【作者】 李丽华；

【导师】 王栋；

【作者基本信息】 大连理工大学 ， 环境工程， 2005， 硕士

【摘要】 气升式环流反应器具有结构简单、能耗小、剪切速率低、混合性能好、传质效率高、流体力学性能优良等优点,近年来在环境工程领域的生物处理工艺中得到了广泛应用。 为了为气升式内环流生物反应器的设计、放大以及操作条件的确定提供量化依据以及理论工具,本研究在一体积为0.026m~3的气升式内环流反应器内,结合实际生物处理工艺的具体情况,分别以空气-CMC非牛顿流体两相体系和空气-水-活性炭颗粒三相体系作为研究对象,对反应器内的流体力学、混合、传质特性进行了实验研究和理论探讨。 在实验研究工作中,应用先进的在线自动测控技术,采用常规压差法、电导脉冲示踪法、动态通气法分别对相应体系的气含率、液体循环速度,循环时间、混合时间以及体积传质系数进行了测量,考察了液相性质、固含率、表观气速等体系和运行变量的改变对上述参数的影响规律,实现结果表明,对于空气-CMC两相体系,随着液相表观粘度的增加,升流区和降流区气含率、液体循环速度、体积传质系数降低,循环时间和混合时间增大;对于空气-水-活性炭颗粒三相体系,随着固含率的增加,升流区和降流区气含率、液体循环速度、体积传质系数降低,循环时间增大。固体颗粒的加入对气含率和液速径向分布产生了复杂影响作用,导致混合时间随固含率的增加曾现出较为复杂的变化趋势,表现出一定的随机性;上述两种体系的气含率、液体循环速度、体积传质系数均随表观气速的增加而增大,而循环时间和混合时间则随表观气速的增大而降低。 根据实验测试结果,分别使用Fr准数、Ga准数以及无因次颗粒浓度C_s建立了升流区和降流区气含率、液体循环速度,混合时间、循环时间,体积传质系数与操作条件、液相性质、固含率之间的量化关联式。 此外,根据对实验结果的分析,结合已有的能量守恒和漂移通量理论,建立了预测相应体系液体循环速度的流体力学模型,实验值与模型预测值取得了较好的吻合。更多还原

【Abstract】 The airlift loop reactor possesses a lot of advantages in terms of simple structure, low power consumption, low shear rates, effective mixing, high mass transfer rate as well as good hydrodynamic characteristics. Therefore, this kind of reactors has been widely employed in the biological treatment processes of the environmental engineering.In order to provide the sound quantitative basis and theoretical tools for the best design and scale up of the biological airlift reactors, combining with the specific condition in the biological treatment processes, this work conducts experimental study and theoretical analysis on the hydrodynamic, mixing and mass transfer characteristics of the air-CMC non-Newtonian fluid two-phase system and air-water-activated carbon particles three-phase system in a 0.026m3 internal-loop airlift reactor.The gas holdups in the riser and downcomer, liquid circulation velocity, circulation time, mixing time and volumetric mass transfer coefficient are measured through the online gathering and recording system by using classical manometric method, conductance tracer response technique and dynamic gassing-in method, respectively. The effect of parameters such as the liquid-phase properties, solids loading and the superficial gas velocity is studied. It is shown that for the air-CMC solution two-phase system, the gas holdups in the riser and downcomer, liquid circulation velocity and volumetric mass transfer coefficient generally decrease with the increasing of CMC solution apparent viscosity. On the contrary, the circulation and mixing time increase with the increasing of CMC solution apparent viscosity; For the air-water-activated carbon particles three-phase system, the increase of solids loading leads to the decrease of the gas holdups in the riser and downcomer, liquid circulation velocity and volumetric mass transfer coefficient, but the increase of circulation time. Because the progressive introduction of solids exerts a complicated influence on the radial gas holdup and liquid velocity profile, the mixing time changes randomly with the increase of solids loading; For the two systems, the gas holdups in the riser and downcomer, liquid circulation velocity and volumetric mass transfer coefficient increase, but the circulation time and mixing time decrease with the increasing of the gas superficial velocity.Based on the experimental results, the quantitative correlations for these parameters with operation condition, liquid-phase property and solids loading are presented by using Fr number, Ga number and dimensionless solid concentration Cs, respectively.In addition, based on the analysis for the experiment result, combining with the energy balance and drift flow model, the relative mathematical models are developed separately to estimate liquid circulation velocity in the riser for air-CMC solution two-phase system and air-water-activate particle three-phase system. The values predicted by the mathematical models agree with that of experiment well.更多还原