Method and device for producing diesel oil with low freezing point by using heavy aromatics and mixed diesel oil as raw materials

Abstract

The invention relates to the technical field of gasoline processing, in particular to a method and a device for producing diesel oil with a low freezing point by taking heavy aromatics and mixed diesel oil as raw materials, the method comprises the following steps of: 1, mixing the heavy aromatics, the mixed diesel oil and hydrogen, feeding into a hydrofining unit, and carrying out hydrofining reaction under the action of a hydrofining catalyst, a hydrofining reaction product is obtained; step 2, the hydrofining reaction product enters a hydro-upgrading unit and is subjected to hydro-upgrading reaction under the action of a hydro-upgrading catalyst, and a hydro-upgrading reaction product is obtained; and 3, feeding the hydro-upgrading reaction product into a rectification unit, and carrying out rectification separation to obtain naphtha and-35 # diesel oil with a low freezing point. The heavy aromatics, the hydrogen and the mixed diesel oil are mixed, the obtained mixed material is subjected to hydrofining and hydro-upgrading treatment, the-35 # low-freezing-point diesel oil is obtained, the method has the advantages of being short in technological process and small in equipment investment, the field process does not need to be greatly transformed, and the quality improvement and efficiency improvement effects are remarkable.

Description

Technical Field

[0001] The invention relates to the technical field of gasoline processing, in particular to a method and a device for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials. Background Art

[0002] The conventional low-freezing point diesel production plan mainly uses the first-line diesel and the second-line diesel from the atmospheric vacuum unit to mix in proportion and then send them to the diesel hydrogenation unit for hydrorefining treatment. The freezing point of the product low-freezing point diesel can reach below -37°C. The special low-freezing point diesel production plan uses straight-run diesel and catalytic diesel as raw materials, mainly using hydrogenation decondensation and isomerization decondensation catalysts. The yield of -35# low-freezing point diesel exceeds 73%, and the freezing point of diesel products decreases by more than 30°C. At this stage, refineries mainly use the above two methods to produce low-freezing point diesel components.

[0003] Based on FHIDW diesel hydro-modification and de-condensation technology, Zhang Xuehui and others used the synergistic effect of hydro-modification and de-condensation catalysts and isomerization and de-condensation catalysts to broaden the range of processed raw materials, significantly reduce the pour point of diesel products, maintain a high yield of low-condensation diesel, and further improve the product quality of diesel. In the process of industrial application, 79% straight-run diesel and 21% catalytic diesel were used as mixed raw materials, and all indicators of the -35# diesel produced met the National VI standard.

[0004] The Chinese patent document with the publication number CN103773488A discloses a hydrogenation method for reducing the pour point of diesel. The method contacts the raw oil with a hydrorefining catalyst in the first reaction zone for reaction, separates and fractionates the effluent from the first reaction zone to obtain gas, naphtha fraction, low pour point diesel fraction I, and high pour point heavy diesel fraction; the obtained high pour point heavy diesel fraction enters the second reaction zone, contacts with a hydroreforming and pour point reducing catalyst, and undergoes isomerization cracking and pour point reducing reaction; the effluent from the second reaction zone is separated and fractionated to obtain a low pour point diesel fraction II; the low pour point diesel fraction I and the low pour point diesel fraction II are mixed to obtain a low pour point diesel product. The present invention can flexibly produce low pour point diesel of -10 to -50, the cetane number is greatly improved compared with the raw material, and the content of impurities such as sulfur and nitrogen is greatly reduced, which can meet the Euro IV and Euro V clean diesel standards.

[0005] Taking into account special circumstances, such as insufficient hydrogen resources in the refinery system, urgent increase in naphtha production, lack of hydrogenation degreasing catalyst in the diesel hydrogenation unit, and large amount of secondary processed diesel, the refinery uses conventional hydrogenation catalysts to process straight-run diesel and catalytic diesel to produce -35# low-condensation diesel, and produces naphtha as a by-product, which often leads to bottleneck problems. The bottleneck problems include: the density of -35# low-condensation diesel is inversely proportional to the condensation point. If the density is qualified, the condensation point is unqualified, and vice versa; the naphtha yield cannot be guaranteed and fluctuates greatly.

[0006] Heavy aromatics mainly come from aromatics units. It is a general term for a series of solvents composed of isomers of C9 or C10 heavy aromatics. Its composition is complex, and its main components are trimethylbenzene, tetramethylbenzene and its isomers. The main properties of heavy aromatics are high aromatic content, low freezing point and high density. The main treatment measures at this stage include two methods: one is to directly transfer the product diesel out of the factory, but there are often problems such as uneven density mixing, large density difference, darker color of product mixed diesel, and excessive polycyclic aromatic hydrocarbons in product mixed diesel when the transfer ratio is high; the second is to further deep distillation to produce high-boiling point aromatic solvent oil. Due to the increase in deep distillation equipment, it will bring about the problem of increased investment. The problem of post-processing of heavy aromatics has always plagued the optimized operation of refineries. If the advantages of heavy aromatics (low freezing point and high density) are fully utilized to produce low freezing point diesel, quality and efficiency can be improved. Summary of the invention

[0007] The present invention provides a method and device for producing low-freezing point diesel using heavy aromatics and mixed diesel as raw materials, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of unqualified density and freezing point in the current production of -35# low-freezing point diesel using straight-run diesel and catalytic diesel as raw materials.

[0008] One of the technical solutions of the present invention is achieved by the following measures: A method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials, which is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrotreating unit, where a hydrotreating reaction is carried out under the action of a hydrotreating catalyst to obtain a hydrotreating reaction product; In the second step, the hydrofining reaction product enters the hydro-upgrading unit, and undergoes a hydro-upgrading reaction under the action of a hydro-upgrading catalyst to obtain a hydro-upgrading reaction product; In the third step, the hydrogenation and reforming reaction products enter the distillation unit for distillation separation to obtain naphtha and -35# low-condensing diesel.

[0009] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: In the first step, the feed ratio of heavy aromatics to mixed diesel is 4 to 9:131, and the amount of new hydrogen in hydrogen is 25500Nm 3 / h to 26000Nm 3 / h, the circulating hydrogen volume is 14500Nm 3 / h to 15500Nm 3 / h.

[0010] In the first step above, the mixed diesel includes regular first-line diesel, regular second-line diesel and catalytic diesel, wherein the mass ratio of regular first-line diesel, regular second-line diesel and catalytic diesel is 35:55:10.

[0011] In the first step above, the hydrotreating catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is DN3552.

[0012] In the first step, the process conditions of hydrofining are: reaction pressure 10MPa to 10.5MPa (G), volume hydrogen-to-oil ratio 650 to 700, reaction inlet temperature 315°C to 320°C, and reaction outlet temperature 328°C to 338°C. Preferably, the reaction pressure of the hydrofining unit is 10.5MPa (G), the volume hydrogen-to-oil ratio is 665, the reaction inlet temperature is 317.5°C, and the reaction outlet temperature is 336°C.

[0013] In the second step, the hydrogenation catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is Z-FX11.

[0014] In the above second step, the process conditions of the hydro-upgrading unit are: reaction pressure 10MPa to 10.5MPa (G), reaction inlet temperature 333°C to 335°C, and total bed temperature rise 25°C to 26°C. Preferably, the reaction pressure of the hydro-upgrading unit is 10.3MPa (G), the reaction inlet temperature is 330.5°C, and the total bed temperature rise is 25.5°C.

[0015] In the third step, the feed temperature of the distillation unit is 222°C, the tower bottom temperature is 248°C to 252°C, the tower top temperature is 145°C to 150°C, and the tower top operating pressure is set to 0.145MPa to 0.155MPa. The separated product naphtha is obtained at the top of the distillation tower, and the separated product -35# low-condensing diesel is obtained at the bottom of the tower. Preferably, the bottom temperature of the distillation tower is set to 250°C, the tower top temperature is set to 147°C, and the tower top operating pressure is set to 0.15MPa.

[0016] The second technical solution of the present invention is achieved by the following measures: a device for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials, comprising a hydrofining unit, a hydromodification unit and a distillation unit, the distillation unit comprising a distillation tower, an air cooler, a circulating water cooler and a tower top reflux tank, the feed end of the hydrofining unit is fixedly connected with a raw material pipeline, the feed end of the raw material pipeline is fixedly connected with a heavy aromatics pipeline, a hydrogen pipeline and a mixed diesel pipeline, the discharge end of the hydrofining unit and the feed end of the hydromodification unit are fixedly connected with a dehydrogenation pipeline, and the feed end of the hydrofining unit is fixedly connected with a dehydrogenation pipeline. The reforming pipeline, a de-rectification pipeline is fixedly connected between the discharge end of the hydrogenation reforming unit and the first feed end of the distillation tower, a first cooling pipeline is fixedly connected between the top discharge end of the distillation tower and the feed end of the air cooler, a second cooling pipeline is fixedly connected between the discharge end of the air cooler and the feed end of the circulating water cooler, a third cooling pipeline is fixedly connected between the discharge end of the circulating water cooler and the feed end of the top reflux tank, a naphtha product pipeline is fixedly connected to the discharge end of the top reflux tank, and a -35# low-condensation diesel product pipeline is fixedly connected to the bottom discharge end of the distillation tower.

[0017] The following is a further optimization and / or improvement of the second technical solution of the above invention: A reflux pipeline is fixedly connected between the naphtha product pipeline and the second feed end of the distillation tower.

[0018] The present invention mixes heavy aromatics, hydrogen and mixed diesel, and performs hydrofining and hydromodification treatment on the obtained mixture to obtain -35# low-condensing diesel. The process is short and the equipment investment is small. The on-site process does not need to be significantly modified, and the effect of improving quality and efficiency is remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attached Figure 1 This is a schematic diagram of the process flow of Example 9 of the present invention.

[0020] Attached Figure 1 The codes are: 1 for hydrotreating unit, 2 for hydromodification unit, 3 for distillation tower, 4 for air cooler, 5 for circulating water cooler, 6 for top reflux tank, 7 for raw material pipeline, 8 for heavy aromatics pipeline, 9 for hydrogen pipeline, 10 for mixed diesel pipeline, 11 for dehydromodification pipeline, 12 for dedistillation pipeline, 13 for the first cooling pipeline, 14 for the second cooling pipeline, 15 for the third cooling pipeline, 16 for reflux pipeline, 17 for naphtha product pipeline, and 18 for -35# low-condensing diesel product pipeline. DETAILED DESCRIPTION

[0021] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art.

[0022] In the present invention, unless otherwise specified, the equipment and devices used are all the equipment and devices known and used in the art.

[0023] The present invention will be further described below in conjunction with embodiments: Example 1: Figure 1 As shown, the method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrotreating unit 1, and a hydrotreating reaction is carried out under the action of a hydrotreating catalyst to obtain a hydrotreating reaction product; In the second step, the hydrofining reaction product enters the hydro-upgrading unit 2, and undergoes a hydro-upgrading reaction under the action of a hydro-upgrading catalyst to obtain a hydro-upgrading reaction product; In the third step, the hydrogenation and reforming reaction products enter the distillation unit for distillation separation to obtain naphtha and -35# low-condensing diesel.

[0024] Example 2: As an optimization of the above example, in the first step, the feed ratio of heavy aromatics to mixed diesel is 4 to 9:131, and the amount of new hydrogen in hydrogen is 25500 Nm 3 / h to 26000Nm 3 / h, the circulating hydrogen volume is 14500Nm 3 / h to 15500Nm 3 / h.

[0025] Example 3: As an optimization of the above example, in the first step, the mixed diesel includes regular first-line diesel, regular second-line diesel and catalytic diesel, wherein the mass ratio of regular first-line diesel, regular second-line diesel and catalytic diesel is 35:55:10.

[0026] Example 4: As an optimization of the above example, in the first step, the hydrotreating catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is DN3552.

[0027] Example 5: As an optimization of the above example, in the first step, the process conditions of hydrofining are: reaction pressure 10MPa to 10.5MPa (G), volume hydrogen to oil ratio 650 to 700, reaction inlet temperature 315°C to 320°C, reaction outlet temperature 328°C to 338°C. Preferably, the reaction pressure of the hydrofining unit 1 is 10.5MPa (G), the volume hydrogen to oil ratio is 665, the reaction inlet temperature is 317.5°C, and the reaction outlet temperature is 336°C.

[0028] Example 6: As an optimization of the above example, in the second step, the hydrogenation catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is Z-FX11.

[0029] Example 7: Figure 1 As shown, as an optimization of the above embodiment, in the second step, the process conditions of the hydro-upgrading unit 2 are: reaction pressure 10MPa to 10.5MPa (G), reaction inlet temperature 333°C to 335°C, and total bed temperature rise 25°C to 26°C. Preferably, the reaction pressure of the hydro-upgrading unit 2 is 10.3MPa (G), the reaction inlet temperature is 330.5°C, and the total bed temperature rise is 25.5°C.

[0030] Example 8: Figure 1As shown, as an optimization of the above embodiment, in the third step, the feed temperature of the distillation unit is 222°C, the tower bottom temperature is 248°C to 252°C, the tower top temperature is 145°C to 150°C, and the tower top operating pressure is set to 0.145MPa to 0.155MPa, and the separated product naphtha is obtained at the top of the distillation tower 3 and the separated product -35# low-condensing diesel is obtained at the bottom of the tower. Preferably, the bottom temperature of the distillation tower 3 is set to 250°C, the tower top temperature is set to 147°C, and the tower top operating pressure is set to 0.15MPa.

[0031] The present invention mixes heavy aromatics, mixed diesel and hydrogen and then performs hydrofining and hydromodification treatment to obtain -35# low-condensation diesel. After the heavy aromatics, mixed diesel and hydrogen are mixed, they enter the hydrofining reaction, and hydrodesulfurization, olefin saturation and aromatic saturation reactions are performed in a fixed bed reactor to obtain a hydrofining reaction product. The obtained hydrofining reaction product enters the hydromodification unit 2, and the high carbon chain molecules are hydromodified into short carbon chain molecules in the fixed bed reactor, and the depth of the hydromodification is controlled to obtain the hydromodification reaction product. The hydromodification reaction product enters the distillation tower 3 to separate and obtain the naphtha product and -35# low-condensation diesel. The present invention makes full use of the characteristics of high density and low condensation point of heavy aromatics to improve the properties of the mixed raw material oil. After hydrofining and hydromodification treatment, the density and condensation point of the low-condensation diesel are effectively improved, and the quality of the -35# low-condensation diesel product meets the index requirements.

[0032] Example 9: Figure 1 As shown, the device for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials comprises a hydrofining unit 1, a hydromodification unit 2 and a distillation unit, wherein the distillation unit comprises a distillation tower 3, an air cooler 4, a circulating water cooler 5 and a tower top reflux tank 6, a feed end of the hydrofining unit 1 is fixedly connected with a raw material pipeline 7, a feed end of the raw material pipeline 7 is fixedly connected with a heavy aromatics pipeline 8, a hydrogen pipeline 9 and a mixed diesel pipeline 10, a dehydrogenation modification pipeline 11 is fixedly connected between the discharge end of the hydrofining unit 1 and the feed end of the hydromodification unit 2, and the discharge end of the hydromodification unit 2 is fixedly connected with a dehydrogenation modification pipeline 11. A de-distillation pipeline 12 is fixedly connected between the end and the first feed end of the distillation tower 3, a first cooling pipeline 13 is fixedly connected between the top discharge end of the distillation tower 3 and the feed end of the air cooler 4, a second cooling pipeline 14 is fixedly connected between the discharge end of the air cooler 4 and the feed end of the circulating water cooler 5, a third cooling pipeline 15 is fixedly connected between the discharge end of the circulating water cooler 5 and the feed end of the top reflux tank 6, a naphtha product pipeline 17 is fixedly connected to the discharge end of the top reflux tank 6, and a -35# low-condensing diesel product pipeline 18 is fixedly connected to the bottom discharge end of the distillation tower 3.

[0033] Example 10: Figure 1 As shown, as an optimization of the above embodiment, a reflux pipeline 16 is fixedly connected between the naphtha product pipeline 17 and the second feed end of the distillation tower 3 .

[0034] As needed, valves and instruments that enable normal operation of the device for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials are fixedly installed on each pipeline; the hydrotreating unit 1, the hydromodification unit 2 and the distillation unit all use existing reactors and equipment, and the distillation tower 3 is a tray-type distillation tower 3.

[0035] Embodiment 11: The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrofining unit 1, and the hydrofining reaction is carried out under the action of the hydrofining catalyst DN3552. The inlet temperature of the hydrofining reactor is 317°C, the outlet temperature is 336°C, the volume hydrogen-oil ratio is 700, the reaction pressure is 10.3MPa (G), and the hydrofining reaction product is obtained; wherein, the mass ratio of each component in the raw mixed diesel is: regular first-line oil: regular second-line oil: catalytic diesel = 35%: 55%: 10%, the feed rate of mixed diesel is 131t / h, the feed rate of heavy aromatics is 4t / h, and the new hydrogen consumption in hydrogen is 25500Nm 3 / h, circulating hydrogen volume 150000Nm 3 / h.

[0036] In the second step, the hydrotreating reaction product enters the hydrotreating unit 2, and undergoes a hydrotreating reaction under the action of the hydrotreating catalyst Z-FX11. The inlet temperature of the hydrotreating reactor is 333°C, the total bed temperature rises by 25°C, and the reaction pressure is 10.3MPa, to obtain a hydrotreating reaction product.

[0037] In the third step, the hydrogenation and reforming reaction product enters the distillation tower 3, the feed temperature of the distillation tower 3 is 222°C, the top pressure of the distillation tower 3 is 0.15MPa, the bottom temperature is 250°C, the top temperature is 147°C, and the distillation separation obtains naphtha and -35# low-condensing diesel.

[0038] The density of the -35# low-freezing diesel obtained in this example is 790.2Kg / m 3 , freezing point 37.0℃, cetane number 49.1, meeting the factory's ex-factory index requirements, naphtha yield 30.1%, naphtha aromatic potential 56.2.

[0039] Embodiment 12: The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrofining unit 1, and the hydrofining reaction is carried out under the action of the hydrofining catalyst DN3552. The inlet temperature of the hydrofining reactor is 317.5℃, the outlet temperature is 336.5℃, the volume hydrogen-oil ratio is 700, the reaction pressure is 10.5MPa (G), and the hydrofining reaction product is obtained; wherein, the mass ratio of each component in the raw mixed diesel is: regular first-line oil: regular second-line oil: catalytic diesel = 35%: 55%: 10%, the feed rate of mixed diesel is 131t / h, the feed rate of heavy aromatics is 6t / h, and the new hydrogen consumption in hydrogen is 26000Nm 3 / h, circulating hydrogen volume 150000Nm 3 / h.

[0040] In the second step, the hydrotreating reaction product enters the hydrotreating unit 2, and undergoes a hydrotreating reaction under the action of the hydrotreating catalyst Z-FX11. The inlet temperature of the hydrotreating reactor is 333°C, the total bed temperature rises by 25°C, and the reaction pressure is 10.3MPa, to obtain a hydrotreating reaction product.

[0041] In the third step, the hydrogenation and reforming reaction product enters the distillation tower 3, the feed temperature of the distillation tower 3 is 222°C, the top pressure of the distillation tower 3 is 0.15MPa, the bottom temperature is 250°C, the top temperature is 147°C, and the distillation separation obtains naphtha and -35# low-condensing diesel.

[0042] The density of -35# low freezing point diesel obtained in this example is 790.5Kg / m 3 , freezing point 37.2 ℃, cetane number 49.3, meet the factory index requirements, naphtha yield 30.5%, naphtha aromatic potential 56.7.

[0043] Embodiment 13: The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrofining unit 1, and the hydrofining reaction is carried out under the action of the hydrofining catalyst DN3552. The inlet temperature of the hydrofining reactor is 317.5℃, the outlet temperature is 336.5℃, the volume hydrogen-oil ratio is 700, the reaction pressure is 10.5MPa (G), and the hydrofining reaction product is obtained; wherein, the mass ratio of each component in the raw mixed diesel is: regular first-line oil: regular second-line oil: catalytic diesel = 35%: 55%: 10%, the feed rate of mixed diesel is 131t / h, the feed rate of heavy aromatics is 5t / h, and the new hydrogen consumption in hydrogen is 26000Nm 3 / h, circulating hydrogen volume 150000Nm 3 / h.

[0044] In the second step, the hydrotreating reaction product enters the hydrotreating unit 2, and undergoes a hydrotreating reaction under the action of the hydrotreating catalyst Z-FX11. The inlet temperature of the hydrotreating reactor is 333°C, the total bed temperature rise is 25.5°C, the reaction pressure is 10.3MPa, and a hydrotreating reaction product is obtained.

[0045] In the third step, the hydrogenation and reforming reaction product enters the distillation tower 3, the feed temperature of the distillation tower 3 is 222°C, the top pressure of the distillation tower 3 is 0.15MPa, the bottom temperature is 250°C, the top temperature is 147°C, and the distillation separation obtains naphtha and -35# low-condensing diesel.

[0046] The density of the -35# low-freezing diesel obtained in this example is 790.5Kg / m 3 , freezing point 37.5 ℃, cetane number 49.0, meet the factory index requirements, naphtha yield 30.7%, naphtha aromatic potential 56.5.

[0047] Embodiment 14: The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials is carried out according to the following steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrofining unit 1, and the hydrofining reaction is carried out under the action of the hydrofining catalyst DN3552. The inlet temperature of the hydrofining reactor is 317°C, the outlet temperature is 336°C, the volume hydrogen-oil ratio is 700, and the reaction pressure is 10.5MPa (G), and the hydrofining reaction product is obtained; wherein, the mass ratio of each component in the raw mixed diesel is: conventional first-line oil: conventional second-line oil: catalytic diesel = 35%: 55%: 10%, the feed rate of mixed diesel is 131t / h, the feed rate of heavy aromatics is 9t / h, and the new hydrogen consumption in hydrogen is 26000Nm 3 / h, circulating hydrogen volume 150000Nm 3 / h.

[0048] In the second step, the hydrotreating reaction product enters the hydrotreating unit 2, and undergoes a hydrotreating reaction under the action of the hydrotreating catalyst Z-FX11. The inlet temperature of the hydrotreating reactor is 333°C, the total bed temperature rise is 25.5°C, the reaction pressure is 10.3MPa, and a hydrotreating reaction product is obtained.

[0049] In the third step, the hydrogenation and reforming reaction product enters the distillation tower 3, the feed temperature of the distillation tower 3 is 222°C, the top pressure of the distillation tower 3 is 0.15MPa, the bottom temperature is 250°C, the top temperature is 147°C, and the distillation separation obtains naphtha and -35# low-condensing diesel.

[0050] The density of -35# low freezing point diesel obtained in this example is 790.6Kg / m 3, freezing point 37.4 ℃, cetane number 49.3, meet the factory index requirements, naphtha yield 30.3%, naphtha aromatic potential 56.9.

[0051] Comparative example: The raw material is only mixed diesel, the mass ratio of each component in the mixed diesel is: ordinary first-line oil: ordinary second-line oil: catalytic diesel = 35%: 55%: 10%, the mixed diesel feed rate is 140t / h, and the new hydrogen consumption in hydrogen is 26000Nm 3 / h, circulating hydrogen volume 150000Nm 3 / h. The specific steps are as follows: In the first step, the mixed diesel and hydrogen are mixed and then enter the hydrofining unit 1, and the hydrofining reaction is carried out under the action of the hydrofining catalyst DN3552. The inlet temperature of the hydrofining reactor is 317°C, the outlet temperature is 336°C, the volume hydrogen-oil ratio is 700, and the reaction pressure is 10.5MPa (G), and the hydrofining reaction product is obtained; In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, and is subjected to a hydroreforming reaction under the action of a hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333°C, the total bed temperature rise is 25.5°C, and the reaction pressure is 10.3MPa, to obtain a hydroreforming reaction product. In the third step, the hydrogenation and reforming reaction product enters the distillation tower 3, the feed temperature of the distillation tower 3 is 222°C, the top pressure of the distillation tower 3 is 0.15MPa, the bottom temperature is 250°C, the top temperature is 147°C, and the distillation separation obtains naphtha and -35# low-condensing diesel.

[0052] The density of -35# low-freezing diesel obtained in this comparative example is 792.5Kg / m 3 , freezing point 34.1 ℃, naphtha yield 25.1%, naphtha aromatic potential 49.5, due to the lack of low freezing point components in the raw materials, resulting in the product freezing point is unqualified.

[0053] The method of producing low-freezing point diesel using heavy aromatics and mixed diesel as raw materials of the present invention can avoid the problems of uneven density mixing, large density difference, darker color of the product mixed diesel, and excessive polycyclic aromatic hydrocarbons of the product mixed diesel when the heavy aromatics are directly transferred into the product diesel. While solving the production problem of -35# low-freezing point diesel, the method can also produce naphtha as a by-product, and the naphtha yield reaches more than 30%; compared with the naphtha yield after hydrogenation of the mixed diesel used alone without using heavy aromatics, it is 4 to 5 units higher. The aromatic potential of the by-product naphtha of the present invention is 56 to 57, which is 7 to 8 units higher than the aromatic potential of the naphtha after hydrogenation of the mixed diesel used alone without using heavy aromatics, indicating that the method produces higher-quality naphtha as a by-product, providing a higher-quality raw material for the aromatic reforming unit.

[0054] In summary, the present invention mixes heavy aromatics, hydrogen and mixed diesel, and performs hydrofining and hydromodification treatment on the obtained mixture to obtain -35# low-condensing diesel. The method has the characteristics of short process flow and small equipment investment, and the on-site process does not need to be significantly modified, and the effect of improving quality and efficiency is remarkable.

[0055] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials, characterized in that Follow these steps: In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then enter the hydrotreating unit, where a hydrotreating reaction is carried out under the action of a hydrotreating catalyst to obtain a hydrotreating reaction product; In the second step, the hydrofining reaction product enters the hydro-upgrading unit, and undergoes a hydro-upgrading reaction under the action of a hydro-upgrading catalyst to obtain a hydro-upgrading reaction product; In the third step, the hydrogenation and reforming reaction products enter the distillation unit for distillation separation to obtain naphtha and -35# low-condensing diesel.

2. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 1, characterized in that In the first step, the feed ratio of heavy aromatics to mixed diesel is 4 to 9:131, and the amount of new hydrogen in hydrogen is 25500Nm 3 / h to 26000Nm 3 / h, the circulating hydrogen volume is 14500Nm 3 / h to 15500Nm 3 / h.

3. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 1 or 2, characterized in that In the first step, the mixed diesel includes regular first-line diesel, regular second-line diesel and catalytic diesel, wherein the mass ratio of regular first-line diesel, regular second-line diesel and catalytic diesel is 35:55:

10.

4. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 1 or 2, characterized in that In the first step, the hydrotreating catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is DN3552.

5. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 3, characterized in that In the first step, the process conditions of hydrotreating are: reaction pressure 10MPa to 10.5MPa, volume hydrogen-to-oil ratio 650 to 700, reaction inlet temperature 315°C to 320°C, and reaction outlet temperature 328°C to 338°C.

6. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 1, 2 or 5, characterized in that In the second step, the hydrogenation catalyst is a Ni / Mo-alumina supported structure, and the catalyst model is Z-FX11.

7. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 3, characterized in that In the second step, the process conditions of the hydrogenation reforming unit are: reaction pressure 10MPa to 10.5MPa, reaction inlet temperature 333°C to 335°C, and total bed temperature rise 25°C to 26°C.

8. The method for producing low-condensation diesel using heavy aromatics and mixed diesel as raw materials according to claim 4, characterized in that In the third step, the feed temperature of the distillation unit is 220°C to 224°C, the bottom temperature is 248°C to 252°C, the top temperature is 145°C to 150°C, and the top operating pressure is set to 0.145MPa to 0.155MPa. The separated product naphtha is obtained at the top of the distillation tower, and the separated product -35# low-condensing diesel is obtained at the bottom of the tower.

9. A device for implementing the method for producing low-freezing point diesel using heavy aromatics and mixed diesel as raw materials as claimed in any one of claims 1 to 8, characterized in that It includes a hydrorefining unit, a hydromodification unit and a distillation unit. The distillation unit includes a distillation tower, an air cooler, a circulating water cooler and a tower top reflux tank. The feed end of the hydrorefining unit is fixedly connected with a raw material pipeline, the feed end of the raw material pipeline is fixedly connected with a heavy aromatics pipeline, a hydrogen pipeline and a mixed diesel pipeline, a dehydrogenation modification pipeline is fixedly connected between the discharge end of the hydrorefining unit and the feed end of the hydromodification unit, a dedistillation pipeline is fixedly connected between the discharge end of the hydromodification unit and the first feed end of the distillation tower, a first cooling pipeline is fixedly connected between the top discharge end of the distillation tower and the feed end of the air cooler, a second cooling pipeline is fixedly connected between the discharge end of the air cooler and the feed end of the circulating water cooler, a third cooling pipeline is fixedly connected between the discharge end of the circulating water cooler and the feed end of the tower top reflux tank, a naphtha product pipeline is fixedly connected to the discharge end of the tower top reflux tank, and a -35# low-condensation diesel product pipeline is fixedly connected to the bottom discharge end of the distillation tower.

10. The device for producing low-freezing diesel using heavy aromatics and mixed diesel as raw materials according to claim 9, characterized in that A reflux pipeline is fixedly connected between the product pipeline and the second feed end of the distillation tower.

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