KR20210058819A - How to operate liquefied natural gas import facility - Google Patents

Abstract

(Task) Provide technology that responds to demand response while maintaining stable operation of liquefied natural gas import facilities. (Solution means) The liquefied natural gas import facility 2 includes a storage tank 21 for storing liquefied natural gas, a vaporizer 231 for vaporizing the liquefied natural gas discharged therefrom and shipping it in a gaseous state, A gas compression unit 24 driven by an electric motor for boosting the boil-off gas generated in the storage tank 2 and mixing it with the vaporized natural gas is provided. Then, the review of the reduction in power consumption is started in the review initiation process, and the change in the internal pressure of the storage tank 21 is predicted when the gas compression unit 24 is stopped in the stopable period calculation process, and the gas compression unit 24 After calculating the stopable period of ), in the process of determining whether to stop, it is determined whether or not the gas compression unit 24 is stopped based on the comparison result between the reduction period and the stopable period.

Description

How to operate liquefied natural gas import facility

The present invention relates to a method of operating a liquefied natural gas import facility that receives liquefied (LNG), stores it in a storage tank, and vaporizes the LNG to deliver product gas.

Along with the spread of renewable energy, there is a concern that the reliability of the power system is deteriorated. As a countermeasure, demand response (Demand Response: hereinafter also referred to as ``DR'') is a method of adjusting power demand in which the demand side changes the power consumption pattern by setting the price of electricity or payment of incentives. Introduction is being considered.

For example, demands at factories and large retail stores increase or decrease the demand for electricity by switching the operation and shutdown of power consuming devices, or changing the output of their own power generation facilities.

However, especially in the implementation of DR ("Reduced DR") that reduces power demand, demands that do not have self-generation facilities or storage batteries, or whose capabilities are not sufficient, are inevitable to reduce power demand. . As a result, for example, it may be necessary to carry out production adjustments in factories, and it is difficult to participate in the DR plan unless it is clear that the merit of implementing DR exceeds the demerit created by production adjustments. It becomes.

Here, Patent Document 1 describes a demand response system that performs DR by outputting a power supply/demand adjustment command signal directly from the power company to an electric device control device that controls the operation of an electric device on the consumer's side. . However, it is difficult for an external electric power company to directly participate in a demand response system that controls the operation of the electric device when operating an electric device, for example, at a demand price that requires work such as securing safety.

In addition, in Patent Document 2, BOG (Boil Off Gas: LNG component vaporized in an LNG tank) mixed with liquefied natural gas vaporized in a vaporizer by performing load control of the BOG compressor according to the required heat quantity of the gas consumer. Techniques for controlling the amount of are described. On the other hand, in the patent document 2, the technique related to DR is not described.

Japanese Patent No. 643372 Japanese Unexamined Patent Application Publication No. 2018-112218

The present invention has been made under such a background, and provides a technology corresponding to a demand response (DR) while maintaining a stable operation of a liquefied natural gas import facility.

The operating method of the liquefied natural gas import facility of the present invention is a method of operating the liquefied natural gas import facility,

The liquefied natural gas import facility includes a storage tank for storing liquefied natural gas received from the outside, a vaporizer for vaporizing the liquefied natural gas discharged from the storage tank and shipping in a gaseous state, and generated in the storage tank. And a gas compression unit driven by an electric motor for boosting the boil-off gas and mixing it with the natural gas vaporized in the carburetor,

Receiving or assuming that the request for reduction of power consumption including information on the reduction period is received, a review initiation process of initiating a review of the reduction of power consumption, and the internal pressure of the storage tank when the gas compression unit is stopped. Based on the process of calculating a stopable period of predicting a change and calculating a stopable period of the gas compression unit, and a comparison result between the reduction period and the stopable period of the gas compression unit, determining whether or not the gas compression unit is stopped. It characterized in that it includes a process of determining whether to stop or not.

The operating method of the liquefied natural gas import facility may have the following features.

(a) In the step of determining whether to stop, including a gas compression unit stopping step of stopping the gas compression unit when it is determined that it is possible to stop the gas compression unit during the reduction period.

(b) The carburetor is a carburetor for normal operation that vaporizes liquefied natural gas using seawater supplied from a seawater pump driven by an electric motor as a heat source, and an emergency vaporization of liquefied natural gas using the combustion heat of the natural gas as a heat source. In addition to providing a movable carburetor and performing the gas compression unit stop step, performing a carburetor switching step of converting the normal movable carburetor to an emergency operation carburetor to vaporize liquefied natural gas.

(c) In the process of calculating the possible stop period, the change in the internal pressure is predicted based on the change in the gaseous phase volume accompanying the discharge of the liquefied natural gas from the storage tank and the amount of boil-off gas generated in the storage tank. To do. The amount of boil-off gas generated in the storage tank is obtained based on the amount of heat input to the storage tank.

(d) In the process of calculating the allowable stop period, the period in which the predicted value of the change in the internal pressure of the storage tank is less than the upper limit of the operating pressure installed in the storage tank is defined as the allowable stop period.

(e) In the case where the reduction period overlaps with the period in which the liquefied natural gas is received from the outside to the storage tank, a continuation judgment step is made to give priority to continuing the operation of the gas compression unit.

(f) When the determination result in the stop determination process is negative, in order to reduce power consumption, a target to set a target pressure lower than the pressure of the storage tank when the stop determination process is performed A pressure setting step and a pressure reducing step of lowering the internal pressure of the storage tank to a corresponding target pressure, and after the pressure reducing step, re-executing the stop determination step.

The present invention calculates the stopable period of the gas compression unit for extracting the boil-off gas from the storage tank of liquefied natural gas, and determines whether the gas compression unit is stopped based on the result, so that the stable operation of the liquefied natural gas import facility is Demand response can be performed without disturbing.

1 is an explanatory diagram showing the relationship between participants in a DR transaction.
2 is a configuration diagram of an LNG import facility according to an embodiment.
3 is a flow chart of items carried out in an LNG import facility in relation to DR.

1 shows an example of the relationship between participants in a DR transaction. The transmission and distribution companies 11 and the like include general transmission and distribution companies such as local power companies. On the other hand, if a DR contract is made to the transmission and distribution service provider 11, rewards can be obtained. On the other hand, if the request of the DR from the transmission and distribution service provider 11 cannot be satisfied, payment of a penalty may be required.

The resource aggregator 12 collects a plurality of customers 13 and adjusts the supply and demand of DR to reduce the risk of distribution of compensation and payment of penalty. As the content of the supply and demand adjustment, the selection of the demand price 13 capable of responding to the DR request from the transmission and distribution company 11, the allocation of a response period, and the like can be illustrated.

The demand price 13 performs DR, respectively, based on the supply and demand adjustment with the resource aggregator 12. In DR, there are "raise DR", which increases power demand, and "cut DR", which reduces power demand. When the amount of generation of renewable energy is large and it is necessary to increase the demand for electricity, a request for "Impression DR" is issued. On the other hand, in the case where the demand for electricity in the jurisdiction of the transmission and distribution business operator 11 closely follows the supply, a request for "reduction DR" is issued.

The operator of the LNG import facility 2 of this example constitutes one of the demand prices 13 among participants in the aforementioned DR transaction.

In the example shown in FIG. 1, the transmission/distribution company 11 requests (reduction request) the resource aggregator 12 for "reduction DR" including information on the reduction amount and the reduction period. In order to reduce power consumption suitable for the reduction request, the resource aggregator 12 can reduce the amount available for each of a plurality of demand prices 13 (demand prices A, B, and LNG import facilities 2). Adjust supply and demand accordingly. In the example shown in Fig. 1, as a result of the adjustment, it is determined that the demand A and the LNG import facility 2 execute "reduction DR". In addition, since such demand is A, and the LNG import facility 2 reduces the amount of power consumption, the transmission and distribution business operator 11 can obtain an effect of reducing the power load in response to a reduction request.

Here, the LNG import facility 2 shown in FIG. 1 has a function of receiving and storing LNG from the outside, and vaporizing the stored LNG and shipping it to the customer 3. This LNG import facility (2) has a facility configuration applicable to DR compared to the demand price (13) of factories that require production adjustment in implementing the ``Reduction DR'' (hereinafter referred to as DR). There is a thing.

Hereinafter, a configuration example of the LNG import facility 2 of this example will be described with reference to FIG. 2.

The LNG import facility 2 includes an LNG tank 21 for storing LNG, an LNG pump 211 and 22 for delivering LNG from the LNG tank 21 in order to deliver gas to the customer 3, and LNG. A vaporizer (ORV (231), SMV (232) to be described later) that vaporizes the gas to form a vaporized gas state, and a calorie adjustment unit that obtains product gas by adding liquefied petroleum gas (LPG) for adjusting the amount of heat to the vaporized gas ( 26).

The LNG tank 21 is, for example, a storage tank that stores LNG received from the LNG tanker 4 in a liquid state cooled to about -162°C, and its type (terrestrial tank, underground tank, underground tank, etc.) ) Or capacity is not limited. Fig. 2 shows an example of a ground-type tank in which the upper surface of a cylindrical side wall is covered with a dome-shaped roof.

The LNG stored in the LNG tank 21 is transferred to the carburetors 231 and 232 through an LNG pump 211 arranged and installed in the LNG tank 21 and a delivery pump 22 for boosting pressure.

The LNG import facility (2) of this example is an ORV (Open Rack Vaporizer) 231, a vaporizer that vaporizes LNG using seawater (SW) supplied from a seawater pump (not shown) driven by an electric motor as a heat source, and natural gas. It is possible to convert and use the SMV (Submerged-combustion Vaporizer) 232, which is a vaporizer that vaporizes LNG using the combustion heat of In the LNG import facility 2, during normal operation, the LNG is vaporized using the ORV 231, and the SMV 232 is in a standby state for emergency operation such as when a power outage occurs. For example, in the LNG import facility 2, a plurality of ORVs 231 and SMVs 232 are installed.

In addition, instead of the ORV 231, an intermediate fluid vaporizer (IFV) that heats an intermediate medium such as propane using seawater and vaporizes LNG with the intermediate medium may be used as a vaporizer for normal operation. In IFV, seawater is also supplied using a seawater pump driven by an electric motor.

The calorific value adjusting unit 26 mixes the vaporized gas with LPG for calorific value adjustment, and ships the product gas having the calorific value required by the customer 3. To the heat quantity adjustment unit 26, LPG (butane or propane) stored in the LPG tank 25 is delivered in a liquid state through the LPG pump 251. This LPG is vaporized using a heat medium in the heat quantity adjusting unit 26, and is mixed with the vaporized gas sent out from the ORV 231 to become a product gas. The product gas whose heat amount has been adjusted by the heat amount adjustment unit 26 is delivered to the customer 3.

In addition, in the LNG tank 21 storing LNG, part of the LNG vaporizes due to heat input from the outside, and BOG is generated. In order to prevent the pressure in the LNG tank 21 from becoming excessive, a BOG compressor 24 which is a gas compression unit for extracting BOG is connected to the LNG tank 21. The BOG compressor 24 of this example is driven by an electric motor (not shown).

The BOG compressor 24 is, for example, a multi-stage BOG compressor having three compression stages as shown in FIG. 2, and a BOG of about 12 to 22 kPaG (pressure on the suction side of the first compression stage) is 2 to 7.5. The pressure is raised to about MPaG (pressure on the discharge side of the final compression stage). The boosted BOG merges with the LNG vaporized in the vaporizer (ORV 231 or SMV 232), the amount of heat is adjusted, and then is delivered to the customer 3 as a product gas.

In the LNG import facility 2 having the above-described configuration, by stopping the BOG compressor 24, power consumption of about several megawatts can be reduced. Even if the BOG compressor 24 is stopped, there is no influence on the LNG pumps 211 and 22, and the LNG can be transported continuously. In addition, by stopping the ORV 231, power consumption of about several hundred kilowatts can be reduced. When the ORV 231 is stopped, if the SMV 232 is operated, it is possible to continuously vaporize the LNG.

From this point of view, the LNG import facility 2 can be said to be a demand price 13 having an applicable facility configuration in participating in the DR transaction.

On the other hand, if the BOG compressor 24 is stopped for a long time and the pressure in the LNG tank 21 exceeds the upper limit of the operating pressure, for example, BOG is released toward the flare (not shown), and gas from the flare. There is a loss that burns. In addition, when the pressure in the LNG tank 21 rises, a safety valve (not shown) operates, and excess BOG is dissipated into the atmosphere.

In particular, in the LNG import facility 2, the import of LNG from the LNG tanker 4 is performed once to several times a month. At this time, the amount of BOG generated in the LNG tank 21 is increased to several times, for example, about four times as usual. In this way, it may be difficult to stop the BOG compressor 24 during a period in which a large amount of BOG is generated.

Therefore, by predicting the change in the internal pressure of the LNG tank 21 when the BOG compressor 24 is stopped, and specifying the stopable period of the BOG compressor 24, the stable operation of the LNG import facility 2 is hindered. Without work, it is possible to determine whether or not DR is being implemented.

Hereinafter, an example of a method of calculating the stopable period of the BOG compressor 24 will be described.

When the stop time of the BOG compressor 24 (the start time of the BOG accumulating pressure in the BOG compressor 24) is t1 and the restart time of the BOG compressor 24 (the time when the BOG accumulating pressure ends) is t2, the BOG compressor ( The stop period of 24) becomes (t2-t1).

When the LNG discharge flow rate from the LNG tank 21 is F [m 3 /h] and the level of LNG in the LNG tank 21 at time t1 is L1 [m], the liquid level L2 [m] at time t2 ] Is expressed by the following equation (Equation 1) (ID[m] is the inner diameter of the LNG tank 21).

In addition, when the gas phase volume of the LNG tank 21 at time t1 is V1 [m3], the gas phase volume V2 [m3] at time t2 is expressed by the following equation (Equation 2).

In addition, the amount of heat input to the LNG tank 21 from the outside, such as a heater (not shown) for preventing freezing of the outside air or the ground on a unit time basis, is measured as Qtank [J/h], and the heat input from the LNG pump 211 is measured. When Qpump[J/h] and the amount of heat input from other facilities are Qetc[J/h], the amount of BOG generated per unit time in the LNG tank 21 Wbog[kg/h] is the following equation (math It is expressed by Equation 3) (where λ is the latent heat of evaporation [J/kg] of LNG).

Further, the pressure in the LNG tank 21 at time t1 is p1 [kPaG], the pressure at time t2 is p2 [kPaG], and the density of BOG at each pressure is ρ1, ρ2 [kg/ ㎥].

When the temperature in the LNG tank 21 is constant and BOG is not discharged from the LNG tank 21, the amount of BOG generated in the LNG tank 21 during the stop period (t2-t1) and the LNG tank 21 ), the following equation (Equation 4) is obtained by taking the mass balance based on the vapor phase volume change.

And, if V1 and V2 are eliminated in (Equation 4) from the relationship of (Equation 1 and 2) and summarized, the following equation (Equation 5) is obtained.

Since the LNG tank 21 is equipped with a liquid level gauge, the LNG tank 21 during the period is based only on the change in the liquid level of the LNG in the LNG tank 21 at each time of the liquid level t1 and t2. You can see the pressure change inside. As already explained, the density (ρ1, ρ2) of BOG is determined according to the pressures (p1, p2) at each time, so the calculation of the stop period using (Equation 5) depends on the pressure change in the LNG tank 21. It is done on the basis of.

Therefore, the BOG compressor 24 is stopped by setting the upper limit of the operating pressure of the LNG tank 21 as the pressure p2 of the LNG tank 21 at the time t2 (the density ρ2 of the BOG at that time). Under one condition, it is possible to specify a stopable period (t2-t1) for maintaining the pressure in the LNG tank 21 below the upper limit of the operating pressure. In addition, as already described, the change in the level of the LNG (L2-L1) during the stopable period can be predicted from (Equation 1).

In the LNG importing facility 2 of this example, the implementation of DR can be judged based on the calculation result of the stopable period of the BOG compressor 24 described above.

Hereinafter, with reference to FIG. 3, a description will be given of specific contents when DR is performed in the LNG import facility 2.

The LNG import facility (2) operates the LNG pumps (211, 22), ORV (231), BOG compressor (24), etc. during normal operation to produce products with the quantity of heat and flow required for the customer (3). The gas is shipped (P11). At this time, operation data (I12: discharge flow rate (F), the level of LNG in the LNG tank 21 (L1), heat input amount (Qtank)) required for the calculation of the possible stop period using the above-described (Equations 1 to 5) The outside air temperature for calculating ?, the amount of heat supplied from the heater (not shown), etc.) is continuously acquired.

In addition, the LNG importing facility (2) expects to receive a request for implementing DR (reduction of power consumption) based on changes in outside air temperature and power supply and demand forecasts announced by the transmission and distribution service provider (11). Review of reductions can be started (review start process).

In this case, based on the acquired operation data and prediction of temperature change (prediction of Qtank), (Equations 3 and 5) are calculated to determine the pressure change in the LNG tank 21 from the time when DR is expected. Make predictions (P13). Then, based on the pressure change, the possible stop time of the BOG compressor 24 is calculated (P14).

The above-described calculation may be performed offline by the operator using a computer, or may be automatically calculated using an operation management system of the LNG importing facility 2 such as a DCS (Distributed Control System). The prediction of the pressure change in the LNG tank 21 and the calculation of the stopable time of the BOG compressor 24 correspond to the process of calculating the stopable period of this example.

In addition, for the carburetor, the number of ORVs 231 and SMVs 232 currently operating and the power consumption of the seawater pump are calculated (P21).

When it is determined that the transmission and distribution operator 11 needs to implement DR, the resource aggregator 12 makes a prior contact regarding the reduction in power consumption (I01). In addition, in FIG. 3, description of the resource aggregator 12 is abbreviate|omitted. This contact contains, for example, information on the implementation period (reduction period) of the DR or the requested reduction power.

Upon receiving the prior notification, the duration of the DR and the previously calculated stopable period are compared, and it is reviewed whether the BOG compressor 24 is stopped (P15: stop determination process). For example, if the stopable period of the BOG compressor 24 is longer than the implementation period of the DR, it may be determined that the implementation of the DR is possible.

Then, after prior contact, upon receiving a request for reduction of power consumption (I02) from the resource aggregator 12, a judgment to actually stop the BOG compressor 24 is made (P16), and an operation stop operation is executed (P17: gas Compression part stop process).

Further, based on the grasping result of the operation status of the ORV 231 and SMV 232 (all ORVs 231 are activated in normal operation), the power that can be further reduced is grasped (P22). And, for example, after adjusting with the resource aggregator 12 to the effect that power consumption can be further reduced, the carburetor is switched from the ORV 231 to the SMV 232 when a request for reduction of power consumption (I02) is received. (P23: carburetor conversion process).

On the other hand, as a result of reviewing whether the BOG compressor 24 is stopped by receiving prior notification (P15), for example, if it is found that the stopable period of the BOG compressor 24 is shorter than the DR implementation period, the resource aggregator It is judged that it is not possible to secure a possible suspension period suitable for the request from (12).

At this time, if there is sufficient time between receiving the prior notification and receiving the actual power consumption reduction request, operation adjustment to reduce the pressure in the LNG tank 21 may be performed. The content of operation adjustment is to increase the mixing ratio of BOG to product gas, thereby increasing the amount of BOG discharged from the LNG tank 21, or by requesting the customer 3 to increase the amount of product gas imported to increase the amount of LNG transported. Increasing the liquid level of LNG and the like can be exemplified.

Here, if it is determined that it is difficult to stop the BOG compressor 24 in the step P15 of checking whether to stop, the target pressure is lower than the pressure of the LNG tank 21 at the time of making the determination. The target pressure is calculated (P31: target pressure setting process). The target pressure pressure is set to a target pressure in which the stopable time of the BOG compressor 24 calculated by the method as described above is longer than the duration of the DR implementation.

Then, if it is determined that operation adjustment of lowering the internal pressure of the LNG tank 21 to the target pressure is possible (P32), the operation adjustment is performed (P33: pressure reduction step). Then, the prediction of the change in the internal pressure of the LNG tank 21 (P13), the calculation of the possible stoppage period of the BOG compressor 24 (P14) are performed, and the examination of whether to stop is performed again (P15). When the internal pressure of the LNG tank 21 reaches the target pressure by operation adjustment, the BOG compressor 24 is in a state in which it can be determined that it is possible to stop the power consumption from the resource aggregator 12. Upon receiving the reduction request (I02) of, the BOG compressor 24 is judged to be stopped (P16), and an operation stop operation is executed (P17).

On the other hand, as already described, if the LNG import period from the LNG tanker 4 and the implementation period of DR overlap, in which the amount of BOG generated is several times the normal time, the BOG compressor ( There is a high possibility that the stop of 24) cannot be performed. Therefore, in this case, it is possible to omit the examination of whether the BOG compressor 24 is stopped, and to make a judgment giving priority to continuing the operation of the BOG compressor 24 (continuation determination process).

In addition, by adjusting the wiring schedule of the LNG tanker 4 so that LNG is imported on Saturdays, Sundays, and holidays, where there is little possibility of a DR implementation request, the LNG acceptance period and the DR implementation period overlap. Can also be avoided.

According to the operating method of the LNG import facility 2 according to the present embodiment, the following effects are obtained. The possible stoppage period of the BOG compressor 24 for extracting BOG from the LNG tank 21 is calculated, and based on the result, it is determined whether the BOG compressor 24 is stopped, so that the stable operation of the LNG import facility 2 is performed. DR can be performed without disturbing.

Here, in the example described with reference to FIG. 3, in anticipation of the implementation of DR, the prediction of the change in the internal pressure of the LNG tank 21 (P13) and the calculation of the stopable period of the BOG compressor 24 (P14) are performed in advance, An example of examining whether or not the BOG compressor 24 is stopped by receiving prior notification of the implementation of DR is shown.

However, this examination order can be changed suitably. For example, if there is enough time to execute this (stop the BOG compressor 24) after receiving the power consumption reduction request (I02), the change in the internal pressure of the LNG tank 21 will be reduced after receiving the reduction request. It is also possible to perform prediction, calculation of a stopable period of the BOG compressor 24 (P13, 14: a process of calculating a stopable period), and a review of whether to stop (P15: a process of determining whether to stop).

11: Transmission and distribution business
12: resource aggregator
13: Demand
2: LNG import facility
21: LNG tank
211, 22: LNG pump
231: Open Rack Vaporizer (ORV)
232: Submerged-combustion Vaporizer (SMV)
24: BOG compressor
3: Demand

Claims (8)

As a method of operating liquefied natural gas import facilities,
The liquefied natural gas import facility includes a storage tank for storing liquefied natural gas received from the outside, a vaporizer for vaporizing the liquefied natural gas discharged from the storage tank and shipping in a gaseous state, and generated in the storage tank. A gas compression unit driven by an electric motor for boosting the boil-off gas and mixing it with the natural gas vaporized in the vaporizer
Receiving or assuming that the request for reduction of power consumption including information on the reduction period is received, a review initiation process of initiating a review of the reduction of power consumption, and the internal pressure of the storage tank when the gas compression unit is stopped. A process of calculating a stopable period of predicting a change and calculating a stopable period of the gas compression unit, and determining whether or not the gas compression unit is stopped based on the comparison result between the reduction period and the stopable period of the gas compression unit. Including the process of determining whether to stop,
A method of operating a liquefied natural gas import facility, characterized in that. The method according to claim 1,
The operation method of the liquefied natural gas import facility, comprising a step of stopping the gas compression unit to stop the gas compression unit when it is determined that it is possible to stop the gas compression unit during the reduction period in the stop determination process. . The method according to claim 2,
The carburetor is a carburetor for normal operation that vaporizes liquefied natural gas using seawater supplied from a seawater pump driven by an electric motor as a heat source, and an emergency operation for vaporizing liquefied natural gas using the combustion heat of the natural gas as a heat source. Having a carburetor,
In addition to performing the gas compression unit stopping step, performing a carburetor conversion step of converting the carburetor for normal operation to a carburetor for emergency operation to vaporize liquefied natural gas,
A method of operating a liquefied natural gas import facility, characterized in that. The method according to claim 1,
In the process of calculating the possible stop period, the change in the internal pressure is predicted based on the change in the gaseous phase volume accompanying the discharge of the liquefied natural gas from the storage tank and the amount of boil-off gas generated in the storage tank. How to operate the liquefied natural gas import facility. The method of claim 4,
A method of operating a liquefied natural gas import facility, characterized in that the amount of boil-off gas generated in the storage tank is obtained based on the amount of heat input to the storage tank. The method according to claim 1,
In the process of calculating the allowable stop period, the period in which the predicted value of the change in the internal pressure of the storage tank is less than the upper limit of the operating pressure installed in the storage tank is defined as the stopable period. The method according to claim 1,
Liquefied natural gas, characterized in that it comprises a continuation determination step of making a determination prioritizing continuing the operation of the gas compression unit when the reduction period overlaps a period in which the liquefied natural gas is received from the outside to the storage tank. How to operate gas import facilities. The method according to claim 1,
A target pressure setting process of setting a target pressure lower than the pressure of the storage tank when the stop determination process is performed in order to reduce power consumption when the determination result in the stop determination process is negative And, a pressure reducing process of lowering the internal pressure of the storage tank to a corresponding target pressure, and after the pressure reducing process, the process of determining whether to stop is re-executed.

Images