Effect of Flue Gas Recirculation on Burner Performance and Emissions

Abstract

Flue gas recirculation (FGR) is an effective applicable way to reduce emissions. In the present study, external FGR was employed in non-premixed combustion using kerosene as liquid fuel to investigate its effect on flame stability, appearance and emissions. Flame stability can be attained through a reasonable range of recycling ratios up to 40%. Flame appearance exhibits shorter flame with increasing FGR% due to the increased turbulent mixing. Flame temperature was reduced because of dilution effect and increased specific heat of FGR. The flame luminosity decreased and bluish flame increased by increasing FGR%. As a result of the flame temperature decrease, an obvious reduction of NO emissions can be achieved. The NO can be dropped from about 90 ppm to a single digit number. Emissions of CO and UHC increased at high recycling ratios near to flame blow-off and more increase took place at leaner conditions i.e. lowest flame temperature.

Analysis of Polycyclic Aromatic Hydrocarbon Emissions from a Pilot Scale Silicon Process with Flue Gas Recirculation

“…At 1000 Nm 3 /h, the PAH concentration increased from 16.0 to 559.7 μg/Nm 3 with decreasing O 2 levels (20.7–13.3 vol %) and increasing FGR (0–82.5%), which are parameters that show a strong correlation in this study. This follows the trend presented in other work where the level of unburned hydrocarbons increased with increasing levels of FGR. , This overall trend, also observed in modeling, is a consequence of the lower availability of oxygen and the reduction in temperature, due to which the extent of oxidation of the PAH is reduced. All eight modeled aromatic species showed a steady increase in concentration, with A1 and A2 (benzene and naphthalene) being the dominating species.…”

“…This work show a 9 times increase in PAH by mass emission factors when the EGR was set to 5%. In the work of Abdelaal et al, 19 FGR is used in an attempt to reduce NO formation from dimethyl ether fuel combusted by temperature decrease. In this case, NO is reduced, but for FGR above 20% a noticeable increase in CO and unburned hydrocarbons (UBHs) occurs from 0 to 0.45% and 0 to 650 ppm, respectively, at 40% FGR and 3% O 2 .…”

Analysis of nitro- and oxy-PAH emissions from a pilot scale silicon process with flue gas recirculation

“…[20][21][22] The method has also been found to increase the level of hydrocarbon species (including PAHs), when temperature and oxygen concentrations reach a certain level due to reduced oxidation efficiency. [23][24][25] Wittgens et al 26 investigated the possibility of including a post-combustion chamber for increased energy recovery with reduced PAH and NO x emissions in the ferroalloy industry with positive results. Together with the PhD thesis of Andersen (2023), 27 studying ue gas recirculation (FGR) for the silicon process, and Kamord (2012), 4 studying NO x formation in the silicon process, these represent a body of work forming the basis for understanding the off-gas systems and the current status for emissions of PAHs from the SAF-based Si production process.…”