Abstract
Japan is poor in natural resources, so it is very beneficial if components dissolved in seawater can be used as resources. In our laboratory, the reactive crystallization process with the solution of components dissolved in seawater has been investigated by the absorption of CO2 gas that causes the greenhouse effect. In this study, Ca ion was selected as a component of seawater so calcium carbonate particles were produced by gas-liquid reactive crystallization. A multistage column crystallizer was used, which is a column crystallizer partitioned with perforated plates. From an economical viewpoint, the multistage column crystallizer has been developed to overcome the redundancy of equipment due to the duplication of mixers and hardware in the cascade of MSMPR crystallizers. The aims of this study are to evaluate the characteristics of the multistage column crystallizer and to control the particle size of calcium carbonate. The staging effects of the multistage column crystallizer and the effects of operating parameters on the particle size and conversion of Ca ion were experimentally investigated by the three-stage column crystallizer.
The following conclusions were obtained:
1. The particle size distribution of calcium carbonate obtained in the multistage column crystallizer becomes sharp compared to that obtained in the standard column crystallizer.
2. With increasing initial concentration of calcium hydroxide, the particle size decreases and the particles are agglomerated easily.
3. When large particles are required, agglomerated particles are preferable to primary particles that are produced in the low-supersaturated liquid.
