METHOD FOR REMOVING ASPHALTENES, RESINS AND HEAVY METALS FROM CRUDE OIL

Abstract

Presented is a method for using an ethyl acetate solvent to remove all or most of the asphaltenes, resins and heavy metals from crude oil. The oil is filtered to remove the precipitants and the permeate is then deasphalted oil, rich in ethyl acetate solvent. The ethyl acetate may be recovered by flashed solvent recovery system and recycled back. Filter elements are regenerated with toluene and recovered by a flashed solvent recovery system.

Claims

1. A method for removing asphaltenes, resins, and heavy metals from crude oil, comprising: adding a volume of crude oil into a mixing chamber; adding a volume of ethyl acetate into said mixing chamber, wherein said volume of ethyl acetate is at an approximate ratio to said volume of crude oil in a range from 1:1 to 4:1 to form a solution; mixing said solution until said solution is separated into precipitants and a permeate, wherein said precipitants comprise asphaltenes, resins, heavy metals, or a combination of asphaltenes, resins, and heavy metals, and wherein said permeate comprises deasphalted oil and said ethyl acetate; separating said precipitants from said permeate using a filter, wherein said filter has pores in the size in the range of 5 nm to 10 nm; and regenerating ethyl acetate from said permeate leaving deasphalted oil.

2. The method of claim 1, wherein said solution is at ambient temperature.

3. The method of claim 1, further comprising heating said solution to a temperature in the range of 80 F. to 130 F.

4. The method of claim 1, further comprising using said recovered ethyl acetate in additional iterations of the method of claim 1.

5. The method of claim 1, wherein said filter uses a ceramic membrane which can handle maximum pressure 10 bar and maximum temperature of 450 F.

6. The method of claim 5, wherein said filter is capable of being backwashed with a solvent and then said filter may be reused in additional iterations of the method of claim 1.

7. The method of claim 6, wherein said solvent is toluene.

8. The method of claim 7, wherein there are multiple of said filters.

9. The method of claim 8, wherein said filters comprise a first filter used in said separating step, and a secon filter used in said regenerating step.

10. The method of claim 3, wherein said filter is capable of being backwashed with a solvent and then said filter may be reused in additional iterations of the method of claim 1.

11. The method of claim 10, wherein said solvent is toluene.

12. The method of claim 11, wherein there are multiple of said filters.

13. The method of claim 12, wherein said filters comprise a first filter used in said separating step, and a second filter used in said regenerating step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a process flow diagram illustrating a method for using an ethyl acetate solvent for deasphalting of crude oil.

[0030] FIG. 2 is a flow chart illustrating a proposed ethyl acetate solvent deasphalting of atmospheric bottoms of Uinta Black waxy crude oil.

[0031] FIG. 3 is a flow chart illustrating an embodiment of the filtration system.

[0032] FIG. 4 illustrates an embodiment of an ultrafiltration membrane module.

[0033] FIG. 5 is a table of a saturates, aromatic, resin and asphaltenes (SARA) analysis report for black waxy Uinta crude oil.

[0034] FIG. 6 is a table of a SARA analysis report for atmospheric crude oil bottoms.

[0035] FIG. 7 is a table illustrating the results of a SARA analysis for both DAO and precipitant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0036]

TABLE-US-00001 Ref. Element A Ethyl Acetate Regeneration System B Toluene Regeneration System 10 Crude Oil 12 Crude Feed 14 Crude Feed Pump 16 Crude Feed Preheater 18 Desalter 20 Crude Furnace Heater 22 Steam 24 Atmosphere Crude Tower 26 Residue Mineral Spirits 28 Odorless Mineral Spirts 30 Kerosene 32 Diesel 34 Crude Bottoms 36 Crude Bottoms Pump 38 Mixer/Precipitator 40 Reflux Drum 42 Naphtha 44 Ethyl Acetate Makeup 46 Ethyl Acetate 48 Filtration System 50 EARS Heater 52 EARS Flash Drum 54 EARS Tower 56 Deasphalted Oil 58 Ethyl Acetate Reflux Cooler 60 Ethyl Acetate Reflux Drum 62 Ethyl Acetate Pump 70 Toluene Reflux Cooler 72 Toluene Reflux Drum 74 Toluene Pump 76 Precipitated Impurities 78 Toluene 100 Filter 102 Filter Membrane 104 Filtrate 106 Concentrate 108 Plugged Passageway 110A First End Slots 110B Second End Slots 112 Filter First End 114 Filter Second End

[0037] Referring to the figures, FIG. 1. illustrates a process flow diagram of a method for removing asphaltenes, resins and heavy metals from crude oil.

[0038] Crude oil 10 is pumped from a storage tank 12 into the system using crude feed pump 14. The crude oil 10 is preheated with a crude feed preheater 16. The temperature of the crude oil 10 may be controlled and set to a desired temperature range required for desalting by a cross exchanger 18. A cross-flow heat exchanger 18 is mainly composed of a cooling core (not shown) and a fan (not shown). The crude oil 10 to be warmed flows through the core channels (not shown) and the fan (not shown) moves air, or other temperature equalizing fluid, through the cross exchanger 18 in order to optimize and equalize the temperature of the crude oil 10.

[0039] The crude oil 10 is desalted in electrical desalter 18 where any salts in the crude oil 10 will be removed. As an initial step, water is mixed with the heated crude oil 10. During mixing, salt content in the crude oil 10 is washed with the water and a water/oil emulsion is formed. The salt is dissolved in the water in the crude oil 10, not in the crude oil itself. The emulsion then enters the desalter 18 where it is subject to the action of an intense electric fieldoften in the range of 16,000 to 30,000 volts AC. The high voltage provides the coalescing force and accelerates separation of the water laden with salt in the oil 10. As coalescence proceeds, water droplets grow large enough to overcome the viscosity of the crude oil 10 and settle to the bottom due to gravity. Cleaned crude oil 10, freed of the salt, rises to the surface and is separated from the salt contaminants. Efficiency of a desalter 18 is usually 95% in a single stage and up to 99% in two stages.

[0040] The preheated crude oil 10 is then transported to a furnace heater 20 where it is heated further up to a desired temperature. The crude oil 10 is then fed to the atmospheric crude tower 24. The atmospheric crude tower 24 provides distillation of the crude oil 10. In atmospheric distillation, the desalted crude oil 10 is heated to about 750 F. then fed to a vertical distillation column (not shown) under pressure. The crude 10 vaporizes and separates into various fractions by condensing on 30-50 fractionation trays, each corresponding to a different condensation temperature. Lighter fractions condense and collect toward the top of the column (not shown). Vapors will be condensed and collected in a reflux drum 40.

[0041] Condensed vapors will be separated to oil 10 and water. Oil 10 will be the naphtha product 42 which is both refluxed to crude oil tower 24 and collected as naphtha product 42 to naphtha storage tank (not shown) via a pump (not shown).

[0042] Residue Mineral Spirits (RMS) product 26 will be drawn as a side draw from the column 24 will be cooled with crude 10-RMS 26 cross exchanger (not shown) before pumped to storage tank (not shown) via RMS product pump (not shown).

[0043] Odorless Mineral Spirts (OMS) product 28 is drawn as a side draw from the column 24 will be cooled in crude 10-OMS 28 cross exchanger (not shown) before pumping to storage tank (not shown) via OMS product pump (not shown).

[0044] Kerosene product 30 is drawn as a side draw from the column 24 will be cooled in crude 10-kerosene 30 cross exchanger (not shown) before pumping to storage tank (not shown) via kerosene product pump (not shown).

[0045] Diesel product 32 will be drawn as a side draw from the column 24 will be cooled with crude 10-diesel 32 cross exchanger (not shown) before pumped to storage tank (not shown) via diesel product pump (not shown).

[0046] The filtration system 48 acts to de-asphalt the crude oil 10 via solvent extraction. Crude bottoms 34 from the atmosphere crude tower 24 are pumped using a crude bottoms pump 36 to the deasphalting system 48. Bottoms 34 are mixed with ethyl acetate (solvent) 46 in mixer settler 38 and then passed through cooler 58 to cool the mixture where the asphaltene precipitation will take place. The precipitated asphaltenes will be filtered in filtration system 48 (further shown in FIG. 3) to separate the precipitant asphaltenes and impurities from the deasphalted oil 10 along with solvent 46. The crude oil 10 is now deasphalted oil 56, and along with solvent 46 will be the filtrate coming out of the filtration system 48.

[0047] The ethyl acetate regeneration system (EARS) is illustrated in the figure as A. Ethyl acetate solvent 46 will be recovered in ethyl acetate regeneration tower 54. Filtrate is heated in the solvent steam evaporator 50, vapor and liquid is separated in flash drum 52. Liquid from the flash drum 53 which has both ethyl acetate solvent 46 and DAO 56 will fed to ethyl acetate regeneration tower 54, where ethyl acetate solvent 46 will be recovered at the overhead of the column 54. The vapor from the flash drum 52 and ethyl acetate regeneration tower 54 overhead vapor will be condensed in ethyl acetate reflux cooler 58 and collected in ethyl acetate reflux drum 60. Ethyl acetate solvent 46 will be recycled back to the mixer settler 38 before that it is heated back to desired temperature with cross exchangers 50. Makeup solvent 44 due to any loss will be fed through via makeup pump 62. Bottoms DAO 56 from ethyl acetate regeneration tower 54 is pumped via DAO storage pump 62 to the DAO storage tank 60.

[0048] The toluene regeneration system (TRS) is illustrated in the figure as B. Regeneration/cleaning of the filter membrane, or element, 100 in filtration system B will be done by using toluene solvent 78. Cleaning/regeneration of filter elements 100 needs to be performed once the filter elements 100 are clogged. Toluene solvent 78 will be recovered in toluene regeneration tower 68. Filtrate will be heated in the TRS heater 64, vapor and liquid will be separated in flash drum, or toluene reflux drum, 72. Liquid from the flash drum 72, which has both toluene and impurities 76, will be fed to toluene regeneration tower 68, where toluene solvent 78 will be recovered at the overhead of the column. The vapor from the flash drum 72 and toluene regeneration tower 68 is condensed in toluene reflux cooler 70 and collected in toluene reflux drum 72. The toluene reflux pump 74 will be used to recycle back toluene 78 for cleaning the filter elements 100. Bottoms will be rich in asphaltenes, while resins will be waste and needed to be discarded or can be used as another product.

[0049] FIG. 2 illustrates a filtration system which separates the asphaltenes, resins and heavy metals from the paraffin bottoms effectively and produces paraffin of the purity required. The filters must be capable of being backwashed and then be reused and have a multi-year service life element which can handle the pressure and temperature for the filtration system. Ceramic membranes may be used to remove asphaltene and Ni, V metals. The current invention uses filters to remove asphaltenes. It is believed that ceramic filter element filtration with different solvents can remove approximately 94.4 wt. % asphaltenes and other heavy metals. The economics for the filter and solvent recovery process for asphaltenes is better than the current ROSE de-asphalting process, primarily because of needing less solvent to remove the asphaltenes. Conventionally, the solvents hexane, pentane and heptane have been used, but they only precipitate asphaltenes. The current invention uses ethyl acetate solvent, which will precipitate asphaltenes, resins and heavy metals. The figures illustrate an embodiment for removing impurities like asphaltenes, resins and heavy metals from crude oil bottoms.

[0050] First filter will be a part of the filtering cycle, while the second filter is in the regeneration cycle. This system is very flexible as multiple filters (first and second) may be added in series for larger capacity units. Filter elements use ceramic membranes which can handle maximum pressure 10 bar and maximum temperature of 450 F. Pore size of the filter elements is in the range of 5 nm to 10 nm. This much smaller than the average particle size of the asphaltenes, resins and heavy metals when they are initially precipitated, which is expected to be in a range of about 1000 nm to 1200 nm. Toluene is used for cleaning/regenerating the filter membranes. Toluene will also reduce the size of the particles. Obviously, the size of the particles cannot be reduced so much that the filters are unable to catch the particles. Generally though, once the asphaltenes, resins and heavy metal particles are dissolved in toluene, the resulting average particle size is reduced to an expected range of about 10 nm to 20 nm. Thus, when initially precipitated, the average particle size is expected to be greater than 1000 nm, which is much greater than pore size of the membranes, and when dissolved with Toluene the particle size is reduced to about 10 nm to 20 nm but still large enough such that the ceramic membrane is still able to filter out the asphaltene, resin and heavy metal particles.

[0051] FIG. 3 illustrates a proposed filtration system. In one embodiment, filters 1 and 2 are in series and filters 3 and 4 are in series. Filters 1 and 2 are in the filtration cycle, while filters 3 and 4 are in the regeneration cycle. In the filtration cycle, feed, ethyl acetate, and crude bottoms along with recycled concentrate will be fed into filter 2. Precipitated asphaltenes and other impurities are filtered, leaving a filtrate of DAO and ethyl acetate. Unfiltered concentrate is fed into filter 1, which is in series with filter 2 where further filtration would take place to remove impurities. Precipitates with impurities, asphaltenes, resins and heavy hydrocarbons, are retained on the filter membranes. This process is continued until filter elements 1 and 2 are clogged making further filtration inefficient. Ethyl acetate from the filtrate is recovered in a solvent recovery system leaving behind the deasphalted oil. The number of filter elements in series may be increased based on the capacity of the filtration system. When filters 1 and 2 become clogged, filters 3 and 4 may be put into the filtration cycle. While filters 3 and 4 are in use in the filtration cycle filters, filters 1 and 2 may be regenerated by cleaning them with toluene and readied to again be used in the filtration cycle. The toluene used for cleaning the filter may be recovered in the solvent recovery system.

[0052] The system solvent deasphalting and filtration system can be used for processing various types of heavy crude oils and crude oil bottoms. If this system is used on heavy crude oils, the advantages can include: [0053] 1. Downstream equipment is protected from clogging due to the asphaltene impurities; [0054] 2. Handling of the fluid will be easier; and [0055] 3. Maintaining the crude oil at a high temperature is not required for the crude oil to flow helping to reduce energy costs.

[0056] FIG. 4 illustrates an embodiment of an ultrafiltration (UF) membrane module, or filter, 100 that may be used in the filtration system B. The UF membrane module 100 is a large diameter, monolith membrane module with permeate conduits. The silica and titania UF membranes 102 have low fouling characteristics in ultrafiltration of heavy oils 10. The silica membrane 102 has a pore size of about 5 nm and the titania membrane about 10 nm. The starting point for application of the UF membranes 102 is a two-layer microfiltration (MF) membrane coating on a SiC support. Individual MF layers 102 comprise (a) a first mixed oxide MF membrane layer (pore size approx. 0.5 m), and (b) an -alumina MF membrane layer (pore size approx. 0.1 m).

[0057] The UF membrane module 100 has an outer shell 116, that is anticipated to generally be in a tubular shape, but the outer circumference can be virtually any shape combined with a hollow interior. The module's 100 hollow interior is filled (to some extent) with a multiplicity of MF membrane layers 102. Feed (feed, ethyl acetate, and crude bottoms along with recycled concentrate) 10 is pumped into a first end 112 of the module 100 where the passageways are created with the silica membrane 102. The feed 10 flows through the pores in the membrane 102 and precipitated asphaltenes and other impurities are caught, leaving a filtrate 104 of DAO and ethyl acetate 46. The filtrate 104 flows through the pores in the membranes 102 toward the second end 114 out the of the module 100 through first slots 110A and second slots 110B. The second slots 110B may be plugged at the second end 114. Crude concentrate 106 exists the filter second end 114. Plugged passages 108 isolate the filtrate 106.

[0058] FIG. 5 is a table illustrating the results of a SARA analysis for black waxy Uinta crude oil determining the saturates, aromatic, resin and asphaltenes. A SARA analysis first step is to precipitate asphaltene, resin and heavy metal particles by mixing feed with solvent and filter the solution to recover the precipitate particles. The asphaltenes and resins are shown precipitated with ethyl acetate solvent and the solution filtered to remove resins and asphaltenes. A filter separator is used to remove the asphaltenes and resins. Filter media can be regenerated/cleaned by Toluene as asphaltenes, and resins are soluble in toluene.

[0059] The wax content in the Crude oil content which was high in paraffinic content (62 wt. % wax) and needs to be extracted. Extraction of wax, impurities like Asphaltenes, resins and aromatics are to be removed from the crude oil. All the paraffins, asphaltenes, aromatics and resins end up in atmospheric crude oil bottoms. Crude oil atmospheric crude distillation is performed in order to extract light hydrocarbon fractions leaving behind the atmospheric residue. Atmospheric residue was used as feed stock for deasphalting.

[0060] FIG. 6 is a table illustrating the results of a SARA analysis for atmospheric residue bottoms to determine the saturates, aromatic, resin and asphaltenes. Wax content was found to have 88.3 wt. % wax.

[0061] FIG. 7 is a table illustrating the results of a SARA analysis for both DAO and precipitant. Crude bottoms were mixed with Ethyl acetate in 1:4 ratio to precipitate both asphaltenes and resins. The solution is heated and mixed thoroughly on a stirring hot plate for proper precipitation of asphaltenes and resins. Precipitated asphaltenes in the solution were vacuum filtered with 0.4 m fritted Buchner flask. Permeate collected after filtration is deasphalted oil with ethyl acetate. Collected permeate DAO heated to evaporate ethyl acetate leaving behind deasphalted oil. Raffinate unfiltered precipitate is collected by mixing with toluene. Raffinate collected after filtration was heated to evaporate toluene to leave behind the precipitant.

[0062] SARA analysis for both DAO and precipitant was performed. Asphaltenes present in atmospheric residue was decreased from 9.33 wt. % to 0.64 wt. %, resins from 0.78 wt. % to 0.64 wt. %. The precipitant fraction has high asphaltene content indicating the asphaltenes are precipitated with ethyl Acetate solvent with 23.4 wt. % shown in table 3.

[0063] Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.

[0064] Unless otherwise specifically noted, the elements and articles depicted in the drawings are not necessarily drawn to scale, but they are illustrative of the described implementations and are intended to disclose the elements and articles illustrated as part of the specification, and the drawings further indicate relative size, angles, shapes, arrangement, placement, and like information to one of ordinary skill in the art regarding the elements and articles in the drawing.

[0065] Throughout this disclosure, a hyphenated form of a reference numeral refers to a specific instance of an element and the un-hyphenated form of the reference numeral refers to the element generically or collectively. Thus for example, widget 12-1 would refer to a specific widget of a widget class 12, while the class of widgets may be referred to collectively as widgets 12 and any one of which may be referred to generically as a widget 12.

[0066] As used herein, removably attached, removably attachable, or removable mean that a first object that is coupled to a second object may be decoupled from the second object, or taken away from an attached position relative to the second object, using some force or movement. Removably attached, removably attachable, or removable further mean that if the first object is not coupled with the second object, the first object may be coupled to the second object or returned to the attached position, using some force or movement. Both the decoupling and the coupling may be accomplished without damaging either the first object or the second object.

[0067] When the terms substantially, approximately, about, or generally are used herein to modify a numeric value, range of numeric values, or list numeric values, the term modifies each of the numerals. Unless otherwise indicated, all numbers expressing quantities, units, percentages, and the like used in the present specification and associated claims are to be understood as being modified in all instances by the terms approximately, about, and generally. As used herein, the term approximately encompasses +/5 of each numerical value. For example, if the numerical value is approximately 80, then it can be 80+/5, equivalent to 75 to 85. As used herein, the term about encompasses +/10 of each numerical value. For example, if the numerical value is about 80, then it can be 80+/10, equivalent to 70 to 90. As used herein, the term generally encompasses +/15 of each numerical value. For example, if the numerical value is about 80, then it can be 80%+/15, equivalent to 65 to 95. Accordingly, unless indicated to the contrary, the numerical parameters (regardless of the units) set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the exemplary embodiments described herein. In some ranges, it is possible that some of the lower limits (as modified) may be greater than some of the upper limits (as modified), but one skilled in the art will recognize that the selected subset will require the selection of an upper limit in excess of the selected lower limit.

[0068] At the very least, and not limiting the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0069] The terms inhibiting or reducing or any variation of these terms refer to any measurable decrease, or complete inhibition, of a desired result. The terms promote or increase or any variation of these terms includes any measurable increase, or completion, of a desired result.

[0070] The term effective, as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0071] The terms a or an when used in conjunction with the term comprising in the claims and/or the specification may mean one, but it is also consistent with the meaning of one or more, at least one, and one or more than one.

[0072] The term each refers to each member of a set, or each member of a subset of a set.

[0073] The terms comprising (and any form of comprising, such as comprise and comprises), having (and any form of having, such as have and has), including (and any form of including, such as includes and include) or containing (and any form of containing, such as contains and contain) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0074] In interpreting the claims appended hereto, it is not intended that any of the appended claims or claim elements invoke 35 U.S.C. 112(f) unless the words means for or step for are explicitly used in the particular claim.

[0075] It should be understood that, although exemplary embodiments are illustrated in the figures and description, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and description herein. Thus, although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various embodiments may include some, none, or all of the enumerated advantages. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention. Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components in the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.