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

Abstract

The present application relates to the technical field of gasoline processing, and is a method and device for producing low-freezing diesel oil from heavy aromatic hydrocarbons and mixed diesel oil, wherein the former is carried out according to the following steps: in the first step, the heavy aromatic hydrocarbons, the mixed diesel oil and hydrogen are mixed and then fed into a hydrofining unit to perform a hydrofining reaction under the action of a hydrofining catalyst, thereby obtaining a hydrofining reaction product; in the second step, the hydrofining reaction product is fed into a hydro-upgrading unit to perform a hydro-upgrading reaction under the action of a hydro-upgrading catalyst, thereby obtaining a hydro-upgrading reaction product; and in the third step, the hydro-upgrading reaction product is fed into a rectification unit to perform rectification separation, thereby obtaining naphtha and -35# low-freezing diesel oil. The heavy aromatic hydrocarbons, hydrogen and mixed diesel oil are mixed, and the obtained mixture is subjected to hydrofining and hydro-upgrading treatment, thereby obtaining -35# low-freezing diesel oil. The present application has the characteristics of a short process flow, small equipment investment, no need for substantial modification of the on-site process flow, and remarkable effects of upgrading and increasing efficiency.

Description

Technical Field

[0001] This invention relates to the field of gasoline processing technology, and is a method and apparatus for producing low-pour-point diesel fuel using heavy aromatics and blended diesel fuel as raw materials. Background Technology

[0002] Conventional low-pour-point diesel production mainly involves mixing diesel from atmospheric and vacuum distillation units (both line 1 and line 2) in a specific ratio, followed by hydrorefining in a diesel hydrotreating unit. The resulting low-pour-point diesel can have a pour point below -37°C. Specialized low-pour-point diesel production methods use straight-run diesel and catalytic diesel as feedstocks, primarily employing hydrodepour and isomerization depour catalysts. These methods achieve a -35# low-pour-point diesel yield exceeding 73%, and the pour point reduction of the diesel product exceeds 30°C. Currently, refineries mainly use these two methods to produce low-pour-point diesel components.

[0003] Based on the FHIDW diesel hydrotreating and pour point depressing technology, Zhang Xuehui et al. utilized the synergistic effect of hydrotreating and pour point depressing catalysts and isomerization-modified and pour point depressing catalysts to broaden the range of feedstocks for processing. This significantly reduced the pour point of diesel products while maintaining a high yield of low-pour-point diesel and further improving the quality of the diesel product. In industrial applications, using a mixture of 79% straight-run diesel and 21% catalytic diesel as feedstock, the produced -35# diesel met all the China VI emission standards.

[0004] Chinese patent document CN103773488A discloses a hydrotreating method for lowering the pour point of diesel fuel. In this method, feedstock oil is reacted with a hydrorefining catalyst in a first reaction zone. The effluent from the first reaction zone is separated and fractionated to obtain gas, naphtha fraction, low-pour-point diesel fraction I, and high-pour-point heavy diesel fraction. The high-pour-point heavy diesel fraction enters a second reaction zone and reacts with a hydrotreating catalyst to undergo isomerization cracking and pour point depressing reaction. The effluent from the second reaction zone is further separated and fractionated to obtain low-pour-point diesel fraction II. Low-pour-point diesel fraction I and low-pour-point diesel fraction II are mixed to obtain low-pour-point diesel fuel. This invention can flexibly produce low-pour-point diesel fuel ranging from -10 to -50, with a significantly higher cetane number than the feedstock and a substantial reduction in impurities such as sulfur and nitrogen, meeting Euro IV and Euro V clean diesel standards.

[0005] Considering special circumstances, such as insufficient hydrogen resources in refinery systems, urgent need to increase naphtha production, lack of hydrotreating catalysts in diesel hydrotreating units, and large volumes of secondary processed diesel, refineries often encounter bottlenecks when using conventional hydrotreating catalysts to process straight-run diesel and catalytic diesel to produce -35# low-pour-point diesel, while also generating naphtha as a byproduct. These bottlenecks include: the density and pour point of -35# low-pour-point diesel are inversely proportional; if the density is acceptable, the pour point will be unacceptable, and vice versa; and naphtha yield cannot be guaranteed and fluctuates significantly.

[0006] Heavy aromatics mainly originate from aromatics units. They are a collective term for a series of solvents composed of isomers of C9 or C10 heavy aromatics. Their composition is complex, with trimethylbenzene, tetramethylbenzene, and their isomers being the main components. The main properties of heavy aromatics are high aromatic content, low pour point, and high density. Currently, the main processing methods include two approaches: one is to directly blend them into the finished diesel fuel, but this often results in uneven density mixing, large density differences, a darker color in the blended diesel fuel, and excessive polycyclic aromatic hydrocarbon levels when the blending ratio is high; the other is to further distill to produce high-boiling-point aromatic solvent oil, but this increases investment due to the addition of deep distillation equipment. The downstream processing of heavy aromatics has long plagued refinery optimization. Fully utilizing the advantages of heavy aromatics (low pour point, high density) to produce low-pour-point diesel fuel can improve quality and efficiency. Summary of the Invention

[0007] This invention provides a method and apparatus for producing low-pour-point diesel fuel using heavy aromatics and blended diesel fuel as raw materials, overcoming the shortcomings of the prior art. It can effectively solve the problems of unqualified density and pour point in the current production of -35# low-pour-point diesel fuel using straight-run diesel fuel and catalytic diesel fuel as raw materials.

[0008] One of the technical solutions of the present invention is achieved through the following measures: a method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil, comprising the following steps:

[0009] The first step involves mixing heavy aromatics, blended diesel fuel, and hydrogen, which then enters the hydrorefining unit. Under the action of a hydrorefining catalyst, a hydrorefining reaction is carried out to obtain the hydrorefining reaction products.

[0010] The second step involves the hydrorefining reaction product entering the hydroreforming unit, where it undergoes a hydroreforming reaction under the action of a hydroreforming catalyst to obtain the hydroreforming reaction product.

[0011] The third step involves the hydrotreating reaction products entering the distillation unit, where they are separated to obtain naphtha and -35# low-pour-point diesel.

[0012] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0013] In the first step described above, the feed ratio of heavy aromatics to mixed diesel is 4 to 9:131, and the amount of fresh hydrogen in the hydrogen is 25,500 Nm³. 3 / h to 26000Nm 3 / h, circulating hydrogen capacity is 14500 Nm³ 3 / h to 15500Nm 3 / h.

[0014] In the first step above, the blended diesel includes conventional first-line diesel, conventional second-line diesel, and catalytic diesel, wherein the mass ratio of conventional first-line diesel, conventional second-line diesel, and catalytic diesel is 35:55:10.

[0015] In the first step above, the hydrorefining catalyst is a Ni / Mo-alumina supported structure, and the catalyst type is DN3552.

[0016] In the first step described above, the process conditions for hydrorefining are: reaction pressure of 10 MPa to 10.5 MPa (G), hydrogen-to-oil ratio of 650 to 700, inlet temperature of 315°C to 320°C, and outlet temperature of 328°C to 338°C. Preferably, the reaction pressure of the hydrorefining unit is 10.5 MPa (G), the hydrogen-to-oil ratio is 665, the inlet temperature is 317.5°C, and the outlet temperature is 336°C.

[0017] In the second step above, the hydrogenation catalyst is a Ni / Mo-alumina supported structure, and the catalyst type is Z-FX11.

[0018] In the second step described above, the process conditions for the hydrotreating unit are: reaction pressure of 10 MPa to 10.5 MPa (G), reaction inlet temperature of 333°C to 335°C, and total bed temperature rise of 25°C to 26°C. Preferably, the reaction pressure of the hydrotreating unit is 10.3 MPa (G), the reaction inlet temperature is 330.5°C, and the total bed temperature rise is 25.5°C.

[0019] In the third step described above, the feed temperature of the distillation unit is 222°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. Naphtha is obtained as the separated product at the top of the distillation column, and -35# low-pour-point diesel oil is obtained as the separated product at the bottom. Preferably, the bottom temperature of the distillation column is set to 250°C, the top temperature to 147°C, and the top operating pressure to 0.15MPa.

[0020] The second technical solution of the present invention is achieved through the following measures: an apparatus for producing low-pour-point diesel oil from heavy aromatics and mixed diesel oil as raw materials, comprising a hydrorefining unit, a hydroreforming unit, and a distillation unit. The distillation unit includes a distillation column, an air cooler, a circulating water cooler, and a top reflux tank. The feed end of the hydrorefining unit is fixedly connected to a raw material pipeline, and the feed end of the raw material pipeline is fixedly connected to a heavy aromatics pipeline, a hydrogen pipeline, and a mixed diesel oil pipeline. The discharge end of the hydrorefining unit and the feed end of the hydroreforming unit are fixedly connected by a connection to the hydrorefining unit. The hydrorefining pipeline is fixedly connected to the first feed end of the distillation column via a distillation pipeline. The top discharge end of the distillation column is fixedly connected to the feed end of the air cooler via a first cooling pipeline. The discharge end of the air cooler is fixedly connected to the feed end of the circulating water cooler via a second cooling pipeline. The discharge end of the circulating water cooler is fixedly connected to the feed end of the top reflux tank via a third cooling pipeline. The discharge end of the top reflux tank is fixedly connected to a naphtha product pipeline. The bottom discharge end of the distillation column is fixedly connected to a -35# low-pour-point diesel product pipeline.

[0021] The following are further optimizations and / or improvements to the second technical solution of the above invention:

[0022] The aforementioned naphtha product pipeline is fixedly connected to the second feed end of the distillation column via a reflux pipeline.

[0023] This invention mixes heavy aromatics, hydrogen, and blended diesel fuel, and then performs hydrorefining and hydromodification treatment on the resulting mixture to obtain -35# low-pour-point diesel fuel. It features a simple process flow, low equipment investment, and no need for major on-site process modifications, resulting in significant quality improvement and efficiency enhancement. Attached Figure Description

[0024] Appendix Figure 1 This is a schematic diagram of the process flow of Embodiment 9 of the present invention.

[0025] Appendix Figure 1 The codes in the table are as follows: 1 for hydrorefining unit, 2 for hydroreforming unit, 3 for distillation column, 4 for air cooler, 5 for circulating water cooler, 6 for top reflux tank, 7 for feedstock pipeline, 8 for heavy aromatics pipeline, 9 for hydrogen pipeline, 10 for mixed diesel pipeline, 11 for pipeline to hydroreforming, 12 for pipeline to distillation, 13 for first cooling pipeline, 14 for second cooling pipeline, 15 for third cooling pipeline, 16 for reflux pipeline, 17 for naphtha product pipeline, and 18 for -35# low-pour-point diesel product pipeline. Detailed Implementation

[0026] This invention is not limited to the following embodiments; specific implementation methods can be determined based on the technical solution of this invention and actual circumstances. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art.

[0027] Unless otherwise specified, all equipment and devices used in this invention are existing and commonly known in the art.

[0028] The present invention will be further described below with reference to embodiments:

[0029] Example 1: As Figure 1 As shown, the method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil is carried out according to the following steps:

[0030] In the first step, heavy aromatics, mixed diesel and hydrogen are mixed and then fed into hydrorefining unit 1. Under the action of hydrorefining catalyst, hydrorefining reaction is carried out to obtain hydrorefining reaction products.

[0031] The second step involves the hydrorefining reaction product entering the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of a hydroreforming catalyst to obtain the hydroreforming reaction product.

[0032] The third step involves the hydrotreating reaction products entering the distillation unit, where they are separated to obtain naphtha and -35# low-pour-point diesel.

[0033] 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 fresh hydrogen in the hydrogen is 25,500 Nm³. 3 / h to 26000Nm 3 / h, circulating hydrogen capacity is 14500 Nm³ 3 / h to 15500Nm 3 / h.

[0034] Example 3: As an optimization of the above example, in the first step, the mixed diesel includes conventional first-line diesel, conventional second-line diesel and catalytic diesel, wherein the mass ratio of conventional first-line diesel, conventional second-line diesel and catalytic diesel is 35:55:10.

[0035] Example 4: As an optimization of the above example, in the first step, the hydrorefining catalyst is a Ni / Mo-alumina supported structure, and the catalyst type is DN3552.

[0036] Example 5: As an optimization of the above embodiment, in the first step, the process conditions for hydrorefining are: reaction pressure 10 MPa to 10.5 MPa (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 hydrorefining unit 1 is 10.5 MPa (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.

[0037] 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 type is Z-FX11.

[0038] Example 7: As Figure 1 As shown, as an optimization of the above embodiment, in the second step, the process conditions of the hydrotreating unit 2 are: reaction pressure of 10 MPa to 10.5 MPa (G), reaction inlet temperature of 333°C to 335°C, and total bed temperature rise of 25°C to 26°C. Preferably, the reaction pressure of the hydrotreating unit 2 is 10.3 MPa (G), the reaction inlet temperature is 330.5°C, and the total bed temperature rise is 25.5°C.

[0039] Example 8: As Figure 1 As shown, as an optimization of the above embodiment, in the third step, the feed temperature of the distillation unit is 222°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. Naphtha is obtained as a separated product at the top of distillation column 3, and -35# low-pour-point diesel is obtained as a separated product at the bottom. Preferably, the bottom temperature of distillation column 3 is set to 250°C, the top temperature is set to 147°C, and the top operating pressure is set to 0.15MPa.

[0040] This invention involves mixing heavy aromatics, blended diesel oil, and hydrogen, followed by hydrorefining and hydromodification to obtain -35# low-pour-point diesel oil. The mixture of heavy aromatics, blended diesel oil, and hydrogen then undergoes a hydrorefining reaction in a fixed-bed reactor, where hydrodesulfurization, olefin saturation, and aromatics saturation reactions are performed to obtain the hydrorefining product. This hydrorefining product then enters a hydromodification unit 2, where high-carbon-chain molecules are hydromodified into short-carbon-chain molecules in a fixed-bed reactor. The depth of hydromodification is controlled to obtain the hydromodified product. Finally, the hydromodified product enters a distillation column 3 for separation to obtain naphtha and -35# low-pour-point diesel oil. This invention fully utilizes the high density and low pour point of heavy aromatics to improve the properties of the blended feedstock. Through hydrorefining and hydromodification, the density and pour point of the low-pour-point diesel oil are effectively improved, and the quality of the -35# low-pour-point diesel oil product meets the required specifications.

[0041] Example 9: As Figure 1As shown, the apparatus for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil includes a hydrorefining unit 1, a hydroreforming unit 2, and a distillation unit. The distillation unit includes a distillation column 3, an air cooler 4, a circulating water cooler 5, and a top reflux tank 6. A feed line 7 is fixedly connected to the feed end of the hydrorefining unit 1. A heavy aromatics line 8, a hydrogen line 9, and a blended diesel oil line 10 are fixedly connected to the feed end of the feed line 7. A line 11 is fixedly connected between the discharge end of the hydrorefining unit 1 and the feed end of the hydroreforming unit 2. The discharge end of the hydroreforming unit 2 is connected to the feed line 11. A distillation pipeline 12 is fixedly connected between the top end of the distillation column 3 and the first feed end. A first cooling pipeline 13 is fixedly connected between the top discharge end of the distillation column 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. A -35# low-pour-point diesel product pipeline 18 is fixedly connected to the bottom discharge end of the distillation column 3.

[0042] Example 10: As Figure 1 As shown, as an optimization of the above embodiment, a reflux line 16 is fixedly connected between the naphtha product line 17 and the second feed end of the distillation column 3.

[0043] As required, each pipeline of the unit that produces low-pour-point diesel oil from heavy aromatics and mixed diesel oil is fixedly equipped with valves and instruments that enable it to operate normally. The hydrorefining unit 1, the hydroreforming unit 2 and the distillation unit all use existing reactors and equipment, and the distillation column 3 is a tray distillation column 3.

[0044] Example 11: The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil is carried out according to the following steps:

[0045] In the first step, heavy aromatics, blended diesel, and hydrogen are mixed and fed into hydrorefining unit 1. The hydrorefining reaction takes place under the action of hydrorefining catalyst DN3552. The inlet temperature of the hydrorefining reactor is 317℃, the outlet temperature is 336℃, the volumetric hydrogen-to-oil ratio is 700, and the reaction pressure is 10.3 MPa (G). The hydrorefining reaction product is obtained. The mass ratio of each component in the feedstock blended diesel is: conventional first-line diesel: conventional second-line diesel: catalytic diesel = 35%: 55%: 10%. The feed rate of blended diesel is 131 t / h, the feed rate of heavy aromatics is 4 t / h, and the fresh hydrogen consumption in the hydrogen is 25500 Nm³. 3 / h, circulating hydrogen capacity 150000 Nm³ 3 / h.

[0046] In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of the hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333℃, the total temperature rise of the bed is 25℃, and the reaction pressure is 10.3MPa, yielding the hydroreforming reaction product.

[0047] The third step involves the hydrotreating reaction product entering distillation column 3. The feed temperature of distillation column 3 is 222℃, the top pressure of distillation column 3 is 0.15MPa, the bottom temperature is 250℃, and the top temperature is 147℃. The distillation process separates naphtha and -35# low-pour-point diesel oil.

[0048] The -35# low-pour-point diesel oil obtained in this embodiment has a density of 790.2 kg / m³. 3 The solidification point is 37.0℃, the cetane number is 49.1, which meets the requirements for delivery. The naphtha yield is 30.1%, and the aromatic potential of the naphtha is 56.2.

[0049] Example 12: The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil is carried out according to the following steps:

[0050] In the first step, heavy aromatics, mixed diesel oil, and hydrogen are mixed and fed into hydrorefining unit 1. The hydrorefining reaction takes place under the action of hydrorefining catalyst DN3552. The inlet temperature of the hydrorefining reactor is 317.5℃, the outlet temperature is 336.5℃, the volume hydrogen-to-oil ratio is 700, and the reaction pressure is 10.5 MPa (G). The hydrorefining reaction product is obtained. The mass ratio of each component in the feedstock mixed diesel oil is: conventional first-line diesel oil: conventional second-line diesel oil: catalytic diesel oil = 35%: 55%: 10%. The feed rate of mixed diesel oil is 131 t / h, the feed rate of heavy aromatics is 6 t / h, and the fresh hydrogen consumption in the hydrogen is 26000 Nm³. 3 / h, circulating hydrogen capacity 150000 Nm³ 3 / h.

[0051] In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of the hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333℃, the total temperature rise of the bed is 25℃, and the reaction pressure is 10.3MPa, yielding the hydroreforming reaction product.

[0052] The third step involves the hydrotreating reaction product entering distillation column 3. The feed temperature of distillation column 3 is 222℃, the top pressure of distillation column 3 is 0.15MPa, the bottom temperature is 250℃, and the top temperature is 147℃. The distillation process separates naphtha and -35# low-pour-point diesel oil.

[0053] The density of the -35# low-pour-point diesel oil obtained in this embodiment is 790.5 kg / m³. 3The solidification point is 37.2℃, the cetane number is 49.3, which meets the requirements for leaving the factory. The naphtha yield is 30.5%, and the aromatic potential of the naphtha is 56.7.

[0054] Example 13: The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil is carried out according to the following steps:

[0055] In the first step, heavy aromatics, mixed diesel oil, and hydrogen are mixed and fed into hydrorefining unit 1. The hydrorefining reaction takes place under the action of hydrorefining catalyst DN3552. The inlet temperature of the hydrorefining reactor is 317.5℃, the outlet temperature is 336.5℃, the volume hydrogen-to-oil ratio is 700, and the reaction pressure is 10.5 MPa (G). The hydrorefining reaction product is obtained. The mass ratio of the components in the feedstock mixed diesel oil is: conventional first-line diesel oil: conventional second-line diesel oil: catalytic diesel oil = 35%: 55%: 10%. The feed rate of mixed diesel oil is 131 t / h, the feed rate of heavy aromatics is 5 t / h, and the fresh hydrogen consumption in the hydrogen is 26000 Nm³. 3 / h, circulating hydrogen capacity 150000 Nm³ 3 / h.

[0056] In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of the hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333℃, the total temperature rise of the bed is 25.5℃, and the reaction pressure is 10.3MPa, yielding the hydroreforming reaction product.

[0057] The third step involves the hydrotreating reaction product entering distillation column 3. The feed temperature of distillation column 3 is 222℃, the top pressure of distillation column 3 is 0.15MPa, the bottom temperature is 250℃, and the top temperature is 147℃. The distillation process separates naphtha and -35# low-pour-point diesel oil.

[0058] The density of the -35# low-pour-point diesel oil obtained in this embodiment is 790.5 kg / m³. 3 The solidification point is 37.5℃, the cetane number is 49.0, which meets the requirements for leaving the factory. The naphtha yield is 30.7%, and the aromatic potential of the naphtha is 56.5.

[0059] Example 14: The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil is carried out according to the following steps:

[0060] In the first step, heavy aromatics, blended diesel, and hydrogen are mixed and fed into hydrorefining unit 1. The hydrorefining reaction takes place under the action of hydrorefining catalyst DN3552. The inlet temperature of the hydrorefining reactor is 317℃, the outlet temperature is 336℃, the volumetric hydrogen-to-oil ratio is 700, and the reaction pressure is 10.5 MPa(G). The hydrorefining reaction product is obtained. The mass ratio of each component in the feedstock blended diesel is: conventional first-line diesel: conventional second-line diesel: catalytic diesel = 35%: 55%: 10%. The feed rate of blended diesel is 131 t / h, the feed rate of heavy aromatics is 9 t / h, and the fresh hydrogen consumption in the hydrogen is 26000 Nm³. 3 / h, circulating hydrogen capacity 150000 Nm³ 3 / h.

[0061] In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of the hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333℃, the total temperature rise of the bed is 25.5℃, and the reaction pressure is 10.3MPa, yielding the hydroreforming reaction product.

[0062] The third step involves the hydrotreating reaction product entering distillation column 3. The feed temperature of distillation column 3 is 222℃, the top pressure of distillation column 3 is 0.15MPa, the bottom temperature is 250℃, and the top temperature is 147℃. The distillation process separates naphtha and -35# low-pour-point diesel oil.

[0063] The density of the -35# low-pour-point diesel oil obtained in this embodiment is 790.6 kg / m³. 3 The solidification point is 37.4℃, the cetane number is 49.3, which meets the requirements for leaving the factory. The naphtha yield is 30.3%, and the aromatic potential of the naphtha is 56.9.

[0064] Comparative Example: The feedstock used was only blended diesel fuel, with the following mass ratio of components: conventional diesel fuel : conventional diesel fuel : catalytic diesel fuel = 35% : 55% : 10%. The feed rate of the blended diesel fuel was 140 t / h, and the fresh hydrogen consumption in the hydrogen was 26000 Nm³. 3 / h, circulating hydrogen capacity 150000 Nm³ 3 / h. The specific steps are as follows:

[0065] The first step involves mixing diesel and hydrogen and then introducing them into hydrorefining unit 1. Under the action of hydrorefining catalyst DN3552, a hydrorefining reaction is carried out. The inlet temperature of the hydrorefining reactor is 317℃, the outlet temperature is 336℃, the volume hydrogen-to-oil ratio is 700, and the reaction pressure is 10.5MPa(G), to obtain the hydrorefining reaction product.

[0066] In the second step, the hydrorefining reaction product enters the hydroreforming unit 2, where it undergoes a hydroreforming reaction under the action of the hydroreforming catalyst Z-FX11. The inlet temperature of the hydroreforming reactor is 333℃, the total temperature rise of the bed is 25.5℃, and the reaction pressure is 10.3MPa, yielding the hydroreforming reaction product.

[0067] The third step involves the hydrotreating reaction product entering distillation column 3. The feed temperature of distillation column 3 is 222℃, the top pressure of distillation column 3 is 0.15MPa, the bottom temperature is 250℃, and the top temperature is 147℃. The distillation process separates naphtha and -35# low-pour-point diesel oil.

[0068] The density of the -35# low-pour-point diesel oil obtained in this comparative example is 792.5 kg / m³. 3 The product has a freezing point of 34.1℃, a naphtha yield of 25.1%, and an aromatic potential of 49.5. Due to insufficient low-freezing-point components in the raw materials, the product's freezing point is not up to standard.

[0069] The present invention provides a method for producing low-pour-point diesel fuel from heavy aromatics and blended diesel fuel. This method avoids the problems associated with directly blending heavy aromatics into the product diesel fuel, such as uneven density mixing, large density differences, darker color of the blended diesel fuel, and excessive polycyclic aromatic hydrocarbon (PAH) levels when the blending ratio is high. While solving the production challenges of -35# low-pour-point diesel fuel, this method also produces naphtha as a byproduct, with a naphtha yield exceeding 30%. Compared to using only blended diesel fuel after hydrogenation without heavy aromatics, the naphtha yield is 4 to 5 units higher. The aromatic potential of the naphtha produced by this invention is 56 to 57, which is 7 to 8 units higher than that of naphtha produced by hydrogenation of blended diesel fuel without heavy aromatics. This indicates that the method produces higher-quality naphtha as a byproduct, providing a superior feedstock for aromatics-type reforming units.

[0070] In summary, this invention mixes heavy aromatics, hydrogen, and blended diesel fuel, and then performs hydrorefining and hydromodification treatment on the resulting mixture to obtain -35# low-pour-point diesel fuel. This method features a simple process flow, low equipment investment, and requires no major modifications to the on-site process, resulting in significant improvements in quality and efficiency.

[0071] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil, characterized in that... Follow these steps: The first step involves mixing heavy aromatics, blended diesel fuel, and hydrogen, which then enters the hydrorefining unit. Under the action of a hydrorefining catalyst, a hydrorefining reaction is carried out to obtain the hydrorefining reaction products. The second step involves the hydrorefining reaction product entering the hydroreforming unit, where it undergoes a hydroreforming reaction under the action of a hydroreforming catalyst to obtain the hydroreforming reaction product. The third step involves the hydrotreating reaction products entering the distillation unit, where they are separated to obtain naphtha and -35# low-pour-point diesel.

2. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 1, characterized in that... In the first step, the feed ratio of heavy aromatics to blended diesel is 4 to 9:131, and the amount of fresh hydrogen in the hydrogen is 25,500 Nm³. 3 / h to 26000Nm 3 / h, circulating hydrogen capacity is 14500 Nm³ 3 / h to 15500Nm 3 / h.

3. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 1 or 2, characterized in that... In the first step, the blended diesel includes conventional first-line diesel, conventional second-line diesel, and catalytic diesel, wherein the mass ratio of conventional first-line diesel, conventional second-line diesel, and catalytic diesel is 35:55:

10.

4. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 1 or 2, characterized in that... In the first step, the hydrorefining catalyst is a Ni / Mo-alumina supported structure, and the catalyst type is DN3552.

5. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 3, characterized in that... In the first step, the process conditions for hydrorefining are: reaction pressure 10 MPa to 10.5 MPa, 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-pour-point diesel oil from heavy aromatics and blended diesel oil 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 type is Z-FX11.

7. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 3, characterized in that... In the second step, the process conditions of the hydrotreating unit are: reaction pressure 10 MPa to 10.5 MPa, reaction inlet temperature 333°C to 335°C, and total bed temperature rise 25°C to 26°C.

8. The method for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 4, characterized in that... In the third step, the feed temperature of the distillation unit is 220℃ to 224℃, the bottom temperature is 248℃ to 252℃, the top temperature is 145℃ to 150℃, and the top operating pressure is set to 0.145MPa to 0.155MPa. Naphtha is obtained as the separated product at the top of the distillation column, and -35# low-pour-point diesel is obtained as the separated product at the bottom of the column.

9. An apparatus for implementing the method for producing low-pour-point diesel oil from heavy aromatics and blended diesel as raw materials according to any one of claims 1 to 8, characterized in that... It includes a hydrorefining unit, a hydroreforming unit, and a distillation unit. The distillation unit includes a distillation column, an air cooler, a circulating water cooler, and a top reflux tank. The feed end of the hydrorefining unit is fixedly connected to a feedstock pipeline. The feed end of the feedstock pipeline is fixedly connected to a heavy aromatics pipeline, a hydrogen pipeline, and a mixed diesel pipeline. The discharge end of the hydrorefining unit is fixedly connected to the feed end of the hydroreforming unit via a pipeline to the hydroreforming unit. The discharge end of the hydroreforming unit is fixedly connected to the first feed end of the distillation column via a pipeline to the distillation unit. The top discharge end of the distillation column is fixedly connected to the feed end of the air cooler via a first cooling pipeline. The discharge end of the air cooler is fixedly connected to the feed end of the circulating water cooler via a second cooling pipeline. The discharge end of the circulating water cooler is fixedly connected to the feed end of the top reflux tank via a third cooling pipeline. The discharge end of the top reflux tank is fixedly connected to a naphtha product pipeline. The bottom discharge end of the distillation column is fixedly connected to a -35# low-pour-point diesel product pipeline.

10. The apparatus for producing low-pour-point diesel oil from heavy aromatics and blended diesel oil according to claim 9, characterized in that... A reflux line is fixedly connected between the product pipeline and the second feed end of the distillation column.

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