Method and system for producing low-carbon olefins and aromatic hydrocarbons by catalytic cracking of inferior crude oil

Abstract

The invention relates to a method and system for producing low-carbon olefins and aromatic hydrocarbons by catalytic cracking of inferior crude oil, and the method comprises the following steps: crude oil is distilled and separated into crude oil light fractions and crude oil heavy fractions, the crude oil heavy fractions are subjected to a catalytic cracking reaction in a first reactor, and the crude oil light fractions are subjected to a catalytic cracking reaction in a second reactor; after the reaction product and the spent catalyst are subjected to gas-solid separation, the spent catalyst is subjected to steam stripping and scorching regeneration and then returns to the reactor for recycling; and separating the reaction product to obtain ethylene, propylene, a difficult-to-convert component and other products, wherein the difficult-to-convert component enters the second reactor to be further subjected to catalytic cracking reaction to obtain ethylene and propylene. When the catalytic cracking method and system are used for the catalytic cracking reaction of crude oil, chemical raw materials such as ethylene and propylene can be produced with high selectivity, and efficient utilization of crude oil resources is realized.

Description

Technical Field

[0001] The present application relates to the field of petrochemical industry, and in particular, to a catalytic cracking method and system for producing low-carbon olefins and aromatics from inferior crude oil. Background Art

[0002] Ethylene, propylene and BTX (benzene-toluene-xylene) are key basic organic synthetic raw materials with huge demand. They can be used to produce a variety of organic chemical products, including many important high-end organic chemical products. They are closely related to people's food, clothing, housing and transportation, and are an important guarantee for the country's high-quality and sustainable development. The existing technical route for producing propylene and BTX from petroleum is developed on the basis of the traditional petroleum refining process that mainly produces oil products. There are problems such as long production process, low chemical yield and insignificant economic benefits. The technical measures to solve this problem are to develop key core technologies that mainly produce chemicals and can direct the conversion of crude oil hydrocarbon molecules into chemicals. Therefore, in recent years, petrochemical companies at home and abroad have been actively exploring the technical route of directly producing chemicals from crude oil, so as to make the processing path from crude oil to low-carbon olefins and BTX and other chemicals shorter, with lower energy consumption and smaller investment.

[0003] WO2005113722A3 and CN200780047937.2 disclose a process for producing crude oil directly into chemicals, wherein the crude oil directly enters a steam cracking furnace, and is flash evaporated to separate light components and heavy components, the light components (gaseous components) enter the steam cracking furnace for cracking, and the heavy components (liquid components) are used as refinery raw materials.

[0004] CN 201380015214.X discloses a process for producing olefins and aromatics from crude oil by integrating hydroprocessing, steam cracking and catalytic cracking processes. After the crude oil is hydroprocessed, impurities such as sulfur and high-boiling substances are removed, and the hydrogenated products are separated by distillation. The light components enter the steam cracking unit, and the heavy components are subjected to the catalytic cracking unit to maximize the production of olefins.

[0005] CN201780078199.1 discloses a method and system for converting crude oil into petrochemicals and fuel products by integrating steam cracking and fluid catalytic cracking. Crude oil is separated into straight-run naphtha and lighter component fractions, one or more intermediate distillate fractions, and atmospheric residue fractions. Vacuum distillate oil is then separated from the atmospheric residue fraction as a catalytic cracking feedstock. The light fraction is hydrogenated and used as naphtha and diesel fuel oil.

[0006] The above crude oil processing routes all use steam cracking as the main technical means to produce light olefins. Due to the high energy consumption of steam cracking technology and the poor flexibility of product solutions, researchers are also actively developing technical solutions for producing light olefins by catalytic cracking.

[0007] The method for preparing low-carbon olefins and aromatics by catalytic cracking of crude oil disclosed in CN20181189551.1 and CN201811190135.3 comprises the following steps: after desalting and dehydrating the crude oil, the crude oil is divided into light and heavy components, and the light component, i.e., light feed, and the heavy component, i.e., heavy feed, are respectively placed in two catalytic cracking reactors, and are contacted with a high-temperature catalyst under a steam atmosphere to react to produce low-carbon olefins and aromatics. Alternatively, the light component and the heavy component react in different reaction zones of the same reactor.

[0008] CN 201810523356.1 discloses a method for processing a whole fraction of crude oil. The method separates the whole fraction of crude oil to obtain light distillate oil, middle distillate oil and heavy distillate oil. The middle distillate oil and the heavy distillate oil are reacted in a first riser, and the light distillate oil is reacted in a fluidized bed reactor connected in series with the riser. The reaction conditions in the reactor vary according to the properties of the raw materials.

[0009] Existing crude oil catalytic cracking technologies all use crude oil distillation to separate fractions and then perform catalytic cracking reactions, that is, light fractions and heavy fractions enter their own reaction zones or reactors for catalytic cracking reactions. Different catalytic cracking reaction environments are selected according to the performance differences of different fractions, which is beneficial to improving the conversion rate of crude oil molecular cracking reactions to a certain extent. However, due to the large differences in molecular size and structure between light crude oil fractions and heavy crude oil fractions in crude oil, when the reaction system shares a catalyst, the properties of the catalyst are difficult to take into account the catalytic cracking reaction performance of both light crude oil fractions and heavy crude oil fractions, resulting in relatively low selectivity for the target product. Summary of the invention

[0010] The purpose of this application is to provide a method and system for catalytic cracking of inferior crude oil based on the current catalytic cracking technology, which will help to improve the yield and selectivity of low-carbon olefins and aromatics and achieve efficient utilization of crude oil resources.

[0011] The first aspect of the present invention provides a method for producing low-carbon olefins and aromatics by catalytic cracking of low-quality crude oil, comprising:

[0012] (1) distilling crude oil into a light crude oil fraction and a heavy crude oil fraction, wherein the cutting point of the light crude oil fraction and the heavy crude oil fraction is in the range of 280-360° C.;

[0013] (2) the heavy crude oil fraction and the first regenerated catalyst from the regenerator enter the first reactor for catalytic cracking reaction, and optionally, the reaction product contacts with the introduced supplementary catalyst and continues to react;

[0014] (3) the second regenerated catalyst and the fresh catalyst are mixed in a catalyst mixing zone at the lower part of the second reactor to obtain a catalyst mixture, the catalyst mixture flows toward the downstream of the second reactor under the action of a fluidizing medium, and sequentially contacts with the light fraction of crude oil and the difficult-to-convert component fed into the second reactor to undergo cracking reaction;

[0015] (4) The mixture of the reaction products of the first reactor and the second reactor and the catalyst to be produced enters the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products;

[0016] (5) The separated spent catalyst with coke is stripped and then enters the regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor and the second reactor for use in the reaction cycle.

[0017] The crude oil is selected from one or more of intermediate base crude oil, intermediate-cycloalkyl crude oil, and cycloalkyl-intermediate base crude oil, and the difficult-to-convert component is a C4 component and / or a light distillate oil with a final boiling point less than 280-360°C.

[0018] The method according to the first aspect, wherein the properties of the crude oil meet at least one of the following indicators: the characteristic factor K value is not greater than 12.2, the density is 800-935 kg / m 3 , the residual carbon is 2-10% by weight, and the total content of nickel and vanadium is 5-50ppm.

[0019] The method according to the first aspect, wherein the C4 component comprises gaseous hydrocarbons rich in C4 fraction produced by the device itself and / or other devices, wherein the content of C4 olefins in the gaseous hydrocarbons rich in C4 fraction is greater than 50% by weight;

[0020] Preferably, the difficult-to-convert raw material is a gaseous hydrocarbon rich in C4 fraction produced by the device.

[0021] According to the method of the first aspect, the difficult-to-convert components include light distillate oil with a final boiling point of less than 280-360° C. produced by the device and optionally one or more of the following fractions:

[0022] Straight-run naphtha, straight-run kerosene, and straight-run diesel produced by other primary processing units;

[0023] Other secondary processing units produce topped oil, raffinate oil, hydrocracked light naphtha, pentane oil, coker gasoline, Fischer-Tropsch synthetic oil, catalytic cracking light gasoline, hydrogenated gasoline, and hydrogenated diesel.

[0024] According to the method of the first aspect, the reaction conditions of the first reactor include: a reaction temperature of 510-650°C, a weight hourly space velocity of 1-20 hours -1 The weight ratio of catalyst to oil is (3-50):1, and the catalyst density is 120-290 kg / m 3 , and / or the reaction pressure is 130-450 kPa;

[0025] Preferably, the heavy crude oil fraction enters the first reactor after being steam atomized, and the water-oil weight ratio is (0.03-0.8):1.

[0026] The method according to the first aspect, wherein the reaction conditions of the second reactor include: reaction temperature of 580-750°C, reaction time of 0.05-5 seconds, catalyst-oil weight ratio of (1-50):1, catalyst density of 20-100 kg / m 3 , and / or the reaction pressure is 130-450 kPa;

[0027] Preferably, the light fraction of crude oil enters the second reactor after being steam atomized, and the weight ratio of water to oil is (0.03-0.5):1.

[0028] The method according to the first aspect, wherein in the second reactor, the weight ratio of the fresh catalyst to the regenerated catalyst is 0.01-0.3:1; and / or

[0029] The reaction conditions of the difficult-to-convert components are: reaction temperature of 560-720° C., and / or reaction time of 0.1-3 seconds.

[0030] According to the method of the first aspect, the regeneration condition of the regenerator includes:

[0031] Temperature 550-700°C, preferably 600-650°C;

[0032] The gas superficial velocity is 0.2-1.2 m / s, preferably 0.4-0.8 m / s; and / or

[0033] The average residence time of the catalyst is 1-10 minutes, preferably 2-6 minutes.

[0034] According to the method of the first aspect, the CO concentration in the regeneration flue gas of the regenerator is 0.5-6% by volume.

[0035] A second aspect of the present invention provides a catalytic cracking system, comprising:

[0036] The crude oil distillation unit is used to distill crude oil into light crude oil fractions and heavy crude oil fractions.

[0037] The catalytic cracking reaction unit comprises:

[0038] The first reactor is provided with a first pre-lifting medium inlet, a first regenerated catalyst inlet, a supplementary catalyst inlet, a crude oil heavy fraction inlet and a first oil agent mixture outlet;

[0039] The second reactor is provided with a catalyst mixing zone, a crude oil light fraction inlet, a difficult-to-convert component inlet, and a second oil agent mixture outlet in sequence, and the catalyst mixing zone is provided with a second pre-lifting medium inlet, a second regenerated catalyst inlet, and a fresh catalyst inlet for mixing the regenerated catalyst circulated back to the second reactor with the fresh catalyst;

[0040] An oil agent separation device, used for separating the first oil agent mixture from the first reactor and the second oil agent mixture from the second reactor into reaction oil gas and a catalyst to be generated through the oil agent separation device; and

[0041] A settler, used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is provided below the settler for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet;

[0042] Preferably, the first reactor and the second reactor are arranged in parallel;

[0043] a reaction product separation unit, the reaction product separation unit being in communication with the oil agent separation device and being used for separating the reaction oil gas separated by the oil agent separation device; and

[0044] A regenerator, wherein the regenerator is provided with an inlet for regenerated catalyst, an inlet for oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and at least one regenerated catalyst outlet; the inlet for regenerated catalyst of the regenerator is fluidly connected to the outlet of the regenerated catalyst of the stripping section; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the first reactor for recycling a part of the regenerated catalyst back to the first reactor; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the second reactor for recycling a part of the regenerated catalyst back to the first reactor.

[0045] According to the system of the second aspect, one or more supplementary catalyst inlets are provided on the first reactor, and the positions of the one or more supplementary catalyst inlets are each independently located at a height greater than 0% to 90% of the total height of the first reactor, preferably at a height of 20% to 80% of the total height of the first reactor, and more preferably at a height of 30% to 75%.

[0046] Compared with the prior art, the method and system of the present invention have the following beneficial effects:

[0047] 1) The relatively difficult light fractions in crude oil are subjected to catalytic cracking reaction in a separate reactor, and fresh agent is added to the regenerated catalyst to adjust the acid properties of the regenerated catalyst, provide a suitable catalyst for the light fractions of crude oil, and improve the conversion rate of the cracking reaction of the light fractions of crude oil and the selectivity of low-carbon olefins.

[0048] 2) In the process of catalytic cracking of crude oil, the single-pass conversion rate is not pursued. The light distillate oil that is difficult to convert is recycled. By setting up specific reaction zones, a higher overall conversion rate and higher light olefin selectivity can be achieved.

[0049] 3) The regenerator adopts an incomplete regeneration method, so that the regenerated catalyst carries a small amount of carbon. These carbons adhere to the heavy metals deposited during the reaction, which can alleviate the problem of decreased reaction selectivity caused by the destruction of the molecular sieve framework by heavy metals in crude oil.

[0050] By adopting the catalytic cracking method of the present application, chemical raw materials such as ethylene and propylene can be efficiently produced directly from crude oil, achieving efficient utilization of crude oil resources, alleviating the situation of excess refined oil, and helping refineries to transform, develop and extend from oil refining to chemical raw material production, reducing production costs and increasing refineries' profit margins. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application but do not constitute a limitation to the present application. In the accompanying drawings:

[0052] Figure 1 A schematic diagram of a process for producing light olefins and aromatics by catalytic cracking of crude oil according to an embodiment of the present application.

[0053] Description of reference numerals:

[0054] 100, first reactor; 101, first pre-lifting medium inlet; 102, crude oil heavy fraction inlet; 103, regeneration inclined tube; 104, oil-agent mixture outlet; 105, supplementary catalyst inlet; 200, settler; 201, stripping section; 202, stripping medium inlet; 203, to-be-regenerated inclined tube; 204, oil-agent separation device; 205, gas collecting chamber; 206, large oil and gas pipe; 300, second reactor; 301, second pre-lifting medium inlet; 302, fresh catalyst inlet; 303, second regenerated catalyst inlet; 304, crude oil light fraction inlet; 305, difficult-to-convert raw material inlet; 306, catalyst mixing zone; 400, regenerator; 401, oxygen-containing gas inlet; 402, gas distributor; 404, cyclone separator; 405, regeneration flue gas pipeline; 600, crude oil distillation unit; 601, light fraction outlet; 602, heavy fraction outlet. DETAILED DESCRIPTION

[0055] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0056] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0057] Any specific numerical value disclosed herein (including the endpoint of the numerical range) is not limited to the exact value of the numerical value, but should be understood to also cover values ​​close to the exact value, such as all possible numerical values ​​within the range of ±5% of the exact value. In addition, for the disclosed numerical range, the endpoint values ​​of the range, the endpoint values ​​and the specific point values ​​in the range, and the specific point values ​​can be arbitrarily combined to obtain one or more new numerical ranges, and these new numerical ranges should also be regarded as specifically disclosed herein.

[0058] In the present application, the terms "upstream" and "downstream" are based on the flow direction of the reactants. For example, when the reactants flow from bottom to top, "upstream" means the position below, while "downstream" means the position above.

[0059] In this article, low-carbon olefins are a general term for ethylene, propylene and butene, and light aromatics (BTX) are a general term for benzene (BTX), toluene (T) and xylene (X).

[0060] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0061] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0062] The present invention provides a method for producing low-carbon olefins and aromatics by catalytic cracking of inferior crude oil, which comprises:

[0063] (1) distilling crude oil into a light crude oil fraction and a heavy crude oil fraction, wherein the cutting point of the light crude oil fraction and the heavy crude oil fraction is in the range of 280-360° C.;

[0064] (2) the heavy crude oil fraction and the first regenerated catalyst from the regenerator enter the first reactor for catalytic cracking reaction, and optionally, the reaction product contacts with the introduced supplementary catalyst and continues to react;

[0065] (3) the second regenerated catalyst and the fresh catalyst are mixed in a catalyst mixing zone at the lower part of the second reactor to obtain a catalyst mixture, the catalyst mixture flows toward the downstream of the second reactor under the action of a fluidizing medium, and sequentially contacts with the light fraction of crude oil and the difficult-to-convert component fed into the second reactor to undergo cracking reaction;

[0066] (4) The mixture of the reaction products of the first reactor and the second reactor and the catalyst to be produced enters the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products;

[0067] (5) The separated spent catalyst with coke is stripped and then enters the regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor and the second reactor for use in the reaction cycle.

[0068] The crude oil is selected from one or more of intermediate base crude oil, intermediate-cycloalkyl crude oil, and cycloalkyl-intermediate base crude oil, and the difficult-to-convert component is a C4 component and / or a light distillate oil with a final boiling point less than 280-360°C.

[0069] The present application will be further described below with reference to the preferred implementation modes shown in the accompanying drawings, but the present application is not limited thereby.

[0070] Figure 1 A preferred embodiment of the crude oil catalytic cracking method of the present application is provided, wherein the crude oil distillation unit 600 is provided with a light fraction outlet 601 and a heavy fraction outlet 602; the catalytic cracking reactor comprises a first reactor 100, a second reactor 300, and a regenerator 400. The first reactor 100 is provided with a first pre-lifting medium inlet 101, a first regenerated catalyst inlet connected to a regeneration inclined tube 103, a crude oil heavy fraction inlet 102, a supplementary catalyst inlet and an oil agent mixture outlet 104 from bottom to top. The second reactor 300 is provided with a bottom catalyst mixing zone 306, a crude oil light fraction inlet 304 at the bottom and a difficult-to-convert raw material inlet 305 at the middle and upper reaches. The catalyst mixing zone 306 is provided with a second pre-lifting medium inlet 301, a fresh catalyst inlet 302 and a second regenerated catalyst inlet 303.

[0071] The pre-lifting medium enters the bottom of the first reactor 100 through the first pre-lifting medium inlet 101. The lifting medium can be dry gas, water vapor or a mixture thereof, which is mixed with the hot regenerated catalyst from the regeneration inclined tube 103 and moves upward. The reaction raw materials, such as the preheated crude oil heavy fraction, are mixed with atomizing steam through the pipeline 602 and injected into the lower part of the first reactor 100 through the feed crude oil heavy fraction inlet 102, mixed with the high-temperature regenerated catalyst and subjected to catalytic cracking reaction. The reacted oil agent is mixed and moves upward, and is mixed with the supplementary catalyst introduced through the supplementary catalyst inlet 105 and continues to move upward.

[0072] The hot regenerated catalyst from the regeneration inclined tube 303 and the fresh catalyst from the fresh catalyst inlet 302 enter the catalyst mixing zone 306 at the bottom of the second reactor 300, move upward and are fully mixed under the lifting action of the pre-lifting medium from the second pre-lifting medium inlet 301, and the mixed catalyst contacts the mixture of the light crude oil fraction 601 and atomized steam introduced through the light crude oil fraction inlet 304 at the outlet of the catalyst mixing zone 306 and undergoes a catalytic cracking reaction, and the generated oil-agent mixture moves upward, contacts the difficult-to-convert components introduced through the difficult-to-convert raw material inlet 305, and undergoes a catalytic cracking reaction.

[0073] The reaction oil gas and the catalyst to be regenerated from the first reactor and the second reactor flow upward through the oil-agent mixture outlet 104 and enter the oil-agent separation device 204 such as a cyclone separator for gas-solid separation. The reaction oil gas obtained by separation is led out of the device through the gas collecting chamber 205 and the large oil-gas pipe 206 and enters the subsequent separation system; the catalyst to be regenerated obtained by separation enters the stripping section 201 at the lower part of the settler 200, and after being stripped by the stripping medium from the stripping medium inlet 202, it enters the regenerator 400 through the inclined pipe 203 to be regenerated.

[0074] The catalyst to be regenerated contacts with the oxygen-containing gas injected through the oxygen-containing gas inlet 401 and the gas distributor 402 and undergoes an incomplete combustion reaction, releasing heat. After the catalyst is regenerated, part of the regenerated catalyst is supplied to the first reactor via pipeline 103, and part of the regenerated catalyst is circulated to the second reactor via pipeline 303; the regenerated flue gas is separated from the entrained catalyst by the cyclone separator 404 and enters the energy recovery system via the regenerated flue gas pipeline 405.

[0075] The crude oil applicable to the catalytic cracking method provided in the present application is selected from one or more mixed crude oils of intermediate base crude oil, intermediate-cycloalkyl crude oil or cycloalkyl-intermediate base crude oil. Any component in the first key component and the second key group of the intermediate base crude oil belongs to the intermediate base attribute; the first key component of the intermediate-cycloalkyl crude oil is the intermediate base attribute and the second key group is the cycloalkyl attribute; the first key component of the cycloalkyl-intermediate base crude oil is the cycloalkyl attribute and the second key group is the intermediate base attribute.

[0076] In one embodiment, the properties of the crude oil meet at least one of the following indicators: the characteristic factor K value is not greater than 12.2, the density is 800-935 kg / m 3 , the residual carbon is 2-10% by weight, and the total content of nickel and vanadium is 5-50ppm.

[0077] In the present application, the difficult-to-convert component is one of the carbon four components or the light distillate oil with a final boiling point less than 280-360°C, or a mixture thereof.

[0078] In one embodiment, the C4 component refers to a low molecular hydrocarbon compound that exists in gaseous form at room temperature and pressure with C4 fraction as the main component, including alkanes, alkenes and alkynes with 4 carbon atoms in the molecule. It includes gaseous hydrocarbon products rich in C4 fraction produced by the device of the present invention, and may also include gaseous hydrocarbons rich in C4 fraction produced by other device processes, among which the C4 fraction produced by the device of the present invention is 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 preferably above 70% by weight.

[0079] In one embodiment, the light distillate oil with a final boiling point of less than 280-360°C includes the light distillate oil with a final boiling point of less than 280-360°C produced by the device of the present invention. It may also include a mixture of one or more of primary processed straight-run naphtha, straight-run kerosene, and straight-run diesel; a secondary processed topped oil, raffinate oil, hydrocracking light naphtha, pentane oil, coker gasoline, Fischer-Tropsch synthetic oil, catalytic cracking light gasoline, hydrogenated gasoline, and hydrogenated diesel.

[0080] In one embodiment, the C4 component includes gaseous hydrocarbons rich in C4 fraction produced by the device itself and / or other devices, wherein the content of C4 olefins in the gaseous hydrocarbons rich in C4 fraction is greater than 50% by weight;

[0081] Preferably, the difficult-to-convert raw material is a gaseous hydrocarbon rich in C4 fraction produced by the device.

[0082] In one embodiment, the difficult-to-convert components include a light distillate oil having a final boiling point of less than 280-360° C. produced by the device and optionally one or more of the following fractions:

[0083] Straight-run naphtha, straight-run kerosene, and straight-run diesel produced by other primary processing units;

[0084] Other secondary processing units produce topped oil, raffinate oil, hydrocracked light naphtha, pentane oil, coker gasoline, Fischer-Tropsch synthetic oil, catalytic cracking light gasoline, hydrogenated gasoline, and hydrogenated diesel.

[0085] In one embodiment, the reaction conditions of the first reactor include: reaction temperature of 510-650°C, weight hourly space velocity of 1-20 hours -1 The weight ratio of catalyst to oil is (3-50):1, and the catalyst density is 120-290 kg / m 3 , and / or the reaction pressure is 130-450 kPa, the catalyst mass flow rate Gs is 15-150 kg / (m 2 ·Second);

[0086] Preferably, the heavy crude oil fraction enters the first reactor after being steam atomized, and the water-oil weight ratio is (0.03-0.8):1.

[0087] In one embodiment, the reaction conditions of the second reactor include: reaction temperature of 580-750°C, reaction time of 0.05-5 seconds, catalyst-oil weight ratio of (1-50):1, catalyst density of 20-100 kg / m 3 , and / or the reaction pressure is 130-450 kPa, the catalyst mass flow rate Gs is 180-500 kg / (m 2 ·Second);

[0088] Preferably, the light fraction of crude oil enters the second reactor after being steam atomized, and the weight ratio of water to oil is (0.03-0.5):1.

[0089] In one embodiment, in the second reactor, the weight ratio of fresh catalyst to regenerated catalyst is 0.01-0.3:1; and / or

[0090] The reaction conditions of the difficult-to-convert components are: reaction temperature of 560-720° C., and / or reaction time of 0.1-3 seconds.

[0091] In one embodiment, the catalyst is supplemented into the first reactor to carry out the cracking reaction, and the supplemented catalyst accounts for 0-30 wt % of the total circulating amount of the catalyst in the first reactor.

[0092] In some embodiments, the supplemental catalyst may account for 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 5 wt%, or 30 wt% of the total catalyst circulation in the first reactor.

[0093] According to the present application, the catalyst is added into the first reactor from one or more supplementary catalyst inlets provided on the side wall of the first reactor, mixed with the reaction product of the feedstock oil and the regenerated catalyst, and the catalytic cracking reaction is continued; wherein, the supplementary catalyst can be one or more selected from the group consisting of a regenerated catalyst, a catalyst to be regenerated, and a semi-regenerated catalyst. The added catalyst can account for 0-30% by weight of the total circulation amount of the catalyst in the first reactor, and the positions of the one or more supplementary catalyst inlets are independently located at a height greater than 0% to 90% of the total height of the first reactor, preferably at a height of 20% to 80% of the full dense phase reaction zone, and more preferably at a height of 30% to 75%. Supplementing the catalytic cracking catalyst in the fast fluidized bed can adjust the agent-oil ratio within a large range, provide more active centers for the cracking reaction, and at the same time, enhance the flexibility of the reaction temperature adjustment, and effectively adjust the gradient of the temperature and catalyst activity in the fast fluidized bed. In addition, supplementing the catalytic cracking catalyst in the fast fluidized bed can maintain the uniformity of the catalyst density of the reactor as much as possible, effectively adjust the catalyst density distribution, ensure that the cracking reaction is fully and effectively carried out, and improve the selectivity of the target product.

[0094] In one embodiment, the catalyst of the present application comprises, based on the dry weight of the catalyst, 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.

[0095] In one embodiment, the zeolite includes a medium-pore zeolite and an optional large-pore zeolite, wherein the medium-pore zeolite is selected from ZSM series zeolites, ZRP zeolites, and any combination thereof; the large-pore zeolite is selected from rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite and high silicon Y-type zeolite, and any combination thereof.

[0096] In one embodiment, the medium pore zeolite accounts for 10-100 wt %, preferably 50-90 wt %, of the total weight of the zeolite on a dry basis.

[0097] In the present application, the medium-pore zeolite and large-pore zeolite follow the conventional definition in the art, that is, the average pore diameter of the medium-pore zeolite is about 0.5-0.6 nm, and the average pore diameter of the large-pore zeolite is about 0.7-1.0 nm.

[0098] As an example, the large-pore zeolite can 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 silicon Y type zeolite. The medium-pore zeolite can be selected from zeolites with MFI structure, such as ZSM series zeolites and / or ZRP zeolites. Optionally, the above-mentioned medium-pore zeolites can also 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 U.S. Patent No. 5,232,675A. 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 of similar structure. A more detailed description of ZSM-5 can be found in U.S. Patent No. 3,702,886A.

[0099] According to the present application, the inorganic oxide is used as a binder, preferably silicon dioxide (SiO2) and / or aluminum oxide (Al2O3). The clay is used as a matrix (ie, a carrier), preferably kaolin and / or halloysite.

[0100] In one embodiment, the regeneration conditions of the regenerator include:

[0101] Temperature 550-700°C, preferably 600-650°C;

[0102] The gas superficial velocity is 0.2-1.2 m / s, preferably 0.4-0.8 m / s; and / or

[0103] The average residence time of the catalyst is 1-10 minutes, preferably 2-6 minutes.

[0104] In one embodiment, the CO concentration in the regeneration flue gas of the regenerator is 0.5-6% by volume.

[0105] In one embodiment, the carbon content on the regenerated catalyst is from 0.06 to 0.5 weight percent.

[0106] According to the present application, the distillation of crude oil into light fractions and heavy fractions is a process technology well known to those skilled in the art. The separation of the catalytic cracking reaction product and the catalyst to be produced is well known to those skilled in the art, for example, it can be carried out in a settler using a cyclone separator, and the further separation of the reaction oil and gas to obtain dry gas, liquefied gas, light fraction oil in the difficult-to-convert components, and cracked heavy oil is also well known to those skilled in the art, and the dry gas and liquefied gas can be further separated by conventional separation means in the art to obtain target products such as ethylene and propylene and C4 components.

[0107] The present invention also provides a catalytic cracking system, comprising:

[0108] The crude oil distillation unit is used to distill crude oil into light crude oil fractions and heavy crude oil fractions.

[0109] The catalytic cracking reaction unit comprises:

[0110] The first reactor is provided with a first pre-lifting medium inlet, a first regenerated catalyst inlet, a supplementary catalyst inlet, a crude oil heavy fraction inlet and a first oil agent mixture outlet;

[0111] The second reactor is provided with a catalyst mixing zone, a crude oil light fraction inlet, a difficult-to-convert component inlet, and a second oil agent mixture outlet in sequence, and the catalyst mixing zone is provided with a second pre-lifting medium inlet, a second regenerated catalyst inlet, and a fresh catalyst inlet for mixing the regenerated catalyst circulated back to the second reactor with the fresh catalyst;

[0112] An oil agent separation device, used for separating the first oil agent mixture from the first reactor and the second oil agent mixture from the second reactor into reaction oil gas and a catalyst to be generated through the oil agent separation device; and

[0113] A settler, used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is provided below the settler for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet;

[0114] Preferably, the first reactor and the second reactor are arranged in parallel;

[0115] a reaction product separation unit, the reaction product separation unit being in communication with the oil agent separation device and being used for separating the reaction oil gas separated by the oil agent separation device; and

[0116] A regenerator, wherein the regenerator is provided with an inlet for regenerated catalyst, an inlet for oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and at least one regenerated catalyst outlet; the inlet for regenerated catalyst of the regenerator is fluidly connected to the outlet of the regenerated catalyst of the stripping section; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the first reactor for recycling a part of the regenerated catalyst back to the first reactor; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the second reactor for recycling a part of the regenerated catalyst back to the first reactor.

[0117] In one embodiment, the catalyst mixing zone is arranged coaxially with the second reactor.

[0118] In one embodiment, one or more supplementary catalyst inlets are provided on the first reactor, and the positions of the one or more supplementary catalyst inlets are independently located at a height greater than 0% to 90% of the total height of the first reactor, preferably at a height of 20% to 80% of the total height of the first reactor, and more preferably at a height of 30% to 75%.

[0119] The total height of the first reactor is the total height from the crude oil heavy fraction inlet to the first oil mixture outlet. Figure 1 In one embodiment, a gas distributor is provided at the bottom of the regenerator, so that the oxygen-containing gas injected through the oxygen-containing gas inlet enters the regenerator through the gas distributor. According to the present application, the gas distributor may adopt a main air distributor well known to those skilled in the art. For example, the main air distributor may be a distribution plate and a distribution pipe. Preferably, the distribution pipe is an annular distribution pipe and a dendrite distribution pipe.

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

[0121] The following examples will further illustrate the present application, but are not intended to limit the present application.

[0122] The feedstock oil used in the following examples and comparative examples is imported crude oil, which is an intermediate base crude oil collected from a branch of Sinopec. Its properties are shown in Table 1. The crude oil is distilled at a real boiling point with a cut point of 300° C. to obtain a light crude oil fraction and a heavy crude oil fraction. The weight ratio of the light crude oil fraction to the heavy crude oil fraction is 1:9. The catalyst used is a commercial catalytic cracking catalyst purchased from the Catalyst Branch of Sinopec Corporation, and the trade name is DMMC-2.

[0123] Example 1

[0124] Using the feedstock oil and DMMC-2 catalyst shown in Table 1, Figure 1 The experiment was carried out on the pilot plant shown in the figure, wherein the structure of the reactor used is as follows:

[0125] The first reactor (fluidized bed reactor) has a total height of 7 meters and an inner diameter of 0.3 meters. The second reactor (dilute phase transport bed reactor) has a height of 7 meters and an inner diameter of 0.2 meters, wherein the catalyst mixing zone has a height of 1 meter.

[0126] The crude oil is distilled into light fractions and heavy fractions, and the distillation cut point is 300°C. The hot regenerated catalyst of the regeneration inclined tube 103 enters the lower part of the first reactor and moves upward under the action of the pre-lifting medium. The preheated crude oil heavy fraction and the atomized steam are injected into the lower part of the first reactor through the feed pipeline, mixed with the existing catalyst in the catalytic cracking reactor and subjected to catalytic cracking reaction. The post-reaction logistics enters the subsequent oil separation equipment and product separation equipment, wherein a stream of hot regenerated catalyst is supplemented to the first reactor, and its supplementation position is located at 50% of the height of the first reactor, wherein the amount of the supplemented regenerated catalyst accounts for 10% by weight of the reactor catalyst circulation amount;

[0127] The hot regenerated catalyst in the regeneration inclined tube 303 and the fresh catalyst inlet 302 enter the catalyst mixing zone 306, and move upward under the lifting effect of the pre-lifting medium injected through the second pre-lifting medium inlet 301. The light fraction of crude oil enters the outlet of the catalyst mixing zone 306 through the inlet 304 with a water-oil weight ratio of 0.2:1, contacts the mixed catalyst and undergoes catalytic cracking reaction. The reaction oil mixture moves upward, contacts the difficult-to-convert components introduced in the downstream of the second reactor, and continues the catalytic cracking reaction.

[0128] The catalyst with coke obtained from the first reactor and the second reactor and the reaction oil and gas enter the oil agent separation device 204 such as a cyclone separator for gas-solid separation. The reaction oil and gas obtained by separation are led out of the device through the gas collecting chamber 205 and the large oil and gas pipe 206 and enter the subsequent separation system; the catalyst with coke obtained by separation enters the lower part of the settler 200 and enters the regenerator 400 through the inclined pipe 203 to be regenerated.

[0129] The catalyst with coke enters the regenerator and contacts with air to produce an incomplete combustion reaction. The regenerated catalyst returns to the first reactor and the second reactor for reaction circulation. The regenerated flue gas enters the energy recovery system through the regeneration flue gas pipeline 405.

[0130] The operating conditions and product distribution are listed in Table 2 and Table 3. As can be seen from Table 3, the yield of light olefins and light aromatics in this embodiment reaches 45.60% by weight, and accordingly, the total selectivity of light olefins and light aromatics can reach 56.50% by weight.

[0131] Comparative Example 1

[0132] The crude oil and DMMC-2 catalyst shown in Table 1 were used to conduct the test on a medium-sized device. The reactor was a conventional riser reactor connected in series with a fluidized bed reactor. The preheated crude oil entered the riser reaction zone and the fluidized bed reactor in turn to contact with the catalytic cracking catalyst for catalytic cracking reaction. After the reaction, the logistics entered the subsequent oil agent separation device and product separation equipment. The separated catalyst to be regenerated entered the lower part of the regenerator and contacted with the air distributed into the regenerator through the main air distributor to cause a scorching reaction. The regenerated catalyst returned to the reactor for recycling. The operating conditions and product distribution are listed in Tables 2 and 3.

[0133] It can be seen from the results in Table 3 that the yield of light olefins and light aromatics in this comparative example reaches 35.28% by weight, and the total selectivity of light olefins and light aromatics is 45.40% by weight.

[0134] It can be seen from the results of the above examples and comparative examples that when the catalytic cracking method and system of the present application are used to carry out catalytic cracking reaction of crude oil, the utilization rate of crude oil atoms is high and the yield of light olefins and aromatics is significantly improved.

[0135] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0136] 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 application will not further describe various possible combinations.

[0137] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the content invented by the present application.

[0138] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0139] The present application has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, various replacements and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

[0140] Table 1 Properties of crude oil used

[0141] Crude oil classification Intermediate base crude oil Characteristic factor K value 11.9 <![CDATA[Density (20 °C) / (kg / m 3 )]]> 880.2 Carbon content / weight% 85.91 Hydrogen content / weight% 12.62 Sulfur content / weight% 0.865 Nitrogen content / weight% 0.23 Carbon residue value / weight% 4.09 Metal content / (mg / kg) Fe 3.3 Ni 14 V 12 Na 0.1 Ca 0.3

[0142] Table 2 Reaction conditions of Example 1 and Comparative Example 1

[0143]

[0144]

[0145] Table 3 Comparison of reaction results between Example 1 and Comparative Example 1

[0146] Example 1 Comparative Example 1 Product distribution, weight % gas 50.8 40.36 Ethylene 6.98 3.97 Of which propylene 19.96 16.51 Of which butene 11.97 10.59 liquid 41.92 49.86 Among them, light aromatics 6.68 4.22 total 100.00 100.00 Conversion rate, % 80.71 77.71 Yield of light olefins and light aromatics, % 45.60 35.28 Selectivity of light olefins and light aromatics, % 56.50 45.40

Claims

1. A method for producing low-carbon olefins and aromatics by catalytic cracking of low-quality crude oil, comprising: (1) distilling crude oil into a light crude oil fraction and a heavy crude oil fraction, wherein the cutting point of the light crude oil fraction and the heavy crude oil fraction is in the range of 280-360° C.; (2) the heavy crude oil fraction and the first regenerated catalyst from the regenerator enter the first reactor for catalytic cracking reaction, and optionally, the reaction product contacts with the introduced supplementary catalyst and continues to react; (3) the second regenerated catalyst and the fresh catalyst are mixed in a catalyst mixing zone at the lower part of the second reactor to obtain a catalyst mixture, the catalyst mixture flows toward the downstream of the second reactor under the action of a fluidizing medium, and sequentially contacts with the light fraction of crude oil and the difficult-to-convert component fed into the second reactor to undergo cracking reaction; (4) The mixture of the reaction products of the first reactor and the second reactor and the catalyst to be produced enters the oil separation device for gas-solid separation, and the separated reaction oil and gas are led out of the device for further separation to obtain ethylene, propylene, difficult-to-convert components and other products; (5) The separated spent catalyst with coke is stripped and then enters the regenerator for oxygen-containing regeneration. The regenerated catalyst is returned to the first reactor and the second reactor for use in the reaction cycle. The crude oil is selected from one or more of intermediate base crude oil, intermediate-cycloalkyl crude oil, and cycloalkyl-intermediate base crude oil, and the difficult-to-convert component is a C4 component and / or a light distillate oil with a final boiling point less than 280-360°C.

2. The method according to claim 1, characterized in that The properties of the crude oil meet at least one of the following indicators: the characteristic factor K value is not greater than 12.2, and the density is 800-935 kg / m 3 , the residual carbon is 2-10% by weight, and the total content of nickel and vanadium is 5-50ppm.

3. The method according to claim 1, characterized in that The C4 component includes gaseous hydrocarbons rich in C4 fraction produced by the device itself and / or other devices, wherein the content of C4 olefins in the gaseous hydrocarbons rich in C4 fraction is greater than 50% by weight; Preferably, the difficult-to-convert raw material is a gaseous hydrocarbon rich in C4 fraction produced by the device.

4. The method according to claim 1, characterized in that The difficult-to-convert components include the light distillate oil produced by the device with a final boiling point of less than 280-360° C. and optionally one or more of the following fractions: Straight-run naphtha, straight-run kerosene, and straight-run diesel produced by other primary processing units; Other secondary processing units produce topped oil, raffinate oil, hydrocracked light naphtha, pentane oil, coker gasoline, Fischer-Tropsch synthetic oil, catalytic cracking light gasoline, hydrogenated gasoline, and hydrogenated diesel.

5. The method according to claim 1, characterized in that The reaction conditions of the first reactor include: reaction temperature of 510-650°C, weight hourly space velocity of 1-20 hours -1 The weight ratio of catalyst to oil is (3-50):1, and the catalyst density is 120-290 kg / m 3 , and / or the reaction pressure is 130-450 kPa; Preferably, the heavy crude oil fraction enters the first reactor after being steam atomized, and the water-oil weight ratio is (0.03-0.8):

1.

6. The method according to claim 1, characterized in that The reaction conditions of the second reactor include: reaction temperature of 580-750°C, reaction time of 0.05-5 seconds, catalyst-oil weight ratio of (1-50):1, catalyst density of 20-100 kg / m 3 , and / or the reaction pressure is 130-450 kPa; Preferably, the light fraction of crude oil enters the second reactor after being steam atomized, and the weight ratio of water to oil is (0.03-0.5):

1.

7. The method according to claim 1, characterized in that In the second reactor, the weight ratio of fresh catalyst to regenerated catalyst is 0.01-0.3:1; and / or The reaction conditions of the difficult-to-convert components are: reaction temperature of 560-720° C., and / or reaction time of 0.1-3 seconds.

8. The method according to claim 1, characterized in that The regeneration conditions of the regenerator include: Temperature 550-700°C, preferably 600-650°C; The gas superficial velocity is 0.2-1.2 m / s, preferably 0.4-0.8 m / s; and / or The average residence time of the catalyst is 1-10 minutes, preferably 2-6 minutes.

9. The method according to claim 8, characterized in that The CO concentration in the regeneration flue gas of the regenerator is 0.5-6% by volume.

10. A catalytic cracking system comprising: The crude oil distillation unit is used to distill crude oil into light crude oil fractions and heavy crude oil fractions. The catalytic cracking reaction unit comprises: The first reactor is provided with a first pre-lifting medium inlet, a first regenerated catalyst inlet, a supplementary catalyst inlet, a crude oil heavy fraction inlet and a first oil agent mixture outlet; The second reactor is provided with a catalyst mixing zone, a crude oil light fraction inlet, a difficult-to-convert component inlet, and a second oil mixture outlet in sequence. a second pre-lift medium inlet, a second regenerated catalyst inlet, and a fresh catalyst inlet for mixing the regenerated catalyst and the fresh catalyst that are circulated back to the second reactor; An oil agent separation device, used for separating the first oil agent mixture from the first reactor and the second oil agent mixture from the second reactor into reaction oil gas and a catalyst to be generated through the oil agent separation device; and A settler, used for settling and collecting the spent catalyst separated by the oil agent separation device, a stripping section is provided below the settler for stripping the spent catalyst, and the stripping section is provided with a spent catalyst outlet and a stripping medium inlet; Preferably, the first reactor and the second reactor are arranged in parallel; a reaction product separation unit, the reaction product separation unit being in communication with the oil agent separation device and being used for separating the reaction oil gas separated by the oil agent separation device; and A regenerator, wherein the regenerator is provided with an inlet for regenerated catalyst, an inlet for oxygen-containing gas, a gas distributor, a cyclone separator, a regenerated flue gas pipeline and at least one regenerated catalyst outlet; the inlet for regenerated catalyst of the regenerator is fluidly connected to the outlet of the regenerated catalyst of the stripping section; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the first reactor for recycling a part of the regenerated catalyst back to the first reactor; one regenerated catalyst outlet is connected to the regenerated catalyst inlet of the second reactor for recycling a part of the regenerated catalyst back to the first reactor.

11. The system according to claim 10, characterized in that The first reactor is provided with one or more supplementary catalyst inlets, and the positions of the one or more supplementary catalyst inlets are independently located at a height greater than 0% to 90% of the total height of the first reactor, preferably at a height of 20% to 80% of the total height of the first reactor, and more preferably at a height of 30% to 75% of the total height of the first reactor.

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