三种生物质的热解动力学研究

为进一步研究生物质的热解动力学,在氮气气氛和不同的加热速率下对马尾松、棉杆和杉木试样进行了热分析实验.结果表明,由于生物质中矿物质对热解的催化作用,灰分含量越高,热解温区越低;用占生物质质量约10%的碳酸钠对生物质进行处理后,其热解温区也明显降低;用Ozawa-Flynn-Wall法计算的活化能随转化率的增加而增加,这是由于生物质中不同成分如半纤维素与纤维素等的热解特性不同所致;联合运用Satava法和Ozawa-Flynn-Wall法确定了低温区和高温区热解的最佳机理函数,发现Avrami-Ero-feev方程、Jander方程和Zhuralev,Lesokin and Tempelmen(Z-L-T)方程分别可以用来很好地描述不同温区的热解过程.热解机理是随机成核和随后生长或三维扩散.除了高温催化段以外,在其他温区用两种方法计算的活化能均很接近.

Kinetic study on thermolysis of three different biomass species

To further study the thermolytic kinetics of biomass,thermal analysis of samples of pine wood,cotton stalk and fir wood was conducted at various heating rates under nitrogen atmosphere.Results show that the pyrolysis temperature scope is decreased with the increasing ash content ascribed to the catalytic effects of minerals in the biomass.The sodium carbonate accounting for about 10% of the biomass by weight lowers the thermolysis temperature scope apparently.Activation energies calculated with Ozawa-Flynn-Wall method increase with the increasing conversion due to different thermolysis characteristics of the components such as hemicellulose and cellulose in the biomass.The best mechanism functions for thermolysis at low and high temperature scopes are determined by combining Satava method and Ozawa-Flynn-Wall method.It is found that Avrami-Erofeev equation,Jander equation and Zhuralev,Lesokin and Tempelmen(Z-L-T)equation are appropriate for describing the thermolysis at different temperature scopes.The thermolysis mechanism is either three-dimensional random nucleation and nuclei growth or three-dimensional diffusion.Activation energy values calculated by Satava method are in agreement with those calculated by Ozawa-Flynn-Wall method except for those of catalytic thermolysis at high temperature scope.