Numerical Investigation Of Gas-Solid Two-Phase Transfer Process In Rotary Kiln Based On CFD-DEM Coupled Method

The chain grate-rotary kiln pelletizing process is widely used because of its stable product quality and low energy consumption.The rotary kiln is the key equipment for high-temperature heating and roasting of pellets.The rotary kiln is a rotating high-temperature closed environment,the process parameters are difficult to detect,so it is difficult to realize the fine control of the rotary kiln,which becomes the bottleneck of energy saving and consumption reduction of the rotary kiln.For this reason,I intend to carry out a multi-physics numerical simulation of the combustion and pellet heating process in the rotary kiln,and to clarify the influence mechanism of the operating parameters on the multi-physics distribution characteristics of the rotary kiln and the temperature rise process of the pellets.Provide theoretical guidance to further improve the quality of pellets and optimize the production process.In this thesis,a rotary kiln of an enterprise is taken as the object,and the method of coupling computational fluid dynamics（CFD）-discrete element method（DEM）is used to carry out numerical simulation research on the combustion in the rotary kiln and the heating process of pellets.The main work and conclusions are as follows:（1）Based on the DEM method,the Box-Behnken method is used to establish a prediction model for the relationship between contact parameters of pellet particles and the natural accumulation angle.On this basis,the numerical simulation of the collision and movement process of pellet particles in the rotary kiln is carried out,and the information such as the shape of the material surface and the speed of the particles is obtained.（2）Based on the CFD method,the chemical reaction and transmission process of the two fuels,pulverized coal and coal gas in the rotary kiln are numerically simulated,and the temperature field and flow field in the gas phase region have been obtained.（3）The CFD-DEM coupling numerical simulation method for the gas-solid transport process of the pelletizing rotary kiln has been established through the coupled boundary of gas-solid two-phase,and the temperature prediction of the particle heating process in the pelletizing rotary kiln has been realized.After calculation,the temperature distribution of particles at the outlet of the rotary kiln is uneven;the gas phase temperature at the material surface shows a trend of increasing first and then decreasing;the concentration of CO₂ in the concentration distribution of components at the outlet of the rotary kiln is about 3.16%,and the concentration of NOx is about 23ppm;The online temperature monitoring data verifies the accuracy of the simulation results.（4）Based on the numerical simulation method of CFD-DEM coupling,the influence of operating parameters on the multi-physics field in the rotary kiln is studied.The increase of the rotational speed of the rotary kiln is beneficial to the temperature uniformity improvement of the particles at the outlet,but the residence time of the particles in the kiln is shortened;the increase of the initial temperature of the particles is beneficial to the roasting process of the pellets;the change of the injection ratio of pulverized coal and gas will affect the distribution of the high temperature zone in the gas phase and the calcination time of the particles.47 Figures,8 Tables,74 References...