KR20180112285A - Apparatus and Method for Boil-Off Gas Control of Liquefied Gas Storage Tank - Google Patents

Abstract

The present invention relates to an apparatus and method for suppressing boil-off gas in a liquefied gas storage tank. More specifically, the present invention relates to an apparatus and method for reducing or suppressing boil-off gas in a ship such as a conveyor ship for conveying liquefied gas or an offshore structure. According to the present invention, the apparatus for suppressing boil-off gas in liquefied gas storage tank comprises: a liquefied gas storage tank covered by an insulating space and storing liquefied gas; a cooling means cooling incombustible fluids to be supplied to the insulating space; and a fluid circulating line connecting the insulating space to the cooling means and providing a route for the incombustible fluids. Moreover, low-temperature incombustible fluids cooled in the cooling means can be circulated in the insulating space.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and a method for suppressing evaporative gas in a liquefied gas storage tank,

More particularly, the present invention relates to an apparatus for reducing or suppressing the generation of evaporative gas in a ship or an offshore structure such as a ship carrying a liquefied gas, ≪ / RTI >

Since the liquefaction temperature of natural gas is a cryogenic temperature of about -163 ° C at normal pressure, LNG evaporates even if its temperature is slightly higher than -163 ° C. In the case of LNG carriers, for example, LNG storage tanks of LNG carriers are heat-treated, but since external heat is continuously transferred to LNG, LNG is stored in the LNG storage tank during LNG transport by the LNG carrier. The boil-off gas (BOG) is generated continuously in the tank.

Conventionally, when BOG is continuously generated in the LNG storage tank, the pressure of the LNG storage tank is increased and dangerous. Therefore, in order to maintain the pressure of the LNG storage tank in a safe state, BOG generated in the LNG storage tank is supplied to a gas combustor , Gas Combustion Unit) or by discharging the BOG to the outside, a method of directly re-liquefying the BOG generated by applying a separate refrigerant cycle, liquefying only a part of the BOG, and supplying the remainder to the engine as fuel is commercialized .

In order to control the pressure of the LNG storage tank, the BOG is used as the propelling fuel of the LNG carrier. Since the gas fuel is to be supplied, the compressor (compressor) having a larger installation ratio (CAPEX) a compression method using a compressor or the like may be applied. Depending on the type of engine, the constituent system may not be changed or applied. In addition, a method of re-liquefying the BOG may be a supercooling device for re- The cost of the ship is increased, and the light weight of the ship is increased. In addition, discharging or incineration of the BOG results in the loss of LNG.

Meanwhile, there is a method of increasing the design pressure of the LNG storage tank to allow a certain level of pressure rise, thereby reducing the generation of evaporated gas by absorbing the calorific value due to the increase in sensible heat due to pressure rise. It is necessary to reinforce the structure of the storage tank to withstand the high pressure and it is not possible to prevent the generation of the evaporation gas from the source. Therefore, if the pressure exceeds the design pressure over time, the evaporation gas must be discharged and consumed .

Thus, controlling the pressure of the LNG storage tank is a very important factor directly related to safety and cost. Accordingly, the present invention is directed to solve the problems of the related art and to provide a liquefied gas storage tank Which is capable of suppressing the production of evaporation gas which is essentially generated in the liquefied gas storage tank or reducing the amount of the evaporation gas.

According to an aspect of the present invention, there is provided a liquefied gas storage tank surrounded by a heat insulating space and storing liquefied gas. Cooling means for cooling the incombustible fluid to be supplied to the heat insulating space; And a fluid circulation line connecting the heat insulating space and the cooling means and providing a path of the incombustible fluid, wherein the heat insulating space is provided with a plurality of evaporation chambers, in which the low temperature incombustible fluid cooled by the cooling means circulates, A gas suppression device is provided.

Preferably, the cooling means includes: a refrigerant cycle for circulating the refrigerant; A first heat exchanger for cooling the incombustible fluid to be supplied to the heat insulating space by the cold heat of the refrigerant cooled in the refrigerant cycle; And a refrigerant circulation line connecting the first heat exchanger and the refrigerant cycle to provide a path so that high temperature refrigerant flows from the first heat exchanger to a refrigerant cycle and low temperature refrigerant is supplied from the refrigerant cycle to the first heat exchanger can do.

Preferably, the cooling means includes: a compressor for compressing the incombustible fluid to be supplied to the heat insulating space; A cooler for cooling the compressed incombustible fluid in the compressor; And expansion means for thermally expanding the cooled incombustible fluid, so that the incombustible fluid can be directly cooled.

Preferably, the waste heat recovery apparatus for recovering the waste heat of the non-combustible fluid to be supplied to the heat insulating space.

Preferably, the cooling means may further include a second heat exchanger for precooling the high-temperature refrigerant discharged after the heat exchange in the first heat exchanger before introducing the high-temperature refrigerant into the refrigerant cycle.

Preferably, the waste heat recovery apparatus may be a third heat exchanger for precooling the incombustible fluid introduced into the cooling means before introducing the incombustible fluid into the cooling means.

Preferably, circulation means for introducing the non-combustible fluid cooled in the cooling means into the heat insulating space may be further included.

According to another aspect of the present invention, there is provided a non-combustible fluid supply apparatus for supplying a non-combustible fluid to a heat-insulating space of a liquefied gas storage tank, comprising a low-temperature refrigerant circulating in a refrigerant cycle, Temperature incombustible fluid cooled by heat exchange and supplying the cooled low-temperature incombustible fluid, wherein the high-temperature incombustible fluid whose temperature has risen in the heat insulating space is joined to the incombustible fluid stream to be heat-exchanged or vented to the outside, A method of suppressing evaporative gas in a storage tank is provided.

Preferably, the high-temperature refrigerant is precooled by recovering the waste heat of the high-temperature refrigerant circulating after the incombustible fluid is cooled to cool the heat source.

According to another aspect of the present invention, there is provided a method for supplying a non-combustible fluid to a heat-insulating space of a liquefied gas storage tank, the non-combustible fluid being supplied by cooling using a cooling cycle, Wherein the incombustible fluid whose temperature has risen at the lower temperature side is joined to the incombustible fluid stream to be cooled or vented to the outside to keep the heat insulating space at a low temperature.

Preferably, the hot, incombustible fluid may be precooled by recovering waste heat of the hot, incombustible fluid and cooling the source of heating prior to joining the hot incombustible fluid having a raised temperature in the insulating space to the cooling stream.

According to another aspect of the present invention, there is provided a method of manufacturing a liquefied gas storage tank, comprising: supplying a nonflammable fluid to a heat insulating space of a liquefied gas storage tank; Supplying a liquefied gas to a storage space of the liquefied gas storage tank; Discharging a high temperature incombustible fluid whose temperature has risen in the heat insulating space and cooling a mixture of the discharged high temperature incombustible fluid or the newly generated incombustible fluid and the high temperature incombustible fluid; And circulating the cooled incombustible fluid to the heat insulating space. A method for suppressing evaporation gas in a liquefied gas storage tank is provided.

Preferably, the cooling of the incombustible fluid may be achieved by heat-exchanging the incombustible fluid with a refrigerant circulating in the refrigerant cycle, or by direct cooling of the incombustible fluid by compression, cooling, and expansion by supplying the incombustible fluid into a cooling cycle.

Preferably, recovering the waste heat of the high-temperature refrigerant after heat exchange with the incombustible fluid may be further included.

Preferably, the method further comprises the step of recovering the waste heat of the hot, incombustible fluid before feeding into the cooling cycle.

The evaporation gas suppression device and the suppression method of the liquefied gas storage tank according to the present invention can suppress the generation of the evaporation gas which is essentially generated in the liquefied gas storage tank when conveying the cryogenic liquefied gas, have.

Further, the pressure of the heat insulating space of the storage tank can be maintained at a predetermined pressure or more, and the cause of ignition can be eliminated.

In addition, the evaporation gas suppression device and the suppression method of the liquefied gas storage tank according to the present invention can be easily applied to both a modified vessel and a new-type vessel regardless of the engine type of the vessel in a simple configuration, .

In addition, economic loss can be reduced by blocking or reducing the amount of liquefied gas being lost by evaporation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram briefly showing an evaporative gas suppression apparatus for a liquefied gas storage tank according to a first embodiment of the present invention; FIG.
FIG. 2 is a schematic view showing an evaporative gas suppression device of a liquefied gas storage tank according to a second embodiment of the present invention.
FIG. 3 is a schematic view illustrating an apparatus for suppressing evaporation of gas in a liquefied gas storage tank according to a third embodiment of the present invention.
4 is a schematic view showing an apparatus for suppressing the evaporation of gas in a liquefied gas storage tank according to a fourth embodiment of the present invention.
5 is a flowchart briefly showing a method of operating a liquefied gas storage tank according to an embodiment of the present invention.
6 is a graph showing the temperature distribution of the liquefied gas storage tank according to the flowchart shown in FIG.

In order to fully understand the operational advantages of the present invention and the objects attained by the practice of the present invention, reference should be made to the accompanying drawings, which illustrate preferred embodiments of the present invention, and to the contents of the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. The same elements are denoted by the same reference numerals even though they are shown in different 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.

The liquefied gas stored in the liquefied gas storage tank according to the present invention is present in a gaseous state at room temperature or normal pressure such as Liquefied Natural Gas (LNG), Liquefied Petroleum Gas (LPG), or Liquefied Ethane Gas (LEG) Refers to the fluid to be stored and transported.

This liquefied gas continuously generates BOG (Boil-Off Gas) due to thermal energy entering from the outside in the storage tank, pressure change inside the tank, sloshing phenomenon, etc., And a means for controlling the pressure inside the storage tank, including means for discharging the BOG, should be provided.

The ship on which the liquefied gas storage tank is provided may be a ship operating a liquefied gas such as an LNG carrier, an LPG carrier, an LNG regasification vessel, an LNG bunkering ship, In this specification, a ship is a concept including a floating structure, such as an LNG FSRU (Floating Storage Regulation Unit), an LNG FPSO (Floating Production Storage Offloading), and an LNG RV (Regasification Vessel).

1 to 6, the liquefied gas is LNG, the liquefied gas storage tank is an LNG storage tank, the liquefied gas storage tank is an LNG storage tank, and the liquefied gas storage tank is an LNG storage tank. The ship is an LNG carrier, for example.

One embodiment of the present invention to be described below includes the generation of evaporative gas (BOG) generated by spontaneous vaporization of a liquefied gas in a liquefied gas storage tank 10 storing a liquefied gas, for example, a cryogenic liquefied natural gas (LNG) And the amount of the generated gas can be reduced.

The liquefied gas storage tank 10 includes a storage space 11 in which the liquefied gas is stored and a thermal insulation space 12 and 13 for inspecting the storage space 11 in the embodiments of the present invention, The spaces 12 and 13 include a first insulation space 12 between a primary barrier and a secondary barrier surrounding the storage space 11 and a second insulation space 13 between the secondary barrier and the hull .

Further, the embodiments to be described later include a fluid circulation line (not shown) that provides a path for supplying and discharging the incombustible fluid to and from the heat insulating spaces 12 and 13 to maintain a constant pressure, The incombustible fluid supplied to the heat insulating spaces 12 and 13 not only keeps the constant pressure of the heat insulating space but also can prevent a fire from occurring even if the liquefied gas stored in the storage space 11 leaks.

However, the nonflammable fluid supplied to the heat insulation spaces 12 and 13 can be heated by the supply temperature of the incombustible fluid or by the external heat transferred to the heat insulation spaces 12 and 13 from the heat insulation material such as the primary barrier, To the liquefied gas stored in the storage space 11. This heat causes the liquefied gas to evaporate.

Thus, according to embodiments described below, the fluid circulation line includes a fluid supply line (ISL) that provides a path for the cooled, low temperature, incombustible fluid to be fed into the thermal insulation space 12, A fluid discharge line (IDL) for providing a path for discharging the high temperature incombustible fluid from the heat insulating space (12), and a fluid replenishment line (not shown) for supplementarily supplying the incombustible fluid newly generated as the fluid circulation line.

Thus, according to one embodiment of the present invention, the heat insulating space 12 can be maintained at the set temperature by circulating the incombustible fluid to the heat insulating space 12, thereby suppressing evaporation of the liquefied gas, or The amount of evaporation can be reduced.

Further, the apparatus for suppressing the evaporation of gas in the liquefied gas storage tank according to the embodiments of the present invention includes cooling means for cooling the incombustible fluid to be supplied to the heat insulating space 12, To provide a path for the low temperature, incombustible fluid cooled in the cooling means to be fed into the thermal insulation space (12).

The nonflammable fluid supplied to the heat insulating space 12 along the fluid circulation line can be cooled and supplied to the set temperature in the cooling means and cooled by supplying the incombustible fluid to the heat insulating space 12, It is possible to block or suppress the generation of the generated evaporative gas. That is, the cryogenic fluid is supplied to the heat insulating space 12 to suppress the evaporation of the cargo, and at the same time, the incombustible fluid is supplied, thereby eliminating the cause of ignition.

In the embodiments of the present invention, the first heat insulating space 12 is cooled by the cooling means and is supplied to the heat insulating spaces 12 and 13, preferably the first heat insulating space 12, It is possible to maintain the temperature at about 150 ° C to -170 ° C, preferably about -160 ° C or so.

In addition, according to embodiments to be described below, the apparatus may further include a non-incombustible fluid generating apparatus 20 for producing a non-incombustible fluid, the fluid replenishing line may be connected from the incombustible fluid generating apparatus 20, 20 can be supplied or supplemented to the heat insulating spaces 12, 13.

Further, one or more valves (not designated) may be provided on the fluid supply line (ISL) and the fluid discharge line (IDL) to control the flow rate of the fluid, The flow rate of the non-combustible fluid supplied to the heat insulating spaces 12, 13 or discharged from the heat insulating spaces 12, 13 can be adjusted.

The fluid supply line ISL may be provided with a venting part VE for discharging the low temperature incombustible fluid flowing through the fluid supply line ISL and the fluid discharge line IDL may be provided to the fluid discharge line IDL. A venting part VE for discharging a high temperature incombustible fluid may be provided and a venting part VE may be used to ventilate the incombustible fluid as needed for pressure control or to cope with an emergency situation . The venting part (VE) can be connected to a vent mast.

The incombustible fluid may be any fluid or mixed fluid selected from the group consisting of nitrogen and carbon dioxide. In the following embodiments, nitrogen gas (Nitrogen, N ₂ ) will be exemplified.

Referring to FIG. 1, an evaporation gas suppression apparatus for a liquefied gas storage tank according to a first embodiment of the present invention includes a refrigerant cycle 40 for circulating a refrigerant as a cooling means, a refrigerant cycle And a first heat exchanger (31) for exchanging heat between the low temperature refrigerant and the high temperature incombustible fluid to be supplied to the first heat insulating space (12).

In the first heat exchanger (31), the high temperature incombustible fluid is cooled by heat exchange with the low temperature refrigerant supplied from the refrigerant cycle (40), and the low temperature refrigerant is heated.

The nonflammable fluid discharged from the first heat exchanger 31 after heat exchange is supplied to the first heat insulating space 12 along the fluid supply line ISL as the cooled low temperature incombustible fluid and the heat exchanged in the first heat exchanger 31 The refrigerant which is discharged later is circulated to the refrigerant cycle (40) along the refrigerant circulation line (RCL) with the heated high-temperature refrigerant.

The refrigerant cycle 40 can cool the high temperature refrigerant and supply the cooled low temperature refrigerant to the first heat exchanger 31. The refrigerant circulation line RCL is connected to the first heat exchanger 31 and the refrigerant cycle 40 to provide a path of the refrigerant so that the high temperature refrigerant is circulated from the first heat exchanger 31 to the refrigerant cycle 40 and the low temperature refrigerant is circulated from the refrigerant cycle 40 to the first heat exchanger 31 .

The refrigerant circulation line RCL is provided with a valve (not shown) for controlling the flow path and the flow rate of the low-temperature refrigerant supplied from the refrigerant cycle 40 to the first heat exchanger 31, A valve (not shown) for controlling the flow path and the flow rate of the high-temperature refrigerant recovered in the refrigerant cycle 40 may be provided.

The valves provided in the refrigerant circulation line (RCL) are also involved in controlling the flow rate and temperature of the nonflammable fluid supplied to the first heat insulating space (12) by being controlled in combination or individually with the valves provided on the above-mentioned fluid circulation line can do.

In this embodiment, the refrigerant cycle 40 may be, for example, a nitrogen refrigerant cycle 40, and the nitrogen refrigerant cycle 40 may be one that compresses nitrogen with a vaporization point of about -196 DEG C One or more intermediate coolers for cooling the compressed nitrogen downstream of the at least one compressor, a cooler and a cooler for cooling the compressed nitrogen in the compressor, one or more expanders for expanding the high pressure nitrogen cooled in the cooler to further cool to the cryogenic temperature Means. The expansion means may be an expander or a Row-Thomson valve, and may be cooled by thermal expansion of the compressed refrigerant.

In the cooler of the refrigerant cycle (40), the refrigerant compressed in the compressor and the refrigerant to be introduced into the compressor are heat-exchanged, and the compressed refrigerant can be cooled by the refrigerant to be introduced into the compressor.

The high temperature refrigerant which has cooled the incombustible fluid in the first heat exchanger (31) is circulated to the refrigerant cycle (40) and cooled to low temperature by compression, cooling and expansion, and the low temperature refrigerant is again supplied to the first heat exchanger 31 to cool the incombustible fluid.

The low-temperature incombustible fluid cooled in the first heat exchanger 31 is supplied to the first heat insulating space 12 along the fluid supply line ISL. The incombustible fluid heat-exchanged in the first heat exchanger 31 flows through the fluid Along with the high temperature incombustible fluid introduced into the first heat exchanger 31 along the discharge line IDL or the fluid non-combustible fluid introduced into the first heat exchanger 31 along the fluid discharge line IDL The newly generated incombustible fluid may be mixed in the replenished incombustible fluid generating apparatus 20 or may be a non-incombustible fluid supplementarily supplied along the fluid replenishing line.

According to the present embodiment, the fluid circulation line is arranged to bypass the first heat exchanger 31 so that the incombustible fluid cooled in the first heat exchanger 31 is supplied again to the front end of the first heat exchanger 31, or And a bypass line BL for bypassing the first heat exchanger 31 at a front end of the first heat exchanger 31 and providing a path to be supplied to a downstream end of the first heat exchanger 31.

The flow rate or temperature of the cooled low-temperature incombustible fluid supplied to the first heat insulating space 12 can be adjusted by controlling the opening and closing amount of the valve provided in the bypass line BL.

The flow rate or temperature of the nonflammable fluid supplied to the first adiabatic space 12 is supplied to the fluid circulation line such as fluid discharge line IDL, fluid supply line ISL, fluid replenishment line, as well as valves provided in the bypass line BL A valve provided in the refrigerant circulation line RCL, and a venting part VE may be controlled and controlled in combination.

As shown in FIG. 3, the fluid supply line (ISL) is provided with a circulation means (50) for applying pressure to smoothly supply the low temperature incombustible fluid cooled in the first heat exchanger (31) to the first heat insulating space (12) There may be more. For example, the circulation means 50 may be a blower.

Therefore, according to the present embodiment, the incombustible fluid is cooled by heat exchange with the refrigerant in the first heat exchanger 31, the cooled low-temperature incombustible fluid is supplied to the first heat insulating space 12, The high-temperature incombustible fluid whose temperature has risen in the second heat exchanger 12 is discharged, and a part or the whole of the fluid is re-supplied to the first heat exchanger 31, cooled by heat exchange with the refrigerant, and then supplied to the first heat insulating space 12.

In order to maintain the temperature and pressure of the first heat insulating space 12, a high temperature incombustible fluid discharged from the first heat insulating space 12 or a part of the low temperature incombustible fluid supplied to the first heat insulating space 12 And the incombustible fluid generated in the incombustible fluid generator 20 is supplementarily supplied to the fluid circulation line to be cooled by heat exchange with the refrigerant in the first heat exchanger 31 It may be supplied to the first heat insulating space 12.

The high-temperature refrigerant whose temperature has risen after cooling the high-temperature incombustible fluid in the first heat exchanger 31 is introduced into the refrigerant cycle 40, cooled to a low temperature in the refrigerant cycle 40, ). ≪ / RTI >

5, when the liquefied gas, in this embodiment, LNG is unloaded into the storage space 11 of the liquefied gas storage tank 10, the incombustible fluid generated in the incombustible fluid generating apparatus 20, In the example, nitrogen gas is supplied to the first heat insulating space 12. The nitrogen gas supplied to the first heat insulating space 12 preferably has a temperature of about 50 DEG C or lower and flows into the first heat insulating space 12 along the bypass line BL without being cooled by the first heat exchanger 31 May be introduced.

When nitrogen gas is filled in the first heat insulating space 12 with an appropriate pressure, LNG unloading is carried out into the storage space 11. The temperature of the LNG to be unloaded is about -163 DEG C. When the unloading is started, the operation of the refrigerant cycle 40 is started, and the addition of nitrogen gas or incombustible fluid generated from the first heat insulating space 12 And the supplied nitrogen gas is cooled through heat exchange with the refrigerant in the first heat exchanger (31). In the first heat exchanger (31), the nitrogen gas is cooled to about -130 DEG C or lower, preferably about -160 DEG C or so, using the cooling heat of the refrigerant, and is supplied to the first heat insulating space (12).

As shown in FIG. 6, by supplying the low-temperature incombustible fluid cooled in the first heat-insulating space 12, the temperature of the first heat-insulating space 12 can be maintained at a very low temperature, and therefore, generation of evaporation gas can be suppressed.

Hereinafter, an evaporation gas suppression apparatus for a liquefied gas storage tank according to a second embodiment of the present invention will be described with reference to FIG. The evaporation gas suppression device of the liquefied gas storage tank according to the second embodiment of the present invention may include a cooling cycle 32 for directly cooling the high temperature incombustible fluid as the cooling means.

The cooling cycle 32 of the present embodiment can cool the incombustible fluid while circulating the cycle, instead of cooling the incombustible fluid by heat exchange with the low temperature refrigerant.

For example, the cooling cycle 32 may include a compressor for compressing the hot incombustible fluid introduced into the refrigeration cycle 32 and a cooler for cooling the incombustible fluid compressed in the compressor, It is possible to supply the incombustible fluid cooled to the cryogenic temperature including the expansion means to the first heat insulating space 12. In the cooler of the refrigeration cycle 32, the compressed non-combustible fluid compressed in the compressor and the non-combustible fluid to be introduced into the compressor can be heat-exchanged, and the compressed non-combustible fluid can be cooled by the non-combustible fluid to be introduced into the compressor.

In the cooling cycle 32, the high temperature incombustible fluid is cooled to a low temperature by compression, cooling, and expansion, and the low temperature incombustible fluid is supplied to the first heat insulating space 12 to maintain the first heat insulating space 12 at a cryogenic temperature .

The low temperature incombustible fluid cooled in the cooling cycle 32 is supplied to the first heat insulating space 12 along the fluid supply line ISL as in the above-described embodiments in which the incombustible fluid cooled in the cooling cycle 32 Is filled with a high temperature incombustible fluid introduced into the cooling cycle 32 along the fluid discharge line IDL or a high temperature incombustible fluid introduced into the cooling cycle 32 along the fluid discharge line IDL, The newly generated incombustible fluid may be mixed in the supplied incombustible fluid generating apparatus 20 or it may be a incombustible fluid supplementarily supplied along the fluid replenishing line.

The fluid circulation line can also be used to bypass the cooling cycle 32 so that the non-combustible fluid cooled in the cooling cycle 32 is re-supplied to the front end of the cooling cycle 32, (BL) bypassing the cooling cycle (32) and providing a path to be fed to the end of the cooling cycle (32).

The flow rate or temperature of the cooled low-temperature incombustible fluid supplied to the first heat insulating space 12 can be adjusted by controlling the opening and closing amount of the valve provided in the bypass line BL.

The flow rate or temperature of the nonflammable fluid supplied to the first adiabatic space 12 is supplied to the fluid circulation line such as fluid discharge line IDL, fluid supply line ISL, fluid replenishment line, as well as valves provided in the bypass line BL The valve and the venting part VE may be controlled and controlled in combination.

As shown in FIG. 4, the fluid supply line (ISL) is provided with circulation means (50) for applying pressure to smoothly supply the low temperature incombustible fluid cooled in the cooling cycle (32) to the first heat insulating space . For example, the circulation means 50 may be a blower.

Thus, according to the present embodiment, the incombustible fluid is cooled directly in the cooling cycle 32, the cooled low-temperature incombustible fluid is supplied to the first heat-insulating space 12, and the temperature in the first heat- The high-temperature incombustible fluid may be discharged, and some or all of the fluid may be re-supplied to the cooling cycle 32, cooled, and then supplied to the first heat insulating space 12.

In order to maintain the temperature and pressure of the first heat insulating space 12, a high temperature incombustible fluid discharged from the first heat insulating space 12 or a part of the low temperature incombustible fluid supplied to the first heat insulating space 12 And the incombustible fluid generated in the incombustible fluid generator 20 is supplementarily supplied to the fluid circulation line to be cooled in the cooling cycle 32 and then discharged to the first heat insulating space 12 .

5, when the liquefied gas, in this embodiment, LNG is unloaded into the storage space 11 of the liquefied gas storage tank 10, the incombustible fluid generated in the incombustible fluid generating apparatus 20, In the example, nitrogen gas is supplied to the first heat insulating space 12. At this time, the nitrogen gas supplied to the first heat insulating space 12 preferably has a temperature of about 50 DEG C or lower and is introduced into the first heat insulating space 12 along the bypass line BL without cooling in the cooling cycle 32 It is possible.

When nitrogen gas is filled in the first heat insulating space 12 with an appropriate pressure, LNG unloading is carried out into the storage space 11. The temperature of the unloaded LNG is about -163 DEG C. When the unloading starts, the nitrogen gas discharged from the first heat insulating space 12 or the nitrogen gas further supplied from the incombustible fluid generating apparatus 20 is supplied to the cooling cycle 32 And cooled. In the cooling cycle 32, the nitrogen gas can be cooled to about -130 DEG C or lower, preferably about -160 DEG C, and supplied to the first heat insulating space 12. [

As shown in FIG. 6, by supplying the low-temperature incombustible fluid cooled in the first heat-insulating space 12, the temperature of the first heat-insulating space 12 can be maintained at a very low temperature, and therefore, generation of evaporation gas can be suppressed.

Hereinafter, an evaporation gas suppression device for a liquefied gas storage tank according to a third embodiment of the present invention will be described with reference to FIG.

The apparatus for suppressing the evaporation of gas in the liquefied gas storage tank according to the third embodiment of the present invention includes a refrigerant cycle (40) for circulating refrigerant as a cooling means, a low-temperature refrigerant cooled in the refrigerant cycle (40) A first heat exchanger (31) for heat exchange and a waste heat recovery device (61).

In the first heat exchanger (31), the high temperature incombustible fluid is cooled by heat exchange with the low temperature refrigerant supplied from the refrigerant cycle (40), and the low temperature refrigerant is heated.

The incombustible fluid discharged after heat exchange in the first heat exchanger 31 is cooled and is a low temperature incombustible fluid and is supplied to the first heat insulating space 12 along the fluid supply line ISL and is discharged from the first heat exchanger 31 The refrigerant discharged after the heat exchange is circulated through the refrigerant cycle (40) along the refrigerant circulation line (RCL) with the heated high-temperature refrigerant.

In the refrigerant cycle 40, the low-temperature refrigerant cooled by the high-temperature refrigerant can be supplied to the first heat exchanger 31. The refrigerant circulation line RCL is connected to the first heat exchanger 31, The refrigerant cycle 40 is connected between the recovery device 61 and the refrigerant cycle 40 so that the high temperature refrigerant flows from the first heat exchanger 31 and the waste heat recovery device 61 to the refrigerant cycle 40, And provides the path of the refrigerant to be circulated to the first heat exchanger (31).

The refrigerant circulation line RCL is provided with a valve (not shown) for controlling the flow rate and the flow rate of the low-temperature refrigerant supplied from the refrigerant cycle 40 to the first heat exchanger 31, the first heat exchanger 31, A valve (not shown) for controlling the flow path and the flow rate of the high-temperature refrigerant recovered from the waste heat recovery device 61 to the refrigerant cycle 40 may be provided.

In this embodiment, the refrigerant cycle 40 may be, for example, a nitrogen refrigerant cycle 40, and the nitrogen refrigerant cycle 40 may be one that compresses nitrogen with a vaporization point of about -196 DEG C One or more intermediate coolers for cooling the compressed nitrogen downstream of the at least one compressor, a cooler and a cooler for cooling the compressed nitrogen in the compressor, one or more expanders for expanding the high pressure nitrogen cooled in the cooler to further cool to the cryogenic temperature Means. The expansion means may be an expander or a line-Thomson valve and may be cooled by thermal expansion of the compressed nitrogen.

In the cooler of the refrigerant cycle (40), the refrigerant compressed in the compressor and the refrigerant to be introduced into the compressor are heat-exchanged, and the compressed refrigerant can be cooled by the refrigerant to be introduced into the compressor.

The high temperature refrigerant which has cooled the incombustible fluid in the first heat exchanger (31) is circulated to the refrigerant cycle (40) and cooled to low temperature by compression, cooling and expansion, and the low temperature refrigerant is again supplied to the first heat exchanger 31 to cool the incombustible fluid.

According to the present embodiment, the refrigerant is circulated on the refrigerant circulation line RCL between the first heat exchanger 31 and the refrigerant cycle 40 and circulated in the first heat exchanger 31 to the refrigerant cycle 40 after heat exchange. A waste heat recovering device 61 for recovering the waste heat of the high-temperature refrigerant is further provided.

The waste heat recovery device 61 can recover the waste heat of the high-temperature refrigerant and precool the high-temperature refrigerant before the refrigerant is introduced into the refrigerant cycle 40. In this embodiment, a second heat exchanger 61 for lowering the temperature of the high-temperature refrigerant by heating the heating source utilized in the ship may be provided as the waste heat recovering apparatus.

In the second heat exchanger 61, the high-temperature refrigerant supplied from the first heat exchanger 31 to the refrigerant cycle 40 along the refrigerant circulation line RCL and the high-temperature refrigerant supplied from the high- (Not shown) heated by the second heat exchanger 61 and then heat-exchanged with a low-temperature heat source supplied to the second heat exchanger 61. The high-temperature refrigerant is cooled by heat exchange and the low-temperature heat source is heated.

The heating source used in the ship may be, for example, glycol water flowing along the heating source circulation line (GL1), and the glycol water may be utilized as a heat source for maintaining the temperature of the hold-up coffer dam or vaporizing the LNG . In the present embodiment, the medium in which heat exchange with the high-temperature refrigerant in the second heat exchanger 61 is glycol water is described as an example, but the present invention is not limited thereto.

Therefore, according to the present embodiment, the heating means for recirculating the heating source utilized in the ship is not separately provided, and the glycol water is heated using the waste heat of the high-temperature refrigerant in the second heat exchanger (61) . The glycol water may be supplied to the heating device after being heated in the second heat exchanger (61), and the second heat exchanger (61) may be utilized as the preheating means of the glycol water.

In addition, since the refrigerant in which the waste heat is recovered in the second heat exchanger (61) is supplied to the refrigerant cycle (40), the heat duty of the refrigerant cycle (40) can be reduced.

The low-temperature incombustible fluid cooled in the first heat exchanger 31 is supplied to the first heat insulating space 12 along the fluid supply line ISL. The incombustible fluid heat-exchanged in the first heat exchanger 31 flows through the fluid Along with the high temperature incombustible fluid introduced into the first heat exchanger 31 along the discharge line IDL or the fluid non-combustible fluid introduced into the first heat exchanger 31 along the fluid discharge line IDL The newly generated incombustible fluid may be mixed in the replenished incombustible fluid generating apparatus 20 or may be a non-incombustible fluid supplementarily supplied along the fluid replenishing line.

According to the present embodiment, the fluid circulation line is arranged to bypass the first heat exchanger 31 so that the incombustible fluid cooled in the first heat exchanger 31 is supplied again to the front end of the first heat exchanger 31, or And a bypass line BL for bypassing the first heat exchanger 31 at a front end of the first heat exchanger 31 and providing a path to be supplied to a downstream end of the first heat exchanger 31.

The flow rate or temperature of the cooled low-temperature incombustible fluid supplied to the first heat insulating space 12 can be adjusted by controlling the opening and closing amount of the valve provided in the bypass line BL.

The flow rate or temperature of the nonflammable fluid supplied to the first heat insulating space 12 is not limited to the valve provided in the bypass line BL but also to the fluid circulation line such as the fluid discharge line IDL, the fluid supply line ISL, The valve provided in the refrigerant circulation line RCL and the venting part VE may be controlled in combination.

The fluid supply line (ISL) may further include circulation means (50) for applying pressure to supply the low temperature incombustible fluid cooled by the first heat exchanger (31) to the first heat insulating space (12) smoothly. For example, the circulation means 50 may be a blower.

Therefore, according to the present embodiment, the incombustible fluid is cooled by heat exchange with the refrigerant in the first heat exchanger 31, the cooled low-temperature incombustible fluid is supplied to the first heat insulating space 12, The high-temperature incombustible fluid whose temperature has risen in the first heat exchanger 12 is discharged to supply a part or the entirety to the first heat exchanger 31 to cool it by heat exchange with the refrigerant,

In order to maintain the temperature and pressure of the first heat insulating space 12, a high temperature incombustible fluid discharged from the first heat insulating space 12 or a part of the low temperature incombustible fluid supplied to the first heat insulating space 12 And the incombustible fluid generated in the incombustible fluid generator 20 is supplementarily supplied to the fluid circulation line to be cooled by heat exchange with the refrigerant in the first heat exchanger 31 It may be supplied to the first heat insulating space 12.

The refrigerant whose temperature has risen after cooling the high-temperature incombustible fluid in the first heat exchanger (31) is heat-exchanged with the heating source of the ship in the second heat exchanger (61), in this embodiment, with the glycol water to heat the glycol water The refrigerant is introduced into the refrigerant cycle 40 after the temperature is lowered, cooled to a low temperature in the refrigerant cycle 40, and then recycled to the first heat exchanger 31.

5, when the liquefied gas, in this embodiment, LNG is unloaded into the storage space 11 of the liquefied gas storage tank 10, the incombustible fluid generated in the incombustible fluid generating apparatus 20, In the example, nitrogen gas is supplied to the first heat insulating space 12. The nitrogen gas supplied to the first heat insulating space 12 preferably has a temperature of about 50 DEG C or lower and flows into the first heat insulating space 12 along the bypass line BL without being cooled by the first heat exchanger 31 May be introduced.

When nitrogen gas is filled in the first heat insulating space 12 with an appropriate pressure, LNG unloading is carried out into the storage space 11. The temperature of the LNG to be unloaded is about -163 DEG C. When the unloading is started, the operation of the refrigerant cycle 40 is started, and the addition of nitrogen gas or incombustible fluid generated from the first heat insulating space 12 And the supplied nitrogen gas is cooled through heat exchange with the refrigerant in the first heat exchanger (31). In the first heat exchanger (31), nitrogen gas can be cooled to about -130 DEG C or lower, preferably about -160 DEG C or so, using the cooling heat of the refrigerant and supplied to the first heat insulating space (12).

As shown in FIG. 6, by supplying the low-temperature incombustible fluid cooled in the first heat-insulating space 12, the temperature of the first heat-insulating space 12 can be maintained at a very low temperature, and therefore, generation of evaporation gas can be suppressed.

Hereinafter, an evaporation gas suppression apparatus for a liquefied gas storage tank according to a fourth embodiment of the present invention will be described with reference to FIG. The evaporation gas suppression device of the liquefied gas storage tank according to the fourth embodiment of the present invention may include a cooling cycle 32 and a waste heat recovery device 62 for directly cooling the high temperature incombustible fluid as the cooling means.

The cooling cycle 32 of the present embodiment can cool the incombustible fluid while circulating the cycle, instead of cooling the incombustible fluid by heat exchange with the low temperature refrigerant.

For example, the cooling cycle 32 may include a compressor that compresses a hot, incombustible fluid introduced into the refrigeration cycle 32, a chiller that cools the compressed non-combustible fluid in the compressor, and a swell The non-combustible fluid cooled to a cryogenic temperature can be supplied to the first heat insulating space 12. In the cooler of the refrigeration cycle 32, the compressed non-combustible fluid compressed in the compressor and the non-combustible fluid to be introduced into the compressor can be heat-exchanged, and the compressed non-combustible fluid can be cooled by the non-combustible fluid to be introduced into the compressor.

In the cooling cycle 32, the high-temperature incombustible fluid is cooled to a low temperature by compression, cooling, and expansion, and the low-temperature incombustible fluid is again supplied to the first heat insulating space 12 to maintain the first heat insulating space 12 at a very low temperature .

The low temperature incombustible fluid cooled in the cooling cycle 32 is supplied to the first heat insulating space 12 along the fluid supply line ISL so that the heat exchanged in the cooling cycle 32 The incombustible fluid is supplied to the high temperature incombustible fluid introduced into the refrigeration cycle 32 along the fluid discharge line IDL or a fluid refill line with the high temperature incombustible fluid introduced into the refrigeration cycle 32 along the fluid discharge line IDL The newly generated incombustible fluid may be mixed in the non-incombustible fluid generating apparatus 20 supplemented and supplied, or it may be a non-incombustible fluid supplementarily supplied along the fluid replenishing line.

According to the present embodiment, the waste heat of a high-temperature incombustible fluid introduced into the cooling cycle 32 from the first heat insulating space 12, which is provided between the cooling cycle 32 of the fluid circulation line and the liquefied gas storage tank 10, The waste heat recovering device 62 is further provided.

The waste heat recovery device 62 may recover the waste heat of the high-temperature incombustible fluid to precool the high-temperature incombustible fluid before it is introduced into the cooling cycle 32. In this embodiment, as the waste heat recovering apparatus, a third heat exchanger 62 for lowering the temperature of the high-temperature incombustible fluid by heating the heat source utilized in the ship may be provided.

In the third heat exchanger 62, the high-temperature incombustible fluid supplied from the first heat insulating space 12 to the cooling cycle 32 along the fluid circulation line ISL and the high- (Not shown) heated by the first heat exchanger 62, and then the low-temperature heat source supplied to the third heat exchanger 62 is heat-exchanged. By the heat exchange, the high temperature incombustible fluid is cooled and the low temperature heat source is heated .

The heating source used in the ship may be, for example, glycol water flowing along the heating source circulation line (GL2), and the glycol water may be utilized as a heat source for maintaining the temperature of the hold-up coffer dam or vaporizing the LNG . In this embodiment, the medium in which heat exchange with the high-temperature incombustible fluid in the third heat exchanger 62 is glycol water is described as an example, but the present invention is not limited thereto.

Therefore, according to the present embodiment, it is possible to heat the glycol water by using the waste heat of the high-temperature incombustible fluid in the third heat exchanger 62 without separately providing the heating means for recirculating the heating source utilized in the ship, The nonflammable fluid can be precooled. The glycol water may be supplied to the heating device after being heated in the third heat exchanger 62 and the third heat exchanger 62 may be utilized as the preheating means of the glycol water.

In addition, since the waste heat is recovered in the third heat exchanger 62 and the non-combustible fluid is supplied to the cooling cycle 32, the heat duty of the cooling cycle 32 can be reduced.

The fluid circulation line can also be used to bypass the cooling cycle 32 so that the non-combustible fluid cooled in the cooling cycle 32 is re-supplied to the front end of the cooling cycle 32, (BL) bypassing the cooling cycle (32) and providing a path to be fed to the end of the cooling cycle (32).

The flow rate or temperature of the cooled low-temperature incombustible fluid supplied to the first heat insulating space 12 can be adjusted by controlling the opening and closing amount of the valve provided in the bypass line BL.

The flow rate or temperature of the nonflammable fluid supplied to the first adiabatic space 12 is supplied to the fluid circulation line such as fluid discharge line IDL, fluid supply line ISL, fluid replenishment line, as well as valves provided in the bypass line BL The valve and the venting part VE may be controlled and controlled in combination.

The fluid supply line (ISL) may further include a circulation means (50) for applying pressure so that the low temperature incombustible fluid cooled in the cooling cycle (32) is supplied smoothly to the first heat insulating space (12). For example, the circulation means 50 may be a blower.

Thus, according to the present embodiment, the incombustible fluid is recovered from the third heat exchanger 62 to recover the waste heat, precooled and then directly cooled in the cooling cycle 32, and the cooled, low-temperature incombustible fluid is discharged to the first heat- And the high temperature incombustible fluid whose temperature has risen in the first heat insulating space 12 is discharged so that a part or the whole of the fluid is re-supplied to the third heat exchanger 62 and the cooling cycle 32, (12).

In order to maintain the temperature and pressure of the first heat insulating space 12, a high temperature incombustible fluid discharged from the first heat insulating space 12 or a part of the low temperature incombustible fluid supplied to the first heat insulating space 12 And the incombustible fluid generated in the incombustible fluid generator 20 is supplementarily supplied to the fluid circulation line to be cooled in the cooling cycle 32 and then discharged to the first heat insulating space 12 .

In the third heat exchanger 62, the heating source of the ship, in this embodiment, the non-combustible fluid whose temperature has been lowered after heating the glycol water by heat exchange with the glycol water is introduced into the cooling cycle 32, And then supplied to the first heat insulating space 12.

5, when the liquefied gas, in this embodiment, LNG is unloaded into the storage space 11 of the liquefied gas storage tank 10, the incombustible fluid generated in the incombustible fluid generating apparatus 20, In the example, nitrogen gas is supplied to the first heat insulating space 12. At this time, the nitrogen gas supplied to the first heat insulating space 12 preferably has a temperature of about 50 DEG C or lower and is introduced into the first heat insulating space 12 along the bypass line BL without cooling in the cooling cycle 32 It is possible.

When nitrogen gas is filled in the first heat insulating space 12 with an appropriate pressure, LNG unloading is carried out into the storage space 11. The temperature of the LNG to be unloaded is about -163 DEG C. When the unloading starts, the nitrogen gas that has been discharged from the first heat insulating space 12 or the nitrogen gas that is further supplied from the incombustible fluid generating apparatus 20 is supplied to the third heat exchanger 62 And the cooling cycle 32. In this way, The nitrogen gas that has passed through the third heat exchanger 62 and the cooling cycle 32 has a temperature of about -130 DEG C or lower, preferably about -160 DEG C, and nitrogen gas cooled at a cryogenic temperature is introduced into the first heat insulating space 12, .

As shown in FIG. 6, by supplying the low-temperature incombustible fluid cooled in the first heat-insulating space 12, the temperature of the first heat-insulating space 12 can be maintained at a very low temperature, and therefore, generation of evaporation gas can be suppressed.

As described above, according to the evaporation gas suppressing apparatus and the suppressing method of the liquefied gas storage tank according to the present invention, the incombustible fluid cooled by the cryogenic coolant is supplied to the heat insulating space 12 by using a simple structure such as a cooling means , It is possible to prevent or prevent the evaporation of the liquefied gas by external heat and to prevent the risk of ignition by the leaked liquefied gas and thus to significantly reduce the loss of the liquefied gas by evaporation It is easy to maintain.

In addition, regardless of the engine type of the ship, it can be easily applied to existing ships and new dry vessels, and economic benefits can be expected by reducing the loss of cargo.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or scope of the invention as defined in the appended claims. . Therefore, the above-described embodiments are to be considered as illustrative rather than restrictive, and thus the present invention is not limited to the above description, but may be modified within the scope of the appended claims and equivalents thereof.

10: Liquefied gas storage tank
11: Storage space
12: Insulation space
31, 32, 40, 61, 62: cooling means
50: circulation means
VE: Benting part
ISL: fluid supply line
IDL: fluid discharge line
RCL: Refrigerant circulation line
GL1, GL2: Heating source circulation line
BL: Bypass line

Claims (15)

A liquefied gas storage tank surrounded by the heat insulating space and storing liquefied gas;
Cooling means for cooling the incombustible fluid to be supplied to the heat insulating space; And
And a fluid circulation line connecting the heat insulating space and the cooling means and providing a path of the incombustible fluid,
Wherein the low-temperature incombustible fluid cooled by the cooling means circulates in the heat insulating space. The method according to claim 1,
Wherein the cooling means comprises:
A refrigerant cycle for circulating the refrigerant;
A first heat exchanger for cooling the incombustible fluid to be supplied to the heat insulating space by the cold heat of the refrigerant cooled in the refrigerant cycle; And
And a refrigerant circulation line connecting the first heat exchanger and the refrigerant cycle to provide a path so that the high temperature refrigerant flows from the first heat exchanger to the refrigerant cycle and the low temperature refrigerant is supplied from the refrigerant cycle to the first heat exchanger , An evaporation gas suppressing device for a liquefied gas storage tank. The method according to claim 1,
Wherein the cooling means comprises:
A compressor for compressing the incombustible fluid to be supplied to the heat insulating space;
A cooler for cooling the compressed incombustible fluid in the compressor; And
And expansion means for thermally expanding the cooled incombustible fluid,
Wherein the non-combustible fluid is directly cooled. The method according to claim 1,
And a waste heat recovery device for recovering waste heat of the incombustible fluid to be supplied to the heat insulating space. The method of claim 2,
Wherein the cooling means comprises:
And a second heat exchanger for precooling the high-temperature refrigerant discharged from the first heat exchanger after heat exchange into the refrigerant cycle. The method of claim 4,
In the waste heat recovery device,
And a third heat exchanger for precooling the incombustible fluid introduced into the cooling means before introducing the incombustible fluid into the cooling means. 7. The method according to any one of claims 1 to 6,
And circulation means for introducing the non-combustible fluid cooled in the cooling means into the heat insulating space. The incombustible fluid is supplied to the heat insulating space of the liquefied gas storage tank,
A low-temperature incombustible fluid cooled by heat exchange between a low-temperature refrigerant circulating in the refrigerant cycle and a high-temperature incombustible fluid to be supplied to the heat insulating space,
Wherein the high temperature incombustible fluid whose temperature has risen in the heat insulating space keeps the heat insulating space at a low temperature by joining or venting to the incombustible fluid flow to be heat-exchanged. The method of claim 8,
And recovering the waste heat of the high-temperature refrigerant circulating after the incombustible fluid is cooled to cool the heat source, thereby pre-cooling the high-temperature refrigerant. The incombustible fluid is supplied to the heat insulating space of the liquefied gas storage tank,
The nonflammable fluid is cooled and supplied using a cooling cycle,
Wherein the incombustible fluid whose temperature has risen in the heat insulating space is kept at a low temperature by joining or venting to the incombustible fluid flow to be cooled. The method of claim 10,
The evaporation of the liquefied gas storage tank that preheats the hot, incombustible fluid by withdrawing the waste heat of the hot, incombustible fluid and cooling the source of heating prior to joining the hot incombustible fluid whose temperature has risen in the insulating space to the cooling flow, Gas suppression method. Supplying an incombustible fluid to the heat insulating space of the liquefied gas storage tank;
Supplying a liquefied gas to a storage space of the liquefied gas storage tank;
Discharging a high temperature incombustible fluid whose temperature has risen in the heat insulating space and cooling a mixture of the discharged high temperature incombustible fluid or the newly generated incombustible fluid and the high temperature incombustible fluid; And
And circulating the cooled incombustible fluid to the heat insulating space. The method of claim 12,
The cooling of the non-
The non-combustible fluid is cooled by heat exchange with the refrigerant circulating in the refrigerant cycle,
Wherein the incombustible fluid is supplied to the refrigeration cycle and is directly cooled by compression, cooling and expansion. 14. The method of claim 13,
And recovering waste heat of the high-temperature refrigerant after heat exchange with the incombustible fluid. 14. The method of claim 13,
Recovering waste heat of the hot, incombustible fluid prior to feeding to the refrigeration cycle.

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