基于微分积分法和Friedman等转化率法的生物质热解动力学研究

Study on Biomass Pyrolysis Kinetics Based on Differential-integral Method and Friedman Iso-conversional Method

生物质热解动力学是生物质热解反应器设计和优化的理论基础。本文在5、10、15℃/min等3种不同升温速率下对核桃壳、纤维素以及木质素进行了热重分析,并通过微分积分法和Friedman等转化率法进行热解动力学研究。结果表明,木质素含量高的生物质固体残渣含量高,反应速率低;纤维素含量高的生物质固体残渣少,反应速率高;升温速率的加快会使最大失重速率增大,热解过程向更高的温度范围移动。对3种生物质样品进行热解动力学研究,发现微分积分法的R2明显高于Friedman等转化率法,计算的动态参数更准确可靠;微分积分法中一维扩散反应模型(D1)是反应核桃壳、纤维素和木质素热解过程的机理模型,该方法计算得到的3种生物质样品活化能表现为纤维素>核桃壳>木质素。

Biomass pyrolysis kinetics is the theoretical basis for the design and optimization of biomass pyrolysis reactor.In this paper,the walnut shell,cellulose and lignin were analyzed by thermogravimetric analysis at three different heating rates of 5,10,15℃/min,and the pyrolysis kinetics was studied by differential-integral method and Friedman iso-conversional method.The results showed that biomass with high lignin content had high solid residue content and low reaction rate;biomass with high cellulose content has less solid residue and high reaction rate;the acceleration of heating rate would increase the maximum weight loss rate and move the pyrolysis process to a higher temperature range.The pyrolysis kinetics of three biomass samples was studied.It was found that the R2 of differential-integral method was significantly higher than that of Friedman iso-conversional method,and the calculated dynamic parameters were more accurate and reliable.The one-dimensional diffusion reaction model(D1)in the differential-integral method was the mechanism model for the pyrolysis of walnut shell,cellulose and lignin.The activation energies of three biomass samples calculated by this method were as follows:cellulose>walnut shell>lignin.