Gas-Solid Injection in Fluidized Beds for Biomass Wastes Valorization
Résumé
The processing of biomass and biomass wastes towards renewable energy and green fuels plays an important role for the decarbonisation of global economy and mitigation of climate change. The injection of solid fuels into fluidized bed reactors for thermochemical conversion is challenging due to the inherent complexity of the multiphase system, related to the fast gassolid transport and jet interaction with bed bubbles. Ultimately, solid feeding impacts on process reliability, conversion efficiency and design robustness. In this study, the gas-solid transport and pneumatic injection in gas-solid systems was investigated. A pressurized air feeder was used to inject a batch of sawdust powders into fixed and fluidised beds at lab scale. First, the horizontal feeder was characterised as a function of the operating parameters (feeder pressure, secondary gas velocity, initial biomass content), which showed an impact on the solids flux and flow concentration. Then, these parameters were used to define a transport regime operation map for the injection line. The experimental results were used to evaluate the CPFD approach MP-PIC (Multiphase Particle in Cell) with the software Barracuda TM . The gassolid transport simulations under different feeder operating conditions showed a fair agreement with the experimental results, in terms of solids flux and flow concentration. Finally, different tracking techniques (fluorescent particle tracking, pitot tubes, and electric capacitance tomography, ECVT) were used and compared to assess the penetration and dispersion of the biomass into fixed and fluidized beds. The jet propagation was captured with transient/3D images with the ECVT, and the biomass concentration across the jet length was quantified with the fluorescent particle tracking technique. Similar jet penetration lengths were obtained with the different techniques, and it was generally more under higher solids flux from the injector. Ultimately, the pros and cons of each tracking technique were highlighted.
Domaines
Génie chimiqueOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
---|