System and method for efficient BOG utilization and waste heat recovery of LNG transport ship

Abstract

The invention discloses an LNG transport ship BOG efficient utilization and waste heat recovery system and method.The method includes the steps that firstly, BOG is stored and adjusted through a BOG buffer tank, the BOG is combusted through a natural gas boiler to generate high-temperature steam, then heat energy of the high-temperature steam is transmitted to a liquid organic working medium through a steam and organic working medium heat exchanger, the liquid organic working medium is gasified, and the liquid organic working medium is recycled; the gaseous organic working medium expands to do work in the turbine generator set, efficient conversion from heat energy to electric energy is achieved, then the gaseous organic working medium enters the organic working medium condenser to be condensed and returned, and cyclic utilization of the organic working medium is achieved. The GCU processing mode of a traditional LNG transport ship is replaced, waste of natural gas is reduced, the comprehensive utilization rate of BOG is increased, meanwhile, ship fossil fuel consumption is reduced, and emission of greenhouse gas is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of efficient utilization of BOG in LNG carriers, and particularly relates to a system and method for efficient utilization of BOG and waste heat recovery in an LNG carrier. Background Art

[0002] Currently, the commonly used BOG treatment technology in LNG carriers is to use the GCU unit equipped on the ship to burn the BOG that the ship cannot handle in time. This technology, on the one hand, causes waste of the cargo natural gas, and on the other hand, the combustion products increase the greenhouse gas emissions in the atmosphere.

[0003] The commonly used BOG treatment technology in LNG carriers is to use the GCU equipped on the ship to burn the BOG that the ship cannot handle in time.

[0004] The existing disadvantages at present: The existing technology, on the one hand, causes waste of the cargo natural gas, and on the other hand, the combustion products increase the greenhouse gas emissions in the atmosphere. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a system and method for efficient utilization of BOG and waste heat recovery in an LNG carrier to solve the problems existing in the above-mentioned prior art.

[0006] In a first aspect, to achieve the above object, the present invention provides a system for efficient utilization of BOG and waste heat recovery in an LNG carrier, including:

[0007] A BOG buffer tank, a natural gas boiler, a steam and organic working fluid heat exchanger, an organic working fluid turbine generator set, and an organic working fluid condenser connected in sequence;

[0008] The natural gas boiler is used for burning BOG and generating high-temperature water vapor;

[0009] The steam and organic working fluid heat exchanger is used for changing the liquid organic working fluid into a gaseous organic working fluid;

[0010] The organic working fluid turbine generator set is used for converting the thermal energy carried by the liquid organic working fluid into electric energy;

[0011] The organic working fluid condenser is used for condensing the low-pressure organic working fluid steam into a liquid state.

[0012] Optionally, it further includes a cooling water circulation pump, and the cooling water circulation pump is used for providing cooling for the organic working fluid condenser.

[0013] Optionally, it further includes an organic working fluid gas-liquid separator, which is used for separating the gaseous organic working fluid and the liquid organic working fluid by gas-liquid separation and transporting the liquid organic working fluid to the steam and organic working fluid heat exchanger.

[0014] Optionally, it further includes an organic working fluid pump for maintaining the circulation of the organic working fluid.

[0015] Optionally, it further includes a grid-connection device for connecting the power generation output to the ship's power grid.

[0016] Optionally, it further includes an organic working fluid filling device for the filling and recovery of the organic working fluid.

[0017] In a second aspect, the present invention further provides a method for the efficient utilization of BOG and waste heat recovery of an LNG carrier, which is used to implement a system for the efficient utilization of BOG and waste heat recovery of an LNG carrier. The method includes:

[0018] Outputting evaporator gas through the BOG buffer tank, burning it in a natural gas boiler to generate high-temperature steam, the high-temperature steam enters a steam-organic working fluid heat exchanger to heat the organic working fluid, generating gaseous working fluid, the gaseous working fluid does work in an organic working fluid turbine generator set to generate electric energy, and the remaining gaseous working fluid enters an organic working fluid condenser to condense into a liquid state and then returns to the steam-organic working fluid heat exchanger.

[0019] Optionally, during the process that the remaining gaseous working fluid enters the organic working fluid condenser to condense into a liquid state and then returns to the steam-organic working fluid heat exchanger, it further includes:

[0020] After condensation, the gaseous working fluid and the liquid organic working fluid are separated by a gas-liquid separation method, and the liquid organic working fluid is transported to the steam-organic working fluid heat exchanger.

[0021] In a third aspect, the present invention further provides a computer terminal device, including:

[0022] One or more processors;

[0023] A memory coupled to the processor for storing one or more programs;

[0024] When the one or more programs are executed by the one or more processors, the one or more processors implement a system for the efficient utilization of BOG and waste heat recovery of an LNG carrier.

[0025] In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, a system for the efficient utilization of BOG and waste heat recovery of an LNG carrier is implemented.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] A system and method for efficient utilization of BOG and waste heat recovery of an LNG carrier provided by the present invention first stores and regulates BOG using a BOG buffer tank, burns BOG in a natural gas boiler to generate high-temperature steam, then transfers the heat energy of the high-temperature steam to a liquid organic working medium through a steam-organic working medium heat exchanger to vaporize it. The gaseous organic working medium expands and does work in a turbine generator set to achieve efficient conversion of heat energy into electrical energy, and then enters an organic working medium condenser to condense and return to liquid, realizing the recycling of the organic working medium. The present invention replaces the GCU treatment method of traditional LNG carriers, reduces the waste of natural gas, improves the comprehensive utilization rate of BOG, reduces the consumption of ship fossil fuels, reduces greenhouse gas emissions, and meets the regulatory requirements of the International Maritime Organization for ship carbon emissions. In addition, through the recovery and utilization of heat energy, the present invention reduces the operating cost of the LNG carrier, avoids dependence on expensive imported GCU equipment, improves the independent control ability, and effectively improves the economic and environmental benefits of the LNG carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which form a part of this application, are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0029] Figure 1 It is a schematic diagram of the system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the accompanying drawings and combine with the embodiments to detail this application.

[0031] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0032] First, the technical terms involved in the following embodiments are described:

[0033] LNG: Liquefied Natural Gas;

[0034] BOG: Boil-Off Gas, evaporation gas;

[0035] GCU: Gas Combustion Unit;

[0036] Attained EEXI: Attained Energy Efficiency Index;

[0037] Attained CII: Attained Carbon Intensity Index;

[0038] At present, the BOG on LNG carriers is usually co-processed by returning it to the cargo hold through reliquefaction and burning it off with a GCU. Burning off BOG with a GCU wastes a significant amount of cargo natural gas, resulting in a large amount of energy waste. The present invention proposes using a natural gas boiler to burn BOG (BOG as boiler fuel) to generate high-temperature steam. A portion of the steam can be used for the daily use of the ship, and the remaining steam is used for preheating. An organic Rankine cycle (ORC) is adopted to heat a low-boiling organic working fluid to drive an "organic working fluid turbine generator" to generate electricity, replacing a portion of the generator's power generation. Such an arrangement solves the problem of the high cost of equipping LNG carriers with GCUs and the long-term problem of importing GCUs on the one hand; on the other hand, it solves the efficient utilization of BOG on LNG ships, saves the fossil fuels consumed by ship power generation, and simultaneously achieves the effect of reducing the attained EEXI and attained CII of the ship, improving the ship's carbon intensity rating.

[0039] The complete power generation equipment consists of a BOG buffer storage tank, a natural gas boiler (an existing equipment on the ship), a steam and organic working fluid heat exchanger, an organic working fluid turbine generator set, an organic working fluid condenser, a cooling water circulation pump, an organic working fluid pump, an organic working fluid gas-liquid separator, a power generation grid connection device, an organic working fluid filling equipment, etc.

[0040] The rollability of a ship is an inherent property during ship navigation. Therefore, during the navigation of an LNG carrier, the LNG cargo evaporation gas (BOG) will inevitably be discharged from the cargo maintenance system. The present invention proposes an efficient and innovative energy utilization efficiency improvement system, aiming to significantly improve the energy utilization efficiency by using a natural gas boiler to burn BOG to generate high-temperature steam. During this process, a portion of the generated high-temperature steam is directly allocated for the daily needs of the ship, such as heating and power supply, while the remaining steam further participates in a more efficient energy conversion process.

[0041] Embodiment 1

[0042] As Figure 1 shown, this embodiment provides a method for the efficient utilization of BOG and waste heat recovery on an LNG carrier, including:

[0043] Output evaporator gas through a BOG buffer tank, burn it in a natural gas boiler to generate high-temperature steam. The high-temperature steam enters a steam and organic working fluid heat exchanger to heat the organic working fluid, generating gaseous working fluid. The gaseous working fluid does work in an organic working fluid turbine generator set to generate electricity, and the remaining gaseous working fluid enters an organic working fluid condenser to condense into a liquid and returns to the steam and organic working fluid heat exchanger.

[0044] As an implementation method in this embodiment, when the remaining gaseous working medium enters the organic working medium condenser and condenses into a liquid state, the process of returning it to the steam and organic working medium heat exchanger further includes:

[0045] After condensation, the gaseous working medium and the liquid organic working medium are separated by gas-liquid separation, and the liquid organic working medium is transported to the steam and organic working medium heat exchanger.

[0046] Specifically, the BOG with sufficient constant pressure in the buffer storage tank is transported to the natural gas boiler for combustion to generate high-temperature steam. Part of the steam is directly used for the daily needs of the ship, and the remaining high-temperature steam transfers heat energy to the organic working medium through the steam and organic working medium heat exchanger. The heated organic working medium expands and does work in the turbine generator set, pushing the turbine to rotate, and then generating electric energy. The high-temperature gas after passing through the turbine enters the condenser and condenses into a liquid state under the action of the cooling water circulation pump. The cooled liquid organic working medium flows back to the gas / organic working medium heat exchanger through the organic working medium pump to form a closed cycle. During this cycle, the organic working medium gas-liquid separator separates the gaseous and liquid organic working media to ensure that the organic working medium in the cycle is in a pure liquid state, thereby improving the overall work efficiency. The electric energy generated by the turbine generator set is finally transported to the ship's power grid through the grid connection device to provide the required power for the ship.

[0047] Based on this, a method for efficient utilization of BOG and waste heat recovery on an LNG carrier provided by an embodiment of the present invention first stores and regulates BOG using a BOG buffer tank, burns BOG in a natural gas boiler to generate high-temperature steam, and then transfers the heat energy of the high-temperature steam to the liquid organic working medium through a steam and organic working medium heat exchanger to vaporize it. The gaseous organic working medium expands and does work in the turbine generator set to achieve efficient conversion of heat energy into electric energy, and then enters the organic working medium condenser for condensation and liquid return to realize the recycling of the organic working medium. The present invention replaces the GCU treatment method of traditional LNG carriers, reduces the waste of natural gas, improves the comprehensive utilization rate of BOG, simultaneously reduces the consumption of fossil fuels on the ship, reduces greenhouse gas emissions, and meets the regulatory requirements of the International Maritime Organization for ship carbon emissions. In addition, through the recovery and utilization of heat energy, the present invention reduces the operating cost of the LNG carrier, avoids dependence on expensive imported GCU equipment, improves the independent controllability, and thus effectively improves the economic and environmental benefits of the LNG carrier.

[0048] The present invention also has the following effects:

[0049] 1. Replaces part of the power generation by the generator, saving the fossil fuels consumed by ship power generation;

[0050] 2. Solves the problem of equipping GCU on LNG carriers at great expense and solves the problem of being dependent on imported GCU for a long time;

[0051] 3. Solved the problem of efficient utilization of BOG in LNG ships, and at the same time achieved the effect of reducing the attained EEXI and attained CII of the ships, improving the ship's carbon intensity rating.

[0052] 4. Avoided a large amount of GHG emissions generated by the traditional combustion of BOG using GCU.

[0053] Example Two

[0054] In this embodiment, a computer terminal device is provided, including:

[0055] One or more processors;

[0056] A memory, coupled to the processor, for storing one or more programs;

[0057] When the one or more programs are executed by the one or more processors, the one or more processors implement the methods in the above embodiments.

[0058] In this embodiment, a computer-readable storage medium is further provided, on which a computer program is stored. When the computer program is executed by a processor, the methods in the above embodiments are implemented.

[0059] In this embodiment, an electronic device is further provided, including a memory and a processor. A computer program is stored in the memory, and the processor is configured to run the computer program to execute the methods in the above embodiments.

[0060] The above program can run in a processor, or can also be stored in a memory (or referred to as a computer-readable medium). The computer-readable medium includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device.

[0061] These computer programs can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process or multiple processes and / or blocks. Different steps can be implemented by different modules. Figure 1 One process or multiple processes and / or blocks Figure 1 Steps for implementing the functions specified in one block or multiple blocks. Different steps can be implemented by different modules.

[0062] This embodiment provides such a device or system. The system is called a system for efficient utilization of BOG and waste heat recovery of an LNG carrier, including:

[0063] A BOG buffer tank, a natural gas boiler, a steam and organic working fluid heat exchanger, an organic working fluid turbine generator set, and an organic working fluid condenser connected in sequence;

[0064] The natural gas boiler is used to burn BOG and generate high-temperature steam;

[0065] The steam and organic working fluid heat exchanger is used to change the liquid organic working fluid into a gaseous organic working fluid;

[0066] The organic working fluid turbine generator set is used to convert the thermal energy carried by the liquid organic working fluid into electrical energy;

[0067] The organic working fluid condenser is used to condense the low-pressure organic working fluid steam into a liquid state.

[0068] As an implementation manner in this embodiment, it further includes a cooling water circulation pump, which is used to provide cooling for the organic working fluid condenser.

[0069] As an implementation manner in this embodiment, it further includes an organic working fluid gas-liquid separator, which is used to separate the gaseous organic working fluid and the liquid organic working fluid by gas-liquid separation and transport the liquid organic working fluid to the steam and organic working fluid heat exchanger.

[0070] As an implementation manner in this embodiment, it further includes an organic working fluid pump, which is used to maintain the circulation of the organic working fluid.

[0071] As an implementation manner in this embodiment, it further includes grid connection equipment, which is used to connect the power generation output to the ship's power grid.

[0072] As an implementation manner in this embodiment, it further includes an organic working fluid filling and recovery equipment, which is used for the filling and recovery of the organic working fluid.

[0073] The system or device is used to implement the functions of the methods in the above embodiments. Each module in the system or device corresponds to each step in the method. Those that have been described in the method will not be elaborated here.

[0074] Specifically, the core technology of this system lies in that the thermal energy of high-temperature water vapor is transferred to a low-boiling-point organic working fluid through a steam-organic working fluid heat exchanger. After absorbing the thermal energy, the latter is converted into a high-pressure and high-temperature gas, which drives an organic working fluid turbine generator set to generate electricity, thereby partially replacing the traditional power generation method.

[0075] This system consists of multiple components, mainly including: a BOG buffer storage tank for storing and boosting pressure, a natural gas boiler for burning BOG and generating high-temperature water vapor (usually using existing equipment on the ship), a steam-organic working fluid heat exchanger for transferring the thermal energy of water vapor to the organic working fluid, an organic working fluid turbine generator set for converting the thermal energy of the organic working fluid into electrical energy, an organic working fluid condenser for condensing the organic working fluid gas, a cooling water circulation pump for providing cooling to the condenser, an organic working fluid pump for maintaining the organic working fluid circulation, an organic working fluid gas-liquid separator for ensuring the organic working fluid circulation efficiency, and a grid connection device for connecting the power generation output to the ship's power grid. In addition, the system is also equipped with an organic working fluid filling device to ensure the continuous and stable operation of the system.

[0076] Specifically, the working process of the system is as follows: The BOG with a constant pressure and sufficient amount in the buffer storage tank is transported to the natural gas boiler for combustion to generate high-temperature water vapor. Part of the steam is directly used for the daily needs of the ship, and the remaining high-temperature water vapor transfers the thermal energy to the organic working fluid through the steam-organic working fluid heat exchanger. The heated organic working fluid expands and does work in the turbine generator set, pushing the turbine to rotate and thereby generating electrical energy. The high-temperature gas after passing through the turbine enters the condenser and condenses into a liquid under the action of the cooling water circulation pump. The cooled liquid organic working fluid returns to the gas / organic working fluid heat exchanger through the organic working fluid pump to form a closed cycle. During this cycle, the organic working fluid gas-liquid separator separates the gaseous and liquid organic working fluids to ensure that the organic working fluid in the cycle is in a pure liquid state, thereby improving the overall work efficiency. The electrical energy generated by the turbine generator set is finally transported to the ship's power grid through the grid connection device to provide the required power for the ship.

[0077] A system and method for efficient utilization of BOG and waste heat recovery of an LNG carrier provided by the present invention use the high-temperature water vapor generated by burning BOG to heat the organic working fluid and drive the turbine generator to generate electricity, while achieving efficient waste heat recovery. Compared with traditional technologies, it has the following effects:

[0078] Using a natural gas boiler to burn BOG and generate electricity through a turbine partially replaces the operation of the ship's generator, significantly reducing the consumption of fossil fuels required for ship power generation, saving energy and reducing operating costs.

[0079] By combining the efficient utilization of BOG with waste heat recovery, the traditional mode of relying on GCU combustion to treat BOG is avoided, the problem of relying on high-cost imported GCU equipment is solved, and the problem that related equipment in the existing technology is " " by foreign technologies is broken through.

[0080] The overall design of the system realizes the full utilization of BOG on LNG carriers, while reducing greenhouse gas (GHG) emissions, significantly reducing the attained EEXI and attained CII of the ship, thereby improving the ship's carbon intensity rating and contributing to the development of low-carbon shipping.

[0081] Through the waste heat recovery mechanism, resource waste is effectively reduced, the heat energy generated by combustion is converted into electric energy, providing clean energy for the ship, and avoiding the problem of a large amount of greenhouse gas emissions caused by the traditional GCU burning BOG.

[0082] Based on this, the technical solution provided by the present invention takes into account both economy and environmental protection, and provides a practical technical path for the energy efficiency improvement and carbon emission reduction goals of LNG carriers.

[0083] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A system for efficient utilization and waste heat recovery of BOG of LNG carriers, characterized in that: include: BOG buffer tank, natural gas boiler, steam and organic working fluid heat exchanger, organic working fluid turbine generator set, and organic working fluid condenser connected in sequence; The natural gas boiler is used to burn BOG and generate high-temperature steam; The steam and organic working medium heat exchanger is used to convert liquid organic working medium into gaseous organic working medium; The organic working fluid turbine generator set is used to convert the heat energy carried by the liquid organic working fluid into electrical energy; The organic working medium condenser is used to condense low-pressure organic working medium vapor into liquid.

2. The system according to claim 1, characterized in that It also includes a cooling water circulation pump, which is used to provide cooling for the organic working medium condenser.

3. The system according to claim 1, characterized in that It also includes an organic working fluid gas-liquid separator, which is used to separate the gaseous working fluid and the liquid organic working fluid by gas-liquid separation, and transport the liquid organic working fluid to the steam and organic working fluid heat exchanger.

4. The system according to claim 1, characterized in that It also includes an organic working fluid pump for maintaining the circulation of the organic working fluid.

5. The system according to claim 1, characterized in that It also includes grid-connection equipment for connecting the generated power output to the ship's power grid.

6. The system according to claim 1, characterized in that It also includes organic working fluid filling equipment, which is used for filling and recycling organic working fluid.

7. A method for efficient utilization and waste heat recovery of BOG of LNG carrier, characterized in that: The method comprises: The evaporator gas is output through the BOG buffer tank and burned in the natural gas boiler to generate high-temperature water vapor. The high-temperature water vapor enters the steam and organic working fluid heat exchanger to heat the organic working fluid to generate gaseous working fluid. The gaseous working fluid performs work in the organic working fluid turbine generator set to generate electrical energy. The remaining gaseous working fluid enters the organic working fluid condenser to condense into liquid and returns to the steam and organic working fluid heat exchanger.

8. The method according to claim 7, characterized in that The remaining gaseous working fluid enters the organic working fluid condenser and condenses into liquid, and then returns to the steam and organic working fluid heat exchanger. The process also includes: After condensation, the gaseous working fluid and the liquid organic working fluid are separated by gas-liquid separation, and the liquid organic working fluid is transported to the steam and organic working fluid heat exchanger.

9. A computer terminal device, characterized in that: include: one or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the system for efficient utilization and waste heat recovery of BOG of an LNG carrier according to any one of claims 1-6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, a system for efficient utilization and waste heat recovery of BOG of an LNG carrier as described in any one of claims 1 to 6 is implemented.

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