BOG reliquefaction recovery device for gas station

Abstract

The utility model discloses a BOG reliquefaction recovery device for a gas station. The BOG reliquefaction recovery device comprises a cold side flow channel of a heat regenerator, a temperature controller, a compressor, a water cooler, a flowmeter, a hot side flow channel of the heat regenerator, an air inlet valve, a first storage tank liquid phase valve, a first storage tank, a first storage tank gas phase valve, a refrigerator air inlet valve, a refrigerator, a second storage tank liquid inlet valve and a second storage tank which are sequentially connected, a liquid outlet of the second storage tank is connected with the first storage tank liquid phase valve through a second storage tank liquid outlet valve, and a gas outlet of the second storage tank is connected with a refrigerator gas inlet valve through a second storage tank gas phase valve. According to the utility model, not only can the BOG in the LNG storage tank of the LNG filling station be recovered, but also the BOG in the storage tank of the transportation tank car can be recovered, and meanwhile, the liquefaction recovery efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the field of liquefied natural gas, in particular to a BOG reliquefaction recovery device for a gas filling station. Background Art

[0002] LNG filling stations usually have an LNG storage tank of about 60 cubic meters for storing LNG. Due to various heat leaks in the LNG filling system, such as heat leakage of the storage tank, heat transfer in the pipeline, pre-cooling process before filling, LNG gasification in the pipeline after filling, self-pressurization unloading during the unloading process, heating of the submersible pump, etc., part of the LNG is gasified into boil-off gas (BOG), causing the pressure of the LNG storage tank to rise. Since the LNG storage tank is a pressure vessel, when the pressure reaches the set pressure of the safety valve, it will trigger the discharge. The discharge of BOG into the atmosphere is not only a waste of energy, but also brings air pollution, emission noise, and potential safety hazards of combustion and explosion.

[0003] In order to solve the BOG emission problem of LNG filling stations, BOG can be reliquefied by using a refrigerator. For example, a Chinese patent document with publication number CN206449402U discloses a LNG filling station tank pressure stabilization system, including an LNG storage tank and a BOG reliquefaction device, wherein the LNG storage tank has a gas outlet and a liquid inlet, and the BOG reliquefaction device has a gas inlet and a liquid outlet, wherein the gas outlet is connected to the gas inlet through a gas pipeline, and a control valve is provided on the gas pipeline; the liquid outlet is connected to the liquid inlet through a liquid pipeline. By outputting the BOG in the LNG storage tank and sending it to the BOG reliquefaction device to liquefy and generate liquid, and then sending the liquid back to the LNG storage tank, the BOG in the LNG storage tank can be reduced, the pressure in the LNG storage tank can be reduced, and the pressure in the LNG storage tank can be controlled within a reasonable range, while the BOG can be recovered and the BOG can be avoided from being released.

[0004] A Chinese patent document with publication number CN103759496A discloses a small skid-mounted liquefied natural gas boil-off gas reliquefaction and recovery device, comprising: a cryogenic storage tank, a heat recovery cryogenic refrigerator, an external finned condensing heat exchanger, a pressure testing device, a temperature testing device, a heating device, and a control system. According to the actual pressure of the cryogenic storage tank and the requirements of the heat load, the cold end temperature and the output cooling capacity of the cryogenic refrigerator are monitored and adjusted steplessly in real time to achieve zero loss of the LNG storage tank system.

[0005] In order to achieve better cooling effect, Stirling refrigerators were used to reliquefy BOG. ​​Stirling refrigerators can provide 1000W cooling capacity at liquid nitrogen temperature and 1500W cooling capacity at LNG temperature, which is significantly better than competing models such as GM refrigerators in cooling capacity and efficiency. Some systems based on Stirling refrigerators for direct cooling of liquefied BOG have been developed in advance. However, since the cooling capacity of the Stirling refrigerator is concentrated in the cold head heat exchanger for release, the heat exchange area is limited, resulting in high heat flux density and large heat exchange temperature difference, which is directly reflected in the loss of cooling capacity at the system level. Utility Model Content

[0006] The utility model provides a BOG reliquefaction recovery device for a gas filling station, which can not only recover the BOG in the LNG storage tank of the LNG filling station itself, but also recover the BOG in the storage tank of a transport tank truck, while increasing the efficiency of liquefaction recovery.

[0007] A BOG reliquefaction recovery device for a gas filling station, comprising a cold side flow channel of a regenerator, a temperature controller, a compressor, a water cooler, a flow meter, a hot side flow channel of the regenerator, an air inlet valve, a first storage tank liquid phase valve, a first storage tank, a first storage tank gas phase valve, a refrigerator air inlet valve, a refrigerator, a second storage tank liquid inlet valve and a second storage tank connected in sequence;

[0008] The liquid outlet of the second storage tank is connected to the liquid phase valve of the first storage tank through the second storage tank liquid outlet valve, and the gas outlet of the second storage tank is connected to the gas inlet valve of the refrigerator through the second storage tank gas phase valve.

[0009] Furthermore, the BOG reliquefaction recovery device of the gas filling station of the utility model also includes a fan air inlet valve, a fan heat regenerator and a fan; wherein the fan heat regenerator includes a cold side flow channel and a hot side flow channel, and the first storage tank gas phase valve, the fan air inlet valve, the cold side flow channel of the fan heat regenerator, the fan, the hot side flow channel of the fan heat regenerator, and the refrigerator are connected in sequence.

[0010] Furthermore, the fan is a low-temperature centrifugal fan.

[0011] Furthermore, a vacuum cold box is arranged outside the fan and the fan heat regenerator for thermal insulation.

[0012] Furthermore, the refrigerator is a Stirling refrigerator.

[0013] Furthermore, the compressor is an oil-free compressor or an oil-containing compressor with an oil filtering function.

[0014] The specific working method of the utility model of the present invention is as follows:

[0015] Step 1, recovering BOG from the tank truck: connecting the gas phase port of the tank truck for recovering BOG to the cold side flow channel of the regenerator, and the BOG gas in the tank truck enters the cold side flow channel of the regenerator, and then flows through the thermostat to enter the compressor for pressurization. The thermostat ensures that the BOG gas temperature is higher than the lowest suction temperature of the compressor. After the compressor compresses the BOG gas, it is cooled by the water cooler, and then the flow is measured by the flow meter, and then it enters the hot side flow channel of the regenerator, cools down after heat exchange, and then flows through the intake valve and the first tank liquid phase valve to enter the first tank, and mixes with the liquid phase in the first tank. After mixing, the liquid temperature in the first tank rises and the tank pressure rises;

[0016] Step 2, liquefying the BOG in the first storage tank: the BOG gas in the first storage tank flows into the refrigerator through the first storage tank gas phase valve and the refrigerator air inlet valve, is cooled and liquefied by the refrigerator, and then flows into the second storage tank through the second storage tank liquid inlet valve for storage; as the BOG in the first storage tank continuously flows out, the pressure and temperature of the first storage tank decrease;

[0017] Step 3, liquid reflux in the second storage tank: close the second storage tank liquid inlet valve, the second storage tank liquid outlet valve, and the second storage tank gas phase valve, and start the self-pressurization of the second storage tank to increase the pressure to a pressure greater than the pressure of the first storage tank; then open the second storage tank liquid outlet valve and the first storage tank liquid phase valve, close the gas inlet valve, and the liquid in the second storage tank refluxes into the first storage tank through the second storage tank liquid outlet valve and the first storage tank liquid phase valve;

[0018] Step 4, equalize the pressure of the second tank: close the second tank outlet valve and the first tank liquid phase valve, open the second tank gas phase valve and the first tank gas phase valve; the BOG in the second tank is connected to the gas phase of the first tank through the second tank gas phase valve and the first tank gas phase valve, and the pressures of the two tanks are finally balanced; the volume of the second tank is much smaller than that of the first tank, so the pressure after balance will only be slightly higher than the pressure of the first tank before balance;

[0019] Alternatively, BOG in the second storage tank is liquefied separately: the gas phase valve of the first storage tank and the liquid outlet valve of the second storage tank are closed, and the gas phase valve of the second storage tank, the air inlet valve of the refrigerator, and the liquid inlet valve of the second storage tank are opened; the BOG in the second storage tank enters the refrigerator through the gas phase valve of the second storage tank and the air inlet valve of the refrigerator, is cooled and liquefied by the refrigerator, and then flows back to the second storage tank through the liquid inlet valve of the second storage tank.

[0020] Furthermore, the following steps may be included:

[0021] Accelerate the liquefaction of BOG in the first storage tank: open the gas phase valve of the first storage tank, the air inlet valve of the fan, the liquid inlet valve of the second storage tank, and the gas phase valve of the second storage tank, and close the air inlet valve of the refrigerator and the liquid outlet valve of the second storage tank. The BOG gas in the first storage tank flows into the refrigerator through the gas phase valve of the first storage tank, the air inlet valve of the fan, the cold side flow channel of the fan regenerator, the fan, and the hot side flow channel of the fan regenerator. After being cooled and liquefied by the refrigerator, it flows into the second storage tank through the liquid inlet valve of the second storage tank for storage;

[0022] Accelerate the liquefaction of BOG in the second storage tank: close the gas phase valve of the first storage tank, the liquid outlet valve of the second storage tank and the air inlet valve of the refrigerator, open the gas phase valve of the second storage tank, the air inlet valve of the fan and the liquid inlet valve of the second storage tank, and the BOG in the second storage tank enters the refrigerator through the gas phase valve of the second storage tank, the air inlet valve of the fan, the cold side flow channel of the fan regenerator, the fan and the hot side flow channel of the fan regenerator. After being cooled and liquefied by the refrigerator, it flows back to the second storage tank through the liquid inlet valve of the second storage tank.

[0023] Compared with the prior art, the utility model has the following beneficial effects:

[0024] 1. The utility model can liquefy and recover BOG in the storage tank of the LNG filling station, and can also recover BOG in the tank truck by first cooling the LNG in the storage tank of the filling station and then mixing it with the BOG in the tank truck. This form can absorb more BOG in the tank truck in a short time by accumulating cold energy without increasing the liquefaction capacity; in addition, the additional low-temperature fan can enhance the flow heat exchange between the BOG gas and the refrigerator, and a heat regenerator is set in the necessary parts of the system to recover cold energy.

[0025] 2. The utility model further integrates the function of directly recovering BOG from the LNG transport tanker, so that the BOG recovery device can not only recover the BOG in the LNG storage tank of the LNG filling station, but also recover the BOG in the tank of the transport tanker. Furthermore, the utility model utilizes the cold storage capacity of the liquid in the LNG storage tank of the LNG filling station, and can mix it with the BOG in the tanker in a short time to liquefy most of it, thus solving the problem that the tanker stays too long to recover BOG and affects the transportation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of a BOG reliquefaction recovery device for a gas filling station according to the utility model.

[0027] In the figure: regenerator 1, thermostat 2, compressor 3, water cooler 4, flow meter 5, air inlet valve 6, first storage tank liquid phase valve 7, first storage tank 8, first storage tank gas phase valve 9, refrigerator air inlet valve 10, refrigerator 11, second storage tank liquid inlet valve 12, second storage tank 13, second storage tank liquid outlet valve 14, second storage tank gas phase valve 15, fan air inlet valve 16, fan regenerator 17, fan 18. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0029] like Figure 1As shown, a BOG reliquefaction recovery device for a gas filling station includes a regenerator 1, a thermostat 2, a compressor 3, a water cooler 4, a flow meter 5, an air inlet valve 6, a first storage tank liquid phase valve 7, a first storage tank 8, a first storage tank gas phase valve 9, a refrigerator air inlet valve 10, a refrigerator 11, a second storage tank liquid inlet valve 12, a second storage tank 13, a second storage tank liquid outlet valve 14, and a second storage tank gas phase valve 15. Among them, the regenerator 1 includes a cold side flow channel and a hot side flow channel; the cold side flow channel of the regenerator 1, the temperature controller 2, the compressor 3, the water cooler 4, the flow meter 5, the hot side flow channel of the regenerator 1, the air inlet valve 6, the first storage tank liquid phase valve 7, the first storage tank 8, the first storage tank gas phase valve 9, the refrigerator air inlet valve 10, the refrigerator 11, the second storage tank liquid inlet valve 12, the second storage tank 13, and the second storage tank liquid outlet valve 14 are connected in sequence; the second storage tank liquid outlet valve 14 is connected to the first storage tank liquid phase valve 7; the second storage tank 13 is connected to the refrigerator air inlet valve 10 through the second storage tank gas phase valve 15.

[0030] The utility model also includes a fan air intake valve 16, a fan heat regenerator 17, and a fan 18; wherein the fan heat regenerator 17 includes a cold side flow channel and a hot side flow channel; the first storage tank gas phase valve 9, the fan air intake valve 16, the cold side flow channel of the fan heat regenerator 17, the fan 18, the hot side flow channel of the fan heat regenerator 17, and the refrigerator 11 are connected in sequence.

[0031] In the embodiment of the utility model, the refrigerator 11 is a Stirling refrigerator, the compressor 3 is an oil-free compressor or an oil-containing compressor with oil filtering function, and the fan 18 is a low-temperature centrifugal fan. The fan 18 and the fan regenerator 17 are insulated using a vacuum cold box.

[0032] The specific working method of the utility model is as follows:

[0033] (1) Recovering BOG from a tank truck: The gas phase port of the tank truck for recovering BOG is connected to the cold side flow channel of the regenerator 1. The BOG gas in the tank truck enters the cold side flow channel of the regenerator 1 through the gas phase port of the tank truck, and then flows through the thermostat 2 to the compressor 3 for pressurization. The thermostat 2 has a heating capacity to ensure that the BOG gas temperature is higher than the lowest suction temperature of the compressor. After the compressor 3 compresses the BOG gas, it is cooled by the water cooler 4. After the flow rate is measured by the flow meter 5, it enters the hot side flow channel of the regenerator 1, cools down after heat exchange, and then flows through the intake valve 6 and the first tank liquid phase valve 7 to enter the first tank 8 to mix with the liquid phase in the first tank. After mixing, the liquid temperature in the first tank 8 rises and the tank pressure rises.

[0034] (2) Liquefying the BOG in the first storage tank 8: The BOG gas in the first storage tank 8 flows into the refrigerator 11 through the first storage tank gas phase valve 9 and the refrigerator air inlet valve 10. After being cooled and liquefied by the refrigerator 11, the BOG gas flows into the second storage tank 13 through the second storage tank liquid inlet valve 12 for storage. As the BOG in the first storage tank 8 continues to flow out, the pressure and temperature of the first storage tank 8 decrease.

[0035] (3) Liquid reflux in the second storage tank 13: close the second storage tank liquid inlet valve 12, the second storage tank liquid outlet valve 14, and the second storage tank gas phase valve 15, and start the self-pressurization of the second storage tank 13 to increase the pressure to a level greater than the pressure of the first storage tank 8. Then open the second storage tank liquid outlet valve 14 and the first storage tank liquid phase valve 7 and close the gas inlet valve 6. The liquid in the second storage tank refluxes into the storage tank 8 through the second storage tank liquid outlet valve 14 and the first storage tank liquid phase valve 7.

[0036] (4) Pressure equalization of the second storage tank 13: close the second storage tank liquid outlet valve 14 and the first storage tank liquid phase valve 7, and open the second storage tank gas phase valve 15 and the first storage tank gas phase valve 9; the BOG in the second storage tank is connected to the gas phase of the first storage tank 8 through the second storage tank gas phase valve 15 and the first storage tank gas phase valve 9, and the pressures of the two are finally balanced; since the volume of the second storage tank 13 is much smaller than that of the first storage tank 8, the pressure after balance is only slightly higher than the pressure of the first storage tank 8 before balance.

[0037] (5) Liquefying the BOG in the second storage tank 13: The pressure in the second storage tank 13 is relatively high after the pressurization. In addition to the pressure equalization operation in step (4), the BOG in the second storage tank 13 can also be liquefied separately. The first storage tank gas phase valve 9 and the second storage tank liquid outlet valve 14 are closed, and the second storage tank gas phase valve 15, the refrigerator air inlet valve 10, and the second storage tank liquid inlet valve 12 are opened. The BOG in the second storage tank 13 enters the refrigerator 11 through the second storage tank gas phase valve 15 and the refrigerator air inlet valve 10, is cooled and liquefied by the refrigerator 11, and then flows back to the second tank 13 through the second storage tank liquid inlet valve 12.

[0038] (6) Accelerating the liquefaction of BOG in the first storage tank 8: Open the first storage tank gas phase valve 9, the fan air inlet valve 16, the second storage tank liquid inlet valve 12, and the second storage tank gas phase valve 15; close the refrigerator air inlet valve 10 and the second storage tank liquid outlet valve 14; the BOG gas in the first storage tank 8 flows into the refrigerator 11 through the first storage tank gas phase valve 9, the fan air inlet valve 16, the cold side flow channel of the fan regenerator 17, the fan 18, and the hot side flow channel of the fan regenerator 17; after being cooled and liquefied by the refrigerator 11, it flows into the second storage tank 13 through the second storage tank liquid inlet valve 12 for storage.

[0039] (7) Accelerating the liquefaction of BOG in the second storage tank 13: Close the first storage tank gas phase valve 9, the second storage tank liquid outlet valve 14 and the refrigerator air inlet valve 10, and open the second storage tank gas phase valve 15, the fan air inlet valve 16 and the small tank liquid inlet valve 12. The BOG in the second storage tank 13 passes through the second storage tank gas phase valve 15, the fan air inlet valve 16, the cold side flow channel of the fan regenerator 17, the fan 18, the hot side flow channel of the fan regenerator 17, and the refrigerator 11. After being cooled and liquefied by the refrigerator 11, the BOG flows back to the second storage tank 13 through the second storage tank liquid inlet valve 12.

[0040] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A BOG reliquefaction recovery device for a gas filling station, characterized in that: It comprises a cold side flow channel of a heat regenerator (1), a temperature controller (2), a compressor (3), a water cooler (4), a flow meter (5), a hot side flow channel of the heat regenerator (1), an air inlet valve (6), a first storage tank liquid phase valve (7), a first storage tank (8), a first storage tank gas phase valve (9), a refrigerator air inlet valve (10), a refrigerator (11), a second storage tank liquid inlet valve (12) and a second storage tank (13) which are connected in sequence; The liquid outlet of the second storage tank (13) is connected to the first storage tank liquid phase valve (7) via the second storage tank liquid outlet valve (14), and the gas outlet of the second storage tank (13) is connected to the refrigerator gas inlet valve (10) via the second storage tank gas phase valve (15).

2. The BOG reliquefaction recovery device for a gas filling station according to claim 1, characterized in that: It also includes a fan air intake valve (16), a fan heat exchanger (17) and a fan (18); wherein the fan heat exchanger (17) includes a cold side flow channel and a hot side flow channel, and the first storage tank gas phase valve (9), the fan air intake valve (16), the cold side flow channel of the fan heat exchanger (17), the fan (18), the hot side flow channel of the fan heat exchanger (17), and the refrigerator (11) are connected in sequence.

3. The BOG reliquefaction recovery device for a gas filling station according to claim 2, characterized in that: The fan (18) is a low-temperature centrifugal fan.

4. The BOG reliquefaction recovery device for a gas filling station according to claim 2, characterized in that: A vacuum cold box is arranged outside the fan (18) and the fan heat regenerator (17) for thermal insulation.

5. The BOG reliquefaction recovery device for a gas filling station according to claim 1, characterized in that: The refrigerator (11) is a Stirling refrigerator.

6. The BOG reliquefaction recovery device for a gas filling station according to claim 1, characterized in that: The compressor (3) is an oil-free compressor or an oil-containing compressor with an oil filtering function.

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