Study On The Dry Flue Gas Desulfurizaiton By CuO/γ-Al₂O₃

One of the most effective means to reduce the SO₂ emission from coal-fired boiler is always to be equipped with FGD components for the time being. Since getting mature, the dry or wet limestone(lime)-gypsum FGD process, the spray drying absorption FGD process and the process of injecting sorbents into boiler furnace or flue, with their different degrees of pitfalls, have confronted with the problem of application in China to the end. The combined SO₂/NO_x removal technology is illuminated with a widened road of application. In other countries though the research and development of the copper oxide process has been becoming mature, its commercialization has a long way to go. In China, we are just to start the research on this technology, hence, to study on the processes in which how does CuO take effectiveness on the desulfurization, denitration and regeneration processes in detailed and quantitative description, and to solve the problems during this technology being applied for the commercialized production, are becoming a request of exigency in original intellectual property creation. Above all, this thesis summarizes existing FGD processes and reviews the technological development of the supported copper oxide process for dry flue gas desulfurization, denitration simultaneously both inside and outside China, from which a self-based research idea and improvement plan is raised. Below is the relevant research work based on it. Sample preparation and the flue gas desulfurization activities of the CuO/γ-Al₂O₃ sorbent-catalyst are at the root of this study. These samples with different copper content are prepared by incipient wet impregnation and CuO is dispersed onto porous carrier as γ-Al₂O₃, which has a quite high specific surface area. The sulfur removal efficiency is assumed to focus on the correlation between the desulfurization activities and the factors of copper loading, concentration of SO₂ and O₂, space velocity of flue gas and the reaction temperature. Experiments of desulfurization are carried out in a packed-bed quartz down-flow reactor using the simulated flue gas and on the condition of different samples mentioned above. The data from these experiments are conducted to make intrinsic chemical kinetics analysis to get the relevant kinetic parameters, which is the guidance for further process development. The value in practical application of CuO/γ-Al₂O₃ being a high efficiency flue gas desulfurizer is acknowledged by the positive conclusions from desulfurization experiments. In respect that the cost reduction and the future commercial application, the regeneration performance of sulfurated CuO/γ-Al2O3 would play a critical role in this process. In this thesis, the regeneration experiments on sulfurated samples are taken place by utilizing the reducing gas as methane to determine an opportune reaction conditions and to judge how does the repeated desulfurization-regeneration cycles affect the consumption of sorbent-catalyst. The regeneration behavior of various samples is also studied by thermogravimetric analysis under same conditions above. On studying of the deactivation of sorbent-catalyst in the processing of desulfurization, a conclusion is given out regarding the sintering and forming of compounds are the main cause. The cost of metal oxide itself and the higher desulfurization reaction temperature are the main factors that are lagging the commercialization of CuO/γ-Al2O3 dry FGD process. A creative attempt on decreasing the desulfurization reaction temperature and improving the sulfur removal efficiency by adding catalyst promoter is useful on its generalization and application. Some different kinds of catalyst promoters are selected and added into CuO/γ-Al2O3 to modify the desulfurization activities on the purpose of investigating these promoters'effects on desulfurization and their possible mechanism of how they take effect. The results show that several catalyst promoters could conspicuously enhance the activities and decrease the reaction temperature on desulfurization. In order to study the performance and the property of sorbent-catalyst, some available physical and chemical characterization methods are adopted, such as chemical analysis for copper content by atomic emission spectrum, BET surface area and pore distribution & construction testing, X-ray diffraction for phase identification, Electronic probe microscopy appearance & quantitative analysis and X-ray photoelectron spectroscopy for surface species analysis. Systematic research aiming at different types of desulfurizer and the desulfurizers in different reaction phase is conducted in order that we can find the relationships between the desulfurization activities and the sorbent-catalyst preparation, chemical constitution and its components, from those results we can determine the form and the structure of surface species and indicate the reaction mechanism of the catalyst promoter. All the characterization results approve that the physical structure of the desulfurizer and its surface species'degree of dispersion have close relationship on the desulfurization activities, and the catalyst promoter can modify these properties to enhance the sulfur removal efficiency. It also reveals the secret why the sorbent-catalyst can maintain the higher desulfurization activities after multiple cycles of desulfurization-regeneration.The process of CuO/γ-Al2O3 dry flue gas desulfurization is a heterogeneous catalytic reaction in deed that based on chemical adsorption. In the end of this thesis, an approach of ab initio calculation comes from quantum chemistry theory is conducted to study the chemical adsorption during CuO/γ-Al2O3 desulfurization reaction, the stationary state configuration and energy of chemical adsorption between metal oxides and SO2 or O2 are figured out to explain the influence derived from adsorption on desulfurization reaction. On account of the study on chemical adsorption between desulfurizer and gas molecule is limited by existing experimental technique, using advanced computational chemistry method to investigate the adsorption behavior of surface species can determine the effect of adsorption on chemical reaction and indicate its mechanism on a microscopic view. The creativity within this research has its unique characteristics, which should deserve relevant value in the domain of its subject. Keywords: copper oxide flue gas desulfurization experiment study...