Phase separation time

For a required total vapor-phase separation time, 0,. the horizontal nozzle-to-nozzle length, L is ... 

Ikeda, H., Suzuki, A. 2001. Empirical correlations for radiolytic degradation of -dodecane density viscosity and phase separation time. J. Nucl. Sci. Technol. 38 (12) 1138-1140. 

In the early stage of spinodal decomposition, varies with phase separation time, therefore it cannot be scaled by a single length parameter (t). It is necessary to normalize the structure function by the invariant function, i.e.. 

Figure 8. Log-log plots of the maximum wavenumber versus phase separation time for 50/50 blends.

Figure 11. Log-log plots of scattered intensity against scattering wavenumber for various phase separation time at 260, 270 and 280°C. 

The simulation result for the time evolution of structure factors as a function of the scattering vector q for an A/B 75/25 (v/v) binary blend is shown in Fig. 9 where time elapses in order of Fig. 9c to 9a. The structure factor S(q,t) develops a peak shortly after the onset of phase separation, and thereafter the intensity of the peak Smax increases with time while the peak position qmax shifts toward smaller values with the phase-separation time. This behavior suggests that the phase separation proceeds with evolution of periodic concentration fluctuation due to the spinodal decomposition and its coarsening processes occurring in the later stage of phase separation. These results, consistent with those observed in real polymer mixtures, indicate that the simulation model can reasonably describe the phase separation process of real systems. 

Transient Processes. There are several transient processes such as formation and coalescence of oil drops as well as their flow through porous media, that are likely to occur during the flooding process. Figure 12 shows the coalescence or phase separation time for hand-shaken and sonicated macroemulsions as a function of salinity. It is evident ithat a minimum in phase separation time or the fastest coalescence rate occurs at the optimal salinity (53). The rapid coalescence could contribute significantly to the formation of an oil bank from the mobilized oil ganglia. This also suggests that at the optimal salinity of the system, the interfacial viscosity must be very low to promote the rapid coalescence. 

Figure 14 shows a very interesting and an important correlation between the rate of coalescence in macroemulsions and the apparent viscosity in the flow through porous media. It was observed that a minimum in apparent viscosity for the flow of macroemulsions in porous media coincides with a minimum in phase separation time at the optimal salinity. This correlation between the phenomena occurring in the porous medium and outside the porous medium allows us to use coalescence measurements as a screening criterion for many oil recovery formulations for their possible behavior in porous media. It is. very likely that a rapidly coalescing macroemulsion may give a lower apparent viscosity for the flow in porous media (53). 

The other observations were reported elsewhere, however. Figure 13.3 shows polymer made the surfactant system emulsification better, and Figure 13.4 shows polymer slightly changed the value of electrophoretic mobility. The addition of polymer into an ASP system does not change IFT but shortens the phase separation time of emulsions. In these examples, when alkali concentration was below 1%, as the concentration was increased, the phase separation time decreased. When alkali concentration was above 1%, the phase separation time increased with the concentration. Thus, polymer apparently reduced the interaction between oil and alkali when alkali concentration was high. 

RP separation (Spherisorb ODS column) with 0.5% cysteine (pH 5) as mobile phase (separation time <6 min), post-column CV (NaBH4) and ICP-MS... 

The effect of the shearing on miscibility in polymer blends has been reported to give a modification of the phase diagram (21-24). In our case, we cannot discuss this point because the differences measured in phase-separation times can also be attributed to thermal problems. 

The choice of PEG-2000 for metal ion partitioning studies is perhaps not too surprising. This polymer is inexpensive, commercially available, nonflammable, nontoxic, and durable. The ABSs formed with PEG-2000 are easily separated by centrifugation and the phases have manageable viscosities [7,11]. Phase separation times are dependent on system composition and temperature, but dispersion numbers for many of these ABSs are comparable to those of many oil/water systems utilized in traditional solvent extraction [11]. The dispersion number [34], a unitless quantity, is used to... 

In summary, various phenomena occurring at an optimal salinity in relation to enhanced oil recovery by macroemulsion and microemulsion flooding are schematically shown in Figure 6. It has been demonstrated that a maximum in oil recovery correlates well with several equilibrium and transient properties of surfactant flooding in the form of macroemulsion and microemulsion systems. Results have shown that a maximum in oil recovery, a minimum in surfactant adsorption, a minimum in apparent viscosity of the emulsion, a minimum in phase separation time, an equal solubilization of oil/brine phases in middle phase microemulsion, and a minimum in interfacial tension occur at an optimal salinity of the system. 

The mixer-settler (Fig. 6-28) consists of a mixing chamber (mixed vessel, pump, mixing nozzle, static mixer, etc.) and an adjoining separator, which is separated by a slit plate from the mixing chamber. In the mixing chamber, the feed and solvent are intensively mixed and remain in contact for the duration of the mass transfer of the key component. The mixing device has to be operated such that an optimum droplet size is obtained, i. e., a compromise between the small droplets favored for mass transfer and large droplets for small phase separation times. An optimum stirrer revolution speed is found from the minimum of the curve for... 

Some microemulsions are thermodynamically stable, /. e., they form immediately, and the oil and water phases cannot be separated without an energy input. However, most systems are not thermodynamically stable, althou they always present a long term kinetic stability. If the water and oil phase separation does occur in a microemulsion system, the process will take several orders of magnitude longer (months to years) compared to the phase separation time interval of a classical emulsion [33,34],... 

An oil/brine/surfactant/alcohol system often forms a middle phase microemulsion in an appropriate salinity range. The salinity at which the middle phase microemulsion contains an equal volume of oil and brine is defined as the optimal salinity (9). At the optimal salinity, the interfacial tension is in the millidynes/cm range at both oil/microemulsion and microemulsion/brine interfaces, and the oil recovery is maximum (6,9). Moreover, we have shown (10) that at optimal salinity, the coalescence time or phase-separation time is minimum for oil/brine/surfactant/alcohol systems. When these systems are pumped through porous media, a minimum pressure drop or apparent viscosity is observed at the optimal salinity (10). All these phenomena occurring at optimal salinity are summarized in Figure 11. In a recent study, we have also found that the surfactant loss in porous media is minimum at the optimal salinity. Therefore, besides ultralow interfacial tension, a favorable coalescence process for mobilized oil ganglia and the minimum apparent viscosity (or minimum AP) of the oil bank and the minimum surfactant loss are the other factors contributing towards the maximum oil recovery at the optimal salinity. 

The salinity at which the middle phase microemulsion contains equal volumes of oil and brine is defined as the optimal salinity. The oil recovery is found to be maximum at or near the optimal salinity (8,10). At optimal salinity, the phase separation time or coalescence time of emulsions and the apparent viscosity of these emulsions in porous media are found to be minimum (11,12). Therefore, it appears that upon increasing the salinity, the surfactant migrates from the lower phase to middle phase to upper phase in an oil/brine/surfactant/alcohol system. The -> m u transition can be achieved by also changing any of the following variables Temperature, Alcohol Chain Length, Oil/Brine Ratio, Surfactant Solution/Oil Ratio, Surfactant Concentration and Molecular Weight of Surfactant. The present paper summarizes our extensive studies on the low and high surfactant concentration systems and related phenomena necessary to achieve ultralow interfacial tension in oil/brine/surfactant/alcohol systems. 

Extraction based on Extraction time (s) Two phase separation time... 

At the end of phase separation time, in order to stop the any further growth of the structure, the bottle was immediately removed and immersed in a liquid nitrogen bath. Note that the time taken to transfer the sample into liquid nitrogen bath in most cases was less than 1 s. 

PMAA/MAA/ water composition Phase separation temperature, Tps ( C) Phase separation time, tps Drying time, td (h) Smallest pore size ( xm) Comment (type of stiucture, etc.)... 

Figure 1.4.36-1.4.38 shows SEM micrographs of the PMAA membranes formed via thermal inversion process starting with a 7%/3%/90% solution of PMAA/MAA/water at room temperature and quenched at 80°C. The micrographs show fibrous, interconnected network, with open pores, indicative of spinodal decomposition. As phase separation time increases to about 2 min, a cellular... 

It is evident from these figures that coarsening occurs even at the early stages of spinodal decomposition in the reactive system. Figure 1.5.4 shows their corresponding composition profiles at indicated phase separation time values. 

Nonreactive Phase Separation time = 18.1 sec Reactive Phase Separation time = 33.9 sec... 

Thermal evolution would be the primary processing history for the various systems of interest. The ramp-and-hold thermal history can be incorporated in the model simulation, based on the ratio of the ramp time to the characteristic time of the behavior of the system (such as phase separation). This method has been employed for spinodal decomposition with temperature drop in a polymer/solvent system (Laxminarayan and Caneba, 1991), and a Deborah number (De) is used to signify the ratio of the characteristic phase separation time to the temperature ramp characteristic time. Thus, if De is infinite, the system would be under sudden quenching. Results of the work for a nonreactive binary polymer/solvent system established bounds for dimensionless interdomain distance (interdomain distance divided by its value during sudden quenching) vs De. Also, the dimen-... 

Table IT Phase separation time (seconds) under the different conditions...

Authors have also shown that values of dCp/d T change with temperature at different phase separation times and, correspondingly, the fraction of interphase changes in the course of phase separation. The approach considered above may be applied, as follows, only to those systems that are separating in two pure phases. The application of the Freed equation to IPNs may be done if... 

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