Abstract Chemical-looping combustion (CLC) is a novel combustion techology offering the potential to provide uninterrupted and reliable heat and power production from fossil or bio-derived fuels with integrated, intrinsic CO2 capture and minimal energy penalty. Operation of CLC at elevated pressures provides the potential for integration with a combined cycle, which makes the use of solid fuels significantly more feasible. To date, only a few experimental studies investigating CLC processes and oxygen carrier performance under pressurised conditions have been reported in the open literature. This article reports findings from investigations into the effect of pressure, temperature and CO concentration on the intrinsic reaction kinetics of an Al2O3-supported Fe-based oxygen carrier. Our study employed an innovative pressurised fluidised-bed reactor, designed for operation at temperatures up to 1273 K and pressures up to 20 bara, to simulate ex-situ gasification of solid fuels at elevated pressures. An intrinsic reaction model was developed and pseudo-intrinsic rate constants were derived. Differences in the activation energies and pre-exponential factors of the Al2O3-supported Fe2O3 and a pure Fe2O3 oxygen carriers were observed, indicating a change in reaction mechanism when Al2O3 was present. Subsequently, an adapted random pore model was developed to describe the variation of reaction rate with solid conversion. The good agreement between the adapted random pore model and empirical measurements indicated that the change in mechanism was due to a significantly higher product layer diffusivity for the Al2O3-supported Fe2O3 oxygen carrier compared with the pure Fe2O3 material. When pressurised, the observed reaction order with respect to CO was slightly lower than 1. The model developed using atmospheric pressure measurements was successfully applied to predict reaction kinetics at elevated pressures up to 5 bara providing further validation of the model.

中文翻译：

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铁基氧载体的加压化学循环燃烧：还原动力学测量和建模

摘要 化学循环燃烧 (CLC) 是一种新颖的燃烧技术，具有从化石或生物衍生燃料提供不间断和可靠的热能生产的潜力，具有集成的内在 CO2 捕获和最小的能量损失。在高压下运行 CLC 提供了与联合循环集成的潜力，这使得固体燃料的使用更加可行。迄今为止，公开文献中仅报道了少数研究加压条件下 CLC 过程和氧载体性能的实验研究。本文报告了压力、温度和 CO 浓度对 Al2O3 负载的 Fe 基氧载体的固有反应动力学影响的研究结果。我们的研究采用了创新的加压流化床反应器，设计用于在高达 1273 K 的温度和高达 20 bara 的压力下运行，以模拟高压下固体燃料的异地气化。开发了本征反应模型并推导了伪本征速率常数。观察到 Al2O3 负载的 Fe2O3 和纯 Fe2O3 氧载体的活化能和指前因子的差异，表明存在 Al2O3 时反应机制发生了变化。随后，开发了一种适应的随机孔模型来描述反应速率随固体转化率的变化。适应的随机孔模型和经验测量之间的良好一致性表明，与纯 Fe2O3 材料相比，Al2O3 负载的 Fe2O3 氧载体的产品层扩散率显着更高，因此机制的变化。