Method and system for extracting hydrogen from continuous reforming product

Abstract

The invention relates to a method and a system for extracting hydrogen from continuous reformate, the method is characterized in that pre-separated gas and a reformate phase separated by a reformate separation unit enter a low-temperature hydrogen extraction tower, hydrogen extraction treatment is carried out under relatively mild pressure and temperature conditions, and a tower top freezer is arranged in the low-temperature hydrogen extraction tower, on one hand, on the other hand, on the other hand, the temperature of the tower top freezer is reduced; the effect of hydrogen extraction treatment can be ensured, so that the purity of hydrogen produced by reforming and the yield of light hydrocarbon in the reformed and dehydrogenated oil can be ensured; on the other hand, the energy consumption of the system can be reduced. Besides, the pre-separated gas and the reformate phase are subjected to heat exchange with a hydrogen extraction treatment product before hydrogen extraction treatment, so that the energy of each component can be recovered, and the energy consumption of the system can be further reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of petrochemical engineering, and in particular to a method and system for continuously extracting hydrogen from reforming products. Background Art

[0002] Continuous reforming is a petroleum refining process that converts naphtha fractions from upstream refinery units into reformed oil rich in aromatics. A large amount of hydrogen is produced as a by-product during the oil conversion process. This hydrogen product is one of the main sources of hydrogen for hydrogenation units in refineries. In order to improve the purity of downstream hydrogen sources, a reforming hydrogen purification system is generally provided in low-pressure continuous reforming.

[0003] The continuous reforming hydrogen production and purification system is conducive to improving the purity of hydrogen and recovering liquid at higher pressure and lower temperature, but it will lead to higher energy consumption of the system. At present, the newly built continuous reforming unit has the problem of not being able to take into account the problem of improving the purity of reforming hydrogen, increasing the yield of reforming dehydrogenated oil and reducing energy consumption. Summary of the invention

[0004] The purpose of the present disclosure is to provide a method and system for continuously extracting hydrogen from reforming products to solve the problem in the prior art that it is impossible to simultaneously improve the purity of reforming hydrogen, increase the yield of reforming dehydrogenated oil and reduce energy consumption.

[0005] The first aspect of the present disclosure provides a method for hydrogen stripping of a continuous reforming product, the method comprising: allowing the continuous reforming product to enter a reforming product separation unit for pre-separation treatment to obtain a pre-separated gas and a reforming oil phase; allowing the pre-separated gas to enter a gas-liquid separation unit for gas-liquid separation treatment to obtain a separated liquid phase and a separated gas phase; allowing the separated gas phase to enter a low-temperature hydrogen stripping tower for countercurrent contact with the reforming oil for hydrogen stripping treatment to obtain a hydrogen stripping oil phase and a hydrogen stripping gas phase; the operating conditions of the low-temperature hydrogen stripping tower include: a tower top temperature of 6 to 35°C, a tower The bottom temperature is 25-55°C, and the pressure at the top of the low-temperature hydrogen extraction tower is 2.1-3.5MPa; the hydrogen extraction gas phase is cooled to 4-20°C by the top refrigerator and then discharged from the low-temperature hydrogen extraction tower; the top refrigerator is arranged inside the low-temperature hydrogen extraction tower and at the upper part of the low-temperature hydrogen extraction tower; the hydrogen extraction oil phase is mixed with the separated liquid phase after heat exchange with the separated gas phase through the first heat exchanger to obtain reformed dehydrogenated oil; the cooled hydrogen extraction gas phase is heat exchanged with the reforming oil phase through the second heat exchanger to obtain reforming hydrogen.

[0006] Optionally, the operating conditions of the low-temperature hydrogen extraction tower include: a tower top temperature of 6 to 35° C., a tower bottom temperature of 25 to 55° C., and a tower top pressure of 2.1 to 3.5 MPa.

[0007] Optionally, before the hydrogen extraction treatment is carried out, the separated gas phase is cooled in turn by the first heat exchanger and the gas phase cooler before entering the lower part of the low-temperature hydrogen extraction tower; the reformed oil is cooled in turn by the second heat exchanger and the oil phase freezer before entering the upper part of the low-temperature hydrogen extraction tower.

[0008] Optionally, the temperature of the separated gas phase after cooling by the gas phase cooler is 35-45°C and the pressure is 2.2-3.6 MPa; the temperature of the reformed oil phase after cooling by the oil phase freezer is 4-20°C and the pressure is 2.24-3.64 MPa.

[0009] Optionally, the cold sources used by the tower top freezer, the gas phase cooler and the oil phase freezer each independently include chilled water and / or circulating water, preferably chilled water and / or circulating water produced by a petrochemical enterprise.

[0010] Optionally, the temperature of the reforming hydrogen production is 28-42°C, the pressure is 2.06-3.46 MPa, and the hydrogen content is 93-96.5 mol%; the temperature of the hydrogen extraction gas phase after cooling by the tower top refrigerator is 8-12°C, the pressure is 2.08-3.48 MPa, and the hydrogen content is 93-96.5 mol%.

[0011] Optionally, the gas-liquid separation unit includes a primary liquid separation device and a secondary liquid separation device arranged in series; the gas-liquid separation process includes: allowing the pre-separated gas to enter the primary liquid separation device for sequential cooling, liquid separation and compression to obtain a primary separated liquid phase and a primary separated gas phase; allowing the primary separated gas phase to enter the secondary liquid separation device for sequential cooling, liquid separation and compression to obtain a secondary separated liquid phase and the separated gas phase.

[0012] Optionally, the temperature of the separated gas phase is 105-130° C., the pressure is 2.22-3.62 MPa, and the hydrogen content is 87-91 mol%.

[0013] The second aspect of the present disclosure is a system for continuously extracting hydrogen from reformed products by using the method described in the first aspect of the present disclosure, the system comprising a reformed product separation unit, a gas-liquid separation unit, a low-temperature hydrogen extraction tower, a tower top freezer, a first heat exchanger, and a second heat exchanger; the tower top freezer is arranged inside the low-temperature hydrogen extraction tower and located at the upper part of the low-temperature hydrogen extraction tower; the reformed product separation unit comprises a continuous reformed product inlet, a pre-separation gas outlet, and a reformed oil phase outlet; the gas-liquid separation unit comprises a pre-separation gas inlet, a separation gas phase outlet, and a separation liquid phase outlet; the low-temperature hydrogen extraction tower comprises a separation gas phase inlet, a reformed oil phase inlet, a hydrogen extraction oil phase outlet, and a hydrogen extraction gas phase outlet; the tower top freezer comprises a cold source inlet and a cold source outlet; the continuous reformed product inlet of the reformed product separation unit is used to communicate with the continuous reformed product The material sources are connected; the pre-separation gas outlet of the reforming product separation unit is connected with the pre-separation gas inlet of the gas-liquid separation unit; the separation gas phase outlet of the gas-liquid separation unit is connected with the inlet of the first heat exchanger; the outlet of the first heat exchanger is connected with the separation gas phase inlet of the low-temperature hydrogen extraction tower; the reforming oil phase outlet of the reforming product separation unit is connected with the inlet of the second heat exchanger; the outlet of the second heat exchanger is connected with the reforming oil phase inlet of the low-temperature hydrogen extraction tower; the hydrogen extraction oil phase outlet of the low-temperature hydrogen extraction tower is connected with the cold source inlet of the first heat exchanger; the hydrogen extraction gas phase outlet of the low-temperature hydrogen extraction tower is connected with the cold source inlet of the second heat exchanger; the cold source inlet of the tower top freezer is used to be connected with the outlet of the chilled water device, and the cold source outlet is used to be connected with the inlet of the chilled water device.

[0014] Optionally, the system also includes a gas phase cooler and an oil phase freezer; the inlet of the gas phase cooler is connected to the outlet of the first heat exchanger, and the outlet is connected to the separation gas phase inlet of the low-temperature hydrogen extraction tower; the cold source inlet of the gas phase cooler is used to be connected to the outlet of the chilled water device, and the outlet is used to be connected to the inlet of the chilled water device; the inlet of the oil phase freezer is connected to the outlet of the second heat exchanger, and the outlet is connected to the separation liquid phase inlet of the low-temperature hydrogen extraction tower; the cold source inlet of the oil phase freezer is used to be connected to the outlet of the chilled water device, and the outlet is used to be connected to the inlet of the chilled water device.

[0015] Through the above technical scheme, the pre-separated gas and reformed oil phases separated by the reforming product separation unit enter the low-temperature hydrogen extraction tower, and are subjected to hydrogen extraction treatment under relatively mild pressure and temperature conditions; and a tower top freezer is set in the low-temperature hydrogen extraction tower to further condense the small amount of liquid phase in the gas phase. On the one hand, this scheme can ensure the effect of hydrogen extraction treatment, and thus ensure the purity of reforming hydrogen and the yield of light hydrocarbons in reformed dehydrogenated oil; on the other hand, it avoids energy loss caused by hydrogen extraction treatment under very low temperature and very high pressure conditions, and can reduce the energy consumption of the system. In addition, the pre-separated gas and reformed oil phases are heat exchanged with the hydrogen extraction product before hydrogen extraction treatment, which can recover the energy of each component, and thus can further reduce the energy consumption of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0017] Figure 1 The present invention shows a flow chart of a method for continuously extracting hydrogen from reforming products.

[0018] Description of Reference Numerals

[0019] 1 reforming product separation tank; 2 circulating hydrogen compressor; 3 primary cooler; 4 primary liquid separator tank; 5 primary booster; 6 secondary cooler; 7 secondary liquid separator tank; 8 secondary booster; 9 first heat exchanger; 10 gas phase cooler; 11 low temperature hydrogen extraction tower; 12 tower top freezer; 13 second heat exchanger; 14 oil phase freezer. DETAILED DESCRIPTION

[0020] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0021] In the present disclosure, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of a device in normal use. Figure 1 In the drawing direction, "inside" and "outside" refer to the outline of the device. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0022] The first aspect of the present disclosure provides a method for hydrogen stripping of a continuous reforming product, the method comprising: allowing the continuous reforming product to enter a reforming product separation unit for pre-separation treatment to obtain a pre-separated gas and a reforming oil phase; allowing the pre-separated gas to enter a gas-liquid separation unit for gas-liquid separation treatment to obtain a separated liquid phase and a separated gas phase; allowing the separated gas phase to enter a low-temperature hydrogen stripping tower 11 for countercurrent contact with the reforming oil for hydrogen stripping treatment to obtain a hydrogen stripping oil phase and a hydrogen stripping gas phase; the operating conditions of the low-temperature hydrogen stripping tower 11 include: a tower top temperature of 6 to 35°C, a tower bottom temperature of 2 5~55℃, the pressure at the top of the low-temperature hydrogen extraction tower 11 is 2.1~3.5MPa; the hydrogen extraction gas phase is cooled to 4~20℃ by the top freezer 12 and then discharged from the low-temperature hydrogen extraction tower 11; the top freezer 12 is arranged inside the low-temperature hydrogen extraction tower 11 and at the upper part of the low-temperature hydrogen extraction tower 11; the hydrogen extraction oil phase is mixed with the separated liquid phase after heat exchange with the separated gas phase through the first heat exchanger 9 to obtain reformed dehydrogenated oil; the cooled hydrogen extraction gas phase is heat exchanged with the reforming oil phase through the second heat exchanger 13 to obtain reformed hydrogen.

[0023] Through the above technical scheme, the pre-separated gas and reformed oil phase separated by the reformed product separation unit enter the low-temperature hydrogen extraction tower 11, and the hydrogen extraction treatment is carried out under relatively high pressure and relatively low temperature conditions. On the one hand, the effect of the hydrogen extraction treatment can be guaranteed, and then the purity of the reformed hydrogen and the yield of light hydrocarbons in the reformed dehydrogenated oil can be guaranteed; on the other hand, the energy loss caused by the hydrogen extraction treatment under very low temperature and very high pressure conditions can be avoided, and the energy consumption of the system can be reduced. At the same time, a tower top freezer 12 is set in the low-temperature hydrogen extraction tower 11, and the hydrogen extraction gas phase obtained by the hydrogen extraction treatment flows upward. After contacting the tower top freezer 12, the small amount of liquid phase in the gas phase is further condensed, which can further improve the purity of the reformed hydrogen and the yield of light hydrocarbons in the reformed dehydrogenated oil. In addition, the pre-separated gas and reformed oil phases are heat exchanged with the hydrogen extraction treatment product before the hydrogen extraction treatment, which can recover the energy of each component, and then the energy consumption of the system can be further reduced.

[0024] The continuous reforming product used in the present disclosure is produced by an upstream unit of a petroleum refinery that converts a naphtha fraction into an aromatic-rich reformed oil, and contains a large amount of hydrogen.

[0025] The reforming product separation unit used in the present disclosure is a conventional choice in the art, and this application does not make special requirements. For example, the reforming product separation unit used in the present disclosure includes a reforming product separation tank 1 and a circulating hydrogen compressor 2. In this embodiment, the continuous reforming product is separated into circulating hydrogen and reforming oil phases in the reforming product separation tank 1, and after the pre-separated gas is compressed by the circulating hydrogen compressor 2, a part of it is returned to the upstream continuous reforming device to participate in the reaction, and the other part enters the downstream gas-liquid separation unit as the pre-separated gas.

[0026] Among them, the volume ratio of the circulating hydrogen returned to the upstream continuous reforming unit to all circulating hydrogen can be flexibly adjusted according to actual production needs. The preferred volume ratio of the circulating hydrogen returned to the upstream continuous reforming unit to all circulating hydrogen is (0.5-0.8):1.

[0027] The operating conditions of the reforming product separation tank 1 include: a temperature of 39-50°C and a pressure of 0.24 MPa. In this embodiment, the temperature of the continuous reforming product produced by the continuous reforming device is 480-520°C, the pressure is 0.33-0.34 MPa, and the hydrogen content is 75.8-79.5 mol%. The temperature of the reforming tank top gas after being treated by the reforming product separation tank 1 is 39-50°C, the pressure is 0.24 MPa, and the hydrogen content is 85.2-90.4 mol%.

[0028] In one embodiment, the number of stages of the gas-liquid separation unit can be one or more stages, and the number of stages of the gas-liquid separation unit can be flexibly adjusted according to the properties of the pre-separated gas.

[0029] The number of stages of the gas-liquid separation unit is preferably 2, that is, the gas-liquid separation unit includes a primary liquid separation device and a secondary liquid separation device arranged in series. In this embodiment, the gas-liquid separation process includes: allowing the pre-separated gas to enter the primary liquid separation device for sequential cooling, liquid separation and compression to obtain a primary separated liquid phase and a primary separated gas phase; allowing the primary separated gas phase to enter the secondary liquid separation device for sequential cooling, liquid separation and compression to obtain a secondary separated liquid phase and the separated gas phase.

[0030] Among them, each level of liquid separation device includes at least a cooler, a liquid separation tank and a supercharger arranged in series in sequence, and the outlet of the supercharger of the previous level is connected to the inlet of the cooler of the next level, so that the gas phase generated by the liquid separation device of the previous level can enter the liquid separation device of the next level.

[0031] Among them, in a specific implementation manner, the pre-separated gas is sequentially cooled by a primary cooler 3, separated by a primary liquid separator 4, and pressurized by a primary supercharger 5, and a primary separated liquid phase is obtained from the bottom of the primary liquid separator 4, and a primary separated gas phase is obtained from the outlet of the primary supercharger 5; the primary separated gas phase is sequentially cooled by a secondary cooler 6, separated by a secondary liquid separator 7, and pressurized by a secondary supercharger 8, and a secondary separated liquid phase is obtained from the bottom of the secondary liquid separator 7, and the separated gas phase is obtained from the outlet of the secondary supercharger 8.

[0032] The first-stage separated liquid phase, the second-stage separated liquid phase and the hydrogen-extracted oil phase after heat exchange are mixed to obtain reformed dehydrogenated oil.

[0033] Among them, in order to ensure the separation effect of the gas-liquid separation unit while improving the rationality of the load of each level of gas-liquid separation device, the temperature and pressure of each level of the liquid separation device can be limited. For example, the temperature ratio of the next level of the liquid separation device to the previous level of the liquid separation device is (2.52~2.9):1, and the pressure ratio is (2.1~2.4):1; the temperature and pressure can also be selected according to the properties of the material in each level of the liquid separation device.

[0034] Among them, the temperature of the separated gas phase is 105-130°C, the pressure is 2.22-3.62MPa, and the hydrogen content is 87-91mol%. Preferably, the temperature of the separated gas phase is 115-127°C, the pressure is 2.3-3.2MPa, and the hydrogen content is 87.3-90.8mol%.

[0035] In one embodiment, before the hydrogen extraction treatment is performed, the separated gas phase is cooled by the first heat exchanger 9 and the gas phase cooler 10 in sequence, and then enters the lower part of the low-temperature hydrogen extraction tower 11; the reformed oil phase is cooled by the second heat exchanger 13 and the oil phase freezer 14 in sequence, and then enters the upper part of the low-temperature hydrogen extraction tower 11. In this embodiment, after the separated gas phase is cooled by the first heat exchanger 9 and the gas phase cooler 10 in sequence, the separated gas phase can be cooled twice and the temperature can be quickly reduced to a relatively low level; after the reformed oil phase is cooled by the second heat exchanger 13 and the oil phase freezer 14 in sequence, the reformed oil phase can be cooled twice and the temperature can be quickly reduced to a relatively low level; the separated gas phase after cooling enters the lower part of the low-temperature hydrogen extraction tower 11, and the reformed oil phase after cooling enters the upper part of the low-temperature hydrogen extraction tower 11. At this time, the gas phase moves upward and contacts with the oil phase moving downward in countercurrent, which enhances the mass transfer between gas and liquid and can improve the effect of hydrogen extraction treatment.

[0036] Among them, the temperature of the separated gas phase after cooling by the gas phase cooler 10 is 35-45°C and the pressure is 2.2-3.6 MPa; the temperature of the reformed oil phase after cooling by the oil phase freezer 14 is 4-20°C and the pressure is 2.24-3.64 MPa.

[0037] The type of the low-temperature hydrogen extraction tower 11 is a plate tower or a packed tower. The low-temperature hydrogen extraction tower 11 used in the present disclosure is a plate tower type low-temperature hydrogen extraction tower 11, wherein the total number of plates is flexibly adjusted according to the conditions of hydrogen extraction treatment and the properties of the materials, for example, the number of plates can be 5 to 25. In addition, the distance between two adjacent plates can be flexibly selected according to actual production needs.

[0038] Among them, in order to further improve the effect of hydrogen extraction treatment, the operating conditions of the low-temperature hydrogen extraction tower 11 are preferably: the top temperature is 8-20°C, the bottom temperature is 30-48°C, and the pressure at the top of the low-temperature hydrogen extraction tower 11 is 2.1-3MPa. In this embodiment, both pressurization and cooling can achieve the effect of improving the purity of hydrogen, but with the increase of pressure and the decrease of temperature, the influence of pressurization and cooling on improving the purity of hydrogen slows down. Therefore, blindly lowering the temperature or increasing the pressure cannot obtain a better separation effect, and it is necessary to carry out both temperature and pressure. The present invention discloses that the gas phase and the liquid phase are in countercurrent contact under the above-mentioned preferred relatively low temperature and relatively high pressure conditions, which can further enhance the mass transfer between gas and liquid, further improve the purity of hydrogen, increase the oil recovery generated by reforming, and reduce the energy consumption of the device.

[0039] The temperature of the reforming hydrogen production is 28-42° C., the pressure is 2.06-3.46 MPa, and the hydrogen content is 93-96.5 mol%.

[0040] Among them, in order to further improve the effect of countercurrent treatment, a gas-phase feed distributor and a liquid-phase feed distributor can be set in the internal chamber of the low-temperature hydrogen extraction tower 11; the inlet of the gas-phase feed distributor extends to the outside of the low-temperature hydrogen extraction tower 11 and forms a separated gas phase inlet, and the inlet of the liquid-phase feed distributor extends to the outside of the low-temperature hydrogen extraction tower 11 and forms a reforming oil phase inlet; the injection direction of the opening of the gas-phase feed distributor is vertically upward, and the injection direction of the opening of the liquid-phase feed distributor is vertically downward.

[0041] Among them, in order to further improve the effect of hydrogen extraction treatment, a top freezer 12 is set at the upper part of the internal chamber of the low-temperature hydrogen extraction tower 11, so that the hydrogen extraction gas phase can be further cooled and condensed during its upward movement, thereby further improving the purity of hydrogen and increasing the oil yield generated by reforming.

[0042] The tower top freezer 12 is essentially a heat exchange coil arranged in the low-temperature hydrogen extraction tower 11. The inlet and outlet of the heat exchange coil both extend to the outside of the low-temperature hydrogen extraction tower 11. In order to improve the cooling effect of the tower top freezer 12, the parameters of the heat exchange coil are limited. The material of the heat exchange coil is one or more of 10# steel, 09MnNiDR steel, 16MnDR steel and 15MnNiDR steel, the total length is 1.5 to 3m and the wall thickness is 3 to 5mm.

[0043] The tower top freezer 12 may be arranged at the upper part of the internal chamber of the cryogenic hydrogen extraction tower 11. In order to further improve the effect of hydrogen extraction treatment, the height of the tower top freezer 12 is limited. Specifically, the ratio of the distance between the tower top freezer 12 and the bottom of the cryogenic hydrogen extraction tower 11 to the height of the cryogenic hydrogen extraction tower 11 is (0.6-0.95):1, preferably (0.8-0.9):1.

[0044] In order to further enhance the effect of the hydrogen extraction treatment, a wire mesh demister may be provided on the top of the inner chamber of the low-temperature hydrogen extraction tower 11 .

[0045] Among them, the cold sources used by the tower top freezer 12, the gas phase cooler 10 and the oil phase freezer 14 each independently include chilled water and / or circulating water, preferably chilled water and / or circulating water produced by petrochemical enterprises. In this embodiment, since the temperature of the hydrogen extraction treatment disclosed in the present invention is relatively high compared with the prior art, there is no need to use a deep cooling system, and only the chilled water and / or circulating water produced by petrochemical enterprises can meet the requirements. The low-temperature process is simple, which can not only reduce the investment in refrigeration equipment and the energy consumption of refrigeration equipment operation, but also the cold source is relatively stable, and there is no problem of being unable to provide a cold source due to a refrigeration equipment operation failure.

[0046] According to the above embodiment, by improving the device, conditions and method of hydrogen extraction treatment, the temperature of the hydrogen extraction gas phase is 11-15°C, the pressure is 2.1-3.5MPa, and the hydrogen content is 93-95.9mol%. After being refrigerated by the tower top freezer 12, the quality of hydrogen is further improved. The temperature of the hydrogen extraction gas phase after being cooled by the tower top freezer 12 is 8-12°C, the pressure is 2.08-3.48MPa, and the hydrogen content is 93-96.5mol%. It can be seen that the method disclosed in the present invention reduces the energy consumption of the system while improving the purity of reforming hydrogen production and the yield of reforming dehydrogenated oil.

[0047] In one embodiment, the reforming hydrogen is dechlorinated in a reforming hydrogen dechlorination tank and then sent to a PSA device for further purification.

[0048] In one embodiment, the reforming dehydrogenated oil enters the reforming dehydrogenated oil dechlorination tank, the dechlorinated reforming dehydrogenated oil is heat exchanged with the depentanized oil at the bottom of the depentanizer and enters the depentanizer for fractionation, the fuel gas at the top of the depentanizer returns to the inlet of the first-stage inlet air cooler of the reforming hydrogen booster, the C3-C5 light hydrocarbons produced at the top of the depentanizer are sent to the light hydrocarbon aromatization unit, the bottom of the depentanizer is heated by a reboiler, and the depentanized oil at the bottom of the tower is sent to the aromatics unit after recovering the heat.

[0049] In one embodiment, if Figure 1 As shown, the method for continuously extracting hydrogen from reforming products comprises:

[0050] The continuous reforming product is sent to the reforming product separation tank 1 for pre-separation after heat exchange and cooling to 39-50°C to obtain circulating hydrogen and reforming oil phase; after the circulating hydrogen is pressurized by the circulating hydrogen compressor 2, part of the circulating hydrogen is circulated back to the continuous reforming reaction system, and the other part enters the downstream device as pre-separation gas.

[0051] The pre-separated gas is sequentially cooled by a primary cooler 3, separated by a primary liquid separator 4 and pressurized by a primary supercharger 5, a primary separated liquid phase is obtained from the bottom of the primary liquid separator 4, and a primary separated gas phase is obtained from the outlet of the primary supercharger 5; the primary separated gas phase is sequentially cooled by a secondary cooler 6, separated by a secondary liquid separator 7 and pressurized by a secondary supercharger 8, a secondary separated liquid phase is obtained from the bottom of the secondary liquid separator 7, and the separated gas phase is obtained from the outlet of the secondary supercharger 8; the temperature of the separated gas phase is 105-130°C, the pressure is 2.22-3.62MPa, and the hydrogen content is 87-91mol%.

[0052] The separated gas phase is cooled by the first heat exchanger 9 and the gas phase cooler 10 in sequence, and then enters the lower part of the low-temperature hydrogen extraction tower 11; the reformed oil phase is cooled by the second heat exchanger 13 and the oil phase freezer 14 in sequence, and then enters the upper part of the top of the low-temperature hydrogen extraction tower 11; the temperature of the separated gas phase after cooling by the gas phase cooler 10 is 35-45°C and the pressure is 2.2-3.6MPa; the temperature of the reformed oil phase after cooling by the oil phase freezer 14 is 4-20°C and the pressure is 2.24-3.64MPa;

[0053] The separated gas phase enters the low-temperature hydrogen stripping tower 11 to countercurrently contact with the reformed oil for hydrogen stripping treatment to obtain a hydrogen stripping oil phase and a hydrogen stripping gas phase, and then the hydrogen stripping gas phase is cooled by the tower top refrigerator 12. The operating conditions of the low-temperature hydrogen extraction tower 11 include: a tower top temperature of 6 to 35°C, a tower bottom temperature of 30 to 48°C, a pressure of the low-temperature hydrogen extraction tower 11 of 2.1 to 3.5 MPa, and a number of plates of the low-temperature hydrogen extraction tower 11 of 5 to 25; the temperature of the hydrogen extraction gas phase is 11 to 15°C, the pressure is 2.1 to 3.5 MPa, and the hydrogen content is 93 to 95.9 mol%; the temperature of the hydrogen extraction gas phase after cooling by the tower top freezer 12 is 8 to 12°C, the pressure is 2.08 to 3.48 MPa, and the hydrogen content is 93 to 96.5 mol%; the temperature of the reforming hydrogen production is 28 to 42°C, the pressure is 2.06 to 3.46 MPa, and the hydrogen content is 93 to 96.5 mol%.

[0054] The cooled hydrogen extraction gas phase is heat exchanged with the reforming oil phase to 28-42°C through the second heat exchanger 13 to obtain reforming hydrogen. The reforming hydrogen is dechlorinated in the reforming hydrogen dechlorination tank and then sent to the PSA device for further purification. The hydrogen extraction oil phase is heat exchanged with the separated gas phase through the first heat exchanger 9 and mixed with the separated liquid phase to obtain reforming dehydrogenated oil; the reforming dehydrogenated oil enters the reforming dehydrogenated oil dechlorination tank, the dechlorinated reforming dehydrogenated oil is heat exchanged with the depentanized oil at the bottom of the depentanizer and enters the depentanizer for fractionation, the fuel gas at the top of the depentanizer returns to the first-stage inlet air cooler inlet of the reforming hydrogen booster, the C3-C5 light hydrocarbons extracted from the top of the depentanizer are sent to the light hydrocarbon aromatization unit, the bottom of the depentanizer uses a reboiler for heating, and the depentanized oil at the bottom of the tower is sent to the aromatics unit after recovering heat.

[0055] In a second aspect of the present disclosure, a system for continuously extracting hydrogen from reformed products using the method described in the first aspect of the present disclosure is provided, the system comprising a reformed product separation unit, a gas-liquid separation unit, a low-temperature hydrogen extraction tower 11, a tower top freezer 12, a first heat exchanger 9 and a second heat exchanger 13; the tower top freezer 12 is arranged inside the low-temperature hydrogen extraction tower 11 and is located at the upper part of the low-temperature hydrogen extraction tower 11; the reformed product separation unit comprises a continuous reformed product inlet, a pre-separation gas outlet and a reformed oil phase outlet; the gas-liquid separation unit comprises a pre-separation gas inlet, a separation gas phase outlet and a separation liquid phase outlet; the low-temperature hydrogen extraction tower 11 comprises a separation gas phase inlet, a reformed oil phase inlet, a hydrogen extraction oil phase outlet and a hydrogen extraction gas phase outlet; the tower top freezer 12 comprises a cold source inlet and a cold source outlet; the continuous reformed product inlet of the reformed product separation unit is used to communicate with the continuous reformed product inlet of the reformed product separation unit; The reformed product source is connected; the pre-separation gas outlet of the reformed product separation unit is connected to the pre-separation gas inlet of the gas-liquid separation unit; the separation gas phase outlet of the gas-liquid separation unit is connected to the inlet of the first heat exchanger; the outlet of the first heat exchanger is connected to the separation gas phase inlet of the low-temperature hydrogen extraction tower 11; the reformed oil phase outlet of the reformed product separation unit is connected to the inlet of the second heat exchanger; the outlet of the second heat exchanger is connected to the reformed oil phase inlet of the low-temperature hydrogen extraction tower 11; the hydrogen extraction oil phase outlet of the low-temperature hydrogen extraction tower 11 is connected to the cold source inlet of the first heat exchanger; the hydrogen extraction gas phase outlet of the low-temperature hydrogen extraction tower 11 is connected to the cold source inlet of the second heat exchanger; the cold source inlet of the tower top freezer 12 is used to be connected to the outlet of the chilled water device, and the cold source outlet is used to be connected to the inlet of the chilled water device.

[0056] In one embodiment, the system also includes a gas phase cooler and an oil phase freezer; the inlet of the gas phase cooler is connected to the outlet of the first heat exchanger, and the outlet is connected to the separation gas phase inlet of the low-temperature hydrogen extraction tower 11; the cold source inlet of the gas phase cooler is used to be connected to the outlet of the chilled water device, and the outlet is used to be connected to the inlet of the chilled water device; the inlet of the oil phase freezer is connected to the outlet of the second heat exchanger, and the outlet is connected to the separation liquid phase inlet of the low-temperature hydrogen extraction tower 11; the cold source inlet of the oil phase freezer is used to be connected to the outlet of the chilled water device, and the outlet is used to be connected to the inlet of the chilled water device.

[0057] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0058] Example 1

[0059] Continuous reforming product hydrogen extraction system Figure 1 As shown;

[0060] Taking a 2.6 million tons / year continuous reforming unit as an example, the methods for extracting hydrogen from continuous reforming products include:

[0061] The continuous reforming product is sent to the reforming product separation tank 1 for pre-separation after heat exchange and cooling to 40°C to obtain circulating hydrogen and reforming oil phase; after the circulating hydrogen is pressurized by the circulating hydrogen compressor 2, part of the circulating hydrogen is circulated back to the continuous reforming reaction system, and the other part enters the downstream device as pre-separation gas.

[0062] The pre-separated gas is cooled by a primary cooler 3, separated by a primary liquid separator 4 and pressurized by a primary supercharger 5 in sequence, a primary separated liquid phase is obtained from the bottom of the primary liquid separator 4, and a primary separated gas phase is obtained from the outlet of the primary supercharger 5; the primary separated gas phase is cooled by a secondary cooler 6, separated by a secondary liquid separator 7 and pressurized by a secondary supercharger 8 in sequence, a secondary separated liquid phase is obtained from the bottom of the secondary liquid separator 7, and a separated gas phase is obtained from the outlet of the secondary supercharger 8; the temperature of the separated gas phase is 117°C, the pressure is 2.4MPa, and the hydrogen content is 90mol%.

[0063] The separated gas phase is cooled by the first heat exchanger 9 and the gas phase cooler 10 in sequence, and then enters the lower part of the low-temperature hydrogen extraction tower 11; the reformed oil phase is cooled by the second heat exchanger 13 and the oil phase freezer 14 in sequence, and then enters the upper part of the low-temperature hydrogen extraction tower 11; the temperature of the separated gas phase after cooling by the gas phase cooler 10 is 40°C and the pressure is 2.34MPa; the temperature of the reformed oil phase after cooling by the oil phase freezer 14 is 10°C and the pressure is 2.43MPa;

[0064] The separated gas phase enters the low-temperature hydrogen extraction tower 11 and contacts with the reformed oil in countercurrent to carry out hydrogen extraction treatment, thereby obtaining a hydrogen extraction oil phase and a hydrogen extraction gas phase, and then the hydrogen extraction gas phase is cooled by the tower top refrigerator 12. The operating conditions of the low-temperature hydrogen extraction tower 11 include: the tower top temperature is 13°C, the tower bottom temperature is 39°C, the tower top pressure of the low-temperature hydrogen extraction tower 11 is 2.28MPa, and the actual number of plates of the low-temperature hydrogen extraction tower 11 is 20; the temperature of the hydrogen extraction gas phase is 13°C, the pressure is 2.28MPa, and the hydrogen content is 95.44mol%; the temperature of the hydrogen extraction gas phase after cooling by the tower top refrigerator 12 is 10°C, the pressure is 2.25MPa, and the hydrogen content is 95.49mol%;

[0065] The cooled hydrogen extraction gas phase is heat exchanged with the reforming oil phase to 35°C through the second heat exchanger 13 to obtain reforming hydrogen. The reforming hydrogen is dechlorinated in the reforming hydrogen dechlorination tank and then sent to the PSA device for further purification. The hydrogen extraction oil phase is heat exchanged with the separated gas phase through the first heat exchanger 9 and mixed with the separated liquid phase to obtain reforming dehydrogenated oil; the reforming dehydrogenated oil enters the reforming dehydrogenated oil dechlorination tank, and the dechlorinated reforming dehydrogenated oil is heat exchanged with the depentanized oil at the bottom of the depentanizer and enters the depentanizer for fractionation. The fuel gas at the top of the depentanizer returns to the inlet of the first inlet air cooler of the reforming hydrogen booster. The C3-C5 light hydrocarbons extracted from the top of the depentanizer are sent to the light hydrocarbon aromatization unit. The bottom of the depentanizer uses a reboiler for heating, and the depentanized oil at the bottom of the tower is sent to the aromatics unit after recovering heat.

[0066] Product properties are shown in Table 1, and energy consumption is shown in Table 2.

[0067] Example 2

[0068] The method for continuously extracting hydrogen from reforming products is the same as in Example 1, except that the operating conditions of the low-temperature hydrogen extraction tower 11 include: a tower top temperature of 12°C, a tower bottom temperature of 40°C, and a pressure of 3.28 MPa. The product properties are shown in Table 1, and the energy consumption is shown in Table 2.

[0069] Comparative Example 1

[0070] The method for extracting hydrogen from continuous reforming products is the same as that in Example 1, the continuous reforming products are sent to the reforming product separation tank after heat exchange and cooling to 40°C, the hydrogen-containing gas pressurization system at the tank top is consistent with that in Example 1, the hydrogen-containing gas is pressurized to remove the entrained liquid and then cooled to 55°C and mixed with the pressurized reforming product separation tank bottom liquid, the mixed reforming products are successively heat exchanged with the re-contact tank top gas and the re-contact tank bottom liquid, and then cooled to 10°C by the re-contact freezer before entering the re-contact tank, the re-contact tank pressure is 2.26MPa, and the re-contact tank top gas is reforming hydrogen. Product properties are shown in Table 1, and energy consumption is shown in Table 2.

[0071] Comparative Example 2

[0072] The method for hydrogen extraction of the continuous reforming product is the same as that in Example 1, except that the tower top freezer 12 is not provided in the low-temperature hydrogen extraction tower, and the hydrogen extraction gas phase obtained by the hydrogen extraction process is directly discharged from the system. The product properties are shown in Table 1, and the energy consumption is shown in Table 2.

[0073] Table 1 Product properties in Examples and Comparative Examples

[0074] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Purity of hydrogen produced by reforming, mol% 95.49 95.84 93.78 95.44 Reforming hydrogen production, kg / h 24057 22766 31057 24404 Depentane oil, kg / h 268206 268173 267601 267954 C3~C5 light hydrocarbons, kg / h 18747 20071 12352 18652 Depentanizer top circulating fuel gas, kg / h 1250 5615 5894 1233

[0075] Table 2 Energy consumption in the examples and comparative examples

[0076] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Booster unit shaft power, kW 12175 15587 12405 12175 Total cooling load of chillers, MW 2.456 2.469 4.587 2.456 Depentanizer reboiler heat load, MW 12.366 12.151 15.436 12.488

[0077] As shown in Table 1 and Table 2, according to the comparison between Example 1 and Comparative Example 1, it can be seen that by using the method disclosed in the present invention, the purity of reforming hydrogen production is increased by 1.71 mol%, the yield of C3-C5 light hydrocarbons is increased by 51.8wt%, and the yield of depentanized oil is increased by 0.23wt%; the shaft power of the booster unit is reduced by 1.85%, the refrigeration load is reduced by 46.46%, the heat load of the depentanizer reboiler is reduced by 19.89%, and the energy consumption of the device operation is reduced by 1.39kg standard oil / t continuous reforming feed. Taking the utility electricity price of 0.6 yuan / kWh, chilled water of 7 yuan / t, and fuel gas of 3,000 yuan / t as an example, the total operating cost can be reduced by 30.05 million yuan / year. The static equipment investment increased by 301,200 yuan. By comparing Example 1 and Comparative Example 2, it can be seen that a tower top freezer is provided in the low-temperature hydrogen extraction tower, and the hydrogen extraction gas phase obtained by the hydrogen extraction treatment flows upward. When it contacts the tower top freezer, a small amount of liquid phase in the gas phase is further condensed, which can further improve the purity of reforming hydrogen and the yield of light hydrocarbons in the reforming dehydrogenated oil.

[0078] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0080] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for continuously extracting hydrogen from reforming products, characterized in that: The method includes: The continuous reforming product enters the reforming product separation unit for pre-separation treatment to obtain pre-separated gas and reforming oil phase; Allowing the pre-separated gas to enter a gas-liquid separation unit for gas-liquid separation treatment to obtain a separated liquid phase and a separated gas phase; The separated gas phase enters a low-temperature hydrogen extraction tower (11) and is countercurrently contacted with the reformed oil phase for hydrogen extraction treatment to obtain a hydrogen extraction oil phase and a hydrogen extraction gas phase; the operating conditions of the low-temperature hydrogen extraction tower (11) include: a tower top temperature of 6 to 35° C., a tower bottom temperature of 25 to 55° C., and a tower top pressure of 2.1 to 3.5 MPa; The hydrogen extraction gas phase is cooled to 4-20° C. by a tower top freezer (12) and then discharged from the low-temperature hydrogen extraction tower (11); the tower top freezer (12) is arranged inside the low-temperature hydrogen extraction tower (11) and at the upper part of the low-temperature hydrogen extraction tower (11); The hydrogen-extracted oil phase is subjected to heat exchange with the separated gas phase through a first heat exchanger (9) and then mixed with the separated liquid phase to obtain reformed dehydrogenated oil; and the cooled hydrogen-extracted gas phase is subjected to heat exchange with the reformed oil phase through a second heat exchanger (13) to obtain reformed hydrogen.

2. The method according to claim 1, characterized in that The operating conditions of the low-temperature hydrogen extraction tower (11) include: a tower top temperature of 8 to 20° C., a tower bottom temperature of 30 to 48° C., and a tower top pressure of 2.1 to 3 MPa.

3. The method according to claim 1, characterized in that Before the hydrogen extraction treatment is performed, the separated gas phase is cooled in the first heat exchanger (9) and the gas phase cooler (10) in sequence and then enters the lower part of the low-temperature hydrogen extraction tower (11); The reformed oil phase is cooled in the second heat exchanger (13) and the oil phase freezer (14) in sequence and then enters the upper part of the low-temperature hydrogen extraction tower (11).

4. The method according to claim 3, characterized in that The temperature of the separated gas phase after cooling by the gas phase cooler (10) is 35-45°C and the pressure is 2.2-3.6 MPa; The temperature of the reformed oil phase after cooling in the oil phase freezer (14) is 4 to 20°C and the pressure is 2.24 to 3.64 MPa.

5. The method according to claim 3, characterized in that: The cold sources used by the tower top freezer (12), the gas phase cooler (10) and the oil phase freezer (14) independently include chilled water and / or circulating water, preferably chilled water and / or circulating water produced by a petrochemical enterprise.

6. The method according to claim 1, characterized in that The reforming hydrogen production temperature is 28-42°C, the pressure is 2.06-3.46MPa, and the hydrogen content is 93-96.5mol%; The temperature of the hydrogen extraction gas phase after being cooled by the tower top freezer (12) is 8-12°C, the pressure is 2.08-3.48 MPa, and the hydrogen content is 93-96.5 mol%.

7. The method according to claim 1, characterized in that The gas-liquid separation unit comprises a primary liquid separation device and a secondary liquid separation device arranged in series; The gas-liquid separation process comprises: allowing the pre-separated gas to enter a primary liquid separation device for sequential cooling, liquid separation and compression to obtain a primary separated liquid phase and a primary separated gas phase; The first-stage separated gas phase enters a second-stage liquid separation device for sequential cooling, liquid separation and compression to obtain a second-stage separated liquid phase and the separated gas phase.

8. The method according to claim 7, characterized in that The temperature of the separated gas phase is 105-130° C., the pressure is 2.22-3.62 MPa, and the hydrogen content is 87-91 mol%.

9. A system for continuously extracting hydrogen from reforming products using the method according to any one of claims 1 to 8, characterized in that: The system comprises a reforming product separation unit, a gas-liquid separation unit, a low-temperature hydrogen extraction tower (11), a tower top refrigerator (12), a first heat exchanger (9) and a second heat exchanger (13); the tower top refrigerator (12) is arranged inside the low-temperature hydrogen extraction tower (11) and located at the upper part of the low-temperature hydrogen extraction tower (11); The reforming product separation unit comprises a continuous reforming product inlet, a pre-separated gas outlet and a reforming oil phase outlet; The gas-liquid separation unit comprises a pre-separation gas inlet, a separation gas phase outlet and a separation liquid phase outlet; The low-temperature hydrogen extraction tower (11) comprises a separation gas phase inlet, a reforming oil phase inlet, a hydrogen extraction oil phase outlet and a hydrogen extraction gas phase outlet; The tower top freezer (12) comprises a cold source inlet and a cold source outlet; The continuous reformed product inlet of the reformed product separation unit is used to communicate with a continuous reformed product source; the pre-separation gas outlet of the reformed product separation unit is communicated with the pre-separation gas inlet of the gas-liquid separation unit; the separation gas phase outlet of the gas-liquid separation unit is communicated with the inlet of the first heat exchanger (9); the outlet of the first heat exchanger (9) is communicated with the separation gas phase inlet of the low-temperature hydrogen extraction tower (11); the reformed oil phase outlet of the reformed product separation unit is communicated with the inlet of the second heat exchanger (13); the outlet of the second heat exchanger (13) is communicated with the reformed oil phase inlet of the low-temperature hydrogen extraction tower (11); the hydrogen extraction oil phase outlet of the low-temperature hydrogen extraction tower (11) is communicated with the cold source inlet of the first heat exchanger (9); the hydrogen extraction gas phase outlet of the low-temperature hydrogen extraction tower (11) is communicated with the cold source inlet of the second heat exchanger (13); the cold source inlet of the tower top freezer (12) is used to communicate with the outlet of the chilled water device, and the cold source outlet is used to communicate with the inlet of the chilled water device.

10. The system according to claim 9, characterized in that The system also includes a gas phase cooler (10) and an oil phase freezer (14); The inlet of the gas phase cooler (10) is connected to the outlet of the first heat exchanger (9), and the outlet is connected to the separated gas phase inlet of the low-temperature hydrogen extraction tower (11); the cold source inlet of the gas phase cooler (10) is used to communicate with the outlet of the chilled water device, and the outlet is used to communicate with the inlet of the chilled water device; The inlet of the oil phase freezer (14) is connected to the outlet of the second heat exchanger (13), and the outlet is connected to the separated liquid phase inlet of the low-temperature hydrogen extraction tower (11); the cold source inlet of the oil phase freezer (14) is used to be connected to the outlet of the chilled water device, and the outlet is used to be connected to the inlet of the chilled water device.

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