Abstract
The influence of operating conditions on the crystal growth rate of salt particles was investigated to realize both a high suspension density and a high crystal growth rate, for in order to improve the efficiency of the salt crystallization process in an evaporation crystallizer. A semibatch-type, stirred vessel fitted with a draft tube was used as the crystallizer. First, a method of direct heating with a coil-heater set around the outer side of the draft tube was investigated in order to attain a high evaporation rate in the vessel. Subsequently, operating conditions, such as heating rate, γe, and the amount of initial injection of the seed crystals, M0, were investigated in order to attain both a high suspension density and a high crystal growth rate. It was clarified, as a result, that a crystal growth rate higher than 300μm/hr on the basis of D90 and a suspension density higher than 30 vol% ca n be maintained under the conditions of γe=804kg/hr, and M0=0.05 to 0.10kg. Thus, the feasibility of greatly improving the efficiency of the salt crystallization process in an industrial evaporation crystallizer was verified by these investigations.
