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 )