Simultaneous NOx and SOx Reduction from Oxyfuel Exhaust Gases using Acidic Solutions Containing Hydrogen Peroxide

AbstractThis study aims at reducing nitrogen and sulfur oxides contents in oxyfuel exhaust gases by absorption (transfer from the gas to the liquid) into acidic solutions containing hydrogen peroxide, producing stable nitric and sulfuric acids in the liquid phase. Absorption tests were achieved at 20°C and atmospheric pressure in a laboratory cables-bundle contactor (height of 54cm); a range of partial pressures (600-2000ppm SO2, 3000ppm NOx with different NO2/NOx ratios) and liquid phase concentrations (0-4mol/l for each acid, 0-1mol/l for H2O2) was investigated. The effects of the different operating parameters were thoroughly studied and discussed. The presence of acids, especially H2SO4, has a negative effect on both SO2 and NOx absorption rates, while HNO3 was found to promote the global NOx absorption, depending on the NO2/NOx ratio. There was no significant CO2 absorption observed during the absorption tests. Modelings of SO2 absorption, on the one hand, and of NOx absorption, on the other hand, were successfully performed using experimental results, allowing the determination of global parameters of absorption grouping solubility, diffusivity and kinetic constants, function of acids concentrations and temperature. These original parameters can be used in the design of industrial columns