基于TGA-FTIR和无模式函数积分法的稻壳热解机理研究

Determination of Pyrolysis Characteristics and Kinetics of Rice Husk Using TGA-FTIR and Model-free Integral Methods

利用热重红外联用技术(TGA-FTIR)和无模式函数积分法,研究了不同升温速率(5、10、20、30℃/min)下,稻壳的热解特性和热解动力学,深入探讨其热解机理。TG和DTG研究表明,稻壳的热解过程分为干燥、快速热解和炭化3个阶段,随着升温速率的增加,TG和DTG曲线向高温一侧移动。稻壳热解气体成分含量最多的是CO2,醛、酮、酸类以及烷烃、醇类和酚类等有机物。通过无模式函数积分法:FWO法和KAS法,计算得到的活化能随着转化率(α)增加数值波动明显,证明稻壳热解过程发生复杂的重叠、平行和连续的化学反应。0.1≤α<0.35,半纤维素的支链首先降解,然后是主链降解。0.35≤α≤0.7,纤维素首先转化为中间产物活性纤维素,然后活性纤维素再次降解。0.7<α≤0.8,主要是木质素降解,生物质中可降解的挥发分减少以及低反应活性的焦炭的不断生成是造成此阶段活化能快速增加的主要原因。总之,生物质三组分化学成分和结构差异造成不同转化率下活化能的差异。

The pyrolysis characteristics and kinetics of rice husk（ RH） were studied by using TGA-FTIR instrument and model-free integral method under different heating rates（ 5、10、20、30 ℃ / min）. The TG and DTG curves demonstrated that the pyrolysis process of RH consisted of the drying stage,degradation stage and carbonization stage. According to the FT-IR analysis,the prominent volatile components generated by the pyrolysis of RH were aldehydes,ketones,organic acids,CO2,and alkanes,phenols,etc. The activation energies dependent on the conversion rate were estimated by two model-free integral methods,i. e.,Flynn-Wall-Ozawa（ FWO） and Kissinger-Akahira-Sunose（ KAS） method at different heating rate. The fluctuation of activation energies could be interpreted by the multiple,parallel,and simultaneous reaction occurred in the pyrolysis process. For the first area of 0. 1 ≤ α 0. 35（ α was the conversion rate）,this could be mainly attributed to the hemicellulose degradation. The degradation firstly started on the branch chain of the hemicellulose,then random scission on the lineal chain occourred. For the second area of 0. 35≤α≤0. 7,cellulose initially pyrolyzed to active cellulose,then the degradation of active cellulose occurred.For the third area of 0. 7 α≤ 0. 8,the highest activation energy was observed due to the degradation of lignin.