Effect of O2 enrichment on acid gas oxidation and formation of COS and CS2 in a rich diffusion flame

O-2 enriched combustion is applied to a non-premixed acid gas (AG) flame, in which AG and air are injected separately into a vertical reactor via a coaxial burner at atmosphere pressure. Equilibrium predictions of AG oxidation were performed using Aspen Plus and lab-scale experiments with particular focus on formation of COS Land CS2 were undertaken under different combustion conditions. The effects of equivalence ratio (Phi = 0.8, 1.0 and 3.0) and initial O-2 concentration (OC) in air (21, 30 and 50 vol%) have been studied and the flame is interpreted by analyzing the axial temperature and species concentration distributions along the reactor. AG diffusion flame could be divided into three zones, namely AG decomposition, oxidation and complex reaction zones, among which decomposition zone is tightly associated with formation of COS and CS2. It is shown that a) generally determines the flame temperature and controls the H2S oxidation degree and production rate of H-2 and CO. Reactivity of CO2 primarily expressed via CO2 + H = CO + OH during the fuel rich flame. COS is primarily produced in the flame inner core via reactions jointing CO2 and sulfur species, consequently its formation shows a low sensitivity to (13 in the air-supplied flame. O-2 enrichment basically contributes to higher flame temperature, accelerated H2S oxidation and advanced CO production. Also an increasing tendency for H2S to decompose into H-2 and S-2 can be observed. And this factor directly triggers the formation of COS and CS2 via increasing the presence of CO and sulfur species. COS is formed within extended channels involving the primary production by reaction of SH + CO2 and the secondary by reactions between CO and sulfur species. The CS2 formation is more complex, mainly comprises of reactions involving CS intermediate and evidently it is enhanced under O-2 enriched combustion.