STUDY OF INFLUENCES ON THE ALUMINA/CAUSTIC (A/C) RATIO AND DISCHARGE DIGESTION (DBO) CAUSTIC OF THROUGH DESIGN OF EXPERIMENTS (DOE) STATISTIC TOOL

摘要

On the digestion stage of the Bayer process occurs the extraction of alumina contained in to bauxite. The Caustic/Alumina ratio determines the extraction efficiency and stability the digested slurry, as the caustic of discharge digestion determines the digestion delta caustic. Through laboratory experiments at Hydro-Alunorte refinery and the DOE, the influences of the input variables of digestion were evaluated and calculated a statistic model to predict the DBO caustic and A/C ratio. The experiments occurred as the same process conditions of the temperature and pressure by changing the following parameters: weight of bauxite, caustic and temperature digestion, time reaction, CaO and moisture in bauxite, the permutation of these variables totaled 128 reactions. The studies of influences results affirm that the digestion caustic and weight of bauxite are variables of major influence on the A/C ratio and DBO caustic. The statistic model allowed for better monitoring of these variables.