JP2012516263A - Evaporative gas treatment apparatus and method for electric propulsion LNG carrier having reliquefaction function - Google Patents

Abstract

The evaporative gas cooler 10 that receives the natural evaporative gas generated in the LNG cargo trap and exchanges heat with the refrigerant for cooling, and the natural evaporative gas cooled by the evaporative gas cooler 10 receives the DFDE propulsion system engine 3, a gas compressor 20 that compresses at a usable gas pressure, and a natural evaporative gas that has been heated through the gas compressor 20 is cooled to a temperature that can be used by the DFDE propulsion engine 3, and the DFDE propulsion engine Engine supply gas cooler 30 supplied to side 3 and excess natural evaporative gas not used in DFDE propulsion system engine 3 are supplied downstream from engine supply gas cooler 30 to exchange heat with refrigerant to cool and reliquefy The liquefaction heat exchanger 50 supplied to the LNG cargo ship side is used, and natural evaporative gas generated in the LNG cargo ship is used as a power source necessary for ship operation. Both to realize the minimization of natural evaporation gas waste and re-liquefying the excess gas not used for propulsion.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to an evaporative gas processing apparatus and method for an electric propulsion LNG carrier having a reliquefaction function, and more specifically, natural evaporative gas generated in an LNG cargo tank is efficiently used for propulsion of a ship. However, the present invention relates to an evaporative gas processing apparatus and method for an LNG carrier capable of minimizing wasteful use of surplus gas that is not used for propulsion.

  A liquefied natural gas carrier (LNG ship) is a ship that carries liquefied natural gas (LNG) from a production base to an underwriting base, and is usually referred to as an LNG ship or LNG carrier (LNG carrier). LNG (Liquefied Natural Gas) is a natural gas mainly composed of methane (CH4) liquefied at atmospheric pressure to below 162 ° C, and the ratio of LNG liquid to gas volume is about 1/600. The LNG specific gravity in the liquefied state is 0.43 to 0.50.

  LNG ships are classified into independent tank type and membrane type according to the type of cargo trap. As the independent tank type, there is the Mors type developed by Norwegian Moss Rosenberg, which has a technical patent, and the membrane type is Mark III, which has patented technology by GTT, France. And NO96 E2 type.

  LNG ships that are currently dried and operated naturally generate evaporative gas of about 4 to 6 tons per hour during cargo loading operation, but are equipped with a reliquefaction facility that liquefies evaporative gas again, or double fuel By adopting a diesel-electric (DFDE) propulsion engine, if necessary, crude gas and (evaporated) gas are used alternately as fuel, reducing enormous gas waste.

  However, LNG ships equipped with existing reliquefaction facilities are equipped with engines that use HFO (Bunker C) as fuel, resulting in a surge in operating costs due to the increase in HFO prices. -Existing electric propulsion vessels adopting a Dual Fuel Diesel Electric (DFDE) propulsion engine will use the entire amount of naturally occurring gas at loads that fall within the design operating speed of 18 knots to 20.5 knots or less. However, there is a problem that a large amount of gas must be incinerated or released into the atmosphere at the start of operation or arrival at the terminal.

  When an existing electric propulsion LNG ship is operated in an economic speed range of about 17 knots, excess gas of about 30% of the maximum natural gas generation amount remains, but (for example, in the case of a 173 k cbmLNG ship, 17 When operating in knots, use of 3,700 kg / h out of about 5,100 kg / h of naturally generated gas will leave about 1,400 kg / h of surplus gas), such surplus There is a demand for the development of an evaporative gas treatment system that can efficiently process and operate gas without waste.

  In combining the existing DFDE propulsion system engine and the existing reliquefaction equipment, if evaporative gas is compressed to the extent that the gas pressure (4 to 6 bar) used in the existing DFDE propulsion system engine can be realized, The re-liquefaction efficiency has to be greatly reduced due to the temperature rise, and it is necessary to provide a separate compressor only for the DFDE propulsion type engine or move the existing re-liquefaction equipment with low re-liquefaction efficiency. There is a limit.

  The present invention, which was devised to solve the problems as described above, combines an electric propulsion ship using a DFDE propulsion type engine with a reliquefaction facility, and allows the evaporation gas necessary for the operation of the electric propulsion ship to be generated. An evaporative gas processing apparatus and method for an electric propulsion LNG carrier ship having a reliquefaction function capable of efficiently processing and operating natural evaporative gas without waste by reliquefying surplus gas generated after use The purpose is to provide.

  In addition, by combining reliquefaction equipment with an electric propulsion ship that uses a DFDE propulsion engine, a reliquefaction function that can realize high reliquefaction efficiency without having a separate compressor only for the DFDE propulsion engine It is another object of the present invention to provide an evaporative gas processing apparatus and method for an electric propulsion LNG carrier having the following.

  The present invention for achieving the object as described above is to supply natural boil-off gas (N-BOG) generated in a liquefied natural gas cargo tank (not shown). Evaporative gas cooler 10 that receives heat and cools the refrigerant and cools it, and receives natural evaporative gas cooled by the evaporative gas cooler 10 to promote DFDE (Dual Fuel Diesel Electric) A gas compressor 20 that compresses at a gas pressure that can be used for the engine 3, and natural evaporative gas that has been heated through the gas compressor 20 is cooled to a temperature that can be used for the DFDE propulsion engine 3. Engine supply gas cooler 30 to be supplied to the DFDE propulsion system engine 3 side, and excess (evaporated) natural evaporative gas not used in the DFDE propulsion system engine 3 from the downstream side of the engine supply gas cooler 30 An electric propulsion having a reliquefaction function, comprising: a reliquefaction heat exchanger 50 that is supplied and heat-exchanged with a refrigerant to cool, reliquefy and supply the refrigerant to the LNG cargo ship side. The technical point is an evaporative gas treatment device for an LNG carrier.

  Here, a plurality of refrigerant compressors 61a installed so as to compress the gaseous refrigerant in multiple stages, and the refrigerant that has been compressed through the refrigerant compressor 61a and expanded in temperature are expanded, and the LNG cooling point Refrigerant compander (Compander: compression expander) 61 provided with a refrigerant expander 61b that cools to a lower temperature, and the refrigerant that flows in or out of the refrigerant compressor 61a is cooled to compress the refrigerant compressor 61a. It is desirable to further include a refrigerant cooler 62 that increases efficiency.

  In addition, a refrigerant is connected to a refrigerant supply device (not shown), selectively receives the refrigerant, and has a storage space and a gas discharge port that can accommodate a large amount of gaseous refrigerant inside, and has a flow and heat. It is desirable to further include a refrigerant buffer tank 63 that compensates for the refrigerant lost during the exchange, or buffers the shock caused by fluctuations in the pressure and flow rate of the refrigerant supply conduit to relieve the overload pressure.

  Then, the refrigerant that has passed through the refrigerant compander 61 is supplied to the reliquefaction heat exchanger 50, and the refrigerant that has been heated through the reliquefaction heat exchanger 50 is supplied to the refrigerant buffer tank 63. 1 refrigerant supply conduit 64 a and the refrigerant that has passed through the refrigerant compander 61 are supplied to the evaporative gas cooler 10, and the refrigerant that has been heated through the evaporative gas cooler 10 is supplied to the refrigerant buffer tank 63. It is desirable to further include a second refrigerant supply conduit 64b for supplying.

  The temperature control valve 65 further adjusts the flow rate of the refrigerant passing through the second refrigerant supply conduit 64b in proportion to the temperature and flow rate of the natural evaporative gas passing through the evaporative gas cooler 10. It is desirable.

  Then, the refrigerant that has passed through the plurality of refrigerant compressors 61a is supplied to the reliquefaction heat exchanger 50, passes through the reliquefaction heat exchanger 50, and passes through the first refrigerant supply conduit 64a. And a third refrigerant supply conduit 64c for supplying the refrigerant cooled by the heat exchange to the refrigerant expander 61b.

  The engine supply gas cooler 30 may be a fresh water cooler that exchanges heat using fresh water as a refrigerant, and the refrigerant cooler 62 may be a sea water cooler that exchanges heat using sea water as a refrigerant. desirable.

The refrigerant is preferably N ₂ having a lower cooling point than LNG and not explosive.

  The evaporative gas cooler 10 has an open LNG outflow path (not shown) at the bottom so that LNG partially liquefied by heat exchange with the refrigerant is separated and supplied to the LNG cargo yard by gravity. It is desirable.

  A gas flow meter 41 for measuring a supply amount of natural evaporative gas flowing into the DFDE propulsion system engine 3; a gas amount required by the DFDE propulsion system engine 3 in accordance with a load fluctuation caused by ship operation; It is desirable to further include a load distribution valve 42 for adjusting the flow rate of the natural evaporative gas flowing into the reliquefaction heat exchanger 50 according to the amount of gas measured by the gas flow meter 41.

  The refrigerant compander 61 desirably adjusts the flow rate or flow rate of the refrigerant in proportion to the flow rate passing through the load distribution valve 42.

And a storage space that can accommodate both liquid LNG reliquefied by the reliquefaction heat exchanger 50 and supplied to the LNG cargo tank side, and gas or N ₂ separated and generated from the reliquefied LNG. An LNG evaporative gas separator 70 having a gas discharge port for discharging the internal gas to the outside, and supplying only the reliquefied LNG in a state in which the gas or N ₂ is separated to the LNG cargo ship side, It is desirable to include it.

  In addition, when the LNG reliquefied by the reliquefaction heat exchanger 50 is not naturally supplied to the LNG cargo side due to gravity and pressure loss in the piping, the liquefied LNG is forced to the LNG cargo side. It is desirable to further include an LNG supply pump 80 installed on the LNG supply conduit to supply.

  When the reliquefied heat exchanger 50 operates abnormally due to failure, damage, malfunction, or is stopped, the amount of gas required by the DFDE propulsion system engine 3 is exceeded. It is desirable to further include a gas incinerator 90 that receives the supply of natural evaporation gas and incinerates and removes it.

  In addition, when a ship is operated at a preset economic operation speed, an operation state display device (not shown) that generates a signal that makes the state during economic operation recognizable with the naked eye or hearing in the ship's steering room, It is desirable to further include.

  The present invention also provides an evaporative gas pre-treatment stage for primarily cooling natural evaporative gas (N-BOG) generated in a liquefied natural gas cargo tank; An evaporative gas compression stage in which a natural evaporative gas first cooled in the processing stage is supplied and compressed at a gas pressure usable for a DFDE (Dual Fuel Diesel Electric) propulsion engine, and the evaporation The evaporative gas cooling stage in which the natural evaporative gas heated through the gas compression stage is secondarily cooled at a temperature usable for the DFDE propulsion system engine 3 and supplied to the DFDE propulsion system engine 3 side, and the DFDE propulsion A surplus gas reliquefaction stage in which excess natural evaporative gas that is not used in the engine 3 is cooled and reliquefied by the reliquefaction heat exchanger 50 and supplied to the LNG cargo ship side. The electric propulsion LNG carrier evaporated gas processing method having a reliquefaction that features the other technical gist.

  Here, when the reliquefaction heat exchanger 50 operates abnormally due to a failure, damage, malfunction, or when the operation is stopped, the amount of gas required by the DFDE propulsion system engine 3 is exceeded. It is desirable to further include a surplus gas incineration stage in which the natural evaporative gas is supplied and incinerated and removed.

  The present invention having the above-described configuration combines the DFDE propulsion type engine supply evaporative gas processing equipment and the reliquefaction equipment to reliquefy the surplus evaporative gas that is not used for the operation of the electric propulsion LNG carrier. There is an effect that it is possible to realize economical efficiency and efficiency that minimizes wasteful use of evaporative gas.

  In addition, natural evaporative gas passes through an evaporative gas cooler, a gas compressor, and an engine supply gas cooler in sequence, and has a pressure and temperature suitable for use in a DFDE propulsion engine and a high pressure that is easy to reliquefy. It is possible to implement a high reliquefaction efficiency with stable application of the DFDE propulsion system engine without further providing a compressor that is compressed in an expensive facility only for the operation of the DFDE propulsion system engine. effective.

  The gas amount suitable for the load applied to the DFDE propulsion system engine is supplied, or the difference between the gas amount currently supplied to the DFDE propulsion system engine and the gas amount required by the DFDE propulsion system engine is Other than being able to easily realize automation while stably adjusting and applying the amount of gas supplied to the DFDE propulsion system engine or reliquefaction heat exchanger by the load distribution valve while checking and comparing through the flow meter There is an effect.

  In addition, by further providing a gas incinerator on the path for supplying the natural evaporative gas that has passed through the engine supply gas cooler to the DFDE propulsion system engine side, the reliquefaction heat exchanger may be damaged, malfunctioned, or malfunctioned. If it operates abnormally or stops operating, the gas incinerator can be moved to incinerate and remove natural evaporative gas to an extent that exceeds the amount of gas required by the DFDE propulsion type engine. There is another effect that the sex can be secured.

  The evaporative gas cooler 10 and the temperature control valve 65 allow the natural evaporative gas to be constant within a set temperature range suitable for the operation of the gas compressor 20 regardless of the temperature of the natural evaporative gas in the LNG cargo shed. Can be cooled and supplied to the gas compressor 20 side, and if the LNG liquid level in the LNG cargo tank is low, the natural evaporative gas compression and supply are difficult to be performed smoothly, and the injected LNG It is possible to solve the problem that the compressor is forced to be burdened by mixing.

It is the schematic which showed 1st Example of the evaporative gas processing apparatus of the electric propulsion LNG carrier which has a reliquefaction function by this invention. It is the flowchart which showed 1st Example of the evaporative gas processing method of the evaporative gas processing apparatus of the electric propulsion LNG carrier which has a reliquefaction function by this invention.

  The evaporative gas treatment apparatus and method of the electric propulsion LNG carrier having the above-described configuration and having the reliquefaction function will be described in detail with reference to the following drawings.

  FIG. 1 is a schematic view showing a first embodiment of an evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to the present invention, and FIG. 2 is an electric propulsion LNG carrier having a reliquefaction function according to the present invention. It is a flowchart which shows 1st Example of the evaporative gas processing method of this evaporative gas processing apparatus.

  An evaporative gas processing apparatus for an electric propulsion LNG carrier having a reliquefaction function according to the present invention uses natural boil-off gas (N-BOG) generated in a liquefied natural gas cargo tank. The present invention relates to an evaporative gas processing apparatus that re-liquefies so that wasteful use of surplus gas that is not used for propulsion can be minimized while operating efficiently for propulsion, as shown in FIG. In addition, it has a structure largely constituted by the evaporative gas cooler 10, the gas compressor 20, the engine supply gas cooler 30, and the reliquefaction heat exchanger 50.

  The evaporative gas cooler 10 receives the supply of natural evaporative gas generated in an LNG cargo tank (not shown), exchanges heat with the refrigerant and primarily cools, and the gas compressor 20 performs the evaporation. The natural evaporative gas cooled by the gas cooler 10 is supplied and compressed at a gas pressure (for example, 4 to 6 bar) that can be used for the DFDE (Dual Fuel Diesel Electric) propulsion system engine 3.

  When an LNG outflow path (not shown) is formed at the lower part of the evaporative gas cooler 10, it is partially liquefied by heat exchange with the refrigerant, and gravity is applied to the natural evaporative gas passage or the lower part of the storage space of the evaporative gas cooler 10. Thus, the liquid LNG naturally flowed and trapped by the gas can be flowed and supplied to the LNG cargo shed side through the LNG outflow passage in a state of being separated to the lower side of the natural evaporation gas.

  A natural evaporative gas generated by an LNG cargo tank (not shown) is supplied, and heat is exchanged with a refrigerant to cool it first, so that the gas compressor 20 is cooled by the evaporative gas cooler 10. The evaporative gas is supplied and compressed at a gas pressure (for example, 4 to 6 bar) that can be used for the DFDE (Dual Fuel Diesel Electric) propulsion system engine 3.

  The engine supply gas cooler 30 can use natural evaporative gas, which has been heated through the gas compressor 20 (for example, heated from −140 ° C. to 70 to 80 ° C.) for the DFDE propulsion type engine 3. The liquefied heat exchanger 50 is used for the DFDE propulsion type engine 3 after being cooled at a suitable temperature (for example, 70 to 80 ° C. is cooled to 10 to 50 ° C.) and supplied to the DFDE propulsion type engine 3 side. Excess natural evaporative gas not supplied is supplied downstream of the engine supply gas cooler 30, exchanged heat with the refrigerant, cooled, reliquefied, and supplied to the LNG freight side.

  Natural evaporative gas is compressed at a high pressure that facilitates re-liquefaction while passing through the evaporative gas cooler 10, the gas compressor 20, and the engine supply gas cooler 30 in order, and used for the DFDE propulsion type engine 3. The compressor and the expensive equipment are not further provided only for the operation of the DFDE propulsion system engine 3, but with the operation of the DFDE propulsion system engine 3. High reliquefaction efficiency can be realized.

  In adjusting the gas supply amount to the DFDE propulsion system engine 3 side, a gas flow meter 41 for measuring the supply amount of natural evaporative gas flowing into the DFDE propulsion system engine 3 and a load fluctuation due to ship operation are adjusted. The load distribution valve for adjusting the flow rate of the natural evaporative gas flowing into the reliquefaction heat exchanger 50 according to the gas amount required by the DFDE propulsion type engine 3 and the gas amount measured by the gas flow meter 41 42 is desirable.

  Gas is supplied at a flow rate suitable for the load applied to the DFDE propulsion system engine 3, or the amount of gas currently being supplied to the DFDE propulsion system engine 3 and the amount of gas required by the DFDE propulsion system engine 3 While confirming and comparing the difference with the gas flow meter 41, while stably adjusting and applying the amount of gas supplied to the DFDE propulsion type engine 3 or the reliquefaction heat exchanger 50 by the load distribution valve 42, Automation can be implemented easily.

The refrigerant applied evaporative gas cooler 10, the re-liquefaction heat exchanger 50, LNG cooling point is not explosive and (-150~-160 ℃) lower cooling point than _{N 2} (cooling point: -196 ° C. In order to supply the refrigerant to the evaporative gas cooler 10 and the reliquefaction heat exchanger 50, the refrigerant compander 61, the refrigerant cooler 62, the refrigerant buffer tank 63, the first, second, third, It is desirable to apply a liquefaction plant made up of the refrigerant supply conduits 64a, 64b, 64c and the temperature control valve 65.

  The refrigerant compander 61 passes through the refrigerant compressor 61a and a plurality of refrigerant compressors 61a installed to compress the gaseous refrigerant in multiple stages (for example, compress 4 to 10 bar at 40 to 60 bar). The refrigerant that has been compressed and heated is expanded (for example, pressure drop from 40 to 60 bar to 4 to 6 bar) and cooled at a temperature lower than the LNG cooling point (for example, -20 ° C is cooled to -150 to -160 ° C). The flow rate or flow rate of the refrigerant is increased or decreased in proportion to the flow rate of the refrigerant expander 61b that passes through the load distribution valve 42, that is, the flow rate of the natural evaporation gas that passes through the reliquefaction heat exchanger 50. It is desirable to adjust.

  The refrigerant cooler 62 is installed between the plurality of refrigerant compressors 61a so as to cool the refrigerant flowing into or out of the refrigerant compressor 61a, and increases the compression efficiency of the refrigerant compressor 61a. It is installed between the refrigerant compressor 61a and the refrigerant expander 61b to increase the cooling efficiency of the refrigerant expander 61b.

  The refrigerant buffer tank 63 is connected to a refrigerant supply device (not shown) and selectively receives a refrigerant as required, and stores a storage space and a gas discharge port (see FIG. (Not shown) to compensate for refrigerant lost during flow and heat exchange, or to buffer shocks due to refrigerant supply conduit pressure, flow rate fluctuations, etc. to relieve overload pressure.

  The first refrigerant supply conduit 64a supplies the refrigerant that has passed through the refrigerant compander 61 (for example, a refrigerant of −150 to −160 ° C. and 4 to 6 bar) to the reliquefaction heat exchanger 50, so that the reliquefaction is performed. A refrigerant that has passed through the heat exchanger 50 and has been heated is supplied to the refrigerant buffer tank 63 side, and a flow path that can be returned is provided.

  The second refrigerant supply conduit 64b supplies the refrigerant that has passed through the refrigerant compander 61 (for example, a refrigerant of −150 to −160 ° C. and 4 to 6 bar) to the evaporative gas cooler 10 so that the evaporative gas cooling is performed. A flow path capable of supplying and returning the refrigerant heated through the machine 10 to the refrigerant buffer tank 63 side is provided.

  For temperature control to increase and adjust the flow rate of the refrigerant passing through the second refrigerant supply conduit 64b on the second refrigerant supply conduit 64b in proportion to the temperature and flow rate of the natural evaporative gas passing through the evaporative gas cooler 10. When the valve 65 is provided, the evaporative gas cooler 10 can be implemented and maintained so as to have a constant cooling performance.

  If there is relatively little LNG contained in the LNG cargoe (e.g., the Ballast Voyage state compared to the state where the LNG is loaded voyage inside the LNG cargoe), The temperature of the natural evaporative gas, which is located on the upper side of the LNG cargo tank and is more clearly separated from the liquid LNG accommodated on the lower side of the LNG cargo tank, is relatively high. Become.

  If the temperature of the natural evaporative gas rises, the compression efficiency of the compressor installed outside the LNG cargo tank will be reduced so as to compress the natural evaporative gas.供給 Supplying pre-cooler and spray LNG for spraying liquid or low temperature LNG into the LNG cargo tank to lower the temperature at the compressor inlet side installed outside A separate pump is provided for this purpose.

  In existing electric propulsion LNG carriers, especially when the liquid level of LNG in the LNG cargo tank is low, it is necessary to operate the precooler and the pump. However, there is a lot of LNG drowning in the LNG cargo tank due to the movement of the ship. If this is the case, it is difficult for the LNG to be sucked in and supplied smoothly, and thus the precooler and the pump are difficult to operate stably, and a separate facility capable of stably sucking in the low liquid level LNG is provided. There is a difficulty in having to stop the operation of the precooler and the pump or the operation of supplying the natural evaporation gas to the DFDE propulsion system engine side.

  According to the present invention, the evaporative gas cooler 10 and the temperature control valve 65 are set within a set temperature range suitable for the operation of the gas compressor 20 irrespective of the temperature of the natural evaporative gas in the LNG cargo tank. Natural evaporative gas can be cooled and supplied to the gas compressor 20 side, and when the liquid level of LNG in the LNG cargo tank is already low, natural evaporative gas compression and supply are difficult to be performed smoothly, It is possible to solve the problem that the compressor is forcedly loaded by mixing the injected LNG.

  The third refrigerant supply conduit 64c supplies the refrigerant that has passed through the plurality of refrigerant compressors 61a to the reliquefaction heat exchanger 50, so that the reliquefaction heat can be obtained without using a separate cooling heat exchanger. The refrigerant is cooled (for example, cooled to −20 ° C. to 40 ° C.) by heat exchange with the refrigerant passing through the first refrigerant supply conduit 64a while passing through the exchanger 50, and supplied to the refrigerant expander 61b.

  The engine-supplied gas cooler 30 is preferably a fresh water cooler that exchanges heat using fresh water with a low risk of corrosion as a refrigerant, and the plurality of refrigerant coolers 62 use seawater that can be easily obtained in large quantities as a refrigerant. It is desirable to apply a seawater cooler that exchanges heat.

On the pipe for supplying the LNG reliquefied by the reliquefaction heat exchanger 50 to the LNG cargo shed side, both the reliquefied liquid LNG and the gas or N ₂ separated and generated by the reliquefied LNG are combined. When an LNG evaporative gas separator 70 having a storage space that can be accommodated and a gas discharge port (not shown) that discharges the gas inside the storage space to the outside is installed, the gas or N ₂ is separated. Only liquefied LNG can be supplied to the LNG freight side.

  Then, when the LNG supply pump 80 is installed on the pipe for supplying the LNG reliquefied by the reliquefaction heat exchanger 50 to the LNG cargo shed side, the LNG reliquefied by the reliquefaction heat exchanger 50 is When the LNG cargo pump side is not naturally supplied due to gravity or pressure loss in the piping, the LNG supply pump 80 can be operated to forcibly supply the re-liquefied LNG to the LNG cargo tank side.

  The existing reliquefaction equipment includes a pair having the same performance for the safety of surplus gas processing, but the natural evaporative gas that has passed through the engine supply gas cooler 30 is used as the engine 3 of the DFDE propulsion system. If the gas incinerator 90 is further provided outside the reliquefaction heat exchanger 50 on the supply path to the side, the reliquefaction heat exchanger 50 operates abnormally due to failure, damage, malfunction, or When the operation is stopped, the gas incinerator 90 is moved to incinerate and remove natural evaporative gas to the extent that the amount of gas required by the engine 3 of the DFDE propulsion system is exceeded, thereby ensuring operational safety. Can do.

  According to the present invention, regardless of whether or not the electric propulsion LNG carrier is operating at a preset economic operating speed, the excess gas that is not used for propulsion of the ship is reliquefied and returned to the LNG cargo tank. An operation status display device (not shown) that generates a signal that allows the ship's wheelchair to recognize whether the electric propulsion LNG carrier is operating at a preset economic operation speed. It is also desirable that the ship is operated more stably in an optimal state.

  An evaporative gas processing method for an electric propulsion LNG carrier having a reliquefaction function according to the present invention uses an evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to the present invention having the above-described structure. As shown in FIG. 2, the method relates to a processing method, and is largely performed in an evaporative gas pretreatment stage, an evaporative gas compression stage, an evaporative gas cooling stage, and an excess gas reliquefaction stage.

  In the evaporative gas pretreatment stage, natural evaporative gas (Natural Boil-Off Gas: N-BOG) generated in the liquefied natural gas cargo tank is primarily cooled using the evaporative gas cooler 10. In the evaporative gas compression stage, the gas compressor 20 is used to receive the natural evaporative gas primarily cooled in the evaporative gas pretreatment stage and receive DFDE (Dual Fuel Diesel-Electric: Dual Fuel). Diesel Electric) Compressed with gas pressure that can be used for propulsion type engines.

  In the evaporative gas cooling stage, the natural evaporative gas heated through the evaporative gas compression stage using the engine supply gas cooler 30 is secondarily cooled at a temperature usable for the DFDE propulsion system engine 3. The liquefied heat is supplied to the DFDE propulsion type engine 3 side, and in the excess gas reliquefaction stage, the reliquefaction heat exchanger 50 is used to reliquefy heat exchange of excess natural evaporative gas that is not used in the DFDE propulsion type engine 3. It is cooled and reliquefied by the vessel 50 and supplied to the LNG cargo ship side.

  When the reliquefied heat exchanger 50 operates abnormally due to failure, damage, malfunction, or is deactivated, it is required for the DFDE propulsion type engine 3 using the gas incinerator 90. After passing through the excess gas incineration stage where the natural evaporative gas is supplied to the extent that it exceeds the amount of gas, the natural evaporative gas is incinerated and removed to the extent that the amount of gas required by the DFDE propulsion engine 3 is exceeded. Thus, operational safety can be ensured.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and together with embodiments in which the above-described embodiments are simply combined with existing known techniques. The technology that can be modified and used by those skilled in the art to which the present invention pertains in the claims and detailed description of the present invention should naturally be considered as included in the technical scope of the present invention. .

  As described above, the present invention having the above-described configuration combines the DFDE propulsion type engine supply evaporative gas treatment facility and the reliquefaction facility to recycle the surplus evaporative gas that is not used for the operation of the electric propulsion LNG carrier. By liquefying, there is an effect that it is possible to realize economic efficiency and efficiency that minimizes wasteful use of natural evaporation gas.

  In addition, natural evaporative gas passes through an evaporative gas cooler, a gas compressor, and an engine supply gas cooler in sequence, and has a pressure and temperature suitable for use in a DFDE propulsion engine and a high pressure that is easy to reliquefy. It is possible to implement a high reliquefaction efficiency with stable application of the DFDE propulsion system engine without further providing a compressor that is compressed in an expensive facility only for the operation of the DFDE propulsion system engine. effective.

  The gas amount suitable for the load applied to the DFDE propulsion system engine is supplied, or the difference between the gas amount currently supplied to the DFDE propulsion system engine and the gas amount required by the DFDE propulsion system engine is Other than being able to easily realize automation while stably adjusting and applying the amount of gas supplied to the DFDE propulsion system engine or reliquefaction heat exchanger by the load distribution valve while checking and comparing through the flow meter There is an effect.

  In addition, by further providing a gas incinerator on the path for supplying the natural evaporative gas that has passed through the engine supply gas cooler to the DFDE propulsion system engine side, the reliquefaction heat exchanger may be damaged, malfunctioned, or malfunctioned. If it operates abnormally or stops operating, the gas incinerator can be moved to incinerate and remove natural evaporative gas to an extent that exceeds the amount of gas required by the DFDE propulsion type engine. There is another effect that the sex can be secured.

  The evaporative gas cooler 10 and the temperature control valve 65 allow the natural evaporative gas to be constant within a set temperature range suitable for the operation of the gas compressor 20 regardless of the temperature of the natural evaporative gas in the LNG cargo shed. Can be cooled and supplied to the gas compressor 20 side, and if the LNG liquid level in the LNG cargo tank is low, the natural evaporative gas compression and supply are difficult to be performed smoothly, and the injected LNG It is possible to solve the problem that the compressor is forced to be burdened by mixing.

3 DFDE propulsion system engine 10 evaporative gas cooler 20 gas compressor 30 engine supply gas cooler 41 gas flow meter 42 load distribution valve 50 reliquefaction heat exchanger 61 refrigerant compander 61a refrigerant compressor 61b refrigerant expander 62 refrigerant cooling Machine 63 refrigerant buffer tank 64a first refrigerant supply conduit 64b second refrigerant supply conduit 64c third refrigerant supply conduit 65 temperature control valve 70 LNG evaporative gas separator 80 LNG supply pump 90 gas incinerator

Claims (17)

An evaporative gas cooler 10 that receives a supply of natural evaporative gas (N-BOG) generated in a liquefied natural gas cargo tank and cools it by exchanging heat with the refrigerant;
A gas compressor 20 that receives natural evaporative gas cooled by the evaporative gas cooler 10 and compresses the natural evaporative gas at a gas pressure that can be used for a DFDE (Dual Fuel Diesel Electric) propulsion type engine 3;
An engine supply gas cooler 30 that cools natural evaporative gas heated through the gas compressor 20 to a temperature usable for the DFDE propulsion system engine 3 and supplies the natural evaporative gas to the DFDE propulsion system engine 3 side;
Re-liquefaction of excess natural evaporative gas that is not used in the DFDE propulsion system engine 3 is supplied downstream of the engine supply gas cooler 30 and heat-exchanged with the refrigerant to be cooled and re-liquefied and supplied to the LNG freight side An evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function, comprising a heat exchanger 50. A plurality of refrigerant compressors 61a installed to compress the gaseous refrigerant in multiple stages;
A refrigerant expander 61b provided with a refrigerant expander 61b that passes through the refrigerant compressor 61a, expands the refrigerant that has been compressed and heated, and cools it at a temperature lower than the cooling point of LNG;
The refrigerant cooler 62 further comprising a refrigerant cooler 62 that cools the refrigerant flowing into or out of the refrigerant compressor 61a and increases the compression efficiency of the refrigerant compressor 61a. An evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function.   Refrigerant lost during flow and heat exchange with a storage space capable of receiving a large amount of gaseous refrigerant in the interior and a gas discharge port connected to a refrigerant supply device and selectively receiving refrigerant The refrigerant buffer tank 63 further includes a refrigerant buffer tank 63 that compensates for the above-mentioned problem or buffers the shock caused by fluctuations in the pressure and flow rate of the refrigerant supply conduit to relieve the overload pressure. An evaporative gas treatment apparatus for an electric propulsion LNG carrier having the reliquefaction function described. A first refrigerant that supplies the refrigerant that has passed through the refrigerant compander 61 to the reliquefying heat exchanger 50 and supplies the refrigerant that has been heated through the reliquefying heat exchanger 50 to the refrigerant buffer tank 63. A supply conduit 64a;
A second refrigerant supply conduit that supplies the refrigerant that has passed through the refrigerant compander 61 to the evaporative gas cooler 10 and supplies the refrigerant that has been heated through the evaporative gas cooler 10 to the refrigerant buffer tank 63. The evaporative gas processing apparatus for an electric propulsion LNG carrier having a reliquefaction function according to claim 3, further comprising: 64b.   And a temperature control valve 65 for adjusting the flow rate of the refrigerant passing through the second refrigerant supply conduit 64b in proportion to the temperature and flow rate of the natural evaporative gas passing through the evaporative gas cooler 10. The evaporative gas processing apparatus of the electric propulsion LNG carrier which has a reliquefaction function of Claim 4 characterized by these.   The refrigerant that has passed through the plurality of refrigerant compressors 61a is supplied to the reliquefaction heat exchanger 50, and heat exchange with the refrigerant that passes through the first refrigerant supply conduit 64a while passing through the reliquefaction heat exchanger 50. The evaporative gas of the electric propulsion LNG carrier having a reliquefaction function according to claim 2, further comprising a third refrigerant supply conduit 64c for supplying the refrigerant cooled by the refrigerant to the refrigerant expander 61b. Processing equipment.   The engine supply gas cooler 30 is composed of a fresh water cooler that exchanges heat using fresh water as a refrigerant, and the refrigerant cooler 62 is composed of a sea water cooler that exchanges heat using sea water as a refrigerant. The evaporative gas processing apparatus of the electric propulsion LNG carrier which has the reliquefaction function of Claim 2 to do. The evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to claim 1, wherein the refrigerant is N ₂ having a lower cooling point than LNG and not explosive.   The evaporative gas cooler (10) has an LNG outflow path open at the bottom so that LNG partially liquefied by heat exchange with a refrigerant is separated and supplied to the LNG cargo yard by gravity. Item 10. An evaporative gas treatment apparatus for an electric propulsion LNG carrier having the reliquefaction function according to Item 1. A gas flow meter 41 for measuring a supply amount of natural evaporative gas flowing into the DFDE propulsion system engine 3;
The natural evaporative gas flowing into the reliquefaction heat exchanger 50 is determined by the amount of gas required by the DFDE propulsion engine 3 and the amount of gas measured by the gas flow meter 41 in accordance with load fluctuations due to ship operation. The evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to claim 1, further comprising a load distribution valve for adjusting a flow rate.   The electric propulsion LNG having a reliquefaction function according to claim 10, wherein the refrigerant compander 61 adjusts the flow rate or flow rate of the refrigerant in proportion to the flow rate passing through the load distribution valve 42. Evaporative gas treatment equipment for transport ships. A storage space that can accommodate both liquefied LNG reliquefied by the reliquefied heat exchanger 50 and supplied to the LNG cargo tank side, and gas or N ₂ separated and generated by the reliquefied LNG;
An LNG evaporative gas separator 70 having a gas discharge port for discharging the internal gas to the outside, and supplying only the reliquefied LNG in a state where the gas or N ₂ is separated to the LNG cargo ship side. The evaporative gas processing apparatus of the electric propulsion LNG carrier having the reliquefaction function according to claim 1,   When the LNG reliquefied by the reliquefaction heat exchanger 50 is not naturally supplied to the LNG cargo shed side due to gravity and pressure loss in the piping, the liquefied LNG is forcibly supplied to the LNG cargo shed side. The evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to claim 1, further comprising an LNG supply pump 80 installed on the LNG supply conduit.   When the re-liquefied heat exchanger 50 operates abnormally due to a failure, damage, malfunction, or when the operation is stopped, natural evaporation to the extent that the amount of gas required by the DFDE propulsion type engine 3 is exceeded. The evaporative gas treatment apparatus for an electric propulsion LNG carrier having a reliquefaction function according to claim 1, further comprising a gas incinerator 90 that receives and incinerates and removes gas.   When the ship is operated at a preset economic operation speed, the system further includes an operation state display device that generates a signal that allows the state of the economic operation to be recognized with the naked eye or the auditory sense in the ship's wheelhouse. The evaporative gas processing apparatus of the electric propulsion LNG carrier which has the reliquefaction function of Claim 1 characterized by the above-mentioned. An evaporative gas pretreatment stage for primary cooling of natural evaporative gas (Natural Boil-Off Gas: N-BOG) generated in a liquefied natural gas cargo tank;
In the evaporative gas pretreatment stage, the evaporative gas compression stage compresses at a gas pressure that can be used for a DFDE (Dual Fuel Diesel Electric) propulsion system engine by receiving the supply of the natural evaporative gas first cooled in the evaporative gas pretreatment stage. When,
An evaporative gas cooling stage in which the natural evaporative gas heated through the evaporative gas compression stage is secondarily cooled at a temperature usable for the DFDE propulsion system engine 3 and supplied to the DFDE propulsion system engine 3 side;
A surplus gas reliquefaction stage in which excess natural evaporative gas that is not used in the DFDE propulsion system engine 3 is cooled and reliquefied by the reliquefaction heat exchanger 50 and supplied to the LNG cargo bunker side. An evaporative gas treatment method for an electric propulsion LNG carrier having a reliquefaction function.   When the reliquefied heat exchanger 50 operates abnormally due to failure, damage, malfunction, or when the operation is stopped, the natural evaporative gas exceeds the amount of gas required by the DFDE propulsion type engine 3 The method for treating an evaporative gas of an electric propulsion LNG carrier having a re-liquefaction function according to claim 16, further comprising a surplus gas incineration step of incinerating and removing after being supplied.

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