Abstract The nonisothermal thermogravimetric analysis was implemented for gasification of sawdust char (SD-char), wheat straw char (WS-char), rice husk char (RH-char), bamboo char (BB-char) and anthracite coal (AC) in the presence of CO2. The dependence of activation energy upon conversion for different biochars and AC was obtained by the integral isoconversional nonlinear (NL-INT) method which is a model-free method. Based on the activation energy values from the NL-INT method, a model-fitting method called random pore model (RPM) was used to estimate the kinetic parameters including the preexponential factor and pore structure parameter from the experimental data. The results are shown that the gasification reactivity of different samples from high to low can be sorted as that of WS-char, SD-char, BB-char, RH-char and AC. In the early stage of gasification, the activation energy values of biochars increase generally with an increase in the conversion degree, whereas the value of AC decreases. Thereafter, the activation energy values remain almost unchanged when the conversion is up to some extent. When the conversion degree varies between about 0.3 and 0.9, these carbon materials can be sorted in the order of average activation energy from low to high as WS-char, SD-char, AC, RH-char and BB-char, respectively, 134.3, 143.8, 168.5, 184.8 and 193.0 kJ/mol. It is shown that a complex multistep mechanism occurs in the initial stage of gasification, while a single-step gasification mechanism exists in the rest of the gasification process. The RPM is suitable for describing the gasification of biomass chars and AC except the initial gasification. Additionally, it is found that the kinetic compensation effect (KCE) still exists in the gasification reactions of biochars and AC. However, the AC deviates markedly from the KCE curve. This may be caused by the similarity of carbonaceous structure of biochars and the difference in reactivity between biochars and AC.

中文翻译：

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基于积分等转化非线性方法的生物炭和无烟煤CO2气化动力学分析

摘要 对木屑炭（SD-char）、麦秆炭（WS-char）、稻壳炭（RH-char）、竹炭（BB-char）和无烟煤（AC）的气化进行了非等温热重分析。 CO2 的存在。通过积分等转化非线性 (NL-INT) 方法，这是一种无模型方法，获得了活化能对不同生物炭和 AC 转化率的依赖性。基于 NL-INT 方法的活化能值，使用称为随机孔模型 (RPM) 的模型拟合方法从实验数据估计动力学参数，包括指前因子和孔结构参数。结果表明，不同样品的气化反应活性从高到低可分为WS-char、SD-char、BB-char、RH-char和AC。在气化初期，生物炭的活化能值普遍随着转化度的增加而升高，而AC值则降低。此后，当转化率达到一定程度时，活化能值几乎保持不变。当转化率在0.3~0.9之间变化时，这些碳材料可以按照平均活化能从低到高的顺序分别为WS-char、SD-char、AC、RH-char和BB-char，134.3 、143.8、168.5、184.8 和 193.0 kJ/mol。结果表明，气化的初始阶段存在复杂的多步机制，而气化过程的其余部分则存在单步气化机制。RPM 适用于描述生物质炭和活性炭的气化，但初始气化除外。此外，发现生物炭与活性炭的气化反应中仍然存在动力学补偿效应（KCE）。然而，AC 明显偏离 KCE 曲线。这可能是由于生物炭碳结构的相似性以及生物炭与活性炭之间反应性的差异造成的。