Estudo do comportamento do ferro no licor do processo bayer - um estudo de caso.

Abstract

Despite the high demand of alumina in the market, there is an increasing demand of a purer product, in order to increase the aluminum production of high pureness aluminum, that, in turn, will feed the production of the high purity alloys, whose edge of profit is highly elevated. It is know that the iron content into alumina is one of the key-factors of success for this strategy. Given this, this research aimed to comprehend the iron chemistry in Bayer Process, understand the effects of iron concentration in bauxite and the involvement of Clarification process conditions as determinants of soluble iron concentration in Bayer liquor. This would allow the development of a mathematical model to preview the iron content in alumina from the total in bauxite. This work verified that the soluble iron concentration into Bayer liquor has been the main contributor for the iron content in the alumina, around 95% of total amount. The remaining iron is presented as one of the components of solids in suspension in green liquor, which were not removed during filtration process or comes from eventual contamination sources like contaminated packing water from lake. The specific model for Recovery Area, obtained from an iron mass balance, had shown an excellent adherence with real concentration, giving good foresee ability an also indicated a global iron holding time of 4-6 days, depending on Precipitation flow. However, the model for the Extraction Area was achieved by two methods in parallel: the use of curves of iron extraction already published, associated to “bias” or fitting factors that was gotten through historical data correlations and a simulation, in laboratory, of extraction’s steps, in order to obtain an experimental model. Both did not demonstrate a very good foresee ability. It believe that will be necessary to do a strong work in decrease the “blow off” liquor analysis variability. Nevertheless, the global Refinery model, obtained by the junction of previews models, shows a good foresee ability besides of indicate a global holding time of iron into the process around 16 days.