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Analysis of reaction mechanism and kinetics of biomass in pyrolysis and gasification

生物质热解气化反应机理及动力学分析

基本信息

批准号：
20760520
负责人：
FUSHIMI Chihiro
金额：
$ 2.75万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Young Scientists (B)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2009
项目状态：
已结题

项目摘要

Biomass gasification is a promising technology because of the high thermal efficiency. However, a large amount of condensable organic compounds (tar) which causes blockages and corrosion of pipes are evolved in biomass gasification.In this study, the inhibition of the gasification rate of biomass char by H_2 and tar was investigated. At first, the reaction rate of char in steam gasification was measured using a thermobalance reactor by varying partial pressure of H_2 (P_<H2>=0, 3, 10, 25kPa). The rate of steam gasification was decelerated by the presence of H_2 and the inhibition was significant when the partial pressure of H_2 was high (P_<H2>=25kPa). It was found that reverse oxygen exchange occurred at first period and dissociative adsorption of H_2 on char occurred at second period. The effect of levoglucosan, which is major component of pyrolysis product from cellulose, on the reaction rate of char was also measured with a newly developed drop-tube/fixed bed thermobalance reactor. It was found that not only H_2 but also other hydrocarbons evolved by pyrolysis of levoglucosan substantially inhibit char gasification when the feed rate of levoglucosan was high (250mg/min).In addition, the effects of alkali and alkaline earth metals (AAEM), which can act as an excellent catalyst for the gasification and combustion reactions, on the interactions between the three major components of biomass (cellulose, xylan and lignin) were investigated. It is found that AAEM decreased the generation of water-soluble tar derived from cellulose. AAEM do not have significant influence on the interaction between cellulose and xylan.

生物质气化由于热效率高，是一项很有前途的技术。然而生物质气化过程中会产生大量的可凝结有机化合物(焦油),导致管道堵塞和腐蚀。本研究主要研究了H_2和焦油对生物质焦气化速率的抑制作用。首先，利用热天平反应器通过改变H_2分压(P_<H2>=0、3、10、25kPa)来测量蒸汽气化中炭的反应速率。 H_2的存在使蒸汽气化速率减慢，且当H_2分压较高(P_<H2>=25kPa)时抑制作用显着。结果发现,第一阶段发生了反向氧交换,第二阶段发生了H_2在炭上的解离吸附。左旋葡聚糖是纤维素热解产物的主要成分，它对炭反应速率的影响也用新开发的落管/固定床热天平反应器进行了测量。研究发现，当左旋葡聚糖的进料速率较高（250mg/min）时，不仅H_2，而且左旋葡聚糖热解放出的其他碳氢化合物都显着抑制焦炭气化。此外，碱金属和碱土金属（AAEM）可以作为气化和燃烧反应的优良催化剂，对三种主要物质之间相互作用的影响研究了生物质的成分（纤维素、木聚糖和木质素）。结果发现，AAEM 减少了源自纤维素的水溶性焦油的产生。 AAEM 对纤维素和木聚糖之间的相互作用没有显着影响。