JSC “Chelyabinsk Zinc Plant”, Chelyabinsk, Russia:

Degtyarev A. M., Head of Waelz-shop
Ivakin D. A., Head of Technological Bureau of Engineering Center, e-mail: dai@zinc.ru
Shumilin Yu. P., Leading Production Engineer of Engineering Center
Mayorov S. P., Deputy Manufacturing Head of Waelz-shop

This article gives the results of mastering of technology of Waelz oxide calcination in pipe furnace in Chelyabinsk Zinc Plant. A flow hardware diagram is shown together with calcination process modes. Waelz oxide calcination technology includes the following measures:
- pelletizing of powdered oxide into pellets; calcination in pipe furnace;
- pellet cooling; milling of calcined oxide in ball-rod mill; gase cooling and cleaning with secondary fumes' recovering. Calcined product is prepared to leaching, while secondary fumes are washed with sodium carbonate and water from chlorine and fluorine.
Calcination is carried out in oxidizing atmosphere at the temperature of 900–1100 °C for efficient removal of halides and oxidation of iron (II), arsenic and metal sulfides. Residence time of material in high temperature zone is not less than 2–3 hours. The calcination technology, mastered in Chelyabinsk Zinc Plant allows to carry out the following measures:
– removing of Waelz oxide halides (up to a residual content of Cl <0.06% and F <0.01%);
– oxidation of Fe (II) and As, reduced their passing into solution during Waelz oxide leaching;
– increasing of solubility of zinc (up to 91%) and cadmium (80%) in Waelz oxide, simplifying its leaching technology and reducing metal loss;
– reduction of material amount approximately by 2 times, increasing the leaching flowsheet productivity.
As a result of the calcination technology, the shop processing Waelz oxide efficiency was increased by 33–36%. The wash water volume is 15–20 times lower during secondary fumes washing than during Waelz oxide washing, and obtained solution is suitable for concentration and evaporation.

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