Industrial Implementation Characteristics of Aluminates Liquor Low-Temperature Desilication Technology

Abstract

Low-temperature desilication process was investigated during alkali aluminosilicate raw materials treatment by mode of production of alumina by sintering method at industrial conditions. Nepheline concentrate used as seed for desilication. During the research process, temperature changed from 85 to 100 °C and seeding from 9.6 to 31.0 kg/m³. Accomplishment of desilication at the first stage with use of nepheline concentrate as seed reduces steam consumption for the desilication process and allows to simplify the equipment decision in comparison with autoclave conditions. However, when the non autoclave desilication is applied, the amount of solid phase in a state of circulating slurry substantially increase and contains up to 30 % of the liquid phase in the form of desilicated liquor. The best results achieved at temperatures close to the maximum and amount of seed more than 20 kg/m³. It was established that during low-temperature desilication aluminate liquors dilute with nepheline pulp liquid phase while entering desilication in contrast to autoclave one. This dilution results in aluminate liquor hydrolysis, and the material flows gain which needs increasing volume of settling tanks and equipment; the latter leads to decrease of feeding sinter leaching liquor concentration. As the result of hydrolysis the solid phase after the desilication has in its composition an average amount of mass Al₂O₃ equal to 3,0 % in the type of Al(OH)₃. As well, liquor dilution results in increase of heat consumption for the liquor evaporation in the soda production area.