Numerical simulation of material flow and heat transfer characteristics of cement rotary kiln

According to the analysis of material movement and heat transfer characteristics in the process of pulverized coal combustion, the rotary kiln was considered as a calculation field composed of high-temperature flue gas flow and material flow, which were coupled with each other. Based on heat transfer on the wall surface, heat flow equation was used to describe heat flux of the material through kiln wall. A heat transfer model with heat transfer compensation was proposed to describe the heat transfer between material and high-temperature flue gas. This model was used to simulate the combustion of pulverized coal, material flow and sintering in the rotary kiln. In addition, flow and temperature distribution of the material under different working conditions were studied. The results show that the heat transfer and movement of the material in the rotary kiln can be accurately reflected by the model. The increase of the rotational speed improves the axial acceleration of the material in the rotary kiln. The increase of material flow rate in the rotary kiln results in the decrease of the temperature of the material, but improves the temperature difference between surface material and internal material. The increase of the material filling rate enlarges the area of the outer recirculation zone and improves the temperature of cooling zone. When the material filling rate reaches 12%, Coanda effect will be induced, causing the rotary kiln flame shift toward material direction near the material area. © 2019, Central South University Press. All right reserved.