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Content archived on 2022-12-27

DEMONSTRATION OF AN ENERGY-SAVING PROCESS FOR LEAD SMELTING

Objective

To modify an existing QSL reactor to enable the demonstration of the energy-saving, low-pollution process. This requires operating the unit on a continuous basis -vs. the current batch-operation - for 6 months and then switching to cheaper feedstock for an other 6 months.
The object of the project supported by the European Community was the demonstration that the QSL process exhibits only 50 % of the energy consumption required in conventional lead smelting. The target of the test as described wasreached almost completely with the demonstration plant over a test period of considerable duration.
In addition, success was also attained in replacing the high-grade anthracite used for heating and reduction purposes by low-grade fuels. The feasibility of using natural and light oil as reduction agents increases the flexibility of the process.
In the 30,000 TPY QSL-plant of the Berzelius company, initial tests were run to show that it can be operated with an energy-saving of approximately 50%, using lower-value feedstock while reducing SO2 and dust emissions by over 80%
The key of the QSL process is that it is a one-step process - compared to two steps in conventional lead-smelting - taking place in one single reactor. This enables the reduction of SO2 emissions by some 93 per cent and dust by 80%.
The lead-concentrate (feed) is mixed with fluxes, water and recycled flue dust in a mixer and is then pelletised into so-called green pellets which are kept wet to avoid dusting problems. They are fed into the reactor which is separated into an oxidation and a reduction zone. In the oxidation zone oxygen is blown in to oxidise the lead sulfides to metallic lead and high-lead slag. The high-lead slag passes into the reduction zone, which is separated from the oxidation zone by a weir. Pulverized coal and air or oxygen are blown into the reduction zone from the bottom. The coal reduces the lead oxide contained in the slag to metallic lead,which recombines with the primary lead from the oxidation zone before being tapped. The reduced low-lead slag leaves the reactor via an overflow and is either granulated or processed to recover the zone.
The SO2-containing off-gas leaves the oxidation zone of the reactor at appr. 1100 deg. C. It is cooled to less than 800 deg. C. in a vertical uptake before passing to a waste heat boiler, an electro-filter and a sulfuric acid plant. The remaining flue dusts go back to the above mixer.
To confirm the initial tests, the reactor needs to operate continuously for 6 months (Phase I) after which the feedstock will be switched to cheaper sulfur-containing coal and waste-fuels such as Petroleum coke (Phase II).
The cost of the project is DM 10,9 million of which approximately DM 5 million covers Phase I. The benefit of the project is an estimated 30-35% reduction in bothinvestment and operating costs i.e. for a 100,000 TPY lead smelter the investment is approximately DM 150 million for a conventional plant vs. DM 100 million for a QSL-plant and the energy saving equivalent to 10.4 TOE.
Patent coverage exists through 5 different patents.

Call for proposal

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Coordinator

MHD BERZELIUS DUISBURG GMBH
EU contribution
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Address
RICHARD-SEIFFERT-STRASSE 20
4100 DUISBURG-WANHEIM
Germany

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Total cost
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