Continuous double recrystallization of light soda ash into super dense soda ash

In this work, a new process is explored for the bulk densification of light soda ash. Advantages of the new process are that no (crystal) water needs to be evaporated and that a crystalline super dense soda ash is produced at atmospherical conditions. The so-called "mixed-solvent" process is based on the fact that the transition temperature at which monohydrous and anhydrous soda in contact with an aqueous solution are in equilibrium, can be lowered when a second solvent is applied. Continuous double recrystallization experiments were carried out in mixtures of water and ethylene glycol: first, light soda was recrystallized into monohydrate below the transition temperature, then the temperature was raised above the transition temperature, and monohydrate was converted into solid, anhydrous soda with a high bulk density. Values of up to 1400 kg/m(3) were measured. Further, a significant amount of chloride was removed from the soda during the two recrystallization steps. The potential industrial applications of the double recrystallization process are described by Oosterhof et al.