Source Reduction Research Partnership
Metropolitan Water District of Southern California
Environmental Defense Fund
Source Reduction of
Chlorinated Solvents
Prepared for
Alternative Technology Division
Toxic Substances Control Program
California Department of
Toxic Substances Control
and
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
June 1991
•*v*S?
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Source Reduction Research Partnership
Metropolitan Water District of Southern California
Environmental Defense Fund
Source Reduction of
Chlorinated Solvents
FLEXIBLE FOAM MANUFACTURE
Prepared for
Alternative Technology Division
California Department of
Toxic Substances Control
P.O. Box 806
Sacramento, CA 95812-0806
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
June, 1991
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TABLE OF CONTENTS
I. ACKNOWLEDGMENT i
II. DISCLAIMER jj
III. PREFACE
I. INTRODUCTION
II. BACKGROUND 6
FOAM PRODUCTION PROCESS 7
FOAM AND BLOWING AGENT USE .. 13
FOAM INDUSTRY CHARACTERIZATION 16
RESULTS OF VISITS/SURVEYS 22
FUTURE INDUSTRY TRENDS 23
III. SOURCE REDUCTION OPTIONS FOR SLABSTOCK 36
FOAM BLOWING
PRODUCT SUBSTITUTION 36
CHEMICAL SUBSTITUTION 39
EQUIPMENT MODIFICATION 47
PROCESS MODIFICATION 49
“AB” PROCESS 49
RECOVERY AND RECYCLE 52
IV. SOURCE REDUCTION OPTIONS FOR 60
SOLVENT APPLICATIONS
RECOVERY AND REUSE 60
V. ANALYSIS OF SOURCE REDUCTION OPTIONS 62
FOR FOAM BLOWING APPLICATIONS
SELECTION OF BLOWING AGENT OPTIONS 62
“NO FURTHER ANALYSIS” OPTIONS 62
“LIMITED ANALYSIS” OPTIONS 64
- FULL ANALYSIS OPTIONS 73
VI. ANALYSIS OF SOURCE REDUCTION OPTIONS 88
FOR SOLVENT APPLICATION IN FOAM PLANTS
SELECTION OF SOLVENT OPTIONS 88
VII. ANALYSIS OF SOURCE REDUCTION OPTIONS 91
FOR SOLVENT APPLICATIONS
SELECTION OF SOLVENT OPTIONS 91
OFF-SITE RECYCLING 91
SUMMARY OF RECYCLING 92
VIII. SUMMARY AND CONCLUSIONS 95
SUMMARY OF SOLVENT CLEANING OPTIONS POTENTIAL 96
IX. BIBLIOGRAPHY 100
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LIST OF FIGURES
2.1 CHEMICAL REACTIONS INVOLVED IN FOAM PRODUCTION 8
2.2 TYPICAL FOAM LINE 12
2.3 PRODUCT MIX OF A TYPICAL SLABSTOCK PLANT 24
2.4 PRODUCT NIX FOR PLANT #1 25
2.5 PRODUCT NIX FOR PLANT #2 26
26 PRODUCT MIX FOR PLANT #3 27
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LIST OF TABLES
1.1 QUALITATIVE POTENTIAL OF SOURCE REDUCTION 3
OPTIONS FOR BLOWING AGENTS
1.2 QUALITATIVE POTENTIAL OF SOURCE REDUCTION 6
OPTIONS FOR SOLVENT CLEANING
2.1 TYPICAL SLABSTOCK FOAM FORMULATIONS 9
2.2 HISTORICAL FLEXIBLE FOAM PRODUCTION 14
2.3 SLABSTOCK FOAM USE BY APPLICATION — 1985 15
2.4 U.S. FLEXIBLE POLYURETHANE SLABSTOCK PLANTS 16
2 • 5 SOUTHERN CALIFORNIA FLEXIBLE POLYURETHANE 19
SLABSTOCK PLANTS
2.6 PROFILE OF SURVEYED PLANTS 20
2.7 FOAM MARKETS OF SURVEYED PLANTS 21
2.8 PROJECTED STATUS OF FOAM INDUSTRY - 199]. 34
2.9 CURRENT AND FUTURE BLOWING AGENT USE 35
3.]. PROPERTIES OF CURRENT AND PROPOSED 37
BLOWING AGENTS
3.2 HEALTH AND ENVIRONMENTAL CHARACTERISTICS OF 41
CURRENT AND PROPOSED BLOWING AGENTS
5.1 CLASSIFICATION OF BLOWING AGENT OPTIONS 63
5.2 ANNUAL COST INCREASE AND METH EMISSIONS 65
5.3 ANNUAL COST INCREASE AND METH EMISSIONS
REDUCTION FOR TCA SUBSTITUTION 66
5.4 ANNUAL COST INCREASE AND METH EMISSION 70
REDUCTION FOR POLYURETHANE MODIFICATION
5.5 ANNUAL COST INCREASE AND METH EMISSION 71
REDUCTION FOR LIQUID ABSORPTION
5.6 ANNUAL COST INCREASE AND METH EMISSION 72
5.7 SUMMARY OF ANNUAL COST AND BLOWING AGENT 74
USE REDUCTIONS FOR “LIMITED ANALYSIS”
OPTIONS U.S.
5.8 SUMMARY OF ANNUAL COST AND BLOWING AGENT 75
5.9 CHARACTERISTICS OF SMALL, MEDIUM AND LARGE PLANTS 76
5.10 CAPITAL COSTS FOR CARBON ADSORPTION SYSTEM’ 79
5.11 ANNUALIZED OPERATING COST FOR CARBON ADSORPTION 80
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5.12 ANNUAL COST AND METH EMISSION REDUCTION FOR 82
CARBON ADSORPTION SYSTEM
5.13 ANNUAL COST AND METH EMISSION REDUCTION FOR 87
MINIMUM DENSITY SPECIFICATION
6.1 CLkSSIFICATION OF SOURCE REDUCTION OPTIONS 89
FOR SOLVENT CLEANING USES
6.2 ANNUAL COST AND METH USE REDUCTION FROM RECYCLING 93
7]. SUNM RY OF SOURCE REDUCTION OPTIONS IN THE 96
FLEXIBLE FOAM INDUSTRY
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i.
ACKNOWLEDGMENT
The principal sponsors of this project, The Metropolitan
Water District of Southern California and the Environmental
Defense Fund gratefully acknowledge major support from the
Switzer Foundation and from the U.S. Environmental Protection
Agency, The California Department of Health Services, and the
City of Los Angeles, (Los Angeles Department of Water and
Power). Additional support was received from Southern California
Edison Company.
The Environmental Defense Fund also gratefully
acknowledges the support of the Andrew Norman Foundation an the
Michael J. Connell Foundation for the exploratory phase that led
to the formation of the Source Reduction Research Partnership and
the development of the research plan.
The principal project sponsors recognize the effort and
contributions of many people from industry and government who
helped in preparation of these reports. These efforts and
contributions are being gratefully acknowledged.
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ii
DISCLAIMER
The statements and conclusions of this report do not
necessarily represent those of the State of California, the U.s.
Environmental Protection Agency or any other contributors. The
mention of any commercial products, their source or their use in
connection with material reported herein is not to be construed
as either an actual or implied endorsement of such products.
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— iii —
PREFACE
This report is one of twelve reports that evaluate the
opportunities for source reduction of chlorinated solvents in
twelve specific industries. The twelve reports are part of a
large-scale study sponsored by the Source Reduction Research
Partnership (SRRP), a joint venture by the Metropolitan Water
District of Southern California and the Environmental Defense
Fund. The reports cover the following industries and industrial
practices:
1. Aerosols Manufacture
2. Adhesives Manufacture
3. Chemical Intermediates Manufacture
4. Dry Cleaning of Fabrics
5. Electronic Products Manufacture
6. flexible Foam Manufacture
7. Food Products Manufacture
8. Paint Removal
9. Pesticides Formulating
10. Pharmaceuticals Manufacture
11. Solvent Cleaning
12. Textiles Manufacture
The objectives of the SRRP study include a survey and
evaluation of existing and potential techniques for reducing the
generation of halogenated solvent wastes, and thus their
potential release into the environment, across a wide range of
the industrial users of thee. solvents.
Each of the industry-specific reports begins with a
description of the industry and processes where halogenated and
solvents are used. Sources and causes of releases are described
and regulatory regime discussed for waste streams of concern.
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— iv —
Subsequent sections focus on source reduction
opportunities through chemical substitution, process
modification, product substitution and recovery/reuse. For major
solvent using industries, select source reduction options were
analyzed for their economic feasibility.
The information in the reports was compiled and analyzed
by the SRRP project staff, employed by the Partnership to carry
out the project research. Each report was reviewed by industry
representatives and/or other experts familiar with the specific
industry and the relevant technologies and issues, and then
reviewed and edited by an additional expert consultant.
The intent of the sponsors is to provide all interested
parties with useful information on available and potentially
available methods for source reduction of halogenated solvents,
in the context of specific industries and processes, and an
evaluation in context of the various source reduction Options.
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—1-
I. INTRODUCTION
The five major chlorinated solvents most widely used in
conrn erce today include trichioroethylene (TCE), pechioroethylefle
(PERC), i,1,1 trichloroethafle (TCA), methylene chloride (METH),
and i,l, 2 _trichloro ].,2,2triflu0r0ethane (CFC—113). Two of
these--METH and TCA--are employed in the production of flexible
polyurethane slabstock foam, which is used in a diverse range of
applications including furniture cushioning, carpet underlay and
packaging applications. Carbon dioxide is the primary blowing
agent for flexible slabstock foam. METH and TCA function as
auxiliary blowing agents that expand the cells of the foam.
The flexible foam industry uses about 18 thousand metric
tons (mt) of METH annually as an auxiliary blowing agent; an
additional 5 thousand mt of METH is employed for various solvent
cleaning purposes in the slabstock and molded foam industries. A
few foam plants have recently adopted TCA as an auxiliary blowing
agent and its current use probably does not exceed 3 thousand
mt. By the end of 1990, however, its use is likely to amount to
17 thousand mt. Because TCA has been adopted so recently, most
of the analysis presented here focuses on METH. It does include
a discussion, where appropriate, of differences between the two
blowing agents that would change the applicability of the source
reduction options.
It is possible that METH and TCA use in foam blowing
operations may increase in the next few years because of
regulations and a tax on the major alternative, CFC-ll.
Production of this latter chemical will be restricted because it
is part of a family of chemical--the chiorofluorocarbons
(CFCs)--that are suspected of depleting the stratospheric ozone
layer Congress placed a tax on the chemical that became
effective in January, 1990. METH is currently under intense
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—2—
regulatory scrutiny as well. The Occupational Safety and Health
Administration (OSHA) is expected to lower the permissible
workplace exposure level significantly in the near future. METH
is on the California Proposition 65 list and the state has recently
announced that it will regulate the chemical as a toxic air
contaminant. TCA contributes to ozone depletion as well but its
ozone depletion potential is only about one-tenth that of
CFC-ll. Its production may be restricted in the future.
Table 1.1 summarizes the source reduction options
evaluated in this study for foam blowing operations along with
their advantage and disadvantages.
This study includes a full cost and METH emissions
reduction analysis of two blowing agent options; a minimum density
specification for foam and use of carbon adsorption for vapor
recovery. The results suggest that a minimum density foam
specification would be cost-effective at a blowing agent price of
$1.03 per kilogram which can be compared with current prices for
METH and TCA of $0.64 and $0.91 per kilogram respectively.
Carbon adsorption alone would be cost-effective at a blowing
agent price of $0.34 per kilogram but the analysis does not apply
for TCA. A minimum density foam specification followed by
adoption of carbon adsorption would be cost—effective at a
blowing agent price of $4.26 per kilogram.
CFC-11 will be phased out by the end of the century and
will no longer be available for use as a blowing agent. The
congressionally mandated tax that became effective in January
1990 approximately doubled the price of CFC-ll. The foamers
still using CFC-3.1 will increasingly attempt to adopt METH and
TCA which are much less costly to use. State and local
governments are discouraging the use of METH and some may
require foamers using METH to install vapor recovery. For this
reason, the study includes a full analysis of the recovery
option. METH recovery has never been demonstrated and recovery
is unlikely to lead to more than about a 30 percent reduction in
NETH use. A more promising option for the foam industry is
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—3—
Table 1.1
QUALITATIVE POTENTIAL OF SOURCE REDUCTION OPTIONS
FOR BLOWING AGENTS
Option Use Reduction 8 Time Frameb
Product Substitution
Non-polyurethane Alternatives Small Short
Specify Minimum Density Foam Medium Short
Chemical Substitution
Acetone Medium Short
CFC-ll Large Short
HCFC-l23 Large Long
HCFC-141b Large Long
Equipment Modification
Max-Foam Process Small Short
Vertifoam Process Small Medium
Process Modification
AB Process Medium Medium
Polyurethane Nodification/ Large Medium
Additives
Recovery and Recycle
Liquid Absorption Medium Medium
Vapor Condensation Medium Medium
Carbon Adsorption Medium Medium
Brayton cycle Medium Medium
Membrane System Medium Medium
Polymeric Adsorption System Medium Medium
8 Low indicates none to 10 percent; medium indicates 10 to 40
Percent; large indicates more than 40 percent.
hort indicates immediate; medium indicates an immediate to
three year implementation long indicates more than a three year
implementation.
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—4—
polyurethane modification and development of additives. This
option is likely to become available over the next five years and
it would be capable of eliminating auxiliary blowing agent use
altogether. Currently, there are some additives available that
can reduce-—but not completely eleiminate---blowing agent use. If
foamers were required to install recovery, a much less promising
option, industry resources would be diverted from R&D funds for
investigating additives which over the long-term offer the best
solution.
Table 12 sununarizes the source reduction options
evaluated in this study for solvent cleaning uses. Again, it
also presents a qualititative estimate of the ?4ETH use reduction
that could be realized and the time frame over which the option
could be adopted.
The balance of this document discusses the state of the
flexible slabstock foam industry. Section II focuses on the
slabstock foam production process and provides characteristics of
the industry structure. Section III describes the source
reduction options that might be used to reduce the use of 14ET}I as
a blowing agent in slabstock foam production. Section Iv
presents the results of the use reduction and cost analysis of
the blowing agent options. Section V identifies and discusses
the source reduction options for reducing METH use as a cleaning
solvent in flexible slabstock and molded foam operations.
Section VI presents the analysis of the cleaning options.
Finally, Section VII summarizes the findings.
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—5—
Table 1.2
QUALITATIVE POTENTIAL OF SOURCE REDUCTION OPTIONS
FOR SOLVENT CLEANING
a
USE REDUCTION TIME FRAME
Chemical Substitutiofl
DBE Large Short
NXP Large Short
Recovery and Recycle of Waste
On—Site Distillation Small Short
Off-Site Distillation Small Short
a
Short indicates immediate to two year implementation.
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—6—
II • BACKGROUND
In the United States, flexible foam manufacture began in
the l950s. These foams are important for their cushioning
characteristics in the manufacture of furniture, bedding, carpet
underlay, automobile seats and various other applications.
Flexible foams can be molded into their final shape as in
automobile seats, for instance--or they can be produced as
slabstock, a large continuous bun that can be sawed into pieces
with desired dimensions.
Blowing agents are used to form the cells in the foam,
imparting flexibility. Carbon dioxide is the primary blowing
agent in all flexible foams. In some high density, firmer
foams--so called water blown foams-—carbon dioxide is the sole
blowing agent. In less firm, softer foams, two auxiliary blowing
agents, trichiorofuorOiflethafle (CFC-ll) and METH, have
traditionally been employed. Another auxiliary blowing
agent--TCA--has recently been tested successfully. Slabstock
foam can be solely water blown or it can be blown with CFC-ll,
METH or TCA as auxiliary blowing agents. Molded foam can be
water blown or it can be blown with CFC—13. as an auxiliary
blowing agent; METH is not used ira the production of molded foam.
The remainder of this section is divided into four
parts. The first subsection summarizes urethane chemistry and
the foam production process. The second subsection presents
estimates of the use of blowing agents. The third subsection
provides information Ofl plant location and industry
characteristics. The fourth subsection summarizes the results of
the surveys. The fifth subsection discusses the future of this
dynamic industry in the light of impending regulatory changes.
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—7 —
LOAN PRODUCTION PROCESS
The major chemical reactions that place in foam
manufacture are shown in Figure 2.1. The urethane polymer is
formed as shown in equation (1) through the reaction of an
isocyanate (— IWO) with a polyol (—OH). In the second set of
reactions the isocyanate (—NCO) reacts with water to form a urea,
evolving carbon dioxide gas. The carbon dioxide produced in the
reaction produced in the reaction functions as the primary
blowing agent. The disubstituted areas formed in the next
reaction are rigid linkages that impart the polymer its strength.
The more water used in the foam formula, the greater the
urea formation and the more rigid the foam. The more water, the
more carbon dioxide is liberated, giving a less dense foam.
Thus, increasing the water which forms the primary blowing agent,
leads to a less dense foam but also one that is more rigid. As
discussed below, auxiliary blowing agents—-like CFC—l1 or
METH--are used to reduce foam density further without
simultaneously increasing the rigidity and for control of the
reaction temperature.
The isocyanate used in slabstock production is toluence
diisocyanate (TDI), a mixture of two different diisocyanate
isomers. The polyols most widely used are based on diols or
triols, and are in the molecular weight range of 3,000 to 6,000.
Other ingredients that are necessary in the foam formulations
include catalysts, aurfactants, fillers, flame retardants,
colorants, and auxiliary blowing agents.
Table 2.1 shows several typical formulations that employ
METH and CFC-3.l as auxiliary blowing agents. It is conventional
to present the components of various formulations in parts per
hundred of polyol (php). Thus, in Table 2.1, levels of all
ingredients are given in terms. The amine catalyst, ranging from
0.1 to 1.0 php in Table 2.3. increases the rate of the
isocyanate/water reaction which forms carbon dioxide, the primary
blowing agent. The tin (stannous octoate) catalyst speeds up the
polyol/isocyanate reaction in the formation of the polyurethane.
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ISOCYANATE/POLYOL REACTION TO FORM POLYURETIIANES
- a -14 = C = 0 + - R’- OH -> - R - N - C - 0 - Ii ’ -
I It I’)
1 0
ISOCYANATE POLYOL. POLYURETHANE
ISOCYM1ATE/WA ER REACTION TO FORM DISUBSTITUTED URE1 S
-R-N=C0 + H-O-H > -R-H- -O-H
ISOCYANATE WATER
UNSTABLE ACID
19
+ CO 21
CARBON DIOXIDE 12)
-fl-N-H + -R-NC0 > -R-N-C-N-R
I I I I 13)
(I HO ft
ISOCYAZIATE DISUBSTITUTED UREA
Figure 2.1 • CHEMICAL REACTiONS INVOLVED 114 FOAM PRODUCTION
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?ABLE 2.1. TYP1C1 L SIABSTOCK FOM FORMULATIONS
PARTS PER hUNDRED POLYOb (php)
FORMULATION 1 2 3 4 5 6
a a a 1 a
POLYO 1. 100 100 100 100 100 100
C
ISOCYAMATE (WI) NA .15.0 46.0 NA 42.5 NA
AI4INE A?ALYST 0.15 0.2 0.2 0.1 1.0 0.3
STAMI00S OCTOATE CAThLYST 0. B 0.65 0.3 0.275 1 .75 0.38
SURFACTM1T 1.2 1.3 1.2 1.0 2.0 1.4
WATER 3.5 3.4 2.6 4.3 3.5 3.5
METB 25 20 10 4 — —
CFC—11 - - - - 13.5 25
PROPERTIES
DENSITY (1b/ft ’) 0.98 1.0 1.6 1.21 1.4 1.0
d
25% IFD Ciba) 10 13 19 33 NA 13
65% lID (ibs) 19 24 34 60 NA 23
a
Polymer with molecular weight 3010.
b
Polymer with molecular weight 3040.
C
NA Means not available.
d
IFO (Indentation Force Deflection) Is a a.easure of foam firmness.
Sources: U.S. EPA (1908); Sayad and WiLliams (1979a); Sayad and Williams (1979b).
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— 10 —
The surfactant is used to control the size of the cells and to
stabilize the foam as it rises. The IFD or Identation Force
Deflection given in Table 2.1 is a measure of the firmness of the
foam. It is the force required to compress the original foam
height by 25 percent or 65 percent. The higher the IFD, the
firmer the foam. The softest foams have IFDs less than 18
whereas the firmest foams have IFDs of more than 40.
In comparing columns 3 and 4 of Table 2.1, foam density
decreases with increasing water; greater use of water also
increases firmness (IFD). A rule of thumb in evaluating blowing
agents is that 1 php of water is roughly equivalent to 10 php
CFC-ll or 8.5 php methylene chloride (Oertel et al, 1985). This
source suggest that because of it lower molecular weight, about
15 percent less METH is required to produce the same amount of
foam produced with CFC-11. An industry representative indicates
that, in practice, 5 to 10 percent less METH is required.
Slabstock foam is produced on a conveyor belt that can
be a variety of lengths, called a foam line. The process is
depicted in Figure 2.2. The foam producing reactions occur in
the foam tunnel which is surrounded by plastic or metal
curtains. The reactants are pumped to the mixing head and
discharged through a nozzle where they pur onto the belt. In the
foam tunnel, the reactants form a “bun” which reaches its maximum
height within two to four minutes. Roughly half the auxiliary
blowing agent is lost in the foam tunnel and the balance is lost
within 24 hours. The foam leaves the tunnel ready to be sawed
into buns from which the finished products can be cut. The
bunstock is sawed and the cut sections are transported by the
conveyor to the Curing and storage area.
The slabstock line must be heavily ventilated. The
exhaust vapors contain TDI, a hazardous chemical which has a
Permissible Exposure Level (PEL) of 0.005 ppm and Short Term.
Exposure Level (STEL) of 0.02 ppm. There are generally one or
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more large ducts along the foam line which circulate ambient
plant air through teli conveyor. By the time the foam has left
the tunnel, most of the reactions have taken place. The foam
then goes to the curing area which genrally has much lower
venilation levels because most the TDI has already been consumed
in the foam reactions.
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tONSOIf
WATER
$ ANT
CAlMEST
TO SAIlS —‘-——————-- [ IIIIIIIII}
& e lm wue
VARfiICAIPON & STOMGE
I: i :;:i Iqi r1R1
IIG I*E22
TYPICAL FOAM LINE
SelelCi FARMEC .1 ii. 1S1
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— 13 —
FOAY AND BLOWING AGENT USE
Table 2.2 shows the historical nationwide production of
flexible slabstock and molded foam combined. Table 2.3 specifies
the use of slabstock foam in a variety of applications for 1985.
Furniture and carpet underlay applications together accounted for
roughly two—thirds of the total slabstock production.
CFC—l]. use in slabstock foam amounted to 11.4 thousand
mt in 1985 (Hainmitt et al, 1986). Use of METH in slabstock foam
in 1984 is estimated at 10.1 thousand mt (Pandullo and Nash,
1986). In 1989, about 18 thousand mt of METH was employed in
foam production. CFC-ll use in slabstock foam manufacture has
declined and was lower, at 68 thousand mt. Until the early
1980s, most slastock was produced with CFC-1l. Because of
improved economics in the METH process, there was a switch to
NETH. Developments in better amine catalysts have allowed
increased METH use, even in the lower density foams where CFC—ll
has been traditionally used (Modern Plastics, 1982; Sayad and
Williams, 1979a; Sayad and Williams, 1979b; Moore, 1982).
In 1987, production of flexible foam amounted to about
700 thousand mt. Slabstock represented roughly 570 thousand mt
and molded foam accounted for about 130 thousand mt. About 60
percent of the slabstock foam produced today is made using CFC-l1
or METH as auxiliary blowing agents; the remaining 40 percent is
blown with only water, the primary blowing agent. Much of the
molded foam is made with only a primary blowing agent. CFC-11 is
the sole auxiliary blowing agent used in molded foam
applications. METH has not been used as a blowing agent in
molded foam production because it has a greater tendency to be
retained in the mold which can cause foam collapse or surface
defects. Although the METH does not function as a blowing agent,
it is apparently used to clean the molds and the foam mixing
heads. Such cleaning uses of METH in both slabstock and molded
operations are estimated at 5.2 thousand mt currently.
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Table 2.2
HISTORICAL FLEXIBLE FONI PRJDUCTION
YEAR PRODUCTIONS’
(thousand metric tons)
1960 38
1965 108
1970 276
.1975 435
1980 f 75
1985 675
1986 NA ’
1987 700
Includes slabstock and molded foams.
b NA means not available.
Sources: Mooz and QuInn (1980); Haninitt et al (1986); Industry Sources.
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Table 2.3
SLABSTOCK FOAM USE BY APPLICATION 1985
APPLICATION USE
(U ousa ids ot metric tons)
Furniture 225
Carpet Underlay 150
Transportation 85
Bedding
Textiles 15
Packaging 15
Scrap 5
Miscellaneous S
TOTAL 570
Source: U.S. EPA (1988); Industry Sources.
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— 16 -
FOAM INDUSTRY CHARACTERIZATION
There were 47 firms located throughout the U .S.
operating 106 plants involved in the production of flexible
slabstock foam in 1985. Significant consolidation has occurred
over the last few years and there are now 26 firms with 81 U.S.
plants. The firms and their plant locations are listed in Table
2.4. The plants using METH in 1989.in Table 2.4 are those with
an asterick next to the name (Industry Sources). METH was used
by 50 plants or 62 percent of the foam plants operating in 1989.
TCA is presently employed by seven U.S. plants or about 9 percent
of the plants. The remaining plants exclusively use CFC-1l.
Table 2.5 summarizes the plants operating in Southern
California. Of these six Southern California plants, four use
METH, and until recently, the two others used CC-li. These
plants have now converted to TCA. One of the plants using METH
also uses TCA.
Slabstock foam is a low value, low-density product.
Since transportation costs of the foam can be significant,
foamers generally locate near their markets. A number of the
foam plants listed in Table 2.4 are located in the Southeastern
U.S. where there is a large concentration of major furniture
manufacturers. Slabstock foam is not especially capital
intensive so that entrance into the business is relatively easy.
On the other hand, small producers, who are dependent on narrow
profit margins, can go out of business easily as well.
Several of the foam producers, as indicated in Table
2.4, are large companies with multiple plants across the U.S.
These large firms produce between about 4.5 and 13.6 thousand mt
of foam annually and use between about 200 and 590 at of blowing
agent. 1 Medium sized firms prodoce between 2.3 and 4.5
1 A rule of thumb is that, on average, blowing agent
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— 17 —
Table 2.4
U.S. FL aE.E P YU I Z SLABS’1 ( PLP NTS
a a
con pany Facility Location Corpany Facility Location
American Foam Miami FL’ Foamex Products Auburn IN’
Conysra GA’
Austin Urethane Americus GA’ Cornelius NC’
Corry PA’
Cram Industries Coi ton CA’ Dallas TX
Conovar NC’ Eddystone Ph
Elkhart IN Elkhart IN’
Ft. Smith AZ’ Fort Wayne IN’
Kent WA’ Mesquite TX
Newman GA’ Milan TN’
San Leandro CA Orlando FL’
Tupelo MS San Bernardino CA’
Santa Teresa NM
Eastort Easton PA’ Verona MS ’
E.R. Carpenter Conover NC’ Future Foam Anaheim CA
Elkhart IN’ Beaumont TX
Richmond VA’ Council Bluffs IA’
Lathrop CA Mic3dleton WI’
Riverside CA’ Newton KS’
Russeliville KY’ Northglenn cot
Temple TX’ Omaha NB
Tupelo MS ’
General Foam Bridgeview IL’
ylexib-le Foam Cairo IL’ I. Rutherford N3’
Prolucts (Ohio Chattanooga TN’ West Hazelton PA’
Dec ratiVe) Elkhart IN Paramus N3
Houston TX
Mansfield TX General Foam of St. Paul MN’
Spencerville OH’ Minnesota
Florifoaln Miami FL Great Western Orange CA
Hickory Springs Americus GA’
Coesnerce CA’
Cookevills TN
Pt. Smith AR’
Hayward CA
Hickory NC’
Portland OR
Verona MS’
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— 18 —
Table 2.4 (Cont’d.)
U.S. P C&E POLYLJRETh7 INE SI).BS’1 ( PL 1S
a
Company Facility Location Company Facility Location
Lear Ziegler West CMcago IL* Trinity Poem of High Point NC
North Carolina
Leggett & Putt Brerthan TX*
Cold Water MS* Woodbridge Chattanooga Th’
High Point NC*
Moonechie N 1 W.T. Burnett & Co. Baltimore M D
Newburyport MA .lessup MD
Tupelo MS t
NC 70 5 T h Mt. A.iry NCt
Olympic Proäucts Greensboro NC
(Cone Mills) Tupelo MS
b
Penn Toam Rau sville PA
Plastaner Livonia M I
Prestige Asbboro NC
Recticel Foani Leroy NY
LaPorte INt
Morristown TNt
Scottdell, Inc. Swanton OH
Superior Products Plantersville MS
a
* indicates the plant .siploys 1 TH as a blowing agent.
b -
There was a fire in this plant and it ii currently not operating.
SourCes: 3.S. EPA (1988); Panullo and Nash (1986); Industry Sources.
-------
— 19 —
Table 2.5
SOUTHERN CALIFORNIA FLEXIBLE POLYURETHANE
SLABSTOCK PLANTS
a
Co mpanY Facility Locatioft
Cram Industries Coznpton, CA*
E.R. Carpenter Riverside, CA*+
Foainex San Bernardino, CA*
Future Foam Anaheim, CA+
Great Western Orange,CA+
Hickory Springs Commerce, CA*
a*
indicates the plant employs NETH as a blowing agent.
indicates the plant employs TCA as a blowing agent.
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— 20 —
Table 2.6
PROFILE OF SURVEYED PLANTS
ANNUAL A1 UAL
PLANT FOAN PROOUCTION BLOWING AGENT USE
(thousand int) (mt)
4,500 272
9,000 454
fl 4,500 272
-------
— 21 —
Table 2.7
lOAN MARKETS OF SURVEYED PLANTS
MARKET PLANT #1 PLANT #2 PLANT #3
PERCENT
Furniture 70 50 40
Carpet Underlay 20 15
Bedding 10 10 35
TransportatiOn 15
NisceUafleOUSa 20 5 10
aincludes nedical pads, packaging and quilting.
-------
— 22 —
thousand mt of foam and use between about 100 and 200 Tnt of
blowing agent each year. Small firms produce less than 2.3
thousand mt of foam or 100 mat of blowing agent annually. The
three plants surveyed are in the large size range.
Equipment used by small and large foamners is similar
because the buns are all of the same size. The difference is
that the small foamner may operate the plant for only an hour each
day for three or four days a week whereas a very large foamner may
operate a full 8-hour shift or a full five days a week (Palmer et
al, 1980; Industry Source). Many foam plants cannot operate
eight hours per day because of space limitations in the curing
and storage area.
RESULTS OF VISITS/SURVEYS
SRRP staff visited or surveyed in-depth three slabstock
foam plants, tow of them in California and one in North
Carolina. All three plants used CFC-ll as an auxiliary blowing
agent. Table 2.6 shows the profile for these plants-—the amount
of foam produced and the level of blowing agent use. These
plants together account for about 3 percent of the nationwide
slabstock foam production and about 4 percent of the blowing
agent use. The two California plants represent one—third of
those located in Southern California.
Table 2.7 illustrates the product lines for each of the
three foam plants. Each plant sells a significant fraction of
foam to the furniture industry, the largest use indicated in
Table 2.3 Only two of the plants sell to the carpet underlay
market——the second largest foam end use in Table 2.3.
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— 23 —
As mentioned earlier, about 40 percent of the foam
produced today is blown solely with water. Plants l and #2
produce 15 and 20 percent of their foam respectively only with
water, whereas plant #3 produces much more-—60 percent-—with
water alone. This variation is likely due to the difference in
product mix (see Table 2.7) since plants #1 and #3 produce
identical amounts of foam and use the same amount of auxiliary
blowing agent.
Figure 2.3 shows the product mix for a typical slabstock
plant. It indicates the percent of a particular plant output
devoted to the production of foam with various IFDs at 25 percent
compression. In effect, it shows the distribution of foams in
terms of firmness. Traditionally, some foainers used pure METH
for certain grades of foam and pure CFC-11 for certain other
grades. Whereas some foamers used METH for foams down to 15 IFD,
others use it for foams no softer than 30 IFD. Some foamers use
a 50-50 blend of CFC—].1 and MEPH supplied by the chemical
producers (Mooz et al, 1982).
Figures 2.4, 2.5 and 2.6 display the product mix for the
three surveyed plants. The distribution of Plant #1 is very
like tat of the typical plant shown in Figure 2.2. More than
three-fourths of the plant output is in the range of 20 to 40
IFD. In contrast, Plant #2’s product output is more diverse;
only 55 percent of the plant output is between 20 and 40 IFD.
Plant #3 has a reasonably diverse output as well.
FUTURE INDUSTRY TRENDS
As mentioned earlier, 18 thousand at of METH and 6.8
thousand at of CFC-11 were used in 1989 as auxiliary blowing
agents in the production of s]abstock foam. 5.2 thousand at of
NETH is also used in the foam industry as a solvent to clean foam
mixing heads and for other cleaning purposes in both slabstock
and molded foam operations.
-------
- 24 —
IFD AT 25 PERCENT COMPRESSION
FIGURE 2.3
PROOUCTMIXOFA TYPICAL SL4BSTOCKPLANT
35
30
I-
25
20
ul S
2
LL
C-)
w
0 .
5
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
SOURCE MOOZ it *1. isai
-------
35
IFD AT 25 PERCENT COMPRESSION
FiGURE 2.4
PRODUCT MIX FOR PtA NT #1
0 .
0
0
0
w
C-,
w
a-
5
0
0 5 10 15 20 25 30 35 ) 45 50 55 60 65 10 15 80 85 90
U,
SOURCE: SR RP. SITE VISIT
-------
35
0 5 10 15 20 25 30 35 40 45 1 55 60 65 70 15 80 85 90
IFD AT 25 PERCENT COMPRESSION
FiGURE 2.5
PROIJUCT MIX FOR PLANT#2
0 .
a
z
0
LI
0
LU
C-,
LU
0
15
5
0
0\
SOIJflC(: 5.11 liP. SITE VISIT
-------
35
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
lID AT 25 PERCENT COMPRESSION
FIGURE 2.6
PRODUCTMIX FOR PL4NT#3
25
20
I’
15
5
0
SOURCE: S.R.R P. SITE ViSIT
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— 28 —
In September of 1987, the U.S. signed the Montreal
Protocol, an international agreement to limit production of ozone
depleting substances (Montreal Protocol, 1987). On December 14,
1987, EPA proposed a domestic regulation that would implement the
Montreal Protocol in the U.S. (Fed Reg, 1987). In August of
1988, EPA promulgated the final regulation (Fed Reg, 1988). This
regulation capped the production of CFC—11, a fully halogenated
CFC, at the 1986 level beginning in Ju1y, 1989. It specifies
that in 1993 and 1998, the production level will be reduced to
eighty percent and half of the 1986 production level
respectively. In January, 1990, a Congressional tax was placed
0nCFC-l1, approximately doubling its price. This ha made it
increasingly expensive for foamers to use CFC-1l. At an
international meeting in 1990 on ozone depleting substances, it
is likely that an agreement will be reached to phase out
CFCs--including CFC-ll--altogether by the end of the century.
The molded foam industry has almost completely moved
away from use of an auxiliary blowing agent. It is estimated
that virtually all molded foam will eventually be “water blown”
(Carroll and Ziv, 1982; U.S. EPA, 1988). In any case, it is
unlikely that METH could substitute for CFC-11 in molded foam
production. In contract, some slabstock foamers have converted
to METH and TCA because of the regulation on CFC-11. In the next
year, largely because of the tax on CFC—11, virtually all
slabstock foainers are likely to convert to METH or TCA. In the
short-term some conversion to METH is likely; as discussed in the
next section, over the long—term, other options that reduce the
need for an auxiliary blowing agent may be available.
In February, 1989, the Polyurethane Foam Association
(PFA)--a trade organization representing slabstock
foainers—-announced plans for a cutback in CFC-ll use in the light
of reports that significant ozone depletion had already
occurred. The PFA announced that its members will phase out the
use of CFC-11 altogether by the end of the century. By the end
of 1989, the members would achieve a 20 percent reduction from
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— 29 —
1986 levels (PFA, 1989). The PFA said that elimination of CFC-12.
would be achieved through adoption of alternative HCFC blowing
agents (see chemical substitution in the next section),
alternative foam chemistries (see process modification/additives
in the next section) and recovery/recycle (see recovery and
recycle in the next section).
Another blowing agent for slabstock foam, TCA, has been
recently tested and adopted by seven commercial plants. By the
end of 1990, there are projected to be 15 to 20 plants using TCA.
One foam producer has been conducting trials with
acetone as a blowing agent. Acetone is cheaper than the other
blowing agents and the producer is planning to patent and adopt
this process in several plants.
In order to perform an analysis of the potential offered
by various source reduction options, it is necessary to know the
present level of METH and TCA use and the likely use in the next
few years. What follows is a discussion of the factors that
influence the choice of a blowing agent and an estimate of the
level of substitution and increased METH and TCA use that could
occur over the next few years.
Factor Influencing Blowing Aaent Substitution
There are a variety of factors that have influenced
foamers to choose a particular blowing agent. These include raw
material cost, foam quality, scrap rate and ventilation levels.
Other factors such as more restrictive regulations on METH and
the regulation of and tax CFC—11 will influence the future choice
of blowing agent.
Raw Material Cost - The present price of CFC—11, about $1.76 per
kilogram, is significantly higher than the price of METH, at
about $0.64 per kilogram (CMR, 1989). The Congressional tax
raises the price of CFC-11 even higher, to $4.78 per kilogram.
-------
— 30 —
Because METH has a lower molecular weight than CFC-ll, only 90 to
95 percent of the blowing agent is required to accomplish the
same foam expansion. Roughly the same amount of TCA and CFC—11
are required because their molecular weights are nearly equal.
Since the blowing agent accounts for 5 to 15 percent of
the total raw material costs in slabstock production, there has
traditionally been a significant cost advantage to using METH in
place of CFC-ll. This is offset to some extent by an increase in
the catalyst requirement with METH. In Table 2.1, for instance,
formulations 2 and 6 have essentially identical densities and
IFDs. Only 20 php METH is necessary in formulation 2, compared
with 25 php CFC-1]. in formulation 6. Although slightly more
amine cataly st is required in the CFC-ll formulation,
significantly more stannous octoate catalyst is required for the
methylene chloride formulation. Because the blowing agent
volumes are much higher than the catalyst volumes, however, on
balance the raw material cost for the METH formulation would be
lower. Although actual cost savings would depend on the foam
grade, estimates of the savings with METH are estimated to 2 to 4
percent (Mooz et al, 1982) and 6 to 12 percent (Industry
Source). In the last several years, many foaxners have converted
from CFC-ll METH.
The current price of TCA is $0.91 per kilogram. TCA
will be a more expensive blowing agent to use because of its
higher price and because of its higher molecular weight somewhat
more TCA than METH will be required to produce an equivalent
amount of foam. If cost were the only determining factor,
foainers would choose MET!! over TCA as a blowing agent. Because
of the new tax on CFC-11, all foainers will convert as quickly as
possible from CFC—11 to MET!! or TCA.
Foam Quality - Many foamers claim that a better quality foam can
be produced using CFC—11 even though there have been substantial
improvements in catalyst and polyol. technology for Use
specifically with METH. In particular, the softer low density
foams have traditionally been made with CFC-ll.
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— 31 —
scraP R&t - It is not clear whether there is actually a higher
scrap rate with METH, although some foamers insist this is the
case. Foam production rates may amount to as much 1,000 pounds
per minute. The cost for increased scrap production could be
prohibitive but probably would no be a factor with experience.
ventilation Levels — The Permissible Exposure Level (PEL) in the
workplace of CFCll is 1,000 ppm. In contrast, the PEL for METH
set by law is 500 ppm. The Occupational Safety and Health
Administration (OSHA) will shortly issue a new standard for METH
and it is expected to be in the 25 to 50 ppm range. The PEL of
TCA is 350 ppm.
The lower PEL requirement for METH will not make a
difference on the foam line itself where ventilation levels are
already high to dilute the TDI in the foam formulation. As
indicated earlier, this chemical has a PEL of 0.005 ppm. One
estimate suggests that between one-third and half of the blowing
agent is emitted during bun curing and storage in the curing
area. The curing area in many foam facilities may not presently
have sufficient ventilation to accommodate a conversion from
CFC-ll to METH, particularly with the expected lower PEL.
providing additional ventjlation could be costly. A conversion
to TCA which has a higher PEL would require less ventilation, but
would impose additional raw material costs. Many Southern
california producers cure and store the buns outside.
Other Regulations - The Consumer Product Safety Commission (CPSC)
has required certain consumer products containing METH to carry a
label. The chemical has shown increased tumor incidence in some
animal tests (NTP, 1986), although the validity of the results
remain controversial. EPA is considering listing METH under
Section 112 of the Clean Air Act as a hazardous air pollutant.
California lists METH under Proposition 65 and has recently
classified the material as a toxic air contaminant.
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— 32 —
In Southern California, the South Coast Air Quality
Management District (SCAQMD) recently passed a rule requiring
foamers to reduce their blowing agent use by 40 percent by the
end of 1992 (SCAQMD, 1989). This reduction can be accomplished
through vapor recovery or through use of an exempt blowing agent.
Many other states across the nation are examining
whether to list METH as a toxic air.contazninant. In New Jersey,
for example, a tough law capping the emissions at a specific
level is in place. Texas is trying to discourage emissions of
METH. According to one industry source, virtually all foamers in
Texas and New Jersey are óonverting or have converted from METH
to CFC -1l. In Table 2.6, there are 7 foam plants in Texas, and
only two of which use METH. There are two plants in Texas,
Jersey and both use cFc-ll. In California, the recent listing of
METH as a toxic air contaminant will likely cause foainers to
convert away from METH. In these three states, because of
regulatory pressure on METH and federal regulatory pressure and
tax on CFC-11, foamers are likely to convert to TCA.
Estimate of Future Blowing Agent Use
All of the factors discussed here have influenced the
choice of blowing agent in the past and will influence the choice
in the future. During the 1970s, virtually all foamers used
CFC—1l. In the late 1970s and early 1980$, many foamers
converted to METH. Catalyst packages for use with METH were
improved so that foam quality was high and there was a slight raw
materials cost advantage to using METH.
In 1987, the Montreal Protocol was signed and in 1988,
EPA passed a regulation that capped the production level of
CFC -12. at the 1986 level in July of 1989. About that time, TCA
was found to be an adequate blowing agent and successful
commercial trials were conducted. In January of 1990, Congress
placed a heavy tax on CFC—ll and later in the year, it was
expected than an agreement would be reached to phase out CFC-11
altogether by the end of the century.
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— 33 —
The tax made CFC-ll more expensive and 11 foamers using
it either have converted to other blowing agents or will convert
by the end of 1990. The first choice of most foamers would be
NETH. The chemical is less costly than TCA and somewhat less of
it is required to produce an equivalent amount of foam. In many
states, however, local government agencies will not grant permits
to use METH. In such cases, the foamers will convert to TCA. As
mentioned earlier, one foam producer is using acetone in one
plant. The substance is photochemically reactive and many states
would not be likely to grant a permit for its use without air
emission controls. It is less expensive than other blowing
agents, however, and this producer will probably eventually
convert five plants. In the light of all these factors, Table
2.8 presents SRRP staff estimates of the status of the foam
industry by the beginning of 1991.
The values show that there will be 57 plants using METH
nationwide, 19 plants using TCA and 5 using acetone. In Southern
California there are presently four plants using METH and the
other two have or will convert to TCA.
Table 2.9 compares current blowing agent use with the
SRRP staff estimates of the blowing agent use in the beginning of
1991. Total blowing agent use in the beginning of 1991. Total
blowing agent use will decline slightly because some CFC—11
foamers will convert to METI!; the latter blowing agent is more
efficient. The values of Table 2.9 demonstrate that Southern
California blowing agent use in early 1991 will account for abou
8 percent use. This represents 7 percent of nationwide METH use
and 13 percent of nationwide TCA use.
-------
Tabl.t’ 2.8
PROJECTED ST1 PUS OF FONI INDUSTRY - 199!
NUMBER OF PLN’ITS
Blowing Agent in U.S. In Southern Calilornia
a
1IETH 57 4
TCA 20 2
cpc-1I 0 0
Acetone 5 0
Total 82 6
a
One of the Southern California plants uses both METH and TCA. it is
categorized in the METH column.
-------
Tabic? 2.9
CURRENT MID FUTURE BLOWING AGENT USE
BLOWING AGENT USE
(thousand nit)
CFC-11 IIETH TCA Acetone Total
U.S.
1989 LB 18 0 0 24.8
a b c
1991 0 19.53 5.89 1.23 26.65
Southetn CaLifornia
1989 0.541 1.30 0 0 1.92
1991 0 1.38 0.71 0 2.09
a
Assumes an average CFC-1i plant use and that the METII requirement will he 90 percent of that
for PC-l1.
b
Assumes requirement for TCA is 30 percent more than that of CFC-11.
C
Assumes requirement for acetone is 42 percent that of CFC-I1 and 68 percent that of METI1.
Source: SRRP staff estimates.
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— 36 —
III. SOURCE REDUCTION OPTIONS FOR SLABSTOCK FOAM BLOWING
This section discusses five classes of source reduction
options: product substitution; chemical substitution; equipment
modification; process modification and recovery and reuse of
chlorinated solvents. Most of the chiorintated solvent losses in
foam production are in the form of atmospheric emissions and all
losses occur before the foam leaves .the plant. All source
reduction options, therefore, focus on reducing emissions (or
use) of the chlorinated solvent with the exception of the
recovery options, no options that involve liquid or solid waste
are examined.
PRODUCT SUBSTITUTION
Two options for product substitution are analyzed. They
include substitution of non-polyurethane foam alternatives and
implementation of a requirement for minimum foam density. Each
of these options changes the form or type of product that is
ultimately produced.
Non-polyurethane Alternatives
There are a variety of products that have been used in
the past or are used today in place of flexible slabstock foam.
They include substitutes like cotton batting, coil springs, and
rubberized horsehair that were used before flexible foam was
developed. Other options like natural or synthetic fiberfill and
latex or rubber foams are in use today to some extent. There is
only one producer of latex and rubber foams in the U.S. and one
industry source indicates the process is very costly and it
generates large volumes of contaminated effluents. Still other
products, like porous plastic or semiflexible foams are not yet
in development (U.S. EPA, 1988).
Some of these products are competitive with flexible
foams in certain markets. Natural and synthetic fiberglass and
latex foam, for instance, are competitive with flexible foam in
-------
— 37 —
the rough underlay sector. One source estimates that the
introduction of non-flexible foam cushioning material might
reduce emissions of CFC-ll blown foam by 5 to 15 percent (U.S.
EPA, 1988). However, because of flexible foam advantages, a
significant substitution is likely to occur only if a regulation
requiring it is passed.
? 4inimum Density Foam
Generally, more blowing agent is required to produce low
density foams than high density foams. This is apparent from a
comparison of columns two and three or columns five and six of
Table 3.1. Even in high density foams, however, significant
levels of auxiliary blowing agent are required to make soft
foams. Specifying a minimum density foam limit would reduce the
amount of auxiliary blowing agent required in the production
process. The reduction achievable would depend on the density
limit that was chosen. As mentioned earlier, the regulatory
pressure may cause foamers to reduce their blowing agent use. To
do this, most of them may simply stop producing the lower density
foams altogether. This would primarily affect CFC-l1. which has
historically been used for low density soft foams, but would
almost certainly affect METH and TCA as well.
This strategy offers advantages and disadvantages. In
the furniture market, for example, higher density foams
frequently are of better quality and are more durable. Indeed,
the lowest density foams in this application area are used in
lower priced furniture. Higher density foam would be more costly
because more poluo]. and isocyariate catalyst would be required per
unit volume of foam output. Thus, although the foam would have
greater durability, it would be more expensive as well. In
furniture, however, the cost of the foam itself does not
significantly influence the price of the final product. In this
market, the requirement for minimum foam disnist would result in
a more expensive, but more durable piece of furniture.
-------
Fable 3.1
PROPERTIES OF CURRENT t ND PL OPOSED BLOWING AGENTS
Vapor
Chemical Molecular Boiling Pressure at Gas Solvent
Weight Point 25 degrees C E [ [ ICICflCYa Strength
(degrees C) (nvn Hg) (Percent)
b
T4ETH 84.9 39.8 400 38-50 High
CFC-11 137.4 23.8 792 55 Low
HCFC123 153.0 28.7 685 50 Low to
Moderate
HCFC-141b 116.9 32.0 600 45 Low to High
C
HCFC-133a 118.5 6.1 N1 40 High
TCA 133.5 74.1 135 NA High
Acetone 58.08 56.2 227 N1 NA
a
Percent of total theoretical vapor converted to foam cell void volume.
b
Use of appropriate catalysts increases this value to nearly 50.
C
NA is not available.
Sources: DuPont (1980); DuPont (1986); Ostrowski (1989).
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— 39 —
One source estimates that 30 to 50 percent of the CFC-ll
emitted from slabstock foam production could be eliminated
through specifying a minimum density standard (U.S. EPA, 1988).
An industry source believes the number is much lower——perhaps 10
to 20 percent. Since much less I4ETH than CFC—1l is used in the
lower density formulations, the reduction in ?IETH that is
possible would be significantly smaller. Again the reduction
that could be achieved would depend on the density level that was
chosen.
CHEMICAL SUBSTITUTION
There are several substitutes that have been proposed to
replace METH as the auxiliary blowing agent in slabstock foam.
One of these—-CFC--1l--will be banned by the end of the century.
Two others--TCA and acetone--have recently been adopted by a few
foainers. Others, discussed below, would not be available for
several years.
Certain properties of these other chemicals are compared
with those of METH and CFC-l1 in Table 3.1 In general, to be a
viable candidate for substitution, a blowing agent must have
certain characteristics. It must not react with foam ingredients
and it must not dissolve the polymer. Its boiling point should
fall within a certain range and it must have adequate gas
efficiency (ability to create open cell volume). Other desirable
qualities are that the substitute pose minimal damage to human
health and the environment.
CFC—ll
The current regulatory status of CFC-1l was discussed in
the previous section. In principle, CFC-ll could completely
replace METH and TCA in flexible slabstock foams applications. A
number of previous studies have looked at the cost and technical
feasibility of substituting METH for CFC-l]. a the auxiliary
blowing agent (Palmer et al, 1980; Mooz et a]., 1982; Hammitt et
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— 40 —
al, 1986; Camm et al, 1986; U.S. EPA, 1988; U.S. EPA 1987). Such
studies implicitly contain the analysis of the reverse
substitution--CFC-ll for METH. There is now a consensus that
CFC-ll depletes the ozone layer and the chemical will be phased
out by the end of the century. CFC-11 substitution is therefore
riot a good option for reducing or eliminating emissions of METH
and TCA and it is mentioned here only for completeness.
Acetone
This blowing agent was investigated by a chemical
producer in the past. It is now undergoing a commercial trial
and the foam producer plans to license it. Apparently acetone is
a technically suitable blowing agent.
There are some disadvantages to its use, however. It is
flammable and this cold pose a problem in the curing and storage
area because about half the blowing agent remains in the foam at
that stage. The facility would have to be made explosion proof
and insurance costs would almost certainly be higher. Acetone is
also photochemically reactive and some air districts might not
allow its use without air emission controls.
The molecular weight of acetone at 58.08 is much lower
that that of METH. Only about 70 percent as much acetone as METH
would be required to blow an equivalent amount of foam. The
price of acetone--$o.64 per kilogram--is identical to that of
METH.
Hydrochlorofluprocprbpris (HCFCs )
Because CFC-11 is under intense regulatory scrutiny,
there have been significant resources devoted to identifying
potential alternative blowing agents. The CFC producers have
been and are particularly active in this regard and they have
identified three HCFCs that have properties suitable for a
blowing agent (DuPont, 1986; DuPont, 1980). In addition to the
-------
— 41 —
required technical characteristics, alternatives should have low
acute toxicity, low chronic toxicity, low or no flanu ability,
they must not contribute to ozone depletion in the upper
atmosphere, and they must not contribute to ozone depletion in
the upper atmosphere, and they must not contribute significantly
to photochemical smog formation in the lower atmosphere. The CFC
producers have identified two chemicals that hold promise as
future substitutes for CFC-ll and, by extension, METH and TCA.
Work on a third candidate was discontinued because it was
embryotoxic. Table 3.2 compares the health and environmental
characteristics of ?4ETH, CFC—ll, TeA, acetone and the HCFC
blowing agents.
HCFC—123 - This chemical, HCFC-123 or
1,1-dichloro—2,2,2-trifluoroethane, contains chlorine but is not
fully halogenated. CFC5 that are not fully halogenated contain
hydrogen which makes them less stable. As a consequence, they
have shorter atmospheric lifetimes and break down more readily in
the lower atmosphere. HCFC-123, because it is not fully
halogenated, probably does not cause significant ozone depletion
and recent estimates place the ozone depletion potential at 2
percent that of CFC-11 (DuPont, 1988).
A shorter atmospheric lifetime suggest that HCFC—123
could contribute to the formation of photocheinical smog in the
lower atmosphere. However, the available data suggest that the
lifetime is long enough that photochemical reactivity will not be
a problem. In fact, EPA has published a rule exempting the
chemical as a smog contributor (Fed Reg, 1989).
HCFC—123 does not appear to be acutely toxic but DuPont
suggest an internal exposure level of 100 ppm for the chemical
which is fairly low. The CFC producers worldwide have, together,
initiated lifetime animal studies to determine if the chemical
poses chronic problems. The results of these tests will not be
available for three to four years.
-------
Table 3.2
IIF.ALTI1 NI) ENV I UONMENTAI. C I IAIIACTEII I ST t Cs DE
CURRENT AND PROPOSEL) I%I.OWING AGENTS
Ozone
Chemical Depletion Miolochemical flammab’e Toxicity
Potentiala S g
METLI Ho Ho Ho Jndor
Eva 1 nat ion
CFC-11 1.0 No No Low
b
IICFC 123 0.02 No No in Progress
IICFC-141b 0.08 Ho No Weak Mutagen,
In Progress
C
HCFC-133a NA NA No Embryotoxic
TCA 0.10 No No Low
Acetone Ho Yes Yes Low
a
Ozone Depletion Potential (01W) is the capability of depleting ozone of one kilogram of
the substance relative to a kilogram of CFC-ll which has a defined ODP of 1.0.
b
HCFC-123 and HCFC-141b are undergoing lifetime animal tests jointly sponsored
by domestic and foreign CFC producers.
C
NA means not available.
Sources: DuPont (1980); DuPont (19%).
-------
— 43 —
The properties of HCFC—123 are shown in Table 3.1. The
boiling point is midway between those of CFC-ll and METH. Its
vapor pressure also lies between that of CFC—ll and METH Its
solvent power is greater than that of CFC-ll but us less than
that of METH. HCFC—123 has been successfully tested in flexible
foam production. The test results suggest that the alternative
could be used in formulations containing CFC-ll today with only
minor changes. One producer is building a commercial production
plant for HCFC-123 and if the lifetime animal tests identify no
problems, HCFC-123 will be produced on a commercial scale.
DuPont, the largest CFC producer, estimates a bulk price
for the chemical of $1.00 to $2.00 per pound or $2.20 to $4.40
per kilogram (U.S. EPA, 1988). This can be compared with bulk
prices for CFC—ll and METH of $4.78, and $$0.64 per kilogram
respectively (CMR, 1989).2 The molecular weight of HCFC-123 is
153-—higher than that of CFC—ll (137.4) and of METH (84.9). This
indicates that, in principle, about 80 percent more HCFC-123 than
METH would be required as an auxiliary blowing agent for a given
amount of foam. In field trials, it has been found that up to 25
percent more HCFC-123 than theoretically expected was required to
make foam with equivalent properties to that blown with CFC-l1.
The solvency of HCFC-123 is somewhat higher than that of CFC-ll
and this is likely to be the reason for the higher requirement
(Plastics Technology, 1989). This would increase the cost of
using this expensive alternative even further.
- EPA is considering a restriction or ban on
1,1,1-trichioroethane (TCA) because it contributes to ozone
depletion. This latter chemical has an ozone depletion potential
only one-tenth that of CFC-11 but its production level is very
high. EPA may ultimately regulate other minor contributors to
ozone depletion like HCFC-123 if they achieve widespread use.
2 The CFC—1l bulk price includes the Congressionally
mandated tax of $1.37 per pound or $3.02 per kilogram that became
effective in January, 1990.
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HCFC-123 like nearly all other halogenated chemicals, also
contributes to global warming. The regulatory future of
HCFC-123--which doe contribute to ozone depletion and global
warming to a small extent——is therefore in question before it has
even been produced commercially. Because of the uncertainty of
EPA ’s future actions on modest ozone depleters, the foam industry
cannot look to HCFC-123 as a permanent solution.
Although HCFC-123 holds short-term promise as a
substitute blowing agent, it probably will bot be available for
three or four years until animal testing is complete. Even if
commercial production begins, the chemical will almost certainly
be much more expensive than METH and it may also eventually be
regulated. In spite of these drawbacks, the alternative could
potentially reduce METH use and emissions in slabstock foam
production by 100 percent.
HCFC-141b - This }ICFC, 1,1-dichloro-l-fluoroethane, is not fully
halogenated. It has a short atmospheric lifetime, indicating it
will break down in the lower atmosphere. Like HCFC—123,
HCFC-l4lb has been exempted as a smog contributor by EPA (Fed
Reg, 1989). However, its ozone depletion potential is still
relatively high--about 8 percent that of CFC-1l—-and, as
mentioned earlier, EPA may eventually regulate it as an ozone
depleter.
As indicated in Table 3.1, the boiling point and vapor
pressure of HCFC-141b lie between those of METH and CFC-ll.
Although its solvency for polyurethane is higher than that of
CFC-11, it is probably no more than that of METH. The molecular
weight of HCFC-l4lb is higher than that of METH suggesting that
roughly 40 percent more blowing agent would be required to
produce the same amount of foam. In field trials, however, 17
percent less HCFC—l4lb was required than theoretically expected
to make foam having equivalent properties to that blown with
conventional blowing agents (Plastics Technology, 1989). One of
the plants SRRP staff surveyed-—Plant #2—-has tried HCFC-141b in
foam formulations and it apparently performed well.
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One drawback of HCFC-141b is that its flammability limit
is lower than that of METH and it is somewhat toxic.
Flammability can impose additional dangers in the workplace and
can increase costs for fire protection. The CFC producers are
now sponsoring chronic tests on the chemical and results should
be available in three to four years. Other problems are that it
does deplete the ozone layer to a small extent and it has global
warming potential. These two factors again suggest that EPA may
eventually regulate the chemical.
There is an existing commercial production process for
HCFC—l4lb. HCFC—1442b is produced today by Pennwalt for use as a
propellant in perfume formulations. HCFC-141b can be coproduced
with HCFC-142b using TCA as a feedstock (see the companion
document on Intermediates). A second producer has announced it
will build a plant. If the lifetime animal studies reveal no
toxicity problems, production of HCFC-141b could be initiated
immediately.
The flexible foam industry prefers HCFC-141b over
HCFC-123 primarily because it will be cheaper and less of it is
required to blow an equivalent amount of foam. The cost of using
HCFC-141b will therefore be significantly less than the cost of
using HCFC-123.
HCFC-l33Aa - At one stage, HCFC-133a appeared to offer some
promise as a blowing agent. Its properties, according to Table
3.1, illustrate that it would be an acceptable substitute.
Although its boiling point is lower and vapor pressure higher
than the other blowing agents, its boiling point is apparently
within the acceptable range. In spite of the fact that it could
prove to be an appropriate alternative technically, work has been
discontinued on HCPC—133a because it is embryotoxic.
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TCA — TCA has an ozone depletion factor about one—tenth that of
CFC-ll. EPA has not yet decided whether to restrict or perhaps
ban TCA as an upper atmospheric ozone depleter. Because if its
uncertain regulatory future, TCA’s viability as an alternative
blowing agent is in question.
A technical problem with TCA is its high boiling point,
74.1 degrees C, as indicated in Table 3.1. This is outside the
range that is normally acceptable for blowing agents, a range of
from 30 to 50 degrees C. In principle, TCA could be used because
peak bun temperatures reach between 120 and 170 degrees C, but
the higher boiling point can significantly delay volatilization.
Dow chemical has done demonstration trials with TCA, foainers have
performed commercial trials and all have been successful. In
fact, to the surprise of many experienced foam experts, it turns
out that the high boiling point does not present a major
problem. The amount of catalyst used with METH needs to be
changed slightly for use with TCA but the same catalyst that is
Used with METH is suitable. The chemical has been adopted by a
few foamers and one of them reports that it is more difficult to
make the low density foams with TCA than with METH. It is likely
that adjustments to the polyols used with TCA will solve this
problem in the future.
An issue that could arise with the use of ‘ rCA is its
SUsceptability to hydrolysis. If TCA comes in contact with
Water, if can decompose, forming hydrochloric acid which does
Corrode carbon steel equipment. Water is an ingredient in foam
Production (See Figure 2.1) but the water and blowing agent are
Ot premixed so decomposition would not occur during the
Production process. As discussed later, the susceptability to
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hydrolysis would increase the cost of recovery of TCA vapors with
carbon adsorption, if steam were used for desorption.
Because of its higher molecular weight, about 60 percent
more TCA than METH is theoretically required to blow an
ec uiva1ent volume of foam. One foainer indicates that, in
practice, the number is lower, at 4O percent. TCA’s current
price--about $0.91 per kilogram--is much higher than that of METH
which is $0.64 per kilogram. This would discourage conversion to
TCA except in cases where regulatory pressure to reduce METH us
is intense.
EQUIPMENT MODIFICATION
There are two equipment changes that might be effective
in reducing blowing agent use. They include the Max-Foam process
licensed by Unifoam AG and the Vertifoam process developed by
Hyznan International. As discussed later under the category by
vapor recovery, both firms have developed recovery systems using
carbon adsorption for use with their equipment.
Max—Foam Process
Max—Foam is a trough-feed process that produces a
flat-topped bunstock that minimizes trim waste and increase the
gas efficiency of the blowing agent (Edge-sweets, undated a).
Most foamers have apparently adopted this process and it has
become the standard feedstock configuration.
One industry source suggest that nearly all foamers have
converted to the Max-Foam Process. Another source estimates the
number of plants that employ the process at 60 to 80. In fact,
all three of the foaiuers the SRRP staff surveyed have converted
to this process. It is probable that all foam plants will adopt
the process in the next few years as they purchase new
equipment.
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One surveyed foamer indicated that the equipment is priced 20
percent higher than other equipment.
The reduction in METH use that could be achieved by the
remaining plants adopting the Max-Foam process is very small
although there appears to be disagreement on the magnitude of the
potential reduction. One foamer surveyed by SRRP staff stated
that there was no savings. A second foamer indicated that the
savings in blowing agent use were not significant. The third
foamer suggested that the savings in blowing agent use amounted
to .10 percent. One knowledge industry supplier maintains that
the process does not reduce blowing agent use at all.
Vertjfoam Process
Forty-one Vertifoam machines had been installed
worldwide by 1987 (Webb and Griffiths, 1987). There have been
five Vertjfoam units installed in the U.S. since 1982 and four of
them are operating today. The process takes place in a vertical
expansion chamber that is totally enclosed. Preinixed feed is
introduced at the bottom of this chamber and the rising foam is
drawn up through the chamber. As the foam emerges from the top,
slabs are cut (Edge—Sweets, Undated a; Edge-Sweets, undated b).
Because the METH emissions pass upward through the
forming bun, the gas efficiency in the vertical system is
improved over that of a conventional horizontal configuration.
This increased efficiency and the fact that the METH emissions
are better confined, are the major advantages of the Vertifoani
system. Confining the emissions could also lead to better
opportunities for recovery and reuse of the blowing agent (see
the discussion of recovery below).
Retrofit of the systems is existing facilities is
difficult because the equipment is 50 feet high and many
facilities may not be able to accommodate that height.
Furthermore, capital costs are higher than for conventional
systems. One source claims that
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raw material savings with the system range from 4 to 11 percent
for CFC—1]. (U.S. EPA, 1988). However, industry sources claim
that the Vertifoam configuration does not reduce METH use at all
and that the process is inefficient and ineffective except in
small markets.
PROCESS MODIFICATION
There are two process modifications that could be
effective in reducing or eliminating the requirement for METH
aux,iliary blowing agent. The first is a process that uses an
alternative blowing agent which reduces the amount of auxiliary
blowing agent that is necessary. The second involves
modifications in the polyurethane foam and development of
additives that could eliminate use of an auxiliary blowing agent.
“ AB” PROCESS
This blowing method was developed by a Belgium firm,
Kabel—und-GumlniWerke AG, and is licensed by a Swiss Firm,
Innochem, S.A. The Alternative Blowing (AB) process employs
formic acid (HCOOH) instead of water as the primary blowing
agent. Instead of only carbon dioxide (C0 2 ) liberated in the
traditional foam blowing process, in the AB process, the formic
acid reacts with an isocyanate to produce equal volumes of
carbon dioxide and carbon monoxide (CO) which then function as
primary blowing agents. Because twice as much Co CO 2 is
produced in the formic acid reaction, there is a lower
requirement for an auxiliary blowing agent. A disadvantage is
that the CO produced in the process is flammable and toxic posing
a danger to workers.
Equipment costs for converting to this process were
estimated at between $5000 and $10,000 in 1983 by the license
(CMR, 1983). One former estimates the cost of conversion at
$10,000 to $15,000 today for stainless steel equipment that is
corrosion resistant. One industry expert believes these reported
costs are
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significantly underestimated, he estimates the total cost of
conversion at $250,000. Other costs would include operating
costs and royalty payments to the licensee. Automatic monitoring
equipment for detecting CO would also have to be installed. Raw
materials costs would be significantly reduced since one kilogram
of formic acid could replace 4 kilograms of METH (CMR, 1983).
The current price of formic acid is ‘$0.88 per kilogram compared
to a price of METH at $0.64 per kilogram (CMR, 1989).
The process developers claim that AB formulations give
equivalent density and hardness, but a significant reduction in
the silicone surfactant level is required. Otherwise, the cells
of the foam are too fine or overstabilized. Apparently, amine
catalyst adjustment is also necessary (CMR, 1983). There are
reports that the physical properties of the foam produced with
this process are inferior. One industry source claims that foams
of less than 1.2 pounds per cubic foot cannot be made using the
AB process. He also estimates that use of the process might
result in a reduction of 50 percent at most in blowing agent
use. Another industry source estimates the use reduction at 25
percent.
There are no plants in this country that currently
employ he formic acid process. Foamers are reluctant to take on
the additional risks that come with use of formic acid and
production of CO. The OSHA PELs of the two chemicals are very
low—-5 and 35 ppm, respectively. Although it could be argued
that the presence of the TDI already mandates high ventilation
levels, additional precautions would be required. CO emissions
In the curing areaa would likely be high and increased
ventilation would almost certainly be necessary. Furthermore,
emissions of CO are regulated by EPA and local air districts. A
significant investment might be required to tighten up the plant
to lower CO emissions and an after burner may be required on the
stack to oxidize the CO to CO 2 . In addition, because formic
acid is corrosive, foamers would have to install stainless steel
equipment.
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polyurethane Modifications/Additives
There are a number of chemical modification options
being examined that could eliminate the requirement for an
auxiliary blowing agent. These include polyol modifications,
extended range polyol modifications, and formulation
modification/additives.
Polvo ]. Modifications . Extended range HR (High resilience)
polyols are being investigated by several firms. The HR
technology is used today in the production of molded foam.
Historically only about 5 percent of U.S. slabstock
production--the higher density foams above 3 lb/ft 3 —--uses HR
formulations. This foam is primarily used in higher quality
commercial furniture. With process changes, solely water—blown
foams might eventually account for a somewhat larger fraction of
the foam produced. However, the HR process is not especially
promising for most slabstock foam operations since production of
low density foams using the process is technically more
difficult.
The second formulation modification involves a new
polyol system under investigation at Union Carbide and other
firms. Union Carbide’s process is called Ultracel and it employs
higher molecular weight polymers and requires the addition of
diethanolainifle which reduces the formation of ureas and improves
froth viscosity and stabily. The process might be capable of
producing foams in the medium to high density range (1.5 to 2.5
lb/ft 3 ) that are relatively firm, between 25 and 40 ILD. with
this system, it is possible to vary the hardness of the foam by
altering the amount of diethanolamine without using an auxiliary
blowing agent (U.S. EPA, 1988). The process presently cannot
produce the low density softer foams.
BASF has introduced a similar system which whips the
chemicals into a froth before they polymerize. It is a water
based process for producing foams down to 3.4 lb/ft 3 densities
(C&EN, 1989)
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The third modified formulation is a system under
investigation by Montedison S.p.A., an Italian firm. This
systems uses a special polyol that could produce very soft foams
with densities down to 1.3 lb/ft 3 . Higher density foams with
high softness could also be produced with this process without
the use of an auxiliary blowing agent. Certain density foams,
those below 1.3 lb/ft 3 , currently made with auxiliary blowing
agent, could not be made with this system (Consoli et al, 1981;
Consoli et al, 1984).
The fourth system was recently introduced by Union
Carbide. An additive called Geolite is put into the foam
formulation. It reduces the density and hardness of the foam so
that it requires less auxiliary blowing agent. Again, it cannot
eliminate auxiliary blowing agent use for all foam grades.
Although modified polyol systems such as those described
here could ultimately reduce the use of auxiliary blowing agent
significantly, they would probably be more costly. The increased
cost of the new polyols would not be entirely offset by the lower
blowing agent costs. Furthermore, the new foam chemistries
cannot yet produce foams in the lower density range--below about
1.3 lb/ft 3 . These systems are still in the development stage,
and commercialization is probably several years away. They do
offer great promise, however, for significantly reducing METH use
in flexible foam. In fact, foamers believe that alternate foam
chemistries are one of the best alternatives over the long-term.
Reformation to water blown foams for densities above about 1.3
lb/ft 3 in conjunction with a minimum density limit could
eliminate auxiliary blowing agent altogether.
RECOVERY AND RECYCLE
There are a variety of recovery techniques that can be
considered for capturing METH from foam operations. These
include liquid absorption, vapor condensation and carbon
adsorption. The only one of these that has been examined
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in-depth for use in flexible foam plants is carbon adsorption.
There are two newer vapor recovery techniques that might also be
used for recovery of METH. These include the Brayton Cycle Heat
Pump technology and a membrane method. Each of these techniques
is discussed below.
LicTuid Absorption
Liquid absorption has been employed commercially to
remove particular substances from gas streams. The soluble
component in the gas mixture is transferred into a liquid
absorbent. A good absorbent will not react with the sorbent and
the boiling points of the absorbent and sorbent should differ
significantly so that the two can be separated by distillation.
One study evaluated a system for recovery of METH in a
slabstock plant using 1—hexanol (Farmer et al, 1987). Three
cases of liquid absorption for a model plant producing 5,400 mt
of foam and using 218 tnt of METH annually were evaluated. It was
estimated that the emissions (or use) of METH could be reduced by
32 to 45 percent. On this basis the control cost-effectiveness
was placed at between $2,800 to $3,100 per metric ton of METH
emissions avoided.
The disadvantages of this process include reactivity of
hexane with the TDI in the stream to form urethanes which could
foul the column and increase maintenance costs. Also, captured
METH would probably not be directly reusable because the
stabilizer additives would be depleted in the process. Liquid
absorption has not yet been demonstrated at the pilot or
commercial level for slabstock plants.
Vapor Condensation
This method involves refrigerating the gas stream below
the dew point of the components. As the stream is cooled, METH
and water will condense out. For optimal recovery of METH, the
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stream should be chilled to —100 degrees F which would require
use if CFC refrigerant. As mentioned earlier, the CFC5 are
likely to be phased out by the end of the century. The trace
components in a flexible foam plant-—the TDI and amines, for
instance—-could be condensed with the water, posing a waste water
treatment problem. In contrast, the METH stabilizers may not
condense with the METH and reblending would be necessary before
the METH could be reused.
Farmer et al (1987) estimated the cost of vapor
condensation using a model plant. They assumed a 28.5 percent
recovery of the METH used in a plant producing 5,400 nit of foam
and using 218 nit of METH annually. The cost-effectiveness
considering only the capital cost was estimated at $5,600 per nit
of METH emissions avoided.
Carbon Adsorption
The feasibility of carbon adsorption for recovery of
CFC-11 from flexible foam operations has been examined in a
number of studies (Palmer et al, 1980; Mooz and Quinn, 1980; Mooz
et al, 1982; Urano and Yamainoto, 1985; Camin et al, 1986; U.s.
EPA, 1988). There was one pilot demonstration of carbon
adsorption for CFC-11 recovery, but not in this country; (Axel
Sporon-Fiedler, 1986, Nutt and Skidmore, 1987). In this
experiment which took place in Denmark, the maximum blowing agent
recovery was 40 percent which was achieved only after
improvements to the foam line exhaust system were made. The
system was heavily corroded and it was eventually dismantled. A
commercial demonstration of CFC-].1 was performed (Pauw, 1988). A
collection efficiency of 40 percent was achieved, again only wit
exhaust system modifications. In the U.S., there was reportedly
a test at a foam plant in 1968 which resulted in a 33 percent
collection efficiency of CFC-11. There are no published data on
this test and foam industry representatives ate not familiar with
the experiment. Various technical problems remain unresolved.
No pilot or commercial demonstrations on flexible foam plants
using METH have occurred.
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55 —
Carbon adsorption using granular activated carbon (GAC)
has been employed for many years to capture solvents before they
are emitted to the atmosphere. GAC preferentially adsorbs
organic molecules from a gas stream. When the carbon bed is
heated, generally with steam, the organic material is desorbed
and retained in the steam. After condensation, the organic
molecules can be separated from the ‘water for reuse.
Alternatives to steam desorption, such as nitrogen, vacuum or hot
air, are sometimes employed. Two carbon beds, one for adsorption
and the other for desorption are typically used.
There are several major obstacles to implementing carbon
adsorption in foam plants. First, capital costs of the system
depend greatly on the volume flow of air in the plant. In
flexible foam plants where high air flows are required to dilute
the TDI, the cost of carbon adsorption would be substantial.
Costs of recovery also depend on the amount of METH that can be
captured in the airstream. For foamers who use CFC-ll, between
70 and 90 percent of the emissions occur on the line. In
contrast less METH, only 55 to 67 percent, is emitted on the
line; the balance is emitted in the curing area. Thus, the
efficiency of capture for METH would be lower than for CFC-ll,
and carbon adsorption costs would be correspondingly higher.
Estimates of the CFC-ll emissions in foam plants that can be
captured range from about 10 to 80 percent (U.S. EPA, 1988;
Sporon—Fiedler, 1986; Nutt and Skidmore, 1987). Under pilot
plant conditions, the actual percentage of the CFC—11 used that
could be recovered was very low-—in the 10 to 40 percent range,
depending on whether or not the line had been modified for better
collection of blowing agent (Sporon-Fiedler, 1986; Nutt and
Skidmore, 1987). Because METH emissions are more dispersed
throughout the plant, the capture rate for that chemical would
probably be much less.
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The second problem that arises in evaluating carbon
adsorption in foam plants is the presence of TDI and amine
catalysts which can deactivate the carbon (Urano and Yamamoto,
1985). These are present in the airstreams and the adsorbed TDI
reacts with water to form urea residues that coat the carbon and
resist regeneration. In one pilot study on CFC—ll, the TDI
irreversibly fouled the carbon bed which was projected to have a
useful life of only three years (Farmer et al, 1987). One
proposed solution is to use a sacrificial carbon bed between the
foam tunnel and the main adsorbers to adsorb the TDI. The METH
would bypass this bed and adsorb to the main beds and the TDI
would remain on the front bed.
A third problem involves the question of whether the
METH desorbed from the carbon bed could be reused directly
without purification. There would be small amounts of other
components like water and amines in the recovered blowing agent.
It is necessary to employ a particular high purity METH
formulation in foam blowing to guarantee that the foam is
processed correctly and is not discolored. Furthermore, a
stabilizer should be added to the METH and it would be dangerous
for foamers to handle it in concentrated form. Thus,
purification and reformulation of the blowing agent might require
an expertise that foainers currently do not have.
A fourth problem that arises with carbon adsorption is
that there are inter-media transfers—-from atmospheric emissions
to contaminated water and solid waste. The sacrificial carbon
bed contaminated with TDI would require disposal or incineration
if regeneration of the carbon were the chosen option. Indeed,
these beds would contain insoluble urea residues formed in the
reaction of TDI with water in the foam blowing process or from
the steam. Waste carbon from foam operations has never been
regenerated so it is not clear whether this option would be
effective. If it were not, the carbon would pose a solid water
disposal problem.
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When steam is used for desorption, the water stream
resulting from the desorption of the METH bed might contain
unreacted ingredients and products. It may require treatment if
local regulations prevented its release to the sewer.
Regeneration of the carbon with a heated inert gas like air or
nitrogen instead of steam is also an option. This would reduce
the water contaminated problem.
There are two measures that might be taken in existing
foam plants to improve the economics of recovery. First, the
foam line could be better enclosed so the efficiency of capture
of the METH was higher. Today, foam lines are “leaky” because of
the high ventilation levels required to dilute the TDI while
workers visually monitor the foam. It is not clear whether this
efficiency could be improved by capturing the METH from the
curing room as well as from the foam line. Enclosure of the
curing area may be difficult, however, because of the presence of
overhead cranes. A possible solution is to place the recovery
system at floor level where most of the heavier than air METH
leaves the buns.
One study estimated the recovery cost using carbon
adsorption in a plant producing 5,400 mt of foam using 218 mt of
NETH annually (Farmer et al, 1987). This analysis assumed that
modifications would have to be made in the plant to reduce the
exhaust air flow so as to reduce the size of the carbon beds. As
mentioned earlier, there are high ventilation levels in foam
plants because of the TDI. Large volumes of air are drawn
through the foam pouring equipment to dilute and withdraw vapors
emitted during foam rise. The opening at the feed trough is
frequently left open during production to allow the operator to
view the process. Air flows are in the range of 5,000 to 30,000
cubic feet per minute. Venti1at on levels in the curing area are
lower because very little unreacted TDI is released at this
point. The analysis assumed that modifications to the foam line
would be made to reduce the exhaust air flow.
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Assuming various net METH recovery efficiencies, Farmer
et al (1987) estimated the carbon system recovery costs. In one
case, which involved treatment of the exhaust from the foam
tunnel, it was assumed that a 33 percent net METH recovery could
be obtained. The control cost was $2,900 per nit of METH. In a
second case, with recovery of exhaust from both the foam tunnel
and the curing area, the net efficiency was 48 percent and the
cost was estimated at $2,770 per nit. In a third case, treatment
of the foam tunnel, curing area and bun saw exhaust hood would
give a net recovery efficiency of 51 percent at a cost of $4,290
per nit.
Recovery and reuse of METH using carbon adsorption holds
only limited future promise since significant technical issues
remain unresolved.
Brayton Cycle Heat Pu n ( CHP )
The Department of Energy (DOE) has been supporting the
development of the BCHP in conjunction with 3M and Garrett Air
Research since 1978. The technique uses a reverse Brayton
refrigeration cycle. It cools gas streams to very low
temperatures——commonly -80 degrees F——and condenses the
components for collection. The technique requires the use of a
carbon bed with hot gas regeneration, and according to the
manufacturer, the energy savings are significant and efficiencies
are better than for other processes. This method has been
demonstrated at 3M for solvent recovery on commercial sized
magnetic tape manufacturing facilities (Nucon, 1989).
There are two themodynamic advantages to this method.
First, in the Brayton cycle an increased pressure is used. The
dew point temperature of a substance in the gas stream increases
as the gas pressure increases. This cycle operates more
efficiently than other systems which condense the components at
atmospheric pressure. Second, the Brayton cycle employed a
turboexpander
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where most of the work input to the compressor stages is
recovered. A disadvantage is that water vapor will be present in
the system. This water may react with or solubilize trace
components like TDI and urea, remove METH stabilizers and present
a wastewater treatment problem.
The BCHP has never been demonstrated in a foam plant for
recovery of METH. One study did estimate the cost of this system
in a plant producing 5,400 nit of foam and using 218 mt of METH
annually (Farmer et al, 1987). The control costs were about
$2,800 per nit of MET}I recovered assuming a net recovery
efficiency of 33 to 46 percent.
Membrane System
Another new system is being proposed to collect vapors
from air streams. A semipermeable composite membrane is used to
separate the organic solvent from air. The membrane modules
allow a large membrane surface area to be picked into a small
volume. Organic solvents are preferentially drawn through the
membrane by a vacuum pump and the solvent is condensed and
removed as a liquid. The firm manufacturing the membranes claims
that comparison with carbon adsorption shows that the membrane
process is more cost-effective if the solvent concentration is
relatively high--0.5 percent or higher——and the airstreazn to be
treated is small-—between about 100 and 1,000 standard cubic feet
per minute (Wijaxns et al, undated). This would pose problems in
a foam plant where the METH concentration is low and the airflow
is high. Capital costs of the systems are in the range of $400
to 1,000 per standard cubic feet per minute of airflow (MTR,
undated).
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IV. SOURCE REDUCTION OPTIONS FOR SOLVENT APPLICATIONS
In earlier sections, it was mentioned that a significant
amount of !4ETH—-5.2 thousand mt--is used annually for various
solvent purposes in the flexible foam industry. One major use is
to clean the foam heads that deliver the foam formulation
ingredients in both slabstock and molded foam production.
Another large use is to clean the molds in molded foam
production.
SRRP staff surveyed or visited three slabstock
manufacturers and one molded foam manufacturer for information on
METH use for cleaning. Plant #1, described earlier, purchases
6.8 mt of METH annually for this purpose. The METH, after
cleaning, is added to the CFC-ll and used as a blowing agent in
the production of the slabstock foam. Plant #2 uses 18.1 mt
annually to clean the equipment three times per day. The firm
has on—site recovery and generates 4.5 mt of waste which is sent
to an out—of—state disposal facility. The waste represents about
25 percent of purchases. Plant #3 uses 36.6 mt of METH for
cleaning each year. The plant generates 30 nit of waste each year
which costs about $42,000 to dispose of. This level of waste
seems high when compared with METH purchases, particularly since
NETH is volatile. The molded foam producer uses about one-half
mt annually to clean the equipment once per day.
In this section, only recovery and reuse options are
discussed. Although many other options could be applicable, the
low use level did not warrant their detailed investigation.
RECOVERY AND REUSE
One of the foam plants we surveyed-—Plant #2—-uses an
on-site recovery unit. It is a simple off-the shelf distillation
unit with a plastic liner. The METH is separated from the
contaminates for reuse in the cleaning process. The contaminated
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— 61 —
sludge is sent off—site for disposal. Another foamer claims that
the used METH contains polyurethane contaminants that interfere
with the recycling process. Nevertheless, it does appear as if
on-site distillation would be feasible; the polyurethane residue
would simply remain in the sludge.
Another foainer reuses the spent METH directly in the
blowing agent formulation. He claims that it works very well and
that the contaminants-—which would probably be solid polyurethane
particles--do not interfere with foam production. Indeed, this
technique appears to be a good way to reduce the virgin METH
requirement for cleaning. A problem could arise particularly if
the foamer used CFC-l3. as a blowing agent. The catalyst package
would be appropriate for CFC-ll and the presence of high
quantities of METH could alter the foam quality or uniformity.
Off—site recycling of the spent METH might also be
feasible. The foamer could send the spent solvent to the
recycler and could purchase back recycled, instead of virgin
solvent. One recycler we contacted was hesitant to take the METH
from a foamer because he believed the spent solvent could
contain TDI which he did not want to deal with because of its
acute toxicity. In fact, however, a subsequent analysis of the
spent METH revealed no TDI and, indeed, all of it should be
reacted by the time the equipment is cleaned. Because the
polyurethane could pose some processing problems, recycling the
solvent for reuse in cleaning foam equipment would probably be
more expensive than recycling solvent in traditional cleaning
processes.
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— 62 —
V. ANALYSIS OF SOURCE REDUCTION OPTIONS
FOR FOAM BLOWING APPLICATIONS
A significant amount of NETH--some 18 thousand mt-—is
used today as a blowing agent in slabstock foam manufacture. As
discussed in the last section, there are a variety of options
for reducing the use or release of !4ETH in this process. In this
section, the options are classified into three categories and the
cost and blowing agent use reduction are estimated.
SELECTION OF BLOWING AGENT OPTIONS
SRRP staff has defined three categories of options as
illustrated in Table 5.1. Options in column one are those that
are not analyzed further. This category includes options that
could achieve only small use reductions, options that have not
been demonstrated, options that are either technically or
institutionally infeasible, options that are already penetrating
the market or options that have known potential or cost. The
second column includes options for which a limited analysis was
performed. These are options that appear to hold promise but for
which the information on cost and blowing agent use reduction is
incomplete.
Options in the third category, full analysis, are those
that appear promising and for which the information on cost and
use reduction is more complete. These options are examined in
some detail for small, medium and large foainers. They include
recovery and reuse of blowing agent and specification of a
minimum density level for foam production.
“ NO FURTHER 1’NALYSIS” OPTIONS
Table 5.1 shows the options that fall into this
category. Non-polyurethane alternatives are competitive with
foam in some products but greater substitution would change the
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Table 5.1
Classification of l3lowing Agent 0ptiofl
NO FURTHER ANALYSIS LIMITED ANALYSIS FULL ANALYSIS
Non—polyurethane Alternatives Specify Minimum Density Foam
Acetone Substitution
CFC-ll Substitution HCFC Substitution Carbon Adsorption
TCA Substitution TCA Substitution
Max—Foam Process Polyurethane Modifications!
Additives
Vertifoam Process Liquid Adsorption
AB Process Vapor Condensation
Brayton Cycle
Membrane System
Polymeric Adsorption System
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— 64 —
nature of’ the product at perhaps a higher cost. Only small use
reductions could be achieved. Even though acetone appears to be
a promising substitution option, the information that would allow
even a limited analysis is not currently available to the SRRP
staff. CFC—l1 will not be produced after the end of the century
so it is not a viable substitution option. The Max-foam process
is already used by most foamers and will be adopted by the rest
in the next few years. It reduces blowing agent use only to a
small extent, if at all. The Vertifoam process requires building
modifications and may not reduce blowing agent use. The AB
process is unlikely to be used in the U.S. because of the
toxicity of formic acid and carbon monoxide. The membrane system
and Brayton Cycle are undemonstrated. None of these options will
be considered further.
“ LIMITED ANALYSIS” OPTIONS
As Table 5.1 indicates, there are four options in this
category. Each is separately discussed below.
HCFC Substitution
For purposes of this analysis, it is assumed that both
HCFC-123 and HCFC-141b emerge form the lifetime animal tests with
low or no toxicity and become available in 1993 to foamers.
Further, it is assumed that HCFC’S will not be regulated as ozone
depleters by EPA and that HCFC-141b’s moderate flammability does
not pose a problem in flexible slabstock foam production.
As indicated earlier, there are 56 plants in the U.S.
that together use 18 thousand mt of METH annually. In the next
few years, that value may increase somewhat because of the
regulation on CFC-11 but so will the number of plants using
METH. There are five plants in Southern California that use
METH. Nationwide, the average foamer uses 31 mt of METH each
year.
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— 65 —
As mentioned previously, because HCFC—123 has a much
higher molecular weight than METH, about 80 percent more of the
chemical would be required to blow an equivalent amount of foam.
About 40 percent more HCFC—141b is required. The average foam
plant will use about 580 nit of HCFC-123 and 450 mt of HCFC-141b
annually.
The price of HCFC—123 is estimated at between $2.20 and
$4.40 per kilogram; for analysis the midpoint at $3.30 can be
used. No estimates for the price of HCFC-141b could be
obtained. $2.00 per kilogram was assumed. These prices are much
higher than the price of METH which is currently $0.64 per
kilogram.
It is conceivable that a blend of HCFC-123 and HCFC-141b
might be employed. The nonflammable HCV-123 would suppress the
moderate flammability of HCFC-141b. At the same time, the
expected lower price of HCFc—l4lb would encourage use of as much
of this chemical in the blend as possible.
Table 5.2 suimnarizes the results of substitution of
HCFCs for METH. In the case of HCFC—123, the substitution would
cost about $5,300 per nit of METH emissions avoided. For
HCFC-l4lb, the value would be less--about $2,200 per nit. For the
50/50 mixture by weight of the two HCFCs, the cost is about
$3,700 per nit of METH emissions avoided.
It should be noted that these figures are likely to
significantly underestimate the actual cost which would include
the costs of reformulation and identification of appropriate
catalyst packages. During reformation, the foam industry would
experience dislocations and many foam runs could result in
unusable foam. Thus, the actual cost for HCFC substitution could
be substantially higher than the figures of Table 5.2 indicate.
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Table 5.2
ANNUAL COST INCREASE AND METII EMISSIONS REDUCTION FOR HCFC SUBSTITUTION
HCFC Average Annual Cost (million $) Annual METJI Emissions Reduction (mt)
To To Southern To To To Southern To
_________ Foamer California Nation Foamer California Nation
HCFC—123 1.7 8.5 95.3 321 1,605 18,000
HCFC—141b 0.7 3.5 38.8 321 1,605 18,000
a
Combination 1.2 6.0 67.1 321 1,605 18,000
a
Combination represents a 50/50 mixture by weight of HCFC-123 and HCFC-141b.
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— 67 —
TCA Substitution
There is presently no information on the costs of the
new TCA catalyst package; for this analysis, these costs can be
ignored. The current price of TCA is about $0.91 per kilogram
which can be compared with a METH price of $0.64 per kilogram
(CMR, 1989). The molecular weight of TCA is about 60 percent
greater than that of METH so the blowing agent use requirement
will be correspondingly larger. Thus 28.8 thousand mt of TCA
would be necessary to replace the 18 thousand mt of METH
currently used. Nationwide the annual cost would be $14.7
million or $0.8 million per metric ton of METH emissions
avoided. Table 5.3 summarizes the cost, the avoided METH
emissions and the increase in TCA emissions that would accompany
a conversion. A comparison of the values of Tables 5.2 and 5.3
demonstrates that TCA substitution is much cheaper than HCFC
substitution.
Polyurethane Modification
The modified polyol. systems offered by Union Carbide and
the Italian firm, Montpolimeri S.p.A. hold promise for producing
foams down to about 1.3 pounds per cubic foot without the use of
auxiliary blowing agent.
The density range of these new polyol systems tends to
be somewhat higher than for traditional systems. This would
increase the raw materials cost. The polyols themselves are also
more expensive. All of these factors will lead to an increased
cost of the foam. Because these new technologies are still in
the development stage, the cost of ultimately adopting them is
unknown.
Only modest modifications to the feed delivery system
would be required so plant equipment conversion costs would be
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Tab]e 5.3
ANNUAL COST INCREASE AND METII EMISSIONS REDUCTION FOR TCA SUBSTITUTION
To To To
_____________________ Foamer Southern California U.S .
Average Annual Cost 0.3 1.3 14.7
(million $)
Annual METH Emissions 321 1,284 18,000
Reduction (at)
Annual TCA Emissions 514 2,568 28,762
Increase (at)
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— 69 —
small. The major cost would be increased raw material and one
source estimates that this cost would be In the range of 10 to 30
percent (Farmer et al, 1987). Using this cost range and assuming
that 30 to 60 percent of the METH blown slabstock is affected and
a reduction in the METH use per unit of affected foam is 50 to
100 percent, Farmer et al (1987) estimate a control
cost—effectiveness of $4,400 to $45,000 per metric ton of METH
emissions avoided. If one adopts the low estimate of $4,400 per
metric ton of emissions avoided and again assumes that the
average plant uses 321 mt of METH annually, the results shown in
Table 5.4 are obtained. -
Liquid Absorption
Farmer et a3. (1987) estimated a cost of $2,800 to $3,100
per metric ton of METH emissions avoided for a liquid absorption
system in a foam plant using 218 at of METH each year. The
average plant uses more METH, 321 at. There is no reason to
expect that the cost per at would differ significantly in this
larger plant. The Farmer et al (1987) analysis assumed a
recovery efficiency of 32 to 45 percent, but this range reflected
plant improvements to collect more METH. The SRRP staff assumed
a lower recovery efficiency of 25 percent (see discussion in next
subsection on carbon adsorption). Table 5.5 presents the results
for liquid absorption in the average foam plant with 25 percent
recovery efficiency and the upper limit to cost in Farmer et al
(1987).
Refrigerated Condensation
Farmer et al (1987) estimated the cost of recovery of
218 mt at $5,600 per at of METH emissions avoided assuming a
recovery efficiency of 28.5 percent. Again, results are applied
directly to a larger plant using 321 at of METH and assume a
recovery efficiency of 25 percent, we get the results presented
in Table 5.6.
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Table 5.4
ANNUAL COST INCREASE AND METH EMISSION REDUCTION FOR POLYURETHANE MODIFICATION
To Foamer To Southern To U.S.
____________________ ____________ California _________________
Average Annual Cost 0.4 1.6 23.3
(million $)
Annual METH Emission 69 274 3,910
Reduction (mt)
Cost Increase Per 5,960 5,960 5,960
METH Emission
Avoided (S/nit)
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Table 5.5
ANNUAL COST INCREASE AND METII EMISSION REDUCTION FOR LIQUID
ABSORPTION
To Southern
LIQUID ABSORPTION To Foamer California To U.S .
Average Annual Cost 0.2 1.0 13.7
(million $)
Annual METH Savings 86 343 4,888
(mt)
Cost Per METH Emissions 2,800 2,800 2,800
Avoided ($/mt)
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‘rable 5.6
ANNUAL COST INCREASE AND METH EMISSION REDUCTION
FOR VAPOR CONDENSATION
To Southern
VAPOR CONDENSATLON To Foainer Cal. i fornia To U .S
Average Annual Cost 0.5 1.9 27.4
(million $)
Annual METH savings 86 343 4,887
(at)
Cost Per HETH Emissions 5,600 5,600 5,600
Avoided (S/at)
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— 73 —
Summary of “Limited Analysis” Ortions
Tables 5.7 and 5.8 summarize the “limited analysis”
option results. TCA substitution is the least costly option,
followed by HCFC —141b substitution. Substitution of HCFC-123 is
a much higher cost option. It’s worth noting here that there is
a great deal of uncertainty in the ôost and emission reduction
figures. Another factor that is important to stress is that the
chemical substitution options lead to increased use of an
alternative chemical that may pose hazards of a different sort
than METH. The recovery options also present a different type of
risk in the foam of water pollution and solid waste. The impact
of these issues cannot really be quantified but they must remain
part of the consideration of alternatives.
FULL ANALYSIS OPTIONS
As Table 5.1 indicates, two options were selected for
full analysis: specification of a minimum density level and
carbon adsorption for recovery of METH vapors. Two scenarios
were defined to consider and evaluate these options. In Scenario
1, the analysis was made for carbon adsorption alone. In
Scenario 2, the analysis includes both minimum density
specification and carbon adsorption. In this latter case, the
minimum density specification reduces blowing agent use and
emissions so that the potential of carbon adsorption for reducing
emissions is less.
The minimum density and carbon adsorption options are
examined for three plant sizes. As mentioned earlier, large
firms produce between 9 and 45 thousand iut of foam and use about
250 to 1,360 mt of METH each year. Roughly one-third of the
plants fall into this category (Mooz and Quinn, 1980). The large
size plant that we consider produces 12.4 thousand mt of foam and
uses about75o at of METH annually. Medium sized firms produce in
the range of 3 to 9 thousand at of blowing agent. An estimated
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Table 5.7
SUMMARY OF ANNUAL COST AND BLOWING AGENT USE REDUCTIONS
FOR “LIMITED ANALYSIS” OPTIONS - U.S.
Option Annual Cost Annual Meth Cost Per METH
(million $) Emission Reduction Emissions Avoided
(mt) ($/mt)
HCFC—123 117.3 19,530 6,005
HCFC—141b 39.9 19,530 2,004
HCFC Combination 78.6 19,530 4,025
Polyurethane 23.3 3,910 5,960
Modification/Additives
Liquid Absorption 13.7 4,888 2,800
Vapor Condensation 274 4,887 5,600
a
Parenthesis indicate a cost credit.
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Table 5.8
SUMMARY OF ANNUAL COST AND BLOWING AGENT USE REDUCTIONS FOR
“LIMITED ANALYSIS” OPTIONS—--SOUTHERN CALIFORNIA
Option Annual Cost Annual METI! Cost Per METH
(millions $) Emission Reduction Emissions Avoided
(mt) ($/mt)
Lr’
HCFC—123 8.2 1,380 6,005
HCFC—141b 2.8 1,380 2,044
HCFC Combination 5.5 1,380 4,025
Polyurethane Modification/ 1.6 274 5,960
Additives
Liquid Absorption 3.0 343 2,800
Vapor Condensation 1.9 343 5,600
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— 76 —
15 percent of the plants fall into this category (Mooz and Quinn,
1980). A model medium sized plant produces 3.3 thousand nit of
foam annually arid has a blowing agent use of about 200 nit of METH
annually. Small plants produce less than 3 thousand nit of foam
and use less than about 115 mt of METH each year. About 50
percent of plants fall into this category. The small plant uses
about 100 mt of METH each year. These data are summarized in
Table 5.9.
Scenario 1. Carbon Adsorption Along . There have been no carbon
adsorption pilot or commercial demonstrations on METH but there
have been such demonstrations on CFC—11. As mentioned earlier,
these operations had very low recovery efficiencies, in the range
of 10 to 40 perCent, depending on whether the line had been
modified for better collection. For NETH, since a smaller
percentage is emitted on the foam line, the collection efficiency
would be even lower.
One study estimated the cost of a carbon adsorption
system for a plant producing 54 thousand nit of foam annually
operating 200 days per year with a 2 hour pouring period at an
average pouring rate of 230 kilograms per minute (Farmer et al,
1987). The study assumed that the foam line was 30 meters long
with overhead exhaust stacks. The cost estimates include
modification to the foam line--improved conveyor enclosure at the
entrance and exit of the foam tunnel and addition of horizontal
vapor withdrawal ducts on the line.
Equipment for retrofitting carbon adsorption systems in
existing foam plants would be similar. Such systems depend on
the pouring rate and the exhaust ventilation rate and this does
not vary significantly from plant to plant. The size of the
system and its capital cost depends most heavily on the exhaust
level rather than on the foam output of the plant. Operating
costs, on the other hand, are dependent on the foam output and on
the size of the equipment.
-------
‘Fabip 5.9
CHARACTERISTICS OF SMALL, MEDIUM AND LARGE PLANTS
PLANT SIZE ANNUAL FOAM ANNUAL METH
PRODUCTION USE (mt)
(thousand mt)
Large 12.6 550
Medium 4.0 175
Small 2.0 90
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— 78 —
The Farmer et al (1987) study sized and costed out a
carbon adsorption system using 218 thousand mt of METH annually.
This is virtually identical to the medium sized foam plant
described in Table 5.10. A large plant produces 3.75 times as
much foam. The medium sized plant operates 2 hours per day.
This suggest that the large plant would operate for 7.5 hours per
day at the same pouring rate. The operating time for the small
plant is about one hour per day.
The bed chosen in the Farmer et al (1987) analysis to
treat tunnel exhaust at 5,000 ppm contained 5,100 kg of carbon
and was 0.9 meters deep. This should be adequate for the large
plant size under consideration. For this analysis, same size
carbon bed is used to treat the tunnel exhaust from small, medium
and large plants and in doing so the capital cost of carbon
adsorption system may be overestimated for medium and small
users.
The cost of the system includes a single pass
sacrificial guard bed that will capture the TDI. The system
treats 5,000 standard cubic feet per minute (scfm) stream for an
8-hour period for the large plant, a 2—hour period for the medium
sized plant and a 1—hour period for the small plant. A steam
desorption system is included. In all cases, a
regeneration/drying phase would be required to prepare the carbon
for the next adsorption phase.
Tables 5.10 and 5.11 present the capital costs and the
annualized operating costs respectively for this carbon
adsorption system for small, medium and large plants. Note that
the capital cost of the unit is much larger than the operating
cost so that the variation among small, medium and large foamers
is minimal. The annual cost to a foamer to implement the carbon
adsorption recovery is in the range of $250,000.
-------
Table 5.10
CAPITAL COSTS FOR CARBON ADSORPTION SYSTEM
Capital Equipment Cost ($1,000)
Adsorbers 256
a
Other Equipment 69.7
Tunnel Enclosure 17.9
Total Equipment Cost 343.6
b
Total Installed Direct Costs 566.9
C
Indirect Capital 295.2
d
Total Depreciable Capital 862.1
e
Total Capital Investment 948.3
a
bther equipment includes a guard bed, a condenser, a decanter/condensat
storage tank, a storage tank for recovered METLI and pumps.
b
Installed direct costs are the total equipment cost plus 65 percent of
purchased equipment.
C
Includes engineering and supervision at 10 percent of direct capital,
miscellaneous field construction expenses at 5 percent, contractor fees
at 10 percent, contingencies at 15 percent, startup expenses at 2 percel
and interest during construction at 10 percent.
d
Sum of Total Installed Direct Costs and Indirect Capital.
e
Includes working captial at 10 percent of total depreciable capital.
-------
T I)1e S.iI
AKKUAL.IZEfY OP flATLHG cosi FOfl ciwnou ADSORPTION
COST ITEM COST ($1,000)
Small Medium Larqe
a
Direct operating and Maintenance Costs 21.8 32.8 52.3
b
Indirect Cost 178.1 119.9 181.6
Total Annual Operating and Maintenance Costs 199.9 212.7 233.9
a
Estimate for medius plant taken from Farmer et at ( l987) with 6.) percent adjustment for inflation.
Valuem for small end large plants adjusted to account (or shorter and longer operation respectively.
b
Includes $154,300 as a capital recovery factor determined by ascuming a 10 percent interest rate and a
10-year equipment life. Also includes overhead which is estimated at 30 percent of operating labor 91d
mainte,iercce; administration estimated at 50 percent of operating labor costs; and insurance and property
taxes estimated at $la,900.
Note: Values are tro* Farmer et at (1987) with costs adjusted for
inflation between late 1987 through mid 1989. flurea I of f. bor and
statistics indicates that the producer Price Index for industrial
Commodities, Machinery and Equlpsient rose 6.) percent over the
period
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— 8 ]. —
Another source estimates the annual recovery cost for a
comparable facility to be somewhat higher--at between $283,000
and $466,000 (South Coast AQMD, 1989).
The SRRP staff estimate of the net METH recovery through
carbon adsorption is 30 percent, with the improvements in the
line to facilitate vapor capture. Estimates for CFCD-ll capture
range from 10 to 40 percent and since METH emissions on the foam
line are lower, a lower value was chosen. The cost and METH
emissions avoided for small, medium and large plants are
summarized in Table 5.12
It is not clear whether the captured METH could be
reused directly in the foam production process without further
processing. Although one recycler analyzed the METH used in
equipment cleaning at our request (see next section), the METH
from the foam blowing process may contain different components.
There are three possibilities for the captured METH.
First, it could be reused directly as a blowing agent. Second,
it could be sold to an off-site recycle for a net credit. Third,
it could be distilled on—site and reused in the foam blowing
process. The first option is the most favorable economically for
the foamer. If the METH were directly usable in the process,
then small, medium and large foamers would get a purchase credit
$19,200, $38,400 and $144,000 respectively. These savings
provide an impressive offset to the total annualized costs in
Table 5.12. In fact, the cost of the process under these
circumstances would be $6.00, $3.20 and $0.56 per kilogram of
then small, medium and large foamers would get a purchase
$19,200, $38,400 and $144,000 respectively. These savings
provide an impressive offset to the total annualized costs in
Table 5.12. In fact the cost of the process under these
circumstances would be $6.00, $3.20 and $0.56 per kilogram of
emissions avoided for small, medium and large formers
-------
Table 5.12
ANNUAL COST AND METH EMISSION REDUCTION FOR
CARBON ADSORPTION SYSTEM
Average Annual Cost Annual METH Emission Reduction
(million $) (mt)
To Foamer
Small 0.20 27
Medium 0.21 53
Large 0.23 165
a
Southern California 0.89 436
b
Nationwide 12.40 5,840
a
Assumes two medium sized and two large plants.
b
Assumes 47 percent of the plants are large, 13 percent are medium sized and
40 percent are small.
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— 83 —
respectively. The process appears to be cost-effective today for
large foamers but only if direct reuse of the blowing agent were
possible.
The more likely option is the second one since foazners
are unlikely to accept the recovered solvent for direct reuse.
Furthermore, if contaminants are present in high concentratons,
the catalyst package might no longer be appropriate. These wold
have to be removed before the blowing agent could be reused. One
recycler indicates that he pays $1.25 per gallon for waste METH
disposal. If the solvent is contaminated at the 30 prcent level,
the foamr will get a credit of $0.50 per gallon or about $0.10
per kilogram. This would be a net annual credit of $3,000,
$6,000 and $22,500 for small, medium and large foamners
respectively.
It is worth noting that the carbon adsoroption recovery
process could be cost—effective today for foamers who employ
CFC-ll as a blowing agent. The present price of that chemical is
$1.76 per kilogram, well above the price of METH. Somewhat more
CFC—l1 could be recovered since more is emitted on the line. For
large foaines in particular, if the blowing agent could be
directly reused, it would be cot-effective today to install a
recovery system.
Scenario 2: Specification of Minimum Density Followed by Carbon
Adsorption . Detailed information on all flexible foam markets is
requird foa a complete cost and use reduction analysis for a
minimum density specification. This information would include
data on METH use as a function of ILD and foam density and the
levels of use and the end markets for the foam as a function of
ILD and foam density. These data are not available and the
analysis must, by necessity, incorporate certain assumptions.
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— 84 —
Slabstock foam is a low margin product. If higher
density foams were produced, larger quantities of raw materials
like polyols, catalysts and isocyantates would be required and
the cost of producing the foam would increase commensurately. In
effect, higher quantities of raw material would be required for a
given volume of foam,. For example, if the foam density
increased from 1.0 lb/ft 3 to 1.2 lb/ft 3 . then the raw
material requirements and their costs would increase by 20
percent. The price of the foam would increase and he
fabricators, who are very competitive, might not continue to use
glabstock foam, particularly in markets where low cost and 1 .0w
density are important. Thus, in some markets, there would be a
shift from low to higher density foams; in other markets, there
might be a shift to other products or foam made with other
blowing agents like CFC—ll, for instance.
The furniture market accounts for about 40 percent of
slabstock flexible foam use as indicated in Table 2.3. Low
quality furniture is made with low density foam as cushionng. In
the furniture market, the cost of the other furniture components
is generally much higher density foam would probabily not
increase the price of the furniture item significantly. An added
benefit would be an increase in the durability of the furniture.
In the furniture market, it is likely that a cost increase from
adoption of higher density foam would simply be passed on to the
consumer.
The structure of the carpet underlay market segment is
much different. As the values of Table 2.3 show, this segment
represents 26 percent of the slabstock market. As mentioned
earlier, a].tenative materials including synthetic and natural
fiberfill and jute are used today in carpet underlay applicaitons
and are competitive with slabstoók foam. In this case, if higher
density foam were used and the cost increased, a significant part
of the market could go to the alternatives which would then be
cheaper.
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— 85 —
The difference between the furniture and rug underlay
markets demonstrates the diverse effects a minimum density
requirement would have on different markets. Foam producers sell
to fabricators who are influenced heavily in the end use markets
by competitive pricing. Although the information on market/ILD
interrelationships is not available, one can estimate the use
reduction and cost of a minimum density requirement.
The analyis, distinguishes among small, medium and large
plants and assumes a uniform density distribution from plant to
plant. Most foamers tend to sell to a variety of markets and
produce a range of foams with various ILDs. It is likley that
such plants also produce a range of densities and the impacts of
a minimum density requirement are proportional to the amount of
foam produced below the cutoff level.
According to Table 2.1, densities as low as 0.9 to 1.0
lb/ft 3 are achieved for some foams. If the minimun density
cutoff level is set at 1.3 lb/ft 3 , raw material cost would
increase about 18 percent (Farmer et al, 1987). An industry
source estimates that raw material costs are about $0.75 per
pound of foam produced or $1.65 per kilogram of foam produced.
An 18 percent increase in raw material cost implies an annual
cost increase of about $300 per mt of affected foam.
The figures of Table 2.2 indicate that 700 thousand mt
of flexible foam—-including both slabstock and molded foam--was
produced in 1987. In 1985, the figure was 603 thousand mt and
440 thousand t of it was s]abstock. If the same proportion is
assumed to be valid in 1987, then 511 thousand mt of slabstock
foam was produced in that year. METH is used by 57 percent of
the plants and 18 thousand mt of METH and 10.8 thousand mt of
CFC-11 are used today. For this analysis, it is assumed that 60
percent of the slabstock foam or about 300 thousand mt was
produced using METH.
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— 86 —
One source estimates that the portion of METH blown
slabstock output that would be affected by a minimum density
specification is 30 to 40 percent. The same source assumes that
the reduction in METH use per unit of affected foam is 20 to 40
percent and that the level of METH in the replaced foam is 6
percent. The 6 percent figure corresponds to about 10 parts per
hundred polyol (php) which is representative of several typical
NETH formulations. In Table 2.1, for instance, the weight
percent METH and CFC-11 range from 4 to 25 php (Farmer et al,
1987). If the midpoints of the ranges for the affected foam and
the reduction in METH use for the affected foam are adopted, then
1,890 mt of METH use (or emission) would be avoided annually.
Table 5.13 summarizes the results for small, medium and
large foam plants in Southern California and nationwide. The
figures suggest that this Option would cost the nation about $7
million and reduce METH use by 1,440 mt. The price of METH at
which this option becomes cost-effective is about $1 per
kilogram. This can be compared with the current METH price of
$0.64 per kilogram.
The values of Table 5.13 show that it would cost the
nation $19.5 million annually to implement a minimum density
specification followed by carbon adsorption. Over 5,400 thousand
nit of METH emissions are avoided.
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Table 5.13
ANNUAL COST AND METH EMISSION REDUCTION FOR MINIMUM DENSITY SPECIFICATION
Average Annual Cost Annual METII Emission Reductiona
(million $) (mt)
Foamer
Small 0.04 7
Medium 0.1 14
Large 0.2 45
Southern California 0.6 120
Nationwide 7.1 1,440
aCalculatioQs assume that there is a minimum density specification of
.1.3 lb/ft ; that 20 percent of the METII blown slabstock is affected; that
there is a 30 percent reduction in METH use per unit of affected foam; and
that the level of METH in the affected foam is 6 percent.
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— 88 —
VI. ANALYSIS OF SOURCE REDUCTION OPTIONS
FOR SOLVENT APPLICATIONS IN FOAM PLANTS
Approximately 5 thousand mt is used to clean foam heads,
equipment and molds in slabstock and molded foam production
operations. In this section options were selected for limited
and full analysis.
ECTION OF SOLVENT OPTIONS
Table 6.1 summarizes the source reduction options and
classifies them for further analysis. The substitution
options——use of DBE or NNP—-are “No Analysis” options because of
their doubtful feasibility. On-site and off-site recycling was
found to be promising and, thus qualifying “Full Analysis”
options.
The figures of Table 2.2 indicate that 700 thousand mt
of flexible foam—-including both slabstock and molded foam--was
produced in 1987. In 1985, the figure was 603 thousand mt and
440 thousand mt of it was a slabstock. If the same proportion is
assumed to be valid in 1987, then 511 thousand mt of slabstock
foam was produced in that year. METI! is used by 57 percent of
the plants and 18 thousand mt of METH and 10.8 thousand mt of
CFC—11 are used today. For this analysis, it is assumed that 60
percent of the slabstock foam or about 300 thousand mt was
produce using METH.
One source estimates that the portion of METh blown
slabstock output that would be affected by a minimum density
specification if 30 to 40 percent. The same source assumes that
the reduction in METH use per unit of affected foam is 20 to 40
percent and that the level of METH in the replaced foam is 6
percent. The 6 percent figure corresponds to abut 20 parts per
hundred polyol (php) which is representative of several typical
METH formulations. In Table 2.1, for instance, the weight
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— 89 —
TABLE 6.1
CLASSIFICATION OF SOURCE REDUCTION
OPTIONS FOR SOLVENT CLEANING USES
NO FURTHER ANALYSIS LIMITED ANALYSIS FULL ANALYSIS
Substitution of DBE On-site Distillation
Substitution of NNP Off-site Distillation
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- 90 —
percent METH and CFC—1]. range from 4 to 25 php (Farmer et al,
1987). If the midpoints of the ranges for the affected foam and
the reduction in )IETH Use for the affected foam are adopted, then
1,890 nit of METH use (or emission) would be avoided annually.
Table 5.12 summarizes the results for small, medium and
large foam plants in Southern California and nationwide. The
figures suggest that this option would cost the nation about $7
nijilion and reduce METH use by about 1,440 nit. The price of METH
at which this option becomes cost-effective is about $1 per
kilogram. This can be compared with the current METH price of
$0.64 per kilogram.
The values of Table 5.12 show that it would cost the
nation 39.5 million annually to implement a minimum density
specification followed by carbon adsorption Just over 5,400
thousand ‘nit of METH emissions are avoided.
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— 91 —
VII. ANALYSIS OF SOURCE REDUCTION OPTIONS
FOR SOLVENT APPLICATIONS IN FOAM PLANTS
Approximately 5 thousand nit is used to clean foam heads,
equipment and molds in slabstock and molded foam production
operations. In this section, certain options were selected for
limited and full analysis.
SELECTION OF SOLVENT OPTIONS
Table 6.1 summarizes the source reduction options and
classifies them for further analysis. The substitution
options——use of DBE or NNP—-are “No Analysis” options because of
their feasibility. On—site and off-site recycling was found to
be promising and, thus qualifying. “Full Analysis” options.
If the foamer buys back nit of recycled solvent, the net
annual benefit is $3,600. It is presently cost—effective to use
an off-site recycler and purchase recycled rather than virgin
solvent for cleaning.
OFF-SITE RECYCLING
One of the plants in the survey cleans equipment three
times per day. The other two plants did not report the frequency
of cleaning. A plant which uses 32 nit of METH annually to clean
the equipment with an operating schedule of 200 days per year,
uses 160 kilograms or 32 gallons daily. The foamer could
purchase a 10 gallon per hour still and operate it one hour per
day plus one hour for warm up. One industry source estimates the
electricity costs for the year at $500. Labor requirements would
be one hour per week. At a burdened rate of $20 per hour, the
labor charges would be $1,000 annually. Total operating and
maintenance costs are $1,500 per year.
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— 92 —
A self—contained still capable of processing 10 gallons
per hour has a capital cost of about $9,000. Assuming an
interest rate of 10 percent and an equipment lifetime of 10
years, the capital recovery factor is 0.163 and the annual
capital charges are $1,470. Total annual costs are about $2,970.
This analysis assumes that’three-fourths of the METH is
emitted and on-fourth or 8 mt of METH is waste. At a
distillation efficiency of 90 percent, the foamer must pay for
disposal of the sludge from the on-site distillation process,
however. The volume of sludge requiring disposal is 0.8 mt of
METH annually and 3.4 mt of sludge. This 3.4 mt of sludge arises
from the 8 mt of METH which is contaminated to the 30 percent
level giving a total waste volume of 11.4 mt. The total volume
requiring disposal is 4.2 mt. At a charge of $1.25 per gallon,
the cost will be $1,160 per year. The net cost to the foamer for
purchase of the equipment and waste disposal is $4,130 annually.
The foamner, because he recycles and reuses the METH
on-site can forego purchases of 7.2 mt of the chemical each
year. This savings amounts to $4,608 each year. The foamer can
also purchase recycled solvent for the balance of the 24.8 mt of
solvent annually. If this solvent is purchased at 3.75 cents per
pounds less than virgin solvent, then the saving amounts to
$2,046. The total savings outweighs the cost by $2,524
annually. This suggests that it is presently cost—effective to
adopt on-site distillation.
SUNMARY OF RECYCLING OPTIONS
Table 6.2 summarizes the annual cost savings that could
be realized from purchasing solvent that has been recycled
off-site and from purchase and use of an on-site still. The
figures show that there are cost savings achievable for both
options. It is more cost—effective to use an off—site recycler
than it is to purchase an on-site still. The still we consider
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lable 6.2
ANNUI L COST 7 ND METII USE REDUCTION FROM RECYCLING
a
1 NNUfiL COST 1 NNUAL VIRGIN METII USE REDUCTION
($ thousands) (int)
To Southern To Southern
To Foamer California To Nation To Foamer California To Nation
b
Off—Site Recycling (3.6) (54.0) (586.8) 8.0 120.0 1,304.0
On—Site Recycling (2.5) (37.5) (407.5) 7.2 108.0 1,173.6
a
Includes only the recycled solvent purchased in place of the waste solvent.
b
Parentheses indicate a credit.
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— 94 —
is capable of processing 10 gallons per hour and would be used
only a few hours per day. A smaller cheaper still would probably
suffice and equipment at half the cost of the one estimated here
would make on—site recycling more cost-effective than off-site
recycling.
The values of Table
virgin purchases that either
achieve. The figures do not
other than those to replace
case of off—site recycling,
solvent to the recycler and
6.3 show the reduction in METH
on— or off-site recycling could
include credit or for purchases
the waste solvent. That is, in the
the foamer sends 8 mt of contaminated
buys back 8 mt of reclaimed solvent.
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— 95 —
VIII. SUMMARY AND CONCLUSIONS
Approximately 18 thousand nit of METH are used as the
auxiliary blowing agent in slabstock foam production today. In
the next few years, as foamers move away from CFC—l1, METH use
might increase to about 195 thousand nit. About 5 thousand nit of
NETH is used to clean foam heads, equipment and molds in
slabstock and molded foam production operations.
In the 1970s, CFC-].1 was the most widely used auxiliary
blowing agent. In the late l970s, improvements in the catalyst
package made METH a technically viable alternative for virtually
all grades of foam. Since METH was somewhat less expensive to
use, its use increased significantly throughout the 1980s. In
the mid 1980s, regulatory pressure increased on CFC —11 because
the chemical depletes stratospheric ozone. At about the same
time, national and local regulators increased their scrutiny of
METH and began taking actions to discourage its use. In 1989,
TCA was identified as a suitable blowing agent and a few
commercial trials were conducted. In January of 1990, the
congressional tax was levied on CFC-l1 and the blowing agent
became prohibitively expensive to use. AT this stage, virtually
all foamers using CFC11 made the decision to switch to METH or
TCA and they began doing so. METH is the first choice for all
foamers because it is less expensive to use than TCA. In some
states and localities, however, regulators will not grant permits
to use METH because of its perceived toxicity. In these cases,
foamers will convert to the more expensive TCA. By the end of
1990, conversion will be complete and CFC-11 will no longer be
used as a blowing agent in flexible slabstock foam.
The conversion away from CFC-ll will cause an increase
in the use of METH and TCA. In some states and localities, there
will, be increasing pressure to reduce blowing agent use. In
Southern California, for instance, the SCAQMD recently passed a
rule requiring a 40 percent reduction in blowing agent use by the
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— 96 —
end of 1990. This reduction can be achieved through adoption of
exempt blowing agents, which in this case, include TCA and the
HCFCs. Since the HCFCs will not be available until the 1993/1994
time frame, this option cannot be presently exercised. Other
ways of achieving the reduction are adopting TCA, converting away
from production of less dense foams—-minimum density concept--and
implementing vapor recovery.
The most promising option for the flexible foam industry
is the development of new polyols and additives that will
entirely eliminate the need for an auxiliary blowing agent. This
is the option preferred by the foam industry and it is the one
that is preferred from a societal standpoint. Industry experts
estimate that within two years, additives will be developed to
make foam of all grades at comparable quality without the use of
auxiliary blowing agent.
The analysis performed here has focused heavily on a
minimum density specification and carbon adsorption recovery
because data were available on the cost and use reduction
associated with these options and because regulatory agencies are
moving toward a requirement for blowing agent use reduction.
Recovery presents a dilemma. The high air flows in foam plants
will render recovery systems expensive; another drawback is that
only a fraction of the blowing agent can be collected. With
improvements to the ventilation system on the line and capture of
the blowing agent in the curing and storage area, a higher
fraction of the blowing agent can be collected.
SUNMARY OF SOLVENT CLEANING OPTIONS POTENTIAL
On— and off—site recycling are promising options that could be
implemented immediately. Table 71 summarizes the various
options.
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Table 7.1
Summary of Source Reduction
options in the Flexible Foam Industry
OPTIONS ADVANTAGES DISADVANTAGES
PRODUCT SUBSTITUTION
Non—Polyurethane alternatives Can reduce emissions from Uncertain environmental and cot
(cotton batting, fiberfill, polyurethane foam tradeoffs, relatively minor
etc.) manufacture reductions
Minimum density foam Reduction in aux. blowing Higher cost
agent use, greater
CHEMICAL SUBSTITUTION durability
CFC—l1 instead of METH Less toxic, can be directly Higher cost, faces elimination as
substituted ozone depleter.
Acetone instead of METH Less toxic, 30% less is Flammable and photoreactive,
needed, less costly controls are required, process not
developed
NCFC5 instead of METH Can be directly substituted Higer cost, more required untested
toxicity, some are photoreactive,
commercially still unavailable
TCA instead of MET)! Non-photcheiniallY, reactive Ozone depleter (uncertain
proven performance regulatory future), succeptability
to hydrolysis, more required,
higher cost
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Table 7.1 (cont’d)
OPTION ADVANTAGES DISADVANTAGES
Equipment Jjodification
Max—Foam Process Minimizes Trimuaste, may Minimal reduction in blowing agent
increase efficiency of use
blowing agent
Vertifoam Process Increased gas efficiency, Retrofit is difficult, higher
Emissions are confined capital costs, process may be
alowing gas ecovery, reduces inefficient
gas use
Process Modification
“AB” Process More CO/CO 2 CO is toxic and flammable, high
produced—reducing need for conversion costs,, additional
blowing agent, raw materials chemicals required, product
cost reduced quality may be inferior, formic
acid is corrosive
Polyurethane Mcdi ficat ionsf
Additives
- HR Process High quality product Technically difficult
— Polyol System Does not need auxiliary Cannot produce low density, soft
blowing agent foams
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Table 7.1 (cont’d)
OPTION ADVANTAGES DISADVANTAGES
Produces foams of high, Can’t produce foam lover than 1.3
Montedison Prcess medium, and low densitites, lb/ft. Experimental stage
high softness foams
producible without auxiliary
blowing agent
Geolite Process Reduces need for auxiliary Cannot eliminate auxiliary agent,
blowing agent Experimental stage
Recycle & Recovery
Liquid Absorption May significantly reduce Fora undesired by products,
METH use and emissions, increase maintenance costs,
captures METH captured METH not directly usable
Vapour Absorption Recovers significant METH Requires CFC refrigerant, waste
amounts water problem, METh may lose
stabilizers
Carbon Absorption Recovers 30-40% of the Potential high capital costs,
- blowing agent (CFC—ll) carbon beds sensitive to
deactivation, captured METH may
require purification, increased
waste water and solids problem,
process retrofit may be necessary
Brayton Cycle Heat Pump Energy savings, High Water Vapour Contamination, Waste
Efficiency, successful Water Problem
Commercial Demonstration
Membrane System Cost Effective, Low Capital Requires High Solvent
Costs Concentration
Solvent Recovery & Reuse
On—site distillation Reduces hazardous waste Additional manpower training costs
Direct Reuse Low costs Blowing agent may be contaminated
Off—site recycling Reduces amount of virgin More expensive than for cleaners,
solvent required potentially increased technical
and health problems
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— 100 —
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— 102 —
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