Kinetics of chlorides removal process from waelz-oxide during heating under the influence of electromagnetic emission

The global consumption of galvanized products leads to an increase in the volume of zinc-containing waste. Zinc-containing waste may be processed in the zinc production in the form of secondary zinc-containing raw materials. Waelz-oxide is formed during the processing of secondary zinc raw materials by traditional methods. Waelz-oxide is subject to pretreatment by calcination at temperature of about 1000 °С for chlorides removal. The development of technologies and equipment opens up new opportunities for heating and calcination of Waelz-oxide. Many dielectric materials are heated in accordance with the Joule-Lenz law under the influence of electromagnetic emission. Heating and calcination of Waelz-oxide under the influence of electromagnetic emission is an innovative method for use in metallurgy. High heating speed, selective processing of the material and the absence of fuel combustion products are the main advantages of the heating and calcination process by electromagnetic emission. A pilot laboratory microwave installation has been developed to conduct research on the heating of Waelz-oxide under the influence of electromagnetic emission. The experimental and laboratory microwave installation is equipped with an automatic control module based on an Arduino microcontroller to maintain the specified temperature and duration of calcination. The kinetics of chlorides removal process from Waelz-oxide when heated under the influence of electromagnetic emission was studied at a pilot laboratory installation. The possibility of heating and calcination of Waelz-oxide under the influence of electromagnetic emission is confirmed. In this work, the duration of heating of Waelz-oxide up to the temperatures of 600, 700, 800, 900 and 1000 °С is studied. The duration of Waelz-oxide heating up to temperatures of 600 and 1000 °С increases from 80 to 164 sec with sample weight of 30 g. The influence of the temperature and duration of calcination on the efficiency of chlorides removal from Waelz-oxide is studied. At temperature of 600 °С and retention time up to 150 sec, the efficiency of chlorides removal was 30 %, the chlorine content in the calcined sample was 0.70 wt. %. When heated up to the temperature of 1000 °С and retention time up to 600 sec, the efficiency of chlorides removal increases to 96.4 %, the residual chlorine content in calcined Waelz-oxide is 0.04 wt. %. Processing of experimental data in accordance with Yander equation shows that the process of chlorides removal is implemented in the diffusion mode. During heating under the influence of electromagnetic emission the apparent activation energy of chlorides removal process from Waelz-oxide was 66.3 kJ/mol.