Enhancement of the precipitation extent of Al(OH)3 crystals in the Bayer process within a down-scaled tank

Depending on the size of the precipitation circuit equipment compared with other parts of the Bayer process and its long residence time, the precipitation stage could be the most significant step for producing alumina and directly influence the overall production efficiency. In the present study, a 1/100 downscaled precipitation tank of a real industrial Bayer tank has been constructed, and different experimental scenarios have been evaluated to find the optimal conditions for maximizing the precipitation extent of aluminum hydroxide. Since each of the considered parameters significantly affects precipitation extent, determining the most appropriate limit of each input parameter under examination constitutes optimal conditions for this investigation. The actual Bayer liquor from an Iranian bauxite mine has been used to mimic the industrial conditions. Some preliminary scenarios, including changes in stirring rate, seed concentration, and tank temperature have been tested and more effective strategies have been identified. According to the proposed optimal condition of the response surface method (RSM), controlling the condition at T = 50 degrees C, a stirring rate of 230 rpm, and a seed concentration of 327 g/L leads to an increase in the extent of precipitation between 46% and 53%.