液滴分布对稠油乳状液黏度影响的实验研究

采用聚焦光束反射测量仪对辽河油田稠油乳状液微粒进行"动态"监测,考察了含水率、搅拌转速和温度对稠油乳状液液滴粒径大小影响,定性分析了微观液滴分布对乳状液粘度的影响机理。结果表明,随着含水率的增大,乳状液体系中粒径显著增大,小液滴数量增大,体系黏度增大,当乳状液发生转相后,黏度大幅度降低,微观表现为小液滴数量增大,乳状液液滴平均直径增大;随着搅拌转速的增大,乳状液体系中粒径显著减小,小液滴数量增大,使得分散相更均匀的分散在连续相中,稠油乳状液黏度呈现下降的趋势;随着温度的升高,乳状液体系中粒径显著增大,小液滴数量增大,稠油乳状液液滴直径的增大,增大了体系液滴直径分布,导致乳状液体系黏度的降低。     

稠油/水乳状液表观粘度实验研究

通过实验研究稠油/水乳状液的表观粘度与分散相液滴直径、含水率和温度的关系。分散相液滴直径越大,表观粘度越小;与轻质油/水乳状液不同,稠油/水乳状液在较低的含水率时即表现出很强的剪切稀释性;温度变化对稠油/水乳状液的表观粘度有显著影响而对相对粘度影响很小。在考虑了剪切率的相对粘度预测模型中,Pal(1989)模型的预测结果与实际测量值较为接近。     

乳化条件对稠油乳状液黏度和稳定性的影响

表面活性剂的使用能够提高乳状液的稳定性并降低稠油的黏度。研究了两性表面活性剂CAB-35和有机碱TEOA的二元体系对稠油黏度和稳定性的影响,考察油水比、温度、搅拌速度对乳状液黏度和液滴平均粒径大小的影响。结果表明,当CAB-35质量分数为0.75%时乳状液黏度最小为17.79 mPa·s;添加TEOA可以提高稠油乳状液的稳定性,分水率达到11.3%,降黏率达到95.24%。随着油水比的增加,乳状液液滴粒径变小,黏度增大,乳状液更稳定。温度升高,乳状液液滴发生聚并,黏度减小,乳状液稳定性变差。随着搅拌速度的增加,能形成较小的液滴,黏度增大,乳状液稳定性增强。     

稠油及其乳状液流变性研究

以国内某油田稠油及其乳状液为研究对象,采用Anton Paar MCR 302可视化流变仪对其黏温特性和流变性进行研究。测量了稠油在不同温度下的黏度,以及不同含水率、温度及剪切速率下该稠油乳状液的表观黏度,根据实验结果对其关系进行综合分析,并观察反相点附近的稠油乳状液微观形态。结果表明,该稠油的黏温特性在测量范围内能较好的符合Arrhenius方程,稠油乳状液黏度与含水率、温度的综合关系能够符合对数关系模型,在不同的含水率下,稠油乳状液黏度公式Richardson公式中的k值是关于温度的函数,从微观上可以证明该稠油样品的反相点在40%～50%之间,另外,剪切速率对稠油乳状液黏度的影响随温度的变化而变化。因此,对稠油乳化降黏输送时需考虑温度、含水率及剪切速率等多种因素的影响。     

油包水乳状液微观特性进展研究

油包水乳状液的微观特性是影响乳状液稳定性的重要因素。为了降低采出液破乳难度、减小管线运输负担,有必要弄清楚乳状液的微观特性。影响油包水乳状液稳定性的微观因素主要有四部分:乳滴的大小、形状以及分布,乳状液界面张力,界面膜性质和界面剪切黏度。阐述了影响乳滴大小、形状、分布主要因素的研究进展,并简要介绍了乳状液液滴粒径分布的测量方法;报告了油包水乳状液界面张力大小主要影响因素的研究现状;阐述了界面膜的分子密度与机械强度对油包水乳状液稳定性的影响;对乳状液界面剪切黏度的影响因素进行了研究,对界面剪切黏度的研究现状作出评述,并介绍了测量界面剪切黏度的方法。     

原油乳状液黏度影响因素及规律性研究

研究了不同剪切速率下,二元、三元不同油水比、不同碱含量、不同二元配方条件下形成的乳状液体系黏度的影响因素及其规律。结果表明,高剪切速率下,油水比为7:3形成的三元乳状液最稳定,黏度最大;较高剪切速率下,油水比低于1:1的二元乳状液体系黏度很低,发生相转变;不加碱时,形成的二元乳状液体系黏度较大;加碱时,三元乳状液体系在较低剪切速率下形成的乳状液体系黏度较大,当剪切速率增加到一定值时,三元乳状液发生相转变,黏度降低,且随剪切速率增加变化不明显;低剪切速率下,聚合物+活性剂形成的二元体系乳状液黏度最大,碱+活性剂形成的二元体系乳状液黏度最小;当剪切速率超过一定值时,聚合物+碱形成的二元体系乳状液黏度最大,聚合物+活性剂形成的二元体系乳状液黏度最小。     

桑枝多糖黏度特性的研究

采用布氏黏度计对桑枝多糖的黏度进行测定,分别考察温度、剪切速率以及pH值对桑枝多糖黏度的影响,结果表明:桑枝多糖溶液为假塑性流体,随着温度的升高其黏度逐渐降低且两者的关系符合阿累尼乌斯模型,温度和浓度对其黏度的综合影响可用数学模型η=-5.924 5exp 2.48/RT-0.123 8C+3.421×10-4C2)进行预测,适用范围温度20~80℃,浓度1%~8%;剪切速率对其黏度的影响可用幂律模型η=Mγn进行拟合,黏度随剪切速率的增加而降低,酸和碱均使桑枝多糖溶液黏度下降,中性条件下黏度值最高,说明桑枝多糖是中性多糖.     

湍流分散系统中液滴尺寸的模拟与研究

在考虑分散相黏度对液滴破碎频率影响的基础上,进一步研究了分散相黏度对液滴聚并的影响.在液膜排液时间的计算式中,引入了分散相黏度,建立了新的液滴聚并频率的表达式.通过数值求解群体平衡方程,得出搅拌槽内液-液湍流分散系统的Sauter平均直径.与实验数据比较发现,改进模型可以较好地预测分散系统的Sauter平均直径,其结果优于Coulaloglou 和 Tavlarides模型.计算结果表明分散相黏度对液滴平均直径有着双重影响,抑制破碎,导致液滴直径增大;抑制聚并,从而导致液滴直径减小.     

湍流分散体系中液滴破碎频率模型的黏性修正

在分析研究分散相黏度对液滴变形和破碎影响的基础上,提出了一个改进的液滴破碎频率模型并拓展了液滴破碎判据标准.同时通过Monte Carlo模拟的随机方法,得到了湍流搅拌槽中液-液分散体系的液滴直径分布和Sauter平均直径d₃₂.通过与文献中关于d₃₂的实验结果比较发现,该模型预测的Sauter平均直径更接近实验值,对于黏性分散相改进的液滴破碎频率模型要优于Coulaloglou和Tavlarides提出的模型.计算结果表明对于黏性分散相液滴,其黏度限制了液滴变形,使得液滴破碎频率被大大减少, 液滴直径明显增加,液滴直径分布向右偏移.     

高频脉冲电场作用下乳状液液滴动力学模型

基于乳状液中液滴在电场中的受力情况的分析，建立了W/O乳状液中液滴振荡固有频率公式，从理论角度分析和解释了高频脉冲电场对W/O乳状液的破乳机理，从力学的角度分析了最佳频率存在的理论基础，并推导出了最佳频率的计算公式。该固有频率与液滴尺寸、界面张力、黏度、温度、密度等有关。为了验证最佳频率公式的可靠性，用正辛烷乳状液进行了室内实验。实验结果表明，理论最佳频率公式的预测结果与实验测得的最佳频率结果吻合，经修正后与白油实验结果也非常接近。     

Flow characteristics of surfactant stabilized water-in-oil emulsions

In this paper, an investigation was carried out to study the effect of water fraction and flow conditions on the flow characteristics of surfactant stabilized water-in-oil emulsion. Pressure drop measurements were conducted in 2.54-cm and 1.27-cm horizontal pipes. The influence of water fraction and the flow conditions on emulsion stability, type, conductivity, droplet size distribution, viscosity and pressure drop were reported. The results showed a significant increase in the emulsion stability, viscosity and pressure drop with increasing water fraction up to 70%. In addition, shear thinning behavior was observed for the emulsions especially at high water fractions. Furthermore, pressure drop measurements of high concentrated emulsions showed pipe diameter dependency especially at high Reynolds (Re) numbers. Moreover, drag reduction was observed with decreasing water fraction. The viscosity of surfactant-stabilized water-in-oil emulsions was modeled with a modified fluidity-additivity model.     

油水乳化液流变性研究进展

综述了油水乳化液流变性研究进展，介绍了目前国内外乳化液流变性的研究情况、乳化液的流变模式及乳化液流变性的评价方法。乳化液的剪切应力-剪切速率关系明显受油滴尺寸的影响，在含油量一定时，表观黏度随油滴尺寸的减小而增加。绝大多数乳化液在低剪切速度下(低于50s^-1)，呈现剪切变稀行为；在剪切速率超过1000s^-1时呈现牛顿行为。高含水原油的视黏度是温度、含水率以及剪切速率的函数。介绍了乳化液的3种流变模式，并给出了流变性评价方法实例。提出了油水乳化液流变性研究的发展方向。     

纳米流体黏度特性

引言纳米流体是将纳米粒子添加到基液中形成的稳定悬浮混合液。近10年来,国内外许多学者对纳米流体的导热性能进行了大量研究,添加纳米粒子后溶液的导热能力明显加强。Jung等[1]对微渠道中的纳米流体对流传热特性进行了研究,研究发现粒径为170nm、体积分数为1.8%的Al2O3-水纳     

A STUDY OF SILICONE OIL-IN-WATER EMULSIONS

Emulsions of silicone oil-in water were formed using a Brinkmann Polytron homogenizer with Igepal CO-530 as an emulsifier. Silicone viscosities ranged from 10 to 33,000 mPa.s at 25°C. Rheological characteristics and particle size analyses of silicone oil-in-water emulsions were studied. At high volume fraction of the dispersed phase (70%-75%), silicone oil-in-water emulsions were stable. At lower volume fractions (50%-60%), emulsions formed were less stable and the two phases easily separated in a few days. The emulsions formed with high volume fraction silicone oil show highly non-Newtonian behavior (shear thinning). Emulsions made with low viscosity oils had lower viscosities than those made from high viscosity oils. Relative viscosity-concentration data could be correlated by the Frankel and Acrivos Equation. Increasing the emulsifier concentration of 70% oil-in-water emulsions resulted in a decrease in mean droplet size and an increase in emulsion viscosity. Increasing the intensity of agitation also resulted in higher viscosity and smaller droplet size until a critical energy input above which droplet size increased. Emulsification with low shear mixing provides more control in decreasing mean droplet size with time.     

Thixotropic Behavior of Oil‐in‐Water Emulsions Stabilized with Ethoxylated Amines at Low Shear Rates

Oil‐in‐water (O/W) emulsification is a lubricating pipeline method based on the reduction of the energy frictional loss produced during viscous flow. The flow behavior of heavy O/W emulsions formulated with nonionic surfactants is described. The effects of pH and salinity of the aqueous phase on droplet diameter, stability, and apparent viscosity of O/W emulsions were evaluated. The low‐shear Couette flow of O/W emulsions displayed intense shear‐thinning and thixotropic behavior. Thixotropy was associated to the droplet deformation energy caused by shear rate changes. The droplet deformation and alignment led to the apparent viscosity reduction compared to the fluid at rest. Thixotropic behavior is supposed to balance between the breakdown and recovery of droplet ordered structures. Emulsion formulation parameters were influenced by the aqueous phase pH, enabling to manage the emulsion properties. The droplet mean diameter of < 18 µm resulted in very stable emulsions.     

Rheological properties of bitumen in water emulsions with added solids

Experimental work was carried out to investigate the rheological properties of bitumen in water emulsions containing solids of different shape and size. The bitumen volumetric concentration was varied up to 60%, solids free basis, and the solids volume fraction (total volume basis) was varied up to 0.2. Irregular-shaped silica sand (average diameter: 9 and 33 μm) and smooth spherical glass beads (average diameter: 27 and 44 μm) were used as the added solids. In the low shear stress range, shear thinning behavior was observed for bitumen in water emulsions. At high shear stress, the viscosity of the emulsions became fairly independent of the shear stress. The addition of solids to the bitumen emulsions increased the mixture viscosity. The addition of irregular-shaped silica sand gave a higher viscosity than a similar addition of the spherical glass beads. The viscosity of the emulsion/solids mixtures was influenced by the solids size as well; the smaller size particles gave a higher viscosity. The addition of solids to the bitumen emulsions also induced shear thickening (dilatancy) behavior at high solids volume fraction. The degree of the shear thickening increased with the oil concentration.     

Feasibility study of water as thinner for polyvinyl chloride plastisol

In the traditional formula of polyvinyl chloride (PVC) gloves, the diluent of PVC plastisol is usually organic solvent, which causes serious environmental pollution during the molding process. The aim of this study was to develop a low viscosity PVC plastisol emulsion (PDE) using water as a thinner by blending PVC emulsion (PVCE) with diisononyl phthalate (DINP) emulsion. DINP emulsion (DINPE) was prepared by a compound emulsifier of polyoxyethylene octyl phenol ether-10 and sorbitan monooleate. The effects of compound emulsifier concentration on the stability and microstructure of DINPE were investigated. The results showed that the optimal compound emulsifier concentration of DINPE was 10 wt%. In addition, the PDE obtained by blending exhibited a relatively uniform unimodal droplet size distribution. The steady state data revealed that the emulsions were shear-thinning pseudoplastic liquid. The effect of solid content and temperature on the apparent viscosity of PDE were also evaluated. The mechanical spectra obtained suggested the presence of weak gel structure in the PDE. The mechanical test results showed that the tensile strength and elongation at break of PVC film obtained by PDE were 12.62 MPa and 310.31%, respectively. This study demonstrated that water was effective in reducing the viscosity of PVC plastisol, which would promote the application of water thinner in glove production.     

Experimental study on the rheological behavior of tetrafluoroethane (R-134a) hydrate slurry

Information on the rheological characteristics of clathrate hydrate slurry is vital due to its diverse applications including hydrate slurry transportation as in seawater desalination by gas hydrate process, gas delivery through slurry pipelines, cold thermal energy storage, and secondary refrigeration by hydrate slurries. The current study experimentally investigated the rheological behavior of Tetrafluoroethane (Freon) hydrate slurry formed from R-134a and water serving as a medium for sea water desalination. Experiments were performed in a flow loop with a volume of 5.68?L and an inner pipe diameter of 21.5?mm, which was immersed in a constant temperature bath to maintain hydrate stable condition. Experiments were conducted with two phases in the loop; solid hydrate particles and liquid water. The hydrate solid volume fraction ranged from 15.8 to 31.7?vol%. Pressure drops along the straight section of the pipe were monitored while temperature, solid volume fraction and flow rate were kept constant at desired values. The experimental results indicated that Freon slurry can be considered as a pseudo-plastic fluid. The shear-thinning characteristics of Freon slurry became more pronounced as the hydrate solid fraction increased. An empirical power law type equation that relates the apparent viscosity of the Freon slurry to the hydrate solid volume fraction and shear rate was developed and compared with experimental values. The experimental results well supported the values of the apparent viscosity calculated from the modeled equations.     

Determining Bitumen Viscosity Through Drop Shape Recovery

In determining the viscosity of bitumen using conventional methods, the measurements must be conducted at extremely slow shear rates to avoid dissipative heating. In this study, bitumen viscosity is measured at room temperature using a drop shape recovery technique which, as will be shown, is immune to any problem of dissipative heating. The method involves stretching a small droplet of bitumen (and in general, of any viscous liquid) with micropipettes and allowing it to recover to its original spherical shape; the dimensions of the droplet can be as small as several micrometres. The shape recovery process is driven by capillary forces and rate‐limited by the droplet viscosity. As such, knowing the interfacial tension, the droplet viscosity can be determined accurately from the relaxation dynamics. With conventional viscometers, the problem of dissipative heating often increases linearly with the viscosity and quadratically with the shear rate. This is in contrast with shape recovery experiments, where dissipative heating is independent of shear rate and varies inversely with the viscosity.