Axial segregation behaviour of a reacting biomass particle in fluidized bed reactors: experimental results and model validation

Abstract

Axial segregation behaviour of a single biomass particle in a lab-scale bubbling fluidized bed has been investigated from both experimental and modelling perspectives. Experiments were conducted using beech wood particles of different sizes, ranging from 8 to 12 mm under either oxidizing or inert conditions. The fluidized bed reactor was operated at temperatures and fluidization velocity ratios, U/Umf, in the range of 500–650 °C and 1–2, respectively. A one-dimensional model has been developed to predict the axial location of the particle over time, taking into account both dynamic and thermal conversion mechanisms. X-ray imaging techniques allowed to identify endogenous bubbles released during devolatilization and carry out direct measurements of their size. This information was used to propose an expression for the lift force acting on the fuel particle. The model showed very accurate predictions and the segregation behaviour of the fuel particle appeared to be independent of the nature of the fluidizing medium.