p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

37) ll-B-11 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:29 AM Sheet 37of 99 
$ 

FINAL 

P.2 

A-88-02 

MIDWEST RESEARCH INSTITUTE 

4505 Creedmoor Road 

Raleigh, N.C. 27612 

Telephone (919) 781-5750 

p "• \v, \\ \ •'"• \ 

8

1

 \\ 8U - :' .•• 

Date: July 29, 1986 ,'' \ J\H * 8 ^ l" 

(Finalized August 28, 1986) ] •* 

Subject: Site Visit—Piedmont Industrial Plating 

Chromium Electroplating NESHAP 

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

MRI Project 7717-K 

From: Randy Strait /Ll 

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 

about the chromium electroplating operation at this plant and to determine 

the suitability of this plant for chromium emissions testing to assess the 

effect of scrubber water recirculation on scrubber performance. 

II. Place and Date 

Piedmont Industrial Plating 

Post Office Box 5813 

200 Monroe Street 

Statesville, North Carolina 28677 

(704) 872-2766 

May 29, 1986 

III. Attendees 

Piedmont Industrial Plating 

Bob Miller, Plant Manager 

U. S. Environmental Protection Agency 

Al Vervaert, ISB 

Midwest Research Institute 

Randy Strait 

/ 
P.3 

IV. Discussion 

We arrived at the plant at 1:00 p.m. The visit consisted of a tour 

of the plant and a discussion about the hard chromium electroplating 

operation and chromium emissions capture and control equipment. 

A. General 

Piedmont Industrial Plating is a job shop that performs hard 

chromium electroplating of textile machinery parts and industrial rolls 

and tubing. 

B. Process Information 

There are three hard chromium plating tanks used at this plant, 

which are arranged as shown in Figure 1. The dimensions and operating 

parameters for each tank are listed in Table 1. 

The long tank is used to plate long industrial rolls and tubing as 

well as smaller parts. The tank is equipped with one 6,000- and three 

1,000-ampere rectifiers. When plating industrial rolls or tubing, the 

6,000-ampere rectifier is used. When plating smaller and different kinds 

of parts, up to four work stations can be set up in the tank. Three of 

the work stations are charged with the 1,000-ampere rectifiers, and one 

work station is charged with the 6,000-ampere rectifier. The 10-foot tank 

contains up to five work stations, and each work station is charged with a 

separate 1,000-ampere rectifier. The deep tank currently is not being 

used. 

The plant is in the process of installing a fourth hard chromium 

plating tank. The tank is 14 feet (ft) in length, 4.5 ft in width, and 

5 ft in depth and will contain about 2,350 gallons (gal) of plating 

solution. 

Porous pots are used at this plant primarily to reduce trivalent 

chromium contamination of the plating baths. The concentration of 

trivalent chromium ions increases to levels that contaminate the plating 

baths when the surface area of the cathodes plated is substantially larger 

than the surface area of the anodes. The pots are made of ceramic that 

contains pores ranging from 0.5 to 1.0 micrometers in diameter. The pots 

are placed in a plating bath to oxidize trivalent chromium to hexavalent 

chromium while plating is performed. Several anodes are placed around the 

outside of each pot, and a cathode is placed inside each pot. The anodes 

and cathode are both formed from an alloy consisting of 94-percent lead 

and 6-percent antimony. About 9 volts and 300 amperes of direct current 

are applied to the anodes surrounding each pot. Trivalent chromium ions 

present in the bath migrate to the anodes where they react with oxygen to 

form chromic acid (Cr03). The porous pots provide a selective membrane 

that prevents the hexavalent chromium anions in the bath from flowing to 

the cathode where they would be reduced and deposited. A secondary 

function of the pots is to remove metal contaminants from the plating 

<5L 
STACK 

DUALL 

SINGLE 

PACKED-BED 

SCRUBBER 

WALL 

LEGEND 

AIRFLOW 

WALL 

LONG TANK 

" ^ 

CAPTURE 

HOODS 10-FOOT 

TANK 

-A 

CAPTURE 

HOODS 

(* 

Figure 1. Schematic of Piedmont Industrial Plating 

hard chromium plating operation. 

J*. 
TABLE 1. DIMENSIONS AND OPERATING PARAMETERS OF HARD CHROMIUM 

PLATING TANKS AT PIEDMONT INDUSTRIAL PLATING 

Tank 

identification 

Dimensions 

(1, w, d) , ft.a 

Capacity, 

gal 

Hours of. 

operation 

Voltage, 

volts0 

Current, 

amperes

 ,e 

Method of 

cooling 

Constituents, 

_oz/_gal_r 

CrO: H?S0, 

Long tank 

10-foot 

tank 

Deep tank 

23, 3, 4 

10, 3, 4 

3, 4, 10 

2,064 

898 

898 

8, 5, 50 

8, 5, 50 

12 

12 

12 

9,000 

5,000 

Water 

Water 

32 

32 

0.32 

0.32 

4,000 Water 

*1 = length, w = width, d = depth. 

Dhours/day, days/week, weeks/year. 

^Tank not currently in use. 

Maximum operating values. 

eA total of four work stations can be used in the long tank: three of the work stations are charged 

with a 6,000 ampere work station. A total of five work stations are used in the 10-foot tank: each 

work station is charged with separate 1,000 ampere rectifiers. 

Cr03 = chromic acid, H2 S04 = sulfuric acid. 

>4> Tl 
P.6 

solution. Some metal contaminants contained in the plating solution are 

transformed to cations and flow through the pots to the cathode where they 

deposit either on the cathode or on the inside of the pots forming an 

olive-drab green sludge. The pots are removed from the tank and cleaned 

every 24 to 32 hours because accumulation of sludge in the pots increases 

resistance and decreases the amount of current required to oxidize 

trivalent chromium to hexavalent chromium efficiently. 

C. Emissions Control 

The long tank and 10-foot tank are equipped with double-sided draft 

hoods, and the deep tank is equipped with a single-sided draft hood. The 

hoods were manufactured and installed by Keslmac Metals Company located in 

Greensboro, North Carolina. 

Emissions from all three tanks are ducted together and vented to a 

single packed-bed horizontal-flow scrubber manufactured by Duall 

Industries, Inc. The scrubber was purchased as used equipment and was 

installed at the plant approximately 2 years ago. The gas flow rate of 

the scrubber is 11,500 actual cubic feet per minute (acfm), and the water 

flow rate is 34.5 gallons per minute. The scrubber water drains into a 

sump in the bottom of the scrubber and is recirculated by a 1.5-horsepower 

pump and sprayed countercurrent to the gas flow in front of the packed 

bed. A sensor is used to monitor the water level in the sump which 

contains about 100 gal of water. Approximately 25 gal of clean water are 

automatically added over the packed bed when the sensor calls for more 

water to make up for evaporation losses, which occurs about four times per 

day. Clean water is used to wash down the scrubber once per day, and the 

scrubber water is then drained into the plating tanks. The chromic acid 

concentration of the scrubber water is estimated to range from 1 to 

2 ounces per gallon of water. The scrubber is equipped with a chevronblade mist eliminator that is installed behind the packed bed to control 

water and chromic-acid droplets that may break through the packed bed. 

The mist eliminator is not washed down but is inspected frequently. If 

droplets appear in the mist eliminator, the packed bed is reconditioned to 

prevent the breakthrough of droplets. 

The scrubber is located outside of the plant. There are 3 ft of 

straight ductwork between the outside wall of the building and an elbow 

that connects to the inlet of the scrubber. The stack contains about 6 ft 

of straight ductwork. The outside diameter of the ductwork is 24 inches 

at both the inlet and outlet of the scrubber. 

The plant plans to install a fan/separator scrubber manufactured by 

Tri-Mer® Corporation to control chromium emissions from the fourth tank 

that is being installed. The unit was purchased as used equipment. The 

gas flow rate of the scrubber should be about 8,000 acfm. The ductwork at 

the inlet of the scrubber will be a straight section ranging from 6 to 

9 ft.in length and 24 to 28 inches in outside diameter. 

TT 
P.7 

D. Conclusions 

The plant appears to be an excellent candidate for conducting 

emissions tests to determine the effect of scrubber water recirculation on 

scrubber performance for the following reasons: (1) The three chromium 

plating tanks at this facility appear to have effective emission capture 

systems, (2) the Duall single packed-bed scrubber used to control chromium 

emissions at the plant is representative of the types of scrubbers 

commonly applied to control chromium emissions from hard chromium plating 

operations, (3) chromic acid additions to the scrubbing water can be 

easily made, (4) there is adequate lengths of straight duct at both the 

inlet and outlet of the scrubber for testing, and (5) Mr. Miller is very 

cooperative and has volunteered to assist us in the performance of the 

tests. 

Because the scrubber was installed as used equipment, Duall 

Industries should be contacted and asked to inspect the unit before a 

final decision is made to test the scrubber to ensure that it is operating 

normally, sized correctly, and representative of the single packed-bed 

scrubber currently manufactured by Duall. 

i