SiC production using SiO 2 and Cagglomerates
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Due to the possible shortage of high-quality fossil carbon materials and charcoal for the Si industry, this study will focus on the possibility of using natural gas as the substitute of commercially scarce high quality carbon sources in the Si industry. There are a huge natural gas reserves all over the world and the reserves of Norway ranks the 7th in the world. This implies that using natural gas in the Si industry in Norway might bring several benefits. Firstly, it will be the stable carbon sources that substitute the scarce traditional carbon sources. This will bring the strategic security of raw materials for the industry. Secondly, the transportation of the carbon from the other part of the world will be decreased when natural gas substitute part of the reductants in the Si production process. Thirdly, the low impurity content in natural gas will bring fewer trace elements, which is helpful to obtain a higher quality product. In addition, as suggested by previous studies, when the carbon in the form of natural gas is used in Si production in the form of agglomerate, the endothermic reaction between SiO2 and 3C may react directly in the charge layer of the silicon furnace. It will then consume part of the heat and the temperature will be lowered. When SiO-rich gas from the inner zone of furnace passes though the charge layer, the SiO gas will be cooled and condensed. This will finally increase the Si yield by capturing more SiO gas inside the furnace. Ringdalen from SINTEF Materials and Chemistry firstly proposed the possibility of deposit the carbon cracked form natural gas directly on the surface of quartz particles. The cracked carbon successfully deposited on the quartz surface and forms the carbon layer. This provides an alternative way for using of carbon form hydro-carbon gas as the new reductant materials of silicon production. In this study, the reaction mechanism of quartz and carbon agglomerates at temperature range of 1600oC-1675oC will be investigated using quartz and carbon black as raw materials at first. The difference of behavior for different carbon materials will also be studied. Another part of the work is to establish a mathematical expression for the reaction rate based on the experimental experiments, a kinetic model. At the end, the heat and mass balance for the silicon production will be modelled. The changes of temperature at different zones, Si yield (SiO loss) and energy consumption will be investigated when the amount of quartz and carbon pellet is increased. This modelling is used to verify the influence on the furnace with the ideal situation when agglomerated quartz and carbon is charged.