CO2热物理化学效应对富氧燃烧煤粉着火及炭粒燃烧影响机理研究

富氧煤粉燃烧是一种有效实现CO2减排并控制NOx和SO2等多种污染物排放的煤粉燃烧新技术。尽管目前国内外对富氧燃烧煤粉着火及燃烧进行了较多研究，但由于CO2热物理化学特性与N2明显不同，CO2的多种热物理化学效应（稀释效应、热效应、化学效应、扩散效应等）同时存在且相互影响，也难以有效分离。已有的研究结果是这些效应全部或部分耦合的影响，不能准确地反映富氧煤粉燃烧的内在机理和物理化学实质。本项目提出了一种采用合适比例CO2/Ar混合气来调节燃烧火焰温度并有效分离CO2热物理化学效应的方法，在可控热氛围的透光式微量煤粉燃烧与FTIR发射-透射测温联用实验装置上，研究不同氧浓度和燃烧温度下CO2/O2、（CO2+Ar）/O2和N2/O2气氛煤粉着火、炭粒燃烧及颗粒温度的变化，定量确定分离的CO2热物理化学效应对煤粉着火和炭粒燃烧的影响，从而揭示CO2气氛对富氧燃烧煤粉着火和炭粒燃烧影响的内在机理。

Oxy-coal combustion with flue gas recirculation is one of the most promising techniques to control carbon dioxide (CO2) emission as well as nitrogen oxide and sulfur dioxide in the near term. In oxy-coal combustion processes, the thermophysical and chemical properties of CO2 such as heat capacity, heat and mass diffusivity and CO2-char gasification reaction is significantly different from those of N2 in conventional pulverized coal combustion, moreover the CO2 effects (including dilute effect, thermal effect, direct chemical effect and diffusion effect) on pulverized coal ignition and char combustion occur simultaneously and are intimately coupled. Although many studies have been devoted to the effects of CO2 on coal ignition, char combustion and NOx formation, their presented results are totally or partially the combination of these effects because it is very difficult to separate CO2 effects from one to another. Up to now, their impacts on oxy-coal combustion have not yet been clearly understood and no fine descriptions of the mechanisms are available.. The applicants propose a novel method of adjusting the flame temperature in CO2/O2 condition back to the value corresponding to the N2/O2 condition without changing the oxygen concentration by replacing an appropriate portion of CO2 with argon (Ar) in the oxidizer, and use it to separate the different effects of CO2 on oxy-coal ignition and combustion. An optical laminar entrained flow reactor coupled with FTIR emission-transmission particle temperature measurements is constructed to provide the well-controlled combustion environments. The coal particle ignition, char combustion characteristics and the evolution of burning particle temperatures are measured and investigated at comparable CO2/O2, CO2/Ar/O2 and N2/O2 environments with the given oxygen concentrations and combustion temperatures, and the separating effects of CO2 on coal particle ignition and char combustion characteristics are quantitatively identified and compared. The motivation of the project is to firstly elucidate the separating CO2 effects on underlying mechanisms of coal particle ignition delay and char combustion reactivity for oxy-coal combustion.