JP6609176B2 - Ship - Google Patents

Description

  The present invention relates to a ship including a gas engine for propulsion.

  Conventionally, a ship including a tank for storing liquefied natural gas and a propulsion gas engine in which boil-off gas generated in the tank is supplied as fuel gas is known. Such ships include a mechanical propulsion type in which a gas engine directly drives a propeller for propulsion and an electric propulsion type in which a gas engine rotates and drives a propeller for propulsion through a generator and a motor. is there.

  For example, Patent Document 1 discloses a mechanical propulsion-type ship 100 as shown in FIG. In this ship 100, the boil-off gas generated in the tank 110 is guided to the MEGI engine (two-stroke engine) by the supply line 120 as fuel gas. The supply line 120 is provided with a multistage compressor 121 that compresses the boil-off gas to a high pressure of 15 to 40 MPa. A branch line 130 branches from the supply line 120 inside the compressor 121, and this branch line 130 is connected to the DF engine. The DF engine is used for propulsion and power generation.

  Further, a return line 140 branches from the supply line 120 on the downstream side of the compressor 121, and the return line 140 is connected to the tank 110. The return line 140 is provided with an expansion valve 141 and a gas-liquid separator 142 in order from the upstream side. The high-pressure and high-temperature boil-off gas returned to the tank 110 through the return line 140 is cooled and at least partially liquefied by the low-pressure and low-temperature boil-off gas flowing in the supply line 120 in the heat exchanger 160, and then the expansion valve 141. Is expanded into a low-pressure and low-temperature gas-liquid two-phase state. The gas-liquid two-phase boil-off gas is separated into a gas component and a liquid component by the gas-liquid separator 142, and only the liquid component is returned to the tank 110. On the other hand, the gas component is led from the gas-liquid separator 142 to the supply line 120 through the recirculation line 150 and merges with the boil-off gas flowing into the heat exchanger 160.

  Further, in the ship 100 shown in FIG. 6, the boil-off gas cooled by the heat exchanger 160 is additionally cooled by the gas component flowing in the recirculation line 150 by the cooler 170.

Special table 2015-505941 gazette

  In the ship 100 shown in FIG. 6, the boil-off gas returned to the tank 110 through the return line 140 is cooled only by the cold heat of the boil-off gas flowing through the supply line 120 and the recirculation line 150. Therefore, the reliquefaction rate of the boil-off gas flowing through the return line 140 (ratio of the reliquefaction amount to the boil-off gas return amount) is not very good.

  Then, an object of this invention is to provide the ship which can improve the reliquefaction rate of the boil-off gas returned to a tank through a return line.

  In order to solve the above-described problems, the ship of the present invention includes a main gas engine that rotationally drives a propeller for propulsion, a tank that stores liquefied natural gas, and a boil-off gas generated in the tank as a fuel gas. A first supply line provided with a compressor, leading to the engine, a return line provided with an expansion device branched from the first supply line downstream of the compressor and connected to the tank, and for power generation An auxiliary gas engine, a second supply line for taking out the liquefied natural gas from the tank and leading the vaporized gas obtained by vaporizing the liquefied natural gas to the auxiliary gas engine as a fuel gas, and the compressor in the first supply line Heat exchange between the boil-off gas flowing to the upstream side portion and the boil-off gas flowing to the upstream portion from the expansion device in the return line. Part of the liquefied natural gas by performing heat exchange between the first heat exchanger, the boil-off gas flowing out from the first heat exchanger in the return line, and the liquefied natural gas flowing in the second supply line Or the 2nd heat exchanger which vaporizes all is provided, It is characterized by the above-mentioned.

  According to the above configuration, the high-pressure and high-temperature boil-off gas returned to the tank through the return line is cooled by the low-pressure and low-temperature boil-off gas flowing in the first supply line in the first heat exchanger, and then the second heat The exchanger is cooled by liquefied natural gas flowing to the second supply line. And since the boil-off gas cooled in this way is expanded with an expansion | swelling apparatus, the boil-off gas returned to a tank can be partially reliquefied. In addition, since the second heat exchanger cools the boil-off gas using not only the sensible heat of the liquefied natural gas but also latent heat, the reliquefaction rate of the boil-off gas returned to the tank through the return line can be improved. it can.

  The second heat exchanger may be formed integrally with the first heat exchanger. According to this structure, a 1st heat exchanger and a 2nd heat exchanger can be made into a single unit, and installation space can be reduced.

  The second supply line may be provided with a forced vaporizer that forcibly vaporizes liquefied natural gas that has not been vaporized in the second heat exchanger. According to this configuration, even when the amount of boil-off gas returned to the tank through the return line is small, a sufficient amount of vaporized gas can be supplied to the auxiliary gas engine.

  In the second supply line, a gas-liquid separator is provided between the second heat exchanger and the forced vaporizer, and the ship has an upstream end connected to the gas-liquid separator, You may further provide the bypass line by which the gas component isolate | separated by the said gas-liquid separator which a downstream end was connected to the said 2nd supply line in the downstream rather than the said forced vaporizer flows. According to this configuration, since only the liquid component separated by the gas-liquid separator is guided to the forced vaporizer, the amount of heat used for forced vaporization by the forced vaporizer can be suppressed.

  The gas-liquid separator is a first gas-liquid separator, and the second supply line has a cooler, a second gas, in order from the upstream side to the downstream side of the connection point of the downstream end of the bypass line. A liquid separator and a heater may be provided. According to this configuration, since the heavy components are removed from the vaporized gas by the action of the cooler and the second gas-liquid separator, the vaporized gas having a high methane number can be supplied to the sub-gas engine. Moreover, since the heater is provided in the downstream rather than the 2nd gas-liquid separator, the vaporization gas of suitable temperature can be supplied to a subgas engine.

  The ship described above flows into or out of the first heat exchanger in the return gas and the vaporized gas flowing in the second supply line between the gas-liquid separator and the heater. A third heat exchanger that performs heat exchange with the boil-off gas may be further provided. According to this configuration, the boil-off gas returned to the tank can be further cooled, and the reliquefaction rate of the boil-off gas can be further improved. In particular, if the boil-off gas flowing into the first heat exchanger is cooled by the third heat exchanger, more heat is taken from the boil-off gas than when the boil-off gas flowing out from the first heat exchanger is cooled. be able to.

  The third heat exchanger may be formed integrally with at least the first heat exchanger. According to this structure, a 1st heat exchanger and a 3rd heat exchanger or a 1st-3rd heat exchanger can be made into a single unit, and an installation space can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the reliquefaction rate of the boil off gas returned to a tank through a return line can be improved.

1 is a schematic configuration diagram of a ship according to a first embodiment of the present invention. It is a Mollier diagram of boil-off gas flowing through the first supply line and the return line. It is a schematic block diagram of the ship which concerns on 2nd Embodiment of this invention. It is a schematic block diagram of the ship which concerns on 3rd Embodiment of this invention. It is a schematic block diagram of the ship which concerns on 4th Embodiment of this invention. It is a schematic block diagram of the conventional ship.

(First embodiment)
FIG. 1 shows a ship 1A according to the first embodiment of the present invention. The marine vessel 1A includes a main gas engine 11 for propulsion and a sub gas engine 13 for power generation (that is, for inboard power). In the illustrated example, one main gas engine 11 and one sub gas engine 13 are provided, but a plurality of main gas engines 11 may be provided, or a plurality of sub gas engines 13 may be provided.

  In the present embodiment, the ship 1A is a liquefied natural gas (hereinafter referred to as LNG) carrier, and a plurality of tanks 15 for storing LNG are installed in the ship 1A as cargo tanks. However, the ship 1A may be an LNG fuel ship equipped with one or more tanks 15 for storing LNG as fuel tanks.

  The temperature of the liquid phase (ie, LNG) in the tank 15 is about −160 ° C. The pressure of the gas phase (that is, boil-off gas) in the tank 15 is desirably a low pressure that is slightly higher than the atmospheric pressure (0.1 MPa).

  In the tank 15, LNG is vaporized by natural heat input, and boil-off gas (hereinafter referred to as BOG) is generated. BOG generated in the tank 15 from all or a part of the tank 15 is guided to the main gas engine 11 as fuel gas by the first supply line 2. On the other hand, LNG in all or part of the tank 15 is taken out from the tank 15 by the second supply line 4 and is vaporized while flowing through the second supply line 4. Vaporized gas (hereinafter referred to as VG) vaporized by LNG is guided as a fuel gas to the secondary gas engine 13 through the second supply line 4.

  Further, the second supply line 4 and the first supply line 2 are connected by a supply line 7, and the VG vaporized by LNG while flowing through the second supply line 4 is also led to the main gas engine 11 through the supply line 7. . That is, the fuel gas supplied to the main gas engine 11 is BOG and / or VG. The replenishment line 7 is provided with a pressure control valve 71 (which may be a flow control valve) and a check valve 72. Although not shown, another supply line may be connected from the middle of the compressor 21 to the second supply line 4 so that not only VG but also BOG as fuel gas may be supplied to the auxiliary gas engine 13.

  In the present embodiment, the ship 1A is a mechanical propulsion type, and the main gas engine 11 directly drives the propeller for propulsion 12 to rotate. However, the ship 1A may be an electric propulsion type, and the main gas engine 11 may rotationally drive the propeller 12 for propulsion through a generator and a motor.

  The main gas engine 11 is a diesel cycle type two-stroke engine having a high fuel gas injection pressure of about 20 to 35 MPa, for example. However, the main gas engine 11 may be an Otto cycle type two-stroke engine having an intermediate pressure of, for example, a fuel gas injection pressure of about 1 to 2 MPa. Alternatively, in the case of electric propulsion, the main gas engine 11 may be an Otto cycle type four-stroke engine having a low fuel gas injection pressure of, for example, about 0.5 to 1 MPa. The main gas engine 11 may be a gas-only combustion engine that burns only fuel gas, or may be a dual fuel engine that burns one or both of fuel gas and fuel oil (binary fuel engine). In this case, the fuel gas may be burned by the Otto cycle, and the fuel oil may be burned by the diesel cycle).

  The auxiliary gas engine 13 is an Otto cycle type four-stroke engine having a low fuel gas injection pressure of about 0.5 to 1 MPa, for example, and is connected to the generator 14. The auxiliary gas engine 13 may be a gas-only engine that burns only fuel gas, or may be a dual fuel engine that burns one or both of fuel gas and fuel oil.

  In the present embodiment, the first supply line 2 guides BOG from all the tanks 15 to the main gas engine 11. However, the first supply line 2 may lead BOG from one or several of the tanks 15 to the main gas engine 11. Specifically, the first supply line 2 includes the same number of branch paths 2a as the tank 15 and one common path 2b. Each branch path 2 a extends from the upstream end of the common path 2 b to the inside of the corresponding tank 15, and the downstream end of the common path 2 b is connected to the main gas engine 11. A compressor 21 is provided in the common path 2b.

  In the present embodiment, the compressor 21 compresses the BOG to the supercritical state, in other words, to a pressure higher than the supercritical pressure Ps (intersection of the saturated liquid line L1 and the saturated vapor line L2) in FIG. For example, the pressure of BOG discharged from the compressor 21 is about 20 to 35 MPa, and the temperature is about 35 to 55 ° C.

  The return line 3 branches from the common path 2 b of the first supply line 2 on the downstream side of the compressor 21. The return line 3 is connected to all the tanks 15 in this embodiment. However, the return line 3 may be connected to one or several of the tanks 15. Specifically, the return line 3 includes the same number of branch paths 3a as the tank 15 and one common path 3b. The upstream end of the common path 3b is connected to the common path 2b of the first supply line 2, and each branch path 3a extends from the downstream end of the common path 3b to the inside of the corresponding tank 15. The tip of each branch path 3a may be located in the gas phase or in the liquid phase. Each branch passage 3a is provided with an expansion device 32 (for example, an expansion valve such as a Joule-Thomson valve that realizes adiabatic expansion change, an expansion turbine, an ejector, or the like). On the other hand, a flow control valve 31 is provided in the common path 3b. However, in the common path 3b, a pressure control valve may be provided instead of the flow control valve 31, or neither the flow control valve nor the pressure control valve may be provided.

  Depending on the load of the main gas engine 11, the amount of BOG used in the main gas engine 11 may be smaller than the amount of BOG generated in the tank 15. The return line 3 is a line for returning such surplus BOG (difference between the BOG generation amount and the BOG usage amount) to the tank 15.

  In the present embodiment, the second supply line 4 takes out LNG from all the tanks 15. However, the second supply line 4 may take out LNG from one or several of the tanks 15. Specifically, the second supply line 4 includes the same number of branch paths 4a as the tank 15 and one common path 4b. A pump 41 is disposed in each tank 15. Each branch path 4 a extends from the upstream end of the common path 4 b to the corresponding pump 41 in the tank 15, and the downstream end of the common path 4 b is connected to the auxiliary gas engine 13.

  Further, in the present embodiment, a first heat exchanger 61 and a second heat exchanger 62 are provided to cool the BOG returned to the tank 15 through the return line 3. The first heat exchanger 61 includes a BOG that flows in an upstream portion of the common path 2b of the first supply line 2 relative to the compressor 21 and a common path 3b of the return line 3 (that is, an upstream portion of the expansion device 32). Heat exchange with the BOG flowing in The second heat exchanger 62 performs heat exchange between the BOG flowing out of the first heat exchanger 61 in the common path 3b of the return line 3 and the LNG flowing in the common path 4b of the second supply line 4 to perform LNG. Vaporize part or all of

  In other words, after the high-pressure and high-temperature BOG returned to the tank 15 through the return line 3 is cooled by the low-pressure and low-temperature BOG flowing in the common path 2b of the first supply line 2 in the first heat exchanger 61, The second heat exchanger 62 cools the LNG flowing through the common path 4b of the second supply line 4.

  A first gas-liquid separator 42, a forced vaporizer 43, a cooler 51, a second gas-liquid separator 52, and a heater 53 are provided in order from the upstream side in the common path 4b of the second supply line 4. . Further, a bypass line 5 is connected to the common path 4b so as to bypass the forced vaporizer 43. The upstream end of the replenishment line 7 described above is connected to the second supply line 4 between the cooler 51 and the second gas-liquid separator 52. However, the upstream end of the supply line 7 may be connected to the second supply line 4 between the second gas-liquid separator 52 and the heater 53. On the other hand, the downstream end of the supply line 7 is connected to the first supply line 2 between the first heat exchanger 61 and the compressor 21.

  The first gas-liquid separator 42 separates the gas-liquid two-phase LNG flowing out from the second heat exchanger 62 into a gas component and a liquid component. The first gas-liquid separator 42 is connected to the upstream end of the bypass line 5, and the downstream end of the bypass line 5 is connected to the second supply line 4 between the forced vaporizer 43 and the cooler 51. Yes. In other words, the cooler 51 is located downstream of the connection point of the downstream end of the bypass line 5 in the second supply line 4. The gas component separated by the first gas-liquid separator 42 flows through the bypass line 5.

  The forced vaporizer 43 forcibly vaporizes the liquid component separated by the first gas-liquid separator 42, that is, LNG that has not been vaporized by the second heat exchanger 62, and generates VG. The VG flowing out from the forced vaporizer 43 merges with the gas component from the bypass line 5 and then flows into the cooler 51.

  The cooler 51 cools the VG to generate a liquid component whose main component is a component other than methane. The generated liquid component is collected by the second gas-liquid separator 52. As a result, most of the heavy components (for example, ethane, propane, butane, etc.) are removed from the VG, so that VG having a high methane number can be supplied to the auxiliary gas engine 13. The liquid component collected by the second gas-liquid separator 52 is returned to the one or more tanks 15 through the drain line 54. Further, the VG that has passed through the second gas-liquid separator 52 is heated by the heater 53. As a result, VG having an appropriate temperature can be supplied to the auxiliary gas engine 13. For example, the cooler 51 cools VG to −140 to −100 ° C., and the heater 53 heats the VG so that the VG temperature at the inlet of the auxiliary gas engine 13 becomes 5 to 50 ° C.

  Next, the state change of the BOG flowing through the first supply line 2 and the return line 3 will be described with reference to FIGS.

  First, the low pressure and low temperature saturated (point A) BOG flows from the tank 15 into the first heat exchanger 61 through the first supply line 2 and is cooled by cooling the high pressure and high temperature BOG flowing through the return line 3. (Superheated) (Point A → Point B). Thereafter, the BOG is compressed to a supercritical state by the compressor 21 (point B → point C). The BOG flowing into the return line 3 from the first supply line 2 is cooled by the first heat exchanger 61 (point C → point D) and then cooled by the second heat exchanger 62 (point D → point E). ). BOG is liquefied by cooling in the first heat exchanger 61 or cooling in the second heat exchanger 62. The liquid BOG that has flowed out of the second heat exchanger 62 is expanded by the expansion device 32 to be in a low-pressure and low-temperature gas-liquid two-phase state (point E → point F). Thereby, BOG is partially reliquefied.

  As described above, in the ship 1A of the present embodiment, the BOG cooled by the first heat exchanger 61 and the second heat exchanger 62 is expanded by the expansion device 32, so that the BOG returned to the tank 15 is It can be partially liquefied. Moreover, since the second heat exchanger 62 cools the BOG using not only the sensible heat of LNG but also the latent heat, the reliquefaction rate of the BOG returned to the tank 15 through the return line 3 can be improved. .

  Furthermore, in the present embodiment, when the main gas engine 11 is stopped, the BOG can be partially liquefied only by driving the compressor 21. This is because the secondary gas engine 13 for power generation is always operating, and LNG always flows through the second supply line 4. Therefore, the BOG can be partially reliquefied with a small amount of electric power by rationally using the second supply line 4 for power generation as a cold heat source.

(Second Embodiment)
Next, with reference to FIG. 3, the ship 1B which concerns on 2nd Embodiment of this invention is demonstrated. In the present embodiment and third and fourth embodiments to be described later, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the first embodiment, the first heat exchanger 61 and the second heat exchanger 62 are provided separately. However, in the present embodiment, the second heat exchanger 62 is integrated with the first heat exchanger 61. Is formed. For this reason, the 1st heat exchanger 61 and the 2nd heat exchanger 62 can be made into the single unit 6, and an installation space can be reduced.

(Third embodiment)
Next, a ship 1C according to a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, as a configuration for cooling the BOG returned to the tank 15 through the return line 3, a third heat exchanger 63 is provided in addition to the first heat exchanger 61 and the second heat exchanger 62. Yes.

  The third heat exchanger 63 is between the VG flowing into the second supply line 4 between the second gas-liquid separator 52 and the heater 53 and the BOG flowing into the first heat exchanger 61 in the return line 3. Perform heat exchange. According to this configuration, the BOG returned to the tank 15 can be further cooled, and the BOG reliquefaction rate can be further improved.

  By the way, the 3rd heat exchanger 63 is VG which flows into the 2nd supply line 4 between the 2nd gas-liquid separator 52 and the heater 53, and BOG which flows out from the 1st heat exchanger 61 in the return line 3. Heat exchange may be performed between them. However, if the BOG is cooled on the upstream side of the first heat exchanger 61 by the third heat exchanger 63 as shown in FIG. 4, the BOG is compared to the case where it is cooled on the downstream side of the first heat exchanger 61. Can take away a lot of heat.

  In addition, although illustration is abbreviate | omitted, you may preliminarily cool the boil-off gas which flows into the return line 3 in the upstream of the 3rd heat exchanger 63 with fresh water or seawater.

(Fourth embodiment)
Next, with reference to FIG. 5, the ship 1D which concerns on 4th Embodiment of this invention is demonstrated. In the present embodiment, the third heat exchanger 63 is formed integrally with the first heat exchanger 61 and the second heat exchanger 62. According to this structure, the 1st-3rd heat exchangers 61-63 can be made into the single unit 6, and an installation space can be reduced. However, although illustration is omitted, the third heat exchanger 63 may be formed integrally with only the first heat exchanger 61. Even in this configuration, the first heat exchanger 61 and the third heat exchanger 63 can be formed as a single unit, and the installation space can be reduced.

(Other embodiments)
The present invention is not limited to the first to fourth embodiments described above, and various modifications can be made without departing from the gist of the present invention.

  For example, the compressor 21 may compress BOG to a pressure lower than the supercritical pressure Ps. In this case, the BOG returned to the tank 15 through the return line 3 is cooled by the first heat exchanger 61 and becomes a gas-liquid two-phase state. However, if the BOG is compressed to a supercritical state as in the above embodiment, the BOG reliquefaction rate can be increased as compared with the case where the BOG is compressed to a pressure lower than the supercritical pressure Ps.

  Further, on the upstream side of the cooler 51 of the second supply line 4, the first gas-liquid separator 42 and the bypass line 5 may be omitted, and only the forced vaporizer 43 may be provided. However, if the first gas-liquid separator 42 and the bypass line 5 are provided as in the first to fourth embodiments, the liquid component separated by the first gas-liquid separator 42 is included in the forced vaporizer 43. Therefore, the amount of heat used for forced vaporization by the forced vaporizer 43 can be suppressed.

  Further, when the first gas-liquid separator 42 and the bypass line 5 are omitted, the forced vaporizer 43 may also be omitted. However, if the forced vaporizer 43 is provided as in the first to fourth embodiments, even if the amount of BOG returned to the tank 15 through the return line 3 is small, a sufficient amount of VG is transferred to the secondary gas. It can be supplied to the engine 13.

  The second supply line 4 is not necessarily provided with the cooler 51, the second gas-liquid separator 52, and the heater 53.

  Further, one or both of the main gas engine 11 and the auxiliary gas engine 13 are not necessarily a reciprocating engine, and may be a gas turbine engine.

1A, 1B Ship 11 Main gas engine 12 Propeller for propulsion 13 Sub gas engine 15 Tank 2 First supply line 21 Compressor 3 Return line 32 Expansion device 4 Second supply line 42 First gas-liquid separator 43 Forced vaporizer 5 Bypass Line 51 Cooler 52 Second gas-liquid separator 53 Heater 61 First heat exchanger 62 Second heat exchanger 63 Third heat exchanger

Claims (6)

A main gas engine that rotationally drives a propeller for propulsion;
A tank for storing liquefied natural gas;
A first supply line provided with a compressor for guiding boil-off gas generated in the tank to the main gas engine as fuel gas;
A return line provided with an expansion device, branched from the first supply line downstream of the compressor and connected to the tank;
A sub-gas engine for power generation,
A second supply line that takes out liquefied natural gas from the tank and guides the vaporized gas obtained by vaporizing the liquefied natural gas to the auxiliary gas engine as fuel gas;
A first heat exchanger that exchanges heat between the boil-off gas that flows to the upstream side of the compressor in the first supply line and the boil-off gas that flows to the upstream side of the expansion device in the return line;
Second heat that exchanges heat between the boil-off gas flowing out from the first heat exchanger and the liquefied natural gas flowing in the second supply line in the return line to vaporize a part or all of the liquefied natural gas. An exchanger ,
The ship provided with the forced vaporizer which forcibly vaporizes the liquefied natural gas which was not vaporized with the said 2nd heat exchanger in the said 2nd supply line .   The ship according to claim 1, wherein the second heat exchanger is formed integrally with the first heat exchanger. In the second supply line, a gas-liquid separator is provided between the second heat exchanger and the forced vaporizer,
A bypass line in which an upstream end is connected to the gas-liquid separator and a downstream end is connected to the second supply line on the downstream side of the forced vaporizer and the gas component separated in the gas-liquid separator flows. The ship according to claim 1, further comprising: The gas-liquid separator is a first gas-liquid separator,
Wherein the second supply line, downstream of the connection point of the downstream end of the bypass line, in order from the upstream side, the cooler, the second gas-liquid separator and heater is provided, in claim 3 The listed ship. A vaporized gas flowing into the second supply line between the second gas-liquid separator and the heater, and a boil-off gas flowing into the first heat exchanger or flowing out of the first heat exchanger in the return line; The ship of Claim 4 further provided with the 3rd heat exchanger which performs heat exchange between. The ship according to claim 5 , wherein the third heat exchanger is formed integrally with at least the first heat exchanger.

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