KR102165064B1 - Roll-over effect protection apparatus for lng storage and method thereof - Google Patents

Abstract

The present invention relates to a system for preventing reversal of a liquefied natural gas facility, and more particularly, by using a relief pipe connected to the upper and lower portions of the liquefied natural gas storage tank, the boil-off gas generated from the liquefied natural gas through a relief pipe. The present invention relates to a system for preventing reversal of a liquefied natural gas facility and a method for preventing a roll-over phenomenon by transferring it into the liquefied natural gas.
According to the present invention, a storage tank in which liquefied natural gas is stored, a relief pipe having one side connected to the upper portion of the storage tank and the other side connected to the lower portion of the storage tank, and collecting boil-off gas generated from the liquefied natural gas An inversion phenomenon prevention system including a compressor supplying the inside of liquefied natural gas through a pipe is provided.

Description

System and method to prevent reversal phenomenon of liquefied natural gas storage tank {ROLL-OVER EFFECT PROTECTION APPARATUS FOR LNG STORAGE AND METHOD THEREOF}

The present invention relates to a system for preventing reversal of a liquefied natural gas facility, and more particularly, by using a relief pipe connected to the upper and lower portions of the liquefied natural gas storage tank, the boil-off gas generated from the liquefied natural gas through a relief pipe. The present invention relates to a system for preventing reversal of a liquefied natural gas facility and a method for preventing a roll-over phenomenon by transferring it into the liquefied natural gas.

Natural gas is transported in gaseous form through gas pipelines on land or at sea, or after being liquefied into liquefied natural gas (LNG) or liquefied petroleum gas (LPG), it is stored in LNG carriers or LPG carriers. Is carried.

Liquefied natural gas is obtained by cooling natural gas to cryogenic temperatures (approximately -163°C), and its volume is reduced to approximately 1/600 compared to the gas state, so it is very suitable for long-distance transportation through sea.

Recently, LNG drilled or produced in deep seas such as LNG FPSO (floating, production, storage and offloading), LNG FSRU (floating storage and regasification unit), and FLNG (floating LNG) are unloaded by LNG carriers that transport LNG to consumption areas. Demand for floating structures that store them before they are stored is gradually increasing, and these floating structures also include storage tanks installed on LNG carriers or LNG RVs. On the other hand, when the liquefied natural gas is stored in the storage tank, stratification of the liquefied gas, which is divided into several layers, occurs due to the difference in components and the resulting difference in specific gravity.

In addition, when the layered state as described above is continuously maintained, evaporation occurs continuously on the surface of the upper layer. At this time, a light nitrogen component is actively vaporized.

Therefore, when the cargo is maintained for a long time in a stable state without flow, the specific gravity and temperature of the upper layer gradually increase compared to the lower layer, and the difference in specific gravity between the upper layer and the lower layer becomes so large that the layered structure cannot be maintained any longer. Due to the reversal of specific gravity, a roll-over phenomenon occurs in which the upper and lower layers are suddenly inverted.

In this way, when a roll-over phenomenon occurs in the storage tank of natural gas, the liquefied gas of the warm upper layer momentarily flows into the lower layer, causing an increase in the temperature of the lower layer, resulting in an instantaneous large amount of natural gas. Is vaporized and the pressure in the storage tank rises rapidly, which may cause an accident in which the tank explodes.

Prior Document 1: Republic of Korea Patent Publication 2010-0115545 (2010.10.28 published) Prior Document 2: Korean Patent Application Publication No. 1999-0088776 (published on Feb. 5, 1999)

The present invention is to solve the above problems, and the density change according to the location of the liquefied natural gas inside the storage tank is frequently measured using a measuring device installed inside the storage tank inside the liquefied natural gas. After measuring, a barometer is installed at the top of the storage tank, and when the measured density is greater than a certain value or the pressure is greater than a certain value, the boil-off gas is supplied through the relief pipe and returned to the inside of the liquefied natural gas, causing the storage tank to explode. The purpose of this is to provide a system for preventing reversal of liquefied natural gas facilities that can be prevented.

According to an aspect of the present invention for achieving the above object, a storage tank for storing liquefied natural gas; A relief pipe having one side connected to an upper portion of the storage tank and the other side connected to a lower portion of the storage tank; And a compressor for supplying the boil-off gas generated from the liquefied natural gas into the liquefied natural gas through the relief pipe.

According to an embodiment of the present invention, the inversion phenomenon prevention system may further include a barometer for measuring the pressure of the gas in the storage tank containing the boil-off gas.

According to an embodiment of the present invention, the inversion phenomenon prevention system may further include a measuring instrument for measuring the temperature and density of the liquefied natural gas.

According to an embodiment of the present invention, the reversal phenomenon prevention system may further include a relief valve for discharging the boil-off gas to the outside of the storage tank.

According to an embodiment of the present invention, the inversion phenomenon prevention system compares the information measured by the barometer and the meter with preset information, and discharges the boil-off gas to the outside through the relief valve, or through the relief pipe. It may further include an automatic control device for automatically controlling to supply the boil-off gas into the liquefied natural gas.

According to an embodiment of the present invention, the automatic control device of the reversal phenomenon prevention system can transmit and receive control information to and from the central management system in real time.

According to another aspect of the present invention, there is provided a method for controlling an inversion phenomenon by returning boil-off gas generated in a liquefied natural gas storage tank to liquefied natural gas, comprising: collecting boil-off gas generated from the liquefied natural gas; Supplying the collected boil-off gas to a relief pipe; And discharging the boil-off gas supplied through the relief pipe into the liquefied natural gas.

According to an embodiment of the present invention, the method for preventing the inversion phenomenon may further include measuring the pressure of the gas in the storage tank containing the boil-off gas.

According to an embodiment of the present invention, the method for preventing the inversion phenomenon may further include measuring the temperature and density of the liquefied natural gas.

According to an embodiment of the present invention, the method for preventing the inversion phenomenon may further include discharging the boil-off gas to the outside of the storage tank.

According to an embodiment of the present invention, the inversion prevention method compares the measured pressure information of the gas, temperature information and density information of the liquefied natural gas with preset information, and discharges the boil-off gas to the outside or the evaporation It may further include automatically controlling the gas to be supplied into the liquefied natural gas.

According to an embodiment of the present invention, the method for preventing reversal phenomenon may further include transmitting and receiving control information to and from the central management system in real time.

According to the system for preventing reversal of the liquefied natural gas facility according to the present invention, by collecting the boil-off gas generated from the liquefied natural gas and discharging it into the liquefied natural gas, stratification and roll-over of the liquefied natural gas The phenomenon can be prevented from occurring.

As a result, it is possible to prevent the storage tank from exploding due to the boil-off gas excessively generated by the roll-over phenomenon, and because the re-liquefaction of the boil-off gas can be partially performed, management and cost efficiency are increased.

1 is a block diagram showing an inversion phenomenon prevention system according to an embodiment of the present invention.
2 is a block diagram showing a system for preventing an inversion phenomenon according to an embodiment of the present invention.
3 is a flowchart showing a method for preventing reversal phenomenon according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples for sufficiently transferring the spirit of the present invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms.

1 is a block diagram showing an inversion phenomenon prevention system according to an embodiment of the present invention.

As shown, the inversion phenomenon prevention system according to an embodiment of the present invention includes a storage tank 100 that stores liquefied natural gas, and collects boil-off gas generated from liquefied natural gas and supplies it to a relief pipe. It consists of a relief pipe 10 connecting the upper and lower portions of the compressor 20 and the storage tank 100. In addition, the inversion phenomenon prevention system includes a relief valve 30 for ejecting the gas collected in the upper portion of the storage tank 100 containing the evaporated gas to the outside, a barometer 40 for measuring the pressure of the gas, and the storage tank 100 An automatic control device that is installed in each location in the interior of the liquefied natural gas to measure the temperature and density of the liquefied natural gas and controls the reversal phenomenon prevention system based on the information measured by the measuring instrument 50 and the barometer 40 ( 60) may be further included.

The storage tank 100 is equipped with a sealing and insulating barrier to store liquefied gas such as LNG in a cryogenic state, but it cannot completely block heat transmitted from the outside. Accordingly, in the storage tank 100, the temperature is maintained below the evaporation point of the liquefied natural gas by continuously using a cooling device to prevent evaporation of the liquefied gas due to the temperature increase.

The relief pipe 10 is a pipe connecting the upper and lower ends of the storage tank 100 to return the boil-off gas to the inside of the liquefied natural gas when the temperature of the liquefied natural gas rises and the boil-off gas is generated. For example, the relief pipe 10 is installed outside the storage tank 100 to connect the upper and lower portions of the storage tank 100, or inside the storage tank 100, one side of the pipe faces the top and the other side It can be installed facing down. One side of the relief pipe 10 may be connected to the bottom or side of the storage tank 100, and the other side may be connected to the top or side of the storage tank 100. A plurality of relief pipes 10 may be installed, and each pipe may be individually operated to supply boil-off gas to the lower portion.

The compressor 20 is a device that supplies boil-off gas to the lower portion of the storage tank 100. The compressor 20 is connected to the relief pipe 10 and supplies the boil-off gas collected in the upper portion of the storage tank 100 to the relief pipe 10 connected to the upper portion of the storage tank 100. The compressor 20 may adjust the amount of boil-off gas supplied as liquefied natural gas through the relief pipe 10, and a plurality of compressors may be driven. The compressor may be replaced with a pump or a compressor that supplies boil-off gas.

The relief valve 30 is installed on the upper side of the storage tank 100 and ejects gas to the outside to prevent explosion when the gas above the storage tank 100 containing evaporated gas rises to a predetermined pressure. It operates only above the allowable pressure, but can be operated by the automatic control device 60 which will be described later. When the relief valve 30 is opened, the gas inside the storage tank 100 is ejected to the outside, thereby lowering the internal pressure, and when it is closed, the gas inside the storage tank 100 cannot escape to the outside.

The barometer 40 is a device that measures the gas pressure inside the storage tank 100 and may be installed at each location in the storage tank 100. For example, since the amount of evaporated gas generated may vary depending on the amount of liquefied natural gas loaded, it is installed in the upper, middle and lower portions of the storage tank 100 to measure the pressure of the gas.

The measuring instrument 50 is a device that measures the temperature and density of each liquid level of liquefied natural gas. For example, an LTD (Level, Temperature and Density) measuring instrument 50 may be used, and the LTD measuring instrument 50 is a measuring instrument 50 capable of measuring the temperature and density and the level of natural gas in one measuring device. to be. In addition, it is also possible to measure the density and temperature of each layer of natural gas, and if necessary, a number of identical sensors may be installed at the same time, etc. If a device capable of measuring the temperature and density of each layer of liquefied natural gas A measuring instrument 50 having a configuration can be used.

The automatic control device 60 is a device that controls the inversion phenomenon prevention system based on the gas pressure measured by the barometer 40 and the density and temperature of each layer measured by the measuring device 50. The automatic control device 60 receives the measured information from each device and controls it by comparing it with preset pressure, temperature, and density information. In the control method, the pressure of the gas is reduced by driving the relief valve 30 or the boil-off gas is supplied as liquefied natural gas by driving the compressor 20. The operation of the relief valve 30 and the compressor 20 as described above may be automatically performed by a command of the automatic control device 60, and both devices may be operated simultaneously. The automatic control device 60 may be connected to the barometer 40, the measuring instrument 50, the relief valve 30, and the compressor 20 in a wired or wireless manner in order to transmit each control command and receive the measured information. .

The control device has a communication function and can transmit and receive measured information received from each equipment and a control command transmitted to the relief valve 30 and the compressor 20 with a central management system (not shown) in real time. The central control device may receive the measured information from the automatic control device 60, and may directly transmit a command to the automatic control device 60 to control the operation of each equipment.

According to an embodiment of the present invention, when the temperature of the liquefied natural gas in the storage tank 100 increases and evaporation gas is generated, the pressure of the gas measured by the barometer 40 and the measuring instrument 50 and the liquefied natural gas It sends information about temperature and density to the control unit. The control device supplies the boil-off gas to the relief pipe 10 through the compressor 20 if control is possible within the storage tank 100 based on the information. The boil-off gas is discharged from the lower portion of the storage tank 100 and partially re-liquefied and dissolved due to the low temperature of the liquefied natural gas. If the boil-off gas generation rate is high and it is impossible to control inside the storage tank 100, the compressor 20 is driven primarily to supply the boil-off gas as liquefied natural gas, and the relief valve 30 is secondarily opened. Erupt outward. As a result, it is possible to prevent the risk of explosion due to the generation of boil-off gas inside the storage tank 100 and prevent a roll-over phenomenon.

2 is a block diagram showing a system for preventing an inversion phenomenon according to an embodiment of the present invention. The embodiment of FIG. 2 is substantially similar to the inversion phenomenon prevention system of FIG. 1. Description of the same configuration will be omitted, and differences will be described in detail below.

The automatic control device 60 is connected to a barometer 40, a measuring instrument 50, a relief valve 30, a central management system 70, and a compressor 20. The automatic control device 60 receives the measured information from the barometer 40 and the measuring instrument 50. Each of the barometer 40 and the measuring instrument 50 sends the individually measured information to the automatic control device 60, and the automatic control device 60 sends the relief valve 30 and the compressor 20 based on the received individual information. Can drive. For example, the automatic control device 60 not only controls the relief valve 30 and the compressor 20 by synthesizing all information received from the barometer 40 and the meter 50, but also receives from the barometer 40 With just one piece of information, the relief valve 30 and the compressor 20 can be controlled.

The automatic control device 60 may transmit and receive all received information and control information with the central management system 70. The central management system 70 may directly control the equipment by transmitting a control command to the automatic control device 60 based on information received from the automatic control device 60.

3 is a flowchart showing a method for preventing reversal phenomenon according to an embodiment of the present invention. When boil-off gas is generated from the liquefied natural gas stored in the storage tank (S300), an explosion risk occurs as the atmospheric pressure inside the storage tank increases by the boil-off gas. At this time, the boil-off gas is supplied by the compressor to the relief pipe connected to the upper portion of the storage tank (S310). The relief pipe connected to the lower portion of the storage tank discharges boil-off gas into the liquefied natural gas (S320) to reduce the risk of explosion of the storage tank and prevent a roll-over phenomenon.

10: relief piping 20: compressor
30: relief valve 40: barometer
50: measuring instrument 60: automatic control device
70: central management system 100: storage tank

Claims (12)

A storage tank in which liquefied natural gas is stored;
A relief pipe having one side discharged from the upper portion of the storage tank, extending from the outside of the storage tank, and then connected to the other end of the storage tank;
A compressor for supplying the boil-off gas generated from the liquefied natural gas into the liquefied natural gas stored in the storage tank through the relief pipe;
A barometer measuring the pressure of the gas in the storage tank containing the boil-off gas;
A measuring instrument for measuring the temperature and density of the liquefied natural gas;
A relief valve for discharging the boil-off gas to the outside of the storage tank; And
By comparing the information measured by the barometer and the measuring device with preset information, the boil-off gas is discharged to the outside through the relief valve, or the boil-off gas is automatically supplied to the inside of the liquefied natural gas through the relief pipe. An automatic control device to control;
Including,
As a result of transmitting and receiving control information in real time with the central management system in the automatic control device, the automatic control device,
When the level of the boil-off gas generation is controllable inside the storage tank, the boil-off gas is discharged from the top of the storage tank to the outside of the storage tank and then flows into the bottom of the storage tank along the relief pipe to liquefy So that it is supplied inside of natural gas,
When the level of the boil-off gas generation is not controllable inside the storage tank, the boil-off gas is first discharged from the top of the storage tank to the outside of the storage tank and then flows into the bottom of the storage tank along the relief pipe. The liquefied natural gas is supplied to the inside of the liquefied natural gas, and the boil-off gas is secondarily discharged to the outside of the storage tank through the relief valve.
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