vvEPA
United States Air and Energy Engineering
Environmental Protection Research Laboratory
Agency Research Triangle Park NC 27711
EPA/600/8-87/034i
August 1987
Research and Development
Prevention Reference
Manual: Chemical
Specific
Volume 9. Control of
Accidental Releases of
Chlorine
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EPA/600/8-87/0341
August 1987
PREVENTION REFERENCE MANUAL:
CHEMICAL SPECIFIC
VOLUME 9: CONTROL OF ACCIDENTAL
RELEASES OF CHLORINE
By:
D.S. Davis
G.B. DeWolf
J.D. Quass
K.P. Wert
Radian Corporation
Austin, Texas 78766
Contract No. 68-02-3994
Work Assignment 94
EPA Project Officer
T. Kelly Janes
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
AIR AND ENERGY ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
U.£, Environmental Protection Agency
R.-"r1.oii J, L ••»••; try (.'u'L-lf-)
2?.0 G. Du_iborn btreet, Boom 1670
CbiOttgo. 1L 60604
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
11
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ABSTRACT
Recent headlines of accidental releases of toxic chemicals at Bhopal and
Chernobyl have created the current public awareness of toxic release problems.
As a result of other, perhaps less dramatic incidents in the past, portions of
the chemical industry were aware of this problem long before these events.
These same portions of the industry have made advances in this area. Interest
in reducing the probability and consequences of accidental toxic chemical
releases that might harm workers within a process facility and people in the
surrounding community prompted the preparation of this manual and a planned
series of companion manuals addressing accidental releases of toxic chemicals.
Chlorine has an IDLH (Immediately Dangerous to Life and Health) concen-
tration of 25 ppm. which makes it a substantial acute toxic hazard.
Reducing the risk associated with an accidental release of chlorine
involves identifying some of the potential causes of accidental releases that
apply to the processes that use chlorine. In this manual examples of poten-
tial 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 pos-
sible prevention, protection, and mitigation measures are provided.
'-w
ACKNOWLEDGEMENTS
This manual was prepared under the overall guidance and direction of T.
Kelly Janes, Project Officer, with the active participation of Robert P.
Hangebrauck, William J. Rhodes, and Jane M. Crum, all of U.S. EPA. In addi-
tion, 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, Kelly P. Wert, and Sharon L. Wevill. Contributions were also provided
by other staff members. Secretarial support was provided by Roberta J.
Brouwer and others. A special thanks is given to the many other people, both
in government and industry, who served on the Technical Advisory Group and as
peer reviewers.
iii
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TABLE OF CONTENTS
Section Page
ABSTRACT ill
ACKNOWLEDGEMENTS iii
FIGURES vii
TABLES viii
1 INTRODUCTION 1
1.1 Background 1
1.2 Purpose of this Manual 2
1.3 Uses of Chlorine 2
1.4 Organization of the Manual 3
2 CHEMICAL CHARACTERISTICS 5
2.1 Physical Properties 5
2.2 Chemical Properties and Reactivity 5
2.3 Toxicological and Health Effects 10
3 FACILITY DESCRIPTIONS 13
3.1 Chlorine Manufacture 13
3.2 Chlorine Consumption 17
3.2.1 Drinking Water, Wastewater, and Cooling Tower
Chlorination 17
3.2.2 Bleach Production 23
3.2.3 Chlorohydrocarbon Manufacture 26
3.2.4 Phosgene Manufacture 33
3.2.5 Chlorofluorocarbon Manufacture 35
3.2.6 Propylene Oxide Manufacture 37
3.2.7 Hydrogen Chloride Manufacture 40
3.2.8 Miscellaneous Inorganic Chemical Manufacture . . 42
3.3 Repackaging . . . 48
3.4 Storage and Transfer 48
4 PROCESS HAZARDS . ..... 51
4.1 Potential Causes of Release . . . . 51
4.1.1 Process Causes ...... 53
4.1.2 Equipment Causes 54
4.1.3 Operational Causes 55
5 HAZARD PREVENTION AND CONTROL 56
5.1 Background .. .......... 56
5.2 Process Design 57
5.3 Physical Plant Design 59
5.3.1 Equipment 59
5.3.2 Plant Siting and Layout 77
5.3.3 Transfer and Transport Facilities 79
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TABLE OF CONTENTS (Continued)
Number Page
5.4 Protection Technologies 80
5.4.1 Enclosures 80
5.4.2 Scrubbers 81
5.5 Mitigation Technologies 85
5.5.1 Secondary Containment Systems 88
5.5.2 Flotation Devices and Foams 93
5.5.3 Mitigation Techniques for Chlorine Vapor .... 96
5.6 Operation and Maintenance Practices 98
5.6.1 Management Policy 98
5.6.2 Operator Training 99
5.6.3 Maintenance and Modification Practices 103
5.7 Control Effectiveness 107
5.8 Illustrative Cost Estimates for Controls 110
5.8.1 Prevention an'd Protection Measures 110
5.8.2 Levels of Control 110
5.8.3 Cost Summaries 113
5.8.4 Equipment Specifications and Detailed Costs . . 113
5.8.5 Methodology 113
6 REFERENCES 154
APPENDIX A - GLOSSARY 158
APPENDIX B - TABLE B-l. METRIC (SI) CONVERSION FACTORS 162
VI
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FIGURES
Number Page
2-1 Volume - temperature relation of liquid chlorine in a
container loaded to its authorized limit 8
3-1 Conceptual process diagram of typical chlorine manufacturing
process 14
3-2 Conceptual process diagram of typical liquid chlorine feed
water chlorination system 19
3-3 Conceptual diagram of typical chlorinator 21
3-4 Conceptual process diagram of typical batch sodium hypochlorite
process 24
3-5 Conceptual process diagram of typical continuous sodium
hypochlorite manufacturing process 25
3-6 Conceptual process diagram of typical chlorohydrocarbon
manufacturing process 27
3-7 Photochlorination reactors 31
3-8 Conceptual diagram of typical phosgene manufacturing process . 34
3-9 Conceptual diagram of chlorofluorination process 36
3-10 Conceptual process diagram of typical chlorhydrin process ... 38
3-11 Conceptual process diagram of typical hydrogen chloride
manufacturing process 41
3-12 Conceptual process diagram of typical anhydrous aluminum
chloride manufacturing process 43
3-13 Conceptual process diagram of typical phosphorous trichloride
manufacturing process 45
3-14 Conceptual process diagram of typical titanium tetrachloride
manufacturing process 47
3-15 Typical bulk chlorine storage and tank car unloading system . . 50
5-1 Liquid chlorine expansion chamber for liquid chlorine only . . 69
5-2 Computer model simulation showing the effect of diking on the
vapor cloud generated from a release of refrigerated chlorine . 92
vii
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TABLES
Number Page
2-1 Physical Properties of Chlorine 6
2-2 Exposure Limits for Chlorine 11
2-3 Predicted Human Health Effects of Exposure to Various
Concentrations of Chlorine 12
3-1 Typical Uses of Chlorine 18
3-2 Typical Chlorohydrocarbons Manufactured From Chlorine and
Hydrocarbon Feedstocks 28
5-1 Key Process Design Considerations for Chlorine Processes ... 58
5-2 Corrosion of Metals in Dry Chlorine 61
5-3 Summary of Chlorine Institute Piping Material Recommendations . 68
5-4 Summary of Chlorine Institute Guidelines for Valves 71
5-5 Typical Alkaline Solution for Chlorine Scrubbing 83
5-6 Typical Chlorine Absorption Data 84
5-7 Example of Performance Characteristics for an Emergency Packed
Bed Scrubber for Chlorine 86
5-8 Foam Capabilities to Suppress or Minimize the Release of Toxic
Vapors From a Chlorine Spill 95
5-9 Aspects of Training Programs for Routine Process Operations . . 102
5-10 Examples of Major Prevention and Protection Measures for
Chlorine Releases 108
5-11 Estimated Typical Costs of Some Prevention and Protection
Measures for Chlorine Releases Ill
5-12 Summary Cost Estimates of Potential Levels of Controls for
Chlorine Storage Tank and Hypochlorite Bleach Reactor 114
5-13 Example of Levels of Control for Chlorine Storage Tank .... 115
Vlll
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TABLES (Continued)
Number Page
5-14 Example of Levels of Control for Chlorine Bleach Reactor ... 117
5-15 Estimated Typical Capital and Annual Costs Associated With
Baseline Chlorine Storage System 119
5-16 Estimated Typical Capital and Annual Costs Associated With
Level 1 Chlorine Storage System 120
5-17 Estimated Typical Capital and Annual Costs Associated With
Level 2 Chlorine Storage System 122
5-18 Estimated Typical Capital and Annual Costs Associated With
Baseline Continuous Sodium Hypochlorite Production 124
5-19 Estimated Typical Capital and Annual Costs Associated With
Level 1 Continuous Sodium Hypochlorite Production 126
5-20 Estimated Typical Capital and Annual Costs Associated With
Level 2 Continuous Sodium Hypochlorite Production 128
5-21 Equipment Specifications Associated With Chlorine Storage
System 130
5-22 Material and Labor Costs Associated With Baseline Chlorine
Storage System 133
5-23 Material and Labor Costs Associated With Level 1 Chlorine
Storage System 134
5-24 Material and Labor Costs Associated With Level 2 Chlorine
Storage System 136
5-25 Equipment Specifications Associated With Chlorine Bleach
Reactor System 138
5-26 Material and Labor Costs Associated With Baseline Continuous
Sodium Hypochlorite Production 140
5-27 Material and Labor Costs Associated With Level 1 Continuous
Sodium Hypochlorite Production 142
5-28 Material and Labor Costs Associated With Level 2 Continuous
Sodium Hypochlorite Production 144
IX
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TABLES (Continued)
Number Page
5-29 Format For Total Fixed Capital Cost 147
5-30 Format for Total Annual Cost 148
5-31 Format For Installation Costs 153
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SECTION 1
INTRODUCTION
1.1 BACKGROUND
Increasing concern about the potentially disastrous consequences of
accidental releases of toxic chemicals resulted from the Bhopal, India acci-
dent of December 3. 1984, which killed approximately 2,000 people and injured
thousands more. A toxic cloud of methyl isocyanate was released. Concern
about the safety of process facilities handling hazardous materials increased
further 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, inci-
dents in the past. 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.
Historically, there have been a number of significant releases of chlo-
rine both in the United States and in other areas of the globe. Between 1950
and 1976, 16 reported major chlorine releases caused a total of twelve fatali-
ties and at least 633 injuries. The largest release occurred in 1967 in
Newton, Alabama, when a rail tank car was punctured in a wreck. Over 50 tons
of chlorine escaped, but no deaths occurred. The release with the highest
fatalities occurred in 1952 in Wilson, West Germany, when a boiler which had
been converted into a chlorine storage tank failed. Approximately 15 tons of
chlorine escaped, killing seven people (1).
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1.2 PURPOSE OF THIS MANUAL
The purpose of this manual is to provide technical information about the
prevention of accidental releases of chlorine. The manual addresses techno-
logical and procedural issues related to release prevention, associated with
the storage, handling, and process operations involving chlorine as it is used
in the United States This manual does not address uses of chlorine 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 at facilities that use.
store, handle, or manufacture chlorine. It is not intended as a specification
manual, and in fact refers the reader to additional technical manuals and
other information sources for more complete information on the topics dis-
cussed. Other information sources include manufacturers and distributors of
chlorine, and technical literature on design, operation, and loss prevention
in facilities handling toxic chemicals.
1.3 USES OF CHLORINE
Chlorine (Cl,) is one of the major commodity chemicals used in industry.
It is co-produced electrolytically with sodium hydroxide (caustic soda) from
sodium chloride brine in specially designed cells. In 1979. the most produc-
tive year to date (1987). 12.3 million tons of chlorine gas and 7.3 million
tons of liquid chlorine were produced as reported by the Chlorine Institute
(2). In 1986. approximately 10.6 million tons of chlorine gas were produced
(3).
The major industrial uses of chlorine include chemical synthesis of
chlorinated chemicals, cooling tower water treatment, and disinfection of
drinking water and wastewater. Approximately three-quarters of the total
chlorine produced in the U.S. is consumed by the chemical industry (A).
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Numerous references in the technical literature provide information on both
the manufacture and uses of chlorine.
The predominant uses of chlorine in the U.S. include (2,4):
• Organic and inorganic chemical synthesis;
• Bleach manufacture;
• Cooling tower water treatment;
• Drinking water treatment;
• Wastewater disinfection; and
• Repackaging.
Major cooling tower water treatment users include oil refineries, power
plants, and chemical plants. Wastewater disinfection and drinking water
treatment are similar applications and take place predominantly in municipal
or county facilities. General chemical synthesis includes the manufacture of
chlorocarbons, chlorofluorocarbons, and a variety of other chlorinated organic
and inorganic chemicals and products, including bleach products. Chlorine is
also repackaged from bulk quantities into smaller cylinders for resale.
In the United States, chlorine is stored in small cylinders (e.g., 150
Ib), one-ton cylinders, bulk storage tanks, railroad tank cars and tank trucks
used for temporary stationary storage.
1.4 ORGANIZATION OF THE MANUAL
Following this introductory section, the remainder of this manual pre-
sents technical information on specific hazards and categories of hazards for
chlorine releases and their control. Ae stated previously, these are examples
only and are representative of only some of the hazards that may be related to
accidental releases.
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Section 2 discusses physical, chemical and toxicological properties of
chlorine. Section 3 describes the types of facilities which manufacture and
use chlorine in the United States. Section 4 discusses process hazards
associated with these facilities. Hazard prevention and control are discussed
in Section 5. Costs of example storage and process facilities reflecting
different levels of control are also presented in Section 5. The examples are
for illustration only and do not necessarily represent a satisfactory alterna-
tive 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 and Appendix B presents selected conversion factors
between metric (SI) and English measurement units.
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SECTION 2
CHEMICAL CHARACTERISTICS
This section of the report describes the physical, chemical and toxico-
logical properties of chlorine as they relate to accidental release hazards.
2.1 PHYSICAL PROPERTIES
Chlorine is an elemental chemical which exists as a gas at ambient
conditions, but liquifies at moderate pressures. Some of its common physical
properties are listed in Table 2-1.
Chlorine is slightly water soluble. The yellow-green gas has a strong
characteristic odor. Because chlorine gas is about 2.5 times more dense than
air, it tends to stay close to the ground when released into the atmosphere.
Liquid chlorine has a clear amber color; one volume of liquid can vaporize to
about 460 volumes of gas.
Liquid chlorine has a large coefficient of thermal expansion as shown in
Figure 2-1. As a result, liquid-full equipment can pose a special hazard. A
liquid-full vessel is a vessel that is not vented and is filled with liquid
chlorine 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 chlorine with little or no vapor space. In these situations, there is
no room for thermal expansion of the liquid, and temperature increases can
result in containment failure.
2.2 CHEMICAL PROPERTIES AND REACTIVITY
Chlorine is considered to be neither explosive nor flammable in the
normal sense. However, chlorine is an oxidizer which will, like oxygen,
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TABLE 2-1. PHYSICAL PROPERTIES OF CHLORINE
Reference
CAS Registry Number
Chemical Formula
Molecular Weight
Normal Boiling Point
Melting Point
Liquid Specific Gravity (H«0 = 1)
Vapor Specific Gravity (air = 1)
Vapor Pressure
Vapor Pressure Equation
log Pv = A - B
T+C
07782-50-5
C12
70.914
-29.3 °F « 14.7 psia
«
-149.8 °F
1.41 @ 68 °F
2.5 @ 68 °F
93 psia @ 68 °F
where: Pv = vapor pressure, mmHg
T = temperature, °C
A = 6.93790, a constant
B = 861.34, a constant
C = 246.33, a constant
5
5
2
2
6
7
Liquid Viscosity
Solubility in Water
Specific Heat at Constant Volume
(Vapor)
Specific Heat at Constant Pressure
(Vapor)
Specific Heat at Constant Pressure
(Liquid)
0.345 centipoise
6.08 lb/100 gal @ 68 °F
and 14.7 psia
0.085 Btu/(lb-°F) @ 59 °F
0.115 Btu/(lb-°F)
0.226 Btu/(lb-°F)
2
2
(Continued)
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TABLE 2-1 (Continued)
Reference
Latent Heat of Vaporization
Liquid Surface Tension
Average Coefficient of Thermal
Expansion. 0-60 °F
123.8 Btu/lb @ -29.3 °F
25.4 dynes/cm @ -22 °F
0.00110/ °F
2
8
6
Additional propeties useful in determining other properties from physical
property correlations:
Critical Temperature
Critical Pressure
Critical Density
Energy of Molecular Interaction
Effective Molecular Diameter
291.2 °F
1118.36 psia
35.77 lb/ft3
357 K
4.115 Angstroms
2
2
8
9
9
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101
99
97
95
w 93
IU
s "
h-
I
uj 89 ^~
0.
87 -
85 -
83 -
81
-20
I
I
20 40 60 80
TEMPERATURE - «F
100
120
140
160
Figure 2-1. Volume - temperature relation of liquid chlorine in a
container loaded to its authorized limit.
Source: Adapted from Reference 6.
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support the burning of most combustible materials. Because chlorine is a
strong oxidizer, it reacts readily with reducing agents. Chlorine will react
with metals and other elements as well as inorganic and organic compounds.
The most significant chemical properties contributing to the potential for
accidental releases are as follows:
• As a result of hydrolysis, moist chlorine contains hydro-
chloric and hypochlorus acids which are very corrosive to
most common metals. Dry chlorine, however, tends not to
react with metals until an activation temperature specific
to the metal has been reached. Above this temperature,
the reaction proceeds rapidly; carbon steel, for example,
ignites in chlorine at 483°F (10). Titanium ignites upon
contact with dry chlorine at ambient temperatures.
Chlorine also can react explosively with powdered metals.
• Under certain conditions, chlorine will react rapidly with.
most of the elements. It will, for example, react vio-
lently with hydrogen to form hydrogen chloride. This
explosive reaction can take place if either component is
present at concentrations greater than approximately 15
percent in a mixture (11).
• Because of its great affinity for hydrogen, chlorine tends
to remove hydrogen atoms from other compounds. For
example, chlorine reacts with hydrogen sulfide to form
hydrogen chloride and sulfur. Chlorine combines with
carbon monoxide to form phosgene and with sulfur dioxide
to form sulfuryl chloride. Both of these reaction pro-
ducts are toxic and corrosive. Chlorine reacts with
ammonia or ammonium compounds to form various mixtures of
chloramines, depending on the conditions. One of these
chloramines is nitrogen trichloride which becomes highly
explosive, even at relatively low concentrations in the
range of a few percent.
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• Chlorine dissolves rapidly in strong alkali solutions to
produce hypochlorite solution. When chlorine is absorbed
in alkali solutions, excess chlorine causes an acid
condition which promotes the release of large quantities
of chlorine and oxygen. This decomposition can occur with
explosive force (11).
• The strong oxidizing ability of chlorine allows it to
react vigorously with organics to form chlorinated deriva-
tives and hydrogen chloride. Flammable gases and vapors
can form explosive mixtures with chlorine. Some of these
compounds include gasoline, alcohols, ethers, acetylene.
oils, greases, organic solvents, and other hydrocarbons.
2.3 TOXICOLOGICAL AND HEALTH EFFECTS
Chlorine is a highly toxic, severe skin and lung irritant. The toxico-
logical effects of chlorine have been well documented, both through animal
studies and accidental human exposure (12,13).
Exposure to low concentration of chlorine causes a stinging or burning
sensation in the eyes. nose, and throat; choking; and sometimes headache due
to irritation of the accessory nasal sinuses. There may be redness of the
face, tearing, sneezing, coughing, and huskiness or loss of voice. Bleeding
of the nose may occur and sputum from the larynx and trachea may be blood-
tinged. Inhalation of chlorine in higher concentrations affects both the
upper and lower respiratory tract and also produces pulmonary edema. The most
pronounced symptoms are suffocation, constriction in the chest, and tightness
in the throat. A concentration of 833 parts per million (ppm) breathed for 30
to 60 minutes has caused death (12). Skin contact with the liquid or vapor
may result in ulceration and necrosis. Table 2-2 presents a summary of some
of the relevant exposure limits for chlorine. Table 2-3 presents a summary of
predicted human health effects of exposure to various concentrations of
chlorine.
10
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TABLE 2-2. EXPOSURE LIMITS FOR CHLORINE
Limit
Concentration
(ppm)
Description
Reference
IDLH
25
PEL
TCLo
LCLo
15
430
The concentration defined ae posing an 14
immediate danger to life and health (i.e.
causes irreversible toxic effects for a
30-minute exposure).
A time-weighted 8-hour exposure to this 13
concentration, as set by the Occupational
Safety and Health Administration (OSHA).
should result in no adverse effects for
the average worker.
This concentration is the lowest published 13
concentration causing toxic effects
(irritation) for a 1-minute exposure.
This concentration is the lowest published 13
lethal concentration for a human over a
30-minute exposure.
11
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TABLE 2-3. PREDICTED HUMAN HEALTH EFFECTS OF EXPOSURE TO VARIOUS
CONCENTRATIONS OF CHLORINE
ppm
Predicted Effect
3.5
A
30
40-60
1,000
Odor threshold
concentration tolerated
without serious effects for a 1-hour
exposure
Minimum concentration known to cause
coughing.
May be dangerous in 30 minutes.
Likely to he fatal after only a few
deep breaths.
Source: Reference 2.
12
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SECTION 3
FACILITY DESCRIPTIONS
This section provides brief descriptions of the manufacture and uses of
chlorine in the United States. Major hazards of these processes associated
with accidental releases are discussed in Section 4. Preventive measures
associated with these hazards are discussed in Section 5.
3.1 CHLORINE MANUFACTURE
Chlorine is manufactured primarily by electrolysis of brine in three
types of cells: diaphragm, mercury, and membrane. Approximately 95 percent
of U.S. chlorine is produced in such cells, with diaphragm cells being the
predominant method (4). Other methods of production including the electroly-
sis and the oxidation of hydrochloric acid are also used on a limited scale.
Such methods are not a major source of chlorine. A flow diagram of a typical
chlorine manufacturing process using a diaphragm cell is shown in Figure 3-1.
In a typical diaphragm cell, sodium or potassium chloride brine is
electrolyzed to chlorine gas at a graphite, impregnated carbon, or titanium or
tantalum based dimensionally stable (DSA*) anode. Sodium or potassium ions
from the brine migrate through an asbestos diaphragm to the cathode, where
sodium or potassium hydroxide is formed and hydrogen gas is liberated. The
diaphragm cell typically operates at a temperature in the range of 176-210°F
(15). The electrolyte is heated by the passage of current through the cell
resistance. The gas leaving the anode is highly corrosive wet chlorine
containing oxygen, nitrogen, hydrogen, and/or carbon dioxide, depending on the
exact cell type used. The wet chlorine is cooled either in titanium heat
exchangers or by direct contact with water in a packed tower and then dried by
countercurrent scrubbing with sulfuric acid in a contact tower. The dried
13
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WATER
CONCENTRATED
SULFURIC ACID
CHLORINE
FREE VENT
CHLORINE
RECOVERY
CHLORINE
GAS PRODUCT
f LIQUID CHLORINE
PRODUCT
Figure 3-1. Conceptual process diagram of typical chlorine manufacturing process,
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chlorine is either transported as a gas by pipeline to point of use or is
compressed, liquified, and pumped to storage tanks.
The membrane cell process is similar to the diaphragm cell in that
chlorine and hydrogen are co-produced by the electrolysis of a saturated brine
solution. However, an ion exchange polymer membrane serves to prevent chlo-
rine and hydrogen from coming in contact.
The mercury cell process differs from the diaphragm cell in that the
cathode is a moving bed of mercury. As in the diaphragm cell, chlorine
accumulates at the anode, but the sodium or potassium ions form an amalgam
with mercury at the cathode. The dilute amalgam is then fed to a decomposer
(packed-bed reactor) where it reacts with water to form sodium hydroxide,
hydrogen, and mercury. The mercury is then recycled to the electrolysis cell.
High hazard areas in chlorine manufacture, excluding bulk storage and
transfer, which are discussed separately in Section 3, include the following:
• Electrolysis cell,
• Chlorine cooling,
• Acid scrubber,
• Chlorine compressor, and
• Chlorine liquefaction.
The electrolysis cell is a critical area of the process since a poten-
tially hazardous situation exists as a result of combination of chlorine and
hydrogen, and hydrogen and oxygen present in the same manufacturing system.
If the gases are allowed to contact, a highly explosive mixture could result.
When the concentrations of both chlorine and hydrogen are both greater than
approximately fifteen percent, the mixture can explode when initiated ther-
mally or by U.V. radiation (11). Likewise, combination of hydrogen with air
at hydrogen levels above four percent can also lead to fire and/or explosions.
Additionally, since wet chlorine is produced in the cell, corrosion leading to
15
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equipment failure is possible. A properly designed system should use materials
which take this into account.
The cooling section of the process is subject to the corrosive attack of
wet chlorine. A properly designed system should use materials of construc-
tion, such as titanium, which take this corrosion potential into account.
Undetected corrosion could eventually result in equipment failure and release
of chlorine. Overpressure and release of chlorine through a relief valve
could occur with loss of cooling. In addition, loss of cooling could result
in insufficient drying in the acid scrubber since this operation is tempera-
ture sensitive, requiring more acid at higher temperatures (see below).
Proper operation of the sulfuric acid scrubber is important in preventing
a hazardous release. Since the scrubber is used to dry the chlorine, a loss
of or insufficient flow of sulfuric acid would result in corrosive wet chlo-
rine being sent to downstream processing with possible equipment failure from
corrosive attack. If packed towers are used, an additional hazard can result
from sulfuric acid reacting with residual caustic soda present in the chlorine
gas to form solid sodium sulfate over a long period of time. This could
eventually lead to plugging of the packing or process piping and result in
overpressure.
The chlorine compression section presents hazards of overpressure of a
pressurized gas system and possible compressor failure from corrosion caused
by insufficient water removal from the chlorine gas.
One potentially hazardous by-product of chlorine manufacture is nitrogen
trichloride. Nitrogen trichlorde is unstable and highly explosive. It can be
formed from a combination of chlorine with nitrogen compounds in the brine
feed, ammonia in the water used in direct-contact cooling, or nitrogen com-
pounds in sulfuric acid used in chlorine drying. If chlorine containing
nitrogen trichloride is evaporated, explosive concentrations of nitrogen
trichloride may be reached.
16
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An additional consideration in chlorine manufacture is the potential
presence of various noncondensible gases (i.e.. carbon dioxide, oxygen, air,
hydrogen) in the raw chlorine from the electrolysis cell. As the chlorine is
condensed from the system during the liquefaction stage, the amount of non-
condensibles in the liquefaction equipment increases. These must be purged in
order to prevent overpressure. Liquefaction is controlled so that the hydro-
gen gas concentration in the residual gas stream is maintained below 5%. This
level of hydrogen is reported to be safe from explosion under all conditions
of operation (i.e. temperature, pressure, and composition) (16).
3.2 CHLORINE CONSUMPTION
The most important industrial uses of chlorine are based on its general
reactivity and it properties as an oxidizer. Table 3-1 presents a listing of
some of the end uses of chlorine. Aliphatic organic compounds are chlorinated
through addition and substitution reactions; aromatic organic compounds are
chlorinated in a substitution process. Chlorine is also used to produce a
wide variety of inorganic chemicals; bleach production is a major use of
chlorine. The primary application for chlorine is based on its oxidizing
properties for water treatment. This includes drinking water, wastewater and
sewage, and cooling tower water where chlorination kills microorganisms and
oxidizes some organic compounds.
This subsection summarizes the major technical features, related to
release hazards, of typical chlorine processing facilities that might be found
in the United States.
3.2.1 Drinking Water. Wastewater. and Cooling Tower Chlorination
Conventional chlorination facilities are composed of three parts:
chlorine supply, metering system, and injector system. A typical water
chlorination system is shown in Figure 3-2. In some systems, chlorine gas is
17
-------
TABLE 3-1. TYPICAL USES OF CHLORINE
o Organic Chemical Manufacture
allyl chloride
amyl chloride
benzene hexachloridfr -~~^
carbon tetrachloride'
chloral
chlorinated naphthalenes
chlorinated paraffins
chlorinated waxes
chloroacetic acid
chloroacetyl chloride
chloroanilines
chloroanthraquinone
oo chlorobenzene
chlorofluoro hydrocarbons
o Inorganic Chemical Manufacture
anhydrous aluminum chloride
antimony pentachloride
antimony trichloride
arsenic trichloride
bismuth trichloride
chlorinated isocyanurates
chlorine trifluoride
ferric chloride
hydrochloric acid
o Bleach Manufacture
chloroform
chlorophenols
chloroprene
chlorosulfonic acid
chlorotoluenes
dichlorobenzenes
2-4-dichlorophenoxyactic acid
dichloropropane
dichloropropenes
ethyl chloride
ethylene dichloride
hexachlorocyclopentadiene
hexachloroethane
methallyl chloride
iodine monochloride
iodine trichloride
mercuric chloride
mercurous chloride
molybdenum pentachloride
phosphorus oxychloride
phosphorus pentachloride
phosphorus trichloride
o Sanitizing and Disinfecting Agent
(e.g., for municipal water supplies, swimming pools)
o Waste and Sewage Treatment
o Slimicide
methyl chloride
methylene chloride
perchloroethylene
perchloromethyl mercaptan
phosgene
polychlorinated biphenyls
tetrachlorobenzene
tetrachlorophthalic anhydride
trichlorobenzene
1,1,1-trichloroethane
1,1,2-trichloroethane
t richloroethylene
2,4.5-trichlorophenoxy-acetic
acid
silicon tetrachloride
sulfur dichloride
sulfur monochloride
sulfuryl chloride
stannous chloride
titanium tetrachloride
titanium trichloride
zinc chloride
Source: Adapted from Reference 17.
-------
EXPANSION
TANKS
CI2 PRESSURE
RELIEF
VALVE
VENT
ADDITIONAL
ONE - TON Ct2 C
CYLINDERS /
TRAP
LEG
ONE-TON
O2 CYLINDER
$
Figure 3-2. Conceptual process diagram of typical liquid chlorine feed
water chlorination system.
-------
fed directly to the chlorinator instead of a liquid feed-evaporator system as
shown.
For chlorine supply, most facilities use chlorine packaged in containers
ranging from 150-pound cylinders to single unit tank cars.
The chlorine gas metering system in a chlorination facility is known as
the chlorinator. As shown in Figure 3-3, it consists of an inlet chlorine
pressure regulating valve, a rotameter, a chlorine orifice, a manual feed rate
adjuster, a vacuum differential regulating valve, a pressure-vacuum relief
valve, and an injector. The vacuum created as water flows through the injec-
tor first opens the differential regulating valve, then the vacuum relief
valve. This allows air to enter the system. This vacuum is also exerted on
the inlet chlorine pressure regulating valve, allowing it to open, so that
when the chlorine supply is open, the gas will flow through to the injector.
As soon as the gas satisfies the vacuum created by the injector, the vacuum
relief valve automatically closes, stopping the flow of air into the chlori-
nator. The following items are required for the safe control and operation of
a chlorinator:
• Inlet chlorine pressure-reducing valve to reduce the
cylinder pressure to a constant downstream pressure
less than atmospheric:
• Manually and automatically adjustable chlorine
metering orifice;
• Automatic pressure vacuum relief device;
• Rotameter for indicating chlorine feed rate;
• Differential vacuum regulating valve; and
20
-------
VENT
VACUUM
REGULATING
VALVE
REMOTE FROM
CHLOHINATOR
SOLUTION
DISCHARGE
INJECTOR
VACUUM GAUGE I
(7)
VACUUM TRIMMER
& DRAIN RELIEF VALVE I
CHLORINE
OAS INLET
INJECTOR
INJECTOR
WATER SUPPLY
Figure 3-3. Conceptual diagram of typical chlorinator.
Source: Adapted from Reference 2.
21
-------
• Chlorine pressure and injector vacuum gauges.
The injector is the primary functional component of the chlorinator. It
develops the vacuum which causes the chlorine to flow from the storage supply
through the chlorinator and then into itself. At the injector, the chlorine
dissolves in water to form hypochlorous acid. This solution flows in the
lines to the point of application. The injector system is usually composed of
the following items:
• Water pressure gauge;
• Back pressure gauge located immediately downstream
from the injector;
• Water pressure switch for the low water pressure
alarm; and
• Water flow meters.
Remotely located injectors usually have a vacuum gauge and a vacuum line
shutoff valve.
Additional information concerning the various types of chlorination
facilities, equipment used, and specific design considerations is available
from White (2).
The primary hazards associated with chlorination systems arise from the
large inventory of stored chlorine and the chlorine evaporator. Excess feed
to the evaporator or overheating could lead to overpressure and a possible
release. The possibility of liquid chlorine feed lines being blocked while
liquid full also presents a possibility of chlorine release.
22
-------
Hazards associated with handling and hookup of chlorine cylinders or
containers include human errors that could cause damage, or faulty connections
that could lead to a release. A chlorine container that is improperly con-
nected to the feed system could result in backflow of water into the cylinder,
and internal corrosion which might go undetected until a failure occurs.
Nitrogen is sometimes used for padding a chlorine feed tank or cylinder. The
possibility exists for chlorine to enter a nitrogen line if the system is not
designed correctly.
3.2.2 Bleach Production
Bleach is a hypochlorite solution prepared by chlorination of sodium
hydroxide or calcium hydroxide. The respective reactions are as follows.
2 NaOH + C12 > NaOCl + NaCl + H20
2 Ca(OH)2 + 2 C12 > Ca(OCl)2 + CaCl2 + 2H2
-------
AIR FOR ,
MIXING *>
NaOH
SOLUTION
[ CAUSTIC |
1 TANK I
^ 'I _J~
II II ^Q
— n
f
1 1
^^
-
o oo
U •»
•
•••M^M
0 0
\
0 EXPANSION
TANK
I !
0*0
» • 0
• 00
ki
~~ LIQUID
CHLORINE
[
•^^
CHLORINATION
TANK
- — OIFFUSER
FINISHED
STORAGE
^T LOAD CELL I
1 INDICATOR |
1
•tX}-) | CHLORINE
MX}— I TANK
A A
i
«
*-
§
Figure 3-4. Conceptual process diagram of typical batch sodium hypochlorite
process.
Source: Adapted from Reference 18.
-------
AIR FOR i
COOLED ~
WATER C
TEMPERATURE
INDICATOR
FINISHED
BLEACH TO
STORAGE
LOAD CELL
INDICATOR
RECIRCULATING
PUMP
Figure 3-5. Conceptual process diagram of typical continuous sodium
hypochlorite manufacturing process.
Source: Adapted from Reference 18.
-------
• Reactor cooling system; and
• Batch reactor agitation.
When chlorine is absorbed in alkali solutions, the stability of the
process is pH dependent. The pH of the solution should be monitored to ensure
that there is free alkali present, since excess chlorine can promote an acid
condition causing the release of chlorine and oxygen. This decomposition can
occur explosively (11). Poor control of the chlorine feed rate could cause
such a process failure.
Chlorination of caustics is exothermic and liberates 24.65 kcal/mol when
chlorine gas is used. Reactor cooling is required, which is partially achiev-
ed using liquid chlorine feed. Thorough agitation is necessary to prevent
local overchlorination as well as to improve the effectiveness of both the
cooling system and the oxidation potentiometer used to monitor the reaction
(11). The primary hazard is a runaway reaction from an excess chlorine feed
rate, cooling system failure, or loss of agitation.
3.2.3 Chlorohydrocarbon Manufacture
Chlorohydrocarbons (chlorocarbons) are manufactured by the chlorination
of hydrocarbon feedstock. A typical chlorocarbon manufacturing process is
presented in Figure 3-6.
The dominant types of chlorination processes are:
• Thermal chlorination,
• Photochemical chlorination, and
• Catalytic chlorination.
Table 3-2 presents a list of typical organic chemicals prepared by these
processes and brief details about the specific systems used.
26
-------
10
HYDROCARBON
CHLORINE
1 H
c m
>
COOLING j_
WATER INLET C" ~
CATALYST ?
FEED
PREPARATION
1
1 i r
A * i
\ ! .
HYDROCARBON FEED /
CHLORINE RECYCLE
r ~i
^. EFFLUENT 1
H COOLING ' W
|_ J
COOLING
WATER OUTLET
!
CRUDE
SEPARATION
FINAL PI
SEPAP
CHLOROCARBON
^ PRODUCT
FKXKJCT
IATION.
fc REACTION
^BY-PRODUCTS
Figure 3-6. Conceptual process diagram of typical chlorohydrocarbon
manufacturing process.
-------
TABLE 3-2. TYPICAL CHLOROHYDROCARBONS MANUFACTURED FROM CHLORINE AND HYDROCARBON FEEDSTOCKS
Organic Chemical
Chlorination Reaction
Type Phase
Reactants
Reactor Reactor
Temperature Pressure
[psig]
00
Allyl Chloride
Ethyl Chloride
Thermal
Thermal
Vapor Chlorine, propylene 932-950
Vapor Chlorine ethane 716-824
Heterogeneous Vapor Chlorine, dichloroethane 536-842
Catalytic
Trichloroethylene
Benzyl Chloride
Benzene Hexachloride Photochemical Liquid Chlorine, benzene
Thermal or Liquid Chlorine, toluene
Photochemical
149-212
59-77
15
15
Chlorobenzene
Chlorinated
Paraffins
Methyl Chloride
Methylene Chloride
Perchloroethylene
Homogeneous
Catalytic
Photochemical
Thermal
Thermal
Thermal
Heterogeneous
Catalytic
Liquid
Liquid
Vapor
Vapor
Vapor
Vapor
Chlorine, benzene - -
ferric chloride
(catalyst)
Chlorine, liquid 194-212
paraffin
Chlorine, methane 752 -
Chlorine, methane 905-950
Chlorine, ethylene 1,022-1,292
Chlorine, methane 572 -
Fuller's earth
(catalyst)
(Continued)
-------
TABLE 3-2. TYPICAL CHLOROHYDROCARBONS MANUFACTURED FROM CHLORINE AND HYDROCARBON FEEDSTOCKS (Con't)
Organic Chemical
Chlorination Reaction
Type Phase
Reactants
Reactor Reactor
Temperature Pressure
[°F] [psig]
Carbon Tetrachloride Thermal
Chloroform
Het erogeneous
Catalytic
Thermal
Vapor Chlorine, methane
Vapor Chlorine, methane
Fuller's earth
(catalyst)
Vapor Chlorine, methane
914-1.292
572
905-950
Tetrachloroethylene
Chloroprene
Thermal
Heterogeneous
Catalytic
Thermal
Vapor Chlorine, ethane/
propane, ethylene
dichloride, chlorine,
steam, oxygen
Vapor Chlorine, butadiene
1.022-1.292
797
554-626
5-15
Ethylene Dichloride Homogeneous
Catalytic
Hexachloroethane
Homogeneous
Catalytic
Liquid Chlorine, ethylene,
ferric chloride
(catalyst)
Liquid Chlorine, tetrachlo-
roethylene, ferric
chloride (catalyst)
122-149
212-284
Source: Reference (11).
-------
Thermal Chlorination—
Thermal Chlorination uses thermal energy to initiate and carry out the
reaction between chlorine and a hydrocarbon feedstock. Thermal Chlorination
reactions are typically gas phase reactions in continuous tubular or fluidized
bed reactors. Operating temperatures in excess of 482°F are required for such
reactions (11).
Photochemical Chlorination—
Photochemical Chlorination uses ultraviolet light as the energy source
for reacting chlorine with a hydrocarbon feedstock. Photochemical Chlorina-
tion reactions are typically carried out at temperatures ranging from 32-257°F
(11). Photochemical reactors can be batch or continuously operated. Figure
3-7 shows examples of both batch and continuous reactors. A typical batch
reactor consists of a large, stirred, jacketed vessel with lamps inserted
through the top. The lamps are usually nitrogen blanketed and water cooled.
A typical continuous reactor is tubular, with individual lamps positioned
along its longitudinal axis.
Catalytic Chlorination—
Catalytic Chlorination uses a catalyst to enhance the Chlorination
reaction rate between chlorine and a hydrocarbon feedstock. Catalytic
Chlorination can be homogeneous or heterogeneous.
Homogeneous Catalytic Chlorination—in homogeneous catalytic Chlorination
the catalyst is dissolved in a liquid reaction medium. Homogeneous catalytic
reaction systems can be batch or continuous. Batch reactors are typically
stirred tanks and continuous reactors are either stirred tank or tubular
reactors.
Heterogeneous Catalytic Chlorination—Heterogeneous catalytic chlorina-
tion processes use a solid catalyst with reactants in a gas or liquid phase.
Heterogeneous catalytic reactors are typically continuous fixed bed (packed
bed) or fluidized bed reactors.
30
-------
LIGHTING UNITS
m~\
CHLORINE
INLET
JACKET
INLET
JACKET
OUTLET
MIXER
PRODUCT
BATCH SYSTEM
CHLORINE
FEED
HYDROCARBON
FEED
LIGHTING
UNITS
PRODUCT
FLOW SYSTEM
Figure 3-7. Photochlorination reactors.
Source: Adapted from Reference 11
31
-------
High hazard areas in these processes include:
• Chlorine feed rate control,
• High temperature reactors,
• Reactor cooling system,
• Cooling of lamps (in photochemical processes),
• Mixing of reactants,
• Seals on the reactor head or stirrer shaft, and
• Chlorine recycle circuits.
An excessively high chlorine feed rate could result in overpressurizing
the reactor or cause unreacted chlorine to pass through the reactor to down-
stream processing where it might cause a process upset leading to overpressure
or emergency venting. In addition, in fluidized bed reactors, carry over of
solid particles could also cause a process upset downstream.
Since chlorination of hydrocarbons is often exothermic, failure of the
reactor cooling system could lead to a runaway reaction. In addition, local-
ized hot spots could occur in catalytic reactions resulting in equipment
failure.
An additional hazard with tubular or jacketed reactions is the potential
for leakage of the cooling medium into the reactor section or reactor contents
into the cooling medium section of the reactor system. Since water is often
used as a cooling medium, undetected corrosion from wet chlorine could lead to
equipment failure.
Failures to cool the reactor lamps in a photochemical reactor could cause
the reaction rate to diminish, again resulting in a buildup of excessive
chlorine.
A failure of agitation in stirred tank processes could have a similar
result, or could result in local overheating leading to equipment failure. In
32
-------
addition, a loss of mixing in any system could lead to overchlorination or
undesired by-products to pass to downstream processes where they might cause a
process upset leading to overpressure or emergency venting.
Chlorine recycle circuits are subject to corrosion, with general vessel,
piping, valve, or pump failure. Where chlorine is recycled, traces of mois-
ture may enter the system and concentrate in the recycle stream, thus con-
tributing to corrosion.
3.2.4 Phosgene Manufacture
Phosgene is manufactured by the reaction of chlorine and carbon monoxide
over a highly absorptive activated charcoal catalyst in a tubular reactor.
Figure 3-8 presents a block diagram of a typical phosgene production process.
The reactor typically operates at 392°F under a slight positive pressure (11).
The reaction is exothermic and liberates 26.22 kcal/mole (11,19). The reactor
is water cooled to remove the excess heat and maintain the reactor temperature
below 572°F, since phosgene decomposes above this temperature (19). Carbon
monoxide and chlorine are fed to the reactor in either equimolar proportions
or with a small excess of carbon monoxide to ensure complete conversion of
chlorine.
High hazard areas in the process include:
• Chlorine feed rate control; and
• Reactor cooling systems.
Concerns for these hazard areas are the same as those discussed in
Section 3.2.3 for catalytic chlorination reactions.
33
-------
HYDROCARBON
SOLVENT
u>
CARBON
MONOXIDE
CHLORINE
REACTOR
1
CONDENSER
SCRUBBER
LIQUID
PHOSGENE
PHOSGENE SOLUTION AND
• UNCONDENSED PHOSGENE
FOR PLANT USE
STORAGE
TANKS
Figure 3-8. Conceptual diagram of typical phosgene
manufacturing process.
-------
3.2.5 Chlorofluorocarbon Manufacture
Chlorofluorination is one of the primary methods used in the manufacture
of chlorofluorocarbons. This process differs from other Chlorofluorocarbon
processes in that hydrocarbon feedstocks are simultaneously chlorinated and
fluorinated within the reactor system using chlorine and fluorine reactants.
in place of just chlorinated hydrocarbon and fluorine feedstocks.
As shown in Figure 3-9. hydrocarbon reacts with chlorine and hydrogen
fluoride in the presence of a catalyst. The reaction is carried out adi-
abatically in the vapor phase using a fluidized bed reactor. The reactor
typically operates at temperatures in the range of 698°F to 842°F and pres-
sures of 40 to 70 psig (16). A large recycle stream of chlorocarbon and
fluorocarbon compounds serves as a heat sink to prevent the temperature from
exceeding 842°F. This is to avoid overfluorination and excessive carbon
formation (16). Carbonaceous deposits can reduce the catalyst activity and
result in incomplete reaction. Crude product vapors evolved from the reactor
are fed to an enriching column for further processing.
The exit gas stream from the enriching column is sent to a refrigerated
condenser. The uncondensed vapor is sent to a caustic vent scrubber for
removal of any residual chlorine before venting.
High hazard areas in the process include:
• Feed treatment to remove water from hydrocarbon feed.
• Chlorine feed rate control.
• Reactor cooling system,
• Enriching column, and
• Vent gas scrubber.
The feed treatment process to remove water is a critical area of the
process because water in the process system promotes corrosion. Water and
35
-------
VENT GAS
U>
CHLORINE<
ANHYDROUS.
HF
10% CAUSTIC
HF
RECYCLE
HF AND CHLOROCARBON RECYCLE
CCI2F3
DISTILLAflON
COLUMN
TOCCI
^ STORA
CHLOROCARBON
RECYCLE
TO CCI3F
STORAGE
to
o
Figure 3-9. Conceptual diagram of chlorofluorination process.
-------
chlorine combine to form hydrochloric and hypochlorous acids which rapidly
attack many materials including carbon steel. A properly designed system
should use materials of construction which take this corrosion potential into
account and allow a certain moisture concentration to be maintained. Defi-
ciencies could lead to protracted corrosion problem resulting eventually in
equipment failure.
Concerns for chlorine feed rate and reactor cooling are the same as those
discussed in Section 3.2.3 for catalytic chlorination reactions.
The enriching column is subject to potential overheating and overpres-
sure. Loss of cooling in condensers could be a cause for overpressure. The
reboiler and bottoms pump are potential weak points in these systems since
operating conditions are severe.
A failure in the vent gas scrubber system could result in venting small
quantities of residual chlorine along with the process off-gases. It should
also be noted that a failure in the process train upstream from this scrubber
could lead to a large release of chlorine unless the system has adequate
safety controls as an inherent part of the process.
3.2.6 Propylene Oxide Manufacture
Propylene oxide is typically produced by the chlorohydrin process. A
block diagram of the chlorohydrin process is shown in Figure 3-10.
Propylene and chlorine in approximately equal molar amounts are mixed
with an excess of water in a stirred tank reactor. Because of the corrosive
nature of the reactor, it is commonly constructed of brick, rubber, or lined
with a plastic material (11). The reaction is carried out under atmospheric
pressure at temperatures in the range of 104-194°F. Excess water is used to
reduce the propylene chlorohydrin and chloride ion concentrations in the
reactor, thereby minimizing the formation of by-product propylene dichloride.
37
-------
INERT AND
LOW - BOILING
COMPOUNDS
PHOPYLENE }
CHLORINE £
WATER ^
00
Figure 3-10. Conceptual process diagram of typical chlorohydrin process.
-------
In addition, excess water also prevents formation of an organic phase of
propylene dichloride with which chlorine and propylene react rapidly. The
unreacted propylene is water-washed and recycled to the reactor.
The chlorohydrin product from the reactor is treated with aqueous base to
produce crude propylene oxide. Propylene oxide is removed from alkaline
solution in a stripping column and sent to a purification section for final
treatment.
High hazard areas in this process include:
• Chlorine feed rate control,
• The propylene feed system and reactor.
• Water feed rate control, and
• Reactor cooling system.
Concerns for the chlorine feed rate control and reactor cooling system
were discussed in Section 3.2.3. Of special concern in this process is the
possible formation of explosive mixtures of propylene and air. Precautions
must be taken to exclude any air from the propylene feed, recycle, and reac-
tion systems. A propylene explosion or fire in the reactor area could cause a
chlorine release.
Excess water is required to reduce the formation of the by-product
propylene dichloride. If an organic phase of propylene dichloride were
allowed to form in the reactor, propylene and chlorine would react rapidly
resulting in a runaway reaction. Additionally, the water stream is used to
maintain the temperature of the exothermic reaction constant.
The addition of water to a vessel containing chlorine can result in
undetected corrosion. Such a system should be constructed of materials which
take this corrosion potential into account to prevent possible equipment
failure.
39
-------
3.2.7 Hydrogen Chloride Manufacture
One method of hydrogen chloride manufacture is direct synthesis from
chlorine and hydrogen. Figure 3-11 shows a typical hydrogen chloride manu-
facturing process.
Chlorine and hydrogen are fed to a vertical water-cooled combustion
chamber constructed of karbate or impervious graphite (16). The reaction of
hydrogen and chlorine is highly exothermic. The equilibrium flame temperature
for adiabatic reaction is approximately 4,514°F (11). At this temperature,
the gaseous mixture contains approximately 4.2 percent free chlorine gas by
volume (11). However, as the gases are cooled, the free hydrogen and chlorine
rapidly combine and at a temperature of 392°F, the concentration of free
chlorine is negligible (11). The feed to the burner is controlled so that the
gas exiting the combustion chamber contains greater than 99 percent hydrogen
chloride gas.
The hydrogen chloride gas is absorbed in water in an absorber/cooler to
produce hydrochloric acid. The absorber/cooler is a vertical shell and tube
heat exchanger constructed of impervious graphite (11). A tail-gas scrubber
is used to remove any residual hydrogen chloride from the absorber weak gas
stream before being released to the atmosphere.
High hazard areas of these processes include:
• Chlorine feed rate control,
• Hydrogen feed system,
• Reactor cooling system, and
• Scrubber.
Concerns for the chlorine feed rate control and reactor cooling system
were discussed previously in Section 3.2.3. In addition, if the hydrogen feed
system were to fail and the chlorine flow was not shut off, then chlorine
40
-------
CHLORINE
HYDROGEN
COOLING
WATER
I
COMBUSTION HC
CHAMBER
icoc
WATER
WATER OVERFLOW
CC<
WATE
FEED I _
WATER '
IGAS
_ 1
OUTLET^ (^
3LING J _. ABS°
R INI FT C _____
r
g
RBER
INERTS TO
ATMOSPHERE
t
TAIL - GAS —
SCRUBBER ^*
WEAK
ACID
WEAK GAS __
__ PRODUCT
•- ACID
Q
Figure 3-11. Conceptual process diagram of typical hydrogen chloride
manufacturing process.
-------
could go through the system and out the tail gas scrubber or product acid
lines.
Caustic scrubbers are used to prevent the release of hydrogen chloride to
the atmosphere. If the caustic feed to the scrubber were to fail, the possi-
bility exists for a direct release of hydrogen chloride. In addition, impro-
perly sized systems could also lead to a direct release in the event of a
large quantity of chlorine in the vent stream. Additional concerns for
scrubbing systems are discussed in Section 5.4 Protection Technologies.
3.2.8 Miscellaneous Inorganic Chemical Manufacture
Many inorganic chemicals are manufactured using chlorine as a reactant.
This subsection briefly discusses the manufacturing processes associated with
several of these chemicals. These processes are typical of the inorganic
chloride chemicals in general.
High hazard areas of these processes include:
• Chlorine feed rate control, and
• Reactor cooling system.
Concerns for hazards associated with these operations were discussed
previously in Section 3.2.3.
Aluminum Chloride—
Anhydrous aluminum chloride is manufactured by the direct chlorination of
aluminum metal. Figure 3-12 presents a process diagram of a typical manufac-
turing scheme.
Scrap aluminum or a mixture of scrap and pig aluminum are fed to a
refractory furnace in which the aluminum is melted. Dry chlorine gas is then
passed into the molten aluminum to form aluminum chloride vapor, which leaves
-------
CAUSTIC t
ALUMINUM
CHLORINE i
1
REACTOR
1
VENT GAS TO
ATMOSPHERE
CAUSTIC
SCRUBBER
AIR - COOLED
CONDENSER
SIZING AND
PACKAGING
UNREACTED CAUSTIC
i AND NEUTRALIZATION
PRODUCTS
, ALUMINUM CHLORIDE
PRODUCT
Figure 3-12.
Conceptual process diagram of typical anhydrous aluminum
chloride manufacturing process.
-------
the furnace through a vapor duct. An air cooled condenser cools the vapor and
collects the aluminum chloride, a crystalline solid, which is periodically
removed from the condensers. A conveyor system transfers- the aluminum chlo-
ride to sizing and packaging operations.
The chlorine feed rate is controlled so that unreacted chlorine is not
present in the exit gases (16). However, a protective scrubber is commonly
placed after the aluminum chloride condensers to collect any unreacted chlo-
rine (16).
Mercuric Chloride—
Mercuric chloride is produced by the direct chlorination of mercury in a
batch process.
The process consists of feeding mercury, by gravity, into a heated silica
retort whose mouth is fitted into a large chamber constructed of chlorine-
resistant materials (typically lead or tile-lined) (11). Gaseous chlorine, at
a pressure slightly greater than atmospheric, is fed to the retort above the
mercury surface. The mercury burns with a green flame, subliming a solid
product which collects on the floor of the chamber. The chlorination reaction
requires approximately 4-6 days and a slight excess of chlorine to assure
complete conversion to the mercuric state (11). Following chlorination, dry
compressed air is blown into the chamber to expel any excess chlorine, and is
sent to a scrubber tower for chlorine removal. The material in the chamber is
fed to a glass-lined or reinforced-plastic tank, slurried with water and
washed several times by decantation.
The chamber must be large since cooling is accomplished by convection and
heat dissipation by conduction through the walls of the chamber (11).
-------
Phosphorus Trichloride—
Phosphorous trichloride is manufactured by direct chlorination of phos-
phorus. Figure 3-13 presents a block diagram of a typical manufacturing
scheme.
The reaction is carried out in a stirred tank reactor. Gaseous chlorine
and liquid phosphorous are continuously fed to the reactor along with a
precharge of phosphorous trichloride'which is refluxed continuously. A
portion of the phosphorous trichloride is sent to a distilling pot where it is
contacted with additional chlorine to convert unreacted phosphorous. The
crude phosphorous trichloride is purified by fractional distillation in a
packed column and sent to storage.
Sulfur Chloride—
Sulfur chloride is manufactured by direct chlorination of sulfur in batch
processes.
The process consists of feeding liquid sulfur to a batch reactor contain-
ing sulfur chloride from a previous batch. Chlorine is introduced continuous-
ly into the liquid sulfur through a sparger tube. The chlorination reaction
is slow and as a result, the chlorine addition rate is controlled to prevent
excessive chlorine buildup and undesired sulfur product formation. The
reaction is typically carried out at a temperature of 464°F and atmospheric
pressure (11). The reaction is often catalyzed using iron, iodine, or a small
amount of ferric chloride.
Titanium Tetrachloride—
Titanium tetrachloride is manufactured by the chlorination of titanium
compounds in the presence of coke which acts as a reducing agent. Mineral
rutile, beneficated ilmenite, and leucoxene are the most commonly used titan-
ium compounds by industry (11). Figure 3-14 presents a process diagram of a
typical titanium tetrachloride manufacturing process.
45
-------
LIQUID
PHOSPHORUS'
CHLORINE
GAS
REFLUX
CONDENSER
WATER - COOLED
REACTOR
i
PACKED
DISTILLATION
COLUMN
1
CONDENSER
PHOSPHORUS
> TRICHLORIDE
STORAGE
STEAM - HEATED
REACTOR
J
fe
Q
Figure 3-13.
Conceptual process diagram of typical phosphorous trichloride
manufacturing process.
-------
CAUSTIC i
1
VENT GAS TO
' ATMOSPHERE
CAUSTIC
SCRUBBER
MINERAL RUTILE
AND COKE
UNREACTED CAUSTIC
» AND NEUTRALIZED
PRODUCTS
REACTOR
CHLORINE |
I
CONDENSER
FILTRATION
DISTILLATION
L.
SOLID WASTE
IMPURITIES
TITANIUM
TETRACHLORIDE
Co
o
PRODUCT
Figure 3-14.
Conceptual process diagram of typical titanium tetrachloride
manufacturing process.
-------
The titanium ores can be chlorinated in batch furnaces, molten salt, or
fluidized beds. However, the chlorination process is typically carried out as
a continuous process in a fluid-bed reactor. The bed consists of a mixture of
mineral rutile or other titanium compound and coke which are introduced at the
top of the bed. Chlorine is used as the fluidizing medium and is fed to the
bottom of the bed. The chlorine feed rate is such that fine reactant parti-
cles are not ^carried over by the product gases. The chlorination reactor
operates at a temperature in the range of 1,472-1,832°F and at atmospheric
pressure (20).
The exit stream from the reactor is condensed to a slurry containing
impurities. The impurities are removed by filtration followed by fractional
distillation (rectification) (20). The effluent gases are sent to a caustic
scrubber to prevent release of chlorine to the atmosphere.
3.3 REPACKAGING
In many facilities, chlorine is repackaged for resale and further use.
Chlorine is commonly repackaged into cylinders. Hazards associated with this
operation include overpressure, overfilling, mechanical damage, fire exposure,
and chemical contamination.
The Chlorine Institute Pamphlet 8 (21) provides an in-depth description
of chlorine packaging operations. Equipment used in repackaging operations
should be constructed from materials compatible with chlorine. Pressure
relief systems are used to prevent possible equipment overpressure. In
addition, care is taken to prevent overfilling of cylinders.
3.4 STORAGE AND TRANSFER
When a facility uses large quantities of chlorine, the chlorine is
unloaded directly from a rail car or from a rail car to stationary storage.
48
-------
The essential components of a typical storage tank and tank car unloading
system include a storage tank with a weighing device and sun shield, air
padding system, eductor. chlorine gas and liquid headers, unloading platform.
gages, pressure switches and alarms, flexible connections, and expansion
tanks. The Chlorine Institute Pamphlet 66 (22) provides detailed information
on chlorine tank car unloading. Figure 3-15 shows a typical tank car unload-
ing facility (6,23).
Hazards associated with chlorine storage facilities include overpressure,
overfilling, and corrosion. An additional hazard is associated with contami-
nation caused by backflow of process materials into the storage tank. Back-
flow not only jeopardizes raw material quality, it also poses an accidental
release hazard. For example, if backflow were to occur in a bleach manu-
facturing operation, caustic solution might be introduced to the chlorine
storage tank where it could react exothermically. causing overpressure and
discharge through a relief valve. If the overpressure relief system failed to
function, the storage tank could be ruptured by the pressure, resulting in a
catastrophic release.
While the above concerns also apply to refrigerated liquid chlorine
storage facilities, the refrigeration system poses an additional concern.
Loss of refrigeration could result in overpressure and a release through
pressure relief devices due to thermal expansion of both the liquid and
gaseous chlorine. Failure of such relief devices would result in equipment
failure and a direct release.
49
-------
AIR PADDING SYSTEM
MOTOR
LIQUID Clj 1 TO
GASEOUS Cl2 I PROCESS
• » TO WASTE
-OO-rf? EDUCTOR
1U
40 SOPSI
H 2O SUPPLY
KEY FOR SYMBOLS:
E=3 RUPTURE DISK
EXCESS FLOW VALVE
PRESSURE RELIEF VALVE
(/) PRESSURE GAUGE
CHLORINE
STORAGE TANK
ANGLE VALVE
CONTROL VALVE
[X] STANDARD VALVE
||| FLANGE CONNECTION
TANK EVACUATION SYSTEM
Figure 3-15. Typical bulk chlorine storage Qf\A tank
car unloading system.
-------
SECTION A
PROCESS HAZARDS
Chlorine 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.
Properties of chlorine which can promote equipment failure are its
reactivity and its high liquid coefficient of thermal expansion. Reactivity
manifested in corrosion is a likely general cause of equipment failure.
Evaporators and metering and control equipment are especially sensitive if
they are in intermittent use where moisture might enter the system.
Potential chlorine releases may be in the form of either liquid or vapor.
Liquid spills can occur when chlorine is released at or below its boiling
point of -29.3°F, or when a sudden release of chlorine at temperatures above
-29.3°F results in vapor flashing, thus cooling at least part of the remaining
material to -29.3°F. Direct releases of vapor or gas can also occur.
4.1 Potential Causes of Release
The extensive use of 150-pound cylinders and one-ton containers to store
chlorine makes them a particular concern in the United States. A list
compiled by the Chlorine Institute shows historical causes of chlorine
emissions in order of a combined ranking of frequency and size (2):
1. Fire;
2. Flexible connection failure;
3. Fusible plug failure;
51
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4. Human error;
5. Valve packing failure;
6. Gasket failure;
7. Piping failure:
8. Equipment failure;
9. Collision; and
10. Container failure.
Although fire is not the most frequent hazard, it may be the most ser-
ious. Fire can melt the fusible plug of a container at 158°F. causing the
discharge of most of the chlorine in the container. Defective fusible plugs
have also failed to melt, allowing a fire to rupture the container. A number
of leaks have been caused by defective fusible plugs without a fire. Corro-
sion or poor bonding between the lead alloy plug and the plug retainer allows
moisture accumulation and corrosion at the connection, leading to leakage of
chlorine.
Probably the most frequent cause of chlorine emissions is failure of the
copper tubes which are commonly used to connect cylinders and ton containers
to process equipment. A corrosion cycle begins when the tube is disconnected
for a container change. Moisture in the air enters the tube, promoting
corrosion; repeated removal and reconnection of tubing will induce failure.
Historically, other piping failures have been rare, but may have been caused
by corrosion, thermal expansion of chlorine, or by impact damage.
Valve packing failure on the cylinders is usually a minor problem which
can be corrected by tightening the packing nut. A potential hazard exists
with overtightening if too large a wrench is used; a brass valve is easily
damaged or broken. For serious leaks, the Chlorine Institute provides safety
kits for each type of container (6).
Because of the strict standards and monitoring programs followed by
chlorine packagers, container failures are very rare. In a period of 15
years, the Chlorine Institute accident reports indicate that approximately 15
52
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million 68 kg (150-pound) and ton containers were shipped with only two
reported failures (2). Collisions with containers are rare, but are a possi-
ble cause of a release (2).
Failures leading to accidental chlorine re.', eases may be broadly classi-
fied as due to process, equipment, or operational causes. This classification
is for convenience only. Causes discussed below are intended to be illustra-
tive, not exhaustive.
4.1.1 Process Causes
Process causes are related to the fundamentals of process chemistry.
control, and general operation. Possible process causes of a chlorine release
include:
• Excessively high chlorine feed rate to a bleach or
chlorocarbon reactor leading to excessive exothermic
reaction, combined with failure of the cooling system;
• Backflow of chlorination water to a chlorine cylinder;
• Loss of agitation in batch reactor systems;
• Excess chlorine feed leading to overfilling or
overprassuring equipment:
• Photo-lamp failure in photochemical reactor; and
• Overpressure of chlorine storage vessel due to overheating
from reactions. This situation may be caused by contami-
nation, fire exposure, or unrelieved overfilling.
53
-------
A.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. Overheating is also a possibili-
ty, especially for chlorine evaporators and bleach reac-
tors;
• 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;
• Thermal fatigue and shock in bleach reactors and chlorine
evaporation;
• Brittle fracture in any equipment, but especially in
carbon steel equipment subjected to extensive corrosion.
Equipment constructed of high alloys, especially high
strength alloys selected to reduce the weight of major
process equipment, might be especially sensitive where
some corrosion has occurred, or severe operating condi-
tions are encountered;
54
-------
• Creep failure in equipment subjected to extreme operation-
al upsets, especially excess temperature. This can occur
in equipment subjected to a fire that may have caused
damage before being brought under control; and
• All forms of corrosion, including external corrosion from
fugitive emissions of chlorine, could lead to equipment
weakening. Stress corrosion cracking is also a possibili-
ty since this is characteristic of certain metals exposed
to halogens.
4.1.3 Operational Causes
Operational causes of accidental releases are a result of incorrect
operating and maintenance procedures 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;
• Lack of inspection and non-destructive testing of vessels
and piping to detect corrosion weakening.
• Incomplete knowledge of the properties of a specific
chemical; and
• Incomplete knowledge of the process or chemical system.
55
-------
SECTION 5
HAZARD PREVENTION AND CONTROL
5.1 BACKGROUND
Prevention of accidental releases relies on a combination of techno-
logical, administrative, and operational practices. These practices apply to
the design, construction, and operation of facilities where chlorine is stored
and used. Considerations in these areas can be grouped as follows:
• Process design considerations;
• Physical plant design considerations;
• 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 chlorine to the environment, or result in an equipment failure
which would 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.
The following subsections discuss some specific considerations regarding
release prevention related to each of the areas mentioned above. In addition,
illustrative cost estimates for different levels of control as applied to
56
-------
storage and process facilities are also included. More detailed discussions
will be found in a manual on control technologies, part of this manual series.
5.2 PROCESS DESIGN
Process design considerations involve the fundamental characteristics of
the processes which use chlorine. These considerations include an evaluation
of how deviations from expected process design considerations 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 involved, and the variables of flow, pressure, temperature, composi-
tion, and level. Additional considerations may include quantity measuring
systems, 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 used, process
pressure and temperature conditions, the unit operations used, sequence of
operations, the process control strategies, and instrumentation used.
Table 5-1 shows the relationship between some specific key process design
considerations and the 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 the key considerations ensures a safe system.
It does mean that the designated key considerations must be properly addressed
if a system is to be safe.
The most significant process design considerations are aimed at prevent-
ing overheating and overpressuring systems containing chlorine. If chlorine
is fed under its own vapor pressure, the primary cause of overpressure would
be overheating. Where chlorine is fed by nitrogen padding of a storage vessel
or through pumps or compressors, overpressuring could occur without overheat-
ing. Equipment failure without overpressure is possible if corrosion has
weakened process equipment. Temperature monitoring is important, not only
because of potential overpressure or equipment weakening due to overheating.
57
-------
TABLE 5-1. KEY PROCESS DESIGN CONSIDERATIONS FOR CHLORINE PROCESSES
Process Design Consideration
Process or Unit Operation
Contamination (with water and
organics especially)
Flow control of chlorine feeds
Temperature monitoring; heating
media flow control
Adequate pressure relief
pH control
Mixing
Temperature monitoring; cooling
media flow control
Corrosion monitoring
Temperature monitoring
All
All
Chlorination reactors, chlorine
vaporizer in any feed system
All
Bleach process
Bleach process, batch and continu-
ous stirred tank chlorination
Chlorination reactors, refriger-
ated storage
All
All
58
-------
but also because chlorine can react with many metals above a certain activa-
tion temperature. Conversely, chlorine can cool itself while off-gasing and
potentially reach temperatures below the safe operating range for some metals.
In addition, vessels containing liquid chlorine at room temperature or above
should be designed to be in the leak before fracture region over the entire
range of temperatures from the boiling point to maximum temperature and
pressure of the vessel.
5.3 PHYSICAL PLANT DESIGN
Physical plant design considerations include equipment, siting and
layout, and transfer/transport facilities. Vessels, piping and valves,
process machinery, instrumentation, and factors such as location of systems
and equipment must all be considered. The following subsections cover various
aspects of physical plant design beginning with a discussion of materials of
construction.
5.3.1 Equipment
Materials of Construction—
The two most important considerations in selecting materials for chlorine
service are the temperature and moisture content of the chlorine. The temper-
ature is important because the corrosiveness of chlorine increases with
increasing temperature, and most metals will ignite at a given temperature in
the presence of chlorine. The moisture content is also critical because,
though dry chlorine is noncorrosive Cat normal to moderate temperatures),
moist or wet chlorine is very corrosive to most metals.
Equipment construction materials must be chosen to prevent deterioration
or product contamination. Steel, cast iron, wrought iron, most copper alloys,
most nickel alloys, certain stainless steel, and lead are common materials of
construction for chlorine processes (1). Other materials which are resistant
to the corrosiveness of wet chlorine are titanium, nickel-copper and nickel-
59
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chromium-molybdenum alloys, high silica iron, platinum, silver, tantalum, and
zirconium. While titanium may be used with wet chlorine, it reacts rapidly,
even violently, with dry chlorine. Tantalum is inert with both wet and dry
chlorine up to 300°F (6). For handling wet chlorine at low pressures, suitable
materials include hard rubber, unplasticized polyvinyl chloride, polyvinylidine
chloride, fully-halogenated fluorocarbon resins, reinforced polyester resin,
or certain other non-metallics (6,11). Before one of these materials is chosen
the conditions and requirements of the chlorine system must be considered
carefully. Many of the non-metals can be used as lining materials in higher
pressure wet chlorine systems which require the strength of metals and the
chemical resistance of polymers. Chlorination vessels and reactors are often
constructed of fiberglass-reinforced plastic (FRP) or carbon steel lined with
a polymeric material.
Table 5-2 compares the corrosion resistance of a number of common metals
and alloys in the presence of dry chlorine (11). The usual material of
construction for dry chlorine at moderate temperatures is mild steel. How-
ever, since wet chlorine attacks this metal severely, it is essential to
exclude water from chlorine systems that use mild steel. The typical water
content of commercial chlorine is 20-60 ppm; this is considered acceptable
with the common materials of construction. The corrosiveness of chlorine on
mild steel also is temperature dependent. Corrosion of mild steel is signifi-
cant at 392°F and rapid at around 446°F. It is typical to restrict the use of
mild steel to applications where the chlorine temperature is below about 248°F
(1). Below 2A8°F, iron, copper, lead, nickel, platinum, steel, silver, and
tantalum are chemically resistant to dry chlorine gas or liquid (11).
Vessels—
The predominant vessels that are involved in chlorine service in the U.S.
include storage cylinders, fixed storage tanks, rail cars used for storage,
evaporators, and chemical reactors. The role of these vessels in chlorine
service was discussed in Section 3.
60
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TABLE 5-2. CORROSION OF METALS IN DRY CHLORINE
Approximate temperature (°F) at which given corrosion rate is exceeded in
short-time tests in dry CLn
nickel
Inconel
Hastelloy B
Hastelloy C
Hastelloy A
platinum
magnesium
Chromel A
Monel
18-8-Mo stainless steel
18-8 stainless steel
Hastelloy D
deoxidized copper
carbon steel
aluminum 2S
gold
cast iron
silver
0.0025 in.
per month
950
950
950
900
900
900
850
850
750
600
550
400
350
250
250
250
200
100
0.005 in.
per month
1,000
1.000
1,000
1.000
1.000
950
900
900
850
650
600
450
450
300
300
300
250
150
0.05 in.
per month
1.100
1.050
1.100
1.050
1.100
1.000
950
1.000
900
750
650
550
500
300
300
350
350
150
0.05 in.
per month
1.200
1,200
1.200
1,200
1.200
1.050
1,000
1,150
1,000
850
750
500
350
350
400
450
450
0.1 in.
per month
1,250
1,250
1,250
1.050
1.050
1.000
900
850
55°d
350*
350d
400
450°
500
These values are based on short-time laboratory tests under controlled conditions. They should
be interpreted only as being indicative of the limitations of the materials, and should not be
.used for estimation of the service life of equipment.
Ignites at about 601°F.
^Ignites at 450-500°F.
Ignites at 400-450°F.
Source: Adapted from Reference 10.
-------
Chlorine storage vessels likely to be encountered in the U.S. range in
size from 150-pound pressure cylinders to multi-thousand ton, spherical
refrigerated chlorine storage tanks. Because of the relatively large inven-
tories contained in chlorine storage vessels, they represent one of the most
hazardous aspects of a chlorine system. The vessels most commonly used for
transfer and storage of chlorine are well standardized and are described in
detail in various Chlorine Institute literature (23,24,25). These containers
include: cylinders up to 150-pound capacity, one-ton containers, 15-ton con-
tainers, single-unit tank cars (16, 30, 55, 85, and 90 tons capacity), 15- to
20-ton tank trucks, and 150- to 300-ton barge tanks. Up to about 450 tons of
chlorine may be stored safely in high strength tanks as a liquid under pres-
sure. Larger quantities are usually stored at atmospheric pressure as a
refrigerated liquid in single and double-walled horizontal cylindrical or
spherical vessels (6,11). Detailed design considerations are found in Chlo-
rine Institute Pamphlet 78: "Refrigerated Liquid Chlorine Storage" (24).
Rail cars in chlorine service must meet Department of Transportation
(DOT) Specifications (22).
Exact specifications for reactors used in bleach manufacture and organic
and inorganic chlorination processes are unavailable, but at a minimum the
reactors would be expected to conform to the ASME Unfired Pressure Vessel Code
since they are subject to pressurization with a gas.
Vaporizing equipment for chlorine is available in capacities ranging from
400 Ib/day to 10,000 Ib/day (25). Several types of vaporizers, including
electric heat, hot water, and steam types are used in chlorine service.
Detailed design considerations are available in Chlorine Institute Pamphlet 9:
"Chlorine Vaporizing Equipment" (25).
The Chlorine Institute specifies that chlorine vaporizing equipment must
be protected by a pressure relief device (25). In addition, vaporizers must
conform to the ASME Unified Pressure Vessel Code.
62
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For most chlorine vessels, overpressure protection is provided by an
adequate overpressure relief venting system which cannot be isolated from
service. The relief system should be sized for flashing liquid caused by:
• Fire exposure (NFPA 30);
• Thermal expansion,
• Internal reaction/decomposition, and
• Excess supply rates
Release prevention considerations for all vessels include prevention of:
overpressure, overfilling, overheating, and corrosion. With liquid chlorine,
overfilling and overheating are especially important because of the high
coefficient of thermal expansion associated with liquid chlorine.
Overpressure protection on vessels is provided by relief devices. These
devices provide protection against catastrophic rupture or explosion by
allowing a controlled release of overpressured contents. The types of devices
used depend on the vessel service and potential causes of overpressure.
Relief devices for overpressure caused by fire or other overheating of
150-pound cylinders and ton containers are usually fusible metal plugs which
melt between 158°F and 165°F. The normal service seen by cylinders or ton
containers does not usually require other overpressure protection on the
cylinders or ton containers themselves. When cylinders are padded with
nitrogen to pressure-feed chlorine at pressures above its vapor pressure,
overpressure protection should be provided in the nitrogen feed system. This
ensures that the nitrogen cannot exceed the working pressure of the chlorine
vessels or any parts of the downstream system connected to these vessels.
Chlorine cylinders and ton containers themselves are rated for several hundred
pounds per square inch (6). In addition, a check valve should be installed on
the nitrogen feed line to insure that no chlorine enters the nitrogen supply
system.
63
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Larger vessels are usually equipped with pressure relief valves and
rupture disks. A rupture disk upstream of a relief valve is a common config-
uration in chlorine service since chlorine tends to corrode pressure relief
valves. In addition to general provisions of good practices for the design
and sizing of relief devices (1). these devices should be sized according to
guidelines given by the Chlorine Institute as a minimum standard (26). These
guidelines include materials of construction, flow capacity, connections, and
relief system configuration.
Chlorine tank cars are equipped with spring-loaded safety relief devices
which have a breaking pin assembly designed to function at a specified pres-
sure. Tank trucks are similarly equipped.
It should be noted that while these devices are designed to prevent a
catastrophic sudden release of vessel contents, a significant release of
chlorine to the air could still occur. Protection from such an event might be
achieved if the relief device discharge were routed to a caustic scrubber.
Scrubber protection systems are discussed in Subsection 5.4 of this manual.
The pressure relief considerations discussed above also apply to chlorine
evaporators and reactors except that there is a greater likelihood of two-
phase flow in these cases. The effect of two-phase flow on relief device
design should be taken into account and could result in a design different
from that specified by the Chlorine Institute for relief devices on chlorine
storage systems.
Prevention of overfilling can be accomplished using level sensing de-
vices, pressure relief devices, and adequately trained personnel. Level
sensing devices for chlorine service must be selected while taking into
account the corrosiveness of chlorine, especially in contact with moisture.
Relief devices for overfilling may be the same or similar to those used for
gas pressure relief. The overfill relief would discharge to an overflow tank
or other suitable receiver. Consideration should be given to two-phase flow
64
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in the design of such relief systems. Protection against overpressure from a
tank with a domed or arched roof filled with liquid chlorine with little or no
vapor space can be provided by a short vented dip pipe. Relief from over-
pressure by liquid thermal expansion can be achieved with a relief device.
Because of the high coefficient of thermal expansion, the weight of
chlorine in a tank must not exceed the nominal chlorine capacity of the tank
or exceed 125% filling density (125% of the weight of water at 60°F that the
tank will hold). The Chlorine Institute recommends having two tanks, each 20
percent larger than the shipping tank. This allows continuous operation and
complete unloading of tank cars.
The Chlorine Institute provides guidelines on the materials of construc-
tion for stationary storage tanks (23). Except where the Institute indicates
otherwise, the tanks should be constructed according to parts UW and UCS of
the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. The tanks
usually are constructed of normalized carbon steel. To allow for corrosion,
the wall thickness should be 1/8 inch greater than that required by the design
formula in the Code. The tank should be designed so that it can accept a tank
car dome assembly. These assemblies can be purchased from chlorine tank car
manufacturers. In the event of leakage, these assemblies allow the use of
Chlorine Institute Emergency Kit "C" (6).
In addition to venting provisions, the containers should have valve
arrangements which allow the vessel to be isolated from the process to which
the chlorine is being fed. In addition, concerns about corrosion dictate that
moisture be excluded from the tanks. Tanks should not be situated in standing
water and care should be taken to prevent exposure to moist air such as
applying a moisture proof material to the outside of the vessel. External
corrosion can be as important as internal corrosion since air always contains
moisture and minor leaks could lead to equipment failure.
65
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A further concern is backflow of material into the storage vessels. When
chlorine is being absorbed in a liquid, the potential exists for the liquid to
be drawn back into the chlorine container. This has resulted in numerous
accidents. Such backflow can be prevented by a vacuum-breaking device or a
barometric leg, check valves, and positive displacement pumps, or combination
of the above (6).
Careful attention should be given to vessel corrosion; vessels in chlo-
rine service should be constructed of suitab'le materials of construction with
adequate corrosion allowances. Special attention should be given to welds and
to external corrosion under insulation.
Piping—
As with chlorine vessels, chlorine pipework design must reflect the
pressure, temperature, and corrosion concerns associated with the use of
chlorine. There are some general guidelines for both wet and dry chlorine
piping systems. The first is simplicity of design; the number of joints and
connections should be minimized. In addition to being securely supported,
pipes should be sloped, with drainage provided at the low points. Piping
should be constructed to allow room for thermal expansion of the pipe and
should be protected from exposure to fire and high temperatures. Valves
should be placed so that leaking pipes and equipment may be isolated, but no
section of piping should be isolable from some form of overpressure relief or
expansion chamber.
Piping and associated equipment should also be dry and grease- and
oil-free since chlorine can react vigorously with organic compounds. Valves
and instrumentation should be supplied by the manufacturer as "degreased and
dried for chlorine duty."
For dry chlorine systems, carbon steel pipe is commonly used. Carbon
steel such as ASTM A106 or seamless ASTM A53 is suitable in many cases.
Materials which are not recommended include aluminum, titanium, tin, ordinary
66
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grey iron, malleable iron fittings, general purpose valves, and porcelain
valves.
Chlorine Institute Pamphlet 6, "Piping Systems for Dry Chlorine" (26)
contains detailed information on materials of construction for pipes, fit-
tings, flanges, valves, gaskets, nuts, bolts, unions, and other components of
a dry chlorine system. Table 5-3 summarizes Chlorine Institute recommenda-
tions for piping materials for given operating temperature ranges.
A chief concern in liquid chlorine lines is overpressure due to thermal
expansion of the chlorine, or pressure pulses caused by rapid valve closure.
These pressures can rupture the pipes. Where applicable, an expansion cham-
ber, such as the one shown in Figure 5-1, may be installed to prevent a
rupture caused by thermal expansion. An expansion chamber device typically
consists of a rupture disc and a receiver chamber which can hold about 20-30%
of the capacity of the protected line. The chamber is equipped with a pres-
sure indicator or alarm switch set to function upon rupture. The chamber
should be constructed in accordance with Section VIII of the ASME Code for
Unfired Pressure Vessels (23). Sudden pressure pulses can be avoided by
selecting valves which do not close abruptly.
Another concern in liquid chlorine systems is low temperature toughness.
Materials must be carefully selected when temperatures are significantly below
ambient. The materials chosen should be resistant to brittle fracture over
the entire range of process conditions. The Chlorine Institute Pamphlet 6
(26) provides additional information on materials of construction for low
temperature operations.
The extremely corrosive nature of wet chlorine requires special corrosion
resistant materials depending upon the requirements and operating conditions
of the system. Wet chlorine is corrosive to all the common construction
metals; however, nickel-copper and nickel-chromium-molybdenum alloys are
widely used. Tantalum is inert to both wet and dry chlorine. Titanium can be
67
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TABLE 5-3. SUMMARY OF CHLORINE INSTITUTE PIPING MATERIAL RECOMMENDATIONS
Phase
Gas
Gas, Liquid
Gas, Liquid
Gas, Liquid
Temperature
Range (°F)
-20 to 300
-20 to 300
-50 to 300
-150 to 300
Maximum
Pressure
(psia)
<150
<300
<300
£300
Pipe Specifications
Sched-
System
Class8 150, Carbon Steel
Class8 300, Carbon Steel
Class 300. Alloy Steel
Class 300, Alloy Steel
Size
3/4 - 1-1
2-6
3/4 - 1-1/2
2-6
—
—
ule
80
40
80
80
—
—
ASTM Grade
A53 A.B
A106 A.B
A53 A.B
A333 1
A333 3
Type
S
S
S
oo
Source: Adapted from Reference 26.
ANSI Class refers to pressure ratings at specified temperature as set by the American National
Standards Institute (ANSI). For a carbon steel flange. Class 150 means a 150 psig pressure rating
at 500°F, and Class 300 means a 300 psig pressure rating at 850°F.
-------
00
in
•6-3/4"
expansion
" chamber
liquid
chlorine
line
pressure switch with
'protective diaphragm
reducing ell
rupture disk
Figure 5-1. Liquid chlorine expansion chamber for liquid chlorine only.
(Exact specifications for materials and fittings are provided
in Reference 2. Substitutions should not be made without
consultation with a recognized authority on chlorine system
design and construction,)
69
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used with wet chlorine, but reacts violently with dry chlorine. Lined pipes
can be used if the lining materials are chosen according to the operating
conditions. Some polymer lining materials which are inert to chlorine in-
clude: tetrafluoropolyethylene. polyvinylidine fluoride, and ethylene chloro-
trifluoro-ethylene. Polymeric materials which may be used in chlorine service
for limited purposes include polyvinylidine chloride, polyvinyl chloride,
chlorinated polyvinyl chloride, acrylonitrile butadiene styrene, polyethylene,
polypropylene fiberglass-reinforced polyester, and hard rubber (6,26). If
lined pipes are used, it is important that* the integrity of the lining be
maintained. Penetration of chlorine through the liner could lead to insidious
undetected pipe wall corrosion beneath the liner.
Many of the considerations for piping also apply to valves. Valves for
chlorine service should be strong enough to withstand the expected pressure,
resistant to corrosion, easy to remove and maintain, and should have a
leak-tight gland or be leakproof such as a diaphragm or bellow-sealed valves.
Table 5-4 provides a summary of guidelines for valve selection (26).
Ball and plug valves must be designed so that excess pressure in the body
cavity (as well as in the ball or plug) will relieve spontaneously toward the
high pressure side. This is accomplished by 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. 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 (26). All valves
must be supplied and maintained dry as well as grease— and oil-free.
Because of the corrosiveness of chlorine, spring-loaded or gravity-
operated check valves may not be suitable to prevent backflow. Instead,
power-operated control valves with suitable instrumentation may be preferable
for primary service with a check valve backup (26).
70
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TABLE 5-4. SUMMARY OF CHLORINE INSTITUTE GUIDELINES FOR VALVES
Maximum
Chlorine Temperature Pressure Valve Rating
Phase Range (°F) (psia) Type (Ib) Class Connection Material
Gas -20 to 300 £300 Globe 800 - Screwed Forged Steel
Ball 300 - Screwed Cast Steel
Plug 300 - Screwed Ductile Iron
Globe - 150 Flanged Cast Steel
Ball - 150 Flanged Ductile Iron
Plug - 150 Flanged Ductile Iron
Gas. Liquid -20 to 300 £300 Globe 800 - Screwed Forged Steel
Ball 800 - Screwed Cast Steel
Plug 300 - Screwed Ductile Iron
Globe - 300 Flanged Cast Steel
Ball - 300 Flanged Cast Steel
Plug - 300 Flanged Cast Steel
Source: Adapted from Reference 26.
-------
Excess flow valves are used in chlorine vessels, tank cars, and areas
where unintentional high liquid discharge rates need to be prevented. In the
event that a liquid discharge line is broken, the resulting high flow rate
would cause the valve to close off, restricting the escape of chlorine. The
Chlorine Institute has detailed information on valve materials, designs, and
size for excess flow valves (22).
For maintenance and emergencies, it is often useful to be able to isolate
vessels and other chlorine process equipment. In some cases, however, a
single valve is 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 chlorine, proper training is essential to
ensure safe operation of these isolation techniques.
Process Machinery—
Process machinery refers to rotating or reciprocating equipment that may
be used in the transfer or processing of chlorine. This includes pumps and
compressors which may be used to move liquid or gaseous chlorine where gas
pressure padding is insufficient or inappropriate.
Pumps—Many of the concerns and considerations for chlorine piping and
valves also apply to pumps. To assure that a given pump is suitable for
chlorine service, the system designer should obtain information from the pump
manufacturer certifying that the pump will perform properly in this applica-
tion.
Pumps should be constructed with materials which are resistant to chlo-
rine at operating temperatures and pressures. They should be installed dry
and oil-free. It is especially important that their design not allow chlorine
or lubricating oil to enter seal chambers where they may contact one another.
Net positive suction head (NPSH) considerations are especially important for
chlorine since pumping the liquid near its boiling point may be common (chlo-
rine is a gas at typical ambient conditions). The pump supply tank should
72
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have high and "low level alarms; the pump should be interlocked to shut off at
low supply level or low discharge pressure. External pumps should be situated
inside a diked area and should be accessible in the event of a tank leak.
In many cases, the potential for seal leakage rules out the use of
rotating shaft seals. One solution is to use pump types which isolate the
seals from the process stream. The seals are typically cartridge canister
double type (27). The buffer fluid between the mechanical seal is commonly
light oil. Another solution is to use pump types which eliminate shaft seals
altogether such as canned-motor, vertical extended-spindle submersible,
magnetically-coupled, and diaphragm pumps (27).
Canned motor pumps are centrifugal units in which the motor housing is
interconnected with the pump casing. Here, the process liquid actually served
as the bearing lubricant. An alternative concept is the vertical pump often
used on storage tanks. Vertical pumps consist of a submerged impeller housing
connected by an extended drive shaft to the motor. The advantages of this
arrangement are that the shaft seal is above the maximum liquid level (and is
therefore not made wet by the pumped liquid) and the pump is self priming
because the liquid level is above the impeller.
The Chlorine Institute suggests that vertical pumps be provided with
double packed seal chambers which are designed to prevent contact of chlorine
and any reactive material. Seal gas should be dry, oil-free, and inert to
chlorine. They recommend that the seal gas pressure be at least 10 psi over
tank pressure, and that a seal gas back-up system be considered (26).
Magnetically-coupled pumps replace the drive shaft with a rotating
magnetic field as the pump-motor coupling device. Diaphragm pumps are
positive displacement units in which a reciprocating flexible diaphragm drives
the fluid. This arrangement eliminates exposure of packing and seals to the
pumped liquid.
73
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Centrifugal pumps often have a recycle loop back to the feed container
which prevents overheating in the event that the pump is deadheaded (i.e., the
discharge valves close). This is an important consideration in chlorine
systems since the corrosiveness of chlorine increases rapidly with increasing
temperature. Deadheading also is a concern with positive displacement pumps.
To prevent rupture, positive displacement pumps commonly have a pressure
relief valve which bypasses to the pump suction. Because of the probability
of eventual diaphragm failure, the use of diaphragm pumps should be carefully
considered in view of this hazard potential.
Pumps are not always necessary; in many circumstances, liquid chlorine is
moved by pressure padding. With chlorine cylinders and ton containers, the
liquid may be displaced from the vessel by the force of chlorine vapor pres-
sure. As discussed earlier, this process is temperature dependent. With
other types of vessels, an inert gas such as dry nitrogen may be used to force
liquid from the tank. Padding system designs must reflect the operating
conditions and limitations (e.g.. required flow rate) and therefore must be
custom designed for a process.
Compressors—Chlorine compressors include reciprocating, centrifugal,
liquid-ring rotary, and non-lubricated screw compressors. Detailed descrip-
tions of these compressors may be found in the technical literature (5).
Like pumps, compressors have the potential for heat buildup and shaft
seal leakage. Heat sources in a compressor include the heat of compression as
well as the heat generated through mechanical friction. Heat buildup in
chlorine compressors is a particular concern because chlorine corrosion
increases with increasing temperature. Most multistaged compressors can be
equipped with intercoolers which limit heat buildup and increase compressor
efficiency by reducing the volume of gas going to the next compression stage.
Both air and water cooling are used, but water systems must be designed to
prevent leakage and mixing of water and chlorine gas.
74
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While it is often possible to avoid using rotary shaft seals with chlo-
rine pumps, compressors in chlorine service usually require special seals such
as double labyrinth seals. These seals have a series of interlocking touch
points which, by creating many incremental pressure drops, reduce total
leakage. To further reduce leakage, dry air is injected into the seal. In
the event of deadheading, a compressor discharge can have a pressure relief
mechanism which vents to the compressor inlet or to a scrubber system. The
former appears to be satisfactory for a short term downstream flow interrup-
tion. Where a sustained interruption might occur, relief to a scrubber system
would be safer.
Miscellaneous Equipment—
Pressure Relief Devices—For transportation equipment, the Chlorine
Institute has drawings and specifications for chlorine relief valves. For
vessels, an acceptable relief valve is of angle body construction with a
closed bonnet and a screwed cap over the adjusting screw. These valves
normally are used in combination with a rupture disc or a breaking pin assem-
bly. Typical valve construction materials include a cast carbon steel body; a
nickel-plated steel spring; and nickel-copper or nickel-chromium-molybdenum
alloy nozzle, disc adjusting ring, nozzle ring, and spindle guide. The inlet
flange should be Class 300 and the outlet flange should be Class 150 or 300.
Valves of this construction which also have Viton® "0" ring seat seals need
not have a rupture disc or breaking pin. Other types of pressure relief
devices are acceptable as long as they are constructed of materials suitable
for chlorine service and meet the general requirements of the ASME boiler and
Pressure Vessel Code, Section VIII, Division 1 (26).
Rupture discs are constructed of chlorine resistant materials such as
silver, tantalum, or impervious graphite. Impervious graphite rupture discs
fragment upon overpressure and therefore should not be used in conjunction
with relief valves. Connections smaller than two inches can be screwed,
flanged or socket-welded; connections two inches or larger should be flanged
75
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or butt-welded. The flanges should be constructed of forged carbon steel and
be rated in accordance with their associated piping system. Because operating
pressures exceeding 70% of disc burst pressure may induce premature failure, a
considerable margin should be allowed when sizing rupture discs. When it is
possible to draw a vacuum on the disc, supports should be provided (25).
Measures should be taken to ensure that process equipment is not isolated
from its relief system. To provide continuous pressure relief protection.
when a device is out of service for maintenance, equipment may be provided
with dual relief systems, each sized to provide the total required flow
capacity. Piping and valves should be arranged so that one of the systems
always provides protection. Stop valves installed between a vessel and its
relief device should have a full port area that is at least equal to that of
the pressure relief device inlet. These valves should be locked open or have
handles removed when the protected vessel is in use. If the discharge is to
be piped to a closed disposal system, such as a scrubber, the pressure drop
caused by the additional piping must be considered and the relief device sized
accordingly. Relief device sizing guidelines are provided in Chlorine Insti-
tute Pamphlet 5 (23).
Instrumentation—A primary consideration for instrumentation in chlorine
service is corrosion resistance. Diaphragm pressure switches usually have a
diaphragm constructed of silver, tantalum, or nickel-copper alloy. The upper
body seal is steel, and the lower body seal is steel or nickel-copper alloy.
Direct reading pressure gauges often have a nickel-copper alloy bourdon tube.
The pressure range for both types of pressure measurement devices should be
twice the operating pressure (26). Other instrumentation, such as temperature
and flow measurement devices, also should be constructed of chlorine resistant
materials.
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5.3.2 Plant Siting and Layout
The siting and layout of a particular chlorine facility is a complex
issue which requires careful consideration of numerous factors. These in-
clude: other processes in the area, the proximity of population centers,
prevailing winds, local terrain, and potential natural external effects such
as flooding. The rest of this subsection describes general considerations
which might apply to siting and layout of chlorine facilities.
Siting of facilities or individual equipment items should be done in a
manner that minimizes 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. The site 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 hazards of re-
leases. Large distances between large inventories and sensitive receptors is
desirable.
Layout refers to the placement and arrangement of equipment in the
process facility. Some general layout considerations include the following:
• Large inventories of chlorine should be kept away from
sources of fire or explosion hazard;
• Vehicular traffic should not go too near chlorine 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 chlorine across
or next to roadways;
77
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• Chlorine piping preferably should not be located adjacent
to other piping which is under high pressure or tempera-
ture, or which carries flammable materials;
• 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
• 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 chlo-
rine (1). These techniques provide for a systematic evaluation of key siting
and layout factors.
Because heat increases chlorine corrosiveness and causes thermal expan-
sion of liquid chlorine, measures should be taken to situate piping, storage
vessels, and other chlorine equipment to minimize heat exposure. Hot process
piping, equipment, steam lines, and other sources of direct or radiant heat
should be avoided. Storage should also be situated away from control rooms,
offices, utilities, storage, and laboratory areas. Special precautions should
be taken to keep chlorine storage vessels away from potential fire or explo-
sion sources.
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. Dikes reduce evaporation while containing the liquid. It
is also possible to equip a diked area to allow drainage to an underground
containment sump. This sump would be vented to a scrubber system for safe
discharge. A full containment system using a specially constructed building
78
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vented to a scrubber is another possible option. This type of secondary
containment could be considered for large volume, liquid chlorine storage
tanks. However, secondary hazards abound with such a system, and extreme care
in layout and design are required to protect the operators.
5.3.3 Transfer and Transport Facilities
Transfer and transport facilities where both road and rail tankers are
loaded or unloaded are likely accident areas because of vehicle movement and
the intermittent nature of the operations. Therefore, special attention
should be given to the design of these facilities.
As mentioned in the previous section, tank car and tank truck facilities
should be located away from potential sources of heat, fire, and explosion.
Equipment in these areas should also be protected from impact by vehicles and
other moving equipment. These tank vehicles should be securely moored during
transfer operations; an interlocked barrier system is commonly used. Suffi-
cient space should be available to avoid congestion of vehicles or personnel
during loading and unloading operations. Vehicles, especially trucks, should
be able to move into and out of the area without reversing. High curbs around
transfer areas and barriers around equipment should be provided to protect
equipment from vehicle collisions.
When possible, the transfer of chlorine should be made using fixed rigid
piping. In situations which require flexible hoses or tubes, precautions must
be taken to ensure sound connections. The use of breakaway valves with
autoclosing shutoff valves should also be considered to prevent pullaway type
accidents. Avoiding cross contamination of chemical materials is also a key
concern which is sometimes addressed by having dedicated pipe lines or hoses
designed so that interconnections with inappropriate lines are not possible.
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5.4 PROTECTION TECHNOLOGIES
This subsection describes two types of protection technologies for
containment and neutralization. These are:
• Enclosures; 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 chlorine
spilled or vented from storage or process equipment, thereby preventing
immediate discharge of the chemical to the environment. The enclosures
contain the spilled liquid or gas until it can be transferred to other con-
tainment, discharged at a controlled rate which would not be injurious to
people or the environment, or transferred at a controlled rate to scrubbers
for neutralization.
The use of specially designed enclosures for either chlorine 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 litera-
ture, along with the opposing idea that sometimes enclosure may be appropriate
(1) . The desirability of enclosure depends partly on the frequency with which
personnel must be involved with the equipment. A common design rationale for
not having an enclosure where toxic materials are used is to prevent the
accumulation of toxic concentrations 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 whenever
lethal or flammable concentrations are detected.
80
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Care must be taken when an enclosure is built around pressurized
equipment. It would not be practical to design an enclosure to withstand the
pressures associated with the sudden release 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 appear to be suitable for chlo-
rine are concrete block or concrete sheet buildings, or bunkers. Chlorine
reactivity may preclude buildings of metal or wood. An enclosure would have a
ventilation system designed to draw in air when the building is vented to a
scrubber. The bottom section of a building used for stationary storage con-
tainers should be liquid tight to retain any liquid chlorine that might be
spilled. Buildings around rail tank cars used for storage do not lend
themselves well to effective liquid containment. However, containment could
be accomplished if the floor of the building is 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 chlorine 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 Scrubbers
Scrubbers are a traditional method for absorbing toxic gases from process
streams. These devices can be used to control chlorine releases-'from vents
and pressure relief discharges from storage equipment, process equipment, or
secondary containment enclosures.
81
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Chlorine discharges could be contacted with an aqueous scrubbing medium
in any of several types of scrubbing devices. An alkaline solution is required
to achieve effective absorption because absorption rates with water alone
would require unreasonably high liquid-to-gas ratios. However, water scrub-
bing could be used in a make-shift scrubber in an emergency if an alkaline
solution were not available. Typical alkaline solutions for an emergency
scrubber are presented in Table 5-5.
Types of scrubbers that might be appropriate include spray towers, packed
bed scrubbers, and Venturis. Other types of special designs might be suit-
able, but complex internals subject to corrosion do not seem, to be advisable.
Whichever type of scrubber is selected, a key consideration 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. Some typical
absorption data for a packed scrubber used for chlorine are presented in Table
5-6.
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 contin-
uous circulation of scrubbing liquor through the system. This may be practical
where the emergency scrubber also serves as a routine vent scrubber. For many
facilities this would not be practical, and the scrubber system might be tied
into a trip system which would turn it on when needed. However, with this
system a quantity of chlorine would be released prior to actuation of the
scrubber (i.e., starting up a blower and turning on the flow of liquid).
The scrubbing 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
82
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TABLE 5-5. TYPICAL ALKALINE SOLUTION FOR CHLORINE SCRUBBING
Caustic Soda Soda Ash Hydrated Lime
Container Capacity 100% Water, Water, Water,
(Ib) (Ib) (gal) (Ib) (gal) (Ib) (gal)
100 125 40 300 100 125 125
150 188 60 450 150 188 188
2,000 2,500 800 6,000 2,000 2,500 2,500
Source: Reference 6
Hydrated lime solution must be continuously agitated to ensure aqueous
mixture.
83
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TABLE 5-6. TYPICAL CHLORINE ABSORPTION DATA
Size of
Packed Tower
Liquid Rate
[lb/(hr-ftZ)]
Overall Mass
Transfer Coefficient
KLa (lb-mole)/[hr-ft3-
mole fraction solute
in liquid]
Height of
Transfer Unit
Basis: Packed tower, 1-inch rings, operating at 70°F.
Source: Adapted from Reference 28.
H
OL
(ft)
4-inch diameter 1,000
2,000
A. 000
6.000
10,000
15.000
20,000
14-inch diameter 1,000
2,000
4,000
6.000
10.000
15,000
20,000
14
20
30
38
50
61
74
11
16
24
30
40
48
59
1.3
1.7
2.3
2.6
3.2
3.6
4.2
1.6
2.1
2.8
3.3
4.0
4.6
5.5
84
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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
internals.
Design of emergency scrubbers can follow standard techniques discussed in
the literature, carefully taking into account the additional considerations
just mentioned. An example of the sizing of an emergency packed bed scrubber
is presented in Table 5-7. This example provides some idea of the size of a
typical emergency scrubber for various flow rates. This is an example only
and should not be used as the basis for an actual system which might differ
based on site specific requirements.
Another approach is the drowning tank, where the chlorine 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. How-
ever, 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. In addition, pre-
cautions must be taken to prevent backflow of the scrubbing liquid through the
lines to a chlorine containing vessel since explosions can occur. Such an
event could occur as a result from overflowing of the scrubber.
5.5 MITIGATION TECHNOLOGIES
If, in spite of all precautions, a large release of chlorine 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
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TABLE 5-7. EXAMPLE OF PERFORMANCE CHARACTERISTICS FOR AN EMERGENCY
PACKED BED SCRUBBER FOR CHLORINE
Basis: Inlet stream of 50% Cl. in 50% air.. Constant gas flow per unit
cross-sectional area or 290 scfm/ft .
Packing: 2-inch plastic Intalox® saddles.
Pressure Drop: 0.5-inch water column
Scrubbing Medium: 8% (wt) NaOH solution
Removal Efficiency, % 50 90
Liquid-to-Gas Ratio
(gal/thousand scf)
—at flooding 240 240
—operating 144 144
Packed Height, ft. 1.3 4.4
Column Diameter and Cooresponding Gas Flow Rates for Both Removal Efficiencies
Column
Diameter Flow Rate
(ft) (scfm)
0.5 60
1.0 240
2.0 960
6.6 10,000
86
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release should be determined, and the leak should be stopped., if this is
possible. The next primary concern become reducing the consequences of the
released chemical to the plant and the surrounding community. Reducing the
consequences of an accidental release of a hazardous chemical is referred to
as mitigation. Mitigation technologies include such measures as physical
barriers, water sprays and fogs, and foams where applicable. The purpose of a
mitigation technique is to divert, limit, or disperse the chemical that has
been spilled or released to the atmosphere in order to reduce the atmospheric
concentration and the area affected by the chemical. The mitigation technol-
ogy chosen for a particular chemical depends on the specific properties of the
chemical including its flammability, toxicity, reactivity, and those proper-
ties which determine its dispersion characteristics in the atmosphere.
If a release occurs from a pressurized chlorine storage tank above the
boiling point, a quantity of liquid will immediately flash off as vapor, while
the remaining liquid will be cooled to the normal boiling point of -29.3°F.
Heat transfer from the air and ground will result in further vaporization of
the released liquid. Since the chlorine accidentally released from a refri-
gerated storage tank is already at or below its normal boiling point, a
comparable quantity of vapor will not flash off, as with the pressurized
release discussed above, but heat transfer from the environment will cause
evaporation and the formation of a vapor cloud. It is therefore desirable to
minimize the area available for heat transfer to a liquid spill which in turn
will minimize the rate of evaporation. Mitigation technologies which are used
to reduce the rate of evaporation of a released liquified gas include secon-
dary 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.
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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 chlorine 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 with minimum potential for escalation of the event.
Secondary containment systems for chlorine 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
• A diked area, with a capacity as large as the largest tank served.
These measures are designed to prevent the accidental discharge of liquid
chlorine from spreading to uncontrolled areas.
The most common type of containment system is a low wall dike surrounding
one or more storage tanks. Generally, no more than three tanks are enclosed
within one diked area to reduce risk. Dike heights usually range from three
to twelve feet depending on the area available to achieve the required volume-
tric capacity. The dike walls should be liquid tight and able to withstand
the hydrostatic pressure and temperature of a spill. Low wall dikes may be
constructed of steel, concrete or earth. If earthen dikes are used, the dike
wall must be constructed and maintained to prevent leakage through the dike.
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
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dikes to provide additional vapor containment. If there is more than one tank
in the diked areas, the tanks should be situated on berms above the maximum
liquid level attainable in the impoundment.
A low wall dike can effectively contain the liquid portion of an acciden-
tal release and keep the liquid from entering uncontrolled areas. By prevent-
ing the liquid from spreading, the low wall dike can reduce the surface area
of the spill. Reducing the surface area will reduce the rate of evaporation.
The low wall dike will partially protect the spill from wind; this can reduce
the rate of evaporation. A dike with a vapor fence will provide extra protec-
tion from wind and will be even more effective at reducing the rate of evapor-
ation.
A low wall dike will not reduce the impact of a gaseous chlorine release.
A dike also creates the potential for chlorine and trapped water to mix in the
dike, which may accelerate the rate of evaporation and form highly corrosive
hydrochloric and hydrochlorous acids. If materials that would react violently
with chlorine are stored within the same diked area then the dike will increase
the potential for mixing the materials in the event of a simultaneous leak. A
dike also limits access to the tank during a spill.
A remote impounding basin is well suited to storage systems where more
than one tank is served and a relatively large site is available. The flow
from a chlorine 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 chlo-
rine, the trenches that lead to the remote impounding basin as well as the
basin itself should be covered to reduce the rate of evaporation. Addi-
tionally, the impounding basin should be located near the tank area to minimize
the amount of chlorine that evaporates as it travels to the basin.
This type of system has several advantages. The spilled liquid is removed
from the immediate tank area. This allows access to the tank during the spill
and reduces the probability that the spilled liquid will damage the tank.
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piping, electrical equipment, pumps or other equipment. In addition, the
covered impoundment will reduce the rate of evaporation from the spill by
protecting the spill from wind or heating from sunlight.
A limitation of a remote impounding basin is that there is still the
potential for water or other incompatible materials to be trapped in the
impoundment and mix with the incoming chlorine. Remote impounding basins do
not reduce the impact of a gaseous chlorine release.
Although few authorities for chlorine facilities require them, 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. May-imum 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 contact area. 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 annual space remaining open to the atmosphere. The
available area surrounding the storage tank will dictate the minimum height of
the wall. For high wall impoundments, the walls may be designed with a volu-
metric 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 pip penetration and pump may be provided, or a low dike may be placed
around the entire wall.
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An example of the effect of diking as predicted by one vapor dispersion
model is shown in Figure 5-2 (29). With diking, the predicted maximum IDLH
exposure occurs at a distance of 1.195 feet at 6 minutes after release.
Without diking, the predicted maximum IDLH exposure occurs at a distance of
2,802 feet at 12 minutes after exposure.
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
the structure, the difficulty of access to certain components, and the fact
that complete vapor containment cannot be guaranteed for all potential events.
Provision should be made for drainage of rainwater from diked areas.
This will involve the use of sumps and separate drainage pumps, since direct
drainage to stormwater sewers would presumably allow any spilled chlorine to
follow the same route. Alternatively, a slope rain hood may be used over the
diked area which could also serve to direct the rising vapors to a single
release point (30). 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 trans-
fer from the environment to the spilled liquid. the floor of an impoundment
should be sealed with a clay blanket to prevent the chlorine from seeping into
the ground; percolation into the ground causes the ground to cool more quickly,
increasing the vapor generation rate. Absorption of the chlorine into water
in the soil would also release additional heat.
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PPM
LE9END:
> 28.0
> 1OO.
> i.oooe+oa PPM
0 .5
miles
1
mile
1.5
miles
2
miles
Release from a tank surrounded by a 25 ft. diameter dike.
Elapsed Time: 6 minutes
LESEND:
> 2B.O
> 280. PPM
> 2.BOOE+OS PPM
0 .5
miles
1
mile
1.8
mi les
2
ml les
Release from a tank with no dike.
Elapsed Time: 12 minutes
Common Release Conditions:
o
Storage Temperature = 29.3 F
Storage Pressure = 14.7 psia
Ambient Temperature = 85°F
Wind Speed = 10 mph
Atmospheric Stability Class = C
Quantity Released = 5,000 gallons
through a 2-inch hole
Figure 5-2. Computer Model Simulation Showing the Effect of Diking on the Vapor
Cloud Generated From a Release of Refrigerated Chlorine.
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5.5.2 Flotation Devices and Foams
This subsection discusses the applicability, availability, and effective-
ness of additional mitigation technologies for use in reducing the surface
area of spilled chlorine and thereby minimizing the amount of toxic vapor
released to the surrounding environment.
Flotation Devices—
Placing an impermeable flotation device over a spilled chemical is a
direct approach for containing toxic vapors with nearly 100 percent effi-
ciency. However, being able to use such devices requires acquisition in
advance of a spill and storage until needed. In addition, deployment may be
difficult in all but small spills.
Although such devices are potentially effective, no systems are currently
available for use in mitigating chlorine spills. The primary deterrent to
their use is the cost associated with material and dispersal equipment. Such
a system would require the dispersal of a minimum of 280 particles per square
foot of spill surface (30). Based on 1986 prices, material costs would be
approximately $100 per square foot, with dispersal equipment costs running 100
times this cost (31).
Foams—
One approach to a chlorine spill is dilution of chlorine with water.
However, chlorine is only slightly soluble in water and a large quantity would
be required for dilution. In addition, dilution of chlorine with water results
in the formation of highly corrosive hydrochloric and hydrochlorous acids. As
such, the Chlorine Institute states that water should never be sprayed directly
on a chlorine leak since water will make the leak worse (6). A water-based
foam cover provides an alternative means of diluting the chlorine.
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
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a function of the chemical spilled, foam type, spill size, and atmospheric
conditions. With regard to liquified gases, it has been found that with some
materials, foams have a net positive effect, but with others, foams may exag-
gerate the hazard.
Several studies of the effect of foam on chlorine have been conducted in
the past (32,33). These studies have given mixed results. Although much
information has yet to be determined, it has been shown that for the current
grades of commercially available foam systems (i.e., protein-derived material
and surfactant-based concentrates), application of foam to liquid chlorine
results in rapid destruction of the foam along with a gross exaggeration of
the boil-off rate (32,34). This effect may last through several successive
applications depending on the type of foam, the expansion, and the rate of
application.
As foam is applied, the interaction of the chlorine and the collapsing
foam results in the formation of a layer of ice and chlorine hydrate that
tends to float on the chlorine surface (34). As the foam application is con-
tinued, this layer eventually becomes continuous and a foam covering can then
be built on top of the chlorine surface. When this occurs, a reduction in the
downwind concentration can be achieved as a result of a slowing of the release
rate of chlorine vapor (34).
Sufficient data are not presently available to define the variables needed
to implement such a system (i.e., best foam type, expansion type, application
rate, and duration of application). Based on preliminary research studies,
medium expansion expansion foams (300 to 350:1) appear to work best, but low
expansion foams have also shown some benefit (34). The results of a labora-
tory test program conducted by the Mine Safety Application (MSA) Research
Corporation (32) to evaluate the applicability and effectiveness of various
foams for various hazardous chemicals including chlorine is presented in Table
5-8 (32).
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TABLE 5-8. FOAM CAPABILITIES TO SUPPRESS OR MINIMIZE THE RELEASE OF TOXIC
VAPORS FROM A CHLORINE SPILL
Foam Type Capability
Low-expansion surfactant Acceptable in some situations
High-expansion surfactant Acceptable in some situations
Protein Acceptable in some situations
Fluoroprotein Acceptable in some situations
Alcohol Unsuitable
Aqueous film-forming foams (AFFF) Unsuitable
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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 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 perfor-
mance.
Even if the vaporization rate of chlorine is substantially reduced within
a short time after a spill, a vapor cloud will still be formed which poses a
serious threat to life and limb downwind. Dispersion and/or removal of the
chlorine vapor in the atmosphere is the subject of the following section.
5.5.3 Mitigation Techniques for Chlorine Vapor
The extent to which the escaped chlorine vapor can be removed or dis-
persed in a timely manner will be a function of the quantity of vapor
released, the ambient conditions, and the physical characteristics of the
vapor cloud. The behavior and characteristics of the chlorine cloud will be
dependent on a number of factors. These include the physical state of the
chlorine before its release, the location of the release, and the atmospheric
and environmental conditions. Many possibilities exist concerning the shape
and motion of the vapor cloud, and a number of predictive models of dispersion
have been developed. As a result of the higher specific gravity of pure chlo-
rine, large accidental releases of chlorine will often result in the formation
of chlorine-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 possible means of dispersing as well as removing toxic vapors from
the air is with the use of water sprays or fogs. The low solubility of chlo-
rine in water, however, limits the effectiveness of such systems for chlorine
removal from the air. An alternative is to use a mild aqueous alkaline spray
system such as an ammonia injected water spray system which would act as a
neutralizing agent. Although such systems do not appear to be widely used for
the mitigation of chlorine vapor, they are used for other toxic chemicals of
similar nature (35).
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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 nozzle
from the point of release, the fog pattern, nozzle flow rate, pressure, and
nozzle rotation. If water sprays are used to mitigate chlorine vapors from a
diked area containing spilled liquid chlorine, great care must be taken not to
direct water into the liquid chlorine itself.
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 Beresford (36). Although such systems, have not been
used for the mitigation of chlorine vapor, they have been effectively used for
other toxic chemicals of similar nature (36).
The method consists of coarse water sprays discharging upwards from the
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 include large volumes of air
at ground level as the water discharges upwards (36). 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 pre-
sented in Beresford (36). 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. 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.
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In general, techniques used to disperse or control vapor emissions should
emphasize simplicity and reliability. In addition to the mitigation techniques
discussed above, physical barriers such as buildings and rows of trees may
help to contain the vapor cloud and control its movement. A presentation of
additional information will be found in a manual on control technologies, part
of this manual series.
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 poli-
cies 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 chlorine
releases. Within the chlorine industry, these procedures and practices vary
widely because of difference 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 com-
pany functions such as production and sales. The effectiveness of any safety
program, however, is determined by a company's commitment to it, as demon-
strated throughout the management structure. Specific goals must be derived
from the safety policy and supported by all levels of management. Safety and
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loss prevention should be an explicit management objective. Ideally, manage-
ment should establish the specific safety performance measures, provide incen-
tives for attaining safety goals, and commit company resource 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
(1.37):
• Ensuring worker competency;
• Developing and enforcing standard operating procedures;
• Adequate documentation of policy and procedures;
• 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 also a key factor in the
prevention of accidental chlorine releases. Many case studies documenting
industrial incidents note the contribution of human error to accidental
releases (1). Release incidents may be caused by using improper routine
operating procedures, 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
99
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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 impor-
tant 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 characteristics of
the plant management system, and tradition.
Some general characteristics of quality industrial training programs
include:
• 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, rou-
tine operations, and upsets, emergencies, and accidental
releases; and
• Frequent supplemental training and the use of up-to-date
training materials.
In many instances, training is carried our 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
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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 of differences in employee turn-
over.
A list of the aspects typically involved in the training of process
operators for routine process operations is presented in Table 5-9.
Emergency training includes topics such as:
• Recognition of alarm signals;
• Performance of specific functions (e.g., shutdown switches);
• 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 (1,37):
• 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
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TABLE 5-9. 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, record-keeping, reporting
Source: Reference 1.
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- 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.
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 (1):
• 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
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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 (1).
Permit systems and up-to-date maintenance procedures minimize the poten-
tial for accidents during maintenance operations. Pennit-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.
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 (1).
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.
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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 (1,37).
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.
The use and availability of clearly defined procedures collected in
maintenance 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 (38,39). 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
(1). Several authors think industrial plant operating manuals should include
(1.37,38,39):
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• Process descriptions*
• A comprehensive safety and occupational health section,
• Information regarding environmental controls,
• Detailed operating instructions, including startup and shut-
down procedures,
• Upset and emergency procedures.
• Sampling instructions,
• 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
itenrs 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) (1). Full
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documentation of the maintenance required for protective devices is a particu-
larly 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 may involve numerous combinations of
process design, equipment design, and operational measures, are especially
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
5-10 summarizes what appear to be major design, equipment, and operational
measures applicable to the primary hazards identified for the chlorine appli-
cations in the United States. The items listed in Table 5—10 are for illus-
tration only and do not necessarily represent satisfactory control options 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 appro-
priate. Each case must be evaluated individually. A presentation of more
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TABLE 5-10. EXAMPLES OF MAJOR PREVENTION AND PROTECTION MEASURES
FOR CHLORINE RELEASES
Hazard Area
Prevention/Protection
External fire
Line, pipe, and valve
failure
Flexible connection
failures
Fusible plug failure
Human error
Container failure
Vehicular collisions
Water intrusion
Corrosion
Excess chlorine
rates
Overheated
reactor
Water sprays to cool exposed chlorine
storage vessels; siting away from
flammables; refrigeration systems;
heat shield
Replacement of copper with Monel in
small lines; more frequent
inspections and maintenance
Minimized use; higher quality
components; operator training in
proper assembly
Inspection/certification; storage in
a containment building
Increased training and supervision;
use of checklists; use of automatic
systems
Adequate pressure relief; inspection
and maintenance; corrosion
monitoring; siting away from fire and
mechanical damage
Location; physical barriers; warning
signs; training
Pad gas drying; backflow prevention;
equipment purging with dry gas
Inspections, maintenance, and
corrosion monitoring
Enhanced flow control; limited
over-design of feed systems;
fail-shut control valves
Redundant temperature sensing and
alarms; interlocked chlorine feed
shut-off; pH control for bleach
reactor
(Continued)
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TABLE 5-10 (Continued)
Hazard Area
Prevention/Protection
Heating media flow
control
Overpressure
Direct relief discharges
to atmosphere
Major tank or line
rupture in storage
Failure of mixing in
bleach reaction
Enhanced flow control; redundant
temperature sensing and alarm
Enhanced pressure relief
(non-isolatable. adequate-sized, no
discharge restrictions, safe
discharge point)
Emergency scrubber system; tank
enclosures
Diking; enclosure with scrubber;
corrosion monitoring; overpressure
protection; siting away from
flammables and mechanical damage;
inspection and non-destructive
testing
Interlock chlorine feed shut-off on
loss of mixing power
109
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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 chlorine storage
and process facilities that might be found in the U.S..
5.8.1 Prevention and Protection Measures
Preventive measures reduce the probability of an accidental release from
a process or storage facility by increasing the reliability of both process
systems operations and equipment. Along with an increase in the reliability
of a system is an increase in the capital a.nd annual costs associated with
incorporating prevention and protection measures into a system. Table 5-11
presents costs for some of the major design, equipment, and operational
measures applicable to the primary hazards identified in Table 5-10 for chlo-
rine applications in the U.S.
5.8.2 Levels of Control
Prevention of accidental releases relies on a combination of technologi-
cal, administrative, and operational practices as they apply to the design,
construction, and operation of facilities where hazardous chemicals are used
and stored. Inherent in determining the degree to which these practices are
carried out is their costs. At a minimum, equipment and procedures should be
in accordance with applicable codes, standards, and regulations. However,
additional measures can be taken to provide extra protection against an acci-
dental release.
The levels of control concept provides a means of assigning costs to
increased levels of prevention and protection. The minimum level is referred
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TABLE 5-11. ESTIMATED TYPICAL COSTS OF SOME PREVENTION AND PROTECTION
MEASURES FOR CHLORINE RELEASES3
Prevention/Protection Measure
Replacement of copper lines with Monel*
Pressure relief.
- relief valve
- rupture disk
Physical barriers
- curbing
- 3 ft retaining wall
Flow control loop
Temperature sensor
pH control
Interlock system for feed shut-off
Alarm system
Diking
- 3 ft high
- top of tank height
Corrosion monitoring
Increased inspections and maintenance
Capital Cost
(1986 $)
150-200
1.000-2.000
1.000-1.200
750-1.000
1.500-2.000
4.000-6.000
250-400
7.500-10.000
1.500-2.000
250-500
1.200-1.500
7.000-7.500
Annual Cost
(1986 $/yr)
20-25
120-250
120-150
90-120
175-250
500-750
30-50
900-1,300
175-250
30-75
150-175
850-900
200-400
250-500
TJased on a 10,000-gallon fixed chlorine storage tank system and a
2.000-gallon continuous sodium hypochlorite bleach reactor system.
3Based on 10-20 hr @ $20/hr.
:3ased on 12.5-25 hr @ $20/hr.
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to as the "Baseline" system. This system consists of the elements required
for normal safe operation and basic prevention of an accidental release of
hazardous 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 such as
alarm and interlock systems designed specifically for the prevention of an
accidental release. The extra accidental release prevention measures incorpo-
rated into "Level 2" are reflected in its cost, which is much higher than that
of the baseline system.
When comparing the costs of the various levels of control, it is impor-
tant to realize that higher costs do not necessarily imply improved safety.
The measures 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 in-
creased 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.
112
-------
Levels-of-control cost estimates were prepared for a 42 ton fixed chlo-
rine storage tank system with a 10,000 gal capacity and a sodium hypochlorite
bleach batch reactor system with 2.000 gal capacity. These systems are
representative of storage and process facilities that might be found in the
SCAQMD.
5.8.3 Cost Summaries
Table 5-12 presents a summary of the total capital and annual costs for
each of the three levels of controls for the chlorine storage system and the
chlorine bleach reactor system. The costs presented correspond to the systems
described in Table 5-13 and Table 5-14. Each of the level costs include the
cost of the basic system plus any added controls. Specific cost information
and breakdown for each level of control for both the storage and process
facilities are presented in Tables 5-13 through 5-20.
5.8.4 Equipment Specifications and Detailed Costs
Equipment specifications and details of the capital cost estimates for
the chlorine storage and the chlorine bleach reactor systems are presented in
Tables 5-21 through 5-28.
5.8.5 Methodology
Format for Presenting Cost Estimates—
Tables are provided for control schemes associated with storage and pro-
cess facilities for chlorine '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 systems.
113
-------
TABLE 5-12. SUMMARY COST ESTIMATES OF POTENTIAL LEVELS OF CONTROLS FOR
CHLORINE STORAGE TANK AND HYPOCHLORITE BLEACH REACTOR
Total Total
Level of Capital Cost Annual Cost
Control (1986 $) (1986 $/yr)
Chlorine Storage Tank; Baseline 208,000 25.000
60 ton Fixed Chlorine Level No. 1 510.000 60.000
Tank with 10,000 gal Level No. 2 786.000 92.000
Capacity
Continuous Sodium Hypochlorite Baseline 105,000 13,000
Bleach Reactor System With Level No. 1 123,000 16,000
2,000 gal Chlorination Level No. 2 130,000 17,000
Tank
114
-------
TABLE 5-13 EXAMPLE OF LEVELS OF CONTROL FOR CHLORINE STORAGE TANKa
Process: 60 ton fixed chlorine storage tank
10.000 gal
Controls
Baseline
Level No. 1
Level No. 2
Process:
Flow:
None
Single check-
valve on tank-
process feed line
None
Add second check
valve.
None
Add a reduced-pressure
device with internal
air gap and relief
vent to scrubber.
Temperature:
Pressure:
Quantity:
Location:
Materials of
Construction:
Vessel:
None
Single pressure
relief valve,
vent to atmos-
phere, provide
local pressure
indicator.
Local level
indicator.
None
Add second relief
valve, secure
non-is datable
installation; vent
to scrubber.
Add remote level
indicator.
Away from traffic. Away from traffic,
flammables, and flammables, and
other hazardous other hazardous
processes. processes.
Carbon steel.
Tank pressure
specification
225 psig.
Carbon steel with
increased corrosion
allowances. (1/8
inch)
Tank pressure
specification
300 psig.
Add temperature
indicator.
Add rupture disks
under relief valves;
provide local pressure
indication on space
between disk and
valves; vent to
scrubber.
Add level alarm. Add
high-low level inter-
lock shut-off for both
inlet and outlet
lines.
Away from traffic,
flammables, and other
hazardous processes.
Kynar* lined carbon
steel.
Tank pressure
specification
375 psig.
(continued)
115
-------
TABLE 5-13 (Continued)
Process: 60 ton fixed chlorine storage tank
10,000 gal
Controls
Baseline
Level No. 1
Level No. 2
Piping:
Process
Machinery:
Enclosures;
Sch. 80 carbon Sch. 80 Kynar« Sch. 80 Monel®.
steel lined carbon steel.
*
Centrifugal pump. Centrifugal pump. Magnetically-coupled
carbon steel, Kynar® lined steel, centrifugal pump
stuffing box double mechanical Kynar® lined steel.
seal. seal.
None
Steel building.
Concrete building.
Diking:
Scrubbers:
Mitigation:
None
None
None
3 ft high dike.
Top of tank height,
10 ft.
Water scrubber for Alkaline scrubber for
relief and building relief and building
vents. vents.
Water sprays.
Alkaline water sprays
and barriers.
The examples in this table are appropriate for many, but not all
applications. This is only an exemplary system. Design must be suited to
fit the specific service.
A reduced pressure device is a modified double check valve.
116
-------
TABLE 5-14. EXAMPLE OF LEVELS OF CONTROL FOR CHLORINE BLEACH REACTOR
Process: Continuous Sodium Hypochlorite Production
Controls
Baseline
Tier #1
Tier #2
Process:
Temperature:
Pressure:
Flow:
Adequate cooling
system.
Local temperature
indicator.
Single pressure re-
lief valve. Vent to
atmosphere. Expan-
sion tank on chlo-
rine feed line.
Limited over-design
of feed systems.
Add redundant sensing
and alarm. Add remote
indicator.
Add local pressure
indicator on tank.
Vent relief valve to
scrubber.
Local flow indicator Add remote indicator.
on C12 feed line.
Interlock systems
on feed systems.
Add temperature
switch to shut off
Cl_ feed when temp.
rises above a certain
set point.
Add rupture disk and
provide local pressure
indication on space
between disk and valve.
Add flow switch to
shut off chlorine feed
on loss of cooling
medium.
Quantity:
Mixing:
Composition:
None
Provide adequate
mixing.
pH monitoring and
control.
None
Add alarm on loss of
recirculating pump.
Same
Level alarm.
Interlock chlorine
feed on loss of
mixing.
Same
(Continued)
-------
TABLE 5-1A(Continued)
Controls
Baseline
Tier #1
Tier #2
oo
Material of
Construction:
Fiberglass-rein-
forced plastic -
epoxy lined.
Same
Same
Vessel :
Piping:
Process
Machinery:
Enclosure:
Diking:
Atmospheric tank.
Sch. 40 CPVC for
bleach solutions.
Centrifugal pump,
Hastelloy C construc-
tion, stuffing box.
None
None
Same
Sch. 80 CPVC for
bleach solutions.
Same
Steel building.
Curbing around process
area.
Same
Same
Same
Concrete building
Retaining wall
process area.
around
The examples in this table are appropriate for many, but not all applications. This is
only an exemplary system. Design must be suited to fit the specific service.
-------
TABLE 5-15. ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
BASELINE CHLORINE STORAGE SYSTEM
Capital Cost Annual Cost
(1986 $) (1986 $/yr)
Vessels:
Storage tank 170,000 20.000
Expansion tanks (3) 6.500 760
Piping and Valves:
Pipework 2.300 270
Expansion loop 160 20
Check valve 280 35
Ball valves (5) 3.200 370
Excess flow valves (2) 500 60
Angle valves (2) 2.100 250
Relief valve 2.000 230
Process Machinery:
Centrifugal pump 4.000 470
Instrumentation:
Pressure gauges (4) 1.500 180
Load cell 16.000 1.800
Procedures and Practices:
Visual tank inspection (external) 15
Visual tank inspection (internal) 60
Relief valve inspection 15
Piping inspection 300
Piping maintenance 120
Valve inspection 30
Valve maintenance 350
Total Costs 208,000 25.000
119
-------
TABLE 5-16. ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
LEVEL 1 CHLORINE STORAGE SYSTEM
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Expansion loop
Check valve
Ball valves (5)
Excess flow valves (2)
Angle valves (2)
Relief valve
Process Machinery:
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Flow indicator
Load cell
Remote level indicator
Enclosures:
Steel building
Scrubbers:
Water scrubber
Diking:
3 ft high concrete diking
220.000
6.500
5.900
160
570
3.200
500
2,100
4.000
6.400
1.500
3.700
16.000
1.900
10.000
226.000
1,400
26.000
760
690
20
65
370
60
250
470
750
180
430
1,800
220
1.200
26.000
160
(Continued)
120
-------
TABLE 5-16 (Continued)
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Procedures and Practices:
Visual tank inspection (external)
Visual tank inspection (internal)
Relief valve inspection
Piping inspection
Piping maintenance
Valve inspection
Valve maintenance
15
60
30
300
120
35
400
Total Costs
510.000
60,000
121
-------
TABLE 5-17. ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
LEVEL 2 CHLORINE STORAGE SYSTEM
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Expansion loop
Reduced pressure device
Ball valves (5)
Excess flow valves (2)
Angle valves (2)
Relief valve
Rupture disks (2)
Process Machinery:
Centrifugal pump
Instrumentation:
Temperature indicator
Pressure gauges (6)
Flow indicator
Load cell
Remote level indicator
Level alarm
High-low level shutoff
Enclosures:
Concrete building
Scrubbers:
Alkaline scrubber
Diking:
10 ft high concrete diking
411.000
6,500
12.000
160
1.500
3.200
500
2.100
4.000
1.100
8.500
2.200
2.200
3.700
16,000
1.900
380
1.900
19.000
280.000
7,600
48.000
760
1.500
20
180
370
60
250
470
130
1.000
260
260
430
1.800
220
45
220
2,200
33,000
880
(Continued)
122
-------
TABLE 5-17(Continued)
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Procedures and Practices:
Visual tank inspection (external)
Visual tank inspection (internal)
Relief valve inspection
Piping inspection
Piping maintenance
Valve inspection
Valve maintenance
15
60
50
300
120
35
400
Total Costs
786,000
92.000
123
-------
TABLE 5-18. ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
BASELINE CONTINUOUS SODIUM HYPOCHLORITE PRODUCTION
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (3)
34.000
2.200
7.300
1.800
2.000
21,000
1.110
4.100
260
870
220
235
2.500
130
Temperature control
- Controller
- Sensor
- Control valve
pH Control
- Controller
- pH detector
- Control valve
Composition control
- Controller
- ORP sensing cell
- control valve
Flow control
- Controller
- Flowmeter
- Control valve
1.800
180
2.700
1.800
7,300
2.700
1.800
7.300
3.600
1.800
2,300
2.700
220
20
330
220
870
330
220
870
430
220
280
330
(Continued)
124
-------
TABLE 5-18 (Continued)
Capital Cost Annual Cost
(1986 $) (1986 $/yr)
Procedures and Practices:
Visual tank inspection (external) 15
Visual tank inspection (internal) 60
Relief valve inspection 15
Piping inspection 600
Piping maintenance 250
Valve inspection 40
Valve maintenance 400
Total Costs 105,000 13.000
125
-------
TABLE 5-19. ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
LEVEL 1 CONTINUOUS SODIUM HYPOCHLORITE PRODUCTION
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
34,000
2.200
9,100
1.800
2,000
21.000
4.100
260
1.100
220
230
2.500
Pressure gauges (4)
Flow indicator
Local temp, indicator
Temperature alarm
Temperature control
- Controller
- Sensor
- Control valve
pH Control
- Controller
- pH detector
- Control valve
Composition control
- Controller
- ORP sensing cell
- Control valve
1,400
3,600
2.200
360
1,800
360
2,700
1,800
7,300
2.700
1.800
7,300
3,600
180
430
260
45
220
45
330
220
870
330
220
870
430
(Continued)
126
-------
TABLE 5-19 (Continued)
Capital Cost Annual Cost
(1986 $) (1986 $/yr)
Flow control
- Controller 1.800 220
- Flowmeter 2.300 280
- Control valve 2.700 330
Diking:
Curbing around reactor 910 110
Enclosure:
Steel building 8.300 1.000
Procedures and Practices:
Visual tank inspection (external) 15
Visual tank inspection (internal) 60
Relief valve inspection 15
Piping inspection 600
Piping maintenance 250
Valve inspection 40
Valve maintenance 400
Total Costs 123.000 16.000
127
-------
TABLE 5-20.
ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
LEVEL 2 CONTINUOUS SODIUM HYPOCHLORITE PRODUCTION
Capital Cost
(1986 $)
Annual Cost
(1986 $/yr)
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
34.000
2.200
9,100
1.800
2.000
21.000
4.100
260
1.100
220
230
2.500
Level alarm
Mixing interlock system
Pressure gauges (4)
Flow interlock system
Flow indicator
Flow control
- Controller
- Flowmeter
- Control valve
Local temp, indicator
Temperature alarm
Temperature control
- Controller
- Sensors (2)
- Control valve
pH Control
- Controller
- pH detector
- Control valve
Composition control
- Controller
- ORP sensing cell
- control valve
360
1.800
1.400
1.800
3.600
1,800
2,300
2.700
2.200
360
1.800
360
2,700
1,800
7,300
2.700
1.800
7,300
3.600
45
220
180
220
430
220
280
330
260
45
220
45
330
229
870
330
220
870
430
(Continued)
128
-------
TABLE 5-20 (Continued)
Capital Cost Annual Cost
(1986 $) (1986 $/yr)
Diking:
3 ft retaining wall 1.300 200
Enclosure:
Concrete building 11.000 1.300
Procedures and Practices:
Visual tank inspection (external) 15
Visual tank inspection (internal) 60
Relief valve inspection 20
Piping inspection 600
Piping maintenance 120
Valve inspection 40
Valve maintenance 400
Total Costs 130.000 17.000
129
-------
TABLE 5-21. EQUIPMENT SPECIFICATIONS ASSOCIATED WITH CHLORINE STORAGE SYSTEM
Equipment Item
Equipment Specification
Reference
u>
o
Vessels:
Storage tank
Expansion tank
Piping and Valves:
Pipework
Check valve
Ball valve
Excess flow valve
Angle valve
Relief valve
Baseline: 10,000 gal. carbon steel. 225 psig rating
Level 1: 10.000 gal. carbon steel with 1/8 in.
corrosion protection, 300 psig rating
Level 2: 10,000 gal. Kynar* lined carbon steel,
375 psig rating
Standard carbon steel pressure vessel with rupture disk
and pressure gauge
Baseline: 1 in. schedule 80 carbon steel
Level 1: 1 in. schedule 80 Kynar® lined carbon steel
Level 2: 1 in. schedule 80 Monel*
1 in. vertical left check valve, Monel* trim
40,41.42,43
40.41
44
41.45
300 lb.. screwed, cast steel body, Monel* ball and stem, 40,41,45
reinforced PTFE seat, PTFE seals
1.25 in. standard valve 41
1 in. carbon steel, cast 46
1 in. x 2 in., class 300 inlet and outlet flange, angle 41
body closed bonnet with screwed cap, carbon steel body,
Monel* trim
(Continued)
-------
TABLE 5-21 (Continued)
Equipment Item
Equipment Specification
Reference
Reduced pressure
device
Rupture disk
Process Machinery:
Centrifugal pump
Instrumentation:
Temperature
indicator
Pressure gauge
Flow indicator
Load cell
Level alarm
High-low level
shutoff
Double check valve type device with internal air gap 40
and relief valve
1 in. Monel* disk and carbon steel holder
Level 2: Magnetically-coupled, Monel* construction.
Thermocouple, thermowell, electronic indicator
Diaphragm sealed, Monel* diaphragm. (0-1,000 psi)
Differential pressure cell, transmitter, associated
flowmeter
42,47,48
Baseline: single stage, carbon steel construction.
Level 1: single stage, Kynar* lined, double mechanical 5.41
seal
5.41
40,41,49
40.41.49
40,49
Electrically operated load cell with electronic indicator 40,49.50
Indicating and audible alarm 41.46,51
Solenoid valve, switch, and relay system 40,41.46,49
(Continued)
-------
TABLE 5-21 (Continued)
Equipment Item Equipment Specification Reference
Enclosure:
Building Level 1: 26 gauge steel walls and roof. door. ' 46
ventilation system
Level 2: 10 in. concrete walls. 26 gauge steel
roof, door
Scrubber: Level 1: Spray tower. Monel® construction, water sprays, 52
6 ft. x 18 ft.
Level 2: Spray tower. Monel* construction, alkaline
sprays
Diking: Level 1: 6 in. concrete walls, high 46
Level 2: 10 in. concrete walls, top of tank height
-------
TABLE 5-22. MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE CHLORINE STORAGE SYSTEM
u>
Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Expansion loop
Check valves
Ball valves (5)
Excess flow valves (2)
Angle valves (2)
Relief valve
Materials
Cost
79.000
3,500
550
75
160
2.000
300
1.400
1.300
Labor
Cost
35.000
880
1.000
35
30
150
40
40
50
Direct
Costs
(1986 $)
114.000
4.380
1.550
110
190
2.150
340
1,440
1.350
Indirect
Costs
40.000
1.500
542
40
65
750
120
500
470
Capital
Cost
170,000
6,500
2,300
160
280
3.200
500
2.100
2.000
Process Machinery:
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Load cell
1.900
800
8.400
800
200
2.100
2.700
1.000
10,500
950
350
3.700
4.000
1.500
16.000
Total Costs
99.000
41,000
140.000
49,000
208,000
-------
TABLE 5-23. MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1 CHLORINE STORAGE SYSTEM
Vessels:
Storage tank
Expansion tanks (3)
Piping and Valves:
Pipework
Expansion loop
Check valves
Ball valves (5)
Excess flow valves (2)
Angle valves (2)
Relief valve
Process Machinery:
Centrifugal pump
Instrumentation:
Pressure gauges (4)
Flow indicator
Load cell
Remote level indicator
Materials
Cost
102.000
3.500
3.300
75
320
2.000
300
1,400
2.600
3,000
800
2,000
8,400
1,000
Labor
Cost
46.000
880
680
35
60
150
40
40
100
1.300
200
500
2.100
250
Direct
Costs
(1986 $)
148.000
4.380
3.980
110
380
2.150
340
1.440
2,700
4,300
1,000
2,500
10,500
1.250
Indirect
Costs
52.000
1.500
1.400
40
140
750
120
500
950
1.500
350
880
3,700
440
Capital
Cost
220,000
6,500
5.900
160
570
3.200
500
2.100
4,000
6,400
1.500
3.700
16.000
1.900
(Continued)
-------
TABLE 5-23 (Continued)
Materials Labor Direct Indirect Capital
Cost Cost Costs Costs Cost
(1986 $)
Enclosures:
Steel building 4.600 2.300 6.900 2.400 10.000
Scrubbers:
Water scrubber 105.000 47.000 152.000 53,000 226.000
Diking:
3 ft high concrete diking 390 520 910 320 1.400
t_1 ^__————————__^_____.^______—_-_______^——-_—__^^^——__^^—^__^—^^-^—___^^^_—___^^____^__^___—
o>
01 Total Costs 241.000 102.000 343.000 120.000 510.000
-------
TABLE 5-24. MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 CHLORINE STORAGE SYSTEM
Materials
Cost
Labor
Cost
Direct
Costs
Indirect
Costs
(1986$)
Capital
Cost
Vessels:
Storage tank 191.000 86.000 277,000 97,000 411,000
Expansion tanks (3) 3,500 880 4,380 1.500 6,500
Piping and Valves:
Pipework 4,800 3.500 8.300 2.900 12.000
Expansion loop 75 35 110 40 160
Reduced pressure device 800 200 1.000 350 1.500
Ball valves (5) 2.000 150 2.150 750 3.200
_ Excess flow valves (2) 300 40 340 120 500
£ Angle valves (2) 1.400 40 1.440 500 2.100
Relief valve 2.600 100 2.700 950 4.000
Rupture disks (2) 650 75 725 260 1.100
Process Machinery:
Centrifugal pump 4,000 1,700 5,700 2,000 8,500
Instrumentation:
Temperature indicator 1,200 300 1,500 530 2,200
Pressure gauges (6) 1,200 300 1,500 530 2,200
Flow indicator 2,000 500 2,500 880 3,700
Load cell 8,400 2.100 10.500 3.700 16.000
Remote level indicator 1.000 250 1,250 440 1.900
Level alarm 200 50 250 90 380
High-low level shutoff 1.000 250 1,250 440 1.900
(Continued)
-------
TABLE 5-24 (Continued)
LO
Enclosures:
Concrete building
Scrubbers:
Alkaline scrubber
Diking:
10 ft high concrete dike
Total Costs
Materials Labor Direct Indirect Capital
Cost Cost Costs Costs Cost
(1986 $)
6.100 6.600 12.700
4,400
2.200 2.900
5.100
1,800
365.000 165,000 529.000 186.000
19.000
130.000 59.000 189.000 66.000 280,000
7.600
786.000
-------
TABLE 5-25. EQUIPMENT SPECIFICATIONS ASSOCIATED WITH CHLORINE BLEACH REACTOR SYSTEM
Equipment Item
Equipment Specification
Reference
oo
Vessels:
Chlorination
tank
Expansion tank
Piping and Valves:
Pipework
Ball valves
Glove valves
Relief valve
Process Machinery:
Centrifugal pump
Instrumentation:
Level alarm
Interlock system
2.000 gal. fiber-reinforced plastic tank
Standard carbon steel pressure vessel with rupture disk 40,41
and pressure gauge
Baseline: 1 in. schedule 80 Monel*. chlorine feed line
2 in. schedule 40 CPVC for bleach solutions
Levels 1 & 2: 2 in. schedule 80 CPVC for bleach
solutions
300 lb., screwed, cast steel body, Monel* ball and trim.
Class 150, flanged, cast steel. Monel* disk and seat
1 in. x 2 in., class 300 inlet and outlet flange, angle
body, closed bonnet with screwed cap, carbon steel
body, Monel* trim
Hastelloy C construction, stuffing box
Indicating and audible alarm
Solenoid valve, switch, and relay system
41.44
40.41.45
40.41,45
41
41,46.51
40.41,46.49
(Continued)
-------
TABLE 5-25 (Continued)
UJ
VD
Equipment Item
Pressure gauge
Flowmeter
Control valve
Controller
Temperature
indicator
Temp, sensor
pH detector
ORP sensing cell
Diking:
Enclosure:
Equipment Specification
Diaphragm sealed, Monel® diaphragm, 0-500 psi
D/P cell and transmitter and associated flow indicator
1 in. and 1 in. globe valves, Monel* trim
Standard PID controller
Thermocouple, thermowell, and electronic indicator
Thermocouple and associated thermowell
Electrode, electrode chamber, amplifier-transducer and
indicator
Standard calomel oxidation-reduction potential sensing
cell
Level 1: 6 in concrete curbing
Level 2: 3 ft. high retaining wall
Level 1: 26 gauge steel walls and roof, door.
ventilation system
Level 2: 10 in. concrete walls, 26 gauge steel
roof, door
Reference
40.
40.
40.
40.
40.
40.
40.
40.
46
46
41,49
41.49
53
54.55
41.49
41.49
50
50
-------
TABLE 5-26. MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE CONTINUOUS
SODIUM HYPOCHLORIDE PRODUCTION
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Materials
Cost
16,000
1.200
3.000
1,000
1.300
Labor
Cost
7.440
300
2.000
250
50
Direct
Costs
(1986 $)
23.440
1.500
5.000
1.250
1.350
Indirect
Costs
5.900
380
1.300
320
340
Capital
Cost
34.000
2.200
7.300
1.800
2,000
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (3)
Temperature control
10,000
600
4.300
150
14.300
750
3.600
190
21.000
1,100
- Controller
— Sensor
- Control valve
pH Control
- Controller
- pH detector
- Control valve
1,000
100
1.500
1,000
4,000
1.500
250
25
380
250
1.000
380
1,250
125
1,880
1.250
5.000
1.880
320
30
470
430
1.300
470
1.800
180
2.700
1.800
7,300
2,700
(Continued)
-------
TABLE 5-26 (Continued)
Composition control
- Controller
- ORP sensing cell
- Control valve
Flow control
- Controller
- Flowmeter
- Control valve
Total Costs
Materials
Cost
1.000
4.000
2.000
1.000
1.300
1.500
53.000
Labor
Cost
250
1.000
500
250
300
380
20.000
Direct
Costs
(1986 $)
1.250
5.000
2.500
1.250
1.600
1.880
73.000
Indirect
Costs
320
1.300
630
320
400
470
18.000
Capital
Cost
1.800
7.300
3.600
1.800
2.300
2.700
105.000
-------
TABLE 5-27.
MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 1 CONTINUOUS
SODIUM HYPOCHLORIDE PRODUCTION
ro
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Pressure gauges (4)
Flow indicator
Local temperature indicator
Temperature alarm
Temperature control
- Controller
- Sensors (2)
- Control valve
Materials
Cost
16.000
1.200
3.800
1.000
1.300
10.000
800
2.000
1.200
200
1.000
200
1.500
Labor
Cost
7. AGO
300
2.500
250
50
4.300
200
500
300
50
250
50
380
Direct
Costs
(1986 $)
23.400
1.500
6.300
1.250
1.350
14.300
1,000
2.500
1.500
250
1,250
250
1.880
Indirect
Costs
5,900
380
1.600
320
340
3.600
250
630
380
60
320
60
470
Capital
Cost
34.000
2.200
9.100
1,800
2.000
21.000
1,400
3,600
2.200
360
1.800
360
2,700
(Continued)
-------
TABLE 5-27 (Continued)
U)
pH Control
- Controller
- pH detector
- Control valve
Composition control
- Controller
- ORP sensing cell
- Control valve
Flow control
- Controller
- Flowmeter
- Control valve
Diking:
Curbing around reactor
Enclosure:
Steel building
Total Costs
Materials
Cost
1,000
4,000
1,500
1,000
4.000
2.000
1.000
1.300
1.500
500
4.600
63.000
Labor
Cost
250
1.000
380
250
1.000
500
250
325
375
130
1.200
22,000
Direct
Costs
(1986 $)
1.250
5,000
1.880
1.250
5.000
2.500
1.250
1.600
1,880
630
5.800
85,000
Indirect
Costs
320
1.300
470
320
1.300
630
320
400
470
160
1.500
21.000
Capital
Cost
1.800
7.300
2.700
1,800
7.300
3.600
1.800
2.300
2.700
910
8.300
123.000
-------
TABLE 5-28. MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 CONTINUOUS
SODIUM HYPOCHLORITE PRODUCTION
Vessels:
Chlorination tank
Expansion tank
Piping and Valves:
Pipework
Ball and globe valves (8)
Relief valve
Process Machinery:
Centrifugal pumps (2)
Instrumentation:
Level alarm
Mixing interlock system
Pressure gauges (4)
Flow interlock system
Flow indicator
Flow control
- Controller
- Flowmeter
- Control valve
Materials
Cost
16,000
1,200
3,800
1.000
1.300
1,000
200
10,000
800
1.000
2,000
1,000
1.300
1,500
Labor
Cost
7.400
300
2,500
250
50
4.300
50
250
200
250
500
250
300
380
Direct
Costs
(1986 $)
23.400
1.500
6.300
1.250
1.350
14.300
250
10,250
1,000
1,250
2.500
1.250
1.600
1.880
Indirect
Costs
5.900
380
1.600
320
330
3.600
60
320
250
320
630
320
400
470
Capital
Cost
34.000
2.200
9,100
1.800
2.000
21.000
360
1.800
1.400
1.800
3.600
1.800
2.300
2,700
(Continued)
-------
TABLE 5-28 (Continued)
Cn
Local temp, indicator
Temperature alarm
Temperature control
- Controller
- Sensors (2)
- Control valve
pH Control
- Controller
- pH detector
- Control valve
Composition control
- Controller
- ORP sensing cell
- Control valve
Diking:
3 ft retaining wall
Enclosure:
Concrete building
Total Costs
Materials
Cost
1,200
200
1.000
200
1.500
1.000
A. 000
1.500
1.000
4.000
2.000
900
6.100
67.000
Labor
Cost
300
50
250
50
380
250
1.000
380
250
1.000
500
230
1.500
23.000
Direct
Costs
(1986 $)
1.500
250
1.250
250
1.880
1.250
5.000
1.880
1.250
5.000
2.500
1.130
7.600
90.000
Indirect
Costs
380
60
320
60
470
320
1.300
470
320
1.300
630
290
1.900
23.000
Capital
Cost
2.200
360
1.800
360
2.700
1.800
7.300
2.700
1,800
7,300
3,600
1,600
11,000
130,000
-------
Capital Cost—All capital costs presented in this report are shown as
total fixed capital costs. Table 5-29 defines the cost elements comprising
total fixed capital as it is used here.
The computation of total fixed capital as shown in Table 5-29 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 uninstalled equipment costs by
computing costs of installation separately. To obtain the total fixed capital
cost, other costs obtained by utilizing factors are added to the total direct
costs.
The first group of other cost elements is indirect costs. These include
engineering and supervision, construction expenses, and various other expenses
such as administration expenses, for example. These costs are computed by
multiplying total direct costs by a factor shown in Table 5-29. The factor is
approximate, is obtained from the cost literature, and is based on previous
experience with capital projects of a similar nature. Factors can have a
range of values and vary according to technology area and for individual
technologies within an area. Appropriate factors were selected for use in
this report based on judgement and experience.
When the indirect costs are added to the total direct costs, total bare
module cost is obtained. Some additional cost elements such as contractor's
fee and contingency are calculated by applying and adding appropriate factors
to the total bare module cost as shown in Table 5-29 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 5-30 defines the cost elements
and appropriate factors comprising these costs. Additional annual costs are
146
-------
TABLE 5-29. FORMAT FOR TOTAL FIXED CAPITAL COST
Item No. Item Cost
1 Total Material Cost
2 Total Labor Cost
3 Total Direct Cost Items 1+2
4 Indirect Cost Items (Engi-
neering & Construction
Expenses) 0.35 x Item 3a
5 Total Bare Module Cost Items (3 + 4)
6 Contingency (0.05 x Item 5)b
7 Contractor's Fee 0.05 x Item 5
8 Total Fixed Capital Cost Items (5 +6 +7)
For storage facilities, the indirect cost factor is 0.35. For process
facilities, the indirect cost factor is 0.25.
For storage facilities, the contingency cost factor is 0.05. For process
facilities, the contingency cost factor is 0.10.
147
-------
TABLE 5-30. FORMAT FOR TOTAL ANNUAL COST
Item No. Item Cost
1 Total Direct Cost
2 Capital Recovery on Equip-
ment Items 0.163 x Item 1
3 Maintenance Expense on
Equipment Items 0.01 x Item 1
4 Total Procedural Items
5 Total Annual Cost Items (2+3+4)
Based on a recovery factor at 10% cost of capital for 10 years.
148
-------
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 chlorine process and
storage facilities using the best costs for available sources. The primary
sources of cost information are Peters and Timmerhaus (40), Chemical Engineer-
ing (56), and Valle-Riestra (57) 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.
Costs in this document reflect the "typical" or "average" representation
for specific equipment items. This restricts the use of data in this report
to:
• Preliminary estimates used for policy planning;
• Comparison of relative costs of different levels or systems;
and
• Approximations of costs that might be incurred for a specific
application.
The costs in this report are considered to be "order of magnitude" with a
+50 percent margin. This is because the costs are based on preliminary
estimates and many are updated from literature sources. Large departures from
the design basis of a particular system presented in this manual or the advent
of a different technology might cause the system cost to vary by a greater
149
-------
extent than this. If used as intended, however, this document will provide a
reasonable 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
reported in the literature were updated using cost indices for materials and
labor.
Costs expressed in base year dollars may be adjusted to dollars for ano-
ther year by applying cost indices as shown in the following equation:
new base year cost = old base year cost x nf[ ^ase ?ear f
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 direct-
ly 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, scrubbers,
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 free-on-board based freight basis (f.o.b.) with
carbon steel as the basis (January 1979 dollars) were determined using the
following equation from Peters and Timmerhaus (40) :
150
-------
Cost = [50(Weight of Vessel in Pounds)"0'34]
The vessel weight is determined using appropriate design equations as given by
Peters and Timmerhaus (40) which allow for all thickness adjustments for corro-
sion 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 (40). The vessel costs are updated using cost factors.
Finally, a shipping cost amounting to 10 percent of the purchased cost is
added to obtain the delivered equipment cost.
Piping—Piping costs were obtained using cost information and data pre-
sented by Yamartino (44). A simplified approach is used in which it is
assumed that a certain length of piping containing a given number of valves,
flanges, and fittings is contained in the storage or process facility. The
data presented by Yamartino (44) permit cost determinations for various
lengths, sizes, and types of piping systems. Using these factors, a repre-
sentative estimate can be obtained for each of the storage and process
facilities.
Diking—Diking costs were estimated using Mean's Manual (46) for rein-
forced concrete walls. The following assumptions were made in determining the
costs. The dike contains the entire contents of a tank in the event of a leak
or release. Two dike sizes are possible: a three-foot high dike, six-inches
thick and a top-of-tank height dike ten inches thick. The tanks are raised
off the ground and are not volumetrically included in the volume enclosed by
the diking. These assumptions facilitate cost determination for any size
diking system.
Enclosures—Enclosure costs were estimated using Mean's Manual (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.
151
-------
The concrete building is ten-inches thick with a 26-gauge steel roof and a
metal door. The steel building has 26 gauge roofing and siding and metal
door. The cost of a ventilation system was determined using a typical 1,000
scfm unit and doubling the cost to account for duct work and requirements for
the safe enclosure of hazardous chemicals.
Scrubbers—Scrubber costs were estimated using the following equation
from the Card (52) manual for spray towers based on the actual cubic feet per
minute of flow at a chamber velocity of 600 feet/minute.
Costs = 0.235 x (ACFM + 43,000)
A release rate of 10,000 ft /minute was assumed for the storage vessel systems
and an appropriate rate was determined for process system based on the quan-
tity of hazardous chemicals present in the system at any one time. For the
o
chlorine bleach reactor system, a release rate of 10,000 ft /minute was
assumed. In addition to the spray tower, the costs also include pumps and a
storage tank for the scrubbing medium. The costs presented are updated to
June 1986 dollars.
Installation Factors—
Installation costs were developed for all equipment items included in
both the process and storage systems. The costs include both the material and
labor costs for installation of a particular piece of equipment. The costs
were obtained directly from literature sources and vendor information or indi-
rectly by assuming a certain percentage of the purchased equipment cost
through the use of estimating factors obtained from Peters and Timmerhaus (40)
and Valle-Riestra (57). Table 5-31 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.
152
-------
TABLE 5-31. FORMAT FOR INSTALLATION COSTS
Equipment Item Factor or Reference
Vessels:
Storage Tank 0.45
Expansion Tank 0.25
Piping and Valves:
Pipework Ref. 44
Expansion Loop Ref. 41
Reduced Pressure Device Ref. 41
Check Valves Ref. 41
Gate Valves Ref. 41
Ball Valves Ref. 41
Excess Flow Valves Ref. 41
Angle Valves Ref. 46
Relief Valves Ref. 41
Rupture Disks Ref. 49
Process Machinery:
Centrifugal Pump 0.43
Gear Pump 0.43
Instrumentation:
All Instrumentation Items 0.25
Enclosures: Ref. 46
Diking: Ref. 46
Scrubbers: 0.45
153
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SECTION 6
REFERENCES
1. Lees, Frank P. Loss Prevention in the Process Industries, Volumes 1 & 2,
Butterworths, London, England, 1983.
2. White, G.C. (ed). The Handbook of Chlorination. Second Edition, Van
Nostrand Reinhold Company, New York, NY, 1986.
3. World Chemical Outlook. Chemical and Engineering News, December 15,
1986.
4. Chemical Products Synopsis. Mannsville Chemical Products, Cortland, NY,
1985.
5. Green, D.W. (ed.). Perry's Chemical Engineers' Handbook. Sixth Edition.
McGraw-Hill Book company. New York, NY, 1984.
6. Chlorine Manual. The Chlorine Institute, New York, NY, 1983.
7. Dean, J. (ed.). Lange's Handbook of Chemistry. Twelfth Edition, McGraw-
Hill Book Company, New York, NY. 1979.
8. Weast, R.C. (ed.). CRC Handbook of Chemistry and Physics. 63rd Edition,
CRC Press. Inc.. Boca Raton. FL, 1982.
9. Bird, R.B., W.E. Stewart, and E.N. Lightfoot. Transport Phenomena. John
Wiley & Sons. 1960.
10. Safety Aspects of Storage, Handling and Use of Chlorine and Sulfur Diox-
ide. National Joint Health and Safety Committee for the Water Science,
London, England, April 1982.
11. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley and Sons,
Third Edition, 1978, Volume 1.
12. Braker. William, et al. Effects of Exposure to Toxic Gases - First Aid
and Medical Treatment. Second Edition, Matheson. Lindhurst, NJ, 1977.
13. Lewis, R.J.S., and R.L. Tatken (eds.). Registry of Toxic Effects of
Chemical Substances, DHEW - NIOSH Publication No. 79-100, January 1985
Update, NIOSH, Cincinnati, OH.
14. NIOSH/OSHA Pocket Guide to Chemical Hazards, DHEW (NIOSH) Publication No.
78-210, September 1985.
154
-------
15. Sommers."H.A. Chemical Engineering Progress. March 1965. p. 97 ff.
16. McKetta. J. Encyclopedia of Chemical Processing and Design, Marcel
Dekker Publishing Company. NY, 1985.
17. Lawler, G.M. (ed.). Chemical Origins Markets. Fifth Edition Chemical
Information Services, Stanford Research Institute, 1977.
18. White, G. C. (ed.). Handbook of Chlorination. Van Nostrand Reinhold
Company, New York. 1972.
19. U.S. Environmental Protection Agency. Locating and Estimating Air Emis-
sions From Sources of Phosgene. EPA-450/4-84-007i. Research Triangle
Park, NC, September 1985.
20. Jones, D.J. The Production of Titanium Tetrachloride. R.H. Chandler
Ltd., London, 1969.
21. Pamphlet 8: Chlorine Packaging Manual. The Chlorine Institute, NY 1985.
22. Pamphlet 66: Chlorine Tank Car Loading, Unloading. Air Padding, Hydro-
static Testing. The Chlorine Institute, New York, NY, 1979.
23. Pamphlet 5: Non-Refrigerated Liquid Chlorine Storage. The Chlorine
Institute, NY, 1982.
24. Pamphlet 78: Refrigerated Liquid Chlorine Storage. The Chlorine Insti-
tute, NY, 1984.
25. Pamphlet 9: Chlorine Vaporizing Equipment. The Chlorine Institute, NY,
1979.
26. Pamphlet 6: Piping Systems for Dry Chlorine. The Chlorine Institute,
New York, NY, 1985.
27. Perry, R.Y.. and C.H. Chilton. Chemical Engineers' Handbook. Fifth
Edition, McGraw-Hill. New York, 1973.
28. Vivian, J.E., and R.P. Whitney. Chemical Engineering Progress. November
1947.
29. Radian Corporation Laboratory Notebook Number 215. Work for EPA Contract
68-02-3994, Work Assignment 94, Page 5, 1986.
30. Aarts. J.J., and D.M. Morrison. Refrigerated Storage Tank Retainment
Walls. CEP Technical Manual, Volume 23, American Institute of Chemical
Engineers, New York, NY, 1981.
31. Bennett. G.F., F.S. Feates. and I. Wilder. Hazardous Material Spills
Handbook. McGraw-Hill Book Company, New York, NY, 1982.
155
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32. Gross, S.'S., and R.H. Hiltz (MSA Company). Evaluation of Foams for Miti-
gating Air Pollution From Hazardous Spills. EPA-600/2-82-029 (NTIS PB82-
227117). U.S. EPA. Cincinnati. March 1982.
33. Buschman. C.H. Experiment on the Dispersion of Heavy Gases and Abatement
of Chlorine Clouds. Fourth International Symposium on Transport of
Hazardous Cargos by Sea and Inland Waterways. National Academy of
Sciences. 1975.
34. Hiltz, P.H... and S.S. Gross. The Use of Foams to Control the Vapor Hazard
from Liquified Gas Spills. • Proceedings of National Conference on Control
of Hazardous Material Spills, May 1980.
35. Private communication with industry consultant; name withheld by request,
August 1986.
36. Beresford, T.C. The Use of Water Spray Monitors and Fan Sprays and Dis-
persing Gas Leakage. Institute of Chemical Engineers Symposium Proceed-
ings on the Containment and Dispersion of Gases by Water Sprays, Manches-
ter, England, 1981.
37. Chemical Manufacturers Association. Process Safety Management (Control
of Acute Hazards). Washington, D.C., May 1985.
38. Stus, T.F. On Writing Operating Instructions. Chemical Engineering,
November 26. 1984.
39. Burk, A.F. Operating Procedures and Review. Presented at the Chemical
Manufacturers Association Process Safety Management Workshop. Arlington,
VA, May 7-8, 1985.
40. Peters, M.S., and K.D. Timmerhaus. Plant Design and Economics for Chemi-
cal Engineers. McGraw-Hill Book Company, New York, NY, 1980.
41. Richardson Engineering Services, Inc. The Richardson Rapid Construction
Cost Estimating System, Volumes 1-4. San Marcos, CA, 1986.
42. Pkulic, A., and H.E. Diaz. Cost Estimating for Major Process Equipment.
Chemical Engineering. October 10. 1977.
43. Hall, R.S., J. Matley, and K.J. McNaughton. Cost of Process Equipment.
Chemical Engineering, April 5, 1982.
44. Yamartimo, J. Installed Cost of Corrosion-Resistant Piping-1978. Chemi-
cal Engineering, November 20. 1978.
45. Telephone communication between J.D. Quass of Radian Corporation and a
representative of Mark Controls Corporation. Houston, TX, August 1981.
46. R.S. Means Company. Inc. Building Construction Cost Data. 1986 (44th
Edition). Kingston. MA.
156
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47. Telephone communication between J.D. Quass of Radian Corporation and a
representative of Zook Enterprises. Chagrin Falls, OH. August 1986.
48. Telephone communication between J.D. Quass of Radian Corporation and a
representative of Fike Corporation, Houston, TX, August 1986.
49. Liptak. E.G. Cost of Process Instruments. Chemical Engineering. Septem-
ber 7. 1970.
50. Liptak. B.G. Costs of Viscosity, Weight, Analytical Instruments. Chemi-
cal Engineering. September 21, 1970.
51. Liptak, B.G. Control-Panel Costs, Process Instruments. Chemical Engi-
neering. October 5, 1970.
52. Capital and Operating Costs of Selected Air Pollution Control Systems.
EPA-450/5-80-002. U.S. Environmental Protection Agency. 1980.
53. Liptak, B.G. Safety Instruments and Control-Valve Costs. Chemical Engi-
neering. November 2. 1970.
54. Telephone communication between J.D. Quass of Radian Corporation and a
representative of Fischer Controls, Stafford, TX, August 1986.
55. Telephone communication between J.D. Quass of Radian Corporation and a
representative of Foxboro Corporation, Corpus Christi, TX, August 1986.
56. Cost indices obtained from Chemical Engineering. McGraw-Hill Publishing
Company, New York, NY, November 1972, June 1974, December 1985, and
August 1986.
57. Valle Riestra, J.F. Project Evaluation in the Chemical Process Indus-
tries. McGraw-Hill Book Company, New York, NY, 1983.
157
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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.
Cavitation; The formation and collapse of vapor bubbles in a flowing liquid.
Specifically the formation and collapse of vapor cavities in a pump when there
is sufficient resistance to flow at the inlet side.
Chlorofluorocarbons; Organic compounds containing chlorine and/or fluorine
atoms within the molecule.
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
destructing continuous process exhaust gas emissions.
158
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Creep failure: Failure of a piece of metal as a result of creep. Creep is
time dependent deformation as a result of stress. Metals will deform when
exposed to stress. High levels of stress can result in rapid deformation and
rapid failure. Lower levels of stress can result in slow deformation and
protracted failure.
Deadheading; Closing or nearly closing or blocking the discharge outlet or
piping of an operating pump or compressor.
Facility; A location at which a process or set of processes are used to
produce, refine or repackage chemicals, or a location where a large enough
inventory of chemicals are stored so that a significant accidental release of
a toxic chemical is possible.
Hazard; A source of danger. The potential for death, injury or other forms
of damage to life and property.
Hygroscopic; Readily absorbing and retaining moisture, usually in reference
to readily absorbing moisture from the air.
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 0.25% 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.
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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.
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.
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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.
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.
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TABLE B-l.
APPENDIX B
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
fto
in2
ft0
in3
ft3
gal
Ib
short ton (ton)
short ton (ton)
atm
mm Hg
psia
psig
°F
°C
Btu/lb
Btu/lbmol
kcal/gmol
Btu/lb-°F
•3
lb/ftj
Ib/gal
oz/gal
quarts/gal
gal /m in
gal/ day
ftj/nin
ft/min
ft/sec
centipoise (CP)
To
cm
m
cm
m
cm3
m
m
kg
Mg
metric ton (t)
kPa
kPa
kPa
kPa*
°c*
K*
kJ/kg
kJ/kgmol
kJ/kgmol
kJ/kg-°C
3
kg/m
kg/m
cm/m
m»/min
nu/day
m/min
m/min
m/sec
Pa-s (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)x(6.895)
(5/9)x(°F-32)
°C+273. 15
2.326
2.326
4.184
4.1868
16.02
119.8
7.490
25.000
0.0038
0.0038
0.0283
0.3048
0.3048
0.001
^Calculate as indicated
GOVERNMENTMINTINGOmCE:1987-7it8-12V 67032
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