Stability and oxidative stabilisation of sulphided calcareous sorbents from entrained flow gasifiers

The stability of different sulphided materials (pure CaS particles, sulphid ed calcium hydroxide, sulphided limestone, sulphided dolomite and sulphided calcium magnesium acetate) when exposed to a moistened stream of air at am bient conditions has been studied. For all the analysed sorbents, the relea se of H2S during exposure to a moistened stream of air is a function of the calcium sulphide content of the sorbent. The ratio between the amount of r eleased sulphur and the amount of sulphur stabilised as sulphate or element al sulphur is also a function of the initial calcium sulphide content of th e sorbent. Additionally, the performance of air oxidation at different temp eratures (800-980 degrees C) for stabilisation of the sulphided sorbents ha s been analysed. The final apparent conversion achieved during air oxidatio n of the sulphided sorbents, including particles of sulphided calcium aceta te, in the temperature range 800-980 degrees C shows an inverse dependence with the (calcium sulphide content)/(specific surface area) ratio of the so rbents. The total amount of SO2 released during air oxidation at high tempe rature is a function of the initial calcium sulphide content of the samples . Conversion degrees up to 100% have been obtained. For all sorbents, the c onditions for complete stabilisation and negligible SO2 release during oxid ation were established. The differences found in final oxidation conversion s and stability of the oxidised sorbents for increasing oxidation temperatu res can be explained in terms of the oxidation mechanisms for low (< 890 de grees C) and high temperatures. (C) 2000 Elsevier Science Ltd. All rights r eserved.