Process and system for direct cracking of crude oil to produce olefins

Abstract

The present invention relates to a method and system for cracking crude oil, which includes sending crude oil to a first set of tubes in a convection section of a cracking furnace for preheating, then vaporizing the crude oil to obtain a first vapor phase and a first liquid phase, high-pressure extracting the first liquid phase to obtain non-asphalt oil and asphalt, mixing the first vapor phase and the non-asphalt oil with steam, or mixing the first vapor phase with the non-asphalt oil and then with steam, then sending it to a second set of tubes in the convection section of the cracking furnace to raise its temperature, then sending it to a radiant section of the cracking furnace to crack it to obtain cracked products, and separating the cracked products to obtain low-carbon olefins. In the present invention, crude oil is preheated and vaporized in a cracking furnace, and then the resulting vapor phase is passed into the cracking furnace. The resulting liquid phase is passed through a supercritical extraction section to separate the extracted oil, which is then passed into the cracking furnace. This method can effectively improve the cracking efficiency of crude oil, improve the yield of low-carbon olefins in the products, extend the operating cycle, and reduce the coking of the vaporized crude oil mixture in the cracking process.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to the field of crude oil cracking, in particular to a process and system for cracking crude oil, and more particularly to a process and system for direct cracking of crude oil to prepare olefins.

[0002] [Background technology] Low-carbon olefins usually refers to a general term for unsaturated hydrocarbons with four or less carbon atoms, mainly including ethylene, propylene, butadiene, and other organic chemical raw materials with high economic value. With the development of China's economy, the demand for these organic chemical raw materials is increasing year by year. Although the production scale of low-carbon olefins is also increasing year by year, it cannot meet the increasing demand.

[0003] For a long time, China has always used naphtha as the main raw material for preparing low-carbon olefins. However, in recent years, with the large-scale development of oilfield-related gas in the Middle East and shale gas in the United States, these cheap oil and gas resources have been widely used as ethylene raw materials, and the price of ethylene-related products has fallen. In order to respond to the influence of market competition, expanding the raw material source of the ethylene cracker and reducing the cost of raw materials has become an effective means for traditional ethylene businesses to reduce costs and improve efficiency. Therefore, using special heavy hydrocarbons, especially untreated crude oil, as raw materials for the cracking furnace to produce low-carbon olefins can reduce the raw material cost and energy consumption of the olefin production unit and quickly respond to the changes in supply and demand of cracking raw materials in the market.

[0004] In order to fully utilize crude oil resources and improve the yield of low-carbon olefins, cracking furnaces are usually used to crack various hydrocarbon feedstocks into olefins by vapor gas cracking. Commonly used cracking furnaces are composed of a convection section and a radiant section. Crude oil is generally divided into four components: saturates, aromatics, colloids and asphaltene, and saturates and asphaltene are the most stable and least stable components in crude oil, respectively. Crude oil contains high molecular weight non-volatile components with boiling points above 590°C. When these non-volatile components are preheated in the convection section of a conventional cracking furnace, some of them will not be gasified, and the non-gasified non-volatile components will be mixed into the radiant section together with the mixed gas flow, causing coking deposits in the radiant section or clogging the radiant section, thus affecting the yield of cracked products.

[0005] CN101583697A discloses a method for cracking synthetic oil-containing feedstock, the method including: 1) liquid processing the aliquot having a broad boiling range, the aliquot including a) a normally liquid hydrocarbon portion boiling in the range of 50°F to 800°F and substantially free of residues, and b) a pyrolyzed liquid hydrocarbon portion in the range of 600°F to 1050°F, to produce a synthetic crude oil, the synthetic crude oil boiling in the range of 73°F to 1070°F, having more than 25 wt% aromatics, more than 25 wt% naphthenes, 0.3 ... 1) obtaining a synthetic crude oil having less than 0.02 wt. % S and less than 0.02 wt. % asphaltenes and substantially free of non-asphaltenes residuals; 2) adding a normally liquid hydrocarbon component boiling in the range of 100°F to 1050°F to the synthetic crude oil; and 3) cracking the mixture resulting from 2) in a cracking furnace including a radiant coil outlet to obtain a cracked effluent, wherein the cracking is conducted under conditions sufficient to achieve a radiant coil outlet temperature that is greater than the optimum radiant coil outlet temperature for separately cracking the synthetic crude oil.

[0006] In the process, existing feedstocks for ethylene production are mixed into crude oil to dilute the crude oil, improve the cracking performance of the crude oil, and improve the conversion rate of olefins. However, this process is limited by the source of existing feedstocks for ethylene production, and cannot effectively utilize a large amount of crude oil for the production of low-carbon olefins.

[0007] CN1957068A discloses the steam cracking of a hydrocarbon feedstock containing salts and / or particulate matter, the method comprising: a) adding an unsalted feedstock containing salts and any particulate matter to a convection section of a dry distillation furnace; b) raising the temperature of the hydrocarbon feedstock; c) feeding the hydrocarbon feedstock to a flash / separation vessel located upstream of the dry point; d) separating the hydrocarbon feedstock into a vaporized gas phase from which non-volatile components and salts have been substantially removed and a liquid phase enriched in non-volatile components and salts, the liquid phase comprising 5% liquid phase at all points in the convection section upstream of the flash / separation vessel, and maintaining the salts and any particulate matter in suspension; e) removing 50-95% of the hydrocarbon feedstock in the vaporized gas phase from the flash / separation vessel and cracking the vaporized gas phase to produce an effluent containing olefins; and f) removing at least 5% of the hydrocarbon feedstock in the liquid phase from the flash / separation vessel along with the suspended salts and any particulate matter. US3617493 also discloses a process for cracking crude oil with steam, similar to the above process.

[0008] CN1041967A discloses a method for thermally cracking a low-quality feedstock containing a heavy fraction in a cracking furnace, in which the low-quality feedstock is recovered from a preheater of the cracking furnace, and the heavy fraction is separated and removed from the low-quality feedstock by a method of vaporization, and then returned to the preheater before the feedstock is subjected to thermal cracking.

[0009] The above methods of cracking feedstock all use a flash tank to process and vaporize the crude oil passing through the convection section of the cracking furnace, and then pass the gas phase through the radiant section for cracking. However, after the feedstock is flashed, at least 5% of the hydrocarbon feedstock still remains in liquid, which affects the yield of low carbon olefins. Moreover, the separated liquid phase is directly used as fuel oil, resulting in the waste of feedstock.

[0010] Therefore, there remains a need for improved methods and systems for cracking crude oil that can reduce coking during cracking of crude oil and increase the yield of low carbon olefins.

[0011] Summary of the Invention In order to overcome the problems of insufficient crude oil vaporization, susceptibility to coking during cracking, and low yield of low carbon olefins in the prior art, the present invention provides a method and system for cracking crude oil, particularly relates to a method and system for directly cracking crude oil to prepare olefins, which can improve the utilization rate and cracking efficiency of crude oil feedstock, extend the operation cycle, reduce coking during cracking, and simultaneously improve the yield of low carbon olefins in the product.

[0012] In one aspect, the present invention provides a method for cracking crude oil, comprising the steps of: Step 1. Passing crude oil through a first set of tubes in a convection section of a cracking furnace for preheating and then vaporizing the crude oil to obtain a first vapor phase and a first liquid phase; Step 2: subjecting the first liquid phase to high pressure extraction to obtain non-asphalt oil and asphalt; Step 3: mixing the first gas phase and the non-asphalt oil with steam, respectively, or mixing the first gas phase with the non-asphalt oil and then with steam, then sending it to the convection section of the cracking furnace for heating to a crossover temperature, then sending it to the radiant section of the cracking furnace for cracking to obtain cracked products, and separating the cracked products to obtain low carbon olefins.

[0013] Specifically, the present invention provides a method for cracking crude oil, comprising the steps of: Step 1. Passing crude oil through a first set of tubes in a convection section of a cracking furnace for preheating and then vaporizing the crude oil to obtain a first vapor phase and a first liquid phase; Step 2: subjecting the first liquid phase to high pressure extraction to obtain non-asphalt oil and asphalt; Step 3: mixing the first gas phase and the non-asphalt oil with steam, respectively, or mixing the first gas phase with the non-asphalt oil and then with steam, then sending it to a second set of tubes in the convection section of the cracking furnace for heating to a crossover temperature, then sending it to the radiant section of the cracking furnace for cracking to obtain cracked products, and separating the cracked products to obtain low carbon olefins.

[0014] In the present invention, the first gas phase obtained after the vaporization of crude oil is passed through a cracking furnace, and the non-asphalt oil (including extracted oil) separated from the first liquid phase after high pressure extraction is passed through the cracking furnace. This method can effectively improve the utilization rate and cracking efficiency of crude oil, improve the yield of low carbon olefins in the product, extend the operation cycle, and reduce the coking of the vaporized crude oil mixture during cracking.

[0015] In the present invention, the crude oil includes light crude oil, medium crude oil, heavy crude oil, and extra heavy crude oil such as crude oil after dehydration and desalting. The relative density of light crude oil at 20°C is less than 0.8661, the relative density of medium crude oil at 20°C is 0.8661-0.9162, the relative density of heavy crude oil at 20°C is 0.9162-0.9968, and the relative density of heavy crude oil at 20°C is more than 0.9968. Preferably, the crude oil in the present invention can be medium crude oil, heavy crude oil, and extra heavy crude oil.

[0016] In a preferred embodiment, the total colloids and asphaltenes content in the crude oil is greater than 1 wt%, preferably the total colloids and asphaltenes content in the crude oil is greater than 5 wt%.

[0017] In the present invention, the crude oil is not limited to the above, and may also include oil obtained by primary processing of crude oil, oil obtained by secondary processing of crude oil, and liquefied coal.Preferably, the primary processing includes atmospheric distillation and / or vacuum distillation, and the oil obtained by primary processing of crude oil includes light naphtha, naphtha, diesel oil, residual oil, etc.Preferably, the secondary processing includes thermal cracking, catalytic cracking, hydrocracking, delayed coking, and catalytic reforming, and the oil obtained by secondary processing of crude oil includes hydrocracked tail oil, hydrogenated diesel oil, gasoline, raffinate oil, etc.

[0018] In a preferred embodiment, in step 1, the outlet temperature of the preheated crude oil is about 120 to 350° C., preferably about 120 to 315° C., and more preferably about 150 to 300° C. Here, the outlet temperature of the preheated crude oil refers to the temperature at which the crude oil flows out of the convection section of the cracking furnace after being preheated in the convection section.

[0019] In a preferred embodiment, in step 1, the liquid content in the first gas phase is 10 g / m 3 Less than 200 mg / m 3 is less than.

[0020] In a preferred embodiment, in step 1, the vaporization is at least one of stripping, flash vaporization and cyclone separation, with cyclone separation being preferably used for the vaporization.

[0021] In a preferred embodiment, in step 1, a cyclone separator is used for vaporization.

[0022] In a further preferred embodiment, the cyclone separator is selected from a volute cyclone separator, an axial guide vane cyclone separator, a cylindrical cyclone separator, a combined cone-cylinder cyclone separator or a direct current cyclone separator.

[0023] In a further preferred embodiment, the cyclone separator comprises internal members including a skimming cartridge located at an upper end of the cyclone separator and / or a baffle and vortex breaker at a lower portion of the cyclone separator.

[0024] Here, the cyclone separator has the advantages of being small in volume and having high separation efficiency.

[0025] In the present invention, the term "cyclone separator" refers to a cyclone separator in a broad sense, including not only the narrow sense of "cyclone separator" but also separation devices having similar principles in such technical fields, such as hydrocyclone separators. Unless otherwise specified, the cyclone separator described in the present invention is a cyclone separator in a broad sense. According to the present invention, the working medium of the cyclone separator for vaporization is mostly gas. In addition, as long as the preheated crude oil can be separated at 120-350°C, preferably 120-315°C, and the separation efficiency can reach 90% or more, any cyclone separator commonly used in the field can be selected.

[0026] Here, the number of cyclone separators can be selected according to need, and one or more cyclone separators can be provided. When multiple cyclone separators are provided, the multiple cyclone separators can be connected in parallel or in series.

[0027] In one embodiment, in step 2, the high-pressure extraction includes an extraction process, an optional settling process, and a solvent recovery process. If the settling process is not performed, the first liquid phase is subjected to an extraction process and a solvent recovery process to obtain asphalt and non-asphalt oil, respectively. The asphalt is discharged to the outside, and the non-asphalt oil can be sent to a cracking furnace for subsequent cracking. If the settling process is performed, the first liquid phase is subjected to an extraction process, a settling process, and a solvent recovery process to obtain extracted oil, settled oil, and asphalt, respectively. The settled oil and asphalt are discharged to the outside, and the extracted oil can be sent to a cracking furnace for subsequent cracking.

[0028] As for whether the first liquid phase needs to be subjected to sedimentation separation treatment, it should be pointed out that this mainly depends on the feed crude oil. When the heavy hydrocarbon content of the crude oil is low, in the high-pressure extraction, the first liquid phase needs to be subjected to extraction treatment to remove asphalt, and then directly subjected to solvent recovery treatment to recover the solvent, to obtain non-asphalt oil, which can be applied to cracking. When the heavy hydrocarbon content of the crude oil is high, the first liquid phase needs to be subjected to extraction treatment to remove asphalt, and then further subjected to sedimentation treatment to remove the sedimented oil, and then the material removed from the asphalt and sedimented oil needs to be subjected to solvent recovery treatment to recover the solvent, to obtain the extracted oil, which can be applied to cracking.

[0029] In the present invention, the term "high pressure" generally refers to a pressure of about 0.5 to 40 MPa, preferably about 0.8 to 25 MPa, and more preferably about 1 to 10 MPa.

[0030] In a preferred embodiment, in step 2, the first liquid phase is subjected to high pressure extraction to obtain extracted oil, settled oil and asphalt.

[0031] In a preferred embodiment, in step 2, the first liquid phase is subjected to high pressure extraction to obtain extracted oil, settled oil and asphalt. In step 3, the first gas phase and extracted oil are mixed with steam respectively, or the first gas phase is mixed with extracted oil and then mixed with steam, then sent to the second group of tubes in the convection section of the cracking furnace to heat up to the crossover temperature, then sent to the radiant section of the cracking furnace to crack and obtain cracked products, and the cracked products are separated to obtain low carbon olefins.

[0032] In a further preferred embodiment, in step 2, the first liquid phase is subjected to high-pressure extraction to obtain extracted oil, sedimented oil and asphalt. In step 3, the first gas phase and extracted oil are mixed with steam, respectively, then sent to the second tube group of the convection section of the cracking furnace to be heated to the crossover temperature, and then sent to the radiant section of the cracking furnace to be cracked to obtain cracked products, and the cracked products are separated to obtain low-carbon olefins. In a preferred embodiment, in step 2, the high-pressure extraction includes extraction, sedimentation and solvent recovery, which are preferably carried out in an extraction column, a sedimentation column and a solvent recovery column, respectively.

[0033] In a further preferred embodiment, the extraction process is carried out in the presence of a solvent, preferably the solvent is a low carbon hydrocarbon, more preferably the low carbon hydrocarbon includes, but is not limited to, at least one selected from the group consisting of propane, butane, pentane, propylene and butene. In a preferred embodiment, the high pressure extraction comprises the following steps: Step (I) subjecting the first liquid phase and the solvent to an extraction treatment to extract a first light phase component containing a non-asphalt portion and the solvent and asphalt, and discharging the asphalt to the outside; Wherein, preferably, the extraction process is carried out in an extraction column, more preferably, the first liquid phase is fed to the top of the extraction column, the solvent is fed to the bottom of the extraction column, a first light component containing a non-asphalt part and the solvent is obtained at the top end of the column, and asphalt is obtained at the bottom of the column and discharged to the outside; Here, the solvent extracts the non-asphalt portion in the first liquid phase (which portion is preferably recovered from the top end of the extraction column) and the asphalt is discharged from the bottom of the extraction column for further processing; Step (II) subjecting the first light component to a temperature increase treatment, and then subjecting the first light component to a sedimentation separation treatment to obtain a second light phase component containing the solvent and the extracted oil and a sedimented oil, and discharging the sedimented oil to the outside; Here, preferably, the sedimentation separation treatment is carried out in a sedimentation column, more preferably, the second light fraction containing the solvent and the extracted oil is recovered from the top end of the sedimentation column, and the settled oil is obtained at the bottom of the sedimentation column and discharged to the outside; Step (III) A step of subjecting the second light component to a temperature increase treatment, followed by a solvent recovery treatment to obtain a recovered solvent and an extracted oil.

[0034] Here, the solvent obtained in step (III) is recycled, optionally after cooling, and the extracted oil is sent to a cracking furnace for subsequent cracking.

[0035] In a preferred embodiment, in step (I), the ratio of the solvent to the first liquid phase is about (0.1-20):1, preferably (1-10):1, for example 4:1.

[0036] In the high-pressure extraction of the present invention, the first light phase component containing the non-asphalt portion and the solvent extracted by the extraction process is subjected to a temperature increase treatment before the sedimentation separation treatment, and the second light phase component containing the solvent and the extracted oil obtained by the sedimentation separation treatment is subjected to a temperature increase treatment before the solvent recovery treatment. The purpose of the temperature increase is to reduce the density and solubility of the solvent, thereby causing a part or all of the crude oil components dissolved in the solvent to precipitate.

[0037] In the present invention, the extraction treatment, the precipitation separation treatment, and the solvent recovery treatment are carried out under high pressure. Preferably, the pressures of the extraction treatment, the precipitation separation treatment, and the solvent recovery treatment are independently about 0.5 to 40 MPa, preferably about 0.8 to 25 MPa, more preferably about 1 to 10 MPa, and more preferably the pressures of the extraction treatment, the precipitation separation treatment, and the solvent recovery treatment are the same or approximately the same.

[0038] In a preferred embodiment, the temperature of the extraction treatment is about 30 to 300°C, preferably about 50 to 200°C.

[0039] In a preferred embodiment, the temperature of the sedimentation treatment is about 0.5 to 50°C higher, preferably about 1 to 30°C higher, than the temperature of the extraction treatment.

[0040] In a preferred embodiment, the temperature of the solvent recovery treatment is about 0.5 to 50° C. higher, preferably about 1 to 30° C. higher, than the temperature of the precipitation separation treatment.

[0041] In a preferred embodiment, the high pressure extraction comprises supercritical extraction.

[0042] In a preferred embodiment, the high pressure extraction is carried out under supercritical conditions, and the temperature and pressure conditions set during the extraction process in step (I) bring the solvent into the supercritical or near supercritical liquid phase region, where the solvent extracts the non-asphalt portion in a first liquid phase, which is preferably recovered from the top end of the extraction column, and the asphalt is discharged from the bottom of the extraction column for further processing.

[0043] In a preferred embodiment, the extraction, sedimentation and solvent recovery processes are all carried out under supercritical or near supercritical conditions.

[0044] In a preferred embodiment, the extraction treatment conditions in the supercritical extraction treatment are a pressure of about 1 to 10 MPa, preferably about 3 to 6 MPa, and / or a temperature of about 50 to 200°C, preferably about 80 to 160°C.

[0045] In a preferred embodiment, the conditions for the sedimentation separation treatment in the supercritical extraction treatment are a pressure of about 1 to 10 MPa, preferably about 3 to 6 MPa, and / or a temperature about 1 to 30°C higher, preferably about 3 to 8°C higher than the temperature of the extraction treatment.

[0046] In a preferred embodiment, in the supercritical extraction process, the conditions for the solvent recovery process are a pressure of about 1 to 10 MPa, preferably about 3 to 6 MPa, and / or a temperature about 1 to 30° C. higher, preferably about 5 to 20° C. higher than the temperature of the sedimentation separation process.

[0047] Here, the pressures of the extraction, sedimentation and solvent recovery processes are independently about 1-10 MPa, preferably about 3-6 MPa, and preferably the pressures of the extraction, sedimentation and solvent recovery processes are the same or similar. In a preferred embodiment, the pressure and temperature conditions of the extraction, sedimentation and solvent recovery processes are controlled to ensure that the three processes are carried out in a supercritical or near-supercritical state.

[0048] In a preferred embodiment, step 3 comprises the following substeps: Step 3.1 mixing the first gas phase with water vapor and then sending it to a first tube row of a second tube group in a convection section of a cracking furnace for heating to a crossover temperature, and then sending it to a first radiant section of the cracking furnace for a first cracking, to obtain a first cracked product; Step 3.2 mixing the non-asphalt oil with steam and then sending it to a second tube row of a second tube group in the convection section of the cracking furnace for heating to a crossover temperature, and then sending it to a second radiant section of the cracking furnace for a second cracking to obtain a second cracked product; Step 3.3: Separating the first cracking product and the second cracking product from each other or mixing them and then separating them to obtain low carbon olefins.

[0049] In a more preferred embodiment, step 3 comprises the following substeps: Step 3.1 mixing the first gas phase with water vapor and then sending it to a first tube row of a second tube group in a convection section of a cracking furnace for heating to a crossover temperature, and then sending it to a first radiant section of the cracking furnace for a first cracking, to obtain a first cracked product; Step 3.2 mixing the extracted oil with steam and then sending it to a second tube row of a second tube group in the convection section of the cracking furnace for heating to a crossover temperature, and then sending it to a second radiant section of the cracking furnace for a second cracking to obtain a second cracked product; Step 3.3: Separating the first cracking product and the second cracking product from each other or mixing them and then separating them to obtain low carbon olefins.

[0050] In a preferred embodiment, in the present invention, the first gas phase and the non-asphalt oil (preferably extracted oil) are cracked in different environments.Specifically, the lightest first gas phase is cracked at a relatively high temperature to maximize the cracking degree and increase the product yield.On the other hand, the relatively heavy non-asphalt oil (preferably extracted oil) is cracked at a relatively low temperature to reduce the degree of coking.

[0051] In a preferred embodiment, the crossover temperature in step 3.1 is about 500 to 750°C, preferably about 540 to 700°C.

[0052] In a preferred embodiment, the outlet temperature of the first radiant section in step 3.1 is about 780-950°C, preferably about 800-900°C.

[0053] In a preferred embodiment, the residence time of the first decomposition in step 3.1 is about 0.05 to 1 second, preferably about 0.1 to 0.7 seconds.

[0054] In a preferred embodiment, the water to oil ratio of the first split in step 3.1 is about (0.1-2):1, preferably about (0.4-1.5):1.

[0055] Here, the water to oil ratio refers to a weight ratio.

[0056] In a preferred embodiment, the crossover temperature in step 3.2 is about 520-760° C., preferably about 550-710° C., and more preferably lower than the crossover temperature in step 3.1.

[0057] In a preferred embodiment, the outlet temperature of the second radiant section in step 3.2 is about 750-950° C., preferably about 760-900° C., and more preferably lower than the outlet temperature of the first radiant section in step 3.1.

[0058] In a preferred embodiment, the residence time of the second decomposition in step 3.2 is about 0.05 to 1 second, preferably about 0.1 to 0.7 seconds.

[0059] In a preferred embodiment, the water to oil ratio of the second split in step 3.2 is about (0.1-2):1, preferably about (0.4-1.5):1.

[0060] In a preferred embodiment, in step 3.3, the separation is carried out as follows: the cracked product is continuously sent to a quenching and cracked gas separation system to obtain products such as hydrogen, methane, ethylene, propylene, butadiene, pyrolysis tar oil, etc., and the separation process in the prior art can be used for separation.

[0061] In a further preferred embodiment, the cracked gas is heat exchanged prior to separation.

[0062] Here, in order to further improve the yield of low-carbon olefins in the product, the cracked gas can be subjected to heat exchange treatment before separation, thereby further improving the yield of low-carbon olefins in the product and reducing the coking of the cracked gas during cooling and separation.

[0063] Preferably, the steam in steps 3.1 and 3.2 is superheated steam in the convection section of a cracking furnace.

[0064] In another aspect, the present invention provides a crude oil cracking system, preferably for carrying out the method of the present invention, comprising a cracking furnace, a vaporization section, and a high pressure extraction section, the cracking furnace comprising a convection section and a radiant section arranged in sequence along a flow direction, the vaporization section having thereon a first vapor phase outlet and a first liquid phase outlet.

[0065] In a preferred embodiment, the convection section forms a closed loop connection with the material inlet of the vaporizer section and the first vapor phase outlet of the vaporizer section.

[0066] In a preferred embodiment, the first liquid phase outlet of the vaporizer is connected to the high pressure extraction section for delivering the first liquid phase produced in the vaporizer to the high pressure extraction section.

[0067] In a preferred embodiment, the high pressure extraction section comprises a sequentially connected extraction section, an optional settling section, and a solvent recovery section.

[0068] In a further preferred embodiment, the extraction section, the settling section and the solvent recovery section all comprise a light phase outlet and a heavy phase outlet.

[0069] In a preferred embodiment, the extraction section is provided with a solvent inlet and a first liquid phase inlet, the first liquid phase inlet being connected to the first liquid phase outlet of the vaporization section, and the solvent inlet being connected to the light phase outlet of the solvent recovery section.

[0070] In a preferred embodiment, the high pressure extraction section comprises a settler section, the light phase outlet of the extraction section being connected to the material inlet of the settler section.

[0071] In a preferred embodiment, the high pressure extraction section comprises a settler section, the light phase outlet of which is connected to the material inlet of the solvent recovery section.

[0072] In a preferred embodiment, the heavy phase outlet of the solvent recovery section and the first vapor phase outlet of the vaporization section are connected separately or after joining to the material inlet of the convection section of the cracking furnace.

[0073] In a preferred embodiment, the vaporization section is a cyclone separator, preferably the cyclone separator is selected from a rectangular inlet cyclone separator, a volute cyclone separator, an axial guide vane cyclone separator, a cylindrical cyclone separator, a combined cone-cylinder cyclone separator, a counter-flow cyclone separator, a direct current cyclone separator or a direct current multi-cyclone tube separator; preferably a volute cyclone separator, an axial guide vane cyclone separator, a cylindrical cyclone separator, a combined cone-cylinder cyclone separator or a direct current cyclone separator. The cyclone separator comprises internal members including a skimming cartridge and / or a baffle located at an upper end of the cyclone separator and a vortex breaker located at a lower portion of the cyclone separator.

[0074] In a preferred embodiment, the system further includes a cracking product separation section for separating the cracking products obtained via the cracking furnace.

[0075] In a preferred embodiment of the present invention, crude oil is sent to the first tube group of the convection section of the cracking furnace for preheating, then separated by the vaporization section to form a first gas phase and a first liquid phase, the first gas phase is sent to the first tube row of the second tube group in the convection section of the cracking furnace, the first liquid phase is sent to the high-pressure extraction section, the first liquid phase is sequentially processed by the extraction section, the settling section and the solvent recovery section, and at the same time, the solvent is introduced into the high-pressure extraction section. The asphalt is discharged to the outside from the extraction section, the settling oil is discharged to the outside from the settling section, the gas phase solvent is recovered from the solvent recovery section and recycled to the extraction section, and the extracted oil is recovered and sent to the second tube row of the second tube group in the convection section of the cracking furnace. The first gas phase and the extracted oil are cracked in the first radiant section and the second radiant section of the cracking furnace, respectively, to obtain cracked products, which are processed by the cracked product separation section to obtain low-carbon olefins.

[0076] In a preferred embodiment, the high pressure extraction section may include a supercritical extraction section.

[0077] Compared with the prior art, the advantageous effects of the present invention include, but are not limited to, the following: in the present invention, crude oil is preheated and vaporized in a cracking furnace, and then the obtained first gas phase is passed into the cracking furnace, and the obtained first liquid phase is passed into the high-pressure extraction section, and the non-asphalt oil, preferably the extracted oil, separated by high-pressure extraction is passed into the cracking furnace, thus the colloids and asphaltene in the crude oil can be effectively removed, so that the non-asphalt oil (including the extracted oil) is substantially free of colloids and asphaltene, thereby improving the utilization rate and cracking efficiency of crude oil, improving the yield of low-carbon olefins in the product, extending the operation cycle to more than 42 days, and reducing the coking of the vaporized crude oil mixture during cracking.

[0078] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic structural diagram of the system of the present invention.

[0079] FIG. 2 shows a schematic structural diagram of the system of the present invention.

[0080] FIG. 3 shows a schematic structural diagram of the system employed in the fifth embodiment.

[0081] In Figures 1, 2 and 3 there is: 1 - cracking furnace, 2 - first group of tubes of the convection section, 3 - first radiant section, 4 - vaporization section, 5 - high pressure extraction section, 6 - extraction section, 7 - settling section, 8 - solvent recovery section, 9 - cracked product separation section, 10 - second group of tubes of the convection section, 11 - second radiant section.

[0082] In FIG. 1, crude oil is sent to the first tube group 2 in the convection section of the cracking furnace 1 for preheating, then separated in the vaporization section 4 to form a first gas phase and a first liquid phase, the first gas phase is sent to the first tube row of the second tube group 10 in the convection section of the cracking furnace 1 for heating to the crossover temperature, sent to the first radiation section 3 for the first cracking to obtain a first cracking product, the first liquid phase is sent to the high-pressure extraction section 5, the first liquid phase is sequentially treated in the extraction section 6, the settling section 7 and the solvent recovery section 8 as necessary, and at the same time, the solvent is introduced into the high-pressure extraction section 5. In addition, when the settling separation treatment is not required, the first liquid phase is sequentially treated in the extraction section 6 and the solvent recovery section 8, and is not treated in the settling separation section 7. The asphalt is discharged from the extraction section 6 to the outside, the gaseous solvent is recovered from the solvent recovery section 8 and recycled to the extraction section 5, the non-asphalt oil is recovered and sent to the second tube row of the second tube group 10 in the convection section of the cracking furnace 1 to be heated to the crossover temperature, and then passed through the second radiant section 11 for the second cracking to obtain a second cracked product. The first cracked product and the second cracked product are treated by the cracked product separation section 9 to obtain low-carbon olefins. When a settling separation process is required, the first liquid phase is treated in the settling separation section 7 as shown in FIG. 2, which will be described in detail later.

[0083] In FIG. 2, crude oil is sent to a first tube group 2 in a convection section of a cracking furnace 1 for preheating, then separated in a vaporization section 4 to form a first gas phase and a first liquid phase, the first gas phase is sent to a first tube row of a second tube group 10 in the convection section of the cracking furnace 1 for heating to a crossover temperature, sent to a first radiant section 3 for a first cracking to obtain a first cracking product, the first liquid phase is sent to a high-pressure extraction section 5, the first liquid phase is sequentially treated in an extraction section 6, a settling section 7 and a solvent recovery section 8, and at the same time, a solvent is introduced into the high-pressure extraction section 5. The asphalt is discharged to the outside from the extraction section 6, the settled oil is discharged to the outside from the settling separation section 7, the gas phase solvent is recovered from the solvent recovery section 8 and recycled to the extraction section 5, the extracted oil is recovered and sent to the second tube row of the second tube group 10 in the convection section of the cracking furnace 1 for heating to the crossover temperature, and then passed through the second radiant section 11 for second cracking to obtain a second cracked product. The first cracked product and the second cracked product are treated by the cracked product separation section 9 to obtain low carbon olefins.

[0084] In FIG. 3, crude oil is sent to the first tube group 2 in the convection section of the cracking furnace 1 for preheating, and then separated in the vaporization section 4 to form a first gas phase and a first liquid phase, the first gas phase is sent to the second tube group 10 in the convection section of the cracking furnace 1, the first liquid phase is sent to the high-pressure extraction section 5, the first liquid phase is sequentially treated in the extraction section 6, the settling section 7 and the solvent recovery section 8, and at the same time, the solvent is introduced into the high-pressure extraction section 5. The asphalt is discharged to the outside from the extraction section 6, the settling oil is discharged from the settling section 7, the gas phase solvent is recovered from the solvent recovery section 8 and recycled to the extraction section 5, and the extracted oil is recovered and sent to the second tube group 10 in the convection section of the cracking furnace 1. The first gas phase and the extracted oil are cracked in the first radiant section 3 of the cracking furnace 1 (here, the cracking furnace 1 only includes the first radiant section 3) to obtain cracked products, which are processed by the cracked product separation section 9 to obtain low-carbon olefins.

[0085] [Example] The present invention will be specifically described below in conjunction with specific examples.It should be noted that the following examples are only used to further illustrate the present invention and should not be interpreted as limitations on the protection scope of the present invention.Some non-essential improvements and adjustments made by those skilled in the art for the invention according to the content of the present invention still belong to the protection scope of the present invention.

[0086] It should be noted that various specific technical features described in the following specific embodiments can be combined as appropriate under circumstances that are not contradictory, and in order to avoid unnecessary repetition, the present invention does not describe various possible combinations.

[0087] The cracking furnace used in Examples 1-4 of the present invention is a double radiant cracking furnace (double hearth cracking furnace), specifically a CBL-VII type cracking furnace (purchased from Sinopec Group Co., Ltd.). The cracking furnace used in Example 5 of the present invention and the comparative example is a single radiant cracking furnace (single hearth cracking furnace), specifically a CBL-III type cracking furnace (purchased from Sinopec Group Co., Ltd.).

[0088] The crude oil used in the following Examples and Comparative Examples has a specific gravity of 0.8724 (20°C), a colloid content of 8.8 wt%, an asphaltene content of 0.2 wt%, and a distillation range analysis shown in Table 1, measured by the ASTM D5307 method.

[0089] [Table 1]

[0090] Example 1 The embodiment was carried out using the system shown in FIG. 2, in which a guide vane type cyclone separator with an internal member was used as the vaporization section, the extraction section 6 was an extraction column, the sedimentation separation section 7 was a sedimentation column, and the solvent recovery section 8 was a solvent recovery column.

[0091] (1) The dehydrated and desalted crude oil was preheated to 288°C in the convection section 2 of the cracking furnace 1 to obtain preheated crude oil with a pressure of 0.12MPa. The preheated crude oil was sent to a cyclone separator for vaporization to obtain a first gas phase and a first liquid phase, and the liquid content in the first gas phase was 270mg / m 3 The colloid content in the first liquid phase was 11.3 wt %, and the asphaltene content in the first liquid phase was 0.26 wt %.

[0092] (2) The first liquid phase was sent to the top of the extraction column, and the solvent n-butane was passed through the bottom of the extraction column, the mass ratio of the solvent to the first liquid phase was 4:1, the pressure of the extraction column was 4 MPa, and the temperature of the extraction column was 160 ° C. The non-asphalt part in the first liquid phase was extracted with the solvent and recovered from the top of the extraction column, and the asphalt was discharged from the bottom of the column. The solvent and non-asphalt part recovered from the top of the extraction column were heated to 165 ° C, then passed through a settling column, the solvent and extracted oil were recovered from the top of the settling column, and the settled oil was recovered from the bottom of the settling column. The solvent and extracted oil recovered from the top of the settling column were heated to 180 ° C, passed through a solvent recovery column, the solvent and extracted oil were separated, the solvent was recovered from the top of the column, and the temperature was lowered to 160 ° C, recirculated, and the extracted oil was recovered from the bottom of the column. No colloids or asphaltenes were detected in the extracted oil (according to the analytical method SY / T 7550-2000).

[0093] (3) After the first gas phase was mixed with water vapor (water to oil ratio 0.7), the mixture was sent to the first tube row of the second tube bundle in the convection section of the cracking furnace to heat it up to the crossover temperature (600°C), and then sent directly to the first radiant section for the first cracking to obtain the first cracking product. The operation parameters of the first radiant section 3 were furnace tube outlet temperature 810°C, residence time 0.22 seconds.

[0094] (4) After the extracted oil was mixed with steam (water to oil ratio of 0.75), the mixture was sent to the second tube row of the second tube bundle in the convection section of the cracking furnace, raised to the crossover temperature (575°C), and then sent directly to the second radiant section 11 for a second cracking, obtaining a second cracking product. The operating parameters of the second radiant section 11 were furnace tube outlet temperature of 770°C and residence time of 0.21 seconds.

[0095] (5) The first cracked product and the second cracked product were mixed and then passed through a quenching section and a separation section (using LUMMUS continuous separation process) to separate the cracked products, and separated to obtain low carbon olefins.

[0096] The cracked gas was separated to obtain low carbon olefins, with the ethylene yield of 25.07 wt%, the propylene yield of 13.79 wt%, the 1,3-butadiene yield of 4.66 wt%, and the triene yield of 43.52 wt%. The operation cycle was 50 days.

[0097] Example 2 The embodiment was carried out using the system shown in FIG. 2, in which a guide vane type cyclone separator with an internal member was used as the vaporization section, the extraction section 6 was an extraction column, the sedimentation separation section 7 was a sedimentation column, and the solvent recovery section 8 was a solvent recovery column.

[0098] (1) The dehydrated and desalted crude oil was preheated to 230°C in the convection section 2 of the cracking furnace 1 to obtain preheated crude oil with a pressure of 0.13 MPa. The preheated crude oil was sent to a cyclone separator for vaporization to obtain a first gas phase and a first liquid phase, and the liquid content in the first gas phase was 150 mg / m 3 The colloid content in the first liquid phase was 10.2 wt %, and the asphaltene content in the first liquid phase was 0.33 wt %.

[0099] (2) The first liquid phase was sent to the top of the extraction column in the supercritical extraction section, and mixed solvent C4 (50% n-butane and isobutane, respectively) was passed through the bottom of the extraction column, the mass ratio of the solvent to the first liquid phase was 3:1, the pressure of the extraction column was 4 MPa, and the temperature of the extraction column was 150 ° C. The non-asphalt part in the first liquid phase was extracted with the solvent and recovered from the top of the extraction column, and the asphalt was discharged from the bottom of the column. The solvent and non-asphalt part recovered from the top of the extraction column were heated to 162 ° C, then passed through a sedimentation column, the solvent and extracted oil were recovered from the top of the sedimentation column, and the sedimented oil was recovered from the bottom of the sedimentation column. The solvent and extracted oil recovered from the top of the sedimentation column were heated to 180 ° C and passed through a solvent recovery column, the solvent and extracted oil were separated, the solvent was recovered from the top of the column, and the temperature was lowered to 150 ° C, recirculated, and the extracted oil was recovered from the bottom of the column. No colloids or asphaltenes were detected in the extracted oil (according to the analytical method SY / T 7550-2000).

[0100] (3) After the first gas phase was mixed with water vapor (water to oil ratio 0.65), the mixture was sent to the first tube row of the second tube bundle in the convection section of the cracking furnace, heated to the crossover temperature (610°C), and then sent directly to the first radiant section for the first cracking to obtain the first cracking product. The operation parameters of the first radiant section 3 were furnace tube outlet temperature 815°C, residence time 0.25 seconds.

[0101] (4) After the extracted oil was mixed with steam (water to oil ratio of 0.65), the mixture was sent to a second tube row of a second tube bank in the convection section of the cracking furnace, raised to a crossover temperature (585°C), and then sent directly to a second radiant section 11 for a second cracking, obtaining a second cracking product. The operating parameters of the second radiant section 11 were furnace tube outlet temperature 785°C, residence time 0.2 seconds.

[0102] (5) The first cracked product and the second cracked product were mixed and then passed through a quenching section and a separation section (using LUMMUS continuous separation process) to separate the cracked products, and separated to obtain low carbon olefins.

[0103] The cracking products were separated to obtain low carbon olefins, with the ethylene yield being 25.31 wt%, the propylene yield being 13.41 wt%, the 1,3-butadiene yield being 4.73 wt%, and the triene yield being 43.46 wt%. The operation cycle was 52 days.

[0104] Example 3 The embodiment was carried out using the system shown in FIG. 2, in which a guide vane type cyclone separator with an internal member was used as the vaporization section, the extraction section 6 was an extraction column, the sedimentation separation section 7 was a sedimentation column, and the solvent recovery section 8 was a solvent recovery column.

[0105] (1) The dehydrated and desalted crude oil was preheated to 315°C in the convection section 2 of the cracking furnace 1 to obtain preheated crude oil with a pressure of 0.12MPa. The preheated crude oil was sent to a cyclone separator for vaporization to obtain a first gas phase and a first liquid phase, and the liquid content in the first gas phase was 200mg / m 3 , the colloid content in the first liquid phase was 11.9 wt %, and the asphaltene content in the first liquid phase was 0.27 wt %.

[0106] (2) The first liquid phase was sent to the top of the extraction column, and the solvent n-butane was passed through the bottom of the extraction column, the mass ratio of the solvent to the first liquid phase was 8:1, the pressure of the extraction column was 3 MPa, and the temperature of the extraction column was 140 ° C. The non-asphalt part in the first liquid phase was extracted with the solvent and recovered from the top of the extraction column, and the asphalt was discharged from the bottom of the column. The solvent and non-asphalt part recovered from the top of the extraction column were heated to 148 ° C, then passed through a settling column, the solvent and extracted oil were recovered from the top of the settling column, and the settled oil was recovered from the bottom of the settling column. The solvent and extracted oil recovered from the top of the settling column were heated to 180 ° C, passed through a solvent recovery column, the solvent and extracted oil were separated, the solvent was recovered from the top of the column, and the temperature was lowered to 140 ° C, recirculated, and the extracted oil was recovered from the bottom of the column. No colloids or asphaltenes were detected in the extracted oil (according to the analytical method SY / T 7550-2000).

[0107] (3) After the first gas phase was mixed with water vapor (water to oil ratio 0.80), the mixture was sent to the first tube row of the second tube bundle in the convection section of the cracking furnace to heat it up to the crossover temperature (600°C), and then sent directly to the first radiant section for the first cracking to obtain the first cracking product. The operation parameters of the first radiant section 3 were furnace tube outlet temperature 800°C, residence time 0.28 seconds.

[0108] (4) After the extracted oil was mixed with steam (water to oil ratio of 1), the mixture was sent to the second tube row of the second tube bundle in the convection section of the cracking furnace, heated to the crossover temperature (570°C), and then sent directly to the second radiant section 11 for second cracking to obtain a second cracking product. The operating parameters of the second radiant section 11 were furnace tube outlet temperature 765°C, residence time 0.15 seconds.

[0109] (5) The first cracked product and the second cracked product were mixed and then passed through a quenching section and a separation section (using LUMMUS continuous separation process) to separate the cracked products, and separated to obtain low carbon olefins.

[0110] The cracked gas was separated to obtain low carbon olefins, the yield of ethylene was 22.85 wt%, the yield of propylene was 12.57 wt%, the yield of 1,3-butadiene was 4.27 wt%, and the yield of trienes was 39.69 wt%. The operation cycle was 48 days.

[0111] Example 4 The embodiment was carried out using the system shown in FIG. 2, in which a guide vane type cyclone separator with an internal member was used as the vaporization section, the extraction section 6 was an extraction column, the sedimentation separation section 7 was a sedimentation column, and the solvent recovery section 8 was a solvent recovery column.

[0112] (1) The dehydrated and desalted crude oil was preheated to 200°C in the convection section 2 of the cracking furnace 1 to obtain preheated crude oil with a pressure of 0.12 MPa. The preheated crude oil was sent to a cyclone separator for vaporization to obtain a first gas phase and a first liquid phase, and the liquid content in the first gas phase was 100 mg / m 3The colloid content in the first liquid phase was 9.9 wt %, and the asphaltene content in the first liquid phase was 0.22 wt %.

[0113] (2) The first liquid phase was sent to the top of the extraction column, and the solvent n-butane was passed through the bottom of the extraction column, the mass ratio of the solvent to the first liquid phase was 10:1, the pressure of the extraction column was 18 MPa, and the temperature of the extraction column was 160 ° C. The non-asphalt part in the first liquid phase was extracted with the solvent and recovered from the top of the extraction column, and the asphalt was discharged from the bottom of the column. The solvent and non-asphalt part recovered from the top of the extraction column were heated to 170 ° C, then passed through a sedimentation column, the solvent and extracted oil were recovered from the top of the sedimentation column, and the sedimented oil was recovered from the bottom of the sedimentation column. The solvent and extracted oil recovered from the top of the sedimentation column were heated to 180 ° C, passed through a solvent recovery column, the solvent and extracted oil were separated, the solvent was recovered from the top of the column, the temperature was lowered to 160 ° C, recirculated, and the extracted oil was recovered from the bottom of the column. No colloids or asphaltenes were detected in the extracted oil (according to the analytical method SY / T 7550-2000).

[0114] (3) After the first gas phase was mixed with water vapor (water to oil ratio 0.6), the mixture was sent to the first tube row of the second tube bundle in the convection section of the cracking furnace, heated to the crossover temperature (620°C), and then sent directly to the first radiant section for the first cracking to obtain the first cracking product. The operation parameters of the first radiant section 3 were furnace tube outlet temperature 820°C, residence time 0.2 seconds.

[0115] (4) After the extracted oil was mixed with steam (water to oil ratio of 0.8), the mixture was sent to the second tube row of the second tube bundle in the convection section of the cracking furnace, raised to the crossover temperature (590°C), and then sent directly to the second radiant section 11 for a second cracking, obtaining a second cracking product. The operating parameters of the second radiant section 11 were furnace tube outlet temperature of 790°C and residence time of 0.21 seconds.

[0116] (5) The first cracked product and the second cracked product were mixed and then passed through a quenching section and a separation section (using LUMMUS continuous separation process) to separate the cracked products, and separated to obtain low carbon olefins.

[0117] The cracked gas was separated to obtain low carbon olefins, the yield of ethylene was 23.51 wt%, the yield of propylene was 14.58 wt%, the yield of 1,3-butadiene was 4.35 wt%, and the yield of trienes was 42.44 wt%. The operation cycle was 49 days.

[0118] Example 5 The embodiment was carried out using the system shown in FIG. 3, in which a cyclone separator was used as the vaporizer, and the decomposition furnace consisted of only the first radiating section 3.

[0119] Steps (1)-(2) of Example 1 were repeated, except that the first gas phase and the extracted oil were cracked together, as detailed in step (3) below: (3) The first gas phase and the extracted oil were mixed with steam (water to oil ratio 0.7) respectively, then the mixture was sent to the convection section of the cracking furnace to heat up to the crossover temperature (585°C), and then sent directly to the first radiant section 3 for cracking to obtain cracked products. The operation parameters of the first radiant section 3 were furnace tube outlet temperature 780°C, residence time 0.22 seconds. The cracked products were passed through the quench section and separation section (using LUMMUS continuous separation process) to separate the cracked products, and low carbon olefins were obtained.

[0120] The cracked gas was separated to obtain low carbon olefins, and the product yield was slightly lower than that of Example 1, with an ethylene yield of 24.25 wt%, a propylene yield of 12.61 wt%, a 1,3-butadiene yield of 4.51 wt%, and a triene yield of 41.37 wt%, but the operation cycle was shorter than that of Example 1, being only 42 days.

[0121] Comparative Example 1 In the comparative example, a conventional cracking furnace was used for cracking.

[0122] The dehydrated and desalted crude oil was sent directly to the cracking furnace, passed through the convection section to be heated to the crossover temperature (580°C), and then passed directly to the radiant section for cracking. The cracking conditions were: water to oil ratio 0.75, radiant section outlet temperature 790°C, radiant section outlet pressure 0.11MPa, residence time 0.22 seconds. The cracked gas was subjected to continuous separation process of LUMMUS. Analysis of the steam cracking reaction products showed that the yield of ethylene was 21.49 wt%, the yield of propylene was 13.29 wt%, the yield of 1,3-butadiene was 4.03 wt%, and the yield of trienes was 38.81 wt%. The operation cycle was 5 days.

[0123] From the results of the Example and Comparative Example 1, it can be seen that when using the conventional cracking unit, the crude oil was used to maintain an operating cycle of only 5 days, but the present invention can ensure that the crude oil was normally used in the cracking unit, and the use of the vaporization section and the high-pressure extraction section to process the crude oil can effectively reduce the occurrence of coking and achieve an operating cycle of more than 42 days. Furthermore, under the same processing conditions, the Example effectively improved the yield of low-carbon olefins compared with the Comparative Example. [Brief description of the drawings]

[0124] [Figure 1] FIG. 1 shows a schematic structural diagram of the system of the present invention. [Diagram 2] FIG. 2 shows a schematic structural diagram of the system of the present invention. [Diagram 3] FIG. 3 shows a schematic structural diagram of the system employed in the fifth embodiment.

Claims

1. 1. A method for cracking crude oil, comprising the steps of: Step 1. Sending crude oil to a first set of tubes in a convection section of a cracking furnace for preheating and then vaporizing the crude oil to obtain a first vapor phase and a first liquid phase; Step 2. High pressure extraction of the first liquid phase to obtain non-asphalt oil and asphalt; Step 3: mixing the first gas phase and the non-asphalt oil with steam, respectively, or mixing the first gas phase with the non-asphalt oil and then with steam, then sending it to a second set of tubes in the convection section of the cracking furnace for heating to a crossover temperature, then sending it to the radiant section of the cracking furnace for cracking to obtain cracked products, and separating the cracked products to obtain low carbon olefins; The step 3 includes the following substeps: Step 3.1 mixing the first gas phase with water vapor and then sending it to a first tube row of the second tube bundle in the convection section of the cracking furnace for heating to a crossover temperature and subsequently to a first radiant section of the cracking furnace for a first cracking to obtain a first cracked product; Step 3.2 mixing the non-asphalt oil with steam and then sending it to a second tube row of the second tube bundle in the convection section of the cracking furnace for raising the temperature to a crossover temperature and subsequently sending it to a second radiant section of the cracking furnace for a second cracking to obtain a second cracked product; Step 3.3: separating the first cracked product and the second cracked product, respectively or mixing and then separating them, to obtain lower carbon olefins.

2. In step 1, the vaporization is at least one of stripping, flash vaporization, and cyclone separation; and / or 2. The method according to claim 1, wherein in step 2, the high pressure extraction includes an extraction process, an optional sedimentation process and a solvent recovery process.

3. The method according to claim 1, characterized in that the high pressure extraction includes supercritical extraction.

4. In step 2, the first liquid phase is subjected to high pressure extraction to obtain extracted oil, settled oil and the asphalt; The method according to any one of claims 1 to 3, characterized in that in step 3, the first gas phase and the extracted oil are mixed with the steam, respectively, or the first gas phase is mixed with the extracted oil and then mixed with the steam, and then sent to the second set of tubes in the convection section of the cracking furnace for heating to a crossover temperature, and then sent to the radiant section of the cracking furnace for cracking to obtain the cracked products, and the cracked products are separated to obtain the low carbon olefins.

5. The step 3 includes the following substeps: Step 3.1 mixing the first gas phase with the steam and then sending it to a first tube row of the second tube bundle in the convection section of the cracking furnace for heating to a crossover temperature and subsequently to a first radiant section of the cracking furnace for a first cracking to obtain a first cracked product; Step 3.2 mixing the extracted oil with the steam and then sending it to a second tube row of the second tube bundle in the convection section of the cracking furnace for raising the temperature to a crossover temperature and subsequently sending it to a second radiant section of the cracking furnace for a second cracking to obtain a second cracked product; 5. The method of claim 4, further comprising: separating the first cracked product and the second cracked product, or mixing and then separating the first cracked product and the second cracked product, to obtain lower carbon olefins.

6. In step 1, the outlet temperature of the crude oil after preheating is 120 to 350° C.; and / or The liquid content in the first gas phase is 10 g / m ３ The method according to any one of claims 1 to 5, characterized in that the

7. In step 1, the outlet temperature of the crude oil after preheating is 120 to 315°C, and / or A method according to any one of claims 1 to 5, characterized in that the liquid content in the first gas phase is less than 200 mg / m 3 .

8. 5. The method according to claim 4, wherein in step 2, the high-pressure extraction comprises the extraction process, the settling process, and the solvent recovery process, and the extraction process is carried out in the presence of a solvent selected from the group consisting of propane, butane, pentane, propylene, and butene.

9. The high pressure extraction is carried out under supercritical conditions and includes the following steps: Step (I) subjecting the first liquid phase and the solvent to an extraction treatment to extract a first light phase component containing a non-asphalt portion and the solvent and the asphalt, and discharging the asphalt to the outside; Step (II) subjecting the first light component to a temperature increase treatment, and then subjecting the first light component to the sedimentation separation treatment to obtain a second light phase component containing the solvent and the extracted oil and a sedimented oil, and discharging the sedimented oil; 9. The method according to claim 8, further comprising: step (III) subjecting the second light component to elevated temperature treatment and then performing the solvent recovery treatment to obtain recovered solvent and the extracted oil.

10. the pressure of the extraction process, the sedimentation process and the solvent recovery process is independently 1 to 10 MPa; and / or The temperature of the extraction process is between 50 and 200°C, and / or The temperature of the sedimentation treatment is 1 to 30° C. higher than the temperature of the extraction treatment, and / or 10. The method according to claim 9, wherein the temperature of the solvent recovery treatment is 1 to 30° C. higher than the temperature of the sedimentation treatment.

11. The pressure of the extraction process, the sedimentation process and the solvent recovery process is independently 3 to 6 MPa, and / or The temperature of the extraction process is between 80 and 160°C, and / or The temperature of the sedimentation treatment is 3 to 8° C. higher than the temperature of the extraction treatment, and / or 10. The method according to claim 9, wherein the temperature of the solvent recovery treatment is 5 to 20° C. higher than the temperature of the sedimentation treatment.

12. The crossover temperature in step 3.1 is between 500 and 750° C.; and / or The outlet temperature of the first radiator in step 3.1 is 780 to 950°C; and / or The residence time of the first decomposition in step 3.1 is 0.05 to 1 second; and / or 12. The method according to any one of claims 5 to 11, characterized in that the water to oil ratio of the first cracking in step 3.1 is (0.1-2):

1.

13. The crossover temperature in step 3.1 is 540 to 700°C, and / or The outlet temperature of the first radiator in step 3.1 is 800 to 900° C.; and / or The residence time of the first decomposition in step 3.1 is 0.1 to 0.7 seconds; and / or 12. The method according to any one of claims 5 to 11, wherein the water to oil ratio of the first cracking in step 3.1 is (0.4-1.5):

1.

14. The crossover temperature in step 3.2 is 520 to 760° C.; and / or The outlet temperature of the second radiant section in step 3.2 is 750 to 950° C.; and / or The residence time of the second decomposition in step 3.2 is 0.05 to 1 second; and / or 14. The method according to any one of claims 5 to 13, wherein the water to oil ratio of the second cracking in step 3.2 is (0.1-2):

1.

15. The method of claim 14, wherein the crossover temperature in step 3.2 is 550 to 710° C.; and / or The outlet temperature of the second radiator in step 3.2 is 760 to 900° C.; and / or The residence time of the second decomposition in step 3.2 is 0.1 to 0.7 seconds; and / or 14. The method according to any one of claims 5 to 13, wherein the water to oil ratio of the second cracking in step 3.2 is (0.4-1.5):

1.

16. A crude oil cracking system for carrying out the method according to any one of claims 1 to 15, comprising a cracking furnace, a vaporization section and a high-pressure extraction section, the cracking furnace comprising a convection section and a radiant section arranged in sequence along a flow direction, the high-pressure extraction section comprising an extraction section, an optional settler section and a solvent recovery section connected in sequence, the extraction section, the settler section and the solvent recovery section all having a light phase outlet and a heavy phase outlet, the vaporization section having a first vapor phase outlet and a first liquid phase outlet, the extraction section comprises a solvent inlet and a first liquid phase inlet, the first liquid phase inlet being connected to the first liquid phase outlet of the vaporization section, and the solvent inlet being connected to the light phase outlet of the solvent recovery section; and / or the high pressure extraction section comprises a settler section, the light phase outlet of the extraction section being connected to the material inlet of the settler section; and / or the light phase outlet of the settling section is connected to the material inlet of the solvent recovery section; and / or A system, characterized in that the heavy phase outlet of the solvent recovery section and the first vapor phase outlet of the vaporization section are connected to the material inlet of the convection section of the cracking furnace, either separately or after joining together.

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