The impact of operating conditions of red sludge autoclave leaching with high-modulus alkali-aluminate solutions such as duration, temperature, limestone dosing rate, caustic alkali concentration, and pulp liquid-to-solid ratio on extraction of valuable components: alumina and alkali has been explored. The behavior of hydrogarnet sludge during thickening, washing and filtration has been checked under laboratory conditions. Researches were held and optimum parameters of solutions’ caustic module conversion have been chosen. The optimum alternative of process chart of hydrochemical branch as applied to red sludge processing at «Aluminium of Kazakhstan» JSC has been chosen.
We have studied the influence of activating ferrous additives on alumina and alkali recovery during the process of red mud lixiviation in autoclaves with the use of high-modulus alkalialuminate solutions and in the presence of lime. The effectiveness of usage of additives, containing sodium and calcium ferrites, during hydrochemical processing of red muds of Bayer process according to hydrogarnet technology, has been shown: increase in alumina recovery by 5-8 %, the possibility to conduct the process at average temperatures 240-260 °С and reduced concentrations of caustic alkali up to 200 g/dm3.
