JP2010185482A - In-pipe ice deicing system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in-pipe ice deicing system and method, capable of removing surely ice, without dropping, into a tank inside, the ice deposited onto an inner wall of a pipe such as a spare pipe over a long period, or without dropping molten water of the ice into the tank inside. <P>SOLUTION: This in-pipe ice deicing system/method includes a gas emission part 20 for emitting a sublimating gas for sublimating the ice X into steam to be removed, toward the ice deposited portion X in a pipe, a temperature detecting part 30 for detecting a temperature of the sublimating gas supplied to the gas emission part 20, and a control part 40 for controlling a state of the sublimating gas in the gas emission part 20, based on a detection result from the temperature detecting part 30, and the ice deposited portion X is sublimated into the steam to be removed, by bringing the sublimating gas emitted from the gas emission part 20, into contact with the ice deposited portion X. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an in-tube ice removal system and method for removing ice adhering to a pipe.

  When storing the liquid in the tank, various conditions such as the liquid temperature, the liquid density, and the liquid level of the stored liquid are grasped for safety management, quality control, inventory management, and the like. Therefore, the tank administrator inserts various measuring devices such as temperature sensors, liquid density meters, and level sensors into the tank using piping such as spare pipes connected to the tank in the event of trouble with the equipment used. Various states of the stored liquid may be measured.

  Here, when the liquid storage tank stores the low-temperature liquid, when the outside air enters the spare pipe, the water present in the outside air is cooled from the liquid storage tank side and becomes ice and adheres to the inner wall of the spare pipe. Sometimes. When such ice adhesion occurs, it becomes difficult to install various measuring devices such as a temperature sensor, a liquid density meter, and a level sensor.

  In relation to this problem, in a low temperature liquefied gas vaporization facility, a technique is known in which ice adhering to the surface of a tube constituting an evaporator is melted by the heat of a heater (see, for example, Patent Document 1). It is conceivable to apply the technique to a system and method for removing icing in a tube.

  In addition, there is a technique in which an electric heating body is brought into contact with a frozen portion in the piping with respect to the frozen pipe, and the electric heating body is energized to defrost the frozen portion (see, for example, Patent Document 2). .

  In addition, there is a technique for defrosting the frozen part by inserting a nozzle into the frozen pipe and injecting pressurized hot water from the nozzle toward the frozen part (see, for example, Patent Document 3).

JP-A-10-252994 JP 2001-182106 A Utility Model Registration No. 3086843

  However, when the technique of Patent Document 1 is applied as it is, for example, to an application for removing icing in a pipe connected to a liquid storage tank, water generated by melting of ice is generated inside the tank. There is a risk of falling. Alternatively, it is conceivable that the ice is peeled off from the inner wall of the spare tube due to the rise in the ice temperature, and the ice pieces fall into the tank. The dropping of molten water or ice pieces into these tanks is not preferable from the viewpoint of quality control of the stored liquid.

  Also in Patent Document 2, there is a high risk that the molten water falls into the tank as the frozen part in the pipe is melted.

  Furthermore, in patent document 3, since warm water is used for the defrosting of the freezing part inside piping, this warm water flows into the tank as it is along with the melted water.

  Therefore, the present invention has been made in view of the above problems, and its purpose is to prevent ice attached to the inner wall of a pipe such as a spare pipe over a long period of time without dropping it into the tank or melting the ice. It is an object of the present invention to provide an in-tube ice removal system and method capable of reliably removing ice without dropping water into the tank.

  The characteristic configuration of the in-pipe icing removal system according to the present invention includes a gas discharge unit that discharges a sublimation gas for sublimating and removing ice into water vapor toward an icing site in the pipe, and the gas discharge unit. A temperature detection unit that detects the temperature of the sublimation gas supplied to the control unit, and a control unit that controls the state of the sublimation gas in the gas discharge unit based on the detection result of the temperature detection unit, The sublimation gas released from the gas discharge part comes into contact with the icing site, so that the icing site is sublimated to water vapor and removed.

In order to remove the ice adhering to the pipe and its melted water from the pipe without dropping it into the lower tank or the like, the solid ice is directly changed to the state of water vapor as a gas, that is, Sublimation is effective. In order to generate such sublimation from ice to water vapor, it is necessary to set the temperature and pressure (water vapor partial pressure) around the icing site to conditions below the triple point of water.
In this regard, in the pipe icing removal system of this configuration, the sublimation gas for removing the ice by sublimating it into water vapor is discharged from the gas discharge part toward the icing part in the pipe. At this time, the temperature detection unit detects the temperature of the sublimation gas, and the control unit controls the state of the sublimation gas in the gas discharge unit based on the detection result. Thereby, for example, it becomes possible to adjust the sublimation gas discharged from the gas discharge portion toward the icing site to a condition that is not more than the triple point of water. In this case, the ice adhering to the pipe gradually changes to water vapor without melting or peeling off from the inner wall of the pipe, and finally disappears from the pipe. As a result, for example, various measurement devices such as a temperature sensor, a liquid density meter, and a level sensor can be inserted into the pipe from which the ice has been removed, and various measurements can be performed.

  In the in-pipe icing removal system according to the present invention, it is preferable that a gas generation unit for generating a raw gas used for preparation of the sublimation gas is provided upstream of the gas discharge unit.

  With the in-pipe icing removal system of this configuration, the sublimation gas can be prepared from the raw gas generated in the gas generation unit, so the sublimation gas has a wide range of preparation, and the optimum sublimation gas according to the conditions. Can be prepared.

  In the pipe icing removal system according to the present invention, the sublimation gas preferably contains liquefied nitrogen-derived nitrogen gas obtained by vaporizing liquefied nitrogen.

  In the in-pipe deicing system of this configuration, the sublimation gas is configured to include liquefied nitrogen-derived nitrogen gas obtained by vaporizing liquefied nitrogen, so that the sublimation gas contains almost moisture. Absent. Therefore, since the water vapor partial pressure is kept very low, the sublimation of the ice adhering in the pipe to the water vapor can be further promoted.

  In the in-pipe icing removal system according to the present invention, the system includes a merging unit that mixes an adjustment gas with the liquefied nitrogen-derived nitrogen gas, the control unit based on a detection result of the temperature detection unit. It is preferable to control the amount of the temperature adjusting gas mixed with the liquefied nitrogen-derived nitrogen gas.

  In the pipe icing removal system of this configuration, the adjustment gas is mixed with the liquefied nitrogen-derived nitrogen gas at the junction, and further, the control unit is based on the temperature of the sublimation gas detected by the temperature detection unit. The mixing amount of the temperature adjusting gas to the liquefied nitrogen-derived nitrogen gas at the junction is controlled. Therefore, the sublimation gas is adjusted to a condition where the water temperature is not more than the triple point of water by a relatively easy operation of controlling the amount of gas mixture, and the sublimation of ice adhering in the piping to water vapor can be promoted.

  In the in-pipe icing removal system according to the present invention, the control unit controls the sublimation gas released from the gas discharge unit to a temperature at which the water is in a gaseous state at a temperature equal to or lower than a triple point of water. Is preferred.

  In the in-pipe icing removal system of this configuration, the sublimation gas discharged from the gas discharge unit is reliably controlled by the control unit at a temperature below the triple point of water and at a pressure at which water becomes a gaseous state. For this reason, the sublimation of the ice adhering in the pipe to the water vapor can be further promoted.

  In the in-pipe icing removal system according to the present invention, it is preferable that the in-pipe icing removal system includes a gas discharge unit that discharges moisture-containing gas containing water vapor generated by exposing the icing part with the sublimation gas to the outside of the pipe. .

  In the pipe icing removal system of this configuration, the moisture-containing gas containing water vapor generated by exposing the icing site with the sublimation gas is discharged from the gas discharge part to the outside of the pipe. An increase in the water vapor partial pressure inside is prevented. Therefore, sublimation of ice adhering in the pipe to water vapor can be further promoted.

  The characteristic configuration of the in-pipe icing removal method according to the present invention includes a gas releasing step for releasing a sublimation gas for sublimating ice into water vapor to remove it toward an icing site in the pipe, and the gas releasing step. A temperature detection step for detecting the temperature of the sublimation gas released in step (b), and a state of the sublimation gas released in the gas release step based on the temperature of the sublimation gas detected in the temperature detection step. A control step of controlling, and the sublimation gas released through the control step comes into contact with the icing site, thereby sublimating the icing site into water vapor and removing it.

In order to remove the ice adhering to the pipe and its melted water from the pipe without dropping it into the lower tank or the like, the solid ice is directly changed to the state of water vapor as a gas, that is, Sublimation is effective. In order to generate such sublimation from ice to water vapor, it is necessary to set the temperature and pressure (water vapor partial pressure) around the icing site to conditions below the triple point of water.
In this regard, in the in-pipe icing removal method of this configuration, as a gas release step, a sublimation gas for sublimating and removing ice into water vapor is discharged toward the icing part in the pipe. In the temperature detection step, the temperature of the sublimation gas is detected, and the state of the sublimation gas released in the gas release step is controlled based on the detected temperature. Thereby, for example, it becomes possible to adjust the sublimation gas released toward the icing site in the gas release step to a condition that is below the triple point of water. In this case, the ice adhering to the pipe gradually changes to water vapor without melting or peeling off from the inner wall of the pipe, and finally disappears from the pipe. As a result, for example, various measurement devices such as a temperature sensor, a liquid density meter, and a level sensor can be inserted into the pipe from which the ice has been removed, and various measurements can be performed.

  In the in-pipe icing removal method according to the present invention, it is preferable to execute a gas generation step of generating a raw gas used for preparing the sublimation gas.

  If the method for removing icing in the pipe of this configuration is used, the sublimation gas can be prepared from the raw gas generated in the gas generation step, so the sublimation gas has a wide range of preparation, and the optimum sublimation gas according to the conditions. Can be prepared.

  In the in-pipe icing removal method according to the present invention, performing a gas discharge step of discharging a moisture-containing gas containing water vapor generated by exposing the icing part with the sublimation gas to the outside of the pipe. preferable.

  In the pipe icing removal method of this configuration, the moisture-containing gas containing water vapor generated by exposing the icing site with the sublimation gas is discharged outside the pipe in the gas discharge process. An increase in the water vapor partial pressure inside is prevented. Therefore, sublimation of ice adhering in the pipe to water vapor can be further promoted.

1 is a block diagram schematically showing an in-tube ice removal system for carrying out the in-tube ice removal method of the present invention. Water state diagram showing the areas where water can take each state (solid, liquid, and gas)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the configurations described in the embodiments and drawings described below, and various modifications are possible.

[In-pipe icing removal system]
FIG. 1 is a block diagram schematically showing an in-tube ice removal system 100 of the present invention.

The cryogenic liquid storage tank 50 to which the in-pipe icing removal system 100 is applied is a tank used for storing a substance liquefied in a low temperature state.
The cryogenic liquid storage tank 50 has a double structure consisting of an outer tank portion 51 and an inner tank portion 52, and the cryogenic liquid is stored inside the inner tank portion 52. Between the inner tank part 52 and the outer tank part 51, a heat insulating material is filled as needed. Further, the upper space inside the inner tank portion 52 is filled with vaporized gas (Boil Off Gas; BOG) of a low-temperature liquid. Thereby, a positive pressure is applied to the internal space of the cryogenic liquid storage tank 50 by the BOG.

  Further, a spare pipe 53 having a valve 54 is connected to the cryogenic liquid storage tank 50 in a form penetrating the outer tank portion 51 and the inner tank portion 52. A device for measuring various states such as the liquid temperature, the liquid density, and the liquid level of the low-temperature liquid stored in the low-temperature liquid storage tank 50 can be installed by using the spare pipe 53.

  Here, the temperature of the internal atmosphere of the auxiliary pipe 53 is normal temperature in the vicinity of the outer end of the auxiliary pipe 53, but the temperature gradually decreases toward the inner side of the low temperature liquid storage tank 50, and the low temperature liquid storage tank 50. It is about 0 degreeC in the predetermined position between the outer tank part 51 and the inner tank part 52 of this. Therefore, when external air intrudes for some reason, moisture in the atmosphere condenses inside the spare pipe 53 at this predetermined position, and it becomes easy to adhere to the inner wall of the spare pipe 53 as ice. If such an ice adhesion phenomenon continues for a long period of time, the ice may accumulate thickly on the inner wall of the preliminary tube 53.

  Therefore, in the in-pipe icing removal system 100 of the present embodiment, the sublimation gas adjusted to a predetermined condition to be described later with respect to the ice X adhering to the inner wall of the auxiliary pipe 53 connected to the low-temperature liquid storage tank 50. The ice X is sublimated into water vapor by directly spraying G0 and removed from the spare pipe 53.

More specifically, the sublimation gas G0 is, for example, liquefied nitrogen G1 having a boiling point of about −196 ° C. and nitrogen gas G2 having a room temperature of about 20 ° C. It is generated by mixing at the junction 3 so that the temperature is adjusted to -20 to -5 ° C, preferably about -10 ° C. Therefore, in this embodiment, the liquefied nitrogen G1 and the room temperature nitrogen gas G2 are the raw gases used for the preparation of the sublimation gas, and the liquefied nitrogen tank 1 for supplying the liquefied nitrogen G1 and the room temperature nitrogen gas G2 are used. The gas generator 10 is configured by the nitrogen cylinder 2 that supplies the gas. In addition, as the gas production | generation part 10, you may include piping members (piping 4,5, valve | bulb 6,7,9 etc.), incidental equipment (liquid feed pump 11), and other arbitrary equipment (dehumidifier etc.) which are not illustrated. Absent.
On the other hand, in the present invention, the stored low-temperature liquid BOG can be used as the sublimation gas G0 as it is or in a state where the BOG and the normal temperature nitrogen gas G2 are mixed.

  The sublimation gas G0 obtained by preparing the raw gas from the gas generation unit 10 passes through the pipe 8 and is inserted into the spare pipe 53. The gas discharge unit 20 (this is the nozzle pipe part 21 and the nozzle body 22). And is discharged toward the ice X adhering to the inner wall of the preliminary pipe 53. The pipe 8 is a dedicated pipe for supplying the sublimation gas G0.

  Next, the conditions under which the ice X adhering to the inner wall of the preliminary pipe 53 sublimates to water vapor will be described. First, the three states of water (solid, liquid, and gas) will be described.

  FIG. 2 is a state diagram (phase diagram) of water showing a region where water can take each state (solid, liquid, and gas). As is well known, at normal pressure (1013 hPa), solid water (that is, ice) changes to a liquid at about 0 ° C., and changes to a gas (water vapor) at about 100 ° C. However, when the pressure (which means water vapor pressure here) decreases, the transition point from the solid to the liquid hardly changes as shown in FIG. 2, but the transition point from the liquid to the gas suddenly increases from about 100 ° C. When the pressure drops to a predetermined low pressure state (about 6.1 hPa), the transition point from the solid to the liquid and the transition point from the liquid to the gas overlap (about 0.01 ° C.). This overlapping point is the triple point of water. In this state (about 0.01 ° C., about 6.1 hPa), the three states of solid (ice), liquid (water), and gas (water vapor) are in equilibrium. Will coexist. When the pressure is further reduced, the liquid state does not exist and water is transferred between the solid and the gas.

  Therefore, in order to sublimate the ice X into water vapor, the temperature around the ice X to which the sublimation gas G0 is blown (that is, the internal atmosphere of the auxiliary pipe 53 between the outer tank 51 and the inner tank 52) and The pressure (water vapor partial pressure) needs to be a condition below the triple point of the water. In the present embodiment, the ice X is in the state indicated by α in FIG. 2 (temperature: about −100 to −5 ° C., pressure: about 0.00001 to 4 hPa). It is necessary to set the state of the region shown (temperature: about −50 to −5 ° C., pressure: about 0.00001 hPa or less). In order to realize this, the temperature and generation state (mixing ratio of liquefied nitrogen G1 and nitrogen gas G2 at normal temperature, supply amount of generated G0, etc.) of the sublimation gas G0 generated by the gas generation unit 10 are changed. I need to control it.

  Therefore, in the in-pipe icing removal system 100 of this embodiment, a temperature sensor that detects the temperature of the sublimation gas G0 supplied from the gas generation unit 10 to the gas discharge unit 20 in the pipe 8 through which the sublimation gas G0 passes. A temperature detector 30 is provided. Further, a control unit 40 that controls the state of the sublimation gas G0 in the gas discharge unit 20 based on the detection result of the temperature sensor 30 is provided. As the temperature sensor 30, for example, a thermocouple capable of detecting a temperature range from normal temperature to about minus several tens of degrees Celsius can be employed. The control unit 40 can be constructed as a computer that comprehensively controls the in-pipe icing removal system 100, for example.

By recognizing the temperature of the sublimation gas G0 passing through the pipe 8, the control unit 40 ensures that the temperature of the sublimation gas G0 immediately before being discharged from the gas discharge unit 20 toward the ice X is water. The conditions are adjusted to be below the triple point. For example, if the temperature of the sublimation gas G0 detected by the temperature sensor 30 is higher than the temperature necessary to achieve the triple point of water (ie, about 0.01 ° C.), the control unit 40 may set the nitrogen cylinder 2 The opening degree of the valve 7 provided in the pipe 5 connected to is reduced to reduce the mixing amount of the nitrogen gas G2 at normal temperature with respect to the liquefied nitrogen G1. Further, if necessary, the flow rate of the liquefied nitrogen G1 is increased by increasing the opening degree of the valve 6 provided in the pipe 4 connected to the liquefied nitrogen tank 1 or increasing the discharge amount of the liquid feed pump 11. . By these operations, the temperature of the generated sublimation gas G0 is lowered.
On the other hand, when the temperature of the sublimation gas G0 detected by the temperature sensor 30 is too lower than the temperature necessary to achieve the triple point of water, the control unit 40 is provided in the pipe 5 connected to the nitrogen cylinder 2. The opening degree of the valve 7 is increased to increase the mixing amount of the nitrogen gas G2 at normal temperature with respect to the low temperature liquefied nitrogen G1. Further, if necessary, the opening degree of the valve 6 provided in the pipe 4 connected to the liquefied nitrogen tank 1 is decreased, or the discharge amount of the liquid feed pump 11 is decreased to decrease the flow rate of the liquefied nitrogen G1. . By these operations, the temperature of the generated sublimation gas G0 is raised.

  By the way, when the distance between the temperature sensor 30 provided in the pipe 8 and the nozzle main body 22 of the gas discharge unit 20 is large, the sublimation gas G0 travels from the position of the temperature sensor 30 to the nozzle main body 22. There is a risk that G0 is heated and the temperature rises. Therefore, in consideration of such a temperature rise, the control unit 40 causes the temperature of the sublimation gas G0 at the position of the temperature sensor 30 to be somewhat lower than the temperature necessary to achieve the triple point of water. Thus, the opening degree adjustment of the valves 6 and 7 is performed. As a result, the temperature of the sublimation gas G0 is surely made equal to or lower than the triple point of water when it reaches the nozzle body 22.

  Further, the supply amount (flow velocity) of the sublimation gas G0 is set to an appropriate supply amount by appropriately adjusting the opening degree of the valve 9 provided in the pipe 8 on the downstream side of the merging unit 3 by the control unit 40. The For example, according to an experiment, when the pipe 8 has a diameter of about 200 mm and ice having a thickness of about 200 mm adheres over substantially the entire cross section of the pipe 8, the nozzle body 22 of the gas discharge unit 20. It is preferable to set the flow rate of injection of the sublimation gas G0 from 5 to 100 m / s.

  In addition, the opening degree adjustment of the valves 6, 7, and 9 by the control unit 40 described above is an example, and other opening degree adjustment patterns can be executed. Further, in FIG. 1, the valves 6 and 9 are omitted, so that the liquefied nitrogen G1 is always kept flowing, and the control unit 40 only adjusts the opening degree of the valve 7 so that the nitrogen at room temperature is supplied to the liquefied nitrogen G1. It is also possible to appropriately adjust the mixing amount of the gas G2.

  Thus, based on the temperature of the sublimation gas G0 detected by the temperature sensor 30, the control unit 40 supplies the mixed amount of the normal temperature nitrogen gas G2 to the liquefied nitrogen G1 in the junction 3 and the supply of the sublimation gas G0. The amount can be controlled.

  On the other hand, instead of executing automatic valve control by the control unit 40, it is also possible for the operator to adjust the temperature and supply amount of the sublimation gas G0 by manual valve operation while checking the thermometer.

  Regarding the water vapor pressure of the sublimation gas G0, the liquefied nitrogen G1 and the room temperature nitrogen gas G2 that are raw materials of the sublimation gas G0 contain almost no water. (That is, about 6.1 hPa or less). Therefore, if the control part 40 adjusts the opening degree of the valve | bulb 6,7,9 suitably and controls the temperature and supply amount of the sublimation gas G0 sent from the gas production | generation part 10 to the gas discharge | release part 20, the nozzle main body 22 will be demonstrated. The sublimation gas G0 released from the water can be made into conditions suitable for removing the ice X.

  As described above, in this embodiment, the control unit 40 adjusts the opening degree of the valves 6, 7, 9 based on the temperature of the sublimation gas G 0 detected by the temperature sensor 30. The state of the gas G0 is determined.

  Therefore, in the in-pipe icing removal system 100 of the present embodiment, the state of the sublimation gas G0 is appropriately controlled, so that the ice X adhering to the inside of the preliminary pipe 53 is melted or separated from the inner wall of the preliminary pipe 53. Without being carried out, it gradually changes to water vapor and can be reliably removed from the inside of the spare pipe 53. As a result, for example, various measurement devices such as a temperature sensor, a liquid density meter, and a level sensor can be inserted into the spare pipe 53 from which the ice X has been removed, and various measurements can be performed.

  By the way, in the pipe icing removal system 100 of the present embodiment, a moisture-containing gas containing water vapor generated by exposing the ice X to the sublimation gas G0 is generated. Part) 55 can be discharged to the outside of the spare pipe 53. For example, as shown in FIG. 1, the gas discharge pipe 55 is configured as a branch pipe with a valve 56 that branches from the spare pipe 53 to the side. The valve 56 is normally closed, but opens during a period when the sublimation removal operation for the ice X is being performed. Then, since the positive pressure is applied to the inside of the cryogenic liquid storage tank 50, the moisture-containing gas is discharged from the gas discharge pipe 55 together with a part of the BOG. Thereby, the raise of the water vapor partial pressure in the inside of the preliminary | backup pipe | tube 53 and the low-temperature liquid storage tank 50 is prevented. As a result, the sublimation of the ice adhering to the inside of the preliminary tube 53 to water vapor can be further promoted.

[In-pipe icing removal method]
In the present invention, the in-pipe ice removal method can be executed using the in-pipe ice removal system 100 described above. That is, the following steps (1) to (3) are performed.
(1) A gas release step of releasing a sublimation gas for sublimating and removing ice into water vapor toward an icing site in the pipe.
(2) A temperature detection step of detecting the temperature of the sublimation gas released in the gas release step.
(3) A control step of controlling the state of the sublimation gas released in the gas release step based on the temperature of the sublimation gas detected in the temperature detection step.
As described above, in the present embodiment, the ice X adhering to the inner wall of the preliminary pipe 53 is in the state indicated by α in FIG. The ice X is sprayed with a sublimation gas generated so as to be in a predetermined sublimation gas generation state (that is, generated at a temperature equal to or lower than the triple point of water and at a pressure at which water becomes a gas state). Thereby, the state of the region indicated by β in FIG. 2 is obtained. In this way, the ice X is sublimated from solid to water vapor and removed from the inside of the preliminary tube 53.
If necessary, the gas generating step for generating the raw gas used for the preparation of the sublimation gas, or the moisture-containing gas containing water vapor generated by exposing the ice X with the sublimation gas, A gas discharge process for discharging to the outside is executed.

  According to the in-pipe icing removal method of the present invention, the sublimation gas released toward the ice X in the gas release step is optimal for removing icing adjusted to a condition that is surely below the triple point of water. Since the gas for sublimation can be used, the ice X adhering to the inner wall of the preliminary pipe 53 is gradually changed into water vapor without being melted or peeled off from the inner wall of the preliminary pipe 53 and reliably removed. can do. Therefore, for example, various measurement devices such as a temperature sensor, a liquid density meter, and a level sensor can be inserted into the spare tube 53 from which the ice X has been removed, and various measurements can be performed.

  Further, since the sublimation gas can be prepared from the raw gas generated by the gas generation step, the sublimation gas can be prepared in a wide range, and the optimum sublimation gas can be prepared according to the conditions.

  Further, in the gas discharge process, the moisture-containing gas containing water vapor generated by exposing the ice X to the sublimation gas is discharged to the outside of the spare pipe 53, so that the inside of the spare pipe 53 and the cryogenic liquid storage tank 50 An increase in the partial pressure of water vapor is prevented. Therefore, the sublimation of the ice adhering to the inner wall of the preliminary pipe 53 to water vapor can be further promoted.

[Another embodiment]
(1) In the embodiment described above, the temperature of the sublimation gas G0 at the position of the temperature sensor 30 is water in preparation for a case where the distance between the temperature sensor 30 provided in the pipe 8 and the nozzle body 22 of the gas discharge unit 20 is large. The degree of opening of the valves 6 and 7 is adjusted so that the temperature is somewhat lower than the temperature required to achieve the triple point. However, the temperature sensor 30 is measured using a correction coefficient or a correction map. It is conceivable to correct the sublimation gas G0 temperature so that the condition below the triple point of water can be achieved at the time of blowing out from the nozzle body 22. By performing such correction, the sublimation gas G0 can be reliably set to a condition below the triple point of water while reducing the amount of liquefied nitrogen G1 produced from the liquefied nitrogen tank 1.

(2) In the above embodiment, the component of the sublimation gas G0 is nitrogen gas or BOG, but other components may be used as long as they do not affect the quality of the low-temperature liquid stored in the low-temperature liquid storage tank 50. Various types of gas can be used. Examples of such a gas include carbon dioxide and air.

3 Joining section 10 Gas generating section 20 Gas releasing section 30 Temperature sensor (temperature detecting section)
40 Control section 55 Branch pipe (gas discharge section)
100 In-pipe icing removal system X Ice (Icing part)

Claims (9)

A gas discharge part for discharging a sublimation gas for sublimation of ice into water vapor and removing it toward an icing site in the pipe;
A temperature detector for detecting the temperature of the sublimation gas supplied to the gas discharge unit;
A control unit for controlling the state of the sublimation gas in the gas discharge unit based on the detection result of the temperature detection unit;
An in-pipe icing removal system in which the sublimation gas released from the gas discharge unit contacts the icing site to sublimate the icing site to water vapor and remove it.   The in-pipe icing removal system according to claim 1, wherein a gas generation unit that generates a raw gas used for preparation of the sublimation gas is provided upstream of the gas discharge unit.   The in-pipe ice removal system according to claim 1 or 2, wherein the sublimation gas includes liquefied nitrogen-derived nitrogen gas obtained by vaporizing liquefied nitrogen. Comprising a merging section for mixing an adjustment gas into the liquefied nitrogen-derived nitrogen gas;
The in-pipe icing removal system according to claim 3, wherein the control unit controls a mixing amount of the temperature adjustment gas to the liquefied nitrogen-derived nitrogen gas in the merging unit based on a detection result of the temperature detection unit. .   The said control part controls the sublimation gas discharge | released from the said gas discharge | release part to the pressure below the triple point of water, and the pressure from which water turns into a gaseous state as described in any one of Claims 2-4. In-pipe deicing system.   6. The gas discharge unit according to claim 1, further comprising a gas discharge unit configured to discharge moisture-containing gas containing water vapor generated by exposing the icing part with the sublimation gas to the outside of the pipe. In-pipe icing removal system. A gas releasing step for releasing a sublimation gas for removing ice by sublimating into water vapor toward an icing site in the pipe;
A temperature detection step of detecting the temperature of the sublimation gas released in the gas release step;
A control step of controlling the state of the sublimation gas released in the gas release step based on the temperature of the sublimation gas detected in the temperature detection step;
An in-pipe deicing removal method in which the sublimation gas released through the control step comes into contact with the icing site to sublimate the icing site to water vapor and remove it.   The in-pipe icing removal method according to claim 7, wherein a gas generation step of generating a raw gas used for preparation of the sublimation gas is executed.   The in-pipe deicing removal method according to claim 7 or 8, wherein a gas discharge step of discharging moisture-containing gas containing water vapor generated by exposing the icing part with the sublimation gas to the outside of the pipe is performed. .

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