Flue gas desulfurization with phosphate rock in a fluidized bed

Abstract

In the present study, the suitability of Mazıdağı (Turkey) phosphate ore as an alternative raw material for limestone and dolomite in flue gas desulfurization has been investigated. Raw and calcined phosphate samples were sulfated in a differential fluidized bed reactor at 500–900°C in air and 0.3% SO 2. Effects of the parameters affecting sulfation, e.g. temperature, SO 2 concentration and sorbent particle size were studied. Also, the changes in the pore structure and products obtained at the end of sulfation were investigated using XRD, scanning electron microscopy, mercury porosimetry and BET surface area methods. It was observed that the sulfation conversion increased with temperature. It was also seen that there is a clear advantage of using calcined sorbent at low temperature where the calcination rate is low. In the calcined sample, sulfation conversion reached 90% at 900°C (30 min) while in uncalcined sample, the sulfation conversion was 76% at the same temperature. This conversion ratio is higher than those with limestone and dolomite. From the results of X-ray powder diffraction analysis and SEM photographs, it was confirmed that the parts with only calcite in the phosphate ore reacted with SO 2 and that the parts with phosphorus are unreacted. Although the initial conversion increases linearly at all concentrations of SO 2, at higher levels of SO 2 concentration the mouths of the pores choke faster than the SO 2 can diffuse inside the pores after 4 min. It was also observed that the sulfation conversion increased with decreasing particle size.