Liquefied carbon dioxide discharge device, floating body, and liquefied carbon dioxide discharge method

Abstract

This liquefied carbon dioxide discharge facility is provided with: a tank capable of storing liquefied carbon dioxide; a discharge pipe that passes through the inside and outside of the tank from below to above and discharges the liquefied carbon dioxide in the tank to the outside of the tank; a pump which is provided in the discharge pipe and which delivers the liquefied carbon dioxide in the tank to the outside of the tank; and a pump control unit that controls the pump so as to reduce the rotational speed of the pump as the liquid level of the liquefied carbon dioxide in the tank decreases, on the basis of the liquid level of the liquefied carbon dioxide in the tank.

Description

Technical Field

[0001] The present invention relates to a liquefied carbon dioxide discharge device, a floating body and a liquefied carbon dioxide discharge method.

[0002] This application claims priority based on patent application No. 2022-096365 filed in Japan on June 15, 2022, and the contents are incorporated herein by reference. Background Art

[0003] For example, the fuel tank disclosed in Patent Document 1 is provided with a loading pipe (pipe) for loading liquefied gas (LNG: Liquefied Natural Gas) into the fuel tank and a discharge pipe (pipe) for taking out the liquefied gas from the fuel tank. The loading pipe and the discharge pipe are introduced into the tank from near the top to near the bottom. A pump for extracting the liquefied gas in the tank is provided at the lower end of the discharge pipe.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2018-528119 Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] When liquefied carbon dioxide is contained in a storage tank, the liquefied carbon dioxide may solidify and generate dry ice for the following reasons. That is, the pressure of the liquefied carbon dioxide at the lower ends of the loading piping and the discharge piping opened in the storage tank corresponds to the operating pressure of the storage tank. In the structure disclosed in Patent Document 1, the pump provided at the lower end of the discharge piping is arranged at a position lower than the liquid level of the liquefied carbon dioxide in the storage tank. Therefore, the head pressure generated by the height difference between the liquid level of the liquefied carbon dioxide in the storage tank and the pump acts on the pump. After the discharge of the liquefied carbon dioxide in the storage tank begins, the head pressure of the liquefied carbon dioxide acting on the pump decreases as the remaining amount of liquefied carbon dioxide in the storage tank decreases.

[0009] When the pump is running, for example, the flow rate of the liquefied carbon dioxide increases around the impeller of the pump. In addition, in order to adjust the flow rate in the discharge piping, when the discharge piping is equipped with a valve, if the valve opening is reduced, the flow rate of the liquefied carbon dioxide increases locally. In this way, if the flow rate of the liquefied carbon dioxide increases, the static pressure of the liquefied carbon dioxide will drop. In addition, a local static pressure drop similar to the cavitation phenomenon will occur in the center of the impeller of the pump. In addition, if the liquid level of the liquefied carbon dioxide in the storage tank drops and the head pressure of the liquefied carbon dioxide acting on the pump decreases, the portion where the static pressure drop of the liquefied carbon dioxide occurs will be lower than the triple point pressure of carbon dioxide, and there is a possibility that the liquefied carbon dioxide will gasify and generate dry ice through its latent heat of evaporation.

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquefied carbon dioxide discharge device, a floating body, and a liquefied carbon dioxide discharge method capable of suppressing the generation of dry ice and smoothly performing the liquefied carbon dioxide discharge operation.

[0011] Means for solving technical problems

[0012] In order to solve the above-mentioned problems, the liquefied carbon dioxide discharge equipment involved in the present invention includes a storage tank, a discharge pipe, a pump and a pump control unit. The storage tank is capable of storing liquefied carbon dioxide. The discharge pipe penetrates the inside and outside of the storage tank from the bottom to the top. The discharge pipe discharges the liquefied carbon dioxide in the storage tank to the outside of the storage tank. The pump is arranged on the discharge pipe. The pump sends the liquefied carbon dioxide in the storage tank to the outside of the storage tank. The pump control unit controls the pump in a manner that the rotation speed of the pump is reduced as the liquid level of the liquefied carbon dioxide in the storage tank decreases.

[0013] The method for discharging liquefied carbon dioxide according to the present invention is a method for discharging liquefied carbon dioxide in a liquefied carbon dioxide discharging device. The liquefied carbon dioxide discharging device includes a storage tank, a discharge pipe, and a pump. The storage tank can store liquefied carbon dioxide. The discharge pipe penetrates inside and outside the storage tank from bottom to top. The discharge pipe discharges the liquefied carbon dioxide in the storage tank to the outside of the storage tank. The pump is provided on the discharge pipe. The pump sends the liquefied carbon dioxide in the storage tank to the outside of the storage tank. The method for discharging liquefied carbon dioxide includes the following steps: a step of starting the discharge of liquefied carbon dioxide; a step of reducing the rotation speed of the pump; and a step of ending the discharge of the liquefied carbon dioxide. In the step of starting the discharge of liquefied carbon dioxide, the pump is operated. In the step of starting the discharge of liquefied carbon dioxide, the liquefied carbon dioxide in the storage tank is sent to the outside of the storage tank through the discharge pipe, and the discharge of the liquefied carbon dioxide is started. In the step of reducing the rotation speed of the pump, the rotation speed of the pump is reduced as the liquid level of the liquefied carbon dioxide in the storage tank decreases. In the step of ending the discharge of the liquefied carbon dioxide, the pump is stopped to end the discharge of the liquefied carbon dioxide.

[0014] Effects of the Invention

[0015] According to the liquefied carbon dioxide discharge equipment, floating body, and liquefied carbon dioxide discharge method of the present invention, it is possible to suppress the generation of dry ice in the discharge pipe and to smoothly perform the liquefied carbon dioxide discharge operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a plan view showing a schematic structure of a floating body according to an embodiment of the present invention.

[0017] Figure 2 It is a side cross-sectional view showing a storage tank and a discharge pipe provided in a floating body according to an embodiment of the present invention.

[0018] Figure 3 It is a diagram showing a hardware configuration of a control device provided in a floating body according to an embodiment of the present invention.

[0019] Figure 4 This is a functional block diagram showing a control device provided in a floating body according to an embodiment of the present invention.

[0020] Figure 5 This is a flowchart showing the procedure of a method for discharging liquefied carbon dioxide in a floating body according to an embodiment of the present invention.

[0021] Figure 6 This is a diagram showing an example of changes in the rotation speed of a pump in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention.

[0022] Figure 7 This is a diagram showing a state where a first switching condition is satisfied in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention.

[0023] Figure 8 This is a diagram showing a state when the second switching condition is reached in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention. DETAILED DESCRIPTION

[0024] Below, reference Figures 1 to 8 , a liquefied carbon dioxide discharge device, a floating body, and a liquefied carbon dioxide discharge method according to an embodiment of the present invention are described.

[0025] (Ship structure)

[0026] like Figure 1 As shown in FIG. 1 , in the embodiment of the present invention, a ship (floating body) 1 as a floating body carries liquefied carbon dioxide. The ship 1 includes at least a hull 2 ​​as a floating body and a discharge facility 10 for liquefied carbon dioxide.

[0027] (Structure of the hull)

[0028] The hull 2 ​​has a pair of side 3A, 3B constituting its outer shell, a bottom (not shown) and an upper deck 5. The side 3A, 3B has a pair of side outer plates forming the port and starboard sides respectively. The bottom (not shown) has a bottom outer plate connecting these side 3A, 3B. Through these pair of side 3A, 3B and the bottom (not shown), the outer shell of the hull 2 ​​is U-shaped in a cross section orthogonal to the bow and stern direction Da. The upper deck 5 illustrated in this embodiment is a full-through deck exposed to the outside. On the hull 2, for example, on the upper deck 5 on the stern 2b side, an upper structure 7 having a living area is formed. In addition, the position or size of the upper structure 7 can be appropriately changed.

[0029] A cargo loading area (cargo hold) 8 is formed in the hull 2 ​​on the bow 2a side of the superstructure 7. The cargo loading area 8 is recessed toward the bottom of the ship (not shown) below the upper deck 5 and is open upward.

[0030] (Structure of equipment for discharging liquefied carbon dioxide)

[0031] A plurality of liquefied carbon dioxide discharge facilities 10 are arranged in a row along the bow and stern direction Da in the cargo loading area 8. In the embodiment of the present invention, for example, two liquefied carbon dioxide discharge facilities 10 are arranged at intervals in the bow and stern direction Da.

[0032] Figure 2It is a side cross-sectional view showing a storage tank and a discharge pipe provided in a floating body according to an embodiment of the present invention.

[0033] like Figure 2 As shown, the liquefied carbon dioxide discharge facility 10 of the present embodiment includes a storage tank 11 , a loading pipe 20 , a discharge pipe 30 , a detection unit 40 , and a control device 50 .

[0034] The storage tanks 11 of these multiple liquefied carbon dioxide discharge devices 10 are fixed to the hull 2. The storage tank 11 illustrated in this embodiment is cylindrical and extends along the bow and stern direction Da, and liquefied carbon dioxide L can be stored inside it. The storage tank 11 of this embodiment is configured to make the long side direction Dx consistent with the bow and stern direction Da. The storage tank 11 has a cylindrical portion 12 and a head portion 13. The long side direction Dx of the cylindrical portion 12 is consistent with the bow and stern direction Da, and the cross-sectional shape orthogonal to its long side direction Dx is circular. The head portion 13 is respectively arranged at the two ends of the long side direction Dx of the cylindrical portion 12. Each head portion 13 has a spherical surface that protrudes toward the bow and stern direction Da, such as a hemisphere, and respectively closes the openings at both ends of the long side direction Dx of the cylindrical portion 12. In addition, the storage tank 11 is not limited to a cylindrical shape, and the storage tank 11 can also be other shapes such as a sphere and a square.

[0035] The loading pipe 20 loads the liquefied carbon dioxide L supplied from an external vessel such as a liquefied carbon dioxide supply facility on land into the storage tank 11. The loading pipe 20 includes a first loading pipe section 21 and a second loading pipe section 22.

[0036] The first loading piping section 21 is detachably connected to a supply pipe (not shown) that supplies liquefied carbon dioxide from a liquefied carbon dioxide supply facility outside the ship. The first loading piping section 21 is arranged outside the storage tank 11. The first loading piping section 21 in this embodiment extends above the vertical direction Dv of the storage tank 11 in a direction (e.g., horizontal direction) that intersects the vertical direction Dv.

[0037] The base end 22p (in other words, the upper end in the vertical direction Dv) of the second loading piping section 22 is connected to the first loading piping section 21. The second loading piping section 22 passes through the top of the tank 11 and extends from the upper side in the vertical direction Dv to the lower side inside and outside the tank 11. The front end 22q (in other words, the lower end in the vertical direction Dv) of the second loading piping section 22 opens downward at the lower part inside the tank 11.

[0038] The discharge pipe 30 is a pipe for discharging the liquefied carbon dioxide L in the storage tank 11 to the outside of the ship such as the liquefied carbon dioxide storage facility on land. The discharge pipe 30 includes a first discharge pipe section 31 and a second discharge pipe section 32. An on-off valve (not shown) is provided on the discharge pipe 30. The on-off valve (not shown) is opened by an opening operation of a worker when discharging the liquefied carbon dioxide L in the storage tank 11, and is closed otherwise.

[0039] The first discharge piping section 31 is connected to a delivery pipe (not shown) that delivers the liquefied carbon dioxide in the storage tank 11 to a liquefied carbon dioxide storage facility outside the ship in a detachable manner. The first discharge piping section 31 is arranged outside the storage tank 11. The first discharge piping section 31 in this embodiment extends above the up-down direction Dv of the storage tank 11 in a direction (e.g., horizontal direction) that intersects the up-down direction Dv.

[0040] The first end 32s of the second discharge piping portion 32 (in other words, the lower end in the vertical direction Dv) is located at the lower part of the tank 11, more specifically, near the lowest part of the tank 11. The second discharge piping portion 32 passes through the top of the tank 11 and extends in the vertical direction Dv throughout the inside and outside of the tank 11. The second end 32t of the second discharge piping portion 32 (in other words, the upper end in the vertical direction Dv) is connected to the first discharge piping portion 31.

[0041] The pump 35 is provided in the discharge piping 30. More specifically, the pump 35 is connected to the first end 32s of the second discharge piping portion 32. The pump 35 can suck the liquefied carbon dioxide L in the storage tank 11 and send the sucked liquefied carbon dioxide L to the second discharge piping portion 32. As the pump 35, a centrifugal pump having an impeller can be exemplified.

[0042] The detection unit 40 detects at least the liquid level Lh of the liquefied carbon dioxide L stored in the tank 11. The detection unit 40 of the present embodiment includes a liquid level detection unit 41 and a pressure detection unit 42.

[0043] The liquid level detection unit 41 detects the liquid level height Lh of the liquefied carbon dioxide L stored in the storage tank 11. The liquid level detection unit 41 of the present embodiment detects the height of the liquid level from the pump 35 to the liquefied carbon dioxide L, that is, the liquid level height Lh. The liquid level detection unit 41 outputs a signal of the detection value of the detected liquid level height Lh to the control device 50. As the liquid level detection unit 41, an ultrasonic liquid level sensor capable of measuring in a non-contact manner, a laser liquid level sensor, or a float-type liquid level gauge in contact with the liquid surface can be exemplified.

[0044] The pressure detector 42 detects the pressure P of the gas phase in the tank 11. The pressure detector 42 illustrated in the present embodiment is provided near the top portion which is the highest position in the tank 11. The pressure detector 42 outputs a signal of the detected value of the pressure P to the control device 50.

[0045] (Structure of control device)

[0046] The control device 50 controls the operation of each part of the liquefied carbon dioxide discharge device 10 when discharging the liquefied carbon dioxide L. In the present embodiment, the control device 50 controls the operation of the pump 35 based on the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 when discharging the liquefied carbon dioxide L from the storage tank 11.

[0047] (Hardware structure diagram)

[0048] Figure 3 It is a diagram showing a hardware configuration of a control device provided in a floating body according to an embodiment of the present invention.

[0049] like Figure 3 As shown, the control device 50 is a computer including a CPU 51 (Central Processing Unit), a ROM 52 (Read Only Memory), a RAM 53 (Random Access Memory), a storage device (Storage) 54 such as a HDD (Hard Disk Drive), and a signal transceiver module 55. The signal transceiver module 55 receives signals of detection values ​​from the liquid level detection unit 41 and the pressure detection unit 42.

[0050] (Functional Block Diagram)

[0051] Figure 4 This is a functional block diagram of a control device provided in a floating body according to an embodiment of the present invention.

[0052] like Figure 4 As shown, the CPU 51 in the control device 50 executes a program stored in a storage device 54 such as a HDD, thereby realizing the functional structures of the signal input unit 71, the pump control unit 72, and the output unit 73.

[0053] The signal input unit 71 receives detection value signals from the liquid level detection unit 41 and the pressure detection unit 42 via the signal transceiver module 55 .

[0054] The pump control unit 72 controls the pump 35 based on the detection result of the detection unit 40. The pump control unit 72 controls the operation, stop, and rotation speed of the pump 35. The pump control unit 72 generates a control signal for controlling the start, stop, rotation speed, and the rate of change of the rotation speed of the pump 35. In addition, when the liquid level Lh of the liquefied carbon dioxide in the storage tank 11 decreases, the pump control unit 72 controls the pump 35 in such a manner as to reduce the rotation speed of the pump 35.

[0055] The output unit 73 outputs the control signal generated by the pump control unit 72 to the pump 35 via the signal transceiver module 55 .

[0056] (Procedure for discharging liquefied carbon dioxide from a ship)

[0057] Figure 5 This is a flowchart showing the procedure of a method for discharging liquefied carbon dioxide in a floating body according to an embodiment of the present invention. Figure 6 This is a diagram showing an example of changes in the rotation speed of a pump in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention.

[0058] like Figure 5 As shown, the method S10 for discharging liquefied carbon dioxide L in the ship 1 involved in the embodiment of the present invention includes a step S11 for starting the discharge of liquefied carbon dioxide L, a step S12 for determining whether the first switching condition is satisfied, a step S13 for reducing the rotation speed of the pump 35, a step S14 for determining whether the second switching condition is satisfied, a step S15 for reducing the rate of change of the rotation speed of the pump 35, a step S16 for determining whether the lower limit value of the liquid level height Lh of the liquefied carbon dioxide L is reached, and a step S17 for ending the discharge of the liquefied carbon dioxide L.

[0059] In the step S11 of starting the discharge of the liquefied carbon dioxide L, first, the on-off valve (not shown) provided in the discharge pipe 30 is opened, and the pump 35 is started by the pump control unit 72. In the step S11 of starting the discharge of the liquefied carbon dioxide L, the liquid level Lh in the storage tank 11 is sufficiently high, and the pressure of the liquefied carbon dioxide L near the inlet of the pump 35 is in a state sufficiently higher than the triple point pressure.

[0060] like Figure 6As shown, in the step S11 of starting the discharge of the liquefied carbon dioxide L, the pump 35 is rotated at a preset first rotation speed R1 by the pump control unit 72. As a result, the liquefied carbon dioxide L in the storage tank 11 is discharged from the first end 32s of the discharge pipe 30 through the discharge pipe 30 to the outside of the storage tank 11. The pump 35 continues to discharge the liquefied carbon dioxide L in the storage tank 11, whereby the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 gradually decreases. And, as the discharge of the liquefied carbon dioxide L starts, the liquid level detection unit 41 and the pressure detection unit 42 of the detection unit 40 start to output signals of the detection values ​​of the liquid level Lh and the pressure P at predetermined intervals. These output detection value signals are input to the signal input unit 71 of the control device 50.

[0061] In step S12 of determining whether the first switching condition is satisfied, the pump control unit 72 receives a signal of the detection value from the detection unit 40 input to the signal input unit 71 at predetermined intervals. Then, the pump control unit 72 determines whether the detection value of the detection unit 40 satisfies the preset first switching condition.

[0062] Figure 7 This is a diagram showing a state where a first switching condition is satisfied in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention.

[0063] The first switching condition is a condition for reducing the rotation speed of the pump 35 when the liquid level Lh of the liquefied carbon dioxide L in the tank 11 becomes low.

[0064] like Figure 7 As shown, the first switching condition of the present embodiment is a condition for determining whether the pressure (Ph+P) obtained by adding the head pressure Ph based on the liquid level Lh of the liquefied carbon dioxide L and the pressure P of the gas phase in the storage tank 11 is close to the triple point pressure of the liquefied carbon dioxide L. Here, the pressure P of the gas phase in the storage tank 11 in the present embodiment is maintained at a predetermined first reference pressure Ps1 as a pressure higher than the atmospheric pressure by a pressure regulating device not shown. If the first reference pressure Ps1 is set to a pressure higher than the triple point pressure and as low as possible, it is advantageous in that the allowable pressure of the storage tank 11 can be reduced.

[0065] When the first reference pressure Ps1 is adjusted to be constant, the detection value of the pressure P of the gas phase in the storage tank 11 can be omitted as the first switching condition. In addition, the head pressure Ph changes according to the liquid level Lh. Therefore, in the present embodiment, as the first switching condition for determining whether the pressure (Ph+P) obtained by adding the head pressure Ph and the pressure P is close to the triple point pressure of the liquefied carbon dioxide L, only the liquid level Lh is used. That is, in the present embodiment, the threshold value of the liquid level Lh as the first switching condition, i.e., the first reference level Ls1, is obtained in advance, and when the liquid level Lh detected by the detection unit 40 is lower than the first reference level Ls1, the pump control unit 72 determines that the first switching condition is satisfied. In addition, although the case where only the liquid level Lh is used as the first switching condition is described, the pump control unit 72 may also use the pressure (Ph+P) obtained by adding the head pressure Ph based on the liquid level Lh to the pressure P of the gas phase in the storage tank 11 for determination. As the first reference pressure Ps1 of the present embodiment, about 10 bar can be exemplified. Furthermore, the maximum value of the head pressure Ph in the storage tank 11 can be exemplified as approximately 2 bar.

[0066] In the step S12 of determining whether the first switching condition is satisfied, when it is determined that the first switching condition is not satisfied (No in S12), the step S12 of determining whether the first switching condition is satisfied is repeated at a predetermined time interval. On the other hand, in the step S12 of determining whether the first switching condition is satisfied, when it is determined that the first switching condition is satisfied (Yes in S12), the process proceeds to the step S13 of reducing the rotation speed of the pump 35.

[0067] In the step S13 of reducing the rotation speed of the pump 35, the pump control unit 72 controls the pump 35 so that the rotation speed of the pump 35 is lower than the first rotation speed R1 (refer to Figure 6 ). More specifically, the pump control unit 72 of the present embodiment is linked to the decrease in the liquid level Lh, and sets the rotation speed of the pump 35 to the second rotation speed R2 that gradually decreases. Here, the liquid level Lh of the liquefied carbon dioxide L gradually decreases with the passage of time, so the rotation speed of the pump 35 also continuously and gradually decreases with the passage of time.

[0068] Furthermore, in the step S13 of reducing the rotation speed of the pump 35, the rotation speed of the pump 35 is controlled so that the rate of change when the rotation speed of the pump 35 is set to the second rotation speed R2 and gradually reduced (in other words, the rate of reduction per unit time of the rotation speed of the pump 35) becomes a preset constant first rate of change δ1. Thus, as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases, the rotation speed of the pump 35 also decreases.

[0069] Therefore, in step S13 of reducing the rotation speed of the pump 35, even if the head pressure Ph decreases and the pressure of the liquefied carbon dioxide L near the inlet of the pump 35 decreases, since the rotation speed of the pump 35 also decreases, the flow rate of the liquefied carbon dioxide L around the impeller of the pump 35 can be suppressed, and a state can be set in which a static pressure drop is not likely to occur.

[0070] In step S14 of determining whether the second switching condition is satisfied, a signal of the detection value of the detector 40 is input to the signal input unit 71 at predetermined intervals. Then, the pump control unit 72 determines whether the detection value of the detector 40 satisfies the second switching condition.

[0071] Figure 8 This is a diagram showing a state when the second switching condition is reached in the method for discharging liquefied carbon dioxide according to the embodiment of the present invention.

[0072] The second switching condition is a condition for reducing the rate of change (rate of decrease) of the rotation speed of the pump 35 when the liquid level of the liquefied carbon dioxide L in the tank 11 approaches the height of the inlet of the pump 35 .

[0073] like Figure 8 As shown, in this embodiment, as the second switching condition, a second reference level Ls2 (predetermined threshold value) which is a threshold value of the liquid level Lh of the liquefied carbon dioxide L is used. Here, in this embodiment, the second reference level Ls2 is set to be lower than the first reference level Ls1 (reference Figure 7 ) and is higher than the first end 32s of the second discharge piping portion 32.

[0074] In step S14 of determining whether the second switching condition is satisfied, the pump control unit 72 determines whether the liquid level Lh is below the second reference level Ls2 based on the detection value of the liquid level detection unit 41 of the detection unit 40. In the result of this determination, when it is determined that the liquid level Lh of the liquefied carbon dioxide L is below the second reference level Ls2 (Yes in S14), since the second switching condition is satisfied, the process proceeds to step S15 of reducing the rate of change of the rotation speed of the pump 35. On the other hand, when it is determined that the second switching condition is not satisfied (No in S14), step S14 of determining whether the second switching condition is satisfied is repeated every predetermined time.

[0075] like Figure 6 As shown, in the step S15 of reducing the rate of change of the rotation speed of the pump 35, the rotation speed of the pump 35 is set to the third rotation speed R3. The rate of change δ2 of the rotation speed of the pump 35 per unit time at the third rotation speed R3 is smaller than the first rate of change δ1 of the second rotation speed R2. Thus, the falling speed of the liquid level Lh per unit time can be reduced.

[0076] In the step S16 of determining whether the lower limit value of the liquid level height Lh of the liquefied carbon dioxide L has been reached, the pump control unit 72 determines whether the liquid level height Lh of the liquefied carbon dioxide L in the storage tank 11 has reached a preset lower limit value. The lower limit value of the liquid level height Lh of the liquefied carbon dioxide L in the storage tank 11 is the lower limit value of the liquid level height Lh of the liquefied carbon dioxide L in the storage tank 11 that can be discharged by the pump 35. The lower limit value is set according to the specifications of the pump 35 in the storage tank 11, for example.

[0077] In step S16 of determining whether the liquid level Lh of the liquefied carbon dioxide L has reached the lower limit value, when it is determined that the liquid level Lh of the liquefied carbon dioxide L has not reached the lower limit value (Yes in S16), step S16 of determining whether the liquid level Lh of the liquefied carbon dioxide L has reached the lower limit value is repeated at predetermined intervals. On the other hand, when it is determined that the liquid level Lh of the liquefied carbon dioxide L has reached the lower limit value (No in S16), the process proceeds to step S17 of terminating the discharge of the liquefied carbon dioxide L.

[0078] In step S17 of finishing the discharge of the liquefied carbon dioxide L, the pump 35 is stopped by the pump control unit 72. Thus, the discharge operation of the liquefied carbon dioxide L in the storage tank 11 is finished.

[0079] (Effect)

[0080] In the liquefied carbon dioxide L discharge equipment 10, the ship 1, and the liquefied carbon dioxide L discharge method S10 of the above-mentioned embodiment, when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases and satisfies the first switching condition, the pump 35 is controlled in such a manner as to reduce the rotation speed of the pump 35. As a result, the flow rate of the liquefied carbon dioxide L can be suppressed around the impeller of the pump 35. Therefore, the pressure drop of the liquefied carbon dioxide L due to the decrease in static pressure can be suppressed, and the liquefied carbon dioxide L can be suppressed from solidifying around the pump 35 to generate dry ice.

[0081] Furthermore, since the flow rate of the liquefied carbon dioxide L can be adjusted by the pump 35, it is not necessary to provide a throttle for flow rate adjustment in the first discharge pipe section 31 of the discharge pipe 30. As a result, the risk of dry ice generation due to throttling can be avoided.

[0082] Furthermore, when the liquid level Lh of the liquefied carbon dioxide L in the tank 11 is high, the head pressure acting on the pump 35 is large, so even if the flow rate of the liquefied carbon dioxide L increases, dry ice is not easily generated in the vicinity of the impeller of the pump 35. In this state, compared with the case where the liquid level Lh of the liquefied carbon dioxide L in the tank 11 is low, the liquefied carbon dioxide L in the tank 11 can be discharged more efficiently by increasing the rotation speed of the pump 35. As a result, when the liquefied carbon dioxide L is discharged from the tank 11, the generation of dry ice in the discharge pipe 30 can be suppressed, and the discharge operation can be smoothly performed.

[0083] Furthermore, in the above-described embodiment, the pump 35 is controlled so that the rotation speed of the pump 35 is continuously reduced as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases. Thus, as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases, the head pressure of the liquefied carbon dioxide L acting on the pump 35 also continuously decreases. As a result, the rotation speed of the pump 35 can be continuously reduced in accordance with the decrease in the head pressure, thereby efficiently discharging the liquefied carbon dioxide L while suppressing the generation of dry ice.

[0084] Furthermore, in the above-described embodiment, when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 becomes lower than the second reference level Ls2 and the second switching condition is satisfied, the rate of change of the rotation speed of the pump 35 is reduced. Thus, when the discharge of the liquefied carbon dioxide L is completed, it is possible to suppress the gas in the gas phase in the storage tank 11 from flowing into the pump 35. As a result, the discharge of the liquefied carbon dioxide L by the pump 35 can be efficiently and smoothly performed to near the lower limit level Lsd of the liquefied carbon dioxide L.

[0085] (Other Implementations)

[0086] As mentioned above, the embodiment of the present invention has been described in detail with reference to the drawings, but the specific structure is not limited to this embodiment, and design changes and the like are also included within the scope that does not depart from the gist of the present invention.

[0087] In the above embodiment, in the step S14 of determining whether the second switching condition is satisfied and the step S15 of reducing the rate of change of the rotation speed of the pump 35, the rate of change of the rotation speed of the pump 35 is reduced during the process of reducing the rotation speed of the pump 35, but the step S14 of determining whether the second switching condition is satisfied and the step S15 of reducing the rate of change of the rotation speed of the pump 35 may be omitted. In this case, the rotation speed of the pump 35 may be continuously reduced at a constant rate of change until the pump 35 stops.

[0088] Furthermore, in the above embodiment, the case where the rotation speed of the pump 35 is linearly changed according to the change in the liquid level Lh is described, but the present invention is not limited to the case where the rotation speed is linearly changed, and for example, the rotation speed may be changed in a curve.

[0089] Furthermore, in the above-mentioned embodiment, the case where the rotation speed of the pump 35 is continuously reduced is described, but the present invention is not limited thereto. For example, the rotation speed of the pump 35 may be gradually reduced. In this case, when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 is high, the rotation speed of the pump 35 may be maintained at a constant rotation speed, and when the liquid level Lh of the liquefied carbon dioxide L becomes low, the rotation speed of the pump 35 may be reduced to maintain a constant rotation speed lower than that when the liquid level Lh is high.

[0090] Furthermore, in the above-mentioned embodiment, the case where the pressure P of the gas phase in the tank 11 is constant and approaches the triple point pressure of the liquefied carbon dioxide L as the head pressure decreases is exemplified. That is, the case where the rotation speed of the pump 35 is controlled only according to the liquid level Lh, assuming that the pressure P of the gas phase in the tank 11 is constant is described. However, the pump control unit 72 may control the rotation speed of the pump 35 according to both the pressure P of the gas phase in the tank 11 and the liquid level Lh of the liquefied carbon dioxide L in the tank 11 so that the inlet pressure of the pump 35 does not approach the triple point pressure. In this case, for example, when the pressure P of the gas phase in the tank 11 is sufficiently high relative to the triple point pressure, even if the liquid level Lh decreases, the control to reduce the rotation speed of the pump 35 may not be performed.

[0091] Furthermore, in the above embodiment, the liquid level Lh is detected by the detector 40 , but the liquid level Lh may be obtained from the rotation speed of the pump 35 and the elapsed time from the start of the discharge of the liquefied carbon dioxide L.

[0092] In the above embodiment, the rotation speed of the pump 35 is automatically controlled by the pump control unit 72, but the present invention is not limited thereto. For example, the operator may visually check the pressure P of the gas phase and the liquid level Lh in the tank 11 and manually set the rotation speed of the pump 35.

[0093] Furthermore, in the above embodiment, the discharge facility 10 of liquefied carbon dioxide L installed on a floating body such as a ship has been described, but the discharge facility of liquefied carbon dioxide L of the present invention can also be applied to a discharge facility of liquefied carbon dioxide L on land.

[0094] <Note>

[0095] The discharge equipment 10 of the liquefied carbon dioxide L, the floating body 1, and the discharge method S10 of the liquefied carbon dioxide L described in the embodiment can be understood, for example, as follows.

[0096] (1) The liquefied carbon dioxide discharge equipment 10 involved in the first embodiment includes: a storage tank 11 capable of storing liquefied carbon dioxide L; a discharge pipe 30 that penetrates the inside and outside of the storage tank 11 from bottom to top and discharges the liquefied carbon dioxide L in the storage tank 11 to the outside of the storage tank 11; a pump 35 that is provided in the discharge pipe 30 and sends the liquefied carbon dioxide L in the storage tank 11 to the outside of the storage tank 11; and a pump control unit 72 that controls the pump 35 in a manner such that the rotation speed of the pump 35 is reduced as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases.

[0097] In this structure, if the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 becomes low, even if the head pressure generated by the height difference between the liquid level of the liquefied carbon dioxide L and the pump 35 provided in the discharge pipe 30 becomes small, the rotation speed of the pump 35 can be reduced, so that the pressure drop of the liquefied carbon dioxide L in the vicinity of the impeller of the pump 35 where the flow velocity locally increases can be suppressed. Therefore, the liquefied carbon dioxide L is suppressed from solidifying around the pump 35 to generate dry ice.

[0098] Furthermore, when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 is high and the head pressure acting on the pump 35 is large, the rotation speed of the pump 35 can be increased compared to when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases, thereby enabling the liquefied carbon dioxide L in the storage tank 11 to be effectively discharged.

[0099] (2) The liquefied carbon dioxide discharge device 10 involved in the second embodiment is the liquefied carbon dioxide discharge device 10 of (1), wherein the pump control unit 72 controls the pump 35 in such a manner that the rotation speed of the pump 35 continuously decreases as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases.

[0100] In such a configuration, the rotation speed of the pump 35 can be continuously reduced in accordance with the decrease in the head pressure, so that the liquefied carbon dioxide L can be efficiently discharged while suppressing the generation of dry ice.

[0101] (3) The float 1 involved in the third embodiment is the float 1 of (2), wherein the pump control unit 72 adjusts the rate of change of the rotational speed of the pump 35 per unit time, and the pump control unit 72 reduces the rate of change of the rotational speed of the pump 35 when the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 becomes below a specified threshold value.

[0102] In this structure, when approaching the lower limit value of the liquid level height Lh that can be discharged by the pump 35, the speed of the liquid level height Lh falling can be suppressed, so that the gas in the gas phase in the storage tank 11 can be suppressed from flowing into the pump 35 near the lower limit value of the liquid level height.

[0103] (4) The floating body 1 according to the fourth aspect includes the floating body main body 2 and any one of the liquefied carbon dioxide discharge equipment 10 (1) to (3) provided on the floating body main body 2 .

[0104] Examples of the floating body 1 include ships and offshore floating equipment. Examples of the floating body main body 2 include a ship hull and an offshore floating equipment floating body main body.

[0105] In such a configuration, it is possible to suppress the generation of dry ice when discharging the liquefied carbon dioxide L stored in the tank 11 while suppressing the pressure P of the gas phase in the tank 11 of the floating body 1 .

[0106] (5) The method for discharging liquefied carbon dioxide according to the fifth embodiment is a method for discharging liquefied carbon dioxide L in a liquefied carbon dioxide discharging device 10, wherein the liquefied carbon dioxide discharging device 10 comprises: a storage tank 11 capable of storing liquefied carbon dioxide L; a discharge pipe 30 penetrating the inside and outside of the storage tank 11 from bottom to top and discharging the liquefied carbon dioxide L in the storage tank 11 to the outside of the storage tank 11; and a pump 35 provided in the discharge pipe 30 and discharging the liquefied carbon dioxide L in the storage tank 11 to the outside of the storage tank 11. The carbon dioxide L is delivered to the outside of the storage tank 11, and the discharge method S10 of the liquefied carbon dioxide L includes the following steps: operating the pump 35 to deliver the liquefied carbon dioxide L in the storage tank 11 to the outside of the storage tank 11 through the discharge piping 30, thereby starting the discharge process of the liquefied carbon dioxide L; reducing the rotation speed of the pump 35 as the liquid level Lh of the liquefied carbon dioxide L in the storage tank 11 decreases; and stopping the pump 35 to end the discharge process of the liquefied carbon dioxide L.

[0107] As the liquid level Lh of the liquefied carbon dioxide L in the tank 11 decreases, the rotation speed of the pump 35 is reduced. Therefore, the pressure drop of the liquefied carbon dioxide L is suppressed, and the liquefied carbon dioxide L is suppressed from freezing around the pump 35 to generate dry ice.

[0108] Industrial Applicability

[0109] According to the liquefied carbon dioxide discharge equipment, floating body, and liquefied carbon dioxide discharge method of the present invention, it is possible to suppress the generation of dry ice in the discharge pipe and to smoothly perform the liquefied carbon dioxide discharge operation.

[0110] Explanation of symbols

[0111] 1-ship (floating body), 2-hull (floating body body), 2a-bow, 2b-stern, 3A, 3B-side, 5-upper deck, 7-superstructure, 8-cargo loading area, 10-liquefied carbon dioxide discharge equipment, 11-storage tank, 11t-top, 12-cylindrical part, 13-sealing part, 20-loading piping, 21-first loading piping part, 22-second loading piping part, 22p-base end, 22q-front end, 30-discharge piping, 31-first discharge piping part, 32-second discharge piping part, 32s-first end, 32t-second end, 35-pump, 40-detection part, 41-liquid level detection part, 42-pressure detection part, 50-control device, 51-CPU, 52-ROM, 53-RAM, 54-storage device, 55-signal transceiver module, 71-signal input part, 72-pump Control unit, 73-output unit, Da-bow and stern direction, Dv-up and down direction, Dx-long side direction, L-liquefied carbon dioxide, Lh-liquid level, Ls1-first reference level, Ls2-second reference level, Lsd-lower limit level, P-pressure, Ph-head pressure, Ps1-first reference pressure, Ps2-second reference pressure, R1-first speed, R2-second speed, R3-third speed, S10-liquefied carbon dioxide discharge method, S11-process of starting liquefied carbon dioxide discharge, S12-process of determining whether the first switching condition is satisfied, S13-process of reducing the speed of the pump, S14-process of determining whether the second switching condition is satisfied, S15-process of reducing the rate of change of the speed of the pump, S16-process of determining whether the lower limit value is reached, S17-process of ending the discharge of liquefied carbon dioxide.

Claims

1. A liquefied carbon dioxide discharge device, comprising: Storage tanks, capable of storing liquefied carbon dioxide; a discharge pipe, which penetrates inside and outside the storage tank from bottom to top and discharges the liquefied carbon dioxide in the storage tank to the outside of the storage tank; a pump, which is provided in the discharge pipe and delivers the liquefied carbon dioxide in the storage tank to the outside of the storage tank; and The pump control unit controls the pump so as to reduce the rotation speed of the pump as the liquid level of the liquefied carbon dioxide in the storage tank decreases.

2. The liquefied carbon dioxide discharge device according to claim 1, wherein: The pump control unit controls the pump so that the rotation speed of the pump continuously decreases as the liquid level of the liquefied carbon dioxide in the storage tank decreases.

3. The liquefied carbon dioxide discharge device according to claim 1, wherein: The pump control unit reduces a rate of decrease in the rotation speed of the pump per unit time when the liquid level of the liquefied carbon dioxide in the tank becomes equal to or lower than a predetermined threshold value.

4. A floating body, comprising: the main floating body; and The liquefied carbon dioxide discharge equipment according to any one of claims 1 to 3, which is provided in the floating body.

5. A method for discharging liquefied carbon dioxide, which is a method for discharging liquefied carbon dioxide in a liquefied carbon dioxide discharging device, wherein the liquefied carbon dioxide discharging device comprises: A storage tank capable of storing liquefied carbon dioxide; a discharge pipe penetrating the inside and outside of the storage tank from bottom to top and discharging the liquefied carbon dioxide in the storage tank to the outside of the storage tank; and a pump provided in the discharge pipe and sending the liquefied carbon dioxide in the storage tank to the outside of the storage tank, The method for discharging liquefied carbon dioxide comprises the following steps: The pump is operated to discharge the liquefied carbon dioxide in the storage tank to the outside of the storage tank through the discharge pipe, thereby starting the process of discharging the liquefied carbon dioxide; The step of reducing the rotation speed of the pump as the liquid level of the liquefied carbon dioxide in the storage tank decreases; and The pump is stopped to terminate the step of discharging the liquefied carbon dioxide.

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