煤粉燃烧过程中灰膜形成比例实验研究

煤焦颗粒燃烧过程中,灰膜形成显著影响其燃烧特性。因此,本文借助高温沉降炉研究了61~75,75~90和90~125μm三种粒径黄陵烟煤在1273和1673 K温度下的燃烧特性与灰膜形成比例;借助扫描电镜(SEM)详细观测空心微珠颗粒内部结构,提出灰膜比例计算公式,并分析温度,粒径和碳转化率对灰膜比例的影响。结果表明,高温下大部分灰分在焦炭烧尽阶段以灰膜形式存在。灰膜比例随温度和碳转化率增加而增加,随煤粉粒径增大而减小。高温下灰分用于形成灰膜比例相对较高,这为煤焦燃尽阶段的低反应性提供了合理的解释。煤焦颗粒动态燃烧过程中灰膜形成比例随燃烧工况变化而变化。该研究为煤焦颗粒燃烧动力学模拟灰膜比例选择提供了关键数据支撑。

Experimental Study on Ash Film Fraction During Pulverized Coal Combustion

To measure the ash film fraction during pulverized coal combustion,the Huangling bituminous coal with three size fractions of 61-75,75-90,and 90-125μm was burnt under 1273 and 1673 K in a drop-tube furnace.We observed the internal structure of the collected cenospheres by using the Scanning Electron Microscope(SEM).The ash film fraction was then calculated by the self-developed equation to provide measured values of ash film fraction under different conditions for further development of the kinetic models.The effects of temperature,particle size and carbon conversion ratio on the ash film fraction were also investigated.The results show that the ash film fraction exceeds 0.85 at high temperatures,which indicates that the majority of ash is distributed as ash film at the char burnout stage.The ash film fraction increases with higher temperature and carbon conversion,but it drops for coal particles of larger sizes.The high ash film fractions at high temperatures account for low reactivity in the late stages of char combustion The ash film fraction as a function of the carbon conversion ratio changes under different combustion conditions.This study provides essential information for further development of the char burning kinetic model.