燃烧过程中焦炭的孔隙结构演变与颗粒物的形成

Evolution of Porous Coke Structure and the Formation of Particulate Matter During Combustion

通过煤粉在沉降炉中的燃烧,研究了燃烧过程中煤焦的孔隙结构演变及其对颗粒物(PM)形成的影响,分析了煤焦颗粒的比表面和孔径分布。将不同气氛下燃烧生成的颗粒物通过Dekati低压撞击器(DLPI)分级,分级范围从0.03到10μm。研究表明:初始煤粒径的减小会使焦炭孔隙率增大,使焦炭在燃烧中更容易破碎,从而形成更多的超微米颗粒物;温度的升高虽然也会增加焦炭的孔隙率,但是对超微米颗粒物排放浓度的影响随不同的燃烧气氛而不同;氧气浓度的增加则有利于超微米颗粒物的形成。

Evolution of porous coke structure is the main reason of coke＇ s fragmentation during combustion of coal and exerting a significant influence on the formation of pariticulate matter （PM）. This evolution process and its influence on the formation of particulate matter during combustion has been studied by combustion tests conducted in a drop tube furnace. The coke was got from pulverized coal by pyrolysis in a nitrogenous atmoasphere. The coke particle＇s specific surface area as well as the pore size distribution were analyzed. Particulate matters begot by combustion in different atmospheres were then classified, with the help of a Dekati Low Pressurelmpecter （ DLPI）, into different size ranges from 0.03 up to 10 μm. Results indicate： coke＇s porosity increases with reducing size of the original coal particles, causing the coke to fragmentate during combustion ever the more readily, thereby generating ever the more supermicronized particulate matter. Though coke＇s porosity also increases with rising temperature, but its influence on the concentration of emitted supermicron particle varies with the combustion atmosphere concerned, while increasing oxygen concentration always favors the generation of supermicron sized particles.