r/EPA
United States
Environmental Protection
Agency
Control Technology
Center
Research Triangle Park NC 27711
EPA-4BO/3-87-022
October 1987
Evaluation of Potential
Emissions of TDI
from Two Facilities
control ^technology center
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EPA-450/3-87-022
EVALUATION OF POTENTIAL EMISSIONS OF
TDI FROM TWO FACILITIES
CONTROL TECHNOLOGY CENTER
SPONSORED BY:
Emission Standards and Engineering Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Air and Energy Engineering Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Center for Environmental Research Information
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
October 1987
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NOTICE
This report was prepared by Radian Corporation, Research Trianyle
Park, NC. It has been reviewed for technical accuracy by the Emission
Standards and Engineering Division of the Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products is not intended
to constitute endorsement or recommendation for use.
ACKNOWLEDGEMENT
This report was prepared for the Control Technology Center by
Andrew J. Miles of Radian Corporation. The EPA project officer was
Robert E. Rosensteel of the Office of Air Quality Planning and Standards.
Also serving on the EPA project team was T. Kelly Janes of the Air and
Energy Engineering Research Laboratory.
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TABLE OF CONTENTS
Section
Summary S-l
1.0 Introduction 1-1
1.1 Scope 1-1
1.2 Overview 1-1
2.0 Hazard Evaluation 2-1
2.1 Physical and Chemical Properties of TDI 2-1
2.2 Potential for Sudden and Accidental Releases 2-5
2.2.1 General Considerations 2-5
2.2.2 TDI Users 2-6
2.3 Process Evaluation 2-8
3.0 Facility Visits 3-1
3.1 Plant Visit #1 3-1
3.2 Plant Visit #2 3-14
m
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LIST OF TABLES
Number Page
1-2 Physical Properties of TDI 2-2
2-2 Example Method for Preliminary Hazard Evaluation
at a Facility 2-7
2-3 Example of Factors Affecting Process Hazards 2-10
2-4 Ranking of Probability of Release 2-11
LIST OF FIGURES
Number paqe
2-1 Diagram of Vapor Pressure for Toluene Diisocyanate .... 2-3
3-1 Diagram of Pruett-Schaffer Facility 3-3
3-2 Schematic Drawing of the Pruett-Schaffer TDI Process ... 3-4
3-3 Schematic Drawing of the Scrubber 3-7
3-4 Diagram of Raw Material Storage Areas 3-9
3-5 Suggested Hood Designs 3-13
3-6 Schematic Drawing of Urethane Alkyds Process at PPG. . . . 3-16
IV
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SUMMARY
This report summarizes the technical assistance provided to the Allegheny
County health Department (ACHD) by the Control Technology Center (CTC). The
request by the ACHD was to examine potential air impacts from facilities using
toluene diisocyanate in their manufacturing processes. The CTC group was
composed of Robert Rosensteel of the Office of Air Quality Planning and
Standards, Kelly Janes of Air and Energy Engineering Research Laboratory, and
Andrew Miles of Radian Corporation.
S-l
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1.0 INTRODUCTION
1.1 SCOPE
The Control Technology Center (CTC) was established by the Environmental
Protection Agency's (EPA) Office of Research and Development and the Office
of Air Quality Planning and Standards to assist State and local air
pollution control agencies in the implementation of their air toxics and
other pollution control programs. Three levels of assistance can be
accessed through the CTC. First, a CTC HOTLINE has been established to
provide telephone assistance on matters relating to air pollution control
technology. Second, more in-depth engineering assistance can be provided
when appropriate. Third, the CTC can provide technical guidance through
publication of technical guidance documents, development of personal
computer software, and presentation of workshops on control technology
matters.
This document reports the results of direct engineering assistance
provided by the CTC for the Allegheny County Health Department (ACHD).
The scope of the assistance was determined by the specific needs of the
county and the findings presented in this report may not be applicable to
other facilities and operations which were not visited. Also, control
technology presented in this document is not necessarily endorsed by EPA
for establishment of the basis for regulations, since the decision of
whether or not to regulate a source category and the selection of the
technology on which to base regulations are responsibilities of the
individual State or local authorities. This document is, however, intended
to provide technical information which may assist in making such decisions.
1.2 OVERVIEW
This report summarizes and presents the results of the plant visits
made by the CTC team to two toluene diisocyanate (TDI) user facilities in
Allegheny County, Pennsylvania. The purpose of the visit was to examine
potential ambient air impacts from facilities using TDI in their production
1-1
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processes. ACHD headquarters was visited also to gather background infomation
and to discuss the five existing and one proposed TDI user facilities in
the county.
The five TDI users in Allegheny County and one potential new user are
listed below.
Maximum Quantity
Annual Usage, Ibs.* Stored On-Site, Ibs.*
Pruett-Schaffer Chemical Company 460,000 90,000
Koppers Company, Inc. 350,000 60,000
(potential new source in county)
PPG Industries, Inc. 71,350 20,340
Mobay Chemical Corporation 27,500 1,800
Puritan Paint and Oil 5,000 1,000
Mine Safety Appliance 1
913,851 173,140
Each of the facilities listed was briefly discussed with ACHD personnel
to determine which facilities were of most concern and should be surveyed.
Following these discussions the decision was made to visit the Pruett-
Schaffer facility, the largest TDI user identified in the county. Also,
if time permitted, it was decided to visit the PPG Industries facility, a
well controlled facility, according to ACHD personnel, with which they
had no major concerns. Subsequently, visits were made to these two
facilities to gather site-specific information and to identify potential
sources of emissions under routine and non-routine conditions. During
the course of the visits, several recommendations were made which may
have been outside the usual authority of the Bureau of Air Pollution
Control. These recommendations generally are in the area of worker safety
or spill control.
The remainder of this report is organized as follows. Section 2.1
presents the general approach to hazardous identification of chemical
facilities and Section 2.2 discussed one TDI/polyol reaction. Details of
the two facility visits, pertinent findings and conclusions are presented
in Section 3.0
*To convert pounds to kilograms multiply by 0.454
1-2
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2.0 HAZARD EVALUATION
As discussed in the introduction to this report, the Allegheny Health
Department requested technical assistance to evaluate potential emissions from
both routine and non-routine conditions at the TDI user facilities studied
under this work assignment. Storage, transfer, and chemical processing of TDI
results in both fugitive and process emissions under routine conditions.
These emissions are generally quantifiable, and are permitted; in addition,
some sources are controlled. Non-routine occurrences are often labeled as
sudden and accidental releases and are the result of a fire, explosion or
spill. This chapter summarizes physical and chemical properties of TDI and
describes a general classification of sudden and accidental releases and then
briefly evaluates the potential for a toxic air pollutant (TAP) release for
one of the TDI/polyol chemical processes being used in Allegheny County.
2.1 PHYSICAL AND CHEMICAL PROPERTIES OF TDI
TDI is a colorless-to-pale-yellow liquid of characteristic pungent odor.
Most of the TDI marketed commercially is a mixture of 80 percent 2,4-toluene
diisocyanate and 20 percent 2,6-toluene diisocyanate. At room temperature,
this mixture is.water-white to pale yellow mobile liquid. The physical
properties of TDI are given in Table 2-1. The boiling point is 250°C, the
flash point is 127°C, and the fire point is 142°C.
Figure 2-1 presents a vapor pressure temperature curve for TDI. At 25 C
_2
TDI has a low vapor pressure of 3 x 10 millibars, which corresponds to a
concentration of the saturated vapor of about 30 ppm in the atmosphere.
TDI is an extremely reactive chemical which requires careful handling.
In contact with water it reacts readily producing heat and forming carbon
dioxide and insoluble ureas. The pressure created by the evolved heat and
carbon dioxide is sufficient to rupture a closed container. Contact with
compounds containing free hydrogen can produce even more violent reactions, as
is discussed later in this report. TDI reacts with acids, bases, ammonia,
2-1
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TABLE 2-1. PHYSICAL PROPERTIES OF TDI
Item
100
TDI Isomer Ratio 2.4- to 2.6-
80:20
65:35
Physical state at normal temps.
Viscosity (centipoise at 25°C)
Purity
Color
Odor
Solubility in water
Specific Gravity (g/ml) (at 25°C)
Boiling temperature (°C)
Flash temperature (°C)
Fire temperature (°C)
Autoignition temperature (°C)
Liquid
(3-6) 3-6 (3-6)
>99.5%
Colorless to pale yellow
Characteristic pungent
none, reacts
1.21 1.21 1.21
251 251 251
(135) 135 (135)
(142) 142 (142)
(277) 277 (277)
Freezing temperature (°C)
Vapor density (air = 1)
Vapor pressure (mbar at 25°C)
Explosion Limits (% v/v)
Lower
Upper
Molecular Weight
22 <15
6.0 6.0
.03 .03
0.9
9.5
174 174
<8
6.0
.03
174
Note: ( ) expected value for 80:20 material.
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10
CO
i. 10-1
3
CO
CO
CO
o
Q.
OJ
10-'
10-"
l
10
20 30 40 50 60
Temperature °C
13.33
1.33
'0.133
0.013
0.0013
70 80 90 100
cc
CM
CM
CM
O
Figure 2 -1. Diagram of Vapor Pressure for Toluene Diisocyanate
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primary and secondary amines and alcohols; surface active materials and
organo-metallic catalysts such as mercury and tin compounds.
TDI is not generally corrosive towards metals or other materials at
normal temperatures. However, isocyanates may attack and embrittle many
plastics and rubber materials in a short time. Recommendations concerning the
appropriate materials of construction or flexible hoses, etc., can be obtained
from raw materials suppliers or equipment manufacturers.
The primary potential health effects associated with exposure to TDI and
other isocyanates include respiratory effects (irritation/inflammation of the
respiratory tract, pulmonary hypersensitivity, lung function decrements),
dermal sensitization, and skin and eye irritation. Exposure to TDI at
concentrations below current occupational exposure levels (OSHA--20 ppb and
ACGIH--5 ppb) have caused elicitation of pulmonary hypersensitivity (e.g.,
asthma-like symptoms) in previously sensitized individuals.
In addition, TDI has been classified as a Group B2 carcinogen based on
the EPA Guidelines for Carcinogen Risk Assessment (51 FR 33992). This
classification indicates that there is sufficient evidence of carcinogenicity
from animal studies and that TDI is a probable human carcinogen.
TDI has a sharp, pungent odor which can be detected by 50 percent of
people at concentrations as low as 0.05 ppm. This odor and the strong
irritating effect of the vapors on eyes and upper respiratory tract may be
expected to alert workers to the presence of excessive concentrations of TDI
vapors in air.
The immediately dangerous to life or health (IDLH level) set for TDI is
given as 10 ppm. The IDLH represents a maximum concentration from which one
could escape within 30 minutes without any escape-impairing symptoms or any
irreversible health effects. This concentration can be readily attained in
the vapor space of closed vessels containing TDI since it corresponds to the
saturated upper pressure of TDI at 12°C (53.6°F) and ambient temperatures are
usually higher. Therefore, special precautions should be taken when entering
a vessel that has been in TDI service to avoid exposure.
2-4
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2.2 POTENTIAL FOR SUDDEN AND ACCIDENTAL RELEASES
2.2.1 General Considerations
There are several factors that must be considered when evaluating a
facility's potential for a sudden and accidental release. These include the
chemical and physical properties of the material stored and used; the quantity
of these materials; the type of storage, process and waste handling
operations; and the proximity of sensitive receptors and routes of exposure.
The primary intent of this section is to discuss potential means of ranking
hazardous materials used at a facility from the physical and chemical
properties standpoint. Other factors will not be addressed.
Sudden and accidental disaster scenarios can be grouped into five broad
categories:
o fires,
o explosions,
o release of a hazardous air pollutant (HAP),
o spill of hazardous chemical into surface water body, and
o contamination of potable aquifer.
The likelihood of any of these scenarios occurring at a given facility
depends in part on the physical and chemical properties of the chemicals being
handled at the facility. A significant determinant for a potential sudden and
accidental occurrence affecting people or property off-site is the quantities
of materials involved (i.e., in storage or in use). Other factors that must
be considered in assessing the degree of hazard presented by a chemical or
chemical process is the potential vector, or route of exposure: How would the
people/property off-site be exposed to the pollutant of concern? Routes of
exposure include inhalation, ingestion (water and food), and skin contact. In
a sudden and accidental exposure, i.e., acute exposure—the issue of avoidance
also has to be considered. Specifically, if the occurrence of a sudden and
accidental incident is known, ingestion of pollutants appearing in a surface
water body can be avoided by treating the water contaminated with a spill or
by not consuming contaminated food. An alternate source of water or food can
be found.
2-5
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It is more difficult to avoid exposure to airborne pollutants since an
alternate source of supply is not available, and the populace does not have
gas masks on hand. For these reasons it is generally hypothesized that an
accidental toxic gas release or an explosion/fire have greater potential to
harm the general population than spills. In addition, the potential for off
site impacts varies by chemical and physical properties such that gases are
worse than liquids, which in turn are much worse than solids due to relative
mobilities and ability to disperse, etc.
Therefore, the first step in hazard evaluation of any given facility
should be to identify the chemicals used at the facility and the quantities in
storage. The chemicals can then be evaluated to determine what type or types
of hazard they present. One means of doing this is to prepare a list as shown
in Table 2-2. The entries on the table indicate whether the material has a
fire or explosion potential, is a TAP based on the TLV, or is a hazardous
substance under 40 CFR Section 116.4. The designation of hazardous substance
can be used as an indicator of the water pollution potential of the chemical.
The reactivity column can be used to indicate which combinations of materials
stored or used at the facility should be avoided. These data are used in the
process evaluation, which is performed after the preliminary hazard
identification process. Entries in the table are made using the plant
inventory and commonly available references such as 40 CFR Section 116.4 and
the material safety data sheets provided for each material by the supplier.
Based on the above review of the chemical and physical properties and
quantities of materials stored at the example facility, the primary potential
disaster scenario example for the facility can be identified.
2.2.2 TDI Users
The example Table 2-2 presents specific data for TDI, the chemical of
concern in this evaluation. The data in the table suggest that the primary
concern from a sudden and accidental standpoint would be as a hazardous air
pollutant due to the very low TLV. However, TLV's alone do not completely
encompass all chemical properties that contribute to a specific chemical being
a TAP. However, the normal physical state for TDI is liquid and the vapor
pressure of TDI is low at ambient conditions, as shown in Figure 2-1.
Therefore, a ready vector does not exist. The table also shows that since the
2-6
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TABLE 2-2. EXAMPLE METHOD FOR PRELIMINARY HAZARD EVALUATION AT A FACILITY
Material
Toluene d11socyanate
F1re or
Explosion Potential
Combustible
decomposes and emits
toxic fumes of cyanide
and NO when heated
X
Crlter^
Potential Hazardous
TAP Substance
Yes Yes; RQ 100
TLV .005 ppm
Reactivity
Bases, amines,
alcohols, water
RQ = Reportable Quantity (Ibs) 40 CFR Section 116.4, and CERCLA list of hazardous substances.
Note: Fire potential, potential HAP and reactivity taken from material safety data sheets for each chemical,
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decomposition products of TDI in a fire are highly toxic, exposure of TDI to
fire should be avoided.
2.3 PROCESS EVALUATION
A second aspect of a facility-specific hazard evaluation involves
determining how the chemicals of concern are used or produced at the facility.
This section presents the results of a brief evaluation of the reaction of
toluene diisocynate with sucrose polyether, considering the processing
equipment in use at one of the Allegheny County TDI user facilities. However,
the chemical processes in use at the two facilities visited during the survey
were similar in that they were conducted irv a batch mode with little
instrumentation. The major difference between the processes at the two
facilities was the reactant combined with TDI. The results from this
evaluation should be applicable to both facilities.
Efforts have been made to obtain relevant information on the
thermodynamics and kinetics of the TDI/polyol reactions used at both
facilities; however, the TDI manufacturers contacted were unwilling to provide
information. One source, a technical information bulletin entitled
"Recommendations for the Handling of Toluene diisocyanate (TDI)," was
obtained. This bulletin offered the following information on TDI reactivity:
TDI is heavier than water and will sink to the bottom of
water-filled containers. Although it reacts with water, the rate
of reaction is slow at temperatures below 50°C because the
reaction produces insoluble urea at the interface which limits
mass transfer. At higher temperatures, or in well dispersed
systems the reaction becomes progressively more vigorous. This
reaction of TDI with water liberates carbon dioxide gas and a
solid, insoluble mass of polyureas is formed. Pressure can build
up in closed containers.
TDI will also react with basic chemicals such as sodium
hydroxide (caustic soda), ammonia, primary and secondary amines
and with acids and alcohols. The reaction may be violent,
generating heat which can result in an increased evolution of
isocyanate vapor and in the presence of water the formation of
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carbon dioxide, leading to increased pressure within closed
containers.
The high reactivity of isocyanates is the basis for the
poly-addition process for preparation of polyurethane plastics
and foams.
This information, coupled with several references, including "Double Duty
Scrubber for TDI Fumes," Plant/Operations Progress, October, 1983, Vol. 2,
No. 4, pp. 243-146; and "Exotherm Data Acquisition in Polyurethane Foam
Formation Using a Microcomputer," Analytical Instrumentation, 15(3), 201-213
(1986) indicate that in some instances TDI can react vigorously with polyols
and a runaway reaction could occur.
Many process characteristics, such as those presented in Table 2-3, can
affect hazard potential. These characteristics are arranged in a manner
compatible with a model developed by Radian Corporation to estimate the
probability of a release of hazardous air pollutants (HAP's) to the
atmosphere. That model was designed to generate a numeric result that could
be used to determine the relative probability/severity of a HAP release from
different processes on a generic national level. One part of the model, the
probability of a release value, can be evaluated meaningfully for a single
process, and is somewhat applicable to the focus of this study. The results
of the evaluation for production of a prepolymer resin by combination of TDI
and sucrose polyether give a value of 4 for the probability of an air release.
The evaluation placed urethane prepolymer production in last position out of
36 processes evaluated to date as shown in Table 2-4. This indicates that the
reaction has a low potential to release a toxic air pollutant as a result of a
sudden, accidental occurrence.
Considering all types of sudden or accidental occurrences, the chemical
processes involving TDI use in Allegheny County are considered to be below
average in terms of their potential contribution to the initiation/propagation
of a sudden or accidental release of a toxic air pollutant compared with the
range of processes in the chemical industry. The elements that tend to reduce
this potential include the low hazard nature of the products, the low
temperatures and pressures used in the process, the relatively low complexity
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TABLE 2-3. EXAMPLE OF FACTORS AFFECTING PRXESS HAZARDS
Parameter
TDI and Sucrose Polyether
Hazard Contribution Rating
Verbal Numeric*
Mode of operation
Thermodynamics
Type of Instrumentation
Severity of process conditions
Complexity of the process
Type of reaction
Types of separations
Material volatility
Material atmospheric reactivity
Volumes processed
Overall probability of release factor
from the model (on a 1 to 10 scale)
Batch
Exothermic
Operator hand control
Low temperature, atmospheric
Below average
Addition
None
Non volatile
TDI
Small
Above average
Higher than average
Above average
Below average
Below average
Average
Below average
Below average
Average
Below average
7
7
9
3
3
5**
0
3
5
3
4
*Numer1c rankings are assigned on a 1 to 10 basis, with a 1 representing an extremely low hazard
contribution, 5 an average contribution and 10 an extremely high hazard contribution.
**The categories "Type of Reaction" and "Type of Separations" are each rated on a 1 to 5 scale and
added to get a 1 to 10 rating for a combined field "Types of Processes."
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TABLE 2-4. RANKING OF PROBABILITY OF RELEASE
Vinyl Chloride by Thermal Cracking of EDC 44
Ethylene by the Pyrolysis of NGL 42
Crude Terephthalic Acid-Air Oxid. of Xylene 38
Carbon Tetrachloride by Chlorinolysis 36
Glycerin by the Isomerization Route 35
Acetic Acid by Butane Oxidation 35
Kynar Monomer 27
Isotron 142b 26
Allyl Chloride from Propylene 25
Maleic Anhydride by Batch Oxid. Benzene 24
Maleic Anhydride-Cont. Oxid. Benzene 23
Ethylene Glycol-Hydration of Ethylene Oxide 23
Acetic Acid by Oxidation of Acetaldehyde 22
Ally! Alcohol from Acrolein 22
Acrolein by Oxidation of Propylene 22
Formaldehyde by the Silver Process 22
Chloroformates by Phosgenation of Alcohols 22
Methane Sulfonyl Chloride from Methyl Mercaptan 21
Diketene by Dimerization of Ketene 19
Acetic Anhydride-Pyrolysis of Acetic Acid 19
n-Propyl Mercaptan from Propylene and H-S 19
Methyl Mercaptan from Methanol and H-S 18
Formaldehyde by the Metal Oxide Process 17
Ethylene Oxide by Direct Oxidation 16
Diethyl amine from Ethanol and Ammonia 16
Diethyl aminoethanol from Diethylamine and Ethylene Oxide 15
Acetic Acid by Methanol Carbonylation 15
Epichlorohydrin from Ally! Chloride 14
Glycerin from Allyl Chloride 12
Glycerin from Epichlorohydrin 11
Purified Terephatalic Acid from Crude TPA 9
Kynar Polymer 8
Methanol from Natural Gas 6
Hydrogen Fluoride from Fluorspar 6
Fatty Acid Chlorination with PCI- 4
*Urethane Prepolymer Resin from TDI and Sucrose Polyether 4
Note: Processes are listed in order of decreasing probability of release
*Subject process at Allegheny County
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of the process, and the lack of any exotic types of separation equipment.
Other factors which tend to increase the potential hazard of the process are
the toxic nature of the raw material, the lack of instrumentation used, and
the lack of specific information or the potential for a runaway reaction to
occur.
Other aspects of each facility's production process, including operating
details, the fire potential, and potential for spills will be discussed in the
facility-specific sections in Chapter 3 of this report. However, many other
facility-specific features can be included in a review of a facility to
determine its potential for a sudden, accidental release and their impacts.
These include the following:
o pressure control and relief system evaluation,
o fire protection/prevention evaluation,
o maintenance practices evaluation,
o environmental control devices and waste management facility
evaluation,
o electrical system review,
o chemical compatibility in storage area evaluation,
o structural integrity review,
o evaluation of operator training,
o emergency/contingency plans evaluation,
o evaluation of coordination with local emergency services,
o plant layout evaluation,
o evaluation of the effects of plant location with respect to
community impacts,
o evaluation of the environmental implications of a disaster, and
o evaluation of exposure associated with product or byproduct
transportation.
A detailed evaluation of all of these aspects is beyond the scope of this
work assignment; therefore, these items will not be covered during the
facility evaluation. However, where applicable in the facility-specific
discussions, reference will be made to some of these topics.
2-12
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3.0 FACILITY VISITS
This section consists of reports of the trips made to the Pruett-Schaffer
Chemical Company and to PPG Industries, Inc. Each trip report discusses the
chemical process used, TDI storage and any recommendations based on the team's
observations.
3.1 PLANT VISIT #1
I. Purpose
The purpose of the plant visit was to observe the urethane prepolymer
production process and equipment and to gather information on the control
techniques used at the Pruett-Schaffer facility.
II. Place and Date
Pruett-Schaffer Chemical Company
Tabor Street
Pittsburgh, PA 15204
March 10, 1987
III. Attendees
Elliott R. Coyle Jr., Pruett-Schaffer Chemical Company
Joseph L. Ruffing, Jr., P.E., Allegheny County Health Department
Richard Baker, Allegheny County Health Department
Robert E. Rosensteel, EPA/OAQPS
Andrew J. Miles, Radian Corporation
T. Kelly Janes, EPA/AEERL
IV. Discussion
This section describes briefly Pruett-Schaffer's prepolymer process used
at Pruett-Schaffer and then discusses emission sources, work practices and
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air pollution control used at the facility. Raw material storage is also
discussed.
The Pruett-Schaffer Chemical Company manufactures industrial protective
coatings, both water-based and solvent-based, using sheer mixing through
milling techniques. The facility also manufactures a polyurethane pre-polymer
resin in batched lots and warehouses and ships small amounts of industrial
chemicals. The manufacture of the pre-polymer resin is the subject of this
trip report.
The facility is located on a small plot of land in a mixed residential
and commercial neighborhood in Pittsburgh. The portion of the facility which
is the subject of this report occupies a concrete block building on the
northern property edge adjacent to a right-of-way. A residential neighborhood
borders the facility on the east and south, and there is a warehouse north of
the building across the right-of-way (see Figure 3-1).
Process Description
Pruett-Schaffer uses approximately 460,000 Ib/yr of toluene diisocyanate
(TDI) in the manufacture of polyurethane pre-polymer resin. This resin in
turn is used as one portion of a two-part urethane system for rigid foams in
boat building. A schematic drawing of the batch process is given in
Figure 3-2. The facility operates the process four days a week and produces
some 96 batches a year. Each batch takes approximately 14 hours to produce.
The process is operated only during the day shift, when all chemical
additions, raw material addition, and product withdrawal are completed.
In a typical batch the reactor is charged with some 7,675 pounds of feed,
consisting of 80 percent of TDI and 20 percent sucrose polyether. For a
typical batch the reaction sequence is as follows: 11 drums of TDI are
charged to the reactor using a positive displacement pump; when charging is
complete the pump and associated charge lines are flushed with mineral
spirits. At present the mineral spirits are recirculated. According to plant
personnel, little if any waste mineral spirits have been generated. Following
charging with TDI, three drums of the sucrose polyether are added one after
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CA>
I
oo
ST/IFFORD Sr.
cfjlr
Figure 3-1. Diagram of Pruett-Schaffer Facilities.
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OJ
I
_- ,/ Suction
y\—Jr Point
City
Water
Floating Bed
Scrubber
Suction
Point
Product
Drum
Air + CO,
to Atmosphere
Gas
Outlet
Water
ln
L
Blower
Water Out
Bypass
Regulator
Settling
Tank
To
Sewer
Water
Injection
Pump
Water
Pump
Urea
Solids
Figure 3-2. Schematic Draw;.'., of the Pruet t-bhaffer TDI Process
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the other. The sucrose polyether is withdrawn from a bulk storage tank
located in the same room as the reactor and placed in 55-gallon drums. Each
drum is weighed prior to addition. The filled drums of sucrose polyether are
heated on a gas-fired burner located in an adjacent room to lower the
viscosity and to help the material to flow. The drums containing the hot
material (no temperature specified or measured) is then placed on a pallet and
lifted by fork!ift truck to the top of the reactor. The sucrose polyether is
then slowly added to the stirred reactor through a 12- to 14-inch manway over
a period of several hours. During addition cooling water is circulated
through the reactor jacket and the contents is agitated. The temperature of
the reactor contents is monitored, using a single thermocouple attached to a
circular chart recorder. According to plant personnel, the reaction of the
TDI with a sucrose polyether (SPE) is mildly exothermic and the temperature of
the reactor rises to 125°F (51.6°C) within one to two hours. This temperature
can go as high as 150°F (65.6°C). The temperature is controlled by the rate
of SPE addition and the flow of cooling water. Addition of the first and
second drum of SPE takes about four to five hours. The reactor is allowed to
cool to 115-120°F (46-48.9°C) before the second drum is added. The third drum
of SPE is weighed, heated, and added to the reactor on subsequent day shifts.
The rate of addition is decreased for the second and third drum of SPE The
viscosity of the finished product and its free TDI content is checked to see
if they meet product specifications. Then the batch is placed in empty TDI
drums for subsequent shipment.
The temperature of the finished product can be as high as 110-120°F
(43.3-46°C) during drumming. However, neither the temperature nor flow rate
of the cooling water through the jacket is monitored. The operator determines
if the cooling water is flowing by observing valve positions, and by listening
for flow in the drainage pipes and by observing the drum outlet. There is no
level indicator on the reactor vessel; however, none is needed since the
quantity of materials charged for every batch is fixed and, according to
Pruett-Schaffer personnel, overfilling has never occurred. Some spillage of
finished product was noted around the manway on the reactor indicating that
the vessel is close to 100 percent full at the end of the batch. Typical
3-5
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practice in the batch chemical processing industry is to operate batch
reactors at 67-80 percent liquid capacity to avoid spillage.
According to plant personnel, loss of agitation or loss of cooling water
does not cause a runaway reaction. However, a crust may form on top of the
reactor. Addition of excess SPE is unlikely since the material is extremely
viscous and flows very slowly. Further, the manway on the reactor is too
small for the drum to fall in.
Air Emissions Control
There are several potential emission sources for the urethane pre-polymer
manufacturing process. These include the reactor, drum unloading, and drum
loading operations. Fugitive emissions from these sources are controlled by
two pickup points with a total airflow of 2,100 scfm ducted to a national dust
collector hydro-filter scrubber. This is a moving or floating bed scrubber
consisting of three plates or trays covered with glass or ceramic spheres.
These are kept in motion by the gas velocity moving through the bed and by the
jetting action of the nozzles located under each tray. A schematic drawing of
the scrubber is given in Figure 3-3. The scrubbing medium used is city water.
The water can be used on a once-through or a circulating basis. The design
water recirculation rate is 60 gallons per minute. There have been no
performance tests of the scrubber since it became operational and no analyses
of the scrubber effluent have been made. TDI reacts with water to form amides
and, subsequently, ureas. However, no data are available on reaction rates.
Calculations performed by Allegheny County Health Department representatives
based on best available information indicate 99.9 percent removal of TDI.
Emissions from the reactor are largely the result of gas liberated by the
reaction of the sucrose polyether with TDI as well as gas displaced during the
reactor filling operations. Emissions are therefore a function of the rate of
material addition and the temperature of the batch. Under the concurrent
control system the displaced vapors exit the reactor through a 12- to 14-inch
diameter manway on the reactor and are picked up by a suction point located
within six inches of the opening. Similarly, emissions resulting during drum
3-6
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SAS OUTLtT TO BiCW'e/-?
Figure 3-3. Schematic Drawing of the Scrubber.
3-7
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filling are controlled by a pickup point consisting of an eight-inch flexible
hose placed adjacent to the drum openings during the gravity filling
operation.
Raw Material Storage
Drum quantities of TDI are stored at one of three locations at the
facility. There are two storage locations inside the building: one in the
room away from the reactor and the second inside a wooden steam-heated
enclosure in the room containing the reactor and sucrose polyether storage
tank (see Figure 3-4). Several other raw materials are stored in the same
location, including gasoline (stored outside subsequent to the visit) and
titanium dioxide and aluminum powder in mineral spirits.
Several old reaction kettles are located in the building. Up to 90 drums
of TDI can be stored in the building. If additional quantities of TDI are
purchased these are stored on a concrete slab outside the building, adjacent
to a slotted yard drain. There is a single floor drain located inside the
building. This is kept plugged when the prepolymer product is being produced.
Operator Training
There is no formalized operator training at the Pruett-Schaffer facility.
In general, one man is responsible for all aspects of the prepolymer
operation, from weighing the raw materials, loading the vessel, and making the
product, to filling shipping containers. There are no written operating
instructions and all aspects of the operation were learned by rote. If the
single operator is not available, one of the managers runs the operation when
there is a demand for the product.
Emergency and Contingency Plans
In the past, the facility has prepared a contingency plan dealing with
fires; however, the plan does not cover spills or toxic g-as releases for the
TDI/prepolymer operation. According to plant personnel, the local fire
department was scheduled to visit the facility a few days after the team's
visit to help revise the plan.
3-8
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OJ
IO
o o
Divided Kettles
TGas
Fired
Drum
Heater
Raw Material
Storage
TDI Storage
Area
OOO
ooo
OOO
Operator
Station
Concrete Block Wall
Slot Drain
Reactor
Sucrose
Polyether
Storage
Tank
Stack
Q_
as Fired
Boiler
ll
O
o
o
0
Heated
jp Storage
for TDI
x-xAlum
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Raw Material
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D
Scrubber
and Equipment
Concrete Slab
-------
Recommendations
Several recommendations were generated as a result of the plant visit.
These are presented and discussed below.
!• Improve fire protection and contingency plan. To lower the potential
for a fire in the TDI/pre-polymer building, the amounts of combustible
materials stored in the building should be reduced. Improved housekeeping is
mandatory. During the visit, considerable quantities of cardboard boxes were
noted at several locations in the building. These were stored adjacent to the
wooden TDI drum warming structure. In addition, several half-full pails of
pre-polymer or resin were left adjacent to the reactor. A half-full drum of.
gasoline was stored in the building adjacent to a direct-fired space heater
and several small drums of aluminum powder in mineral spirits were located
adjacent to the aluminum paint mix tank.
Because of the potential for release of large quantities of toxic
decomposition products as well as TDI vapors, resulting from a TDI fire it is
recommended that:
a. TDI be segregated from other combustible and flammable materials and
sources of ignition to the maximum extent possible.
b. All extraneous packing materials, and used pails of prepolymer
should be removed from the building and disposed of properly.
c. Consideration should be given to replacing the wooden enclosure used
for warming TDI with one constructed of non-flammable materials.
d. Fire extinguishers should be properly mounted and located following
fire department and insurance company recommendations.
e. The fire department should be informed of the presence of
considerable inventories of TDI in the building and should ascertain
the best methods of fighting a fire or controlling a spill involving
the material.
f. Facility management should prepare a housekeeping inspection
checklist for the area to ensure that the area is kept clean and
free of extraneous flammable and combustible materials.
g. An emergency and contingency plan should be written which considers
how the impacts from a fire or a spill would be mitigated.
3-10
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h. The nearest downwind sensitive receptors should be identified (i.e.,
a community center, hospital, schools) and means of alerting them
determined.
i. The nearest hospital emergency room should also be contacted and
given appropriate material safety data sheets and first aid
information.
2. Provide additional process monitoring and control. The reaction
between TDI and sucrose polyether is exothermic. However, information on the
degree of exothermicity and the potential for a runaway reaction was not
available from Pruett-Schaffer personnel or producers of TDI. Pruett-Schaffer
personnel felt that the reaction could be monitored using temperature
indicators and controlled by the rate of addition of sucrose polyether, and
that cooling water failure or agitator failure would not lead to a runaway
reaction and subsequent release of TDI and SPE.
It is recommended that:
a. The temperature indicator and recorder be moved from the wall
adjacent to the reactor to a more distant location so the operator
need not be in the immediate vicinity of the reactor when monitoring
the operation. Alternatively, dual location of the temperature
indicator and recorder could be provided at the remote position.
b. Some means of positively identifying water flow to the reactor
jacket should be provided. This could include a simple flow
indicator or hourly visual checks of the discharge and recording
these observations on a log sheet.
c. Some means of monitoring water flow in the scrubber circuit should
also be provided.
d. For new employee training, the company needs to develop a written
procedure that will prevent the inadvertent heating of a drum
containing TDI rather than the sucrose polyether.
The emissions capture system on the reactor and the drumming operation
could also be improved. It is recommended that:
a. The existing ductwork be modified to include taking suction from the
reactor through one or both of the existing two-inch nipples. The
size of the nipple may have to be increased to avoid potential
plugging problems, lower the pressure drop and allow sufficient air
3-11
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to be pulled through the reactor opening to maintain a face velocity
of 100 to 200 feet per minute. This would change the direction of
air flow and prevent fugitive emissions of TDI leaving the reactor
through the manway (see Figure 3-3).
b. Some means of temporarily reducing the amount of open area at the
manway (e.g., a loose-fitting lid with a funnel connection) would
lower the volume of air required for effective capture of fugitive
emissions.
c. The existing flexible hose system for capture of emissions during
drumming and pumping should also be modified to improve capture.
Some suggested hood designs are shown in Figure 3-5. These designs
are taken from the industrial ventilation manual and have been
proven in practice.
3. Improve spill procedures. Several improvements to the spill
procedures are recommended:
a. Written procedures for control of TDI spills should be included in
the emergency and contingency plan for the facility.
b. A spill cleanup solution should be prepared and kept in the
TDI/pre-polymer building to neutralize spills (the recommended
solution is a mixture of water, surfactant, and alcohol or
*
ammonia). A bucket containing this solution should be placed under
the discharge pipe on the reactor to contain and neutralize small
drips and spills.
c. The batch size should be reduced so that the reactor is no more than
80 percent liquid full at the end of the run. This would eliminate
the overfilling which has apparently occurred sometimes in the past.
One other recommendation which does not affect the fire potential but is
a general safety item is that all the air supply bottles should be securely
fastened and chained to the wall and not left standing freely. Also, a
respirator program should be prepared since the operator uses an air supplied
respirator.
*
Technical Information, Recommendations for the Handling of Toluene
Diisocyanate (TDI), November 1980, compiled by International Isocyanate
Institute.
3-12
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Close clearance
co
Figure 3-5. Suggested Hood Design
Taken from American Conference of Governmental Hygienists Ventilation Manual
en
IT)
CO
8
i^
8
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3.2 PLANT VISIT #2
I. Purpose
The purpose of the plant visit was to observe the urethane alkyds
production process and equipment and to gather information on the control
techniques used at the PPG facility.
II. Place and Date
PPG Industries, Inc.
125 Col fax Street
Springdale, PA 15144
March 11, 1987
III. Attendees
Joseph L. Ruffin Jr., P.E., Allegheny County Health Department
Richard Baker, Allegheny County Health Department
David Jucha, PPG Industries, Inc.
C. F. Wallace, PPG Industries, Inc.
Other PPG personnel
Robert E. Rosensteel, EPA/OAQPS
Andrew J. Miles, Radian Corporation
T. Kelly Janes, EPA/AEERL
IV. Discussion
This section briefly describes the urethane alkyds production process at
PPG Industries, Inc., and also discusses the air pollution control equipment
used at the facility to control TDI emissions and methods of TDI storage.
The PPG facility at 125 Col fax Street manufactures a variety of paint and
resin products. Paint manufacturing consists of combining resins, solvents,
pigments, and additives through the milling and grinding equipment. Resin
manufacturing consists of combining reagents in heated reactors and reaction
vessels and/or mixing and blending of raw materials and resins to form a
usable product. The manufacture of two urethane alkyds using TDI is the
subject of this report.
3-14
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V. Process Description
PPG currently uses approximately 71,000 Ib/yr of toluene diisocyanate
(TDI) in the manufacture of two urethane alkyd products. These products are
used in paint formulation elsewhere in the facility or at other PPG locations.
A schematic drawing of the batch process used at PPG for both urethane alkyds
is shown in Figure 3-6. The facility currently operates the process five days
a week and produces 30 to 40 batches per year. Each batch takes approximately
four hours to produce.
Currently, two different alkyds are produced: one uses 3,500 gallons of
resin and 220. gallons of TDI, and the second uses 2,000 gallons of resin and
100 gallons of TDI.
In a typical batch, the resin is charged to the reactor and heated to
180°F (82°C). The requisite amount of TDI is then charged through a pump and
meter into the agitated resin in the vessel. The mix typically undergoes a 5
to 10°F (2.8-5.6°C) rise in temperature due to the exotherm. After the
temperature has peaked in the reactor, heat is then applied to complete the
reaction. Completed resin is then pumped to another processing area. The
reaction vessel has a nominal volume of approximately 4,500 gallons.
According to plant personnel, there is sufficient volume left for any
expansion resulting from the reaction. Loss of cooling or agitation in the
reaction vessel is no particular problem, since the exotherm is only 5 to
10°F (2.8-5.6°C). Addition of excess TDI is avoided by the use of the meters
in the transfer lines. These meters are read before and after TDI is added.
Air Emissions Control
There are several potential emission sources for the urethane alkyd
process. These include tank truck unloading, transfer from the bulk storage
tank, and emissions during the reaction. All of these emission sources are
controlled using a two-stage water ejector system. Water used in the ejectors
is constantly recirculated. No data were available on either the air flow
rates or the water flow rates in the ejectors. However, data in the
literature suggest that this type of scrubber can be very effective in
controlling TDI emissions.
3-15
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Vent Lines
Liquid Lines
Flow
Switch
Tank Truck
Unloading
To Bulk
Storage
Tank
s
le
:
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9
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Figure 3-6. Schematic Drawing of Urethane Alkyds Process at PPG
-------
Emissions from the reactor and the storage vessels are largely the result
of gas displaced during the storage tank and reactor filling operations. No
gas is liberated by the reaction of the resin with TDI. Emissions, therefore,
are a function of the rate of material addition and the temperature of the
batch. Emissions from the reactor at 80-90°C could be as high as 2,000 parts
per million if equilibrium of TDI were achieved. However, the actual vapor
pressure exerted by the TDI will be lowered in proportion to its mole fraction
in the reactor. Even at 5 mole percent the vapor pressure of TDI would be
higher than the IDLH of 10 ppm. It may be advisable to consider using an
alternate scrubbing medium in the recirculating system such as aqueous ethyl
alcohol with 1 to 2 percent potassium hydroxide, to improve the scrubbing
efficiency. The two-stage scrubber may in fact work well. However, there
have been no emission tests of the system, although an ambient sample was
taken during tank truck unloading around one of the vents on the scrubbers
approximately three feet downwind, and no TDI was detected.
Raw Materials Storage and Unloading
The PPG facility has one bulk storage tank for TDI with a 2,000 gallon
capacity isolated in a room on the first floor of the facility. There are
four openings or piped conduits in the floor of the tank room. Any spills
occurring in the tank would not be contained in the area.
TDI is received by tank truck in 1,200 to 1,500 gallon shipments. The
tank truck unloading area consists of a concrete pad. During tank truck
unloading the yard drain in the vicinity is plugged. In addition, quantities
of a neutralizing solution consisting of water, ammonium hydroxide, and
detergent are kept at the door adjacent the unloading area in the event of a
spill. The unloading line is also equipped with low flow air-actuated valves
which close if a line rupture occurs. Some area sampling has been conducted
during the tank truck unloading. Very low levels, less than 5 ppb, in the
immediate vicinity during unloading of TDI have been noted. A maximum of
13 ppb was detected at a hose connection during initial hookup for unloading.
3-17
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Other Items
The facility has written procedures to be followed for tank truck
unloading and production of the polymer. In addition, the facility has
prepared detailed emergency and contingency plans for the operation. All PPG
facilities participate in local community awareness (CAER) programs and they
are now actively involving the Springdale Fire Department.
Recommendations
Very few recommendations were generated as a result of the plant visit.
These are presented below.
1. Provide spill protection in the bulk tank ro>om, and monitor for TDI
in the basement under the tank in the event of a spill. If a spill
were to occur from the bulk storage tank or associated pumps and
piping, it would not be contained. Some means of plugging the four
pipe conduits should be provided along with curbing inside the
doorway to help contain the spill.
2. Conduct a performance test on the scrubber or devise a method of
monitoring the scrubber performance. If scrubber performance is
unsatisfactory, consider changing the scrubber medium to aqueous
ammonia and potassium hydroxide.
3-18
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/3-87-022
2. 3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE 5. REPORT DATE
Evaluation of Potential Emissions of TDI from Two October 1987
Facilities
7. AUTHOR(S)
9. PERFORMING ORGANIZATION NAME M
Office of Air Quality Plan
Environmental Protection A
Research Triangle Park, Nor
12. SPONSORING AGENCY NAME AND ADC
DAA of Air Quality Planm'n
Office of Air and Radiatio
U.S. Environmental Protect
Research Triangle Park, No
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
4D ADDRESS 10. PROGRAM ELEMENT NO.
ning and Standards
jenCy 11. CONTRACT/GRANT NO.
th Carolina 27711
JRESS 13. TYPE OF REPORT AND PERIOD COVERED
g and Standards Final
n 14. SPONSORING AGENCY CODE
ion Agency
rth Carolina 27711 EPA/200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Two facilities which use TDI were inspected by EPA at the request of a county air
pollution control agency. The inspections were performed to identify potential
sources of routine and accidental releases of TDI. This report presents the results
of the inspections.
17.
a. DESCRIPTORS
Air Pollution
Pollution Control
Volatile Organic Compounds
Air Toxics
Toluene Diisocyanate
TDI
18. DISTRIBUTION STATEMENT
Unlimited
KEY WORDS AND DOCUMENT ANALYSIS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air Pollution Control 13g
Stationary Sources
Accidental Releases
19. SECURITY CLASS (This Report 1 21. NO. OF PAGES
Unclassified 38
20. SECURITY CLASS (This page) 22. PRICE
Unclassified
EPA F
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