H2S Recovery from a Kraft Black Liquor Gasification Gas with a Calcium-Based Process: The Effect of Calcium Recycling, 2001 Engineering / Finishing & Converting Conference Proceedings

M. P. d’Entremont, A. R. P. van Heiningen--H2S can be selectively removed from a kraft black liquor gasification gas by reaction with calcined lime. The sulfided lime is then converted into lime mud and high sulfidity white liquor by reaction with NaOH. The dewatered lime mud is reused for sulphur capture. In the present study, the effect of recycling the calcium containing solids was investigated for two industrial limestones. It was found that H2S is fully captured at 750C and atmospheric conditions by a packed bed of the fresh calcined limestone. The maximum sulphur capture capacity (or CaS yield) was found to be 72 and 90% respectively. After three recycles, the maximum sulphur capture efficiency drops by respectively 66% and 63% relative to that of the fresh calcined limestone. The decrease is explained by the sintering tendency of the calcium containing solids. It is concluded that with appropriate modifications the regenerative calcium-based H2S recovery process may be a viable alternative for selective sulphur removal of an industrial kraft black liquor gasification gas.