SPECIFIC FEATURES OF CRYSTALLIZATION IN MULTIPHASE DISPERSE SYSTEMS

A mathematical model is proposed that describes crystallization of a m ixture of several disperse phases in a gas medium, The models reveal i mportant features of crystallization in such systems: (a) crystallizat ion of each disperse phase is a multistage process; (b) the rate of cr ystallization in each phase decreases with increasing number and volum e of disperse phases in the system; (c) the total distribution functio n of the crystal size in the mixed disperse phase exhibits a polymodal character; (d) if a liquid disperse phase is present in the system, a part of initially formed crystals begins to dissolve in liquid drops at a certain instant of time; (e) dispersed phases with small crystal nucleation rates stabilize crystallization in the gas medium. The mode l is experimentally confirmed by data on the crystallization of NH4Br formed in the gas medium during the reaction between NH3 and HBr in th e presence of an aqueous dispersed phase. The evolution of NH4Br parti cles during crystallization was studied by electron microscopy in the transmission and scanning modes, The analysis of the size distribution functions of NH4Br particles formed in the system showed a good agree ment between experimental data and the results of model calculations.