p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

88) ll-B-62 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:31 AM Sheet 88 of 99 
MRI® 

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A-88-02 

MIDWEST RESEARCH INSTITUTE 

"••I -<i-V2 . Suite 350 

401 Harrison Oaks Boulevard 

Cary. N.C. 27513 

Date: February 14, 1989 

(Finalized May 5, 1989) 

Subject: California Air Resources Board (CARB) 

Demonstration Testing Project 

Chromium Electroplating NESHAP 

EPA Contract 68-02-3817; ESD Project 85/02a 

MRI Project 7717-K 

From: Robin Barker 

To: Andrew M. Smith 

ESD/ISB/SSS (MD-13) 

United States Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

I. Introduction 

The California Air Resources Board (CARB), in conjunction with the 

Metal Finishing Association of Southern California, has undertaken a 

program to perform demonstration tests on various control devices to 

determine their effectiveness for removing chromic acid mist generated 

from hard chromium plating tanks. During the week of January 23, 1989, CARB 

performed emissions tests on a Monsanto Enviro-Chem fiber-bed mist 

eliminator. These emissions tests were conducted at Electronic Chrome 

Company in Santa Fe Springs, California. Mr. Andrew M. Smith of the U. S. 

Environmental Protection Agency (EPA) and Ms. Robin Barker of Midwest 

Research Institute (MRI) were present during the emissions tests to 

observe process and control device operations and testing procedures. In 

addition, EPA and MRI personnel visited two other facilities where CARB 

plans to perform demonstration tests on a ventilation system and scrubber 

unit manufactured by CM&E International, a fan/separator scrubber 

manufactured by Tri-Mer, Inc., and a fiber-bed mist eliminator 

manufactured by CECO. 

II. Monsanto Fiber-Bed Mist Eliminator—Electronic Chrome Company 

A. Process Description 

Electronic Chrome Company is a medium size job shop that performs 

hard chromium plating of aircraft parts and oil drilling equipment. The 

company has six hard chromium plating tanks in operation. During this 

emission test program, Tank No. 1 was the only tank tested. 

Tank No. 1 is 1.7 meters (m) (5.5 feet [ft]) long, 0.76 m (2.5 ft) 

wide, and 4.0 m (13.0 ft) deep and holds approximately 4,960 liters (a) 

(1,310 gallons [gal]) of plating solution. The freeboard space in the 

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tank is 9.0 to 10.0 centimeters (cm) (3.5 to 4.0 inches [in.]). The 

plating solution contains chromic acid in a concentration of about 

240 grams per liter (g/a) (32 ounces per gallon [oz/gal]), and sulfuric 

acid is used as a bath catalyst. The normal operating temperature of the 

bath is approximately 52° to 54°C (125° to 130°F). A heating and cooling 

system is installed on the tank to maintain the plating temperature within 

the normal operating range. The plating solution is continuously 

filtered, and the tank is air agitated to maintain uniform chromic acid 

concentration and plating bath temperature. Two rectifiers are used to 

control the current in the tank. The maximum rated current and voltage 

for both rectifiers is 5,000 amperes and 15 volts. 

Tank No. 1 is equipped with double-sided lateral hoods, and the 

ventilation air is ducted into a main duct along with the ventilation air 

from Tank No. 3, which is 2.1 m (7.0 ft) long, 0.86 m (2.8 ft) wide, and 

1.9 m (6.3 ft) deep. The total ventilation rate for both tanks is 

99 actual cubic meters per minute (m /min) (3,500 actual cubic feet per 

minute [ft /min]). Figure 1 presents a schematic of the ventilation 

system on Tank Nos. 1 and 3. Emissions from both plating tanks are 

controlled by a double packed-bed scrubber located on the roof of the 

plating shop. The recirculation water from the scrubber is used 1n both 

tanks as makeup for plating solution evaporation losses. Twice a day a 

total of approximately 190 i (50 gal) of recirculation water is drained to 

the plating tanks. 

B. Process Operation During Testinq 3 

Monsanto Enviro-Chem donated a small, 11 m /min (400 ft /min) fiberbed mist eliminator for use in the demonstration test. The main duct in 

the ventilation system was breeched to provide a slip stream to be treated 

by the fiber-bed mist eliminator. Figure 2 presents a schematic of the 

ventilation system, slip stream, and the fiber-bed mist eliminator. Prior 

to the demonstration test, preliminary testing was conducted at locations 

in the slip stream and main ventilation duct to determine the representativeness of the slip stream with respect to gas velocity and total 

chromium concentration. The preliminary tests were conducted by Pacific 

Environmental Services, Inc., of Arcadia, California, a contractor for the 

Metal Finishing Association of Southern California. 

The preliminary test results indicate that the velocity in the slip 

stream (5.8 meters per second [m/s]) (18.9 feet per second [ft/s]) was 

30 percent lower than the velocity in the main duct 8.3 m/s (27.3 ft/s). 

The hexavalent chromium concentration measured in the slip stream6was 

0.00356 milligram per dry standard cubic meter (mg/dscm) (1.6x10" grain 

per dry standard cubic foot [gr/dscf]) compared to a hexavalent chromium 

concentration of 0.00239 mg/dscm (1.0x10" gr/dscf) measured in the main 

duct. Test results indicate that sampling at the inlet to the fiber bed 

mist eliminator was only 86 percent isokinetic, which does not fall within 

the acceptable EPA range for isokinetic testing (90 to 110 percent). 

Outlet sampling was within the acceptable isokinetic range at 103 percent 

of isokinetic. 

a2^ 
TO SCRUBBER 

LEGEND: 

AA - Reference point 

BB - Reference point 

CC - Reference point 

PLATING TANK NO. 3 

PLATING TANK NO. 1 

co 

Figure 1. Schematic of ventilation system on Tank Nos. 1 and 3 at Electronic Chrome Company. 

(v> 
TO SCRUBBER 

LEGEND: 

AA - Reference point 

BB - Reference point 

CC - Reference point 

FLOOR 

ROOF -

FIBER-BED MIST 

ELIMINATOR 

SLIP STREAM 

• . A 

UV 

PARTICULATE 

FILTER 

SEAL POT 

Figure 2. Schematic of ventilation system, slip stream, and fiber-bed mist eliminator 

at Electronic Chrome Company. 

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Three mass emission test runs each ranging from 6 to 10 hours in 

duration were conducted simultaneously at the inlet and outlet of the 

demonstration test unit. Tank No. 3 was not operated during any of the 

emission tests. Test ports are designated as letters A, B, and C on 

Figure 2. The duct diameter at the inlet was 15 cm (6.0 in.) and at the 

outlet location was 14 cm (5.5 in.). Location A was used as the sampling 

port, and location B was used to determine the velocity and flow 

characteristics for inlet testing. There was approximately 0.76 m 

(2.5 ft) of straight duct between the two locations. Location C was used 

to determine flow characteristics at the outlet and to perform outlet 

sampling. 

Two test ports were used at the inlet of the control device as 

recommended by EPA Method IA for sampling in ducts less than 30 cm 

(12 in.) in diameter. Continuous monitoring of the velocity was desired, 

so a velocity traverse was performed at the sampling port and at a port 

downstream, to confirm that there was no variation in velocity between the 

two points. During testing, the velocity was monitored continuously at 

the downstream port. When sampling was completed, another velocity 

traverse was performed at both ports to ensure there still was no 

variation in velocity between the two locations. Two test ports are 

reconmended to minimize the flow restriction of the gas stream when the 

sampling probe and pitot tube are both placed in the same port. 

A filter was located upstream from the fiber-bed mist eliminator to 

remove any particulate that might cause plugging in the mist eliminator. 

The glass fibers in the particulate filter are approximately 100 microns 

(4.0 thousandths of an inch [mils]) in diameter. The pressure drop across 

the filter was 0.25 kilopascals (kPa) (1.0 in. w.c) . Particulate filters 

are considered standard preventive maintenance equipment before fiber-bed 

mist eliminators for all of Monsanto Enviro-Chem installations. Figure 3 

presents a schematic of the fiber-bed mist eliminator. The mist 

eliminator consists of two concentric screens attached to a top flange and 

a bottom drain plate. Glass fiber is wound into the annular space between 

these screens to form a bed with a radial thickness of 5 to 8 cm (2 to 

3 in.). The glass fibers in the annular space are approximately 

10 microns (0.4 mil) in diameter, and the pressure drop across the unit is 

2.0 kPa (8.0 in. of water column). The actual flowrate in the slip 

stream during outlet testing was 8.0 dry standard m /min (280 dry standard 

ft/min). 

The fiber-bed mist eliminator is equipped with two spray nozzles. 

One spray nozzle is located at the top of the unit and is used to wash 

down any large particulate which may clog the mist eliminator, and the 

other spray nozzle is located at the bottom of the unit and is used as an 

aerosol spray to remove any contaminants that can crystallize in the mist 

eliminator and cause plugging or improper drainage. These spray nozzles 

were not operating during the emission tests because no increase in 

pressure drop was observed above the design level which would indicated 

potential plugging. The fiber bed must be replaced when the design 

pressure drop is exceeded by 0.75 to 1.0 kPa (3 to 4 in. w.c) . 
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The critical design parameters for fiber-bed mist eliminators are 

the pressure drop across the unit, the collection efficiency required, 

fiber diameter, bed thickness, surface area of the fiber-bed, and the gas 

flow rate. Fiber-bed mist eliminators manufactured by Monsanto EnviroChem are designed for specific operations at a given plant. The 

demonstration unit was designed for a maximum gas flow rate of 11 m /min 

(400 ft /min) at a pressure drop of 2.0 kPa (8.03in. w.c) . The unit will 

operate efficiently at gas flow rates up to 11 m /min (400 ft /min) if the 

design pressure drop is not exceeded. This is because fiber-bed mist 

eliminators designed to remove particles by Brownian diffusion do not have 

a lower limit on gas velocity; as velocity decreases, collection 

efficiency of particles increases. 

During test run Nos. 1 and 2, two hydraulic rods measuring 11.0 cm 

(4.5 in.) in diameter and 2.8 m (9.0 ft) in length were plated at a 

current of 3,100 amperes. During test run No. 3, one roll measuring 15 cm 

(6.0 in.) in diameter and 3.7 m (12.0 ft) in length was plated at a 

current of 3,700 amperes. During emission testing, only one rectifier was 

required to control the current in the tank. The tank's air agitation 

system and recirculation system were not in operation during testing. At 

CARB's direction, polypropylene balls were added to the plating tank. 

Approximately 80 percent of the tank's surface area was covered by the 

polypropylene balls. As observed during visits at other facilities that 

use polypropylene balls, the balls were displaced several inches away from 

the cathode (item plated) by the hydrogen gases formed at the cathode 

during periods of actual plating (i.e., current flow). 

Other observations made during testing that cause concern over the 

quality or representativeness of the demonstration include: (1) the total 

ventilation rate for Tanks 1 and 3 was 99 actual m /min (3,500 actual 

ft /min), which is 50 percent less than tha^ required by ANSI guidelines 

for tanks baffled on one side (190 actual m /min [6,860 actual ft /min]), 

and visible misting was observed escaping the tanks' ventilation system; 

(2) the parts were plated in the front portion of the tank where capture 

was the least efficient; (3) use of the polypropylene balls in the plating 

tank may lower control efficiency because of low inlet loadings or changes 

in the particle size distribution; (4) the ports were not sealed around 

the sample probe during testing to ensure that no dilution air was 

introduced to the duct; (5) the point in the duct at which the slip stream 

was drawn was an elbow where cyclonic or turbulent flow was likely to 

exist; (6) the meter boxes for the sampling trains were left unmanned 

periodically during the test runs; and (7) sample recovery was not 

completed onsite where procedures could be observed; instead, sample 

trains were taken to a local laboratory at the end of each run where the 

samples were recovered and analyzed for the chromium content. 

III. CM&E Ventilation and Scrubber System—Electrolyzinq, Inc. 

A demonstration test of the CM&E ventilation and scrubber system was 

conducted at Electrolyzing, Inc., in Los Angeles, California, during the 

week of January 30, 1989. The facility is a small job shop that performs 

hard chromium plating of aircraft parts. The plating tank used by CARB in 

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8 

the demonstration test is approximately 2.4 m (8.0 ft) long, 0.84 m 

(2.75 ft) wide,, and 0.61 m (2.0 ft) deep and holds approximately 950 i 

(250 gal) of plating solution. The plating tank is equipped with a 

rectifier rated at 1,500 amperes and 12 volts. During the demonstration 

test, the plating tank was scheduled to be operated at 1,000 amperes. In 

addition, polypropylene balls were used on the surface of the plating 

solution. The ventilation system on the tank consists of a total 

enclosing hood that has sliding side panels to allow for the placement of 

parts in and out of the tank. The ventilation rate during testing was 

expected to range from 2.8 to 3.4 actual m /min (100 to 120 actual 

ft/min). There is approximately 23 to 31 m (75 to 100 ft) of flexible 

hose between the hood and control device. The inlet sampling location was 

in a section of duct approximately 1.5 m (5.5 ft) upstream of the control 

device, and the outlet sampling location was in the stack approximately 

1.5 m (5.0 ft) downstream of the control device. 

IV. Tri-Mer Fan/Separator and CECO Fiber-Bed Mist Eliminator Chroma! 

Plating Company 

One demonstration test each will be conducted on a Tri-Mer 

fan/separator and a CECO fiber-bed mist eliminator at Chromal Plating 

Company in Los Angeles, California, during February 1989. The facility is 

a medium size job shop that performs hard chromium plating for the 

aircraft industry. A full-scale Tri-Mer fan/separator unit will be 

installed and tested on plating Tank No. 1. A small CECO filter will be 

evaluated on a slip stream pulled from the main exhaust duct on plating 

Tank No. 2. Tank No. 1 is 1.5 m (5.0 ft) long, 0.91 m (3.0 ft) wide, and 

1.5 m (5.0 ft) deep and holds approximately 1,890 «, (500 gal) of plating 

solution. Tank No. 2 is 1.8 m (6.0 ft) long, 2.1 m (7.0 ft) wide, and 

2.4 m (8.0 ft) deep and holds 8,930 i (2,360 gal) of plating solution. 

The chromic acid concentration in both plating baths is 240 g/j, 

(32 oz/gal), and sulfuric acid is used as a bath catalyst. 

During testing, Tank Nos. 1 and 2 will be operating at about 

1,500 and 5,000 amperes, respectively. The normal operating temperature 

for the plating baths is about 49°C (120°F). All of the plating tanks in 

the shop are ducted together on the roof and vented to a packed-bed 

scrubber. To accomodate testing, the duct from Tank No. 1 will be 

disconnected from the main trunk line and the airflow will be redirected 

to the Tri-Mer scrubber, which has its own fan system. The design airflow 

for the Tri-Mer scrubber is 85 actual m /min (3,000 actual ft /min). To 

allow the CECO filter to be tested within its design flow rate range, a 

slip stream will be pulled from a section of straight duct used to vent 

Tank No. 2. 

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