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, which first fractionates the crude oil in a fractionating tower, and then introduces the first liquid phase fraction obtained by fractionation into a flash tower for second separation, to obtain a plurality of gas phase fractions for steam cracking, thereby realizing effective subdivision of the fractions in the crude oil; the process and control scheme are simpler, and for specific light crude oil such as paraffin-based crude oil, different fractions can be efficiently cracked, the yield of olefins is high, and the existing steam cracking technology can be maximally applied, the technology is mature and the operation is simple; the combination of the fractionating tower and the flash tower can more easily control the steam-out of different fractions; the atmospheric and vacuum devices, heating furnaces and the like are cancelled, thereby saving investment; the present disclosure is suitable for a wide range of crude oils, and the separated fractions can be flexibly utilized.

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 continuous economic development, my country's demand for low-carbon olefin organic chemical raw materials has been increasing year by year. However, the existing production scale of low-carbon olefins cannot meet the growing production demand. Therefore, my country still relies heavily on imports of ethylene and its derivatives every year. In recent years, however, the traditional naphtha-based process for producing low-carbon olefins has faced challenges such as high raw material costs and lack of competitiveness due to the impact of cheap international raw materials and coal chemical processes. In addition, the development of new energy vehicles has reduced the demand for oil products. Therefore, in order to cope with the impact of market competition, expand the raw material sources of ethylene cracking units, shorten the processing flow of refining units, and focus on developing crude oil as a raw material for steam cracking, thereby reducing raw material costs, overcoming the constraints of raw material varieties, and reducing investment in refining units, these measures have become effective means for traditional ethylene enterprises to reduce costs and increase efficiency, thereby improving production flexibility.

[0003] Compared to traditional cracking feedstocks, using crude oil 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, for different crude oil sources, it is crucial to clearly define which feedstocks are suitable for cracking and which require secondary processing. Therefore, the design of the cracking furnace and the production process flow need to be tailored to the characteristics of crude oil.

[0004] CN111196936A discloses a combined processing method and apparatus for direct crude oil cracking to produce olefins. The method first employs pretreatment such as desalting and dehydration to remove impurities, then feeds the crude oil into an 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 radiant 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 hydrotreating unit for further processing before being returned to the convection and radiant sections. This method directly feeds superheated crude oil into the gas-liquid separator, making it difficult to achieve the desired gas-liquid separation effect.

[0005] CN107001955B discloses a method for thermally cracking crude oil and heavy feedstock in a pyrolysis reactor to produce olefins. The method describes a scheme combining a cracking furnace convection section with multi-stage (up to three stages) separators and fractionating towers. While this method improves cracking selectivity by using multi-stage separators and fractionating towers to separate the mixture into gas and liquid phases and by cracking different fractions using different radiant furnace tubes, it is cumbersome, requires significant investment, and is unsuitable for light crude oil.

[0006] CN100564484C discloses a method for steam cracking of heavy hydrocarbon feedstocks, wherein the heavy hydrocarbon feedstocks mainly include: crude oil, naphtha, gas oil, fuel oil, natural gasoline (condensate oil), residue oil, etc. The method describes a flash steaming separation process, but it is difficult to separate the gas and liquid components well by simply flashing, especially it is difficult to avoid the entrainment of heavy components into the gas phase, which can easily cause coking in the convection section and thus cause severe coking in the radiant section furnace tubes.

[0007] CN101528894A and CN101778929A describe a process technology for producing ethylene from crude oil / condensate through cracking. 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 or 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 protective naphtha and lighter components. The separated liquid phase enters a packed tower below for further separation, but it does not disclose how the separated heavy components are subsequently processed. Furthermore, the evaporation units in these two patents disclose stripping towers using packed or tray-like structures. The upper evaporation zone contains a gas-liquid separator, enabling 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 through steam cracking, which helps to prevent coking during crude oil gasification and achieve efficient gas-liquid separation.

[0009] To achieve the above objectives, the first aspect of this disclosure provides a method for producing olefins from crude oil through steam cracking. The method includes the following steps: S1, introducing crude oil into a fractionating tower for first separation to obtain a first gaseous fraction, a second gaseous fraction, a third gaseous fraction, and a first liquid fraction; S2, mixing the first liquid fraction with a first portion of steam to obtain a first liquid fraction mixture stream; mixing the first liquid fraction mixture stream with a second portion of steam and then introducing it into a flash tower for second separation to obtain a fourth gaseous fraction and a second liquid fraction; S3, mixing the first gaseous fraction with a third portion of steam to obtain a first mixture to be cracked; mixing the second gaseous fraction with a fourth portion of steam to obtain a second mixture to be cracked; S4, introducing the first mixture to be cracked and the second mixture to be cracked into the convection section of a steam cracking unit for heating, and then introducing them into the radiation section of the steam cracking unit for cracking.

[0010] Optionally, the first vapor fraction is a mixture of the first light component and its carried vapor in the crude oil; the second vapor fraction is a mixture of the second light component and its carried vapor in the crude oil; and the third vapor fraction is a mixture of the third light component and its carried vapor in the crude oil. The final boiling point temperature of the first light component in the crude oil is 80–180°C; the initial boiling point of the second light component is not higher than the final boiling point of the first light component, preferably 60–140°C; the final boiling point temperature of the second light component is 160–250°C; and the initial boiling point of the third light component is not higher than the final boiling point temperature of the second light component. The boiling point is preferably 140–230°C; the final boiling point of the third light component is 250–350°C; the fourth vapor fraction is a mixture containing the fourth light component and its carried vapor, and the final boiling point of the fourth light component is 350–410°C; the first liquid fraction contains the first heavy component of the crude oil, and the initial boiling point of the first liquid fraction is not higher than the final boiling point of the third light component, preferably 230–330°C; the second liquid fraction contains the second heavy component of the crude oil, and the initial boiling point of the second liquid fraction is not higher than the final boiling point of the fourth light component.

[0011] Optionally, all of the third vapor fraction is heated in the convection section of a steam cracking unit and then cracked in the radiant section; or all of the third vapor fraction is further processed in a refining unit; or a portion of the third vapor fraction is heated in the convection section of a steam cracking unit and then cracked in the radiant section, while another portion of the third vapor fraction is further processed in a refining unit. Preferably, when the BMCI value of the crude oil component in the third vapor fraction is 30 or higher, at least a portion of the third vapor fraction is processed in a refining unit as an aromatic feedstock or for further processing. Preferably, before processing at least a portion of the third vapor fraction, the portion of the third vapor fraction and the feedstock oil to be preheated are introduced into a cooler for heat exchange to obtain preheated feedstock oil and third vapor fraction cooled liquid material; then the third vapor fraction cooled liquid material is processed in a refining unit. Optionally, the method further includes: heating all of the fourth vapor fraction in the convection section of a steam cracking unit. The fourth vapor fraction is heated in one section and then enters the radiant section of the steam cracking unit for cracking; or all of the fourth vapor fraction is sent to the refining unit for further processing; or a portion of the fourth vapor fraction is heated in the convection section of the steam cracking unit and then enters the radiant section of the steam cracking unit for cracking, while another portion of the fourth vapor fraction is sent to the refining unit for further processing; when the BMCI value of the crude oil component in the fourth vapor fraction is above 30, the fourth vapor fraction is sent to the refining unit as an aromatic feedstock or for further processing; preferably, before sending at least a portion of the fourth vapor fraction to the refining unit for further processing, the portion of the fourth vapor fraction and the feedstock oil to be preheated are first introduced into a cooler for heat exchange to obtain preheated feedstock oil and fourth vapor fraction cooled liquid material; then the fourth vapor fraction cooled liquid material is sent to the refining unit for further processing; optionally, the method further includes: wherein at least a portion of the second light component or the third light component can be sent to the second flash tower as a separation aid, and contacted countercurrently with the vapor mixture obtained from the second flash tower.

[0012] Optionally, along the height direction of the steam cracking device, the convection section is sequentially provided with independent first mixing superheating section, second mixing superheating section, third mixing superheating section, fourth mixing superheating section, dilution steam superheating section, fifth mixing superheating section, sixth mixing superheating section, seventh mixing superheating section, and eighth mixing superheating section from top to bottom; the method further includes: heating the first liquid phase fraction mixture stream to 280-450°C in the first mixing superheating section, and then feeding the heated first liquid phase fraction mixture stream and the second portion of steam into the flash tower for the second separation; heating the third gas phase fraction in the second mixing superheating section first, and then mixing it with the fifth portion of steam to obtain the third mixture to be cracked; further heating the third mixture to be cracked to 450-630°C in the seventh mixing superheating section to obtain the third mixture to be cracked. The process involves: first, heating the second vapor fraction in the third mixing superheater section, then mixing it with the fourth portion of steam to obtain the second mixture to be cracked; further heating the second mixture to be cracked in the sixth mixing superheater section to 500–680°C to obtain the second feed stream to be cracked; first, heating the first vapor fraction in the fourth mixing superheater section to obtain the first mixture to be cracked; then mixing it with the third portion of steam and heating it in the fifth mixing superheater section to 550–720°C to obtain the first feed stream to be cracked; optionally, heating the fourth vapor fraction in the eighth mixing superheater section to 400–600°C to obtain the fourth feed stream to be cracked; and then feeding the first feed stream to be cracked, the second feed stream to be cracked, the optional third feed stream to be cracked, and the optional fourth feed stream to be cracked into the radiation section of the steam cracking device for steam cracking.

[0013] Optionally, the second, third, fourth, and fifth portions of steam are all dilution steam heated to 400–575°C via the dilution steam superheating section; optionally, in the first feed stream to be cracked, the weight ratio of steam to the crude oil components contained in the first feed stream to be cracked is 0.35–1, preferably 0.4–0.6; in the second feed stream to be cracked, the weight ratio of steam to the crude oil components contained in the second feed stream to be cracked is 0.4–1, preferably 0.5–0.7; the third… In the feed stream to be cracked, the weight ratio of steam to crude oil components in the third feed stream to be cracked is 0.45–1, preferably 0.6–0.8; in the fourth feed stream to be cracked, the weight ratio of steam to crude oil components in the fourth feed stream to be cracked is 0.55–1, preferably 0.7–0.9; optionally, the first feed stream to be cracked, the second feed stream to be cracked, the optional third feed stream to be cracked, and the optional fourth feed stream to be cracked can be respectively fed into different radiant furnaces of the same cracking furnace or into different cracking furnaces for cracking.

[0014] Optionally, the convection section further includes a raw material preheating section, which is located above the first mixing superheating section; the method further includes: buffering the second liquid phase fraction in a buffer tank and then pumping it out; allowing crude oil and waste heat material from the storage tank to enter a quench water preheater for first heat exchange, respectively, to obtain first preheated crude oil and cooled material; optionally, the temperature of the first preheated crude oil is 70-120℃ and the pressure is 0.1-0.2 MPaG; or allowing crude oil from the storage tank to undergo first heat exchange in a quench water preheater and then introducing it into the convection section of a steam cracking unit for further heating, 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... The method further includes: obtaining desalted crude oil; heating the desalted crude oil in the feedstock preheating section of the steam cracking unit to obtain second preheated crude oil; using the second preheated crude oil as the feedstock crude oil in the fractionation tower for the first separation; preferably, the temperature of the second preheated crude oil is 200-400°C; optionally, the method further includes: dividing the second liquid phase fraction from the buffer tank into three parts, sending the first part of the second liquid phase fraction into a hydrogenation unit for hydrogenation treatment, sending the second part of the second liquid phase fraction into a catalytic cracking unit for catalytic cracking treatment; and refluxing the third part of the second liquid phase fraction back into the buffer tank; optionally, the crude oil is at least one of paraffinic crude oil, intermediate-based crude oil, and naphthenic crude oil.

[0015] Optionally, the method further includes: using at least a portion of the second liquid fraction from the buffer tank as a heat source to enter a steam generator to generate steam, wherein the generated steam can be used as supplementary steam for the first portion of steam, the second portion of steam, the third portion of steam, and the fourth portion of steam; optionally, the method further includes: subjecting the desalted crude oil from the desalting preprocessor to external preheating treatment outside the convection section before entering the fractionation tower, wherein the heat source for the external preheating treatment is waste heat material from any device; the external preheating treatment is independent of the preheating treatment in the raw material preheating section.

[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 flash tower, and a steam cracking unit. The steam cracking unit includes a convection section and a radiation section, with the convection section positioned above the radiation section along the height of the steam cracking unit. The fractionating tower has a crude oil inlet, a first vapor phase fraction outlet, a second vapor phase fraction outlet, a third vapor phase fraction outlet, and a first liquid phase fraction outlet. The flash tower has a first liquid phase fraction inlet, a fourth vapor phase fraction outlet, and a second liquid phase fraction outlet. The first liquid phase fraction outlet of the fractionating tower is connected to the first liquid phase fraction inlet of the flash tower. Furthermore, a first portion of the steam inlet is provided on the connecting pipeline between the first liquid phase fraction outlet and the first liquid phase fraction inlet; the radiating section of the steam cracking device is provided with a first feedstock inlet to be cracked, a second feedstock inlet to be cracked, an optional third feedstock inlet to be cracked, and an optional fourth feedstock inlet to be cracked; the first feedstock inlet to be cracked is connected to the first vapor phase fraction outlet of the fractionating tower, the second feedstock inlet to be cracked is connected to the second vapor phase fraction outlet of the fractionating tower, the third feedstock inlet to be cracked is connected to the third vapor phase fraction outlet of the fractionating tower, and the fourth feedstock inlet to be cracked is connected to the fourth vapor phase fraction outlet of the flash tower.

[0017] Optionally, along the height direction of the steam cracking unit, the convection section is provided with, from top to bottom, an independent feed preheating section, a first mixing superheating section, a second mixing superheating section, a third mixing superheating section, a fourth mixing superheating section, a dilution steam superheating section, a fifth mixing superheating section, a sixth mixing superheating section, a seventh mixing superheating section, and an eighth mixing superheating section. The first mixing superheating section has a first superheating inlet and a first superheating outlet; the first superheating inlet is connected to the first liquid fraction outlet of the fractionation tower via a first pipeline; the first superheating outlet is connected to the flash steam... The first liquid phase fraction inlet of the column is connected; the second mixing superheated section is provided with a second superheated inlet and a second superheated outlet, and the second superheated inlet is connected to the third vapor phase fraction outlet of the fractionating column through a second pipeline; the third mixing superheated section is provided with a third superheated inlet and a third superheated outlet, and the third superheated inlet is connected to the second vapor phase fraction outlet of the fractionating column through a third pipeline; the fourth mixing superheated section is provided with a fourth superheated inlet and a fourth superheated outlet, and the fourth superheated inlet is connected to the first vapor phase fraction outlet of the fractionating column through a fourth pipeline; the fifth mixing... The superheating section is provided with a fifth superheating inlet and a fifth superheating outlet. The fifth superheating inlet is connected to the fourth superheating outlet of the fourth mixing superheating section via a fifth pipeline. The fifth superheating outlet is connected to the first feedstock inlet of the radiation section. The sixth mixing superheating section is provided with a sixth superheating inlet and a sixth superheating outlet. The sixth superheating inlet is connected to the third superheating outlet of the third mixing superheating section via a sixth pipeline. The sixth superheating outlet is connected to the third feedstock inlet of the radiation section. The seventh mixing superheating section is provided with a seventh superheating inlet and a seventh superheating outlet. The seventh superheated inlet is connected to the second superheated outlet of the second mixing superheated section via a seventh pipeline; the eighth mixing superheated section is provided with an eighth superheated inlet and an eighth superheated outlet, the eighth superheated inlet is connected to the fourth vapor fraction outlet of the flash tower, and the eighth superheated outlet is connected to the fourth feedstock inlet of the radiation section; the dilution steam superheated section is provided with a secondary dilution steam superheated inlet and a secondary dilution steam superheated outlet; optionally, the flash tower is a high-efficiency gas (vapor) liquid separation flash tower, and the gas (vapor) outlet of the flash tower is one or more.

[0018] Optionally, the first pipeline is provided with a primary dilution steam first inlet; the fifth pipeline is provided with a secondary dilution steam second inlet; the sixth pipeline is provided with a secondary dilution steam third inlet; and the seventh pipeline is provided with a secondary dilution steam fourth inlet. The primary, secondary, and secondary dilution steam first, second, third, and fourth inlets are respectively connected to the secondary dilution steam superheat outlet of the dilution steam superheating section. Optionally, each of the primary, secondary, and secondary dilution steam first, second, third, and fourth inlets is equipped with a material mixer for mixing the material and steam introduced into the mixer. Optionally, the system further includes a buffer tank, a pump, a desalination pre-processor, 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 liquid phase heavy component reflux inlet, a steam purging port, and a nitrogen purging port. The pump includes an inlet and an outlet. The desalination pre-processor is provided with a crude oil desalination inlet and a crude oil desalination outlet. The quench water preheater is provided with... The system includes 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; wherein 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 of the desalting preprocessor is connected to the crude oil preheating inlet of the feed preheating section; the liquid phase heavy component buffer inlet of the buffer tank is connected to the second liquid phase fraction outlet of the flash distillation tower, and the liquid phase heavy component buffer outlet is connected to the pump inlet; the pump outlet, optionally, is used to connect to a catalytic cracking unit. The system is connected to the feed inlet 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, and a heavy component outflow flow meter; the liquid phase heavy component reflux inlet is located at the top of the buffer tank, and the flow control unit controls the amount of liquid phase heavy component entering the buffer tank from the pump; wherein, the level transmitter is connected to the inside of the buffer tank to control the liquid level inside 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 involves first fractionating crude oil in a fractionation tower, then introducing the first liquid fraction obtained from the fractionation into a flash tower for second separation to obtain various gaseous fractions for steam cracking. This achieves effective fractionation of crude oil, has a wide range of applicability to crude oil, and the separated fractions can be used flexibly. For example, for specific light crude oils such as paraffin-based crude oil, different fractions can be efficiently cracked, resulting in high olefin yields and maximizing the application of existing steam cracking technology. The technology is mature and simple to operate. For crude oils with high aromatic content, fractions can be flexibly selected for steam cracking or used as refining feedstock.

[0021] 2. Compared with other crude oil cracking technologies, the combination of fractionation tower and flash tower in this disclosure makes it easier to control the distillation of different fractions and effectively control the dry point of the bottom distillate (first liquid phase fraction).

[0022] 3. Compared with the conventional method of processing crude oil in an atmospheric and vacuum distillation tower of a refining unit, in which part of the crude oil is fed into another refining unit and part of it is used as cracking feedstock to enter the cracking furnace for cracking, this disclosure simplifies the process, eliminates atmospheric and vacuum distillation units, heating furnaces, etc., and saves investment.

[0023] 4. This disclosure can improve the quality and efficiency of existing integrated refining and chemical plants, and can also be used for the production of ethylene in new integrated refining and chemical plants. For newly built integrated refining and chemical plants, fewer refining units such as atmospheric and vacuum distillation units and reforming units can be built. For light paraffin-based crude oil, no refining unit needs to be built. Attached Figure Description

[0024] 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:

[0025] Figure 1 This is a schematic diagram of the process flow for the crude oil steam cracking to produce olefins provided in this disclosure;

[0026] Figure 2 This is a schematic diagram of the process flow for the crude oil steam cracking to produce olefins provided in this disclosure.

[0027] Explanation of reference numerals in the attached figures

[0028] 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 mixing superheating section, 7-Dilution steam superheating section, 8-Fifth mixing superheating section, 9-Sixth mixing superheating section, 10-Seventh mixing superheating section, 11-And eighth mixing superheating sections, 12-Buffer tank, 13-Pump, 15-Desalination pre-processor, 16-Quick cool water preheater, 17-Flash tower, 18-Radiation section, b-Pump reflux control valve, c-Level control valve, d-Pump outlet flow meter, e-Heavy component outflow flow meter, f-Crude oil feed flow meter

[0029] 101-Crude oil, 102-Waste heat material, 104-Desalted crude oil, 105-Second preheated crude oil, 106-First vapor phase fraction, 107-Second vapor phase fraction, 108-Third vapor phase fraction, 109-First liquid phase fraction, 111-First part primary dilution steam, 112-Heated first liquid phase fraction mixture stream, 113-First part heated secondary dilution steam, 114-Fourth vapor phase fraction, 115-Second liquid phase fraction, 116- The refluxed second liquid phase fraction, 117-secondary dilution vapor after second heating, 118-third mixture to be cracked, 119-third feed stream to be cracked, 121-secondary dilution vapor after third heating, 122-second mixture to be cracked, 124-secondary dilution vapor after fourth heating, 126-first mixture to be cracked, 127-first feed stream to be cracked, 128-second feed stream to be cracked after heating, 131-fourth feed stream to be cracked after heating. 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] See Figure 1 The first aspect of this disclosure provides a method for producing olefins from crude oil through steam cracking, the method comprising the following steps:

[0034] S1. The crude oil is fed into fractionation tower 2 for the first separation to obtain the first gas phase fraction, the second gas phase fraction, the third gas phase fraction and the first liquid phase fraction;

[0035] S2. Mix the first liquid fraction with the first part of steam to obtain a first liquid fraction mixture stream; mix the first liquid fraction mixture stream with the second part of steam and then enter the flash distillation tower 17 for a second separation to obtain a fourth gaseous fraction and a second liquid fraction.

[0036] S3. Mix the first vapor fraction with the third part of steam to obtain the first mixture to be cracked; mix the second vapor fraction with the fourth part of steam to obtain the second mixture to be cracked.

[0037] S4. The first mixture to be cracked and the second mixture to be cracked are respectively introduced into the convection section of the steam cracking device for heating, and then respectively introduced into the radiation section 18 of the steam cracking device for cracking.

[0038] This disclosure provides a method and system for producing olefins from crude oil through steam cracking. Crude oil undergoes a first fractionation in a fractionation tower, and the first liquid fraction is then introduced into a flash tower for a second separation, yielding multiple gaseous fractions for steam cracking. This method achieves effective fractionation of crude oil, has a wide range of applicability to different types of crude oil, and allows for flexible utilization of the separated fractions. For example, it can efficiently crack different fractions of specific light crude oils, such as paraffin-based crude oils, achieving high olefin yields and maximizing the application of existing steam cracking technologies. The technology is mature and simple to operate. For crude oils with high aromatic content, fractions can be flexibly selected for steam cracking or used as refining feedstocks. Compared with other crude oil cracking technologies… In comparison, the combination scheme of the fractionation tower and flash tower in this disclosure makes it easier to control the distillation of different fractions and effectively control the dry point of the bottom distillate (first liquid fraction). Moreover, compared with the conventional method in which crude oil is processed by the atmospheric and vacuum distillation tower of the refining unit and then partly enters another refining unit and partly enters the cracking furnace as cracking feedstock, this disclosure simplifies the process, eliminates the atmospheric and vacuum distillation unit, heating furnace, etc., and saves investment. It can achieve quality and efficiency improvement with existing integrated refining and chemical units, and can also be used for the production of ethylene in new integrated refining and chemical units. For newly built integrated refining and chemical units, fewer refining units such as atmospheric and vacuum distillation units and reforming units can be built, and for light paraffin-based crude oil, no refining unit can be built.

[0039] In one embodiment, the crude oil used in this disclosure is at least one of paraffinic crude oil, intermediate-based crude oil, or naphthenic crude oil.

[0040] In a preferred embodiment, the first vapor phase fraction is a mixture of a first light component in crude oil and the vapor it carries, the second vapor phase fraction is a mixture of a second light component in crude oil and the vapor it carries, and the third vapor phase fraction is a mixture of a third light component in crude oil and the vapor it carries.

[0041] The final boiling point temperature of the first light component in the crude oil is 80–180°C;

[0042] The initial boiling point of the second light component is not higher than the final boiling point of the first light component, preferably 60-140°C; the final boiling point temperature of the second light component is 160-250°C.

[0043] The initial boiling point of the third light component is not higher than the final boiling point of the second light component, preferably 140-230°C; the final boiling point temperature of the third light component is 250-350°C.

[0044] The fourth vapor fraction is a mixture containing the fourth light component of crude oil and the carried vapor, wherein the final boiling point temperature of the fourth light component is 350–410°C.

[0045] The first liquid fraction contains the first heavy component of crude oil, and the initial boiling point of the first liquid fraction is not higher than the final boiling point of the third light component, preferably 230-330°C.

[0046] The second liquid fraction contains the second heavy component of crude oil, and the initial boiling point of the second liquid fraction is not higher than the final boiling point of the fourth light component.

[0047] In this disclosure, the fractionation tower 2 is a conventionally selected device in the art; the gas (vapor) phase outlet of the flash tower 17 can be one or more.

[0048] In a preferred embodiment, the method further includes: heating all of the third vapor fraction in the convection section of a steam cracking unit, and then allowing it to undergo cracking in the radiation section 18 of the steam cracking unit; or

[0049] The entire third vapor fraction is fed into the refining unit for further processing; or

[0050] A portion of the third gas phase fraction is heated in the convection section of a steam cracking unit and then cracked in the radiation section 18 of the steam cracking unit, while another portion of the third gas phase fraction is fed into a refining unit for further processing. Preferably, when the BMCI value of the crude oil component in the third gas phase fraction is 30 or higher, at least a portion of the third gas phase fraction is fed into a refining unit as an aromatic feedstock or for further processing.

[0051] In a preferred embodiment, such as Figure 1 and Figure 2As shown, the method further includes: heating all of the fourth gaseous fraction in the convection section of the steam cracking unit, and then allowing it to enter the radiation section 18 of the steam cracking unit for cracking; or

[0052] The entire fourth vapor fraction is fed into the refining unit for further processing; or

[0053] A portion of the fourth vapor fraction is heated in the convection section of the steam cracking unit and then cracked in the radiation section 18 of the steam cracking unit, while another portion of the fourth vapor fraction is further processed in the oil refining unit.

[0054] When the BMCI value of the crude oil component in the fourth gas phase fraction is above 30, the fourth gas phase fraction is fed into the refining unit as an aromatic feedstock or for further processing.

[0055] The "BMCI value" (USBureau of Mines Correlation Index) refers to the aromatics index, which represents the aromaticity index of a type of oil.

[0056] In this disclosure, the obtained third or fourth gas phase fraction can be processed differently depending on 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 fourth gas phase fraction as a feedstock for cracking into the steam cracking unit or to directly introduce the fourth gas phase fraction into the refining unit. Alternatively, a portion of the fourth gas phase fraction can be introduced into the steam cracking unit as a feedstock for cracking, and the remaining portion can be introduced into the refining unit for secondary processing, thereby improving the overall process utilization efficiency.

[0057] In one specific embodiment, this disclosure further includes the following step: when the crude oil is paraffinic crude oil, at least a portion of the fourth vapor-phase fraction obtained from flash tower 17 is introduced into a refining unit for processing. In this embodiment, introducing the vapor-phase mixture fractionated from paraffinic crude oil into a refining unit allows fractions unsuitable as steam cracking feedstock to be used for the production of aromatic oils, thus enabling flexible utilization of fractions separated from different types of crude oil. In another specific embodiment, when the crude oil is naphthenic crude oil, all of the fourth vapor-phase fraction obtained from flash tower 17 is introduced into the radiant section of the steam cracking unit, but not into the refining unit, to further improve the olefin yield.

[0058] In a preferred embodiment, the method further includes: before allowing at least a portion of the third vapor fraction to enter the refining unit for further processing, introducing the portion of the third vapor fraction and the feedstock oil to be preheated into a cooler for heat exchange to obtain preheated feedstock oil and third vapor fraction cooled liquid material; and then allowing the third vapor fraction cooled liquid material to enter the refining unit for further processing.

[0059] In another preferred embodiment, the method further includes: before allowing at least a portion of the fourth vapor fraction to enter the refining unit for further processing, introducing the portion of the fourth vapor fraction and the feedstock oil to be preheated into a cooler for heat exchange to obtain preheated feedstock oil and fourth vapor fraction cooled liquid material; and then allowing the fourth vapor fraction cooled liquid material to enter the refining unit for further processing.

[0060] In this disclosure, the feedstock oil to be preheated can be any feedstock oil obtained in any step before entering the fractionation tower 2, and the cooler can be used in series with other devices in the system of this disclosure that process the feedstock oil before entering the separation tower.

[0061] In a preferred embodiment, the method further includes: wherein at least a portion of the second light component or the third light component may be introduced into the second flash tower as a separation aid, and countercurrently contacted with the gas phase mixture obtained from the second flash tower.

[0062] 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 mixing superheating section 6, a dilution steam superheating section 7, a fifth mixing superheating section 8, a sixth mixing superheating section 9, a seventh mixing superheating section 10, and an eighth mixing superheating section 11; the method further includes:

[0063] The first liquid phase distillate mixture is fed into the first mixing superheating section 3 and heated to 280-450°C. Then, the heated first liquid phase distillate mixture and the second part of the steam are fed into the flash tower 17 for the second separation.

[0064] The third vapor fraction is first heated in the second mixing superheating section 4, and then mixed with the fifth part of steam to obtain the third mixture to be cracked; the third mixture to be cracked is further heated to 450-630°C in the seventh mixing superheating section 10 to obtain the third feed stream to be cracked.

[0065] The second vapor fraction is first heated in the third mixing superheating section 5, and then mixed with the fourth part of steam to obtain the second mixture to be cracked; the second mixture to be cracked is further heated to 500-680°C in the sixth mixing superheating section 9 to obtain the second feed stream to be cracked;

[0066] The first vapor fraction is first heated in the fourth mixing superheating section 6 to obtain the first mixture to be cracked; then it is mixed with the third part of steam and then heated to 550-720°C in the fifth mixing superheating section 8 to obtain the first feed stream to be cracked.

[0067] Optionally, the fourth gaseous fraction is introduced into the eighth mixing and superheating section 11 and heated to 400-600°C to obtain the fourth feed stream to be cracked;

[0068] The first, second, optional third, and optional fourth feed streams to be cracked are respectively introduced into the radiation section 18 of the steam cracking device for steam cracking.

[0069] In a preferred embodiment, the second part of steam, the third part of steam, the fourth part of steam, and the fifth part of steam are all dilution steam heated to 400-575°C via the dilution steam superheating section 7.

[0070] This disclosure includes multiple independent superheating sections in the convection section, which can be used to heat various components, greatly improving heat utilization efficiency and cracking yield. Furthermore, different fractions are subdivided and heated to different temperatures across a wide temperature range, ensuring that each feedstock is cracked under optimal conditions, resulting in a high olefin yield.

[0071] Specifically, the conditions under which the first, second, third, and fourth feed streams to be cracked after heating undergo steam cracking in the radiation section in this disclosure can be conventional conditions in the art. The catalyst can be any type of catalyst known in the art.

[0072] In a preferred embodiment, the weight ratio of steam to crude oil components contained in the first feed stream to be cracked is 0.35 to 1, preferably 0.4 to 0.6.

[0073] In the second feed stream to be cracked, the weight ratio of steam to crude oil components in the second feed stream to be cracked is 0.4 to 1, preferably 0.5 to 0.7; in the third feed stream to be cracked, the weight ratio of steam to crude oil components in the third feed stream to be cracked is 0.45 to 1, preferably 0.6 to 0.8.

[0074] In the fourth feed stream to be cracked, the weight of steam and crude oil components contained in the fourth feed stream to be cracked is 0.55 to 1, preferably 0.7 to 0.9; optionally, when the fourth gas phase fraction is not subjected to steam cracking, the weight of steam and crude oil components contained in the fourth gas phase fraction is 0.55 to 1, preferably 0.7 to 0.85.

[0075] Optionally, the first, second, optional third, and optional fourth pyrolysis streams can be fed into different radiant furnaces of the same pyrolysis furnace or different pyrolysis furnaces for pyrolysis.

[0076] In one implementation, such as Figure 1 As shown, the convection section is further provided with a raw material preheating section 1, which is located above the first mixing superheating section 3;

[0077] The method also includes:

[0078] The second liquid phase fraction is buffered by buffer tank 12 and then sent out by pump 13;

[0079] 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℃ and the pressure is 0.1-0.2MPaG; 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;

[0080] The first preheated crude oil is fed into the desalting preprocessor 15 for desalting pretreatment to obtain desalted crude oil;

[0081] The desalted crude oil is heated in the feed preheating section 1 of the steam cracking unit to obtain second preheated crude oil. This second preheated crude oil is then used as the feed crude oil and enters the fractionation tower 2 for the first separation. Preferably, the temperature of the second preheated crude oil is 200–400°C. In this embodiment, crude oil from the storage tank undergoes a first heat exchange with waste heat material (such as quench water), and the desalted crude oil undergoes a second heat exchange with the second liquid phase fraction. This achieves heat exchange between multiple materials, increasing the temperature of the crude oil to be processed and cooling the second liquid phase fraction in the output system. Introducing the second preheated crude oil into the feed preheating section further improves the overall heat utilization rate of the process.

[0082] In one specific embodiment, the crude oil preheating process can also utilize waste heat from the ethylene unit instead of quench water for heat exchange, followed by heat exchange with the high-temperature heavy oil obtained from the crude oil cracking process for preheating. Alternatively, the crude oil can first exchange heat with waste heat from the ethylene unit, then undergo desalting treatment, and finally exchange heat with the high-temperature heavy oil (second liquid phase fraction) obtained from the crude oil cracking process. The process flow provided by this disclosure has high energy utilization efficiency, fully combining the thermal energy of the ethylene unit with the heating requirements of the process flow itself, further reducing the energy consumption of the ethylene unit, realizing heat energy recovery and utilization, and also saving investment.

[0083] In one embodiment, the method further includes: dividing the second liquid phase fraction from the buffer tank 12 into three parts; allowing the first part of the second liquid phase fraction to enter a hydrogenation unit for hydrogenation treatment; allowing the second part of the second liquid phase fraction to enter a catalytic cracking unit for catalytic cracking treatment; and allowing the third part of the second liquid phase fraction to be refluxed back into the buffer tank 12.

[0084] In one embodiment, the method further includes: using at least a portion of the second liquid fraction from the buffer tank 12 as a heat source to enter a steam generator to generate steam, wherein the generated steam can be used as supplementary steam for the first portion of steam, the second portion of steam, the third portion of steam, and the fourth portion of steam.

[0085] In one embodiment, the method further includes: subjecting the desalted crude oil from the desalting pre-processor 15 to external preheating treatment outside the convection section before entering the fractionation tower 2, wherein the heat source for the external preheating treatment is waste heat material from any 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.

[0086] The operating temperatures used in this disclosure are all within the normal operating range under conventional operating conditions of the pyrolysis furnace after pressure equilibrium.

[0087] 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 flash tower 17, and a steam cracking unit. The steam cracking unit includes a convection section and a radiation section 18. Along the height direction of the steam cracking unit, the convection section is located above the radiation section 18.

[0088] Fractionating tower 2 is provided with a crude oil inlet, a first vapor phase fraction outlet, a second vapor phase fraction outlet, a third vapor phase fraction outlet, and a first liquid phase fraction outlet; flash tower 17 is provided with a first liquid phase fraction inlet, a first inlet for secondary dilution steam, a fourth vapor phase fraction outlet, and a second liquid phase fraction outlet; wherein the first liquid phase fraction outlet of fractionating tower 2 is connected to the first liquid phase fraction inlet of flash tower 17; and a first part of the steam inlet is provided on the connecting pipeline between the first liquid phase fraction outlet and the first liquid phase fraction inlet.

[0089] The radiation section 18 of the steam cracking unit is provided with a first feedstock inlet, a second feedstock inlet, a third feedstock inlet, and an optional fourth feedstock inlet; the first feedstock inlet is connected to the first vapor fraction outlet of the fractionating tower 2, the second feedstock inlet is connected to the second vapor fraction outlet of the fractionating tower 2, the third feedstock inlet is connected to the third vapor fraction outlet of the fractionating tower 2, and the fourth feedstock inlet is connected to the fourth vapor fraction outlet of the flash tower 17.

[0090] In this disclosure, the fractionation tower 2 can be a device conventionally selected by those skilled in the art. Specifically, the radiant section of the steam cracking unit includes a first cracking furnace tube, a second cracking furnace tube, a third cracking furnace tube, and a fourth furnace tube, which are independently arranged. The first cracking furnace tube has a raw material inlet to form a first raw material inlet to be cracked, the second cracking furnace tube has a raw material inlet to form a second raw material inlet to be cracked, the third cracking furnace tube has a raw material inlet to form a third raw material inlet to be cracked, and the fourth cracking furnace tube has a raw material inlet to form a fourth raw material inlet to be cracked. Optionally, the first cracking furnace tube, the second cracking furnace tube, the third cracking furnace tube, and the fourth furnace tube can be different radiant section furnace tubes in the same furnace chamber of the same cracking furnace; or radiant furnace tubes in different radiant sections of the same cracking furnace; or radiant furnace tubes from different cracking furnaces, which can be set according to the actual situation.

[0091] 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 with the following independent sections: raw material preheating section 1, first mixing superheating section 3, second mixing superheating section 4, third mixing superheating section 5, fourth mixing superheating section 6, dilution steam superheating section 7, fifth mixing superheating section 8, sixth mixing superheating section 9, seventh mixing superheating section 10, and eighth mixing superheating section 11.

[0092] The first mixing superheating section 3 is provided with a first superheating inlet and a first superheating outlet; the first superheating inlet is connected to the first liquid phase distillate outlet of the fractionation tower 2 through a first pipeline; the first superheating outlet is connected to the first liquid phase distillate inlet of the flash tower 17.

[0093] The second mixing superheating section 4 is provided with a second superheating inlet and a second superheating outlet. The second superheating inlet is connected to the third gas phase distillate outlet of the fractionation tower 2 through a second pipeline.

[0094] The third mixing superheating section 5 is provided with a third superheating inlet and a third superheating outlet. The third superheating inlet is connected to the second gas phase distillate outlet of the fractionation tower 2 through a third pipeline.

[0095] The fourth mixing superheating section 6 is provided with a fourth superheating inlet and a fourth superheating outlet. The fourth superheating inlet is connected to the first gas phase distillate outlet of the fractionation tower 2 through a fourth pipeline.

[0096] The fifth mixing superheating section 8 is provided with a fifth superheating inlet and a fifth superheating outlet. The fifth superheating inlet is connected to the fourth superheating outlet of the fourth mixing superheating section 6 through a fifth pipeline; the fifth superheating outlet is connected to the first feedstock inlet to be cracked in the radiation section 18.

[0097] The sixth mixing superheating section 9 is provided with a sixth superheating inlet and a sixth superheating outlet. The sixth superheating inlet is connected to the third superheating outlet of the third mixing superheating section 5 through a sixth pipeline; the sixth superheating outlet is connected to the third feedstock inlet to be cracked in the radiation section 18.

[0098] The seventh mixing superheating section 10 is provided with a seventh superheating inlet and a seventh superheating outlet. The seventh superheating inlet is connected to the second superheating outlet of the second mixing superheating section 4 through a seventh pipeline.

[0099] The eighth mixing superheating section 11 is provided with an eighth superheating inlet and an eighth superheating outlet. The eighth superheating inlet is connected to the fourth vapor fraction outlet of the flash tower 17, and the eighth superheating outlet is connected to the fourth feedstock inlet to be cracked in the radiation section 18.

[0100] The dilution steam superheating section 7 is equipped with a secondary dilution steam superheating inlet and a secondary dilution steam superheating outlet.

[0101] In one specific embodiment, the raw material preheating section 1, the first mixing superheating section 3, the second mixing superheating section 4, the third mixing superheating section 5, the fourth mixing superheating section 6, the dilution steam superheating section 7, the fifth mixing superheating section 8, the sixth mixing superheating section 9, the seventh mixing superheating section 10, and the eighth mixing superheating section 11 can be different heat exchange tubes of the mixing superheating section of the convection section of the same steam cracking device, or heat exchange tubes of the mixing superheating section of different steam cracking devices.

[0102] In a preferred embodiment, the first pipeline is provided with a first inlet for primary dilution steam; the fifth pipeline is provided with a second inlet for secondary dilution steam; the sixth pipeline is provided with a third inlet for secondary dilution steam; and the seventh pipeline is provided with a fourth inlet for secondary dilution steam. The first, second, third, and fourth inlets for secondary dilution steam are respectively connected to the superheated outlet of the dilution steam superheating section (7).

[0103] Optionally, a material mixer is provided at each of the primary dilution steam inlet, the secondary dilution steam inlet, the secondary dilution steam inlet, and the secondary dilution steam inlet to mix the material and steam introduced into the mixer. The mixer used in this disclosure can make the material and steam mix more evenly and prevent coking. Any type of mixer known in the art that satisfies the above mixing effect can be used.

[0104] In one implementation, such as Figure 1 As shown, the system also includes a buffer tank 12, a pump 13, a desalination pre-processor 15, and a quench water preheater 16;

[0105] 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;

[0106] 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 of the desalting preprocessor 15 is connected to the crude oil preheating inlet of the raw material preheating section 1.

[0107] The liquid phase heavy component buffer inlet of the buffer tank 12 is connected to the second liquid phase distillate outlet of the flash tower 17, and the liquid phase heavy component buffer outlet is connected to the inlet of the pump 13; optionally, the outlet of the pump 13 is used to connect to the feed inlet of the catalytic cracking unit and / or the feed inlet of the hydrotreating unit.

[0108] 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, and a heavy component outflow flow meter; the liquid phase heavy component reflux inlet is located at the top of the buffer tank 12, and the flow control unit controls the amount of liquid phase heavy component entering the liquid phase heavy component reflux inlet of the buffer tank 12 from the pump 13;

[0109] The level transmitter is connected to the interior of the buffer tank 12 to control the level of liquid inside the buffer tank 12.

[0110] The present disclosure will be further described below with reference to specific embodiments.

[0111] Example 1

[0112] See Figure 1 The process flow shown uses Shunbei crude oil with an API value of 37-46, and specifically includes the following steps:

[0113] S1. The crude oil 101 from the storage tank and the waste heat material 102 are preheated by the quench water preheater 16 to obtain the first preheated crude oil (first heat exchange, the temperature of the first preheated crude oil is 70-120℃, and the pressure is 0.1-0.2MPaG). Then, it is desalted and impurities are removed by the desalting pretreatment unit 15 to obtain desalted crude oil 104. The desalted crude oil 104 enters the raw material preheating section 1 of the convection section to be heated to 200-400℃ to obtain the second preheated crude oil 105.

[0114] S2. The second preheated crude oil 105 obtained in the above steps is fed into fractionation tower 2 for the first separation of light and heavy components, separating the following four fractions: first vapor fraction 106 (a mixture of naphtha and lighter components and carried vapor, with a final boiling point of 80-180°C), second vapor fraction 107 (a mixture of jet fuel fraction and carried vapor, with an initial boiling point of 60-140°C and a final boiling point of 160-250°C), third vapor fraction 108 (a mixture of light diesel to heavy diesel fraction and carried vapor, with an initial boiling point of 140-230°C and a final boiling point of 250-350°C), and first liquid fraction 109 (with a final boiling point of 230-330°C). The separated fractions can proceed to the following steps as needed, or they can be sent to a refining unit for secondary processing.

[0115] S3. The secondary dilution steam is heated to 250-560°C via the dilution steam superheating section 7.

[0116] The first liquid fraction 109 is mixed with the first part of the primary dilution steam 111 to obtain a first liquid fraction mixture stream; the first liquid fraction mixture stream is then heated to 280-450°C in the first mixing superheating section 3; then the heated first liquid fraction mixture stream 112 and the first part of the secondary dilution steam 113 are respectively fed into the flash distillation tower 17 for the second separation to obtain the fourth gaseous fraction 114 (the light component in the first liquid fraction, with a final boiling point temperature of 350-410°C) and the second liquid fraction 115;

[0117] The third vapor fraction 108 is first heated to 220-280°C in the second mixing superheating section 4, and then mixed with the secondary dilution steam 117 after the second part of heating, to obtain the third mixture to be cracked 118; the second vapor fraction 107 is first heated to 250-300°C in the third mixing superheating section 5, and then mixed with the secondary dilution steam 121 after the third part of heating, to obtain the second mixture to be cracked 122; the first vapor fraction 106 is first heated to 270-330°C in the fourth mixing superheating section 6, and then mixed with the secondary dilution steam 124 after the fourth part of heating, to obtain the first mixture to be cracked 126.

[0118] S4. The first mixture to be cracked 126 is introduced into the fifth mixing superheating section 8 and heated to 550-720°C to obtain the first pyrolysis stream 127 after heating; the second mixture to be cracked 122 is introduced into the sixth mixing superheating section 9 and heated to 500-680°C to obtain the second pyrolysis stream 128 after heating; the third mixture to be cracked 118 is introduced into the seventh mixing superheating section 10 and heated to 450-630°C to obtain the third pyrolysis stream 119 after heating; the fourth vapor fraction 114 is introduced into the eighth mixing superheating section 11 and heated to 400-600°C to obtain the fourth pyrolysis stream 131.

[0119] In the first feed stream to be cracked, the weight ratio of steam to crude oil components in the first feed stream to be cracked is 0.4 to 0.6; in the second feed stream to be cracked, the weight ratio of steam to crude oil components in the second feed stream to be cracked is 0.5 to 0.7; in the third feed stream to be cracked, the weight ratio of steam to crude oil components in the third feed stream to be cracked is 0.6 to 0.8; and in the fourth feed stream to be cracked, the weight ratio of steam to crude oil components in the fourth feed stream to be cracked is 0.7 to 0.9.

[0120] S5, the first pyrolysis stream 127, the second pyrolysis stream 128, the third pyrolysis stream 119, and the fourth pyrolysis stream 131 after heating are respectively entered into different furnace tubes of the radiation section 18 of the steam pyrolysis device for pyrolysis.

[0121] S6. The second liquid fraction 115 obtained after separation by flash distillation tower 17 enters buffer tank 12, and the liquid level in the buffer tank is controlled by flow control unit. The flow control unit can also control the amount of the second liquid fraction 116 returning to buffer tank 12 via the outlet of pump 13.

[0122] Example 2

[0123] See Figure 2 The process flow shown uses Shunbei crude oil with an API value of 37-46, and specifically includes the following steps:

[0124] S1. The crude oil 101 from the storage tank and the waste heat material 102 are preheated by the quench water preheater 16 to obtain the first preheated crude oil (first heat exchange, the temperature of the first preheated crude oil is 70-120℃, and the pressure is 0.1-0.2MPaG). Then, it is desalted and impurities are removed by the desalting pretreatment unit 15 to obtain desalted crude oil 104. The pretreated crude oil 104 enters the raw material preheating section 1 of the convection section to be heated to 200-400℃ to obtain the second preheated crude oil 105.

[0125] S2. The second preheated crude oil 105 obtained in the above steps is fed into fractionation tower 2 for the first separation of light and heavy components, separating the following four fractions: first vapor fraction 106 (a mixture of naphtha and lighter components and carried vapor, with a final boiling point of 80-180°C), second vapor fraction 107 (a mixture of jet fuel fraction and carried vapor, with an initial boiling point of 60-140°C and a final boiling point of 160-250°C), third vapor fraction 108 (a mixture of light diesel to heavy diesel fraction and carried vapor, with an initial boiling point of 140-230°C and a final boiling point of 250-350°C), and first liquid fraction 109 (with a final boiling point of 230-330°C). The separated fractions can proceed to the following steps as needed, or they can be sent to a refining unit for secondary processing.

[0126] S3. The secondary dilution steam is heated to 250-560°C via the dilution steam superheating section 7.

[0127] The first liquid fraction 109 is mixed with the first part of the primary dilution steam 111 to obtain a first liquid fraction mixture stream; the first liquid fraction mixture stream is then heated to 280-450°C in the first mixing superheating section 3; then the heated first liquid fraction mixture stream 112 and the first part of the secondary dilution steam 113 are respectively fed into the flash distillation tower 17 for the second separation to obtain the fourth gaseous fraction 114 (the light component in the first liquid fraction, with a final boiling point temperature of 350-410°C) and the second liquid fraction 115;

[0128] The third vapor fraction 108 is first heated to 220-280°C in the second mixing superheating section 4, and then mixed with the secondary dilution steam 117 after the second part of heating, to obtain the third mixture to be cracked 118; the second vapor fraction 107 is first heated to 250-300°C in the third mixing superheating section 5, and then mixed with the secondary dilution steam 121 after the third part of heating, to obtain the second mixture to be cracked 122; the first vapor fraction 106 is first heated to 270-330°C in the fourth mixing superheating section 6, and then mixed with the secondary dilution steam 124 after the fourth part of heating, to obtain the first mixture to be cracked 126.

[0129] S4. The first mixture to be cracked 126 is introduced into the fifth mixing superheating section 8 and heated to 550-720°C to obtain the first cracked material stream 127 after heating; the second mixture to be cracked 122 is introduced into the sixth mixing superheating section 9 and heated to 500-680°C to obtain the second cracked material stream 128 after heating; the third mixture to be cracked 118 is introduced into the seventh mixing superheating section 10 and heated to 450-630°C to obtain the third cracked material stream 119 after heating; wherein, in the first cracked material stream, the weight ratio of steam to crude oil components contained in the first cracked material stream is 0.4-0.6; in the second cracked material stream, the weight ratio of steam to crude oil components contained in the second cracked material stream is 0.5-0.7; and in the third cracked material stream, the weight ratio of steam to crude oil components contained in the third cracked material stream is 0.55-0.8.

[0130] The fourth vapor fraction 114 is cooled in a cooler, and the resulting liquid fraction is then sent to a refining unit (not shown). The weight of the vapor and the crude oil components contained in the fourth vapor fraction is 0.7 to 0.9.

[0131] S5, the first pyrolysis stream 127, the second pyrolysis stream 128, and the third pyrolysis stream 119 after heating are respectively fed into different furnace tubes of the radiation section 18 of the steam pyrolysis unit for pyrolysis.

[0132] S6. The second liquid fraction 115 obtained after separation by flash distillation tower 17 enters buffer tank 12, and the liquid level in the buffer tank is controlled by flow control unit. The flow control unit can also control the amount of the second liquid fraction 116 returning to buffer tank 12 via the outlet of pump 13.

[0133] 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.

[0134] 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.

[0135] 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, The method includes the following steps: S1. The crude oil is fed into the fractionation tower (2) for the first separation to obtain a first gas phase fraction, a second gas phase fraction, a third gas phase fraction and a first liquid phase fraction; the first gas phase fraction is a mixture of the first light component in the crude oil and the vapor it carries, the second gas phase fraction is a mixture of the second light component in the crude oil and the vapor it carries, and the third gas phase fraction is a mixture of the third light component in the crude oil and the vapor it carries. The final boiling point temperature of the first light component in the crude oil is 80~180℃; The initial boiling point of the second light component is not higher than the final boiling point of the first light component. The initial boiling point of the second light component is 60~140℃, and the final boiling point of the second light component is 160~250℃. The initial boiling point of the third light component is not higher than the final boiling point of the second light component. The initial boiling point of the third light component is 140~230℃, and the final boiling point of the third light component is 250~350℃. The first liquid fraction contains the first heavy component of crude oil, the initial boiling point of the first liquid fraction is not higher than the final boiling point of the third light component, and the initial boiling point of the first liquid fraction is 230~330℃. S2. Mix the first liquid fraction with the first part of steam to obtain a first liquid fraction mixture stream; mix the first liquid fraction mixture stream with the second part of steam and then enter the flash tower (17) for a second separation to obtain a fourth gaseous fraction and a second liquid fraction. The fourth vapor fraction is a mixture containing the fourth light component of crude oil and the vapor it carries, and the final boiling point temperature of the fourth light component is 350~410℃. The second liquid fraction contains the second heavy component of crude oil, and the initial boiling point of the second liquid fraction is not higher than the final boiling point of the fourth light component; S3. Mix the first vapor fraction with the third part of steam to obtain the first mixture to be cracked; mix the second vapor fraction with the fourth part of steam to obtain the second mixture to be cracked. S4. The first mixture to be cracked and the second mixture to be cracked are respectively introduced into the convection section of the steam cracking device for heating, and then respectively introduced into the radiation section (18) of the steam cracking device for cracking.

2. The method according to claim 1, characterized in that, The method further includes: heating all of the third vapor fraction in the convection section of the steam cracking unit, and then allowing it to enter the radiation section (18) of the steam cracking unit for cracking; or The entire third vapor fraction is fed into the refining unit for further processing; or A portion of the third gaseous fraction is heated in the convection section of the steam cracking unit and then cracked in the radiation section (18) of the steam cracking unit, while another portion of the third gaseous fraction is further processed in the refining unit.

3. The method according to claim 2, characterized in that, When the BMCI value of the crude oil component in the third gas phase fraction is 30 or higher, at least a portion of the third gas phase fraction is allowed to enter the refining unit as an aromatic feedstock or for further processing.

4. The method according to claim 2, characterized in that, Before at least a portion of the third vapor fraction is introduced into the refining unit for further processing, the portion of the third vapor fraction and the feedstock oil to be preheated are first introduced into a cooler for heat exchange to obtain preheated feedstock oil and third vapor fraction cooled liquid material; then the third vapor fraction cooled liquid material is introduced into the refining unit for further processing.

5. The method according to claim 2, characterized in that, The method further includes: heating all of the fourth vapor fraction in the convection section of the steam cracking unit, and then allowing it to enter the radiation section (18) of the steam cracking unit for cracking; or The entire fourth vapor fraction is fed into the refining unit for further processing; or A portion of the fourth gaseous fraction is heated in the convection section of the steam cracking unit and then cracked in the radiation section (18) of the steam cracking unit, while another portion of the fourth gaseous fraction is processed in the refining unit. When the BMCI value of the crude oil component in the fourth gas phase fraction is above 30, the fourth gas phase fraction is fed into the refining unit as an aromatic feedstock or for further processing.

6. The method according to claim 5, characterized in that, Before at least a portion of the fourth vapor fraction is introduced into the refining unit for further processing, the fourth vapor fraction and the feedstock oil to be preheated are introduced into a cooler for heat exchange to obtain preheated feedstock oil and fourth vapor fraction cooled liquid material; then the fourth vapor fraction cooled liquid material is introduced into the refining unit for further processing.

7. The method according to claim 1, characterized in that, The method further includes: wherein at least a portion of the second or third light component may be introduced into the second flash tower as a separation aid, and countercurrently contacted with the gaseous mixture obtained from the second flash tower.

8. The method according to claim 2, characterized in that, 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 mixing superheating section (6), a dilution steam superheating section (7), a fifth mixing superheating section (8), a sixth mixing superheating section (9), a seventh mixing superheating section (10), and an eighth mixing superheating section (11); the method further includes: The first liquid phase distillate mixture is fed into the first mixing superheating section (3) and heated to 280~450°C. Then the heated first liquid phase distillate mixture and the second part of steam are fed into the flash tower (17) for the second separation. The third gaseous fraction is first heated in the second mixing superheating section (4), and then mixed with the fifth part of steam to obtain the third mixture to be cracked; the third mixture to be cracked is further heated to 450~630°C in the seventh mixing superheating section (10) to obtain the third feed stream to be cracked; The second vapor fraction is first heated in the third mixing superheating section (5), and then mixed with the fourth part of steam to obtain the second mixture to be cracked; the second mixture to be cracked is further heated to 500~680°C in the sixth mixing superheating section (9) to obtain the second feed stream to be cracked; The first gaseous fraction is first heated in the fourth mixing superheating section (6) and then mixed with the third part of steam to obtain the first mixture to be cracked; the first mixture to be cracked is then heated in the fifth mixing superheating section (8) to 550~720℃ to obtain the first feed stream to be cracked.

9. The method according to claim 8, characterized in that, The fourth gaseous fraction is introduced into the eighth mixing superheating section (11) and heated to 400~600℃ to obtain the fourth pyrolysis feed stream; The first, second, optional third, and optional fourth feed streams to be cracked are respectively introduced into the radiation section (18) of the steam cracking device for steam cracking.

10. The method according to claim 8, characterized in that, The second part of steam, the third part of steam, the fourth part of steam and the fifth part of steam are all dilution steam heated to 400~575°C via the dilution steam superheating section (7).

11. The method according to claim 9, characterized in that, In the first feed stream to be cracked, the weight ratio of steam to crude oil components contained in the first feed stream to be cracked is 0.35~1; In the second feed stream to be cracked, the weight ratio of steam to crude oil components in the second feed stream to be cracked is 0.4~1; in the third feed stream to be cracked, the weight ratio of steam to crude oil components in the third feed stream to be cracked is 0.45~1. In the fourth feed stream to be cracked, the weight of steam and the crude oil components contained in the fourth feed stream to be cracked is 0.55~1.

12. The method according to claim 11, characterized in that, In the first feed stream to be cracked, the weight ratio of steam to crude oil components contained in the first feed stream to be cracked is 0.4~0.6; In the second feed stream to be cracked, the weight ratio of steam to crude oil components in the second feed stream to be cracked is 0.5~0.7; in the third feed stream to be cracked, the weight ratio of steam to crude oil components in the third feed stream to be cracked is 0.6~0.

8. In the fourth feed stream to be cracked, the weight of steam and the crude oil components contained in the fourth feed stream to be cracked is 0.7~0.

9.

13. The method according to claim 9, characterized in that, The first, second, optional third, and optional fourth pyrolysis streams can be fed into different radiant furnace chambers of the same pyrolysis furnace or different pyrolysis furnaces for pyrolysis.

14. The method according to claim 8, characterized in that, The convection section is further provided with a raw material preheating section (1), which is located above the first mixing superheating section (3); the method further includes: The crude oil and waste heat material from the storage tank are respectively fed into the quench water preheater (16) for the first heat exchange to obtain the first preheated crude oil and cooled material; 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 a second preheated crude oil; the second preheated crude oil is then used as the crude oil to enter the fractionation tower (2) for the first separation.

15. The method according to claim 14, characterized in that, The method further includes: buffering the second liquid fraction in a buffer tank (12) and then pumping it out through a pump (13).

16. The method according to claim 14, characterized in that, The temperature of the first preheated crude oil is 70~120℃ and the pressure is 0.1~0.2MPaG; or the crude oil from the storage tank is introduced into the convection section of the steam cracking unit after undergoing the first heat exchange in the quench water preheater (16), and the obtained preheated crude oil is used as the first preheated crude oil.

17. The method according to claim 14, characterized in that, The temperature of the second preheated crude oil is 200~400℃.

18. The method according to claim 15, characterized in that, The method further includes: dividing the second liquid phase fraction from the buffer tank (12) into three parts, allowing the first part of the second liquid phase fraction to enter the hydrogenation unit for hydrogenation treatment, allowing the second part of the second liquid phase fraction to enter the catalytic cracking unit for catalytic cracking treatment, and allowing the third part of the second liquid phase fraction to be refluxed into the buffer tank (12).

19. The method according to claim 14, characterized in that, The crude oil is at least one of paraffinic crude oil, intermediate-based crude oil, and naphthenic crude oil.

20. The method according to claim 15, characterized in that, The method further includes: allowing at least a portion of the second liquid fraction from the buffer tank (12) to enter the steam generator as a heat source to generate steam, wherein the generated steam can be used as supplementary steam for the first portion of steam, the second portion of steam, the third portion of steam and the fourth portion of steam.

21. The method according to claim 14, characterized in that, The method further includes: subjecting the desalted crude oil from the desalting pre-processor (15) to external preheating treatment outside the convection section before entering the fractionation tower (2), wherein the heat source for the external preheating treatment is waste heat material from any device; the external preheating treatment is independent of the preheating treatment in the raw material preheating section (1).

22. A system for producing olefins by crude oil steam cracking, characterized in that, The system includes a fractionation tower (2), a flash tower (17), and a steam cracking unit, wherein the steam cracking unit includes a convection section and a radiation section (18), and the convection section is located above the radiation section (18) along the height direction of the steam cracking unit; wherein, The fractionation tower (2) is provided with a crude oil inlet, a first vapor phase distillate outlet, a second vapor phase distillate outlet, a third vapor phase distillate outlet, and a first liquid phase distillate outlet; the flash tower (17) is provided with a first liquid phase distillate inlet, a fourth vapor phase distillate outlet, and a second liquid phase distillate outlet; wherein the first liquid phase distillate outlet of the fractionation tower (2) is connected to the first liquid phase distillate inlet of the flash tower (17), and a first part of the steam inlet is provided on the connecting pipeline between the first liquid phase distillate outlet and the first liquid phase distillate inlet; The radiation section (18) of the steam cracking device is provided with a first feedstock inlet, a second feedstock inlet, an optional third feedstock inlet, and an optional fourth feedstock inlet; the first feedstock inlet is connected to the first vapor phase outlet of the fractionation tower (2), the second feedstock inlet is connected to the second vapor phase outlet of the fractionation tower (2), the third feedstock inlet is connected to the third vapor phase outlet of the fractionation tower (2), and the fourth feedstock inlet is connected to the fourth vapor phase outlet of the flash tower (17).

23. The system according to claim 22, 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 mixing superheating section (6), a dilution steam superheating section (7), a fifth mixing superheating section (8), a sixth mixing superheating section (9), a seventh mixing superheating section (10), and an eighth mixing superheating section (11), wherein, The first mixing superheated section (3) is provided with a first superheated inlet and a first superheated outlet; the first superheated inlet is connected to the first liquid phase distillate outlet of the fractionation tower (2) through a first pipeline; the first superheated outlet is connected to the first liquid phase distillate inlet of the flash tower (17); The second mixing superheated section (4) is provided with a second superheated inlet and a second superheated outlet. The second superheated inlet is connected to the third gas phase distillate outlet of the fractionation tower (2) through a second pipeline. The third mixing superheating section (5) is provided with a third superheating inlet and a third superheating outlet. The third superheating inlet is connected to the second gas phase distillate outlet of the fractionation tower (2) through a third pipeline. The fourth mixing superheating section (6) is provided with a fourth superheating inlet and a fourth superheating outlet. The fourth superheating inlet is connected to the first gas phase distillate outlet of the fractionation tower (2) through a fourth pipeline. The fifth mixing superheating section (8) is provided with a fifth superheating inlet and a fifth superheating outlet. The fifth superheating inlet is connected to the fourth superheating outlet of the fourth mixing superheating section (6) through a fifth pipeline. The fifth superheating outlet is connected to the first raw material inlet to be cracked in the radiation section (18). The sixth mixing superheating section (9) is provided with a sixth superheating inlet and a sixth superheating outlet. The sixth superheating inlet is connected to the third superheating outlet of the third mixing superheating section (5) through a sixth pipeline. The sixth superheating outlet is connected to the third feedstock inlet of the radiation section (18). The seventh mixing superheating section (10) is provided with a seventh superheating inlet and a seventh superheating outlet. The seventh superheating inlet is connected to the second superheating outlet of the second mixing superheating section (4) through a seventh pipeline. The eighth mixing superheating section (11) is provided with an eighth superheating inlet and an eighth superheating outlet. The eighth superheating inlet is connected to the fourth gas phase distillate outlet of the flash tower (17), and the eighth superheating outlet is connected to the fourth raw material inlet to be cracked in the radiation section (18). The dilution steam superheating section (7) is provided with a secondary dilution steam superheating inlet and a secondary dilution steam superheating outlet.

24. The system according to claim 23, characterized in that, The flash tower (17) is a high-efficiency gas-liquid separation flash tower, and the gas phase outlet of the flash tower (17) is one or more.

25. The system according to claim 23, characterized in that, The first pipeline is provided with a primary dilution steam first inlet; the fifth pipeline is provided with a secondary dilution steam second inlet; the sixth pipeline is provided with a secondary dilution steam third inlet; the seventh pipeline is provided with a secondary dilution steam fourth inlet; the secondary dilution steam first inlet, secondary dilution steam second inlet, secondary dilution steam third inlet and secondary dilution steam fourth inlet are respectively connected to the secondary dilution steam superheat outlet of the dilution steam superheat section (7).

26. The system according to claim 25, characterized in that, Material mixers are provided at the first inlet of primary dilution steam, the second inlet of secondary dilution steam, the third inlet of secondary dilution steam, and the fourth inlet of secondary dilution steam to mix the materials and steam introduced into the mixers.

27. The system according to claim 25, 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 of the desalting preprocessor (15) 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 second liquid phase distillate outlet of the flash distillation tower (17), and the liquid phase heavy component buffer outlet is connected to the inlet of the pump (13).

28. The system according to claim 27, characterized in that, The output port of the pump (13) is connected to the feed inlet of the catalytic cracking unit and / or the feed inlet of the hydrotreating unit.

29. The system according to claim 27, characterized in that, The system also includes a flow control unit, which includes a level transmitter, a pump reflux control valve, a level control valve, a pump outlet flow meter, and a heavy component delivery flow meter; the liquid phase heavy component reflux inlet is located at the top of the buffer tank (12), and the flow control unit controls the amount of liquid phase heavy component entering the liquid phase heavy component reflux inlet of the buffer tank (12) from the pump (13); The level transmitter is connected to the inside of the buffer tank (12) to control the level inside the buffer tank (12).

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