A system and method for naphtha product coupling

Abstract

The present application provides a system and method for naphtha product coupling, the system realizes the mixed dehydrogenation of C3 and C4 alkanes separated from naphtha hydrocracking product and LPG by hydrocracking, C3 and C4 separation, LPG mixing, mixed dehydrogenation, oligomerization reaction, and the oligomerization of olefins separated from the dehydrogenation product; the present application realizes the deep coupling of heat and hydrogen; the method of the present application can reduce the consumption of purchased hydrogen by more than 85%, reduce the energy consumption of the system by more than 30%, and significantly improve the economic and environmental benefits of naphtha processing.

Description

Technical Field

[0001] This invention relates to the field of energy industry technology, and in particular to a system and method for coupling naphtha products. Background Technology

[0002] Naphtha is an important intermediate product in the petroleum refining process. In traditional processes, naphtha is usually used as a feedstock for ethylene production via steam cracking or for producing light oil products through hydrocracking. However, with the increasing demand from the chemical industry for low-carbon olefins and high-value-added oil products, traditional single-processing technologies can no longer meet the needs of efficient resource utilization.

[0003] In existing technologies, naphtha hydrocracking, C3-C4 component separation, mixed dehydrogenation, oligomerization, and other processes are usually operated independently, which has the following technical drawbacks:

[0004] Hydrogen waste: The hydrocracking unit consumes a large amount of purchased hydrogen, while the hydrogen produced as a by-product of the dehydrogenation unit is not effectively recycled and utilized, resulting in low hydrogen resource utilization and high production costs.

[0005] Excessive energy consumption: The lack of effective thermal integration between units means that the high-temperature reaction heat of hydrocracking and the waste heat of the dehydrogenation unit cannot be recovered in stages, resulting in high overall energy consumption and large carbon emissions of the system.

[0006] For example, CN202310054993.7 discloses a method for hydrocracking naphtha, which only optimizes the hydrocracking unit and fails to couple it with subsequent dehydrogenation and separation processes; CN202410540746.7 discloses a method for hydrocracking light oil to produce olefin feedstock, which only achieves preliminary separation of products and does not involve deep coupling of thermal hydrogen and carbon, and the system energy consumption and hydrogen consumption are still at a high level.

[0007] Therefore, developing a naphtha processing technology that can achieve deep coupling of heat and hydrogen has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] The technical problem this invention aims to solve is the waste of hydrogen sources in existing naphtha processes, the failure to effectively recover and utilize hydrogen, excessive energy consumption, and large carbon emissions. To address this, this invention provides a system and method for coupling naphtha products, which separates C3 and C4 alkanes from naphtha hydrocracking products, mixes them with LPG (liquefied petroleum gas) for mixed dehydrogenation, and then uses a deep hydrogen-carbon coupling method to perform oligomerization of the olefins separated from the dehydrogenation products. This method solves the problems of wasted hydrogen sources, high energy consumption, and insufficient separation accuracy in existing technologies.

[0009] To address the aforementioned technical problems, in a first aspect, the present invention provides a naphtha product coupling system, comprising a hydrocracking reactor, a thermally integrated heat exchanger, a hydrocracking cooler, a C1-C2 dehydrogenator, a propane dehydrogenator, a butane dehydrogenator, a mixed dehydrogenation reactor, an LPG mixed feed heater, a mixed dehydrogenation product cooler, a mixed dehydrogenation product separation unit, an oligomerization reactor, a pressure swing adsorption device, a heating furnace, and a compression unit.

[0010] The hydrocracking reactor includes a hydrocracking product pipeline, a dehydrogenation by-product hydrogen pipeline, and a feedstock pipeline;

[0011] The integrated heat exchanger includes a preheated mixed LPG feed line, a preheated mixed LPG feed line, an olefin feed line, a preheated olefin discharge line, and a hydrocracking discharge line.

[0012] The C1~C2 separator includes a C1~C2 separator feed pipe, a C1~C2 separator discharge pipe, and a C1~C2 (containing hydrogen) discharge pipe;

[0013] The propane dehydrogenator includes a propane dehydrogenator feed pipeline, a propane dehydrogenator discharge pipeline, and a C4+ product discharge pipeline;

[0014] The butane removal tower includes a butane removal tower feed pipeline, a butane removal tower discharge pipeline, and a C5+ product discharge pipeline;

[0015] The heating furnace includes a heating furnace feed pipe and a heating furnace discharge pipe;

[0016] The mixed dehydrogenation reactor includes a mixed dehydrogenation reactor feed pipeline and a mixed dehydrogenation reactor discharge pipeline;

[0017] The LPG mixing feed heater includes a preheated LPG feed pipeline, a first discharge pipeline of the LPG mixing feed heater, a discharge pipeline of the mixing dehydrogenation reactor, and a second discharge pipeline of the LPG mixing feed heater.

[0018] The mixed dehydrogenation product cooler includes an inlet pipe and an outlet pipe.

[0019] The mixed dehydrogenation product separation unit includes a separation unit feed pipeline, an olefin discharge pipeline, C3 and C4 discharge pipelines, and a hydrogen discharge pipeline.

[0020] The oligomerization reactor includes an olefin feed line and an oligomerization product line;

[0021] The pressure swing adsorption device includes a primary hydrogen production pipeline, a fuel gas recovery pipeline, and a fuel gas discharge pipeline;

[0022] The hydrocracking reactor is connected to a thermally integrated heat exchanger via a hydrocracking product pipeline. The thermally integrated heat exchanger is connected to a hydrocracking cooler via a hydrocracking feed pipeline. The thermally integrated heat exchanger is connected to an oligomerization reactor via an olefin feed pipeline. The hydrocracking cooler is connected to a C1-C2 decarbonylator via a C1-C2 separator feed pipeline. The C1-C2 decarbonylator is connected to a propane stripper feed pipeline via a C1-C2 separator discharge pipeline. The propane stripper then passes through a propane stripper... Propane is discharged from the tower outlet pipeline, and butane is discharged from the butane removal tower through the top outlet pipeline. Propane and butane are first combined, and then connected to the preheated mixed LPG feed pipeline along with the C3 and C4 outlet pipelines of the mixed dehydrogenation product separation unit, forming a mixed LPG feedstock. The C5+ product outlet pipeline of the butane removal tower is connected to the feedstock pipeline. The integrated heat exchanger is connected to the LPG mixed feed heater through the preheated mixed LPG feed pipeline. The second LPG mixed feed heater... The discharge pipeline is connected to the inlet of the heating furnace. The heating furnace is connected to the mixed dehydrogenation reactor via the feed pipeline of the mixed dehydrogenation reactor. The mixed dehydrogenation reactor is connected to the hot-side inlet pipeline of the LPG mixed feed heater via the discharge pipeline of the mixed dehydrogenation reactor. The LPG mixed feed heater is connected to the mixed dehydrogenation product cooler via the first discharge pipeline of the LPG mixed feed heater. The mixed dehydrogenation product cooler is connected to the mixed dehydrogenation product separation unit via the feed pipeline of the separation unit. The mixed dehydrogenation product separation unit is connected to the olefin feed pipeline via the olefin discharge pipeline. The mixed dehydrogenation product separation unit is connected to the preheated mixed LPG feed pipeline via the C3 and C4 discharge pipelines. The mixed dehydrogenation product separation unit is connected to the pressure swing adsorption (PSA) unit via the hydrogen discharge pipeline. The PSA unit is connected to the compression unit via the primary hydrogen production pipeline. The compression unit is connected to the hydrocracking reactor via the dehydrogenation by-product hydrogen pipeline. The PSA unit is connected to the heating furnace via the fuel recovery pipeline.

[0023] The core innovation of this invention lies in achieving deep coupling between heat and hydrogen:

[0024] Hydrogen coupling: After purification, more than 90% of the hydrogen from the mixed dehydrogenation byproducts is supplied to the hydrocracking unit as a hydrogen source, realizing internal circulation of the hydrogen source and significantly reducing the consumption of purchased hydrogen. The hydrogen self-sufficiency rate can reach more than 85%. Thermal coupling: The high-temperature product (360~400℃) at the outlet of the hydrocracking unit is used to preheat the mixed LPG feedstock through a thermal integrated heat exchanger. The feedstock is preheated from room temperature to 500~530℃, recovering the heat of reaction while reducing the heating load of the dehydrogenation unit. The overall energy consumption of the system is reduced by more than 30%.

[0025] Meanwhile, this invention creatively couples units such as the hydrocracking reactor, integrated heat exchanger, mixed dehydrogenation reactor, and oligomerization reactor, breaking the traditional single-feed processing model. Compared with existing technologies, the process coupling of this invention is not a simple assembly of units, but rather a precise matching of products and byproducts of each unit through pipeline connections and circulation design. For example, the waste heat from hydrocracking products provides energy for preheating LPG feedstock and olefins, and dehydrogenation products further preheat LPG feedstock. Hydrogen byproducts from dehydrogenation and surplus hydrogen from the hydrocracking unit provide a hydrogen source for hydrocracking. Unreacted C3 and C4 components are recycled back to the dehydrogenation reactor, forming a double cycle.

[0026] This invention also achieves efficient utilization of energy and resources through a thermally integrated heat exchanger. On the one hand, it utilizes the waste heat of hydrocracking products to preheat LPG feedstock while simultaneously cooling the hydrocracking products, eliminating the need for additional heating or cooling equipment and significantly reducing system energy consumption compared to traditional processes. On the other hand, it establishes a cycle of hydrogen, C3, C4 components, propane, and butane, greatly improving resource utilization.

[0027] In this invention, C3 and C4 refer to alkanes or alkenes containing 3 carbon atoms, and C4 refers to alkanes or alkenes containing 4 carbon atoms. C1 to C2 refer to chemical components containing 1 or 2 carbon atoms, generally alkanes or alkenes. C4+ products refer to alkanes or alkenes with 4 or more carbon atoms, and C5+ products refer to alkanes or alkenes with 5 or more carbon atoms.

[0028] In a second aspect, the present invention provides a method for coupled recycling of naphtha products, the method comprising recycling naphtha and LPG using the system described in the first aspect to produce carbon-containing products.

[0029] Preferably, the method includes the following steps:

[0030] (1) Naphtha is transported to the hydrocracking reactor through the feed pipeline of the hydrocracking reactor, and the hydrocracking reaction yields hydrocracking products;

[0031] (2) The hydrocracking products obtained in step (1) are transported to the thermal integrated heat exchanger through the hydrocracking product pipeline. After cooling, they are separated into propane and butane through the hydrocracking discharge pipeline, the hydrocracking cooler, the propane removal tower, and the butane removal tower. Then they are mixed with the C3 and C4 alkanes separated by the mixed dehydrogenation product separation unit. The mixed material is calculated by the raw material blending module to determine the LPG feedstock that needs to be sent out.

[0032] After being preheated by a thermal integrated heat exchanger, an LPG mixing feed heater, and a heating furnace, the mixed LPG material enters the mixed dehydrogenation reactor through the feed pipeline of the mixed dehydrogenation reactor.

[0033] (3) In step (2), the mixed LPG material is mixed and reacted in the mixed dehydrogenation reactor to obtain dehydrogenation products and hydrogen. The dehydrogenation products pass through the discharge pipeline of the mixed dehydrogenation reactor, sequentially through the LPG mixed feed heater and the mixed dehydrogenation product cooler, and then through the feed pipeline of the separation unit to enter the mixed dehydrogenation product separation unit to obtain olefin components, C3 and C4 components and hydrogen.

[0034] The hydrocracking products described in step (2) are reacted in a depropanizer to obtain propane and C4+ components;

[0035] (4) The olefin component mentioned in step (3) enters the oligomerization reactor through the olefin discharge pipeline, the thermal integrated heat exchanger, and the olefin feed pipeline, and undergoes an oligomerization reaction to obtain the oligomerization product.

[0036] The C3 and C4 components mentioned in step (3) are sent back to the thermal integrated heat exchanger through the C3 and C4 discharge pipelines and the preheated mixed LPG feed pipeline, and then sent to the mixed dehydrogenation reactor through the heating furnace;

[0037] The hydrogen gas mentioned in step (3) is purified by the pressure swing adsorption device through the hydrogen gas outlet pipeline, and then compressed by the compression unit through the primary hydrogen gas pipeline and transported back to the hydrocracking reactor.

[0038] In step (3), the C4+ component is transported to the debutane tower through the C4+ product discharge pipeline and the debutane tower feed pipeline, and reacted to obtain butane and C5+ component. The C5+ component is connected to the feed pipeline through the C5+ product discharge pipeline and sent back to the hydrocracking reactor.

[0039] Preferably, the temperature of the hydrocracking reaction in step (1) is 320~400℃, for example, 320℃, 350℃, 380℃ or 400℃, etc.; the pressure is 4~10 MPa, for example, 4 MPa, 6 MPa, 8 MPa or 10 MPa, etc.; the hydrogen-to-oil ratio is 400~1000:1, for example, 400:1, 600:1, 800:1 or 1000:1, etc.; and the mass hourly space velocity is 1~2 h⁻¹. -1 For example, it could be 1 hour. -1 2 h -1 The catalyst is a Ni-W / Al2O3 hydrocracking catalyst.

[0040] Preferably, the preheating in step (2) is to heat the temperature from room temperature to 500~530℃, for example, 500℃, 510℃, 520℃ or 530℃.

[0041] Preferably, the temperature of the mixed dehydrogenation reaction in step (3) is 580~600℃, for example, 580℃, 590℃ or 600℃, the pressure is 0.1~0.3MPa, for example, 0.1 MPa, 0.2 MPa or 0.3 MPa, and the mass hourly space velocity is 0.8~1.5h. -1 For example, it could be 0.8 h -1 0.9 h -1 1 h -1 1.2 h -1 1.4 h -1 or 1.5 h -1 The catalyst is a Pt-Sn / Al2O3 dehydrogenation catalyst.

[0042] Preferably, the temperature of the oligomerization reaction in step (4) is 180~200℃, for example, 180℃, 190℃ or 200℃, etc., and the pressure is 3.0~6.0MPa, for example, 3 MPa, 4 MPa, 5 MPa or 6 MPa, etc., with a mass hourly space velocity of 1.0~3.0h. -1 For example, it could be 1 hour. -1 2 h -1 3 h -1 The catalyst is a solid phosphoric acid catalyst.

[0043] Implementing this invention has the following beneficial effects:

[0044] This invention provides a method for deep coupling of heat, hydrogen, and carbon by mixing C3 and C4 alkanes separated from naphtha hydrocracking products with LPG for mixed dehydrogenation, and then performing oligomerization on the olefins separated from the dehydrogenation products. This method deeply integrates five units: hydrocracking, pure C3 and C4 separation, LPG mixing, mixed dehydrogenation, and oligomerization, achieving deep coupling of heat and hydrogen. Hydrogen byproducts from the dehydrogenation unit are supplied to the hydrocracking unit, enabling internal hydrogen source circulation and reducing the consumption of purchased hydrogen. The high-temperature products from hydrocracking are used to preheat the dehydrogenation feedstock, achieving cascade utilization of reaction heat and reducing system energy consumption. Experimental results show that the method of this invention can reduce purchased hydrogen consumption by more than 85% and system energy consumption by more than 30%, significantly improving the economic and environmental benefits of naphtha processing. Attached Figure Description

[0045] Figure 1This is a schematic diagram of the system provided in Embodiment 1 of the present invention, wherein 1-hydrocracking reactor; 2-integrated heat exchanger; 3-propane removal tower; 4-butane removal tower; 5-mixed dehydrogenation reactor; 6-mixed dehydrogenation product separation unit; 7-C4+ product discharge pipeline; 8-butane removal tower feed pipeline; 9-butane removal tower discharge pipeline; 10-preheated mixed LPG feed pipeline; 11-preheated mixed LPG feed pipeline; 12-mixed dehydrogenation reactor feed pipeline; 13-mixed dehydrogenation reactor discharge pipeline; 14-separation unit feed pipeline; 15-olefin discharge pipeline; 16-olefin feed pipeline; 17-C3 and C4 discharge pipelines; 18-hydrogen discharge pipeline; 19-pressure swing adsorption device; 20-initial hydrogen pipeline; 21-oligopolymerization reactor; 22-hydrocracking product 23-Feed Pipeline; 24-Hydrocracking Discharge Pipeline; 25-Propane Removal Tower Feed Pipeline; 26-Propane Removal Tower Discharge Pipeline; 27-C5+ Product Discharge Pipeline; 28-Oligomerization Product Pipeline; 29-C1~C2 Separator; 30-C1~C2 Separator Feed Pipeline; 31-C1~C2 Separator Discharge Pipeline; 32-C1~C2 (containing hydrogen) Discharge Pipeline; 33-Hydrocracking Cooler; 34-LPG Mixed Feed Heater; 35-LPG Mixed Feed Heater First Discharge Pipeline; 36-LPG Mixed Feed Heater Second Discharge Pipeline; 37-Mixed Dehydrogenation Product Cooler; 38-Heating Furnace; 39-Compression Unit; 40-Dehydrogenation By-product Hydrogen Pipeline; 41-Gas Recovery Pipeline; 42-Gas Discharge Pipeline.

[0046] Figure 2 This is a schematic diagram containing text of the naphtha product coupling system provided by the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] This example provides a system and method for deep coupling of thermal hydrogen and carbon polymerization of C3 and C4 alkanes separated from naphtha hydrocracking products with LPG for mixed dehydrogenation, and the olefins separated from the dehydrogenation products for oligomerization.

[0050] A naphtha product coupling system includes a hydrocracking reactor 1, a thermal integrated heat exchanger 2, a hydrocracking cooler 33, a C1-C2 descrambling separator 29, a propane descrambling tower 3, a butane descrambling tower 4, a mixed dehydrogenation reactor 5, a mixed dehydrogenation product separation unit 6, an oligomerization reactor 21, a pressure swing adsorption device 19, an LPG mixed feed heater 34, a mixed dehydrogenation product cooler 37, a heating furnace 38, and a compression unit 39.

[0051] The hydrocracking reactor 1 includes a hydrocracking product pipeline 22, a dehydrogenation by-product hydrogen pipeline 40, and a feed pipeline 23; the integrated heat exchanger 2 includes a preheated mixed LPG feed pipeline 10, a preheated mixed LPG feed pipeline 11, an olefin feed pipeline 15, a preheated olefin discharge pipeline 16, and a hydrocracking discharge pipeline 24; the C1-C2 separator 29 includes a C1-C2 separator feed pipeline 30, a C1-C2 separator discharge pipeline 31, and a C1-C2 (containing hydrogen) discharge pipeline 32; the propane dehydrogenator 3 includes a propane dehydrogenator feed pipeline 25, a propane dehydrogenator discharge pipeline 26, and a C4+ product discharge pipeline 7; the butane dehydrogenator 4 includes a butane dehydrogenator feed pipeline 8, a butane dehydrogenator discharge pipeline 9, and a C5+ product discharge pipeline 27; the mixed dehydrogenation reaction The apparatus 5 includes a feed line 12 and an outlet line 13 for the mixed dehydrogenation reactor; the LPG mixed feed heater 34 includes a preheated mixed LPG feed line 11, a first outlet line 35, and a second outlet line 36; the mixed dehydrogenation product cooler 37 includes an inlet line 35 and an outlet line 14; the mixed dehydrogenation product separation unit 6 includes a separation unit feed line 14, an olefin outlet line 15, C3 and C4 outlet lines 17, and a hydrogen outlet line 18; the oligomerization reactor 21 includes an olefin feed line 16 and an oligomerization product line 28; the pressure swing adsorption device 19 includes a primary hydrogen production line 20, a fuel gas recovery line 41, and a fuel gas outlet line 42;

[0052] Connections between units: Hydrocracking reactor 1 is connected to integrated heat exchanger 2 via hydrocracking product pipeline 22; integrated heat exchanger 2 is connected to hydrocracking cooler 33 via hydrocracking feed pipeline 24; integrated heat exchanger 2 is connected to oligomerization reactor 21 via olefin feed pipeline 16; hydrocracking cooler 33 is connected to de-C1~C2 separator 29 via de-C1~C2 separator feed pipeline 30; de-C1~C2 separator 29 is connected to propane stripper feed pipeline 25 via de-C1~C2 separator discharge pipeline 31; propane stripper... Propane is discharged from column 3 via the propane removal column outlet pipe 26, and butane is discharged from column 4 via the top outlet pipe 9. Propane and butane are first combined, and then connected together with the C3 and C4 outlet pipes 17 of the mixed dehydrogenation product separation unit 6 to the preheated mixed LPG feed pipe 10, forming a mixed LPG feedstock. The C5+ product outlet pipe 27 of the butane removal column 4 is connected to the feedstock feed pipe 23. The integrated heat exchanger 2 is connected to the LPG mixed feed heater 34 via the preheated mixed LPG feed pipe 11. The LPG mixed feed heater has a second outlet. Pipeline 36 is connected to the inlet of heater 38. Heater 38 is connected to mixed dehydrogenation reactor 5 via feed pipe 12. Mixed dehydrogenation reactor 5 is connected to the hot-side inlet of LPG mixed feed heater 34 via discharge pipe 13. LPG mixed feed heater 34 is connected to mixed dehydrogenation product cooler 37 via first discharge pipe 35. Mixed dehydrogenation product cooler 37 is connected to mixed dehydrogenation product separation unit 6 via feed pipe 14. Unit 6 is connected to olefin feed line 16 via olefin discharge line 15. Mixed dehydrogenation product separation unit 6 is connected to preheated mixed LPG feed line 10 via C3 and C4 discharge lines 17. Mixed dehydrogenation product separation unit 6 is connected to pressure swing adsorption (PSA) unit 19 via hydrogen discharge line 18. PSA unit 19 is connected to compression unit 39 via primary hydrogen production line 20. Compression unit 39 is connected to hydrocracking reactor 1 via dehydrogenation by-product hydrogen production line 40. PSA unit 19 is connected to heater 38 via fuel recovery line 41. For detailed connection relationships and schematic diagrams, please refer to [reference needed]. Figure 1 and Figure 2 .

[0053] A method for coupled recycling of naphtha products, using the above-mentioned system, includes the following specific steps:

[0054] (1) Straight-run naphtha (initial boiling point 62℃, final boiling point 168℃, saturated hydrocarbon content 92.8wt%, of which n-alkanes are 44.7wt% and isoalkanes are 48.1wt%) is fed into the hydrocracking reactor 1 through the feed line 23. The reactor is then subjected to a temperature of 360℃, a pressure of 4 MPa, a hydrogen-to-oil ratio of 400:1, and a mass hourly space velocity of 1.5 h⁻¹.-1 Under the conditions, a hydrocracking reaction was carried out using a Ni-W / Al2O3 hydrocracking catalyst to obtain hydrocracking products (mainly containing C3~C8 components), of which the content of C3 and C4 components was 27.5wt%, the content of C5+ components was 70.5wt%, and the remainder was C1, C2 and hydrogen. The product outlet temperature was 375℃.

[0055] (2) The hydrocracking product obtained in step (1) (temperature about 360°C) is transported to the thermal integrated heat exchanger 2 through the hydrocracking product pipeline 22, cooled to 200°C, and then cooled to 100°C through the hydrocracking cooler 33. It is then transported to the de-C1~C2 separator 29 through the de-C1~C2 separator feed pipeline 30 to separate and discharge the C1~C2 light components (methane, ethane and hydrogen). The remaining material is transported to the de-propane tower 3 and the de-butane tower 4 through the de-C1~C2 separator discharge pipeline 31 to separate propane and butane. Among them, the C3 and C4 alkanes separated by the mixed dehydrogenation product separation unit 6 are mixed with propane and butane. The mixed material is calculated by the raw material blending module to determine the LPG feedstock that needs to be sent out.

[0056] Meanwhile, LPG (mainly containing propane and butane) is transported to the thermal integrated heat exchanger 2 through the preheated mixed LPG feed pipeline 10, where it exchanges heat with the hydrocracking products and is preheated to 220°C. Then, it is heated to 350°C by the LPG mixed feed heater 34, and then preheated to 580°C by the heater 38. Finally, the preheated mixed LPG feed enters the mixed dehydrogenation reactor 5 through the mixed dehydrogenation reactor feed pipeline 12.

[0057] (3) The LPG material mixed in step (2) is in the mixed dehydrogenation reactor 5 at a temperature of 580℃, a pressure of 0.2MPa, and a mass hourly space velocity of 1h. -1 Under the specified conditions, a Pt-Sn / Al2O3 dehydrogenation catalyst is used for a mixed dehydrogenation reaction to obtain dehydrogenation products (containing olefin components) and hydrogen. The dehydrogenation products pass through the discharge pipe 13 of the mixed dehydrogenation reactor sequentially through the LPG mixed feed heater 34 and the mixed dehydrogenation product cooler 37, and then through the feed pipe 14 of the separation unit into the mixed dehydrogenation product separation unit 6 to obtain olefin components, C3 and C4 components, and hydrogen. After separation, olefin components (of which the total olefin yield is 43.5 wt%), C3 and C4 components (propylene 22.3 wt%, butene 22.5 wt%), and hydrogen (byproduct hydrogen purity 94.5 wt%) are obtained. The first discharge pipe 35 of the LPG mixed feed heater is the side outlet of the LPG mixed feed heater 34 and serves as the feed channel of the mixed dehydrogenation product cooler. The second discharge pipe 36 of the LPG mixed feed heater serves as the feed channel of the heating furnace 38.

[0058] The hydrocracking products described in step (2) are reacted in the propane depropanizer 3 to obtain propane and C4+ components;

[0059] (4) The olefin component mentioned in step (3) is heated by the integrated heat exchanger 2 and enters the oligomerization reactor 21 through the olefin feed pipeline 16, at a temperature of 200℃, a pressure of 3.5MPa, and a mass hourly space velocity of 1.5h. -1 Under certain conditions, oligomerization was carried out using a solid phosphoric acid catalyst to obtain oligomers (C6~C16 isoolefins), which were discharged and collected through oligomer pipeline 28.

[0060] The C3 and C4 components mentioned in step (3) are fed through the C3 and C4 discharge pipes 17 and the LPG feed pipe 10 to form a mixed LPG feedstock. After being heated by the integrated heat exchanger 2, the LPG mixed feed heater 34 and the heating furnace 8, the feedstock is sent to the mixed dehydrogenation reactor 5 to continue participating in the dehydrogenation reaction.

[0061] The hydrogen gas mentioned in step (3) is purified by the pressure swing adsorption device 19 after passing through the hydrogen gas outlet pipeline 18, and then transported back to the compression unit 39 for pressurization through the primary hydrogen gas pipeline 20. After being pressurized, it is connected to the hydrocracking reactor 1 through the dehydrogenation by-product hydrogen gas pipeline 40 and sent to the hydrocracking reactor 1 to provide a hydrogen source for the hydrocracking reaction.

[0062] The C4+ component reaction in step (3) is transported to the butane de-butane tower 4 through the C4+ product discharge pipeline 7 and the butane de-butane tower feed pipeline 8, and the reaction yields butane and C5+ components. The C5+ components are connected to the raw material feed pipeline 23 through the C5+ product discharge pipeline 27 and sent back to the hydrocracking reactor 1.

[0063] Among them, the fuel gas delivered by the pressure swing adsorption device 19 is connected to the heating furnace 38 through the gas recovery pipeline 41, and another pipeline is sent to the fuel gas network through the gas discharge pipeline 42.

[0064] In this embodiment, the hydrogen produced as a byproduct of dehydrogenation is purified and 91% is supplied to the hydrocracking unit. The external hydrogen consumption of the hydrocracking unit is reduced from 1.2wt% to 0.18wt%, a reduction of 85%. Thermal coupling: The thermal integrated heat exchanger recovers 12.8MW of heat, and the heating load of the dehydrogenation unit is reduced by 42%.

[0065] Comparative Example 1

[0066] In this comparative example, the hydrocracking reactor, propane de-propane tower, butane de-propane tower, mixed dehydrogenation reactor, and oligomerization reactor are connected sequentially and operated independently without thermal hydrogen-carbon coupling. The remaining raw materials and operating parameters are the same as in Example 1.

[0067] The results showed that the consumption of purchased hydrogen was 1.2 wt%, the system energy consumption was 582 kg of standard oil / t of feedstock, the dehydrogenation catalyst life was 120 days, and the carbon resource utilization rate was 87.6%. All indicators were significantly worse than those of Example 1 of the present invention.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for coupling naphtha products, characterized in that, It includes a hydrocracking reactor, a thermal integrated heat exchanger, a hydrocracking cooler, a C1-C2 dehydrogenation separator, a propane dehydrogenation tower, a butane dehydrogenation tower, a mixed dehydrogenation reactor, an LPG mixed feed heater, a mixed dehydrogenation product cooler, a mixed dehydrogenation product separation unit, an oligomerization reactor, a pressure swing adsorption unit, a heating furnace, and a compression unit. The hydrocracking reactor includes a hydrocracking product pipeline, a dehydrogenation by-product hydrogen pipeline, and a feedstock pipeline; The integrated heat exchanger includes a preheated mixed LPG feed line, a preheated mixed LPG feed line, an olefin feed line, a preheated olefin discharge line, and a hydrocracking discharge line. The C1~C2 separator includes a C1~C2 separator feed pipe, a C1~C2 separator discharge pipe, and a C1~C2 (containing hydrogen) discharge pipe; The propane dehydrogenator includes a propane dehydrogenator feed pipeline, a propane dehydrogenator discharge pipeline, and a C4+ product discharge pipeline; The butane removal tower includes a butane removal tower feed pipeline, a butane removal tower discharge pipeline, and a C5+ product discharge pipeline; The heating furnace includes a heating furnace feed pipe and a heating furnace discharge pipe; The mixed dehydrogenation reactor includes a mixed dehydrogenation reactor feed pipeline and a mixed dehydrogenation reactor discharge pipeline; The LPG mixing feed heater includes a preheated LPG feed pipeline, a first discharge pipeline of the LPG mixing feed heater, a discharge pipeline of the mixing dehydrogenation reactor, and a second discharge pipeline of the LPG mixing feed heater. The mixed dehydrogenation product cooler includes an inlet pipe and an outlet pipe. The mixed dehydrogenation product separation unit includes a separation unit feed pipeline, an olefin discharge pipeline, C3 and C4 discharge pipelines, and a hydrogen discharge pipeline. The oligomerization reactor includes an olefin feed line and an oligomerization product line; The pressure swing adsorption device includes a primary hydrogen production pipeline, a fuel gas recovery pipeline, and a fuel gas discharge pipeline; The hydrocracking reactor is connected to a thermally integrated heat exchanger via a hydrocracking product pipeline. The thermally integrated heat exchanger is connected to a hydrocracking cooler via a hydrocracking feed pipeline. The thermally integrated heat exchanger is connected to an oligomerization reactor via an olefin feed pipeline. The hydrocracking cooler is connected to a C1-C2 decarbonylator via a C1-C2 separator feed pipeline. The C1-C2 decarbonylator is connected to a propane stripper feed pipeline via a C1-C2 separator discharge pipeline. The propane stripper then passes through a propane stripper... Propane is discharged from the tower outlet pipeline, and butane is discharged from the butane removal tower through the top outlet pipeline. Propane and butane are first combined, and then connected to the preheated mixed LPG feed pipeline along with the C3 and C4 outlet pipelines of the mixed dehydrogenation product separation unit, forming a mixed LPG feedstock. The C5+ product outlet pipeline of the butane removal tower is connected to the feedstock pipeline. The integrated heat exchanger is connected to the LPG mixed feed heater through the preheated mixed LPG feed pipeline. The second LPG mixed feed heater... The discharge pipeline is connected to the inlet of the heating furnace. The heating furnace is connected to the mixed dehydrogenation reactor via the feed pipeline of the mixed dehydrogenation reactor. The mixed dehydrogenation reactor is connected to the hot-side inlet pipeline of the LPG mixed feed heater via the discharge pipeline of the mixed dehydrogenation reactor. The LPG mixed feed heater is connected to the mixed dehydrogenation product cooler via the first discharge pipeline of the LPG mixed feed heater. The mixed dehydrogenation product cooler is connected to the mixed dehydrogenation product separation unit via the feed pipeline of the separation unit. The mixed dehydrogenation product separation unit is connected to the olefin feed pipeline via the olefin discharge pipeline. The mixed dehydrogenation product separation unit is connected to the preheated mixed LPG feed pipeline via the C3 and C4 discharge pipelines. The mixed dehydrogenation product separation unit is connected to the pressure swing adsorption (PSA) unit via the hydrogen discharge pipeline. The PSA unit is connected to the compression unit via the primary hydrogen production pipeline. The compression unit is connected to the hydrocracking reactor via the dehydrogenation by-product hydrogen pipeline. The PSA unit is connected to the heating furnace via the fuel recovery pipeline.

2. A method for coupled recycling of naphtha products, characterized in that, The method includes using the system described in claim 1 to recycle naphtha and LPG to produce carbon-containing products.

3. The method according to claim 2, characterized in that, The method includes the following steps: (1) Naphtha is transported to the hydrocracking reactor through the feed pipeline of the hydrocracking reactor, and the hydrocracking reaction yields hydrocracking products; (2) The hydrocracking products obtained in step (1) are transported to the thermal integrated heat exchanger through the hydrocracking product pipeline. After cooling, they are separated into propane and butane through the hydrocracking discharge pipeline, the hydrocracking cooler, the propane removal tower, and the butane removal tower. Then they are mixed with the C3 and C4 alkanes separated by the mixed dehydrogenation product separation unit. The mixed material is calculated by the raw material blending module to determine the LPG feedstock that needs to be sent out. After being preheated by a thermal integrated heat exchanger, an LPG mixing feed heater, and a heating furnace, the mixed LPG material enters the mixed dehydrogenation reactor through the feed pipeline of the mixed dehydrogenation reactor. (3) In step (2), the mixed LPG material is mixed and reacted in the mixed dehydrogenation reactor to obtain dehydrogenation products and hydrogen. The dehydrogenation products pass through the discharge pipeline of the mixed dehydrogenation reactor, sequentially through the LPG mixed feed heater and the mixed dehydrogenation product cooler, and then through the feed pipeline of the separation unit to enter the mixed dehydrogenation product separation unit to obtain olefin components, C3 and C4 components and hydrogen. The hydrocracking products described in step (2) are reacted in a depropanizer to obtain propane and C4+ components; (4) The olefin component mentioned in step (3) enters the oligomerization reactor through the olefin discharge pipeline, the thermal integrated heat exchanger, and the olefin feed pipeline, and undergoes an oligomerization reaction to obtain the oligomerization product. The C3 and C4 components mentioned in step (3) are sent back to the thermal integrated heat exchanger through the C3 and C4 discharge pipelines and the preheated mixed LPG feed pipeline, and then sent to the mixed dehydrogenation reactor through the heating furnace; The hydrogen gas mentioned in step (3) is purified by the pressure swing adsorption device through the hydrogen gas outlet pipeline, and then compressed by the compression unit through the primary hydrogen gas pipeline and transported back to the hydrocracking reactor. In step (3), the C4+ component is transported to the debutane tower through the C4+ product discharge pipeline and the debutane tower feed pipeline, and reacted to obtain butane and C5+ component. The C5+ component is connected to the feed pipeline through the C5+ product discharge pipeline and sent back to the hydrocracking reactor.

4. The method according to claim 4, characterized in that, The hydrocracking reaction in step (1) is carried out at a temperature of 320-400℃, a pressure of 4-10 MPa, a hydrogen-to-oil ratio of 400-1000:1, and a mass hourly space velocity of 1-2 h⁻¹. -1 The catalyst is a Ni-W / Al2O3 hydrocracking catalyst.

5. The method according to claim 4, characterized in that, The preheating mentioned in step (2) is to heat the temperature from room temperature to 500~530℃.

6. The method according to claim 4, characterized in that, The temperature of the mixed dehydrogenation reaction in step (3) is 580~600℃, the pressure is 0.1~0.3MPa, and the mass hourly space velocity is 0.8~1.5h. -1 The catalyst is a Pt-Sn / Al2O3 dehydrogenation catalyst.

7. The method according to claim 4, characterized in that, The oligomerization reaction in step (4) is carried out at a temperature of 180~200℃, a pressure of 3.0~6.0MPa, and a mass hourly space velocity of 1.0~3.0h. -1 The catalyst is a solid phosphoric acid catalyst.

Images