Sub-dew point claus process for reducing hydrogen sulfide emission from sulfur recovery units

Abstract

Increasing the efficiency of the sulfur recovery and decreasing the hydrogen sulfide emission are significant from both economic and environmental aspects. The cold bed adsorption (CBA) process is an approach to address the above concerns. The bench scale CBA experiments including adsorption and regeneration stages at temperatures of 140 °C and 280 °C are investigated against an industrial scale modified Claus process by using a commercial Al2O3 catalyst. Implementing CBA increases the H2S conversion of a modified Claus process sulfur recovery unit about 5%, but it is not efficient to convert CS2 and COS to the elemental sulfur. Period times of 12, 7 and 3 h are appropriate for the adsorption, desorption and cooling stages, respectively. After cycles of CBA process, the surface area and pore volume of the commercial Al2O3 Claus catalyst decrease from 385 m2/g and 0.34 cm3/g to 337 m2/g and 0.31 cm3/g, respectively as a result of condensing the elemental sulfur inside its micro- and meso- pores. The proposed CBA process is applicable to reduce the H2S emission, CAPEX and OPEX of sulfur recovery units.