JP5019840B2 - Liquefied gas supply system and liquefied gas supply method. - Google Patents

Description

  The present invention relates to a liquefied gas supply system and a liquefied gas supply method applicable to an LNG supply system that replenishes LNG in a storage tank of a liquefied natural gas (LNG) satellite base.

  Specifically, the control means for controlling the supply amount of the liquefied gas supplied simultaneously from the upper part and the lower part of the storage tank according to the pressure change inside the storage tank, the gas pressure inside the storage tank is kept constant. Thus, the liquefied gas can be supplied while being automatically controlled.

  Currently, when the primary receiving base that first receives LNG is away from the demand area, a secondary receiving base (satellite base) close to the demand area is arranged and natural gas is supplied from the satellite base to the demand area. ing. In such a satellite base, a vaporizer is usually arranged together with a storage tank, and LNG is stored in a storage tank in a liquid state, vaporized by the vaporizer to become natural gas, and supplied to a demand area.

  In addition, these satellite bases are often arranged for the purpose of supplying to factories and common facilities, etc., and the satellite bases must always supply natural gas stably to their demand areas. . That is, even when LNG is replenished to the storage tank, it is necessary to keep the LNG supply from the storage tank to the vaporizer constant.

  Here, in order to stably supply LNG to the vaporizer, it is important to keep the gas pressure of boil-off gas (BOG) naturally generated in the upper part of the storage tank constant. When the gas pressure of BOG changes, the amount of LNG outflow to the vaporizer changes, which affects the amount of natural gas supplied to the demand area. Therefore, when replenishing the storage tank with LNG, it is necessary to efficiently supply LNG in a short time and to supply a gas tank with a minimum change in gas pressure.

  However, if LNG is supplied from the upper part of the storage tank at the time of LNG replenishment, the upper BOG is reliquefied by the supplied cryogenic LNG, so that the gas pressure of the BOG decreases. On the other hand, when LNG is supplied from the lower part of the storage tank, the volume of the upper BOG generation area decreases, so that the gas pressure of the BOG increases. In order to solve this problem, a method of supplying LNG simultaneously from piping connected to the upper and lower parts of the storage tank is taken as one measure.

  Regarding such a liquefied natural gas receiving method, a method for controlling the boil-off gas generation amount as disclosed in Patent Document 1 is disclosed. According to this boil-off gas generation amount control method, first, as a pipe for supplying LNG to a storage tank (ground tank), a bottom feed pipe is inserted from the side of the storage tank, and a top feed pipe and Insert the bottom feed tube with funnel.

  When supplying LNG having a higher liquid density than the LNG in the storage tank when supplying LNG to the storage tank in which these feed pipes are inserted, a top feed pipe and a bottom feed pipe with a funnel are provided. Use in combination to adjust the amount of gas supplied to both feed pipes, and to supply LNG with a lower liquid density than the LNG in the storage tank, combine the bottom feed pipe and the bottom feed pipe with funnel. Used to adjust the gas supply to both feed pipes. Thereby, the amount of BOG generation at the time of LNG acceptance can be held at the design value level.

JP 2001-324096 A (page 3, FIG. 1)

  However, according to the method for controlling the boil-off gas generation amount disclosed in Patent Document 1, LNG is supplied while monitoring the gas pressure with the human eye. Therefore, it takes time to supply and may cause an unexpected accident due to misjudgment or lack of experience.

  Accordingly, the present invention has been created in view of the above-described problems, and a liquefied gas supply system and a liquefied gas supply capable of supplying a liquefied gas while automatically controlling the gas pressure inside the storage tank to be constant. It aims to provide a method.

The liquefied gas supply system according to the present invention is a liquefied gas supply system comprising a storage tank, an upper pipe for supplying liquefied gas from the upper part of the storage tank, and a lower pipe for supplying liquefied gas from the lower part of the storage tank. The first adjusting means for adjusting the liquefied gas supply amount from the upper pipe, the second adjusting means for adjusting the liquefied gas supply quantity from the lower pipe, and the liquefied gas via the first and second adjusting means. due to the fact that but supplied, a pressure measuring means for measuring the pressure changes inside the storage tank, depending on the pressure change measured by the pressure measuring means, at least one of the first adjusting means及beauty second adjusting means and control means for controlling one, the control means when the pressure change in the internal storage tank is increasing direction, the first adjusting means so as to increase the supply amount from the upper pipe and the lower distribution When at least one of the second adjusting means is controlled so as to reduce the supply amount from the first tank, and the pressure change in the storage tank is in the decreasing direction, the first supply unit reduces the supply amount from the upper pipe. the adjusting means and and is characterized that you control at least one of the second adjusting means so as to increase the supply amount of the lower pipe.

According to the liquefied gas supply system according to the present invention, when the liquefied gas is supplied to the storage tank, the first adjusting means adjusts the liquefied gas supply amount from the upper pipe. The second adjusting means adjusts the liquefied gas supply amount from the lower pipe. The pressure measuring means measures a change in pressure inside the storage tank due to the supply of the liquefied gas via the first and second adjusting means. On the assumption of this, the control means, in response to pressure changes measured by the pressure measuring means is adapted to control at least one of the first adjusting means及beauty second adjustment means.

When the pressure change inside the storage tank is in the increasing direction, the control means described above is configured to decrease the supply amount from the first adjustment means and the lower pipe so as to increase the supply amount from the upper pipe . When at least one of the two adjustment means is controlled and the pressure change in the storage tank is in a decreasing direction, the supply from the first adjustment means and the lower pipe is made to reduce the supply amount from the upper pipe. At least one of the second adjusting means is controlled to increase the amount.

  Therefore, since the liquefied gas can be supplied while automatically controlling the gas pressure inside the storage tank to be constant, the liquefied gas can be efficiently replenished to the storage tank. Further, it is possible to prevent the storage tank from being damaged due to the pressure change inside the storage tank.

The liquefied gas supply method according to the present invention is a method of supplying a liquefied gas to a storage tank, the step of supplying the liquefied gas from the upper part of the storage tank, the step of supplying the liquefied gas from the lower part of the storage tank, due to the fact that the upper and liquefied gas from the bottom of the tank is supplied, a step of measuring a pressure change inside the storage tank, depending on the measured pressure changes, at least one of the upper及beauty bottom of the storage tank and adjusting the liquefied gas supply amount possess, in adjusting the liquefied gas supply amount, when the pressure change in the internal storage tank is increased direction, increasing the supply amount of the liquefied gas from the top of the storage tank Adjust at least one of the liquefied gas adjustment amount and the liquefied gas adjustment amount to reduce the supply amount of liquefied gas from the lower part of the storage tank so that the pressure inside the storage tank If the liquefaction is decreasing, the liquefied gas adjustment amount to decrease the liquefied gas supply amount from the upper part of the storage tank and the liquefied gas adjustment to increase the liquefied gas supply amount from the lower part of the storage tank It is characterized by adjusting at least one of the quantities .

  According to the liquefied gas supply method according to the present invention, when supplying the liquefied gas to the storage tank, the liquefied gas can be supplied while being automatically controlled so that the gas pressure inside the storage tank becomes constant. The liquefied gas can be replenished. Further, it is possible to prevent the storage tank from being damaged due to the pressure change inside the storage tank.

According to the liquefied gas supply system and the liquefied gas supply method according to the present invention, in response to pressure changes within the storage tank, a control means for controlling at least one of the first adjusting means及beauty second adjusting means The control means includes a first adjustment means for increasing the supply amount from the upper pipe and a second for decreasing the supply quantity from the lower pipe when the pressure change inside the storage tank is in an increasing direction. When the pressure change inside the storage tank is in a decreasing direction by controlling at least one of the adjustment means, the supply amount from the first adjustment means and the lower pipe so as to reduce the supply quantity from the upper pipe a it shall be controlled at least one of the second adjusting means so as to increase. With this configuration, the liquefied gas can be supplied to the storage tank while automatically controlling the gas pressure inside the tank to be constant, so that the liquefied gas can be supplied efficiently. Further, it is possible to prevent the storage tank from being damaged due to the pressure change inside the storage tank.

  Next, a liquefied gas supply system and a liquefied gas supply method as examples of embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of an LNG supply system 100 as an embodiment according to the present invention. An LNG supply system 100 shown in FIG. 1 constitutes an example of a liquefied gas supply system, for example, for replenishing (supplying) LNG to a storage tank installed at a satellite base of LNG.

  Here, first, the satellite base 30 in which the LNG is replenished by the LNG supply system 100 will be briefly described. The satellite base 30 mainly includes a storage tank 10, a pipe 11, a pump 12, and a vaporizer 13, and is arranged near a demand area away from the primary receiving base of LNG.

  The storage tank 10 for receiving LNG transported from the primary receiving base is installed in the site of one or more satellite bases 30 and stores LNG for supplying natural gas to demand areas. One end of a pipe 11 is connected to the lower part of the storage tank 10 and is used as a path for taking out LNG from the storage tank 10. A pump 12 is connected to the other end of the pipe 11 and operates to draw LNG out of the storage tank 10 and supply it to the subsequent stage. A carburetor 13 is disposed at the subsequent stage of the pump 12, and LNG supplied from the pump 12 is vaporized to send out natural gas. The natural gas delivered from the vaporizer 13 is supplied toward the demand area and used, for example, as fuel. Thus, in the satellite base 30, the LNG to store is vaporized and the natural gas is supplied to a demand place in the site.

  The LNG supply system 100 according to the present invention is for replenishing such satellite base 30 with LNG, and includes a storage tank 10, an upper pipe 1, a lower pipe 2, a valve 3, a valve 4, an internal pressure gauge 5, and a control. A device 6 is provided.

  The storage tank 10 is constructed within the site of the satellite base 30 as described above, and in this example, in a cylindrical shape having rounded upper and lower surfaces. The inside of the storage tank 10 is divided into two areas, and an LNG storage area 20 is present at the bottom and a BOG generation area 21 is present at the top. The lower LNG storage area 20 stores the supplied LNG (liquid). The upper BOG generation region 21 is filled with BOG (gas) obtained by naturally vaporizing the stored LNG with a predetermined gas pressure.

  The upper pipe 1 is inserted (connected) into the upper part of the storage tank 10 filled with BOG, and forms a path for supplying, for example, LNG conveyed by the tank lorry from the upper part of the storage tank 10. One end of the upper pipe 1 is inserted from the upper portion of the storage tank 10 and the other end is drawn out to a position, for example, about 1 m above the ground, which is convenient for connecting to the supply hose of the tank lorry. Called 1a).

  A valve 3 constituting an example of a first adjusting means is connected to the supply port 1a of the upper pipe 1 drawn from the storage tank 10 so as to adjust the supply amount of LNG from the upper pipe 1 to the storage tank 10. Controlled. As the valve 3, an electromagnetic valve having a valve whose opening degree can be adjusted according to an input control signal, an air driving valve, or the like is used. One end of the valve 3 is fixedly connected to the supply port 1a of the upper pipe 1 and the other end. Is detachably connected to the supply hose of the tank truck.

  On the other hand, the lower pipe 2 is inserted in the lower part of the storage tank 10 in which LNG is stored, thereby forming a path for supplying LNG from the tank lorry from the lower part of the storage tank 10. One end of the lower pipe 2 is inserted from the lower part of the storage tank 10 and the other end is pulled out to a position adjacent to the supply port 1a of the upper pipe 1 (hereinafter, this one end is referred to as a supply port 2a).

  The supply port 2a of the lower pipe 2 drawn out from the storage tank 10 is connected to a valve 4 that constitutes an example of the second adjusting means so as to adjust the supply amount of LNG from the lower pipe 2 to the storage tank 10. Controlled. For the valve 4, for example, an electromagnetic valve, an air drive valve, or the like whose opening degree is controlled by a control signal, which has the same specifications as the valve 3, is used. One end is fixedly connected to the supply port 2 a of the lower pipe 2. The end is detachably connected to the tank hose supply hose.

  Also, an internal pressure gauge 5 that constitutes an example of a pressure measuring means is provided in the BOG generation region 21 where the gas pressure fluctuates when LNG is supplied from the upper and lower portions of the storage tank 10 via the valve 3 and the valve 4. Is provided to measure the gas pressure. The internal pressure gauge 5 is preferably fixed near the top of the storage tank 10 where LNG does not reach and outputs the measured gas pressure information.

The gas pressure information output from the internal pressure gauge 5 is input to the control device 6 that constitutes an example of the control means, and is used to adjust the valve 3 and the valve 4. The control device 6, in accordance with the gas pressure information measured by the internal pressure meter 5, and outputs a control signal to at least one of the valve 3及beauty valves 4, by adjusting the opening degree of the valve, BOG generation region 21 The gas pressure is controlled to be constant. The control device 6, when the internal pressure change storage tank 10 is increasing direction, the valve 3及beauty to increase the supply amount from the upper pipe 1, so as to decrease the supply amount of the lower portion pipe 2 controlling at least one of valves 4, when the internal pressure change storage tank 10 is the decreasing direction, the valve 3 and to decrease the supply amount from the upper pipe 1, the supply amount of the lower pipe 2 controlling at least one of valves 4 to increase. In this way, the LNG supply system 100 is configured.

  Subsequently, an LNG supply method by the LNG supply system 100 will be described. FIG. 2 is a flowchart showing a control example of LNG replenishment from the tank lorry to the storage tank 10.

  First, before starting the process of FIG. 2, the worker performs connection work between the tank holly supply hose and the valve 3 and the valve 4 of the satellite base. LNG supplied from a tank lorry is an extremely low temperature liquid of −160 ° C. or less, for example, and is extremely dangerous when touching human skin. Therefore, the operator works with great care so that there is no liquid leakage.

  When the connection is completed, the operator operates the tank lorry so that the LNG outflow to the storage tank 10 can be started. As a method for causing LNG to flow out from the tank lorry, for example, there is a method using a pressurizer. This is because by taking out two hoses separately from the supply hose from the tank lorry and connecting them to the pressurizer, the LNG that naturally flows out from one hose is vaporized in the pressurizer and returned to the tank lorry from the other hose again. The gas pressure in the tank lorry is increased to push LNG out of the supply hose. The pressurizer used in this example has a function of sensing the pressure in the piping of the storage tank 10 on the receiving side and controlling the amount of LNG to be pushed out.

  Under these processing conditions, in step A1 of the flowchart shown in FIG. 2, the control device 6 determines whether or not an execution command has been input (determination 1). When the above connection work is completed, the worker turns on a start button (not shown) in the control device 6, for example. When the start button is turned on, an execution command for starting the replenishment control to the control device 6 is input. The control device 6 determines whether or not an execution instruction has been input. If the result of determination 1 is that an instruction has been input, the process proceeds to step A2, and if an instruction has not yet been input, the process returns to step A1.

  When it progresses to step A2, the control apparatus 6 reads the measured value of the internal pressure gauge 5 of the storage tank 10. FIG. This measured value is stored in a memory or the like in the control device 6 and used as a reference value for subsequent determination.

  In step A3, the control device 6 opens the valve 4. The control device 6 outputs a control signal to the valve 4 to open the valve 4 with a predetermined opening degree. Thereby, supply of LNG is started from the lower pipe 2 of the storage tank 10. In this example, the control device 6 proceeds with the valve 4 being a fixed opening.

  In step A4, the control device 6 opens the valve 3. The control device 6 outputs a control signal in the same manner as the valve 4, and opens the valve 3 with a predetermined opening degree. Thereby, the supply of LNG is started from the upper pipe 1 of the storage tank 10. Thereafter, the opening degree of the valve 3 is appropriately adjusted by the control device 6.

  In step A5, the control device 6 determines whether or not the replenishment of LNG has been completed (determination 2). This determination 2 is performed, for example, by reading a measured value of a fuel gauge (not shown) of the storage tank 10 so that the control device 6 determines whether or not a predetermined LNG is stored in the storage tank 10. If the result of determination 2 is that replenishment of LNG is not completed, the process proceeds to step A6, and if completed, the process proceeds to step A12.

  When the process proceeds to Step A12, the control device 6 closes the valve 3 and the valve 4 and ends the control routine. At this time, it is preferable to notify the worker by an alarm sound or the like. When the control routine is finished, the worker stops the outflow of LNG from the tank lorry, removes the supply hose, and finishes the replenishment work.

  When the process proceeds to step A6, the control device 6 obtains the gas pressure information from the internal pressure gauge 5 in order to measure the gas pressure in the BOG generation area 21 that changes due to the supply of LNG from the upper and lower parts of the storage tank 10. read out.

  In step A7, it is determined whether or not the gas pressure has changed based on the gas pressure information read from the internal pressure gauge 5 in step A6 (determination 3). This determination is made by comparing with the reference gas pressure read in step A2. The control device 6 sets a certain allowable range based on the reference gas pressure, and determines whether or not it is within the range. As a result of determination 3, if the gas pressure has not changed (the change is within the allowable range), the process proceeds to step A8, and if the gas pressure has changed (the change is outside the allowable range), the process proceeds to step A9.

  When the process proceeds to step A8, there is no need to adjust the gas pressure, so the process returns to step A5 without adjusting the valve 3.

  When the process proceeds to step A9, in order to adjust the LNG supply amount from the upper pipe 1 according to the change in the measured gas pressure, it is next determined whether the gas pressure has increased or decreased ( Decision 4). This determination is also made by comparison with the reference value read in step A2, as in step 7A. As a result of determination 4, if the change in gas pressure is in the increasing direction, the process proceeds to step A10, and if the change in gas pressure is in the decreasing direction, the process proceeds to step A11.

  When the process proceeds to step A10, the control device 6 outputs a control signal, adjusts the opening degree of the valve 3 to increase, and increases the LNG supply amount from the upper pipe 1. By adjusting in this way, re-liquefaction of BOG can be promoted and the gas pressure in the storage tank 10 can be lowered to an appropriate value. After the adjustment, the process returns to step A5 and determination 2 is performed again.

  When the process proceeds to step A11, the control device 6 outputs a control signal, adjusts the opening degree of the valve 3 to be small, and decreases the LNG supply amount from the upper pipe 1. By adjusting in this way, the LNG supplied from the lower pipe 2 is relatively increased, and the proportion of the LNG storage area 20 is increased in the storage tank 10. As a result, the volume of the BOG generation region 21 decreases and the gas pressure increases. After the adjustment, the process returns to step A5 and determination 2 is performed again.

  The control device 6 repeats the processing of step A5 to step A11 until the determination of completion of LNG replenishment is made in the determination 2 of step A5, and controls the LNG replenishment while appropriately changing the opening degree of the valve 3. Thus, the replenishment from the tank lorry to the storage tank 10 is completed.

According to LNG supply system 100 as an embodiment according to the present invention, at least one of the valve 3及beauty valves 4 to adjust the supply amount of LNG supplied simultaneously the upper and the lower portion of the storage tank 10 One is controlled by the control device 6. Therefore, since LNG can be supplied while automatically controlling the gas pressure inside the storage tank 10 to be constant, the storage tank 10 can be efficiently replenished with LNG.

  In this example, the case where the valve 4 is a fixed opening and the gas pressure of the storage tank 10 is controlled by adjusting the opening degree of the valve 3 has been described. However, the present invention is not limited to this, and the valve 3 is fixed. The opening degree of the valve 4 may be adjusted by opening. Thus, the system can be simplified by controlling either one of the valves for adjustment.

  However, of course, the opening degree of both the valve 3 and the valve 4 may be adjusted. If both opening degrees are adjusted, the supply amount as a whole can be kept substantially constant, so that replenishment in a shorter time becomes possible.

  In addition to the valve 3 and the valve 4, a valve capable of controlling the opening degree may be provided and the opening degree of the valve may be adjusted.

  Further, the connection ports of the valve 3 and the valve 4 with the tank lorry may be unified. By doing so, the LNG supply method according to the present invention can be applied to a tank lorry having one supply hose.

  In this example, a pressurizer is arranged in the tank lorry to supply LNG to the storage tank 10. However, for example, pumps (not shown) are arranged in the supply paths of the upper pipe 1 and the lower pipe 2, respectively. It may be possible to pull out from the tank truck. In this case, the control device 6 can also adjust the balance between the upper and lower supply amounts by controlling the power of the pump.

  The present invention is very suitable when applied to LNG replenishment to an LNG satellite station.

It is a figure which shows the structural example of the LNG supply system 100 as an Example. 5 is a flowchart showing an example of control of LNG replenishment by the LNG supply system 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Upper piping, 2 ... Lower piping, 3, 4 ... Valve, 5 ... Internal pressure gauge, 6 ... Control apparatus, 10 ... Storage tank, 11 ... Piping, 12 ... Pump, 13 ... Vaporizer, 20 ... LNG storage area, 21 ... BOG generation area, 30 ... Satellite base, 100 ... LNG supply system

Claims (2)

A storage tank;
An upper pipe for supplying liquefied gas from the upper part of the storage tank;
In a liquefied gas supply system comprising a lower pipe for supplying liquefied gas from the lower part of the storage tank,
First adjusting means for adjusting a liquefied gas supply amount from the upper pipe;
Second adjusting means for adjusting the amount of liquefied gas supplied from the lower pipe;
Pressure measuring means for measuring a pressure change inside the storage tank due to the supply of the liquefied gas via the first and second adjusting means;
In response to the pressure change measured by the pressure measuring means, and control means for controlling at least one of said first adjusting means及beauty second adjusting means,
The control means includes
When the pressure change inside the storage tank is increasing,
Controlling at least one of the first adjusting means so as to increase the supply amount from the upper pipe and the second adjusting means so as to decrease the supply quantity from the lower pipe;
When the pressure change inside the storage tank is decreasing,
Wherein the first adjusting means to decrease the supply amount from the upper pipe and characterized that you control at least one of said second adjusting means so as to increase the supply amount from the lower pipe Liquefied gas supply system. A method of supplying liquefied gas to a storage tank,
Supplying liquefied gas from the upper part of the storage tank;
Supplying liquefied gas from the lower part of the storage tank;
Measuring the pressure change inside the storage tank due to the supply of liquefied gas from the upper and lower parts of the storage tank;
Wherein in response to pressure changes to be measured, have a the step of adjusting one of the liquefied gas supply amount at least one of the upper及beauty bottom of the storage tank,
When adjusting the liquefied gas supply amount,
If the pressure change inside the storage tank is increasing,
At least one of the liquefied gas adjustment amount so as to increase the supply amount of the liquefied gas from the upper part of the storage tank and the liquefied gas adjustment amount so as to reduce the supply amount of the liquefied gas from the lower part of the storage tank. Adjust one side,
When the pressure change inside the storage tank is decreasing,
At least one of the liquefied gas adjustment amount so as to decrease the supply amount of the liquefied gas from the upper part of the storage tank and the liquefied gas adjustment amount so as to increase the supply amount of the liquefied gas from the lower part of the storage tank. A liquefied gas supply method characterized by adjusting one of them.

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