Numerical Simulation of Carbonation of Steel Slag in Fluidized Bed

The steel slag carbonate reaction can effectively transform free calcium oxide in steel slag into carbonates and achieve the purpose of volume stability. The carbonation process of steel slag and kinetics are investigated by unreacted core model in this paper. The parameters, such as variation of pore structure of the particle during the reaction process are determined according to the literatures. The diffusion coefficient is modified and the relationship between the diffusion coefficient and the conversion ratio is obtained. By this model, the reaction controlling step for different particle size is estimated. It is found that the particle size of steel slag should be controlled within 180 mu m. Moreover, the numerical simulation method is adopted to simulate the carbonation reaction of steel slag in a fluidized bed. The Euler multiphase fluid model is used to describe the gas-solid flow in the fluidized bed. The modified unreacted core model combines with UDF custom program to calculate the chemical reaction rate. The coupling among gas-solid flow, mass transfer and chemical reaction in a fluidized bed is implemented. The results show that particle size, reaction temperature, blowing speed, and CO2 concentration all have a certain effect on the reaction. By reducing the particle size, and increasing the reaction temperature, the blowing speed and the CO2 concentration, the reaction efficiency will be improved. The CO2 concentration has a great influence on the reaction rate.