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, and the method comprises the following steps: pre-separated gas and reformate phase separated by a reformate separation unit enter a low-temperature hydrogen extraction tower, and hydrogen extraction treatment is carried out under the conditions of relatively high pressure and relatively low temperature, on one hand, on the other hand, the pre-separated gas and the reformate phase enter the low-temperature hydrogen extraction tower; furthermore, the purity of hydrogen produced by reforming and the yield of light hydrocarbon in dehydrogenated oil produced by reforming can be ensured; on the other hand, the energy consumption of the system can be reduced. Meanwhile, an in-tower cooling device is arranged in the middle of the low-temperature hydrogen extraction tower, so that the purity of hydrogen produced by reforming and the yield of light hydrocarbon in dehydrogenated oil produced by reforming can be further improved. 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] The continuous reforming reaction mainly consists of cycloalkane dehydrogenation, alkane dehydrogenation cyclization, alkane isomerization, cracking and pyrolysis. According to its reaction principle, the lower the reaction pressure, the more conducive it is to improving the yield of reformed oil products. However, low re-contact pressure leads to a large amount of light hydrocarbons in the reforming hydrogen, which reduces the purity of hydrogen. In order to improve the purity of downstream hydrogen sources, a reforming hydrogen purification system is generally set up in low-pressure continuous reforming.

[0003] The continuous reforming hydrogen production and purification system is beneficial to improving the purity of hydrogen and the liquid yield at higher pressures and lower temperatures. For example, the purity of the reforming hydrogen produced by the continuous reforming device is between 92% and 94%, but it will cause the system to have higher energy consumption and cannot take into account the issues of improving the purity of the reforming hydrogen produced, increasing the yield of the dehydrogenated oil produced by reforming, 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 continuous reforming products, the method comprising: allowing the continuous reforming products 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 countercurrently contact with the reforming oil phase in a low-temperature hydrogen stripping tower for hydrogen stripping treatment to obtain a hydrogen stripping gas phase and a hydrogen stripping oil phase; the conditions for the hydrogen stripping treatment include: a tower top temperature of 5 to 35° C., a tower bottom temperature of 19 to 49° C., and a pressure of 2.1 to 3.5 MPa; allowing the hydrogen stripping oil phase to exchange heat with the separated gas phase through a first heat exchanger, and mixing the obtained material with the separated liquid phase to obtain reforming dehydrogenated oil; allowing the hydrogen stripping gas phase to exchange heat with the reforming oil phase through a second heat exchanger to obtain reforming hydrogen; allowing part of the hydrogen stripping oil phase to be used as a mid-stage produced liquid and then cooled by a cooling device in the tower and then returned to the low-temperature hydrogen stripping tower.

[0006] Optionally, the operating conditions of the low-temperature hydrogen stripping tower include: a tower top temperature of 8 to 20° C., a tower bottom temperature of 24 to 42° C., and a pressure of the low-temperature hydrogen stripping tower of 2.1 to 3 MPa.

[0007] Optionally, before the hydrogen extraction treatment, the reformed oil phase 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; the separated gas phase is cooled by the first heat exchanger before entering the lower part of the low-temperature hydrogen extraction tower.

[0008] Optionally, the temperature of the separated gas phase after cooling by the first heat exchanger is 35-45°C, the pressure is 2.2-3.6 MPa, and the hydrogen content is 87-91 mol%; the temperature of the reforming 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 in-tower cooling device includes a in-tower cooler for reducing the temperature of the middle-section produced liquid; the cold sources used by the oil phase freezer and the in-tower cooler each independently include chilled water and / or circulating water, preferably chilled water and / or circulating water produced by petrochemical enterprises.

[0010] Optionally, the temperature of the middle section produced liquid after being cooled by the cooler in the tower is 4 to 20°C, preferably 8 to 12°C.

[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 purity is 87-91 mol%; 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%.

[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 cooling device in the tower, a first heat exchanger and a second heat exchanger; 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 inlet, a middle section produced liquid inlet, a middle section produced liquid outlet, a hydrogen extraction tower bottom oil outlet and a hydrogen extraction tower top gas outlet; the cooling device in the tower comprises a middle section produced liquid inlet and a middle section produced liquid outlet; the continuous reformed product inlet of the reformed product separation unit is used to be connected to a continuous reformed product source; the pre-separation gas outlet of the reformed product separation unit is connected to the pre-separation gas outlet of the gas-liquid separation unit The gas inlet is connected; the separated 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 separated gas phase inlet of the low-temperature hydrogen extraction tower; the reforming oil phase outlet of the reforming product separation unit is connected to the inlet of the second heat exchanger; the outlet of the second heat exchanger is connected to 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 to the cold source inlet of the first heat exchanger; the hydrogen extraction gas phase outlet of the low-temperature hydrogen extraction tower is connected to the cold source inlet of the second heat exchanger; the middle section produced liquid outlet of the low-temperature hydrogen extraction tower is connected to the middle section produced liquid inlet of the cooling device in the tower, and the middle section produced liquid inlet is connected to the middle section produced liquid outlet of the cooling device in the tower; the cold source inlet of the cooling device in the tower 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.

[0014] Optionally, the system also includes an oil phase freezer; 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 the hydrogen extraction treatment is carried out at a relatively mild pressure and temperature, and the temperature of the upper part of the tower is maintained at a relatively low level by setting a cooling device in the tower. On the one hand, this scheme can ensure the effect of the hydrogen extraction treatment, and thus ensure the purity of the reforming hydrogen and the yield of light hydrocarbons in the reformed dehydrogenated oil; on the other hand, it avoids the energy loss caused by the hydrogen extraction treatment under very low temperature and very high pressure conditions, and can reduce the energy consumption of the system. In addition, before the hydrogen extraction treatment, the pre-separated gas and reformed oil phases are heat exchanged with the hydrogen extraction treatment product, 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 supercharger; 6 secondary cooler; 7 secondary liquid separator tank; 8 secondary supercharger; 9 first heat exchanger; 10 low-temperature hydrogen extraction tower; 11 second heat exchanger; 12 oil phase freezer; 13 mid-tower cooler. 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] In a first aspect, the present disclosure provides a method for hydrogen stripping of continuous reforming products, the method comprising: allowing the continuous reforming products 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 countercurrently contact with the reforming oil phase in a low-temperature hydrogen stripping tower 10 for hydrogen stripping treatment to obtain a hydrogen stripping gas phase and a hydrogen stripping oil phase; the conditions for the hydrogen stripping treatment include: a tower top temperature of 5 to 35° C., a tower bottom temperature of 19 to 49° C., and a pressure of 2.1 to 3.5 MPa; allowing the hydrogen stripping oil phase to exchange heat with the separated gas phase through a first heat exchanger 9, and mixing the obtained material with the separated liquid phase to obtain reforming dehydrogenated oil; allowing the hydrogen stripping gas phase to exchange heat with the reforming oil phase through a second heat exchanger 11 to obtain reforming hydrogen; allowing part of the hydrogen stripping oil phase to be used as a mid-stage produced liquid and then cooled by a cooling device in the tower and then returned to the low-temperature hydrogen stripping tower 10.

[0023] Through the above technical scheme, the pre-separated gas and reformed oil phase separated by the reforming product separation unit enter the low-temperature hydrogen extraction tower 10, 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 cooling device is set in the middle of the low-temperature hydrogen extraction tower 10, and the temperature of the hydrogen extraction oil phase obtained by the hydrogen extraction treatment gradually increases when it flows downward, until it reaches the middle of the low-temperature hydrogen extraction tower 10, and a part of the hydrogen extraction oil phase is cooled by the tower cooling device and returned to the middle of the low-temperature hydrogen extraction tower 10; the hydrogen extraction gas phase flows upward, and when it reaches the middle of the low-temperature hydrogen extraction tower 10, the temperature gradually decreases, which can keep the temperature of the top of the tower at a relatively low level, and 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 hydrogenation product before hydrogenation treatment, so that the energy of each component can be recovered, thereby further reducing the energy consumption of the system.

[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 0.24MPa. In this embodiment, the temperature of the continuous reforming product produced by the continuous reforming device is 480-520°C, the pressure is 0.33-0.34MPa, and the hydrogen content is 75.8-79.5mol%. 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 0.24MPa, and the hydrogen content is 85.2-90.4mol%.

[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 reformed oil phase is cooled by the second heat exchanger 11 and the oil phase freezer 12 in sequence, and then enters the upper part of the low-temperature hydrogen extraction tower 10; the separated gas phase is cooled by the first heat exchanger 9 and then enters the lower part of the low-temperature hydrogen extraction tower 10. In this embodiment, after the separated gas phase is cooled by the first heat exchanger 9, the temperature is quickly reduced to a relatively low level; after the reformed oil phase is cooled by the second heat exchanger 11 and the oil phase freezer 12 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 the temperature is reduced enters the lower part of the low-temperature hydrogen extraction tower 10, and the reformed oil phase after the temperature is reduced enters the upper part of the low-temperature hydrogen extraction tower 10. 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 first heat exchanger 9 is 35-45°C, the pressure is 2.2-3.6MPa, and the hydrogen content is 87-91mol%; the temperature of the reforming oil phase after cooling by the oil phase freezer 12 is 4-20°C, and the pressure is 2.24-3.64MPa.

[0037] The type of the low-temperature hydrogen extraction tower 10 is a plate tower or a packed tower. The low-temperature hydrogen extraction tower 10 used in the present disclosure is a plate tower type low-temperature hydrogen extraction tower 10, 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 10 are preferably: the top temperature is 8-20°C, the bottom temperature is 24-42°C, and the pressure of the low-temperature hydrogen extraction tower 10 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 both temperature and pressure need to be carried out together. 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 hydrogen extraction phase is 9-13° C., the pressure is 2.1-3.5 MPa, and the hydrogen content is 93-96.5 mol%.

[0040] After the hydrogen-extracting gas phase is heat-exchanged in the second heat exchanger 11, the temperature of the reformed hydrogen obtained is 28-42°C, the pressure is 2.06-3.46MPa, and the hydrogen content is 93-96.5mol%.

[0041] 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 10; the inlet of the gas-phase feed distributor extends to the outside of the low-temperature hydrogen extraction tower 10 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 10 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.

[0042] Among them, in order to further improve the effect of gas-liquid separation, a mid-tower cooling device can be set outside the low-temperature hydrogen extraction tower 10, so that the middle section of the produced liquid can be cooled by the mid-tower cooling device and then returned to the low-temperature hydrogen extraction tower 10, thereby reducing the temperature above the middle part of the low-temperature hydrogen extraction tower 10, and further improving the effect of gas-liquid separation.

[0043] The number of cooling devices in the tower is 1 to 4, preferably 2.

[0044] Among them, the present disclosure preferably sets two cooling devices in the tower, which are respectively set on the tower plates at 1 / 3 and 2 / 3 of the tower, and the height of the two tower plates can float up and down.

[0045] The cooling device in the tower at least includes a tower cooler 13 for reducing the temperature of the produced liquid in the middle section; the tower cooler 13 is in the form of a conventional choice in the art, as long as it can cool the produced liquid in the middle section. The tower cooler 13 is preferably in the form of a heat exchanger.

[0046] The weight ratio of the middle section produced liquid to the hydrogen extraction oil phase is (0.4-2.3): 1. In this embodiment, limiting the amount of the middle section produced liquid can not only ensure that the temperature of the middle and upper sections of the low-temperature hydrogen extraction tower 10 is as low as possible, but also reduce energy consumption.

[0047] The cold sources used by the oil phase freezer 12 and the mid-tower cooler 13 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 to the prior art, there is no need to use a deep cooling system, and only 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.

[0048] In order to further enhance the effect of hydrogen extraction treatment, a wire mesh demister may be provided on the top of the inner chamber of the low-temperature hydrogen extraction tower 10 .

[0049] According to the above embodiment, by improving the device, conditions and method of hydrogen extraction treatment, the middle section produced liquid is cooled to 4-20°C, preferably 8-12°C in the tower cooler 13, which can further reduce the temperature of the middle and upper sections of the low-temperature hydrogen extraction tower 10, thereby improving the gas-liquid separation effect, and can reduce the energy consumption of the system while increasing the purity of reforming hydrogen production and the yield of reforming dehydrogenated oil.

[0050] In one embodiment, the reforming hydrogen is dechlorinated in a reforming hydrogen dechlorination tank and then sent to a PSA device for further purification.

[0051] In one embodiment, the reformed dehydrogenated oil enters a reformed dehydrogenated oil dechlorination tank, the dechlorinated reformed dehydrogenated oil is heat exchanged with the depentanized oil at the bottom of a depentanizer and enters a 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 extracted from the top of the depentanizer are sent to a 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 an aromatics unit after recovering heat.

[0052] In one embodiment, if Figure 1 As shown, the method for continuously extracting hydrogen from reforming products includes:

[0053] 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.

[0054] 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%.

[0055] The separated gas phase is cooled by the first heat exchanger 9 and then enters the lower part of the low-temperature hydrogen extraction tower 10; the reformed oil phase is cooled by the second heat exchanger 11 and the oil phase freezer 12 in sequence and then enters the upper part of the low-temperature hydrogen extraction tower 10; the temperature of the separated gas phase after cooling by the first heat exchanger 9 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 12 is 4-20°C and the pressure is 2.24-3.64MPa;

[0056] The separated gas phase enters a low-temperature hydrogen extraction tower 10 and contacts with the reformed oil in countercurrent flow 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 10 include: a tower top temperature of 6 to 35° C., a tower bottom temperature of 24 to 42° C., a pressure of the low-temperature hydrogen extraction tower 10 of 2.1 to 3.5 MPa, and a number of plates of the low-temperature hydrogen extraction tower 10 of 5 to 25; the temperature of the hydrogen extraction gas phase is 9 to 13° C., the pressure is 2.1 to 3 MPa, and the hydrogen content is 93 to 96.5 mol%; a portion of the hydrogen extraction oil phase is used as a mid-stage produced liquid and is cooled to 4 to 20° C. by a tower cooler 13 and then returned to the low-temperature hydrogen extraction tower 10.

[0057] The cooled hydrogen extraction gas phase is heat exchanged with the reformed oil phase through the second heat exchanger 11 to obtain reformed hydrogen, wherein the reformed hydrogen has a temperature of 28-42°C, a pressure of 2.06-3.46 MPa, and a hydrogen content of 93-96.5 mol%. The reformed hydrogen is dechlorinated in the reformed hydrogen dechlorination tank and then sent to the PSA device for further purification. The hydrogen-extracted 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 reformed dehydrogenated oil enters the reformed dehydrogenated oil dechlorination tank, the reformed dehydrogenated oil after dechlorination 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 extracted from the top of the depentanizer are sent to the light hydrocarbon aromatization unit, the bottom of the depentanizer adopts a reboiler for heat supply, and the depentanized oil at the bottom of the tower is sent to the aromatics unit after recovering the heat.

[0058] The second aspect of the present disclosure is a system for continuously extracting hydrogen from reformed products 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 10, a cooling device in the tower, a first heat exchanger 9 and a second heat exchanger 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 10 comprises a separation gas phase inlet, a reformed oil inlet, a middle section produced liquid inlet, a middle section produced liquid outlet, a hydrogen extraction tower bottom oil outlet and a hydrogen extraction tower top gas outlet; the cooling device in the tower comprises a middle section produced liquid inlet and a middle section produced liquid outlet; the continuous reformed product inlet of the reformed product separation unit is used to be connected to a continuous reformed product source; 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 separated 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 separated gas phase inlet of the low-temperature hydrogen extraction tower 10; the reforming oil phase outlet of the reforming product separation unit is communicated with the inlet of the second heat exchanger 11; the outlet of the second heat exchanger 11 is communicated with the reforming oil phase inlet of the low-temperature hydrogen extraction tower 10; the hydrogen extraction oil phase outlet of the low-temperature hydrogen extraction tower 10 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 10 is communicated with the cold source inlet of the second heat exchanger 11; the middle section produced liquid outlet of the low-temperature hydrogen extraction tower 10 is communicated with the middle section produced liquid inlet of the cooling device in the tower, and the middle section produced liquid inlet is communicated with the middle section produced liquid outlet of the cooling device in the tower; the cold source inlet of the cooling device in the tower 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.

[0059] In one embodiment, the system also includes an oil phase freezer 12; the inlet of the oil phase freezer 12 is connected to the outlet of the second heat exchanger 11, and the outlet is connected to the separation liquid phase inlet of the low-temperature hydrogen extraction tower 10; the cold source inlet of the oil phase freezer 12 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.

[0060] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0061] Example 1

[0062] Continuous reforming product hydrogen extraction system Figure 1 As shown;

[0063] Taking a 2.6 million tons / year continuous reforming unit as an example, the methods for extracting hydrogen from continuous reforming products include:

[0064] 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.

[0065] 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 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 89.8mol%.

[0066] The separated gas phase is cooled by the first heat exchanger 9 and then enters the lower part of the low-temperature hydrogen extraction tower 10; the reformed oil phase is cooled by the second heat exchanger 11 and the oil phase freezer 12 in sequence and then enters the upper part of the low-temperature hydrogen extraction tower 10; the temperature of the separated gas phase after being cooled by the first heat exchanger 9 is 40°C and the pressure is 2.35MPa; the temperature of the reformed oil phase after being cooled by the oil phase freezer 12 is 10°C and the pressure is 2.43MPa;

[0067] The separated gas phase enters the low-temperature hydrogen extraction tower 10 and contacts with the reformed oil in countercurrent to perform hydrogen extraction treatment, thereby obtaining a hydrogen extraction oil phase and a hydrogen extraction gas phase; the operating conditions of the low-temperature hydrogen extraction tower 10 include: a tower top temperature of 12° C., a tower bottom temperature of 32° C., a pressure of the low-temperature hydrogen extraction tower 10 of 2.28 MPa, and a number of plates of the low-temperature hydrogen extraction tower 10 of 20; the temperature of the hydrogen extraction gas phase is 12° C., the pressure is 2.28 MPa, and the hydrogen content is 95.79 mol%; a portion of the hydrogen extraction oil phase is used as a mid-stage produced liquid and is cooled to 10° C. by a second-stage tower cooler 13, and then returned to the low-temperature hydrogen extraction tower 10;

[0068] The cooled hydrogen extraction gas phase is heat exchanged with the reforming oil phase to 35°C through the second heat exchanger 11 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 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.

[0069] Product properties are shown in Table 1, and energy consumption is shown in Table 2.

[0070] Example 2

[0071] 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 10 include: a tower top temperature of 11° C., a tower bottom temperature of 33° 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.

[0072] Comparative Example 1

[0073] The method for extracting hydrogen from continuous reforming products is the same as in Example 1, except that the continuous reforming reaction product is sent to the reforming product separation tank after heat exchange and cooling to 40°C, the tank top hydrogen-containing gas pressurization system is consistent with the embodiment, 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 product is 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 refrigerator and then enters 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.

[0074] Comparative Example 2

[0075] The method for continuously extracting hydrogen from reforming products is the same as that in Example 1, except that the middle section of the low-temperature hydrogen extraction tower is not provided with a tower cooler 13, and the separated gas phase is cooled by the first heat exchanger 9 and then cooled to 40° C. by a water cooler before entering the tower. The product properties are shown in Table 1, and the energy consumption is shown in Table 2.

[0076] Table 1 Product properties in Examples and Comparative Examples

[0077] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Purity of hydrogen produced by reforming, mol% 95.79 96.07 93.78 95.44 Reforming hydrogen production, kg / h 23145 21974 31056 24404 Depentane oil, kg / h 268033 268212 267602 267954 C3~C5 light hydrocarbons, kg / h 19832 20824 12352 18652 Depentanizer top circulating fuel gas, kg / h 1250 6389 5894 1233

[0078] Table 2 Energy consumption in the examples and comparative examples

[0079] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Booster unit shaft power, kW 12189 15782 12405 12175 Total cooling load of chillers, MW 3.764 3.88 4.587 2.456 Depentanizer reboiler heat load, MW 12.362 12.198 15.436 12.488

[0080] 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 2.01 mol%, the yield of C3-C5 light hydrocarbons is increased by 60.56 wt%, and the yield of depentane oil is increased by 0.16 wt%; the shaft power of the booster unit is reduced by 1.74%, the refrigeration load is reduced by 17.94%, the heat load of the depentane tower reboiler is reduced by 19.91%, and the energy consumption of the device operation is reduced by 1.16 kg 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 16.75 million yuan / year. The static equipment investment increased by 301,200 yuan. According to the comparison between Example 1 and Comparative Example 2, it can be seen that the tower cooler is set in the middle section of the low-temperature hydrogen extraction tower, which can further improve the purity of reforming hydrogen production and the yield of light hydrocarbons in the reformed dehydrogenated oil.

[0081] 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.

[0082] 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.

[0083] 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; the pre-separated gas enters the gas-liquid separation unit for gas-liquid separation treatment to obtain a separated liquid phase and a separated gas phase; The separated gas phase and the reformed oil phase are countercurrently contacted in a low-temperature hydrogen extraction tower (10) to perform hydrogen extraction treatment to obtain a hydrogen extraction gas phase and a hydrogen extraction oil phase; the conditions of the hydrogen extraction treatment include: a tower top temperature of 5 to 35° C., a tower bottom temperature of 19 to 49° C., and a pressure of 2.1 to 3.5 MPa; The hydrogen-extracted oil phase is subjected to heat exchange with the separated gas phase through a first heat exchanger (9), and the obtained material is mixed with the separated liquid phase to obtain reformed dehydrogenated oil; the hydrogen-extracted gas phase is subjected to heat exchange with the reformed oil phase through a second heat exchanger (11) to obtain reformed hydrogen; A portion of the hydrogen extraction oil phase is used as the middle stage produced liquid and is cooled by a cooling device in the tower and then returned to the low temperature hydrogen extraction tower (10).

2. The method according to claim 1, characterized in that: The operating conditions of the low-temperature hydrogen extraction tower (10) include: a tower top temperature of 8 to 20° C., a tower bottom temperature of 24 to 42° C., and a pressure of the low-temperature hydrogen extraction tower (10) of 2.1 to 3 MPa.

3. The method according to claim 1, characterized in that Before the hydrogen extraction treatment is performed, the reformed oil phase is cooled in the second heat exchanger (11) and the oil phase freezer (12) in sequence and then enters the upper part of the low-temperature hydrogen extraction tower (10); The separated gas phase is cooled by the first heat exchanger (9) and then enters the lower part of the low-temperature hydrogen extraction tower (10).

4. The method according to claim 3, characterized in that The temperature of the separated gas phase after cooling by the first heat exchanger (9) is 35-45°C, the pressure is 2.2-3.6 MPa, and the hydrogen content is 87-91 mol%; The temperature of the reformed oil phase after cooling in the oil phase freezer (12) 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 in-tower cooling device comprises an in-tower cooler (13) for reducing the temperature of the middle section produced liquid; The cold sources used by the oil phase freezer (12) and the mid-tower cooler (13) 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 5, characterized in that The temperature of the middle section produced liquid after being cooled by the mid-tower cooler (13) is 4 to 20°C, preferably 8 to 12°C.

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 2.22-3.62MPa, and the hydrogen purity is 87-91mol%; The reforming hydrogen production temperature is 28-42° C., the pressure is 2.06-3.46 MPa, and the hydrogen content is 93-96.5 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 (10), a cooling device in the tower, a first heat exchanger (9) and a second heat exchanger (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 (10) comprises a separation gas phase inlet, a reforming oil inlet, a middle section produced liquid inlet, a middle section produced liquid outlet, a hydrogen extraction tower bottom oil outlet and a hydrogen extraction tower top gas outlet; The cooling device in the tower includes a middle section produced liquid inlet and a middle section produced liquid outlet; The continuous reformed product inlet of the reformed product separation unit is used to communicate with the 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 separated 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 separated gas phase inlet of the low-temperature hydrogen extraction tower (10); the reformed oil phase outlet of the reformed product separation unit is communicated with the inlet of the second heat exchanger (11); the outlet of the second heat exchanger (11) is communicated with the low-temperature hydrogen extraction tower (10) The reforming oil phase inlet of the low-temperature hydrogen extraction tower (10) is connected; the hydrogen extraction oil phase outlet of the low-temperature hydrogen extraction tower (10) is connected to the cold source inlet of the first heat exchanger (9); the hydrogen extraction gas phase outlet of the low-temperature hydrogen extraction tower (10) is connected to the cold source inlet of the second heat exchanger (11); the middle section produced liquid outlet of the low-temperature hydrogen extraction tower (10) is connected to the middle section produced liquid inlet of the cooling device in the tower, and the middle section produced liquid inlet is connected to the middle section produced liquid outlet of the cooling device in the tower; the cold source inlet of the cooling device in the tower 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 an oil phase freezer (12); The inlet of the oil phase freezer (12) is connected to the outlet of the second heat exchanger (11), and the outlet is connected to the separated liquid phase inlet of the low-temperature hydrogen extraction tower (10); the cold source inlet of the oil phase freezer (12) 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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