JP6600247B2 - Ship - Google Patents

Description

  The present invention relates to a ship including a main gas engine for propulsion and a sub gas engine for power generation.

  Conventionally, a ship including a main gas engine for propulsion and a sub gas engine for power generation is known. For example, Patent Document 1 discloses a ship 100 as shown in FIG.

  Specifically, the ship 100 includes a tank 110 that stores liquefied natural gas, a main gas engine 130 for propulsion, and a sub gas engine 140 for power generation. The main gas engine 130 is a diesel cycle type engine with a high fuel gas injection pressure, and the sub gas engine 140 is a dual fuel engine with a low fuel gas injection pressure.

  The tank 110 is connected to the high-pressure compressor 120 via the air supply line 101, and the high-pressure compressor 120 is connected to the main gas engine 130 via the first supply line 102. The air supply line 101 guides the boil-off gas generated in the tank 110 to the high-pressure compressor 120, and the high-pressure compressor 120 compresses the boil-off gas to a high pressure (for example, about 30 MPa). The first supply line 102 guides high-pressure boil-off gas discharged from the high-pressure compressor 120 to the main gas engine 130.

  Further, the second supply line 103 is connected to the auxiliary gas engine 140 from the middle of the high-pressure compressor 120. When the amount of boil-off gas generated is larger than the fuel gas consumption of the main gas engine 130, surplus gas is supplied to the sub gas engine 140 through the second supply line 103.

  Furthermore, the ship 100 shown in FIG. 6 has a configuration for supplying a sufficient amount of fuel gas to the main gas engine 130 even when the amount of boil-off gas generated is smaller than the fuel gas consumption of the main gas engine 130. It has been adopted. Specifically, a pump 150 is disposed in the tank 110, and the pump 150 is connected to the suction drum 160 through the first supply line 104. The suction drum 160 is connected to the high-pressure pump 170 through the second supply line 105, the high-pressure pump 170 is connected to the gas heater 180 through the third supply line 106, and the fourth supply line 107 is connected to the first supply line 102 from the gas heater 180. ing.

  Further, a connection line 190 is branched from the first supply line 102 at a downstream side of a position where the fourth supply line 107 is connected, and the connection line 190 is connected to the second supply line 103. The communication line 190 is provided with a check valve 191 with a pressure adjustment function. That is, the high-pressure gas in the first supply line 102 can be supplied to the auxiliary gas engine 140 after the pressure is reduced.

Japanese Patent Laying-Open No. 2015-145243

  However, in the ship 100 shown in FIG. 6, when the amount of boil-off gas generated is smaller than the consumption of the main gas engine 130, it is necessary to operate the high-pressure pump 170 in addition to the high-pressure compressor 120. From the viewpoint of preventing air pollution, it is desirable to reduce the amount of fuel oil consumed in the secondary gas engine 140, which is a dual fuel engine, as much as possible. It is necessary to let

  Accordingly, an object of the present invention is to provide a ship that can supply a sufficient amount of fuel gas to a main gas engine and a sub gas engine without using a high-pressure pump.

  In order to solve the above problems, a ship of the present invention includes a main gas engine for propulsion, a tank for storing liquefied natural gas, an air supply line for guiding boil-off gas generated in the tank to a compressor, A first supply line for guiding boil-off gas discharged from the compressor to the main gas engine, a sub-gas engine for power generation, and liquefied natural gas discharged from a pump disposed in the tank are guided to a forced vaporizer. A liquid supply line, a second supply line that guides the vaporized gas generated by the forced vaporizer to the sub-gas engine, and a bridge line that guides the vaporized gas from the second supply line to the gas supply line. It is characterized by comprising.

  According to the above configuration, since the liquefied natural gas is forcibly vaporized by the forced vaporizer and the vaporized gas is supplied to the secondary gas engine, a sufficient amount of fuel is supplied to the secondary gas engine without using a high-pressure pump. Gas can be supplied. Thereby, combustion of the fuel oil in a subgas engine becomes unnecessary, or the consumption of fuel oil can be suppressed. Moreover, when the boil-off gas is insufficient with respect to the fuel gas consumption of the main gas engine, the vaporized gas generated by the forced vaporizer is merged with the boil-off gas sucked into the compressor through the bridge line. Can do. Therefore, a sufficient amount of fuel gas can be supplied to the main gas engine without using a high-pressure pump. Note that the phrase “without using a high-pressure pump” does not exclude the provision of a high-pressure pump on a ship as an alternative means in the event of a compressor failure.

  The pump may discharge the liquefied natural gas so that the pressure of the vaporized gas generated by the forced vaporizer is higher than the fuel gas injection pressure of the auxiliary gas engine. According to this configuration, it is not necessary to provide a compressor in the second supply line, and the cost can be reduced.

  For example, the ship includes a first adjustment valve provided in the liquid supply line and capable of changing an opening degree, a second adjustment valve provided in the bridge line and capable of changing an opening degree, And a control device that controls the first regulating valve and the second regulating valve.

  The ship includes a pressure gauge that detects a pressure of the boil-off gas in the tank or the boil-off gas flowing through the air supply line, and the control device detects the amount of liquefied natural gas in the tank and the pressure gauge. The available amount of boil-off gas is calculated from the pressure of the boil-off gas, and when the available amount of boil-off gas is smaller than the fuel gas consumption of the main gas engine, the available amount of boil-off gas is The first regulating valve may be controlled. By the way, although the amount of boil-off gas generated varies depending on the pressure of the boil-off gas in the tank, it substantially depends on the amount of liquefied natural gas in the tank. For this reason, when the amount of liquefied natural gas supplied to the forced vaporizer is determined by comparing the fuel gas consumption of the main gas engine with the amount of boil-off gas generated, the pressure of the boil-off gas in the tank is arbitrarily requested. It is difficult to adjust within the range. In contrast, the available amount of boil-off gas is calculated from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the amount of liquefied natural gas supplied to the forced vaporizer is calculated accordingly. If determined, the boil-off gas is actively used when the pressure of the boil-off gas in the tank is high, and the amount of boil-off gas used can be reduced when the pressure of the boil-off gas in the tank is low. Therefore, the pressure of the boil-off gas in the tank can be easily adjusted within the required range.

  For example, the ship includes a pressure gauge that detects the pressure of boil-off gas in the tank or the boil-off gas that flows through the air supply line, and a flow meter that detects the flow rate of the boil-off gas that flows through the air supply line. The control device calculates an available amount of boil-off gas from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the flow rate of the boil-off gas detected by the flow meter is calculated. The second regulating valve may be controlled so that the boil-off gas can be used.

  Alternatively, the ship includes a pressure gauge that detects the pressure of the boil-off gas in the tank or the boil-off gas flowing in the air supply line, and a flow meter that detects the flow rate of the vaporized gas flowing in the bridge line, The control device calculates an available amount of boil-off gas from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the flow rate of the vaporized gas detected by the flow meter is The second adjustment valve may be controlled so as to be a deviation between the fuel gas consumption of the main gas engine and the available amount of the boil-off gas.

  Alternatively, the ship is a first pressure gauge that detects the pressure of the boil-off gas in the tank or the boil-off gas flowing in the air supply line, and is upstream of the position where the bridge line is connected in the air supply line. And a second pressure gauge that detects the pressure of the bridge line on the downstream side of the second regulating valve, and the control device detects the boil-off gas detected by the first pressure gauge. The second regulating valve may be controlled such that a deviation between the pressure of the bridge line and the pressure of the bridge line detected by the second pressure gauge becomes a predetermined value.

  Alternatively, the pressure gauge is a first pressure gauge located upstream of a position where the bridge line in the air supply line is connected, and detects the pressure of the bridge line downstream of the second regulating valve. 2 pressure gauges, and the control device is configured so that a deviation between the pressure of the boil-off gas detected by the first pressure gauge and the pressure of the bridge line detected by the second pressure gauge becomes a predetermined value. The second adjustment valve may be controlled.

  According to the present invention, a sufficient amount of fuel gas can be supplied to the main gas engine and the auxiliary gas engine without using a high-pressure pump.

1 is a schematic configuration diagram of a ship according to a first embodiment of the present invention. It is a graph which shows the relationship between the deviation of the pressure of the boil-off gas in a tank, and a setting pressure, and the available amount of boil-off gas. It is a schematic block diagram of the ship of a modification. 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 conventional ship.

(First embodiment)
FIG. 1 shows a ship 1A according to the first embodiment of the present invention. The ship 1A includes a tank 11 that stores liquefied natural gas (hereinafter referred to as LNG), a main gas engine 13 for propulsion, and a sub-gas engine 16 for power generation (that is, for inboard power).

  In the illustrated example, only one tank 11 is provided, but a plurality of tanks 11 may be provided. In the present embodiment, the ship 1A is an LNG carrier, and the ship 1A is equipped with a plurality of cargo tanks. That is, the tank 11 shown in FIG. 1 is each of a plurality of cargo tanks. In the illustrated example, one main gas engine 13 and one sub gas engine 16 are provided, but a plurality of main gas engines 13 may be provided, or a plurality of sub gas engines 16 may be provided. Good.

  In this embodiment, the ship 1A is a mechanical propulsion type, and the main gas engine 13 directly rotates and drives a screw propeller (not shown). However, the ship 1A may be an electric propulsion type, and the main gas engine 13 may rotationally drive the screw propeller via a generator and a motor.

  The main gas engine 13 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 13 may be an Otto cycle type two-stroke engine whose fuel gas injection pressure is an intermediate pressure of about 1 to 2 MPa, for example. Alternatively, in the case of electric propulsion, the main gas engine 13 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 13 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 16 is an Otto cycle type four-stroke engine having a low fuel gas injection pressure of, for example, about 0.5 to 1 MPa, and is connected to a generator (not shown). The auxiliary gas engine 16 may be a gas 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.

  The fuel gas of the main gas engine 13 is mainly boil-off gas (hereinafter referred to as BOG) generated in the tank 11 by natural heat input, and the fuel gas of the auxiliary gas engine 16 is mainly forced by LNG. The vaporized gas (hereinafter referred to as VG).

  Specifically, the tank 11 is connected to the compressor 12 by an air supply line 21, and the compressor 12 is connected to the main gas engine 13 by a first supply line 22. Further, a pump 14 is disposed in the tank 11, and the pump 14 is connected to the forced vaporizer 15 by a liquid feed line 31. The forced vaporizer 15 is connected to the auxiliary gas engine 16 by the second supply line 32.

  The air supply line 21 guides BOG generated in the tank to the compressor 12. In the present embodiment, the compressor 12 is a multistage high pressure compressor. The compressor 12 compresses the BOG to a high pressure. The first supply line 22 guides high-pressure BOG discharged from the compressor 12 to the main gas engine 13. However, the compressor 12 may be a low-pressure compressor, for example, when the fuel gas injection pressure of the main gas engine 13 is low.

  The liquid feed line 31 guides LNG discharged from the pump 14 to the forced vaporizer 15. The forced vaporizer 15 forcibly vaporizes LNG using, for example, steam generated in a boiler as a heat source, and generates VG. The second supply line 32 guides the VG generated by the forced vaporizer 15 to the auxiliary gas engine 16. The second supply line 32 is preferably provided with devices (for example, a cooler and a gas-liquid separator) for removing heavy components such as ethane from VG. As a result, VG having a high methane number can be supplied to the auxiliary gas engine 16.

  Further, a first bridge line 41 is connected to the air supply line 21 from the second supply line 32. The first bridge line 41 guides VG from the second supply line 32 to the air supply line 21 when the BOG is insufficient with respect to the fuel gas consumption Q1 of the main gas engine 13. As a result, BOG and VG are supplied to the main gas engine 13 as fuel gas.

  A second bridge line 51 is connected to the second supply line 32 from the middle of the compressor 12. The second bridge line 51 guides the BOG from the compressor 12 to the second supply line 32 when the BOG is greater than the fuel gas consumption Q1 of the main gas engine 13. As a result, VG and BOG (in some cases, only BOG) are supplied to the auxiliary gas engine 16 as fuel gas.

  The liquid supply line 31, the first bridge line 41, and the second bridge line 51 are provided with a first adjustment valve 33, a second adjustment valve 42, and a third adjustment valve 52, respectively, whose opening degree can be changed. These regulating valves 33, 42, 52 are controlled by the control device 6. In FIG. 1, only some signal lines are drawn for the sake of simplicity.

  In the present embodiment, each of the second adjustment valve 42 and the third adjustment valve 52 plays a role of opening or closing the bridge line (41 or 51). However, an opening / closing valve may be provided in the first bridge line 41 separately from the second adjustment valve 42, or an opening / closing valve may be provided in the second bridge line 51 separately from the third adjustment valve 52. .

  Further, in the present embodiment, the pressure of the VG generated by the forced vaporizer 15 in the pump 14 (in other words, the outlet pressure of the forced vaporizer 15) is higher than the fuel gas supply pressure of the auxiliary gas engine 16. Thus, LNG is discharged. That is, the pressure of VG flowing through the second supply line 32 is higher than the pressure of BOG in the tank 11. For this reason, when opening the 1st bridge line 41, the 2nd adjustment valve 42 reduces the pressure of VG to the same extent as the pressure of BOG in the tank 11. FIG. The air supply line 21 is provided with a check valve 23 on the upstream side of the position where the first bridge line 41 is connected. This prevents VG from the first bridge line 41 from flowing into the tank 11.

  The controller 6 includes a first gas engine controller (not shown) for controlling the fuel gas injection timing of the main gas engine 13 and a second gas engine controller for controlling the fuel gas injection timing of the auxiliary gas engine 16. Various signals are transmitted from (not shown). Then, the control device 6 calculates the fuel gas consumption Q1 of the main gas engine 13 from the signal transmitted from the first gas engine controller, and the auxiliary gas engine 16 from the signal transmitted from the second gas engine controller. The fuel gas consumption Q2 is calculated. However, the control device 6 may acquire the fuel gas consumption Q1 directly from the first gas engine controller. Further, the control device 6 may perform control based on the pressure of the VG flowing in the second supply line 32 without calculating the fuel gas consumption Q2 of the auxiliary gas engine 16.

  Furthermore, in the present embodiment, the air supply line 21 includes a pressure gauge 61 that detects the pressure Pb of the BOG flowing through the air supply line 21 and a flowmeter 62 that detects the flow rate Qb of the BOG flowing through the air supply line 21. Is provided. The pressure gauge 61 and the flow meter 62 are provided on either the upstream side or the downstream side of the check valve 23 as long as the pressure gauge 61 and the flow meter 62 are located upstream of the position where the first bridge line 41 is connected in the air supply line 21. Also good. However, the pressure gauge 61 may be provided in the tank 11 to detect the pressure of the BOG in the tank 11.

  The control device 6 first calculates the available amount Qa of BOG from the amount of LNG in the tank 11 and the BOG pressure Pb detected by the pressure gauge 61. Specifically, the control device 6 adds the pressure loss from the upstream end of the air supply line 21 to the position of the pressure gauge 61 to the pressure Pb of the BOG detected by the pressure gauge 61, and the BOG in the tank 11 is added. The pressure Pt is calculated. As shown in FIG. 2, the usable amount Qa of BOG increases as the deviation ΔP (= Pt−Ps) between the BOG pressure Pt in the tank 11 and the set pressure Ps increases. Here, the set pressure Ps is a pressure at which the BOG usable amount Qa becomes equal to the BOG generation amount Qn. Note that the BOG generation amount Qn varies depending on the pressure of the BOG in the tank 11, but substantially depends on the amount of LNG in the tank 11. Further, since the capacity of the tank 11 which is a cargo tank is very large, even when BOG and / or LNG is used as the fuel gas, the height of the liquid level of the LNG in the tank 11 does not change so much. For this reason, in this embodiment, the amount of LNG in the tank 11 is not a variable but is treated as a constant value (different between full load and empty load). Then, the control device 6 calculates an available amount Qa of BOG from the amount of LNG in the tank 11 and the deviation ΔP between the calculated pressure Pt of the BOG in the tank 11 and the set pressure Ps. However, when the capacity of the tank 11 is small, a level meter that detects the amount of LNG in the tank 11 may be provided in the tank 11 and the amount of LNG in the tank 11 may be treated as a variable.

  Next, the control device 6 compares the available amount Qa of BOG with the fuel gas consumption amount Q1 of the main gas engine 13. When the available amount Qa of BOG is larger than the fuel gas consumption Q1 of the main gas engine 13 (when BOG is more than the fuel gas consumption Q1 of the main gas engine 13), the control device 6 uses the second regulating valve. 42 is fully closed and the third adjustment valve 52 is opened to a predetermined opening.

  Further, the control device 6 determines that the deviation ΔQ (= Qa−Q1) between the BOG usable amount Qa and the fuel gas consumption Q1 of the main gas engine 13 is larger than the fuel gas consumption Q2 of the auxiliary gas engine 16. (ΔQ> Q2), the first adjustment valve 33 is fully closed after the operation of the forced vaporizer 15 is stopped. On the other hand, when ΔQ <Q2, the first adjustment valve 33 is opened to a predetermined opening degree. In the case of ΔQ> Q2, instead of fully closing the first adjustment valve 33, the operation of the forced vaporizer 15 can be continued with the opening degree of the first adjustment valve 33 stopped without stopping the operation of the forced vaporizer 15. A minimum opening may be used.

  The return line 34 branches from the liquid supply line 31 upstream of the first adjustment valve 33, and the portion of the LNG discharged from the pump 14 that is limited by the first adjustment valve 33 passes through the return line 34. Returned to the tank 11. When ΔQ> Q2 (that is, when Qa> Q1 + Q2), the difference between them is burned by a gas combustion device (not shown) or released into the atmosphere. Alternatively, when ΔQ> Q2, the difference between ΔQ and Q2 may be temporarily stored in the tank 11 if the pressure of the BOG in the tank 11 is lower than the set pressure of the safety valve (not shown).

  Conversely, when the available amount Qa of BOG is smaller than the fuel gas consumption Q1 of the main gas engine 13 (when the BOG is insufficient with respect to the fuel gas consumption Q1 of the main gas engine 13), the control device 6 The third adjustment valve 52 is fully closed, and the first adjustment valve 33 is controlled according to the available amount Qa of BOG. For example, when the BOG usable amount Qa is larger than the BOG generation amount Qn obtained in advance by calculation, the opening degree of the first adjustment valve 33 is relatively small, and the BOG usable amount Qa is reduced to BOG. When the amount is less than the generated amount Qn, the opening degree of the first regulating valve 33 is relatively increased. Further, the control device 6 controls the second regulating valve 42 so that the BOG flow rate Qb detected by the flow meter 62 becomes the BOG available amount Qa.

  As described above, in the marine vessel 1A of the present embodiment, LNG is forcibly vaporized by the forced vaporizer 15 and the VG is supplied to the secondary gas engine 16, so that the secondary gas engine is not used without using a high-pressure pump. A sufficient amount of fuel gas can be supplied to 16. Thereby, combustion of the fuel oil in the auxiliary gas engine 16 becomes unnecessary or the consumption amount of the fuel oil can be suppressed. Moreover, when the BOG is insufficient with respect to the fuel gas consumption Q 1 of the main gas engine 13, the VG generated by the forced vaporizer 15 is taken into the BOG through the first bridge line 41. Can be joined. Therefore, a sufficient amount of fuel gas can be supplied to the main gas engine 13 without using a high-pressure pump.

  Further, in the present embodiment, when the BOG available amount Qa is smaller than the fuel gas consumption amount Q1 of the main gas engine 13, the first regulating valve 33 is controlled according to the BOG available amount Qa. As described above, the BOG generation amount Qn varies depending on the pressure of the BOG in the tank 11, but substantially depends on the amount of LNG in the tank 11. For this reason, when the supply amount of LNG to the forced vaporizer 15 is determined by comparing the fuel gas consumption amount Q1 of the main gas engine 13 with the BOG generation amount Qn, the pressure of the BOG in the tank 11 is arbitrarily set. It is difficult to adjust within the required range. On the other hand, the available amount Qa of BOG is calculated from the amount of LNG in the tank 11 and the BOG pressure Pb detected by the pressure gauge 61, and the supply amount of LNG to the forced vaporizer 15 is determined accordingly. In this case, when the pressure of the BOG in the tank 11 is high, the BOG is actively used, and when the pressure of the BOG in the tank 11 is low, the amount of BOG used can be reduced. Therefore, the pressure of the BOG in the tank 11 can be easily adjusted within the required range.

<Modification>
In the above embodiment, when ΔQ> Q2, the difference between them is burned by a gas combustion apparatus (not shown) or released into the atmosphere. However, a return line 71 as shown in FIG. 3 may be adopted, and the difference between ΔQ and Q2 may be partially liquefied and returned to the tank 11. Alternatively, when the return line 71 is employed, the second bridge line 51 may be omitted.

  Specifically, the return line 71 branches from the first supply line 22 and is connected to the tank 11. The tip of the return line 71 may be located above the liquid level of LNG in the tank 11 or may be located below the liquid level. The return line 71 is provided with an expansion device 72 such as an expansion valve.

  Further, the return line 71 and the liquid supply line 31 are provided with a heat exchanger 73. The heat exchanger 73 cools the BOG flowing in the return line 71 upstream of the expansion device 72 (BOG returned to the tank 11) with LNG flowing in the liquid supply line 31. By being expanded after this cooling, the BOG returned to the tank 11 is partially reliquefied. On the other hand, the LNG flowing in the liquid feeding line 31 may be partially vaporized by taking heat from the BOG.

  Note that the modification shown in FIG. 3 is also applicable to second and third embodiments described later.

(Second Embodiment)
Next, with reference to FIG. 4, the ship 1B which concerns on 2nd Embodiment of this invention is demonstrated. In the present embodiment and the third embodiment 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 present embodiment, instead of the flow meter 62 shown in FIG. 1, a flow meter 63 that detects the flow rate Qv of VG flowing in the first bridge line 41 is provided in the first bridge line 41. The flow meter 63 may be located on either the upstream side or the downstream side of the second adjustment valve 42. Then, the control device 6 determines that the BOG usable amount Qa is smaller than the fuel gas consumption Q1 of the main gas engine 13 (when the BOG is insufficient with respect to the fuel gas consumption Q1 of the main gas engine 13). The second regulating valve 42 is controlled so that the flow rate Qv of VG detected by the total 63 becomes a deviation ΔA (= Q1−Qa) between the fuel gas consumption amount Q1 of the main gas engine 13 and the BOG usable amount Qa. To do.

  Also in this embodiment, the same effect as the first embodiment can be obtained.

(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, the pressure gauge 61 described in the first embodiment is the first pressure gauge 61. The first pressure gauge 61 is preferably provided in the vicinity of the tank 11 of the air supply line 21 or in the tank 11. Moreover, in this embodiment, the 2nd pressure gauge 64 is provided in the 1st bridge line 41 instead of the flow meter 62 shown in FIG. The second pressure gauge 64 detects the pressure Pv of the first bridge line 41 on the downstream side of the second adjustment valve 42.

  Then, when the BOG usable amount Qa is smaller than the fuel gas consumption Q1 of the main gas engine 13 (when the BOG is insufficient with respect to the fuel gas consumption Q1 of the main gas engine 13), the control device 6 The deviation between the pressure Pb of the BOG detected by the first pressure gauge 61 and the pressure Pv of the first bridge line 41 detected by the second pressure gauge 64 becomes a predetermined value α (Pb−Pv = α). The second adjustment valve 42 is controlled. The predetermined value α may be constant, but is preferably changed according to the BOG pressure P detected by the first pressure gauge 61 and / or the BOG available amount Qa. For example, when the BOG pressure Pb detected by the first pressure gauge 61 is high and the BOG available amount Qa is large, the predetermined value α is increased. Conversely, if Pb is low and Qa is small, α is made small.

  Also in this embodiment, the same effect as the first embodiment can be obtained.

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

  For example, the pump 14 may have a function of pumping up LNG to the forced vaporizer 15, and a compressor may be provided in the second supply line 32. However, if the fuel gas injection pressure of the auxiliary gas engine 16 is ensured by the pump 14 as in the first to third embodiments, it is not necessary to provide a compressor in the second supply line 32, and the cost can be reduced. it can.

  Further, the first bridge line 41 may be provided with a pressure reducing valve that outputs a constant secondary pressure even when the primary pressure fluctuates, and a check valve, instead of the second regulating valve 42. According to this configuration, VG is automatically replenished when the pressure of the BOG flowing through the air supply line 21 falls below the secondary pressure of the pressure reducing valve.

  In the first to third embodiments, the first regulating valve 33 is not necessarily controlled according to the available amount Qa of BOG. For example, when VG flows from the second supply line 32 to the first bridge line 41, the pressure of VG flowing through the second supply line 32 decreases, so the first adjustment is made according to the pressure of VG flowing through the second supply line 32. The valve 33 may be controlled.

  Further, one or both of the main gas engine 13 and the auxiliary gas engine 16 are not necessarily a reciprocating engine, and may be a gas turbine engine.

1A to 1C Ship 11 Tank 12 Compressor 13 Main gas engine 14 Pump 15 Forced vaporizer 16 Sub gas engine 21 Air supply line 22 First supply line 31 Liquid supply line 32 Second supply line 33 First adjustment valve 41 First bridge Line 42 Second adjustment valve 6 Control device 61 Pressure gauge, first pressure gauge 62, 63 Flow meter 64 Second pressure gauge

Claims (8)

A main gas engine for propulsion,
A tank for storing liquefied natural gas;
An air supply line for guiding boil-off gas generated in the tank to the compressor;
A first supply line for guiding boil-off gas discharged from the compressor to the main gas engine;
A sub-gas engine for power generation,
A liquid feed line for guiding liquefied natural gas discharged from a pump disposed in the tank to a forced vaporizer;
A second supply line that leads the vaporized gas generated in the forced vaporizer to the sub-gas engine;
A bridge line for guiding the vaporized gas from the second supply line to the air supply line;
A ship equipped with.   The ship according to claim 1, wherein the pump discharges liquefied natural gas so that a pressure of the vaporized gas generated by the forced vaporizer is higher than a fuel gas injection pressure of the auxiliary gas engine. A first adjustment valve provided in the liquid supply line and capable of changing an opening;
A second adjusting valve provided in the bridge line, the opening degree of which can be changed;
The ship of Claim 1 or 2 provided with the control apparatus which controls a said 1st regulating valve and a said 2nd regulating valve. A pressure gauge for detecting the pressure of the boil-off gas in the tank or the boil-off gas flowing in the air supply line;
The controller calculates an available amount of boil-off gas from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the available amount of the boil-off gas is the amount of the main gas engine. 4. The ship according to claim 3, wherein the first control valve is controlled according to an available amount of the boil-off gas when the amount is less than a fuel gas consumption amount. 5. A pressure gauge for detecting the pressure of the boil-off gas in the tank or the boil-off gas flowing in the air supply line;
A flow meter for detecting the flow rate of the boil-off gas flowing in the air supply line,
The control device calculates an available amount of boil-off gas from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the flow rate of the boil-off gas detected by the flow meter is The ship according to claim 3 or 4 which controls said 2nd regulating valve so that it may become the amount which can use boil off gas. A pressure gauge for detecting the pressure of the boil-off gas in the tank or the boil-off gas flowing in the air supply line;
A flow meter for detecting the flow rate of the vaporized gas flowing in the bridge line,
The control device calculates an available amount of boil-off gas from the amount of liquefied natural gas in the tank and the pressure of the boil-off gas detected by the pressure gauge, and the flow rate of the vaporized gas detected by the flow meter is The marine vessel according to claim 3 or 4, wherein the second adjustment valve is controlled so as to be a deviation between a fuel gas consumption amount of a main gas engine and an available amount of the boil-off gas. A first pressure gauge for detecting the pressure of the boil-off gas in the tank or the boil-off gas flowing through the air supply line, the first pressure gauge being located upstream of a position where the bridge line is connected in the air supply line. When,
A second pressure gauge that detects the pressure of the bridge line downstream of the second regulating valve;
The control device controls the second adjustment valve so that a deviation between the pressure of the boil-off gas detected by the first pressure gauge and the pressure of the bridge line detected by the second pressure gauge becomes a predetermined value. The ship according to claim 3. The pressure gauge is a first pressure gauge located on the upstream side of a position where the bridge line in the air supply line is connected,
A second pressure gauge for detecting the pressure of the bridge line downstream of the second regulating valve;
The control device controls the second adjustment valve so that a deviation between the pressure of the boil-off gas detected by the first pressure gauge and the pressure of the bridge line detected by the second pressure gauge becomes a predetermined value. The ship according to claim 4.

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