O_2/CO_2气氛煤粉粒径对PM_(2.5)形成的影响

Effect of coal granule size on formation of PM_(2.5) in O_2/CO_2 atmosphere during coal combustion

采用管式炉研究了煤粉粒径对可吸入颗粒物排放特性的影响.试验煤种为徐州烟煤,煤粉粒径分别为135～220μm,91～135μm,61～91μm和0～61μm;燃烧试验在1123K,O2/CO2气氛下进行.试验用荷电低压撞击器(ELPI)采集燃烧后的可吸入颗粒物.结果显示:煤粉粒径是燃烧过程中影响PM2.5(2.5μm以下颗粒物)生成的重要因素,粒径越小,生成的PM2.5越多;4种粒径煤粉燃烧后生成的PM2.5粒径分布都是相似的双峰分布,峰值点分别出现在0.2和2.5μm左右.随着煤粉粒径的减小,S,Na和K几种元素的浓度值增加很大,Ca和Si的浓度值减少很多,而Fe的浓度值变化不大.粒径小于0.317μm的颗粒可能通过气化-凝结机理形成,超微米颗粒则可能是通过亚微米颗粒凝聚、聚结和矿物质熔融、破碎、聚结形成.

The influence of coal granule size on the emission characteristics of inhalable particles was studied with a tube furnace. Xuzhou bituminous coal was used, grouped in four size ranges： 135 - 220μm, 91 - 135 μm, 61 -91μm and 0 -61 μm. The combustion tests were carded out at 1 123 K under O2/CO2 conditions. The inhalable particulates after combustion were collected into an electri- cal low pressure-impactor （ELPI）. Results indicate that the coal granule＇s size is an important factor for the formation of PM2.5 （ particulates with diameters less than 2.5μm） during combustion. The smaller the coal granule size is, the more PM2. 5 is formed. The size distributions of PM2.5 formed after combustion of coal granule with different size are similar, displaying two peaks around 0. 2 μm and 2. 5 μm respectively. With decreasing of coal granule size, the concentrations of S, Na, and K increase rapidly; Ca and Si decrease strikingly and Fe changes a little. The ash particles smaller than 0. 317μm may form via the mechanism of vaporization and condensation, and the supermicron-size ash particles may form by coagulation and coalescence of the submicron-size ash, and fragmentation and coalescence of mineral matter.