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.