A system and method for improving the yield of triolefins and triphenyls in an ethylene plant

Abstract

The invention discloses a method for improving the yield of triolefin triphenyl in an ethylene device, and belongs to the technical field of ethylene production. The invention adds a pre-separation device before the ethylene cracking device, and adds an aromatic extraction device after the ethylene cracking device, so as to perform rectification and separation on the naphtha cracking raw material, and after extraction and separation, the raw material is sent to the ethylene cracking device for split-furnace cracking to produce triolefin triphenyl, and the yield of triolefin triphenyl is improved by setting the optimal cracking reaction temperature and adjusting the optimal dilution steam mass ratio. The process flow of the invention is simple and can be applied to the commercial large-scale industrial production of ethylene products.

Description

Technical Field

[0001] The invention belongs to the technical field of ethylene production, and specifically relates to a method for improving the yields of ethylene, propylene, butadiene, benzene, toluene and xylene by distilling and extracting naphtha NAP to obtain high-quality cracking raw materials for entering a cracking furnace. Background Art

[0002] Ethylene is a basic organic chemical raw material that is a symbol of the petrochemical industry and occupies a very important position in the national economy. The steam pyrolysis unit is one of the few petrochemical production units in the chemical industry that can carry out chemical reactions without any catalyst. The main products of the steam pyrolysis unit are olefin products such as ethylene, propylene, butadiene, and aromatic products such as benzene, toluene, and xylene. In order to advance the technology of steam pyrolysis technology, there are continuous reports on the optimization of cracking raw materials, especially the optimization of naphtha raw materials.

[0003] The invention patent with patent application number CN201110425362.1 discloses a process method and device for optimizing naphtha, which discloses the use of extraction method, using composite solvent to separate naphtha into raffinate oil rich in alkanes and extracted oil rich in cycloalkanes and aromatics, and then using distillation method to separate the extracted oil from the used extractant; the separated and purified raffinate oil is used as cracking raw material to enter the ethylene cracking device for cracking, and the extracted oil is used as reforming raw material to enter the catalytic reforming device for reforming. Based on the adsorption separation and extraction separation of naphtha raw materials, this method designs a process flow for optimizing the utilization of naphtha, adopts extraction separation technology to separate naphtha into raffinate oil rich in alkanes and extracted oil rich in cycloalkanes and aromatics; and then successively undergoes water washing, stripping, and distillation processes to recycle the extractant. It saves resources, reduces energy consumption, is conducive to sustainable development, helps to improve the level of the entire oil refining and ethylene industry, and has great economic benefits, environmental benefits, and social benefits. However, the patent only discloses the naphtha extraction and separation technology, the technical scheme that the raffinate oil is rich in alkanes, and the extracted oil is rich in cycloalkanes and aromatics. The raffinate oil is only rich in alkanes and does not contain cycloalkanes, and the utilization rate of naphtha as a cracking raw material is not high.

[0004] The invention patent with patent application number CN201210333626.5 discloses a method for increasing the production of light olefins and aromatics by steam cracking of naphtha, and discloses a method for increasing the production of light olefins and aromatics by steam cracking of naphtha with an aromatic content of 9% or more as raw material. The method adds a backwash-free polar solvent extraction aromatics system before the steam cracking device, reduces the aromatics content in the naphtha cracking raw material; improves the selectivity of olefins in the cracking process, directly increases the yield of light olefins, and reduces the coking rate of the equipment and the temperature of the cracking reaction, and prolongs the decoking cycle. The method effectively recovers the aromatic components while pretreating the cracking raw material feed, so that the total aromatics yield is increased by more than 40% compared with the case without pretreatment. The method uses a backwash-free solvent extraction process, optimizes the cracking raw material, expands the source of raw materials, increases the yield of light olefins and aromatics, and effectively reduces the energy consumption of the device and equipment investment. However, the patent only discloses a technical solution for treating naphtha raw materials by using a newly added backwash-free solvent extraction pre-separation process, and three separation tower systems are required to achieve the purpose of material separation.

[0005] The invention patent with patent application number CN202010682905.7 discloses a high-yield device and method for low-carbon olefins and aromatics, including two riser reactors, two settlers, two fractionating towers, a gasoline hydrodesulfurization device, a gasoline cutting distillation device and an aromatics extraction device. The first riser reactor, the first settler, the catalytic gasoline outlet of the first fractionating tower, the feed inlet of the second riser reactor, the second settler, the second fractionating tower, the catalytic gasoline outlet of the second fractionating tower, the gasoline hydrodesulfurization device, the gasoline cutting distillation device, and the gasoline heavy fraction outlet of the gasoline cutting distillation device are connected in sequence to the aromatics extraction device. The high-yield device has a simple structure and uses a catalytic cracking-aromatics extraction combined process to process low-quality heavy oil. While producing low-carbon olefins and aromatics, it does not produce low-quality catalytic gasoline and catalytic diesel, realizing the transformation of the refining device to the chemical device, and has significant economic and social benefits. However, this patent only discloses devices and methods for producing more low-carbon olefins and aromatics. It is necessary to set up a catalytic cracking device, a gasoline hydrodesulfurization device, a gasoline cutting distillation device, and an aromatics extraction device to realize the transformation of the refining device into a chemical device. Summary of the invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for improving the triolefin triphenyl yield of an ethylene plant, so as to solve the problems of low triolefin triphenyl yield, low naphtha raw material utilization and long process flow in the prior art.

[0007] Technical solution: To solve the above technical problems, the present invention adopts the following technical solution:

[0008] A system for improving the triolefin triphenyl yield of an ethylene unit, comprising a pre-separation unit, an ethylene cracking unit, an aromatics extraction unit, and a cracked gasoline hydrogenation unit;

[0009] The pre-separation device is connected to the ethylene cracking device and the aromatics extraction device through pipelines respectively;

[0010] The ethylene cracking device is connected to the pyrolysis gasoline hydrogenation device through a pipeline, and the pyrolysis gasoline hydrogenation device is connected to the aromatics extraction device through a pipeline.

[0011] The method for preparing triolefin triphenyls by using the system for improving the triolefin triphenyls yield of the ethylene device is as follows: in an ethylene cracking device with a nominal capacity of 11.5 to 3 million tons / year, firstly, naphtha is sent to a dividing wall tower of a pre-separation device, and C5 and below fractions, C6 to C8 fractions, and C9 and above fractions in the naphtha are separated by a rectification separation method; secondly, the naphtha of the C6 to C8 fraction is sent to an aromatics extraction device, and aromatics and non-aromatics in the C6 to C8 fractions are separated by an extraction separation method; then, the non-aromatic residual naphtha is sent to a cracking furnace of the ethylene cracking device for split-furnace cracking reaction; finally, the cracked gas flowing out of the cracking furnace is separated and refined to obtain olefin products such as ethylene, propylene, butadiene, and aromatic products such as benzene, toluene, and xylene; and at the same time, the aromatics extraction device also obtains aromatic products such as benzene, toluene, and xylene by extraction separation.

[0012] A stream of material enters the middle side of the partition wall tower of the pre-separation device, which is naphtha from outside the boundary; three streams of material are discharged from the top of the tower, the other side of the middle, and the bottom of the tower, which are light naphtha of C5 and below fractions, medium naphtha of C6-C8 fractions, and heavy naphtha of C9 and above fractions; a partition wall is set in the tower to prevent the feed on one side of the middle from mixing with the discharge on the other side of the middle.

[0013] The ethylene cracking unit sets different cracking reaction temperatures and adjusts different dilution steam mass ratios according to the properties of different cracking raw materials to maximize the yield of triolefins and triphenyls in the cracking gas flowing out of the cracking furnace.

[0014] The cracking gasoline hydrogenation unit adopts a full-fraction two-stage hydrogenation reaction process. After hydrogenation, the fractions are separated to obtain three streams of materials, namely hydrogenated C5, C6-C8 fraction hydrogenated gasoline, and hydrogenated C9.

[0015] The process of the present invention is as follows:

[0016] The naphtha (101) from outside the boundary enters the pre-separation device (P), and is separated by distillation in the dividing wall tower of the pre-separation device (P). The naphtha (101) is divided into three parts: C5 and below fractions are light naphtha (102), C9 and above fractions are heavy naphtha (103), and C6-C8 fractions are medium naphtha (104). The light naphtha (102) and heavy naphtha (103) are respectively sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The medium naphtha (104) is sent to the aromatic extraction device (A), and the hydrogenated gasoline (109) is also sent to the aromatic extraction device (A). The aromatics and non-aromatics in the medium naphtha and the hydrogenated gasoline are separated by extraction separation in the extraction tower, and the residual naphtha (108) of the non-aromatics flowing out of the aromatic extraction device (A) is sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The ethylene cracking device (E) undergoes steam thermal cracking reaction, and the effluent cracking gas is separated and refined to obtain hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), cracked gasoline (105), and cracked tar (206), wherein the hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), and cracked tar (206) are sent out of the boundary as products or by-products. The remaining cracked gasoline (105) is sent to the cracked gasoline hydrogenation device (G), and the fractions are separated after the whole fraction is hydrogenated, and the hydrogenated gasoline is divided into three, wherein the hydrogenated carbon five (106) and the hydrogenated carbon nine (107) are respectively sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The hydrogenated gasoline (109) of the C6-C8 fraction and the medium naphtha (104) are sent to the aromatic extraction unit (A), and separated by extraction in the extraction tower. The residual oil (108) is returned to the ethylene cracking unit (E) to obtain benzene (207), toluene (208) and C8 aromatics (209) as by-products and sent out of the unit.

[0017] The process parameters of the present invention are as follows:

[0018] The feed material at the middle side of the dividing wall tower of the pre-separation device (P) is naphtha (101); the discharge materials at the tower top, the other middle side, and the tower bottom are light naphtha (102), medium naphtha (104), and heavy naphtha (103), respectively; the operating pressure is 0.03-0.09 MPaA, the tower top operating temperature is -8-22°C, and the tower bottom operating temperature is 112-152°C;

[0019] The pyrolysis reaction temperature of the steam of the cracking raw material of the light naphtha (102) in the cracking furnace of the ethylene cracking unit (E) is 820-860°C, the reaction pressure is 0.14-0.22MPaA, and the mass ratio of the dilution steam is DS:HC=0.50-0.60:1.00;

[0020] The pyrolysis reaction temperature of the heavy naphtha (103) cracking raw material steam of the cracking furnace of the ethylene cracking unit (E) is 820-860°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC=0.50-0.60:1.00;

[0021] The pyrolysis reaction temperature of the ethylene cracking unit (E) cracking furnace for hydrogenating carbon five (106) cracking raw material steam is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC=0.50-0.60:1.00;

[0022] The pyrolysis reaction temperature of the ethylene cracking unit (E) cracking furnace hydrogenated carbon nine (107) cracking raw material steam thermal cracking reaction temperature is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC=0.50-0.60:1.00;

[0023] The steam cracking reaction temperature of the cracking raw material of the raffinate naphtha (108) of the cracking furnace of the ethylene cracking unit (E) is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC=0.45-0.55:1.00;

[0024] The operating pressure of the ethylene distillation tower in the ethylene cracking unit (E) is 1.70 to 2.40 MPaA, the operating temperature at the top of the tower is -38 to -22°C, the operating temperature at the bottom of the tower is -12 to 0°C, and polymerization-grade ethylene products flow out of the top of the tower.

[0025] The operating pressure of the propylene distillation tower in the ethylene cracking unit (E) is 1.70-2.00 MPaA, the operating temperature of the tower top is 40-48°C, the operating temperature of the tower bottom is 48-60°C, and the polymerization-grade propylene product flows out of the tower top.

[0026] The pyrolysis gasoline hydrogenation unit (G) adopts a two-stage hydrogenation reaction process of the whole fraction of pyrolysis gasoline. The reaction pressure in the hydrogenation reactor is 2.0-3.0 MPaA, and the space velocity of fresh pyrolysis gasoline is 2.0-6.0 h -1 The active components of the catalyst are palladium and palladium oxide, the carrier is alumina, the first stage hydrogenation reaction temperature is 40-120°C, the second stage hydrogenation reaction temperature is 220-340°C, the first stage hydrogenation reaction hydrogen-to-oil ratio is 80-150:1, and the second stage hydrogenation reaction hydrogen-to-oil ratio is 300-800:1.

[0027] Beneficial effects:

[0028] The present invention relates to a system and method for improving the triolefin and triphenyl yield of an ethylene device. The system and method comprises the steps of performing rectification and extraction separation on naphtha to obtain high-quality cracking raw materials, which are then fed into an ethylene cracking device for split-furnace cracking. The optimal cracking reaction temperature is set, and the optimal dilution steam mass ratio is adjusted to maximize the triolefin yields of ethylene, propylene, butadiene, etc. and the triphenyl yields of benzene, toluene, xylene, etc. of the cracking gas flowing out of the cracking furnace. The triolefin yield is increased by about 4%, the triphenyl yield is increased by about 2%, and the total triolefin and triphenyl yield is increased by about 6%, thereby achieving good technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention provides a schematic structural diagram of a steam cracking device.

[0030] Figure 1 In the figure, A is an aromatics extraction unit, P is a pre-separation unit, E is an ethylene cracking unit, and G is a cracking gasoline hydrogenation unit.

[0031] 101 is naphtha, 102 is light naphtha, 103 is heavy naphtha, 104 is medium naphtha, 105 is pyrolysis gasoline, 106 is hydrogenated C5, 107 is hydrogenated C9, 108 is raffinate, 109 is hydrogenated gasoline, 201 is hydrogen, 202 is methane, 203 is ethylene, 204 is propylene, 205 is pyrolysis C4, 206 is pyrolysis tar, 207 is benzene, 208 is toluene, and 209 is C8 aromatics. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0033] The naphtha (101) from outside the boundary enters the pre-separation device (P), and is separated by distillation in the dividing wall tower of the pre-separation device (P). The naphtha (101) is divided into three parts: C5 and below fractions are light naphtha (102), C9 and above fractions are heavy naphtha (103), and C6-C8 fractions are medium naphtha (104). The light naphtha (102) and heavy naphtha (103) are respectively sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The medium naphtha (104) is sent to the aromatic extraction device (A), and the hydrogenated gasoline (109) is also sent to the aromatic extraction device (A). The aromatics and non-aromatics in the medium naphtha and the hydrogenated gasoline are separated by extraction separation in the extraction tower, and the residual naphtha (108) of the non-aromatics flowing out of the aromatic extraction device (A) is sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The ethylene cracking device (E) undergoes steam thermal cracking reaction, and the effluent cracking gas is separated and refined to obtain hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), cracked gasoline (105), and cracked tar (206), wherein the hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), and cracked tar (206) are sent out of the boundary as products or by-products. The remaining cracked gasoline (105) is sent to the cracked gasoline hydrogenation device (G), and the fractions are separated after the whole fraction is hydrogenated, and the hydrogenated gasoline is divided into three, wherein the hydrogenated carbon five (106) and the hydrogenated carbon nine (107) are respectively sent to the cracking furnace of the ethylene cracking device (E) for split-furnace cracking. The hydrogenated gasoline (109) of the C6-C8 fraction and the medium naphtha (104) are sent to the aromatic extraction unit (A), and separated by extraction in the extraction tower. The residual oil (108) is returned to the ethylene cracking unit (E), and benzene (207), toluene (208) and C8 aromatics (209) are also obtained as by-products and sent out of the unit.

[0034] Comparative Example 1

[0035] Patent application number CN201210333626.5 in the prior art discloses a method for increasing the production of light olefins and aromatics by steam cracking of naphtha, which discloses a triene yield of 49.05-52.43wt%, a triphenyl yield of 16.10-29.76wt%, and a total triene and triphenyl yield of 65.15-82.19wt%. However, the method has the problems of low triene and triphenyl yield, low naphtha raw material utilization, and long process flow.

[0036] Example 1

[0037] like Figure 1The process flow shown in the figure is a method for improving the triolefin triphenylene yield of an ethylene unit. The nominal capacity is an ethylene cracking unit of 115,000 tons / year. The process parameters are shown in the attached table. Using the method described in the present embodiment, the triolefin yield is 53.51wt%, the triphenylene yield is 18.02wt%, and the total triolefin triphenylene yield is 71.53wt%, achieving good technical results.

[0038] Example 2

[0039] like Figure 1 The process flow shown in the figure is a method for improving the triolefin triphenylene yield of an ethylene plant. The nominal capacity is an ethylene cracking plant of 1 million tons / year. The process parameters are shown in the attached table. By using the method described in the present embodiment, the triolefin yield is 54.42wt%, the triphenylene yield is 20.31wt%, and the total triolefin triphenylene yield is 74.73wt%, achieving good technical effects.

[0040] Example 3

[0041] like Figure 1 The process flow shown in the figure is a method for improving the triolefin triphenylene yield of an ethylene unit. The nominal capacity is an ethylene cracking unit of 1.5 million tons / year. The process parameters are shown in the attached table. Using the method described in the present embodiment, the triolefin yield is 56.84wt%, the triphenylene yield is 30.05wt%, and the total triolefin triphenylene yield is 86.89wt%, achieving good technical results.

[0042] Example 4

[0043] like Figure 1 The process flow shown in the figure is a method for improving the triolefin triphenylene yield of an ethylene plant. The nominal capacity is 3 million tons / year ethylene cracking plant, and a double ethylene cracking production line is set. The process parameters are shown in the attached table. Using the method described in this embodiment, the triolefin yield is 55.80wt%, the triphenylene yield is 25.86wt%, and the total triolefin triphenylene yield is 81.66wt%, achieving good technical effects.

[0044] Table 1 List of process parameters and technical results of the present invention

[0045] Example 1 Example 2 Example 3 Example 4 Nominal capacity of ethylene plant (10,000 tons / year) 11.5 100 150 300 Process parameters Dividing wall column operating pressure (MPaA) 0.03 0.04 0.09 0.07 Dividing wall tower top operating temperature (℃) -8 -2 22 16 Dividing wall tower top operating temperature (℃) 112 126 152 144 Light naphtha reaction temperature (℃) 820 831 860 847 Light naphtha reaction pressure (MPaA) 0.14 0.16 0.22 0.20 Dilution steam mass ratio (m:m) 0.50 0.52 0.60 0.57 Heavy naphtha reaction temperature (℃) 820 831 860 847 Heavy naphtha reaction pressure (MPaA) 0.14 0.16 0.22 0.20 Dilution steam mass ratio (m:m) 0.50 0.52 0.60 0.57 Hydrogenation C5 reaction temperature (℃) 825 834 865 851 Hydrogenation C5 reaction pressure (MPaA) 0.14 0.16 0.22 0.20 Dilution steam mass ratio (m:m) 0.50 0.53 0.60 0.58 Hydrogenation C9 reaction temperature (℃) 825 834 865 851 Hydrogenation carbon nine reaction pressure (MPaA) 0.14 0.16 0.22 0.20 Dilution steam mass ratio (m:m) 0.50 0.53 0.60 0.58 Raffinate naphtha reaction temperature (℃) 825 837 865 858 Raffinate naphtha reaction pressure (MPaA) 0.14 0.15 0.22 0.19 Dilution steam mass ratio (m:m) 0.45 0.48 0.55 0.52 Hydrogenation reaction pressure (MPaA) 2.0 2.3 3.0 2.7 <![CDATA[Fresh pyrolysis gasoline hourly space velocity (h -1 )]]> 2.0 3.2 6.0 4.8 First stage hydrogenation reaction temperature (℃) 40 60 120 80 Second stage hydrogenation reaction temperature (℃) 220 260 340 300 Hydrogen to oil ratio of primary hydrogenation reaction 80 100 150 120 Hydrogen to Oil Ratio in Secondary Hydrogenation 300 400 800 600 Technical Results Triene yield (wt%) 53.51 54.42 56.84 55.80 Triphenyl yield (wt%) 18.02 20.31 30.05 25.86 Total yield of triolefin triphenylene (wt%) 71.53 74.73 86.89 81.66

Claims

1. A method for preparing triolefin triphenyl, characterized in that: The triolefin triphenyl is prepared by a system for improving the triolefin triphenyl yield of an ethylene device, wherein the system for improving the triolefin triphenyl yield of an ethylene device comprises a pre-separation device (P), an ethylene cracking device (E), an aromatics extraction device (A), and a cracked gasoline hydrogenation device (G); The pre-separation device (P) is connected to the ethylene cracking device (E) and the aromatics extraction device (A) through pipelines respectively; The ethylene cracking unit (E) is connected to the pyrolysis gasoline hydrogenation unit (G) through a pipeline, and the pyrolysis gasoline hydrogenation unit (G) is connected to the aromatics extraction unit (A) through a pipeline; The steps include: (1) Naphtha (101) from outside enters the pre-separation device (P), and is separated by distillation in the dividing wall column of the pre-separation device (P). The naphtha (101) is divided into three parts: C5 and below fractions are light naphtha (102), C9 and above fractions are heavy naphtha (103), and C6 to C8 fractions are medium naphtha (104); (2) Light naphtha (102) and heavy naphtha (103) are respectively sent to the cracking furnace of the ethylene cracking unit (E) for separate cracking, and medium naphtha (104) is sent to the aromatics extraction unit (A); (3) Aromatics and non-aromatics in the naphtha and hydrogenated gasoline are separated by extraction separation in the extraction tower of the aromatics extraction unit (A), and the non-aromatics residual naphtha (108) flowing out of the aromatics extraction unit (A) is sent to the cracking furnace of the ethylene cracking unit (E) for separate cracking; (4) The ethylene cracking unit (E) performs steam thermal cracking reaction, and the effluent cracking gas is separated and refined to obtain hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), cracked gasoline (105), and cracked tar (206), wherein the hydrogen (201), methane (202), ethylene (203), propylene (204), cracked carbon four (205), and cracked tar (206) are sent out of the boundary as products or by-products; (5) The pyrolysis gasoline (105) is sent to the pyrolysis gasoline hydrogenation unit (G), and after the whole fraction is hydrogenated, the fraction is separated to separate the hydrogenated gasoline into three parts: hydrogenated C5 (106), hydrogenated C9 (107), and hydrogenated gasoline of C6-C8 fraction (109); wherein the hydrogenated C5 (106) and hydrogenated C9 (107) are respectively sent to the cracking furnace of the ethylene cracking unit (E) for separate cracking; (6) The hydrogenated gasoline (109) of the C6-C8 fraction and the medium naphtha (104) are sent to the aromatics extraction unit (A), and the residual naphtha (108) is returned to the ethylene cracking unit (E) through extraction separation in the extraction tower. Benzene (207), toluene (208) and C8 aromatics (209) are also obtained as by-products and sent out of the unit; The ethylene cracking unit (E) cracking furnace light naphtha (102) cracking raw material steam thermal cracking reaction temperature is 820-860°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC = 0.50-0.60:1.00; The ethylene cracking unit (E) has a (103) cracking furnace heavy naphtha cracking raw material steam thermal cracking reaction temperature of 820-860°C, a reaction pressure of 0.14-0.22 MPaA, and a dilution steam mass ratio of DS:HC = 0.50-0.60:1.00; The ethylene cracking unit (E) cracking furnace hydrogenates C5 (106) cracking raw material steam thermal cracking reaction temperature is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC = 0.50-0.60:1.00; The ethylene cracking unit (E) cracking furnace hydrogenated carbon nine (107) cracking raw material steam thermal cracking reaction temperature is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC = 0.50-0.60:1.00; The steam cracking reaction temperature of the raffinate naphtha (108) cracking raw material of the cracking furnace of the ethylene cracking unit (E) is 825-865°C, the reaction pressure is 0.14-0.22MPaA, and the dilution steam mass ratio is DS:HC = 0.45-0.55:1.00; The pre-separation device (P) is a dividing wall tower, wherein the feed at the middle side is naphtha (101); the discharges at the top, the other middle side, and the bottom are light naphtha (102), medium naphtha (104), and heavy naphtha (103), respectively; the operating pressure is 0.03-0.09 MPaA, the operating temperature at the top is -8-22°C, and the operating temperature at the bottom is 112-152°C; The pyrolysis gasoline hydrogenation unit (G) adopts a two-stage hydrogenation reaction process of the whole fraction of pyrolysis gasoline. The reaction pressure in the hydrogenation reactor is 2.0-3.0 MPaA, and the space velocity of pyrolysis gasoline is 2.0-6.0 h -1 The active components of the catalyst are palladium and palladium oxide, the carrier is alumina, the first stage hydrogenation reaction temperature is 40-120°C, the second stage hydrogenation reaction temperature is 220-340°C, the first stage hydrogenation reaction hydrogen-to-oil ratio is 80-150:1, and the second stage hydrogenation reaction hydrogen-to-oil ratio is 300-800:1.

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