Title: Numerical investigation of CO₂ and NO_x emission in a CFB combustor with flue gas recycle and oxy-fuel combustion redesign

Authors: Zhenxing Li; Yangyan Gao; Shaohua Wu; Yanhong Hao

Addresses: College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, China; School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin, 541004, China ' College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, China ' College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, China ' College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, China

Abstract: Flue gas recirculation (FGR) technology and oxy-fuel combustion strategy are combined to recycle CO₂ in a CFB combustor and to limit the emission of NO_x and CO₂. The combustion process in O₂/N₂ and O₂/CO₂ atmospheres is numerically investigated in the CFB combustor. The NO_x emission can be effectively reduced using FGR technology both in O₂/N₂ atmosphere or O₂/CO₂ atmosphere, which is inversely proportional to the FGR ratio. With O₂/CO₂ mixtures as the oxidant, the average combustion temperature is lower than that with O₂/N₂ mixtures when the mole fraction of O₂ is 21%. However, increasing FGR ratio has little effect on NO_x emission and CO₂ enrichment, even if CO₂ gas is enriched in the flue gas. While using O₂/CO₂ mixtures as the oxidant, CO₂ could account for more than 90 vol.% in the dried flue gas, thus the CO₂ can be easily captured from the flue gas.

Keywords: flue gas recycle; O₂/CO₂ atmosphere; CFD simulation; circulating fluidised bed combustor.

DOI: 10.1504/IJGW.2021.118359

International Journal of Global Warming, 2021 Vol.25 No.2, pp.177 - 190

Received: 09 Dec 2020
Accepted: 16 Feb 2021
Published online: 23 Oct 2021 *

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