Process and system for the direct catalytic cracking of crude oil to produce light olefins and aromatics

Abstract

The application relates to a method and system for producing low-carbon olefins and aromatic hydrocarbons through direct catalytic cracking of crude oil, which comprises the following steps: catalytic cracking of crude oil in a first fluidized reactor, catalytic cracking of refractory components in a second fluidized reactor, gas-solid separation of reaction products and spent catalyst, stripping of the spent catalyst, supplement of green coke, coke burning regeneration, and return of the regenerated catalyst to the reactor for recycling; and separation of the reaction products to obtain ethylene, propylene, refractory components and other products, wherein the refractory components are further subjected to catalytic cracking in the second fluidized reactor to obtain ethylene and propylene. When the catalytic cracking method and system are used for catalytic cracking of crude oil, low-carbon olefins and light aromatic hydrocarbons and other chemical raw materials can be produced with high selectivity, and efficient utilization of crude oil resources is realized.

Description

Technical Field

[0001] This application relates to the petrochemical field, and more specifically, to a method and system for the direct catalytic cracking of crude oil to produce low-carbon olefins and aromatics. Background Technology

[0002] With overcapacity in oil refining and a slowing demand for refined oil products, ethylene, propylene, and BTX (benzene-toluene-xylene) are key basic organic synthesis raw materials in huge demand, while demand for chemical products remains strong. Existing technologies for producing propylene and BTX from petroleum are developed based on traditional oil refining processes, which suffer from long production processes, low chemical yields, and insignificant economic benefits. The key to solving these problems is to develop core technologies that enable the targeted conversion of crude oil hydrocarbon molecules into chemicals. Therefore, in recent years, international petrochemical companies, represented by ExxonMobil and Saudi Aramco, have begun to innovate traditional refining processes. These companies have revolutionized traditional oil refining processes, elevating integrated refining and chemical production to a new level of direct crude oil-to-chemicals conversion.

[0003] ExxonMobil is a pioneer in the research and development of crude oil steam cracking to olefins, and was the first company to build an industrial-scale demonstration plant. It has also applied for a series of patents, such as CN101583697. The company's direct olefins process involves crude oil directly entering a steam cracker, where it undergoes flash evaporation to separate light and heavy components. The light components (gaseous components) are then further cracked in the steam cracker, while the heavy components (liquid components) are used as refinery feedstock. If the selected crude oil is sufficiently light and has no fractions above 593°C (i.e., no bottom residue), it can be produced without relying on a refinery. The company's first industrial-scale plant used ultralight paraffinic Tapis crude oil with an API gravity of 42.7 as feedstock.

[0004] Saudi Aramco's technological strength lies in its use of crude oil pretreatment and hydrotreating technologies to minimize the impact of non-volatile components in crude oil on steam cracking. Simultaneously, a vapor-liquid (steam and liquid) separation device is installed between the convection and radiant sections of the steam cracker to remove non-volatile liquids (liquid phases), ensuring that the material entering the radiant section is free of liquid entrainment, thus preventing coking in the furnace tubes. The heavier components are then fed into the catalytic cracking unit. This can be described as an integrated process for producing olefins and aromatics from crude oil, combining hydrotreating, steam cracking, and catalytic cracking.

[0005] Sinopec's crude oil-to-chemicals technology is mainly divided into two technical routes. The first is crude oil steam cracking technology, which uses light crude oil as raw material and has a chemical yield of about 50%. The second is catalytic cracking technology, in which crude oil is desalted and dehydrated to separate light and heavy components. The light components (light feed) and the heavy components (heavy feed) are reacted with high-temperature catalysts in two separate catalytic cracking reactors under a steam atmosphere to produce high-value-added products. Alternatively, the light components and heavy components can react in different reaction zones of the same reactor, with a total yield of low-carbon olefins and light aromatics of over 50%.

[0006] Due to the presence of heavy components in crude oil that are difficult to vaporize, existing crude oil-to-chemicals technologies are only suitable for low-sulfur paraffin-based crude oils with an API gravity of around 45. Other crude oil-to-chemicals technologies vary among companies depending on the processing methods for heavy components in the crude oil, but all employ fractionation, combining processes based on the properties of distillate oils at different boiling points to produce chemicals. Compared to traditional refining processes, this only changes the boiling point and quantity of the fractionated oils and integrates existing processing techniques, failing to achieve a fundamental technological revolution. Furthermore, these existing combined technologies are more suitable for light crude oils or paraffin-based crude oils; when using heavy crude oils or intermediate-based crude oils as feedstocks, the yield of high-value-added chemical feedstocks such as low-carbon olefins and aromatics is low. Summary of the Invention

[0007] The purpose of this application is to provide a method and system for producing low-carbon olefins and aromatics by catalytic cracking of crude oil. This method not only has good adaptability to crude oil and high yields of low-carbon olefins and aromatics, but also solves the problem of insufficient heat in the catalytic cracking reaction of potentially high-quality crude oil.

[0008] A first aspect of the present invention provides a method for producing low-carbon olefins and aromatics by direct catalytic cracking of crude oil, comprising:

[0009] (1) The feedstock oil and the first regenerated catalyst from the regenerator enter the first fluidized bed reactor for catalytic cracking reaction to obtain a first oil-catalyst mixture containing the first reaction product and the first regenerated catalyst;

[0010] (2) The second regenerated catalyst and the fresh catalyst from the regenerator enter the catalyst mixing zone of the second fluidized reactor and are mixed. They then come into contact with the difficult-to-convert components and undergo catalytic cracking to obtain a second oil-agent mixture containing the second reaction product and the second regenerated catalyst.

[0011] (3) The first oil mixture and the second oil mixture enter the oil separation equipment for gas-solid separation. The separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, aromatics, difficult-to-convert components and other products.

[0012] (4) The separated raw catalyst is stripped and then enters the coking unit. After being mixed with the third regenerated catalyst from the regenerator and heated, it comes into contact with the raw coking raw material to produce a coking reaction, thus obtaining the raw catalyst with coke.

[0013] (5) The spent catalyst with coke enters the regenerator and comes into contact with oxygen-containing gas to undergo a carbonization reaction. The first part of the regenerated catalyst is returned to the first fluidized bed reactor for reaction recycling. The second part of the regenerated catalyst enters the catalyst mixing zone of the second fluidized bed reactor and is mixed with the fresh catalyst for reaction recycling.

[0014] The feedstock is full-fraction crude oil, and the difficult-to-convert components are light hydrocarbons or light distillate oils produced by the unit itself or by other units.

[0015] According to the method described in the first aspect, the feedstock is a conventionally sourced full-fraction crude oil;

[0016] Preferably, the feedstock oil further includes optional mineral oil and / or synthetic oil, wherein the mineral oil is selected from one or more of coal liquefaction oil, oil sands oil and shale oil, and the synthetic oil is a distillate oil obtained by FT synthesis of coal, natural gas or bitumen.

[0017] According to the method of the first aspect, the light hydrocarbons include gaseous hydrocarbon products rich in C4 fractions produced by the device itself and gaseous hydrocarbons rich in C4 fractions produced by other devices, wherein the C4 olefin content in the gaseous hydrocarbons rich in C4 fractions is greater than 50% by weight.

[0018] Preferably, the difficult-to-convert component is a C4 fraction produced by the device itself.

[0019] According to the method described in the first aspect, the light distillate oil is selected from one or more of the following: light distillate oil produced by the unit with a final boiling point of less than 280-350°C; straight-run naphtha, straight-run kerosene, and straight-run diesel oil from other primary processing units; and topping oil, residue oil, hydrocracked light naphtha, pentane oil, coking gasoline, Fischer-Tropsch synthetic oil, catalytic cracked light gasoline, hydrotreated gasoline, and hydrotreated diesel oil from other secondary processing units.

[0020] According to the method of the first aspect, the first fluidizing reactor is selected from one or more of the following in series: a turbulent bed reactor, a fast bed reactor, and a dilute phase transport bed reactor; and / or

[0021] The second fluidized bed reactor is a dilute phase transport bed reactor.

[0022] According to the method described in the first aspect, the catalytic cracking reaction conditions in the first fluidized bed reactor are as follows:

[0023] The reaction temperature is 510-650℃;

[0024] The reaction time is 1-20 seconds;

[0025] The weight ratio of catalyst to feedstock is (3-50):1; and / or

[0026] The reaction pressure is 130-450 kPa;

[0027] Preferably, the raw oil is preheated and steam atomized before entering the first fluidized bed reactor. The preheating temperature is 180-350℃, and the water-to-oil weight ratio is (0.03-0.8):1.

[0028] According to the method described in the first aspect, one or more inlets for difficult-to-convert components are provided on the second fluidization reactor;

[0029] Preferably, the one or more difficult-to-convert component inlets are each independently located at the outlet end of the catalyst mixing zone of the second fluidized bed reactor or in the middle and upper reaches of the second fluidized bed reactor, and the light hydrocarbons and light distillate oils of the difficult-to-convert component are introduced into the second fluidized bed reactor at the same or different difficult-to-convert component inlets;

[0030] More preferably, the light hydrocarbons of the difficult-to-convert component are introduced into the second fluidization reactor at one or more difficult-to-convert component inlets upstream of the light distillate oil introduction location.

[0031] According to the method described in the first aspect, the catalytic cracking reaction conditions in the second fluidized bed reactor are as follows:

[0032] The reaction temperature is 580-750℃;

[0033] The reaction time is 0.05-5 seconds; and / or

[0034] The weight ratio of catalyst to feedstock is (1-50):1;

[0035] Preferably, the difficult-to-convert component is introduced into the second fluidized bed reactor after being atomized by steam, and the weight ratio of water vapor to feed oil is (0.03-0.5):1.

[0036] According to the method described in the first aspect, wherein the weight ratio of fresh catalyst to regenerated catalyst in the catalyst mixing zone of the second fluidized reactor is 0.01-0.3:1.

[0037] According to the method described in the first aspect, the outlet temperature of the coking device is 550-650°C, and / or the linear velocity is 1.2-2.2 m / s.

[0038] A second aspect of the present invention provides a system for the direct catalytic cracking of crude oil to produce low-carbon olefins, comprising:

[0039] The catalytic cracking reaction unit includes:

[0040] The first fluidization reactor is provided with a first pre-lifting medium inlet, a first regeneration catalyst inlet, a feed oil inlet and a first oil-agent mixture outlet;

[0041] The second fluidized bed reactor is provided with a catalyst mixing zone, one or more inlets for difficult-to-convert components and a second oil-agent mixture outlet. The catalyst mixing zone is provided with a second pre-lifting medium inlet, a second regenerated catalyst inlet and a fresh catalyst inlet.

[0042] An oil-liquid separation device is connected to both the outlet of the first oil-liquid mixture from the first fluidized bed reactor and the outlet of the second oil-liquid mixture from the second fluidized bed reactor, such that the first oil-liquid mixture from the first fluidized bed reactor and the second oil-liquid mixture from the second fluidized bed reactor are separated into reaction oil gas and catalyst to be generated by the oil-liquid separation device; and

[0043] A settling device is used to settle and collect the catalyst to be generated after being separated by the oil-based separation equipment. A stripping section is provided below the settling device for stripping the catalyst to be generated. The stripping section is provided with a catalyst outlet and a stripping medium inlet.

[0044] A reaction product separation unit, which is connected to an oil separation device, is used to separate the reaction oil and gas separated by the oil separation device into products including low-carbon olefins, aromatics and difficult-to-convert components.

[0045] Catalyst regeneration unit, including

[0046] A coking unit is used to bring the catalyst to be generated separated from the catalytic cracking reaction unit into contact with the coking raw material to produce a coking reaction and obtain a catalyst with coke. It is provided with a catalyst inlet, a fluidized medium inlet, a coking raw material inlet, a first gas distributor, a catalyst distributor and a coking catalyst outlet. The catalyst inlet is in fluid communication with the catalyst outlet of the stripping section of the settling tank.

[0047] The regenerator includes a coke catalyst inlet, an oxygen-containing gas inlet, a second gas distributor, a cyclone separator, a regenerated flue gas pipeline, and at least one regenerated catalyst outlet. The coke catalyst inlet of the regenerator is in fluid communication with the coke catalyst outlet of the regenerator. One regenerated catalyst outlet is connected to the first regenerated catalyst inlet of the first fluidized bed reactor for recycling a portion of the regenerated catalyst back to the first fluidized bed reactor. Another regenerated catalyst outlet is connected to the second regenerated catalyst inlet of the catalyst mixing zone of the second fluidized bed reactor for introducing a portion of the regenerated catalyst into the catalyst mixing zone to mix with the fresh catalyst.

[0048] A regenerated catalyst circulation pipeline is provided between the coking unit and the regenerator, which is used to allow a portion of the regenerated catalyst to enter the coking unit and mix with the catalyst to be generated to jointly react with the coking raw material.

[0049] According to the system described in the second aspect, the distance from the connection port of the regenerated catalyst circulation pipe on the coking unit to the bottom of the coking unit is 5% to 10% of the height of the coking unit; and / or

[0050] The distance between the raw coke inlet and the bottom of the coking unit is 20% to 50% of the height of the coking unit.

[0051] Compared with the prior art, the method and system of the present invention have the following advantages:

[0052] 1) It can realize direct catalytic cracking of crude oil, reduce the crude oil distillation process, simplify the process, and reduce operating costs.

[0053] 2) In the process of crude oil catalytic cracking, the single-pass conversion rate is not pursued. The components that are difficult to convert during the reaction are recycled. By setting up specific reaction zones, a higher total conversion rate and a higher selectivity for low-carbon olefins can be achieved.

[0054] 3) Setting up a coking unit can solve the problem of insufficient heat balance when processing high-quality crude oil.

[0055] Using the method described in this application, crude oil can be directly and efficiently used to produce chemical raw materials such as ethylene and propylene, alleviating the oversupply of refined oil products, promoting the deep integration of the refining and petrochemical industries, and facilitating the high-quality development of the refining and chemical industry. Attached Figure Description

[0056] The specific embodiments described herein are used together to explain this application, but do not constitute a limitation thereof. In the accompanying drawings:

[0057] Figure 1 A schematic diagram of a process for producing high value-added products from crude oil according to one embodiment of this application.

[0058] Explanation of reference numerals in the attached figures:

[0059] 100. First fluidized bed reactor; 101. First pre-lifting medium inlet; 102. Crude oil inlet; 103. First regenerated catalyst inlet; 104. First oil-agent mixture outlet; 200. Settler; 201. Stripping section; 202. Stripping medium pipeline; 203. Inclined tube for regeneration; 204. Oil-agent separation device; 205. Gas collecting chamber; 206. Large oil and gas pipeline; 300. Coking unit; 301. Fluidized medium inlet; 302. Gas distributor; 303. External catalyst circulation pipe; 304. Coking unit. Raw material inlet; 305, catalyst distributor; 400, regenerator; 401, oxygen-containing gas inlet; 402, main air distributor; 404, cyclone separator; 405, regenerated flue gas pipeline; 406, regenerated catalyst outlet; 500, second fluidized bed reactor; 501, second pre-lifting medium inlet; 502, fresh catalyst inlet; 503, second regenerated catalyst inlet; 504, light hydrocarbon inlet; 505, light distillate oil inlet; 506, catalyst mixing zone; 507, second oil-catalyst mixture outlet. Detailed Implementation

[0060] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0061] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0062] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0063] In this article, low carbon olefins are a collective term for ethylene, propylene, and butene, and light aromatic hydrocarbons (BTX) are a collective term for benzene (BTX), toluene (T), and xylene (X).

[0064] In this application, the terms "upstream" and "downstream" refer to the direction of reaction material flow. For example, when the reaction material flows from bottom to top, "upstream" refers to the position located at the bottom, while "downstream" refers to the position located at the top.

[0065] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0066] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0067] This invention provides a method for the direct catalytic cracking of crude oil to produce low-carbon olefins and aromatics, comprising:

[0068] (1) The feedstock oil and the first regenerated catalyst from the regenerator enter the first fluidized bed reactor for catalytic cracking reaction to obtain a first oil-catalyst mixture containing the first reaction product and the first regenerated catalyst;

[0069] (2) The second regenerated catalyst and the fresh catalyst from the regenerator enter the catalyst mixing zone of the second fluidized reactor and are mixed. They then come into contact with the difficult-to-convert components and undergo catalytic cracking to obtain a second oil-agent mixture containing the second reaction product and the second regenerated catalyst.

[0070] (3) The first oil mixture and the second oil mixture enter the oil separation equipment for gas-solid separation. The separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, aromatics, difficult-to-convert components and other products.

[0071] (4) The separated raw catalyst is stripped and then enters the coking unit. After being mixed with the third regenerated catalyst from the regenerator and heated, it comes into contact with the raw coking raw material to produce a coking reaction, thus obtaining the raw catalyst with coke.

[0072] (5) The spent catalyst with coke enters the regenerator and comes into contact with oxygen-containing gas to undergo a carbonization reaction. The first part of the regenerated catalyst is returned to the first fluidized bed reactor for reaction recycling. The second part of the regenerated catalyst enters the catalyst mixing zone of the second fluidized bed reactor and is mixed with the fresh catalyst for reaction recycling.

[0073] The feedstock is full-fraction crude oil, and the difficult-to-convert components are light hydrocarbons or light distillate oils produced by the unit itself or by other units.

[0074] The present application will be further described below with reference to the preferred embodiments shown in the accompanying drawings, but this does not limit the present application.

[0075] Figure 1A preferred embodiment of the catalytic cracking method of this application is provided, wherein the first fluidized bed reactor 100 is provided with a first pre-lifting medium inlet 101, a first regenerated catalyst inlet 103, and a crude oil inlet 102 from bottom to top. The second fluidized bed reactor 500 is provided with a bottom catalyst mixing zone 506, a lower light hydrocarbon inlet 504, and a mid-to-upper light distillate oil inlet 505. The catalyst mixing zone 506 is provided with a second pre-lifting medium inlet 501, a fresh catalyst inlet 502, and a second regenerated catalyst inlet 503.

[0076] The pre-lifting medium enters the bottom of the first fluidized bed reactor 100 through the first pre-lifting medium inlet 101. The lifting medium can be dry gas, water vapor, or a mixture thereof. It mixes with the hot regenerated catalyst from the first regenerated catalyst inlet 103 and moves upward. The reaction feedstock, such as preheated crude oil and atomized steam, is injected into the lower part of the first fluidized bed reactor 100 through the crude oil inlet 102, where it mixes and contacts with the high-temperature regenerated catalyst and undergoes catalytic cracking reaction.

[0077] The hot regenerated catalyst from the second regenerated catalyst inlet 503 and the fresh catalyst from the fresh catalyst inlet 502 enter the catalyst mixing zone 506 at the bottom of the second fluidized bed reactor 500. Under the lifting action of the pre-lifting medium from the second pre-lifting medium inlet 501, they move upward and mix thoroughly. At the outlet of the catalyst mixing zone 506, the mixed catalyst contacts the difficult-to-convert feedstock, such as light hydrocarbons and atomized steam introduced through the light hydrocarbon inlet 504 and undergoes a catalytic cracking reaction. The resulting oil-catalyst mixture moves upward and contacts the difficult-to-convert components, such as light distillate oil introduced through the pipeline 505, and undergoes a catalytic cracking reaction.

[0078] The reaction oil and gas generated by the catalytic cracking reaction in the first and second fluidized bed reactors, along with the catalyst to be generated, flow upwards and enter the oil-catalyst separation device 204 (such as a cyclone separator) through the first oil-catalyst mixture outlet 104 and the second oil-catalyst mixture outlet 507, respectively, for gas-solid separation. The separated reaction oil and gas are led out through the gas collecting chamber 205 and the large oil-gas pipe 206 to enter the subsequent separation system; the separated catalyst to be generated enters the lower stripping section 201 of the settling tank 200, and after being stripped by the stripping medium from the stripping medium pipeline 202, it enters the coking unit 300 through the catalyst to be generated inclined pipe 203.

[0079] The fluidizing medium enters the coking unit 300 from the bottom of the coking unit 300 through the gas distributor 302 via the fluidizing medium inlet 301. The fluidizing medium can be nitrogen, water vapor, or a mixture thereof. High-temperature regenerated catalyst from external catalyst circulation pipe 303 enters the lower part of coking unit 300, mixes with fluidizing gas and moves upward, contacts the catalyst from the waiting-to-be-generated inclined pipe 203 and continues to move upward, contacts the supplementary fuel oil from coking raw material inlet 304 and undergoes coking reaction; catalyst with coke flows upward, enters regenerator 400 through catalyst distributor 305, contacts oxygen-containing gas injected through oxygen-containing gas inlet 401 and main air distributor 402 and undergoes complete combustion reaction, completely releasing heat, the regenerated catalyst is sent out of regenerator through regenerated catalyst outlet 406, part of the regenerated catalyst is recycled to the first fluidized bed reactor through the first regenerated catalyst inlet 103, and part of the regenerated catalyst is used to the second fluidized bed reactor through the second regenerated catalyst inlet 503; the regenerated flue gas is separated from the entrained catalyst by cyclone separator 404 and enters energy recovery system through regenerated flue gas pipeline 405.

[0080] The crude oil for which the process method provided in this application is applicable is selected from one or more of crude oil, mineral oil, and synthetic oil. The crude oil is a full-range crude oil from a conventional source, the mineral oil is selected from one or more of coal liquefaction oil, oil sands oil, and shale oil, and the synthetic oil is a distillate oil obtained by FT synthesis of coal, natural gas, or bitumen.

[0081] In this application, the difficult-to-convert component is light hydrocarbon or light distillate oil from this device or from external sources.

[0082] In one embodiment, the light hydrocarbons in the difficult-to-convert component are C4 components. These C4 components refer to low-molecular-weight hydrocarbons existing in gaseous form at room temperature and pressure, with C4 fractions as the main component. They include alkanes, alkenes, and alkynes with four carbon atoms in their molecules. This includes gaseous hydrocarbon products rich in C4 fractions produced by the apparatus of this invention, and may also include gaseous hydrocarbons rich in C4 fractions produced by processes in other apparatuses, with the C4 fraction produced by the apparatus of this invention being preferred. The C4 hydrocarbons are preferably C4 fractions rich in olefins, wherein the content of C4 olefins is greater than 50% by weight, preferably greater than 60% by weight, and most preferably greater than 70% by weight.

[0083] In one embodiment, the feedstock is a conventionally sourced full-fraction crude oil;

[0084] Preferably, the feedstock oil further includes optional mineral oil and / or synthetic oil, wherein the mineral oil is selected from one or more of coal liquefaction oil, oil sands oil and shale oil, and the synthetic oil is a distillate oil obtained by FT synthesis of coal, natural gas or bitumen.

[0085] In one embodiment, the light hydrocarbons include gaseous hydrocarbon products rich in C4 fractions produced by the device itself and gaseous hydrocarbons rich in C4 fractions produced by other devices, wherein the C4 olefin content in the gaseous hydrocarbons rich in C4 fractions is greater than 50% by weight.

[0086] Preferably, the difficult-to-convert component is a C4 fraction produced by the device itself.

[0087] In one embodiment, the light distillate oil is selected from one or more of the following: light distillate oil produced by the unit with a final boiling point of less than 280-350°C; straight-run naphtha, straight-run kerosene, and straight-run diesel oil from other primary processing units; and topping oil, residue oil, hydrocracked light naphtha, pentane oil, coking gasoline, Fischer-Tropsch synthetic oil, catalytic cracked light gasoline, hydrotreated gasoline, and hydrotreated diesel oil from other secondary processing units.

[0088] In one embodiment, the first fluidizing reactor is selected from one or more of the following in series: a turbulent bed reactor, a fast bed reactor, and a dilute phase transport bed reactor; and / or

[0089] The second fluidized bed reactor is a dilute phase transport bed reactor.

[0090] In one embodiment, the first fluidized bed reactor is selected from one or a combination of several of turbulent bed, fast bed, and dilute phase transport bed. It can be one or a combination of two reactors connected in series, including those with constant linear velocity, constant diameter, variable diameter, upward transport lines, and downward transport lines. To ensure sufficient reaction of the feedstock oil and depending on different target product quality requirements, the reaction zone can be 2-8, preferably 2-3. The gas velocity in the turbulent bed and fast bed reactors is 0.1 m / s to 2 m / s, and the gas velocity in the dilute phase transport bed is 2 m / s to 20 m / s.

[0091] In one embodiment, the second fluidized bed reactor is selected from a dilute phase conveyed bed reactor, which can be a conventional constant diameter reactor or a reactor of various types with varying diameters.

[0092] In one embodiment, the catalytic cracking reaction conditions in the first fluidized bed reactor are as follows:

[0093] The reaction temperature is 510-650℃;

[0094] The reaction time is 1-20 seconds;

[0095] The weight ratio of catalyst to feedstock is (3-50):1; and / or

[0096] The reaction pressure is 130-450 kPa;

[0097] Preferably, the raw oil is preheated and steam atomized before entering the first fluidized bed reactor. The preheating temperature is 180-350℃, and the water-to-oil weight ratio is (0.03-0.8):1.

[0098] In this application, the catalytic cracking reaction temperature of the first fluidized bed reactor refers to the reactor outlet temperature.

[0099] In one embodiment, the second fluidized bed reactor is provided with one or more inlets for difficult-to-convert components;

[0100] Preferably, the one or more difficult-to-convert component inlets are each independently located at the outlet end of the catalyst mixing zone of the second fluidized bed reactor or in the middle and upper reaches of the second fluidized bed reactor, and the light hydrocarbons and light distillate oils of the difficult-to-convert component are introduced into the second fluidized bed reactor at the same or different difficult-to-convert component inlets;

[0101] More preferably, the light hydrocarbons of the difficult-to-convert component are introduced into the second fluidization reactor at one or more difficult-to-convert component inlets upstream of the light distillate oil introduction location.

[0102] In one embodiment, the second fluidized bed reactor is provided with one or more, such as one, two or more, inlets for difficult-to-convert feedstocks, which may each be independently located in the lower part of the second fluidized bed reactor. More preferably, the difficult-to-convert feedstock inlets are each independently located in the middle to upstream part of the catalytic cracking reactor.

[0103] In one embodiment, the light hydrocarbons and light distillate oils of the difficult-to-convert components can be introduced into the second fluidized bed reactor at the same location or at different locations. Preferably, the light hydrocarbons are introduced into the second fluidized bed reactor at one or more locations downstream of the light distillate oil introduction location.

[0104] In one embodiment, the catalytic cracking reaction conditions in the second fluidized bed reactor are as follows:

[0105] The reaction temperature is 580-750℃;

[0106] The reaction time is 0.05-5 seconds; and / or

[0107] The weight ratio of catalyst to feedstock is (1-50):1;

[0108] Preferably, the difficult-to-convert component is introduced into the second fluidized bed reactor after being atomized by steam, and the weight ratio of water vapor to feed oil is (0.03-0.5):1.

[0109] In one embodiment, the weight ratio of fresh catalyst to regenerated catalyst in the catalyst mixing zone of the second fluidized bed reactor is 0.01-0.3:1.

[0110] In one embodiment, the outlet temperature of the coking device is 550-650°C, and / or the linear velocity is 1.2-2.2 m / s.

[0111] In one embodiment, the atomizing medium of the coking device is nitrogen, and the mass ratio of the atomizing medium to the combustion oil is 1:1 to 1:100.

[0112] In one embodiment, the temperature inside the regenerator is 550-750°C, more preferably 600-730°C, and even more preferably 650-700°C; the apparent linear velocity of the gas is 0.3-3 m / s, preferably 0.5-2.5 m / s, more preferably 0.6-1.5 m / s, and the average residence time of the catalyst to be generated is 0.6-8 minutes, preferably 0.8-6 minutes, and more preferably 1-5 minutes.

[0113] In one embodiment, the catalyst of the present invention, on a dry basis and based on the dry weight of the catalyst, comprises 1-50% by weight, preferably 5-45% by weight, more preferably 10-40% by weight, of zeolite; 5-99% by weight, preferably 10-80% by weight, more preferably 20-70% by weight, of inorganic oxides; and 0-70% by weight, preferably 5-60% by weight, more preferably 10-50% by weight, of clay.

[0114] In one embodiment, the zeolite includes mesoporous zeolite and optionally macroporous zeolite, wherein the mesoporous zeolite is selected from ZSM series zeolite, ZRP zeolite, and any combination thereof; and the macroporous zeolite is selected from rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite, and high silica Y-type zeolite, and any combination thereof.

[0115] In one embodiment, the mesoporous zeolite accounts for 10-90% by weight, preferably 50-80% by weight, on a dry basis, of the total weight of the zeolite.

[0116] In this application, the terms mesoporous zeolite and macroporous zeolite are defined according to conventional definitions in the art, namely, the average pore size of mesoporous zeolite is about 0.5-0.6 nm, and the average pore size of macroporous zeolite is about 0.7-1.0 nm.

[0117] As an example, the macroporous zeolite may be selected from one or more of rare earth Y (REY) type zeolite, rare earth hydrogen Y (REHY) type zeolite, ultrastable Y type zeolite obtained by different methods, and high-silica Y type zeolite. The mesoporous zeolite may be selected from zeolites with an MFI structure, such as ZSM series zeolites and / or ZRP zeolite. Optionally, the above-mentioned mesoporous zeolites may be modified with non-metallic elements such as phosphorus and / or transition metal elements such as iron, cobalt, and nickel. A more detailed description of ZRP zeolite can be found in US Patent 5,232,675A. The ZSM series zeolites are preferably selected from one or more mixtures of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other zeolites with similar structures. A more detailed description of ZSM-5 can be found in US Patent 3,702,886A.

[0118] According to this application, the inorganic oxide, as a binder, is preferably silicon dioxide (SiO2) and / or aluminum oxide (Al2O3). The clay, as a matrix (i.e., carrier), is preferably kaolin and / or hydrous kaolin.

[0119] According to this application, the methods for separating reaction products to obtain cracked gas, cracked light gasoline, cracked light distillate oil, and cracked heavy oil are also well known to those skilled in the art. The cracked gas can be further separated into target products such as ethylene and propylene and C4 components using conventional separation methods in the art.

[0120] According to this application, the oil separation equipment and the reaction product separation equipment are well known to those skilled in the art. For example, the oil separation equipment may include a cyclone separator, a settling tank, and a stripper, while the reaction product separation equipment may be a distillation tower, etc.

[0121] This invention also provides a system for the direct catalytic cracking of crude oil to produce low-carbon olefins, comprising:

[0122] The catalytic cracking reaction unit includes:

[0123] The first fluidization reactor is provided with a first pre-lifting medium inlet, a first regeneration catalyst inlet, a feed oil inlet and a first oil-agent mixture outlet;

[0124] The second fluidized bed reactor is provided with a catalyst mixing zone, one or more inlets for difficult-to-convert components and a second oil-agent mixture outlet. The catalyst mixing zone is provided with a second pre-lifting medium inlet, a second regenerated catalyst inlet and a fresh catalyst inlet.

[0125] An oil-liquid separation device is connected to both the outlet of the first oil-liquid mixture from the first fluidized bed reactor and the outlet of the second oil-liquid mixture from the second fluidized bed reactor, such that the first oil-liquid mixture from the first fluidized bed reactor and the second oil-liquid mixture from the second fluidized bed reactor are separated into reaction oil gas and catalyst to be generated by the oil-liquid separation device; and

[0126] A settling device is used to settle and collect the catalyst to be generated after being separated by the oil-based separation equipment. A stripping section is provided below the settling device for stripping the catalyst to be generated. The stripping section is provided with a catalyst outlet and a stripping medium inlet.

[0127] A reaction product separation unit, which is connected to an oil separation device, is used to separate the reaction oil and gas separated by the oil separation device into products including low-carbon olefins, aromatics and difficult-to-convert components.

[0128] Catalyst regeneration unit, including

[0129] A coking unit is used to bring the catalyst to be generated separated from the catalytic cracking reaction unit into contact with the coking raw material to produce a coking reaction and obtain a catalyst with coke. It is provided with a catalyst inlet, a fluidized medium inlet, a coking raw material inlet, a first gas distributor, a catalyst distributor and a coking catalyst outlet. The catalyst inlet is in fluid communication with the catalyst outlet of the stripping section of the settling tank.

[0130] The regenerator includes a coke catalyst inlet, an oxygen-containing gas inlet, a second gas distributor, a cyclone separator, a regenerated flue gas pipeline, and at least one regenerated catalyst outlet. The coke catalyst inlet of the regenerator is in fluid communication with the coke catalyst outlet of the regenerator. One regenerated catalyst outlet is connected to the first regenerated catalyst inlet of the first fluidized bed reactor for recycling a portion of the regenerated catalyst back to the first fluidized bed reactor. Another regenerated catalyst outlet is connected to the second regenerated catalyst inlet of the catalyst mixing zone of the second fluidized bed reactor for introducing a portion of the regenerated catalyst into the catalyst mixing zone to mix with the fresh catalyst.

[0131] A regenerated catalyst circulation pipeline is provided between the coking unit and the regenerator, which is used to allow a portion of the regenerated catalyst to enter the coking unit and mix with the catalyst to be generated to jointly react with the coking raw material.

[0132] In one embodiment, the distance from the connection port of the regenerated catalyst circulation pipe on the coking unit to the bottom of the coking unit is 5% to 10% of the height of the coking unit; and / or

[0133] The distance between the raw coke inlet and the bottom of the coking unit is 20% to 50% of the height of the coking unit.

[0134] In this application, the coking unit may be provided with one or more, such as one, two, or more fuel oil inlets. These fuel oil inlets may be independently located at the outlet end of the coking unit or at the bottom of the coking unit. More preferably, each fuel oil inlet is independently located in the middle to upper part of the coking unit. More preferably, the distance from each fuel oil inlet to the bottom of the coking unit is independently 20% to 50% of the coking unit's height. The fuel oil may include straight-run distillate or secondary processed distillate. Preferably, the secondary processed distillate may be selected from one or more blends of catalytic cracking diesel, catalytic cracking slurry oil, coking gasoline, coking diesel, and coking wax oil.

[0135] In one embodiment, the fluidizing medium of the coking device enters the coking device through a first gas distributor located at the bottom.

[0136] According to this application, the first gas distributor can be a main air distributor well known to those skilled in the art. For example, the main air distributor can be a distribution plate or a distribution pipe. Preferably, the distribution pipe is an annular distribution pipe or a tree-shaped distribution pipe.

[0137] In this application, a catalyst distribution plate can be installed at the bottom of the catalyst inlet of the regenerator, for example, at the outlet end of the coking unit. According to this application, the catalyst distribution plate can be one or more of various industrially common types, such as flat, arched, disc-shaped, annular, and umbrella-shaped plates. Using a catalyst distribution plate helps to ensure uniform concentration of the catalyst in contact with the oxygen-containing gas along the axial direction of the regenerator for the coking reaction, improving coking efficiency and reducing the occurrence of localized hot spots in the catalyst bed.

[0138] By setting up a coking unit, the injected fuel oil is mixed with the catalyst under low temperature and oxygen-free fluidization conditions to form coke. The catalyst with coke attached is back-mixed in the coking unit to make the coke evenly distributed on the catalyst, which helps to achieve a uniform temperature distribution on the catalyst surface.

[0139] In one embodiment, a second gas distributor is provided at the bottom of the regenerator, so that oxygen-containing gas injected through the oxygen-containing gas inlet enters the regenerator through the second gas distributor. According to this application, the second gas distributor can be a main air distributor well known to those skilled in the art. For example, the main air distributor can be a distribution plate or a distribution pipe. Preferably, the distribution pipe is an annular distribution pipe or a dendritic distribution pipe.

[0140] The following embodiments will further illustrate this application, but do not limit this application.

[0141] The feedstock used in the following examples and comparative examples was Kuwaiti crude oil, the properties of which are shown in Table 1. The catalyst used was a commercial catalytic cracking catalyst purchased from the Catalyst Division of China Petroleum & Chemical Corporation (Sinopec), with the trade name DMMC-2.

[0142] Example 1

[0143] Using the feedstock and DMMC-2 catalyst shown in Table 1, in Figure 1 The experiment was conducted on the medium-sized apparatus shown, in which the reactor structure is as follows:

[0144] Both the first and second fluidized bed reactors are riser reactors of equal diameter. The first fluidized bed reactor has a total height of 7 meters and an inner diameter of 0.3 meters, while the second fluidized bed reactor has a height of 7 meters and an inner diameter of 0.2 meters. The catalyst mixing zone has a height of 1 meter, and the coking unit has an inner diameter of 0.3 meters and a height of 2 meters. The distance between the coking feed inlet 304 and the bottom of the coking unit is 30% of the coking unit's height. The outlet of the coking unit is directly connected to the bottom opening of the regenerator, and a catalyst distributor is installed at the outlet.

[0145] The hot regenerated catalyst at the first regenerated catalyst inlet 103 enters the lower part of the first fluidized bed reactor and moves upward under the action of the pre-lifting medium. Preheated crude oil and atomized steam are injected into the lower part of the first fluidized bed reactor through the feed pipeline at a water-to-oil weight ratio of 0.2:1. They mix and contact with the existing catalyst in the catalytic cracking reactor and undergo catalytic cracking reaction to generate the first reaction product and the catalyst to be generated.

[0146] The hot regenerated catalyst from the second regenerated catalyst inlet 503 and the fresh catalyst from the fresh catalyst inlet 502 enter the catalyst mixing zone 506. Under the lifting action of the pre-lifting medium injected through the second pre-lifting medium inlet 501, they move upward. The C4 fraction of the difficult-to-convert component enters the outlet of the catalyst mixing zone 506 through the light hydrocarbon inlet 504. The water-oil weight ratio is 0.2:1. It contacts the mixed catalyst and undergoes a catalytic cracking reaction. The reaction oil mixture moves upward and contacts the light distillate oil of the difficult-to-convert component introduced through the light distillate oil inlet 505 and undergoes a catalytic cracking reaction to generate the second reaction product and the catalyst to be generated.

[0147] The first and second reaction products and the catalyst to be generated enter the oil-solid separation device 204, such as a cyclone separator, for gas-solid separation. The resulting reaction oil and gas are led out through the gas collection chamber 205 and the large oil and gas pipe 206 and enter the subsequent separation system. The catalyst containing coke obtained from the separation enters the lower part of the settling tank 200 and enters the coking tank 300 through the inclined tube 203.

[0148] Nitrogen gas is introduced into the bottom of the coking unit 300, where it mixes sequentially with the regenerated catalyst and the catalyst to be regenerated, causing the catalyst to be regenerated to heat up. The coking feedstock, which is catalytic cracked diesel oil, is injected into the coking unit after being atomized by nitrogen. The mass ratio of the atomizing medium to the coking feedstock fuel oil is 0.05:1. The feedstock contacts the material in the coking unit and undergoes a coking reaction. The catalyst containing coke enters the regenerator, where it comes into contact with air and undergoes a complete combustion reaction. The regenerated catalyst is returned to the first fluidized bed reactor and the second fluidized bed reactor for recycling. The regenerated flue gas enters the energy recovery system through pipeline 405.

[0149] Operating conditions and product distribution are listed in Tables 2 and 3. As can be seen from Table 3, the ethylene yield in this embodiment reached 7.78% by weight, the propylene yield reached 19.11% by weight, and the total yield of low-carbon olefins and light aromatics was 45.83%.

[0150] Comparative Example 1

[0151] Using the feedstock oil and DMMC-2 catalyst shown in Table 1, experiments were conducted on a medium-sized plant. The reactor consisted of a conventional riser reactor (first fluidized bed reactor) and a series fluidized bed reactor (second fluidized bed reactor). Preheated feedstock oil sequentially entered the riser reaction zone and the fluidized bed reactor to contact the catalytic cracking catalyst for catalytic cracking. The post-reaction stream entered subsequent oil-catalyst separation and product separation equipment. The separated regenerated catalyst entered the lower part of the regenerator, where it reacted with air distributed into the regenerator via the main air distributor to undergo a coking reaction. The coked feedstock was injected into the dense phase catalyst bed, where it reacted with the high-temperature air to release heat. The regenerated catalyst was returned to the reactor for recycling. Operating conditions and product distribution are listed in Tables 2 and 3.

[0152] As can be seen from the results in Table 3, the yield of ethylene in this comparative example reached 5.56% by weight, the yield of propylene reached 15.85% by weight, and the total yield of low-carbon olefins and light aromatics was 39.04%.

[0153] The results from the above examples and comparative examples show that when using the catalytic cracking method and system of this application for crude oil catalytic cracking reaction, the yield of low-carbon olefins is significantly improved and the crude oil atom utilization rate is high. When the heat balance is insufficient, using a coking unit can make the coke combustion environment in the regenerator mild and stable, and the radial and axial catalyst temperatures help maintain the physical and chemical properties of the catalyst.

[0154] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0155] 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. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0156] Furthermore, various different embodiments of this application can be combined in any way, as long as they do not violate the spirit of this application, they should also be regarded as the content of this application.

[0157] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0158] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

[0159] Table 1 Properties of the crude oil used

[0160]

[0161] Table 2 Reaction conditions of Example 1 and Comparative Example 1

[0162]

[0163] Table 3 Comparison of reaction results between Example 1 and Comparative Example 1

[0164]

Claims

1. A method for producing low-carbon olefins and aromatics through direct catalytic cracking of crude oil, comprising: (1) The feedstock oil and the first regenerated catalyst from the regenerator enter the first fluidized bed reactor for catalytic cracking reaction to obtain a first oil-catalyst mixture containing the first reaction product and the first regenerated catalyst; (2) The second regenerated catalyst and the fresh catalyst from the regenerator enter the catalyst mixing zone of the second fluidized reactor and are mixed. They then come into contact with the difficult-to-convert components and undergo catalytic cracking to obtain a second oil-agent mixture containing the second reaction product and the second regenerated catalyst. (3) The first oil mixture and the second oil mixture enter the oil separation equipment for gas-solid separation. The separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, aromatics, difficult-to-convert components and other products. (4) The separated raw catalyst is stripped and then enters the coking unit. After being mixed with the third regenerated catalyst from the regenerator and heated, it comes into contact with the raw coking raw material to produce a coking reaction, thus obtaining the raw catalyst with coke. (5) The spent catalyst with coke enters the regenerator and comes into contact with oxygen-containing gas to undergo a carbonization reaction. The first part of the regenerated catalyst is returned to the first fluidized bed reactor for reaction recycling. The second part of the regenerated catalyst enters the catalyst mixing zone of the second fluidized bed reactor and is mixed with the fresh catalyst for reaction recycling. The feedstock is full-fraction crude oil, and the difficult-to-convert components are light hydrocarbons or light distillate oils produced by the unit itself or by other units. The feedstock is conventionally sourced full-fraction crude oil; In the catalyst mixing zone of the second fluidized bed reactor, the weight ratio of fresh catalyst to regenerated catalyst is 0.01-0.3:

1. The fluidizing medium of the coking device is nitrogen, water vapor, or a mixture thereof.

2. The method according to claim 1, characterized in that, The feedstock oil also includes mineral oil and / or synthetic oil, wherein the mineral oil is selected from one or more of coal liquefaction oil, oil sands oil and shale oil, and the synthetic oil is a distillate oil obtained by FT synthesis of coal, natural gas or bitumen.

3. The method according to claim 1, characterized in that, The light hydrocarbons include gaseous hydrocarbon products rich in C4 fractions produced by the unit itself and gaseous hydrocarbons rich in C4 fractions produced by other units, wherein the C4 olefin content in the gaseous hydrocarbons rich in C4 fractions is greater than 50% by weight.

4. The method according to claim 3, characterized in that, The difficult-to-convert component is the C4 fraction produced by the unit itself.

5. The method according to claim 1, characterized in that, The light distillate oil is selected from one or more of the following: light distillate oil produced by the unit with a final boiling point of less than 280-350℃; straight-run naphtha, straight-run kerosene, and straight-run diesel oil from other primary processing units; and topping oil, residue oil, hydrocracked light naphtha, pentane oil, coking gasoline, Fischer-Tropsch synthetic oil, catalytic cracked light gasoline, hydrotreated gasoline, and hydrotreated diesel oil from other secondary processing units.

6. The method according to claim 1, characterized in that, The first fluidized bed reactor is selected from one or more of the following in series: turbulent bed reactor, fast bed reactor, and dilute phase transport bed reactor; and / or The second fluidized bed reactor is a dilute phase transport bed reactor.

7. The method according to claim 1, characterized in that, The catalytic cracking reaction conditions in the first fluidized bed reactor are as follows: The reaction temperature is 510-650℃; The reaction time is 1-20 seconds; The weight ratio of catalyst to feedstock is (3-50):1; and / or The reaction pressure is 130-450 kPa.

8. The method according to claim 7, characterized in that, The feedstock oil is preheated and steam atomized before entering the first fluidized bed reactor. The preheating temperature is 180-350℃, and the water-to-oil weight ratio is (0.03-0.8):

1.

9. The method according to claim 1, characterized in that, The second fluidized bed reactor is provided with one or more inlets for difficult-to-convert components.

10. The method according to claim 9, characterized in that, The one or more difficult-to-convert component inlets are each independently located at the outlet end of the catalyst mixing zone of the second fluidized bed reactor or in the middle and upper reaches of the second fluidized bed reactor. The light hydrocarbons and light distillate oils of the difficult-to-convert component are introduced into the second fluidized bed reactor at the same or different difficult-to-convert component inlets.

11. The method according to claim 10, characterized in that, The light hydrocarbons of the difficult-to-convert component are introduced into the second fluidized bed reactor at one or more difficult-to-convert component inlets upstream of the light distillate oil inlet.

12. The method according to claim 1, characterized in that, The catalytic cracking reaction conditions in the second fluidized bed reactor are as follows: The reaction temperature is 580-750℃; The reaction time is 0.05-5 seconds; and / or The weight ratio of catalyst to feedstock is (1-50):

1.

13. The method according to claim 12, characterized in that, The difficult-to-convert components are introduced into the second fluidized bed reactor after being atomized with steam, and the weight ratio of steam to feed oil is (0.03-0.5):

1.

14. The method according to claim 1, characterized in that, The outlet temperature of the coking unit is 550-650℃, and / or the linear velocity is 1.2-2.2 m / s.

15. A system for implementing the method according to any one of claims 1 to 14, comprising: The catalytic cracking reaction unit includes: The first fluidization reactor is provided with a first pre-lifting medium inlet, a first regeneration catalyst inlet, a feed oil inlet and a first oil-agent mixture outlet; The second fluidized bed reactor is provided with a catalyst mixing zone, one or more inlets for difficult-to-convert components and a second oil-agent mixture outlet. The catalyst mixing zone is provided with a second pre-lifting medium inlet, a second regenerated catalyst inlet and a fresh catalyst inlet. An oil-liquid separation device is connected to both the outlet of the first oil-liquid mixture from the first fluidized bed reactor and the outlet of the second oil-liquid mixture from the second fluidized bed reactor, such that the first oil-liquid mixture from the first fluidized bed reactor and the second oil-liquid mixture from the second fluidized bed reactor are separated into reaction oil gas and catalyst to be generated by the oil-liquid separation device; and A settling device is used to settle and collect the catalyst to be generated after being separated by the oil-based separation equipment. A stripping section is provided below the settling device for stripping the catalyst to be generated. The stripping section is provided with a catalyst outlet and a stripping medium inlet. A reaction product separation unit, which is connected to an oil separation device, is used to separate the reaction oil and gas separated by the oil separation device into products including low-carbon olefins, aromatics and difficult-to-convert components. Catalyst regeneration unit, including A coking unit is used to bring the catalyst to be generated separated from the catalytic cracking reaction unit into contact with the coking raw material to produce a coking reaction and obtain a catalyst with coke. It is provided with a catalyst inlet, a fluidized medium inlet, a coking raw material inlet, a first gas distributor, a catalyst distributor and a coking catalyst outlet. The catalyst inlet is in fluid communication with the catalyst outlet of the stripping section of the settling tank. The regenerator includes a coke catalyst inlet, an oxygen-containing gas inlet, a second gas distributor, a cyclone separator, a regenerated flue gas pipeline, and at least one regenerated catalyst outlet. The coke catalyst inlet of the regenerator is in fluid communication with the coke catalyst outlet of the regenerator. One regenerated catalyst outlet is connected to the first regenerated catalyst inlet of the first fluidized bed reactor for recycling a portion of the regenerated catalyst back to the first fluidized bed reactor. Another regenerated catalyst outlet is connected to the second regenerated catalyst inlet of the catalyst mixing zone of the second fluidized bed reactor for introducing a portion of the regenerated catalyst into the catalyst mixing zone to mix with the fresh catalyst. A regenerated catalyst circulation pipeline is provided between the coking unit and the regenerator, which is used to allow a portion of the regenerated catalyst to enter the coking unit and mix with the catalyst to be generated to jointly react with the coking raw material.

16. The system according to claim 15, characterized in that, The distance from the connection port of the external regeneration catalyst circulation pipeline on the coking unit to the bottom of the coking unit is 5% to 10% of the height of the coking unit; and / or The distance between the raw coke inlet and the bottom of the coking unit is 20% to 50% of the height of the coking unit.

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