Oxidation behaviour of desulphurization residues from gasification and fuel-rich combustion

One method of stabilizing CaS in desulphurization residues is to oxidize it to more stable CaSO4. In the present work the effects of operating variabl es on the CaS oxidation were investigated using a thermogravimetric analyse r and mass spectrometer. It was found that the level of conversion of CaS t o CaSO4 reached a maximum at approximately 920 degrees C. At temperatures b elow 920 degrees C, there remained a significant amount of unreacted CaS in the sample particles. At 1000 degrees C, there hardly remained any CaS but the conversion of CaS to the undesirable CaO reached 55.4%. Increasing the concentration of SO2 in the gas phase improved the sulphation. The convers ion to CaSO4 increased as the degree of sulphidation of the residues decrea sed. An efficiency parameter of the CaS oxidation was proposed and was also used to evaluate the oxidation process. A correlation has been suggested w hich can make the estimation of the CaS conversion and the reaction rate po ssible. From the results, recommendations for the oxidation process have be en made. (C) 1998 Elsevier Science Ltd. All rights reserved.