Development of Charge Pelletizing Technology Based on Electric Arc Furnace Dust for Pyrometallurgical Processing in Rotary Kilns

New technology is developed for Waelz treatment of electric arc furnace dust with the addition of calcium oxide to a charge. In this case, lead and halides are transferred into distillates. Calcium ferrite and zinc oxide remain in clinker. Clinker is sent for leaching zinc followed by zinc electrolysis from solution. The insoluble residue of calcium ferrite is used in ferrous metallurgy. The efficiency of this technology is determined by the process of charge preparation for loading into a Waelz kiln. In order to provide complete reaction of zinc ferrite with calcium oxide, it is necessary to provide effective component mixing; in order to provide selectivity of halide and lead liberation, reducing distillate volume, a powder mixture is pelletized. Exploratory research is conducted for preparing pellets of a mixture of electric arc furnace dust with lime, and the effect of some binder reagents on pellet strength is demonstrated. The following optimum parameters are determined for charge pelletizing from electric arc furnace dust and calcium-containing flux under conditions of a plate-like granulator: pelletizing duration 15 min; granule moisture content 19-20%. With the use of an intense type mixer-pelletizer, the optimum moisture content is 13-14%, which is connected with the improved conditions for pellet compaction. Comparison of various inorganic and organic additives for mixture granulation shows that the best are additives containing sodium hydrate sulfate, although their optimum consumption is unacceptable for the technology of material pyrometallurgical treatment. The presence in the production mixture of calcium-containing flux makes it possible to use it also as a binding additive for pelletizing calcium hydroxide in the form of an aqueous suspension. Feeding a pelletized mixture of electric arc furnace dust with lime into a Waelz kiln makes it possible to provide effective reaction of charge components in the kiln and to reduce to reduce escape of dust.