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OAR Box 1313 

Preppedby LaTeiaShed 

Document Number: 

15) l-B-8 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:27 AM Sheet 15 of 99 
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MIDWEST RESEARCH INSTITUTE 

ZH- fc" S 4505 Creedmoor Road 

Raleigh, N.C. 27612 

Telephone (919) 781-5750 

FINAL FILE COPY 

Date: May 21, 1985 

(Finalized: June 28, 1985) 

Subject: Site V1s1t--Chevrolet-Ponttac-Canada Group 

Survey of Chromium Emissions Sources—Chromium Plating 

EPA Contract 68-02-3817; ESED Project 85/02 

MRI Project 7711-L 

From: Barb Duletsky [h ^ 

To: Al Vervaert 

ESED/ISB/SSS (MD-13) 

U. S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

I. Purpose 

The purpose of this site visit was to gather background Information 

on the decorative chromium plating operation at the subject plant and to 

determine the suitability of the plant for chromium emissions testing. 

II. Place and Date 

Chevrolet-Pontiac-Canada Group r " \'S 

General Motors Corporation '"'"-' ii! 

13000 Eckles Road -••;, .,'.; 

Livonia, Michigan 48151 ".:.j JAN I o |99| >. j 

(313) 464-5081 \ \ 

MarCh 15> W85 LEJttAJRTOCKJT 

III. Attendees 

Chevrolet-Pontiac-Canada Group (CPC) 

John Kary, Chief Manufacturing Metallurgist 

Larry Slersma, Environmental Control Engineer 

Reggie Sobczynski, Senior Chemist 

U. S. Environmental Protection Agency (EPA) 

Al Vervaert, Lead Engineer 

Midwest Research Institute (MRI) 

Barb Duletsky 

Principal Laboratories 425 Volker Boulevard, Kansas City. Missouri 64110 
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IV. Discussion 

We arrived at the plant around 1:30 p.m. The visit began with a 

discussion about the emission control system in place on the decorative 

chromium plating Unes at the CPC Group, Livonia plant. Following this, 

we were given a tour of the plating facility, during which Mr. Slersma 

provided operating Information on the chromium plating Unes and the 

associated control devices. 

A. General 

CPC 1s an original equipment manufacturer (OEM) of bumpers for the 

automotive Industry. There are five decorative chromium plating Unes at 

this plant: Line Nos. 1 through 3 were installed 25 to 30 years ago, and 

U n e Nos. 4 and 5 were installed 15 years ago. The plant operates two 

shifts per day, 5 days per week. 

B. Process 

Each plating Un e consists of about 20 tanks that contain various 

plating and cleaning solutions. The Unes are serviced by automatically 

controlled conveyors that transfer racks containing up to 14 bumpers to 

each tank 1n sequence. The chromium plating segment of each Un e consists 

of a plating tank and several rinse tanks. 

Each chromium plating tank measures 20 feet (ft) 1n length, 12 ft 1n 

width, and 9 ft 1n depth and is divided Into three cells that are 6.7 ft 

1n length. Each 3-celled tank holds 17,000 gallons of plating solution, 

which contains chromic acid in a concentration of 33 to 50 ounces per 

gallon (oz/gal). Sulfuric acid is used as a catalyst in a 180:1 (chromic 

a d d to sulfuric add ) ratio. The solutions have not been disposed of 

since they were originally made up; make-up water and chromic ad d are 

added continually to replace losses due to evaporation and drag-out. The 

total chromic add consumption at this plant 1s 15,000 pounds per month. 

Typically, a rack remains in one cell of a chromium plating tank for 

a little over 2 minutes to receive a chromium plate thickness of 

0.012 mils. The electrodes in each cell are charged by two separate 

transformer/rectifiers. During a typical plating cycle, the tank operates 

at 16 to 17 volts (V) and 8,500 to 10,000 amperes (A). The electrical 

settings are determined by the required current density for a particular 

rack of bumpers. Typical current densities are in the range of 150 to 

200 A/ft . 

C. Emission Control 

Plant personnel said that about 99 percent of the gas emitted from a 

chromium plating tank is due to the formation of hydrogen gas bubbles at 

the surface of the lead anodes. The remaining 1 percent is caused by the 

formation of oxygen gas at the surface of the Items being plated. 

Operating current 1s the predominant factor affecting emissions from a 

typical tank. 

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The ventilation system on the tanks appeared to be effectively 

drawing mist Into the control system during the visit. Each chromium 

plating tank has six hoods (two on each cell) that draw emissions from 

along the 12-ft width. About 30,000 cubic feet of air per minute (cfm) 

are drawn from the plating tanks on Un e Nos. 1 through 3. About 

35,000 cfm are drawn from the tanks on Un e Nos. 4 and 5. OSHA requires 

that ambient chromium levels remain below 0.05 mg/m , and monthly 

monitoring has shewn the levels at this plant to be under 0.02 mg/m , 

Indicating that good ventilation 1s achieved. 

This plant has had about six different control device configurations 

since 1t began operating. The present configuration, which was Installed 

less than 10 years ago, is shown 1n Figure 1. The emission control system 

1s unique and combines both off-the-shelf and specially designed 

equipment. Each system routes exhaust gases from one chromium plating 

tank through a packed-bed spray tower scrubber, an Impingement mist 

eliminator, a 2-1nch-th1ck polypropylene blanket, a fan, a water 

Impingement tank, another Impingement mist eliminator, and a 2-1nch-th1ck 

fiberglass blanket. 

Each scrubber measures 16 feet 1n height and 9 feet 1n diameter, and 

has 4 feet of packing. There 1s a 6-1nch pressure drop across each 

scrubber. The packing in each scrubber consists of "Maspac®" tower 

packing. These objects are made of Saran® (Dow Chemical) and have been 1n 

service since 1975. Previously, polypropylene was used as a packing 

material, but this disintegrated and had to be replaced after only 

1.5 years. Chromic acid not only disintegrates certain plastics, 1t 

corrodes metal ducts as well. Parts of the control system that come into 

contact with chromic ad d mist are made of titanium or 

fiberglass-reinforced PVC to withstand the corrosive acid attack. 

The scrubber packing is flushed with clean water for 15 minutes each 

week. Condensate from the scrubber and spent water from the water 

impingement tank are drained to an evaporator extension tank where they 

are concentrated. The concentrate is returned to the chromium plating 

tank as make-up solution. Plant personnel estimated that the efficiency 

of chromium utilization at this plant increased from 10 percent to over 

90 percent when this recovery system was installed. 

The scrubber also serves as the cooling device for controlling the 

temperature of the plating bath. The excess heat 1n the plating tank 1s 

transferred to the recirculating scrubber scrubbing liquid via a 

I1qu1d/I1qu1d heat exchanger. The warmed scrubbing liquid enters the 

scrubber above the tower packing and flows by gravity down through the 

packing. The contaminated air that 1s drawn from the plating tank enters 

the scrubber below the tower packing and 1s drawn up through the packing 

by the exhaust fan. The flow of air 1s counter to the flow of the 

scrubbing liquid. The liquid washes the chrome contamination out of the 

air stream and also warms the air stream, resulting 1n the absorbtion 

(evaporation) of 4 gallons of liquid into the air stream. This 

evaporation process cools the scrubbing liquid. The cooled lqiuld 1s 

recirculated to the heat exchanger and reheated. 
CHROME JKOVCTY EDMU5T SYSTEM 

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Figure 1. Typical emission control system on chromium plating tank 

at the CPC Group, Livonia, plant. 

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The removal efficiency of the control system on one of the tanks was 

tested about 6 years ago. The results of this isokinetic sampling will be 

made available to EPA upon receipt of a written request. Ports on the 

inlet side of the scrubber are still 1n place; however, the duct 

containing ports on the outlet side has been replaced since the test was 

performed. Visual Inspection showed the control systems to be very 

efficient, as no visible emissions were observed exiting from the 

stacks. 

D. Conclusions 

The control systems on the decorative chromium plating tanks at the 

CPC Group plant are effective in removing chromic ad d mist from the 

plating tank exhaust gas. The control devices are of unique design, 

however, and not representative of those typically found 1n the Industry. 

Suitable test sites for each system are located upstream of the scrubber, 

downstream of the scrubber (upstream of the fan), and upstream of the 

final mist eliminator (downstream of the fan). The overall efficiency of 

the systems cannot be measured because there are no stacks on the outlets. 

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