Pressurised chemical-looping combustion of an iron-based oxygen carrier: reduction kinetic measurements and modelling
Pressurised chemical-looping combustion of an iron-based oxygen carrier: reduction kinetic measurements and modelling
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DOI：
10.1016/j.fuproc.2017.11.018
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发表时间：
2018-03
影响因子：
7.5
通讯作者：
Zili Zhang;Joseph G. Yao;Matthew E Boot-Handford;P. Fennell
中科院分区：
文献类型：
--
作者：
Zili Zhang;Joseph G. Yao;Matthew E Boot-Handford;P. Fennell
化学循环燃烧（CLC）是一种新型的燃烧技术，它可以从化石燃料或生物衍生燃料中提供不间断的、可靠的热量和电力生产，同时具有集成的、固有的二氧化碳捕获和最小的能量损失。CLC在高压下运行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，在公开文献中只有少数研究加压条件下CLC过程和氧载体性能的实验研究被报道。本文报道了压力、温度和CO浓度对al2o3负载铁基氧载体本征反应动力学的影响。我们的研究采用了一种创新的加压流化床反应器，设计用于在温度高达1273 K和压力高达20 bara的情况下运行，以模拟固体燃料在高压下的非原位气化。建立了本征反应模型，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数前因子的差异，表明al2o3存在时反应机理发生了变化。随后，建立了一个适应随机孔隙模型来描述反应速率随固体转化率的变化。调整后的随机孔隙模型与经验测量结果吻合良好，表明机理的变化是由于al2o3负载的fe2o3氧载体比纯fe2o3材料具有更高的产物层扩散系数。加压时，观察到的相对于CO的反应阶数略低于1。利用大气压力测量建立的模型成功地应用于预测高达5 bara的高压下的反应动力学，进一步验证了该模型。
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 CO2capture 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 Fe2O3and a pure Fe2O3oxygen carriers were observed, indicating a change in reaction mechanism when Al2O3was 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 Fe2O3oxygen carrier compared with the pure Fe2O3material. 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.