Simulation study of droplet vaporization effects on gas-solid fluidized bed

Rapid evaporation of gas oil droplets has significant effects on the gas-solid mixing phenomena near the nozzle region in a fluid catalytic cracking (FCC) process. A three-dimensional CFD model of the reactor has been developed to consider three phase hydrodynamics, heat and mass transfer as well as evaporation of the feed droplets into a gas-solid flow. In this model, the gas and solid flow fields are determined by the Eulerian method and the droplet flow field by the Lagrangian method. A recently reported drag model was employed to investigate the influence of circulating flows inside a droplet on its evaporation hydrodynamic. The distributions of volume fraction of each phase, gas and catalyst velocities, gas and particle temperatures as well as gas oil vapor species in the gas phase were computed. In addition, temperature variations and evaporation rates of gas oil droplet in the riser reactor were simulated. The CFD simulation results showed that the droplet evaporation into the gas phase caused higher local velocities of the gas and solid particles, lower solid concentrations and reduced solid temperatures.