Numerical Simulation Of Biomass Fuel Calciner Based On Multi Field Coupling

Because of the non-renewable and the rising price of fossil energy.The large cement production line in foreign countries is also in the period of energy transformation.Biomass energy as a kind of widely distributed and abundant renewable clean energy,has become the preferred alternative energy for the cement industry.However,due to the fact that there is basically no experience of using biomass fuel in the actual decomposing furnace,there is no understanding of the similarities and differences between biomass fuel and traditional fuel in the combustion process.Though this paper uses Fluent software,using multi-model coupling combined with UDF method to develop a calculation model which is applied to the simulation of the decomposing furnace and simulate all the reaction process in it.Then make a prediction and analysis of the combustion process of biomass fuels,the specific content of the work and research results are as follows:A coupling calculation model suitable for the working condition is established in view of the decomposing furnace in the 6000 TPD cement production line.The standard k-e model is selected as the turbulence model.The P1 model is used as the radiation heat transfer model.The double matching rate model is used as the volatilization analysis model,and the kinetic / diffusion control reaction rate model is used as the coke combustion model.The combustion process of fuel particles is simulated by using the DPM model in the Euler-Lagrange method.The Eulerian multiphase flow model in Euler-Euler method is used to simulate the gas-phase reaction and the limestone decomposition reaction.The two models are coupled into the simulation of decomposing furnace.The geometric model of the fluid region in decomposition furnace is established based on the design parameters of the decomposing furnace.A hexahedral grid model is established by using ICEM CFD software and a variety of grid division techniques.The boundary conditions used for the calculation are set up according to the actual conditions The reaction rate model in Fluent has been developed,and UDF has been applied to realize the import of custom limestone decomposition rate and NO generation rate.The decomposition furnace internal velocity field and temperature field and the distribution of components and limestone decomposition rate has acquired based on heavy oil combustion.compared with the actual operation results to verify the validity of the simulation results also shows the reliability of the model established in this paper.Using the established model to make simulation analysis of the combustion process of the fuel mixed by heavy fuel oil and wood pellets.Analyzed the effect of entrance position,proportion of biomass particles in the mixed fuel and particle size on the key parameters in the decomposition furnace.It is concluded that the entrance of biomass particles should be set between the first contraction and the entrance of tertiary air,the proportion of biomass particles in fuel is 20% will get better combustion effect.At the same time,biomass particle size has great influence on the emissions of NOx and has little effect on the rate of decomposition of limestone,Therefore,on the premise of meeting the requirements of environmental protection,biomass particles with a particle size less than 5mm should be used.