CFD Simulations of a Square-Based Spouted Bed Reactor and Validation with Experimental Tests Using Rice Straw as Feedstock

Abstract

The present work aims to develop a model to simulate the fluid dynamic behavior of processes related to the exploitation of biomass as energy source by means of gasification. In particular, the attention has been focused on a spouted bed reactor with a square base using rice straw as feedstock. Spouted Bed reactors are attracting particular attention for their use in gasification processes. In these devices, the gas is introduced through a single nozzle at the center of the base and, as a result, a particular fluid dynamic pattern is followed which results in an enhanced solid circulation movement increasing therefore the mass and energy transfer rates. A Computational Fluid Dynamic (CFD) modeling technique was used to simulate the previously described fluid flow. The Eulerian-Eulerian method was applied to predict the gas-solid flow behavior and the kinetic theory of granular flow was incorporated within the method as closure equation. The gas and particle dynamics were investigated through the simulation of different operational regimes by varying the gas flow rate at the inlet and the amount of initial solids in the initial bed of particles. The obtained model was validated through experimental activities on a square based-reactor with a pyramidal bottom. Air was used as the gas phase and the particles were a mixture of rice straw and silica. The fluid dynamic parameters (minimum spouting velocity, Ums and pressure drop along the bed of particles, ?P) of the system were recorded for each case and compared with the values provided by the developed model. The resulting model will be used to optimize the fluid dynamic parameters defining the process and it will lead to an improvement of the gas-solid mass transfer and the minimisation of the energy requirements of the system.