Abstract:

The changes in pore structure characteristics of biomass particles during pyrolysis were studied.The samples were characterized by N₂ isothermal adsorption/desorption method and scanning electronic microscopy (SEM).The results indicated that pyrolysis temperature had a notable impact on the pore structure and morphology of biomass char.Pyrolysis temperature was found to influence the size and the shape of char particles.A high temperature led to plastic deformation of particles resulting in smooth surfaces and large cavities.BET specific surface area first increased and then decreased.The change of pore volume was similar to that of BET specific surface area below 500℃.The fractal dimension (D_FHH) calculated by fractal Frenkel-Halsey-Hill (FHH) equation could represent pore structure satisfactorily.The fractal analysis showed that pyrolysis temperature had a close relationship with D_FHH.The fractal dimension could be correlated with BET specific surface area.

Key words:

生物质, 热解, 孔隙结构, 吸附/脱附, 分形维数

摘要：

利用氮气等温吸附/脱附法（-196℃）和扫描电镜（SEM）等研究了热解过程中生物质颗粒孔隙结构的演化规律，并用分形维数来描述焦颗粒内部孔隙表面形态的复杂程度。结果表明，热解温度对生物质焦的孔结构和表面形态有显著影响。热解过程中孔网络结构在发生演变，孔的形状发生了一定变化，且孔径有先变小后变大的趋势。高温导致焦颗粒发生塑性变形，使得孔隙扩大和孔表面更加光滑。随着温度的升高，生物质焦的BET比表面积先增大后减小，500℃以前，孔容积的变化规律与比表面积相近。通过分形FHH方程回归得到的分形维数能较好地表征颗粒内部孔隙表面的分形特征。其分形特征与热解温度密切相关，分形维数的变化与BET比表面积有一定关联。

关键词:

生物质, 热解, 孔隙结构, 吸附/脱附, 分形维数