NUMERICAL SIMULATION OF COAL GASIFICATION IN A CIRCULATING FLUIDIZED BED GASIFIER

Vikrant Sharma,Vijay K Agarwal

doi:10.1590/0104-6632.20190363s20180423

Vikrant Sharma, Vijay K Agarwal

Open Access

https://doi.org/10.1590/0104-6632.20190363s20180423

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Abstract

Abstract This paper presents a 3D full-loop simulation of a circulating fluidized bed gasifier. The model is validated with experimental results from the literature. The validated model is thereupon used to compare Bubbling Fluidized Bed (BFB) and Circulating Fluidized Bed (CFB) gasifiers to highlight the effect of a change in fluidization regime from bubbling to fast fluidization on hydrodynamics, temperature and gas composition. Feed temperature as well as Air/Coal (A/C) and Steam/Coal (S/C) ratios are kept constant, whereas the velocity of the feed (Air-Steam) is increased so as to get into the fast fluidization regime. It was concluded that the flue gas from the CFB is richer in desired gases, i.e., CO and H2 than that from BFB. H2 remains approximately the same, CO2 and CH4 decreased to a negligible amount and CO approximately doubles when the regime is changed. In addition, tar content in the gas also decreases.

Highlights

Energy and a healthy environment are essential for humanity, societies and economies to develop and thrive
The objective of this paper is to present a three-dimensional full-loop simulation of a Circulating Fluidized Bed (CFB) gasifier and compare it with the performance of a Bubbling Fluidized Bed (BFB) gasifier to highlight the effect of regime change on various hydrodynamic, heat and mass transfer variables
Grid independence Computational Fluid Dynamic (CFD) models are solved on discretized grids by numerical methods

Summary

FLUIDIZED BED GASIFIER

(Submitted: September 4, 2018 ; Revised: December 21, 2018 ; Accepted: April 1, 2019). Abstract - This paper presents a 3D full-loop simulation of a circulating fluidized bed gasifier. The model is validated with experimental results from the literature. The validated model is thereupon used to compare Bubbling Fluidized Bed (BFB) and Circulating Fluidized Bed (CFB) gasifiers to highlight the effect of a change in fluidization regime from bubbling to fast fluidization on hydrodynamics, temperature and gas composition. Feed temperature as well as Air/Coal (A/C) and Steam/Coal (S/C) ratios are kept constant, whereas the velocity of the feed (Air-Steam) is increased so as to get into the fast fluidization regime. H2 remains approximately the same, CO2 and CH4 decreased to a negligible amount and CO approximately doubles when the regime is changed.

INTRODUCTION

GOVERNING EQUATIONS

RESULTS AND DISCUSSION

CONCLUSIONS