Physicochemical Characterizations and Desulfurization Properties in Coal Combustion of Three Calcium and Sodium Industrial Wastes

To recycle industrial wastes and reduce SO2 pollutant emission in coal combustion, the mineralogical compositions, porosity structures, surface morphologies, and desulfurization properties of three calcium and sodium industrial wastes were investigated via X-ray diffraction (XRD), porosimeter, scanning electron microscopy (SEM), and a fixed-bed reactor. (1) White lime mud (WLM) mainly composed of CaCO3 with Na2O and K2O impurities has smaller CaCO3 particles and a higher surface area than limestone. But calcined WLM has larger CaO particles and a lower surface area than limestone calcined at 1200 degrees C for 300 s. (2) Calcium carbide residue (CCR) mainly composed of Ca(OH)(2), has the highest surface area and smaller Ca(OH)(2) particles than the CaCO3 particles in WLM. Its surface area monotonously and dramatically decreases at 1200 degrees C for 300 s, but the sintered CaO particles are still smaller than those in the limestone. (3) When brine sludge (BS), mainly composed of NaCl and CaCO3, is heated at 1200 degrees C for 300 s, the NaCl/CaO eutectic solvent facilitates the aggregation of some complex composites to form many larger particles. (4) WLM gives the highest desulfurization efficiency of 80.4% at 1000 degrees C and 65.0% at 1100 degrees C in coal combustion. Combined CCR and limestone give a synergistic desulfurization efficiency of 45.8% at 1200 degrees C. BS with a molar ratio of Na/Ca at 1:15 effectively promotes the synergistic desulfurization efficiency of combined CCR and limestone to a peak of 54.9% at 1200 degrees C.