United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/ 2-78-127
June 1978
Research and Development
Evaporative Recovery
of Chromium Plating
Rinse Waters
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1 Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-78-127
June 1978
EVAPORATIVE RECOVERY OF CHROMIUM PLATING RINSE WATERS
by
Leonard N. Elicker
Advance Plating Company
Cleveland, Ohio 44103
and
Roger W. Lacy
Corning Glass Works
Corning, New York 14830
Grant No. S-8037-81
Project Officer
John Ciancia
Industrial Pollution Control Division
Industrial Environmental Research Laboratory
Edison, New Jersey 08817
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental
Research Laboratory - Cincinnati, U.S. Environmental Protection
Agency, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
-------
FOREWORD
When energy and material resources are extracted, processed,
converted, and used, the related pollutional impacts on our
environment and even on our health often require that new
and increasingly more efficient pollution control methods be
used. The Industrial Environmental Research Laboratory -
Cincinnati (IERL-CI) assists in developing and demonstrating
new and improved methodologies that will meet these needs
both efficiently and economically.
This report is a product of the above efforts. These studies
were undertaken to describe the methodology and determine
the economics of a new evaporative approach for recovering
chemicals from metal finishing rinse waters. The testing
was performed in a typical chrome plating job shop. This
evaporative recovery method combines simplicity and ease of
operation with the capabilities to effectively reduce chromic
acid consumption.
Such information will be of value both to EPA's regulatory
program (Effluent Guidelines Division) and to the industry
itself in arriving at meaningful and achievable discharge
levels. Within EPA's R & D program the information will be
used as part of the continuing program to develop and evaluate
improved and less costly technology to minimize industrial
waste discharges. Besides its direct application to effluents
from metal finishing industry, this technology may find
application to treat metal-containing wastes generated by a
host of other industries.
For further information concerning this subject the Industrial
Pollution Control Division should be contacted.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
111
-------
ABSTRACT
This demonstration project was initiated to document the
practicality of a new evaporative approach for recovering
chromic acid from metal finishing rinse waste waters, as
well as to determine the economics of the system under
actual operating conditions in a typical job shop. An
additional objective involved verification of the theoretical
equations relating to countercurrent rinsing used in system
sizing and design.
The six-month study of chrome plating operations was conducted
by Advance Plating Company, a large job shop in Cleveland,
Ohio. The plating line was a Udylite sidearm 350 two-lane
machine utilizing a Udylite K-40 proprietary chromic acid
solution. The design of the recovery system centered around
a Corning PCR-60 vacuum climbing-film evaporative recovery
unit manufactured by Corning Glass Works. An Industrial
Filter cation exchange column was installed to remove con-
taminants from the rinse waters prior to concentration.
The active study program involved collecting and evaluating
operating and maintenance data to determine the economics of
the recovery approach as well as to investigate the effects
of varying rinse flow rates on recovery economics and rinsing
quality. The data obtained on the effects of varying the
rinse flow rate were used to study the relationship between
theoretical mathematical formulas and actual counterflow
system performance.
Results of the study showed that the recovery system can be
accommodated by an electroplating job shop with little
impact on the existing operation. The recovered chromic
acid can be successfully recycled back into the plating bath
without affecting product quality. The recovery system can
decrease chromic acid consumption significantly and is
economically viable, particularly when chemical destruction
is being practiced. The study also confirmed the accuracy
of theoretical equations for system sizing and design.
This report is submitted in fulfillment of Grant No. S-803781
by Advance Plating Company under the (partial) sponsorship
of the U.S. Environmental Protection Agency. This report
covers the period June 1, 1976 to September 30, 1976, and
work was completed as of August 15, 1976.
IV
-------
CONTENTS
Foreword ........................
Abstract ........................ iv
Figures ......................... vi
Tables ......................... vii
1. Introduction ................ 1
2. Conclusions ................. 2
3 . Recommendations ............... 3
4. Materials and Methods ............ 4
Site description ............. 4
Installation description ......... 4
Evaporator description .......... 8
Monitoring equipment ........ ... 10
j
5. The Test Program .............. 13
6. Results and Discussion ........... 15
v
-------
FIGURES
Number Page
1 1975 chrome consumption of Advance Plating .... 6
2 Recovery system at Advance Plating 7
3 Advance Plating recovery system layout 9
4 Recorder trace showing equipment start,
drain, stop cycles 11
5 Sample event recorder trace (2X) 12
6 Chrome concentration in first rinse tank 19
7 Chrome concentration in second rinse tank 20
8 Chrome concentration in third rinse tank 21
9 1975-1976 chrome consumption at Advance Plating 25
10 1975-1976 chrome consumption per rack plated at
Advance Plating 26
11 Costs for evaporating one gallon of water 35
r
12 Operation costs of the cation exchanger 36
13 Frequency of cation regeneration 37
14 Hourly operating costs of evaporator and
cation exchanger 38
VI
-------
TABLES
Number Page
1 1975 Chrome Consumption at Advance Plating 5
2 Chrome Concentrations in First, Second,
and Third Counterflow Rinse Tanks 18
3 1976 Chrome Consumption at Advance Plating 24
4 Chemical Analysis of Plating Bath 28
5 Chemical Analysis of Plating Bath 29
6 Recovery System Availability , 31
7 Cost Comparison 33
8 Savings by Recovery 40
9 Annual Out-Of-Pocket Savings 41
VII
-------
SECTION 1
INTRODUCTION
Presently, the commonly used procedure for treating metal
finishing waste waters involves separation of oil and
grease, oxidative destruction of cyanides, reduction of
chromates, neutralization, separation of the metal hydroxides
and disposal of the sludge. However, the quality of the
treated effluents is generally not suitable for recycling
and the precipitated heavy metal sludges present a potential
pollution problem when disposed of on land. As a result of
these limitations and the Federal legislative goal of no
discharge of pollutants, there has been significant emphasis
on developing, demonstrating and expanding the application
of process technology for recovering metals from metal
finishing waste waters, as well as sludges.
Recent years have seen a rapidly expanding collection of
knowledge and experience in chemical recovery efforts within
the metal finishing industry. This growing technology, both
in well-established processes and the development of new
processes, now offers metal finishers many options in
equipment selection. As a result, metal finishers now need
more information concerning the economics and performance of
the variety of recovery systems available.
Among the more attractive approaches for recovering chemicals
from metal finishing waste waters are evaporation, ion
exchange, reverse osmosis, electrodialysis, and electrolytic
techniques.
The present study focuses on providing more comprehensive
performance and economic information on a new evaporative
approach for recovering chemicals and purifying chromic acid
rinse waters for reuse.
-------
SECTION 2
CONCLUSIONS
A full-scale climbing film evaporative recovery system with
associated equipment can be successfully integrated into an
electroplating "job shop" with minimum impact on the existing
operation and without additional manpower.
Under typical plating shop conditions, the consumption of
chromic acid can decrease 80% with a minimum of equipment
supervision. Recovery can reduce the chromic acid in the
effluent from dragout by 99.98%.
The concentration and purity of the recovered chromic acids,
when accompanied by good housekeeping practices, is adequate
for recycling back into the plating bath without affecting
product quality.
The installed cdst of the equipment is sufficiently low that
equipment payback may be two years or less.
Engineering equations and nomographs currently used to
predict rinse tank concentrations under different conditions
can be used accurately for 1, 2, or 3 rinse tanks at low
rinse ratios.
-------
SECTION 3
RECOMMENDATIONS
This full-scale inplant study demonstrated the economic
validity of an evaporative recovery system for waste waters.
The project also showed that the effluent from plating rinse
dragout can be virtually eliminated.
It is recommended that the preferred technology for chromium
electroplating pollution abatement be structured around
recovery systems as opposed to neutralization and sludge
generating systems that translate a water pollution problem
into a landfill pollution problem. Recovery will significantly
reduce pollutants by internal process recycle and offer
savings from the elimination of neutralization chemicals.
Though this study was concerned only with decorative chromium
operations, other electroplating solutions are currently
being recycled successfully. It is recommended that the
Environmental Protection Agency document those systems
operating successfully and initiate efforts to study shop
impact and recovery economics for the remainder.
-------
SECTION 4
MATERIALS AND METHODS
SITE DESCRIPTION
The site selected for the demonstration project was Advance
Plating Company, Cleveland, Ohio. The plating line involved
was a Udylite Sidearm 350 two-lane machine with several
cleaning stations, a copper strike tank, a copper plate
tank, three nickel plating tanks, and a chrome plating tank,
all with appropriate rinses. This report concerns only the
chrome plating operation.
Advance Plating processes 20,000 to 25,000 racks per month
through this line which averages 20 hours of operation a
day, five days a week. The machine processes automotive
parts, appliance components, and plumbing fixtures. Though
most of the parts are zinc diecast, containing a small
percentage of aluminum, some are brass and steel.
The chromic acid used is a Udylite K-40 proprietary solution
which contains Type 107 fluoride catalyst and MSP-2 wetting
agent for mist control and dragout reduction. Barium
carbonate is added as required to maintain the proper
sulphate level.
The company's chrome consumption for this line in 1975 is
shown in Table 1 and in Fig. 1. It ranged from 225 kg
(496 Ib) to 420 kg (926 Ib) per month.
INSTALLATION DESCRIPTION
The layout of the chrome plating line and recovery loop
evaluated in this project is shown schematically in Fig. 2.
The system has four rinse tanks. The first three are in a
counterflow configuration. The fourth is a still rinse.
The first and second rinses are air-agitated. Water in the
third rinse, which also has a spray system, is kept circulating
in the tank by a pump. The fourth tank is emptied and
refilled with fresh water daily, and is maintained at 130 F
to facilitate drying.
-------
TABLE 1. 1975 CHROME CONSUMPTION-ADVANCE PLATING
ui
Month
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Days of
Operation
22
20
20
22
21
20
18
21
-
-
-
_
Chrome Consumption
kg (Ib)
225
300
329
420
314
300
240
240
254
360
269
284
(496)
(662)
(725)
(926)
(693)
(662)
(529)
(529)
(560)
(794)
(593)
(626)
Number
Racks
10,
13,
14,
16,
14,
17,
11,
11,
-
-
-
_
of
Plated
329
230
373
443
987
587
729
861
Chrome Consumption
Per Rack g (Ib)
21.
22.
22.
25.
20.
17.
20.
20.
-
-
-
_
8
7
9
5
9
1
5
2
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
-
048)
050)
051)
056)
046)
038)
045)
045)
-------
500
(1102)
400
(885)
Cfl
.a
300
S> (663)
a
LU
^
D
C/3
Z
o
o
LU
O 200
c: (441)
O
100
(220)
I I I I I I
L I I I
JFMAMJJASO
FIGURE 1. 1975 CHROME CONSUMPTION AT ADVANCE PLATING
D
-------
MAKE-UP WATER
CHROME
PLATE
CF CF
fin
R-1
R-2
R-3
DISTILLED WATER
CHROME
FROM
SCRUBBER;
1 S RECOVERED
/ CHROME
31
CATION
O
EXCHANGER
•^
\\
RINSE
FEED
I
K
fa
ICHR(
VSTO
^
)
c \
DME)
RE/
STEAM
i
P
w^m
^/AC
«
UMP
EVAPORATOR
V 1
-^ —
— ^
^
— AIR
H2O
COOL
TOWER
FIGURE 2. ADVANCE PLATING RECOVERY SYSTEM LAYOUT
-------
Rinse water containing the dragged-out chrome plating
solution flows from the first rinse tank to a two-chambered
rinse feed tank. This two-chamber configuration was used
for flow measurements, and is discussed later.
The dilute chrome rinse is pumped from one rinse feed tank
chamber into an Industrial Filter rubber-lined cation
exchanger to prevent the buildup of metallic impurities.
This column contains eight cubic feet of Dow Chemical MSC-1
resins. From the cation exchanger, the rinse water flows to
the second rinse feed tank chamber. Rinse water is then
drawn from thi's "clean" side into the evaporator by system
vacuum on demand from the evaporator level-control.
EVAPORATOR DESCRIPTION
The evaporator employed was a Corning PCR-60 plating chemical
recovery unit manufactured by Corning Glass Works. Fig. 3
shows the unit installed at Advance Plating.
Dilute rinse entering the evaporator mixes with solution
already in the unit. Water is boiled off by the steam-
heated boiler with vertical tubes — a climbing film evaporator.
The water vapor and concentrated solution enter the separator
chamber where the concentrated acid drops into the recirculatory
loop and the water vapor exits through the mist pad into the
condenser. Condensed water is removed from the system
by a liquid ring vacuum pump, and is returned to the third
rinse tank in the counter-flow rinse system.
The recovered acid remains in the system while additional
water is boiled off. An automatic controller senses when
the recovered acid reaches a pre-set concentration and
initiates a drain cycle. At Advance Plating, this concentration
was 65 ounces per gallon. The evaporator then drains 20
gallons of recovered concentrated acid into a product storage
tank. This drain cycle takes four minutes and occurs usually
once in 16 operating hours.
Services to the unit are steam, maintained between 1 and 6
psig, cooling water at flow rates up to 50 gallons per
minute, and vacuum maintained between 9 and 14 inches of
mercury.
The Corning plating chemical recovery evaporators are fully
automatic and self-alarming. The water balance is controlled
by a level controller which admits dilute feed at the same
rate at which the evaporator is boiling. The concentration
sensor assures the chemical balance of the system whether
the parts being plated are flat and have little dragout or
-------
FIGURE 3. RECOVERY SYSTEM AT ADVANCE PLATING
-------
whether they are eschuteons with pockets that create large
amounts of dragout. Recovered acid concentrate is preselected
according to the needs at hand. The setting of 65 ounces
per gallon at Advance Plating assured that the removed
volume of concentrate would be accommodated when returned to
the plating tank. Other applications have used dumping
concentrations as low as 30 ounces per gallon and as high as
160 ounces per gallon.
MONITORING EQUIPMENT
In addition to the evaporator system's standard sensing and
control equipment, special monitoring equipment was added in
order to obtain additional information demanded by the
project's objectives.
A Fisher Governor differential pressure transmitter was
installed in parallel with the evaporator's automatic
concentration controller. These continuously sensed chrome
density within the evaporator. The transmitter supplied a
3- to 15-psig signal proportional to chrome density. This
signal was recorded on a Rustrak Model 2162 strip chart
recorder.
The recorder ran 24 hours a day, and indicated when the
evaporator was started, when concentrated plating solution
was removed, when the unit was shut down, and the time
intervals between operations. These data (see Fig. 4)
enabled us to calculate the total amount of chrome recovered.
Additional special instrumentation monitored the total
amount of dilute rinse feed entering the evaporator. This
was accomplished using an event recorder that noted the time
required for the smaller section of the feed tank to drain.
This information indicated the flow rate in gallons per
hour. The total steam used was determined by measuring
steam condensate flow in a similar manner. The third recorder
trace indicated the addition of make-up water to the system.
Calculations using the data from the event recorder were
performed in the following manner (refer to Fig. 5):
Rinse Feed Rate
The volume of water in the rinse feed tank is represented by
the difference between the highest liquid level (point A, as
feed to the measuring chamber is stopped) and the lowest
liquid level (point B, as feed to the measuring chamber is
started). This was measured to be 166.54 liters (44 gal).
The time (from A to B) required to empty the chamber was
10
-------
O)
CM
START
CD
CO
O5
DRAIN
oo
STOP
FIGURE 4. RECORDER TRACE SHOWING
START, DRAIN AND STOP CYCLES
11
-------
h
PUMP
ACTUATION
HIGHEST
A LIQUID LEVEL
L
PUMP
ACTUATION
LIQUID LEVEL
D D O O OOOOOUOOOOUOOOU
FIGURE 5. SAMPLE EVENT RECORDER TRACE (2X)
-------
determined by measuring the distance between A and B and
calculating its time equivalent. The boil-off rate of the
evaporator is then:
volume of chamber/time to empty
Steam Condensate Rate
The volume in the chamber of the steam condensate tank was
measured to be 6.245 liters (1.65 gal). Multiplying the
frequency of the pump actuations (C and D, for example) by
the volume provides the steam condensate rate.
TEST PROGRAM
The test program for this project was divided into three
investigation areas: Establish a data base; conduct the
active study program; collect operating and maintenance cost
data. Data for these areas was collected simultaneously.
The Data Base
The data base was established on information gathered before
the recovery system became operational. Five aspects were
studied and further contributed to the study program and
cost analysis:
1. Measurement of trace contaminants in the bath.
2. Measurement of rinse flow rates through the
counterflow rinse system.
3. Analysis of chrome concentration in each rinse
tank.
4. History of chromic acid additions to the plating
bath.
5. History of the production rate (number of racks
plated per month).
A sixth measurement recording wetting agent additions was
not accomplished due to difficulty in obtaining accurate
readings. '
A discussion of these variables is given later in comparison
to corresponding data obtained during the operation of the
recovery system.
13
-------
The Active Study Program
The scope of the active study program involved determining
the effect that varying rinse flow rates had on recovery
economics and rinsing quality. These data were used to
determine the relationship between the theoretical mathematical
formulas used in sizing evaporator equipment and actual
counterflow system performance.
Cost Data Collection
The determination of operating costs and recovery efficiency
of the evaporative recovery system relied on measurements
made prior to operation (the data base) as well as actual
operating data. For this purpose, additional information
was recorded on variables such as cooling water flow rates,
steam and electrical consumption, and rate of return of the
product to the plating bath.
14
-------
SECTION 5
RESULTS AND DISCUSSION
CHROME CONSUMPTION AND DRAGOUT
Key reasons for collecting data on chrome usage prior to the
start-up of the recovery system were to determine the
plating bath dragout rate and to establish a basis for
comparison when looking at recovery economics.
Average dragout rate can be calculated by using the average
operating time of 20 hours per day, the number of operating
days per month and the chrome consumption for that month.
As mentioned earlier, the chrome consumption for Advance
Plating in 1975 is presented in Table 1 and Fig. 1. Using
these figures, the calculation provides an average chrome
usage of 2.73 liters (0.72 gal) of bath per hour. Previous
experience has shown that approximately 10% of the chrome
used is actually plated on the ware while 90% is dragged out
to the rinse waters.
Using that same ratio, a dragout rate of 2.46 liters (0.65
gal) of plating bath per hour can be expected. The average
plating bath concentration at the time the data was collected
was 300 g/1 (40 oz/gal).
In order to verify the magnitude of the dragout rate, a
second method of measurement was also used. For this
measurement, the first rinse tank was filled with clear tap
water. The chrome content in the first rinse was measured
hourly for four hours with the following results:
Sample Taken gm/1 Cr03
Start 0.0022
After 1 hour 0.92
After 2 hours 1.90
After 3 hours 2,77
After 4 hours 3.81
Average increase in concentration per hour was 0.95 g/1 or
0.127 oz/gal. The volume of the rinse tank is 1014 liters
(268 gal) making the amount of chrome carried into the first
15
-------
rinse tank 963 gm (34 oz) per hour or 3.1 liters (0.81 g)
per hour of dragout. Bath concentration was measured at
312 g/l (42 oz/gal).
The first calculated dragout rate of 2.46 1/hr (0.65 gph)
represents an average over an extended period of time. This
number may be slightly inaccurate because of changing bath
concentrations and the fact that during a working day not
all racks of ware are chrome plated.
The second calculation of 3.10 1/hr would be nearer the
maximum dragout rate encountered, since it assumes that all
plated parts go through the chrome plating tank. The actual.
figure lies between these two numbers and the use of any
dragout rate within these values is accurate for the scope
of this evaluation. For analytical purposes in this report,
we use 2.84 liters/hour (0.75 gph) at a bath concentration
of 300 grams/liter (40 oz/gal).
RINSE TANK PERFORMANCE
The theoretical rinsing equations discussed by Pinkerton and
Graham^ have been shown by Abegg^ to be in the general
form:
CO = R(n+1)-l
Ci
which, for large values of R, reduces to:
Co = R1 , (2)
Ci
where Co = concentration in the plating bath, C^ = concentration
in the "ith« rinse tank in the series (i = 0, 1, 2, ... n),
n = number of rinse stages in the countercurrent series, and
R = rinse ratio defined as rinse flow rate/dragout rate.
A.K. Graham and H.L. Pinkerton, Electroplating Engineering
Handbook, Chapter 34, Rinehold Publishing Corp., NY. 1971.
Dr. C. Abegg, "A Practical Simplified Form of the General
Countercurrent Rinsing Equation". Corning Glass Works,
Corning, NY, internal document.
16
-------
With this equation, the concentration in any countercurrent
rinse position can be calculated. This, of course, assumes
perfect rinsing. Pinkerton and Graham state: "Good practice
will approach this ideal as closely as possible by incorporating
the following features:
1. Vigorous agitation of the rinse water with air.
2. Introduction of fresh water at the bottom of the
tank.
3. Placing the overflow weir at the opposite end of
the tank from the point at which water is introduced."
Advance Plating incorporates a rinsing system that is
probably more typical than perfect. The first recommendation
is incorporated in the first two tanks; the second is found
in all three tanks, while the third is not used at all.
Samples of the rinse tank waters from each of the three
counterflow rinse tanks were taken at regular intervals and
analyzed for chrome content (Table 2). Since the dragout
rate from the plating bath was calculated and the rinse flow
rate was known, the rinse ratio can be calculated. Comparison
of the data collected and theoretical curves indicate close
agreement between the actual and calculated performances in
the first rinse tank (Fig. 6). The curve represents theoretical
concentrations based on the actual dragout rate at Advance
Plating. The points (from the data in Table 2) are actual
concentrations at given rinse rates.
Data on rinse flow rates taken before start-up of the
recovery system illustrate the typical use of higher rinsing
rates. (The data points at high rinse ratios are shown near
the horizontal slope of the curve.) The data plotted below
rinse ratio 100 was taken during the active test program and
reflect operation at very low rinse ratios typical of such a
recovery system.
\
Similar agreement between actual and theoretical performances
for the second and third rinse tanks is shown in Pigs. 7 and
8.
From this comparison of actual and theoretical data, the
following conclusions and recommendations are drawn:
1. Agreement between theoretical and actual performances
for the first, second and third rinse tanks at
lower rinse ratios is excellent and tends to
verify dragout estimates.
17
-------
TABLE 2. CHROME CONCENTRATIONS IN FIRST,
SECOND AND THIRD COUNTERFLOW RINSE TANKS
00
Date
10/3/75
10/10/75
10/15/75
10/17/75
10/22/75
10/24/75
1/14/76
1/16/76
2/4/76
3/2/76
3/10/76
7/15/76
7/16/76
7/20/76
First
Rinse
g/1 (oz/gal)
1.
0.
1.
1.
0.
0.
3.
3.
4.
6.
3.
20.
27.
31.
08
75
13
13
56
75
00
00
50
00
80
00
50
70
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(2.
(3.
(4.
126)
100)
150)
150)
075)
100)
400)
400)
600)
800)
500)
660)
660)
220)
Second
Rinse
ppro
15.
37.
-
-
-
-
125.
119.
104.
110.
132.
640.
1260.
2000.
0
5
0
0
0
0
0
0
0
0
Third
Rinse
ppm
4.
-
-
-
-
-
15.
18.
14.
23.
78.
67.
184.
240.
5
0
0
0
0
0
0
0
0
Rinse
Rate
1/hr (gph)
1272
1090
636
659
659
704
136
151
148
151
167
45
31
34
(336)
(288)
(168)
(174)
(174)
(186)
(36)
(40)
(39)
(40)
(44)
(12)
(8)
(9)
Rinse
Ratio
R
420
360
210
217
217
232
45
50
49
50
55
15
10
11
-------
50-
45-
40-
D>
*f
Z
at
OT
Z
cc
C/5
DC
30-
25-
ACTUAL CHROME
CONCENTRATION LEVELS, g/l
z
HI
o
o
o
20-
15-
•THEORETICAL LEVELS
10-
I
100
150
I
200
I
250
I
300
I
350
I
400
450
FIGURE 6,
RINSE RATIO
CHROME CONCENTRATION IN FIRST RINSE TANK
-------
ACTUAL CHROME
CONCENTRATION LEVELS, ppm
10
20
30
60
70
80
FIGURE 7.
50
RINSE RATIO
CHROME CONCENTRATION IN SECOND RINSE TANK
-------
300
E
Q.
a.
C/J
£
Q
(X
I
250
200
ACTUAL CHROME
CONCENTRATION LEVELS, ppm
150
o
o
o
111
o
DC
o
100
50
50
RINSE RATIO
60
70
FIGURE 8. CHROME CONCENTRATION IN THIRD RINSE TANK
-------
2. Higher than theoretical values in the third rinse
tank at high rinse ratios are probably due to
either or both of two factors: Less-than-perfect
rinsing conditions; and, at higher flow rates,
distilled water returning from the evaporator
still containing trace amounts of chrome.
3. If chrome content of less than 10 ppm is desired
in the final rinse, the distilled water should be
returned to the next-to-last tank and the final
rinse should be maintained as a flowing rinse
outside the recovery loop.
One important question concerns the effect that low rinse
ratios have on the cleanliness of the final product.
Discussions with production personnel at Advance Plating
revealed that at all times, even with rinse ratios as low as
12, the quality of rinsing was adequate. Throughout the
test program, no change in the appearance of the ware due to
inadequate rinsing was noticed.
CHROME RECOVERY
A comparison of the bath concentration and the concentration
in the third rinse in the system gives the percent of chrome
recovered. That is:
% Recovery = (C -Cn> X 100 , (3)
~C~o
where C0 = plating bath concentration, and Cn = concentration
of the last rinse tank in the recovery loop. A theoretical
recovery rate of 99-98% is achieved by using a value for C
from Fig. 8, a recommended rinse ratio of 15 and a bath
concentration of 300 grams/liter. Compared to a system
without recovery, the evaporator reduced to 0.02% the
chromic acid in the effluent from dragout.
As shown earlier, the dragout rate from the plating tank is
approximately 2.84 1/hr (0.75 gph) at a bath concentration
of 300 grams/liter (40 oz/gal). This gives a recovery rate
of 850 grams/hr (1.875 lbs/hr) of chromic acid. This number
will be used later when considering the economics of the
evaporator's operation.
REDUCTION IN CHROME CONSUMPTION
Part of the data-gathering program involved recording chrome
consumption for the plating line before and after recovery
system start-up. With this data, the degree to which
contaminants leaving the plating line is reduced can be
determined.
22
-------
Table 3 shows the monthly chrome consumption of Advance
Plating after recovery began in mid-January 1976. Fig. 9
combines the information from Tables 1 and 3 giving 1975-
1976 chrome consumption. Fig. 10 is an extension of Fig. 1
and graphically shows how the consumption was adjusted for
changes in production rates.
From the last columns in Tables 1 and 3, the average chrome
consumption per rack plated before and after start-up of the
recovery system is compared to show an 80% decrease from 20
grams to 4 grams per rack. February consumption was treated
as being prior to start-up since the reclaimed chrome was
not recycled into the plating bath until March.
Several factors can explain the difference between the 99+%
theoretical recovery rate and the 80% actual reduction rate
for chrome consumption.
One factor to be considered is the fact that the installation
is owned by and under the control of the plating shop. If,
at the shop's discretion, the unit is not operated, no
recovery takes place.
A second factor is down-time due to equipment failure, which
produces a zero recovery rate during the time the equipment
is not operating. This factor will be discussed in more
detail later.
A third consideration is that this evaporator sys'tem was
installed such that it could not be operated while the ion
exchange unit was being regenerated. Operating the evaporator
during this regeneration period, however, would not have
any unfavorable effects on the plating bath since cation
buildup would have been minimal. It should be noted that
this system will be changed to allow simultaneous regeneration
and recovery.
And, finally, 10% of the chrome is plated on the ware.
CONTROL OF CONTAMINANTS
The primary function of the cation exchanger was to remove
cationic contaminants from the chrome-bearing rinse waters
prior to concentration by the evaporator. The ion exchanger
was initially sized by measuring the chrome build-up in the
first rinse tank over four hours. The tank was first filled
with tap water and operated as a still rinse. In determining
the contaminant level, it was assumed that contaminant
dragout would be proportional to contaminant concentration
in the plating bath.
23
-------
TABLE 3. 1976 CHROME CONSUMPTION-ADVANCE PLATING
to
Month
January
February
March
April
May
June
July
Chrome Consumption
kg (Ib)
314
314
0
91
204
91
91
(694)
(694)
(0)
(200)
(450)
(200)
(200)
Numbers of
Racks Plated
Chrome Consumption
Per Rack
g db)
Not Available
19,
23,
22,
24,
24,
18,
555
273
970
432
538
239
16
0
4
8
3
5
.4
.0
.0
.3
.7
.0
(0.
(0.
(0.
(0.
(0.
036)
(0)
009)
018)
008)
Oil)
-------
(Jl
500
(1102)
400
O (885)
o
o
uj 300
S (663
O
-------
to
en
27.2
(0.06)
22.3
(0.05)
18.1
(0.04)
o
O
cc
x
O
13.6
(0.03)
9.0
(0.02)
4.5
(0.01)
EVAPORATOR
START-UP
DATA
INCOMPLETE
I
I
I
1
1
I
I
I
I
I
1
I
JFMAMJ JAJ FMAM
FIGURE 10. 1975-1976 CHROME CONSUMPTION PER RACK PLATED AT ADVANCE PLATING
-------
The earlier presentation of this data showed the dragout
rate to be 2.84 1/hr (0.75 gph). Table 4 presents a chemical
analysis of the contaminants in the plating bath and the
still-rinse water.
Discussion with representatives of Industrial Filter indicate
that the cations are absorbed in their ion exchange units at
a level of 1.5 Ibs. for each cubic foot of resin. This
suggested that a four-cubic-foot exchanger would handle the
contaminant loading. The eight-cubic-foot unit was chosen
for this study in order to provide margin for extra capacity.
Periodically, plating bath and recovered solution samples
were sent to an independent laboratory in Cleveland for
chemical analysis. Results of these analyses are presented
in Table 5 and are discussed in the following section.
SYSTEM IMPACT
Plating Quality
During the first three months of operation, no notable
plating quality problems were encountered. In May, a
problem with clouding of the ware resulted in a higher than
normal reject level. Since rinsing quality had no effect on
the appearance of the ware, contamination of the plating
bath was suspected.
In mid-June the plating bath was replaced with a similar
solution from another plating operation being moved into
Advance Plating's shop. This action was taken because the
replacement bath was readily available. The replaced
plating bath was not examined further, so the actual cause
of the ware clouding was never determined. However, some
probable causes were studied. Chemical analysis by the bath
supplier indicated a less than optimum ratio of active
fluoride to total fluoride in the catalyst. This condition
may have been caused by a high level of aluminum cations
complexing excessive amounts of free fluoride.
Three possible solutions to this problem have been proposed
and will be implemented in the near future:
1. Remove more quickly any parts dropped into the
plating bath.
2. Artificially increase dragout so that the bath has
less dwell time in the plating tank before being
cycled through the cation exchanger. This minimizes
the effect of dropped parts.
27
-------
TABLE 4. CHEMICAL ANALYSIS DATED JUNE 19, 1975
SOLUTION CHECKED - PLATING BATH
DRAGOUT RATE - 2.84 LITERS/HOUR
Content
Metal Ion Grams/ Liter
Trivalent Cr
Iron
Copper
Nickel
Zinc
Magnesium
Calcium
Sodium
Tin
1.1
0.17
0.32
0.67
3.7
0.038
0.030
0.49
0.028
Dragged Out Of
Plating Bath in 1 Hour
gm oz.
3.12
0.48
0.91
1.90
10.51
0.108
0.085
1.39
0.080
0.11
0.017
0.032
0.067
0.374
0.004
0.003
0.049
0.003
Total Contaminants/Hour
Contaminant Level After One Week
(3 shift/day operation)
18.58
2230
0.66
79.2
(4.95 Ib)
28
-------
TABLE 5. CHEMICAL ANALYSIS OF PLATING BATH
(All data in grams/liter)
Metal Ion
Total Cr
Trivalent Cr
Iron
Copper
Nickel
Zinc
Magnesium
Calcium
Sodium
Tin
Aluminum
Before
Start- Up
131.00
1.10
0.17
0-32
0.67
3.70
0.038
0.030
0.49
0.28
0.11
Start
+3 Months
118.00
0.31
0.22
0.37
1.90
7.00
0.39
0.38
0.79
0.084
0.37
Start
+4 Months
119.00
0.20
0.48
0.37
2.00
6.80
0.40
0-48
0-77
0.07
0.32
Recovered
Solution
117.00
0.38
0.97
0.16
0.58
2.00
0.19
0.50
0.93
0.052
0-16
29
-------
3. Better programming of cation regeneration.
Plant Operations
In order to describe the effect the recovery system had on
plant operations, a session was held at the conclusion of
the project with plant personnel at all levels, from equipment
operator to president. Comments on the system made during
this meeting emphasized several important factors:
Operational
1. Operator averaged 10 minutes per day routinely
attending the unit.
2. Operator spent two hours per week regenerating the
ion exchange system.
3. No additional people hired; the full operation was
handled by existing manpower -- one man.
4. No rinsing problems noted throughout the test
program.
5. Manual chromic acid additions were drastically
reduced.
6. Discovered that the evaporator drained when plant
air was shut off for the weekend - manual valve
installed to prevent recurrence.
Routine Maintenance
Other than normal operation of equipment, the system
required only minor maintenance.
SYSTEM RELIABILITY
The reliability of the recovery system was determined from
the traces on the differential pressure recorder chart. In
this data, "availability" was defined as including all
periods in which the recovery system was functional, even
though it was not actually being run. If the unit failed
while operating or if it couldn't be started because of
mechanical problems, it was considered as being unavailable
or "down". Table 6 details the availability of the equipment.
30
-------
TABLE 6. RECOVERY SYSTEM AVAILABILITY
Month Hours Up
Jan. 761
Feb. 76
Mar. 76
Apr. 76
May 76
June 76
July 76
Feb-July Total:
192
367
391
309
343
371
2613
2042
Hours Down
572
5
13
2
0
14
0
34
% Operational
77%
99%
97%
99%
100%
91%
100%
98.3%
Start-up mid-January.
2 Downtime included travel time of an engineer from Corning,
New York to Cleveland to observe repair.
3 Recorders turned off for a portion of the month, yielding
a lower total operating time being monitored.
31
-------
It should be noted that the high downtime figures in January
and June directly resulted from Coming's desire to observe
first-hand any problems encountered. As a result of this
policy, travel time from Corning, New York, to Cleveland
significantly increased the total downtime.
No repair took longer than one hour to complete.
COST ANALYSIS
Installation Costs
This demonstration project has proven the validity of the
theoretical rinsing equations. With the average dragout at
Advance Plating of 2.84 1/h (0.75 gph) an evaporator with a
capacity of 45.42 1/h (12 gph) would be suitable. The Model
PCR-60 evaporator used at Advance Plating was selected in
order to achieve the objectives of the study. The impact
upon system cost is shown in Table 7 by comparing the costs
of the demonstration unit and one that is properly sized - a
Model PCR-20.
Operating Costs
A major objective of this study was to evaluate the economics
of the operating evaporative recovery system. This system
is economically viable if the system operating costs are
less than the savings as measured by
(a) Reduced procurement of new chromic acid,
(b) Reduced procurement of chemicals required to
prepare the chromic acid effluent for waste disposal,
(c) Reduced charges for the transportation and landfilling
of the sludge, and
(d) The cost of the water previously used in rinsing.
At Advance Plating these savings were:
a. Purchase price ... $.915 per pound at Advance
Plating.
b. Neutralization chemicals ... not done at Advance
Plating.
32
-------
TABLE 7. COST COMPARISON
Demonstration
Unit
PCR-20 Cr
Equipment
Evaporator (PCR-60 Cr)
Tanks
Pumps
Cation Exchanger
Piping , .
Cooling Tower
Miscellaneous
$ 32,500.00
1,647.66
753.55
6,195.00
2,496.55
3,339.27
453.13
$ 47,385.16
$ 19,900.00
1,647.66
753.55
6,195.00
2,496.55
3,339.27
453.13
$ 34,785.16
(1)
Cooling tower costs were calculated at 20%
of total tower installation since only a
portion of the water is used for the recovery
system.
Installation - Labor and Materials
Site Preparation
Plumbing
Electrical
Equipment Erection
Miscellaneous
$ 257.33
2,864.07
1,228.75
268.63
501.99
$ 5,120.77
$ 257.33
2,864.07
1,228.75
268.63
501.99
$ 5,120.77
Total Installation Cost
Equipment
Labor and Materials
$ 47,385.16
5,120.77
$ 52,505.93
$ 34,785.16
5,120.77
$ 39,905.93
The above totals do not include those expenses relating only
to purchase and installation of monitoring equipment required
specifically for this project.
33
-------
c. Sludging and trucking to landfill ... not done at
Advance Plating.
d. Rinse waters saved by recycling ... not evaluated.
The cost to operate the recovery system is made up of the
following factors:
a. Utility costs to operate the evaporator: steam,
water, electricty.
b. Labor costs to operate the evaporator.
c. Chemical and utility cost to operate the cation
exchanger.
d. Labor costs to operate the cation exchanger.
They are discussed below.
Utility and Labor Costs ... Evaporator
Detailed experiments have shown that boiler steam efficiency
is 93%. Fig. 11 details the utility and labor costs to
operate an evaporator. The electrical consumption was based
upon the vacuum pump motor horsepower and the horsepower to
recirculate the condenser cooling water through the cooling
tower. Cooling tower make-up water rate was 2% of the flow
rate through the condenser. All utility charges were those
in effect at Advance Plating during the study.
Utility and Labor Costs ... Cation Exchanger
The operation of the cation exchanger was also a major
contribuion to operating costs. These charges are shown in
Figs. 12 and 13. Figure 14 shows the total operating costs
per hour versus the size of the evaporator selected. The
larger the evaporator, the greater the cost for steam.
Savings Realized
Table 8 also shows that for each pound of proprietary
chromic acid recovered, Advance Plating saves approximately
$.50 over the purchase of new chrome. When considering the
use of chemical treatment as an alternative adds additional
cost, the savings are significantly greater.
Opinions as to the actual cost of chemical destruct are
varied and it is beyond the scope of this project to determine
them. However, the cost to treat one pound of chromic acid
34
-------
Figure 11. Costs for evaporating
one gallon of water
Utilities
^ Steam ($1.70/M Ibs using 80% conversion from natural gas
to steam)
8.33 Ibs/gal. x 1.08 (efficiency) x $1.70/M lbs.= $.015/gal
Electricity (.0314/KWH)
6 HP (0.745 KW/HP) ($0.0314/KWH) ( 6Q * h—) = $0.003/gal.
Cooling water ($0.56/M gal.) .
(3000 gph) (0.02) ($0.56/M gal.) ( 60 h—) = $0.00056/gal,
Utility Cost to Evaporate One Gallon of Water = $0.0186/gal,
Labor
Start time, stop time and observance of evaporator totalled
10 minutes/day. For a 100-hour week, labor cost was:
(10 minutes/day x (5 day/week) x ( -^ hour/minutes)
($18.00/hr) (-- hours/week) = $.15/hour
35
-------
Figure 12. Operation costs of the cation exchanger
Utilities
Electricity
2 HP (0.745 KW/HP) ($0.0314/KWH) = $0.047/hr
Regeneration Chemicals for Each Cycle
H2So4: 122 Ibs x $.044/lb = 5.40
Caustic: 104 Ibs x .087/lb = 9.00
$14.00
Labor Cost
2 hours for a Regeneration - 2 hrs x $18/hr = $36.00
36
-------
Figure 13. Frequency of cation regeneration
Cation unit used had 8 cu. ft. resin. This can be loaded to
12 #. However, for programming purposes, 8# loading is the
regeneration time.
81 Loading
.7 ounce/cations hour
16 ounces
1#
=
Cation Regeneration Costs
Labor
Regeneration Chemicals
$36.00
14. 40
$40.40
$/Hour
.221
Utilities
Total
.047
$.268/hr
37
-------
00
S3.50
$3.00
$2.50
DC
I
e»
co"
"co $2.00
O
O
-U
z
I $1.50
O
S1.OO
$.50
10
20
30
40
50 60
CAPACITY GPM
70
80
90
1OO
FIGURE 14.
HOURLY OPERATING COSTS OF THE SYSTEM EVAPORATOR
AND CATION EXCHANGER VERSUS CAPACITY
-------
can be simply added to the out-of-pocket savings detailed in
Table 8 for the total savings over a treatment system. For
example, assume a destruct cost of $1.00 per pound and a
counterflow rinsing system using a 20 GPH evaporator, then
the total savings realized per pound of chrome recovered is
$1.50.
Estimated Savings in Your Shop
A model to estimate savings for every electroplater is shown
in Table 9 using the following assumptions.
1. Utility costs are identical to those at Advance
Plating.
2. Evaporator is sized at 15 times the average
dragout.
3. Concentration of chromic acid is 300 grams/liter
(40 oz/gal).
4. Purchase price of proprietary decorative chrome is
$.915/lb.
39
-------
TABLE 8. SAVINGS BY RECOVERY
Dragout Gallons/hour .75
Ib/hour 1.875
Value of recovered chrome @ $.915/lb ......... . ................. $1.72
Reduction of neutralization chemicals .......................... none used
Reduction of sludge trucking charges ........................... none used
Reduction in water usage ....................................... not evaluated
_
Total savings $/Hour $1.72
Cost to operate a 20 GPH recovery system (Fig. 13) $/Hour ...... $ .79
Net savings $/Hour $ .93
or
Net savings $/# chrome recovered $ .50
-------
TABLE 9. ANNUAL OUT-OF-POCKET SAVINGS* ($)
DRAGOUT #/HOUR
1
2
4
10
WITHOUT
1 SHIFT
$ 1160
$ 2320
$ 4640
$11600
WASTE TREATMENT
2 .SHIFTS 3 SHIFTS
$ 2320 $ 3480
$ 4640 $ 6960
i
$ 9280 $13920
$23200 $34800
WITH WASTE TREATMENT
MULTIPLY ABOVE VALUES
COST FOR
DESTRUCTION
$ .25/lb
$ .50/lb
$ .75/lb
$1.00/lb
BY THESE FACTORS
FACTOR
1.43
1.86
2.29
2.72
*Rinse Ratio 15:1
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. |2.
EPA-600/2-78-127
4. TITLE AND SUBTITLE
Evaporative Recovery of Chromium Plating Rinse
Waters
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
June 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
Leonard N. Elicker, Advance Plating Company
Roger W. Lacy, Corning Glass Works, Corning, N.Y.
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Advance Plating Company
Cleveland, Ohio 44103
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
S803781
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab., Cinn, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
IB. ABSTRACT Tnis demonstration project documents the practicaXity or a new evaporative
approach for recovering chromic acid from metal finishing rinse waste waters, as well
as the economics of the system under actual operating conditions.
The six-month study of chrome plating operations was conducted by Advance Plating
Company in Cleveland, Ohio. The design of the recovery system centered around a
Corning PCR-60 climbing-film evaporative recovery unit manufactured by Corning Glass
Works, a cation exchange column and monitoring equipment.
The test design established a preliminary data base from information collection prior
to system operation. Histories of chemical use were also compiled to aid in the
cost analysis.
The active study program involved collecting and evaluating data to determine the
economics of the recovery approach as well as investigating the effects of varying
rinse flow rates economics and rinsing quality. Results of the study showed that the
system can be accommodated with little impact on the existing operation. The recovered
chromic acid can be recycled back into the bath without affecting product quality.
The recovery system can decrease chromic acid consumption significantly and is econom-
ically viable.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Evaporation
hromic acid
Materials Recovery
Waste water
Electroplating
Chrome Plating line
Vacuum, climbing-film
evaporator
68D
3. DISTRIBUTION STATEMENT
lelease to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
50
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
42
* U.S. GOVERNMENTPRINTING OFFICE: 1978—757-140/1359
------- |