KR101122548B1 - Liquefied natural gas reliquefaction apparatus - Google Patents

Abstract

The present invention relates to a LNG reliquefaction apparatus, which is provided in a reliquefaction line and a reliquefaction line which provides a path for the evaporated gas discharged from the LNG storage tank to be converted into LNG through a reliquefaction process and supplied to the LNG storage tank. And a compressor configured to compress the evaporated gas discharged from the LNG storage tank, a cooling unit installed in the reliquefaction line to cool the evaporated gas compressed by the compressor, and LNG supplied through the reliquefaction line to the LNG storage tank. And an injection unit installed to inject into the stored LNG. Therefore, the present invention removes thermal stratification present in the liquid portion and the gas portion in the LNG storage tank by injecting the reliquefied LNG into the LNG storage tank to suppress the generation of the evaporated gas, and thus the evaporated gas required for the reliquefaction process By reducing the amount of re-liquefaction, the processing capacity of reliquefaction can be reduced, thereby reducing the size and cost of the equipment, and saving the energy required for the reliquefaction process by re-liquefying the low temperature evaporative gas. By re-liquefying only the CH-based components from which nitrogen, which is an inert gas, is removed, the purity of LNG is improved, and the high-temperature evaporative gas is combusted to save energy consumed in preheating.

Evaporative Gas, LNG, Reliquefaction, Cooling Unit, Vortex Tube, Injection Nozzle

Description

LUKE liquefaction apparatus {LIQUEFIED NATURAL GAS RELIQUEFACTION APPARATUS}

The present invention is the LNG reliquefaction apparatus to remove the thermal stratification present in the liquid portion and the gas portion in the LNG storage tank to suppress the generation of evaporated gas, and to save energy and cost required for the reliquefaction process and combustion process It is about.

In general, liquefied natural gas (hereinafter referred to as "LNG") is a colorless, transparent cryogenic liquid that cools natural gas containing methane as -162 ℃ to reduce its volume to one hundredth. Say. As such LNG is used as an energy resource, an efficient transportation method for transporting this gas in large quantities from the production base to the acquisition site of the demand site has been considered. Accordingly, an LNG carrier capable of transporting a large amount of LNG by sea has been developed. It became.

The LNG carrier naturally generates a boil-off gas (BOG) to maintain a constant level of pressure in a cargo tank, and a device for reliquefying the boil-off gas is provided.

Referring to the accompanying drawings a reliquefaction apparatus provided in a conventional LNG carrier as follows.

1 is a block diagram showing an apparatus for reliquefaction of a LNG carrier according to the prior art. As shown, the reliquefaction apparatus of the LNG carrier according to the prior art converts the boil-off gas discharged from the cargo tank 2 of the LNG carrier 1 into LNG by the reliquefaction process to the LNG storage tank 2. A reliquefaction line 11 providing a path for resupply, a compressor 12 installed in the reliquefaction line 11 to compress the evaporation gas, a heat exchanger 13 installed in the reliquefaction line 11, and The refrigerant supply unit 14 may be configured to circulate the refrigerant to the heat exchanger 13 so that the evaporated gas may be liquefied by the heat exchanger with the refrigerant in the heat exchanger 13.

In the reliquefaction line 11 branched from the rear end of the compressor 12, the combustion line 15 is connected to the combustor 3, the on-off valve 15a for opening and closing the flow of evaporated gas to the combustion line 15 and Heaters 16 for preheating the evaporated gas are respectively installed. Therefore, the evaporation gas is supplied to the combustor 3 through the combustion line 15 by the operation of the on / off valve 15a to be consumed by combustion.

As described above, in the LNG reliquefaction apparatus according to the prior art, since the evaporation gas is continuously generated in the cargo tank, the amount of the evaporation gas that requires reliquefaction is increased, thereby increasing the processing capacity of reliquefaction. The size and installation cost of the had a problem that increases.

The present invention has been made to solve the above problems, by reducing the amount of evaporation gas required for the reliquefaction treatment by suppressing the generation of the evaporation gas, thereby reducing the size and equipment cost of the device by reducing the reliquefaction treatment capacity Decrease.

In the LNG reliquefaction apparatus according to the present invention, in the apparatus for reliquefying the boil-off gas generated from the LNG storage tank, the boil-off gas discharged from the LNG storage tank is converted into LNG through the reliquefaction process and supplied to the LNG storage tank A reliquefaction line providing a path for the regeneration, a compressor installed in the reliquefaction line to compress the boil-off gas discharged from the LNG storage tank, and a cooling unit installed in the reliquefaction line to cool the boil-off gas compressed by the compressor. And an injection unit installed to inject LNG supplied through the reliquefaction line into LNG stored in the LNG storage tank.

The present invention removes thermal stratification present in the liquid portion and the gas portion in the LNG storage tank by injecting the reliquefied LNG into the LNG storage tank to suppress the generation of the evaporated gas, thereby the amount of evaporated gas required for the reliquefaction treatment Reducing the processing capacity of the reliquefaction by reducing the size of the device to reduce the size and cost of the equipment, and further, by separating the evaporation gas into a high temperature evaporation gas and a low temperature evaporation gas to reliquefy the low temperature evaporation gas In order to save energy required for the reliquefaction process, and to re-liquefy only the CH-based components from which nitrogen, such as inert gas, is removed, the purity of the LNG is improved, and the high-temperature evaporative gas is burned to burn. It has the effect of saving energy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

2 is a block diagram showing the LNG re-liquefaction apparatus according to an embodiment of the present invention. As shown, the LNG reliquefaction apparatus according to an embodiment of the present invention is a device for reliquefying the boil-off gas generated from the LNG storage tank 4, the reliquefaction line 110 for providing a re-liquefaction path of the boil-off gas ), The compressor 120 and the cooling unit 130 installed in the reliquefaction line 110, and the LNG supplied through the reliquefaction line 110 to the LNG stored in the LNG storage tank (4) The four parts 140 may be included.

LNG reliquefaction apparatus according to an embodiment of the present invention is a cargo tank in which the LNG (cargo) is stored in the LNG carrier, a fuel tank in which the LNG (fuel) is stored in the vessel, installed to store LNG on the land It can be used to reliquefy the boil-off gas generated from various LNG storage tanks 4, such as storage tanks.

The reliquefaction line 110 is installed to provide a path for the evaporated gas discharged from the LNG storage tank 4 to be converted into LNG through a reliquefaction process and supplied to the LNG storage tank 4.

The compressor 120 is installed in the reliquefaction line 110 to compress the evaporated gas discharged from the LNG storage tank 4.

The cooling unit 130 is installed in the reliquefaction line 110 to cool the evaporated gas compressed by the compressor 120 to be converted into LNG by the reliquefaction process. For example, the cooling unit 130 is installed in the reliquefaction line 110. By supplying the heat exchanger 131 and the refrigerant circulating through the refrigerant circulation line 132a to the heat exchanger 131, the refrigerant supply unit 132 for allowing the evaporative gas to be cooled by heat exchange with the refrigerant in the heat exchanger 131. It may include.

The injection unit 140 is installed to inject the LNG supplied through the reliquefaction line 110 into the LNG stored in the LNG storage tank 4, for this purpose, the LNG storage tank 4 is connected to the reliquefaction line 110. It may include an injection tube 141 installed in the upper portion, and an injection nozzle 142 installed in the injection tube 141 to inject the LNG supplied through the injection tube 141 downward.

The injection pipe 141 is fixed to an upper portion of the LNG storage tank 4, and when the LNG storage tank 4 is provided with a plurality of LNG storage tanks, such as an LNG carrier or an onshore LNG storage facility, the LNG storage tank from the reliquefaction line 110. (4) It may be made of a plurality to be connected to each branch line (not shown) branched to each, and may have a variety of structures to be arranged over the entire upper portion in the LNG storage tank (4).

The injection nozzle 142 may be installed in a plurality of injection pipes 141, it is directed downward to smoothly inject the LNG toward the LNG stored in the LNG storage tank (4).

Meanwhile, the LNG reliquefaction apparatus according to the present invention is a combustion line branched from the rear end of the compressor 120 in the reliquefaction line 110 and connected to the combustor 5 in order to burn and consume the evaporated gas without undergoing the reliquefaction process. 150 may be included, and the energy separation unit 160 may be installed at a branch point of the combustion line 150.

The combustion line 150 may be provided with an on-off valve 151 for opening and closing or controlling the flow of the boil-off gas, and a heater 152 for preheating the boil-off gas and supplying it to the combustor 5.

The energy separation unit 160 is installed at the point where the combustion line 150 diverges from the reliquefaction line 110, and separates the evaporation gas into a low temperature evaporation gas and a high temperature evaporation gas to re-liquefy the low temperature evaporation gas. In addition to the supply to the 110, the high temperature evaporated gas to be supplied to the combustion line 150.

The energy separation unit 160 is, for example, when the evaporation gas compressed by the compressor 120 is supplied to the supply port 161, the energy separation unit 160 is separated into a low temperature evaporation gas and a high temperature evaporation gas by energy separation. Vortex tubes may be discharged through the discharge holes 163 and 164, respectively.

The vortex tube, which is an embodiment of the energy separation unit 160, is supplied with the evaporation gas compressed by the compressor 120 to the vortex chamber 162 through the supply port 161 to rotate at a high speed to form a primary vortex. The first vortex evaporating gas is moved to the second discharge port 164 so that a part of the evaporating gas is discharged by the control valve (not shown), and the remaining evaporating gas is returned by the control valve (not shown). The secondary vortex is formed to be discharged through the first discharge port 163.

That is, the vortex tube loses heat while the flow of the evaporation gas that forms the secondary vortex passes through the low pressure region located inside the flow of the evaporation gas that forms the primary vortex, and thus the cooling unit 130 through the first discharge port 163. ) To the low temperature, and the evaporation gas of the secondary vortex forming the inner flow is reduced compared to the evaporation gas of the primary vortex forming the external flow, resulting in a decrease in kinetic energy. This provides heat to the evaporation gas of the primary vortex forming the external flow, thereby raising the temperature to be discharged to the combustor 5 side through the second discharge port 164 at a high temperature.

The reliquefaction line 110 is below the reliquefaction capacity generated from the LNG storage tank 4 or else necessary to ensure that the evaporation gas is supplied to the cooling unit 130 by bypassing the energy separation unit 160, It may include a bypass line 111 connected to bypass the energy separation unit 160, and an opening and closing valve 112 installed in the bypass line 111 to open and close the movement of the evaporation gas.

In addition, the reliquefaction line 110 is branched from the rear end of the cooling unit 130 in order to be able to supply LNG to the lower portion of the LNG storage tank 4, the lower supply line connected to the lower portion of the LNG storage tank (4) And 113, opening and closing valves 114 and 115 for opening and closing the movement of LNG through the lower supply line 113, and a check valve 116 installed in the lower supply line 113 to prevent backflow of LNG. have

Referring to the operation of the LNG reliquefaction apparatus according to the present invention having such a configuration as an example as follows.

The boil-off gas discharged from the LNG storage tank 4 through the reliquefaction line 110 is compressed by the compressor 120 and is cooled by the cooling unit 140 to be converted into LNG by reliquefaction, thereby converting the LNG into a LNG storage tank ( 4), at this time, LNG supplied to the LNG storage tank 4 through the reliquefaction line 110 is injected from the injection nozzle 142 of the injection unit 140 in the LNG storage tank (4) It is injected into the stored LNG, thereby removing the thermal stratification present in the liquid portion and the gas portion in the LNG storage tank (4) to suppress the generation of evaporation gas, thereby reducing the amount of evaporation gas required for the reliquefaction treatment This allows the capacity of the reliquefaction process to be reduced, thereby reducing the size of the apparatus and the cost of the installation.

On the other hand, the evaporation gas compressed by the compressor 120 passes through the energy separation unit 160, thereby separating the low temperature evaporation gas and the high temperature evaporation gas by the energy separation action, and the high temperature evaporation gas is combustor 5. To reduce the energy consumption of the heater 152 consumed to heat the evaporated gas, and to re-liquefy by allowing the low temperature evaporated gas from which nitrogen of the inert component is removed to the cooling unit 130 in the energy separation process. Improve the purity of the LNG, the low-temperature evaporated gas is supplied to the cooling unit 130 to increase the cooling efficiency and to reduce the energy required for the reliquefaction process, and to reduce the cooling capacity of the cooling unit 130 It can reduce the energy consumption for preheating during combustion.

At this time, the energy separation of the boil-off gas through the energy separation unit 160 is when the amount of boil-off gas generated in the LNG storage tank 4 is equal to or greater than the reliquefaction capacity, for example, in the case of the LNG carrier, such as in the initial full sea voyage. The amount of the evaporated gas re-liquefied through the energy separation unit 160 corresponds to the reliquefaction capacity of the reliquefaction apparatus.

On the other hand, when the amount of boil-off gas generated in the LNG storage tank 4 is less than or equal to the reliquefaction capacity, for example, in the case of general full-scale navigation in an LNG carrier, the boil-off gas discharged to the outside of the LNG storage tank 4 through the compressor 120 may be The energy separation unit 160 may be bypassed through the bypass line 111 to be liquefied by the cooling unit 130, and then injected into the upper portion of the LNG storage tank 4 by the injection unit 140. .

In addition, the LNG passing through the cooling unit 130 may be supplied to the lower portion of the LNG storage tank 4 through the lower supply line 113 by the operation of the opening and closing valves 114 and 115.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. And will be included in the described technical idea.

1 is a block diagram showing a reliquefaction apparatus of the LNG carrier according to the prior art,

2 is a block diagram showing the LNG re-liquefaction apparatus according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

110: reliquefaction line 111: bypass line

112: on-off valve 113: lower supply line

114,115: on-off valve 116: check valve

120: compressor 130: cooling unit

131: heat exchanger 132: refrigerant supply unit

140: injection unit 141: injection tube

142: injection nozzle 150: combustion line

151: on-off valve 152: heater

160: energy separation unit 161: supply port

162: vortex chamber 163: first discharge port

164: second discharge port

Claims (6)

In the device for reliquefaction of the evaporated gas generated from the LNG storage tank, A reliquefaction line which provides a path for the boil-off gas discharged from the LNG storage tank to be converted into LNG through a reliquefaction process and supplied to the LNG storage tank; A compressor installed in the reliquefaction line and compressing the boil-off gas discharged from the LNG storage tank; A cooling unit installed in the reliquefaction line to cool the evaporated gas compressed by the compressor; An injection unit installed to inject LNG supplied through the reliquefaction line into LNG stored in the LNG storage tank; A combustion line branched from the rear end of the compressor in the reliquefaction line and connected to a combustor; Installed at the branch point of the combustion line, the evaporation gas is separated into a low temperature evaporation gas and a high temperature evaporation gas to supply a low temperature evaporation gas to the reliquefaction line and to supply a high temperature evaporation gas to the combustion line. Energy separator LNG reliquefaction apparatus comprising a. The method of claim 1, The injection unit, An injection pipe connected to the reliquefaction line and installed at an upper portion of the LNG storage tank; An injection nozzle installed in the injection pipe and spraying LNG supplied through the injection pipe downward; LNG reliquefaction apparatus comprising a. delete The method of claim 1, The energy separation unit, When the boil-off gas compressed by the compressor is supplied to the supply port, LNG re-liquefaction apparatus comprising a vortex tube which is separated into a low-temperature evaporation gas and a high-temperature evaporation gas by energy separation and discharged through the first and second discharge ports, respectively. The method of claim 1, The reliquefaction line, A bypass line connected to bypass the energy separation unit; On-off valve installed in the bypass line LNG reliquefaction apparatus comprising a. The method according to claim 1 or 5, The reliquefaction line, A lower supply line branched from a rear end of the cooling unit and connected to a lower portion of the LNG storage tank; On and off valve for opening and closing the movement of the LNG through the lower supply line, Check valve installed in the lower supply line to prevent backflow of LNG LNG reliquefaction apparatus comprising a.

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