鼓泡床条件下石墨颗粒燃烧行为的试验与模型研究

Experimental and Model Study on Combustion Behavior of Graphite Particles in Bubbling Bed

通过鼓泡床焚烧方式可以实现对废弃石墨的大幅减容,为了探究石墨在鼓泡床内的燃烧行为,以单石墨颗粒为研究对象,利用鼓泡床试验台对其燃烧特性开展了试验研究,并结合数学模型分析了床层温度、床料粒径、石墨粒径等因素的影响关系。结果表明:鼓泡床层温度的降低和流化风速的增加都会使得烟气中CO浓度增加;随着床层温度由700℃增加至900℃,石墨颗粒燃烧速率逐渐加快,但增加幅度逐渐减小,显示出燃烧由化学反应控制逐渐转向传质过程控制,在900℃时的燃烧速率主要受传质过程影响;在满足了最小流化风速的前提下,提高鼓泡床内流化风速不能显著增加床层内的气相传质系数;石墨粒径的减小和床料粒径的增加均能提高床层内的传质系数,从而促进比燃烧速率的增加.

The substantial reduction of waste graphite can be achiered by bubbing bed combusting.In order to explore the combustion behavior of graphite in bubbling bed,the combustion characteristics of graphite particles were investigated by bubbling bed test bench,and the influence of bed temperature,bed particle size,graphite particle size and other factors was analyzed by mathematical model.The results show that the CO concentration in flue gas increases with the decrease of bubbling bed temperature and the increase of fluidizing wind speed.As the bed temperature increases from 700℃ to 900 ℃,the combustion rate of graphite particles increases gradually,but the increase amplitude decreases gradually,showing that the control of chemical reaction gradually changes to the control of mass transfer process.At900℃,the combustion rate of graphite is mainly affected by the mass transfer process.Under the premise of meeting the minimum fluidizing wind speed,increasing the fluidizing wind speed in bubbling bed cannot significantly increase the mass transfer coefficient in the bed.Both the decrease of graphite particle size and the increase of bed particle size can improve the mass transfer coefficient in the bed,thus promoting the increase of specific combustion rate.