Spectroscopic Observation of Heavy Oil Luminous Flames in an Industrial Regenerative Furnace

Abstract

A spectroscopic method has been applied to measure two-dimensional temperature distribution in luminous spray flames. A test furnace, incorporating a pair of regenerative burners, was used to examine the behavior of heavyfuel oil flames with very high-temperature combustion air. The spectroscopic method used here is based on the two-color thermometry, in which the ratio of spectral intensities of continuum emission is taken at two closely located wavelengths. The two-dimensional distribution of flame temperatures is obtained by the use of a charge-coupled device camera fitted with an optical bandpass filter to provide a much higher resolution compared to that measured with thermocouples. This method was applied to characterize the luminous flames formed under two different conditions during the combustion of heavy oil. The two different kinds of flames formed were either premixed or diffused by the use of air preheats to very high temperatures of 1373 K. A far more uniform temperature distribution was found for the diffusion flame case. In contrast, under premixed conditions, local high-temperature regions were found around the fuel injector exit. The concentration of NO x in flue gas has also been measured for the two different combustion conditions. The temperature distributions obtained from the premixed and diffusion flame conditions are discussed, as are the NO x emission levels from these flames. The results show lower NO x emission for diffusion flames as compared to premixed flames with high air preheats. These results are discussed because standards they provide new for uniform thermal field and ultralow pollution from flames with very high air preheats.