Dynamic Stability of Heavy Crude Oil-in-Water Emulsions

The transport of heavy oil as concentrated oil-in-water (O/W) emulsions is one of the most promising pipeline techniques, and how to ensure a steady flow is the key to the successful application of this technology. Most of the previous studies focused on the static stability of the emulsions. However, the stability changes constantly with time and external shearing in the transportation. In this paper, a stable O/W emulsion was prepared for its dynamic stability to be tested by three methods of small-scale flow loop, rheology and stirring, respectively. The results indicated that the O/W emulsion with 30 vol.% water and 0.2 wt.% OP-10 could well satisfy the transport requirement. A critical temperature existed to make the rheological property of the emulsion rapidly deteriorate. For low-Reynolds-number turbulent pipe flow, an appropriate increase of temperatures and shear rates was conducive to the flocculation-dissociation balance of the internal phase, which could effectively reduce the apparent viscosity of the emulsion and the flow frictional resistance. High flow rate of O/W emulsions could be transported at relatively low temperatures to ensure great dynamic stability, and low flow rate of that could be done at relatively high temperatures to obtain low apparent viscosity.     

Laminar Flow Emulsification Process to Control the Viscosity Reduction of Heavy Crude Oils

The formation of heavy crude oil in water (O/W) emulsion by a low energy laminar controlled flow has been investigated. The emulsion was prepared in an eccentric cylinder mixer. Its geometry allows the existence of chaotic flows that are able to mix well highly viscous fluids. This new mixer design is used to produce high internal phase ratio emulsions for three oils: castor oil and two heavy crude oils of different initial viscosity (Zuata and Athabasca crude oils). The influence of the stirring conditions, geometrical parameters, and water volume fraction on the rheological properties of the resulting O/W emulsion is studied.     

表面张力对PEO稀溶液粘度行为的影响

测定了不同分子量聚氧化乙烯(PEO)在水和苯溶剂中的粘度,发现在低浓度区PEO水溶液的比浓粘度出现负偏离, PEO苯溶液比浓粘度与浓度之间依旧满足线性关系.表面张力测定结果表明, PEO分子显著降低了水的表面张力,而苯的表面张力则不受影响.PEO水溶液和纯溶剂水表面张力的不同干扰了高分子溶液和溶剂在粘度计中流过时间的测量,导致低浓度区PEO水溶液比浓粘度出现负偏离.利用PEO水溶液和水表面张力测定结果,结合乌式粘度计的几何尺寸,定量分析了PEO水溶液和纯溶剂水表面张力的差异对粘度测量结果的影响,计算结果与实验结果基本相符.如果用PEO水溶液流过时间对浓度作图的外推值t0*计算相对粘度,可以完全消除PEO水溶液和水表面张力差异对粘度测量的影响.     

Viscosity, Surface Tension, and Refractive Index Measurements of Mixtures of Isomeric Butanediols with Water

Solution properties of aqueous mixtures of isomeric butanediols have been investigated employing viscosity, surface tension, and index of refraction measurements as functions of temperature. The deviation of viscosity, surface tension, and molar refraction from ideal solution behavior is evaluated from the experimental data. The deviation from ideality is discussed in terms of molecular interactions between the components. Surface activity of the diols is evident from the surface tension measurements. It is found that the degree of hydrophobicity of the diols varies in the order 1,2 > 2,3 > 1,3 > 1,4. The strength of interaction of diols with the water varies in the order 2,3 > 1,4 1,3 > 1,2.     

Emulsions of Heavy Crude Oils. II. Viscous Responses and Their Influence on Emulsion Stability Measurements

The stability of 30 heavy crude oil emulsions was studied in a parallel-plate laboratory coalescer (DC field). Particularly, viscous responses and their influence on the emulsion stability measurements were investigated. In addition to highlighting previous results from the same experimental setup and discussing these based on recent experience, new results at different temperatures and volume fractions of water were presented. A new semi-empirical model for the characteristic time of the destabilization process was presented. The electrical forces were modelled with a point-dipole approximation and the hydrodynamic resistance to droplet transport was modelled with an empirical term including the logarithmic viscosity of the oil phase. The new model clearly performed much better than the previous model, particularly for very viscous crude oils. Studies of the performance of industrial electrocoalescers have showed that simple electrostatic theory can potentially explain complex separation phenomena when the resistance to the coalescence step is reduced by an efficient demulsifier. The ultimate goal is to build a model for both the laboratory setup and the industrial coalescer so that laboratory experiments can be used to predict the behavior of the industrial process.     

Walnut Oil Nanoemulsion: Optimization of the Emulsion Capacity,Cloudiness, Density,and Surface Tension

Response surface methodology (RSM) in conjunction with central composite rotatable design (CCRD) was employed to find out the influence of preparation properties of walnut oil/water nanoemulsion namely ultrasonic time (5–15 minutes), walnut oil content (4–10% w/w) and concentration ratio of Span 80 to Tween 80 (K ₀, 0.55–0.80) on response variables including emulsion capacity, cloudiness, density and surface tension. The calculated regression models with high value of coefficient of determination (0.910–0.973) and insignificant lack of fit test indicated satisfactory agreement of empirical models with experimental observations. The results revealed linear term of walnut oil concentration was the most significant (p < 0.05) parameter on the all responses. The overall optimum region to achieve the ideal characteristics was ultrasonic time of 11.74 minutes, walnut oil content of 4.00% (w/w) and K ₀ of 0.80.     

An Experimental Study on the Viscosity of Water-in-Oil Emulsions

Water-in-oil (W/O) emulsions are very common in the petroleum industry, and their viscosities are the principle parameters for the operation design. Typical correlations composed by one or two factors cannot always fit the apparent viscosity of W/O emulsions very well, especially when applied to the crude oil/water emulsions. The viscosities of W/O emulsions, which were made from three kinds of crude oil, were measured by Anton Paar MCR302 viscometer at atmospheric pressure with different temperatures as well as shear rates. The experiment results indicate that W/O emulsion would exhibit Newtonian characteristic when water content is no higher than 0.2 and non-Newtonian characteristic otherwise. According to the experimental data, a modified correlation based on the Broughton–Squires model and Ronningsen model was introduced to predict the viscosity of W/O emulsions, and the comparison results showed that the new modified correlation has better accuracy than the original models.     

吊片法测试液体表面张力的实验设计

表面张力是液体的重要物性数据,在科学研究、工业生产和日常生活中皆有广泛应用。介绍了采用吊片法测量液体表面张力的实验设计,该实验过程简单,准确度高,实验内容和时间易于调节,对于培养学生认真细致的科研作风有很大帮助。     

二乙醇胺-N-甲基二乙醇胺-水溶液表面张力实验研究

用ZBY-1全自动表面张力仪测定了288～333 K温度范围内, 二乙醇胺(Diethanolamine, DEA)、N-甲基二乙醇胺(N-methyldiethanolamine, MDEA)及其混合水溶液的表面张力, 并分析了混合溶液的表面熵和表面焓等热力学性质与醇胺浓度的关系.     

Investigations of the Effects of Xanthan and Sodium Caseinate on the Formation and Stability of an Oil-in-Water Emulsion Stabilized by a Nonionic Surfactant Using a Response Surface Method

Effects of xanthan and sodium caseinate concentrations on the rheological properties and stability of an oil-in water emulsion stabilized by a nonionic surfactant (Tween 20) were investigated. In order to evaluate the influence of component concentrations on the emulsion properties, a response surface method was applied. It was shown by polynomial simulation and modelization of responses of storage modulus and creaming index that in absence of Tween 20, the oily droplets were flocculated by bridging of sodium caseinate macromolecules, when those are insufficient to cover the entire interface. Additionally, it was noted that xanthan reinforces the polymeric network in the aqueous phase when the caseinate is not moved toward the phase. On the other hand, in presence of nonadsorbed caseinate, the polysaccharide develops segregative interactions by thermodynamic incompatibility. These nonadsorbed macromolecules can also flocculate the fatty globules by depletion.     

由表面活性物质溶液的动界面张力外推求平衡界面张力的研究

表面活性物质溶液的界面张力往往随时间而变,难以测得平衡界面张力J。Kloubek^[1]曾应用经验式:1/(δ_H2O-δ_t)=b/(At^1/2)+1/A,以[1/(δ_H2O-δ_t)]对1/t^1/2作图外推求得溶液的平衡表面张力,但所得结果仅与文献值大致相符。本文从理论上分析该经验式的由来,以及产生偏离的原因,并寻求了解决的办法。     

Double-Layer Contribution to the Surface Tension of Halides of Alkali Metals

Effects of interface charging on the surface tension of simple halides of alkali metals are analyzed. The surface tension, computed within the density functional theory in an approximation of the squared density gradient using a parametrized profile and a mean spherical approximation for a local free energy, satisfactorily conforms to experiment.     

A DOE Approach to Investigate the Influence of Process-Parameters and Composition on the Stability of Emulsions Stabilized by Marine Polysaccharides Prepared by High-Pressure Homogenization

The influence of pre-homogenization conditions (speed and duration at a rotor–stator system), homogenization pressure, and quantitative composition of the emulsions on the droplet size and stability of the resulting emulsions is investigated using design of experiments. A mix of marine polysaccharides (e.g., alginate and fucoidane) from Ascophyllum nodosum is used as emulsifier to form O/W-emulsions with medium-chained triglycerides. It was found that the amount of emulsifier is the most relevant parameter for emulsions' stability whereas the influence of the homogenization pressure is more distinct at low polysaccharide contents. In contrast, the parameters of pre-homogenization do not influence the droplet size significantly.      

双子表面活性剂Dynol-604溶液的动态表面张力研究

通过测定双子表面活性剂Dynol-604的动态表面张力(DST),研究了温度和浓度等对其DST的影响,详细表征了DST随时间的变化过程,计算了动态表面张力的各种参数(t_i,t^*,t_m,R_1/2).结果表明,其表面张力降低迅速,γ_m值也很低.探讨了上述参数的物理意义和变化规律.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

液体表面张力的概念解析及相关问题的讨论

液体表面张力是了解表面现象过程中的重要概念,然而物理化学教材对该概念的阐述却未能做到详实易懂。因此,通过较多立体图示,详细讨论了液体表面张力的产生原因、弯曲液面边缘所受表面张力的方向以及施力相界面等相关问题,以期对教材中未能阐述的内容作以适当补充,降低初学者在概念理解上的难度。     

Behavior of the Surface Tension and the Viscosity in the Eutecticregion of the Liquid Feb alloy

Abstract

Thermodynamic and transport properties of pure liquid metals show interesting correlations near the melting temperature. This is well known for the case of the surface tension σ and the shear viscosity η In this paper we investigate the possible extension of these correlations to binary alloys, taking the FeB alloy as a case study. Based on literature data we analyze the variation of σ and η as a function of temperature and concentration in a deep eutectic region of the phase diagram of this alloy, as well as the possible correlations between those two quantities. Substantial differences with respect to the behavior in pure metals are found.     

Studies on the Effects of Additional Components on Micellization of CTAB via Surface Tension Measurements

The effects of Tris-HCl buffer solution on the cmc of cetyltrimethylammonium bromide (CTAB) were studied by surface tension measurement. The result shows that the effect of the buffer solution depends on the interaction between CTAB and NaCl and the structure accelerants of water, Tris. A series of parameters, including the critical micelle concentration (cmc), the surface tension at cmc (γ_cmc), the adsorption efficiency (pC₂₀), and the effectiveness of surface tension reduction (∏_cmc) were obtained from the surface tension measurements in the presence of glycine with different concentration in the Tris-HCl buffer solution at 27°C. In addition, maximum surface excess concentration (Γ _max) and minimum surface area per molecule (A_min) at the air-water interface were estimated according to the Gibbs adsorption isotherm. The thermodynamic parameters (Δ C _p,m , Δ H _m,tr , Δ C _p,m,tr ) of micellization for CTAB in the absence and presence of glycine at different temperature were also been obtained.     

Effect of Glyphosate Isopropylamine on the Surface Tension and Surface Dilational Rheology Properties of Polyoxyethylene Tallow Amine Surfactant

In order to develop the substitutes for polyoxyethylene tallow amine (POEA), the understanding the interaction of glyphosate isopropylamine and POEA is essential. The surface behaviors of POEA and POEA in the presence of 1 wt% glyphosate isopropylamine have been investigated at the air-water interface by the drop shape analysis method. The influences of surface tension, dilational frequency, and bulk concentration on the surface properties were expounded. The experiment results show that the adsorption films of POEA behave elastic in nature at low bulk concentration. With increasing in bulk concentration, the dilational modulus, dilational elasticity, and dilational viscosity pass through a maximum value, the phase angle increase monotonically. These phenomena can be attributed to the diffusion-exchange process between the bulk and the interface. The addition of 1 wt% glyphosate isopropylamine significantly influences on the POEA surface tension and dilational properties. The dilational modulus, dilational elasticity, and dilational viscosity obvious decrease in general, and the values of phase angle significant change after the addition of 1 wt% glyphosate isopropylamine. Glyphosate isopropylamine and POEA form a new complex in the solution and the surface activity and surface dilational properties of complex is different from POEA.     

体系pH值、乳化温度和电解质离子对异丙甲草胺水乳剂稳定性的影响

通过测定药物液滴的平均粒径和Zeta电位研究了体系pH值、 乳化温度和电解质离子对乳化剂三苯乙烯基苯酚聚氧乙烯醚磷酸酯三乙醇胺盐(SCP)稳定的异丙甲草胺水乳剂稳定性的影响. 结果发现, 体系的pH值影响SCP分子在水中的电离能力, 当pH=9时, SCP完全电离, 能为液滴提供较大的静电稳定作用, 水乳剂稳定性最好; 乳化温度低时, SCP分子向液滴界面扩散慢, 且舒展不完全, 液滴所带负电荷较少, 水乳剂稳定性差; 温度升高后, 水相黏度减小, 布朗运动加剧, 液滴碰撞合并几率增大, 且SCP分子热运动增强, 易从界面逃逸, 液滴间静电斥力减弱, 同时SCP亲水性下降, 水乳剂稳定性变差; 电解质离子会压缩界面双电层, 降低Zeta电位, 液滴带电量减少而聚结, 离子浓度越大, 电荷数越大, 水乳剂稳定性越差. 在相同的离子浓度下, 水合半径小的Ca²⁺压缩双电层能力强于Mg²⁺, 添加Ca²⁺后水乳剂稳定性更差.