CN105683039B - Liquefied gas transport fuel gas feed system peculiar to vessel - Google Patents

Abstract

1st fuel gas feeding pipe (14) is set, and regard the boil-off gas (BOG) in cargo tank (11) as fuel gas by high-pressure compressor (13) provides to sustainer (12).2nd fuel gas feeding pipe (26) is set, by pump (27) to draw the liquefied gas in cabin (11), and high pressure gas is generated using high pressure liquid pump (29), gas heater (30).In navigation when liquefied gas loads, when only with BOG fuel gas with regard to it is enough when be used only the 1st fuel gas feeding pipe (14), the 1st fuel gas feeding pipe (14) and the 2nd fuel gas feeding pipe (26) are then applied in combination when deficiency.In navigation in liquefied gas zero load, the 1st fuel gas feeding pipe (14) is used only when carrying out spray operation, the 2nd fuel gas feeding pipe (26) is used only when without spray operation.

Description

Liquefied gas transport marine fuel gas supply system

technical field

The present invention relates to a fuel gas supply system suitable for a liquefied gas carrier equipped with a low-speed diesel engine capable of gas combustion as a main engine.

Background technique

From the viewpoint of reducing the environmental load and improving energy consumption, gas-combustion low-speed diesel engines have been used as the main engines of LNG carriers in recent years. as fuel for the main engine. However, it is necessary to supply fuel gas having a pressure of about 30 MPa to the gas combustion low-speed diesel engine. Therefore, in the case of using boil-off gas as fuel, the boil-off gas needs to be compressed to about 30 MPa by a high-pressure gas compressor, but the method of using a high-pressure gas compressor has a problem of high power consumption. On the other hand, as a method of generating high-pressure fuel gas with low power consumption, a configuration is known in which liquefied natural gas is pressurized by a high-pressure liquid pump and heated to produce a high-pressure gas of about 30 MPa (Patent Literature 1).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2012-177333

Contents of the invention

The problem to be solved by the invention

When the liquefied gas in the tank is turned into a high-pressure gas by a high-pressure liquid pump, since the boil-off gas is not consumed as fuel, it is necessary to prepare for forced combustion in order to prevent the pressure rise in the cargo compartment caused by the boil-off gas. A gas combustion unit for boil-off gas and a reliquefaction unit for returning boil-off gas to a liquid state. However, when the boil-off gas is burned, the environmental load increases and the energy efficiency of the entire transport ship decreases. In addition, in order to operate the reliquefaction device, generally more energy is required than the operation of the high-pressure gas compressor.

The object of the present invention is to provide a fuel gas supply system. In a liquefied gas carrier, a high-pressure gas compressor and a high-pressure liquid pump are used in combination, and the treatment of boil-off gas and the energy source are consistent with the navigation status of the liquefied gas carrier. Consumption is optimized and the load on the environment is further reduced.

means to solve the problem

The fuel gas supply system for liquefied gas transportation ships of the present invention is characterized in that it has: a low-speed diesel engine capable of gas combustion and used as a main engine; a cabin for storing liquefied gas; a high-pressure gas compressor for generating The vaporized gas is compressed; the high-pressure liquid pump pressurizes the liquefied gas in the cabin; the first fuel gas supply pipeline supplies fuel gas from the cabin to the low-speed diesel engine through the high-pressure gas compressor; and the second fuel gas supply The pipeline, which supplies fuel gas from the tank to the low-speed diesel engine through the high-pressure liquid pump, when the fuel consumption of the main engine is less than the amount of boil-off gas produced during the voyage when the liquefied gas is loaded, and when the liquefied gas is empty during the voyage Spraying operation (when liquefied gas is introduced into the cabin, in order to prevent the damage of the cabin caused by the sharp temperature difference, the liquefied gas remaining in the cabin is sprayed in the cabin and the heat of vaporization of the liquefied gas is used. When the cargo compartment is pre-cooled), fuel gas is supplied to the low-speed diesel engine only through the first fuel gas supply pipeline, and only the second fuel gas is passed through the second fuel gas when the liquefied gas is not loaded during the voyage. The gas supply line is used to supply fuel gas to the low speed diesel engine. However, in the above-mentioned spraying operation, when the pressure in the cabin is increased to a predetermined pressure due to spraying, the spraying is temporarily suspended, and the gas in the cabin is consumed as fuel to lower the cabin pressure, and then the spraying is started again. Operation, the same operation is repeated many times until the temperature of the tank drops to a predetermined temperature, and the period during which the gas in the cargo tank is preferentially used as fuel due to the interruption of spraying is also included in the series of spraying operations. In addition, even in the unloaded state, in order to use the liquefied gas as the spray liquid for cabin cooling or the fuel for the main engine, some liquefied gas should be stored instead of leaving the cabin completely empty.

Furthermore, it is preferable to supply fuel gas to the low-speed diesel engine using the first fuel gas supply line and the second fuel gas supply line when the fuel consumption of the main engine exceeds the boil-off gas generation during voyage with liquefied gas loaded. In addition, the fuel gas supply system can also adopt the following configuration: it has: a gas recovery pipeline, which reliquefies the fuel gas compressed by the high-pressure gas compressor and sends it back to the cabin; Heat exchange is performed between the recovery line and the portion of the first fuel gas supply line that connects the chamber and the high-pressure gas compressor, and reliquefaction of the fuel gas is performed by the heat exchanger. In addition, at this time, it is also possible to provide a connection line for sending the boil-off gas existing between the heat exchanger and the cabin in the gas recovery line back to the upstream side of the first fuel gas supply line from the heat exchanger. s position.

A liquefied gas carrier according to the present invention is characterized by comprising the fuel gas supply system for a liquefied gas carrier described above.

Invention effect

According to the present invention, it is possible to provide a fuel gas supply system that uses a combination of a high-pressure gas compressor and a high-pressure liquid pump in a liquefied gas carrier, and that treats boil-off gas and consumes energy in accordance with the navigation status of the liquefied gas carrier. Optimize and further reduce the load on the environment.

Description of drawings

FIG. 1 is a block diagram showing the configuration of a fuel gas supply system as a first embodiment of the present invention.

Fig. 2 is a graph showing (a) when liquefied gas is loaded, (b) when liquefied gas is unloaded (spray operation), and (c) when liquefied gas is unloaded (no spray operation) in the first embodiment. A graph of the relationship between the sailing speed and the used fuel consumption in the sailing mode.

3 is a block diagram showing the configuration of a fuel gas supply system as a second embodiment of the present invention.

Fig. 4 is a graph showing the relationship between the sailing speed and the used fuel consumption when the liquefied gas is loaded in the second embodiment.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a fuel gas supply system as a first embodiment of the present invention.

The fuel gas supply system 10 of this embodiment is applied to a ship that transports liquefied gas such as natural gas, and the liquefied gas (LNG in this embodiment) is loaded in the liquid cargo tank 11 . The main engine 12 is a low-speed diesel engine capable of gas combustion, and can supply boil-off gas (NATURAL BOG) naturally generated in the cabin 11 to the main engine 12 through a first fuel gas supply line 14 including a high-pressure gas compressor 13 . That is, the cabin 11 and the high-pressure gas compressor 13 are connected through the upstream pipeline 14A, and the high-pressure gas compressor 13 and the main engine 12 are connected through the downstream pipeline 14B.

That is, the boil-off gas generated in the cabin 11 is delivered to the high-pressure gas compressor 13 via the upstream pipeline 14A, for example, is compressed to approximately 30 MPa and delivered to the downstream pipeline 14B as "high-pressure gas", and then passed through the downstream pipeline. The check valve 15 and the flow regulating valve 16 on the road 14B are sent to the main engine 12 . Furthermore, in this embodiment, the high-pressure gas compressor 13 is also connected to the low-pressure fuel gas supply pipeline 17, and outputs "low-pressure gas" with a relatively low pressure.

The low-pressure fuel gas supply pipeline 17 is connected to the binary fuel combustion boiler 20 via, for example, a check valve 18 and a flow regulating valve 19, and is connected to a binary fuel combustion internal combustion generator ( D/G) 23 and other connections. In the boiler 20 and the internal combustion generator 23 , it is possible to co-combust fuel gas and oil, and to use low-pressure gas supplied from the high-pressure gas compressor 13 as fuel when excess boil-off gas exists.

In addition, in the present embodiment, the connection between the check valve 15 and the flow rate adjustment valve 16 and the pipe connected to the internal combustion generator 23 in the downstream pipe 14B of the first fuel gas supply pipe 14 is connected through the connecting pipe 24 . The check valve 21 in the pipeline communicates with the flow regulating valve 22, and a check valve 25 with a pressure regulating function is arranged on the connecting pipeline 24. That is, the high-pressure gas supplied to the downstream pipe 14B may be supplied to the binary fuel combustion internal combustion generator 23 through the check valve 25 with a pressure adjustment function as needed.

Furthermore, the fuel gas supply system 10 of the present embodiment is further provided with a second fuel gas supply line 26 . The second fuel gas supply line 26 has a pump 27 disposed near the bottom of the chamber 11 , and the liquefied gas in the chamber 11 is sucked up by the pump 27 and temporarily stored in the suction cylinder 28 . The high-pressure liquid pump 29 is connected to the suction cylinder 28 to pressurize the liquefied gas from the suction cylinder 28 . The liquefied gas pressurized by the high-pressure liquid pump 29 is heated and vaporized in the gas heater 30 to become a high-pressure gas. The generated high-pressure gas is supplied to a section between the check valve 15 and the flow rate adjustment valve 16 in the downstream line 14B of the first fuel gas supply line 14 via the check valve 31 .

Next, the fuel gas supply system 10 supplying the main engine 12 according to the navigation situation will be described with reference to FIG. 2 . Figure 2(a) to Figure 2(c) respectively show the relationship between (a) the sailing speed when the liquefied gas is loaded and the fuel consumption used, and (b) the spraying during the voyage when the liquefied gas is empty. The relationship between the sailing speed and the used fuel consumption during operation, and (c) the graph of the relationship between the sailing speed and the used fuel consumption when no spraying work is performed during the voyage when the liquefied gas is empty. In addition, in FIG. 2( a ) to FIG. 2( c ), the horizontal axis represents the sailing speed of the ship, and the vertical axis represents the fuel consumption.

In Fig. 2(a) to Fig. 2(c), the curve S is a curve showing the relationship between the ship speed and the fuel consumption (fuel gas supply amount/unit hour), and the fuel consumption is approximately three times the ship speed. The square is proportional. A straight line L (NATURALBOG) in (a) of FIG. 2 is an amount per unit time when the liquefied gas (natural gas) in the tank 11 is naturally evaporated into boil-off gas.

That is, in (a) of FIG. 2 , when only boil-off gas is used and all of it is used as fuel for the main engine 12 , the ship speed corresponding to the intersection point P of the curve S and the straight line L is obtained. On the other hand, in the region on the lower speed side than the operating point P, the difference between the straight line L and the curve S is the remaining evaporated gas, and in the region on the higher speed side than the operating point P, the difference between the curve S and the straight line L is the fuel that needs to be added. quantity.

Therefore, during voyage when liquefied gas is loaded, only the first fuel gas supply line 14 is used at the operating point P (100% speed of natural BOG) and the region on the lower speed side than the operating point P (deceleration operation region). And the operation of the main engine 12 is performed using boil-off gas only. And the surplus gas is utilized as fuel for the boiler 20 and the internal combustion generator 23, and the surplus gas which cannot be consumed nevertheless is burned. In addition, in a region on the higher side than the operating point P (high-speed operation region), an insufficient amount of fuel is supplied through the second fuel gas supply line 26 . That is, the pump 27 , the high-pressure liquid pump 29 , and the gas heater 30 are driven to generate high-pressure gas from the liquefied gas in the tank 11 , and the high-pressure gas is supplied to the main engine 12 together with high-pressure gas compressed by the high-pressure gas compressor 13 . In addition, the cruising speed of the ship is set to the operation point P or a speed slightly lower than the operation point P.

(b) of FIG. 2 is a graph showing the navigation pattern when the spraying operation is performed during the navigation when the liquefied gas is empty. In this sailing mode, only the first fuel gas supply line 14 is used. That is, in the cabin 11 , a shower operation is performed, and boil-off gas generated by the shower operation is supplied to the main engine 12 as fuel gas. In addition, although it is a voyage with liquefied gas empty, in order to use liquefied gas as spray liquid for tank cooling or fuel for the main engine, some liquefied gas is also stored, and not all tanks 11 are completely empty. .

On the other hand, (c) of FIG. 2 is a graph corresponding to the navigation pattern when the spraying work is not performed during the navigation when the liquefied gas is empty. In this sailing mode, the first fuel gas supply line 14 is not used and the high-pressure gas compressor 13 is turned off. And only the second fuel gas supply line is used to drive the pump 27 , the high-pressure liquid pump 29 and the gas heater 30 to generate high-pressure gas from the liquefied gas in the tank 11 and supply it to the main engine 12 .

Since the ship sails at a cruising speed most of the time, it operates near the operating point P in (a) of FIG. 2 , for example. That is, according to the first embodiment, when the liquefied gas is charged, almost only the high-pressure gas compressor is driven, and most of the boil-off gas is consumed as fuel for the main engine. And when only the operation in the high-speed operation region is required, the high-pressure liquid pump is driven to directly generate high-pressure gas from the liquefied gas. Moreover, during the voyage when the liquefied gas is empty, since there is no spraying operation for most of the time, most of the voyages are in the (c) mode of Figure 2, and the high-pressure gas compressor is not operated but the high-pressure liquid pump is used. for fuel gas supply. On the other hand, when the spraying operation is performed and boil-off gas is generated, the high-pressure gas compressor is driven and almost all of the boil-off gas is used as fuel for the main engine, so there is no problem of boil-off gas treatment. Therefore, installation of a reliquefaction device can be omitted.

Next, a fuel gas supply system according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4 . The fuel gas supply system of the second embodiment further includes a gas recovery system in addition to the fuel gas supply system of the first embodiment, and the other configurations are substantially the same as those of the first embodiment. Therefore, the same reference numerals are assigned to the same configurations as those of the first embodiment, and description thereof will be omitted.

In the fuel gas supply system 40 of the second embodiment, a gas recovery line 41 is connected between the high-pressure gas compressor 13 and the check valve 15 of the downstream line 14B. The gas recovery line 41 liquefies high-pressure gas derived from boil-off gas discharged from the high-pressure gas compressor 13 through the heat exchanger 42 connected to the upstream line 14A of the first fuel gas supply line 14 . And the liquefied liquefied gas is stored in the gas-liquid separator 43 . The liquefied gas (LNG) stored in the gas-liquid separator 43 is returned to the tank 11 by the pump 44 or the self-pressure of the gas-liquid separator 43 . Then, the boil-off gas present in the gas-liquid separator 43 returns to the upstream side of the heat exchanger 42 in the upstream line 14A of the first fuel gas supply line 14 via the connection line 45 .

As described above, according to the second embodiment, the same effect as that of the first embodiment is obtained, and in the low-speed operation region during the liquefied gas loading voyage, it is possible to more effectively process the excess boil-off gas. In addition, in the second embodiment, since the gas compressed by the high-pressure gas compressor is liquefied by the heat exchanger, the reliquefaction process can be performed more efficiently.

Furthermore, in the second embodiment, since the gas recovery system is provided, the generation amount of boil-off gas per unit time is substantially reduced. That is, in Fig. 4, when the production amount of evaporated gas per unit time before the start-up of the gas recovery system is the straight line L1, after the start-up of the gas recovery system, the production amount drops to the straight line L2, and the intersection point with the curve S moves from P1 to P2. Therefore, it is possible to further suppress the generation of excess boil-off gas when the cruising speed is reduced to perform deceleration cruising.

In addition, the main engine may be a low-speed diesel engine that exclusively burns gas, or a dual-fuel low-speed diesel engine that burns gas and fuel oil. In this case, for example, oil may be used as additional fuel in a high-speed operation range.

Label description

10: fuel gas supply system (first embodiment); 11: cargo tank; 12: main engine; 13: high-pressure gas compressor; 14: first fuel gas supply line; 14A: upstream line; 14B: downstream line 20: binary fuel combustion boiler; 23: binary fuel combustion internal combustion generator; 26: second fuel gas supply pipeline; 27: pump; 28: suction cylinder; 29: high pressure liquid pump; 30: gas heating 40: fuel gas supply system (second embodiment); 41: gas recovery pipeline; 42: heat exchanger; 43: gas-liquid separator; 44: pump.

Claims (9)

1. A liquefied gas transport marine fuel gas supply system, characterized in that it has: A low-speed diesel engine, capable of gas combustion, is used as the main engine; tanks for storing liquefied gas; a high-pressure gas compressor, which compresses the boil-off gas generated in the cabin; a high-pressure liquid pump, which pressurizes the liquefied gas in the cabin; a first fuel gas supply line that supplies fuel gas from the chamber to the low-speed diesel engine through the high-pressure gas compressor; and a second fuel gas supply line for supplying fuel gas from the chamber to the low-speed diesel engine through the high-pressure liquid pump, When the fuel consumption of the low-speed diesel engine is equal to or less than the amount of boil-off gas generated during voyage loaded with liquefied gas, and when spraying operation is performed during voyage without liquefied gas, only the first fuel gas is passed The supply pipeline is used to supply fuel gas to the low-speed diesel engine. During the voyage when the liquefied gas is empty, when the spraying operation is not performed, fuel is only supplied to the low-speed diesel engine through the second fuel gas supply pipeline. gas. 2. The fuel gas supply system for liquefied gas transport ships according to claim 1, wherein: During voyage with liquefied gas loaded, when fuel consumption exceeds boil-off gas production, fuel gas is supplied to the low-speed diesel engine using the first fuel gas supply line and the second fuel gas supply line. 3 . The fuel gas supply system for a liquefied gas carrier ship according to claim 1 , wherein check valves are provided on the first fuel gas supply line and the second fuel gas supply line. 4 . 4. The fuel gas supply system for liquefied gas transport ships according to claim 3, characterized in that, a 3rd fuel gas supply pipeline is provided, and the 3rd fuel gas supply pipeline is connected from the high-pressure gas compressor to the binary system. Fuel fired internal combustion generators are supplied with relatively low pressure fuel gas. 5 . The fuel gas supply system for a liquefied gas carrier ship according to claim 4 , wherein the third fuel gas supply line supplies fuel gas to the binary fuel combustion internal combustion generator via a check valve. 6. The fuel gas supply system for a liquefied gas carrier ship according to claim 5, wherein the downstream side of the check valve of the first fuel gas supply line is connected to the third fuel gas supply line. The downstream side of the check valve is connected through a connecting pipeline, and a check valve with a pressure adjustment function is arranged on the connecting pipeline. 7. The fuel gas supply system for liquefied gas transport ships according to any one of claims 1 to 6, characterized in that the fuel gas supply system for liquefied gas transport ships also has: a gas recovery line that reliquefies the gas compressed by the high pressure gas compressor and returns it to the tank; and a heat exchanger for exchanging heat between the gas recovery line and a portion of the first fuel gas supply line connecting the chamber and the high-pressure gas compressor, Reliquefaction of the gas is carried out by means of the heat exchanger. 8. The fuel gas supply system for liquefied gas transport ships according to claim 7, characterized in that: This liquefied gas transportation marine fuel gas supply system further has a connecting line for sending the evaporated gas existing between the heat exchanger and the tank in the gas recovery line back to the first fuel. The position of the gas supply line on the upstream side of the heat exchanger. 9. A liquefied gas carrier, characterized in that it has: The fuel gas supply system for liquefied gas transport ships according to any one of claims 1 to 8.