INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 125

1. Headline: QSL Process, developed to smelt lead sulphide

concentrates and sulphate secondaries, reduces fuel

requirements by 60% and waste gases by 80%.

2. Background: See below.

3. Cleaner Production Principle: new technology

4. Description of Cleaner Production Application: The QSL

Process has been developed to smelt lead sulphide

concentrates as well as sulphate and mixed oxide-sulphate

secondaries such as flue dusts, battery paste or

lead-silver residues. As in conventional lead smelting,

the gangue minerals contained in the raw materials are

separated from the molten metal in the form of a fluid

siliceous slag. Instead of two separate steps of

sintering and blasting in a furnace, the QSL Process is a

one-step process of continuous smelting of the charge,

with the resulting pellets directly fed to the oxidation

and reduction zones of the reactor. Sulphur dioxide gas

emissions of about 15 to 25% by volume are utilized in the

manufacture of sulfuric acid. Any sulphur contained in

reduction coal or fuel is recovered, and the precipitated

flue dust is directly recycled to the mixing section.

Material/Energy Balance and Substitution

FEEDSTOCKS: Lead concentrate, fuel (coal), oxygen,

nitrogen, fluxes, electrical energy

WASTES: Air exhaust, dust, discarded slag

MEDIUM: Gaseous, solid

5. Economics

CAPITAL COST: DM 90-110 million

OPERATION/MAINTENANCE: 235 DM/t lead bullion

DISPOSAL & FEEDSTOCK: 30 million DM in capital cost, 149

DM/t lead bullion in operating costs

6. Advantages

FEEDSTOCK REDUCTION: 60% reduction in fuel consumption,

recycling of precipitated flue dust

WASTE PRODUCTION: Waste gases are reduced from 20,000 to

25,000 m3/t of lead (20 mg dust/m3), to 4,000 to 5,000

m3/t of lead (10 to 20 mg dust/m3). Sulphur dioxide gas

can be used in sulfuric acid production, instead of

emitting to the air.

IMPACT: The QSL Process is a continuous one-step process

with low investment and operating costs compared to the

conventional technology. Energy recovery reduces the fuel

requirements by 60%, and sulphur contained in the raw

materials is recovered. The volume of waste gases emitted

to the environment is reduced by 80%, and the SO2

emissions are eliminated.

7. Constraints: No information provided.

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

Technology, United Nations Economic and Social Counsel,

"Continuously Operating Direct Lead Smelting Process

(QSL)", Monograph ENV/WP.2/5/Add.114

9. Keywords: Germany, metal, lead, lead smelting, new

technology, QSL process, sulfur dioxide, flue dust,

sulfur, ISIC 3720.

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: 400-114-A-327 )