Materials explaining the mechanism of spatial differentiation of solution composition with the participation of the gas phase and its role in the creation of non-equilibrium conditions that ensure recrystallization of solid products are presented. Calculations of equilibrium in a number of systems of alumina production are presented. Indicators of non-equilibrium of solutions and their dependence on the leading technological parameters of the process are established.
The mechanism of mass crystallization of synthetic gibbsite at decomposition of aluminate solutions is proposed. The leading role of nucleation and supersaturation in the formation of granulometry of aluminum hydroxide precipitate is shown. The methodology and experimental results of induction period determination during gibbsite precipitation from aluminate solution are presented. The surface energy of solid phase formation during carbonization of aluminate solution as a function of critical nucleation size is determined.
Theoretically substantiated multistage carbonization process and changes of solid phase formation conditions at different stages of aluminate solutions decomposition. As a result of laboratory studies adequate mathematical dependences of process parameters on technologically significant factors were obtained. Their analysis made it possible to establish the decisive contribution of the technological mode of induction period to formation of the fractional composition of aluminum hydroxide precipitate. It was also shown that the increase in the yield of large fractions of synthetic gibbsite of spherulitic structure is provided by increasing the supersaturation of aluminate solution associated with an increase in the CO 2 content in the gas phase and blowing rate at all investigated temperature values.
Materials on recrystallization of synthetic gibbsite are presented. A theoretical substantiation of equilibrium recrystallization based on the difference in solubility of macro- and micro-particles is given. Experimental data confirming the theoretical justification are presented.
The methodology of stage-by-stage optimization of aluminate solutions decomposition is substantiated and described. Experimental materials and their mathematical processing in the form of regression equations are presented. The choice of the optimal technological regime according to the indicators of A1 2 0 3 -ZN 2 0 yield, fractional composition and CO2 content has been carried out.