Kinetics Influence of Operation Conditions on Crystal Growth of Calcium Nitrate Tetrahydrate in a Circulating Fluidized Bed

Abstract

In order to improve the traditional freezing crystallization process of calcium nitrate in nitric phosphate process, crystal growth experiments by adding Ca(NO3)2·4H2O seeds in supersaturated calcium nitrate solution in a Circulating Fluidized Bed (CFB) crystallizer were carried out on crystal growth kinetics. The results showed that the growth of Ca(NO3)2·4H2O crystals is a complicated mass transfer process. The mean mass crystal growth rate (RG) of Ca(NO3)2·4H2O increased linearly with the fluid circulated velocity at fixed relative supersaturation and enlarged with relative supersaturation increasing. The crystallization kinetics follows the first order equation. The overall activation energy and the order of the overall growth kinetics of Ca(NO3)2·4H2O crystals were calculated by the isothermal method. The RG of Ca(NO3)2·4H2O crystals remains basically stationary within the entire crystallization time in the CFB crystallizer. The results have a deep significance to exploit a new CFB crystallization process for the production of Ca(NO3)2·4H2O crystals instead of the traditional one.

Keywords

• circulating fluidized bed (cfb)
• calcium nitrate tetrahydrate
• mass transfer
• crystal growth rate
• crystal growth kinetics