热分析仪中生物质炭氧化特性及面反应动力学分析

OXIDATION CHARACTERISTICS AND KINETICS OF BIOCHAR IN THERMALANALYZER BASED ON SURFACE REACTION

为明确生物质堆积燃烧或大颗粒炭燃烧动力学特性,应用同步热分析仪对不同生物质炭(玉米秸、稻壳、榆树皮和柏木)在不同横截面积坩埚(0.21、0.42 cm^(2))中使用不同高度样品量(满坩埚、1/10坩埚)进行实验,分析样品失重速率与反应面积(坩埚横截面积)和样品量的关系。结果表明:失重速率与反应面积成正比,与样品量无关,表明生物质炭的堆积燃烧为面反应;灰分少、氧扩散阻力小的柏木炭的热重数据更能体现动力学特性,其基于面反应的动力学参数指前因子As=40.5 m/s,活化能E=61.5 kJ/mol。

To determine the kinetic characteristics of piled combustion of biomass or bulk char,the oxidation experiments of different biochar including maize stover char,rice husk char,elm bark char and cypress char were conducted in a simultaneous thermal analyzer.In these experiments,crucibles with different cross sectional area(0.21,0.42 cm^(2))and samples with different height(full crucible,1/10 crucible)were used to analyze the mass loss rate.The results show that the mass loss rate is proportional to reaction area and irrelevant to sample size,indicating that the piled combustion of biochar is surface reaction.Thermogravimetric data of cypress char can better reflect kinetic characteristics due to its lowest ash content and diffusion resistance of oxygen,and its oxidation kinetics based on surface reaction are obtained as the frequency factor AS=40.5 m/s and activation energy E=61.5 kJ/mol.