Natural gas vent recovery system

Abstract

This invention discloses a natural gas venting and recovery system, which includes a heat exchange device, an exhaust device, a liquid discharge device, and a gas transmission device. The heat exchange device includes a main heat exchanger and a liquid nitrogen input pipe. The main heat exchanger has a liquid nitrogen channel, a first heat exchange channel, and a second heat exchange channel. One end of the liquid nitrogen input pipe is connected to the inlet of the liquid nitrogen channel, and the other end is used for supplying liquid nitrogen. The exhaust device is used to supply natural gas and guide it to the inlet of the first heat exchange channel. The liquid discharge device includes a discharge pipe and a discharge pump. The two ends of the discharge pipe are respectively connected to the outlet of the first heat exchange channel and the inlet of the second heat exchange channel. The discharge pump is installed on the discharge pipe. The gas transmission device is used to connect to the outlet of the second heat exchange channel and output natural gas. The gas transmission device directly transports the natural gas back to the natural gas pipeline or facility for on-site consumption, thereby improving the recovery and utilization rate of vented natural gas and reducing energy waste.

Description

Technical Field

[0001] This invention belongs to the field of natural gas venting technology, and specifically relates to a natural gas venting and recovery system. Background Technology

[0002] Natural gas pipeline maintenance, hot work, and relocation all require venting the natural gas from the pipeline. This vented natural gas can be recovered and reused. Currently, the main methods for natural gas venting and recovery are compression venting and recovery and liquefaction venting and recovery. Compression venting and recovery typically uses multi-stage reciprocating compressors. However, due to the compressor's own pressure ratio limitations, its efficiency drops sharply once the pressure of the natural gas to be recovered decreases to a certain value. Furthermore, the maximum operating pressure ratio of the compressor limits the pressure of the natural gas that can be recovered. The large pressure ratio and numerous stages of the compressor result in a heavy and large venting and recovery system, making it difficult to move and transport, and inflexible in use. In addition, existing liquefaction venting and recovery methods typically recover liquefied natural gas (LNG). LNG needs to be stored separately and transported by tanker truck to other usage locations for consumption. Finding suitable usage methods is difficult, resulting in inconvenient use and low utilization rates, easily leading to energy waste. Summary of the Invention

[0003] In view of the above-mentioned defects or deficiencies, the present invention provides a natural gas venting and recovery system, which aims to solve the technical problems of inconvenient use and low utilization rate of recovered liquefied natural gas, which easily leads to energy waste.

[0004] To achieve the above objectives, the present invention provides a natural gas vent recovery system, the natural gas vent recovery system comprising:

[0005] The heat exchange device includes a main heat exchanger and a liquid nitrogen input pipe. The main heat exchanger has a liquid nitrogen channel, a first heat exchange channel and a second heat exchange channel. One end of the liquid nitrogen input pipe is connected to the inlet of the liquid nitrogen channel, and the other end is used for supplying liquid nitrogen.

[0006] An exhaust system is used to supply natural gas and direct it to the inlet of the first heat exchange channel;

[0007] The draining device includes a drain pipe and a drain pump. The two ends of the drain pipe are respectively connected to the outlet of the first heat exchange channel and the inlet of the second heat exchange channel. The drain pump is installed on the drain pipe.

[0008] A gas transmission unit is used to connect to the outlet of the second heat exchange channel and output natural gas.

[0009] In this embodiment of the invention, the heat exchange device further includes an auxiliary heat exchanger, which has a third heat exchange channel and a fourth heat exchange channel. An exhaust device is used to supply natural gas input and select the inlet of the third or fourth heat exchange channel to be connected with the inlet of the first heat exchange channel. A gas transmission device is used to select the outlet of the fourth heat exchange channel to be connected with the outlet of the second heat exchange channel and output natural gas when the third heat exchange channel is connected with the first heat exchange channel, and to select the outlet of the third heat exchange channel to be connected with the outlet of the second heat exchange channel and output natural gas when the fourth heat exchange channel is connected with the first heat exchange channel.

[0010] In this embodiment of the invention, the exhaust device includes an exhaust pipe group and an exhaust valve group. The exhaust pipe group includes a first exhaust pipe, a second exhaust pipe, a third exhaust pipe, and a fourth exhaust pipe. One end of the first exhaust pipe is used for natural gas input, and the other end is connected to the inlet of the third heat exchange channel. The two ends of the second exhaust pipe are respectively connected to the outlet of the third heat exchange channel and the inlet of the first heat exchange channel. One end of the third exhaust pipe is used for natural gas input, and the other end is connected to the inlet of the fourth heat exchange channel. The two ends of the fourth exhaust pipe are respectively connected to the outlet of the fourth heat exchange channel and the inlet of the first heat exchange channel. The exhaust valve group is used to control the on / off state of the first exhaust pipe, the second exhaust pipe, the third exhaust pipe, and the fourth exhaust pipe.

[0011] In this embodiment of the invention, the exhaust pipe assembly further includes an exhaust main pipe, one end of which branches to form a first exhaust pipe and a third exhaust pipe, and the other end is used for natural gas input. A first pressure regulator is provided on the exhaust main pipe.

[0012] In this embodiment of the invention, the gas transmission device includes a gas transmission pipe group and a gas transmission valve group. The gas transmission pipe group includes a first gas transmission pipe, a second gas transmission pipe, a third gas transmission pipe, and a fourth gas transmission pipe. The two ends of the first gas transmission pipe are respectively connected to the outlet of the second heat exchange channel and the inlet of the fourth heat exchange channel. One end of the second gas transmission pipe is connected to the outlet of the fourth heat exchange channel, and the other end is used to output natural gas. The two ends of the third gas transmission pipe are respectively connected to the outlet of the second heat exchange channel and the inlet of the third heat exchange channel. One end of the fourth gas transmission pipe is connected to the outlet of the third heat exchange channel, and the other end is used to output natural gas. The gas transmission valve group is used to control the on / off state of the first gas transmission pipe, the second gas transmission pipe, the third gas transmission pipe, and the fourth gas transmission pipe.

[0013] In this embodiment of the invention, the gas pipeline group further includes a main gas pipeline, one end of which branches to form a second gas pipeline and a fourth gas pipeline, and the other end is used to output natural gas. A second pressure regulator is provided on the main gas pipeline.

[0014] In this embodiment of the invention, the auxiliary heat exchanger also has a switching channel, and the heat exchange device further includes a first input pipe, a second input pipe and a switching valve group. The two ends of the first input pipe are respectively connected to the outlet of the liquid nitrogen channel and the first end of the switching channel. The two ends of the second input pipe are respectively connected to the outlet of the liquid nitrogen channel and the second end of the switching channel. The switching valve group is used to select whether the first input pipe or the second input pipe is connected to the outlet of the liquid nitrogen channel.

[0015] In this embodiment of the invention, the heat exchange device further includes an output main pipe, one end of which is used to output nitrogen gas, and the other end branches to form a first output pipe and a second output pipe. The first output pipe is connected to the second end of the switching channel, and the second output pipe is connected to the first end of the switching channel. The switching valve group is also used to select the first output pipe to be connected to the switching channel when the first input pipe is connected to the outlet of the liquid nitrogen channel, and to select the second output pipe to be connected to the switching channel when the second input pipe is connected to the outlet of the liquid nitrogen channel.

[0016] In this embodiment of the invention, the draining device further includes a third pressure regulator, which is disposed on the drain pipe and located between the drain pump and the inlet of the second heat exchange channel.

[0017] In this embodiment of the invention, the draining device further includes a first storage tank, which is disposed on the draining pipe and located between the outlet of the first heat exchange channel and the draining pump. The first storage tank is used to store liquefied natural gas.

[0018] And / or, the heat exchange device further includes a second storage tank, which is located at the end of the liquid nitrogen inlet pipe away from the liquid nitrogen channel and is used to store liquid nitrogen.

[0019] Through the above technical solution, the natural gas venting and recovery system provided in this embodiment of the invention has the following beneficial effects:

[0020] In the technical solution of this invention, the natural gas venting and recovery system delivers liquid nitrogen to the liquid nitrogen channel through a liquid nitrogen input pipe, and delivers the natural gas to be vented to the first heat exchange channel through an exhaust device. The natural gas in the first heat exchange channel exchanges heat with the low-temperature liquid nitrogen introduced into the liquid nitrogen channel, so that the gaseous natural gas is liquefied into liquefied natural gas (LNG). Then, the LNG is delivered to the second heat exchange channel through a drain pipe and a drain pump to pressurize the LNG. The LNG in the second heat exchange channel exchanges heat with the gaseous natural gas in the first heat exchange channel, so that the LNG is vaporized into natural gas gas. The natural gas gas can then be directly delivered back to the natural gas pipeline or facility for on-site consumption through a gas transmission device, or it can be recycled and reused in the form of compressed natural gas. The gaseous natural gas has a wide range of applications, is flexible and convenient to use, and does not require separate storage of LNG and transportation of LNG to other usage locations, thus improving the recovery and utilization rate of vented natural gas and reducing energy waste.

[0021] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. Those skilled in the art can obtain other drawings based on the structures shown in these drawings without any inventive effort. In the drawings:

[0023] Figure 1 This is a schematic diagram of a natural gas venting and recovery system according to an embodiment of the present invention;

[0024] Figure 2 This is a structural block diagram of a natural gas venting and recovery system according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the flow direction of natural gas in the first flow channel according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the flow direction of natural gas in the second flow channel according to an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures

[0028] 10. Heat exchanger; 11. Main heat exchanger; 111. Liquid nitrogen channel; 112. First heat exchange channel; 113. Second heat exchange channel; 12. Liquid nitrogen inlet pipe; 121. Liquid nitrogen regulating valve; 13. Auxiliary heat exchanger; 131. Third heat exchange channel; 132. Fourth heat exchange channel; 133. Switching channel; 14. First inlet pipe; 15. Second inlet pipe; 16. Main outlet pipe; 161. First outlet pipe; 162. Second outlet pipe; 163. Nitrogen regulating valve; 164. Gas-liquid separator; 7. Second storage tank; 20. Exhaust device; 21. First exhaust pipe; 22. Second exhaust pipe; 23. Third exhaust pipe; 24. Fourth exhaust pipe; 25. Main exhaust pipe; 251. First pressure regulator; 30. Drainage device; 31. Drainage pipe; 32. Drainage pump; 33. Third pressure regulator; 34. First storage tank; 40. Gas supply device; 41. First gas supply pipe; 42. Second gas supply pipe; 43. Third gas supply pipe; 44. Fourth gas supply pipe; 45. Main gas supply pipe; 451. Second pressure regulator. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0030] The natural gas venting and recovery system of the present invention is described below with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the present invention provides a natural gas venting and recovery system, which includes a heat exchange device 10, an exhaust device 20, a liquid discharge device 30, and a gas transmission device 40. The heat exchange device 10 includes a main heat exchanger 11 and a liquid nitrogen input pipe 12. The main heat exchanger 11 has a liquid nitrogen channel 111, a first heat exchange channel 112, and a second heat exchange channel 113. One end of the liquid nitrogen input pipe 12 is connected to the inlet of the liquid nitrogen channel 111, and the other end is used for supplying liquid nitrogen. The exhaust device 20 is used to supply natural gas and guide it to the inlet of the first heat exchange channel 112. The liquid discharge device 30 includes a liquid discharge pipe 31 and a liquid discharge pump 32. The two ends of the liquid discharge pipe 31 are respectively connected to the outlet of the first heat exchange channel 112 and the inlet of the second heat exchange channel 113. The liquid discharge pump 32 is installed on the liquid discharge pipe 31. The gas transmission device 40 is used to connect to the outlet of the second heat exchange channel 113 and output natural gas.

[0032] Specifically, the liquid nitrogen inlet pipe 12 is used to supply liquid nitrogen and transport it to the liquid nitrogen channel 111 of the main heat exchanger 11. The exhaust device 20 can be directly connected to the pipeline or facility that needs to vent natural gas, without the need for pretreatment of the natural gas. The exhaust device 20 transports the natural gas to be vented in the pipeline to the first heat exchange channel 112 of the main heat exchanger 11, so that the liquid nitrogen in the liquid nitrogen channel 111 exchanges heat with the gaseous natural gas flowing through the first heat exchange channel 112 and liquefies the gaseous natural gas into liquefied natural gas (LNG). Liquefied natural gas (LNG) flows from the outlet of the first heat exchange channel 112 into the drain pipe 31. The drain pump 32 pumps the LNG into the second heat exchange channel 113 and increases the pressure of the LNG. The LNG flows through the second heat exchange channel 113. The gaseous natural gas in the first heat exchange channel 112 exchanges heat with the LNG in the second heat exchange channel 113 to vaporize the LNG in the second heat exchange channel 113 into natural gas gas and at the same time liquefy the gaseous natural gas in the first heat exchange channel 112 into LNG. The natural gas gas flows from the outlet of the second heat exchange channel 113 into the gas transmission device 40. The gas transmission device 40 can be connected to natural gas pipelines, facilities or compressed natural gas (CNG) storage tanks and output gaseous natural gas.

[0033] The natural gas venting and recovery system of this invention delivers liquid nitrogen to the liquid nitrogen channel 111 via the liquid nitrogen input pipe 12, and delivers the natural gas to be vented to the first heat exchange channel 112 via the exhaust device 20. The natural gas in the first heat exchange channel 112 exchanges heat with the cryogenic liquid nitrogen introduced into the liquid nitrogen channel 111, so that the gaseous natural gas is liquefied into liquefied natural gas. Then, the liquefied natural gas is delivered to the second heat exchange channel 113 via the drain pipe 31 and the drain pump 32 to pressurize the liquefied natural gas. The liquefied natural gas in the second heat exchange channel 113 exchanges heat with the gaseous natural gas in the first heat exchange channel 112, so that the liquefied natural gas is vaporized into natural gas gas. Then, the natural gas gas can be directly delivered back to the natural gas pipeline or facility for local consumption via the gas transmission device 40, or it can be recovered and reused in the form of CNG. The gaseous natural gas has a wide range of applications, is flexible and convenient to use, and does not require separate storage of liquefied natural gas and transportation of liquefied natural gas to other usage locations using tank trucks or other transportation devices, thereby improving the recovery and utilization rate of vented natural gas and reducing energy waste.

[0034] Furthermore, the discharge pump 32 can be a multi-stage cryogenic liquid pump from the prior art. The multi-stage cryogenic liquid pump can start and connect some stages individually to pump liquefied natural gas, or it can start and connect all stages to pump liquefied natural gas. This allows the discharge pump 32 to increase the pressure of liquefied natural gas during the process of pumping liquefied natural gas in the discharge pipe 31 to the second heat exchange channel 113. Moreover, the discharge pump 32 is smaller in size, has less vibration, and consumes less power than the compressor, which reduces the overall weight and size of the natural gas venting and recovery system. This makes it easier to design the natural gas venting and recovery system as a skid-mounted or other mobile type, making transportation flexible and convenient, and applicable to a wide range of situations.

[0035] In embodiments of the present invention, such as Figure 2 As shown, the heat exchange device 10 also includes an auxiliary heat exchanger 13, which has a third heat exchange channel 131 and a fourth heat exchange channel 132. An exhaust device 20 is used to supply natural gas and select the connection between the inlet of the third heat exchange channel 131 or the fourth heat exchange channel 132 and the inlet of the first heat exchange channel 112. A gas transmission device 40 is used to select the connection between the outlet of the fourth heat exchange channel 132 and the outlet of the second heat exchange channel 113 when the third heat exchange channel 131 and the first heat exchange channel 112 are connected, and to select the connection between the outlet of the third heat exchange channel 131 and the outlet of the second heat exchange channel 113 when the fourth heat exchange channel 132 and the first heat exchange channel 112 are connected, and to output natural gas. It should be noted that natural gas contains components that are easily condensed at low temperatures. These easily condensed components condense into solids, which can easily clog the flow channels, causing ice blockage.

[0036] like Figure 3As shown, the exhaust device 20 connects the inlet of the third heat exchange channel 131 to the inlet of the first heat exchange channel 112, and the gas transmission device 40 connects the outlet of the fourth heat exchange channel 132 to the outlet of the second heat exchange channel 113. This allows the third heat exchange channel 131, the first heat exchange channel 112, the drain pipe 31, the second heat exchange channel 113, and the fourth heat exchange channel 132 to be sequentially connected and form a first flow channel. The exhaust device 20 transports the natural gas to be vented into the third heat exchange channel 131, so that the gaseous natural gas flows through the third heat exchange channel 131 and the first heat exchange channel 112, and is liquefied into liquefied natural gas in the first heat exchange channel 112. The liquefied natural gas flows through the drain pipe 31 into the second heat exchange channel 113, and is vaporized into natural gas gas in the second heat exchange channel 113. The natural gas gas flows through the fourth heat exchange channel 132 and can be directly transported back to the natural gas pipeline or facility for local consumption through the gas transmission device 40.

[0037] Understandably, such as Figure 4 As shown, when natural gas condenses in the first flow channel, the exhaust device 20 connects the inlet of the fourth heat exchange channel 132 to the inlet of the first heat exchange channel 112, and the gas transmission device 40 connects the outlet of the third heat exchange channel 131 to the outlet of the second heat exchange channel 113. This allows the fourth heat exchange channel 132, the first heat exchange channel 112, the drain pipe 31, the second heat exchange channel 113, and the third heat exchange channel 131 to be sequentially connected and form the second flow channel. The exhaust device 20 then transports the natural gas to be vented into the fourth heat exchange channel 132, allowing the gaseous natural gas to flow through the fourth heat exchange channel. The gas flows through channel 132 and the first heat exchange channel 112, where it is liquefied into liquefied natural gas. The liquefied natural gas then flows through the drain pipe 31 into the second heat exchange channel 113, where it is vaporized into natural gas. The high temperature of the natural gas allows the condensed solids to be heated and vaporized when flowing through the third heat exchange channel 131, and the vaporized gas components are mixed back into the natural gas, further improving the natural gas recovery and utilization rate, reducing energy waste, and effectively preventing condensed solids from clogging the flow channels and avoiding ice blockage.

[0038] The natural gas venting and recovery system of this invention achieves switching between the first and second flow channels by selecting the third heat exchange channel 131 by the exhaust device 20 and the fourth heat exchange channel 132 by the gas transmission device 40, or by selecting the fourth heat exchange channel 132 by the exhaust device 20 and the third heat exchange channel 131 by the gas transmission device 40. This keeps the low-temperature heat exchange area in the natural gas venting and recovery system essentially unchanged, and eliminates the need for pretreatment of the vented natural gas to remove easily condensable components or the introduction of other backup heat exchange devices 10 to prevent flow channel blockage. This effectively reduces the overall weight and volume of the natural gas venting and recovery system, saves costs, and improves venting and recovery efficiency.

[0039] In a preferred embodiment of the present invention, the number of main heat exchangers 11 can be one or more, and the number of auxiliary heat exchangers 13 can be one or more. The main heat exchangers 11 and auxiliary heat exchangers 13 are connected in sequence through an exhaust device 20, a liquid drain pipe 31, and a gas transmission device 40. The natural gas venting and recovery system of the present invention does not limit the number of main heat exchangers 11 and auxiliary heat exchangers 13. Furthermore, both the main heat exchangers 11 and auxiliary heat exchangers 13 can adopt high-pressure resistant coiled tube heat exchangers, high-pressure resistant plate-fin heat exchangers, high-pressure resistant tubular heat exchangers, or other high-pressure resistant heat exchangers in the prior art. The intermediate point operating temperature of the auxiliary heat exchanger 13 is higher than the enrichment condensation temperature of the condensable components in the natural gas to be recovered. Specifically, the intermediate point operating temperature of the auxiliary heat exchanger 13 is T0, and the enrichment condensation temperature of the condensable components in the natural gas to be recovered is T1. 1℃≤(T0-T1)≤20℃, so that the condensed solids can be re-vaporized and merged with the natural gas, effectively preventing flow channel blockage. Furthermore, 3℃≤(T0-T1)≤8℃ can both absorb and fuse solids and reduce energy consumption.

[0040] In this embodiment of the invention, the exhaust device 20 includes an exhaust pipe group and an exhaust valve group. The exhaust pipe group includes a first exhaust pipe 21, a second exhaust pipe 22, a third exhaust pipe 23, and a fourth exhaust pipe 24. One end of the first exhaust pipe 21 is used to supply natural gas input, and the other end is connected to the inlet of the third heat exchange channel 131. The two ends of the second exhaust pipe 22 are respectively connected to the outlet of the third heat exchange channel 131 and the inlet of the first heat exchange channel 112. One end of the third exhaust pipe 23 is used to supply natural gas input, and the other end is connected to the inlet of the fourth heat exchange channel 132. The two ends of the fourth exhaust pipe 24 are respectively connected to the outlet of the fourth heat exchange channel 132 and the inlet of the first heat exchange channel 112. The exhaust valve group is used to control the on / off state of the first exhaust pipe 21, the second exhaust pipe 22, the third exhaust pipe 23, and the fourth exhaust pipe 24.

[0041] Furthermore, the gas transmission device 40 includes a gas transmission pipe group and a gas transmission valve group. The gas transmission pipe group includes a first gas transmission pipe 41, a second gas transmission pipe 42, a third gas transmission pipe 43, and a fourth gas transmission pipe 44. The two ends of the first gas transmission pipe 41 are respectively connected to the outlet of the second heat exchange channel 113 and the inlet of the fourth heat exchange channel 132. One end of the second gas transmission pipe 42 is connected to the outlet of the fourth heat exchange channel 132, and the other end is used to output natural gas. The two ends of the third gas transmission pipe 43 are respectively connected to the outlet of the second heat exchange channel 113 and the inlet of the third heat exchange channel 131. One end of the fourth gas transmission pipe 44 is connected to the outlet of the third heat exchange channel 131, and the other end is used to output natural gas. The gas transmission valve group is used to control the on / off state of the first gas transmission pipe 41, the second gas transmission pipe 42, the third gas transmission pipe 43, and the fourth gas transmission pipe 44.

[0042] like Figure 3As shown, the exhaust valve assembly connects the first exhaust pipe 21 to the inlet of the third heat exchange channel 131, and the two ends of the second exhaust pipe 22 are respectively connected to the outlet of the third heat exchange channel 131 and the inlet of the first heat exchange channel 112. The gas transmission device 40 connects the two ends of the first gas transmission pipe 41 to the outlet of the second heat exchange channel 113 and the inlet of the fourth heat exchange channel 132, and the second gas transmission pipe 42 is connected to the outlet of the fourth heat exchange channel 132. This allows one end of the first exhaust pipe 21 to be directly connected to the pipeline or facility that needs to be vented, so that the natural gas to be vented flows sequentially through the first exhaust pipe 21, the third heat exchange channel 131, and the second exhaust pipe 22 into the first heat exchange channel 112. The gaseous natural gas in the first heat exchange channel... The gas is liquefied into liquefied natural gas (LNG) within 112. The LNG flows through the drain pipe 31 and enters the second heat exchange channel 113, where it is vaporized into natural gas. The natural gas then flows sequentially through the first gas transmission pipe 41 and the fourth heat exchange channel 132 into the second gas transmission pipe 42. The second gas transmission pipe 42 can be connected to natural gas pipelines, facilities, or CNG storage tanks to output natural gas. The first exhaust pipe 21, the third heat exchange channel 131, the second exhaust pipe 22, the first heat exchange channel 112, the drain pipe 31, the second heat exchange channel 113, the first gas transmission pipe 41, the fourth heat exchange channel 132, and the second gas transmission pipe 42 are sequentially connected to form the first flow channel. This enables the on-site consumption of recovered natural gas or its recovery and utilization in the form of CNG, improving the natural gas recovery and utilization rate and reducing energy waste.

[0043] Understandably, such as Figure 4As shown, when natural gas condenses in the first flow channel, the exhaust valve group connects the third exhaust pipe 23 to the inlet of the fourth heat exchange channel 132, and the two ends of the fourth exhaust pipe 24 are respectively connected to the outlet of the fourth heat exchange channel 132 and the inlet of the first heat exchange channel 112. The gas transmission device 40 connects the two ends of the third gas transmission pipe 43 to the outlet of the second heat exchange channel 113 and the inlet of the third heat exchange channel 131, and the fourth gas transmission pipe 44 is connected to the outlet of the third heat exchange channel 131. This allows one end of the third exhaust pipe 23 to be directly connected to the pipeline or facility that needs to release natural gas, so that the natural gas to be released flows sequentially through the third exhaust pipe 23, the fourth heat exchange channel 132, and the fourth exhaust pipe 24 into the first heat exchange channel 112. The gaseous natural gas liquefies into liquefied natural gas in the first heat exchange channel 112. Liquefied natural gas (LNG) flows through the drain pipe 31 and enters the second heat exchange channel 113, where it is vaporized into natural gas gas. The natural gas gas then flows sequentially through the third gas transmission pipe 43 and the third heat exchange channel 131 into the fourth gas transmission pipe 44. The fourth gas transmission pipe 44 can connect to natural gas pipelines, facilities, or CNG storage tanks to output natural gas gas. The third exhaust pipe 23, the fourth heat exchange channel 132, the fourth exhaust pipe 24, the first heat exchange channel 112, the drain pipe 31, the second heat exchange channel 113, the third gas transmission pipe 43, the third heat exchange channel 131, and the fourth gas transmission pipe 44 are sequentially connected to form the second flow channel. This not only enables on-site consumption of recovered natural gas, improving the recovery rate and reducing energy waste, but also heats and absorbs condensed solids, causing the condensed solids to vaporize and merge with the natural gas gas, effectively preventing condensed solids from clogging the flow channel and avoiding ice blockage. Furthermore, when natural gas condenses in the second flow channel, it can be switched to the first flow channel to vent and recover natural gas and absorb the condensed solids, making it flexible and convenient to use.

[0044] In a preferred embodiment of the present invention, the exhaust valve assembly includes a first exhaust valve on the first exhaust pipe 21, a second exhaust valve on the second exhaust pipe 22, a third exhaust valve on the third exhaust pipe 23, and a fourth exhaust valve on the fourth exhaust pipe 24. The gas transmission valve assembly includes a first gas transmission valve on the first gas transmission pipe 41, a second gas transmission valve on the second gas transmission pipe 42, a third gas transmission valve on the third gas transmission pipe 43, and a fourth gas transmission valve on the fourth gas transmission pipe 44. When the first flow channel is selected for natural gas venting and recovery, the first exhaust valve, the second exhaust valve, the first gas transmission valve, and the second gas transmission valve are open, while the third exhaust valve, the fourth exhaust valve, the third gas transmission valve, and the fourth gas transmission valve are closed. When the second flow channel is selected for natural gas venting and recovery, the third exhaust valve, the fourth exhaust valve, the third gas transmission valve, and the fourth gas transmission valve are open, while the first exhaust valve, the second exhaust valve, the first gas transmission valve, and the second gas transmission valve are closed. This enables switching between the first and second flow channels, making it flexible and convenient to use.

[0045] Those skilled in the art will understand that the exhaust valve assembly and gas delivery valve assembly of this application are not limited to the above-described structural forms. Pipeline connections, three-way valves, or other structural forms that can switch between the first flow channel and the second flow channel should also be within the protection scope of this application.

[0046] In this embodiment of the invention, the auxiliary heat exchanger 13 also has a switching channel 133, and the heat exchange device 10 further includes a first input pipe 14, a second input pipe 15 and a switching valve group. The two ends of the first input pipe 14 are respectively connected to the outlet of the liquid nitrogen channel 111 and the first end of the switching channel 133. The two ends of the second input pipe 15 are respectively connected to the outlet of the liquid nitrogen channel 111 and the second end of the switching channel 133. The switching valve group is used to select whether the first input pipe 14 or the second input pipe 15 is connected to the outlet of the liquid nitrogen channel 111.

[0047] like Figure 3 As shown, when the natural gas venting and recovery system switches to the first flow channel for natural gas venting and recovery, the switching valve group selects the two ends of the first input pipe 14 to be connected one-to-one with the outlet of the liquid nitrogen channel 111 and the first end of the switching channel 133, respectively. This allows liquid nitrogen to flow sequentially through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111, and the first input pipe 14, and then flow into the switching channel 133 from the first end of the switching channel 133. This initially liquefies the gaseous natural gas flowing through the third heat exchange channel 131, further improving the recovery efficiency. It can be understood that, as... Figure 4 As shown, when the natural gas venting and recovery system switches to the second flow channel for natural gas venting and recovery, the two ends of the switching valve group select the second input pipe 15 to be connected to the outlet of the liquid nitrogen channel 111 and the second end of the switching channel 133 respectively, so that liquid nitrogen flows through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111 and the second input pipe 15 in sequence, and flows into the switching channel 133 from the second end of the switching channel 133, so as to initially liquefy the gaseous natural gas flowing through the fourth heat exchange channel 132, and further improve the recovery efficiency.

[0048] In this embodiment of the invention, the heat exchange device 10 further includes an output main pipe 16, one end of which is used to output nitrogen gas, and the other end branches to form a first output pipe 161 and a second output pipe 162. The first output pipe 161 is connected to the second end of the switching channel 133, and the second output pipe 162 is connected to the first end of the switching channel 133. The switching valve group is also used to select the first output pipe 161 to be connected to the switching channel 133 when the first input pipe 14 is connected to the outlet of the liquid nitrogen channel 111, and to select the second output pipe 162 to be connected to the switching channel 133 when the second input pipe 15 is connected to the outlet of the liquid nitrogen channel 111.

[0049] like Figure 3As shown, when the natural gas venting and recovery system switches to the first flow channel for natural gas venting and recovery, the switching valve group selects the two ends of the first input pipe 14 to be connected to the outlet of the liquid nitrogen channel 111 and the first end of the switching channel 133 respectively, and selects the first output pipe 161 to be connected to the second end of the switching channel 133. This allows liquid nitrogen to flow sequentially through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111 and the first input pipe 14, and then flow into the switching channel 133 from the first end of the switching channel 133. The liquid nitrogen initially liquefies the gaseous natural gas flowing through the third heat exchange channel 131, and the liquid nitrogen is vaporized into nitrogen gas in the switching channel 133. The nitrogen gas flows sequentially from the second end of the switching channel 133 into the first output pipe 161 and is discharged from the end of the output pipe 16 away from the switching channel 133, thereby improving the natural gas recovery and utilization rate and reducing energy waste.

[0050] Understandably, such as Figure 4 As shown, when the natural gas venting and recovery system switches to the second flow channel for natural gas venting and recovery, the switching valve group selects the two ends of the second input pipe 15 to be connected to the outlet of the liquid nitrogen channel 111 and the second end of the switching channel 133 respectively, and selects the second output pipe 162 to be connected to the first end of the switching channel 133. This allows liquid nitrogen to flow sequentially through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111, and the second input pipe 15, and then flow into the switching channel 133 from the second end of the switching channel 133. The liquid nitrogen will initially liquefy the gaseous natural gas flowing through the fourth heat exchange channel 132, and the liquid nitrogen will be vaporized into nitrogen gas in the switching channel 133. The nitrogen gas will flow sequentially from the first end of the switching channel 133 into the second output pipe 162, and then be discharged from the end of the output pipe 16 away from the switching channel 133. This improves the natural gas recovery and utilization rate and reduces energy waste.

[0051] Furthermore, a gas-liquid separator 164 is provided on the output main pipe 16. The gas-liquid separator 164 is used to separate nitrogen gas and liquid nitrogen in the output main pipe 16. The separated nitrogen gas is discharged from the output main pipe 16, and the separated liquid nitrogen can be recovered and reintroduced into the liquid nitrogen input pipe 12, further reducing energy waste. In addition, a liquid nitrogen regulating valve 121 is provided on the liquid nitrogen input pipe 12, and a nitrogen regulating valve 163 is provided on the output main pipe 16. The liquid nitrogen regulating valve 121 is used to regulate the flow rate of liquid nitrogen, and the nitrogen regulating valve 163 is used to regulate the flow rate of nitrogen gas, so as to improve the stability of the system.

[0052] In a preferred embodiment of the present invention, the switching valve group includes a first input valve on the first input pipe 14, a second input valve on the second input pipe 15, a first output valve on the first output pipe 161, and a second output valve on the second output pipe 162. When the first flow channel is selected for natural gas venting and recovery, the first input valve and the first output valve are opened, and the second input valve and the second output valve are closed. When the second flow channel is selected for natural gas venting and recovery, the second input valve and the second output valve are opened, and the first input valve and the first output valve are closed, thereby realizing the switching between liquid nitrogen flow direction and nitrogen flow direction, which is flexible and convenient to use.

[0053] Those skilled in the art will understand that the switching valve assembly of this application is not limited to the above-described structural form. Pipeline connection, three-way valve, or other structural forms that can switch the flow direction of liquid nitrogen and nitrogen should also be within the protection scope of this application.

[0054] In this embodiment of the invention, the exhaust pipe assembly further includes an exhaust main pipe 25, one end of which branches to form a first exhaust pipe 21 and a third exhaust pipe 23, and the other end is used for natural gas input. A first pressure regulator 251 is provided on the exhaust main pipe 25. Figure 2 As shown, one end of the exhaust pipe 25 branches into a first exhaust pipe 21 and a third exhaust pipe 23. The other end of the exhaust pipe 25 can be directly connected to the pipeline or facility that needs to vent natural gas, so that the natural gas to be vented can enter the exhaust pipe 25 and flow through the exhaust pipe 25 into the first exhaust pipe 21 or the third exhaust pipe 23. There is no need to perform pretreatment such as removal of easily condensable components from the natural gas to be vented, which improves the venting recovery efficiency. In addition, the exhaust pipe 25 is equipped with a first pressure regulator 251, which is used to reduce the pressure drop of the natural gas to be vented, so as to facilitate the recovery of natural gas.

[0055] In this embodiment of the invention, the gas pipeline assembly further includes a main gas pipeline 45, one end of which branches to form a second gas pipeline 42 and a fourth gas pipeline 44, and the other end is used to output natural gas. A second pressure regulator 451 is provided on the main gas pipeline 45. Figure 2 As shown, one end of the main gas transmission pipe 45 branches to form a second gas transmission pipe 42 and a fourth gas transmission pipe 44. The other end of the main gas transmission pipe 45 can be connected to a natural gas pipeline, facility or CNG storage tank to directly output natural gas. Gaseous natural gas has a wide range of applications and is flexible and convenient to use, which improves the recovery and utilization rate of vented natural gas and reduces energy waste. In addition, the main gas transmission pipe 45 is equipped with a second pressure regulator 451, which is used to reduce the pressure drop of natural gas to facilitate the application of the output natural gas.

[0056] Furthermore, the drainage device 30 also includes a third pressure regulator 33, which is disposed on the drainage pipe 31 and located between the drainage pump 32 and the inlet of the second heat exchange channel 113. Figure 2 As shown, the third pressure regulator 33 is used to reduce the pressure drop of liquefied natural gas, further reducing energy consumption and improving system stability.

[0057] In a preferred embodiment of the present invention, the natural gas venting and recovery system further includes a controller, which is communicatively connected to the first pressure regulator 251, the second pressure regulator 451, and the third pressure regulator 33, respectively. The controller is configured to, upon receiving a pressure adjustment command, sequentially adjust the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 to their respective preset pressure drop ranges. Specifically, the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 can all reduce the pressure drop. By sequentially reducing the pressure drop of the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 to their respective preset pressure drop ranges, the pressure of the natural gas is increased, so that the pressure of the natural gas output from the gas transmission main pipe 45 meets the usage requirements and can be directly connected to the natural gas pipeline or facility, ensuring the local consumption of the recovered natural gas.

[0058] In this embodiment of the invention, as shown in Table 1, which is a composition table of the natural gas to be vented, and with an ambient temperature of 30°C, the liquid nitrogen consumption can be obtained by using a natural gas venting and recovery system to vent and recover the natural gas as shown in Table 2. Table 2 is a table of liquid nitrogen consumption for vented and recovered natural gas. The pressure required for the gas transmission main pipe 45 to output natural gas to the natural gas pipeline or facility is 8.0 MPa. According to Table 2, using a natural gas venting and recovery system to vent and recover natural gas is not only green and environmentally friendly, reducing pollution, but also reduces costs and energy waste.

[0059] Table 1. Composition of Natural Gas to be Vented

[0060]

[0061] Table 2. Consumption of Liquid Nitrogen from Vented Natural Gas Recovery

[0062]

[0063] In this embodiment of the invention, the draining device 30 further includes a first storage tank 34, which is disposed on the drain pipe 31 and located between the outlet of the first heat exchange channel 112 and the draining pump 32. The first storage tank 34 is used to store liquefied natural gas. Figure 1 and Figure 2As shown, gaseous natural gas flows through the first heat exchange channel 112 and is liquefied into liquefied natural gas. The liquefied natural gas can be stored in the first storage tank 34 so that it can be subsequently gasified through the second heat exchange channel 113 and consumed locally or transported to other places of use, effectively reducing energy waste and improving the recycling rate.

[0064] Furthermore, the heat exchange device 10 also includes a second storage tank 17, which is located at the end of the liquid nitrogen inlet pipe 12 away from the liquid nitrogen channel 111 and is used to store liquid nitrogen. Figure 1 and Figure 2 As shown, the liquid nitrogen in the second storage tank 17 can be transported to the liquid nitrogen channel 111 through the liquid nitrogen input pipe 12 to liquefy natural gas. Using the second storage tank 17 to store liquid nitrogen facilitates the design of the natural gas venting and recovery system as a skid-mounted or other mobile type, making transportation flexible and convenient, and applicable to a wide range of situations.

[0065] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0066] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A natural gas venting and recovery system, characterized in that, The natural gas venting and recovery system includes: The heat exchange device (10) includes a main heat exchanger (11) and a liquid nitrogen input pipe (12). The main heat exchanger (11) has a liquid nitrogen channel (111), a first heat exchange channel (112) and a second heat exchange channel (113). One end of the liquid nitrogen input pipe (12) is connected to the inlet of the liquid nitrogen channel (111), and the other end is used for supplying liquid nitrogen. An exhaust device (20) is provided for supplying natural gas and directing it to the inlet of the first heat exchange channel (112); The draining device (30) includes a drain pipe (31) and a drain pump (32). The two ends of the drain pipe (31) are respectively connected to the outlet of the first heat exchange channel (112) and the inlet of the second heat exchange channel (113). The drain pump (32) is installed on the drain pipe (31). Gas transmission device (40) is used to connect to the outlet of the second heat exchange channel (113) and output natural gas; The heat exchange device (10) further includes an auxiliary heat exchanger (13), which has a third heat exchange channel (131) and a fourth heat exchange channel (132). The exhaust device (20) is used to supply natural gas input and select the inlet of the third heat exchange channel (131) or the fourth heat exchange channel (132) to be connected with the inlet of the first heat exchange channel (112). The gas transmission device (40) is used to select the outlet of the fourth heat exchange channel (132) to be connected with the outlet of the second heat exchange channel (113) and output natural gas when the third heat exchange channel (131) is connected with the first heat exchange channel (112), and to select the outlet of the third heat exchange channel (131) to be connected with the outlet of the second heat exchange channel (113) and output natural gas when the fourth heat exchange channel (132) is connected with the first heat exchange channel (112).

2. The natural gas venting and recovery system according to claim 1, characterized in that, The exhaust device (20) includes an exhaust pipe group and an exhaust valve group. The exhaust pipe group includes a first exhaust pipe (21), a second exhaust pipe (22), a third exhaust pipe (23), and a fourth exhaust pipe (24). One end of the first exhaust pipe (21) is used for natural gas input, and the other end is connected to the inlet of the third heat exchange channel (131). The two ends of the second exhaust pipe (22) are respectively connected to the outlet of the third heat exchange channel (131) and the inlet of the first heat exchange channel (112). One end of the third exhaust pipe (23) is used for natural gas input, and the other end is connected to the inlet of the fourth heat exchange channel (132). The two ends of the fourth exhaust pipe (24) are respectively connected to the outlet of the fourth heat exchange channel (132) and the inlet of the first heat exchange channel (112). The exhaust valve group is used to control the on / off state of the first exhaust pipe (21), the second exhaust pipe (22), the third exhaust pipe (23), and the fourth exhaust pipe (24).

3. The natural gas venting and recovery system according to claim 2, characterized in that, The exhaust pipe assembly also includes an exhaust main pipe (25), one end of which branches to form the first exhaust pipe (21) and the third exhaust pipe (23), and the other end is used for natural gas input. The exhaust main pipe (25) is provided with a first pressure regulator (251).

4. The natural gas venting and recovery system according to claim 1, characterized in that, The gas delivery device (40) includes a gas delivery pipe group and a gas delivery valve group. The gas delivery pipe group includes a first gas delivery pipe (41), a second gas delivery pipe (42), a third gas delivery pipe (43), and a fourth gas delivery pipe (44). The two ends of the first gas delivery pipe (41) are respectively connected to the outlet of the second heat exchange channel (113) and the inlet of the fourth heat exchange channel (132). One end of the second gas delivery pipe (42) is connected to the outlet of the fourth heat exchange channel (132), and the other end is used to output gas. Natural gas is supplied through the third gas pipeline (43), which is connected to the outlet of the second heat exchange channel (113) and the inlet of the third heat exchange channel (131) at both ends. One end of the fourth gas pipeline (44) is connected to the outlet of the third heat exchange channel (131), and the other end is used to supply natural gas. The gas supply valve group is used to control the on / off state of the first gas pipeline (41), the second gas pipeline (42), the third gas pipeline (43), and the fourth gas pipeline (44).

5. The natural gas venting and recovery system according to claim 4, characterized in that, The gas pipeline group also includes a main gas pipeline (45), one end of which branches to form the second gas pipeline (42) and the fourth gas pipeline (44), and the other end is used to output natural gas. A second pressure regulator (451) is provided on the main gas pipeline (45).

6. The natural gas venting and recovery system according to claim 1, characterized in that, The auxiliary heat exchanger (13) also has a switching channel (133). The heat exchange device (10) further includes a first input pipe (14), a second input pipe (15), and a switching valve group. The two ends of the first input pipe (14) are respectively connected to the outlet of the liquid nitrogen channel (111) and the first end of the switching channel (133). The two ends of the second input pipe (15) are respectively connected to the outlet of the liquid nitrogen channel (111) and the second end of the switching channel (133). The switching valve group is used to select whether the first input pipe (14) or the second input pipe (15) is connected to the outlet of the liquid nitrogen channel (111).

7. The natural gas venting and recovery system according to claim 6, characterized in that, The heat exchange device (10) further includes an output main pipe (16), one end of which is used to output nitrogen gas, and the other end branches to form a first output pipe (161) and a second output pipe (162). The first output pipe (161) is connected to the second end of the switching channel (133), and the second output pipe (162) is connected to the first end of the switching channel (133). The switching valve group is also used to select the first output pipe (161) to be connected to the switching channel (133) when the first input pipe (14) is connected to the outlet of the liquid nitrogen channel (111), and to select the second output pipe (162) to be connected to the switching channel (133) when the second input pipe (15) is connected to the outlet of the liquid nitrogen channel (111).

8. The natural gas venting and recovery system according to any one of claims 1 to 7, characterized in that, The draining device (30) also includes a third pressure regulator (33), which is located on the drain pipe (31) and between the drain pump (32) and the inlet of the second heat exchange channel (113).

9. The natural gas venting and recovery system according to any one of claims 1 to 7, characterized in that, The draining device (30) further includes a first storage tank (34), which is disposed on the drain pipe (31) and located between the outlet of the first heat exchange channel (112) and the draining pump (32). The first storage tank (34) is used to store liquefied natural gas. And / or, the heat exchange device (10) further includes a second storage tank (17), which is located at one end of the liquid nitrogen input pipe (12) away from the liquid nitrogen channel (111) and is used to store liquid nitrogen.

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