A method and system for steam cracking of crude oil to produce olefins

Abstract

The present disclosure relates to a method and system for producing olefins by steam cracking of crude oil, comprising the following steps: feeding a raw material crude oil into a fractionating column for first separation to obtain a light distillation range component, a middle distillation range component and a heavy distillation range component; feeding the heavy distillation range component and steam into a separation device for second separation to obtain a gas phase mixture and a liquid phase heavy component; mixing the light distillation range component with steam to obtain a first mixture, and mixing the middle distillation range component with steam to obtain a second mixture; feeding the first mixture, the second mixture and at least part of the gas phase mixture after heating into a radiant section of a steam cracking device for steam cracking to obtain a cracking product containing ethylene and propylene. The present disclosure can adapt to the demand of different crude oils as cracking raw materials and improve the yield of olefins.

Description

Technical Field

[0001] This disclosure relates to the field of hydrocarbon processing, and more specifically, to a method and system for producing olefins by crude oil steam cracking. Background Technology

[0002] With the development of my country's economy, the demand for low-carbon olefin organic chemical raw materials has been increasing year by year. Although the production scale of low-carbon olefins has also been growing year by year, it is still unable to meet the ever-increasing production demand. In 2019, my country's ethylene production capacity reached 30.66 million tons, an increase of 5.34 million tons compared with 2018. However, my country's equivalent demand for ethylene in 2019 reached 47.2 million tons, which still cannot meet market demand. Therefore, my country still relies on imports for a large amount of ethylene and its derivatives every year. In recent years, impacted by cheap raw materials such as Middle Eastern light hydrocarbons and US shale oil, as well as coal chemical processes, the traditional naphtha-based process for producing low-carbon olefins has encountered problems such as high raw material costs and lack of competitiveness. In addition, the development of new energy vehicles has reduced the demand for oil products from automobiles. Therefore, in order to cope with the impact of market competition, expanding the raw material sources of ethylene cracking units, shortening the processing flow of refining units, using crude oil as the raw material for steam cracking, reducing raw material costs, getting rid of the constraints of raw material varieties, and reducing investment in refining units have become effective means for traditional ethylene enterprises to reduce costs and increase efficiency.

[0003] Compared to traditional cracking feedstocks, crude oil used as feedstock in steam cracking furnaces presents several challenges, including a high final boiling point (above 540℃), high gum content, difficulty in vaporization, and a tendency to coke. Furthermore, it's crucial to determine which crude oils are suitable for cracking and which require secondary processing, depending on their origin. Therefore, the design of cracking furnaces and production processes need to be tailored to the characteristics of crude oils from different sources. Currently, international companies such as ExxonMobil, Saudi Aramco, Iqbals Chemical, and Lummus are conducting in-depth research on crude oil cracking technology, while domestic companies like Shanghai Junming Chemical Engineering Design Co., Ltd. are prominent examples.

[0004] Shanghai Junming Chemical Engineering Design Co., Ltd. disclosed a combined processing method and apparatus for direct crude oil cracking to produce olefins (CN111196936A). The method first employs pretreatment such as desalting and dehydration to remove impurities, then feeds the crude oil into the ethylene cracking convection section for heating. The heated feed is then sent to a gas-liquid separator, where lighter hydrocarbon gases are separated and sent to the convection and radiation sections for steam cracking to produce olefins. The liquid exiting the gas-liquid separator contains components such as atmospheric residue oil and is sent to a hydrogenation unit for further processing before being returned to the convection and radiation sections. However, this method directly feeds superheated crude oil into the gas-liquid separator, making it difficult to achieve the desired gas-liquid separation effect.

[0005] Lummus Technologies LLC discloses a method (CN107001955B) for the thermal cracking of crude oil and heavy feedstock in a pyrolysis reactor to produce olefins. This method describes a scheme combining a cracking furnace convection section with multi-stage (up to three stages) separators and fractionation towers. This method allows for multiple gas-liquid separations of the crude oil-steam mixture and feeds mixtures of different densities into different radiant furnace tubes for cracking. The method mentions that the crude oil is preheated in an external heat exchanger before entering the cracking furnace convection section, but the source of the heat is not specified. While this method improves cracking selectivity through multi-stage separators, fractionation towers, and the cracking of different fractions in different radiant furnace tubes, it is cumbersome, requires significant investment, and is unsuitable for light crude oil.

[0006] ExxonMobil has a long history of developing crude oil cracking for ethylene production. As early as January 1970, ExxonMobil proposed using crude oil steam cracking to produce chemical feedstocks. It's important to note that ExxonMobil's crude oil cracking technology doesn't directly use purchased crude oil in the steam cracking unit; instead, it involves pretreatment. This pretreatment mainly includes feedstock blending, hydrotreating, and flash evaporation / separation. In February 2005, ExxonMobil Chemicals Patents applied for Chinese patent CN100564484C—a method for steam cracking heavy hydrocarbon feedstocks—which detailed the above process. The heavy hydrocarbon feedstocks mainly include crude oil, naphtha, gas oil, fuel oil, natural gasoline (condensate), and residual oil. This method describes a flash steam separation process; however, simple flash evaporation alone is insufficient to effectively separate the gas and liquid components, especially to avoid entraining heavy components into the gas phase, which can easily cause coking in the convection section and subsequently severe coking in the radiant section furnace tubes.

[0007] Ignesta Chemicals describes a process for producing ethylene from crude oil / condensate through cracking in patents CN101528894A and CN101778929A. CN101528894A describes a process where, after preheating the crude oil / condensate in the convection section, the separated light components enter the cracking furnace's convection section for superheating before entering the radiant section for cracking. The heavier components are sent to an atmospheric distillation tower and a vacuum distillation tower for further separation. CN101778929A describes a process where, after preheating a feedstock containing 30% heavy feedstock such as crude oil or condensate in the convection section, the feedstock enters the upper part of a separation unit, separating out the protective naphtha and lighter components. The separated liquid phase enters a packed tower below for further separation, but it does not specify how the separated heavy components are processed. Both patents use a stripping tower with packed or tray-like structures in the evaporation unit. The upper evaporation zone contains a gas-liquid separator for gas-liquid separation. However, the liquid phase after flash evaporation is relatively heavy and viscous, and the packing material and tray openings are prone to clogging. Summary of the Invention

[0008] The purpose of this disclosure is to provide a method and system for producing olefins from crude oil steam cracking, which can adapt to the needs of different feedstocks as cracking feedstocks and can effectively improve olefin yield.

[0009] To achieve the above objectives, the first aspect of this disclosure provides a method for producing olefins from crude oil through steam cracking, comprising the following steps: S1, feeding crude oil into a fractionating tower for first separation, separating light-range components, medium-range components, and heavy-range components; S2, mixing the light-range components with steam to obtain a first mixture; mixing the medium-range components with steam to obtain a second mixture; S3, mixing the heavy-range components with steam and feeding them into a separation unit for second separation, separating a gaseous mixture and a liquid-phase heavy component; S4, feeding the first mixture and the second mixture into the convection section of the steam cracking unit for superheating, and then into the radiative section of the steam cracking unit for steam cracking to obtain cracking products containing ethylene and propylene.

[0010] Optionally, the final boiling point of the light-range component obtained from the first separation is 80–160°C; the initial boiling point of the middle-range component is not higher than the final boiling point of the light-range component, preferably 60–140°C; the final boiling point of the middle-range component is 250–350°C; the initial boiling point of the heavy-range component is not higher than the final boiling point of the middle-range component, preferably 230–330°C; the final boiling point of the gas-phase mixture obtained from the second separation is 350–460°C; the initial boiling point of the liquid-phase heavy component is not higher than the final boiling point of the gas-phase mixture; optionally, the crude oil is at least one of paraffinic crude oil, naphthenic crude oil, or intermediate-based crude oil.

[0011] Optionally, the method further includes: superheating all of the gaseous mixture in the convection section of a steam cracking unit, and then steam cracking it in the radiative section of the steam cracking unit to obtain cracking products containing ethylene and propylene; or superheating a portion of the gaseous mixture in the convection section of a steam cracking unit, and then steam cracking it in the radiative section of the steam cracking unit, while allowing another portion of the gaseous mixture to enter a refining unit for further processing; preferably, before allowing the gaseous mixture to enter the refining unit for further processing, the portion of the gaseous mixture and the feedstock oil to be preheated are first introduced into a cooler for heat exchange to obtain preheated feedstock oil and cooled liquid phase material of the gaseous mixture; then the cooled liquid phase material of the gaseous mixture is allowed to enter the refining unit for further processing; preferably, when the BMCI value of the crude oil component in the gaseous mixture is 30 or higher, at least a portion of the gaseous mixture is sent to the refining unit.

[0012] Optionally, along the height direction of the steam cracking device, the convection section is sequentially provided with independent raw material preheating section, first mixing superheating section, second mixing superheating section, third mixing superheating section, fourth steam superheating section, fifth mixing superheating section, sixth mixing superheating section, and optionally a seventh mixing superheating section; step S3 includes: mixing the heavy distillation range component with a first portion of steam and then heating it in the first mixing superheating section of the steam cracking device to obtain a heated first mixture of heavy distillation range components; mixing the heated first mixture of heavy distillation range components with a second portion of steam to obtain a second mixture of heavy distillation range components; optionally, the temperature of the second mixture of heavy distillation range components is 200-410°C; and allowing the second mixture of heavy distillation range components to enter the separation device for the second separation.

[0013] Optionally, along the height direction of the steam cracking device, the radiation section is located below the convection section; step S4 includes: a) mixing the light-range component with the third part of steam and then heating it in the third mixing superheating section of the steam cracking device, and then heating it to 550-750°C in the fifth mixing superheating section of the steam cracking device to obtain the first feed stream to be cracked; or, mixing the light-range component with the third part of steam and then heating it in the third mixing superheating section of the steam cracking device, and then mixing it with the fourth part of steam and then heating it to 550-750°C in the fifth mixing superheating section of the steam cracking device to obtain the first feed stream to be cracked. a) The medium-range component is mixed with the fifth portion of steam and then heated in the second mixing superheating section of the steam cracking unit. It is then mixed with the sixth portion of steam and heated to 450–700°C in the sixth mixing superheating section of the steam cracking unit to obtain the second feed stream to be cracked. Optionally, c) The gas-phase mixture is heated to 400–650°C in the seventh mixing superheating section of the steam cracking unit to obtain the third feed stream to be cracked. The first feed stream to be cracked is then steam-cracking in the first cracking furnace tube of the radiant section of the steam cracking unit to obtain the first cracking product. The second feed stream to be cracked is then steam-cracking in the radiant section of the steam cracking unit. The second pyrolysis furnace tube of the radiating section undergoes steam pyrolysis to obtain the second pyrolysis product; optionally, the third feed stream to be pyrolyzed enters the third pyrolysis furnace tube of the radiating section of the steam pyrolysis device for steam pyrolysis to obtain the third pyrolysis product; preferably, the first part of steam, the second part of steam, the third part of steam, the fourth part of steam, the fifth part of steam, and the sixth part of steam are each independently superheated steam or unsuperheated section steam; the method further includes: after the steam enters the fourth steam superheating section of the steam pyrolysis device for superheating treatment, it is divided into three parts, which are respectively used as the second part of steam, the fourth part of steam, and the sixth part of steam; preferably, the steam enters the fourth steam superheating section... The temperature of the steam after heat treatment is 400–575°C; in step a, the total weight of the third part of dilution steam and the optional fourth part of steam is 0.3–1, preferably 0.4–0.7, relative to the weight of the crude oil component in the light distillation range component; in step b, the total weight of the fifth part of steam and the sixth part of dilution steam is 0.35–1, preferably 0.6–0.8, relative to the weight of the crude oil component in the medium distillation range component; in step S3, the total weight of the first part of steam and the second part of steam is 0.45–1, preferably 0.7–0.9, relative to the weight of the crude oil component in the gas phase mixture.

[0014] Optionally, the method further includes: buffering the liquid phase heavy components in a buffer tank before sending them out; allowing crude oil and waste heat material from the storage tank to enter a quench water preheater for a first heat exchange to obtain first preheated crude oil and cooled material; optionally, the temperature of the first preheated crude oil is 70-120°C; or allowing crude oil from the storage tank to enter the convection section of a steam cracking unit for further heating after the first heat exchange in the quench water preheater, and using the obtained preheated crude oil as the first preheated crude oil; allowing the first preheated crude oil to enter a desalination preprocessor for desalination pretreatment to obtain desalted crude oil; and allowing the crude oil to enter the storage tank for desalination pretreatment to obtain desalted crude oil. Desalted crude oil is heated in the feed preheating section of the steam cracking unit to obtain second preheated crude oil; the second preheated crude oil is then used as the feed crude oil to enter the fractionation tower for the first separation; optionally, the temperature of the second preheated crude oil is 200-400°C; optionally, the method further includes: subjecting the crude oil to external preheating treatment outside the convection section before entering the fractionation tower; the heat source for the external preheating treatment is waste heat material from any unit in the ethylene plant or combined unit; the external preheating treatment is independent of the preheating treatment in the feed preheating section.

[0015] Optionally, the method further includes: dividing the cooled heavy components into three parts, allowing the first part of the cooled heavy components to enter a hydrogenation unit for hydrogenation treatment, allowing the second part of the cooled heavy components to enter a catalytic cracking unit for catalytic cracking treatment; and allowing the third part of the cooled heavy components to be refluxed into the buffer tank; optionally, the method further includes: allowing at least a portion of the liquid phase heavy components to enter a steam generator for treatment to generate steam; and allowing a portion of the steam to be used as supplementary steam for one or more of the first part of steam, the second part of steam, the third part of steam, the fourth part of steam, the fifth part of steam, and the sixth part of steam.

[0016] A second aspect of this disclosure provides a system for producing olefins from crude oil through steam cracking. The system includes a fractionating tower, a separation unit, and a steam cracking unit. The steam cracking unit includes a convection section and a radiating section, with the convection section positioned above the radiating section along the height of the steam cracking unit. The fractionating tower has a crude oil inlet, a light-range component outlet, a medium-range component outlet, and a heavy-range component outlet. The separation unit has a feedstock inlet, a first steam inlet, a gas-phase mixture outlet, and a liquid-phase heavy component outlet. The heavy-range component outlet of the fractionating tower is connected to the feedstock inlet of the separation unit. The radiating section of the steam cracking unit has a first feedstock inlet, a second feedstock inlet, and a third feedstock inlet. The first feedstock inlet is connected to the light-range component outlet of the fractionating tower, the second feedstock inlet is connected to the medium-range component outlet, and the third feedstock inlet is connected to the gas-phase mixture outlet of the separation unit.

[0017] Optionally, along the height direction of the steam cracking unit, the convection section includes, from top to bottom, a feed preheating section, a first mixing superheating section, a second mixing superheating section, a third mixing superheating section, a fourth steam superheating section, a fifth mixing superheating section, a sixth mixing superheating section, and a seventh mixing superheating section, each independent of the others. The feed preheating section has a crude oil preheating inlet and a crude oil preheating outlet, the crude oil preheating outlet being connected to the feed crude oil inlet of the fractionation tower. The first mixing superheating section has a heavy distillation range component heating inlet and a heavy distillation range component heating outlet. The second mixing superheating section has a medium distillation range component inlet and a second mixture outlet. The third mixing superheating section has a light distillation range component inlet and a first mixture outlet. The fourth steam superheating section is provided with a steam heating inlet and a steam heating outlet; the fifth mixing superheating section is provided with a first mixed material inlet and a first feedstock to be cracked outlet; the sixth mixing superheating section is provided with a second mixed material inlet and a second feedstock to be cracked outlet; the seventh mixing superheating section is provided with a gas phase mixed material inlet and a third feedstock to be cracked outlet; wherein, the light distillation range component inlet of the third mixing superheating section is connected to the light distillation range component outlet of the fractionation tower through a first pipeline, and the first mixed material outlet is connected to the first mixed material inlet of the fifth mixing superheating section through a second pipeline; the first feedstock to be cracked outlet of the fifth mixing superheating section is connected to the first feedstock to be cracked inlet of the radiant section; optionally, the first pipeline... A third steam inlet is provided, and a fourth steam inlet is provided on the second pipeline; the inlet of the middle-range component of the second mixing superheated section is connected to the outlet of the middle-range component of the fractionating column via the third pipeline, and the outlet of the second mixture is connected to the inlet of the second mixture of the sixth mixing superheated section via the fourth pipeline; the outlet of the second feedstock to be cracked in the sixth mixing superheated section is connected to the inlet of the second feedstock to be cracked in the radiant section; optionally, a fifth steam inlet is provided on the third pipeline, and a sixth steam inlet is provided on the fourth pipeline; the heating inlet of the heavy-range component of the first mixing superheated section is connected to the outlet of the heavy-range component of the fractionating column via the fifth pipeline, and the heating outlet of the heavy-range component is connected to... The raw material inlet of the separation device is connected; optionally, the fifth pipeline is provided with a first part of the steam inlet, and the sixth pipeline is provided with a second part of the steam inlet; optionally, the gas phase mixture inlet of the seventh mixing superheating section is connected to the gas phase mixture outlet of the separation device, and the third raw material outlet to be cracked is connected to the third cracking raw material inlet of the radiation section; optionally, the radiation section includes a first cracking furnace tube, a second cracking furnace tube, and a third cracking furnace tube that are independently arranged; the first cracking furnace tube is provided with a raw material inlet to form a first raw material inlet to be cracked, the second cracking furnace tube is provided with a raw material inlet to form a second raw material inlet to be cracked, and the third cracking furnace tube is provided with a raw material inlet to form a third raw material inlet to be cracked;The steam heating inlet of the fourth steam superheating section is connected to a steam source, and the steam heating outlet of the fourth steam superheating section is connected to the second part of the steam inlet, the fourth part of the steam inlet, and the sixth part of the steam inlet, respectively.

[0018] Optionally, the system further includes a buffer tank, a pump, a desalting preprocessor, and a quench water preheater. The buffer tank is provided with at least a liquid-phase heavy component buffer inlet, a liquid-phase heavy component buffer outlet, a cooling heavy component reflux inlet, a steam purging port, and a nitrogen purging port. The pump includes an inlet and an outlet. The desalting preprocessor is provided with a crude oil desalting inlet and a crude oil desalting outlet. The quench water preheater is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a crude oil heat exchange first inlet, and a crude oil heat exchange first outlet. The crude oil heat exchange first outlet of the quench water preheater is connected to the crude oil desalting inlet of the desalting preprocessor, and the crude oil desalting outlet is connected to the crude oil preheating inlet of the raw material preheating section. The liquid-phase heavy component buffer inlet of the buffer tank is connected to the... The liquid phase heavy component outlet of the separation unit is connected, and the liquid phase heavy component buffer outlet is connected to the pump inlet. Optionally, the cooling heavy component outlet is used to connect to the feed inlet of the catalytic cracking unit and / or the feed inlet of the hydrotreating unit. Optionally, the system further includes a flow control unit, which includes a level transmitter, a pump reflux control valve, a level control valve, a pump outlet flow meter, a heavy component outflow flow meter, and a crude oil feed flow meter. The top of the buffer tank is also provided with a heavy component reflux inlet. The flow control unit can determine the vaporization ratio of the separation unit through the heavy component outflow flow meter and the crude oil feed flow meter. The level transmitter is connected to the internal space of the buffer tank to control the liquid level in the buffer tank.

[0019] Through the above technical solution, this disclosure provides a method and system for producing olefins from crude oil steam cracking, the beneficial effects of which include at least:

[0020] 1. This disclosure introduces crude oil as feedstock into a fractionation tower for the first separation, obtaining light-range, medium-range, and heavy-range components. The heavy-range component is then subjected to a second separation to obtain a gas-phase mixture and a liquid-phase heavy component. Compared with existing atmospheric distillation towers, this reduces the bottom operating temperature. Furthermore, the crude oil components are subdivided, allowing for the selection of fractions suitable for olefin production as steam cracking feedstock based on the crude oil composition and processing requirements. Fractions unsuitable for cracking can be used to produce aromatic components or sold as oil products. This achieves the goal of selecting olefins, aromatics, and oils as appropriate. Moreover, due to the subdivision, each fraction used as cracking feedstock can be cracked under optimal conditions, resulting in a higher olefin yield.

[0021] 2. Compared with other crude oil cracking technologies, the process disclosed herein has clear fractionation and can maximize the application of existing steam cracking technology. The technology is mature and the operation is simple.

[0022] 3. This disclosure eliminates the heating furnace of the atmospheric and vacuum distillation unit, simplifying the process and saving investment;

[0023] 4. This disclosure has a wide range of applicability to crude oil, and the separated fractions can be flexibly utilized to improve the quality and efficiency of existing integrated refining and chemical plants. They can also be used in new integrated refining and chemical plants to produce olefins such as ethylene. For newly built integrated refining and chemical plants, fewer refining units such as atmospheric and vacuum distillation and reforming units can be built. For light paraffin-based crude oil, the separated light fractions can be used as feedstock for steam cracking, so refining units may not be necessary.

[0024] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 This is a schematic diagram of a system process for producing olefins from crude oil steam cracking according to one embodiment of the present disclosure;

[0027] Figure 2 This is a schematic diagram of a system process for producing olefins from crude oil steam cracking according to one embodiment of the present disclosure.

[0028] Explanation of reference numerals in the attached figures

[0029] 1-Raw material preheating section, 2-Fracturing tower, 3-First mixing superheating section, 4-Second mixing superheating section, 5-Third mixing superheating section, 6-Fourth steam superheating section, 7-Fifth mixing superheating section, 8-Sixth mixing superheating section, 9-Seventh mixing superheating section, 10-Separation unit, 11-Radiation section, 12-Buffer tank, 13-Pump, 15-Desalting pre-processor, 16-Quick coolant preheater, 101-Crude oil (crude oil from storage tank), H1-Residual heat material, 102-Pretreated crude oil (desalted crude oil), 104-Heated crude oil (second preheated crude oil), 105-Light distillation range component, 106-Middle distillation range component, 107-Heavy distillation range component, 1 08-Third section steam (primary dilution steam), 109-Fourth section steam (secondary dilution steam), 110-First feed stream to be cracked, 111-Fifth section steam (primary dilution steam), 112-Sixth section steam (secondary dilution steam), 113-Second feed stream to be cracked, 114-First section steam (primary dilution steam), 115-Heated heavy distillation range component mixture, 116-Second section steam (secondary dilution steam), 117-Gas phase mixture, 118-Liquid phase heavy components, 119-Third feed stream to be cracked, 120-Cooled heavy components, 121-Crack products, 122-Crack products, 123-Crack products Detailed Implementation

[0030] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0031] In this disclosure, unless otherwise stated, the terms "first," "second," and "third" are used only to distinguish different components and do not imply any actual connection order. In this disclosure, directional terms such as "upper," "lower," "top," and "bottom" generally refer to the upper and lower, top and bottom, of the device in its normal operating state. "Inner" and "outer" refer to the outline of the device.

[0032] In this disclosure, the terms "primary dilution steam," "secondary dilution steam," "first part steam," and "second part steam" are used only to distinguish the steam introduced in different steps and do not contain any actual meaning such as the properties of the steam itself.

[0033] The first aspect of this disclosure provides a method for producing olefins from crude oil through steam cracking, such as... Figure 1 As shown, it includes the following steps:

[0034] S1. The raw crude oil is fed into fractionation tower 2 for the first separation, separating light-range components, medium-range components and heavy-range components.

[0035] S2. The light-range component is mixed with steam to obtain a first mixture; the medium-range component is mixed with steam to obtain a second mixture.

[0036] S3. The heavy distillation range component is mixed with steam and then enters the separation device 10 for a second separation, separating the gas phase mixture and the liquid phase heavy component.

[0037] S4. The first mixture and the second mixture are respectively fed into the convection section of the steam cracking device for superheating, and then into the radiation section 11 of the steam cracking device for steam cracking to obtain cracking products containing ethylene and propylene.

[0038] This disclosure introduces crude oil feedstock into a fractionating tower for first separation, resulting in light-range, medium-range, and heavy-range components. The heavy-range component then undergoes a second separation to obtain a gas-phase mixture and a liquid-phase heavy component. This fine segmentation of the crude oil feedstock allows for the selection of fractions suitable for olefin production as steam cracking feedstock based on the crude oil composition and processing requirements. Fractions unsuitable for cracking can be used to produce aromatics or sold as oil products. This achieves the goal of selecting the appropriate fraction for olefins, aromatics, or oil. Furthermore, due to this segmentation, each fraction used as cracking feedstock can be cracked under optimal conditions, resulting in a higher olefin yield. Compared with other crude oil cracking technologies, the process disclosed herein is simpler and can maximize the application of existing steam cracking technologies. The technology is mature and easy to operate. This disclosure eliminates the heating furnace of the atmospheric and vacuum distillation unit, simplifying the process and saving investment. This disclosure has a wide range of applicability to crude oil, and the separated fractions can be flexibly utilized to achieve quality improvement and efficiency enhancement with existing integrated refining and chemical units. It can also be used in new integrated refining and chemical units to produce olefins such as ethylene. For newly built integrated refining and chemical units, fewer refining units such as atmospheric and vacuum distillation and reforming units can be built. For light paraffin-based crude oil, the separated light fractions can be used as steam cracking feedstock, so refining units can also be eliminated.

[0039] In one specific embodiment, the light distillation range component obtained by the first separation includes naphtha and lighter components; the medium distillation range component includes kerosene fraction and light diesel oil fraction; and the light component in the heavy distillation range component of the gas phase mixture obtained by the second separation includes heavy diesel oil and lighter components.

[0040] In this disclosure, each fraction obtained from the fractionation tower 2 and the separation device 10 carries steam, and the distillation range temperature of each fraction in this disclosure is the crude oil component obtained from the fraction excluding steam.

[0041] In a preferred embodiment, the final boiling point of the light-range component obtained from the first separation is 80–160°C; the initial boiling point of the middle-range component is not higher than the final boiling point of the light-range component, preferably 60–140°C; the final boiling point of the middle-range component is 250–350°C; the initial boiling point of the heavy-range component is not higher than the final boiling point of the middle-range component, preferably 230–330°C; the final boiling point of the gas-phase mixture obtained from the second separation is 350–460°C; and the initial boiling point of the liquid-phase heavy component is not higher than the final boiling point of the gas-phase mixture. It should be understood that the initial or final boiling point of each fraction in this disclosure is a range value, and in actual operation, it can be any temperature within the range. Furthermore, this disclosure allows for the selection of the separated fractions according to actual production needs.

[0042] In this disclosure, the fractionation tower 2 is a conventionally selected device in the art; the separation device 10 is an integrated separation device, such as a flash separator or a cyclone separator; preferably, it is a high-efficiency gas / vapor-liquid separation device, and the gas (vapor) phase outlet of the gas-liquid separator can be one or more.

[0043] In one embodiment, the crude oil feedstock is at least one of paraffin-based crude oil, intermediate-based crude oil, or naphthenic crude oil.

[0044] In one embodiment, the method further includes: superheating all of the gaseous mixture in the convection section of a steam cracking unit, and then subjecting it to steam cracking in the radiation section 11 of the steam cracking unit to obtain cracking products containing ethylene and propylene; or

[0045] The entire gas-phase mixture is fed into the refining unit for further processing; or

[0046] A portion of the gaseous mixture is fed into the convection section of the steam cracking unit for superheating, and then into the radiation section 11 of the steam cracking unit for steam cracking, while the other portion of the gaseous mixture is fed into the refining unit for further processing.

[0047] The inventors of this disclosure have discovered that, depending on the type of crude oil feedstock, the gas-phase mixture obtained from the second separation can be processed in different ways, demonstrating a wide range of adaptability to crude oil feedstocks and allowing for flexible utilization of the separated fractions, thereby maximizing resource utilization. A detailed explanation follows.

[0048] In one specific embodiment, this disclosure further includes the following step: when the crude oil is paraffin-based crude oil, at least a portion of the gaseous mixture is introduced into a refining unit for processing. In this embodiment, introducing the gaseous mixture fractionated from paraffin-based crude oil into a refining unit allows fractions unsuitable for steam cracking to be used in the production of aromatic oils. This enables flexible utilization of fractions separated from different types of crude oil, allowing for the selection of olefins, aromatics, or oils as appropriate.

[0049] In one specific embodiment, when the feedstock crude oil is naphthenic crude oil, all of the gas phase mixture is introduced into the radiation section of the steam cracking unit, but not into the refining unit, in order to further improve the olefin yield.

[0050] In a preferred embodiment, before the gaseous mixture enters the refining unit for further processing, the gaseous mixture and the feedstock oil to be preheated are first introduced into a cooler for heat exchange, resulting in preheated feedstock oil and cooled liquid phase material of the gaseous mixture; then, the cooled liquid phase material of the gaseous mixture enters the refining unit for further processing. In this disclosure, the feedstock oil to be preheated can be any feedstock oil obtained in any step before entering the fractionation tower. The cooler can be connected in series with other devices in this system that process the feedstock oil before it enters the separation tower to further improve heat utilization.

[0051] In a preferred embodiment, when the BMCI value of the crude oil component in the gas-phase mixture is 30 or higher, at least a portion of the gas-phase mixture is sent to a refining unit. The "BMCI value" (USBureau of Mines Correlation Index) refers to the aromaticity index, representing the aromatization index of a petroleum product.

[0052] In one implementation, such as Figure 1 As shown, along the height direction of the steam cracking device, the convection section is provided with, from top to bottom, an independent first mixing superheating section 3, a second mixing superheating section 4, a third mixing superheating section 5, a fourth steam superheating section 6, a fifth mixing superheating section 7, a sixth mixing superheating section 8, and an optional seventh mixing superheating section 9; step S3 includes:

[0053] The heavy distillation range component is mixed with a first portion of steam and then heated in the first mixing superheating section 3 of the steam cracking device to obtain a heated first mixture of heavy distillation range components; the heated first mixture of heavy distillation range components is then mixed with a second portion of steam to obtain a second mixture of heavy distillation range components; optionally, the temperature of the second mixture of heavy distillation range components is 200-410°C.

[0054] The second mixture of the heavy distillation range components is introduced into the separation device 10 for the second separation. In this embodiment, the heavy distillation range components obtained from the first separation are introduced into the convection section of the steam cracking device for heating with a first portion of steam (e.g., primary dilution steam), which can improve the overall heat utilization efficiency of the process. Furthermore, mixing the heavy distillation range components with steam and then performing the second separation under the conditions of a second portion of steam (e.g., secondary dilution steam) can further improve the second separation efficiency of the heavy distillation range components. Simultaneously, this disclosure provides multiple independent superheating sections in the convection section, which can be used to heat multiple components, greatly improving heat utilization efficiency and cracking yield.

[0055] In one implementation, such as Figure 1 As shown, along the height direction of the steam cracking device, the radiation section 11 is located below the convection section; step S4 includes:

[0056] a) The light-range component is mixed with the third portion of steam and then introduced into the third mixing superheating section 5 of the steam cracking device for heating, and then into the fifth mixing superheating section 7 of the steam cracking device for heating to 550-750°C to obtain the first feed stream to be cracked; or, the light-range component is mixed with the third portion of steam and then introduced into the third mixing superheating section 5 of the steam cracking device for heating, and then mixed with the fourth portion of steam and then into the fifth mixing superheating section 7 of the steam cracking device for heating to 550-750°C to obtain the first feed stream to be cracked;

[0057] b. The middle-range component is mixed with the fifth part of steam and then enters the second mixing superheating section 4 of the steam cracking device for heating. Then it is mixed with the sixth part of steam and then enters the sixth mixing superheating section 8 of the steam cracking device for heating to 450-700°C to obtain the second feed stream to be cracked.

[0058] Optionally, c, the gaseous mixture is introduced into the seventh mixing superheating section 9 of the steam cracking device and heated to 400-650°C to obtain a third feed stream to be cracked;

[0059] The first stream of material to be cracked is introduced into the first cracking furnace tube of the radiant section 11 of the steam cracking device for steam cracking to obtain a first cracking product; the second stream of material to be cracked is introduced into the second cracking furnace tube of the radiant section 11 of the steam cracking device for steam cracking to obtain a second cracking product; optionally, the third stream of material to be cracked is introduced into the third cracking furnace tube of the radiant section 11 of the steam cracking device for steam cracking to obtain a third cracking product.

[0060] In this embodiment, the light-range and medium-range fractions are first mixed and heated with the third portion of steam, and then mixed and heated with the fourth portion of steam (the light-range fraction may not be mixed with the fourth portion of steam, depending on process requirements), resulting in the feed stream to be cracked. Steam is introduced into the light-range and medium-range fractions for steam cracking, and superheating is performed in different superheating sections of the convection section, improving heat utilization and overall process integration. In this embodiment, different feedstocks are introduced into their respective cracking furnace tubes, facilitating control of cracking conditions for different feedstocks. This embodiment further improves heat utilization; and the different fractions are subdivided and heated to different temperatures (e.g., across temperatures), ensuring that each fraction used as cracking feedstock can be cracked under optimal conditions, resulting in a high olefin yield.

[0061] Specifically, the conditions under which the first, second, and third feed streams to be cracked undergo steam cracking in the radiation section in this disclosure can be conventional conditions in the art, and the catalyst can be selected from catalysts known in the art.

[0062] In this disclosure, conventionally selected separation devices can also be used to separate the steam cracking products obtained from the radiation section 11, separating products such as ethylene and propylene.

[0063] In one specific embodiment, the first portion of steam, the second portion of steam, the third portion of steam, the fourth portion of steam, the fifth portion of steam, and the sixth portion of steam are each independently superheated steam or steam in the non-superheated section, which can be adjusted according to actual needs. Furthermore, in this disclosure, the location for superheating the steam can be the superheated section inside the steam cracking device, or it can be superheated using other heat sources outside the steam cracking device.

[0064] In a preferred embodiment, such as Figure 1 As shown, the method further includes: after the steam enters the fourth steam superheating section 6 of the steam cracking device for superheating treatment, it is divided into three parts, which are respectively used as the second part of steam, the fourth part of steam and the sixth part of steam; preferably, the temperature of the steam after being superheated by the fourth steam superheating section 6 is 400-575°C.

[0065] In a preferred embodiment, in step a, the total weight of the third part of dilution steam and the optional fourth part of steam is in a weight ratio of 0.3 to 1, preferably 0.4 to 0.7, to the crude oil component in the light distillation range component.

[0066] In step b, the total weight of the fifth part of steam and the sixth part of dilution steam is in a weight ratio of 0.35 to 1 to the crude oil component in the medium-range distillation component, preferably in a range of 0.6 to 0.8.

[0067] In step S3, the total weight of the first part of steam and the second part of steam is 0.45 to 1, preferably 0.7 to 0.9, relative to the weight of the crude oil component in the gas phase mixture.

[0068] In this disclosure, since the light-range component, the middle-range component, and the gas phase mixture obtained by separation all contain steam, the amount of steam introduced is controlled based on the mass of the components from crude oil remaining after removing steam from the light-range component, the middle-range component, and the gas phase mixture.

[0069] In one implementation, such as Figure 1 As shown, the method also includes:

[0070] The liquid phase heavy components are buffered by buffer tank 12 before being sent out;

[0071] The crude oil and waste heat material from the storage tank are respectively introduced into the quench water preheater 16 for the first heat exchange to obtain the first preheated crude oil and the cooled material; optionally, the temperature of the first preheated crude oil is 70-120°C; or the crude oil from the storage tank is introduced into the convection section of the steam cracking unit after the first heat exchange in the quench water preheater 16, and the obtained preheated crude oil is used as the first preheated crude oil.

[0072] The first preheated crude oil is fed into the desalting preprocessor 15 for desalting pretreatment to obtain desalted crude oil;

[0073] The second preheated crude oil is fed into the feedstock preheating section 1 of the steam cracking unit for heating to obtain the second preheated crude oil; the second preheated crude oil is then fed into the fractionation tower 2 as the feedstock crude oil for the first separation; optionally, the temperature of the second preheated crude oil is 200-400°C.

[0074] In this embodiment, the crude oil from the storage tank is first exchanged with the waste heat material, and the desalted crude oil is exchanged with the liquid phase heavy components for a second heat exchange. This achieves heat exchange between multiple materials, which not only increases the temperature of the crude oil to be processed but also cools the liquid phase heavy components of the output system. The second preheated crude oil is introduced into the raw material preheating section for heating, further improving the overall heat utilization rate of the process.

[0075] In one embodiment, the process sequence for preheating crude oil can also be to use the waste heat from the ethylene unit instead of the quench water for heat exchange, and then preheat it by exchanging heat with the high-temperature heavy oil obtained from the crude oil cracking process; or the crude oil can first exchange heat with the waste heat from the ethylene unit, then undergo desalting treatment, and then exchange heat with the high-temperature heavy oil obtained from the crude oil cracking process.

[0076] The process disclosed herein has a high energy utilization rate, fully combining the thermal energy of the ethylene plant with the heating requirements of the process itself, further reducing the energy consumption of the ethylene plant, realizing heat recovery and utilization, and saving investment.

[0077] In one implementation, such as Figure 1 As shown, the method further includes: dividing the cooled heavy components into three parts, allowing the first part of the cooled heavy components to enter a hydrogenation unit for hydrogenation treatment, allowing the second part of the cooled heavy components to enter a catalytic cracking unit for catalytic cracking treatment, and allowing the third part of the cooled heavy components to be refluxed into the buffer tank 12.

[0078] In this disclosure, the obtained gas-phase mixture and liquid-phase heavy components can be treated differently according to the lightness or heaviness of the crude oil and its source and composition. For example, depending on whether the crude oil is paraffinic or naphthenic, it can be decided whether to introduce the gas-phase mixture as a feedstock for cracking into the steam cracking unit or directly into the refining unit. Alternatively, part of the gas-phase mixture can be introduced into the steam cracking unit as a feedstock for cracking, and the remaining part can be introduced into the refining unit for secondary processing to improve the overall process utilization efficiency.

[0079] In one embodiment, the method further includes: allowing at least a portion of the liquid phase heavy components to enter a steam generator for processing to generate steam; and using a portion of the steam as supplementary steam for one or more of the first portion of steam, the second portion of steam, the third portion of steam, the fourth portion of steam, the fifth portion of steam, and the sixth portion of steam.

[0080] In one embodiment, the method further includes: detecting the temperature of the liquid phase material in the buffer tank 12 to obtain a temperature signal; before the crude oil enters the fractionation tower 2, it undergoes external preheating treatment outside the convection section, the heat source for which is waste heat material from any unit in the ethylene plant or combined unit; the external preheating treatment is independent of the preheating treatment in the raw material preheating section 1. This further improves the heat utilization effect, especially the utilization effect of waste heat material obtained from other units within the plant area. The external preheating treatment of the material is independent of the heating step in the superheating section of the steam cracking unit and can be selected according to the actual situation.

[0081] A second aspect of this disclosure provides a system for producing olefins from crude oil through steam cracking, such as... Figure 1 As shown, the system includes a fractionation tower 2, a separation unit 10, and a steam cracking unit. The steam cracking unit includes a convection section and a radiation section 11. Along the height direction of the steam cracking unit, the convection section is located above the radiation section 11.

[0082] The fractionating tower 2 is provided with a crude oil inlet, a light distillation range component outlet, a medium distillation range component outlet, and a heavy distillation range component outlet; the separation unit 10 is provided with a raw material inlet to be separated, a first steam inlet, a gas phase mixture outlet, and a liquid phase heavy component outlet; the heavy distillation range component outlet of the fractionating tower 2 is connected to the raw material inlet to be separated of the separation unit 10.

[0083] The radiation section 11 of the steam cracking unit is provided with a first feedstock inlet, a second feedstock inlet, and a third feedstock inlet; the first feedstock inlet is connected to the light distillation range component outlet of the fractionation tower 2, the second feedstock inlet is connected to the medium distillation range component outlet, and the third feedstock inlet is connected to the gas phase mixture outlet of the separation unit 10.

[0084] In this disclosure, the fractionation tower 2 is a device conventionally chosen by those skilled in the art.

[0085] In one specific embodiment, the radiant section of the steam pyrolysis unit includes a first pyrolysis furnace tube, a second pyrolysis furnace tube, and a third pyrolysis furnace tube, which are independently arranged. The first pyrolysis furnace tube has a raw material inlet to form a first raw material inlet to be pyrolyzed, the second pyrolysis furnace tube has a raw material inlet to form a second raw material inlet to be pyrolyzed, and the third pyrolysis furnace tube has a raw material inlet to form a third raw material inlet to be pyrolyzed. Optionally, the first pyrolysis furnace tube, the second pyrolysis furnace tube, and the third pyrolysis furnace tube can be different radiant section furnace tubes entering the same furnace chamber of the same pyrolysis furnace; or radiant furnace tubes in different radiant sections of the same pyrolysis furnace; or radiant furnace tubes from different pyrolysis furnaces, which can be set according to the actual situation.

[0086] In one embodiment, the separation device 10 is a gas-liquid separator; preferably, the gas-liquid separator is a high-efficiency gas / vapor-liquid separation device, wherein the gas-vapor phase outlet of the gas-liquid separator can be one or more.

[0087] In one implementation, such as Figure 2 As shown, the system also includes an oil refining unit, the raw material inlet of which is connected to the gas-phase mixture outlet of the separation unit 10.

[0088] In one implementation, such as Figure 1 As shown, along the height direction of the steam cracking unit, the convection section is arranged from top to bottom as follows: raw material preheating section 1, first mixing superheating section 3, second mixing superheating section 4, third mixing superheating section 5, fourth steam superheating section 6, fifth mixing superheating section 7, sixth mixing superheating section 8 and seventh mixing superheating section 9, which are independent of each other.

[0089] The raw material preheating section 1 is equipped with a crude oil preheating inlet and a crude oil preheating outlet, and the crude oil preheating outlet is connected to the raw material crude oil inlet of the fractionation tower 2;

[0090] The first mixing superheating section 3 is equipped with a heating inlet and an outlet for heavy distillation range components; the second mixing superheating section 4 is equipped with an inlet for medium distillation range components and an outlet for the second mixture; the third mixing superheating section 5 is equipped with an inlet for light distillation range components and an outlet for the first mixture; the fourth steam superheating section 6 is equipped with a steam heating inlet and a steam heating outlet; the fifth mixing superheating section 7 is equipped with an inlet for the first mixture and an outlet for the first feedstock to be cracked; the sixth mixing superheating section 8 is equipped with an inlet for the second mixture and an outlet for the second feedstock to be cracked; the seventh mixing superheating section 9 is equipped with an inlet for the gas phase mixture and an outlet for the third feedstock to be cracked.

[0091] The light distillation range component inlet of the third mixing superheating section 5 is connected to the light distillation range component outlet of the fractionation tower 2 via a first pipeline; the first mixed material outlet is connected to the first mixed material inlet of the fifth mixing superheating section 7 via a second pipeline; the first raw material outlet to be cracked of the fifth mixing superheating section 7 is connected to the first cracking raw material inlet of the radiation section 11; optionally, a third steam inlet is provided on the first pipeline, and a fourth steam inlet is provided on the second pipeline.

[0092] The inlet of the middle-range component of the second mixing superheating section 4 is connected to the outlet of the middle-range component of the fractionation tower 2 through a third pipeline; the outlet of the second mixture is connected to the inlet of the second mixture of the sixth mixing superheating section 8 through a fourth pipeline; the outlet of the second feedstock to be cracked of the sixth mixing superheating section 8 is connected to the inlet of the second feedstock to be cracked of the radiation section 11; optionally, a fifth steam inlet is provided on the third pipeline and a sixth steam inlet is provided on the fourth pipeline.

[0093] The heavy distillation range component heating inlet of the first mixing superheating section 3 is connected to the heavy distillation range component outlet of the fractionation tower 2 through a fifth pipeline, and the heavy distillation range component heating outlet is connected to the raw material inlet of the separation device 10; optionally, a first part of the steam inlet is provided on the fifth pipeline, and a second part of the steam inlet is provided on the sixth pipeline.

[0094] Optionally, the gas phase mixture inlet of the seventh mixing and superheating section 9 is connected to the gas phase mixture outlet of the separation device 10, and the third raw material outlet to be cracked is connected to the third raw material inlet of the radiation section 11.

[0095] In one specific embodiment, in the system of this disclosure, mixers can be respectively installed at the first to sixth steam inlets to mix the light-range, medium-range, and heavy-range components with the steam, thereby making the mixing of materials and steam more uniform and preventing coking. Any type of mixer known in the art that satisfies the above-mentioned mixing effect can be used.

[0096] In one specific embodiment, the first to seventh mixing superheating sections in this disclosure can be different heat exchange tubes in the upper mixing superheating section of the convection section of the same steam cracking unit, or heat exchange tubes in the upper mixing superheating section of different steam cracking units.

[0097] In one embodiment, the radiation section 11 includes a first pyrolysis furnace tube, a second pyrolysis furnace tube, and a third pyrolysis furnace tube that are independently arranged with each other; the first pyrolysis furnace tube is provided with a raw material inlet to form a first raw material inlet to be pyrolyzed, the second pyrolysis furnace tube is provided with a raw material inlet to form a second raw material inlet to be pyrolyzed, and the third pyrolysis furnace tube is provided with a raw material inlet to form a third raw material inlet to be pyrolyzed.

[0098] The steam heating inlet of the fourth steam superheating section 6 is connected to the steam source, and the steam heating outlet of the fourth steam superheating section 6 is connected to the second part steam inlet, the fourth part steam inlet and the sixth part steam inlet respectively.

[0099] In one embodiment, the system further includes a buffer tank 12, a pump 14, a desalination pre-processor 15, and a quench water preheater 16;

[0100] The buffer tank 12 is provided with at least a liquid phase heavy component buffer inlet, a liquid phase heavy component buffer outlet, a cooling heavy component reflux inlet, a steam purging port, and a nitrogen purging port; the pump 13 includes an inlet and an outlet; the desalting preprocessor 15 is provided with a crude oil desalting inlet and a crude oil desalting outlet; the quench water preheater 16 is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a crude oil heat exchange first inlet, and a crude oil heat exchange first outlet;

[0101] Among them, the crude oil heat exchange first outlet of the quench water preheater 16 is connected to the crude oil desalting inlet of the desalting preprocessor 15, and the crude oil desalting outlet is connected to the crude oil preheating inlet of the raw material preheating section 1.

[0102] The liquid phase heavy component buffer inlet of buffer tank 12 is connected to the liquid phase heavy component outlet of separation device 10, the liquid phase heavy component buffer outlet is connected to the input port of pump 13, and the output port of pump 13 is used to connect to the feed inlet of catalytic cracking device and / or the feed inlet of hydrotreating device.

[0103] In one embodiment, the system further includes a flow control unit, which includes a level transmitter, a pump reflux control valve b, a level control valve c, a pump outlet flow meter d, a heavy component outflow flow meter e, and a crude oil feed flow meter f; the top of the buffer tank 12 is also provided with a heavy component reflux inlet; the flow control unit can determine the vaporization ratio of the separation device 10 through the heavy component outflow flow meter e and the crude oil feed flow meter f; wherein, the level transmitter is connected to the internal space of the buffer tank 12 to control the liquid level in the buffer tank 12.

[0104] The present disclosure will be further described below with reference to specific embodiments.

[0105] Example 1

[0106] This embodiment uses a certain crude oil as an example. The API value of this crude oil is 41. This embodiment can realize the comprehensive utilization of different light and heavy fractions of crude oil. This embodiment adopts... Figure 1 The system shown specifically includes the following steps:

[0107] Crude oil 101 undergoes preliminary preheating (first heat exchange, resulting in first preheated crude oil at a temperature of 70–120°C) after passing through quench water preheater 16. It then passes through desalting pre-processor 15 for desalting and impurity removal. The pretreated crude oil 102 enters the feedstock preheating section 1 in the convection section of the steam cracking unit for further heating (the resulting second preheated crude oil at a temperature of 200–400°C). The heated crude oil 104 then enters fractionation tower 2 as feedstock for light and heavy component separation (i.e., first separation). The following fractions are separated: light-range fractions (including naphtha and lighter fractions, with a final boiling point of 80–160°C) 105, medium-range fractions (kerosene fractions and fractions below light diesel oil, with an initial boiling point of 60–140°C and a final boiling point of 250–350°C) 106, and heavy-range fractions (with an initial boiling point of 230–330°C) 107. Depending on actual production needs, the separated fractions can undergo the following steps, or they can be further processed in a refining unit (not shown in the diagram):

[0108] The light-range component 105 separated after the above steps is mixed with unsuperheated primary dilution steam (third part steam) 108 and then enters the third mixing superheating section 5 of the convection section of the steam cracking unit. It is then mixed with secondary dilution steam (fourth part steam) 109 that has been heated by the fourth steam superheating section 6 (the weight ratio of the sum of the primary dilution steam 108 and the secondary dilution steam 109 to the weight of the crude oil component in the light-range component is 0.4 to 0.7). Subsequently, it enters the fifth mixing superheating section 7 of the convection section and is heated to a temperature spanning 550 to 750°C to obtain the first feed stream to be cracked 110. The first feed stream to be cracked 110 is introduced into the furnace tube of the radiation section 11 for high-temperature steam cracking reaction to obtain cracking product 121.

[0109] The medium-range component 106 separated after the above steps is mixed with unsuperheated primary dilution steam (fifth part steam) 111 and then enters the second mixing superheating section 4 of the convection section of the steam cracking unit. It is then mixed with secondary dilution steam (sixth part steam) 112 that has been heated to 400-575°C in the fourth steam superheating section 6 (the weight ratio of the sum of the primary dilution steam 111 and the secondary dilution steam 112 to the weight of the crude oil component in the medium-range component is 0.6-0.8). Subsequently, it enters the sixth mixing superheating section 8 of the convection section and is heated to a temperature spanning 450-700°C to obtain the second feed stream 113 to be cracked. The second feed stream 113 to be cracked is introduced into the furnace tube of the radiation section 11 for high-temperature steam cracking reaction to obtain cracking product 122.

[0110] After the above steps, the heavy distillation range component 107 is separated and mixed with unsuperheated primary dilution steam (first part steam) 114. The mixture is then heated to 200-410°C in the first mixing superheating section 3 of the convection section of the steam cracking unit. The heated heavy distillation range component mixture 115 and the secondary dilution steam (second part steam) 116 are then introduced into the separation unit 10 for a second separation (wherein, the weight ratio of the sum of the primary dilution steam 114 and the secondary dilution steam 116 to the weight of the crude oil component in the gas phase mixture is 0.7-0.9). This yields a gas phase mixture 117 and a liquid phase heavy component 118 (the gas phase mixture is a mixture containing the light components of the heavy distillation range component and steam, and the liquid phase heavy component contains the heavy components of the heavy distillation range component; the final boiling point of the gas phase mixture is 350-460°C; the initial boiling point of the liquid phase heavy component is not higher than the final boiling point of the gas phase mixture).

[0111] The gaseous mixture 117 is introduced into the seventh mixing and superheating section 9 of the convection section and heated to a temperature spanning 400-600°C to obtain the third pyrolysis stream 119; the third pyrolysis stream 119 is introduced into the furnace tube of the radiation section 11 for high-temperature steam pyrolysis reaction to obtain pyrolysis product 123.

[0112] The liquid phase heavy component 118 is introduced into the buffer tank 12, and then introduced into the refining unit for secondary processing, or into the hydrogenation unit for hydrogenation treatment, or into the steam generator for treatment to obtain steam. The obtained steam can be used as supplementary steam for the steam in any of the above steps.

[0113] Example 2

[0114] This embodiment uses a certain crude oil as an example. The API value of this crude oil is 41. This embodiment can realize the comprehensive utilization of different light and heavy fractions of crude oil. This embodiment adopts... Figure 2 The system shown specifically includes the following steps, wherein the conditions for steam pyrolysis are the same as in Example 1:

[0115] Crude oil 101 undergoes preliminary preheating (first heat exchange, resulting in first preheated crude oil at a temperature of 70–120°C) after passing through quench water preheater 16. It then passes through desalting pre-processor 15 for desalting and impurity removal. The pretreated crude oil 102 enters the feedstock preheating section 1 in the convection section of the steam cracking unit for further heating (the resulting second preheated crude oil at a temperature of 200–400°C). The heated crude oil 104 then enters fractionation tower 2 as feedstock for light and heavy component separation (i.e., first separation). The following fractions are separated: light-range fractions (including naphtha and lighter fractions, with a final boiling point of 80–160°C) 105, medium-range fractions (kerosene fractions and fractions below light diesel oil, with an initial boiling point of 60–140°C and a final boiling point of 250–350°C) 106, and heavy-range fractions (with an initial boiling point of 230–330°C) 107. Depending on actual production needs, the separated fractions can undergo the following steps, or they can be further processed in a refining unit (not shown in the diagram):

[0116] The light-range component 105 separated after the above steps is mixed with unsuperheated primary dilution steam (third part steam) 108 and then enters the third mixing superheating section 5 of the convection section of the steam cracking unit. It is then mixed with secondary dilution steam (fourth part steam) 109 that has been heated by the fourth steam superheating section 6 (the weight ratio of the sum of the primary dilution steam 108 and the secondary dilution steam 109 to the weight of the crude oil component in the light-range component is 0.4 to 0.7). Subsequently, it enters the fifth mixing superheating section 7 of the convection section and is heated to a temperature spanning 550 to 750°C to obtain the first feed stream to be cracked 110. The first feed stream to be cracked 110 is introduced into the furnace tube of the radiation section 11 for high-temperature steam cracking reaction to obtain cracking product 121.

[0117] The medium-range component 106 separated after the above steps is mixed with unsuperheated primary dilution steam (fifth part steam) 111 and then enters the second mixing superheating section 4 of the convection section of the steam cracking unit. It is then mixed with secondary dilution steam (sixth part steam) 112 that has been heated to 400-575°C in the fourth steam superheating section 6 (the weight ratio of the sum of the primary dilution steam 111 and the secondary dilution steam 112 to the weight of the crude oil component in the medium-range component is 0.6-0.8). Subsequently, it enters the sixth mixing superheating section 8 of the convection section and is heated to a temperature spanning 450-700°C to obtain the second feed stream 113 to be cracked. The second feed stream 113 to be cracked is introduced into the furnace tube of the radiation section 11 for high-temperature steam cracking reaction to obtain cracking product 122.

[0118] After the above steps, the heavy distillation range component 107 is separated and mixed with unsuperheated primary dilution steam (first part steam) 114. The mixture is then heated to 200-410°C in the first mixing superheating section 3 of the convection section of the steam cracking unit. The heated heavy distillation range component mixture 115 and the secondary dilution steam (second part steam) 116 are then introduced into the separation unit 10 for a second separation (wherein, the weight ratio of the sum of the primary dilution steam 114 and the secondary dilution steam 116 to the weight of the crude oil component in the gas phase mixture is 0.7-0.9). This yields a gas phase mixture 117 and a liquid phase heavy component 118 (the gas phase mixture is a mixture containing the light components of the heavy distillation range component and steam, and the liquid phase heavy component contains the heavy components of the heavy distillation range component; the final boiling point of the gas phase mixture is 350-460°C; the initial boiling point of the liquid phase heavy component is not higher than the final boiling point of the gas phase mixture).

[0119] The gaseous mixture 117 is cooled to the liquid phase in a cooler, and then the liquid phase gaseous mixture obtained by cooling is sent to the oil refining unit (the oil refining unit is not shown).

[0120] The heavy components are introduced into a refining unit for secondary processing, or into a hydrogenation unit for hydrogenation, or into a steam generator for processing to obtain steam. The obtained steam can be used as supplementary steam for the steam in any of the above steps.

[0121] In this embodiment, depending on actual needs, a portion of the gaseous mixture 117 can also be introduced into the seventh mixing superheating section 9 of the convection section for heating to a temperature spanning 500-600°C to obtain the third pyrolysis stream 119; the third pyrolysis stream 119 is then introduced into the furnace tube of the radiation section 11 for high-temperature steam pyrolysis reaction (not shown in the figure).

[0122] Comparative Example 1

[0123] The method is similar to that of Example 1, except that the heavy distillation component 107 obtained from the first separation is not introduced into the separation device 10 for the second separation. Instead, the heavy distillation component 107 is mixed with unsuperheated primary dilution steam (first part steam) 114 and then introduced into the first mixing superheating section 3 of the convection section of the steam cracking device to be heated to 200-410°C. The heated heavy distillation component mixture 115 is then mixed with the secondary dilution steam (second part steam) 116 after being heated by the fourth steam superheating section 6 and directly introduced into the seventh mixing superheating section 9 of the convection section to be heated to 500-600°C. The resulting stream is introduced into the furnace tube of the radiation section 11 as the third pyrolysis stream 119 for high-temperature steam cracking reaction. No processing steps involving liquid phase heavy components are performed, and the resulting cracking product is denoted as 123.

[0124] The yields of the main products obtained from the steam cracking process in Example 1 and Comparative Example 1 are listed in Table 1 below.

[0125] Table 1

[0126]

[0127] As shown in the table above, compared with the crack product 123' obtained by cracking the heavy distillate component without second separation in Comparative Example 1, the crack product 123 obtained by introducing the heavy distillate component into the separation device for second separation and then cracking the gas-phase mixture obtained from the second separation has a higher yield of ethylene, propylene, butadiene and aromatics, especially the yield of low-carbon olefins ethylene, propylene and butadiene is higher, indicating that the method provided by this application can improve the yield of low-carbon olefins.

[0128] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0129] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0130] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for producing olefins from crude oil through steam cracking, characterized in that, Includes the following steps: S1. The crude oil feedstock is fed into the fractionation tower (2) for the first separation, separating light-range components, medium-range components, and heavy-range components; the final boiling point of the light-range components is 80~160℃, the initial boiling point of the medium-range components is 60~140℃, the final boiling point of the medium-range components is 250~350℃, and the initial boiling point of the heavy-range components is 230~330℃. S2. The light-range component is mixed with steam to obtain a first mixture; the medium-range component is mixed with steam to obtain a second mixture. S3. The heavy distillation component is mixed with steam and then fed into the separation device (10) for a second separation, separating the gaseous mixture and the liquid heavy component. S4. The first mixture and the second mixture are respectively fed into the convection section of the steam cracking device for superheating, and then fed into the radiation section (11) of the steam cracking device for steam cracking to obtain cracking products containing ethylene and propylene. The method further includes: superheating all of the gaseous mixture in the convection section of a steam cracking unit, and then steam cracking it in the radiation section (11) of the steam cracking unit to obtain cracking products containing ethylene and propylene; or A portion of the gaseous mixture is fed into the convection section of the steam cracking unit for superheating, and then into the radiation section (11) of the steam cracking unit for steam cracking, while another portion of the gaseous mixture is fed into the refining unit for further processing.

2. The method according to claim 1, characterized in that, The initial boiling point of the medium-range component is not higher than the final boiling point of the light-range component, and the initial boiling point of the heavy-range component is not higher than the final boiling point of the medium-range component. The final boiling point of the gas-phase mixture obtained by the second separation is 350~460℃; the initial boiling point of the liquid-phase heavy component is not higher than the final boiling point of the gas-phase mixture. Optionally, the crude oil is at least one of paraffinic crude oil, naphthenic crude oil, or intermediate-based crude oil.

3. The method according to claim 1, characterized in that, Before the gaseous mixture is fed into the refining unit for further processing, the gaseous mixture and the feed oil to be preheated are introduced into a cooler for heat exchange to obtain preheated feed oil and cooled liquid phase material of the gaseous mixture; then the cooled liquid phase material of the gaseous mixture is fed into the refining unit for further processing.

4. The method according to claim 1, characterized in that, When the BMCI value of the crude oil component in the gas phase mixture is 30 or higher, at least a portion of the gas phase mixture is sent to the refining unit.

5. The method according to claim 1, characterized in that, Along the height direction of the steam cracking device, the convection section is provided with, from top to bottom, an independent raw material preheating section (1), a first mixing superheating section (3), a second mixing superheating section (4), a third mixing superheating section (5), a fourth steam superheating section (6), a fifth mixing superheating section (7), a sixth mixing superheating section (8), and an optional seventh mixing superheating section (9); Step S3 includes: The heavy distillation range component is mixed with the first part of steam and then heated in the first mixing superheating section (3) of the steam cracking device to obtain a heated first mixture of heavy distillation range components; the heated first mixture of heavy distillation range components is mixed with the second part of steam to obtain a second mixture of heavy distillation range components; optionally, the temperature of the second mixture of heavy distillation range components is 200~410℃. The second mixture of the heavy distillation components is fed into the separation device (10) for the second separation.

6. The method according to claim 5, characterized in that, Along the height direction of the steam cracking device, the radiation section (11) is located below the convection section; step S4 includes: a. The light-range component is mixed with the third part of steam and then heated in the third mixing superheating section (5) of the steam cracking device, and then heated to 550~750°C in the fifth mixing superheating section (7) of the steam cracking device to obtain the first feed stream to be cracked; or, the light-range component is mixed with the third part of steam and then heated in the third mixing superheating section (5) of the steam cracking device, and then mixed with the fourth part of steam and then heated to 550~750°C in the fifth mixing superheating section (7) of the steam cracking device to obtain the first feed stream to be cracked; b. The middle-range component is mixed with the fifth part of steam and then enters the second mixing superheating section (4) of the steam cracking device for heating. Then it is mixed with the sixth part of steam and then enters the sixth mixing superheating section (8) of the steam cracking device for heating to 450~700℃ to obtain the second feed stream to be cracked. Optionally, c, the gaseous mixture is heated to 400~650°C in the seventh mixing superheating section (9) of the steam cracking device to obtain the third pyrolysis material stream; The first stream of material to be cracked is introduced into the first cracking furnace tube of the radiant section (11) of the steam cracking device for steam cracking to obtain the first cracking product; the second stream of material to be cracked is introduced into the second cracking furnace tube of the radiant section (11) of the steam cracking device for steam cracking to obtain the second cracking product; optionally, the third stream of material to be cracked is introduced into the third cracking furnace tube of the radiant section (11) of the steam cracking device for steam cracking to obtain the third cracking product. The method further includes: after the steam enters the fourth steam superheating section (6) of the steam cracking device for superheating treatment, it is divided into three parts, which are respectively used as the second part steam, the fourth part steam and the sixth part steam; In step a, the total weight of the third part of steam and the optional fourth part of steam is 0.3 to 1 times the weight of the crude oil component in the light distillation range component. In step b, the total weight of the fifth and sixth portions of steam is 0.35 to 1 of the weight of the crude oil component in the medium-range distillation component. In step S3, the total weight of the first part of steam and the second part of steam is 0.45 to 1 times the weight of the crude oil component in the gas phase mixture.

7. The method according to claim 6, characterized in that, The first part of steam, the second part of steam, the third part of steam, the fourth part of steam, the fifth part of steam, and the sixth part of steam are each independently either superheated steam or non-superheated steam.

8. The method according to claim 6, characterized in that, The temperature of the steam after being superheated in the fourth steam superheating section (6) is 400~575℃.

9. The method according to claim 6, characterized in that, In step a, the total weight of the third part of steam and the optional fourth part of steam is 0.4 to 0.7 of the weight of the crude oil component in the light distillation range component. In step b, the total weight of the fifth and sixth portions of steam is 0.6 to 0.8 of the weight of the crude oil component in the medium-range distillation component. In step S3, the total weight of the first part of steam and the second part of steam is 0.7 to 0.9 of the weight of the crude oil component in the gas phase mixture.

10. The method according to claim 1, characterized in that, The method also includes: The liquid phase heavy components are buffered in the buffer tank (12) and then sent out.

11. The method according to claim 5, characterized in that, The method also includes: The crude oil and waste heat material from the storage tank are respectively introduced into the quench water preheater (16) for the first heat exchange to obtain the first preheated crude oil and the cooled material; optionally, the temperature of the first preheated crude oil is 70~120℃; or the crude oil from the storage tank is introduced into the convection section of the steam cracking unit after the first heat exchange in the quench water preheater (16) for further heating, and the obtained preheated crude oil is used as the first preheated crude oil. The first preheated crude oil is fed into the desalting preprocessor (15) for desalting pretreatment to obtain desalted crude oil; The desalted crude oil is heated in the feed preheating section (1) of the steam cracking unit to obtain the second preheated crude oil; the second preheated crude oil is used as the feed crude oil and enters the fractionation tower (2) for the first separation; optionally, the temperature of the second preheated crude oil is 200~400℃; Optionally, the method further includes: subjecting the crude oil to external preheating treatment outside the convection section before it enters the fractionation tower (2); the heat source for the external preheating treatment is waste heat material from any unit in the ethylene plant or combined unit; the external preheating treatment is independent of the preheating treatment in the feedstock preheating section (1).

12. The method according to claim 10, characterized in that, The method further includes: dividing the liquid phase heavy components into three parts, allowing the first part of the liquid phase heavy components to enter the hydrogenation unit for hydrogenation treatment, allowing the second part of the liquid phase heavy components to enter the catalytic cracking unit for catalytic cracking treatment, and allowing the third part of the liquid phase heavy components to be refluxed into the buffer tank (12).

13. The method according to claim 6, characterized in that, The method further includes: allowing at least a portion of the liquid phase heavy components to enter a steam generator for processing to generate steam; and using a portion of the steam as supplementary steam for one or more of the first portion of steam, the second portion of steam, the third portion of steam, the fourth portion of steam, the fifth portion of steam, and the sixth portion of steam.

14. A system for producing olefins by crude oil steam cracking, characterized in that, The system includes a fractionation tower (2), a separation device (10), and a steam cracking device, wherein the steam cracking device includes a convection section and a radiation section (11), and the convection section is located above the radiation section (11) along the height direction of the steam cracking device; wherein, The fractionating tower (2) is provided with a crude oil inlet, a light distillation range component outlet, a medium distillation range component outlet, and a heavy distillation range component outlet; the separation device (10) is provided with a raw material inlet to be separated, a first steam inlet, a gas phase mixture outlet, and a liquid phase heavy component outlet; the heavy distillation range component outlet of the fractionating tower (2) is connected to the raw material inlet to be separated of the separation device (10); The radiation section (11) of the steam cracking device is provided with a first feedstock inlet, a second feedstock inlet and a third feedstock inlet; the first feedstock inlet is connected to the light distillation range component outlet of the fractionation tower (2), the second feedstock inlet is connected to the medium distillation range component outlet, and the third feedstock inlet is connected to the gas phase mixture outlet of the separation device (10).

15. The system according to claim 14, characterized in that, Along the height direction of the steam cracking device, the convection section includes, from top to bottom, a raw material preheating section (1), a first mixing superheating section (3), a second mixing superheating section (4), a third mixing superheating section (5), a fourth steam superheating section (6), a fifth mixing superheating section (7), a sixth mixing superheating section (8), and a seventh mixing superheating section (9), which are independent of each other. The raw material preheating section (1) is provided with a crude oil preheating inlet and a crude oil preheating outlet, and the crude oil preheating outlet is connected to the raw material crude oil inlet of the fractionation tower (2); The first mixing superheating section (3) is provided with a heating inlet and a heating outlet for heavy distillation components; the second mixing superheating section (4) is provided with an inlet for medium distillation components and a second mixture outlet; the third mixing superheating section (5) is provided with an inlet for light distillation components and a first mixture outlet; the fourth steam superheating section (6) is provided with a steam heating inlet and a steam heating outlet; the fifth mixing superheating section (7) is provided with a first mixture inlet and a first feedstock to be cracked outlet; the sixth mixing superheating section (8) is provided with a second mixture inlet and a second feedstock to be cracked outlet; the seventh mixing superheating section (9) is provided with a gas phase mixture inlet and a third feedstock to be cracked outlet; The light-range component inlet of the third mixing superheating section (5) is connected to the light-range component outlet of the fractionation tower (2) via a first pipeline, and the first mixture outlet is connected to the first mixture inlet of the fifth mixing superheating section (7) via a second pipeline; the first feedstock outlet to be cracked in the fifth mixing superheating section (7) is connected to the first cracking feedstock inlet of the radiation section (11); optionally, a third steam inlet is provided on the first pipeline, and a fourth steam inlet is provided on the second pipeline; The inlet of the middle-range component of the second mixing superheat section (4) is connected to the outlet of the middle-range component of the fractionation tower (2) through a third pipeline, and the outlet of the second mixture is connected to the inlet of the second mixture of the sixth mixing superheat section (8) through a fourth pipeline; the outlet of the second feedstock to be cracked of the sixth mixing superheat section (8) is connected to the inlet of the second feedstock to be cracked of the radiation section (11); optionally, a fifth steam inlet is provided on the third pipeline, and a sixth steam inlet is provided on the fourth pipeline; The heavy distillation range component heating inlet of the first mixing superheating section (3) is connected to the heavy distillation range component outlet of the fractionation tower (2) through a fifth pipeline, and the heavy distillation range component heating outlet is connected to the raw material inlet of the separation device (10); optionally, a first part of the steam inlet is provided on the fifth pipeline, and a second part of the steam inlet is provided on the sixth pipeline; Optionally, the gas phase mixture inlet of the seventh mixing and superheating section (9) is connected to the gas phase mixture outlet of the separation device (10), and the third raw material outlet to be cracked is connected to the third raw material inlet of the radiation section (11). Optionally, the radiation section (11) includes a first pyrolysis furnace tube, a second pyrolysis furnace tube, and a third pyrolysis furnace tube that are independently arranged with each other; the first pyrolysis furnace tube is provided with a raw material inlet to form a first raw material inlet to be pyrolyzed, the second pyrolysis furnace tube is provided with a raw material inlet to form a second raw material inlet to be pyrolyzed, and the third pyrolysis furnace tube is provided with a raw material inlet to form a third raw material inlet to be pyrolyzed. The steam heating inlet of the fourth steam superheating section (6) is connected to the steam source, and the steam heating outlet of the fourth steam superheating section (6) is connected to the second part steam inlet, the fourth part steam inlet and the sixth part steam inlet respectively.

16. The system according to claim 15, characterized in that, The system also includes a buffer tank (12), a pump (13), a desalination pre-processor (15), and a quench water preheater (16). The buffer tank (12) is provided with at least a liquid phase heavy component buffer inlet, a liquid phase heavy component buffer outlet, a liquid phase heavy component reflux inlet, a steam purging port, and a nitrogen purging port; the pump (13) includes an inlet and an outlet; the desalting preprocessor (15) is provided with a crude oil desalting inlet and a crude oil desalting outlet; the quench water preheater (16) is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a crude oil heat exchange first inlet, and a crude oil heat exchange first outlet; The crude oil heat exchange first outlet of the quench water preheater (16) is connected to the crude oil desalting inlet of the desalting preprocessor (15), and the crude oil desalting outlet is connected to the crude oil preheating inlet of the raw material preheating section (1). The liquid phase heavy component buffer inlet of the buffer tank (12) is connected to the liquid phase heavy component outlet of the separation device (10), and the liquid phase heavy component buffer outlet is connected to the inlet of the pump (13). The outlet of the pump (13) may optionally be connected to the feed inlet of the catalytic cracking device and / or the feed inlet of the hydrotreating device. Optionally, the system further includes a flow control unit, which includes a level transmitter, a pump reflux control valve (b), a level control valve (c), a pump outlet flow meter (d), a heavy component outflow flow meter (e), and a crude oil feed flow meter (f); the top of the buffer tank (12) is also provided with a heavy component reflux inlet; the flow control unit can determine the vaporization ratio of the separation device (10) through the heavy component outflow flow meter (e) and the crude oil feed flow meter (f); wherein, the level transmitter is connected to the internal space of the buffer tank (12) to control the liquid level in the buffer tank (12).

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