System for producing low-carbon olefin and light aromatic hydrocarbon from ethylene tar

Abstract

The invention discloses a system for producing low-carbon olefin and light aromatic hydrocarbon from ethylene tar, and relates to the technical field of petrochemical engineering. A light fraction outlet of the ethylene tar fractionating device is sequentially connected with a hydrogenation device, a catalytic cracking main lifting pipe and a catalytic cracking main fractionating tower; a heavy fraction outlet of the ethylene tar fractionating device is sequentially connected with a coking tower, a coking fractionating tower, a catalytic cracking second lifting pipe and a catalytic cracking auxiliary fractionating tower; a main riser catalytic rich gas discharge pipeline of the catalytic cracking main fractionating tower and a second riser catalytic rich gas discharge pipeline of the catalytic cracking auxiliary fractionating tower are both connected to a gas separation device so as to extract low-carbon olefins; the main riser catalytic gasoline pipeline and the second riser catalytic gasoline pipeline are both connected to a gasoline fractionating tower, and a catalytic gasoline light fraction pipeline of the gasoline fractionating tower is connected to an aromatic hydrocarbon combination device to obtain light aromatic hydrocarbon. According to the invention, the hydrogen consumption can be reduced, the full fraction of the ethylene tar is fully utilized, and the added value of the product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum chemical industry, in particular to a system for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar. BACKGROUND

[0002] As a by-product with high polymerization degree produced in the process of ethylene cracking, ethylene tar is mainly composed of condensed ring aromatic hydrocarbons with short alkyl side chains. Due to the high polymerization and high carbon content of ethylene tar, it is currently mainly used for producing low-value-added products such as road asphalt, fuel blending oil and carbon black, and has not been fully utilized.

[0003] At present, some methods for improving the added value of ethylene tar have also been disclosed.

[0004] For example, Chinese patent CN116004284A discloses a method for producing clean fuel oil from ethylene tar. In this method, ethylene tar is fractionated into light fraction and heavy fraction, the heavy fraction is mixed with conventional coking raw material, and delayed coking is performed to obtain coking gasoline and coking diesel. The obtained coking gasoline is subjected to hydrofining, and the coking diesel is mixed with the light fraction of ethylene tar and subjected to hydroprocessing. The reaction effluent is separated together with the hydrofining product of coking gasoline in a fractionating column to obtain clean gasoline and diesel products. This invention mainly focuses on improving the yield of light fuel oil.

[0005] For example, Chinese patent CN116004284A discloses a method and system for hydrogenation of ethylene tar to light hydrocarbons. However, the aromatic hydrocarbon resources in the heavy aromatic solvent oil are not fully utilized. Chinese patent CN103102976A discloses a method for treating ethylene tar, which mainly focuses on improving the yield of chemical raw material naphthalene. Technical development and economic analysis of hydrogenation of ethylene tar to produce aromatic hydrocarbons (Suying, He Libin, Liaoning Chemical, Vol. 50, No. 12) discloses a technology for producing BTX light aromatic hydrocarbons by three-stage hydrogenation using ethylene tar as raw material. However, this method requires high hydrogen consumption and needs to design special equipment, which is costly.

[0006] In summary, there is no relatively mature technology for producing light aromatic hydrocarbons and low-carbon olefins from ethylene tar on the market. Developing a technology for producing light aromatic hydrocarbons and low-carbon olefins from the whole fraction of ethylene tar and fully utilizing the rich aromatic hydrocarbon resources in ethylene tar is an effective development of the technology for producing light aromatic hydrocarbons and low-carbon olefins from ethylene tar. SUMMARY

[0007] The present application aims to provide a system for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, which is different from the prior art and provides a production system for high-value utilization of ethylene tar.

[0008] In order to solve the above technical problems, the specific scheme adopted by the present application is: a system for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, comprising an ethylene tar fractionation device; a light fraction outlet of the ethylene tar fractionation device is connected with a hydrogenation device, a main catalytic cracking lift pipe of a dual-lift pipe catalytic cracking device and a main catalytic cracking fractionation tower of the dual-lift pipe catalytic cracking device in sequence;

[0009] A heavy fraction outlet of the ethylene tar fractionation device is connected with a coking tower, a coking fractionation tower, a second catalytic cracking lift pipe of the dual-lift pipe catalytic cracking device and a secondary catalytic cracking fractionation tower of the dual-lift pipe catalytic cracking device in sequence;

[0010] A main lift pipe catalytic gas-rich exhaust pipe of the main catalytic cracking fractionation tower and a second lift pipe catalytic gas-rich exhaust pipe of the secondary catalytic cracking fractionation tower are both connected to a gas fractionation device to extract low-carbon olefins;

[0011] A main lift pipe catalytic gasoline pipe of the main catalytic cracking fractionation tower and a second lift pipe catalytic gasoline pipe of the secondary catalytic cracking fractionation tower are both connected to a gasoline fractionation tower, and a catalytic gasoline light fraction pipe of the gasoline fractionation tower is connected to an aromatic hydrocarbon combination device to obtain light aromatic hydrocarbons;

[0012] A catalytic gasoline heavy fraction pipe of the gasoline fractionation tower is connected to the second catalytic cracking lift pipe; a main lift pipe catalytic diesel pipe of the main catalytic cracking fractionation tower, a second lift pipe catalytic diesel pipe of the secondary catalytic cracking fractionation tower and a coking diesel pipe of the coking fractionation tower are all connected to the hydrogenation device; and a main lift pipe catalytic oil slurry pipe of the main catalytic cracking fractionation tower and a second lift pipe catalytic oil slurry pipe of the secondary catalytic cracking fractionation tower are both connected to the coking tower.

[0013] As a further optimization of the above technical solution: the ethylene tar fractionation device is communicated with the coking tower through an ethylene tar heavy fraction pipe, and a coking heating furnace is arranged on the ethylene tar heavy fraction pipe.

[0014] As a further optimization of the above technical solution: the main lift pipe catalytic oil slurry pipe and the second lift pipe catalytic oil slurry pipe are both connected to the coking tower through the ethylene tar heavy fraction pipe, and the connection positions of the main lift pipe catalytic oil slurry pipe, the second lift pipe catalytic oil slurry pipe and the ethylene tar heavy fraction pipe are located upstream of the coking heating furnace.

[0015] As a further optimization of the above technical solution: a catalytic cracking regenerator is further included, and the second catalytic cracking lift pipe and the main catalytic cracking lift pipe are both connected to the second catalytic cracking lift pipe.

[0016] As a further optimization of the above technical solution: a catalytic cracking regenerator is further included, a main lift pipe settler is connected to the main catalytic cracking lift pipe, a second lift pipe settler is connected to the second catalytic cracking lift pipe, and the main lift pipe settler and the second lift pipe settler are both connected to the catalytic cracking regenerator.

[0017] As the further optimization of the above technical scheme: the mixture after reaction in the catalytic cracking main riser is discharged from the upper part of the main riser into the main riser settler, the main riser reaction oil gas separated by the main riser settler is transported to the catalytic cracking main fractionating tower through the main riser reaction oil gas pipeline, and the catalyst separated by the main riser settler is transported to the catalytic cracking regenerator.

[0018] As the further optimization of the above technical scheme: the mixture after reaction in the catalytic cracking second riser is transported to the second riser settler, the second riser reaction oil gas separated by the second riser settler is transported to the catalytic cracking auxiliary fractionating tower through the second riser reaction oil gas pipeline, and the catalyst separated by the second riser settler is transported to the catalytic cracking regenerator.

[0019] As the further optimization of the above technical scheme: the coking fractionating tower is provided with a coking wax oil discharge pipeline and a coking sewage discharge pipeline.

[0020] As the further optimization of the above technical scheme: the catalytic cracking main fractionating tower is provided with a main riser catalytic gas rich discharge pipeline and a main riser catalytic sewage discharge pipeline.

[0021] As the further optimization of the above technical scheme: the catalytic cracking auxiliary fractionating tower is provided with a second riser catalytic gas rich discharge pipeline and a second riser catalytic sewage discharge pipeline.

[0022] As the further optimization of the above technical scheme: the top of the aromatic hydrocarbon combination device is provided with a light aromatic hydrocarbon discharge pipeline, and the bottom is provided with a raffinate gasoline discharge pipeline.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The present application adopts the existing ethylene tar fractionating device, double riser catalytic cracking device and other equipment, and processes the ethylene tar which is difficult to process by the chemical enterprise through the selective cutting fractionation-selective hydrogenation-double riser catalytic cracking-coking combined process, matches the corresponding processing technology and operation condition for different intermediate products, fully converts the ethylene tar into low carbon olefin and light aromatic hydrocarbon high-quality chemical raw material, significantly improves the product added value, and the hydrogen consumption is low.

[0025] The ethylene tar light fraction obtained by cutting and separating the ethylene tar is first subjected to selective hydrogenation saturation, the polycyclic aromatic hydrocarbons in the ethylene tar light fraction are saturated into monocyclic aromatic hydrocarbons, then the monocyclic aromatic hydrocarbons are cracked in the main riser of a dual-riser catalytic cracking device, and a catalytic gasoline containing a large amount of monocyclic aromatic hydrocarbon components is obtained; the aromatic-rich gasoline heavy fraction obtained by selective cutting and fractionation of the main riser catalytic gasoline is fed into the second riser for further cracking under higher reaction severity to produce a gasoline containing C6-C8 light aromatic hydrocarbons and low-carbon olefins such as ethylene and propylene; the second riser catalytic gasoline is returned to the cutting and fractionation device to further tap the aromatic resources in the gasoline; the aromatic-rich gasoline light fraction is fed into an aromatic extraction device to produce light aromatic hydrocarbons such as BTX; the ethylene tar heavy fraction is fed into a delayed coking device together with the catalytic oil slurry generated by the main riser and the second riser to perform coking reaction and lightening treatment, and then the coking diesel oil and catalytic diesel oil rich in aromatic components are returned to the hydrogenation device for selective hydrogenation saturation, thereby further improving the utilization of aromatic-rich resources; the hydrogenation products are also subjected to further conversion by the catalytic cracking device to produce catalytic gasoline products containing a large amount of monocyclic aromatic hydrocarbon components, and the easily cracked coking gasoline can produce more low-carbon olefins such as ethylene and propylene in the second riser under high severity. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 a system schematic diagram of the present application;

[0027] Figure 2 a system schematic diagram of comparative example 1;

[0028] BRIEF DESCRIPTION OF DRAWINGS: 1, ethylene tar raw material, 2, ethylene tar fractionation device, 3, ethylene tar light fraction pipeline, 4, hydrogenation device, 5, hydrogen, 6, hydrogenated light fraction pipeline, 7, catalytic cracking main riser, 8, main riser reaction oil gas, 9, catalytic cracking main fractionating column, 10, main riser catalytic gas rich gas exhaust pipeline, 11, main riser catalytic sewage exhaust pipeline, 12, main riser catalytic gasoline pipeline, 13, main riser catalytic diesel pipeline, 14, main riser catalytic oil slurry pipeline, 15, gasoline fractionating column, 16, catalytic gasoline light fraction pipeline, 17, catalytic gasoline heavy fraction pipeline, 18, ethylene tar heavy fraction pipeline, 19, coking heating furnace, 20, coking tower, 21, coking oil gas pipeline, 22, coking fractionating column, 23, coking gas rich gas exhaust pipeline, 24, coking sewage exhaust pipeline, 25, coking gasoline pipeline, 26, coking diesel pipeline, 27, catalytic cracking second riser, 28, second riser reaction oil gas pipeline, 29, catalytic cracking auxiliary fractionating column, 30, second riser catalytic gas rich gas exhaust pipeline, 31, second riser catalytic sewage exhaust pipeline, 32, second riser catalytic gasoline pipeline, 33, second riser catalytic diesel pipeline, 34, second riser catalytic oil slurry pipeline, 35, aromatic hydrocarbon combination device, 36, light aromatic hydrocarbon exhaust pipeline, 37, raffinate gasoline exhaust pipeline, 38, catalytic cracking regenerator, 39, catalytic cracking main air, 40, coking wax oil exhaust pipeline, 41, catalytic cracking riser, 42, catalytic cracking fractionating column, 43, catalytic gas rich gas exhaust pipeline, 44, catalytic sewage exhaust pipeline. DETAILED DESCRIPTION

[0029] The following specific embodiments are used to further illustrate the technical solutions of the present application, and the parts not described and disclosed in the following embodiments, such as the specific structure of the ethylene fractionation device, the hydrogenation device, the coking tower, the dual-riser catalytic cracking device, the catalytic cracking regenerator, and the aromatic hydrocarbon combination device, should be understood as the prior art known or should be known by those skilled in the art.

[0030] The present application discloses a system for producing low-carbon olefins and light aromatic hydrocarbons from ethylene tar, which comprises an ethylene tar fractionation device 2, and the light fraction outlet of the ethylene tar fractionation device 2 is sequentially connected with a hydrogenation device 4, a catalytic cracking main riser 7 of a dual-riser catalytic cracking device, and a catalytic cracking main fractionating column 9.

[0031] The light fraction outlet of the ethylene tar fractionation device 2 is communicated with the feed inlet of the hydrogenation device 4 through the ethylene tar light fraction pipeline 3 to transport the ethylene tar light fraction into the hydrogenation device 4 to be selectively saturated, and the polycyclic aromatic hydrocarbons in the ethylene tar light fraction are saturated into monocyclic aromatic hydrocarbons to obtain a hydrogenated light fraction; the reaction temperature of the selective saturation in the ethylene tar fractionation device 2 is 320-400℃, the hydrogen partial pressure is 5.0-10.0 MPa, the volume space velocity is 0.5-3 h -1 -1, the volume ratio of hydrogen to oil is 300-800:1, and the selective saturation catalyst of the polycyclic aromatic hydrocarbons can be one or a combination of hydrogenation refining catalysts and hydrogenation cracking catalysts; the active metal in the selective saturation catalyst of the polycyclic aromatic hydrocarbons includes one or several of nickel, cobalt, molybdenum or tungsten, and the mass of the active metal is 10%-30%.

[0032] The discharge outlet of the hydrogenation device 4 is communicated with the main riser of the dual-riser catalytic cracking device through the hydrogenated light fraction pipeline 6 to transport the hydrogenated light fraction into the catalytic cracking main riser 7. The reaction temperature of the cracking reaction in the catalytic cracking main riser 7 is 500-600℃, the catalyst / oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa (gauge pressure), the reaction time is 2-5 s, the atomized water vapor accounts for 1-5 w% of the feed amount, and the catalyst for the cracking reaction in the catalytic cracking main riser 7 is a conventional catalytic cracking catalyst.

[0033] The outlet of the catalytic cracking main riser 7 is connected to a main riser settler, a catalytic cracking regenerator 38 is arranged below the main riser settler, and a main riser reaction oil gas pipeline 8 that is communicated with a catalytic cracking main fractionating column 9 is arranged at the top of the main riser settler. The mixture after the reaction in the catalytic cracking main riser 7 is separated into reaction oil gas and catalyst in the main riser settler, the reaction oil gas is transported to the catalytic cracking main fractionating column 9 through the main riser reaction oil gas pipeline 8, the catalyst is transported to the catalytic cracking regenerator 38 for regeneration and recycling to the catalytic cracking main riser 7 and / or the catalytic cracking second riser 27.

[0034] The reaction oil gas is fractionated into catalytic rich gas, catalytic sewage, catalytic gasoline, catalytic diesel and catalytic oil slurry in the column, and the catalytic cracking main fractionating column 9 is connected with a main riser catalytic rich gas discharge pipeline 10, a main riser catalytic sewage discharge pipeline 11, a main riser catalytic gasoline pipeline 12, a main riser catalytic diesel pipeline 13 and a main riser catalytic oil slurry pipeline 14 to discharge the fractionated materials outside the column. The main riser catalytic diesel pipeline 13 is connected to the ethylene tar light fraction pipeline 3 and is transported to the hydrogenation device 4 with the ethylene tar light fraction.

[0035] The heavy fraction outlet of the ethylene tar fractionation device 2 is connected with a coking tower 20, a coking fractionation tower 22, a catalytic cracking second riser 27 of a dual riser catalytic cracking device and a catalytic cracking auxiliary fractionation tower 29 in sequence. Specifically, the heavy fraction outlet of the ethylene tar fractionation device 2 is connected to the feed inlet of the coking tower 20 through an ethylene tar heavy fraction pipeline 18 to send the ethylene tar heavy fraction into the coking tower 20 for coking reaction.

[0036] The discharge outlet of the coking tower 20 is connected to the coking fractionation tower 22 through a coking oil gas pipeline 21, and the coking oil gas obtained after reaction in the coking tower 20 is transported to the coking fractionation tower 22 for fractionation. The coking fractionation tower 22 is fractionated to obtain coking rich gas, coking sewage, coking gasoline, coking diesel and coking wax oil. Therefore, the coking fractionation tower 22 is connected with a coking rich gas discharge pipeline 23, a coking sewage discharge pipeline 24, a coking wax oil discharge pipeline 40, a coking gasoline pipeline 25 and a coking diesel pipeline 26 to discharge the fractionated materials outside the tower.

[0037] The coking gasoline pipeline 25 is connected with the catalytic cracking second riser 27 to make the easy cracking coking gasoline react in the high severity catalytic cracking second riser 27, which can increase the production of ethylene, propylene and other low carbon olefins. The reaction temperature of the second riser catalytic cracking reaction is 550-650 ℃, the catalyst to oil ratio is 5-15, the reaction pressure is 0.1-0.5 MPa (gauge pressure), the reaction time is 2-5 s, the atomized water vapor accounts for 1-5 w% of the feed amount, and the catalyst in the catalytic cracking second riser 27 is selected from conventional catalytic cracking catalysts.

[0038] The catalytic cracking second riser 27 is connected with a second riser settler, and the second riser settler is connected with a catalytic cracking regenerator 38. The catalyst separated by the second riser settler is transported to the catalytic cracking regenerator 38 for regeneration and then is transported to the catalytic cracking second riser 27 and / or the catalytic cracking main riser 7 for recycling. The top of the second riser settler is provided with a second riser reaction oil gas pipeline 28, and the reaction oil gas separated by the second riser settler is connected to the catalytic cracking auxiliary fractionation tower 29 through the second riser reaction oil gas pipeline 28. The reaction oil gas is fractionated in the catalytic cracking auxiliary fractionation tower 29 to obtain catalytic rich gas, catalytic sewage, catalytic gasoline, catalytic diesel and catalytic oil slurry. The catalytic cracking auxiliary fractionation tower 29 is connected with a second riser rich gas discharge pipeline, a second riser catalytic sewage discharge pipeline 31, a second riser catalytic gasoline pipeline 32, a second riser catalytic diesel pipeline 33 and a second riser catalytic oil slurry pipeline 34 to discharge the fractionated materials outside the tower.

[0039] The main riser catalytically enriched gas discharge pipeline 10 of the catalytic cracking main fractionating column 9 and the second riser catalytically enriched gas discharge pipeline 30 of the catalytic cracking auxiliary fractionating column 29 are both connected to a gas fractionation device (not shown in the figure) to extract low carbon olefins, and the operating conditions of the gas fractionation device are consistent with the industrial conventional operating conditions.

[0040] The main riser catalytically cracked gasoline pipeline 12 and the second riser catalytically cracked gasoline pipeline 32 are both connected to the gasoline fractionating column 15, and the catalytically cracked gasoline is cut and fractionated into catalytically cracked gasoline light fraction and catalytically cracked gasoline heavy fraction in the gasoline fractionating column 15, and the cutting temperature is 50-180℃, the gasoline light fraction is distilled from the upper part of the column, and the gasoline heavy fraction is distilled from the lower part of the column, the obtained gasoline light fraction is rich in C6-C8 light aromatic hydrocarbons, and the obtained gasoline heavy fraction is rich in C9+ aromatic hydrocarbons.

[0041] The gasoline fractionating column 15 is provided with a catalytically cracked gasoline light fraction pipeline 16 and a catalytically cracked gasoline heavy fraction pipeline 17, the catalytically cracked gasoline heavy fraction pipeline 17 is connected to the catalytic cracking second riser 27, and the catalytically cracked gasoline light fraction pipeline 16 is connected to the aromatic hydrocarbon combination device 35 to obtain light aromatic hydrocarbons and raffinate gasoline, and the aromatic hydrocarbon combination device 35 is provided with a light aromatic hydrocarbon discharge pipeline 36 and a raffinate gasoline discharge pipeline 37, and the raffinate gasoline is subsequently used as a gasoline blending component. The catalytically cracked gasoline light fraction is pre-hydrogenated, aromatic hydrocarbon extracted and aromatic hydrocarbon fractionated in the aromatic hydrocarbon combination device 35. The pre-hydrogenation conditions can be selected as follows: reaction temperature 300-420℃, hydrogen partial pressure 2.5-3.5 MPa, hydrogen / oil volume ratio 300-500:1, and volume space velocity 1.5-4 h-1. The extraction solvent is one or more of sulfolane, dimethyl sulfoxide, dimethyl formamide, N-methyl pyrrolidone, N-formyl morpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, methanol or acetonitrile. The mass ratio of the extraction solvent to the catalytically cracked gasoline light fraction is 3-8:1, the overhead temperature of the extraction column used for extraction is 130-190℃, and the pressure is 1.1-2.0 MPa.

[0042] The main riser catalytically cracked diesel pipeline 13, the second riser catalytically cracked diesel pipeline 33 and the coking diesel pipeline 26 are all connected to the hydrogenation device 4, and in the specific embodiment of the present application, the main riser catalytically cracked diesel pipeline 13, the second riser catalytically cracked diesel pipeline 33 and the coking diesel pipeline 26 are all connected to the ethylene tar light fraction pipeline 3 and are transported together with the ethylene tar light fraction into the hydrogenation device 4.

[0043] The main riser catalytically cracked slurry pipeline 14 and the second riser catalytically cracked slurry pipeline 34 are both connected to the coking tower 20 to transport the catalytically cracked slurry into the coking tower.

[0044] In the specific embodiments of the present application, the main riser catalytic oil slurry pipeline 14 and the second riser catalytic oil slurry pipeline 34 are both connected to the ethylene tar heavy fraction pipeline 18 and are transported together with the ethylene tar heavy fraction into the coking tower 20 for delayed coking reaction, the coking heating furnace 19 is arranged on the ethylene tar heavy fraction pipeline 18, and the connection positions of the main riser catalytic oil slurry pipeline 14 and the second riser catalytic oil slurry pipeline 34 with the ethylene tar heavy fraction pipeline 18 are located upstream of the coking heating furnace 19. The selected reaction temperature in the coking tower 20 is 420-500 DEG C, the reaction pressure is 0.10-0.15 MPa, and the circulation ratio is 0.10-0.30.

[0045] Since the main riser catalytic oil slurry and the second riser catalytic oil slurry are both heavy products obtained from the catalytic cracking process, the added value of the products is low and the products are difficult to handle, in the further processing of the products, the present application circulates the products back to the delayed coking device, and since the delayed coking device can process relatively poor raw materials, the yield of low-carbon olefins and light aromatic hydrocarbons is further improved by back-refining the catalytic oil slurry.

[0046] The process flow of the system of the present application for preparing light aromatic hydrocarbons and low-carbon olefins from ethylene tar is as follows:

[0047] The ethylene tar raw material 1 enters the ethylene tar fractionation device 2 to obtain ethylene tar light fraction and ethylene tar heavy fraction;

[0048] The ethylene tar light fraction enters the hydrogenation device 4 to react with hydrogen 5 to obtain hydrogenated light fraction, the hydrogenated light fraction enters the catalytic cracking main riser 7 of the dual-riser catalytic cracking device to undergo catalytic cracking reaction, and the obtained main riser reaction oil gas 8 enters the catalytic cracking main fractionation tower 9 for fractionation, the main riser catalytic rich gas obtained by the fractionation of the catalytic cracking main fractionation tower 9 enters the subsequent gas separation unit to obtain ethylene and propylene and other low-carbon olefins, the main riser catalytic cracking wastewater is discharged, and the main riser catalytic gasoline enters the gasoline fractionation tower 15 for fractionation and cutting, and the fractionation and cutting obtain catalytic gasoline light fraction and catalytic gasoline heavy fraction;

[0049] The ethylene tar heavy fraction and the catalytic slurry are preheated by the coking heating furnace 19 and then enter the coking tower 20 to perform a coking reaction, the coking oil gas obtained is separated in the coking fractionating tower 22, the coking rich gas goes to the subsequent gas separation device to obtain ethylene and propylene and other low carbon olefins, the coking sewage is discharged, the coking gas oil is discharged, the coking gasoline and the catalytic gasoline heavy fraction enter the second riser 27 of the dual riser catalytic cracking device to perform a catalytic cracking reaction under a higher severity, the second riser reaction oil gas is separated in the catalytic cracking auxiliary fractionating tower 29, the second riser catalytic rich gas goes to the subsequent gas separation device to obtain ethylene and propylene and other low carbon olefins, the second riser catalytic cracking sewage is discharged, the second riser catalytic gasoline is separated in the gasoline fractionating tower 15, the second riser catalytic diesel returns to the hydrogenation device 4 to perform selective hydrogenation saturation, and the second riser catalytic slurry returns to the coking heating furnace 19 to perform subsequent coking reaction.

[0050] The main riser catalytic gasoline and the second riser catalytic gasoline are separated into catalytic gasoline light fraction by the gasoline fractionating tower 15, the catalytic gasoline light fraction enters the aromatic complex device 35 to perform aromatic extraction to obtain light aromatic hydrocarbon and raffinate gasoline, and the raffinate gasoline is used as a gasoline blending component; in this process, the catalytic cracking main wind 39 is introduced into the catalytic cracking regenerator 38 to perform cyclic regeneration on the catalytic cracking catalyst.

[0051] In order to verify the advantages of the dual riser catalytic cracking device in the present application, the following detection experiments and comparison experiments are performed by using the process equipment of the present application.

[0052] Detection experiment 1

[0053] The detection experiment 1 adopts the process flow as shown in Table 1, and the properties of the ethylene tar are shown in Table 2, and the main operating conditions of the whole process are shown in Table 2, and the product distribution of the whole process is shown in Table 3. Figure 1

[0054] Detection experiment 2

[0055] According to the process flow described in detection experiment 1, the difference lies in that the cutting temperature of the ethylene tar is different, the main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0056] Detection experiment 3

[0057] According to the process flow described in example 1, the difference lies in that the cutting temperature of the ethylene tar and the reaction temperature of the catalytic cracking main riser 7 are different, the main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0058] Detection experiment 4

[0059] ​The process flow as described in example 1 is adopted, except that the cutting temperature of ethylene tar, the reaction temperature of catalytic cracking main riser 7 and the reaction temperature of the second riser are different, the main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3.

[0060] Comparative test 1

[0061] According to the system as shown in Figure 2 The process flow is described in detail as follows: ethylene tar raw material 1 enters the ethylene tar fractionation device 1 to be fractionated to obtain ethylene tar light fraction and ethylene tar heavy fraction, the ethylene tar light fraction enters the hydrogenation device 4 to react with hydrogen to obtain the hydrogenation light fraction, which enters the catalytic cracking riser 41 to undergo catalytic cracking reaction, and the obtained catalytic cracking reaction oil gas enters the catalytic cracking fractionation tower 42 for fractionation, the catalytic rich gas is discharged through the catalytic rich gas discharge pipeline 43 to the subsequent gas separation device to obtain ethylene, propylene and other low-carbon olefins, the catalytic sewage is discharged through the catalytic sewage discharge pipeline 44, and the catalytic gasoline enters the gasoline fractionation tower 15 for fractionation to obtain catalytic gasoline light fraction and catalytic gasoline heavy fraction, and the catalytic gasoline light fraction enters the aromatic complex device 35 for aromatic extraction to obtain light aromatic and raffinate gasoline.

[0062] The ethylene tar heavy fraction and the catalytic oil slurry obtained by reacting in the catalytic cracking fractionation tower 42 are preheated in the coking heating furnace 19 and then enter the coking tower 20 for coking reaction, and the obtained coking oil gas enters the coking fractionation tower 22 for separation, the coking rich gas is discharged through the coking rich gas discharge pipeline 23 to the subsequent gas separation unit to obtain ethylene, propylene and other low-carbon olefins, the coking sewage is discharged through the coking sewage discharge pipeline 24, the coking gasoline and the catalytic gasoline heavy fraction enter the catalytic cracking riser 41 from the lower raw material nozzle for catalytic reaction, the coking diesel enters the hydrogenation device 4 for selective hydrogenation saturation, the coking gas oil is discharged through the coking gas oil discharge pipeline 40, and the catalytic cracking regenerator 38 is provided with the catalytic cracking main air 39 to recycle and regenerate the catalytic cracking catalyst.

[0063] The main difference between the test and tests 3 and 4 is that the catalytic cracking single riser is operated, the hydrogenation light fraction, the gasoline heavy fraction and the coking gasoline directly enter the catalytic cracking single riser for cracking, the main operating conditions are shown in Table 2, and the product distribution of the whole process is shown in Table 3. Table 1 Ethylene tar properties Table 2 Main operating conditions Table 3 Product distribution of the whole process

[0064] As can be seen from Table 3, the system of the present application can convert ethylene tar into high-value-added low-carbon olefins and light aromatic products. Under the operating conditions in the test, the yield of low-carbon olefins + light aromatic products can generally reach more than 40 w%. Compared with Comparative Test 1, Tests 3 and 4 using the system provided by the present application can further tap the aromatic resources in the raw material, significantly improve the BTX yield of the process, and thus improve the yield of low-carbon olefins + light aromatic products. By selecting appropriate ethylene tar cutting temperature and operating conditions, the yield of low-carbon olefins + light aromatic products can be further improved, thereby improving the overall economic benefit of the process.

[0065] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A system for producing low-carbon olefins and light aromatics from ethylene tar, characterized by: including an ethylene tar fractionation unit (2); The light fraction outlet of the ethylene tar fractionation unit (2) is sequentially connected to a hydrogenation unit (4), a catalytic cracking main riser (7) of a double-rise catalytic cracking unit, and a catalytic cracking main fractionation tower (9); The heavy fraction outlet of the ethylene tar fractionation unit (2) is sequentially connected to a coking tower (20), a coking fractionation tower (22), a catalytic cracking second riser (27) of a double-riser catalytic cracking unit, and a catalytic cracking secondary fractionation tower (29); The main riser catalytic rich gas discharge pipeline (10) of the catalytic cracking main fractionating tower (9) and the second riser catalytic rich gas discharge pipeline (30) of the catalytic cracking auxiliary fractionating tower (29) are both connected to a gas separation device to extract light olefins; The main riser catalytic gasoline pipeline (12) of the catalytic cracking main fractionating tower (9) and the second riser catalytic gasoline pipeline (32) of the catalytic cracking secondary fractionating tower (29) are both connected to the gasoline fractionating tower (15), and the catalytic gasoline light fraction pipeline (16) of the gasoline fractionating tower (15) is connected to the aromatics complex (35) to obtain light aromatics; The catalytic gasoline heavy fraction pipeline (17) of the gasoline fractionating tower (15) is connected to the catalytic cracking second riser (27); the main riser catalytic diesel pipeline (13) of the catalytic cracking main fractionating tower (9), the second riser catalytic diesel pipeline (33) of the catalytic cracking secondary fractionating tower (29) and the coking diesel pipeline (26) of the coking fractionating tower (22) are all connected to the hydrogenation unit (4); the main riser catalytic oil slurry pipeline (14) of the catalytic cracking main fractionating tower (9) and the second riser catalytic oil slurry pipeline (34) of the catalytic cracking secondary fractionating tower (29) are both connected to the coking tower (20).

2. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The ethylene tar fractionation device (2) is connected to the coking tower (20) through the ethylene tar heavy fraction pipeline (18), and a coking heating furnace (19) is provided on the ethylene tar heavy fraction pipeline (18).

3. The system for producing light olefins and light aromatics from ethylene tar according to claim 2, characterized in that: The main riser catalytic oil slurry pipeline (14) and the second riser catalytic oil slurry pipeline (34) are both connected to the coking tower (20) through the ethylene tar heavy fraction pipeline (18), and the connection points of the main riser catalytic oil slurry pipeline (14), the second riser catalytic oil slurry pipeline (34) and the ethylene tar heavy fraction pipeline (18) are located upstream of the coking heating furnace (19).

4. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The invention also comprises a catalytic cracking regenerator (38), a catalytic cracking main riser (7) connected to a main riser settler, a catalytic cracking second riser (27) connected to a second riser settler, and both the main riser settler and the second riser settler are connected to the catalytic cracking regenerator (38).

5. The system for producing light olefins and light aromatics from ethylene tar according to claim 4, characterized in that: The mixed material after the reaction in the catalytic cracking main riser (7) is discharged from the upper portion thereof into the main riser settler. The main riser reaction oil and gas separated in the main riser settler are transported to the catalytic cracking main fractionation tower (9) through the main riser reaction oil and gas pipeline (8). The catalyst separated in the main riser settler enters the catalytic cracking regenerator (38).

6. The system for producing light olefins and light aromatics from ethylene tar according to claim 4, characterized in that: The mixed material after the reaction in the second riser (27) of the catalytic cracking enters the second riser settler. The second riser reaction oil and gas separated in the second riser settler are transported to the catalytic cracking secondary fractionation tower (29) through the second riser reaction oil and gas pipeline (28). The catalyst separated in the second riser settler is transported to the catalytic cracking regenerator (38).

7. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The coking fractionation tower (22) is provided with a coking wax oil discharge pipeline (40) and a coking wastewater discharge pipeline (24).

8. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: A main riser catalytic rich gas discharge pipeline (10) and a main riser catalytic wastewater discharge pipeline (11) are provided on the catalytic cracking main fractionating tower (9).

9. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The catalytic cracking secondary fractionation tower (29) is provided with a second riser catalytic rich gas discharge pipeline (30) and a second riser catalytic wastewater discharge pipeline (31).

10. The system for producing light olefins and light aromatics from ethylene tar according to claim 1, characterized in that: The top of the aromatics combined unit (35) is provided with a light aromatics discharge pipeline (36), and the bottom is provided with a raffinate gasoline discharge pipeline (37).

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