Modelling of the gas flow in fluidized beds

Abstract

Fluidized bed technology plays an important role in the transition of the current energy system to full sustainability, both as main first choice for thermochemical biomass conversion (which is considered CO2 neutral) and as basis for chemical looping combustion (CLC), which is considered to be the second generation of carbon capture applications, since it allows CO2 capture with no inherent energy penalty. The aim of the work is to formulate and implement a proper description of the gas flow inside a fluidized bed, covering a variety of scales and applications. This will be done by the development of an own code, since this provides enhanced flexibility with respect to already developed modelling tools available on the market. The influence of four parameters (inlet velocity, exchange coefficient between phases in the dense bed, dense bed height and lateral diffusion coefficient) in regular fluidized bed combustion is studied, in particular considering a lateral injection of volatiles resembling biomass combustion. The results have been mostly in line with the expectations, showing a high dependence of the system from the gas mixing more than kinetics, and, on the other hand, that the exchange between phases in the dense bed and the dense bed height are not influential parameters.