Abstract:

This experimental study was conducted on the addition of methane and steam to biomass gasification in a two-stage reactor, taking pine wood as material. The effects of the methane on biomass ratio, α, and the steam to carbon ratio, S/C, on gas yield, carbon conversion, tar yield, tar composition and dew point were explored. The results showed the yield of H₂ increased by 57.4% as α changed from 0 to 0.4, so the addition of methane could be beneficial to the generation of hydrogen-rich syngas. The tar yield decreased by 30.5% and the yield of second and fifth classes of tars reached a minimum when α was 0.2. It was found that appropriate amounts of CH₄ can promote the conversion of tar, especially the conversion of macromolecule tar and phenols. With the increase of S/C, the yield of H₂ increased and the CO yield decreased. The content of all classes of tars decreased as S/C increased from 1 to 1.5. However, when the S/C was further increased to 2, the second and fifth classes of tars increased, indicating that steam can promote the conversion of tar to syngas, but excessive steam inhibits the decomposition of phenols and macromolecular tars. Both methane and steam in moderation can increase the H₂ yield of syngas, reduce the tar yield, improve the quality of the syngas, and aid the further utilization of the gasification products.

Key words: biomass, gasification, steam, methane, syngas, tar

摘要：

以松木木屑为生物质原料，在两段式反应器上进行甲烷、水蒸气对生物质催化气化影响的实验研究，考察了甲烷与生物质之比α、水碳比S/C对气体产率、碳转化率、焦油产率、焦油组分和露点温度影响的变化规律。结果表明：α从0增加到0.4，合成气中H₂的产率增加了57.4%，甲烷的加入有利于生成富含氢气的合成气；α为0.2时碳转化率最高，为86.9%，焦油产率下降了30.5%，第二、五类焦油的产率达到最低，可见适量CH₄的添加能促进焦油的转化，特别是大分子焦油和酚类的反应。随着S/C的提高，H₂产率升高，CO产率降低；S/C从1增加到1.5，各类焦油的含量均有所降低，当S/C进一步增加到2时，第二、五类焦油含量却有所上升，说明水蒸气可以促进焦油向气体分子转化的反应，但过量的水蒸气抑制酚类和大分子焦油的分解。总之，甲烷和水蒸气的适量添加均可以提高合成气中H₂的含量，降低焦油产率，提高合成气的品质，有利于气化产物的进一步利用。

关键词: 生物质, 气化, 水蒸气, 甲烷, 合成气, 焦油