JP2015152163A - Liquefied gas clear-off system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefied gas clear-off system capable of stably clearing off liquefied gas from a liquid storage tank while preventing enlargement of an entire system even if a liquid surface of the liquefied gas is lowered as the liquefied gas from the liquid storage tank is cleared off from the liquid storage tank.SOLUTION: A liquefied gas clear-off system X of this invention comprises a liquid storage tank 1 for storing liquefied gas; a liquefied gas transferring line 42 for transferring the liquefied gas discharged out of the liquid storage tank 1; a variable volume type gas holder 3 having the first gas storage part 34 for storing gas gasified from liquefied gas and enabling a volume of the first gas storing part 34 to be variable; and a gas supplementation line 45 communicated with both the first gas storing part 34 and an inner upper space of the liquid storage tank 1.

Description

  The present invention relates to a liquefied gas discharge system that evaporates liquefied gas and discharges it as gas.

  In addition to industrial gases such as liquefied nitrogen, liquefied oxygen, liquefied argon, and liquefied carbon dioxide, fuel gases such as liquefied natural gas (LNG) and liquefied propane gas (LPG) are stored in liquid form in a liquid storage tank for vaporization. Evaporation and vaporization with a vessel or the like is used as an important industrial technique for repeatedly storing and consuming liquefied gas in each industrial field. Liquefied nitrogen, liquefied oxygen and liquefied argon are stored at a low temperature liquid of −180 ° C. or lower, liquefied carbon dioxide gas is −25 ° C. or lower, liquefied natural gas is −160 ° C. or lower, and liquefied propane gas is stored at a low temperature of −40 ° C. or lower. ing. When the liquefied gas from the liquid storage tank passes through the discharge line (liquefied gas transfer line) or the vaporizer, it is affected by pressure loss. In order to stably discharge the liquefied gas from the liquid storage tank, the liquefied gas from the liquid storage tank It is necessary that the gas extrusion pressure is always maintained at a predetermined pressure. The extrusion pressure of the liquefied gas can be expressed as a total value of the pressure of the liquid phase in the liquid storage tank (liquid head pressure of the liquefied gas) and the pressure of the gas phase (gas pressure in the upper space inside the liquid storage tank). However, if the liquid level of the liquefied gas decreases as the liquefied gas in the liquid storage tank is discharged, both the liquid phase pressure and the gas phase pressure decrease, and the liquefied gas extrusion pressure is maintained appropriately. An impossible situation could have occurred.

  Conventional techniques disclosed in the following Patent Documents 1 and 2 are known with respect to the point where the extrusion pressure of the liquefied gas should be maintained. In Patent Document 1, a liquid storage tank different from the original liquid storage tank is provided, and the gas phase or liquid phase is connected by connecting the upper gas phases of these liquid storage tanks or connecting the lower liquid phases. The pressure drop was prevented. However, since the method of Patent Document 1 requires another liquid storage tank, the entire system is increased in size. In Patent Document 2, a fixed-capacity gas holder for temporarily storing vaporized gas discharged from the vaporizer is provided, and the vaporized gas delivered from the gas holder is sent out as consumed gas after adjusting the pressure by a pressure reducing valve. In addition, a configuration is disclosed in which a part of the decompressed gas is replenished in the upper space of the liquid storage tank. However, since the method of Patent Document 2 uses a fixed-capacity gas holder, pressure adjustment with the pressure reducing valve loses pressure energy due to a change in pressure inside the gas holder. Therefore, the pressure of the gas after passing through the pressure reducing valve is considerably reduced, and even if such a low pressure gas is replenished to the upper part of the liquid storage tank, it is substantially possible to maintain the liquefied gas extrusion pressure appropriately. It was difficult.

JP 2010-203524 A JP 2012-67787 A

  The present invention has been conceived under such circumstances, and the liquid level of the liquefied gas decreases as the liquefied gas is discharged from the liquid storage tank while preventing the entire system from becoming large. However, an object of the present invention is to provide a liquefied gas discharge system capable of stably discharging liquefied gas from a liquid storage tank.

  The liquefied gas discharge system provided by the present invention includes a liquid storage tank for storing liquefied gas, a liquefied gas transfer line for transferring the liquefied gas discharged from the liquid storage tank, and a gas vaporized by the liquefied gas. It has a first gas storage section for storing, and communicates with any of the variable capacity type gas holder in which the capacity of the first gas storage section can be changed, and the internal upper space of the first gas storage section and the liquid storage tank. A gas replenishment line.

  Preferably, the apparatus further includes a vaporizer for vaporizing the liquefied gas, and the liquefied gas transfer line is provided at the liquefied gas discharge port provided at both ends of the liquid storage tank and the vaporizer. The liquefied gas inlet is connected to the liquefied gas inlet, and the liquefied gas inlet is at a position lower than the liquefied gas outlet.

  Preferably, the gas holder is provided so as to be displaceable while maintaining a gas seal state between the main body configured in a container shape and the main body, and the interior of the main body includes the first gas storage unit and A shut-off section partitioned into a second gas storage section, and a gas pressure adjusting means for adjusting the second gas storage section to a predetermined gas pressure.

  Preferably, the blocking unit includes a diaphragm.

  Preferably, the main body is provided with a gas inlet and a gas outlet, each of which communicates with the second gas storage unit and allows gas to be taken in and out of the second gas storage unit. The means is connected to the gas introduction port, and supplies a gas supply line for supplying gas toward the second gas storage unit, a first pressure control valve provided in the gas supply line, and the gas discharge port. A gas discharge line for discharging gas from the second gas storage unit; and a second pressure control valve provided in the gas discharge line.

  Preferably, the first pressure control valve allows the supply of gas toward the second gas storage unit when the gas pressure of the second gas storage unit is lower than the first reference pressure, and the second pressure control valve The pressure control valve allows the gas to be discharged from the second gas storage unit when the gas pressure in the second gas storage unit exceeds a second reference pressure that is higher than the first reference pressure.

  Preferably, the gas pressure in the second gas storage part is adjusted in the range of atmospheric pressure to 1.0 MPaG.

  Preferably, the liquefied gas is liquefied natural gas (LNG).

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a schematic block diagram which shows an example of the liquefied gas discharge system which concerns on this invention. It is a principal part longitudinal cross-sectional view which shows schematic structure of an example of a gas holder. It is a principal part longitudinal cross-sectional view which shows schematic structure of the other example of a gas holder.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows an example of a liquefied gas discharge system according to the present invention. The liquefied gas discharge system X of the present embodiment includes a liquid storage tank 1, a vaporizer 2, a gas holder 3, and lines 41 to 45 connected thereto.

  The liquid storage tank 1 is for storing liquefied gas. The liquid storage tank 1 has a double outer wall, and a heat insulating material is filled between the two walls and the pressure is reduced to a vacuum to block intrusion heat from the outside air. In the liquid storage tank 1, for example, liquefied natural gas (LNG) is stored at a temperature of at least -161.5 ° C. The liquid storage tank 1 is supported by a support 11 on the ground, and is disposed at a predetermined height position from the ground. In the following, the description may be made assuming that the liquefied gas is liquefied natural gas (LNG), but the present invention is not limited to this.

  A liquefied gas introduction line 41 and a liquefied gas transfer line 42 are connected to the lower part of the liquid storage tank 1. The liquefied gas introduction line 41 is a flow path for supplying liquefied natural gas to the liquid storage tank 1. For example, LNG transported by a tank truck is introduced into the liquid storage tank 1 through the liquefied gas introduction line 41. A check valve 411 is provided in the liquefied gas introduction line 41.

  The liquefied gas transfer line 42 is a flow path for transferring the liquefied gas discharged from the liquid storage tank 1 to the vaporizer 2. The upstream end of the liquefied gas transfer line 42 is connected to the liquefied gas discharge port 12 provided at the lower end of the liquid storage tank 1. The downstream end of the liquefied gas transfer line 42 is connected to a liquefied gas inlet 221 provided in the vaporizer 2 described later. A shutoff valve 421 is provided in the liquefied gas transfer line 42.

  The vaporizer 2 is for evaporating and vaporizing liquefied gas, and includes a container body 21 and a heat transfer tube 22 disposed inside the container body 21. The heat transfer tube 22 is a flow path through which the liquefied gas introduced into the container body 21 flows. The heat transfer tube 22 is wound in a coil shape, and has a liquefied gas inlet 221 that is an upstream end and a gas outlet 222 that is a downstream end. The liquefied gas inlet 221 is located at a position lower than the liquefied gas outlet 12 of the liquid storage tank 1.

  The container body 21 is a sealed container for housing a heat medium. A heat medium for heating and vaporizing the liquefied gas in the heat transfer tube 22 is accommodated in the container body 21 in a replenishable manner. Examples of the heat medium include warm water. Although detailed illustration explanation is omitted, for example, the heat medium is introduced into the container body 21 through the heat medium introduction line and discharged from the container body 21 through the heat medium discharge line. The liquefied gas in the heat transfer tube 22 is heated and evaporated by heat exchange with the surrounding heat medium, and the vaporized gas is discharged to the outside of the container body 21 through the gas discharge port 222. A gas line 43 is connected to the gas discharge port 222. The heat medium discharged from the container body 21 is reheated by a reheating means (not shown), supplied again to the vaporizer 2 (container body 21), and recycled.

  The gas holder 3 is a variable capacity gas holder that can accommodate the gas from the vaporizer 2. In this embodiment, as shown in FIG. 2, the gas holder 3 includes a main body portion 31, a diaphragm 32, and a piston 33, and is configured as a piston type.

  The main body 31 is made of a metal such as iron or stainless steel and has a cylindrical container shape. The main body 31 has a lower main body 311 and an upper main body 312, and can be separated into upper and lower parts, and is integrally combined by joining the flanges of the lower main body 311 and the upper main body 312 with bolts 313. A gas inlet 314 and gas outlets 315 and 318 are provided at appropriate positions of the lower body 311. The gas inlet port 314 is connected to the downstream end of the gas line 43, and the gas outlet port 315 is connected to the gas line 44. A gas supplement line 45 is connected to the gas outlet 318. A gas inlet 316 for introducing a pressure adjusting gas such as air and a gas outlet 317 for discharging the pressure adjusting gas are provided on the upper portion of the upper body 312.

  The diaphragm 32 is molded from synthetic rubber reinforced with fibers, and is a series of film bodies. The diaphragm 32 includes an annular flange portion 321, a cylindrical portion 322 extending at one end side connected to the inner peripheral edge of the flange portion 321, and a bottom portion 323 that closes the other end side of the cylindrical portion 322. The diaphragm 32 is accommodated in the main body 31 while the flange 321 is sandwiched between the flanges of the lower main body 311 and the upper main body 312 in a sealed state. The diaphragm 32 can be moved up and down (displaceable) while maintaining the gas seal state with the lower main body 311 (main body portion 31), and corresponds to a blocking portion in the present invention.

  A region partitioned by the diaphragm 32 and the lower main body 311 (main body portion 31) is a first gas storage portion 34 for storing natural gas. A region defined by the diaphragm 32 and the upper main body 312 (main body portion 31) is a second gas storage portion 35 for storing the pressure adjusting gas. That is, the internal space of the main body 31 is partitioned into a first gas storage unit 34 and a second gas storage unit 35 with the diaphragm 32 interposed therebetween.

  The piston 33 is made of metal such as iron or stainless steel, for example, and is disposed inside the cylindrical portion 322 of the diaphragm 32. The piston 33 includes a cylindrical piston cylinder portion 331 extending in the vertical direction, and a piston bottom portion 332 connected to the lower end of the piston cylinder portion 331. The piston 33 is supported by the diaphragm 32 in a state where the piston bottom portion 332 is aligned with the bottom portion 323 of the diaphragm 32.

  A guide roller 335 is provided near the upper end of the piston cylinder portion 331 via a fixture 334. At least three guide rollers 335 are provided, and these guide rollers 335 are arranged at different positions in the circumferential direction of the piston cylinder portion 331. The guide rollers 335 are preferably arranged at regular intervals in the circumferential direction of the piston cylinder portion 331. Each guide roller 335 is in contact with the inner peripheral surface of the upper body 312 and is rotatable about a horizontal axis. Although details will be described later, the diaphragm 32 and the piston 33 supported by the diaphragm 32 move up and down while maintaining a substantially constant posture by the guide roller 335.

  As shown in FIG. 1, a gas supply line 36 is connected to the gas inlet 316 of the upper main body 312. The gas supply line 36 communicates with the second gas storage unit 35 and is a flow path for supplying pressure adjusting gas from a gas supply unit (not shown) toward the second gas storage unit 35. A pressure control valve 361 is provided in the gas supply line 36.

  A gas discharge line 37 is connected to the gas discharge port 317. The gas discharge line 37 communicates with the second gas storage unit 35 and is a flow path for discharging the pressure adjusting gas from the second gas storage unit 35. The gas discharge line 37 is provided with a pressure control valve 371.

  The second gas storage unit 35 is adjusted by the pressure control valves 361 and 371 so as to have a predetermined gas pressure. The gas pressure in the second gas storage unit 35 is set, for example, in the range of atmospheric pressure to 1.0 MPaG, preferably in the range of 0.2 to 0.3 MPaG. The pressure control valve 361 is a pressure increase control valve that allows gas supply to the second gas storage unit 35 when the gas pressure in the second gas storage unit 35 is lower than the first reference pressure. The pressure control valve 371 allows gas to be discharged from the second gas storage unit 35 when the gas pressure of the second gas storage unit 35 exceeds a second reference pressure that is higher than the first reference pressure. This is a control valve for pressure reduction.

  Specifically, for example, when adjusting the gas pressure of the second gas storage unit 35 to be in the range of 0.24 to 0.26 MPaG, when the gas pressure of the second gas storage unit 35 is reduced to 0.24 MPaG, The pressure control valve 361 is opened to supply pressurized air (pressurized gas), and the pressure of the second gas storage unit 35 is increased to 0.24 MPaG or more. On the other hand, when the gas pressure in the second gas storage unit 35 rises to 0.26 MPaG, the pressure control valve 371 for pressure reduction opens, and the gas is discharged from the second gas storage unit 35. The pressure is reduced to 26 MPaG or less. By repeating such opening and closing operations of the pressure control valves 361 and 371, it becomes possible to always control the second gas storage unit 35 in a pressure range of 0.24 to 0.26 MPaG. The gas supply line 36, the gas discharge line 37, and the pressure control valves 361 and 371 described above serve as gas pressure adjusting means in the present invention.

  As shown in FIG. 1, one end of the gas replenishment line 45 is connected to the gas discharge port 318 of the lower body 311, and the other end is connected to the upper part of the liquid storage tank 1. Thereby, the gas replenishment line 45 leads to both the first gas storage part 34 and the upper space inside the liquid storage tank 1. For example, a check valve 451 is provided in the gas replenishment line 45. If the pressure drop is small, a pressure reducing valve or a pressure control valve may be used instead of the check valve 451.

  The gas line 44 connected to the gas discharge port 315 of the gas holder 3 is connected to a gas consumption facility (not shown). The natural gas stored in the first gas storage unit 34 is sent to the gas consuming facility via the gas line 44 and consumed.

  During the operation of the liquefied gas discharge system X, liquefied natural gas (LNG) is discharged through the liquid storage tank 1, and the LNG is introduced into the vaporizer 2 through the liquefied gas transfer line 42. In the vaporizer 2, LNG evaporates and becomes natural gas, and the natural gas is sent to the gas holder 3 through the gas line 43. Natural gas that has passed through the gas line 43 is introduced into the gas holder 3 through the gas inlet 314 and is temporarily stored in the first gas storage unit 34. The natural gas in the first gas storage unit 34 is sent to the above-described gas consumption facility via the gas discharge port 315 and the gas line 44 and consumed. In this way, LNG continuously discharged from the liquid storage tank 1 is evaporated and vaporized in the vaporizer 2, and the vaporized natural gas is continuously consumed via the gas holder 3.

  The first gas storage part 34 is partitioned from the upper side second gas storage part 35 with the displaceable diaphragm 32 interposed therebetween. In the present embodiment, the diaphragm 32 and the piston 33 supported by the diaphragm 32 move up and down while maintaining a substantially constant posture by the guide roller 335. With such a configuration, even if the amount of natural gas (consumed gas amount) discharged from the first gas storage unit 34 (gas holder 3) through the gas discharge port 315 varies, the capacity of the first gas storage unit 34 is changed. Is changed, the internal pressure (gas pressure) of the first gas storage unit 34 is stably maintained substantially constant.

  For example, when the amount of natural gas introduced into the gas holder 3 (first gas storage unit 34) through the gas inlet 314 is a substantially constant flow rate, the amount of natural gas discharged from the gas outlet 315 (consumed gas amount) ) Decreases, the internal pressure of the first gas storage unit 34 tends to increase. Then, the diaphragm 32 and the piston 33 supported by the diaphragm 32 are pushed up, and natural gas is stored in the first gas storage portion 34. In FIG. 2, the state in which the piston 33 is raised is represented by a virtual line. On the other hand, when the amount of natural gas discharged from the gas outlet 315 increases, the piston 33 descends. The difference between the volume of the first gas storage part 34 in the state indicated by the imaginary line with the piston 33 at the highest position and the volume of the first gas storage part 34 in the state indicated by the solid line at the lowest position of the piston 33 is The capacity of the gas holder 3 (first gas storage unit 34) can be increased or decreased.

  On the other hand, the first gas storage part 34 and the internal upper space of the liquid storage tank 1 communicate with each other via a gas replenishment line 45. As a result, the gas pressure in the first gas storage part 34 reaches the upper space inside the liquid storage tank 1 via the gas replenishment line 45. Therefore, the gas pressure P <b> 1 in the internal upper space is maintained substantially equal to the gas pressure in the first gas storage unit 34.

  Here, the extrusion pressure for discharging the liquefied natural gas in the liquid storage tank 1 toward the vaporizer 2 is the gas pressure P1 in the upper space inside the liquid storage tank 1 and the liquid head of the liquefied natural gas in the liquid storage tank 1. When the pressure H1 is used, it is expressed as P1 + H1. In the present embodiment, since the liquefied gas introduction port 221 of the vaporizer 2 is located at a position lower than the liquefied gas discharge port 12 of the liquid storage tank 1, the remaining amount of liquefied natural gas in the liquid storage tank 1 is reduced and the liquefied natural gas is concerned. Even if the liquid level of the gas is lowered, the liquid head pressure H1 is always a positive value. Further, the gas pressure P1 in the upper space inside the liquid storage tank 1 is stably maintained by being controlled by the gas pressure of the capacity variable type gas holder 3 (first gas storage unit 34). Therefore, the extrusion pressure (P1 + H1) of the liquefied natural gas in the liquid storage tank 1 is always a predetermined value or more. According to such a configuration, even when the liquid level of the liquefied natural gas in the liquid storage tank 1 is lowered as the natural gas is consumed, the discharge of the liquefied natural gas from the liquid storage tank 1 is stably continued. Is done.

  Unlike the present embodiment, when the stable gas pressure is not supplied in the upper space inside the liquid storage tank 1, the volume of the upper space inside the liquid storage tank 1 when the liquid level of the liquefied gas in the liquid storage tank 1 decreases. Will increase. As the volume of the internal upper space increases, the gas pressure decreases in the internal upper space. This is an impediment to the discharge of liquefied gas from the liquid storage tank 1.

Moreover, in this embodiment, the 2nd gas accommodating part 35 is controlled so that it may become a predetermined gas pressure as mentioned above. Thereby, the internal pressure (gas pressure) of the first gas storage unit 34 is determined by the gas pressure of the air (pressure adjusting gas) fed into the second gas storage unit 35 on the upper side. The pressure is adjusted in the range of 0.2 to 0.3 MPaG. The internal pressure (gas pressure) of the first gas storage part 34 in which natural gas is stored is a value obtained by dividing the air pressure in the second gas storage part 35 by the load of the diaphragm 32 and the piston 33 by the horizontal sectional area of the main body 31. (Specifically, 100 to 300 kg / m ² ≈0.001 to 0.003 MPa). The pressure value (0.001 to 0.003 MPa) applied by the load of the diaphragm 32 and the piston 33 becomes a negligible value as compared with the gas pressure (0.2 to 0.3 MPa) of the second gas storage unit 35. Therefore, the internal pressure of the first gas storage unit 34 in which natural gas is stored is substantially equal to the air pressure in the second gas storage unit 35.

  As can be understood from the above, according to the present embodiment, the internal pressure of the first gas storage portion 34 on the lower side of the gas holder 3 and the air pressure of the second gas storage portion 35 on the upper side are kept in balance. However, the diaphragm 32 is displaced, and the capacity of the gas holder 3 (first gas storage unit 34) is changed. Therefore, for example, even if the amount of gas consumed in the gas consuming equipment through the gas holder 3 fluctuates, the gas (natural gas) stored in the gas holder 3 can be stably supplied to the gas consuming equipment at a predetermined pressure. .

  Unlike the present embodiment, when the consumption gas (natural gas) is stored in the fixed-capacity gas holder, the pressure in the gas holder varies due to the variation of the consumption gas amount. The pressure in the gas holder decreases when the consumed gas amount is larger than the natural gas amount introduced into the gas holder, and conversely increases when the consumed gas amount is smaller than the natural gas amount introduced into the gas holder. Therefore, when the natural gas stored in the fixed-capacity gas holder is consumed at a stable pressure, the pressure control valve provided on the downstream side of the gas holder controls from the minimum value of the pressure fluctuation in the gas holder. Loss of 0.1 MPaG (this value is generally known in the above-mentioned Patent Document 2 already described as a prior art document).

  On the other hand, in this embodiment, even if the amount of consumed gas fluctuates, the first gas storage unit 34 in which natural gas is stored balances with the gas pressure of the second gas storage unit 35 whose pressure is adjusted. It is possible to supply natural gas corresponding to fluctuations in the amount of consumed gas while maintaining the internal pressure almost constant.

  In the gas holder 3, the first gas storage portion 34 that stores natural gas is substantially adjusted by adjusting the gas pressure of the second gas storage portion 35. Thus, according to the pressure control of the first gas storage unit 34 using the gas pressure, the gas pressure of the first gas storage unit 34 can be maintained at a relatively high pressure. The gas pressure of the second gas storage unit 35 can be adjusted to, for example, about 1.0 MPaG, and the first gas storage unit 34 can also be in a high pressure state of about 1.0 MPaG. Thereby, for example, it is possible to cope with a case where a high pressure is required for the gas consumed through the first gas storage unit 34.

  Furthermore, according to the configuration in which the gas pressure of the first gas storage part 34 can be substantially adjusted, the gas pressure P1 in the upper space inside the liquid storage tank 1 maintained at substantially the same pressure as the first gas storage part 34 is also achieved. High pressure can be achieved. This is more preferable for stably continuing the discharge of the liquefied natural gas from the liquid storage tank 1.

  The gas pressure in the second gas storage unit 35 is adjusted using the gas supply line 36, the gas discharge line 37, and the pressure control valves 361 and 371 described above. According to such a configuration, the gas pressure in the second gas storage unit 35 can be appropriately adjusted so as to fall within a predetermined range.

  FIG. 3 shows another example of the gas holder according to the present invention. The gas holder 3A shown in FIG. 3 includes a body 31A, a diaphragm 32A housed in the body 31A, and a weight 33A, and is configured as a balloon type. In FIG. 3, the same or similar elements as those in the above embodiment are denoted by the same reference numerals as those in the above embodiment, and description thereof will be omitted as appropriate.

  The body 31A is made of a metal such as iron or stainless steel and has a cylindrical shape as a whole. A gas inlet 314 and gas outlets 315 and 318 are provided at appropriate positions below the body 31A. The gas inlet 43 is connected to the downstream end of the gas line 43, and the gas outlet 315 is connected to the gas line 44 (see FIG. 1). A gas replenishment line 45 is connected to the gas outlet 318 (see FIG. 1). The diaphragm 32A is molded from synthetic rubber reinforced with fibers, and is a hemispherical film body. A peripheral edge portion of the diaphragm 32A is fixed to a mounting bracket 319 provided on the inner surface of the body 31A. A gas inlet 316 and a gas outlet 317 for taking in and out air (pressure adjusting gas) are provided in the upper portion of the body 31A. The diaphragm 32A can be moved up and down (displaceable) while maintaining the gas seal state between the diaphragm 31A and corresponds to a blocking portion in the present invention.

  A region defined by the diaphragm 32A and the lower portion of the body 31A is a first gas storage portion 34 for storing natural gas. In addition, a region defined by the diaphragm 32A and the upper portion of the body 31A is a second gas storage portion 35 for storing air (pressure adjusting gas). That is, the internal space of the body 31A is partitioned into the first gas storage part 34 and the second gas storage part 35 with the diaphragm 32A interposed therebetween.

  The weight 33A is for stabilizing the operation of the diaphragm 32A, and is fixed to the center upper surface of the diaphragm 32A.

  A gas supply line 36 is connected to the gas inlet 316, and a pressure control valve 361 is provided in the gas supply line 36 (see FIG. 1). A gas discharge line 37 is connected to the gas discharge port 317, and a pressure control valve 371 is provided in the gas discharge line 37 (see FIG. 1). The second gas storage unit 35 is adjusted to have a predetermined gas pressure by a pressure control valve 361 for increasing pressure and a pressure control valve 371 for decreasing pressure.

  In the present embodiment, the first gas storage section 34 is partitioned from the upper side second gas storage section 35 with a displaceable diaphragm 32A interposed therebetween. The diaphragm 32A can move up and down while maintaining a gas seal state with the body 31A. According to such a configuration, during operation of the liquefied gas discharge system X, the amount of natural gas (consumed gas amount) discharged from the first gas storage unit 34 (gas holder 3) through the gas discharge port 315 varies. Even so, the internal pressure (gas pressure) of the first gas storage unit 34 is stably maintained substantially constant by changing the capacity of the first gas storage unit 34.

  For example, when the amount of natural gas introduced into the gas holder 3A (first gas storage unit 34) via the gas inlet 314 is a substantially constant flow rate, the amount of natural gas discharged from the gas outlet 315 (consumed gas amount) ) Decreases, the diaphragm 32A swells upward while the internal pressure of the region (first gas storage portion 34) surrounded by the diaphragm 32A and the lower portion of the body 31A is maintained, and the first gas storage portion 34 is naturally expanded. Gas is stored. In FIG. 3, the state in which the diaphragm 32A swells is represented by a virtual line. On the other hand, when the discharge amount of the natural gas from the gas discharge port 315 increases, the diaphragm 32A is deflated downward while the internal pressure of the first gas storage unit 34 is maintained. In addition, the difference between the volume of the first gas storage unit 34 in the state indicated by the imaginary line in which the diaphragm 32A is most expanded and the volume of the first gas storage unit 34 in the state indicated by the solid line in which the diaphragm 32A is most deflated is The capacity can be increased or decreased in the gas holder 3A (first gas storage portion 34).

  On the other hand, the first gas storage part 34 and the internal upper space of the liquid storage tank 1 communicate with each other via a gas replenishment line 45. As a result, the gas pressure in the first gas storage part 34 reaches the upper space inside the liquid storage tank 1 via the gas replenishment line 45. Therefore, the gas pressure P <b> 1 in the internal upper space is maintained substantially equal to the gas pressure in the first gas storage unit 34.

  Here, the extrusion pressure for discharging the liquefied natural gas in the liquid storage tank 1 toward the vaporizer 2 is the gas pressure P1 in the upper space inside the liquid storage tank 1 and the liquid head of the liquefied natural gas in the liquid storage tank 1. When the pressure H1 is used, it is expressed as P1 + H1. In the present embodiment, since the liquefied gas introduction port 221 of the vaporizer 2 is located at a position lower than the liquefied gas discharge port 12 of the liquid storage tank 1, the remaining amount of liquefied natural gas in the liquid storage tank 1 is reduced and the liquefied natural gas is concerned. Even if the liquid level of the gas is lowered, the liquid head pressure H1 is always a positive value. Further, the gas pressure P1 in the upper space inside the liquid storage tank 1 is stably maintained by being controlled by the gas pressure of the variable capacity gas holder 3A (first gas storage unit 34). Therefore, the extrusion pressure (P1 + H1) of the liquefied natural gas in the liquid storage tank 1 is always a predetermined value or more. According to such a configuration, even when the liquid level of the liquefied natural gas in the liquid storage tank 1 is lowered as the natural gas is consumed, the discharge of the liquefied natural gas from the liquid storage tank 1 is stably continued. Is done.

Moreover, the 2nd gas accommodating part 35 is controlled so that it may become a predetermined gas pressure as mentioned above. Thereby, the internal pressure (gas pressure) of the first gas storage unit 34 is determined by the gas pressure of the air (pressure adjusting gas) fed into the second gas storage unit 35 on the upper side. The pressure is adjusted in the range of 0.2 to 0.3 MPaG. The internal pressure (gas pressure) of the first gas storage portion 34 in which natural gas is stored is a value obtained by dividing the air pressure in the second gas storage portion 35 by the load of the diaphragm 32A and the weight 33A by the horizontal sectional area of the body 31A ( Specifically, 100 to 300 kg / m ² ≈0.001 to 0.003 MPa) is added. The pressure value (0.001 to 0.003 MPa) applied by the load of the diaphragm 32A and the weight 33A is a negligible value compared with the gas pressure (0.2 to 0.3 MPa) of the second gas storage unit 35. Therefore, the internal pressure of the first gas storage unit 34 in which natural gas is stored is substantially equal to the air pressure in the second gas storage unit 35.

  As understood from the above, according to the present embodiment, the internal pressure of the first gas storage portion 34 on the lower side of the gas holder 3A and the air pressure of the second gas storage portion 35 on the upper side are kept in balance. However, the diaphragm 32A is displaced, and the capacity of the gas holder 3A (first gas storage unit 34) is changed. Therefore, for example, even if the amount of gas consumed in the gas consuming equipment through the gas holder 3A varies, the gas (natural gas) stored in the gas holder 3A can be stably supplied to the gas consuming equipment at a predetermined pressure. .

  While specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention. The specific configuration of each part of the gas holder according to the present invention is not limited to the above embodiment.

  In the said embodiment, although the structure which connects the end of the gas replenishment line 45 to the gas exhaust port 318 of a gas holder (3, 3A) was demonstrated, it is not limited to this. The gas replenishment line 45 only needs to communicate with the first gas storage unit 34. For example, one end of the gas replenishment line 45 is connected to the gas line 43 in a branched manner, and gas replenishment is performed via a part of the gas line 43. You may make it the line 45 and the 1st gas accommodating part 34 connect.

  In the said embodiment, although the 1st gas accommodating part 34 demonstrated and demonstrated as an example the structure located in the lower part side on both sides of a diaphragm (32, 32A), it is not limited to this, 1st gas accommodating You may comprise so that the part 34 may be located in the upper part side (namely, sandwiching a diaphragm) on the gas holder. Further, as the pressure adjusting gas sent to the second gas storage unit 35, an inert gas such as nitrogen or argon may be used instead of air.

X Liquefied Gas Dispensing System 1 Liquid Storage Tank 11 Strut 12 Liquefied Gas Discharge Port 2 Vaporizer 21 Container 22 Heat Transfer Tube 221 Liquefied Gas Inlet 222 Gas Discharge Port 3, 3A Gas Holder 31 Main Body 31A Body (Main Body)
311 Lower body 312 Upper body 316 Gas inlet 317 Gas outlet 32, 32A Diaphragm (blocking part)
321 Hook 322 Cylindrical part 323 Bottom 33 Piston 33A Weight 331 Piston cylinder 332 Piston bottom 334 Mounting tool 335 Guide roller 34 First gas storage 35 Second gas storage 36 Gas supply line 361 Pressure control valve (first pressure) Control valve)
37 Gas exhaust line 371 Pressure control valve (second pressure control valve)
41 liquefied gas introduction line 411 check valve 42 liquefied gas transfer line 421 shutoff valves 43 and 44 gas line 45 gas replenishment line 451 check valve

Claims (8)

A liquid storage tank for storing liquefied gas;
A liquefied gas transfer line for transferring the liquefied gas discharged from the liquid storage tank;
A variable-capacity gas holder having a first gas storage part for storing gas obtained by vaporizing the liquefied gas, the capacity of the first gas storage part being variable;
A liquefied gas discharge system comprising: a gas replenishment line that communicates with both the first gas storage unit and the internal upper space of the liquid storage tank. A vaporizer for vaporizing the liquefied gas;
Both ends of the liquefied gas transfer line are respectively connected to a liquefied gas discharge port provided at the lower end of the liquid storage tank and a liquefied gas inlet provided in the vaporizer,
The liquefied gas discharge system according to claim 1, wherein the liquefied gas inlet is at a position lower than the liquefied gas outlet.   The gas holder is provided to be displaceable while maintaining a gas seal state between a main body configured in a container shape and the main body, and the first gas storage unit and the second gas are disposed inside the main body. 3. The liquefied gas discharge system according to claim 1, further comprising: a blocking portion that is partitioned into a storage portion; and a gas pressure adjusting unit that adjusts the second gas storage portion to a predetermined gas pressure.   The liquefied gas discharge system according to claim 3, wherein the blocking unit includes a diaphragm. The main body is provided with a gas inlet and a gas outlet, each of which communicates with the second gas storage unit and allows gas to be taken in and out of the second gas storage unit.
The gas pressure adjusting means is connected to the gas introduction port, a gas supply line for supplying gas toward the second gas storage unit, a first pressure control valve provided in the gas supply line, 5. The gas discharge port according to claim 3, comprising a gas discharge line connected to a gas discharge port and configured to discharge gas from the second gas storage unit, and a second pressure control valve provided in the gas discharge line. Liquefied gas dispensing system. The first pressure control valve permits the supply of gas toward the second gas storage unit when the gas pressure of the second gas storage unit is lower than the first reference pressure;
The second pressure control valve allows the gas to be discharged from the second gas storage unit when the gas pressure of the second gas storage unit exceeds a second reference pressure that is higher than the first reference pressure. The liquefied gas discharge system according to claim 5.   The liquefied gas discharge system according to any one of claims 3 to 6, wherein a gas pressure in the second gas storage unit is adjusted in a range of atmospheric pressure to 1.0 MPaG.   The liquefied gas discharge system according to any one of claims 1 to 7, wherein the liquefied gas is liquefied natural gas (LNG).

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