Clean diesel oil production system and production process

Abstract

The invention discloses a clean diesel oil production system and a clean diesel oil production process. The clean diesel oil production system comprises a normal pressure device and a hydrogenation device, and the hydrogenation device comprises a gas-phase hydrogen mixing unit, a gas-phase hydrogenation reactor, a gas-liquid separation unit, a mixed hydrogen dissolving unit and a liquid-phase hydrogenation reactor which are communicated in sequence; a side-line diesel oil raw material outlet of the normal pressure device is communicated with a diesel oil raw material inlet of the gas-phase hydrogen mixing unit; a liquid-phase component outlet of the gas-liquid separation unit is communicated with an inlet of the hydrogen mixing and dissolving unit. The system and the process provided by the invention can directly process the side-draw diesel oil raw material of the normal-pressure device, greatly reduce the energy consumption and the operation cost of the device, and are suitable for modification and upgrading of refinery plant devices for producing clean diesel oil.

Description

Technical Field

[0001] The invention belongs to the field of clean oil refining, and in particular relates to a clean diesel production system and a production process. Background Art

[0002] As people's living standards improve, they pay more and more attention to environmental protection issues, and accordingly formulate more stringent environmental protection laws and regulations, especially in the field of automotive oil products. The current National VI diesel standard requires the sulfur content of refined diesel to be less than 10µg / g, and the automotive diesel standards in the following stages have lower restrictions on the aromatic content of refined oil varieties. In addition, the world's crude oil is showing a trend of becoming heavier and inferior, and the quality of secondary processed products such as catalytic diesel and coking diesel has declined, and the content of impurities such as sulfur and nitrogen has become higher and higher. Therefore, it is necessary to improve existing processes and develop new processes, which is a new direction that needs to be studied in the field of oil refining.

[0003] At present, the main processing method for the production of refined diesel is still hydrofining, which removes impurities such as sulfur, nitrogen, oxygen, and metals in the raw oil by hydrogenation under certain conditions, and saturates a certain proportion of aromatics. In the diesel fraction, as the oil product distillation range becomes heavier, the content of impurities such as sulfur and nitrogen in the oil product increases accordingly. At the same time, the content of aromatics, especially polycyclic aromatic hydrocarbons, increases accordingly. The processing and removal of oil products are more difficult. Moreover, as the oil product fraction becomes heavier, the molecular weight of the corresponding sulfide also increases accordingly, and the amount of sulfides containing methyl substituents such as dibenzothiophene and 4,6-dimethyldibenzothiophene will also increase accordingly. Due to its large molecular weight and the steric hindrance caused by the methyl substituents contained in the molecule, it is difficult for the sulfur atoms on the molecule to contact the active center on the catalyst, resulting in a significant increase in the difficulty of removing sulfides from the oil product. On a catalyst with suitable acidity and acid amount, the removal rate of sulfides can be increased by increasing the reaction temperature. As the raw material distillation range becomes heavier, the molecules of nitrides also become larger, and the content of nitrides also increases accordingly. Their removal is closely related to the pressure of the reaction system. The use of catalysts with excellent hydrogenation performance can significantly improve the removal rate of nitrides under higher reaction pressure conditions.

[0004] CN111321005A discloses a low-energy consumption, long-cycle diesel production hydrogenation process, the raw material is separated into light and heavy materials, the heavy fraction raw oil enters the first reactor for hydrogenation refining reaction, the light fraction is mixed with the outflow material of the first reactor and enters the second reactor for hydrogenation refining reaction, and the outflow material of the second reactor is separated by a gas-liquid separator and enters the subsequent fractionation system. In this method, the raw material is fractionated in advance to obtain the light and heavy components, and two feeding systems are used, which increases the investment cost of the device and increases the energy consumption of the device.

[0005] CN102443429A discloses a hydroprocessing method for producing ultra-low sulfur diesel, which is carried out by dissolving all hydrogen I into diesel fraction raw oil to enter the first reaction zone for liquid phase hydrogenation reaction, reacting at a reaction temperature of 340-400°C, and mixing the effluent of the first hydrogenation reactor with hydrogen II to enter the second hydroprocessing reaction zone, contacting with a hydroprocessing catalyst in a pure liquid phase or low hydrogen-to-oil ratio state, and reacting at a reaction temperature of 240-320°C; the effluent of the second hydroprocessing reaction zone is cooled and separated to obtain a diesel product. In this processing method, since the hydrogen required for the reaction is mainly provided by dissolved hydrogen, for oil products containing a large proportion of secondary processed diesel in the raw materials, the reaction hydrogen consumption is high, and the hydrogen dissolved in the oil products is insufficient to meet the reaction requirements. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a clean diesel production system and production process. The system and process of the present invention can directly process diesel raw materials produced from the side line of the atmospheric pressure device, greatly reducing the energy consumption and operating costs of the device, and is suitable for the transformation and upgrading of refinery devices for producing clean diesel.

[0007] The clean diesel production system of the present invention comprises a normal pressure device and a hydrogenation device, wherein the hydrogenation device comprises a gas phase hydrogenation unit, a gas phase hydrogenation reactor, a gas-liquid separation unit, a mixed hydrogenation unit and a liquid phase hydrogenation reactor which are connected in sequence; the side line diesel feedstock outlet of the normal pressure device is connected to the diesel feedstock inlet of the gas phase hydrogenation unit; the liquid phase component outlet of the gas-liquid separation unit is connected to the inlet of the mixed hydrogenation unit.

[0008] The gas phase hydrogen mixing unit is used to mix the diesel raw material drawn out from the side with hydrogen. The gas phase hydrogen mixing unit is provided with a diesel raw material inlet, a hydrogen inlet and a hydrogen mixed material outlet. The hydrogen mixed material outlet is connected to the raw material inlet of the gas phase hydrogenation reactor. The gas phase hydrogen mixing unit adopts a commercial ceramic membrane tube hydrogen mixer, and may also adopt a common baffle plate hydrogen mixer, etc. The gas phase hydrogen mixing unit ensures the vaporization of the diesel component drawn out from the side line, and replenishes the hydrogen required for the desulfurization reaction of the diesel component.

[0009] The gas phase hydrogenation reactor is a fixed bed reactor, which is used to carry out gas phase hydrogenation reaction on diesel feedstock and hydrogen to obtain hydrodesulfurization products. The gas phase hydrogenation reactor is filled with hydrodesulfurization catalyst; the upper part or top of the gas phase hydrogenation reactor is provided with a feedstock inlet, and the lower part or bottom is provided with a hydrodesulfurization product outlet.

[0010] The gas-liquid separation unit is used to separate the gas-phase hydrogenation product into a liquid component and a gas component, wherein the liquid component enters the mixed hydrogen dissolving unit after being pressurized by a booster pump. The structure of the gas-liquid separation unit is not particularly limited and can be a conventional choice in the art, for example, a gas-liquid separator. The gas-liquid separation unit is provided with a gas-phase component outlet at the top and a liquid-phase component outlet at the bottom.

[0011] The mixed hydrogen dissolving unit is used to supplement the hydrogen required for the liquid phase component to supplement the reaction. The mixed hydrogen unit is preferably able to meet the reaction conditions and hydrogen consumption requirements in the liquid phase hydrogenation reactor. The present invention has no special limitation on the selection of the mixed hydrogen dissolving unit, as long as the liquid phase component can be mixed with hydrogen. Preferably, the mixed hydrogen dissolving unit is selected from at least one of a membrane tube type hydrogen dissolving assembly, a hydrogen mixer (which can be a high-efficiency hydrogen mixer), a microbubble generator and a bubble fractalizer. For example, a hydrogen mixer with strong convection back mixing or a hydrogen mixer with micropores to generate microbubbles is used to increase the solubility. It is preferred to use a support plate with evenly distributed pores and downcomers to increase the gas phase dispersion.

[0012] The liquid phase hydrogenation reactor is a fixed bed reactor, which is used to carry out liquid phase hydrogenation reaction on the pressurized hydrogenated logistics to obtain liquid phase hydrogenation reaction products. The liquid phase hydrogenation reactor is filled with a hydrogenation dearomatization catalyst. The bottom of the liquid phase hydrogenation reactor is provided with a liquid phase hydrogenation reaction product outlet.

[0013] The clean diesel production system of the present invention also includes a condensing unit, which is used to partially liquefy the gas phase components of the gas-liquid separation unit. The liquefied components can enter the subsequent stripping separation unit as diesel components or directly serve as ethylene cracking materials. The gas phase components can be recycled after hydrogen sulfide is removed by the circulating hydrogen desulfurization system.

[0014] The clean diesel production system of the present invention further comprises a stripping unit, the inlet of which is connected to the outlet of the liquid phase hydrogenation reaction product of the liquid phase hydrogenation reactor and / or to the outlet of the gas phase component of the gas-liquid separation unit. The stripping unit is used to perform hydrogen sulfide removal treatment on the liquid phase hydrogenation reaction product and / or the liquid phase component after liquefaction of the gas phase obtained by the gas-liquid separation unit.

[0015] Preferably, the liquid phase hydrogenation reaction product outlet of the liquid phase hydrogenation reactor is connected to the gas phase component outlet of the gas-liquid separation unit for mixing the liquid phase hydrogenation reaction product and the gas phase component obtained by the gas-liquid separation unit and then performing hydrogen sulfide removal treatment.

[0016] The present invention also provides a production process for clean diesel, comprising the following steps: (1) The diesel feedstock extracted from the side line of the atmospheric pressure device is directly introduced into the gas phase hydrogenation unit and mixed with hydrogen, and then enters the gas phase hydrogenation reactor, where it undergoes a hydrodesulfurization reaction with a hydrodesulfurization catalyst under gas phase hydrogenation conditions to obtain a hydrodesulfurization product; (2) The hydrodesulfurization product is separated into gas and liquid. After separation, the liquid component is pressurized and mixed with hydrogen before entering the liquid phase hydrogenation reactor to undergo a liquid phase hydrogenation reaction with the hydrodearomatization catalyst to obtain a liquid phase hydrogenation reaction product.

[0017] In the process of the present invention, the properties of the diesel raw material extracted from the side line of the atmospheric pressure device are as follows: distillation range is 160~385℃, density ≯0.88g / m 3 , S≯20000μg / g, N≯1000μg / g, polycyclic aromatic hydrocarbon content≯20wt%. The temperature range of the sideline diesel is 160~380℃, preferably 280~350℃, and the extraction pressure can be consistent with the operation of the atmospheric tower in the atmospheric device.

[0018] In the process of the present invention, the operating conditions of the gas phase reactor are as follows: pressure of 0.1-3.0 MPa, preferably 0.5-2.0 MPa; hydrogen-to-oil volume ratio of 20-500, preferably 50-200; temperature of 280-400°C, preferably 300-380°C; volume space velocity of 0.1-4.0 h -1 , preferably 0.8~2.0h -1 .

[0019] In the process of the present invention, the hydrodesulfurization catalyst is a conventional supported catalyst, wherein the support is an inorganic refractory oxide selected from one or more of alumina, amorphous silica-alumina, silicon dioxide or titanium oxide, etc.; the hydrogenation active metal includes a metal component of Group VIB and / or Group VIII, wherein Group VIB is selected from tungsten and / or molybdenum, and Group VIII is selected from nickel and / or cobalt. For example, the Mo-Co type FHUDS-5 and FHUDS-7 catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. (abbreviated as FRIPP) are diesel hydrofining catalysts.

[0020] In the process of the present invention, protective agents with different functions can be graded in the gas phase hydrogenation reactor, such as the FBN series bird's nest protective agent developed by FRIPP, which can significantly reduce the increase of bed pressure drop. For raw materials containing Si impurities, the FHRS series silicon trapping agent developed by FRIPP can be graded. For raw materials containing arsenic impurities, the FDAS arsenic removal agent developed by FRIPP can be graded.

[0021] In the process of the present invention, the pressurization process generally passes through a booster pump and then enters a mixed hydrogen dissolving unit for hydrogen mixing. The material after hydrogen mixing meets the reaction conditions of a liquid phase hydrogenation reactor and provides the required hydrogen for reactions such as hydrogenation dearomatization and hydrogenation denitrogenation occurring in the liquid phase hydrogenation reactor. The amount of hydrogen mixing can be calculated based on the hydrogen-consuming substances in the raw materials, and the amount of hydrogen mixing can be set in excess.

[0022] In the process of the present invention, the conditions of the liquid phase hydrogenation reaction are as follows: pressure 2~12.0MPa, preferably 4~10.0MPa; temperature 200~400°C, preferably 300~380°C; volume space velocity 0.1~4.0, preferably 0.5~2.0.

[0023] In the process of the present invention, the hydrodearomatization catalyst comprises a carrier and a hydrogenation active metal component; the hydrogenation active metal comprises a metal component of Group VIB and / or Group VIII, wherein Group VIB is selected from tungsten and / or molybdenum, and Group VIII is selected from nickel and / or cobalt. The hydrorefining catalyst is, for example, the Mo-Ni type FHUDS-10 catalyst developed by FRIPP.

[0024] In the process of the present invention, the liquid phase material after condensation of the gas phase component obtained by the gas-liquid separation can be used as ethylene cracking material, or mixed with the effluent of the liquid phase hydrogenation reactor and then stripped and fractionated to obtain a refined diesel component with an S content of less than 10 μg / g and an aromatics content of less than 5wt%.

[0025] Compared with the existing diesel production technology, the present invention has the following advantages: (1) The present invention directly combines the hydrogenation device with the atmospheric pressure device. The diesel raw material extracted from the side line is directly mixed with hydrogen (generally using pipeline hydrogen) without heat exchange and enters the gas phase reactor for gas phase hydrogenation reaction to remove the sulfide in the raw material. The raw material meets the feed requirements of the gas phase reactor, eliminating the need for heating equipment and reducing the investment cost of the device. At the same time, the raw material directly enters the device for processing and does not need to be stored in the tank area, which reduces the possibility of increased rubber quality and increased processing difficulty caused by storage of the raw material, and extends the operation cycle of the device. The present invention can be directly modified and upgraded on the existing atmospheric pressure device.

[0026] (2) The conventional diesel hydrorefining process generally only cuts the fractions and performs hydrotreatment according to the molecular size. It is impossible to perform separate hydrotreatment on different types of impurities, which results in mutual restriction between the hydrotreatment processes of different impurities, affecting the efficiency of the hydrotreatment reaction and over-hydrogenation. The present invention uses the high-temperature and low-pressure gas phase reaction process in the first step to cause a desulfurization reaction under relatively low pressure and high temperature conditions without or with less denitrification and aromatic saturation reactions, thereby reducing the inhibition of the desulfurization reaction by ammonia generated by the denitrification reaction under conventional reaction conditions, which is beneficial to the desulfurization reaction. The hydrogen sulfide generated after the gas phase reaction desulfurization is directly discharged from the top of the gas-liquid separator without entering the liquid phase hydrogenation reactor, thereby reducing the inhibition of hydrogen sulfide on the denitrification reaction in the liquid phase hydrogenation reactor, thereby improving the denitrification and aromatic saturation efficiency of the second reactor. This process performs separate hydrotreatments on desulfurization, denitrification and aromatic saturation, greatly improving the reaction efficiency of each.

[0027] (3) The present invention can set different reaction systems and reaction conditions according to the characteristics of different substances, thereby reducing the reaction hydrogen consumption of the device. Under high temperature and low pressure conditions, the gas phase hydrogenation reactor is loaded with a MoCo catalyst with good direct desulfurization activity in the reactor. Under conditions that are not conducive to hydrodesulfurization, the sulfide in the raw material is removed through the direct desulfurization path, thereby reducing the hydrogen consumption of the desulfurization reaction. At the same time, the hydrogen consumption required for desulfurization is calculated according to the desulfurization rate, which can reduce the reaction hydrogen oil volume ratio and thus reduce the reaction hydrogen consumption. By setting up a liquid phase hydrogenation reactor, the denitrogenation and aromatic saturation reactions can be controlled at a higher pressure in the liquid phase hydrogenation reactor. By dissolving hydrogen in the oil product, the mass transfer efficiency of hydrogen to the catalyst surface can be improved, which is beneficial to the hydrogenation reaction. At the same time, a hot separator is set between the two reactors. The temperature of the material at the separator outlet is relatively high. In addition, the material needs to be pressurized before entering the liquid phase reactor, which can increase the amount of hydrogen dissolved, which is beneficial to the hydrogenation reaction and the energy consumption of the device is reasonably utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a production process of clean diesel of the present invention; Among them, diesel raw materials-1 and hydrogen-2; hydrogen mixing unit-3; gas phase hydrogenation reactor-4; gas-liquid separation unit-5; liquid separation tank-6; high-fraction gas-7; booster pump-8; mixed hydrogen dissolution unit-9; liquid phase hydrogenation reactor-10; stripping fractionation system-11; refined naphtha product-12; clean diesel product-13. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with embodiments, but it should be understood that the protection scope of the present invention is not limited by the embodiments.

[0030] In the present invention, unless otherwise specified, percentages and contents are all based on mass. Figure 1 The process flow of the present invention is described in detail.

[0031] The invention discloses a production process of clean diesel, comprising a normal pressure device, a hydrogenation device and a stripping fractionation system, wherein the hydrogenation device comprises a gas-phase hydrogenation unit, a gas-phase hydrogenation reactor, a gas-liquid separation unit, a mixed hydrogenation unit and a liquid-phase hydrogenation reactor which are connected in sequence; the gas-phase hydrogenation unit 3 is provided with a diesel feedstock inlet, a hydrogen inlet and a hydrogenation material outlet, and the diesel feedstock 1 and the hydrogen 2 are mixed in the gas-phase hydrogenation unit 3 and then enter the gas-phase hydrogenation reactor 4 for hydrogenation reaction, and the gas-phase hydrogenation reactor 4 can be provided with a feedstock inlet at the upper part or the top, and a hydrodesulfurization product outlet at the lower part or the bottom. The hydrodesulfurization product enters the gas-liquid separation unit 5 for gas-liquid separation to obtain gas phase components and liquid phase components, wherein the gas phase component enters the liquid separator 6 after cooling to separate the high-fraction gas 7 and the light naphtha component; the liquid phase component separated by the separator 5 is pressurized by the booster pump 8 and enters the mixed hydrogen dissolving unit 9, and the mixed material enters the liquid phase hydrogenation reactor 10 to undergo liquid phase hydrogenation reaction, and the hydrogenated material is mixed with the light naphtha component separated by the liquid separator and enters the stripping separation unit 11 to obtain the naphtha component 12 and the clean diesel component 13 respectively. Embodiment 1~3

[0032] The above process flow is adopted, and two fixed bed reactors are connected in series. The first reactor is a gas phase hydrogenation reactor, and a separator, a booster pump, and a second reactor are sequentially arranged thereafter. The second reactor is a liquid phase hydrogenation reactor, and a fractionation system is arranged after the second reactor. Among them, 50mL Mo-Co type catalyst A is filled in the first reactor, and catalyst A, the carrier of catalyst A is alumina, contains a small amount of auxiliary agent, the content of active metal Mo in terms of oxide is 23%, the content of active metal Co in terms of oxide is 5%, and the rest is carrier. 50mL Mo-Ni type catalyst B is filled in the second reactor, and the carrier of catalyst B is alumina, contains a small amount of auxiliary agent, the content of active metal Mo in terms of oxide is 24%, the content of active metal Ni in terms of oxide is 4%, and the rest is carrier.

[0033] Ordinary third-line diesel was used as the raw material. The properties of the catalyst are shown in Table 1, the properties of the ordinary third-line diesel raw material are shown in Table 2, and the reaction process conditions and evaluation results are shown in Table 3. Comparative Example 1

[0034] The conventional fixed bed hydrogenation process was adopted, and two hydrogenation reactors were connected in series, namely, reactor 1 and reactor 2. After the reactor, high fractionation, low fractionation, stripping, fractionation and other processes were conventionally arranged to obtain diesel products and naphtha products. Reactor 1 was filled with 50mL Mo-Co type diesel hydrogenation catalyst A, and reactor 2 was filled with 50mL Mo-Ni type diesel hydrogenation catalyst B. Hydrogen was passed once. The raw materials and catalyst properties were the same as those in Examples 1-3, and the reaction process conditions and results were shown in Table 3. Comparative Example 2

[0035] A diesel liquid phase hydrogenation process was adopted, and a hydrogenation reactor was set up. The reactor was loaded with 60 mL of Mo-Ni type catalyst B and 40 mL of Mo-Co type catalyst A (same as in Example 1-3) from top to bottom. High fractionation, low fractionation, stripping and other processes were set up normally after the reactor. The diesel raw material was the same as in Example 1-3, and the reaction process conditions and results are shown in Table 3. Comparative Example 3

[0036] A conventional fixed bed hydrogenation reactor was used to carry out the reaction under normal conditions. The reactor was loaded with 60 mL of Mo-Ni type catalyst B and 40 mL of Mo-Co type catalyst A (same as in Example 1-3) from top to bottom. A separator, stripping and other processes were normally set after the reactor. Hydrogen was passed once. The diesel feedstock was the same as in Example 1-3, and the reaction process conditions and results are shown in Table 3.

[0037] Table 1 Physicochemical properties of catalysts Catalyst No. A B Active Metals Mo-Co Mo-Ni <![CDATA[MoO3,wt%]]> 23.0 24.0 CoO, wt% 5.0 NiO, wt% 4.0 shape Shamrock Shamrock Diameter, mm 1.1～1.3 1.1～1.3 <![CDATA[Specific surface area, m 2 ·g -1 > 214 207 <![CDATA[Pore volume, mL·g -1 > 0.35 0.34 Table 2 Raw oil properties Oil properties <![CDATA[Density (20 °C), kg·m -3 > 854.6 Distillation range, ℃ 221~381 <![CDATA[S,μg·g -1 ]]> 12350 <![CDATA[N,μg·g -1 ]]> 114 PAHs, wt% 14.7 Table 3 Hydrogenation process conditions and results Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Gas Phase Reactor Pressure, MPa 0.5 1.0 1.5 6.0 8.0 6.5 Temperature, °C 360 370 380 370 370 365 Hydrogen to oil volume ratio, v / v 100 150 150 500 - 500 <![CDATA[Space velocity, h -1 > 1.0 1.0 1.0 1.0 0.5 0.5 Liquid Phase Reactor (Reactor 2) Pressure, MPa 6.5 6.5 6.5 6.5 Temperature, °C 340 350 360 360 <![CDATA[Space velocity, h -1 > 1.0 1.0 1.0 1.0 Refined diesel product properties S, μg / g 9.2 7.1 5.4 6.0 6.8 6.3 N, μg / g 3.5 2.7 2.2 2.8 2.6 2.5 PAHs, wt% 4.2 3.7 3.3 3.5 3.7 3.6 Chemical hydrogen consumption, m% 1.2 1.3 1.4 1.4 1.3 1.5

Claims

1. A clean diesel production system, characterized in that The invention comprises a normal pressure device and a hydrogenation device, wherein the hydrogenation device comprises a gas phase hydrogenation unit, a gas phase hydrogenation reactor, a gas-liquid separation unit, a mixed hydrogenation unit and a liquid phase hydrogenation reactor which are connected in sequence; the side line diesel feedstock outlet of the normal pressure device is connected to the diesel feedstock inlet of the gas phase hydrogenation unit; the liquid phase component outlet of the gas-liquid separation unit is connected to the inlet of the mixed hydrogenation unit.

2. The system according to claim 1, characterized in that: The gas phase hydrogen mixing unit is used to mix the diesel feedstock extracted laterally with hydrogen. The gas phase hydrogen mixing unit is provided with a diesel feedstock inlet, a hydrogen inlet and a hydrogen mixed material outlet. The hydrogen mixed material outlet is connected to the feedstock inlet of the gas phase hydrogenation reactor.

3. The system according to claim 1, characterized in that: The gas phase hydrogenation reactor is a fixed bed reactor, which is used to carry out gas phase hydrogenation reaction on diesel feedstock and hydrogen to obtain hydrodesulfurization products. The gas phase hydrogenation reactor is filled with hydrodesulfurization catalyst; the upper part or top of the gas phase hydrogenation reactor is provided with a feedstock inlet, and the lower part or bottom is provided with a hydrodesulfurization product outlet.

4. The system according to claim 1, characterized in that: The gas-liquid separation unit is used to perform gas-liquid separation on the gas-phase hydrogenation product to obtain a liquid component and a gas component, wherein the liquid component enters the mixed hydrogen dissolving unit after being pressurized; the gas-liquid separation unit is provided with a gas-phase component outlet at the top and a liquid-phase component outlet at the bottom.

5. The system according to claim 1, characterized in that: The mixed hydrogen dissolving unit is used to supplement the hydrogen required for the reaction of the liquid phase components; the mixed hydrogen dissolving unit is selected from at least one of a membrane tube hydrogen dissolving component, a hydrogen mixer, a microbubble generator and a bubble fractalizer; preferably, a support plate with evenly distributed pores and a downcomer is used to improve the gas phase dispersion.

6. The system according to claim 1, characterized in that: The liquid phase hydrogenation reactor is a fixed bed reactor, which is used to carry out liquid phase hydrogenation reaction on the pressurized hydrogenated logistics to obtain liquid phase hydrogenation reaction products. The liquid phase hydrogenation reactor is filled with a hydrogenation dearomatization catalyst; and a liquid phase hydrogenation reaction product outlet is arranged at the bottom of the liquid phase hydrogenation reactor.

7. The system according to claim 1, characterized in that: It also includes a condensing unit, which is used to partially liquefy the gas phase components of the gas-liquid separation unit and enter the subsequent stripping unit as a diesel component or ethylene cracking material. The unliquefied gas phase components are recycled after the hydrogen sulfide is removed by the circulating hydrogen desulfurization system.

8. The system according to claim 1, characterized in that: It also includes a stripping unit, the inlet of which is connected to the outlet of the liquid phase hydrogenation reaction product of the liquid phase hydrogenation reactor and / or the outlet of the gas phase component of the gas-liquid separation unit; the stripping unit is used to desulfurize the liquid phase component of the liquid phase hydrogenation reaction product and / or the gas phase obtained by the gas-liquid separation unit after liquefaction.

9. The system according to claim 1, characterized in that: The liquid phase hydrogenation reaction product outlet of the liquid phase hydrogenation reactor is connected to the gas phase component outlet of the gas-liquid separation unit for mixing the liquid phase hydrogenation reaction product with the gas phase component obtained by the gas-liquid separation unit and then performing hydrogen sulfide removal treatment.

10. A process for producing clean diesel, characterized in that The method comprises the following steps: (1) directly introducing the diesel feedstock extracted from the side line of the atmospheric pressure device into a gas phase hydrogenation unit, mixing with hydrogen, and then entering into a gas phase hydrogenation reactor, and reacting with a hydrodesulfurization catalyst under gas phase hydrogenation conditions to produce a hydrodesulfurization product; (2) The hydrodesulfurization product is separated into gas and liquid. After separation, the liquid component is pressurized and mixed with hydrogen before entering the liquid phase hydrogenation reactor to undergo a liquid phase hydrogenation reaction with the hydrodearomatization catalyst to obtain a liquid phase hydrogenation reaction product.

11. The production process according to claim 10, characterized in that: The properties of the diesel raw material extracted from the side line of the atmospheric pressure device are as follows: distillation range is 160~385℃, density ≯0.88g / m 3 , S≯20000μg / g, N≯1000μg / g, polycyclic aromatic hydrocarbons content≯20wt%; the temperature range of the sideline diesel is 160~380℃, preferably 280~350℃, and the extraction pressure is consistent with the operation of the normal pressure device.

12. The production process according to claim 10, characterized in that: The operating conditions of the gas phase reactor are as follows: pressure of 0.1-3.0 MPa, preferably 0.5-2.0 MPa; hydrogen-oil volume ratio of 20-500, preferably 50-200; temperature of 280-400°C, preferably 300-380°C; volume space velocity of 0.1-4.0 h -1 , preferably 0.8~2.0h -1 .

13. The production process according to claim 10, characterized in that: The hydrodesulfurization catalyst is a conventional supported catalyst, wherein the carrier is an inorganic refractory oxide selected from one or more of alumina, amorphous silica-alumina, silicon dioxide or titanium oxide; the hydrogenation active metal includes VIB and / or VIII group metal components, wherein the VIB group is selected from tungsten and / or molybdenum, and the VIII group is selected from nickel and / or cobalt.

14. The production process according to claim 10, characterized in that: One or more of a bird's nest protective agent, a silicon scavenger or a arsenic removal agent is filled in a graded manner in a gas phase hydrogenation reactor.

15. The production process according to claim 10, characterized in that: The conditions of the liquid phase hydrogenation reaction are as follows: pressure 2-12.0 MPa, preferably 4-10.0 MPa; temperature 200-400° C., preferably 300-380° C.; volume space velocity 0.1-4.0, preferably 0.5-2.

0.

16. The production process according to claim 10, characterized in that: The hydrodearomatization catalyst comprises a carrier and a hydrogenation active metal component; the hydrogenation active metal comprises a VIB and / or VIII group metal component, wherein the VIB group is selected from tungsten and / or molybdenum, and the VIII group is selected from nickel and / or cobalt.

17. The production process according to claim 10, characterized in that: The gas phase component obtained by the gas-liquid separation is condensed and the liquid phase material is used as ethylene cracking material, or mixed with the effluent of the liquid phase hydrogenation reactor and then stripped and fractionated to obtain a refined diesel component with an S content of less than 10 μg / g and an aromatics content of less than 5wt%.

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