NUCLEATION, AGGLOMERATION AND CRYSTAL MORPHOLOGY OF CALCIUM-CARBONATE

A pH-stat MSMPR crystallizer is used to obtain the nucleation rate equ ation of calcite formed in the Na2CO3-CaCl2 reacting system. The exper iments are conducted for seeded and unseeded runs. Effects of breakage and agglomeration on the crystal-size distribution are demonstrated. In a continuous operation, the agglomeration of nuclei followed by the breakage of agglomerates occurs at the transient state, while the agg lomeration is significant at the steady state. Taking crystal agglomer ation into account, the corrected nucleation rate and agglomeration ra te are obtained simultaneously. The agglomeration rate is a function o f relative supersaturation and magma density, and the corrected nuclea tion rate is approximately two- to fivefold of the apparent nucleation rate, which is the nucleation rate without considering the agglomerat ion effect. Discussed also is the formation of calcium carbonate polym orphism.