IONIC GEL EXTRACTION IN AN ELECTRIC FIELD

This paper reports the successful synthesis of an ionic gel with good swelling property and high sensitivity to the electric field. This gel shrinks rapidly as an electric field with a low supply voltage is applied across it, and the overall shrinking process can be completed in 15 minutes. The gel would swell again when the the electric field is removed. A theoretical analysis and experimental study have been carried out on the kinetics of swelling and shrinking of the disk shape gels. The modeling of kinetics of swelling and shrinking of the disk gels is in good accordance with the experimental results.     

静电强化乳液中油滴(纳米尺度)聚并过程(英文)

Oil droplets in nanometer scale which are dispersed in water cannot be separated easily.An attractive technique is carried out by electrical phenomena to demulsify oil in water emulsion.In this research,non-uniform electric field or dielectrophoresis(DEP) is applied to remove sunflower oil(which is dispersed in the water).Effects of temperature,time and voltage(using AC-electric field) were considered to get the highest DEP-force(Fdi) and the best results.The oil particles sizes with average of approximately 76 nm have been shown using a ZetaSizer Nano ZS,Model ZEN 1600(Malvern Instrument Ltd.).The maximum separation efficiency of 85% is obtained at the optimum temperature of 38 ℃ and voltage of 3000 V.     

支流电场中的单气泡行为

The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct current （DC） electric field with bubbles attached to the orifice. The air bubbles were slowly generated in the transformer oil pool at different orifices, so that the effect of flow on bubble shape was eliminated. The results showed that the bubbles were elongated and the departure volume decreased when the electric field was intensified. The major and minor axes, aspect ratio and departure volume increased with increasing the orifice diameter. Both the electric field and orifice size have great influence on bubble behavior. The bubble deformation was also simulated to compare with the experimental results. The numerical and experimental data qualitatively agree with each other.     

Ultrasonic Electro-oxidation Process of Molybdenite Concentrate

The oxidation of MoS2 concentrate in NaCl solution electrolysis environment and the impact of ultrasonic field on the leaching process of Mo were investigated. The decomposition process of MoS2 can be accelerated by ultrasonic field. When there are iron ions, anode potential is decreased about 0.7 V than that without iron ions, iron ions in the solution play an electronic transmission role by directly joining the electrode reaction of anode and oxidation leaching process. The results indicate that the leaching rate of Mo can achieve 99.5% with ultrasonic field exertion working 4 min in every 5 min under the conditions that the liquid-solid ratio is 20, mixing rate 500 r/min, iron ion concentration 6%, leaching temperature 40℃, pH (initialization) 1, and leaching time 4 h, respectively.     

Simulation of Liquid Velocity Field in a Gas-Liquid Bubble Column

A simplified turbulent model and a modified k-Σ two equation model are proposed todescribe the liquid velocity profiles in a bubble column taking into consideration of the effect of gasdrag force and gas hold-up.In the simplified mode1 the Reynolds equation of motion was adoptedand the turbulent viscosity was calculated from an empirical correlation which was deduced fromour experimental data.The calculated liquid velocity profiles were compared between the proposedmodel and the standard k-Σ two equation model as well as experimental data.The result shows thatthe proposed model simulates and predicts the liquid velocity field most satisfactorily and in goodagreement with the experimental measurement.     

Emission control in the combustion of coal–water and organic coal–water fuels

Promising methods for decreasing anthropogenic emissions due to the combustion of coals of different ranks and coal–water fuel (CWF) and organic coal–water fuel (OCWF) slurries on their basis are considered. The maximum concentrations of the main anthropogenic emissions of sulfur, nitrogen, and carbon oxides (SO _x , NO _x , and CO _x ) formed upon the combustion of solid fuels in a powdered state and as the components of CWF and OCWF slurries were determined. The concentrations of the most hazardous oxides formed upon the combustion of coals of different ranks (brown and black coals) and CWF and OCWF slurries were compared. The experimental results substantiated the use of CWF and OCWF slurries for emission control in coal-burning power engineering. The addition of a combustible liquid component to a CWF slurry (the production of an OCWF slurry) makes it possible to ensure acceptable environmental and energy characteristics.     

Dimorphism of water at 0‡c. refinement of the cluster-hygroscopic microstructure of water

The structural and physical behavior of water in the temperature range from 0 to 35‡C was examined. The possible enantiotropic mechanism of formation of two morphological modifications of (H₂O)₈ clusters at 0‡C (dimorphism of water) was demonstrated: liquid phase — body-centered cubic packing of the water molecules (bcc packing), ice — double tetrahedral (diamond) packing. The partial density of ice clusters at 0‡C is equal to 838 g/liter, and the maximum density of water is observed when (H₂O)₆ clusters predominate in the water. Translated fromKhimicheskie Volokna, No. 6. pp. 44–46, November–December, 1998.     

Hydrate formation in oil–water systems: Investigations of the influences of water cut and anti-agglomerant

To investigate the characteristics of hydrate formation in oil–water systems, a high-pressure cell equipped with visual windows was used where a series of hydrate formation experiments were performed from natural gas + diesel oil + water systems at different water cuts and anti-agglomerant concentrations. According to the temperature and pressure profiles in test experiments, the processes of hydrate formation under two kinds of experimental procedures were analyzed first. Then, based on the experimental phenomena observed through the visual windows, the influences of water cut and anti-agglomerant on the places of hydrate formation and distribution, hydrate morphologies and hydrate morphological evolvements were investigated. Hydrate agglomeration, hydrate deposition and hydrate film growth on the wall were observed in experiments. Furthermore, three different mechanisms for hydrate film growth on the wall were identified. In addition, the influences of water cut and anti-agglomerant on the induction time of hydrate formation were also studied.     

电场作用下双液滴聚合特性

乳状液破乳分离是目前高含水期油田开采过程中难以解决的技术问题,电场破乳方法具有高效清洁等优点,是解决该问题的有效手段。采用数值模拟与试验验证相结合的方法研究电脱水过程中阶跃、斜坡电场诱导下双液滴的聚合与分离特性。结果表明,在斜坡电场作用下,界面张力引起的泵吸作用大于电场力引起的颈缩作用,有利于液滴聚并,且液滴发生二次乳化现象的概率降低。而施加阶跃电场时,一定范围内能够达到液滴破乳的目的,但液滴在聚并过程中易发生二次乳化现象。从电场对连续相影响的角度分析发现,阶跃电场不仅对液滴具有驱动作用,对连续相的影响也较为明显,阶跃电场会增大连续相内湍流作用,不利于电脱水过程。因此,采用斜坡信号诱导液滴聚合能够降低二次乳化现象发生的概率。     

新型静电聚结器中水滴聚结特性研究

传统电脱水器采用裸电极,含水率较高时在高强电场作用下容易发生击穿现象,今设计了包覆绝缘层的高压电极并加工了新型静电聚结器,可有效避免击穿现象的发生。采用水/原油乳状液为实验介质,并利用显微高速摄像系统结合图像处理技术对水滴的聚结规律进行了观察和分析,探索了电场强度、流量、含水率等因素对水滴聚结特性的影响。结果表明:包覆绝缘层的高压电极可有效防止电击穿现象的发生,增加电场强度有助于油水分离,但高于临界场强后容易导致液滴破碎;含水率为10%、20%、30%时,最优电场强度不同,分别是372、320和204 kV m 1;含水率10%和30%乳化物液滴粒径增大倍数明显大于含水率20%的工况;电场作用时间影响液滴聚结效果,高强电场在低流量下具有很显著的作用;随着流量的增加电场作用降低,但高强电场在高流量下依然使液滴粒径明显增大。     

非均匀电场下乳化油中液滴变形动力学行为

外加电场下液滴的变形动力学行为是乳化液电脱水机理研究的重要内容。基于Cahn-Hilliard方程的相场方法,建立了液滴在非均匀电场下的仿真模型,研究了电场作用下乳化液中液滴在形变、移动和聚结过程中电荷密度和电场力的分布规律,以及流场和电场的耦合作用。仿真分析了液滴粒径、电场强度以及电场非均匀系数对液滴运动行为的影响。利用实验室小型脱水系统开展了乳化液脱水实验,并通过高速摄像机对乳化液中液滴的运动行为进行了观测与分析。研究结果表明,在非均匀电场中液滴表面的极化电荷分布不均,由液滴中部向两端逐渐增大,在靠近电场集中方向处的电荷密度和Maxwell应力值最大;在一定范围内增大电场强度、电场非均匀系数或液滴粒径,可使液滴形变量增大,液滴向电场集中区域的移动速度以及液滴间的聚结速度增加。     

直流脉冲电场下液滴-界面聚并行为

为了深入探究直流脉冲电场下液滴-界面聚并行为,针对去离子水作为分散相、葵花油作为连续相的体系,分别改变电场参数（电场强度、频率、波形）和物性参数（界面张力、电导率、液滴粒径、固体颗粒）进行显微实验研究,得到了液滴-界面聚并机制及各参数的影响规律。实验结果表明,液滴-界面存在完全聚并和不完全聚并两种机制,决定因素是泵吸和颈缩过程的相互作用。电场强度增大,不完全聚并程度增大,而电场频率的作用则相反,这与电场力大小和液滴稳定程度有关。随表面活性剂浓度增大,二次液滴急剧增大,超过临界胶束浓度后,小幅减小。随电导率和SiO₂浓度增大,不完全聚并程度均先增大后减小,而随液滴粒径增大,不完全聚并程度持续增大。大部分工况下,液滴在直流稳恒电场下不完全聚并程度高于直流脉冲电场。为脉冲静电破乳机理的深入探讨及高效紧凑脉冲电脱盐脱水设备的研发奠定了理论基础。     

Non-coalescence and chain formation of droplets under an alternating current electric field

The dynamic behaviors of two droplets and droplet cluster under an alternating current (AC) electric field are investigated. Two droplets generally undergo transformation from complete coalescence to partial coalescence and finally to non-coalescence as the electric capillary number Ca_p increases. The critical electric capillary number Ca_pc for complete coalescence in the AC electric field remains unchanged and is twice as large as that in the direct current (DC) electric field when the frequency f ≥ 250 Hz. Charge transfer and reversal of electric field result in the reversal of the direction of electric force, which is the fundamental mechanism of non-coalescence of two droplets and chain formation in droplet cluster. The number of rebounds dramatically increases as f increases, promoting the stability of droplet chain. The droplet chains in the high-frequency AC electric field are longer and more stable than those in the low-frequency AC electric field.     

The effect of interfacial tension on secondary drop formation in electro-coalescence of water droplets in oil

The coalescence of water droplets in oils may be enhanced by application of an electric field. This approach is commonly used in the crude oil and petroleum industry to separate water from crude oil. However, the process could lead to the formation of fine secondary droplets during the process of coalescence. This is obviously undesirable, as it becomes more difficult to separate finer water droplets. In this work the effects of interfacial tension, manipulated by the use of surfactants, and electric field strength on the formation of secondary droplets are investigated. Two competing processes of necking and pumping determine whether secondary droplets are formed. The dimensionless groups Weber Number (describing droplet deformation and necking due to the electric field) and Ohnesorge Number (describing the pumping of water into the continuous phase in the process of coalescence) may be coupled to give a new dimensionless group WO, describing the volume fraction of secondary droplets that are formed. WO Number describes the ratio of the electrical stress energy that causes necking over the energy required for pumping the viscous fluid out of the droplets. For a wide range of interfacial tensions, brought about by the use of non-ionic and anionic surfactants and electric field strengths, a good unification of data is obtained. The outcome of this work will be useful for optimizing the design of the electro-coalescence systems.     

Electro-coalescence of an aqueous droplet at an oil-water interface

The coalescence of an aqueous droplet at an oil-water interface under an electric field has been investigated, with a view to quantify conditions that give rise to secondary droplet formation. Two patterns of drop-interface coalescence may occur: complete coalescence and partial coalescence. The former is obviously the desirable pattern for industrial coalescers. However in practice, the process of coalescence could actually produce smaller droplets, which become more difficult to remove, and hence undesirable. This is caused by either necking, due to extensive elongation of the droplet, or reaction to a fast and energetic coalescence and is referred to as partial coalescence. The volume of the droplets formed in this way has been analyzed as a function of the initial droplet size, electric field strength and the distance between the droplet and the interface. The expansion speed of the neck connecting the droplet and interface at the beginning of the pumping process has also been quantified. These results are useful in optimizing the electro-coalescence process.     

操作参数对W/O乳状液水滴静电迁移聚并的影响

用导热油和蒸馏水配制成W/O乳状液，在高压高频脉冲电场下通过显微实验考察了含水率、乳化强度、温度等操作参数对高压高频脉冲电聚结和水滴迁移聚并的影响。结果表明，含水率低时，水滴碰撞几率和偶极聚结力的实验结果与理论分析结果相符，含水率高时脱水效果下降；乳化强度越强，水滴碰撞速率越大，偶极聚结力越小，乳化强度适中，电聚结效果越好；操作温度越高，布朗运动越强，连续相粘度越小，液膜排液阻力减小，对水滴聚结越有利。     

Flocculation and Separation of Oil Droplets in Ultrasonic Standing Wave Field

A new method for breaking oil in water emulsion based on flocculation of droplets in high intensity ultrasonic standing wave field was developed in this study and the effect of initial droplets size, type of disperse phase as well as the time of sonication and the height of emulsion in the chamber on the extent of interdroplet interactions were investigated. The results showed that type of disperse phase affects the efficiency of separation process through controlling the initial size of droplets. For the two types of disperse phase in question the efficiency of separation was calculated to be 42.7% for canola oil/water emulsion and 37% for sunflower oil/water emulsion. The time of sonication was found to have a positive contribution to the percent of flocculation and coalescence, so that the largest aggregates were formed after 30 minutes treatment. Also, the optimum height of emulsion in the treatment chamber was determined to be λ/4 at which the strongest flocculation and highest percent of coalescence took place. Increasing the height of emulsion did not significantly influence the course of aggregation and separation.     

高压脉冲电场破乳的影响因素探讨

在高压脉冲电场中,W/O乳状液的分散相液滴产生聚结和沉降,可与连续相分离开来。采用以新型电极作为内电极的同心圆柱状破乳装置对模拟W/O乳状液进行破乳,对其影响因素电极、试验电压、破乳时间、温度等进行试验研究。试验结果表明：采用3#电极时破乳率最高;随着试验电压的提高,时间增长,温度升高,其破乳率都能提高。对各影响因素的影响机理进行了分析,同时指出了试验的不足之处。