Oxy-Fuel Combustion of Lean Acid Gas in the Absence of Methane Co-Combustion for So2 Emissions Reduction Under Claus Conditions

Abstract

As an auxiliary fuel in the lean acid gas combustion, natural gas co-combustion increased SO2 emissions downstream section in Claus process. In this study, oxy-fuel combustion was applied to replace the natural gas co-combustion to reduce SO2 emission from lean acid gas. Aspen Plus model was successfully verified by the plant data, and utilized to compare the oxy-fuel combustion and CH4 co-combustion of lean acid gas. The experiments were conducted in a coaxial jet double channel burner to analyze the distribution of flame temperature and gas products along the reactor. Both simulation and experimental results showed that oxy-fuel combustion of lean acid gas reduced the SO2 amount under Claus conditions, and had a superiority in the CO and H2 formation. The flame temperature was higher in the CH4 co-combustion, and reduced with the increase of H2S amount, whereas in the oxy-fuel combustion was increased. Presence of CH4 improved the conversion of H2S and reduced the COS amount. COS formation was mainly in the flame region, and closely related to CO and CO2. Chemical decomposition was the dominant pathway of H2S consumption, H2 and S2 as the main products. In the oxidation of H2S, the conversion of H2S into SO2 involved mainly recombination and oxidation between the intermediate sulfur species. This study provided novel insights into the application of oxy-fuel combustion to Claus process for SO2 emission reduction from lean acid gas.

Keywords: oxy-fuel combustion, CH4 co-combustion, lean acid gas, SO2 emission, Aspen Plus model