JP4275061B2 - Fuel supply apparatus and LNG ship equipped with the same - Google Patents

Description

  The present invention relates to a fuel supply device that supplies boil-off gas from an LNG tank and LNG as fuel, and an LNG ship equipped with the same.

In LNG ships and the like, it is necessary to safely and efficiently treat the generated boil-off gas, and it is used as fuel for boilers or internal combustion engines. When the required amount is insufficient with only the boil-off gas, the LNG in the LNG tank is generally forcibly evaporated with steam or hot water and supplied together with the boil-off gas.
As a boiler fuel supply device, for example, one disclosed in Patent Document 1 has been proposed.
In this method, boil-off gas and LNG are slowly heated by a natural gas from the downstream side, introduced into a compressor, boosted, heated by a heater, and supplied to a boiler.

JP 2003-227608 A (paragraphs [0010] to [0016] and FIG. 1)

However, in Patent Document 1, the boil-off gas supplied, vaporized LNG, and natural gas recirculated from the downstream are all introduced into the compressor. There is a problem that the apparatus becomes large and the cost is high.
In addition, it is necessary to increase or decrease the amount of natural gas introduced in accordance with the load fluctuation of the consumer. As a result, the operation of the compressor largely fluctuates, which makes it difficult to stably supply the consumer.
Furthermore, in order to avoid that the LNG component and the high boiling point component that are forcibly evaporated remain as drain, it is necessary that the temperature introduced into the compressor be higher than the boiling point of the unvaporized component, and the size of the compressor is further increased. There is a problem that the maximum flow rate on the basis of the weight flow rate decreases and the maximum discharge pressure also decreases as the power consumption increases as the power consumption increases.

  In view of the above problems, the present invention provides a fuel supply device capable of smoothly performing natural gas supply with load fluctuation at a consumer and temperature fluctuation of boil-off gas from a cargo tank without affecting the performance of the compressor. And it aims at providing the LNG ship provided with this.

In order to solve the above problems, the present invention employs the following means.
In other words, the fuel supply apparatus according to the present invention is a natural gas that boosts the boil-off gas generated in the LNG tank that stores LNG by a compressor and forcibly evaporates the LNG in the LNG tank by forcibly evaporating the LNG in the LNG tank. And a forced evaporation line to be supplied to the upstream side of the compressor in the fuel supply line, and a downstream end portion of the forced evaporation line, and the forcedly evaporated natural gas is reduced to the same pressure as the cargo tank pressure. An opening adjustment valve for supplying fuel to the fuel supply line and a branch on the upstream side of the opening adjustment valve in the forced evaporation line, connected to the downstream side of the compressor in the fuel supply line, and higher than the compressor discharge And a high-pressure supply line for starting supply of natural gas under pressure.

According to the present invention, the substantially atmospheric pressure boil-off gas generated in the LNG tank is pressurized by the compressor and supplied to the utilization section as fuel. When the required amount of the boil-off gas is increased due to an increase in the load of the use section, the forced evaporation line is operated to force the LNG in the LNG tank to evaporate into natural gas, which is mixed with the boil-off gas and compressed. Will be supplied.
At this time, the natural gas is depressurized to the same atmospheric pressure as the cargo tank by the opening adjustment valve and the depressurization mechanism, and supplied to the compressor. In order to further increase the load on the utilization unit and increase the amount of LNG supplied from the LNG tank, the flow rate adjustment valve upstream of the vaporizer is opened and LNG is supplied. On the other hand, the amount of gas supplied to the inlet side of the compressor is restricted by the opening adjustment valve and the pressure reducing mechanism, so the increase in the supply amount of LNG is caused by the forced evaporation line and the high pressure supply line upstream of the opening adjustment valve. The pressure will increase. When the pressure in the forced evaporation line and the high pressure supply line becomes higher than the compressor outlet pressure, the natural gas is supplied from the high pressure supply line to the downstream side of the compressor in the fuel supply line, and is supplied to the fuel supply line. The amount of natural gas produced can be increased directly without going through a compressor.

On the other hand, when the load on the utilization unit decreases and the amount of LNG supplied from the LNG tank decreases, the pressure in the forced evaporation line and high pressure supply line upstream of the opening adjustment valve decreases. When this pressure falls below the compressor outlet pressure, the supply of natural gas from the high pressure supply line to the fuel supply line is automatically shut off by the check valve, and the natural gas supplied to the fuel supply line passes through the compressor. Only the amount to do.
Thus, according to the present invention, the supply amount of natural gas can be increased or decreased smoothly without causing instability of control due to interference between the compressor and the vaporizer outlet pressure in accordance with the load fluctuation in the utilization section. .
Further, since the gas supplied to the downstream side of the compressor in the fuel supply line by the high-pressure supply line is directly supplied to the utilization unit without going through the compressor, the compressor is Miniaturization and power saving can be achieved.

  The fuel supply apparatus according to the present invention includes a vaporizer for evaporating LNG to form natural gas in the forced evaporation line, and a vaporizer that is provided downstream of the vaporizer and is supplied to the natural gas introduced from the vaporizer. A slow heat generator that sprays LNG before entering the tank and lowers the temperature of natural gas, and a portion where unvaporized components such as high-boiling hydrocarbons contained in the sprayed LNG fall under the gravity and accumulate it. , Is provided.

According to the present invention, the slow heat generator sprays LNG bypassing the vaporizer onto the natural gas vaporized by the vaporizer, and lowers the temperature of the natural gas. Therefore, the fuel supply line is adjusted by adjusting the amount of LNG to be sprayed. The temperature of the natural gas supplied to can be adjusted.
For this reason, it is possible to control by lowering the temperature of the natural gas introduced into the compressor by supplying the natural gas having a low temperature to the boil-off gas whose temperature has been increased by heat input from the surrounding environment from the opening adjustment valve. Therefore, the compression rate and compression efficiency of the compressor can be improved. When the compression rate is improved in this way, the driving power of the compressor can be reduced and stable operation can be performed. Further, since the compressor volume flow rate is reduced, the compressor can be downsized, the manufacturing cost can be reduced, and the operation cost can be reduced.

  The fuel supply apparatus according to the present invention includes a gas supply line that connects a lower portion of the heat sink and the fuel supply line and has a heating means in the middle.

In the lower part of the heat sink, drain formed by condensing a small amount of components such as natural gas or propane or ethane is stored by increasing the pressure when the load is increased and maintaining a low temperature atmosphere.
According to the present invention, this drain is pushed out to the gas supply line by the pressure in the slow heat generator, heated by the heater in the middle, gasified and supplied to the fuel supply line. can do.

  Moreover, the LNG ship concerning this invention was equipped with the propulsion means which has a fuel supply apparatus as described in any one of Claim 1 thru | or 3.

  According to the present invention, since the fuel supply device that can smoothly follow the load fluctuation of the propulsion means is provided, the LNG ship can perform smooth operation even if there is a load fluctuation.

  According to the present invention, it is possible to smoothly increase or decrease the supply amount and supply pressure of natural gas without affecting the performance of the compressor according to the load fluctuation in the utilization unit.

Embodiments according to the present invention will be described below with reference to the drawings.
[First embodiment]
Hereinafter, a fuel supply device 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The fuel supply device 1 of this embodiment is applied to an LNG ship driven by a steam turbine main engine, and supplies natural gas as fuel to a boiler (utilization unit) that generates steam.
FIG. 1 is a block diagram showing an overall schematic configuration of the fuel supply device 1.
The fuel supply device 1 includes an LNG tank 3 that stores LNG, a fuel supply line 5 that supplies boil-off gas generated in the LNG tank 3 to a boiler (not shown), and a fuel supply line that forcibly evaporates LNG in the LNG tank 3. 5 is provided with a forced evaporation line 7 for supplying to 5.

The fuel supply line 5 is provided with a compressor 9, a supply heater 11, and a supply pressure adjustment valve 13 along the flow direction of the boil-off gas.
The compressor 9 pressurizes and heats the boil-off gas and supplies it to the downstream side. A supply check valve 15 is provided on the downstream side of the compressor 9 so that the supplied boil-off gas does not flow backward to the compressor. A return line 17 is provided to connect between the supply check valve 15 and the compressor 9 and the upstream side of the compressor 9. A pressure control valve 19 is provided in the return line 17, and when the outlet pressure of the compressor 9 is lower than the upstream pressure of the supply check valve 15, the boil-off gas is returned to the upstream side of the compressor 9 and recirculated. It is configured as follows.

The supply heater 11 raises the temperature of the boil-off gas supplied to the boiler. A heater bypass line 21 is provided by connecting the upstream side and the downstream side of the supply heater 11. The heater bypass line 21 is provided with a bypass flow rate adjustment valve 23. The bypass flow rate adjusting valve 23 is configured such that its opening / closing and opening degree are controlled in order to keep the measured value of the thermometer 25 for measuring the boil-off gas temperature of the fuel supply line 5 on the downstream side constant.
The supply pressure adjusting valve 13 is for adjusting the flow rate and pressure of the boil-off gas supplied to the boiler.

In the forced evaporation line 7, along the flow direction of LNG or natural gas, a cargo pump 27 that supplies LNG stored in the LNG tank 3, an LNG flow rate adjustment valve 29 that adjusts the flow rate of LNG, and LNG is evaporated. A vaporizer 31, a heat sink 33, and a pressure reducing valve (opening adjustment valve) 35 are provided.
The vaporizer 31 heats and evaporates LNG to produce natural gas, and a heating method using steam or hot water is used.
On the upstream side of the vaporizer 31 in the fuel supply line 7, an LNG branch pipe 37 that supplies LNG to the slow heat generator 33 is provided. The LNG branch pipe 37 is provided with a flow rate adjustment valve 39 at a position before entering the slow heat generator 33.

The slow heat heater 33 is a part of a substantially cylindrical vertical pressure vessel or vertical pipe, and the forced evaporation line 7 from the vaporizer 31 is connected to the lower side surface rather than the center of the side surface. An LNG introduction pipe 41 connected to the LNG branch pipe 37 is inserted at a position above the side surface of the slow heat generator 33. A plurality of spray holes are provided in the lower part of the LNG introduction pipe 41, and the introduced LNG is sprayed.
In the space between the connection portion from the vaporizer 31 and the LNG introduction pipe 41, an obstacle for gas-liquid contact is arranged, and the dispersed LNG comes into contact with the introduced natural gas to vaporize LNG. And the temperature of the natural gas is lowered.
A forced evaporation line 7 that supplies natural gas to the fuel supply line 5 is connected to the upper end of the slow heat generator 33.

The pressure reducing valve 35 is configured to supply to the downstream side at the same pressure as the cargo tank, for example, atmospheric pressure (first predetermined pressure) even when the pressure of the introduced natural gas is high.
The forced evaporation line 7 is connected to supply natural gas to the upstream side of the compressor 9 in the fuel supply line 5. An eductor 43 serving as a decompression mechanism and an eductor is provided in a supply portion of the forced evaporation line 7 to the fuel supply line 5.
As shown in FIG. 2, the eductor 43 is provided with an accelerating unit 45 in which a flow path connected to the forced evaporation line 7 is first throttled.
Natural gas supplied from the forced evaporation line 7 is accelerated by the acceleration unit 45 and introduced into the fuel supply line 5. The boil-off gas sent from the side of the acceleration unit 45 is sucked and accelerated by the accelerated natural gas. Thereby, since the pressure rise in a junction part is changed into a flow velocity, a pressure rise can be avoided.

A high pressure supply line 47 is provided to connect a branch point A between the slow heat exchanger 33 and the pressure reducing valve 35 and a junction B located downstream of the supply check valve 15 (compressor 9) in the fuel supply line 5. It has been.
An eductor 48 and a check valve 49 are provided on the junction B side of the high pressure supply line 47. The check valve 49 is configured to supply natural gas from the high pressure supply line 47 to the fuel supply line 5 when the pressure in the upstream high pressure supply line 47 exceeds the discharge pressure of the compressor, for example, 200 kPaA.
The eductor 48 has the same structure as the eductor 43, and a high pressure supply line 47 is connected to the acceleration unit 45.
Natural gas supplied from the high-pressure supply line 47 is accelerated by the acceleration unit 45 and introduced into the fuel supply line 5. The boil-off gas sent from the side of the acceleration unit 45 is sucked and accelerated by the accelerated natural gas. Thereby, since the pressure rise in a junction part is converted into a flow velocity, a pressure rise can be avoided.

A gas supply line 51 is connected to the lower end of the lower drain reservoir of the slow heat generator 33. A heater coil (heating means) 53 for heating the gas supply line 51 is provided on the side of the slow heat generator 33 of the gas supply line 51. The other end of the gas supply line 51 is connected to a junction C located downstream of the junction B (compressor 9) in the fuel supply line 5.
A gas supply check valve 55 is provided on the confluence point C side of the gas supply line 51. The gas supply check valve 55 is configured to supply the evaporated vapor of drain from the gas supply line 51 to the fuel supply line 5 when the pressure of the upstream gas supply line 51 exceeds a certain pressure, for example, 200 kPaA. Yes.
The gas supply line 51 is branched in the middle and connected to the vent line 59 of the cargo tank 3, and can be returned as gas to the cargo tank 3 when the liquid level rise of the drain reservoir exceeds a certain line. It is configured as follows.

The operation of the fuel supply device 1 for the boiler according to the present embodiment described above will be described.
When the boiler load is low at the time of startup or the like, the boil-off gas alone is sufficient fuel.
In this case, the boil-off gas under atmospheric pressure generated in the LNG tank 3 is sent to the compressor 9 through the fuel supply line 5 in a state of about −140 to −160 ° C. At this time, the temperature is raised to about −100 to −70 ° C. at the inlet of the compressor 9 by heat input from the surrounding environment in the middle of the piping.
In the compressor 9, this boil-off gas is compressed and pressurized. When the pressure of the pressurized boil-off gas is higher than the gas pressure upstream of the supply check valve 15, for example, approximately 200 kPaA, the boil-off gas is downstream from the supply check valve 15 without being recirculated in the return line 17. Sent.

This boil-off gas is further heated by the supply heater 11, and is sent to the boiler at, for example, about 40 ° C. At this time, in the supply heater, the boil-off gas is heated to a temperature higher than 40 ° C., mixed with the boil-off gas before being heated by the supply heater 11 passing through the heater bypass line 21, and cooled to about 40 ° C. I am doing so. This is performed by adjusting the opening or opening / closing of the bypass flow rate adjustment valve 23 according to the measured value of the thermometer 25 that measures the temperature of the boil-off gas, and adjusting the amount of cooling boil-off gas passing through the heater bypass line 21. .
The boil-off gas whose temperature has been adjusted is adjusted to a predetermined pressure by the supply amount adjusting valve 13 and supplied to the boiler as fuel.

When the load on the boiler increases and the amount of fuel becomes insufficient with only the boil-off gas, the forced evaporation line 5 is activated.
The cargo pump 27 is activated to pump up the LNG in the LNG tank 3 and supply it to the vaporizer 31. At this time, the supply amount of LNG is adjusted by the LNG flow rate adjustment valve 29 according to the boiler load.
The LNG introduced into the vaporizer 31 is heated by steam or hot water. The heated LNG evaporates into natural gas and is supplied to the lower part of the slow heat generator 33.

The introduced natural gas is introduced through the LNG branch pipe 37 and comes into contact with the LNG sprayed from the lower part of the LNG introduction pipe 41. By this contact, LNG is vaporized and the boil-off gas is cooled. Both are mixed and made into a natural gas whose temperature is controlled, and is carried out from the slow heat generator 33. This outlet temperature can be set to an appropriate temperature by adjusting the supply amount of LNG by the flow rate adjusting valve 39.
In this embodiment, this temperature is adjusted to be approximately −120 ° C.
The natural gas is supplied from the pressure reducing valve 35 to the accelerating unit 45 of the eductor 43 under atmospheric pressure, mixed with the boil-off gas, and introduced into the compressor 9. At this time, the temperature of the mixture of natural gas and boil-off gas introduced into the compressor 9 is approximately −100 ° C.
This temperature can be set to an appropriate value according to the set value of the temperature of the natural gas.

As described above, the natural gas having a low temperature is supplied from the pressure reducing valve 35 to the boil-off gas, and the temperature of the natural gas introduced into the compressor 9 can be lowered. Therefore, the compression rate and the compression efficiency of the compressor 9 are improved. Can be made.
When the compression rate is improved in this manner, the driving power of the compressor 9 can be reduced, and stable operation can be performed. Further, since the compressor capacity can be reduced, the manufacturing cost can be reduced and the operating cost can also be reduced.
Furthermore, if the temperature of the introduced natural gas or the like is reduced, the weight flow rate of the compressor 9 is increased, so that more natural gas or the like can be compressed and discharged downstream. For this reason, fuel can be increased efficiently with respect to an increase in boiler load.

When the boiler load further increases, the opening of the flow rate adjustment valve 29 is adjusted so that the amount of LNG pumped up by the cargo pump 27 and sent to the vaporizer increases accordingly.
As the amount of LNG supplied in the forced evaporation line 7 increases, the amount of temperature-adjusted natural gas generated in the slow heat generator 33 increases.
On the other hand, since the maximum amount of natural gas supplied from the pressure reducing valve 35 to the fuel supply line 5 is substantially constant, the upstream side of the pressure reducing valve 35, that is, the slow heat generator 33, the high pressure supply line 47 and the slow heat cooler 33. Natural gas is stored by the balance of the balance between the forced evaporation line 7 and the pressure reducing valve 35.
When natural gas is stored, the pressure of natural gas increases. When the pressure of the natural gas reaches or exceeds the compressor outlet pressure, for example, approximately 200 kPa, the check valve 49 is opened, and the natural gas is supplied from the high pressure supply line 47 to the junction B of the fuel supply line 5.
In this state, the pressure reducing valve 39 can be closed.
If it is closed, it is not necessary to lower the temperature of the gas that has been forcibly evaporated, so the temperature can be raised by a vaporizer, for example, up to 40 ° C. In that case, it can operate | move without generation | occurrence | production of the heavy part drain of the slow heat exchanger lower part.

In this way, the subsequent LNG increase is supplied to the fuel supply line 7 located on the downstream side of the compressor 9, mixed with the one from the compressor 9, and supplied to the boiler.
On the other hand, when the boiler load decreases and the required amount of LNG decreases, the amount of LNG supplied from the LNG tank 3 is decreased. As a result, the forced evaporation line 7 and the high-pressure supply line 47 on the upstream side of the pressure reducing valve 35 are reduced. The pressure of decreases. When this pressure falls below the discharge pressure of the compressor, for example, approximately −200 kPaA, the check valve 49 is closed, the supply of natural gas from the high pressure supply line 47 to the fuel supply line 5 is shut off, and the natural gas supplied to the fuel supply line Gas is only to the inlet side of the compressor. Further, if the LNG supply amount decreases, the amount also decreases, and the boil-off gas is the only natural gas supplied to the fuel supply line when the vaporizer is stopped. The flow rate below this is adjusted by the flow rate adjusting means of the compressor, for example, the compressor rotation speed, the guide vane and the recirculation valve.

Thus, according to the present embodiment, the supply amount of natural gas is adjusted by the high-pressure supply line 47 provided in parallel with the compressor 9 together with the forced evaporation line 7 whose supply amount is limited by the pressure reducing valve 35. Therefore, the supply amount of natural gas can be smoothly increased or decreased according to the load fluctuation of the boiler.
Further, the mixture of the natural gas and the boil-off gas passing through the compressor 9 does not exceed a certain amount, and the flow rate fluctuations are reduced. For this reason, a compressor can be reduced in size and power saving.

Further, since the pressure in the slow heat generator 33 is increased and the temperature is set low, high-boiling components such as propane and ethane and natural gas contained in a small amount are condensed in the lower portion of the slow heat generator 33. , Stored as drain.
The drain is pushed out to the gas supply line 51 or the vent line that returns to the cargo tank as the high pressure in the slow heat generator 33 acts as a back pressure.
The drain supplied to the gas supply line 51 is heated by the heater coil 53, evaporated, and introduced into the fuel supply line 5 via the eductor 43.
As described above, in the present embodiment, the drain stored in the lower part of the heat sink 33 is processed while being effectively used as fuel.

[Second Embodiment]
Next, the fuel supply device 1 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing an overall schematic configuration of the fuel supply device 1.
The fuel supply apparatus 1 in the present embodiment is different from that in the first embodiment described above in the position of the fuel supply line 5 supplied by the gas supply line 51. Since other components are the same as those of the first embodiment described above, a duplicate description of these components is omitted here.
In addition, the same code | symbol is attached | subjected to the member same as 1st embodiment mentioned above.

In the present embodiment, the other end of the gas supply line 51 connected to the lower end portion of the slow heat generator 33 is connected to the side portion of the acceleration unit 45 in the eductor 43 of the fuel supply line 5 on the upstream side of the compressor 9. Has been.
The gas supply line 51 is branched in the middle and connected to the vent line 59 of the cargo tank 3, and can be returned as gas to the cargo tank 3 when the liquid level rise of the drain reservoir exceeds a certain line. It is configured as follows.

As described above, in this embodiment, the evaporated gas of the drain is supplied as fuel to the fuel supply line 5 on the side of the acceleration unit 45 of the eductor 43 that is upstream of the compressor 9, so that it is supplied to the low pressure portion. The Rukoto.
For this reason, this drain can be smoothly supplied to the fuel supply line 5 by the pressure in the slow heat generator 33 acting as a back pressure.
Since other operations and effects are the same as those in the first embodiment described above, a duplicate description is omitted.

It is a block diagram which shows the fuel supply apparatus concerning 1st embodiment of this invention. It is sectional drawing which shows the eductor concerning 1st embodiment of this invention. It is a block diagram which shows the fuel supply apparatus concerning 2nd embodiment of this invention.

Explanation of symbols

1 Fuel Supply Device 3 LNG Tank 5 Fuel Supply Line 7 Forced Evaporation Line 9 Compressor 31 Vaporizer 33 Slow Heater 35 Pressure Reducing Valve 47 High Pressure Supply Line 51 Gas Supply Line 53 Heater Coil

Claims (4)

A fuel supply line that boosts the boil-off gas generated in the LNG tank that stores LNG by a compressor and supplies the boosted gas to the utilization unit;
Forcibly evaporating the LNG in the LNG tank into natural gas, and supplying it to the upstream side of the compressor in the fuel supply line;
An opening degree adjusting valve provided at a downstream end portion of the forced evaporation line, for reducing the forced vaporized natural gas to the same pressure as the cargo tank pressure by adjusting the opening degree, and supplying to the fuel supply line; a fixed pressure reducing mechanism; ,
A high-pressure supply line that branches off the upstream side of the pressure reducing valve in the forced evaporation line, is connected to the downstream side of the compressor in the fuel supply line, and starts supplying natural gas at a pressure higher than the compressor discharge;
A fuel supply device comprising: In the forced evaporation line,
A vaporizer that uses steam or hot water as a heat source and evaporates LNG into natural gas;
A slow heat generator that is provided downstream of the vaporizer, sprays LNG before entering the vaporizer to the natural gas introduced from the vaporizer, and lowers the temperature of the gas by mixing and contacting the natural gas;
A storage part for storing unsteamed components such as high-boiling hydrocarbons contained in LNG sprayed on the heat sink dropped by gravity;
The fuel supply device according to claim 1, further comprising: 3. The fuel supply device according to claim 1, further comprising a gas supply line that connects the storage portion, the fuel supply line, and the cargo tank, and has heating means in the middle. An LNG ship comprising propulsion means having the fuel supply device according to any one of claims 1 to 3.

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