阅读说明：本技术 催化裂解的工艺和系统 (Process and system for catalytic cracking ) 是由 沙有鑫 朱根权 杨超 成晓洁 马文明 于 2019-01-09 设计创作，主要内容包括：本发明涉及催化裂化领域,公开了一种催化裂解的工艺和系统。所述工艺包括：在下行管反应器中,重质原料与催化裂化催化剂接触反应,得到第一反应产物和待生催化剂；将第一反应产物和待生催化剂送入流化床反应器上部的沉降段进行气固分离,分离得到的待生催化剂进入流化床反应器中；在提升管反应器中,轻质原料与催化裂化催化剂接触反应,得到第二反应产物和待生催化剂；将第二反应产物和待生催化剂送入流化床反应器中,与催化裂化催化剂接触反应,得到第三反应产物和待生催化剂；对来自流化床反应器的待生催化剂进行再生。本发明提供的工艺和系统能够在提高低碳烯烃和柴油产率的同时改善柴油质量,增加低碳烯烃与干气产率的比值,优化产物分布。(The invention relates to the field of catalytic cracking, and discloses a catalytic cracking process and a catalytic cracking system. The process comprises the following steps: in a descending tube reactor, a heavy raw material and a catalytic cracking catalyst are in contact reaction to obtain a first reaction product and a spent catalyst; feeding the first reaction product and the spent catalyst into a settling section at the upper part of the fluidized bed reactor for gas-solid separation, and feeding the separated spent catalyst into the fluidized bed reactor; in the riser reactor, the light raw material and a catalytic cracking catalyst are in contact reaction to obtain a second reaction product and a spent catalyst; feeding the second reaction product and the spent catalyst into a fluidized bed reactor, and carrying out contact reaction with a catalytic cracking catalyst to obtain a third reaction product and the spent catalyst; regenerating the spent catalyst from the fluidized bed reactor. The process and the system provided by the invention can improve the quality of the diesel oil while improving the yield of the low-carbon olefin and the diesel oil, increase the ratio of the yield of the low-carbon olefin to the yield of the dry gas and optimize the distribution of products.)

1. A process for catalytic cracking, the process comprising:

(1) in a descending tube reactor, contacting a heavy raw material with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a first reaction product and a spent catalyst;

(2) feeding the first reaction product and the spent catalyst obtained in the step (1) into a settling section at the upper part of a fluidized bed reactor for gas-solid separation, feeding the first reaction product obtained by separation out of the fluidized bed reactor, and feeding the spent catalyst obtained by separation into the fluidized bed reactor;

(3) in the riser reactor, the light raw material is contacted with a catalytic cracking catalyst to carry out catalytic cracking reaction to obtain a second reaction product and a spent catalyst;

(4) feeding the second reaction product and the spent catalyst obtained in the step (3) into a fluidized bed reactor, and contacting the second reaction product and the spent catalyst with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a third reaction product and the spent catalyst;

(5) and in the regenerator, regenerating the spent catalyst from the fluidized bed reactor to obtain a regenerated catalyst.

2. The process of claim 1, wherein the process further comprises: and (3) carrying out gas-solid separation on the third reaction product and the spent catalyst through a settling section at the upper part of the fluidized bed reactor, sending the third reaction product obtained by separation out of the fluidized bed reactor, and sending the spent catalyst obtained by separation into the fluidized bed reactor.

3. The process of claim 1 or 2, wherein the process further comprises: the step of stripping is carried out before regenerating the spent catalyst from the fluidized bed reactor, preferably in a stripper in the lower part of the fluidized bed reactor.

4. The process of claim 1 or 2, wherein the process further comprises: separating the first reaction product and the third reaction product to obtain dry gas, liquefied gas, gasoline, diesel oil and oil slurry; at least part of the separated liquefied gas and/or gasoline and/or diesel oil is sent into the riser reactor as the light raw material to contact with a catalytic cracking catalyst for catalytic cracking reaction; and the number of the first and second groups,

the process further comprises: feeding at least part of the separated oil slurry into the riser reactor to contact with a catalytic cracking catalyst for catalytic cracking reaction;

preferably, the weight ratio of gasoline fed to the riser reactor to heavy feedstock fed to the downer reactor is (0.05-0.3) to 1, more preferably (0.1-0.2) to 1;

preferably, the weight ratio of diesel fed to the riser reactor to heavy feedstock fed to the downer reactor is (0.02-0.3) to 1, more preferably (0.05-0.2) to 1;

preferably, the weight ratio of the slurry oil fed to the riser reactor to the heavy feedstock fed to the downer reactor is (0.01-0.2):1, more preferably (0.05-0.15): 1.

5. The process of claim 1, wherein,

in the step (1), the catalytic cracking reaction conditions include: the temperature is 510-690 ℃, preferably 520-650 ℃; the agent-oil ratio is 5-20, preferably 7-18; the reaction time is 0.5 to 8 seconds, preferably 1.5 to 4 seconds;

in the step (3), the catalytic cracking reaction conditions include: the temperature is 520 ℃ to 720 ℃, preferably 530 ℃ to 700 ℃; the agent-oil ratio is 8-26, preferably 10-24; the reaction time is 1-10 seconds, preferably 2-7 seconds;

in the step (4), the catalytic cracking reaction conditions include: the temperature is 480-650 ℃, preferably 500-640 ℃; the weight hourly space velocity is 1-35 h^-1Preferably 2 to 33 hours^-1(ii) a The agent-oil ratio is 6-20, preferably 7-18; the reaction pressure is 0.15 to 0.35MPa, preferably 0.2 to 0.35 MPa.

6. The process of claim 1 or 5, wherein the process further comprises: and (3) using the regenerated catalyst obtained in the step (5) as the catalytic cracking catalyst of the step (1) and/or the step (3) and/or the step (4).

7. The process of claim 6 wherein from 10 to 70 wt.% of the regenerated catalyst is fed to the downer reactor of step (1), from 20 to 60 wt.% of the regenerated catalyst is fed to the fluidized bed reactor of step (4), and from 10 to 40 wt.% of the regenerated catalyst is fed to the riser reactor of step (3), based on the total weight of the regenerated catalyst exiting the regenerator per unit time.

8. The process of claim 1, 5, 6 or 7 wherein the catalytic cracking catalyst contains a zeolite, an inorganic oxide and optionally a clay; based on the total weight of the catalytic cracking catalyst, the content of the zeolite is 1-50 wt%, the content of the inorganic oxide is 5-99 wt%, and the content of the clay is 0-70 wt%;

the zeolite comprises shape selective zeolite and Y-type zeolite with average pore diameter less than 0.7 nm; the content of the shape-selective zeolite with the average pore diameter of less than 0.7 nanometer is 25 to 90 weight percent and the content of the Y-type zeolite is 10 to 75 weight percent on a dry basis and by taking the total weight of the zeolite as a reference; the shape-selective zeolite with the average pore diameter less than 0.7 nanometer is selected from ZSM series zeolite, ZRP zeolite, ferrierite, chabazite, dachiardite, erionite, A zeolite, column zeolite, turbid zeolite and one or more than two of the zeolites obtained after physical and/or chemical treatment; the Y-type zeolite is at least one of rare earth Y-type zeolite, rare earth hydrogen Y-type zeolite, ultrastable Y-type zeolite and rare earth ultrastable Y-type zeolite;

the inorganic oxide is silicon dioxide and/or aluminum oxide.

9. The process of claim 1 or 7, wherein the heavy feedstock is selected from at least one of vacuum wax oil, atmospheric wax oil, coker wax oil, deasphalted oil, furfural refined raffinate oil, coal liquefaction oil, oil sand oil, shale oil, Fischer-Tropsch synthesis oil, and animal and vegetable fats; the light raw material is gasoline and/or C rich in olefin₄Hydrocarbons and/or diesel.

10. A system for catalytic cracking, characterized in that the system comprises a downer reactor (2), a fluidized bed reactor (3), a regenerator (7) and a riser reactor (9);

the fluidized bed reactor (3) sequentially comprises a settling section (4), a fluidized bed reaction section and a stripping section (5) from top to bottom;

the downer reactor (2) is communicated with a settling section (4) of the fluidized bed reactor (3);

the riser reactor (9) is communicated with the fluidized bed reaction section of the fluidized bed reactor (3);

the regenerator (7) is respectively communicated with the downer reactor (2), the fluidized bed reactor (3) and the riser reactor (9).

11. The system of claim 10, wherein,

the downer reactor (2) is provided with a catalyst inlet positioned at the top, a heavy raw material inlet positioned at the upper part and a material outlet positioned at the bottom;

the fluidized bed reactor (3) is provided with a catalyst inlet, a first material inlet, a second material inlet, a catalyst outlet and a product outlet; the catalyst inlet and the second material inlet are positioned in a fluidized bed reaction section of the fluidized bed reactor (3), the first material inlet is positioned in a settling section (4) of the fluidized bed reactor (3), and the product outlet is positioned in the settling section (4) of the fluidized bed reactor (3), preferably positioned at the top of the settling section (4); the catalyst outlet of the fluidized bed reactor (3) is positioned at the lower part of the stripping section (5);

the riser reactor (9) is provided with a catalyst inlet positioned at the bottom, a light raw material inlet positioned at the lower part and a material outlet positioned at the top; preferably, the riser reactor (9) is also provided with an oil slurry inlet positioned at the lower part or the bottom;

the material outlet of the downer reactor (2) is communicated with a first material inlet of a settling section (4) of the fluidized bed reactor (3);

and the material outlet of the riser reactor (9) is communicated with the second material inlet of the fluidized bed reaction section of the fluidized bed reactor (3).

12. A system according to claim 10 or 11, wherein the regenerator (7) is provided with a catalyst inlet and a catalyst outlet;

the catalyst inlet of the regenerator (7) is communicated with the stripping section (5) of the fluidized bed reactor (3);

and a catalyst outlet of the regenerator (7) is respectively communicated with a catalyst inlet of the fluidized bed reactor (3), a catalyst inlet of the downer reactor (2) and a catalyst inlet of the riser reactor (9).

13. The system according to claim 10 or 11, wherein the riser reactor (9) extends into the second material inlet of the fluidized bed reactor (3) from bottom to top and has a material outlet at the top of the riser reactor (9) in the fluidized bed reactor (3).

14. The system according to any one of claims 10-13, wherein the system further comprises a product separation device (12), the product separation device (12) being provided with a product inlet, a dry gas outlet, a liquefied gas outlet, a gasoline outlet, a diesel outlet and a slurry oil outlet;

the inlet of the product separation device (12) is communicated with the product outlet of the settling section (4) of the fluidized bed reactor (3);

a liquefied gas outlet and/or a gasoline outlet and/or a diesel oil outlet of the product separation device (12) are communicated with a light raw material inlet of the riser reactor (9);

the oil slurry outlet of the product separation device (12) is communicated with the light raw material inlet of the riser reactor (9), and preferably, the oil slurry outlet of the product separation device (12) is communicated with the oil slurry inlet of the riser reactor (9).

15. The system according to any one of claims 10-13, wherein the downer reactor (2) is an equal diameter downer, an equal linear velocity downer or a variable diameter downer;

the riser reactor (9) is an equal-diameter riser, an equal-linear-speed riser or a variable-diameter riser;

the fluidized bed reactor (3) is selected from one of a fixed fluidized bed, a bulk fluidized bed, a bubbling bed reactor, a turbulent bed reactor, a fast bed reactor, a transport bed reactor and a dense phase bed reactor.

Technical Field

The present invention relates to a catalytic cracking process and system.

Background

Small-molecule olefins such as ethylene, propylene and butylene are the most basic organic synthesis raw materials. At present, the main production process of small molecular olefins worldwide is a steam cracking process, but a high-temperature cracking furnace is easy to coke, so the process basically takes light oil as a raw material, such as natural gas, naphtha and light diesel oil, and can also take hydrocracking tail oil as a raw material. At present, the trend of crude oil heaviness and deterioration is more obvious in China, the yield of light oil such as naphtha is lower, and the contradiction between the supply and demand of raw materials of a steam cracking process and a catalytic reforming process is increasingly serious. Since the mid-eighties of the twentieth century, the petrochemical science and research institute of the national petrochemical corporation began to research the catalytic cracking family technology for preparing low carbon olefins from heavy oil, and succeeded in developing the catalytic cracking (DCC, USP4980053 and USP5670037) technology for maximum production of propylene and the catalytic thermal cracking (CPP, USP6210562) technology for maximum production of ethylene. So far, the two technologies mainly use a single riser reactor or a single riser reactor combined with a dense-phase fluidized bed reactor structure, and the yield of the dry gas and the coke is relatively high while the yield of the low-carbon olefin is improved.

In recent years, much attention has been paid to technologies for cracking heavy oil and producing light olefins in multiple reactors, which select different reactors for different raw materials, including an upward reactor, a downward reactor and a fluidized bed reactor, and even select different catalysts, so as to ensure that the raw materials react in a reaction environment more suitable for the characteristics of the raw materials.

For example, CN101074392A discloses a method for producing propylene and high-quality gasoline and diesel oil by two-stage catalytic cracking, which mainly utilizes a two-stage riser catalytic cracking technology, adopts a catalyst rich in shape-selective zeolite, takes heavy petroleum hydrocarbons or various animal and vegetable oils rich in hydrocarbons as raw materials, performs optimized combination of feeding modes for reaction materials of different properties, and controls suitable reaction conditions for different materials, so as to achieve the purposes of improving propylene yield, considering light oil yield and quality, and inhibiting generation of dry gas and coke. The feeding of the first section of riser is fresh heavy raw oil, and light hydrocarbon raw material can be fed into the lower part or the bottom of the first section of riser; the second section of riser is fed with gasoline and circulating oil with high olefin content, and can be fed in layers or mixed, and the lower part or the bottom of the second section of riser can be fed with other light hydrocarbon raw materials.

For another example, CN101045667A proposes a catalytic conversion method for increasing the yield of low-carbon olefins, in which a hydrocarbon oil raw material is injected into a down-flow reactor through a raw material nozzle, and contacts with a regenerated catalyst and an optional carbon deposition catalyst, a cracked product is separated from a spent catalyst, the cracked product is separated to obtain low-carbon olefins, at least a part of the rest of the products is introduced into a riser reactor to contact with a regenerant for reaction, and oil gas is separated from the spent catalyst. The method tries to effectively inhibit the secondary reaction of the low-carbon olefin and improve the yield of the low-carbon olefin by separating the generated low-carbon olefin from the spent catalyst in time. However, it is difficult to satisfy the conversion rate of heavy oil and light hydrocarbon only by using the down-flow reactor and the riser reactor, and the maximization of the yield of the low carbon olefin cannot be realized, and it can be seen from the disclosed examples that the yield ratio of the low carbon olefin to the dry gas is below 3, the raw material cannot be fully utilized, and the low-value product is high.

For another example, CN101210191A proposes a catalytic cracking process in which a downflow reactor and a riser reactor are connected in series. The method comprises the steps of enabling preheated raw oil to enter a descending reactor to be in contact with a high-temperature regenerated catalyst from a regenerator, vaporizing and carrying out cracking reaction, enabling oil gas discharged from an outlet of the descending reactor to enter a riser reactor to continue reacting, introducing another strand of regenerated catalyst from an inlet of the riser reactor, and enabling the oil gas discharged from an outlet of the riser reactor and the catalyst to enter a settling separator to be separated. According to different target products, different catalysts can be adopted in the riser reactor compared with the descending reactor, so that the gasoline yield can be improved, and the product quality can be improved. However, the catalytic cracking process using a downflow reactor and a riser reactor in series inevitably causes heavy oil to interfere with the reaction of light oil, so that light hydrocarbons are not further converted, and light olefins may be further reacted, thereby resulting in a decrease in the yield of light olefins.

For another example, CN102690682A proposes a catalytic cracking process for producing propylene, which comprises: the heavy raw material and a first catalytic cracking catalyst which takes Y-type zeolite as a main active component are subjected to contact reaction in a first riser, oil gas and the catalyst after the reaction are separated, the oil gas is introduced into a product separation system, the catalyst is introduced into a first in-situ gas regeneration after being stripped in the first riser, and the regenerated catalyst is introduced into a first riser reactor for recycling. The light hydrocarbon and a second catalytic cracking catalyst which takes shape-selective zeolite with the average pore diameter less than 0.7nm as a main active component are in contact reaction in a second riser reactor, the obtained oil gas is introduced into a fluidized bed reactor which is connected with the second riser reactor in series for reaction, the oil gas after the fluidized bed reaction is introduced into a product separation system, the catalyst is introduced into a second stripper for stripping and then introduced into a second regenerator for regeneration, and the regenerated catalyst is introduced into the second riser reactor for recycling. The stripper of the catalytic cracking device is divided into two independent stripping zones by a partition plate, and the two stripping zones and the two risers form two independent reaction, stripping and regeneration routes respectively.

Based on the prior art, still remains to be developed a new can improve the low carbon olefin yield, optimization product distribution catalytic cracking process and system.

Disclosure of Invention

The invention aims to provide a novel catalytic cracking process and a novel catalytic cracking system, which can improve the quality of diesel oil, increase the ratio of low-carbon olefin to dry gas and optimize the distribution of products while improving the yield of low-carbon olefin and diesel oil.

The invention is based on a combined reactor consisting of a downer reactor, a fluidized bed reactor and a riser reactor, and adopts the same catalytic cracking catalyst in the downer reactor, the fluidized bed reactor and the riser reactor through the optimization of a process scheme, heavy raw materials are catalytically cracked into reaction products containing low-carbon olefins in the downer reactor, light raw materials continue to react in the fluidized bed reactor after reacting in the riser reactor, so that different feeding materials are catalytically cracked in a proper reactor, the heavy oil conversion rate is effectively improved, the light raw materials are promoted to be cracked again, and the ratio of the low-carbon olefins to the dry gas yield is obviously increased.

In order to achieve the above object, an aspect of the present invention provides a process for catalytic cracking, wherein the process comprises:

(1) in a descending tube reactor, contacting a heavy raw material with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a first reaction product and a spent catalyst;

(2) feeding the first reaction product and the spent catalyst obtained in the step (1) into a settling section at the upper part of a fluidized bed reactor for gas-solid separation, feeding the first reaction product obtained by separation out of the fluidized bed reactor, and feeding the spent catalyst obtained by separation into the fluidized bed reactor;

(3) in the riser reactor, the light raw material is contacted with a catalytic cracking catalyst to carry out catalytic cracking reaction to obtain a second reaction product and a spent catalyst;

(4) feeding the second reaction product and the spent catalyst obtained in the step (3) into a fluidized bed reactor, and contacting the second reaction product and the spent catalyst with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a third reaction product and the spent catalyst;

(5) and in the regenerator, regenerating the spent catalyst from the fluidized bed reactor to obtain a regenerated catalyst.

Preferably, the process further comprises: separating the first reaction product and the third reaction product to obtain dry gas, liquefied gas, gasoline, diesel oil and oil slurry; at least part of the separated liquefied gas and/or gasoline and/or diesel oil is sent into the riser reactor as the light raw material to contact with a catalytic cracking catalyst for catalytic cracking reaction; and the number of the first and second groups,

the process further comprises: feeding at least part of the separated oil slurry into the riser reactor to contact with a catalytic cracking catalyst for catalytic cracking reaction;

preferably, the weight ratio of gasoline fed to the riser reactor to heavy feedstock fed to the downer reactor is (0.05-0.3) to 1, more preferably (0.10-0.2) to 1;

preferably, the weight ratio of diesel fed to the riser reactor to heavy feedstock fed to the downer reactor is (0.02-0.3) to 1, more preferably (0.05-0.2) to 1;

preferably, the weight ratio of the slurry oil fed to the riser reactor to the heavy feedstock fed to the downer reactor is (0.01-0.2):1, more preferably (0.05-0.15): 1.

In a second aspect, the present invention provides a catalytic cracking system, wherein the system comprises a downer reactor, a fluidized bed reactor, a regenerator and a riser reactor; the fluidized bed reactor sequentially comprises a settling section, a fluidized bed reaction section and a stripper from top to bottom; the downer reactor is communicated with a settling section of the fluidized bed reactor; the riser reactor is communicated with a fluidized bed reaction section of the fluidized bed reactor; the regenerator is respectively communicated with the downer reactor, the fluidized bed reactor and the riser reactor.

The descending tube reactor is arranged along the flowing direction of the heavy raw material, and then the first reaction product obtained after the reaction in the descending tube reactor and the carbon-deposited catalyst to be generated are subjected to high-efficiency gas-solid separation in the settling section of the fluidized bed reactor, so that the heavy raw material can be effectively cracked into propylene and gasoline, and the generated low-carbon olefin can be directly sent to the product separation device without further reaction. In addition, the catalyst back-mixing phenomenon in the traditional riser reactor can be avoided to the maximum extent by utilizing the downer reactor, and the catalyst activity is improved. Preferably, after the first reaction product obtained by reacting the heavy raw material in the downer reactor is subjected to product separation, at least part of the separated oil slurry is fed into the riser reactor and then continues to react in the fluidized bed reactor, so that the reaction process of effectively cracking the heavy raw material (oil slurry) into the low-carbon olefin and the gasoline in the fluidized bed reactor is further enhanced.

The invention relates to gasoline and/or C rich in olefin₄Hydrocarbon and/or diesel oil are used as light raw materials and are introduced into the riser reactor, the carbon deposit amount of the catalyst is less in the reaction process of the light raw materials, and the performance change of the catalyst is not obvious, so that the influence of the back mixing phenomenon in the upward flow process on the reaction of the light raw materials is not obvious. The spent catalyst after reaction still has higher activity, and can be introduced into the fluidized bed reactor to continuously contact with the light raw material and promote the reaction of the light raw material. The high-temperature regenerant from the regenerator is supplemented to the inlet of the fluidized bed reactor to regulate the severity (comprising the reaction temperature and the ratio of the agent to the oil) of the fluidized bed reactor.

According to the invention, preferably, the diesel fraction obtained by separating the first reaction product after the heavy raw material is reacted in the downer reactor is selectively introduced into the riser reactor together with the light raw material, and/or the liquefied gas/gasoline/diesel fraction obtained by separating the third reaction product after the light raw material is reacted in the riser reactor and the fluidized bed reactor is selectively introduced into the riser reactor together with the light raw material, so that the re-catalytic cracking reaction of the diesel fraction can be flexibly controlled, the yield of low-carbon olefin is further improved, and the quality of diesel is improved at the same time.

The invention preferably introduces the oil slurry obtained by separating the heavy raw material after the reaction in the downer reactor into the riser reactor to contact with the high-activity regenerant, thereby effectively improving the conversion rate of the heavy oil.

Drawings

FIG. 1 is a schematic flow diagram of one embodiment of the process of the present invention, also including a schematic structural diagram of one embodiment of the system of the present invention.

Description of the reference numerals

1 catalyst tank 2 downer reactor 3 fluidized bed reactor

4 settling section, 5 stripping section and 6 spent catalyst inclined pipes

7 regenerator 8 first regeneration inclined tube 9 riser reactor

10 second regeneration inclined tube 11 third regeneration inclined tube 12 product separation device

13 heavy feed line 14 first atomizing steam line 15 oxygen-containing gas line

16 stripping steam line 17 pre-lift medium line 18 return slurry oil line

19 second atomized water vapor pipeline 20 light raw material pipeline 21 oil gas pipeline

22 regeneration flue gas line 23 gaseous hydrocarbon line 24 gasoline line

25 diesel oil line 26 light cycle oil line 27 separation slurry line

28 lifting medium line

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

According to the invention, the process of catalytic cracking comprises:

(1) in a descending tube reactor, contacting a heavy raw material with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a first reaction product and a spent catalyst;

(2) feeding the first reaction product and the spent catalyst obtained in the step (1) into a settling section at the upper part of a fluidized bed reactor for gas-solid separation, feeding the first reaction product obtained by separation out of the fluidized bed reactor, and feeding the spent catalyst obtained by separation into the fluidized bed reactor;

(3) in the riser reactor, the light raw material is contacted with a catalytic cracking catalyst to carry out catalytic cracking reaction to obtain a second reaction product and a spent catalyst;

(4) feeding the second reaction product and the spent catalyst obtained in the step (3) into a fluidized bed reactor, and contacting the second reaction product and the spent catalyst with a catalytic cracking catalyst to perform catalytic cracking reaction to obtain a third reaction product and the spent catalyst;

(5) and in the regenerator, regenerating the spent catalyst from the fluidized bed reactor to obtain a regenerated catalyst.

As shown in fig. 1, the catalytic cracking process includes:

sending the heavy raw material into the upper part of the descending tube reactor 2 to contact with the catalytic cracking catalyst from the top of the descending tube reactor 2 and carrying out catalytic cracking reaction from top to bottom to obtain a first product and a spent catalyst;

feeding the obtained first product and spent catalyst into a settling section 4 at the upper part of a fluidized bed reactor 3 for gas-solid separation, and feeding the spent catalyst into the fluidized bed reactor 4;

feeding the light raw material into the bottom of a riser reactor 9 to contact with a catalytic cracking catalyst and carrying out a cracking reaction from bottom to top to obtain a second product and a spent catalyst;

feeding the obtained second product and spent catalyst into a fluidized bed reactor 3 to contact with a catalytic cracking catalyst and perform catalytic cracking reaction to obtain a third product and spent catalyst;

the spent catalyst from the fluidized bed reactor is sent to a regenerator 7 for regeneration to obtain a regenerated catalyst.

In the catalytic cracking process, the same catalytic cracking catalyst is adopted in the downer reactor, the fluidized bed reactor and the riser reactor, the heavy raw material is catalytically cracked in the downer reactor into a reaction product containing low-carbon olefins, and the reaction product is continuously reacted in the fluidized bed reactor after the light raw material reacts in the riser reactor, so that the catalytic cracking of different feeding materials in the proper reactors is realized. Preferably, the product of the heavy raw material after catalytic cracking reaction is separated and then taken as the light raw material to be introduced into the riser reactor for reaction, so that the heavy oil conversion rate can be effectively improved, the light raw material is promoted to be cracked again, and the ratio of the low-carbon olefin to the dry gas yield is remarkably increased.

The invention carries out catalytic cracking on light raw materials in the riser reactor 9 and the fluidized bed reactor 3, and carries out catalytic cracking on heavy raw materials in the downer reactor 2, thereby not only respectively carrying out catalytic cracking on different raw materials and improving the selectivity of a target product, but also sending a second reaction product with lower carbon content obtained by the cracking reaction of the light raw materials into the fluidized bed reactor 3 again for cracking, and sending a regenerated catalyst into the fluidized bed reactor to improve the average activity of the catalytic cracking catalyst and increase the conversion rate of the catalytic cracking of the fluidized bed reactor 3.

According to the invention, the process further comprises: separating the first reaction product and the third reaction product to obtain dry gas, liquefied gas, gasoline, diesel oil and slurry oil so as to convert light hydrocarbons in the catalytic cracking product; the process also comprises the step of feeding at least part of the separated liquefied gas and/or gasoline and/or diesel oil as the light raw material into the riser reactor to contact with a catalytic cracking catalyst for catalytic cracking reaction. According to the invention, preferably, the diesel fraction obtained by separating the first reaction product after the heavy raw material is reacted in the downer reactor is selectively introduced into the riser reactor together with the light raw material, and/or the liquefied gas/gasoline/diesel fraction obtained by separating the third reaction product after the light raw material is reacted in the riser reactor and the fluidized bed reactor is selectively introduced into the riser reactor together with the light raw material, so that the re-catalytic cracking reaction of the diesel fraction can be flexibly controlled, the yield of low-carbon olefin is further improved, and the quality of diesel is improved at the same time.

According to the present invention, in order to increase the conversion rate of heavy oil, the process further comprises: and sending at least part of the separated oil slurry into the riser reactor to contact with a catalytic cracking catalyst for catalytic cracking reaction.

According to the invention, the spent catalyst from the fluidized bed reactor respectively comes from the spent catalyst after the contact reaction with the heavy raw material in the downer reactor, the spent catalyst after the contact reaction with the light raw material in the riser reactor and the continuous reaction in the fluidized bed reactor, and the spent catalyst after the reaction of the catalyst which is supplemented into the fluidized bed reactor and the light raw material.

The regeneration of the spent catalyst according to the present invention is well known to the person skilled in the art. Therefore, in order to regenerate the spent catalyst from the reaction of the downer reactor, the riser reactor and the fluidized bed reactor together, the catalytic cracking process further comprises: and (3) carrying out gas-solid separation on the third reaction product and the spent catalyst through a settling section 4 at the upper part of the fluidized bed reactor 3, sending the third reaction product obtained by separation out of the settling section 4 of the fluidized bed reactor 3, and sending the spent catalyst obtained by separation into the fluidized bed reactor.

According to the invention, the process further comprises: a step of stripping before regenerating the spent catalyst from the fluidized bed reactor. The step of stripping the spent catalyst is well known to those skilled in the art, for example, contacting the spent catalyst with atomized steam, the specific stripping conditions being well known to those skilled in the art. Preferably, the stripping is carried out in a stripper in the lower part of the fluidized bed reactor, in order not to add additional equipment. As shown in fig. 1, feeding the first reaction product and the spent catalyst in the step (1) into a settling section 4 at the upper part of a fluidized bed reactor 3 for gas-solid separation, feeding the separated first reaction product out of the fluidized bed reactor 3, feeding the separated spent catalyst into a stripping section 5 at the lower part of the fluidized bed reactor 3 for stripping, and feeding the stripped spent catalyst into a regenerator 7; and carrying out gas-solid separation on the third reaction product and the spent catalyst through a settling section 4 at the upper part of the fluidized bed reactor 3, sending the separated third reaction product out of the settling section 4 of the fluidized bed reactor 3, and sending the separated spent catalyst into a steam stripping section 5 at the lower part of the fluidized bed reactor 3 for steam stripping and then into a regenerator 7.

According to the invention, the process further comprises: and (3) using the regenerated catalyst obtained in the step (5) as the catalytic cracking catalyst of the step (1) and/or the step (3) and/or the step (4). The regenerated catalyst is continuously reused in the steps, so that the whole system can continuously run, the cost can be saved, and additional catalyst regeneration equipment is not required to be built. As shown in fig. 1, the resulting regenerated catalyst is fed to the bottom of the riser reactor 9, to the top of the downer reactor 2 and to the bed reactor section of the fluidized bed reactor 3. It should be noted that, in order to promote the catalytic cracking reaction, the catalyst for catalytic cracking fed into the downer reactor, the catalyst for catalytic cracking fed into the riser reactor, and the catalyst for regeneration fed into the fluidized bed reactor are all uncooled catalysts, i.e. the temperature is 500-900 ℃, preferably 600-800 ℃.

According to the present invention, different weights of regenerated catalyst can be selectively fed from the regenerator 7 to the fluidized bed reactor 3, the downer reactor 2 and the riser reactor 9, depending on the different feeds to the different reactors. Preferably, more than 0 to less than 100 wt%, preferably 10 to 70 wt%, of the regenerated catalyst is fed to the downer reactor 2 of step (1), more than 0 to less than 100 wt%, preferably 20 to 60 wt%, of the regenerated catalyst is fed to the fluidized bed reactor 3 of step (4), and 0 to less than 100 wt%, preferably 10 to 40 wt%, of the regenerated catalyst is fed to the riser reactor 9 of step (3), based on the total weight of the regenerated catalyst leaving the regenerator per unit time, to better satisfy the agent-to-oil ratio in each reactor.

According to the invention, the yield of the low-carbon olefin can be further improved and the distribution of reaction products can be optimized by combining different feeds of different reactors and preferably further optimizing the reaction conditions of different reactors.

In accordance with the present invention, the conditions under which the catalytic cracking reaction is carried out by contacting the heavy feedstock with the catalytic cracking catalyst in the downer reactor generally include reaction temperature and reaction time. In order to allow the heavy raw material to be more fully contacted with the catalyst in the downer reactor to perform the catalytic cracking reaction, the conditions of the catalytic cracking reaction comprise: the reaction temperature (outlet temperature at the bottom of the downer reactor 2) is 510-690 ℃, preferably 520-650 ℃; the agent-oil ratio is 5-20, preferably 7-18; the reaction time is from 0.5 to 8 seconds, preferably from 1.5 to 4 seconds. Wherein, the catalyst-oil ratio refers to the mass ratio of the catalytic cracking catalyst to the heavy raw material. The heavy feedstock feed atomizing steam comprises from 2 to 50 wt%, preferably from 5 to 15 wt%, of the total weight of the heavy feedstock and atomizing steam.

In accordance with the present invention, the conditions for contacting the light feedstock with the catalytic cracking catalyst in the riser reactor to effect the catalytic cracking reaction generally include reaction temperature and reaction time. In order to allow the light raw material to be more fully contacted with the catalyst in the riser reactor to perform the catalytic cracking reaction, the conditions of the catalytic cracking reaction comprise: the reaction temperature (outlet temperature at the top of the riser reactor) is 520-720 ℃, preferably 530-700 ℃; the agent-oil ratio is 8-26, preferably 10-24; the reaction time is from 1 to 10 seconds, preferably from 2 to 7 seconds. Wherein, the catalyst-oil ratio refers to the weight ratio of the catalytic cracking catalyst to the light raw material. The light feedstock feed atomizing steam comprises from 2 to 50 wt%, preferably from 5 to 15 wt%, of the total weight of the light feedstock, optional slurry oil and atomizing steam.

According to the invention, in the fluidized bed reactor, the second product after riser reaction and the spent catalyst continue to further react in the fluidized bed reactor, thereby promoting the further conversion of light hydrocarbon. In order to enable the light hydrocarbon to be more fully contacted with spent catalyst with certain catalytic cracking activity and supplemented fresh catalytic cracking catalyst in the fluidized bed reactor to carry out catalytic cracking reaction, the conditions of the catalytic cracking reaction comprise: the reaction temperature is 480-650 ℃, preferably 500-640 ℃; the weight hourly space velocity is from 1 to 35 per hour, preferably from 2 to 33 per hour; the agent-oil ratio is 6-20, preferably 7-18; the reaction pressure (absolute pressure, outlet pressure) is from 0.15 to 0.35MPa, preferably from 0.2 to 0.35 MPa. Wherein the catalyst-to-oil ratio refers to the weight ratio of the catalytic cracking catalyst to the second reaction product.

The catalytic cracking catalyst is a catalyst which can be used for producing reaction products containing low-carbon olefins by catalytic cracking of heavy raw materials and light raw materials. The catalytic cracking catalyst is commercially available or may be prepared according to methods known to those skilled in the art. In particular, theThe catalytic cracking catalyst contains a zeolite, an inorganic oxide and optionally a clay. Based on the weight of the catalytic cracking catalyst, the content of the zeolite is 1-50 wt%, the content of the inorganic oxide is 5-99 wt%, and the content of the clay is 0-70 wt%. Preferably, in order to increase the yield of propylene and increase the conversion, the zeolite comprises shape selective zeolite and Y-type zeolite with the average pore diameter of less than 0.7 nm; the content of the shape-selective zeolite with the average pore diameter of less than 0.7 nanometer is 25-90 wt% and the content of the Y-type zeolite is 10-75 wt% on a dry basis and based on the total weight of the zeolite. Wherein the shape selective zeolite with the average pore diameter of less than 0.7 nanometer can be at least one of ZSM series zeolite, ZRP zeolite, ferrierite, chabazite, dachiardite, erionite, A zeolite, column zeolite and turbid zeolite, and one or more than two of the zeolites obtained after physical and/or chemical treatment. The ZSM-series zeolite may be one or a mixture of two or more selected from ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other zeolites of similar structure. For more details on ZSM-5 see USP3702886 and for more details on ZRP see USP5232675, CN1211470A, CN 1611299A. The Y-type zeolite may be at least one selected from rare earth Y-type zeolite (REY), rare earth hydrogen Y-type zeolite (REHY), ultrastable Y-type zeolite (USY), and rare earth ultrastable Y-type zeolite (REUSY). The inorganic oxide may be silicon dioxide (SiO) as a binder₂) And/or aluminum oxide (Al)₂O₃). The clay selected as a matrix, i.e., carrier, may be kaolin and/or halloysite.

The types of heavy and light feedstocks are well known to those skilled in the art in light of the present invention.

The heavy raw material is heavy hydrocarbon and/or various animal and vegetable oil raw materials rich in hydrocarbon, and the heavy hydrocarbon can be one or more than one mixture selected from petroleum hydrocarbon, mineral oil and synthetic oil. The petroleum hydrocarbon may be vacuum wax oil, atmospheric residue, a mixture of vacuum wax oils and partial vacuum residue, or other secondary processing hydrocarbon oils such as one or more of coker wax oil, deasphalted oil, and furfural refined raffinate oil. The mineral oil can be one or more selected from coal liquefied oil, oil sand oil and shale oil. The synthetic oil can be distillate oil obtained by F-T synthesis of coal, natural gas or asphalt. The various animal and vegetable oils rich in hydrocarbon can be various animal and vegetable oils. The heavy raw material is preferably selected from at least one of vacuum wax oil, normal pressure wax oil, coking wax oil, deasphalted oil, furfural refined raffinate oil, coal liquefied oil, oil sand oil, shale oil, Fischer-Tropsch synthetic oil and animal and vegetable oil.

The light feedstock is preferably an olefin-rich gasoline and/or C₄Hydrocarbons and/or diesel, said olefin-rich gasoline being selected from gasoline fractions produced by the present process and/or gasoline fractions produced by other plants. The gasoline fraction produced by other equipment can be one or more than one of catalytic cracking crude gasoline, catalytic cracking stable gasoline, coker gasoline, visbreaker gasoline and other gasoline fractions produced by oil refining or chemical process, preferably gasoline fraction produced by said process. The olefin content of the olefin-rich gasoline may be 25 to 95% by weight, preferably 35 to 90% by weight, and most preferably 50% by weight or more. The end point of the gasoline rich in olefin is not more than 204 ℃, and can be a full-boiling range gasoline fraction with the boiling range of 35-204 ℃ or a narrow fraction thereof, such as a gasoline fraction with the end point not more than 85 ℃, and preferably a gasoline fraction with the boiling range of 40-85 ℃. Said C is₄By hydrocarbon is meant₄The low molecular hydrocarbon containing C4 alkane, olefin and alkyne existing in gas form at normal temperature and normal pressure with fraction as main component may be C-rich hydrocarbon produced by the present process₄The gaseous hydrocarbon products of the fraction can also be C-rich products produced by other plant processes₄Gaseous hydrocarbons of the fraction, of which C self-produced by the process is preferred₄And (6) cutting. Said C is₄The olefin content of the hydrocarbon is more than 50% by weight, preferably more than 60% by weight, and most preferably 70% by weight or more. The diesel oil refers to diesel oil fraction produced by the process and/or diesel oil fraction produced by other devices. It is composed ofThe gasoline fraction produced by the device can be one or a mixture of more than one of catalytic cracking diesel oil, straight-run diesel oil, hydrofined diesel oil, hydrocracking diesel oil, biodiesel, coking diesel oil, visbreaking diesel oil and other diesel oil fractions produced in oil refining or chemical processes, and the diesel oil fraction produced by the process is preferably selected. The oil slurry refers to the oil slurry produced by the process. The final distillation point of the diesel oil is not more than 350 ℃, and the diesel oil can be full-distillation range diesel oil fraction with the distillation range of 205-350 ℃ or narrow fraction thereof. In the light raw material, C₄The weight ratio of hydrocarbon to gasoline may be (0-2):1, preferably (0-1.2):1, more preferably (0-0.8): 1; the weight ratio of diesel to gasoline may be (0-2):1, preferably (0-1.2):1, more preferably (0-0.8): 1. Preferably, the weight ratio of the olefin-rich gasoline fed to the riser reactor to the heavy feedstock fed to the downer reactor is (0.05-0.3):1, more preferably (0.1-0.2): 1. Preferably, the weight ratio of the diesel fraction fed to the riser reactor to the heavy feedstock fed to the downer reactor is (0.02-0.3):1, more preferably (0.05-0.2): 1. Preferably, the weight ratio of the slurry oil fed to the riser reactor to the heavy feedstock fed to the downer reactor is (0.01-0.2):1, more preferably (0.05-0.15): 1.

According to the invention, the system for catalytic cracking comprises: a downer reactor 2, a fluidized bed reactor 3, a regenerator 7 and a riser reactor 9. The fluidized bed reactor 3 sequentially comprises a settling section 4, a fluidized bed reaction section and a stripping section 5 from top to bottom. The downer reactor 2 is communicated with a settling section 4 of the fluidized bed reactor 3. The riser reactor 9 is in communication with the fluidized bed reaction section of the fluidized bed reactor 3. The regenerator 7 is respectively communicated with the downer reactor 2, the fluidized bed reactor 3 and the riser reactor 9.

According to the present invention, as shown in fig. 1, the downer reactor 2 is provided with a catalyst inlet at the top, a heavy feedstock inlet at the upper part and a material outlet at the bottom. In order to facilitate the separation of the product and the regeneration of the catalyst to be regenerated, the fluidized bed reactor 3 comprises a fluidized bed reaction section, a stripping section 5 arranged below the fluidized bed reaction section, and a settling section 4 arranged above the fluidized bed reaction section, wherein the fluidized bed reaction section, the stripping section 5 and the settling section 4 can be coaxially arranged and are in fluid communication. The fluidized bed reactor 3 is provided with a catalyst inlet, a first material inlet, a second material inlet, a catalyst outlet and a product outlet; the catalyst inlet and the second material inlet are positioned in a fluidized bed reaction section of the fluidized bed reactor 3, the first material inlet is positioned in a settling section 4 of the fluidized bed reactor 3, and the product outlet is positioned in the settling section 4 of the fluidized bed reactor 3, preferably at the top of the settling section 4. The catalyst outlet of the fluidized bed reactor 3 is located in the lower part of the stripping section 5. Preferably, the steam stripping section 5 strips steam and oil gas obtained by reaction, introduces the steam and the oil gas into the bottom of the fluidized bed reactor, and discharges the steam and the oil gas out of the reactor after passing through the fluidized bed reactor, so that the partial pressure of the oil gas can be reduced, the retention time of the oil gas in the settling section is shortened, and the yield of the low-carbon olefin is increased. The riser reactor 9 is provided with a catalyst inlet positioned at the bottom, a light raw material inlet positioned at the lower part and a material outlet positioned at the top; preferably, the riser reactor 9 is further provided with an oil slurry inlet at the lower or bottom part. Preferably, the riser reactor 9 extends into the second material inlet of the fluidized bed reactor 3 from bottom to top and the material outlet at the top of the riser reactor 9 is located in the fluidized bed reactor 3. The material outlet of the downer reactor 2 is communicated with a first material inlet of a settling section 4 of the fluidized bed reactor 3. The material outlet of the riser reactor 9 is communicated with the second material inlet of the fluidized bed reaction section of the fluidized bed reactor 3.

According to the present invention, the downer reactor may be selected from one or a combination of two of a constant diameter downer, a constant linear velocity downer and a variable diameter downer.

According to the present invention, the riser reactor may be selected from one or a combination of two of a constant diameter riser, a constant linear velocity riser and a variable diameter riser. According to the present invention, the outlet of the riser reactor is preferably provided with a low pressure outlet distributor, which may have a pressure drop of less than 10KPa, which may be an existing distributor, such as an arch distributor or the like.

According to the present invention, the fluidized bed reactor may be selected from one of a fixed fluidized bed, a bulk fluidized bed, a bubbling bed, a turbulent bed, a fast bed, a transport bed and a dense phase bed reactor.

According to the present invention, as shown in fig. 1, the regenerator 7 is provided with a catalyst inlet and a catalyst outlet; the catalyst inlet of the regenerator 7 is in communication with the stripping section 5 of the fluidized bed reactor 3. And the catalyst outlet of the regenerator 7 is respectively communicated with the catalyst inlet of the fluidized bed reactor 3, the catalyst inlet of the downer reactor 2 and the catalyst inlet of the riser reactor 9. Preferably, the catalyst outlet of the regenerator 7 is communicated with the catalyst inlet of the fluidized bed reactor 3 through a third regeneration inclined tube 11, is communicated with the catalyst inlet of the downer reactor 2 through a second regeneration inclined tube 10, and is communicated with the catalyst inlet of the riser reactor 9 through a first regeneration inclined tube 8.

According to the invention, the first reaction product and the spent catalyst leaving the downer reactor 2 and the third reaction product and the spent catalyst leaving the fluidized bed reactor 3 enter the settling section 4, and after the spent catalyst carried in the first reaction product and the third reaction product are settled and separated, the first reaction product and the third reaction product can be subjected to subsequent product separation. And separating the first reaction product and the third reaction product to obtain dry gas, liquefied gas, gasoline, diesel oil and oil slurry. The product separation may be performed in a product separation unit. The product separation device can be the prior art, and the invention has no special requirement. According to the present invention, as shown in fig. 1, the system preferably further comprises a product separation device 12, the product separation device 12 being provided with a product inlet, a dry gas outlet, a liquefied gas outlet, a gasoline outlet, a diesel outlet and a slurry outlet. The inlet of the product separation unit 12 is in communication with the product outlet at the settling section 4 of the fluidized bed reactor 3. In order to further improve the yield of the low carbon system, the liquefied gas outlet and/or the gasoline outlet and/or the diesel oil outlet of the product separation device 12 are communicated with the light raw material inlet of the riser reactor 9. The slurry oil outlet of the product separation device 12 is communicated with the light raw material inlet of the riser reactor 9, and preferably, the slurry oil outlet of the product separation device 12 is communicated with the slurry oil inlet of the riser reactor 9.

The process and system of the present invention are further described with reference to the accompanying drawings in which:

as shown in fig. 1, the high-temperature regenerated catalyst is introduced into the riser reactor 9, the downer reactor 2 (the catalyst tank 1 at the top) and the fluidized bed reactor 3 through a first regenerating agent inclined tube 8, a second regenerating inclined tube 10 and a third regenerating inclined tube 11, respectively. Preheated or not preheated light raw material gasoline fraction rich in olefin and/or C4 hydrocarbon and/or diesel oil is injected into a riser reactor 9 through a light raw material pipeline 20, preheated oil slurry is mixed with atomized steam from a second atomized steam pipeline 19 according to a certain proportion through a return oil slurry pipeline 18, then the mixture is injected into the riser reactor 9, and is mixed and reacted with a high-temperature catalyst which passes through a first regeneration inclined pipe 8 and is lifted by lifting gas from a pre-lifting medium pipeline 17, reaction oil gas (second reaction product) and a catalyst mixture are introduced into a fluidized bed reactor 3 through an outlet distributor (not marked in the figure) of the riser reactor 9 for continuous reaction, and finally the mixture enters a settling section 4 for separation of the oil gas and the catalyst; the separated oil gas (first reaction product/third reaction product) enters a subsequent product separation device 12 through an oil gas pipeline 21, and the separated spent catalyst enters a regenerator 7 through a spent inclined tube 6 preferably after being stripped in a stripping section 5. The preheated heavy raw material is mixed with atomized water vapor from a first atomized water vapor pipeline 14 according to a certain proportion through a heavy raw material pipeline 13, then the mixture is injected into a descending tube reactor 2 to contact and react with a high-temperature mixing agent (comprising a fresh catalyst and a regenerated catalyst) from a catalyst tank 1, and a reaction oil gas (a first reaction product) and a catalyst mixture enter a settling section 4 through an outlet distributor (not marked in the figure) of the descending tube reactor 2 to be separated from the catalyst; the separated oil and gas (first reaction product/third reaction product) enters the subsequent product separation device 12 through an oil and gas pipeline 21. The reaction products are separated in a product separation unit 12 from gaseous hydrocarbons (which are led off via a gaseous hydrocarbon line 23),Gasoline (drawn from gasoline line 24), diesel (drawn from diesel line 25), light cycle oil (drawn from light cycle oil line 26), and oil slurry (drawn from separated oil slurry line 27). The cracked gaseous hydrocarbons from the gaseous hydrocarbon line 23 can be separated and refined to obtain polymer grade propylene product and olefin-rich C4 fraction, wherein the olefin-rich C4 fraction can be returned to the riser reactor 9 for further conversion to ethylene and propylene. The gasoline led out from the gasoline pipeline 24 can be partially or completely returned to the reaction system for conversion, or the gasoline can be cut into light gasoline and heavy gasoline fractions, the light gasoline is partially or completely returned to the reaction system for conversion, and the light gasoline is preferably returned to the riser reactor 9 for conversion; the diesel oil led out from the diesel oil pipeline 25 can be partially or completely returned to the riser reactor 9 for conversion; the slurry oil withdrawn from the separated slurry oil line 27 may be partially or completely returned to the riser reactor 9 for further conversion. The catalyst obtained by separation in the settling section 4 enters the fluidized bed reactor 3, then enters the stripping section 5, stripping steam is injected through a stripping steam pipeline 16 and is in countercurrent contact with the carbon deposition catalyst, reaction oil gas carried by the carbon deposition catalyst is stripped as much as possible, and then the reaction oil gas is introduced into the settling section 4 through the fluidized bed reactor 3 and is led out of the reactor together with other oil gas through an oil gas pipeline 21. The stripped catalyst is sent to a regenerator 7 through a spent catalyst inclined pipe 6 for coke burning regeneration. Oxygen-containing gas is injected into the regenerator 7 through an oxygen-containing gas line 15 and regeneration flue gas is led out through a regeneration flue gas line 22. The regenerated catalyst enters different reactors for recycling through a first regeneration inclined tube 8, a second regeneration inclined tube 10 and a third regeneration inclined tube 11. In the above embodiment, the pre-lift medium introduced into the pre-lift medium line 17 of the pre-lift section of the riser reactor may be selected from steam, C1-C4 hydrocarbons or conventional catalytic cracking dry gas, steam being preferred in the present invention. In the above embodiment process, the lifting medium introduced into the lifting medium line 28 of the downer reactor 2 for lifting the regenerant into the catalyst tank 1 may be selected from the group consisting of steam, C1-C4 hydrocarbons, N₂Or conventional catalytic cracking dry gas, the dry gas being preferred in the present invention.

The present invention will be described in detail below by way of examples.

The raw oil and the catalytic cracking catalyst used in the following examples and comparative examples were the same. The feedstock A used was a cracking feedstock, the specific properties of which are shown in Table 1. The adopted catalytic cracking catalyst is MMC-2 produced by China petrochemical Qilu catalyst factory, contains shape-selective zeolite with the average pore diameter of less than 0.7 nanometer and a Y-type molecular sieve, and the specific properties of the catalyst are shown in Table 2.