SftJDY TO SUPPORT NiW SOURCE PERFORMANCE
STANDARDS FOR
• SOLVENT METAL CLEANING OPERATIONS "
Contract No. 68-02-1329
Task Order No. 9
Final Report
June 30, W6
Prepared By:
K> S. Surprenont
0. W. Richards
The Dow Chemical Company
Midland, Michigan
Prepared For:
Emission Standard and Engineering Division
Office of Air Quality Planning
U. S. Environmental Protection Agency
-------
STUDY TO SUPPORT NEW SOURCE PERFORMANCE STANDARDS FOR
SOLVENT METAL CLEANING OPERATIONS
Contract No. 68-02-1329
Task Order #9
Final Report
April 30, 1976
Prepared By:
K. S. Surprenant
D. W. Richards
The Dow Chemical Company
Midland, Michigan
Prepared For:
Emission Standard and Engineering Division
Office of Air Quality Planning
U. S. Environmental Protection Agency
-------
PROLOGUE
This work was conducted under contract with the Environmental
Protection Agency. Sections 1 (Summary), 2 (Introduction),
and 9 (Proposed Standards) will be written by the Environ-
mental Protection Agency and are not contained in this report.
The intent of this study was to provide a factual background
for preparing regulatory controls to reduce hydrocarbon
emissions from future solvent metal cleaning operations. The
method employed was to seek actual operations representing the
best performance of existing emission control technology and
measure the effectiveness of these systems. The information
was supplemented by a literature review, laboratory testing
and wide industrial experience, including major solvent and
equipment manufacturers.
The definition of photochemical reactivity is still being
revised. However, it is well recognized that some hydro-
carbons are serious contributors to the formation of oxidants
in the atmosphere, while others generate little or no oxidants.
Further, the sole basis for hydrocarbon control is to attain
the primary oxidant standard (160 mg/M or 0.08 ppm). The
reactivities of various hydrocarbons are being studied cur-
rently, and their oxidant generating potential is defined with
new information. For the purpose of this report, the definition
of photochemical reactivity was taken from Federal Register
Vol. 37, July 27, 1972, p. 15101, Section 52.777.
-------
TABLE OF CONTENTS
Page
SOLVENT METAL CLEANING 3-1
3.1 General: Industry Description 3-1
3.2 Solvent Metal Cleaning Processes and
Their Emissions 3-3
3.2.1 Cold Cleaning 3-4
3.2.2 Vapor Degreasing 3-16
3.2.3 Selection of Solvent Metal
Cleaning Processes 3-43
3.2.4 Emissions from Solvent
Metal Cleaning 3-45
References 3-60
EMISSION CONTROL TECHNIQUES 4-1
4.1 General Description of Potential
Control Techniques 4-1
4.1.1 Incineration 4-1
4.1.2 Liquid Absorption 4-3
4.1.3 Carbon Adsorption 4-5
4.1.4 Refrigerated Freeboard Chillers 4-13
4.1.5 Refrigeration Condensation 4-16
4.1.6 Alkaline Washing • 4-19
4.1.7 Good Operating Practices 4-30
4.2 Emission Control Performance 4-37
4.2.1 Carbon Adsorption 4-41
4.2.2 Refrigerated Freeboard Chiller 4-59
-------
-XI-
4.2.3 Equipment Design 4-73
4.3 Alkaline Washing '4-93
4.4 Comparison of Emission Controls 4-94
References 4-98
5. MODIFICATIONS AND RECONSTRUCTION 5-1
6. DUAL EMISSION CONTROL SYSTEMS 6-1
7. ENVIRONMENTAL IMPACT 7-1
7.1 Air Pollution Impact 7-2
7.2 Water Pollution Impact 7-4
7.3 Solid Waste Disposal Impact 7-8
7.4 Energy Impact 7-8
7.5 Other Environmental Impacts 7-10
7.6 Environmental Impact of Delayed New
Source Standards or No Standards 7-11
8. ECONOMIC IMPACT 8-1
-------
-HI-
TABLE OF FIGURES
Figure 3-1
Figure 3-2
Figure 3-3
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
Figure 3-10
Figure 3-11
Figure 3-12
Figure 3-13
Figure 3-14
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Figure 4-6
Figure 4-7
SPRAY CLEANING EQUIPMENT
OPEN TOP DEGREASER
OPEN TOP DEGREASER WITH OFF-SET
CONDENSER COILS
TWO-COMPARTMENT DEGREASER WITH OFF-SET
BOILING CHAMBER
TWO-COMPARTMENT DEGREASER
DEGREASER WITH LIP EXHAUST
CROSS-ROD CONVEYORIZED DEGREASER
MONORAIL CONVEYORIZED DEGREASER
VIBRA DEGREASER
FERRIS WHEEL DEGREASER
MESH BELT CONVEYORIZED DEGREASER
EXTERNAL STILL
DIAGRAM OF EMISSION SURVEY
PERSPECTIVE OF SOLVENT METAL CLEANING
EMISSIONS
CARBON ADSORPTION SYSTEM
ADSORPTION CYCLE
DEGORPTION CYCLE
REFRIGERATED FREEBOARD CHILLER
VAPOR PRESSURE CHART
ALKALINE SOAK TANK
ROTARY DRUM WASHER
3-7
3-18
3-21
3-22
3-23
3-25
3-28
3-29
3-29A
3-32
3-33
3-35
3-47
3-59
4-8
4-9
4-10
4-14
4-17
4-21
4-22
-------
-IV-
Figure 4-8
Figure 4-9
Figure 4-10
Figure 4-11
Figure 4-12
Figure 4-13
Figure 4-14
Figure 4-15
Figure 4-16
Figure 4-17
Figure 4-18
Figure 4-19
Figure 4-20
Figure 4-21
Figure 4-22
Figure 4-23
Figure 4-24
Figure 4-25
Figure 4-26
ROTARY DRUM WASHER
MESH BELT WASHER
MONORAIL WASHER
SAVINGS TO COST RATIOS FOR
CARBON ADSORBERS VERSUS VENT CONCENTRATIONS
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR CARBON ADSORPTION
MAXIMUM OPERATING CAPACITIES FOR
VARIOUS CARBON ADSORBERS
CARBON ADSORPTION VERSUS DEGREASER SIZE
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR CARBON ADSORPTION
REFRIGERATED FREEBOARD CHILLER PRICING
HORSEPOWER REFRIGERATION NEEDED VERSUS
DEGREASER SIZE
REFRIGERATION COIL DESIGN AND PRICING
REFRIGERATED FREEBOARD CHILLER
(SAVINGS/COST RATIO)
REFRIGERATED FREEBOARD CHILLER
(FLUOROCARBON 113)
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR REFRIGERATED FREEBOARD CHILLERS
REFRIGERATED FREEBOARD CHILLER (ONE HORSE-
POWER COMPRESSOR)
TYPICAL CALCULATION FOR SAVINGS:COST RATIO
FOR FREEBOARD HEIGHT
INCREASED FREEBOARD (SAVINGS/COST RATIO)
AUTOMATIC COVER (SAVINGS/COST RATIO)
TYPICAL CALCULATION OF SAVINGS:COST RATIO
FOR AUTOMATIC COVERS
Figure 4-27 EMISSION CONTROL METHODS COMPARISON
4-23
4-24
4-25
4-46
4-48
4-52
4-56
4-57
4-62
4-63
4-64
4-66
4-67
4-68
4-71
4-77
4-78
4-83
4-84
4-95
-------
-v-
TABLE OF TABLES
Page
Table 3-1
Table 3-2
Table 3-3
Table 3-4
Table 3-5
Table 3-6
Table 3-7
Table 3-8
Table 3-9
Table 3-10
Table 3-11
Table 3-12
Table 3-13
Table 3-14
Table 3-15
Table 4-1
Table 4-2
Table 4-3
COMMON METAL CLEANING SOLVENTS
VAPOR DECREASING SOLVENTS
VOLUME OF SOLVENT CONDENSING ON
100 POUNDS OF MILD STEEL
FLUOROCARBON 113 AZEOTROPES
PROCESS TRACES IN SOLVENT METAL CLEANING
SOLVENT USAGE FOR VAPOR DECREASING
SOLVENT USAGE FOR ROOM TEMPERATURE CLEANING
TOTAL U.S. DEMAND FOR CHLORINATED SOLVENTS
PERCENTAGE ESTIMATES OF U.S. DEMAND USED
IN METAL CLEANING
ESTIMATED USE OF CHLORINATED SOLVENTS IN
VAPOR DECREASING
ESTIMATED USE OF CHLORINATED SOLVENTS IN
COLD CLEANING
COLD CLEANING EMISSIONS
PROJECTED COLD CLEANING EMISSIONS FROM
METAL WORKING INDUSTRY
SOLVENT USAGE IN PARTS WASHERS
SOLVENT EMISSIONS FROM METAL CLEANING
WORKING BED CAPACITIES
CATEGORIES OF METAL CLEANING BY PROCESS
INDUSTRY INFORMATION SOURCES
3-2-a
3-38
3-41
3-43
3-44
3-48
3-48
3-49
3-51
3-52
3-52
3-53
3-53
3-56
3-57
4-11
4-30
4-39
-------
-VI-
Table 4-4 CARBON ADSORBER PRICING AND
DESIGN INFORMATION 4~54
Table 4-5 EVAPORATION RATE IN SOLVENT PRICING 4-86
Table 7-1 NATIONAL EMISSION ESTIMATES FROM
METAL CLEANING 7-3
Table 7-2 INHIBITORS THAT SHOULD HAVE NO ADVERSE
ENVIRONMENTAL IMPACT 7-6
Table 7-3 INHIBITORS WHICH MAY BE SAFE BY ANALOGY 7-7
Table 7-4 POTENTIAL PROBLEM INHIBITORS 7-7
Table 8-1 EXAMPLES OF DISTRIBUTOR PRICING 8-2
-------
Page 3-1
3. SOLVENT METAL CLEANING
3.1 General: Industry Description
The phrase Solvent Metal Cleaning is used in this text to
describe those processes using non-aqueous solvents to re-
move soils from metal surfaces. These solvents are derived
from the petroleum hydrocarbons. Examples of such solvents
include mineral spirits, trichloroethylene, methyl ethyl
ketone and isopropyl alcohol. Organic solvents such as
these can be used alone or in combination with one another
to remove water insoluble soils from parts to be painted,
plated, repaired, inspected, assembled, heat treated or
machined further. Solvent metal cleaning is usually chosen
after experience has indicated that satisfactory cleaning is
not obtained with water or detergent solutions.
Water or water solutions are usually thought of first when a
cleaning requirement is defined. The availability, low cost
and familiarity combine to make water the first consideration
for cleaning. However, water has several disadvantages as a
cleaning agent. These include a low solubility for organic
soils such as greases, a slow evaporation rate, electrical
conductivity, a high surface tension and a propensity to cause
rusting. One or more of these properties are usually
-------
Page 3-2
responsible for the selection of an organic solvent to per-
form a given metal cleaning operation.
A typical solvent metal cleaning operation would solubilize
oils, greases, waxes, tars, and in some cases water. When
these soils have been removed from the part, insoluble matter
such as sand, metal chips, buffing abrasives or fibers held
by the solvent soluble soils are flushed away at the same
time. Thus, electric motor windings and contacts can be
cleaned with some solvents without disassembly. Water or
water solutions would be totally impractical cleaning agents
for this use. A broad spectrum of organic solvents is avail-
able. Choices between the solvents are based on the solu-
bility of the soil, toxicity, flammability, evaporation rate,
effect on non-metallic portions of the part cleaned and
numerous other properties. Some of the most important prop-
erties of solvents commonly used in metal cleaning are sum-
marized in Table 3-1. For instance, a 1,1,2-trichloro-l,2,2-
trifluoroethane (Fluorocarbon 113) might be chosen where the
assembly to be cleaned contained parts made from polycarbonate,
An alcohol or ketone might be selected to remove water from a
small electronic component. A heavily grease laden part might
require hot perchloroethylene.
As would be expected the metal working industry is a major
user of solvent metal cleaning. Eight SIC codes (Numbers 25
-------
Table 3-1
COMMON METAL CLEANING SOLVENTS*
Type of Solvent/
Solvent
Alcohols
Ethanol (95%)
Isopropanol
Methanol
Aliphatic Hydrocarbons
Heptane
Kerosene
Stoddard
Mineral Spirits 66
Aromatic Hydrocarbons
Benzene***
SC 150
Toluene
Turpentine
Xylene
Chlorinated Solvents
Carbon Tetrachloride***
Methylene Chloride
Perchloroethylene
1,1,1-Trichloroethane
Trichloroethylene
Fluorinated Solvents
Trichlorotrifluoro-
ethane (FC-113)
Solvency for
Metal Working
Soils
poor
poor
poor
good
good
good
good
good
good
good
good
good
excellent
excellent
excellent
excellent
excellent
Toxicity
(ppm)
1000*
400*
200*
500*
500
200
200
10*
200
200*
100*
100*
10*
500*
100*
350*
100*
Flash Evaporation
Point
60°F
55°F
58°F
<20°F
149°F
105°F
107°F
10°F
151°F
45°F
91°F
81°F
none
none
none
none
none
Rate
24.
19
45
26
0.
2.
1.
132
0.
17
2.
4.
Ill
363
16
103
62.
* *
7
63
2
5
48
9
7
4
Water
Solubility
(% wt.)
oo
oo
00
<0.1
<0 . 1
<0.1
<0 . 1
<0 . 1
<0 . 1
<0 .1
<0.1
<0.1
<0 .1
0.2
<0 .1
<0 .1
<0 . 1
Boiling Point
(Range)
165-176°F
179-181°F
147-149°F
*01-207°F
354-525°F
313-380°F
318-382°F
176-177°F
370-410"?
230-232°F
314-327°F
281-284°F
170-172°F
104-105. 5°F
250-254°F
165-194°F
188-190°F
Pounds
Per Gal.
6.76
6.55
6.60
5.79
6.74
6.38
6.40
7.36
7.42
7.26
7.17
7.23
13.22
10.98
13.47
10.97
12.14
Price
Per
$
$
$
$
$
$
$
$
$
$
$
$
$
$
S
$
1.
1.
1.
0.
0.
0.
0.
_
1.
0.
2.
0.
3.
2.
3.
2.
3.
Gal.
59
26
11
86
66
62
62
-
06
90
40
96
70
83
33
78
13
•o
»
CJ
(0
>
Ketones
Acetone
Methyl ethyl ketone
good
good
good
1000*
1000*
200*
<0°F
28°F
439
122
45
27
117°F
132-134°F
174-176°F
13.16
6.59
6.71
$10.92
$ 1.45
$ 1.74
*Federal Register, June 27, 1974, Vol. 39, No. 125.
**Evaporation Rate determined by weight loss of 50 mis in a 125 ml beaker on an analytical balance (Dow Chemical Co. method).
***Not recommended or sold for metal cleaning (formerly standards in industry).
****Primary source from The Solvents and Chemicals Companies "Physical Properties of Common Organic Solvents" and Price List
(July 1, 1975).
-------
Page 3-3
and 33 - 39) describe .these industry categories. Examples
of industries within these classifications include auto-
motive, electronics, appliances, furniture, jewelry, plumbing,
aircraft, refrigeration, business machinery and fasteners.
All are frequent users of organic solvents for metal cleaning.
However, the use of solvents for metal cleaning is not limited
to these opeations. Solvent metal cleaning is used in non-
metal working industries such as printing, chemicals, plastics,
rubber, textiles, glass, paper and electric power. Often, the
function of the organic solvents in these industries is to
provide maintenance cleaning of electric motors, fork lift
trucks, printing presses, etc. Even in non-manufacturing
industries, solvent metal cleaning is commonplace. Most
automotive, railroad, bus, aircraft, truck and electric tool
repair stations use these chemicals. In short, most busi-
nesses do solvent metal cleaning, at least part time if not
regularly. The number of companies routinely using solvent
metal cleaning operations exceeds one million. Large using
companies often have over 100 applications at one plant
location.
3.2 Solvent Metal Cleaning Processes and Their Emissions
Solvent metal cleaning can be categorized into room tempera-
ture operations (called cold cleaning) and vapor degreasing.
-------
Page 3-4
3.2.1 Cold Cleaning
Within the cold cleaning classification/ most of the
operations are simple and use room temperature solvent.
This class of solvent cleaning can be broken down further
into: 1) wiping, 2) spraying or flushing, 3) immersing or
dipping, and 4) cold solvent washers.
3.2.1.1 Wiping
This method of cleaning combines the solubility character-
istics of the solvent employed with "Grandma's Elbow Grease"
rubbing action. A cloth, brush or sponge is wetted from a
container of solvent and is used to remove soil from sur-
faces. This cleaning method requires almost no equipment
investment. It can be located almost anywhere and moved
from one place to another with complete ease. It is also
very practical in cleaning machinery in-place and without
disassembly. Large pieces produced at low unit level may
be impractical to clean by alternate means. An example of
such production or maintenance cleaning would be in the
manufacture or repainting of large cranes. Generally, the
quality of cleaning needed is low. Almost no opportunity
exists to control solvent emissions from these operations.
-------
Page 3-5
The choice of solvent for wipe cleaning is predicated
largely on:
1. Low cost per volume
2. Slow evaporation
3. Low flammability
4. Low vapor toxicity
5. Low adverse effect on skin exposure
6. Solubility for the soils involved
This method of cleaning is often chosen because it requires
no equipment capital expenditure. As mentioned, there is
little or no opportunity to recover solvent used in this
operation. This usually means that the solvent with the
lowest volume price has the first consideration for this
cleaning application. For these reasons, a simple petroleum
distillate cut, like kerosene, is most often used. A wide
variety of such petroleum solvents are available with vary-
ing evaporation rates, flash points and aromatic chemical
contents. These products are offered under a variety of
names such as Oleum Spirits, Stoddard Solvent, Mineral
Spirits, Naphthol and VM and P Naphtha. These products
have boiling ranges between 300-400°F and will be referred
to as Stoddard Solvent. Toluene is occasionally used also.
Solvent blends, more often referred to as "safety solvents,"
are used less often where greater solvency is required.
-------
Page 3-6
\
These solvent blends usually consist of one or more
chlorinated hydrocarbons combined with a petroleum solvent.
They may be formulated for increased solvency or to diminish
the flammability of the petroleum hydrocarbon. Almost any
solvent composition can be used because distillation recovery
is not practiced. The oxygenated solvents, including alcohols,
ethers and ketones, are used very infrequently.
Disposal of used solvent by open evaporation to the atmos-
phere and the discarding of solvent-wet dirty rags are the
major sources of emissions to the atmosphere. Spillage and
evaporation from parts cleaned and from the solvent container
are minor emission sources.
3.2.1.2 Spraying or Flushing
As in the case of wipe cleaning, the solvent is carried to
the parts in this cleaning operation. Figure 3-1 illustrates
a common design. Although it can be accomplished on a gravity
basis, normally the solvent is pumped to the part or blown
with compressed air. The difference between spraying and
flushing is whether the solvent is broken up into fine liquid'
droplets or used as a continuous stream. Spray cleaning may
employ either very coarse or fine particles of solvent. How-
ever, fine sprays should be avoided due to increased hazard
from flammability or inhalation as well as greater solvent
-------
Page 3-7
Figure 3-1
SPRAY CLEANING EQUIPMENT
-------
Page 3-8
evaporative and air-entrainment losses. Spray cleaning is
often used to clean external surfaces of complex parts or
assemblies where the internal portion of the part is pro-
tected from solvent exposure. For instance, the removal of
lubricant or entrapment of solvent in a compressor or bear-
ing assembly would cause an equipment failure. Flushing,
too, can be used to clean external surfaces but is often
used to clean internal part surfaces such as tubing, complex
metal castings or heat exchangers. Both spray and flush
cleaning require solvent drainage from the part to carry the
soil away from the article being cleaned, preventing soil
from redepositing with the evaporation of the solvent. The
equipment costs for these cleaning methods are only slightly
higher than wipe cleaning, but the labor costs associated
with cleaning can be several times lower. Spray and flush
cleaning provide only low mechanical energy for the removal
of solvent insoluble soils. More work parts can be processed
by spraying than wiping, particularly if the surface structure
is intricate. When spray cleaning is done consistently in a
production operation, a ventilated spray chamber similar to
a paint spray booth is often needed. Maintenance or inter-
mittent spray or flush cleaning can often be done without
special ventilation. This manner of operation permits nuch
greater portability. Such a system is often used to clean
large electric motors in-place.
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Page 3-9
Routine production spray or flush cleaning operations
usually provide for collecting overspray and solvent
drainage from parts. In these operations, major emission
factors are from evaporation off wet parts and the dis-
posal of dirty solvent. Again, Stoddard like solvents
dominate this market. These solvents are seldom distilled
by users because of their low cost and the relative high
cost for stills designed to handle flammable solvents
safely. In maintenance cleaning by this technique, there
is often no opportunity to collect the solvent overspray
and drainage. Typically, shop rags are used to mop up
drained solvent and discarded.
The opportunity to control emissions of evaporated or air-
entrained solvent are minimal. These cleaning methods do
permit the control of solvent emissions which commonly
occur due to the disposal of dirty solvent in landfills.
Frequently, dirty solvent from flushing and spraying is
disposed of rather than repurified for reuse. This makes
low solvent-cost a major criterion. Using this practice,
the choice of solvent is essentially the same as for wipe
cleaning with the exception that low flammability must be
emphasized. Solvent blends are used to obtain a compromise
between price and flammability. Chlorinated solvents or
Fluorocarbon 113 are chosen more frequently when the cleaning
-------
Page 3-10
requirement is more demanding and/or the solvent employed
will be distilled and recovered for reuse. Distillation
of these solvents is frequently practiced because of
1) their higher cost, and 2) low cost equipment is avail-
able for non-flammable solvents.
The only major exception to this general picture is the
service offered by Safety Kleen Corporation. This service
provides both the solvent and the equipment on a rental
basis, mostly to automotive repair companies. This service
includes the pick-up and distillation of used solvent.
Further information on this service is presented ir;
Appendix E-l. The solvent employed in this service is a
petroleum distillate fraction (Stoddard).
3.2.1.3 Immersion or Dip Cleaning
Containers of solvent ranging from cup size to large tanks
are used to clean parts by immersion.
Small containers of solvent are used to clean electronic
components and to clean parts at machining stations before
checking part tolerances. Although the volume of the solvent
in a container is small, it is common for firms to have a
great many cleaning stations. Further, the solvent used in
these containers may be changed frequently throughout the
-------
Page 3-11
day to maintain sufficiently clean solvent and to prevent
soil redeposition on the parts.
The common size tank or parts washer would range between
18 and 24 inches in width and 3 to 4 feet in length with a
working depth of 15 to 30 inches. The working volume of
solvent would range from about 15 to 50 gallons. A typical
tank often has a small recirculating pump to flush the
parts with solvent and a cover with a fusible link support
arm to close the tank in case of fire. A large number
(probably 700,000) of these parts washers are located in
service garages and automotive dealerships alone. Nearly
all kinds of parts are cleaned in this type of equipment.
The solvent cleaning action may be supplemented by flushing,
spraying, wiping or brushing.
A small portion of these tanks, usually in manufacturing
plants, are equipped with filtration equipment. Also, some
cold cleaning tanks are equipped with ultrasonic generators
to speed the cleaning action and to remove insoluble soils
from the parts. With ultrasonic cleaning, normal plant
electricity (60 cycle) is converted to electric power having
a frequency of about 20,000 cycles or 20 KHZ up to 40 KHZ.
This current is converted into a mechanical vibration on the
tank walls or bottom. The mechanical vibration ruptures the
-------
Page 3-12
solvent causing tiny cavities. The cavities then collapse
and cause a scrubbing action on the surface of the parts
being cleaned.
Essentially all varieties of solvents discussed above are
used in dip cleaning. Again, petroleum distillate fractions
dominate dus to their lower cost, particularly where solvent
is discarded after use. Solvent blends with the chlorinated
hydrocarbons and the pure chlorinated hydrocarbons follow in
volume of use. Toluene, Fluorocarbon 113 and the ketones
(acetone and methyl ethyl ketone) follow in use rate. Special
solubility characteristics play a distinct role in the choice
of solvent for this widely varying method of solvent cleaning.
For instance, solvent blends are prepared for the removal of
carbon and solder fluxes, Fluorocarbon 113 is compatible with
solvent sensitive plastics (polycarbonate), alcohols or
ketones remove moisture and fingerprints, and 1,1,1-trichloro-
ethane is used to develop photoresist films in the manufacture
of printed circuit boards. The larger volume of solvent
present at a single location, than in wipe stations, causes
flammability and toxicity to be more important parameters in
the selection of a solvent. Evaporation rate may be less
important if the equipment is kept covered when not in use.
However, this is not a common practice. Where distillation
is practiced, one of the chlorinated hydrocarbons or
-------
Page 3-13
Fluorocarbon 113 is usually chosen to permit the use of non-
explosion proof equipment and greater safety.
Some control of solvent vapor emissions to the atmosphere is
possible in cleaning operations of this type. Evaporative
losses can be limited through the use of covers on the equip-
ment at all times except when the tank is in immediate use.
Present disposal methods of waste solvent often result in
evaporation to the atmosphere. Even operations which require
a low quality of cleaning seldom contaminate the solvent used
to a level greater than 10 percent by volume. Thus, the used
solvent usually consists of over 90 percent recoverable sol-
vent and less than 10 percent soil removed from the parts.
The losses from the system on parts being cleaned, referred
to as solvent drag-out, results in uncontrolled emissions.
Air agitation of cold cleaning tanks is sometimes practiced
although not recommended because it severely increases
evaporative losses.
The most important routes of emissions from immersion cleaning
are: 1) disposal of waste solvent, 2) solvent drag-out on or
in parts and 3) evaporation from the cleaning tanks. Due to
variations in equipment, work practices, choice of solvent and
volume of work, any of the routes of emission may be the major
source in a given operation. Intra-plant transfer, storage
and leaks are sources of lesser emissions.
-------
Page 3-14
3.2.1.4 Conveyorized Cold Cleaning
Conveyor!zed cold cleaning equipment is much less common;
however, three basic types are in use: spiral solvent
washers, mesh belt washers and printed circuit board washers.
The spiral washers are essentially horizontal perforated drums
with a spiral internal vane to move the parts through the drum.
The parts to be cleaned by this system are fed into the drum
and may be tumbled in a bath of solvent as they are conveyed
by the rotation of the drum. Solvent is sprayed on the parts
as they are conveyed through the drum and drains through the
perforations in the drum to the holding tank below for recycl-
ing. The last portion of the drum conveyor removes the solvent
remaining on the parts by drawing air through the parts and
out the exhaust system. These solvent washers are designed
similar to the alkaline washers shown on Figures 4-7, 4-8,
4-9 and 4-10 but are smaller in size. Similarly, mesh belt
washers convey the metal parts through a spray station and a
drying station. Both solvent washers are enclosed in a cabi-
net. The solvent used in this equipment is a high flash point
Stoddard. Due to the potential fire hazard, this equipment is
often accompanied by automatic fire detection and extinguishing
equipment. No practical emission control equipment is known
to exist for this solvent equipment design.
-------
Page 3-15
In the manufacture of printed circuit boards, the elec-
tronic components are fastened to one side of the board
and the electrical circuit connections made by soldering
the opposite side. To accomplish this, a solder flux is
used and must be removed. This solder flux is removed in
closed conveyorized printed circuit board washers. The
circuit boards may be conveyed through the washer by a
monorail chain and trolley system or by a dual chain system
to hold the circuit boards. The flux removal is effected
by spraying and/or brushing the circuit boards as they pass.
The solvent drains to a holding tank and is recycled through
the spray system. Similar equipment can be used to photo-
graphically develop the circuits on the basic board. This
process takes place before the assembly of the electronic
components on the board and involves exposing a light
sensitive film on the board to a pattern of ultraviolet
light. The exposed film becomes insoluble in the developer
solvent, and the pattern is reproduced on the board by
removing the unexposed film with the developer solvent.
Chlorinated solvents, particularly trichloroethylene and
1,1,1-trichloroethane, are used for these operations.
The emissions from conveyorized cold cleaning systems using
Stoddard or similar solvent come from exhaust ventilation
and solvent disposal. Small emissions can occur from:
-------
Page 3-16
solvent drag-out, leaks, evaporation during non-use periods
and in transporting solvent to the equipment. No retro-fit
emission control equipment is commercially recommended for
these operations.
Conveyorized cold cleaning operations with non-flammable
solvent are nearly always equipped with a still. Thus, the
emissions from solvent disposal are reduced greatly. These
systems are employing carbon adsorption at a growing rate to
recover emissions from the exhaust vents.
3.2.2 Vapor Degreasing
Vapor degreasing makes use of a convenient difference between
the soils removed in solvent metal cleaning and the solvents
used to remove them — that of boiling point. The solvents
boil at a much lower temperature than the soils. Consequently,
a mixture of solvent and metal working soils can be boiled,
and the vapors produced will be essentially pure solvent.
These pure solvent vapors will condense on metal parts until
the parts' temperature approaches the boiling point of the
pure solvent. The condensed solvent dissolves the soils
present on the parts and drains from them as new solvent
condenses.
-------
Page 3-17
Mechanically, a vapor degreaser (Figure 3-2) is a box
designed to contain the solvent. At least one chamber is
equipped with heating coils using steam, electricity or gas
to boil the solvent. As the solvent boils, pure solvent
vapors are created which are heavier than air. These heavy
vapors displace the air within the equipment. The upper
level of these pure vapors is controlled by condenser coils
located part way up the sidewalls of the degreaser. The
condenser coils are supplied with a heat exchange fluid,
usually water, and designed so that they are capable of con-
densing the solvent vapors generated by the boiling action.
These condenser coils may be limited to one spiral coil at
one end of the degreaser for smaller equipment. For larger
vapor degreaslng systems, the condenser coils are located
around the entire periphery of the internal walls of the
degreaser. Most vapor degreasers are equipped with a water
jacket which provides additional condensing capability and
reduces losses caused by convection.
The freeboard of a vapor degreaser is the distance from the
top of the vapor zone to the top of the degreaser tank (see
Figure 3-2). This distance is established by the location of
the condenser coils. The freeboard is usually 50 to 60 per-
cent of the width of the degreaser for perchloroethylene,
trichloroethylene and 1,1,1-trichloroethane. Fluorocarbon 113
-------
Page 3-18
Figure 3-2
OPEN TOP DEGREASER
Safety Thermostat
Condensing Coils
Temperature
Indicator
Cleanout Door
Solvent Level Sight Glass"
Freeboard
Water Jacket
Condensate Trough
Water Separator
Heating Elements
Work Rest And Protective Grate
-------
Page 3-19
and methylene chloride degreasers are designed to have a
freeboard equal to at least 75 percent of the degreaser
width. These freeboard recommendations are standard in
the industry and are made to protect the solvent vapor
zone from disturbance caused by air movement around the
equipment.
All vapor degreasers should be equipped with a safety vapor
thermostat located just above the condenser coils. This
device detects the rise of solvent vapors if the flow of
condenser water is interrupted and prevents the escape of
solvent vapors by turning off the heat supplied to the
boiling chamber. Nearly all vapor degreasers are equipped
with a water separator. The condensed solvent and any
water contaminating the degreaser is collected in a trough
below the condenser coils and directed to the water separator.
The water separator is a simple box which allows the insoluble
water to float on the solvent and be separated from the system
while the solvent alone is allowed to flow from the bottom of
this chamber back to the vapor degreasing operation.
The simplest cleaning cycle involves lowering metal parts into
the vapor zone and allowing the condensing solvent to rinse
off any soil. When the parts essentially stop condensing
solvent, they are slowly withdrawn from the vapor zone and
-------
Page 3-20
the vapor degreaser. The solvent wetting the parts is
vaporized by the heat stored in the parts as they are
removed from the pure solvent vapors. The cleaning action
of the condensed solvent is often increased by spraying the
parts with solvent below the vapor zone, immersing the
parts in a clean solvent chamber within the degreaser or
by immersing the parts in the boiling solvent and then in
a clean solvent chamber. In all cases, the parts are
allowed to condense solvent until it reaches the solvent
vapor temperature to provide a final rinse with pure solvent
and to heat the parts so that liquid solvent retained in
them will vaporize as they are being removed from the vapor
zone.
3.2.2.1 Open Top Vapor Degreasers
Figures 3-3, 3-4, and 3-5 describe the vapor degreasing
process and depict the most popular open top degreaser
designs. Eighty-five percent of the degreasers in use are
of these types. The range in size of these units varies.
between table top models with open top dimensions of I1 x 2'
up to degreasers which are 110* long x 61 wide. A typical
open top degreaser would have an open top about 3' wide x 6'
long.
-------
Page 3-21
Figure 3-3
OPEN TOP DEGREASER WITH OFFSET CONDENSER COILS
-------
Figure 3-4
TWO COMPARTMENT DEGREASER WITH OFFSET BOILING CHAMBER
Offset Solvent
Boiling Chamber
Solvent Overflow
Dam
arm Solvent
Immersion Chamber
(a
-------
Page 3-23
Figure 3-5
TWO COMPARTMENT DEGREASER
Warm Solvent
Overflow Dam
Solvent Boiling
Chamber
Warm Solvent
Immersion Chamber
-------
Page 3-24
Historically, degreasers of the typical size and smaller
were supplied with a single piece unhinged metal cover.
The inconvenience of using this cover has resulted in
general disuse or, at best, use only during prolonged
periods when the degreaser would not be used — for
example, weekends. More recently manufactured small open
top degreasers are more often equipped with roll-type
plastic covers, canvas curtains or hinged and counter-
balanced metal covers; essentially all manually controlled
and operated. Larger open top degreasers usually are
equipped with segmented metal covers. The largest open top
degreasers (200 sq. ft. and larger) often have manually con-
trolled powered covers. Lip exhausts such as that shown on
Figure 3-6 are not uncommon but are installed on less than
50 percent of the existing open top degreasers. These exhaust
systems are designed to capture any solvent vapors escaping
from the degreasers and carry them away from the operating
personnel. To the extent that they disturb the vapor zone,
they cause greater losses (see Appendix C-12). Where these
exhaust systems exist, the covers are designed to seal the
degreaser off below the lip exhaust slot level.
Open top degreasers represent a compromise between the
extreme low capital investment of cold cleaning and the
more capital intensive conveyorized systems discussed next.
As such, they are often located in one or more convenient
-------
Page 3-25
Figure 3-6
DEGREASER WITH LIP EXHAUST
-------
Page 3-26
sites in the plant. In contrast, conveyorized vapor
degreasers tend to be central cleaning stations where the
parts to be cleaned are transported to the machine. Open
top degreasers process parts manually and are frequently
used for only a small portion of the workday or shift.
Major emission sources from open top degreasers include the
following:
1. Vapor disturbance caused by air movement (fans,
drafts) across the top of the degreaser.
2. Solvent evaporation during non-use periods. These
losses can be avoided by covering the equipment.
3. Diffusion (the slow migration of solvent vapors
into the air above) is limited by equipment design.
This is a physical process which cannot be pre-
vented entirely.
4. Drag-out on parts may be a major or minor source
of emissions depending on the parts configuration,
racking method and operating technique.
-------
Page 3-27
Minor emission sources are:
1. Most degreasing solvent is distilled and recovered
for re-use. Thus, the disposal of waste solvent
is greatly reduced. Small.amounts of solvent re-
main in still bottom waste.
2. Intra-plant transport of solvent and storage.
3. Leaks.
3.2.2.2
Conveyorized degreasers employ exactly the same process
techniques as those for the open top degreasers. The only
significant difference between various types of conveyorized
vapor degreasers is in material handling. Open top degreasers
use hand held baskets or overhead cranes powered electrically
or with compressed air motors. In conveyorized equipment,
much more, and sometimes all, of the manual-parts handling
associated with vapor degreasing has been eliminated. The
most common of the conveyorized vapor degreasers are the
Cross-rods, Monorails and Vibra degreasers (Figures 3-7, 3-8
and 3-9 respectively).
-------
Page 3-28
Figure 3-7
CROSS-ROD CONVEYORIZED DEGREASER
-------
Page 3-29
Figure 3-8
MONORAIL CONVEYORIZED DEGREASER
-------
Page 3-29-A
Figure 3-9
VIBRA DEGREASER
Workload Discharger Chute
Ascending
Vibrating
Trough
Condensers
Distillate
Trough
Workload
Entry Chute
Distillate Return
For Counter-
flow Wash
-------
Page 3-30
The Cross-rod degreaser obtains its name from the rods
between the two power driven chains which convey the parts
through the equipment. The parts may be transported in
pendant baskets or, where tumbling of the parts is desired,
they can be carried in perforated cylinders. These cylinders
are caused to rotate within the solvent immersion steps and/or
the vapor zone. This rotation is obtained by rack and pinion
design. This type of equipment lends itself particularly
well to handling small parts which need to be immersed in
solvent to obtain satisfactory cleaning or require tumbling
to provide solvent drainage from cavities in the parts.
Cross-rods and other conveyorized degreasers are nearly
always hooded or covered. The enclosure of a vapor degreaser
diminishes solvent losses from the system as the result of
air movement within the plant.
A Monorail vapor degreaser (Figure 3-8) is usually chosen
when the transportation system between plant manufacturing
operations is using a monorail conveyor also. This design
lends to automatic cleaning with vapor, solvent spray and
vapor. The parts may be conveyed in one side and out the
other as illustrated, or the Monorail can turn 180° while
the parts are in the vapor or spray portions of the equip-
ment and exit the equipment through a tunnel parallel to the
entrance.
-------
Page 3-31
In a Vibra degreaser (Figure 3-9) dirty parts are fed
through a chute which directs them into a pan flooded with
distilled solvent. The pan is connected immediately to a
spiral tray. The pan and spiral tray are vibrated, causing
the parts to move from the pan up the spiral tray to the
exit chute. The parts condense solvent vapor as they are
vibrated up the spiral and dry as soon as they leave the
vapor zone. These degreasers are capable of processing a
very large workload of small parts per unit of floor space.
The vibratory conveying creates considerable noise. This
noise level can be handled at least partially by acoustical
insulation of the equipment or by enclosing the system in a
noise-control booth.
Solvent emissions from conveyorized vapor degreasers are
similar in source to those described for open top degreasers.
However, the enclosures common for these degreasers reduce
emissions from natural air drafts or fans. Also, the con-
veyor design usually eliminates most poor degreaser operation
and major drag-out sources.
Other less common conveyorized degreasers include the Ferris
Wheel (Figure 3-10), the Mesh Belt conveyorized degreaser
(Figure 3-11), Metal Strip degreasers and special degreasers
designed for printed circuit boards.
-------
Page 3-32
Figure 3-10
FERRIS WHEEL DEGREASER
-------
Figure 3-11
MESH BELT CONVEYORIZED DEGREASER
fP
OJ
I
OJ
U)
-------
Page 3-34
3.2.2.3 Stills
Distillation equipment is widely used in support of non-
flammable solvent operations. The capital investment in
these stills is readily recovered by the solvent conserved.
Emissions, as the result of waste solvent disposal, are
reduced by as much as 90% by stills. Well run stills emit
no significant quantities of solvent in their operation due
to their closed design.
The larger open top degreasers and most all conveyorized
degreasers are equipped with stills (see Figure 3-12) . As
described earlier, vapor degreasing solvents can be separated
from the oils and greases by boiling. Essentially, pure
solvent vapors are generated. These solvent vapors are
condensed, collected and returned as pure solvent to the
vapor degreasing operation. In addition to the stills con-
nected directly to a single vapor degreaser, firms which have
several open top degreasers often employ a central still
which repurifies dirty solvent from the several operations.
Open top degreasers even without stills can operate with
solvent containing 15-25 percent soil by volume. This con-
trasts with the practice of discarding cold cleaning solvent
with a soil content of 5-10 percent. Further, an open top
degreaser can be operated as a still to recover some of the
solvent for itself. This procedure often concentrates the
-------
Page 3-35
Figure 3-12
EXTERNAL STILL
Water
Separator
Condensate
Collection
Trough
Steam Inlets
Freeboard
Water Jacket
Water Inlet
Automatic
Level Control
~"T3>Steam Outlets
-------
Page 3-36
the soil level in the waste solvent to a level of 20-40
percent. In stills, the metal cleaning soil with dirty
solvent can be concentrated to levels between 60-85 percent
commonly. Special techniques and/or equipment can concen-
trate the soil level to 95 percent or greater.
3.2.2.4 Degreaser Design Influence on Emissions
The solvent adhering to the surface of parts cleaned in a
vapor degreaser is flash evaporated as the parts are with-
drawn from the degreaser. By comparison, parts withdrawn
from cold cleaning operations remain wet with solvent which
ultimately evaporates uncontrolled to the atmosphere. This
combined with the ability of vapor degreasing operations to
tolerate higher soil concentrations has caused most solvent
metal cleaning users to regard an open top vapor degreaser
as an emission control system when compared to cold cleaning.
Most conveyorized degreasers use significantly less solvent
per unit of work cleaned than open top degreasers. However,
the larger size of the equipment and the much larger volume
of work processed by this equipment usually results in more
solvent use per machine. In this sense, conveyorized vapor
degreasers can be regarded as a means of controlling emission
losses where the production volume justifies either one con-
veyor system or several open top degreasers.
-------
Page 3-37
3.2.2.5 Vapor Degreasing Solvents
Many solvents can qualify for the various applications in
cold cleaning. However, relatively few solvents can meet
the demands of vapor degreasing. Many of the qualities
used in selecting a vapor degreasing solvent are summarized
in Table 3-2.
Some explanation of each of these solvent parameters is
necessary for a complete understanding:
Price - The July 7, 1975, issue of Chemical Marketing
Reporter was used as a source for these prices. Where
necessary, the price quotations in dollars per pound
were converted to the dollars per gallon figure used
in the table. Prices reflect bulk purchases, e.g. tank
car or tank truck.
Flammability - All vapor degreasing solvents have no
flammability as determined by standard flash point test
methods. In industrial practice, none of them repre-
sent a significant fire hazard when used properly in
vapor degreasing or cold cleaning. Perchloroethylene,
Fluorocarbon 113 and methylene chloride have no flammable
compositions in air at room temperature. Trichloroethylene
-------
0)
en
CM
Parameter
Table 3-2
VAPOR DECREASING SOLVENTS
Trichloro-
trifluoroethane Methylene
Trichloroethylene Trichloroethane Perchloroethylene Fluorocarbon 113 Chloride
00
CO
1
ro
Price
($/Gal.)
Flash Point
Toxicity
Solvency
2.15
None
100 ppm
Strong
2.12
None
350* ppm
Moderate
2.16
None
100 ppm
Moderate
5.99
None
1000 ppm
Mild
1.82
None
500 ppm
Strong
Photochemical
Reactivity
Vapor Density
(Air = 1.0)
Volume of
Condensate
Yes
4.5
No
4.6
No
5.7
No
6.5
No
2.9
(Gals.)
Stabilization
Boiling Point
Molecular
Weight
1.00
Yes
189°F
131
0.86
Yes
165°F
133
1.57
Yes
250°F
166
0.54
No
118°F
187
0.19
Yes
104°F
35
*American Conference of Governmental Industrial Hygienists (1974)
-------
Page 3-39
and 1,1,1-trichloroethane have flammable concentrations
in air between 8.0-10.5 percent by volume in air.
Toxicity - The values shown are derived from the American
National Standards Institute. Individuals exposed to a
time-weighted average concentration of this value or
less in an eight-hour workday are adequately protected
from a health standpoint. The American National Standards
Institute also designates acceptable ceiling concentrations
and peak concentrations which should not be exceeded for
shorter time periods.
Solvency - The solvent strength should be adequate to
remove the soils on the parts without damaging the
parts themselves. Difficult soils such as partially
cured paint films require strong solvency. On the other
hand, sensitive plastics such as polystyrene may require
the use of a very mild solvent.
Photochemical Reactivity - The definition of a photo-
chemically reactive solvent is taken from Federal
Register, Volume 37, No. 145, Thursday, July 27, 1972,
p. 15101, Section 52.777. This text describes these
solvents (except trichloroethylene) as "virtually non-
reactive."
-------
Page 3-40
Vapor Density - The vapor density can be estimated
by dividing the molecular weight of the solvent by
the average molecular weight of air (29). This
property of the solvent is an indicator of the resis-
tance of the vapor zone to disturbance from air tur-
bulence above it. The less dense vapors with lower
values can be expected to be disturbed more easily than
more dense solvent vapors.
Volume of Solvent Condensate - The derivation of the
values is shown in Table 3-3. This value is expressed
in gallons of solvent condensing on 100 pounds of mild
steel.
Stabilization - With the exception of Fluorocarbon 113
all of the vapor degreasing solvents require chemical
additives to protect the solvents from decomposition.
All of the vapor degreasing solvents are stable under
the stresses of most vapor degreasing operations when
properly stabilized. However, the presence of stabi-
lizing additives does complicate the application of some
emission control techniques. This subject will be
discussed in greater detail under the Emission Control
Techniques.
-------
Table 3-3
VOLUME OF SOLVENT CONDENSING ON
100 LBS. OF MILD STEEL
Property
B.P. (°F)
Lbs./Gal.
Latent Heat
(Btu/Lb.)
Fluorocarbon Methylene
Trichloroethylene 1,1,1-Trichloroethane Perchloroethylene 113 Chloride
189
12.1
102
165
11.0
102
250
13.5
90
118
13.2
63
104
11.0
142
0)
tn
(0
Volume of
Condensate
(Gals.)
1.00
O.S6
1.57
0.54
0.19
Volume of Condensate =
100 Lbs. Steel x Specific Heat of Steel x Temperature Rise
Density of Solvent x Latent Heat of Solvent
Volume of Condensate =
100 Lbs x 0.11 Btu/Lb.-°F x (B.P. -77°F)
Lbs. Solvent/Gal. X Btu/Lb. Solvent
-------
Page 3-42
Boiling Point - Vapor degreasing solvents must be
sufficiently low boiling to permit them to be easily
separated from the soils removed in metal cleaning.
However, their boiling point must be sufficiently
high to prevent boiling at ambient temperatures and
to permit their vapors to be condensed easily, pre-
ferably with plant cooling water.
In addition to the basic solvents, a number of azeotropes
of Fluorocarbon 113 are used in vapor degreasing (Table 3-4).
Normal mixtures of solvents with different boiling points
will change in composition when they are distilled. Azeo-
tropes are unusual mixtures of solvents which can be
distilled without changing the composition. Although the
composition of many azeotropes can be expected to change
with evaporation at room temperature, the Fluorocarbon 113
azeotropes maintain essentially the same composition through-
out evaporation. In each case, these azeotropes change the
solvency characteristics of the basic Fluorocarbon 113 for
special cleaning applications.
-------
Page 3-43
Table 3-4
FLUOROCARBON 113 AZEOTROPES
Second Solvent % By Weight Boil Point
Acetone 11 111°F
Ethanol 4 112°F
Methyl Alcohol 6 104°F
Methylene Chloride 50 97°F
3.2.3 Selection of Solvent Metal Cleaning Processes
Non-routine cleaning needs are often controlled by the
individual worker, and the choice of cleaning method depends
substantially on what is available. Even in cases where the
choice of process is made by management, an in-depth exami-
nation of the available choices is not common. In Table 3-5,
some of the major criteria which can be used to select a
solvent metal cleaning process are defined. The order of
priority among these criteria can be greatly changed where
one cleaning need may be dramatically different from another.
In special cases, parameters not even listed may be most
critically needed. In some aerospace or electronics cleaning,
for example, the soil content of the solvent itself may be
the foremost consideration. The judgments made in the
rating system of this table relate to the usual methods and
the normal equipment used for each process. A great many
-------
Table 3-5
PROCESS CHOICES IN SOLVENT METAL CLEANING
Criteria
Chemical Cost/Use
Flammable Hazard
Capital Cost
** Labor Cost
a, Cleaning Quality
Oi Utility Cost/Energy
Consumption
Maintenance Cost
Mobility or Decentralized
Cleaning
Temperature of Parts
(Handling Ease)
Emission Control
Soil Disposal/Distillation
Cold Cleaning Vapor Degreasing
Flammable Solvents Halogenated Solvents Open Top Conveyorized
2
4
1
4
4
1
1
2
1
4
4
4
1
1
4
3
1
1
1
1
3
3
2
1
3
2
2
4
4
3
4
2
2
1
1
4
1
1
3
4
4
4
1
1
-------
Page 3-45
exceptions can be cited where the choice of solvent is
unusual or the system considered is of special design.
The rating system employed is: 1) first choice, 2) second
choice, etc.
3.2.4 Emissions from Solvent Metal Cleaning
3.2.4.1 Appendix A
This Appendix reports the results of a nationwide survey.
The results include the geographic distribution of metal-
working industries, the quantities of solvent reported by
type and by process, the present emission control practices,
and waste solvent disposal methods. Inherent in any such
survey, limitations must be imposed from an operational and
cost standpoint. Specifically, this survey polled the eight
SIC categories of manufacturers who are the largest users of
solvent metal cleaning. Only plants employing 20 or more
people were surveyed. The specific methodology for the survey
is described in Appendix A. The areas of use for solvent
metal cleaning not polled by this survey include: 1) manu-
facturing firms outside the eight SIC codes, which included
paper, glass, textiles, and chemicals; 2) firms employing 19
or fewer people; and 3) maintenance or service operations,
e.g., automotive maintenance, railroad repair, electric motor
rebuilding, etc. A graphic representation of the survey is
-------
Page 3-46
shown in Figure 3-13. In addition, any such survey depends
on the interviewee having a complete knowledge of the infor-
mation requested. As mentioned earlier, solvent metal clean-
ing is not the central business activity of almost any user.
Also, solvent uses may be so intermittent or many in number
that only the individual worker has knowledge of them. To
overcome these limitations, the techniques described below
were employed. Also, Appendix A provides survey data on
degreasing equipment, waste solvent disposal and emission
control equipment.
3.2.4.2 Chlorinated Solvent Producer Estimates
The quantities of solvents used by metal working firms
employing 20 or more people are summarized in Tables 3-6 and
3-7. To extend the survey information to include users not
encompassed by the survey, other information was required.
The U.S. Tariff Commission requires producers of some chemicals
to report their production. Included in that list of chemicals
are the chlorinated hydrocarbons. Table 3-8 summarizes the
production, export, import, and demand for the chlorinated
solvents for all of 1974. However, not all of the chlorinated
solvents produced are used in solvent metal cleaning. For
that reason, each of the chlorinated solvent manufacturers was
asked to estimate the percentile of the U.S. production which
-------
Page 3-47
People
Involved
Metal
working
Firms
20
Figure 3-13
FIRMS
Manufacturing
Service
Non-Metal working
Firms
Service Firms
Surveyed
Unsurveyed
-------
Page 3-48
Table 3-6
SOLVENT USAGE FOR VAPOR DECREASING
Solvent:
Fluorocarbons
Methylene Chloride
1,1,1-Trichloroethane
Trichloroethylene
Perchloroethylene
Plants
Using
Gal/Mo
(xlO3)
Lbs/Yr
(xlO3)
Average
Lbs/Yr/Plant
1,104
142
1,910
5,447
1,486
234
62
899
774
283
36,660
8,184
118,668
111,456
44,148
36,154
57,634
62,130
20,461
29,709
Table 3-7
SOLVENT USAGE FOR ROOM TEMPERATURE CLEANING
Solvent;
Acetone
Alcohols
Carbon Tetrachloride*
Ethers
Fluorocarbons
Methylene Chloride
Methyl-Ethyl-Ketone
Perchloroethylene
Petroleum Solvents
Safety Blends
Toluene
1,1,1-Trichloroethane
Trichloroethylene
Plants
Using
Gal/Mo
(xlO3)
Lbs/Yr
(xlO3)
Average
Lbs/Yr/PIant
1,215
945
162
27
1,026
324
648
702
6,344
2,079
837
2,106
2,295
110
77
12
2
125
52
86
61
926
180
138
511
299
8,712
6,098
1,584
-
19,500
6,864
6,811
9,516
73,339
16,200
11,923
67,452
43,056
7,170
6,453
9,778
—
19,006
21,185
10,511
13,556
11,560
7,792
14,245
32,028
18,760
*Not offered commercially for sale for this use due to toxic
properties and legal restrictions.
-------
Page 3-49
Table 3-8
TOTAL U.S. DEMAND FOR CHLORINATED SOLVENTS
Methylene Chloride
Perchloroethylene
1,1,1-Trichloroethane
Trichloroethylene
106 LBS
PRODUCTION
582.2
726.7
580.2
411.0
EXPORTS
101.4
28.9
80.6
43.1
IMPORTS
12.3
23.7
0.0
1.3
DEMAND
493.1
721.5
499.6
369.2
U.S. Tariff Commission Report For 1974
-------
Page 3-50
is used for cold cleaning and vapor degreasing. This
information is summarized in Table 3-9. By combining the
information from the two previous tables, the estimated
use of chlorinated solvents in vapor degreasing can be
obtained (see Table 3-10). The same method was used to
obtain Table 3-11 showing the estimated use of chlorinated
solvents in cold cleaning. By comparing the chlorinated
solvent emission estimates as obtained from the chlorinated
solvent producers to those obtained by survey, the total
solvent emissions from manufacturing firms can be estimated.
The sum of the chlorinated solvents (carbon tetrachloride,
methylene chloride, perchloroethylene, 1,1,1-trichloroethane
and trichloroethylene) from the survey amounts to 128 million
pounds per year. Carbon tetrachloride is included in this
sum although it is not sold to the metal cleaning market.
Therefore, the quantities reported as carbon tetrachloride
are one of the other chlorinated hydrocarbons in reality.
The total chlorinated solvents used for cold cleaning, based
on producer estimates, is 331 million pounds per year. Using
the producer estimates as a standard, the survey results account
for only 38.7 percent of the solvent actually used in manu-
facturing industries (Table 3-12). Thus, the survey results
on the chlorinated solvents usage in all manufacturing
industries by dividing the survey results by 0.387.
-------
Page 3-51
Table 3-9
PERCENTAGE ESTIMATES OF U.S. DEMAND
USED IN METAL CLEANING*
Vapor Degreasing Cold Cleaning
Methylene Chloride
Avg.
4%
1
5
4
1
3%
4%
10
15
4
7
Avg."
Perchloroethylene
Avg,
10
16
13
15
7
10
15
12.3%
3%
2
5
2
15
12
Avg. 5.7%
1,1,1-Trichloroethane
30
60
25
15
20
40
Avg. 32%
42
55
15
50
65
55
Avg. 47%
Trichloroethylene
86
85
80
85
90
Avg. 85.2%
2
5
5
5
5
Avg. 4.4%
*Estimates Provided by U.S. Manufacturers
-------
Page 3-52
Table 3-10
ESTIMATED USE OF CHLORINATED SOLVENTS IN VAPOR DECREASING
Methylene Chloride
Perchloroethylene
1,1,1-Trichloroethane
Trichloroethylene
Total
U.S. Demand
493.1 x 106 Lbs
721.5
499.6
369.2
Producer
Estimated
Percent Use
3.0
12.3
32.0
85.2
Quantity
15 x 106
89
160
315
Lbs
579 x 10 Lbs
U.S. Tariff Commission Report for 1974
Table 3-11
ESTIMATED USE OF CHLORINATED SOLVENTS IN COLD CLEANING
Methylene Chloride
Perchloroethylene
1,1,1-Trichloroethane
Trichloroethylene
Total
U.S. Demand
493.1 x 106 Lbs
721.5
499.6
369.2
Percent Use
8.0
5.7
47.0
4.4
Quantity
39 x 106
41
235
16
Lbs
331 x 10 Lbs
U.S. Tariff Commission Report for 1974
-------
Page 3-53
Table 3-12
COLD CLEANING EMISSIONS
(Chlorinated Solvents Only)
Survey Results 128 x 10 Lbs/Year
Producer Estimates 331 x 10 Lbs/Year
Projection Factor 0.387
Table 3-13
PROJECTED COLD CLEANING EMISSIONS
FROM METALWORKING INDUSTRY
Survey Total 271 x 10 Lbs
Projection Factor 0.387
Projected Emissions From g
Metalworking Industry 700 x 10 Lbs
-------
Page 3-54
There is every reason to believe that this same factor
would apply to other solvents used in cold cleaning. The
survey reported a total of 271 million pounds of cold
cleaning solvents being used. Dividing the survey result
by the factor 0.387 yields 700 million pounds of cold clean-
ing solvents used in manufacturing industries (Table 3-13).
3.2.4.3 Service or Maintenance Industries
This category of industry was not a portion of the survey
results. Although cold cleaning is used almost exclusively
in the service and maintenance areas, the extrapolation of
solvent usage in manufacturing cold cleaning does not contain
the solvent used in this business area because the chlorinated
solvents used as a basis for the extrapolation are almost un-
used in these businesses. The solvent most often used in main-
tenance cleaning operations is Stoddard or a similar petroleum
solvent. A large segment of the service industry is car and
truck repair locations, with an estimated 362,000 members in
1973. Petroleum companies were contacted to determine the
types and quantities of solvents used. However, these companies
had very little knowledge of the use of their products as sol-
vents because they represent such a small fraction when com-
pared to the volume used for energy. In short, the most
knowledgeable people regarding this area of solvent metal
cleaning were found to be the equipment manufacturers.
-------
Page 3-55
Interviews with the leading manufacturers of equipment
(metal parts washers) primarily for service and maintenance
firms led to useful information. Details of these inter-
views are summarized in Appendices E-2 and E-3. Between
500,000 and 1,000,000 parts washers are estimated to be in
use today. Although some parts washers are used in manu-
facturing industries, homemade parts washers and the use of
five or fifteen gallon drums for parts cleaning make this
estimated range extremely conservative. For estimation of
solvent usage in this area, 900,000 units were assumed to be
in use. About two parts washers were estimated to be at each
car and truck repair location (362,000 sites) on an average.
Thus, this category alone could account for 700,000 metal
parts washers. The capacity of solvent used in a parts
washer varies between roughly 15 and 300 gallons, while the
average was estimated at 30 gallons. To obtain satisfactory
cleaning, the parts washer manufacturers recommend that the
solvent be changed every two to three months. However, they
report that some customers change as seldom as twice per year.
Three solvent changes per year were accepted as typical.
In discussions with several maintenance firms, it was con-
firmed that most of the solvent used is either consumed in
use or is disposed in ways which would cause evaporation to
the atmosphere. For instance, a few firms reported the
-------
Page 3-56
the disposal of the waste solvent with waste crankcase oil.
The waste crankcase oil was then used as a dust control
agent for roads. From this information Table 3-14 was pre-
pared estimating the solvent emissions from service or
maintenance industries.
Table 3-14
SOLVENT USAGE IN PARTS WASHERS
Refilling (30 Gals. Three Times Per Yr.) 90 Gals.
Drag-out/Wiping 45 Gals.
Evaporation* 25 Gals.
Estimated Total Per Year Per Washer 160 Gals.
*0.1 Lbs./8 Hr.-Ft.2 x 6 Ft.2 x 280 Days/Yr. x 1/6.7 Lbs./Gal.
= 25 Gals./Yr<
The 900,000 parts washers include approximately 150,000 washers
supplied by Safety Kleen Corporation. The Safety Kleen washers
will be treated separately because specific solvent use data is
available on this equipment. Also, this equipment is designed
differently from the typical washer. The remaining 750,000
parts washers, consuming approximately 160 gallons of solvent
per year, use a total of 120 million gallons per year. There-
fore, the 120 million gallons is equivalent to 804 million
pounds. The 150,000 Safety Kleen washers are reported to
-------
Page 3-57
consume 8.2 million gallons of solvent or approximately 55
million pounds. Thus, the total solvent emitted from the
service/maintenance industries is estimated to be 860 million
pounds per year.
3.2.4.4 Total Solvent Emissions from Metal Cleaning
The total solvent emissions from metal cleaning are estimated
in Table 3-15.
Table 3-15
SOLVENT EMISSIONS FROM METAL CLEANING
Vapor Degreasing
Lbs. x 106 Tons x 106/Yr,
Chlorinated Solvents
Fluor ocarbon 113
TOTAL
Cleaning
Manufacturing
Service/Maintenance
579
37
616
700
860
0.29
0.02
0.31
0.35
0.43
TOTAL 1560 0.78
GRAND TOTAL 2176 1.09
-------
Page 3-58
Approximately 72 percent of the solvent emissions are from
cold cleaning operations; 28 percent are from vapor degreas-
ing. The national hydrocarbon emission estimates for 1972
included 15.7 million tons per year from mobile sources and
12.1 million tons per year from stationary sources, for a
total of 27.8 million tons per year. Figure 3-14 summarizes
the contribution of cold cleaning and vapor degreasing
emissions as related to the total hydrocarbon emissions and
the stationary source hydrocarbon emissions. Existing
regulations are usually based on Rule 66. These regulations
permit emissions up to 40 pounds/day (or 8 pounds/hour) or an
85% emission reduction or conversion to exempt solvents
(essentially non-photochemically reactive). Solvent metal
cleaning users have complied with existing laws by substitut-
ing low or non-photochemically reactive solvents. These laws
are summarized in Appendix D. No metal cleaning operation has
been reported to have achieved the 85% emission control
suggested by current regulations.
-------
Page 3-59
Figure 3-14
PERSPECTIVE OF SOLVENT METAL CLEANING
EMISSIONS
TOTAL HYDROCARBON
EMISSIONS
STATIONARY HYDROCARBON
EMISSIONS
Other
91%
Tons/Year
Mobile
Tons/Year
Stationary
Cold
Cleaning
6.4%
Vapor
Degreasing
2.6%
2.8% Cold Cleaning
1.1% Vapor Degreasing
-------
Page 3-60
References
General Metal Cleaning
1. "Heat Treating, Cleaning and Finishing," Metals Handbook,
Vol. 2, published by American Society for Metals.
2. Spring, Samuel, Ph.D., Metal Cleaning, published by
Reinhold Publishing Corp., 1963.
3. Pollack, A. and P. Westphal, An Introduction to Metal
Degreasing and Cleaning, published by Robert Draper Ltd.,
1963.
Cold Cleaning
4. Cold Cleaning with Halogenated Solvents - STP 403,
published by the American Society for Testing and
Materials, 1966.
5. "Solvent Cleaning, Which One to Choose," Products
Finishing, May, 1965.
-------
Page 3-61
Vapor Degreasing
6. Handbook of Vapor Degreasing - No. 310, published by
the American Society for Testing and Materials, 1962.
7. Modern Vapor Degreasing, The Dow Chemical Company.
8. Today's Concepts of Solvent Degreasing, Detrex Chemical
Industries, Inc.
9. Vapor Degreasing with Chlorinated Solvents, Ethyl
Corporation.
10. Standard Practices Metal Degreasing with Chlorinated
Solvents, E. I. DuPont DeNemours & Co.
11. Vapor Degreasing Handbook, Diamond Shamrock Corporation.
12. Metal Degreasing, The Uddeholm Company.
13. Vapor Degreasing Solvent Selection Guide for Compliance
with OSHA & EPA Regulations, Baron-Blakeslee.
14. Vapor Degreasing Questions and Answers Handbook, Phillips
Manufacturing Company.
-------
Page 3-62
15. Ramsey, R. B., Jr., "The Niche for Fluorinated Solvents,"
Metal Progress, April, 1975.
-------
Page 4-1
4. EMISSION CONTROL TECHNIQUES
This segment of the report has two parts. The first is a
general discussion of each technology that might be used to
control emissions from solvent metal cleaning. The second
evaluates the various technologies which have been demon-
strated to be practical and evaluated under manufacturing
conditions.
4.1 General Description of Potential Control Techniques
4.1.1 Incineration
Incineration has been known and used for some time to control
emissions to the atmosphere, particularly from large paint
systems. It is accomplished by direct thermal oxidation or
by catalytic oxidation. When direct thermal oxidation is
used the vented gases must be heated to a temperature of
approximately 1400 to 1600°F and held long enough to permit
the complete oxidation of the hydrocarbons contained in the
air stream. Using catalytic combustion, the exhaust gases
can be heated to a temperature of 600° to 900°F with the same
effect according to the literature. Obviously, these techniques
could be used for petroleum hydrocarbons and oxygenated solvents
(isopropyl alcohol or acetone). Although the chlorinated
hydrocarbons are used primarily because they are non-flammable
-------
Page 4-2
under normal use conditions, they can be pyrolyzed at
temperatures in the range of these incineration processes.
The pyrolytic decomposition of chlorinated hydrocarbons
will contain chlorine, hydrochloric acid, and phosgene
depending upon the conditions of oxidation. These products
would have to be removed from the off gas stream of the
incinerator before exhausting to the atmosphere.
As discussed earlier, there are approximately 900,000 cold
cleaning tanks in use in the service/maintenance industries.
The number of cold cleaning tanks in the manufacturing
industries is estimated at roughly one-half the earlier
figure. The total number of cold cleaning tanks is in the
vicinity of 1.35 million units. Using a conservative venti-
lation capture velocity of 100 ft. per minute per sq. ft. of
open top area, an average tank of 6 sq. ft. surface would
require 600 cu. ft. per minute ventilation. The ventilation
exhaust would contain only trace quantities of hydrocarbon
vapors — less than 50 ppm. Since air has a density of
0.075 pounds per cu. ft. at room temperature and a specific
heat of 0.25 Btu per pound °F, the energy demand to heat the
air-solvent mixture 800°F can be calculated:
Annual Exhaust Volume/Unit = 600 cfm x 60 Mins./Hr. x
8 Hrs./Day x 240 Days/Yr,
Annual Exhaust Volume/Unit = 69 x 10 Ft.
-------
Page 4-3
Annual Heat Required/Unit = 69 x 106 Ft.3 x 0.075 Lbs./Ft.3
x 0.25 Btu/Lb.-°F x 800°F
Annual Heat Required/Unit = 1.0 x 10 Btu
Total Annual Heat Required = (1.0 x 109 Btu/Unit) x
(1.35 x 106 Units)
Total Annual Heat Requirement = 1.4 x 10 Btu
The total heat requirement for this incineration, 1.4 x 10
Btu, can be compared to the estimated total U.S. energy demand
of 65 x 10 Btu in 1970. This new heat demand would increase
the total U.S. energy requirement by about two percent. Note
that the energy demand was calculated based on an eight-hour
day and the use of catalytic combustion. Those installations
operating more than one shift per day or using direct thermal
oxidation would require much more heat. The use of heat
recovery heat exchangers could reduce the overall energy
demand between 40 to 80 percent. However, this would require
a substantially greater capital investment. The existing
commercial systems are designed to handle only extremely large
emission sources. No emission testing was conducted on this
method of emission control due to the impractical energy
requirements involved.
4.1.2 Liquid Absorption
Liquid Absorption is a well known process in which a liquid
medium is used to extract a soluble vapor from a gas stream.
-------
Page 4-4
This process takes place in a packed column to provide con-
tact between the fluid and the gas stream. The fluid is
pumped to the top of the column, distributed over the packing
and drains by gravity counter-current to the gas stream being
treated. With proper column conditions and fluid choice,
removal of the dilute solvent vapors from air could be
effectively accomplished. However, as the vapors become more
dilute in air, the column size required becomes much larger
and the air stream becomes saturated with liquid absorbent
fluid.
For instance, trichloroethylene vapors in air could be sub-
stantially reduced by absorption in mineral oil. Absorption
and recovery of the solvent stabilizer system would be unlikely,
so restabilization of the recovered solvent would be needed.
At a column temperature of 30°C (86°F) the air stream leaving
the column would contain about 120 ppm mineral oil. From an
air pollution view, this process would often result in removal
of one chemical emission and the generation of another. The
same effect can be achieved by the simple substitution of a
non-photochemically reactive solvent in the basic use operation
without the large capital expense for the adsorption equipment.
Chilling the absorbing fluid would diminish the content of it
in the exhaust air. Cooling to a temperature below 0°C (32°F)
would cause ice formation in the column since water is insoluble
-------
Page 4-5
in mineral oil. This could be avoided by prerefrigeration
of the air stream. However, the use of refrigeration would
greatly enlarge the energy consumption. The energy require-
ment is already very large because relatively large volumes
of mineral oil would have to be heated nearly to its boiling
point to recover relatively small quantities of solvent.
Except for the recovery of 1) high concentrations of solvent
vapors in air, 2) very valuable vapors or 3) highly toxic
chemical vapors, this method of emission control is impractical.
The use of this technology could be feasible where chlorinated
solvents were absorbed in metal cutting lubricant oils. The
presence of the chlorinated solvent in cutting oils increases
tool cutting speeds and tool life. This practice would avoid
the large energy needed for distillation but would result in
slow re-release to the atmosphere during use as a metal cutting
lubricant. The same method could be used for petroleum hydro-
carbon solvent absorption in fuel oil. The mixture of solvent
and fuel oil after absorption could be used as fuel. No systems
representing this technique are known to exist in solvent metal
cleaning.
4.1.3 Carbon Adsorption
In this process, specially prepared or activated carbon is
used to capture dilute solvent vapors in an air stream. The
-------
Page 4-6
activation of the carbon is accomplished by creating enormous
surface areas within the carbon structure. These surface
areas (estimated to be as large as 200 million square feet
per cubic foot) attract and trap the solvent vapor molecules.
Activated carbon is reported to have been developed by
Dr. N. K. Chaney, originally for protection'against toxic
gases in World War I.
When it was discovered that the captured vapors could be
recovered from the carbon by passing steam through it and
condensing the steam and desorbed vapors, this system became
a commercial means of recovering solvent vapors. Many adsorp-
tion media have been examined, but activated carbon remains
the most effective for general solvent vapor recovery.
Although carbon adsorption was applied in many commercial
areas, it was not introduced to solvent metal cleaning until
the late 1950's. Even now, only a few hundred carbon adsorp-
tion systems are working in support of solvent metal cleaning
operations.
Carbon adsorption solvent recovery requires two separate
operations: 1) adsorption of the solvent vapors onto the
carbon and 2) desorption of the solvent vapors with steam.
Typical carbon adsorption equipment embodies two separate
carbon beds so that the adsorption process can take place
-------
Page 4-7
continuously in at least one carbon adsorption bed. (See
Figure 4-1.) The beds are programmed to operate on the
adsorption cycle either together or singly. However, only
one bed at a time is operated on the desorption cycle. The
adsorption cycle is graphically shown on Figure 4-2. The
exhaust air from the metal cleaning operation is drawn by a
fan and directed down through the activated carbon bed, with
the desorbed air being exhausted through the duct at the
bottom. The air from solvent metal cleaning typically con-
tains anywhere from 100 to 1,000 ppm. The adsorption cycle
is interrupted before the bed becomes saturated with solvent.
The upper and lower dampers close, preventing the flow of air
through the carbon bed, and steam is injected through the
steam inlet line below the carbon bed. (See desorption cycle,
Figure 4-3.) The steam sweeps through the carbon and vaporizes
the solvent from it. The combined solvent and steam vapor are
condensed in a shell and tube condenser, and the combined
liquid volumes are separated in the decanter or water separator
immediately below. This gravity means of separating the water
and solvent can be employed only when the solvent and water
are immiscible. When the recovered solvent is soluble in
water, distillation or other means must be employed to separate
the solvent and water. The carbon used to form the beds is in
the form of pellets or coarse granules.
-------
Figure 4-1
Solvent-Laden Air Inlet —
Condenser
n
Bed "A"
I
„ nl
a .
Bed "B"
J
•—Water
Separator
,1 1.
/ll
(a
iQ
I
00
— Steam Line
Clean Air Exhaust
-------
Page 4-9
Figure 4-2
ADSORPTION CYCLE
Solvent-Laden
Air Inlet
Activated Carbon
Bed
Clean Air
Exhaust
-------
Page 4-10
Figure 4-3
DESORPTION CYCLE
-------
Page 4-11
Both the equipment and the carbon bed itself are reported to
have an operating life of at least 15 years. Attrition of
the carbon bed occurs very slowly as the result of oxidation
as well as thermal and mechanical action. The capacity of
activated carbon for a specific solvent is a characteristic
of the solvent itself. Generally, higher boiling solvents
have greater bed capacities. Although the total solvent
capacity in carbon may approach the weight of the carbon it-
self, the working capacity is much smaller. This capacity
can be described as that quantity which can be desorbed in a
given desorption cycle with low pressure (5-10 psig steam) and
re-adsorbed in the next adsorption cycle. Some typical working
carbon bed capacities are shown in Table 4-1.
Table 4-1
WORKING BED CAPACITIES
Solvent % of Carbon Bed Weight
Acetone 8
Heptane 6
Isopropyl Alcohol 8
Methylene Chloride 10
Perchloroethylene 20
Stoddard Solvent 2-7
1,1,1-Trichloroethane 12
Trichloroethylene 15
Trichlorotrifluoroethane 8
VM&P Naphtha 7
-------
Page 4-12
The working bed capacity can be reduced by contaminating
the bed with dust particles, by adsorbing a material which
can not be desorbed such 'as mineral oil, or by chemical
reaction within the bed to produce high boiling, non-
desorbable products.
A combination of solvent vapors in an air stream can often
be adsorbed. However, the solvent concentrations in the air
stream coming from a solvent blend will usually be rich in
the most volatile solvents and lean in the less volatile when
compared to the original composition. Thus, the recovered
solvent from a mixture will seldom contain a similar concen-
tration of the various solvents used in the system. In
addition, any co-solvents which have high water solubility
such as acetone or ethyl alcohol used in combination with
Fluorocarbon 113 would tend to be removed from the recovered
solvent by extraction with the condensing steam. Again, the
small chemical additives (stabilizers) added to solvents to
prevent decomposition are frequently not recovered with the
solvent. In these cases, continued use of the recovered sol-
vent is practical only if sufficient stabilization occurs by
mixing recovered solvent with fresh solvent or if the stabili-
zers themselves are re-added to the recovered solvent.
Carbon adsorption equipment is available in a series of sizes
The size is usually determined by the required volume of air
-------
Page 4-13
flow needed to ventilate the solvent metal cleaning oper-
ation. The quantity and specific solvent to be adsorbed
can also influence the size. The equipment sizes handle
ventilation rates between 600 and 10,000 cfm. Larger
systems are engineered on a custom basis. The emission
control efficiency and cost effectiveness of this process
were examined in actual industrial operations and reported
in Section 4.2.1.
4.1.4 Refrigerated Freeboard Chillers
This emission control device operates in conjunction with
vapor degreasing. The vapors created within a vapor de-
greaser are prevented from overflowing the equipment by
means of condenser coils and a freeboard water jacket.
Refrigerated freeboard chillers are an addition to this
basic system. In appearance, they seem to be a second set
of condenser coils located slightly above the primary con-
denser ceils of the degreaser. See Figure 4-4. Functionally,
however, they achieve a different purpose. The condenser
coils control the upper limit of the vapor zone. The refrig-
erated freeboard chiller coils limit the diffusion of solvent
vapors from the vapor zone into the work atmosphere. This is
accomplished by chilling the air immediately above the vapor
zone and creating a cold air blanket. In addition, the
-------
Page 4-14
Figure 4-4
REFRIGERATED FREEBOARD CHILLER
-------
Page 4-15
turnover of the chilled air within the degreaser to the
general atmosphere can be expected to be less.
Patent* coverage of this emission control method is limited
to designs that control the heat exchange temperature at
32°F or colder. Manufacturers operating within this patent
recommend a heat exchange temperature of -20°F. Commercial
systems are also available operating between 34° and 40°F.
Most of the major manufacturers of vapor degreasing equip-
ment offer both types of freeboard chillers.
The ice formed on some freeboard chillers operated at temper-
atures lower than 32°F does contain substantial quantities of
the solvent being used in the vapor degreasing operation.
These systems are designed with a timed defrost cycle to
remove the ice from the coils and restore the heat exchange
surface efficiency. Although the liquid water and solvent
formed during the defrost cycle is directed by design to the
solvent condensate collection trough and on to the water
separator, water contamination of the vapor degreaser system
is not uncommon. Although water contamination of vapor
degreasing solvents has an adverse effect on the stabilizer
*U.S. Patent 3,375,177 was issued to Autosonic Inc.
March 26, 1968
-------
Page 4-16
systems, major stabilizer depletions from this source are
uncommon. Water is a major source of equipment corrosion
and can diminish the working life of the equipment signifi-
cantly. Emission testing of this control method is reported
in 4.2.2.
4.1.5 Refrigeration Condensation
Direct condensation of solvent vapors from exhaust air
streams has been considered and even attempted by a few
firms as a means of recovering solvent. No successes have
been reported. Some insight into the problem is gained by
examining Figure 4-5. The vapor pressures shown for the
chlorinated hydrocarbons is from published data. The vapor
pressure curve for Stoddard solvent is actually taken from
the vapor pressures of n-Decane or 1,2,3-trimethylbenzene.
These two chemicals have boiling points in the mid-range
of Stoddard and may be used to estimate the properties of
the complex solvent mixture really present.
Vapor condensation will occur when the air stream is refrig-
erated to a temperature causing the vapor concentration to
exceed the solvent vapor pressure at that temperature.
Although momentary concentrations may reach 1000 ppm in some
operations, the average concentration of chlorinated solvent
-------
Page 4-17
Figure 4-5
2
3
4
5
M«thyl«n« chlorida
1,1 Dichloroethane
Chloroform
1,1,1 -Trichloroathan*
Carbon tetrachloride
6
7
8
9
lO
Ethytene didiloride (1,2-di<*loro«th«na)
Trichloroslhyieo*
1 , 1 ,2-Trichloro«thane
Perchloroethylena
Stoddard Solvent
1 1
12
13
14 ;
15 i
10,000
5000
-20-C .10 O'C 10- 20' 30- 4O- 50" «>• 70' 3O- 90- lOO- 120' 140' 60' 180- 200' J20' 240'C
1000
10 20 30 40 50 60 70 80 9O 10O 120 140 160 180200220240
-20 -10
-------
4-18
vapors from metal cleaning seldom exceeds 300 ppm (0.23
millimeters Hg.). Thus, direct condensation of even per-
chloroethylene would not occur until the temperature was
reduced to about -40°C. Similarly, if a vapor concentration
of about 50 ppm (0.04 millimeters Hg.) is assumed for
Stoddard, a lower refrigeration temperature is needed before
any solvent can be condensed. At these temperatures ice is
rapidly formed on the heat exchange surfaces and reduces the
heat exchange efficiency. The ice also requires the removal
of a large amount of heat (1300 Btu's per pound). Further,
the problem of removing the condensed mist of solvent from
the moving air stream is difficult. The cost of refrigeration
equipment and energy consumption prohibit the practical appli-
cation of this emission control method when vapor concen-
trations are as low as those from solvent metal cleaning.
Refrigeration has been used in the dry cleaning industry with
perchloroethylene and Fluorocarbon 113 where the refrigerated
air is heated and recycled to dry solvent from the clothes.
Where this technology is employed, the solvent must not have
flammable compositions with air throughout the temperature
range experienced. No industrial applications of this tech-
nology were reported during the testing program associated
with metal cleaning. One industrial application was reported
after this test program had been completed. The equipment
-------
4-19
manufacturer, Autosonics Inc., has reported good emission
control from this installation.
4.1.6 Alkaline Washing
One of the more obvious means of reducing solvent emissions
to the atmosphere from metal cleaning is to use aqueous
cleaning agents. The most common aqueous cleaning method
is alkaline washing. On an industrial basis, alkaline
washing is very similar to dishwashing. As mentioned earlier,
alkaline washing is so common in industry that it is nearly
always considered before solvent cleaning when a cleaning
requirement is recognized. The need for both alkaline wash-
ing and solvent metal cleaning is well demonstrated by the
fact that 41% of the users of solvent metal cleaning also
employ alkaline washing (see Appendix A, Exhibit III-A).
Alkaline washing compounds are supplied as both liquid and
solid mixtures. These formulations contain various quantities
of caustic; the sodium or potassium carbonates, phosphates,
silicates and borates; soaps; and petroleum surfactants.
These alkaline washing compounds are usually used at concen-
trations of 1/2 to 2 ounces per gallon. However, concentrations
of 6 to 12 ounces per gallon may be used in non-agitated soak
tanks.
-------
Page 4-20
Typical suggested operating temperatures for alkaline baths
range from 160° to 190°F. Recently, room temperature alka-
line washing compounds have been offered to reduce the
large energy requirements of this cleaning method. These
room temperature alkaline compounds may be heated to tempera-
tures up to 130°F and often require longer cleaning action.
The cleaning agents in these formulations emulsify water
insoluble soils. Good rinsing is required to remove the
residues of the soil emulsions formed in the cleaning baths.
If the process following the cleaning operation requires dry
parts, the last step in the operation is drying the parts.
These process steps are carried out in a variety of equipment
including soak tanks, rotary drum washers, mesh belt washers
and monorail washers. This equipment is illustrated in
Figures 4-6 thru 4-10.
Alkaline washing has several advantages and disadvantages when
compared to solvent metal cleaning. The advantages of alka-
line washing are:
Cost Per Gallon - The cost per gallon of an alkaline
washing solution is only a few cents. This low cost per
gallon is often the basis for assuming that alkaline
washing is cheaper than solvent cleaning. A number of
cost comparisons have been reported in the literature
showing vapor degreasing to be competitive with or lower
-------
Figure 4-6
ALKALINE SOAK TANK
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-------
Figure 4-7
ROTARY DRUM WASHER
10
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Figure 4-8
ROTARY DRUM WASHER
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O O OO OOOSXB®«
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Figure 4-9
MESH BELT WASHER
tu
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Figure 4-10
MONO-RAIL WASHER
O
-------
Page 4-26
in cost than alkaline washing. However, the low cost
per gallon does economically tolerate spills, leakage
losses and solution drag-out.
Pre-Wet Process Operation - When alkaline washing is
used before plating, phosphatizing or other wet pro-
cesses, drying of the parts is unnecessary. A large
energy demand is avoided by not drying the parts.
Further, alkaline washing creates a hydrophilic metal
surface which enhances the wet processing operations.
Straight Through Cleaning - The confinement of solvent
liquid and vapors in metal cleaning systems requires
the parts to be raised and lowered into the cleaning
system. In alkaline washing systems, the parts can be
processed on one horizontal plane.
High Pressure Spray - The lesser need for confinement
in alkaline washing permits higher spray pressures.
The removal of insoluble particles or metal chips can
be enhanced if the sprays are specifically directed to
accomplish this purpose. Physical cleaning from the
spraying action can occur even when proper operating
temperatures and concentrations are not being followed.
-------
Page 4-27
Cleaning of Special Soils - The removal of soaps,
certain buffing compounds and solid dry lubricants
is accomplished with alkaline washing. The special
cleaning action in these cases may result from chemical
reaction with the soils or be due to the higher spray-
ing pressures.
Air Pollution - In the sense of solvent vapor emissions/
no air pollution occurs from alkaline washing. However,
mist containing detergent is entrained in the exhaust
systems and discharged to the atmosphere. Quantities
of water and heat are also discharged in the same manner,
particularly where the parts require drying.
Some of the disadvantages of alkaline washing compared to
solvent cleaning are:
Water Pollution - Although many large firms have water
treatment systems, the alkaline washing process itself
tends to dilute and discharge the cleaning additives as
well as all of the soils removed from the parts. By
contrast, solvent metal cleaning concentrates the soils
removed from the metal parts and no water pollution
occurs.
-------
Page 4-28
Lower Quality Cleaning - Solvent vapor degreasing is
usually chosen for cleaning precision small parts.
The higher quality cleaning provided by vapor de-
greasing has been demonstrated by lower rejection
rates of parts vacuum welded or induction fused after
both cleaning systems.
High Energy Demand - In addition to the higher energy
requirement for vaporizing water than solvent, large
quantities of heated water vapor mist are exhausted
from alkaline cleaning systems.
Long Start-Up Time - The quantities of alkaline wash-
ing solution in a washer are often quite large. In
some cases the time required to heat the system up to
operating temperatures may require a significant portion
of an operating shift. To avoid poor cleaning before
the temperatures are achieved or loss of production,
alkaline washing equipment may be heated constantly even
during non-operating intervals, or the heating may begin
hours before the operating shift.
Rust - Any residual water on ferrous parts can con-
tribute to rust formation. Again, the residues left
by insufficient rinsing can cause rusting by adsorbing
-------
Page 4-29
atmospheric moisture. These residues contribute to
poor machine feeding in subsequent machining operations.
Corrosion or Staining - Non-ferrous metals, particu-
larly, may be subject to corrosion or staining if the
alkaline washing compound is not properly selected or
the concentrations controlled.
Electrically Conductive Residues - Entrapped water or
detergent residues have high electrical conductivity.
Where electrical insulating properties are important,
alkaline washing is seldom used.
Water Sensitive Parts - Alkaline washing is not used to
clean assemblies that demand low moisture content, such
as refrigeration equipment.
Recognizing the various advantages and disadvtanges of
alkaline washing versus solvent metal cleaning, some general-
izations can be made of areas where one or the other cleaning
process dominates. These areas are summarized in Table 4-2.
-------
Page 4-30
Table 4-2
CATEGORIES OF METAL CLEANING BY PROCESS
Solvent Cleaning Alkaline Washing
Non-Ferrous Metals Ferrous Metals
Small Parts Large Work Pieces
High Precision Parts Low Tolerance Parts
High Cleaning Requirements Lower Cleaning Standards
Electric and Electronic Pre-Plating, Phosphatizing
Parts and Assemblies or Other Wet Processes
Although there are exceptions to these generalizations, the
areas of application of each cleaning process are sufficiently
distinct that there is little competition between the two
cleaning processes. Consequently, most solvent metal cleaning
operations could not be converted to alkaline washing as a
means of controlling emissions to the atmosphere.
4.1.7 Good Operating Practices
The basic procedures for operating solvent metal cleaning
systems have been described by numerous chemical suppliers
and equipment manufacturers. Various societies have also
published information to guide solvent users. Thesa good
operating practices have also been the subject of numerous
articles. However, they are not recovery techniques; rather,
-------
Page 4-31
they are recommended methods of operating the basic systems
safely and economically. Inherently, these techniques
effect emission control as well.
4.1.7.1 Cold Cleaning
Covers - Covers are supplied for essentially all cold
cleaning systems and should be used to prevent un-
necessary evaporative losses. The use of covers
during down shifts, weekends and holidays is critical.
Intermittently used cleaning tanks should be closed in
periods of disuse greater than a half hour in length.
Control of Waste Solvent - The bulk of waste solvent
from cold cleaning operations is solvent, usually over
85% by volume. Simple distillation equipment is avail-
able to recover chlorinated solvents and Fluorocarbon
113 due to their non-flammability. Stills are also
manufactured for flammable solvents but must be designed
as explosion proof systems. Solvent recovery services
are available in most areas of the country.
Ventilation - The ventilation associated with cold
cleaning systems should be maintained at the minimum
level to prevent unnecessary evaporation. The venti-
lation duct work should be located above the cover
-------
Page 4-32
level of a cold cleaning tank so that vapors are not
withdrawn from the tank when the tank is covered. If
the tank is located in a pit, the pit should also be
ventilated. Required ventilation rates are described
under the Occupational Safety and Health Act.
Drainage - A drainage area should be provided for
parts after cleaning to allow the solvent to drip from
the parts and be collected. Preferably/ this drainage
area should be within the tank.
Choice of Cold Cleaning Method - The order of selecting
a cold cleaning method from best to poorest is:
immersion cleaning, flushing, coarse spraying, and
wiping.
Spraying - Aspiration of a solvent with compressed air
is not recommended. Spraying should be accomplished
with the coarsest possible spray pattern developed by
a mechanical spray nozzle. A large collection trough
should be provided to capture the over-spray and drain-
age of solvent and return it to storage. Spraying
solvent greatly increases the risk of fire, particularly
when a fine spray is used. Spraying also aggravates
evaporative losses. Explosion-proof switches, wiring
-------
Page 4-33
and ventilation equipment should be provided where
any fire hazard exists. (Note - Even non-flammable
solvents can have ignitable mixtures in air as dis-
cussed earlier.)
Compressed Air Blow Off - The use of compressed air to
blow off and dry solvent cleaned parts is not recom-
mended. When necessary, low pressure air should be used
and protection should be provided to protect operating
personnel from solvent droplets and solid particles.
The Occupational Safety and Health Act defines the
safety requirements for compressed air use.
Protective Clothing - Nearly all solvents extract oils
from the skin and make it subject to cracking. Pro-
tective gloves should be worn to avoid this exposure.
Goggles and/or aprons should be worn whenever solvent
may contact other areas of the body.
Compressed Air Agitation - The use of compressed air
for mixing cleaning solvent baths is not recommended.
4.1.7.2 Vapor Degreasing
Covers - Open top vapor degreasers should be covered
during down shifts, weekends or non-operating periods
of a half hour or more.
-------
Page 4-34
Drafts - All vapor degreasers, particularly open top
degreasers, should be located so that natural drafts
from windows and doors are held to a minimum. Baffles
may be constructed to prevent mild drafts from upsetting
the vapors within the vapor degreaser. Operator fans
and space heaters should not be directed toward or across
degreasers.
Spraying - Spraying within a manually operated degreaser
should be conducted only below the vapor zone. Unless
special design considerations have been made, spray
nozzles within conveyorized degreasers should be directed
horizontally or downward to prevent disturbing the vapor
zone.
Drag-out Losses - Parts should be arranged in work bas-
kets or carriers to provide the maximum solvent drainage.
Workloads should be held in the vapor zone until the
vapor temperature is reached (usually 30 seconds after
spraying or immersion in warm solvent) . A 15-second
holding period immediately above the vapor zone is recom-
mended for parts with large surface areas. Drag-out
losses can be minimized by processing workloads in rotary
baskets or fixtures in conveyorized equipment.
-------
Page 4-35
Leaks - Vapor degreasing equipment should be inspected
for leaks at pump seals, entry port gaskets, and sight
glasses regularly. All leaks should be repaired
immediately. Hot solvent evaporates rapidly; thus,
small leaks may be more significant than they appear.
Distillation - Stills can be directly connected to
vapor degreasers to provide a constant source of fresh,
clean solvent and to remove the soils accumulated by
the degreaser. The use of a still enables the degreaser
to be operated for longer periods without the need for
maintenance cleaning, reduces the interruption of pro-
duction cleaning, and concentrates the oils removed by
the solvent. This concentration of the oils reduces
disposal costs and provides maximum solvent conservation.
Where several degreasers are in use, a central still can
provide most of the same advantages. Distillation on
site is preferred, however, solvent reclaiming services
are available in most locations.
Ventilation - As in cold cleaning, the ventilation rates
should be held to the minimum necessary to provide a safe
working atmosphere. The Occupational Safety and Health
Act defines the acceptable vapor concentrations for
worker exposure. Ventilation ducts should be located
-------
Page 4-36
above the cover so that they do not draw from within
the degreaser when it is closed. Excess exhaust
causes unnecessarily high emission rates.
Size and Weight of Workload - The size of the work
pieces or baskets should not exceed two-thirds the
area of open top degreasers. The weight of the work-
load should be controlled to be within the working
capacity of the degreaser. The workload weight is
excessive if it causes the vapor zone to collapse well
below the condenser coils.
Equipment Design and Safety Devices - Manufacturers
who specialize in the design and construction of vapor
degreasers are available. On a long-term basis, these
firms provide the more economical sources for equipment.
The most important safety device is the safety vapor
thermostat. This device detects the solvent vapors if
they should rise above the condenser coils. When the
vapors are sensed, the heat is turned off. Both safety
and solvent economy is assured in this way. Safety vapor
thermostats should be of the manual reset type and should
be checked for operation frequently. Other valuable
safety devices include solvent level controls, boiling
sump thermostats, and condenser water flow switches.
-------
Page 4-37
Maintenance - Degreasers should be maintained so that
proper solvent flow is assured. Removal of accumulated
oils, metal chips, and parts should be done on a routine
basis, usually at least quarterly.
Water Contamination - Water contamination of degreasing
equipment is a major source of equipment corrosion and
increases solvent losses. The amount of water entering
a degreaser should be controlled to a minimum.
Basket or Carrier Design - Parts carriers should be free
draining and of minimum weight. Preferred basket design
employs expanded metal or heavy wire screen.
Conveyor Speed - The maximum vertical conveyor or over-
head hoist speed is 11 or 12 feet per minute.
Cloth Cleaning - A vapor degreaser will not safely clean
garments, gloves, shop rags, etc. There is no means of
removing the solvent from the cloth, and large solvent
losses are experienced.
4.2 Emission Control Performance
In addition to the literature review, various representatives
of firms and agencies connected with solvent metal cleaning
-------
Page 4-38
were contacted to determine where emission controls should
be evaluated. These contacts are summarized in Table 4-3.
The preferred method of selecting specific test locations
was on recommendation from the emission control equipment
manufacturers. This method was preferred because the equip-
ment manufacturers have the widest knowledge of the instal-
lations for each control technology and are motivated to
supply test sites which represent the best efficiency.
Suggested test locations were screened on a geographic basis
to limit travel costs and to provide a diversity of solvents
being controlled. Most of the final evaluation sites were
suggested by the equipment manufacturers. No studies were
conducted on petroleum solvent cleaning systems due to the
lack of sites applying emission control technology to these
applications. Where technically feasible, the results
obtained on an emission control technology will be extended
to estimate the probable effectiveness when applied to
petroleum solvents.
-------
Page 4-39
Table 4-3
I. National Technical Organizations
a. Synthetic Organic Chemical Manufacturers Association
b. National Paint and Coatings Association, Inc.
c. American Oil Chemists Society
II. Industry
a. Benjamin Moore and Company
b. Esso Research and Engineering
III. Consulting Firms
a. Noyes Data Corporation
b. Skeist Laboratories, Inc.
c. Charles H. Kline Co., Inc.
d. Pedco-Environmental Specialists, Inc.
e. GCA/Technology Division
IV. State and Local Agencies
a. Rhode Island Division of Air Pollution Control
b. Los Angeles County Air Pollution Control District
c. California Air Resources Board
d. Cleveland Division of Air Pollution Control
e. Ohio Environmental Protection Agency
f. Illinois Environmental Protection Agency
g. Maricopa County Department of Health Services
h. Texas Air Control Board
V. Chlorinated or Fluorinated Solvents Producers
Dow
DuPont
Allied
Stauffer
Hooker
Diamond Shamrock
Ethyl
Vulcan
PPG
VI. Vapor Degreasing Equipment Manufacturers
Baron/Blakeslee
Branson
Detrex
Phillips
-------
Page 4-40
VII. Carbon Adsorption Equipment Manufacturers
Vic Manufacturing
Hoyt Manufacturing
Baron/Blakeslee
Phillips Manufacturing
Artisan Industries
VIII. Solvent Resellers
Western Eaton Solvents and Chemicals
Detrex
Baron/Blakeslee
Phillips
American Mineral Spirits
IX. Refrigeration Conservation Equipment Suppliers
Autosonics
Baron/Blakeslee
Detrex
Phillips
X. Journals
Metal Finishing
Industrial Finishing
Factory Magazine
Air Pollution Control Digest
XI. Room Temperature ("Cold Cleaning") Equipment
Manufacturers'
Kleer-Flo
Graymills
Safety-Kleen
XII. Miscellaneous
Massachusetts Department of Labor
U.S. Department of Commerce
-------
Page 4-41
The efficiencies of emission control by various techniques
are reported in a series of appendices attached. However,
some of the results reported are based on the total solvent
use (including storage, leaks, and clean out residues).
Others express the emission control as a percentage excluding
the miscellaneous sources of solvent loss. The summaries
below will adjust for the differences in methods of collecting
and analyzing data. Each control is examined in terms of
overall efficiency and cost to the user.
4.2.1 Carbon Adsorption
This emission control technique was evaluated at five test
sites. Reports covering the evaluations are presented in
Appendices C-4, C-8, C-9, C-10, and C-ll. Brief summaries
are as follows:
Appendix C-10
The carbon adsorber at this test site (a manufacturer
of carbon adsorption equipment) was a Model 572AD in
support of an open top degreaser operated with tri-
chloroethylene. A reduction in solvent consumption
of approximately 65% was reported by the manufacturing
personnel relative to operations without the adsorber.
Some of the factors responsible for this high degree of
-------
Page 4-42
solvent conservation were: 1) a degreaser that is
operated extremely well, 2) an adsorber that is some-
what oversized based on the amount of solvent vapors
it must adsorb, and 3) no solvent losses due to de-
greaser clean-out during testing.
Appendix C-9
This test involved a Model 536AD adsorber used to
control emissions of trichloroethylene from a cross-
rod degreaser. The use of the adsorber provided a 20%
reduction in solvent emissions during actual testing.
Recovery efficiency was negatively influenced by low
production rates. Records of earlier operations indi-
cated approximately 50% emission control may have been
attained at full production. Recoverable solvent losses
are related to production, whereas non-recoverable loss
often are not, e.g. losses during down time, distillation
losses, etc.
Appendix C-ll
The use of a carbon adsorber to control emissions from
an enclosed cold cleaning system (circuit board cleaner)
was studied. A 60% solvent recovery was experienced
-------
Page 4-43
when the adsorber was operating. The adsorber was
a Model 536AD and the solvent was trichloroethylene.
Appendix C-8
Due to some unique circumstances involving both the
operation of the degreaser and the adsorber, emissions
at this site were actually ^8% higher while the ad-
sorber was in use. Increased ventilation from the
carbon adsorber aggravated solvent losses from this
open top degreaser. An unusually shallow freeboard
contributed to the ineffective recovery of perchloro-
ethylene as well. These circumstances contributed to
more losses through the bed than are typical.
Appendix C-4
The carbon adsorption system at this test site, a
Model 536AD, was used to control emissions of 1,1,1-
trichloroethane from a "Riston" develop system. A
reduction in solvent consumption of 21% was observed.
The recovered solvent was returned to the operation
without restabilization and did not significantly
effect the overall stabilization of the Riston develop
system. The water effluent from the carbon adsorber
decanter contained 2,000 to 14,000 ppm organic material
-------
Page 4-44
entering the drain system. Hastelloy was used for
adsorber shell construction rather than coated mild
steel.
Four of the five carbon adsorption systems studies required
repair or adjustment to function effectively before testing
could be initiated. Successful emission control by carbon
adsorption is highly dependent on user maintenance of the
equipment. With proper maintenance and operation, most
solvent metal cleaning emissions could be controlled by 30-60%
with existing carbon adsorption designs.
Solvent recovered from the adsorbers in all but one test
contained extremely low concentrations of stabilizers or
none at all. This demonstrates, therefore, that recovered
solvent must be restabilized or blended with fresh solvent
before reuse.
When the recovery efficiency is less than 40% or the operation
is not taxing to the solvent stabilizer system, the new sol-
vent added may maintain adequate stabilizer levels. A
stabilizer blend is available for trichloroethylene at $5.83
per gallon. One gallon will reconstitute 12 gallons of
unstabilized trichloroethylene. This cost amounts to $0.449/
gallon. No restabilization cost was used in the economic
relationship developed below. Only one evaluation site
practiced restabilization routinely.
-------
Page 4-45
Cost relationships for several standard double tank carbon
adsorbers are presented in Figure 4-11. The relationships
are expressed as ratios of savings (dollar values of solvent
conserved) to total annual operating costs. The assumptions
used to generate these relationships are as follows:
1. Carbon adsorber pricing was obtained from
Vic Manufacturing on October 4, 1975.
2. Adsorber design information was supplied by
Vic Manufacturing and Hoyt Manufacturing.
3. Equipment calculated at a 15-year depreciation
rate (10% interest rate on investment).
4. Building space calculated at a 25-year depreciation
rate (10% interest rate on investment).
5. Insurance calculated at 2%.
6. Maintenance calculated at 4%.
7. Trichloroethylene pricing was obtained from the
Chemical Marketing Reporter, July 7, 1975.
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Page 4-47
In Figure 4-11, the vertical lines represent the range of
savings to cost ratios for the various carbon adsorber
models using trichloroethylene. A ratio of one indicates
a "break even" situation where the user recovers the exact
annual operating cost of the adsorber. Ratios above one
represent profitable operating conditions, while those below
one represent non-profitable conditions. The bottom points
(lowest savings) on each line were generated by assuming a
constant flow of air to the adsorber (at the rated cfm of
the adsorber) containing 25 ppm of trichloroethylene, a 95%
bed efficiency, and a one shift/day operation. The top
points (highest savings) were generated by assuming a constant
air flow containing 500 ppm of trichloroethylene, a 95% bed
efficiency, and a three shift/day operation. A typical cal-
culation is presented in Figure 4-12. Points were also plot-
ted on each line for the lowest savings and highest savings
obtained by operating two shifts/day. Finally, two additional
lines were generated for the Model 536 adsorber using Stoddard
solvent and Fluorocarbon 113.
Some of the conclusions that can be drawn from Figure 4-11
are:
1. At low concentrations of trichloroethylene, none of
the carbon adsorbers can be operated profitably. A
-------
Page 4-48
Figure 4-12
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR CARBON ADSORPTION
Lowest Savings/Cost Ratio - Model 572AD
Assume: 1) Constant flow of 25 ppm trichloroethylene
in air
2) 95% carbon bed efficiency
3) One shift/day (2000 hrs./yr.)
4) Solvent is trichloroethylene at $2.15/gal.
Savings
25 ppm (at 5500 cfm) = 2.76 lbs./nr.*
2.76 Ibs./hr. x 2000 hrs./yr. x 0.95 = 5244 Ibs./yr.
5244 Ibs./yr. v 12 Ibs./gal. x $2.15/gal. = $940
$940 Savings/Year
Costs/Year
Capital
Equipment $22,085
15% Installation 3,313
$25,398 x 0.13147** = $3339
2
Building Space 111 ft.2
50% Indirect 56 ft.
167 ft.2 x $25.9+/ft.2 x 0.11017++ = 477
Insurance (2%/yr.)
Equipment $25,389 x 0.02 = 508
Building $ 4,325 x 0.02 = 87
Maintenance (4%/yr.)
Equipment $25,389 x 0.04 = 1016
Total Capital Cost/Year = $5427
-------
Page 4-49
Figure 4-12 (Cont.)
Costs/Year (Continued)
Operating (Desorb 25 times/year)
Steam
700 Ibs./nr. x 25 hrs./yr. x 1000 BTU/lbs.
x $2.3/106 BTU = $ 40
Electric
20 Hp x 0.746 KWH/Hp x 2000 hrs./yr.
x $0.025/KWH = $ 746
Water
21 gpm x 25 hrs./yr. x 60 min./hr.
x $0.04/103 gal. = $ 1
Total Operating Cost/Year = $ 789
Total Capital Cost/Year = §5427
Total Cost/Year = $6214
Savings/Cost Ratio = |g2i4 = 0.15 (Lowest)
* 25 ppm x 5500 ft. /min. x 60 mins./hr. x 5.35 mg/m x
0.02832 M3/ft.3 x 0.001 mgs./gm. >: 0.00220 gms./lbs.
** 0.13147 is the factor for returning principle and 10%
interest over a 15 year life
+ Cost derived from "Modern Cost-Engineering Techniques"
pg. 103 by H. Popper
++ 0.11017 is the factor for returning principle and 10%
interest over a 25 year life
-------
Page 4-50
Figure 4-12 (Cont.)
Best Savings/Cost Ratio - Model 572AD
Assume: 1) Constant flow of 500 ppm trichloroethylene in air
2) 95% Carbon bed efficiency
3) Thru shifts/day (6000 hrs./yr.)
4) Solvent is trichloroethylene at $2.15/gal.
Savings
500 ppm (at 5500 cfm) = 55.1 Ibs./hr.
55.1 Ibs./hr. x 6000 hrs./yr. x 0.95 = 314,070 Ibs./yr.
314,070 Ibs. T 12 Ibs./gal. x $2.15/gal. = $56,271/yr.
$56,271 Savings/Year
Costs/Year
Capital (same as in lowest calculation) = $5427
Operating (Desorb 30 times/week)
Steam
700 Ibs./hr. x 1500 hrs./yr. x 1000 BTU/lbs.
x $2.3/106 BTU = $2415
Electric
20 Hp x 0.746 KWH/Hp x 6000 hrs./yr.
x $0.025/KWH = $2238
Water
21 gpm x 1500 hrs./yr. x 60 mins./hr.
x $0.04/103 gal. = $ 76
Total Costs/Year = $10,156
Savings/Cost Ratio = ??Sf??7 = 5*54 (Best)
— ~" -- m y X U / J_ D O
-------
Page 4-51
constant flow of approximately 200 ppm is
required just to break even for all the models.
The vapor concentration must be determined on
an individual basis, considering alternate
technology. Operating a greater number of shifts
per day does not significantly increase the sav-
ings to cost ratio at low concentrations.
2. At high concentrations of trichloroethylene, all
of the adsorbers can be operated at a profit.
3. The price of a solvent has bhe greatest influence
in determining whether a given adsorber can be
operated profitably. This is demonstrated by the
lines shown for the Model 536 adsorber. In the
case of the least expensive solvent (Stoddard),
the adsorber can not be operated profitably under
any conditions, while adsorbers using the most
expensive common solvent (Fluorocarbon 113) can
be operated profitably under almost all conditions
Figure 4-13 shows the areas of maximum solvent recovery
capacity for each carbon adsorber model discussed earlier.
This capacity is attained when one bed is adsorbing for one
hour at the same time the other bed is desorbing. The
-------
Page 4-52
Figure 4-13
MAXIMUM OPERATING CAPACITIES FOR VARIOUS CARBON ADSORBERS
6000
5500
5000
4500
4000
3500
CFM 3000
2500
2000
1500
1000
500-
.5 1 1.52 2.53 3.54 4.5 5 5.56 6.5 7 7.5 8 8.5 9 9.510
Inlect Concentrations of Trichloroethylene (approximately 103)
-------
Page 4-53
horizontal cfm lines were generated by the ventilation
rate taken from Table 4-4 for each model adsorber. The
curved portion of each line represents the maximum amount
of solvent that one bed will hold for the specified model.
These data were also taken from Table 4-4. If the ratio of
adsorption to desorption time is varied from that used in
Figure 4-13, other areas of less capacities will be defined.
The importance of Figure 4-13, however, is to demonstrate
that for a given inlet concentration and fan velocity, a
specific model carbon adsorber can be identified based on
adsorption capacity. Once this has been accomplished, the
profitability of the model forecasted can be determined from
Figure 4-11.
In other 'applications, the controlling design requirement is
the need for specific ventilation rates. These situations
call for selecting the model with a minimum design ventilation
with both beds adsorbing. These data are available from
Table 4-4. Since increasingly stringent worker exposure
regulations might require greater ventilation rates than today,
larger capacity equipment should be considered.
As mentioned previously, the price of a solvent determines
whether or not an adsorber can be operated profitably. An
even more important factor in emission control, however, is
-------
Table 4-4
CARBON ADSORBER PRICING* AND DESIGN INFORMATION
CFM
in
1
£
(0
04
Model
534 AD**
536 AD
554 AD
572 AD
584 AD
596 AD
Maximum
Both Tanks
Adsorbing
1,200
1,300
3,000
5,500
7,500
10,000
Minimum
One Tank
Desorbing
700
800
1700
3000
3800
5000
Motor
Horsepower
1.5
3
15
20
30
50
Pr ice
$5,845
$9,320
$13,990
$22,085
$35,550
$46,445
Building
Space
30.6 ft
36.4
68.5
111
145
212
Working Bed
Capacity
(Trichloro-
ethylene)
23 Ibs,
56
150
225
450
675
*Pricing from Vic Manufacturing Company (8-15-75 Price List).
Minnesota and do not include shipping and installation.
Prices are F.O.B. Minneapolis,
**Automatic Double (Two Tanks).
-------
Page 4-55
whether or not an adsorber can be operated efficiently
with respect to the entire solvent cleaning system.
A figure of 0.5 Ib./ft. - hr. has been used industry-wide
to estimate the solvent consumed in open top degreasers for
2
many years. Further, 50 cfm per ft. of open top vapor
degreaser area is the design criterion for ventilation with
carbon adsorption. To assure that most users could attain
the forecasted results, a slightly conservative estimate of
40% overall emission control was employed with the earlier
estimates to develop Figure 4-14. This figure shows the
ranges of savings:cost ratios for three sizes of equipment.
As in the earlier calculation, the upper end of the range is
based on three shifts per day while the lower is one shift.
The open top degreaser area for the best condition is the
maximum based on the design ventilation of the carbon adsorber.
Conversely, the least condition is based on the open top de-
greaser area with the ventilation rate of the next smaller
carbon adsorber. Figure 4-15 outlines the typical calculations
used to obtain Figure 4-14.
Test results and industry experience demonstrate that carbon
beds will normally adsorb ^95% of the solvent vapors that pass
through them. The percentage reduction of solvent emissions
for metal cleaning systems using the adsorbers, however, is
usually much lower. Accounting for solvent which cannot be
-------
Paqe 4-56
Figure 4-14 1_. 1'
CARBON ADSORPTION vs DEGREASER SIZE
rn-
•H4-)
Savings: Cost Ratio _
10° '
itrrrr
Break-Even Line J-
536AD
: 572AD r"
10
— 554AD
H--
-------
Page 4-57
Figure 4-15
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR CARBON ADSORPTION
Lowest Savings/Cost Ratio for Model 572AD
As stone; 1) Degreaser loss rate of 0.5 lbs./ft.2 - hr.
2) An efficiency of 40% recovery
3) A minimum ventilation rate of 50 cfm per ft.
of open top area
4) One shift per day (2000 hrs./yr.)
5) Degreaser size derived from the ventilation
rate of next lower adsorber model (554AD)
(3000 cfm •=• 50 cfm/ft. = 60 ft.2 degreaser)
Solvent Savings
0.50 lbs./ft.2 - hr. x 60 ft.2 x 2000 hrs./yr.
x 0.40 = 24,000 Ibs./yr,
24,000 Ibs./yr. T 12 Ibs./gal. x $2.15/gal. = $4300/yr.
Savings — $4300/Yr.
Costs/Year
Capital (same as previous Typical Calculation) - $5427
Operating (Desorb 150 times/yr.)
Steam
700 Ibs./hr. x 150 hrs./yr x 1000 BTU/lbs.
x $2.3/106 BTU = $ 242
Electric
20 Hp x 0.746 KWH/Hp x 2000 hrs./yr.
x $0.025/KWH = $ 746
Water
21 gpm x 60 min./hr. x 150 hrs./yr.
x $0.04/103 gals. = $ 8
Total Cost/Year = $6423
Savings/Cost Ratio = = 0.66
-------
Page 4-58
Figure 4-15 (Cont.)
Best Savings/Cost Ratio for Model 572AD
Assume; 1) Degreaser loss rate of 0.50 Ibs./hr.
2) An efficiency of 40% recovery 2
3) A minimum ventilation rate of 50 cfm/ft.
of open top area
4) Three shifts per day (6000 hrs./yr.)
5) Degreaser size derived from maximum ventilation
rate (5500 cfm * 50 cfm/ft.2 = 100 ft.2
Savings
0.50 lbs./ft.2 - hr. x 6000 hrs./yr. x 110 ft.2
x 0.40 = 132,000 Ibs,
132,000 lbs./yr. * 12 Ibs./gal. x $2.15/gal. = $23,650
Savings/Year — $23,650
Costs/Year
Capital $5427
Operating (Desorb 1000 times/yr.)
Steam
700 lbs./hr. x 1000 hrs./yr. x 1000 BTU/lbs.
x $2.3/106 BTU = $1610
Electric
20 Hp x 0.746 KWH/Hp x 6000 hrs./yr.
x $0.025/KWH = $2238
Water
21 gpm x 60 min./hr. x 1000 hrs./yr.
x $0.04/10 gal. = $ 50
Total Cost/Year = $9325
Savings/Cost Ratio = !2Qf^° = 2.54
-------
Page 4-59
reclaimed by the adsorber (that lost by drag-out on parts,
leaks, and spills and disposal of degreaser sludges and
still residues), adsorbers were found to reduce overall
system emissions from 20%-65%.
The difference between this range and the 95% bed efficiencies
can be attributed to the ability of a given cleaning system
and its ventilation apparatus to "capture" the solvent vapors
and deliver them to the adsorption beds. The percent capture
of solvent vapors by the vent system is the critical parameter
controlling the overall system efficiency. Improved venti-
lation design for new systems might significantly increase the
carbon adsorber's overall emission control efficiency. Higher
ventilation rates alone would not be expected to provide this
advantage and would require larger capacity adsorption equip-
ment.
4.2.2 Refrigerated Freeboard Chiller
Testing of this emission control technology was conducted at
three locations. Complete records on each evaluation are
summarized in Appendices C-3, C-5, and C-7. The results are
briefly reviewed below.
-------
Page 4-60
Appendix C-5
A 16% reduction in solvent consumption was experienced
in an open top degreaser operating with 1,1,1-trichloro-
ethane. This evaluation provided abnormally low solvent
conservation due to the unusually consistent use of a
degreaser cover. The installation of the freeboard
chiller at this location was completed in 1968. Thus,
the results may not reflect the efficiency possible with
current design parameters.
Appendix C-3
Two refrigerated freeboard chillers were studied at this
location. Both were installed recently on open top de-
greasers operating with methylene chloride. The solvent
consumption was reduced 40% and 43%, respectively, through
the use of the refrigerated freeboard chillers when com-
pared to the solvent consumption experienced in the same
degreasers without the use of the freeboard chillers.
Appendix C-7
A refrigerated freeboard chiller was found to conserve
50-60% of the solvent consumed in the operation without
the control. The operation being controlled was a
-------
Page 4-61
perchloroethylene "U"-Bend Monorail degreaser. The
control efficiency determined at this location in-
cluded solvent losses from distillation, leakage, and
filter changes. Both of the other studies excluded
losses from these sources. Use of the degreaser
exhaust system was required when the chiller was off.
The exhaust was not needed with the chiller. Thus,
the variation in exhaust use favored high control
efficiency results.
Solvent losses due to distillation residues, storage, and
transfer would diminish the overall efficiency reported by
the first two evaluations. Allowing for this effect and
some reasonable variation in the effectiveness that could be
obtained throughout the total population, a 40% overall
efficiency was used to forecast the savings:cost relation-
ship of this equipment. Other assumptions used to develop
this forecast include:
1. A solvent loss rate of 0.50 pounds per square
foot hour.
2. Refrigeration freeboard chiller pricing per
Autosonics Inc. on November 3, 1975. See
Figure 4-16.
-------
Page 4-62
Figure 4-16
REFRIGERATED FREEBOARD CHILLER PRICING*
Degreaser Size Refrigeration
(Peripheral Feet)
less 10
10 - 16
16 - 21
21 - 35
35 - 47
47 - 70
70 -110
* Including Installation
3. Design parameters supplied by Autosonics Inc.,
Figures 4-17 and 4-18.
4. A 15-year equipment life.
5. A 10% time value of money.
Most refrigerated freeboard chillers have been added to
existing vapor degreasers. The pricing used for the savings:
cost ratios is based on this kind of installation.
Horsepower
1/2
3/4
1
1 1/2
2
3
5
Price
$2,635
2,725
3,845
5,035
5,855
6,580
9,200
-------
Figure 4-17
HORSE-POWER REFRIGERATION NEEDED VERSUS DEGREASER SIZE
20'
Width
10'
'/2hp
0
10'
20' 30'
Length
(a
*>•
I
-------
Page 4-64
Figure 4-18
REFRIGERATION COIL DESIGN AND PRICING
Number of Coils
Peripheral Footage Price
Degreaser
Width (feet)
^VJ
10
lo
ID
14
12
m
2
10 Coils
9
8
7
6
5
4
3
2
$104
95
86
77
68
59
50
41
32
Degreaser Length
-------
Page 4-65
If this equipment were installed as a part of the original
vapor degreaser construction, the cost could be reduced to
about two-thirds of the present retro-fit pricing. Current
pricing includes installations costs.
The economic relationships of this equipment are summarized
in Figure 4-19 for trichloroethylene and Figure 4-20 for
trichlorotrifluoroethane (FC-113). The ranges of savings:
cost ratios are developed by assuming conditions of operation
and design which represent the "best" and "least" situations.
The "least" situation is defined by: 1) a relatively narrow
degreaser, 2) one shift per day (2,000 hr./yr.), and 3) the
lowest peripheral footage of coil suggested for a given com-
pressor size. The "best" situation is described by: 1) a
relatively square degreaser, 2) three-shift operation
(6,000 hr./yr.), and 3) the maximum footage for a refrigera-
tion horsepower size. A typical calculation is shown in
Figure 4-21. A savings:cost ratio of one indicates an
installation which neither costs nor saves the user.
Similar sets of ranges could be calculated for 1,1,1-trichloro-
ethane, perchloroethylene, and methylene chloride. However,
when the solvent loss rate is assumed to be the sarae in all
cases, the variation in the savings to cost ratios vary only
slightly with the densities of the solvents per gallon and
-------
Page 4-66
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Page 4-67
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-------
Page 4-68
Figure 4-21
TYPICAL CALCULATION OF SAVINGS/COST RATIO
FOR REFRIGERATED FREEBOARD CHILLERS
Lowest Savings:Cost Ratio
Assume: 1) Degreaser size — 2' x 6'
2) 1 Shift/day operation (2000 hrs./yr.)
3) Trichloroethylene is used at $2.15/gal.
4) Horsepower compressor 2
5) Degreaser loss rate of 0.50 Ibs./ft. - hr.
Solvent Savings/Year
°-5° lb« x 2' x 6' x 200° hr- x 0.40 control eff. = "00
Ft.2 - Hr. Yr. ias./yr,
4,800 Ibs. T 12 Ibs./gal/ x $2.15/gal. = 860
Costs/Year
Capital
Compressor — $3,845
Coils (161 x $32/ft.) 512
Total $4,357
Cost of capital @ 10% factor 0.13147
$4,357 x 0.13147 = $573
Operating
. „ 0.746 Kwh 0 _,n . $0.025 1C_
1 Hp x g-; x 8,760 hrs. x ,— = 163
Maintenance and Insurance (6% of capital)
$4,357 x 0.06 = 261
Total Costs/Yr. $997
$ 8 60
Savings/Cost Ratio = ^^- = 0.86
r
-------
Page 4-69
Figure 4-21 (Cont.)
Best Savings/Cost Ratio
Assume: 1) Degreaser Size (51 x 5')
2) 3 Shifts/day (6000 hrs./yr.)
3) Trichloroethylene is used at $2.15/gal.
4) 1 horsepower compressor
5) Degreaser loss rate of 0.50 lbs./ft. - hr.
Solvent Savings/Year
0.50 lbs./ft.2 - hr. x 5' x 5' x 6000 hr./yr.
x 0.40 = 30,000 Ibs./yr,
30,000 Ibs./yr. -=• 12 Ibs./gal. x $2.15/gal. = $5375
Costs/Year
Capital
Compressor -- $3845
Coil (201 x $41/ft.) — 820
$4665
Cost of capital @ 10% factor 0.13147
$4665 x 0.13147 = $613
Operating
1 Hp x 0.746 KWH/Hp x 8760 hrs./yr.
x $0.025/KWH = $163
Maintenance and Insurance (6% of Capital)
$4665 x 0.06 = $280
Total Costs/Year $1056
$5 375
Savings/Cost Ratio = 1,^' = 5.09
-------
Page 4-70
their cost per gallon. Thus, the savings to cost ratios
for 1,1,1-trichloroethane would be 7-1/2% higher than tri-
chloroethylene in each case, whereas perchloroethylene and
methylene chloride with be 11% and 8% less, respectively.
These variations are illustrated in Figure 4-22. This
figure also demonstrates the effect of a lower (30%) emission
control efficiency.
All of the vapor degreasing solvents do not experience the
same loss rates in pounds per square-foot hour as suggested
above, according to industry authorities. However, there is
debate among industry sources on which solvents consume more
or less and by what magnitude. The operating conditions of
a vapor degreasing evaluation comparing the various solvents
can influence the relative solvent consumption rates. Due
to the controversy and the varying conditions which occur in
actual industrial operations, variations in solvent consumption
rates are deliberately excluded from the above calculations.
From the figures, several conclusions can be drawn relating to
the use of refrigerated freeboard chillers to control solvent
emissions from vapor degreasing.
1. Considering only mathematical calculations as per
Figure 4-21, larger and more square vapor degreasers
-------
Page 4-71
J
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IFRIGERATED FREEBOARD CHILL
(1 HORSEPOWER COMPRESSOR)
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Page 4-72
can be expected to operate at a more favorable
savings to cost ratio than small and narrow
equipment.
2. The use of a refrigerated freeboard chiller is
more profitable to the user when installed on
equipment using more costly vapor degreasing
solvents.
3. Refrigerated freeboard chillers on vapor de-
greasers operated two or more shifts per day
are likely to be profit generating to their
users with the exception of the smallest
degreasers (having less than 10 peripheral feet).
4. Existing technology does not suggest that more
expensive refrigeration designs would improve
the efficiency of emission control, such as more
coils or lower refrigeration temperatures.
Although some stabilizer depletion can be expected from the
introduction of water by the refrigerated freeboard chiller,
the stabilizer reductions experienced in the evaluation sites
were not abnormal for ordinary vapor degreasing operations.
Some loss of the water soluble co-solvents of the Fluorocarbon
113 azeotropes with acetone or ethanol can be expected due to
-------
Page 4-73
water extraction. Also, some added corrosion can be
expected as the result of water entering vapor degreasing
operations from frost on the refrigerated coils. No cost
assessment was made for this corrosive effect. No new
water or air pollution is observed from this emission
control system.
Emission control evaluations were not made on the application
of this technology to room temperature cleaning operations.
The use of refrigerated air above a cold cleaning tank could
be expected to reduce the evaporative losses but would not be
expected to recover the solvent escaping the system as drag-
out on the parts cleaned. Nor would it reduce the solvent
emissions which result from the disposal of waste solvent
from these systems. Due to the intermittent use of most cold
cleaning operations, the use of a cover could be expected to
provide a more efficient means of controlling evaporative
losses. Distillation equipment is readily available to re-
cover solvent from the waste solvent of cold cleaning operations
4.2.3 Equipment Design
There are some equipment design variables which strongly
influence emissions from solvent metal cleaning. The air
pollution control benefits of 1) increased freeboard,
-------
Page 4-74
2) automatic covers, 3) conveyorized equipment, and
4) stills are explored as a single category in this section.
4.2.3.1 Increased Freeboard
/
Appendix C-12 describes laboratory testing to determine the
emission control possible from increasing the freeboard-to-
degreaser width ratio. The heated degreaser solvent loss
rate, without parts being cleaned, was reduced between 27
and 55 percent by increased freeboard height. Because
laboratory results may not be fully attained in industrial
operations, a conservative estimate of 'emission control of
30% is used below.
In developing the economic relationship of increased free-
board height, only the cost of the additional sheet metal
and welding at the time of original manufacture is included.
It should be noted that increased freeboard heights on vapor
degreasers or cold cleaning tanks can result in additional
installation costs. These costs are associated with increas-
ing the ceiling height in the vicinity of the operation,
increasing the pit depth or creating a pit where one would
not be needed with a shallower freaboard. In addition, the
work platform height would need to be increased incrementally
for some metal cleaning operations. These costs are associated
with the specific plant facility. Thus, generalized cost
-------
Page 4-75
estimates cannot be made. The incremental cost of increased
freeboard height is calculated based on the additional square
feet of metal needed at $10.00 per square foot of 12 gauge
stainless steel. This latter estimate was provided by Detrex
Chemical Industries, Inc.
The Occupational Safety and Health Act requires a vapor de-
greaser freeboard height of one-half the width of the tank
or a maximum of 36 inches. To calculate the savings:cost
ratio for additional freeboard height this standard was in-
creased. A freeboard height equal to the width of the
degreaser was used for degreasers up to four feet in width.
For degreasers larger than four feet wide, the freeboard was
calculated at 0.8 times the width of the degreaser or a
maximum of 48 inches. The savings-to-cost ratios were based
on trichloroethylene and its price. As in the case described
under freeboard chillers, the savings-to-cost ratios would
vary with the price and density of each solvent. Little
change would be expected between the vapor degreasing solvents,
excepting Fluorocarbon 113 and methylene chloride. The free-
board height recommendation for the latter two solvents has
been 0.75 times the width of the degreaser. Thus, the percent
decrease in emission would be much lower than the 30% fore-
casted for the other solvents since degreasers for these two
solvents already have higher freeboards. A typical calculation
for the savings:cost ratio on one degreaser size is included.
-------
Page 4-76
The savingsrcost ratios for different degreaser sizes are
plotted in Figure 4-24. The savings:cost ratio curve is
discontinuous due to the different criteria used for narrow
versus wide degreasers in freeboard height. The low end of ,
savings:cost represents one shift per day while the upper
end is calculated on three shifts per day. Due to the low
cost of adding increased freeboard height when the equipment
is originally constructed, all illustrations of increased
freeboard height result in a profitable return to the equip-
ment user. Although increases in platform construction, pit
depth or ceiling elevation could reduce the savings-to-cost
ratios, most often these added costs would be incremental to
those associated with a degreaser installation employing the
current freeboard standards.
Cold cleaning tanks typically have shallow freeboards. Although
no data were collected on this subject, it can be reasonably
forecasted that higher freeboard tanks would have a positive
effect on controlling evaporative emission from these metal
cleaning operations. This would be particularly true where
the more volatile solvents are employed. More volatile solvents
could be defined as those solvents which evaporate more rapidly
than water on a weight basis. The greatest emission control
advantage would occur with highly volatile solvent such as
methylene chloride or Fluorocarbon 113. Reducing evaporative
losses would not improve emission control unless combined with
-------
Page 4-77
Figure 4-23
TYPICAL CALCULATION FOR SAVINGS:COST RATIO
FOR FREEBOARD HEIGHT
Degreaser Size 4' x 12'
4' - New Freeboard Standard
2' - Normal Freeboard Standard
2' - Increased Freeboard Height
Capital Cost
2' x 32' Peripheral Feet x $10/Ft.2 = $640
Annual Cost
Capital $640 x 0.13147* = $84
Insurance (2%) = $13
Maintenance (None)
Total Cost $97
Estimate of Solvent Use with Normal Freeboard (40 Hrs./Wk.)
0.5 lb./Ft.2 Hr. x 4' x 12' x 2000 Hrs./yr. = 48,000 Lbs./Yr.
Estimate of Solvent Conserved with Increased Freeboard
- 1/3 of Solvent Losses (Drag-out, etc.) Are Not Controlled
- 30% Emission Control
48,000 Lbs./Yr. x 0.6667 x 0.3 = 9600 Lbs./Yr.
Estimated Savings
9600 Lbs./Yr. T 12 Lbs./Gal. x $2.15/Gal. = $1720
Savings;Cost Ratio (One Shift)
$1720/$97 = 17.7
* Factor for 15-Year Life at 10% Value of Money
-------
Page 4-78
Figure 4-24
~T I7TT
INCREASED FREEBOARD
(TRICHLOROETHYLENE)
Savings: Cost Ratio
i
i
103
,_ i , I i
Break-Even Line
10-f—
Open Top Degreaser
A
B
C
D
E
r/3' x 3'
T/2 x 6'
4' x 12'
5' x 24'
5' x 40'
Degreaser Size
-------
Page 4-79
control of the disposal of waste solvent. Cold cleaning
solvents with as little as 5% soil often do not provide
adequate cleaning. Therefore, they are waste material.
This waste solvent is often disposed of in a manner which
results in evaporation to the atmosphere, particularly in
the case of low cost solvents. However, the use of auto-
matic closures to prevent evaporation entirely would be
more effective than increased freeboard height.
4.2.3.2 Automatic Covers
Vapor degreasing and cold cleaning equipment ordinarily
have covers. Usually these covers are manually operated
and cumbersome to use. As a result, covers are usually
not used during operating shifts. In some cases, covers
are not used even on weekends and down shifts. Because
of these use patterns, the opportunity exists to control
unnecessary and nonproductive solvent emissions which
occur when the equipment is not in immediate use. Open
top vapor degreasers and cold cleaning tanks are often
used for actual cleaning only 25% of the work shift time.
Cover designs which would close whenever work was not being
processed would conserve these emissions. Appendices C-2
C-3, C-5, and C-12 provide background on the emission control
which can be achieved by this means.
-------
Page 4-80
Appendix C-2 - This study indicated a 24% emission
control with trichloroethylene and a 27% emission
control with 1,1,1-trichloroethane by use of a
cover. Both studies were done in the same open
top vapor degreaser. The results of this study
are slightly conservative because an automatic
cover was not truly simulated. Rather, the opera-
tors were encouraged to use the cover during
prolonged periods of disuse, including down
shifts and weekends.
Appendix C-3 - Two open top degreasers using methylene
chloride were evaluated in this study. One was equipped
with a cover; the other was not. A comparison of their
solvent emission rates indicated that the covered
degreaser controlled solvent losses by 50% + 5%. This
assumes that the two degreasers would have approximately
equal emissions if both were uncovered.
Appendix C-5 - An open top vapor degreaser operated
with 1,1,1-trichioroethane three shifts per day
experienced 40% lower emission rates with a cover
than without. This study closely approximated
the effectiveness of an automatic cover.
-------
Page 4-81
Appendix C-12 - Laboratory testing of an open top
degreaser identified the solvent loss rate of an
idling degreaser to be between 0.1 and 0.4 pound
per square foot per hour with a current freeboard
height design. An automatic cover could be expected
to control nearly 100% of these losses. This study
also documented a two-fold increase in solvent
emission rates caused by lip exhaust ventilation.
Where lip exhaust ventilation is not required to
assure safe operating conditions for workers, its
use increases emissions to the environment needlessly.
The cost of constructing automatic covers for vapor degreasers
varies dramatically with design, drive mechanism and materials
of construction. Effective covers can be constructed of
canvas, Mylar, reinforced fiberglass, metal sheets or metal
interlocking slats. Rough cost estimates were obtained
from both Detrex Chemical Industries and Kinnear Division
of Harsco Corporation. Based on these estimates the following
cost table was prepared:
Open Top Degreaser Size Cost
2 1/2 Ft. x 6 Ft. $1500
4 Ft. x 12 Ft. $2250
5 Ft. X 40 Ft. $5000
-------
Page 4-82
The cost could be expected to be reduced somewhat if
installed as a part of original equipment manufacture
and might increase to nearly double these prices when
the more costly materials of construction are employed.
Small tanks could employ a foot actuated lever opening
system and gravity or spring loading to automatically
close the equipment. This type of design could be used
on tanks with an open top area up to 2' x 4 ' and would
cost substantially less than the cover estimated for the
2 1/2' x 6' degreaser above. Larger covers are powered
by compressed air or a small electric motor and can be
actuated by a microswitch.
Figure 4-25 charts the savings to cost ratio ranges based
on the automatic cover costs stated earlier. The lower
end of the range expresses the savings-to-cost relationship
when the degreaser is operated on a one-shift basis only.
The upper range is established by estimating the solvent
conserved on a three-shift operation (6,000 hours per year).
A typical savings-to-cost ratio calculation is presented
in Figure 4-26. Again, trichloroethylene was used to establish
a value of the solvent conserved. Higher priced solvents
will yield proportionally higher savings-to-cost ratios.
No direct emission testing was made on automatic covers
for cold cleaning tanks. However, it is easily forecasted
-------
Page 4-83
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Page 4-84
Figure 4-26
TYPICAL CALCULATION OF SAVINGS:COST RATIO
FOR AUTOMATIC COVERS
Degreaser Sixe 4' x 12"
Capital Cost ' $2250
Cost/Yr.
Capital (15 Yrs. @ 10%) $296
Insurance (2%) $ 45
Maintenance (4%) $ 90
Total $431
Estimate of Solvent Use W/0 Automatic Cover
0.5 Lbs./Ft.2 Hrs. x 48 Ft.2 x 2000 Hrs./Yr. = 48,000 Lbs./Yr.
Estimated Solvent Saved with Cover
- 1/3 Solvent Losses Not Subject to Control
- 35% Emission Control
48,000 Lbs./Yr. x 0.6667 x 0.35 = 11,200 Lbs./Yr.
Estimated Savings
11,200 Lbs./Yr. x 1/12 Lbs./Gal. x $2.15/Gal. = $2007
Savings:Cost Ratio (One Shift)
$2007/$431 = 4.66
-------
Page 4-85
that more volatile and more valuable cold cleaning solvents
can benefit most from this simple means of emission control.
The evaporation rates and solvent prices are summarized in
Table 4-5. The need for control of evaporative losses from
cold cleaning tanks employing Stoddard solvent would seem
doubtful were it not for the fact that over a million of these
systems are estimated to exist. Again, the control of evapora-
tive losses from cold cleaning systems may not reduce the
emissions to the atmosphere unless control of waste solvent is
implemented simultaneously.
4.2.3.3 Conveyorized Degreasers
Industry experience has shown that conveyorized vapor degreasers
use less solvent per ton of work processed than open top de-
greasers. This is illustrated again when a comparison is made
between Appendix C-2 and C-9.
In Appendix C-2, an open top degreaser cleaning small parts after
heat treating used 99 pounds of trichloroethylene per tons of
parts. The evaluation was repeated with 1,1,1-trichloroethane
and found to consume 80 pounds per ton. In both cases, the
solvent use rate chosen was with the cover in use for prolonged
periods of degreaser idle time and during down shifts. The sol-
vent consumption rate without the use of the cover was greater
still.
-------
Table 4-5
EVAPORATION RATE AND SOLVENT PRICING
CO
•<*
Solvent
Stoddard
Perchloroethylene
Water
Heptane
Trichloroethylene
Methanol
1,1,1-trichloroethane
Acetone
Methylene Chloride
Fluorocarbon 113
Relative
Evaporation Rate'
Estimated 2
Evaporation Rate (Lbs./Ft. )
0.09
0.25
0.25
0.40
0.63
0.65
1.00
1.40
3.50
3.85
0.010
0.029
0.029
0.047
0.073
0.076
0.12
0.16
0.41
0.45
Price Gallon
0.48"
2.16'
0.70
2.15'
0.55
2.12'
0.92
1.82'
5.99'
The Solvents & Chemicals Companies Price List July 1, 1975
"Chemical Marketing Reporter July 7, 1975
Measured at Room Temperature
-------
Page 4-87
A solvent use rate of 10.1 gallons per day was determined
in Appendix C-9. The work processed rate per day was 3.50
tons. Thus, the solvent use rate per ton was 35.0 pounds.
In the latter case the work was processed in a cross-rod
vapor degreaser with trichloroethylene as the solvent. A
carbon adsorption system was recovering 20% of the total
solvent added to this degreasing operation. Consequently, the
solvent use rate without the carbon adsorption system would
have been approximately 44 pounds per ton. These two studies
were chosen for comparison because of the similarity in parts
being cleaned in terms of size and ease of solvent drainage,
and because they offer the most careful records of the quantity
of work processed. Other cases showing even greater contrast
in solvent consumption could be made but would not be as
valid.
Another comparison between conveyorized and open top vapor de-
greasing is reviewed in Appendix E-4.
The production workload to be cleaned in a given operation may
not justify the use of a conveyorized vapor degreaser. In
other cases, the cost and the material handling required to
transport product to and from a large centralized conveyorized
degreaser would be a severe penalty. Also, many conveyorized
vapor degreasers do not lend themselves to the extreme variations
-------
Page 4-88
of parts being cleaned in a given plant. However, where
practical, this comparison and industry experience indicate
that emission losses to the atmosphere will be less per ton
of work cleaned in conveyorized vapor degreasing equipment
than open top degreasers.
4.2.3.4 Distillation Equipment
The control of solvent emissions from metal cleaning operations
directly to the atmosphere inherently increases the quantity of
dirty solvent to be handled. Therefore, the prevention of
emissions from the disposal of waste solvent becomes more
important as emission control efficiency increases. In the
case of cold cleaning, distillation recovery of solvent repre-
sents the most important means of controlling atmospheric
pollution, particularly with low cost and less volatile sol-
vents. A further advantage of distillation is the effect of
concentrating soils (oils and solid matter). This makes the
disposal of the soils removed much more controllable. Current
methods of solvent waste disposal include: 1) in-house distil-
lation, 2) use of a contract distillation service, 3) use of a
contract incineration service, 4) land fill disposal, 5) dust
control on roads and coal piles, and 6) disposal in sewage
systems.
-------
Page 4-89
In vapor degreasing, the use of stills is fairly common. For
instance, nearly all conveyorized vapor degreasers and large
open top degreasers are equipped with stills. These stills
have been customary because they reduce the maintenance cost
of cleaning out the vapor degreasing system, enable the system
to remove soils collected without interrupting the cleaning
process and recover valuable quantities of solvent. Again,
users employing multiple open top degreasers often use a still
to recover solvent from all of them. The use of distillation
is based solely on the recovered value of the solvent at these
locations. Another large group of vapor degreasing operations
use a contract reclaiming service. Contract distillation ser-
vices commonly charge about one-half the market value of the
solvent distilled based on the number of gallons returned to
their customers. Often the service charge is increased if the
percent solvent in the solvent waste is low. Except in terms
of extreme market short supply conditions the price of reclaimed
solvent is always substantially below the cost of the new sol-
vent. Thus, the user of this service is always at an economic
advantage if the recovered product is returned in a quality
permitting reuse in his operation.
The economics of distilling vapor degreasing solvent in-house
are determined by the quantity of solvent which can be recovered.
Baron-Blakeslee and Detrex Chemical Industries report the avail-
ability of such stills in the price range between $2500 and $3500
-------
Page 4-90
These stills are constructed of stainless steel and are
capable of distilling 60 gallons per hour. Using a $3000
price and a 15% of capital as the installation cost, the
total capital investment would be approximately $3450. A
direct floor space of approximately 3' x 4' is estimated.
This combined with a 50% indirect floor space of six square
feet provides a total plant area of 18 square feet. At a
cost of $25.9 per square foot, this amounts to $466.00 of
building capital. A 15-year life is estimated for the equip-
ment and a 25-year life is used for the building. In both
cases, a 10% time value of money is used to estimate the
annualized capital costs.
Annual Cost of Distillation Equipment
(60 gph Still)
Equipment ($3450 x 0.13147) $454
Building Capital ($466 x 0.11017) $ 51
Insurance (2%) $ 60
Maintenance (4%) $120
TOTAL $685
The operating cost per gallon of recovered solvent should
be less than $0.20. If the value of the solvent (trichloro-
ethylene) is $2.15 per gallon, the recovered value after
operating costs equals $1.95 per gallon. Therefore, the
-------
Page 4-91
total cost of this installation can be recovered from the
first 351 gallons distilled per year. This quantity of
solvent could be reclaimed in a single shift if sufficient
dirty solvent is available.
Without the use of a still, waste solvent from vapor degreas-
ing may contain as little as 10% oil or up to approximately
30% oil. With distillation, the solvent content of this
material can be reduced to 20% by weight (12-15% by volume)
in most operations. This distillation would recover over 90%
of the solvent contained in the waste. Although waste solvent
may account for as much as 30% of the total solvent used in
vapor degreasing, it ordinarily would be responsible for about
one-half of that.
Cold cleaning or room temperature solvent cleaning operations
are seldom equipped with distillation equipment. The exceptions
to this involve conveyorized cold cleaning operations with
chlorinated or fluorinated solvents and very large corporations
using a great many cold cleaning tanks with flammable solvents.
The distillation of chlorinated or fluorinated solvents used in
cold cleaning is no different than described above for vapor
degreasing. In contrast, distillation equipment for flammable
solvents is more expensive. This combined with the lower
recovered value from most flammable solvents would increase
-------
Page 4-92
the quantity of solvent recovered some 6-12 times to recover
the annual operating cost of the equipment. Where the soils
removed in parts cleaning do not contain sulphur or chlorine-
containing oils, simple filtration would prepare these wastes
for a use in oil furnaces for their fuel value. The fuel
value will be considerably less than the solvent value, but
the capital investment should be considerably less.
Another alternative is offered by the Safety Kleen Corporation,
(see Appendix E-l). This firm provides a service of supplying
both the solvent and cold cleaning equipment to users. The
solvent used is periodically collected and replaced with fresh
solvent by Safety Kleen and the used solvent is collected and
distilled in central locations.
Proportionally, the share of solvent used in cold cleaning
which becomes waste solvent is much higher than that experi-
enced in vapor degreasing. Obviously, the more volatile sol-
vents experience more evaporative losses and proportionally
less of the total solvent used becomes waste solvent than the
less volatile materials. In either case, the control of
emissions from the disposal of waste solvent is more critical
in cold cleaning than vapor degreasing and will become more
important as operating losses are diminished by emission
control methods.
-------
Page 4-93
4.3 Alkaline Washing
A single evaluation was made of alkaline washing as an alter-
nate method of metal cleaning which would not result in emissions
of hydrocarbons to the atmosphere. This evaluation is summarized
in Appendix C-l. No single evaluation can identify the relation-
ship between alkaline washing and vapor degreasing or cold
cleaning. Even with the literature references, the wide
range of process equipment for both cleaning systems is barely
examined. The literature and the evaluation summarized in
Appendix C-l do permit two generalizations. First, alkaline
washing requires 2-3 times the energy of vapor degreasing
to clean a comparable workload. Since the energy requirements
for cold cleaning are less than those of vapor degreasing, the
energy requirement for alkaline washing compared to cold cleaning
would show an even greater disparity in favor of cold cleaning.
Second, the cost comparison of cleaning by either process is
essentially equal where the cleaning operation can be performed
by either process, However, if poor cleaning were to result
due to the choice of the wrong process, the cost associated
with reprocessing unsatisfactorily cleaned parts again would
rapidly favor the cleaning process which can provide the more
acceptable cleaning quality.
The soils removed by alkaline washing become greatly diluted
as a water emulsion, and the potential for water pollution is
-------
Page 4-94
created. Large firms very often have their own water treatment
facility whereas small firms would tend to discharge this
effluent to the municipal sewer system. In contrast, solvent
metal cleaning provides the opportunity for concentrating the
soils for disposal or reprocessing. Some firms already use
distillation residues as metal cutting lubricants.
In the great majority of instances, industy authorities report
that these different cleaning processes are not interchangeable
and that the penalties paid for employing one in the place of
the other are much greater than the comparative cost studies
indicate in the literature. This is largely true because of the
deliberate selection of test cleaning operations which can be
performed nearly equally by either process.
4.4 Comparison of Emission Controls
Figure 4-27 is constructed using relatively favorable conditions
for the three available means of controlling solvent emissions
from metal cleaning operations. Trichloroethylene pricing was
used throughout the estimations to derive this figure. An open
top vapor degreaser with an open top surface area of 4* x 6.5'
was used in each case. This size degreaser was chosen because
it is the maximum size for a model 356AD carbon adsorber and
the maximum size in peripheral footage for a 1 hp compressor
-------
Page 4-95
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Page 4-96
refrigerated freeboard chiller. Although this size open
top degreaser is not typical in dimensions, it is reason-
ably representative from an open top square foot area and
represents favorable conditions for both the carbon ad-
sorption and refrigerated freeboard chiller design factors.
A uniform solvent loss rate of 0.5 pounds per square foot-
hour was taken as the solvent emission rate prior to the
installation of the emission control means in each case.
As in prior calculations, a 15-year equipment life, a
25-year building life and a 10% value of money were estimated.
A 40% overall emission control efficiency was taken for carbon
adsorption. No cost was assigned to restabilizing solvent
recovered. Also, the degreaser size was deliberately chosen
to make use of the maximum ventilation provided by a Model 536AD.
With the refrigerated freeboard chiller, the degreaser open
top size was chosen to utilize the maximum peripheral footage
for a 1 hp compresEor system. An overall emission control
efficiency for the refrigerated freeboard chiller was taken
to be 40%.
The equipment design calculations are based on the combined
effect of increased freeboard and an automatic cover. In
Case "A" no cost is assigned for the construction of a pit
-------
Page 4-97
for the degreaser or increased cost for a higher work plat-
form. In Case "B" a $5,000 cost estimate was chosen for the
construction of a shallow pit to cover those cases where the
increased freeboard would interfere with the work processing.
The pit construction capital was treated as a building invest-
ment and assigned a 25 year life. In addition, the combined
effectiveness of the increased freeboard and automatic cover
was estimated to reduce solvent emissions by 40%.
Figure 4-27 illustrates the saving:cost ratios for each emission
control method on a one-shift, two-shift and three-shift basis.
In each instance, it was assumed that good distillation practices
were employed and solvent losses in still residues were held
to a minimum. Although the conditions chosen were favorable
to each of the control techniques, this figure demonstrates
again that emission control techniques can be employed without
a profit penalty to the user. Today's technology will permit
emission control from solvent metal cleaning operations up
to a level of about 35% or a maximum of 40% with little or
no operating cost penalty. Under particularly ideal conditions,
an emission control efficiency of about 60% is possible. No
known technology is available to control solvent emissions from
solvent metal cleaning operations by 85% or greater with the
exception of solvent substitution or total process change.
-------
Page 4-98
References
Emission Control Techiques General
1. North Atlantic Treaty Organization on the Challenges of
Modern Society, Expert Panel for Air Pollution Control
Technology; Air Pollution. Control Techniques for
Hydrocarbon and Organic Solvent Emissions from Stationary
Sources, October, 1973.
2. "Air Pollution Controls in the Small Electroplating Shop,"
Plating, January, 1972.
3. "Vapor Degreasing Can Reduce Pollution, "Canadian Machinery
and Metal Working, November, 1972.
4. Control Techniques for Hydrocarbon and Organic Solvent
Emissions from Stationary Sources - AP-68, March, 1970,
Public Health Service.
5. Effect of Los Angeles County Air Pollution Control District
Rule 66 on Cleaning and Degreasing Operations, Society of
Automotive Engineers 1968.
6. Air Pollution Engineering Manual, Environmental Protection
Agency - AP-40, May, 1973.
-------
Page 4-99
7. Systems and Costs to Control Hydrocarbon Emissions from
Stationary Sources, Environmental Protection Agency - 450,
September, 1974.
8. Control Techniques for Hydrocarbon and Organic Solvent
f
Emissions from Stationary Sources, U. S. Department of
Health, Education, and Welfare - AP68.
9. Air and Gas Clean-Up Equipment, Noyes Data Corporation, 1972.
10. Chilton, Cecil H. and Robert H. Perry, Chemical Engineers
Handbook, McGraw-Hill Book Company, Fifth Edition.
Inc inera tion
11. Kent, R. W., Thermal Versus Catalytic Incineration,
November, 1975.
12. Grouse, L. F. and D. E. Waid, "Efficient Design of After
Burners for Incineration of Many Industrial Fumes," Air
Engineering, August, 1967.
13. Mueller, James, "Understanding Energy," Industrial Finishing,
February and March, 1975.
-------
Page 4-100
14. "Catalytic Fume Abatement for Coil Coaters Uses Less Fuel,"
Products Finishing, November, 1974.
15. Elnicki, W., Thermal Incineration - A Control Mode for One
Aspect of Air Pollution, AER - Worldwide Corporation.
16. "Emerging Technology of Chlorinolysis," Environmental Science
and Technology, January, 1974.
Carbon Adsorption
17. Grandjacques, B., Air Pollution Control and Energy Savings
with Carbon Adsorption Systems, Calgon Corporation, Report
No. APC 12-A.
18. Solvent Recovery with Active Carbon, Sutcliffe Speakman
& Co., Ltd.
19. Larson, D. M., "Control of Organic Solvent Emissions,"
Metal Finishing, Vic Manufacturing Company, December, 1973.
20. Barnebey, H. L. and W. L. Davis, "Costs of Solvent Recovery
Systems," Chemical Engineering, Barnebey-Cheney Co.,
December 29, 1958.
-------
Page 4-101
21. Cannon, T. E., "Air Pollution Control Through Carbon
Adsorption," Plating, April, 1974.
22. Cannon, T. E., "Energy Recovery from Solvent Vapors,"
Pollution Engineering, Vic Manufacturing Co., November, 1974,
23. Solvent Recovery by the Columbia Activated Carbon System,
Union Carbide and Carbon Corp., 1940.
24. Resorb; Regenerated Activated Carbon Adsorption Systems,
Barnebey-Cheney.
25. Ray, A. B., "Recovery of Solvent Vapors," Chemical and
Metallurgical Engineering, May, 1940.
26. Solvent Recovery, Vulcan-Cincinnati, Inc.
27. Pour Your Solvent Expense Back into the Business and Get
Rid of a Hazardous Pollutant, Hoyt Manufacturing Corp.,
May, 1974.
28. Drew, J. W., "Design for Solvent Recovery," Chemical
Engineering Progress, Chem-Pro Equipment Corp.,
February, 1975.
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Page 4-102
29. Manzone, R. R. and D. W. Oakes, "Profitably Recycling
Solvents from Process Sytems," Pollution Engineering/
Hoyt Manufacturing Corp., October, 1973.
30. Lee, D. R., "How to Design Charcoal Adsorption Systems for
Solvent Vapor Recovery," Heating, Piping and Air Conditioning
May, 1970.
31. Cutting Costs; How to Recover Over 50% of Solvent Used,
American Jewelry Manufacturer, July, 1969.
32. Manzone, R. R., "Recycling Solvent from Finishing Process
Airstreams," Knitting Times, Hoyt Manufacturing Corp.
33. "Clean Air Maintenance During Metal Degreasing Operations
with the Application of Chlorinated Solvents," Fachber,
Oberflaechen Tech., June, 1973.
34. Package Sorption Device System Study, EPA Contract
EHSD 71-2, April, 1973.
35. "Environmental Protection and Chlorinated Hydrocarbons,"
Oberflaeche, 1973.
36. "Solvent Vapor Recovery System," Metal Finishing Journal
(London), September, 1972.
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Page 4-103
37. "Recovery of Solvent from Exhaust Air of Degreasing
Installations," Metalloberflaeche, November, 1970.
38. "Ford Plant Filters Noxious Vapors with Activated Carbon
System," Filtration Engineering, December, 1969.
Refrigerated Freeboard Chillers
39. Vapor Degreasing Without Exhaust Ventilation; The
"Cold Trap," Autosonics Inc.
40. Rekstad, G. M., "Upheaval in Vapor Degreasing," Factory,
January, 1974.
41. Vapor Degreasing; Reducing Vapor Degreaser Losses,
Technical Information Bulletin No. 20, E. I. du Pont
de Nemours & Co.
42. Staheli, A. H., "Throwing a Cold Blanket on the Vapor
Degreasing Emissions Problem," Mechanical Engineering,
August, 1973.
43. Detrex Freeboard Chiller, Detrex Chemical Industries, Inc.
-------
Page 4-104
Refrigeration
44. Robinson, Clark S., The Recovery of Vapors with Special
Reference to Volatile Solvents, 1942.
45. Gasoline Vapor Recovery Systems, Ingersoll-Rand,
Southwest Industries Div., 1972.
46. Hydrocarbon Vapor Recovery Unit for Gasoline Bulk Stations,
Edwards Engineering Corp.
Alkaline Washing
47. "Metal Cleaning Costs," American Society of Metals Committee,
Metal Progress, August 15, 1955.
48. Graham, A. K., Electroplating Engineering Handbook,
Van Nostrand Reinhold Co., pg. 127-176.
49. Kearney, T. J. and C. E. Kircher, "How to Get the Most
from Solvent-Vapor Degreasing," Parts I & II, Metal
Progress, April and May, 1960.
50. Metal Cleaning Cost Analysis, E. I. du Pont de Nemours
& Co., Inc.
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Page 4-105
51. "H20f The High-Priced Solvent?," Circuits Manufacturing,
August, 1969.
52. "Metal Cleaning Bends with Social Pressures," Iron Age,
February 17, 1975.
53. Appendices Q, R, S of Third Interim Report, Control of
Organic Solvent Emissions into Atmosphere, Aerospace
Industries Association of America.
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Page 5-1
5. Modifications and Reconstruction
Approximately half of all the solvent metal cleaning
operations perform maintenance cleaning. The extreme
variations in use of this equipment would make establishing
a statistical norm essentially impossible. Thus, it would
not be possible to define any significant variations from
a norm in emission rate which could be used as a guide to
institute new source performance standards.
The emission rates which occur from production oriented
solvent metal cleaning operations are more predictable.
However, a large percentage of the metal cleaning operations
associated with production are located in facilities which
have large numbers of solvent metal cleaning operations.
These operations employ various kinds of solvents, employ
a variety of process equipment, process widely different
kinds of parts, and operate on different work schedules.
Due to the number of operations and their variety, the use
of internal solvent transfer records would add an extremely
burdensome record-keeping task. The use of analytical
means to estimate solvent emission rates where possible is
very expensive and must supplemented by estimates of sol-
vent emissions which escape detection and records of waste
solvent disposal. No analytical means have been demonstrated
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Page 5-2
for directly measuring emission rates from operations with-
out ventilation systems. Consequently, even production
solvent metal cleaning operations do not provide the oppor-
tunity to provide the statistical information needed to
define significantly increased solvent emission rates with-
t
out exorbitant costs.
Repair or replacement of any of the elements of vapor de-
greasing or cold cleaning equipment would not be expected
to cause significant modifications of the solvent emission
rate from a given operation. Examples of repair or replace-
ment would include:
1. Solvent plumbing
2. Condenser water plumbing
3. Replacement of electrical heaters
4. Replacement of conveyor gears, chains, drives
5. Safety thermostats
6. Steam regulators, traps
7. Gas burner repairs
The application of standards of performance for new station-
ary sources can most easily be defined as covering new in-
stallations or replacement of the basic tank system employed
in a solvent metal cleaning operation.
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Page 6-1
6. Dual Emission Control Systems
In Section 4 each of the practical emission control techniques
was discussed in relation to vapor degreasing and cold cleaning
individually. Generally, emission controls used individually
can reduce solvent losses to the atmosphere by approximately
30% to 60%. Although little data was developed on emission
control effectiveness with two or more methods employed, some
forecast can be made in this regard. The quantitative effect
on emission control of employing two methods could be expected
to differ between cold cleaning and vapor degreasing, but the
qualitative action of the emission control methods should be
the same. Consequently, both cold cleaning and vapor degreasing
will be discussed together.
In operations where distillation is not practiced and where
waste solvent is ultimately emitted to the atmosphere, the
use of distillation equipment combined with any other emission
control technique will have an additive effect on total
emission control. On an overall basis nationally, distillation
of cold cleaning waste solvent will provide a greater contri-
bution to emission control than in vapor degreasing. This is
due to the larger quantity and portion of solvent which becomes
waste solvent in cold cleaning and to the much less frequent
practice of distillation in cold cleaning operations.
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Page 6-2
The emission control effectiveness of a refrigerated free-
board chiller combined with an automatic cover was found to
be complementary (only partially additive) on 1,1,1-trichloro-
ethane. See Appendix C-5. With the cover in operation, a
16% emission control effectiveness was found for the refrig-
f
erated freeboard chiller. This result would be expected for
solvents having higher vapor density and low volatility.
In contrast, methylene chloride (with its lighter vapor
density) was evaluated under similar conditions in Appendix C-3,
A 43% emission control was achieved with this less dense and
more volatile solvent. In most cold cleaning and vapor de-
greasing operations, the addition of a refrigerated freeboard
chiller to an automatic cover would not be expected to reduce
emissions by more than approximately 15%. Similarly, the
increased emission control expected for increased freeboard
design when coupled with an automatic cover is only about
5% to 15%.
The effectiveness of an automatic cover, increased freeboard
or a refrigerated freeboard chiller relies on its ability to
isolate the air and solvent within the cleaning operation
from the general operating atmosphere. On the other hand,
the major influence on the overall effectiveness of carbon
adsorption is the ability of the ventilation system to
collect escaping solvent vapors. The ventilation needed
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Page 6-3
to achieve this end partially disturbs the air within the
solvent cleaning operation. Excessive ventilation can
result in increased solvent emissions from the solvent
metal cleaning operation even though the emissions are
captured by the carbon adsorption system. Thus, carbon
adsorption combined with refrigerated freeboard chillers
would not be expected to be complementary. Again, combining
carbon adsorption with automatic covers and/or increased
freeboard designs would be expected to offer marginal
advantages at best.
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Page 7-1
7. Environmental Impact
Solvent emissions from vapor degreasing operations can be
reduced by 40% by selecting the appropriate emission control
method in combination with waste solvent distillation. The
emission control by itself can reduce emissions by 35%.
Distillations of waste solvent can prevent another 5% of
solvent emissions from occurring. The emission control
methods are:
1. Carbon Adsorption
2. Refrigerated Freeboard Chillers
3. Increased Freeboard and Automatic Covering Equipment.
Solvent emission control in the maintenance and service
industries of cold cleaning can effect a 50% emission
reduction due to the less frequent use of these operations.
Most of the emission control can be obtained by control of
waste solvent. Individual operations may attain emission
control efficiencies in the range of 60%. However, these
high emission control operations will be offset by operations
already using emission control devices where further emission
control is not possible and by those operations which experience
difficulty in achieving 40% emission control.
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Page 7-2
Conveyorized degreasers contribute to the overall emission
control potential. As discussed earlier, conveyorized
vapor degreasers can be regarded as an emission control
technology compared to open top degreasers on a work
processed basis. The capital costs associated with con-
veyorized vapor degreasers is much higher than that for
open top degreasers. An additional capital burden of
expensive control systems on conveyorized vapor degreasers
could discourage the conversion of open top degreasing
operations to conveyorized systems and cause more rather
than less solvent emissions to the atmosphere. Alternately,
conveyorized vapor degreasers could be regarded as an
acceptable emission control method when they replace two
or more open top vapor degreasers.
7.1 Air Pollution Impact
The impact of the control of emissions from solvent metal
cleaning is summarized in Table 7-1. This table uses the
format developed in the report, "Impact of New Source
Performance Standards on 1985 National Emissions from
Stationary Sources," by the Research Corporation of New
England, Wethersfield, Connecticut.
-------
Table 7-1
NATIONAL EMISSION ESTIMATES FROM METAL CLEANING
1
IS
D4
CLEANING OPERATION
Cold Cleaning
Maintenance/
Service
Manufacturing
Vapor De greasing
Open Top
Conveyorized
EgK « EnK P0 PC A (1975) B C Tft Tg TN Ts~TN
(Lbs/Yr) N (Lbs/Yr) % S (Thousands of Units)
1,000 50 500 4 2 900 432 197 900 1097 783 314
2,000 40 1,200 4 2 350 168 77 700 854 658 196
510
22,000 40 13,200 5 3 21.9 13.8 7.5 482 647 472 175
40,000 40 24,000 2 1.5 3.76 0.82 0.6 150 174 152 22
197
TOTALS
2232
2772
2065
707
(E K) • emission rate from an average unit with no NSPS
(E^K) = emission rate from an average unit with NSPS - minimum rate
n = control efficiency - maximum level
PB » annual growth rate of units used for replacements
P_ = annual growth rate of units used for new capacity
A = number of units existing in 1975
B = number of new units (since 1975) used for replacements
C - number of new units (since 1975) used for new capacity
T - national emission in 1975
a
T = national emission in 1985 without NSPS
T = national emission in 1985 with NSPS
VTn
reduction in emission rate in 1985 resulting from NSPS
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Page 7-4
The direct air pollution impact has been described above.
No secondary or adverse air pollutants should result from
any of the emission control methods.
7.2- Water Pollution Impact
The only evidence indicating any contribution to water
pollution from the emission control techniques evaluated
for solvent metal cleaning was found in association with
carbon adsorption. The steam used to desorb the solvent
collected on the carbon bed is condensed with the solvent
in the condenser and separated from the solvent by gravity
in the water separator. The steam condensate was found to
contain up to several thousand parts per million of solvent
and/or solvent stabilizers. In current practice, the steam
condensate is immediately diluted with the condenser water.
This dilution is approximately 20/1 reducing the hydrocarbon
levels to 1000 ppm or less in most cases. In most cases,
this stream would be further diluted with other plant waste
water, probably several thousand times. Research by The Dow
Chemical Company has shown that low parts per million con-
centrations of chlorinated solvents are rapidly diffused
from water with mild agitation. Thus, the chlorinated
and fluorinated solvents would not appear to cause any
significant water pollution from this source. Dr. R. E. Bailey
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Page 7-5
of The Dow Chemical Company's Environmental Sciences Research
Laboratories has reviewed the compounds used as stabilizers
for chlorinated solvents. His findings are reviewed in
Tables 7-2, 7-3 and 7-4. Table 7-2 lists those compounds
which are biodegradable and/or show a low level of toxicity
to fish. The second list (Table 7-3) includes compounds
without complete data but could be expected to be biodegrad-
able or volatilized from water systems by information on
analogous compounds. The third group (Table 7-4) lists
potential problem stabilizers. However, the quantities
involved from this source of pollution may not be regarded
as presenting any realistic problem due to rapid dilution
in plant effluent.
If the water pollution effects from this source were regarded
as important, the levels of all of these compounds should
be reduced dramatically by sparging compressed air through
the steam condensate before releasing it to the sewer.
Compressed air is available at nearly all carbon adsorption
locations. The added capital costs for this operation
would be nominal and the air containing the compounds can
be directed back to the carbon adsorption bed for readsorp-
tion and recovery.
-------
Table 7-2
INHIBITORS THAT SHOULD HAVE NO ADVERSE ENVIRONMENTAL IMPACT
nJ
Inhibitor
1,2-Butylene Oxide
1,4-Dioxane
Toluene
Methyl Ethyl Ketone
Isobutanol
Sec-butanol
AeryIonitrile
Epichlorohydrin
Ethyl Acetate
Tetrahydrofuran
Propylene Oxide
Amylene (1-Pentene)
Isopropanol
1,3-Dioxolane
Nitromethane
BOD20
% of Tneory
60
30
60
75
80
85
75
50
80
45
75
5
80
0
30
Fish Tox.
Max. Safe
ppm
>100
>100
>100
>1000
>100
>100
20
15
>100
>100
>100
30
>100
300
1000
Water
Solubility
9.5/100*
00
few ppm
37/100
10/100
12.5/100
6/100
8.5/100
almost «
59/100
few ppm
Volatile from
Water
CO
oo
10/100
*9.5 g dissolves in 100 g water
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Page 7-7
Table 7-3
INHIBITORS WHICH MAY BE SAFE BY ANALOGY
BUT WE HAVE NO REAL DATA
Butylene - very volatile from water
Glycidol - probably rapidly biodegrades
n-Propanol - probably rapidly biodegrades
Cyclohexane - volatile from water
California lists TLM* 15,500 ppm
but it only dissolves to the
extent of a few ppm in water.
Acetonitrile - California data - TLM 1,000 ppm,
max. safe > 100 ppm for fish.
*Threshold Limit Median - a dose or concentration
which kills one-half the population.
Table 7-4
POTENTIAL PROBLEM INHIBITORS
Diisobutylene - BODSQ =0,1 ppm max. safe for fish,
slightly soluble in water..
Triethylamina - BOD-n =0, 30 ppm max. safe for fish,
» sol. H20 > 19°C.
*BOD is the Bio-Chemical Oxygen Demand. A high BOD value
indicates a compound that is easily decomposed by micro-
organisms .
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Page 7-8
7.3 Solid Waste Disposal Impact
No solid waste disposal problems are presented by emission
control systems for solvent metal cleaning. Distillation,
as discussed earlier, makes the controlled disposal of
t
solid and liquid wastes removed from the parts cleaned
more practicable.
7.4 Energy Impact
The various emission control methods do require different
amounts of energy. These energy requirements are discussed
individually below.
Carbon Adsorption - The operating specifications for
carbon adsorption call for the consumption of three
pounds of steam per pound of solvent based on the
solvent capacity of the bed. Since one pound of steam
is approximately equal to 1,000 Btu's, about 3,000 Btu's
are required for each pound of solvent. The steam use
is a function of time rather than the percent saturation
of the carbon bed. Thus, the quantity of steam consumed
per desorption cycle is the same whether or not the
carbon bed is approaching its capacity for solvent.
Consequently, the energy consumed when the bed is
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Page 7-9
desorbed at one-half bed capacity is approximately
6,000 Btu's per pound of solvent recovered. At one-
quarter of the bed capacity the energy used is approxi-
mately 12,000 Btu's per pound of solvent. In addition,
an electric motor of 3-50 horsepower is required to
provide the ventilation needed. For ordinary vapor
degreaser sizes a 3-15 horsepower motor is adequate.
Refrigerated Freeboard Chiller - This system depends
on simple refrigeration. Common degreasers can be
equipped with this emission control system using
compressor motors from 1-3 horsepower (roughly
2500-7500 Btu/hr.).
Distillation - The distillation of metal cleaning
solvents can be achieved with an energy expenditure
of about 150-300 Btu's per pound. A fractional horse-
power motor may be needed to deliver the waste solvent
to the still.
Automatic Cover - Most cover mechanisms can be
powered with fractional horsepower motors up to
one horsepower for larger equipment. Small metal
cleaning operations can be equipped with covers
which close by gravity or by use of a spring and
are opened manually.
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Page 7-10
Increased Freeboard - No increased operating energy
is required by this method of emission control.
Typical open top degreasers use 60 to 240 pounds of steam
per hour. If 160 pounds of steam condensate per hour is
taken and the degreaser is operated one shift per day,
a carbon adsorption recovery system would increase energy
use about 25% for two desorption cycles per day. Similarly,
a refrigerated freeboard chiller would add about 5% to the
total energy consumption of the system. Where distillation
is used continuously, it provides advantages beyond that of
solvent emission control. These advantages include supplying
a constant source of clean solvent for improved cleaning and
reduced maintenance costs. The energy requirement needed
for controlling emissions which could result from solvent
waste disposal would represent only 1-2% of a vapor degreasing
operation. No comparison can be made in the case of cold
cleaning because these operations often require no energy
for the basic operation. Automatic covers and/or increased
freeboard require little or no additional energy than the
basic system.
7.5 Other Environmental Impacts
No other adverse environmental results such as (noise, heat,
radiation) from the use of any of the techniques to control
emissions are expected.
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Page 7-11
7.6 Environmental Impact of Delayed New Source Standards
or No Standards
State and local codes have restricted the quantities of
photochemically reactive solvents which can be emitted
from these sources in areas where controls are needed to
attain the primary air quality standards. Most industrial
areas have these regulations. The response to these regu-
lations has been to use "virtually non-photochemically
reactive" solvents. Even in regions without controls, the
conversion to exempt solvents has been substantial and is
continuing.
Delay of standards development in solvent metal cleaning
would permit the generation of standard support documents
for the coatings and dry cleaning applications. Like sol-
vent metal cleaning, these applications use substantial
quantities of solvents. Examining the solvent using
processes together would provide the maximum opportunity
to develop consistent standards and the exchange of emission
control technology.
The adverse effect of no New Source Standards cr delay in
implementing standards for solvent metal cleaning operations
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Page 7-12
cannot be quantified yet with respect to oxidant levels.
The contribution of hydrocarbon emissions from solvent
metal cleaning is less than 4% of the estimated national
total hydrocarbon emissions and is approximately equal to
9% of the stationary hydrocarbon emissions. Further,
large numbers of solvent metal cleaning operations have
converted to "virtually non-photochemically reactive"
solvents. The ability of these solvents to produce
oxidants is still being studied.
The economic advantages offered to most users of solvent
metal cleaning should be adequate to cause emission controls
to be used voluntarily if these advantages are fully under-
stood by the public.
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Page 8-1
8. Economic Impact
The spectrum of industries using solvent metal cleaning
is so great that the only known economic indicator of them
is the gross national product. Late 1974 and early 1975
*•
have been periods of particularly slow business levels.
Fortunately, emission controls evaluated for solvent metal
cleaning can be profitable to users rather than an economic
burden in many cases. However, the levels of performance
required must be within the capability of the emission
controls.
The savings:cost relationships for the various control
techniques were examined in evaluating the emission controls
proper and reported in Section 4.2. The solvent pricing
for these evaluations was taken from the Chemical Marketing
Reporter. This pricing source reports chemical pricing
with large volume purchasing. Smaller quantities of solvents
are sold through chemicaJ distributors. Pricing for smaller
quantities is necessarily higher. Representative of this
is the price list published by the Solvents and Chemicals
Companies July 1, 1975. Extracting from that source
Table 8-1 can be prepared.
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Page 8-2
Table 8-1
EXAMPLES OF DISTRIBUTOR PRICING ($/GALLON)
Truck Load 10-39 3-9 1-2
Solvent (40 Drums) Drs. Drs. Drs.
Methylene Chloride 2.50 2.60 2.82 3.04
Stoddard 0.50 0.56 0.62 0.72
1,1,1-Trichloroethane 2.56 2.67 2.78 3.00
Toluene 0.80 0.84 0.90 1.00
Small businesses use lesser volumes of solvent but at a
greater unit cost. Thus, the value of solvent conserved
by emission control equipment is higher for the smaller user.
This improves the opportunity to recover the invested capital
and operating costs at smaller firms. The sole question of
impact on small business becomes one of availability of
capital.
In general, the control of emissions from solvent metal clean-
ing can have a favorable economic impact on industry if:
1. Emission control requirements are set within the
limits of the emission control equipment.
2. The user has the option of selecting any of the
emission control methods discussed in this report.
3. A costly means of proving compliance is not required.
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