水泥回转窑传热特性数值模拟

Numerical simulation of heat transfer characteristics of cement rotary kiln

回转窑是水泥生产过程中能耗最高的装置,回转窑内气固两相流、煤燃烧与传热等的数值模拟研究,对提高回转窑的能源利用率有重要意义。以装备四通道旋流燃烧器的回转窑作为研究对象,建立符合回转窑内部流体特性的计算流体力学模型以及不同斜度的燃烧器-回转窑三维模型,利用FLUENT软件对回转窑内的热辐射和煤粉燃烧等进行数值模拟,研究不同回转窑斜度和燃烧器工况对回转窑内流场分布、温度分布以及熟料表面空气温度分布的影响。结果表明,当回转窑斜度为0.035时,熟料平面上的烧成带范围达到最大;旋流风速选择90m/s为宜,过低的旋流风速会使火焰不稳定,而过高的旋流风速会引起煤粉的扩散,不利于火焰温度的升高;提高轴流风速可以缩短黑火头的长度,但这会导致火焰峰值温度降低,且当轴流风速达到200m/s时,回转窑火焰出现紊乱。

Rotary kiln is the highest energy consumption in the cement production process.The numerical simulation of gas-solid two-phase flow,coal combustion and heat transfer in rotary kiln is of great significance to the energy saving and emission reduction of rotary kiln.The 3-D model of the burner-rotary kiln with different inclination and the integrated computational fluid dynamics (CFD) model were established by using the rotary kiln equipped with four-channel swirl burner as the research object.The thermal radiation and pulverized coal combustion in rotary kiln were numerically simulated by FLUENT software.The effects of different rotary kiln inclination and burner condition on the distribution of flow field,temperature distribution and air temperature distribution of clinker were studied.The results indicated that when the slope of the rotary kiln was 0.035,the firing zone on the clinker plane reaches the maximum.The low swirling wind speed will make the flame unstable,and too high swirl wind speed will cause the spread of coal,is not conducive to the flame temperature rise,so the swirl speed was set to 90 m/s more appropriate.Increasing the axial wind speed can shorten the length of the black flame,but which will reduce the flame peak temperature.When the axial flow rate reaches 200 m/s,the rotary kiln flame is disordered.