CA2148704A1 - Desalter solvent extraction system - Google Patents
Desalter solvent extraction systemInfo
- Publication number
- CA2148704A1 CA2148704A1 CA002148704A CA2148704A CA2148704A1 CA 2148704 A1 CA2148704 A1 CA 2148704A1 CA 002148704 A CA002148704 A CA 002148704A CA 2148704 A CA2148704 A CA 2148704A CA 2148704 A1 CA2148704 A1 CA 2148704A1
- Authority
- CA
- Canada
- Prior art keywords
- desalter
- aqueous phase
- phase
- organic components
- fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G31/00—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for
- C10G31/08—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for by treating with water
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
- B01D17/02—Separation of non-miscible liquids
- B01D17/0205—Separation of non-miscible liquids by gas bubbles or moving solids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
- B01D17/02—Separation of non-miscible liquids
- B01D17/0208—Separation of non-miscible liquids by sedimentation
- B01D17/0214—Separation of non-miscible liquids by sedimentation with removal of one of the phases
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/26—Treatment of water, waste water, or sewage by extraction
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G33/00—Dewatering or demulsification of hydrocarbon oils
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G33/00—Dewatering or demulsification of hydrocarbon oils
- C10G33/06—Dewatering or demulsification of hydrocarbon oils with mechanical means, e.g. by filtration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/32—Hydrocarbons, e.g. oil
Abstract
An improvement in crude oil refining is disclosed wherein a desalter (50) is operated so as to produce an organics phase (12) of reduced salts content ready for feeding to a distillation step and an aqueous phase of high salts content. By withdrawing the organics phase (14) from a higher level relative to the rag layer in said desalter (50) and after a relatively longer residence time than in conventional desalting operations, substantially little if any of the rag layer's content from the desalter (50) is included in the withdrawn organics phase (12) and the latter is suitable for feed to a distillation step (64). The resulting heavily organics-contaminated aqueous phase is mixed with an extractant comprising a gas converted to a solvent-condition fluid state under critical or near-critical temperature and pressure conditions to provide substantially organics-free waste water (26) suitable for discharge and to form a fluid extract of organics (32) from which benzene and other oil fractions can be recovered.
Description
f O,;,'';'!W0 94/16033 2 ~ 7 n '1 PCT/US94100347 -- 1 -- ;.. -~, - DESALTER SOLVENT EXTRACTION SYSTEM
The present invention relates generally to a process for treating crude oil as 2 part of an oil refining p~ocess and, more particularly, for improving the desalting 3 operation by employing a secondary processing step wherein the aqueous phase 4 withdrawn from the desalter is processed tO remove substantially all organics prior 5 to discharge as wastewater.
The present invention relates generally to a process for treating crude oil as 2 part of an oil refining p~ocess and, more particularly, for improving the desalting 3 operation by employing a secondary processing step wherein the aqueous phase 4 withdrawn from the desalter is processed tO remove substantially all organics prior 5 to discharge as wastewater.
6 It is well known in the oil refining art to employ a desalting step for 7 separating certain solids and water soluble components, especially brine, from the 8 crude oil. Such a desalting process is described, for example, in U.S. Pat. Nos.
9 3,798,153 (Arndt e~ al.) and 4,684,457 (McKechnie et al.). Typically in the 10 desalting operation, fresh water or a low-salinity brine is added to a stream of crude 11 oil, the combined stream is mixed and heated to a temperature of about 250-300 12 F, and the heated mixture is fed to a desalter tank. By action of gravity, sometimes 13 aided by electrical means, the mixture in the desalter tank separates into a lighter, 14 oil layer with a reduced salt content and a heavier, aqueous layer contaminated with 15 salts, solids and hydrocarbon components. The oil phase can be continuously 16 withdrawn from the upper region of the desalter tank to maintain steady-state 17 conditions while the contaminated aqueous phase is continuously bled from the lower 18 region of the desalter. As noted in the aforementioned Arndt et al. patent, the 19 desalting step is typically carried out at an elevated temperature to increase the 20 efficiency of the separation of brine from oil, while heat-exchanger fouling is 21 red~lced by removing salts before the oil is heated much above 300 F.
22 The oil and aqueous phases in the desalter, however, do not form a clean, 23 sharp boundary. Instead, the two phases are typically separated by so-called "rag"
24 layers comprising brine and solids emulsified with oil. Moreover, these rag layers 2s do not remain stationary but have an undesirable tendency to wander, thereby 2 6 reducing the efficiency and effectiveness of the desalting operation. To insure good 27 separation and to avoid contaminating the oil phase with contents of the rag layers, 28 the oil phase must be drawn from a point well above the rag layers and at a 29 controlled rate. In conventional processing, some of the desalter rag layers are S'JBSTITUTE SHEEl WO 94/16033 PCT/IJ594/00347 i~
-2- 1 .
either treated by high chemical addition or are passed along with the aqueous phase 2 or the oil phase, thereby requiring expensive downstream processing.
3 Another problem with the conventional desalting operation is that the aqueous 4 phase withdrawn from the bottom of the desalter typically contains a significant proportion of dissolved or entrained organic components. These organic components - 6 may include boih certain lighter petroleunl fractions, such as benzene, as well a~
7 heavier hydrocarbons. Recovery of these organic components is desirable not only 8 because of their economic value but, in addition, because discharge or disposal of g such contaminated water is ecologically detrimental and may be illegal.
Thus, it is conventional to subject the aqueous phase withdrawn from the 11 desalter to downstream treatment to remove most of the organic components and to 12 render the brine suitable either for disposal or recycling. The aforementioned 13 McKechnie et al. patent, for example, describes a cross-flow membrane separator 14 process for treating the oil-containing brine withdrawn from a desalter. While it is 15 known, as taught by U.S. Patent No. 4,568,447 (Pujado) to employ a solvent in the 6 supercritical state for the removal of trace quantities of organic compounds from an 17 aqueous stream, such a process has not been used for downstream processing of the 18 aqueous phase coming from a desalter, nor would such treatment, by itself, solve the 19 problems of an inefficient desalter operation and a partially contaminated oil phase 2 o feedstock from the desalter.
21 Another problem with the conventional desalting operation is that, in order 22 to achieve reasonable cost-effectiveness, the rag layer is maintained at a relatively 23 fixed level and the oil phase is withdrawn at such a rate that the oil phase still 24 contains enough remaining brine to cause downstream processing problems unless 25 that brine level is further reduced by additional treatment. Accordingly, it is well 26 known to subject the oil phase coming from the desalter to addidonal processing 27 prior to the flashing, furnace and disdllation steps of a conventional oil refining 28 operation. The aforementioned Arndt et al. patent, for example, describes heating 2 9 pa~tially desalted oil by injecting a hot fluid into the partially desalted oil 3 o immediately prior to the flashing step. This process substitutes for heating the oil 31 phase by the more conventional means of a heat exchanger, which would be subject . 32 to heavy fouling by the salts remaining in the partially desalted oil. While it is ` s WO 94/16033 2 1 ~ $~ 7 ~ li PCTIUS9410û347 known, as taught by U.S. Pat. Nos. 4,522,707 (Kriegel et al.) and 4,797,198 2 (Wetzel et al.) to treat used or salvage oil with a gas under supercri~ical conditions 3 as part of a purification and reconditioning operation, such a process has not been 4 used for downstream processing of the oil phase from a desalter, nor would such treatment, by itself, solve the problems of an inefficient desalter operation and a 6 contaminated aqueous phase raffinate.
7 These and other problems with and limitations of the prior art desalting and 8 refining operations are overcome ~,vith the desalter solvent extraction system of this g invention. Specifically, the system of this invention improves the efficiency of the 10 desalter operation, eliminates the need for secondary treatment of the oil phase feedstock prior to distillation, and provides a less-contaminated aqueous phase at 12 lower cost than conventional secondary treatment for the aqueous phase raffinate 13 from a desalter.
14 Accordingly, it is a general object of this invention to provide a more15 efficient and effective crude oil refining process.
6 Another general object of this invention is to improve the efficiency and 7 effectiveness of the desalter operation in crude oil refining.
8 Another object of this invention is to provide from a desalter an oil phase 19 sufficiently free of brine and other contaminants so that deposition of such 2 o contaminants in the crude preheating tower is minimized.
21 It is also an object of this invention to provide an oil phase from the desalter 22 sufficiently free of brine and other contaminants that it can be fed directly to a 2 3 distillation step without secondary processing.
2 4 A further object of this invention is to reduce the loss of organic components in the aqueous phase raffinate from the desalter.
2 6 Still another object of this invention is to provide an aqueous phase raffinate 2 7 sufficiently free of contaminants that it can be discharged as waste water.
28 Specifically, it is an object of this invention to provide a desalter treatment 2 9 process so efficient and effective as to provide an aqueous phase withdrawn from the 3 0 desalter leaving a substantially salt and brine-free oil phase feedstock.
31 These and other objects and advantages of this invention will be better32 understood from the following description, which is to be read together with the 2 1 4 8 7 f~ 1 ~r ~/ 4 accompanying drawing wherein there is an illustrative flow diagram of a desalter2 train incorporating the desalter solvent extraction system of this invention.3 Generally, the present invention comprises a method of processing a 4 feedstock of crude oil containing water and salts, and involves the usual prior art s step of desalting the feedstock by mixing with water followed by separation into an - 6 organic component-c~ntaining phase of reduc~ salts content and an aqueous phase 7 containing a major portion of the salts. The aqueous phase is then mixed with an 8 extractant fluid that is a gas under standard ambient conditions of temperature and g pressure, but which is under such conditions of temperature and pressure as tolO render it a fluid solvent for the organic components, but substantially less for water, thus forming a fluid extract of the organics in the extractant fluid and a raffinate 12 comprising water and salts. The fluid extract is then separated from the raffinate to 13 leave an aqueous salt solution substantially free of the organic components.
14 Referring now to the drawing, there is shown a typical embodiment of 15 apparatus for effecting the method of the present invenbon where, as in the 16 conventional desalting operation, inlet stream of raw crudc oil in conduit lO is mixed 7 with a water stream in conduit 34 and fed to desalter tank S0. To facilitate 18 sq~ on, the crude oil feed is pre-treated by adding additional watertbrine, or by 19 heabng to about 250-300F, or both, as described in U.S. Pat. No.3,798,153 20 (Arndt et al.). An oil phase stream is continuously withdrawn through conduit l2 21 from the upper region of desalter 50, and an aqueous phase stream is continuously 2 2 withdrawn through conduit 14 from the lower region of the desalter. Compared with 23 conventional desalting processes, however, for purposes of this invention the rag 24 layer (shown schematically as a dashed line in tank 50) is maintained at a relatively 2s lower level, thereby avoiding drawing substantially any of the rag layers content into 26 the oil phase stream, the rag layer being drawn out separately through conduit 36 2 7 into the aqueous phase or together with the aqueous phase.
28 In the preferred embodiment of this invention, the rag layer level and29 withdrawal rate are selected to achieve an oil phase that can be sufficiently free of 3 o brine, solids and otber contaminants so as to provide a suitable feedstock to be fed 31 directly to a distillation step, for exarnple carried out in distillation column 64, 3 2 without secondary purification, as required for example in the Arndt et al. patent.
~. 21~87nA- ~
i` `' WO 94/16033 PCT/US94/00347 --5 ~
Similar to any unit operation~ there is a trade-off between the quality of oi]
2 phase stream in conduit 12 and contamination of aqueous phase stream in conduil 14.
3 More particularly, by withdrawing the oil phase stream from desalter 50 at a 4 relatively lower rag layer level and following a longer residence time as compared 5 with conventional desalting processes, the requirement of steady-state conditions 6 necessitates withdrawing the aqueous phase stream through conduit 14 following a 7 relatively shorter residence time. Just as the relatively longer residence time of the 8 oil phase 12 leads to a less-contaminated oil phase, the relatively shorter residence g time of the aqueous phase stream from the desalter leads to a more contaminated 0 aqueous phase, perhaps including some or all of the so-called "rag" layers. ln other 11 words, in accordance with the present invention, the desalter is intentionally operated 12 to optimize the quality of the oil phase feedstock at the expense of wastewater 13 quality. Conduit 14 is connected to feed extractor 52 through valve 15 for secondary 14 treatment. Alternatively, a rag layer stream is withdrawn through conduit 36 15 separately from the aqueous stream and is sent to solvent extraction system 52 16 through valve 37. The aqueous phase withdrawn from tank 50, being substantially 17 cleaner, can then be sent to conventional downstream treatment by operating valve 18 15 to divert the stream to conduit 17.
19 ~ctractor 52 comprises a sealed, pressurized mixing tank, preferably a liquid-2 o liquid contacting tower, of suitable construction to withstand processing conditions.
21 lnside extractor 52, the aqueous stream from conduit 14 is mixed with a stream, 22 introduced through conduit 16, of a suitable extractant fluid that is a gas under 23 standard ambient conditions of temperature and pressure. The extractant fluid, 24 however, is under such conditions of temperature and pressure as to render it a fluid 25 solvent for the organic components carried over in the aqueous phase stream, but 2 6 substantially less for water. Treatment with this extractant fluid forms a fluid extract 27- of the organic components and a brine raffinate. The stream of the extractant fluid 28 may comprise a combination of recycled extractant, as hereinafter described, and a 29 stream of make-up extractant as needed carried along conduit 20 from extractant 3 o make-up pump tank S4 and pumped into conduit 16.
31 As discussed in U.S. Pat. No. 4,147,624 (Modell) and No. 4,349,415 32 (DeFilippi et al.), which are incorporated herein by reference, a large number of 21ll87gl~
r gaseous compounds have been recognized to have solvent properties when converted2 to a fluid or fluid-like state. Such compounds, which are gases at ambient 3 temperature and pressure, but which can be converted to a solvent-condition fluid 4 state, include: hydrocarbons such as methane, ethane, propane, butane, ethylene, and s propylene; halogenated hydrocarbons such as halomethanes and haloethanes; and 6 inorganics such as carbon dioxide, ammonia, sulfur dioxide, nitrous oxide, hydrogen 7 chloride, and hydrogen sulfide; and chemically compatible mixtures of two or more 8 of the foregoing compounds.
g Bxtractor 52 may be operated in any way that insures thorough mixing of lo aqueous phase stream from conduit 14 and extractant stream from conduit 16, for 11 example a countercurrent process, such that substantially all of the oil and other 12 organic components of the aqueous phase are dissolved in the extractant and a two-13 phase system is formed. The aqueous phase in extractor 52, comprising water, undissolved solids and some extractant fluid, is continuously withdrawn from the5 extractor through conduit 22 through a pressure-reducing valve 5S. The pressure-16 reduced stream in conduit 22 is directed into water separator 56 where, because of 17 a reduced pressure, residual extractant forms a vapor phase which is bled off through 18 line 24 and fed to vapor tank 58. A substantially clean waste water stream in line 19 26, suitable for discharge, is withdrawn from separator 56.
2 o The organic extractor `phase, comprising extractant fluid and dissolved 21 organics, is continuously withdrawn from extractor 52 through conduit 28 through 22 pressure-reducing valve 60. The pressure-reduced stream in conduit 28 is directed 23 into organics separator 62 where, because of a reduced pressure and heat, the24 extractant fluid is flashed off to forrn a vapor phase which, in turn, is bled off 25 through line 30 to vapor tank 56. The separated organic components form a liquid 26 phase in separator 62, which liquid phase is withdrawn through line 32 and typically 27 can be returned to join the crude oil feedstock conduit 10 to desalter tank 50. The 28 extractant vapors in vapor tank 58 are condensed and the extractant is then recycled 29 through line 18 to join line 16 feeding extractor 52.
3 o The extraction system of this invention results in numerous improvements and 31 efficiencies as compared with conventional refining operations. Some of the major 3 2 advantages that are realized by incorporating the extraction system of this invention t~.~ 21 L`C ~3 7 ~
` X; WO 94/16033 PCT/US94/00347 -7~
into a refinery desalter opera~ion include the following: (1) It allows desalter2 operations to be optimized on crude quality alone; this results in improved quality 3 of desalted crude, and increased crude utilization. (2) It produces wastewater with 4 an oil content in the 5-10 ppm range and a benzene content in the 10-500 ppb range.
5 (3) A major process source of both oil and solids to the waste treatment system is 6 nearly eiiminated, thus reducing the treatment and disposal costs as well as reducing 7 long-term liabilities associated with disposal of oily solids~ (4) It will increase 8 refinery on-line time by reducing fouling of equipment. (5) The solvent extraction g system has the capability of treatmg other pumpable refinery wastes, such as slop 10 oil, to recover organics, minimi~e chemical consumption and eliminate some prior 11 art processes.
12 Since certain changes may be made in the above-described apparatuses and 13 processes without deparhng from the scope of the invention herein involved, it is 14 intended that all matter contained in the above description shall be interpreted in an 15 illustrative and not in a limiting sense.
-2- 1 .
either treated by high chemical addition or are passed along with the aqueous phase 2 or the oil phase, thereby requiring expensive downstream processing.
3 Another problem with the conventional desalting operation is that the aqueous 4 phase withdrawn from the bottom of the desalter typically contains a significant proportion of dissolved or entrained organic components. These organic components - 6 may include boih certain lighter petroleunl fractions, such as benzene, as well a~
7 heavier hydrocarbons. Recovery of these organic components is desirable not only 8 because of their economic value but, in addition, because discharge or disposal of g such contaminated water is ecologically detrimental and may be illegal.
Thus, it is conventional to subject the aqueous phase withdrawn from the 11 desalter to downstream treatment to remove most of the organic components and to 12 render the brine suitable either for disposal or recycling. The aforementioned 13 McKechnie et al. patent, for example, describes a cross-flow membrane separator 14 process for treating the oil-containing brine withdrawn from a desalter. While it is 15 known, as taught by U.S. Patent No. 4,568,447 (Pujado) to employ a solvent in the 6 supercritical state for the removal of trace quantities of organic compounds from an 17 aqueous stream, such a process has not been used for downstream processing of the 18 aqueous phase coming from a desalter, nor would such treatment, by itself, solve the 19 problems of an inefficient desalter operation and a partially contaminated oil phase 2 o feedstock from the desalter.
21 Another problem with the conventional desalting operation is that, in order 22 to achieve reasonable cost-effectiveness, the rag layer is maintained at a relatively 23 fixed level and the oil phase is withdrawn at such a rate that the oil phase still 24 contains enough remaining brine to cause downstream processing problems unless 25 that brine level is further reduced by additional treatment. Accordingly, it is well 26 known to subject the oil phase coming from the desalter to addidonal processing 27 prior to the flashing, furnace and disdllation steps of a conventional oil refining 28 operation. The aforementioned Arndt et al. patent, for example, describes heating 2 9 pa~tially desalted oil by injecting a hot fluid into the partially desalted oil 3 o immediately prior to the flashing step. This process substitutes for heating the oil 31 phase by the more conventional means of a heat exchanger, which would be subject . 32 to heavy fouling by the salts remaining in the partially desalted oil. While it is ` s WO 94/16033 2 1 ~ $~ 7 ~ li PCTIUS9410û347 known, as taught by U.S. Pat. Nos. 4,522,707 (Kriegel et al.) and 4,797,198 2 (Wetzel et al.) to treat used or salvage oil with a gas under supercri~ical conditions 3 as part of a purification and reconditioning operation, such a process has not been 4 used for downstream processing of the oil phase from a desalter, nor would such treatment, by itself, solve the problems of an inefficient desalter operation and a 6 contaminated aqueous phase raffinate.
7 These and other problems with and limitations of the prior art desalting and 8 refining operations are overcome ~,vith the desalter solvent extraction system of this g invention. Specifically, the system of this invention improves the efficiency of the 10 desalter operation, eliminates the need for secondary treatment of the oil phase feedstock prior to distillation, and provides a less-contaminated aqueous phase at 12 lower cost than conventional secondary treatment for the aqueous phase raffinate 13 from a desalter.
14 Accordingly, it is a general object of this invention to provide a more15 efficient and effective crude oil refining process.
6 Another general object of this invention is to improve the efficiency and 7 effectiveness of the desalter operation in crude oil refining.
8 Another object of this invention is to provide from a desalter an oil phase 19 sufficiently free of brine and other contaminants so that deposition of such 2 o contaminants in the crude preheating tower is minimized.
21 It is also an object of this invention to provide an oil phase from the desalter 22 sufficiently free of brine and other contaminants that it can be fed directly to a 2 3 distillation step without secondary processing.
2 4 A further object of this invention is to reduce the loss of organic components in the aqueous phase raffinate from the desalter.
2 6 Still another object of this invention is to provide an aqueous phase raffinate 2 7 sufficiently free of contaminants that it can be discharged as waste water.
28 Specifically, it is an object of this invention to provide a desalter treatment 2 9 process so efficient and effective as to provide an aqueous phase withdrawn from the 3 0 desalter leaving a substantially salt and brine-free oil phase feedstock.
31 These and other objects and advantages of this invention will be better32 understood from the following description, which is to be read together with the 2 1 4 8 7 f~ 1 ~r ~/ 4 accompanying drawing wherein there is an illustrative flow diagram of a desalter2 train incorporating the desalter solvent extraction system of this invention.3 Generally, the present invention comprises a method of processing a 4 feedstock of crude oil containing water and salts, and involves the usual prior art s step of desalting the feedstock by mixing with water followed by separation into an - 6 organic component-c~ntaining phase of reduc~ salts content and an aqueous phase 7 containing a major portion of the salts. The aqueous phase is then mixed with an 8 extractant fluid that is a gas under standard ambient conditions of temperature and g pressure, but which is under such conditions of temperature and pressure as tolO render it a fluid solvent for the organic components, but substantially less for water, thus forming a fluid extract of the organics in the extractant fluid and a raffinate 12 comprising water and salts. The fluid extract is then separated from the raffinate to 13 leave an aqueous salt solution substantially free of the organic components.
14 Referring now to the drawing, there is shown a typical embodiment of 15 apparatus for effecting the method of the present invenbon where, as in the 16 conventional desalting operation, inlet stream of raw crudc oil in conduit lO is mixed 7 with a water stream in conduit 34 and fed to desalter tank S0. To facilitate 18 sq~ on, the crude oil feed is pre-treated by adding additional watertbrine, or by 19 heabng to about 250-300F, or both, as described in U.S. Pat. No.3,798,153 20 (Arndt et al.). An oil phase stream is continuously withdrawn through conduit l2 21 from the upper region of desalter 50, and an aqueous phase stream is continuously 2 2 withdrawn through conduit 14 from the lower region of the desalter. Compared with 23 conventional desalting processes, however, for purposes of this invention the rag 24 layer (shown schematically as a dashed line in tank 50) is maintained at a relatively 2s lower level, thereby avoiding drawing substantially any of the rag layers content into 26 the oil phase stream, the rag layer being drawn out separately through conduit 36 2 7 into the aqueous phase or together with the aqueous phase.
28 In the preferred embodiment of this invention, the rag layer level and29 withdrawal rate are selected to achieve an oil phase that can be sufficiently free of 3 o brine, solids and otber contaminants so as to provide a suitable feedstock to be fed 31 directly to a distillation step, for exarnple carried out in distillation column 64, 3 2 without secondary purification, as required for example in the Arndt et al. patent.
~. 21~87nA- ~
i` `' WO 94/16033 PCT/US94/00347 --5 ~
Similar to any unit operation~ there is a trade-off between the quality of oi]
2 phase stream in conduit 12 and contamination of aqueous phase stream in conduil 14.
3 More particularly, by withdrawing the oil phase stream from desalter 50 at a 4 relatively lower rag layer level and following a longer residence time as compared 5 with conventional desalting processes, the requirement of steady-state conditions 6 necessitates withdrawing the aqueous phase stream through conduit 14 following a 7 relatively shorter residence time. Just as the relatively longer residence time of the 8 oil phase 12 leads to a less-contaminated oil phase, the relatively shorter residence g time of the aqueous phase stream from the desalter leads to a more contaminated 0 aqueous phase, perhaps including some or all of the so-called "rag" layers. ln other 11 words, in accordance with the present invention, the desalter is intentionally operated 12 to optimize the quality of the oil phase feedstock at the expense of wastewater 13 quality. Conduit 14 is connected to feed extractor 52 through valve 15 for secondary 14 treatment. Alternatively, a rag layer stream is withdrawn through conduit 36 15 separately from the aqueous stream and is sent to solvent extraction system 52 16 through valve 37. The aqueous phase withdrawn from tank 50, being substantially 17 cleaner, can then be sent to conventional downstream treatment by operating valve 18 15 to divert the stream to conduit 17.
19 ~ctractor 52 comprises a sealed, pressurized mixing tank, preferably a liquid-2 o liquid contacting tower, of suitable construction to withstand processing conditions.
21 lnside extractor 52, the aqueous stream from conduit 14 is mixed with a stream, 22 introduced through conduit 16, of a suitable extractant fluid that is a gas under 23 standard ambient conditions of temperature and pressure. The extractant fluid, 24 however, is under such conditions of temperature and pressure as to render it a fluid 25 solvent for the organic components carried over in the aqueous phase stream, but 2 6 substantially less for water. Treatment with this extractant fluid forms a fluid extract 27- of the organic components and a brine raffinate. The stream of the extractant fluid 28 may comprise a combination of recycled extractant, as hereinafter described, and a 29 stream of make-up extractant as needed carried along conduit 20 from extractant 3 o make-up pump tank S4 and pumped into conduit 16.
31 As discussed in U.S. Pat. No. 4,147,624 (Modell) and No. 4,349,415 32 (DeFilippi et al.), which are incorporated herein by reference, a large number of 21ll87gl~
r gaseous compounds have been recognized to have solvent properties when converted2 to a fluid or fluid-like state. Such compounds, which are gases at ambient 3 temperature and pressure, but which can be converted to a solvent-condition fluid 4 state, include: hydrocarbons such as methane, ethane, propane, butane, ethylene, and s propylene; halogenated hydrocarbons such as halomethanes and haloethanes; and 6 inorganics such as carbon dioxide, ammonia, sulfur dioxide, nitrous oxide, hydrogen 7 chloride, and hydrogen sulfide; and chemically compatible mixtures of two or more 8 of the foregoing compounds.
g Bxtractor 52 may be operated in any way that insures thorough mixing of lo aqueous phase stream from conduit 14 and extractant stream from conduit 16, for 11 example a countercurrent process, such that substantially all of the oil and other 12 organic components of the aqueous phase are dissolved in the extractant and a two-13 phase system is formed. The aqueous phase in extractor 52, comprising water, undissolved solids and some extractant fluid, is continuously withdrawn from the5 extractor through conduit 22 through a pressure-reducing valve 5S. The pressure-16 reduced stream in conduit 22 is directed into water separator 56 where, because of 17 a reduced pressure, residual extractant forms a vapor phase which is bled off through 18 line 24 and fed to vapor tank 58. A substantially clean waste water stream in line 19 26, suitable for discharge, is withdrawn from separator 56.
2 o The organic extractor `phase, comprising extractant fluid and dissolved 21 organics, is continuously withdrawn from extractor 52 through conduit 28 through 22 pressure-reducing valve 60. The pressure-reduced stream in conduit 28 is directed 23 into organics separator 62 where, because of a reduced pressure and heat, the24 extractant fluid is flashed off to forrn a vapor phase which, in turn, is bled off 25 through line 30 to vapor tank 56. The separated organic components form a liquid 26 phase in separator 62, which liquid phase is withdrawn through line 32 and typically 27 can be returned to join the crude oil feedstock conduit 10 to desalter tank 50. The 28 extractant vapors in vapor tank 58 are condensed and the extractant is then recycled 29 through line 18 to join line 16 feeding extractor 52.
3 o The extraction system of this invention results in numerous improvements and 31 efficiencies as compared with conventional refining operations. Some of the major 3 2 advantages that are realized by incorporating the extraction system of this invention t~.~ 21 L`C ~3 7 ~
` X; WO 94/16033 PCT/US94/00347 -7~
into a refinery desalter opera~ion include the following: (1) It allows desalter2 operations to be optimized on crude quality alone; this results in improved quality 3 of desalted crude, and increased crude utilization. (2) It produces wastewater with 4 an oil content in the 5-10 ppm range and a benzene content in the 10-500 ppb range.
5 (3) A major process source of both oil and solids to the waste treatment system is 6 nearly eiiminated, thus reducing the treatment and disposal costs as well as reducing 7 long-term liabilities associated with disposal of oily solids~ (4) It will increase 8 refinery on-line time by reducing fouling of equipment. (5) The solvent extraction g system has the capability of treatmg other pumpable refinery wastes, such as slop 10 oil, to recover organics, minimi~e chemical consumption and eliminate some prior 11 art processes.
12 Since certain changes may be made in the above-described apparatuses and 13 processes without deparhng from the scope of the invention herein involved, it is 14 intended that all matter contained in the above description shall be interpreted in an 15 illustrative and not in a limiting sense.
Claims (14)
[received by the International Bureau on 4 May 1994 (04.05.94);
original claims 2-4, 9 and 12 amended;
remaining claims unchanged (2 pages)]
What is claimed is:
1. Method of processing a feedstock of crude oil, water and salts, wherein said feedstock is separated in a desalter into an oil phase containing primarilyorganic components with a reduced salts content, and an aqueous phase containinga major portion of said salts and a portion of said organic components, together with a rag layer, said method comprising the steps of:
separately withdrawing said oil phase and said aqueous phase from said desalter;
processing said aqueous phase with an extractant fluid that is a gas under standard ambient conditions of temperature and pressure, but which is under suchconditions of temperature and pressure as to render said extractant fluid a solvent for the organic components in said aqueous phase, but substantially less for water, so as to form a fluid extract of said organic components from said aqueous phase in said extractant fluid and a raffinate comprising primarily water and said salts; and separating said fluid extract from said raffinate to leave an aqueous solution substantially free of said organic components.
separately withdrawing said oil phase and said aqueous phase from said desalter;
processing said aqueous phase with an extractant fluid that is a gas under standard ambient conditions of temperature and pressure, but which is under suchconditions of temperature and pressure as to render said extractant fluid a solvent for the organic components in said aqueous phase, but substantially less for water, so as to form a fluid extract of said organic components from said aqueous phase in said extractant fluid and a raffinate comprising primarily water and said salts; and separating said fluid extract from said raffinate to leave an aqueous solution substantially free of said organic components.
2. Method as defined in claim 1 wherein said step of processing includes processing said aqueous phase and said rag layer.
3. Method as defined in claim 1 wherein the rag layer level in said desalter is disposed so as to avoid drawing substantially any of the content of said rag layer from said desalter into the withdrawn oil phase.
4. Method as defined in claim 3 wherein said level and the rate of withdrawal are selected to provide a withdrawn oil phase sufficiently free of said water and salts as to provide a suitable feedstock for direct feed to a distillation step.
5. Method as defined in claim 1 wherein said aqueous phase is withdrawn from said desalter without drawing substantial portions of said oil phase from said desalter into the withdrawn aqueous phase.
6. Method as defined in claim 1 wherein said rag layer is withdrawn from said desalter either with or separately from said aqueous phase.
7. Method as defined in claim 1 further including the step of flashing off said extractant fluid from said fluid extract to recover said organic components from said extract.
8. Method as defined in claim 7 further including the step of recycling said extractant fluid from the flashing step to the step of treating.
9. Method as defined in claim 7 further including the step of providing said organic components as feedstock to a distillation system.
10. Method as defined in claim 9 including the step of adding said recovered organic components to said feedstock.
11. Method as defined m claim 1 including the steps of adding other refinery waste streams to said withdrawn aqueous phase so that the combined aqueous phaseand refinery waste streams are treated together with said extractant fluid.
12. Method as defined in claim 1 wherein said extractant fluid is selected from the group consisting of hydrocarbons, halogenated hydrocarbons, carbon dioxide, ammonia, sulfur dioxide. nitrous oxide, hydrogen chloride, hydrogen sulfide, and chemically compatible mixtures thereof.
13. In a process of refining crude oil in a desalter in which a crude oil feedstock is separated into an organic phase containing primarily organic components and having a reduced salts content, a first aqueous phase containing a major portion of said salts and a portion of said organic components, and a rag layer being positioned between said organic phase and first aqueous phase, the improvement comprising:
so withdrawing said organic phase from said desalter as to avoid including substantially any of the contents of said rag layer in the withdrawn organic phase;
withdrawing said first aqueous phase from said desalter; and treating said first aqueous phase with an extractant fluid that is a gas under standard ambient conditions of temperature and pressure, but which is under suchconditions of temperature and pressure as to render said extractant fluid a solvent for the organic components in said first aqueous phase, but substantially less for water, so as to form a fluid extract of said organic components from said first aqueousphase in said extractant fluid, and a raffinate comprising primarily water and said salts and being substantially free of said organic components.
so withdrawing said organic phase from said desalter as to avoid including substantially any of the contents of said rag layer in the withdrawn organic phase;
withdrawing said first aqueous phase from said desalter; and treating said first aqueous phase with an extractant fluid that is a gas under standard ambient conditions of temperature and pressure, but which is under suchconditions of temperature and pressure as to render said extractant fluid a solvent for the organic components in said first aqueous phase, but substantially less for water, so as to form a fluid extract of said organic components from said first aqueousphase in said extractant fluid, and a raffinate comprising primarily water and said salts and being substantially free of said organic components.
14. In a process of refining crude oil in a desalter as defined in claim 13 including the step of withdrawing said rag layer either separately or together with said aqueous phase from said desalter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US240293A | 1993-01-08 | 1993-01-08 | |
| US002,402 | 1993-01-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2148704A1 true CA2148704A1 (en) | 1994-07-21 |
Family
ID=21700593
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002148704A Abandoned CA2148704A1 (en) | 1993-01-08 | 1994-01-10 | Desalter solvent extraction system |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2148704A1 (en) |
| WO (1) | WO1994016033A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2852557A1 (en) * | 2012-05-21 | 2015-04-01 | Solex Water Ltd. | Methods and systems for water recovery |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6066350A (en) * | 1997-02-07 | 2000-05-23 | Cargill Incorporated | Method and arrangement for processing cocoa mass |
| US8147678B2 (en) * | 2008-10-15 | 2012-04-03 | Bp Corporation North America Inc. | Devices and processes for deasphalting and/or reducing metals in a crude oil with a desalter unit |
| WO2012015666A2 (en) * | 2010-07-27 | 2012-02-02 | Conocophillips Company | Refinery desalter improvement |
| US20140317998A1 (en) * | 2013-04-30 | 2014-10-30 | Pall Corporation | Methods and systems for processing crude oil |
| US8981174B2 (en) | 2013-04-30 | 2015-03-17 | Pall Corporation | Methods and systems for processing crude oil using cross-flow filtration |
| US9499748B2 (en) | 2013-05-30 | 2016-11-22 | Exxonmobil Research And Engineering Company | Petroleum crude oil desalting process and unit |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8432278D0 (en) * | 1984-12-20 | 1985-01-30 | British Petroleum Co Plc | Desalting crude oil |
| US4568447A (en) * | 1985-07-29 | 1986-02-04 | Uop Inc. | Process for the removal of trace quantities of hydrocarbonaceous compounds from an aqueous stream |
-
1994
- 1994-01-10 WO PCT/US1994/000347 patent/WO1994016033A1/en active Application Filing
- 1994-01-10 CA CA002148704A patent/CA2148704A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2852557A1 (en) * | 2012-05-21 | 2015-04-01 | Solex Water Ltd. | Methods and systems for water recovery |
| CN104619649A (en) * | 2012-05-21 | 2015-05-13 | 索利克斯水有限公司 | Methods and systems for water recovery |
| EP2852557A4 (en) * | 2012-05-21 | 2015-06-03 | Solex Water Ltd | Methods and systems for water recovery |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1994016033A1 (en) | 1994-07-21 |
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