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Title:
LIQUID SEPARATION PROCESS AND APPARATUS FOR PRACTISING SAME
Document Type and Number:
WIPO Patent Application WO/2002/055171
Kind Code:
A2
Abstract:
The present invention is a process and an apparatus for separating at least two resolvable liquids while concurrently reducing rag phase development and stabilizing rag phase volume and location during the separation. In a process where a feed stream of two resolvable liquids is dispersed into a vessel and then allowed to separate under the force of gravity into an upper phase and a lower phase, the present invention utilizes an aspirator to withdraw a steam of rag phase material from the interface of two resolvable liquid phases. The flow velocity of the feed stream powers the aspirator. The outlet of the aspirator is located such that the stream of rag phase material is dispersed within the feed stream.

Inventors:
WINSLOW JOSEPH DONALD JR (US)
Application Number:
PCT/US2002/000678
Publication Date:
July 18, 2002
Filing Date:
January 10, 2002
Export Citation:
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Assignee:
PETRECO INTERNATIONAL INC (US)
WINSLOW JOSEPH DONALD JR (US)
International Classes:
B01D17/02; B01D17/025; B01D17/05; C10G31/08; C10G33/02; C10G33/06; (IPC1-7): B01D/
Foreign References:
US3938738A1976-02-17
US6129212A2000-10-10
EP0514543A11992-11-25
US4200550A1980-04-29
US5811013A1998-09-22
US4029570A1977-06-14
US4722781A1988-02-02
GB1407281A1975-09-24
Other References:
DATABASE WPI Section Ch, Week 198233 Derwent Publications Ltd., London, GB; Class H01, AN 1982-69799E XP002235252 & SU 874 096 A (NEFTEKHIMPROMAVTOMA), 25 October 1981 (1981-10-25)
PATENT ABSTRACTS OF JAPAN vol. 010, no. 144 (C-349), 27 May 1986 (1986-05-27) & JP 61 002790 A (TOA NENRYO KOGYO KK), 8 January 1986 (1986-01-08)
Attorney, Agent or Firm:
Tyler, Gene L. (Mossman & Sriram P.C. 2603 Augusta Suite 700 Houston, TX, US)
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Claims:
WHAT IS CLAIMED IS :
1. A process for separating two or more resolvable liquids comprising: (1) admixing at least two liquids to form an admixture; (2) transporting the admixture into a vessel ; (3) dispersing the admixture within the vessel; (4) allowing the admixture to resolve into at least three phases; and (5) discharging at least two of the phases as separate streams from the vessel, wherein: (a) the three phases comprise an upper phase, a lower phase and a rag phase at the interface of the upper phase and the lower phase; and (b) a stream from the rag phase is transported from the rag phase by aspiration and introduced into: (i) at least one of the at least two liquids prior to the formation of the admixture; or (ii) the admixture, prior to the dispersing of the admixture within the vessel, such that there is agitation of the rag phase stream and the admixture sufficient to disperse the rag phase stream into the admixture; and the rag phase stream transported from the rag phase is transported by means of aspiration by the admixture or at least one of the at least two liquids.
2. The process of Claim 1 wherein the at least two liquids are crude oil and brine.
3. The process of Claim 2 wherein the upper phase is a crude oil phase.
4. The process of Claim 3 wherein the upper phase is treated by electrical eduction.
5. The process of Claim 4 wherein the process is a continuous process.
6. The process of Claim 3 wherein the lower phase is a brine phase and includes solids and watersoluble liquids.
7. The process of Claim 6 wherein one of the discharged phases is the brine phase that is further treated to remove solids and watersoluble liquids and recycled back into the process.
8. The process of Claim 3 wherein the crude oil phase is discharged and stored for collection and refining.
9. The process of Claim 1 wherein a stream is removed from the vessel at a level which is above, below, or both above and below the level at which a rag phase is expected to form and tested for rag phase material content.
10. An apparatus for separating two or more resolvable liquids comprising: (1) a first feed and a second feed that pass into a mixer; (2) an outlet from the mixer that passes into an emulsion distributor inside a vessel; (3) an aspirator inlet located inside the vessel such that it is at the level of a rag phase when the vessel is in use to separate two or more resolvable liquids ; (4) at least one aspirator outlet positioned upstream of an emulsion distributor outlet.
11. The apparatus of Claim 10 wherein the first feed and second feed first form a common header before passing into the mixer.
12. The apparatus of Claim 11 wherein the mixer is selected from the group consisting of a pump impeller, a static mixer, a homogenizing mixer, a length of pipe with sufficient turbulent flow to disperse two resolvable liquids, and combinations thereof.
13. The apparatus of Claim 12 wherein the apparatus also includes at least one electrical eduction device in the vessel.
14. The apparatus of Claim 10 wherein the apparatus is a crude oil desalter or dehydrator.
15. The apparatus of Claim 10 wherein the apparatus includes 2 or more emulsion distributors.
16. The apparatus of Claim 10 wherein aspirator inlet is located on the emulsion distributor.
17. The apparatus of Claim 16 wherein there are more than one aspirator inlet on the emulsion distributor.
18. The apparatus of Claim 17 wherein at least one aspirator inlet is at a level selected from the group consisting of above, below, and both above and below the level of a rag phase when the apparatus is in use to separate two resolvable liquids.
19. The apparatus of Claim 18 wherein a line leading from the aspirator outlet above, below, or both above and below the level of a rag phase when the apparatus is in use to separate two resolvable liquids passes through an observation port and a device to test for the presence of rag phase material.
20. An apparatus for distributing an emulsion within a vessel used for separating two or more resolvable liquids comprising an emulsion distributor head body having at one end a feeder inlet and at the other end an outlet and in between a riser wherein the riser includes an aspirator inlet.
21. The apparatus of Claim 20 wherein there is an aspirator outlet located upstream of the emulsion distributor head outlet.
22. The apparatus of Claim 20 wherein there is more than one aspirator inlet.
23. The apparatus of Claim 20 wherein there is more than one aspirator outlet.
Description:
Title : LIQUID SEPARATION PROCESS AND APPARATUS FOR PRACTICING SAME BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the separation of resolvable liquids. The present invention particularly relates to the separation of resolvable liquids wherein the liquids are oil and water.

2. Background of the Art The separation of liquids in general and oil and gas from other reservoir liquids in particular is an important commercial process. For example, U. S. Patent No. 4,250,114, to Biller, discloses a chemical process wherein an acid catalyzed condensation product of aniline and formaldehyde is purified with high recoveries by means of dissolving the liquid condensation product in aniline, admixing the solution with water, and then performing a separation. U. S. Patent No. 4,548,702, to York, et al., discloses a process for the production of shale oil that includes a separation of oil and water wherein dust and other undesired materials are removed from the oil during the separation.

Removal of impurities as in 4,548,702, to York, et al., can be an important effect of doing liquid separations. Another process that discloses a purification of crude oil by means of an immiscible liquid separation is that of US Patent No. 4,722,781, to Swartz, et al. Therein, crude oil is desalted by admixing the crude oil with water and allowing the crude oil and water admixture to resolve into a desalted crude layer and a water phase with an emulsion layer or cuff between the desalted crude layer and the water layer. Also disclosed in Swartz is a method of reducing the cuff layer by a combination of recycling the cuff into the feed streams and diluting the material from the cuff with a light diluent oil.

3. Summary of the Invention In one aspect the present invention is a process for separating two or more resolvable liquids comprising: (1) admixing at least two liquids to form an admixture; (2) transporting the admixture into a vessel ; (3) dispersing the admixture within the vessel ; (4) allowing the admixture to resolve into at least three phases; and (5) discharging at least two of the phases as separate streams from the vessel, wherein: (a) the three

phases comprise an upper phase, a lower phase and a rag phase at the interface of the upper phase and the lower phase; and (b) a stream from the rag phase is transported from the rag phase by aspiration and introduced into: (i) at least one of the at least two liquids prior to the formation of the admixture; or (ii) the admixture, prior to the dispersing of the admixture within the vessel, such that there is agitation of the rag phase stream and the admixture sufficient to disperse the rag phase stream into the admixture; and the rag phase stream transported from the rag phase is transported by means of aspiration by the admixture or at least one of the at least two liquids.

In another aspect the present invention is an apparatus for separating two or more resolvable liquids comprising: (1) a first feed and a second feed that pass into a mixer; (2) an outlet from the mixer that passes into an emulsion distributor inside a vessel ; (3) an aspirator inlet located inside the vessel such that it is at the level of a rag phase when the vessel is in use to separate two or more resolvable liquids; (4) at least one aspirator outlet positioned upstream of the emulsion distributor outlet.

In still another aspect, the present invention is an apparatus for distributing an emulsion within a vessel used for separating two or more resolvable liquids comprising an emulsion distributor head body having at one end a feeder inlet and at the other end an outlet and in between a riser wherein the riser includes an aspirator inlet.

The present invention is useful in any application that includes the separation of two or more resolvable liquids by density wherein a layer of slow to resolve material forms between the lighter liquid and the more dense liquid. This slow to resolve material can accumulate and interfere with the separation process. As already recited above, this material is sometimes referred to as a"cuff"but is more frequently referred to as a"rag", "rag layer", or"rag phase." In the process of the present invention, two resolvable liquids are admixed and then separated. For purposes of the present invention, resolvable liquids are those which: (1) have significantly different densities, (2) are substantially insoluble one in the other, and (3) will, after being dispersed within each other, separate into layers underthe force of gravity. Exemplary are many polar and non-polar liquid pairs, such as water and oil. In the alternative, some organic materials can be purified by creating a hydrophilic form of the desired product, such as a salt of an amine or organic acid, extracting an aqueous solution of the salt with an organic solvent such as hexane, then changing the pH to recover the organic product.

A separation apparatus useful with the present invention works using gravity to separate liquids. One of ordinary skill in the art of separating resolvable liquids is well

familiar with using such apparatus. Such apparatus are most often used in a continuous process where a constant ratio of feed liquids is fed into and out of the apparatus.

Preferable there is no rag phase, but few processes do not generate a rag phase over long periods of operation. In normal operational mode, most such apparatus are operated to minimize rag phase formation and to keep the same ratio of the three phases such that the interface between the phases stay at the same place within the vessel of the separation apparatus.

While the present invention can be used with any process that includes separation of resolvable liquids, it is most useful with those processes wherein a rag phase is formed during the separation. Depending on the process, the rag phase can include both solids and emulsified liquids. Often, the separation process is a convenient point for removal of non-liquid impurities such as, for example, sand and other insoluble minerals from oil or, in an organic synthetic process, liquid by-products.

One oil production process with which the present invention can be practiced is the known as dehydration. In this process, oil containing too much entrapped water to make further processing desirable without first removing the water is treated to reduce its water content. In the dehydration process, steps to increase the separation of water from oil can be taken including, but not limited to, electrical eduction and the addition of chemical additives. In this process, a feed stream of oil is admixed with water and sent to a settler wherein the lighter oil phase rises to the top of the vessel and the heavier water phase sinks to the bottom. The resulting oil layer is drawn off and further processed while the water layer is either recycled, treated and discarded, or combinations thereof. Ultimately, the oil layer is collected and refined.

Another process with which the present invention is particularly useful is the process of separating oil from the other liquids and minerals present in the production stream from an oil well. This process, sometimes referred to as desalting, can be a second processing step after dehydration and includes taking a first feed stream of oil containing brine from an oil well, admixing the first feed stream with a second feed stream of water, and then sending the oil, brine and water admixture to a vessel. This vessel, sometimes referred to as a settler or a desalter, provides a period of low agitation during which the lighter oil phase rises to the top of the vessel and the heavier water diluted brine phase sinks to the bottom of the vessel. The resulting oil layer is drawn off through a first vessel outlet and further processed while the diluted brine layer is drawn off through a second vessel outlet and either recycled; treated to remove solids and water soluble liquids, and discarded; or combinations thereof.

The present invention is particularly useful with processes using electrical eduction. For purposes of the present invention, electrical eduction is the process whereby an electric potential is placed across a non-polar non-conducting liquid, the non- polar liquid having inclusions of micro-droplets of a polar liquid, the electric potential serving to induce coalescence of the micro-droplets into droplets large enough to efficiently separate from the non-polar liquid. In electrical eduction processes, formation of a rag phase can be a problem because the eduction preferably takes place near the interface of the liquids which is where the rag phase forms. As a rag phase accumulates, it can move into the eduction electrodes and reduce the efficiency of the eduction process. In extreme cases, if the rag phase is sufficiently conductive, it can conduct a current between the electrodes that renders the eduction process ineffective.

For these reasons, it is preferable to practice eduction in separation apparatus that control and stabilize rag phase development and location.

One aspect of the present invention is the removal of a stream of a rag phase material formed during the separation of two resolvable liquids. In the present invention, the removal is accomplished using an aspirator. The aspirator inlet is located within a vessel used to accomplish the separation such that the inlet is at the preferred level at which to maintain a rag phase. In one preferred embodiment of the present invention, multiple aspirator inlets are placed within the vessel such that streams are removed from the desired level for a rag phase and at levels above, below or both above and below the desired rag phase layer. Such a multiple aspirator inlet configuration can facilitate the maintenance of a stable level of a rag phase.

Facilitating a stable level for a rag phase in a separation is an important part of the present invention. One skilled in the art of building devices for separating liquids will design the vessels used to do the separation such that the shapes and volumes of the vessels are optimized to achieve the best separation possible. One aspect of this design process is calculating approximately how long, under the anticipated operating conditions, it will take to achieve a separation so that an optimal ratio of liquids could be fed into the separation apparatus. If a rag phase in a separation apparatus were allowed to increase unchecked, it could cause the ratio of the phases to become so skewed from the optimal ratio as to reduce the efficiency of the separation, or taken to extreme, render the separation device ineffective when one phase is carried over into a stream intended to be a product stream of the other phase.

An embodiment of the present invention having multiple aspirator inlets located at several levels within a separation vessel can facilitate a stable rag phase level by

drawing rag phase material away from not just the anticipated level of the rag phase, but also the levels above and below the desired rag phase level. During periods of"upset," wherein fluctuation in the chemical makeup of the resolvable liquids or variability in the operating conditions of a separation apparatus reduces the efficiency of the separation device, rag phases can increase in volume, change level or both. If the rag phase increases in volume, then as the level of the interface of the rag phase passes the other aspirator inlets, the volume of rag phase being removed would increase thereby delaying or stopping the rag phase volume increase. Change in the level of the rag phase similarly would move the rag phase interface past another inlet and at least postpone having the rag phase move into a product stream. By monitoring the composition of the multiple aspirator inlets, an early warning of an upset could be received when a stream that normally does not include rag phase material starts showing rag phase material.

Such monitoring can be done visually or electronically.

The present invention includes an aspirator outlet through which a stream of rag phase material is recycled back into a separation apparatus. In the practice of the present invention, the aspirator outlet can be located at any location within the separation apparatus upstream from the point at which the materials to be separated are dispersed within the separation apparatus. For example, in an application wherein an electric pumps pulls from a supply of a first resolvable liquid and a supply of a second resolvable liquid and the liquids are admixed by the impeller of the pump, the outlet for the aspirator is preferably upstream of the pump, but it could also be downstream subject to the condition that there would be sufficient mixing downstream of the pump that the rag phase material would be dispersed within the mixture prior to the admixture being dispersed within the separation apparatus.

The process of the present invention is useful for reducing the volume of a rag phase in a separation process because part of the extant rag layer is removed and dispersed within new feed to the separation apparatus. When rag phase material is dispersed, it does not all reform as slow to resolve liquids. For example, if 50 ml of a first liquid are admixed with 50 ml of a second liquid and allowed to separate under the force of gravity, the resultant product may be 49 ml of a first phase and 49 ml of a second phase and 2 ml of a rag phase. If the two ml of rag phase material were carefully removed and dispersed within an admixture of 50 additional mi of both liquids that was then allowed to separate, it is very unlikely that there would be 4 ml of rag phase material present. It is much more likely that there would be only 2 ml of rag phase material present.

Mixing of the two resolvable liquids in the practice of the present invention can be done by any means known to one of ordinary skill in the art of separating resolvable liquids. For example, the impeller of a pump can be used as an mixer. Static mixers can also be used with the process of the present invention. Care should be taken that these methods of mixing and any other low shear method of mixing used with the present invention can achieve a sufficient dispersal of the two resolvable liquids in the applications to which they are applied. Electrical mixers can be used with the process of the present invention, but in many applications the energy costs of such mixers are prohibitive. In some instances turbulence from pumping the resolvable liquids afterthey have been combined in the same line may even be sufficient. Preferably, the mixers used with the practice of the present invention are energy efficient homogenizing mixers such as those disclosed in U. S. Patent No. 6,106,145 to Winslow, but any mixing device or process which can effectively disperse one resolvable liquid within another can be used with the present invention.

While mixing of two resolvable liquids is a step in the process of the present invention, it is recognized that, in some applications, the two resolvable liquids will be first acquired or seen by one practicing the invention already admixed. For example, in oil and gas production, oil will nearly always have some amount of brine co-produced with it as both oil and brine are nearly always co-resident in oil producing formations. It is the intention of the applicant that this mixing which occurs in situ and as oil is produced is within the scope of the mixing element of the claims.

4. Brief Description of the Drawings For a detailed understanding of the present invention, reference should be made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: Figure 1 is a schematic illustration of an apparatus for separating oil and brine according to the method of the present invention.

Figure 2 is a schematic illustration of an emulsion distribution head useful with the process of the present invention.

Figure 3 is a schematic illustration showing a section of the emulsion distribution head from Figure 2.

Figure 4 is a schematic illustration of an alternative embodiment of an apparatus for separating oil and brine according to the method of the present invention.

It will be appreciated that the figures are not necessarily to scale and the proportions of certain features are exaggerated to show detail.

5. Detailed Description of the Preferred embodiments Figure 1 is a schematic illustration of an apparatus for separating oil and brine according to one embodiment of the method of the present invention. In this illustration, oil from an oil source, which may have some brine already in it, (101) and brine from a brine source (102) pass through check valves (150 and 151) and through lines (133 and 134), coming together at a header (130) which includes a pump (120) which feeds to a vessel (103). Mixing of the brine and oil begins in the header (130) due to turbulence and the two liquids are further admixed mechanically by the action of the pump impeller when passing through the pump (120). In a preferred embodiment, the pump (120) also includes a homogenizing mixer (not shown).

The header (130) passes through the vessel (103) and attaches at the inlet of an emulsion distribution head (104). The oil and brine admixture, hereinafter referred to as the"emulsion", passes through the body of the emulsion distribution head (not detailed in this illustration), exits the emulsion distribution head through an outlet (not detailed in this illustration), and is distributed into the oil phase layer (105) where most of the emulsion separates into an oil phase which is comparatively low in density and a brine phase which is comparatively high in density. The newly separated oil phase integrates into the oil phase layer (105), but the heavier brine phase falls through the oil phase and is integrated into the brine phase layer (106).

The remaining emulsion, which is slow to resolve, is intermediate in density and falls to and is integrated into the rag phase layer (107). The emulsion distribution head (104) includes an aspirator inlet (not detailed in this illustration) which removes a stream of rag phase material using the aspiration force cause by the flow velocity of the emulsion within the emulsion distribution head body (not detailed in this illustration) where it is admixed with emulsion as it exits the aspirator through the aspirator outlet (not detailed in this illustration). The flow velocity of the emulsion within the emulsion distribution head (104) is sufficiently high that the resulting turbulence substantially disperses the rag phase material into the emulsion.

Comparatively dry oil is removed from the vessel (103) through the upper outlet (161) into the oil outlet line (131) and fed to a pump (121) and pumped on for further processing. Brine is removed from the vessel (103) through the lower outlet (162) into the brine outlet line (132) that feeds into a pump (122) that pumps the brine to a valve

(140). The valve (140) can be controlled such that the brine can be recycled via a recycle line (135), treated for disposal via a waste water line (136), and combinations thereof.

Figure 2 is a schematic illustration of an emulsion distribution head (104) useful with the process of the present invention. A water and oil emulsion (207) enters the emulsion distribution head (104) by means of an inlet (201) and passes into and through the riser (205) and exits through the four outlets (202,202A, 202B, and 206). A stream of rag phase material (204) is removed from the rag phase layer (107) by means of an aspirator inlet (203). The stream of rag phase material (204) is aspirated into the emulsion (207) within a emulsion distribution head outlet (206) through an aspirator outlet (not shown).

Figure 3 is a schematic illustration showing a section of the emulsion distribution head from Figure 2. This figure is an expanded view of section H in Figure 2. This illustration shows the emulsion (207) in the emulsion distributor head outlet (206) passing by and causing an aspiration force on the aspirator outlets (301 and 301A). Recycled rag phase material (204) is drawn into and dispersed within the emulsion (207) as it leaves the distributor head outlet (206).

Figure 4 is a schematic illustration of an alternative embodiment of an apparatus for de-salting crude oil according to the method of the present invention. Several elements of this illustration are common with the elements in Figure 1 and Figure 2 and for convenience have been assigned the same number designations. The process of this embodiment is substantially identical to that of Figure 1 except that: (A) the aspirator inlet (203) is not a part of the emulsion distribution head (104), (B) the recycled rag phase material exits the aspirator though an aspirator outlet (402) into the emulsion header (130), and (C) the recycled rag phase material passes through a visual inspection port or a conductivity meter (401).

Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the inventions and should not be construed to limit scope of the claims thereof.