Tail gas recovery method and system of LNG fuel cabin and application of tail gas recovery method and system

Abstract

The invention discloses a tail gas recovery method and system for an LNG fuel cabin and application of the tail gas recovery system. The tail gas recovery method comprises the following steps that (1) to-be-recovered gas is input into the miscellaneous gas input pipe, and the to-be-recovered gas of the miscellaneous gas input pipe passes through the nitrogen residual cold recovery device and then is output to the condenser; (2) the liquid nitrogen supply device conveys liquid nitrogen to the nitrogen supply pipe, and / or the nitrogen supply device conveys normal-temperature nitrogen to the nitrogen supply pipe; nitrogen in the nitrogen supply pipe passes through the interior of the condenser and then is output to the nitrogen residual cold recovery device. (3) the to-be-recycled gas absorbs the cooling capacity of the condenser, and to-be-recycled components of the to-be-recycled gas are liquefied and output to a natural gas storage mechanism; unrecycled components of the to-be-recycled gas are output to the tail gas emission mechanism through the miscellaneous gas output pipe. According to the scheme, direct combustion treatment can be replaced to maintain the low pressure of the fuel cabin, and the problem that waste is caused due to the fact that natural gas injected through an existing differential pressure method is mainly subjected to combustion treatment is solved.

Description

Technical Field

[0001] The present invention relates to the field of tail gas recovery, and in particular to a tail gas recovery method and system for an LNG fuel tank and applications thereof. Background Art

[0002] LNG fuel tanks are filled using the pressure differential method. LNG will naturally evaporate when it enters the fuel tank, causing the pressure inside the tank to increase and hinder filling. Therefore, during the filling process, it is necessary to continuously reduce the gaseous natural gas to maintain the low pressure of the fuel tank. At present, the pressure treatment method of the fuel tank is mainly based on direct combustion, but this treatment method is too wasteful. Because a 2000m 3 The first filling of the fuel tank may discharge 20 to 40 tons of natural gas depending on the filling process. Although the existing technology of natural gas filling by pressure difference method is convenient, it is costly and not conducive to sustainable development. Summary of the Invention

[0003] The purpose of the present invention is to provide a tail gas recovery method for LNG fuel tanks, which can first use a nitrogen supply mechanism to transmit nitrogen through a condenser and a nitrogen residual cold recovery device, and then use a miscellaneous gas input pipe to first pass through the nitrogen residual cold recovery device and then into the condenser. Nitrogen at different positions is used to recover the components to be recovered. The method can replace the direct combustion treatment to maintain the low pressure of the fuel tank.

[0004] The present invention also provides an LNG fuel tank tail gas recovery system, which is used to execute the above-mentioned LNG fuel tank tail gas recovery method.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A method for recovering tail gas from an LNG fuel tank comprises the following steps:

[0007] (1) The gaseous natural gas from the LNG fuel tank is fed into the stray gas inlet pipe as the gas to be recovered. The gas to be recovered from the stray gas inlet pipe passes through the nitrogen waste cooling recovery device and is then output to the condenser;

[0008] (2) The liquid nitrogen supply device delivers liquid nitrogen to the nitrogen supply pipe, and / or the nitrogen gas supply device delivers nitrogen gas at room temperature to the nitrogen supply pipe; the nitrogen in the nitrogen supply pipe passes through the interior of the condenser and is output to the nitrogen residual cooling recovery device;

[0009] (3) The recovered gas absorbs the cooling capacity of the condenser, and the recovered components of the recovered gas are liquefied and output to the natural gas storage mechanism; the unrecovered components of the recovered gas are output to the tail gas emission mechanism through the miscellaneous gas output pipe.

[0010] It can be optimized that in step (1), the intake gas composition detection device and the intake gas parameter detection device detect the gas to be recovered, and send the intake gas detection results to the PLC module in real time;

[0011] In step (2), the PLC module receives the air intake detection result in real time, and the PLC module adjusts the output parameters of the liquid nitrogen supply device and the nitrogen supply device to control the cooling capacity of the condenser according to the air intake detection result.

[0012] Optimally, in the step (1), the intake flow rate detection device of the intake parameter detection device detects the flow rate of the gas to be recovered in the stray gas input pipe, the intake temperature detection device detects the temperature of the gas to be recovered in the stray gas input pipe, the intake pressure detection device detects the pressure of the gas to be recovered in the stray gas input pipe, and the intake gas composition detection device detects the gas composition of the gas to be recovered in the stray gas input pipe, and the flow rate, temperature, pressure and gas composition of the gas to be recovered are sent to the PLC module in real time as the intake detection results;

[0013] In step (2), the PLC module receives the air intake detection result in real time, and the PLC module adjusts the output parameters of the liquid nitrogen supply device and the nitrogen supply device according to the air intake detection result to control the cooling capacity of the condenser.

[0014] It can be optimized that in the step (3), the unrecovered components of the gas to be recovered are output to the tail gas pipe of the tail gas emission mechanism through the miscellaneous gas output pipe, the tail gas component detection device detects the gas composition of the unrecovered components in the tail gas pipe; the tail gas flow detection device detects the flow of the unrecovered components in the tail gas pipe, the tail gas temperature detection device detects the temperature of the unrecovered components in the tail gas pipe, and the tail gas pressure detection device detects the pressure of the unrecovered components in the tail gas pipe; the flow, temperature, pressure and composition of the unrecovered components are sent to the PLC module in real time as the tail gas detection results;

[0015] In step (2), the PLC module receives the intake air detection results and the exhaust gas detection results in real time. The PLC module controls the cooling capacity of the condenser by adjusting the output parameters of the liquid nitrogen supply device and the nitrogen supply device according to the intake air detection results and the exhaust gas detection results.

[0016] Optimally, in the partial condensers of step (2), the output end of one condenser is connected to the input end of another condenser through a transfer tube, and a transfer valve is provided on the transfer tube; the PLC module controls the transfer valve to be opened or closed according to the intake gas detection results and the exhaust gas detection results;

[0017] When the transfer valve is open, the two condensers connected by the transfer tube are connected in series; when the transfer valve is closed, the two condensers connected by the transfer tube are connected in parallel; the PLC module plans the transmission path of the gas to be recovered based on the intake and exhaust gas detection results, and adjusts the stray gas valve body to control the flow direction and flow of the gas to be recovered.

[0018] An LNG fuel tank tail gas recovery system includes: a condensing mechanism, a nitrogen supply mechanism, a miscellaneous gas recovery mechanism, a tail gas discharge mechanism and a natural gas storage mechanism;

[0019] The condensing mechanism includes: a condenser;

[0020] The nitrogen supply mechanism includes: a liquid nitrogen supply device, a nitrogen gas supply device, a nitrogen residual cooling recovery device and a nitrogen supply pipe;

[0021] The output end of the liquid nitrogen supply device and the output end of the nitrogen gas supply device are respectively connected to the nitrogen supply pipe; the number of the condensers is multiple; the nitrogen supply pipe passes through the interior of the multiple condensers and then passes through the nitrogen residual cooling recovery device;

[0022] The impurity gas recovery mechanism includes: an impurity gas input pipe and an impurity gas output pipe;

[0023] The stray gas input pipe passes through the nitrogen waste cooling recovery device, and the output end of the stray gas input pipe is respectively connected to the input ends of the plurality of condensers; the output end of the stray gas output pipe is connected to the tail gas discharge mechanism;

[0024] The input end of the natural gas storage mechanism is connected to the output end of the condenser at the bottom.

[0025] Optimally, it further includes: a PLC module;

[0026] The PLC module is communicatively connected to the impurity gas recovery mechanism and the nitrogen supply mechanism;

[0027] The impurity gas recovery mechanism further includes: an intake gas component detection device and an intake gas parameter detection device;

[0028] The intake parameter detection device includes: an intake flow detection device, an intake temperature detection device and an intake pressure detection device;

[0029] The intake gas composition detection device, the intake air flow detection device, the intake air temperature detection device and the intake air pressure detection device are respectively installed on the stray air input pipe and are located between the input end of the stray air input pipe and the nitrogen waste cooling recovery device;

[0030] The exhaust gas emission mechanism includes: an exhaust pipe and an exhaust gas detection device;

[0031] The exhaust gas detection device includes: an exhaust gas composition detection device, an exhaust gas flow detection device, an exhaust gas temperature detection device and an exhaust gas pressure detection device;

[0032] The input end of the exhaust pipe is connected to the output end of the stray gas output pipe; the exhaust flow detection device, exhaust temperature detection device and exhaust pressure detection device are respectively installed on the exhaust pipe 41; the exhaust detection device 42 is communicatively connected to the PLC module 6.

[0033] Optimally, the condensing mechanism further includes: a transfer tube and a transfer valve;

[0034] The output end of one of the condensers is connected to the input end of the other condenser through the transfer tube, and the transfer valve is installed on the transfer tube;

[0035] The stray gas recovery mechanism further includes: a stray gas valve body; the stray gas valve body is installed on the stray gas input pipe, and the stray gas valve body is communicatively connected to the PLC module.

[0036] Optimally, the liquid nitrogen supply device and the nitrogen gas supply device respectively include: a nitrogen source container, a nitrogen outlet pipe and a control valve;

[0037] The output end of the nitrogen source container is connected to the input end of the nitrogen outlet pipe, the output end of the nitrogen outlet pipe is connected to the input end of the nitrogen supply pipe, and the control valves are respectively installed on the nitrogen outlet pipes.

[0038] The invention discloses an application of an exhaust gas recovery system in recovering exhaust gas from an LNG fuel tank using a pressure difference method. The exhaust gas recovery system is the above-mentioned exhaust gas recovery system for an LNG fuel tank.

[0039] Compared with the prior art, one of the above technical solutions has the following beneficial effects:

[0040] This solution provides a tail gas recovery method for LNG fuel tanks. It can first use a nitrogen supply mechanism to transmit nitrogen through a condenser and a nitrogen residual cooling recovery device, and then use a miscellaneous gas input pipe to first pass through the nitrogen residual cooling recovery device and then into the condenser. Nitrogen at different positions is used to recover the components to be recovered. This solution can replace the practice of direct combustion treatment to maintain low pressure in the fuel tank, and solves the problem of waste caused by the existing pressure differential method of filling natural gas mainly being burned. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of one embodiment of the tail gas recovery system;

[0042] in:

[0043] Condensation mechanism 1, nitrogen supply mechanism 2, impurity gas recovery mechanism 3, tail gas emission mechanism 4, natural gas storage mechanism 5; PLC module 6;

[0044] Condenser 11; transfer pipe 12, transfer valve 13;

[0045] Liquid nitrogen supply device 21, nitrogen gas supply device 22, nitrogen residual cooling recovery device 23, nitrogen supply pipe 24;

[0046] Nitrogen source container 201, nitrogen outlet pipe 202, control valve 203;

[0047] stray gas inlet pipe 31, stray gas outlet pipe 32; intake gas composition detection device 33, intake gas parameter detection device 34; stray gas valve body 35;

[0048] Intake air flow detection device 341, intake air temperature detection device 342, intake air pressure detection device 343;

[0049] exhaust pipe 41, exhaust gas detection device 42;

[0050] Exhaust gas composition detection device 421 , exhaust gas flow detection device 422 , exhaust gas temperature detection device 423 , exhaust gas pressure detection device 424 . DETAILED DESCRIPTION

[0051] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0052] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", "inner end", "outer end", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of the features, and are used to distinguish the described features, without distinction of order or importance. In the description of the present invention, unless otherwise specified, "multiple" means more than two.

[0053] like Figure 1, a tail gas recovery method for an LNG fuel tank, comprising the following steps:

[0054] (1) The mixed gas inlet pipe 31 inputs the gaseous natural gas from the LNG fuel tank as the gas to be recovered. The gas to be recovered from the mixed gas inlet pipe 31 passes through the nitrogen waste cooling recovery device 23 and is then output to the condenser 11;

[0055] (2) The liquid nitrogen supply device 21 delivers liquid nitrogen to the nitrogen supply pipe 24, and / or the nitrogen supply device 22 delivers nitrogen at room temperature to the nitrogen supply pipe 24; the nitrogen in the nitrogen supply pipe 24 passes through the interior of the condenser 11 and is output to the nitrogen residual cold recovery device 23; generally, the condenser 11 is to liquefy and recover gaseous natural gas, and the temperature is preferably -162 to -178°C. Within this temperature range, the components to be recovered in the gaseous natural gas are liquefied but not solidified.

[0056] (3) The recovered gas absorbs the cooling capacity of the condenser 11, and the recovered components of the recovered gas are liquefied and output to the natural gas storage mechanism 5; the unrecovered components of the recovered gas are output to the tail gas emission mechanism 4 through the miscellaneous gas output pipe 32.

[0057] This solution provides a tail gas recovery method for LNG fuel tanks. The method first utilizes a nitrogen supply mechanism 2 to transfer nitrogen through a condenser 11 and a nitrogen waste cooling recovery device 23. The nitrogen is then transferred through a miscellaneous gas inlet pipe 31 through the nitrogen waste cooling recovery device 23 and then into the condenser 11. Nitrogen at different locations is used to recover the components to be recovered. This method can replace the practice of direct combustion treatment to maintain low pressure in the fuel tank, solving the problem of waste caused by the existing pressure differential method of natural gas injection, which is mainly treated by combustion.

[0058] It can be optimized that in the step (1), the intake gas composition detection device 33 and the intake gas parameter detection device 34 detect the gas to be recovered, and send the intake gas detection results to the PLC module 6 in real time;

[0059] In step (2), the PLC module 6 receives the air intake detection result in real time, and the PLC module 6 adjusts the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22 to control the cooling capacity of the condenser 11 according to the air intake detection result.

[0060] Output parameters include, for example, the output ratio, pressure, and flow rate of nitrogen. The PLC module 6 adjusts the control valve 203 to an optimal opening based on the gas composition, flow rate, pressure, and temperature of the gas to be recovered, as well as the current temperature and pressure of nitrogen in the liquid nitrogen supply device 21 and the nitrogen gas supply device 22, to ensure that the temperature of the gas to be recovered at the output end of the nitrogen pipe 202 meets the specified temperature.

[0061] Optimally, in step (1), the intake air flow rate detection device 341 of the intake air parameter detection device 34 detects the flow rate of the gas to be recovered in the stray gas input pipe 31, the intake air temperature detection device 342 detects the temperature of the gas to be recovered in the stray gas input pipe 31, the intake air pressure detection device 343 detects the pressure of the gas to be recovered in the stray gas input pipe 31, and the intake air gas composition detection device 33 detects the gas composition of the gas to be recovered in the stray gas input pipe 31. The flow rate, temperature, pressure and gas composition of the gas to be recovered are sent to the PLC module 6 in real time as the intake air detection results;

[0062] In step (2), the PLC module 6 receives the air intake detection result in real time, and the PLC module 6 adjusts the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22 according to the air intake detection result to control the cooling capacity of the condenser 11.

[0063] Optimally, in the step (3), the unrecovered components of the gas to be recovered are output to the tail gas pipe 41 of the tail gas emission mechanism 4 via the miscellaneous gas output pipe 32, and the tail gas component detection device 421 detects the gas composition of the unrecovered components in the tail gas pipe 41; the tail gas flow detection device 422 detects the flow of the unrecovered components in the tail gas pipe 41, the tail gas temperature detection device 423 detects the temperature of the unrecovered components in the tail gas pipe 41, and the tail gas pressure detection device 424 detects the pressure of the unrecovered components in the tail gas pipe 41; the flow, temperature, pressure and composition of the unrecovered components are sent to the PLC module 6 in real time as the tail gas detection results;

[0064] In step (2), the PLC module 6 receives the intake air detection results and the exhaust gas detection results in real time. The PLC module 6 controls the cooling capacity of the condenser 11 by adjusting the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22 according to the intake air detection results and the exhaust gas detection results.

[0065] In this solution, when the unrecovered components are output from the tail gas pipe 41, the flow rate, temperature, pressure, and composition are detected by the tail gas detection device 42. Immediately after the unrecovered components are output from the condenser 11, their temperature best reflects the cooling capacity of the condenser 11. The temperature of the unrecovered components in the tail gas pipe 41 is higher than that of the condenser 11. When the PLC module 6 recognizes that the temperature of the unrecovered components exceeds a preset range, it can control and adjust the control valves 203 of both the liquid nitrogen supply device 21 and the nitrogen supply device 22 to bring the temperature of the unrecovered components within the preset range and ensure that the cooling capacity of the condenser 11 meets the preset range. Both the liquid nitrogen from the liquid nitrogen supply device 21 and the room temperature nitrogen from the nitrogen supply device 22 are precisely input under the control of the PLC module 6 to ensure that the temperature in the condenser 11 remains within the preset range.

[0066] This system can determine whether the system is operating normally by measuring the temperatures of the intake air temperature detection device 342 and the exhaust gas temperature detection device 423. It can also determine the actual recovery effect of the system by measuring the flow rate difference between the intake air flow detection device 341 and the exhaust gas flow detection device 422. Furthermore, it can determine the difference between theory and practice by analyzing the composition of the exhaust gas composition detection device 421 and the intake gas composition detection device 33. This composition analysis facilitates data reference for subsequent system improvements. Furthermore, the exhaust gas composition detection device 421 and the intake gas composition detection device 33 are located at the intake and outlet ends of the system, respectively. By performing a gas composition test at both the intake and outlet ends of the system, the system's recovery efficiency can be intuitively determined.

[0067] Optimally, in the partial condensers 11 of step (2), the output end of one condenser 11 is connected to the input end of another condenser 11 through a transfer tube 12, and a transfer valve 13 is provided on the transfer tube 12; the PLC module 6 controls the transfer valve 13 to be opened or closed according to the intake gas detection result and the exhaust gas detection result;

[0068] When the transfer valve 13 is opened, the two condensers 11 connected through the transfer tube 12 are connected in series; when the transfer valve 13 is closed, the two condensers 11 connected through the transfer tube 12 are connected in parallel; the PLC module 6 plans the transmission path of the gas to be recovered according to the intake gas detection results and the exhaust gas detection results, and adjusts the mixed gas valve body 35 to control the flow direction and flow rate of the gas to be recovered.

[0069] In one embodiment, when the system needs to switch the condensers 11 from parallel to series, it is necessary to ensure that the temperature of the unrecovered components in the tail gas pipe 41 is below a certain temperature (e.g., below -162°C) and that some condensers 11 do not have sufficient cooling capacity. At this time, the PLC module 6 can control the switching valve 13 to open, so that the condensers 11 are connected in series, and adjust the mixed gas valve body 35 of some mixed gas input pipes 31 to control the flow direction and flow of the gas to be recovered, so that the gas to be recovered is sent to other parallel condensers 11 at a lower flow rate or first passes through other parallel condensers 11. After a period of time, the overall temperature of the multiple condensers 11 in series drops to a preset range, at which time a larger flow of gas to be recovered can be sent to the condensers 11 in series. When the input flow rate of the gas to be recovered decreases, the PLC module 6 can control the switching valve 13 to close, and only a single or limited number of condensers 11 are used. During this period, the liquid nitrogen from the liquid nitrogen supply device 21 and the room temperature nitrogen from the nitrogen supply device 22 are accurately input under the control of the PLC module 6 to ensure that the temperature in the condenser remains within the preset range.

[0070] In step (3), the components to be recovered from the condenser 11 are output to the natural gas storage mechanism 5 through the output end below the condenser 11 under the action of gravity.

[0071] At the output end below the condenser 11 , the components to be recovered will sink below the condenser 11 after being liquefied, and thus can be output to the natural gas storage mechanism 5 solely by the action of gravity.

[0072] An exhaust gas recovery system for an LNG fuel tank comprises: a condensing mechanism 1, a nitrogen supply mechanism 2, a miscellaneous gas recovery mechanism 3, an exhaust gas discharge mechanism 4, and a natural gas storage mechanism 5;

[0073] The condensing mechanism 1 includes: a condenser 11;

[0074] The nitrogen supply mechanism 2 includes: a liquid nitrogen supply device 21, a nitrogen gas supply device 22, a nitrogen residual cooling recovery device 23 and a nitrogen supply pipe 24;

[0075] The output end of the liquid nitrogen supply device 21 and the output end of the nitrogen gas supply device 22 are respectively connected to the nitrogen supply pipe 24; the number of the condensers 11 is multiple; the nitrogen supply pipe 24 passes through the interior of the multiple condensers 11 and then passes through the nitrogen residual cooling recovery device 23;

[0076] The impurity gas recovery mechanism 3 includes: an impurity gas input pipe 31 and an impurity gas output pipe 32;

[0077] The stray gas input pipe 31 passes through the nitrogen waste cooling recovery device 23, and the output end of the stray gas input pipe 31 is respectively connected to the input ends of the plurality of condensers 11; the output end of the stray gas output pipe 32 is connected to the tail gas discharge mechanism 4;

[0078] The input end of the natural gas storage mechanism 5 is connected to the output end of the condenser 11 at the bottom.

[0079] This solution provides an exhaust gas recovery system for an LNG fuel tank. The system first utilizes a nitrogen supply mechanism 2 to deliver nitrogen to a condenser 11 and a nitrogen waste cooling recovery device 23, and then utilizes a miscellaneous gas inlet pipe 31 to first pass through the nitrogen waste cooling recovery device 23 before being delivered to the condenser 11. This system fully utilizes nitrogen at different locations to recover the components to be recovered. This solution can replace the practice of direct combustion treatment to maintain low pressure in the fuel tank, solving the problem of waste caused by combustion treatment of natural gas added using the existing pressure differential method.

[0080] Specifically, the nitrogen supply mechanism 2 includes a liquid nitrogen supply device 21 and a nitrogen gas supply device 22. The liquid nitrogen supply device 21 is mainly used to store liquid nitrogen, and the nitrogen gas supply device 22 is mainly used to store nitrogen gas. Liquid nitrogen is obtained by cooling nitrogen gas to a temperature below -195.8°C. Therefore, the temperature of the nitrogen output by the liquid nitrogen supply device 21 is lower than the temperature of the nitrogen output by the nitrogen gas supply device 22. In this solution, at least one of the liquid nitrogen supply device 21 and the nitrogen gas supply device 22 can be selected as needed to output nitrogen to the nitrogen supply pipe 24, so that low-temperature liquid nitrogen and / or room-temperature nitrogen gas is output to the nitrogen supply pipe 24. When relatively low-temperature nitrogen is required, the liquid nitrogen output ratio of the liquid nitrogen supply device 21 can be increased in this solution. When relatively higher temperature nitrogen is required, this solution can increase the nitrogen output ratio of the nitrogen supply device 22; the nitrogen supply pipe 24 passes through the interior of the condenser 11 to provide cooling capacity for the condenser 11, and then passes through the nitrogen waste cooling recovery device 23; after nitrogen provides the main cooling capacity in a single or multiple condensers 11, it finally passes through the nitrogen waste cooling recovery device 23, and the cooling capacity of the nitrogen waste cooling recovery device 23 will be lower than that of the condenser 11; for this reason, this solution cleverly uses the nitrogen waste cooling recovery device 23 to further utilize the waste cooling of nitrogen, mainly when the gas to be recovered enters the stray gas recovery mechanism 3, the gas to be recovered first passes through the nitrogen waste cooling recovery device 23 through the stray gas input pipe 31, and then is output to the condenser 11. The nitrogen waste cooling recovery device 23 utilizes the waste cooling of nitrogen to pre-cool the gas to be recovered. The recovered gas absorbs the cooling energy of the low-temperature nitrogen in the nitrogen waste cooling recovery device 23, initially reducing its temperature. The recovered gas is then output to the condenser 11 through the output end of the miscellaneous gas inlet pipe 31. The recovered gas further absorbs cooling energy within the condenser 11. Generally, the main components of the recovered gas are nitrogen and methane, with small amounts of ethane and propane, and trace amounts of helium and argon. Since this solution allows the selection of either the liquid nitrogen supply device 21 or the nitrogen supply device 22 to output nitrogen of different temperatures to the nitrogen supply pipe 24 as needed, the nitrogen in the nitrogen supply pipe 24 passes through the condenser 11, so the lowest temperature of the condenser 11 can be -195°C. 8℃; when the condenser 11 needs to be heated, the nitrogen supply device 22 can be used to deliver nitrogen to the nitrogen supply pipe 24; in this way, the present solution can adjust the temperature of the condenser 11 to -185.7℃, liquefy the argon, and the argon sinks to the bottom wall of the condenser 11 under the action of gravity, and the argon can be collected at the output end below the condenser 11, or the argon recovery step can be omitted based on the small amount of argon; similarly, the present solution can adjust the temperature of the condenser 11 to -185.7℃~-83℃, so that the methane, ethane and propane components to be recovered can be liquefied separately or simultaneously, and a single or multiple combustible gases can be collected at the output end below the condenser 11 through the natural gas storage mechanism 5, so that the combustible gases are gathered in the natural gas storage mechanism 5.The remaining nitrogen and a small amount of helium are non-toxic gases and can be directly discharged through the miscellaneous gas output pipe 32 to the exhaust gas discharge mechanism 4, which then recovers the nitrogen and a small amount of helium or directly discharges them. In this way, this solution can utilize nitrogen from different locations to recover the components to be recovered. This can replace the practice of direct combustion to maintain low pressure in the fuel tank, solving the problem of waste caused by the existing pressure differential method of natural gas injection, which is mainly burned.

[0081] Optimally, it further includes: a PLC module 6;

[0082] The PLC module 6 is communicatively connected to the impurity gas recovery mechanism 3 and the nitrogen supply mechanism 2;

[0083] The impurity gas recovery mechanism 3 further includes: an intake gas component detection device 33 and an intake gas parameter detection device 34;

[0084] The intake parameter detection device 34 includes: an intake flow detection device 341, an intake temperature detection device 342 and an intake pressure detection device 343;

[0085] The intake gas composition detection device 33, the intake air flow detection device 341, the intake air temperature detection device 342 and the intake air pressure detection device 343 are respectively installed on the stray air input pipe 31 and are located between the input end of the stray air input pipe 31 and the nitrogen waste cooling recovery device 23;

[0086] The exhaust gas emission mechanism 4 includes: an exhaust pipe 41 and an exhaust gas detection device 42;

[0087] The exhaust gas detection device 42 includes: an exhaust gas component detection device 421, an exhaust gas flow detection device 422, an exhaust gas temperature detection device 423 and an exhaust gas pressure detection device 424;

[0088] The input end of the exhaust pipe 41 is connected to the output end of the miscellaneous gas output pipe 32; the exhaust gas flow detection device 422, the exhaust gas temperature detection device 423 and the exhaust gas pressure detection device 424 are respectively installed on the exhaust pipe 41; the exhaust gas detection device 42 is communicatively connected to the PLC module 6.

[0089] This solution can further incorporate a PLC module 6. This PLC module 6 is a well-known digital computing and operating electronic system designed for use in industrial environments. It typically utilizes a programmable memory to store instructions for executing logical operations, sequential control, timing, counting, and arithmetic operations, and controls various types of mechanical equipment or production processes through digital or analog input and output. To this end, the PLC module 6 of this solution is communicatively connected to the stray gas recovery mechanism 3 and the nitrogen supply mechanism 2. The intake gas composition detection device 33 can be a well-known mechanism capable of detecting gas composition, capable of analyzing the gas to be recovered inputted from the input end of the stray gas input pipe 31. The intake gas parameter detection device 34 can be used to detect a physical parameter of the gas to be recovered, such as at least one of flow rate, temperature, and pressure. The intake gas composition detection device 33 and the intake parameter detection device 34 can feed back the detection results to the PLC module 6. The PLC module 6 can regulate the nitrogen supply mechanism 2 according to the detection results, and can adjust the output parameters of the liquid nitrogen supply device 21 and the nitrogen gas supply device 22, thereby controlling the cooling capacity of the condenser 11 and the nitrogen waste cooling recovery device 23 by controlling the cooling capacity of the nitrogen supply pipe 24.

[0090] The communication connection method here refers to the communication between connected devices through signal transmission interaction, which can be divided into wired connection and wireless connection; wired connection includes conventional data cable connection; wireless connection includes conventional WiFi, Bluetooth, infrared, NFC, etc.

[0091] This solution preferably uses an intake flow detection device 341, an intake temperature detection device 342 and an intake pressure detection device 343 to detect the parameters of the gas to be recovered before the gas to be recovered enters the condenser 11. The intake flow detection device 341 corresponds to detecting the flow rate of the gas to be recovered, the intake temperature detection device 342 corresponds to detecting the temperature of the gas to be recovered, and the intake pressure detection device 343 corresponds to detecting the pressure of the gas to be recovered; in this way, the intake parameter detection device 34 can feed back the flow parameters, temperature parameters and pressure parameters of the gas to be recovered as intake detection results to the PLC module 6, and the PLC module 6 adjusts the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22 according to the above-mentioned intake detection results.

[0092] This solution can also add an exhaust gas composition detection device 421, an exhaust gas flow detection device 422, an exhaust gas temperature detection device 423 and an exhaust gas pressure detection device 424 with exhaust gas detection functions in the exhaust pipe 41; similar to the intake parameter detection device 34, the exhaust gas composition detection device 421 can be used to analyze the gas composition of the exhaust gas in the exhaust pipe 41; the exhaust gas flow detection device 422 corresponds to detecting the flow rate of the exhaust gas in the exhaust pipe 41, the exhaust gas temperature detection device 423 corresponds to detecting the temperature of the exhaust gas in the exhaust pipe 41, and the exhaust gas pressure detection device 424 corresponds to detecting the pressure of the exhaust gas in the exhaust pipe 41. In this way, the exhaust gas composition detection device 421, the exhaust gas flow detection device 422, the exhaust gas temperature detection device 423 and the exhaust gas pressure detection device 424 obtain the gas composition, flow, temperature and pressure parameters of the exhaust gas when it is discharged, and can feed back the results to the PLC module 6 in real time. The PLC module 6 combines the feedback of the impurity gas recovery mechanism 3 to control the cooling capacity of the condenser 11 and the nitrogen waste cooling recovery device 23 in real time by controlling the cooling capacity of the nitrogen supply pipe 24.

[0093] Optimally, the condensing mechanism 1 further includes: a transfer tube 12 and a transfer valve 13;

[0094] The output end of one of the condensers 11 is connected to the input end of the other condenser 11 through the transfer tube 12 , and the transfer valve 13 is installed on the transfer tube 12 ;

[0095] The stray gas recovery mechanism 3 further includes a stray gas valve body 35 ; the stray gas valve body 35 is installed on the stray gas input pipe 31 , and the stray gas valve body 35 is communicatively connected to the PLC module 6 .

[0096] The number of condensers 11 can be multiple, and a transfer pipe 12 can connect two adjacent condensers 11. The transfer pipe 12 is provided with a transfer valve 13. In this solution, the transfer valve 13 controls the flow rate and pressure of the transfer pipe 12. Some condensers 11 are connected. After the impurity gas input pipe 31 inputs the gas to be recovered, the gas to be recovered passes through the intake parameter detection device 34. The PLC module 6 determines whether to open or close the transfer valve 13 based on the result. The operation can be automatic. For example, when the gas flow rate of the gas to be recovered is large, at least two condensers 11 are used to recover the gas simultaneously. The transfer valve 13 can be replaced by a known valve body.

[0097] The stray gas inlet pipe 31 is installed with a stray gas valve body 35. Since there are multiple condensers 11, the input end of the condenser 11 is connected to the stray gas inlet pipe 31. Therefore, after the gas to be recovered is input into the stray gas inlet pipe 31, the gas to be recovered can be output to different condensers 11 through different stray gas inlet pipes 31; in this regard, the PLC module 6 can control the stray gas valve body 35 according to the feedback of the intake gas composition detection device 33 and the intake parameter detection device 34, thereby controlling the gas to be recovered to enter part of the stray gas inlet pipe 31 and enter different condensers 11; since some condensers 11 are connected through the transfer tube 12, the PLC module 6 can flow through a specific number of condensers 11, thereby controlling the path of the gas to be recovered according to the feedback results, ensuring that the temperature of the condenser 11 is suitable for the gas to be recovered with specific parameters, thereby improving the recovery efficiency.

[0098] The switching valve 13 is a solenoid valve, and the switching valve 13 is communicatively connected to the PLC module 6 .

[0099] The PLC module 6 can control the solenoid valve in real time according to the feedback results of the intake gas composition detection device 33 and the intake parameter detection device 34, thereby controlling the communication state between the condensers 11 and 11.

[0100] Optimally, the liquid nitrogen supply device 21 and the nitrogen gas supply device 22 respectively include: a nitrogen source container 201, a nitrogen outlet pipe 202 and a control valve 203;

[0101] The output end of the nitrogen source container 201 is connected to the input end of the nitrogen outlet pipe 202 , the output end of the nitrogen outlet pipe 202 is connected to the input end of the nitrogen supply pipe 24 , and the control valves 203 are respectively installed on the nitrogen outlet pipes 202 .

[0102] Liquid nitrogen supply device 21 and nitrogen supply device 22 include nitrogen source container 201, go out nitrogen pipe 202 and control valve 203 respectively, the nitrogen source container 201 of liquid nitrogen supply device 21 is used for storing and / or transmitting liquid nitrogen;The nitrogen source container 201 of nitrogen supply device 22 is used for storing and / or transmitting nitrogen;After going out nitrogen pipe 202 receives the nitrogen of nitrogen source container 201, it can be delivered to nitrogen supply pipe 24 by pressurization (such as using pump body) mode, and control valve 203 can control nitrogen in the flow of going out nitrogen pipe 202.To this, liquid nitrogen supply device 21 and nitrogen supply device 22 can adjust control valve 203 according to the instruction of PLC module 6, to cooperate the flow parameter, temperature parameter and pressure parameter of gas to be recovered, ensure that system can regulate the cold capacity of condenser 11 and nitrogen waste cold recovery device 23 in real time according to the input situation of gas to be recovered.

[0103] An application of an exhaust gas recovery system in recovering exhaust gas from an LNG fuel tank using a pressure differential method is characterized in that the exhaust gas recovery system is an exhaust gas recovery system for an LNG fuel tank according to any of the above embodiments.

[0104] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for recovering tail gas from an LNG fuel tank, characterized in that: The following steps are involved: (1) The gaseous natural gas from the LNG fuel tank is fed into the stray gas inlet pipe as the gas to be recovered. The gas to be recovered from the stray gas inlet pipe passes through the nitrogen waste cooling recovery device and is then output to the condenser; (2) The liquid nitrogen supply device delivers liquid nitrogen to the nitrogen supply pipe, and / or the nitrogen gas supply device delivers nitrogen gas at room temperature to the nitrogen supply pipe; the nitrogen in the nitrogen supply pipe passes through the interior of the condenser and is output to the nitrogen residual cooling recovery device; (3) The recovered gas absorbs the cooling capacity of the condenser, and the recovered components of the recovered gas are liquefied and output to the natural gas storage mechanism; the unrecovered components of the recovered gas are output to the tail gas emission mechanism through the miscellaneous gas output pipe.

2. The tail gas recovery method of an LNG fuel tank according to claim 1, characterized in that: In step (1), the intake gas composition detection device and the intake gas parameter detection device detect the gas to be recovered, and send the intake gas detection results to the PLC module in real time; In step (2), the PLC module receives the air intake detection result in real time, and the PLC module adjusts the output parameters of the liquid nitrogen supply device and the nitrogen supply device to control the cooling capacity of the condenser according to the air intake detection result.

3. The tail gas recovery method of an LNG fuel tank according to claim 2, characterized in that: In the step (1), the intake flow rate detection device of the intake parameter detection device detects the flow rate of the gas to be recovered in the stray gas input pipe, the intake temperature detection device detects the temperature of the gas to be recovered in the stray gas input pipe, the intake pressure detection device detects the pressure of the gas to be recovered in the stray gas input pipe, and the intake gas composition detection device detects the gas composition of the gas to be recovered in the stray gas input pipe. The flow rate, temperature, pressure and gas composition of the gas to be recovered are sent to the PLC module in real time as the intake detection results; In step (2), the PLC module receives the air intake detection result in real time, and the PLC module adjusts the output parameters of the liquid nitrogen supply device and the nitrogen supply device according to the air intake detection result to control the cooling capacity of the condenser.

4. The tail gas recovery method of an LNG fuel tank according to claim 3, characterized in that: In the step (3), the unrecovered components of the gas to be recovered are output to the tail gas pipe of the tail gas emission mechanism through the miscellaneous gas output pipe, and the tail gas component detection device detects the gas composition of the unrecovered components in the tail gas pipe; The tail gas flow detection device detects the flow of the unrecovered components in the tail gas pipe, the tail gas temperature detection device detects the temperature of the unrecovered components in the tail gas pipe, and the tail gas pressure detection device detects the pressure of the unrecovered components in the tail gas pipe; The flow rate, temperature, pressure and composition of the unrecovered components are sent to the PLC module in real time as tail gas detection results; In step (2), the PLC module receives the intake air detection results and the exhaust gas detection results in real time. The PLC module controls the cooling capacity of the condenser by adjusting the output parameters of the liquid nitrogen supply device and the nitrogen supply device according to the intake air detection results and the exhaust gas detection results.

5. The tail gas recovery method of an LNG fuel tank according to claim 4, characterized in that: In the partial condenser of step (2), the output end of one condenser is connected to the input end of another condenser through a transfer tube, and a transfer valve is provided on the transfer tube; the PLC module controls the transfer valve to be opened or closed according to the intake gas detection results and the exhaust gas detection results; When the transfer valve is open, the two condensers connected by the transfer tube are connected in series; when the transfer valve is closed, the two condensers connected by the transfer tube are connected in parallel; the PLC module plans the transmission path of the gas to be recovered based on the intake and exhaust gas detection results, and adjusts the stray gas valve body to control the flow direction and flow of the gas to be recovered.

6. An LNG fuel tank tail gas recovery system, characterized in that: include: Condensation mechanism, nitrogen supply mechanism, impurity gas recovery mechanism, tail gas emission mechanism and natural gas storage mechanism; The condensing mechanism includes: a condenser; The nitrogen supply mechanism includes: a liquid nitrogen supply device, a nitrogen gas supply device, a nitrogen residual cooling recovery device and a nitrogen supply pipe; The output end of the liquid nitrogen supply device and the output end of the nitrogen gas supply device are respectively connected to the nitrogen supply pipe; the number of the condensers is multiple; the nitrogen supply pipe passes through the interior of the multiple condensers and then passes through the nitrogen residual cooling recovery device; The impurity gas recovery mechanism includes: an impurity gas input pipe and an impurity gas output pipe; The stray gas input pipe passes through the nitrogen waste cooling recovery device, and the output end of the stray gas input pipe is respectively connected to the input ends of the plurality of condensers; the output end of the stray gas output pipe is connected to the tail gas discharge mechanism; The input end of the natural gas storage mechanism is connected to the output end of the condenser at the bottom.

7. The tail gas recovery system for an LNG fuel tank according to claim 6, characterized in that: Also includes: PLC module; The PLC module is communicatively connected to the impurity gas recovery mechanism and the nitrogen supply mechanism; The impurity gas recovery mechanism further includes: an intake gas component detection device and an intake gas parameter detection device; The intake parameter detection device includes: an intake flow detection device, an intake temperature detection device and an intake pressure detection device; The intake gas composition detection device, the intake air flow detection device, the intake air temperature detection device and the intake air pressure detection device are respectively installed on the stray air input pipe and are located between the input end of the stray air input pipe and the nitrogen waste cooling recovery device; The exhaust gas emission mechanism includes: an exhaust pipe and an exhaust gas detection device; The exhaust gas detection device includes: an exhaust gas composition detection device, an exhaust gas flow detection device, an exhaust gas temperature detection device and an exhaust gas pressure detection device; The input end of the exhaust pipe is connected to the output end of the stray gas output pipe; the exhaust flow detection device, exhaust temperature detection device and exhaust pressure detection device are respectively installed on the exhaust pipe 41; the exhaust detection device 42 is communicatively connected to the PLC module 6.

8. The tail gas recovery system for an LNG fuel tank according to claim 7, characterized in that: The condensing mechanism further includes: a transfer tube and a transfer valve; The output end of one of the condensers is connected to the input end of the other condenser through the transfer tube, and the transfer valve is installed on the transfer tube; The stray gas recovery mechanism further includes: a stray gas valve body; the stray gas valve body is installed on the stray gas input pipe, and the stray gas valve body is communicatively connected to the PLC module.

9. The tail gas recovery system for an LNG fuel tank according to claim 8, characterized in that: The liquid nitrogen supply device and the nitrogen gas supply device respectively include: a nitrogen source container, a nitrogen outlet pipe and a control valve; The output end of the nitrogen source container is connected to the input end of the nitrogen outlet pipe, the output end of the nitrogen outlet pipe is connected to the input end of the nitrogen supply pipe, and the control valves are respectively installed on the nitrogen outlet pipes.

10. An application of an exhaust gas recovery system in recovering exhaust gas from an LNG fuel tank using a pressure differential method, characterized in that: The tail gas recovery system is an tail gas recovery system for an LNG fuel tank as described in any one of claims 6-9.

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