Sustainable Aluminum and Iron Production

Sammanfattning: Aluminium and iron/steel are truly sustainable materials. As a result, the global metallurgical industry strives to produce products, which contribute to the global effort by reducing resource use, recycling and reusing materials where possible, and to help create the economic and supply frameworks needed to do this.Aluminium is a material that is infinitely recyclable and remarkably plentiful. Almost three quarters of all the aluminium that has ever been produced is still in use today, and approximately 90% is used in the transport- and construction sector. Recycling aluminium scrap requires 95% less energy than primary production with no loss of quality or volume. The BD produced during secondary production of aluminium contains high amounts of water-soluble compounds, i.e. NaCl, KCl, and AlN. As a result, it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results.Iron/steel is one of the few materials with a truly closed recycling loop, as it is not consumed. It is used again and again without any loss of quality or strength. Unlike most materials, iron/steel can be “upcycled” meaning that its quality and strength can be enhanced through recycling. The iron/steel industry is responsible for nearly 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results and they were in a good agreement.