Effects of the Stirred Tank's Design on Power Consumption and Mixing Time in Liquid Phase

The influence of the stirrer type and of the geometrical parameters of both tank and agitator (clearance of an impeller from tank bottom, impeller diameter, draft tube and geometry of the tank bottom) on power consumption and mixing time in liquid phase under turbulent regime conditions (Re > 10⁴) have been studied. Different types of agitators have been used, namely Rushton turbine, 45° pitched‐blade turbine, MIXEL TT and TTP propellers and 1‐stage or 2‐stage EKATO‐INTERMIG propellers. All these stirrers were tested with the same power consumption per unit mass of liquid. On the basis of measured power consumption per unit mass, which is required to achieve the same degree of mixing, the results obtained in the present work show that the TTP propeller is the most efficient in liquid phase. Recommendations on the optimum geometric configuration have been made for each type of stirrer.     

喷雾液滴与不混溶液的混合

提出将水喷雾成液滴再与另一种不混溶液相混合的方法,并以水为分散相,煤油为连续相进行实验研究．在带搅拌器的混合器内选择三点取样测定液滴大小随时间的变化,考察了水油比及搅拌的影响．实验结果表明该方法能够得到细小而均匀的液滴,而且液滴的维持需要选择合适的相比和搅拌速度．     

Promotion of Chemical Reactions by a Grid in a Shear Mixing Layer

The effects of a turbulence‐generating grid on fluid mixing and a passive chemical reaction are experimentally investigated in a liquid shear mixing layer under a nonpremixed condition. The grid is installed at three streamwise locations to find the optimal location to promote the chemical reaction. The results show that the grid generates disturbances at small scales that enhance fluid mixing and the chemical reaction. However, the turbulence intensity and mass diffusion in the mixing layers with the grid decrease rapidly and become even smaller than those in the mixing layer without the grid in a downstream region. Therefore, in the present study, the chemical production is maximized when the grid is installed at where the flow is turning to a developed mixing layer.     

Coalescence Extraction – A Benign Extraction Tool

This paper deals with ‘Coalescence Extraction’, in which no intensive mixing is required. It is based on the use of a primary solvent, which, in combination with the feed, forms a homogeneous solution. This homogeneous phase has enormous potential for the treatment of cell fragments and other highly viscous materials. In the next step a secondary solvent (Composition‐Induced Phase Separation, CIPS) or a significant temperature change (Temperature‐Induced Phase Separation, TIPS) is used to enter the spinodal two‐phase region in which an extract and a raffinate are formed. The phases separate within seconds, even in the presence of emulsifying agents.     

Effects of geometry and operating conditions on the mixing behavior of an in-line impinging stream mixer

The present study investigated experimentally the effects of various geometric and operating parameters on the mixing characteristics of model liquids undergoing mixing in a novel in-line mixer, viz. an in-line impinging stream (IS) mixer. First, the mixer with one set of three inlet jets was used. Later two sets of inlet jets were used in order to increase the number of impingement zones and hence the mixing capability of the mixer. A statistical analysis was performed to indicate the best geometry of the mixer based on the data of both the mixing effectiveness and the pressure loss due to impingement of liquid streams.     

错流射流混合过程的基本特性及影响因素

错流射流已被证明是强化流体热质传递最有效的方法之一。介绍了错流射流的结构、基本特性以及在混合过程中的影响因素,并展望了其发展前景。     

A METHOD OF ESTIMATION OF TURBULENT DIFFUSION IN A CIRCULAR PIPE BASED ON SPATIAL-DEPENDENCE MATRIX

Considering that a scalar quantity (mass or heat) is transported on a turbulent lump where fluid particles show almost same behavior, a new method of numerical calculation for the turbulent diffusion is proposed. This method is based on the spatial-dependence matrix, which is one of the tools of pattern analysis. The usefulness of the method is examined by experiments on the turbulent diffusion of the tracer which is injected into the source point on the pipe axis and it is confirmed that the reasonable feature of turbulent diffusion is estimated by the method.     

Mixing of a wet granular medium: Influence of the liquid addition method

Mixing is an important operation in the elaboration of concrete. This process generally involves high energy consumption. The method by which the liquid is added influences this consumption. The liquid can be added progressively with a constant flow, instantaneously at the beginning of the mixing process, or in several stages.Our results show that the power usually consumed with a progressive liquid addition can be reduced by adding liquid in several stages, by modifying the number of additions and by varying the amount of liquid added for each addition.For a final-state mixture, oversaturated in liquid, instantaneous addition provides the lowest energy consumption. However, for a final state that is less saturated, the lowest energy intensity is obtained by adding the liquid in two stages. The first amount corresponds to a saturation rate located in the funicular regime, and is higher than the second amount.Finally, for saturation states located before the capillary regime, a progressive increase in the energy signal is observed after an instantaneous addition of the liquid. Moreover, the capillary state is obtained using an amount of liquid for which this state is not usually reached by progressive addition. This phenomenon is more pronounced where the particle size is reduced and the rotation velocity increased.     

新型气升式环流反应器液相破碎效果的实验比较

针对石油废水生物降解过程中所遇到的水相、油相难以快速均匀混合的问题,通过对气升式环流反应器动力学原理的分析,在其基础上进行了改进,设计出新型气升式环流反应器,通过验证了推理设计的正确。在本新型气升式反应实验中,以煤油和水为介质,０．４ｍ＾３／ｈ的通气量是较佳的工作条件,证明了新型气升式反应器处理特殊条件液液两相均匀混合的可行性。     

A method for measuring the imbibation rate of powder in a liquid

Mixing of powders into liquids is a common unit operation. Mixing can be divided into several steps: imbibation of the powder into the liquid being the first. Under some circumstances, for instance, if the powder has poor wetting properties, imbibation can be the rate-determining step. In this study imbibation in a commercial mixer was studied and a method to measure powder imbibation in a model that simulates the commercial mixer was developed. The imbibation mechanism in the commercial mixer is based on a wave drawing the powder down into the liquid, and surface flow transporting it towards the wave. A wave imbibation model was constructed based on the same mechanisms, in which physical parameters such as wave height, surface velocity and surface residence time could be varied. An experimental procedure was used to determine the maximum imbibation rate. Measurements were found to have good reproducibility, with a standard error of means of 4.7% for spray-dried sodium caseinate. The maximum imbibation rates were found to be of the same magnitude in the commercial mixer and the wave imbibation model: 0.04 kg/s m in the commercial mixer and 0.06–0.16 kg/s m in the wave imbibation model for spray-dried sodium caseinate powder.