BOG (Boil Off Gas) dehydrogenation system

Abstract

The utility model provides a BOG (Boil Off Gas) dehydrogenation system, which belongs to the technical field of gas separation and comprises a dehydrogenation device, the dehydrogenation device is connected with a mixed gas source unit and a circulating heat exchange medium unit, and one end, far away from the mixed gas source unit, of the dehydrogenation device is connected with a dehydrogenation mixed gas unit; the dehydrogenation device comprises a heat exchange box body, a plurality of hydrogen storage alloy tank bodies are arranged in the heat exchange box body, each hydrogen storage alloy tank body is connected with a mixed gas inlet and a mixed gas outlet, the mixed gas inlet is connected with a mixed gas source unit, and the mixed gas outlet is connected with a dehydrogenation mixed gas unit; the BOG gas dehydrogenation system further comprises a control system, and the control system is connected with the dehydrogenation device. According to the BOG dehydrogenation system disclosed by the utility model, the purpose of hydrogen separation is achieved by adopting reversible reaction of hydrogen storage alloy and hydrogen adsorption, the process is carried out under the conditions of normal temperature and low pressure, and compared with the existing methods of low-temperature separation, high-pressure adsorption and the like, the energy consumption is greatly reduced, and energy conservation and emission reduction are facilitated.

Description

Technical Field

[0001] This utility model relates to the field of gas separation technology, specifically to a BOG gas dehydrogenation system. Background Art

[0002] Hydrogen energy, as a highly efficient and clean energy source, has attracted widespread attention. Among its applications, hydrogen storage alloys, due to their high hydrogen storage capacity and good cycle stability, are widely used in hydrogen storage and transportation. However, effectively separating hydrogen from mixed gases remains a significant challenge in practical applications. Furthermore, liquefied natural gas (LNG) plants generate large amounts of boil-off gas (BOG) during production, containing significant amounts of methane, helium, and other resources. The recovery and utilization of these resources is crucial for improving the economic efficiency of LNG plants.

[0003] Boiling gas (BOG) dehydrogenation technology is crucial for the recovery and utilization of BOG during natural gas production. Existing solutions primarily employ physical methods, such as cryogenic separation and high-pressure adsorption, to separate hydrogen. However, these methods often consume significant amounts of energy, involve complex equipment, and incur high operating costs. Another approach utilizes chemical adsorbents, such as activated carbon and zeolite, to adsorb hydrogen. However, these adsorbents exhibit poor selectivity, readily adsorbing other gases and resulting in low hydrogen purity. Therefore, developing novel BOG gas removal devices is of significant importance for resource recovery and utilization.

[0004] The patent with publication number CN105371105A discloses a hydrogen absorption low-strain metal hydride hydrogen storage tank. Specifically, it discloses that the device uses an internal coil to achieve heat exchange during the hydrogen absorption and desorption process. However, this patent has problems with poor device operation safety and heat exchange efficiency.

[0005] The patent with publication number CN108131563A discloses a metal hydride hydrogen storage tank with a spiral structure. Specifically, it discloses the use of an internal spiral to relieve the expansion stress of the hydrogen storage alloy. However, the device in this patent can only store hydrogen and cannot absorb hydrogen during gas flow to perform BOG gas dehydrogenation.

[0006] The patent with publication number CN110550606A discloses an apparatus and method for preparing high-purity hydrogen from hydrogen-containing gas under unsteady conditions. Specifically, it discloses the use of multiple devices such as a pressure swing adsorption unit, a hydrogen absorption unit, and a gas buffer tank to achieve hydrogen absorption from hydrogen-containing gas. However, the apparatus setup of this patent is relatively complex. Utility Model Content

[0007] The purpose of this invention is to provide a BOG gas dehydrogenation system to solve the technical problems of existing BOG gas dehydrogenation devices, such as low purity of separated hydrogen, high energy consumption, and high operating costs.

[0008] To achieve the above objectives, one embodiment of the present invention provides a BOG gas dehydrogenation system, including a dehydrogenation device, which is connected to a mixed gas source unit and a circulating heat exchange medium unit, and the end of the dehydrogenation device away from the mixed gas source unit is connected to a dehydrogenated mixed gas unit.

[0009] The dehydrogenation unit includes a heat exchange box, inside which are installed several hydrogen storage alloy tanks. Each hydrogen storage alloy tank is connected to a mixed gas inlet and a mixed gas outlet. The mixed gas inlet is connected to a mixed gas source unit, and the mixed gas outlet is connected to a dehydrogenation mixed gas unit.

[0010] The BOG gas dehydrogenation system also includes a control system, which is connected to the dehydrogenation unit.

[0011] Preferably, at least two dehydrogenation devices are provided, one of which absorbs hydrogen and the other releases hydrogen.

[0012] Preferably, one end of the hydrogen-releasing dehydrogenation device is connected to the mixed gas source unit and the circulating heat exchange medium unit.

[0013] Preferably, each hydrogen storage alloy tank is connected to an inlet pipe and an outlet pipe at both ends, with the inlet pipe connected to the mixed gas inlet and the outlet pipe connected to the mixed gas outlet.

[0014] Preferably, the heat exchange box is provided with a circulating medium inlet and a circulating medium outlet on both sides, and the circulating medium inlet and the circulating medium outlet are connected to the circulating heat exchange medium unit.

[0015] Preferably, the heat exchange box is equipped with several rectangularly arranged hydrogen storage alloy tanks, and each hydrogen storage alloy tank is connected in parallel.

[0016] Preferably, each hydrogen storage alloy tank is equipped with a filter screen inside.

[0017] Preferably, the hydrogen storage alloy inside each hydrogen storage alloy tank includes at least one of AB5 series hydrogen storage alloy, AB2 series hydrogen storage alloy, and AB series hydrogen storage alloy.

[0018] Preferably, the circulating heat exchange medium unit includes a cooling medium module and a heating medium module.

[0019] Preferably, valves are installed between the dehydrogenation device and the mixed gas source unit and the circulating heat exchange medium unit, and a booster pump is installed between the dehydrogenation device and the dehydrogenated mixed gas unit.

[0020] In summary, the beneficial effects of this utility model are as follows:

[0021] 1. The BOG gas dehydrogenation system of this utility model uses a reversible reaction between hydrogen storage alloy and hydrogen adsorption to achieve hydrogen separation. The above process is carried out under normal temperature and low pressure conditions. Compared with existing low temperature separation and high pressure adsorption methods, it greatly reduces energy consumption and is conducive to energy conservation and emission reduction. At the same time, compared with existing physical methods, the hydrogen separation method of this utility model also has the advantages of simple equipment and easy implementation, which can greatly reduce equipment investment and operating costs and is conducive to large-scale application.

[0022] 2. In the BOG gas dehydrogenation system of this invention, the hydrogen storage alloy in the hydrogen storage alloy tank is selective, reacting only with hydrogen and not adsorbing other gases. Therefore, high-purity hydrogen can be obtained, which improves its application value in the field of hydrogen energy.

[0023] 3. The BOG gas dehydrogenation system of this utility model not only achieves effective separation of hydrogen, but also proposes a new BOG gas treatment method, that is, while removing hydrogen, it recovers resources such as methane and helium in the BOG gas, avoiding waste of resources and improving the economic benefits of LNG plants.

[0024] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention will be apparent from the effects described in the description and the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the dehydrogenation device in this utility model;

[0026] Figure 2 This is a top view of the dehydrogenation device in this utility model;

[0027] Figure 3 This is a side view of the dehydrogenation device in this utility model;

[0028] Figure 4 This is a schematic diagram of the BOG gas dehydrogenation system in one embodiment of the present invention.

[0029] Among them, 1-heat exchange box, 2-hydrogen storage alloy tank, 3-mixed gas inlet, 4-inlet pipe, 5-circulating medium inlet, 6-circulating medium outlet, 7-mixed gas outlet, 8-outlet pipe, 9-circulating heat exchange medium unit, 10-mixed gas source unit, 11-first valve, 12-second valve, 13-third valve, 14-second dehydrogenation device, 15-first dehydrogenation device, 16-fourth valve, 17-fifth valve, 18-sixth valve, 19-seventh valve, 20-dehydrogenated mixed gas unit, 21-ninth valve, 22-emergency venting unit, 23-hydrogen unit, 24-tenth valve, 25-eleventh valve, 26-venting unit, 27-eighth valve. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0031] This invention provides a BOG gas dehydrogenation system, including a dehydrogenation device connected to a mixed gas source unit 10 and a circulating heat exchange medium unit 9. The end of the dehydrogenation device furthest from the mixed gas source unit 10 is connected to a dehydrogenated mixed gas unit 20. The working process is as follows: the mixed gas from the mixed gas source unit 10 flows into the dehydrogenation device, where it undergoes hydrogen absorption under the action of a cooling medium module in the circulating heat exchange medium unit 9. The hydrogen-removed mixed gas then flows into the dehydrogenated mixed gas unit 20. Valves are installed between the dehydrogenation device and both the mixed gas source unit 10 and the circulating heat exchange medium unit 9. A booster pump is installed between the dehydrogenation device and the dehydrogenated mixed gas unit 20.

[0032] Dehydrogenation devices, such as Figures 1-3 As shown, the device includes a heat exchange chamber 1, inside which are arranged a matrix of hydrogen storage alloy tanks 2. These tanks 2 are connected in parallel, a configuration that rapidly reduces the velocity of the high-pressure, high-speed mixed gas, ensuring sufficient contact between the hydrogen in the mixed gas and the hydrogen storage alloy, thus improving the separation efficiency of the mixed gas and hydrogen. The heat exchange chamber 1 employs external heat exchange, using a shell-and-tube heat exchanger to enclose the array structure of the hydrogen storage alloy tanks 2.

[0033] Each hydrogen storage alloy tank 2 is connected to an inlet pipe 4 and an outlet pipe 8 at both ends. The inlet pipe 4 is connected to the mixed gas inlet 3, and the outlet pipe 8 is connected to the mixed gas outlet 7. The mixed gas inlet 3 is connected to the mixed gas source unit 10, and the mixed gas outlet 7 is connected to the dehydrogenated mixed gas unit 20. The mixed gas in the mixed gas source unit 10 enters the hydrogen storage alloy tank 2 through the inlet pipe 4 to complete the hydrogen absorption process. The mixed gas after hydrogen removal flows into the dehydrogenated mixed gas unit 20 through the outlet pipe 8. The purpose of connecting the inlet and outlet of the hydrogen storage alloy tank 2 in parallel with the inlet pipe 4 and the outlet pipe 8 is to perform mixed gas diversion and convergence.

[0034] The heat exchange chamber 1 has a circulating medium inlet 5 and a circulating medium outlet 6 on both sides, which are connected to the circulating heat exchange medium unit 9. The circulating heat exchange medium unit 9 includes a cooling medium module and a heating medium module. When the dehydrogenation unit is performing hydrogen absorption, a cooling medium is introduced into the heat exchange chamber 1; when the dehydrogenation unit is performing hydrogen release, a heating medium is introduced into the heat exchange chamber 1.

[0035] Each hydrogen storage alloy tank 2 is equipped with a filter screen inside. The filter screen stabilizes the hydrogen storage alloy and prevents it from entering the main pipeline with the flow of the mixed gas. The hydrogen storage alloy inside each hydrogen storage alloy tank 2 includes at least one of AB5 series hydrogen storage alloy, AB2 series hydrogen storage alloy, and AB series hydrogen storage alloy.

[0036] The BOG gas dehydrogenation system also includes a control system for controlling the entire BOG gas dehydrogenation system. The control system is connected to the dehydrogenation unit. The control system monitors the operating status of the BOG gas dehydrogenation system in real time and controls the opening and closing of valves to achieve automatic operation of the dehydrogenation system.

[0037] Furthermore, at least two dehydrogenation devices are provided, one of which absorbs hydrogen and the other releases hydrogen. One end of the hydrogen-releasing dehydrogenation device is connected to the mixed gas source unit 10 and the circulating heat exchange medium unit 9, while the other end, away from the mixed gas source unit 10, is connected to other modules. The specific connections depend on the actual situation and hydrogen recovery can be performed.

[0038] The present invention discloses a method for using a BOG gas dehydrogenation system, comprising: the mixed gas source in the mixed gas source unit 10 flows through the dehydrogenation device to remove hydrogen, and the mixed gas after hydrogen removal flows into the dehydrogenated mixed gas unit 20.

[0039] Preferably, the method of using the BOG gas dehydrogenation system includes: the mixed gas source in the mixed gas source unit 10 flows through one of the dehydrogenation devices to remove hydrogen, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit 20; the other dehydrogenation device releases hydrogen under the action of heating.

[0040] Example: This example uses two dehydrogenation units.

[0041] A BOG gas dehydrogenation system, such as Figure 4 As shown, it includes two dehydrogenation devices, namely the first dehydrogenation device 15 and the second dehydrogenation device 14.

[0042] The first dehydrogenation device 15 and the second dehydrogenation device 14 are both connected to a mixed gas source unit 10 and a circulating heat exchange medium unit 9. The other end of the first dehydrogenation device 15 and the second dehydrogenation device 14 are both connected to a dehydrogenated mixed gas unit 20 and other units. The other units include an emergency venting unit 22, a venting unit 26 and a hydrogen unit 23. Other units can be selected according to actual conditions.

[0043] A first valve 11, a second valve 12, and a third valve 13 are provided between the first dehydrogenation unit 15, the second dehydrogenation unit 14, and the mixed gas source unit 10. A fourth valve 16 is provided between the first dehydrogenation unit 15 and other units. A fifth valve 17 is provided between the first dehydrogenation unit 15 and the dehydrogenated mixed gas unit 20. A sixth valve 18 is provided between the second dehydrogenation unit 14 and the dehydrogenated mixed gas unit 20. An eighth valve 27 is provided between the second dehydrogenation unit 14 and other units. A seventh valve 19 is provided between the first dehydrogenation unit 15, the second dehydrogenation unit 14, and the dehydrogenated mixed gas unit 20. A ninth valve 21, a tenth valve 24, and an eleventh valve 25 are provided between the first dehydrogenation unit 15, the second dehydrogenation unit 14, and other units. Among them, the ninth valve 21 is connected to the emergency venting unit 22, the tenth valve 24 is connected to the hydrogen unit 23, and the eleventh valve 25 is connected to the venting unit 26.

[0044] A method of using a BOG gas dehydrogenation system includes:

[0045] (1) Dehydrogenation is performed in the first dehydrogenation unit 15, and hydrogen is released in the second dehydrogenation unit 14:

[0046] First dehydrogenation device 15 dehydrogenation: During this process, valves 11, 12, 17, and 19 are opened, and BOG gas flows through the first dehydrogenation device 15 to remove hydrogen. At this time, the circulating heat exchange medium is the cooling medium, which absorbs the heat generated during the hydrogen absorption process of the hydrogen storage alloy, reduces the temperature of the first dehydrogenation device 15, and improves the hydrogen absorption efficiency of the hydrogen storage alloy.

[0047] The second dehydrogenation unit 14 releases hydrogen: During this process, the eighth valve 27 is open, the sixth valve 18 is closed, and either the ninth valve 21 or the tenth valve 24 is opened selectively depending on the actual situation. If hydrogen recovery is required, the tenth valve 24 is opened and the ninth valve 21 is closed; otherwise, the ninth valve 21 is opened and the tenth valve 24 is closed. At this time, the circulating heat exchange medium is the heating medium, which provides heat to the second dehydrogenation unit 14. Since the hydrogen storage alloy absorbs heat during the hydrogen release process, the temperature of the second dehydrogenation unit 14 decreases, which in turn reduces the hydrogen release efficiency of the hydrogen storage alloy. Therefore, heat needs to be provided to improve the hydrogen release efficiency.

[0048] Hydrogen storage alloys can release hydrogen by heating, and then repeatedly absorb hydrogen to achieve the regeneration and reuse of the device.

[0049] (2) Dehydrogenation occurs in the second dehydrogenation unit 14, and hydrogen is released from the first dehydrogenation unit 15:

[0050] Dehydrogenation in the second dehydrogenation unit 14: During this process, valves 11, 13, 18, and 19 are opened, and BOG gas flows through the second dehydrogenation unit 14 to remove hydrogen; at this time, the circulating heat exchange medium is the cooling medium, which cools the second dehydrogenation unit 14.

[0051] Hydrogen is released from the first dehydrogenation unit 15: during this process, the second valve 12, the fifth valve 17, and the eighth valve 27 are closed; the fourth valve 16 is opened, and either the ninth valve 21 or the tenth valve 24 is opened according to the actual situation; at this time, the circulating heat exchange medium is the heating medium, and the heating medium heats the first dehydrogenation unit 15.

[0052] During the above process, when the BOG gas dehydrogenation system is running, the first dehydrogenation device 15 and the second dehydrogenation device 14 will always be in operation, with one group performing dehydrogenation and the other group releasing hydrogen. At the same time, multiple dehydrogenation devices can be added according to actual needs.

[0053] Although specific embodiments of this utility model have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A BOG gas dehydrogenation system, characterized in that: The device includes a dehydrogenation unit, which is connected to a mixed gas source unit and a circulating heat exchange medium unit. The end of the dehydrogenation unit away from the mixed gas source unit is connected to a dehydrogenated mixed gas unit. The dehydrogenation device includes a heat exchange box, inside which are arranged several hydrogen storage alloy tanks. Each hydrogen storage alloy tank is connected to a mixed gas inlet and a mixed gas outlet. The mixed gas inlet is connected to a mixed gas source unit, and the mixed gas outlet is connected to a dehydrogenation mixed gas unit. The BOG gas dehydrogenation system also includes a control system, which is connected to the dehydrogenation unit.

2. The BOG gas dehydrogenation system as described in claim 1, characterized in that: The dehydrogenation device is provided in at least two parts, one of which absorbs hydrogen and the other releases hydrogen.

3. The BOG gas dehydrogenation system as described in claim 2, characterized in that: One end of the hydrogen dehydrogenation device is connected to the mixed gas source unit and the circulating heat exchange medium unit.

4. The BOG gas dehydrogenation system as described in claim 1, characterized in that: Each of the hydrogen storage alloy tanks is connected to an inlet pipe and an outlet pipe at both ends. The inlet pipe is connected to the mixed gas inlet, and the outlet pipe is connected to the mixed gas outlet.

5. A BOG gas dehydrogenation system as described in claim 1 or 4, characterized in that: The heat exchange box is provided with a circulating medium inlet and a circulating medium outlet on both sides, and the circulating medium inlet and the circulating medium outlet are connected to the circulating heat exchange medium unit.

6. The BOG gas dehydrogenation system as described in claim 1, characterized in that: The heat exchange box is equipped with several rectangularly arranged hydrogen storage alloy tanks, and each of the hydrogen storage alloy tanks is connected in parallel.

7. A BOG gas dehydrogenation system as described in claim 1, characterized in that: Each of the hydrogen storage alloy tanks is equipped with a filter screen inside.

8. The BOG gas dehydrogenation system as described in claim 1, characterized in that: The hydrogen storage alloy inside each of the hydrogen storage alloy tanks includes at least one of AB5 series hydrogen storage alloy, AB2 series hydrogen storage alloy, and AB series hydrogen storage alloy.

9. A BOG gas dehydrogenation system as described in claim 1, characterized in that: The circulating heat exchange medium unit includes a cooling medium module and a heating medium module.

10. A BOG gas dehydrogenation system as described in claim 1, characterized in that: Valves are installed between the dehydrogenation device and the mixed gas source unit and the circulating heat exchange medium unit, and a booster pump is installed between the dehydrogenation device and the dehydrogenated mixed gas unit.

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