Abstract Coal char reactivity is the essential for gasifier design and operation. Char structure and reactivity are dynamic with reaction during gasification. To obtain the relationship between dynamic structure and reactivity, char samples at different carbon conversion were prepared at 1223 K by a rapid heating thermogravimetric analyzer (R-TGA). The ex-situ char reactivity was investigated in TGA between 1073 and 1223 K, and was correlated with the dynamic structure. Besides of XRD and SEM results, nano-computed tomography (nano-CT) revealed the morphology of carbon matrix and minerals during gasification. Results showed that reaction rate of in-situ char significantly increased firstly and then decreased, which was attributed to the gas switch step, the increase of graphitization degree and inhibition effect of minerals. In contrast, the reactivity of ex-situ char was initially controlled by chemical structure and later by the abundant catalytic activity of minerals. The reactivity decreased slightly and then increased with increasing carbon conversion. The unreaction core model (URCM) was more suitable to interpret the gasification kinetics based on the dynamic char structure and fitting coefficient. Meanwhile, the results by iso-conversional method also supported the validity of URCM, but also indicated that the activation energy of char gasification gradually increased during in-situ gasification.

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基于 CO2 气化过程中动态炭结构的炭反应性和动力学

摘要 煤焦反应性是气化炉设计和运行的关键。在气化过程中，炭的结构和反应性是动态的。为了获得动态结构和反应性之间的关系，通过快速加热热重分析仪 (R-TGA) 在 1223 K 下制备了不同碳转化率的炭样品。在 TGA 中研究了 1073 至 1223 K 之间的异位炭反应性，并与动态结构相关。除了 XRD 和 SEM 结果，纳米计算机断层扫描 (nano-CT) 还揭示了气化过程中碳基质和矿物质的形态。结果表明，原位炭的反应速率先升高后降低，这与气体转换步骤、石墨化程度的提高和矿物的抑制作用有关。相比之下，异位炭的反应性最初受化学结构控制，后来受矿物丰富的催化活性控制。随着碳转化率的增加，反应性略有下降，然后增加。基于动态炭结构和拟合系数，未反应核心模型（URCM）更适合解释气化动力学。同时，等转化方法的结果也支持了URCM的有效性，但也表明在原位气化过程中炭气化的活化能逐渐增加。基于动态炭结构和拟合系数，未反应核心模型（URCM）更适合解释气化动力学。同时，等转化方法的结果也支持了URCM的有效性，但也表明在原位气化过程中炭气化的活化能逐渐增加。基于动态炭结构和拟合系数，未反应核心模型（URCM）更适合解释气化动力学。同时，等转化方法的结果也支持了URCM的有效性，但也表明在原位气化过程中炭气化的活化能逐渐增加。