KR20150007459A - Control System and Method for Liquefied LNG Storage - Google Patents

Abstract

The present invention relates to an LNG storage control system and an LNG storage control method and, more specifically, to an LNG storage control system and an LNG storage control method capable of storing a cryogenic LNG at regular levels in the LNG storage tanks such that the hull of an FLNG or the like can have a stable restoring force, thereby contributing to a restoring force and a structural stability of the hull of an FLNG or the like to be installed in the sea for a long time. Provided are an LNG storage control system and an LNG storage control method using the same, wherein the LNG storage control system comprises: an end flash drum receiving and storing an LNG; LNG supply lines connected to supply the LNG from the end flash drum to a plurality of first and second LNG storage tanks positioned on the port side and the starboard side of a hull symmetrically, and arranged in a longitudinal direction of the hull; first and second opening and closing valves installed in the LNG supply lines, and used to open or close the supply of the LNG to the first and the second LNG storage tanks; and a control part controlling the first and the second opening and closing valves such that the LNG can be stored to be supplied from the end flash drum to each pairs of the first and the second LNG storage tanks based on each time, and symmetrically be arranged on the port side and the starboard side.

Description

Technical Field [0001] The present invention relates to a liquefied LNG storage control system,

The present invention relates to a liquefied LNG storage control system and method, and more particularly, to a liquefied LNG storage control system and method configured to store LNG liquefied at a cryogenic temperature in a FLNG or the like at a uniform level in an LNG storage tank .

In general, natural gas is transported in the form of gas through land or sea gas pipelines, or stored in the LNG carrier in the form of Liquefied Natural Gas (LNG). Here, LNG is suitable for long distance transportation through the sea by reducing the volume of methane-based natural gas to approximately -163 ° C and reducing its volume to one-sixth.

Conventional liquefied LNG storage systems include a liquefied gas storage system for a liquefied natural gas liquefied gas liquefied gas storage system of Korean Patent Laid-Open No. 10-2007-0081882, Liquefied compressor and a liquefied natural gas carrier liquefied natural gas carrier which supplies the re-liquefied LNG to a plurality of storage tanks through the existing stripping / spray main header A liquefaction system comprising: a supply pipe having a plurality of split pipes connected to each of a plurality of storage tanks in a stripping / spray main header; a plurality of supply pipes arranged in the supply pipe; A first valve installed to control supply of the re-liquefied natural gas to the tank, and a second valve installed to control the supply of the re-liquefied natural gas A plurality of second valves installed on the divided pipes for supplying / blocking the respective liquefied natural gas to the storage tanks, and a second and third valves for detecting the presently chargeable amount of the plurality of storage tanks and sequentially supplying the liquefied natural gas to the storage tank. And a control unit for controlling the valve.

However, in the conventional liquefied LNG storage system, a relatively small amount of evaporation gas is re-liquefied in LNGC (LNG Carrier) and stored in the LNG storage tank, so that the produced natural gas is directly liquefied in the sea and stored in the LNG storage tank (Floating LNG). Particularly, FLNG is affected by waves more than LNGC due to the nature of the structure, and storage of liquefied LNG has a great influence on stability and structural stability of hull because it is installed on the sea for more than 20 years. The conventional liquefied LNG storage system can not solve this problem.

Korean Patent Publication No. 10-2007-0081882

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide an LNG storage tank in which LNG liquefied at cryogenic temperature is stored at a uniform level, And to contribute to the structural stability and stability of the ship such as FLNG installed in the ship.

According to an aspect of the present invention, there is provided a system for controlling liquefied LNG to be stored in an LNG storage tank, the system comprising: an end flash drum for receiving and storing the liquefied LNG; An LNG supply line symmetrically located at the port and starboard sides of the hull from the end flash drum and connected to supply LNG to the first and second LNG storage tanks arranged in plural along the longitudinal direction of the hull; First and second open / close valves installed to open and close the LNG supply of the first and second LNG storage tanks to the LNG supply line; And a controller for controlling the first and second open / close valves so that the LNG from the end flash drum is stored on a time base basis for each pair of first and second LNG storage tanks symmetrical to the port and starboard liquefied LNG storage A control system is provided.

The LNG supply line includes an LNG rundown header supplied with LNG from the end flash drum and installed along the longitudinal direction of the hull; And first and second branch lines branched from the LNG rundown header and connected to the first and second LNG storage tanks, respectively, and in which the first and second open / close valves are installed, respectively.

A level transmitter installed in each of the first and second LNG storage tanks; And a safety valve installed in each of the first and second branch lines to correspond to each of the level transmitters and operated by receiving a signal of the level transmitter or an external signal.

An LNG connection line connected to the LNG rundown header from the end flash drum; A third open / close valve installed in the LNG connection line; And a level controller for sensing the level of the end flash drum and controlling the third open / close valve.

Further comprising a setting unit configured to set a storing order of the LNG or a supplying time of the LNG to the plurality of first and second LNG storage tanks and the controller sets the storing order of the LNG set in the setting unit, The first and second open / close valves can be controlled to correspond to the first and second open / close valves.

The end flash drum can supply and store liquefied LNG in the process of liquefying natural gas at the top side of the FLNG.

According to another aspect of the present invention, there is provided a system for controlling liquefied LNG to be stored in an LNG storage tank, comprising: an end flash drum for receiving and storing the liquefied LNG; And first and second LNG storage tanks symmetrically located on the hull with respect to the port and star, respectively, and arranged in plural along the longitudinal direction of the hull, and the first and second LNG storage tanks And a control unit for causing the LNG to be stored in a time base from the end flash drum by controlling the on-off valves on a pair basis.

According to another aspect of the present invention, there is provided a method of controlling liquefied LNG stored in an LNG storage tank, comprising the steps of: 1 and the second LNG storage tank, the LNG is stored in time base from the end flash drum where the liquefied LNG is stored in the first and second LNG storage tanks in the minimum order symmetrical to the port and star; And repeating the first and second LNG storage tanks stored in the first and second LNG storage tanks in the next sequence symmetric to the port and star timbres from the end flash drum, 1 and the second LNG storage tank so that the LNG is stored in order.

Further comprising the step of setting a storage order of the LNG or a supply time of the LNG to the plurality of first and second LNG storage tanks so that the first and second LNG storage tanks correspond to the storage order of the LNG or the supply time of the LNG. 2 LNG storage tank can be made to store LNG.

And storing the liquefied LNG in the liquefaction process of the natural gas at the top side of the FLNG in the flash drum.

 According to another aspect of the present invention, there is provided a method of controlling liquefied LNG to be stored in an LNG storage tank, comprising the steps of: placing a plurality of liquefied natural gas (LNG) The liquefied LNG storage control method in which the LNG is stored in a time base from the end flash drum in which the liquefied LNG is stored for each pair of the first and second LNG storage tanks symmetrical to the port and star in the first and second LNG storage tanks / RTI >

According to the present invention, LNG that has been liquefied at a very low temperature is stored at a uniform level in the LNG storage tank so that the hull such as FLNG has a stable restoring force. Thus, the hull stability and structural stability of FLNG installed in long- Contribution.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a liquefied LNG storage control system according to an embodiment of the present invention; FIG.
2 is a flowchart illustrating a liquefied LNG storage control method according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the following examples can be modified in various forms, and the scope of the present invention is not limited to the following examples.

1 is a configuration diagram illustrating a liquefied LNG storage control system according to an embodiment of the present invention.

1, a liquefied LNG storage control system 100 according to an exemplary embodiment of the present invention includes an end flash drum 110 for receiving and storing liquefied LNG, The first and second LNG storage tanks 10 and 20 are disposed symmetrically with respect to each other on the starboard side and are arranged in plural along the longitudinal direction of the ship. The first and second LNG storage tanks 10 And a controller 150 for storing the LNG from the end flash drum 110 under the control of the on-off valves 141 and 142 in a time-based manner.

The end flash drum 110 can receive and store liquefied LNG from a sub cooling heat exchanger (not shown). Also, the end flash drum 110 can supply and store liquefied LNG in the process of liquefying natural gas, for example, on the top side of FLNG (Floating LNG). FLNG is a LNG-FPSO (LNG-Floating, Production, Storage) system that is directly used for liquefied natural gas and stored in an LNG storage tank and used to transport LNGC (LNG Carrier) and Offloading). The endflash drum 110 also supplies LNG to the first and second LNG storage tanks 10 and 20 through the LNG supply lines 120, 131 and 132.

The LNG supply lines 120, 131 and 132 are connected to the first and second LNG storage tanks 10 , 20 to supply LNG. The LNG supply lines 120, 131 and 132 may include an LNG rundown header 120 supplied with LNG from the end flash drum 110 and installed along the longitudinal direction of the ship, The first and second branch lines 131 and 132 connected to the first and second LNG storage tanks 10 and 20 and branching from the first and second open / close valves 120 and 120, respectively, 132 < / RTI > In this embodiment, four pairs of the first and second LNG storage tanks 10 and 20 are provided, for example. Thus, the first and second branch lines 131 and 132 and the first and second open / (141, 142) are also provided.

The LNG rundown header 120 is connected to the end flash drum 110 by the LNG connection line 171 and receives LNG from the end flash drum 110. The LNG connection line 171 is connected to the third on- And a level controller 173 for detecting the level of the end flash drum 110 and controlling the opening of the third on-off valve 172 may be installed in the end flash drum 110 have. Accordingly, the level controller 173 can adjust the opening degree of the third on-off valve 172 by sensing the level of the end flash drum 110 so that the level of the end flash drum 110 is maintained at a predetermined level, The third on-off valve 172 can be controlled to be shut off when the level of the second on-off valve 110 is equal to or lower than the set level. In addition, the LNG connection line 171 may be provided with a safety valve 174 which can be shut off for safety in an emergency.

A level transmitter 161 may be installed in each of the first and second LNG storage tanks 10 and 20. A safety valve 162 may be installed in the first and second branch lines 131 and 132 to correspond to the level transmitter 161, respectively.

The level transmitter 161 measures the level of each of the first and second LNG storage tanks 10 and 20 and outputs it to the external device as a detection signal to detect the level of the first and second LNG storage tanks 10 and 20 Level, or may output it to the safety valve 162 as a detection signal.

The safety valve 162 is connected to the level transmitter 161, which corresponds to each of the first and second LNG storage tanks 10 and 20, that is, the first and second LNG storage tanks 10 and 20 in which the supply of the LNG is opened and closed by the safety valve 162 Signal is received and the supply of LNG is cut off so that the first or second LNG storage tanks 10, 20 do not exceed a predetermined level, or as another example, an external signal, for example, Lt; RTI ID = 0.0 > LNG < / RTI > for safety in an emergency.

The first and second open / close valves 141 and 142 may be installed in the LNG supply lines 120, 131 and 132, specifically, the first and second branch lines 131 and 132, respectively. That is, the first on-off valve 141 is installed on the first branch line 131 and the second on-off valve 142 is installed on the second branch line 132. The first and second open / close valves 141 and 142 may be a control valve to be operated under the control of the controller 150.

The control unit 150 controls the first and second LNG storage tanks 10 and 20 so that the LNG from the end flash drum 110 is stored in a time-based manner for each pair of the first and second LNG storage tanks 10 and 20, And controls the second opening / closing valves 141 and 142. That is, the controller 150 controls the first and second LNG storage tanks 10 and 20 symmetrically provided on the left and right sides of the hull, Closing valves 141 and 142 are controlled so that the LNG is stored together in both the first and second LNG storage tanks 10 and 20, 20 are kept at a uniform level so that the LNG is stored.

The control unit 150 may be, for example, an integrated control safety system (ICSS) or a part of the ICSS. The ICSS is an integrated control, setting, and memory function and performs control and monitoring necessary for FLNG or plant operation System. To this end, the control unit 150 includes a timer 151 for counting the set time and outputting a signal to control the first and second open / close valves 141 and 142 on a time basis, And a memory unit 152 for storing the program. When the LNG is supplied to the first and second LNG storage tanks 10 and 20, the controller 150 opens only the corresponding first and second open / close valves 141 and 142, The shutoff valves 141 and 142 are kept shut.

The setting unit 180 may be provided to input the storage order of the LNG to the first and second LNG storage tanks 10 and 20 or the supply time of the LNG. At this time, the controller 150 may control the first and second open / close valves 141 and 142 to correspond to the LNG storage order or the LNG supply time set in the setting unit 180. Meanwhile, the LNG storage order of the first and second LNG storage tanks 10 and 20 according to the setting of the setting unit 180 may be, for example, in the order of arrangement of the first and second LNG storage tanks 10 and 20 Or alternatively, it can be set in the reverse order or irrespective of the arrangement order such as 1, 4, 2, 3, and so on.

 Meanwhile, the operator adjusts the supply time of the LNG by the setting unit 180 so that cooling of the first and second branch lines 131 and 132 of the first and second LNG storage tanks 10 and 20 is not required.

FIG. 2 is a flowchart illustrating a liquefied LNG storage control method according to another embodiment of the present invention, which will be described with reference to a liquefied LNG storage control system 100 according to an embodiment of the present invention.

As shown in FIG. 2, the liquefied LNG storage control method according to another embodiment of the present invention includes a plurality of first and second liquefied natural gas (LNG) storage control systems disposed symmetrically with respect to the shipboard and the starboard, The liquefied LNG stored in the end flash drum 110 for each pair of the first and second LNG storage tanks 10 and 20 symmetrical to the port and star in the 2 LNG storage tanks 10 and 20 is time- based. Specific steps for this are described as follows.

First, among the first and second LNG storage tanks 10 and 20, which are symmetrically located on the hull and located symmetrically with respect to the longitudinal direction of the hull, 1 and the second LNG storage tanks 10 and 20 so that the LNG is stored in the time base from the end flash drum 110 in which the liquefied LNG is stored (S12 and S13). The controller 150 may include first and second branch lines 131 and 132 branched from the end flash drum 110 and connected to the first and second LNG storage tanks 10 and 20 requiring LNG storage, The first and second open / close valves 141 and 142 provided in the respective LNG storage tanks 10 and 20 are opened (S12). During the supply time of the LNG set in the first and second LNG storage tanks 10 and 20, Closing of the first and second open / close valves 141 and 142 is maintained (S13). The liquefied LNG may be stored in the flash drum 110 during the liquefaction process of the natural gas at the top side of the FLNG so that the liquefied LNG is filled in the flash drum 110. [

The first and second LNG storage tanks 10 and 20 of the first order are stored at a uniform level with respect to each other (S12). Then, the first and second LNG storage tanks 10 and 20 The first and second LNG storage tanks 10 and 20 which are symmetrical to the port and starboards are present (S14), and the first and second LNG storage tanks 10 and 20 And 20 so that the LNG is stored in the first and second LNG storage tanks 10 and 20 in order so that the LNG is stored in order from the end flash drum 110 in step S15, May be performed by controlling the first and second open / close valves 141 and 142 by the control unit 150 as described above.

The storage of the LNG is stored in the designated storage tank for a preset time, then passed to the next storage tank. When the storage of the LNG is completed in all the storage tanks, the LNG is returned to the first designated storage tank.

The setting unit 180 may further include a step S11 of setting the storing order of the LNG or the supply time of the LNG to the first and second LNG storage tanks 10 and 20, (S11) may be performed prior to the storage step S12 of the LNG for the first and second LNG storage tanks 10, 20 in the first order. In addition, the order of storing the LNG in the first and second LNG storage tanks 10 and 20 may be set in the same order as the order of arranging the first and second LNG storage tanks 10 and 20, , The reverse order, or the order of 1, 4, 2, 3, and so on. The controller 150 may control the first and second LNG storage tanks 10 and 20 to store the LNG in the first and second LNG storage tanks 10 and 20 so as to correspond to the LNG storage order or the LNG supply time set in the setting unit 180. [ Closing valves 141 and 142, respectively.

As described above, according to the liquefied LNG storage control system and method of the present invention, since the cryogenic liquefied LNG is stored in a balanced level in the port and starboard LNG storage tanks, the hull such as FLNG has a stable restoring force This can contribute to the resilience and structural stability of hull such as FLNG installed on the sea for a long period of over 20 years.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. It is.

10: first LNG storage tank 20: second LNG storage tank
110: end flash drum 120: LNG rundown header
131: first branch line 132: second branch line
141: first open / close valve 142: second open / close valve
150: controller 151: timer
152: memory unit 161: level transmitter
162: Safety valve 171: LNG connection line
172: third open / close valve 173: level controller
174: Safety valve 180: Setting section

Claims (11)

A system for controlling liquefied LNG to be stored in an LNG storage tank,
An end flash drum for receiving and storing the liquefied LNG;
An LNG supply line symmetrically located at the port and starboard sides of the hull from the end flash drum and connected to supply LNG to the first and second LNG storage tanks arranged in plural along the longitudinal direction of the hull;
First and second open / close valves installed to open and close the LNG supply of the first and second LNG storage tanks to the LNG supply line; And
And a controller for controlling the first and second open / close valves so that the LNG is stored on a time basis for each pair of the first and second LNG storage tanks symmetrical to the port and starboard from the end flash drum, system. The method according to claim 1,
Wherein the LNG supply line includes:
An LNG run down header supplied with LNG from the end flash drum and installed along the longitudinal direction of the hull; And
A liquefied LNG storage control system including a first and a second branch line branched from the LNG rundown header and connected to the first and second LNG storage tanks respectively and having the first and second open / . The method of claim 2,
A level transmitter installed in each of the first and second LNG storage tanks; And
And a safety valve installed in each of the first and second branch lines so as to correspond to each of the level transmitters and operated by receiving a signal of the level transmitter or an external signal. The method of claim 2,
An LNG connection line connected to the LNG rundown header from the end flash drum;
A third open / close valve installed in the LNG connection line; And
And a level controller for sensing the level of the end flash drum and controlling the third opening / closing valve. The method according to any one of claims 1 to 4,
Further comprising a setting unit for setting a storing order of the LNG or a supplying time of the LNG to the first and second LNG storage tanks,
Wherein,
Wherein the control unit controls the first and second open / close valves to correspond to the storage order of the LNG set in the setting unit or the supply time of the LNG. The method according to any one of claims 1 to 4,
The end flash drum includes:
Liquefied LNG storage control system that receives and stores liquefied LNG in liquefaction process of natural gas at the top side of FLNG. A system for controlling liquefied LNG to be stored in an LNG storage tank,
An end flash drum for receiving and storing the liquefied LNG; And
A pair of first and second LNG storage tanks symmetrically located in the port and starboard out of the first and second LNG storage tanks, which are symmetrically located on the hull and symmetrically arranged along the longitudinal direction of the hull, And a controller for controlling the opening / closing valve so that the LNG is stored in a time base from the end flash drum. A method for controlling liquefied LNG to be stored in an LNG storage tank,
The first and second LNG storage tanks are arranged symmetrically with respect to the ship body and the starboard in the longitudinal direction of the hull, Causing the tank to store the LNG from the endflash drum storing the liquefied LNG in a time base; And
By repeating the first and second LNG storage tanks stored in the first and second LNG storage tanks in the next sequence symmetrical to the port and star timbres from the end flash drum, And causing the LNG to be stored in order in the second LNG storage tank. The method of claim 8,
Further comprising setting a storage order of the LNG or a supply time of the LNG for the plurality of first and second LNG storage tanks,
Wherein the LNG storing unit is configured to store the LNG stored in the first and second LNG storage tanks so as to correspond to the storing order of the LNG or the supplying time of the LNG. The method according to claim 8 or 9,
Further comprising the step of storing liquefied LNG in the liquefaction process of the natural gas at the top side of the FLNG in the flash drum. A method for controlling to store liquefied LNG in an LNG storage tank,
A pair of first and second LNG storage tanks symmetrically located in the port and starboards among a plurality of first and second LNG storage tanks symmetrically positioned on the hull with respect to the port and starboard and arranged along the longitudinal direction of the hull, Wherein the LNG is stored in a time base from an end flash drum where the liquefied LNG is stored.

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