Pyrolysis gasoline processing method and processing reaction system

Abstract

The invention relates to a pyrolysis gasoline processing method and a processing reaction system, and the method comprises the following steps: in a first hydrogenation reactor, pyrolysis gasoline contacts with a hydrogenation protective agent at a reaction temperature of 140-250 DEG C to carry out a selective hydrogenation reaction, enters a second hydrogenation reactor after the reaction, and contacts with a hydrofining catalyst at a reaction temperature of 220-360 DEG C to carry out a hydrofining reaction; the liquid phase in the reactants enters a stripping tower to remove hydrogen sulfide and light components and then enters a rectifying tower for fractionation, C6-C8 fractions are obtained at the top of the tower, and C9 < + > fractions are obtained at the bottom of the tower; wherein the reaction effluent of the second hydrogenation reactor is firstly used as a heat source of a reboiler at the bottom of the stripping tower, and then is sequentially subjected to heat exchange with feed material flows of the second hydrogenation reactor and the first hydrogenation reactor; and the tower top gas phase of the rectifying tower exchanges heat with the feeding material flow of the stripping tower, is condensed and cooled, and then is fed into a rectifying tower top reflux tank. According to the method and the system provided by the invention, the aromatic hydrocarbon in the pyrolysis gasoline can be recovered to the maximum extent, and the total energy consumption of the device is remarkably reduced.

Description

Cracked gasoline processing methods and processing reaction systems Technical Field

[0001] This invention relates to a method and reaction system for processing and utilizing petroleum hydrocarbon fractions, and more specifically, to a method and reaction system for refining cracked gasoline in the presence of hydrogen. Background Technology

[0002] Against the backdrop of my country's "dual carbon" target, in order to gradually reduce carbon emissions, the energy consumption structure will undergo significant changes. The consumption share of traditional energy sources such as coal and oil will gradually decrease, while the consumption share of green energy sources such as wind, solar, electricity, and nuclear power will gradually increase. Therefore, the demand for oil products used as traditional fuels will soon reach its peak, and my country's refining capacity will face the problem of overcapacity.

[0003] With slowing oil consumption, refining companies need to explore new product directions to address the problem of overcapacity in oil production. One promising path is the transformation of refining into chemical processing. Converting some oil products into chemical feedstocks or finished chemical products can extend the carbon emission cycle of hydrocarbons, effectively reducing carbon emissions when the feedstock processing scale remains the same. Traditional catalytic cracking technology primarily produces gasoline, with byproducts such as diesel, liquefied petroleum gas (LPG), and fuel gas. To meet the demands of this transformation, catalytic cracking technology has been widely adopted in recent years. Unlike catalytic cracking, catalytic cracking uses heavy oil as feedstock, with propylene as the primary product, and byproducts such as ethylene and aromatic-rich catalytic cracked gasoline. If the aromatics in catalytic cracked gasoline are recovered and utilized, the maximum amount of heavy oil feedstock can be converted into basic chemical feedstocks such as ethylene, propylene, and aromatics.

[0004] Catalytic cracking gasoline has a high aromatic content. Depending on the feedstock of the catalytic cracking unit, as well as the reaction conditions and light hydrocarbon reprocessing methods, the total aromatic content in catalytic cracking gasoline fluctuates between 50% and 90% by weight, with C6-C8 aromatics varying between 30% and 60% by weight. Since the application market for C9+ heavy aromatics is relatively small and their separation is more difficult, aromatic recovery mainly targets C6-C8 aromatics. The recovery of C6-C8 aromatics primarily employs solvent extraction. The refined catalytic cracking gasoline is fractionated using a distillation column to obtain a fraction mainly composed of C6-C8 hydrocarbons. Then, taking advantage of the different solubility characteristics of aromatics and non-aromatics in the extraction solvent, solvent extraction technology is used to obtain aromatics and non-aromatics. The aromatics are further separated to obtain benzene, toluene, and C8 mixed aromatic products. To ensure the quality of aromatic products and reduce the consumption of extraction solvents, the aromatic extraction unit has relatively stringent requirements for the feedstock of refined cracked gasoline. The main requirements are that the sulfur content is not greater than 1.0 mg / kg, the nitrogen content is not greater than 1.0 mg / kg, and the bromine value is not greater than 0.5 gBr / 100g.

[0005] Catalytic cracking gasoline, besides having insufficient sulfur and nitrogen content to meet the feedstock requirements of aromatics extraction units, also lacks sufficient olefin content. Therefore, suitable refining methods are needed to produce qualified aromatics extraction feedstock, with hydrorefining being currently the most effective technology. Catalytic cracking gasoline has a high diene content, which easily polymerizes and cokes at the top of the catalyst bed during hydrorefining, affecting the stable operation of the unit. Furthermore, during desulfurization and denitrification in hydrorefining, aromatics are easily lost due to hydrogenation saturation. Additionally, the energy consumption is high during the separation of hydrorefining products to obtain C6-C8 fractions. Ethylene cracking gasoline is also rich in aromatics, although its aromatic distribution differs from that of catalytic cracking gasoline. However, it also requires hydrorefining to produce qualified aromatics extraction feedstock before aromatics are recovered using aromatics extraction technology.

[0006] CN101724456A discloses a hydrogenation method for producing aromatics extraction feedstock. By dividing the reaction system into a first hydrogenation unit and a second hydrogenation unit, and by loading three different types of hydrogenation protective agents into the first hydrogenation unit and reacting at a lower temperature, the method effectively solves the problem of the impact of dienes contained in gasoline feedstock on the operational stability of the unit. In the embodiments of this method, the aromatics saturation rates of refined gasoline are 8.26% and 9.57%, respectively. The high aromatics saturation rate leads to significant aromatics loss during the hydrogenation refining process. Furthermore, the liquid product obtained after cooling, separation, and stabilization of the hydrogenation refining product is the aromatics extraction feedstock. However, the obtained liquid product still needs to be fractionated to obtain C6-C8 fractions as aromatics extraction feedstock. The energy consumption required for fractionating C6-C8 fractions accounts for 50-80% of the total energy consumption of the entire unit. Therefore, the energy consumption of the unit obtaining aromatics extraction feedstock using this method in practical applications is relatively high. In summary, in the industrial application of cracked gasoline to obtain qualified aromatics extraction feedstock through hydrorefining, it is necessary to develop cracked gasoline hydrorefining technology that reduces energy consumption. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a processing method and reaction system for cracked gasoline based on the existing technology, using hydrorefining technology as a means, while producing aromatic extraction feedstock, by-product gasoline blending components or feedstock for heavy aromatic recovery unit, with low aromatic hydrogenation saturation rate and low total energy consumption of the unit.

[0008] In a first aspect, the present invention provides a method for processing pyrolysis gasoline, comprising:

[0009] (1) The cracked gasoline feedstock and hydrogen enter the first hydrogenation reactor and undergo selective hydrogenation reaction in contact with the hydrogenation protection agent at a reaction temperature of 140-250℃; the reaction effluent from the first hydrogenation reactor enters the second hydrogenation reactor and undergoes hydrogenation refining reaction in contact with the hydrogenation refining catalyst at a reaction temperature of 220-360℃; the reaction effluent from the second hydrogenation reactor enters the high-pressure separator, and the separated liquid phase enters the stripping tower. After stripping to remove hydrogen sulfide and light components, it enters the distillation tower. The top of the tower yields the C6-C8 fraction as the aromatics extraction feedstock, and the bottom of the tower yields the C9+ fraction.

[0010] (2) Before entering the high-pressure separator, the reaction effluent from the second hydrogenation reactor is first used as a heat source for the reboiler at the bottom of the stripping tower, and then exchanges heat with the feed stream of the second hydrogenation reactor and the feed stream of the first hydrogenation reactor in sequence.

[0011] (3) The top gas phase of the distillation column first exchanges heat with the feed stream of the stripping column and is then condensed and cooled before being sent to the top reflux tank of the distillation column.

[0012] Secondly, the present invention provides a cracked gasoline processing reaction system, comprising: a first hydrogenation reactor, a second hydrogenation reactor, a high-pressure separator, a stripping tower, and a distillation tower connected in series; the first hydrogenation reactor is filled with a hydrogenation protective agent and configured to carry out a selective hydrogenation reaction of dienes in gasoline; the second hydrogenation reactor is filled with a hydrogenation refining catalyst and configured to carry out a gasoline hydrogenation refining reaction; the discharge pipeline of the second hydrogenation reactor exchanges heat with the bottom of the stripping tower; the liquid phase outlet pipeline of the high-pressure separator exchanges heat sequentially with the top vapor phase pipeline of the distillation tower and the bottom discharge pipeline of the distillation tower.

[0013] The beneficial effects of the pyrolysis gasoline processing method and reaction system provided by this invention are as follows:

[0014] (1) After hydrorefining cracked gasoline with high aromatic content, the resulting C6-C8 fraction is used as feedstock for aromatic extraction to recover benzene, toluene, and mixed C8 aromatics. The C9+ fraction is used as a gasoline blending component or feedstock for heavy aromatic recovery units. Utilizing the high aromatic content of cracked gasoline, the production of aromatics as a basic chemical feedstock is maximized. In the context of overcapacity in oil refining, this is conducive to the transformation of oil refining into chemical processing and helps reduce carbon emissions.

[0015] (2) The requirements for sulfur content of raw materials in aromatic extraction devices are relatively strict, while the requirements for sulfur content in gasoline blending components are relatively lenient. This invention can adopt relatively mild process conditions to produce qualified raw materials for aromatic extraction while producing qualified raw materials for gasoline blending components or heavy aromatic recovery devices. The aromatic saturation rate is low, which improves the recovery rate of aromatics.

[0016] (3) The hydrorefining reaction of cracked gasoline is a strongly exothermic reaction. By using the reaction effluent from the second hydrorefining reactor as the heat source for the reboiler at the bottom of the stripping tower, the heat of the hydrorefining reaction can be fully recovered and utilized, which helps to reduce the energy consumption of the unit.

[0017] (4) The gaseous flow rate at the top of the distillation column is very large and the temperature is high. The gaseous flow rate at the top of the distillation column is used to preheat the feed of the stripping column. Through thermal coupling, the latent heat of phase change of the gaseous flow rate at the top of the distillation column is fully recovered, which significantly reduces the energy consumption of the hydrorefining unit.

[0018] (5) The reaction effluent from the second hydrogenation reactor and the gaseous stream from the top of the distillation column still have a high temperature after heat recovery through heat exchange. The present invention uses low-temperature hot water to recover the low-temperature waste heat of these two streams, further reducing the energy consumption of the device. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the process flow of the pyrolysis gasoline processing method provided by the present invention.

[0020] Figure 2 is a schematic flowchart of the pyrolysis gasoline processing method in Example 2.

[0021] Figure 3 is a schematic diagram of the process for processing pyrolysis gasoline in Comparative Example 1.

[0022] Figure 4 is a schematic diagram of the process for processing pyrolysis gasoline in Comparative Example 2.

[0023] in:

[0024] 7-First hydrogenation reactor; 13-Second hydrogenation reactor; 27-High pressure separator

[0025] 30 - Circulating hydrogen desulfurization equipment; 32 - Circulating hydrogen compressor; 42 - Stripping tower

[0026] 55 - Distillation column; 48, 64 - Top reflux tank

[0027] 2, 51, 66, 70, 74 - Logistics transfer pumps; 5, 9, 15, 19, 38, 40, 58 - Heat exchangers

[0028] 23, 44, 60, 77 - Air coolers; 25, 46, 62, 79 - Water coolers

[0029] 11, 72 - Heating furnace, others are pipelines Detailed Implementation

[0030] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0031] In a first aspect, the present invention provides a method for processing pyrolysis gasoline, comprising:

[0032] (1) The cracked gasoline feedstock and hydrogen enter the first hydrogenation reactor and undergo selective hydrogenation reaction in contact with the hydrogenation protection agent at a reaction temperature of 140-250℃; the reaction effluent from the first hydrogenation reactor enters the second hydrogenation reactor and undergoes hydrogenation refining reaction in contact with the hydrogenation refining catalyst at a reaction temperature of 220-360℃; the reaction effluent from the second hydrogenation reactor enters the high-pressure separator, and the separated liquid phase enters the stripping tower. After stripping to remove hydrogen sulfide and light components, it enters the distillation tower. The top of the tower yields the C6-C8 fraction as the aromatics extraction feedstock, and the bottom of the tower yields the C9+ fraction.

[0033] (2) Before entering the high-pressure separator, the reaction effluent from the second hydrogenation reactor is first used as a heat source for the reboiler at the bottom of the stripping tower, and then exchanges heat with the feed stream of the second hydrogenation reactor and the feed stream of the first hydrogenation reactor in sequence.

[0034] (3) The gas phase at the top of the distillation column exchanges heat with the feed stream of the stripping column and is condensed and cooled before being sent to the reflux tank at the top of the distillation column.

[0035] Optionally, the liquid phase at the bottom of the distillation column exchanges heat with the feed stream of the stripping column, and is then cooled before being discharged. In one embodiment, the liquid phase at the bottom of the distillation column after heat exchange exchanges heat with hot water to recover low-temperature waste heat. In another embodiment, the liquid phase at the bottom of the distillation column after heat exchange exchanges heat through an air cooler and a water cooler, respectively, before being discharged.

[0036] In the method provided by the present invention, based on the total weight of the catalyst and calculated as oxides, the hydrogenation protective agent contains: 2-15% by weight of molybdenum and / or tungsten, 0.2-6% by weight of nickel and / or cobalt, and the balance is aluminum oxide;

[0037] Preferably, the hydrogenation protective agent contains 3-13% by weight of molybdenum and / or tungsten, 1-4% by weight of nickel and / or cobalt, and the balance is aluminum oxide.

[0038] Preferably, the first hydrogenation reactor is filled with at least two types of hydrogenation protective agents, with the metal content of the hydrogenation protective agents increasing along the flow direction of the reactants; more preferably, the particle size of the hydrogenation protective agents decreases along the flow direction of the reactants. Using two or more protective agents, and filling them in a manner that increases metal content and decreases particle size, can improve the removal rate of diolefins from cracked gasoline, thereby increasing the lifespan of the hydrorefining catalyst in the second hydrogenation reactor and the overall operating cycle of the unit.

[0039] In the method provided by the present invention, based on the total weight of the catalyst and calculated as oxides, the hydrogenation refining catalyst contains: 10-30% by weight of molybdenum and / or tungsten, 0.01-5% by weight of nickel and / or cobalt, and the balance is aluminum oxide;

[0040] Preferably, the hydrorefining catalyst contains 15-25% molybdenum and / or tungsten by weight, 2-4% nickel and / or cobalt by weight, and the balance is alumina.

[0041] In the method provided by this invention, the reaction conditions of the first hydrogenation reactor are: hydrogen partial pressure of 1.0–4.0 MPa and volume hourly space velocity of 2.0–8.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200–1000 Nm 3 / m 3 ;

[0042] Preferably, the reaction temperature is 160–220 °C, the hydrogen partial pressure is 2.0–3.5 MPa, and the volume hourly space velocity is 3–6 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300–600 Nm. 3 / m 3 .

[0043] In the method provided by this invention, the reaction conditions of the second hydrogenation reactor are: hydrogen partial pressure 1.0–4.0 MPa, and volume hourly space velocity 1.0–3.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200–1000 Nm 3 / m 3 ;

[0044] Preferably, the reaction temperature is 240–320°C, the hydrogen partial pressure is 2.0–3.5 MPa, and the volume hourly space velocity is 1.5–2.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300–600 Nm. 3 / m 3 .

[0045] In the method provided by the present invention, the operating conditions of the high-pressure separator are: temperature of 30-50°C and pressure of 1.5-4.0 MPa.

[0046] In the method provided by the present invention, the operating conditions of the stripping tower are: pressure of 0.2-1.0 MPa, top temperature of 50-120°C, and bottom temperature of 160-230°C.

[0047] Preferably, the pressure is 0.3 to 0.7 MPa, the top temperature is 60 to 100°C, and the bottom temperature is 170 to 210°C.

[0048] In the method provided by the present invention, the operating conditions of the distillation column are: pressure of 0.1-0.6 MPa, top temperature of 140-220°C, and bottom temperature of 200-260°C.

[0049] Preferably, the pressure is 0.15–0.30 MPa, the top temperature is 160–190°C, and the bottom temperature is 210–230°C.

[0050] In step (2), preferably, the reaction effluent from the second hydrogenation reactor is used as a heat source for the reboiler at the bottom of the stripping tower, and after exchanging heat with the feed stream of the second hydrogenation reactor and the feed stream of the first hydrogenation reactor in sequence, it is then exchanged with hot water to recover the low-temperature waste heat, and then cooled and separated into gas and liquid.

[0051] In step (3), preferably, after exchanging heat with the feed stream from the stripping tower, the overhead vapor phase of the distillation column exchanges heat with hot water to recover the low-temperature waste heat of the overhead vapor phase stream. After cooling, it is introduced into the reflux tank at the top of the distillation column. In the method provided by the present invention, the cracked gasoline feedstock is selected from one or more of catalytic cracked gasoline, heavy oil high-efficiency catalytic cracked gasoline, and ethylene cracked gasoline; preferably, the aromatic content in the cracked gasoline feedstock is 50-90% by weight.

[0052] In the method provided by this invention, the sulfur content of the C6-C8 fraction obtained from the top of the distillation column is no greater than 1.0 mg / kg, the nitrogen content is no greater than 1.0 mg / kg, and the bromine value is no greater than 0.5 gBr / 100g, which meets the requirements of the aromatic hydrocarbon extraction device for the raw materials; the sulfur content of the C9+ fraction obtained from the bottom of the distillation column is 1.0-10.0 mg / kg, which meets the requirements of the gasoline blending component or heavy aromatic hydrocarbon recovery device for the raw materials.

[0053] Secondly, the present invention provides a cracked gasoline processing reaction system, comprising: a first hydrogenation reactor, a second hydrogenation reactor, a high-pressure separator, a stripping tower, and a distillation tower connected in series; the first hydrogenation reactor is filled with a hydrogenation protective agent and configured to carry out a selective hydrogenation reaction of dienes in gasoline; the second hydrogenation reactor is filled with a hydrogenation refining catalyst and configured to carry out a gasoline hydrogenation refining reaction; the discharge pipeline of the second hydrogenation reactor exchanges heat with the bottom of the stripping tower; the liquid phase outlet pipeline of the high-pressure separator exchanges heat sequentially with the top vapor phase pipeline of the distillation tower and the bottom discharge pipeline of the distillation tower.

[0054] In this invention, the heat exchange between the discharge pipeline of the second hydrogenation reactor and the reboiler of the stripping tower refers to the connection between the discharge pipeline of the second hydrogenation reactor and the reboiler of the stripping tower, enabling heat exchange between the stream in the discharge pipeline of the second hydrogenation reactor and the stream in the reboiler of the stripping tower during the application of the reaction system. Similarly, the heat exchange between the liquid phase outlet pipeline and the vapor phase pipeline at the top of the distillation column, and the heat exchange between the liquid phase outlet pipeline and the discharge pipeline at the reboiler of the distillation column, all refer to the connection between the pipelines.

[0055] In the reaction system provided by the present invention, the stripping column is equipped with a bottom reboiler, which is heated by the effluent from the second hydrogenation reactor, and also has a top cooler and a top reflux tank; the distillation column is equipped with a bottom reboiler, and also has a top cooler and a top reflux tank.

[0056] In one embodiment, the distillation column is equipped with a bottom reboiler.

[0057] The first hydrotreating reactor is filled with a hydrotreating protectant, which mainly removes diolefins from cracked gasoline and prevents diolefins from coking in the second hydrotreating reactor, thus avoiding affecting the stability of the unit's operation. The hydrotreating protectant has low hydrotreating activity and its composition is as follows: based on the total weight of the catalyst and calculated as oxides, the content of molybdenum and / or tungsten is 2-15% by weight, the content of nickel and / or cobalt is 0.2-6% by weight, and the balance is alumina.

[0058] Preferably, the hydrogenation protective agent packed in the first hydrogenation reactor is packed in a graded manner, and there are no fewer than two types of hydrogenation protective agents packed in. The active metal components of the packed hydrogenation protective agents are different. The active metal content of the hydrogenation protective agent that first comes into contact with the reactants is lower, and the active metal content of the hydrogenation protective agents increases sequentially along the flow direction of the reactants. In addition to different activities, the packed hydrogenation protective agents are also different in particle size. The particle size of the hydrogenation protective agent that first comes into contact with the reactants is the largest, and the particle size of the hydrogenation protective agents decreases sequentially along the flow direction of the reactants.

[0059] The second hydrotreating reactor is filled with a hydrorefining catalyst, primarily for removing impurities such as sulfur and nitrogen from cracked gasoline and saturating olefins. The hydrorefining catalyst is composed of: based on the total weight of the catalyst and calculated as oxides, molybdenum and / or tungsten content of 10-30% by weight, nickel and / or cobalt content of 0.01-5% by weight, and the balance being alumina.

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings. The drawings only show the main equipment and pipelines, illustrating the main features of the method and reaction system provided by the present invention, but do not limit the present invention.

[0061] In Figure 1, cracked gasoline is introduced through pipeline 1, pressurized by reaction feed pump 2, mixed with circulating hydrogen from pipeline 3 and 34 via pipeline 3, and then enters pipeline 4. After passing through the first reaction feed heat exchanger 5 and exchanging heat with the reaction products, it enters the first hydrogenation reactor 7 via pipeline 6. Under the action of the hydrogenation protectant, diolefins, gums, and trace metal impurities in the cracked gasoline are removed by hydrogenation. The effluent from the first hydrogenation reactor 7 is led out through pipeline 8, exchanged heat with the reaction products through the furnace front heat exchanger 9, and then introduced into the reaction heating furnace 11 via pipeline 10, and then into the second reaction heating furnace 11 via pipeline 12. The second hydrogenation reactor 13 contains three beds of hydrogenation refining catalyst. An internal structure is installed between adjacent catalyst beds, and lower-temperature circulating hydrogen is added to the internal structure to mix with the higher-temperature reaction stream. Effective control of the reaction temperature facilitates the full utilization of catalyst selectivity, reducing aromatic hydrocarbon hydrogenation losses while simultaneously desulfurizing, denitrogenating, and saturating olefins. The outlet stream of the second hydrogenation reactor 13 is led out through pipeline 14, first serving as a heat source for the reboiler 15 at the bottom of the stripping tower, fully utilizing the heat of the hydrogenation refining reaction, and then... The heat transfer medium is introduced into the heat exchanger 19 via pipeline 16, furnace front heat exchanger 9, pipeline 17, primary reactor feed heat exchanger 5, and pipeline 18. This heat is then recovered from the excess low-temperature heat in the outlet stream of the second hydrogenation reactor. The recovered heat is then mixed with deoxygenated water supplied via pipeline 21 via pipeline 20 and introduced into the reaction product air cooler 23 via pipeline 22. From there, it is introduced into the high-pressure separator 27 via pipeline 24, reaction product water cooler 25, and pipeline 26. Sulfur-containing wastewater is discharged via pipeline 28, and the gaseous stream, i.e., circulating hydrogen, is discharged via pipeline 29. The circulating hydrogen desulfurization facility 30 controls the hydrogen sulfide content in the circulating hydrogen. To prevent excessive hydrogen sulfide content in the circulating hydrogen from affecting the desulfurization effect of the hydrorefining reaction, the desulfurized circulating hydrogen is introduced into the circulating hydrogen compressor 32 via pipeline 31. The pressurized circulating hydrogen is drawn out through pipeline 33 and divided into three streams. One stream is mixed with the cracked gasoline feedstock via pipeline 34, and the other two streams are introduced into the second hydrorefining reactor as cold hydrogen via pipelines 35 and 36 respectively. The liquid phase stream from the high-pressure separator 27 is introduced into the stripper 42 via pipeline 37, stripper feed preheater 38, pipeline 39, stripper feed heater 40, and pipeline 41 respectively.

[0062] The main function of stripping tower 42 is to remove light components, such as H2, C1-C4 hydrocarbons, and a small amount of C5 hydrocarbons, from the hydrorefining liquid phase product, as well as to remove hydrogen sulfide and water. The gaseous stream from the top of the tower is drawn out by pipeline 43 and introduced into the stripping tower reflux tank 48 via stripping tower top air cooler 44, pipeline 45, stripping tower top water cooler 46, and pipeline 47. Non-condensable gas is drawn out by pipeline 49, and liquid phase is drawn out by pipeline 50. After being pressurized by stripping tower top reflux pump 51, most of it is returned to the top of the stripping tower as reflux via pipeline 52, and a small portion is drawn out as light hydrocarbons via pipeline 53. A reboiler 15 is installed at the bottom of the stripping tower. The heat required for separation is provided by the outlet stream of the second hydrorefining reactor. The bottom stream of the stripping tower is introduced into the distillation tower 55 via pipeline 54.

[0063] The main function of distillation column 55 is to cut hydrorefined cracked gasoline into C6-C8 fractions and C9+ fractions. The C6-C8 fraction is used as a feedstock for aromatics extraction, and the C9+ fraction is used as a gasoline blending component or a feedstock for heavy aromatics recovery units. The vapor stream from the top of distillation column 55 is drawn out through pipeline 56 and first preheats the feed to the stripping column through the stripping column feed preheater 38 to recover most of the latent heat of phase change of the vapor stream. Then, it is introduced into the top gas-heat medium water heat exchanger 58 through pipeline 57 to recover the maximum amount of latent heat of phase change of the vapor stream. Then, it is introduced into the top reflux tank 64 of distillation column through pipeline 59, distillation column top air cooler 60, pipeline 61, distillation column top water cooler 62 and pipeline 63 respectively. The liquid phase in the reflux tank is drawn out through pipeline 65 and pressurized by the distillation column top reflux pump 66. Part of it is returned to the top of the distillation column as reflux through pipeline 67, and the other part is drawn out through pipeline 68 as aromatics extraction feed. The liquid stream from the bottom of the distillation column is drawn from pipeline 69. Part of it is pressurized by the bottom circulation pump 70 and then returned to the bottom of the distillation column via pipeline 71, the bottom reboiler 72, and pipeline 73, respectively. The heat required for the distillation process is provided by the bottom reboiler. The other part of the liquid stream from the bottom of the column is pressurized by the bottom discharge pump 74 and then cooled by pipeline 75, the stripping column feed heater 40, pipeline 76, the C9+ fraction air cooler 77, pipeline 78, the C9+ fraction water cooler 79, and pipeline 80 after recovering the heat of the C9+ fraction. It is then used as a raw material for gasoline blending components or heavy aromatics recovery units.

[0064] The following examples further illustrate the practical application and technical effects of the present invention, but do not limit the present invention.

[0065] In the examples and comparative examples:

[0066] The hydrogenation protectants used were produced by the Catalyst Division of China Petroleum & Chemical Corporation, with industrial grades RG-30A, RG-30B and RGO-3, respectively. Their main properties are shown in Table 1.

[0067] Table 1

[0068]

[0069] The hydrorefining catalysts RGA-1 and RS-1 used were produced by the Catalyst Division of China Petroleum & Chemical Corporation (Sinopec), and their main properties are shown in Table 2.

[0070] Table 2

[0071]

[0072] Example 1

[0073] Example 1 uses the process flow shown in Figure 1. The feedstock for the cracked gasoline is catalytic cracked gasoline, obtained from CNOOC Ningbo Daxie Petrochemical Co., Ltd., and its main properties are shown in Table 3.

[0074] Along the flow direction of the reactant stream, the hydrogenation protective agents packed in the first hydrogenation reactor are RG-30A (14.2% by weight), RG-30B (28.6% by weight), and RGO-3 (57.2% by weight).

[0075] The second hydrogenation reactor is filled with the hydrogenation refining catalyst RGA-1.

[0076] The heat exchange process includes: (1) The effluent from the second hydrogenation reactor is first used as the heat source for the reboiler at the bottom of the stripping tower, and then exchanges heat with the feed stream of the second hydrogenation reactor and the feed stream of the first hydrogenation reactor in sequence, and then enters the high-pressure separator after cooling. (2) The vapor phase at the top of the distillation column exchanges heat with the feed stream of the stripping tower and condenses, and then is sent to the reflux tank at the top of the distillation column after cooling. (3) The liquid phase at the bottom of the distillation column exchanges heat with the feed stream of the stripping tower, and then is discharged after cooling. (4) The effluent from the second hydrogenation reactor and the vapor phase at the top of the distillation column exchange heat with hot water before entering the air cooler to recover low-temperature waste heat.

[0077] The main process conditions of the first and second hydrogenation reactors are shown in Table 4, and the reaction results are shown in Table 5.

[0078] As shown in Table 5, with a sulfur content of 480 mg / kg, a nitrogen content of 69.7 mg / kg, and a bromine value of 41 gBr / 100g in the cracked gasoline feedstock, after hydrotreating, hydrorefining, and distillation separation, C6-C8 fractions with sulfur content <1.0 mg / kg, nitrogen content <1.0 mg / kg, and bromine value <0.5 gBr / 100g are produced, meeting the requirements for aromatics extraction feedstock. Simultaneously, a C9+ fraction with a sulfur content <10.0 mg / kg is produced, meeting the requirements for gasoline blending components. The C6-C8 aromatics saturation rate is 4.98%, and the total aromatics saturation rate is 4.86%. The total energy consumption of the unit is 17.2 kg standard oil / ton of feedstock.

[0079] Example 2

[0080] The process flow is shown in Figure 2. The catalyst loading method in the cracked gasoline feedstock and the second hydrogenation reactor is the same as in Example 1. The difference is that the first hydrogenation reactor is filled with the hydrogenation protection agent RGO-3.

[0081] The heat exchange process includes: (1) The effluent from the second hydrogenation reactor is first used as the heat source for the reboiler at the bottom of the stripping tower, and then exchanges heat with the feed stream from the second hydrogenation reactor and the feed stream from the first hydrogenation reactor in sequence, and then enters the high-pressure separator after cooling. (2) The vapor phase at the top of the distillation column exchanges heat with the feed stream from the stripping tower and condenses, and then is sent to the reflux tank at the top of the distillation column after cooling. (3)

[0082] The effluent from the second hydrogenation reactor and the overhead vapor from the distillation column exchange heat with hot water before entering the air cooler for cooling, thus recovering low-temperature waste heat.

[0083] The difference from Example 1 is that the liquid phase at the bottom of the distillation column 55 does not exchange heat with the feed stream of the stripping column 42, but is cooled by the air cooler 77 and the water cooler 79 before being sent out.

[0084] The main process conditions are shown in Table 4, and the main reaction results are shown in Table 5.

[0085] As shown in Table 5, the C6-C8 fractions produced in Example 2 have sulfur content <1.0 mg / kg, nitrogen content <1.0 mg / kg, and bromine value <0.5 gBr / 100g, meeting the requirements for aromatics extraction feedstock. The C9+ fraction produced has a sulfur content <10.0 mg / kg, meeting the requirements for clean gasoline blending components. The total energy consumption of the unit is 19.4 kg standard oil / ton of feedstock, which is about 12.8% higher than that of Example 1.

[0086] Comparative Example 1

[0087] The process flow of Comparative Example 1 is shown in Figure 3. The first hydrogenation reactor is filled with hydrogenation protection agent RGO-3, and the second hydrogenation reactor is filled with hydrogenation refining catalyst RS-1. The cracked gasoline feedstock is the same as that in Example 1.

[0088] The difference from Example 1 is that: (1) the outlet stream of the second hydrogenation reactor is led out by pipeline 14 and directly to heat exchanger 9 to exchange heat with the outlet stream of the first hydrogenation reactor, and the reboiler 15 at the bottom of the stripping tower uses externally supplied steam as a heat source; (2) the gaseous stream at the top of the distillation tower 55 is directly led to the top heat exchanger 58; (3) the liquid phase at the bottom of the distillation tower 55 is directly led to air cooler 77 and water cooler 79 for cooling and then sent out.

[0089] The main reaction conditions are shown in Table 4, and the main reaction results are shown in Table 5.

[0090] As shown in Tables 4 and 5, when the C6-C8 and C9+ fractions obtained in Comparative Example 1 all meet the requirements of sulfur content <1.0 mg / kg, nitrogen content <1.0 mg / kg, and bromine value <0.5 gBr / 100 g, the reaction temperature of the second hydrogenation reactor is about 30 °C higher than that in Example 1. This means that a higher reaction severity is required to produce qualified products. As a result, the aromatic saturation rate of the C6-C8 fraction reaches 9.68%, which is about 94.4% higher than that in Example 1, and the total aromatic saturation rate reaches 9.57%, which is about 96.9% higher than that in Example 1.

[0091] The energy consumption of the apparatus in Comparative Example 1 was 22.1 kg of standard oil per ton of raw material, which was about 28.5% higher than that of Example 1.

[0092] Comparative Example 2

[0093] The process flow of Comparative Example 2 is shown in Figure 4. The first hydrogenation reactor is filled with the hydrogenation protection agent RGO-3, and the hydrogenation refining catalyst in the second hydrogenation reactor is RS-1. The cracked gasoline feedstock is the same as in Example 1.

[0094] The difference from Comparative Example 1 is that: (1) the outlet stream of the second hydrogenation reactor is heated by the first reactor feed in the heat exchanger 5, and then mixed with the supplemented deoxygenated water before being directly introduced into the reaction product air cooler 23; (2) the gaseous stream at the top of the distillation column is directly cooled in the distillation column top air cooler 60.

[0095] The main reaction conditions are shown in Table 4, and the main reaction results are shown in Table 5.

[0096] As shown in Tables 4 and 5, after hydrorefining and distillation of the cracked gasoline feedstock, when the obtained C6-C8 and C9+ fractions all meet the requirements of sulfur content <1.0 mg / kg, nitrogen content <1.0 mg / kg, and bromine value <0.5 gBr / 100g, the reaction temperature of the second hydrorefining reactor is about 30°C higher than that in Example 1. This means that a higher reaction severity is required to produce qualified products. As a result, the aromatic saturation rate of the C6-C8 fraction reaches 9.68%, which is about 94.4% higher than that in Example 1, and the total aromatic saturation rate reaches 9.57%, which is about 96.9% higher than that in Example 1.

[0097] The energy consumption of the apparatus in Comparative Example 2 was 33.6 kg of standard oil per ton of raw material, which was about 95.3% higher than that of Example 1.

[0098] Table 3

[0099] Density of cracked gasoline feedstock (20℃), kg / m³ 3823.0 Diene value, gI2 / 100g; 8.9 Sulfur content, mg / kg; 480 Nitrogen content, mg / kg; 69.7 Bromine value, gBr / 100g; 41 C6~C8 Aromatic content, wt%; 43.08 Total aromatic content, wt%; 71.32 D-86 Distillation range, ℃ 50~190 surface

[0100] Table 4

[0101] Main Process Conditions Example 1 Example 2 Comparative Example 1 Comparative Example 2 First Hydrogenation Reactor Hydrogenation Protective Agent RG Series RGO-3 RGO-3 RGO-3 Feed Rate, t / h 1.200 1.200 1.200 1.200 Reaction Temperature, °C 165 160 165 165 Hydrogen Partial Pressure, MPa 3.2 3.4 3.2 3.2 Hydrogen-to-Oil Ratio, Nm³ 3 / m 3 500600500500 Volumetric space velocity, h -1 2.22.02.22.2 Second Hydrogenation Reactor Hydrogenation Refining Catalyst RGA-1 RGA-1 RS-1 RS-1 Reaction Temperature, °C 280 270 310 310 Hydrogen Partial Pressure, MPa 3.2 3.4 3.2 3.2 Hydrogen-to-Oil Ratio, Nm 3 / m 3 500600500500 Volumetric space velocity, h -1 1.51.41.51.5 surface

[0102] Table 5

[0103]

[0104]

Claims

1. A method for processing pyrolysis gasoline, characterized in that, include: (1) The cracked gasoline feedstock and hydrogen enter the first hydrogenation reactor and undergo selective hydrogenation reaction in contact with the hydrogenation protection agent at a reaction temperature of 140-250°C; the reaction effluent from the first hydrogenation reactor enters the second hydrogenation reactor and undergoes hydrogenation refining reaction in contact with the hydrogenation refining catalyst at a reaction temperature of 220-360°C; the reaction effluent from the second hydrogenation reactor enters the high-pressure separator, and the separated liquid phase enters the stripping tower. After stripping to remove hydrogen sulfide and light components, it enters the distillation tower for fractionation. The top of the tower yields C6-C8 fractions as aromatics extraction feedstock, and the bottom of the tower yields C9+ fractions; (2) Before entering the high-pressure separator, the reaction effluent from the second hydrogenation reactor is first used as the heat source for the reboiler at the bottom of the stripping tower, and then exchanges heat with the feed stream of the second hydrogenation reactor and the feed stream of the first hydrogenation reactor in sequence; (3) The top gas phase of the distillation tower exchanges heat with the feed stream of the stripping tower and is condensed and cooled before being sent to the top reflux tank of the distillation tower.

2. The method for processing pyrolysis gasoline according to claim 1, characterized in that, The liquid phase at the bottom of the distillation column exchanges heat with the feed stream of the stripping column, and is then cooled before being discharged.

3. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, Based on the total weight of the catalyst and calculated as oxides, the hydrogenation protective agent contains: 2-15% by weight of molybdenum and / or tungsten, 0.2-6% by weight of nickel and / or cobalt, with the balance being alumina; preferably, the hydrogenation protective agent contains: 3-13% by weight of molybdenum and / or tungsten, 1-4% by weight of nickel and / or cobalt, with the balance being alumina. Preferably, the first hydrogenation reactor is filled with at least two types of hydrogenation protective agents, with the metal content of the hydrogenation protective agents increasing along the flow direction of the reactants; preferably, the particle size of the hydrogenation protective agents decreases along the flow direction of the reactants.

4. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, Based on the total weight of the catalyst and calculated as oxides, the hydrorefining catalyst contains: 10-30% by weight of molybdenum and / or tungsten, 0.01-5% by weight of nickel and / or cobalt, and the balance being alumina; preferably, the hydrorefining catalyst contains: 15-25% by weight of molybdenum and / or tungsten, 2-4% by weight of nickel and / or cobalt, and the balance being alumina.

5. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The reaction conditions for the first hydrogenation reactor are: hydrogen partial pressure of 1.0–4.0 MPa and volume hourly space velocity of 2.0–8.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200–1000 Nm 3 / m 3 Preferably, the reaction temperature is 160–220°C, the hydrogen partial pressure is 2.0–3.5 MPa, and the volume hourly space velocity is 3–6 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300–600 Nm. 3 / m 3 .

6. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The reaction conditions for the second hydrogenation reactor are: hydrogen partial pressure 1.0–4.0 MPa, and volume hourly space velocity 1.0–3.0 h⁻¹. -1 Hydrogen-to-oil volume ratio 200–1000 Nm 3 / m 3 Preferably, the reaction temperature is 240–320°C, the hydrogen partial pressure is 2.0–3.5 MPa, and the volume hourly space velocity is 1.5–2.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300–600 Nm. 3 / m 3 .

7. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The operating conditions of the high-pressure separator are: temperature 30-50℃ and pressure 1.5-4.0MPa.

8. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The operating conditions of the stripping tower are: pressure of 0.2-1.0 MPa, top temperature of 50-120°C, and bottom temperature of 160-230°C; preferably, pressure of 0.3-0.7 MPa, top temperature of 60-100°C, and bottom temperature of 170-210°C.

9. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The operating conditions of the distillation column are: pressure of 0.1-0.6 MPa, top temperature of 140-220°C, and bottom temperature of 200-260°C; preferably, pressure of 0.15-0.30 MPa, top temperature of 160-190°C, and bottom temperature of 210-230°C.

10. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The cracked gasoline feedstock is selected from one or more of catalytic cracked gasoline, heavy oil high-efficiency catalytic cracked gasoline, and ethylene cracked gasoline; preferably, the aromatic content in the cracked gasoline feedstock is 50-90% by weight.

11. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The effluent from the second hydrogenation reactor exchanges heat with the feed stream from the first hydrogenation reactor, and then exchanges heat with hot water to recover low-temperature waste heat.

12. The method for processing pyrolysis gasoline according to claim 1 or 2, characterized in that, The overhead gas phase of the distillation column exchanges heat with the feed stream of the stripping column, and then exchanges heat with the heat transfer medium water to recover low-temperature waste heat.

13. A pyrolysis gasoline processing reaction system, characterized in that, include: The system comprises a first hydrogenation reactor, a second hydrogenation reactor, a high-pressure separator, a stripping tower, and a distillation tower connected in series. The first hydrogenation reactor is filled with a hydrogenation protective agent and configured to perform selective hydrogenation of diolefins in gasoline. The second hydrogenation reactor is filled with a hydrogenation refining catalyst and configured to perform gasoline hydrogenation refining. The discharge line of the second hydrogenation reactor exchanges heat with the bottom of the stripping tower. The liquid phase outlet line of the high-pressure separator exchanges heat sequentially with the top vapor phase line of the distillation tower and the bottom discharge line of the distillation tower.

14. The pyrolysis gasoline processing reaction system according to claim 13, characterized in that, The stripping column is equipped with a bottom reboiler heated by the output from the second hydrogenation reactor, and also has a top cooler and a top reflux tank; the distillation column is equipped with a bottom reboiler, a top cooler, and a top reflux tank.

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