Emulsions conductivity

Further discussion of emulsion conductivity and some practical examples for emulsions flowing in pipelines are given in [85],... 

Water-C02 Emulsions and C02-Water Emulsions Conductivity and Dielectric Measurements... 

The conductivity and high-frequency dielectric constant of an emulsion are both indicators of which phase (water or CO2) is the continuous one. If CO2 is the continuous phase in an emulsion, the emulsion conductivity will be extremely low. In contrast, if water is the continuous phase, substantial conductivity will be observed, provided that ionic solutes are present. Likewise, the dielectric of a CO2-continuous emulsion should be similar to that of CO2 (ca. 1.2), whereas the dielectric of a water-continuous emulsion should approach that of water (ca. 80). Emulsions were created by using a high-pressure emulsifier (Emulsiflex, Avestin) to provide high-shear mixing for systems containing CO2, water, and Mn(PFPE)2 surfactant as shown in Figure 2.4-8. 

Install a conductivity probe in the column feed line (237, 239). Water or oil-water emulsions conduct electricity far better than oil. A high-conductivity signal will therefore detect water and can be used for shutting down the feed pump. This technique was found particularly effective (239) for rerunning slop from refineiy... 

Figure 1 Variation of emulsion conductivity as a funciicHi of the water frociion, for a SAD < 0 (respectively SAD > 0) formulation at left (respectively right). (After Ref. 2l.

In such a situation special care is advisable since the water transfer would change the external phase proportion 0 . as well as its electrolyte concentration K . If the most inside droplets (Wj) contain a higher electrolyte concentration, water would be transferred from outside water (W>) to inside water (W,). i.e.. 0 would decrease, while the electrolyte concentration in W, would increase, as would K., These opposite effects on the emulsion conductivity would make it quite insensitive to the mass transfer occurrence, and another detection method would have to be found. 

Experimental studies that were carried out to analyze the influence of formulation on the emulsion conductivity, stability, viscosity, and drop size indicate that there exists a general [ nomenological pattern of variation for all tested systems. 

Figure 10 Vaiiaiion of the emulsion conductivity along two formulation scans. Salinity scan (left) and surfaclanl hydrophilicity scan (right. (After Ref. 66).

Many experimental results show chat when the formulation is scanned through optimum formulation, the emulsion conductivity changes from high to low (or vice versa depending on the direction of tlie effect of the scanned variable). 

Chen et al. (179) used optieal microscopy to study the same crude-oil emulsions in an electric field. They modeled the system with a computer simulation based on a hard-sphere model describing the droplets as stabilized by a rigid asphaltene film. They identified two different types of coalescence. The mobile interfaeial films led to low emulsion conductivities owing to immediate droplet/droplet coalescence, and the incompressible interfaeial film led to low emulsion conductivities due to droplet-chain formation and... 

A common method to guard against this type of incident is a conductivity probe, installed as shown in Figure 17-4. Water or a hydrocarbon-water emulsion conducts electricity far belter than oil. Increased electrical current flow through the conductivity probe indicates the presence of water. A signal from the probe can then be used to shut down the slop pump. 

This concept, developed by Shinoda [24, 25], is closely related to the HLB balance concept described above. Shinoda and co-workers found that many 0/W emulsions stabilised with nonionic surfactants undergo a process of inversion at a critical temperature (PIT). The PIT can be determined by following the emulsion conductivity (a small amount of electrolyte is added to increase the sensitivity) as a function of temperature. The conductivity of the O/W emulsion increases with rising temperature till the PIT is reached, above which there will be a rapid reduction in conductivity W/O emulsion is formed). 

Adding Teflon emulsion, conductive polymers, carbon liber, and rutile structured oxidate to PAM as adhesives can promote the transformation of a-Pb02 into p-Pb02, enhancing electrode performance. 

The emulsion conductivity changes drastically near HLD = 0, indicating that emulsion inversion takes place there, irrespectively of the variable used to alter the HLD. According to the Bancroft rule, the wedge theory, and more modem curvature conceptualizations, HLD < 0 is associated with O/ W emulsions and HLD > 0 with W/O emulsions. Near HLD = 0 an emulsion of the microemulsion-oil-water (MOW) three-phase system could be occurring, but there is no clear-cut indication about what constitutes its external phase. 

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