CN110655953A - Processing method and system of diesel raw material - Google Patents

Abstract

The invention relates to a method and a system for processing diesel fuel. The method comprises: separating diesel fuel into light diesel fraction and heavy diesel fraction; subjecting the obtained heavy diesel fraction to hydrorefining to obtain a hydrorefined product; The hydrogen refining product is subjected to the first catalytic cracking reaction; the obtained first catalytic cracking product and the semi-prepared catalyst are subjected to the second catalytic cracking reaction; the obtained light diesel fraction is subjected to the third catalytic cracking reaction to obtain the third catalytic cracking product and the second catalytic cracking reaction. A catalyst to be produced; separating the obtained second catalytic cracking product and the third catalytic cracking product to obtain a low-carbon olefin product, a light naphtha product, a heavy naphtha product, a circulating oil product and an oil slurry product; separating the obtained heavy naphtha product The product is subjected to aromatics extraction, and the obtained raffinate is introduced into the third catalytic cracking reactor for the third catalytic cracking reaction. The method and system of the present invention can improve the yield of propylene, butenes and aromatics.

Description

Method and system for processing diesel fuel

technical field

The present invention relates to a method and system for processing diesel fuel.

Background technique

Ethylene, propylene and light aromatic hydrocarbons (benzene, toluene and xylene, referred to as BTX) are the basic chemical raw materials, and the traditional petrochemical industry is based on steam cracking to produce ethylene. In my country, the main raw material for steam cracking is naphtha, while crude oil in my country is generally heavy, the yield of light oil is low, and the raw materials for steam cracking production are obviously insufficient. Therefore, the traditional steam cracking process in my country is restricted by the supply of raw materials. , the wide application of steam cracking units using shale gas as raw material in North America is constantly pressing the economy of the process of using naphtha as the raw material for ethylene cracking. Compared with the ethylene product market, propylene is less affected by the shale gas revolution, and the market gap for propylene is still relatively large. Therefore, in the period of relatively low crude oil prices, the development of process technology for producing more propylene will have broad application prospects in the future.

At present, one of the main devices for the production of propylene in refinery and chemical enterprises is the catalytic cracking device. The main raw materials of the catalytic cracking unit include naphtha, diesel oil, wax oil and residual oil. After the residual oil is hydrotreated, the yield of propylene in the catalytic cracking unit can reach 20% or even more than 30%. However, the propylene yield of catalytic crackers using diesel as feedstock is low. Therefore, by choosing a suitable process route, there is a large room for improvement to increase the yield of diesel catalytic cracking of propylene and to produce light aromatics.

Chinese patent CN106590741A discloses a catalytic conversion method for prolific production of low-carbon olefins and light aromatics. In the method, the aromatic-rich gasoline component and the initial catalytic cracking product are further catalytically cracked to finally obtain a liquefaction rich in low-carbon olefins. gas, gasoline fractions rich in light aromatics, diesel fractions and oil slurries. However, the raw material oil used can be at least one of C4 distillate oil, gasoline, diesel oil, crude oil, wax oil, coal liquefied oil and oil sand oil. This method can further catalytically crack the gasoline components rich in aromatic hydrocarbons and convert all the The obtained aromatic-rich gasoline components are subjected to aromatics extraction, but the raw materials are not optimized, and the sources of gasoline components are limited, so the yield of light aromatics is limited.

Chinese patent CN101063047A discloses a kind of heavy feedstock hydrotreating-catalytic cracking method that improves propylene yield, heavy distillate oil and optional light cycle oil from catalytic cracking unit can be together in one reaction zone, or can be separately The reaction is carried out in two hydrogenation reaction zones filled with different hydrogenation catalysts. After the reaction effluent is cooled, separated and fractionated, the obtained heavy liquid phase fraction goes to the catalytic cracking unit, and the catalytic cracking reaction product is separated by the separator to obtain the final product. product. The method provided by the patent improves the properties of the wax oil feedstock of the catalytic cracking unit through the method of hydrotreating, but does not cut the diesel feedstock. On the one hand, during the hydrogenation process, the hydrogen consumption is increased, and on the other hand, the production of light aromatics is reduced. and the light naphtha fraction was not refined, further reducing the yield of light olefins.

Chinese patent CN101139529A discloses a coking diesel-steam cracking combined process method. The method uses heavy hydrocoking diesel as raw material, and after hydrotreating in a fixed bed, generates oil for fraction cutting, and the cutting point is 260-320°C. The hydrogenated heavy components are directly fed into the cracking furnace, and the yield of low-carbon olefins ethylene, propylene and butadiene is about 27%. The fractions are not utilized properly, resulting in lower yields of final olefins.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method and system for processing diesel feedstock, the method and system of the present invention can improve the yield of propylene, butene and aromatics.

In order to achieve the above object, the present invention provides a method for processing diesel fuel, the method comprising:

Separating the diesel fuel into a light diesel oil fraction and a heavy diesel oil fraction, wherein the cut point of the light diesel oil fraction and the heavy diesel oil fraction is in the range of 220-240° C.;

The obtained heavy diesel oil fraction is introduced into a hydrotreating reactor to contact with a hydrotreating catalyst and carry out hydrotreating treatment to obtain a hydrotreating product;

The obtained hydrorefining product is introduced into the first catalytic cracking reactor to contact with the first catalytic cracking catalyst and carry out the first catalytic cracking reaction to obtain the first catalytic cracking product and the semi-to-be-generated catalyst;

introducing the obtained first catalytic cracking product and the semi-to-be-grown catalyst into a second catalytic cracking reactor to carry out a second catalytic cracking reaction to obtain the second catalytic cracking product and the first to-be-grown catalyst;

The obtained light diesel oil fraction is introduced into the third catalytic cracking reactor to contact with the second catalytic cracking catalyst and carry out the third catalytic cracking reaction to obtain the third catalytic cracking product and the second catalyst to be produced;

The obtained second catalytic cracking product and the third catalytic cracking product are separated to obtain low-carbon olefin product, light naphtha product, heavy naphtha product, circulating oil product and oil slurry product;

sending the obtained first and second ready-made catalysts into a regenerator for regeneration, and the obtained regenerated catalysts are used as the first and second catalytic cracking catalysts;

The obtained heavy naphtha product is subjected to aromatic hydrocarbon extraction to obtain extract oil and raffinate oil containing aromatic hydrocarbons, and the obtained raffinate oil is introduced into the third catalytic cracking reactor for the third catalytic cracking reaction.

Optionally, the method also includes at least one of the following steps:

(1), the gained light naphtha product is introduced in the described third catalytic cracking reactor to carry out the described third catalytic cracking reaction;

(2), introducing gained recycle oil product into described hydrorefining reactor to carry out described hydrorefining treatment;

(3), introducing at least part of the second catalyst to be produced from the third catalytic cracking reaction into the second catalytic cracking reactor to carry out the second catalytic cracking reaction.

Optionally, the cetane number of the diesel feedstock is less than 25, and the distillation range is in the range of 170-400°C.

Optionally, the diesel feedstock includes catalytically cracked diesel, with or without coking diesel.

Optionally, the hydrofinishing catalyst comprises a carrier and an active metal component supported on the carrier, and the carrier is selected from the group consisting of alumina, silica, alumina-silica, titania, magnesia, oxide Silicon-magnesium oxide, silicon oxide-zirconia, silicon oxide-thorium oxide, silicon oxide-beryllium oxide, silicon oxide-titanium oxide, silicon oxide-zirconium oxide, titanium oxide-zirconium oxide, silicon oxide-alumina-thorium oxide, At least one of silica-alumina-titanium oxide, silica-alumina-magnesia and silica-alumina-zirconia, the active metal component is at least one selected from the group VIB metal elements and At least one metal element selected from Group VIII; based on the total weight of the hydrofinishing catalyst, the content of at least one metal element selected from Group VIB calculated as oxide is 1-30% by weight, calculated as oxide The content of at least one metal element selected from Group VIII is 3-35% by weight;

The conditions of the hydrorefining treatment include: hydrogen partial pressure 3-12MPa, reaction temperature 260-450°C, hydrogen oil volume ratio 400-1600Nm ³ /m ³ , liquid hourly volume space velocity 0.3-4.0h ^-1 .

Optionally, in the hydrorefining process, the polycyclic aromatic hydrocarbon saturation rate of the heavy diesel oil fraction is not less than 85% by weight, the total aromatic hydrocarbon saturation rate of the heavy diesel oil fraction is 12-35% by weight, and the content of the hydrorefining product is The distillation range is in the range of 200-400°C.

Optionally, the conditions of the first catalytic cracking reaction include: the reaction temperature is 500-650° C., the reaction time is 0.5-8s, the reaction pressure is 0.10-1.0MPa, the first catalytic cracking catalyst and the hydrorefined product are The weight ratio of (2-100): 1, the weight ratio of atomized steam and hydrofinished product is (0.05-0.5): 1;

The reaction temperature of the second catalytic cracking reaction is 10-100° C. higher than the reaction temperature of the first catalytic cracking reaction, and the weight hourly space velocity of the second catalytic cracking reaction is 1-35 h ⁻¹ .

The conditions of the third catalytic cracking reaction include: the reaction temperature is 600-750 ° C, the reaction time is 0.5-10s, the reaction pressure is 0.1-1.0MPa, and the weight ratio of the second catalytic cracking catalyst to the light diesel fraction is ( 4-100): 1.

Optionally, the reaction temperature of the third catalytic cracking reaction is 30-100°C higher than the reaction temperature of the second catalytic cracking reaction.

Optionally, the first catalytic cracking catalyst and the second catalytic cracking catalyst each independently comprise a zeolite, an inorganic oxide binder and optionally a clay;

Based on the total weight of the catalyst, the content of the zeolite is 10-50% by weight, the content of the inorganic oxide is 5-90% by weight, and the content of the clay is 0-70% by weight;

The zeolite is at least one selected from the group consisting of Y-type or HY-type zeolite with or without rare earth, ultra-stable Y-type zeolite with or without rare earth, and zeolite with MFI structure.

Optionally, the distillation range of the light naphtha product is within 65-135°C, the distillation range of the heavy naphtha product is within 130-175°C, and the distillation range of the circulating oil product Within 175-450℃.

Optionally, the first catalytic cracking reactor and the third catalytic cracking reactor are both riser reactors, and the second catalytic cracking reactor is a fluidized bed reactor.

The present invention also provides a processing system for diesel raw materials, which comprises a fractionation device, a hydrotreating reactor, a first catalytic cracking reactor, a second catalytic cracking reactor, a third catalytic cracking reactor, a regenerator, a second catalytic cracking reactor, and a second catalytic cracking reactor. Oil separation device and product separation device;

The fractionation device is provided with a diesel raw material inlet, a light diesel fraction outlet and a heavy diesel fraction outlet, the hydrorefining reactor is provided with a hydrogen inlet, a feed oil inlet and a hydrorefining product outlet, and the first catalytic cracking reactor is provided with , The second catalytic cracking reactor and the third catalytic cracking reactor are independently provided with a material inlet and a material outlet, the second oil separation device is provided with a material inlet, an oil and gas outlet and a catalyst outlet, and the regenerator is provided with A catalyst inlet and a catalyst outlet, the product separation device is provided with an oil and gas inlet, a light olefin outlet, a light naphtha outlet, a heavy naphtha outlet, a circulating oil outlet and an oil slurry outlet;

The heavy diesel fraction outlet of the fractionation device is communicated with the feed oil inlet of the hydrotreating reactor, and the hydrotreating product outlet of the hydrotreating reactor is communicated with the material inlet of the first catalytic cracking reactor, The material outlet of the first catalytic cracking reactor is communicated with the material inlet of the second catalytic cracking reactor, and the material outlet of the second catalytic cracking reactor is communicated with the material inlet of the second oil separation device, The light diesel fraction outlet of the fractionation device is communicated with the material inlet of the third catalytic cracking reactor, the material outlet of the third catalytic cracking reactor is communicated with the material inlet of the second oil separation device, and the The catalyst outlet of the second oil separation device is communicated with the catalyst inlet of the regenerator, and the catalyst outlet of the regenerator is communicated with the material inlets of the first catalytic cracking reactor and the third catalytic cracking reactor respectively. The oil and gas outlet of the oil separation device is communicated with the oil and gas inlet of the product separation device;

The system also includes an aromatic hydrocarbon extraction device, the aromatic hydrocarbon extraction device is provided with an extraction solvent inlet, an extraction raw material inlet, a raffinate oil outlet and an extraction oil outlet, and the extraction raw material inlet of the aromatic hydrocarbon extraction device is connected to the The heavy naphtha outlet of the product separation device is communicated with, and the raffinate oil outlet is communicated with the material inlet of the third catalytic cracking reactor.

Optionally, the system further includes a first oil separation device, the first oil separation device is provided with a material inlet, a catalyst outlet and an oil and gas outlet, and the material outlet of the third catalytic cracking reactor is connected to the first oil and gas outlet. The material inlet of an oil separation device is in communication, the catalyst outlet of the first oil separation device is in communication with the material inlet of the second catalytic cracking reactor, and the oil and gas outlet of the first oil separation device is connected with the second catalytic cracking reactor. The material inlet of the secondary oil separation device is communicated; and/or

The light naphtha outlet of the product separation device communicates with the material inlet of the third catalytic cracking reactor; and/or

The circulating oil outlet of the product separation device communicates with the feed oil inlet of the hydrotreating reactor.

Optionally, the first catalytic cracking reactor and the third catalytic cracking reactor are both riser reactors, and the second catalytic cracking reactor is a fluidized bed reactor.

The method and system of the present invention can obtain high yields of propylene, High value products such as ethylene and aromatics.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached image:

FIG. 1 includes a schematic flowchart of a specific embodiment of the method of the present invention, and also includes a schematic structural diagram of a specific embodiment of the system of the present invention.

Figure 2 is a schematic flow chart of the method in Comparative Example 1 of the present invention.

Description of reference numerals

1 Line 2 Diesel Fractionator 3 Line

4 pipelines 5 hydrotreating reactors 6 circulating hydrogen compressors

7 pipelines 8 pipelines 9 pipelines

10 Separator 11 Pipeline 12 The first catalytic cracking reactor

13 The second catalytic cracking reactor 14 The regenerator 15 The third catalytic cracking reactor

16 The first oil separation device 17 The second oil separation device 18 The product separation device

19 pipeline 20 pipeline 21 pipeline

22 line 23 line 24 line

25 Aromatic extraction unit 26 Line 27 Line

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

The invention provides a method for processing diesel fuel, the method comprising:

Separating diesel fuel into light diesel oil fraction and heavy diesel oil fraction, wherein the cut point of the light diesel oil fraction and the heavy diesel oil fraction is in the range of 220-240°C, preferably 225-235°C, more preferably 228-235°C ;

The obtained heavy diesel oil fraction is introduced into a hydrotreating reactor to contact with a hydrotreating catalyst and carry out hydrotreating treatment to obtain a hydrotreating product;

The obtained hydrorefining product is introduced into the first catalytic cracking reactor to contact with the first catalytic cracking catalyst and carry out the first catalytic cracking reaction to obtain the first catalytic cracking product and the semi-to-be-generated catalyst;

introducing the obtained first catalytic cracking product and the semi-to-be-grown catalyst into a second catalytic cracking reactor to carry out a second catalytic cracking reaction to obtain the second catalytic cracking product and the first to-be-grown catalyst;

The obtained light diesel oil fraction is introduced into the third catalytic cracking reactor to contact with the second catalytic cracking catalyst and carry out the third catalytic cracking reaction to obtain the third catalytic cracking product and the second catalyst to be produced;

The obtained second catalytic cracking product and the third catalytic cracking product are separated to obtain a low-carbon olefin product, a light naphtha product, a heavy naphtha product, a circulating oil product and an oil slurry product; the low-carbon olefin can include ethylene and Propylene;

sending the obtained first and second ready-made catalysts into a regenerator for regeneration, and the obtained regenerated catalysts are used as the first and second catalytic cracking catalysts;

The obtained heavy naphtha product is subjected to aromatic hydrocarbon extraction to obtain extract oil and raffinate oil containing aromatic hydrocarbons, and the obtained raffinate oil is introduced into the third catalytic cracking reactor for the third catalytic cracking reaction.

According to the present invention, the method may further comprise at least one of the following steps: (1), introducing the obtained light naphtha product into the third catalytic cracking reactor to carry out the third catalytic cracking reaction; (2), applying the The obtained circulating oil product is introduced into the hydrotreating reactor for the hydrotreating treatment; (3), at least part of the second catalyst to be grown obtained from the third catalytic cracking reaction is introduced into the second catalytic cracking reactor for the process the second catalytic cracking reaction. Steps (1)-(2) can improve the utilization rate of raw materials and the yield of light olefins, and step (3) can improve the utilization rate of the second to-be-grown catalyst with low coke formation obtained by the third catalytic cracking reaction.

According to the present invention, diesel feedstocks are well known to those skilled in the art, and may include, for example, catalytically cracked diesel fuel, with or without coking diesel fuel, the cetane number of the diesel feedstock may be less than 25, and the distillation range may be 170-400° C. Within the range of , the aromatic hydrocarbons in diesel feedstock mainly include monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons, of which bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons account for most of the total aromatic hydrocarbon content. Hydrorefining treatment can take place reactions such as hydrodesulfurization, hydrodenitrogenation, aromatics hydrosaturation, and hydrodemetallization. One of the important purposes is to saturate at least part of the polycyclic aromatic hydrocarbons in the heavy diesel fraction to improve cracking performance and produce More olefins and aromatic hydrocarbons, in the hydrorefining process, the polycyclic aromatic hydrocarbon saturation rate of the heavy diesel oil fraction can be not less than 85% by weight, preferably not less than 90% by weight, preferably not more than 95% by weight, heavy diesel oil. The total aromatic saturation rate of the fraction can be 12-35% by weight, preferably 15-32% by weight, and the distillation range of the hydrorefined product is preferably in the range of 200-400°C; wherein,

The PAH saturation rate of the heavy diesel fraction was calculated using the following formula:

A2m=(A2f-A2p)/A2f×100wt%;

In the formula: A2m is the polycyclic aromatic hydrocarbon saturation rate of the heavy diesel oil fraction, % by weight;

A2f is the weight fraction of polycyclic aromatic hydrocarbons in the heavy diesel oil fraction, % by weight;

A2p is the weight fraction of polycyclic aromatic hydrocarbons in the heavy diesel fraction hydrorefining product, wt%.

The total aromatic saturation of the heavy diesel fraction was calculated using the following formula:

Ata=(Aaf−Aap)/Aaf×100wt%;

In the formula: Ata is the total aromatic saturation rate of the heavy diesel oil fraction, % by weight;

Aaf is the weight fraction of all aromatics in the heavy diesel fraction, wt%;

Aap is the weight fraction of all aromatics in the heavy diesel fraction hydrorefining product, wt%.

According to the present invention, the separation method of diesel feedstock is well known to those skilled in the art, such as fractional distillation, and the light diesel fraction obtained by fractional distillation can be directly subjected to catalytic cracking without hydrogenation, thereby reducing hydrogen consumption and producing more olefins and olefins. Aromatic hydrocarbons.

According to the present invention, the hydrofinishing catalyst may comprise a support and an active metal component supported on the support, and the support may be selected from the group consisting of alumina, silica, alumina-silica, titania, and magnesia , silica-magnesia, silica-zirconia, silica-thorium oxide, silica-beryllium oxide, silica-titania, silica-zirconia, titania-zirconia, silica-alumina-oxide At least one of thorium, silica-alumina-titania, silica-alumina-magnesia and silica-alumina-zirconia, the active metal component is at least one metal selected from Group VIB element and at least one selected from the group VIII metal elements, the VIB group metal elements are preferably molybdenum and/or tungsten, the VIII group metal elements are preferably cobalt and/or nickel; The content of at least one metal element selected from Group VIB in terms of oxide is 1-30% by weight, and the content of at least one metal element selected from Group VIII in terms of oxide is 3-35% by weight ; Hydrorefining catalyst can be extruded or spherical, bulk density can be 0.4-1.3g/cm ³ , catalyst average particle diameter (spherical diameter or bar diameter) can be 0.08-1.2mm, specific surface area can be 100 -300m ² /g.

According to the present invention, the conditions of the hydrorefining treatment may include: hydrogen partial pressure 3-12MPa, preferably 6-12MPa, reaction temperature 260-450°C, preferably 280-400°C, hydrogen oil volume ratio 400-1600Nm ³ /m ³ , preferably 500-1000 Nm ³ /m ³ , liquid hourly volume space velocity 0.3-4.0 h ^-1 , preferably 0.5-2.0 h ^-1 .

In the present invention, aromatic hydrocarbon extraction is well known to those skilled in the art, and is used to separate out aromatic hydrocarbons in heavy naphtha products. For example, it can be carried out in an extraction tower. The ratio can be 2.5-5.0, the temperature at the top of the extraction tower can be 70-100°C, and the temperature at the bottom of the extraction tower can be 55-85°C, and those skilled in the art can also use other solvents and process parameters.

According to the present invention, the catalytic cracking reaction is well known to those skilled in the art and will not be repeated in the present invention. The present invention sets different reactors for different raw materials and can set different reaction conditions to optimize the cracking performance of each raw material. The conditions of the first catalytic cracking reaction may include: the reaction temperature is 500-650°C, preferably 540-600°C, the reaction time is 0.5-8s, preferably 1-5s, and the reaction pressure (absolute pressure) is 0.10-1.0 MPa, the weight ratio of the first catalytic cracking catalyst to the hydrorefined product is (2-100): 1, preferably (5-50): 1, and the weight ratio of the atomized steam to the hydrorefined product is (0.05 -0.5): 1, preferably (0.1-0.25): 1; the reaction temperature of the second catalytic cracking reaction is 10-100°C higher than the reaction temperature of the first catalytic cracking reaction, preferably 20-60°C higher, the The weight hourly space velocity of the second catalytic cracking reaction is 1-35h ^-1 , preferably 2-33h ^-1 ; the conditions of the third catalytic cracking reaction include: the reaction temperature is 600-750°C, preferably 600-700°C, The reaction time is 0.5-10s, preferably 2-8s, the reaction pressure (absolute pressure) is 0.1-1.0MPa, and the weight ratio of the second catalytic cracking catalyst to the light diesel fraction is (4-100): 1, preferably (5-80): 1. Further preferably, the reaction temperature of the third catalytic cracking reaction is higher than that of the second catalytic cracking reaction, preferably 30-100°C higher, more preferably 40-80°C higher, thereby improving the yield of light olefins and aromatics.

According to the present invention, preferably the reaction raw materials sent into each reactor are preheated, and the preheating temperature is not higher than the reaction temperature, for example, the hydrorefined product sent into the first catalytic cracking reactor is preheated to 250-450 ° C, The light diesel fraction, raffinate and light naphtha products fed to the third catalytic cracking reactor are preheated to 100-250°C.

In the present invention, the oil-agent mixture obtained from the third catalytic cracking reactor and the second catalytic cracking reactor can be mixed and then the oil-agent separation can be carried out, or they can be separated separately. After rough separation of the oil in the oil separation device, the obtained second catalyst to be produced is sent to the second catalytic cracking reactor for reaction, and the obtained third reaction product carrying the catalyst is carried out together with the oil obtained in the second catalytic cracking reactor. separation.

According to the present invention, the first catalytic cracking catalyst and the second catalytic cracking catalyst may be the same or different, preferably the same, and the first catalytic cracking catalyst and the second catalytic cracking catalyst may each independently comprise a zeolite, an inorganic oxide binder and Optional clay; based on the total weight of the catalyst, the content of the zeolite may be 10-50% by weight, the content of inorganic oxides may be 5-90% by weight, and the content of clay may be 0-70% by weight (when When the clay content is 0% by weight, it means no clay); the zeolite can be selected from Y-type or HY-type zeolite with or without rare earth, ultra-stable Y-type zeolite with or without rare earth, and zeolite with MFI structure At least one of the zeolites, the inorganic oxide binder can be alumina and/or silica, and the clay can be kaolin, halloysite and the like.

According to the present invention, the separation method of the catalytic cracking product is well known to those skilled in the art, the distillation range of the light naphtha product can be within 65-135°C, and the distillation range of the heavy naphtha product can be Within 130-175°C, the distillation range of the cycle oil product may be within 175-450°C.

According to the present invention, catalytic cracking reactors are well known to those skilled in the art, and the first catalytic cracking reactor, the second catalytic cracking reactor and the third catalytic cracking reactor may each independently comprise a riser reactor, a flow At least one of the chemical bed reactor and the descending tube reactor, each reactor can be of equal diameter or variable diameter, preferably, the first catalytic cracking reactor and the third catalytic cracking reactor are both riser reactors , the second catalytic cracking reactor is a fluidized bed reactor.

As shown in FIG. 1, the present invention also provides a processing system for diesel raw materials, the system includes a fractionation device 2, a hydrotreating reactor 5, a first catalytic cracking reactor 12, a second catalytic cracking reactor 13, a third catalytic cracking reactor 13, and a third catalytic cracking reactor. The catalytic cracking reactor 15, the regenerator 14, the second oil separation device 17 and the product separation device 18; the fractionation device 2 is provided with a diesel feedstock inlet, a light diesel fraction outlet and a heavy diesel fraction outlet, and the hydrorefining reaction The reactor 5 is provided with a hydrogen inlet, a feed oil inlet and a hydrorefined product outlet, and the first catalytic cracking reactor 12, the second catalytic cracking reactor 13 and the third catalytic cracking reactor 15 are independently provided with a material inlet and an outlet. Material outlet, the second oil separation device 17 is provided with a material inlet, an oil and gas outlet and a catalyst outlet, the regenerator 14 is provided with a catalyst inlet and a catalyst outlet, and the product separation device 18 is provided with oil and gas inlets, low-carbon olefins outlet, light naphtha outlet, heavy naphtha outlet, circulating oil outlet and oil slurry outlet; the heavy diesel fraction outlet of the fractionation device 2 is communicated with the feed oil inlet of the hydrotreating reactor 5, and the hydrogenation The hydrorefining product outlet of the refining reactor 5 is communicated with the material inlet of the first catalytic cracking reactor 12 , and the material outlet of the first catalytic cracking reactor 12 is connected with the material inlet of the second catalytic cracking reactor 13 Communication, the material outlet of the second catalytic cracking reactor 13 is communicated with the material inlet of the second oil separation device 17, and the light diesel fraction outlet of the fractionation device 2 is connected with the third catalytic cracking reactor 15. The material inlet is connected, the material outlet of the third catalytic cracking reactor 15 is communicated with the material inlet of the second oil separation device 17 , the catalyst outlet of the second oil separation device 17 is connected with the catalyst inlet of the regenerator 14 The catalyst outlet of the regenerator 14 is connected with the material inlet of the first catalytic cracking reactor 12 and the third catalytic cracking reactor 15 respectively, and the oil and gas outlet of the second oil separation device 17 is connected with the product The oil and gas inlet of the separation device 18 is communicated; the system also includes an aromatic hydrocarbon extraction device 25, which is provided with an extraction solvent inlet, an extraction raw material inlet, a raffinate oil outlet and an extraction oil outlet, and the aromatic hydrocarbons are The extraction raw material inlet of the extraction device 25 is communicated with the heavy naphtha outlet of the product separation device 18 , and the raffinate oil outlet is communicated with the material inlet of the third catalytic cracking reactor 15 .

According to the present invention, the system may further include a first oil separation device 16, the first oil separation device 16 may be provided with a material inlet, a catalyst outlet and an oil and gas outlet, and the material of the third catalytic cracking reactor 15 The outlet can be communicated with the material inlet of the first oil separation device 16, the catalyst outlet of the first oil separation device 16 can be communicated with the material inlet of the second catalytic cracking reactor 13, the first oil The oil and gas outlet of the oil separation device 16 may be communicated with the material inlet of the second oil separation device 17; and/or the light naphtha outlet of the product separation device 18 may be communicated with the third catalytic cracking reactor 15. The material inlet is in communication; and/or the circulating oil outlet of the product separation device 18 may be in communication with the feed oil inlet of the hydrofinishing reactor 5 . The installation of the first oil separation device can improve the utilization rate of the second catalyst to be produced with low coke formation obtained by the third catalytic cracking reaction, and the recycling of the circulating oil product and the light naphtha product can improve the utilization rate of raw materials and improve the low carbon Yields of olefins and aromatics.

According to the present invention, catalytic cracking reactors are well known to those skilled in the art, and the first catalytic cracking reactor, the second catalytic cracking reactor and the third catalytic cracking reactor may each independently comprise a riser reactor, a flow At least one of the chemical bed reactor and the descending tube reactor, each reactor can be of equal diameter or variable diameter, preferably, the first catalytic cracking reactor and the third catalytic cracking reactor are both riser reactors , the second catalytic cracking reactor is a fluidized bed reactor.

According to a preferred specific embodiment, the method of the present invention adopts the process shown in FIG. 1 to carry out, specifically:

The diesel raw material is introduced into the diesel fractionation tower 2 through the pipeline 1 and separated into the light diesel oil fraction and the heavy diesel oil fraction, and the heavy diesel oil fraction is introduced into the hydrotreating reactor 5 through the pipeline 4 for hydrotreating treatment, and the hydrotreating reaction effluent is obtained. .

The hydrotreating reaction effluent is introduced into the separator 10 through the pipeline 9 for separation, and the hydrogen-rich gas in the gas-phase product at the top of the separator obtained by the separation is processed by the circulating hydrogen compressor 6 and the supplementary new hydrogen from the pipeline 7 is processed. The mixed hydrogen is obtained by mixing, and the mixed hydrogen is recycled back to the hydrofinishing reactor 5 through the line 8 . The liquid-phase product separated by the separator 10 is introduced into the bottom of the first catalytic cracking reactor 12 as a hydrorefining product through the line 11 to contact with a part of the regenerated catalyst from the regenerator 14 and carry out the first catalytic cracking reaction; the first catalytic cracking The first catalytic cracking product and the semi-prepared catalyst obtained from the outlet of the reactor 12 enter the second catalytic cracking reactor 13 arranged coaxially from the bottom to the top for the second catalytic cracking reaction. The light diesel fraction separated by the diesel fractionator 2 enters the third catalytic cracking reactor 15 through the pipeline 3 to contact with another part of the regenerated catalyst from the regenerator 14 and carry out the third catalytic cracking reaction; then the third catalytic cracking reactor 15 The third reaction product and the second catalyst obtained at the outlet are introduced into the first oil separation device 16 for separation, and the second catalyst obtained by separation is introduced into the second catalytic cracking reactor 13 for the second catalyst cleavage reaction. And the second catalytic cracking product obtained at the outlet of the second catalytic cracking reactor and the first catalyst to be produced and the third catalytic cracking product from the third catalytic cracking reactor 15 are introduced into the second oil separation device 17 for carrying out. Separation to obtain oil and gas and catalyst to be produced respectively, the separated catalyst to be produced is introduced into the regenerator 14 for regeneration, and the oil and gas obtained from the separation is introduced to the further product separation device 18 for separation to obtain low-carbon olefins, light naphtha Oil, heavy naphtha, circulating oil and catalytic cracking oil slurry are drawn out through line 23, line 19, line 20, line 24 and line 21, respectively. The circulating oil is recycled to the hydrofinishing reactor 5 . The heavy naphtha is introduced into the aromatics pumping device 25 through the pipeline 24, and the extracted oil containing aromatics is obtained through the pipeline 27 and the raffinate is extracted through the pipeline 26. The raffinate is introduced through the pipeline 22 and the light naphtha from the pipeline 19. The third catalyst The cracking reactor 15 performs the third catalytic cracking reaction. The first and third catalytic cracking reactors are both riser reactors, the third catalytic cracking reactor is a fluidized bed reactor, the first catalytic cracking reactor and the second catalytic cracking reactor are coaxially arranged, and the second catalytic cracking reactor is arranged coaxially. The cracking reactor is arranged above the third catalytic cracking reactor.

It should be noted that dry gas, ethylene, propylene, etc. can be obtained after separation by the product separation device. In the above preferred embodiment of the present invention, the ethylene, propylene, etc. are represented by light olefins.

The present invention will be described in detail below by means of examples. The various raw materials used below are commercially available unless otherwise specified.

The reactions of the following examples were carried out in a catalytic cracking medium-scale plant and a fixed-bed diesel hydrogenation pilot plant. The first and third catalytic cracking reactors are both riser reactors, the third catalytic cracking reactor is a fluidized bed reactor, the first catalytic cracking reactor and the second catalytic cracking reactor are arranged coaxially, and the second catalytic cracking reactor The cracking reactor is arranged above the third catalytic cracking reactor, the inner diameter of the first catalytic cracking reactor is 24mm and the height is 6m, the inner diameter of the second catalytic cracking reactor is 40mm and the height is 2m, and the third catalytic cracking reactor has an inner diameter of 40mm and a height of 2m. The inner diameter is 24mm and the height is 8m.

The hydrorefining catalysts used in the examples and the comparative examples are the same, and they are all strip-shaped nickel-tungsten catalysts with alumina as a carrier, wherein, based on the total amount of the hydrorefining catalyst, the hydrorefining catalyst contains 24.5 % by weight of WO ₃ , 4.50% by weight of NiO, and the balance is the carrier.

The catalytic cracking catalysts used in the examples and the comparative examples are the same, and they are all MMC-2. The catalyst is produced by the Qilu branch of Sinopec Corp., and the properties of the catalyst are shown in Table 2.

In the embodiment, the aromatic hydrocarbon extraction solvent is sulfolane, the solvent ratio of the extraction tower is 4.2, the temperature at the top of the extraction tower is 80°C, and the temperature at the bottom of the extraction tower is 60°C.

Yield of a certain product in the distribution of catalytic cracking products=weight of a certain product obtained by the product separation device 18/weight of diesel feedstock×100%.

Example 1

The present embodiment adopts the process flow diagram shown in Fig. 1 to carry out, and the concrete steps are as follows:

Diesel feedstock D is introduced into diesel fractionation tower 2 and separated into light diesel fraction E with distillation range < 230°C and heavy diesel fraction F with distillation range >230°C, diesel feedstock D, light diesel fraction E and heavy diesel The properties of diesel fraction F are shown in Table 1. The heavy diesel oil fraction is introduced into the hydrotreating reactor 5 for hydrotreating treatment to obtain a hydrotreating reaction effluent.

The hydrotreating reaction effluent is introduced into the separator 10 for separation, and the hydrogen-rich gas in the gas-phase product at the top of the separator 10 obtained by the separation is processed by the circulating hydrogen compressor 6 and mixed with supplementary new hydrogen to obtain mixed hydrogen. For recycling back to the hydrofinishing reactor 5. The liquid phase product separated by the separator is introduced into the first catalytic cracking reactor 12 as a hydrorefining product, and a part of the regenerated catalyst from the regenerator 14 enters the first catalytic cracking reactor to participate in the first catalytic cracking reaction; the first catalytic cracking reaction; The first catalytic cracking product obtained from the outlet of the catalytic cracking reactor together with the semi-to-be-grown catalyst enters the second catalytic cracking reactor 13 for the second catalytic cracking reaction.

The light diesel fraction E is introduced into the third catalytic cracking reactor 15 in contact with the regenerated catalyst from the regenerator 14 for a third catalytic cracking reaction, and the second spent catalyst and the third catalytic cracking from the third catalytic cracking reactor are After the product is separated by the first oil separation device 16, the second catalyst to be produced is introduced into the second catalytic cracking reactor to participate in the second catalytic cracking reaction.

The mixture of the second catalytic cracking product obtained at the outlet of the second catalytic cracking reactor and the first catalyst to be produced and the third catalytic cracking product from the third catalytic cracking reactor are introduced into the second oil separation device 17 for carrying out Separation to obtain the reaction oil and gas and the catalyst to be produced respectively, the separated catalyst to be produced is introduced into the regenerator for regeneration, and the reaction oil and gas obtained from the separation is introduced into the product separation device 18 for further separation to obtain low-carbon olefins, light naphtha (the distillation range is 65-135°C), heavy naphtha (the distillation range is 130-175°C), the circulating oil (the distillation range is 175-400°C) and the catalytic cracking oil slurry. The circulating oil is recycled to the hydrofinishing reactor. The heavy naphtha is introduced into the aromatic hydrocarbon extraction device 25 to separate the extracted oil and raffinate containing aromatic hydrocarbons, and the raffinate oil is introduced into the third catalytic cracking reactor for the third catalytic cracking reaction.

The reaction conditions and product distribution of the hydrotreating reactor in this example are shown in Table 3, and the reaction conditions of the catalytic cracking reactor are shown in Table 4. The product distribution obtained by the method of this example is shown in Table 4.

Comparative Example 1

The comparative example adopts the combined process of traditional diesel fixed bed hydrogenation and traditional catalytic cracking. The process flow diagram of Comparative Example 1 is shown in Figure 2. The difference from Example 1 is that Comparative Example 1 does not have a third catalytic cracking reactor. specifically:

Diesel feedstock D is introduced into diesel fractionation tower 2 and separated into light diesel fraction E with distillation range < 230°C and heavy diesel fraction F with distillation range >230°C, diesel feedstock D, light diesel fraction E and heavy diesel The properties of diesel fraction F are shown in Table 1. The heavy diesel oil fraction is introduced into the hydrotreating reactor 5 for hydrotreating treatment to obtain a hydrotreating reaction effluent.

The hydrotreating reaction effluent is introduced into the separator 10 for separation, and the hydrogen-rich gas in the gas-phase product at the top of the separator 10 obtained by the separation is processed by the circulating hydrogen compressor 6 and mixed with supplementary new hydrogen to obtain mixed hydrogen. For recycling back to the hydrofinishing reactor 5. The liquid phase product separated by the separator is introduced into the first catalytic cracking reactor 12 as a hydrorefined product and the light diesel fraction F, and a part of the regenerated catalyst from the regenerator 14 enters the first catalytic cracking reactor to participate in the first catalytic cracking reactor. Catalytic cracking reaction; the first catalytic cracking product obtained from the outlet of the first catalytic cracking reactor and the semi-to-be-grown catalyst together enter the second catalytic cracking reactor 13 for the second catalytic cracking reaction with the supplemented regenerated catalyst.

The mixture of the second catalytic cracking product obtained at the outlet of the second catalytic cracking reactor and the catalyst to be formed is introduced into the second oil separation device 17 for separation, and the reaction oil and gas and the catalyst to be formed are obtained respectively, and the catalyst to be formed is separated. It is introduced into the regenerator for regeneration, and the separated reaction oil and gas is introduced into the product separation device 18 for further separation to obtain low-carbon olefins, light naphtha (with a distillation range of 65-135° C.), and heavy naphtha (with a distillation range of 65-135° C.). 130-170°C), circulating oil (175-331°C distillation range) and catalytic cracking oil slurry. The circulating oil is recycled to the hydrofinishing reactor. The heavy naphtha is introduced into the aromatic hydrocarbon extraction device 25 to separate the extracted oil and raffinate containing aromatic hydrocarbons, and the raffinate oil is introduced into the first catalytic cracking reactor 12 through the pipeline 22 for reaction.

The reaction conditions and product distribution of the hydrotreating reactor in this comparative example are shown in Table 3, and the reaction conditions of the catalytic cracking reactor are shown in Table 4. The product distribution obtained by the method of this comparative example is shown in Table 4.

It can be seen from the results in Table 4 that the yields of ethylene and propylene in Example 1 are increased by 2.7 percentage points and 2.7 percentage points respectively compared with Comparative Example 1; the yield of aromatic hydrocarbons is increased by 4.7 percentage points.

Example 2

Embodiment 2 adopts the same technological process as embodiment 1 to carry out, the difference is, the reaction conditions and product distribution of the hydrotreating reactor of embodiment 2 are as shown in table 3, and the reaction conditions of catalytic cracking reactor are as shown in table shown in 4. The product distribution obtained by the method of Example 2 is shown in Table 4.

Comparative Example 2

Comparative example 2 adopts the same technological process as comparative example 1 to carry out, the difference is, the reaction conditions and product distribution of the hydrotreating reactor of comparative example 2 are as shown in table 3, and the reaction conditions of catalytic cracking reactor are as shown in table shown in 4. The product distribution obtained by the method of Comparative Example 2 is shown in Table 4.

As can be seen from the results in Table 4, the ethylene and propylene yields of Example 2 are increased by 1.9 percentage points and 5.0 percentage points respectively compared with Comparative Example 2; the aromatics yield is increased by 6.5 percentage points.

Example 3

This example is carried out by a method similar to that of Example 1, the difference is that the reaction temperature in the third catalytic cracking reactor in the catalytic cracking reaction zone of this example is 50°C higher than that in the second catalytic cracking reactor ℃, specifically, the reaction conditions and product distribution of the hydrotreating reactor of this embodiment are shown in Table 3, and the reaction conditions of the catalytic cracking reactor are shown in Table 4. The product distribution obtained by the method of this example is shown in Table 4.

Comparative Example 3

Basically the same as Example 1, the difference is: the light diesel oil fraction is subjected to hydrorefining and then carries out the third catalytic cracking reaction, the hydrorefining treatment conditions of the light diesel oil fraction are the same as the heavy diesel oil fraction, and the third catalytic cracking reaction The conditions are the same as in Example 1, and the conditions of the catalytic cracking reactor and the specific reaction results are shown in Table 5.

It can be seen from the results in Table 5 that the yields of ethylene and propylene in Example 1 did not change compared to Comparative Example 3; the yield of aromatics was increased by 3.0 percentage points.

Comparative Example 4

Basically the same as Example 1, the difference is: only the hydrorefining product is carried out the first catalytic cracking reaction without the second catalytic cracking reaction, the first catalytic cracking product of the gained is directly sent into the product separation device for separation, and the specific reaction is carried out. The conditions are the same as in Example 1, and the conditions of the catalytic cracking reactor and the specific reaction results are shown in Table 5.

As can be seen from the results in Table 5, the ethylene and propylene yields in Example 1 are increased by 1.7 percentage points and 2.7 percentage points respectively compared with Comparative Example 4; the aromatics yield is increased by 4.1 percentage points.

Comparative Example 5

Basically the same as Example 1, the difference is: the cutting point of the light diesel oil fraction and the heavy diesel oil fraction is 260 ° C, the specific reaction conditions are the same as those in Example 1, and the conditions of the catalytic cracking reactor and the specific reaction results are shown in Table 5.

As can be seen from the results in Table 5, the yields of ethylene and propylene in Example 1 are increased by 2.3 percentage points and 2.8 percentage points respectively compared with Comparative Example 5; the yield of aromatic hydrocarbons is increased by 3.7 percentage points.

It can be seen from the results of the examples and comparative examples of the present invention that the method of the present invention organically combines the fixed bed hydrogenation process and the catalytic cracking process according to the properties of inferior diesel, especially the different fractions of catalytic diesel products, which can significantly improve the combination Yields of high value products such as propylene, ethylene and aromatics in the process.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, These simple modifications all belong to the protection scope of the present invention.

In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner unless they are inconsistent. In order to avoid unnecessary repetition, the present invention provides The combination method will not be specified otherwise.

In addition, the various embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content of the present invention.

Table 1 Raw material oil

raw oil diesel fuel D Gas Oil Distillate E Heavy Diesel Distillate F Density (20℃), (g/cm³) 0.9357 0.8786 0.9960 Sulfur content, (μg/g) 2500 1300 3200 Nitrogen content, (μg/g) 350 128 536 Total Aromatics, wt% 81.1 70.9 82.7 Monocyclic aromatic hydrocarbon content, wt% 25.6 60.4 12.2 PAH content, wt% 53.9 10.2 71.1 Distillation range (ASTM D-86)/℃ initial boiling point 175 175 231 50% by volume 253 219 279 end point 331 231 331 cetane number 19 / /

Table 2 Catalytic cracking catalyst properties

catalyst MMC-2 Chemical composition, wt% RE₂O₃ (weight ratio of rare earth oxide to catalyst) 0.56 Composition of active metal elements, wt% (relative to the total amount of active metal oxides) Fe₂O₃ 5.8 CeO₂ 5.2 La₂O₃ 5.1 Nd₂O₃ 3.4 Y₂O₃ 12.2 Al₂O₃ 54.0 physical properties Specific area, m²/g 120 Pore volume, cm³/g 0.17 Apparent density, g/cm³ 0.91 Sieved, wt% 0-20μm 0.8 0-40μm 10.4 0-80μm 70.8 0-110μm 88.5 0-149μm 97.8 >149μm 2.2 Average particle size, μm 64.3

The reaction conditions of table 3 hydrotreating reactor

Table 4 Reaction conditions and product distribution of catalytic cracking reaction zone

*Light olefins include ethylene and propylene.

Table 5 Reaction conditions and product distribution of catalytic cracking reaction zone

*Light olefins include ethylene and propylene.

Claims (14)

1. a processing method of diesel fuel, the method comprising: Separating the diesel fuel into a light diesel oil fraction and a heavy diesel oil fraction, wherein the cut point of the light diesel oil fraction and the heavy diesel oil fraction is in the range of 220-240° C.; The obtained heavy diesel oil fraction is introduced into a hydrotreating reactor to contact with a hydrotreating catalyst and carry out hydrotreating treatment to obtain a hydrotreating product; The obtained hydrorefining product is introduced into the first catalytic cracking reactor to contact with the first catalytic cracking catalyst and carry out the first catalytic cracking reaction to obtain the first catalytic cracking product and the semi-to-be-generated catalyst; introducing the obtained first catalytic cracking product and the semi-to-be-grown catalyst into a second catalytic cracking reactor to carry out a second catalytic cracking reaction to obtain the second catalytic cracking product and the first to-be-grown catalyst; The obtained light diesel oil fraction is introduced into the third catalytic cracking reactor to contact with the second catalytic cracking catalyst and carry out the third catalytic cracking reaction to obtain the third catalytic cracking product and the second catalyst to be produced; The obtained second catalytic cracking product and the third catalytic cracking product are separated to obtain low-carbon olefin product, light naphtha product, heavy naphtha product, circulating oil product and oil slurry product; sending the obtained first and second ready-made catalysts into a regenerator for regeneration, and the obtained regenerated catalysts are used as the first and second catalytic cracking catalysts; The obtained heavy naphtha product is subjected to aromatic hydrocarbon extraction to obtain extract oil and raffinate oil containing aromatic hydrocarbons, and the obtained raffinate oil is introduced into the third catalytic cracking reactor for the third catalytic cracking reaction. 2. The method according to claim 1, further comprising at least one step of: (1), the gained light naphtha product is introduced in the described third catalytic cracking reactor to carry out the described third catalytic cracking reaction; (2), introducing gained recycle oil product into described hydrorefining reactor to carry out described hydrorefining treatment; (3), introducing at least part of the second catalyst to be produced from the third catalytic cracking reaction into the second catalytic cracking reactor to carry out the second catalytic cracking reaction. 3. The method of claim 1, wherein the diesel feedstock has a cetane number of less than 25 and a distillation range in the range of 170-400°C. 4. The method of claim 1, wherein the diesel feedstock comprises catalytically cracked diesel, with or without coking diesel. 5. The method of claim 1, wherein the hydrofinishing catalyst comprises a support and an active metal component supported on the support, the support being selected from the group consisting of alumina, silica, alumina-oxidized Silicon, titanium oxide, magnesium oxide, silicon oxide-magnesia, silicon oxide-zirconia, silicon oxide-thorium oxide, silicon oxide-beryllium oxide, silicon oxide-titanium oxide, silicon oxide-zirconia, titanium oxide-zirconia, At least one of silica-alumina-thorium oxide, silica-alumina-titanium oxide, silica-alumina-magnesia and silica-alumina-zirconia, the active metal component is at least one One is selected from the group VIB metal element and at least one is selected from the group VIII metal element; based on the total weight of the hydrotreating catalyst, the content of at least one selected from the group VIB metal element in terms of oxide is 1- 30% by weight, the content of at least one metal element selected from Group VIII in terms of oxide is 3-35% by weight; The conditions of the hydrorefining treatment include: hydrogen partial pressure 3-12MPa, reaction temperature 260-450°C, hydrogen oil volume ratio 400-1600Nm ³ /m ³ , liquid hourly volume space velocity 0.3-4.0h ^-1 . 6. The method according to claim 1, wherein, in the hydrorefining treatment, the polycyclic aromatic hydrocarbon saturation rate of the heavy diesel oil fraction is not less than 85% by weight, and the total aromatic hydrocarbon saturation rate of the heavy diesel oil fraction is 12-35 weight % %, the distillation range of the hydrorefined product is in the range of 200-400°C. 7. The method according to claim 1, wherein, the conditions of the first catalytic cracking reaction include: the reaction temperature is 500-650° C., the reaction time is 0.5-8s, the reaction pressure is 0.10-1.0MPa, the first 1. The weight ratio of the catalytic cracking catalyst to the hydrorefined product is (2-100): 1, and the weight ratio of the atomized steam to the hydrorefined product is (0.05-0.5): 1; The reaction temperature of the second catalytic cracking reaction is 10-100°C higher than the reaction temperature of the first catalytic cracking reaction, and the weight hourly space velocity of the second catalytic cracking reaction is 1-35 h ⁻¹ ; The conditions of the third catalytic cracking reaction include: the reaction temperature is 600-750 ° C, the reaction time is 0.5-10s, the reaction pressure is 0.1-1.0MPa, and the weight ratio of the second catalytic cracking catalyst to the light diesel fraction is ( 4-100): 1. 8. The method according to claim 7, wherein the reaction temperature of the third catalytic cracking reaction is 30-100°C higher than the reaction temperature of the second catalytic cracking reaction. 9. The method of claim 1, wherein the first catalytic cracking catalyst and the second catalytic cracking catalyst each independently comprise a zeolite, an inorganic oxide binder, and optionally a clay; Based on the total weight of the catalyst, the content of the zeolite is 10-50% by weight, the content of the inorganic oxide is 5-90% by weight, and the content of the clay is 0-70% by weight; The zeolite is at least one selected from the group consisting of Y-type or HY-type zeolite with or without rare earth, ultra-stable Y-type zeolite with or without rare earth, and zeolite with MFI structure. 10. The method according to claim 1, wherein the distillation range of the light naphtha product is within 65-135°C, and the distillation range of the heavy naphtha product is within 130-175°C, The distillation range of the cycle oil product is in the range of 175-450°C. 11. The method of claim 1, wherein the first catalytic cracking reactor and the third catalytic cracking reactor are riser reactors, and the second catalytic cracking reactor is a fluidized bed reactor. 12. A processing system for diesel fuel, the system comprising a fractionation device (2), a hydrotreating reactor (5), a first catalytic cracking reactor (12), a second catalytic cracking reactor (13), a third a catalytic cracking reactor (15), a regenerator (14), a second oil separation device (17) and a product separation device (18); The fractionation device (2) is provided with a diesel feed inlet, a light diesel fraction outlet and a heavy diesel fraction outlet, and the hydrorefining reactor (5) is provided with a hydrogen inlet, a feed oil inlet and a hydrorefining product outlet, the The first catalytic cracking reactor (12), the second catalytic cracking reactor (13) and the third catalytic cracking reactor (15) are each independently provided with a material inlet and a material outlet, and the second oil separation device (17) ) is provided with a material inlet, an oil and gas outlet and a catalyst outlet, the regenerator (14) is provided with a catalyst inlet and a catalyst outlet, and the product separation device (18) is provided with an oil and gas inlet, a light olefin outlet, and a light naphtha outlet , heavy naphtha export, circulating oil export and oil slurry export; The heavy diesel fraction outlet of the fractionation device (2) is communicated with the feed oil inlet of the hydrotreating reactor (5), and the hydrotreating product outlet of the hydrotreating reactor (5) is connected to the first The material inlet of the catalytic cracking reactor (12) is communicated, the material outlet of the first catalytic cracking reactor (12) is communicated with the material inlet of the second catalytic cracking reactor (13), and the second catalytic cracking reaction The material outlet of the device (13) is communicated with the material inlet of the second oil separation device (17), and the light diesel fraction outlet of the fractionation device (2) is connected with the material of the third catalytic cracking reactor (15). The inlet is communicated, the material outlet of the third catalytic cracking reactor (15) is communicated with the material inlet of the second oil separation device (17), and the catalyst outlet of the second oil separation device (17) is connected to the regeneration The catalyst inlet of the regenerator (14) is communicated with the catalyst outlet of the regenerator (14), and the catalyst outlet of the regenerator (14) is communicated with the material inlet of the first catalytic cracking reactor (12) and the third catalytic cracking reactor (15). The oil and gas outlet of the secondary oil separation device (17) communicates with the oil and gas inlet of the product separation device (18); The system further includes an aromatic hydrocarbon extraction device (25), the aromatic hydrocarbon extraction device (25) is provided with an extraction solvent inlet, an extraction raw material inlet, a raffinate oil outlet and an extraction oil outlet, and the aromatic hydrocarbon extraction device ( The extraction raw material inlet of 25) is communicated with the heavy naphtha outlet of the product separation device (18), and the raffinate oil outlet is communicated with the material inlet of the third catalytic cracking reactor (15). 13. The system according to claim 12, wherein the system further comprises a first oil separation device (16), the first oil separation device (16) is provided with a material inlet, a catalyst outlet and an oil and gas outlet, The material outlet of the third catalytic cracking reactor (15) is communicated with the material inlet of the first oil separation device (16), and the catalyst outlet of the first oil separation device (16) is connected to the second oil separation device (16). The material inlet of the catalytic cracking reactor (13) is communicated, and the oil and gas outlet of the first oil separation device (16) is communicated with the material inlet of the second oil separation device (17); and/or The light naphtha outlet of the product separation device (18) communicates with the material inlet of the third catalytic cracking reactor (15); and/or The circulating oil outlet of the product separation device (18) is communicated with the feed oil inlet of the hydrotreating reactor (5). 14. The system of claim 12, wherein the first catalytic cracking reactor and the third catalytic cracking reactor are riser reactors, and the second catalytic cracking reactor is a fluidized bed reactor.

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