Kinetics of uncatalyzed oxidation of ammonium sulfite from wet ammonia desulfurization

The kinetics of oxidation of ammonium sulfite from flue gas desulfurization by ammonia process was studied by changing initial ammonium sulfite concentration, pH, air flow rate, temperature, and concentration of ammonium sulfate in a bubble reactor. The experimental results show that the oxidation rate of ammonium sulfite decreased with the increase of pH but increased with the increase of temperature and airflow rate when the concentration of ammonium sulfate is 0.15 mol/L, temperature of 25–60°C, and an airflow rate of 150–400 L/h. When the concentration of ammonium sulfate increases from 0.2 to 1.0 mol/L, the oxidation rate of ammonium sulfite decreases. At pH 5.0, the activation energy of the apparent oxidation is 26.40 kJ/mol. A kinetics model containing SO32−, SO4, and O2 is used to simulate the oxidation of ammonium sulfate. The results can provide a theoretical basis for the uncatalyzed oxidation of ammonium sulfite in the process of wet ammonia desulfurization process.