THERMOCHEMICAL REFORMING PROCESS AND PLANT FOR ULTRA HEAVY CRUDE AND TAR

Abstract: In a process and plant for the treatment of heavy and ultra-heavy petroleum crudes and tars, the crude is extracted from the crude-bearing formation or mineral sand run by means of hot flue gases and hydrogen donor solvent. After separation from solid mineral content, the extracted crude is hydro­ genated and subjected to multi-stage fractionation, to obtain a light pipe-line quality product. The vapour phase from the final fractionation stage is condensed to provide the solvent for extraction. The liquid phases of the fractionation stages pre­ ceding the last are recycled to a thermochemical high tem­ perature reformer in which reforming of the hydrocarbon stream with deposition of coke takes place under the heat of combustion gases from a high temperature high pressure furnace, which combustion gases subsequently provide the flue gases for the extraction stage. In the hydrogenator, the extracted crude is reacted with the reformed hydrocarbon stream and hydrogen generated in a water gas reaction by the passage of steam over the high temperature deposited coke.

Description: This invention relates to the reforming of ultra heavy petroleum crudes and tars extracted from subterranean or surface formations or from the sand run from mines. With the traditional method of extraction and reforming of crudes, only large-scale refinery installations with specialized technology have been able to carry out the operations for upgrading and reforming heavy crudes and tars into light products. Ultra heavy tars generally constitute a feed stock for asphalt production plants only. None of the existing refinery technologies can perform the conversion (reforming) of crude at the mining site into pipeline quality light products. Prior methods of employing light solvents for ultra heavy tar extraction in any kind of in-situ operation, or from sand run from a surface mine, have largely failed due to precipitation of the asphalt fraction and plugging of the formation, or losses in sand run extraction. Light solvent has been commonly used at the refinery to remove the asphalt fraction from the heavy crude, but the cost of refinery light solvent is prohibitive when considered for any of the extraction processes in-situ. Large refinery installations are designed to accept specific qualities of crude feed stock only. Ultra heavy crude has a unique specification and requires unique storing and transporting facilities. The only practical approach to the storing and transporting of ultra heavy crude has been to keep it under high temperature and/or dilute it with refined solvent which is recoverable at the refinery and can be transported back to the mining/extraction field. A lot of energy is thus consumed merely to deliver the product to the refinery where, despite the amount of energy consumed, such heavy crude remains a degraded low priced product, hardly saleable in the world market. Accordingly, it is an object of the present invention to provide a process and apparatus for the reforming of heavy and ultra heavy crudes and tars into pipeline quality products. Particularly to be treated are crudes having a gravity below 15° API (at 16°C) extracted in situ from the crude-bearing formation or the sand run excavated from a surface mine. From US-A-4008764 it is already known to recover petroleum from formations containing viscous petroleum, including tar sand deposits, by injecting into the formation a mixture of a liquid solvent, especially a hydrocarbon solvent, and a carrier gas, the solvent and carrier gas being stripped from the recovered petroleum and recycled for re-use. The solvent and carrier gas mixture may be heated and, although not preferred, the carrier gas may be a flue gas or exhaust gas. The European Patent Application EP-A-0144203, filed on the same date as the present application and claiming the same priority date, discloses a process for the recovery of heavy and ultra heavy hydrocarbons from formations containing petroleum deposits which comprises the steps of injection into the formation a hot flue gas, obtained from the combustion of fuel at high temperature and pressure, and a hydrogen donor solvent liquid, and then raising the hydrocarbons thereby mobilised and liquefied by gas lift. The hot flue gas of the process is produced in a similar thermochemical reforming plant adjacent to the well head (see figures). According to the present invention, there is provided a process for the extraction and reforming of heavy and ultra-heavy petroleum crudes and tars, comprising an extraction stage in which hydrocarbon crude from a crude-bearing medium is extracted by the action of hot flue gases and solvent, and characterised in that the solvent is a hydrogen donor solvent, and after the extraction stage further processing of the extracted hydrocarbon crude takes place in a reforming stage employing high temperature combustion gases, the combustion gases employed in this reforming stage subsequently providing the flue gases employed in the extraction stage. Preferably, the extracted crude is subjected to a hydrogenation treatment in which it is reacted with hydrogen and a reformed hydrocarbon stream, and the hydrogenated crude then undergoes multi-stage fractionation, the liquid phase of the last stage of fractionation being taken off as product while the liquid phase or phases of one or more stages of fractionation preceding the last are recycled to provide a stream for thermal reforming at high temperature by the heat of the combustion gases which stream after reforming provides said reformed hydrocarbon stream for the hydrogenation treatment. The hydrogen for the hydrogenation treatment may be principally obtained by a water gas reaction in which steam is decomposed by passage over coke at a high temperature maintained by the combustion gases, the coke having been deposited from the reformed hydrocarbon stream during the high temperature reforming. The solvent employed in the extraction of the crude may be obtained from the condensed vapour phase of the last stage of fractionation. The invention further provides plant for the performance of the process, including a thermochemical reforming reactor comprising, in sequence, a high temperature high pressure furnace section for generating combustion gases, a thermochemical reforming section containing reforming coils surrounded by the combustion gases and through which a stream of hydrogenated crude hydrocarbons flows for reforming, and a quencher-hydrogenator section in which the extracted crude is hydrogenated by reaction with hydrogen and the reformed stream of hydrocarbons from the reforming section. Processes and plant for performing the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic of plant for processing ultra heavy hydrocarbons recovered from a well, and Figure 2 shows the plant adapted to process feedstock from the sand run excavated in an open cast mine. Ultraheavy crudes and tars require a high temperature, approximately 700°C, for thermocracking. The recovered ultra heavy crude will commonly have properties as follows: gravity below 15° API (16°C) down to 0° API, in the raw state; high sulphur content, usually not less than 3%; high conradson carbon content; high coke yield; high requirement of hydrogen for hydrogenation, not less than 250-500 cu. ft. (7-14 m³) per barrel (0.16 m³) of crude; high sand content, as a result of recovery from nonconsolidated formations, or from mined sand runs; high degree of emulsification, as a result of gas-lifting by the use of flue gas, high inlet temperature at inlet to the plant, as a result of heating in the production wells; decreased viscosity at inlet to the plant, not exceeding 5.10 - ³Pa.s. (5cP). In the example shown in Figure 1, the feed stock for the plant is obtained from a 'daisy' well 10 with a central solvent injection and production bore 12 surrounded by six slanting gas injection bores 13. The feed stock from the annular casing 14 of the production bore 12, which will typically be an emulsion of crude, solvent, water and gas, enters a main separator 11 at elevated temperature and pressure, for example, 450°F (232°C) and 460 PSIG (3151 x 10³ N /m²). The main separator 11, which has internal vertical apertured baffles 31, separates the diluted crude from the water and sand. Vaporized hydrocarbons are condensed in a condenser 15 which is an inlet stage of gas scrubber 16 from which carbon dioxide and nitrogen are vented. The condenser has a coil which is cooled by raw water pumped from a well or reservoir by a pump 17. The water, after passing through the condenser 15, is introduced into the cooling coil system 18 of the desander-desalter separator 19 from where it passes into a furnace water jacket 20 of a high pressure thermochemical reformer 21 and thence as steam into the coil of a steam superheater 22 at about 450°F (232°C). Between the water jacket 20 and the steam superheater 22, a by-pass stream is withdrawn at a process control valve 24 and injected continuously, or cyclically, into thermochemical reforming coils 23 through process control valves 25, 26. Superheated steam from the steam superheater 22 is injected into a sand jet-washing system 27 in the main separator 11 where it condenses, and whence it carries entrained sand into the desanding-desalting separator 19. The water is cooled somewhat in the separator 19, and the settling sand is discharged, at 28, by a screw feeder 32. Separated, largely de-emulsified crude in solvent, under the internal pressure of the main separator 11, is introduced at a temperature of about 420°F (216°C) into a quencher-hydrogenator 29 in which it is reacted with superheated thermally cracked hydrocarbon, and hydrogen generated principally in the coil system 23 of the thermochemical reformer 21 from which it enters the quencher-hydrogenator usually at a temperature not less than 1300°F (704°C). Quenched and hydrogenated crude under the internal pressure of the quencher-hydrogenator 29 leaves at about 850°F (454°C) and is introduced into a first stage fractionator 30 at an inlet temperature of, for example, 800°F (427°C). The heavy liquid fraction separated in the fractionator 30 is recycled by a pump 33 to the process control valves 26, 25 and through the coils 23 of the thermochemical reformer into the quencher-hydrogenator 29. The light vapour fraction from the fractionator 30 is condensed in an air-cooled condenser 34 and pumped by a pump 36 at about 550°F (288°C) into a second stage fractionator 35, from where the liquid fraction, which is a heavy distillate, is pumped off by a pump 37 and recycled, via a process control valve 44 and the valves 25, 26, through the coils 23 in the thermochemical reformer to the quencher-hydrogenator 29. The lighter vapour fraction from the fractionator 35 is condensed in an air-cooled condenser 38 and pumped by a pump 39 at about 300°F (149°C) to a third stage fractionator 40. The liquid fraction from the third stage fractionator is a final pipeline quality commercial product, up to 40° API gravity, and is pumped away by a pump 41 via process control valves 42, 43 to a final reformed product pipeline 45. The vapour fraction from the fractionator 40 is condensed in an air-cooled condenser 46 and injected by a pump 47 via a process control valve 48, at a temperature of about 200°F (93°C), down the central pipe 49 of the production bore 12 to act as hydrogen donor solvent to dissolve and partially reform the in situ crude by hydrogenation in the presence of flue gas components and in reaction with them. Alternatively, or in addition, this vapour fraction or a part of it can be utilised for the same purpose in a vessel serving as an ultra heavy crude extractor. The hydrogen donor solvent is a highly hydrogenated naphthene fraction having a boiling range usually between 150° and 250°F (66° - 121°C). The amount of solvent needed for crude extraction is usually approximately 25% by weight of the recovered crude. Further portions of it can be blended with the final product or employed to dilute the hydrocarbon liquids returning to the thermochemical reformer from the first and second stage fractionators. The core of the entire plant is the high pressure, high temperature thermochemical reforming reactor 21, which produces high temperature combustion gases and which performs the following functions: i) thermal cracking, ii) thermochemical reforming, iii) hydrogen generation, iv) coke deposition and decoking. The superheated flue gases leaving the thermochemical reformer at about 900°F (482°C) and 900 PSI (6165 x 10³ N /m²) are fed to the outer casing 50 of the production well and thence into the gas injection bores 13 to react with the hydrogen donor solvent and the in situ crude. Hot water at about 200°F (93°C) is also supplied into the outer casing 50 from the desander-desalter 19 by a pump 51. Alternatively, or in addition, the flue gases can be utilised similarly in a vessel serving as a mined crude extractor-reformer. The thermochemical reforming reactor 21 has a water-jacketed high pressure refractory furnace 52 with a burner system fed by high pressure fuel pumps 53 and a compressor 54 into which the gaseous fraction from the condenser 46 is introduced for use as fuel. The main fuel for the furnace may be gas or liquid hydrocarbon or pulverised coal, but is preferably obtained from the crude being treated in the process. It is injected at high pressure, together with compressed air which can, if desired, be oxygen enriched. The furnace 52 opens into the section of the reactor containing the reforming coils 23, which is followed by the section containing the steam super-heater 22. The system is designed to restrict the decompression and flow of the combustion gases from the furnace so that a high intensity condensed flame is obtained and a very high combustion gas temperature is reached, not less than 3000°F (1649°C). The coil system 23 of the thermochemical reformer has dual interconnected passageways 55, 56 controlled by the process control valves 24, 25, 26. While one pass is charged with heavy hydrocarbons from the fractionators 30, 35 for thermal cracking and coke deposition, the other pass is fed with steam from the by-pass valve 24 to provide a water gas reaction with the deposited coke and generate hydrogen. The hydrogen mixes with the crude and partially refined hydrocarbons and provides the hydrogenation reaction in the quencher-hydrogenator 29. The process control valves 24, 25, 26 are operated to switch the flows of hydrocarbons and steam cyclically between the coil passages 55 and 56 so as to maintain the water gas reaction, but the hydrogen flow into the quencher hydrogenator, and hence the hydrogenation reaction, is substantially continuous. Additional hydrogen is generated in the quencher hydrogenator by reaction of the flue gases with residual steam from the coils 23. The function of the water jacket 20 around the furnace 52 is to raise the water temperature to generate steam for the water gas reaction with the deposited coke. Provision for a large amount of coke deposition is made by enlargement of the diameter of the tubing of each coil to form a coke deposition chamber in which the hydrocarbon flow velocity is decreased, these chambers being situated toward the furnace end of the reforming section where combustion is still continuing around the coils 23 so that the coke deposition chambers are exposed to a very high heat intensity. With deposition of a sufficient amount of coke, there is a lowering of the hydrocarbon viscosity, and that means a better hydrocarbon quality is obtained after just the first stage of reforming. The coke deposition chambers are constructed from high quality metal alloy resistant to high temperature and high external pressure. The process valves 24, 25, 26 have controllers designed to provide manual or automatic control of the entire water gas reaction in the thermochemical reformer. The plant can also be adapted to extract and reform ultra heavy crude and tar from the sand run excavated in an open cast mine as shown in Figure 2. The main components of the plant and their functions remain unchanged when operating on sand run. The feed stock is a heated mixture of partially reformed crude obtained by extraction of the sand run in a silo or retort 60 by means of the hydrogen donor solvent and flue gas components. The silo has an internal screw-conveyor system 61 extending horizontally beyond the silo to a length sufficient to obtain extraction of the crude from the sand run by countercurrent flow of the superheated flue gases and solvent. The flights of the screw-conveyor are of an open type with openings between the core-shaft 63 and the main screw band of the conveyor. The core-shaft is a tube with openings 62 along it that are fitted with hard metal jet nozzles through which the flue gases from the thermochemical reformer 21 and solvent from the condenser 46 are injected into the constantly rotating and conveyed sand run. During the process of injecting the flue gases and solvent, the crude in the conveyed sand is liquefied, partially reformed and extracted from the sand through bottom filters 64. The extracted crude at an outlet temperature of, for example, 200°F (93°C) can be further processed in a hydrocyclone-desilter, to remove mineral particles, or can be pumped, as shown, by a pump 65 directly into the regular main separator 11. Sand from which the crude has been extracted is delivered from a terminal compacting section 66 of the screw- conveyor which is maintained at the hottest temperature by the incoming superheated flue gases. The incoming hydrogen donor solvent, however, is introduced through a feed tube 67 that extends axially through the compacting section of the screw-conveyor, within the tubular shaft 63 of the conveyor, to the middle section of the screw-conveyor beyond the compacting section 66. The flue gases, in their flow countercurrent to the direction of conveyance of the sand run, assist in retaining the vapour of the hydrogen donor solvent in contact with the crude-bearing sand and promote its reaction with the crude. The countercurrently flowing flue gases and solvent together strip out crude from the sand primarily in the major section of length of the screw-conveyor 61 that, in the direction of conveyance of the sand, lies upstream of the terminal compacting section 66 of the conveyor. In the compacting section, the flue gases alone strip out the residual crude. The solvent vapour and dissolved hydrocarbons permeate through the sand run and are quenched and condensed to liquid in a condensing section 69 before leaving the silo or retort. The flue gases after their countercurrent passageway along the screw-conveyor 61 permeate through the pile of sand run 68 awaiting treatment deposited in the silo 60. These gases react with moisture in the sand run, which leads to partial decontamination of the flue gases in regard to their SO₂ and NO x content. The final pollution control is achieved in the condenser/gas scrubber 16 where two streams of gases, one from the main separator 11 and the other from the silo or retort 60, are mixed together and, after having been stripped of condensate, if any, are scrubbed free of traces of SO₂. Thus both in the case of extraction from a production well and in the case of extraction from excavated sand run, a single stream of high temperature combustion gases serves both to promote non-catalytic reforming of the crude hydrocarbons after extraction and partakes in the actual extraction process. Moreover, the hydrogen donor solvent used in the extraction process is obtained as a by-product of the reforming process. The plant is readily capable of being set up and operated in the field at the well-head or mining site, and can indeed be mobile, and it will produce a regular light pipe-line quality product from heavy crude materials that were hitherto barely saleable. Advantageously, for easy transport and assembly the main thermochemical reformer and reactor together with the quencher hydrogenator can be constructed as a long tubular vessel in three or possibly four segments each of which can be individually detached for maintenance or replacement. The first segment will be the furnace section, the second will be the section containing the reforming coils and the steam superheater and the third section will be the quencher hydrogenator; or alternatively, the reforming coils and the steam superheater can be in two separable sections instead of the same section. The tubular segments need not exceed 5 ft. (1.52 m) in diameter and they will all be heavily thermally insulated internally and can also be externally surrounded by cold water jackets, if desired. The length of the tubular segments will be sufficient to ensure proper mixing, heat exchange and reaction amongst the various components partaking in the process. The train of tubular segments can, if convenient, be assembled at the factory. `" ` ` In addition to the main train of segments forming the thermochemical reforming rector, there will be a second train consisting of the fractionators and their coolers and a third train consisting of the main separator with its gas scrubber and the desander-desalter. Each of these two further trains can also, if convenient, be factory assembles. It would, of course, also be possible, as an alternative to add the main separator or extraction vessel to the train forming the thermochemical reforming reactor as an additional tubular segment.

Claims: A process for the extraction and reforming of heavy and ultra-heavy petroleum crudes and tars, comprising an extraction stage in which hydrocarbon crude from a crude-bearing medium is extracted by the action of hot flue gases and solvent, and characterised in that the solvent is a hydrogen donor solvent, and after the extraction stage further processing of the extracted hydrocarbon crude takes place in a reforming stage employing high temperature combustion gases, the combustion gases employed in this reforming stage subsequently providing the flue gases employed in the extraction stage. A process according to Claim 1, wherein the extracted crude is subjected to a hydrogenation treatment in which it is reacted with hydrogen and a reformed hydrocarbon stream, and the hydrogenated crude then undergoes multi-stage fractionation, the liquid phase of the last stage of fractionation being taken off as product while the liquid phase or phases of one or more stages of fractionation preceding the last are recycled to provide a stream for thermal reforming at high temperature by the heat of the combustion gases which stream after reforming provides said reformed hydrocarbon stream for the hydrogenation treatment. A process according to Claim 2, wherein the hydrogen for the hydrogenation treatment is principally obtained by a water gas reaction in which steam is decomposed by passage over coke at a high temperature maintained by the combustion gases, the coke having been deposited from the reformed hydrocarbon stream during the high temperature reforming. A process according to Claim 3, wherein the high temperature hydrocarbon reforming and the water gas reaction occur in separate dual passageways surrounded by the combustion gases, the hydrocarbon stream and the steam flow being cyclically switched so as to change over the passageways in which they respectively flow at intervals. A process according to Claim 2, or Claim 3, or Claim 4, wherein the condensed vapour phase of the last stage of fractionation provides the solvent employed in extraction of the crude. A process according to Claim 3, or Claim 4, wherein the steam for the water gas reaction is generated by passage of water through a water jacket of a furnace in which the combustion gases are generated. A process according to any one of Claims 2 to 6, wherein before hydrogenation the extracted crude is treated in a separator to separate solid mineral content and salts. A process according to Claims 6 and 7, wherein a portion of the steam from the furnace water jacket is superheated by the combustion gases and then injected into the separator. A process according to Claim 8, wherein water and the separated solid mineral content is transferred from the separator to a desander in which the mineral content settles and the water is cooled by heat exchange with ingoing feed water supplying the furnace water jacket. A process according to any one of the preceding Claims, wherein the combustion gases are generated by combustion at high pressure of fuel obtained from the hydrocarbon crude. A process according to any one of Claims 1 to 10, wherein the extraction step is carried out on crude-bearing excavated sand run in a silo or retort equipped with a screw-conveyor, the flue gases and solvent flowing in countercurrent to the sand run being conveyed by the conveyor. Plant for the performance of the process of the preceding Claims, including a thermochemical reforming reactor comprising, in sequence, a high temperature high pressure furnace section for generating combustion gases, a thermochemical reforming section containing reforming coils surrounded by the combustion gases and through which a stream of hydrogenated crude hydrocarbons flows for reforming, and a quencher-hydrogenator section in which the extracted crude is hydrogenated by reaction with hydrogen and the reformed stream of hydrocarbons from the reforming section. Plant according to Claim 12, wherein the reforming coils are dual coils each including an enlarged diameter coke deposition chamber situated where it is subjected to the greatest heat of the combustion gases, and process control valves are provided for switching flows between the dual passageways at intervals so as to interchange the hydrocarbon stream with a steam flow that generates hydrogen by water gas reaction with the deposited coke. Plant according to Claim 12 or Claim 13, wherein the furnace section is water-jacketted and a process control valve is provided to admit steam generated in the water jacket to the reforming coils for the water gas reaction. Plant according to Claim 14, further comprising a steam superheater section between the reforming section and the quencher-hydrogenator section in which steam generated in the furnace water jacket is superheated by the combustion gases for use in the separation of solid minerals and salts from the extracted crude before hydrogenation. Plant according to Claim 15, wherein the furnace, reforming, superheater and quencher-hydrogenator sections are contained in sequence in a continuous tubular vessel built up from separable tubular segments. Plant according to any one of Claims 12 to 16, further including a train of fractionators and condensers receiving the extracted crude after hydrogenation and supplying the hydrocarbon stream for reforming, a final product stream and a stream of solvent for use in the extraction of the crude. Plant according to any one of Claims 12 to 17, further including a main separator in which the extracted crude is treated with superheated steam, and a desander in which water and solid mineral content from the main separator are cooled and separated. Plant according to any one of Claims 12 to 18, further including an extraction silo or retort equipped with a screw-conveyor which conveys excavated crude-bearing sand run in countercurrent to flue gases and solvent, the screw-conveyor having a tubular core-shaft fitted with jet nozzles for the introduction of flue gases and/or solvent into the conveyed sand run.

Inventors: ZAKIEWICZ, BOHDAN M., DR.
Applicants: ZAKIEWICZ, BOHDAN M., DR.
Application year: 1984
Main classification: C10G1
IPC codes: C10G1