Numerical Simulation of Coaxial Evaporating Spray in Nozzle Region of Circulating Fluidized Reactor

Full field hydrodynamic mixing of a coaxial evaporating spray in the nozzle region of a circulating fluidized reactor was numerically investigated. An Eulerian-Lagrangian numerical code was developed for the field description of evaporating spray characteristics with strong phase interactions among evaporating droplets, solids and gas. The gas-solid flow is simulated using multi-fluid method coupled with kinetic theory modeling for inter-particle collisions while the spray is treated as the discrete droplets in a pseudo-continuum gas-solid flow. The Lagrangian simulation of the spray provides the needed coupling terms for the Eulerian simulation of gas-solid flows, such as droplet evaporation rate and interactions among phase of droplets, gas and solids. Phase distributions of temperature, velocity and concentration were achieved to explain the mixing process of evaporating spray in gas-solid flows. Effects of inlet solids loading and droplet size distribution on both spray structure and spray penetration depth were illustrated. An experimental system of liquid nitrogen spray into a circulating fluidized bed of fluid catalytic cracking particles is set up to provide experimental validation of our model. Good comparisons of the simulation and measurements are illustrated.