A process and system for the production of olefins by cracking of a wide-cut feedstock containing heavy components

Abstract

The present disclosure relates to a method and system for cracking wide-cut feedstock containing heavy components to produce olefins. The wide-cut feedstock is mixed with a first portion of steam, then mixed with a second portion of steam, and then introduced into a fractionating column for separation. The light fraction and the middle fraction obtained by fractionation are heated in a convection section and then introduced into different furnace tubes of a radiant section of a steam cracking device for cracking. Alternatively, part of the fraction is sent to a refinery for secondary processing to produce other products. This method can efficiently crack different fractions of light crude oil or condensate oil, has high olefin yield, saves energy, and can maximize the use of existing steam cracking technology, which is mature and easy to operate. The method eliminates the need for atmospheric and vacuum distillation devices, thereby saving investment. The method has a wide range of crude oil adaptability and improves the comprehensive utilization rate of different fractions of wide-cut feedstock.

Description

Technical Field

[0001] This disclosure relates to the field of hydrocarbon processing, and more specifically, to a method and system for cracking a wide-fraction feedstock containing heavy components to produce olefins. Background Technology

[0002] In recent years, the demand for low-carbon olefin organic chemical raw materials has been increasing year by year, while the production scale of low-carbon olefins cannot meet the growing production demand. Furthermore, in recent years, the traditional naphtha-based process for producing low-carbon olefins has faced challenges due to the impact of cheap raw materials such as Middle Eastern light hydrocarbons and US shale oil, as well as coal chemical processes. These challenges include high raw material costs and a lack of competitiveness. In addition, the development of new energy vehicles has reduced the demand for fuel oil. Therefore, to cope with the impact of market competition, expand the raw material sources for ethylene cracking units, shorten the processing flow of refining units, and develop a cracking process that uses crude oil as a feedstock for steam cracking, thereby reducing raw material costs, overcoming the constraints of raw material varieties, reducing investment in refining units, and improving production flexibility, has become an effective means for traditional ethylene enterprises to reduce costs and increase efficiency. When using crude oil as a feedstock for steam cracking furnaces, compared with traditional cracking feedstocks, the steam cracking process using crude oil feedstock is prone to defects such as high final boiling point (greater than 520℃), high gum content, difficulty in vaporization, and easy coking. Therefore, how to make corresponding treatments and improvements to the cracking furnace design and production process to suit the characteristics of crude oil has been extensively studied. For example, currently, major international companies such as ExxonMobil, Saudi Aramco, Equista Chemicals, and Lummus have conducted in-depth research on crude oil cracking technology, while domestic companies such as Shanghai Junming Chemical Engineering Design Co., Ltd. are also involved.

[0003] Shanghai Junming Chemical Engineering Design Co., Ltd. disclosed a combined processing method and apparatus for producing low-carbon olefins from crude oil through direct steam cracking (CN111196936A). This method first removes impurities through pretreatment such as desalting and dehydration, then feeds the crude oil into the ethylene cracking convection section for heating. The heated feed is then sent to a gas-liquid separator, where lighter hydrocarbon gases are separated and sent to the convection and radiation sections for steam cracking to produce olefins. However, the liquid exiting the gas-liquid separator in this process contains components such as atmospheric residue oil, requiring further processing in a hydrogenation unit before being returned to the convection and radiation sections. Therefore, directly feeding superheated crude oil into the gas-liquid separator in this method makes it difficult to achieve the desired gas-liquid separation effect. Lums Technology Co., Ltd. disclosed a method for thermally cracking crude oil and heavy feed in a pyrolysis reactor to produce olefins (CN107001955B). This method describes a scheme combining the convection section of a cracking furnace with multi-stage (up to three stages) separators and fractionation towers. This method can perform multiple gas-liquid separations on a crude oil-steam mixture and send mixtures of different densities to different radiant furnace tubes for cracking. While this method uses multi-stage separators and fractionation towers to separate the mixture and uses different radiant furnace tubes to crack different fractions, it still suffers from problems such as complex equipment, high investment, and unsuitability for light crude oil steam cracking. ExxonMobil has proposed using crude oil steam cracking to produce low-carbon chemical feedstocks. It should be noted that ExxonMobil's crude oil cracking technology does not directly use purchased crude oil in the steam cracking unit, but rather performs pretreatment first. This pretreatment process mainly includes: feedstock blending, hydrotreating, and flash evaporation / separation. In February 2005, ExxonMobil Chemicals Patent Company applied for Chinese patent CN100564484C—Method for Steam Cracking of Heavy Hydrocarbon Feedstock, which provides a detailed description of the above process. The heavy hydrocarbon feedstock mainly includes: crude oil, naphtha, gas oil, fuel oil, natural gasoline (condensate oil), and residual oil. The method describes a flash vaporization separation process. However, it is difficult to separate the gas and liquid components well by simply flashing, especially to avoid the entrainment of heavy components into the gas phase, which can easily cause coking in the convection section and then lead to severe coking in the radiant section furnace tubes.

[0004] Ignesta Chemicals describes a process technology for producing ethylene from crude oil / condensate through cracking in patents CN101528894A and CN101778929A. CN101528894A describes a process where, after preheating the crude oil / condensate in the convection section, the separated light components enter the cracking furnace for superheating in the convection section before entering the radiant section for cracking. The heavier components are sent to atmospheric and vacuum distillation towers for further separation. However, this process still retains atmospheric and vacuum distillation units, and the overall process is not simplified. The stream entering the radiant section for cracking is also a mixture, without differentiation for cracking. CN101778929A describes a process where, after preheating the 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. The treatment of the separated heavy components is not described. Furthermore, the evaporation units of the two patents mentioned above use packed distillation columns, in which the upper evaporation zone contains a gas-liquid separator to achieve gas-liquid separation. However, the distillation columns used in the two patents are packed, which may easily cause blockage for heavy components in crude oil. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method and system for producing olefins by cracking a wide-fraction feedstock containing heavy components, which can adapt to the needs of different crude oils or condensates as cracking feedstocks and efficiently crack different fractions in crude oils and condensates.

[0006] To achieve the above objectives, the first part of this disclosure provides a method for producing olefins by cracking a wide-range feedstock oil. The method includes the following steps: S1, mixing the wide-range feedstock oil with a first portion of steam to obtain a first mixture; S2, mixing the first mixture with a second portion of steam and then feeding it into a fractionating tower for fractionation to obtain light, middle, and heavy fractions; S3, heating the light fraction in the convection section of a steam cracking unit; and then heating the light fraction in the radiative section of the steam cracking unit for steam cracking to obtain cracking products containing olefins.

[0007] Optionally, the final boiling point of the light fraction is 80–180°C; the initial boiling point of the middle fraction is not higher than the final boiling point of the light fraction, preferably 60–160°C, and the final boiling point of the middle fraction is 250–430°C; the initial boiling point of the heavy fraction is not higher than the final boiling point of the middle fraction; preferably, the heavy components contained in the wide-range feedstock oil include at least components with a boiling point of 500°C or higher, and more preferably, based on the total weight of the wide-range feedstock oil, the content of heavy components in the wide-range feedstock oil is 5–50% by weight; optionally, the wide-range feedstock oil containing heavy components is crude oil containing heavy components or condensate oil containing heavy components.

[0008] Optionally, the method further includes: mixing all of the middle fraction with the superheated third portion of steam and then heating it in the convection section of a steam cracking unit to obtain a heated first mixture of middle fractions; then introducing the heated first mixture of middle fractions into the radiative section of the steam cracking unit for steam cracking; or introducing all of the middle fractions into a refining unit for further processing; or dividing the middle fractions into two parts, mixing the first part of the middle fraction with the superheated third portion of steam and then heating it in the convection section of the steam cracking unit to obtain a heated second mixture of middle fractions; introducing the heated second mixture of middle fractions into the radiative section of the steam cracking unit for steam cracking, and then introducing the second part of the middle fractions into the refining unit for further processing; preferably, before introducing the middle fractions into the refining unit for further processing, the middle fractions and the wide-range feedstock oil to be preheated are first introduced into a cooler for heat exchange to obtain preheated wide-range feedstock oil and cooled liquid middle fractions; and then introducing the cooled liquid middle fractions into the refining unit.

[0009] Optionally, the fractionating column is provided with a dividing device in the middle, which divides the fractionating column into an upper column and a lower column along the height direction of the fractionating column. The dividing device is provided with a liquid phase material channel, which only allows liquid phase material from the upper column to enter the lower column and does not allow gaseous material from the lower column to enter the upper column. Optionally, the lower column is a rectification column with condensation reflux and bottom reboiling functions. The method further includes: mixing the first mixture with the second part of steam and then flashing it into the upper column of the fractionating column to separate the light fraction and the flash liquid phase fraction; allowing the flash liquid phase fraction to enter the lower column through the liquid phase material channel of the dividing device; and performing rectification of the flash liquid phase fraction in the lower column to separate the middle fraction and the heavy fraction.

[0010] Optionally, along the height direction of the steam cracking device, the convection section is sequentially provided with a first feedstock superheating section, a second mixing superheating section, a third steam superheating section, a fourth mixing superheating section, and a fifth mixing superheating section, which are independent of each other from top to bottom; the method further includes: mixing the wide-fraction feedstock oil with primary dilution steam to obtain a first mixture; heating the first mixture in the second mixing superheating section; heating the secondary dilution steam in the third steam superheating section; and then mixing the heated first mixture with the heated secondary dilution steam and entering the fractionation tower for fractionation treatment; preferably, the temperature of the heated first mixture is 200-400°C; the temperature of the heated secondary dilution steam is 400-575°C; optionally, the primary dilution steam is primary dilution steam heated to a temperature of 250-450°C by an external heating device outside the convection section or the steam cracking device; optionally, the heat source of the external heating device is medium-pressure steam or other high-temperature heat source; optionally, the method further includes The process includes: heating the light fraction to 550–680°C in the fourth mixing superheating section to obtain a first material to be cracked; optionally, dividing the heated secondary dilution steam from the third steam superheating section into two parts, using one part of the heated secondary dilution steam as the second part of steam, mixing it with the first mixture, and then entering the fractionation tower; mixing the other part of the heated secondary dilution steam with at least a portion of the middle fraction from the fractionation tower and then entering the fifth mixing superheating section to be heated to 400–650°C to obtain a second material to be cracked; and then introducing the first material to be cracked and the optional second material to be cracked into the radiation section for steam cracking; preferably, the ratio of the total weight of the dilution steam in the first material to be cracked to the weight of the feed oil in the first material to be cracked is 0.4–0.1, preferably 0.45–0.65; and the ratio of the total weight of the dilution steam in the second material to be cracked to the weight of the feed oil in the second material to be cracked is 0.5:1, preferably 0.65–0.85.

[0011] Optionally, the method further includes: buffering the heavy fraction from the fractionation tower in a buffer tank and then pumping it out; allowing the wide-fraction feedstock oil and waste heat material from the storage tank to undergo a first heat exchange in a quench water preheater to obtain a first preheated wide-fraction feedstock oil and cooling material; optionally, the temperature of the first preheated wide-fraction feedstock oil is 70–120°C; or allowing the crude oil from the storage tank to undergo a first heat exchange in the quench water preheater and then be introduced into the convection section of a steam cracking unit for further heat exchange, using the obtained preheated crude oil as the first preheated wide-fraction feedstock oil; allowing the first preheated wide-fraction feedstock oil to undergo desalting pretreatment in a desalting preprocessor to obtain desalted wide-fraction feedstock oil; and allowing the desalted wide-fraction feedstock oil to undergo a first heat exchange in a desalting preprocessor to obtain a first preheated wide-fraction feedstock oil. The feedstock oil enters the first feedstock preheating section of the steam cracking unit for heating, and then mixes with the primary dilution steam to obtain the first mixture. Optionally, the method further includes: dividing the heavy fraction from the buffer tank into three parts, sending the first part of the heavy fraction into a hydrogenation unit for hydrogenation treatment, sending the second part of the heavy fraction into a catalytic cracking unit for catalytic cracking treatment, and refluxing the third part of the heavy fraction back into the buffer tank. Optionally, the fractionating tower and the buffer tank are arranged in a vertical combination with the fractionating tower above and the buffer tank below, or the bottom of the fractionating tower is used as the buffer tank. Optionally, the liquid stream obtained from the fractionating tower can be sent out after heat recovery.

[0012] Optionally, the method further includes: processing at least a portion of the heavy fraction in a dilution steam generator to obtain dilution steam; using a portion of the dilution steam as the primary dilution steam and a portion of the dilution steam as the secondary dilution steam; optionally, the method further includes: subjecting the desalted wide-fraction feedstock oil 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, and the external preheating treatment is independent of the preheating treatment in the first feedstock superheating section.

[0013] Part II of this disclosure provides a system for cracking a wide-fraction feedstock containing heavy components to produce olefins. The system includes a fractionating tower and a steam cracking unit. The steam cracking unit includes a convection section and a radiating section, with the convection section located above the radiating section along the height of the steam cracking unit. The fractionating tower has a wide-fraction feedstock inlet, a light fraction outlet, a middle fraction outlet, and a heavy fraction outlet. The wide-fraction feedstock inlet is located at the upper part of the fractionating tower, and a first steam mixing inlet and a second steam mixing inlet are also provided on the inlet pipeline. The radiating section of the steam cracking unit has a first feedstock inlet to be cracked and an optional second feedstock inlet to be cracked and a cracking product outlet. The first feedstock inlet to be cracked is connected to the light fraction outlet of the fractionating tower, and the second feedstock inlet to be cracked is connected to the middle fraction outlet of the fractionating tower.

[0014] Optionally, the fractionation tower is provided with a dividing device in the middle; along the height direction of the fractionation tower, the dividing device divides the fractionation tower into an upper tower and a lower tower, and the dividing device is provided with a liquid phase material channel, which only allows the liquid phase material of the upper tower to enter the lower tower and does not allow the gas phase material of the lower tower to enter the upper tower; wherein the upper tower is a flash tower, and the lower tower is a rectification tower with condensation reflux and bottom reboiling functions; the wide-fraction feed oil inlet is located in the upper part of the upper tower, and the light fraction is located at the top of the upper tower; the middle fraction outlet is located in the middle of the lower tower, and the heavy fraction outlet is located in the lower part of the lower tower; optionally, a third steam inlet is also provided on the connecting pipeline between the middle fraction outlet of the fractionation tower and the second feed inlet to be cracked.

[0015] Optionally, along the height direction of the steam cracking unit, the convection section is provided with, from top to bottom, an independent first feedstock superheating section, a second mixing superheating section, a third steam superheating section, a fourth mixing superheating section, and a fifth mixing superheating section; the first feedstock superheating section has a first superheating inlet and a first superheating outlet; the second mixing superheating section has a second superheating inlet and a second superheating outlet; the first superheating outlet and the second superheating inlet are connected by a first pipeline, and a primary dilution steam inlet is also provided on the first pipeline, the primary dilution steam inlet forming the first partial steam mixing inlet; the second superheating outlet is connected to the wide-fraction feedstock oil inlet of the fractionation tower, and the second superheating outlet is connected to the wide-fraction feedstock oil inlet of the fractionation tower. A first inlet for superheated secondary dilution steam is provided on the connecting pipeline between the feedstock inlets, and the first inlet for superheated secondary dilution steam forms the second part of the steam mixing inlet; preferably, a mixer is provided at the first inlet for superheated secondary dilution steam; the third steam superheating section is provided with a third superheated inlet and a third superheated outlet; the third superheated inlet is connected to the secondary dilution steam source, and the third superheated outlet is connected to the first inlet for superheated secondary dilution steam; the fourth mixing superheater is provided with a fourth superheated inlet and a fourth superheated outlet; the fifth mixing superheater is provided with a fifth superheated inlet and a fifth superheated outlet; the fourth superheated inlet is connected to the light fraction outlet of the fractionation tower, and the fourth superheated outlet... The first feedstock inlet of the radiant section is connected to the first feedstock inlet to be cracked; the fifth superheated inlet is connected to the middle fraction outlet of the fractionation tower, and a second superheated secondary dilution steam inlet is provided on the connecting pipeline between the fifth superheated inlet and the middle fraction outlet, the second superheated secondary dilution steam inlet forming the third steam mixing inlet; the second superheated secondary dilution steam inlet is connected to the third superheated outlet of the third steam superheating section; the fifth heating outlet of the fifth mixing superheater is connected to the second feedstock inlet to be cracked in the radiant section; optionally, a mixer is provided on the first pipeline, the mixer on the first pipeline is provided with a wide-fraction feedstock oil mixing inlet and a primary dilution steam mixing inlet. The system includes an inlet and an outlet for the mixed feedstock; the wide-fraction feedstock mixing inlet is connected to the first superheated outlet of the first feedstock superheating section, and the mixed feedstock outlet is connected to the second superheated inlet of the second mixing superheating section; optionally, the system further includes a buffer tank, a pump, a desalting preprocessor, and a quench water preheater; the buffer tank is provided with at least a heavy fraction buffer inlet, a heavy fraction buffer outlet, a heavy fraction reflux inlet, a steam purging port, and a nitrogen purging port; the pump includes an inlet and an outlet; the desalting preprocessor is provided with a wide-fraction feedstock desalting inlet and a wide-fraction feedstock desalting outlet; the quench water preheater is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a wide-fraction feedstock heat exchange first inlet, and a wide-fraction feedstock heat exchange first outlet;The first outlet of the wide-fraction feedstock oil heat exchanger of the quench water preheater is connected to the wide-fraction feedstock oil desalting inlet of the desalting preprocessor, and the wide-fraction feedstock oil desalting outlet of the desalting preprocessor is connected to the first superheating inlet of the first feedstock superheating section; the heavy fraction buffer inlet of the buffer tank is connected to the heavy fraction outlet of the fractionation tower, the heavy fraction buffer outlet is connected to the inlet of the pump, and the outlet of the pump is used to connect to the feedstock inlet of the catalytic cracking unit and / or the feedstock inlet of the hydrotreating unit; wherein, the level transmitter is connected to the inside of the buffer tank to control the liquid level in the buffer tank.

[0016] Through the above technical solution, this disclosure provides a method and system for producing olefins by cracking a wide-fraction feedstock, the beneficial effects of which include at least:

[0017] 1. The broad-fraction feedstock containing heavy components is mixed with the first part of steam, and then mixed with the second part of steam before entering the fractionation tower for separation. The light fraction and optional middle fraction obtained from the fractionation are then heated in the convection section and introduced into different furnace tubes in the radiant section of the steam cracking unit for cracking. Alternatively, all or part of the middle fraction can be sent to the refining unit for secondary processing to produce other products. This achieves efficient cracking of different fractions of the broad-fraction feedstock containing heavy components, resulting in high olefin yield, energy saving, and maximum utilization of existing steam cracking technology. The technology is mature and the operation is simple.

[0018] 2. The method provided in this disclosure has the advantage of being adaptable to a wide range of crude oils. Specifically, for light paraffin-based crude oils suitable for direct steam cracking, it is beneficial to feed the light and middle fractions into the radiant section of the cracking furnace for cracking under optimal dilution ratios and cracking conditions, thereby obtaining high olefin yields and saving energy. The heavy fraction can be further processed into olefins through catalytic cracking, ultimately maximizing the utilization of high-quality crude oil. For crude oils with high aromatic content, the light fraction is steam cracked to produce olefins, while the middle fraction can be used as cracking feedstock, aromatic feedstock, or jet fuel, or introduced into the refining unit for further processing. The heavy fraction can be hydrogenated and used as lubricating oil or cracking feedstock. The method can be flexibly determined according to the source of the crude oil, maximizing the comprehensive utilization rate of different fractions of the wide-range feedstock oil, achieving the goal of using olefins where appropriate, aromatics where appropriate, and oil where appropriate.

[0019] 3. Compared with the conventional process where wide-range feedstock oil is processed in the atmospheric and vacuum distillation tower of the refining unit, and then part of it enters the refining unit and part of it is used as cracking feedstock to enter the cracking furnace for cracking, the steam cracking process for wide-range feedstock oil such as light crude oil or condensate oil provided in this disclosure simplifies the process, eliminates the atmospheric and vacuum distillation unit, and thus saves investment.

[0020] 4. Since the liquid phase at the top of the fractionation tower enters the lower tower as a flash gas, this liquid phase absorbs or cools the gas phase exiting the tower, which helps to prevent heavy fractions from being carried into the gas phase and also facilitates the separation of heavy fractions from middle fractions.

[0021] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0022] 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:

[0023] Figure 1 This is a schematic flow diagram of a method for producing olefins by cracking a wide-fraction feedstock oil according to one embodiment of the present disclosure;

[0024] Figure 2 This is a schematic flow diagram of a method for producing olefins by cracking a wide-fraction feedstock oil according to one embodiment of the present disclosure.

[0025] Explanation of reference numerals in the attached figures

[0026] 1-First feedstock superheating section, 2-Second mixing superheating section, 4-Fracturing tower, 6-Third steam superheating section, 7-Radiation section, 8-Fourth mixing superheating section, 9-Fifth mixing superheating section, 12-Buffer tank, 13-Pump, 15-Desalting pre-processor, 16-Quick coolant preheater, 101-Crude oil, 102-Heated crude oil, 104-Desalted crude oil, 105-Heated crude oil, 106-Primary dilution steam, 107-Mixture of heated crude oil and steam, 108-Secondary dilution steam, 109-Light fraction, 110-Middle fraction, 111-Heavy fraction, 112-First feedstock to be cracked, 113-Second feedstock to be cracked, 114-Secondary dilution steam, 116-Waste heat material Detailed Implementation

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The first aspect of this disclosure provides a method for producing olefins by cracking a wide-fraction feedstock containing heavy components, such as... Figure 1 As shown, the method includes the following steps:

[0031] S1. Mix the wide-fraction feedstock oil with the first part of the steam to obtain the first mixture.

[0032] S2. The first mixture is mixed with the second part of steam and then fed into the fractionation tower 4 for fractionation to obtain light fraction, middle fraction and heavy fraction; S3. The light fraction is fed into the convection section of the steam cracking device for heating; the heated light fraction is fed into the radiation section 7 of the steam cracking device for steam cracking to obtain cracking products containing olefins.

[0033] This disclosure provides a method for producing olefins from a wide-fraction feedstock through cracking. The method involves mixing a wide-fraction feedstock containing heavy components with a first portion of steam, then with a second portion of steam, and finally separating the mixture in a fractionation tower. The resulting light fraction and optional middle fraction are then heated in the convection section and introduced into different furnace tubes in the radiant section of a steam cracking unit for further cracking. Alternatively, all or part of the middle fraction can be sent to a refining unit for secondary processing to produce other products. This method achieves efficient cracking of different fractions of light crude oil or condensate (such as paraffin-based crude oil or paraffin-based condensate), resulting in high olefin yields, energy savings, and maximum utilization of existing steam cracking technology. The technology is mature and simple to operate. This method differs from conventional methods where the wide-fraction feedstock is processed in an atmospheric and vacuum distillation tower in a refining unit, with one portion entering the refining unit and the other portion used as cracking feedstock in the cracking furnace. Compared to traditional cracking processes, the steam cracking process for light crude oil or condensate provided in this disclosure simplifies the process and eliminates the need for an atmospheric and vacuum distillation unit, thus saving investment. The method provided in this disclosure has the advantage of being adaptable to a wide range of crude oils. Specifically, for light paraffin-based crude oils suitable for direct steam cracking, it is beneficial to feed the light and middle fractions into the radiant section of the cracking furnace separately for cracking under optimal dilution ratios and cracking conditions, thereby obtaining high olefin yields and saving energy. The heavy fraction can be further processed by catalytic cracking to produce olefins, ultimately maximizing the utilization of high-quality crude oil. For crude oils with high aromatic content, the light fraction is steam cracked to produce olefins, the middle fraction is used as an aromatic feedstock or jet fuel, and the heavy fraction can be hydrotreated to produce lubricating oil or as a cracking feedstock, thereby improving the comprehensive utilization rate of different fractions of the wide-range feedstock oil.

[0034] In this disclosure, the wide-range feedstock containing heavy components includes crude oil or condensate containing heavy components. Specifically, the crude oil can be selected from light crude oil, medium crude oil, or heavy crude oil, such as paraffinic crude oil, intermediate-based crude oil, or naphthenic crude oil; condensate also contains heavy components, and therefore is also applicable to the method provided in this disclosure. This disclosure is applicable to a variety of different wide-range feedstocks.

[0035] In a preferred embodiment, the heavy components contained in the wide-fraction feedstock are at least components with a boiling point of 500°C or higher. More preferably, the content of heavy components is 5-50% by weight, based on the total weight of the wide-fraction feedstock.

[0036] In this disclosure, the "light fraction" is a mixture containing light fractions from crude oil and carried vapor, wherein the light fractions from crude oil include naphtha containing a portion of kerosene and lighter fractions; the "middle fraction" is a mixture containing medium fractions from crude oil and carried vapor, wherein the medium fractions from crude oil include diesel vapor fractions heavier than naphtha containing a portion of kerosene but lighter than heavy diesel; the "heavy fraction" contains heavy fractions from crude oil, wherein the heavy fractions from crude oil are liquid fractions heavier than heavy diesel. The light and medium fractions obtained by the fractionation tower in this disclosure already carry vapor, therefore, there is no need to introduce steam into the system in subsequent processes, simplifying the process. The boiling range temperatures of each fraction referred to in this disclosure refer to the components of the feedstock oil obtained by separation, excluding vapor.

[0037] In a preferred embodiment, the final boiling point of the light fraction is 80–180°C; the initial boiling point of the middle fraction is not higher than the final boiling point of the light fraction, and the final boiling point of the middle fraction is 250–430°C; the initial boiling point of the heavy fraction is not higher than the final boiling point of the middle fraction.

[0038] It should be understood that the initial or final boiling point of each fraction in this disclosure is a range value, and in actual operation, it can be any temperature within the range. Furthermore, this disclosure allows for the selection of the separated fractions according to actual production needs.

[0039] In one specific implementation, such as Figure 1 or Figure 2 As shown, the method further includes: mixing all of the middle fraction with the superheated third portion of steam and then heating it in the convection section of a steam cracking unit to obtain a heated first mixture of middle fractions; and then subjecting the heated first mixture of middle fractions to steam cracking in the radiation section 7 of the steam cracking unit; or

[0040] All of the middle fraction is fed into the refining unit for further processing; or

[0041] The middle fraction is divided into two parts. The first part of the middle fraction is mixed with the superheated third part of steam and then heated in the convection section of the steam cracking unit to obtain a heated second mixture of middle fraction. The heated second mixture of middle fraction is then fed into the radiation section 7 of the steam cracking unit for steam cracking, and the second part of the middle fraction is fed into the refining unit for further processing.

[0042] In this process, all the middle fraction is introduced into the convection section for heating before being introduced into the cracking furnace for cracking, such as... Figure 1 As shown; the middle fraction separated from fractionation tower 4 is sent to the refining unit for secondary processing, such as... Figure 2 As shown; or, a portion of the middle fraction can be introduced into the radiant section for steam cracking, while another portion can be sent to a refining unit for secondary processing (not shown). Those skilled in the art can adjust and select based on actual needs or the composition of the wide-range feedstock. In this disclosure, for light paraffinic crude oil suitable for direct steam cracking, the light and middle fractions can be separately fed into the radiant section of the cracking furnace for cracking; for crude oil with high aromatic content, the light fraction is suitable for steam cracking to produce olefins, the middle fraction can be used as aromatic feedstock or jet fuel, and the heavy fraction can be hydrotreated to produce lubricating oil or as cracking feedstock. This disclosure selects fractions suitable for olefin production as cracking feedstock based on the crude oil composition and processing requirements, and uses fractions unsuitable for cracking to produce aromatics or sell as oil products, achieving flexibility in utilizing olefins, aromatics, and oil as appropriate.

[0043] In a preferred embodiment, before the middle fraction enters the refining unit for further processing, this portion of the middle fraction and the feedstock oil to be preheated are first introduced into a cooler for heat exchange, resulting in preheated feedstock oil and cooled liquid-phase middle fraction; the cooled liquid-phase middle fraction then enters the refining unit. In this disclosure, the feedstock oil to be preheated can be any feedstock oil obtained in any step before entering the fractionation tower 4, and the cooler can be used in series with other devices in this system that process the feedstock oil before it enters the separation tower.

[0044] In a preferred embodiment, such as Figure 1 As shown, the fractionating column 4 is provided with a dividing device in the middle. Along the height direction of the fractionating column 4, the dividing device divides the fractionating column 4 into an upper column and a lower column. The dividing device is provided with a liquid material channel. The liquid material channel only allows the liquid material of the upper column to enter the lower column, and does not allow the gaseous material of the lower column to enter the upper column. Optionally, the lower column is a distillation column with condensation reflux and bottom reboiling functions.

[0045] The method also includes:

[0046] The first mixture is mixed with the second part of the steam and then enters the upper section of the fractionation tower 4 for flash evaporation to separate the light fraction and the flash liquid fraction.

[0047] The flash liquid phase fraction is introduced into the lower column through the liquid phase material channel of the separator; the flash liquid phase fraction is then subjected to rectification in the lower column to separate the middle fraction and the heavy fraction.

[0048] In this embodiment, the fractionation tower is configured with a special structure where the upper section is a flash tower and the lower section is a rectification tower. Only the liquid phase material after flash evaporation in the upper section is allowed to enter the lower section tower. The light fraction of the wide-range feedstock oil can be separated by flash evaporation in the flash tower first. Then, the heavier liquid phase material obtained after flash evaporation flows by gravity into the lower section tower and is introduced into the lower section tower for further rectification to further separate the middle and heavy fractions of the wide-range feedstock oil. This disclosure uses a fractionation tower with a special structure to more fully separate the light, middle and heavy fractions of the wide-range feedstock oil (especially to separate the fractions with a boiling point below 460°C as much as possible for subsequent steam cracking), which is beneficial to improving the olefin yield obtained from subsequent steam cracking. In this disclosure, the structure of the separating device in the fractionation column 4 for separating the upper and lower columns can be a structure known in the art, capable of satisfying the requirement that "only liquid phase material from the upper column is allowed to enter the lower column, and gaseous phase material from the lower column is not allowed to enter the upper column." For example, the liquid phase material channel of the upper column can be extended to a position below the liquid level in the lower column, and the gas phase space can be sealed by a liquid seal to ensure that the gaseous phase material cannot backflow into the upper column through the liquid phase material channel.

[0049] In a preferred embodiment, the mass ratio of the separated light fraction to the separated middle fraction is preferably close to 1:1. In this disclosure, by controlling the temperature of the mixture entering the fractionation tower, the amounts of light and heavy fractions can be controlled to be equal or similar. This facilitates allowing these two fractions to enter different radiation sections of a dual-radiation section pyrolysis furnace or half of a single-radiation section pyrolysis furnace during subsequent steam cracking.

[0050] In one implementation, such as Figure 1 As shown, along the height direction of the steam cracking device, the convection section is sequentially provided with a first raw material superheating section 1, a second mixing superheating section 2, a third steam superheating section 6, a fourth mixing superheating section 8, and a fifth mixing superheating section 9, which are independent of each other from top to bottom; the method further includes:

[0051] The wide-fraction feedstock oil is mixed with primary dilution steam to obtain the first mixture.

[0052] The first mixture is fed into the second mixing superheating section 2 for heating; secondary dilution steam is fed into the third steam superheating section 6 for heating; then the heated first mixture and the heated secondary dilution steam are mixed and fed into the fractionation tower 4 for fractionation treatment.

[0053] In this embodiment, the first mixture and the secondary dilution steam are introduced into the convection section of the steam cracking unit for heating, which can increase the temperature of the stream introduced into the fractionation tower and improve the separation efficiency; it can also make full use of the heat of the steam cracking unit itself and improve the heat utilization efficiency.

[0054] In a preferred embodiment, the temperature of the first mixture after heating is 200–400°C; the temperature of the secondary dilution steam after heating is 400–575°C; and the temperature of the preheated wide-fraction feedstock oil is 120–200°C.

[0055] Optionally, the primary dilution steam is primary dilution steam heated to a temperature of 250–450°C by an external heating device outside the convection section or steam cracking unit; optionally, the heat source of the external heating device is medium-pressure steam or other high-temperature heat sources. Specifically, a steam heating section can be added to the convection section to heat the steam, or other waste heat materials can be used to heat the primary dilution steam outside the steam cracking unit.

[0056] In one implementation, such as Figure 1 As shown, the method further includes: heating the light fraction to 550-680°C in the fourth mixing superheating section 8 to obtain the first material to be cracked;

[0057] Optionally, the heated secondary dilution steam from the third steam superheating section 6 is divided into two parts. One part of the heated secondary dilution steam is used as the second part of steam and mixed with the first mixture before entering the fractionation tower 4. The other part of the heated secondary dilution steam is mixed with at least a portion of the middle fraction from the fractionation tower 4 and then entered the fifth mixing superheating section 9 and heated to 400-650°C to obtain the second material to be cracked.

[0058] The first material to be cracked and the optional second material to be cracked are respectively introduced into the radiation section 7 for steam cracking.

[0059] In this embodiment, the first material to be cracked and the optional second material to be cracked are heated to the initial cracking temperature (cross temperature) by the heat of the convection section, and then introduced into the cracking furnace tube of the radiation zone for cracking. This allows different material streams to be cracked to be cracked under suitable cracking conditions.

[0060] Specifically, the conditions for steam cracking of the first and second feed streams can be the same or different, and can be adjusted according to the actual situation. Specifically, the first and second feed streams can be introduced into different radiant furnace tubes in the same furnace chamber of the same cracking furnace, or into radiant furnace tubes in different radiant furnace chambers of the same cracking furnace, or into radiant furnace tubes of different cracking furnaces for cracking.

[0061] Specifically, the conditions for steam cracking of the first and second feed streams in the radiation section in this disclosure can be conventional conditions in the art, and the catalyst can be selected from those known in the art. For example, the COT for cracking the first and second feed streams is 745–880°C, preferably 760–870°C.

[0062] In a preferred embodiment, the weight ratio of the total weight of dilution vapor in the first material to be pyrolyzed to the weight of the feed oil in the first material to be pyrolyzed is 0.4 to 0.1, preferably in the range of 0.45 to 0.65.

[0063] The ratio of the total weight of dilution steam in the second pyrolysis material to the weight of feedstock oil in the second pyrolysis material is 0.5:1, preferably within the range of 0.65 to 0.85. The inventors have discovered that in the overall process flow provided in this disclosure, when the weight ratio of the primary dilution steam introduced into the system to the feedstock oil (corresponding to jet fuel fraction) in the first pyrolysis material and the weight ratio of the secondary dilution steam to the feedstock oil (corresponding to light diesel oil and heavier fractions, when separated) in the second pyrolysis material or the middle fraction meets the above ranges, the dilution ratio of the fractions to steam in the first and second pyrolysis material streams can be kept within a suitable range, resulting in a high olefin yield and easy control.

[0064] In one implementation, such as Figure 1 As shown, the method further includes: allowing the heavy fraction from the fractionating column 4 to enter the buffer tank 12 for buffering before being pumped out by the pump 13;

[0065] The wide-fraction feedstock 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 wide-fraction feedstock oil and the cooled material; optionally, the temperature of the first preheated wide-fraction feedstock oil is 70-120°C; or the crude oil from the storage tank is introduced into the convection section of the steam cracking unit after the first heat exchange in the quench water preheater 16, and the preheated crude oil obtained is used as the first preheated wide-fraction feedstock oil;

[0066] The first preheated wide-fraction feed oil is fed into the desalting preprocessor 15 for desalting pretreatment to obtain desalted wide-fraction feed oil.

[0067] The desalted wide-fraction feedstock oil is fed into the first feedstock preheating section 1 of the steam cracking unit for heating, and then mixed with primary dilution steam to obtain the first mixture.

[0068] This implementation method enables heat exchange between various materials, which not only increases the temperature of the wide-fraction feedstock oil but also cools the liquid-phase heavy fraction in the output system, further improving the overall heat utilization rate of the process.

[0069] In one embodiment, the preheating process of wide-fraction feedstock oil can also be carried out by using the waste heat of the ethylene unit instead of the quench water heat exchange, and then preheating it by exchanging heat with the high-temperature heavy oil obtained from the crude oil cracking process; the crude oil can also be preheated by exchanging heat with the waste heat of the ethylene unit first, then desalting, and then exchanging heat with the high-temperature heavy oil obtained from the crude oil cracking process.

[0070] The process disclosed herein has a high energy utilization rate, fully combining the thermal energy of the ethylene plant with the heating requirements of the process itself, further reducing the energy consumption of the ethylene plant, realizing heat recovery and utilization, and saving investment.

[0071] In one embodiment, the method further includes: dividing the heavy fraction from the buffer tank 12 into three parts, allowing the first part of the heavy fraction to enter a hydrogenation unit for hydrogenation treatment, allowing the second part of the heavy fraction to enter a catalytic cracking unit for catalytic cracking treatment, and allowing the third part of the heavy fraction to be refluxed back into the buffer tank 12.

[0072] In one specific embodiment, the fractionating tower 4 and the buffer tank 12 are arranged in a vertical combination with the fractionating tower above and the buffer tank 12 below, or the bottom of the fractionating tower 4 is used as the buffer tank 12, thus saving space occupied by the device.

[0073] In one specific embodiment, the liquid stream obtained from the fractionation tower 4 can be sent out after heat recovery, thereby improving the overall heat recovery efficiency of the system.

[0074] In one embodiment, the primary dilution steam and the secondary dilution steam are obtained through the following steps: at least a portion of the heavy fraction is fed into a dilution steam generator for processing to obtain dilution steam; a portion of the dilution steam is used as the primary dilution steam, and a portion of the dilution steam is used as the secondary dilution steam.

[0075] Optionally, the method further includes: detecting the temperature of the liquid material in the buffer tank 12 and obtaining a temperature signal; adjusting the reflux rate of the third heavy fraction according to the temperature signal, so that the temperature of the liquid material in the buffer tank 12 is controlled at 150-300°C. Preferably, when the heavy fraction is used to generate dilution vapor, the temperature of the liquid material in the buffer tank 12 is controlled at 190-300°C.

[0076] In a preferred embodiment, the method further includes: subjecting the desalted wide-fraction feedstock oil from the desalting pre-processor 15 to external preheating treatment outside the convection section before entering the fractionation tower 4. The heat source for the external preheating treatment is waste heat material from any unit, and this external preheating treatment is independent of the preheating treatment in the first feedstock superheating section 1. The heat source for the external preheating treatment is waste heat material from any unit. 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 actual conditions.

[0077] The operating temperatures used in this disclosure are all within the normal operating range after pressure equilibrium under conventional operating conditions of the pyrolysis furnace. Optionally, pressure control measures can be added to adjust the pressure related to gasification according to the properties of crude oil and actual cutting needs, thereby controlling the relevant operating temperatures accordingly.

[0078] A second aspect of this disclosure provides a system for cracking a wide-fraction feedstock to produce olefins, such as... Figure 1 As shown, the system includes a fractionation tower 4 and a steam cracking unit. The steam cracking unit includes a convection section and a radiation section 7. Along the height direction of the steam cracking unit, the convection section is located above the radiation section 7.

[0079] Fractionating tower 4 is provided with a wide-range feedstock inlet, a light-range outlet, a middle-range outlet, and a heavy-range outlet; the wide-range feedstock inlet is located at the top of fractionating tower 4, and the inlet pipeline of the wide-range feedstock inlet is also provided with a first part of steam mixing inlet and a second part of steam mixing inlet.

[0080] The radiation section 7 of the steam cracking unit is provided with a first feedstock inlet and an optional second feedstock inlet and a cracking product outlet; the first feedstock inlet is connected to the light fraction outlet of the fractionating tower 4, and the second feedstock inlet is connected to the middle fraction outlet of the fractionating tower 4.

[0081] In one specific embodiment, the radiant section of the steam pyrolysis unit includes a first pyrolysis furnace tube and a second pyrolysis furnace tube, which are independently arranged. The first pyrolysis furnace tube has a raw material inlet to form a first raw material inlet to be pyrolyzed, and the second pyrolysis furnace tube has a raw material inlet to form a second raw material inlet to be pyrolyzed. Optionally, the first pyrolysis furnace tube and the second pyrolysis furnace tube can be radiant furnace tubes in different radiant sections of the same pyrolysis furnace; or radiant furnace tubes in different radiant sections of the same pyrolysis furnace; or radiant furnace tubes from different pyrolysis furnaces, which can be set according to the actual situation.

[0082] In a preferred embodiment, such as Figure 2As shown, a dividing device is provided in the middle of the fractionation tower 4; along the height direction of the fractionation tower 4, the dividing device divides the fractionation tower 4 into an upper tower and a lower tower. The dividing device is provided with a liquid material channel, which only allows the liquid material flow of the upper tower to enter the lower tower and does not allow the gaseous material of the lower tower to enter the upper tower.

[0083] The upper section is a flash distillation tower, and the lower section is a distillation tower with condensation reflux and bottom reboiling functions. The inlet for the wide-fraction feed oil is located at the top of the upper section, and the inlet for the light fraction is located at the top of the upper section. The outlet for the middle fraction is located in the middle of the lower section, and the outlet for the heavy fraction is located at the bottom of the lower section.

[0084] Optionally, a third steam inlet is also provided on the connecting pipeline between the middle fraction outlet of the fractionation tower 4 and the inlet of the second feedstock to be cracked.

[0085] Specifically, there can be one or more gas (vapor) phase outlets in both the upper and lower sections of the tower.

[0086] The specific working principle of the fractionation tower with the special structure disclosed herein includes: a mixture of wide-range feedstock oil and steam enters the upper column through the wide-range feedstock oil inlet at the top of the upper column for flash distillation, resulting in light fractions and flash liquid fractions. The light fractions flow out through the light fraction outlet at the top of the upper column, while the flash liquid fractions flow by gravity into the lower column through the liquid material channel on the separator. The flash liquid fractions are then distilled in the lower column to separate the middle fractions and heavy fractions. The middle fractions are introduced through the middle fraction outlet, and the heavy fractions are drawn out through the heavy fraction outlet, thus achieving the fractionation of wide-range feedstock oil.

[0087] In one implementation, such as Figure 2 As shown, the system may also include an oil refining unit, the feed inlet of which is connected to the middle fraction outlet of the fractionation tower 4.

[0088] In one implementation, such as Figure 1 As shown, along the height direction of the steam cracking unit, the convection section is provided with a first raw material superheating section 1, a second mixing superheating section 2, a third steam superheating section 6, a fourth mixing superheating section 8, and a fifth mixing superheating section 9, which are independent of each other from top to bottom;

[0089] The first feedstock superheating section 1 is provided with a first superheating inlet and a first superheating outlet; the second mixing superheating section 2 is provided with a second superheating inlet and a second superheating outlet; the first superheating outlet and the second superheating inlet are connected through a first pipeline, and a primary dilution steam inlet is also provided on the first pipeline, which forms a first part of the steam mixing inlet; the second superheating outlet is connected to the wide-fraction feedstock oil inlet of the fractionation tower 4, and a superheated secondary dilution steam first inlet is provided on the connecting pipeline between the second superheating outlet and the wide-fraction feedstock oil inlet, which forms a second part of the steam mixing inlet; preferably, a mixer is provided at the superheated secondary dilution steam first inlet;

[0090] The third steam superheating section 6 is equipped with a third superheating inlet and a third superheating outlet; the third superheating inlet is connected to the secondary dilution steam source, and the third superheating outlet is connected to the first inlet of the superheated secondary dilution steam.

[0091] The fourth mixing superheater 8 is provided with a fourth superheat inlet and a fourth superheat outlet; the fifth mixing superheater 9 is provided with a fifth superheat inlet and a fifth superheat outlet; the fourth superheat inlet is connected to the light fraction outlet of the fractionation column 4, and the fourth superheat outlet is connected to the first feedstock inlet to be cracked in the radiant section 7; the fifth superheat inlet is connected to the middle fraction outlet of the fractionation column 4, and a second superheated secondary dilution steam inlet is provided on the connecting pipeline between the fifth superheat inlet and the middle fraction outlet, which forms the third part of the steam mixing inlet; the second superheated secondary dilution steam inlet is connected to the third superheat outlet of the third steam superheating section 6; the fifth heating outlet of the fifth mixing superheater 9 is connected to the second feedstock inlet to be cracked in the radiant section 7.

[0092] Specifically, in this disclosure, the first raw material superheating section 1, the second mixing superheating section 2, the third steam superheating section 6, the fourth mixing superheating section 8, and the fifth mixing superheating section 9 can be different heat exchange tubes in the upper mixing superheating section of the convection section of the same steam cracking device, or heat exchange tubes in the upper mixing superheating section of different steam cracking devices.

[0093] In one specific implementation, such as Figure 1 As shown, a mixer is provided on the first pipeline. The mixer on the first pipeline has a wide-fraction feedstock oil mixing inlet, a primary dilution steam mixing inlet, and a mixture outlet. The wide-fraction feedstock oil mixing inlet is connected to the first superheat outlet of the first feedstock superheating section 1, and the mixture outlet is connected to the second superheat inlet of the second mixing superheating section 2.

[0094] In this embodiment, the mixer is used to mix the raw material with primary dilution steam, which 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.

[0095] 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;

[0096] The buffer tank 12 is provided with at least a heavy fraction buffer inlet, a heavy fraction buffer outlet, a heavy fraction reflux inlet, a steam purging port, and a nitrogen purging port; the pump 13 includes an inlet and an outlet; the desalting pre-processor 15 is provided with a wide-fraction feedstock desalting inlet and a wide-fraction feedstock desalting outlet; the quench water preheater 16 is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a wide-fraction feedstock heat exchange first inlet, and a wide-fraction feedstock heat exchange first outlet;

[0097] The first outlet of the wide-fraction feedstock oil heat exchanger of the quench water preheater 16 is connected to the wide-fraction feedstock oil desalting inlet of the desalting preprocessor 15, and the wide-fraction feedstock oil desalting outlet of the desalting preprocessor 15 is connected to the first superheating inlet of the first feedstock superheating section 1.

[0098] The heavy fraction buffer inlet of buffer tank 12 is connected to the heavy fraction outlet of fractionation tower 4, the heavy fraction buffer outlet is connected to the inlet of pump 13, and the outlet of pump 13 is used to connect to the feed inlet of catalytic cracking unit and / or the feed inlet of hydrotreating unit.

[0099] The level transmitter is connected to the inside of the buffer tank 12 to control the level of liquid inside the buffer tank 12.

[0100] Example 1

[0101] This embodiment adopts Figure 1 The process flow shown uses crude oil with an API value of 37-46 as a wide-range feedstock. The objective of this embodiment is to ensure that as many light components with a boiling point below 450°C as possible enter the cracking furnace for cracking reaction. Specifically, it includes the following steps:

[0102] S1. After the crude oil 101 and the waste heat material 116 pass through the quench water preheater 16, they are preheated (first heat exchange, heated to the desalination temperature of 70-120°C). Then, the heated crude oil 102 is desalted and impurities are removed by the desalination pretreatment unit 15, so that the desalted crude oil 104 is entered into the first raw material preheating section 1 of the convection section and heated to 120-200°C.

[0103] S2. The heated crude oil 105 is mixed with the primary dilution steam 106 (first part of steam) through a mixer and then enters the second mixing superheating section 2 in the convection section to be superheated to 200-400°C. Then, the secondary dilution steam 108 (second part of steam) heated to 450-575°C through the third steam superheating section 6 in the convection section is mixed with the mixture 107 from the second mixing superheating section 2 and then enters the upper section of the fractionation tower as the first mixture.

[0104] The following fractions are separated in fractionation tower 4: light fraction 109 (a mixture of naphtha containing some kerosene and lighter light components with steam), middle fraction 110 (a mixture of diesel vapor phase middle components and steam that are heavier than naphtha containing some kerosene but less than heavy diesel), and heavy fraction 111 (heavy components greater than heavy diesel). The final boiling point of the light fraction is 80–180°C, the initial boiling point of the middle fraction is not higher than the final boiling point of the light fraction, the final boiling point of the middle fraction is 250–430°C, and the initial boiling point of the heavy fraction is not higher than the final boiling point of the middle fraction. The separated fractions may proceed to the following steps as needed, or they may be sent to a refining unit for secondary processing.

[0105] S3. The light fraction 109 obtained after heating in the above steps enters the fourth mixing superheating section 8 in the convection section and is heated to 550-680°C to obtain the first material to be cracked 112 (wherein the weight ratio of the total weight of the primary dilution steam in step S2 to the weight of the feed oil in the first material to be cracked is 0.45-0.65:1); the middle fraction 110 is mixed with another part of the secondary dilution steam 114 (the third part of the steam) heated to 450-575°C by the third steam superheating section 6 in the convection section, and then enters the fifth mixing superheating section 9 in the convection section and is heated to 400-650°C to obtain the second material to be cracked 113 (wherein the weight ratio of the total weight of the secondary dilution steam in step S2 to the weight of the feed oil in the middle fraction is 0.65-0.85:1);

[0106] S4. The two materials to be pyrolyzed, after the above steps, are respectively fed into different radiant furnace tubes in the same furnace chamber of the same pyrolysis furnace, or into radiant furnace tubes in different radiant furnace chambers of the same pyrolysis furnace, or into radiant furnace tubes of different pyrolysis furnaces for pyrolysis.

[0107] S5. The heavy fraction 111 separated by the fractionation tower enters the buffer tank 12 and is then sent out. The liquid phase heavy diesel oil and heavier crude oil components after waste heat utilization are introduced into the refining unit for secondary processing, or into the hydrogenation unit for hydrogenation treatment, or into the dilution steam generator for treatment to obtain dilution steam. The obtained dilution steam can be used as primary dilution steam and secondary dilution steam.

[0108] Example 2

[0109] This embodiment adopts Figure 2 The process flow shown uses crude oil with an API value of 37-46 as a wide-fraction feedstock; the objective of this embodiment is to separate as many components of the crude oil as possible with a boiling point below 450°C. Specifically, it includes the following steps:

[0110] S1. After the crude oil 101 and the waste heat material 116 pass through the quench water preheater 16, they are preheated (first heat exchange, heated to the desalination temperature of 70-120°C). Then, the heated crude oil 102 is desalted and impurities are removed by the desalination pretreatment unit 15, so that the desalted crude oil 104 is entered into the first raw material preheating section 1 of the convection section and heated to 120-200°C.

[0111] S2. After the heated crude oil 105 is mixed with the primary dilution steam 106 (first part of steam) through a mixer, it enters the second mixing superheating section 2 in the convection section and is superheated to 200-400°C. Then, the secondary dilution steam 108 (second part of steam) heated to 450-575°C through the third steam superheating section 6 in the convection section is mixed with the mixture 107 from the second mixing superheating section 2 and enters the upper section of the fractionation tower 4 as the first mixture.

[0112] The following fractions are separated in fractionation tower 4: light fraction 109 (a mixture of naphtha containing some kerosene and lighter light components with steam), middle fraction 110 (a mixture of diesel vapor phase middle components and steam that are heavier than naphtha containing some kerosene but less than heavy diesel), and heavy fraction 111 (heavy components greater than heavy diesel). The final boiling point of the light fraction is 80–180°C, the initial boiling point of the middle fraction is not higher than the final boiling point of the light fraction, the final boiling point of the middle fraction is 250–430°C, and the initial boiling point of the heavy fraction is not higher than the final boiling point of the middle fraction. The separated fractions may proceed to the following steps as needed, or they may be sent to a refining unit for secondary processing.

[0113] S3. The light fraction 109 obtained after heating in the above steps enters the fourth mixing superheating section 8 in the convection section and is heated to 550-680°C to obtain the first material to be cracked 112 (wherein the total weight of the dilution steam in step S2 and the weight ratio of the feed oil in the first material to be cracked is 0.45-0.65:1).

[0114] The middle fraction 110 is cooled to the liquid phase in a cooler, and the heavy fraction obtained after cooling is sent to the refining unit (not shown) for secondary processing.

[0115] S4. The first material to be cracked 112, after the above steps, is fed into the radiant furnace tube for cracking.

[0116] S5. The heavy fraction 111 separated by the fractionation tower enters the buffer tank 12, and then is sent to the refining unit for secondary processing, or introduced into the hydrogenation unit for hydrogenation treatment, or sent to the dilution steam generator for treatment to obtain dilution steam, which may be used as primary dilution steam.

[0117] 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.

[0118] 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.

[0119] 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 by cracking a wide-fraction feedstock containing heavy components, characterized in that, The method includes the following steps: S1. Mix the wide-fraction feedstock oil with the first part of the steam to obtain the first mixture. S2. The first mixture is mixed with the second part of steam and then fed into the fractionation tower (4) for fractionation to obtain light fraction, middle fraction and heavy fraction; S3. The light fraction is heated in the convection section of the steam cracking unit; the heated light fraction is then heated in the radiation section (7) of the steam cracking unit for steam cracking to obtain cracking products containing olefins. The fractionating tower (4) is provided with a dividing device in the middle. Along the height direction of the fractionating tower (4), the dividing device divides the fractionating tower (4) into an upper tower and a lower tower. The dividing device is provided with a liquid material channel. The liquid material channel only allows the liquid material of the upper tower to enter the lower tower and does not allow the gaseous material of the lower tower to enter the upper tower. The method further includes: The first mixture is mixed with the second part of steam and then enters the upper section of the fractionation tower (4) for flash evaporation to separate the light fraction and the flash liquid fraction. The flash liquid phase fraction is introduced into the lower column through the liquid phase material channel of the separator; the flash liquid phase fraction is then subjected to rectification in the lower column to separate the middle fraction and the heavy fraction. Along the height direction of the steam cracking device, the convection section is provided with, from top to bottom, an independent first feed superheating section (1), a second mixing superheating section (2), a third steam superheating section (6), a fourth mixing superheating section (8), and a fifth mixing superheating section (9); the method further includes: The wide-fraction feedstock 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 wide-fraction feedstock oil and the cooling material; the temperature of the first preheated wide-fraction feedstock oil is 70~120℃; or the crude oil from the storage tank is introduced into the convection section of the steam cracking unit after the first heat exchange in the quench water preheater (16) for further heating, and the obtained preheated crude oil is used as the first preheated wide-fraction feedstock oil; The first preheated wide-fraction feedstock oil is fed into the desalting preprocessor (15) for desalting pretreatment to obtain desalted wide-fraction feedstock oil; The desalted wide-fraction feedstock oil is fed into the first feedstock superheating section (1) of the steam cracking unit for heating, and then mixed with primary dilution steam to obtain the first mixture. The first mixture is fed into the second mixing superheating section (2) for heating; the heated secondary dilution steam from the third steam superheating section (6) is divided into two parts, and one part of the heated secondary dilution steam is used as the second part of the steam, which is mixed with the heated first mixture and then fed into the fractionation tower (4) for fractionation; the temperature of the heated first mixture is 200-400°C; the temperature of the heated secondary dilution steam is 400-575°C; The light fraction is heated to 550-680°C in the fourth mixing superheating section (8) to obtain the first material to be cracked; another part of the heated secondary dilution steam is mixed with at least part of the middle fraction from the fractionation tower (4) and then heated to 400-650°C in the fifth mixing superheating section (9) to obtain the second material to be cracked. The first material to be cracked and the second material to be cracked are respectively introduced into the radiation section (7) for steam cracking.

2. The method according to claim 1, characterized in that, The final boiling point of the light fraction is 80~180℃; The initial boiling point of the middle fraction is not higher than the final boiling point of the light fraction, and the final boiling point of the middle fraction is 250~430℃. The initial boiling point of the heavy fraction is not higher than the final boiling point of the middle fraction; The wide-fraction feedstock contains at least components with a boiling point of 500°C or higher, and the content of heavy components in the wide-fraction feedstock is 5-50% by weight, based on the total weight of the feedstock. The wide-fraction feedstock containing heavy components is crude oil or condensate oil containing heavy components.

3. The method according to claim 1, characterized in that, The method further includes: mixing all of the middle fraction with the superheated third portion of steam and then heating it in the convection section of a steam cracking unit to obtain a heated first mixture of middle fractions, and then allowing the heated first mixture of middle fractions to enter the radiation section (7) of the steam cracking unit for steam cracking; or The middle fraction is divided into two parts. The first part of the middle fraction is mixed with the superheated third part of steam and then heated in the convection section of the steam cracking unit to obtain a heated second mixture of middle fraction. The heated second mixture of middle fraction is then fed into the radiation section (7) of the steam cracking unit for steam cracking, and the second part of the middle fraction is fed into the refining unit for further processing.

4. The method according to claim 3, characterized in that, Before the middle fraction is fed into the refining unit for further processing, the middle fraction and the wide-range feed oil to be preheated are introduced into the cooler for heat exchange to obtain the preheated wide-range feed oil and the cooled liquid middle fraction; the cooled liquid middle fraction is then fed into the refining unit.

5. The method according to claim 1, characterized in that, The lower section of the column is a distillation column with condensation reflux and bottom reboiling functions.

6. The method according to claim 1, characterized in that, The primary dilution steam is primary dilution steam heated to a temperature of 250~450°C by an external heating device outside the convection section or steam cracking device; the heat source of the external heating device is medium-pressure steam or other high-temperature heat source.

7. The method according to claim 6, characterized in that, The total weight of dilution vapor in the first material to be pyrolyzed is 0.4 to 1 compared with the weight of the feed oil in the first material to be pyrolyzed. The ratio of the total weight of dilution vapor in the second material to be cracked to the weight of the feed oil in the second material to be cracked is 0.5:

1.

8. The method according to claim 6, characterized in that, The total weight of dilution vapor in the first material to be pyrolyzed is 0.45 to 0.65 of the weight of the feed oil in the first material to be pyrolyzed. The ratio of the total weight of dilution steam in the second material to be cracked to the weight of the feed oil in the second material to be cracked is 0.65 to 0.

85.

9. The method according to claim 1, characterized in that, The method also includes: The heavy fraction from the fractionating column (4) is buffered in the buffer tank (12) and then pumped out by the pump (13); The method further includes: dividing the heavy fraction from the buffer tank (12) into three parts, allowing the first part of the heavy fraction to enter the hydrogenation unit for hydrogenation treatment, allowing the second part of the heavy fraction to enter the catalytic cracking unit for catalytic cracking treatment, and allowing the third part of the heavy fraction to be refluxed back into the buffer tank (12). The fractionating tower (4) and the buffer tank (12) are arranged in an upper and lower configuration with the fractionating tower above and the buffer tank (12) below, or the bottom of the fractionating tower (4) is used as the buffer tank (12).

10. The method according to claim 9, characterized in that, The method also includes: At least a portion of the heavy fraction is fed into a dilution steam generator for processing to obtain dilution steam; a portion of the generated dilution steam is used as the primary dilution steam, and a portion of the generated dilution steam is used as the secondary dilution steam. The method further includes: subjecting the desalted wide-fraction feedstock oil from the desalting pre-processor (15) to external preheating treatment outside the convection section before entering the fractionation tower (4), wherein the heat source for the external preheating treatment is waste heat material from any device, and the external preheating treatment is independent of the preheating treatment in the first feedstock superheating section (1).

11. A system for the method of cracking a wide-fraction feedstock containing heavy components to produce olefins as described in claim 1, characterized in that, The system includes a fractionation tower (4) and a steam cracking device, the steam cracking device including a convection section and a radiation section (7), the convection section being located above the radiation section (7) along the height direction of the steam cracking device; The fractionation tower (4) is provided with a wide-fraction feedstock inlet, a light fraction outlet, a middle fraction outlet and a heavy fraction outlet; the wide-fraction feedstock inlet is located at the top of the fractionation tower (4), and a first part of the steam mixing inlet and a second part of the steam mixing inlet are also provided on the inlet pipeline of the wide-fraction feedstock inlet; The radiation section (7) of the steam cracking device is provided with a first feedstock inlet, a second feedstock inlet, and a cracking product outlet; the first feedstock inlet is connected to the light fraction outlet of the fractionating tower (4), and the second feedstock inlet is connected to the middle fraction outlet of the fractionating tower (4); The fractionation tower (4) is provided with a separation device in the middle; along the height direction of the fractionation tower (4), the separation device divides the fractionation tower (4) into an upper tower and a lower tower. The separation device is provided with a liquid material channel, which only allows the liquid material flow of the upper tower to enter the lower tower and does not allow the gaseous material of the lower tower to enter the upper tower. The upper section of the column is a flash distillation column, and the lower section of the column is a distillation column with condensation reflux and bottom reboiling functions. The inlet of the wide-fraction feed oil is located at the upper part of the upper section of the column, and the outlet of the light fraction is located at the top of the upper section of the column. The outlet of the middle fraction is located in the middle of the lower section of the column, and the outlet of the heavy fraction is located at the bottom of the lower section of the column.

12. The system according to claim 11, characterized in that, A third steam inlet is also provided on the connecting pipeline between the middle fraction outlet of the fractionation tower (4) and the inlet of the second raw material to be cracked.

13. The system according to claim 11, characterized in that, Along the height direction of the steam cracking device, the convection section is provided with a first raw material superheating section (1), a second mixing superheating section (2), a third steam superheating section (6), a fourth mixing superheating section (8) and a fifth mixing superheating section (9) that are independent of each other from top to bottom. The first raw material superheating section (1) is provided with a first superheating inlet and a first superheating outlet; the second mixing superheating section (2) is provided with a second superheating inlet and a second superheating outlet; the first superheating outlet and the second superheating inlet are connected by a first pipeline, and a primary dilution steam inlet is also provided on the first pipeline, the primary dilution steam inlet forming the first partial steam mixing inlet; the second superheating outlet is connected to the wide-fraction raw material oil inlet of the fractionation tower (4), and a superheated secondary dilution steam first inlet is provided on the connecting pipeline between the second superheating outlet and the wide-fraction raw material oil inlet, the superheated secondary dilution steam first inlet forming the second partial steam mixing inlet; a mixer is provided at the superheated secondary dilution steam first inlet; The third steam superheating section (6) is provided with a third superheating inlet and a third superheating outlet; the third superheating inlet is connected to the secondary dilution steam source, and the third superheating outlet is connected to the first inlet of the superheated secondary dilution steam. The fourth mixing superheating section (8) is provided with a fourth superheating inlet and a fourth superheating outlet; the fifth mixing superheating section (9) is provided with a fifth superheating inlet and a fifth superheating outlet; the fourth superheating inlet is connected to the light fraction outlet of the fractionating tower (4), and the fourth superheating outlet is connected to the first feedstock inlet to be cracked in the radiation section (7); the fifth superheating inlet is connected to the middle fraction outlet of the fractionating tower (4), and a second superheated secondary dilution steam inlet is provided on the connecting pipeline between the fifth superheating inlet and the middle fraction outlet, which forms the third part of the steam mixing inlet; the second superheated secondary dilution steam inlet is connected to the third superheating outlet of the third steam superheating section (6); the fifth heating outlet of the fifth mixing superheating section (9) is connected to the second feedstock inlet to be cracked in the radiation section (7).

14. The system according to claim 13, characterized in that, The first pipeline is equipped with a mixer, which has a wide-fraction feedstock oil mixing inlet, a primary dilution steam mixing inlet, and a mixture outlet; the wide-fraction feedstock oil mixing inlet is connected to the first superheat outlet of the first feedstock superheating section (1), and the mixture outlet is connected to the second superheat inlet of the second mixing superheating section (2); 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 heavy fraction buffer inlet, a heavy fraction buffer outlet, a heavy fraction 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 wide-fraction feedstock oil desalting inlet and a wide-fraction feedstock oil desalting outlet; the quench water preheater (16) is provided with a quench water heat exchange inlet, a quench water heat exchange outlet, a wide-fraction feedstock oil heat exchange first inlet, and a wide-fraction feedstock oil heat exchange first outlet; The first outlet of the wide-fraction feedstock oil heat exchanger of the quench water preheater (16) is connected to the wide-fraction feedstock oil desalting inlet of the desalting preprocessor (15), and the wide-fraction feedstock oil desalting outlet of the desalting preprocessor (15) is connected to the first superheating inlet of the first feedstock superheating section (1). The heavy fraction buffer inlet of the buffer tank (12) is connected to the heavy fraction outlet of the fractionation tower (4), the heavy fraction buffer outlet is connected to the input port of the pump (13), and the output port 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. 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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