US 3736249 A
Description (OCR text may contain errors)
May 29, 1973 J. E. LAWSON, JR 3,736,249
HYDROCARBONACEOUS FEED TREATMENT Filed Feb. 22, 1972 GAS 2 HYDROCRACKI NG I GAS l2 FEED 2 1 PITCH T PRODUCT l 8/ 5 H I COKI NG u COKE United States Patent Ofice 3,736,249 Patented May 29, 1973 3,736,249 HYDROCARBONACEOUS FEED TREATMENT John E. Lawson, Jr., Richardson, Tex., assignor to Atlantic Richfield Company, New York, N.Y. Filed Feb. 22, 1972, Ser. No. 227,949 Int. Cl. Cb 55/00; C10g 23/02 US. Cl. 208-80 12 Claims ABSTRACT OF THE DISCLOSURE IA method for treating a hydrocarbonaceous feed which contains at least one residue fraction wherein a portion of the feed is subjected to residual hydrocracking conditions while another portion of the feed is subjected to coking conditions, utilizing the pitch residue obtained from the hydrocracking step as feed to the coking step and combining the liquid hydrocarbonaceous output of the hydrocracking and coking steps to form the final product of the process.
BACKGROUND OF THE INVENTION Heretofore, it has been proposed to treat a hydrocarbonaceous feed material which contains one or more residue fractions by the sole use of a residual hydrocracking operation in order to produce a hydrocarbonaceous liquid product which meets certain predetermined specifications, e.g., containing substantially all hydrocarbon components boiling below 1000 E, and separately producing a pitch residue. The pitch represents the residue fraction(s) of the feed material and is not very useful except as burning fuel.
The residual hydrocracking operation by itself cannot produce controlled amounts of pitch residue without using up excessive amounts of hydrogen. Whatever amount of pitch residue that was produced while keeping hydrogen consumption down to an economic level was considered a necessary evil to be lived with, rather than something which could be controlled to the operators advantage.
Heretofore, delayed coking has been used by itself to produce coke from a residue fraction feed.
SUMMARY OF THE INVENTION According to this invention a liquid hydrocarbonaceous product which meets predetermined yield specifications is obtained while limiting the amount of residue material produced by the process to that amount which can be usefully disposed of by the operator and also more efliciently utilizing hydrogen in producing this liquid product.
The process according to this invention splits the incoming hydrocarbonaceous feed between a residual hydrocracking process and a coking process and utilizes the pitch residue from the hydrocracking process as part of the feed to the coking process. The final hydrocarbonaceous liquid product of the process is a combination of the liquid products of the hydrocracking and coking processes. This final product meets the predetermined yield specifications for such an upgraded product. The coke produced is in a controlled amount so that great excesses of residual material are not produced. This coke product also has a substantially lower hydrogen content than the pitch from the hydrocracking process so that compared to hydrocracking alone, more hydrogen stays in the process and contributes to the production of the final liquid product.
Thus, according to this invention the feed material is split between two particular processes and the residue material from one process is utilized as part of the feed for the other process in order to achieve control over the final amount of residue produced by the overall process. This is accomplished while still producing a liquid product which meets desired yield and, further, while conserving and more eifectively utilizing the hydrogen added to the hydrocracking process.
Accordingly, it is an object of this invention to provide a new and improved method for treating hydrocarbonaceous feed containing at least one residual fraction. It is another object to provide a new and improved method for upgrading hydrocarbonaceous feed containing at least one residual fraction. It is another object to provide a new and improved method for producing a hydrocarbonaceous liquid product while at the same time producing only controlled and desired amounts of residue material. It is another object to provide a new and improved method for producing a liquid hydrocarbonaceous product utilizing a residual hydrocracking step wherein the hydrogen employed is more efiiciently used in the production of the desired liquid product rather than lost from the process by way of the residual material produced by the process.
Other aspects, objects, and advantages of this invention will be apparent to those skilled in the art from this disclosure and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION The drawing shows a schematic diagram of one embodiment of this invention. More specifically, the drawing shows a feed material entering the system by way of pipe 1 and being split into two portions by way of pipes 2 and 3. The portion in pipe 2 passes to a residual hydrocracking operation 4 while the portion in pipe 3 passes to a coking operation 5. Gas formed in operations 4 and 5 is removed by way of pipes '6 and 7, respectively. Pitch formed in hydrocracking section 4 is passed by way of pipe 8 to coking operation 5 wherein the pitch in pipe 8 is utilized as feed material to the coker along with that portion of the feed which is in pipe 3. Coke residue is removed from the coking operation by way of conduit 9. The liquid hydrocarbonaceous products produced by units 4 and 5 issue therefrom, respectively, by way of pipes 10 and 11, and are combined in pipe 12 as the final hydrocarbonaceous product of the overall process.
The final product in pipe 12 meets the desired and predetermined specifications for liquid of that type. The coke residue in conduit 9 has a low hydrogen content and is produced in a controllable amount so that no more coke is produced than that which is desired while still meeting specifications for the product in pipe 12.
The feed for pipe 1 can be any hydrocarbonaceous material which has at least one residual fraction therein. By the term hydrocarbonaceous is meant a material which is substantially a hydrocarbon-containing material but which can contain minor amounts of nonhydrocarbon constituents such as oxygen, nitrogen, sulfur, and the like. The feed thus can be any naturally-occurring crude oil or one or more fractions of naturally-occurring crude oil if the crude oil has previously been subjected to topping or other preliminary fractionation processes. The feed can also be a hydrocarbonaceous liquid obtained from one of solid coal, oil shale, or tar sands. Mixtures of two or more of the above feed materials can be used so long as the feed in pipe 1 contains at least one residue fraction. By the terms residue fraction or residue fractions is meant at least one material normally considered in the refining of petroleum products as residue material, e.g., pitch, tar asphalt, asphaltenes, combinations thereof, and the like.
The process of this invention can be employed as an upgrading process in the production of synthetic crude oil or in a refining process which operates on either naturally-occurring crude oil or its fractions or synthetic crude oil or combinations thereof. If the process is utilized for upgrading in a synthetic crude oil context, the final product in pipe 12 is a liquid which can be hydrogenated or further treated to produce a synthetic crude oil capable of pipelining to and processing in a refinery. If the process of this invention is utilized in a refining context, the final product in pipe 12 is a liquid that can be processed by known refining techniques into conventional petroleum products such as Diesel fuel, gasoline, and the like.
Whether the process of this invention is utilized in synthetic crude oil upgrading context or a general refining context, it is of value because the amount of coke residue produced by the process in conduit 9 can be controlled and limited without hindering the ability of the final product in pipe 12 to meet specifications and at the same time obtaining more effective utilization of the hydrogen employed in the hydrocracking operation.
The more efficient utilization of hydrogen is achieved by employing the pitch in pipe 8 as feed to coking unit 5. The pitch in pipe 8, coming from a hydrocracking unit wherein hydrogen is fed to the hydrocracking unit from outside the process by a pipe not shown, contains substantial amounts of combined hydrogen, e.g., at least about weight percent hydrogen based on the total weight of the pitch. Coking unit 5 does not receive a separate hydrogen stream from outside the process as does hydrocracking unit 4. Coker 5 does not, therefore, have large amounts of hydrogen circulating therein and any molecules which are broken up into smaller molecules in the coking process will utilize hydrogen from the pitch to satisfy bonds which are left unsatisfied due to the breakup of the molecules into smaller parts. Therefore, the hydrogen in the pitch for pipe 8 will preferentially gavitate to the gaseous and liquid products in pipes 7 and 11 of coker 5. This in turn yields a coke residue which has a substantially lower hydrogen content, e.g., at least about one-third less hydrogen in the coke residue than in the pitch residue. The hydrogen which is in the pitch and which would otherwise be lost if the hydrocracking unit 4 were utilized by itself is reclaimed in substantial amounts and ends up at least in part in the liquid product in pipe 11. This contributes materially to the quality of the final product in pipe 12, by more efiiciently utilizing the hydrogen initially intro duced into hydrocracking unit 4.
By controlling the amount of feed split between pipes 2 and 3 in relation to each other and in relation to the pitch in pipe 8, the quantity of coke in conduit 9 can be controlled without upsetting the specification-meeting qualities of the product in pipe 12. The amount of coke produced by way of conduit 9 can be controlled to be just that amount which meets a specific need thereby eliminating the need of having to dispose of excess amounts of residual material, i.e., residue produced in amounts beyond that which can be advantageously used by the operator. For example, to decrease the final coke yield an increased amount of feed from pipe 1 can be passed to unit 4. The operator can also control the operating conditions for the entire process so that just sufiicient coke is produced to meet the operators need for burning fuel. For example, to obtain less coke, less pitch is produced by unit 4 by keeping the temperature and pressure the same in unit 4 but lowering the space velocity or by keeping the pressure and space velocity the same and raising the temperature, etc. In this manner, whatever coke is produced by way of conduit 9 can be burned by the operator to generate heat and no excess coke is produced which has to be disposed of by the operator to his expense and loss.
Depending upon the particular specifications for the product of pipe 12 and the amount of coke desired to be produced by way of conduit 9, the relative amounts of feed in pipes 2 and 3 will vary quite widely but there will be some amount of feed in each pipe during the operation of the process.
In the particular combination of hydrocracking and coking units according to this invention, the vacuum distillation tower which is conventionally present in a hydrocracking unit can be eliminated without eliminating the function of that distillation tower. This is an optional advantage depending upon how the operator desires to run the process in that the vacuum tower can be utilized in hydrocracking unit 4 of this invention or can be eliminated with reliance being placed instead on the coking unit 5.
The use of high hydrogen content pitch in pipe 8 as a partial feed material to coking unit 5 contributes to the capability of producing more liquid in pipe 11 and less coke in conduit 9, thereby providing an additional dimension to the control of the amount of coke produced in conduit 9.
The gas removed by way of pipes 6 and 7 can be combined and used as burning fuel by the operator or disposed of as desired. The disposition of the coke is no problem since no more coke is produced than that amount which the operator already knows he can use.
The residual hydrocracking unit 4 can be any unit of that type known in the art which is capable of breaking up large hydrocarbonaceous molecules into smaller hydrocarbonaceous molecules, speaking on a physical size basis. The breakup is accomplished by subjecting the molecules in the presence of hydrogen to an elevated temperature for a time snificient to effect the molecule breakup. The hydrogen present satisfies bonds left after the molecule breakup thereby fixing the broken up molecules in their subdivided state. Generally, the elevated temperature employed is at least about 800 'F. and the residence time at this temperature is at least about one hour. At least about 200 standard cubic feet per barrel of feed being treated is supplied to the hydrocracking unit. The residual hydrocracking unit can employ processes known as hydrovisbreaking, H-OIL, ISOMAX, RESIDFINING, and the like.
Coking unit 5 can be composed of any known coking process. These coking processes typically take in a residual fraction feed and produce both hydrogen-rich lighter hydrocarbons (which end up in the gas and liquid product of pipes 7 and 11) and residual coke which is lower in hydrogen content than said lighter hydrocarbons or said feed. Coking processes also subject their feed to an elevated temperature, e.g., at least about 800 F., for time sufficient to form coke in the desired amount. Suitable processes for coking unit 5 include delayed coking, FLUID CDKJNG, FLEXICOKING, and the like.
The residual hydrocracking and coking processes are well-known in the art and therefore further description is not necessary to inform one skilled in the art.
EXAMPLE A naturally-occurring crude oil containing pitch, asphalt and asphaltenes is passed by way of pipe 1 and split so that 50 weight percent goes into pipe 2 with the remainder entering pipe 3.
Hydrocracking unit 4 employs hydrovisbreaking wherein the feed is passed into an empty reactor, heated to about 850 F. for about one hour in the presence of molecular hydrogen which is added at a rate of about 400 standard cubic feet per barrel of feed in pipe 2.
The liquid product in pipe 10 contains substantially all the hydrocarbon fractions which were in the feed in pipe 2 and which boil below 1000 F. The pitch in pipe 8 contains about 8 weight percent hydrogen based on the total weight of the pitch and all of the pitch output from hydrocracking unit 4 passes to coking unit 5.
Coking unit 5 utilizes delayed coking wherein the mixture of pitch from pipe 8 and feed from pipe 3 is passed into a drum and heated at about 900 F.,for about four hours after which coke is separated by way of conduit 9 and the remaining liquid is passed by way of pipe 11 to be combined with the liquid product in pipe to produce the final product in pipe 12.
The liquid product in pipe 11 also contains hydrocarbons having boiling points below 1000 F. so that the final product in pipe 12 meets the specification of containing substantially no hydrocarbons boiling above 1000 F. The coke in conduit 9 contains about 4 weight percent hydrogen based upon the weight of the pitch added by way of pipe 8 so that at least half of the hydrogen in pipe 8 has been utilized in forming the gas and liquid in pipes 7 and 11 rather than being Wasted in the coke in conduit 9.
Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A method for treating a hydrocarbonaceous feed which contains at least one residue fraction, said method providing an optimum amount of final product which meets predetermined specifications, said method also providing separate from said final product a low hydrogen content final residue in a predetermined and controlled amount, said method comprising splitting said feed into two portions, residual hydrocracking a first of said two portions to form a first liquid product and a separate pitch residue, said pitch containing a substantial amount of hydrogen, coking the second of said two portions to form a second liquid product and a separate coke residue, said coke containing a substantially smaller amount of hydrogen than said pitch, passing said pitch from said residual hydrocracking step to said coking step as feed for said coking step, combining said first and second liquid products, said combined products forming said final product, said coke being said final residue.
2. A method according to claim 1 wherein said hydrocarbonaceous feed is one of naturally occurring crude oil, at least one fraction of naturally occurring crude oil, hydrocarbonaceous liquid obtained from solid coal, hydrocarbonaceous liquid obtained from oil shale, hydrocarbonaceous liquid obtained from tar sands, and mixtures of two or more thereof, said feed containing a residue fraction selected from the group consisting of pitch, tar, asphalt, asphaltenes and combinations thereof.
3. A method according to claim 1 wherein said method is controlled to produce just sufficient final residue to meet a predetermined fuel burning requirement so that no residue is produced beyond that amount required to serve as fuel.
4. A method according to claim 1 wherein said residual hydrocraoking step comprises subjecting said feed portion in the presence of hydrogen to an elevated temperature for a time sufiicient to break up large molecules in said feed, said hydrogen saturating said broken molecules thereby fixing same in the subdivided state.
5. A method according to claim 4 wherein said elevated temperature is at least about 800 B, said residence time is at least about one hour, and at least about 200 standard cubic feet per barrel of feed portion is supplied to said step.
6. A method according to claim 1 wherein said residual hydrocracking comprises hydrovisbreaking.
7. A method according to claim 1 wherein the pitch residue from said residual hydrocracking step contains at least about 4 weight percent hydrogen based on the total weight of said pitch residue.
8. A method according to claim 1 wherein said coking step comprises subjecting said feed portion and said pitch residue to an elevated temperature for a time suflicient to form coke in the desired amount, said coke containing substantially less hydrogen than said pitch residue feed.
9. A method according to claim 8 wherein said elevated temperature is at least about 800 F.
10. A method according to claim 8 wherein said coke contains at least about one-third less hydrogen than said pitch residue feed.
11. A method according to claim 1 wherein said final product contains substantially all hydrocarbon fractions in said feed which boil below a preset temperature.
12. A method according to claim 11 wherein said final product contains substantially all hydrocarbon fractions in said feed which boil below 1000= F.
References Cited UNITED STATES PATENTS 2,871,182 1/1959 Weekman 208- 2,988,501 6/1961 InWOOd 208-21-1 3,238,117 3/1966 Arey et a1. 208-53 3,238,118 3/1966 Arey et a1. 208--59 3,684,688 8/1972 Roselius 208-50 DELBBRT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner