谷壳热解/气化的热重-红外联用分析

KINETIC STUDY ON PYROLYSIS AND GASIFICATION OF RICE HUSK BY USING TG-FTIR ANALYSIS

利用热重分析(TGA)和傅里叶红外光谱(FTIR)联用技术对典型生物质热解和气化特性及其气体产物的释放规律进行了研究,并确定了其热解和气化机理。研究表明,谷壳在 N_2和 CO_2气氛下的热解失重主要集中在220～600℃,并且具有相似的热解特性;在800℃以后谷壳在 N_2和 CO_2气氛下反应所对应的热重曲线出现了较大的差异。气体产物主要在240～600℃析出,主要成分为 H_2O、CO、CH_4、C_xH_y(x>1)和一些有机碳水化合物,其中 H_2O 的析出温度较低,而 CH_4和 CO 析出温度相对较高;由于谷壳气化过程中存在 CH_4和 CO_2重整反应,使得 H_2O析出呈现双峰形式,并且 CH_4含量相对于热解时偏小,CH_4的析出特性曲线仅有一个峰,CO 的析出特性曲线是双峰形式,且 CO 的释放曲线和谷壳反应速率曲线有着相似的特征温度和变化趋势。谷壳的热解服从两步反应机理,低温段的热解机理函数为 f(α)=(1-α)^(2/3),高温段的热解机理函数为 f(α)=(1-α)^(2.5);而气化机理函数为 f(α)=(1-α)^(2/3)。

The properties and reaction kinetics of the pyrolysis and gasification of rice husk were investigated in the thermogravimetric analyzer （TGA） coupled with a Fourier transform infrared （FTIR） spectrometer with various atmospheres. The results showed that the weight loss happened from 220℃ to 600℃ and rice husk displayed similar pyrolysis characteristics under the two atmospheres, N2 and CO2. The gas products emitted from rice husk were detected on-line with Fourier transform infrared spectroscopy （FTIR）. The main gas products were H2O, CO, CH4, CxHy（x 〉 1）and some organics carbohydrate mixtures. H2O was released at the lower temperature, whereas CH4 and CO were released at the higher temperatmre. There were similar characteristic temperature and evolution tendency between the emission curve of CO and the reaction rate curve of rice husk. The pyrolysis of rice husk followed two-step reaction mechanisms. The pyrolysis mechanism function was f（ a ） = （1 - a ）^2/3 in the low temperature part and f（ a ） = （1 - a ）^2.5 in the high temperature part. The gasification mechanism function was f（ a ） = （ 1 - a ）^2/3.