metal industry

INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

Case Study # 171

1. Headline: Resource Recovery and Environmental Control in

a Nickel-Chrome Plating Industry

2. Background: See below.

3. Cleaner Technology Principle: New technology. The

technology is a Chrome-NapperTM system which circulates

rinsewater through elctrolytic cells containing an ion

transfer membrane. Low concentrations of chromium are

maintained in the rinsewater. An Aqua Napper is also used

to reclaim chrome from the drag-in/drag-out process water

and allow for countercurrent rinsing.

4. Description of Cleaner Technology Application:

Process and Waste Information: The manufacturing process

consists of two nickel-chrome plating lines. Four rinsing

tanks and a drag-out tank are followed by the chrome bath,

a drag-in tank, and five rinsing tanks in countercurrent.

Prior to the clean technology, effluents from the running

rinses on both plating lines were discharged to a

conventional chemical destruct treatment system consisting

of bisulfite reduction of chromate, ph adjustment, and the

settling of chromium (III) hydroxide and sludge disposal.

In the new process, the final rinsewater is circulated

through electrolytic cells containing a 1.2 cm thick ion

permeable membrane separating two compartments. The

membrane surrounds an inner compartment, approximately 3.4

liters in volume, in which chrome is concentrated. A

direct electric current applied across the cell

electrodes results in the chrome concentration in the

acolyte solution. Low chromium concentrations are thereby

maintained in the rinsewater and the acolyte solution is

returned to the chrome bath after reaching a predetermined

concentration. An Aqua Napper was also installed to

reclaim chrome from the drag-in/drag-out process water and

to make countercurrent rinsing possible. At full

operation, the energy requirement is about 300,000 KWH/yr.

The technology reduced the chromium concentration in the

final rinse bath from 32 mg/l to an average of 9.8 mg/l.

Further reduction to 7 mg/l may be possible since some

spills could be prevented. Chrome savings results from

use of the Aqua Napper and it was estimated that 95% of

the total chrome recovery of 210 kg/month occurs in this

system. Water consumption decreased from 173 liters/min.

to 97 liters/min. Sludge production was negligible. The

only waste produced is water from the final rinse tank.

Scale of Operation: Information was not provided on the

scale of operation although it was indicated that 320 kg

of chromium oxide flakes were used from April - September

1982.

Stage of Development: The equipment has been in operation

since 1982.

Level of Commercialization: The equipment is fully

commercially available. The supplier, Innova in

Clearwater, Florida has experience in delivering the

installation.

Material/Energy Balances and Substitutions:

Material Category Quantity Before

Quantity After

Waste Generation:

Chrome loss 210 kg/month N/A

sales

Feedstock Use: N/A N/A

Water Use: 173 l/min 97

l/min Energy Use: N/A

300,000 kWh/yr

A chrome loss of 0.94 kg/$1000 sales was reported before

the new system was in place compared with 0.14 kg/$1000

loss with the new system.

5. Economics

Investment Costs: Investment and IEC Demonstration

Programme costs totalled $156,790 in 1982.

Operational & Maintenance Costs: Costs for 1982 were

reported as follows:

Labor at $9.00/hr:

Operation $1350

Maintenance $1300

Plant Overhead $1325

Materials

Membranes $3000

Demineralizer $3900

Electricity $8540

$19,415

Annual costs of the Chrome-Napper system were reported as

$30,043. An estimated $13,300/yr of chrome is recovered

from the system.

Payback Time: Conventional treatment at full operation

would cost $53,571/yr. Payback time will be approximately

5 years.

6. Advantages

Chromium losses exceeded the municipal sewer by-law limit

of 10 mg/l as a result of poor performance of the

conventional system. Rather than upgrade the chemical

destruct system, Dovercourt looked for alternative

technologies to allow chrome recovery and substantially

reduce or completely eliminate sludge disposal.

Purchases of chrome oxide (CrO3) flakes are decreased,

resulting in savings of $13,300. The new process results

in savings of $23,500 in operating costs over conventional

treatment.

In a two year period prior to installation of the system,

the sewer by-law limit was exceeded in 14 of 16 samples.

After installation, this occurred in 5 of 15 samples, all

related to specific activities in the plant and all

preventable.

7. Constraints

The Chrome-Napper must be operated using cool rinsewater.

As this gave problems with product quality, the fifth and

final rinse tank was converted into a hot running rinse

and the Chrome Napper was connected to the fourth tank.

After ten months of operation, Dovercourt was forced to

shut down one of its lines, due to build-up of unwanted

cations, preventing plating of chrome. At the time the

report was written, the cause of this phenomenon was still

unknown. The problem had not occurred in the other

plating lines to which the Chrome-Napper had been

installed, neither at Dovercourt, nor elsewhere.

8. Contacts and Citation

Evaluation of the Chrome-Napper System for Resource

Recovery and Environmental Control at Dovercourt

Electroplating Co., Ltd.

IEC Beak Consultants, Ltd.

6870 Goreway Drive, Mississauga

Ontario L4V lPl, Canada.

Industry/Program Contact and Address

Mr. M. Schulz

Head Training Section

Environment Canada

3439 River Road South

Ottawa, Ontario K1 OH3

Canada

TEL: 1 (613) 991-1954

FAX: 1 (613) 991-1635

9. Keywords: Canada, metal, electroplating, new technology,

ion exchange, membrane, ISIC 3471, nickel, chrome,

rinsing, sludge, water saving.

10. Reviewer's Comments: This case study was originally

compiled by the UNEP IE Working Group on Metal Finishing.

It underwent a UNEP IE funded technical review in 1994 for

quality and completeness. It was edited for the ICPIC

diskette in July 1995.

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