Investigation of the process of heating zinc-containing products by microwave radiation

Zinc is a demanded material in the world. In terms of consumption of non-ferrous metals, zinc is the third after aluminum and copper among. Lack of ore reserves, an increase in production and consumption of zinc lead to an increase in the share of processed secondary zinc-containing raw materials. Waelz oxide is formed from the processing of secondary zinc-containing raw materials. Waelz oxide is a promising source of metallic zinc. The Waelz oxide feed is limited due to the chloride and fluoride content. It is required to preliminarily remove chlorides and fluorides from Waelz oxide. To remove halogens, Waelz oxide washing technologies are used in aqueous and aqueous-alkaline solutions. An alternative method for removing halogens is the technology of pyrometallurgical calcination of Waelz oxide. Microwave heating is a promising method for the thermal treatment of Waelz oxide. Benefits of microwave heating: transmission of electromagnetic energy, without heat; high heating rate; selective heating of materials; volumetric heating of materials. Thermodynamic analysis of chemical and phase transformations of Waelz oxide components during heating has been carried out. The temperatures at which the required content of chlorides and fluorides from zinc-containing products is reached have been determined. The possibility of heating zinc-containing substances when exposed to an electromagnetic field of ultrahigh frequency has been experimentally confirmed. In laboratory conditions, the dependence of an increase in the temperature of a zinc-containing product on the duration of microwave irradiation has been studied. The duration of heating the products to a temperature of 1000 ° C was 128-188 s. The heat and material balances of heating samples in laboratory conditions have been calculated. Coefficient of useful action is energy that has been converted into heat. The efficiency was 60-64%. The residual content of chloride ions in the calcining products is less than 0.05 wt%.