Study On Catalytic Removal Of NO_x From Coal-fired Flue Gas

Selective catalytic reduction (SCR) of NOX with NH3 has been investigated in a fixed-bed reactor by the use of the V2O5/TiO2 catalysts prepared by impregnation. For the particle catalysts of 100/140 meshes, the SCR is a first order reaction and its active energy is 95.1 kJ/mol. The reaction temperature, contact time, V2O5 content in the catalyst and the injection quantity of NH3 affect the SCR reaction. The optimum reaction temperature, contact time, V2O5 mass fraction and n(NH3)/n(NOx) are 310℃, 200ms, 4.5%, and 1.2 respectively. Under the optimum reaction conditions, NOx removal efficiency of 90% can be obtained. For the pallet catalysts, the gas flow rate and the thinner thickness of the catalysts has advantageous influence on the denitriflcation reaction. The removal efficiency of NOX increases as the gas flow rate increases, but runs to steady when the flux reached 410kg/(m2h). On the other hand, the pallet-catalyst thickness from 0.1cm to 0.2 cm leads to the decrease of NOX removal efficiency from 83% to 40%, and to the decrease of inter-diffusion efficiency factor from 0.254 to 0.127. The overall NOX removal efficiency is expressed as an explicit function of space velocity and other parameters, and a simple analytic solution is obtained. There is a good agreement between the experimental and modeling results. It is shown that the model equation can successfully reflect the conversion trend, and this provides the theoretical basis for designing a catalytic reactor.By the use of the MoO3(WO3)/TiO2 catalysts of 100 mesh prepared by mixing and under the lower temperature range (<310℃), the NOX removal efficiency could be increased as the temperature is increased and the space velocity is decreased. However, at the higher temperature(>310℃), the side reaction of NH3 oxidation is strengthened, and NOX conversion would be decreased if the reaction time was over-lengthened and the reaction temperature was heightened. At 310℃ NOX removal efficiency reached 92% when the space velocity was 12000h~-1. Analytic results of FT-IR spectrum and XRD showed that MoO3 can be distributed as a monolayer on the surface of TiO2 particles which leads to the formation of the stable Mo=O bond, and that the addition of MoO3 had no effect on the structure and topology of TiO2 (anatase). The kinetic results show that SCR active energy is 14.45 kJ/mol, 87.3 kj/mol, and 9.5 kJ/mol respectively for the MoO3(6%)/TiO2, WO3(7)/TiO2, and V2O5(1.4)-Mo03(6%)/Ti02 catalystsThe Cu-ZSM-5 Me-Cu-ZSM-5 (Me= Ni, Co, Ce) and Ni-Ce-ZSM-5 catalysts were prepared by ion exchanging, and were then applied to NO direct decomposition. The preparation condition, the ion-exchanged condition, pretreatment techniques, reaction condition, and the doping of the second ions Me~n+ have superior influences on the activity...