Simulation Of Gas-solid Reaction Flow By Lattice Gas Automata Model

Gas-solid reaction flow is a common phenomenon in petroleum, chemical and metallurgical industry. Since the reaction is a complex nonlinear process which contains the flow, heat transfer, mass transfer as well as chemical reaction and it is susceptible to fluctuations in the system, so the process is difficult to be analyzed effectively by standard methods. The gas-solid reaction flow research has two categories of experiment and numerical simulation methods. Because of the experiment method needs high cost, and it is difficult to obtain detailed data which is limited by the detection means. At the same time, with the rapid development of computer technology in recent years, the numerical simulation has become as important as the experiment method.Numerical simulation of gas-solid reaction flow is important to the design of the reactor, but due to the complexity of the research question, it becomes difficulty in theory and application research. At present, the simulation of gas-solid reaction flow is always based on the macro level which usually uses the finite difference and finite volume method of(Computational Fluid Dynamics, CFD) for solving model. But this method is difficult to deal with the boundary, algorithm design, parallel process as well as the coupling of links in reaction. The Lattice Gas Automata(LGA) is a simplified mesoscopic model of time discrete, space discrete and fluid discrete, which is based on molecular dynamics. It not only has fewer assumptions under microscopic, but also has an advantage of not caring about the details of the molecular motion in macroscopic, and it also can obtain the macro nonlinear behavior through the statistical method. All of the processes use a set of self-organization evolution rules to replace the complex mechanism model, and it is more effective in dealing with complex boundary as well as the coupling of links in reaction.A gas-solid reaction flow LGA model with multi-substance and multi-energy is developed on the basis of LGA method and considering the unreacted core model for solid particles to simulate gas-solid reaction flow problems. Gas particles are marked with different components and energy states, and a selecting probability of collision rule is designed to account for the diffusion and propagation among different particles according to the gradient of each component concentration. Moreover, energy evolution rules during heat exchange process are introduced, and a reaction probability correlation is derived considering the structure of the macroscopic rate equation and the reaction heat effect is also quantified by thermodynamics.A kind of software is designed for achieving the human-computer interaction as well as the visualization of simulation results with visual studio 2005, which gives help for the quantitative analysis.Firstly, numerical simulations of both isothermal and non-isothermal reductions of Fe2O3 to Fe3O4 in CO are carried out under the experimental conditions of the investigation performed by literatures. Results show that, compared with isothermal condition at the same time, the conversion was increased by an average value of 6.92% under the non-isothermal condition, and the results lie in the upper and lower limits of the experimental outputs reported in the literature which indicates the feasibility of present reaction flow model. Furthermore, detailed information of velocity field, temperature field and concentration field during reaction processes can be effectively captured by present LGA model. Under different conditions, a series of reactive simulations of the single particle of Fe2O3 are also carried out and the results show that the temperature, concentration, particle diameter and the porosity are significant to the reaction.Secondly, a series of numerically reactive simulations of a group of Fe2O3 particles with CO under different porosities and a study of the velocity field, temperature and concentration cloud are carried out. Results show that the model can effectively captures the details of the flow, mass transfer, heat transfer as well as reaction in the system, and the internal reaction is not consistent and increasing the fluid velocity as well as porosity can improve the reaction efficiency.Finally, a packed bed, which is filled with random position and different sizes of Fe2O3 particles, is also simulated by the model and the analyses of the flow field, temperature field and the gas concentration field in it are carried out. Results show that because of the wall effect, distribution structure of solid particles as well as the rule heat transfer and heat effect, the distribution of the velocity field, temperature field and concentration field are not uniform. In addition, a simulation of gas-solid reaction flow, which is based on the actual metallurgical packed bed of black and white pixels figure, is also carried out, and the reaction flow phenomena are successfully obtained.