Abstract:

To obtain high-quality bio-syngas with low tar content from sorghum straw,two-stage prolysis (prolysis+cracking) was performed in a two-stage fixed bed reactor based on the research on its one-stage prolysis characteristics,and the catalytic effects of oil shale ash on cracking the volatile products from pyrolysis were investigated.The results showed that compared to the one-stage prolysis,the two-stage prolysis strengthened the correlation between water vapor with volatiles (above all pyrolysis gas).High cracking temperatures facilitated cracking and reforming of tar,resulting in generation of more gas products and also enhancements in the bio-syngas (H₂+CO) yield and the H₂/CO volumetric ratio.The oil shale ash significantly promoted gasification of tar.With the oil shale ash added for cracking volatiles at the moderate temperature of 850℃(pyrolysis at 450℃),the gas yield surpassed 40%(mass) with such a low tar yield as 1.0%(mass).Meanwhile,the yield of bio-syngas reached up to 186 ml·g^-1 with its highest content of 64%(vol) in gas products,and the H₂/CO volumetric ratio was above 0.5.The oil shale ash facilitated H₂ generation mainly due to its ferric component capable of catalyzing water-gas shift reaction.

Key words: pyrolysis, cracking, sorghum straw, syngas, oil shale ash

摘要：

为从高粱秸秆生产高品质、低焦油含量生物合成气，基于其单段热解特性研究，借助两段式固定床反应器实施两段热解（热解+裂解），同时考察页岩灰对热解挥发分的催化裂解效果。结果表明：相对单段热解，两段热解强化了水蒸气与挥发分（尤其是与热解气）的交互；提高裂解温度促进焦油裂解和重整，便利了热解气的生成，同时提高合成气（H₂+CO）的产率和H₂/CO体积比；裂解中加入页岩灰显著促进生物焦油气化，大幅降低气体产物焦油含量：裂解温度适中（约850℃）时（450℃热解），热解气产率超过40%（质量），焦油产率低于1.0%（质量），合成气产量约186 ml·g^-1、体积分数高达64%，且H₂/CO比超过0.5。页岩灰便利H₂的生成，主要源于其铁组分对水气变换的催化作用。

关键词: 热解, 裂解, 高粱秸秆, 合成气, 页岩灰