MFiX-TFM simulation of hydrodynamics of a dual fluidized bed system

Abstract

The abundance and replenishable nature of biomass make it a suitable fuel for power generation. Among the various technologies, dual fluidized bed gasification (DFBG) is a suitable technology to generate high-quality syngas from biomass. However, the complexity of hydrodynamics and heat transfer with bed geometry, flow conditions as well as feedstock demands effective research for the design of such system. This study, therefore, focuses on the simulation of hydrodynamics of a dual fluidized bed gasification system. The 2-D two-fluid model (TFM) simulations were performed using Multiphase Flow with Interphase eXchanges (MFiX) software by varying the superficial air velocities for both the gasifier and riser. The influence of superficial air velocity on static pressure, pressure drop, axial and radial voidage, solid velocities, and granular temperature was evaluated. From the simulations, it was observed that with the increase in superficial air velocities, there was an increase in the effective height of pressure drop (66%), voidage, and solid velocities of the gasifier. For the simulation of the riser, similar trends in the profile of hydrodynamic parameters were also observed. The optimum velocity for the gasifier and riser has been suggested to be between 0.15 and 0.35 m/s and 6–7 m/s, respectively.