A marine LNG gas supply system

Abstract

A marine LNG fuel supply system belongs to the technical field of fuel supply, and particularly relates to marine gas supply. It solves the safety problem of excessive boil-off gas in the storage tank leading to excessive pressure in the prior art, as well as the problem of supplying gas to high-pressure main engines and low-pressure equipment. The system includes a fuel storage subsystem, a fuel gas supply subsystem, and a voltage stabilization control subsystem. The fuel storage subsystem is used to store liquefied natural gas and low-pressure gaseous natural gas at a storage temperature and storage pressure within a set range, and is also used to unidirectionally supply low-pressure gaseous natural gas to the fuel gas supply subsystem. The voltage stabilization control subsystem is used to collect the storage pressure of the fuel storage subsystem and to stabilize the storage pressure within the set range. The present invention is applicable to storing natural gas on ships and supplying natural gas to equipment on ships.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel supply, and particularly to marine gas supply. Background Art

[0002] At present, the earth's environment is deteriorating day by day and oil reserves are decreasing day by day. In order to improve the earth's environment and cope with the energy crisis, people have shifted their attention to LNG (Liquefied Natural Gas). Liquefied natural gas has become the preferred fuel to replace traditional petroleum fuels due to its high energy density, rich reserves, low sulfur content, and less air pollution caused by complete combustion. For example, at present, more and more ships choose liquefied natural gas as ship fuel.

[0003] Liquefied natural gas is the liquefied state of natural gas at -162 °C, and its main component is methane (CH4). It has the characteristics of low temperature, easy volatilization, inflammability and explosiveness. Its volume in the gaseous state is 600 times that in the liquid state, and the weight of LNG is only about 45% of that of water with the same volume. It is colorless, odorless, non-toxic and non-corrosive, and the explosion limit after vaporization is 5% - 15%. For safety reasons, the contact between liquefied natural gas and air should be properly isolated at any time. If liquefied natural gas is stored in a storage tank for a long time, a large amount of boil-off gas (BOG) will be generated due to heat absorption.

[0004] The said boil-off gas can increase the storage pressure of liquefied natural gas. When the storage pressure is higher than the safety value, if the boil-off gas in the tank cannot be discharged in time, there is a risk of explosion. At the same time, if the boil-off gas is directly discharged into the atmosphere, it will also cause problems such as energy waste and environmental pollution. Therefore, how to effectively treat the boil-off gas is a problem that needs to be solved.

[0005] When liquefied natural gas is used as ship fuel, the high-pressure gas engines and auxiliary generators on the ship will both use dual-fuel diesel engines, which can use traditional diesel as fuel or compressed liquefied natural gas as fuel. When using liquefied natural gas as fuel, the high-pressure gas main engine and the power generation auxiliary engine on the ship are both natural gas engines. Among them, the supply pressure of the high-pressure gas main engine (referred to as the high-pressure main engine for short) reaches 300 bar, and the supply pressure of the power generation auxiliary engine (or called the low-pressure main engine, low-pressure gas-using equipment) reaches 7 bar. Therefore, if the liquefied natural gas in the storage tank is to be used as fuel, a gas supply system that can heat and pressurize the liquefied natural gas is required. At the same time, when the volume of the storage tank increases, the amount of boil-off gas generated increases, and the consumption of the auxiliary generator and the boiler is lower than the amount of boil-off gas generated, the storage pressure will increase. When the pressure increases to a certain extent, the safety valve will open, and the gas in the storage tank will be emptied through the vent pipe, resulting in fuel waste; in addition, the increase in pressure will also pose a risk of damaging the storage tank. Summary of the Invention

[0006] The present invention solves the safety problem in the prior art that excessive boil-off gas in the storage tank causes excessive pressure, and also solves the problem of supplying gas to a high-pressure main engine and low-pressure equipment.

[0007] A marine LNG gas supply system according to the present invention has the following technical solution:

[0008] The system includes a fuel storage subsystem, a fuel gas supply subsystem, and a pressure stabilization control subsystem;

[0009] The fuel storage subsystem is connected to the fuel gas supply subsystem;

[0010] The fuel storage subsystem is used to store liquefied natural gas and low-pressure gaseous natural gas at a storage temperature and storage pressure within a set range; it is also used to unidirectionally supply low-pressure gaseous natural gas to the fuel gas supply subsystem; the low-pressure gaseous natural gas is gaseous natural gas at 7 to 9 bar.

[0011] The fuel gas supply subsystem is used to convert the low-pressure gaseous natural gas into applicable gaseous natural gas and supply the applicable gaseous natural gas externally;

[0012] The pressure stabilization control subsystem is used to collect the storage pressure of the fuel storage subsystem and to stabilize the storage pressure within the set range.

[0013] Further, a preferred embodiment is provided. The fuel gas supply subsystem includes a high-pressure gas supply unit; the high-pressure gas supply unit is connected to the fuel gas supply subsystem;

[0014] For the high-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

[0015] Further, a preferred embodiment is provided. The fuel gas supply subsystem further includes a low-pressure gas supply unit; the low-pressure gas supply unit is connected to the fuel gas supply subsystem;

[0016] For the low-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C.

[0017] Further, a preferred embodiment is provided. The fuel storage subsystem includes a storage tank, a buffer tank, a two-way valve, a liquid-gas exchange device, a separator, a second one-way valve, and a third one-way valve;

[0018] The storage tank stores liquefied natural gas and low-pressure gaseous natural gas at a storage temperature and storage pressure within a set range;

[0019] The buffer tank stores low-pressure gaseous natural gas at a storage temperature and storage pressure within a set range.

[0020] The two-way valve is connected in series between the storage tank and the buffer tank; the two-way valve is used to regulate the exchange of low-pressure gaseous natural gas between the storage tank and the buffer tank.

[0021] The liquid-gas exchange device is connected in series between the storage tank and the buffer tank; the liquid-gas exchange device is used to convert the liquefied natural gas in the storage tank into low-pressure gaseous natural gas in the buffer tank.

[0022] One end of the separator is connected to the buffer tank.

[0023] The other end of the separator is respectively connected to the high-pressure gas supply unit and the low-pressure gas supply unit.

[0024] The second one-way valve is connected in series between the separator and the high-pressure gas supply unit, and is used to supply the low-pressure gaseous natural gas in the buffer tank to the high-pressure gas supply unit unidirectionally.

[0025] The third one-way valve is connected in series between the separator and the low-pressure gas supply unit, and is used to supply the low-pressure gaseous natural gas in the buffer tank to the low-pressure gas supply unit unidirectionally.

[0026] Furthermore, a preferred embodiment is provided, where the storage tank has a cold insulation layer; the buffer tank has a cold insulation layer.

[0027] Furthermore, a preferred embodiment is provided, where the liquid-gas exchange device includes a submersible pump, a first one-way valve, and an LNG high-pressure heat exchanger.

[0028] The submersible pump is arranged in the storage tank; the submersible pump is connected to one end of the LNG high-pressure heat exchanger; the submersible pump is used to extract the liquefied natural gas in the storage tank and pressurize the liquefied natural gas.

[0029] The first one-way valve is connected in series between the submersible pump and the LNG high-pressure heat exchanger; the first one-way valve is used to supply the liquefied natural gas extracted by the submersible pump to the LNG high-pressure heat exchanger unidirectionally.

[0030] The other end of the LNG high-pressure heat exchanger is connected to the buffer tank; the LNG high-pressure heat exchanger is used to heat the pressurized liquefied natural gas to obtain low-pressure gaseous natural gas and supply the low-pressure gaseous natural gas to the buffer tank.

[0031] Furthermore, a preferred embodiment is provided, where the voltage stabilization control subsystem includes a first pressure sensor, a second pressure sensor, and a voltage stabilization control device.

[0032] The first pressure sensor is configured to collect the storage pressure in the storage tank and send the storage pressure to the voltage stabilization control device;

[0033] The second pressure sensor is configured to collect the storage pressure in the buffer tank and send the storage pressure to the voltage stabilization control device;

[0034] The voltage stabilization control device is configured to adjust the first one-way valve and the two-way valve according to the storage pressure in the storage tank so that the storage pressure in the storage tank is stabilized within a set range; and is further configured to adjust the first one-way valve, the second one-way valve, and the third one-way valve according to the storage pressure in the buffer tank so that the storage pressure in the buffer tank is stabilized within a set range.

[0035] Further, a preferred embodiment is provided, in which the high-pressure gas supply unit includes a heating device, a compressor, and a cooling device;

[0036] One end of the heating device is communicated with the second one-way valve; the other end of the heating device is communicated with one end of the compressor; the heating device is configured to heat the low-pressure gaseous natural gas;

[0037] The other end of the compressor is communicated with one end of the cooling device; the compressor is configured to pressurize the heated low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 200 to 300 bar;

[0038] The cooling device is configured to cool the gaseous natural gas with a pressure of 200 to 300 bar to obtain gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

[0039] Further, a preferred embodiment is provided, in which the heating device is an LNG high-pressure heat exchanger; the cooling device is an LNG high-pressure heat exchanger.

[0040] Further, a preferred embodiment is provided, in which the low-pressure gas supply unit includes a low-pressure heat exchanger;

[0041] One end of the low-pressure heat exchanger is communicated with the third one-way valve; the low-pressure heat exchanger is configured to heat the low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C.

[0042] The present invention has the following beneficial effects:

[0043] 1. A marine LNG gas supply system according to the present invention, through the mutual cooperation among the fuel storage subsystem, the fuel gas supply subsystem and the voltage stabilization control subsystem, supplies the gaseous natural gas evaporated in the fuel storage subsystem to the outside, which not only solves the safety problem of excessive pressure caused by excessive gaseous natural gas evaporated in the fuel storage subsystem, but also solves the natural gas supply problem of external gas-using equipment.

[0044] 2. A marine LNG gas supply system according to the present invention, by setting a voltage stabilization control subsystem, the voltage stabilization control subsystem can adjust the one-way valve and the two-way valve according to the storage pressure, so as to maintain the stability of the storage pressure in the storage tank and the buffer tank, and achieve the effect of reducing safety accidents while keeping the natural gas storage stable.

[0045] A marine LNG gas supply system according to the present invention is suitable for storing natural gas on a ship and supplying natural gas to the equipment on the ship. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0047] Figure 1 It is a flow chart of the liquefied natural gas and gaseous natural gas of a marine LNG gas supply system in an embodiment of the present invention;

[0048] Figure 2 It is a flow chart of the voltage stabilization control method in an embodiment of the present invention;

[0049] Reference numerals: 1, the first pressure sensor; 2, storage tank; 3, submersible pump; 4, the first one-way valve; 5, high-pressure main engine; 6, LNG high-pressure heat exchanger; 7, compressor; 8, buffer tank; 9, separator; 10, the second one-way valve; 11, low-pressure gas-using equipment; 12, low-pressure heat exchanger; 13, the third one-way valve; 14, the second pressure sensor; 15, two-way valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] To make the technical solutions and advantages of the present invention more clearly described, the following will further describe in detail and completely the specific embodiments of the present invention in conjunction with the accompanying drawings. The following embodiments are only a part of the embodiments of the present invention, rather than all the implementation schemes; the embodiments described below are intended to explain the present invention and should not be construed as a limitation of the present invention; the reasonable combination of the technical features defined in each embodiment of the present invention, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0051] Embodiment 1. In combination with Figure 1 and Figure 2 to illustrate this embodiment, this embodiment provides a marine LNG gas supply system, and the specific implementation content is as follows:

[0052] The system includes a fuel storage subsystem, a fuel gas supply subsystem, and a voltage stabilization control subsystem;

[0053] The fuel storage subsystem is connected to the fuel gas supply subsystem;

[0054] The fuel storage subsystem is used to store liquefied natural gas and low-pressure gaseous natural gas at a storage temperature and storage pressure within a set range; it is also used to unidirectionally supply low-pressure gaseous natural gas to the fuel gas supply subsystem; the low-pressure gaseous natural gas is gaseous natural gas at 7 to 9 bar.

[0055] The fuel gas supply subsystem is used to convert the low-pressure gaseous natural gas into applicable gaseous natural gas and supply the applicable gaseous natural gas externally;

[0056] The voltage stabilization control subsystem is used to collect the storage pressure of the fuel storage subsystem and to stabilize the storage pressure within the set range.

[0057] In this embodiment, the applicable gaseous natural gas refers to the gaseous natural gas required by the external gas-using equipment connected to the fuel gas supply subsystem. The gaseous natural gas required by the external gas-using equipment has a set pressure and temperature.

[0058] For example:

[0059] For an external high-pressure main engine, generally the required natural gas should have a pressure of 200 to 300 bar and a temperature of 25 to 50 °C; for the high-pressure main engine, the applicable gaseous natural gas refers to gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

[0060] External low-pressure gas-using equipment generally requires natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C; for the said low-pressure gas-using equipment, the applicable gaseous natural gas refers to gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C.

[0061] Embodiment 2. In combination with Figure 1 and Figure 2 describe this embodiment. This embodiment further defines the fuel gas supply subsystem in a marine LNG fuel supply system described in Embodiment 1. The specific implementation content is as follows:

[0062] The fuel gas supply subsystem includes a high-pressure gas supply unit; the high-pressure gas supply unit is connected to the fuel gas supply subsystem;

[0063] For the high-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

[0064] In this embodiment, the high-pressure gas supply unit is used to supply natural gas to high-pressure gas-using equipment such as high-pressure main engines.

[0065] Furthermore, a preferred embodiment is provided. The fuel gas supply subsystem further includes a low-pressure gas supply unit; the low-pressure gas supply unit is connected to the fuel gas supply subsystem;

[0066] For the low-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C.

[0067] In this embodiment, the low-pressure gas supply unit is used to supply natural gas to low-pressure gas-using equipment such as low-pressure auxiliary engines.

[0068] Furthermore, a preferred embodiment is provided. The fuel gas supply subsystem only includes the low-pressure gas supply unit; the low-pressure gas supply unit is connected to the fuel gas supply subsystem.

[0069] In this embodiment, the system can supply natural gas only to high-pressure gas-using equipment, or only to low-pressure gas-using equipment, or simultaneously to high-pressure gas-using equipment and low-pressure gas-using equipment.

[0070] Embodiment 3. In combination with Figure 1 and Figure 2 describe this embodiment. This embodiment further defines the fuel storage subsystem in a marine LNG fuel supply system described in Embodiment 2. The specific implementation content is as follows:

[0071] The fuel storage subsystem includes a storage tank 2, a buffer tank 8, a two-way valve 15, a liquid-gas exchange device, a separator 9, a second one-way valve 10, and a third one-way valve 13;

[0072] The storage tank 2 stores liquefied natural gas and low-pressure gaseous natural gas at a storage temperature and a storage pressure within a set range;

[0073] The buffer tank 8 stores low-pressure gaseous natural gas at a storage temperature and a storage pressure within a set range;

[0074] The two-way valve 15 is connected in series between the storage tank 2 and the buffer tank 8; the two-way valve 15 is used to regulate the exchange of low-pressure gaseous natural gas between the storage tank 2 and the buffer tank 8;

[0075] The liquid-gas exchange device is connected in series between the storage tank 2 and the buffer tank 8; the liquid-gas exchange device is used to convert the liquefied natural gas in the storage tank 2 into low-pressure gaseous natural gas in the buffer tank 8;

[0076] One end of the separator 9 is communicated with the buffer tank 8;

[0077] The other end of the separator 9 is respectively communicated with the high-pressure gas supply unit and the low-pressure gas supply unit;

[0078] The second one-way valve 10 is connected in series between the separator 9 and the high-pressure gas supply unit, and is used to supply the low-pressure gaseous natural gas in the buffer tank 8 to the high-pressure gas supply unit unidirectionally;

[0079] The third one-way valve 13 is connected in series between the separator 9 and the low-pressure gas supply unit, and is used to supply the low-pressure gaseous natural gas in the buffer tank 8 to the low-pressure gas supply unit unidirectionally.

[0080] In this embodiment, for the storage tank 2:

[0081] The set range of the storage temperature is from -160°C to -150°C;

[0082] The set range of the storage pressure is from 7 to 9 bar.

[0083] In this embodiment, for the buffer tank 8:

[0084] The set range of the storage temperature is from -65°C to -55°C;

[0085] The set range of the storage pressure is from 7 to 9 bar.

[0086] In this embodiment, the liquefied natural gas in the storage tank 2 will generate a large amount of evaporation gas, i.e., gaseous natural gas, due to heat absorption during long-term storage. Therefore, when the storage tank 2 is not connected to the outside, the gaseous natural gas inside it will increase more and more, which may cause safety problems. In this embodiment, by providing a buffer tank and a two-way valve, the pressure inside the storage tank can be adjusted.

[0087] Furthermore, in an embodiment of the present invention, the storage tank 2 has a cold insulation layer; the buffer tank 8 also has a cold insulation layer.

[0088] In this embodiment, the cold insulation layer is used to maintain the storage temperature inside the storage tank 2 and the buffer tank 8 within a set range.

[0089] Furthermore, in a preferred embodiment of the marine LNG fuel supply system described in this embodiment:

[0090] The liquid-gas exchange device includes a submersible pump 3, a first one-way valve 4, and an LNG high-pressure heat exchanger 6;

[0091] The submersible pump 3 is arranged inside the storage tank 2; the submersible pump 3 is connected to one end of the LNG high-pressure heat exchanger 6; the submersible pump 3 is used to extract the liquefied natural gas inside the storage tank 2 and pressurize the liquefied natural gas.

[0092] The first one-way valve 4 is connected in series between the submersible pump 3 and the LNG high-pressure heat exchanger 6; the first one-way valve 4 is used to supply the liquefied natural gas extracted by the submersible pump 3 to the LNG high-pressure heat exchanger 6 unidirectionally.

[0093] The other end of the LNG high-pressure heat exchanger 6 is connected to the buffer tank 8; the LNG high-pressure heat exchanger 6 is used to heat the pressurized liquefied natural gas to obtain low-pressure gaseous natural gas and supply the low-pressure gaseous natural gas to the buffer tank 8.

[0094] In this embodiment, the submersible pump 3 is used to pressurize the liquefied natural gas to 8 bar.

[0095] In this embodiment, the LNG high-pressure heat exchanger 6 is used to heat the pressurized liquefied natural gas to -65°C to -55°C, at which time the liquefied natural gas is converted into low-pressure gaseous natural gas; the pressure of the low-pressure gaseous natural gas is within the set range of the storage pressure of the buffer tank 8, and the temperature of the low-pressure gaseous natural gas is also within the set range of the storage temperature of the buffer tank 8.

[0096] Specifically, the LNG high-pressure heat exchanger 6 has both a heating function and a cooling function.

[0097] The LNG high-pressure heat exchanger 6 includes a number of heating pipelines, a number of cooling pipelines, and an ethylene glycol aqueous solution pipeline;

[0098] The number of heating pipelines are used to transport liquefied natural gas or gaseous natural gas, and to heat the liquefied natural gas or gaseous natural gas;

[0099] The number of cooling pipelines are used to transport liquefied natural gas or gaseous natural gas, and to cool the liquefied natural gas or gaseous natural gas;

[0100] There is ethylene glycol aqueous solution flowing in the ethylene glycol aqueous solution pipeline;

[0101] The LNG high-pressure heat exchanger 6 adjusts the temperature in the number of heating pipelines and the number of cooling pipelines by adjusting the flow rate of the ethylene glycol aqueous solution in the ethylene glycol aqueous solution pipeline.

[0102] When using the LNG high-pressure heat exchanger 6 for heating, it is only necessary to convey the substance to be heated to any one of the heating pipelines of the LNG high-pressure heat exchanger 6.

[0103] When using the LNG high-pressure heat exchanger 6 for cooling, it is only necessary to convey the substance to be cooled to any one of the cooling pipelines of the LNG high-pressure heat exchanger 6.

[0104] In this embodiment, the flow direction of the ethylene glycol aqueous solution in the ethylene glycol aqueous solution pipeline is opposite to the flow direction of the substance in the number of heating pipelines; at the same time, the flow direction of the ethylene glycol aqueous solution in the ethylene glycol aqueous solution pipeline is the same as the flow direction of the substance in the number of cooling pipelines.

[0105] Specifically, the first one-way valve 4 is used to unidirectionally convey the liquefied natural gas extracted by the submersible pump 3 to any one of the heating pipelines of the LNG high-pressure heat exchanger 6;

[0106] Any one of the heating pipelines of the LNG high-pressure heat exchanger 6 is used to heat the liquefied natural gas extracted by the submersible pump 3 to obtain gaseous natural gas at a temperature of -65°C to -55°C, and convey the gaseous natural gas at a temperature of -65°C to -55°C to the buffer tank 8.

[0107] Embodiment 4. Combine Figure 1 and Figure 2 To illustrate this embodiment, this embodiment is a further limitation on the pressure stabilization control subsystem in the marine LNG gas supply system described in Embodiment 3. The specific implementation content is as follows:

[0108] The pressure stabilization control subsystem includes a first pressure sensor 1, a second pressure sensor 14, and a pressure stabilization control device;

[0109] The first pressure sensor 1 is configured to collect the storage pressure in the storage tank 2 and send the storage pressure to the voltage stabilizing and regulating device;

[0110] The second pressure sensor 14 is configured to collect the storage pressure in the buffer tank 8 and send the storage pressure to the voltage stabilizing and regulating device;

[0111] The voltage stabilizing and regulating device is configured to adjust the first one-way valve 4 and the two-way valve 15 according to the storage pressure in the storage tank 2, so that the storage pressure in the storage tank 2 is stabilized within a set range; and is further configured to adjust the first one-way valve 4, the second one-way valve 10 and the third one-way valve 13 according to the storage pressure in the buffer tank 8, so that the storage pressure in the buffer tank 8 is stabilized within a set range.

[0112] Embodiment Five, in combination with Figure 1 and Figure 2 This embodiment will be described. This embodiment further limits the high-pressure gas supply unit in a marine LNG gas supply system described in Embodiment Three. The specific implementation content is as follows:

[0113] The high-pressure gas supply unit includes a heating device, a compressor 7 and a cooling device;

[0114] One end of the heating device is communicated with the second one-way valve 10; the other end of the heating device is communicated with one end of the compressor 7; the heating device is configured to heat the low-pressure gaseous natural gas;

[0115] The other end of the compressor 7 is communicated with one end of the cooling device; the compressor 7 is configured to pressurize the heated low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 200 to 300 bar;

[0116] The cooling device is configured to cool the gaseous natural gas with a pressure of 200 to 300 bar to obtain gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

[0117] In this embodiment, the other end of the cooling device is communicated with the high-pressure main engine 5. The high-pressure gas supply unit supplies suitable gaseous natural gas to the high-pressure main engine 5.

[0118] In this embodiment, the heating device is configured to heat the low-pressure gaseous natural gas to 20 to 30 °C.

[0119] In this embodiment, when the compressor 7 pressurizes the heated low-pressure gaseous natural gas, the temperature of the low-pressure gaseous natural gas will rise again, and finally high-temperature and high-pressure gaseous natural gas is obtained. For high-pressure gas-using equipment, they need high-pressure gaseous natural gas, but do not need high-temperature gaseous natural gas. Therefore, subsequently, the cooling device needs to be used to cool the gaseous natural gas processed by the compressor 7.

[0120] In this embodiment, the cooling device is used to cool the pressurized gaseous natural gas (i.e., high-temperature and high-pressure gaseous natural gas) to 25 to 50 °C, obtain gaseous natural gas with a pressure of 300 bar and a temperature of 25 to 50 °C, and transport it to the high-pressure main engine 5.

[0121] Furthermore, a preferred embodiment is provided. The heating device is an LNG high-pressure heat exchanger; the cooling device is an LNG high-pressure heat exchanger.

[0122] Specifically, according to the above embodiment, the LNG high-pressure heat exchanger 6 has both a heating function and a cooling function; the LNG high-pressure heat exchanger 6 includes a plurality of heating pipelines and a plurality of cooling pipelines.

[0123] From the perspective of simplifying the equipment, the LNG high-pressure heat exchanger 6 can be reused, that is

[0124] The heating device is the LNG high-pressure heat exchanger 6; the cooling device is also the LNG high-pressure heat exchanger 6. Specifically:

[0125] Any one of the heating pipelines of the LNG high-pressure heat exchanger 6 is used as the heating device.

[0126] Any one of the cooling pipelines of the LNG high-pressure heat exchanger 6 is used as the cooling device.

[0127] Embodiment Six. Combining Figure 1 and Figure 2 This embodiment is described. This embodiment further limits the low-pressure gas supply unit in a marine LNG gas supply system described in Embodiment Three. The specific implementation content is as follows:

[0128] The low-pressure gas supply unit includes a low-pressure heat exchanger 12;

[0129] One end of the low-pressure heat exchanger 12 is communicated with the third one-way valve 13; the low-pressure heat exchanger 12 is used to heat the low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C

[0130] In this embodiment, the other end of the low-pressure heat exchanger 12 is connected to the low-pressure gas-using equipment 11. The low-pressure gas supply unit supplies applicable gaseous natural gas to the low-pressure gas-using equipment 11.

[0131] In this embodiment, the low-pressure heat exchanger 12 has an ethylene glycol aqueous solution pipeline and a heating pipeline; the low-pressure heat exchanger 12 adjusts the temperature in the heating pipeline by adjusting the flow rate of the ethylene glycol aqueous solution in the ethylene glycol aqueous solution pipeline; the flow direction of the gaseous natural gas in the heating pipeline is opposite to the flow direction of the ethylene glycol aqueous solution in the ethylene glycol aqueous solution pipeline.

[0132] Embodiment Seven, in combination with Figure 1 and Figure 2 describe this embodiment. This embodiment provides a voltage stabilization control method, and the specific implementation content is as follows:

[0133] The voltage stabilization control method is implemented by using the above-mentioned marine LNG gas supply system.

[0134] The voltage stabilization control method is used to stabilize the storage pressures in the storage tank 2 and the buffer tank 8 within a set range.

[0135] The method includes:

[0136] S1. Obtain the storage pressures of the storage tank 2 and the buffer tank 8;

[0137] S2. According to the storage pressures, execute a pressure balance control step; the pressure balance control step includes:

[0138] S2.1. When the storage pressure of the storage tank 2 is lower than 7 bar, execute a storage tank pressurization sub-step; the storage tank pressurization sub-step includes:

[0139] S2.1.1. Increase the opening degree of the first one-way valve 4 and open the two-way valve 15 so that the low-pressure gaseous natural gas in the buffer tank 8 flows unidirectionally into the storage tank 2;

[0140] S2.1.2. Continue to obtain the storage pressure of the storage tank 2 until the storage pressure of the storage tank 2 reaches 8 bar, then restore the first one-way valve 4 to its original opening degree and close the two-way valve 15;

[0141] S2.2. When the storage pressure of the storage tank 2 is higher than 9 bar, execute a storage tank depressurization sub-step; the storage tank depressurization sub-step includes:

[0142] S2.2.1. Open the two-way valve 15 so that the low-pressure gaseous natural gas in the storage tank 2 flows unidirectionally into the buffer tank 8;

[0143] S2.2.2. Continue to obtain the storage pressure of the storage tank 2 until the storage pressure of the storage tank 2 reaches 8 bar, and then close the two-way valve 15;

[0144] S2.3. When the storage pressure of the buffer tank 8 is lower than 7 bar, execute the buffer tank pressurization sub-step; the buffer tank pressurization sub-step includes:

[0145] S2.3.1. Increase the opening degree of the first one-way valve 4;

[0146] S2.3.2. Continue to obtain the storage pressure of the buffer tank 8 until the storage pressure of the buffer tank 8 reaches 8 bar, and then restore the first one-way valve 4 to its original opening degree;

[0147] S2.4. When the storage pressure of the buffer tank 8 is higher than 9 bar, execute the buffer tank depressurization sub-step; the buffer tank depressurization sub-step includes:

[0148] S2.4.1. Increase the opening degrees of the second one-way valve 10 and the third one-way valve 13;

[0149] S2.4.2. Continue to obtain the storage pressure of the buffer tank 8 until the storage pressure of the buffer tank 8 reaches 8 bar, and then restore the second one-way valve 10 and the third one-way valve 13 to their original opening degrees.

[0150] The above further describes the technical solutions provided by the present invention through several specific embodiments to highlight the advantages and beneficial effects of the technical solutions provided by the present invention. However, the above several specific embodiments are not used as limitations on the present invention. Any reasonable modifications and improvements to the present invention, reasonable combinations of implementation manners, and equivalent replacements within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A marine LNG gas supply system, characterized in that, The system includes a fuel storage subsystem, a fuel gas supply subsystem, and a pressure stabilization control subsystem; The fuel storage subsystem is connected to the fuel gas supply subsystem; The fuel storage subsystem is used to store liquefied natural gas and low-pressure gaseous natural gas at storage temperatures and storage pressures within a set range; it is also used to unidirectionally supply low-pressure gaseous natural gas to the fuel gas supply subsystem; the low-pressure gaseous natural gas is gaseous natural gas at 7 to 9 bar; The fuel gas supply subsystem is used to convert the low-pressure gaseous natural gas into applicable gaseous natural gas and supply the applicable gaseous natural gas externally; The pressure stabilization control subsystem is used to collect the storage pressure of the fuel storage subsystem and to stabilize the storage pressure within the set range; The fuel gas supply subsystem includes a high-pressure gas supply unit; the high-pressure gas supply unit is connected to the fuel gas supply subsystem; For the high-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C; The fuel gas supply subsystem further includes a low-pressure gas supply unit; the low-pressure gas supply unit is connected to the fuel gas supply subsystem; For the low-pressure gas supply unit, the applicable gaseous natural gas is gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C; The fuel storage subsystem includes a storage tank (2), a buffer tank (8), a two-way valve (15), a liquid-gas exchange device, a separator (9), a second one-way valve (10), and a third one-way valve (13); The storage tank (2) stores liquefied natural gas and low-pressure gaseous natural gas at storage temperatures and storage pressures within a set range; The buffer tank (8) stores low-pressure gaseous natural gas at storage temperatures and storage pressures within a set range; The two-way valve (15) is connected in series between the storage tank (2) and the buffer tank (8); the two-way valve (15) is used to regulate the exchange of low-pressure gaseous natural gas between the storage tank (2) and the buffer tank (8); The liquid-gas exchange device is connected in series between the storage tank (2) and the buffer tank (8); the liquid-gas exchange device is used to convert the liquefied natural gas in the storage tank (2) into low-pressure gaseous natural gas in the buffer tank (8); One end of the separator (9) is connected to the buffer tank (8); The other end of the separator (9) is respectively connected to the high-pressure gas supply unit and the low-pressure gas supply unit; The second one-way valve (10) is connected in series between the separator (9) and the high-pressure gas supply unit and is used to unidirectionally supply the low-pressure gaseous natural gas in the buffer tank (8) to the high-pressure gas supply unit; The third one-way valve (13) is connected in series between the separator (9) and the low-pressure gas supply unit and is used to unidirectionally supply the low-pressure gaseous natural gas in the buffer tank (8) to the low-pressure gas supply unit; The liquid-gas exchange device includes a submersible pump (3), a first one-way valve (4), and an LNG high-pressure heat exchanger (6); The submersible pump (3) is arranged inside the storage tank (2); the submersible pump (3) is communicated with one end of the LNG high-pressure heat exchanger (6); the submersible pump (3) is used for pumping the liquefied natural gas inside the storage tank (2) and pressurizing the liquefied natural gas. The first one-way valve (4) is connected in series between the submersible pump (3) and the LNG high-pressure heat exchanger (6); the first one-way valve (4) is used for unidirectionally supplying the liquefied natural gas pumped by the submersible pump (3) to the LNG high-pressure heat exchanger (6). The other end of the LNG high-pressure heat exchanger (6) is communicated with the buffer tank (8); the LNG high-pressure heat exchanger (6) is used for heating the pressurized liquefied natural gas to obtain low-pressure gaseous natural gas and supplying the low-pressure gaseous natural gas to the buffer tank (8). The voltage stabilization control subsystem includes a first pressure sensor (1), a second pressure sensor (14) and a voltage stabilization control device. The first pressure sensor (1) is used for collecting the storage pressure inside the storage tank (2) and sending the storage pressure to the voltage stabilization control device. The second pressure sensor (14) is used for collecting the storage pressure inside the buffer tank (8) and sending the storage pressure to the voltage stabilization control device. The voltage stabilization control device is used for adjusting the first one-way valve (4) and the two-way valve (15) according to the storage pressure inside the storage tank (2) so that the storage pressure inside the storage tank (2) is stabilized within a set range; and is also used for adjusting the first one-way valve (4), the second one-way valve (10) and the third one-way valve (13) according to the storage pressure inside the buffer tank (8) so that the storage pressure inside the buffer tank (8) is stabilized within a set range.

2. The marine LNG gas supply system according to claim 1, wherein, The storage tank (2) has a cold insulation layer; the buffer tank (8) has a cold insulation layer.

3. The marine LNG gas supply system according to claim 1, characterized in that, The high-pressure gas supply unit includes a heating device, a compressor (7) and a cooling device. One end of the heating device is communicated with the second one-way valve (10); the other end of the heating device is communicated with one end of the compressor (7); the heating device is used for heating the low-pressure gaseous natural gas. The other end of the compressor (7) is communicated with one end of the cooling device; the compressor (7) is used for pressurizing the heated low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 200 to 300 bar. The cooling device is used for cooling the gaseous natural gas with a pressure of 200 to 300 bar to obtain gaseous natural gas with a pressure of 200 to 300 bar and a temperature of 25 to 50 °C.

4. A marine LNG gas supply system according to claim 3, characterized in that, The heating device is an LNG high-pressure heat exchanger; the cooling device is an LNG high-pressure heat exchanger.

5. The marine LNG gas supply system according to claim 1, characterized in that, The low-pressure gas supply unit includes a low-pressure heat exchanger (12). One end of the low-pressure heat exchanger (12) is communicated with the third one-way valve (13); the low-pressure heat exchanger (12) is used for heating the low-pressure gaseous natural gas to obtain gaseous natural gas with a pressure of 7 to 9 bar and a temperature of 25 to 50 °C.

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