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.