NUMERICAL INVESTIGATION OF AN INDUSTRIAL SCALE CIRCULATING FLUIDIZED BED FURNACE: EFFECTS OF POSITION OF COAL FEEDERS AND COAL FEEDING RATES

摘要

This study developed a model to investigate the transient 3D numerical simulation of air and sand particle hydrodynamics along with coal combustion in an industrial scale CFB furnace. This model used the Dense Discrete Phase Model (DDPM) to model the interactions of sand (inert bed material) and coal particles with the gas phase. DDPM is an Eulerian-Lagrangian model in which gas flow is modeled in Eulerian frame of reference and particle movement is simulated in Lagrangian one. DDPM is an extension of Discrete Phase Model (DPM); however, unlike the standard formulation of DPM, DDPM considers the solid volume fraction in solving the Navier-stokes equations for gas phase species. Furthermore, Multiphase Eulerian-Granular Model is used to calculate the particle interaction on the Eulerian frame of reference. This interaction is then mapped to the particles on the Lagrangian frame of reference. In this study, several user defined functions (UDF) were used to extend ANSYS FLUENT original code. These UDFs were used for reinjection of particles to the boiler (the cyclone were not modeled), calculation of the pressure drop, circulation rate, and controlling the boiler mass load. The ultimate goal of this study was to determine the effects of two different positions of coal feeders and feeding rates on particle transport hydrodynamics and coal combustion. For these two cases, distributions of gas temperature, solid volume fraction, pressure, and mole fractions of combustion products were displayed and compared with operating data obtained from a 340 MWe CFB boiler located in Yeosu, South Korea.