Ice crystallization developments for the butane direct-contact process

The circulation pattern of the ice slurry in freeze desalting by direct-contact vaporization of an immiscible refrigerant can profoundly affect the quality of the product crystals. In order to understand better the interaction between crystal growth and relaxation a study was conducted on a continuous crystallizer equipped with a slurry recycle loop which functioned as an isothermal holding zone. As the freezer space velocity was increased from 0.45 min−1 to 1 min−1, the permeability of the ice formed increased about 2.5 fold. An increase in production rate from 1.44 to 3.6 kg/lit.hr. had no effect on permeability or on crystal size. Indications are that in scale-up, much higher values of space velocity are practical and that brine entrainment by the vapor will be the limiting design factor.