Liquefied natural gas ship cold energy utilization system and liquefied natural gas ship

Abstract

The invention provides a liquefied natural gas carrier cold energy utilization system and a liquefied natural gas carrier. The cold energy utilization system comprises a first branch, a second branch, a first power generation unit and a combustion unit. The first branch conveys the boil-off gas to the first heat exchanger, so that the boil-off gas serves as a heat source for heat exchange and then is output, and the boil-off gas is cooled in the first heat exchanger; the second branch conveys the liquefied natural gas into the first heat exchanger for heat exchange, and then the liquefied natural gas is gasified into natural gas to be output; the first power generation unit generates power by using gas pressure; and the boil-off gas after power generation and the natural gas enter the combustion unit for combustion. The cold energy of the liquefied natural gas can be utilized, and the gasification efficiency can be improved; power generation is driven by gas pressure, and energy conservation and environmental protection are achieved; the gasification efficiency can be improved by utilizing heat energy of primary waste gas, and popularization and use are facilitated.

Description

Technical Field

[0001] This application relates to the technical field of ship design, and more particularly, to a cold energy utilization system for a liquefied natural gas ship and a liquefied natural gas ship. Background Art

[0002] In the shipbuilding industry, innovative applications are carried out in multiple aspects such as navigation optimization, ship form optimization, energy-saving equipment, and clean fuels to achieve the industry goals of green, energy-saving, and environmental protection.

[0003] Liquefied Natural Gas (LNG), the storage and transportation of LNG both require a cryogenic storage tank at about -163°C and 0.1 MPa. In the prior art, the cold energy of LNG available on LNG ships cannot be fully utilized. Therefore, there is an urgent need for a system to utilize LNG cold energy to improve the energy utilization rate of ships and achieve the industry goals of green, energy-saving, and environmental protection. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a cold energy utilization system for a liquefied natural gas ship and a liquefied natural gas ship, which can utilize the cold energy of liquefied natural gas and at the same time accelerate the gasification of liquefied natural gas.

[0005] In a first aspect, a cold energy utilization system for a liquefied natural gas ship is provided, including:

[0006] A liquid tank for storing liquefied natural gas, and a deep well pump is arranged in the liquid tank, and the deep well pump is used to output liquefied natural gas.

[0007] A first branch, one end of the first branch is connected to the top of the liquid tank, and the other end of the first branch is connected to a first heat exchanger. The first branch is used to output the evaporation gas in the liquid tank to the first heat exchanger, so that the evaporation gas is used as the heat source of the first heat exchanger for heat exchange and then output. At the same time, the evaporation gas is cooled in the first heat exchanger.

[0008] A second branch, one end of the second branch is connected to the deep well pump, and the other end of the second branch is connected to the first heat exchanger. The second branch is used to transport liquefied natural gas to the first heat exchanger for heat exchange and then gasify it into natural gas and output.

[0009] A first power generation unit, at least including a first generator and a first turbine, and the first turbine is connected to the first generator. The evaporation gas in the first branch is cooled in the first heat exchanger and then converges with the gasified natural gas in the second branch and is connected to the first turbine. The evaporation gas and natural gas drive the first turbine to rotate, and the first turbine drives the first generator to generate electricity.

[0010] The combustion unit is connected to the first turbine. The evaporated gas and natural gas after power generation enter the combustion unit for combustion.

[0011] In an implementable manner, the combustion unit includes an output end. The output end is connected to the waste gas reuse unit and is used for the primary waste gas generated by combustion. The waste gas reuse unit at least includes a third branch. A second heat exchanger is arranged on the third branch, and the third branch transports the primary waste gas into the second heat exchanger as a heat source.

[0012] The second branch extends out of the liquid tank and is divided into a first heat exchange branch and a second heat exchange branch. The first heat exchange branch and the second heat exchange branch are arranged in parallel. The first heat exchanger is arranged on the first heat exchange branch, and the second heat exchanger is arranged on the second heat exchange branch.

[0013] The liquefied natural gas in the second heat exchange branch is gasified into natural gas after heat exchange in the second heat exchanger and output to the first power generation unit.

[0014] In an implementable manner, the third branch extends out of the second heat exchanger and is connected to the second power generation unit. The second power generation unit at least includes a second turbine and a second generator. The second turbine is connected to the second generator, and the gas in the third branch drives the second turbine to rotate so that the second generator generates electricity.

[0015] In an implementable manner, the third branch extends out of the second power generation unit and is connected to the carbon capture unit. The carbon capture unit at least includes an absorption tower and a liquid carbon dioxide storage tank. The gas outlet end of the third branch is directly connected to the absorption tower.

[0016] In an implementable manner, a separation tower is arranged on the first branch between the liquid tank and the first heat exchanger. The separation tower is used to separate the liquid in the evaporated gas.

[0017] In an implementable manner, a compressor is arranged on the first branch between the separation tower and the first heat exchanger. The compressor is used to pressurize the evaporated gas to a predetermined pressure.

[0018] In an implementable manner, the first heat exchanger is arranged on the ship deck.

[0019] In an implementable manner, a buffer tank is arranged on the pipeline between the first power generation unit and the combustion unit.

[0020] According to the second aspect of the present application, there is also provided a liquefied natural gas carrier, including the liquefied natural gas ship cold energy utilization system provided in the first aspect.

[0021] Compared with the prior art, the beneficial effects of the present application are:

[0022] In the technical solution of the present application, through the settings of the first branch and the second branch, the cold energy of liquefied natural gas can be utilized to cool the compressed gas of the evaporation gas, and at the same time of utilizing the cold energy, the gasification of liquefied natural gas can be accelerated. Through the setting of the first power generation unit, power generation is driven by the pressure of the gas, which is green and environmentally friendly; at the same time, the gas can be cooled, saving the original cooling mechanism and simplifying the ship system. Through the setting of the waste gas reuse unit, the heat energy of the primary waste gas can be utilized to accelerate the gasification of liquefied natural gas, improve the gasification efficiency, and at the same time, the primary waste gas can be cooled, which is energy-saving and environmentally friendly. Through the setting of the second power generation unit, power can be generated by using waste gas, which is energy-saving and environmentally friendly. The secondary waste gas cooled by the second heat exchanger is directly connected to the absorption tower of the carbon capture unit, reducing the impact on the carbon dioxide absorbent in the absorption tower and also reducing the use of cooling water, saving energy and electricity. Brief Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of a cold energy utilization system for a liquefied natural gas ship according to an embodiment of the present invention.

[0024] Among them, the description of the reference numerals is as follows:

[0025] 1, liquid tank; 2, separation tower; 3, compressor; 4, first heat exchanger; 5, first turbine; 6, first generator; 7, buffer tank; 8, combustion unit; 9, second heat exchanger; 10, second turbine; 11, second generator; 12, carbon capture unit; 13, absorption tower; 14, liquid carbon dioxide storage tank; 15, deep well pump; LNG, liquefied natural gas; BOG, evaporation gas; NG, natural gas; HTEG, primary waste gas; LTEG, secondary waste gas. Detailed Embodiments

[0026] The following further describes in detail the specific embodiments of the present invention with reference to the drawings. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0027] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In addition, in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0030] According to the first aspect of the present application, referring to Figure 1 , first, a cold energy utilization system for a liquefied natural gas carrier is provided, including:

[0031] A liquid tank 1 for storing LNG, a deep well pump 15 is arranged in the liquid tank 1, and the deep well pump 15 is used to output LNG;

[0032] A first branch, one end of the first branch is connected to the top of the liquid tank 1, and the other end of the first branch is connected to a first heat exchanger 4. The first branch is used to output the boil-off gas (BOG) in the liquid tank 1 to the first heat exchanger 4, so that the BOG is used as the heat source of the first heat exchanger 4 for heat exchange and then output. At the same time, the BOG is cooled in the first heat exchanger 4;

[0033] A second branch, one end of the second branch is connected to the deep well pump 15, and the other end of the second branch is connected to the first heat exchanger 4. The second branch is used to transport LNG into the first heat exchanger 4 for heat exchange and then vaporize it into natural gas (NG) and then output;

[0034] A first power generation unit, at least including a first generator 6 and a first turbine 5, the first turbine 5 is drivingly connected to the first generator 6; the BOG in the first branch is cooled in the first heat exchanger 4 and then converges with the vaporized NG in the second branch and is connected to the first turbine 5. The BOG and NG drive the first turbine 5 to rotate, and the first turbine 5 drives the first generator 6 to generate electricity.

[0035] A combustion unit 8, connected to the first turbine 5, and the post-power generation BOG and NG enter the combustion unit 8 for combustion.

[0036] It should be noted that the combustion unit 8 is connected to the gas supply system or combustion equipment on the ship, etc., and at least includes a main engine, a boiler, a generator, etc.

[0037] In the prior art, the BOG generated in the liquid tank 1 during the navigation of the ship due to shaking or the influence of the surrounding temperature needs to be cooled by using water glycol or the like. Through the setting of the second branch, the cold energy of LNG can be utilized, and while utilizing the cold energy, the gasification of LNG can be accelerated. Through the setting of the first power generation unit, power is generated by driving with the pressure of the gas, and after the power is integrated, it is connected to the ship's power grid system, which is more environmentally friendly.

[0038] In an implementable manner, the combustion unit 8 includes an output end, the output end is connected to the exhaust gas recycling unit, the output end is for the primary exhaust gas generated by combustion, the exhaust gas recycling unit at least includes a third branch, and a second heat exchanger 9 is arranged on the third branch. The third branch conveys the primary exhaust gas into the second heat exchanger 9 as a heat source. The second branch extends out of the liquid tank 1 and is divided into a first heat exchange branch and a second heat exchange branch, and the first heat exchange branch and the second heat exchange branch are arranged in parallel; the first heat exchanger 4 is arranged on the first heat exchange branch, and the second heat exchanger 9 is arranged on the second heat exchange branch; the LNG in the second heat exchange branch is gasified into NG after heat exchange in the second heat exchanger 9 and output to the first power generation unit.

[0039] It should be noted that the primary exhaust gas is high-temperature exhaust gas (abbreviated as HTEG), which has the characteristics of high temperature and high pressure. Therefore, the second heat exchanger 9 improves the gasification efficiency of LNG by recycling the heat of the HTEG.

[0040] Specifically, as Figure 1 shown, after the LNG output by the deep well pump 15 is input into the second heat exchanger 9, it exchanges heat with the HTEG and is gasified into NG, and then converges with the NG in the first heat exchange branch and is jointly input into the first power generation unit for power generation. Through the setting of the exhaust gas recycling unit, the present application can recycle the HTEG, improve the gasification efficiency, and at the same time can cool the HTEG, which is energy-saving and environmentally friendly.

[0041] In an implementable manner, the third branch extends out of the second heat exchanger 9 and is connected to the second power generation unit. The second power generation unit at least includes a second turbine 10 and a second generator 11. The HTEG after heat exchange and cooling becomes secondary exhaust gas, and the secondary exhaust gas is low-temperature exhaust gas (abbreviated as LTEG). The LTEG converges in the second turbine 10, and the second turbine 10 rotates by using the gas pressure and drives the second generator 11 to generate electricity. After the power is integrated, it is connected to the ship's power grid system. Through the setting of the second power generation unit, power can be generated by using the exhaust gas, which is energy-saving and environmentally friendly.

[0042] In an implementable manner, the third branch extends out of the second power generation unit and then is connected to the carbon capture unit 12. The carbon capture unit 12 at least includes an absorption tower 13 and a liquid carbon dioxide storage tank 14. The gas outlet end of the third branch is directly connected to the absorption tower 13. In the carbon capture unit 12 of the present application, the cooling mechanism in the existing carbon capture system is omitted. The LTEG cooled by the second heat exchanger 9 is directly connected to the absorption tower 13, reducing the influence on the carbon dioxide absorbent in the absorption tower 13 and also reducing the use of cooling water, saving energy and electricity.

[0043] In an implementable manner, a separation tower 2 is arranged on the first branch between the liquid tank 1 and the first heat exchanger 4, and the separation tower 2 is used to separate the liquid in the BOG.

[0044] In an implementable manner, a compressor 3 is arranged on the first branch between the separation tower 2 and the first heat exchanger 4. The compressor 3 is used to pressurize the BOG to a predetermined pressure to meet the combustion requirements of the subsequent combustion unit 8. And by pressurizing the BOG, heat is released during the compression of the BOG to improve the heat exchange rate in the first heat exchanger 4.

[0045] In an implementable manner, the first heat exchanger 4 is an evaporator. By reasonably utilizing the BOG through the evaporator, direct emission causing energy waste and environmental pollution is avoided. The heat energy of the BOG is used to gasify the LNG, and at the same time, the BOG is processed and used as fuel continuously, improving the energy utilization rate, realizing the optimal allocation of energy, providing a continuous and stable fuel supply for the combustion unit 8, and ensuring the normal operation of the power system of the ship and other systems that require gas.

[0046] In an implementable manner, the first heat exchanger 4 is arranged on the ship deck, considering that heat such as solar energy can be utilized to improve the heat exchange efficiency of the first heat exchanger 4.

[0047] In an implementable manner, a buffer tank 7 is arranged on the pipeline between the first power generation unit and the combustion unit 8 to buffer the gas, provide a continuous and stable fuel supply for the combustion unit 8, and ensure the normal operation of the power system of the ship and other systems that require gas.

[0048] According to the second aspect of the present application, a liquefied natural gas ship is further provided, including the liquefied natural gas ship cold energy utilization system provided in the first aspect.

[0049] In summary, in the prior art, the BOG generated by the liquid tank 1 due to shaking or the influence of the surrounding temperature during the ship's navigation needs to be cooled by using water glycol or the like. Through the settings of the first branch and the second branch, the present application can utilize the cold energy of LNG to cool the compressed gas of BOG, and can accelerate the gasification of LNG while utilizing the cold energy. Through the setting of the first power generation unit, power generation is driven by the pressure of the gas, which is green and environmentally friendly. Through the setting of the waste gas reuse unit, the heat energy of HTEG can be utilized to accelerate the gasification of LNG, improve the gasification efficiency, and at the same time can cool down HTEG, which is energy-saving and environmentally friendly. Through the setting of the second power generation unit, waste gas can be utilized for power generation, which is energy-saving and environmentally friendly. The LTEG cooled by the second heat exchanger 9 is directly connected to the absorption tower 13 of the carbon capture unit 12, which reduces the influence on the carbon dioxide absorbent in the absorption tower 13 and also reduces the use of cooling water, saving energy and electricity.

[0050] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A cold energy utilization system for a liquefied natural gas ship, characterized in that: include: A liquid tank for storing liquefied natural gas, wherein a deep well pump is arranged in the liquid tank, and the deep well pump is used for outputting the liquefied natural gas; a first branch, one end of which is connected to the top of the liquid tank, and the other end of which is connected to the first heat exchanger, and the first branch is used to output the boil-off gas in the liquid tank to the first heat exchanger, so that the boil-off gas is used as a heat source of the first heat exchanger for heat exchange before being output, and at the same time, the boil-off gas is cooled in the first heat exchanger; a second branch, one end of which is connected to the deep well pump, and the other end of which is connected to the first heat exchanger, and the second branch is used to transport liquefied natural gas to the first heat exchanger for heat exchange and then gasify it into natural gas for output; The first power generation unit at least includes a first generator and a first turbine, wherein the first turbine is connected to the first generator; after the boil-off gas in the first branch is cooled in the first heat exchanger, it is combined with the gasified natural gas in the second branch and then connected to the first turbine, the boil-off gas and the natural gas drive the first turbine to rotate, and after the first turbine rotates, it drives the first generator to generate electricity; The combustion unit is connected to the first turbine, and the evaporated gas and natural gas after power generation enter the combustion unit for combustion.

2. The cold energy utilization system for liquefied natural gas ships according to claim 1, characterized in that: The combustion unit includes an output end, the output end is connected to the exhaust gas recycling unit, the output end is used to burn the primary exhaust gas generated, the exhaust gas recycling unit includes at least a third branch, a second heat exchanger is arranged on the third branch, and the third branch transports the primary exhaust gas to the second heat exchanger as a heat source; The second branch extends out of the liquid tank and is divided into a first heat exchange branch and a second heat exchange branch, the first heat exchange branch and the second heat exchange branch are arranged in parallel; the first heat exchanger is arranged on the first heat exchange branch, and the second heat exchanger is arranged on the second heat exchange branch; The liquefied natural gas in the second heat exchange branch is gasified into natural gas after heat exchange in the second heat exchanger and output to the first power generation unit.

3. The cold energy utilization system for liquefied natural gas ships according to claim 2, characterized in that: The third branch extends out of the second heat exchanger and is connected to the second power generation unit. The second power generation unit includes at least a second turbine and a second generator. The second turbine is connected to the second generator. The gas in the third branch drives the second turbine to rotate so that the second generator generates electricity.

4. The cold energy utilization system for liquefied natural gas ships according to claim 3, characterized in that: The third branch extends out of the second power generation unit and is connected to the carbon capture unit. The carbon capture unit at least includes an absorption tower and a liquid carbon dioxide storage tank. The gas outlet end of the third branch is directly connected to the absorption tower.

5. The cold energy utilization system for liquefied natural gas ships according to claim 1, characterized in that: A separation tower is arranged on the first branch between the liquid tank and the first heat exchanger, and the separation tower is used to separate the liquid from the evaporated gas.

6. The cold energy utilization system for liquefied natural gas ships according to claim 1, characterized in that: A compressor is provided on the first branch between the separation tower and the first heat exchanger, and the compressor is used to pressurize the boil-off gas to a predetermined pressure.

7. The cold energy utilization system for liquefied natural gas ships according to claim 1, characterized in that: The first heat exchanger is arranged on the deck of the ship.

8. The cold energy utilization system for liquefied natural gas ships according to claim 1, characterized in that: A buffer tank is arranged on the pipeline between the first power generation unit and the combustion unit.

9. A liquefied natural gas carrier, characterized in that: A cold energy utilization system for a liquefied natural gas ship comprising any one of claims 1 to 8.

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