Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Reexamination Certificate
2001-03-09
2003-04-29
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
C204S157150, C210S748080, C210S732000, C516S143000
Reexamination Certificate
active
06555009
ABSTRACT:
FIELD OF THE INVENTION
The invention includes a method for demulsification of water-in-oil emulsions using sonication and recovering oil therefrom. The invention also includes a method for determining the strength of an interfacial film formed at the oil-water interface. The oil of the emulsion can be of any type including crude oils, crude oil distillates, vegetable oils, animal oils, synthetic oils and mixtures thereof.
BACKGROUND OF THE INVENTION
High TAN and asphaltene content crude oils possess the tendency to form stable water-in-crude oil emulsions. Such crude oil typically contains from about 1 to about 60 volume % water. The polar naphthenic acids and asphaltenes in the crude oil stabilize dispersed water droplets. Further, sub-micron size solids like silica and clay, when present in the crude oil, interact with the polar acids and asphaltenes and enhance the stability of the emulsions formed. Formation of stable water-in-crude oil emulsions result in difficulty in separation of water and crude oil. In most cases, known technologies for separation result in an intermediate emulsion rag layer. Further processing of the rag layer is essential to recover the crude oil and discharge the water. The problem is faced both at production facilities and in refinery desalters.
Electrostatic demulsification in the presence of chemical demulsifiers is the most widely used technology for demulsification of water-in-crude oil emulsions.
Gravity settling and centrifugation in conjunction with chemical demulsifiers are also employed.
Recently, a microwave technology (See for example U.S. Pat. Nos. 6,086,830 and 6,077,400) patented by Imperial Petroleum Recovery Corporation has emerged for treatment of hard to treat emulsions especially the rag layer.
Thermal flash methods are also known in the art.
SUMMARY OF THE INVENTION
The instant invention includes a method for demulsifying a water-in-oil emulsion comprising the steps of:
(a) sonicating said emulsion at an energy of about 25 to about 500 watts/cm
2
;
(b) separating said emulsion into an oil phase and an aqueous phase; and
(c) recovering said phases.
The invention may further optionally comprises adding demulsifier to said emulsion prior to or during said sonication step (a).
The invention likewise includes a method for determining the strength of an interfacial film present at the oil-water interface of a water-in-oil emulsion comprising;
(a) sonicating a series of at least three samples of said water-in-oil emulsion wherein each of said samples is sonicated at an energy of at least about 25 watt/cm
2
higher than the preceeding sample;
(b) separating each of said sonicated water-in-oil emulsion samples into a water phase and an oil phase
c) determining the percent water separated for each of said samples in said series of samples; and
(d) determining said strength of said interfacial film which strength corresponds to the energy of sonication at which the greatest percentage of water from said series of sample is separated from said water-in-oil emulsion by identifying the energy at which the greatest percentage of water was separated.
The invention also includes a method for separation of a water-in-oil emulsion in a process scheme including an on-line sonicator comprising the steps of:
a) collecting a water-in-oil emulsion from said process scheme;
(b) sonicating said emulsion, wherein said emulsion is sonicated in a series of at least three samples and wherein each of said samples is sonicated at an energy of at least about 25 watt/cm
2
higher than the preceeding sample;
(c) separating each of said samples of sonicated water-in-oil emulsion into a water phase and an oil phase;
(d) determining the percent water separated for each of said samples in said series of samples; and
(e) determining said strength of said interfacial film which strength corresponds to the energy of sonication at which the greatest percentage of water from said series of sample is separated from said water-in-oil emulsion by identifying the energy at which the greatest percentage of water was separated.
(f) setting the said on-line sonicator to a sonication energy level corresponding to said determined interfacial film strength: and
(g) sonicating said water-in-oil emulsion in said on-line sonicator set to said determined interfacal film strength; and
(h) separating said sonicated emulsion into a layer comprising water and a layer comprising oil.
DETAILED DESCRIPTION OF THE INVENTION
The invention includes a method for recovering oil from a water-in-oil emulsion. In such emulsions, particularly those containing crude oils, the organic acids, asphaltenes, basic nitrogen-containing compounds and solid particles present in the crude form an interfacial film at the water/oil interface. The instant invention affords a way to break the film and demulsify the emulsion, thereby forming a plurality of layers from which oil can be recovered.
The invention may further comprise adding a demulsifier to said water-in-oil emulsion. Use of a demulsifier is believed to weaken the interfacial film present in the emulsion with demulsifier at the oil/water interface. Such a film is weaker than the film formed absent the demulsifier. Thus, use of a demulsifier can lower the sonication energy required to break the interfacial film of the emulsion. One skilled in the art will readily recognize that the sonication energy can be lowered by use of demulsifiers and the advantages associated with their use in hard to break emulsions.
The invention is applicable to any type of water-in-oil emulsion, and is particularly suitable for solids containing water-in-oil emulsions, and is applicable to crude oil emulsions comprising components which may include solids, asphaltenes, organic acids, basic nitrogen compounds and mixtures thereof. Thus, the invention can be applied to water-in-oil emulsions of crude oils, vegetable oils, animal oils, synthetic oils and mixtures thereof. As used herein crude oils include any oils comprising organic acids, and may also contain asphaltenes, solids and basic nitrogen containing compounds. Typically, the solids, if present in the emulsion, will have an average total surface area of ≦1500 square microns, more preferably about 25 to about 1500 square microns, even more preferably about 50 to 1500 and most preferably about 100 to about 1500 square microns.
Sonication is the act of subjecting a system to sound (acoustic) waves. The velocity of sound in liquids is typically about 1500 meters/sec. Ultrasound spans the frequency of about 15 kHz to 10 MHz with associated wavelengths of about 10 to 0.02 cm. The invention may be practiced at frequencies of about 15 kHz to about 20 MHz. The output energy at a given frequency is expressed as sonication energy in units of watts/cm
2
. The sonication provided for in the instant invention is typically accomplished at energies of about 25 to about 500 watts/cm
2
.
Following the sonication, the sonicated emulsion is separated by methods such as centrifugation, gravity settling, hydrocyclones, application of an electrostatic field, microwave treatment or combinations thereof or by any other methods known to the skilled artisan for phase separation. The oil may then be recovered as a separate phase. Sonication alone may be sufficient to separate the emulsion into phases or may be combined with another separation method or ceased and the emulsion separated by other methods known to the skilled artisan for phase separation.
The process may be conducted at temperatures of the water-in-oil emulsion of about 20 to about 200° C. and at pressures from ambient to 200 psig (1480.4 kPa).
Use of demulsifiers in the invention is optional. If such demulsifiers are utilized, the demulsifiers may be selected from any known demulsifiers that will not degrade during sonication. Such demulsifiers can be readily selected by the skilled artisan. Typically, the demulsifiers will have a molecular weight of about 500 to about 5000, preferably about 500 to about 2000 and a hydrophilic lipophilic balance of above 9 and preferably from 9 t
Bakun Estelle C.
ExxonMobil Research and Engineering Company
Hruskoci Peter A.
Varadaraj Ramesh
LandOfFree
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