A Numerical Simulation Of The Gas-Solid Two-Phase Flow In A Spouted Bed

For the purpose of providing a theoretical guidance to a new kind of clinker firing device used for manufacture of ecological cement, an experiment project has been carried out. The device planned is a certain type of reactor in which coarse granules are spouted in a fluidization state. This thesis presents main results and cognitions achieved in the program, concentrating on the numerical simulation dynamic characteristics of coarse granules spouted bed.The gas-solid flow in a spouted bed is modeled by a combined approach in which discrete particle method and computational fluid dynamics are used to calculate the movements of the solids and gases, respectively. The coupling between gas phase and solid phase was achieved directly by applying the principle of Newton's third law of motion. In this way, a model of math-physics was established. And then a numerical simulation program of two-phase flow was developed applying to a three-dimensional (3D) spouted bed or fluidized bed. The program was used to predict the gases and particles motion, pressure drop and fluidized states at various conditions.The simulation was used to predict the conditions in a 3D laboratory device of spouted bed of dimensions 0.11 × 0.012× 0.9m, with a nozzle located at the centre of the bed-base. For the condition of gas velocity of 22m/s, simulation results indicated that the two distinct regions existed, which are a narrow conical-core spout and a stagnant annulus. The position of spout located in the center of spouted bed and its width gradually increased in z direction and its maximum was l/5~l/4 of the bed width. The stagnant zone appeared near the wall, its height and width was 3/4 and 1/4 of the bed width, respectively. The particles flow pattern observed was asymmetric. The particles in the narrow spout moved upwards, however, in the annulus the ones moved slowly downward. These two flow patterns of granules formed a circulating motion of the whole particles in the bed. Pressure drop increased with gas velocity increasing, and the value of AP reached a maximum of 4100Pa at the inlet gas velocity of 30m/s (superficial gas velocity is 2.73m/s). After that, a minor decrease in pressure drop was observed at a further increase in the inlet gas velocity of 5~6m/s from 30m/s, then pressure drop maintain about a constant. It was determined that the pressure drop increased as the particle material density increased.