JP2010196825A - Low temperature liquefied gas delivery device and low temperature liquefied gas delivery method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low temperature liquefied gas delivery device and a low temperature liquefied gas delivery method capable of efficiently delivering low temperature liquefied gas, by reducing even equipment cost with a simple device constitution. <P>SOLUTION: This low temperature liquefied gas delivery device 50 is constituted by including a delivery pipe 55 for delivering the low temperature liquefied gas connected to and stored in a storage tank 20, a delivery pump 57 arranged in the middle of a pipe of the delivery pipe 55, a bypass pipe 61 having an automatic control valve 59 arranged in the delivery pipe 55 so as to bypass the delivery pump 57 and a control device 70 for controlling the delivery pump 57 and the automatic control valve 59. Pressure of the storage tank 20 is increased by confining boil-off gas, and when the control device 70 determines that this pressure is pressure suitable for a force feed by gas pressure, the low temperature liquefied gas is delivered via the bypass pipe 61 without operating the delivery pump 57. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a low-temperature liquefied gas discharge device that discharges a low-temperature liquefied gas from a storage tank that stores low-temperature liquefied gas such as liquefied carbon dioxide gas to a tank receiving tank that transports the low-temperature liquefied gas, and the low-temperature liquefied gas discharge device. The present invention relates to a low-temperature liquefied gas discharge method used.

Today, CO ₂ capture and storage (CCS) technology that collects and stores carbon dioxide released into the atmosphere from the viewpoint of preventing global warming (CO ₂ Capture and Storage: CCS) has been studied and developed.

  There are reports that carbon dioxide emissions in industrialized countries account for more than half of the total emissions from power generation activities and industrial activities mainly from power plants. (For example, refer nonpatent literature 1). For this reason, power plants and the like are actively developing technologies for recovering carbon dioxide generated by the combustion of fossil fuels such as coal.

  The carbon dioxide separation and recovery method includes a chemical absorption method in which carbon dioxide is chemically absorbed in the absorption liquid and then heated to release and recover the carbon dioxide, and the carbon dioxide is physically absorbed in the absorption liquid and then heated to carbon dioxide. There are a physical absorption method for separating and recovering, an adsorption separation method for separating and recovering after adsorbing to zeolite, etc., a membrane separation, a cryogenic separation method, and the like. A technique for storing the separated and recovered carbon dioxide in the ground or ocean after being liquefied has been studied and developed.

  As described above, since most of carbon dioxide is discharged with power production activities and industrial activities, the separation and recovery of carbon dioxide is performed at a power plant or factory. On the other hand, since liquefied carbon dioxide is stored in the ground or in the ocean, it is necessary to transport the liquefied carbon dioxide separated and recovered and liquefied and temporarily stored in the site to a storage location. In the case of storing liquefied carbon dioxide in the ocean, it is necessary to transport it with a tanker or the like, and these are also being studied technically.

  When transporting liquefied carbon dioxide with a tanker or the like and storing it in the ocean, an operation is required to discharge the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank provided on the land side, such as a power plant, to a receiving tank such as a tanker. It becomes. In general, a method of using a discharge pump and a method of discharging a low-temperature liquefied gas using a pressurized gas are used to discharge the stored low-temperature liquefied gas to another tank or container.

  Several methods have been proposed so far for the method of discharging the low-temperature liquefied gas using the pressurized gas. For example, if heating the storage tank directly requires extra energy, a vapor generation container is used separately from the storage tank to generate a vapor by heating a part of the liquefied gas. A method using steam as a pressurized gas has been proposed (see, for example, Patent Document 1). In addition, a method has been proposed in which the generated boil-off gas is pressurized by a compressor, and LNG is discharged using this gas as a pressurized gas (see, for example, Patent Document 2).

JP 2007-285370 A JP 2000-240894 A

Japan Environmental Technology Research Organization, Illustrated CO2 Storage Technology, Industrial Research Co., Ltd., 2006, p44

  The method of discharging the low-temperature liquefied gas stored in the storage tank using the pressurized gas can be said to be a useful method because a discharge pump is unnecessary and the running cost is not required. However, the technique described in Patent Document 1 requires a container for generating steam, a heating device for generating steam, and a discharge container in addition to the storage tank, which increases the equipment cost. The technique described in Patent Document 2 also requires a pressurized tank, a pressurized line for introducing pressurized gas to the pressurized tank, and the like in addition to the storage tank. Further, the techniques described in Patent Document 1 and Patent Document 2 require complicated operations including liquid transfer from a storage tank to a pressurized tank. Currently, development of an apparatus and method capable of discharging low-temperature liquefied gas with a simple apparatus configuration at low equipment costs and running costs is awaited.

  An object of the present invention is to provide a low-temperature liquefied gas discharge device and a low-temperature liquefied gas discharge method capable of efficiently discharging low-temperature liquefied gas with a simple apparatus configuration and low equipment cost.

  The present invention described in claim 1 is a low-temperature liquefied gas discharge device for discharging low-temperature liquefied gas stored in a storage tank to a receiver, and a discharge pipe for discharging the low-temperature liquefied gas stored in the storage tank; An automatic control valve in the middle of the pipe line, which is a discharge pump as a first discharge means interposed in the middle of the discharge pipe, and a second discharge means provided in the discharge pipe so as to bypass the discharge pump A low-temperature liquefied gas discharge device comprising: a bypass pipe having a controller; and a control device that controls an operation of the discharge pump and a valve opening degree of the automatic control valve based on a predetermined condition.

  According to a second aspect of the present invention, in the low-temperature liquefied gas discharge device according to the first aspect, the control device receives a pressure of the storage tank and a pressure of a receiver that is a discharge destination of the low-temperature liquefied gas, The pressure difference between the storage tank and the receiver is calculated, and when it is determined that the pressure difference exceeds a predetermined value, control is performed to discharge the low-temperature liquefied gas stored in the storage tank via the bypass pipe. When the pressure difference is determined to be equal to or less than a predetermined value, control is performed so that the low-temperature liquefied gas stored in the storage tank is discharged through the discharge pump.

  According to a third aspect of the present invention, in the low-temperature liquefied gas discharge device according to the first aspect, the storage tank includes a plurality of storage tanks, and each storage tank includes a pressure detector and the discharge pipe, A discharge pump, and a bypass pipe having the automatic control valve, wherein the control device receives a pressure of each storage tank and a pressure of a receiver to which a low-temperature liquefied gas is discharged, and connects each storage tank and the receiver. The pressure difference is calculated, the low temperature liquefied gas is discharged from the storage tank in which the pressure difference exceeds a predetermined value via the bypass pipe, and when the pressure difference reaches a predetermined value, the pressure difference is passed through the bypass pipe. Discharging is stopped, and when it is determined that all the pressure differences between each storage tank and the receiver are equal to or less than a predetermined value, control is performed so that the low-temperature liquefied gas is discharged through the discharge pump. You .

  According to the present invention, the boil-off gas generated when the low-temperature liquefied gas is received in the storage tank and / or the boil-off gas generated from the low-temperature liquefied gas stored in the storage tank is sealed in the storage tank, and the pressure of the storage tank is reduced. A low-temperature liquefied gas discharge method characterized in that the low-temperature liquefied gas is discharged using the low-temperature liquefied gas discharge device according to any one of claims 1 to 3.

  The low-temperature liquefied gas discharge device according to the present invention includes a bypass pipe having a discharge pump and an automatic control valve as a discharge means, and further controls the operation of the discharge pump and the valve opening degree of the automatic control valve based on predetermined conditions. Since the control device is provided, it becomes possible to properly use the discharge means according to the pressure of the storage tank or the pressure difference between the storage tank and the receiver to which the low-temperature liquefied gas is discharged, and the running cost can be reduced. . In addition to the discharge pump, the discharge pipe is provided with a bypass pipe having an automatic control valve, so that the capacity of the discharge pump can be reduced or the number of the discharge pumps can be reduced. Moreover, since the structure of the low-temperature liquefied gas discharge device is relatively simple, the equipment cost is low.

  Further, according to the present invention, the control device calculates a pressure difference between the storage tank and the receiver to which the low-temperature liquefied gas is discharged, and determines that the pressure difference exceeds a predetermined value. Control to discharge the low-temperature liquefied gas stored in the storage tank via the discharge pump, and control to discharge the low-temperature liquefied gas stored in the storage tank via the discharge pump when the pressure difference is determined to be less than the predetermined value. Therefore, it is efficient and the running cost at the time of payout operation can be reduced.

  According to the present invention, when the low-temperature liquefied gas stored from the plurality of storage tanks is discharged, the control device calculates the pressure difference between the storage tank and the receiver to which the low-temperature liquefied gas is discharged, and the pressure difference Discharges low temperature liquefied gas from the storage tank that exceeds the predetermined value via the bypass pipe, and stops the discharge through the bypass pipe when the pressure of the storage tank reaches the predetermined pressure. When the pressure difference with the receiver is equal to or less than a predetermined value, control is performed so that the low-temperature liquefied gas is discharged through the discharge pump, so that the running cost during the discharge operation can be reduced. In addition, since the low temperature liquefied gas is discharged preferentially from the high pressure storage tank, even if boil-off gas is generated in the storage tank, the pressure in the storage tank does not become higher than necessary, and the boil-off gas is released into the atmosphere. In addition, there is no need to separately process the boil-off gas, which is efficient.

  Further, the low temperature liquefied gas discharge method according to the present invention encloses the boil-off gas generated when the low-temperature liquefied gas is received in the storage tank and / or the boil-off gas generated from the low-temperature liquefied gas stored in the storage tank in the storage tank, and adds this. It is efficient because it is used as a pressure gas to raise the pressure of the storage tank and is discharged by the low-temperature liquefied gas discharge device according to the present invention, and the running cost during the discharge operation can be kept low. Further, since a pressurized tank, a heating device, etc. for producing pressurized gas are not required, the configuration of the low-temperature liquefied gas discharge device is simple and the equipment cost is reduced.

It is a process flow figure showing the schematic structure of the low temperature liquefied gas storage equipment provided with the low temperature liquefied gas discharge device 50 as a 1st embodiment of the present invention. It is a flowchart which shows the control procedure at the time of discharge of the control apparatus 70 which comprises a part of low temperature liquefied gas discharge apparatus 50 of FIG. It is a process flow figure showing a schematic structure of a low-temperature liquefied gas storage plant provided with low-temperature liquefied gas discharge device 51 as a 2nd embodiment of the present invention. It is a flowchart which shows the control procedure at the time of discharge of the control apparatus 72 which comprises a part of low temperature liquefied gas discharge apparatus 51 of FIG.

  FIG. 1 is a process flow diagram showing a schematic configuration of a low-temperature liquefied gas storage facility provided with a low-temperature liquefied gas discharge device 50 (hereinafter sometimes simply referred to as a discharge device 50) as a first embodiment of the present invention. . Hereinafter, a case where liquefied carbon dioxide gas is used as a low-temperature liquefied gas and the liquefied carbon dioxide gas is discharged to a receiving tank (not shown) of a liquefied carbon dioxide transport ship (hereinafter referred to as tanker) will be described as an example.

  The low-temperature liquefied gas storage facility is a receiving device that receives into the storage tank 20 liquefied carbon dioxide delivered from a liquefying device (not shown), a storage tank 20 that stores liquefied carbon dioxide, and a tanker that stores liquefied carbon dioxide in the storage tank 20 And a payout device 50 for paying out to a receiving tank (not shown).

  The receiving device includes a receiving line 5 for supplying liquefied carbon dioxide gas sent from a liquefying device (not shown) to the storage tank 20, a spray pipe 13 attached to the storage tank 20 connected to the receiving line 5, and a receiving line 5. The control apparatus 70 which controls the flow volume of the liquefied carbon dioxide gas etc. which are received in the storage tank 20 via this is provided.

  The receiving line 5 is connected to the receiving pipe 7 and the receiving pipe 7 to supply the liquefied carbon dioxide gas from the upper part of the storage tank 20, and is connected to the receiving pipe 7 to supply the liquefied carbon dioxide gas from the lower part of the storage tank 20. A lower supply pipe 11 is included. One end of the receiving pipe 7 is connected to a liquefaction apparatus for producing liquefied carbon dioxide gas (not shown), and an upper supply pipe 9 and a lower supply pipe 11 are connected to the other end.

  The upper supply pipe 9 is a pipe for supplying liquefied carbon dioxide gas from the upper part of the storage tank 20, and connects the receiving pipe 7 and one end, and the other end is a spray pipe 13 attached to the upper part in the storage tank 20. Connect with. Further, a flow rate adjusting valve 15 is provided in the middle of the pipeline, and the flow rate adjusting valve 15 varies the valve opening degree according to a command from the control device 70. Since the spray pipe 13 is at a position higher than the highest liquid level stored in the storage tank 20 and is always located in the gas phase portion 21, the liquefied carbon dioxide gas supplied from the upper supply pipe 9 passes through the spray pipe 13. And sprayed onto the gas phase portion 21 of the storage tank 20. The liquefied carbon dioxide sprayed on the gas phase section 21 cools the gas in the gas phase section 21 and re-liquefies it. Therefore, when the liquefied carbon dioxide gas is received from the upper supply pipe 9, the pressure of the storage tank 20 tends to decrease.

  The lower supply pipe 11 is a pipe for supplying liquefied carbon dioxide gas from the lower part of the storage tank 20, and connects the receiving pipe 7 and one end, and the other end connects to the lower part in the storage tank 20. Further, a flow rate adjusting valve 17 is provided in the middle of the pipeline, and the flow rate adjusting valve 17 varies the valve opening degree according to a command from the control device 70. The liquefied carbon dioxide gas supplied from the lower supply pipe 11 is supplied to the liquid phase part 23 of the storage tank 20. When the liquefied carbon dioxide gas is received from the lower supply pipe 11, the pressure of the storage tank 20 tends to increase due to the volume reduction of the gas phase portion 21 accompanying the reception and the boil-off gas generated by the vaporization of the liquefied carbon dioxide gas.

  The flow rate control valves 15 and 17 provided in the upper supply pipe 9 and the lower supply pipe 11 are automatic control valves that vary the valve opening based on a command from the control device 70, and use a known low-temperature valve. Can do.

The spray pipe 13 is connected to the upper supply pipe 9 and is used to spray the liquefied carbon dioxide gas sent from the upper supply pipe 9 onto the gas phase portion 21 of the storage tank 20. The spray tube 13 is located in the upper part of the storage tank 20 and higher than the highest liquid level to be stored, and is always located in the gas phase part 21. The spray pipe 13 is formed by a ring-shaped pipe line, and a spray nozzle (not shown) for spraying the supplied liquefied carbon dioxide gas is attached to the pipe line. A plurality of spray nozzles are attached to the ring-shaped pipe line at a predetermined interval so as to spray the liquefied carbon dioxide gas uniformly to the gas phase portion 21 of the storage tank 20. As the spray nozzle, a known spray nozzle can be used. In place of the spray nozzle, spray holes may be provided in the ring-shaped pipe line at predetermined intervals.

  The storage tank 20 has a spherical shape, and stores therein liquefied carbon dioxide gas having a temperature of about −55 ° C. and a pressure of about 0.6 MPa. The storage tank 20 is equipped with a liquid level detector 25 for detecting the liquid level of the stored liquefied carbon dioxide gas and a pressure detector 27 for detecting the pressure of the gas phase portion 21 of the storage tank 20. Connect and transmit the liquid level and pressure of the storage tank 20 to the controller 70. A spray pipe 13 connected to the upper supply pipe 9 is attached to the upper part of the storage tank 20.

  A gas pipe 31 is connected to the upper portion of the storage tank 20. One end of the storage tank 20 is connected to the gas phase portion 21 of the storage tank 20 and the other end is connected to the gas loading arm 29. A gas line 33 is formed by the gas pipe 31 and the gas loading arm 29. This gas pipe 31 is provided with a shut-off valve 35 in the middle of the pipe line, and when the liquefied carbon dioxide gas is discharged to the tanker receiving tank via the discharge pump 57, the gas phase of the tanker receiving tank via the gas loading arm 29 is provided. Communicate with the department. Further, a gas discharge pipe 37 for protecting the storage tank 20 and a safety valve (not shown) are provided in the upper part of the storage tank 20, and provided in the gas discharge pipe 37 when the pressure in the storage tank 20 exceeds a predetermined pressure. The gas release valve 39 thus opened opens, and part of the gas in the storage tank 20 is released into the atmosphere. When the pressure rises abnormally, a safety valve is activated to protect the storage tank 20. On the other hand, in addition to the lower supply pipe 11 that supplies liquefied carbon dioxide gas from the lower part of the storage tank 20, a tank main valve 41 to which the discharge pipe 55 is connected is provided at the lower part of the storage tank 20.

  The payout device 50 is a device for paying out the liquefied carbon dioxide gas stored in the storage tank 20 to the receiving tank of the tanker. The payout pipe 55 and the payout pipe 55 are connected to the storage tank 20 via the tank main valve 41. The operation of the bypass pipe 61 having the automatic control valve 59 in the middle of the pipeline and the delivery pump 57 provided in the delivery pipe 55 so as to bypass the delivery pump 57 and the delivery pump 57 provided in the middle of the delivery pump 57 and the bypass pipe 61 includes a control device 70 for controlling the valve opening degree of the automatic control valve 59 provided in 61.

  The discharge pipe 55 has one end connected to the tank main valve 41 and the other end connected to the liquid loading arm 63. The liquid loading arm 63 connects the tanker coupling portion 65 as an end to a tanker side coupling portion (not shown), and freely changes the arm position following the height of the tank receiving tank. A shutoff valve 67 is provided in the vicinity of the end of the liquid loading arm 63 on the side of the counter discharge pipe 55. A payout line 69 is formed by the payout pipe 55 and the liquid loading arm 63.

  The payout pump 57 is attached in the middle of the payout pipe 55, operates based on a command from the control device 70, and is a first payout means that pumps the liquefied carbon dioxide gas stored in the storage tank 20 to the tank receiving tank. As the payout pump 57, a known payout pump that has been conventionally used can be used.

  A bypass pipe 61 having an automatic control valve 59 in the middle of the pipe line is a second discharge means, and is connected to the discharge pipe 55 so as to bypass the discharge pump 57. The automatic control valve 59 is a valve that adjusts the flow rate of the liquefied carbon dioxide gas that is pressure-fed to the receiving tank of the tanker by changing the valve opening degree based on a command from the control device 70, and uses a known automatic control valve for low temperature. Can do.

  The control device 70 includes an input / output unit that can transmit and receive signals and input / output data, a storage unit that stores data and programs, a calculation unit that reads and reads data and programs from the storage unit, and a control unit that controls each unit. . The control device 70 is connected to the liquid level detector 25 and the pressure detector 27 attached to the storage tank 20 and receives signals from them, and also receives the liquid level signal and pressure signal of the tank receiving tank. Based on the level data and pressure data, the operation of the discharge pump 57 is controlled according to a predetermined procedure, the shutoff valve 35 attached to the gas line 33, the automatic control valve 59 provided in the bypass pipe 61, and the liquid loading arm 63. The valve opening degree including opening / closing of the valve of the provided shut-off valve 67 is controlled.

  The control device 70 is further provided in the flow rate control valve 15 provided in the upper supply pipe 9 and the lower supply pipe 11 in accordance with a predetermined procedure based on the liquefied carbon dioxide production schedule information of the liquefier not shown. The flow control valve 17 is controlled, and the liquefied carbon dioxide gas sent from the liquefying device is received in the storage tank 20. Although the control device 70 controls the entire low-temperature liquefied gas storage facility including the control of the receiving device in addition to the dispensing device 50, it goes without saying that a dedicated control device for the dispensing device 50 may be provided. Such a control apparatus 70 is realizable using a computer and a programmable logic controller.

  Next, the discharge procedure of the low-temperature liquefied gas discharge device 50 will be described together with the control procedure of the control device 70. FIG. 2 is a flowchart showing a control procedure of the control device 70 at the time of payout. This control procedure is programmed and installed in the control device 70. Here, the connection of the discharge line 69 and the gas line 33 and the cool-down operation are completed, and the low-temperature liquefied gas can be discharged. In this state, the shutoff valve 67 interposed in the tank main valve 41 and the discharge line 69 is opened, the automatic control valve 59 interposed in the bypass pipe 61 is closed, and the discharge pump 57 is stopped. The shutoff valve 35 interposed in the gas line 33 is closed.

  When the dispensing start button (not shown) is turned ON and a dispensing command is received, the control device 70 receives the dispensing command transmitted from the tanker side and the pressure of the storage tank 20 detected by the pressure detector 27 attached to the storage tank 20. The pressure of the receiving tank is subtracted from the pressure of the storage tank 20 to calculate the pressure difference (intertank differential pressure) between the pressure of the storage tank 20 and the pressure of the receiving tank (step S1). The controller 70 constantly takes in the pressure of the storage tank 20 and the pressure of the receiving tank transmitted from the tanker side until the dispensing operation is completed, stores it in the storage unit, reads out these data as necessary, and calculates and processes them. I do.

  The control device 70 determines whether or not the inter-tank differential pressure calculated in step S1 exceeds a predetermined value (step S2), and when determining that the inter-tank differential pressure exceeds a predetermined value, the control device 70. Controls to open the automatic control valve 59 interposed in the bypass pipe 61 with the discharge pump 57 stopped (step S3). At this time, the shutoff valve 35 interposed in the gas line 33 is kept closed. As a result, the liquefied carbon dioxide gas stored in the storage tank 20 is pumped to the tank receiving tank through the bypass pipe 61 using the pressure difference between the tanks as a driving force. On the other hand, when it is determined in step S2 that the inter-tank differential pressure calculated in step S1 is equal to or less than a predetermined value, the discharge pump 57 is operated and the liquefied carbon dioxide gas is pumped to the tanker receiving tank via the discharge pump 57 ( Step S4).

  When the discharge of the liquefied carbon dioxide gas is continued through the bypass pipe 61, the pressure of the storage tank 20 decreases as the liquid level of the storage tank 20 decreases. On the other hand, in the tank receiving tank, the liquid level rises as liquefied carbon dioxide is received, and the pressure rises due to boil-off gas generated as liquefied carbon dioxide is received. As a result, the pressure difference between the pressure of the storage tank 20 and the pressure of the receiving tank decreases with the discharge of the liquefied carbon dioxide gas. For this reason, during the dispensing operation, the control device 70 takes in the pressure of the storage tank 20 and the pressure of the receiving tank transmitted from the tanker side, calculates the pressure difference between the storage tank 20 and the receiving tank, and the pressure difference is a predetermined value. At this point, the discharge pump 57 is operated and the liquefied carbon dioxide gas is pumped to the tanker receiving tank through the discharge pump 57 (step S4). When the discharge pump 57 is operated, the automatic control valve 59 interposed in the bypass pipe 61 is closed.

  If the discharge pump 57 is operated and the discharge of the liquefied carbon dioxide gas is continued, the pressure difference between the storage tank 20 and the receiving tank becomes small as in the case of the discharge of the liquefied carbon dioxide gas via the bypass pipe 61. When there is almost no difference between the storage tank 20 and the receiving tank, the shutoff valve 35 interposed in the gas line 33 is gradually opened, and finally the shutoff valve 35 is controlled to be fully opened. As a result, the gas line 33 functions as a pressure equalizing line, and the low-temperature liquefied gas can be stably discharged through the discharge pump 57.

  When the liquid level in the tank on the tanker side reaches a predetermined level, the dispensing operation is finished (step S5).

  The predetermined value in step S2 can be set as follows. The inter-tank differential pressure determined in step S <b> 2 determines whether the liquefied carbon dioxide gas is discharged using the pressure difference between the storage tank 20 and the receiving tank or the liquefied carbon dioxide gas is discharged via the discharge pump 57. Is to do. If the inter-tank differential pressure is set to a low level, the liquefied carbon dioxide discharge operation using the pressure difference can be performed for a long time, so that the operating time of the discharge pump 57 can be shortened and the running cost can be reduced. Is small, the payout ability is lowered, and the payout time is lengthened. When the inter-tank differential pressure is set to a high level, the effect is opposite to that when the inter-tank differential pressure is set to a low level. Based on these characteristics, the tank-to-tank differential pressure may be set as appropriate in relation to the dispensing time. In addition, instead of the inter-tank differential pressure, the pressure may be controlled by the pressure value of the storage tank 20.

  As described above, the dispensing procedure of the low temperature liquefied gas dispensing apparatus 50 basically transfers the liquefied carbon dioxide gas using the pressure difference when the pressure difference between the storage tank 20 and the receiving tank is high, When the pressure difference is small, the liquefied carbon dioxide gas is transferred by the discharge pump 57. As described above, since the two discharge means are provided, the liquefied carbon dioxide gas can be reliably discharged regardless of the pressure difference between the storage tank 20 and the receiving tank. Further, since the liquefied carbon dioxide gas can be transferred using the pressure difference, the operation time of the discharge pump 57 can be reduced, and the running cost during the discharge operation can be reduced. In addition, when the liquefied carbon dioxide gas is discharged using the pressure difference, the gas pressure in the storage tank 20 is used, so that no separate pressurizing gas and pressurizing device are required.

  Discharging of liquefied carbon dioxide gas using the pressure difference between the storage tank 20 and the receiving tank can be rephrased as a discharging operation using the gas pressure by increasing the pressure (gas pressure) of the gas phase portion 21 of the storage tank 20. . For this reason, in order to discharge the liquefied carbon dioxide gas using the inter-tank differential pressure, it is necessary to increase the pressure of the storage tank 20.

  Next, the pressurization procedure of the storage tank 20 will be described. In the discharge of the low-temperature liquefied gas using the low-temperature liquefied gas discharge device 50, in the discharge operation of the liquefied carbon dioxide gas using the differential pressure between the tanks, the pressurized gas is produced using the pressurizing device or the heating device and used. Instead of discharging the liquefied carbon dioxide gas, the liquefied carbon dioxide gas is discharged using the pressure of the storage tank 20. For this reason, the pressurization procedure of the storage tank 20 is important.

  Considering the discharge of liquefied carbon dioxide gas using the pressure difference, it is preferable that the pressure of the storage tank 20 is high. However, even if the pressure is higher than necessary, the gas relief valve 39 provided to protect the storage tank 20 opens. Since the boil-off gas is released, it is preferable to set the pressure slightly lower than the set pressure of the gas relief valve 39. Of course, if the design pressure of the storage tank 20 is increased, it goes without saying that the pressure of the storage tank 20 can be further increased, but this leads to an increase in the manufacturing cost of the storage tank 20, so that the pressurized pressure is set in consideration of economy. There should be.

  The pressure of the storage tank 20 at the start of the dispensing operation is generated when the liquefied carbon dioxide gas to be stored is vaporized by the pressure when the acceptance of the liquefied carbon dioxide gas into the storage tank 20 is completed and after the acceptance is completed. It can be divided into the pressure increased by the boil-off gas. The amount of boil-off gas generated is generally proportional to the elapsed time. Here, as a method of increasing the pressure of the storage tank 20, the generated boil-off gas is actively used, the boil-off gas is sealed in the storage tank 20, and the pressure of the storage tank 20 is intentionally increased.

  The pressure of the storage tank 20 when the acceptance of the liquefied carbon dioxide gas into the storage tank 20 is completed is preferably adjusted so as to be a predetermined pressure in consideration of the time from the completion of the reception to the start of the dispensing. When the time from the end of acceptance to the start of payout is long, the pressure of the storage tank 20 at the end of acceptance is low, and when the time from the end of acceptance to the start of payout is short, the pressure of the storage tank 20 at the end of acceptance Is a pressure slightly lower than the set pressure of the gas relief valve 39. As a result, the pressure of the storage tank 20 is increased by the boil-off gas generated from the end of acceptance to the start of dispensing, and a pressure suitable for dispensing the liquefied carbon dioxide gas utilizing the inter-tank differential pressure can be achieved. Moreover, since it is not necessary to dissipate the generated boil-off gas into the atmosphere, it is preferable from the viewpoint of the environment. It is preferable that the relationship between the standby time and the pressure increase rate of the storage tank 20 is grasped in advance and the pressure of the storage tank 20 at the end of acceptance is determined.

  Adjustment of the pressure of the storage tank 20 at the time of completion of acceptance can be adjusted as follows. The receiving apparatus of the low-temperature liquefied gas storage facility includes an upper supply pipe 9 that supplies liquefied carbon dioxide gas from the upper part of the storage tank 20 and a lower supply pipe 11 that supplies liquefied carbon dioxide gas from the lower part of the storage tank 20. When the liquefied carbon dioxide gas is received into the storage tank 20 from the lower supply pipe 11, a part of the supplied liquefied carbon dioxide gas becomes boil-off gas, so that the pressure in the storage tank 20 increases. On the other hand, when the liquefied carbon dioxide is received into the storage tank 20 from the upper supply pipe 9, the supplied liquefied carbon dioxide cools the boil-off gas in the gas phase portion 21 and re-liquefies the boil-off gas. The pressure in the direction decreases. By properly using these two supply pipes having different functions and effects, the pressure of the storage tank 20 at the end of receiving can be adjusted.

  FIG. 3 is a process flow diagram showing a schematic configuration of a low-temperature liquefied gas storage plant including the low-temperature liquefied gas discharge device 51 as the second embodiment of the present invention. FIG. 4 is a flowchart showing a control procedure of the control device 72 at the time of payout. The low-temperature liquefied gas dispensing device 51 shown in the second embodiment is a device for dispensing liquefied carbon dioxide gas stored in a plurality of storage tanks 20, and is liquefied carbonic acid in a plurality of storage tanks 20 by a single control device 72. Control gas delivery. Except for the control device 72, the low-temperature liquefied gas discharge device 50 shown in the first embodiment is provided for each of the plurality of storage tanks 20.

  The low-temperature liquefied gas storage plant provided with the low-temperature liquefied gas discharge device 51 shown in the second embodiment is generally provided with three low-temperature liquefied gas storage facilities provided with the low-temperature liquefied gas discharge device 50 shown in the first embodiment. Consists of configuration. Among the low-temperature liquefied gas storage facilities, the same components as those of the low-temperature liquefied gas storage facilities shown in the first embodiment are given the same reference numerals, and description thereof is omitted. In addition, in order to distinguish three facilities, it attaches | subjects each code | symbol and distinguishes. For example, the storage tank 20 shown in the first embodiment is denoted as 20a, 20b, 20c in the storage tank shown in the second embodiment. The control device is not provided for every three facilities, and the three facilities are controlled by one control device 72 at the same time. The hardware configuration and functions of the control device 72 are the same as those of the control device 70 shown in the first embodiment.

  The low-temperature liquefied gas storage plant provided with the low-temperature liquefied gas discharge device 51 shown in the second embodiment is characterized by the discharge procedure, and will be described together with the control procedure of the control device 72. This control procedure is programmed and installed in the controller 72 in advance. Here, the connection of all the discharge lines 69a, 69b, 69c and the gas lines 33a, 33b, 33c and the cool-down operation are completed, and the low-temperature liquefied gas can be discharged. In this state, the shut-off valves 67a, 67b, 67c interposed in the tank original valves 41a, 41b, 41c and the discharge lines 69a, 69b, 69c are opened, and the automatic control valve interposed in the bypass pipes 61a, 61b, 61c. 59a, 59b and 59c are closed, and the discharge pumps 57a, 57b and 57c are stopped. Further, the shutoff valves 35a, 35b, 35c interposed in the gas lines 33a, 33b, 33c are closed. Also, all the payout lines 69a, 69b, 69c and the gas lines 33a, 33b, 33c are connected to the same receiving tank of the tanker.

  The liquid level of the storage tank is storage tank 20a> storage tank 20b> storage tank 20c, and the amount of liquid that can be received in the tank receiving tank is larger than the total storage amount of the storage tank 20a and the storage tank 20b. It is assumed that the total amount of liquid stored in the three storage tanks 20a, 20b, and 20c is smaller. The storage tanks 20a, 20b, and 20c are each set with a minimum liquid level (low level) that can be dispensed. When the liquid level detectors 25a, 25b, and 25c detect the liquid levels, the controller 72 It is assumed that the dispensing from the storage tanks 20a, 20b, 20c is controlled to be stopped.

  When the payout start button (not shown) is turned ON and the control device 72 receives a payout command, each storage tank 20a detected by the pressure detectors 27a, 27b, 27c attached to the storage tanks 20a, 20b, 20c. , 20b, 20c and the pressure of the receiving tank transmitted from the tanker side, subtract the pressure of the receiving tank from the pressure of each storage tank 20a, 20b, 20c, and each storage tank 20a, 20b, 20c and the receiving tank (Pressure difference between tanks) is calculated (step S11). The control device 72 always takes in the pressure of the storage tanks 20a, 20b, 20c and the pressure of the receiving tank transmitted from the tanker side until the dispensing operation is completed, stores it in the storage unit, and stores these data as necessary. Performs read operation and processing.

  It is determined whether or not any one of the three tank differential pressures calculated in step S11 exceeds a predetermined value (step S12). When it is determined that all the inter-tank differential pressures are equal to or lower than the predetermined value, the discharge of the liquefied carbon dioxide gas is started from the storage tank 20a having the highest liquid level via the discharge pump 57a (step S13). When the liquid level in the storage tank 20a reaches a predetermined value (level low) (step S14), the discharge pump 57a is stopped (step S15). Similarly, when it is determined that all the inter-tank differential pressures are equal to or lower than a predetermined value, the storage tank 20b having the second highest liquid level is discharged in the same manner as the storage tank 20a. Note that the liquefied carbon dioxide discharge procedure using the discharge pumps 57a, 57b, and 57c is the same as that in the first embodiment, and thus the description thereof is omitted.

  On the other hand, when it is determined that any one of the tank differential pressures exceeds a predetermined value, the storage tank 20a (20b, 20c) having the largest tank differential pressure among the tank differential pressures is calculated. An automatic control valve 59a (59b, 59c) is used to discharge liquefied carbon dioxide gas via a bypass pipe 61a (61b, 61c) provided in a discharge line 69a (69b, 69c) of the storage tank 20a (20b, 20c). ) Is controlled (step S16). At this time, the discharge pumps 57a, 57b, and 57c provided in the discharge pipes 55a, 55b, and 55c are kept stopped.

  When it is determined that the pressure difference between the storage tank 20a (20b, 20c) that is paying out and the tank receiving the tanker has reached a predetermined value in accordance with the payout operation (step S17), the bypass pipe 61a (61b, 61c) The automatic control valve 59a (59b, 59c) interposed in the middle is closed, and the discharge of the liquefied carbon dioxide gas is stopped (step S18).

  The control device 72 again determines whether any one of the tank differential pressures exceeds a predetermined value (step S12), and any one of the tank differential pressures has a predetermined value. Is determined, the storage tank 20b (20c) having the largest tank differential pressure among the tank differential pressures is calculated and provided in the discharge line 69b (69c) of the storage tank 20b (20c). The automatic control valve 59b (59c) is controlled to discharge the liquefied carbon dioxide gas through the bypass pipe 61b (61c) (step S16).

  When the liquid level in the tank on the tanker side reaches a predetermined level, the dispensing operation is finished (step S19).

  As described above, a plurality of storage tanks 20a, 20b, and 20c are provided, and when the liquefied carbon dioxide gas stored from these storage tanks 20a, 20b, and 20c is discharged, the discharge pumps 57a and 57b discharge the liquefied carbon dioxide gas by the gas pressure. , 57c, the running cost can be reduced. Moreover, it is generated in the standby storage tanks 20b, 20c (20a) by preferentially discharging liquefied carbon dioxide from the storage tank 20a (20b, 20c) having the highest pressure among the storage tanks 20a, 20b, 20c. The boil-off to be performed can be effectively used for pressurization of the storage tanks 20b and 20c (20a), and the generated boil-off gas does not need to be diffused to the atmosphere, so that it is efficient and environmentally friendly. In the above-described embodiment, an example in which liquefied carbon dioxide gas is discharged one by one has been shown, but control may be performed so that two or more tanks are simultaneously discharged. Needless to say, the number of storage tanks is not limited to three.

DESCRIPTION OF SYMBOLS 20 Storage tank 27 Pressure detector 50 Low temperature liquefied gas discharge apparatus 51 Low temperature liquefied gas discharge apparatus 55 Discharge pipe 57 Discharge pump 59 Automatic control valve 61 Bypass pipe 70 Control apparatus 72 Control apparatus

Claims (4)

A low-temperature liquefied gas discharge device for discharging low-temperature liquefied gas stored in a storage tank to a receiver,
A discharge pipe connected to a storage tank to discharge low-temperature liquefied gas to be stored;
A dispensing pump which is a first dispensing means interposed in the middle of the dispensing pipe;
A bypass pipe having an automatic control valve in the middle of a pipe line, which is a second discharge means provided in the discharge pipe so as to bypass the discharge pump;
A control device for controlling the operation of the dispensing pump and the valve opening of the automatic control valve based on a predetermined condition;
A low-temperature liquefied gas dispensing device comprising:   The control device receives a pressure of the storage tank and a pressure of a receiver that is a discharge destination of the low temperature liquefied gas, calculates a pressure difference between the storage tank and the receiver, and the pressure difference becomes a predetermined value. If it is determined that the pressure difference is exceeded, control is performed so that the low-temperature liquefied gas stored in the storage tank is discharged via the bypass pipe, and if the pressure difference is determined to be equal to or less than a predetermined value, storage is performed via the discharge pump. 2. The low-temperature liquefied gas discharge device according to claim 1, wherein the low-temperature liquefied gas stored in the tank is controlled to be discharged. The storage tank comprises a plurality of storage tanks,
Each storage tank includes a pressure detector and a bypass pipe having the discharge pipe, the discharge pump, and the automatic control valve,
The control device receives the pressure of each storage tank and the pressure of a receiver that is a delivery destination of the low-temperature liquefied gas, calculates the pressure difference between each storage tank and the receiver, and the pressure difference becomes a predetermined value. The low-temperature liquefied gas is discharged from the storage tank that has exceeded the bypass pipe, and when the pressure difference reaches a predetermined value, the discharge through the bypass pipe is stopped, and each storage tank and the receiver 2. The low-temperature liquefied gas discharge device according to claim 1, wherein when it is determined that all the pressure differences are equal to or less than a predetermined value, the low-temperature liquefied gas is discharged through the discharge pump.   The boil-off gas generated when the low-temperature liquefied gas is received in the storage tank and / or the boil-off gas generated from the low-temperature liquefied gas stored in the storage tank is contained in the storage tank, and the pressure of the storage tank is increased. A low-temperature liquefied gas discharge method using the low-temperature liquefied gas discharge apparatus according to claim 1.

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