桉树热解产物热物性参数演变特性研究

Thermal Parameters Properties Evolution of Eucalyptus Pyrolysis Bio-char

在自行设计的生物质固定床热解装置上,进行了150~850℃温度范围内,每隔100℃的桉树芯材木屑的固定床热解实验,并进行固态产物的热物性参数测试。结果表明:随着温度的升高,桉树芯材热解炭的固态产率逐渐减小,低位热值逐渐增大,450℃热解炭的热值比木屑原料提高了95.53%;堆积密度先减小后增大,体积能量密度持续增大,750℃热解炭的体积能量密度比原料增大了63.21%;热解炭的比热容和导热系数与热解炭内部的含水率、骨架结构,即孔道开度和密度有密切的关系。随着热解温度的升高,热解炭的比热容呈U字型趋势先减小而后增大,导热系数先轻微减小后以指数形式大幅增大,得到比热容和导热系数随温度的变化曲线方程,拟合度分别为0.932 0和0.995 3。

In recent years,with the growth of population and shortage of fossil energy,the environmental pollution problem has become more severe. Eucalyptus planted in south China is a kind of biomass resource with large quantity and high quality. The thermochemical conversion of biomass（ pyrolysis,gasification,or combustion） is one of the most promising non-nuclear forms of future energy. It is a renewable source of energy and has many advantages from the ecological point of view. Pyrolysis of wood is a very complicated physical and chemical process which can transform biomass into useful fuel,such as bio-char,bio-oil and gas. Studying its thermo-physical properties is of great significance for the design of the equipment,control of process parameters and quality of the product. In the self-designed fixed bed pyrolysis device,the eucalyptus wood chips were paralyzed in the temperature range of 150 ~ 850℃. The remaining bio-char proceeds to be tested for the thermal parameters,including solid yield,bulk density,volume energy density,specific heat and heat conductivity coefficient. The results showed that with the increase of temperature,the solid yield was decreased and the weight loss rate in temperature range of 150 ~ 350℃ was up to 31. 40% per 100℃; the lower heating value（ LHV） of samples was increased gradually. The LHV of bio-char at 750℃ was 95. 53% higher than that of the raw eucalyptus. Bulk density was decreased first and then increased while the volume energy density（ VED） was increased in the whole experimental temperature range. The VED of bio-char at 750℃ was up to 63. 21% more intensive than the raw material. The specific heat and heat conductivity coefficient were closely related to the moisture content and pores structure in bio-char. With the increase of treated temperature,the specific heat of sample presented a U-shaped tendency which was decreased firstly and then increased significantly. The heat conductivity coefficient was increased according to exponential growth after slight decrease. The fitting equations of specific heat Cpand heat conductivity coefficient λ with temperature were obtained and the fitting degrees R^2 were 0. 932 0 and 0. 995 3,respectively.