The study of caustic recovery increase in settling and decreasing the destructive environmental effects in alumina factory

Bauxite contains aluminium hydroxides in large percentage and is therefore largely used for the production of alumina (Al2O3) through the Bayer chemical process, which is based on the reaction with sodium hydroxide under heat and pressure. The red mud probably represents the main problem in the alumina production and its disposal constitutes an environmental problem, most of all for its caustic nature. The objective of this research is to investigate the use of Na2O for settlement enhancement of red mud of Alumina production plant of JaJarm, Iran in which the mud washing operation is performed to recover the alumina and Na2O.In what follows, this operation is described. Firstly sample is taken from the overflow thickener of the red mud. Then, the effect of Na2O on the settling velocity is measured. A washer is added to the existing washers to increase Na2O recovery. ASPEN software is employed to simulate the unit to determine the contribution of the added washer to the Na2O recovery. The results show a reduction from 5.5 percent to 4.8 percent in the Na2O in the red mud as well as an increase in the recovered Na2O from the overflow. These lead to faster settling and greater production capacity. On the other hand the lower amount of Na2O in red mud dispatching the disposal, the destructive environmental effects are remarkably lower.

Keywords:

Alumina , Caustic , Environmental , Simulation