BOG gas dehydrogenation system and use method thereof

Abstract

The invention discloses a BOG gas dehydrogenation system and a use method thereof, and belongs to the technical field of gas separation. The BOG gas dehydrogenation system comprises a dehydrogenation device, the dehydrogenation device is connected with a mixed gas source unit and a circulating heat exchange medium unit, and the end, away from the mixed gas source unit, of the dehydrogenation device is connected with a dehydrogenation mixed gas unit. According to the BOG gas dehydrogenation system, the purpose of hydrogen separation is achieved through the 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 existing methods of low-temperature separation, high-pressure adsorption and the like, energy consumption is greatly reduced, and energy conservation and emission reduction are facilitated; meanwhile, compared with an existing physical method, the hydrogen separation method further has the advantages of being simple in equipment and easy to implement, the equipment investment and the operation cost can be greatly reduced, and large-scale application is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a BOG gas dehydrogenation system and a method for using the same. Background Art

[0002] As energy becomes increasingly scarce, hydrogen energy, as an efficient and clean energy source, has received widespread attention. Among them, hydrogen storage alloys are widely used in hydrogen energy storage and transportation due to their high hydrogen storage capacity and good cycle stability. However, in practical applications, how to effectively separate hydrogen from mixed gases is an important challenge. In addition, liquefied natural gas (LNG) plants produce a large amount of boil-off gas (BOG) during the production process, which contains a large amount of methane, helium and other resources. The recycling of these resources is of great significance to improving the economic benefits of LNG plants.

[0003] BOG gas dehydrogenation technology is an important technology for recycling BOG gas in the natural gas production process. The existing solutions mainly use physical methods such as low-temperature separation and high-pressure adsorption to achieve hydrogen separation. However, these methods often consume a lot of energy, and the equipment is complex and the operating cost is high. Another method is to use chemical adsorbents such as activated carbon and zeolite to adsorb hydrogen. However, these adsorbents have poor selectivity and are easy to adsorb other gases, resulting in low purity of hydrogen. Therefore, the development of a new BOG gas removal device is of positive significance for resource recycling.

[0004] The patent with publication number CN105371105A discloses a hydrogen-absorbing low-strain metal hydride hydrogen storage tank, which specifically discloses that the device uses an internal coil to achieve heat exchange in the hydrogen absorption and desorption process of the device. However, the patent has problems with the operating safety and heat exchange efficiency of the device.

[0005] Patent publication number CN108131563A discloses a metal hydride hydrogen storage tank with a spiral structure, which specifically discloses the use of a built-in spiral to relieve the expansion stress of the hydrogen storage alloy. However, the device in the patent can only store hydrogen and cannot absorb hydrogen during gas flow to dehydrogenate BOG gas.

[0006] The patent with publication number CN110550606A discloses a device and method for preparing high-purity hydrogen from hydrogen-containing gas under non-steady state. It specifically discloses the use of multiple devices such as pressure swing adsorption unit, hydrogen absorption unit, gas buffer tank, etc. to achieve hydrogen absorption of hydrogen-containing gas, but the device setting of this patent is relatively complicated. Summary of the invention

[0007] The object of the present invention is to provide a BOG gas dehydrogenation system and a method of using the same, so as to solve the technical problems of the prior art BOG gas dehydrogenation device in that the separated hydrogen has low purity, consumes a lot of energy and has high operating cost.

[0008] To achieve the above object, an embodiment of the present invention provides a BOG gas dehydrogenation system, including a dehydrogenation device, the dehydrogenation device 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 device comprises a heat exchange box, a plurality of hydrogen storage alloy tanks are arranged inside the heat exchange box, each hydrogen storage alloy tank 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;

[0010] A circulating medium inlet and a circulating medium outlet are respectively arranged on both sides of the heat exchange box, and the circulating medium inlet and the circulating medium outlet are connected to the circulating heat exchange medium unit;

[0011] The BOG gas dehydrogenation system also includes a control system, which is connected to the dehydrogenation device.

[0012] In one of the preferred solutions of the present invention, at least two dehydrogenation devices are provided, one of which absorbs hydrogen and the other releases hydrogen.

[0013] In one of the preferred solutions of the present invention, one end of the dehydrogenation device for dehydrogenating is connected to the mixed gas source unit and the circulating heat exchange medium unit.

[0014] In one of the preferred solutions of the present invention, an air inlet pipe and an air outlet pipe are connected to both ends of each hydrogen storage alloy tank body, the air inlet pipe is connected to the mixed gas inlet, and the air outlet pipe is connected to the mixed gas outlet.

[0015] In one of the preferred solutions of the present invention, a filter screen is provided inside each hydrogen storage alloy tank.

[0016] In one of the preferred solutions of the present invention, 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.

[0017] In one of the preferred solutions of the present invention, the circulating heat exchange medium unit includes a cooling medium module and a heating medium module.

[0018] In one of the preferred solutions of the present invention, valves are provided between the dehydrogenation device and the mixed gas source unit and the circulating heat exchange medium unit, and a booster pump is provided between the dehydrogenation device and the dehydrogenation mixed gas unit.

[0019] Based on a BOG gas dehydrogenation system disclosed in the present invention, the present invention also discloses a method for using the BOG gas dehydrogenation system, including: a mixed gas source in a mixed gas source unit flows through a dehydrogenation device to remove hydrogen, and the mixed gas after hydrogen removal flows into a dehydrogenation mixed gas unit.

[0020] One of the preferred schemes of the present invention is a method for using the BOG gas dehydrogenation system, comprising: a mixed gas source in a mixed gas source unit flows through one of the dehydrogenation devices to remove hydrogen, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit; and another dehydrogenation device releases hydrogen under the action of heating.

[0021] In summary, the beneficial effects of the present invention are:

[0022] 1. The BOG gas dehydrogenation system of the present invention adopts the reversible reaction of hydrogen storage alloy and hydrogen adsorption to achieve the purpose of hydrogen separation. The above process is carried out under normal temperature and low pressure conditions. Compared with the existing low-temperature separation, high-pressure adsorption and other methods, it greatly reduces energy consumption and is conducive to energy conservation and emission reduction. At the same time, compared with the existing physical methods, the hydrogen separation method of the present invention 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.

[0023] 2. The hydrogen storage alloy in the hydrogen storage alloy tank in the BOG gas dehydrogenation system of the present invention is selective and reacts only with hydrogen without adsorbing other gases. Therefore, high-purity hydrogen can be obtained, thereby improving its application value in the field of hydrogen energy.

[0024] 3. The BOG gas dehydrogenation system of the present invention not only realizes the effective separation of hydrogen, but also proposes a new BOG gas treatment method, that is, while removing hydrogen, it recovers methane, helium and other resources in the BOG gas, thereby avoiding waste of resources and improving the economic benefits of the LNG plant.

[0025] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by implementing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the dehydrogenation device in the present invention;

[0027] Figure 2 A top view of the dehydrogenation device of the present invention;

[0028] Figure 3 It is a side view of the dehydrogenation device in the present invention;

[0029] Figure 4FIG. 1 is a schematic structural diagram of a BOG gas dehydrogenation system in one embodiment of the present invention.

[0030] 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 emptying unit, 23-hydrogen unit, 24-tenth valve, 25-eleventh valve, 26-emptying unit, 27-eighth valve. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a BOG gas dehydrogenation system, comprising a dehydrogenation device, the dehydrogenation device is connected to a mixed gas source unit 10 and a circulating heat exchange medium unit 9, and one end of the dehydrogenation device away from the mixed gas source unit 10 is connected to a dehydrogenation mixed gas unit 20. The working process is: the mixed gas of the mixed gas source unit 10 flows into the dehydrogenation device, and the hydrogen absorption process is completed under the action of the cooling medium module in the circulating heat exchange medium unit 9, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit 20. Valves are arranged between the dehydrogenation device and the mixed gas source unit 10 and the circulating heat exchange medium unit 9, and a booster pump is arranged between the dehydrogenation device and the dehydrogenation mixed gas unit 20.

[0033] Dehydrogenation units, such as Figure 1-Figure 3 As shown, it includes a heat exchange box 1, and a plurality of hydrogen storage alloy tanks 2 arranged in a matrix are arranged inside the heat exchange box 1. Each hydrogen storage alloy tank 2 is connected in parallel. This connection method can quickly reduce the flow rate of the high-pressure and high-speed mixed gas, so that the hydrogen in the mixed gas is fully in contact with the hydrogen storage alloy, and improve the separation efficiency of the mixed gas and hydrogen. The heat exchange box 1 adopts the form of external heat exchange, which is a shell-and-tube heat exchanger, and wraps the array structure composed of the hydrogen storage alloy tanks 2.

[0034] The two ends of each hydrogen storage alloy tank body 2 are connected with an inlet pipe 4 and an outlet pipe 8, the inlet pipe 4 is connected to the mixed gas inlet 3, 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 dehydrogenation mixed gas unit 20. The mixed gas in the mixed gas source unit 10 enters the hydrogen storage alloy tank body 2 through the inlet pipe 4 to complete the hydrogen absorption process, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit 20 through the outlet pipe 8. The purpose of connecting the inlet and outlet of the hydrogen storage alloy tank body 2 in parallel with the inlet pipe 4 and the outlet pipe 8 is to split and merge the mixed gas.

[0035] A circulating medium inlet 5 and a circulating medium outlet 6 are respectively provided on both sides of the heat exchange box 1, and the circulating medium inlet 5 and the circulating medium outlet 6 are connected to a circulating heat exchange medium unit 9, and the circulating heat exchange medium unit 9 includes a cooling medium module and a heating medium module. When the dehydrogenation device performs hydrogen absorption treatment, the cooling medium is introduced into the heat exchange box 1; when the dehydrogenation device performs hydrogen release treatment, the heating medium is introduced into the heat exchange box 1.

[0036] A filter screen is provided inside each hydrogen storage alloy tank 2 to stabilize the hydrogen storage alloy and prevent it from flowing into the main pipeline along with 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.

[0037] The BOG gas dehydrogenation system also includes a control system for controlling the entire BOG gas dehydrogenation system, and the control system is connected to the dehydrogenation device. 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 realize the automatic operation of the dehydrogenation system.

[0038] Furthermore, at least two dehydrogenation devices are provided, one of which absorbs hydrogen and the other releases hydrogen. One end of the dehydrogenation device for releasing hydrogen is connected to the mixed gas source unit 10 and the circulating heat exchange medium unit 9, and the end away from the mixed gas source unit 10 is connected to other modules. The specific connection depends on the actual situation, and hydrogen can be recovered.

[0039] The present invention also discloses a method for using the BOG gas dehydrogenation system, comprising: a mixed gas source in a mixed gas source unit 10 flows through a dehydrogenation device to remove hydrogen, and the mixed gas after hydrogen removal flows into a dehydrogenation mixed gas unit 20.

[0040] 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.

[0041] Example: This example takes two dehydrogenation units as an example

[0042] A BOG gas dehydrogenation system, such as Figure 4 As shown, it includes two dehydrogenation devices, namely a first dehydrogenation device 15 and a second dehydrogenation device 14;

[0043] The first dehydrogenation device 15 and the second dehydrogenation device 14 are both connected to the mixed gas source unit 10 and the circulating heat exchange medium unit 9. The other ends of the first dehydrogenation device 15 and the second dehydrogenation device 14 are both connected to the dehydrogenation mixed gas unit 20 and other units, including the emergency emptying unit 22, the emptying unit 26 and the hydrogen unit 23. The other units can be selected according to actual conditions.

[0044] A first valve 11, a second valve 12 and a third valve 13 are arranged between the first dehydrogenation device 15, the second dehydrogenation device 14 and the mixed gas source unit 10, a fourth valve 16 is arranged between the first dehydrogenation device 15 and other units, and a fifth valve 17 is arranged between the first dehydrogenation device 15 and the dehydrogenated mixed gas unit 20; a sixth valve 18 is arranged between the second dehydrogenation device 14 and the dehydrogenated mixed gas unit 20, and an eighth valve 27 is arranged between the second dehydrogenation device 14 and other units; a seventh valve 19 is arranged between the first dehydrogenation device 15, the second dehydrogenation device 14 and the dehydrogenated mixed gas unit 20; a ninth valve 21, a tenth valve 24 and an eleventh valve 25 are arranged between the first dehydrogenation device 15, the second dehydrogenation device 14 and other units, wherein the ninth valve 21 is connected to the emergency emptying unit 22, the tenth valve 24 is connected to the hydrogen unit 23, and the eleventh valve 25 is connected to the emptying unit 26.

[0045] A method for using a BOG gas dehydrogenation system, comprising:

[0046] (1) The first dehydrogenation device 15 dehydrogenates, and the second dehydrogenation device 14 discharges hydrogen:

[0047] Dehydrogenation in the first dehydrogenation device 15: During this process, the first valve 11, the second valve 12, the fifth valve 17, and the seventh valve 19 are opened, and the BOG gas flows through the first dehydrogenation device 15 to remove hydrogen; at this time, the circulating heat exchange medium is a 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;

[0048] The second dehydrogenation device 14 dehydrogenates: during this process, the eighth valve 27 is opened, the sixth valve 18 is closed, and the ninth valve 21 or the tenth valve 24 is selectively opened according to actual conditions. If hydrogen needs to be recovered, 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 a heating medium, which provides heat for the second dehydrogenation device 14. Since the hydrogen storage alloy absorbs heat during the dehydrogenation process, the temperature of the second dehydrogenation device 14 decreases, which in turn causes a decrease in the dehydrogenation efficiency of the hydrogen storage alloy. Therefore, heat needs to be provided to improve the dehydrogenation efficiency.

[0049] The hydrogen storage alloy releases the hydrogen in it by heating, and then can repeatedly absorb hydrogen to achieve the regeneration of the device.

[0050] (2) The second dehydrogenation device 14 dehydrogenates, and the first dehydrogenation device 15 discharges hydrogen:

[0051] Dehydrogenation in the second dehydrogenation device 14: During this process, the first valve 11, the third valve 13, the sixth valve 18, and the seventh valve 19 are opened, and the BOG gas flows through the second dehydrogenation device 14 to remove hydrogen; at this time, the circulating heat exchange medium is the cooling medium, and the cooling medium cools the second dehydrogenation device 14;

[0052] The first dehydrogenation device 15 releases hydrogen: 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 the ninth valve 21 or the tenth valve 24 is selectively opened according to actual conditions; at this time, the circulating heat exchange medium is the heating medium, and the heating medium heats the first dehydrogenation device 15;

[0053] During the above process, when the BOG gas dehydrogenation system is in operation, the first dehydrogenation device 15 and the second dehydrogenation device 14 are always maintained, with one group performing dehydrogenation and the other group releasing hydrogen. At the same time, multiple groups of dehydrogenation devices can be added according to actual needs.

[0054] Although the specific implementation of the present invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A BOG gas dehydrogenation system, characterized in that: The dehydrogenation device comprises a dehydrogenation device, wherein the dehydrogenation device is connected to a mixed gas source unit and a circulating heat exchange medium unit, and one end of the dehydrogenation device away from the mixed gas source unit is connected to a dehydrogenation mixed gas unit; The dehydrogenation device comprises a heat exchange box, a plurality of hydrogen storage alloy tanks are arranged inside the heat exchange box, each of the hydrogen storage alloy tanks 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; A circulating medium inlet and a circulating medium outlet are respectively provided on both sides of the heat exchange box, and the circulating medium inlet and the circulating medium outlet are connected to the circulating heat exchange medium unit; The BOG gas dehydrogenation system further includes a control system, which is connected to the dehydrogenation device.

2. A BOG gas dehydrogenation system according to claim 1, characterized in that: At least two dehydrogenation devices are provided, one of which absorbs hydrogen and the other releases hydrogen.

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

4. A BOG gas dehydrogenation system according to claim 1, characterized in that: An air inlet pipe and an air outlet pipe are connected to both ends of each hydrogen storage alloy tank body. The air inlet pipe is connected to the mixed gas inlet, and the air outlet pipe is connected to the mixed gas outlet.

5. A BOG gas dehydrogenation system according to claim 1 or 4, characterized in that: A filter screen is arranged inside each hydrogen storage alloy tank.

6. A BOG gas dehydrogenation system according to claim 1, characterized in that: The hydrogen storage alloy in 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.

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

8. A BOG gas dehydrogenation system according to claim 1, characterized in that: Valves are arranged between the dehydrogenation device and the mixed gas source unit and the circulating heat exchange medium unit, and a booster pump is arranged between the dehydrogenation device and the dehydrogenation mixed gas unit.

9. A method for using a BOG gas dehydrogenation system according to any one of claims 1 to 8, characterized in that: include: The mixed gas source in the mixed gas source unit flows through the dehydrogenation device to remove hydrogen, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit.

10. The method for using a BOG gas dehydrogenation system according to claim 9, characterized in that: The method for using the BOG gas dehydrogenation system includes: the mixed gas source in the mixed gas source unit flows through one of the dehydrogenation devices to remove hydrogen, and the mixed gas after hydrogen removal flows into the dehydrogenation mixed gas unit; and the other dehydrogenation device releases hydrogen under the action of heating.

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