Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
NUMERICAL INVESTIGATION OF FLOW REGIMES IN BIOMASS PYROLYSIS
Submission Author:
Albino Leiroz , RJ , Brazil
Co-Authors:
Filipe Leite Brandão, Gabriel Lisbôa Verissimo, Manuel Ernani Cruz
Presenter: Gabriel Lisbôa Verissimo
doi://10.26678/ABCM.ENCIT2016.CIT2016-0145
Abstract
Pyrolysis involves many physical and chemical phenomena that are complex to model in detail. When pyrolysis occurs in fluidized beds, the combination of hydrodynamics, mixing/segregation, chemical reactions and heat transfer phenomena hinders the development of models with realistic chemical kinetic mechanisms. Therefore, the utilization of simplified kinetic schemes becomes important for obtaining practical results, especially for CFD modeling of biomass gasification processes. Different models for biomass pyrolysis have been described in the literature. It has been reported in the literature that the description of the pyrolysis process by kinetic models is important for the success of Euler-Euler CFD studies. Besides, despite of the turbulent nature of the phenomena within the fluidized bed reactors, the assumption of the prevalence of laminar conditions is usual due to computational costs associated or the lack of an appropriate turbulence model. The present work considers the wood pyrolysis process in a fluidized bed reactor using an Euler-Euler approach. In particular, the influence of the flow regime assumption on the product composition predicted by the CFD model is analyzed. It is found that when turbulent regime is considered, the reactor temperature is slightly lower than laminar simulations for most of the kinetic models. Furthermore, it is found that depending on the pyrolysis kinetic model, the reaction rates profiles along the reactor for the laminar and turbulent assumptions differ substantially. For some of the models considered, the difference occurs in the reaction intensity, with the reaction rates achieving greater values when turbulent regime is assumed. For other models, it is possible to observe that the laminar assumption decreases the reaction rates. For the products distribution, despite no significant deviations are observed between the kinetic models studied when laminar and turbulent flow regimes are considered, a 10% deviation is observed for the char content.
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