Recovery of Sulphur by Modified Claus Process Using Cold Bed Adsorption

Abstract

A single stage conventional Claus catalytic reactor was modified by adding a cold bed adsorption (CBA) reactor operating in low temperatures in series with the former. Activated alumina catalysts in the form of cylindrical pellets impregnated with a promoter were used for the Claus reaction at low temperatures “(~175°C) to enhance the H2S conversion from 70% in the Claus reactor to more than 99 percent in the modified setup:2HS+SO2=3xSx+2H2O;ΔH=−109.2kJmol;for x=1,where X may vary from 2 to 8 and Sx represents the sulphur species like S2, S3, S4...S8. This has been possible by Operating the CBA reactor at temperatures below the dew point of sulphur in the reaction mixture. Effects of temperature and catalyst bed depth in the CBA reactor indicated that H2S conversion tends toward 100% at a temperature of 175°C, and 12 inch catalyst bed depth would be considered optimum at a conversion of 99.5%. At 15-18 inch bed depth, the increase in H2S conversion is negligible. At the lowest temperature studied (175°C), the exit gases contained only 0.05% (mole) of the acid gases. The catalytic deactivation through the deposited sulphur was not studied but it was predicted that the deactivation of catalysts did not occur as fast as was expected because sulphur partly plays the role of an autocatalyst in the Claus reaction. Catalyst regeneration by simple elimination of the deposited sulphur did not result in full recovery of the activity of the fresh catalyst.