Numerical Simulation Of Gas-solid Flow In Spouted Beds For The Preparation Of Activated Carbon From Biomass

Activated carbon is a kind of porous carbonaceous material with a developed specific surface area and strong adsorption function, which is widely used in many fields of production and life. Biomass is rich in carbon, China as a large agricultural country has plentiful biomass resources, such as crop stalks and shells. This paper mainly studies the gas-solid spouted technology of biomass energy into high quality activated carbon process of gas-solid two-phase flow numerical simulation.The equation of mass conservation, momentum conservation and energy conservation of the gas-solid two-phase mechanics model are analyzed in this paper. According to the hydrodynamics characteristic of gas-solid two-phase in conical-cylindric spouted bed, the flow behavior is simulated using the Euler- Euler double fluid model. Drag force is the main interaction between gas and particle, Gidaspow model or the Syamlal-O 'Brien model as the drag coefficient of two phases in this paper is more suitable for.According to the material characteristics, this paper determines the basic structure size of the spouted bed. Then calculate the minimum spouting velocity, the maximum static bed height, and clearly the operating range of it. Using GAMBIT software for establishing the 2D model, meshing, setting the boundary conditions. Then input it onto FLUENT platform to complete the numerical solution of the model. The particle volume fraction distribution,particle phase velocity vector diagram and gas velocity distribution of the particles in different time were analyzed. The results show that the simulation can be realized in the spout, annulus, fountain region to form a continuous, stable and rational spouting. This is in line with the actual situation. It is concluded that the particle velocity is larger in the spout with smaller particle size fraction, and the particle velocity is smaller in the annulus,fountain area with larger particle size fraction. In the process of energy exchange of gas-solid two-phase drag effect is far greater than the inter particle collision and particle friction, the friction between the particles and the walls.The study found that the incidence of spouting velocity, cone bottom angle, nozzle diameter, drag model, simulation time step have significant influence on the characteristics of two-phase flow in the spouted bed. The simulation results show that: The flow field profile is perfect when the gas velocity is 8.5m/s, the incident angle is 60°, the tapered nozzle size is 30mm, Gidaspow model or Syamlal-O'Brien model and the Brien time step is 0.0001s. This can provide a theoretical basis for the actual operation of the spouted bed.