United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-94/026 March 1994
Project Summary
Onsite Solvent Recovery
Arun R. Gavaskar, Robert F. Olfenbuttel, and Jody A. Jones
This study evaluated the product
quality, waste reduction/pollution pre-
vention, and economic aspects of three
technologies for onsite solvent recov-
ery: atmospheric batch distillation,
vacuum heat-pump distillation, and low-
emission vapor degreasing. The atmo-
spheric and vacuum distillation units
were tested on spent methyl ethyl ke-
tone and spent methylene chloride, re-
spectively. Samples of spent, recycled,
and virgin solvents at two industrial
sites underwent physical and chemical
tests to determine solvent quality. The
quality of the recycled solvent was
found to be acceptable for use in the
specific applications. Significant waste
reduction was achieved by reducing
the volume of spent solvent to a few
gallons of distillation residue needing
disposal.
The low-emission vapor degreaser is
a fully enclosed alternative to conven-
tional, open-top vapor degreasing. It
was found to reduce air emissions by
more than 99%, compared to a conven-
tional vapor degreaser of the same pro-
duction capacity.
Compared to disposal, the atmo-
spheric and vacuum distillation units
reduced operating costs significantly.
The estimated payback period for these
units was found to be less than 2 yr.
The low-emission vapor degreaser re-
duced operating costs by reducing sol-
vent losses and labor costs. The
estimated payback for this unit was
approximately 10 yr. The cost estimates
were based on a full range of consider-
ations including equipment, engineer-
ing, installation, operation, mainte-
nance, and energy use. The estimates
did riot, however, include potential
changes in liabilities or impacts due to
regulations planned or in the process
of being implemented.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
introduction
This; study, performed under the U.S.
Environmental Protection Agency's (EPA's)
Waste Reduction and Innovative Technol-
ogy Evaluation (WRITE) Program, was a
cooperative effort between EPA's Risk
Reduction Engineering Laboratory (RREL)
and the Washington Department of Ecol-
ogy. The objective of the WRITE Program
is to evaluate, in a typical workplace envi-
ronment, examples of prototype or inno-
vative .commercial technologies that have
potential for source reduction or recycling.
The study evaluated three technologies
for recovering and reusing waste solvent
on site: atmospheric batch distillation,
vacuum heat-pump distillation, and low-
emission vapor degreasing. Comparing the
three units was not an objective of this
study. Rather, the suitability of each tech-
nology, to its respective application was
examined. In each technology category,
a specific unit offered by a specific manu-
facturer was tested. Other variations of
these units (with varying capabilities) may
be available from several vendors.
Printed on Recycled Paper
-------
The two liquid-distillation units were
tested at industrial sites that have pur-
chased and are using the units. The at-
mospheric unit was tested on spent methyl
ethyl ketone (MEK) at a site where MEK
is used to clean the spray painting lines
between colors. The recycled solvent was
reused for the same purpose, with the
residue shipped off as hazardous waste.
The vacuum unit was tested on spent
methylene chloride (MC) at a site that
manufactures wires and cables. The MC
is used for cold (immersion) cleaning of
wires and cables to remove markings (ink).
Atmospheric Batch Distillation
and Vacuum Heat-Pump Distilla-
tion
Atmospheric distillation is the simplest
technology available to recover liquid spent
solvents. Units that can distill as little as 5
gal or as much as 55 gal/batch are avail-
able. Some units can be modified to oper-
ate under vacuum for higher-boiling
solvents (>135°C). Contaminant compo-
nents with lower boiling points than the
solvent or that form an azeotrope with the
solvent cannot be separated (without frac-
tionation) and may end up in the distillate.
The unit used in this study (Figure 1) was
Model LS-55D,* manufactured by Finish
Thompson, Inc. The distillation residue,
often a relatively small fraction of the spent
solvent, is disposed of as hazardous
waste.
The vacuum unit tested, Model 040 is
manufactured by Mentec AG in Switzer-
land and supplied in the United States by
Vaco-Solv Chicago, Inc. It is configured
similar to a conventional vacuum distilla-
tion system except that the pump, in addi-
tion to drawing a vacuum, functions as a
heat pump (Figure 2). No external heating
or cooling is applied. The heat pump gen-
erates a vacuum for distillation and com-
presses vapors for condensation. Model
040 is suitable for solvents with boiling
points up to 80°C, Spent solvent is con-
tinuously sucked into the evaporator by a
valve. The vacuum drawn generates va-
pors, which are sucked into the heat pump,
compressed, and sent to the condenser.
The temperature stabilizes automatically
according to the specific solvent and the
ambient air. The condenser surrounds the
evaporator to allow heat exchange be-
tween the cool spent solvent and the warm
condensing vapors.
The product quality objective for the
two liquid-distillation units was to show
that the recycled solvent was of sufficient
quality for reuse. One 55-gal drum of spent
solvent was processed each day through
the batch and continuous units. For each
unit, one drum of spent solvent was pro-
' Mention ol trade names or commercial products does
not constitute endorsement or recommendation for
use.
Contaminated
Solvent
Stillbag
Heated
Walls
Electric
Heat Source
Reclaimed
Solvent
Figure 1. Atmospheric distillation unit.
(Source: Finish Thompson, Inc.)
cessed in ~12 hr. The atmospheric unit
left 16 gal of residue and the vacuum unit
left 3 gal. The amount of residue left be-
hind is a function;of the application and
not the distillation; units. „Samples of the
spent and recycled solvents were ana-
lyzed by standard ASTM method.s'tb de-
termine the improvement in quality. Virgin
solvent samples also were collected at
each site and subjected to the same tests
for comparison. :
During the vacuum unit test, the "virgin"
sample was found to be a sample of MC
obtained by the site from a solvent recy-
cling company. Th,e "virgin" solvent speci-
fications meet the requirements for the
company's application, and it has been
used satisfactorily at the site in the past.
The vacuum unit was being operated at a
faster rate than. recommended by the
manufacturer. Bebause the unit's built-in
condenser-evaporator heat exchange was
not sufficient for this rate, site personnel
had attached an lair-cooled condenser at
the outlet to restrict vapor loss to -4 gal/
55 gal of spent solvent. To prevent the
release of this vapor into the work area,
the vapor was led through a pipe to the
roof of the facility and discharged per state
regulations.
Table 1 shows the characterization re-
sults for samples from the atmospheric
and vacuum units. In appearance and
color, the spent samples varied vastly from
the clear recycled and virgin samples. All
the measured parameters showed a sig-
nificant improvement from spent to re-
cycled samples but were not quite up to
virgin grade. The water content increase
in the recycled samples from the atmo-
spheric unit was traced to a slight leakage
from the water-cooled condenser that was
worn out due to long use. Repairing the
leak after the testing, site personnel re-
ported that the problem had been cor-
rected. :
MEK purity of the recycled sample from
the atmospheric unit substantially in-
creased from 78% to -85%. The large
decrease in nonvolatile matter during re-
cycling accountsifor most of this increase.
Of the 15% impurity in the recycled
sample, 5% is water as discussed above.
The remaining 10% impurity probably is
due to the codistilling out of paint thinner
solvents (proprietary blends) present in
the spent solvent. MC purity of the re-
cycled solvent from the vacuum unit was
86%, comparing lavorably with the "virgin"
sample purity of [90%.
Some performance characteristics of MC
(a halogenated solvent) also were evalu-
ated. The pH of the water extract of the
recycled solvent was fairly close to the
"virgin" value of; 7. The spent sample pH
-------
Condensate Trap
Vapor Filter
Overflow
Protection
*- Feed
Level
Control
Spent Solvent
Vaporizer
Residue Slu
Condenser
Distillate
Figure 2. Vacuum heat-pump distillation unit.
(Source: Vaco-Solv Chicago, Inc.)
of 5 indicates the presence of potentially
corrosive components. The corrosion test
on steel and aluminum (ASTM D2251)
yielded noticeable corrosion only in the
case of the steel strip placed in the spent
solvent sample. No such corrosion was
evident due to the recycled solvent, indi-
cating that recycling improved the quality.
Table 2 shows the waste reduction
achieved by the two distillation technolo-
gies at the respective sites. Through recy-
cling, large volumes of spent solvent waste
were reduced to small volumes of distilla-
tion residue, which is disposed of as RCRA
hazardous waste. Both MEK and MC are
hazardous chemicals listed on the Toxic
Releases Inventory (TRI). These solvents
also are on EPA's list of 17 chemicals
targeted" for 33% reduction by 1992 and
50% reduction by 1995.
The economic evaluation compares the
costs of each new technology to conven-
tional practice. Table 3 shows the major
operating costs associated with disposal
and the atmospheric batch unit. For the
unit, recycling saved ~$10,000/yr. The pur-
chase price of the atmospheric batch unit
is $12,995. A detailed calculation based
on worksheets provided in the Facility Pol-
lution Prevention Guide (EPA, 1992) indi-
cated a payback period of less than 2 yr.
For the vacuum unit (Table 4), savings
from recycling are ~$18,300/yr. An explo-
sion-proof vacuum unit costs $23,500. The
payback period for this unit also was less
thsin 2 yr.
Low-Emission Vapor Degreasing
(LEVD)
LEVD currently is used in Europe, where
vapor degreasers are regulated as a point
source. Previous studies (Battelle, 1992)
on conventional open-top vapor degreas-
ers have shown that a large part of the
solvent (more than 90% in some cases) is
losit through air emissions, which are con-
siderable even though vapor degreasers
are required to have primary cooling coils
(ta.pwater cooled) and a certain freeboard
height. Air emissions are mainly workload-
related, caused either by dragout of sol-
vent on the workload itself (and
subsequent vaporization) or by disturbance
in the air-vapor interface during entry and
Table 1. Characterization of Solvent Samples
Sample
Appearance
Atmospheric Unit (MEK)
Spent Dark grey w/sediment
Recycled Clear
Recycled Dupd
Virgin
Vacuum Unit (M(
Spent
Recycled
Recycled Dupd
Virgin
Clear
Clear
y ' :
Dirty grey-brown
Clear
Clear
Clear, tinge of yellow
Color3
__Q
5
5
5
a
5
5
10
Specific
Gravity
0.845
6.827
0.821
0.800
1.220
1.286
1.288
1.298
Nonvolatile
Matter
mg/100mL
6,951
2.6
2.0
2.2
34,101
20.37
17.88
57.16
Conductivity
/j,mhos/cm
7.05
3.30
3.40
1.15
1,063
137
136
36
Water
Content
i %bywt
1.89
5.42
5.56
.0.09
0-27
: 0.25
! 0.24
0.14
Acid
Acceptance*1
NA< ,
NA
NA . '
' NA- ..'--. •
. , 0.032
0.004
0.005
0.003 "
Purity
%c
78.41
• 85.02
85.54
99.09
NA'
86.4
NA
90.1
aOna scale of 5 to 500, with 500 being the darkest color. ASTM D1209 and D2108.
h Measured as equivalent NaOH wt%. ASTM D2942.
c Gas chromatography analysis based on ASTM D2804.
d Duplicate analysis of the same sample.
e Not comparable with standards. Sample was too dirty. •
' NA = not analyzed.
-------
Table 2. Waste Reduction by Atmospheric and Vacuum Units
-Disposal Option -
Wastestream Annual Volume
- Recycling Option -
Wastestream Annual Volume
Atmospheric Un'rt'Test Site:
Spent MEK
Drums
Vacuum Unit Test Site:
Spent MO
Drums
880 gal
17 drums
3,000 gal
55 drums
Distillation residue
Still bags
Cooling water
Drums
Distillation residue
Air emission
Drums
Used oil
262 gal
17 bags
,18,360 gal
5 drums
136 gal
218 gal
3 drums
1gal
Table 3. Major Operating Costs for Atmospheric Unit
Item
Disposal Option
Virgin solvent
Disposal
-labor
— drums
— disposal fee
Atmospheric Unit
Virgin solvent
Operating labor
Routine maintenance
-spare parts
-labor
Energy
Cooling water
Disposal
-labor
-drums
—residua disposal
—still bags
Annual
Usage
880 gal
8hr
17
900 gal
245 gal
17hr
1
12hr
1,265kWh
18,360 gal
3
5
262 gal
17
Unit
Cost
($)
10.50/gal
8/hr
40/drum
400/55 gal
Total
10.50/gal
8/hr
86/each
8/hr
0.04/kWh
' , 1/1000 gal
8/hr
40/drum
675/55 gal
84/12 bags
Total
Annual
Cost
($)
9,240
64
680
6.545
16,529
2,573
136
86
96
51
18
24
200
3,215
119
6,518
exit of the workload. Other sources are
convection and diffusion during startup,
operation, idling, shutdown, and, to a small
extent, equipment leaks. Air emissions are
a concern for metal finishers because
many solvents used in vapor degreasing
have been targeted by EPA in the 33/50
Program. Environmental and Occupational
Safety and Health Administration (OSHA)
regulations have become more stringent.
Pollution control devices available for
conventional vapor degreasers include in-
creased freeboard height, refrigerated
coils, and covers to eliminate drafts and
reduce diffusion. In contrast, LEVDs are
completely enclosed, airtight units. This
evatuatbn used Model 83S (Size 1), manu-
factured in the United States by Durr Au-
tomation, Inc. Figure 3 shows its opera-
tion. About 1 hr before the shift begins, a
timer switches on the heat to the sump.
When the solvent in the sump reaches
vapor temperature, the vapor is still con-
fined to the enclosed jacket around the
working chamber. The parts to be cleaned
(workload) are placed in a galvanized bas-
ket and lowered into the working cham-
ber. Loads can range from 330 to 110 Ib
(of steel parts) in this model. When the lid
is shut and the unit is switched on, com-
pressed air hermetically seals the lid shut
for the duration of the cycle.
Table 5 shows typical cleaning cycle
stages. During "vapor fill," solvent vapors
enter the chamber from the outer jacket,
and degreasing begins. During "conden-
sation," solvent vapors are condensed out
by a refrigerated copling coil at the bottom
of the chamber. During "air recirculation,"
the air-solvent mixture is recirculated
through a chiller tp condense out more
solvent. During "carbon heatup," solvent
adsorbed in the previous cycle is released
(desorbed) to the circulating air and con-
denses out in the chiller. During "adsorp-
tion," the chamber air is recirculated in the
reverse direction-first through the chiller
and then through -the carbon. Most re-
sidual solvent vapor in the cold air is ad-
sorbed on the carbon. A photoionizatibn
detector (PID) probe verifies that the cham-
ber air has less than 1 g/m3 of solvent and
signals the air compressor to release the
seal on the lid 'to end the cycle. If the
chamber air has more than 1 g/m3 of
solvent, the cycle loops back to the des-
orption stage. The entire cycle is pro-
grammed and requires no operator
attention except to; load and unload the
workload. Only a very small amount of
solvent exhausts at the end when the lid
is opened. The LEVD also works as a
distillation unit to clean the liquid solvent
in the sump. During distillation, the unit is
switched on without any workload in the
chamber.
Testing was conducted on the LEVD
using perchloroethylene (PCE) solvent.
Test runs were conducted on machined
steel parts with and without cutting oil on
the parts. Total cycle limes were recorded
for all completed runs. Because the same
batch of parts was used for each run,
parts were either pold (ambient) or hot
depending on the cooling time between
runs. Adding oil to the parts d.id not greatly
affect the total cycle time, but the work-
load mass did. In all the runs starting with
parts dipped in cutting oil, the cleaned
parts were visually examined for traces of
oil or dirt contamination. No contamina-
tion was noticed oni the parts from any pf
these runs. '
The ppllution prevention aspect of the
LEVD was the main focus of this technol-
ogy. The completely enclosed design of
the working chamber allows the potential
for air emissions only when the cleaning
cycle is complete and the lid is opened.
Any solvent vapor riot evacuated from the
chamber during condensation or adsorp-
tion releases to the atmosphere.
Table 6 shows the total cycle times and
emissions recorded from the LEVD by a
flame ionization detector (FID) probe in-
serted (for this test) into the working cham-
ber below the designated vapor level. FID
measurements began during the adsorp-
tion stage and continued until after the lid
was opened. A second FID probe (ambi-
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Table 4, Major Operating Costs for Vacuum Unit
Item
Disposal Potion
Virgin solvent
Disposal
- labor
- drums
- disposal fee
Virgin solvent
Operating labor
Energy
Disposal
- still bottoms
— used oil
-labor
- drums
Routine Maintenance
-oil
- spare parts
- labor
Annual Usage
3000 gal
16 hr
55
3000 gal
246 gal
55hr
985 kWh
136 gal
4 quarts
3hr
'3
4 quarts
a
16 hr
Unit Cost
($)
3.57/gal
8/hr
40
2.50/gal
Total
3.57/gal
8/hr
0.04/kWh
2.50
3.00/quart
8/hr
40/drum
3.50/quart
480 (max)3
8/hr
Total
Annual Cost
($)
10,710
128
2,200
7.500
20,538
878
220
39
340
12
24
120
14
480
128
2,255
The $480 cost for spare parts is a maximum, which assumes that the manufacturer's recommend-
ations are exactly followed and that the maximum number of parts will be replaced during each
overhaul. Actual maintenance costs could be lower.
Working Chamber
Workload
Vapor
Inducer
Electric -»
Heat
Cooling
Coils Li1uid
Solvent
Water
Separator
Water
Liquid Solvent
Legend
— — — ^- Desorption Stage
__ >> Adsorption Stage
^- Liquid Solvent
Figure 3. Low-emission vapor degreaser.
(Source: Durr Automation, Inc.)
ent), positioned outside the unit near the
lid seal, took continuous measurements .
all around the unit during operation, with
special emphasis around the lid to ensure
leak-proof design. Ambient levels (3 to 4
ppm) in the indoor facility on the test days
were consistent.
Figure 4 shows how a typical LEVD
cleaning cycle ends. The same pattern
was evident in the other runs. Time zero
corresponds to the start of measurements
when the FID probe in the working pham-
ber was activated.
Just before the adsorption cycle ended,
the chamber FID read 52 ppm, well below
the targeted 1 g/m3 (150 ppm of PCE).
When the lid was retracted, the chamber
air had full access to the ambient. At this
point, the chamber concentration dropped
shairply as the residual solvent vapor in
the chamber dispersed. The ambient FID
probe showed a corresponding increase
(to 6 ppm). Both FID readings soon stabi-
lized to facility ambient levels (3 to 4 ppm).
Later, as the basket of cleaned parts
was raised out of the chamber, the sec-
ond FID probe was thrust into the basket
near the parts. No elevated readings above
ambient were sensed, indicating that the
parts were free of solvent. Thus, there is
a very small air emission from the LEVD
when the lid is opened. In all the test
runs, the solvent concentration was well
below the targeted 1 g/m3 (150 ppm PCE),
so 1 g/m3 is an achievable concentration.
The volume of the working chamber is 0.6
m3. Assuming that all the residual solvent
vapor (1 g/m3 maximum) in the chamber
is discharged. to the ambient area, the
typical air emission through the opened
topi is 0.6 g (0.00132 lb)/cycle or less. It
takes 1 hr to clean 560 Ib of oiled steel
parts. Therefore, the air emission from
this LEVD mode is 0.00132 Ib of solvent/
hr.
A typical conventional open-top vapor
degreaser cleaning at a similar rate
(~ 560 Ib of steel parts/hr) typically would
emit 0.147 Ib of solvent/ft2/hr (EPA, 1989),
or 0.662 Ib of solvent/hr from its 4.5-ft2
opening during continuous operation.
Therefore, the LEVD reduces air emis-
sions by more-than 99% compared to air
emissions from the typical conventional
open-top vapor degreaser (i.e., with a 0.75
fre>eboard ratio, primary cooling coil, elec-
tric hoist, and no lip exhausts) used in this
calculation.
The OSHA exposure limit for PCE is 25
ppim for an 8-hr time-weighted average
(TWA). Personnel air sampling (in accor-
dsince with OSHA guidelines) was not con-
ducted during this evaluation, but PCE
levels measured with the ambient FID at
all times during operation (3 to 4 ppm)
-------
TabioS. LEVD Cleaning Cycle
Stage
Solvent heatup (once a day)
Solvent spray (optional)
Vapor fill
Degreaslng
Condensation
Airreclrculation
Carbon heatup
Desorptlon
Adsorption
Vendor-Recommended
Time Settings
(sec)
Variable a
10-180
Variable"
20-180
120
120
Variable0
60
60-240 "
Times Set
for This Testing
(sec)
Variable a
not used
Variable b
60
120
120
Variable c
60
240
• Requires ~1 hron days following overnight shutdown when sump solvent temperature drops to 70°C.
After weekend shutdowns, when sump solvent temperature drops to 20°C, it may take 1.5hr for
solvent to reach vapor temperature. Timer on unit allows automatic heatup.
6 Depending on the workload mass and type of metal. Varied from 8.5 mm lor 165 Ib to 36.5 mm for
915 Ib of steel parts.
c Carbon heatup took approximately 22.5 min during testing.
rf At 60 sec, if monitor shows that chamber concentration is above 1 g/m3, then the adsorption stage
proceeds to the ful!240-sec stage. This sequence repeats if necessary.
Table 6. Emissions from LEVD
Run
No*
1
2
3
5
6
8
Target d
Mass of Steel
Parts (Ib)
165
165
900
165 e
165e
915 e
560
Final Chamber
Concentration11
(ppm)
52
75
92
43
47
78
150
Total PCE
Emission0
(Ib/cycle)
0.0005
0.0007
0.0008
0.0004
0.0004
0.0007
0.0013
Total
Cycle Time
(min)
39'
67.5
50.5
40'
69
609
Emission
Rate
(Ib/hr)
0.0011
0.0007
0.0005
0.0006
0.0006
0.0013
Runs 4, 7, and 9 were interrupted to allow other measurements.
° At the moment when the seal on the lid is released.
0 Based on 150 ppm - 1 g/m3 of PCE and a chamber volume of 0.6 m3.
° Normally the machine is programmed to release the lid when solvent concentration in the chamber
falls below 1 g/m3 (150 ppm of PCE). This target was easily met in all the test runs.
0 Workload parts were dipped in cutting oil before the run.
1 Workload parts were already hot from being used in previous runs when inserted into working
chamber. Wence, total cycle times for these runs are lower than normally expected.
o Expected cycle time for 560 Ib of steel parts (workload).
and at the edge of the chamber opening
for about 2.5 min when the lid is retracted
completely (<6 ppm) (Figure 4) are well
under the OSHA exposure limit. The pol-
lution prevention potential of this unit is
further enhanced by its ability to perform
as a liquid solvent distillation system for
cleaning the sump solvent; this capability
was not a part of this evaluation. When
pollution prevention is an objective, the
LEVD also affords greater production flex-
ibility because it has none of the idling
losses between loads or downtime losses
during shutdown of the conventional de-
greaser.
Table 7 lists the LEVD's major operat-
ing costs and the operating costs for a
conventional open-top vapor degreaser
with similar production capacity. With a
vendor-quoted purchase price for the
LEVD of $210,000, the unit results in sav-
ings in annual total operating costs of
~$25,000 mainly from reduced labor costs
(due to larger batch size) and lower sol-
vent requirement (due to solvent recov-
ery). The LEVD pays for itself in -10 yr.
The above is a straightforward cost com-
parison between the LEVD and a conven-
tional vapor degreaser of similar production
capacity. Other cost-benefit factors must
be taken into account when making eco-
nomic decisions. The LEVD does not re-
quire capital and operating expenditures
for auxiliary equip.ment that may be re-
quired for a standard conventional vapor
degreaser (increased freeboard ratio, re-
frigerated coils, lip exhausts, room venti-
lation) in order'meet or anticipate
increasingly stringent environmental and
worker safety regulations. The LEVD is a
self-contained unitthat requires no addi-
tional facility modifications to achieve sig-
nificant emission reductions.
Another consideration is the LEVD's pro-
duction rate. The above calculation used
a production rate of 560 Ib/hr of steel
parts (workload) because most vendors of
conventional degreasers quote capacities
based on steel parts. However, produc-
tion capacity per machine can vary de-
pending on the metal processed. Based
on the thermal diffusivity of various met-
als, total cycle times versus production
rates are plotted jn Figure 5. Brass and
copper can be processed faster than steel
with the LEVD, and aluminum can be pro-
cessed faster up to a point determined,
for a certain shape of parts, by the maxi-
mum mass of aluminum parts that fit into
the basket.
The shape of the parts also may affect
cycle time. Parts with recesses that can
trap solvent should be arranged in the
basket so that the solvent liquid drains
out. Other features offered by the vendor
(oscillating or rotating baskets) should be
used. Otherwise, either the air recircula-
tion stage time must be increased, or the
unit will loop into several adsorption cycles
until the chamber concentration falls be-
low 1 g/m3.
Conclusions and Discussion
All three technologies evaluated in this
study demonstrated good potential for pol-
lution prevention/waste reduction. The two
onsite solvent distillation technologies re-
duced large volumes of hazardous sol-
vent to a few gallons of distillation residue
and produced a reusable recycled prod-
uct. The total U.S. solvent demand is ap-
proximately 160 billion gal/yr. Therefore,
there is considerable potential for recy-
cling and reusing spent solvent. Between
onsite" and offsite recovery, onsite recov-
ery is preferable because of the reduced
transportation hazard.
The largest single use for solvents in
the United States is for vapor degreasing.
The LEVD reduced air emissions signifi-
cantly compared to :emissiohs from a con-
ventional vapor degreaser.
Payback periods for both distillation
technologies are less than 2 yr. The LEVD
is a slightly higher capital investment (with
-------
10000
I
f
I
I
p
1000
100 :
a payback period oi approximately 10 yr),
but it eliminates the need for other poten-
tially expensive auxiliary equipment that
conventional vapor degreasers would re-
quire to meet comparable pollution pre-
vention objectives.
The full report was submitted in partial
fulfillment of Contract Number 68-CO-0003,
Work Assignment 2-36, by Battelle under
the sponsorship of the U.S. Environmen-
tal iProtection Agency.
100
200
300
Time (seconds)
Figure 4. Concentrations at the end of the cleaning cycle for Run 1.
400
500
600
Table 7. Operating Costs for Low-Emission Vapor Degreasing-
Item
Annual
Volume
Unit
Cost
($)
Total
Cost
($)
Conventional Degreaser
Operating labor
Electricity
Cooling water
Maintenance
-labor
-materials
Net solvent loss
4,000 hr
25,500 kWh
480,000 gal
22 hr
2,642lb
8/hr
0.04/kWh
1/1000 gal
8/hr
0.71/Ib
32,000
1,020
480
176
$88
Total
35,640
LEVD
Operating labor
Electricity
Maintenance
- labor
- materials
333 hr
93,725 kWh
262.5 hr
—
8/hr
0.04/kWh
8/hr
—
Total
2,664
3,749
2,100
2.100
10,613
•&V.S. GOVERNMENT PRINTING OFFICE: 1994 - 550467/80201
-------
200 400 600 SOO
Mass of Parts Cleaned Per Cycle, Ib
Figure 5. Variation ofLEVD cycle time for various metals.
1000
1200
Arun R. Gavaskar, Robert F. Olfenbuttel, and Jody A. Jones are with Batelle,
Columbus, OH 43201.
Ivars Lids is the EPA Project Officer (see below).
The complete report, entitled "Onsite Solvent Recovery," (Order No. PB94-
144508; Cost: $19.50, subject to change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/026
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