微波热裂解木屑的基础研究

利用微波热裂解的方法将木屑转化为生物能源,是一种非常有前景的处理和利用废弃生物质转化为能源的工艺,考察了多模谐振腔和单模谐振腔对热裂解的影响,并研究了含水率和加热速率在微波加热下对木屑热裂解的影响,讨论了微波加热与传统加热下生物质热解机理。研究发现单模谐振腔比多模谐振腔更有助于生物质的快速热解。孔隙中的水分是微波热解生物质的主要因素,可以提高加热速率。生物质热解在微波加热与传统加热下的最大差别在于前者是由里及外的加热,可以减少二次反应的发生,提高生物油的收率和质量,固体产物炭的性质也得到了改善。热解油主要是由脂肪族含氧化合物和芳香烃类物质的复杂混合物,热解气体产物主要为CO、CO₂、甲烷和乙烷。

Fundamental Study on the Microwave Pyrolysis of Sawdust

The pyrolysis of sawdust using microwaves is a potential technology for the transformation of biomass waste to high-value bio-energy. The influence of microwave cavities as multimode and single mode to the pyrolysis were investigated, moisture content and heat rate were examined for the influence of microwave processing. It was found that the pore water is the key factor to induce pyrolysis under microwave irradiation; the moisture content can highly increase the pyrolysis possibility and heating rate of the sample bulk. The pyrolysis products depend upon the treatment conditions and moisture content. The mechanism of microwave pyrolysis is quite different from conventional heating pyrolysis. In conventional method, pyrolysis develops toward a direction from the surface to the center, the escape rate of volatile products through the high temperature surface region is slow. Therefore, the pyrolysis carbon will deposit on the pores, and it is difficult to prevent the undesired secondary reactions leading to low liquid yields. On the other hand, microwave heating showed the reverse temperature distribution. Undesired secondary reactions are decreased due to higher volatile gas transfers from the high temperature core region results to clean micro-pores with more open structure and larger specific areas of char than that produced by conventional heating. The liquid product is a mixture of oxygenated aliphatic and aromatic compounds, and the main compositions of the gas product are: CO, CO₂, CH₄ and C₂H₆.