化学链燃烧中赤铁矿氧载体的本征反应动力学研究

本文对一种化学链燃烧所用赤铁矿氧载体进行了本征还原反应动力学研究。氧载体颗粒的比表面积及孔径分布测试显示此种氧载体的孔隙率为0.031,表明此种氧载体结构致密,孔隙结构不发达。热重反应器上进行的程序升温还原实验结果显示氧载体的还原反应分阶段进行,并确定第一还原阶段的温度测试窗口为400~650°C。在排除了氧载体颗粒内外扩散的影响后,批次流化床实验分析确定反应的本征活化能为138.55 k J/mol,指前因子为6.8×1013s-1。通过对内外扩散因素的分析,加深了对此种氧载体颗粒与CO的宏观反应特性的认识。本研究结论与前人关于缩核模型、外扩散控制以及较小的表观活化能的研究结论具有良好的相容性。

Experimental investigation for the intrinsic reduction kinetics of a hematite as oxygen carrier in chemical looping combustion

In this work, the intrinsic kinetics of the first reduction stage of a hematite as oxygen carrier (OC) reduced by carbon monoxide (CO) has been investigated. For the intrinsic kinetics analysis, the BET surface area and the pore size distribution tests showed that the porosity of this kind of OC was 0.031, which revealed that the OC had dense structure with undeveloped pore structure. The temperature programmed reduction experiments were conducted in the thermo gravimetric analyzer, which showed that the reduction of OC was conducted in stages, and the appropriate experimental temperature range for testing the intrinsic kinetics of the first reduction stage was 400~650 °C. Furthermore, a series of formal experiments were conducted in a batch fluidized bed system with different temperatures and different CO concentrations. The intrinsic activation energy and the pre exponential factor were determined as 138.55 kJ/mol and 6.8×1013 s^-1 respectively, after the internal and external diffusion factor been eliminated. The analysis to the internal and external diffusion factors deepened the acknowledgement to the reaction properties of this kind of hematite OC reduced by CO. The researching results of this paper had good compatibility with many previous research conclusions such as shrinking core model, external diffusion control and smaller apparent activation energy.