鼓泡反应器中幂律型流体流动与传质特性

很多废水处理装置涉及非牛顿型流体中的多相流动和传质问题,研究其中的气液传质过程有助于实现装置的优化设计和高效节能运行。以鼓泡反应器内清水和不同质量分数的羧甲基纤维素钠（CMC）水溶液为实验对象,分别研究气相表观气速和液相流变特性对气泡尺寸分布、全局气含率和体积氧传质系数的影响。实验结果表明,液相的流变特性对其传质特性参数均有较大影响。与清水相比,CMC水溶液中气泡平均直径和分布范围更大;清水和CMC水溶液的全局气含率均随表观气速的增加而增大;CMC水溶液的体积氧传质系数随CMC水溶液质量分数的增加而减小。基于实验研究,得出修正的体积氧传质系数公式和适用于幂律型非牛顿流体流动体系氧传递过程的无量纲关联式,可很好地实现非牛顿流体流动的废水处理装置中气液传质参数的计算。     

废水好氧生物处理工艺中氧的传质与强化的理论与实践

废水处理好氧生物工艺供氧过程的控制步骤是气液传质作用,即将气体分子氧转化为足够微生物用于氧化污染物的溶解氧（DO）,包含碳源BOD5的降解、氨氮的硝化和总氮的去除以及无机COD氧化的共同需求。文章指出DO的传质过程由总传质系数K_La决定,废水性质、生物量、污泥龄、微生物耗氧速率、微生物种群等因素都会影响K_La。DO的浓度梯度是气液固三相氧传质的主要推动力,气液传质受水温、水质、氧分压、气泡大小、液体紊流程度和液膜更新速度等的影响,通过提高氧气分压、增大气泡比表面积、强化气液混合以及无泡供氧等方式及其它们的结合,或者控制污泥流态化程度及其污泥龄,可以获得微生物摄氧能力的提高。本文指出在对水质特征、环境条件、微生物特性、反应器流体特性以及运行参数等优化的基础上,结合一些研究新的方向,如无泡供氧、纯氧/富氧曝气的气泡行为,流场分布、湍流构造、浓度梯度的流体行为,挡板内构件、流态化控制的反应器结构优化,以及充分考虑负荷的HRT和SRT的运行工艺条件,可以实现更加全面的节能目标。     

微孔纯氧曝气在甲醇废水中的应用分析

介绍了微孔纯氧曝气机理,从气液传质理论、氧转移率、气-液传质比表面积及微生物生长过程等方面阐述了微孔纯氧曝气在处理甲醇废水中的优越性。同时,介绍了B IOX工艺及无气泡纯氧曝气工艺的特点。最后指出,微孔纯氧曝气以其极大的优点,将会在甲醇废水处理行业中得到广泛的应用。     

Oxygen transfer in a rotating disk reactor with continuous flow

The oxygen transfer characterized by the liquid phase mass-transfer coefficient (k_L) was investigated in a three-phase rotating disk reactor. Experiments were carried out in steady-state liquid flow conditions because this type of operation is more commonly practised, for example, in wastewater treatment system. The oxygen transfer rate was measured by the sodium sulphite method, but the oxidation was carefully controlled so that the mass transfer was not enhanced by the accompanying chemical reaction. A large portion of oxygen transfer occurred by the convective motion on the free surface of the bulk liquid in the trough, which was more significant when the flow rate was high in the axial direction.     

MODELING DISSOLVED OXYGEN CONCENTRATION FOR OPTIMIZING AERATION SYSTEMS AND REDUCING OXYGEN CONSUMPTION IN ACTIVATED SLUDGE PROCESSES: A REVIEW

Aeration accounts for 30% to 75% of the total energy consumption in activated sludge processes (ASPs). This percentage can be significantly reduced since most aeration systems are not optimized for unsteady influent flow rates and oxygen requirements. Reconfiguration, replacement, and the application of optimal dissolved oxygen (DO) control strategies for current aeration systems within the facility and model-based optimization of DO in wastewater treatment plants can lead to impressive increased energy efficiency and savings and improved stability of the system. These measures increase the operational lifetime of the aeration equipment and improve effluent and activated sludge quality. This article provides a review of two critical nonlinear time-varying parameters that characterize the DO concentration dynamics in an ASP: the oxygen uptake rate (OUR), related to microorganism activity, and the volumetric oxygen mass transfer function, represented by the oxygen transfer rate (OTR). Second, the physico-chemical, geometric, and dynamic factors and aerator type affecting the oxygen mass transfer coefficient (K _L a) are thoroughly discussed. The article concludes with model-based optimization, explaining the usefulness of accurate DO models in wastewater treatment, and provides examples for plant-wide or water chain cycle–focused optimizations.     

内循环流化床结构参数及其反应器性能的相关性

内循环三相流化床在化学工程、生物工程及废水处理等领域中均有广泛的应用前景,目前影响这类反应器成功应用于实际废水生物处理的主要原因是缺乏系统的反应器结构参数与反应器性能的相关性分析与量化关系模型,无法实现不同规模与不同应用目标的系统优化设计。基于此,设计了不同尺寸和内构件的反应器,系统研究主要结构参数包括升流管与反应器直径之比、反应器高径比、升流管上方液面高度、底隙高度以及操作参数如固相负荷及通气量等因素对内循环流化床反应器流体力学与传质特性的影响规律;实验分析主要过程参数如气含率、液体循环速度、氧传递系数及混合时间与结构参数、操作参数的相关性。通过总结归纳,分别给出了定量、半定量或定性方面的结论,为反应器的结构放大和性能变化预测提供理论基础.     

水力喷射空气旋流分离器脱氨

空气吹脱被广泛用于从废水中脱氨,但其过程效率有待提高。为了提高过程效率,提出了一种新型气-液吹脱设备——水力喷射空气旋流分离器（WSA）,并以废水中氨的吹脱进行了实验。与传统的吹脱设备相比,WSA表现出较好的气-液传质性能,使氨的吹脱效率大大提高。在氨的吹脱过程中,液相温度和空气流量是影响吹脱过程中氨体积传质系数的主要因素。空气流量对于体积传质系数存在一个临界值,超过此值时,体积传质系数随空气流量增加而迅速增大。液相中存在的固体颗粒物对于吹脱过程的传质几乎没有影响。在该设备中没有填料,不存在堵塞问题,因而可以进行较长时间的分离操作。     

鼓泡填料塔中水与餐厅污水氧传递特征

用不稳定传质模型对鼓泡填料塔中水和污水氧传递进行了理论分析,通过定义表面更新速率和含气率导出了鼓泡填料塔中水和污水中氧传递系数与操作条件和填料特征之间的关系式,并通过实验确定了关系式中特征参数.用关系式计算得到的氧传递系数与实测值基本吻合,最大偏差为20%.结果表明：采用的组合型填料具有优良的氧传递性能;在相同操作条件下餐厅污水中的氧传递系数小于清水中的数值.     

CFD simulation of the hydrodynamics and reactions in an activated sludge channel reactor of wastewater treatment

This paper presents a complete CFD modelling of a wastewater gas-liquid cross-flow reactor, taking into account hydrodynamics, mass transfer and biological reactions. Transfer processes, kinetics model and assumptions made are described in detail. The simulations have been successfully compared to experimental results obtained in a bench scale reactor. Chemical oxygen demand (COD), nitrate, ammonium and oxygen concentrations have been measured along the length of the reactor and compared to the simulated profiles. A very good agreement has been obtained for the COD and nitrate concentration profiles. Agreement for the oxygen concentration profile is reasonably good with respect to the experimental uncertainty. These results have been obtained without any adjustment of the kinetics parameters. The basics of a three-phase CFD model taking into account the transfer between flocs and wastewater, as well as the inhomogeneous concentration of biomass due to the hydrodynamics of the reactor, are proposed as perspectives.     

光催化氧化流化床参数的研究

设计了用于负载型TiO2催化剂的三相流化床光催化反应器,对其参数作了初步的研究,并对其处理含酚废水的性能和催化反应的影响因素及程度进行了分析。与固定床相比,流化床反应器表现出更好的处理效果。它使催化剂和含酚废水充分接触并提供充足的氧气,实现了光、固体催化剂和溶液的大面积有效接触,提高了传质效率,加快了光催化反应速率。在pH值为9.6,催化剂用量为50g,气流量为500L/h和液体流量为8.0L/h,在一个操作周期(12h),流化床反应器的处理能力为19.5mg/g,固定床的处理能力为14.4mg/g。流化床的处理能力比固定床的高35.4%。酚的去除率为99.8%。     

高铁酸钾处理含砷废水

基于对K2FeO4氧化As(III)热力学平衡及As(III)氧化过程氧转移机理的研究,利用高铁酸钾氧化-絮凝一体化工艺处理100 mg/L模拟含砷废水,考察了Fe/As质量比、pH值、反应温度、反应时间等因素对砷去除效果的影响. 结果表明,最优工艺条件为Fe/As质量比3,pH值6,温度25℃,时间30 min,处理后出水的As浓度低于10 mg/L,达到《生活饮用水卫生标准》(GB5749-2006).     

A highly elevated mass transfer rate process for three-phase,liquid-continuous fluidized beds

Average gas holdup and gas-to-liquid mass transfer in three-phase fluidized beds with non-Newtonian fluids were studied. The effects of liquid property, gas distributor type and magnetic field intensity on mass transfer coefficient and overall gas holdup were examined. The volumetric gas-to-liquid mass transfer coefficient was determined by fitting the oxygen concentration profile data across the bed to the axial dispersion model. The average gas holdup and mass transfer coefficient were all correlated with operating parameters including gas velocity and effective viscosity.Experimental results showed that a three-fold increase in mass transfer coefficient and a two-fold increase in average gas holdup were observed with properly designed liquid property and gas distributor. A modified process was developed to highly elevate the volumetric gas-to-liquid mass transfer rate. The bubble coalescing property of three-phase fluidized beds with small particles is eliminated, and its application to biotechnology and enzyme-catalyzed processes with high gas-to-liquid mass transfer rate could be achieved.     

氧在重组毕氏酵母发酵过程中的摄取与传递

引言 在生物发酵过程中,氧的供需是一个至关重要的问题[1-2].好气性微生物需要足够的溶解氧以维持自身的呼吸代谢.     

半弧面斜叶桨的流体力学性能与氧传质特性

氧传质系数是气液搅拌反应器设计的关键参数,研究新型搅拌桨的氧传质性能对气液两相搅拌反应器的强化有着重要的意义。本文实验研究了气体分布器、搅拌转速、气量对氧传质系数、搅拌功耗及气含率的影响,结果表明,氧传质系数随搅拌转速和气量的增加而增加;并建立了氧传质系数与搅拌功耗和表观气速的经验公式,为进一步放大应用提供了基础。采用欧拉-欧拉多相流模型及群体平衡模型对半弧面新型斜叶桨进行了计算流体力学（CFD）数值模拟研究,模拟研究了不同结构、搅拌转速、气量下的流体力学性能和氧传质系数,模拟计算结果与实验值的相对偏差在20%以内;这为研究这一半弧面新型斜叶桨提供了一种可靠的数值模拟方法;优化了半弧面新型斜叶桨的结构,提高了搅拌釜的氧传质效率。     

Efficient mineralization of sugar industry wastewater by catalytic wet air oxidation as an eco-friendly method and its kinetic modelling

In this study, catalytic wet air oxidation using lanthanum cobalt oxide (LaCoO₃) as catalyst was employed for the efficient treatment of synthetic sugar industry wastewater in a single process. A parametric study was performed to determine the optimum conditions. The results showed that reaction temperature and theoretical air percentage were the most effective parameters. Sugar derivatives were almost completely destroyed at the optimum conditions and total organic carbon (TOC) and chemical oxygen demand (COD) removals were determined as 91% and 87%, respectively, indicating a high mineralization degree, which was the main goal of advanced oxidation. The reaction kinetics were investigated by pseudo-homogeneous and heterogeneous models based on two different parameters: sucrose and TOC concentration. The degree of fit showed that the reaction order was determined as two for the pseudo-homogeneous approach. According to the surface concentration calculations for heterogeneous models, the presence of mass transfer limitations was only observed for oxygen as gas reactant. All heterogeneous models also fitted the reaction rate data accurately, but the Mars–van Krevelen was the selected model for sucrose and TOC oxidation with the best fit.     

用混凝-微电解-催化氧化工艺预处理含拉开粉的丁腈橡胶废水

采用混凝-微电解-催化氧化工艺预处理含拉开粉的丁腈橡胶废水,通过静态和动态放大试验探讨了微电解时的pH值、反应时间、铁炭比、气水比以及催化氧化时的pH值、反应时间、氧化剂和催化剂用量等对化学需氧量、悬浮物及拉开粉去除率的影响。结果表明,在微电解反应时pH值为3～4、铁炭比为2/1(质量比)、反应时间为30min、气水比为12/1(体积比),以及催化氧化反应时pH值为5左右、催化剂质量浓度为0.75g/L、氧化剂质量浓度为5g/L、反应时间4h的条件下,处理后废水的悬浮物去除率可达到90%以上,化学需氧量去除率达到45%以上,拉开粉的去除率达到90%以上。生物化学需氧量与化学需氧量比值由0.08提高到0.16,废水可生化性得到提高,水中悬浮物得以大幅度降低,水质得到改善,为后续处理奠定了基础。     

中空纤维膜曝气系统的设计计算

采用中空纤维膜无泡供氧可以极大的提高氧的传递效率,是一种极具发展潜力的新技术。文中主要讨论了影响中空纤维膜曝气系统的氧质量传递系数、氧质量传递的对数平均推动力和膜内的气体流量等设计参数以及相关计算,并给出计算实例。从计算结果可看出,采用中空纤维膜曝气能满足大需氧量要求。     

组合型填料与焦炭填料塔中餐厅污水氧传递研究

本文分别以焦炭和自行开发的新型组合填料为塔内构件，对清水和餐厅污水中的氧传递特征进行了分析和实验研究，纯氧和空气供氧实验结果证实氧传递过程为液膜控制；通过实验测定了清水和餐厅污水在组合型填料和焦碳填料塔中曝气过程溶解氧的变化规律，从实验结果回归得到了上述填料塔内清水与餐厅污水氧转移系数计算关联式，计算值与实测值吻合较好；最后，对相同操作条件下焦炭与组合型填料在清水与餐厅污水中的氧转移系数进行了比较。     

人工肝生物反应器中溶解氧浓度动态分布的模型与数值分析

研究了人工肝生物反应器的结构特点,并在对反应器内部液体流动与气液传质规律进行分析的基础上,结合反应器的实际需要,建立了基于一维轴向扩散模型的人工肝专用生物反应器溶解氧浓度动态分布的数学机理模型. 利用有限差分方法对模型离散化求解,得到了流动速度、氧传质系数及细胞耗氧速率对反应器内部溶解氧浓度分布的影响规律. 通过对模型数值解的分析得到了特定条件下反应器内的优化参数为液体流速0.55 mm/s,传质系数0.31 s-1,扩散系数0.02 mm2/s. 最后,通过仿真数据与实测实验的对比验证了该模型的正确性,其平均误差在±5%以内. 本模型的建立在理论上验证了该专用生物反应器可以提供稳定且均匀的溶解氧浓度分布,同时也为下一代新型反应器的优化设计提供了参考数据和理论依据.     

气升式环流生物反应器微孔气体分布器结构优化与性能

目前,气升式环流生物反应器普遍使用管式气体分布器,管式气体分布器易堵塞,动力效率低。气泡粒径小,动力效率高的微孔气体分布器应用于气升式环流生物反应器的研究少有报道。本文为研究微孔气体分布器应用于气升式环流生物反应器的实际效果,对微孔气体分布器进行结构优化研究,考察分布器形式、直径和安装位置等因素对氧传质系数的影响,进而考察优化后的微孔气体分布器的充氧能力、氧利用率、动力效率等性能参数及其变化规律。指导微孔气体分布器的工业化应用。实验结果表明：盘式微孔气体分布器传质效果优于管式,且盘式微孔气体分布器直径为0.4R时,传质效果最佳;膜盘到导流筒底部距离为1R时,分布器的氧传质系数最大,R为导流筒半径;微孔气体分布器适宜的气体流量为1.5m³/h,充氧能力0.14kg/h,氧利用率为34.63%,动力效率为3.35kg/(kW·h)。