EFFECT OF DEMULSIFIERS ON THE SEPARATION OF WATER-IN-OIL EMULSIONS

The effect of demulsifiers on these parathion of water from crude oil has been studied. A semi-analytical model to predict the hold-up of the dispersed phase with height in a batch sedimenting vessel, where quasi steady-state conditions prevail, is developed. Using the model, parameters are obtained by correlating the experimental results which characterise the type of demulsifier used.     

液滴在斜板层膜上聚结时间的计算

在对聚结过程和分离界面处液滴与层膜流体力学特性分析的基础上,建立了单个液滴在斜板层膜上聚结时间模型,模型计算值与BlassE等人报道的实验结果误差小于10％。     

On the effect of phase fraction on drop size distribution of liquid–liquid dispersions in agitated vessels

The theory of Kolmogorov–Hinze is the base for many studies that have been done on mean drop size and drop size distribution of liquid–liquid dispersions in agitated vessels. Although this theory has been used extensively in the literature, but it does not always give a satisfactory result in the studies and therefore needs to be modified. This paper addresses the effect of phase fraction on drop size distribution in agitated vessels and on the proportionality coefficient and Weber number exponent in the relation d₃₂/D ∝ We^m. The experimental data that were taken from Pacek et al. (1998) and Desnoyer et al. (2003) have been applied to this relation to investigate the effect of phase ratio. It is shown that even at low phase fractions, the Kolmogorov–Hinze theory necessarily does not give the best result with the −0.6 exponent for the Weber number. Furthermore, for the non-coalescing system, a range of exponent for the Weber number typically from −0.6 to −0.43 can be considered where the system may be approximated as a pseudo-coalescing system at Φ = 0.4 in which the obtained results are in good agreement with the results of Pacek et al. (1998).     

Drop Size Distribution in a Standard Twin‐Impeller Batch Mixer at High Dispersed‐Phase Volume Fraction

The preparation of concentrated aqueous silicone oil emulsions has been investigated with particular attention to the effect of the dispersed‐phase volume fraction ? from 0.01 to 0.5 for a wide range of oil viscosities (50 to 1000 cSt). Oil was added on the top surface of a 6‐L vessel. Drop size distribution and Sauter mean diameter, d₃₂, measurements were carried out over 24 h mixing time. Emulsification was found to be relatively sensitive to the oil phase viscosity, μ_d, for the same ? yielding a narrower drop size distribution for low oil viscosity (50 cSt) and a wider drop size distribution for the highly viscous oil (1000 cSt). For the same ?, increasing μ_d resulted in increasing d₃₂. The equilibrium d₃₂ was found to be well correlated to the viscosity number by for ? = 0.5. For the same oil viscosity, d₃₂ was found to increase with increasing ?. A multiregression of d₃₂ with both ? and V_i for various silicone oil viscosity grades was successfully correlated by with a regression coefficient (R²) of 0.975. This shows a very weak dependence of the equilibrium d₃₂ on ?.     

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid‐Liquid Extraction Column

Sauter mean drop sizes (d₃₂) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d₃₂ in a RDC extraction column. The first was based on operating variables, hole‐distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75 %, with a maximum absolute error of 6.8 %.     

Systematic Analysis of Single Droplet Coalescence

Coalescence behavior in liquid‐liquid dispersions is controlled by various parameters. Thus, data from different research groups can differ significantly. Dynamic coalescence processes were analyzed systematically with the EFCE standard test system toluene/water in two different research laboratories. After comparability was proven with standardized batch settling tests and drop rise velocity measurements, the influence of drop size ratio and varying NaCl and NaOH concentrations on coalescence probability was investigated. Since the ions led to a coalescence inhibition, no clear impact of drop size ratio could be observed. The analysis of drop contact showed longer contact times for increasing equivalent drop diameter. This promotes coalescence and corresponds to film drainage model.     

分批加分散剂时苯乙烯悬浮聚合瞬间液滴直径和分布

在苯乙烯悬浮聚合中研究了分批加分散剂体系磷酸三钙(TCP)或 TCP 和聚乙烯醇(PVA)时的加入方式对瞬间液滴大小和分布的影响。考察了体系液滴分散和合一的特点。实验观察到分批加入分散剂体系时液滴大小分布的变化规律,呈由单峰分布过渡到双峰分布,最后又发展为单峰分布。这与分散剂体系一次加入相比,后者仅出现单峰分布逐渐过渡到双峰分布。     

Drop mixing in suspension polymerisation

In suspension polymerisation, monomer is suspended as liquid droplets in a continuous water phase by means of strong agitation and the presence of a suspending agent. As the suspension polymerisation proceeds, the viscosity of a monomer-polymer droplet increases with conversion. Hence, the physical behaviour of the droplet changes during the process. When new dispersible material is added to the existing suspension drops, the new material and existing drops can remain segregated for significant amounts of time. The aim of this project was to study the behaviour of drop mixing when new material is added to the existing suspension polymerisation. This study concentrated on the effect of the dispersed phase viscosity on drop mixing. The results show that viscosity affects drop size and that may then affect the rate of coalescence between drops. A critical drop size exists which determines the coalescence efficiency effect. Above the critical drop size, mixing rate increases as the drop viscosity decreases. While below the critical drop size, drop size of the dispersion determines the coalescence rate; as the drop size increases, coalescence rate also increases. The investigation of the effect of suspending agent shows that Tween 20 is more efficient in stabilising and protecting the drops, based on a weight basis, than PVA as the coalescence rate is lower with Tween 20.     

APPLICATION OF THEORETICAL MODELS TO THE ESTIMATE OF M1CROEMULSIONS PROPERTIES PART I TERNARY SYSTEMS

A model has been developed which adequately describes the phase behavior of alcohol in an oil phase. The model has been also extended to quaternary systems containing a surfactant component.     

APPLICATION OF THEORETICAL MODELS TO THE ESTIMATE OF M1CROEMULSIONS PROPERTIES PART I TERNARY SYSTEMS

A model has been developed which adequately describes the phase behavior of alcohol in an oil phase. The model has been also extended to quaternary systems containing a surfactant component.     

Electrostatic Drop Formation in Liquid/Liquid Systems

Electrostatic drop formation in liquid/liquid systems was studied, using high frequency AC fields (45 kHz). The dispersion of nonconductive into conductive fluids was investigated under various conditions, as are the effect of aqueous phase conductivity, capillary geometry and organic phase viscosity on the resulting drop size. The experimentally determined drop sizes and literature data, were correlated with a model equation, which was derived from a simple force balance, with an empirical term for the electric force. The model parameters were obtained in a toluene/water system and the model allows the prediction of the drop sizes of other organic solvents, if the capillary geometry is kept constant.     

Behavior of Elongated Liquid Jets in Viscous Liquid‐Liquid‐Systems

The stability of jets in elongational flow is exploited to obtain thin threads before breakup. Fine drops can be generated in suitable geometries with comparably large ducts. The examination deals with the stability of liquid threads simultaneously extended with the continuous phase in convergent flow. Breakup limits and regimes are discussed.     

Droplet size and velocity profiles in liquid-liquid horizontal flows

The size and vertical distribution of drops were studied experimentally in dispersed liquid-liquid pipeline flows. Under most conditions the pattern was dual continuous where both phases retain their continuity and there is entrainment in the form of drops of one phase into the other. The investigations were carried out in a stainless steel test section with 38 mm ID with water and oil (density and viscosity ) as test fluids. Mixture velocities from 1.5 to and input oil volume fractions from 20% to 80% were used. A dual sensor impedance probe allowed drop chord length and drop velocity measurements at different locations in a pipe cross section.It was found that in dual continuous flows drop concentration and size decreased with increasing distance from the interface. There were only small differences in size between oil drops in the lower water continuous layer of the flow and water drops in the upper oil continuous layer. Mixture velocity did not affect significantly the drop size of either phase since higher velocities that would result in smaller drops were accompanied by increased entrainment of one phase dispersed into the other that favoured larger drops. The Rosin-Rammler function was found to fit satisfactorily the experimental drop size distributions, while literature correlations on entrained and maximum drop sizes in a turbulent field underpredicted the values found experimentally.