Liquefied gas bunkering system and bunkering method for ships

Abstract

A liquefied gas bunkering system for a ship according to an embodiment of the present invention includes a tank installed on a ship for storing liquefied gas, a top filling line for supplying liquefied gas to an inner upper part of the tank, a bottom filling line for supplying liquefied gas to an inner lower part of the tank, a water level sensor for measuring a water level of the liquefied gas supplied to the tank, and a control unit for adjusting the supply amount of liquefied gas supplied through the top filling line and the supply amount of liquefied gas supplied through the bottom filling line based on a value measured by the water level sensor.

Description

[Technical Field]

[0001] The present invention relates to a liquefied gas bunkering system and a bunkering method for a ship. [Background technology]

[0002] As the International Maritime Organization (IMO) tightens its regulations on greenhouse gas and air pollutant emissions, the shipbuilding and shipping industries are increasingly using natural gas, a clean energy source, as fuel gas for ships, instead of the traditional fuels of heavy oil and diesel.

[0003] Natural gas, which is widely used as fuel gas, is mainly composed of methane and is usually converted into a liquefied gas by reducing its volume to 1 / 600. This liquefied gas is stored and transported in tanks that are insulated and installed in the hull of the ship.

[0004] Meanwhile, during the bunkering process of injecting liquefied gas (e.g., LNG) into a tank, the pressure inside the tank can rise suddenly. Specifically, gas can be generated as the pipe transporting the liquefied gas cools, and gas can be generated as the tank is cooled by the LNG. Evaporative gas accumulated inside the tank can increase the internal pressure of the tank, causing deformation and damage to the tank, so it is necessary to reduce the amount of evaporated gas generated.

[0005] Conventionally, the gas (evaporated gas) generated during the bunkering process is compressed by a compressor and sent back to the liquefied gas supplier where it is re-liquefied, incinerated, or discharged to the outside.

[0006] Therefore, there is a need to improve the conventional bunkering process by, for example, efficiently carrying out bunkering to minimize the amount of evaporative gas generated and minimizing the increase in tank pressure. Summary of the Invention [Problem to be solved by the invention]

[0007] An embodiment of the present invention aims to provide a liquefied gas bunkering system and a bunkering method for a ship that can supply a large amount of liquefied gas for a short period of time while minimizing the pressure increase in a tank that receives liquefied gas during bunkering. [Means for solving the problem]

[0008] According to one aspect of the present invention, the system includes a tank installed on a ship for storing liquefied gas; a top filling line for supplying liquefied gas to an upper inside portion of the tank; a bottom filling line for supplying liquefied gas to a lower inside portion of the tank; a water level sensor for measuring the water level of the liquefied gas supplied to the tank; and a control unit for adjusting the amount of liquefied gas supplied through the top filling line and the amount of liquefied gas supplied through the bottom filling line based on the value measured by the water level sensor.

[0009] The top filling line may be connected to an upper portion of the tank, and the bottom filling line may be branched from the top filling line and extended to an inner lower portion of the tank.

[0010] The top filling line may be connected to the top of the tank, and the bottom filling line may be connected to the bottom of the tank.

[0011] The system may further include a first valve installed in the top filling line to adjust the supply amount of liquefied gas supplied through the top filling line; and a second valve installed in the bottom filling line to adjust the supply amount of liquefied gas supplied through the bottom filling line.

[0012] The top filling line may include an injection line provided to inject liquefied gas into the inside of the tank.

[0013] The injection line may include multiple holes, with the holes being spaced apart at regular intervals to inject fluid directly onto the surface of the liquefied gas.

[0014] The system may further include an ejector provided in at least one of the top filling line and the bottom filling line to suck in a portion of evaporated gas from the tank and condense it into liquefied gas to be supplied to the injection line.

[0015] The apparatus may further include a vapor line that supplies a portion of the evaporated gas in the tank to the ejector, and the vapor line may include a check valve and a control valve that are provided in the vapor line to adjust the flow rate or pressure of the evaporated gas.

[0016] The tank may further include a first temperature sensor for measuring the temperature of the top filling line; and a second temperature sensor for measuring the temperature inside the tank.

[0017] The second temperature sensor may include a third temperature sensor that measures the temperature of the lower part of the tank and a fourth temperature sensor that measures the temperature of the upper part of the tank.

[0018] The apparatus may further include a flow rate sensor installed in the top filling line to measure a flow rate of the liquefied gas supplied through the top filling line.

[0019] The apparatus may further include a first pressure sensor provided in the top filling line to measure the pressure of the top filling line; and a second pressure sensor provided in the tank to measure the pressure inside the tank.

[0020] According to another aspect of the present invention, there may be provided a method for bunkering liquefied gas on a ship, the method including: (a) supplying liquefied gas into the inside of the tank through a top filling line connected to the top of the tank of the ship during bunkering; and (b) supplying liquefied gas into the inside of the tank through a bottom connected to the bottom portion of the tank when the water level of the liquefied gas supplied to the tank through the top filling line reaches a first set value; wherein the amount of liquefied gas supplied through the top filling line is greater than that through the bottom filling line at the beginning of the bunkering process when the tank is filled with liquefied gas to reach the first set value and at the end of the bunkering process when the liquefied gas is filled up to the water level of the top of the tank to reach a second set value.

[0021] In step (a), a method for bunkering liquefied gas on a ship may be provided, in which the temperature of the top filling line and the temperature inside the tank are measured while liquefied gas is flowing into the tank through the top filling line at the beginning of the bunkering process, and when the temperature difference between the top filling line and the tank interior decreases to a set value, the opening degree of a first valve installed on the top filling line is increased to increase the supply amount of liquefied gas.

[0022] In step (b), a water level of the liquefied gas supplied to the tank may be measured, and if the measured water level reaches the first set value, an opening degree of a first valve of the top filling line may be reduced and an opening degree of a second valve of the bottom filling line may be increased.

[0023] When the top filling line and the bottom filling line are used simultaneously to supply liquefied gas, the method may further include a step of measuring temperatures at the lower and upper sides of the tank, respectively, and, if a temperature difference between the lower and upper sides of the tank exceeds a set value, increasing the degree of opening of a first valve installed in the top filling line so that a larger amount of liquefied gas is supplied through the top filling line than through the bottom filling line.

[0024] The top filling line may be connected to an injection line having multiple holes provided at the upper inside portion of the tank, and the method may further include controlling the degree of opening of a first valve of the top filling line based on a pressure difference between the top filling line and the inside of the tank, thereby controlling the flow rate to be uniform through the multiple holes of the injection line.

[0025] There may be provided a method for bunkering liquefied gas on a ship, in which the degree of opening of the first valve of the top filling line is controlled so that the Cd value of the multihole becomes high according to the following mathematical formula:

[0026] <Mathematical formula>

[0027]

number

[0028] In the above mathematical formula, Q is the flow rate of liquefied gas supplied through the top filling line, Cd is the injection efficiency of the multi-hole, A is the cross-sectional area of ​​the entire multi-hole, △P is the difference between the pressure of the top filling line and the pressure inside the tank, and ρ is the fluid density of the top filling line.

[0029] There may be provided a liquefied gas bunkering method in which the Q value is controlled using a first valve so that the Cd value is 0.6 or more. [Effects of the Invention]

[0030] The liquefied gas bunkering system and bunkering method for a ship according to an embodiment of the present invention can minimize the pressure increase in the tank receiving the liquefied gas supply during bunkering, while enabling the supply of a large amount of liquefied gas in a short period of time.

[0031] In addition, by increasing the amount of liquefied gas supplied through the top filling line at the beginning and end of bunkering, the increase in tank pressure can be suppressed, and when the top filling line and bottom filling line are used simultaneously, the flow rate ratio between the two can be determined to minimize the increase in tank pressure and enable effective bunkering.

[0032] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0033] [Figure 1] 10 illustrates a state in which bunkering is performed based on the temperature of the top filling line and the temperature inside the tank at the beginning of bunkering in a liquefied gas bunkering process of a ship according to a first embodiment of the present invention.

[0034] [Figure 2] 10 shows how the valve opening of the top filling line is controlled based on the water level in the tank to determine the flow rate during liquefied gas bunkering on a ship according to the first embodiment of the present invention.

[0035] [Figure 3] 10 illustrates a state in which the flow rate of liquefied gas supplied through a top filling line is controlled based on the temperatures of the lower and upper sides of the tank during the liquefied gas bunkering process of a ship according to a first embodiment of the present invention.

[0036] [Figure 4]This shows how the flow rate of liquefied gas supplied through the top filling line is controlled based on the pressure of the top filling line and the pressure value inside the tank during the liquefied gas bunkering process of the ship according to the first embodiment of the present invention.

[0037] [Figure 5] 4 is a graph showing the state of flow rate supply depending on the water level of liquefied gas in the tank according to the first embodiment of the present invention.

[0038] [Figure 6] 1 shows a liquefied gas bunkering system for a ship according to a second embodiment of the present invention.

[0039] [Figure 7] 10 shows a liquefied gas bunkering system for a ship according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments introduced below are provided as examples so that the concept of the present invention can be fully conveyed to those skilled in the art to which the present invention pertains. The present invention is not limited to the embodiments described below and may be embodied in other forms. In order to clearly explain the present invention, parts not relevant to the description have been omitted from the drawings, and the width, length, thickness, etc. of elements in the drawings may be exaggerated for convenience. The same reference numerals refer to the same elements throughout the specification.

[0041] FIG. 1 shows how bunkering is performed based on the temperature of the top filling line and the temperature inside the tank in the early stage of bunkering in the liquefied gas bunkering process of a ship according to the first embodiment of the present invention, and FIG. 2 shows how the flow rate is determined by controlling the valve opening of the top filling line based on the water level in the tank in the liquefied gas bunkering process of a ship according to the first embodiment of the present invention.

[0042] The liquefied gas bunkering process for a ship according to the first embodiment of the present invention can be applied to various liquefied fuel propelled ships, liquefied fuel RVs (Regasification Vessels), container ships, general commercial ships, LNG FPSOs (Floating, Production, Storage and Offloading), LNG FSRUs (Floating Storage and Regasification Units), etc.

[0043] The liquefied gas stored in the tank 101 may be any one of LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), DME (Dimethylether), and Ethane, which can be stored in a liquid state, but is not limited thereto. In the first embodiment of the present invention, LNG will be used as an example of the liquefied gas.

[0044] Tanks 101 may include membrane tanks, Type A and Type B tanks, etc. that store fuel in a liquefied state while maintaining thermal insulation.

[0045] The top filling line 110 supplies liquefied gas to the upper inside of the tank 101 of the ship. The top filling line 110 is connected to the upper part of the tank 101 of the ship, and the spray line 112 connected to the top filling line 110 is installed at the upper inside of the tank 101. During the bunkering process, the liquefied gas supplied through the top filling line 110 can be sprayed into the tank 101 through the spray line 112.

[0046] The injection line 112 is formed with multiple holes H, and each hole H is arranged at a regular interval to inject liquefied gas into the tank 101. Fluid can be directly injected onto the interface of the liquefied gas through the multiple holes H, and droplets generated by the collision of the injected liquefied gas with the water surface can effectively enhance the cooling of the tank 101. At this time, as the diameter of the holes H becomes smaller, the pressure loss generated in the holes H increases, but the deviation in flow rate between the holes H decreases. Therefore, the supplied flow rate reflects the loss coefficient of the multi-holes H depending on the flow rate, but the design of the multi-holes H can be varied depending on the size and type of the tank 101.

[0047] The bottom filling line 120 supplies liquefied gas to the lower inside of the tank 101. The bottom filling line 120 is connected to the bottom of the tank 101 and supplies liquefied gas to the inside of the tank 101. The diameter of the bottom filling line 120 may be larger than that of the top filling line 110.

[0048] Hereinafter, a liquefied gas bunkering process for a ship according to a first embodiment of the present invention will be described.

[0049] As shown in Figure 1, at the beginning of the bunkering process, liquefied gas is supplied into the tank 101 through a top filling line 110 connected to the top of the tank 101 of the ship. For example, bunkering can be performed from a liquefied gas tank truck, a fixed liquefied gas storage tank on land, a liquefied gas terminal, or an offshore floating liquefied gas storage ship to the tank 101 side.

[0050] At this time, the temperature of the top filling line 110 and the temperature inside the tank 101 are measured by the first and second temperature sensors T1 and T2, respectively, while a minimum amount of liquefied gas is flowing into the tank 101 through the top filling line 110. The flow rate of the liquefied gas supplied through the top filling line 110 is measured by the flow rate sensor F1.

[0051] The control unit 150 performs control operations in conjunction with various means to ensure that the liquefied gas bunkering process is performed effectively. When the temperature difference between the inside of the top filling line 110 and the tank 101 decreases to a set value, the control unit 150 increases the opening degree of the first valve V11 installed in the top filling line 110 based on the flow rate of the liquefied gas measured by the flow rate sensor F1, thereby increasing the flow rate of the liquefied gas supplied through the top filling line 110.

[0052] When liquefied gas is supplied through the top filling line 110 at the beginning of bunkering, evaporation gas is generated in the pipe through which the liquefied gas flows, which causes an increase in pressure in the tank 101. Therefore, in the first embodiment of the present invention, the point at which pipe cooling is completed is determined based on the temperature difference between the top filling line 110 and the inside of the tank 101, and the flow rate of the top filling line 110 is increased to enable full-scale bunkering.

[0053] Increasing the flow rate of the top filling line 110 condenses the gas, thereby suppressing the pressure rise in the tank 101. The flow rate of the top filling line 110 increased in the early stage of bunkering condenses the gas generated during the pipe cooling process, and the flow rate of the top filling line 110 increased in the later stage controls the sensitive pressure behavior of gas with a small volume.

[0054] The ejector 140 may be provided in at least one of the top filling line 110 and the bottom filling line 120. The ejector 140 may be installed on the top filling line 110 close to the injection line 112. The ejector 140 is provided for the purpose of sucking in a portion of the evaporated gas in the tank 101 and condensing it into a liquefied gas to be supplied to the injection line 112. For this purpose, a vapor line 130 is provided for supplying a portion of the evaporated gas in the tank 101 to the ejector 140.

[0055] The ejector 140 uses the Bernoulli principle of the ejector to suck the evaporated gas inside the tank 101 into the vapor line 130, so that the evaporated gas and the liquid fuel are mixed together and supplied to the injection line 112.

[0056] Therefore, the evaporative gas in the tank 101 flows into the ejector 140, which can have the effect of inducing a pressure reduction in the tank 101. In addition, the evaporative gas in the tank 101 is condensed into the liquid fuel supplied through the top filling line 110, so that the evaporative gas in the tank 101 can be continuously supplied to the ejector 140.

[0057] In addition, the vapor line 130 may be provided with a check valve 132 and a control valve 131 that adjust the flow rate or pressure of the evaporated gas supplied to the ejector 140, and the control valve 131 is a flow rate adjustment valve or a pressure adjustment valve, so that the evaporated gas passing through the vapor line 130 can be supplied to the ejector 140 at a constant pressure or flow rate.

[0058] Next, referring to FIG. 2, when the water level of the liquefied gas supplied to the tank 101 through the top filling line 110 reaches a first set value, the liquefied gas is supplied to the inside of the tank 101 through the bottom filling line 120 connected to the bottom portion of the tank 101.

[0059] In this way, liquefied gas can be supplied simultaneously through the top filling line 110 and the bottom filling line 120, so that a larger flow rate can be efficiently supplied to the tank 101.

[0060] The water level of the liquefied gas supplied to the tank 101 can be measured by the water level sensor L1, and the control unit 150 can control the degree of opening of the first valve V11 of the top filling line 110 and the second valve V12 of the bottom filling line 120 based on the value measured by the water level sensor L1.

[0061] To give a specific example, in order to cool the top of the tank 101 up to 20% water level (first set value) of the tank 101, the opening degree of the first valve V11 of the top filling line 110 is increased to increase the flow rate of the liquefied gas supplied to the tank 101.

[0062] Then, when the water level of the tank 101 is between 20% and 80%, the second valve V12 of the bottom filling line 120 is fully opened, and the degree of opening of the first valve V11 of the top filling line 110 is controlled so that the amount of liquefied gas supplied through the top filling line 110 is less than the amount of liquefied gas supplied through the bottom filling line 120.

[0063] Also, when the water level in the tank 101 exceeds 80% (second set value), the degree of opening of the first valve V11 of the top filling line 110 is again increased compared to the degree of opening of the second valve V12 of the bottom filling line 120, so that the amount of liquefied gas supplied through the top filling line 110 is adjusted to be greater than the amount of liquefied gas supplied through the bottom filling line 120.

[0064] This increases the flow rate of the liquefied gas in the top filling line 110 supplied to the tank 101 at the beginning and end of bunkering, promoting cooling and condensation of the gas and minimizing the pressure rise in the tank 101.

[0065] FIG. 3 illustrates a process of controlling the flow rate of liquefied gas supplied through a top filling line based on the temperatures of the lower and upper sides of the tank during liquefied gas bunkering on a ship according to the first embodiment of the present invention.

[0066] Meanwhile, referring to FIG. 3, in the process of bunkering liquefied gas through the top filling line 110 and the bottom filling line 120, the temperatures of the lower and upper sides of the tank 101 are measured by the third and fourth temperature sensors T3 and T4, respectively, and if the temperature difference between the lower and upper sides of the tank 101 exceeds a set value, the control unit 150 can increase the degree of opening of the first valve V1 installed in the top filling line 110 so that the amount of liquefied gas injected through the top filling line 110 is greater than that through the bottom filling line 120.

[0067] That is, by increasing the opening of the first valve V1 of the top filling line 110 and increasing the flow rate of the liquefied gas supplied to the tank 101, it is possible to suppress the pressure rise in the tank 101 and consequently reduce the temperature difference between the bottom and top of the tank 101. The temperature difference between the bottom and top of the tank 101 can be the basis for determining the flow rate ratio of the top filling line 110 and the bottom filling line 120.

[0068] The third and fourth temperature sensors T3 and T4 are attached to the upper and lower sides of the wall of the tank 101 to measure the temperature, and the temperature of the wall of the tank 101 rises as the pressure of the evaporated gas increases. In order to suppress the pressure of the tank 101 during the bunkering process, the temperature of the upper part of the tank 101 must be lowered. If the temperature difference between the upper and lower walls of the tank 101 increases, this is indirect evidence that temperature stratification has occurred in the liquid region. In this case, the opening degree of the first valve V11 of the top filling line 110 is increased to increase the amount of liquefied gas supplied to the upper side of the tank 101.

[0069] In this way, the temperature difference control process between the upper and lower parts of the tank 101 can be used during the middle stage of bunkering when the top filling line 110 and the bottom filling line 120 are used simultaneously, and through this, the flow rate ratio of the top filling line 110 and the bottom filling line 120 can be determined.

[0070] FIG. 4 shows how the flow rate of liquefied gas supplied through the top filling line is controlled based on the pressure of the top filling line and the pressure value inside the tank during the liquefied gas bunkering process of the ship according to the first embodiment of the present invention.

[0071] Referring to FIG. 4, in the liquefied gas bunkering process through the top filling line 110 and the bottom filling line 120 described above, the pressure of the top filling line 110 and the pressure inside the tank 101 are measured by pressure gauges P1 and P2, respectively, and the control unit 150 controls the degree of opening of the first valve V1 of the top filling line 110 based on the measured pressure values, so that the flow rate can be uniformly discharged through the multi-holes H of the injection line 112.

[0072] By supplying a uniform flow rate through the multi-holes H, efficient cooling and condensation of gas can be achieved.

[0073] At this time, the control unit 150 calculates the C of the multi-hole by the following mathematical formula: d The degree of opening of the first valve V1 of the top filling line 110 can be controlled so that the value becomes higher.

[0074] <Mathematical formula>

[0075]

number

[0076] In the above formula, Q is the flow rate of liquefied gas supplied through the top filling line, Cd is the injection efficiency of the multi-hole H, A is the cross-sectional area of ​​the entire multi-hole H, △P is the difference between the pressure of the top filling line and the pressure inside the tank, and ρ is the fluid density of the top filling line. At this time, the Q value can be controlled using the first valve so that the Cd value is preferably 0.6 or more.

[0077] As the flow rate of liquefied natural gas passing through the multi-hole H increases, the resistance of the multi-hole H decreases. As the flow rate of liquefied gas increases, the resistance of the multi-hole H decreases rapidly and gradually, which means that the flow rate is uniformly distributed through the multi-hole H. Therefore, based on the above mathematical formula, it is possible to maintain operating conditions where the resistance of the multi-hole H decreases gradually, and through this, it is possible to supply a large amount of flow rate with a small pressure drop, enabling efficient bunkering.

[0078] The performance of the injection line 112 with multiple holes H varies depending on the flow rate. As the liquefied gas is injected into the tank 101 at a uniform flow rate through each hole H, pressure loss can be effectively reduced and the bunkering process can be carried out quickly and efficiently.

[0079] FIG. 5 is a graph showing the state of flow rate supply depending on the water level of the liquefied gas in the tank according to the first embodiment of the present invention.

[0080] Referring to FIG. 5, as described above, at the beginning of the bunkering process, liquefied gas is supplied into the tank 101 through the top filling line 110 until the water level of the liquefied gas supplied to the tank 101 reaches a first set value.

[0081] Then, after reaching the first set value, the second valve V12 of the bottom filling line 120 is fully opened, and the first valve V11 of the top filling line 110 is adjusted so that the amount of liquefied gas supplied through the bottom filling line 120 is greater than the amount supplied through the top filling line 110.

[0082] Then, at the end of the bunkering process when the liquefied gas is filled up to the water level at the top of the tank 101 to reach the second set value, the first valve V11 of the top filling line 110 and the second valve V12 of the bottom filling line 120 are adjusted so that the amount of liquefied gas supplied through the top filling line 110 is greater than that through the bottom filling line 120.

[0083] When the first valve V11 of the top filling line 110 and the bottom filling line 120 are used simultaneously, as described in Figures 3 and 4, the amount of liquefied gas supplied through the top filling line 110 is adjusted based on the temperature difference between the bottom and top of the tank 101 and the pressure difference between the top filling line 110 and the inside of the tank 101, thereby suppressing the amount of evaporated gas generated, adjusting the pressure inside the tank 101, and effectively injecting liquefied gas, thereby enabling efficient bunkering.

[0084] FIG. 6 shows a liquefied gas bunkering system for a ship according to a second embodiment of the present invention.

[0085] Referring to FIG. 6, the liquefied gas bunkering system for a ship according to the second embodiment of the present invention differs from the first embodiment in the connection structure of the bottom filling line 120, but the other configurations and operating modes of the configurations are the same as those of the first embodiment.

[0086] Specifically, the bottom filling line 120 of the second embodiment branches off from the top filling line 110 and extends to the lower inside of the tank 101. In the second embodiment, the ejector 140 is installed in the top filling line 110, and the bottom filling line 120 branches off from the top filling line 110 at a section past the ejector 140, but the connection structure of the bottom filling line 120 is not limited thereto, and the bottom filling line 120 may branch off at a section before passing through the ejector 140.

[0087] FIG. 7 shows a liquefied gas bunkering system for a ship according to a third embodiment of the present invention.

[0088] Referring to Figure 7, the liquefied gas bunkering system for a ship according to the third embodiment of the present invention differs from the second embodiment in the arrangement structure of the ejector 140, but the other configurations and operating modes of the configurations are the same as those of the second embodiment.

[0089] Specifically, the ejector 140 of the third embodiment is provided in the bottom filling line 120 .

[0090] Although specific embodiments have been illustrated and described above, the present invention is not limited to the above-described embodiments, and those skilled in the art will recognize that various modifications and variations may be made without departing from the spirit and scope of the technical ideas of the invention as set forth in the following claims.

Claims

1. Tanks installed on ships to store liquefied gas injected by bunkering; a top filling line for supplying liquefied gas to the inside upper portion of the tank during the bunkering; a bottom filling line for supplying liquefied gas to the inside lower part of the tank during the bunkering; a water level sensor for measuring the water level of the liquefied gas supplied to the tank; a control unit that adjusts the amount of liquefied gas supplied through the top filling line and the amount of liquefied gas supplied through the bottom filling line according to the value measured by the water level sensor; and an ejector provided in at least one of the top filling line and the bottom filling line, for sucking in a portion of evaporated gas inside the tank during bunkering and condensing it into liquefied gas to be supplied to the tank.

2. The top filling line connected to the top of the tank, The bottom filling line 2. The liquefied gas bunkering system for a ship according to claim 1, wherein the top filling line is branched off and extended to the inside lower portion of the tank.

3. The top filling line connected to the top of the tank, The bottom filling line 2. A liquefied gas bunkering system for a ship according to claim 1, which is connected to the bottom portion of the tank.

4. a first valve provided in the top filling line for adjusting the amount of liquefied gas supplied through the top filling line; and 2. The liquefied gas bunkering system for a ship according to claim 1, further comprising: a second valve provided in the bottom filling line to adjust the amount of liquefied gas supplied through the bottom filling line.

5. The top filling line 2. The liquefied gas bunkering system for a ship according to claim 1, further comprising an injection line for injecting liquefied gas into the inside of the tank.

6. The injection line 6. The liquefied gas bunkering system for a ship according to claim 5, comprising multiple holes, the holes being spaced apart to inject fluid directly onto the surface of the liquefied gas.

7. A liquefied gas bunkering system for a ship as described in claim 1, further comprising: a vapor line that supplies a portion of the evaporated gas from the tank to the ejector.

8. The vapor line 8. The liquefied gas bunkering system for a ship according to claim 7, further comprising a check valve and a control valve provided in the vapor line to adjust the flow rate or pressure of the evaporated gas.

9. a first temperature sensor for measuring the temperature of the top filling line; and 2. The liquefied gas bunkering system for a ship according to claim 1, further comprising: a second temperature sensor for measuring a temperature inside the tank.

10. The second temperature sensor a third temperature sensor for measuring the temperature of a lower portion of the tank; 10. A liquefied gas bunkering system for a ship as described in claim 9, further comprising a fourth temperature sensor for measuring the temperature of the upper part of the tank.

11. The liquefied gas bunkering system for a ship according to claim 1, further comprising a flow rate sensor provided in the top filling line to measure a flow rate of the liquefied gas supplied through the top filling line.

12. a first pressure sensor provided in the top filling line for measuring the pressure of the top filling line; and 2. The liquefied gas bunkering system for a ship according to claim 1, further comprising a second pressure sensor provided in the tank for measuring the pressure inside the tank.

13. (a) supplying liquefied gas into the inside of the tank of the ship through a top filling line connected to the top of the tank during bunkering; and (b) supplying liquefied gas into the tank through a bottom filling line connected to a bottom portion of the tank when the water level of the liquefied gas supplied to the tank through the top filling line reaches a first set value; A liquefied gas bunkering method for a ship, wherein the amount of liquefied gas supplied through the top filling line is greater than that through the bottom filling line at the beginning of the bunkering process when the tank is filled with liquefied gas to reach the first set value and at the end of the bunkering process when the tank is filled with liquefied gas up to the water level at the top of the tank to reach the second set value.

14. In the step (a), At the beginning of the bunkering process, a liquefied gas is flowed into the tank through the top filling line, and the temperature of the top filling line and the temperature of the tank are measured; 14. The liquefied gas bunkering method for a ship according to claim 13, further comprising: increasing the degree of opening of a first valve installed in the top filling line to increase the supply amount of liquefied gas when a temperature difference between the top filling line and the inside of the tank decreases to match a set value.

15. In the step (b), measuring the level of the liquefied gas supplied to the tank; 14. The liquefied gas bunkering method for a ship according to claim 13, wherein, when the measured water level reaches the first set value, the degree of opening of the first valve of the top filling line is reduced and the degree of opening of the second valve of the bottom filling line is increased.

16. When the top filling line and the bottom filling line are used simultaneously to supply liquefied gas, measuring the temperatures of the lower and upper sides of the tank, respectively; 14. The liquefied gas bunkering method for a ship according to claim 13, further comprising the step of increasing the degree of opening of a first valve installed in the top filling line so that a larger amount of liquefied gas is supplied through the top filling line than through the bottom filling line when a temperature difference between the lower and upper sides of the tank exceeds a set value.

17. The top filling line is connected to a spray line having multiple holes formed in the upper inside portion of the tank, 14. The liquefied gas bunkering method for a ship according to claim 13, further comprising the step of controlling an opening degree of a first valve of the top filling line based on a pressure difference between the top filling line and the inside of the tank, thereby controlling the flow rate to be uniformly discharged through multiple holes of the injection line.

18. The degree of opening of the first valve of the top filling line is controlled so that the Cd value of the multi-hole is increased according to the following mathematical formula: <Mathematical formula> [Equation 1] 18. The liquefied gas bunkering method for a ship according to claim 17, wherein, in the mathematical formula, Q is the flow rate of the liquefied gas supplied through the top filling line, Cd is the injection efficiency of the multi-hole, A is the cross-sectional area of ​​the entire multi-hole, ΔP is the difference between the pressure of the top filling line and the pressure inside the tank, and ρ is the fluid density of the top filling line.

19. The liquefied gas bunkering method according to claim 18, wherein the Q value is controlled using a first valve so that the Cd value is 0.6 or more.

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