Numerical Simulation Study of the Influence of Flue Gases Recirculated on NOx Emissions

Abstract

Abstract. Flue gas recirculation is considered to be one of the most promising and cost-effective NO x reduction strategies for combustion systems. Therefore, it has great scientific and practical significances to investigate the flue gas recirculation process. Fluent was used to perform a numerical flue gas recirculation simulation on natural gas combustion in a burner, revealing the relationship between NO x emission and circulation ratio, circulation temperature, and circulation locations. The following conclusions were drawn: the NO x generated with gas recirculation on is less than when there is no gas recirculation; the lower the gas circulation temperature, the less the NO x ; when the circulation is 25%, the NO x generated is low; less NO x is generated if the gas is firstly mixed with the air before combustion.

Review and Perspectives of Novel Flue-Gas Internal Recirculation Combustion Technology for Low Nitrogen Emission: Fundamentals, Performance, Method, and Applications for Conventional Fossil Fuels and Sustainable e-Fuels

“…Li et al discovered that there is an enhancement of nitrogen oxide formation for pressures lower than 5 atm with the recirculated gas method (constant flame temperature). ElKady et al , found that NOx emission declined more than 50% with 35% flue-gas recirculation in a depleted premixed flame of CH 4 under 10 atm (constant flame temperature). The formation of NOx is confirmed to be impacted by the recirculation flue-gas ratio. − Yue et al confirm that a larger recirculation flue-gas proportion inside the reactor is conducive to better stability of the combustion manner in a certain range. Therefore, it is a challenge to stabilize the oxidation in small-scale systems due to the high heat losses and the uncontrollable recirculation flue-gas proportion.…”

“…(3) The formation of NOx is confirmed to be impacted by the recirculation flue-gas ratio. 65−72 Yue et al 71 confirm that a larger recirculation flue-gas proportion inside the reactor is conducive to better stability of the combustion manner in a certain range. Therefore, it is a challenge to stabilize the oxidation in small-scale systems due to the high heat losses and the uncontrollable recirculation flue-gas proportion.…”

“…While the use of natural gas, hydrogen, and light oil in FIR burners has been extensively studied and reported, alternative fuel sources, including liquefied petroleum gas, synthetic gas, heavy oil, and biomass fuel, have received relatively less attention in the literature. The report includes natural gas burners, light oil burners, dual fuel burners for natural gas and hydrogen, and dual fuel burners for natural gas and light oil. , The integrations of FGR technology in biomass fuel − and waste (municipal solid waste and industrial waste) combustion systems have emerged as a crucial factor in reducing fuel-NOx emissions. A novel approach that has shown promising results involves the synergistic combination of high-oxygen waste fuels and FGR .…”