Computational fluid dynamics simulation and parametric study of coal gasification in a circulating fluidized bed reactor

Abstract

A computational fluid dynamics model based on the Eulerian-Eulerian multiphase framework was implemented to simulate the coal gasification processes in a circulating fluidized bed gasifier. The standard k-ε turbulence model is used for gas phase, and the solid phases are modeled with kinetic theory of granular flow. A lumped chemical reaction model was compiled based on the chemical percolation devolatilization model and the METC Gasifier Advanced Simulation gasification model. The user-defined functions are developed to calculate rates of chemical reactions and to recirculate solids from the riser exit to the solid recycle inlet. Sensitivity analysis was performed on char-steam gasification reaction to choose an appropriate kinetic rate in this study. The calculated gas composition out of the riser was first compared with experimental data; then, the flow fields such as solid volume fraction, solid velocity, and species profiles were analyzed, indicating that the model gave reasonable predictions. Furthermore, the effects of the operating temperature, the steam/coal ratio, and the air/coal ratio on the exiting gas composition were numerically studied, and the predicted trends vs these parameters are reasonable and consistent with the findings in the literature, which shows the applicability of the Eulerian multiphase model to simulate coal gasification processes in circulating fluidized bed gasifiers.

Numerical Simulation of Coal Gasification in a Circulating Fluidized Bed Gasifier

“…Furthermore, the fluctuations in the profiles are comparatively more in the case of the CFB gasifier. Comparison between published results for a BFB gasifier (Armstrong et al, 2011) and CFB Gasifier (Zhang et al, 2015;Hassan, 2013) shows a similar trend. It should be noted that negative values of the outlet mass flow rate indicate that flow is going out.…”

Determination of parameters of the carbon­containing materials gasification process in the rotary kiln cooler drum

“…In [1][2][3][4][5][6], DPM or Euler-Lagrange formulations are used to determine the main parameters of the gasification process of solid combustible material, while the papers [7,[9][10][11][12][13] are based on the Euler-Granular Multiphase or Euler-Euler formulations, and in [8 both models are used.…”

“…The paper [7] is devoted to modeling coal gasification processes in a circulating fluidized bed gasifier using the Euler-Euler formulation. A standard − ε k model is used to simulate turbulent flow regimes of the gas phase, while solid phase simulations are based on the kinetic theory of granular flow.…”

“…In the analyzed works [1][2][3][4][5][6][7][8][9][10][11][12][13], specialized equipment for the gasification of solid carbon-containing materials is considered and no attention is paid to the modernization of existing industrial equipment in order to produce synthetic gas. Moreover, the kinetics of the chemical reactions of gasification, presented in these papers, differ significantly.…”

“…This, in turn, led to the appearance of a large number of developments of reactor equipment for gasification and research of gasification of solid fuels and biomass, in particular, by numerical methods of computational hydrodynamics [1][2][3][4][5][6][7][8][9][10][11][12][13]. These works do not consider the use of existing industrial furnace equipment for solid fuel gasification processes.…”