LNG (Liquefied Natural Gas) fuel management system for box ship

Abstract

The invention relates to an LNG fuel management system for a box ship applied to the technical field of LNG fuel systems, the LNG fuel management system comprises an LNG storage tank, a BOG storage tank, a diverter valve, a first branch pipe, a flow valve, a mixing tank and a booster pump, BOG evaporated out of the LNG storage tank is stored in a centralized mode through the BOG storage tank, the internal pressure of the LNG storage tank is effectively reduced, and when the internal pressure of the LNG storage tank is reduced, the LNG fuel management system can effectively reduce the internal pressure of the LNG storage tank. BOG in the BOG storage tank and part of vaporized LNG vaporized by the vaporizer are fed into the mixing tank for heat exchange and mixing, the vaporized LNG is cooled by utilizing the low-temperature BOG, the temperature of the obtained mixed gas is lower than that of the vaporized LNG, the follow-up low-temperature mixed gas is fed into the LNG storage tank to pressurize the LNG storage tank, and the intensity of heat exchange with the BOG in the LNG storage tank is effectively reduced; the low-temperature capacity of BOG is fully utilized, the recycling rate of BOG is effectively increased, the internal pressure of the LNG storage tank is increased, the discharging flow speed of LNG is effectively increased, and the fuel requirement of an engine is met.

Description

Technical Field

[0001] The present invention relates to an LNG fuel management system, in particular to an LNG fuel management system for tank ships applied in the technical field of LNG fuel systems. Background Art

[0002] LNG is the abbreviation of liquefied natural gas. It is a clean energy source. Its main component is methane. The gas produced after combustion is carbon dioxide, which can avoid environmental pollution. The conventional structure of the LNG fuel supply system for seagoing ships includes a fuel tank and a gas supply unit. The gas supply unit draws out the liquid medium in the fuel tank, vaporizes it, and then supplies gas to the ship's engine. LNG can alleviate the shortage of diesel and gasoline, facilitate energy diversification, and avoid the impact of diesel and gasoline shortages on corporate production.

[0003] Chinese patent CN117163269A discloses a "Fuel Management Method and Fuel Management System for LNG Carriers," which uses a fuel controller to precisely control the fuel supply path and prioritizes the use of naturally evaporated BOG as the first fuel, while forcibly evaporating BOG from the evaporator as the second fuel. This avoids the waste of naturally evaporated BOG fuel and the need for additional processing of excess BOG due to excessive BOG supply, thereby improving energy utilization. Chinese patent CN108194835A discloses a "Marine LNG Fuel Gas Supply System," in which a portion of the LNG gasified by the gasification device is transported back to the fuel tank through the booster port, pressurizing the tank body and increasing the LNG flow rate. This ensures the booster speed during fuel tank operation, facilitates the smooth operation of the gas supply system, and improves the reliability of the fuel supply to the ship's main engine.

[0004] LNG needs to be stored at -162°C, but actual storage tanks cannot be completely insulated. External heat is continuously transferred into the tanks through ambient temperature differences, mechanical energy conversion from pump operation, and disturbances during unloading. This causes some LNG to absorb heat and vaporize, forming BOG (boil-off gas). BOG is a byproduct of LNG and continues to be produced as long as LNG is present. The continued accumulation of BOG increases tank pressure and, if left untreated, can cause overpressure rupture. Currently, BOG is mostly recovered directly as fuel, resulting in relatively low BOG utilization rates. Furthermore, the temperature of BOG corresponds to the storage temperature of LNG, making direct BOG recovery prone to low-temperature damage to the fuel system. Summary of the Invention

[0005] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is that the utilization rate of BOG is relatively low, and the temperature of BOG corresponds to the storage temperature of LNG. Directly recovering BOG is likely to cause low-temperature damage to the fuel system.

[0006] To solve the above problems, the present invention provides an LNG fuel management system for a tank ship, comprising an LNG storage tank, a BOG storage tank, a gas supply system module and a management system module. The LNG storage tank is used to store LNG fuel. A pressure valve is fixedly connected to the top of the LNG storage tank, and the output end of the pressure valve is fixedly connected to the BOG storage tank.

[0007] The gas supply system module includes a vaporizer, a buffer tank, and a pressure reducer connected in sequence. A fuel pipe is fixedly connected between the input end of the vaporizer and the LNG storage tank. The output end of the vaporizer is fixedly connected to a diverter valve. One end of the diverter valve outlet is connected to the buffer tank, and the other end of the diverter valve outlet is fixedly connected to a No. 1 branch pipe. A flow valve is fixedly connected to the bottom of the BOG storage tank. The output end of the flow valve and the No. 1 branch pipe are commonly connected to a mixing tank. One end of the mixing tank is fixedly connected to a pressure pump. The output end of the pressure pump and the top of the LNG storage tank are fixedly connected to a No. 2 branch pipe.

[0008] The input end of the management system module is connected to the engine data module, the LNG storage tank data module, the BOG storage tank data module and the mixing tank data module. The LNG storage tank data module is fixedly installed with the LNG storage tank, the BOG tank data module is fixedly installed corresponding to the BOG tank, and the mixing tank data module is fixedly installed corresponding to the mixing tank. The output end of the management system is connected to the PID regulator module, and the output end of the PID regulator module is connected to the control end of the diverter valve, the flow valve and the booster pump.

[0009] In the above-mentioned container ship LNG fuel management system, the overall solution and effect can be summarized in one sentence.

[0010] As a further improvement of the present application, the engine data module is used to monitor the power status of the engine, the LNG tank data module is used to monitor the pressure data, capacity data and temperature data of the LNG tank, the BOG tank data module is used to monitor the pressure data, capacity data and temperature data of the BOG tank, and the mixing tank data module is used to monitor the pressure data, capacity data and temperature data of the mixing tank, thereby realizing the monitoring of the internal pressure data, capacity data and temperature data of the LNG tank, BOG tank and mixing tank, and transmitting the monitoring results to the management system module to provide data basis for the management system.

[0011] As a further improvement of the present application, the PID regulator module is used to send control signals to the diverter valve, flow valve and booster pump based on the LNG tank data, BOG tank data and engine data received by the management system, and automatically adjust the flow rate of the diverter valve, flow valve and booster pump.

[0012] As a further improvement of the present application, a pressure relief valve is fixedly connected to one end of the mixing tank away from the pressure pump, and the output end of the pressure relief valve is fixedly connected to a temporary storage tank. When the pressure inside the mixing tank increases, part of the mixed gas enters the temporary storage tank through the pressure relief valve, thereby effectively reducing the surge pressure caused by the intense heat exchange inside the mixing tank.

[0013] As another improvement of the present application, an inner tube is fixedly connected to the middle of the temporary storage tank, and branch pipe No. 1 is sleeved with the inner tube. Branch pipe No. 3 is fixedly connected between the top of the temporary storage tank and the buffer tank. The vaporized LNG in branch pipe No. 1 passes through the inner tube to realize heat exchange between the vaporized LNG and the low-temperature mixed gas inside the temporary storage tank, thereby achieving pre-cooling of the vaporized LNG, thereby effectively reducing the intensity of heat exchange between the vaporized LNG and BOG.

[0014] As another improved supplement to the present application, a heat transfer collar is provided between the inner tube and the No. 3 branch tube. The heat transfer collar is made of graphene aerogel material, and the inner tube is made of aluminum alloy material. The heat transfer collar is used to effectively improve the heat transfer effect between the inner tube and the No. 3 branch tube.

[0015] As another improvement supplement to the present application, the inner ring of the heat transfer ring is provided with an inner ring groove, and the outer ring of the heat transfer ring is provided with an outer ring groove, and the inner ring grooves and the outer ring grooves are arranged alternately. The heat transfer ring utilizes the inner ring grooves and the outer ring grooves to effectively improve its own deformation ability, so that the heat transfer ring can follow the thermal expansion and contraction of the inner tube.

[0016] As another improvement of the present application, both ends of the inner tube are provided with closed plug rings, which are made of nitrile rubber material. The closed plug rings are used to seal both ends of the inner tube, effectively reducing the cold leakage at both ends of the inner tube.

[0017] In summary, the present invention uses a BOG storage tank to centrally store BOG evaporated from the LNG storage tank, thereby effectively reducing the internal pressure of the LNG storage tank. When the LNG inside the LNG storage tank is rapidly consumed, the internal pressure of the LNG storage tank is reduced. The management system module controls the opening and closing states and the flow passing state of the diverter valve, the flow valve and the booster pump through the PID regulator module. The BOG in the BOG storage tank and the partially vaporized LNG after vaporization by the vaporizer are sent to the mixing tank for heat exchange and mixing. The low-temperature BOG is used to cool the vaporized LNG, and the temperature of the obtained mixed gas is lower than that of the vaporized LNG. Subsequently, the low-temperature mixed gas is sent to the LNG storage tank to pressurize the LNG tank and effectively reduce the intensity of heat exchange with the BOG inside the LNG tank. The low-temperature capacity of the BOG is fully utilized to effectively improve the recovery and utilization rate of the BOG. ​​The increase in the internal pressure of the LNG storage tank effectively increases the discharge flow rate of the LNG, thereby ensuring the fuel demand of the engine and facilitating the smooth operation of the fuel system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a left-side overall three-dimensional structural diagram of the first embodiment of the present application;

[0019] Figure 2 This is a right-side overall three-dimensional structural diagram of the first embodiment of the present application;

[0020] Figure 3 This is a three-dimensional structural diagram of the air supply system module according to the first embodiment of the present application;

[0021] Figure 4 This is a three-dimensional structural diagram of a BOG storage tank and a mixing tank according to the first embodiment of the present application;

[0022] Figure 5 This is a system diagram of the management system module of the first embodiment of this application;

[0023] Figure 6 This is a system diagram of a PID regulator module according to the first embodiment of the present application;

[0024] Figure 7 This is an enlarged view of the temporary storage tank according to the second embodiment of the present application;

[0025] Figure 8 This is a sectional perspective structural diagram of a temporary storage tank according to a second embodiment of the present application;

[0026] Figure 9 This is a three-dimensional structural diagram of the heat transfer ring according to the second embodiment of the present application.

[0027] Description of the numbers in the figure:

[0028] 1. LNG storage tank; 101. Pressure valve; 102. Vaporizer; 103. Buffer tank; 104. Pressure reducer; 105. Fuel pipe; 106. Diverter valve; 107. Branch pipe No. 1; 2. BOG storage tank; 201. Flow valve; 3. Mixing tank; 301. Booster pump; 302. Branch pipe No. 2; 303. Pressure relief valve; 304. Temporary storage tank; 305. Inner tube; 306. Branch pipe No. 3; 307. Heat transfer collar; 308. Inner ring groove; 309. Outer ring groove; 310. Sealing plug ring. DETAILED DESCRIPTION

[0029] Two implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0030] The first implementation method:

[0031] Figures 1 to 4The figure shows an LNG fuel management system for a tank ship, including an LNG storage tank 1, a BOG storage tank 2, a gas supply system module and a management system module. The LNG storage tank 1 is used to store LNG fuel. A pressure valve 101 is fixedly connected to the top of the LNG storage tank 1. The output end of the pressure valve 101 is fixedly connected to the BOG storage tank 2 (the function of the pressure valve 101 is the same as that of the economic valve in the existing LNG storage, also known as an energy-saving valve or a pressure regulating valve. Its main function is to optimize the operating pressure of the storage tank and balance the generation and reuse of BOG (boil-off gas) to reduce energy consumption and operating costs). The gas supply system module includes a vaporizer 102, a buffer tank 103, and a pressure reducer 104 connected in sequence. The input end of the vaporizer 102 is fixed to the LN A fuel pipe 105 is fixedly connected between the BOG storage tank 1 and the BOG storage tank 1. The output end of the vaporizer 102 is fixedly connected to a diverter valve 106. One end of the outlet of the diverter valve 106 is connected to the buffer tank, and the other end of the outlet of the diverter valve 106 is fixedly connected to the No. 1 branch pipe 107. A flow valve 201 is fixedly connected to the bottom of the BOG storage tank 2. The output end of the flow valve and the No. 1 branch pipe 107 are commonly connected to the mixing tank 3. In this application, the mixing tank 3 is vertically arranged corresponding to the BOG storage tank 2, so as to facilitate thermal insulation treatment for the BOG storage tank 2 and the mixing tank 3. Specifically, thermal insulation cement casting can be used. One end of the mixing tank 3 is fixedly connected to a pressure pump 301, and a No. 2 branch pipe 302 is fixedly connected between the output end of the pressure pump 301 and the top of the LNG storage tank 1;

[0032] LNG storage tank 1 stores the LNG fuel required by the container ship's engine. When the BOG evaporation in LNG storage tank 1 increases, the internal pressure of LNG storage tank 1 increases. When the internal pressure of LNG storage tank 1 reaches the threshold of pressure valve 101, pressure valve 101 automatically opens, and the BOG evaporated in LNG storage tank 1 is transferred to BOG storage tank 2, thereby effectively reducing the internal pressure of LNG tank 1. When the container ship is in a cruising state, the engine of the container ship is in a fully loaded working state, and the LNG consumption surges. At this time, the LNG in LNG storage tank 1 is consumed rapidly, causing the internal pressure of LNG tank 1 to decrease. The management system module controls the opening and closing and flow of diverter valve 106, flow valve 201 and booster pump 301 through the PID regulator module. The BOG storage tank 2 BOG enters the mixing tank 3 through the flow valve 201. After being vaporized in the vaporizer 102, part of the vaporized LNG is diverted through the diverter valve 106 and sent to the mixing tank 3 through the No. 1 branch pipe 107. The low-temperature BOG is heat-exchanged and mixed with the vaporized LNG at a temperature close to room temperature. The low-temperature BOG is used to cool the vaporized LNG, and the resulting mixed gas temperature is lower than that of the vaporized LNG. Subsequently, the low-temperature mixed gas is sent to the LNG storage tank 1 by the pressure pump 301 to pressurize the LNG storage tank 1. The temperature of the mixed gas is lower than that of traditional vaporized LNG, effectively reducing the intensity of the heat exchange reaction with the BOG inside the LNG storage tank 1, thereby effectively increasing the discharge flow rate of the LNG, ensuring the fuel demand of the engine, and facilitating the smooth operation of the fuel system.

[0033] Figure 5 and Figure 6As shown, the input end of the management system module is connected to the engine data module, the LNG storage tank data module, the BOG storage tank data module and the mixing tank data module. The LNG storage tank data module is fixedly installed with the LNG storage tank 1, the BOG tank data module is fixedly installed corresponding to the BOG storage tank 2, and the mixing tank data module is fixedly installed corresponding to the mixing tank 3. The output end of the management system is connected to the PID regulator module, and the output end of the PID regulator module is connected to the control end of the diverter valve 106, the flow valve 201 and the booster pump 301. The engine data module is used to monitor the power status of the engine, the LNG storage tank data module is used to monitor the pressure data, capacity data and temperature data of the LNG storage tank 1, and the BOG storage The tank data module is used to monitor the pressure, capacity, and temperature data of BOG tank 2, and the mixing tank data module is used to monitor the pressure, capacity, and temperature data of mixing tank 3. This module monitors the internal pressure, capacity, and temperature data of LNG tank 1, BOG tank 2, and mixing tank 3, and transmits the monitoring results to the management system module to provide data support for the management system. The PID regulator module is used to send control signals to the diverter valve 106, flow valve 201, and booster pump 301 based on the LNG tank data, BOG tank data, and engine data received by the management system, thereby automatically adjusting the flow rate through the diverter valve 106, flow valve 201, and booster pump 301.

[0034] When managing the LNG gas system, the LNG tank data module monitors the pressure, capacity, and temperature data of LNG tank 1, the BOG tank data module monitors the pressure, capacity, and temperature data of BOG tank 2, and the mixing tank data module monitors the pressure, capacity, and temperature data of mixing tank 3. The monitored data information is collected and sent to the management system module for data processing. Then, the PID regulator module sends control signals to the diverter valve 106, the flow valve 201, and the booster pump 301 to automatically adjust the opening and closing states and the flow rate of the diverter valve 106, the flow valve 201, and the booster pump 301. Specifically, when the diverter valve 106 diverts part of the vaporized LNG to be sent to the mixing tank 3 through the first branch pipe 107, the flow rate of the diverter valve 106 is controlled to control the mixing ratio of the vaporized LNG. The flow rate of the flow valve 201 is correspondingly controlled to control the mixing ratio of the BOG, thereby achieving the temperature of the mixed gas.

[0035] Second implementation method:

[0036] Compared with the first embodiment, the temporary storage tank 304 is mainly added. The specific new structure is as follows, and the remaining structures are consistent with the first embodiment.

[0037] Figure 3 、 Figure 4 and Figure 7As shown, a pressure relief valve 303 is fixedly connected to one end of the mixing tank 3 away from the pressure pump 301, and a temporary storage tank 304 is fixedly connected to the output end of the pressure relief valve 303 (the pressure relief valve 303 has a similar function to the pressure valve 101 in the first embodiment). When the pressure inside the mixing tank 3 increases, part of the mixed gas enters the temporary storage tank 304 through the pressure relief valve 303, thereby effectively reducing the surge pressure caused by the intense heat exchange inside the mixing tank 3. A No. 3 branch pipe 306 is fixedly connected between the top of the temporary storage tank 304 and the buffer tank 103. The vaporized LNG in the No. 1 branch pipe 107 passes through the inner barrel 305 to achieve heat exchange between the vaporized LNG and the low-temperature mixed gas inside the temporary storage tank 304, thereby achieving pre-cooling of the vaporized LNG, thereby effectively reducing the intensity of the heat exchange between the vaporized LNG and the BOG.

[0038] When the intense heat exchange causes a surge in pressure inside the mixing tank 3, the internal pressure of the mixing tank 3 exceeds the threshold of the pressure relief valve 303. The pressure relief valve 303 opens, and part of the mixed gas in the mixing tank 3 enters the temporary storage tank 304, thereby effectively reducing the internal pressure of the mixing tank 3. This process can be carried out when the pressure pump 301 is in the off state. That is, the mixed gas enters the temporary storage tank 304 through the pressure relief valve 303 without performing the BOG temperature increase treatment. The vaporized LNG in the No. 1 branch pipe 107 passes through the inner barrel 305 and exchanges heat with the low-temperature mixed gas in the temporary storage tank 304, thereby achieving pre-cooling of the vaporized LNG and effectively reducing the intensity of the heat exchange between the vaporized LNG and BOG. ​​Accordingly, the temperature of the mixed gas in the temporary storage tank 304 is effectively increased through the heat exchange, which facilitates the mixed gas to be collected into the buffer tank 103 through the No. 3 branch pipe 306 and then supplied to the engine of the container ship, facilitating the BOG temperature increase treatment and effectively reducing the impact of the low temperature of the BOG on the fuel system.

[0039] Figure 8 and Figure 9As shown, the middle of the temporary storage tank 304 is fixedly connected to an inner tube 305, the No. 1 branch pipe 107 is sleeved with the inner tube 305, and a heat transfer collar 307 is sleeved between the inner tube 305 and the No. 3 branch pipe 306. The heat transfer collar 307 is made of graphene aerogel material, and the inner tube 305 is made of aluminum alloy material. The heat transfer collar 307 effectively improves the heat transfer effect between the inner tube 305 and the No. 3 branch pipe 306. The inner ring of the heat transfer collar 307 is provided with an inner ring groove 308, and the outer ring of the heat transfer collar 307 is provided with an inner ring groove 308. There are outer ring grooves 309, and inner ring grooves 308 and outer ring grooves 309 are arranged alternately. The heat transfer ring 307 uses the inner ring grooves 308 and outer ring grooves 309 to effectively improve its own deformation ability, so that the heat transfer ring 307 can follow the thermal expansion and contraction of the inner tube 305. Both ends of the inner tube 305 are sleeved with closed plug rings 310. The closed plug rings 310 are made of nitrile rubber material. The closed plug rings 310 are used to seal the two ends of the inner tube 305, effectively reducing the leakage of cold air at both ends of the inner tube 305.

[0040] The heat transfer ring 307 is used to effectively improve the heat transfer effect between the inner tube 305 and the No. 3 branch pipe 306, and the heat transfer ring 307 uses the inner ring groove 308 and the outer ring groove 309 to effectively improve its own deformation ability, so that the heat transfer ring 307 can follow the thermal expansion and contraction of the inner tube 305, effectively maintaining the heat transfer effect between the inner tube 305 and the No. 3 branch pipe 306, and the closed plug ring 310 blocks the two ends of the inner tube 305, effectively reducing the cold leakage at both ends of the inner tube 305.

[0041] In view of current actual needs, the protection scope of the above-mentioned implementation mode adopted in this application is not limited to this. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. An LNG fuel management system for a tank ship, characterized by: The invention comprises an LNG storage tank (1), a BOG storage tank (2), a gas supply system module and a management system module. The LNG storage tank (1) is used to store LNG fuel. A pressure valve (101) is fixedly connected to the top of the LNG storage tank (1). The output end of the pressure valve (101) is fixedly connected to the BOG storage tank (2). The gas supply system module comprises a vaporizer (102), a buffer tank (103), and a pressure reducer (104) connected in sequence; a fuel pipe (105) is fixedly connected between the input end of the vaporizer (102) and the LNG storage tank (1); a diverter valve (106) is fixedly connected to the output end of the vaporizer (102); one end of the outlet of the diverter valve (106) is communicated with the buffer tank; the other end of the outlet of the diverter valve (106) is fixedly connected to a No. 1 branch pipe (107); a flow valve (201) is fixedly connected to the bottom of the BOG storage tank (2); the output end of the flow valve and the No. 1 branch pipe (107) are commonly connected to a mixing tank (3); one end of the mixing tank (3) is fixedly connected to a pressure pump (301); and a No. 2 branch pipe (302) is fixedly connected between the output end of the pressure pump (301) and the top of the LNG storage tank (1); One end of the mixing tank (3) away from the pressure pump (301) is fixedly connected to a pressure relief valve (303), the output end of the pressure relief valve (303) is fixedly connected to a temporary storage tank (304), the middle of the temporary storage tank (304) is fixedly connected to an inner tube (305), the No. 1 branch pipe (107) is sleeved with the inner tube (305), and a heat transfer collar (307) is sleeved between the inner tube (305) and the No. 3 branch pipe (306); The input end of the management system module is connected to an engine data module, an LNG storage tank data module, a BOG storage tank data module and a mixing tank data module; the LNG storage tank data module is fixedly installed with the LNG storage tank (1); the BOG storage tank data module is fixedly installed corresponding to the BOG storage tank (2); and the mixing tank data module is fixedly installed corresponding to the mixing tank (3); the output end of the management system is connected to a PID regulator module; and the output end of the PID regulator module is connected to the control end of the diverter valve (106), the flow valve (201) and the booster pump (301).

2. The LNG fuel management system for a tank ship according to claim 1, characterized in that: The engine data module is used to monitor the power status of the engine, the LNG storage tank data module is used to monitor the pressure data, capacity data and temperature data of the LNG storage tank (1), the BOG storage tank data module is used to monitor the pressure data, capacity data and temperature data of the BOG storage tank (2), and the mixing tank data module is used to monitor the pressure data, capacity data and temperature data of the mixing tank (3).

3. The LNG fuel management system for a tank ship according to claim 1, characterized in that: The PID regulator module is used to send control signals to the diverter valve (106), the flow valve (201) and the booster pump (301) based on the LNG storage tank data, the BOG storage tank data and the engine data received by the management system, so as to automatically adjust the flow rates of the diverter valve (106), the flow valve (201) and the booster pump (301).

4. The LNG fuel management system for a tank ship according to claim 1, characterized in that: A third branch pipe (306) is fixedly connected between the top of the temporary storage tank (304) and the buffer tank (103).

5. The LNG fuel management system for tank ships according to claim 1, characterized in that: The heat transfer collar (307) is made of graphene aerogel material, and the inner tube (305) is made of aluminum alloy material.

6. The LNG fuel management system for a tank ship according to claim 1, characterized in that: The inner ring of the heat transfer ring (307) is provided with an inner ring groove (308), and the outer ring of the heat transfer ring (307) is provided with an outer ring groove (309). The inner ring groove (308) and the outer ring groove (309) are arranged alternately.

7. The LNG fuel management system for a tank ship according to claim 1, characterized in that: Both ends of the inner tube (305) are sleeved with closed plug rings (310), and the closed plug rings (310) are made of nitrile rubber material.

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