【作者】 贾晓强；

【导师】 闻建平；

【作者基本信息】 天津大学 ， 生物化工， 2009， 博士

【摘要】 苯酚是工业废水中常见的污染物,其危害已引起世界各国的普遍重视。生物法能够利用微生物的新陈代谢作用将其降解并转化为无害物质,是目前最通用的苯酚废水处理技术之一。本文开展三相鼓泡塔及气升式环流生物反应器固定化热带假丝酵母处理苯酚废水过程中局部瞬态流体流动、相间传质及生物降解性能的实验、理论模型与数值模拟研究,在生物法处理苯酚废水技术领域具有广阔的应用前景,同时在多相复杂生物反应过程模型化方面也具有重要的学术研究价值。首先分别建立了模拟气液固三相鼓泡塔及气升式环流反应器局部流体力学特性动态行为特征的三维瞬态计算流体力学(CFD)模型,并采用多尺度组分(MUSIG)模型描述气泡尺寸分布行为。通过模型模拟计算分别得到了三相鼓泡塔及气升式环流反应器内的局部时均流体力学特性如气含率、轴向液相速度等随表观气速、轴向高度、固体粒子加入量等操作条件的变化规律,并采用电导探头及三维激光多普勒测速仪实验测量结果验证了该模型的可靠性。同时应用该CFD模型分别合理预测了三相鼓泡塔及气升式环流反应器内的局部瞬态流体力学特性如气含率、固含率、液相速度和气泡尺寸等的时空分布。然后分别建立了模拟气液固三相鼓泡塔及气升式环流生物反应器固定化热带假丝酵母细胞降解苯酚间歇过程降酚性能动态行为特征的三维瞬态CFD模型,模型耦合了三相流体流动、组分相间传质和本征生化反应的相互作用,并采用MUSIG模型描述气泡尺寸分布行为。通过模型模拟计算分别得到了三相鼓泡塔及气升式环流生物反应器内的体积平均流体力学特性、组分质量浓度及组分相间质量输运源项差等随表观气速、初始苯酚浓度、固体粒子加入量等操作条件的变化规律,并通过高效液相色谱及溶氧电极实验测量数据与体积平均液相溶氧和苯酚浓度随时间变化的模型模拟结果进行比较,验证了该模型的可靠性。通过组分相间质量输运源项的比较,发现组分相间传质是过程的限速步骤。同时应用该CFD模型分别合理预测了三相鼓泡塔及气升式环流生物反应器固定化苯酚降解过程中局部瞬态降酚性能的动态行为特征如气含率、平均气泡直径、液相速度、气液固各相氧浓度、液固各相苯酚浓度、固相菌体浓度和气泡尺寸等的时空分布。最后对三相鼓泡塔和气升式环流生物反应器固定化热带假丝酵母苯酚降解性能的CFD模型模拟结果进行了比较,证实气升式环流生物反应器流型规整,苯酚降解性能优于鼓泡塔生物反应器。更多还原

【Abstract】 Phenol is a common pollutant in many industrial effluents, whose damage to the environment as well as to human beings has given rise to the worldwide concern about its effective treatment. Bio-treatment method, which can degrade phenol and then transform it into harmless substances through microorganisms’metabolism effect, has become one of the most popular phenol wastewater treatment methods. The experimentation, theoretical modeling and numerical simulation study on the local transient multi-phase fluid flow, interfacial mass transfer and biodegradation characteristics of the batch phenol biodegradation by immobilized Candida tropicalis in the gas-liquid-solid three-phase bubble column and airlift loop bioreactors, will definitely find its wide application in the field of phenol wastewater bio-treatment, as well as in the aspect of scientific learning of the complicated multi-phase bio-reaction process modeling.Firstly, the three-dimensional (3D) transient computational fluid dynamics (CFD) model has been set up for simulating the dynamic behaviors of the local hydrodynamics in the gas-liquid-solid three-phase bubble column and airlift loop reactors respectively, with multi size group (MUSIG) model adopted to describe the bubble size distribution behaviors. The local time-averaged hydrodynamics such as gas holdup and axial liquid velocity changing with the varied operating conditions such as superficial gas velocity, axial position and solid loading in the three-phase bubble column and airlift loop reactors are calculated through model simulations respectively, and the reliability of the model is validated through the experimental results obtained by conductivity probe and 3D Laser Doppler Anemometry. At the same time, the time and space distributions of the local transient hydrodynamics such as gas holdup, solid holdup, liquid velocity and bubble size in the three-phase bubble column and airlift loop reactors are reasonably predicted by the developed CFD model respectively.Secondly, the 3D transient CFD model has been set up for simulating the dynamic behaviors of the batch phenol biodegradation characteristics by immobilized Candida tropicalis in the gas-liquid-solid three-phase bubble column and airlift loop bioreactors respectively, coupling of the interactions of the three-phase fluid flow, species interfacial mass transfer and intrinsic bio-reaction, with the MUSIG model adopted to describe the bubble size distribution behaviors. The volume-averaged hydrodynamics, species mass concentrations and species interfacial mass transport source differences changing with the varied operating conditions such as superficial gas velocity, initial phenol concentration and solid loading in the three-phase bubble column and airlift loop bioreactors are calculated through model simulations respectively, and the reliability of the model is validated through the experimental results of the liquid phase oxygen and phenol mass concentrations obtained by DO electrode and HPLC. It is found that the species interfacial mass transfer is the rate-limiting step in the process through comparison between the species interfacial mass transport sources. At the same time, the time and space distributions of the local transient dynamic behaviors of the immobilized batch phenol biodegradation such as gas holdup, Sauter mean bubble diameter, liquid velocity, gas, liquid and solid phase oxygen mass concentrations, liquid and solid phase phenol mass concentrations, solid phase cell concentration and bubble size in the three-phase bubble column and airlift loop bioreactors are reasonably predicted by the developed CFD model respectively.At last, phenol biodegradation behaviors between the three-phase bubble column bioreactor and the three-phase airlift loop bioreactor are compared through CFD model simulations, which confirm that the airlift loop bioreactor has a more regular flow pattern, and a better phenol biodegradation performance compared with the bubble column bioreactor.更多还原