Mineral phase formation and zinc removal during sintering of filter cake wastes

A large amount of filter cake wastes are produced from the gas cleaning systems of blast furnace (BF) ironmaking and basic oxygen furnace (BOF) steelmaking processes. The filter cake wastes cannot be directly recycled through the ironmaking process due to the high zinc contents and are therefore, predominantly, stockpiled. The storage of filter cake wastes presents a long- Term environmental issue but also an opportunity to extract or recover the iron content, motivating a search for processes or technologies to allow their cost-effective recycling. In this study, two filter cake wastes from BlueScope Ltd. were sintered at 1 100-1 300°C in argon and air to evaluate the effects of temperature, gas atmosphere and carbon content on the mineral phase formation and zinc removal of sintered filter cake specimens. The fine particles in filter cake can be well aggregated by bonding phases (calcium ferrites and silicates) during sintering due to the presence of flux materials, CaO and SiO2, in the filter cake. Carbon and metallic iron in the filter cake reduced ZnO to zinc vapour during sintering, which enhanced the zinc removal of the filter cake in a reducing gas atmosphere.