低温干馏煤气/富氧大当量比燃烧实验及数值模拟研究

在内热式低温煤干馏中,引入富氧燃烧,同时提高煤气当量比,是在维持炉内温度分布基本不变的前提下提高煤气质量的有效途径。通过不同富氧比及不同尺寸烧嘴下的大当量比煤气/富氧燃烧实验结合数值模拟分析,探究了富氧低温干馏中的内热火焰温度分布特性及其受工艺条件和烧嘴尺寸的影响。结果表明:增大富氧比的同时增大燃料当量比可以维持平均火焰温度与空气助燃工况基本一致,但火焰锋面温度受局部当量比及流动条件影响;减小燃料及氧化剂射流的初始速度差,可以减缓组分混合、延长火焰并降低火焰锋面温度;煤气中三种气体按参与反应的速率快慢排序依次为氢气、一氧化碳、甲烷,随着燃烧反应进入湍流混合速率控制模式,组分间的选择性燃烧特征相对减弱。

Experimental and Numerical Study on Oxy-fuel Combustion of Low-temperature Coal Pyrolysis Gas at Fuel-rich Condition

For the low-temperature pyrolysis of coal with inner heating shaft furnace,adopting oxy-fuel combustion and at the same time increasing the equivalence ratio is an efficient way to improve the quality of the oven gas,with the temperature field inside the furnace essentially unchanged.To investigate the flame feature at the oxy-fuel low-temperature pyrolysis condition and the influence by process parameters and injector configuration,experiments and numerical simulations were carried out to analysis the combustion characteristics under the corresponding oxy-fuel and fuel-rich conditions with different oxygen contents.The results show that increasing the equivalence ratio to a certain content at oxy-fuel condition can keep the average temperature the same as that at air co-combustion condition,but the temperature at the flame front is dependent on the local equivalence ratio and flow condition.Increase in the reactant concentration and the mixing rate can both lead to higher flame front temperature.Decreasing the initial velocity difference between the fuel and oxidizer flow can slow down the mixing rate,increase the flame length and decrease the flame front temperature.The order of the chemical reaction rates that the species participate in the combustion reaction from large to small is hydrogen,carbon monoxide and methane.With the increase in the chemical reaction rate at oxy-fuel rich condition,the combustion mode turns to the turbulent mixing controlled and the selectivity of the combustion reaction among different species become weaker.