United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-042 May 1981
Project Summary
Evaluation of Solvent Loss
from Vapor Degreaser
Systems
R. W Gerstle, V. S. Katari, and E. S. Schindler
The principal objectives of this project
are to develop and implement a program
for assessing solvent loss from de-
greasing systems of various designs,
and to report the test conditions,
procedures, results, and conclusions
in a form usable by air pollution
agencies and industry.
Tests were performed from October
1978 to July 1979 to evaluate the
effects of different variables on the
rate of solvent loss from degreasers.
The variables tested include the fol-
lowing degreaser modifications and
operating conditions:
Freeboard ratio
Load cross-sectional area
Refrigerated freeboard chiller (RFC)
Hoist speed
Lip exhaust
Crosscurrent air velocity
Degreaser size
Solvent type
Lid
The cost of each modification was
analyzed. These analyses were based
on capital costs, annual expenses, and
solvent saved because of the modifi-
cation. The evaluations of solvent loss
or savings were based only on the
degreaser operating period; idle time
(the solvent boiling and cooling period)
was disregarded.
This Project Summary was devel-
oped by EPA's Industrial Environmental
Research 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 and Methods
The U.S. Environmental Protection
Agency has undertaken a study to
evaluate the pollution reduction capa-
bilities of vapor degreasers and new
developments in vapor degreasing sys-
tems and operations.
The tests were conducted in a labora-
tory equipped with temperature, humid-
ity, and ventilation controls. All the
variables (except increases in cross-
current air velocity) were tested under
calm air conditions at an average velocity
of 0.1 m/s (20ft/min). All the tests but
one were conducted in two typical
degreasers (A and B). In one test a
smaller degreaser (C) was used in place
of Degreaser B.
Degreasers A and B had nearly the
same specifications. Degreaser A was
equipped with a refrigerated freeboard
chiller (RFC I) that operated at tempera-
tures above 0°C (32°F). Degreaser B
was equipped with a chiller (RFC II) that
operated at temperatures below -18°C
(0°F). The degreasers had nearly equal
top openings of 1.4 m2( 15 ft2). The other
design difference was the location of
the primary condenser coil. Degreaser A
was equipped with a spiral condenser
coil located horizontally along one end
of the degreaser; Degreaser B was
equipped with coil tubing wrapped
-------
around the perimeter of the degreaser.
Degreaser C had a top opening of 0.35
m2 (3.78 ft2), a 75 percent freeboard
ratio, and a primary condenser similar to
that of Degreaser B.
The two principal degreasers were
used simultaneously in each test to
verify the results and to eliminate the
effect of physical conditions of the units.
(Although Degreasers A and B had
nearly equal top openings, their length
and width dimensions were different.)
The degreasers were virtually isolated
from all extraneous variables that might
affect solvent loss. Ambient air condi-
tions were monitored continuously
throughout the tests.
Each degreaser had a programmed
hoist system with a 6.5-minute cycle
and a simulated load cleaning capacity
of about 454 kg/h (1000 Ib/h). The load
was a clean metal pipe placed in a
basket.
The solvents used in the tests were
1,1,1 -trichloroethane (TE) and methylene
chloride (MC). The primary method of
detecting solvent loss was to weigh
each degreaser at intervals during the
testing period. A relationship of time
versus weight was developed and quan-
tified by a least-squares regression
analysis.
The degreaser modifications were
evaluated by comparing the ranges of
solvent loss under a given test condition.
For each test, the overall range was
established by using the two degreaser
readings as the extremes of the range.
A typical degreaser with no controls
was established as a base case and the
standard against which ihe reduction
capabilities of the various modifications
were evaluated. The range of the solvent
loss reduction capability of a modifica-
tion was established by subtracting the
specific solvent loss reading from the
reading for the base case for each
degreaser.
Effectiveness of Modifications
Tables I and II present a summary of
the solvent reduction capabilities of dif-
ferent variables on operating degreasers
using TE and MC.
Freeboard Ratio
Increases in freeboard ratio degreased
solvent loss (i.e., increased solvent loss
reduction) from operating degreasers
under all conditions tested. The exception
was tests of higher hoist speed (0.08
m/s or 16 ft/min) and normal load (50
percent load area); under these condi-
tions, no effect was seen when the
freeboard ratio exceeded 75 percent. No
indication of decreasing effectiveness
was found with TE, but tests with MC
indicated a decreasing effectiveness as
freeboard ratio increased. With the
latter solvent, more solvent loss reduc-
tion was achieved when the larger load
was used (70 percent load area).
Load Area
Solvent loss increased when an
abnormally large load (70 percent ratio
of basket cross-sectional area to de-
greaser top opening area) was used in
place of a normal load (50 percent ratio,
which is typically specified in the operat-
ing manual). The weight of the load was
not increased in these tests. The increase
in solvent loss was about 5 to 23 percent
from degreasers using TE at 0.04 m/s (8
ft/min) hoist speed; however, it was
about 50 percent from degreasers using
TE at 0.08 m/s (16 ft/min) and from
degreasers using MC at 0.04 m/s (8
ft/min).
Refrigerated Freeboard Chiller
No significant solvent loss reduction
occurred when either of the refrigerated
freeboard chillers was used on an
operating degreaser with TE and a 50
percent load area at 0.04 m/s (8 ft/mi n).
When the freeboard ratio was changed
from 50 to 75 percent, RFC II operating
at -29° to -40°C (-20° to -40°F)achieved
an additional 20 percent reduction in
solvent loss under these same condi-
tions. The chillers did, however, reduce
solvent loss from operating degreasers
with either solvent and with a 70 percent
load area at 0.04 m/s (8 ft/min). The
RFC I either increased solvent loss or
made no difference on a degreaser
operating with MC and a 50 percent
load area; RFC II decreased solvent loss
Tablet.
Effect on Solvent Loss Reduction of Various Modifications to an Operating Degreaser Using 1.1,1 -Trichloroethane
(percentage of reductiorLor increase over the base case*)
Hoist speed, 0.04 m/sc
Load area:' 50%
Load area: 70%
Hoist speed, 0 08 m/s"
RFC: Off
Freeboard
ratio,"
%
50
75
100
125
RFC
Off
0"
7-25
47-53
RFC 1
1°to2°C°
5
8
34
RFC II
-23°to-32°Ch -29°
8
18
47
to -40°C
2
46
51
RFC:
Off
(5-23)1
(3)-4
RFCI
1° to2°C
27
RFC II
-23° to -32°C
14
34
Load
area:
50%
(111
16
9
20
Load
area:
70%
(50)
(5)
*FJase case: FR - 50, RFC: Off, hoist speed - 0.04 m/s, load cross-sectional area = 50%.
b/?ar/o of freeboard height to degreaser width.
C8 ft/min.
"16 ft/min.
"Ratio of load cross-sectional area to degreaser top opening.
1Refrigerated freeboard chiller.
934° to 36°F.
h-10°to-25°F.
' -20° to -40°F.
' Percentages in parentheses represent increases in solvent loss over the base case.
-------
Table II. Effect on Solvent Loss Reduction of Various Modifications to an Operating Degreaser Using Methylene Chloride at a
Hoist Speed of 0.04 m/s*
(percentage of decrease or increase over the base caseb)
Freeboard
ratio, °
%
50
75
125
Load area: 50%
RFC:"
Off
0
17-22
25
RFC!
1° to2°C'
(4)h
5
25
RFC II
-29° to -40°Ca
16
46
61
RFC:
Off
(53)
9
Load area: 70%
RFC 1
1°to2°C
(39)
22
RFC II
-29° to -40°C
(5)
44
a8 ft/min.
"Base case: FR = 50, RFC: Off, hoist speed - 0.04 m/s, load cross-sectional area - 50%.
cRatio of freeboard height to degreaser width.
"Ratio of load cross-sectional area to degreaser top opening.
"Refrigerated freeboard chiller.
'34° to 36°F.
9-20° to -40°F.
"Percentages in parentheses represent increases in solvent loss over the base case.
under these conditions. Further require-
ments are recommended to explain
these phenomena.
Hoist Speed
Tests on degreasers having 100 per-
center more freeboard ratio and cleaning
a normal load area of 50 percent (using
TE solvent) showed greater solvent
losses at 0.08 m/s (16 ft/min) than at
0.04 m/s (8 ft/min). At all freeboard
ratios, tests using a load area of 70
percent showed greater solvent losses
at the higher speed.
Up Exhaust
Tests were conducted on an operating
degreaser equipped with an exhaust
system and using MC as the solvent and
a hoist speed of 0.04 m/s (8 ft/min).
Total solvent loss (through the exhaust
system and the top opening) was in-
creased by more than 100 percent at an
exhaust rate of 0.25 mVs per m2 (50
ftVmin per ft2) and by about 150 percent
at 0.5 mVs per m2 (100ftVmin per ft2).
Crosscurrent Air Velocity
No significant differences in solvent
loss were found when air velocity
across the degreaser top was increased
from 0.1 to0.2m/s(20to40ft/min). At
0.26 m/s (52 ft/min), however, solvent
loss increased by more than 100 percent.
Degreaser Size
Tests were conducted with two de-
| greasers of different sizes using TE and
a 50 percent load area at 0.04 m/s (8
ft/min) hoist speed. The solvent loss
from the smaller degreaser (0.35 m2 or
3.78 ft2 top open area) was about 80
percent less than the loss from a larger
degreaser (1.4 m2 or 15 ft2 top open
area). The solvent loss per unit of top
open area was independent of degreaser
size.
Solvent Type
No differences in solvent loss were
found based on the use of TE or MC.
Lid
An idle degreaser has less solvent
loss than an operating degreaser. Use of
a lid further reduced solvent loss from 0
to 65 percent when TE was the solvent
and 35 percent when MC was the
solvent.
Idle Degreasers
Tests using MC showed that increased
freeboard ratio was not effective in
reducing solvent loss from idle degreaser
holding nonboiling solvent. An increase
in freeboard ratio from 50 to 75 percent
was effective in reducing solvent loss
from an idle degreaser holding boiler
MC. An increase in freeboard ratio
beyond 75 percent, however, did not
achieve any further effectiveness.
The use of RFC I (>0°C or >32°F) did
not affect solvent loss from an idle
degreaser using nonboiling MC; the use
of RFC II at -29° to -40°C (-20° to -40° F)
increased solvent loss under the same
conditions. RFC I was ineffective,
whereas RFC II when operated at -29°
to -40°C (-20° to -40°F) showed a
solvent loss reduction capability of 25 to
30 percent on idle degreasers holding
boiling MC.
Economic Analysis
Cost analyses for each modification
were based on capital costs, annual
expenses, and solvent saved because of
the modification. The evaluations of
solvent loss or savings were based only
on the degreaser operating period; idle
time (the solvent boiling and cooling
period) and disregarded.
Tables III and IV present cost savings
or additional expenses due to the modi-
fication of operating degreasers using
TE and MC. The costs shown were
based on the operation of the degreasers
for one shift per day.
Increased freeboard ratio is the only
modification to a normal degreaser that
shows an economic benefit. Capital
costs are low and annual operating
costs are negligible. The payback of
capital occurs in a time period shorter
than the life of the equipment. As a
result, the savings in solvent loss are
substantially greater than the expenses
incurred by the modification.
-------
Table III. Annual Savings Resulting from Modifications to a Degreaser Using 1.1,1 -Trichloroethane and Operating Only One
Shift Per Day"* (1979 dollars)
Hoist speed. 0 04 m/s' Hoist speed, 0.08 m/s"
RFC: Off
Load area: 50%° Load area: 70%
Freeboard
ratio.
%
50
75
100
125
RFC:1
Off
0
51-291
629-686
RFCI
1° to 2°Cg
(834)'
(778)
1590)
-23° to -32
(997)
(1031)
(521)
RFC II
°Ch -25° to -40°C
(1082)
(523)
(260)
RCF.
Off
(87-355)
(34-133)
RFCI
1°to2°C
(586)
RFC II
-23° to -32° C
(929)
(735)
Load
area:
50%
(166)
168
56
197
Load
area:
70%
(760)
(171)
^Profit due to solvent savings less the cost and operation of modification.
tiLost capacity resulting from increase in freeboard ratio not included in analysis.
C8 ft/min.
"16 ft/min.
eRatio of load cross-sectional area to degreaser top opening.
' Refrigerated freeboard chiller.
g34° to 36°F.
h-/0° to -25°F.
' -20° to -40°F.
1 Values in parentheses represent losses.
Table IV. Annual Savings Resulting from Modifications to a Degreaser Using Methylene Chloride and Operating Only One Shift
Per Day at a Hoist Speed of 0.04 m/s (8 ft/min)*'t>(1979 dollars)
Freeboard
ratio,
%
50
75
125
RFC:"
Off
0
173-186
1 72-289
Load area: 50%c
RFC 1
1° to2°C"
(1179)9
(887)
(733)
RFC II
-29° to -40°C'
(902)
(522)
(354)
RFC:
Off
(535-743)
0-13
Load area: 70%
RFC 1
1°to2°C
(1310)
(759)
RFC II
-29° to -40°C
(1191)
(5911
"Profit due to solvent savings less the cost and operation of modification.
tiLost capacity resulting from increasing freeboard ratio not included in analysis.
cRatio of load cross-sectional area to degreaser top opening.
^Refrigerated freeboard chiller.
e34° to 36°F.
'-20° to-40°F.
'Values in parentheses represent /osses.
-------
/?. I/I/. Gerstle, V. S. Katari, and E. S. Schindler are with PEDCo Environmental.
Inc., Cincinnati, OH 45245.
Charles Darvin is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Solvent Loss from Vapor Degreaser
Systems," (Order No. PB 57-7 76 398; Cost: $3.50 (microfiche only), subject to
change} will be available only from
The EPA Project Officer can be contacted at:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U S. Environmental Protection Agency
Cincinnati, OH 45268
6 US GOVERNMENT PRINTING OFFICE 1961 -757-012/7107
-------
United States Center for Environmental Research Feesfpaid"
Environmental Protection Information
Agency Cincinnati OH 45268 Protectin
Agency
_ EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED Third-Class
Bulk Rate
------- |