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题名: 光催化材料研制和基于CFD的光反应器优化
作者: 罗明汉1
学位类别: 博士后
答辩日期: 2017-11
授予单位: 中国科学院大学
授予地点: 北京
导师: 陈求稳
关键词: 微-介孔,光催化反应器,UV,VUV,CFD ; Micro-Mesoporous,Photo-Reactor,UV,VUV,CFD
其他题名: A Dissertation Submitted to University of Chinese Academy of Sciences For the Post-doctor Research Report
学位专业: 环境工程
中文摘要: 研究表明,生物难于处理的污染物通常具有化学稳定性高, 难以被常规氧化剂完全矿化的特点, 这就要求所采用的化学氧化剂必须具有足够的氧化能力, 因而促进了以产生氢氧自由基为主要特点的高级氧化技术(AOPs)的迅速发展。在过去的30年,针对高级氧化技术在大气和水体污染物处理的研究及应用已经取得了长足的发展。作为AOPs技术的一种,使用UV照射和二氧化钛(TiO2)的光催化氧化(PCO) 在水处理领域显示出显著的优势。光催化氧化技术的组成部分大致可分为与光能产生协同作用的光催化剂、给催化剂提供光能的光波段和产生光催化氧化反应的反应场,其中的每一个组成部分可延伸为一个崭新的研究领域。因此,针对光催化体系中的各组成部分进行交叉研究,有助于探索并设计光催化处理污水的新方法。围绕这一思路,本研究开展了光催化材料的研制和基于CFD的光反应器优化,取得的成果如下: (1)为了克服微孔和介孔分子筛的局限性,应用微-介孔复合材料是一种简单高效且环保的方法,可以改善介孔分子筛的水热稳定性,同时提供大量的活性位点。本研究结合SBA-15介孔材料与ZSM-5的活性位点,通过后合成法在水热硅质材料上合成出不同ZSM-5(38)质量比例的(Xg)ZSM-5-SBA-15复合材料,随后使用溶胶-凝胶方法将不同质量的二氧化钛沉积在复合材料的表面及孔洞之中。制备材料(XmL)TiO2/ZSM-5-SBA-15的光催化性能通过对水溶液中甲基橙(Methyl Orange(MO))的吸附与光催化性能进行表征,并与粉末状TiO2进行了比较。 (2)针对内循环气升式反应器,建立了三相流(气-液-固)模型,通过优化反应器内导流筒的结构、气含率、固含率以及流体循环速度等参数,提升固体光催化剂在反应器中的均匀混合效果,并提高小颗粒催化剂在反应结束之后的回收率。 (3)针对UV/H2O2AOPs处理污水中毒性和难降解有机污染物技术,通过CFD方法,建立了耦合水动力、UV辐射和化学反应动力学过程的数值模型,提高了催化剂停留时间和混合效果,并通过水中毒性和难降解有机污染物的降解效率进行了验证。 (4)基于CFD开发了能够深入分析适用于水处理的VUV/UV技术的数值模型。模型结合了水动力学、组分传输和化学反应动力学模块,可模拟反应器中辐射强度分布,并基于模型结果讨论了VUV/UV光反应器中不同化学组分的反应途径。
英文摘要: Previous studies indicated that the pollutants which are not effective for biological treatment are usually chemically stable and difficult to be completely mineralized by conventional oxidizers. This requires that the employed chemical oxidizers should have sufficient oxidizing ability, which promotes the rapid development of advanced oxidation technology (AOPs) charactered as the production of hydroxyl free radicals. In the past 30 years, the research and application of advanced oxidation technology in the treatment of air and water pollutants have achieved great process. As one type of AOPs, the photocatalytic oxidation (PCO) method using UV irradiation and titanium dioxide (TiO2) shows a significant advantage in the field of water treatment. The PCO technology generally includes three components, which are photocatalysts that work synergistically with light energy, optical wavebands that provide light energy to the catalyst, and reaction fields or reactors that produce photocatalytic oxidation reactions. Each of the components can be extendedinto a new research field. Therefore, the cross-study of the various components of the photocatalytic system is helpful to explore and design a new method of photocatalytic treatment of sewage. Based on this idea, the research carried out the development of photocatalytic materials and the optimization of photoreactor based on CFD, the obtained achievements are listed as following: (1) In order to overcome the limitations of microporous and mesoporous molecular sieves, the post-synthesis method was used to synthesize the micro-mesoporous composite, which not only improved the hydrothermal stability of the mesoporous molecular sieve, but also provided a large number of active sites. In this study, (Xg) ZSM-5-SBA-15 composites were prepared by using SBA-15 mesoporous materials and ZSM-5 (38) microporous materials at different mass ratios. As well, different quality of titanium dioxide (TiO2) was loaded on the surface and in the pores of (Xg) ZSM-5-SBA-15 composite via sol-gel method to prepare (XmL)TiO2/ZSM-5-SBA-15 photocatalyst. The photocatalyst loaded with 0.4 mL of TiO2 showed the best catalytic effect based on the morphology and structure analysis of prepared new material and the testing results of adsorption and photocatalytic performance of methyl orange (MO) dye in aqueous solutions. (2) A three-phase flow (gas-liquid-solid) model was established for the internal recycle airlift reactor. By optimizing the structure of draft tube in the reactor and parameters such as gas content, solid content and fluid circulation velocity, the gas and liquid can be well separated in the bottom zone of the reactor increasing the mixing performance in the reactor at the ratio of r/R = 0.4 and the gas velocity of Ug = 0.5m/s. In this way, the uniform mixing effect of the solid photocatalyst in the reactor is improved, and the recovery efficiency of the small particle of catalyst after the reaction is improved as well. (3) As the technology of UV/H2O2 AOPs is for treating the toxic and refractory organic pollutants in sewage, a numerical model of coupling hydrodynamic, UV radiation and chemical reaction kinetics was established based on the CFD method to simulate the hydrodynamic phenomenon and the chemical reaction process in the designed photocatalytic cyclone reactor. In the hydrodynamic analysis of the new reactor, it was found that the velocity of the fluid is maximized at the inlet and then decreases until the outlet which still provides rotational force for the reaction mixture in the reactor to provide hybrid power and prolong the residence time for different flow rates. Finally, the continuous experiment of degradation of methylene blue by the desgined reactor verified that the simulation was consistent with the experimental results. (4) A numerical model based on CFD was developed to further analyze the VUV/UV technology which is suitable for water treatment. The model combines the hydrodynamics, the component transport model and the chemical reaction kinetic module to simulate the distribution of radiation intensity and the hydrodynamics in the reactor. Based on the modelling results, the reaction pathway of different chemical components in the VUV/UV photoreactor was discussed. In the hydrodynamic analysis, it is found that the fluid at the inlet rised to the outlet along the wall of the reactor in a pusher flow and then flows downward along the surface of the light source in complete mixing for different flow rates. Finally, the continuous experiment of degradation of methylene blue by the designed reactor verified that the simulation was consistent with the experimental results.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38675
Appears in Collections:环境水质学国家重点实验室_学位论文

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