The effect of carbon dioxide during the desulfurization of flue gas with Mardin–Mazıdagı phosphate rock

The effects of temperature, CO2 concentration and particle size on simultaneous calcination/sulfation of Mardin–Mazıdagı phosphate rock in fluidized-bed reactor were investigated. For this, a raw sample was exposed to calcination and sulfation processes in a fluidized-bed reactor to determine the effects of parameters by using a model gas mixture similar to the flue gas composition. The calcination ratio increased with increasing temperature and decreasing particle size, but decreased with increasing CO2 concentration. In sulfation process, however, sulphate conversion ratio increased with increasing CO2 ratio and decreased with decreasing particle size. The sulfation reaction is well represented by the shrinking core model and can be divided into two regions with different rate controlling step. For low conversions, the controlling step was found to be chemical reaction at the interface, but the diffusion through the product layer for high conversion. The activation energies for the chemical reaction at the interface and diffusion through the product layer cases were calculated as 100 and 296 kJ mol−1, respectively.