Effect of Char Combustion Product Distribution Coefficient on the CFD Modeling of Biomass Gasification in a Circulating Fluidized Bed

Abstract

A three-dimensional unsteady-state CFD (computational fluid dynamics) model is built to simulate biomass gasification in a circulating fluidized bed. The RNG (renormalization group) k-epsilon turbulence model is coupled with the enhanced wall treatment to describe the hydrodynamic regime of the gas-particle system. The conservation of momentum, mass, and energy equations are integrated with reaction kinetics to simulate chemical reactions in the gasifier. The impact of product distribution coefficient, θ, for char combustion on the CFD biomass gasification model is examined in nine cases. According to the simulation results, the coefficient of θ has a minor effect on the predictions of outlet gas compositions. However, it is found that the value of θ can influence the profile of gasifier temperature, and the peak temperature regions from the cases assigning 0.50 to the coefficient appear faster than those from the models using higher values of θ.

Heat-Transfer-Corrected Isothermal Model for Devolatilization of Thermally Thick Biomass Particles

“…Therefore, following the literature approach, , the radiative heat transfer is neglected in our CFD simulations. (4) The heat transfer between sand and biomass contacting is neglected ,, because the convective heat transfer dominated the heating process of the large particle in the fluidized bed and the limitation of the Eulerian multifluid model.…”

“…More details can be found in the user guide of ANSYS Fluent 18.0 . The momentum exchange between the gas and solid phase was described by the Gidaspow drag model, which has been applied to model biomass devolatilization in bubbling fluidized bed reactors. ,, The interaction forces between the different solid phases are expressed in terms of the drag force and the enduring contact force in the plastic regime as described in Syamlal et al The heat exchange between the fluid and solid phase is determined by the model derived by Gunn, which applies to a porosity range of 0.35–1.0 and Reynolds number of up to 10 5 , and has been widely used in previous studies to describe the heat transfer between gas and solid phase for biomass gasification. ,, …”

Simulador de propiedades termodinámicas en la conversión de la biomasa forestal de aserrín de pino

“…Específicamente en el modelado y simulación, la resolución de las ecuaciones diferenciales asociadas a los balances de masa, cantidad de movimiento y calor, como el conjunto de ecuaciones asociadas a estimación de propiedades físicas y regímenes de flujo, ha sido realizado computacionalmente a través de programación de métodos numéricos o mediante el uso de simuladores comerciales como ANSYS CFX®, ASPEN PLUS®, COMSOL®, PRO II®, HYSYS®, entre otros, por diferentes investigadores (Nikoo y Mahinpey 2008, Gerber y Oevermann 2014, Liu et al 2014, Shuai et al 2014, Couto et al 2015, Tushar et al 2015, Durán-García y Zeppieri 2017.…”

“…Los simuladores de procesos químicos son software de gran utilidad para el ingeniero de procesos en cualquier área de desempeño, sin embargo su importancia radica en el diseño y evaluación de plantas y equipos de procesos, donde se lleva a cabo la transformación de la materia prima para la obtención y manufactura de productos terminados de alto valor comercial, como lo es la biomasa (biomasa forestal) que se genera de la madera al transformarse en gases combustibles (metano e hidrógeno principalmente) de importante valor energético. Estos paquetes informáticos emplean modelos matemáticos que predicen de la mejor manera posible el comportamiento y las propiedades de las sustancias puras y las mezclas resultantes entre éstas denominados modelos termodinámicos (Walas 1990, Nikoo y Mahinpey 2008, Liu et al 2014, Tushar et al 2015, Durán-García 2016, Durán-García y Zeppieri 2017.…”

CFD modelling of gas flow characteristics for the gas‐heating holder in environmental transmission electron microscope

“…Computational fluid dynamics (CFD) is an independent discipline based on the classical hydrodynamics and numerical calculation method, which describes the numerical solution of the flow field quantitatively . The CFD has been applied in environmental flows to deal with the issues of gaseous pollutant dispersion, mechanical design to optimize equipment performance, the performance of volatile biomass combustion or gasification system, emerging as a powerful and effective tool to simulate the hydrodynamics and mass transfer behaviour of various processes …”