8 6 Helmut Gutenberger and Wojciech Pastuszczyn on ... - Messer

Today we need lead as much as we ever did,
though the number of applications has decreased
sharply. “The popularity that this metal enjoyed just
a few decades ago has declined markedly. This is due
partly to the health hazards <strong>and</strong> environmental pollution
associated with lead compounds, which were
caused by outdated production methods, <strong>and</strong> partly
to the issue of economic efficiency”, explains
Burkhardt Holleis from Application Technology
Metallurgy at Messer Austria.
Nevertheless, the heavy metal is still of great
value, particularly for special applications such as
radiation shields or in accumulators such as car batteries.
Lead (latin Plumbum, chemical symbol Pb) is a very
soft <strong>and</strong> malleable heavy metal with a low melting
point. It very rarely occurs in its pure form in nature,
with lead sulphide (PbS, blue lead, galenite) being
the most important lead mineral. The most frequent
natural deposits are found in seams where the galenite
is mainly found in combination with zinc blende
(ZnS, sphalerite) <strong>and</strong> pyrite (FeS2, iron pyrite).
Primary lead
“Lead metal can either be produced from lead ores
(primary lead) or recycled products (secondary lead)”,
says Holleis. In primary lead production, the lead ore
is first converted, by means of physical processes,
into a fine-grained concentrate with maximum
metal content - this process is called ore dressing.
The ore is crushed <strong>and</strong> graded in several stages.
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During the subsequent flotation in an emulsion, the
fine-grained solids are separated from one another.
In order to convert the enriched lead sulphide into
metals in classic smelting, it is roasted in the sinter
plant with the addition of hot air. The liquid lead
oxide that is separated in this process is reduced to
metallic lead bullion <strong>and</strong> slag in a shaft furnace with
the aid of coke, lime <strong>and</strong> iron. “By adding oxygen,
this process becomes even more effective”, explains
Burkhardt Holleis.
Modern technological methods involve direct
reduction processes. The advantage here relates to
the greater efficiency of the plants, in which the
roasting <strong>and</strong> reduction processes take place in one step.
“Accordingly, environmental pollution is reduced <strong>and</strong>
economic efficiency increased”, says the expert.
Roasting is not fully completed <strong>and</strong> lead oxide
can react with lead sulphide to form metallic lead.
This produces lead bullion <strong>and</strong> slag with a higher
lead concentration than with the previously mentioned
process. The reduction of the slag means
that the remaining lead in it can also be recovered
as a resource. “Here, too, oxygen is used in order to
keep down the production costs”, says Holleis,
highlighting another advantage of the use of oxygen
in smelting. The raw lead now has to be refined
before further processing.
Secondary lead
Liquid lead being tapped from
a short rotary furnace
It is not just the lead in lead-acid batteries that is
recycled, but also the plastic housing <strong>and</strong> the sulphuric
Cover story : 9
YOUR CONTACTS:
Burkhardt Holleis
Application Technology Metallurgy
Messer Austria GmbH
Tel.: +43 (0) 50603-281
burkhardt.holleis@messergroup.com
Languages:
Dr. Martin Demuth
Application Technology Metallurgy
Messer Austria GmbH
Tel.: +43 (0) 50603-205
martin.demuth@messergroup.com
Languages:
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