一种改进的纤维素热解动力学模型

纤维素热解是生物质能利用技术中的一个重要领域，而热解动力学又是其中的关键内容，为了更好地研究该过程，基于Broido-Shafizadeh热解动力学模型进行了验证计算和分析比较，讨论了竞争反应动力学参数、“活性纤维素“的存在与状态以及热解产物二次反应等几个方面的问题，并在此基础上提出了一种改进的纤维素热解动力学模型。改进后的动力学模型采用了新的竞争反应动力学参数，克服了B-S模型中由于试验样品较大，样品颗粒内部存在传热限制而导致的动力学参数偏差；另一方面，计算表明，在快速加热条件下，纤维素热解过程中的活性纤维素相变过程可以影响热解的传热、传质过程，改进后的动力学模型特别强调了该过程的重要性；最后，为了体现 挥发分二次分解对纤维素热解反应的影响，改进模型在反应途径中包含了该过程。经过改进完善后的热解动力学模型更中贴近于客观事实，这将有利于对纤维素热解这一复杂过程展开进一步研究。

An improved kinetic model for cellulose pyrolysis

Cellulose pyrolysis is an important area in biomass thermochemical conversion. Developing advanced pyrolysis technology requires basic understanding of chemical kinetics. This paper deals with the improvement of the kinetic model for cellulose pyrolysis. To study this process, intensive reviews, calculations, comparisons and analyses were carried out based on the well known Broido Shafizadeh kinetic model. An improved kinetic model of cellulose pyrolysis was proposed. First, the validity of the kinetic data on competitive reactions in Broido Shafizadeh model was checked. Through analyses and comparisons, a new kinetics model was developed to overcome the error caused by heat and mass transfer limitation in the parameter deduced experiment. Then, the so called 'active cellulose' was examined. The appearance of liquid 'active cellulose' during pyrolysis was analyzed on the basis of modelcalculation and shown to be important in the case of high heating rate pyrolysis processes and should be considered in the improved kinetic model. At last, the secondary reaction of volatile components was added as a part of the kinetic model. Relevant kinetic data were chosen from literature. The proposed kinetic model for cellulose pyrolysis is a step toward the reality and will certainly benefit further study on cellulose pyrolysis.