Phase relationship of complex multi-component system in chromate cleaner production

摘要

The phase relationships of the complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production are investigated theoretically and experimentally. The phase diagram of main system Fe-Cr_2O_4-KOH-O_2 of oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated. A series of phase diagrams of the separation process at different temperatures, such as K(Na)OH-K(Na)_2CrO_4-H_2O, KOH-KAlO_2-H_2O, K(Na)OH- K(Na)_2CO_3-H_2O, K(Na)OH-K(Na)HCO_3H_2O and K(Na)HCO_3-K(Na)_2CrO_4-H_2O have also been calculated. Some experiments are carried out to verify the calculated results. Our results showed that the sub-molten salt media are suitable for the oxidization and separation processes; FeCr_2O_4 can be oxidized across a wide range of temperature; K(Na)_2CrO_4 can be separated from K(Na)AlO_2 system at appropriate temperature and proper concentration; the crystallization of carbonate is easier than that of K(Na)_2CrO_4.