Radiation Intensity of Propane-Fired Oxy-Fuel Flames: Implications for Soot Formation

Abstract

The changes in the soot-related radiation intensity between two different oxy-fuel flames and an air-fired flame were investigated in a 100 kW oxy-fuel test unit firing propane. The oxy-fuel test cases with 21 and 27 vol % O 2 in the recycled flue gas (RFG) were run with different amounts of dry RFG, which in principle only consisted of CO 2 from combustion and some excess O 2 . The stoichiometric oxygen-to-fuel ratio was kept at 1.15 in all cases. Total radiation intensity was measured with a narrow angle radiometer. Temperature and gas composition measurements served as inputs to computations of gas radiation. A comparison of the computed gas radiation with the measured total radiation intensity enabled estimation of the radiation related to soot. Clear differences were observed in the amount of soot formed in the two oxy-fuel flames (also compared to the air flame). In the oxy-fuel flame with 21 vol % O 2 in the RFG, soot formation is almost completely suppressed, but when the total flow through the burner is reduced by about 20% (by volume) (i.e., from 21 to 27 vol % O 2 in the RFG), the amount of soot present in the flame becomes significant. This change in soot volume fraction affects the radiation emitted from the flames; images of the flames qualitatively confirm these differences in the flame luminosity. Thus, carbon dioxide not only increases the gas radiation, but it can also drastically influence soot formation and the radiation originating from soot during oxy-fuel combustion.

A review of recent developments in carbon capture utilizing oxy-fuel combustion in conventional and ion transport membrane systems

“…They carried out measurements of the radial profiles of gas concentration, temperature and total radiation intensity in the furnace. In another study, Andersson et al [46] presented their findings on the differences in soot-related radiation intensity between two different oxyfuel flames and an air-fired flame. The study was conducted in a 100 kW oxyfuel test unit firing propane while keeping an O 2 -to-fuel ratio of 1.15, relative to stoichiometric.…”

Critical evaluation of the oxygen-enhanced combustion in gas burners for industrial applications and heating systems

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Cho et al 20 studied liquid fuels. Murphy and Shaddix 7 and Smart et al 10 assessed coal and biomass.…”

Modeling CO2Chemical Effects on CO Formation in Oxy-Fuel Diffusion Flames Using Detailed, Quasi-Global, and Global Reaction Mechanisms

“…Likewise, Rehfeldt et al (Rehfeldt, Kuhr, Ehmann, Bergins, Scheffknecht, Maier and Wu 2009) found significantly higher CO concentration in the fuel-rich flame region of oxy-Lausitz lignite coal combustion using a 0.5 MW th pilot scale test facility. Moreover, Andersson et al (Andersson, Johansson, Johnsson andLeckner 2008, Andersson andJohnsson 2007) and Hjartstam et al (Hjartstam, Andersson, Johnsson and Leckner 2009) measured the CO concentrations in a 100 kW th test facility using propane or lignite coal fuels, and they observed consistently higher CO concentrations in the combustion zone near the burner under oxy-fuel conditions than under air-fired conditions when the combustion temperatures are maintained the same. The higher CO in the flame region is expected to affect the pollutant formation processes.…”