Comparison of three combustion modes of H2S-CO2 gas in Claus furnace for promoting reaction temperature

Stabilizing and promoting the temperature of the Claus furnace is important for the continuous conversion of acid gas (H2S and CO2). In this study, the characteristics of three enhanced-combustion modes namely low equivalence ratio, oxygen-enriched and assisted combustion were compared via equilibrium calculation and diffusion flame under the same temperature-promoted condition. Equilibrium calculation was conducted using Gibbs reactor in Aspen Plus software. The flame was interpreted by the axial distributions of the temperature and species concentration. Both equilibrium calculation and experimental results showed enhanced combustion promoted the reactivity of H2S and CO2 and generation of H2 and CO. The diffusion flame could be classified into three zones namely decomposition, oxidation and complex section, among which decomposition section included H2S chemical decomposition and CO2 reactivity. SO2 was scarce in the first section and its generation was sensitive to equivalence ratio. COS and CS2 were generated at flame area while CS2 was only detected in assisted combustion. However, these combustibles could be consumed especially in sufficient oxygen atmosphere. Enhanced combustion exhibited insignificant impact on solid sulfur product. It was revealed assisted combustion generated more valuable H2 and CO while producing significant pollutants COS and CS2. Low equivalence ratio combustion facilitated COS consumption but deviated H2S/SO2 ratio. Overall, oxygen-enriched combustion was considered as the most promising combustion mode for increasing the temperature. This study provided reference for the selection of solutions to improve temperature of acid gas combustion in industrial Claus furnace.