Optimization Simulation And Small-Scale Catalyst Preparation On De NO_x Project

Nitrogen oxides(NOx) are the most prominent air pollutants, which are harmful to the ecological environment and human health. NOx emitted from the stationary sources such as coal-fired boilers and the mobile sources such as motor vehicles are the main sources.Selective catalytic reduction(SCR) is one of the most mature and commericalized techniques,while the catalyst is the key of the SCR process.Computational Fluid Dynamics(CFD) can be used to simulate SCR system in order to provide the theorical reference for de NOx engineering design. The parameters of the deNOx system were improved in this paper, including the number and size of commutated gridirons,the structure size of reactor and the size and number of the guide vanes. The optimum values were determined by CFD. On the basis of the previous models, with the increase of the number of commutated gridirons, the uniformity of flow distribution in the reactor of the internal flow field was not improved, thus the number of commutated gridirons was set to be21. With the increase of the height of commutated gridirons, the uniformity of flow distribution becomes higher and then lower in the internal flow field of the reactor, therefore the optimized height of commutated gridiron was 0.5 m. As the uniformity of flow distribution in the internal flow field is still not reached the requirements, the improvement of the size of the SCR reactor was considered. On the basis of the improved model, the installation position and the number of the guide vanes were changed to 5, causing the significant increase of the uniformity of flow distribution in the internal flow field of the reactor. After the length of the guide vanes were optimized to 1.2 m, the uniformity of flow distribution in the internal flow field of the reactor meets the requirements well.In this work, SAPO-44 zeolites were prepared by hydrothermal method and Cu-SAPO-44 catalysts were prepared by ion-exchange method. The texture structure,morphology and redox property of zeolites and catalysts were characterized by XRD, N2adsorption-desorption, ICP-AES, SEM, XPS and H2-TPR. The results showed that the high purity SAPO-44 zeolites can be prepared using a certain mole ratio of reactants. The crystallinity of Cu-SAPO-44 catalyst was obviously decreased after ion-exchange by Cu ions.The particle size and pore size of Cu-SAPO-44 catalysts were smaller than those of theSAPO-44 zeolites. Cu species were absent on the surface of the catalyst, possibly due to the highly-dispersed Cu species in the interior of catalysts, and hence blocking the pore of zeolites, resulting in the decrease of surface areas. The SCR activity of Cu-SAPO-44 catalyst was measured, which exhibits excellent deNOx activity at 200℃~ 550 ℃. However, the resistance to H2 O and SO2 and hydrothermal stability are a litter poor.