UMMC Technical University, Verkhnyaya Pyshma, Russia:

P. A. Kozlov, Deputy Director for Research
D. A. Ivakin, Head of Metallurgy Laboratory, e-mail: d.ivakin@tu-ugmk.com

Elektrotsink, Vladikavkaz, Russia:

I. I. Khodyko, СEO
E. A. Poroshin, Director for Economics and Planning, e-mail: poroshin@elzn.ru

In zinc and lead metallurgy, oxidized materials, including process dusts of copper and iron and steel sites, as well as proper zinc cakes, are subjected to the waelz process in tube kilns. The cost of recovering metals into an enriched product (i.e. waelz oxide) is mainly due to the cost of fuel and reductant consumed. Undersized blast-furnace coke is used as the latter. With the aim of reducing the cost, a study was carried out, which led to the introduction of petroleum coke, i.e. a waste product of the oil industry, as a high-potential process fuel for Russian zinc producers. Petroleum coke has a low ash content (less than 2%) and a high combustion value (up to 8,000 kCal/kg). Unlike breeze coke, petroleum coke has a low porosity, for which reason it cannot be used for absorbing liquid melts in the furnace. The findings reveal a higher combustion rate of petroleum coke compared with that of breeze coke. For this reason, the former cannot be used as a full replacement of the latter in the waelz process. At the same time, a partial replacement (up to 20%) can help raise the temperature of the exhaust gas and thus reduce the charge drying zone while expanding the reaction zone. For better performance petroleum coke should be pelletized together with zincbearing materials. The process of pelletizing creates a tight contact between the reductant and the components of oxidized zinc- and lead-bearing material. A laboratory study helped determine an optimum composition of the reductant: 10–20% of petroleum coke and 80–90% of breeze coke. The pilot tests carried out in 2.5 40 m waelz kilns proved the possibility of using the low-cost fuel while maintaining the same process efficiency. The total annual savings due to the use of the above reductant are estimated at 21.7 mln rubles.

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