Investigation into the mechanisms by which microwave heating enhances separation of water-in-oil emulsions

Abstract

(2014) Investigation into the mechanisms by which microwave heating enhances separation of water-in-oil emulsions. Fuel, 116 . pp. 516-521. ISSN 1873-7153 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/31942/1/130726_Manuscript%20revised_for%20archiving.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the Creative Commons Attribution Non-commercial No Derivatives licence and may be reused according to the conditions of the licence. For more details see: http://creativecommons.org/licenses/by-nc-nd/2.5/ A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. ABSTRACTThe separation of water-in-oil emulsions made with Azeri crude was investigated using natural gravity settling and microwave heating techniques. Separation times could be reduced by an order of magnitude compared with untreated emulsions.Increasing the salinity of the water phase leads to a 15% average decrease in the settling time for untreated emulsions compared with over 90% for microwave-heatedemulsions. An image analysis technique showed that the observed increases in settling time could not be attributed to changes in viscosity alone. Significant coalescence of water droplets occurs during microwave heating, however the effects of coalescence and viscosity reduction cannot be completely decoupled. Despite this, it is clear that it is the thermal effect of microwave heating that leads to improvements in settling times, and that any advantages in microwave heating over conventional heating can Page 2 of 25 be explained by selective heating of the aqueous phase rather than so-called nonthermal effects. KEYWORDSWater-in-oil emulsion; microwave; coalescence; viscosity; interfacial tension; selective heating INTRODUCTIONEmulsions arise during the production of oil downstream from the well. Water is present with the oil, particularly in the latter stages of the well life when water injection is used to enhance the production rate. On leaving the well the mixture, at high pressure, is let down through a choke valve so that it can be further processed at moderate pressures. The pressure reduction valve creates significant shear within the fluid and it is this pressure drop that causes the emulsions to form. The water must be separated before further downstream transport and processing can commence, and as the oil and water phases are immiscible gravity separation can be utilised to separate the two substances. Gravity separation occurs due to a density difference between oil and water, and the separation of the two phases is governed by the settling velocity, u S . If u S is small then...

Demulsification techniques of water-in-oil and oil-in-water emulsions in petroleum industry

“…As a result, the principal mechanism by which microwave heating enhances the demulsification capability of emulsions is assigned to its thermal effects rather than non-thermal. In accordance with this mechanism, saline emulsions under microwave are separated more quickly since the salts alter the dielectric properties of the water phase (apart from changing the IFT of emulsion), leading to improved heating of the dispersed brine compared with pure water, thereby developing a greater thermal gradient in the continuous phase, which promotes coalescence probability [68,246,252]. Similar mechanism has also been proposed for O/W emulsions, and the expedient impact of salts dissolved in the aqueous phase on their resolution is attributed to the proliferation in solvent conductivity, enabling the acceleration of heating rate as well as the reduction of electrical double layer thickness at the oil-water interface [65,247,255].…”

“…Salt-assisted microwave demulsification of both W/O and O/W emulsions have frequently been announced in the literature [65,72,247,251,252], mechanism of which is described in Section 6.3. In this regard, Xia et al [251] studied the microwave separation of a W/O emulsion (microwave power: 850 W) in presence and absence of small quantity (0.02 mol L -1 ) of varied inorganic salts, and drew the following conclusions:…”

Ionic Liquids as Surfactants – Applications as Demulsifiers of Petroleum Emulsions

“…The radiation favors temperature elevation process by a non-conventional heating mechanism known as dielectric heating. Many works of demulsification have been focused on the effect of microwave irradiation to break emulsions [22][23][24][25][26][27]. Now, the most common technologies employed in petroleum industry are the combined use of heat and chemicals designed to neutralize and eliminate the effects of the emulsifying agents.…”

Oil–water separation property of polymer-contained wastewater from polymer-flooding oilfields in Bohai Bay, China

“…The settling velocity of water droplets may be raised by heating the water and surrounding oil, which reduces both the oil-water interfacial tension and viscosity of the oil. [18] Figure 4 shows the gravitational separation efficiency of the emulsions at various temperatures. As shown, heating exerts little effect on demulsification of S and L samples, even when the temperature was raised up to 90°C (Figure 4(a) and 4(b)).…”