Research on improving zinc concentrate roasting technology at the Zinc Plant of JSC Almalyk Mining and Metallurgical Complex

The article presents the results of a study of the process of roasting zinc concentrates containing iron and silicon using oxygen-enriched air, as well as the development of an optimal composition of the charge to reduce ferrite and silicate formation. Zinc ferrites and silicates are very poorly soluble in sulfuric acid solutions and largely transfer into cakes. The yield of cakes depends on the feedstock composition and, when processing medium-quality concentrate, is 40–45% of the mass of the initial charge. To study the causes that reduce the formation of ferrites and zinc silicates during the roasting process, alkali and alkaline earth metal oxides (CaO, BaO, Na2O, K2O), natural minerals CaCO3, as well as wastewater from the copper concentration plant of JSC AMMC, which contain these compounds, were added to the charge. During roasting, blast enriched with oxygen up to 28% was used, which allowed to significantly increase the productivity of the fluidized bed furnace and reduce the duration from 2 to 1.5 hours. The use of lime in the composition of the charge in the amount of 12 and 15% of the charge mass contributed to the reduction of ferrite formation to 0.6%, silicate formation to 1.2%. Also, the oxidation of sulfides was studied and the degree of desulfurization was determined, which depends on the temperature and duration of roasting. With an increase in the oxygen content in the blast, it becomes possible to charge concentrate with increased humidity into the furnace, which will reduce possible costs for preliminary drying of raw materials.