be comprehensive, and there is no
guarantee that proper attention to these considerations will ensure a safe
system.  However, awareness and control of these items are necessary if a safe
system is to be achieved.

     The process upsets which are the most potentially hazardous with respect
to releases of sulfur dioxide from the processes discussed in Section 3 are
overheating and/or overpressuring and the leakage of moisture into the system.

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  TABLE 5-1.  EXAMPLE PROCESS DESIGN CONSIDERATIONS FOR PROCESSES INVOLVING
              SULFUR DIOXIDE
Process Design Consideration
  Process or Unit Operation
Contamination with water

Flow control of sulfur dioxide
feed

Temperature sensing and heating
media flow control
All

All
Distillation and stripping column
reboilers
Temperature sensing and cooling
medium flow control
Adequate pressure relief
Corrosion monitoring
Temperature monitoring
Chlorine dioxide and sulfonation
reactors, distillation and
stripping column condensers

Storage tanks, reactors,
distillation and stripping columns.
heat exchangers

All, but especially recycle
circuits

Chlorine dioxide and sulfonation
reactors, distillation and stripping
column reboilers
Level sensing and control
Storage tanks, liquid extraction
columns, reboilers and condensers
                                      48

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Overheating is hazardous, because it may lead to overpressure which weakens
process equipment and adds to the potential for leaks at joints and valves.
Wide temperature fluctuations also significantly decrease the lifespan of many
materials of construction.  Overpressure may occur without overheating if
flowrate control is not maintained of both gas and liquid streams.  Careful
monitoring of the moisture content is important to prevent corrosive levels of
sulfurous acid from forming.  This includes regular inspection of moisture
removal equipment along with measuring the moisture content of process streams
and monitoring the pH of cooling water used in the process.

5.3  PHYSICAL PLANT DESIGN

     Physical plant design considerations include equipment, siting and
layout, and transfer/transport facilities.  Vessels, piping and valves,
process machinery, instrumentation, and factors such as location of systems
and equipment must all be considered.  The following subsections cover various
                                                     *
aspects of physical plant design beginning with a discussion about materials
of construction.

5.3.1  Equipment

Materials of Construction (1,4,33)—
     Most common materials of construction are resistant to commercial dry
liquid sulfur dioxide, dry sulfur dioxide gas, and hot sulfur dioxide gas
containing water above its dew point.  These include cast iron, carbon steel,
copper, brass, and aluminum.  However, wet sulfur dioxide gas, sulfurous acid,
and sulfite solutions are all corrosive to many metals including iron, steel,
nickel, copper-nickel alloys, and nickel-chromium-iron alloys, which are
otherwise satisfactory for dry or hot sulfur dioxide service.  Other suitable
materials for most sulfur dioxide service are carbon, graphite, and impreg-
nated carbon.  Lead is also resistant to sulfur dioxide and sulfites under
most conditions.  Zinc, however, may not be used for sulfur dioxide service.
because it is readily oxidized to ZnS-O^.  Table 5-2 is a list of construction
                                       49

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TABLE 5-2.  MATERIALS OF CONSTRUCTION FOR SULFUR DIOXIDE SERVICE (4.33)

                                   For Wet              For Dry
      Material                    or Dry S02          .  S02 Only
 Admirality, Antimonial                                    x
 Aluminum                                                  x
 Brass                                                     x
 Bronze. Commercial                                        x
 Bronze, Olympic, Type A                                   x
 Bronze, Olympic, Type B                                   x
 Bronze, Telnic                                            x
 Chlorimet 2                                               x
 Chlorimet 3                                               x
 Copper                                                    x
»
 Copper, Tellurium                                         x
 Cupro - Nickel, 30%                 *                      x
 Durco D-10                                                x
 Durimet - 1                                               x
 Hastelloy C                                               x
 Haveg                                x
 Haynes Stellite 1                                         x
 Lead                                 x
 Steel, mild                                               x
 Stainless Steel, Type 316            x
 Stainless Steel, Alloy 20            x
 Teflon                               x
 containing over 1000 ppQ of water
                                  50

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materials which have been tested and proven suitable for sulfur dioxide
service (4.33).

     The temperature resistance of a material must be taken into account for
use with hot sulfur dioxide gas or solutions, especially if plastics or resins
are used.  Materials such as ceramic, glass, and stone should also be evalua-
ted for their ability to withstand thermal shock.  These latter materials are
suitable for use with wet gas. sulfurous acid, or sulfite solutions.

     The metals which are best suited for a wide variety of wet, dry, and hot
sulfur dioxide, sulfurous acid, and sulfite service include nickel-chromium
alloys such as Worthite and Durimet 20, and several of the austenitic stain-
less steels.  While type 304 stainless steel may be satisfactory for mild
conditions, types 316 and 317 are usually required for high temperatures or
other severe applications.  In processes which also involve the presence of
sulfuric acid, the use of a 20-grade stainless steel may be warranted. Inconel
is another material which is especially resistant to very hot sulfur dioxide
gas.

     Corrosion is a very serious hazard, and it is important to use appropri-
ate materials for applications which may involve some exposure of the sulfur
dioxide to small amounts of moisture.  At approximately 300 ppm moisture.
liquid sulfur dioxide discolors iron, copper, and brass.  As the moisture
content increases, light scale is produced at approximately 0.1 wt%. with
serious corrosion occurring at 0.2 wt% and higher.  For low moisture contents
or where some corrosion can be tolerated, copper or brass can be used.  The
use of wooden tanks is common for the preparation, handling, and storage of
sulfurous acid, while sulfite pulp digesters are commonly made of steel lined
with acid-resistant brick.  Organic coatings may be used to protect metals
from corrosion unless gas diffusion through the organic film is appreciable.
Organic materials used for sulfur dioxide and sulfurous acid service include
hard rubber at moderate temperatures and butyl rubber which performs similar-
ly.
                                       51

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     For all processes involving the use of sulfur dioxide or other hazardous
materials, special care should be taken to ensure that all replacement parts
or new equipment are made of materials which are compatible with the chemicals
involved in the process.  Materials of construction suitable for specific
pieces of equipment will be discussed in the following subsections which
address the equipment used in sulfur dioxide storage and processing.

Storage Vessels—
     Storage vessels for sulfur dioxide range in size from 150-pound cylinders
to multi-ton tanks.  As stated in Section 3.4.1. these containers are general-
ly constructed of carbon steel according to the ASME Code for Unfired Pressure
Vessels, Section VIII, Division I (29).  The vessels are also typically con-
structed with provisions for keeping process solutions and gases out of the
tank.  The maximum allowable weight of sulfur dioxide which may be stored is
1.25 times the water weight capacity of the container measured at 60 °F (2).
This 4uantity is expressed as a percent of the maximum volume of the container
for various temperatures in Table 5-3 (4).

     A large inventory of sulfur dioxide contained in storage vessels on site
represents one of the most hazardous components of a chemical plant which uses
this material.  The most probable causes of a hazardous release from a storage
vessel include overpressurization from a temperature increase and/or acciden-
tal overfilling, and corrosion resulting from contaminants entering the
storage system or associated piping.  This section discusses the protection
devices and safety procedures associated with the storage of sulfur dioxide
which are designed for the prevention of a hazardous release of this material.

     Several methods for preventing overpressurization of sulfur dioxide
storage vessels are employed depending on the size of the container.  Cylin-
ders and one-ton drums are manufactured with one or more fusible safety plugs
which are designed to melt at a temperature of 165 °F.  This safeguard, while
preventing the container from a potentially explosive rupture, will still
result in the complete release of the sulfur dioxide if a plug becomes hot
                                       52

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TABLE 5-3.   MAXIMUM SAFE VOLUME OF LIQUID SULFUR DIOXIDE IN
             A STORAGE TANK AT VARIOUS TEMPERATURES (A)

                                      Maximum Safe Volume
 Temperature of Liquid             Liquid Sulfur Dioxide in
Sulfur Dioxide in Tank                %  of Full  Volume
	2l	at 125% Filling Density

           30                                  86


           40                                  87


           50                                  88


           60                                  89


           70                                  90


           80                                  91


           90                                  92


          100                                  93
                              53

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enough to melt.  For this reason,  it is important to never allow the tempera-
ture of cylinders or drums to exceed 125 °F or to expose the fusible plugs to
a source of radiant heat.

     Larger storage vessels are generally equipped with a pressure relief
valve which is protected by one or more rupture disks.  These valves allow a
controlled release of overpressurized contents.  To prevent releases of sulfur
dioxide to the atmosphere when a vessel is overpressured, the relief valve may
discharge to an overflow tank in a closed system which in turn is relief
vented to a scrubber system.  To accommodate flashing liquid, relief piping
must be sized for adequate flow.  Tank cars and trucks are equipped with
spring-loaded pressure relief valves which are tested to be vapor tight at 180
psig and set to discharge at 225 psig (4).  For large containers, including
tank cars, it may be feasible to construct a scalable housing around the
container which would be vented to a scrubber system.
      t
     Overfilling of storage vessels may occur during sulfur dioxide transfer
as a result of a malfunctioning measuring device, operator error, or the use
of a damaged container with a reduced filling capacity which has gone unno-
ticed.  The immediate danger of overfilling during transfer operations is an
unexpected overflow and release of liquid or gaseous sulfur dioxide.  The
latent hazard is overpressurization and possible rupture of the container with
an increase in temperature, because the temperature at which it will become
liquid-full is lower than it should be.

     If it is possible for a vessel to be overfilled, it should be fitted with
a relief device which discharges to an overflow tank or other suitable receiv-
er.  To reduce the risk of overfilling during transfer, the storage vessel may
be mounted on a scale which will indicate the weight of fluid in the container
at all times.  All storage vessels should also be equipped with a liquid level
gauging device.  The Compressed Gas Association makes the following recommen-
dations for the design and use of these gauges (2):
                                       54

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The gauge should be designed to permit reading the liquid
level within plus or minus 1% of the capacity of the tank
from full tank level down to at least 20% below full tank.
(Readings below this level may be useful for other pur-
poses but are not required to avoid overfilling.)

Certain precautions must be observed if gauge glasses are
used as liquid level devices.  They should be protected by
solid, transparent shields and guards.  Gauge cocks should
be provided with ball checks which will shut off the flow
if the glass accidentally breaks.  The ball checks will
also allow the gauge cock to remain open at all times
which minimizes the possibility that the glass will break
by liquid expansion.  The gauge should be located such
that the glass and its contents do not differ greatly in
temperature from the container and the sulfur dioxide
inside.

Gauges should be situated to allow ready determination of
the maximum level to which the container may be filled.
It is recommended that the information in Table 5-2 be
attached to the tank near the gauge.

Gauging devices which require bleeding of sulfur dioxide
to the atmosphere, such as a rotary tube, fixed tube or
slip tube, should be designed so that the bleed valve
maximum opening is no greater than a No. 54 drill size.
unless provided with an excess flow valve.

Gauging devices should be designed for a working pressure
of at least 200 pounds gauge.
                             55

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     A short, vented dip pipe can provide protection from overfilling in the
event of failure of the volume or weight measuring device.  However, this
device will not always prevent an overflow of sulfur dioxide liquid.  Further-
more, it will only work if there is no other outlet from the vapor space and
if the line to the vent system has enough capacity.

     In addition to venting provisions, storage vessels should have valve
arrangements which allow the vessel to be isolated from the process to which
the sulfur dioxide is being fed.  Backflow of material into the upper valve
chambers when the feed valve is shut off at the storage tank must be prevented
because of the possibility of a corrosive solution of sulfurous acid being
formed.  This may be accomplished with a vented feed line or a barometric leg.
Moisture must also be excluded from the storage system to prevent corrosion by
sulfurous acid.  For this reason, storage containers should not be in contact
with standing water or exposed to continual dampness.  These conditions must
also be avoided to prevent external rusting of the vessel.

Process and Reaction Vessels-
     General considerations for hazard control for storage vessels also apply
to the design and use of process and reaction vessels.  In the latter type of
vessels, however, there is a greater degree of risk, as these containers are
often exposed to more severe conditions of temperature and/or pressure than a
regular storage vessel.

     Primary considerations for process and reaction vessels include:

     •    Materials of construction,
     •    Pressure relief devices.
     •    Temperature control.
     •    Overflow protection (including high-level alarms). and
     •    Foundations and supports.
                                       56

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     The foundations and supports for vessels are important design considera-
tions, especially for large storage vessels and tall equipment such as distil-
lation columns.  The choice of construction materials is also an important
consideration particularly where low-temperature conditions are encountered.

     If cooling to a condenser is lost, overpressure may occur.  Thus, it is
necessary to use pressure relief valves to protect against leaks and ruptures
which can result from overpressure.  Relief protection is also necessary in
the event of a fire to protect from overpressure.

     Distillation and stripping columns present significant release hazards.
because they contain large amounts of sulfur dioxide in pure form and have a
heat input.  As they are often located outdoors, external factors such as
ambient temperature fluctuations and wind loadings must be properly accounted
for in their design and construction, especially for the support structure.

Piping-
     Schedule 80 steel pipe, butt welded and/or flanged with butt welded
and/or flanged fittings, is normally used to transport pure, dry sulfur
dioxide, since dry sulfur dioxide is virtually non-corrosive (4).  Flanges can
be slip-on and flat face and should be fitted carefully to prevent leaks.
Flanges used for connecting a storage tank and the valves adjacent to it
should be especially well fitted, because a leak before the first valve would
necessitate unloading the tank for repair.

     Because of the corrosive nature of sulfurous acid, sulfur dioxide con-
taining moisture should be transported with 316 SS piping or other example
materials listed in Table 5-2.  Zinc-coated pipe should not be used, because
sulfur dioxide readily oxidizes zinc in the presence of very small quantities
of water.
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     Flexible pipe,  tubing or hose is usually required somewhere in a sulfur
dioxide piping system,  such as when connecting to a cylinder.  A commonly used
material is 500 psig copper tubing with a standard yoke and adapter at the
cylinder end, or a series of reverse bends may be put into the line.  Since
copper is prone to work hardening, the connection should be inspected each
time the cylinder is changed and replaced as necessary.  When making connec-
tions to a cylinder, a new 3% antimony lead or graphitized gasket should be
used (34).  Flexible pipe or hose should never be used where straight piping
is adequate, because it does not have comparable physical strength and can
fail more easily.  Where a flexible connection is required, flexible metal
hose designed for service with corrosive acids under pressure provides an
extra measure of safety if used for carrying undiluted sulfur dioxide.

     Piping connections to a tank car during transfer may be constructed out
of steel, brass, copper, or stainless steel, but never out of galvanized
material (4).  A one-inch air line should be connected to the "GAS" valve on
the tank car with a pressure gauge installed near the car.  A two-inch liquid
unloading line is usually sufficient (4).  Ordinary ground joint or flanged
unions can be used in making the various connections.

     Special material considerations may be required for high or low tempera-
ture applications or other unusual or severe conditions.

     Because liquid sulfur dioxide expands with temperature, bursting of lines
due to hydrostatic pressure must be prevented.  This may be accomplished with
expansion chambers which should be located at the highest point of each
section that may be .closed, trapping liquid sulfur dioxide.  Construction of
these chambers should be in accordance with the ASME Code for Unfired Pressure
Vessels. Section VIII (29).  The size of the vapor chamber should provide
approximately 20% excess volume for expansion (4) .

     The following is a list of general guidelines for the safe transport of
sulfur dioxide in piping systems:
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     •    All pipes, valves, and instrumentation should be installed
          and maintained in a dry. greaseless condition.

     •    Piping systems should have as simple a design as possible
          with a minimum number of joints and connections.

     •    A pressure reducing regulator should be installed when
          connecting to lower pressure piping or systems from
          storage vessels.

     •    In addition to being securely supported, pipes should be
          sloped with drainage provisions at the low points.

     •    Clips or hangers should not fit too tightly to allow for
          thermal expansion of the pipe.

     •    Piping should be protected from exposure to fire and
          high temperatures.

     •    Pressure testing should be done with dry. oil-free air;
          hydraulic testing must not be used because of the diffi-
          culties of drying out the system after the test is com-
          pleted.

     •    Pipelines should always be emptied when sulfur dioxide
          flow is not required to prevent the possible isolation of
          liquid sulfur dioxide between closed valves.

Valves (35) —
     Under normal conditions of flow, ball, gate or plug valves constructed of
Type 316 stainless steel are used for sulfur dioxide service.  In  the case of
gate valves, the use of the rising stem type will prevent rotation of the stem
on the valve seat.  Teflon packing should be used for the seats of ball or
gate valves, and diaphragm valves should have teflon-faced diaphragms.
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     Valves in sulfur dioxide service must be carefully selected in certain
circumstances.  For service where water may mix with the sulfur dioxide in
contact with the valve it must be corrosion resistant.  Valves for such
service may be constructed of or lined with materials listed in Table 5-2.
Diaphragm valves with inner lining of the diaphragm constructed of type 316
stainless steel are suitable for service under corrosive conditions.  For more
severe conditions valves should be constructed of "20-alloys" which minimize
the tendency of a valve to "freeze".  Teflon packing is suitable for wet or
dry sulfur dioxide service.

     Check valves must be installed in the line between the sulfur dioxide
feed vessel and the process to prevent hazardous backflow into the sulfur
dioxide feed line when the shutoff valve is closed, or when the container
supplying sulfur dioxide is empty.  It is important to keep sulfur dioxide
from mixing with moisture in closed equipment* because hydrogen pressure may
be generated leading to an explosion with violent force.  A swing check valve
made of type 316 stainless steel* or Alloy 20 for longer life, should be used.

     A needle valve is often used for accurate flow control at low flow rates.
For high flow rates, a globe valve with V-ports should be used.  These should
also be constructed of type 316 stainless steel, or Alloy 20 for longer life.
Gate valves are better than globe valves for use as a shutoff valve because of
the lower pressure drop in a gate valve.

     Excess flow valves should be considered for sulfur dioxide in vessels,
tank cars, and other places where unintentional high liquid discharge rates
need to be prevented.  In the event that a liquid discharge line is broken,
the resulting high flow rate would cause the valve to close off, restricting
the escape of sulfur dioxide.

Process Machinery—
     Process machinery refers to rotating or reciprocating equipment that may
be used in the transfer or processing of sulfur dioxide.  Included in this
classification are pumps and compressors which may be used to move liquid or
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gaseous sulfur dioxide where gas pressure padding is insufficient or inappro-
priate.

     Pumps—Many of the considerations for sulfur dioxide piping and valves
also apply to pumps.  To assure that a given pump is suitable for a sulfur
dioxide service application, the design engineer should obtain information
from the pump manufacturer certifying that the pump will perform properly in
this application.

     Pumps should be constructed with materials which are resistant to sulfur
dioxide at operating temperatures and pressures.  They should be installed dry
and oil-free.  Lubricating oil should be resistant to breakdown as a result of
contact with sulfur dioxide.  Highly refined mineral oil may be suitable for
many applications (36).  Even with the use of special lubricants, it is
important that pump design not allow sulfur dioxide or lubricating oil to
enter seal chambers where they may contact one another.  Net positive suction
head (NFSH) considerations are especially important for sulfur dioxide, since
pumping the liquid near its boiling point may be common.  (Sulfur dioxide is a
gas at typical ambient conditions.)  The pump's supply tank should have high
and low level alarms; the pump should be interlocked to shut off at low supply
level or low discharge pressure.  External pumps should be situated inside a
diked area and should be accessible in the event of a tank leak.

     In some cases, the potential for seal leakage may rule out the use of
rotating shaft seals.  Some pump types which either isolate the seals from the
process stream or eliminate them altogether include canned-motor, vertical
extended-spindle submersible, magnetically-coupled, and diaphragm (37).

     Canned motor pumps are centrifugal units in which the motor housing is
interconnected with the pump casing.  Here, the process liquid actually serves
as the bearing lubricant.  An alternative concept is the vertical pump often
used on storage tanks.  Vertical pumps consist of a submerged impeller housing
connected by an extended drive shaft to the motor.  The advantages of  this
arrangement are that the shaft seal is above the maximum liquid level  (and  is
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therefore not made wet by the pumped liquid). and the pump is self-priming.
because the liquid level is above the impeller.

     Vertical pumps should be provided with double-packed seal chambers which
are designed to prevent contact of sulfur dioxide and any reactive material.
Seal gas should be dry. oil-free, and inert to sulfur dioxide.  The seal gas
pressure should be greater than tank pressure, and a seal gas backup system
should be considered.

     Magnetically-coupled pumps replace the drive shaft with a rotating
magnetic field as the pump-motor coupling device.  Diaphragm pumps are posi-
tive displacement units in which a reciprocating flexible diaphragm drives the
fluid.  This arrangement eliminates exposure of packing and seals to the
pumped liquid.

     Centrifugal pumps often have a recycle loop back to the feed container
which prevents overheating in the event that the pump is deadheaded (i.e.. the
discharge valves close.)  Deadheading also is a concern with positive dis-
placement pumps.  To prevent rupture, positive displacement pumps commonly
have a pressure relief valve which bypasses to the pump suction.  Because of
the probability of eventual diaphragm failure, the use of diaphragm pumps
should be carefully considered in view of this hazard potential.

     Pumps are not always necessary; in some circumstances, liquid sulfur
dioxide is moved by pressure padding.  With sulfur dioxide cylinders and ton
containers, the liquid may be displaced from the vessel by the force of sulfur
dioxide's vapor pressure.  With other types of vessels, an inert gas such as
dry nitrogen may be used to force liquid from the tank.  Padding system
designs reflect the operating conditions and limitations (e.g., required flow
rate) and therefore must be custom designed for a process.
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          Compressors—Sulfur dioxide compressors include reciprocating,
centrifugal, liquid-ring rotary, and non-lubricated screw compressors.
Detailed descriptions of these compressors may be found in the technical
literature (37).

     While it is often possible to avoid using rotary shaft seals with sulfur
dioxide pumps, compressors in sulfur dioxide service usually require special
seals such as double labyrinth seals.  These seals have a series of interlock-
ing touch points which, by creating many incremental pressure drops, reduce
total leakage.  To further reduce leakage, dry air is injected into the seal.
For reciprocating compressors, a two-compartment distance piece with purge gas
may be used to prevent shaft exposure to sulfur dioxide.  In the event of
deadheading, a compressor discharge can have a pressure relief mechanism which
vents to the compressor inlet or to a scrubber system.  The former appears to
be satisfactory for a short-term downstream flow interruption.  Where a
sustained interruption might occur, relief to a scrubber system would be
safer.  As with pumps, compressors for sulfur dioxide service may require the
use of lubricating oils that are resistant to breakdown by sulfur dioxide.

Miscellaneous Equipment—
     Pressure Relief Devices—Pressure relief devices for sulfur dioxide
service should be constructed in accordance with CGA S-1.3 - "Pressure Relief
Device Standards - Part 3 - Compressed Gas Storage Containers" (38).  All
wetted parts of relief valves and rupture disks should be constructed from
materials compatible with sulfur dioxide at the operating temperature and
pressure.  For balanced relief valves, the balance seals must also be made of
a corrosion resistant material.  For most applications, 316 stainless steel is
an appropriate material of construction.

     Fugitive emissions of sulfur dioxide can result in external corrosion of
a relief valve.  For this reason it may be appropriate to construct the entire
relief device of a material that is resistant to wet sulfur dioxide.
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     Measures should be taken to ensure that process equipment is not isolated
from its relief system.  To provide continuous pressure relief protection when
a device is out of service for maintenance,  equipment may be provided with
dual relief systems, each sized to provide the total required flow capacity.
Piping and valves should be arranged so that one of the systems always
provides protection.  Stop valves installed  between a vessel and its relief
device should have a full port area that is  at least equal to that of the
pressure relief device inlet.  These valves  should be locked open or have
handles removed when the protected vessel is in use.  If the discharge is to
be piped to a closed disposal system, such as a scrubber, the pressure drop
caused by the additional piping must be considered and the relief device sized
accordingly.

     Rupture disks may be used to protect pressure relief valves from constant
contact with the contents of the storage vessel.  Rupture disks should not be
used in sulfur dioxide service where the ruptured disk discharges directly
into the atmosphere.  If the disk relieves the contents of the container
through a spring-loaded pressure relief valve, a small vent should be provided
in the chamber between the disk and the valve to prevent any back pressure on
the rupture disk.  Because operating pressures exceeding 70% of a disk
bursting pressure may induce premature failure, a considerable margin should
be allowed when sizing rupture disks.

     Instrumentation—Rotameters may be used for measuring the rate of flow of
sulfur dioxide gas or liquid.  If liquid sulfur dioxide is being measured
through a meter in which the liquid takes a pressure drop, the sulfur dioxide
liquid must be cooled well below its boiling point to prevent bubbling which
will destroy the accuracy of the measurement (4).  For high pressure work the
glass tube should be enclosed in a vented shield or, preferably, a steel-
armored type.

     Instrumentation must be constructed of materials suitable for sulfur
dioxide service, and special attention should be paid to materials used  for
wet sulfur dioxide.  Thermocouples may be enclosed in glass sleeves for
                                       64

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corrosion protection in some processes.  An additional consideration for all
instruments is that they should be protected from external corrosion which may
be caused by fugitive emissions of sulfur dioxide or other process chemicals.

     Gaskets—Gaskets should be graphited or Teflon impregnated asbestos.
l/16th-inch thick (4).  Gaskets should have smooth faces.  Compensation for
flaws in gasket faces must not be made by the use of thicker gaskets (4).

5.3.2  Plant Siting and Layout

     The siting and layout of a particular sulfur dioxide facility is a
complex issue which requires careful consideration of numerous factors.  These
include the other processes in the area, the proximity of population centers.
prevailing winds, local terrain, and potential natural external effects such
as flooding.

     The objective in siting and layout should be to avoid fires, explosions.
releases of toxic gases and other dangerous incidents, rather than to protect
people from their consequences after the fact.  However, while prevention is
always the first priority, complete prevention may be impossible.  For this
reason, siting and layout of facilities or individual equipment items should
be done in a manner that reduces exposure to persons, both in and out of the
plant, in the event of a release.  Protection for people, control equipment.
and records can be had by locating them in specially designed buildings.
Siting should further provide ready access in the event of an emergency for
both evacuation purposes and the use of emergency equipment.  However, advan-
tage should also be taken of barriers, either man-made or natural which could
reduce the hazards of releases.

     Various techniques are available for formally assessing a plant layout
and should be considered when planning high hazard facilities (39).

     The siting and layout of any facility handling sulfur dioxide should
adhere to the following general guidelines:
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     •     Areas  in which  sulfur  dioxide  hazards  exist  should have an
          adequate number of well marked exits through which person-
          nel  can escape  quickly if  necessary; doors should open
        '  outward and  lead to  unobstructed  passageways:

     •     The  plant  is laid out  so that, whenever possible, there
          are  no confined spaces between equipment; large distances
          between large inventories  and  sensitive receptors is
          desirable;

     •     Access to  platforms  above  ground  level should be by
          stairway in  preference to  cat  ladders, and work areas
          above  ground level should  have alternative means of
          escape;
     \
     •     Large  inventories of sulfur dioxide should be kept away
          from possible sources  of fire  or  explosion;  special
          consideration should be given  to  the location of furnaces
          and  other  permanent  sources of ignition in the plant; and

     •     Storage  facilities should  be located in cool.  dry. well-
          ventilated areas, away from heavily trafficked areas and
          emergency  exits.

     An existing facility may  not be able to conform to all of these criteria.
When this  is true, other prevention  measures must be taken to compensate for
deficiencies in  plant  layout.

     Because heat  causes thermal expansion  of liquid sulfur dioxide, measures
should  be  taken  to  situate piping, storage  vessels, and other sulfur dioxide
equipment  so that  they are not adjacent  to  piping which carries flammable
materials, hot process piping, equipment, steam  lines, and other sources of
direct  or  radiant  heat.  Storage should  also be  situated away from control
rooms,  offices,  utilities, and laboratory areas.
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     In the event of an emergency, there should be more  than  one  entrance  to
the facility which is accessible to emergency vehicles and crews.   Storage
vessel shutoff valves should be readily accessible.  Containment  for liquid
storage tanks can be provided by diking.  Dikes reduce evaporation  while
containing the liquid.  It is also possible to equip a diked  area to allow
drainage to an underground containment sump.  This sump  would be  vented to a
scrubber system for safe discharge.  A full containment  system using a speci-
ally constructed building vented to a scrubber is another possible  option.
This type of secondary containment could be considered for large  volume,
liquid sulfur dioxide storage tanks.

5.3.3  Transfer and Transport Facilities

     Transfer and transport facilities where both road vehicles and rail
tankers are loaded or unloaded are potential accident areas because of vehicle
movement and the intermittent nature of the operations.  Therefore, special
attention should be given to the design of these facilities.

     As mentioned in the previous section, tank car and  tank  truck  facilities
should be located away from sources of heat, fire and explosion.  Before
unloading, tank vehicles should be securely moored; an interlocked  barrier
system is commonly used.  Tank cars should also be protected  on both ends by
derailers or on the switch end if located on a dead end  siding.   Sufficient
space should be available to avoid congestion of vehicles or  personnel during
loading and unloading operations.  Vehicles, especially  trucks, should be able
to move into and out of the area without reversing.  High curbs around trans-
fer areas and barriers around equipment should be provided to protect equip-
ment from vehicle collisions.

     Correct procedures must be followed when unloading  and handling small
sulfur dioxide storage vessels such as cylinders and drums.   Dragging, slid-
ing, or rolling cylinders, even for short distances, is  not acceptable.
Lifting magnets, slings of rope or chain, or any other device in  which the
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cylinders themselves form a part of the carrier should never  be  used for
transporting cylinders.  Drums may be moved over short distances with the use
of hooks which are connected to a chain sling or a lifting  beam  supported by a
hoist or monorail (4).   It is important to instruct operating personnel in the
proper use of such equipment, since additional stresses are imposed on slings
through angles -developed, which the operators may not be aware of,  thus
creating an overload on the system.  Suppliers' vehicles specially  equipped so
that drums lie in cradles cannot be safely loaded or unloaded with  convention-
al fork lift trucks.  A system of runway beams in the drum  storage  area is the
preferred method.

5.4  PROTECTION TECHNOLOGIES

     This subsection describes two types of protection technologies for
containment and neutralization.  These are:

     •    Enclosures, and

     •    Scrubbers.

More detailed discussions on these systems are planned for  other parts of the
prevention reference manual series.

5.4.1  Enclosures

     Enclosures refer  to containment structures which capture any sulfur
dioxide spilled or vented from storage or process equipment,  thereby prevent-
ing immediate discharge of the chemical to the environment.  The enclosures
contain the spilled liquid or gas until it can be transferred to other con-
tainment and discharged at a controlled rate which would  not  be  injurious to
people or the environment, or  transferred at a controlled  rate to scrubbers
for neutralization.
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     Specially designed enclosures for sulfur dioxide storage  or  process
equipment do not appear to be in widespread use.  The principle that  it may  be
preferable to locate toxic operations in the open air has been mentioned  in
the literature (39)., along with the opposing idea that sometimes  enclosure may
be appropriate.   The desirability of enclosure depends partly  on  the  frequency
with which personnel must be involved with the equipment.-  A common design
rationale for not having an enclosure where toxic materials are used  is to
prevent the accumulation of toxic concentrations within enclosed  areas.   How-
ever, if the issue is providing for secondary containment, total  enclosure may
be appropriate.

     If an enclosure is deemed appropriate for a given installation,  it should
be equipped with continuous monitoring equipment and adequate  fire protection.
Alarms should sound whenever lethal or flammable concentrations are detected.

     Care must be taken when an enclosure is built around pressurized
equipment.  From an economic standpoint, it would.not be practical to design
an enclosure to withstand the pressures associated with the sudden failure of
a pressurized vessel.  Therefore, if an enclosure is built around pressurized
equipment, it should be equipped with some type of explosion protection,  such
as rupture plates.  These components are designed to fail at a pressure lower
than the design pressure of the enclosure, thus preventing the entire
structure from failing.

     The type of structures that appear to be suitable for sulfur dioxide are
concrete blocks, or concrete sheet buildings or bunkers.  An enclosure would
have a ventilation system designed to draw in air when it is vented to a
scrubber or the atmosphere.  The bottom section of an enclosure which is  used
for stationary storage containers should be liquid tight to retain any liquid
sulfur dioxide that might be spilled.  Enclosures around rail  cank cars which
are used for storage 'do not normally lend themselves easily to effective
liquid containment.   However, containment can be accomplished  if  the  floor  of
the enclosure is excavated several feet below the track level  while the  tracks
are supported at grade in the center.
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     While the use of enclosures for secondary containment of sulfur  dioxide
spills or releases is not known to be widely used, it might be  considered for
areas near sensitive receptors.

5.4.2  Scrubbers

     Scrubbers are a traditional method for absorbing toxic gases  from  process
streams.  These devices can be used for the control of sulfur dioxide releases
from vents and pressure relief discharges, from process equipment, or from
secondary containment enclosures.

     Sulfur dioxide discharges could be contacted with an aqueous  scrubbing
medium in any of several types of scrubbing devices.  An alkaline  solution is
required to achieve effective absorption, because absorption rates with water
alone might require unreasonably high liquid-to-gas ratios.  However, water
scrubbing could be used if an alkaline solution were not available.   Typical
alkaline solutions for an emergency scrubber could be calcium hydroxide,
derived from slaked lime, or sodium hydroxide or sodium carbonate.

     Types of scrubbers that might be appropriate include spray towers, packed
bed scrubbers, and Venturis.  Other types of special designs might be suit-
able, but complex internals subject to corrosion do not seem to be advisable.

     Whatever type of  scrubber  is selected, a complete system would  include
the scrubber itself, a liquid feed system, and reagent makeup equipment.   If
such  a  system is used  as protection against emergency releases, consideration
must  be given to how it would be activated in time  to respond to an  emergency
load.   One approach used in some process  facilities is to maintain a
continuous circulation of scrubbing liquor through  the system.   For  many
facilities this would  not be practical,  and the  scrubber  system might be  tied
into  a  trip system to  turn it on when  it  is needed.  However, with this system
a quantity of sulfur dioxide would be  released prior  to actuation of the
scrubber  (i.e., starting up a blower and turning on the flow  of liquid).

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     The scrubber system must be designed so as not to present  excessive
resistance to the flow of an emergency discharge.  The pressure drop  should  be
only a small fraction of the total pressure drop through the  emergency
discharge system.  In general, at the liquid-to-gas ratios  required for
effective scrubbing, spray towers have the lowest, and Venturis the highest
pressure drops.  While packed beds may have intermediate pressure  drops at
proper liquid-to-gas ratios, excessive ratios or plugging can increase the
pressure drop substantially.  However, packed beds have higher  removal
efficiencies than spray towers or Venturis.

     In addition, the scrubber system must be designed to handle the  "shock
wave" generated during the initial stages of the release.   This is
particularly important for packed bed scrubbers since there is  a maximum
pressure with which the gas can enter the packed section without damaging the
scrubber internals.

     Design of emergency scrubbers can follow standard techniques  discussed  in
the literature, carefully taking into account the additional  considerations
just discussed.  An example of the sizing of an emergency packed bed  scrubber
is presented in Table 5-4.  This example provides some idea of  the size of a
typical emergency scrubber for various flow rates.  This is an  example only
and should not be used as the basis for an actual system which  might  differ
based on site specific requirements.

     Another approach is the drowning tower where the sulfur  dioxide  vent is
routed to the bottom of a large tank of uncirculating caustic.   The drowning
tower does not have the high contact efficiency of the other  scrubber types,
but can provide substantial capacity on demand.
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      TABLE 5-4.  EXAMPLE OF PERFORMANCE CHARACTERISTICS FOR AN EMERGENCY
                  PACKED BED SCRUBBER FOR SULFUR DIOXIDE


Basis:  Inlet stream of 50% SO. in 50% air.. Constant gas flow per unit
        cross-sectional area of 290 scfm/ft .

Packing:  2-inch plastic Intalox* saddles.

Pressure Drop:  0.5 inch water column

Scrubbing Medium:  8% (wt) NaOH solution

Removal Efficiency, %                        50             90
Liquid to Gas Ratio
  (gal/thousand scf)
    — at flooding                          220            220
    — operating                            130            130

Packed Height, ft.                          4.6           15.3

Column "Diameter and Corresponding Gas Flow Rates for Both Removal Efficiencies


                Column
               Diameter              Flow Rate
                  (ft)                  (scfm)

                 0.5                       60
                 1.0                      240
                 2.0                      960
                 6.6                   10,000
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5.5  MITIGATION TECHNOLOGIES

     If,  in spite of all precautions, a large  release  of  sulfur  dioxide were
to occur, the first priority would be to rescue workers in  the immediate
vicinity of the accident and evacuate persons  from downwind areas.   The source
of the release should be determined, and the leak should  be plugged to  stop
the flow if this is possible.  This  post release mitigation effort  requires
that the source of the release is accessible to trained plant personnel,  and
adequate personnel protection is readily available.-  Personnel protection
includes such items as portable breathing air  and chemically resistant
protective clothing.

     The next primary concern becomes reducing the consequences  of  the
released chemical to the plant and the surrounding community.  Reducing the
consequences of an accidental release of a hazardous chemical is referred to
as mitigation.  Mitigation technologies include such measures as physical
barriers, water sprays and fogs, and foams where applicable.  The purpose of a
mitigation technique is to divert, limit, or disperse  the chemical  that has
been spilled or released to the atmosphere in  order to reduce the atmospheric
concentration and the area affected  by the chemical.   The mitigation technol-
ogy chosen for a particular chemical depends on the specific properties of the
chemical including its flammability, toxicity, reactivity,  and those proper-
ties which determine its dispersion  characteristics in the  atmosphere.

     If a release occurs from a pressurized sulfur dioxide  storage  tank above
the boiling point, a gas cloud or a  quantity of liquid will immediately flash
off as vapor, while the remaining liquid will  be cooled to  the normal boiling
point of 14.0 °F.  Heat transfer from the air  and ground  will result in fur-
ther vaporization of the released liquid.  Since the sulfur dioxide accident-
ally released from a refrigerated storage tank is already at or  below its
normal boiling point, a comparable quantity of vapor will not flash off, as
with the pressurized release discussed above,  but heat transfer  from the
environment will cause evaporation and the formation of a vapor  cloud.   It is
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therefore desirable to minimize the area available for heat  transfer  to a
liquid spill which in turn will minimize the rate of evaporation.   Mitigation
technologies which are used to reduce the rate of evaporation  of a released
liquified gas include secondary containment systems such as  impounding basins
and dikes.

5.5.1  Secondary Containment Systems (40)

     Specific types of secondary containment systems include excavated basins.
natural basins, earth, steel, or concrete dikes, and high impounding  walls.
The type of containment system best suited for a particular  storage tank or
process unit will depend on the risk associated with an accidental release
from that location.  The inventory of sulfur dioxide and its proximity to
other portions of the plant and to the community should be considered when
selecting a secondary containment system.  The secondary containment  system
should have the ability to contain spills with a minimum of  damage to the
facility and its surroundings and with minimum potential for escalation of  the
event.

     Secondary containment systems for sulfur dioxide storage  facilities may
consist of one of the following:

     •    An adequate drainage system underlying the storage vessels
          which terminates in an impounding basin having a capacity
          as large as the largest tank served; or

     •    A dike surrounding the storage area with a capacity  as
          large as the largest tank served.

These measures ara designed to prevent the accidental discharge of liquid
sulfur dioxide from spreading to uncontrolled areas.
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     The most common type of containment system is a low wall  dike  sur-
rounding one or more storage tanks.-  Generally, no more than  three  tanks  are
enclosed within one diked area to reduce risk.  Dike heights usually  range
from three to twelve feet depending on the area available  to  achieve  the  re-
quired volumetric capacity.  The dike walls should be liquid  tight  and able to
withstand the hydrostatic pressure and temperature of a spill.  Low wall  dikes
may be constructed of steel, concrete, or earth.  If earthen  dikes  are used,
dike walls must be constructed and maintained  to prevent leakage  through  the
dike.  Piping should be routed over dike wails, and penetrations  through  the
walls should be avoided if possible.  Vapor fences may be  situated  on top of
the dikes to provide additional vapor storage  capacity.  If there are more
than one tank in the diked area, the tanks should be situated  on  beams above
the maximum liquid level attainable in the impoundment.

     A low wall dike can effectively contain the liquid portion of  an acciden-
tal release and keep the liquid from entering  uncontrolled areas.   By prevent-
ing the liquid from spreading, the low wall dike can reduce the surface area
of the spill.  Reducing the surface area will  reduce the rate  of  evaporation.
The low wall dike will partially protect the spill from wind;  this  can reduce
the rate of evaporation.  A dike with a vapor  fence will provide  extra protec-
tion from wind and will be even more effective at reducing the rate of evapo-
ration.-

     A low wall dike will not reduce the impact of a gaseous  sulfur dioxide
release.  A dike also creates the potential for sulfur dioxide and  trapped
water to mi* in the dike, which may accelerate the rats of evaporation and
form highly corrosive sulfurous acid.  If materials that would react  violently
with sulfur dioxide are stored within the same diked area  then the  dike will
increase the potential for mixing the materials in the event  of a simultaneous
leak.  A dike also limits access to the tank during a  spill.

     A remote impounding basin is well suited  to storage  systems  where more
than one tank are served and a relatively large site is available.   The  flow
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from a sulfur dioxide spill is directed to the basin by dikes and  channels
under the storage tanks which are designed to minimize exposure  of the liquid
to other tanks and surrounding facilities.  Because of sulfur dioxide's high
vapor pressure the trenches that lead to the remote impounding basin as well
as the basin itself should be covered to reduce the rate of evaporation.
Additionally, the impounding basin should be located near the tank area to
minimize the amount of sulfur dioxide that evaporates as it travels to the
basin.

     This type of system has several advantages.  The spilled liquid is re-
moved from the immediate tank area.  This allows access to the tank during the
spill and reduces the probability that the spilled liquid will damage the
tank, piping, electrical equipment, pumps or other equipment.  In  addition,
the covered impoundment will reduce the rate of evaporation from the spill by
protecting the spill from wind or heating from sunlight.
       »
     A limitation of a remote impounding basin is that there is  still the
potential for water or other incompatible materials to be trapped  in the
impoundment and mix with the incoming sulfur dioxide.  Remote impounding
basins do not reduce the impact of a gaseous sulfur dioxide release.

     Although few authorities for sulfur dioxide facilities require them,  high
wall impoundments may be a good secondary containment choice for selected sys-
tems.  Circumstances which may warrant their use include limited storage site
area, the need to minimize vapor generation rates, and/or the tank must be
protected from external hazards.  Maximum vapor generation rates will gen-
erally be lower for a high wall impoundment than for low wall dikes or remote
impoundments because of the reduced surface contact area.  These rates can be
further reduced with the use of insulation on the wall and floor in the annu-
lar space.  High impounding walls may be constructed of low temperature steel,
reinforced concrete, or prestressed concrete.  A wea.ther shield  may be pro-
vided between the tank and wall with the annular space remaining open to the
atmosphere.  The available area surrounding the storage tank will  dictate the
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minimum height of the wall.  For high wall, impoundments,  the walls may be de-
signed with a volumetric capacity  greater  than  that  of  the tank to provide va-
por containment.  Increasing the height  of the  wall  also  raises the elevation
of any released vapor.

     One disadvantage of these  dikes is  that  the  high walls around a tank may
hinder routine external observation.  Furthermore, the  closer the wall is to
the tank, the more difficult it becomes  to access the tank for inspection and
maintenance.  As with low wall  dikes, piping  should  be  routed over the wall if
possible.-  The closeness of the wall to  the tank  may necessitate placement of
the pump outside of the wall, in which case the tank outlet (suction)  line
will have to pass through the wall.  In  such  a  situation,  a low dike encompas-
sing the pipe penetration and pump may be  provided,  or  a  low dike may be
placed around the entire wall.

     An example of the effect of diking  as predicted by a vapor dispersion
model is shown in Figure 5-1  (41).  This figure shows sulfur dioxide vapor
clouds at the time when the farthest distance away from the source is exposed
to concentrations above the IDLH.  With  diking, the  model predicts that
downwind distances up to 3000 feet from  the source of the release could be
exposed to concentrations above the IDLH.   Three  minutes  are required for the
vapors to reach the maximum down wind distance.   Without  diking, the model
predicts that downwind distances up to 5800 feet  from the source could be
exposed to concentrations above the IDLH.   Seven  minutes  are required for the
vapors to reach this distance.

     One further type of secondary containment  system is  one which is struc-
turally integrated with the primary system and  forms a  vapor tight enclosure
around the primary container.   Many types  of  arrangements are possible.  A
double walled tank is an example of such an enclosure.   These systems jiay be
considered where protection of  the primary container and  containment of vapor
for events not involving foundation or wall penetration failure are of great-
est concern.  Drawbacks of an integrated system are  the greater complexity of
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LE8BNO:
	 >  100.
--->  aoo.
	>  40O.
  PPM
  PPM
  PPM
       •0.2S

       miles

Release fro;a a tank
Elapsed Time:  3
                                     0.5              0.75               i

                                   miles            miles            mile

                                 .s-jrr.3-i.iJed  b/  a  25  Et.  diameter dike.
                         Release from a tank with ao  dike.
                         Elapsed Time:   7  minutes
  Common Release Conditions

  Storage Temperature = 85°F
  Storage Pressure =51 psig
  Ambient Temperature = 85°F
                                   Wind Speed = 10 mph
                                   Atmospheric Stability Class = C
                                   Quantity Released = 5000 gallons
                                     through a 2-inch hole
      Figure 5-1.   Computer aodel simulation showing the effect of diking on
                   the vapor cloud generated from a release of liquified
                   sulfur dioxide.
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the structure,  the difficulty of access to certain components, and  the  fact
that complete vapor containment cannot be guaranteed for all potential  events.

     Provision should be made for drainage of rainwater from diked  areas.
This will  involve the use of sumps and separate drainage pumps,  since direct
drainage to stormwater sewers would presumably allow any spilled sulfur
dioxide to follow the same route.  Alternately, a sloped rain hood  may  be  used
over the diked area which could also serve to direct the rising  vapors  to  a
single release point (40).  The ground within the enclosure should  be graded
to cause the spilled liquid to accumulate at one side or in one  corner.  This
will help  to minimize the area of ground to which the liquid is  exposed and
from which it may gain heat.  In areas where it is critical to minimize vapor
generation, surface insulation may be used in the diked area to  further reduce
heat transfer from the environment to the spilled liquid.  The floor of an
impoundment should be sealed with a clay blanket to prevent the  sulfur  dioxide
from seeping into the ground; percolation into the ground  causes the ground to
cool more  quickly, increasing the vapor generation rate.   Absorption of the
sulfur dioxide into water in the soil would also release additional heat.

5.5.2  Flotation Devices and Foams  (42.43)

     Other possible means of reducing the surface area of  spilled  sulfur
dioxide include placing impermeable flotation devices on the surface, and
applying water-based foams.  Placing an impermeable flotation device over  a
spilled chemical is a direct approach for containing toxic vapors with  nearly
100 percent efficiency.  However, being able to use such devices requires
acquisition in advance of a spill and storage until needed, and  in  all  but
small spills deployment may be difficult.  In addition, material and dispersal
equipment  costs are a major deterrent to their use  (42).
            •             • •
     The use of foams' in vapor hazard control has been demonstrated for a
broad range of volatile chemicals.  Unfortunately, it is difficult  to  accu-
rately quantify the benefits of  foam systems, because tne  affects  will  vary  as
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a function of the chemical spilled, foam type, spill  size,  and atmospheric
conditions.  With regard to liquefied gases, it has been  found that with some
materials, foams have a net positive effect, but with others,  foams may
exaggerate the hazard.

     One approach to a sulfur dioxide spill is dilution with water.  However,
dilution of sulfur dioxide with water results in the  formation of highly
corrosive sulfurous acid.-  A water-based foam cover provides an alternative
means of diluting the sulfur dioxide.  When a foam cover  is first applied,  an
increase in the boil off rate is generally observed which causes a short-term
increase in the downwind sulfur dioxide concentration.  The initial foam cover
may be destroyed by violent boiling, in which case a  second application is
necessary.  Once a continuous foam layer is formed, a net positive effect will
be achieved in the downwind area.  The reduction in downwind concentration is
a result of both increased dilution with air, because of  a reduced vaporiza-
tion rate, and the increased buoyancy of the vapor cloud.-  This latter effect
is a result of the vapor being warmed as it rises through the  blanket by tteat
transfer from the foam and by the heat of solution of sulfur dioxide in water;
the warmed vapor cloud will have greater buoyancy and will disperse in an
upward direction more rapidly.

     The extent of the downwind reduction in concentration will depend on the
type of foam used.  Research in this area has indicated that medium to high
expansion foams (300 to 350:1) give significantly better  results than do lov
expansion foams (6 to 8:1) (43).  Furthermore, a. high expansion foam will
cause a smaller initial increase in boil off than a low expansion foam.

     Regardless of the type of foam used, the slower  the  foam's drainage rate,
the better its performance will be.  A slow draining  foam will spread more
evenly, show more resistance to tamperature and pH effects, and collapse more
slowly.  The initial cost for a slow draining roam may be higher than for
other foams, but a cost effective systam. vill be realized in  superior perfor-
aance.
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5.5.3  Mitigation Techniques for Sulfur Dioxide Vapor  (44.45.46)

     The extent to which the escaped sulfur dioxide vapor can be  removed  or
dispersed in a timely manner will be a function of the quantity of vapor  re-
leased,  the ambient conditions, and the physical characteristics  of  the vapor
cloud.   The behavior and characteristics of the sulfur dioxide cloud will be
dependent on a number of factors.  These include the physical state  of the
sulfur dioxide before its release, the location of the release, and  the
atmospheric and environmental conditions.  Many possibilities exist  concerning
the shape and motion of the vapor cloud, and a number of predictive  models of
dispersion have been developed.  As a result of the higher specific  gravity of
pure sulfur dioxide, large accidental releases of sulfur dioxide  will often
result in the formation of sulfur dioxide-air mixtures which are  denser than
the surrounding atmosphere.  This type of vapor cloud is especially  hazardous.
because it will spread laterally and remain close to the ground.

     One means of dispersing as well as removing toxic vapor from*the air is
with the use of water sprays or fogs.  However, dilution of sulfur dioxide
with water results in the formation of highly corrosive sulfurous acid and
presents an additional health hazard to plant personnel as well as corrosion
problems for machinery and equipment.  In addition, to be effective, an
impractically large volume of water would have to be used, although  it may be
beneficial in controlling relatively small releases whose principal  hazard is
to plant personnel (44).  An alternative is to use a mild aqueous alkaline
spray system which would act as a neutralizing agent for the acid.

     The dispersing medium is commonly applied to the vapor cloud by means of
hand-held hoses and/or stationary spray barriers.  For effective  absorption.
it is important to direct fog or spray nozzles from a downwind direction  to
avoid driving the vapors downwind more quickly.  Other important  factors
relating to the effectiveness of alkaline sprays are the distance of the
nozzles from the point of release, the fog pattern, nozzle flow  rate,  pres-
sure, and nozzle rotation.  If the right strategy is followed, a  "capture
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zone" can be created downwind of the release into which  the  sulfur dioxide
vapor will drift and be absorbed.  In low wind conditions, two  fog nozzles
should be placed upwind of the release to ensure that  the  sulfur dioxide cloud
keeps moving downwind against the fog nozzle pressures.-  If  an  alkaline fog is
used to absorb sulfur dioxide vapors from a diked area containing spilled
liquid sulfur dioxide, great care must be taken not  to direct alkaline solu-
tion into the liquid sulfur dioxide itself.

     Spray barriers consist of a series of nozzles which can be directed
either up or down.  If placed directly downwind from the point  of sulfur
dioxide release, these barriers will absorb some of  the  sulfur  dioxide vapors
passing through without significant distortion of the  sulfur dioxide cloud
(45).  Several fog nozzles may be situated farther downwind  to  absorb some of
the remainder of the vapors getting through.

     In general, techniques used to disperse or control  vapor emissions should
emphasize simplicity and reliability.  In addition to 'the  mitigation tech-
niques discussed above, physical barriers such as buildings  and rows of trees
will help to contain the vapor cloud and control its movement.   Hence, reduc-
ing the consequences of a hazardous vapor cloud can  actually begin with a
carefully planned layout of facilities and the use of  imaginative landscaping
around major hazard sites.

5.6  OPERATION AND MAINTENANCE PRACTICES

     Accidental releases of toxic materials result not only  from deficiencies
of design but also from deficiencies of operation.   Unfortunately, human error
is often responsible for the realization of hazards  with potentially damaging
consequences.  The human error hazard manifests itself in  numerous ways, both
indirectly  and directly.  For example, a lax management  policy  which does not
enforce safety standards might be indirectly responsible for an unnecessary
injury or fatality, or an operator may take the wrong  action at a control
panel which would directly  lead  to a hazardous release.  Aspects of plant
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operation which impact the magnitude of the risk of human error include
management policy, operator training, and maintenance and modification
procedures.   These topics are.discussed in the following subsections.

5.6.-1  Management Policy

     Competent and effective management plays a vital role in the prevention
of accidental releases as a result of human error.  The primary responsibili-
ties of managers at chemical plants with large inventories of hazardous
chemicals include the following  (39):

     •    Ensuring worker competency;

     •    Developing, documenting, and enforcing standard operating
          procedures and safety  policies;

     •    Communicating and promoting feedback regarding safety
          issues;

     •    Identification, assessment, and control of hazards; and

     •    Regular plant audits and provisions for independent
          checks.

     Management is ultimately responsible for the competency of workers hired
at facilities which handle hazardous materials.  Because of the serious
consequences that may result from operator error at these installations,  the
qualifications and capabilities  of prospective personnel for high hazard  areas
should be carefully assessed to  ensure that worker skills are matched to  job
responsibilities.  In addition,  the skills of competent operators should  be
maintained by regular training,  safety meetings, and .employee reviews.
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     In the chemical industry, documentation is generally produced which sets
forth standard procedures for equipment operation, maintenance,  inspection,
hazard identification,  and emergencies.  The enforcement of  standard
procedures is therefore one of management's most fundamental  responsibilities
in the area of plant safety and accident prevention.  However, before  proce-
dures can be enforced,  they must be communicated to plant personnel in a
clear, concise style so that they are thoroughly understood.   Emphasis should
be placed on worker safety and the serious consequences of operator error in
processes involving hazardous materials.

     Unfortunately, requiring workers to read documents which contain  safety
policies is often not enough to ensure that they are fully understood  and
followed.  For this reason, verbal communication should be practiced and
encouraged which emphasizes plant safety and promotes feedback.  When  manage-
ment demonstrates a willingness to respond to initiatives from below and
      *
participates directly with workers in improving safety, worker morale  in-
creases, influencing the degree to which standard procedures  are followed.

     Hazard identification, assessment, and control is another area that
should be addressed by management to minimize the potential  for  accidental
chemical releases.  The establishment of formal hazard assessment  techniques
would  provide management with a mechanism for obtaining information which can
be used to rank potential problems and decide how best to allocate hazard
control resources.

     The plant safety audit is one of  the most  frequently used methods for
obtaining safety related information.  A total  plant safety  audit  involves a
thorough evaluation of a plant's design, layout, and procedures, and  is
specifically aimed at identifying and  correcting potentially unsafe
conditions.  The objectives of these audits include alerting operating
personnel to process hazards, determining if  safety procedures need to be
modified, screening for equipment or process  changes  that may have introduced
new hazards, assessing the  feasibility  of applying  new hazard control
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technologies,  identifying additional hazards, and reviewing inspection and
maintenance programs (47).  In-house safety audits can be performed by
appointed safety review committees, or qualified consultants or insurers aiay
be brought in to provide a more objective assessment.

5.6.2  Operator Training

     Accidental chemical releases may result from numerous types of operator
errors including following incorrect operating procedures, failing to
recognize critical situations, or by direct physical mistakes, e.g.. by
turning the wrong valve.  For all of these errors, the fundamental problem may
be the operator's lack of knowledge or understanding of process variables,
equipment operation, or emergency procedures.  It is important for management
to recognize the extent to which a comprehensive operator training program can
decrease the potential for accidental releases resulting from human error.
Some general characteristics of quality industrial training programs include
the following:       •

     •    Establishment of good working relations between management
          and personnel;

     •    Definition of trainer responsibilities and training
          program goals;

     •    Use of documentation, classroom instruction, and field
          training (in some cases supplemented with simulator
          training);

     •    Inclusion of procedures for normal startup and shutdown,
          routine operations, and emergencies; and

     •    Frequent supplemental training and the use of up-to-date
          training materials.
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     Employees in plants which manufacture, process, or store  sulfur  dioxide
should be thoroughly educated about the important aspects of handling this
chemical.  These include the proper means of handling and storing, potential
consequences of improper use and handling, prevention of spills,  cleanup
procedures, maintenance procedures, and emergency procedures.   It is  the job
of the trainer to ensure that the right type and amount of information is
supplied at the right time.  To do this he must not only understand the
technical content of a job, but also those aspects of Che job  where operators
may have difficulty.  It is therefore advantageous for trainers to spend time
observing and analyzing the tasks and skills they will be teaching.

     Two types of training which are especially important cover emergencies
and safety procedures.  Emergency training includes topics such as:

     •    Recognition of alarm signals;
      •>
     •    Performance of specific functions (e.g., shutdown
          switches);

     •    Use of emergency equipment;

     •    Evacuation procedures;

     •    Fire fighting; and

     •    Rehearsal of emergency situations.

Safety training includes not only responses to emergency situations,  but also
accident prevention measures.  Aspects addressed in safety training sessions
include  (39):

     •    Hazard recognition and communication;

     •    Actions to be taken in particular situations;
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     •    Available safety equipment and locations;

     •    When and how to use safety equipment;

     •    Use and familiarity with relevant documentation; and

     •    First aid and CPR.

     The frequency of training and the frequency with which  training materials
are updated are important in maintaining strong training programs.  Chemical
processes may be modified to the extent that equipment changes  require opera-
tional change, and operators must be made aware of the changes  and  safety
considerations that accompany them in a timely manner.  In addition to opera-
tor training programs, organized management training is also beneficial as  it
provides managers with the perspective necessary to formulate good  policies
and procedures and to make changes that will improve the quality of the
overall plant safety program.

5.6.3  Maintenance and Modification Practices

     Plant maintenance is necessary to ensure the structural integrity of
chemical processing equipment; modifications are often necessary to allow more
effective production.   However, since these activities are also potential
causes of accidental chemical releases, proper maintenance and  modification
practices are important to the prevention of accidents.

     Maintenance refers to a wide range of activities, including preventive
maintenance,  production assistance (e.g., adjustment of settings),  servicing
(e.g.,  lubrication and replacement of consumables), running maintenance.
scheduled repairs during shutdown, and breakdown maintenance.   These activi-
ties in turn require specific operations such as emptying, purging, and
cleaning vessels, breaking pipelines, tank repair or demolition, welding, hot
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tapping (attaching a branch to an in-service line), and equipment  removal
(39).

     Proper maintenance and modification programs should be a normal  part  of
plant operation and design procedures, respectively, to reduce the  chances for
an accidental release.-  Maintenance should be based on a priority  system to
ensure that the most critical equipment is taken care of first.  Strict
procedures should apply to process modifications to ensure that modifications
do not create unintended hazards.  Inspections and nondestructive  testing of
vessels,  piping, and machinery should be conducted periodically to  detect
small flaws that could eventually lead to a major release.

     Two of the more common maintenance problems are equipment identification
and equipment isolation (39).  Work performed on the wrong piece of equipment
can have disastrous effects, as can failure to completely isolate  equipment
from process materials and electrical connections.   Other potential sources of
maintenance accidents are improper venting to relieve pressure, insufficient
draining,  and not cleaning or purging systems before maintenance activities
begin.

     Permit systems and up-to-date maintenance procedures minimize  the poten-
tial for accidents during maintenance operations.  Permit-to-work  systems
control maintenance activities by specifying the work to be done, defining
individual responsibilities, eliminating or protecting against hazards, and
ensuring that appropriate inspection and testing procedures are followed.
Such permits generally include specific information such as (39) :

     •    The type of maintenance operations to be conducted,

     •    Descriptions and identifying codes of the equipment to be
          worked on,

     •    Classification of  the area in which work will be
          conducted.
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     •    Documentation of special hazards and control measures.

     •    Listing of the maintenance equipment to be used, and

     •    The date and time when maintenance work will be performed.

     Permit-to-work systems offer many advantages.-  They explain the work to
be done to both operating and maintenance workers.  In terms of equipment
identification and hazard identification, they provide a level of detail that
significantly reduces the potential for errors that could lead to accidents or
releases.   They also serve as historical records of maintenance activities.

     Another form of maintenance control is the maintenance information
system.  Ideally, these systems should log the entire maintenance history of
equipment, including preventative maintenance, inspection and testing, routine
servicing, and breakdown or failure maintenance.-  This type of system is also
used to track incidents caused by factors such as human error, leaks, and
fires which resulted in hazardous conditions, downtime, or direct repair
costs.

     One important maintenance practice is repairing or replacing equipment
that appears to be headed for failure.  A number of testing methods are
available for examining the condition of equipment.-  Some of the most common
types of tests are listed below.

     •    Metal thickness and integrity testing

     •    Vibration testing and monitoring

     •    Relief valve testing
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All of the above testing procedures are nondestructive, i.e..  they  do  not
damage the material or equipment that they test.

     Accidental releases are frequently the result of some aspect of plant
modification.  To avoid confusion with maintenance activities, a modification
is defined as an intentional change in process materials, equipment, operating
procedures, or operating conditions (39).   Accidents result when equipment
integrity and operation are not properly assessed following modification, or
when modifications are made without updating corresponding operation and
maintenance instructions.  Frequently, hazards created by modifications do not
appear in the exact location of the change.  For example, equipment modifica-
tions can invalidate the arrangements for system pressure relief and blowdown
or they can invalidate the function of instrumentation systems.-  Several
factors should be considered in reviewing modification -plans before author-
izing work.  According to Lees, these include (39):

     •    Sufficient number and size of relief valves,

     •    Appropriate electrical area classification,

     •    Elimination of effects which could reduce safety
          standards,

     •    Use of appropriate engineering standards,

     •    Proper materials of construction and fabrication
          standards,

     •    Existing equipment not stressed beyond design limits,

     •    Necessary changes in operating conditions, and
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     •    Adequate instruction and training of operation and
          maintenance teams.

5.7  CONTRX EFFECTIVENESS

     It is difficult to quantify the control effectiveness  of  preventive  and
protective measures to reduce the probability and magnitude of accidental
releases.   Preventive measures, which may involve numerous  combinations of
process design, equipment design, and operational measures, are especially
difficult  to quantify because they reduce a probability rather than  a  physical
quantity of a chemical release.  Protective measures are more  analogous to
traditional pollution control technologies.  Thus, they may be easier  to
quantify in terms of their efficiency in minimizing the adverse effects of  a
chemical that could be released.

     Preventive measures reduce the probability of an accidental release  by
increasing the reliability of both process systems operations  and the  equip-
ment.  Control effectiveness can thus be expressed for both the qualitative
improvements and the quantitative improvements through probabilities.  Table
5-5 summarizes what appear to be some of the major design,  equipment,  and
operational measures applicable to the primary hazards identified for  the
sulfur dioxide processes in the U.S.-  The items listed in this table are  for
illustration only and do not necessarily represent a satisfactory control
option for all cases.-  These control options appear to reduce  the risk associ-
ated with  an accidental release when viewed from a broad perspective.  How-
ever, there are undoubtedly specific cases where these control options will
not be appropriate.   Each case must therefore be evaluated  individually.  A
discussion of reliability in terms of probabilities is planned for other  parts
of the prevention reference manual series.
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5.8  ILLUSTRATIVE COST ESTIMATES FOR CONTROLS

     This section presents cost estimates for different levels  of  control  and
for specific release prevention and protection measures for  sulfur dioxide
storage and process facilities found in the United States.-

5.8.1  Prevention and Protection Measures

     Preventive measures reduce the probability of' an accidental release from
a process or storage facility by increasing the reliability  of  both process
systems operations and equipment.  Along with an increase in the reliability
of a system is an increase in the capital and annual costs associated with
incorporating prevention and protection measures into a system.  Table  5-6
presents costs for some of the major design, equipment, and  operational
measures applicable to the primary hazards identified in Table  5-5 for  the
sulfur dioxide applications discussed in Section 3.

5.8.2  Levels of Control

     Prevention of accidental releases relies on a combination  of  technologi-
cal, administrative, and operational practices as they apply to the design,
construction, and operation of facilities where hazardous chemicals are used
and stored.  Inherent in determining the degree to which these  practices are
carried out is their costs.  At a minimum, equipment and procedures should be
in accordance with applicable codes, standards, and regulations.   However,
additional measures can be taken to provide extra protection against an acci-
dental release.

     The levels of control concept provides a means of assigning costs  to
increased levels of prevention and protection.  At the lower end of the tier
is the "Baseline" system.  This system consists of the elements required for
normal safe operation and basic prevention of an accidental  release of  hazard-
ous material.
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       TABLE 5-5.   EXAMPLES OF MAJOR PREVENTION AND PROTECTION MEASURES
                   FOR SULFUR DIOXIDE RELEASES
Hazard Area
    Prevention/Protection
Water contamination
in hydrocarbon feeds
to extraction tower

Sulfur dioxide flow
control

Temperature sensing
and cooling medium
flow control
Temperature sensing
and heating medium
flow control
Overpressure
Corrosion
Reactor and reboiler
temperatures

Overfilling
Atmosphere releases .
from relief discharges

Storage tank or line
rupture
Continuous moisture monitoring;
Backflow prevention
Redundant flow control loops; Minimal
overdesign of. feed systems

Redundant temperature sensors;
Interlock flow switch to shut off
SO. feed on loss of cooling, with
relief venting to emergency scrubber
system

Redundant temperature sensors;
Interlock flow switch to shut off
SO. feed on loss of heating, with
relief venting to emergency scrubber
system

Redundant pressure relief; not
isolatable; adequate size; discharge
not restricted

Increased monitoring with more
frequent inspections; use of pH
sensing on cooling water and steam
condensate loops; use of corrosion
coupons; visual inspections;
non-destructive testing

Redundant temperature sensing and
alarms

Redundant level sensing, alarms
and interlocks; training of
operators

Emergency vent scrubber system
Enclosure vented to  emergency
scrubber system; diking;  foams;
dilution; neutralization; water
sprays
                                      93

-------
     TABLE 5-6.   ESTIMATED TYPICAL COSTS OF MAJOR PREVENTION AND PROTECTION
                 MEASURES FOR SULFUR DIOXIDE RELEASE*
=^==============
Prevention/Protection Measure
Continuous moisture inonitoring
Flow control loop
Temperature sensor
Capital Cost
(1986 $)
7500-10000
4000-6000
250-400
Annual Cost
(1986 $/yr)
900-1300
500-750
30-50
Pressure relief

  - relief valve

  - rupture disk

Interlock-system for flow shut-off

pH monitoring of cooling water

Alarm system

Level sensor

  - liquid level gauge

  - load cell

Diking

  - 3 ft high

  - top of tank height, 10 ft.

Increased corrosion inspection
  1000-2000

  1000-1200

  1500-2000

 7500-10000

    250-500



  1500-2000

10000-15000



  1200-1500

  7000-7500
  120-250

  120-150

  175-250

 900-1300

    30-75



  175-250

1300-1900



  150-175

  850-900

  200-400
a3ased on a 10,000 gallon fixed sulfur dioxide storage  tank  system and a
 200.000 gallon/day hydrocarbon extraction system.

b3ased on 10-20 hr @ $20/hr.
                                       94

-------
     The second level of control is "Level 1."  "Level 1" includes  the  base-
line system with added modifications such as improved materials of  construc-
tion,  additional controls,  and generally more extensive release prevention
measures.   The costs associated with this level are higher than the baseline
system costs.

     The third level of control is "Level 2."  This system incorporates both
the "Baseline" and "Level 1" systems with additional modifications  designed
specifically for the prevention of an accidental release such as alarm  and
interlock systems.   The extra accidental release prevention measures incorpo-
rated into "Level 2" are reflected in its cost, which is much higher than that
of the baseline system.

     When comparing the costs of the various levels of control.- it  is impor-
tant to realize that higher costs do not necessarily imply improved safety.
The measures applied must be applied correctly.  Inappropriate modifications
or add-ons may not make a system safer.  Each added control option  increases
the complexity of a system.  In some cases the hazards associated with  the
increased complexity may outweigh the benefits derived from the particular
control option.  Proper design and construction along with proper operational
practices are needed to assure safe operation.

     Example "levels of control" cost estimates were prepared for a 42  ton
fixed sulfur dioxide storage tank system with a 10,000 gal capacity and a
sulfur dioxide extraction tower system for a 200.000 gal/day hydrocarbon
extraction facility.-  These cost estimates are presented for illustrative
purposes only.  It is doubtful that any specific installation would find all
of the control options listed in the following tables appropriate for  their
purposes.   An actual system is likely to incorporate some items from  each  of
the levels of control and also some control options not listed.  The  purpose
of these estimates is to illustrate the relationship between cost and  control,
and not to provide an equipment check list.
                                       95

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5.8.3  Simmary of Levels of Control

     Table 5-7 presents a summary of the total capital and  annual costs  for
each of the three levels of controls for the sulfur dioxide storage system and
the sulfur dioxide extraction tower system.  The costs presented correspond to
the systems described in Table 5-8 and Table 5-9.  Each of  the level costs
include the cost of the basic system plus any added controls.   Specific  cost
information and breakdown for each level of control for both the storage and
process facilities are presented in Tables 5-10 through 5-15.-

5.8.4  Equipment Specifications and Detailed Costs

     Equipment specifications and details of the capital cost  estimates  for
the sulfur dioxide storage and the sulfur dioxide extraction tower systems are
presented in Tables 5-16 through 5-23.
      »

5.8.5  Methodology

Format for Presenting Cost Estimates—
     Tables are provided for control schemes associated with storage and pro-
cess facilities for sulfur dioxide showing capital, operating,  and total
annual costs.  The tables are broken down into subsections  comprising vessels,
piping and valves, process machinery,- instrumentation, and  procedures and
practice.  The presentation of the costs in this manner allows for easy  com-
parison of costs for specific items, different levels, and  different systems.

     Capital Cost—All capital costs presented in this report are shown as
total fixed capital costs.  Table 5-24 defines the cost elements comprising
total fixed capital as it is used here.

     The computation of total fixed capital as shown  in Table 5-24 begins with
the total direct cost for the system under consideration.   This total direct
cost is the total direct installed cost  of all capital equipment comprising
                                      96

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      TABLE 5-7.   SUMMARY COST ESTIMATES OF POTENTIAL LEVELS OF CONTROLS
                   FOR SULFUR. DIOXIDE STORAGE TANK AMD EXTRACTION TOWER
                                 Level of
                                 Control
                 Total
              Capital Cost
                (19S6 $)
                     Total
                  Annual Cost
                  (1986 $/yr)
Sulfur Dioxide Tank
63 ton Fixed S02 Tait^ witn
10.000 gal Capacity
Baseline

Level #1

Level #2
  186.000

  549.000

1.360,000
 22.000

 65.000

160.000
Sulfur Dioxide Extraction
Tower System with
5 ft x 20 ft Packed Tower
Baseline

Level #1

Level #2
  189.000

  548.000

  780,000
 24.000

 68.000

 95.000
                                       97

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   TABLE 5-8."  EXAMPLE OF LEVELS OF CONTROL FOR SULFUR DIOXIDE STORAGE TANK

     Process:  63 ton fixed sulfur dioxide storage tank

               10.000 gal
    Controls
     Baseline
    Level No. 1
                                                             Level No. 2
Process:

Flow:
None
None
Temperature:
Pressure:
Quantity:
Location:
Materials of
Construction:
Vessel:
Single check-      Add second check
valve on tank-     valve.
process feed line.
None
Single pressure
relief valve,
vent to atmos-
phere.
Local level
indicator.
Away from traffic.
Carbon steel
Tank pressure
specification
150 psig.
None
Add second relief
valve, secure
non-is datable.
Vent to limited
scrubber.  Provide
local pressure
indicator.

Add remote level
indicator.
Away from traffic
and flamznables.
Carbon steel with
increased corrosion
allowances.  (1/3
inch)

Tank pressure
specification
225 psig.
None

Add a reduced-pressure
device3 with internal
air gap and relief
vent to containment
tank or scrubber.

Add temperature
indicator.

Add rupture disks
under relief valves.
Provide local pressure
indication on space
between disk and
valve.
Add level alarm.  Add
high-low level inter-
lock shut-off for both
inlet and outlet
lines.

Away from traffic,
flammables, and other
hazardous processes.

Stainless steel. Type
316.
                                                        Tank pressure
                                                        specification
                                                        375 ,psig.
 A reduced pressure device is a modified double check valve.
                                                                 (Continued)
                                       98

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                             TABLE 5-8 (Continued)

     Process:   63 ton fixed sulfur dioxide storage tank

               10.000 gal
    Controls
     Baseline
    Level No. 1
     Level No. 2
Piping:
Process
Machinery:
Enclosures:

Diking:

Scrubbers:

Mitigation:
Sch. 80 carbon
steel.
Sch. 80 316 SS
Centrifugal pump.  Centrifugal pump.
carbon steel.      316 SS construc-
stuffing box       tion. double cap-
seal,              acity mechanical
                   seal.
None

None

None

None
Steel building.

3 ft. high.

Water scrubber.

Water sprays.
Sch. 80 Alloy 20 SS
                     Magnetically-couple
                     centrifugal pump. 316
                     SS, construction.
Concrete building.

Top of tank height.

Alkaline scrubber.

Alkaline water sprays
and barriers.
                                       99

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                TABLE 5-9.  EXAMPLE OF LEVELS OF CONTROL FOR SULFUR DIOXIDE EXTRACTION TOWER
           Controls
                       Baseline
                              Level
                                 Level 1/2
o
o
         Process:


         Temperature:


         Pressure:

         Flow:
Quantity:

Corrosion:



Composition:
        Material  of
        Construction:

        Vessel
                 Dryers on feed
                 lines.

                 Local temperature
                 indicator.

                 None

                 Flow control of
                 sulfur dioxide
                 feed.
Local level control.

Visual inspection
and monitoring.
                          Dryers on hydrocar-
                          bon charge and S0?
                          feed lines.
                 Carbon-steel
                 Tank pressure speci-
                 fication 50 psig.
                        Enchanced flow control.
                        Add redundant sensors
                        and alarm.

                        None

                        Redundant flow control
                        loop.
Add level alarm.

Increased monitoring
with increased inspec-
tions.

Occasional moisture
monitoring.  Add mois-
ture alarms on S0? and
hydrocarbon feed.

Acid brick lined carbon
steel.

Tank pressure specifi-
cation 100 psig.
                           Operate tower at lower
                           temperature.

                           Add remote indicator.
None

Add interlock system
to shutoff sulfur
dioxide feed upon
reaching a temperature
above a set point.

Same

Same
                                                   Continuous moisture
                                                   monitoring
                                                   Type 316 stainless-
                                                   steel.

                                                   Tank pressure speci-
                                                   fication 150 psig.
                                                                                       (Continued)

-------
                                   TABLE 5-9  (Continued)
  Controls
      Baseline
      Level
      Level
Piping:
Process
Machinery:
Protective
Barrier:

Enclosures

Scrubbers:

Mitigation:
Sch. 80 carbon steel.
Centrifugal pump
with stuffing box.
carbon steel
construction.

None
None

None

None
Sch. 80 Type 316 stain-
less steel.

Centrigual pump, double
mechanical seal. Type
316 stainless steel
construction.

Curbing around tower.
Steel building.

Water scrubber.

Water sprays.
Sch. 80 Alloy 20
stainless steel.

Magnetically-coupled
centrifugal pump.
Type 316 stainless
steel construction.

3 ft. high retaining
wall.

Concrete building.

Alkaline scrubber.

Alkaline water sprays.

-------
    TABLE 5-10.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
                 BASELINE SULFUR DIOXIDE STORAGE SYSTEM
                                            Capital Cost
                                               (1986 $)
                   Annual Cost
                   (1986 $/yr)
Vessels:

  Storage tank
  Expansion tanks (3}

Piping and Valves:

  Pipework
  Check valve
  Ball valves (5)
  Excess flow valves (2)
  Angle valves (2.)
  Relief valve
131.000
  6.500
  9.200
  1.000
  6.200
  1.900
  7.500
  2.000
15,000
   760
 1.100
   120
   720
   220
   870
   230
Process Machinery:
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Liquid level gauge
Procedures and Practices:
Visual tank inspection (external)
Visual tank inspection (internal)
Relief valve inspection
Piping inspection
Piping maintenance
Valve inspection
Valve maintenance

18.000 ' 2.100

1.500 180
1.500 180

15
60
15
300
120
30
350
Total  Costs
186.000
                                                                     22.000
                                       102

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    TABLE 5-11.  ESTIMATED TYPICAL  CAPITAL  AND  ANNUAL  COSTS ASSOCIATED WITH
                 LEVEL 1 SULFUR DIOXIDE  STORAGE SYSTEM
                                             Capital  Cost
                                               (1986  $)
                    Annual Cost
                    (1986 $/yr)
Vessels:

  Storage tank
  Expansion tanks (3)

Piping and Valves:

  Pipework
  Check valve
  Ball valves (5)
  Excess flow valves  (2)
  Angle valves (2)
  Relief valve

Process Machinery:

  Centrifugal pump

Instrumentation:

  Pressure gauges (4)
  Flow indicator
  Load cell
  Remote level indicator

Enclosures:

  Steel building

Scrubbers:

  Water scrubber

Diking:

  3 ft high concrete  diking
190.000
  6,500
 30,000
  2.000
  6.200
  1,900
  7.500
  4,000
 35.000
  1.500
  3.700
  1.500
  1.900
 10.000
249.000
  1.400
22.000
   760
 3.500
   240
   720
   220
   870
   460
 4.000
   180
   430
   180
   220
 1.200
29.000
   160
                                                                  (Continued)
                                       103

-------
                             TABLE 5-11 (Continued)
                                            Capital Cost
                                              (1986 $)
                     Annual Cost
                     (1986  $/yr)
Procedures and Practices:

  Visual tank inspection (external)
  Visual tank inspection (internal)
  Relief valve inspection
  Piping inspection
  Piping maintenance
  Valve inspection
  Valve maintenance
                           15
                           60
                           30
                          300
                          120
                           35
                          400
Total Costs
549.000
65.000
                                       104

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    TABLE 5-12.   ESTIMATED TYPICAL CAPITAL AND ANNUAL  COSTS  ASSOCIATED WITH
                 LEVEL 2 SULFUR DIOXIDE STORAGE  SYSTEM
                                             Capital  Cost
                                               (1986  $)
                   Annual Cost
                   (1986 $/yr)
Vessels:

  Storage tank
  Expansion tanks (3)

Piping and Valves:

  Pipework
  Reduced pressure device
  Ball valves (5)
  Excess flow valves  (2)
  Angle valves (2)
  Relief valve
  Rupture disks  (2)

Process Machinery:

  Centrifugal pump

Instrumentation:

  Temperature indicator
  Pressure gauges (6)
  Flow indicator
  Load cell
  Remote level indicator
  Level alarm
  High-low level shutoff

Enclosures:

  Concrete building

Scrubbers:

  Alkaline scrubber

Diking:

  10 ft. high diking
879.000
  6,500
 49,000
  5.000
  6.200
  1.900
  7.500
  4.000
  1.100
 43.000
  2.200
  2.200
  3.700
 16.000
  1.900
    750
  1.900
 19,000
302.000
  7.500
102.000
    760
  5.700
    590
    720
    220
    870
    460
    130
  5.000
    260
    260
    440
  1.800
    220
     90
    220
  2.200
 35,000
    370
                                                                (Continued)
                                       105

-------
                             TABLE 5-12 (Continued)
                                            Capital Cost         Annual  Cost
                                              (1986 $)            (1986  $/yr)
Procedures and Practices:

  Visual tank inspection (external)                                      15
  Visual tank inspection (internal)                                      60
  Relief valve inspection                                                50
  Piping inspection                                                    300
  Piping maintenance                                                   120
  Valve inspection                                                       35
  Valve maintenance                                                    400
Total Costs                                 1.360.000              160.000
                                      106

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    TABLE 5-13.   ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
                 BASELINE SULFUR DIOXIDE EXTRACTION TOWER SYSTEM
                                            Capital Cost
                                              (1986 $)
                   Annual Cost
                   (1986 $/yr)
Equipment:

  Extraction tower
  Tower packing
  Expansion tank

Piping and Valves:

  Pipework
  Ball valves (8)

Process Machinery:

  Centrifugal pumps (2)

Instrumentation:

  P. res sure gauges (3)

  Liquid level control
 56,000
 35.000
  2.500
 27,000
 13.000
 35.000
  1.100
6.800
4.200
  300
3.200
1.600
4.200
  130
- Controller
- Sensor
- Control valve
Local temp, indicator
Flow control
- Controller
- Flowmeter
- Control valve
Maintenance and Inspections:
Visual tower inspection (external)
Visual tower inspection (internal)
Piping inspection
Piping maintenance
Valve inspection
Valve maintenance
1.800
2.200
4.500
2.200

1.800
2.300
4.500







220
260
540
260

220
280
540

15
60
900
360
30
350
Total Costs
189.000
                                                                     24.000
                                       107

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TABLE 5-14.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
             LEVEL 1 SULFUR DIOXIDE EXTRACTION TOWER SYSTEM

Equipment :
Extraction tower
Tower packing
Expansion tank
Piping and Valves:
Pipework
Ball valves (8)
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (3)
Level alarm
Liquid level control
- Controller
- Sensor
- Control valve
Local temp, indicator
Temperature sensor
Temperature alarm
Flow control
- Controller
- Flowmeter
- Control valve
Addition flow control loop
Moisture alarm
Capital Cost
(1986 $)

65,000
35.000
2,500

85,000
13.000

66.000

1.100
360
1.800
2.200
4.500
2.200
360
360

1.800
2.300
4.500
9.000
360
Annual Cost
(1986 $/yr)

7,800
4.100
300

10. 000
1.600

8,000

130
45
220
260
540
260
45
45

220
280
540
1.100
45
                                                            (Continued)
                                   108

-------
                             TABLE 5-14  (Continued)
                                            Capital Cost         Annual  Cost
                                               (1986 S)            (1986 S/yr)
Diking:

  Curbing around tower                          1,200                   150

Enclosure:

  Steel  building                               10.000                1.200

Scrubber:

  Water  scrubber                              240.000               29,000

Maintenance and Inspections:

  Visual tower inspection (external)                                    15
  Visual tower inspection (internal)                                    60
  Piping inspection                                                     900
  Piping maintenance                      '                              360
  Valve  inspection                                                      30
  Valve  maintenance                                                     350


Total Costs                                   548.000               68,000
                                      109

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TABLE 5-15.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
             LEVEL 2 SULFUR DIOXIDE EXTRACTION TOWER SYSTEM

Vessels:
Extraction tower
Tower packing
Expansion tank
Piping and Valves:
Pipework
Ball valves (8)
Process Machinery:
Centrifugal pumps (2)
Instrumentation :
Pressure gauges (3)
Level alarm
Liquid level control
- Controller
- Sensor
- Control valve
Local temp, indicator
Remote temp, indicator
Temperature sensor
Temperature alarm
Flow interlock system
Flow control
- Controller
- Flowaietar
- Control valve
Capital Cost
(1986 $)

205.000
35,000
2,500

85.000
13.000

83,000

1.100
360
1.800
2.200
4.500
2.200
1.800
360
360
1.800

1.300
2.300
4.500
Annual Cost
(1986 $/yr)

25,000
4,100
300

10.000
1.600

10, 000

130
45
220
260
540
260
220
45
45
220

220
230
540
                                                             (Continued)
                                  110

-------
                             TABLE 5-15  (Continued)
                                            Capital Cost          Annual  Cost
                                               (1986 $)            (1986  $/yr)
  Additional flow control loop                  9,000                 1,100

  Moisture alarm                                  360                    45

  Moisture monitoring system                    9,000                 1,100

Diking:

3 ft.  high retaining wall                       3.100                  370

Enclosure:

  Concrete building                            18.000                 2,200

Scrubber:

  Alkaline scrubber                           292,000               35.000

Maintenance and Inspections:
Visual tower inspection (external)
Visual tower inspection (internal)
Piping inspection
Piping maintenance
Valve inspection
Valve maintenance
15
60
900
360
30
350
Total Costs                                   780.000               95,000
                                      111

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    TABLE 5-16.  EQUIPMENT SPECIFICATIONS ASSOCIATED WITH SULFUR DIOXIDE STORAGE SYSTEM
Equipment Item
             Equipment Specification
Reference
Vessels:

  Storage tank
  Expansion tank
Baseline:  10,000 gal. carbon steel storage tank 150
psig rating
Level 1:  10,000 gal. carbon steel with 1/8 in.
corrosion protection. 225 psig. rating
Level 2:  10.000 gal. Type 316 stainless steel
375 psig rating

Standard carbon steel pressure vessel with rupture disk
and pressure gauge
Piping and Valves:   Baseline:  100 ft. of 4 in. schedule 80 carbon steel

  Pipework           Level 1:  100 ft. of 4 in. schedule 80 Type 316
                     stainless steel
                     Level 2:  100 ft. of 4 in. schedule 80 Alloy 20
  Ball valve
  Check valve
4 in., Class 300. flanged. Type 316 stainless
steel construction

4 in.. Class 300. vertical lift. Type 316 stainless
steel
  Excess flow valve  4 in.  standard valve

  Angle  valve        4 in..  Type 316 stainless steel
                                                                                 48. 49
                                                                                 50. 51
48. 49
51

49. 53


49. 53


49

54
                                                                              (Continued)

-------
                                    TABLE  5-16  (Continued)
Equipment Item
             Equipment Specification
Reference
  Relief valve



  Reduced pressure
    device

  Rupture disk

Process Machinery:

  Centrifugal pump
 Instrumentation:

   Temperature
     indicator

   Pressure gauge
   Liquid  level
     gauge
1 in. x. 2 in.. Class 300 inlet and outlet flange.
angle body, closed bonnet with screwed cap. Type
316 stainless steel body and trim                           49

Double check valve type device with internal air gap        48
and relief valve

1 in. Type 316 stainless steel and carbon steel holder      50, 55, 56
Baseline:  single stage, carbon steel construction,
stuffing box
Level 1:  single stage. Type 316 stainless steel            49, 57
construction, double mechanical seal
Level 2:  Type 316 stainless steel construction.            48, 49. 52
magnetically-coupled
Thermocouple, thermowell, electronic indicator              48. 49. 52
Diaphragm sealed. Type 316 stainless steel diaphragm.       58, 52
0-1.000 psig

Differential pressure type level gauge
                                                                               (Continued)

-------
                                   TABLE 5-16 (Continued)
 Equipment  Item
             Equipment Specification
Reference
   Flow  indicator


   Level  indicator

   Load  ceil

   Level  alarm

   High-low/ level
     shutoff

Enclosures:

   Building
Scrubbers:
Diking:
Differential  pressure cell,  transmitter, and associated
flowmeter

Electronic differential pressure  type  indicator

Electronic load cell

Indicating and audible alarm

Solenoid valve, switch, and  relay system
Level 1:  26 gauge steel walls and  roof. door.
ventilation system
Level 2:  10 in. concrete walls. 26 gauge  steel
roof

Level 1:  Spray tower. Type 3*16 stainless  steel
construction, water sprays. 3 ft. x 24 ft.
Level 2:  Spray tower. Type 316 stainless  steel
construction, alkaline sprays

Level 1:  6 in. concrete walls. 3 ft. high
Level 2:  10 in. concrete walls, top of  tank
height
48. 52


48, 49, 52

48. 52, 58

49, 54. 59

48. 49. 52
54
                                                                                  54
                                                                                  60
                                                                                  54

-------
TABLE 5-17.  DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE SULFUR DIOXIDE
             STORAGE SYSTEM
•
Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Check valves
Ball valves (5)
Excess flow valves (2)
Angle valves (2)
Relief valve
Process Machinery :
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Liquid level gauge
Total Costs
Materials
Cost


61.000
3.500

2.300
640
4.000
1.200
5.000
1.300

8.500

800
800
89.000
Labor
Cost


27.000
880

3.900
30
150
40
40
50

3.600

200
200
36.000
Direct
Costs
(1986 $)

88.000
4.380

6.200
670
4.150
1.240
5.040
1.350

12. 100

1.000
1.000
125.000
Indirect
Costs


31.000
1.500

2.200
230
1.500
440
1.800
470

4.200

350
350
44.000
Capital
Cost


131.000
6.500

9.200
1.000
6.200
1.900
7.500
2.000

18.000

1.500
1.500
186.000

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TABLE 5-18.  DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1 SULFUR DIOXIDE
             STORAGE SYSTEM

Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Check valves (2)
Ball valves (5)
Excels flow valves (2)
Angle valves (2)
Relief valves (2)
Process Machinery:
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Flow indicator
Liquid level gauge
Remote level indicator
Enclosures:
Steel building
Materials
Cost


88.000
3.500

15.000
1.300
4,000
1.200
5.000
2.600

16.000

800
2.000
800
1.000

4.600
Labor
Cost


40. 000
880

5.000
60
150
40
40
100

7.000

200
500
200
250

2.300
Direct
Costs
(1986 $)

128.000
4.380

20.000
1.360
4.150
1.240
5.040
2,700

23.000

1.000
2.500
1.000
1.250

6.900
Indirect
Costs


45,000
1.500

7.000
480
1.500
440
1.800
940

8.100

350
880
350
440

2.400
Capital
Cost


190. 000
6.500

30.000
2.000
6.200
1,900
7.500
4.000

35.000

1.500-
3.700
1.500
1.900
•
10.000
                                                                            (Continued)

-------
                                  TABLE 5-18 (Continued)
                               Materials      Labor      Direct      Indirect      Capital
                                 Coat	Cost	Costa	Costs	Cost
                                                        (1986 $)
Scrubbers:
                                                  *

  Water scrubber                115.000      52.000     167.000       59.000       249.000

Diking:

3 ft. high concrete                 390         520         910          320         1.400
  diking


Total Costa                     261.000     109.000     370,000      130.000       549.000

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          TABLE 5-19.  DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 SULFUR DIOXIDE
                       STORAGE SYSTEM
                                        Materials
                                          Cost
                                              Labor
                                              Cost
           Direct
           Costs
            Indirect
             Costs
                                                                 (1986 $)
             Capital
              Cost
co
Vessels:

  Storage tank                  408.000
  Expansion tanks  (3)             3.500

Piping and Valves:

  Pipework                       28.000
  Reduced pressure device         3.200
  Ball valves (5)                 4.000
  Excess flow valves (2)          1,200
  Angle valves (2)                5.000
  Relief valve                    2.600
  Rupture disks (2)                 650

Process Machinery:

  Centrifugal Pump               20.000

Instrumentation:
                                                     184.000
                                                         880
5.000
  200
  150
   40
   40
  100
   75
                                                       9.000
          592.000
            4.380
33.000
 3.400
 4.150
 1.240
 5.040
 2.700
   725
           29.000
            207.000
              1.500
12.000
 1.200
 1.500
   440
 1.800
   940
   260
             10.000
             879.000
               6.500
49.000
 5.000
 6.200
 1.900
 7.500
 4.000
 1.100
              43.000
Temperature indicator
Pressure gauges (6)
Flow indicator
Load cell
Remote level indicator
Level alarm
High-low level shutoff
1.200
1.200
2.000
8.400
1.000
400
1.000
300
300
500
2.100
250
100
250
1.500
1.500
2.500
10.500
1.250
500
1.250
530
530
880
3.700
440
180
440
2.200
2.200
3.700
16.000
1.900
750
1.900
                                                                                       (Continued)

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                                  TABLE 5-19 (Continued)
                               Materials      Labor      Direct      Indirect      Capital
                                 Coat	Cost	Costs	Costs	Cost
                                                        (1986 $)
Enclosures:

  Concrete building

Scrubbers:

  Alkaline scrubber

Diking:

  10 ft. high diking
  6.100       6.600      12.700        4.500         19.000
140.000      63.000     203.000        71.000       302,000
  2.200       2.900       5.100
1.800
7.500
Total Costs
640.000     276.000     916.000       321.000      1.360.000

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    TABLE 5-20.   EQUIPMENT SPECIFICATIONS ASSOCIATED WITH  SULFUR DIOXIDE EXTRACTION TOWER
                 SYSTEM
 Equipment Item
             Equipment Specification
Reference
 Vessels:

   Extraction  tower
  Tower packing


  Expansion tank


Piping and Valves:

  Pipework
  Ball valves


Process Machinery:

  Centrifugal pump
Baseline:  5 ft. x 20 ft. packed tower, carbon steel
construction, 50 psig rating
Level 1:  Acid brick lined carbon steel construction.
100 psig rating
Level 2:  Type 316 stainless steel construction.             48
150 psig rating

1-3/4 in. Type 316 stainless steel Raschig                   48
rings at a depth of 10 ft.

Standard carbon steel pressure vessel with rupture disk      48.49
and pressure gauge
Baseline:  300 ft. of 4" schedule 80 carbon steel
Level 1:  4in. schedule 80 Type 316 stainless
steel
Level 2:  4 in. schedule 80 alloy 20 stainless               52
steel

4 in.. Class 300. flanged. Type 316 stainless                49. 53
steel construction
Baseline:  single stage, carbon steel construction.
stuffing box
Level 1:  single stage. Type 316 stainless steel
construction, double mechanical seal                         49, 57
                                                                             (Continued)

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                                   TABLE 5-20  (Continued)
Equipment Item
             Equipment Specification
Reference
  Centrifugal
  Pump

Instrumentation:

  Pressure gauge


  Level alarm

  Liquid level
    control  loop
  Local  tempera-
     ture indicator

  Remote tempera-
     ture indicator

  Temperature
     sensor

  Temperature
     alarm

  Flow  interlock
     system

  Flow  control
     loop
Level 2:  Type 316 stainless steel construction,
magnetically-coupled
Diaphragm sealed. Type 316 stainless steel diaphragm,
0-1,000 psig rating

Indicating and audible alarm

PID controller, 4 in. globe control valve of
stainless steel construction, gravity differential
sensor system

Thermocouple, therraowell, and electronic indicator
Transmitter and  associated electronic indicator
Thermocouple and associated  thermowell
 Indicating and audible alarm
Solenoid valve, switch, and  relay system
PID controller, 4" globe control valve of stainless
steel construction, flowmeter
  Moisture  alarm      Moisture sensor  and  indicating  and  audible  alarm
49. 57




48. 49. 52




48. 52



48. 49. 52


48. 52


48. 49. 52


49. 54. 59
48, 49. 52
54

48. 52
                                                            58
                                                                             (Continued)

-------
                                   TABLE 5-20  (Continued)
Equipment Item
             Equipment Specification
Reference
  Moisture Moni-
    toring System

Diking:
Enclosure:
Scrubber:
Capacitance or Infrared absorption system
Level 1:  0.5 ft. high concrete curbing
Level 2:  3 ft. high concrete retaining wall

Level 1:  26 gauge steel walls and roof. door.
ventilation system
Level 2:  0.8 ft. concrete walls. 26 gauge steel
roof

Level 1:  Spray tower. Type 316 stainless steel construc-
tion, water sprays. 8 ft. x 24 ft.
Level 2:  Spray tower. Type 316 stainless steel construc-
tion, alkaline sprays

-------
     TABLE 5-21.   DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE SULFUR
                  DIOXIDE EXTRACTION TOWER SYSTEM

Equipment :
Extraction tower
Tower packing
Expansion tank
Piping and Valves:
Pipework
Ball valves (8)
Materials
Cost


27.000
17.000
1.200

6.800
8.000
Labor
Cost
•

12,000
7,400
540

12,000
1.200
Direct
Costs
(1986 $)

39.000
24, 400
1.740

18.800
9.200
Indirect
Costs


9.800
6.100
440

4.700
2,300
Capital
Cost


56. 000
35.000
2,500

27,000
13.000
Process Machinery:

  Centrifugal pumps (2)

Instrumentation:

  Pressure gauges (3)

  Liquid level control
17.000
   600
7.200
  150
24,200
   750
6.100
  190
35.000
 1.100
- Controller
- Sensor
- Control valve
Local temp, indicator
Flow control
- Controller
- Flowmeter
- Control valve
Total CoiUu
1.000
1.200
2.500
1.200
1.000
1,300
2.500
88.000
250
300
630
300
250
330
630
43.000
1.250
1.500
3.130
1.500
1.250
1.630
3,130
131.000
320
380
780
380
320
410
780
33.000
1.800
2.200
4.500
2.200
1.800
2.300
4.500
189.000

-------
TABLE 5-22.  DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1 SULFUR
             DIOXIDE EXTRACTION TOWER SYSTEM

Equipment::
Extraction tower
Tower packing
Expansion tank
Piping and Valves:
Pipework
Bail valves (8)
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (3)
Level alarm
Liquid level control
- Controller
- Sensor
- Control valve
Local temperature indicator
Materials
Cost


31.000
17.000
1.200

44. 000
8.000

32.000

600
200
1.000
1.200
2.500
1.200
Labor
Cost


14.000
7.400
540

15.000
1. 200

14.000

150
50
250
300
630
300
Direct
Costs
(1986 $)

45.000
24. 400
1.740

59.000
9.200

46.000

750
250
1.250
1.500
3.130
1.500
Indirect
Costs


11.000
6.100
440

15.000
2.300

12.000

190
65
320
380
780
380
Capital
Cost


65.000
35.000
2.500

85.000
13.000

66.000

1.100
360
1.800
2.200
4.500
2.200
                                                                       (Continued)

-------
                                  TABLE 5-22 (Continued)
Materials
Cost
Labor
Cost
Direct
Costs
Indirect
Costs
Capital
Cost
(1986 $)
Temperature sensor
Temperature alarm
Flow control
- Controller
- Flowmeter
- Control valve
Additional flow control loop
Moisture alarm
200
200
1.000
1.300
2.500
4.800
200
50
50
250
330
630
1.210
50
250
250
1.250
1,630
3.130
6.010
250
65
65
320
410
780
1,600
65
360
360
1.800
2.300
4.500
9,000
360
Diking:
                                                   •
  Curbing around tower              500         350         850          220          1.200

Enclosure:

  Steel building                  4.600       2.300       6,900        1.700         10.000

Scrubber:

  Water scrubber                115.000      52,000     167,000       42,000        240.000


Total Costs                     270.000     111.000     381.000       96.000        548.000

-------
                  TABLE 5-23.   DETAILS OF MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2
                               SULFUR DIOXIDE EXTRACTION TOWER SYSTEM
NJ
CT>

Equipment: :
Extraction tower
Tower packing
Expansion tank
Piping and Valves:
Pipework
Ball valves (8)
Process Machinery ;
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (3)
Level alarm
Liquid level control
- Controller
- Sensor
- Control valve
Materials
Cost


98.000
17.000
1.200

44.000
8.000

40.000

600
200

1.000
1.200
2.500
Labor
Cost


44.000
7.400
540

15.000
1.200

18. 000

. 150
50

250
300
630
Direct
Costs
(1986 $)

142. 000
24. 400
1.740

59.000
9.200

58.000

750
250

1.250
1.500
3.130
Indirect
Costs


36. 000
6.100
440

15. 000
2.300

15. 000

190
65

320
380
780
Capital
Cost


205.000
35.000
2.500

85. 000
13.000

83.000

1.100
360

1.800
2.200
4.500
                                                                                       (Continued)

-------
TABLE 5-23 (Continued)
Materials
Cost
Labor
Cost
Direct
Costs
Indirect
Costs
Capital
Cost
(1986 $)
Local temp, indicator
Remote temp, indicator
Temperature sensor
Temperature alarm
Flow interlock sytem
Flow control
- Controller
- Flowmeter
- Control valve
Additional flow control .loop
Moisture alarm
Moisture monitoring system
Diking:
3 ft. high retaining wall
Enclosure:
Concrete building
1.200
1.000
200
200
1.000
1,000
1.300
2.500
4.800
200
5.000

900

6.000
300
250
50
50
250
250
325
625
1,210
50
1.250

1.200

6.600
1.500
1.250
250
250
1.250
1.250
1.625
3.125
6.010
250
6.250

2.100

12.600
380
320
65
65
320
320
410
780
1.600
65
1.600

530

3.200
2.200
1.800
360
360
1.800
1.800
2.300
4.500
9.000
360
9.000

3.100

18. 000
                                           (Continued) .

-------
                                  TABLE 5-23 (Continued)
                               Materials      Labor      Direct      Indirect      Capital
                                 Cost	Cost	Costs	Costa	Cost
                                                        (1986 $)
Scrubber:

  Alkaline scrubber             140.000      63.000     203.000       51.000       292.000


Total Costs                     379.000     163.000     542.000      135.000       780.000

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             TABLE 5-24.  FORMAT FOR TOTAL FIXED  CAPITAL  COST
     Item No.                 Item                        Cost


        1           Total Material  Cost

        2           Total Labor  Cost

        3           Total Direct Cost               Items  1+2

        4           Indirect Cost Items  (Engi-
                    neering & Construction
                    Expenses)                       0.35 x Item 3a

        5           Total Bare Module  Cost          Items  (3  +  4)

        6           Contingency                     (0.05  x Item 5)b

        7           Contractor's Fee                0.05 x Item 5

        8           Total Fixed  Capital  Cost        Items  (5+6+7)
For storage facilities, the  indirect  cost  factor  is  0.35.   For process
facilities, the indirect cost  factor  is  0.25.

For storage facilities, the  contingency  cost  factor  is  0.05.   For process
facilities, the contingency  cost  factor  is 0.10.
                                     129

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the system.  Depending on the specific equipment item involved,  the  direct
capital cost was available or was derived from uninstalled  equipment costs by
computing costs of installation separately.  To obtain the  total fixed capital
cost, other costs obtained by utilizing factors are added to'the total direct
costs.

     The first group of other cost elements is indirect costs.   These include
engineering and supervision, construction expenses, and various  other expenses
such as administration expenses, for example.  These costs  are computed by
multiplying total direct costs by a factor shown in Table 5-24.   The factor is
approximate, is obtained from the cost literature, and is based  on previous
experience with capital projects of a similar nature.  Factors can have a
range of values and vary according to technology area and for individual
technologies within an area.  Appropriate factors were selected  for  use in
this report based on judgement and experience.
       *
     When the indirect costs are added to the total direct  costs, total bare
module cost is obtained.  Some additional cost elements such as  contractor's
fee and contingency are calculated by applying and adding appropriate factors
to the total bare module cost as shown in Table 5-24 to obtain the total fixed
capital cost.

     Annual Cost—Annual costs are obtained for each of the equipment items by
applying a factor for both capital recovery and for maintenance  expenses to
the direct cost of each equipment item.  Table 5-25 defines the  cost elements
and appropriate factors comprising these costs.  Additional annual costs are
incurred for procedural items such as valve and vessel inspections,  for
example.  When all of these individual costs are added, the total annual cost
is obtained.
                                      130

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            TABLE 5-25-.  FORMAT FOR TOTAL ANNUAL  COST
Item No.                 Item                        Cost


   1           Total Direct Cost

   2           Capital Recovery on Equip-
               ment Items                      0.163  x  Item 1

   3           Maintenance Expense on
                 Equipment Items               0.01 x Item 1

   4           Total Procedural Items

   5           Total Annual Cost               Items  (2+3+4)
                                131

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Sources of Information—
     The costs presented in this report are derived from  cost  information in
existing published sources and also from recent vendor information.   It was
the objective of this effort to present cost levels for sulfur dioxide process
and storage facilities using the best costs for available sources.   The
primary sources of cost information are Peters and Timmerhaus  (48),  Chemical
Engineering (61), and Valle-Riestra (62) supplemented by  other sources and
references where necessary.  Adjustments were made to update all  costs to a
June 1986 dollar basis.  In addition, for some equipment  items, well-
documented costs were not available and they had to be developed  from compo-
nent costs.-

     Costs in this document reflect the "typical" or "average" representation
for specific equipment items.  This restricts the use of  data  in  this report
to:
       >
                                                                              •
     •    Preliminary estimates used for policy planning.

     •    Comparison of relative costs of different levels  or
          systems, and

     •    Approximations of  costs  that  might  be incurred for a specific
          application.

     The  costs  in this report are  considered to be "order of magnitude" with a
+50 percent margin.  This  is because the costs are based  on preliminary
estimates and many are updated from literature sources.   Large departures from
the design basis of a particular system presented in this manual  or the advent
of a different  technology might cause the system cost to  vary  by  a greater
extent  than this.  If used as intended, however,- this document will provide a
reasonable source of preliminary cost information for the facilities covered.
                                      132

-------
     When comparing costs in this manual  to  costs  from  other  references,  the
user should be sure the design bases are  comparable  and that  the  capital  and
annual costs as defined here are  the same as  the costs  being  compared.

Cost Updating—
     All costs in  this report are expressed  in June  1986 dollars.-  Costs
reported in the literature were updated using cost indices  for  materials  and
labor.

     Costs expressed  in base year dollars may be adjusted to  dollars  for
another year by applying  cost indices  as  shown in  the following equation:

     new base year cost = old base  year cost  x new base year  index
                                               old base year  index

The Chemical Engineering  (CE) Plant Cost  Index was used in  updating cost  for
t.his report.  For  June 1986. the  index is 316.3.

Equipment Costs—
     Most of the equipment costs  presented in this manual were  obtained
directly from literature  sources  of vendor information  and  correspond to  a
specific design standard.- Special  cost estimating techniques,  however, were
used in determining the costs associated  with vessels,  piping systems,  scrub-
bers, diking, and  enclosures.  The  techniques used are  presented  in the
following subsections of  this manual.

     Vessels—The  total purchased cost for a vessel, as dollars per pound of
weight of fabricated  unit f.o.b. with  carbon steel as  the basis (January  1979
dollars) was determined using the following  equation from Peters  and Timmer-
haus (48):

               Cost =  [50(Weight  of Vessel in Pounds)"0'34]
                                      133

-------
The vessel weight is determined using appropriate design  equations as given by
Peters and Timmerhaus (48) which allow for wall thickness adjustments for
corrosion allowances, for example.  The vessel weight  is  increased by a factor
of 0.15 for horizontal vessels and 0.20 for vertical vessels to  account for
the added weight due to nozzles, manholes,- and skirts  or  saddles.   Appropriate
factors are applied for different materials of construction as given in Peters
and Timmerhaus (48).  The vessel costs are updated using  cost factors.
Finally a shipping cost amounting to 10 percent of the purchased cost is added
to obtain the delivered equipment cost.

     Piping—Piping costs were obtained using cost information and data
presented by Yamartino (63).  A simplified approach is used in which it is
assumed that a certain length of piping containing a given number of valves.
flanges, and fittings is contained in the storage or process facility,   the
data presented by Yamartino  (63) permit cost determinations for  various
lengths*, sizes, and types of piping systems.  Using these factors, a represen-
tative estimate can be obtained for each of the storage and process facili-
ties.-

     Diking—Diking costs were estimated using Mean's  Manual  (54)  for rein-
forced concrete walls.-  The  following assumptions were made in determining the
costs.  The  dike  contains the entire contents of a tank in the event of a leak
or  release.  Two  dike sizes  are possible:  a three-foot high dike, six-inches
thick and a  top-of-tank height dike ten inches thick.  The tanks are raised
off  the ground and  are not volumetrically included in  the volume enclosed by
the  diking.  These  assumptions facilitate cost determination for any size
diking system.

     Enclosures—Enclosure costs were estimated using  Mean's Manual (54) for
both  reinforced concrete  and steel-walled buildings.   The buildings are
assumed co enclose  the same  area and volume as the top-of-tank height dikes.
The  concrete building is  ten inches thick with a 26-gauge steel  roof and a
metal door.  The  steel building has 26 gauge roofing and  siding  and metal
                                       134

-------
door.  The cost of a ventilation system was  determined using  a  typical  1,000
scfm unit and doubling the cost to  account for  duct work and  requirements  for
the safe enclosure of hazardous chemicals.

     Scrubbers—Scrubber costs were estimated using the following  equation
from the Gard (60) manual for spray towers based  on the actual  cubic  feet  per
minute of flow at a chamber velocity of 600  feet/min.

                        Costs = 0.235 x  (ACFM + 43.000)

A release rate of 10.-000 ft /min was assumed for  the  storage  vessel systems
and an appropriate rate was determined for the  process system based on  the
quantity of hazardous chemicals present in the  system at any  one time.   For
                                                                        3
the sulfur dioxide extraction tower system,  a release rate  of 10.000  ft /min
was assumed.  In addition to the spray tower, the costs also  include  pumps and
a storage tank for the scrubbing medium.  The.costs presented are  updated  to
June  1986 dollars.
Installation  Factors—
      Installation costs  were  developed for  all  equipment  items  included in
both  the  process  and  storage  systems.   The  costs  include  both the  material  and
labor costs for installation  of  a particular  piece  of  equipment.-   The costs
were  obtained directly from literature sources  and  vendor information or
indirectly by assuming a certain percentage of  the  purchased equipment cost
through the use of  estimating factors  obtained  from Peters and  Timmerhaus (48)
and Valle-Riestra (62).   Table 5-26  lists the cost  factors used or the refer-
ence  from which the cost was  obtained  directly.   Many  of  the costs obtained
from  the  literature were updated to  June 1986 dollars  using a 10  percent per
year  rate of  increase for labor  and  cost indices  for materials  associated with
installation.
                                        135

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         TABLE 5-26.  FORMAT FOR INSTALLATION  COSTS
        Equipment Item                 Factor or Reference
Vessels:
     Storage Tank                             0.45
     Expansion Tank                           0.25

Piping and Valves:
     Pipework          '                      Ref. 63
     Expansion Loop                          Ref. 49
     Reduced Pressure Device                 Ref. 49
     Check Valves                            Ref. 49
     Gate Valves                             Ref. 49
     Ball Valves                             Ref. 49
     Excess Flow Valves                      Ref. 49
     Angle Valves                            Ref. 54
     Relief Valves                           Ref. 49
     Rupture Disks                           Ref. 49

Process Machinery:
     Centrifugal Pump    ^                     0.43
     Gear Pump           '                     0.43

Instrumentation:
     All Instrumentation Items                0.25

Enclosures:                                  Ref.- 54

Diking:                                      Ref. 54

Scrubbers:                                    0.45
                             136

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                                   SECTION 6

                                  REFERENCES


 1.   Mark. Herman E..  Othmer.  Donald F.,  Overberger.  Charles G.,  Seaborg.
     Glenn T.. Kirk-Othmer Encyclopedia  of  Chemical Technology.  3rd ed..  vol.
     22.  John Wiley & Sons. 1983.

 2.   Sulfur  Dioxide.   Compressed Gas Association.  Inc.,  Pamphlet  G-3,  3rd
     edition. 1964.

 3.   Dean. J.A.. (ed.).  Lange's Handbook of Chemistry. 12th ed.  McGraw-Hill
     Book Company. 1979.

 4.   Tennessee  Chemical Company.  Atlanta,  GA.   Sulfur Dioxide  Technical
     Handbook.  5th ed.. 1979.

 5.   Bird. R.B., et al.  Transport Phenomena.  John Wiley & Sons. Inc.. 1960.

 6.   Sulfur  Dioxide.   Dangerous Properties of  Industrial  Materials Report.
     Volume  1. No. 3. Jan/Feb 1981.

 7.   Air Products and Chemicals, Inc.. Allentown. PA.  Speciality Gas Material
     Safety Data Sheet.  Revised March 1985.

 8.   Liquid Air Corporation,  Alphagaz  Division, Walnut Creek,  CA.   Material
     Safety Data Sheet.  October 1985.

 9.   U.S. Dept. of Health. Education, and Welfare.  Criteria for a  Recommended
     Standard...Occupational  Exposure  to  Sulfur  Dioxide.   HEW(NIOSH)
     Publication No. 74-111. NTIS Order No. PB-228152. 1974.

10.   Sittig. Marshall.   Handbook of Toxic & Hazardous Chemicals  and Carcin-
     ogens.  2nd edition. Noyes Publications, 1985.

11.   National Joint Health and Safety Committee for the Water Service.  Safety
     Aspects of Storage,  Handling and Use  of  Chlorine and Sulphur  Dioxide.
     London, England, April 1982.

12.   Tennessee Chemical  Company,  Atlanta,  GA.  Material  Safety Data Sheet.
     Revised June 1984.

13.   Schroeter. L.C. Sulfur Dioxide.  Pergamon  Press,  New York  1966.

14.   Lawler, G.M.  (ed.).   Chemical Origins  and Markets,  Fifth Edition.
     Stanford Research Institute, 1977.
                                       137

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15.   U.S. Patent No.  2,703.788.

16.   Britt.  Kenneth W.  Handbook of Pulp and Paper Technology,  2nd  ed.   van
     Nostrand Reinhold Company, 1970.

17.   Austin, George  T.   Shreve's  Chemical  Process  Industries,  5th  ed.
     McGraw-Hill, 1984, pp. 621-625.

18.   Casey,  James P.  (ed.).  Pulp and Paper Chemistry and Chemical  Technology.
     3rd ed.. Volume 1.  John Wiley & Sons, 1980.

19.   Telephone conversation  between M. Stohs  of Radian Corporation and  a
     representative of Champion Paper Company, Pasadena, TX, September  1986.

20.   U.S. Patent No.  3,864,457.

21.   U.S. Patent No.  3,950,500.

22.   Sulfur Dioxide in Water Dechlorination.   Technical  Information Bulletin,
     Stsuffer  Chemical Co..  Industrial  Chemical  Division,  Westport.  CT.
     January 1977.

23.   Treatment of Chromium Waste with  Sulfur Dioxide.  Bulletin 514, Virginia
     Chemicals, Inc., Portsmouth. VA.

24.   Stone  & Webster Engineering Corporation.  Modified Edeleanu Process  for
     Recovery of Aromatics.  Pet. Ref., 30(9), 237-238,  1951.

25.   Bland,  Wm.  F. and Davidson,  R.L.  (eds.).   Petroleum Processing Handbook.
     McGraw-Hill, 1967.

26.  Dickey, S. W.  Diesel Fuel of 50-Cetane Value Produced  in New  Sulfur
     Dioxide Extraction Plant.  Pet. Proc. 3(6), 538-542,  1948.

27.  Telephone  conversation between M.  Stohs of Radian Corporation and  a
     representative  of Tennessee Chemical  Company,  Atlanta,  GA.  September
     1986. -

28.  Telephone  conversation between M.  Stohs of Radian Corporation and  a
     representative  of PB&S Chemical Company,  Henderson, KY, August 1986.

29.  ASME Boiler and  Pressure Vessel Code.  ANSI/ASME BPV-VIII-1, American
     Society of Mechanical Engineers, New York,  NY,  1983.

30.  Chemical Plant  and Petroleum Refinery Piping.   ANSI/ASME  B31.3, American
     National Standards Institute,  Incorporated, New York, NY, 1980.
                                       138

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31.  Steel Valves.  ANSI/ASME B16.34.   American National Standards Institute,
     Incorporated, New York, NY,  1977.

32.  Steel  Pipe  Flanges and Flanged Fittings.  ANSI/ASME  B16.S.   American
     National Standards Institute,  Incorporated, New York.  NY,  1977.

33.  Construction Materials for SO.  Service.   Technical Data Sheet, Tennessee
     Chemical Company. Atlanta. GA;  revised June 1983.

34.  Handling of  Sulfur Dioxide Containers.   Technical Data Sheet. Tennessee
     Chemical Company. Atlanta, GA.

35,  Valves  for  SO.  Service.   Technical  Data Sheet.  Tennessee  Chemical
     Company. Atlanta, GA.

36.  Telephone  conversation between M.  Stohs of Radian  Corporation  and a
     representative of Ingersoil-Rand,  Houston. TX, September  1986.

37.  Green,  D.  W.,  (ed.).   Ferry's Chemical  Engineer's  Handbook. 6th  ed.
     McGraw-Hill, New York. NY. 1984.

38.  Pressure Relief Device Standards - Part  3 - Compressed Gas Storage
     Containers.  Pamphlet  S-1.3.  Compressed  Gas Association,  Inc.. Arlington,
  •  VA,  1984.

39.  Lees,  F.  P.  Loss   Prevention in the  Process   Industries-Hazard
     Identification,  Assessment,  and Control,  Vol.  1  & 2.   Butterworths.
     London, England, 1983.

40.  Aarts, J.  J. and D.  M. Morrison.   Refrigerated Storage Tank Retainment
     Walls.   CEP  Technical Manual, Volume 23, American Institute  of  Chemical
     Engineers. New York. NY,  1981.

41.  Radian Notebook  Number 215.  for EPA Contract 68-02-3994.  Work Assignment
     94.  Page 5.  1986.

42.  Bennett. G.  F.,  F.  S.  Feates. and I. Wilder.   Hazardous Materials Spills
     Handbook.  McGraw-Hill Book  Company. New York. NY.  1982.

43.  Hiltz. R.H.  and  Gross S.S.  The Use of Foams to Control the Vapor Hazard
     From Liquified Gas Spills in  Control  of Hazardous  Materials Spills  -
     Proceedings  1980.  National  Conference  on Control  of  Hazardous  Material
     Spills, Louisville, KY, May  1980.

44.  Canvey:' A Second  Report.   Health  and Safety Executive (U.K.).   London,
     England, 1981.
                                       139

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45.  Greiner. M. L.  Emergency Response Procedures  for Anhydrous Ammonia Vapor
     Release.  CEP Technical Manual. Volume 24, American  Institute of Chemical
     Engineers, New York, NY, 1984.

46.  McQuaid, J. and A.  F.  Roberts.   Loss of  Containment - Its  Effects and
     Control, in Developments  '82 (Institution of  Chemical Engineers Jubilee
     Symposium).  London, England, April 1982.

47.  Kubias, F.O.  Technical Safety Audit.  Presented at  the  Chemical
     Manufacturer's Association Process Safety Management Workshop,  Arlington,
     Va.. May 7-8, 1985.

48.  Peters,  M.S.  and K.D.  Timmerhaus.   Plant  Design and  Economics  for
     Chemical Engineers.  McGraw-Hill Book Company, New York,  NY, 1980.

49.  Richardson Engineering Services, Inc.  The  Richardson Rapid Construction
     Cost Estimating System, Volume 1-4, San Marcos, CA,  1986.

50.  Pikulik, A. and H.E. Diaz.   Cost Estimating  for Major Process Equipment.
     Chemical Engineering. October 10, 1977-

51.  Hall,  R.S., J.  Matley,  and K.J.  McNaughton.   Cost of Process  Equipment.
     Chemical Engineering, April  5, 1982.

52.  Liptak,  B.G.    Costs  of  Process  Instruments.   Chemical Engineering,
     September  7,  1970.

53.  Telephone  conversation between J.D. Quass  of  Radian Corporation  and a
     representative  of Mark  Controls Corporation.   Houston. TX.  August 1986.

54.  R. S.  Means Company, Inc.  Building  Construction Cost Data 1986  (44th
     Edition).  Kingston, MA.

55.  Telephone  conversation between J.D. Quass  of  Radian Corporation  and a
     representative  of Zook  Enterprises.  Chagrin Falls,  OH,  August 1986.

56.  Telephone  conversation between J.D. Quass  of  Radian Corporation  and a
     representative  of Fike  Corporation.  Houston,  TX. August 1986.

57.  Green,  D.W.,  ed.   Perry's Chemical Engineer's Handbook  (Sixth Edition).
     McGraw-Hill Book Company.  New York, NY.  1984.

58.  Liptak,  B.G.   Costs  of  Viscosity,  Weight.  Analytical  Instruments.
     Chemical Engineering.  September 21,  1970.

59.  Liptak,  B.G.   Control-Panel Costs,  Process  Instruments.   Chemical
     Engineering.  October 5,  1970.

60.  Capital and  Operating  Costs of Selected  Air Pollution Control  Systems.
     EPA-450/5-80-002, U.S.  Environmental  Protection  Agency.  1980.
                                       140

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61.  Cost indices obtained  from Chemical Engineering.   McGraw-Hill Publishing
     Company. New York, NY. June  1974. December  1985.  and  August  1986.

62.  Valle-Riestra, J.F.   Froj.ect Evaluation in  the  Chemical Process Indus-
     tries.  McGraw-Hill Book Company, New York,  NY,  1983.

63.  Yamartimo.  J.    Installed  Cost  of  Corrosion-Resistant  Piping-1978.
     Chemical Engineering. November 20.  1978.
                                       141

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                                  APPENDIX A
                                   GLOSSARY

     This glossary defines selected terms used in the text of  this manual
which might be unfamiliar to some users or which might be used differently  by
different authors.

Accidental release;  The unintentional spilling, leaking, pumping, purging,
emitting, emptying, discharging, escaping, dumping, or disposing  of  a  toxic
material into the environment in a manner that is not in compliance  with a
plant's federal, state, or local environmental permits and results in  toxic
concentrations in the air that are a potential health threat to the
surrounding community.

Cavitation;  The formation and collapse of vapor bubbles in a  flowing  liquid.
Specifically the formation and collapse of vapor cavities in a pump  when there
is sufficient resistance to flow at the inlet side.

Creep failure;  Failure of a piece of metal as a result of creep.  Creep is
time dependent deformation as a result of stress.  Metals will deform  when
exposed to stress.  High levels of stress can result in rapid  deformation and
rapid failure.  Lower levels of stress can result in slow deformation  and
protracted failure.

Deadheading;  Closing or nearly closing or blocking the discharge outlet or
piping of an operating pump or  compressor.

Electromotive Series  of Metals;  A List of metals and alloys  arranged
according to their  standard electrode  potentials; which also  reflects their
relative corrosion  potential.
                                      142

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Enthalpy;  A thermodynamic property of a. chemical related to its  energy
content at a given condition of temperature, pressure and physical state.
Enthalpy is the internal energy added to the product of pressure  times volume.
Numerical values of enthalpy for various chemicals are always based on the
change in enthalpy from an arbitrary reference pressure and temperature, and
physical state, since the absolute value cannot be measured.

Facility;  A location at which a process or set of processes are  used to
produce, refine or repackage chemicals, or a location where a large enough
inventory of chemicals are stored so that a significant accidental release of
a toxic chemical is possible.

Hazard;  A source of danger.  The potential for death, injury or  other forms
of damage to life and property.

Hygroscopic;  Readily absorbing and retaining moisture, usually in reference
to readily absorbing moisture from the air.

Mild steel;  Carbon steel containing a maximum of about 0.25% carbon.  Mild
steel is satisfactory for use where severe corrodents are not encountered or
where protective coatings can be used to prevent or reduce corrosion rates to
acceptable levels.

Mitigation;  Any measure taken to reduce the severity of the adverse effects
associated with the accidental release of a hazardous chemical.

Passivation film;  A layer of oxide or other chemical compound  of a metal on
its surface that acts as a protective barrier against corrosion or further
chemical reaction.

Plant;   A location at which a process or set of processes are used to produce,
refine,  or repackage, chemicals.
                                       143

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Prevention;  Design and operating measures applied to a process  to  ensure that
primary containment of toxic chemicals is maintained.  Primary containment
means confinement of toxic chemicals within the equipment intended  for normal
operating conditions.

Process;  The sequence of physical and chemical operations for the  production,
refining, repackaging or storage of chemicals.

Process machinery;  Process equipment, such as pumps, compressors,  heaters, or
agitators, that would not be categorized as piping and vessels.

Protection;  Measures taken to capture or destroy a toxic chemical  that has
breached primary containment,  but before an uncontrolled release to the
environment has occurred.

Toxicicy;  A measure of the adverse health effects of exposure to a chemical.
                                      L44

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                                  APPENDIX B
                  TABLE B-l.  METRIC (SI) CONVERSION FACTORS
Quantity
Length :

Area:

Volume:


Mass (weight) :


Pressure:



Temperature:

Caloric Value:
Enthalpy:

Specific-Heat
Capacity:
Density:

Concentration:

Flowrate:


Velocipy:

Viscosity:
To Convert From
in
ft
in2
ft2
in3
ft3
gal
Ib
short ton (ton)
short ton (ton)
a tin
mm Hg
psia
psig
op
°C •
Btu/lb
Btu/lbmol
kcal/gmol

Btu/lb-°F
lb/ft3
Ib/gal
oz/gal
quarts/gal
gal/min
gal /day
ft3/min
ft/min
ft/sec
centipoise (CP)
To
cm
m
cm2
a.2
cm3
m3
m3
kg
Mg
metric ton (t)
kPa
kPa
kPa
kPa*
"C* *
K*
kJ/kg
kJ/kgmol
kJ/kgmol

kJ/kg-°C
kg/m3
kg/m3
kg/m3
cm3/m3
m3 /min
m3/day
m3/min
m/min
m/sec
kg/m-s
Multiply By
2.54
0.3048
6.4516
0.0929
16.39
0.0283
0.0038
0.4536
0.9072
0.9072
101.3
0.133
6.895
(psig+!4.696)x(6.-895)
(5/9)x(°F-32)
"C+273.15
2.326
2.326
4.184

4. 1868
16.02
119.8
7.490
25.000
0.0038
0.0038
0.0283
0.3048
0.3048
0.001
^Calculate as indicated
                                       145

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                                TECHNICAL REPORT DATA     .
                          (Please read Inunctions on the reverse before completing)
 . REPORT NO.
 EPA-600/8-87-0341
                           2.
                                                       3. RECIPIENT'S ACCESSIOF
.. TITLE AND SUBTITLE
Prevention Reference Manual: Chemical Specific,
 Volume 12: Control of Accidental Releases of Sulfur
 Dioxide
                                   8. REPORT DATE
                                    September 1987
                                   6. PERFORMING ORGANIZATION CODE
'. AUTHOHIS)
D. S. Davis. G. B. DeWolf,  J. D. Quass,  and
 M. Stohs
                                   8. PERFORMING ORGANIZATION REPORT NO
                                    DCN 87-203-023-94-16

                                   10. PROGRAM ELEMENT NO.  :       ~~
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
8501 Mo-Pac Boulevard
Austin,  Texas 78766
                                   11. CONTRACT/GRANT NO.
                                    68-02-3994, Task 94
12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Air and Energy Engineering Research Laboratory
 Research Triangle Park, NC  27711
                                   13. TYPE OF REPORT AND PERIOD COVERED
                                    Task Final; 10/86-6/87
                                   14. SPONSORING AGENCY CODE
                                     EPA/600/13
15.SUPPLEMENTARY NOTES AEERL projec t officer is T.  Kelly Janes, Mail Drop 62B, 919/541
 2852.
is. ABSTRACT Tlie report discusses the control of accidental releases of sulfur dioxide
 (SO2) to the atmosphere.  SO2 has an IDLH (immediately dangerous to life and health)
 concentration of 100 ppm, making it an acute toxic hazard.  Reducing  the risk asso-
 ciated with an accidental release of SO2 involves identifying some of  the potential
 causes of accidental releases that  apply to the processes that use SO2.  This manual
 identifies examples of potential causes and measures that may be taken to reduce the
 accidental release  risk. Such measures include recommendations on: plant design
 practices; prevention, protection,  and mitigation technologies; and operation and
 maintenance practices. Conceptual cost estimates of possible prevention, protection,
 and mitigation measures are provided. Headlines of accidental releases of toxic
 chemicals at Bhopal and Chernobyl have added to the current public awareness  of
 toxic release problems. As  a result  of other, perhaps  less dramatic, incidents in
 the past,  portions of the chemical  industry were aware of this problem long before
 these events.  These same portions of the industry have made advances in this area.
 Interest in reducing the probability and consequences of accidental toxic chemical
 releases that might harm  workers within a  process facility and people  in the  sur-
 rounding community prompted the  preparation of this series  of manuals.
17.
                              KEY WORDS AND DOCUMENT ANALYSIS
a.
                 DESCRIPTORS
                                           b.lOENTIFIERS/OPEN ENDED TERMS
                                                c. COSATI Field/Group
 Pollution
 Sulfur Dioxide
 Emission
 Accidents
 Toxicity
 Design
Maintenance
Cost Estimates
Pollution Control
Stationary Sources
Accidental Releases
13B
07 B
14G
13 L
06T
15E
05A.14A
 3. DISTRIBUTION STATEMENT

 Release to Public
                       19. SECURITY CLASS (This Report}
                       Unclassified
                                           20. SECURITY CLASS (Thispage)
                                           Unclassified
                         21. NO. OF PAGES
                             153
                                                22. PRICE
cPA Form 2220-1 (9-73)
                                         146

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