Natural gas emptying and recycling system

Abstract

The natural gas emptying and recycling system comprises a heat exchange device, a gas exhausting device, a liquid discharging device and a gas conveying device, the heat exchange device comprises a main heat exchanger and a liquid nitrogen input pipe, and the main heat exchanger is provided with a liquid nitrogen channel, a first heat exchange channel and a second heat exchange channel; one end of the liquid nitrogen input pipe is communicated with an inlet of the liquid nitrogen channel, and the other end is used for inputting liquid nitrogen; the exhaust device is used for inputting natural gas and guiding the natural gas to an inlet of the first heat exchange channel, the liquid drainage device comprises a liquid drainage pipe and a liquid drainage pump, the two ends of the liquid drainage pipe communicate with an outlet of the first heat exchange channel and an inlet of the second heat exchange channel in a one-to-one correspondence mode, and the liquid drainage pump is arranged on the liquid drainage pipe. The gas conveying device is used for being communicated with an outlet of the second heat exchange channel and outputting natural gas, the gas conveying device directly conveys the natural gas back to a natural gas pipeline or facility to be absorbed on site, the recycling rate of the vented natural gas is increased, and energy waste is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas venting, and in particular relates to a natural gas venting recovery system. Background Art

[0002] Operations such as natural gas pipeline maintenance, fire, and line modification all require that the natural gas in the pipeline be vented first, and the natural gas vented from the pipeline can be recycled. At present, the main methods for natural gas venting recovery are compression venting recovery and liquefaction venting recovery. Among them, compression venting recovery usually uses a multi-stage reciprocating compressor for venting recovery. Due to the limitation of the compressor's own pressure ratio, when the pressure of the natural gas to be recovered is reduced to a certain value, the working efficiency of the compressor is sharply reduced. At the same time, due to the limitation of the maximum working pressure ratio of the compressor, the pressure of the natural gas that can be recovered is also limited. In addition, the compressor has a large pressure ratio and a large number of stages, resulting in a large weight and size of the entire set of venting recovery equipment, which is difficult to move and transport and inflexible to use. In addition, the existing liquefaction venting recovery is usually recovered in the form of liquefied natural gas (LNG). Liquefied natural gas needs to be stored separately and transported to other use locations by tank trucks before it can be consumed. It is difficult to find a suitable way to use it. Liquefied natural gas is inconvenient to use and has a low utilization rate, which can easily cause energy waste. Summary of the invention

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

[0004] In order to achieve the above object, the present invention provides a natural gas venting and recovery system, which comprises:

[0005] The heat exchange device comprises a main heat exchanger and a liquid nitrogen input pipe, wherein 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 liquid nitrogen input;

[0006] An exhaust device, used for inputting natural gas and directing it to the inlet of the first heat exchange channel;

[0007] The liquid discharge device comprises a liquid discharge pipe and a liquid discharge pump, wherein two ends of the liquid discharge pipe are respectively connected to the outlet of the first heat exchange channel and the inlet of the second heat exchange channel in a one-to-one correspondence, and the liquid discharge pump is arranged on the liquid discharge pipe;

[0008] The gas delivery device is used to communicate with the outlet of the second heat exchange channel and output natural gas.

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

[0010] In an embodiment of the present 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 in a one-to-one correspondence, 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 in a one-to-one correspondence, and the exhaust valve group is used to respectively 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 an embodiment of the present invention, the exhaust pipe group further includes an exhaust main pipe, one end of which branches into a first exhaust pipe and a third exhaust pipe, and the other end is used for natural gas input, and a first pressure regulator is provided on the exhaust main pipe.

[0012] In an embodiment of the present invention, the gas delivery device includes a gas delivery pipe group and a gas delivery valve group, the gas delivery pipe group includes a first gas delivery pipe, a second gas delivery pipe, a third gas delivery pipe and a fourth gas delivery pipe, the two ends of the first gas delivery pipe are respectively connected to the outlet of the second heat exchange channel and the inlet of the fourth heat exchange channel in a one-to-one correspondence, one end of the second gas delivery 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 delivery pipe are respectively connected to the outlet of the second heat exchange channel and the inlet of the third heat exchange channel in a one-to-one correspondence, one end of the fourth gas delivery pipe is connected to the outlet of the third heat exchange channel and the other end is used to output natural gas, and the gas delivery valve group is used to respectively control the on-off status of the first gas delivery pipe, the second gas delivery pipe, the third gas delivery pipe and the fourth gas delivery pipe.

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

[0014] In an embodiment of the present invention, the auxiliary heat exchanger further 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 with the outlet of the liquid nitrogen channel and the first end of the switching channel in a one-to-one correspondence, the two ends of the second input pipe are respectively connected with the outlet of the liquid nitrogen channel and the second end of the switching channel in a one-to-one correspondence, and the switching valve group is used to select the first input pipe or the second input pipe to be connected with the outlet of the liquid nitrogen channel.

[0015] In an embodiment of the present invention, the heat exchange device further includes an output main pipe, one end of which is used to output nitrogen, and the other end of which is branched 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, and the switching valve group is further 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 an embodiment of the present invention, the liquid discharge device further comprises a third pressure regulator, which is disposed on the liquid discharge pipe and located between the liquid discharge pump and the inlet of the second heat exchange channel.

[0017] In an embodiment of the present invention, the liquid discharge device further comprises a first storage tank, which is arranged on the liquid discharge pipe and located between the outlet of the first heat exchange channel and the liquid discharge pump, and the first storage tank is used to store liquefied natural gas;

[0018] And / or, the heat exchange device further comprises a second storage tank, which is arranged at one end of the liquid nitrogen input 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 by the embodiment of the present invention has the following beneficial effects:

[0020] In the technical solution of the present invention, the natural gas venting and recovery system transports liquid nitrogen into the liquid nitrogen channel through the liquid nitrogen input pipe, and transports the natural gas to be vented into the first heat exchange channel through the 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. Then, the liquefied natural gas is transported to the second heat exchange channel through the discharge pipe and the discharge pump to increase the pressure of the liquefied natural gas. The liquefied natural gas in the second heat exchange channel exchanges heat with the gaseous natural gas in the first heat exchange channel, so that the liquefied natural gas is gasified into natural gas gas. Then, the natural gas gas can be directly transported back to the natural gas pipeline or facility through the gas transmission device for on-site consumption, or recycled in the form of compressed natural gas. The gaseous natural gas has a wide range of applications and is flexible and convenient to use. There is no need to store the liquefied natural gas separately and transport it to other use locations, which improves the recovery rate of the vented natural gas and reduces energy waste.

[0021] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative work. In the accompanying drawings:

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

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

[0025] Figure 3 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 Schematic diagram of the flow direction of natural gas in the second flow channel according to an embodiment of the present invention.

[0027] Description of Reference Numerals

[0028] 10 Heat exchange device 20 Exhaust device

[0029] 11 Main heat exchanger 21 First exhaust pipe

[0030] 111 Liquid nitrogen channel 22 Second exhaust pipe

[0031] 112 first heat exchange channel 23 third exhaust pipe

[0032] 113 second heat exchange channel 24 fourth exhaust pipe

[0033] 12 Liquid nitrogen inlet pipe 25 Exhaust main pipe

[0034] 121 Liquid nitrogen regulating valve 251 First pressure regulator

[0035] 13 Auxiliary heat exchanger 30 drainage device

[0036] 131 Third heat exchange channel 31 Drain pipe

[0037] 132 Fourth heat exchange channel 32 Liquid discharge pump

[0038] 133 Switch channel 33 Third voltage regulator

[0039] 14 first input pipe 34 first storage tank

[0040] 15 Second input pipe 40 Gas delivery device

[0041] 16 Output main pipe 41 First gas pipe

[0042] 161 first output pipe 42 second gas pipe

[0043] 162 Second output pipe 43 Third gas pipe

[0044] 163 Nitrogen regulating valve 44 Fourth gas pipeline

[0045] 164 Gas-liquid separator 45 Gas main pipe

[0046] 17 Second storage tank 451 Second voltage regulator DETAILED DESCRIPTION

[0047] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0048] The natural gas venting and recovery system of the present invention will be described below with reference to the accompanying drawings.

[0049] 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 drainage 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 liquid nitrogen input; the exhaust device 20 is used for natural gas input and guides the inlet of the first heat exchange channel 112. The drainage device 30 includes a drainage pipe 31 and a drainage pump 32. The two ends of the drainage 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 in a one-to-one correspondence. The drainage pump 32 is arranged on the drainage pipe 31. The gas transmission device 40 is used to communicate with the outlet of the second heat exchange channel 113 and output natural gas.

[0050] Specifically, the liquid nitrogen input pipe 12 is used to input liquid nitrogen and transport the liquid nitrogen 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 the natural gas, without pre-processing 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 (Liquefied Natural Gas). The liquefied natural gas flows into the discharge pipe 31 from the outlet of the first heat exchange channel 112, and the discharge pump 32 pumps the liquefied natural gas into the second heat exchange channel 113 and increases the pressure of the liquefied natural gas. The liquefied natural gas flows through the second heat exchange channel 113, and the gaseous natural gas in the first heat exchange channel 112 exchanges heat with the liquefied natural gas in the second heat exchange channel 113 to gasify the liquefied natural gas in the second heat exchange channel 113 into natural gas gas and simultaneously liquefy the gaseous natural gas in the first heat exchange channel 112 into liquefied natural gas, and the natural gas gas flows into the gas transmission device 40 from the outlet of the second heat exchange channel 113, and the gas transmission device 40 can be connected to a natural gas pipeline, a facility or a compressed natural gas (Compressed Natural Gas, CNG) storage tank and output gaseous natural gas.

[0051] The natural gas venting and recovery system of the embodiment of the present invention transports liquid nitrogen to the liquid nitrogen channel 111 through the liquid nitrogen input pipe 12, and transports the natural gas to be vented to the first heat exchange channel 112 through the exhaust device 20. The natural gas in the first heat exchange channel 112 exchanges heat with the low-temperature 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 transported to the second heat exchange channel 113 through the discharge pipe 31 and the discharge pump 32 to increase the pressure of 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 gasified into natural gas gas, and then the natural gas gas can be directly transported back to the natural gas pipeline or facility through the gas transmission device 40 for on-site consumption, or recycled in the form of CNG. The gaseous natural gas has a wide range of applications and is flexible and convenient to use. There is no need to store liquefied natural gas separately and use tank trucks and other transportation devices to transport liquefied natural gas to other use locations, thereby improving the recovery rate of the vented natural gas and reducing energy waste.

[0052] Furthermore, the liquid discharge pump 32 may adopt a multi-stage cryogenic liquid pump in the prior art. The multi-stage cryogenic liquid pump may be started partially and connected separately to pump liquefied natural gas, or all stages may be started and connected to pump liquefied natural gas. This allows the liquid discharge pump 32 to increase the pressure of the liquefied natural gas in the process of pumping the liquefied natural gas in the liquid discharge pipe 31 into the second heat exchange channel 113. The liquid discharge pump 32 is smaller in size, has less vibration, and consumes less power than a compressor, thereby reducing the overall weight and size of the natural gas venting and recovery system, making it easier to design the natural gas venting and recovery system as a skid-mounted or other movable form, which is flexible and convenient to transport and has a wide range of applications.

[0053] In the embodiment of the present invention, Figure 2 As shown, the heat exchange device 10 further includes an auxiliary heat exchanger 13, the auxiliary heat exchanger 13 has a third heat exchange channel 131 and a fourth heat exchange channel 132, the exhaust device 20 is used for inputting natural gas and selecting the third heat exchange channel 131 or the fourth heat exchange channel 132 to be connected to the inlet of the first heat exchange channel 112, and the gas delivery device 40 is used for selecting the fourth heat exchange channel 132 to be connected to the outlet of the second heat exchange channel 113 and outputting natural gas when the third heat exchange channel 131 is connected to the first heat exchange channel 112, and selecting the third heat exchange channel 131 to be connected to the outlet of the second heat exchange channel 113 and outputting natural gas when the fourth heat exchange channel 132 is connected to the first heat exchange channel 112. It should be noted that natural gas contains low-temperature easily condensable components, and the easily condensable components condense into solids and easily block the flow channel, causing ice blocking.

[0054] like Figure 3 As shown, the exhaust device 20 selects the third heat exchange channel 131 to be connected to the inlet of the first heat exchange channel 112, and the gas transmission device 40 selects the fourth heat exchange channel 132 to be connected to the outlet of the second heat exchange channel 113, so that 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 are connected in sequence to form a first flow channel, and the exhaust device 20 transmits the natural gas to be discharged 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 gasified 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 through the gas transmission device 40 for on-site consumption.

[0055] Understandably, if Figure 4As shown, when natural gas condenses in the first flow channel, the exhaust device 20 selects the fourth heat exchange channel 132 to be connected to the inlet of the first heat exchange channel 112, and the gas transmission device 40 selects the third heat exchange channel 131 to be connected to the outlet of the second heat exchange channel 113, so that 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 are connected in sequence to form a second flow channel, and the exhaust device 20 transmits the natural gas to be vented to the fourth heat exchange channel 132, so that the gaseous natural gas flows through the fourth heat exchange channel 132. The heat exchange passage 132 and the first heat exchange passage 112 are connected, and are liquefied into liquefied natural gas in the first heat exchange passage 112. The liquefied natural gas flows through the discharge pipe 31 into the second heat exchange passage 113, and is vaporized into natural gas in the second heat exchange passage 113. The high temperature of the natural gas can heat and vaporize the condensed solids when flowing through the third heat exchange passage 131, and mix the vaporized gas components back into the natural gas, further improving the recovery rate of the natural gas, reducing energy waste, and effectively preventing the condensed solids from blocking the flow passage, thus avoiding ice blockage.

[0056] The natural gas venting and recovery system of the embodiment of the present invention selects the third heat exchange channel 131 through the exhaust device 20 and the fourth heat exchange channel 132 through the gas transmission device 40, or the exhaust device 20 selects the fourth heat exchange channel 132 and the gas transmission device 40 selects the third heat exchange channel 131, thereby realizing the switching of the first flow channel and the second flow channel, so that the low-temperature heat exchange area in the natural gas venting and recovery system remains basically unchanged, and there is no need to pretreat the natural gas to be vented to remove easily condensable components or introduce other spare heat exchange devices 10 to prevent flow channel blockage, which effectively reduces the overall weight and volume of the natural gas venting and recovery system, saves costs, and improves the venting and recovery efficiency.

[0057] In a preferred embodiment of the present invention, the number of main heat exchangers 11 may be one or more, the number of auxiliary heat exchangers 13 may be one or more, the main heat exchanger 11 and the auxiliary heat exchanger 13 are connected in sequence through the exhaust device 20, the drain pipe 31 and the gas transmission device 40, and 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; and the main heat exchanger 11 and the auxiliary heat exchanger 13 can both adopt the high-pressure coil heat exchanger, high-pressure plate-fin heat exchanger, high-pressure shell-and-tube heat exchanger or other high-pressure heat exchangers in the prior art, the midpoint operating temperature of the auxiliary heat exchanger 13 is higher than the enrichment and condensation temperature of the condensable components in the natural gas to be recovered, specifically, the midpoint operating temperature of the auxiliary heat exchanger 13 is T0, the enrichment and condensation temperature of the condensable components in the natural gas to be recovered is T1, 1°C≤(T0-T1)≤20°C, so that the condensed solid can be re-gasified and merged with the natural gas gas, effectively preventing the flow channel from being blocked. Furthermore, 3℃≤(T0-T1)≤8℃, which can not only absorb, fuse and condense solids, but also reduce energy consumption.

[0058] In the embodiment of the present 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 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 in a one-to-one correspondence. 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 in a one-to-one correspondence. 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 respectively.

[0059] In addition, 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 in a one-to-one correspondence. 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 natural gas. The two ends of the third gas delivery 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 in a one-to-one correspondence. One end of the fourth gas delivery 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 delivery valve group is used to control the on-off status of the first gas delivery pipe 41, the second gas delivery pipe 42, the third gas delivery pipe 43 and the fourth gas delivery pipe 44 respectively.

[0060] like Figure 3As shown, the exhaust valve group selects the first exhaust pipe 21 to be connected to the inlet of the third heat exchange channel 131, and the two ends of the second exhaust pipe 22 are connected to the outlet of the third heat exchange channel 131 and the inlet of the first heat exchange channel 112 in a one-to-one correspondence, and the gas transmission device 40 selects the two ends of the first gas transmission pipe 41 to be connected to the outlet of the second heat exchange channel 113 and the inlet of the fourth heat exchange channel 132 in a one-to-one correspondence, and the second gas transmission pipe 42 is connected to the outlet of the fourth heat exchange channel 132, so that one end of the first exhaust pipe 21 can be directly connected to the pipeline or facility that needs to be vented with natural gas, so that the natural gas to be vented flows through the first exhaust pipe 21, the third heat exchange channel 131, and the second exhaust pipe 22 in sequence into the first heat exchange channel 112, and the gaseous natural gas in the first heat exchange channel The natural gas is liquefied into liquefied natural gas in 112, and the liquefied natural gas flows through the discharge pipe 31 and enters the second heat exchange channel 113 to be gasified into natural gas gas. The natural gas flows through the first gas pipeline 41 and the fourth heat exchange channel 132 in sequence to enter the second gas pipeline 42. The second gas pipeline 42 can be connected with a natural gas pipeline, facility or CNG storage tank and output natural gas gas; the first exhaust pipe 21, the third heat exchange channel 131, the second exhaust pipe 22, the first heat exchange channel 112, the discharge pipe 31, the second heat exchange channel 113, the first gas pipeline 41, the fourth heat exchange channel 132 and the second gas pipeline 42 are connected in sequence to form a first flow channel, which realizes the on-site consumption of the recovered natural gas or its recycling in the form of CNG, improves the recovery rate of natural gas, and reduces energy waste.

[0061] Understandably, if Figure 4As shown, when natural gas condenses in the first flow channel, the exhaust valve group selects the third exhaust pipe 23 to be connected to the inlet of the fourth heat exchange channel 132, and the two ends of the fourth exhaust pipe 24 are connected to the outlet of the fourth heat exchange channel 132 and the inlet of the first heat exchange channel 112 in a one-to-one correspondence, and the gas transmission device 40 selects the two ends of the third gas transmission pipe 43 to be connected to the outlet of the second heat exchange channel 113 and the inlet of the third heat exchange channel 131 in a one-to-one correspondence, and the fourth gas transmission pipe 44 is connected to the outlet of the third heat exchange channel 131, so that one end of the third exhaust pipe 23 can be directly connected to the pipeline or facility that needs to be vented with natural gas, so that the natural gas to be vented flows through the third exhaust pipe 23, the fourth heat exchange channel 132, and the fourth exhaust pipe 24 in sequence into the first heat exchange channel 112, and the gaseous natural gas is liquefied into liquefied natural gas in the first heat exchange channel 112. Gas, liquefied natural gas flows through the discharge pipe 31 and enters the second heat exchange channel 113 to be gasified into natural gas gas, and the natural gas gas flows through the third gas pipeline 43 and the third heat exchange channel 131 in turn to enter the fourth gas pipeline 44, and the fourth gas pipeline 44 can be connected with the natural gas pipeline, facilities or CNG storage tanks and 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 discharge pipe 31, the second heat exchange channel 113, the third gas pipeline 43, the third heat exchange channel 131 and the fourth gas pipeline 44 are connected in turn to form a second flow channel, which not only realizes the local consumption of recovered natural gas, improves the recycling rate, and reduces energy waste, but also heats and absorbs condensed solids, so that the condensed solids are gasified and merged with natural gas gas, effectively preventing the condensed solids from blocking the flow channel and avoiding ice blocking. In addition, when natural gas condenses in the second flow channel, it can be switched to the first flow channel to vent the recovered natural gas and absorb the condensed solids, which is flexible and convenient to use.

[0062] In a preferred embodiment of the present invention, the exhaust valve group includes a first exhaust valve provided on the first exhaust pipe 21, a second exhaust valve provided on the second exhaust pipe 22, a third exhaust valve provided on the third exhaust pipe 23, and a fourth exhaust valve provided on the fourth exhaust pipe 24, and the gas supply valve group includes a first gas supply valve provided on the first gas supply pipe 41, a second gas supply valve provided on the second gas supply pipe 42, a third gas supply valve provided on the third gas supply pipe 43, and a fourth gas supply valve provided on the fourth gas supply 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 supply valve and the second gas supply valve are opened, and the third exhaust valve, the fourth exhaust valve, the third gas supply valve and the fourth gas supply 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 supply valve and the fourth gas supply valve are opened, and the first exhaust valve, the second exhaust valve, the first gas supply valve and the second gas supply valve are closed, thereby realizing the switching of the first flow channel and the second flow channel, and the use is flexible and convenient.

[0063] Those skilled in the art can understand that the exhaust valve group and the gas supply valve group of the present application are not limited to the above-mentioned structural forms, and may also adopt pipeline connections, three-way valves or other structural forms that can realize switching between the first flow channel and the second flow channel, which should also fall within the protection scope of the present application.

[0064] In the embodiment of the present invention, the auxiliary heat exchanger 13 further 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 in a one-to-one correspondence, and 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 in a one-to-one correspondence. The switching valve group is used to select the first input pipe 14 or the second input pipe 15 to be connected to the outlet of the liquid nitrogen channel 111.

[0065] 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 to the outlet of the liquid nitrogen channel 111 and the first end of the switching channel 133 in a one-to-one correspondence, so that the liquid nitrogen flows through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111 and the first input pipe 14 in sequence, and flows into the switching channel 133 from the first end of the switching channel 133, so as to preliminarily liquefy the gaseous natural gas flowing through the third heat exchange channel 131, thereby 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 switching valve group selects the two ends of the second input pipe 15 to be connected with the outlet of the liquid nitrogen channel 111 and the second end of the switching channel 133 in a one-to-one correspondence, so that the 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 preliminarily liquefy the gaseous natural gas flowing through the fourth heat exchange channel 132, thereby further improving the recovery efficiency.

[0066] In the embodiment of the present invention, the heat exchange device 10 further includes an output main pipe 16, one end of the output main pipe 16 is used to output nitrogen, and the other end is branched 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, and the switching valve group is further 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.

[0067] 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 in a one-to-one correspondence, and selects the first output pipe 161 to be connected to the second end of the switching channel 133, so that the liquid nitrogen flows through the liquid nitrogen input pipe 12, the liquid nitrogen channel 111 and the first input pipe 14 in sequence, and flows into the switching channel 133 from the first end of the switching channel 133. The liquid nitrogen preliminarily liquefies the gaseous natural gas flowing through the third heat exchange channel 131, and the liquid nitrogen is gasified into nitrogen in the switching channel 133. The nitrogen flows into the first output pipe 161 from the second end of the switching channel 133 in sequence, and is discharged from the end of the output main pipe 16 away from the switching channel 133, thereby improving the recovery rate of the natural gas and reducing energy waste.

[0068] Understandably, if 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 in a one-to-one correspondence, and selects the second output pipe 162 to be connected to the first end of the switching channel 133, so that the 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. The liquid nitrogen initially liquefies the gaseous natural gas flowing through the fourth heat exchange channel 132, and the liquid nitrogen is gasified into nitrogen in the switching channel 133. The nitrogen flows into the second output pipe 162 from the first end of the switching channel 133 in sequence, and is discharged from the end of the output main pipe 16 away from the switching channel 133, thereby improving the recovery rate of the natural gas and reducing energy waste.

[0069] Furthermore, a gas-liquid separator 164 is provided on the output main pipe 16, and the gas-liquid separator 164 is used to separate the nitrogen and liquid nitrogen in the output main pipe 16, and the separated nitrogen is discharged from the output main pipe 16, and the separated liquid nitrogen can be recovered to be input into the liquid nitrogen input pipe 12 again, thereby further reducing energy waste; and 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, and the liquid nitrogen regulating valve 121 is used to regulate the flow of liquid nitrogen, and the nitrogen regulating valve 163 is used to regulate the flow of nitrogen, so as to improve the stability of the system.

[0070] In a preferred embodiment of the present invention, the switching valve group includes a first input valve provided on the first input pipe 14, a second input valve provided on the second input pipe 15, a first output valve provided on the first output pipe 161, and a second output valve provided 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 of the liquid nitrogen flow direction and the nitrogen flow direction, which is flexible and convenient to use.

[0071] Those skilled in the art can understand that the switching valve group of the present application is not limited to the above-mentioned structural form, and can also adopt pipeline connection, three-way valve or other structural forms that can switch the flow direction of liquid nitrogen and nitrogen flow, which should also fall within the protection scope of the present application.

[0072] In the embodiment of the present invention, the exhaust pipe group further includes an exhaust main pipe 25, one end of which is branched to form a first exhaust pipe 21 and a 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. Figure 2 As shown, one end of the exhaust main pipe 25 branches to form the first exhaust pipe 21 and the third exhaust pipe 23, and the other end of the exhaust main pipe 25 can be directly connected to the pipeline or facility where natural gas needs to be vented, so that the natural gas to be vented can enter the exhaust main pipe 25 and flow through the exhaust main pipe 25 into the first exhaust pipe 21 or the third exhaust pipe 23. There is no need to perform pretreatment such as removing easily condensable components on the natural gas to be vented, thereby improving the venting recovery efficiency, and the exhaust main pipe 25 is provided with a first pressure regulator 251, which is used to reduce the pressure drop of the natural gas to be vented to facilitate the recovery of the natural gas.

[0073] In the embodiment of the present invention, the gas pipeline group further includes a gas pipeline 45, one end of which is branched 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 gas pipeline 45. Figure 2 As shown, one end of the gas transmission pipe 45 branches to form a second gas transmission pipe 42 and a fourth gas transmission pipe 44, and the other end of the gas transmission pipe 45 can be connected to a natural gas pipeline, a facility or a CNG storage tank to directly output natural gas. The gaseous natural gas has a wide range of applications and is flexible and convenient to use. It improves the recovery rate of vented natural gas and reduces energy waste. A second pressure regulator 451 is provided on the gas transmission pipe 45. The second pressure regulator 451 is used to reduce the pressure drop of the natural gas to facilitate the application of the output natural gas.

[0074] Furthermore, the drainage device 30 further 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 loss and improving system stability.

[0075] In a preferred embodiment of the present invention, the natural gas venting and recovery system also 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, and the controller is configured to: upon receiving a pressure adjustment instruction, sequentially adjust the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 to the corresponding preset pressure drop range; specifically, the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 can all reduce the pressure drop, and the pressure of the natural gas is increased by sequentially reducing the pressure drops of the third pressure regulator 33, the first pressure regulator 251, and the second pressure regulator 451 to the corresponding preset pressure drop range, so that the natural gas pressure output by the gas transmission main 45 meets the use requirements and can be directly connected to the natural gas pipeline or facility, thereby ensuring the on-site consumption of the recovered natural gas.

[0076] In an embodiment of the present invention, as shown in Table 1, Table 1 is a table of natural gas components to be vented. When the ambient temperature is 30°C, the natural gas venting and recovery system is used to vent and recover the natural gas, and the liquid nitrogen consumption as shown in Table 2 can be obtained. Table 2 is a table of liquid nitrogen consumption of vented and recovered natural gas, wherein the pressure required for the gas transmission main 45 to output the natural gas to the natural gas pipeline or facility is 8.0 MPa. According to Table 2, the use of the natural gas venting and recovery system to vent and recover the natural gas is not only green and environmentally friendly, reduces pollution, but also reduces costs and reduces energy waste.

[0077] Table 1 Composition of natural gas to be vented

[0078] Components Mole fraction Components Mole fraction C1 0.97 C2 0.016 C3 0.005 i-C4 0.002 n-C4 0.002 N2 0.005

[0079] Table 2 Consumption of Liquid Nitrogen from Venting Natural Gas

[0080]

[0081] In the embodiment of the present invention, the liquid discharge device 30 further includes a first storage tank 34, which is disposed on the liquid discharge pipe 31 and between the outlet of the first heat exchange channel 112 and the liquid discharge pump 32, and is used to store liquefied natural gas. Figure 1 and Figure 2As shown, the 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 on site or transported to other locations of use, effectively reducing energy waste and improving recycling rate.

[0082] Furthermore, the heat exchange device 10 further includes a second storage tank 17, which is disposed at one end of the liquid nitrogen input 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. The use of 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 movable form, which is flexible and convenient to transport and has a wide range of applications.

[0083] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0084] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0086] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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 comprises: A heat exchange device (10), comprising a main heat exchanger (11) and a liquid nitrogen input pipe (12), wherein the main heat exchanger (11) has a liquid nitrogen heat exchange 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 an inlet of the liquid nitrogen channel (111), and the other end is used for liquid nitrogen input; An exhaust device (20) for supplying natural gas and directing it to the inlet of the first heat exchange channel (112); A liquid discharge device (30), comprising a liquid discharge pipe (31) and a liquid discharge pump (32), wherein two ends of the liquid discharge pipe (31) are respectively connected to an outlet of the first heat exchange channel (112) and an inlet of the second heat exchange channel (113) in a one-to-one correspondence, and the liquid discharge pump (32) is arranged on the liquid discharge pipe (31); A gas delivery device (40) is used to communicate with the outlet of the second heat exchange channel (113) and output natural gas.

2. The natural gas venting and recovery system according to claim 1, characterized in that: The heat exchange device (10) further comprises an auxiliary heat exchanger (13), the auxiliary heat exchanger (13) having a third heat exchange channel (131) and a fourth heat exchange channel (132); the exhaust device (20) is used for inputting natural gas and selecting the third heat exchange channel (131) or the fourth heat exchange channel (132) to be connected to the inlet of the first heat exchange channel (112); the gas delivery device (40) is used for selecting the fourth heat exchange channel (132) to be connected to the outlet of the second heat exchange channel (113) and outputting natural gas when the third heat exchange channel (131) is connected to the first heat exchange channel (112), and for selecting the third heat exchange channel (131) to be connected to the outlet of the second heat exchange channel (113) and outputting natural gas when the fourth heat exchange channel (132) is connected to the first heat exchange channel (112).

3. The natural gas venting and recovery system according to claim 2, characterized in that: The exhaust device (20) comprises an exhaust pipe group and an exhaust valve group, wherein the exhaust pipe group comprises 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) in a one-to-one correspondence; 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) in a one-to-one correspondence; and the exhaust valve group is used to respectively 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).

4. The natural gas venting and recovery system according to claim 3, characterized in that: The exhaust pipe group further comprises an exhaust main pipe (25), one end of which branches into the first exhaust pipe (21) and the third exhaust pipe (23), and the other end of which is used for inputting natural gas. A first pressure regulator (251) is provided on the exhaust main pipe (25).

5. The natural gas venting and recovery system according to claim 2, characterized in that: The gas delivery device (40) comprises a gas delivery pipe group and a gas delivery valve group, the gas delivery pipe group comprises 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) in a one-to-one correspondence, 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. The two ends of the third gas pipeline (43) are respectively connected to the outlet of the second heat exchange channel (113) and the inlet of the third heat exchange channel (131) in a one-to-one correspondence; 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 for outputting natural gas; the gas transmission valve group is used to respectively 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).

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

7. The natural gas venting and recovery system according to claim 2, characterized in that: The auxiliary heat exchanger (13) further comprises a switching channel (133); the heat exchange device (10) further comprises a first input pipe (14), a second input pipe (15) and a switching valve group; 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) in a one-to-one correspondence; 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) in a one-to-one correspondence; the switching valve group is used to select the first input pipe (14) or the second input pipe (15) to be connected to the outlet of the liquid nitrogen channel (111).

8. The natural gas venting and recovery system according to claim 7, characterized in that: The heat exchange device (10) further comprises an output main pipe (16), one end of the output main pipe (16) being used for outputting nitrogen, and the other end of the output main pipe (16) being branched to form a first output pipe (161) and a second output pipe (162), the first output pipe (161) being in communication with the second end of the switching channel (133), and the second output pipe (162) being in communication with the first end of the switching channel (133), and the switching valve group being further used for selecting the first output pipe (161) to be in communication with the switching channel (133) when the first input pipe (14) is in communication with the outlet of the liquid nitrogen channel (111), and for selecting the second output pipe (162) to be in communication with the switching channel (133) when the second input pipe (15) is in communication with the outlet of the liquid nitrogen channel (111).

9. The natural gas venting and recovery system according to any one of claims 1 to 8, characterized in that: The liquid discharge device (30) further comprises a third pressure regulator (33), wherein the third pressure regulator (33) is arranged on the liquid discharge pipe (31) and is located between the liquid discharge pump (32) and the inlet of the second heat exchange channel (113).

10. The natural gas venting and recovery system according to any one of claims 1 to 8, characterized in that: The liquid discharge device (30) further comprises a first storage tank (34), wherein the first storage tank (34) is disposed on the liquid discharge pipe (31) and located between the outlet of the first heat exchange channel (112) and the liquid discharge pump (32), and the first storage tank (34) is used to store liquefied natural gas; And / or, the heat exchange device (10) further comprises a second storage tank (17), wherein the second storage tank (17) is arranged at an end of the liquid nitrogen input pipe (12) away from the liquid nitrogen channel (111) and is used for storing liquid nitrogen.

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