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HIGH TEMPERATURE DECOPPERIZING OF THE LEAD BULLION FROM ZINC BLAST FURNACE

Objective

The general objective is to enable the imperial smelting furnaces of the European Community to treat the zinc copper concentrates available in the worldwide market.
Research was carried out in order to enable the Imperial Smelting Furnaces (ISP) of the European Community to treat the zinc copper concentrates available in worldwide market. The main part of the research was the adaptation of intensive, high temperature, new decopperizing techniques, to the ISP lead bullion and the comparisons of their versabilities (amount of copper, the lead refining plant can extract) and performances.

Direct quenching of the lead bullion was carried out yielding a fine solid or liquid copper rich phase. This involved laboratory experiments of chemical equilibria in high temperature quenching (700 to 900 C), physical characterization of the copper phase, distribution of the copper phase, distribution of the impurities and a kinetics study of copper lead separation (at laboratory scale).

The high temperature decopperizing furnace technique had to be adapted from the one developed for the decopperizing of high sulphur containing lead bullion tapped from a lead blast furnace. This involved studies of chemical equilibria between lead and copper rich phases in the case of ISP bullion, distribution of impurities between lead, matte and other possible phases present (speiss and slag), study and mathematical modelling of the heat transfers inside of the furnace and a process study and optimization (thermal control of the furnace adapted to a discontinuous tapping of the ISF).

The right temperature to process a high temperature decopperizing was found to be around 700 to 750 C, ensuring that the tin remained within the lead matrix.
A final quench performed at 400 C lowers the copper content in the lead matrix at the 0.2% equilibrium value.
From the materials study, the upper working temperature (in terms of industrial durability) remained much lower (600 C, around 200 h for aluminium oxide coatings) than initially planned. The cause is the residual porosity rate (2 to 7%) of the coatings which allows gaseous and liquid lead (even gaseous lead oxide) to penetrate in the coatings and to force their flaking off.

Although the process of decopperizing at high temperature is theoretically possible and although its feasibility has been proven by laboratory tests, it is now clear that its industrial application goes through coating technologies more sophisticated and more varied than initially hoped (duplex coatings for example). Consequently, the usage of such a new process for European lead bullion producers is not applicable in the near future.
The main part of the research will be the adaptation of intensive, high temperature, new decopperizing techniques, to the imperial smelting furnaces(ISF) lead bullion and the comparisons of their versatilities (amount of copper the lead refining plant can extract) and performances.

In the future, all steps of the lead refining could be reconsidered, not only the decopperizing operation. All lead industries of the EEC are concerned, since more than 20 plants refine nearly 750000 tons a year.

The materials study will involve the following stages.
Material choice through a requirements file containing calculation of mechanical stresses, definition of chemical environment (solubility of the materials in the bullion), thermal cycles (first semester).
Samples preparation by coating steel pieces (size 20 cm) with metals or ceramic materials (plasma spray coating). Physical studies on corrosion behaviour of these samples put in contact with liquid lead bullion (containing copper, zinc, sulphur, arsenic, tin and antimony) at a high temperature (800 to 900 degrees celsius) during a few days. Microscopic examinations on adherence between the coating and the core materials (first and second semesters).
Large scale tests. Industrial trials in the zinc smelting plant (2 weeks each trial). Study of mechanical and chemical resistance of pumps and stirrers (second to fifth semesters).

The direct quenching of the lead bullion yielding a fine solid or liquid copper rich phase will involve the following stages.
Laboratory experiments of chemical equilibria in high temperature quenching (700 to 900 degrees celsius). Physical characterization of the copper phase, distribution of the copper phase, distribution of the impurities (second semester).
Kinetics study of copper and lead separation (at laboratory scale) (second semester).
Process optimization for high separation and high final copper content (third to fifth semesters).

In the high temperature decopperizing furnace yielding a liquid copper rich phase, the technique has to be adapted from the one developed by BHAS for the decopperizing of high sulfur containing lead bullion tapped from a lead blast furnace. This will involve the following stages.
Laboratory studies of chemical equilibria between lead and copper rich phase in the case of ISF bullion, distribution of impurities between lead, matte and other possible phases present (speiss and slag) (third semester).
Study and mathematical modelling of the heat transfers inside the furnace (third and fourth semesters).
Process study and optimization (thermal control of the furnace adapted to a discontinuous tapping of the ISF) (third to fifth semesters).

Finally a comparison of processes will involve analysis of flexibility and operating costs (fifth semester).

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Métaleurop Recherche SA
Address
1 Avenue Albert Einstein
78193 Trappes
France

Participants (2)

Commissariat à l'Energie Atomique (CEA)
France
Address
Centre D'études De Grenoble Avenue Des Martyrs
38041 Grenoble
M.I.M. HUETTENWEKE DUISBURG GMBH
Germany
Address
Richard-seiffert-strasse 20
47241 Duisburg