INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

Case Study # 122

1. Headline: Recovery and regeneration of pickling baths

reduces wastewater generation by 33% and increases

recovery rate of chlorides and ferric oxide.

2. Background: See below.

3. Cleaner Production Principle: internal recycling, process

modification, extended use of raw materials

4. Description of Cleaner Production Application:

Chlorhydric acid pickling baths are regenerated and

recycled for pickling of steel plates. The pickling baths

go through a roasting oven where the chlorhydric acid is

recovered, along with ferric oxide powder which is sold.

Residual acid losses are neutralized and settled.

Materials/Energy Balance and Substitution

FEEDSTOCKS: HCL - 2 kg/ton steel, lime - 1 kg, wash water

- 0.2 m3, energy (gas) - 0.125 GJ.

WASTES: Residual used pickling baths and washing water

MEDIUM: Water

5. Economics:

CAPITAL COST: 25,000,000 francs (1979 franc)

OPERATION/MAINTENANCE: 4.90 francs/ton of steel

DISPOSAL & FEEDSTOCK: Capital investment is increased by

21,200,000 francs, but operating costs are decreased by

5.06 francs/ton of steel. Recovered ferric oxide is sold

for 1.10 franc.

6. Advantages:

FEEDSTOCK REDUCTION: HCl requirement reduced by 18 kg/ton

steel, lime is reduced by 8.5 kg, water by 0.2 m3.

WASTE PRODUCTION: Low waste techniques generates 0.2 m3

of wastewater containing 0.25 chloride ions, compared to

0.3 m3 water with 1.3 kg chloride ions with conventional

technology. Ferric oxide mud is reduced from 7 to 0.6 kg.

IMPACT: Wastewater generation is reduced by 33%, with a

high recovery rate of chlorides and ferric oxide. The

technique could be extended to other applications where

chlorides are decomposed and recovery of metals is

profitable.

7. Constraints: No information provided.

8. Contact and Citation: Compendium on Low and Non-waste

Technology, United Nations Economic and Social Counsel,

"Pickling Steel Plates with Chlorhydric Acid, After Hot

Rolling: Recovery and Regeneration of Acid Pickling

Baths", Monograph ENV/WP.2/5/Add.96

9. Keywords: France, metal, iron and steel, pickling,

recycling, process modification, pickling bath, acid,

ferric oxide, chlorine, ISIC 3710.

10. Reviewers Comments: This case study was originally

abstracted for the US EPA Pollution Prevention Information

Clearinghouse. It underwent a UNEP IE funded technical

review in 1994 for quality and completeness. It was edited

for the ICPIC diskette in July 1995.

( DOCNO: 400-096-A-321 )