H2S Evolution during Oil Shale Pyrolysis

H₂S evolution during different oil shale samples pyrolysis was studied in fixed bed in the nitrogen atmosphere. The results show the H₂S evolution is influenced by pyrolysis conditions and properties of oil shale. The yield of H₂S released for two samples had a marked change at 300-600°C of final temperature and 5-50°C/min of heating rate. Both the H₂S yields of two samples increase with grain size increasing. While the H₂S yields of Huadian oil shale was far more than that of Wangqing under same pyrolysis conditions, which may be attributed to low sulfur content and high ash content of Wangqing oil shale. It is shown that the curve of H₂S escaped for Wangqing has a single wave only below 550°C, while two successive waves for Huadian oil shale occur at 440°C and 590°C respectively. The reasons of such results may be attributed to different distribution of organic and pyrite sulfur between Wangqing oil shale and Huadian oil shale. At 600¿, about 10% sulfur is released from Wangqing oil shale, while about 25% sulfur fixed in semi-coke; for Huadian oil shale, about 8% sulfur is distributed in gas while 37% in simi-coke.