Study On Fluid Dynamics Of The Slurry During Phase Transformation Of Flue Gas Desulfurization Gypsum In Mixed Salt Solutions

The basic operation of crystallization is determined by some complex and co-influence factors, and heat transfer and mass transfer are impacted deeply by the properties of fluid dynamics and particle dynamics. Generally, crystallization appears in the system of multi-phases and multi-compounds. The process also includes the changes of the size and the size distribution of particles. Although experience is usually used in the design of crystallizers, the large-sized development and the reliability of crystallizers is still on the basis of the crystallization theory research. The fluid dynamics of crystals suspension is on of the basis of crystallizer design.This paper researched into the fluid dynamics of crystals suspension in the system of flue gas desulfurization gypsum transformation intoα-calcium sulfate hemihydrate in Ca_Mg_K_Cl-H2O. The properties of the fluid dynamics of the gypsum crystal suspension were studied by determining the size distribution of flue gas desulfurization gypsum and the densities and the viscosities of the mixed salts solutions.Flue gas desulfurization gypsum has a property of agglomeration when the gypsum is exposed in air and then absorbs easily the free water of air. The scheme of"warming-sieving-warming -sieving"was used to obtain flue gas desulfurization crystals with typical size. Meanwhile, the laser particle analysis was used to determine the mean size of flue gas desulfurization together with the results of the sieving. The mean size of the gypsum was 45μm. During the experiments of the gypsum suspension fluid dynamics, the gypsum crystals of 45μm was used, and the experiments was carried out in a laboratory-scale fluidized bed crystallizer. The study focused on the fluid dynamics of the gypsum suspension in the system of Ca_Mg_K_Cl-H2O with the concentration of 25 % (by weight). According to experimental results, two kinds of empirical formulae were presented to describe the relationship between the critical fluidized velocity and fluid flow pattern. And further, the second formula was adequate to describe the critical fluidized velocity of the gypsum crystals in high temperature. The critical velocities calculated by the second formula were close to the experimental results. A empirical formula of critical fluidized velocity was also obtained on the basis of the data of the size distribution of flue gas desulfuriztion gypsums and the densities and the viscosities of the mixed salt solution. The calculated results by the formula had acceptable errors during practical utilization.