Research Of Sulphuric Products Recovery From Low SO₂ Concentration Flue Gas With Catalytic Oxidation

Recovery of sulphuric products from low SO2 concentration flue gas with catalytic oxidation was studied using TL-01 catalyst, and two technologies to produce sulphuric acid and ammonium salt were investigated respectively. Firstly, the effects of the parameters, such as space-velocity, oxidation temperature, SO2 and O2 concentration in the inlet flue gas, on the SO2 oxidation efficiency in the stage of catalytic oxidization were studied, and the apparent kinetics of catalytic oxidation was researched preliminarily. The results showed that the oxidation efficiency was affected considerably by the space-velocity and temperature. Under the conditions of space-velocity 1500 h-1, temperature at the head, middle and end part of the bed 440℃, 430℃ and 410℃ respectively, inlet SO2 concentration 3000×10-6 and the O2 content 10%, the oxidization efficiency reached 95.5%,SO2 concentration in the tail gas was below the Chinese standard.Then, the effects of the parameters, such as superficial velocity, condensation temperature, and the SO3 concentration in the converted gas and the content of vapor, on the condensation efficiency and the concentrated sulphuric acid concentration in condensation process were studied. The results showed that the condensation efficiency and the sulphuric acid concentration were affected by superficial velocity considerably, then the condensation temperature. Under the conditions of superficial velocity 0.035 m·s-1(standard condition), the inlet temperature of condenser 240℃, outlet temperature 85℃, SO3 concentration in the converted gas 3000×10-6, the content of vapor 2%, the concentration of sulphuric acid reached 95.9%, and the condensation efficiency exceeded 99.6%, and the concentration of sulphuric acid mist in the tail gas was below the Chinese standard.At last, the effects of the parameters, such as nNH3/nSO3, reaction temperature, SO3 concentration in the converted gas, residence time, on the process of producing ammonium salt were studied. The results showed that nNH3/nSO3 had a significant effect on the concentration of sulphuric acid mist and NH3 in the tail gas, and it determined the composition of the ammonium salt. Under the conditions of nNH3/nSO3 1.85, reaction temperature 70℃, residence time 4s, SO3 concentration in the converted gas 3000×10-6, the concentrations of both sulphuric acid mist and NH3 in the tail gas were below the Chinese standards, and the main composition of the products was (NH4)2SO4, companying with a small quantity of NH4HSO4.