Mild combustion in forward flow furnace of refinery-off gas for low-emissions by deflector

Abstract

Two dimensional numerical simulations were carried out to study the performance of a forward flow furnace. A deflector for application in the furnace was proposed to achieve complete burnout of reactant and low pollutant emissions, simultaneously. The eddy dissipation concept model coupled with detailed reaction mechanism GRI-Mech 2.11 was used. The predictions show a good agreement with the measurements. The effects of the deflector height H, the deflector diameter D, the excess air factor λ, and the ethane content in the refinery-off gas were investigated. The results indicate that there are four zones in the furnace: a central jet zone (a), an ignition zone (b), a combustion reaction zone (c), and a flue gas zone (d), according to the distribution profiles of H2CO and OH. The deflector blocks the reactant jet flow and prolongs the residence time of the flue gases before and behind the deflector which is of benefit for the oxidation of CO. The normalized spatial temperature variations are less than 10.5% and, thus, the temperature distribution in the furnace is very uniform. Moreover, the emissions are low and less than 10 ppm in some cases. Therefore, the mild regime is realized in the forward flow furnace.