圆柱状人工肝生物反应器中溶解氧浓度动态分布模型及其氧浓度变化速率

从人工肝治疗的需要出发,建立了圆柱状专用生物反应器中溶解氧浓度动态分布的数学机理模型,并分析了反应器内部实时氧浓度变化速率,设计出了溶氧变化的在线检测方法,结合模型推导出反应器内部总氧浓度变化量与实时氧浓度变化速率之间的关系. 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,氧浓度变化速率误差在±1%以内,验证了总氧浓度变化量dDO与实时氧浓度变化速率R之间满足dDO=MNDhR/V.     

微曝氧化沟气液两相传质模型构建及传质影响因素分析

基于ANSYS Fluent软件建立了微曝氧化沟气–液两相流动和溶解氧输运模型,对比不同工况下氧体积传质系数的实验测量值和模拟结果,误差在7%以内。采用验证可靠性的模型模拟研究了气泡直径、曝气量和横向流动速度对微曝氧化沟内氧传质的影响。结果表明,气泡直径由1.5 mm增至3 mm时,氧体积传质系数由15.80 h?1降低至5.83 h?1;曝气量由0.5 m3/h增大至2 m3/h时,氧体积传质系数由4.21 h?1增至14.15 h?1,减小气泡直径和增大曝气量能明显提高氧体积传质系数。微曝氧化沟内气–液相间传质及溶解氧的分布受横向流动影响,开启单台和两台推流泵时,氧体积传质系数分别比无横向推流工况增大27.7%和42.4%,横向流动能有效提高气泡羽流内的气含率,增强氧传质效果。     

带波纹隔板的平板式光生物反应器流动特性

在传统平板式光生物反应器中加入波纹形隔板,以其导流作用强化液体循环和气液传质,建立了新型带波纹隔板的平板式光生物反应器. 利用计算流体动力学(CFD)模拟及实验考察了该反应器的流动与传质特性及其影响因素. 结果表明,CFD模拟结果与实验测量值吻合良好,液体在上升区和下降区之间形成了良好的循环,随通气比增加,液相速度、平均气含率和溶氧体积传质系数均近似线性增加. 单位体积能量输入与平均液相体积传质系数之间有良好的线性关系. 综合各相关参数得到优化结构为：下降区/上升区截面积为1.62,隔板顶端到液面的距离为260 mm,隔板底端到反应器底部的距离为20 mm.     

气升式三相内环流生物反应器内流体力学和传质性能的实验研究

本文通过实验研究了气升式三相内环流反应器在非牛顿流体中的流体动力学特性和传质性能.考察了表观气速、导流筒与反应器截面积之比、固体粒子加入量及CMC溶液浓度等操作条件对气升式三相内环流生物反应器中导流筒与环隙内液体循环速度、气含率、固含率及气-液体积传质系数等流动与传质特性参数的影响.     

缩放型导流筒气升式内环流生物反应器流体力学与传质特性

从气相含率、液体循环速度和体积氧传质系数方面研究缩放型导流筒气升式内环流生物反应器内的流体力学与传质特性。实验结果表明,与传统圆柱形导流筒相比较,缩放型导流筒气相含率和体积氧传质系数分别提高８％和１０％以上。气相含率和体积氧传质系数随固含率的增加而提高,液体循环速度随固含率的增加而减小;同一内管反应器随介质粘度的增加,体积氧传质系数减小。此外还在Ｈｉｇｂｉｅ穿透理论和Ｋｏｌｏｍｏｇｏｒｏｆｆ各向同     

三相强制浆料环流反应器的局部传质行为

提出了一种新型的强制外循环三相环流反应器结构,根据结构特点及流动状态的不同,将反应器分为6个不同的流动区域. 在f300 mm′1700 mm的实验装置内,采用氧气气提-空气解吸法,详细考察了内环表观气速0.006~0.19 m/s、外循环液速0.03, 0.05 m/s、固含率5%, 10%, 15%时不同流动区域的体积传质系数. 发现外循环液流影响区体积传质系数最大,最高可达0.754 s-1,外环环隙区最小,不超过0.043 s-1,环流反应器整体体积传质系数与气液分离区体积传质系数接近. 适当扩大内、外环截面积比有利于提高环流反应器的传质性能. 环流反应器整体体积传质系数随内环表观气速和外循环液速的增加而增加,随颗粒浓度的增加略有降低.     

三重环流生物流化床的流体力学与传质特性

从气相含率,液体循环速度和体积氧传质系数方面研究自行设计新型结构的三重环流生物流化床的流体力学与传质特性。流化床反应器的有效体积２３Ｌ,实验条件是以空气为气相,水为液相,树脂为固相,固含率分别为０％,３％,６％和９％。实验结果表明,气相含率是影响反应器流体力学和传质特性的主要因素,气相含率增大可降低液体循环速度,增大体积氧传质系数。     

水力自旋填料在生物反应器处理工艺中的传质性能

SCMT型自旋传质填料在气流作用下无规则旋转,显著改善了反应器中的传质条件,提高了氧传质的速率与效率.试验结果表明：生物反应器内物系间的传质条件对氧传递效率有较大影响,SCMT型自旋传质填料能够创造理想的传质条件,使生物反应器内溶解氧值基本保持一致.SCMT型自旋传质填料与常规聚丙烯阶梯环填料相比,可有效地减少反应时间和降低能耗.使用SCMT型自旋传质填料生物反应器处理城市污水,可以在停留时间为1.0h,气水比为4：1的情况下使出水水质达到城镇污水处理厂污染物排放标准（GBl8918-2002）中规定的二级标准.     

曝气膜生物反应器的CFD模拟

利用Fluent软件对曝气膜生物反应器中气液两相流动进行模拟计算,探讨了进气气泡的直径、进气速度及膜纤维束的长度等因素对膜生物反应器内液体流动、气体分布的影响.结果表明,减小气泡的直径并适当增大进气速度、膜纤维束长度可以有效提高膜生物反应器内气体的分布和液体与气体的接触,从而促进气液两相进行高效的传质.     

波形隔板对平板式生物反应器传质及混合性能的影响

对带波纹隔板的平板式生物反应器,利用计算流体动力学进行流场模拟,验证模型可靠性后,系统分析波纹隔板高/波长(L/l)和波幅/波长(A/l)两个波纹隔板结构参数对反应器传质及流动混合特性的影响. 结果表明,当L/l=12时,传质及流动混合性能较好,液相体积传质系数(kLa)、平均湍动能(Em)、下降区停留时间占循环一周时间之比(q)等表征传质及混合的参数值均较大,得到的液体流速在微藻生长的最佳流速附近. 当A/l=0.8时,反应器的传质性能最优,kLa比采用平直隔板时增加了约10%;当A/l=0.4时,反应器的混合效果最佳,Em比采用平直隔板时增加14.7%.     

环流反应器中肌苷发酵液的氧传递研究

根据肌苷发酵过程主要是溶氧传质控制的结论,本文研究了操作变量和装置结构变量对环流发酵反应器中氧传递的影响,定量地得到气含率,液体循环速度和结构因素对氧传递的关系。对发酵反应器中溶氧浓度分布进行了摸拟计算,依据计算的结果提出了较佳的 D_E/D 和 L_E/D 的结构。     

Photocatalytic degradation rate of oxalic acid on the semiconductive layer of n-TiO2 particles in the batch mode plate reactor Part I: Mass transfer limits

Organic compounds dissolved in water can be decomposed on a layer of n-TiO2 particles irradiated by u.v. light, which generates holes and electrons in the TiO2 material. Dissolved oxygen was used as electron scavenger and holes reacted with water to give OH radicals. The rate of degradation of the dissolved organic compounds by OH radicals is limited by the transfer of either oxygen or of theorganic compounds to the surface of n-TiO2 particles. The consequence of these limits is that, in the batch mode reactor with recirculation of the liquid, the dependence of the concentration of an organic compound on time has either a linear or an exponential form. Experiments with decomposition of oxalic acid in aqueous solutions using a plate reactor (60 cm × 120 cm) confirmed the analysis. Equations for evaluation of the mass transfer coefficient of the dissolved species to the surface of the plate reactor with a moving liquid fil m were developed for the case of the thickness of the Nernst diffusion layer being thinner than the thickness of the liquid. The experimentally obtained decomposition rate of oxalic acid was about 60 to 80% of the theoretical decomposition rate limited by oxygen flux through the film of a moving liquid. The present theory neglects the diffusion of oxygen into the porous layer of n-TiO2.     

CFD在自吸反应器气液流动和传质特性研究中的应用

针对配置气体分布器的六叶轮自吸反应器建立了欧拉气液两相流三维瞬态模型,耦合Higbie气液传质模型,采用CFX软件对其气液混合过程的流场、气含率、吸气速率及溶氧传递过程进行数值模拟,获得了反应器的流动特性、气液分散性能、吸气特性及气液传质特性.分析了反应器内水平及竖直位置上的流型特征及溶氧传递性能,结合实验数据及经验关联式对比分析了对气含率及吸气速率的预测作用.结果表明,六叶轮转子及其配置的气体分布器可以获得较均匀的气液混合,气含率及吸气速率的预测与实验值偏差分别为5.2% 和17.6%,模拟发现在反应器底部近壁处溶氧及混合效果不佳.     

射流鼓泡反应器中液相体积传质系数的测定

羰基合成反应一般采用射流鼓泡反应器,该类反应器气液混合的方式采用射流而非机械搅拌,其主要优点是结构简单、制作简便、维护费用低。研究该类型反应器的传质系数对于其设计、优化及放大操作均具有重要意义。本研究采用缩颈式圆形喷嘴,以动态溶氧法对射流鼓泡反应器内的液相体积传质系数进行测定,考察了表观气速、射流雷诺数对液相体积传质系数的影响。研究发现,随气速增大液相体积传质系数的变化规律为先增大而后保持不变。维持表观气速不变,随雷诺数增加液相体积传质系数增大,但当表观气速小于0.0012 m/s时,雷诺数对传质改善较小。建立了液相体积传质系数的经验关联式,当气体输入功率占总功率56%时,液相体积传质系数最大,气体鼓泡和液体射流的协同作用最强。     

GAS-LIQUID MASS TRANSFER IN JET BUBBLE COLUMN

The jet bubble column consists of a conical entrance section which expands to a cylindrical column. Gas and liquid are co-currently introduced at the bottom of the column by a small diameter inlet pipe which acts like an ejector. The kinetic energy of the gas and liquid jet together with the conical geometry at the lower section of the column cause the formation and dispersion of small bubbles.

Gas-liquid mass transfer in the jet bubble column (61 cm diameter) was measured by a dynamic response technique, in which a step change was made in the gas phase oxygen concentration and the aqueous dissolved oxygen concentration response was measured at various axial and radial locations. It was found that a continuous stirred tank reactor model could be used to evaluate experimental results. The volumetric mass transfer coefficient in this type of system was found to increase with increasing gas flow rate and was about 1.5 times larger than the values obtained at similar conditions in conventional bubble columns. Preliminary measurements and calculations indicate negligible effects of liquid velocity and bed height on the mass transfer coefficient.     

Development of microbubble aerator for waste water treatment using aerobic activated sludge

In large-scale waste water treatment plants, the aerobic biochemical reactor is the most important process, where the oxygen supply into the microorganisms often limits the overall waste water treatment rate. On the other hand, several kinds of microbubble distributors have been developed to enrich the oxygen dissolution in water. Therefore, the application of microbubbles for a waste water treatment system was investigated in this study.The oxygen absorption performance of typical microbubble generators was compared with typical bubble generators. To evaluate each bubble generator, the liquid-phase volumetric oxygen transfer coefficient, gas hold-up and power consumption per unit liquid volume were measured in a bubble column attached to each bubble generator. All the microbubble generators allowed the oxygen to dissolve faster than the typical aerators. The spiral liquid flow type microbubble generator had the highest oxygen transfer coefficient even at a low air flow rate although it used more energy than the typical distributors.To improve an industrial waste water treatment system, a novel aeration system utilizing a spiral liquid flow type microbubble generator was proposed in this study. The present system has some advantages such as compact size, portability and fast oxygen dissolution rate. To ensure the performance for organic waste water treatment, the effects of the aeration rate, dissolved oxygen concentration and device properties on the specific consumption rate of model organic waste were investigated. For the novel aeration system, the most suitable conditions to treat organic waste were found.     

气液逆流接触洗涤器两相洗涤效果和流动特性

针对一种气液逆流接触洗涤器，通过冷模实验，采用溶氧法和压力传感器考察了洗涤器内黏度对气液传质和流动特性的影响。结果表明，黏度对传质的影响并非单调递增或递减的趋势，中间黏度洗涤液下的解析率最高。此外，洗涤器内除了泡沫型(QA/QT=0.4?0.6)，环流型(QA/QT=1.2?1.5)也表现出了良好的传质效果。当洗涤液黏度?=1.00?1.30 mm2/s时，压力在不同轴切比下的变化趋势与相同液量下解析率的变化相似，即传质较佳的流型对应的压力值也高。根据实验结果，将流动参数、传质参数、操作参数结合在一起，给出了解析率和压降的经验关联式，计算值与实验值吻合较好，可供工程设计参考。     

三相循环流化床中的气液相界面积和传质系数

采用溶氧法测量了三相循环流化床中液相溶氧浓度的轴向分布,并按轴向扩散模型处理实验数据,优化得到气液体积传质系数kLa,同时用光纤探头测量了体系中的气含率和气泡大小分布,计算得到了气液相界面积a和气液传质系数kL,并研究了主要操作条件(表观气速、表观液速和固含率)对气液传质系数的影响规律.     

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.