COMPARISON OF EULER-EULER AND EULER-LAGRANGE APPROACH IN NUMERICAL SIMULATION OF MULTIPHASE FLOW IN VENTILATION

This paper presents the results of multiphase flow numerical simulations in ventilation mill and mixing duct with louvers separator of Kostolac B power plant. Due to very low volume fraction of the secondary solid phase, that is well below 10%, simulations are performed using both the mixture model of the Euler-Euler approach and EulerLagrange approach of ANSYS FLUENT software package. The gas mixture distribution at the main and secondary burner feed ducts obtained by the Euler-Euler mixture model is in a good agreement with the experiment. But aforementioned model also gives the same distribution of the pulverized coal at the burners, leading to large differences between the calculations and measurements. Because of that the Euler-Lagrange approach with Discrete Phase Model (DPM) is used where the fluid phase is treated as a continuum, while the dispersed solid phase is solved by tracking a large number of particles through the calculated flow field, i.e. computing the particle trajectories at specified intervals during the fluid phase calculation. Much better agreement of the calculated and measured value of the pulverized coal distribution at the burners is obtained using DPM. The tracking particles of the dispersed phase enables obtaining the influence of the louvers. It is noticed, in the numerical simulation, that due to the narrow gaps between the louvers only a small fraction of the pulverized coal passes through the gaps. The louvers actually act as an obstacle. The DPM model should be used in obtaining accurate distribution of the pulverized coal at the burners.