Experimental Study On Photocatalytic Oxidation For Simultaneous Desulfurization And Denitrification

A new approach and principle of SO₂ and NOx simultaneous removal from flue gas was presented by TiO₂ potocatalyst. In this experriment, TiO₂ supported photocatalyst was prepared with quartz sand particles, and using the removal of simulative SO₂ and NOx flue gas, photocatalytic degradation experiment was carried out on the self-made photoreactor at high concentration level. Many influencing factors were investigated in detail. The chemical and micro-structure analysis on the products of the desulfurization and the denitrification reactions were analysed, the mechanism of simultaneous desulfurization and denitrification by photocatalytic oxidation was deduced. On the basis of the experimental results, the desulfurization model and the denitrification model were proposed.TiO₂ supported photocatalyst was prepared by liquid-phase deposition method, and modification and regeneration of TiO₂ photocatalyst was studied. The performance of TiO₂ photocatalyst was characterized by SEM, TEM, XRD. The anatase TiO₂ existed and the particle size of no-doped and doped TiO₂ photocatalyst were 21.8nm and 17.5nm, respectively.The photocatalytic activity of TiO₂ photocatalyst was evaluated by degradation of methylene blue.Under UV irradiation, photolysis and oxidation of SO₂ couldnot occured and could be absorbed by TiO₂ photocatalyst. UV irradiation, presence of O2, initial concentration, temperature, humidity was most essential factors to photocatalytic oxidiation of SO₂. The photocatalytic oxidation was primary in the removal process of SO₂. Under optimum experimental conditions,the higher removal efficiency of SO₂ with no-doped and doped TiO₂ photocatalyst was 96% and 100%, respectively.NOx could be adsorbed by TiO₂ photocatalyst in the dark, and had no photolysis and oxidation under UV irradiation. Presence of O2 and initial concentration improved the removal efficiency of NOx. In certain temperature and humidity range, to no-doped and doped TiO₂ photocatalyst, the removal efficiency for NOx was obstained about 49% and 53.2%, respectively.The presence of SO₂ and NOx, physical adsorption was mainly without UV irradiation . In certain concentration range, the removal of SO₂ and NOx had a promotion for each other. In this experiment, oxygen was sufficient and the removal efficiency of SO₂ and NOx was obstained over 80% and 40%, respectively. With humidity increasing, the removal efficiency of SO₂ was increased, reached to 100%, and that of NOx declined. The main products of the desulfurization and denitrification reactions were sulfate and nitrite by the analysis of EDS,IC and XPS. On the basis of above results, the mechanism of desulfurization and denitrification was the process of SO₂ and NOx photocatalytic oxidation. BP nerve network model was proposed for the predict of the removal efficiency of SO₂ and NOx, and a better precision was obstained.