热解技术是稻壳有效利用的重要处理方法,其炭、气和油三态产物均具有较高的利用价值.稻壳炭是稻壳热解后产生的固态产物,对环境、农业和新能源等具有重要的影响作用.稻壳炭的理化特性决定了炭产物的利用方式及效果,不同热解温度条件下制得的稻壳炭的理化特性不同,热解温度对稻壳炭理化特性影响较大.对不同热解温度制得的稻壳炭的理化特性进行系统研究有利于稻壳炭的定向制备及高值化利用.为确定热解温度对稻壳炭理化特性的影响作用,在管式炉固定床上制得不同热解温度的炭产物,对稻壳炭工业分析及元素分析、可溶性物质含量、表面官能团和孔结构等特性进行综合分析,以掌握热解温度对生物炭特性的影响规律.热解温度为350,450,550,650,750,850℃,气体流量600mL·min-1,热解停留时间为40min.分别采用TGA2000型工业分析仪和EL-3型元素分析仪测定稻壳炭的工业分析和元素分析,采用自动量热仪测定其低位发热量.采用pH计、电导率仪和离子色谱仪分别测定炭的pH值、总可溶性物质含量和可溶性氮含量.采用VERTEX 70型傅里叶变换红外光谱仪测定稻壳炭表面官能团组成,采用物理化学吸附仪测定孔隙结构特性.结果表明:温度越高稻壳炭的产率越低,随着热解温度的增加,挥发分逐渐析出,含氢和氧官能团及含碳物质逐渐分解,而灰分增加,固定碳和低位热值先增加后降低,分别在550℃和450℃具有最高值.热解温度550～650℃制得的稻壳炭含有较高的可溶性物质含量和发达的孔隙结构特性,该结果对生物炭的制备及应用具有重要的参考意义.
Pyrolysis of rice husk(RK), an effective utilization option, offers different products such as biogas, bio-oil and biochar with higher application value. Rice husk biochar is the solid product of rice husk pyrolysis, which would have important influence on environment, agriculture and new energy. The physicochemical properties characteristics of rice husk biochar determine its utilization ways and effects, and biochar produced under the different pyrolysis temperatures have different physicochemical characteristics. The pyrolysis temperature has a greater influence on the physicochemical properties of rice husk biochar, and the study on the physicochemical properties characteristics of rice husk biochar produced under the different pyrolysis temperatures would be beneficial to the orientation preparation and high value utilization of rice husk biochar. The biochar product of different pyrolysis temperatures was made in a tubular reactor to determine the effect of pyrolysis temperature on the physicochemical properties characteristics of rice husk biochar. The proximate analysis, ultimate analysis, lower heating value (LHV), soluble matter content, surface functional group and pore structure and of rice husk biochar were measured to study the influence of pyrolysis temperature on the characteristics of biochar. The pyrolysis temperatures were 350, 450, 550, 650, 750, 850 ℃, the gas flow rate was 600 mL·min-1, and residence time was 40 min. Proximate analysis of rice husk biochar was conducted in an industrial analyzer TGA2000, and elemental analysis was determined using an elementary analyzer EL-3. Low heating value (LHV) of each sample was measured by an automatic calorimeter instrument. The pH, total soluble matter content and soluble nitrogen content were determined by pH meter, conductivity meter and ion chromatograph. The surface organic functional groups of biochar were measured with Fourier Transform Infrared (FTIR) spectra, and the physical pore structure was analyzed by Brunauer-Emmett-Teller (BET) surface area. Results showed that the yield of biochar was low when the pyrolysis temperature was high. The volatile matter gradually released, and surface functional groups with hydrogen and oxygen gradually decomposed. While the ash increased, the fixed carbon and low heat value first increased and then decreased, with the maximum value at 550 ℃ and 450 ℃. The rice husk biochar produced at and 550-650 ℃ temperature had higher total soluble matter content and developed pore structure characteristics, and the results would be of great significance for the preparation and application of biochar.
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