Avaliação do teor de carbono em alumina carregada usada na redução electrolítica do alumínio

Abstract

The aluminum production process is commonly carried out through the electrolysis of molten alumina between a carbon anode and cathode. Carbon anodes are prepared through cooking in an Anode Cooking Oven (FCA), where smoke is released that contains hydrocarbons and fluorides in its composition. These emissions are subsequently treated in a Smoke Treatment (CTF), using alumina as an adsorption agent. The content of carbon in the alumina of the Smoke Treatment Center should not be more than 0.5% (w/w), to avoid alumina saturation and adverse environmental impacts, this being problem that is the basis of this research work. The present work was carried out in the aluminum smelting company, whose objective was to evaluate the carbon content in the charged alumina, a term used to describe alumina rich in hydrocarbons and fluoride generated at the Tobacco Treatment Center. The work consisted of analyzing the carbon content in alumina loaded at two points of sampling, namely in filters 2 and 3 of the Smoke Treatment Center. O work also included the determination of the tar content emitted per volume of gas to the atmosphere. The test consisted of evaluating the impact of increasing the flow of primary alumina in carbon content. The determination of the carbon content in charged alumina was performed from radiation absorption spectroscopy infrared and the tar content in the gas was determined by solid liquid extraction. The tests carried out showed that the carbon content in alumina charged, keeping the gas flow constant and increasing the alumina flow primary pressure from 1200 to 1538 kg/h and from 1200 to 1406 kg/h, for filters 2 and 3 respectively, it reduces the carbon content from 0.508 to 0.280 % (w/w) and from 0.634 to 0.254 % (w/w). Keeping the alumina flow constant and reducing the flow of gas from 12.43 to 10.76 Nm3 /s and from 16.5 to 9.79 Nm3 /s, for filters 2 and 3 respectively, the carbon content reduces from 0.661 to 0.508 % (w/w) and from 0.676 to 0.512 % (w/w). The amount of tar emitted per volume of gas for the atmosphere reduces from 13 to 3 mg/Nm3 with increasing primary alumina flow from 1000 to 1511 kg/h. In this way, it was possible to verify that the alumina flow primary has a greater impact on the carbon concentration in alumina (TRADUÇÃO NOSSA).