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 )