Recovery device and recovery method for residual gas of LNG (Liquefied Natural Gas) tank car

Abstract

The invention discloses an LNG tank car residual gas recovery device which comprises a skid-mounted base, a shell is fixedly connected to the top of the skid-mounted base, a tank car connecting pipe is arranged on one side of the shell, a storage tank connecting pipe is arranged on the side, located on the tank car connecting pipe, of the shell, a controller is arranged on one side of the front face of the shell, and the LNG tank car residual gas recovery device further comprises a BOG recovery assembly. Wherein the sheet bar is supported through the supporting device. The invention relates to the technical field of LNG tank car residual gas recovery, BOG gas is pumped out of an LNG tank car through a BOG recovery assembly and compressed, the temperature of the BOG gas is adjusted through a temperature control assembly, the conveying pressure of the BOG gas is automatically adjusted, the gas state of the BOG residual gas is converted into liquid LNG, the liquid LNG is conveyed into an LNG storage tank, and recovery of the BOG residual gas in the LNG tank car is achieved. The recovery efficiency of the BOG residual gas is improved, resource waste and existing potential risks caused by direct emission of the residual gas are avoided, and emission of greenhouse gas and economic losses in the LNG transportation and transfer process are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG tanker residual gas recovery, and specifically to an LNG tanker residual gas recovery device and a recovery method. Background Art

[0002] In LNG filling stations, loading stations, and gasification stations, LNG tankers are usually used to transport liquefied natural gas. The process of transferring LNG from a traditional LNG tanker to a storage tank takes about three hours. The LNG tanker first unloads the liquid to the LNG storage tank, and then recovers the residual gas of about 0.55 MPa in the LNG tanker to the municipal medium pressure. After the liquid LNG in the LNG tanker is unloaded, there is still BOG with a relatively high pressure inside that cannot be unloaded. In order to ensure vehicle safety, reduce the vehicle weight to meet the user's verification of the transported volume and facilitate the next loading, the tanker driver vents the BOG after the tanker is unloaded, resulting in waste of natural gas. At the same time, there are significant safety and environmental protection hazards during the venting process.

[0003] In the prior art, the residual gas of LNG tankers is mostly directly vented or simply compressed and recovered. Direct venting will cause a large amount of natural gas to escape, resulting in waste of resources and posing a significant potential danger, exacerbating the greenhouse effect. Although simple compression recovery can reduce the waste of natural gas to a certain extent, the recovery efficiency of BOG is limited.

[0004] In view of these problems, it is particularly important to urgently need an efficient, energy-saving and safe LNG tanker residual gas recovery device. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides an LNG tanker residual gas recovery device and a recovery method, which solve the problems that the residual gas of LNG tankers is mostly directly vented or simply compressed and recovered. Direct venting will cause a large amount of natural gas to escape, resulting in waste of resources and posing a significant potential danger, exacerbating the greenhouse effect. Although simple compression recovery can reduce the waste of natural gas to a certain extent, the recovery efficiency of BOG is limited.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: An LNG truck residual gas recovery device includes a skid-mounted base. A housing is fixedly connected to the top of the skid-mounted base. A tank truck connection pipe is provided on one side of the housing. A storage tank connection pipe is provided on the side of the housing where the tank truck connection pipe is located. A controller is provided on one side of the front of the housing. The LNG truck residual gas recovery device further includes a BOG recovery assembly, a temperature control assembly, and a relief assembly, which are all arranged inside the housing. Among them, the BOG recovery assembly recovers the residual gas in the LNG truck and compresses it into liquefied natural gas and then transports it back to the LNG storage tank. The temperature control assembly adjusts the temperature during the compression of the residual gas recovery. The relief assembly provides overpressure protection during the residual gas recovery process and safely discharges the residual BOG gas in the pipeline and the recovery device to the atmosphere or the flare system.

[0007] Preferably, the BOG recovery assembly includes a BOG buffer tank arranged inside the housing and connected to the tank truck connection pipe; a first screw compressor is connected to the end of the BOG buffer tank away from the tank truck connection pipe; a first plate-fin heat exchanger is connected to the output end of the first screw compressor; a first pressure regulating valve is installed at the end of the first plate-fin heat exchanger away from the first screw compressor; a first gas-liquid separator is arranged inside the housing, and its input end is connected to the output end of the first pressure regulating valve, and the output end at the top is connected to the top of the BOG buffer tank; an LNG buffer tank is connected to the output end at the bottom on one side of the first gas-liquid separator; the input end of a second pressure regulating valve is connected to the end of the LNG buffer tank away from the first gas-liquid separator, and the output end is connected to the storage tank connection pipe. Among them, the first screw compressor compresses the residual gas in the BOG buffer tank and transports it to the first plate-fin heat exchanger, so that the residual gas is cooled and liquefied in the first plate-fin heat exchanger. After gas-liquid separation by the first gas-liquid separator, it is stored in the LNG buffer tank. After the pressure is regulated by the second pressure regulating valve, it is transported to the LNG storage tank through the storage tank connection pipe for recovery.

[0008] Preferably, the temperature control assembly includes a BOG heating component arranged inside the housing; an LNG cooling component arranged inside the housing; a sensing component arranged inside the housing. Among them, through the cooperation of the BOG heating component and the LNG cooling component, the BOG gas before compression is heated, and the BOG gas after compression is cooled. The sensing component senses the temperature and pressure of the storage tanks of the BOG gas, LNG liquid, and mixed coolant.

[0009] Preferably, the BOG heating component includes a gaseous refrigerant storage tank disposed inside the outer shell; the output end of the second screw compressor is connected to the output end of the gaseous refrigerant storage tank; the input end of the second plate fin heat exchanger away from the tanker connection pipe is connected to the output end of the second screw compressor; the third pressure regulating valve is connected to the output end of the second plate fin heat exchanger away from the second screw compressor; the input end of the second gas-liquid separator is connected to the output end of the third pressure regulating valve, and the output end at the top is connected to the input end of the gaseous refrigerant storage tank; the liquid refrigerant storage tank is connected to the output end at one side bottom of the second gas-liquid separator; wherein, by sucking the gaseous mixed refrigerant into the second screw compressor and compressing it, the compressed gas enters the second plate fin heat exchanger for liquefaction, and the heat generated by liquefying the gas is conducted to the BOG gas, and the temperature of the BOG gas is adjusted to within the suction temperature range of the first screw compressor.

[0010] Preferably, the LNG cooling component includes a throttle valve, the input end of the throttle valve is connected to the output end of the liquid refrigerant storage tank; the flow sensor is connected to the output end of the throttle valve and is connected to the input end of the first plate fin heat exchanger away from the first screw compressor; the third gas-liquid separator is connected to the output end of the first plate fin heat exchanger away from the flow sensor; wherein, by transporting the liquid refrigerant from the liquid refrigerant storage tank to the first plate fin heat exchanger, the liquid refrigerant vaporizes inside the first plate fin heat exchanger and absorbs the heat of the BOG gas in the first plate fin heat exchanger, and the temperature of the BOG gas is adjusted to within a preset range.

[0011] Preferably, the sensing component includes temperature sensors, there are multiple temperature sensors, which are respectively installed on the tops of the BOG buffer tank, LNG buffer tank, gaseous refrigerant storage tank and liquid refrigerant storage tank; there are multiple pressure sensors, which are respectively installed on the tops of the BOG buffer tank, LNG buffer tank, gaseous refrigerant storage tank and liquid refrigerant storage tank; wherein, the temperature and the pressure inside the tank of the BOG buffer tank, LNG buffer tank, gaseous refrigerant storage tank and liquid refrigerant storage tank are measured by the temperature sensors and pressure sensors, and the control system controls the working states of the BOG heating component and the LNG cooling component according to the sensing signals.

[0012] Preferably, the venting component includes a venting connection pipe, the venting connection pipe is connected to the top of the LNG buffer tank; the solenoid valve is installed on the outer wall of the venting connection pipe; wherein, through the cooperation of the LNG buffer tank, the venting connection pipe and the solenoid valve, the venting connection pipe is connected to the venting tower. During the recovery of the remaining gas of the LNG tanker, if the internal pressure of the LNG buffer tank exceeds the preset safety range, the solenoid valve automatically opens, and the overpressure BOG gas is safely discharged to the atmosphere or the flare system through the venting connection pipe, preventing the internal pressure of the recovery device from being too high, and after the recovery of the remaining gas of the LNG tanker is completed, the remaining BOG gas in the recovery device and the pipeline can be safely discharged.

[0013] Preferably, the BOG recovery assembly further includes an activated carbon filter, which is installed on the outer wall of the tank truck connecting pipe.

[0014] Preferably, a heat dissipation assembly is provided on the outer wall of the housing. The heat dissipation assembly includes a shutter, which is arranged on the outer wall of the housing; an exhaust fan is installed on the top of the housing; wherein, through the cooperation of the shutter and the exhaust fan, the air inside the housing circulates, avoiding the temperature inside the housing from being too high.

[0015] The present invention also provides an LNG tank truck residual gas recovery method, including the following steps:

[0016] S1. After the LNG in the LNG tank truck is transferred to the LNG storage tank, by controlling the valves installed on the tank truck connecting pipe and the storage tank connecting pipe, the tank truck connecting pipe is communicated with the discharge pipe at the top of the LNG tank truck, and the storage tank connecting pipe is communicated with the input pipe of the LNG storage tank;

[0017] S2. Start the first screw compressor and the second screw compressor through the controller of the residual gas recovery device. Under the action of the pressure difference, the BOG residual gas existing in the LNG tank truck is inhaled into the second plate fin heat exchanger through the tank truck connecting pipe. At the same time, the gaseous refrigerant in the gaseous refrigerant storage tank is inhaled into the second screw compressor for compression, and the high-pressure gaseous refrigerant is transported to the second plate fin heat exchanger. The control system automatically adjusts the third pressure regulating valve, so that the high-pressure gaseous refrigerant is liquefied in the second plate fin heat exchanger and conducts heat to the BOG gas, heating the BOG gas to make it reach the suction temperature range of the first screw compressor. The heated BOG gas is output from the second plate fin heat exchanger and enters the BOG buffer tank for storage;

[0018] S3. The first screw compressor inhales the BOG gas stored in the BOG buffer tank and compresses it, and transports the high-pressure BOG gas to the first plate fin heat exchanger. The mixed refrigerant output from the second plate fin heat exchanger enters the second gas-liquid separator for gas-liquid separation. The liquid refrigerant is transported to the liquid refrigerant storage tank for storage, and the gaseous refrigerant is transported to the gaseous refrigerant storage tank for secondary circulation;

[0019] S4. Automatically control the valves of each connecting pipe through the control system, so that the liquid refrigerant stored in the liquid refrigerant storage tank is transported to the first plate fin heat exchanger under the action of the pressure difference. The liquid refrigerant is converted into gaseous refrigerant inside the first plate fin heat exchanger and absorbs the heat of the high-pressure BOG gas in the first plate fin heat exchanger, cooling the high-pressure BOG gas, and adjusting the pressure of the BOG gas in the first plate fin heat exchanger through the first pressure regulating valve, so that the cooled high-pressure BOG gas is liquefied in the first plate fin heat exchanger;

[0020] S5. The vaporized mixed refrigerant is separated by the third gas-liquid separator. The gaseous refrigerant is transported to the gaseous refrigerant storage tank for recirculation, and the liquid refrigerant is re-transported to the liquid refrigerant storage tank for storage. The liquefied BOG gas is transported to the first gas-liquid separator for gas-liquid separation. The separated liquid LNG is transported to the LNG buffer tank for storage, and the separated gaseous BOG is transported to the BOG buffer tank for secondary compression;

[0021] S6. By adjusting the second pressure regulating valve installed on the storage tank connecting pipe, the output pressure of the liquid LNG is adjusted to within the input pressure range of the LNG storage tank, so that the liquid LNG in the LNG buffer tank is transported to the LNG storage tank for storage through the storage tank connecting pipe under the action of the pressure difference;

[0022] S7. After the recovery of the remaining gas in the LNG truck is completed, the connection between the storage tank connecting pipe and the LNG storage tank is closed, and the connection between the truck connecting pipe and the LNG truck output pipe is disconnected. The solenoid valve is controlled to make the remaining BOG gas in the LNG buffer tank be safely discharged to the atmosphere or the flare system through the relief connecting pipe.

[0023] Beneficial Effects

[0024] The present invention provides an LNG truck remaining gas recovery device and a recovery method. It has the following beneficial effects: Through the cooperation among the skid-mounted base, the housing, the BOG recovery component, the temperature control component, the truck connecting pipe, the storage tank connecting pipe and the controller, the BOG gas is extracted from the LNG truck by the BOG recovery component and compressed. With an advanced intelligent control system, the temperature of the BOG gas can be adjusted by the temperature control component, and the conveying pressure of the BOG gas can be automatically adjusted. The BOG remaining gas can be converted from gaseous state to liquid LNG and transported to the LNG storage tank, recovering the BOG remaining gas in the LNG truck, improving the recovery efficiency of the BOG remaining gas, and thus avoiding the resource waste and potential hazards caused by the direct discharge of the remaining gas, which helps to reduce greenhouse gas emissions and economic losses during the transportation and transfer of LNG.

[0025] Through the cooperation of the BOG heating component, the LNG cooling component and the sensing component, by circulating and transporting the mixed refrigerant between two plate-fin heat exchangers, and changing the form of the mixed refrigerant during the transportation process, so that it absorbs heat and releases heat in the first plate-fin heat exchanger and the second plate-fin heat exchanger respectively, heating the inhaled BOG gas and cooling the compressed BOG gas, keeping the temperature of the BOG gas within a preset range at different processing stages, ensuring the high efficiency and safety of the whole recovery process, which helps to improve the recovery efficiency of the BOG remaining gas. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the present invention;

[0027] Figure 2 It is a schematic structural diagram of the BOG heating component, LNG cooling component and sensing component in the present invention;

[0028] Figure 3 It is a schematic structural diagram of the BOG recovery component, BOG buffer tank and LNG buffer tank in the present invention;

[0029] Figure 4 It is a schematic external view of the present invention;

[0030] Figure 5 It is a schematic external view of the first plate-fin heat exchanger in the present invention;

[0031] Figure 6 It is a schematic external view of the second plate-fin heat exchanger in the present invention;

[0032] Figure 7 is Figure 2 a partial enlarged view of area A in

[0033] In the figure: 1, skid-mounted base; 2, outer shell; 3, BOG recovery component; 4, temperature control component; 5, relief component; 6, tanker connection pipe; 7, storage tank connection pipe; 8, controller; 9, heat dissipation component; 31, BOG buffer tank; 32, first screw compressor; 33, first plate-fin heat exchanger; 34, first pressure regulating valve; 35, first gas-liquid separator; 36, LNG buffer tank; 37, second pressure regulating valve; 38, activated carbon filter; 41, BOG heating component; 42, LNG cooling component; 43, sensing component; 411, gaseous refrigerant storage tank; 412, second screw compressor; 413, second plate-fin heat exchanger; 414, third pressure regulating valve; 415, second gas-liquid separator; 416, liquid refrigerant storage tank; 421, throttle valve; 422, flow sensor; 423, third gas-liquid separator; 431, temperature sensor; 432, pressure sensor; 51, relief connection pipe; 52, solenoid valve; 91, louver; 92, exhaust fan. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Most of the remaining gas in the LNG tanker is directly discharged or simply compressed and recovered. Direct discharge will cause a large amount of natural gas to escape, resulting in waste of resources, and there are greater potential hazards, exacerbating the greenhouse effect. Although simple compression recovery can reduce the waste of natural gas to a certain extent, the recovery efficiency of BOG is limited.

[0036] In view of this, the present invention provides an LNG tanker residual gas recovery device and a recovery method. Through the cooperation among the skid-mounted base, the outer shell, the BOG recovery component, the temperature control component, the tanker connection pipe, the storage tank connection pipe and the controller, after the transfer of liquefied natural gas between the LNG tanker and the LNG storage tank is completed, the BOG gas is extracted from the LNG tanker by the BOG recovery component and compressed. An advanced intelligent control system is adopted. During the residual gas recovery process, the temperature control component is used to adjust the temperature of the BOG gas, and the conveying pressure of the BOG gas is automatically adjusted, so that the BOG residual gas is converted from gaseous state to liquid LNG and transported to the LNG storage tank, realizing the recovery of the BOG residual gas in the LNG tanker, improving the recovery efficiency of the BOG residual gas, avoiding the waste of resources and potential hazards caused by direct discharge of the residual gas, and reducing the emission of greenhouse gases and economic losses during the LNG transportation and transfer process.

[0037] Those skilled in the art should connect the components in this case in sequence. For the specific connection and operation sequence, reference should be made to the following working principle. The detailed connection means are well-known technologies in the art. The following mainly introduces the working principle and process.

[0038] From Figures 1-7 it can be seen that an LNG tanker residual gas recovery device includes a skid-mounted base 1. The top of the skid-mounted base 1 is fixedly connected with an outer shell 2. One side of the outer shell 2 is provided with a tanker connection pipe 6. The outer shell 2 is provided with a storage tank connection pipe 7 on the side of the tanker connection pipe 6. One side of the front of the outer shell 2 is provided with a controller 8. The LNG tanker residual gas recovery device further includes a BOG recovery component 3, a temperature control component 4 and a relief component 5. The BOG recovery component 3 is arranged inside the outer shell 2; the temperature control component 4 is arranged inside the outer shell 2; the relief component 5 is arranged inside the outer shell 2; wherein, the BOG recovery component 3 recovers the residual gas in the LNG tanker and compresses it into liquid natural gas and transports it back to the LNG storage tank. The temperature control component 4 adjusts the temperature during the compression of the residual gas recovery, and the relief component 5 performs overpressure protection during the residual gas recovery process, safely discharging the residual BOG gas in the pipeline and the recovery device to the atmosphere or the flare system;

[0039] In the specific implementation process, it is particularly worth noting that through the cooperation between the skid-mounted base 1 and the outer shell 2, the overall framework and shell of the LNG truck residual gas recovery device are formed, making the device easy to install and improving the flexibility of use. Through the cooperation between the truck connection pipe 6 and the storage tank connection pipe 7, the truck connection pipe 6 and the storage tank connection pipe 7 are connected to the pipelines of the LNG truck and the LNG storage tank for BOG residual gas recovery and the transportation of liquid natural gas. The controller 8 can intelligently control each electrical component in the LNG truck residual gas recovery device to ensure the efficiency and safety of the recovery process. The BOG recovery component 3, as the core part of the device, recovers the residual gas in the LNG truck and compresses it into liquid natural gas and transports it back to the LNG storage tank. The temperature control component 4 adjusts the temperature of the BOG gas so that the temperature of the BOG gas is adjusted to the preset temperature range during the recovery and compression of the residual gas. The relief component 5 conducts overpressure protection during the residual gas recovery process and safely discharges the residual BOG gas in the pipeline and the recovery device to the atmosphere or the flare system. Through the cooperation between the skid-mounted base 1, the outer shell 2, the BOG recovery component 3, the temperature control component 4, the truck connection pipe 6, the storage tank connection pipe 7 and the controller 8, after the transfer of liquefied natural gas between the LNG truck and the LNG storage tank is completed, the BOG gas is extracted from the LNG truck by the BOG recovery component 3 and compressed. An advanced intelligent control system is adopted. During the residual gas recovery process, the temperature control component 4 is used to adjust the temperature of the BOG gas and automatically adjust the transportation pressure of the BOG gas, so that the BOG residual gas is converted from a gaseous state to liquid LNG and transported to the LNG storage tank, realizing the recovery of the BOG residual gas in the LNG truck, improving the recovery efficiency of the BOG residual gas, avoiding resource waste and potential risks caused by direct emission of the residual gas, reducing greenhouse gas emissions and economic losses during the LNG transportation and transfer process. Among them, the specific model of the controller 8 is not limited, as long as it meets the use requirements;

[0040] Further, the BOG recovery assembly 3 includes a BOG buffer tank 31, a first screw compressor 32, a first plate-fin heat exchanger 33, a first pressure regulating valve 34, a first gas-liquid separator 35, an LNG buffer tank 36, and a second pressure regulating valve 37. The BOG buffer tank 31 is disposed inside the outer shell 2 and is connected to the tanker connection pipe 6. The first screw compressor 32 is connected to one end of the BOG buffer tank 31 away from the tanker connection pipe 6. The first plate-fin heat exchanger 33 is connected to the output end of the first screw compressor 32. The first pressure regulating valve 34 is installed at one end of the first plate-fin heat exchanger 33 away from the first screw compressor 32. The first gas-liquid separator 35 is disposed inside the outer shell 2, and its input end is connected to the output end of the first pressure regulating valve 34, and the output end at the top is connected to the top of the BOG buffer tank 31. The LNG buffer tank 36 is connected to the output end at the bottom on one side of the first gas-liquid separator 35. The input end of the second pressure regulating valve 37 is connected to one end of the LNG buffer tank 36 away from the first gas-liquid separator 35, and the output end is connected to the storage tank connection pipe 7. Among them, the remaining gas in the BOG buffer tank 31 is compressed by the first screw compressor 32 and then transported to the first plate-fin heat exchanger 33, so that the remaining gas is cooled and liquefied in the first plate-fin heat exchanger 33. After gas-liquid separation by the first gas-liquid separator 35, it is stored in the LNG buffer tank 36. After the pressure is regulated by the second pressure regulating valve 37, it is transported to the LNG storage tank through the storage tank connection pipe 7 for recovery;

[0041] In the specific implementation process, it is particularly worth noting that through the cooperation among the tank truck connecting pipe 6, the BOG buffer tank 31, the first screw compressor 32, the first plate fin heat exchanger 33 and the first pressure regulating valve 34, the remaining gas in the LNG tank truck is introduced into the BOG buffer tank 31 under the action of the pressure difference. The first screw compressor 32 is used to compress the remaining gas in the BOG buffer tank 31 to increase the gas pressure. The compressed gas enters the first plate fin heat exchanger 33, and the first pressure regulating valve 34 is used to adjust the pressure of the compressed gas so that it is cooled and liquefied in the first plate fin heat exchanger 33, realizing the extraction of the remaining gas in the LNG tank truck and converting the BOG gas into liquid LNG. Through the cooperation among the first plate fin heat exchanger 33, the first gas-liquid separator 35 and the LNG buffer tank 36, after the BOG gas is output from the first plate fin heat exchanger 33, it is subjected to gas-liquid separation through the first gas-liquid separator 35, and the liquid natural gas is introduced into the LNG buffer tank 36. The separated gaseous natural gas is re-introduced into the BOG buffer tank 31 for secondary compression until the gaseous natural gas is completely liquefied. Through the cooperation among the storage tank connecting pipe 7, the LNG buffer tank 36 and the second pressure regulating valve 37, the output pressure of the liquid LNG is adjusted to within the input pressure range of the LNG storage tank through the second pressure regulating valve 37, so that the liquid LNG in the LNG buffer tank 36 is transported to the LNG storage tank for recovery and storage under the action of the pressure difference. Among them, the specific models of the first screw compressor 32 and the first pressure regulating valve 34 are not limited, as long as they meet the usage requirements;

[0042] Further, the temperature control component 4 includes a BOG heating component 41, an LNG cooling component 42 and a sensing component 43. The BOG heating component 41 is arranged inside the housing 2; the LNG cooling component 42 is arranged inside the housing 2; the sensing component 43 is arranged inside the housing 2; among them, through the cooperation of the BOG heating component 41 and the LNG cooling component 42, the BOG gas before compression is heated, and the BOG gas after compression is cooled. The sensing component 43 senses the temperature and pressure of the BOG gas, the LNG liquid and the storage tank of the mixed coolant;

[0043] In the specific implementation process, it is particularly worth noting that through the cooperation among the BOG heating component 41, the LNG cooling component 42, and the sensing component 43, the BOG heating component 41 heats the relatively low-temperature BOG gas to bring it within the suction temperature range of the first screw compressor 32, and the LNG cooling component 42 cools the BOG gas after compression to bring it within the temperature range required for liquefaction, thereby improving the liquefaction efficiency of the BOG gas. The sensing component 43 senses the temperature and pressure of the storage tanks for the BOG gas, LNG liquid, and mixed coolant, and controls the working states of the BOG heating component 41 and the LNG cooling component 42 according to the sensing results to ensure that the temperatures of the BOG gas recovery, LNG liquid output, and mixed coolant circulation are within the preset range;

[0044] Further, the BOG heating component 41 includes a gaseous refrigerant storage tank 411, a second screw compressor 412, a second plate fin heat exchanger 413, a third pressure regulating valve 414, a second gas-liquid separator 415, and a liquid refrigerant storage tank 416. The gaseous refrigerant storage tank 411 is arranged inside the housing 2; the output end of the second screw compressor 412 is communicated with the output end of the gaseous refrigerant storage tank 411; the input end of the second plate fin heat exchanger 413 far from the tanker connection pipe 6 is communicated with the output end of the second screw compressor 412; the third pressure regulating valve 414 is communicated with the output end of the second plate fin heat exchanger 413 far from the output end of the second screw compressor 412; the input end of the second gas-liquid separator 415 is communicated with the output end of the third pressure regulating valve 414, and the output end at the top is communicated with the input end of the gaseous refrigerant storage tank 411; the liquid refrigerant storage tank 416 is communicated with the output end at one side bottom of the second gas-liquid separator 415. Among them, the gaseous mixed refrigerant in the gaseous refrigerant storage tank 411 is sucked into the second screw compressor 412 and compressed, and then enters the second plate fin heat exchanger 413 for liquefaction. The heat generated by the gas liquefaction is conducted to the BOG gas to adjust the temperature of the BOG gas within the suction temperature range of the first screw compressor 32;

[0045] In the specific implementation process, it is particularly worth noting that through the cooperation among the gaseous refrigerant storage tank 411, the second screw compressor 412, the second plate-fin heat exchanger 413, the third pressure regulating valve 414, the second gas-liquid separator 415 and the liquid refrigerant storage tank 416, the gaseous mixed refrigerant in the gaseous refrigerant storage tank 411 is sucked into the second screw compressor 412 and compressed. The compressed gas enters the second plate-fin heat exchanger 413, and the pressure of the compressed gas is regulated by the third pressure regulating valve 414 so that it is liquefied in the second plate-fin heat exchanger 413. The heat generated by the gas liquefaction is conducted to the BOG gas conveyed in another channel of the second plate-fin heat exchanger 413, thereby adjusting the temperature of the BOG gas to within the suction temperature range of the first screw compressor 32. Through the cooperation among the gaseous refrigerant storage tank 411, the second plate-fin heat exchanger 413, the second gas-liquid separator 415 and the liquid refrigerant storage tank 416, the liquefied mixed refrigerant is subjected to gas-liquid separation through the second gas-liquid separator 415. The separated liquid mixed refrigerant is conveyed to the liquid refrigerant storage tank 416, and the separated gaseous mixed refrigerant is re-conveyed to the gaseous refrigerant storage tank 411 for secondary circulation. Among them, the specific models of the second screw compressor 412 and the third pressure regulating valve 414 are not limited, as long as they meet the usage requirements;

[0046] Further, the LNG cooling assembly 42 includes a throttle valve 421, a flow sensor 422 and a third gas-liquid separator 423. The input end of the throttle valve 421 is connected to the output end of the liquid refrigerant storage tank 416; the flow sensor 422 is connected to the output end of the throttle valve 421 and is connected to the input end of the first plate-fin heat exchanger 33 far from the first screw compressor 32; the third gas-liquid separator 423 is connected to the output end of the first plate-fin heat exchanger 33 far from the flow sensor 422. Among them, by conveying the liquid refrigerant from the liquid refrigerant storage tank 416 to the first plate-fin heat exchanger 33, the liquid refrigerant is vaporized inside the first plate-fin heat exchanger 33 and absorbs the heat of the BOG gas in the first plate-fin heat exchanger 33, thereby adjusting the temperature of the BOG gas to within the preset range;

[0047] In the specific implementation process, it is particularly worth noting that through the cooperation among the first plate-fin heat exchanger 33, the liquid refrigerant storage tank 416, the throttle valve 421 and the flow sensor 422, the liquid refrigerant is transported from the liquid refrigerant storage tank 416 to the first plate-fin heat exchanger 33 under the action of the pressure difference, and the flow rate of the liquid refrigerant transported to the first plate-fin heat exchanger 33 is regulated and controlled, so that the liquid refrigerant is vaporized inside the first plate-fin heat exchanger 33 and absorbs the heat of the BOG gas in another channel of the first plate-fin heat exchanger 33, realizing the cooling of the BOG gas to make it reach the temperature range required for liquefaction, thereby improving the liquefaction efficiency of the BOG gas. Through the cooperation among the first plate-fin heat exchanger 33, the gaseous refrigerant storage tank 411, the liquid refrigerant storage tank 416 and the third gas-liquid separator 423, the third gas-liquid separator 423 separates the vaporized mixed refrigerant into gas and liquid. The separated liquid mixed refrigerant is re-transported to the liquid refrigerant storage tank 416, and the separated gaseous mixed refrigerant is transported to the gaseous refrigerant storage tank 411 for recycling. Among them, the specific models of the throttle valve 421 and the flow sensor 422 are not limited, as long as they meet the usage requirements;

[0048] Further, the sensing component 43 includes a temperature sensor 431 and a pressure sensor 432. There are multiple temperature sensors 431, which are respectively installed on the tops of the BOG buffer tank 31, the LNG buffer tank 36, the gaseous refrigerant storage tank 411 and the liquid refrigerant storage tank 416; there are multiple pressure sensors 432, which are respectively installed on the tops of the BOG buffer tank 31, the LNG buffer tank 36, the gaseous refrigerant storage tank 411 and the liquid refrigerant storage tank 416; among them, the temperature and the pressure inside the tanks of the BOG buffer tank 31, the LNG buffer tank 36, the gaseous refrigerant storage tank 411 and the liquid refrigerant storage tank 416 are measured through the temperature sensor 431 and the pressure sensor 432, and the control system controls the working states of the BOG heating component 41 and the LNG cooling component 42 according to the sensing signals;

[0049] In the specific implementation process, it is particularly worth noting that through the cooperation between the temperature sensor 431 and the pressure sensor 432, the temperature and the pressure of each storage tank in the recovery device are measured, and the sensing signals are transmitted to the control system, which is convenient for the control system to control the working states of the BOG heating component 41 and the LNG cooling component 42 according to the sensing signals, ensuring that the temperatures of the BOG gas recovery, the LNG liquid output and the mixed refrigerant circulation are within the preset range, and ensuring that the temperature and the pressure during the whole recovery process are within a safe and efficient range. Among them, the specific models of the temperature sensor 431 and the pressure sensor 432 are not limited, as long as they meet the usage requirements;

[0050] Further, the venting assembly 5 includes a venting connecting pipe 51 and a solenoid valve 52. The venting connecting pipe 51 communicates with the top of the LNG buffer tank 36; the solenoid valve 52 is installed on the outer wall of the venting connecting pipe 51. Among them, through the cooperation of the LNG buffer tank 36, the venting connecting pipe 51 and the solenoid valve 52, the venting connecting pipe 51 is connected to the venting tower. During the process of recovering the remaining gas of the LNG tank truck, if the internal pressure of the LNG buffer tank 36 exceeds the preset safety range, the solenoid valve 52 automatically opens, and the overpressure BOG gas is safely discharged to the atmosphere or the flare system through the venting connecting pipe 51, preventing the internal pressure of the recovery device from being too large. And after the recovery of the remaining gas of the LNG tank truck is completed, the remaining BOG gas in the recovery device and the pipeline can be safely discharged;

[0051] In the specific implementation process, it is particularly worth noting that through the cooperation among the LNG buffer tank 36, the venting connecting pipe 51 and the solenoid valve 52, when the internal pressure of the LNG buffer tank 36 exceeds the preset safety range, the solenoid valve 52 automatically opens, and the overpressure BOG gas is safely discharged to the atmosphere or the flare system through the venting connecting pipe 51, preventing the internal pressure of the recovery device from being too large. And after the recovery of the remaining gas of the LNG tank truck is completed, the remaining BOG gas in the recovery device and the pipeline is safely discharged, improving the safety of the remaining gas recovery. Among them, the specific model of the solenoid valve 52 is not limited, as long as it meets the use requirements;

[0052] Further, the BOG recovery assembly 3 further includes an activated carbon filter 38, and the activated carbon filter 38 is installed on the outer wall of the tank truck connecting pipe 6;

[0053] In the specific implementation process, it is particularly worth noting that the activated carbon filter 38 is used to filter the recovered BOG gas, avoiding dust or impurities from entering the pipeline of the remaining gas recovery device and affecting the normal operation of the equipment, effectively improving the purity of the recovered BOG gas, and ensuring the smooth progress of the subsequent liquefaction and storage processes;

[0054] It can be understood that a double-tower adsorption device can also be added to the input end of the tank truck connecting pipe 6, and the activated carbon filtration + double-tower adsorption system can be used to deeply purify the BOG gas to ensure that the BOG gas is continuously and stably purified;

[0055] Further, a heat dissipation assembly 9 is provided on the outer wall of the housing 2. The heat dissipation assembly 9 includes a louver 91 and an exhaust fan 92. The louver 91 is provided on the outer wall of the housing 2; the exhaust fan 92 is installed on the top of the housing 2. Among them, through the cooperation of the louver 91 and the exhaust fan 92, the internal air of the housing 2 circulates, avoiding the temperature inside the housing 2 from being too high;

[0056] In the specific implementation process, it is particularly worth noting that through the cooperation between the outer shell 2, the shutter 91 and the exhaust fan 92, when the recycling device operates for a long time, the internal components may generate heat during operation, resulting in a temperature rise. According to the set temperature threshold, after reaching a certain temperature, the exhaust fan 92 automatically starts, discharges the high-temperature air inside the outer shell 2 through the shutter 91, and at the same time inhales the low-temperature air from the outside, forming air convection to achieve the effect of cooling, ensuring that the recycling device can operate stably within an appropriate temperature range and extending the service life of the equipment. Among them, the specific model of the exhaust fan 92 is not limited, as long as it meets the use requirements.

[0057] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An LNG truck residual gas recovery device, including a skid-mounted base (1), characterized in that: The top of the skid-mounted base (1) is fixedly connected with a housing (2). One side of the housing (2) is provided with a tanker connection pipe (6). The housing (2) is provided with a storage tank connection pipe (7) on one side of the tanker connection pipe (6). One side of the front of the housing (2) is provided with a controller (8). The LNG tanker residual gas recovery device further includes: A BOG recovery assembly (3), arranged inside the housing (2); A temperature control assembly (4), arranged inside the housing (2); A relief assembly (5), arranged inside the housing (2); Wherein, the BOG recovery assembly (3) recovers the residual gas in the LNG tanker and compresses it into liquefied natural gas and then re-transports it to the LNG storage tank. The temperature control assembly (4) adjusts the temperature during the compression of the residual gas recovery. The relief assembly (5) conducts overpressure protection during the residual gas recovery process and safely discharges the residual BOG gas in the pipeline and the recovery device to the atmosphere or the flare system.

2. The LNG tanker residual gas recovery device according to claim 1, wherein: The BOG recovery assembly (3) includes: A BOG buffer tank (31), arranged inside the housing (2) and connected to the tanker connection pipe (6); A first screw compressor (32), connected to one end of the BOG buffer tank (31) away from the tanker connection pipe (6); A first plate-fin heat exchanger (33), connected to the output end of the first screw compressor (32); A first pressure regulating valve (34), installed at one end of the first plate-fin heat exchanger (33) away from the first screw compressor (32); A first gas-liquid separator (35), arranged inside the housing (2), with its input end connected to the output end of the first pressure regulating valve (34), and the output end at the top connected to the top of the BOG buffer tank (31); An LNG buffer tank (36), connected to the output end at the bottom on one side of the first gas-liquid separator (35); A second pressure regulating valve (37), with its input end connected to one end of the LNG buffer tank (36) away from the first gas-liquid separator (35), and the output end connected to the storage tank connection pipe (7); Wherein, the first screw compressor (32) compresses the residual gas in the BOG buffer tank (31) and transports it to the first plate-fin heat exchanger (33), so that the residual gas is cooled and liquefied in the first plate-fin heat exchanger (33). After gas-liquid separation by the first gas-liquid separator (35), it is stored in the LNG buffer tank (36). After the pressure is regulated by the second pressure regulating valve (37), it is transported to the LNG storage tank through the storage tank connection pipe (7) for recovery.

3. The LNG tanker residual gas recovery device according to claim 2, wherein: The temperature control assembly (4) includes: A BOG heating-up assembly (41), arranged inside the housing (2); An LNG cooling-down assembly (42), arranged inside the housing (2); A sensing assembly (43), arranged inside the housing (2); Among them, through the cooperation of the BOG heating component (41) and the LNG cooling component (42), the BOG gas before compression is heated, and the BOG gas after compression is cooled. The sensing component (43) senses the temperature and pressure of the storage tanks of the BOG gas, LNG liquid, and mixed coolant.

4. The LNG tanker residual gas recovery device according to claim 3, wherein: The BOG heating component (41) includes: A gaseous refrigerant storage tank (411) disposed inside the outer shell (2); A second screw compressor (412) whose output end is connected to the output end of the gaseous refrigerant storage tank (411); A second plate fin heat exchanger (413) whose input end far from the tanker connection pipe (6) is connected to the output end of the second screw compressor (412); A third pressure regulating valve (414) connected to the output end of the second plate fin heat exchanger (413) far from the second screw compressor (412); A second gas-liquid separator (415) whose input end is connected to the output end of the third pressure regulating valve (414), and the output end at the top is connected to the input end of the gaseous refrigerant storage tank (411); A liquid refrigerant storage tank (416) connected to the output end at the bottom on one side of the second gas-liquid separator (415); Among them, by sucking the gaseous mixed refrigerant in the gaseous refrigerant storage tank (411) into the second screw compressor (412) for compression, making it enter the second plate fin heat exchanger (413) for liquefaction, conducting the heat generated by gas liquefaction to the BOG gas, and adjusting the temperature of the BOG gas within the suction temperature range of the first screw compressor (32).

5. The LNG truck residual gas recovery device according to claim 4, wherein: The LNG cooling component (42) includes: A throttle valve (421) whose input end is connected to the output end of the liquid refrigerant storage tank (416); A flow sensor (422) connected to the output end of the throttle valve (421) and also connected to the input end of the first plate fin heat exchanger (33) far from the first screw compressor (32); A third gas-liquid separator (423) connected to the output end of the first plate fin heat exchanger (33) far from the flow sensor (422); Among them, by transporting the liquid refrigerant from the liquid refrigerant storage tank (416) to the first plate fin heat exchanger (33), the liquid refrigerant vaporizes inside the first plate fin heat exchanger (33) and absorbs the heat of the BOG gas in the first plate fin heat exchanger (33), and adjusts the temperature of the BOG gas to a preset range.

6. The LNG tanker residual gas recovery device according to claim 5, characterized in that: The sensing component (43) includes: Multiple temperature sensors (431) respectively installed on the tops of the BOG buffer tank (31), LNG buffer tank (36), gaseous refrigerant storage tank (411), and liquid refrigerant storage tank (416); Multiple pressure sensors (432) respectively installed on the tops of the BOG buffer tank (31), LNG buffer tank (36), gaseous refrigerant storage tank (411), and liquid refrigerant storage tank (416); Among them, the temperature and the pressure inside the tanks of the BOG buffer tank (31), the LNG buffer tank (36), the gaseous refrigerant storage tank (411), and the liquid refrigerant storage tank (416) are measured by the temperature sensor (431) and the pressure sensor (432), and the control system controls the working states of the BOG heating assembly (41) and the LNG cooling assembly (42) according to the sensed signals.

7. An LNG tanker residual gas recovery device according to claim 6, characterized in that: The relief assembly (5) includes: A relief connecting pipe (51) communicating with the top of the LNG buffer tank (36); A solenoid valve (52) installed on the outer wall of the relief connecting pipe (51); Among them, through the cooperation of the LNG buffer tank (36), the relief connecting pipe (51), and the solenoid valve (52), the relief connecting pipe (51) is connected to the relief tower. During the process of recovering the remaining gas of the LNG tanker, if the internal pressure of the LNG buffer tank (36) exceeds the preset safety range, the solenoid valve (52) automatically opens, and the overpressure BOG gas is safely discharged to the atmosphere or the flare system through the relief connecting pipe (51), preventing the internal pressure of the recovery device from being too high. And after the recovery of the remaining gas of the LNG tanker is completed, the remaining BOG gas in the recovery device and the pipeline can be safely discharged.

8. The LNG tanker residual gas recovery device according to claim 7, characterized in that: The BOG recovery assembly (3) further includes: An activated carbon filter (38) installed on the outer wall of the tanker connecting pipe (6).

9. The LNG truck residual gas recovery device according to claim 8, wherein: A heat dissipation assembly (9) is provided on the outer wall of the housing (2), and the heat dissipation assembly (9) includes: A shutter (91) provided on the outer wall of the housing (2); An exhaust fan (92) installed on the top of the housing (2); Among them, through the cooperation of the shutter (91) and the exhaust fan (92), the internal air of the housing (2) circulates, avoiding the temperature inside the housing (2) from being too high.

10. A method for recovering the remaining gas in an LNG tanker, characterized in that: Including the following steps: S1. After the LNG tanker transfers the liquefied natural gas to the LNG storage tank, by controlling the valves installed on the tanker connecting pipe (6) and the storage tank connecting pipe (7), the tanker connecting pipe (6) is communicated with the discharge pipe at the top of the LNG tanker, and the storage tank connecting pipe (7) is communicated with the input pipe of the LNG storage tank; S2. The controller (8) of the residual gas recovery device starts the first screw compressor (32) and the second screw compressor (412). Under the action of the pressure difference, the BOG residual gas existing in the LNG tanker is sucked into the second plate fin heat exchanger (413) through the tanker connecting pipe (6). At the same time, the gaseous refrigerant in the gaseous refrigerant storage tank (411) is sucked into the second screw compressor (412) for compression, and the high-pressure gaseous refrigerant is transported to the second plate fin heat exchanger (413). The control system automatically adjusts the third pressure regulating valve (414) to liquefy the high-pressure gaseous refrigerant in the second plate fin heat exchanger (413) and conduct heat to the BOG gas to heat the BOG gas so that it reaches within the suction temperature range of the first screw compressor (32). The heated BOG gas is output from the second plate fin heat exchanger (413) and then stored in the BOG buffer tank (31). S3. The first screw compressor (32) sucks in the BOG gas stored in the BOG buffer tank (31), compresses it, and transports the high-pressure BOG gas to the first plate-fin heat exchanger (33). The mixed refrigerant output from the second plate-fin heat exchanger (413) enters the second gas-liquid separator (415) for gas-liquid separation. The liquid refrigerant is transported to the liquid refrigerant storage tank (416) for storage, and the gaseous refrigerant is transported to the gaseous refrigerant storage tank (411) for secondary circulation. S4. The control system automatically controls the valves of each connecting pipe, so that the liquid refrigerant stored in the liquid refrigerant storage tank (416) is transported to the first plate-fin heat exchanger (33) under the action of the pressure difference. The liquid refrigerant is converted into gaseous refrigerant inside the first plate-fin heat exchanger (33), absorbs the heat of the high-pressure BOG gas in the first plate-fin heat exchanger (33), cools the high-pressure BOG gas, and adjusts the pressure of the BOG gas in the first plate-fin heat exchanger (33) through the first pressure regulating valve (34), so that the cooled high-pressure BOG gas is liquefied in the first plate-fin heat exchanger (33). S5. The vaporized mixed refrigerant is separated by the third gas-liquid separator (423). The gaseous refrigerant is transported to the gaseous refrigerant storage tank (411) for recirculation, and the liquid refrigerant is transported back to the liquid refrigerant storage tank (416) for storage. The liquefied BOG gas is transported to the first gas-liquid separator (35) for gas-liquid separation. The separated liquid LNG is transported to the LNG buffer tank (36) for storage, and the separated gaseous BOG is transported to the BOG buffer tank (31) for secondary compression. S6. By adjusting the second pressure regulating valve (37) installed on the storage tank connecting pipe (7), the output pressure of the liquid LNG is adjusted to within the input pressure range of the LNG storage tank, so that the liquid LNG in the LNG buffer tank (36) is transported to the LNG storage tank for storage under the action of the pressure difference through the storage tank connecting pipe (7). S7. After the recovery of the remaining gas in the LNG truck is completed, the connection between the storage tank connecting pipe (7) and the LNG storage tank is closed, and the connection between the truck connecting pipe (6) and the LNG truck output pipe is disconnected. The solenoid valve (52) is controlled so that the remaining BOG gas in the LNG buffer tank (36) is safely discharged to the atmosphere or the flare system through the relief connecting pipe (51).

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