Experimental and CFD Investigations of a Biomass Pressurized Feeder for Fixed and Fluidized Beds

Proper injection of biomass into a fluidized bed is a real challenge for industrial and lab-scale thermochemical conversion reactors. It can indeed affect the process performances and generates issues for the extrapolation from lab scale to industrial scale reactors (Bridgwater et al). In this work, we present our investigation on a pneumatic transport biomass pressurized feeder. This feeder is used to inject a batch of biomass into a fixed or fluidized bed at lab scale.

First, we characterized different parameters (feeder pressure, secondary gas velocity, initial biomass content) which play a role on the solid mass flux injected. These parameters were then utilized to define a transport regime operation map in the injection line.

Second, the results of this experimental study where then used to evaluate the CPD approach MP-PIC (Multiphase Particle in Cell) with the software Barracuda^TM. The CFD simulations of different feeder operating conditions showed a fair agreement with the experimental results.

Finally, the penetration and dispersion of the biomass powder injected in a fixed and fluidized bed was characterized by different measurement techniques such as fluorescent particle tracking, pitot tubes and Electrical Capacitance Tomography. In general, a fair agreement was obtained among the jet penetration length measured with different techniques. Quantitative comparison of the results highlighted the advantages and disadvantages associated with each technique.

References :

A.V Bridgwater, G.V.C Peacocke, Fast pyrolysis processes for biomass, Renewable and Sustainable Energy Reviews, Volume 4, Issue 1, March 2000, Pages 1-73