CN110724559B

CN110724559B - Catalytic cracking method and system for producing propylene and high-octane gasoline

Info

Publication number: CN110724559B
Application number: CN201810778071.2A
Authority: CN
Inventors: 张执刚; 龚剑洪; 魏晓丽
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2018-07-16
Filing date: 2018-07-16
Publication date: 2021-05-18
Anticipated expiration: 2038-07-16
Also published as: CN110724559A

Abstract

The invention relates to a catalytic cracking method and a system for producing propylene and high-octane gasoline, wherein the method comprises the following steps: introducing preheated high-quality heavy oil into the dilute phase conveying bed from the lower part of the dilute phase conveying bed to contact with a first catalytic cracking catalyst and perform a first catalytic cracking reaction from bottom to top to obtain a first reaction product and a first catalyst to be generated; introducing preheated inferior heavy oil into the rapid fluidized bed from the lower part of the rapid fluidized bed to contact with a second catalytic cracking catalyst and perform a second catalytic cracking reaction from bottom to top to obtain a second reaction product and a second spent catalyst; and separating the obtained first reaction product and the second reaction product to obtain dry gas, liquefied gas, pyrolysis gasoline, pyrolysis diesel oil and pyrolysis heavy oil. The method and the system have the advantages of low yield of coke and dry gas for catalytic cracking, and high yield of low-carbon olefin and high-octane gasoline.

Description

Catalytic cracking method and system for producing propylene and high-octane gasoline

Technical Field

The invention relates to a catalytic cracking method and a catalytic cracking system for producing propylene and high-octane gasoline.

Background

Propylene is an important organic chemical raw material, the equivalent consumption of propylene in 2016 years is 3380 ten thousand tons, and the equivalent self-supporting rate is 75.2%. The equivalent consumption of propylene in China can reach 3900 ten thousand tons by 2020, and a certain space exists in the gap of the capacity. At present, 61% of propylene in the world comes from a byproduct of ethylene production by steam cracking, 34% of propylene comes from a byproduct of gasoline and diesel oil production by a catalytic cracking unit in an oil refinery, wherein the steam cracking uses light oil such as naphtha as a raw material to produce ethylene and propylene by thermal cracking, the amount of propylene produced by the steam cracking unit tends to decrease with the lightening of the raw material of the steam cracking, and the technical advantage of propylene production from the heavy oil will face a great challenge with the aggravation of the lightening and deterioration of crude oil in a catalytic conversion unit serving as a second major source of propylene production.

Driven by the requirements of environmental protection laws and regulations and increasingly strict requirements of the automobile industry on the quality of fuel, the global automobile gasoline has very fast quality improvement in recent years, and the pace of upgrading the quality of oil products is obviously accelerated. At present, the quantity of catalytic cracking gasoline in China is about 70 percent of the total quantity of a gasoline pool, and the quality of the catalytic cracking gasoline plays a significant role in the overall level of the gasoline pool. The octane number RON of the catalytic cracking gasoline is 90-92 at most, the average octane number RON is 89-90, and the difference between the gasoline quality of the catalytic cracking gasoline and the gasoline quality of other developed countries is large, so that the octane number of the gasoline is improved, and the upgrading and updating of the gasoline are facilitated. In addition, in the process of cleaning gasoline, measures such as controlling the olefin content of the gasoline and desulfurizing all result in different octane number losses, and the contradiction of octane number shortage is more prominent. In conclusion, the development of catalytic cracking technology for producing propylene and producing high-quality fuel oil such as high-octane gasoline to meet the production requirements of chemical raw materials and high-quality fuel oil with continuously improved quality requirements is undoubtedly of great practical significance.

Chinese patent CN 200810246522.4 discloses a catalytic conversion method for preparing propylene and high-octane gasoline, raw oil with different cracking performances enters different reaction zones of a first riser reactor to contact with a catalytic conversion catalyst for cracking reaction, and a crackable component in a product is sent into a second riser reactor for reaction.

Chinese patent CN101724430A proposes that inferior raw oil is sequentially injected into a first reaction zone and a second reaction zone of a catalytic conversion reactor to contact and react with a catalytic conversion catalyst to obtain propylene, gasoline, catalytic wax oil and other products, wherein the catalytic wax oil enters an aromatic hydrocarbon extraction device and is separated to obtain extract oil and raffinate oil; the raffinate oil is recycled to the first reaction zone of the reactor or/and other catalytic conversion devices for further reaction to obtain the target products of propylene and gasoline.

Chinese patent CN98101765.7 discloses a method for simultaneously preparing low-carbon olefin and high-aromatic gasoline from heavy oil, which is to make heavy petroleum hydrocarbon and steam undergo catalytic conversion reaction in a composite reactor composed of a lift pipe and a dense-phase fluidized bed to achieve the purpose of improving the yield of low-carbon olefin, especially propylene, and simultaneously increase the aromatic content in gasoline to about 80 wt%.

Chinese patent CN01119807.9 discloses a method for increasing the yield of ethylene and propylene by catalytic conversion of heavy petroleum hydrocarbon, which is to make hydrocarbon oil raw material contact and react with a catalyst containing pentasil zeolite in a riser or fluidized bed reactor.

As the situation of heaviness and deterioration of crude oil increases, a combined technique of hydrogenation and catalytic conversion is attracting attention of researchers. Chinese patent CN200810240114.8 discloses a method for producing low-carbon olefins and monocyclic aromatics from heavy hydrocarbons, which takes wax oil and residual oil as raw materials to produce qualified catalytic conversion raw materials by hydrogenation, and simultaneously light cycle oil and heavy cycle oil which are byproducts of catalytic conversion are returned to a catalytic conversion raw material hydrogenation unit and are hydrogenated together with the catalytic conversion raw materials to be used as catalytic conversion raw materials to produce the low-carbon olefins and the monocyclic aromatics. The method introduces the catalytic conversion light and heavy cycle oil into the hydrogenation unit for hydrogenation and then takes the catalytic conversion light and heavy cycle oil as a catalytic conversion raw material, so that the yield of high-value products of the catalytic conversion unit can be increased. Chinese patent CN201010257156 discloses a method for preparing light fuel oil and propylene from inferior residual oil, which adopts a method that a residual oil raw material and extract oil extracted from catalytic cracking heavy oil aromatic hydrocarbon are firstly hydrogenated and then enter a catalytic cracking device, improves the feed quality, organically combines the processes of hydrotreating, catalytic cracking and aromatic hydrocarbon extraction, and produces propylene and light fuel oil from the inferior raw material to the maximum extent.

From the prior art, the development of the technology for producing propylene and fuel oil by catalytic conversion of hydrocarbons mainly focuses on the catalytic cracking of heavy oil and the development of combined process technology. The catalytic cracking reactor still adopts the technology of a lifting pipe or a lifting pipe connected with a dense-phase bed reactor in series. Because the distillation range of heavy oil is wider, hydrocarbon molecules are larger, the product structure is complicated, the yield of inferior heavy oil propylene is low, and in order to improve the yield of propylene, the yield of dry gas and coke is greatly increased under the condition of increasing the yield of propylene by adopting higher reaction temperature. In order to efficiently utilize inferior heavy oil resources and meet the increasing demands for propylene and high-quality fuel oil, it is necessary to develop a catalytic conversion method for converting inferior heavy oil feedstock into high value-added products.

Disclosure of Invention

The invention aims to provide a catalytic cracking method and a catalytic cracking system for producing propylene and high-octane gasoline.

In order to achieve the above object, the present invention provides a catalytic cracking process for producing propylene and high octane gasoline, the process comprising:

introducing preheated high-quality heavy oil into the dilute phase conveying bed from the lower part of the dilute phase conveying bed to contact with a first catalytic cracking catalyst and perform a first catalytic cracking reaction from bottom to top to obtain a first reaction product and a first catalyst to be generated; the high-quality heavy oil is one or more selected from vacuum wax oil, coking wax oil, hydrogenated coking wax oil, deasphalted oil, hydrogenated deasphalted oil, paraffin-based atmospheric residue oil, hydrogenated paraffin oil, atmospheric residue oil and hydrocracking tail oil;

introducing preheated inferior heavy oil into the rapid fluidized bed from the lower part of the rapid fluidized bed to contact with a second catalytic cracking catalyst and perform a second catalytic cracking reaction from bottom to top to obtain a second reaction product and a second spent catalyst; the properties of the inferior heavy oil meet one, two, three or four of the following indexes: the density at 20 ℃ is 900-³The carbon residue is 2-10The total content of nickel and vanadium is 2-30ppm by weight, and the value of the characteristic factor K is less than 12.1; the catalyst in the fast fluidized bed is distributed in a full dense phase, and the distribution of the axial solid fraction epsilon in the fast fluidized bed meets the following requirements: epsilon is more than or equal to 0.1 and less than or equal to 0.2;

separating the obtained first reaction product and the second reaction product to obtain dry gas, liquefied gas, pyrolysis gasoline, pyrolysis diesel oil and pyrolysis heavy oil;

and feeding the first spent catalyst and the second spent catalyst into a regenerator for coke burning regeneration, and returning the obtained regenerated catalyst serving as the first catalytic cracking catalyst and the second catalytic cracking catalyst to the bottoms of the dilute phase conveying bed and the fast fluidized bed.

Optionally, the properties of the inferior heavy oil meet one, two, three or four of the following criteria: the density at 20 ℃ is 910-³The carbon residue is 3-8 wt%, the total content of nickel and vanadium is 5-20ppm, and the characteristic factor K value is less than 12.0.

Optionally, the inferior heavy oil is heavy petroleum hydrocarbon and/or other mineral oil; the heavy petroleum hydrocarbon is one or more selected from vacuum residue, poor atmospheric residue, poor hydrogenated residue, coker gas oil, deasphalted oil, vacuum wax oil, high acid value crude oil and high metal crude oil, and the other mineral oil is one or more selected from coal liquefied oil, oil sand oil and shale oil.

Optionally, the first catalytic cracking catalyst comprises, on a dry basis and by weight on a dry basis of the first catalytic cracking catalyst, from 1 to 50 wt% of a zeolite, from 5 to 99 wt% of an inorganic oxide, and from 0 to 70 wt% of a clay;

on a dry basis and based on the weight of the second catalytic cracking catalyst on a dry basis, the second catalytic cracking catalyst comprising from 1 to 50 wt% of a zeolite, from 5 to 99 wt% of an inorganic oxide, and from 0 to 70 wt% of a clay;

the zeolites include medium pore zeolites which are ZSM series zeolites and/or ZRP zeolites and optionally large pore zeolites which are one or more selected from rare earth Y, rare earth hydrogen Y, ultrastable Y and high silica Y.

Optionally, the medium pore zeolite of the first catalytic cracking catalyst comprises from 0 to 50 wt% of the total weight of zeolite on a dry basis;

the medium pore zeolite of the second catalytic cracking catalyst comprises from 0 to 50 wt% of the total weight of zeolite on a dry basis.

Optionally, the medium pore zeolite of the first catalytic cracking catalyst comprises 0 to 20 wt% of the total weight of zeolite on a dry basis;

the medium pore zeolite of the second catalytic cracking catalyst comprises from 0 to 20 wt% of the total weight of zeolite on a dry basis.

Optionally, the dilute phase conveying bed is an equal-diameter dilute phase conveying bed or a variable-diameter dilute phase conveying bed.

Optionally, if the dilute phase transport bed is an equal-diameter dilute phase transport bed, the conditions of the first catalytic cracking reaction include: the reaction temperature is 450-550 ℃, the reaction time is 0.1-5 seconds, and the weight ratio of the catalyst to the oil is (1-30): 1, the weight ratio of water to oil is (0.05-0.3): 1, the catalyst density is 20-100 kg/m³Gas linear speed of 4-18 m/s, reaction pressure of 0.2-1.2 MPa, and catalyst mass flow rate G_sIs 180-500 kg/(meter)²Seconds).

Optionally, if the dilute phase transport bed is a variable-diameter dilute phase transport bed, and the variable-diameter dilute phase transport bed comprises a first reaction zone and a second reaction zone from bottom to top, and the inner diameter of the second reaction zone is greater than that of the first reaction zone, then the conditions of the first catalytic cracking reaction include:

the reaction temperature of the first reaction zone is 500-620 ℃, the reaction time of the first reaction zone is 0.1-5 seconds, and the weight ratio of the catalyst to the oil of the first reaction zone is (5-15): 1, the weight ratio of water to oil in the first reaction zone is (0.05-0.3): 1, the density of the catalyst in the first reaction zone is 20-60 kg/m³The linear speed of gas in the first reaction zone is 10-15 m/s, the reaction pressure in the first reaction zone is 0.2-1.2 MPa, and the mass flow rate G of catalyst_sIs 300-500 kg/(meter)²Seconds);

the reaction temperature of the second reaction zone is 450-550 ℃, the reaction time of the second reaction zone is 1-20 seconds, the weight ratio of the catalyst to the oil of the second reaction zone is 5-15, and the second reaction zone isThe catalyst density in the reaction zone is 60-100 kg/m³The linear speed of the gas in the second reaction zone is 6-12 m/s, the reaction pressure in the second reaction zone is 0.2-1.2 MPa, and the mass flow rate G of the catalyst is_sIs 150-350 kg/(meter)²Seconds).

Optionally, the conditions of the second catalytic cracking reaction include: the reaction temperature is 510-650 ℃, the reaction time is 1-20 seconds, and the weight ratio of the catalyst to the oil is (3-50): 1, the weight ratio of water to oil is (0.03-0.8): 1, catalyst density of 120-³Gas linear speed of 0.8-2.5 m/s, reaction pressure of 130-450 kPa, and catalyst mass flow rate G_sIs 15-150 kg/(meter)²Seconds).

Optionally, the conditions of the second catalytic cracking reaction include: the reaction temperature is 550-620 ℃, the reaction time is 3-15 seconds, and the weight ratio of the catalyst to the oil is (10-30): 1, the weight ratio of water to oil is (0.05-0.5): 1, catalyst density of 150-³Gas linear velocity of 1-1.8 m/s, catalyst mass flow rate G_sIs 20-130 kg/(meter)²Seconds).

Optionally, the method further includes: replenishing the catalyst into the dilute phase conveying bed and/or the fast fluidized bed; wherein the carbon content of the supplemented catalyst is 0-1.0 wt.%.

Optionally, the catalyst supplemented to the dilute-phase conveying bed accounts for 0-50 wt% of the catalyst circulation amount of the dilute-phase conveying bed; the replenished catalyst of the fast fluidized bed accounts for 0-50 wt% of the circulating amount of the fast fluidized bed catalyst.

Optionally, the catalyst supplemented to the dilute-phase conveying bed accounts for 5-30 wt% of the catalyst circulation amount of the dilute-phase conveying bed; the replenished catalyst of the fast fluidized bed accounts for 5-30 wt% of the circulating amount of the fast fluidized bed catalyst.

Optionally, the distance between the catalyst replenishing position of the dilute phase conveying bed and the bottom of the dilute phase conveying bed accounts for 0-2/3 of the total height of the dilute phase conveying bed;

the distance between the catalyst replenishing position of the fast fluidized bed and the bottom of the fast fluidized bed accounts for 0 to 2/3 of the total height of the fast fluidized bed.

Optionally, the regenerated catalyst obtained by the regeneration of the regenerator through coking is cooled to 600-680 ℃ by a cooler and then returns to the bottom of the dilute phase conveying bed and/or the fast fluidized bed.

The invention also provides a catalytic cracking system, which comprises a dilute phase conveying bed, a fast fluidized bed, an oil agent separation device, a reaction product separation device and a regenerator; the dilute phase conveying bed is an equal-diameter dilute phase conveying bed or a variable-diameter dilute phase conveying bed;

the dilute phase conveying bed is provided with a catalyst inlet at the bottom, a high-quality heavy oil inlet at the lower part and an oil agent outlet at the top, the fast fluidized bed is provided with a catalyst inlet at the bottom, a low-quality heavy oil inlet at the lower part and an oil agent outlet at the top, the oil agent separation equipment is provided with an oil agent inlet, a catalyst outlet and a reaction product outlet, the reaction product separation equipment is provided with a reaction product inlet, a dry gas outlet, a liquefied gas outlet, a pyrolysis gasoline outlet, a pyrolysis diesel oil outlet and a pyrolysis heavy oil outlet, and the regenerator is provided with a catalyst inlet and a catalyst outlet;

catalyst inlets of the dilute phase conveying bed and the fast fluidized bed are in fluid communication with a catalyst outlet of the regenerator, oil outlets of the dilute phase conveying bed and the fast fluidized bed are in fluid communication with an oil inlet of the oil separating device, a reaction product outlet of the oil separating device is in fluid communication with a reaction product inlet of the reaction product separating device, and a catalyst outlet of the oil separating device is in fluid communication with a catalyst inlet of the regenerator.

The high-quality heavy oil and the low-quality heavy oil are respectively subjected to catalytic conversion reaction in different reactors. Different reactors may employ different reaction conditions for the nature of the feedstock, which helps to improve feedstock conversion and target product yield.

The invention adopts the fast fluidized bed to effectively improve the density of the reaction catalyst, thereby greatly improving the ratio of the instantaneous catalyst to the raw oil in the reactor, controlling the relatively long reaction time, leading the catalyst to be capable of fully cracking with the inferior heavy oil into the micromolecular olefin, thereby improving the yield of the low-carbon olefin and the gasoline, simultaneously effectively reducing the generation of dry gas and coke, and improving the product distribution and the product quality.

The invention can enable petrochemical enterprises to produce high-added-value chemical raw materials from cheap inferior heavy oil to the maximum extent, is beneficial to promoting the refining and chemical integration process of oil refining enterprises in China, not only solves the problem of petrochemical raw material shortage, but also improves the economic benefit and social benefit of petrochemical industry.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 includes a schematic flow diagram of one embodiment of the method of the present invention and also includes a schematic structural diagram of one embodiment of the system of the present invention.

Fig. 2 includes a schematic flow diagram of another embodiment of the method of the present invention and a schematic structural diagram of another embodiment of the system of the present invention.

Description of the reference numerals

I fast fluidized bed II, first reaction zone III, second reaction zone

1 pipeline 2 dilute phase conveying bed 3 outlet section

4 settler 5 stripping section 6 cyclone

7 gas collection chamber, 8 pipeline, 9 to-be-grown inclined tube

10 regenerator 11 regeneration inclined tube 12 pipeline

13 air distributor 14 line 15 regeneration chute

16 line 17 outlet section

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the invention:

(1) the axial solid fraction is the pressure difference between two points in the axial direction of the reactor measured by a pressure difference meter, the distance between two points in the axial direction divided by the density of the catalyst particles; the unit of the pressure difference is kilogram/meter²The distance between two axial points is measured in meters, and the density of catalyst particles is kg/m³And the two axial points are any two axial points of the reactor.

(2) The reaction time is equal to the volume of the reactor/the logarithmic mean volume flow of oil gas; volume unit of the reactor is meter³The unit of logarithmic mean volume flow of oil and gas is meter³A/second;

logarithmic mean volume flow rate of oil and gas (V)_out-V_in)/ln(V_out/V_in)，V_outAnd V_inThe volume flow of oil gas at the outlet and the inlet of the reactor respectively;

the volume flow of oil gas at the outlet of the reactor is m/rho₃The volume flow of oil gas at the inlet of the reactor is m/rho₄(ii) a m is the feeding amount of raw oil and atomized steam in unit time, and the unit is kilogram/second; rho₃The density of oil gas at the outlet of the reactor is measured in kg/m³；ρ₄The density of the oil gas at the inlet of the reactor is measured in kg/m³。

(3) The density of the catalyst in the reactor is the reaction time multiplied by the catalyst circulation volume divided by the volume of the reactor; the reaction time is in seconds, the catalyst circulation is in kilograms per second, and the reactor volume is in meters³。

(4) And the linear gas velocity is the logarithmic mean volume flow of oil gas/sectional area of the reactor.

(5) Catalyst mass flow rate G_sCatalyst circulation rate ÷ reactor cross-sectional area; the unit of the circulating amount of the catalyst is kilogram/second;

the catalyst circulation amount is divided by the coke generation speed (the carbon content of the spent catalyst-the carbon content of the regenerated catalyst), the unit of the coke generation speed is kilogram/second, and the carbon content of the spent catalyst and the carbon content of the regenerated catalyst are both weight contents;

coke formationVelocity × (CO) flue gas quantity₂% + CO%) +/-Vm × M; vm is the molar volume of gas and takes the value of 22.4 multiplied by 10^-3Rice and its production process³M is the molar mass of carbon and takes the value of 12 multiplied by 10^-3Kilogram/mole;

flue gas amount (regeneration air amount × 79 vol%)/(1-CO)₂％-CO％-O₂%) of the amount of regenerated air in meters³Second, the unit of smoke is meter³Second, CO₂％、CO％、O₂% of CO in the flue gas₂、CO、O₂Volume percent of (c).

The invention provides a catalytic cracking method for producing propylene and high-octane gasoline, which comprises the following steps:

introducing preheated inferior heavy oil into the rapid fluidized bed from the lower part of the rapid fluidized bed to contact with a second catalytic cracking catalyst and perform a second catalytic cracking reaction from bottom to top to obtain a second reaction product and a second spent catalyst; the properties of the inferior heavy oil meet one, two, three or four of the following indexes: the density at 20 ℃ is 900-³2-10 wt% of carbon residue, 2-30ppm of total content of nickel and vanadium, and a characteristic factor K value less than 12.1; the catalyst in the fast fluidized bed is distributed in a full dense phase, and the distribution of the axial solid fraction epsilon in the fast fluidized bed meets the following requirements: epsilon is more than or equal to 0.1 and less than or equal to 0.2;

In the invention, the fast fluidized bed refers to a reactor in which a catalyst is in fast fluidization, the fast fluidization is bubble-free gas-solid contact fluidization, and the important characteristic is that solid particles tend to move in an agglomeration manner. The axial solid fraction epsilon distribution of all heights in the fast fluidized bed meets the following requirements: epsilon is more than or equal to 0.1 and less than or equal to 0.2, the catalyst in the rapid fluidized bed is distributed in a full-dense phase, the catalyst is prevented from being distributed in a dilute-down-dense mode, the actual agent-oil ratio above and below the rapid fluidized bed is kept consistent, the dry gas coke yield is reduced, and the target product yield is improved.

According to the invention, the catalyst is regulated to be in full-dense phase distribution by regulating the linear velocity of gas in the fast fluidized bed and arranging a gas distributor at the feeding position of the fast fluidized bed, wherein the gas distributor can be one or more of gas distributors which are common in industry, such as flat plates, arches, discs, rings and umbrella-shaped gas distributors, so that the raw oil atomized by atomized steam is contacted with the catalyst in a uniform concentration in the axial direction of the reactor to carry out catalytic cracking reaction, and the generation of catalyst-oil ratio coke and thermal reaction coke caused by overhigh or overlow concentration of the catalyst is reduced.

According to the invention, the inferior heavy oil can be totally introduced into the fast fluidized bed at one feeding position, or can be introduced into the fast fluidized bed from two or more feeding positions according to the same or different proportions, and the superior heavy oil can be totally introduced into the dilute phase transfer bed at one feeding position, or can be introduced into the dilute phase transfer bed from two or more feeding positions according to the same or different proportions.

According to the invention, the high-quality heavy oil is heavy oil which is more suitable for catalytic cracking processing, and the low-quality heavy oil is heavy oil which is more unsuitable for catalytic cracking processing than conventional heavy oil, for example, the properties of the low-quality heavy oil can meet one, two, three or four of the following indexes: the density at 20 ℃ is 900-³Preferably 910-³The carbon residue is 2 to 10% by weight, preferably3-8 wt.%, has a total nickel and vanadium content of 2-30ppm, preferably 5-20ppm, and a characteristic factor K value of less than 12.1, preferably less than 12.0. In particular, the low-grade heavy oil can be heavy petroleum hydrocarbons and/or other mineral oils; the heavy petroleum hydrocarbon may be one or more selected from Vacuum Residue (VR), low-grade Atmospheric Residue (AR), low-grade hydrogenated residue, coker gas oil, deasphalted oil, vacuum wax oil, high acid number crude oil, and high metal crude oil, and the other mineral oil may be one or more selected from coal liquefied oil, oil sand oil, and shale oil. The carbon residue in the inferior heavy oil is measured by adopting an ASTMD-189 Conradson carbon residue experimental method.

Catalytic cracking catalysts are well known to those skilled in the art in accordance with the present invention, and for the process of the present invention, the first catalytic cracking catalyst may comprise, on a dry basis and based on the weight of the first catalytic cracking catalyst on a dry basis, from 1 to 50 wt% of a zeolite, from 5 to 99 wt% of an inorganic oxide, and from 0 to 70 wt% of a clay; the second catalytic cracking catalyst may include, on a dry basis and by weight of the second catalytic cracking catalyst on a dry basis, from 1 to 50 wt% of a zeolite, from 5 to 99 wt% of an inorganic oxide, and from 0 to 70 wt% of a clay; the content and type of zeolite, inorganic oxide and clay in the first catalytic cracking catalyst and the second catalytic cracking catalyst may be the same or different, preferably the same. The zeolite may comprise, as active components, a medium pore zeolite and optionally a large pore zeolite, and the medium pore zeolite in the first catalytic cracking catalyst may comprise from 0 to 50 wt%, preferably from 0 to 20 wt%, of the total weight of zeolite on a dry basis; the medium pore zeolite in the second catalytic cracking catalyst may be present in an amount of from 0 to 50 wt%, preferably from 0 to 20 wt%, based on the total weight of zeolite on a dry basis. The medium and large pore zeolites are defined as conventional in the art, i.e., the medium pore zeolite has an average pore size of 0.5 to 0.6nm and the large pore zeolite has an average pore size of 0.7 to 1.0 nm. The large-pore zeolite can be selected from one or more of Rare Earth Y (REY), Rare Earth Hydrogen Y (REHY), ultrastable Y obtained by different methods and high-silicon Y. The medium pore zeolite may be selected from zeolites having MFI structure, such as ZSM series zeolite and/or ZRP zeolite, or non-metal such as phosphorus may be used for the medium pore zeoliteElements and/or transition metal elements such as iron, cobalt, nickel, etc., are modified, as described in more detail in U.S. Pat. No. 5,232,675 for ZRP, and the ZSM-series zeolite is preferably selected from a mixture of one or more of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other zeolites of similar structure, and as described in more detail in ZSM-5, U.S. Pat. No. 3,702,886 for ZSM-5. The inorganic oxide is preferably silicon dioxide (SiO) as a binder₂) And/or aluminum oxide (Al)₂O₃). The clay acts as a matrix (i.e., carrier) and is preferably selected from kaolin and/or halloysite.

According to the invention, the dilute phase conveying bed can be an equal-diameter dilute phase conveying bed or a variable-diameter dilute phase conveying bed, in the variable-diameter dilute phase conveying bed, high-quality raw materials generate macromolecular olefin as much as possible in a first reaction zone with a smaller diameter, the macromolecular olefin enters a second reaction zone with a larger diameter, and cracking, hydrogen transfer, isomerization and aromatic hydrocarbon generation reactions occur under a milder condition, so that gasoline is rich in high-octane number components. If the dilute phase transport bed is an equal-diameter dilute phase transport bed, the conditions of the first catalytic cracking reaction may include: the reaction temperature is 450-550 ℃, the reaction time is 0.1-5 seconds, and the weight ratio of the catalyst to the oil is (1-30): 1, the weight ratio of water to oil is (0.05-0.3): 1, the catalyst density is 20-100 kg/m³Gas linear speed of 4-18 m/s, reaction pressure of 0.2-1.2 MPa, and catalyst mass flow rate G_sIs 180-500 kg/(meter)²Seconds); if the dilute phase transport bed is a variable-diameter dilute phase transport bed, the variable-diameter dilute phase transport bed comprises a first reaction zone and a second reaction zone from bottom to top, the inner diameter of the second reaction zone is larger than that of the first reaction zone, and the ratio of the inner diameter of the second reaction zone to that of the first reaction zone is preferably 1.2-2, then the conditions of the first catalytic cracking reaction may include: the reaction temperature of the first reaction zone is 500-620 ℃, the reaction time of the first reaction zone is 0.1-5 seconds, and the weight ratio of the catalyst to the oil of the first reaction zone is (5-15): 1, the weight ratio of water to oil in the first reaction zone is (0.05-0.3): 1, the density of the catalyst in the first reaction zone is 20-60 kg/m³The linear speed of gas in the first reaction zone is 10-15 m/s, the reaction pressure in the first reaction zone is 0.2-1.2 MPa, and the mass of catalyst isFlow rate G_sIs 300-500 kg/(meter)²Seconds); the reaction temperature of the second reaction zone is 450-550 ℃, the reaction time of the second reaction zone is 1-20 seconds, the catalyst-oil weight ratio of the second reaction zone is 5-15, and the catalyst density of the second reaction zone is 60-100 kg/m³The linear speed of the gas in the second reaction zone is 6-12 m/s, the reaction pressure in the second reaction zone is 0.2-1.2 MPa, and the mass flow rate G of the catalyst is_sIs 150-350 kg/(meter)²Seconds). The conditions of the second catalytic cracking reaction may include: the reaction temperature is 510-650 ℃, the reaction time is 1-20 seconds, and the weight ratio of the catalyst to the oil is (3-50): 1, the weight ratio of water to oil is (0.03-0.8): 1, catalyst density of 120-³Gas linear speed of 0.8-2.5 m/s, reaction pressure of 130-450 kPa, and catalyst mass flow rate G_sIs 15-150 kg/(meter)²Seconds). The conditions of the second catalytic cracking reaction preferably include: the reaction temperature is 550-620 ℃, the reaction time is 3-15 seconds, and the weight ratio of the catalyst to the oil is (10-30): 1, the weight ratio of water to oil is (0.05-0.5): 1, catalyst density of 150-³Gas linear velocity of 1-1.8 m/s, catalyst mass flow rate G_sIs 20-130 kg/(meter)²Seconds).

The separation of the first reaction product and the second reaction product from the spent catalyst according to the present invention is well known to those skilled in the art, and may be performed, for example, in a settler using a cyclone separator, and the further separation of the first reaction product and the second reaction product to obtain dry gas, liquefied gas, pyrolysis gasoline, pyrolysis diesel oil and pyrolysis heavy oil is also well known to those skilled in the art, and the dry gas and liquefied gas may be further separated to obtain the desired products such as ethylene, propylene, etc. by separation means conventional in the art. The first reaction product and the second reaction product may be separated in the same separation apparatus, or may be separated in different separation apparatuses, and the present invention is not particularly limited.

According to the present invention, the first spent catalyst and the second spent catalyst are regenerated by burning, which is well known to those skilled in the art, and can be carried out in a regenerator, an oxygen-containing gas such as air can be introduced into the regenerator to contact with the first spent catalyst and the second spent catalyst, and flue gas obtained by burning regeneration can be separated from the catalyst in the regenerator and then sent to a subsequent energy recovery system. The coking regeneration of the first spent catalyst and the second spent catalyst can be carried out in the same regenerator or in different regenerators.

According to the invention, the method may further comprise: replenishing the catalyst into the dilute phase conveying bed and/or the fast fluidized bed; wherein the carbon content of the supplemented catalyst is 0 to 1.0 wt%, and may be, for example, one or more selected from the group consisting of a regenerated catalyst, a spent catalyst and a semi-regenerated catalyst. The catalyst replenished in the dilute phase conveying bed accounts for 0-50 wt%, preferably 5-30 wt% of the catalyst circulating amount in the dilute phase conveying bed; the fast fluidized bed is replenished with catalyst in an amount of 0 to 50 wt%, preferably 5 to 30 wt%, of the circulating amount of the fast fluidized bed catalyst. The distance between the catalyst replenishing position of the dilute phase conveying bed and the bottom of the dilute phase conveying bed can account for 0-2/3 of the total height of the dilute phase conveying bed; the distance between the catalyst replenishing position of the fast fluidized bed and the bottom of the fast fluidized bed can be 0-2/3 of the total height of the fast fluidized bed. Since the catalytic cracking reaction is a volume expansion reaction, in order to maintain the density at the inlet of the reactor and the density at the outlet of the reactor to be substantially equal or increased, the supplementary spent catalyst in the fast fluidized bed can adjust or maintain the density of the reactor within a wide range to ensure the time required for the cracking reaction. The temperature of the replenished catalyst can be adjusted according to the reaction temperature requirements, for example cold and/or hot regenerated catalyst can be introduced. In addition, the catalyst density uniformity of the reactor can be maintained as much as possible by supplementing the catalytic cracking catalyst in the fast fluidized bed reactor and/or the dilute phase transport bed, the density distribution of the catalyst is effectively adjusted, the cracking reaction is fully and effectively carried out, and the selectivity of the target product is improved.

According to the invention, the regenerated catalyst obtained by the coke-burning regeneration of the regenerator can be cooled to 600-680 ℃ by a cooler and then returned to the bottom of the fast fluidized bed and/or the dilute phase transport bed. The hot regenerated catalyst returns to the reactor after being cooled, which is beneficial to reducing the contact temperature of the oil agent, improving the contact state of the raw oil and the catalyst and improving the selectivity of dry gas and coke formation.

According to the present invention, the oil separating device and the reaction product separating device are well known to those skilled in the art, for example, the oil separating device may include a cyclone, a settler, a stripper, and the like, and the reaction product separating device may be a fractionating tower, and the like.

The invention will be further illustrated by means of specific embodiments in the following description with reference to the drawings, but the invention is not limited thereto.

As shown in fig. 1, a pre-lifting medium enters the bottom of the dilute phase conveying bed 2 from the bottom of the pre-lifting section through a pipeline 1, a regenerated catalyst from a regeneration inclined tube 11 enters the bottom of the dilute phase conveying bed 2, and moves upwards in an accelerated manner along the dilute phase conveying bed under the lifting action of the pre-lifting medium, high-quality heavy oil is injected into the lower part of the dilute phase conveying bed 2 through a pipeline 14, is mixed and contacted with a material flow existing in the dilute phase conveying bed 2 and carries out a first cracking reaction, and a first reaction product and a first catalyst to be generated move upwards in an accelerated manner; the regenerated catalyst from the pipeline 15 enters the bottom of the fast fluidized bed I and moves upwards in an accelerated manner along the fast fluidized bed I under the lifting action of the pre-lifting medium, the inferior heavy oil is injected into the lower part of the fast fluidized bed I through the pipeline 16, the inferior heavy oil generates a second catalytic cracking reaction on the hot catalyst, and a second reaction product and a second spent catalyst move upwards in an accelerated manner; the generated first reaction product, the first spent catalyst, the second reaction product and the second spent catalyst respectively enter the cyclone separator 6 in the settler 4 through the outlet section 17 and the outlet section 3 to realize the separation of the spent catalyst and the reaction product, the reaction product enters the gas collection chamber 7, and the fine powder of the catalyst returns to the settler through the dipleg. Spent catalyst in the settler flows to the stripping section 5. The reaction product oil gas extracted from the spent catalyst enters a gas collection chamber 7 after passing through a cyclone separator. The stripped spent catalyst enters a regenerator 10 through a spent inclined tube 9, air is distributed by an air distributor 13 and then enters the regenerator 10, coke on the spent catalyst in a dense bed layer at the bottom of the regenerator 10 is burned off, the inactivated spent catalyst is regenerated, and flue gas enters a subsequent energy recovery system through a flue gas pipeline 12. The reaction products in the plenum 7 enter the subsequent separation system through a large oil gas line 8. Wherein the pre-lifting medium may be dry gas, water vapor or a mixture thereof.

FIG. 2 differs from FIG. 1 in that the dilute phase transport bed comprises a first reaction zone II and a second reaction zone III, and the first reaction zone II is located below the second reaction zone III, and the inner diameter of the second reaction zone III is larger than that of the first reaction zone II.

The following examples further illustrate the process of the present invention but are not intended to limit the invention thereto.

The high-quality raw oil used in the examples and comparative examples was hydrogenated wax oil, and the low-quality raw oil was hydrogenated residual oil, and the properties thereof are shown in table 1. The catalyst used was a commercial catalyst sold under the trade designation CGP.

Comparative example 1

According to the flow of fig. 1, the raw oil is a mixed oil of hydrogenated residual oil and hydrogenated wax oil, and the ratio of the hydrogenated wax oil to the hydrogenated residual oil is 1: the method comprises the following steps of 1, adopting a CGP catalyst, and carrying out a test on a medium-sized device, wherein the reactor is a reducing riser reactor and is a more advanced reactor structure type for producing propylene and high-quality fuel oil at present. The preheated raw oil enters the lower part of a first reaction zone of a riser reactor to contact with a regenerated catalyst and carry out a first catalytic cracking reaction, the reaction oil, the water vapor and the spent catalyst enter a second reaction zone from an outlet of the reactor to continue the reaction, the material flow after the reaction enters a closed cyclone separator, and the reaction oil, the oil and the spent catalyst are quickly separated; the spent catalyst enters a stripping section under the action of gravity, hydrocarbon products adsorbed on the spent catalyst are stripped by steam, and the stripped catalyst directly enters a regenerator without heat exchange and is in contact with air for regeneration; the regenerated catalyst returns to the bottom of the riser reactor for recycling; the operating conditions and the product distribution are listed in tables 2 and 3.

As can be seen from the results in table 3, the propylene yield was about 6.2 wt%, the gasoline yield was about 36.9 wt%, the octane number was about 92, and the dry gas and coke yields were 2.9 wt% and 9.3 wt%, respectively.

Example 1

According to the process shown in FIG. 1, the high-quality raw oil is hydrogenated wax oil, the low-quality raw oil is hydrogenated residual oil, and the feeding amounts of the two raw materials in different reactors are the same. The experiments were carried out on a medium-sized apparatus using a CGP catalyst using a dilute phase transport bed and a fast fluidized bed combined reactor. In the test process, preheated high-quality raw oil enters the lower part of the dilute phase conveying bed to contact with the regenerated catalyst and carry out a first catalytic cracking reaction. The preheated inferior raw oil enters the lower part of the fast fluidized bed to contact with the catalyst and carry out a second catalytic cracking reaction, the catalyst in the fast fluidized bed is controlled to be in full-dense phase distribution by adjusting the linear velocity of gas and arranging an umbrella-shaped gas distributor at the feeding position, and the axial solid fraction epsilon distribution in the fast fluidized bed is in the range of 0.1-0.2 from bottom to top. The reaction product and the spent catalyst enter a subsequent separation system. Cutting the reaction product in a separation system according to the distillation range; the spent catalyst enters a stripping section under the action of gravity, hydrocarbon products adsorbed on the spent catalyst are stripped by steam, and the stripped catalyst directly enters a regenerator without heat exchange and is in contact with air for regeneration; the regenerated catalyst returns to the riser for reaction and is recycled; the operating conditions and the product distribution are listed in tables 2 and 3.

As can be seen from table 3, the propylene yield was 9.2 wt%, the gasoline yield was about 42.5 wt%, the octane number was as high as 95, and the dry gas and coke yields were 2.8 wt% and 9.1 wt%, respectively.

Example 2

According to the process shown in FIG. 2, the high quality raw oil is hydrogenated wax oil, the low quality raw oil is hydrogenated residual oil, and the feeding amounts of the two raw materials in different reactors are the same. The experiments were carried out on a medium-sized apparatus using a CGP catalyst, using a combined reactor, a variable diameter riser with dual reaction zones and a fast fluidized bed reactor. In the test process, preheated high-quality raw oil enters the lower part of a first reaction zone of the variable-diameter dilute-phase conveying bed to perform catalytic cracking reaction, and after the reaction, material flow and carbon deposit catalyst enter a second reaction zone to continue the catalytic cracking reaction. The preheated poor raw oil enters the lower part of the fast fluidized bed to carry out catalytic cracking reaction, the catalyst in the fast fluidized bed is controlled to be in full dense phase distribution by adjusting the linear velocity of gas and arranging an umbrella-shaped gas distributor at the feeding position, and the axial solid fraction epsilon distribution in the fast fluidized bed is in the range of 0.1-0.2 from bottom to top. The reaction product and the spent catalyst enter a subsequent separation system. Cutting the reaction product in a separation system according to the distillation range to obtain fractions such as dry gas, liquefied gas, pyrolysis gasoline, pyrolysis diesel oil and the like; the spent catalyst enters a stripping section under the action of gravity, hydrocarbon products adsorbed on the spent catalyst are stripped by steam, and the stripped catalyst directly enters a regenerator without heat exchange and is in contact with air for regeneration; the regenerated catalyst returns to the riser for reaction and is recycled; the operating conditions and the product distribution are listed in tables 2 and 3.

As can be seen from table 3, the propylene yield can reach 94 wt%, the gasoline yield is about 43.8 wt%, the octane number is as high as 96, and the dry gas and coke yields are 2.7 wt% and 9 wt%, respectively.

Comparative example 2

Comparative example 2 is substantially the same as example 1 except that no gas distributor is provided, the axial solid fraction epsilon distribution in the fast fluidized bed is gradually increased from top to bottom from 0.1 → 0.2 → 0.3, the operating conditions are the same as example 1, and the product distribution is shown in Table 3.

It can be seen from the results of the examples that the process of the present invention has high yields of propylene and gasoline and has a high research octane number, while having low yields of dry gas and coke.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the content of the present invention as long as it does not depart from the gist of the present invention.

TABLE 1

Raw materials	Hydrogenated wax oil	Hydrogenated residual oil
			Density (20 ℃ C.)/g.Centimeter^-3	0.8993	0.9342
Refractive index/70 deg.C	1.4794	1.5075
			Basic nitrogen/microgram g^-1	293	767
Carbon residue/weight%	0.3	5.58
			Value of characteristic factor K	12.6	11.8
Distillation range/. degree.C
			5% by volume	381	365
10% by volume	394	403
			30% by volume	433	479
50% by volume	463	545
			70% by volume	495	617
Metal content/microgram g^-1
			Fe	/	26.3
Ni	/	9
			Ca	/	5.5
V	/	8
			Na	/	1.2

TABLE 2

TABLE 3

	Comparative example 1	Example 1	Example 2	Comparative example 2
					Conditions of fast fluidized bed
Outlet temperature of	/	550	550	/
					Reaction time in seconds	/	4	4	/
Water to oil weight ratio	/	0.10	0.10	/
					Weight ratio of solvent to oil	/	8	8	/
Catalyst density in kg/m³	/	200	200	/
					Linear velocity of gas, m/s	/	2	2	/
Reaction pressure, kPa	/	340	340	/
					G_sKilogram/(meter)²Second)	/	75	80	/
Product distribution, weight%
					Dry gas	2.9	2.8	2.7	2.9
Liquefied gas	14.1	19.7	20.3	16.7
					Wherein propylene is	6.2	9.2	9.4	7.1
Gasoline (gasoline)	36.9	42.5	43.8	40.5
					Diesel oil	29.4	19.7	18.8	23.9
Heavy oil	7.4	6.2	5.4	6.8
					Coke	9.3	9.1	9.0	9.2
Research octane number of gasoline	92	95	96	93
					Total up to	100.0	100.0	100.0	100.0

Claims

1. A catalytic cracking process for producing propylene and high octane gasoline, the process comprising:

introducing preheated high-quality heavy oil into the dilute phase conveying bed from the lower part of the dilute phase conveying bed to contact with a first catalytic cracking catalyst and perform a first catalytic cracking reaction from bottom to top to obtain a first reaction product and a first catalyst to be generated; the high-quality heavy oil is one or more selected from vacuum wax oil, coking wax oil, hydrogenated coking wax oil, deasphalted oil, hydrogenated paraffin oil, atmospheric residue oil and hydrocracking tail oil;

2. The method of claim 1, wherein the high quality heavy oil is a paraffin-based atmospheric residue.

3. The method of claim 1 wherein the properties of the low quality heavy oil meet one, two, three or four of the following criteria: the density at 20 ℃ is 910-³The carbon residue is 3-8 wt%, the total content of nickel and vanadium is 5-20ppm, and the characteristic factor K value is less than 12.0.

4. The method of claim 1 wherein the low quality heavy oil is heavy petroleum hydrocarbons and/or other mineral oils; the heavy petroleum hydrocarbon is one or more selected from vacuum residue, poor atmospheric residue, poor hydrogenated residue, coker gas oil, deasphalted oil, vacuum wax oil, high acid value crude oil and high metal crude oil, and the other mineral oil is one or more selected from coal liquefied oil, oil sand oil and shale oil.

5. The process of claim 1 wherein the first catalytic cracking catalyst comprises, on a dry basis and based on the weight of the first catalytic cracking catalyst on a dry basis, from 1 to 50 wt% zeolite, from 5 to 99 wt% inorganic oxide, and from 0 to 70 wt% clay;

6. The process of claim 5, wherein the medium pore zeolite of the first catalytic cracking catalyst comprises from 0 to 50 wt% of the total weight of zeolite on a dry basis;

7. The process of claim 5, wherein the medium pore zeolite of the first catalytic cracking catalyst comprises from 0 to 20 wt% of the total weight of zeolite on a dry basis;

8. The method of claim 1, wherein the dilute phase transport bed is a constant diameter dilute phase transport bed or a variable diameter dilute phase transport bed.

9. The method of claim 8, wherein, if the dilute phase transport bed is an isodiametric dilute phase transport bed, the conditions of the first catalytic cracking reaction comprise: the reaction temperature is 450-550 ℃, the reaction time is 0.1-5 seconds, and the weight of the oil isThe ratio is (1-30): 1, the weight ratio of water to oil is (0.05-0.3): 1, the catalyst density is 20-100 kg/m³Gas linear speed of 4-18 m/s, reaction pressure of 0.2-1.2 MPa, and catalyst mass flow rate G_sIs 180-500 kg/(meter)²Seconds).

10. The method of claim 8, wherein if the dilute phase transport bed is a variable diameter dilute phase transport bed, and the variable diameter dilute phase transport bed comprises a first reaction zone and a second reaction zone from bottom to top, and the second reaction zone has a larger inner diameter than the first reaction zone, the conditions of the first catalytic cracking reaction comprise:

the reaction temperature of the second reaction zone is 450-550 ℃, the reaction time of the second reaction zone is 1-20 seconds, the catalyst-oil weight ratio of the second reaction zone is 5-15, and the catalyst density of the second reaction zone is 60-100 kg/m³The linear speed of the gas in the second reaction zone is 6-12 m/s, the reaction pressure in the second reaction zone is 0.2-1.2 MPa, and the mass flow rate G of the catalyst is_sIs 150-350 kg/(meter)²Seconds).

11. The method of claim 1, wherein the conditions of the second catalytic cracking reaction comprise: the reaction temperature is 510-650 ℃, the reaction time is 1-20 seconds, and the weight ratio of the catalyst to the oil is (3-50): 1, the weight ratio of water to oil is (0.03-0.8): 1, catalyst density of 120-³Gas linear speed of 0.8-2.5 m/s, reaction pressure of 130-450 kPa, and catalyst mass flow rate G_sIs 15-150 kg/(meter)²Seconds).

12. The method of claim 1, wherein the conditions of the second catalytic cracking reaction comprise: the reaction temperature is 550-620 ℃, the reaction time is 3-15 seconds, and the weight ratio of the catalyst to the oil is (10-30): 1, the weight ratio of water to oil is (0.05-0.5): 1, catalyst density of 150-³Gas linear velocity of 1-1.8 m/s, catalyst mass flow rate G_sIs 20-130 kg/(meter)²Seconds).

13. The method of claim 1, further comprising: replenishing the catalyst into the dilute phase conveying bed and/or the fast fluidized bed; wherein the carbon content of the supplemented catalyst is 0-1.0 wt.%.

14. The process of claim 13 wherein the dilute phase transport bed is replenished with catalyst in the range of from 0 to 50 wt.% of the dilute phase transport bed catalyst circulation; the replenished catalyst of the fast fluidized bed accounts for 0-50 wt% of the circulating amount of the fast fluidized bed catalyst.

15. The process of claim 13 wherein the dilute phase transport bed is replenished with catalyst in the range of 5 to 30 wt.% of the dilute phase transport bed catalyst circulation; the replenished catalyst of the fast fluidized bed accounts for 5-30 wt% of the circulating amount of the fast fluidized bed catalyst.

16. The process of claim 13, wherein the dilute phase transport bed has a catalyst makeup location that is spaced from the bottom of the dilute phase transport bed by a distance that is between 0 and 2/3 of the total height of the dilute phase transport bed;

17. The method as claimed in claim 1, wherein the regenerated catalyst obtained by coke-burning regeneration of the regenerator is cooled to 680 ℃ by a cooler and then returned to the bottom of the dilute phase transport bed and/or the fast fluidized bed.

18. A catalytic cracking system comprises a dilute phase conveying bed, a fast fluidized bed, an oil agent separation device, a reaction product separation device and a regenerator; the dilute phase conveying bed is an equal-diameter dilute phase conveying bed or a variable-diameter dilute phase conveying bed;

catalyst inlets of the dilute phase conveying bed and the fast fluidized bed are both communicated with a catalyst outlet of the regenerator in a fluid mode, oil outlets of the dilute phase conveying bed and the fast fluidized bed are both communicated with an oil inlet of the oil separating device in a fluid mode, a reaction product outlet of the oil separating device is communicated with a reaction product inlet of the reaction product separating device in a fluid mode, and a catalyst outlet of the oil separating device is communicated with a catalyst inlet of the regenerator in a fluid mode;

the catalyst in the fast fluidized bed is distributed in a full dense phase, and the distribution of the axial solid fraction epsilon in the fast fluidized bed meets the following requirements: epsilon is more than or equal to 0.1 and less than or equal to 0.2; the distance between the catalyst replenishing position of the dilute phase conveying bed and the bottom of the dilute phase conveying bed accounts for 0-2/3 of the total height of the dilute phase conveying bed; and/or the distance between the catalyst replenishing position of the fast fluidized bed and the bottom of the fast fluidized bed accounts for 0-2/3 of the total height of the fast fluidized bed; the catalyst is adjusted to be in full dense phase distribution by adjusting the linear velocity of gas in the fast fluidized bed and arranging a gas distributor at the feeding position of the fast fluidized bed.