Gas displacement method

Abstract

The application provides a tank and a gas replacement method. The method comprises the following steps: in the case that an exhaust port of the tank is open, a second gas is introduced from an air inlet of the tank, and a first gas is discharged from the exhaust port; when a volume fraction of the second gas in the tank is greater than or equal to a first preset volume fraction, the exhaust port is controlled to be closed; when a gas pressure in the tank is greater than or equal to a preset pressure, the air inlet is controlled to be closed; and when a closing time length of the air inlet is greater than or equal to a first preset time length, the exhaust port is controlled to be opened. The combined replacement mode fully plays the advantages of high replacement efficiency of simultaneous charging and discharging and more thorough pressure replacement, improves the overall replacement efficiency while ensuring the safety of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial production, and in particular to a gas replacement method. BACKGROUND

[0002] In the process of industrial production or scientific experiment, it is necessary to replace the initial gas in the related pipeline, container or closed space with inert gas or other gas for the purpose of safety or product protection. Gas replacement is widely used in many fields, including chemical industry, low temperature, aerospace, etc. For example, natural gas pipeline commissioning replacement, low-temperature pipeline and pipeline replacement of aerospace liquid hydrogen filling system, manned space sealed cabin and aerospace solid lubricating film mechanism product, low dew point control of ground atmospheric thermal environment test, etc. Different industries apply different replacement methods.

[0003] However, the existing gas replacement method generally adopts the repeated charging and discharging method for the storage tank, which has low replacement efficiency. SUMMARY

[0004] The present application proposes a gas replacement method to solve the problem of low charging and discharging efficiency in the prior art.

[0005] In a first aspect, the present application proposes a gas replacement method applied to a storage tank storing a first gas, the method comprising:

[0006] In the case that the exhaust port of the storage tank is open, the second gas is introduced from the gas inlet of the storage tank, and the first gas is discharged from the exhaust port;

[0007] When the volume fraction of the second gas in the storage tank is greater than or equal to a first preset volume fraction, the exhaust port is controlled to be closed;

[0008] When the gas pressure in the storage tank is greater than or equal to a preset pressure, the gas inlet is controlled to be closed;

[0009] When the closing time of the gas inlet is greater than or equal to a first preset time, the exhaust port is controlled to be opened;

[0010] When the closing time is greater than or equal to the first preset time, after the exhaust port of the storage tank is opened, the method further comprises:

[0011] When the volume fraction is less than a second preset volume fraction, the exhaust port is controlled to be closed, and the second gas is introduced from the gas inlet until the volume fraction is greater than or equal to the second preset volume fraction; the second preset volume fraction is the volume fraction of the second gas required to meet the replacement requirement.

[0012] Optionally, after the second gas is introduced from the gas inlet of the storage tank in the case that the exhaust port of the storage tank is open, the method further comprises:

[0013] record the duration of the charging of the inlet port by the second gas;

[0014] when the duration is greater than or equal to the second preset duration, control the outlet port to be closed; the second preset duration is determined according to the first preset volume fraction;

[0015] when the gas pressure of the tank is greater than or equal to a preset pressure, control the inlet port to be closed;

[0016] when the duration of the closing of the inlet port is greater than or equal to a first preset duration, control the outlet port to be opened.

[0017] Optionally, the second preset duration is determined by inputting the volume of the tank and the first preset volume fraction into a preset duration determination model.

[0018] Optionally, the volume of the tank is greater than or equal to a preset volume.

[0019] Optionally, the tank comprises a tank body and at least one branch pipeline.

[0020] Optionally, the tank comprises a tank body and at least one blind pipe.

[0021] Optionally, in the case that the outlet port of the tank is open, the second gas is introduced into the inlet port of the tank, comprising:

[0022] In the case that the outlet port of the tank is open, the second gas is introduced into the inlet port of the tank at a preset flow rate.

[0023] In a second aspect, the present application provides a tank, which stores a first gas, and the tank replaces the first gas with a second gas by the gas replacement method according to any one of the first aspect.

[0024] Optionally, the volume of the tank is greater than or equal to a preset volume.

[0025] The gas replacement method provided by the present application has the following technical effects:

[0026] In the embodiment, the inlet port and the outlet port of the tank are opened at the same time to perform the blow replacement, the outlet port is closed when the volume fraction of the second gas reaches the first preset volume fraction, the pressure in the tank is increased, the gas in the tank is fully replaced under a certain pressure, the outlet port is opened to release the pressure after a preset duration, and the gas in the tank meets the replacement requirement. This combined replacement method fully utilizes the advantages of high efficiency of simultaneous charging and discharging replacement and more thorough pressure replacement, improves the overall replacement efficiency while ensuring the safety of the system.

[0027] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification. The embodiments of the application, and their

[0029] Figure 1 A first flow chart of a gas replacement method according to an exemplary embodiment of the present application;

[0030] Figure 2a A gas distribution in a storage tank when the inflation time is 300s according to an exemplary embodiment of the present application;

[0031] Figure 2b A gas distribution in a storage tank when the inflation time is 600s according to an exemplary embodiment of the present application;

[0032] Figure 2c A gas distribution in a storage tank when the inflation time is 900s according to an exemplary embodiment of the present application;

[0033] Figure 2d A gas distribution in a storage tank when the inflation time is 1200s according to an exemplary embodiment of the present application;

[0034] Figure 2e A gas distribution in a storage tank when the inflation time is 1500s according to an exemplary embodiment of the present application;

[0035] Figure 2f A gas distribution in a storage tank when the inflation time is 1800s according to an exemplary embodiment of the present application;

[0036] Figure 3 A second flow chart of a gas replacement method according to an exemplary embodiment of the present application;

[0037] Figure 4a A gas distribution in a storage tank when the replacement number is 1 according to an exemplary embodiment of the present application;

[0038] Figure 4b A gas distribution in a storage tank when the replacement number is 2 according to an exemplary embodiment of the present application;

[0039] Figure 4c A gas distribution in a storage tank when the replacement number is 3 according to an exemplary embodiment of the present application;

[0040] Figure 4d A gas distribution in a storage tank when the replacement number is 4 according to an exemplary embodiment of the present application;

[0041] Figure 4e A schematic diagram of gas distribution in a tank when the number of displacements is 5 is provided for an exemplary embodiment of the present application;

[0042] Figure 5 A schematic diagram of nitrogen concentration variation is provided for an exemplary embodiment of the present application;

[0043] Figure 6 A schematic diagram of pipeline gas distribution is provided for an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0044] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0045] The following detailed description is exemplary description, which is intended to provide further detailed description of the present application. Unless otherwise specified, all technical terms used in the present application have the same meaning as understood by those skilled in the art. The terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the exemplary embodiments according to the present application.

[0046] An exemplary embodiment of the present application provides a gas displacement method, which is applied to a tank storing a first gas, and the method comprises: Figure 1

[0047] S101, in the case that the exhaust port of the tank is open, the second gas is introduced from the gas inlet of the tank, and the first gas is discharged from the exhaust port.

[0048] The first gas is the gas originally stored in the tank, and the second gas is the target gas to be stored in the tank. The tank refers to a device for storing various gases. It includes a tank body and at least one branch pipeline and / or a tank including a tank body and at least one blind pipe. The volume of the tank is greater than or equal to a preset volume, which can be set according to actual conditions. Specifically, it can be a larger volume or a smaller volume. In the present embodiment, it is preferred to be suitable for a large tank. The present embodiment is preferably applied to a large tank, which has more branch pipelines and blind pipes and is not easy to displace.

[0049] In addition, in order to facilitate the exchange of gas, the exhaust port of the tank is generally arranged at the top of the tank, and the gas inlet of the tank is generally arranged at the bottom of the tank.

[0050] In the present embodiment, the displacement gas is filled into the tank through the gas inlet at the bottom of the tank, and the exhaust port is opened at the same time, so that the tank is in the state of simultaneous charging and discharging (blowing displacement), Figures 2a-2f ​The variation of the flow field in the tank during the blowing process, the variation of the gas flow rate, the variation of the gas volume fraction with time, etc. are shown in the figures. Figures 2a-2f Based on the simulation by using Fluent software.

[0051] In one embodiment, in order to, step S101 further comprises:

[0052] In the case that the exhaust port of the tank is open, the second gas is introduced into the tank from the gas inlet at a preset flow rate.

[0053] The preset flow rate is set according to the gas supply capacity balance rate and the gas consumption. The greater the preset flow rate, the shorter the time required for replacement.

[0054] S102, when the volume fraction of the second gas in the tank is greater than or equal to the first preset volume fraction, the exhaust port is controlled to be closed.

[0055] The volume fraction of the second gas can be obtained by using a gas concentration sensor built-in the tank, or can be determined by simulating the volume and shape of the tank and the charging and discharging of the gas. In the case that the volume of the tank is fixed, the longer the charging time of the second gas, the greater the volume fraction of the second gas in the tank. The first preset volume fraction can be set according to the actual situation.

[0056] In the present embodiment, if only the method of simultaneous charging and discharging is used to replace the gas in the tank, although the replacement efficiency is high, it usually faces a problem that the replacement effect is poor for the tank with blind pipes or branch pipes. Therefore, in step S103, when the gas pressure is greater than or equal to a preset pressure, the replacement by pressure is used, that is, the exhaust port of the tank is controlled to be closed, and the gas inlet is still kept open to blow the blind pipes or branch pipes that are not covered.

[0057] S103, when the gas pressure in the tank is greater than or equal to a preset pressure, the gas inlet is controlled to be closed.

[0058] In the present embodiment, since the exhaust port of the tank is closed and the gas inlet is open, if the gas is continuously introduced into the tank, the gas pressure in the tank will rise. When the preset pressure is reached, the gas inlet is closed, so that the gas molecules move under the internal pressure to cover the blind pipes or branch pipes. The preset pressure can be set according to the actual demand.

[0059] In one embodiment, in addition to determining whether the tank meets the stop condition of simultaneous charging and discharging according to the volume fraction of the second gas, the charging time can also be used for determination, see Figure 3 , after step S101, the method further comprises:

[0060] S201, record the gas filling time when the second gas is input into the gas inlet.

[0061] S202, when the gas filling time is greater than or equal to the second preset time length, control the exhaust port to be closed.

[0062] Wherein, in the process of gas filling and discharging, when the volume of the tank is fixed, the gas filling time and the volume fraction of the second gas in the tank are positively correlated. The following table takes the volume of the tank as 105 m³ and the second gas as nitrogen for example:

[0063] ;

[0064] Therefore, the first preset volume fraction required to be reached in the simultaneous gas filling and discharging stage can be determined according to the table, and the second preset time length of the tank can be determined according to the preset volume fraction. For example, if the volume fraction of nitrogen is replaced to 94.41%, it needs to be blown off for 900 s. The gas filling time can also be determined in combination with the volume fraction of the second gas stored in the initial state of the tank and the first preset volume fraction. For example, if the initial volume fraction of nitrogen in the tank is 85.81%, the volume fraction of nitrogen is replaced to 96.94% and needs to be blown off for 900 (1200-300) s.

[0065] In a specific embodiment, in addition to the above table, the second preset time length can also be determined by inputting the volume of the tank and the first preset volume fraction into a pre-constructed time length determination model. The time length determination model is obtained by fitting the first preset integral and the second preset time length at a certain volume, including but not limited to learning models, algorithms, etc., which can be selected according to actual conditions.

[0066] In this embodiment, the simultaneous gas filling and discharging time can be set to fully utilize the advantage of high efficiency of simultaneous gas filling and discharging. In addition, due to the high replacement efficiency of this method, the second preset time length can be appropriately extended to replace more thoroughly under certain conditions. However, when there are more branch pipes or blind pipes in the structure of the tank, this method cannot effectively cover more areas, and the second preset time length should be appropriately reduced.

[0067] S104, when the closing time of the gas inlet is greater than or equal to the first preset time length, control the exhaust port to be opened.

[0068] Wherein, in the method of replacing by pressure, when the gas pressure is greater than or equal to the preset pressure, the gas inlet and the exhaust port are closed to make the tank stand still for the first preset time length, so that the second gas can fully exchange inside the tank to fully cover the blind pipes or branch pipes of the tank. When the standing still ends (i.e. the closing time of the gas inlet is greater than or equal to the first preset time length), the exhaust port is opened to release the pressure of the tank, and the volume fraction of the second gas in the tank can be fully covered to meet the replacement requirements.

[0069] In addition, although the coverage of the pressure replacement method is high, due to the low replacement efficiency of the pressure replacement, multiple inflation and deflation are required to meet the replacement requirements, and the single inflation generally takes a long time, resulting in a long total replacement time and a long working time of the supporting equipment for replacement, which has many safety hazards. Therefore, in the embodiment, the blow replacement is performed first, and then the pressure replacement is performed.

[0070] In one embodiment, if the volume fraction of the second gas in the storage tank still does not meet the replacement requirements after one pressure replacement, the pressure replacement can be repeated, and the specific method further comprises:

[0071] When the volume fraction is less than the second preset volume fraction, the exhaust port is closed, and the second gas is introduced from the gas inlet until the volume fraction is greater than or equal to the second preset volume fraction.

[0072] The second preset volume fraction is the volume fraction of the second gas required to meet the replacement requirements, which can be set according to actual requirements.

[0073] Taking the volume of the storage tank as 105m³ and the second gas as nitrogen as an example, the first gas is set as air, the initial nitrogen volume fraction content is about 78%, and the gas distribution after each pressure replacement is as shown in Figures 4a-4e , and see the following table:

[0074] ;

[0075] According to the results, the gas volume fraction of the second gas after each positive pressure replacement can be obtained under the condition that the volume of the storage tank is determined, and the number of pressure replacements can be determined. For example, if the nitrogen content is required to be higher than 96%, it should be replaced twice. At the same time, the number of pressure replacements can be determined in combination with the initial volume fraction of the second gas stored in the storage tank and the second preset volume fraction to adapt to different initial states. For example, if the initial nitrogen content of the storage tank is 95%, it needs to be replaced to 98% nitrogen content once.

[0076] Generally speaking, the number of pressure replacements in the embodiment is the difference between the total number of pressure replacements M and the number of replacements N corresponding to the volume fraction of the second gas after the blow replacement. Taking nitrogen as an example, the replacement gas volume fraction after 900s of blow replacement is 94.41%, which is better than the volume fraction 94.39% after one positive pressure replacement. Therefore, the blow replacement effect corresponds to one pressure replacement, N=1. If the volume fraction of the second gas is required to be more than 99%, if the total number of pressure replacements M=3, then in the embodiment, the number of positive pressure replacements after 900s of blow replacement is M-N=2 times (the actual mixed amount can reach more than 99.52%).

[0077] The following will be described in detail by taking the replacement of an elongated pipeline such as a natural gas pipeline or a gas supply pipeline as an example:

[0078] The natural gas pipeline replacement generally uses inert gases such as nitrogen and carbon dioxide to replace, so that the oxygen concentration is reduced to a safety value (usually <2%); and then natural gas is used to replace to reach the standard of purity (methane concentration >90%). For long pipelines, due to many branches and long pipelines, they are generally divided into several sections for replacement to avoid mutual influence and reduce overall risk. However, in actual operation, there are still many branch pipelines without discharge outlets; and the segmented replacement efficiency is low. In this case, the replacement method provided in the embodiment can be used to improve the efficiency.

[0079] According to different pipeline use scenarios, the inner diameter of the natural gas conveying pipeline is 100mm-300mm, etc. Taking a DN300 (pipeline parameter) pipeline as an example, the replacement length of the medium-low pressure pipeline is generally set to 0.6km; nitrogen replacement is performed, and the replacement pressure is 0.1MPa; the inlet and outlet are both set to 50mm. When blowing replacement is performed, the nitrogen concentration changes with time as shown in Figure 1 . It can be seen that after blowing for 370s, the average nitrogen concentration can reach 98.5%, and the subsequent blowing replacement efficiency decreases significantly, at which time the blowing is stopped. Continue to perform positive pressure replacement, and after several replacements, the nitrogen content is higher than 99%. The replacement is completed. If the whole process is replaced by positive pressure replacement, it will take 2240s and consume 665m³ of nitrogen. Under the combined replacement, 1310s of time and 345m³ of nitrogen are saved. The nitrogen and gas concentration changes can be seen in Figure 5 and Figure 6 .

[0080] In the embodiment, the combined replacement of blowing replacement and positive pressure replacement is proposed to fully exert the advantages of high efficiency at the initial stage of blowing replacement and thoroughness of positive pressure replacement, to improve the overall replacement efficiency while ensuring thorough replacement and system safety.

[0081] The exemplary embodiment of the present application also provides a storage tank, which stores a first gas, and the storage tank replaces the first gas into a second gas by the gas replacement method of any one of the first aspect, and the volume of the storage tank is greater than or equal to a preset volume.

[0082] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A gas displacement method, characterized by, The method is applied to a tank storing a first gas, and comprises: in a case where an exhaust port of the tank is open, introducing a second gas into an intake port of the tank, and discharging the first gas from the exhaust port; when a volume fraction of the second gas in the tank is greater than or equal to a first preset volume fraction, controlling the exhaust port to be closed; when a gas pressure in the tank is greater than or equal to a preset pressure, controlling the intake port to be closed; when a closing duration of the intake port is greater than or equal to a first preset duration, controlling the exhaust port to be opened; after the exhaust port of the tank is controlled to be opened when the closing duration is greater than or equal to the first preset duration, the method further comprises: when the volume fraction is less than a second preset volume fraction, controlling the exhaust port to be closed, and introducing the second gas into the intake port until the volume fraction is greater than or equal to the second preset volume fraction; the second preset volume fraction is a volume fraction of the second gas required to meet a displacement requirement.

2. The gas displacement method according to claim 1, wherein, after the second gas is introduced into the intake port of the tank in a case where the exhaust port of the tank is open, the method further comprises: recording a gas charging duration of the second gas introduced into the intake port; when the gas charging duration is greater than or equal to a second preset duration, controlling the exhaust port to be closed; the second preset duration is determined according to the first preset volume fraction; when the gas pressure in the tank is greater than or equal to the preset pressure, controlling the intake port to be closed; when the closing duration of the intake port is greater than or equal to the first preset duration, controlling the exhaust port to be opened.

3. The gas displacement method according to claim 2, wherein, The second preset duration is determined by inputting a volume of the tank and the first preset volume fraction into a preset duration determination model.

4. The gas displacement method according to claim 1, wherein, The volume of the tank is greater than or equal to a preset volume.

5. The gas displacement method according to claim 1, wherein, The tank comprises a tank body and at least one branch pipeline.

6. The gas displacement method according to claim 1, wherein, The tank comprises a tank body and at least one blind pipe.

7. The gas displacement method according to claim 1, wherein, the step of introducing the second gas into the intake port of the tank in a case where the exhaust port of the tank is open comprises: in a case where the exhaust port of the tank is open, introducing the second gas into the intake port of the tank at a preset flow rate.

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