United States                  EPA-600/8-87-034J
            Environmental Protection
                                    September 1987
&EPA     Research and
            Development
            PREVENTION REFERENCE MANUAL:
            CHEMICAL SPECIFIC
            VOLUME 10: CONTROL OF
            ACCIDENTAL RELEASES
            OF HYDROGEN CYANIDE
            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

     The accidental releases of a toxic chemical at Bhopal. India in 1984 was
a milestone in creating an increased 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.

     Hydrogen cyanide has an IDLH (Immediately Dangerous to Life and Health)
concentration of 50 ppm, which makes it an acute toxic hazard.

     Reducing the risk associated with an accidental release of hydrogen
cyanide involves identifying some of the potential causes of accidental
releases that apply to the process facilities that use hydrogen cyanide.  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 example prevention, protection, and
mitigation measures are provided.
                                      11

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                               ACKNOWLEDGEMENTS

     This manual was prepared under  the overall guidance and  direction of I.
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.  Special thanks are given to the many  other people.
both in government and industry, who served on the Technical  Advisory Group
and as peer reviewers.

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                               TABLE OF CONTENTS

Section                                                                  Page

ABSTRACT	       ii
ACKNOWLEDGEMENTS	  .  .  .      ill
FIGURES 	       v
TABLES	       vi

1.0  INTRODUCTION	       1
     1.1  Background	       1
     1.2  Purpose of This Manual	       2
     1.3  Sources and Uses of Hydrogen Cyanide	       2
     1.4  Organization of the Manual.	       3

2.0  CHEMICAL CHARACTERISTICS 	       4
     2.1  Physical Properties	"	       4
     2.2  Chemical Properties and Reactivity	       4
     2.3  Tozicological and Health Effects  	  .  .       7

3.0  FACILITY DESCRIPTIONS AND PROCESS HAZARDS  	       10
     3.1  Hydrogen Cyanide Manufacture  	       10
     3.2  Hydrogen Cyanide Consumption  	       14
     '    3.2.1  Manufacture of Adiponitrile  	       14
          3.-2.2  Manufacture of Acetone Cyanohydrin/Methyl
                 Methacrylate 	       18
          3.2.3  Manufacture of Cyanuric Chloride	       -21
          3.2.4  Manufacture of Sodium Cyanide	       21
     3.3  Storage and Transfer	       24

 4.0  PROCESS HAZARDS	       27
     4.1  Potential Causes of Releases  	       27
          4.1.1  Process  Causes	       28
          4.1.2  Equipment Causes	       29
          4.1.3  Operational Causes	       30

 5.0  HAZARD PREVENTION AND CONTROL	       31
     5.1  General Considerations  	       31
     5.2  Process Design	       32
     5.3  Physical  Plant  Design 	       34
          5.3.1  Equipment	       34
          5.3.2  Plant Siting and Layout	       45
          5.3.3  Transfer and Transport Facilities  	       47
     5.4  Protection  Technologies 	       49
          5.4.1  Enclosures	       49
          5.4.2  Flares	       50
          5.4.3   Scrubbers	       54
     5.5  Mitigation  Technologies  	       5g
          5.5.1   Secondary  Containment  Systems   .  	       57
          5.5.2  Flotation  Devices  and  Foams   	       §2
          5.5.3  Mitigation Techniques  for Hydrogen Cyanide Vapor .       64
                                       iv

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                         TABLE OF CONTENTS (Continued)

Section                                                                Page

     5.6  Operation and Maintenance Practices 	       65
          5.6.1  Management Policy  	       66
          5.6.2  Operator Training  	       67
          5.6.3  Maintenance and Modification Practices 	       71

     5.7  Control Effectiveness 	       74
     5.8  Illustrative Cost Estimates for Controls	       75
          5.8.1  Prevention and Protection Measures 	       75
          5.8.2  Levels of Control	       79
          5.8.3  Summary of Levels of Control	       80
          5.8.4  Equipment Specifications and Detailed Costs  ...       93
          5.8.5  Methodology	       93

6.0  REFERENCES	      116

APPENDIX A - GLOSSARY	      120

APPENDIX B - METRIC (SI) CONVERSION FACTORS	      124
                                    FIGURES
                                                                         •
                                                                         Page

3*1  Hydrogen cyanide manufacturing process  	  11

3-2  Manufacturing process for adiponitrile  	  16

3-3  Manufacturing process for acetone cyanohydrin 	  19

3-4  Sodium cyanide manufacturing process  	  22

3-5  Example diagram of hydrogen cyanide tank car unloading facility . .  25

3-6  Example diagram of hydrogen cyanide storage facility  	  26

5-1  Computer model simulation showing the effect of diking on the vapor
     cloud generated from a release of refrigerated hydrogen cyanide . .  61

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                                    TABLES

                                                                        Page

2-1  Physical Properties of Hydrogen Cyanide 	 ,....      5

2-2  Exposure Limits for Hydrogen Cyanide	      9

2-3  Predicted Human Health Effects of Exposure to Various
     Concentrations of Hydrogen Cyanide	      9

3-1  Typical Uses of Hydrogen Cyanide  .	     15

5-1  Key Process Design Considerations for Hydrogen Cyanide
     Processes	     33

5-2  Chemical Resistance of Polymers and Elastomers to Chemical
     Attack by Wet Hydrogen Cyanide	     36

5-3  Important Considerations for Using Flares to Prevent Accidental
     Chemical Releases .... 	     53

5-4  Aspects of Training Programs for Routine Process Operations . .     69

5-5  Examples of Major Prevention and Protection Measures for
     Hydrogen Cyanide Releases 	     76

5-6  Estimated Typical Costs of Major Prevention and Protection
     Measures for Hydrogen Cyanide Release 	     78

5-7  Summary Cost Estimates of Potential Levels of Controls for
     Hydrogen Cyanide Storage Tank and Sodium Cyanide Reactor  ...     81

5-8  Example of Levels of Control for Hydrogen Cyanide Storage Tank.     82

5-9  Example of Levels of Control for Sodium Cyanide Manufacture . .     84

5-10 Capital and Annual Costs Associated With Baseline Hydrogen
     Cyanide Storage System   	     86

5-11 Capital and Annual Costs Associated With Level 1 Hydrogen
     Cyanide Storage System	     87

5-12 Capital and Annual Costs Associated With Level 2 Hydrogen
     Cyanide Storage System   	     88

5-13 Capital and Annual Costs Associated With Baseline Sodium
     Cyanide Reactor System   	     39
                                      vi

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                              TABLES (Continued)

                                                                        Page

5-14 Capital and Annual Costs Associated With Level 1 Sodium
     Cyanide Reactor System  	       90

5*15 Capital and Annual Costs Associated With Level 2 Sodium
     Cyanide Reactor System  	       91

5-16 Equipment Specifications Associated With Hydrogen Cyanide
     Storage System  	       94

5-17 Material and Labor Costs Associated with Baseline Hydrogen
     Cyanide Storage System  	       97

5-18 Material and Labor Costs Associated with Level 1 Hydrogen
     Cyanide Storage System  	       98

5-19 Material and Labor Costs Associated With Level 2 Hydrogen
     Cyanide Storage System  	       99

5-20 Equipment Specifications Associated With Sodium Cyanide
     Reactor System  	      100

5-21 Material and Labor Costs Associated With Baseline Sodium
     Cyanide Reactor System  	      103
                                                                          •
5-22 Material and Labor Costs Associated With Level 1 Sodium Cyanide
     Reactor System	      104

5-23 Material and Labor Costs Associated With Level 2 Sodium Cyanide
     Reactor System	      106

5-24 Format for Total Fixed Capital Cost	      108

5-25 Format for Total Annual Cost	      110

5-26 Format for Installation Costs 	      115
                                       vii

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                                   SECTION 1
                                 INTRODUCTION

1.1  BACKGROUND

     Increasing concern about the potentially disastrous consequences of acci-
dental releases of toxic chemicals resulted from the Bhopal. India accident of
December 3. 1984, which killed approximately 2,000 people and injured thou-
sands more.  A toxic cloud of methyl isocyanate was released.  Concern about
the safety of process facilities handling hazardous materials increased fur-
ther after the accident at the Chernobyl nuclear power plant in the Soviet
Union in April of 1986.

     While headlines of these incidents have created the current awareness of
toxic release problems, there have been other, perhaps less dramatic incidents
in the past.  Interest in reducing the probability and consequences of acci-
dental toxic chemical releases that might harm workers within a process facil-
ity and people in the surrounding community prompted the preparation of this
manual and a planned series of companion manuals.

     Hydrogen cyanide is a major commercial chemical and a low boiling toxic
liquid or gas at typical ambient conditions.  Historically, there have been
few significant releases of hydrogen cyanide in the United States.  However.
there have been a number of deaths, mostly of chemical plant workers, that
have resulted from accidental releases of hydrogen cyanide.

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1.2  PURPOSE OF THIS MANUAL

     The purpose of this manual is to provide technical information about
hydrogen cyanide and specifically about prevention, protection, and mitigation.
measures for accidental releases of hydrogen cyanide.  The manual addresses
technological and procedural prevention, protection, and mitigation measures
associated with the storage, handling, and process operations involving
hydrogen cyanide as it is used in the United States.  This manual does not
address uses of hydrogen cyanide not encountered in the United States.

     This manual is intended as a summary manual for persons charged with
reviewing and evaluating the potential for releases of hydrogen cyanide at
facilities that use. store, handle, or manufacture hydrogen cyanide.  It is
not intended as a specification manual, and in fact refers the reader to addi-
tional technical manuals and other information sources for more complete in-
formation on the topics discussed.  Other information sources include manu-
facturers and distributors of hydrogen cyanide, and technical literature on
design, operation, and loss prevention in facilities handling toxic chemicals.

1.3  SOURCES AND USES OF HYDROGEN CYANIDE

     Two processes for manufacturing hydrogen cyanide (HCN) account for most
of the total hydrogen cyanide produced in this country.  The most widely used
process produces hydrogen cyanide by reacting natural gas (methane). ammonia
and air.  A second widely used process (which is actually a variation of the
first process) is called the DMA process and produces hydrogen cyanide by
reacting methane with ammonia.  In addition to direct manufacture, hydrogen
cyanide is also produced as a by-product of acrylonitrile manufacture.  In
1983 it was estimated that 930 million pounds of hydrogen cyanide were manu-
factured.  At that time, the projected demand for 1988 was 1.186 million
pounds  (1).

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     The major use  of hydrogen cyanide in the U.S.,  as  of 1983.  was for the
production of adiponitrile.  Adiponitrile is  used primarily  as an intermediate
for hexamethlyenediamine. which is  a principal ingredient for nylon-6.6.
Another major use of hydrogen  cyanide is  for  the production  of acetone cyano-
hydrin which is used almost  exclusively as an intermediate for methyl  metha-
crylate.  Methyl methacrylate  is used to  manufacture polymethyl methacrylate
(Plexiglas*).  Hydrogen  cyanide is  also used  in the  manufacture of cyanuric
chloride (an intermediate in pesticide manufacturing),  miscellaneous chelating
agents, sodium cyanide,  and  a  number of other chemical  products.   In 1983.  the
uses of hydrogen cyanide in  the U.S.  were: adiponitrile.  38 percent;  methyl
methacrylate. 35 percent; cyanuric  chloride.  10 percent;  chelating agents 7
percent; sodium cyanide. 5 percent;  other uses.  5 percent (1).

     In the U.S.. hydrogen cyanide  is stored  in small cylinders (e.g.,  150
Ib), railroad tank  cars, and bulk storage tanks.

1.4  ORGANIZATION OF THE MANUAL

     The remainder  of this manual presents technical information on specific
hazards and categories of hazards and their control  as  they  relate to  hydrogen
cyanide.  As stated previously,  these are examples only and  are representative
of only some of the hazards  that may be related to accidental  releases.

     Section 2 discusses physical,  chemical and toxicological  properties of
hydrogen cyanide.   Section 3 describes the types of  facilities which manu-
facture and use hydrogen cyanide in the United States.  Section 4 discusses
process hazards associated with these facilities.  Hazard prevention and con-
trol are discussed  in Section  5.  Costs of example storage and process facili-
ties reflecting different levels of  control through  alternative systems are
also presented in Section 5.   The examples are for illustration only and do
not necessarily represent a  satisfactory  alternative control option in all
cases.  Section 6 presents a reference list.   Appendix  A  is  a glossary of key
technical terms that might not be familiar to all users of the manual.  Appen-
dix B presents selected  conversion  factors between metric (SI) and English
measurement units.

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                                   SECTION 2
                           CHEMICAL CHARACTERISTICS

     This section of the manual describes the physical, chemical, and toxico-
logical properties of hydrogen cyanide as they  relate to accidental release
hazards.

2.1  PHYSICAL PROPERTIES

     Anhydrous hydrogen cyanide is  a colorless  or pale yellow liquid with a
mild odor similar to bitter almonds.  The liquid boils at  78.3°F at 1 at-
mosphere of pressure and forms a colorless-, flammable, toxic gas.  The physi-
cal properties of anhydrous hydrogen cyanide are listed in Table 2-1.
    i
     Hydrogen cyanide is completely soluble in  water.  The gas  is  slightly
less dense than air. although a mixture of hydrogen  cyanide in  moist air may
stay near ground  level.  Liquid  hydrogen cyanide will expand slightly  with
heating. As a result, liquid-full  equipment can pose a hazard  (although as
will be  seen,  the potentially greater danger from trapping liquid  hydrogen
cyanide  in  equipment is the potential for  polymerization).   A  liquid-full
vessel is a vessel  that is  not vented and is filled  with  liquid  hydrogen  cya-
nide with little or no vapor space  present  above the liquid.   A liquid-full
line is  a  section of pipe that is  sealed off  at both ends and  is  full of
liquid hydrogen cyanide with little  or no vapor space.  In  these situations.
there is no room for thermal expansion of the liquid, and  temperature increas-
es can result in containment failure.

2.2  CHEMICAL PROPERTIES AND REACTIVITY

     Three  chemical properties of  hydrogen cyanide  that  contribute to the
potential for an accidental release of the chemical are (2.3):

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                TABLE 2-1.  PHYSICAL PROPERTIES OF HYDROGEN CYANIDE
                                                                     Reference
CAS Registry Number
Chemical Formula
Molecular Weight
Normal Boiling Point
Melting Point
Liquid Specific Gravity (H.0=l)
Vapor Specific Gravity (air=l)
Vapor Pressure
Vapor Pressure Equation:
                    log Pv = A-   -
                                          74-90-8
                                          HCN
                                          27.03
                                          78.3 °F 0 1 atm
                                          8.17 °F
                                          0.6884 0 68 °F
                                          0.947 0 88 °F
                                          0.348 atm 0 32°F
                    where:  Pv = vapor pressure, mm Hg
                             T = temperature, °C
                             A = 7.5282. a constant
                             B = 1329.5. a constant
                             C = 260.4. a constant
Liquid Viscosity

Solubility in Water
Specific Heat at Constant Pressure

Latent Heat of Vaporization
0.2014 centipoise
  0 68 °F
Complete
16.94 Btu/(lbmole-°F)
  0 62.4 °F
10.834 Btu/lbmole 0
  77 °F
                               2
                               3
                               2
                               2
                               2
                                                                         3

                                                                         3
                                                                   (Continued)

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                              TABLE 2-1 (Continued)
                                                                     Reference
Liquid Surface Tension

Heat of Combustion

Autoignition Temperature

Explosive Range. Volume Z in
  air 9 1 atm and 68 °F      min.
                             max.

Flashpoint. TCC (ASTM D-56)
17.2 dynes/cm 9 77 °F

287.000 Btu/lbmole

1.000 °F
6
41

0 °F
3

3

3
Additional properties useful in determining other properties from physical
property correlations.
Critical Temperature
    •
Critical Pressure

Critical Density
362.2 °F

53.2 atm

12.2 lb/ft'
3

3

3

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     •    Hydrogen cyanide  is flammable in  air  at concentrations
          from 6 percent to 41 percent hydrogen cyanide.

     •    The addition of alkaline-chemicals, water and/or heat may
          promote self-polymerization and decomposition of hydrogen
          cyanide.  The  self-polymerization  reaction  is exothermic
          and the heat released will promote further polymerization.
          The heat generation will also result in  the  decomposition
          of hydrogen cyanide into ammonia and formate. The pressure
          rise from polymerization/decomposition  reactions  can be-
          come explosive.  Small amounts of acid such as sulfuric or
          phosphoric will  help  to stabilize the  hydrogen cyanide
          against polymerization.

     •    The addition of  large quantities  of acid  (over 15? by
          weight  of  concentrated  sulfuric acid)  can cause  rapid
          decomposition of hydrogen cyanide.  This decomposition is
          highly  exothermic.  When sulfuric  acid  is  involved the
          decomposition by-products will be  sulfur dioxide and car-
                                                                       4
          bon dioxide.

2.3  TOXICOLOGICAL AND HEALTH EFFECTS

     Hydrogen cyanide is highly  toxic by  ingestion,  inhalation and skin ad-
sorption.  It is  a true noncumulative protoplasmic poisons  (i.e.. it can be
detoxified readily).  Hydrogen  cyanide  combines with  those  enzymes  at the
blood/tissue interfaces that regulate oxygen transfer to the cellular tissues.
Unless the cyanide is removed,  death  results through asphyxia.  The warning
signs of hydrogen cyanide  poisoning  include:  dizziness,  numbness, headache.
rapid pulse, nausea, reddened skin, and blood shot e'yes.  More prolonged expo-
sure can cause  vomiting and  labored breathing followed by unconsciousness,
cessation of breathing,  rapid weak heart beat, and death.  Severe exposure (by
inhalation) can cause immediate unconsciousness;  this rapid knockdown power

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without any irritation or detectable odor to  some  people  makes hydrogen cya-
nide more dangerous than other materials of comparable toxicity (e.g., hydro-
gen sulfide).  Table 2-2 presents a summary of  some  of the relevant exposure
limits for hydrogen cyanide.  Table 2-3 presents a summary of predicted human
health effects of exposure to various  concentrations  of hydrogen cyanide.

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               TABLE 2-2.  EXPOSURE LIMITS FOR HYDROGEN CYANIDE
Exposure    Concentration
 Limit          (ppm)                   Description                  Reference


  IDLH           50          The concentration defined as posing         5
                             immediate danger to life and health
                             C.e.. causes irreversible toxic
                             effects for a 30-minute exposure).

   PEL           10          A time-weighted 8-hour exposure to          6
                             this concentration as set by the
                             Occupational Safety and Health
                             Administration should result in no
                             adverse effects for the average
                             healthy, male worker.

  LCLo           178         This concentration is the lowest pub-       6
                             lished lethal concentration for a human
                             over a 10-minute exposure.
       TABLE 2-3.  PREDICTED HUMAN HEALTH EFFECTS OF EXPOSURE TO VARIOUS
                   CONCENTRATIONS OF HYDROGEN CYANIDE

           ppm                        Predicted Effect
           2-5           Odor threshold.

            20           Causes slight symptoms including headache
                         and dizziness after several hours.

            50           Causes disturbances within an hour.

           100           Dangerous for exposures of 30-60 minutes.

           300           Rapidly fatal unless prompt, effective
                         first aid is administered.


Source:  Adapted from Reference 2.

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                                   SECTION 3
                   FACILITY DESCRIPTIONS AND PROCESS HAZARDS

     This section provides brief descriptions of the uses of hydrogen cyanide
in the United States.   Major hazards of these processes as they relate to
accidental releases are discussed in Section 4.   Preventive measures
associated with these  hazards are discussed in Section 5.

3.1  HYDROGEN CYANIDE  MANUFACTURE

     Two processes for manufacturing hydrogen cyanide account for most of the
total hydrogen cyanide produced in this country.  The most widely used process
is one that produces hydrogen cyanide by reacting natural gas (methane),
ammonia and air.  A second widely used process (which is actually a variation
                                       •
of the first process)  is called the BMA process  which produces hydrogen
cyanide by reacting methane with ammonia.  In addition to direct manufacture,
hydrogen cyanide is also produced as a by-product of acrylonitrile
manufacture.

     A schematic diagram of a hydrogen cyanide manufacturing process is
presented in Figure 3-1.  In this process ammonia, methane (or natural gas)
and air are preheated to about 750 to 900°C, mixed and sent to a packed bed
reactor.  The reactor is typically packed with a catalytic wire gauze composed
of platinum or a platinum rhodium composite (7).  The exit gas from the
reactor contains a mixture of hydrogen cyanide,  ammonia, and water vapor (a
by-product of the reaction).  As illustrated in Figure 3-1, this crude product
mixture is sent to an ammonia absorption column where the ammonia is absorbed
in an ammonium phosphate solution (8).   Most of the hydrogen cyanide exits in
the gas phase where it is absorbed, washed and treated with sulfur dioxide as
an inhibitor to prevent polymerization.  The ammonium phosphate solution is
sent through a series of processing operations where the ammonia is recovered
and recycled back to the reactor.
                                      10

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               NH3
                                                                         WASTE OASES
                                                                           TO FLAIR
                                                              NH3 + HCN
                                                              IN NH4H2PO4
                                                               SOLUTION
••m
ABSORBER
HCN • WATER



COOLANT
   STEAM
             WASTE
             WATER
                                                                                    WASTE
                                                                                    WATER
                                                                                                      HCN WITH SO2
                                                                                                        INHIBITOR
L

r
HCN
STRIPPER ,
1
STEAM -



I
^ ^

V
                                                                                                                 HCN
                                                                                                             FRACTIONATOR
                                                                                                               STEAM
WASTE
WATER
                                                        NH4PO4 SOLUTION
                              Figure 3-1.   Hydrogen cyanide  manufacturing  process.
                                              Adapted  from References 2.  8 and 9.

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     The reaction that produces hydrogen cyanide is endothermic.  To provide
the necessary heat of reaction, forty percent or more of the ammonia and
methane fed to the process are intentionally oxidized in the reactor vessel.
The heat input from the oxidation of the methane and ammonia balanced by the
heat requirements of the hydrogen cyanide reaction will result in a normal
reaction temperature of about 2000 to 2200°F (9).

     High hazard areas in the cyanide manufacturing process include the
following:

     •    Cyanide reactor;

     •    Hydrogen cyanide absorber;

     •    Hydrogen cyanide stripper; and
     i
     •    Hydrogen cyanide fractionator.

     The cyanide reactor is critical because of the high temperatures that are
involved.  Overheating the reactor could result in uncontrollable combustion
reactions or explosions (10).  These uncontrollable combustion reactions or
explosions could result in the physical breakdown of the reactor vessel by
thermal fatigue or overpressure.  There are three possible causes of overheat-
ing.  They include:

     •    Poor heat distribution within the reactor bed, resulting
          in hot spots;

     •    Overheating raw materials before they enter the cyanide
          reactor; or

     •    Loss of composition or quantity control of raw material
          feeds.
                                      12

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     Hot spot formation within the reactor can result in catalyst breakdown or
physical deterioration of the reactor vessel (10).  If the chemical perfor-
mance of the catalyst is destroyed then no reaction will occur.  If the endo-
thermic cyanide reaction has ceased, then the reactor is likely to overheat.
In addition to the potential causes of overheating listed above, it should be
noted that iron is a decomposition catalyst for hydrogen cyanide and ammonia
under the conditions present in the hydrogen cyanide reactor.  Exposed iron
surfaces in the reactor or reactor feed system can result in uncontrolled
decomposition, which could result- in an accidental release by overheating and
overpressure.

     Only a small inventory of hydrogen cyanide will be present in the cyanide
reactor.  Therefore, catastrophic failure of the cyanide reactor is not likely
to directly result in the release of large quantities of hydrogen cyanide.
However, such failure could result in damage to other portions of the system
where larger quantities of hydrogen cyanide are present.
       •
     The hydrogen cyanide absorber, stripper and fractionator are high hazard
areas because they contain inventories of concentrated hydrogen cyanide., All
of the associated pumps, piping and fittings for these systems are also high
hazard areas.  Controlling the pH of these systems is important since the
vapor pressure of hydrogen cyanide is dependent upon pH.  A system designed
for hydrogen cyanide vapor pressure within one pH range may not be able to
handle the increased cyanide vapor pressure at a lower pH.  Reliable pH
control is particularly important at the hydrogen cyanide fractionator where
acid is intentionally added as a stabilizer to the feed stream.  The quantity
of acid that is added at this point is very small.  However, the potential
still exists for a loss of acid flow control.  Large excesses of acid can
result in a violent hydrogen cyanide decomposition reaction.
         •            • •
     The ammonia recovery portion of the hydrogen cyanide manufacturing
process does not contain large quantities of hydrogen cyanide.  However.
inventories of ammonia are present throughout this portion of the system.
                                      13

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Therefore a potential for an accidental release of ammonia exists in  this
section of the process.

3.2  HYDROGEN CYANIDE CONSUMPTION

     The major use of hydrogen cyanide in the U.S. today is for the production
of adiponitrile.  Adiponitrile is used primarily as an intermediate for
hexamethlyenediamine, which is a principal ingredient for nylon-6,6  (1).
Another major use of hydrogen cyanide is for the production of acetone cyano-
hydrin which is used almost exclusively as an intermediate for methyl metha-
ciylate.  Methyl methacrylate is used to manufacture polymethyl methacrylate
(Plexiglas*).  Hydrogen cyanide is also used in the manufacture of cyanuric
chloride  (an intermediate in pesticide manufacturing), miscellaneous  chelating
agents, sodium cyanide, and a number of other chemical products.  Table 3-1
lists a variety of products that might be manufactured using hydrogen cyanide.
        t
     This subsection summarizes some of the major technical features  of
process facilities that might use hydrogen cyanide in the U.S.

3.2.1     Manufacture  of Adiponitrile

     Adiponitrile is commercially manufactured by several different processes
all  of which begin with a different hydrocarbon raw material.  Hydrogen
cyanide is  found only  in those processes that use butadiene as a starting
material.   In some butadiene-based processes, sodium cyanide is used  as the
raw  material  (11).   In other butadiene-based processes hydrogen cyanide is
used as the raw material.  Figure 3-2 illustrates a process that uses hydrogen
cyanide to  manufacture adiponitrile.

     In this process,  hydrogen cyanide and a slight excess of butadiene are
fed  to a  reactor packed with nickel catalyst.  The reaction is carried out at
212°F and sufficient pressure to keep the reactants in solution  (12). The
product mixture contains 2-methyl-3-butenenitrile, 3-pentenenitrile,  and
                                       14

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                 TABLE 3-1.  TYPICAL USES OF HYDROGEN CYANIDE
                           Acetone cyanahydrin
                           Adiponitrile
                           Acrylonitrile
                           Aminopolycarboxylic acids
                           Barium cyanide
                           Beta-amines
                           Cyanuric chloride
                           Diaminomaleonitrile
                           Lactic acid
                           Methionine
                           Sodium cyanide
                           Tertiary alkyl amines
Source:  Adapted from Reference 14.
                                    15

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HYDROGEN
 CYANIDE
   BUTADIENE fc-
   HYDBOQ6N
    CYANIO*
                                 BUTADIENE

                              J
         2 • METHYL - 3 • BUTENENITWLE
             + 3-PENTENENrraiLE
        3-PENTENENITBILE
       * 4 - PENTENENITRILE
                                 T
                                                          LIGHT
                                                       BY - PRODUCTS
                 AOIPONITniLE
                * BY - PRODUCTS     HEAVY
                              BY - PRODUCTS
                                                                    AOIPONITRILE
Figure 3-2.   Manufacturing process  for  adiponitrile.
                               16

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unreacted butadiene.  The unreacted butadiene is separated from the product
.stream and recycled back to the reactor.

     The fractionated product stream from the first hydrocyanation reactor is
passed through a nickel catalyst bed where an isomerization reaction converts
the 2-methyl-3-butenenitrile to 3-pentenenitrile and a small amount of 2-pen-
tenitrile (13).  The 3-pentenenitrile is then passed through another nickel
catalyst bed along with hydrogen cyanide to produce adiponitrile.  Unreacted
pentenenitrile is separated from the product stream by distillation and
recycled back to the reactor.  The crude adiponitrile is purified by
distillation.

     The portions of the process that are of concern when considering a
hydrogen cyanide release are the two hydrocyanation reactors and the hydrogen
cyanide feed and storage system.  The hydrocyanation reactors are run with an
excess of olefin and thus the hydrogen cyanide is completely consumed by
reaction.  Both of these reactions are exothermic and thus there is the
potential for a loss of temperature control and an accidental release by
overpressure.                                                           •

     The hydrocyanation reactions are carried out at relatively mild condi-
tions (around 212°F and 100 to 200 psia).  A loss of temperature control would
probably not result in high enough temperatures to structurally fatigue the
reaction equipment.  The major concern with a loss of temperature control
would be the potential for vaporization of unreacted hydrogen cyanide within
the reactor.  This would result in an increase of pressure in the reactor.
The consequences of such an increase would depend upon the ability of the
pressure relief system to handle the vaporized hydrogen cyanide.  Once the
hydrogen cyanide was vaporized the hydrocyanation re.action would cease and no
additional heat would be generated.  The situation is. therefore, self cor-
recting.  There may be conditions under which loss of temperature control
would result in a polymerization-decomposition of hydrogen cyanide.
                                     17

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     Hydrogen cyanide storage and feed systems are of concern because of the
relatively large inventory of hydrogen cyanide.  Leaks from valves, fittings.
pumps, and storage vessels are of concern.

3.2.2     Manufacture of Acetone Cyanohydrin/Methyl Methacrylate

     Hydrogen cyanide can be combined with acetone to produce acetone cyano-
hydrin which in turn can be combined with methanol to form methyl methacry-
late.  As mentioned in the introduction to this subsection, almost all of the
acetone cyanohydrin produced in this country is carried on to methyl methacry-
late.  Methyl methacrylate is also produced by routes that do not use hydrogen
cyanide (15).

     Figure 3-3 illustrates the acetone cyanohydrin production portion of a
methyl methacrylate process that utilizes hydrogen cyanide (16).  In this
process, hydrogen cyanide, acetone and a catalyst are fed to a continuous
stirred tank reactor to form acetone cyanohydrin.  The reaction catalyst may
be sodium hydroxide or some other alkaline metal salt.  The reaction is run at
a temperature between 70°F and 160°F.  The reaction mixture is fed to a second
stirred tank where sulfuric acid is added to quench the reaction.  The acetone
cyanohydrin is purified by first decanting off the catalyst and then distil-
ling off unreacted raw materials.

     The purified acetone cyanohydrin is then converted to methacrylamide
sulfate by the addition of sulfuric acid.  Methanol in an aqueous solution is
then added along with the methacrylamide sulfate to a multistaged reactor
where methyl methacrylate is formed.  Several purification steps complete the
manufacturing process.

     The high hazard area of this process with regard to preventing an acci-
dental release of hydrogen cyanide is the acetone cyanohydrin production
portion of the process.
                                     18

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  ACETONE
CYANOHYDRIN
  STRIPPER
  ACETONE
CYANOHYOflIN
  REACTOR
                                                      ACETONE CYANOHYORIN
                                                     TO METHYL METHACRYLATE
                                                      PRODUCTION PROCESS
         Figure 3-3.   Manufacturing process for acetone  cyanohydrin.
                                         19

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     The first potentially hazardous location is the acetone cyanohydrin
reactor.  The inventory of hydrogen cyanide in the reactor will be relatively
small.  However,  if the flow of acetone to the reactor were to cease, the
conditions within the vessel would promote hydrogen cyanide polymeri-
zation-decomposition.  The presence of excess hydrogen cyanide as well as
inadequate mixing of the' hydrogen cyanide with the acetone could also lead to
polymerization-decomposition of the cyanide.  Polymerization-decomposition
could lead to overpressure or overheating in the reactor and result in an
accidental release of hydrogen cyanide.  Thus, control of flow, composition.
mixing and temperature are all important in this reactor.

     The reaction quenching vessel is a second potentially hazardous portion
of this process.   Failure to sufficiently quench the reaction with acid could
result in a reversal of the reaction back to hydrogen cyanide and acetone.
Acetone cyanohydrin will convert back to hydrocyanic acid and acetone if the
pH is above a certain level.  One source recommends that the pH for storage of
acetone cyanohydrin not exceed 3 or 4, and the pH under more rigorous* condi-
tions such as those found in a distillation operation should not exceed 2
(17).  The potential hazard, therefore, is that insufficient pH adjustment
will  result in acetone cyanohydrin decomposition in the stripping column.
This would result in a significant increase in the flow of material to the
flare.  This increase in flow could disrupt the performance of the flare and
result in an accidental release of hydrogen cyanide.  Additionally, high
levels of hydrogen cyanide in the stripping column could result in
polymerization- decomposition.

     The other major area of concern in this process is the hydrogen cyanide
storage and feed system.  The potential for an accidental release of hydrogen
cyanide would be high because of the relatively large inventories.
                                    20

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3.2.3     Manufacture of Cyanuric Chloride

     Cyanuric chloride is used for the production of triazine-based herbi-
cides.  It is manufactured in a two-step process.  In the first step chlorine
and hydrogen cyanide are reacted to form cyanogen.  Cyclic trimerization of
the cyanogen yields cyanuric chloride (18).  Another method for the production
of cyanuric chloride involves a single step fluidized bed process (19).

     Very little hydrogen cyanide would be present in the reaction or puri-
fication sections of a cyanuric chloride manufacturing facility.  The initial
cyanuric reaction between hydrogen cyanide and chlorine will proceed rapidly.
leaving little inventory of hydrogen cyanide in the reactor.  The primary area
of concern from the perspective of an accidental release of hydrogen cyanide
would be the initial hydrogen cyanide storage and handling facility.  Pumps,
valves, piping, and vessels that are dedicated to hydrogen cyanide service
would be of particular concern.
                                         •
3.2.4     Manufacture of Sodium Cyanide
                                                                        4
     Sodium cyanide is usually produced by reacting hydrogen cyanide with a
sodium hydroxide solution.  Such manufacturing operations are often located
directly down stream from a hydrogen cyanide manufacturing process.  An
example of a continuous sodium cyanide manufacturing process is presented in
Figure 3-4 (20).  In this process aqueous sodium hydroxide and gaseous
hydrogen cyanide are fed to a vessel that functions as a reactor, evaporator
and crystallizer. where they react to form sodium cyanide.

     The reaction vessel contains aqueous sodium cyanide with a small amount
of unreacted. excess sodium hydroxide.  The sodium hydroxide is fed to the top
of the reaction vessel while the hydrogen cyanide is fed to a recirculation
loop at the bottom of the vessel.  As the two reactants mix in a countercur-
rent fashion, they react to form sodium cyanide.  The reactor is kept under
partial vacuum.  The reduced pressure lowers the boiling point of the
                                      21

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                                                                                    VACUUM
                                                                      CONDENSER
                                             AQUEOUS
                                         SODIUM HYDROXIDE
                     WASTE
                     WATER
to
                         HYDROGEN
                          CYANIDE
                                                                               AQUEOUS SODIUM
                                                                               CYANIDE SOLUTION
                                       RECIRCULATION LOOP
                                       CONTAINING WATER,
                                       SOLUBILIZED SODIUM
                                       CYANIDE AND SOLID
                                        SODIUM CYANIDE
SEMI • DRY
 SODIUM
 CYANIDE
                                                                PRODUCT
                                                              SLIP STREAM
                                   Figure 3-4.  Sodium cyanide manufacturing process (20),

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solution.  The heat of reaction is removed by allowing water to boil off from
the solution.  The temperature of the mixture is therefore kept at its boiling
point.  As the reaction proceeds and water is removed, some of the sodium
cyanide crystallizes out of solution.  A product slip stream is withdrawn from
the reactor recirculation loop and the crystallized sodium cyanide crystals
are filtered out and dried.  The filtrate is returned to the reaction vessel.

     There are two issues of concern when operating a sodium cyanide manufac-
turing operation.  The first concern is that hydrogen cyanide will polymerize
before the reaction with sodium hydroxide occurs.  The conditions in the
reactor are favorable for polymerization if insufficient quantities of sodium
hydroxide are present or if there is incomplete mixing of the hydrogen cyanide
with the sodium hyroxide.  The second concern is that sodium cyanide will
hydrolyze to hydrogen cyanide and sodium formate.  This reaction is very
dependent upon temperature and can become significant at temperatures above
160 to 180°F (20).

     Both of the problems listed above could be of concern from the perspec-
tive of accidental release prevention.  The formation of polymerized cya'nide
could clog pumps and lines which could lead to an accidental release by
overpressuring positive displacement pumps or overheating the contents of
centrifugal pumps.  Additionally, the polymerization reaction is exothermic.
The heat generated by the reaction could result in excessive pressures and
could contribute to additional polymer formation.  Significant hydrolysis of
sodium cyanide would lead to the formation of unexpected quantities of hydro-
gen cyanide which could result in overpressurization of the pump or overload-
ing of the vacuum system; both of which could lead to an accidental release of
hydrogen cyanide.

     As with all processes that handle hydrogen cyanide, the hydrogen cyanide
storage and feed system is of concern because of the relatively large inven-
tory.  A breach of containment within the hydrogen cyanide feed and storage
system could result in an accidental release of the chemical.
                                     23

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3.3  STORAGE AND TRANSFER

     When a facility uses large quantities of hydrogen cyanide, the hydrogen
cyanide is either produced on site or is unloaded from a rail car into
stationary storage.

     Figure 3-5 shows a potential design for a hydrogen cyanide tank car
unloading facility.  The basic components of such a facility include nitrogen
blanketing with pressure relief, grounding cables with clamps, special
high-pressure piping and hoses for hookups of both hydrogen cyanide and
nitrogen systems, tank level measuring device, tank car "come-along" for
accurate positioning, wheel chocks, and derailers.

     Figure 3-6 shows a potential design for a hydrogen cyanide storage tank.
The basic components of such a system are temperature and pressure recorders
and alarms, pressure relief to a flare or other treatment system, sulfuric
acid addition system, liquid level measuring device with alarm, cooling system
and diked enclosure.
                                             •

     The primary hazard associated with the storage of hydrogen cyanide is the
potential for self polymerization.  As described in Section 2-2. self poly-
merization  can  result in rapid temperature and pressure increases in a storage
system and  can  result in a breach of containment.  Several safety precautions
concerning  the  prevention of polymerization will be discussed in Subsection
5.3.1.

     Additional hazards associated with hydrogen cyanide storage include  the
potential  for overfilling, corrosion, and contamination caused by backflow of
process materials  into the storage tank.  Additionally, loss of tank refriger-
ation  could result  in overpressure due to thermal expansion of both the liquid
and  gaseous hydrogen cyanide.  Such an overpressure would probably result in
 the  discharge of hydrogen cyanide through the pressure relief device.  The
 ultimate consequence of  such a release will depend upon the ability, of  the
hydrogen  cyanide containment and protection system  (e.g. a flare or scrubber)
 to handle  such  a load.
                                     24

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N>
Ln
                            PRESSURE
                            INDICATOR
                                                  PRESSURE
                                                   RELIEF
    NITROGEN
   REGULATORS
                       NITROGEN
                                                                                       NITROGEN
                                                                                         FILTER
                                              NITROGEN
                               PRESSURE
                                RELIEF
               THERMOWELL
  FLOW
INDICATOR  VALVE
                                                  EXCESS
                                                 FLOW VALVE
                                                                                  MCN STORAGE
                                                                                     TANK
                             rr / f II i it i111 lit
                                                                 // I///f
                 /////////////////
                       Figure  3-5.  Example diagram of hydrogen cyanide tank  car unloading facility.
                                     Adapted from Reference  3.

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                                                  TO FLARE OR
                                                  SCRUBBER
                     PRESSURE - VACUUM
                      RECORDER ALARM
                     TEMPERATURE
                    RECORDER ALARM
                    ACID
                   ADDITION
                    TANK
                                                             COOLANT
                                                                             COOLANT
                                                                                               TO HCN SAMPLING
                                                                                                  SYSTEM
             FROM
           TANK CAR1
NJ
                                        \
                                           CONTINUOUS
                                            NITROGEN
                                           PURGE BELOW
                                              VALVE
                                                        OPEN VENT WITH
                                                          CONDENSER
HEAT EXCHANGER
   ON PUMP -
AROUND COOLING
 LOOP FOR HCN
                                 TO HCN
                                'PROCESS
                          SUBMERGED
                            PUMPS
                                                                                         PI - PRESSURE INDICATOR

                                                                                         Tl - TEMPERATURE INDICATOR

                                                                                        Lfi
                                                                                        1  — PRESSURE RELIEF VALVE
                                                                                             VALVE

                             Figure  3-6.  Example  diagram of hydrogen cyanide storage  facility.
                                            Adapted  from  Reference 3.

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                                   SECTION 4
                                PROCESS HAZARDS

     Some hazards and potential causes of releases for hydrogen cyanide
releases directly related to its properties and specific processes were
identified in the preceding sections.  This section summarizes these, and
discusses more general hazards common to any facility producing or using
hydrogen cyanide.  Hydrogen cyanide releases can originate from many sources
including ruptures in process equipment, separated flanges, actuated relief
valves or rupture discs, and failed pumps or compressors.  In addition, losses
may occur through leaks at joints and connections such as flanges, valves, and
fittings where failure of gaskets or packing might occur.

     The properties of hydrogen cyanide which can promote equipment failure
are its ability to self polymerize, its flammability and the violent decompo-
sition reaction that can occur between hydrogen cyanide and acidic solufions.

     Potential hydrogen cyanide releases may be in the form of either liquid
or vapor.  Liquid spills can occur when hydrogen cyanide is released at or
below its boiling point of 78.3°F. or when a sudden release of hydrogen
cyanide at temperatures above its boiling point results in vapor flashing.
thus cooling at least part of the remaining material to below its boiling
point.  Direct releases of vapor can also occur.

4.1  POTENTIAL CAUSES OF RELEASES
                                                    *
     Failures leading to accidental releases may be broadly classified as due
to process, equipment, or operational causes.  This classification is for
convenience only.  Causes discussed below are intended to be illustrative, not
exhaustive.  A more detailed discussion of possible causes of accidental re-
leases is planned in other portions of the prevention reference manual series
of which this present manual is a part.

                                      27

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4.1.1  Process Causes

     Process causes are related to the fundamentals of process chemistry*
control and general operation.  Examples of possible process causes of a
                                                      • .             •
hydrogen cyanide release include:

     •    Overheating of cyanide manufacturing reactor resulting in
          rapid thermal decomposition;

     •    Loss of flow/composition control where acid stabilizer is
          added to a hydrogen cyanide stream resulting in excess
          acid.  High acid levels can result in rapid decomposition
          and overpressure;

     •    Loss of flow/composition control where acid stabilizer is
     •     added to a hydrogen cyanide stream resulting in low acid
          levels.  Low acid levels can result in polymerization-
          decomposition;

     •    Loss of flow/composition control where abnormally high
          levels of hydrogen cyanide is fed to a reactor along with
          a basic catalyst or reactant.  Excess hydrogen cyanide is
          likely to polymerize-decompose under such conditions;

     •    Loss of adequate mixing where hydrogen cyanide is fed to a
          reactor along with a basic catalyst or reactant.  Local-
          ized high concentrations of hydrogen cyanide can polyerize-
          decompose;

     •    Loss of pH control where acetone cyanohydrin is present
          resulting in the decomposition to acetone and hydrogen
          cyanide.  Such decomposition could result in overpressure
          and an accidental release;
                                      28

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     •    Overpressure of any storage or process vessels containing
          hydrogen cyanide due to over heating resulting in
          polymerization-decomposition;

     •    Excess hydrogen cyanide feed leading to overfilling or
          overpressuring equipment;

     •    Backflow of alkaline or strongly acidic materials into
          hydrogen cyanide storage or process vessel resulting in
          polymerization-decomposition; and

     •    Catalyst decay in hydrogen cyanide production reaction
          resulting in overheating of the reactor.

4.1.2  Equipment Causes

     Equipment causes of accidental releases result from hardware failure.
Some possible causes include:
                                                                        •
     •    Excessive stress due to improper fabrication,  construc-
          tion,  or installation;

     •    Failure of vessels at normal operating conditions due to
          weakening of equipment from excessive stress,  external
          loadings, or corrosion;

     •    Mechanical fatigue and shock in any equipment.  Mechanical
          fatigue could result from age. vibration, or stress
          cycling, caused by pressure cycling, for example.  Shock
          could  occur from collisions with moving equipment such as
          cranes or other equipment in process or storage areas;

     •    Creep  failure in equipment subjected to extreme operation-
          al  upsets, especially excess temperature.  This can occur
                                      29

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          in equipment  subjected to fire that may have caused damage
          before being  brought  under control;

     •    Failure  of  any equipment  that  is  exposed to hydrogen
          cyanide  due to stress corrosion cracking,  especially
          equipment subject  to  vibration or other forms of mechani-
          cal stress; and

     •    All forms of  corrosion; specific  type will be process and
          material specific.

4.1.3  Operational Causes

     Operational causes of accidental releases are a result of incorrect pro-
cedures or human errors (i.e..  not  following correct procedures).   These
causes include:
    •

     •    Overfilled  storage vessels;

     •    Errors in loading  and unloading procedures;

     *    Inadequate  maintenance in general, but  especially on
          pressure relief systems and other preventive and protec-
          tive systems; and

     •    Lack of  inspection and non-destructive  testing of vessels
          and piping  to detect  corrosion weakening.
                                      30

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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 hydrogen  cyanide  is
stored and used.  Considerations in these areas can be grouped as follows:

     •    Process design;

     •    Physical plant design;
                                                          •

     •    Operating and maintenance practices: and

     •    Protective systems.

     In each of these areas,  consideration must  be given to specific factors
that could lead  to  a process upset  or failure which could directly cause  a
release of hydrogen  cyanide to the environment, or  result in an  equipment
failure which  would  then  cause  the  release.  At  a  minimum,  equipment  and
procedures should be  examined to ensure  that they are  in accordance with
applicable codes, standards, and regulations.  In addition, stricter equipment
and procedural specifications should be in place if extra protection against a
release is considered appropriate.

     Most of the  large  manufacturers  of  hydrogen  cyanide provide  detailed
assistance as  to  proper storage and handling practices  for their  customers
that use the chemical.  One large company requires all  of their customers  to
                                    31

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comply with their  safety practices and  will routinely  inspect customer's
facilities for compliance.  This same company offers an annual seminar on safe
storage and handling practices of hydrogen cyanide.  This seminar  is  attended
by customers  as  well as  other producers that license  technology  from the
sponsoring company (21).  Such practices have contributed significantly toward
reducing the risk of an accidental release of hydrogen cyanide.

     Release  prevention  is  discussed in the following  subsections.   More
detailed discussions will be  found in a  manual  on control technologies, part
of this manual series.

5.2  PROCESS DESIGN

     Process  design involves the fundamental characteristics of the processes
which  use  hydrogen cyanide.   This includes an evaluation of how deviations
from,expected process design conditions might initiate a series of events that
could  result  in an accidental  release.   The primary  focus  is on  how  the
process is controlled in  terms  of the basic  process chemistry, and the vari-
ables  of  flow,  pressure,  temperature,  composition, and quantity.  Additional
process design issues may include mixing systems, fire protection, and process
control  instrumentation.   Modifications to  enhance process  integrity  may
result from review of these factors and would involve changes in quantities of
materials, process  pressure and temperature  conditions, the unit operations,
sequence of operations,  the process  control  strategies,  and  instrumentation
used.

     Table 5-1  shows  the relationship between some  specific  process  design
considerations and individual processes described in Section 3 of this manual.
This does not mean that other factors should be ignored, nor does it mean that
proper  attention to just the considerations in  the table ensures a  safe
system.  The  items listed, and  perhaps others, must be properly addressed if a
system is to  be  safe, however.
                                    32

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TABLE 5-1.  KEY PROCESS DESIGN CONSIDERATIONS FOR HYDROGEN CYANIDE PROCESSES
     Process Design Consideration
   Process or Unit Operation
     Flow control of hydrogen cya-
     nide feed
     Mixing
     Composition monitoring and
     control (including pH)
     Temperature sensing and
     heating/cooling media
     flow control

     Adequate pressure relief
     Level sensing and control
     Corrosion monitoring
All (hydrogen cyanide is almost
always used as the limiting
reactant).

Sodium cyanide reactor, con-
tinuous stirred tank methyl
methacrylate reactor, all
operations where hydrogen cya-
nide is mixed with alkaline or
acidic materials.

Hydrogen cyanide storage ves-
sels, feed to hydrogen cyanide
production process.  Should be
considered for all operations
where high concentrations and/or
large quantities of hydrogen
cyanide are used.

All operations where high con-
centrations and/or large quanti-
ties of hydrogen cyanide are used.

Storage tanks, reactors, distil-
lation and stripping columns,
heat exchangers.

Storage tanks, reboilers and
condensers, batch or continuous
stirred tank reactors

All. but especially equipment
exposed to hydrogen cyanide
and mechanical stress at the
same time.
                                   33

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5.3  PHYSICAL PLANT DESIGN

     Physical plant design includes equipment,  siting and layout, and trans-
fer/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 physi-
cal plant design  beginning with a discussion  of materials of construction.
This section is not intended to provide detailed specifications for the design
of a facility handling hydrogen cyanide.  The discussion  is intended to be
illustrative, but not comprehensive.

5.3.1  Equipment

Materials of Construction—
     The primary  concern in  selecting  the appropriate materials of construc-
tion* is the  prevention of  major hydrogen cyanide solution spills and preven-
tion of contamination of the hydrogen cyanide.

     Anhydrous hydrogen  cyanide  is generally not considered corrosive.   Under
ambient temperatures carbon  steel is an acceptable material of construction.
As an example, for storage vessels, one distributor recommends ASTM A516 grade
60 steel that has been acid  pickled  using a 0.51 H-SO.  solution  for ten to
twelve hours  (3).  However,  there are  conditions under which hydrogen cyanide
will  be corrosive  to  carbon  steel.   In  general carbon  steel  is  only
appropriate  for ambient  storage of hydrogen cyanide.

     Elevated temperatures,  the presence  of an  acid stabilizer, and  the
presence of  water will  all  effect the corrosiveness of a  hydrogen cyanide
solution.  Water  solutions of hydrogen cyanide can  result  in transcrystalline
stress- cracking of carbon steels under stress even at  room  temperature and in
dilute  solution  (2).  Under more severe conditions  of temperature  and
pressure, solutions  of  hydrogen cyanide may  also  result  in stress corrosion
cracking of  stainless steels and nickel-chromium and nickel-copper alloys
                                     34

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 (22).  Additionally,  water solutions of hydrogen cyanide containing sulfuric
acid as a stabilizer  severely corrode carbon steel above 100°F and stainless
steels above 175°F  (2).

     Austenitic stainless steels resist corrosion by sulfur dioxide-stabilized
hydrogen cyanide and  water mixtures at all concentrations and at temperatures
up to the atmospheric boiling point.  Types 316 and 317  stainless steels  have
greater corrosion  resistance than stainless steels without molybdenum (23).
Unstabilized stainless  steels  should be fully annealed to prevent intergran-
ular attack  (23).   In  higher temperature applications,  nickel-chromium and
nickel-copper alloys  must  be used.   Care must be taken  for correct material
selection in these situations, since these materials may also be subject  to
 stress corrosion cracking by hydrogen cyanide.

     A number  of  nonmetallic  materials show  good resistance to hydrogen
cyanide.  Table 5-2 shows a  list of  plastics and elastomers and their relative
resistance to. chemical  attack by aqueous  hydrogen cyanide solutions.   It  is
 important to  realize that  the  conditions under which these  material  were
tested was limited to pure hydrogen cyanide and water  mixtures at the  temper-
ature indicated  on the  chart.  The  addition  of other  chemical constituents
could effect the corrosion  resistance of  the  material.   Higher  temperatures
may also effect  the performance of  these materials.   In addition, this table
says nothing about  the  physical characteristics of these materials.  Although
a material may  show good chemical  resistance  it  may  not have the physical
properties necessary  for use in chemical equipment.  Only materials that  show
excellent chemical resistance to hydrogen  cyanide should be considered for use
in a  facility  that handles  the chemical.   Actual material selection  for  a
given application should be  done in  consultation with a  vendor having  experi-
ence with hydrogen cyanide systems.

Vessels—
     Most hydrogen cyanide  is  stored in  refrigerated atmospheric storage
vessels.   Many  of  the  design  features for hydrogen cyanide  storage  tanks
                                     35

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        TABLE 5-2.   CHEMICAL RESISTANCE OF POLYMERS AND ELASTOMERS TO
                    CHEMICAL ATTACK BY WET HYDROGEN CYANIDE
     Material
Resistance to Chemical Attack*
Chlorinated Polyether
Polyvinylidene Fluoride
Polyamide
Polyethylene
Polyimides
Polyphenylene oxide
Polyphenyl sulfide
Polypropylene
Polystyrene
Polysulf one
Polyvinyl chloride (types I & II)
Chlorinated PVC
Polysulfone
Vinylidene Chloride
Epozy Resin
Furan Resin
Phenolic Resin
Polyesters
Vinyl ester
Natural soft rubber
Butadieneacrylonitrile
Butyl rubber
Chloroprene rubber
Chlorosulfonated polyethylene
Polysulfide rubber
Polyurethane elastomer
     Excellent at 250°F
     Excellent at 275°F
     Unacceptable
     Good at 150°F
     Good at 150°F
     Unacceptable
     Good at 150°F
     Good at 150°F
     Good at 150°F
     Unacceptable
     Excellent at 150°F
     Fair at 150°F
     Unacceptable
     Good at 150°F
     Excellent at 150°F
     Excellent at 150°F
     Excellent at 150°F
     Good at 220°F
     Fair at 150°F
     Good at 150°F
     Unacceptable
     Good at 150°F
     Excellent at 150°F
     Excellent at 150°F
     Excellent at 150°F
     Excellent at 150°F
     The materials listed may or may not show similar chemical resistance at
     higher temperatures.
                                    36

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center around  the  ability of  the  chemical to experience polymerization  -
decomposition.   Because of this, a number  of safety features should be incor-
porated into the design of any hydrogen cyanide storage tank.   A list  of  these
items is presented below:

     e    Tank cooling system;

     e    Temperature monitoring with high temperature alarm;

     e    Tank sampling system;

     •    Grounding connection;

     •    Level monitoring with alarm;

     e    Pressure monitoring with high pressure and vacuum  alarm;

     e    Acid addition system;

     •    Emergency pressure relief;  and

     •    Clean nitrogen supply for maintaining an inert atmosphere
          in the tank.

     In addition to  these features a  number  of other  features  should  be
considered for a hydrogen cyanide storage tank.  Examples  include:

     e    Tank vent with vapor condenser, vent discharge  to  flare.
          scrubber or equivalent treatment device;
         •             . .
     •    Second high level alarm;
                                    37

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     •    Dedicated nitrogen supply (for use with  hydrogen cyanide
          storage only);

     •    Dike around storage tank;  and

     •    Area monitors  that activate  deluge system when hydrogen
          cyanide is detected.

     The cyanide polymerization - decomposition reaction is best detected by a
rise in tank temperature.   The  second method of detection  is  color change.
Hydrogen cyanide that has  not polymerized has a "straw  yellow" appearance.
The color will darken as the reaction  occurs until  it reaches a dark brown;  at
this point the  reaction may be proceeding at  a  dangerous rate.  For these
reasons the temperature  of a hydrogen  cyanide storage tank should be continu-
ously monitored; any increase in temperature should be  considered suspect.
Samples should be withdrawn periodically  from the  storage  tank to observe
physical appearance  and to test for  acidity and water content.  One major
distributor recommends  that  such  samples  should be withdrawn  at least two
times per week  (3).   Others have suggested that sampling be carried  out at
least every twenty four  hours (25).

     Cooling of a hydrogen cyanide tank can be accomplished by a recirculation
loop with a  heat exchanger in the  loop  or by cooling  jackets around the
outside of the vessel.  Leakage of some varieties of coolant into the hydrogen
cyanide  storage  vessel   can promote  polymerization.   For  this  reason a
recirculation loop may  be  more appropriate than a jacketed vessel, as it is
easier to inspect the integrity of a single heat exchanger than the jacket on
an  entire vessel.   Ammonia should never be used as a  refrigerant  as  it can
neutralize the acidic stabilizer in the hydrogen cyanide.

     An acid addition tank should be present on storage tanks so that acid can
be  added to  stabilize a hydrogen  cyanide  tank  where polymerization has been
detected.  The acid  should not be added directly  to the tank, as localized
                                    38

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high concentrations of acid  can  result  in violent  decomposition of  the hydro-
gen cyanide.  A system for mixing the acid, either by addition to the recircu-
lation loop  or by  addition with nitrogen injection should be developed.
Usually the acid addition is designed to  be manually operated once  the poly-
merization reaction has been detected.  However, an automated system to inject
acid based on temperature rise could be developed.  Usually, however, there is
ample time to decide whether acid should be added.

     The purity of  the nitrogen  that  is "fed to the  tank  is very  important.
Contamination brought in  with the nitrogen could  result  in a  polymerization
reaction.  Dryers and  filters should.be  present  on all nitrogen supplies.
Additionally, extreme care  should be  taken to  assure that no cross  contamina-
tion can occur between  the  hydrogen cyanide storage  tank and other systems
using the  same nitrogen supply.   The best  system  in one  where the  hydrogen
cyanide storage tank has  a  nitrogen supply that is dedicated for use by the
hydrogen cyanide storage system only.

     When the tank  is operated at atmospheric  pressure extreme care must be
taken to avoid contamination  through  the  vent  system.  One  possible solution
to this is to have  a vent system that is used only  for the hydrogen cyanide
storage tank.  Another method for reducing the potential  for vent contamina-
tion would be to continuously feed  a  small amount of nitrogen into the tank
and out  the  vent.   Whenever a vented storage vessel is  used  it  should  be
equipped with a vacuum alarm, as the  presence of a vacuum  in  the tank will
create a reverse flow in  the vent and potentially draw air or other forms  of
contamination into the tank.

     Structurally the tank  should be  constructed  according  to a  code quality
design.   One vendor recommends that atmospheric pressure storage vessels be
designed for  25  psig  minimum, with a corrosion allowance of at least 1/16
inch.   The tank should be able to withstand vacuum.   The  tank should have  no
bottom outlets.  Dip pipes  should be of  a large  enough diameter to prevent
high velocity impact with the bottom  of the tank;  such impact can  result  in
                                     39

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erosion-corrosion (3).  This  same  vendor provides additional  specifications
for tank design.

     Vessels such as reactors and heat exchangers that handle hydrogen cyanide
must be designed with many of the same considerations in mind that were listed
above for storage vessels.  Protection must be provided against  the  potential
for polymerization - decomposition.  The  specific precautions will depend on
the process  involved.   Release prevention  considerations for  all vessels
include prevention of overpressure, overfilling, overheating, and corrosion.

     Many of the processes that use hydrogen  cyanide react the chemical with
an alkaline  material  at  elevated temperatures.  In  these  situations precau-
tions to reduce the risk of polymerization will include adequate, mixing, flow
and composition  control  and  temperature  control.   Therefore reaction vessels
of this type must be  designed with adequate monitoring and backup of one or
all of these parameters.

     All vessels that handle  hydrogen  cyanide must be equipped with adequate
overpressure protection.  Where possible the discharge from these overpressure
protection devices should be sent to a protection system such as a scrubber or
flare.  Care must be  taken to prevent  material from other process units from
contaminating  the hydrogen  cyanide system  through the vent system.  Over-
pressure  protection  systems  will be discussed  in a latter portion  of  this
manual.

     Prevention  of  overfilling  can be accomplished  using  level sensing de-
vices, pressure  relief devices* and adequately trained personnel.  Redundant
level sensing  devices are often appropriate where hydrogen cyanide  is  used.
Where a pressure relief  device is  used as overflow protection, the discharge
from the valve should go to a catch tank.   Such a valve should not be used  for
overpressure protection,  as  a valve that is  sized to release vapor  in  the
event of  an  overpressure will be  grossly undersized if it  must release  liquid
in the event of an overpressure.
                                    40

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     Because of  its  flammability, the contents of  hydrogen  cyanide vessels
should be kept under an inert atmosphere unless process requirements dictate
alternate conditions.  This can be done using nitrogen.  The inert gas that is
used  for  such purposes should be filtered and dried.  Precautions must be
taken to prevent cross contamination through the nitrogen system, and in some
cases it may be preferable to have a separate nitrogen supply for the hydrogen
cyanide system.

Piping—
     The characteristics  of  hydrogen cyanide  that  are most important when
designing piping systems are:

     •    The high acute toxicity of the chemical:

     •    Its ability to cause stress corrosion cracking; and

     •    Its ability to polymerize.

     The high  toxicity  of hydrogen cyanide is of concern because even s,mall
leaks in a piping system  can  be  dangerous to operating personnel.  Hydrogen
cyanide piping should be  constructed with welded connections that are fully
radiographed.  The use  of  flanges should be minimized and threaded fittings
should never be used.

     Valves should have a leak-tight gland or be leakproof such as a diaphragm
or bellow-sealed valve.  The  valve  stem  seals  should  be externally adjustable
to stop stem leakage, and the stem should not be removable while the valve is
in service.  Excess  flow valves  should be considered  at the inlet and outlet
of hydrogen cyanide vessels.

     For maintenance and emergencies, it is often useful to be able to isolate
vessels and  other  hydrogen cyanide  process equipment.   Remotely operated
emergency isolation valves should be considered wherever a large release could
prevent access to  an isolation  valve.   In some  cases  a single  valve  is
                                  41

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insufficient to ensure complete isolation, and  the use of slip  plates or a
double block and bleed arrangement may be necessary.  Because of the potential
for releasing trapped hydrogen cyanide, proper training is essential to ensure
safe operation of these isolation techniques.

     Several precautions'must be taken in light of ability of hydrogen cyanide
to cause stress corrosion cracking.  Piping,  valves and fittings should all be
constructed of 316 stainless  steel.   Flange  nuts and bolts  should also be
constructed of a material that is resistant  to hydrogen cyanide attack as
fugitive leaks can attack these as well (3).   Gaskets should be 316 stainless
steel-graphite spiral-wound or similar type,  as  these provide  more sure leak
protection than asbestos composites.  These specifications may not be suffi-
cient  for  high temperature applications.  In such cases hydrogen cyanide
resistant alloys such as inconel may be required.

    •Because of stress corrosion, piping equipment  that  is subject to vibra-
tion, such as near a pump, are of particular  concern.  Piping  should  be ade-
quately supported, as  stress  and vibration over a  long  period of time will
significantly contribute to the potential for stress cracking.   Tees and other
similar fittings should be forged instead of welded as welds are  particularly
susceptible to stress cracking.

     Polymerization of hydrogen cyanide within  a piping  system will result in
restricted or blocked  flow and can result  in  an overpressured  line; both of
which  could contribute to an accidental release.  Dead  ends or rarely used
sections of piping should be avoided  as  polymerization can occur where stag-
nant  hydrogen  cyanide is  present.   Piping should  be  well  insulated  from
exposure to heat.  Even warming by the sun on  uninsulated piping can contri-
bute to polymerization.  Pipe runs should be  pitched  so  that they drain when
flow  is stopped.   Sections of pipe where liquid hydrogen cyanide could be
trapped by valves should be  equipped  with  overpressure protection.  Ball and
plug valves should  be designed so  that  excess  pressure  in  the body  will
relieve spontaneously  toward the high pressure  side.  This is  accomplished by
                                   42

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providing a relief hole in the valve body (or the ball or plug) which bypasses
the upstream  seat.   Modified valves  such  as these must  indicate  the flow
direction on the valve body.

Process Machinery —
     Pumps— Many of  the concerns and  considerations  for hydrogen cyanide
piping and valves also apply  to pumps.   To assure that a given pump is suit-
able for hydrogen cyanide service, the system designer should obtain  informa-
tion from the pump manufacturer certifying that the pump will perform properly
in this application.

     Wetted parts should be made of 316 stainless steel.  Mechanical seals are
preferred over packing for  better leak protection.  Double mechanical seals
with a barrier fluid  provide  even better leak protection.  In some situations
the potential for a leak may  be  so undesirable  that  rotating  shaft  seals  are
not appropriate.  Pumps  that  do not have external rotating shaft seals are,
canned-motor, vertical extended-spindle submersible,  magnetically coupled, and
diaphragm pumps (26).
                                                                        •
     Pumps should be  equipped with overpressure protection.   Positive dis-
placement pumps should have pressure relief that vents  to  a  safe  location.
Alternately, positive displacement pumps can be  equipped with pump-around
loops.  However, because  a  pump-around loop increases the complexity  of  the
system, and the number of valves and  fittings,  it  may  increase  the  risk of a
release.  By  bypassing  the pump,  the pump-round loop also eliminates the
positive displacement pump as a back flow protection device.

     Deadheading a centrifugal pump can  also result  in a  release by overheat-
ing the hydrogen cyanide  trapped within the pump.   This  can  result in the
initiation of a polymerization  - decomposition  reaction within  the pump.  The
pump seal is  very  likely to  fail under these  conditions.   One method of
reducing the risk associated  with  such  an  event is to  install a flammable gas
detector just on the  outside  of  the  mechanical  seal.  The detector could be

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connected to a deluge system  that  could be activated in the event of  even a
small release from the pump seal.

     Pumps handling cyanide solutions  should be located within  a curbed or
diked area.  Remotely operated  shut off valves to stop  the flow  to  a  pump
should be  considered  wherever a release of hydrogen cyanide could  prevent
access to the pump.

     Pressure Relief Devices—In most  cases»  emergency  pressure  relief should
be vented to a treatment device such as  a  flare  or  scrubber.   In some cases,
venting can be done to  a catch  tank although sizing the tank in  such a situa-
tion may be difficult.  A pressure relief  valve  mounted above  a  rupture disk
is suitable for hydrogen cyanide overpressure protection.  The line  below  the
relief valve should be  continually purged, with  nitrogen  so as  to prevent
plugging the  relief  line by  the vapor phase formation of hydrogen  cyanide
polymer.  Two valves with rupture  disks  in parallel are recommended so  that
one  device  can be open to the tank while  the other is  in  service.  In such
situations., it is important to interlock the valves that isolate  the pressure
relief valves from the  process  so  that only one relief valve can be isolated
from the process at one time.

     A  relief valve  is sized so  that  in  the event of a polymerization -
decomposition reaction, the temperature of the tank contents will be control-
led  by  the boil off  rate  of  hydrogen -cyanide.  Thus,  by controlling the
temperature, the  rate  of  polymerization will be controlled at  a manageable
level.  One vendor suggests that relief devices on hydrogen cyanide storage
tanks be set at 5  psig.  This will allow for sufficient heat removal  in the
event of a polymerization - decomposition reaction  (3).  It is  difficult  to
get  a device that can accurately release at this low of a pressure.

     In some  situations,  two-phase flow through the  relief  valve  may  be
possible and  this must be considered.    A  thorough  understanding  of the
kinetics of the hydrogen  cyanide polymerization -  decomposition  reaction  is
                                     44

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important for sizing the relief device.  Vendors of hydrogen cyanide have this
kinetic data and will provide  assistance for sizing overpressure protection.
One vendor has combined kinetic  data with the data developed by the Design
Institute for Emergency Relief Systems.  (DIERS) on two-phase releases to size
relief valves for their customers (27).

     Where possible, pressure  relief vent and treatment systems on hydrogen
cyanide storage and handling equipment  should  not  be  connected  to any other
pieces of  process equipment.  This will help prevent cross-contamination
between systems.  A flame arrester  may be used in  the vent  line.   However.
such a device  should  be cleaned frequently  to prevent plugging by hydrogen
cyanide polymer.

     Instrumentation—Instrumentation should be constructed of materials that
are compatible with hydrogen cyanide service.  In many cases wetted materials
can be made  of 316 SS or of an  elastomer of  plastic with hydrogen cyanide
resistance.  With  the  exception of high temperature  operations,  hydrogen
cyanide is not  a severe environment for most  instrumentation.  However, one
                                                                         •
concern when using instrumentation with hydrogen cyanide is the  potential for
vapor phase polymerization.  Such polymer could plug  measuring  wells or foul
sensors and  isolate the instrument from the  actual  process environment.
Example solutions  for this  are the use of redundant instruments, the use of
instruments that may be cleaned while in service or the use of nitrogen purge
streams to keep the sensing element free from  hydrogen cyanide polymer forma-
tion (a nitrogen purge  should  be used with  caution,  as it could adversely
affect the accuracy of some instruments).

5.3.2  Plant Siting and Layout
                                                      •
     The siting and layout  of  a particular  facility  using hydrogen cyanide
requires careful consideration of  numerous  factors.   These  include:   other
processes in the area, the proximity of population centers, prevailing winds.
local terrain,  and potential natural external  effects such as flooding.  The
                                     45

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rest of this subsection describes general considerations which might apply to
siting and layout of facilities that handle hydrogen cyanide.

     Siting of facilities or individual equipment items  should  be done in a
manner that reduces personnel exposure,  both plant and public,  in the event  of
a release.  Since there are  also other siting considerations,  there  may  be
trade-offs between this requirement  and others in a process, some directly
related to safety.  Siting should provide ready ingress or egress in the event
of an  emergency  and  yet also take advantage of barriers, either man-made or
natural which could reduce the consequences of releases.

     Layout refers  to the placement  and arrangement of  equipment in the
process facility.  General layout considerations include:

     •    Inventories of hydrogen cyanide should be kept away  from
    '     sources of fire  or explosion hazard;

     •    Vehicular traffic should not go too near hydrogen cyanide
          process or storage areas if this can be avoided;

     •    Where  such  traffic  is necessary, precautions  should  be
          taken to reduce  the chances for vehicular collisions with
          equipment, especially pipe racks carrying hydrogen cyanide
          across or next to roadways;

     •    Hydrogen cyanide piping preferably  should not  be located
          adjacent to other piping which is under high pressure or
          temperature;

     •    Storage facilities should  be segregated from  the main
          process unless the hazards of pipe  transport are felt to
          outweigh the hazard of the storage tank for site-specific
          cases; and
                                    46

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     *    Storage should also be  situated away from control rooms.
          offices, utilities, storage, and laboratory areas.

     Various techniques are  available for formally assessing a plant layout
and should be considered when planning high hazard facilities handling hydro-
gen cyanide (28).  These techniques provide for a systematic evaluation of key
siting and layout factors.

     Because heat  increases the  tendency of hydrogen  cyanide  to undergo
polymerization - decomposition, measures  should  be taken to situate piping.
storage vessels,  and  other hydrogen cyanide equipment  in  such  a  way as  to
minimize their exposure to heat.  Hot process piping, equipment, steam lines,
and other sources of direct or radiant heat should be avoided.

     In the event of an emergency, there should be multiple means  of access to
the facility for emergency vehicles and crews.   Storage vessel  shut off valves
should be readily  accessible.   Containment for liquid  storage  tanks can  be
provided by diking.  Flammable gas detectors and adequate fire  protection  must
be provided for all portions of the  process  as hydrogen cyanide is flammable
when mixed with air.

5.3.3  Transfer and Transport Facilities

     Transfer and  transport facilities where  rail tankers are loaded  and
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.

     Rail car unloading and loading facilities should  be  equipped with the
following safety and release prevention features:

     •    Grounding connections for the car and rails;

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     •   A car "come-along"  for accurate positioning,  wheel chocks,
         and  derailers  for runaway  cars;

     •   Warning signs  and lights to identify the area and restrict
         access during  the loading  or unloading;

     •   High pressure  piping and  hoses,  connectors  on hose ends
         that are unique for hydrogen cyanide service and that
         prevent accidental  attachment  of the vapor hose  to  the
         liquid line on the  car. or  the liquid  receiving line to
         the  vapor line of the car;

     •   Rail car temperature monitor and alarm;

     •   Deluge system  for  the rail car  area,  or at  a  minimum
     ,    sufficient fire hoses or monitors to act as  a deluge in
         the  even of a  spill;  and

     •    Some type of drainage control system that prevents runoff
         from a spill from traveling into unwanted areas.

     Usually a tank car  will  be unloaded by applying  nitrogen pressure to the
vapor space, thereby pushing  the liquid out through the rail car dip  tube.  As
mentioned previously, nitrogen used  for -hydrogen  cyanide service must be free
of any  contamination.   Additionally, back  flow  protection should also  be
provided in the nitrogen line.

     In some  situations,  unloading  a tank  car will  require several hours.
When this is the case, the tank car should be treated as  a  storage tank  with
periodic samples withdrawn from the car  to  test for the formation of polymer.
Whenever tank cars are loaded or unloaded, written operating procedures should
be developed and enforced.
                                     48

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5.4  PROTECTION TECHNOLOGIES

     This  subsection describes three  types  of protection technologies  for
containment, treatment and neutralization.  These are:

     •    Enclosures;

     •    Flares; and

     •    Scrubbers.

A presentation of more detailed information on these systems  is  planned in
other portions of the prevention reference manual series.

5.4.1  Enclosures

     Enclosures refer  to  containment structures which capture any  hydrogen-
cyanide spilled or vented from storage or process equipment, thereby prevent-
                                                             t
ing immediate discharge  of the chemical to the environment.  The enclosures
contain the spilled  liquid until it  can  be  transferred  to other containment.
discharged at a controlled rate which would  not be  injurious to people or the
environment* or transferred at a controlled rate to scrubbers for neutraliza-
tion or a flare or incinerator for destruction.

     The use of  specially designed  enclosures  for  either hydrogen cyanide
storage or  process  equipment does not appear  to  be widely practiced.   The
location of toxic operations in the  open air has  been mentioned favorably in
the literature, along with the  opposing  idea that sometimes  enclosure may be
appropriate (29).  The  desirability  of an enclosure  depends  partly on  the
frequency with which personnel must  be involved with  the equipment.  A common
        •            . .
design rationale tor not having an enclosure where toxic materials are used is
to prevent  the accumulation  of toxic concentrations  of  a chemical  within a
work area.   However, if the issue is protecting the community  from  accidental
releases,  then  total enclosure may  be appropriate.  Enclosures  should  be
equipped with continuous monitoring equipment and alarms.  Alarms should sound

                                   49

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whenever lethal  or flammable concentrations  are  detected.  Enclosures  for
hydrogen cyanide should he equipped with adequate fire protection.

     Care must he taken when an enclosure  is  huilt around" pressurized equip-
ment.  It would  not  he practical to design an enclosure  to  withstand the
pressures associated with the sudden  failure of  a pressurized vessel.  An
enclosure would probably fail as a result of the pressure created from such a
release and could create an additional hazard.  In these situations, it may be
determined that an enclosure  is  not appropriate.   If an  enclosure  is built
around pressurized equipment  then it  should  be equipped  with some type of
explosion protection, such as rupture plates that are designed to fail before
the entire structure fails.

     The type of containment structures  that  could be suitable for hydrogen
cyanide are concrete block or concrete sheet buildings,  or bunkers or cor-
rugated metal buildings.   An  enclosure would have a  ventilation  system de-
signed to draw in air when the'building is vented to a scrubber or flare.'  The
bottom section of a building used for stationary storage containers should  be
liquid tight  to retain any liquid  hydrogen cyanide that  might be  spilled.
Buildings around rail  car  unloading stations  do not  lend  themselves well to
effective liquid containment.  However,  containment  could be accomplished if
the floor of  the building  were excavated several  feet below the track level
while the tracks are supported at grade in the center.

     While the use of enclosures for secondary containment of hydrogen cyanide
spills or releases is  not  known  to be widely  used, it can be considered as a
possible protection technology for areas near especially sensitive receptors.

5.4.2  Flares

     Flares are used in the chemical process  industries to dispose of inter-
mittent or  emergency emissions  of hydrogen cyanide waste gases.   The flare
                                     50

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burns the waste gases, forming carbon dioxide and nitrogen oxides.  Flares are
capable of handling larger flow variations than are process combustion devices
such as boilers.

     The two  common styles are  elevated and enclosed ground  flares.   The
height of an  elevated  flare  (sometimes  several  hundred feet) is  determined by
safety considerations  for  the  surrounding  areas because  of the high tempera-
tures and heat  flux at maximum gas rates.   Enclosed ground flares consist of
stages of  multiple burner assemblies  surrounded by  refractory  walls and
acoustical insulation.  They are generally used for small  to medium  flow  rate
applications.  The elevated flare is- used for larger gas  flows.   Often,  an
enclosed ground flare  will be  used in  conjunction with  an elevated flare for
economical operation.

     A flare  system may  collect gases  from just one source or more  often it
may be used to  treat  gases from multiple sources within a process.  Because
most flare systems collect gases  from a variety of sources within a plant, gas
compositions  and flow  rates vary.  Many units include venting steps to  the
flare system  during processing.   Overpressurization  can also cause relief
valves to vent gases to the flare  system.  Depending on the size of  the flare
system, accidental  releases may constitute a large or small fraction of  the
instantaneous gas  flow.   The  flow  rate  under an emergency release  from  a
vessel could  constitute a  significant or negligible portion of the total  flow
rate to a  flare.   This would  depend  on the  time  interval over which the
release occurred and  the  flow  rate of other materials going to the  flare at
the same time.  Flare designs range up to and above 2 million pounds per hour.

     Several design characteristics of flare systems are important when con-
sidering their use as  protection against accidental, chemical releases.   The
design of flares is dictated by the desire to:

     •    Operate the  flare safely over  a  wide  range  of gas flow-
          rates; and
                                     51

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     •    Have acceptable  emissions of  radiant heat,  toxic and
          flammable materials* and noise.

A fundamental flare  design variable is exit velocity.  At maximum  flow,  the
flame should not leave the burner  tip  or be blown out.  This is achieved by
limiting the exit velocity.  A criterion has been recommended by the EPA to
ensure 98 percent destruction efficiency of flared chemicals using a steam
assisted flare (30).  The  addition of an accidental release discharge to an
existing flare must not cause this maximum flow to be exceeded.

     Flares can be useful  protection against accidental releases of hydrogen
cyanide.  However, because  of  potentially dangerous secondary hazards,  their
use requires a thorough analysis for each specific application.

     There are two possible ways a flare system can be used to protect against
accidental  releases.  The  first is to use  an  existing  flare system.  The
second is to use a dedicated  "emergency"  system.   In  essence, a flare system
is a pipe transporting flammable gases to a flame at the exit.   As long as the
flame remains at the end of the pipe,  the system operates safely.   The flame
can enter the pipe  if air  or  oxygen is present above a certain concentration
in the fuel.  In a dedicated flare system, the entire collection network would
have to  be  continually  purged to prevent the  risk of an explosion  when  an
accidental release occurred.

     Since  the  flare collection system  operates  under a positive  pressure
 (above atmospheric). release rates from an emergency relief valve will be less
than  the same discharge  to  the  atmosphere.   In  some instances,  it is
conceivable that the slight delay  in  reducing the pressure  in  a vessel nay
cause tank  damage.   This may  be especially  important when rupture  disks blow.
A sudden overpressurization of the flare collection system due to  a massive
accidental release could damage the pipes or potentially affect the  venting of
other process  units.  Table  5-3  summarizes the  factors  that  need  to be
considered to prevent accidental chemical releases when using a flare system.
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  TABLE 5-3.  IMPORTANT CONSIDERATIONS FOR USING FLARES TO PREVENT
              ACCIDENTAL CHEMICAL RELEASES
«    Maximum flow rate - will it cause a flame blowout?  Will it cause
     mechanical damage due to vibration?

•    Possibility of air, oxygen, or other oxidant entering system?

•    Is gas combustible - will it smother the flare?

•    Will any reactions occur in collection system?

•    Can liquids enter the collection system?

•    Will liquids flash and freeze, or overload knockout drum?

•    Is back pressure of collection system dangerous to releasing vessel?

•    Is releasing vessel gas pressure or temperature dangerous to
     collection system?

•    Will acids or salts enter collection system?

•    Will release go to an enclosed ground or elevated flare?

•    If toxic is not destroyed, what are the impacts on surrounding
     community?
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     The rationale for using  flares to protect against  accidental chemical
releases is that flaring reduces the effects of an atmospheric emission from a
process vessel.  As long as the integrity of  the  flare system is not compro-
mised, some lessening of the  overall  environmental impact'would he expected.
It is difficult to estimate the destruction and removal efficiency  (ORE)  of
flares because of the many variables  associated with  their  operation.   Numer-
ous studies have been conducted to  determine the operational performance  of
flares.  EPA has published a set of flare requirements to ensure 98 percent or
greater destruction of the gases  (30).   In  an emergency condition,  however,
these conditions might not be met.  In  a screening study conducted by EPA. a
100 ppm hydrogen cyanide stream was only 85  percent controlled (31).

     Because of the variable flow capacity,  high flame temperature, capability
for handling a high gas velocity,  and usual  remote location, using a flare to
prevent accidental chemical releases  of  hydrogen  cyanide can be an effective
technique.  Small or isolated vessels in a process which  does not  require
normal venting of a flammable gas,  and  that employ relief  valves and rupture
disks which may have never been used, are  examples of sources that can be
connected to a flare system to prevent accidental releases.

5.4.3  Scrubbers

     Scrubbers are a traditional method for  absorbing toxic gases from process
streams.  These devices can be used to control hydrogen  cyanide releases from
vents and  pressure  relief  discharges  from storage equipment, process equip-
ment, or secondary containment enclosures.

     Hydrogen cyanide discharges could be contacted with an aqueous  scrubbing
medium in any of several types of scrubbing  devices.  An alkaline  solution is
recommended to  achieve effective absorption  because  absorption rates  with
water alone would require high liquid-to-gas ratios.  However, water scrubbing
could be used in a make-shift scrubber in an emergency if an alkaline solution
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was not available.  Typical alkaline solutions for an emergency scrubber would
be calcium hydroxide derived from slaked lime or sodium hydroxide.

     Examples of  scrubber types  that  might be  appropriate include  spray
towers, packed  bed scrubbers,  and Venturis.  Other types of special  designs
might be suitable.  Whichever  type  of  scrubber is selected, a key considera-
tion for emergency systems is the design flow rate to be used.  A conservative
design would use the maximum rate that would be expected from an emergency.

     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  continu-
ous 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 hydrogen  cyanide would be  released prior to  actuation  of  the scrubber
(i.e.. starting up a blower and turning on the flow of liquid).

     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  dis-
charge 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 particu-
larly important for packed bed scrubbers since  there  is  a  maximum pressure
with which the gas  can  enter the packed section without damaging the  scrubber
                                       55

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internals.  Design  of  emergency scrubbers  can follow  standard techniques
discussed in the  literature,  carefully taking  into account the  additional
considerations just discussed.

     Another approach is the drowning tank,  where the hydrogen cyanide vent is
routed to the bottom of a large  tank of uncirculating caustic.  The drowning
tank does not have the high contact  efficiency  of the other scrubber  types.
However, it can provide  substantial  capacity on demand  as  long as the back
pressure of the  hydrostatic head does  not  create  a  secondary hazard, by
impeding an overpressure relief discharge, for example.

5.5  MITIGATION TECHNOLOGIES

     If. in spite of all precautions, a large release of hydrogen cyanide 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 stopped,  if this
is possible.  The next  primary concern is to reduce the consequences  of  the
released chemical on 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 tech-
nology chosen for a particular chemical depends on the  specific properties of
the chemical including its flammability.  toxicity.  reactivity,  and those  pro-
perties which determine its dispersion characteristics in the atmosphere.

     If a release occurs from a refrigerated, liquid hydrogen  cyanide  storage
tank, the spilled liquid would heat up to ambient temperature.  If  the ambient
temperature is above the boiling point of hydrogen cyanide  (78.3°F). then heat
transfer from  the air  and ground would result  in rapid vaporization of  the-
released liquid.  If the ambient temperature is below the boiling  point of the
                                      56

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hydrogen cyanide then vaporization would be slower but a vapor cloud is still
likely to form.  It is  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 liquid include secondary containment systems such as
impounding basins and dikes.

     A post-release mitigation effort requires that the source of the release
be accessible  to  trained plant personnel.   Therefore,  the availability of
adequate personnel protection is  essential.  Personnel protection will  typi-
cally include such  items  as portable breathing air and chemically resistant
protective clothing.

5.5.1  Secondary Containment Systems

     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 hydrogen  cyanide  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 hydrogen cyanide  storage  facilities
commonly 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; and
                                     57

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     •    A diked area,  with a capacity as large as the largest tank
          served.

These measures are designed  to prevent the accidental  discharge of liquid
hydrogen cyanide from spreading to uncontrolled areas.

     The most common  type of containment system is a low wall dike surrounding
one or more storage tanks.  Generally, for hydrogen cyanide, no more than one
tank is enclosed within a diked area to reduce risk.  Dike  heights usually
range from three to twelve feet depending on the area available to achieve the
required 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, or concrete.  Earthen dikes should  not be
used to contain  hydrogen  cyanide  spills, as the high acute  toxicity of the
chemical requires a high degree of certainty that  the containment surface is
impermeable to  the spill.  Piping should be routed over  dike walls,  and
penetrations through the walls should be  avoided if possible.  Vapor  fences
may be situated on top  of the dikes  to provide additional  vapor containment.
If there is more than one tank in  the diked area, the tanks should be situated
on beams above the mflTi'nrnm liquid  level attainable in the impoundment.

     A low-wall dike can effectively contain the liquid  portion of an  acci-
dental release  and keep the  liquid  from entering uncontrolled  areas.   By
preventing 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 evapora-
tion.  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
protection from wind and will be even more effective at  reducing the rate of
evaporation.

     A low-wall dike will not reduce the impact of a gaseous hydrogen  cyanide
release.  If materials  that  would react violently with hydrogen  cyanide  are
stored within the  same  diked  area  then the dike will increase the  potential
                                        58

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for mixing the materials in  the  event  of a simultaneous leak.  A  dike also
limits access to the tank during a spill.

     A covered, remote  impounding basin is well  suited  to storage systems
where a  relatively large site  is available.   The  flow  from the hydrogen
cyanide spill is directed to the basin by dikes and channels under  the storage
tanks which are designed to minimize contact  of the liquid with other tanks
and surrounding facilities.  Because of  the high vapor pressure of hydrogen
cyanide and the high acute toxicity, 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
very near  the  tank area to  minimize the amount  of hydrogen cyanide that
evaporates as it travels to  the  basin.   The impounding basin could be filled
with water to instantly  dilute the liquid  hydrogen  cyanide as it flows  into
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  tne
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.

     High-wall impoundments may  be a good secondary containment choice  for
selected systems.   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 generally be  lower for a high wall impoundment than for low wall dikes or
remote impoundments  because of  the  reduced  surface .area exposed to  the
atmosphere.  These rates can be further reduced with the use  of insulation on
the wall  and  floor  in  the annular  space.  High impounding  walls may be
constructed of low-temperature  steel,  reinforced concrete,  or prestressed
concrete.   A weather shield may be provided between the tank and wall with the
annular space  remaining  open  to  the  atmosphere.   The  available  area
                                       59

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surrounding the storage tank will dictate the minimum height of the wall.  For
high wall impoundments, the walls may be  designed with a volumetric capacity
greater than that of the tank to  provide  vapor 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  outlet (suction) line will
have to pass through the wall.  In such a situation,  a low dike encompassing
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  (32).   This  figure shows hydrogen cyanide vapor
clouds at the  time when the farthest distance away from the  source is  exposed
to concentrations  above the IDLE.   With  diking,  the  model  predicts  that
downwind distances up  to 720 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  downwind distance.  Without diking,  the  model
predicts that  downwind  distances  up  to  2,600  feet from  the  source could be
exposed to concentrations above  the  IDLE'.   Thirteen  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 may 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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  •>  BO.O
  •>  BOO.
  •> a.ooo«+oa PPM
                   O.S
                  miles
 1
mile
 l.S
miles
   2
miles
      Release from a tank surrounded by a 25  ft. diameter dike.
      Elapsed time:  3 minutes:
      Release from a tank with no dike.
      Elapsed time: 13 minutes
Common Release Conditions;
  Storage Temperature • 40 F
  Storage Pressure - 14.7 psia
  Ambient Temperature - 85 °F
       Wind  Speed  •  10 mph
       Atmospheric Stability Class » C
       Quantity  Releases = 5,000 gallons
         through a 2-inch hole
Figure 5^1.•  Computer'model simulation showing  the  effect of diking on the
             vapor cloud generated from a release of  refrigerated hydrogen
             cyanide.
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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  storm water  sewers would presumably allow  any  spilled hydrogen
cyanide 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 (33).  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  clay or concrete to  prevent  the hydrogen
cyanide from seeping into the ground.
         •
5.5.2  Flotation Devices and Foams

     Other possible means of reducing the surface area of  spilled hydrogen
cyanide include  placing  impermeable  flotation  devices  on  the  surface  or
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.  The additional material and disper-
sal equipment costs are a major deterrent to their use.

     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 the effects will vary as
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
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materials, foams  have a net  positive effect, but  with others, foams may
tzaggerate the hazard.

     One approach to  a hydrogen  cyanide  spill is  dilution with  water.  Delug-
ing a spill with water will dilute  the spill  and  reduce the vapor generation
rate.  A  water-based foam  provides an  alternative means  of diluting the
hydrogen cyanide.  When  a  foam cover is first applied,  an increase in the
boil-off rate is generally observed which would cause a short-term increase in
the downwind hydrogen cyanide  concentration.   The initial  foam cover may be
destroyed by violent boiling, in which case a second application ia necessary.
Once a continuous 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 vaporization 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  heat transfer  from
the foam and by the  heat of solution  of  hydrogen  cyanide in water; the warmed
vapor cloud will 'have greater  buoyancy and  will disperse in an upward direc-
tion more rapidly.
                                                                         •
     The extent of the downwind reduction in concentration will depend on the
type of foam used.   Regardless  of  the  type  of foam used,  the slower the
drainage rate of  the foam,   the better  its performance will be.  A  slow-
draining foam will spread more evenly, show more resistance to temperature and
pH effects, and collapse more  slowly.  The  initial cost for a  slow-draining
foam may be higher than  for other foams, but a cost effective system will be
realized in superior performance.

     Even  if  the  vaporization rate of  hydrogen  cyanide is substantially
reduced within a short time after a spill, a vapor cloud will still be formed
which poses  a  serious threat  downwind.   Dispersion and/or removal of  the
hydrogen cyanide vapor in  the atmosphere is  the  subject of  the following
section.
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5.5.3  Mitigation Techniques for Hydrogen Cyanide Vapor

     The extent to which the escaped hydrogen cyanide 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 hydrogen cyanide cloud will be
dependent on a number of  factors.   These include the physical  state  of  the
hydrogen cyanide  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.   Large accidental releases of hydrogen cyanide
may result in the formation of hydrogen cyanide-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 hydrogen cyanide
with water results in the formation of highly toxic hydrocyanic  acid which
presents a health hazard to plant personnel.

     The spray medium is  typically applied to the  vapor  cloud by means  of
hand-held hoses  and/or  stationary water-spray barriers.   Important factors
relating to the effectiveness of spray systems are the distance of the nozzles
from  the point of release,  the spray pattern, nozzle flow  rate, pressure, and
nozzle rotation.

      Several techniques have also been developed to effectively disperse toxic
vapor  resulting from major leaks in piping and equipment.  One  such technique
has been  developed by Beresf ord (34).  Although such  a  system has not been
used  for the mitigation of hydrogen cyanide vapor,  they have been  effectively
used  for  other  toxic  chemicals  of similar nature (34).  Such  techniques  are
not applicable to catastrophic failures of equipment, however.
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     The method consists of coarse water sprays discharging upwards from flat
fan sprays and wide-angled  spray monitors  arranged so that a vent or chimney
effect is created to completely surround the toxic vapor.  Results have shown
that the high velocity water droplets induce large volumes of air at ground
level to move upward as the water discharges upwards  (34).  The air is caused
to move upwards  through the chimney formed by the sprays.  As the air moves
over the ground,  the heavier than air toxic gas is diluted and pushed up  and
out of the top of  the  chimney  where it  disperses  safely.  Design details  are
presented in Beresford (34).   Both types of spray methods are incorporated
into the design  since  the  flat-fan  sprays  effectively stop the lateral spread
of vapor and the monitors provide the -required air movement for dilution  and
dispersal.

     Another means of dispersing a vapor cloud is  with the use of large fans
or blowers which would direct the vapor away from populated or other sensitive
areas (35).  However, this method would only be feasible in very  calm weather
and in sheltered areas; it would not be effective in any wind and difficult to
control if the release occupies a large open area.  A large, mechanical blower
would also be required which lowers the reliability of this mitigation tech-
nique compared to water fogs and sprays.

     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.

5.6  OPERATION AND MAINTENANCE PRACTICES

     Quality hardware,  contained mechanical equipment,  and protective devices
all increase plant safety; however,  they  must  be  supported  by  the safety
policies of management and by constraints on their  operation  and  maintenance.
This section describes how management  policy  and training,  operation, and
maintenance procedures relate to the prevention of accidental hydrogen cyanide
releases.   Within the  chemical  industry,  these procedures and practices vary
                                          65

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widely because  of  differences in the size  and nature of the  processes and
because any determination  of their adequacy is  inherently  subjective.  For
this reason, the following  subsections  focus primarily on fundamental princi-
ples and do not attempt to define specific policies and procedures*

5.6.1  Management Policy

     Management is a key factor  in  the  control of industrial hazards and the
prevention of accidental releases.  Management establishes  the broad policies
and procedures which influence  the  implementation and execution  of  specific
hazard control measures.  It  is  important  that these management policies and
procedures be designed to match the level of risk in the facilities where they
will be  used.   Most organizations  have a  formal safety policy.  Many make
policy statements  to  the effect that safety must rank  equally with other
company  functions  such as production and  sales.  The effectiveness  of any
safety program, however, is  determined  by a company's  commitment to it, as
demonstrated throughout  the management  structure.   Specific goals must be
derived  from the  safety  policy and supported  by all levels of management.
Safety  and loss  prevention should be  an explicit  management objective.
Ideally, management should establish the specific safety performance measures,
provide incentives for attaining safety goals,  and commit company resources to
safety and hazard control.   The advantages of an explicit  policy are that  it
sets the standard by which existing programs can be judged, and it  provides
evidence that safety is viewed as a significant factor in company operations.

     In  the  context of  accident prevention, management is responsible for
 (29.36):

     •    Ensuring worker competency;

     •    Developing and enforcing  standard operating procedures;

     •    Adequate documentation of policy and procedures;
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     •    Communicating and promoting feedback regarding safety
          issues;

     •    Identification, assessment, and control of hazards; and

     •    Regular plant audits and provisions for independent
          checks.

     Additional discussion on the responsibilities of management will be found
in a manual on control technologies, part of this manual series.

5.6.2  Operator Training

     The performance of  operating personnel  is  a key  factor  in  the  prevention
of accidental chemical  releases.   Many case studies  documenting industrial
incidents note the  contribution of human error  to accidental releases  (29).
Release•incidents may ie caused by using improper routine  operating proce-
dures, by insufficient knowledge of  process  variables and equipment, by lack
of knowledge about  emergency or upset procedures, by failure to recognize
critical situations,  and in some cases  by  direct physical  mistake (e.g..
turning the wrong  valve).  A  comprehensive  operator training  program  can
decrease the potential for accidents resulting from such causes.

     Operator training can  include  a wide range of  activities  and  a broad
spectrum of information.  Training,  however,  is distinguished from education
in that it  is  specific  to  particular tasks.  While  general education  is
important and beneficial, it is not  a substitute for specific training.  The
content of a specific training  program depends  on the type of industry,  the
nature of the processes  used,  the operational skills  required,  the  character-
istics of the plant management system, and tradition.

     Some general  characteristics  of  quality  industrial training  programs
include:
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     •    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  upsets,  emergencies,  and acci-
         dental releases;  and

     •    Frequent supplemental training and  the use of up-to-date
     «    training materials.
           •
     In many instances training is carried out jointly  by plant managers and a
training staff  selected by management.   In  others, management is solely
responsible for maintaining training programs.  In either case, responsibili-
ties should be explicitly designated to ensure  that  the quality and quantity
of training provided is  adequate.   Training requirements and practices can be
expected to  differ between small  and large   companies,  partly because of
resource needs and availability, and partly because of  differences in employee
turnover.

     A list  of  the  aspects typically  involved  in the  training  of process
operators for routine process  operations is presented in Table 5-4.

     Emergency training  includes topics such  as:

     •     Recognition of alarm signals;
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   TABLE 5-4.  ASPECTS OF TRAINING  PROGRAMS FOR ROUTINE PROCESS OPERATIONS
          Process  goals,  economics,  constraints,  and priorities
          Process  flow diagrams
          Unit  operations
          Process  reactions,  thermal effects
          Control  systems
          Process  materials quality, yields
          Process  effluents and wastes
          Plant equipment and instrumentation
          Equipment  identification
          Equipment  manipulation
          Operating  procedures
          Equipment  maintenance and  cleaning
          Use of tools
          Permit systems
          Equipment  failure,  services failure
          Fault administration
               Alarm monitoring
               Fault diagnosis
               Malfunction detection
          Communications, recordkeeping.  reporting
Source:   Reference 29.
                                     69

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    •    Performance of specific functions  (e.g., shutdown  switch-
         es);

    •    Use of specific equipment;

    •    Actions to be taken on instruction to evacuate;

    •    Fire fighting; and

    •    Rehearsal of emergency situations.

    Aspects specifically addressed in safety  training  include (29,36}:

    •    Hazard recognition and communication,

    •    Actions to be taken in particular  situations.

    •    Available safety equipment and  locations,

    •    When and how to use safety equipment,

    •    Use and familiarity with documentation  such as,
         - plant design and operating manuals,
         - company safety rules and procedures,
         - procedures relevant to fire,  explosion,  accident,  and
           health hazards,
         - chemical  property and handling information,  and

     •   First  aid and CPR.

     Although emergency  and safety programs typically focus on incidents such
as fires, explosions,  and  personnel  safety,  it is important that prevention of
accidental  chemical releases and release responses be addressed as part of
these programs.
                                       70

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     Much of  the type of  training  discussed above  is  also important  for
management personnel.   Safety  training  gives management  the perspective
necessary to formulate good policies and procedures, and to make changes  that
will improve the quality of  plant safety programs.   Lees suggests  that  train-
ing programs applied to managers include or define (29):

     •    Overview of technical aspects of safety and loss preven-
          tion approach.

     •    Company systems and procedures.

     •    Division of labor between safety personnel and managers in
          with respect to training,  and

     •    Familiarity with documented materials used by workers.

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 a primary
source of accidental  release incidents,  proper maintenance and modification
practices are an important part  of  accidental  release prevention.   Use of a
formal system of controls  is  perhaps  the most  effective way of ensuring that
maintenance and modification  are conducted safely.   In many  cases,  control
systems have had a marked effect on the level of  failures  experienced (29).

     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.
                                        71

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     Maintenance permits originate with the operating  staff.   Permits may be
issued in one or two stages.  In one-stage systems, the operations supervisor
issues permits to the maintenance supervisor*  who is then responsible  for his
staff.  Two-stage systems involves a second permit  issued by the maintenance
supervisor to his workforce (29).

     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, including identification  and quantification of failures responsible for
hazardous conditions, failures responsible for  downtime,  and  failures  respon-
sible for direct repair costs.

     Accidental releases are  frequently  the  result of some  aspect of plant
modification.  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.   In
these situations, it is important  that careful  assessment of  the modification
results has a priority  equal to  that of getting the plant on-line.

     For effective modification control,  there  must be established procedures
for  authorization,  work activities, inspection,  and  assessment,  complete
documentation of changes,  including  the updating of manuals,  and  additional
training to familiarize operators with new equipment and procedures (29,34).

     Formal procedures,  and  checks  on maintenance and  modification practices
must be established to  ensure that such practices enhance rather than adverse-
ly affect plant safety.  As with other plant  practices, procedure development
and  complete  documentation  are  necessary.  However, training,  attitude,  and
the  degree to which  the procedures are  followed also significantly influence
plant safety and release prevention.
                                       72"

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     The use and  availability of  clearly  defined procedures  collected in
naintenance and operating manuals  is  crucial  for  the prevention  of  accidental
releases.   Well written instructions  should  give  enough information about a
process that the worker  with hands on responsibility for operating or  main-  •
taining the process can do  so safely, effectively, and economically.   These
instructions not only document the path  to the desired results,  but also are
the basis for most  industrial training programs  (37.38).   In the  chemical
industry,  operating and maintenance  manuals vary in content and detail.  To
some extent, this variation is a  function of process  type and  complexity;
however, in many  cases  it is a  function of management policy.  Because of
their importance to the safe  operation- of  a chemical process, these manuals
must be as  clear,  straightforward, and complete  as possible.   In addition.
standard procedures should be developed  and  documented before plant startup.
and appropriate revisions should be made throughout plant operations.

     Operation and  maintenance  may be  combined or documented separately.
Procedures should  include startup,  shutdown, hazard identification, upset
conditions, emergency situations,  inspection and testing, and modifications
(29).  Several authors think  industrial plant operating manuals should include
(29.36.37.38):

     •    Process descriptions;

     •    A comprehensive safety and occupational health section;

     •    Information regarding environmental controls;

     •    Detailed  operating  instructions, including  startup and
          shutdown procedures;

     •    Upset and'emergency procedures;

     •    Sampling instructions;
                                      73

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     •    Operating documents (e.g..  logs,  standard calculations);

     •    Procedures related to hazard identification;

     •    Information regarding safety equipment;

     •    Descriptions of job responsibilities;  and

     •    Reference materials.

     Plant maintenance manuals  typically contain  procedures not  only  for
routine maintenance, but also for inspection and  testing,  preventive mainte-
nance, and plant or process modifications.   These procedures include  specific
items such as codes and  supporting documentation  for maintenance and modifi-
cations (e.g., permits to work, clearance certificates),  equipment identifi-
cation and location guides, inspection and lubrication schedules,  information
on lubricants, gaskets, valve packings and seals,  maintenance  stock require-
ments, standard  repair times, equipment turnaround schedules,  and specific
inspection codes (e.g.. for vessels  and pressure systems)  (29).  Full documen-
tation of the maintenance  required  for protective devices is a  particularly
important aspect of formal maintenance systems.

     The preparation of operating and maintenance manuals, their availability.
and the familiarity of workers with their contents are all important to safe
plant operations.  The objective, however, is to  maintain this safe practice
throughout the life of the plant. Therefore,  as processes and conditions  are
modified, documented procedures must also be modified.

5.7  CONTROL 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 nay involve numerous combinations  of
process design,  equipment  design, and operational measures,  are  especially
                                     74

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difficult to quantify because they reduce the probability of a release rather
than a physical quantity of  chemical.  Protective measures are more analogous
to traditional pollution control  technologies.   Thus they may be  easier to
quantify in terms of their efficiency  in  reducing a  quantity of chemical that
could be released.

     Preventive measures reduce the probability of an accidental release by
increasing the  reliability  of process systems operations  and equipment.
Control effectiveness  can  thus be  expressed for both  of the qualitative
improvements achieved and quantitative improvements  as  probabilities.   Table
5-5 summarizes what  appear  to be major  design, equipment,  and operational
measures applicable to the primary hazards identified for the hydrogen cyanide
applications in the U.S.  The items listed  in Table  5-5 are for illustration
only and do not necessarily  represent  a  satisfactory control option for all
cases.  These control  options appear to reduce the  risk  associated with an
accidental release when viewed from a  broad perspective.  However,  there are
undoubtedly specific cases where these control  options will  not be appropri-
ate.  Each case  must be evaluated  individually.   A  presentation  of  more
information about reliability in  terms of probabilities is planned in other
volumes of the prevention reference manual series.

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 hydrogen  cyanide
storage and process facilities that might be 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 storag'e  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
                                      75

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     TABLE 5-5.  EXAMPLES OF MAJOR PREVENTION AND PROTECTION MEASURES FOR
                 HYDROGEN CYANIDE RELEASES
Hazard Area
Prevention/Protection
Temperature control of
cyanide manufacturing
reactor
Flov control where acid
stabilizer is added to
hydrogen cyanide.

Flow/composition control
to continuous reactor
using hydrogen cyanide.

Overpressure
Corrosion
Reactor and reboiler
temperatures

Overfilling
Atmosphere releases frc
relief discharges

Storage tank or line
rupture
Redundant temperature sensors;
interlock feed flow to high
temperature signal.  Interlock
preheater heating fluid flow to
high temp signal.  Pressure relief
valve discharge sent to flare.

Redundant flow control loops; acid
addition line sized to restrict
maximum possible flow.

Redundant flow control loops;
composition monitoring; level
monitoring.

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.
                                                                   (continued)
                                     76

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                             TABLE 5-5 (Continued)
Hazard Area                                 Prevention/Protection
Human error                                 Increased training and
                                            supervision; use of checklists;
                                            use of automatic systems.

External fire                               Water sprays to cool exposed
                                            hydrogen cyanide storage vessels;
                                            siting away from other flammables;
                                            storage tank refrigeration systems.
                                    77

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       TABLE 5-6.  ESTIMATED TYPICAL COSTS OF MAJOR PREVENTION AND
                   PROTECTION MEASURES FOR HYDROGEN CYANIDE RELEASES
Prevention/Protection Measure
Continuous moisture monitoring
Flow control loop
Temperature sensor
Pressure relief
- relief valve
- rupture disk
Interlock system for flow shut-off
pH monitoring
Alarm system
Level sensor
- liquid level gauge
- load cell
Diking (based on a 10.000 gal. tank)
- 3 ft. high
- top of tank height (10 ft.)
Increased corrosion inspection
Capital Cost
(1986 $)
7.500-10.000
4.000-6.000
250-400

1.000-2,000
1,000-1,200
1.500-2.000
7.500-10.000
250-500

1.500-2.000
10,000-15,000

1,200-1,500
7,000-7.500

Annual Cost
(1986 $/yr)
900-1.300
500-750
30-50

120-250
120-150
17*5-250
900-1.300
30-75

175-250
1.300-1.900

150-175
850-900
200-400
Costs shown are for pressure  relief  device only and do not  include  other
equipment items such as  piping  to  scrubbers or flares.
                                     78

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presents costs  for some of  the major design,  equipment,  and  operational
measures applicable  to  the primary hazards identified  in  Table 5-5 for the
hydrogen cyanide applications in the United States.

5.8.2  Levels of Control

     Prevention of accidental  releases relies on  a combination of  techno-
logical, 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 pro-
cedures should  be  in accordance with applicable codes, standards,  and  regu-
lations.  However, additional  measures can be taken to provide extra  pro-
tection against an accidental 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.

     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.
                                        79

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     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.

     These estimates are for  illustrative purposes  only.   It  is  doubtful that
any specific installation would  find  all of  the control  options listed in
these 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 here.   The purpose of these estimates  is to  illus-
trate the relationship  between  cost  and control, and is  not to provide an
equipment check list.

     Levels of control cost estimates were prepared for a 29  ton  fixed  hydro-
gen cyanide storage tank system with a 10.000 gallon capacity and a 2.000 gal.
sodium cyanide reactor system.  These systems are representative of  storage
and process facilities that might be found in the United States.

5.8.3  Summary 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 hydrogen cyanide storage system
and the sodium cyanide reaction 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  informa-
tion and breakdown for each level of control for both the  storage and process
facilities are presented in Tables 5-10 through 5-15.
                                      80

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      TABLE 5-7.   SUMMARY COST ESTIMATES OF POTENTIAL LEVELS OF CONTROLS
                  FOR HYDROGEN CYANIDE STORAGE TANK AND SODIUM CYANIDE
                  REACTOR
             Systt
Level of
Control
    Total         Total
Capital Cost   Annual Cost
  (1986 $)     (1986 $/yr)
Hydrogen Cyanide Storage Tank;
29 ton Fixed Storage Tank with
10•000 Gallon Capacity.
Baseline

Level No. 1

Level No. 2
   100.000       12,000

   141.000       17.000

   360.000       43.000
Sodium Cyanide Reactor System
2.000 Gallon Continuous Reactor
Baseline

Level No. 1

Level No. 2
   147.000       18.000

   221.000       28.000

   417.000       51.000
                                        81

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                      TABLE 5-8.  EXAMPLE OF LEVELS OF CONTROL FOR HYDROGEN CYANIDE  STORAGE TANK
                         Process:  29 Ton Fixed Hydrogen Cyanj.de Storage Tank  -  10.000 gallon
            Controls
          Baseline
        Level No. 1
        Level No. 2
         Flow:
00
to
         Temperature:
         Pressure:
         Quantity:
        Location:
        Materials of
        Construction:
Single check valve on
tank process feed line.
Temperature indicator and
alarm.

Single pressure relief
valve, vent to flare.
Pressure vacuum recorder
alarm.

Local level indicators and
alarms.
Away from traffic.
flammables. and other
hazardous processes.

Carbon steel.
Add second check valve.
Add remote indicator.
Add second relief valve.
secure non-isolatable.
Vent to flare.
Add remote indicator.
Same
Carbon steel with
increased corrosion
allowance (1/16 inch).
Add a reduced - pressure
device with internal air
gap and relief vent to con-
tainment tank or scrubber.

Add redundant sensors and
alarms.

Add redundant alarms.  Add
rupture disks under relief
valves.
Add redundant alarms and
high-low level interlock
shut-off for both inlet
and outlet lines.

Same
Stainless steel. Type 316.
                                                                                                  (continued)

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                                                TABLE 5-8 (Continued)
           Controls
                          Baseline
                                      Level No. 1
                                    Level No. 2
oo
Vessel:


Piping:'


Process
Machinery:

Enclosures:

Diking:

Release
Protection:
                        Tank pressure specification:  Same
                        25 psig
                                                          Tank pressure Specifica-
                                                          tion:  50 psig.
                        Schedule 40. stainless steel  Schedule 80. stainless      Schedule 80 Honel*
                                                      steel
Type 316 stainless steel      Same
submerged pumps.
                                                                                  Same
None

3 ft. high dike

Shared flare system.
None                        Steel Building

Top of tank height. 10 ft.

Same                        Dedicated flare system.
        Mitigation:     None
                                              Foam system.
                                                          Same

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                        TABLE  5-9.  EXAMPLE OF LEVELS OF CONTROL FOR SODIUM CYANIDE MANUFACTURE
                                     Process:  Continuous sodium cyanide reactor
                                     Typical Operating Conditions:  - Temperature:  1AO°F
                                                                    - Pressure:  100 mm Hg
            Controls
          Baseline
        Level No. 1
        Level No. 2
         Process:
        Temperature:
        Pressure:
oo
        Flow:
        Corrosion:
Use of acid stabilizing
system.

Provide temperature control
with remote temperature
indication and alarms.
Provide remote control on
vacuum system with remote
pressure sensing.  Single
pressure relief valve to a
shared flare system.

Provide remote flow control
on NaOH and HCN feed
streams and on heating
medium flow control.

Provide periodic visual
inspection.
        Composition:    None
Operate reactor at a lower
temperature.

Add redundant temperature
sensors and alarms.
Automatic switch to a
cooling system.

Add redundant remote
pressure sensing and
control with alarms.  Add
second relief valve.  Vent
to shared flare system.

Add redundant flow control
loops.
Add increased monitoring
with periodic ultronsonic
inspection.

Provide periodic testing
for HCN polymer formation
in reactor vessel.
Use of interlocks and
backup cooling systems.

Add backup cooling system.
Add rupture disks under
relief valves.  Vent to
dedicated flare.
Add automatic shut-off of
feeds and automatic switch
from heating to cooling
medium.

Add increased monitoring
with more frequent
testing.

Periodic testing for HCN
polymer formation in
reactor vessel and in HCN
feed.
                                                                                             (Continued)

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                                                TABLE 5-9 (Continued)
           Controls
                          Baseline
        Level No. 1
Level No. 2
OD
Ol
        Material  of     Type 316 stainless
        Construction:    steel-clad carbon steel.
Vessel:         Pressure specification:
                Full vacuum. 50 psig
                pressure.

Piping:         Schedule 40 Type 316
                stainless steel.

Process         Centrifugal pump. Type 316
Machinery:      stainless steel, double
                mechanical seal.

Protective      Curbing around reactor.
Barrier:

Enclosure:      None.

Flare:          Shared flare system.
Type 316 stainless
steel-clad carbon steel
with increase corrosion
allowance.

Pressure specification:
Full vacuum. 100 psig
pressure.

Schedule 80 Type 316
stainless steel.

Same.
                                                      3 ft. high retaining wall.


                                                      None.

                                                      Same.
                                                                          Monel* - clad carbon
                                                                          steel.
                                                                                  Pressure specification:
                                                                                  Full vacuum.  150 psig
                                                                                  pressure.

                                                                                  Schedule 80 Monel®
                                                                                  Centrifugal  pump.  Monel*
                                                                                  construction,  double
                                                                                  mechanical seal.
                            Steel building.

                            Dedicated flare  system.

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        TABLE 5-10.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH BASELINE
                     HYDROGEN CYANIDE STORAGE SYSTEM


                                            Capital Cost           Annual Cost
                                              (1986 $)             (1986 $/yr)
Vessels:
  Storage Tank                                 33.000                 3.806

Piping and Valves:
  Pipework                                     10.000                 1.100
  Check Valve*                                    530                    60
  Globe Valves (20)                             8.100                   950
  Relief Valve                                  1.600                   190

Process Machinery:
  Submergihle Pumps (2)                        13.000                 1.500
  Refrigeration System                         22.000                 2.500

Instrumentation:
  Local Temperature Indicator                   1.900                   220
  Temperature Alarm                               380                    45
  Pressure Gauges (2)                            1.485                   170
  Pressure Alarm         .                         380               .45
  Liquid Level Indicator                        1.900                   220
  Level Alarm                                .380                    45

Flare System:                                   4.500                   520

Diking:
  Three-Foot High Concrete Dike                 1.300                   160

Procedures and Practices:
  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance
TOTAL COSTS                                    100.000                12.000
                                      86

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         TABLE 5-11.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH LEVEL 1
                      HYDROGEN CYANIDE STORAGE SYSTEM


                                            Capital Cost          Annual Cost
                                              (1986 $)            (1986 $/yr)


Vessels:
  Storage Tank                                 54.000                6.200

Piping and Valves:
  Pipework                                     15.000                1.800
  Check Valves (2)                              1.000                  120
  Globe Valves (20)                             8.100                  950
  Relief Valve (2)                              3.900                  450

Process Machinery:
  Subnergible Pumps (2)                        13.000                1.500
  Refrigeration System                         22,000                2,500

Instrumentation:
  Local Temperature Indicator                   1.900                  220
  Remote Temperature Indicator                  2.200                  260
  Temperature Alarm                               380                   45
  Temperature Sensor                              380                 .45
  Pressure Gauges  (2)                           1.485                  170
  Pressure Alarm                                  380                   45
  Liquid Level Indicator                        1.900                  220
  Remote Level Indicator                        2.200                  260
  Level Alarm                                     380                   45

Flare System:                                   5.100                  590

Diking:
  Ten-Foot High Concrete Dike                   7.600                  880

Procedures and Practices:
  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance

TOTAL COSTS       .                           141.000               17.000
                                    87

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         TABLE 5-12.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH LEVEL 2
                      HYDROGEN CYANIDE STORAGE SYSTEM


                                            Capital  Cost           Annual Cost
                                              (1986  $)             (1986 $/yr)


Vessels:
  Storage Tank          '                      240.000               28.000

Piping and Valves:
  Pipework                                     20.000                2.400
  Check Valves (2)                              1.000                  120
  Globe Valves (20)                             8.100             -     950
  Relief Valve (2)                              3.900                  450
  Rupture Disks (2)                             1.100                  130

Process Machinery:
  Subotergible Pumps (2)                        13.000                1.500
  Refrigeration System                         22.000                2.500

Instrumentation:
  Local Temperature Indicator                   1.900                  220
  Remote Temperature Indicator                  2.200                  260
  Temperature Alarms (2)                          760                   90
  Temperature Sensor                              380      .             45
  Pressure Gauges (2)                            1.485                  170
  Pressure Alarms (2)                              760                   90
  Liquid Level Indicator                        1.900                  220
  Remote Level Indicator                        2.200                  260
  Level Alarms (2)                                760                   90
  High-low Level Shutoff                        1.900                  220

Flare System:                                  22.000                2.600

Diking:
  Three-Foot High Concrete Dike                 1.400                  160

Enclosures:
  Steel Building                               10.000                1.200

Procedures and Practices:
  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance

TOTAL COSTS                                   360.000               43.000
                                     88

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             TABLE 5-13.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
                          BASELINE SODIUM CYANIDE REACTOR SYSTEM


                                            Capital Cost          Annual Cost
                                              (1986 $)            (1986 $/yr)


Vessels:
  Reactor                                      84.000               10.000
  Heat Exchanger                                  800                   95

Piping and Valves:
  Pipework                                     10.000                1.100
  Glove Valves (20)                             8.100                  950
  Relief Valve                                  1.600                  190

Process Machinery:
  Centrifugal Pump                              6.300                  760

Instrumentation:
  Remote Temperature Indicator                  2.200                  260
  Temperature Alarm                               380                   45
  Temperature Control:
    Controller                                  1.800                  220
    Sensor                         .               380                   45
    Control Valve                               2.700                  320
  Remote Pressure Indicator                     2.200                  260
  Pressure Alarm                                  380                   45
  Flow Control Loops (3):
    Controller                                  5.400                  650
    Flowmeter                                   6.800                  850
    Control Valve                               8,400                1.000

Flare System:                                   4.500                  520

Diking:
  Curbing Around Reactor                          910                  110

Procedures and Practices:
  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance

TOTAL COSTS                                   147.000               18,000
                                     89

-------
TABLE 5-14.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
             LEVEL 1 SODIUM CYANIDE REACTOR SYSTEM

Vessels:
Reactor
Heat Exchanger
Piping and Valves:
Pipework
Glove Valves (20)
Relief Valves (2)
Process Machinery:
Centrifugal Pump
Instrumentation:
Remote Temperature Indicator
Temperature Alarms (2)
Temperature Sensor
Temperature Control:
Controller
Censor
Control Valve
Temperature Switch
'Remote Pressure Indicators (2)
Pressure Control:
Controller
Sensor
Control Valve
Pressure Alarms (2)
Flow Control Loops (3) :
Controller
Flowmeter
Control Valve
Flare System:
Diking:
Three-Foot High Retaining Wall
Procedures and Practices:
Visual Tank Inspection (external)
Visual Tank Inspection (internal)
Relief Valve Inspection
Piping Inspection
Piping Maintenance
Valve Inspection
Valve Maintenance
TOTAL COSTS
Capital Cost
(1986 $)

153.000
800

10.000
8.100
3.200

6.300

2,200
760
380

1.800
380
2.700
540
4.300

1.800
380
2.700
760

5.400
1.400
8.400
4,500

1.300








221.000
Annual Cost
(1986 $/yr)

18.000
95

1,100
950
380

760

260
90
45

220
45
320
65
520

220
45
320
90

650
850
1.000
520

200

15
60
15
300
120
30
350
28,000
                       90

-------
         TABLE 5-15.  CAPITAL AND ANNUAL COSTS ASSOCIATED WITH LEVEL 2
                      SODIUM CYANIDE REACTOR SYSTEM
                                            Capital Cost
                                              (1986 $)
                    Annual Cost
                    (1986 $/yr)
Vessels:
  Reactor
  Heat Exchanger

Piping and Valves:
  Pipework
  Glove Valves (20)
  Relief Valves (2)
  Rupture Disks (2)

Process Machinery:
  Centrifugal Pump

Instrumentation:
  Remote Temperature Indicator
  Temperature Alarms (2)
  Temperature Sensor
  Temperature Control:
    Controller
    Sensor
    Control Valve
  Temperature Switch
  Remote Pressure Indicators  (2)
  Pressure Control:
    Controller
    Sensor
    Control Valve
  Pressure Alarms (2)
  Flow Control Loops (3):
    Controller
    Flowmeter
    Control Valve
  Flow Interlock Systems (2)

Flare System:

Diking:
  Three-Foot High Retaining Wall
300.000
    790
 18.700
  8.500
  3,400
  1.100
  9.300
  2.200
    780
    350

  1.800
    390
  2.800
    SAO
  4.300

  1.800
    390
  2.800
    780

  5.400
  7,000
  8.400
  3.900

 22.000
  1.600
36.000
    95
 2,200
   950
   380
   130
 1.100
   260
    90
    45

   220
    45
   3,20
    65
   520

   220
    45
   320
    90

   650
   850
 1.000
   430

 2.600
   200
                                                                   (Continued)
                                     91

-------
                            TABLE 5-15  (Continued)
                                            Capital  Cost          Annual Cost
                                               (1986  $)             (1986 $/yr)
Enclosure:
  Steel Building        -                         8.400                 1.000

Procedures and Practices:
  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance
TOTAL COSTS                                   417,000                51.000
                                    92

-------
5.8.4  Equipment Specifications and Detailed Costs

     Equipment specifications and details  of  the capital cost estimates  for
the hydrogen  cyanide storage  and the sodium  cyanide reactor systems  are
presented in Tables 5-16 through 5-23.

5.8.5  Methodology

Format for Presenting Costs Estimates—
     Tables are  provided for  control schemes associated with  storage and
process facilities for hydrogen cyanide 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
comparison of  costs for  specific items,  different levels,  and  different
systc
     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
the system.  Depending on  the specific equipment  item  involved,  the direct
capital cost was available  or was derived  from uninstailed 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
                                      93

-------
             TABLE 5-16.  EQUIPMENT SPECIFICATIONS ASSOCIATED WITH
                          HYDROGEN CYANIDE STORAGE SYSTEM
Equipment Itc
        Equipment Specification
Reference
VESSEL:
Storage tank
PIPING & VALVES
Pipework
Check Valve


Globe Valve


Relief Valve
Reduced
Pressure Device

Rupture Disk
PROCESS
MACHINERY:
Submerged Pump
Baseline:  10.000 gal. ASTM AS16 grade 60
           carbon steel* 25 psig rating
Level #1:  10.000 gal. carbon steel with
           1/8 inch corrosion protection.
           25 psig pressure rating
Level #2:  10.000 gal.. Type 316
           stainless steel. 50 psig
           pressure rating
Baseline:  100 ft. of 2 in. Schedule 40
           Type 316 stainless steel
Level II:  100 ft. of 2 in. Schedule 80
           Type 316 stainless steel
Level #2:  100 ft. of 2 in. Schedule 80
           Monel»

2 in. vertical lift check valve.
stainless steel construction

2 in. ANSI Class 300. Type 316 stainless
steel body

1 in. z 2 in., ANSI Class 300 inlet and
outlet flange, angle body, closed bonnet
with screwed cap. Type 316 stainless
steel body and trim

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

1 in. Type 316 stainless steel and carbon
steel holder
Type 316 stainless steel, submergible
pump. 100 gpm capacity
39. 40.
41. 42
43
40. 44
39. 40.
44

40
39
39. 41.
45
39, 46
                                                                   (Continued)
                                      94

-------
                            TABLE 5-16  (Continued)
Equipment Item
        Equipment Specification
                                                Reference
INSTRUMENTATION
Local Tempera-
ture Indicator

Remote Tempera-
ture Indicator

Temperature
Sensor

Temperature
Alarm

Pressure Gauge
Pressure Alarm
Level Alarm
Level Indicator
High-Low Level
Shut-off
Thermocouple, thermowell. and electronic
indicator /recorder

Transmitter and associated electronic
indicator/recorder

Thermocouple and associated thermowell
Indicating and audible alarm
Diaphragm sealed. Type 316 stainless
steel diaphragm. 0-100 psig rating

Indicating and audible alarm
Indicating and audible alarm
Electrical differential pressure type
indicator

Solenoid valve, switch and relay system
                                                39. 40.
                                                47

                                                39. 47
                                                39. 40.
                                                47

                                                40. 46.
                                                48

                                                39. 40.
                                                47

                                                40. 46.
                                                48

                                                40. 46.
                                                48

                                                39. 46
                                                39. 40.
                                                46. 47
ENCLOSURE:
Building


DIKING:
Level #2:  26-gauge steel walls and roof,
           door, ventilation system

Baseline:  6 in. concrete walls, 3 ft.
           high
Level #1:  10 in. concrete walls, top of
           tank height  (10 ft.)
                                                46
                                                 46
                                                                    (Continued)
                                        95

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


FLARE:               Baseline and Level #1:  Elevated flare'         49
                               system based on a release rate
                               of 4,600 Ib/hr and a shared
                               system with a total of five
                               units
                     Level #2:  Elevated flare system based on
                               above flow-rate and a
                               dedicated unit for only this
                               storage facility
                                       96

-------
           TABLE  5-17.   MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE HYDROGEN CYANIDE STORAGE SYSTEM
vO
1986 Dollars
•
Vessels:
Storage Tank
Piping and Valves:
Pipework
Check Valve
Globe Valves (20)
Relief Valve
Process Machinery:
Submergible Pumps (2)
Refrigeration System
Instrumentation:
Local Temperature Indicator
Temperature Alarm
Pressure Gauges (2)
Pressure Alarm
Liquid Level Indicator
Level Alarm
Flare System:
Diking:
Three-foot High Concrete Dike
TOTAL COSTS
Materials
Cost

15,000

3.800
300
5.000
1.000

6.000
10.000

1.000
200
800
200
1.000
200
2.000

390
47.000
Labor
Cost
•
6.800

2.600
50
500
50

2.600
4.500

250
50
200
50
250
50
1.000

510
20.000
Direct
Costs

22.000

6.400
350
5.500
1.100

8.600
14.500

1.250
250
1.000
250
1.250
250
3.000

900
97.000
Indirect
Costs

7.700

2.200
130
1.900
380

3.000
5.000

440
90
350
90
440
90
1.100

320
23.000
Capital
Cost

33.000

10.000
530
8.100
1.600

13,000
22.000

1.900
380
1.485
380
1.900
380
4.500

1.300
100.000

-------
             TABLE 5-18.   MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1 HYDROGEN CYANIDE STORAGE SYSTEM
vO
00
1986 Dollars

Vessels:
Storage Tank
Piping and Valves:
Pipework
Check Valves (2)
Globe Valves (20)
Relief Valves (2)
Process Machinery:
Submergible Pumps (2)
Refrigeration System
Instrumentation:
Local Temperature Indicator
Remote Temperature Indicator
Temperature Alarm
Temperature Sensor
Pressure Gauges (2)
Pressure Alarm
Liquid Level Indicator
Remote Level Indicator
Level Alarm
Flare System:
Diking:
Ten-foot High Concrete Dike
TOTAL COSTS
Materials
Cost

25.000

5.000
600
500
2.500

6.000
10.000

1.000
1.200
200
200
800
200
1.000
1.200
200
3.000

2.200
65.000
Labor
Cost

11.000

5.200
100
500
100

2.600
4.500

250
300
50
50
200
50
250
300
50
1.400

2.900
30.000
Direct
Costs

36.000

10.200
700
5.500
2.600

8.600
14.500

1.250
1.500
250
250
1.000
250
1.250
1.500
250
3.400

5.100
95.000
Indirect
Costs

13.000

3.600 -
250
1.900
900

3.000
5.000

440
530
90
90
350
90
440
530
90
1.200

1.800
33.000
Capital
Cost

54.000

15.000
1.000
8.100
3.900

13.000
22.000

1.900
2.200
380
380
1.485
380
1.900
k 2.200
380
5.100

7.600
141. OOO

-------
            TABLE  5-19.   MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 HYDROGEN CYANIDE STORAGE SYSTEM
vO
vO
1986 Dollars

Vessels:
Storage Tank
Piping and Valves:
Pipework
Check Valves (2)
Globe Valves (20)
Relief Valves (2)
Rupture Disks (2)
Process Machinery:
Submergible Pumps (2)
Refrigeration System
Instrumentation:
Local Temperature Indicator
Remote Temperature Indicator
Temperature Alarms (2)
Temperature Sensor
Pressure Gauges (2)
Pressure Alarms (2)
Liquid Level Indicator
Remote Level Indicator
Level Alarm (s)
High-Low Level Shutoff
Flare System:
Diking:
Three-Foot High Concrete Dike
Enclosures:
Steel Building
TOTAL COSTS
Materials
Cost

110.000

8.000
600
5.000
2.500
650

6.000
10.000

1.000
1.200
400
200
800
400
1.000
1.200
400
1.000
10.000

390

4.600
165.000
Labor
Cost

50.000

5.000
100
500
100
75

2.600
4.500

250
300
100
50
200
100
250
300
100
250
5.000

520

2.300
73.000
Direct
Costs

160.000

14.000
700
5.500
2.600
725

8.600
14.500

1.250
1.500
500
250
1.000
500
1.250
1.500
500
1.250
15.000

910

6.900
238.000
Indirect
Costs

56.000

5.000
250
1.900
900
260

3.000
5,000

440
530
180
90
350
180
440
530
180
440
5.300

320

2.400
84.000
Capital
Cost

24.000

20.000
1.000
8.100
3.900
1.100

13.000
22.000

1.900
2.200
760
380
1.485
760
1.900
2.200
760
1.900
22.000

1.400

10.000
360.000

-------
             TABLE 5-20.   EQUIPMENT SPECIFICATIONS ASSOCIATED WITH
                          SODIUM CYANIDE REACTOR SYSTEM
Equipment Item
        Equipment Specification
Heat Exchanger
PIPING AND VALVES:
Pipework
Globe Valve


Relief Valve




Rupture Dish


PROCESS MACHINERY:

Centrifugal Pump
           carbon steel, full vacuum -
           50 psig rating
Level #1:  Same as baseline with added
           corrosion allowance and full
           vacuum - 100 psig rating
Level #2:  2.000 gal. Monel* clad carbon
           steel, full vacuum - 150 psig
           rating

Type 316 stainless steel construction.
20 ft.  of surface area, shell and tube
type
Baseline:  100 ft. of 2 inch Schedule
           Type 316 stainless steel
Level #1:  100 ft. of 2 inch Schedule 80
           Type 316 stainless steel
Level #2:  100 ft. of 2 inch Schedule 80
           Monel*

2 in. ANSI class 300. Type 316 stainless
steel body

1 in. z 2 in. ANSI class 300 inlet and
outlet flange, angle body, closed bonnet
with screwed cap. Type 316 stainless
steel body and trim

1 in. Type 316 stainless steel and carbon
steel holder
Baseline and Level #1:  Single stage.
    100 gpm capacity. Type 316 stainless
    steel construction, double mechanical
    seal
Level #2:  Same as above except Monel«
           construction
Reference
VESSEL:
Reactor


Baseline: 2.000 gal.
stainless

Type 316
steel-clad
•
39.
41.

40.
42
39
43
39. 40.
44

40
39. 41.
45
40. 50
                                                                   (Continued)
                                         100

-------
                            TABLE 5-20 (Continued)
Equipment Item
        Equipment Specification
Reference
INSTRUMENTATION:

Local Temperature
Indicator

Remote Temperature
Indicator

Temperature Sensor

Temperature Alarm

Temperature
Control Loop


Temperature Switch
Pressure Control
Loop
Remote Pressure
Indicator

Flow Control Loop
Flow Interlock
System

DIKING:
Thermocouple, thermowell. and electronic       39* 40, 47
indicator

Transmitter and associated electronic          39, 47
indicator

Thermocouple and associated thermowell         39. 40, 47

Indicating and audible alarm                   34, 46, 48

PID controller, 2 in. globe control valve      39. 47
of stainless steel construction, and
temperature sensor

Two-stage switch with independently set        39. 47
actuation

PID controller. 2 in. globe control valve      39, 47
of stainless steel construction, pressure
sensor
                                                     *

Transducer, transmitter, and electronic        39. 47
indicator

PID controller. 2 in. globe control valve      39, 47
of stainless steel construction.
flowmeter

Solenoid valve, switch, and relay system       39, 40, 46
Baseline: 0.5 ft. high concrete curbing        46
Level II & 2:  3 ft. high concrete
               retaining wall
                                                                    (Continued)
                                        101

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


ENCLOSURE:           Level f2:   26  gauge steel walls and roof,       46
                                door,  ventilation system

Flare:               Baseline and Level fl:   Elevated flare         49
                         system based  on a total  release rated
                         5.000  Ib/hr and a shared system with
                         a total of five units.
                     Level #2:   Same as above except that
                         system is  dedicated only to this
                         system
                                       102

-------
            TABLE  5-21.   MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE  SODIUM CYANIDE REACTOR SYSTEM
o
OJ
1986 Dollars

Vessels:
Reactor
Heat Exchanger
Piping and Valves:
Pipework
Globe Valves (20)
Relief Valve
Process Machinery:
Centrifugal Pump
Instrumentation:
Remote Temperature Indicator
Temperature Alarm
Temperature Control:
Controller
Sensor
Control Valve
Remote Pressure Indicator
Pressure Alarm
Flow Control Loops (3):
Controller
Flowmeter
Control Valve
Flare System:
Diking:
Curbing Around Reactor
TOTAL COSTS
Materials
Cost

40.000
500

3.800
5.000
1.000

3.000

1.200
200

1.000
200
1.500
1.200
200

3.000
3,900
4,500
2.000

500
73.000
Labor
Cost

18.000
250

2.600
500
50

1.400

300
50

250
50
375
300
50

750
1.000
1.300
1.000
*
130
28.000
Direct
Costs

58.000
550

6.400
5.500
1.100

4.400

1.500
250

1.250
250
1.875
1.500
250

3.750
4.900
5.800
3.000

630
101,000
Indirect
Costs

15.000
140

2.200
1.900
380

1.100

380
90

320
90
470
380
90

940
1.200
1.500
1.100

160
27.000
Capital
Cost

84.000
800

10,000
8.100
1.600

6.300

2.200
380

1.800
380
2.700
2.200
380

5.400
6.800
8.400
4.500

910
'147,000

-------
TABLE 5-22.  MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1  SODIUM CYANIDE REACTOR SYSTEM
1986 Dollars

Vessels:
Reactor
Heat Exchanger
Piping and Valves:
Pipework
Globe Valves (20)
Relief Valves (2)
Process Machinery:
Centrifugal Pump
Instrumentation:
Remote Temperature Indicator
Temperature Alarms (2)
Temperature Sensor
Temperature Control:
Controller
Sensor
Control Valve
Temperature Switch
Remote Pressure Indicators (2)
Pressure Control:
Controller
Sensor
Control Valve
Pressure Alarms (2)
Materials
Cost

73,000
500

3.800
5.000
2.000

3.000

1.200
400
200

1.000
200
1.500
300
2.400

1.000
200
1.500
400
Labor
Cost

33.000
250

2.600
500
100

1.400

300
100
50

250
50
375
75
600

250
50
375
100
Direct
Costs

106.000
550

6.400
5.500
2.200

4.400

1.500
500
250

1.250
250
1.875
375
3.000

1.250
250
1.875
500
Indirect
Costs

27,000
140
•
2.200
1.900
760

1.100

380
180
90

320
90
470
95
760

320
90
470
180
Capital
Cost

153.000
800

10.000
8.100
3.200

6.300

2.200
760
380

1.800
380
. 2.700
540
' 4.300

1.800
380
2.700
760
                                                                                   (Continued)

-------
                                                TABLE 5-22  (Continued)
o
en
1986 Dollars

Flow Control Loops (3):
Controller
Flowmeter
Control Valve
Flare System:
Diking:
Three-Foot High Retaining
TOTAL COSTS
Materials
Cost
3.000
3.900
A.500
2.000
Wall 900
112.000
Labor
Cost
750
1.000
1.300
1.000
230
45.000
Direct
Costs
3.750
4.900
5.800
3.000
1.130
157.000
Indirect
Costs
940
1.200
1.500
1.100
290
42.000
Capital
Cost
5.400
1.400
8.400
4.500
1.300
221.000

-------
              TABLE 5-23.   MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 SODIUM CYANIDE REACTOR SYSTEM
o
cr>
1986 Dollars
Materials
Cost
Vessels:

Reactor 146.000
Heat Exchanger
Piping and Valves:
Pipework
Globe Valves (20)
Relief Valves (2)
Rupture Disks (2)
Process Machinery:
Centrifugal Pump
Instrumentation:
Remote Temperature Indicator
Temperature Alarms (2)
Temperature Sensor
Temperature Control:
Controller
Sensor
Control Valve
Temperature Switch
Remote Pressure Indicators (2)
Pressure Control:
Controller
Sensor
Control Valve
Pressure Alarms (2)
500

8.000
5.000
2.000
650

4.500

1.200
400
200

1.000
200
1.500
300
2.400

1.000
200
1.500
400
Labor
Cost

66.000
250

5.000
500
100
75

2.000

300
100
50

250
50
375
75
600

250
50
375
100
Direct
Costs

210.000
550

13.000
5.500
2.200
725

6.500

1.500
500
250

1.250
250
1.875
375
3.000

1.250
250
1.875
500
Indirect
Costs

53.000
140
.
3.300
1.900
760
260

1.600

380
180
90

320
90
470
95
760

320
90
470
180
Capital
Cost

300.000
790

18.700
8.500
3.400
1.100

9.300

2.200
780
350

1.800
390
2.800
• 540
4.300

1.800
390
2.800
780
                                                                                                 (Continued)

-------
TABLE 5-23 (Continued)
1986 Dollars

Flow Control Loops (3):
Controller
Flowmeter
Control Valve
Flow Interlock Systems (2)
Flare System:
Diking:
Three-Foot High Retaining Wall
Enclosure:
Steel Building
TOTAL COSTS
Materials
Cost
3.000
3.900
4.500
2.000
10.000
900
4.600
206.000
Labor
Cost
750
1.000
1.300
500
5.000
230
1.200
86.000
Direct
Costs
3.750
4.900
5.800
2.500
15.000
1.130
5.800
292.000
Indirect
Costs
940
1.200
1.500
880
3.800
290
1.500
75.000
Capital
Cost
5.400
7.000
8.400
3.900
22.000
1.600
8.400
417.000

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




    1                 Total Material Coat

    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

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

bFor storage facilities, the contingency cost factor is 0.05.  For process
 facilities, the contingency cost factor is 0.10.
                                     108

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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.

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  hydrogen cyanide
process and storage facilities  using the best  costs  for  available sources.
The primary  sources of cost information are Peters  and Timmerhaus  (39).
Chemical Engineering (51).  and  Valle-Riestra  (52)  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
component costs.
                                     109

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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-             0.163 x Item 1
                      merit Items*

    3                 Maintenance Expense on                 0.01 x  Item  1
                      Equipment Items
    4                 Total Procedural It*

    5                 Total Annual Cost                      Items  (2-1-3  +4)




a8ased on a plant life of ten years and an interest rate of ten percent.
                                       110

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     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 esti-
mates 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 reason-
able source of preliminary cost information for the facilities covered.  *

     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 re-
ported 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 costs indices as shown in the following equation:
                                        111

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                            ,  ,             ^   new base year index
     new base year cost = old  base year cost x	.	
                                               old base year index

The Chemical Engineering (CE)  Plant Cost Index was used  in .updating cost for
this 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) were determined using  the  following  equation  from  Peters  and
Timmerhaus (39):

                 Cost = [50(Weight of Vessel in Pounds)~°*34]

The vessel weight is determined using appropriate design equations as given by
Peters and Timmerhaus (39)  which allow for wall thickness adjustments for cor-
rosion 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 (39).  The vessel costs are updated using cost factors.  Final-
ly 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  (43).  A simplified approach  is used in which it is
assumed that  a certain  length of  piping containing a given number of valves.
                                       .112

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flanges,  and fittings  is  contained in the storage or process facility.   The
data presented  by Tamartino  (43)  permit cost  determinations  for various
lengths,  sizes, and  types of piping systems.  Using these factors, a  repre-
sentative estimate can b.e obtained for each of the storage and process facili-
ties.

     Diking—Diking costs were  estimated using Mean's  manual  (46) for  re-
inforced 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 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  (46) for
both reinforced concrete and  steel-walled buildings.   The  buildings  are
assumed to 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 an'd a
metal door.  The  steel building has 26-gauge  roofing  and siding and  metal
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.

     Flares—Flare costs  were  estimated using  the following equation  from
Vatavuk (49) based on  the use of an elevated flare system for a high Btu gas
system.

          Costs = 288  [Mass flow rate of gas]0*398   .

A release rate  of '4.600 Ib/hr was assumed for  the  storage  vessel and  an
appropriate rate was determined for  the  process system based on the quantity
of hazardous chemical present in the system  at any one time.   For the sodium
                                        113

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cyanide reactor system, a release rate  of 1.000 Ib/hr was  assumed.   In ad-
dition* the shared systems were based on a combined discharge for five identi-
cal units.  The dedicated system was based on a single unit.   The costs pre-
sented 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 (39)
and Valle-Riestra (52).  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.
                                      114

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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. 41
  Reduced Pressure Device                                       Ref. 38
  Check Valves                                                  Ref. 38
  Globe Valves                                                  Ref. 38
  Relief Valves                                                 Ref. 38
  Rupture Disks                                                 Ref. 38
   •

PROCESS MACHINERY:
  Centrifugal Pump                                              0.43
  Gear Pump                                                     0.43

INSTRUMENTATION:
  All Instrumentation Items                                     0.25

ENCLOSURES:                                                     Ref. 44

DIKING:                                                         Ref. 44

SCRUBBERS:                                                      0.45
                                       115

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                                   SECTION 6

                                  REFERENCES
1.    Chemical Profile.  Hydrogen Cyanide.  Chemical Marketing Reporter.
     Schnell Publishing Company Inc., June 4, 1984.

2.    Mark,  Herman F..  Othmer, Donald F.. Overberger, Charles G.,  Seaborg.
     Glenn T.  Kirk-Othmer Encyclopedia of Chemical Technology. 3rd  edition.
     Volume 7. John Wiley & Sons, 1983.

3.    Hydrogen Cyanide Storage and Handling.  E.I. du Pont de Nemours &
     Company, Incorporated. Wilmington. OE. 1983.

4.    Dean,  J. (ed.).  Lange's Handbook of Chemistry.  Twelfth Edition.
     McGraw-Hill Book Company. New York, NY. 1979.

5.    Chemical Emergency Preparedness Program Interim Guidance.  Chemical Pro-
     files. 2 volumes.  U.S. Environmental Protection Agency. Washington,  DC,
     December 1985.

6.    Tatken, R.L. and Lewis. R.J. (ed.).  Registry of Toxic Effects  of
     Chemical Substances.  (RTECS).  1981-82 edition. 3 volumes. NIOSH Contract
     No. 210-81-8101.  DHHS  (NIOSH) Publication No. 83-107. June 1983.

7.    U.S. Patent No. 3.360.335.

8.    U.S. Patent No. 3.718.731.

9.    U.S. Patent No. 3,104.945.

10.  U.S. Patent No. 3.215.495.

11.  U.S. Patent No. 2.680.761.

12.  U.S. Patent No. 3.496.215.

13.  U.S. Patent No. 3,536.748.

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

15.  Methyl Methacrylate.  1983 Petrochemical Handbook Issue.  Hydrocarbon
     Processing, Gulf Publishing  Company. Houston. TX. November 1983.

16.  Methyl Methacrylate.  1979 Petrochemical Handbook Issue.  Hydrocarbon
     Processing, Gulf Publishing  Company, Houston. TX, November 1979.
                                       116-

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17.   U.S.  Patent No. 2.537.814.

18.   Strong Outlook for Cyanuric Chloride.  Chemical and Engineering News.
     July 26.  1976.

19.   U.S.  Patent No. 2.762.798.

20.   U.S.  Patent No. 2.993.754.

21.   HCN Safety Symposium.  E.I. DuPont DeNemours and Company. Memphis, TN.

22.   McNaughton. K.J. (ed.).  Materials Engineering I:  Selecting Materials
     for Process Equipment.  McGraw-Hill Publications Company, New York. NY,
     1980.

23.   Metals Handbook Ninth Edition. Volume 3.  American Society for Metals.
     Metals Park. OH. 1980.

24.   Harper. C.A. (ed.).  Handbook of Plastics and Elastromers. McGraw-Hill
     Book Company. New York. NY. 1975.

25.   Telephone conversation between D.S. Davis of Radian Corporation and a
     representative of Monsanto Corporation.  St. Louis. MO. January 1987.

26.   Green. D.W. (ed.).  Perry's Chemical Engineer's Handbook. 6th edition,
     McGraw-Hill Book Company. New York. NY. 1984.                     •    .

27.   Telephone conversation between D.S. Davis of Radian Corporation and a
     representative of E.I. DuPont DeNemours and Company.  Memphis. TN.
     January 1987.

28.   Lewis. D.J.  The Mond Fire, Explosion and TozLcity Index Applied  to Plant
     Layout and Spacing.  Loss Prevention, Volume 13. American Institute of
     Chemical  Engineers, 1980.

29.   Lees, Frank P.  Loss Prevention in the Process Industries. Volumes 1 &  2.
     Butterworths. London. England, 1983.

30.   Federal Register.  Volume 50.  April 16, 1985.  pp. 14.941-14.945.

31.   Pool. J.H. and Soelberg, N.R.  Evaluation of the Efficiency of Industrial
     Flares:  Flare Head Design and Gas Composition.  EPA-600/2-85-106 (NTIS
     PB86-100559). Energy and Environmental Research Corporation, September
     1985.

32.   Radian Notebook No. 215.  EPA Contract 68-02-3994.  Work Assignment 94,
     Page 5. 1986.

33.   Darts. J.J. and D.M. Morrison.  Refrigerated Storage Tank Retainment
     Walls. Chemical Engineering Progress Technical Manual. Volume 23. Ameri-
     can Institute of Chemical Engineers. New York, NY, 1981.

                                      117

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34.  Beresford. T.C.  The Use of Water Spray Monitors and Fan  Sprays  for Dis-
     persing Gas Leakage.  I. Chen. E. Symposium Proceeding.   The Containment
     and Dispersion of Gases by Water Sprays, Manchester. England.  1981.

35.  McQuaid. J. and A. P. Roberts.  Loss of Containment - Its  Effect  and Con-
     trol, in Developments '82 (I. Chem. E. Jubilee Symposium).   London.  Eng-
     land. April 1982.

36.  Chemical Manufacturers Association.  Process Safety Management  (Control
     of Acute Hazards).  Washington. DC. May 1985.

37.  Stus. T.F.  On Writing Operating Instructions.  Chemical  Engineering.
     November 26. 1984.

38.  Burk. A.F.  Operating Procedures and Review.  Presented at  the Chemical
     Manufacturers Association Process Safety Management Workshop.  Arlington.
     VA, May 7-8, 1985.

39.  Peters. M.S. and K.D. Timmerhaus.  Plant Design and Economics  for Chemi-
     cal Engineers.  McGraw-Hill Book Company. New York. NY. 1983.

40.  Richardson Engineering Services. Inc.  The Richardson Rapid Construction
     Cost Estimating System, Volume 1-4, San Marcos. CA. 1986.
       •
41.  Pikulic. A. and H.E. Diaz.  Cost Estimating for Major Process Equipment.
     Chemical Engineering. October 10, 1977.

42.  Hall, R.S., J. Mat ley, and K.J. McNaughton.  Cost of Process Equipment.
     Chemical Engineering. April 5. 1982.

43.  Yarmartino. J.  Installed Cost of Corrosion - Resistant Piping.   Chemical
     Engineering. November 20, 1978.

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

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

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

47.  Liptak, B.C.  Cost of Process Instruments.  Chemical Engineering. Seotem-
     ber 7,  1970.                                                         *

48.  Liptak, B.C.  Control - Panel Costs, Process Instruments.   Chemical Engi-
     neering, October 5, 1970.

49.  Vatavuk. W.M. and R.B. Neveril.  Cost of Flares.  Chemical  Engineering
     February 21. 1983.
                                      118

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

51.  Coat indices obtained from Chemical Engineering.  McGraw-Hill  Publishing
     Company. New York. NY. June 1984, December  1985. and August  1986.

52.  Valle-Riestra. J.F.  Project Evaluation  in  the Chemical  Process Indus-
     tries.  McGraw-Hill Book Company. New York. NY. 1983.
                                       119

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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.

Assessment;  The process whereby  the hazards which have been identified, are
evaluated in order to provide an  estimate for the level of risk.

Containment/control;  A system to which toxic emissions from safety relief
discharges are routed to be controlled.  A caustic scrubber and/or flare can
be containment/control devices.  These systems may serve the dual function of
destrueting continuous process exhaust gas emissions.

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.
                                       120

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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.

Identification;  The recognition of a situation, its causes and consequences
relating to a defined potential, e.g. Hazard Identification.

Mild steel;  Carbon steel containing a maximum of about 0.25Z carbon.  Mild
steel is satisfactory for use where severe corrodants 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.

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.

Primary Containment; The containment provided by the piping, vessels and
machinery used in a facility for handling chemicals under normal operating
conditions.
                                      121

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Probability/potential;  A measure* either qualitative or quantitative, that an
event will occur within some unit of time.

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.

Qualitative Evaluation;  Assessing the risk of an accidental release at a
facility in relative terms; the end result of the assessment being a verbal
    •
description of the risk.

Quantitative Evaluation;  Assessing the risk of an accidental release at a
facility in numerical terms; the end result of the assessment being some type
of number reflects risk, such as faults per year or mean time between failure.

Reactivity;  The ability of one chemical to undergo a chemical reaction with
another chemical.  Reactivity of one chemical is always measured in reference
to the potential for reaction with itself or with another chemical. A chemical
is sometimes said to be "reactive",  or have high "reactivity", without
reference to another chemical.  Usually this means that the chemical has the
ability to react with common materials such as water, or common materials of
construction such as carbon steel.

Redundancy;  For control systems,  redundancy is the presence of a second piece
of control equipment where only one would be required.   The second piece of
equipment is installed to act as a backup in the event  that the primary piece
of equipment fails.   Redundant equipment can be installed to backup all or
selected portions of a control system.

                                      122

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Risk;  The probability that a hazard may be realized at any specified level in
a given span of time.

Secondary Containment;  Process equipment specifically designed to contain
material that has breached primary containment before the material is released
to the environment and becomes an accidental release.  A vent duct and
scrubber that are attached to the outlet of a pressure relief device are
examples of secondary containment.

Toxicity;  A measure of the adverse health effects of exposure to a chemical.
                                       123

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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:

Velocity:

Viscosity:
To Convert From
in
ft
in2
*t?
*3
ft3
gal
Ib
short ton (ton)
short ton (ton)
atm
mm Hg
. psia
psig

OJ
°C
Btu/lb
Btu/lbmol
kcal/gmol
Btu/lb-9F

lb/ft3
Ib/gal
oz/gal
quarts /gal
gal /min
ga^/day
ft /min
ft /min
ft/sec
centipoise (CP)
To
cm
9
cm*
»5
cm3
m3
m3
kg
Mg
metric ton (t)
kPa
kPa
kPa
kPa*

«c*
K*
kJ/kg
kJ/kgmol
kJ/kgmol
kJ/kg-°C

kg/»3
kg/<
kg/m3
cm3/*3
m./min
m3/day
m /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)+14.696]
i(6.895)
(5/9)x(«F-32)
8C+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.
                                      124

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                                TECHNICAL REPORT DATA
                         (Please read Instructions on the reverse before completing)
 . REPORT NO.
 EPA-6007 8-87-034J
                           2.
                                                       3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 Prevention Reference  Manual: Chemical Specific,
 Volume 10: Control of Accidental Releases of
 Hydrogen Cyanide        	         	
              B. REPORT DATE
               September 1987
              6. PERFORMING ORGANIZATION CODE
'. AUTHOR(S)
 D. S. Davis, G. B. DeWolf. and J. D. Quass
              B. PERFORMING ORGANIZATION REPORT NO.
               DCN 87-203-024-98-35
I. PERFORMING ORGANIZATION NAME AND ADDRESS
                                                       10. PROGRAM ELEMENT NO.
 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; 11/86 - 6/87
               14. SPONSORING AGENCY CODE
                EPA/600/13
is.SUPPLEMENTARY NOTES AEERL project officer  is T.  Kelly Janes. Mail Drop 62B,  919/541
 2852.
i*. ABSTRACT
              repOrt discusses the control of accidental releases  of hydrogen cya-
 nide (HCN) to the atmosphere. HCN has an IDLH (immediately dangerous to  life and
 health) concentration of 50 ppm. making  it an acute toxic hazard.  Reducing the risk
 associated with an accidental release of HCN involves identifying some of the poten-
 tial causes of accidental releases that apply to the  process facilities that use HCN.
 The 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 example preven-
 tion, protection,  and mitigation measures are provided. The accidental release of a
 toxic chemical at Bhopal, India, in 1984 was a  milestone in creating an increased
 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 Bhopal. These same portions of the industry have made  ad-
 vances in this area. Interest in reducing the probability and consequences of acciden-
 tal toxic chemical releases that might harm workers within a  process facility and
 people in the surrounding community prompted this and other similar manuals.
                             KEY WORDS AND DOCUMENT ANALYSIS
                DESCRIPTORS
                                          b.lOENTIPIERS/OPEN ENDED TERMS
                           c. COSATI Field/Group
 Pollution    _      Maintenance
 Hydrogen Cyanide Cost Estimates
 Accidents
 Emission
 Toxicity
 Design
  Pollution Control
  Stationary  Sources
  Accidental Releases
 13 B
 07B
 13 L
 14G
 06T
05E
05 A, 14 A
 8. DISTRIBUTION STATEMENT

 Release to Public
  19. SECURITY CLASS (Thit Report)
  Unclassified
21. NO. OF PAGES
    132
  20. SECURITY CLASS (Thispage)
  Unclassified
22. PBICE
  Form 2230-1 (».731
125

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