Zero emission coal (ZEC) process based on calcium looping in which CO2 is captured through a cyclic carbonation/calcination process is a promising technology for hydrogen production. In this process

H2S should be removed before raw gas flows into the downstream carbonator/reformer. In this work

the cycled CaO derived from limestone after multiple carbonation/calcination cycles for CO2 capture was used to remove H2S from raw gas. Cyclic carbonation/calcination of CaO was performed in a dual fixed-bed reactor and then the cycled CaO was sent to a sulfidation reactor for H2S removal. The effects of carbonation/calcination cycle number

sulfidation temperature

H2S concentration and CaO microstructure on sulfidation performance of the cycled CaO from CO2 capture cycles were investigated. The cycled CaO after the long-term carbonation/calcination cycles for CO2 capture still had high H2S removal capacity. Sulfidation conversion of CaO derived from limestone decreased rapidly with increasing number of carbonation/calcination cycles in the first 20 cycles

and then decreased slowly with further increasing cycle number. After sulfidation for 120 min

sulfidation conversion of the CaO after 0 cycle was nearly 100%. And sulfidation conversions of the cycled CaO after 1

20 and 100 cycles were 94%

81% and 74%

respectively. H2S concentration showed a great effect on H2S removal of the cycled CaO. Sulfidation temperature in the range of 800—1000℃ had a little effect on H2S removal of the cycled CaO

and the optimum sulfidation temperature was 900℃. As the cycle number increased

specific surface area of the cycled CaO dropped due to sintering. The pores 20—150 nm in diameter of the cycled CaO which were closely related with H2S adsorption also decreased. Thus

H2S removal capacity of the cycled CaO decayed with the number of cycles.