液-液萃取脉冲筛板塔中两相流动特性的初步研究

实验采用了两种液-液体系和1吋与2吋直径的筛板塔。关联实验数据所得的公式为V_d/x+V_c/（1-x）=V_o（1-x）~n,而不是J.D.Thornton所提出的比较简单的V_d/x+V_c/（1-x）=V_o（1-x）。从1吋塔,煤油-水体系的数据获得n=2.2±0.2。用所得公式计算的“泛点”流速非常接近实验测得的数值。     

用动态响应曲线法研究脉冲筛板萃取柱的传质特性

用动态响应曲线法研究了内径150mm脉冲筛板萃取柱的传质特性,并考虑了轴向混合。实验体系采用30％TBP(煤油)-硝酸-水,操作条件:脉冲频率:1.0～2.5s~(-1),脉冲振幅=0.0067～0.030m,有机相/水相=1/1～3.3/1.实验结果表明,本法与稳态浓度剖面法同样可靠,且省时、省料,可在更宽流比范围内用于大柱径萃取设备的研究。     

A STUDY ON MASS TRANSFER IN PULSED SIEVE-PLATE EXTRACTION COLUMN

Mass transfer experiments have been carried out in a 40mm diameter pulsed sieve-plate extraction column. Both standard and "dispersion-coalescence" type cartridges were tested with 30％ TBP (kerosene as diluent)/ Nitric Acid/Water system. "Ture" volumetric mass transfer coefficient and backmixing     

GENERALIZED PREDICTIVE CONTROL OF A PULSED LIQUID-LIQUID EXTRACTION COLUMN

This paper deals with the application of a general predictive controller to a pulsed liquid-liquid extraction column. The control purpose is to maintain the column in its optimal behaviour zone in spite or flowrates and physical properties of solvent and solute fluctuations. The complex dynamics of the column is modeled by a low order linear discrete model with time varying parameters which are recursively identified. Based on these estimates, the control policy is adapted on line.

The obtained results illustrate the successful application of such an adaptive algorithm.     

GENERALIZED PREDICTIVE CONTROL OF A PULSED LIQUID-LIQUID EXTRACTION COLUMN

This paper deals with the application of a general predictive controller to a pulsed liquid-liquid extraction column. The control purpose is to maintain the column in its optimal behaviour zone in spite or flowrates and physical properties of solvent and solute fluctuations. The complex dynamics of the column is modeled by a low order linear discrete model with time varying parameters which are recursively identified. Based on these estimates, the control policy is adapted on line.

The obtained results illustrate the successful application of such an adaptive algorithm.     

CONTROL OF A PULSED LIQUID-LIQUID EXTRACTION COLUMN BASED ON A MULTILEVEL SYSTEM OF AUTOMATA

This paper presents the real-time application of the learning control theory to the control of a chemical pilot plant: a pulsed liquid-liquid extraction column.

The behaviour of an agitated liquid-liquid extraction column can be related to random mechanisms such as the phenomena of droplets breakage and coalescence. Previous studies on hydrodynamic and mass transfer aspects showed that a pulsed liquid-liquid extraction column had an optimal behaviour for operating conditions close to flooding. These results led to choose the following strategy to control the column in its optimal behaviour zone:

- the measure of the conductivity of the liquid medium below the distributor which gives a good information about flooding, is the controlled variable

-the pulse frequency is the control action.

The learning control algorithm is based on a multilevel system of automata which operates in a random environment. By means of an evaluation unit of the performances of the column which generates either penalty (inaction) or reward on the basis of heuristic rules, the automaton chooses a value of the pulse frequency. This approach is essentially connected to artificial intelligence in so far as human knowledge on the plant is included in these rules.

This algorithm has been implemented on a microcomputer for control purposes. The experimental results presented show the good performances of the approach.     

ARTIFICIAL NEURAL NETWORKS IN LIQUID-LIQUID TWO-PHASE FLOW

This research investigates the use of neural networks for identification of oil-water two-phase flow pattern in a horizontal conduit. The investigation seeks to find out if neural networks are useful tools for this application. In order to find a suitable network, all of the various types of networks available are studied and appropriate networks are selected using MATLAB as a computational tool. Four networks are selected for this investigation: feed-forward back propagation (FFBP), radial based function (RBF), probabilistic neural network (PNN), and learning vector quantization (LVQ) Networks. These various networks are created and tested to evaluate the relationships between key variables and performance. Once the networks are optimized, various architectures are compared based on mean square error (MSE), construction time, complexity, and the ability to identify transition regions. PNN is found to be the best network for this particular application, followed by FFBP, RBF, and LVQ. It is observed that making a network larger or more powerful does not necessarily improve the performance. Moreover, doing so causes a network to lose its ability to generalize by eventually “over-fitting” the training data.     

PREDICTION OF SOLUTE CONCENTRATION CHANGES ALONG PULSED SIEVE PLATE EXTRACTION COLUMNS

Pulsed columns are one of the most important extraction columns that have extensive application in different industries. Obtaining the solute concentration in different heights of the column has a great influence on achieving the physical property changes of the phases along the column. An experimental work of mass transfer in a pilot pulsed sieve plate extraction column at different operating conditions is carried out in this research, and the solute concentration in different heights of the column is obtained for two different systems with medium and high interfacial tensions. The solute concentration changes along the column are calculated using previous models in the literature and the model presented for achieving the effective diffusivity in a previous work of the present authors. Comparison of the experimental results and the models is made and the best one is suggested.     

螺旋管内油-水液液两相流流型

在两种不同放置位置螺旋管内进行了油 -水液液两相流流型的实验研究 ,定义了各种不同流动条件下油-水两相流的流型 ,给出了螺旋管内液液两相流的流型图 .进而讨论了各流型之间转变的机理 ,并考察了螺旋管结构尺寸及放置方式对油水两相流流型及相转变特性的影响 .     

超临界流体萃取筛板塔中二氧化碳/醇/水体系流体力学特性和传质性能的初步研究

在内径25mm的连续逆流超临界流体萃取筛板塔中,对超临界二氧化碳/乙醇/水和二氧化碳/异丙醇/水2种体系的流体力学特性和传质性能进行了实验研究;对实验数据进行了分析处理,得到了描述超临界流体萃取筛板塔流动特性的关联式,应用柱塞流模型对超临界流体萃取筛板塔的传质性能进行了模拟计算.     

超临界流体萃取筛板塔中二氧化碳/醇/水体系流体力学特性和传质性能的初步研究

在内径25mm的连续逆流超临界流体萃取筛板塔中,对超临界二氧化碳/乙醇/水和二氧化碳/异丙醇/水2种体系的流体力学特性和传质性能进行了实验研究;对实验数据进行了分析处理,得到了描述超临界流体萃取筛板塔流动特性的关联式,应用柱塞流模型对超临界流体萃取筛板塔的传质性能进行了模拟计算.     

STUDIES ON FLOODING POINT AND HOLD-UP IN A SOLVENT EXTRACTION COLUMN WITH RECIPROCATING SIEVE PLATES

The flooding point and hold-up of the dispersed phase in an extraction column with reciprocating-sieve plates of 32 mm inside diameter and 1960 mm effective column height have been investigated under thefollowing conditions:Percent perforation of the plates 40%,53.5% and 63.7%,diameters of perforatedholes 7.8,9.0 and 9.8 mm,and distances between plates 20 and 40 mm respectively.Experiments werecarried out with three different liquid-liquid systems covering a rather wide range of physical properties.The relative velocity of the two phases passing through the perforations of the plates is consideredin the present work to be related to the work done by the oscillating plates in the column on unit massof liquid in unit time.Therefore the flooding velocity and hold-up in extraction column with reci-procating sieve plates should be related to A~2F~3 instead of AF as reported before.Equations weredeveloped to correlate the experimental data of flooding point and hold-up respectively.     

汽液液三相精馏总板效率的研究

在Oldershaw精馏塔内,对汽液液三相精馏筛型塔板上的传质特性进行测试,研究了泡沫工况下,汽速、液汽比等操作条件,表面张力梯度、界面张力、乳化液分散粘度等物系性质,以及油水体积比等多种参数对总板效率的影响、对测试数据进行关联,获得了适用于泡沫工况下汽液液三相精馏过程的总板效率估算式,此关联式对设备设计及操作优化有一定的参考价值.     

筛孔塔板气液两相流动的速度场模拟

<正>由于气体的搅动,筛孔塔板上的流动是极其复杂的气液两相流。目前两相流理论尚不成熟,未见运用此理论对塔板流速场的研究报道,Zhang和Yu的研究虽考虑了气相对液相流动的影响,但由于利用单相流理论,计算结果与实际情况有较大偏差。本文利用Elghobashi等建立的两相流双流体模型,建立了塔板上气液两相流二维流速场计算模型。在此基础上,通过调整模型参数,考虑了液层高度对塔板上返流区二维流型的影响,建立了模型参数值与液层高度的关系,实现了考虑液层高度影响的二维流动——拟三维流动的模拟。计算结果与Porter的实验结果基本相符。     

脉冲萃取塔径向扩散系数的测定方法

引　言对于脉冲筛板萃取塔或脉冲填料萃取塔中的轴向混合 ,已有许多人用轴向扩散模型作了研究[1,2 ].但是 ,在脉冲萃取塔工业放大设计的过程中 ,径向混合程度是个不可忽略的重要因素 .然而 ,这方面的研究尚未见报道 .萃取塔中的混合情况会直接影响液液两相传质推动力的大小 .通常 ,希望塔内连续相出现尽可能小的轴向混合 ,使连续相的流形接近活塞流 ,以获得最大的传质推动力 .而对于连续相的径向混合 ,其混合程度越大越有利于径向浓度的均匀 ,有利于获得最大的传质推动力 .因此 ,径向扩散系数大小的确定 ,对于工业规模脉冲萃取塔的设计具有…     

LIQUID-LIQUID EXTRACTION IN A HOLLOW-FIBER DEVICE

Liquid-liquid extraction operations were conducted in a hollow fiber mass transfer device using two systems: phenol/water vs. n-octanol and phenol/hexane vs. water. Individual mass transfer resistances due to the tube-side fluid, the hollow fiber wall (membrane), and the shell-side fluid were determined for runs in which the solvent was held stagnant on the shell-side. Countercurrent flow runs with moving solvent were conducted to show that the degree of extraction rises steadily as the solvent-to-raffinate ratio increases. Factors affecting the mass transfer resistances in this type of device are discussed, and the advantages of hollow fiber units over conventional mixer-settler units are pointed out.     

HHT与神经网络在油气两相流流型识别中的应用

引　言两相流动广泛存在于自然界和许多工业过程中 ,如电力、能源、石油、核工业等 .两相流动中介质的几何分布状况 ,即流型 ,极大地影响着两相流动压力损失、传热特性、流量测量的准确性和流动系统的运动特性 .流型的识别方法研究是目前国际多相流研究领域的热点问题之一[1,2 ] .利用神经网络识别流型 ,需要解决两个问题 :一是特征向量的选取 ;二是神经网络的选择 .其中前者更加重要 .Embrechts等[3] 采用Kohonen网络模型 ,把差压波动信号的傅氏变换系数和正交小波　变换后的小波系数作为网络的输入 ,对水平管内的两相流流型进行辨识 .Mi…     

气液两相流流经环形狭缝通道的流动特性

引言动力、能源、石油化工等领域中广泛应用着各类管壳式换热器,此类换热器的管子与折流板之间、折流板与壳体之间在制造与装配中存在着一定的间隙。这些间隙对壳侧的压降及换热系数有较大影响。对于单相流体,这些间隙产生的泄漏量可占总流量的15％～60％~［1～4]．根据文献报道~［5],大约有50％以上的管壳式换热器涉及气液两相流,迄今为止对气液两相流体流经环形狭缝通道的流动特性研究尚未见有文献报道．本文在水平放置环形狭缝通道中,对空气一水两相混合物流经3种不同间隙环形狭缝通道的流动特性进行了研究,并应用分相模型提出了计…     

FLOW REGIME CHARACTERISTICS IN COCURRENT BUBBLE COLUMN REACTORS

In bubble column reactors, flow regime characteristics significantly influence hydrodynamic and transport phenomena. It is shown that the boundary between the bubble flow and the churn turbulent flow regimes can be predicted analytically. Analytical solutions for both coalescing and non-coalescing liquids are presented. The validity of the analytical expressions is illustrated by comparing the calculated values of the transition velocities to the observed ones in the literature. Finally, the limitations of this technique are pointed out.     

气体"拟颗粒"模型

介绍了适用于气固两相流动的气体“拟颗粒”模型.气体被离散为大量气体微团,即“拟颗粒”;发生碰撞的拟颗粒间有相互作用的粘滞力和压力;气体的运动借助拟颗粒的运动状态来描述,气体间及气体与固体颗粒的相互作用由拟颗粒-拟颗粒、拟颗粒-固体颗粒的作用代替.应用该模型模拟了气体绕流单圆柱和双圆柱的现象,分别计算了单圆柱的曳力系数C