System for producing light aromatic hydrocarbon from ethylene tar

Abstract

A system for producing light aromatic hydrocarbon from ethylene tar relates to the technical field of petrochemical engineering and comprises a flash evaporation device for fractionating ethylene tar, a hydrogenation device connected to a light fraction outlet of the flash evaporation device and a coke tower connected to a heavy fraction outlet of the flash evaporation device, the downstream of the hydrogenation device is sequentially connected with a catalytic cracking lifting pipe; the downstream of the catalytic cracking fractionating tower is connected with a coking fractionating tower; a catalytic diesel oil outlet of the catalytic cracking fractionating tower and a coking diesel oil outlet of the coking fractionating tower are connected to the hydrogenation device through pipelines; a catalytic gasoline outlet of the catalytic cracking fractionating tower and a coker gasoline outlet of the coking fractionating tower are both connected to an aromatic hydrocarbon combination device through pipelines, so that pre-hydrogenation and aromatic hydrocarbon extraction are carried out, and light aromatic hydrocarbon is obtained. By means of the system, ethylene tar which is difficult to treat by chemical enterprises can be converted into BTX and a small amount of gasoline products, rich aromatic hydrocarbon resources in the ethylene tar are fully utilized, and the added value of the products is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petrochemical industry, in particular to a system for producing light aromatic hydrocarbons from ethylene tar. BACKGROUND

[0002] With the rapid development of China's ethylene industry, the production capacity of ethylene cracking device has been increasing year by year. Ethylene tar, a by-product with high polymerization degree produced in the process of ethylene cracking reaction of ethylene cracking raw material, its main component is condensed ring aromatic hydrocarbon with short alkyl side chain. The yield of ethylene tar is affected by cracking raw material and processing conditions, generally accounting for about 20% of ethylene production. Due to the characteristics of high polymerization and high carbon content, ethylene tar is currently mainly used to produce low value-added products such as road asphalt, fuel blending oil and carbon black, and the rich aromatic hydrocarbon resources in ethylene tar have not been fully utilized.

[0003] Chinese patent CN116004284A discloses a method and system for hydrogenation of ethylene tar to produce light hydrocarbons. After removing gum from the pretreated ethylene tar, the first liquid phase hydrogenation and the second gas phase hydrogenation are carried out to separate the light fraction and the heavy fraction in the range of 40-220℃, thereby increasing the production of high value-added light aromatic hydrocarbons or high octane gasoline blending components and recovering and separating heavy aromatic hydrocarbon solvent oil. The method can effectively reduce the content of olefinic aromatic hydrocarbons, indenes and condensed ring aromatic hydrocarbons through hydrogenation treatment, but the aromatic hydrocarbon resources in the heavy aromatic hydrocarbon solvent oil are not fully utilized.

[0004] Chinese patent CN103102976A discloses a method for treating ethylene tar. The method fractionates the ethylene tar into light fraction and heavy fraction, mixes the heavy fraction with conventional coking raw material to carry out delayed coking reaction, and then mixes the coking diesel obtained with the light fraction of ethylene tar to purify naphthalene by rectification / crystallization. The method mainly focuses on improving the yield of chemical raw material naphthalene.

[0005] Chinese patent CN115141651A discloses a system and method for producing chemical raw materials by partitioning and intensifying the production of aromatic hydrocarbon-rich fraction oil. The method processes catalytic cracking diesel, ethylene tar and DCC diesel through a hydrogenation refining reactor to obtain hydrogenation refined products, and then transfers the hydrogenation refined products into light hydrocarbonization reactors with different catalysts to obtain liquid products with an aromatic hydrocarbon purity of 99.9wt% and gas products rich in n-alkanes, thereby realizing the full utilization of aromatic fraction oil. The method hydrogenates the ethylene tar as a whole, which has high requirements for the operation of the hydrogenation refining reactor, and the subsequent light hydrocarbonization process is a single pass, which limits the conversion depth of ethylene tar to produce light aromatic hydrocarbons.

[0006] Technical development and economic analysis of hydrogenation of ethylene tar to produce aromatics (Suying, He Laibin, Liaoning Chemical, Vol. 50, No. 12) discloses a technology for producing BTX light aromatics by three-stage hydrogenation of ethylene tar as raw material. However, this way has large equipment investment and high hydrogen consumption.

[0007] In summary, there is no relatively mature technology for producing light aromatics from ethylene tar in the market at present. Developing ethylene tar full-range production of light aromatics, fully utilizing the rich aromatic resources in ethylene tar, and converting ethylene tar into high-value light aromatics BTX product are effective development of the technical route for producing light aromatics from ethylene tar. SUMMARY

[0008] The present application aims to provide a system for producing light aromatics from ethylene tar, so as to solve the problems of large hydrogen consumption and high processing cost in the prior art for preparing light aromatics from ethylene tar as raw material.

[0009] In order to solve the above technical problems, the specific scheme adopted by the present application is as follows: a system for producing light aromatics from ethylene tar, comprising a flash device for fractionating ethylene tar, a hydrogenation device connected to the light fraction outlet of the flash device, and a coking tower connected to the heavy fraction outlet of the flash device; the downstream of the hydrogenation device is connected with a catalytic cracking riser in sequence, and the downstream of the catalytic cracking fractionating tower is connected with a coking fractionating tower; the catalytic diesel outlet of the catalytic cracking fractionating tower and the coking diesel outlet of the coking fractionating tower are both connected to the hydrogenation device by pipelines; the catalytic gasoline outlet of the catalytic cracking fractionating tower and the coking gasoline outlet of the coking fractionating tower are both connected to an aromatics combination device by pipelines, so as to obtain light aromatics.

[0010] As a further optimization of the above technical solution: the light fraction outlet of the flash device is communicated with the hydrogenation device through an ethylene tar light fraction pipeline; the catalytic diesel fractionated from the catalytic cracking fractionating tower and the coking diesel fractionated from the coking fractionating tower are both connected to the ethylene tar light fraction pipeline by pipelines.

[0011] As a further optimization of the above technical solution: the heavy fraction outlet of the flash device is communicated with the coking tower through an ethylene tar heavy fraction pipeline, and a coking heating furnace is arranged on the ethylene tar heavy fraction pipeline.

[0012] As a further optimization of the above technical solution: the catalytic oil slurry fractionated from the catalytic cracking fractionating tower is connected to the ethylene tar heavy fraction pipeline through a catalytic oil slurry pipeline, and the connection between the catalytic oil slurry pipeline and the ethylene tar heavy fraction pipeline is located upstream of the coking heating furnace.

[0013] As a further optimization of the above technical solution: the ethylene tar heavy fraction pipeline is connected to the bottom of the coking tower, and a coking oil gas pipeline for communicating with the coking fractionating tower is arranged at the top of the coking tower.

[0014] As a further optimization of the above technical solution: the coking fractionating tower is provided with a coking wax oil discharge pipeline at the bottom.

[0015] As a further optimization of the above technical solution: the catalytic cracking riser is connected with a separation unit for separating the mixture in the catalytic cracking riser.

[0016] As a further optimization of the above technical solution: the separation unit is a settler, and the settler is provided with a catalytic cracking regenerator below.

[0017] As a further optimization of the above technical solution: the mixture after reaction in the catalytic cracking riser is connected to the settler from the outlet at the upper end of the catalytic cracking riser, the separated catalyst in the settler is transported to the catalytic cracking regenerator for regeneration, the regenerated catalyst is transported to the catalytic cracking riser for recycling, and the reaction oil gas separated in the settler is transported to the catalytic cracking fractionating tower by the reaction oil gas pipeline above the settler.

[0018] As a further optimization of the above technical solution: the aromatics combination device is provided with a light aromatic hydrocarbon discharge pipeline at the top and a raffinate gasoline discharge pipeline at the bottom.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] Through the system of the present application, the heavy fraction and the light fraction cut and fractionated are respectively processed, so that the full fraction application of the ethylene tar is realized, the yield of the BTX light aromatic hydrocarbon produced by the ethylene tar reaches more than 20%, the ethylene tar which is difficult to process by the chemical enterprise is converted into the BTX and a small amount of gasoline product, the rich aromatic hydrocarbon resource in the ethylene tar is fully utilized, and the product added value is significantly improved.

[0021] In the present application, the ethylene tar light fraction, the catalytic diesel oil and the coking diesel oil are introduced into a hydrogenation device for hydrogenation saturation, the hydrogenated light fraction obtained is introduced into a catalytic cracking riser, the ethylene tar heavy fraction and the catalytic oil slurry are introduced into a delayed coking device, and the catalytic cracking and the delayed coking process do not consume hydrogen, so that the overall hydrogen consumption in the preparation of the light aromatic hydrocarbon from the ethylene tar is reduced, and the catalytic cracking and the delayed coking device are conventional light devices of a refinery, which generally do not need to be newly built, and do not cause too much investment cost.

[0022] The system for producing light aromatic hydrocarbons from ethylene tar provided by the present application cuts and fractionates ethylene tar according to a suitable cutting point through a flash device, and the light fraction of ethylene tar obtained is first subjected to selective hydrogenation saturation in a hydrogenation device to saturate the di-cyclic and above aromatic hydrocarbons (i.e. polycyclic aromatic hydrocarbons) in the light fraction into monocyclic aromatic hydrocarbons, and then enters a catalytic cracking riser to crack the side chains of the monocyclic aromatic hydrocarbons, so as to obtain a catalytic gasoline product containing a large amount of monocyclic aromatic hydrocarbon components; the heavy fraction of ethylene tar obtained after cutting and fractionating in the flash device is subjected to a delayed coking reaction in a coking tower together with catalytic slurry oil to realize lightening treatment, and then the coking diesel oil and catalytic diesel oil rich in aromatic components obtained are returned to the hydrogenation device for selective hydrogenation saturation, so as to further improve the utilization of aromatic-rich resources, and the hydrogenation product is also subjected to further conversion into a catalytic gasoline product containing a large amount of monocyclic aromatic hydrocarbon components through a catalytic cracking device; finally, BTX and other light aromatic hydrocarbon products are extracted through an aromatic hydrocarbon combination device. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flowchart of the system of the present application is shown in the figure;

[0024] BRIEF DESCRIPTION OF DRAWINGS: 1, ethylene tar, 2, flash device, 3, ethylene tar light fraction pipeline, 4, hydrogenation device, 5, hydrogen, 6, hydrogenation light fraction pipeline, 7, catalytic cracking riser, 8, reaction oil gas pipeline, 9, catalytic cracking fractionating tower, 10, catalytic gas-rich effluent pipeline, 11, catalytic sewage effluent pipeline, 12, catalytic gasoline pipeline, 13, catalytic diesel oil pipeline, 14, catalytic slurry oil pipeline, 15, aromatic hydrocarbon combination device, 16, light aromatic hydrocarbon effluent pipeline, 17, raffinate gasoline effluent pipeline, 18, ethylene tar heavy fraction pipeline, 19, coking heating furnace, 20, coking tower, 21, coking oil gas pipeline, 22, coking fractionating tower, 23, coking gas-rich effluent pipeline, 24, coking sewage effluent pipeline, 25, coking gasoline pipeline, 26, coking diesel oil pipeline, 27, coking wax oil effluent pipeline, 28, catalytic cracking regenerator, 29, catalytic cracking main air, 30, coking crude gasoline tank, 31, coking crude gasoline tank. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be further described in detail in combination with specific embodiments. The parts not described and disclosed in detail in the following embodiments, such as the specific structure of the flash device and the process of fractionating ethylene tar, the specific structure and working process of the hydrogenation device, the coking tower, the catalytic cracking riser and the catalytic cracking fractionating tower, should be understood as the prior art known or should be known by those skilled in the art.

[0026] Example 1

[0027] The present invention discloses a system for producing light aromatic hydrocarbons from ethylene tar, comprising a flash device 2 for fractionating ethylene tar, a hydrogenation device 4 connected to the light fraction outlet of the flash device 2, and a coking tower 20 connected to the heavy fraction outlet of the flash device 2. A catalytic cracking riser 7 and a catalytic cracking fractionating tower 9 are sequentially connected downstream of the hydrogenation device 4, a coking fractionating tower 22 is connected downstream of the coking tower 20, a catalytic diesel outlet of the catalytic cracking fractionating tower 9 and a coking diesel outlet of the coking fractionating tower 22 are both connected to the hydrogenation device 4 through pipelines; a catalytic gasoline outlet of the catalytic cracking fractionating tower 9 and a coking gasoline outlet of the coking fractionating tower 22 are both connected to an aromatics combination device 15 through pipelines for pre-hydrogenation and aromatics extraction to obtain light aromatic hydrocarbons.

[0028] Specifically, the flash device 2 is a fractionation device for fractionating ethylene tar. The ethylene tar is cut and fractionated in the flash device 2. The cutting point is 250-350° C., so that the content of dicyclic aromatic hydrocarbons in the light fraction of the ethylene tar reaches the maximum.

[0029] The top of the flash unit 2 is provided with an ethylene tar light fraction outlet for discharging the ethylene tar light fraction fractionated therein. The ethylene tar light fraction outlet is connected to the hydrogenation unit 4 via the ethylene tar light fraction pipeline 3. In the hydrogenation unit 4, the polycyclic aromatic hydrocarbons in the ethylene tar light fraction are selectively hydrogenated and saturated into monocyclic aromatic hydrocarbons to obtain the hydrogenated light fraction. When the ethylene tar light fraction is selectively hydrogenated and saturated in the hydrogenation unit 4, the reaction temperature is selected to be 320-400°C, the hydrogen partial pressure is 5.0-10.0 MPa, and the volume space velocity is 0.5-3h -1 The hydrogen / oil volume ratio is 300 to 800:1. The catalyst for selective hydrogenation and saturation of polycyclic aromatic hydrocarbons can be a combination of one or more of a hydrotreating catalyst and a hydrocracking catalyst. In a preferred embodiment of the present invention, the active metal in the hydrotreating catalyst includes one or more of nickel, cobalt, molybdenum, or tungsten. The mass of the active metal is 10% to 30%.

[0030] A hydrogenated light fraction pipeline 6 is provided between the hydrogenation unit 4 and the catalytic cracking riser 7 to transport the hydrogenated light fraction from the hydrogenation unit 4 to the catalytic cracking riser 7, where it undergoes a cracking reaction to produce products such as catalytic dry gas, catalytic liquefied gas, catalytic gasoline, catalytic diesel, and catalytic slurry oil. The cracking reaction in the catalytic cracking riser 7 is conducted at a temperature of 500-650°C, a catalyst-to-oil ratio of 8-14, a reaction pressure of 0.1-0.5 MPa (gauge pressure), a reaction time of 2-5 seconds, and atomized steam accounting for 1-5% by weight of the feed. Conventional catalytic cracking catalysts are used as catalysts.

[0031] The outlet at the upper end of the catalytic cracking riser 7 is connected with a separation unit for separating the mixed material, which is a settler, and a catalytic cracking regenerator 28 is installed at the lower part of the settler to regenerate and recycle the catalyst in the catalytic cracking riser 7.

[0032] The catalyst outlet of the catalytic cracking regenerator 28 is located at the lower side thereof and communicates with the catalyst inlet of the catalytic cracking riser 7, and the catalyst inlet of the catalytic cracking riser 7 is also located at the lower side thereof. The feed inlet for the hydrogenated light fraction into the catalytic cracking riser 7 is also located at the lower side thereof.

[0033] After the hydrogenated light fraction enters the catalytic cracking riser 7, catalytic cracking reaction occurs under the action of the catalyst, and the reacted mixed material is transported from the outlet at the upper end thereof to the settler, and the separated catalyst in the settler enters the catalytic cracking regenerator 28. The top of the settler is provided with a reaction oil gas pipeline 8 communicating with the catalytic cracking fraction column 9 to transport the separated reaction oil gas in the settler to the catalytic cracking fraction column 9.

[0034] The bottom of the catalytic cracking fraction column 9 is provided with a catalytic oil slurry pipeline 14 to discharge the fractionated catalytic oil slurry; the side of the catalytic cracking fraction column 9 is provided with a catalytic diesel outlet, and the fractionated catalytic diesel is transported to the ethylene tar light fraction pipeline 3 through the catalytic diesel pipeline 13 to flow into the hydrogenation device 4 together with the ethylene tar light fraction for hydrogenation saturation; other components fractionated in the catalytic cracking fraction column 9 enter the catalytic cracking naphtha tank 30 through the top outlet thereof, and are fractionated into catalytic rich gas, catalytic sewage and catalytic gasoline in the catalytic cracking naphtha tank 30. The catalytic cracking naphtha tank 30 is provided with a catalytic rich gas discharge pipeline 10 for discharging the catalytic rich gas, a catalytic sewage discharge pipeline 11 for discharging the catalytic sewage, and a catalytic gasoline pipeline 12 for discharging the catalytic gasoline, and the outlet of the catalytic gasoline pipeline 12 communicates with the aromatic complex device 15.

[0035] The flash device 2 heavy fraction outlet communicates with the ethylene tar heavy fraction pipeline 18 and the coking tower 20, and the coking heater 19 is arranged on the ethylene tar heavy fraction pipeline 18 to heat the ethylene tar heavy fraction entering the coking tower 20. The ethylene tar heavy fraction pipeline 18 is connected to the bottom of the coking tower 20, and the top of the coking tower 20 is provided with a coking oil gas pipeline 21 communicating with the coking fraction column 22.

[0036] The outlet of the catalytic slurry oil pipeline 14 is connected to the ethylene tar heavy fraction pipeline 18, and the connection point of the catalytic slurry oil pipeline 14 and the ethylene tar heavy fraction pipeline 18 is located upstream of the coking furnace 19, so that the catalytic slurry oil and the ethylene tar heavy fraction are heated together by the coking furnace 19 and then transported into the coking tower 20. Since the catalytic slurry oil is a heavy product obtained from catalytic cracking, it is difficult to handle. If it is recycled back to the catalytic cracking unit for cracking reaction, the product distribution of the catalytic cracking unit will be deteriorated. The delayed coking unit can handle relatively poor raw materials, and the yield of light aromatic hydrocarbons can be further improved by processing the catalytic slurry oil through the delayed coking unit.

[0037] The ethylene tar heavy fraction and the catalytic slurry oil are subjected to coking reaction in the coking tower 20 to obtain coking dry gas, coking liquefied gas, coking gasoline, coking diesel, coking wax oil and petroleum coke. The reaction temperature for the coking reaction is 420-500℃, the reaction pressure is 0.10-0.15 MPa, and the circulation ratio is 0.10-0.30.

[0038] The coking wax oil pipeline 27 is provided at the bottom of the coking fractionation tower 22 to discharge the coking wax oil fractionated. The coking diesel outlet is provided at the side of the coking fractionation tower 22, and the coking diesel pipeline 26 is used to transport the coking diesel fractionated to the ethylene tar light fraction pipeline 3, so that the coking diesel, the ethylene tar light fraction and the catalytic diesel are flowed into the hydrogenation unit 4 together for hydrogenation saturation. The other components fractionated in the coking fractionation tower 22 are discharged from the top outlet into the coking gasoline tank 31, and are fractionated into coking rich gas, coking sewage and coking gasoline in the coking secondary flow tank. The coking rich gas discharge pipeline 23 is provided on the coking gasoline tank 31 to discharge the coking rich gas, the coking sewage discharge pipeline 24 is provided to discharge the coking sewage, and the coking gasoline pipeline 25 is provided to discharge the coking gasoline. The outlet of the coking gasoline pipeline 25 is connected to the aromatic hydrocarbon combination unit 15.

[0039] The coking gasoline and the catalytic gasoline are subjected to pre-hydrogenation and aromatic hydrocarbon extraction in the aromatic hydrocarbon combination unit 15 to obtain light aromatic hydrocarbons (i.e. BTX light aromatic hydrocarbons) and raffinate gasoline. The aromatic hydrocarbon combination unit 15 is provided with the light aromatic hydrocarbon discharge pipeline 16 at the top and the raffinate gasoline discharge pipeline 17 at the bottom. The raffinate gasoline is discharged as a gasoline blending component. The pre-hydrogenation reaction temperature in the aromatic hydrocarbon combination unit 15 is 300-420℃, the hydrogen partial pressure is 2.5-3.5 MPa, the hydrogen / oil volume ratio is 300-500:1, the volume space velocity is 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 gasoline (including the catalytic gasoline and the coking gasoline) is 3-8:1, the extraction tower used for the aromatic hydrocarbon extraction has a top temperature of 80-190℃ and a pressure of 1.1-2.0 MPa.

[0040] By the method of the present application, the di- and polycyclic aromatic hydrocarbons in the light fraction of ethylene tar are hydrogenated to monocyclic aromatic hydrocarbons, and the side chains of the aromatic hydrocarbons are broken by catalytic cracking, thereby reducing the hydrogen consumption. The heavy fraction is processed after being lightened by a delayed coking device, and there is no hydrogen consumption in the catalytic cracking and delayed coking processes. Therefore, the overall hydrogen consumption in the processing of ethylene tar is low, and the catalytic cracking and delayed coking devices are conventional lightening devices in a refinery, which generally do not need to be newly built, thereby reducing the investment cost.

[0041] Next, the system of the present application is used to produce light aromatic hydrocarbons from ethylene tar to test the performance of the system.

[0042] Test Test 1

[0043] The ethylene tar 1 is fed into a flash device 2 to be fractionated into a light fraction of ethylene tar and a heavy fraction of ethylene tar. The light fraction of ethylene tar is fed into a hydrogenation device 4 to react with hydrogen 5 to occur selective hydrogenation saturation reaction, and a hydrogenated light fraction is obtained and fed into a catalytic cracking riser 7 to occur catalytic cracking reaction. The obtained catalytic cracking reaction oil gas is fed into a catalytic cracking fractionating tower 9 through a reaction oil gas pipeline 8 to be fractionated. The catalytic rich gas is discharged through a catalytic rich gas discharge pipeline 10 to a subsequent gas separation unit to obtain low-carbon olefins such as ethylene and propylene. The catalytic cracking sewage is discharged through a catalytic sewage discharge pipeline 11. The catalytic gasoline is fed into an aromatic hydrocarbon combination device 15 through a catalytic gasoline pipeline 12 to be extracted to obtain light aromatic hydrocarbons such as BTX and raffinate gasoline. The catalytic diesel is transported to the hydrogenation device 4 through a catalytic diesel pipeline 13 for back refining.

[0044] The heavy fraction of ethylene tar and the catalytic oil slurry fractionated from the catalytic cracking fractionating tower 9 are preheated in a coking heating furnace 19 and then fed into a coking tower 20 to occur coking reaction. The obtained coking oil gas is fed into a coking fractionating tower 22 to be separated. The coking rich gas is discharged through a coking rich gas discharge pipeline 23 to a subsequent gas separation unit to obtain low-carbon olefins such as ethylene and propylene. The coking sewage is discharged through a coking sewage discharge pipeline 24. The coking diesel is transported to the hydrogenation device 4 through a coking diesel pipeline 26 for back refining. The coking wax oil is discharged through a coking wax oil discharge pipeline 27. The coking gasoline is fed into the aromatic hydrocarbon combination device 15 through a coking gasoline pipeline 25 to be extracted to obtain light aromatic hydrocarbons such as BTX and raffinate gasoline. In this process, the catalytic cracking main air 29 is introduced into the catalytic cracking regenerator 28 to cyclically regenerate the catalytic cracking catalyst.

[0045] The properties of the ethylene tar are shown in Table 1, 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.

[0046] Test Test 2

[0047] The process flow is the same as that described in Test 1, except 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.

[0048] Test 3

[0049] The process flow is the same as that described in Test 1, except that the cutting temperature of the ethylene tar and the reaction temperature of the catalytic cracking are different, 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

[0050] As can be seen from Table 3, the system of the present application can convert ethylene tar into high-value light aromatic products, and the BTX yield can reach more than 20%, and by selecting a suitable ethylene tar cutting temperature or using high-severity reaction conditions, the BTX yield can be further improved, thereby improving the overall economic benefit of the process.

[0051] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A system for producing light aromatics from ethylene tar, characterized by: The invention comprises a flash evaporation device (2) for fractionating ethylene tar (1), a hydrogenation device (4) connected to the light fraction outlet of the flash evaporation device (2), and a coking tower (20) connected to the heavy fraction outlet of the flash evaporation device (2); The downstream of the hydrogenation device (4) is connected in sequence with a catalytic cracking riser (7) and a catalytic cracking fractionation tower (9; A coking fractionation tower (22) is connected downstream of the coking tower (20); The catalytic diesel outlet of the catalytic cracking fractionation tower (9) and the coking diesel outlet of the coking fractionation tower (22) are both connected to the hydrogenation unit (4) through pipelines; The catalytic gasoline outlet of the catalytic cracking fractionator (9) and the coking gasoline outlet of the coking fractionator (22) are both connected to an aromatics complex (15) through pipelines to obtain light aromatics (16).

2. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: The light fraction outlet of the flash evaporation device (2) is connected to the hydrogenation device (4) through the ethylene tar light fraction pipeline (3); the catalytic diesel distilled from the catalytic cracking fractionation tower (9) and the coking diesel distilled from the coking fractionation tower (22) are both connected to the ethylene tar light fraction pipeline (3) through pipelines.

3. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: The heavy fraction outlet of the flash evaporation 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).

4. The system for producing light aromatics from ethylene tar according to claim 3, characterized in that: The catalytic oil slurry fractionated by the catalytic cracking fractionation tower (9) is connected to the ethylene tar heavy fraction pipeline (18) through the catalytic oil slurry pipeline (14), and the connection point between the catalytic oil slurry pipeline (14) and the ethylene tar heavy fraction pipeline (18) is located upstream of the coking heating furnace (19).

5. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: The ethylene tar heavy fraction pipeline (18) is connected to the bottom of the coking tower (20), and the top of the coking tower (20) is provided with a coking oil and gas pipeline (21) connected to the coking fractionation tower (22).

6. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: A coking wax oil discharge pipeline (27) is provided at the bottom of the coking fractionation tower (22).

7. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: The catalytic cracking riser (7) is connected to a separation unit for separating the mixed materials therein.

8. The system for producing light aromatics from ethylene tar according to claim 7, characterized in that: The separation unit is a settler, and a catalytic cracking regenerator (28) is arranged below the settler.

9. The system for producing light aromatics from ethylene tar according to claim 8, characterized in that: The mixed material after the reaction in the catalytic cracking riser (7) is connected to the settler from the outlet at the upper end thereof, the catalyst separated in the settler is transported to the catalytic cracking regenerator (28) for regeneration, the regenerated catalyst is transported to the catalytic cracking riser (7) for recycling, and the reaction oil and gas separated in the settler is transported to the catalytic cracking fractionation tower (9) through the reaction oil and gas pipeline (8) above the settler.

10. The system for producing light aromatics from ethylene tar according to claim 1, characterized in that: The top of the aromatics combined device (15) is provided with a light aromatics discharge pipeline (16), and the bottom is provided with a raffinate gasoline discharge pipeline (17).

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