Using a Statistical Model in the Red Mud Filtration to Predict the Caustic Concentration in the Red Mud

Alunorte began its operation in 1995 wi th a nominal capacity of 1.1mi tpy and after three expansions in a row the production in 2009 will be around 6.3mi tpy. Alunorte uses dry-stacking technology to dispose the red mud, deep-thickeners in the mud washing circuit and drum filters for mud filtration, reducing the caustic concentration from 65 g/L in the last washers down to 7 g/L at filters discharge. This paper aims to present a DOE pro gram with two levels and five factors in the red mud filtration area. Dilution, rotation, condensate, level in the basin and vacuum has been considered as control variables. The output variable considered was the caustic concentration in the red mud. The program measured the magnitude of the control variables and the influences on the output variable, making possible to model the filtration process, controlling the caustic concentration in the red mud below the target of 7 g/L.