Numerical Simulation Of Particle Flow Characteristics And Heat Transfer In A Three-dimensional Rotary Kiln

Rotary kiln is a large thermal devices applied in the engineering practice. They are widely used to carry out a wide variety of material processing in industrial departments. This widespread usage is attributed to factors such as the ability to handle different size feedstock, the advantages of good mixing and flexibility of transfer between materials. Due to the complexity of structure of rotary kiln, low thermal efficiency and low product quality are typical problems for rotary kiln operations. With the development of computer technology, the method of numerical simulation analysis can be used to study material particle movement characteristics and gas-solid two-phase heat transfer process in the rotary kiln. This will provide theoretical basis for the optimization of operation in industrial rotary kiln. Therefore, scientific and rational use of numerical simulation to the research on particle flow characteristics and the gas solid two phase heat transfer process in the rotary kiln will have a guiding significance for engineering practice applications.Particle movement characteristics in the rotary kiln play a decisive role on the process of heat transfer between gas-solid two phases. This paper analyzes different motion model of particles and mechanism of particle flow characteristics in the rotary kiln. This paper develops a three-dimensional mathematical model based on the kinetic theory of granular flow and the Euler-Euler two-phase flow to explore the particle motion characteristic in the rotary kiln. The software Fluent is used to solve the Euler-Euler model. The model predictions are verified by comparing with the published experimental data. Simulations show that bed material can be divided into two regions in the transverse plane in kiln:active layer and passive layer; the velocity of active layer is large than that of passive layer; particle velocities make an angle with bed surface at the upper part of the active layer. The influences of influence factors on particle movement characteristics are investigated. When rotational speed of the rotary kiln, degree of fill and particle diameter increase respectively, the size of the active layer thickness and particle velocity increases correspondingly. Then, the mathematical model is applied to an engineering practice in the cement rotary kiln. Simulations show that particle movement characteristics in industrial rotary kiln. The results discussed here will provide a useful basis for the development of comprehensive three-dimensional models of rotary kilns. This will provide a theoretical guidance for the operation on the industrial rotary kiln. By means of the analysis of the reverse flow and complex heat transfer between gas and solid two phase flow, a three-dimensional model of heat transfer between gas-solid two-phase in the rotary kiln can be developed. This mathematical model is established by the previous particle movement characteristics model coupled with energy equation. The results can predict the temperature distribution of gas-solid in the axial and radial direction in the rotary kiln. This will provide theoretical basis to optimize the design of the rotary kiln and kiln waste heat recovery.