废水处理光催化反应器的发展

光催化是一项很有前途的水处理技术,光催化反应器是影响光催化反应效率的重要因素之一。作者对影响光催化反应器效率的因素如光源种类、反应器结构、催化剂状态等进行了分析,并总结了近年来在国内外研制及应用的一些典型的光催化反应器．给出了其结构图．并对其优缺点进行了评价。     

Photocatalytic degradation of gaseous trichloroethene using immobilized ZnO/SnO2 coupled oxide in a flow‐through photocatalytic reactor

The photocatalytic degradation of gaseous trichloroethene (TCE) was investigated on immobilized ZnO/SnO₂ coupled oxide in a flow‐through photocatalytic reactor. It was found that gaseous photocatalysis is an efficient method for volatile organic compounds' abatement and air purification. Degradation of ～100% was found for TCE at the concentrations examined, up to 400 ppmv, in a flow‐through dry synthetic gas stream. In our tested conditions, the flow rate had little influence on the photocatalytic degradation efficiencies of TCE, while the relative humidity had a significant influence on the photocatalytic degradation of TCE. The photocatalytic degradation efficiencies of TCE increased slowly below 20% relative humidity and then decreased as the relative humidity increased further. The deactivation of used immobilized photocatalyst was not observed within the 200 h testing period in the present experiment, although the surface of the photocatalyst changed greatly during the use of the photocatalyst. Copyright © 2004 Society of Chemical Industry     

水处理用超声波反应器的研究现状

介绍了水处理中常用的几种超声波反应器,包括液哨式、清洗槽式、变幅杆式、杯式和平行板式反应器的研究现状。在综合比较各种反应器优缺点后,指出平行板式反应器的出现为超声波水处理技术从实验室走向较大规模的实际工业应用提供了技术支持,其应用前景是最大的。     

Workflow for computational fluid dynamics modeling of fixed-bed reactors packed with metal foam pellets: Hydrodynamics

In recent years, the catalyst pellets made of open-cell metallic foams have been identified as a promising alternative in fixed-bed reactors. A reliable modeling tool is necessary to investigate the suitability of different foam properties and the shapes of foam pellets. In this article, a workflow for a detailed computational fluid dynamics (CFD) model is presented, which aims to study the flow characteristics in the slender packed beds made of metal foam pellets. The CFD model accounts for the actual random packing structure and the fluid flow throughout the interstitial regions is fully resolved, whereas flow through the porous foam pellets is represented by the closure equations for the porous media model. The bed structure is generated using rigid body dynamics (RBD) and the influence of the catalyst loading method is also considered. The mean bed voidage and the pressure drop predicted by the simulations show good agreement with the experimental data.     

Computational fluid dynamics and electrostatic modeling of polymerization fluidized-bed reactors

Electrostatics plays an important role in gas-solid polymerization fluidized-bed reactors. Agglomeration of polymer particles can occur due to either electrostatic and/or thermal effects, and can lead to reactor operability problems if not properly mitigated. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the bulk polymer, polymer fines, and catalyst particles. The multi-phase CFD model for gas-solid flow is based on the kinetic theory of granular flows and the frictional theory. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer fines and polymer). The combined CFD model is first verified using simple test cases and then applied to a pilot-plant-scale polymerization fluidized-bed reactor. The multi-phase CFD model is applied to reproduce qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments.     

A systematic approach for the design of UV reactors using computational fluid dynamics

A wide variation exists in the geometries of UV reactors, which results in completely different hydrodynamics and therefore large differences with respect to the disinfection and oxidation performance. Among the large number of reactor types, it is not known beforehand which reactor type has the best performance with respect to disinfection or oxidation, and if such a reactor is the best reactor out of all the possible reactor designs. In this research, a systematic approach for the design of UV reactors is followed that makes use of computational fluid dynamics (CFD) modeling. To that end, the inactivation of Bacillus subtilis and degradation of atrazine was determined for a wide range of UV systems by means of CFD. The efficacy of UV systems was evaluated and improvements were made by taking measures that increase the mean dose and/or narrow the dose distribution, such as placing mirrors, enhancing the mixing and placing reactors in series. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

固定膜太阳能光催化反应器的研究现状与展望

通过对负载在颗粒状、玻璃棒类、玻璃纤维网、纸质材料和平板型载体上的固定膜催化剂的比较,提出以玻璃纤维网、纸质材料和平板型材料为载体的固定膜催化剂是太阳能光催化反应器研究的良好选择。概述了薄膜瀑布反应器、阶梯反应器和复合抛物面反应器3种新型固定膜太阳能光催化反应器,并指出了未来太阳能光催化技术的研究方向。     

光催化降解含酚废水研究进展

二氧化钛（TiO2）具有化学性质稳定、无毒、成本低、催化效率高等优点,以TiO2为催化剂催化氧化处理含酚废水是近年来发展迅速的一项水处理技术。就光催化剂的负载、改性以及光催化反应器的研究进展等进行了详细的阐述。     

Predictive radiation field modeling for fluidized bed photocatalytic reactors

A predictive model of the radiation distribution for fluidized bed photocatalytic reactors was proposed and solved by means of the Monte Carlo approach coupled with the ray tracing technique. This model considers the interaction between the photocatalytic TiO₂-coated spheres and the photons, taking into account the shadowing effect of the beads, the reflection on the surface of the spheres, and the absorption in the TiO₂ films. This radiation model is completely predictive and does not use any adjustable parameter. Modeling results indicate a strong influence of the bed expansion on the radiation distribution, with the shadowing effect of the beads being the main cause for this dependence. Increasing the bed expansion improves the uniformity of the radiation distribution in the reactor. Nevertheless, an excessively expanded bed would reduce the efficiency of the reactor because the transmittance of the bed increases and a fraction of photons leave the reactor without being absorbed by the TiO₂-coated spheres. The radiation model was evaluated in a laboratory-scale fluidized bed photocatalytic reactor that was designed and built for the elimination of organic pollutants from water streams. TiO₂-coated glass spheres with a diameter of 1.18 mm were used as photocatalyst. The model was validated by comparing the predicted values of the effective transmittance of the bed with experimental results measured under different bed expansions. The performance of the reactor was also assessed experimentally, showing a good efficiency for the photocatalytic degradation of formic acid as a model compound.     

Photocatalytic reactors for environmental remediation: a review

Research in the field of photocatalytic reactors in the past three decades has been an area of extensive and diverse activity with an extensive range of suspended and fixed film photocatalyst configurations being reported. The key considerations for photocatalytic reactors, however, remain the same; effective mass transfer of pollutants to the photocatalyst surface and effective deployments and illumination of the photocatalyst. Photocatalytic reactors have the potential versatility to be applied to the remediation of a range of water and gaseous effluents. Furthermore they have also been applied to the treatment of potable waters. The scale‐up of photocatalytic reactors for waste and potable water treatment plants has also been demonstrated. Systems for the reduction of carbon dioxide to fuel products have also been reported. This paper considers the main photocatalytic reactor configurations that have been reported to date. Copyright © 2011 Society of Chemical Industry     

A computational method for determination of the mass-transfer coefficient in packed-bed immobilized enzyme reactors

A computational method was developed that determined the mass-transfer coefficient k_L or the volumetric mass-transfer coefficient k_La in packed-bed immobilized enzyme (IME) reactors. To study the performance of this method, two experimental systems were considered where an enzyme was immobilized on a non-porous support surface (surface-IME system) or within a porous support (pore-IME system). The values of k_L and k_La determined in these packed-bed IME reactor systems were successfully expressed in terms of the substrate concentration at the reactor inlet and the liquid flow rate. Furthermore, the correlations obtained for k_L and k_La were used to calculate the unconverted fractions of substrate at the reactor outlet. Comparison showed that the calculated results were in satisfactory agreement with the experimental values.     

Computational fluid dynamics of high density circulating fluidized bed riser: Study of modeling parameters

CFD modeling of air and fluid catalytic cracking (FCC) particles in the riser of a high density circulating fluidized bed (HDCFB) has been performed. The implementation of correct inlet conditions was found to be critical for the successful simulation of the hydrodynamics. The simulated profiles of gas and solid velocity and volume fraction were overall in good agreement with experimental data reported in the literature. However, due to the difficulties in accurate modeling of the solid segregation toward the wall, the solid volume fraction was under predicted near the walls. The effect of modeling parameters including different drag models, wall restitution coefficient values, and solid slip conditions have been evaluated. While the wall restitution coefficient did not exhibit a significant effect on the riser hydrodynamics, the appropriate slip condition aided in predicting the solid segregation toward the wall.     

Response surface optimization of the photocatalytic degradation of atenolol using immobilized graphene-TiO2 composite

Photocatalytic processes using semiconductors have been widely explored due to their fascinating benefits in environmental remediation. In this study, a four-factor three-level Box-Benkhen design (BBD) was employed to assess the photocatalytic degradation of atenolol (ATL) using immobilized graphene-TiO₂ as a photocatalyst. The four variables that were considered in the BBD model were the photocatalyst concentration (10%-20%), pH (4-9), ATL concentration (10-30 mg/L), and light intensity (60-260 W/m²). A monolithic-type swirl-flow reactor, which allowed the immobilization of the photocatalyst, was employed in a semi-batch system to study the photocatalytic degradation kinetics of ATL. The optimum conditions where the highest rate constant (0.667 min⁻¹) was observed were graphene-TiO₂ concentration of 10%, pH of 6.5, ATL concentration of 30 mg/L, and light intensity of 160 W/m². The developed model well predicted the observed values indicated by a high R² of 0.897. Reaction rate constants obtained herein using graphene-TiO₂ in immobilized form were compared with slurry system and TiO₂.     

太阳能固定膜光催化反应器的效率评价

以结构简单、光能利用率高的复合抛物面采光板为采光元件,以采用溶胶-凝胶法负载在比表面积大、化学性质稳定的玻璃纤维网上制得的高活性TiO₂固定催化剂制作催化组件,自主设计了一种新型的太阳能光催化反应器。以草酸铁钾化学光量计曝光试验对其光学性能进行了评价,光子采集效率约为0.759。由于固定化催化剂活性良好、装填结构合理,本装置降解苯酚表观量子产率可以达到相同结构悬浆催化体系反应器的1/2,因而具有良好的实用性。     

包埋固定化菌处理微污染水的对比研究

试验以《地表水环境质量标准》中劣Ⅴ类微污染水为研究对象,对比传统A/O工艺、投加包埋固定化菌的A/O工艺以及单独使用包埋固定化菌工艺的运行情况,考察了包埋固定化菌处理微污染水的性能。结果表明,使用包埋固定化菌处理劣Ⅴ类微污染水,出水COD、氨氮分别达到地表水环境质量标准中Ⅲ类、Ⅱ类水标准。研究还表明,向传统活性污泥A/O工艺好氧区中添加包埋固定化菌有助于维持微生物浓度稳定,提高出水水质及稳定性。     

Computational fluid dynamics-based optimization of dimpled steam cracking reactors for reduced CO2 emissions

Spherical dimples in cylindrical tubes enhance heat transfer and lead to a more uniform radial temperature profile. To combine these positive properties with a low pressure drop, a single dimple was optimized through a genetic algorithm. Multiple design parameters such as width, height, and curvature of the dimple were investigated. Heart-shaped dimples outperformed spherical dimples. Three-dimensional reactive simulations of a Millisecond propane steam cracking reactor showed that both the spherically dimpled and the heart-shaped dimpled coil positively affect the light olefin selectivity, mainly through an increase in propylene selectivity. The optimized dimples could reduce the high pressure drop penalty by 21%. Run length simulations proved that the optimized dimple shape results in an additional run length extension of 18%. Next to this, the fuel rate consumption can be decreased by 6% compared to a bare coil, which could theoretically result in 4% less CO₂ emissions.     

Computational fluid dynamics (CFD) modeling of spouted bed: Assessment of drag coefficient correlations

In the computational fluid dynamics (CFD) modeling of gas-solids two-phase flows, drag force is the only accelerating force acting on particles and thus plays an important role in coupling two phases. To understand the influence of drag models on the CFD modeling of spouted beds, several widely used drag models available in literature were reviewed and the resulting hydrodynamics by incorporating some of them into the CFD simulations of spouted beds were compared. The results obtained by the different drag models were verified using experimental data of He et al. [He, Y.L., Lim, C.J., Grace, J.R., Zhu, J.X., Qin, S.Z., 1994a. Measurements of voidage profiles in spouted beds. Canadian Journal of Chemical Engineering 72 (4), 229-234; He, Y.L., Qin, S.Z., Lim, C.J., Grace, J.R., 1994b. Particle velocity profiles and solid flow patterns in spouted beds. Canadian Journal of Chemical Engineering 72 (8), 561-568.] The quantitative analyses showed that the different drag models led to significant differences in dense phase simulations. Among the different drag models discussed, the Gidaspow (1994. Multiphase Flow and Fluidization, Academic Press, San Diego.) model gave the best agreement with experimental observation both qualitatively and quantitatively. The present investigation showed that drag models had critical and subtle impacts on the CFD predictions of dense gas-solids two-phase systems such as encountered in spouted beds.     

Modeling heterogeneous photocatalytic inactivation of E. coli using suspended and immobilized TiO2 reactors

A study was carried out to develop a kinetic model of the photocatalytic inactivation of Escherichia coli using different TiO₂ catalysts. The model developed is based on a reaction scheme that involves effectively coupling mass‐transfer fluxes between bacteria and catalyst surface on one hand and bacterial degradation reaction on the other. The photocatalytic results were derived from experiments led in a batch reactor under both dark and Ultra Violet (UV) irradiation conditions. Using a reference catalyst, the robustness of the developed model was tested under solar conditions. The experimental data validated the model as successfully able to reproduce evolutions in the viable bacteria concentration in the range of parameters studied without any further adjustment of the kinetic parameters. The model was used to simulate the bacterial degradation kinetics under different working conditions to describe the partitioning of both bacterial adhesion and photocatalytic reaction in the solution to be treated © 2015 American Institute of Chemical Engineers AIChE J, 61: 2532–2542, 2015     

催化裂化提升管反应器流动反应耦合模型研究进展

催化裂化(FCC)工艺在重质油轻质化过程中发挥着重要作用, 而FCC提升管反应器的模型化是催化裂化新工艺与新装备的开发、催化裂化装置稳定操作与生产调优等常需做的工作。本文首先根据流动模型与反应模型不同的集成方式对提升管反应器流动-反应耦合模型进行了归纳与分类, 并回顾了国内外流动-反应耦合模型的研究历程, 指出了耦合模型的发展趋势;随后对当前研究较多的计算流体力学(CFD)流动-反应耦合模型进行了较为全面的阐述, 包括对耦合模型的应用场合、模型求解解耦方法的研究情况等均作了介绍, 同时还分析了该类耦合模型所存在的不足之处, 并指出工业提升管反应器在线采样技术的开发在耦合模型的验证工作上的必要性;最后, 对FCC提升管反应器流动-反应耦合模型研究进行了总结与展望, 以期能够为FCC提升管反应器模型化新方法的提出以及耦合模型的验证工作等研究给予借鉴和指导。