The Numerical Simulation Of Two-phase Turbulent Flow With Combustion And Chemical Reactions In A Precalciner

The thesis is based on a study of numerical simulation of gas-solid tow-phase flow in precalciner, which is funded by "863"project. Precalciner is key equipment of the system of precalcination in cement's production process. In precalciner, the fluid parameters, such as concentration distribution, kinetic velocity, stay-time of materiel and fluid velocity, pressure and temperature distribution of gas-phase have a lot of relations to the properties of the combustion of pulverized coal and the decomposition of carbonate. The study aims is to probe the close relation between the fluid parameters and the properties of gas-solid tow-phase flow, the combustion of pulverized coal, the decomposition of carbonate, the relation can be provided as the reference to improve its structure and operation.Based on FLUENT, on two different inlet-conditions, three-dimension turbulence flow in the precalciner was simulated by Realizable k-ε model and SIMPLE method, The distribution of velocity, pressure and temperature showed reasonably that the design of the precalciner is good, and the gas-solid two-phase flow of it were simulated by different multiphase models, such as Discrete Phase Model (DPM), Mixture Model and Eulerian Model, including Mixture and Dispersed. The results showed Eulerian (Mixture) model is the most suitable to simulate the flow of the precalciner. Then based on different relative locality between cement raw meals and tertiary air inlets, different ratio high to diameter of the precalciner, the gas-solid two-phase flow was simulated by Eulerian (Mixture) models. The results, such as the velocity, pressure, temperature and volume fraction are analyzed, which showed that the diffusion and mixture of the cement raw meals and pulverized coal are good to the combustion of pulverized coal and the decomposition of carbonate.Based on above results, the gas-solid two-phase flows with coal's combustion and decomposition of CaCO3 have been simulated by Finite-Rate/Eddy-Dissipation model, which was probed by a lot of computation and analysis. The distributions of the velocity, temperature, pressure and volumefractions are given and analyzed. The results showed that the flow trend of coal's combustion and decomposition of CaCO3 in the precalciner is reasonable. The above results are also useful for the optimization design and local stakeout of the precalciner. Besides, it showed that the method of numerical simulation is feasible to researching the flow of the combustion of pulverized coal and the decomposition of carbonate in precalciner.