A process and system for the production of olefins from heavy hydrocarbons

Abstract

The present disclosure relates to a method and system for producing olefins by cracking heavy hydrocarbons, which comprises the following steps: S1, entering a gas-liquid separator for gas-liquid separation to obtain a first gas phase material and a first liquid phase material; and in the process of separation, introducing a separation aid into the gas-liquid separator to contact with the first gas phase material in countercurrent, so that the heavy components carried in the gas phase material are washed or condensed to obtain a second gas phase material; S2, making the second gas phase material enter the radiant section of a steam cracking furnace for cracking to obtain a cracking product containing olefins. The above technical solution can realize the production of olefins to a greater extent by a shorter process and smaller energy consumption.

Description

Technical Field

[0001] This disclosure relates to the field of petrochemical technology, and more specifically, to a method and system for producing olefins by cracking heavy hydrocarbons. Background Technology

[0002] With economic development, the demand for low-carbon olefin organic chemical raw materials has been increasing year by year. Although the production scale of low-carbon olefins has also been growing annually, it still cannot meet the ever-increasing production demand. In 2019, ethylene production capacity exceeded 30 million tons, an increase of more than 15% compared to 2018. However, the equivalent demand for ethylene in 2019 exceeded 45 million tons, still unable to meet market demand. In addition, in recent years, due to the impact of cheap raw materials and coal chemical processes, the traditional naphtha-based process for producing low-carbon olefins has encountered problems such as high raw material costs and lack of competitiveness. Therefore, in order to cope with the impact of market competition, expanding the raw material sources of ethylene cracking units, using crude oil as a raw material for steam cracking, reducing raw material costs, breaking free from the constraints of raw material varieties, and improving production flexibility have become effective means for traditional ethylene enterprises to reduce costs and increase efficiency.

[0003] Compared with traditional cracking feedstocks, crude oil used as feedstock in steam cracking furnaces has problems such as high final boiling point (greater than 540℃), high gum content, difficulty in vaporization, and easy coking. Therefore, corresponding treatments and improvements need to be made in the design of cracking furnaces and production processes to adapt to the characteristics of crude oil.

[0004] CN111196936A discloses a combined processing method and apparatus for producing olefins from heavy hydrocarbons through cracking. The method first employs pretreatment such as desalting and dehydration to remove impurities, then feeds the material into the ethylene cracking convection section for heating. The heated feed is then sent to a gas-liquid separator, where lighter diesel and even lighter components are separated and sent to the convection and radiant sections for steam cracking to produce olefins. The liquid phase from the gas-liquid separator contains components such as atmospheric residue oil and is sent to a hydrogenation unit for further processing before being returned to the convection and radiant sections. In this method, preheated crude oil is directly fed to the gas-liquid separator. Due to the limitation of the preheating temperature, the first part after flash evaporation has relatively few components. To improve the utilization rate of crude oil, the heavy components are hydrogenated before gas-liquid separation. The separated gas phase is further separated to obtain light naphtha, which is fed into the ethylene cracking furnace as feedstock. The separated heavy naphtha, kerosene, and other components unsuitable for cracking are sent out as byproducts. However, the liquid phase is too heavy for cracking, leading to coking problems, and the process is too complex.

[0005] CN100587030A discloses a method for feeding or cracking a heavy hydrocarbon feedstock containing non-volatile hydrocarbons, comprising: heating the heavy hydrocarbon feedstock; mixing the heavy hydrocarbon feedstock with a fluid and / or a first dilution vapor stream to form a mixture; flashing the mixture to form a vapor phase and a liquid phase; and varying the amount of the fluid and / or first dilution vapor stream mixed with the heavy hydrocarbon feedstock according to at least one selected operating parameter of the method, such as the temperature of the flash stream before entering the flash tank. CN100564484A discloses a method for cracking heavy hydrocarbons, comprising heating the heavy hydrocarbon feedstock; mixing the heavy hydrocarbon feedstock with a fluid and / or a primary dilution vapor stream to form a mixture; flashing the mixture to form a vapor phase and a liquid phase; separating and cracking the vapor phase; and cooling the product discharge in a transfer line exchanger, wherein the amount of the fluid and / or primary dilution vapor stream mixed with the heavy hydrocarbon feedstock is varied according to at least one selected operating parameter of the method (e.g., the temperature of the flash stream before entering the flash / separator vessel). CN102057018A discloses a method and apparatus for cracking liquid hydrocarbon feedstock, using a gas-liquid separator to process a heated gas-liquid mixture to provide a top distillate with reduced residual oil content. The hot liquid bottom stream from the separator is heat-exchanged with the cold hydrocarbon feedstock for cracking to provide a cooled liquid bottom stream and a preheated feedstock. At least a portion of the preheated feedstock is directed to the convection section of a pyrolysis furnace for additional heating and subsequent cracking.

[0006] 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, are superheated in the convection section, and then enter the radiant section for cracking. The heavy components are sent to an atmospheric pressure tower and / or a vacuum tower for further separation. 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 to separate the 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. The evaporation units of these two patents use stripping towers containing packing or trays, with the upper evaporation zone containing a gas-liquid separator to achieve gas-liquid separation.

[0007] CN109694730A discloses a method and apparatus for preparing low-carbon olefins by cracking heavy hydrocarbons. The method uses a cyclone separator to separate crude oil into gas and liquid phases, and then cracks the gas phase. This method can reduce coking and blockage in the radiation section and quench section of the cracking furnace and reduce operating costs. However, the method does not describe in detail the control measures for gas-liquid separation.

[0008] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0009] Existing technologies disclose various methods to control the constant flash vaporization rate and use special flash evaporation equipment to achieve as much flash evaporation as possible. However, they do not describe how to achieve a low level of entrainment of heavy components and impurities. Moreover, the existing technologies for controlling the constant vaporization rate of flash tanks are all quite complex and cannot solve the problem of heavy components and impurities being entrained in the pyrolysis furnace, leading to coking. Instead, they may further shorten the operating cycle of the pyrolysis furnace. Summary of the Invention

[0010] The purpose of this disclosure is to provide a method and system for producing olefins from heavy hydrocarbons through cracking. This method simplifies the atmospheric and vacuum distillation unit in traditional methods and systems, and features a simple and efficient control scheme. It can effectively solve the problem of entrainment of heavy components and impurities during gas-liquid separation, enable long-cycle operation of the cracking furnace, and further reduce the energy consumption of ethylene plants.

[0011] The first aspect of this disclosure provides a method for producing olefins by cracking heavy hydrocarbons, the method comprising the following steps:

[0012] S1. Heavy hydrocarbons are introduced into a gas-liquid separator for gas-liquid separation to obtain a first gas phase material and a first liquid phase material. During the separation process, a separation aid is introduced into the gas-liquid separator to contact the first gas phase material in a countercurrent manner, so that the heavy components carried in the first gas phase material are washed or condensed to obtain a second gas phase material.

[0013] S2. At least a portion of the second gaseous material is introduced into the radiation section of the steam cracking furnace for cracking to obtain cracking products containing olefins.

[0014] The heavy hydrocarbons described in this disclosure include wide-range mixed hydrocarbons with a final boiling point of 540°C or higher. For example, the heavy hydrocarbons may be heavy hydrocarbons with an initial boiling point of 15°C and a final boiling point of 750°C or higher, or hydrocarbon mixtures containing components that are prone to coking under cracking furnace operating conditions.

[0015] Optionally, step S1 includes the following steps:

[0016] The heavy hydrocarbon is first heated, and the first heated heavy hydrocarbon is first mixed with primary dilution steam to obtain a first mixture.

[0017] The first mixture is subjected to a second heating and then mixed with superheated secondary dilution steam to obtain a second mixture.

[0018] The second mixture is then fed into a gas-liquid separator for gas-liquid separation.

[0019] Optionally, the weight ratio of the heavy hydrocarbon to the primary dilution vapor is 1:(0.1-0.5), preferably 1:(0.2-0.4);

[0020] Optionally, the temperature of the first mixture is 150-350°C, preferably 190-300°C;

[0021] Optionally, the heavy hydrocarbon is a light, wide-fraction crude oil; preferably, the API value of the light, wide-fraction crude oil is not less than 35.

[0022] Optionally, the temperature of the first mixture after the second heating is below 400°C, preferably in the range of 250-350°C;

[0023] Optionally, the temperature of the superheated secondary dilution steam is 400-630°C, preferably 450-600°C;

[0024] Optionally, the weight ratio of the heavy hydrocarbon to the superheated secondary dilution steam is 1:(0.2-0.8), preferably 1:(0.3-0.65).

[0025] Optionally, in step S2, the second gaseous material includes carried vapor and light components in the heavy hydrocarbon, wherein the final boiling point of the light components is below 540°C, and the initial boiling point of the heavy components is not higher than the final boiling point of the light components.

[0026] Optionally, the separation aid is selected from one or two of water and liquid hydrocarbons;

[0027] Optionally, the weight ratio of the heavy hydrocarbon to the water is 1:(0.01-0.2), preferably 1:(0.05-0.15); or, the weight ratio of the heavy hydrocarbon to the liquid hydrocarbon is 1:(0.01-0.2), preferably 1:(0.05-0.15).

[0028] Optionally, the temperature of the second gaseous material is 240-420°C, preferably 290-380°C;

[0029] Optionally, the final boiling point of the liquid hydrocarbon is lower than that of the heavy hydrocarbon; preferably, the final boiling point of the liquid hydrocarbon is any value between 200-540°C, more preferably, the final boiling point of the liquid hydrocarbon is any value between 250-450°C, and even more preferably, the final boiling point of the liquid hydrocarbon is any value between 300-400°C.

[0030] Optionally, the method further includes: the separation aid is introduced in a manner selected from at least one of the following: along the axial direction of the gas-liquid separator, the water is introduced above the liquid hydrocarbon is introduced; or along the axial direction of the gas-liquid separator, the water is introduced below the liquid hydrocarbon is introduced; or along the axial direction of the gas-liquid separator, the water and liquid hydrocarbon are located on the same plane.

[0031] Optionally, the method further includes: performing online or periodic offline analysis on target parameters of the heavy hydrocarbons before they are fed into the cracking furnace; optionally, the target parameters include density, distillation range, impurity type and content; optionally, the impurities include one or more of gums, asphaltenes, metals, sulfur, oxygen, nitrogen, and heavy components; and

[0032] The target parameters of the gaseous material from the gas-liquid separator are analyzed online or periodically offline. Optionally, the target parameters include the type and content of impurities. Optionally, the impurities include one or more of the following: colloids, asphaltenes, metallic impurities, sulfur, oxygen, nitrogen, and heavy components; and...

[0033] A predetermined amount of the separation aid to be introduced into the gas-liquid separator is determined; the separation aid is introduced into the gas-liquid separator using the predetermined amount; and then, during the gas-liquid separation process, the amount of the separation aid introduced is adjusted according to the target parameters of the gas phase material obtained from online monitoring or offline analysis.

[0034] Optionally, the steam cracking furnace includes at least a raw material heating section, a first mixing superheating section, an optional dilution steam superheating section, a second mixing superheating section, and a radiation section;

[0035] Optionally, the method further includes:

[0036] The first mixture is introduced into a second convection section for second heating, and then mixed with superheated secondary dilution steam obtained after superheating in the dilution steam superheating section; and

[0037] The gaseous material from the gas-liquid separator is fed into the second mixing and superheating section for the third heating, and then into the radiation section of the steam cracking furnace for steam cracking.

[0038] Optionally, the method further includes: introducing the liquid phase material from the gas-liquid separator into a buffer tank for buffering and then drawing it out by a pump; optionally, allowing at least a portion of the liquid phase material from the pump to flow back to the buffer tank;

[0039] Optionally, the method further includes: introducing heavy hydrocarbons from the storage tank into an electrostatic desalting unit for desalting treatment, and then introducing them into the raw material heating section.

[0040] The second aspect of this disclosure also discloses a system for producing olefins by cracking heavy hydrocarbons, characterized in that the system includes a steam cracking furnace and a gas-liquid separator; the steam cracking furnace includes a convection section and a radiation section arranged from top to bottom;

[0041] The gas-liquid separator is configured to perform gas-liquid separation on the heavy hydrocarbon to obtain a first gas phase material and a first liquid phase material.

[0042] The gas-liquid separator includes a separation aid inlet, wherein the separation aid inlet is configured to introduce the separation aid into the gas-liquid separator during the separation process to contact the first gas phase material in a countercurrent manner, thereby obtaining a second gas phase material;

[0043] The radiant section is configured to allow at least a portion of the second gaseous material to enter the radiant section of the steam cracking furnace for cracking, yielding cracking products containing olefins.

[0044] Optionally, the convection section includes a heavy hydrocarbon heating inlet, a heavy hydrocarbon heating outlet, a gaseous material heating inlet, and a gaseous material heating outlet; wherein the heavy hydrocarbon heating inlet introduces heavy hydrocarbons.

[0045] The radiation section includes a pyrolysis inlet and a pyrolysis product outlet;

[0046] The gas-liquid separator includes a gas-liquid separation inlet, a separation aid inlet, a second gas phase material outlet, and a liquid phase material outlet.

[0047] The gas-liquid separation inlet is connected to the heavy hydrocarbon heating outlet of the convection section, and the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section; the gas phase material heating outlet of the convection section is connected to the pyrolysis inlet of the radiation section.

[0048] Optionally, the convection section of the steam cracking furnace includes, from top to bottom, an independent raw material heating section, a first mixing superheating section, a dilution steam superheating section, and a second mixing superheating section;

[0049] The raw material heating section is provided with a first heating inlet and a first heating outlet; the first heating inlet is formed as the heavy hydrocarbon heating inlet of the convection section;

[0050] Optionally, the first mixing superheating section is provided with a second heating inlet and a second heating outlet; the second heating inlet is connected to the first heating outlet of the raw material heating section through the first pipeline, and a primary dilution steam inlet is provided on the first pipeline; the second heating outlet is connected to the gas-liquid separation inlet of the gas-liquid separator through the second pipeline; and a secondary dilution steam inlet is provided on the second pipeline, with the primary dilution steam inlet located upstream of the secondary dilution steam inlet along the material flow direction; the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section;

[0051] Optionally, the separation aid inlet includes multiple inlets, wherein at least one separation aid inlet is a water inlet and at least one separation aid inlet is a liquid hydrocarbon inlet;

[0052] Optionally, the dilution steam superheating section is provided with a third heating inlet and a third heating outlet. The third heating inlet is connected to the dilution steam source, and the third heating outlet is connected to the second pipeline, with the connection position forming the superheated secondary dilution steam outlet.

[0053] Optionally, the second mixing superheating section is provided with a fourth heating inlet and a fourth heating outlet, wherein the fourth heating inlet is formed as the heating inlet for the gaseous material and the fourth heating outlet is formed as the heating outlet for the gaseous material.

[0054] Optionally, the system further includes a first mixer, a second mixer, and an electro-desalination device. The first mixer is disposed on the first pipeline and includes a first mixing inlet, a second mixing inlet, and a first mixing outlet. The first mixing inlet is connected to the first heating outlet of the raw material heating section, and the second mixing inlet is formed as the inlet of the primary dilution steam for introducing primary dilution steam. The first mixing outlet is connected to the second heating inlet of the first mixing superheating section.

[0055] The second mixer is disposed on the second pipeline; the second mixer includes a third mixing inlet, a fourth mixing inlet, and a second mixing outlet, the third mixing inlet being connected to the second heating outlet of the first mixing superheated section, the fourth mixing inlet being formed as the secondary dilution steam for introducing secondary dilution steam; the second mixing outlet being connected to the gas-liquid separation inlet of the gas-liquid separator;

[0056] The electro-desalting device includes a desalting inlet and a desalting outlet; the desalting inlet is used to introduce crude oil, and the desalting outlet is connected to the first heating inlet of the raw material heating section through a heavy hydrocarbon feed pipeline.

[0057] Optionally, along the axial direction of the gas-liquid separator, the water inlet is located above the gas-liquid separation inlet; preferably, the water inlet is located 0.1-10m above the gas-liquid separation inlet; more preferably, the water inlet is located 1-5m above the gas-liquid separation inlet.

[0058] Optionally, along the axial direction of the gas-liquid separator, the water inlet is located above the liquid hydrocarbon inlet; or the water inlet is located below the liquid hydrocarbon inlet; or the water inlet and the liquid hydrocarbon inlet are basically located on the same plane.

[0059] The water inlet inlet is equipped with a first control valve for the separation aid. Optionally, the first control valve references a signal from a first component analyzer and is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator, to control the amount of separation aid introduced by monitoring the target parameters of the gaseous material. Optionally, the first control valve references a signal from a second component analyzer, which is connected to the heavy hydrocarbon feed pipeline, to control the amount of separation aid introduced by monitoring the target parameters of the heavy hydrocarbon. Optionally, the first control valve simultaneously references signals from both the first and second sets of analyzers to control the amount of separation aid introduced; and / or,

[0060] A second control valve for the separation aid is provided on the inlet pipeline of the liquid hydrocarbon inlet. The second control valve references a signal from a first component analyzer, which is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the gas phase material. Optionally, the second control valve references a signal from a second component analyzer, which is connected to the heavy hydrocarbon feed pipeline, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the heavy hydrocarbon. Optionally, the second control valve simultaneously references signals from both the first and second sets of analyzers to control the introduction amount of the separation aid.

[0061] Optionally, the control signal referenced by the first control valve comes from at least one of the following instruments: a first flow meter, a second flow meter, a third flow meter, a fourth flow meter, a fifth flow meter, a sixth flow meter, and a seventh flow meter;

[0062] The first flow meter is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator and is used to measure the flow rate of the first gaseous material outlet; the second flow meter is connected to the inlet pipeline of the water inlet and is used to measure the flow rate of water; the third flow meter is connected to the inlet pipeline of the liquid hydrocarbon inlet and is used to measure the flow rate of the liquid hydrocarbon; the fourth flow meter is connected to the outlet pipeline of the first liquid material of the gas-liquid separator and is used to measure the flow rate of the first liquid material; the fifth flow meter is connected to the primary dilution steam feed pipeline and is used to measure the primary dilution steam quantity; the sixth flow meter is connected to the secondary dilution steam feed pipeline and is used to measure the secondary dilution steam quantity; the seventh flow meter is connected to the heavy hydrocarbon feed pipeline and is used to measure the heavy hydrocarbon feed quantity.

[0063] Optionally, by monitoring the control signal, the hydrocarbon content in the first gas phase material outlet and the proportion of the hydrocarbon content in the first gas phase material outlet to the total heavy hydrocarbons (net hydrocarbon gasification rate) can be calculated. The amount of separation aid (water, or hydrocarbons or a combination thereof) introduced can be controlled by monitoring the hydrocarbon content or net hydrocarbon gasification rate in the first gas phase material outlet.

[0064] Optionally, the system further includes a buffer tank and a pump. The buffer tank includes a buffer inlet, a buffer outlet, and a reflux inlet. The buffer inlet is connected to the liquid phase material outlet of the gas-liquid separator, and the buffer outlet is connected to the inlet of the pump. The outlet of the pump is connected to the reflux inlet of the optional buffer tank.

[0065] The method provided in this disclosure, compared with conventional methods, has at least the following advantages through the above technical solution:

[0066] (1) This disclosure utilizes an optimized combination of three elements: heavy hydrocarbon feed, gas-liquid separation, and injection of separation aid into the gas phase material obtained from gas-liquid separation. In this case, the injection of separation aid (liquid hydrocarbon or water) into the gas phase space of the gas-liquid separator and its countercurrent contact with the gas phase material can control the entrainment of heavy components and impurities in the gas phase mixture entering the radiation section, thereby avoiding rapid coking in the radiation section.

[0067] (2) The gas-liquid separation control system provided in this disclosure, which integrates the separation aid and the gas phase material in countercurrent contact in the gas-liquid separator, is simpler and more efficient than other disclosed flash evaporation control schemes.

[0068] (3) The system for producing olefins by cracking heavy hydrocarbons provided in this disclosure can be used for the direct steam cracking of wide-range crude oil to produce ethylene, replacing the atmospheric and vacuum towers in the atmospheric and vacuum units of oil refining units, greatly reducing investment and operating costs, and making the control scheme and process simpler. It can make greater use of the experience of atmospheric and vacuum heaters in oil refining units, the experience of atmospheric and vacuum units and existing steam cracking technology to produce olefins. The technology is mature and the operation is simple, especially suitable for the direct steam cracking of paraffinic light crude oil.

[0069] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0070] 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:

[0071] Figure 1 This is an exemplary flow chart of heavy hydrocarbon cracking to produce olefins provided in this disclosure.

[0072] Explanation of reference numerals in the attached figures

[0073] 1-Raw material heating section; 2-First mixing superheating section; 3-Dilution steam superheating section; 4-Second mixing superheating section; 5-Radiation section; 6-Gas-liquid separator; 7-First mixer; 8-Second mixer; 9-Heavy component buffer tank; 10-Pump; 11-Desalination pre-processor. Detailed Implementation

[0074] 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.

[0075] 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.

[0076] In this disclosure, terms such as "primary dilution steam" and "secondary dilution 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.

[0077] All devices used in this disclosure are conventionally chosen structures in the art.

[0078] Through extensive research, the inventors of this disclosure have discovered that the method for direct steam cracking of heavy hydrocarbons should pay more attention to the content of heavy components and impurities entrained in the gas phase during the gas-liquid separation process, as well as whether the obtained gas phase meets the requirements for steam cracking.

[0079] This disclosure provides a method and system for producing olefins from heavy hydrocarbons through cracking. The method has a simple process and can not only achieve high olefin production, but also effectively prevent impurities such as gums and asphaltenes from being carried to the gas phase material obtained from gas-liquid separation by introducing a separation aid in the gas-liquid separator 6, thus preventing coking in the radiation section. This provides a feasible solution for the direct cracking of heavy hydrocarbons to produce olefins. Extensive related experiments have shown that the method provided in this disclosure can prevent heavy components from being carried to the convection section and causing coking there, while also extending the cracking furnace operating cycle by more than 10%, and even more than 15%.

[0080] The first aspect of this disclosure provides a method for cracking heavy hydrocarbons to produce olefins, such as... Figure 1 As shown, the method includes the following steps:

[0081] S1. Heavy hydrocarbons are introduced into gas-liquid separator 6 for gas-liquid separation to obtain a first gas phase material and a first liquid phase material; and during the separation process, a separation aid is introduced into the gas-liquid separator 6 to contact the first gas phase material in a countercurrent manner so that the heavy components carried in the first gas phase material are washed or condensed to obtain a second gas phase material.

[0082] S2. At least a portion of the second gaseous material is fed into the radiation section 5 of the steam cracking furnace for cracking to obtain cracking products containing olefins.

[0083] The heavy hydrocarbons described in this disclosure include wide-range mixed hydrocarbons with a final boiling point of 540°C or higher. For example, the heavy hydrocarbons may be heavy hydrocarbons with an initial boiling point of 15°C and a final boiling point of 750°C or higher, or hydrocarbon mixtures containing components that are prone to coking under cracking furnace operating conditions.

[0084] The heavy hydrocarbon feedstocks used in this disclosure include one or more of the following: paraffin-based crude oil, intermediate-based crude oil, naphthenic crude oil, condensate, gasoline, kerosene, diesel, tail oil, fuel oil, reformate, etc., processed by refinery units such as atmospheric and vacuum distillation, reforming, catalytic cracking, and coking.

[0085] This disclosure utilizes an optimized combination of four elements: a special crude oil preheating process in the convection section of a cracking furnace, gas-liquid separation, and the injection of a separation aid (liquid hydrocarbons or water) into the gas phase obtained from gas-liquid separation. Injecting the separation aid (liquid hydrocarbons or water) into the gas phase space of the gas-liquid separator controls the entrainment of heavy components and impurities, preventing rapid coking in the radiation section. Furthermore, the inventors have surprisingly discovered that without complex control over the temperature and pressure of the mixture entering the gas-liquid separator, controlling the gas phase material after gas-liquid separation allows for a simpler, more direct, and efficient way to prevent coking in the radiation section, enabling long-term operation.

[0086] In one embodiment, step S1 includes the following steps:

[0087] The heavy hydrocarbon is first heated, and the first heated heavy hydrocarbon is first mixed with primary dilution steam to obtain a first mixture.

[0088] The first mixture is subjected to a second heating and then mixed with superheated secondary dilution steam to obtain a second mixture.

[0089] The second mixture is then fed into the gas-liquid separator 6 for gas-liquid separation.

[0090] In one embodiment, optionally, the weight ratio of the heavy hydrocarbon to the primary dilution vapor is 1:(0.1-0.5), preferably 1:(0.2-0.4);

[0091] Optionally, the temperature of the heavy hydrocarbon after the first heating is 90-250°C, preferably 120-200°C.

[0092] Optionally, the temperature of the first mixture is 150-350°C, preferably 190-300°C;

[0093] Optionally, the temperature of the first mixture after the second heating is below 400°C, preferably in the range of 250-350°C;

[0094] Optionally, the temperature of the superheated secondary dilution steam is 400-630°C, preferably 450-600°C;

[0095] Optionally, the weight ratio of the heavy hydrocarbon to the superheated secondary dilution steam is 1:(0.2-0.8), preferably 1:(0.3-0.65).

[0096] In one embodiment, the heavy hydrocarbon is a light, wide-fraction crude oil. Preferably, the API value of the light, wide-fraction crude oil is not less than 35; more preferably, the API value of the light, wide-fraction crude oil is 40, and the final boiling point of the light, wide-fraction crude oil is above 700°C.

[0097] In one embodiment, the primary dilution steam can be either superheated primary dilution steam or unsuperheated primary dilution steam.

[0098] In one embodiment, in step S2, the second gaseous material includes carried vapor and light components from the heavy hydrocarbons, the liquid material includes the heavy components from the heavy hydrocarbons, the final boiling point of the light components is below 540°C, and the initial boiling point of the heavy components is not higher than the final boiling point of the light components. 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 separated fractions according to actual production needs.

[0099] In one specific embodiment, the light components obtained from gas-liquid separation include light or heavy naphtha fractions, jet fuel fractions, light diesel oil fractions, and heavy diesel oil fractions; the heavy components include components heavier than the heavy diesel oil fractions.

[0100] In a preferred embodiment, the separation aid is selected from one or two of water and liquid hydrocarbons; the weight ratio of the heavy hydrocarbon to the water is 1:(0.01-0.2), preferably 1:(0.05-0.15); or, the weight ratio of the heavy hydrocarbon to the liquid hydrocarbon is 1:(0.01-0.2), preferably 1:(0.05-0.15). The method provided in this disclosure, after introducing the separation aid according to the stated weight ratio, can further extend the cracking furnace operating cycle by more than 10%, preferably more than 15%.

[0101] The temperature of the second gas phase mixture is 240-420℃, preferably 290-380℃.

[0102] The final boiling point of the liquid hydrocarbon is lower than that of the heavy hydrocarbon; preferably, the final boiling point of the liquid hydrocarbon is any value between 200-540°C, more preferably, the final boiling point of the liquid hydrocarbon is any value between 250-450°C, and even more preferably, the final boiling point of the liquid hydrocarbon is any value between 300-400°C.

[0103] In a preferred embodiment, the method further includes: the separation aid is introduced in at least one of the following ways: along the axial direction of the gas-liquid separator 6, the water is introduced above the liquid hydrocarbon introduction position; or along the axial direction of the gas-liquid separator 6, the water is introduced below the liquid hydrocarbon introduction position; or along the axial direction of the gas-liquid separator 6, the water introduction position and the liquid hydrocarbon introduction position are substantially on the same plane.

[0104] In one specific embodiment, the liquid hydrocarbon is selected from one or more of the light and heavy naphtha fractions, kerosene fractions, and light and heavy diesel fractions processed by an atmospheric and vacuum distillation system.

[0105] In a preferred embodiment, the method further includes: performing online or periodic offline analysis on target parameters of the heavy hydrocarbons before they are fed into the cracking furnace; optionally, the target parameters include density, distillation range, impurity type and content; optionally, the impurities include one or more of gums, asphaltenes, metals, sulfur, oxygen, nitrogen, and heavy components; and

[0106] The target parameters of the gaseous material from the gas-liquid separator 6 are analyzed online or periodically offline. Optionally, the target parameters include the type and content of impurities. Optionally, the impurities include one or more of the following: colloids, asphaltenes, metallic impurities, sulfur, oxygen, nitrogen, and heavy components; and...

[0107] A predetermined amount of the separation aid to be introduced into the gas-liquid separator 6 is determined; the separation aid is introduced into the gas-liquid separator 6 using the predetermined amount; and then, during the gas-liquid separation process, the amount of the separation aid introduced is adjusted according to the target parameters of the gas phase material obtained by online monitoring or offline analysis.

[0108] Optionally, the impurity content in the liquid hydrocarbon is less than the impurity content in the heavy hydrocarbon;

[0109] For example, the impurity content in the introduced liquid hydrocarbons is controlled within the following ranges: sulfur content less than 400 ppm; resin and asphaltenes content less than 0.15% by weight; metallic impurities (not limited to iron, nickel, vanadium, calcium, etc.) content less than 15 ppb; chlorine and nitrogen content less than 40 ppm; and arsenic content less than 3 ppb. More preferably, the impurity content in the introduced liquid hydrocarbons is controlled within the following ranges: sulfur content less than 200 ppm; resin and asphaltenes content less than 0.05% by weight; metallic impurities (not limited to iron, nickel, vanadium, calcium, etc.) content less than 5 ppb; chlorine and nitrogen content less than 20 ppm; and arsenic content less than 1 ppb.

[0110] Optionally, the amount of separation aid introduced can be adjusted based on the target parameters of the heavy hydrocarbons obtained from online monitoring or periodic offline analysis to control the hydrocarbon content in the separated gaseous material. For example, for every 10% reduction in the API weight of crude oil, preferably, the amount of separation aid introduced is increased by 10-50% by weight; more preferably, the amount of separation aid introduced is increased by 10-30% by weight; more preferably, the amount of separation aid introduced is increased by 15-25% by weight. The increase in separation aid can effectively reduce the separation temperature, further improve the separation effect of light and heavy components, and thus reduce the final boiling point of the gaseous components. This method, through this specific approach, can ensure the maintenance of the expected long operating cycle of the cracking furnace even when the properties of the crude oil deteriorate.

[0111] Alternatively, for example, when the sulfur content in crude oil increases from 1200 ppm to 2000 ppm, the amount of separation aid introduced can be increased by 10-20% by weight, preferably by 5-40% by weight; more preferably by 10-30% by weight; and more preferably by 15-25% by weight. By increasing the amount of separation aid introduced, the sulfur content in the separated gaseous material can be effectively reduced.

[0112] The analytical instruments and apparatus used in this disclosure for online or periodic offline analysis are all conventionally used in the art, such as heavy hydrocarbon component analyzers. Online analysis can be configured using conventional control systems in the art.

[0113] In one embodiment, the steam pyrolysis furnace includes at least a raw material heating section 1, a first mixing superheating section 2, a dilution steam superheating section 3, a second mixing superheating section 4, and a radiation section 5 arranged sequentially from top to bottom;

[0114] The method further includes: introducing the first mixture into a second convection section 2 for second heating, and then introducing it into a second mixer 8 for second mixing with the superheated secondary dilution steam obtained after superheating in the dilution steam superheating section 3; and

[0115] The method further includes: allowing the gaseous material from the gas-liquid separator 6 to enter the second mixing and superheating section 4 for the third heating, and then entering the radiation section 5 of the steam cracking furnace for steam cracking.

[0116] In one embodiment, the method further includes: introducing the liquid phase material from the gas-liquid separator 6 into the buffer tank 9 for buffering and then drawing it out through the pump 10.

[0117] In a preferred embodiment, at least a portion of the liquid material from pump 10 is returned to buffer tank 9.

[0118] In a preferred embodiment, the method further includes: introducing crude oil from the storage tank into the electric desalting unit 11 for desalting treatment, and then introducing it into the raw material heating section 1.

[0119] In one embodiment, the method further includes: before the crude oil enters the cracking furnace, it undergoes external preheating treatment outside the convection section, wherein the heat source for the external preheating treatment is waste heat material from any unit in the ethylene plant or combined unit; the external preheating treatment is independent of the preheating treatment in the feedstock heating section 1, which can further improve the heat utilization efficiency, especially the utilization efficiency of waste heat material obtained from other units in 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.

[0120] A second aspect of this disclosure also provides a system for producing olefins by cracking heavy hydrocarbons, the system comprising a steam cracking furnace and a gas-liquid separator 6; the steam cracking furnace comprising a convection section and a radiation section 5 arranged from top to bottom;

[0121] The gas-liquid separator 6 is configured to perform gas-liquid separation on the heavy hydrocarbon to obtain a first gas phase material and a first liquid phase material.

[0122] The gas-liquid separator 6 includes a separation aid inlet, wherein the separation aid inlet is configured to introduce the separation aid into the gas-liquid separator 6 during the separation process to contact the first gas phase material in a countercurrent manner, thereby obtaining a second gas phase material;

[0123] The radiation section 5 is configured to allow at least a portion of the second gaseous material to enter the radiation section 5 of the steam cracking furnace for cracking, yielding cracking products containing olefins.

[0124] In one embodiment, the convection section includes a heavy hydrocarbon heating inlet, a heavy hydrocarbon heating outlet, a gaseous material heating inlet, and a gaseous material heating outlet; wherein the heavy hydrocarbon heating inlet introduces heavy hydrocarbons; the radiation section 5 includes a cracking inlet and a cracking product outlet;

[0125] The gas-liquid separator 6 includes a gas-liquid separation inlet, a separation aid inlet, a second gas phase material outlet, and a liquid phase material outlet; wherein the gas-liquid separation inlet is connected to the heavy hydrocarbon heating outlet of the convection section, the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section, and the gas phase material heating outlet of the convection section is connected to the pyrolysis inlet of the radiation section 5.

[0126] The gas-liquid separation inlet is the inlet for heavy hydrocarbons or the first mixture to enter the gas-liquid separator, and there may be one or more inlets.

[0127] In one implementation, such as Figure 1 As shown, the convection section of the steam cracking furnace includes at least the raw material heating section 1, the first mixing superheating section 2, the dilution steam superheating section 3, and the second mixing superheating section 4 arranged sequentially from top to bottom;

[0128] The raw material heating section 1 is provided with a first heating inlet and a first heating outlet; the first heating inlet is formed as the crude oil heating inlet of the convection section, and the first heating outlet is formed as the heavy hydrocarbon heating outlet of the convection section;

[0129] The first mixing superheating section 2 is provided with a second heating inlet and a second heating outlet; the second heating inlet is connected to the first heating outlet of the raw material heating section 1 through a first pipeline, and a primary dilution steam inlet is provided on the first pipeline; the second heating outlet is connected to the gas-liquid separation inlet of the gas-liquid separator 6 through a second pipeline; and a secondary dilution steam inlet is provided on the second pipeline, along the material flow direction, with the primary dilution steam inlet located upstream of the secondary dilution steam inlet; the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section;

[0130] Optionally, the separation aid inlet includes multiple inlets, wherein at least one separation aid inlet is a water inlet and at least one separation aid inlet is a liquid hydrocarbon inlet;

[0131] Optionally, the dilution steam superheating section 3 is provided with a third heating inlet and a third heating outlet. The third heating inlet is connected to the dilution steam source, and the third heating outlet is connected to the second pipeline. The connection position forms a superheated secondary dilution steam outlet.

[0132] The second mixing superheating section 4 is provided with a fourth heating inlet and a fourth heating outlet. The fourth heating inlet is formed as a heating inlet for gaseous materials, and the fourth heating outlet is formed as a heating outlet for gaseous materials.

[0133] In one specific implementation, such as Figure 1 As shown, the system also includes a first mixer 7 and a second mixer 8. The first mixer 7 is disposed on the first pipeline and includes a first mixing inlet, a second mixing inlet and a first mixing outlet. The first mixing inlet is connected to the first heating outlet of the raw material heating section 1. The second mixing inlet is formed as the primary dilution steam and is used to introduce the primary dilution steam. The first mixing outlet is connected to the second heating inlet of the first mixing superheating section 2.

[0134] The second mixer 8 is disposed on the second pipeline; the second mixer 8 includes a third mixing inlet, a fourth mixing inlet, and a second mixing outlet. The third mixing inlet is connected to the second heating outlet of the first mixing superheating section 2, and the fourth mixing inlet is formed as the secondary dilution steam for introducing secondary dilution steam; the second mixing outlet is connected to the gas-liquid separation inlet of the gas-liquid separator 6.

[0135] This disclosure includes a second mixer 8, in which secondary steam and raw material heavy hydrocarbons are mixed simultaneously to prevent high-temperature steam from directly contacting the raw material heavy hydrocarbons and causing localized high temperatures and coking.

[0136] In one implementation, such as Figure 1As shown, the system also includes an electro-desalting device 11, which includes a desalting inlet and a desalting outlet; the desalting inlet is used to introduce heavy hydrocarbons, and the desalting outlet is connected to the first heating inlet of the raw material heating section 1 through a heavy hydrocarbon feed pipeline.

[0137] In a preferred embodiment, the gas phase material outlet of the gas-liquid separator 6 is located at the upper part of the gas-liquid separator 6, the liquid phase material outlet is located at the lower part of the gas-liquid separator 6, and the gas-liquid separation inlet is located at the middle part of the gas-liquid separator 6; the separation aid inlet is located between the gas-liquid separation inlet and the gas phase material outlet along the axial direction of the gas-liquid separator 6; along the axial direction of the gas-liquid separator 6, the water inlet is located above the gas-liquid separation inlet; preferably, the water inlet is located 0.1-10m above the gas-liquid separation inlet; more preferably, the water inlet is located 1-5m above the gas-liquid separation inlet;

[0138] In a preferred embodiment, along the axial direction of the gas-liquid separator 6, the water inlet is located above the liquid hydrocarbon inlet; or the water inlet is located below the liquid hydrocarbon inlet; or the water inlet and the liquid hydrocarbon inlet are basically located on the same plane.

[0139] In a preferred embodiment, a first control valve for the separation aid is provided on the inlet pipeline of the water inlet. Optionally, the first control valve references a signal from a first component analyzer and is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator 6, for controlling the amount of separation aid introduced by monitoring the target parameters of the gaseous material. Optionally, the first control valve references a signal from a second component analyzer, which is connected to the heavy hydrocarbon feed pipeline, for controlling the amount of separation aid introduced by monitoring the target parameters of the heavy hydrocarbon. Optionally, the first control valve simultaneously references both the first and second sets of analyzers to control the amount of separation aid introduced; and / or,

[0140] A second control valve for the separation aid is provided on the inlet pipeline of the liquid hydrocarbon inlet. The second control valve references the signal of a first component analyzer, which is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator 6, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the gas phase material. Optionally, the second control valve references the signal of a second component analyzer, which is connected to the heavy hydrocarbon feed pipeline, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the heavy hydrocarbon. Optionally, the second control valve references both the first and second sets of analyzers to control the introduction amount of the separation aid.

[0141] In a preferred embodiment, the control signal referenced by the first control valve comes from at least one of the following instruments: a first flow meter, a second flow meter, a third flow meter, a fourth flow meter, a fifth flow meter, a sixth flow meter, and a seventh flow meter;

[0142] The first flow meter is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator 6 and is used to measure the flow rate of the first gaseous material outlet; the second flow meter is connected to the inlet pipeline of the water inlet and is used to measure the flow rate of water; the third flow meter is connected to the inlet pipeline of the liquid hydrocarbon inlet and is used to measure the flow rate of the liquid hydrocarbon; the fourth flow meter is connected to the outlet pipeline of the first liquid material of the gas-liquid separator 6 and is used to measure the flow rate of the first liquid material; the fifth flow meter is connected to the primary dilution steam feed pipeline and is used to measure the amount of primary dilution steam; the sixth flow meter is connected to the secondary dilution steam feed pipeline and is used to measure the amount of secondary dilution steam; the seventh flow meter is connected to the heavy hydrocarbon feed pipeline and is used to measure the amount of heavy hydrocarbon feed.

[0143] Optionally, by monitoring the control signal, the hydrocarbon content in the first gas phase material outlet and the proportion of the hydrocarbon content in the first gas phase material outlet to the total heavy hydrocarbons (net hydrocarbon gasification rate) can be calculated. The amount of separation aid (water, or hydrocarbons or a combination thereof) introduced can be controlled by monitoring the hydrocarbon content or net hydrocarbon gasification rate in the first gas phase material outlet.

[0144] Both the first and second component analyzers are analytical instruments and devices conventionally used in this field.

[0145] In a preferred embodiment, the system further includes a buffer tank 9 and a pump 10. The buffer tank 9 includes a buffer inlet, a buffer outlet, and a reflux inlet. The buffer inlet is connected to the liquid phase material outlet of the gas-liquid separator 6, and the buffer outlet is connected to the inlet of the pump 10. The outlet of the pump 10 is connected to the reflux inlet of the optional buffer tank 9.

[0146] In one embodiment, the buffer tank 9 is located below the gas-liquid separator 6 along the height direction of the system.

[0147] In a preferred embodiment, the system further includes a dilution steam generator; the dilution steam generator can recover heat from the liquid phase material from the gas-liquid separator 6 to generate dilution steam; the primary dilution steam in the convection section can utilize the steam generated by the dilution steam generator or dilution steam from the pipeline utility, and the two sources of dilution steam can complement each other to heat the feed crude oil to recover heat.

[0148] like Figure 1As shown, in an exemplary embodiment of the system for producing olefins from heavy hydrocarbons provided in this disclosure, the system includes: a steam cracking furnace, a gas-liquid separator 6, a first mixer 7, a second mixer 8, a buffer tank 9, a pump 10, and an electrostatic desalting device 11; the steam cracking furnace includes a convection section and a radiation section 5 arranged from top to bottom;

[0149] The convection section includes a heavy hydrocarbon heating inlet, a heavy hydrocarbon heating outlet, a gaseous material heating inlet, and a gaseous material heating outlet; the heavy hydrocarbon heating inlet introduces heavy hydrocarbons; the radiation section 5 includes a cracking inlet and a cracking product outlet; the gas-liquid separator 6 includes a gas-liquid separation inlet, a water inlet, a liquid hydrocarbon inlet, a gaseous material outlet, and a liquid material outlet; wherein the gas-liquid separation inlet is connected to the heavy hydrocarbon heating outlet of the convection section, the second gaseous material outlet is connected to the gaseous material heating inlet of the convection section, and the gaseous material heating outlet of the convection section is connected to the cracking inlet of the radiation section 5;

[0150] The convection section includes, from top to bottom, a raw material heating section 1, a first mixing superheating section 2, a dilution steam superheating section 3, and a second mixing superheating section 4;

[0151] The raw material heating section 1 is provided with a first heating inlet and a first heating outlet; the first heating inlet is formed as a heavy hydrocarbon heating inlet in the convection section;

[0152] The first mixing superheating section 2 is provided with a second heating inlet and a second heating outlet; the second heating inlet is connected to the first heating outlet of the raw material heating section 1 through a first pipeline, and a primary dilution steam inlet is provided on the first pipeline; the second heating outlet is connected to the gas-liquid separation inlet of the gas-liquid separator 6 through a second pipeline; and a superheated secondary dilution steam inlet is provided on the second pipeline, with the primary dilution steam inlet located upstream of the superheated secondary dilution steam inlet along the material flow direction; the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section;

[0153] The dilution steam superheating section 3 is provided with a third heating inlet and a third heating outlet. The third heating inlet is connected to the dilution steam source, and the third heating outlet is connected to the second pipeline. The connection point forms a superheated secondary dilution steam inlet.

[0154] The second mixing superheating section 4 is provided with a fourth heating inlet and a fourth heating outlet. The fourth heating inlet is formed as the heating inlet for the gaseous material, and the fourth heating outlet is formed as the heating outlet for the gaseous material.

[0155] The first mixer 7 is disposed on the first pipeline. The first mixer 7 includes a first mixing inlet, a second mixing inlet and a first mixing outlet. The first mixing inlet is connected to the first heating outlet of the raw material heating section 1. The second mixing inlet is formed as an inlet for primary dilution steam to introduce primary dilution steam. The first mixing outlet is connected to the second heating inlet of the first mixing superheating section 2.

[0156] The second mixer 8 is disposed on the second pipeline; the second mixer 8 includes a third mixing inlet, a fourth mixing inlet, and a second mixing outlet. The third mixing inlet is connected to the second heating outlet of the first mixing superheating section 2, and the fourth mixing inlet is formed as secondary dilution steam for introducing secondary dilution steam; the second mixing outlet is connected to the gas-liquid separation inlet of the gas-liquid separator 6.

[0157] The electric desalting unit 11 includes a desalting inlet and a desalting outlet; the desalting inlet is used to introduce crude oil, and the desalting outlet is connected to the first heating inlet of the raw material heating section 1 through a heavy hydrocarbon feed pipeline;

[0158] Along the axial direction of the gas-liquid separator 6, the water inlet is located 1m above the gas-liquid separation inlet; the gas phase material outlet of the gas-liquid separator 6 is located at the upper part of the gas-liquid separator 6, the liquid phase material outlet is located at the lower part of the gas-liquid separator 6, and the gas-liquid separation inlet is located in the middle of the gas-liquid separator 6; along the axial direction of the gas-liquid separator 6, the water inlet and the liquid hydrocarbon inlet are located between the gas-liquid separation inlet and the gas phase material outlet; along the axial direction of the gas-liquid separator 6, the water inlet is located above the liquid hydrocarbon inlet; the inlet pipeline of the water inlet is equipped with a first control valve for separation aid, and the first control valve uses a first set of... The first component analyzer is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator 6, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the gas phase material; optionally, the first control valve references the signal of the second component analyzer, which is connected to the feed pipeline of the heavy hydrocarbon, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the heavy hydrocarbon; optionally, the first control valve can simultaneously reference the signals of the first set of analyzers and the second set of analyzers to control the introduction amount of the separation aid; and / or,

[0159] A second control valve for the separation aid is provided on the inlet pipeline of the liquid hydrocarbon inlet. The second control valve references the signal of a first component analyzer, which is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator 6, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the gas phase material. Optionally, the second control valve references the signal of a second component analyzer, which is connected to the feed pipeline of heavy hydrocarbons, and is used to control the introduction amount of the separation aid by monitoring the target parameters of the heavy hydrocarbons. Optionally, the second control valve can simultaneously reference the signals of the first and second analyzers to control the introduction amount of the separation aid.

[0160] The control signal referenced by the first control valve comes from at least one of the following instruments: a first flow meter, a second flow meter, a third flow meter, a fourth flow meter, a fifth flow meter, a sixth flow meter, and a seventh flow meter;

[0161] The first flow meter is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator 6 and is used to measure the flow rate of the first gaseous material outlet; the second flow meter is connected to the inlet pipeline of the water inlet and is used to measure the flow rate of water; the third flow meter is connected to the inlet pipeline of the liquid hydrocarbon inlet and is used to measure the flow rate of the liquid hydrocarbon; the fourth flow meter is connected to the outlet pipeline of the first liquid material of the gas-liquid separator 6 and is used to measure the flow rate of the first liquid material; the fifth flow meter is connected to the primary dilution steam feed pipeline and is used to measure the amount of primary dilution steam; the sixth flow meter is connected to the secondary dilution steam feed pipeline and is used to measure the amount of secondary dilution steam; the seventh flow meter is connected to the heavy hydrocarbon feed pipeline and is used to measure the amount of heavy hydrocarbon feed.

[0162] The hydrocarbon content in the first gas phase material outlet and the proportion of the hydrocarbon content in the first gas phase material outlet to the total heavy hydrocarbons (net hydrocarbon gasification rate) can be calculated by monitoring the control signal. The amount of separation aid (water, or hydrocarbons or a combination thereof) introduced can be controlled by monitoring the hydrocarbon content or net hydrocarbon gasification rate in the first gas phase material outlet.

[0163] The buffer tank 9 includes a buffer inlet, a buffer outlet, and a reflux inlet; the buffer inlet is connected to the liquid phase material outlet of the gas-liquid separator 6, and the buffer outlet is connected to the inlet of the pump 10; the outlet of the pump 10 is connected to the reflux inlet of the optional buffer tank 9.

[0164] Specifically, adopt Figure 1 The specific process flow for crude oil vapor cracking in the system shown includes:

[0165] S1. The crude oil from the storage tank is fed into the electric desalting unit 11 for desalting treatment; before the crude oil is fed into the cracking furnace, the properties of the crude oil are analyzed online or periodically offline; the crude oil is fed into the raw material heating section 1 for first heating to obtain the first preheated material; the first preheated material is fed into the first mixer 7 with the primary dilution steam for first mixing to obtain the first mixture material.

[0166] S2. After the first mixture enters the first mixing superheating section 2 for second heating, it enters the second mixer 8 with superheated secondary dilution steam from the dilution steam superheating section 3 for second mixing to obtain the second mixture.

[0167] S3. The second mixture is introduced into the gas-liquid separator 6 for gas-liquid separation to obtain gaseous and liquid phase materials; the target parameters of the gaseous material from the gas-liquid separator 6 are monitored online; and during the gas-liquid separation process, liquid hydrocarbons and water are introduced into the gas-liquid separator 6 in a pre-set amount to come into countercurrent contact with the first gaseous material, so that the heavy components carried in the gaseous material are washed or condensed to obtain the second gaseous material; along the axial direction of the gas-liquid separator 6, the water is introduced above the liquid hydrocarbon introduction position;

[0168] The liquid material from the gas-liquid separator 6 is introduced into the buffer tank 9 for buffering and then led out by the pump 10, so that at least a portion of the liquid material from the pump 10 is returned to the buffer tank 9.

[0169] S4. The second gaseous material from the gas-liquid separator 6 is introduced into the second mixing and superheating section 4 for third heating, and then enters the radiation section 5 of the steam cracking furnace for cracking to obtain cracking products containing olefins.

[0170] The parameters, control methods, and technical principles of each step involved in this disclosure have been described in detail in the foregoing content and will not be repeated here.

[0171] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0172] Example 1

[0173] The process in this embodiment is as follows: Figure 1 As shown: Taking paraffin-based crude oil 1 as an example, the heavy hydrocarbon is 41, and the liquid hydrocarbon is diesel.

[0174] Specifically, the process includes the following steps: S1, exchanging heat between the crude oil from the storage tank and the hot medium quench water, resulting in a crude oil temperature of 135°C; then, the crude oil enters the desalting pre-processor 11 for desalting, dehydration, and removal of non-metallic impurities. The pre-treated crude oil is more suitable for entering the convection section of the steam cracking furnace; before the pre-treated crude oil enters the cracking furnace, the sulfur content of the crude oil is analyzed online or periodically offline. In this embodiment, the baseline value of the crude oil sulfur content is 1200 ppm. When the sulfur content exceeds 50% by weight of the baseline value during online or offline monitoring during the operation of the device, the amount of the introduced separation aid needs to be adjusted. The amount of the newly added separation aid shall not exceed 100% by weight of the introduced amount.

[0175] The pretreated crude oil is fed into the raw material heating section 1 of the convection section of the steam cracking furnace for first heating to obtain the first preheated material at a temperature of 240-265℃; the primary dilution steam and the first preheated material are fed into the first mixer 7 for first mixing to obtain the first mixture; the weight ratio of crude oil to primary dilution steam is 1:0.2, and the temperature of the first mixture is 190℃.

[0176] S2. The first mixture is fed into the first mixing superheating section 2 for a second heating, and the temperature of the first mixture after the second heating is 240°C. The secondary dilution steam is superheated in the dilution steam superheating section 3, and the temperature of the superheated secondary dilution steam is 450°C. The first mixture after the second heating and the superheated secondary dilution steam are fed into the second mixer 8 for a second mixing to obtain the second mixture. The weight ratio of heavy hydrocarbons to the superheated secondary dilution steam is 1:0.5.

[0177] S3. The second mixture is fed into the gas-liquid separator 6 for gas-liquid separation to obtain gaseous and liquid phase materials. The impurities in the gaseous material obtained by gas-liquid separation are monitored online. The final boiling point and gum / impurity content of the gaseous material are adjusted by injecting water and liquid hydrocarbons. The sulfur content in the liquid hydrocarbons is less than 200 ppm, and other metallic and non-metallic impurities are significantly lower than those in the feed material. The weight ratio of heavy hydrocarbons to water is 1:0.05, and the weight ratio of heavy hydrocarbons to liquid hydrocarbons is 1:0.1. After the introduction of water and liquid hydrocarbons, the final boiling point of the first gaseous material decreases from 470℃ to 455℃, resulting in the second gaseous material with a temperature of 320℃. The gum content in the second gaseous material is controlled to be <0.1% by weight by controlling the amount of liquid hydrocarbons and water. The liquid phase material after gas-liquid separation is transported from the liquid phase material outlet at the bottom of the gas-liquid separator 6 to the buffer tank 9, and then drawn out by the pump 10, with a portion of the liquid phase material being returned to the buffer tank 9.

[0178] Along the axial direction of the gas-liquid separator 6, the water inlet is located 1.5m above the gas-liquid separation inlet;

[0179] The dilution steam generator can recover the heat of heavy components and generate primary dilution steam, which is then supplied to the steam cracking furnace as a primary dilution steam source. The gaseous material contains carried steam and light components from heavy hydrocarbons, while the liquid material contains heavy components from crude oil. The final boiling point of the light components is 480°C, and the initial boiling point of the heavy components is not higher than the final boiling point of the light components. The final boiling point of the liquid hydrocarbons is 400°C.

[0180] S4. The second gaseous material is conveyed from the top of the gas-liquid separator 6 to the mixing superheating section 2 of the steam cracking furnace for a third heating to a cross temperature of 550°C, and then conveyed to the radiation section 5 of the steam cracking furnace for steam cracking reaction to obtain cracking products containing olefins; the steam cracking temperature is 810°C and the time is 0.25s.

[0181] Comparative Example 1

[0182] This comparative example uses the same method as Example 1, the only difference being that no separation aid is introduced into the gas-liquid separator 6. The risk of coking in the convection section is significantly increased, and the coking phenomenon in the radiation section is relatively more severe compared to Example 1.

[0183] Compared with Comparative Example 1, the operating cycle of the pyrolysis furnace in Example 1 increased by 15%.

[0184] Through the above technical solution, this disclosure can completely use crude oil for direct cracking to produce olefins, which greatly reduces the crude oil pretreatment production unit set in traditional oil refining units, increases the operating cycle of steam cracking unit, and produces olefins to the maximum extent with a shorter process and lower energy consumption.

[0185] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0186] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0187] 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 heavy hydrocarbons, characterized in that, The method includes the following steps: S1. Heavy hydrocarbons are introduced into the gas-liquid separator (6) for gas-liquid separation to obtain a first gas phase material and a first liquid phase material. During the separation process, a separation aid is introduced into the gas-liquid separator (6) to come into countercurrent contact with the first gas phase material so that the heavy components carried in the first gas phase material are washed or condensed to obtain a second gas phase material. S2. At least a portion of the second gaseous material is fed into the radiation section (5) of the steam cracking furnace for cracking to obtain cracking products containing olefins.

2. The method according to claim 1, wherein, Step S1 includes the following steps: The heavy hydrocarbon is subjected to a first heating, and the first heated heavy hydrocarbon is mixed with primary dilution steam to obtain a first mixture. The first mixture is subjected to a second heating and then mixed with superheated secondary dilution steam to obtain a second mixture. The second mixture is fed into the gas-liquid separator (6) for gas-liquid separation; The weight ratio of the heavy hydrocarbon to the primary dilution steam is 1:(0.1-0.5). The temperature of the first mixture is 150-350℃; The heavy hydrocarbons are light, wide-fraction crude oils; The temperature of the first mixture after the second heating is below 400°C; The temperature of the superheated secondary dilution steam is 400-630℃; The weight ratio of the heavy hydrocarbon to the superheated secondary dilution steam is 1:(0.2-0.8).

3. The method according to claim 2, wherein, The weight ratio of the heavy hydrocarbon to the primary dilution steam is 1:(0.2-0.4). The temperature of the first mixture is 190-300℃; The API value of the light, wide-fraction crude oil is not less than 35; The temperature of the first mixture after the second heating is 250-350℃; The temperature of the superheated secondary dilution steam is 450-600℃; The weight ratio of the heavy hydrocarbon to the superheated secondary dilution steam is 1:(0.3-0.65).

4. The method according to claim 2, wherein, In step S2, the second gaseous material contains carried vapor and light components in the heavy hydrocarbon, and the first liquid material contains heavy components in the heavy hydrocarbon; the final boiling point of the light components is below 540°C, and the initial boiling point of the heavy components is not higher than the final boiling point of the light components. The separation aid is selected from one or two of water and liquid hydrocarbons; The weight ratio of the heavy hydrocarbon to the water is 1:(0.01-0.2); or, the weight ratio of the heavy hydrocarbon to the liquid hydrocarbon is 1:(0.01-0.2). The temperature of the second gaseous material is 240-420℃; The final boiling point of the liquid hydrocarbon is lower than that of the heavy hydrocarbon; The final boiling point of the liquid hydrocarbon is any value between 200-540°C; The method further includes: the separation aid is introduced in at least one of the following ways: along the axial direction of the gas-liquid separator (6), the water is introduced above the liquid hydrocarbon is introduced; or along the axial direction of the gas-liquid separator (6), the water is introduced below the liquid hydrocarbon is introduced; or along the axial direction of the gas-liquid separator (6), the water is introduced and the liquid hydrocarbon is introduced in the same plane.

5. The method according to claim 4, wherein, The weight ratio of the heavy hydrocarbon to the water is 1:(0.05-0.15). Alternatively, the weight ratio of the heavy hydrocarbon to the liquid hydrocarbon is 1:(0.05-0.15). The temperature of the second gaseous material is 290-380℃; The final boiling point of the liquid hydrocarbon is any value between 200 and 540°C.

6. The method according to claim 5, wherein, The final boiling point of the liquid hydrocarbon is any value between 250 and 450°C.

7. The method according to claim 6, wherein, The final boiling point of the liquid hydrocarbon is any value between 300-400℃.

8. The method according to claim 1, wherein, The method further includes: performing online or periodic offline analysis of target parameters of the heavy hydrocarbons before they are fed into the cracking furnace; the target parameters include density, distillation range, impurity type and content; the impurities include one or more of gums, asphaltenes, metals, sulfur, oxygen, nitrogen, and heavy components; and The target parameters of the gaseous material from the gas-liquid separator (6) are analyzed online or periodically offline. These target parameters include the type and content of impurities, which include one or more of the following: colloids, asphaltenes, metallic impurities, sulfur, oxygen, nitrogen, and heavy components; and... Determine the preset amount of the separation aid to be introduced into the gas-liquid separator (6); introduce the separation aid into the gas-liquid separator (6) using the preset amount; and then, during the gas-liquid separation process, adjust the amount of the separation aid introduced according to the target parameters of the gas phase material obtained by online monitoring or offline analysis.

9. The method according to claim 2, wherein, The steam cracking furnace includes at least a raw material heating section (1), a first mixing superheating section (2), a dilution steam superheating section (3), a second mixing superheating section (4), and a radiation section (5); The method also includes: The first mixture is fed into a first mixing superheating section (2) for second heating, and then mixed with superheated secondary dilution steam obtained from the dilution steam superheating section (3) for second mixing; and The gaseous material from the gas-liquid separator (6) is fed into the second mixing and superheating section (4) for third heating and then into the radiation section (5) of the steam cracking furnace for steam cracking.

10. The method according to claim 9, wherein, The method also includes: The liquid material from the gas-liquid separator (6) is introduced into the buffer tank (9) for buffering and then drawn out by the pump (10); so that at least a portion of the liquid material from the pump (10) is returned to the buffer tank (9). The method further includes: Heavy hydrocarbons from the storage tank are fed into an electro-desalting unit (11) for desalting, and then introduced into the raw material heating section (1).

11. A system for cracking heavy hydrocarbons to produce olefins, characterized in that, The system includes a steam pyrolysis furnace and a gas-liquid separator (6); the steam pyrolysis furnace includes a convection section and a radiation section arranged from top to bottom (5). The gas-liquid separator (6) is configured to perform gas-liquid separation on the heavy hydrocarbon to obtain a first gas phase material and a first liquid phase material; The gas-liquid separator (6) includes a separation aid inlet, wherein the separation aid inlet is configured to introduce the separation aid into the gas-liquid separator (6) during the separation process to contact the first gas phase material in a countercurrent manner, so that the heavy components carried in the first gas phase material are washed or condensed to obtain the second gas phase material; The radiation section (5) is configured to allow at least a portion of the second gaseous material to enter the radiation section (5) of the steam cracking furnace for cracking, yielding cracking products containing olefins.

12. The system according to claim 11, wherein, The convection section includes a heavy hydrocarbon heating inlet, a heavy hydrocarbon heating outlet, a gas phase material heating inlet, and a gas phase material heating outlet; wherein the heavy hydrocarbon heating inlet introduces heavy hydrocarbons; The radiation section (5) includes a pyrolysis inlet and a pyrolysis product outlet; The gas-liquid separator (6) includes a gas-liquid separation inlet, a separation aid inlet, a second gas phase material outlet, and a liquid phase material outlet; The gas-liquid separation inlet is connected to the heavy hydrocarbon heating outlet of the convection section, and the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section; the gas phase material heating outlet of the convection section is connected to the pyrolysis inlet of the radiation section (5). The convection section of the steam cracking furnace includes a raw material heating section (1), a first mixing superheating section (2), a dilution steam superheating section (3), and a second mixing superheating section (4); The raw material heating section (1) is provided with a first heating inlet and a first heating outlet; the first heating inlet is formed as the heavy hydrocarbon heating inlet of the convection section; The first mixing superheating section (2) is provided with a second heating inlet and a second heating outlet; the second heating inlet is connected to the first heating outlet of the raw material heating section (1) through a first pipeline, and a primary dilution steam inlet is provided on the first pipeline; the second heating outlet is connected to the gas-liquid separation inlet of the gas-liquid separator (6) through a second pipeline; and a secondary dilution steam inlet is provided on the second pipeline, and the primary dilution steam inlet is located upstream of the secondary dilution steam inlet along the material flow direction; the second gas phase material outlet is connected to the gas phase material heating inlet of the convection section; The separation aid inlet includes multiple inlets, of which at least one separation aid inlet is a water inlet and at least one separation aid inlet is a liquid hydrocarbon inlet; The dilution steam superheating section (3) is provided with a third heating inlet and a third heating outlet. The third heating inlet is connected to the dilution steam source, and the third heating outlet is connected to the second pipeline. The connection position forms the superheated secondary dilution steam outlet. The second mixing superheating section (4) is provided with a fourth heating inlet and a fourth heating outlet. The fourth heating inlet is formed as the heating inlet for the gaseous material, and the fourth heating outlet is formed as the heating outlet for the gaseous material.

13. The system according to claim 12, characterized in that, The system also includes a first mixer (7), a second mixer (8), and an electro-desalination device (11). The first mixer (7) is disposed on the first pipeline. The first mixer (7) includes a first mixing inlet, a second mixing inlet, and a first mixing outlet. The first mixing inlet is connected to the first heating outlet of the raw material heating section (1). The second mixing inlet is formed as the inlet of the primary dilution steam for introducing primary dilution steam. The first mixing outlet is connected to the second heating inlet of the first mixing superheating section (2). The second mixer (8) is disposed on the second pipeline; the second mixer (8) includes a third mixing inlet, a fourth mixing inlet and a second mixing outlet, the third mixing inlet is connected to the second heating outlet of the first mixing superheat section (2), the fourth mixing inlet is formed as the secondary dilution steam, and is used to introduce the secondary dilution steam; the second mixing outlet is connected to the gas-liquid separation inlet of the gas-liquid separator (6); The electro-desalting device (11) includes a desalting inlet and a desalting outlet; the desalting inlet is used to introduce crude oil, and the desalting outlet is connected to the first heating inlet of the raw material heating section (1) through a heavy hydrocarbon feed pipeline.

14. The system according to claim 12, characterized in that, Along the axial direction of the gas-liquid separator (6), the water inlet is located above the gas-liquid separation inlet; Along the axial direction of the gas-liquid separator (6), the water inlet is located above the liquid hydrocarbon inlet; or the water inlet is located below the liquid hydrocarbon inlet; or the water inlet and the liquid hydrocarbon inlet are located on the same plane. The water inlet is equipped with a first control valve for the separation aid. This first control valve references a signal from a first component analyzer and is connected to the outlet pipeline of the first gaseous material of the gas-liquid separator (6). This is used to control the amount of the separation aid introduced by monitoring the target parameters of the gaseous material. The first control valve also references a signal from a second component analyzer, which is connected to the heavy hydrocarbon feed pipeline. This is used to control the amount of the separation aid introduced by monitoring the target parameters of the heavy hydrocarbon. The first control valve simultaneously references both the first and second sets of analyzers to control the amount of the separation aid introduced; and / or, The liquid hydrocarbon inlet is equipped with a second control valve for the separation aid. The second control valve references the signal from the first component analyzer, which is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator (6) to control the amount of the separation aid introduced by monitoring the target parameters of the gas phase material. The second control valve references the signal from the second component analyzer, which is connected to the heavy hydrocarbon feed pipeline to control the amount of the separation aid introduced by monitoring the target parameters of the heavy hydrocarbon. The second control valve simultaneously references both the first and second analyzers to control the amount of the separation aid introduced. The control signal referenced by the first control valve comes from at least one of the following instruments: a first flow meter, a second flow meter, a third flow meter, a fourth flow meter, a fifth flow meter, a sixth flow meter, and a seventh flow meter; The first flow meter is connected to the outlet pipeline of the first gas phase material of the gas-liquid separator (6) and is used to measure the flow rate of the first gas phase material outlet; the second flow meter is connected to the inlet pipeline of the water inlet and is used to measure the flow rate of water; the third flow meter is connected to the inlet pipeline of the liquid hydrocarbon inlet and is used to measure the flow rate of the liquid hydrocarbon; the fourth flow meter is connected to the outlet pipeline of the first liquid phase material of the gas-liquid separator (6) and is used to measure the flow rate of the first liquid phase material; the fifth flow meter is connected to the primary dilution steam feed pipeline and is used to measure the amount of primary dilution steam; the sixth flow meter is connected to the secondary dilution steam feed pipeline and is used to measure the amount of secondary dilution steam; the seventh flow meter is connected to the heavy hydrocarbon feed pipeline and is used to measure the amount of heavy hydrocarbon feed. The system also includes a buffer tank (9) and a pump (10). The buffer tank (9) includes a buffer inlet, a buffer outlet and a reflux inlet. The buffer inlet is connected to the liquid phase material outlet of the gas-liquid separator (6). The buffer outlet is connected to the inlet of the pump (10). The outlet of the pump (10) is connected to the reflux inlet of the optional buffer tank (9).

15. The system according to claim 14, wherein, The water inlet is located 0.1-10m above the gas-liquid separation inlet.

16. The system according to claim 15, wherein, The water inlet is located 1-5m above the gas-liquid separation inlet.

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