Combined process to produce both a pipelineable crude and carbon fiber from heavy hydrocarbon
11667850 · 2023-06-06
Inventors
Cpc classification
C10G55/04
CHEMISTRY; METALLURGY
C08L95/00
CHEMISTRY; METALLURGY
C08L2555/40
CHEMISTRY; METALLURGY
Y02P20/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
C10G21/00
CHEMISTRY; METALLURGY
C08L95/00
CHEMISTRY; METALLURGY
Abstract
An integrated process that is operated to create both a higher value pipelineable crude and a higher value carbon fiber product from a lower value common heavy hydrocarbon feedstock where the feedstock is processed in a thermal reactor followed by a solvent deasphalting unit with the liquids being gathered and processed to reduce olefins for pipeline transport and the solids are processed to generate a marketable carbon fiber product with any gases generated throughout the entire process reused in the process or sold.
Claims
1. A process for treating a heavy hydrocarbon feedstock, comprising: thermally treating the hydrocarbon feedstock to produce a lighter hydrocarbon stream and a heavier hydrocarbon stream; solvent deasphalting the heavier hydrocarbon stream with a solvent to precipitate asphaltenes and form solid asphaltene precipitates and produce deasphalted oil; separating the deasphalted oil from the solid asphaltene precipitates to produce a solvent-diluted deasphalted oil stream comprising a portion of the solvent and a slurry stream comprising the asphaltene precipitates and residual solvent; separating the solvent-diluted deasphalted oil stream to produce a recovered solvent stream and a deasphalted oil stream; separating the slurry stream to produce a solid asphaltene particulate stream and a recovered solvent stream; and processing the solid asphaltene particulate stream to produce a carbon fiber precursor.
2. The process of claim 1, wherein separating the slurry stream comprises vaporizing the residual solvent to produce a vapour/solid mixture comprising vaporized solvent and the solid asphaltene precipitates, and subjecting the vapour/solid mixture to inertial separation.
3. The process of claim 1, wherein processing the solid asphaltene particulate stream comprises extruding the solid asphaltene particulate stream to produce extruded asphaltenes as the carbon fiber precursor.
4. The process of claim 3, further comprising: spinning the extruded asphaltenes into an asphaltene thread woundable on a spool; stabilizing the asphaltene thread by a first heat treatment to produce a stabilized asphaltene thread; carbonizing the stabilized asphaltene thread by a second heat treatment to produce a carbonized carbon fiber; and conditioning the carbonized carbon fiber to produce a carbon fiber product.
5. The process of claim 3, further comprising graphitizating the carbon fiber precursor to produce a graphene product.
6. The process of claim 3, further comprising: spinning the extruded asphaltenes into an asphaltene thread; and spooling the asphaltene thread to obtain a spooled asphaltene thread having a diameter of below 15 μm and has less than 10% void space.
7. The process of claim 1, wherein the carbon fiber precursor is converted into a carbon fiber product having a tensile strength of at least 150 MPa and a young modulus of at least 20 GPa.
8. The process of claim 1, further comprising, prior to the processing of the solid asphaltene particulate stream, separating insolubles from the solid asphaltene particulate stream, wherein separating the insolubles comprises combining the solid asphaltene particulate stream with an insolubles-producing solvent to produce the insolubles and removing the insolubles from the solid asphaltene particulate stream.
9. The process of claim 8, wherein the insolubles-producing solvent comprises a heterocyclic hydrocarbon.
10. The process of claim 1, wherein the solvent used for the solvent deasphalting comprises one or more of C.sub.5-C.sub.8 hydrocarbons.
11. The process of claim 1, wherein the carbon fiber precursor is converted to activated carbon.
12. A process for treating a heavy hydrocarbon feedstock, comprising: solvent deasphalting the heavy hydrocarbon feedstock with a solvent to precipitate asphaltenes and form solid asphaltene precipitates and produce deasphalted oil; separating the deasphalted oil from the solid asphaltene precipitates to produce a solvent-diluted deasphalted oil stream comprising a portion of the solvent and a slurry stream comprising the asphaltene precipitates and residual solvent; separating the solvent-diluted deasphalted oil stream to produce a recovered solvent stream and a deasphalted oil stream; separating the slurry stream to produce a solid asphaltene particulate stream and a recovered solvent stream; and processing the solid asphaltene particulate stream to produce a carbon fiber precursor.
13. The process of claim 12, wherein separating the slurry stream comprises vaporizing the residual solvent to produce a vapour/solid mixture comprising vaporized solvent and the solid asphaltene precipitates, and subjecting the vapour/solid mixture to inertial separation.
14. The process of claim 12, wherein processing the solid asphaltene particulate stream comprises extruding the solid asphaltene particulate stream to produce extruded asphaltenes as the carbon fiber precursor.
15. The process of claim 14, further comprising: spinning the extruded asphaltenes into an asphaltene thread woundable on a spool; stabilizing the asphaltene thread by a first heat treatment to produce a stabilized asphaltene thread; carbonizing the stabilized asphaltene thread by a second heat treatment to produce a carbonized carbon fiber; and conditioning the carbonized carbon fiber to produce a carbon fiber product, wherein the conditioning comprises surface treating and sizing the carbonized carbon fiber.
16. The process of claim 14, further comprising graphitizating the carbon fiber precursor to produce a graphene product.
17. The process of claim 14, further comprising: spinning the extruded asphaltenes into an asphaltene thread; and spooling the asphaltene thread to obtain a spooled asphaltene thread, wherein the spooled asphaltene thread has a diameter of below 15 μm and has less than 10% void space.
18. The process of claim 12, wherein the carbon fiber precursor is converted to activated carbon.
19. A process for producing a carbon fiber precursor, comprising: solvent deasphalting a hydrocarbon feedstock with a first solvent to precipitate asphaltenes and form solid asphaltene precipitates and produce deasphalted oil; separating the deasphalted oil from the solid asphaltene precipitates to produce a solvent-diluted deasphalted oil stream comprising a portion of the solvent and a slurry stream comprising the asphaltene precipitates and residual solvent; separating the slurry stream to produce a solid asphaltene particulate stream and a recovered solvent stream; solvent deasphalting the solid asphaltene particulate stream with a second solvent, different from the first solvent, to precipitate insolubles contained in the solid asphaltene particulate stream; separating the insolubles from the solid asphaltene particulate stream; and processing the solid asphaltene particulate stream to produce the carbon fiber precursor.
20. The process of claim 19, wherein the first solvent comprises a mixture of C.sub.5-C.sub.8 hydrocarbons.
21. The process of claim 19, wherein the second solvent comprises a heterocyclic hydrocarbon.
22. The process of claim 19, wherein the second solvent comprises one or more of toluene, xylene, benzene, tetrahydrofuran, cyclohexanone, quinoline or pyridine.
23. The process of claim 19, further comprising subjecting the solid asphaltene particulate stream to sparging to remove lighter components prior to processing the solid asphaltene particulate stream to produce the carbon fiber precursor.
24. The process of claim 19, further comprising subjecting the solid asphaltene particulate stream to vacuum distillation to remove lighter components prior to processing the solid asphaltene particulate stream to produce the carbon fiber precursor.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
(2)
DETAILED DESCRIPTION
(3) The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
(4)
(5) As shown in
(6) An olefin saturation process 40 takes the vapour stream 33 from the reactor 30 to convert the olefins in this stream to meet pipeline transport specification. The condensed olefin-saturated liquid exits unit 40 as stream 45 and can be blended into the final product, 200. Any non-condensable vapour exits as stream 43 and can be sent to an H.sub.2S removal unit, such as an amine unit, so vapour can be readily reused in the process or used as a fuel gas.
(7) Stream 32 from the reactor 30 is fed to the solvent deasphalting unit 50. The solvent extraction process 50 can comprise any suitable solvent extraction process that can handle the separation of precipitated solids at operating conditions from the remaining hydrocarbon liquid. An example of a relevant solid-liquid solvent separation process is U.S. Pat. No. 9,976,093 and Canada patent 2,844,000. A recycled solvent stream 63, 73 may be mixed with stream 32 to precipitate a solid asphaltene phase from the liquid 32 stream. Additional makeup solvent may be required to mix with stream 32 in separator 50. The asphaltenes precipitated are a solid powder so a solid/liquid separation can now be made as opposed to the typical liquid/liquid separation. A solid/liquid separation requires less solvent to provide the desired recovery of pipelineable heavy oil. A heavy deasphalted oil leaves the SDA unit, 50, as stream 57. Stream 57 is blended with stream 45 to create the final product, 200, which has physical characteristics which enable it to meet required pipeline transport criteria without having to mix the final hydrocarbon with transport diluents. The solvent used in SDA 50 can be a pure hydrocarbon component ideally in the range of C.sub.6 to C.sub.8 or more practically, a mixture of C.sub.5 to C.sub.8 extracted from readily available natural gas condensate or diluent that comes in with the heavy crude feed.
(8) Stream 53 contains entrained solid asphaltene powder in a solvent liquid phase. Stream 53 is reduced in pressure to flash the solvent to create a vapor/solid mixture as a slurry or suspension that enters the inertial separation unit (ISU), 60, for a solid/vapour separation. Solvent vapour is condensed and returned to the SDA unit 50 for reuse as stream 63. The asphaltene solid powder leaves the ISU as stream 67 and enters an extruder to apply pressure to the solid asphaltenes to remove any remaining entrained solvent. The extruder temperature can be in the 200-350° C. range to create conditions to provide continuous flow as a Non-Newtonian fluid through and out of the equipment. The removed solvent is returned to the SDA unit as stream 73. Some of the generated asphaltene extrudate can be segregrated and sent to the solid fuels market, as stream 71, if the market for carbon fiber is saturated or not economic. As another embodiment, material in stream 71 can be sent to for processing to become activated carbon. The majority of the extruded asphaltenes leave the extruding unit, 70, as stream 75 and is fed to the spinning unit, 80, where “green” carbon fiber is produced as stream 85. “Green” fiber is a term used for hydrocarbon crude derived fiber that has yet to be oxidized or carbonized, and is extremely fragile.) The spinning of the “green” fiber can be accomplished by either melt or jet spinning. Ideally, the diameter of the “green” fiber is less than 15 um, preferably less than 10 um for commercial applications.
(9) The “green” fiber is then stabilized in unit 90. Stabilization is accomplished by heating the fibers in a forced air environment to provide sufficient fresh oxygen to the fiber surfaces air at temperatures in the range of 200-300° C. Heating causes the spun fibers to pick up oxygen molecules on their surfaces to prevent the onset of inter-fiber coalescence or melting and to promote good carbon yield in later carbonization. Stabilization can take between a few minutes up to an hour or two. The stabilized fiber, stream 95, is then carbonized, in unit 100, under an inert environment (no oxygen) and is heated uniformly up to approximately 1000° C., but can go up to 1800° C. to improve both the fiber strength and Young modulus. The carbonizing step can take between a minute to up to an hour or two depending on the final properties desired. The lack of oxygen prevents the fibers from burning in the very high temperatures. As the fibers are heated, they begin to lose their non-carbon atoms, plus a few carbon atoms, in the form of various gases including water vapor, ammonia, carbon monoxide, carbon dioxide, hydrogen, nitrogen, sulfur, evolved metals such as nickel and vanadium and others. As the non-carbon atoms are expelled, the remaining carbon atoms form tightly bonded carbon crystals that are aligned more or less parallel to the long axis of the fiber. In a variant of this process, two furnaces operating at two different temperatures are used to better control the rate of heating during carbonization. The carbonized fiber leaves as stream 108 and can have surface treatment and sizing applied in unit 110. Surface treatment and sizing methods mainly used are acid oxidation, resin addition, plasma treatment, rare earth treatment, and/or gamma irradiation. Surface treatment leads to improved composite properties due to the conditions of improved surface area of the fiber surface, chemical bonding and adhesion between fiber and matrix. Surface treating and sizing is typically used since after carbonizing, the fibers have a surface that does not bond well with epoxies and other materials used in composite materials. To give the fibers better bonding properties, their surface is slightly oxidized. The addition of oxygen atoms to the surface provides better chemical bonding properties and also etches and roughens the surface for better mechanical bonding properties. Oxidation can be achieved by immersing the fibers in various gases such as air, carbon dioxide, or ozone; or in various liquids such as sodium hypochlorite or nitric acid. The fibers can also be coated electrolytically by making the fibers the positive terminal in a bath filled with various electrically conductive materials. The surface treatment process must be carefully controlled to avoid forming tiny surface defects, such as pits, which could cause fiber failure.
(10) The final carbon fiber product, stream 120, is normally general purpose (GP) carbon fiber. This product, 120, has a higher value than either the hydrocarbon feedstock, 5, or the typical disposition for asphaltenes, as a solid fuel.
(11) As an additional embodiment to
(12) The coated fibers are wound onto cylinders called bobbins. The bobbins are loaded into a spinning machine and the fibers are twisted into yarns of various sizes.
(13) Another embodiment, shown in
(14) Unit 65 can be added to perform further treatment and separation of the asphaltene solids. Stream 64 is undesirable solids that hinder the generation of carbon fiber while stream 66 contains flowable hydrocarbon that create voids in the carbon fiber. The material in stream 66 can be added to the hydrocarbon liquid product stream, 200, if the pipeline specifications can be maintained. Otherwise, stream 66 can be recycled to unit 30 for re-processing. Stream 64 can contain coke particles generated in reactor 30 and/or inorganic material in the feed. Unit 65 can contain a second solvent deasphalting step using organic solvents that adsorb heavier molecules than what is used in SDA unit, 50. The solvents that could be used to reject the heaviest, most undesirable solids in the solid asphaltene powder mixture are essentially heterocyclic hydrocarbon based compounds such as toluene, xylene, benzene, tetrahydrofuran, cyclohexanone, quinoline and pyridine among others. Vacuum distillation can also be used in unit 65, alone or in combination with a second deasphalting step, to remove any remaining lighter molecules that could create voids in the carbon fiber. Any lighter material evolved in the vacuum distillation or similar process will end up as stream 66. In addition, sparging can be considered within unit 65 to produce more mesophase material by removing lighter components and altering the orientation of the carbon molecules to promote high performance carbon fiber in stream 130. Sparging is a process similar to air blowing, and for carbon fiber, it is normally conducted with inert nitrogen instead of air.
(15) Carbon fibers can be graphitized in unit 105 after carbonization in unit 100 at temperatures close to 3,000° C. in an non-oxygen environment for improved Young's modulus. This step can create high performance carbon fibers with tensile strength above 1.5 GPA (preferably above 3 GPa) and Young's modulus above 290 GPA, up to 500 GPa. Stream 103 from unit 100 is directed for graphitization in unit 105, while stream 101 is directly set to the final step of surface treatment to create general purpose carbon fiber. The material leaving unit 105, graphitization, as stream 108, will be high performance carbon fiber, stream 130, after surface treatment is performed in unit 110.
(16) In one aspect, the feedstock 5 can be a heavy hydrocarbon (virgin or a previously processed stream), such as the heavy hydrocarbon obtained from a SAGD (steam assisted gravity drainage) process, for example Canadian Oil sands bitumen, or from any other suitable source of heavy hydrocarbon. In another aspect, the feedstock 5 can have an API gravity in the range of 0 to 14.
(17) The thermal cracker, 30, in
(18) The reactor 30 can be operated in a manner, through optimizing primarily five inter-related process variables (Temperature, Pressure, Residence Time, Sweep Gas and Heat Flux), so as to reduce or even prevent coke from forming during the reaction, and minimizing gas production, while also providing optimal conversion of the asphaltene portion of the heavy hydrocarbon to provide the desired mix of refinery-ready feedstock components through pipelineable crude and carbon fiber products.
(19) The first and second variables involve applying a uniform heat flux between 7000-12000 BTU/hr sq.ft (22.1-37.8KW/m.sup.2) to the entire pool of process fluid in the reactor and maintaining a single operating temperature in the reactor between 675-790° F. (357.2-421.1° C.). This may be achieved by the presence of appropriately sized and located heating devices in the reactor. The number of heaters will be set by calculating the optimal dispersion of heat between any two heaters so as to have a uniform temperature throughout the pool and to avoid peak or spot temperatures significantly higher than the target temperature in the reactor. Avoiding peak temperature spots reducing the chance for generating coke in the reactor.
(20) The third reactor variable, residence time, can be between 5 up to 7 hours minutes in the reactor. AS the residence time is increased, the conversion of 975+° F. (523.9+° C.) material to 975° F. (523.9+° C.) material increases and the expected concentration of mesophase material increases.
(21) The fourth reactor variable, operating pressure, can be maintained at near atmospheric pressure, in any case, to be less than 50 psig (345 kPa), with standard pressure control principles used for consistent performance. The pressure range is controlled on the low end to prevent excessive, premature flashing of hydrocarbon, essentially bypassing the reactor, and limited on the high end to reduce secondary cracking and consequent increased gas yields.
(22) The fifth reactor variable, sweep gas 31, may be added to the process fluid in the reactor 30 in the range of 0-80 scf/bbl (0-14.24 Sm.sup.3/Sm.sup.3) if deemed beneficial to improving the reactor performance.
(23) The sweep gas 31 can be natural gas, hydrogen, produced/fuel gas from the process, steam, nitrogen or any other non-reactive, non-condensable gas that will not condense to a liquid.
(24) Sweep gas in the dosage of 0-80 scf/bbl (0-14.24 Sm.sup.3/Sm.sup.3) of feed may be provided to remove the “lighter” hydrocarbon products (i.e. methane to <750° F. (398.9° C.)) boiling point hydrocarbons) as soon as they are formed in the reactor 30 so that there is a minimum of secondary cracking which could increase gas make and potentially increase olefinic naphtha/distillate production. The sweep gas may also allow the reactor to operate closer to the desired operating pressure (<50 psig (345 kPa)) and temperature. The sweep gas 31 can also be used to provide additional heat and/or mixing to the process fluid 14 in the reactor 30.
(25) Each variable may be changed independently, within the ranges suggested, based on the quality of feedstock provided or based on the quality and quantity of each output desired. Since the 5 noted process variables are inter-related, a multi-variable process control scheme with a prescribed objective function (maximum yield to meet minimum product specifications) will be beneficial to ensure the process operates at an optimal point when any one of the variables is changed or the feed/product situation is altered.
(26) The overhead fraction 32 can be directed to a gas liquid separation unit 40, which can comprise a cooler and separation drum, as an example, in which a portion of the overhead fraction 32 that is a condensable liquid product containing naphtha and heavier hydrocarbons can be separated from the gaseous components of the overhead fraction 32. An off-gas line 43 containing undesirable gases such as sour gas, can be provided at the separation drum in unit 40 (not shown) for those gases to be disposed of, recycled, or subjected to further treatment.
(27) One or more liquid hydrocarbon streams can be produced from separation drum (not shown, but in 40).
(28) The bottom fraction 32 can contain hydrocarbons, and thermally modified asphaltenes. Although the characteristics of the bottom fraction 32 taken from the reactor 30 will vary depending on the process fluid 25 input into the reactor 30 and the reactor's operating parameters, in one aspect the bottom fraction 32 can have an API gravity ranging between −5 and 5.
(29) Controllable process variables allow an operator to vary the performance of the reactor 30 to meet the needs of the final product based on changing characteristics of the incoming process fluid 25.
(30) The controllability of the five inter-related variables, residence time, sweep gas, heat flux, temperature and pressure in the reactor 30 allow an operator to vary the performance of the reactor 30.
(31) In this manner, when the characteristics of the feedstock 5 are changed the five inter-related process variables can be optimized to avoid the production of coke and minimize the production of non-condensable vapors which are produced in the reactor 30. For example, the operator can vary the residence time of the process fluid in the reactor 30 based on the characteristics of the process fluid to obtain the desired yields and/or quality of the bottoms output 32, and the overhead output, 33. Alternatively, the operator can vary the sweep gas, temperature or pressure to achieve similar outcomes. The process variables are inter-related and the minimization of coke and avoidance of excess gas make is challenging and is best determined by pilot operations.
(32) The reactor 30 is operated in a manner that significantly limits and even prevents the formation of coke and reduces gas production while converting asphaltenes into more suitable components for downstream processing. Consequently, modified asphaltenes and other heavy components remain in the bottom fraction 32 that is removed from the reactor 30. To maximize the recovery of the desirable refinery feedstock crude and to separate heavy components for carbon fiber production, the bottom fraction 32 from the reactor 30 must be further treated using, for example, a high performance solvent extraction process 50. The treatment of the bottom fraction 32 by solvent extraction process 50 allows the reactor 30 and the solvent extraction process 50 to be used in conjunction, to produce a suitable full range refinery feedstock crude transported via pipeline without the need for transport diluent and a solid asphaltene product for carbon fiber production which can involve the following steps: extrusion, melt spinning, stabilization, carbonization, graphitization, surface treatment, and/or sizing. As stated previously, optional thermal conditioning in Unit 35, and optional solvent deasphalting in Unit 55, can be employed to generate different quality crude and carbon fiber products.
EXAMPLE
(33) 250 lbs/hr (113.4 kg/hr) of diluted bitumen at 22.4 API (918.8 kg/m.sup.3) (stream 5 in
Definitions
(34) Carbon fiber—Fiber containing at least 92 wt % carbon, while the fiber containing at least 99 wt % carbon is usually called a graphite fiber.
(35) General purpose carbon fiber—Carbon fibers that have relatively low tensile strength (less than 1 GPa) and low modulus (less than 100 GPa) respectively. Isotropic-pitch-based carbon fibers belong to this grade and are used in applications that benefit from their low weight and bulkiness, e.g. thermal insulation for a high-temperature furnace, cement reinforcement and activated carbon fiber applications).
(36) Graphene—Graphene is an atomic-scale hexagonal lattice made of a single layer of carbon atoms. It is the basic structural element of many other allotropes of carbon, such as graphite, diamond, charcoal, carbon nanotubes and fullerenes.
(37) Insolubles—Material that precipitates into or remains in the solid form when mixed with a solvent.
(38) Mesophase—A phase of matter intermediate between a liquid and solid, referred to as liquid crystals.
(39) Non-Newtonian fluid— A fluid that its viscosity (the gradual deformation by shear or tensile stresses) is dependent on shear rate or shear rate history. A Non-Newtonian fluid's viscosity can change when under force to either more liquid or more solid.
(40) Pipelineable crude—Heavy hydrocarbon with API less than or equal to 19 (density >920 kg/m3), and/or more than 300 cst that requires some processing to meet pipeline specifications of greater than API 19 (density <920 kg/m3), viscosity less than 300 cSt at reference temperature, sediment and water less than 0.4 wt % and olefins less than 1 wt % or non-detectable by the measurement tool used by the transporter.
(41) Transport hydrocarbon—Diluent, condensate, hydrocarbon with Boiling range of butane to 550° F. nominally
(42) Tensile strength—Measure of the amount of force with which a fiber can be pulled before it breaks.
(43) Young's modulus—Measure of a material's stiffness defined as the axial stress divided by the axial strain. The higher the modulus, the stiffer the material (i.e. the greater the stress necessary to cause deformation).