Thermodynamic evaluation of waste residues pertaining to the reuse of industrial waste and contaminated sites

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Red mud is an iron-rich residue that is produced during the extraction of alumina from bauxite. About 2-4 tonnes of this red mud material are generated for the production of one tonne of aluminum. Because of the size of this waste stream and its causticity, red mud is a major environmental concern. In most cases, the red mud is stored on location close to aluminum companies, and a considerable amount of land is required for this purpose. Development of potential applications for this waste residue that would eliminate its impact on the environment and help restore contaminated sites, is therefore an important consideration. Within the integrated sector of the steel industry, about 400 kg of slag is produced in making one tonne of liquid steel. The amount o disposed slag from the steelmaking converter can be significantly reduced when charging hot metal with low phosphorus and sulphur contents. The novelty of the present proposal is to use waste materials from alumina production as the basis for environment-friendly refining flux in the steel industry in order to generate hot metal with low residual levels of impurities. This will reduce the impact of Canadian industries on the environment and ensure that caustic compounds do not enter the ecosystem. To achieve this goal, the short-term objectives are: 1) To evaluate the physical, chemical and thermal characteristics of red mud waste products as well as synthetic fluxes generated by additions of basic oxides to the red mud materials, 2) To investigate the fundamental thermodynamics that govern phosphorus distribution between red mud based slags and hot metal using an iso-activity method, 3) To measure phosphate and sulphide capacities of red mud based slags using slag-metal equilibration, 4) To evaluate the effect of red mud based slags on the behaviour of refractory lining materials, and 5) To develop a model for the custom design of metallurgical slags derived from red mud and other materials for hot metal pretreatment and steel refining. A longer-term objective is to provide highly qualified personnel with in-depth knowledge in mineral processing, materials production, waste management and environmental control for Canadian industries.