CN115264388A - Device and method for continuously replacing natural gas by nitrogen - Google Patents
Device and method for continuously replacing natural gas by nitrogen Download PDFInfo
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- CN115264388A CN115264388A CN202210819162.2A CN202210819162A CN115264388A CN 115264388 A CN115264388 A CN 115264388A CN 202210819162 A CN202210819162 A CN 202210819162A CN 115264388 A CN115264388 A CN 115264388A
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- natural gas
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- tank
- nitrogen
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 512
- 239000003345 natural gas Substances 0.000 title claims abstract description 252
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 232
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 116
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000005380 natural gas recovery Methods 0.000 claims abstract description 34
- 238000005070 sampling Methods 0.000 claims abstract description 11
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 10
- 239000007789 gas Substances 0.000 claims description 91
- 239000007788 liquid Substances 0.000 claims description 54
- 238000007789 sealing Methods 0.000 claims description 13
- 238000002309 gasification Methods 0.000 claims description 12
- 238000005520 cutting process Methods 0.000 claims description 5
- 238000004891 communication Methods 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 238000006073 displacement reaction Methods 0.000 claims 2
- 238000003860 storage Methods 0.000 abstract description 8
- 238000003912 environmental pollution Methods 0.000 abstract description 5
- 239000002360 explosive Substances 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C13/00—Details of vessels or of the filling or discharging of vessels
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another subclass
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
Abstract
The invention provides a device and a method for continuously replacing natural gas by nitrogen, which relate to the technical field of natural gas storage transportation and supply, and particularly comprise a nitrogen supply unit, a natural gas recovery unit, a diffusing pipe and at least two natural gas tanks, wherein each natural gas tank is provided with an air inlet pipe, an air outlet pipe, a temperature measuring element, a pressure measuring element and a sampling port, the air inlet pipe, the air outlet pipe, the natural gas recovery unit and the diffusing pipe are respectively provided with a switch valve, the nitrogen supply unit is communicated with the air inlet pipes, the air outlet pipe of the natural gas tank positioned at the upstream is communicated with the air inlet pipe of the natural gas tank positioned at the downstream, the air outlet pipe is communicated with the natural gas recovery unit, and the air outlet pipe is communicated with the diffusing pipe. The device for continuously replacing the natural gas in the natural gas tank by the nitrogen reduces the environmental pollution, and has small nitrogen consumption and low replacement cost.
Description
Technical Field
The invention relates to the technical field of natural gas storage, transportation and supply, in particular to a device and a method for continuously replacing natural gas by nitrogen.
Background
In the process of urban gas transmission and distribution operation, storage stations of a pipe network are generally required to be built, each storage station is provided with four large natural gas storage ball tanks for peak regulation during gas peak utilization, the sub-high-pressure natural gas storage ball tanks for peak regulation belong to pressure vessels, according to the regulations of pressure vessel safety technology supervision regulations and pressure vessel regular inspection rules, tank opening detection needs to be carried out regularly, and meanwhile, with the development of the technology, the large natural gas storage ball tanks cannot meet the requirement of the peak regulation of the gas storage of the urban pipe network, and also need to stop operation. The spherical tanks are filled with natural gas which belongs to flammable and explosive gas, the spherical tanks filled with the natural gas are also in flammable and explosive states, manpower and material resources are continuously consumed to maintain the safe state, and if the natural gas is replaced by nitrogen, the spherical tanks do not belong to the flammable and explosive gas and do not need to continuously consume the manpower and material resources to maintain the safe state.
Before large spherical tanks are detected or shut down, the spherical tanks need to be replaced, spherical tank replacement is dangerous work, and if the replacement scheme is selected improperly or the operation is misled, explosive accidents can happen to cause disastrous losses. For this reason, the safety problem is that must be ensured during the replacement of the spherical tank; secondly, the spherical tank replacement still should consider the operation convenience and reduce the pollution of methane gas's emission to the environment, if the improper scheme will cause the replacement work load big, dangerous high.
At present, methods adopted by spherical tank replacement mainly comprise a water replacement method and a nitrogen replacement method, wherein the nitrogen replacement method adopts single tanks for replacement one by one, so that the nitrogen consumption is large, the replacement cost is high, and natural gas spherical tanks do not consider the recovery of natural gas in the pressure reduction process, so that a large amount of methane is discharged into the atmosphere, and the environmental pollution is large.
Disclosure of Invention
The invention aims to provide a device and a method for continuously replacing natural gas by nitrogen, which reduce environmental pollution, have small nitrogen consumption and low replacement cost.
In order to solve the above problems, the present invention provides a device for continuously replacing natural gas with nitrogen, including a nitrogen supply unit, a natural gas recovery unit, a diffusing pipe and at least two natural gas tanks, wherein the nitrogen supply unit is used for supplying nitrogen, each natural gas tank is provided with an air inlet pipe, an air outlet pipe, a temperature measurement element, a pressure measurement element and a sampling port, each air inlet pipe, each air outlet pipe, the natural gas recovery unit and the diffusing pipe are respectively provided with a switch valve, the nitrogen supply unit is communicated with each air inlet pipe, the air outlet pipe of the natural gas tank at the upstream is communicated with the air inlet pipe of the natural gas tank at the downstream, each air outlet pipe is communicated with the natural gas recovery unit, and each air outlet pipe is communicated with the diffusing pipe.
Further, the nitrogen supply unit comprises a liquid nitrogen tank truck, a liquid nitrogen gasification device and a liquid nitrogen buffer device, the liquid nitrogen tank truck, the liquid nitrogen gasification device and the liquid nitrogen buffer device are sequentially connected through a pipeline, an inlet valve and an outlet valve are arranged on the liquid nitrogen tank truck, the liquid nitrogen gasification device and the liquid nitrogen buffer device, a flow meter is further arranged on the liquid nitrogen buffer device, and the liquid nitrogen buffer device is used for being communicated with an air inlet pipe of the natural gas tank.
Further, the pipe is a metal corrugated pipe.
Further, a filter is arranged in the liquid nitrogen buffer device.
The natural gas tank comprises a nitrogen supply unit, a natural gas recovery unit, a diffusing pipe, a natural gas tank, a connecting main pipe and a connecting point of the natural gas tank and the connecting main pipe, wherein the nitrogen supply unit comprises a liquid nitrogen buffer device, the natural gas recovery unit, the diffusing pipe and the gas inlet pipe and the gas outlet pipe of each natural gas tank are connected with the connecting main pipe, the connecting point of the gas inlet pipe of one natural gas tank and the connecting main pipe is positioned between the connecting point of the gas inlet pipe of one natural gas tank on the upstream and the connecting main pipe and the connecting point of the gas outlet pipe of one natural gas tank and the connecting main pipe on the upstream, and the connecting point of the gas outlet pipe of one natural gas tank and the connecting main pipe is positioned between the connecting point of the gas outlet pipe of one natural gas tank on the upstream and the connecting main pipe and the connecting point of the gas inlet pipe of one natural gas tank on the downstream and the connecting main pipe.
Further, the natural gas tanks are identical in structure, a blowoff valve and a bottom inlet are arranged at the bottom of each natural gas tank, a top inlet is arranged at the top of each natural gas tank, a bottom sealing cover plate is arranged on each bottom inlet, and a top sealing cover plate is arranged on each top inlet.
Further, the natural gas recovery unit is a compressor, one end of the compressor is connected with the connecting header pipe, the other end of the compressor is connected with the medium-pressure pipe network, a sixth header pipe switch valve is arranged between the compressor and the connecting header pipe, and a seventh header pipe switch valve is arranged between the compressor and the medium-pressure pipe network.
The method for replacing the natural gas by adopting the device for continuously replacing the natural gas by the nitrogen is characterized by comprising the following steps of: comprises the following steps of (a) carrying out,
conveying the natural gas in each natural gas tank to a natural gas pipeline network until the pressure of the natural gas in each natural gas tank is reduced to 0.02MPa;
(II) cutting off the connection between the downstream-most natural gas tank and the natural gas recovery unit, filling nitrogen into the upstream-most first natural gas tank, and stopping filling nitrogen when the pressure in the first natural gas tank reaches 0.3MPa, so that the gas in the first natural gas tank is fully mixed;
(III) enabling the outlet pipe of the first natural gas tank to be communicated with the inlet pipe of a second natural gas tank, enabling the outlet pipe of the second natural gas tank to be communicated with the inlet pipe of a third natural gas tank, closing the outlet pipe of the most downstream natural gas tank, enabling the outlet pipe of the most downstream natural gas tank to be communicated with a diffusing pipe until the pressure in each natural gas tank is 0.02MPa when the pressures in the natural gas tanks are equal, closing the outlet pipe of the first natural gas tank, and cutting off the communication between the outlet pipe of the most downstream natural gas tank and the diffusing pipe;
repeating the step (II) and the step (III) until the content of combustible gas in the first natural gas tank is less than or equal to 1% and the pressure value is more than or equal to 0.09MPa at the ambient temperature of 40 ℃, and closing the gas inlet pipe and the gas outlet pipe of the first natural gas tank;
and (IV) sequentially filling nitrogen into the natural gas tanks at the downstream of the first natural gas tank according to the step (II) and the step (III) until the content of combustible gas in each natural gas tank is less than or equal to 1 percent and the pressure value is more than or equal to 0.09Mpa at the ambient temperature of 40 ℃.
Further, the step (one) includes the following processes:
opening a switch valve on an air outlet pipe of each natural gas tank, and conveying the natural gas in each natural gas tank to a natural gas medium-pressure pipe network until the pressure of the natural gas in each natural gas tank is reduced to 0.1Mpa;
and connecting the air outlet pipe of each natural gas tank with a natural gas recovery unit, and reducing the pressure of the natural gas in each natural gas tank to 0.02MPa through the natural gas recovery unit.
According to the device for continuously replacing the natural gas by the nitrogen, disclosed by the invention, the gas outlet pipe of each natural gas tank is communicated with the natural gas recovery unit, so that the natural gas in each natural gas tank can be fully recovered, the condition that a large amount of methane is discharged into the atmosphere is avoided, and the environmental pollution is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a device for continuously replacing natural gas with nitrogen according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
The terms "upper", "lower", "front", "rear", "left" and "right" and the like appearing in the embodiments of the present invention indicate directions or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the device referred to must have a specific orientation, be constructed in a specific orientation and be operated, and thus, should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be a mechanical connection; can be directly connected or indirectly connected through an intermediate medium; the specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
If there is a description relating to "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or to imply that the number of technical features indicated is implicit.
A device for continuously replacing natural gas with nitrogen according to an embodiment of the present invention, as shown in fig. 1, includes a nitrogen supply unit, a natural gas recovery unit 31, a diffusing pipe 41, and two or more natural gas tanks, in this embodiment, four natural gas tanks are provided, a first natural gas tank 11, a second natural gas tank 12, a third natural gas tank 13, and a fourth natural gas tank 14, the four natural gas tanks have the same structure, the four natural gas tanks are sequentially provided from upstream to downstream, the nitrogen supply unit is used for supplying nitrogen, the first natural gas tank 11 is provided with a first gas inlet pipe 111, a first gas outlet pipe 112, a first temperature measuring element, a first pressure measuring element, a first sampling port, the second natural gas tank 12 is provided with a second gas inlet pipe 121, a second gas outlet pipe 122, a second temperature measuring element, a second pressure measuring element, and a second sampling port, a third gas inlet pipe, a third gas outlet pipe, a third temperature measuring element, a third pressure measuring element and a third sampling port are arranged on the third natural gas tank 13, a fourth gas inlet pipe, a fourth gas outlet pipe, a fourth temperature measuring element, a fourth pressure measuring element and a fourth sampling port are arranged on the fourth natural gas tank 14, a switch valve is respectively arranged on the first gas inlet pipe 111, the first gas outlet pipe 112, the second gas inlet pipe 121, the second gas outlet pipe 122, the third gas inlet pipe, the third gas outlet pipe, the fourth gas inlet pipe, the fourth gas outlet pipe, the natural gas recovery unit 31 and the diffusing pipe 41, the nitrogen supply unit is communicated with the first gas inlet pipe 111, the second gas inlet pipe 121, the third gas inlet pipe and the fourth gas inlet pipe, the first gas outlet pipe 112 is communicated with the second gas inlet pipe 121, the second gas outlet pipe 122 is communicated with the third gas inlet pipe, the third gas outlet pipe is communicated with the fourth gas inlet pipe, the first gas outlet pipe 112 is communicated with the natural gas recovery unit 31 and the diffusing pipe 41, the second outlet pipe 122 is communicated with the natural gas recovery unit 31 and the diffusing pipe 41, and the third outlet pipe and the fourth outlet pipe are communicated with the natural gas recovery unit 31 and the diffusing pipe 41. Specifically, each switch valve is a ball valve, and the temperature measuring element, the pressure measuring element and the sampling port on each natural gas tank are provided with two groups, one group is arranged at the top of each natural gas tank, and the other group is arranged at the bottom of each natural gas tank. According to the device for continuously replacing the natural gas by the nitrogen, disclosed by the embodiment of the invention, the gas outlet pipe of each natural gas tank is communicated with the natural gas recovery unit, so that the natural gas in each natural gas tank can be fully recovered, the condition that a large amount of methane is discharged into the atmosphere is avoided, and the environmental pollution is reduced.
Optionally, the nitrogen supply unit includes a liquid nitrogen tank car, a liquid nitrogen gasification device, and a liquid nitrogen buffer device, which are connected in sequence through a pipeline, the liquid nitrogen tank car, the liquid nitrogen gasification device, and the liquid nitrogen buffer device are all provided with an inlet valve and an outlet valve, the liquid nitrogen buffer device is further provided with a flowmeter, a pressure gauge, and a thermometer, and the liquid nitrogen buffer device is used for being communicated with the first air inlet pipe 111, the second air inlet pipe 121, the third air inlet pipe, and the fourth air inlet pipe. Liquid nitrogen is stored in the liquid nitrogen tank wagon, an outlet valve of the liquid nitrogen tank wagon, an inlet valve and an outlet valve of the liquid nitrogen gasification device, and an inlet valve and an outlet valve of the liquid nitrogen buffer device are opened, and the liquid nitrogen is in a gas state after passing through the liquid nitrogen gasification device and is filled into each natural gas tank through the liquid nitrogen buffer device. Specifically, each of the inlet valve and the outlet valve is a ball valve.
Optionally, the pipe is a metal corrugated pipe.
Optionally, a filter is arranged in the liquid nitrogen buffer device, and the gasified nitrogen is filtered by the filter in the liquid nitrogen buffer device to remove impurities.
Optionally, the device further comprises a connecting header pipe 51, a liquid nitrogen buffer device of the nitrogen supply unit, a first gas inlet pipe 111, a first gas outlet pipe 112, a second gas inlet pipe 121, a second gas outlet pipe 122, a third gas inlet pipe, a third gas outlet pipe, a fourth gas inlet pipe, a fourth gas outlet pipe, a natural gas recovery unit 31 and a diffusing pipe 41 which are all connected with the connecting header pipe 51, the connecting points of the first gas inlet pipe 111, the first gas outlet pipe 112, the second gas inlet pipe 121, the second gas outlet pipe 122, the third gas inlet pipe, the third gas outlet pipe, the fourth gas inlet pipe, the fourth gas outlet pipe, the diffusing pipe 41 and the connecting header pipe 51 are respectively a first connecting point, a second connecting point, a third connecting point, a fourth connecting point, a fifth connecting point, a sixth connecting point, a seventh connecting point, an eighth connecting point and a ninth connecting point, the connection point of the natural gas recovery unit 31 and the connection header 51 and the connection point of the diffusing pipe 41 and the connection header 51 are at the same point, the third connection point is located between the first connection point and the second connection point, the fourth connection point is located between the second connection point and the fifth connection point, the seventh connection point is located between the fifth connection point and the sixth connection point, the eighth connection point is located between the sixth connection point and the ninth connection point, and first, second, third, fourth, and fifth header switching valves 61, 62, 63, 64, 65 are respectively arranged between the first connection point and the third connection point, between the second connection point and the fourth connection point, between the fourth connection point and the fifth connection point, between the fifth connection point and the seventh connection point, and between the sixth connection point and the eighth connection point on the connection header 51.
Optionally, the natural gas tanks are identical in structure, wherein a blowoff valve and a bottom inlet are arranged at the bottom of the first natural gas tank 11, a top inlet is arranged at the top of the first natural gas tank 11, a bottom sealing cover plate is arranged on the bottom inlet, a top sealing cover plate is arranged on the top inlet, the blowoff valve is used for discharging dirt in the natural gas tank, the bottom sealing cover plate is used for opening or closing the bottom inlet, and the top sealing cover plate is used for opening or closing the top inlet.
Optionally, the bottom sealing cover plate and the top sealing cover plate are detachably connected to the natural gas spherical tank through bolts, the bottom sealing cover plate and the top sealing cover plate can also be detachably connected to the natural gas spherical tank through buckles, and each natural gas spherical tank is connected with a grounding wire.
Optionally, the blowdown valve on each gas ball tank is arranged on the bottom sealing cover plate.
Optionally, the natural gas recovery unit 31 is a compressor, one end of the compressor is connected to the connection header 51, the other end of the compressor is connected to the medium-pressure pipe network, a sixth header switch valve 66 is arranged between the compressor and the connection header 51, a seventh header switch valve 67 is arranged between the compressor and the medium-pressure pipe network, the compressor is connected in parallel to the recovery pipe 311, a switch valve is arranged on the recovery pipe 311, when the pressure of the natural gas in the natural gas tank is higher than the pressure of the medium-pressure pipe network, the natural gas can be recovered through the recovery pipe 311 to reduce the pressure of the natural gas in the natural gas tank to the medium pressure, and then as much natural gas in the natural gas tank as possible is recovered into the gas pipe network through the compressor, so as to further reduce the pressure of the natural gas to 0.02Mpa.
The method for replacing the natural gas by adopting the device for continuously replacing the natural gas by the nitrogen comprises the following steps,
conveying the natural gas in each natural gas tank to a natural gas pipeline network until the pressure of the natural gas in each natural gas tank is reduced to 0.02MPa;
(II) cutting off the connection between each natural gas tank and the natural gas recovery unit 31, filling nitrogen into the first natural gas tank, stopping filling nitrogen when the pressure in the first natural gas tank reaches 0.3MPa, standing for 2 hours, and sampling and analyzing the concentration of natural gas in the tank every 20min in the filling and standing processes;
specifically, a switch valve on an air outlet pipe 112, a first main pipe switch valve 61, a sixth main pipe switch valve 66 and a seventh main pipe switch valve 67 are closed, an outlet valve of a liquid nitrogen tank wagon is opened slowly, an inlet valve and an outlet valve of a liquid nitrogen gasification device and an inlet valve and an outlet valve of a liquid nitrogen buffer device are opened, liquid nitrogen is gasified by the liquid nitrogen gasification device and then enters the liquid nitrogen buffer device, the pressure in the liquid nitrogen buffer device is increased to 0.4MPa gauge pressure and then is filled into the tank through a first air inlet pipe 111 on a first natural gas tank 11, the temperature of nitrogen in the liquid nitrogen buffer device is controlled to be more than 0 ℃, the temperature of the nitrogen entering the first natural gas tank 11 is controlled to be more than +5 ℃, when the pressure in the first natural gas tank 11 reaches 0.3MPa gauge pressure, the liquid nitrogen inlet valve and the switch valve on the first air inlet pipe 111 are closed, the tank is kept still for about 2 hours, the gas in the tank is fully mixed, and the natural gas concentration in the tank is respectively sampled and analyzed from the bottom and the top of the first natural gas tank 11 every 20min in the inflation and still standing processes;
(III) the outlet pipe of the first natural gas tank is communicated with the inlet pipe of the second natural gas tank, the outlet pipe of the second natural gas tank is communicated with the inlet pipe of the third natural gas tank, and so on, the outlet pipe of the most downstream natural gas tank is closed, when the pressures in the natural gas tanks are equal, the outlet pipe of the most downstream natural gas tank is communicated with the diffusing pipe 41 until the pressure in each natural gas tank is 0.02Mpa, the outlet pipe of the first natural gas tank is closed, and the communication between the outlet pipe of the most downstream natural gas tank and the diffusing pipe 41 is cut off;
repeating the step (II) and the step (III) until the content of combustible gas in the first natural gas tank is less than or equal to 1% and the pressure value is more than or equal to 0.09MPa at the ambient temperature of 40 ℃ through two sampling analyses of the tank bottom and the tank top, closing an air inlet pipe and an air outlet pipe of the first natural gas tank, and finishing the replacement of the first natural gas tank;
specifically, the on-off valve on the gas outlet pipe of the first natural gas tank 11, the on-off valves on the gas inlet pipe and the gas outlet pipe of the second natural gas tank 12, the on-off valves on the gas inlet pipe and the gas outlet pipe of the third natural gas tank 13, the on-off valves on the gas inlet pipe and the gas outlet pipe of the fourth natural gas tank 14, and the third main on-off valve 63 are opened, the first main on-off valve 61, the second main on-off valve 62, the fourth main on-off valve 64, the fifth main on-off valve 65, and the on-off valve on the diffusing pipe 41 are closed, the gas in the first natural gas tank 11 enters the fourth natural gas tank 14 through the second natural gas tank 12 and the third natural gas tank 13, the gas in the first natural gas tank 11 is diffused, the second, third, and fourth natural gas tanks are inflated at the same time, and when the pressure in each natural gas tank is 0.02Mpa, the on-off valves on the gas outlet pipe 112 of the first natural gas tank 11 and the diffusing pipe 41 are closed.
And (IV) sequentially filling nitrogen into the second natural gas tank and the third natural gas tank according to the step (II) and the step (III) until the content of combustible gas in each natural gas tank is less than or equal to 1 percent and the pressure value is more than or equal to 0.09Mpa at the ambient temperature of 40 ℃.
Specifically, taking the second natural gas tank 12 as an example, nitrogen is filled into the second natural gas tank 12, the nitrogen filling is stopped when the pressure in the second natural gas tank 12 reaches 0.3MPa, the second natural gas tank is kept stand for 2 hours, and the natural gas concentration in the tank is sampled and analyzed every 20min during the filling and standing processes;
opening the switch valves on the inlet pipe and the outlet pipe of the second natural gas tank 12, the switch valves on the inlet pipe and the outlet pipe of the third natural gas tank 13, the switch valves on the inlet pipe and the outlet pipe of the fourth natural gas tank 14, the first main switch valve 61 and the third main switch valve 63, closing the second main switch valve 62, the fourth main switch valve 64, the fifth main switch valve 65 and the switch valves on the diffusing pipe 41, allowing the gas in the second natural gas tank 12 to enter the fourth natural gas tank 14 through the third natural gas tank 13, diffusing the gas in the second natural gas tank 12, simultaneously inflating the third natural gas tank and the fourth natural gas tank, and closing the switch valves on the outlet pipe 122 of the second natural gas tank 12 and the switch valves on the diffusing pipe 41 when the pressure in each natural gas tank is 0.02Mpa.
Repeating the steps until the content of combustible gas in the second natural gas tank 12 is less than or equal to 1 percent and the pressure value is more than or equal to 0.09MPa at the ambient temperature of 40 ℃ after two sampling analyses of the tank bottom and the tank top, closing the gas inlet pipe and the gas outlet pipe of the second natural gas tank 12, and finishing the replacement of the second natural gas tank 12;
optionally, the step (one) includes the following steps:
opening a switch valve on an air outlet pipe of each natural gas tank, and conveying the natural gas in each natural gas tank to a natural gas medium-pressure pipe network until the pressure of the natural gas in each natural gas tank is reduced to a set value of 0.1Mpa;
the outlet pipe of each natural gas tank is connected with the natural gas recovery unit 31, more natural gas is recovered through the natural gas recovery unit 31, so that the pressure of the natural gas in each natural gas tank is reduced to a set value of 0.02MPa gauge pressure, specifically, the first, second, third, fourth, fifth, sixth and seventh main pipe switch valves 61, 62, 63, 64, 65, 66 and 67 are all opened, and the natural gas in each natural gas tank is recovered to a medium-pressure natural gas pipe through the natural gas recovery unit 31 until the pressure of the natural gas in the natural gas tank is reduced to a set value of 0.02MPa.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.
Claims (9)
1. The device for continuously replacing the natural gas by the nitrogen is characterized by comprising a nitrogen supply unit, a natural gas recovery unit (31), a diffusing pipe (41) and at least two natural gas tanks, wherein the nitrogen supply unit is used for supplying the nitrogen, each natural gas tank is provided with an air inlet pipe, an air outlet pipe, a temperature measuring element, a pressure measuring element and a sampling port, each air inlet pipe, each air outlet pipe, the natural gas recovery unit (31) and the diffusing pipe (41) are respectively provided with a switch valve, the nitrogen supply unit and each air inlet pipe are communicated with each other, the air outlet pipe of the natural gas tank positioned at the upstream is communicated with the air inlet pipe of the natural gas tank positioned at the downstream, each air outlet pipe is communicated with the natural gas recovery unit (31), and each air outlet pipe is communicated with the diffusing pipe (41).
2. The device for continuously replacing natural gas with nitrogen as claimed in claim 1, wherein the nitrogen supply unit comprises a liquid nitrogen tank car, a liquid nitrogen gasification device and a liquid nitrogen buffer device, the liquid nitrogen tank car, the liquid nitrogen gasification device and the liquid nitrogen buffer device are sequentially connected through a pipeline, the liquid nitrogen tank car, the liquid nitrogen gasification device and the liquid nitrogen buffer device are all provided with an inlet valve and an outlet valve, the liquid nitrogen buffer device is also provided with a flow meter, and the liquid nitrogen buffer device is used for being communicated with an inlet pipe of the natural gas tank.
3. The apparatus for continuous displacement of natural gas with nitrogen according to claim 2, wherein the pipeline is a metal corrugated pipeline.
4. The apparatus for continuous displacement of natural gas by nitrogen according to claim 3, wherein a filter is provided in the liquid nitrogen buffer.
5. The apparatus for continuously replacing natural gas with nitrogen according to claim 4, further comprising a connection header pipe (51), wherein the liquid nitrogen buffer device of the nitrogen supply unit, the natural gas recovery unit (31), the diffusing pipe (41), and the intake pipe of each natural gas tank and the outlet pipe of each natural gas tank are connected to the connection header pipe (51), the connection point of the intake pipe of one natural gas tank to the connection header pipe (51) is located between the connection point of the intake pipe of one natural gas tank located upstream and the connection header pipe (51) and the connection point of the outlet pipe of one natural gas tank located upstream and the connection header pipe (51), and the connection point of the outlet pipe of one natural gas tank to the connection header pipe (51) is located between the connection point of the outlet pipe of one natural gas tank located upstream and the connection header pipe (51) and the connection point of the intake pipe of one natural gas tank located downstream and the connection header pipe (51).
6. The device for continuously replacing natural gas with nitrogen as claimed in claim 5, wherein the structures of the natural gas tanks are the same, the bottom of the natural gas tank is provided with a blowoff valve and a bottom inlet, the top of the natural gas tank is provided with a top inlet, the bottom inlet is provided with a bottom sealing cover plate, and the top inlet is provided with a top sealing cover plate.
7. The plant for the continuous replacement of natural gas with nitrogen according to claim 6, characterized in that said natural gas recovery unit (31) is a compressor, one end of said compressor being connected to said connection manifold (51) and the other end of said compressor being connected to a medium-pressure pipe network, a sixth manifold on-off valve (66) being arranged between said compressor and said connection manifold (51), and a seventh manifold on-off valve (67) being arranged between said compressor and said medium-pressure pipe network.
8. A method for replacing natural gas by using the apparatus for continuously replacing natural gas with nitrogen according to any one of claims 1 to 7, characterized in that: comprises the following steps of (a) preparing a solution,
conveying the natural gas in each natural gas tank to a natural gas pipeline network until the pressure of the natural gas in each natural gas tank is reduced to 0.02MPa;
(II) cutting off the connection between the downstream-most natural gas tank and the natural gas recovery unit (31), filling nitrogen into the upstream-most first natural gas tank, and stopping filling nitrogen when the pressure in the first natural gas tank reaches 0.3MPa so as to fully mix the gas in the first natural gas tank;
(III) enabling the outlet pipe of the first natural gas tank to be communicated with the inlet pipe of a second natural gas tank, enabling the outlet pipe of the second natural gas tank to be communicated with the inlet pipe of a third natural gas tank, and so on, closing the outlet pipe of the most downstream natural gas tank, and communicating the outlet pipe of the most downstream natural gas tank with a diffusing pipe (41) until the pressure in each natural gas tank is 0.02MPa when the pressures in each natural gas tank are equal, closing the outlet pipe of the first natural gas tank, and cutting off the communication between the outlet pipe of the most downstream natural gas tank and the diffusing pipe (41);
repeating the step (II) and the step (III) until the content of combustible gas in the first natural gas tank is less than or equal to 1% and the pressure value is more than or equal to 0.09MPa at the ambient temperature of 40 ℃, and closing the gas inlet pipe and the gas outlet pipe of the first natural gas tank;
and (IV) sequentially filling nitrogen into the natural gas tanks at the downstream of the first natural gas tank according to the step (II) and the step (III) until the content of combustible gas in each natural gas tank is less than or equal to 1 percent and the pressure value is more than or equal to 0.09Mpa at the ambient temperature of 40 ℃.
9. The method of claim 8,
the step (one) includes the following processes:
opening a switch valve on an air outlet pipe of each natural gas tank, and conveying the natural gas in each natural gas tank to a natural gas medium-pressure pipe network until the pressure of the natural gas in each natural gas tank is reduced to 0.1Mpa;
and connecting the gas outlet pipe of each natural gas tank with the natural gas recovery unit (31), and reducing the pressure of the natural gas in each natural gas tank to 0.02MPa through the natural gas recovery unit (31).
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| CN115264388B (en) | 2024-01-30 |
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