Intra-Particle Heat- and Mass Transfer Effects on Burner Simulations of Pulverized Biomass
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Due to a willingness to decrease greenhouse gas emissions, alternative ways to produce secondary energy has increased. One method of interest, still not commercially available, is gasification of powdered biomass using a pressurized entrained flow gasifier (PEFG). One of its advantages is that it produces a clean syngas with limited amount of tar formation and methane production.The process of producing biomass powder small enough for a PEFG is energy consuming which means that to optimize the overall plant operation in the future, particle sizes may increase. An increased particle diameter also increases the impact of intra-particle heat and mass transfer on fuel conversion. Computational Fluid Dynamics (CFD) is a useful tool for the optimization of reactor design and operation. The most commonly used model for particle-laden flow today (discrete element model) does not consider intra-particle heat and mass transfer. Efficient way of simulating gasification with the consideration of intra-particle heat and mass transfer is therefore desirable.This thesis has investigated the impact of intra-particle mass and heat transfer on particle conversion. Simulations were carried out on a PEFG where the shape of the flame using isothermal particles were compared to simulations where the pyrolysis had been altered using a sub-model that accounted for intra-particle mass and heat transfer. The sub-model was created by comparing the difference in conversion time between an isothermal particle and a non-isothermal particle and considers both particle size and surrounding gas temperature.The results from the simulations showed that for the particles larger than 1000 μm in diameter the intra-particle mass and heat transfer had an impact of the shape of the flame. It means that CFD simulation needs to account for intra-particle model in the future if the particle diameter is increasing significantly.
Place, publisher, year, edition, pages
2016. , 42 p.
Teknik, Intra-particle, Non-isothermal, Isothermal, Conversion, Pyrolysis, Sub-model, CFD
IdentifiersURN: urn:nbn:se:ltu:diva-44085Local ID: 1e3d0252-ea08-4f4c-beb0-647f67e76941OAI: oai:DiVA.org:ltu-44085DiVA: diva2:1017360
Subject / course
Student thesis, at least 30 credits
Sustainable Energy Engineering, master's level
Validerat; 20160329 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved