JP7575938B2 - Slip methane treatment device and marine propulsion plant - Google Patents

Description

This disclosure relates to a slip methane treatment device and a marine propulsion plant.

In marine gas engines that use LNG (liquefied natural gas) as fuel, some of the methane gas is discharged unburned outside the system. This type of unburned methane discharged from gas engines is called slipped methane. Because methane has a very high global warming potential compared to carbon dioxide, there is a need to treat the slipped methane within the plant that includes the marine gas engine.

Patent document 1 discloses that slip methane emitted from a power generation gas engine is combusted in a combustor.

JP 2004-360559 A

In the system described in Patent Document 1, if the amount of heating fuel input to the combustor for burning slip methane increases, the effect of reducing greenhouse gas emissions in terms of _CO2 becomes limited.

In view of the above circumstances, an object of the present disclosure is to provide a slip methane treatment device capable of reducing greenhouse gas emissions in terms of _CO2 conversion in a marine gas engine, and a marine propulsion plant equipped with the same.

In order to achieve the above object, a slip methane treatment device according to at least one embodiment of the present disclosure includes:
A combustor;
an exhaust gas supply line for supplying exhaust gas containing slip methane discharged from a marine gas engine to the combustor;
a gas-gas heater located in the exhaust gas supply line between the marine gas engine and the combustor;
An exhaust gas economizer;
an exhaust gas discharge line for supplying exhaust gas discharged from the combustor to the exhaust gas economizer;
Equipped with
The gas-gas heater is located between the combustor and the exhaust gas economizer in the exhaust gas discharge line, and is configured to heat the exhaust gas containing the slip methane flowing through the exhaust gas supply line by heat exchange between the exhaust gas containing the slip methane flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line.

In order to achieve the above object, a marine propulsion plant according to at least one embodiment of the present disclosure includes:
The slip methane treatment device;
The marine gas engine;
a reliquefaction unit for reliquefying the boil-off gas of the liquefied natural gas;
A _N2 -rich gas line for supplying N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor;
Equipped with.

According to the present disclosure, there is provided a slip methane treatment device capable of reducing greenhouse gas emissions in terms of _CO2 conversion in a marine gas engine, and a marine propulsion plant equipped with the same.

FIG. 1 is a diagram showing a schematic configuration of a slip methane treatment device 2 (2A) according to one embodiment. FIG. 2 is a diagram showing a schematic configuration of a slip methane treatment device 2 (2B) according to another embodiment. FIG. 2 is a diagram showing a schematic configuration of a marine propulsion plant 50 equipped with the above-mentioned slip methane treatment device 2. 4 is a schematic diagram showing a configuration for introducing N2-rich gas from the N2-rich gas line 62 shown in FIG. 3 into the combustor 8 of the slip methane treatment device 2 (2A or 2B). FIG. 4 is a schematic diagram showing a modified example of the exhaust heat recovery device 14.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention.
For example, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions indicating that things are in an equal state, such as "identical,""equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained.
On the other hand, the expressions "comprise,""include,""have,""includes," or "have" of one element are not exclusive expressions excluding the presence of other elements.

Figure 1 is a diagram showing the schematic configuration of a slip methane treatment device 2 (2A) according to one embodiment. The slip methane treatment device 2 is mounted on a ship (not shown) and is configured to perform combustion treatment of exhaust gas containing methane gas discharged in an unburned state from a marine gas engine 100 (hereinafter, methane gas discharged in an unburned state from a marine gas engine 100 is referred to as "slip methane"). The marine gas engine 100 is a low-pressure premix type diesel engine (main engine) that uses a fuel gas (e.g., natural gas, etc.) containing methane gas as its main fuel, and is connected to a propeller 102 for generating propulsive force for the ship. Hereinafter, the marine gas engine 100 will be simply referred to as the gas engine 100.

As shown in FIG. 1, the slip methane treatment device 2 includes an exhaust gas supply line 4, a fuel line 6, a combustor 8, an exhaust gas exhaust line 10, a gas-gas heater 12, an exhaust heat recovery device 14, a fuel regulating valve 16, a temperature sensor 18, and a combustor temperature control device 20.

The exhaust gas supply line 4 connects the gas engine 100 and the combustor 8, and is configured to supply exhaust gas containing slip methane discharged from the gas engine 100 to the combustor 8.

The fuel line 6 connects a fuel source (not shown) to the combustor 8, and is configured to supply heating fuel to the combustor 8. The heating fuel may be, for example, the same fuel (e.g., natural gas) as the fuel gas supplied to the marine gas engine 100. The fuel line 6 is provided with a fuel regulating valve 16 that can adjust the flow rate of the heating fuel supplied from the fuel line 6 to the combustor 8.

The combustor 8 is configured to generate combustion gas by combusting the heating fuel supplied from the fuel line 6 and the slip methane supplied from the exhaust gas supply line 4. The combustion temperature of the combustor 8 (the temperature of the combustion gas generated in the combustor 8) is set to a temperature at which the slip methane supplied from the exhaust gas supply line 4 self-combusts in the system including the combustor 8 and the exhaust gas discharge line 10, taking into account the residence time of the slip methane in the system. The combustion temperature of the combustor 8 and the size of the combustor 8 may preferably be such that the slip methane can be completely incinerated by the combustor 8 at the flow rate of the exhaust gas of the gas engine 100 at a predetermined load at which the slip methane should be treated.

In the illustrated configuration, a temperature sensor 18 that measures the combustion temperature of the combustor 8 (the outlet temperature of the combustor 8 in the illustrated example) is provided at a position between the combustor 8 and the exhaust gas economizer 22 of the exhaust heat recovery device 14 in the exhaust gas discharge line 10. The temperature sensor 18 measures the combustion temperature of the combustor 8 by measuring the temperature of the exhaust gas in the exhaust gas discharge line 10. The combustor temperature control device 20 controls the opening of the fuel adjustment valve 16 based on the output of the temperature sensor 18 so that the combustion temperature of the combustor 8 approaches a set temperature (target temperature) at which slip methane self-combusts inside the combustor 8. The combustor temperature control device 20 controls the opening of the fuel adjustment valve 16 so as to reduce the deviation between the set temperature of the combustor 8 and the combustion temperature measured by the temperature sensor 18. It is preferable that this set temperature be set to 537°C or higher, which is the ignition point of methane. This set temperature may be, for example, 537°C or higher and 1000°C or lower from the viewpoint of promoting self-combustion of methane while suppressing high costs due to the heat resistance of the combustor 8, and may be 650°C or higher and 850°C or lower (for example, about 800°C) from the viewpoint of suppressing the increase in size of the exhaust gas discharge line 10 while suppressing high costs due to heat resistance. The set temperature of the combustor 8 may be set manually by a person or automatically by the combustor temperature control device 20. The combustor temperature control device 20 may perform, for example, P control or PI control on the combustion temperature of the combustor 8 based on the above deviation.

The combustor temperature control device 20 may be composed of an electric circuit or a computer. When the combustor temperature control device 20 is composed of a computer, it has a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory) and a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and the processor executes a program stored in the storage device to realize its functions.

As shown in FIG. 1, the exhaust gas discharge line 10 connects the combustor 8 to the exhaust gas economizer 22 of the exhaust heat recovery device 14, and is configured to supply the exhaust gas (combustion exhaust gas) heated in the combustor 8 and discharged from the combustor 8 to the exhaust gas economizer 22.

The gas-gas heater 12 is located between the gas engine 100 and the combustor 8 in the exhaust gas supply line 4, and between the combustor 8 and the exhaust gas economizer 22 of the exhaust heat recovery device 14 in the exhaust gas discharge line 10. The gas-gas heater 12 is configured as a heat exchanger that heats the exhaust gas containing slip methane flowing through the exhaust gas supply line 4 by heat exchange between the exhaust gas containing slip methane flowing through the exhaust gas supply line 4 and the exhaust gas flowing through the exhaust gas discharge line 10. Note that each of the combustor 8 and the gas-gas heater 12 may be configured as part of a single common duct burner.

The exhaust heat recovery system 14 includes an exhaust gas economizer 22, a steam turbine 24, a generator 26, a condenser 28, a steam line 30, and a condensate line 32.

The exhaust gas economizer 22 is configured to heat and evaporate water (condensate) supplied from the condensate line 32 by exhaust gas supplied from the exhaust gas discharge line 10, thereby generating steam. The steam generated by the exhaust gas economizer 22 is supplied to the steam turbine 24 through a steam line 30 connecting the exhaust gas economizer 22 and the steam turbine 24, and drives the steam turbine 24. A generator 26 is connected to the steam turbine 24, and the steam turbine 24 is driven by the steam supplied from the exhaust gas economizer 22 through the steam line 30, thereby generating electric power from the generator 26. The electric power obtained from the generator 26 is consumed by the ship on which the gas engine 100 is mounted so as to cover at least a part of the electric power demand (hereinafter referred to as "onboard electric power demand"). The exhaust gas supplied to the exhaust gas economizer 22 from the exhaust gas discharge line 10 is heat exchanged with the water supplied from the condensate line 32 in the exhaust gas economizer 22, and then released into the atmosphere.

The steam that passes through the steam turbine 24 is condensed in the condenser 28 to become condensed water, which is then supplied back to the exhaust gas economizer 22 via a condensate line 32 that connects the condenser 28 to the exhaust gas economizer 22.

The gas-gas heater 12 of the slip methane treatment device 2 is configured to heat the flue gas containing slip methane flowing through the flue gas supply line 4 by heat exchange between the flue gas containing slip methane flowing through the flue gas supply line 4 and the flue gas flowing through the flue gas discharge line 10. Therefore, the temperature of the flue gas supplied from the flue gas supply line 4 to the combustor 8 can be raised before being supplied to the combustor 8. Therefore, the amount of fuel input (the amount of fuel input from the fuel line 6 to the combustor 8) required to make the combustion temperature of the combustor 8 a temperature at which the slip methane self-combusts inside the combustor 8 can be reduced, and greenhouse gas emissions in terms of _CO2 can be reduced.

FIG. 2 is a diagram showing a schematic configuration of a slip methane treatment device 2 (2B) according to another embodiment.
The slip methane treatment device 2 (2B) shown in Figure 2 differs from the above-mentioned slip methane treatment device 2 (2A) in that it is provided with a bypass line 34, a bypass valve 36, and a bypass valve control device 38, but other configurations are similar to those of the above-mentioned slip methane treatment device 2 (2A). In the slip methane treatment device 2 (2B) shown in Figure 2, reference symbols common to the respective components of the slip methane treatment device 2 (2A) shown in Figure 1 indicate the same components as those of the slip methane treatment device 2 (2A) shown in Figure 1, unless otherwise specified, and explanations thereof will be omitted.

As shown in FIG. 2, the bypass line 34 is configured to branch off from the exhaust gas discharge line 10 at a position between the combustor 8 and the gas-gas heater 12 in the exhaust gas discharge line 10, and to merge with the exhaust gas discharge line 10 at a position between the gas-gas heater 12 and the exhaust gas economizer 22 in the exhaust gas discharge line 10. That is, the bypass line 34 is configured to supply the exhaust gas discharged from the combustor 8 directly to the exhaust gas economizer 22, bypassing the gas-gas heater 12 (without supplying it to the gas-gas heater 12). The bypass line 34 is provided with a bypass valve 36 capable of adjusting the flow rate of the exhaust gas flowing through the bypass line 34.

The bypass valve control device 38 is configured to control the bypass valve 36 based on demand information regarding the demand (demand amount) of energy to be recovered by the exhaust gas economizer 22. The bypass valve control device 38 is configured to increase the opening of the bypass valve 36 as the demand for energy indicated by the demand information increases.

For example, the demand information may indicate the onboard electricity demand (the demand for electricity used onboard) of the ship on which the gas engine 100 is installed, and in this case, the bypass valve control device 38 is configured to increase the opening of the bypass valve 36 as the onboard electricity demand indicated by the demand information increases.

The bypass valve control device 38 may be composed of an electric circuit or a computer. When the combustor temperature control device 20 is composed of a computer, it has a storage device such as a RAM or ROM and a processor such as a CPU or GPU, and the processor executes a program stored in the storage device to realize its functions.

Even in the configuration shown in FIG. 2, the combustion temperature of the combustor 8 is set to a temperature at which the slip methane supplied from the exhaust gas supply line 4 will self-combust inside the combustor 8. In addition, a temperature sensor 18 that measures the combustion temperature of the combustor 8 (the outlet temperature of the combustor 8 in the illustrated configuration) is provided in the exhaust gas discharge line 10, and the combustor temperature control device 20 controls the aperture of the fuel adjustment valve 16 based on the output of the temperature sensor 18 so that the combustion temperature of the combustor 8 approaches the above-mentioned set temperature at which the slip methane will self-combust inside the combustor 8. The combustor temperature control device 20 controls the aperture of the fuel adjustment valve 16 so as to reduce the deviation between the set temperature of the combustor 8 and the combustion temperature measured by the temperature sensor 18.

2, the larger the opening of the bypass valve 36, the larger the proportion of the flow rate of the exhaust gas that bypasses the gas-gas heater 12 and flows through the bypass line 34 in the flow rate of the exhaust gas discharged from the combustor 8. That is, the larger the opening of the bypass valve 36, the smaller the heat exchange amount in the gas-gas heater 12 (the heat exchange amount between the exhaust gas flowing through the exhaust gas supply line 4 and the exhaust gas flowing through the exhaust gas discharge line 10) can be, while increasing the heat exchange amount in the exhaust gas economizer 22 (the heat exchange amount between the water flowing through the condensate line 32 and the exhaust gas flowing through the exhaust gas discharge line 10). This increases the amount of heat recovered in the exhaust gas economizer 22, and increases the amount of power generated by the generator 26 connected to the steam turbine 24. In addition, the larger the opening of the bypass valve 36, the less heat is exchanged in the gas-gas heater 12, and the lower the temperature of the exhaust gas entering the combustor 8 from the exhaust gas supply line 4. Therefore, the opening of the fuel regulating valve 16 is increased to increase the amount of fuel fed from the fuel line 6 to the combustor 8.

In this way, the greater the opening of the bypass valve 36, the more of the thermal energy of the exhaust gas discharged from the combustor 8 can be recovered by the exhaust gas economizer 22, and the amount of electricity generated by the generator 26 connected to the steam turbine 24 can be increased.

Therefore, by increasing the opening of the bypass valve 36 as the onboard power demand indicated by the demand information increases as described above, it is possible to increase the amount of power generated by the generator 26 connected to the steam turbine 24 as the onboard power demand increases. In other words, by decreasing the opening of the bypass valve 36 as the onboard power demand indicated by the demand information decreases, it is possible to decrease the amount of power generated by the generator 26 connected to the steam turbine 24 as the onboard power demand decreases. In this way, since it is possible to respond to increases and decreases in onboard power demand by utilizing the exhaust heat generated by the combustion treatment of slip methane, it is not necessary to operate the diesel engine for power generation (or the frequency of operation is reduced) compared to a case in which all of the onboard power is supplied by a diesel engine for power generation or the like, and this makes it possible to realize a reduction in fuel consumption and a reduction in greenhouse gas emissions in terms of _CO2 .

Figure 3 is a diagram showing the schematic configuration of a marine propulsion plant 50 equipped with the above-mentioned slip methane treatment device 2. The slip methane treatment device 2 equipped in the marine propulsion plant 50 may be either the slip methane treatment device 2 (2A) shown in Figure 1 or the slip methane treatment device 2 (2B) shown in Figure 2.

3, the marine propulsion plant 50 includes the slip methane treatment device 2, the gas engine 100, the propeller 102, a power generating gas engine 110, an LNG tank 52, a gas compressor 54, a reliquefaction device 56, a heat exchanger 58, a fuel gas line 60, a _N2 rich gas line 62, and a return line 64. The gas engine 110 is a diesel engine (auxiliary engine) fueled by a fuel gas (e.g., natural gas, etc.) containing methane gas, and is connected to a generator 112 that generates electricity to cover at least a part of the onboard power demand.

LNG (liquefied natural gas) is stored in the LNG tank 52. The fuel gas line 60 is connected to the LNG tank 52 at one end and branches at the other end to connect to the gas engines 100, 110 and the combustor 8 of the slip methane treatment device 2. The portion of the fuel gas line 60 that connects the branch position P1 to the combustor 8 corresponds to the above-mentioned fuel line 6. The gas compressor 54 and the heat exchanger 58 are provided in the fuel gas line 60, and the gas compressor 54 is located between the LNG tank 52 and the heat exchanger 58 in the fuel gas line 60. The fuel gas line 60 branches between the gas compressor 54 and the heat exchanger 58 and connects to the reliquefaction device 56.

Natural gas vaporized in the LNG tank 52 (hereinafter referred to as "boil-off gas") is pressurized by the gas compressor 54, heated by the heat exchanger 58, and then supplied to the gas engines 100 and 110 as fuel gas. The surplus natural gas vaporized in the LNG tank 52 that is not supplied to either of the gas engines 100 and 110 is reliquefied by the reliquefaction device 56 to become LNG, and is returned to the LNG tank 52 via the return line 64. In the exemplary embodiment shown in FIG. 3, in order to suppress the tank internal pressure within a specified value in an emergency such as when the internal pressure of the LNG tank 52 becomes excessively high, a discharge line 72 configured to directly supply the boil-off gas to the combustor 8 via the _N2- rich gas line 62 without supplying it to the gas compressor 54 or the reliquefaction device 56 is provided.

The gas that remains uncondensed when the boil-off gas is reliquefied by the reliquefaction device 56 contains a large amount of _N2 gas and is called _N2- rich gas. The concentration of _N2 in this N2 _- rich gas is higher than the concentration of _N2 in the boil-off gas. The _N2- rich gas is supplied to the combustor 8 of the slip methane treatment device 2 through an N2 _- rich gas line 62 that connects the reliquefaction device 56 and the combustor 8 of the slip methane treatment device 2.

FIG. 4 is a schematic diagram showing a configuration for introducing N2 _- rich gas from the N2 _- rich gas line 62 shown in FIG. 3 into the combustor 8 of the slip methane treatment device 2 (2A or 2B).
As shown in Fig. 4, the combustor 8 can be supplied with heating fuel (main fuel) from a fuel line 6 (fuel gas line 60), and can be supplied with _N2- rich gas from an N2 _- rich gas line 62. In the embodiment illustrated in Fig. 4, the N2 _- rich gas line 62 merges with the fuel line 6 outside the combustor 8, but the N2 _- rich gas line 62 and the fuel line 6 may not merge with each other outside the combustor 8 and may be connected to the combustor 8 independently.

The N2 _- rich gas line 62 is provided with an N2 _- rich gas valve 66 capable of adjusting the flow rate of the N2 _- rich gas, and the N2 _- rich gas valve 66 is in an open state (for example, fully open state) regardless of whether the gas engine 100 is operating or stopped. Therefore, the entire amount of N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device 56 is input to the combustor 8 through the _{N2- rich} gas line 62. In addition, the combustor temperature control device 20 is configured to control the fuel adjustment valve 16 so that the combustion temperature of the combustor 8 approaches the above-mentioned set temperature when the N2-rich gas valve 66 is open. Therefore, the _N2- rich gas from the N2 _- rich gas line 62 is supplied to the combustor 8 preferentially over the heating fuel from the fuel line 6. The burner of the combustor 8 may be configured in consideration of the maximum input fuel amount required to combust and treat the slip methane contained in the exhaust gas at the design point of the gas engine 100 and the maximum processing amount of the N2 _- rich gas, whichever is larger.

Conventionally, N2 _- rich gas generated in the process of re-liquefying boil-off gas in a re-liquefaction device cannot be used as fuel for the gas engines of the main engine or auxiliary engine, so it has been incinerated by a gas combustion unit (GCU) or a dual fuel boiler (DF boiler). When a GCU is used, the energy obtained by combustion in the GCU cannot be effectively utilized, and the installation space of the GCU occupies the limited space on the ship. In addition, when a DF boiler is used, it is necessary to complete the warming of the boiler in advance, and there is a concern that extra fuel will be consumed for the warming. In addition, if the warming can is not held, it is not possible to respond immediately when gas to be treated is generated, and it may be difficult to combust the N2 _- rich gas and keep the internal pressure of the LNG tank 52 within an appropriate range.

In contrast, according to the marine propulsion plant 50, the N2 _- rich gas line 62 is provided for supplying the N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device 56 to the combustor 8, so that the N2 _- rich gas can be incinerated using the combustor 8 for combusting the slip methane. Therefore, there is no need to provide a dedicated device for incinerating the N2 _- rich gas, such as a GCU or DF boiler, and space can be saved and equipment costs can be reduced.

Also, unlike the DF boiler, the slip methane treatment device 2 is always in operation when the gas engine 100 is in operation as the main engine, so there is no need for preparation/standby operations such as a warm-up boiler. Also, by partially supplementing the fuel fed from the fuel line 6 to the combustor 8 for slip methane treatment with N2 _- rich gas, the fuel consumption of the entire marine propulsion plant 50 can be reduced.

Furthermore, normally, when the ship is stopped, the gas engine 100 serving as the main engine is stopped, but even in such a case, N2 _- rich gas can be fed from the N2 _- rich gas line 62 into the combustor 8 for combustion treatment, and the energy of the exhaust gas discharged from the combustor 8 can be recovered as electric power by the generator 26 of the exhaust heat recovery device 14. Note that, when the onboard electric power demand cannot be met only by the exhaust heat recovery by the exhaust heat recovery device 14, it is possible to make up for the shortfall in the onboard electric power demand by starting the gas engine 110 for power generation, for example.

The present disclosure is not limited to the above-described embodiments, but also includes variations of the above-described embodiments and appropriate combinations of these embodiments.

For example, the exhaust heat recovery device 14 of the above-mentioned slip methane treatment device 2 (2A or 2B) may be provided with a dump line 68 shown in FIG. 5. The dump line 68 branches off from the steam line 30 at a position between the exhaust gas economizer 22 and the steam turbine 24 in the steam line 30, and merges with the steam line 30 at a position between the steam turbine 24 and the condenser in the steam line 30. The dump line 68 is configured to guide the steam generated in the exhaust gas economizer 22 to the condenser 28, bypassing the steam turbine 24 (without supplying it to the steam turbine 24). The dump line 68 is provided with a dump valve 70. The dump valve 70 is normally closed, but can be opened to dump the steam (bypass the steam turbine 24 and guide it to the condenser 28) when the load suddenly changes.

In addition, in some of the above-described embodiments, the combustor temperature control device 20 and the bypass valve control device 38 are described separately for convenience, but the combustor temperature control device 20 and the bypass valve control device 38 may be configured using common hardware.

The contents described in each of the above embodiments can be understood, for example, as follows:

(1) A slip methane treatment device according to one embodiment of the present disclosure (for example, the above-mentioned slip methane treatment device 2 (2A, 2B)
a combustor (e.g., combustor 8 described above);
An exhaust gas supply line (e.g., the above-mentioned exhaust gas supply line 4) for supplying exhaust gas containing slip methane discharged from a marine gas engine (e.g., the above-mentioned marine gas engine 100) to the combustor;
a gas-gas heater (such as the gas-gas heater 12 described above) located in the exhaust gas supply line between the marine gas engine and the combustor;
an exhaust gas economizer (e.g., exhaust gas economizer 22 described above);
an exhaust gas discharge line (e.g., the above-mentioned exhaust gas discharge line 10) for supplying the exhaust gas discharged from the combustor to the exhaust gas economizer;
Equipped with
The gas-gas heater is located between the combustor and the exhaust gas economizer in the exhaust gas discharge line, and is configured to heat the exhaust gas containing the slip methane flowing through the exhaust gas supply line by heat exchange between the exhaust gas containing the slip methane flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line.

According to the slip methane treatment device described in (1) above, the slip methane treatment device is equipped with a gas-gas heater, and the gas-gas heater is configured to heat the exhaust gas containing slip methane flowing through the exhaust gas supply line by heat exchange between the exhaust gas containing slip methane flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line.

This makes it possible to raise the temperature of the exhaust gas supplied from the exhaust gas supply line to the combustor before it is supplied to the combustor, thereby reducing the amount of fuel input (the amount of fuel input from the fuel line to the combustor) required to make the combustion temperature of the combustor an appropriate temperature for combusting slip methane, and thus reducing greenhouse gas emissions in terms of _CO2 from the marine gas engine.

(2) In some embodiments, in the slip methane treatment device described in (1) above,
A fuel line (e.g., the above-mentioned fuel line 6) for supplying heating fuel to the combustor;
A fuel regulating valve (e.g., the above-mentioned fuel regulating valve 16) provided in the fuel line;
a combustor temperature control device (e.g., the combustor temperature control device 20 described above) configured to control the combustion temperature of the combustor by controlling the fuel metering valve;
A temperature sensor (e.g., the above-mentioned temperature sensor 18) that measures the temperature of the exhaust gas;
Equipped with
The combustor temperature control device is configured to control the fuel regulating valve based on an output of the temperature sensor so as to bring the combustion temperature of the combustor closer to a set temperature.

According to the slip methane treatment device described in (2) above, the combustor temperature control device can control the fuel adjustment valve based on the output of the temperature sensor so that the combustion temperature of the combustor approaches a set temperature at which the slip methane self-combusts inside the combustor. This makes it possible to suppress oversupply and undersupply to the combustor of heating fuel for combusting and treating the slip methane emitted from the marine gas engine.

(3) In some embodiments, in the slip methane treatment device described in (2) above,
The set temperature is 537° C. or higher.

According to the slip methane treatment device described in (3) above, the combustion temperature of the combustor can be increased to 537°C or higher, which is the ignition point of methane, and the slip methane can be self-combusted in the combustor.

(4) In some embodiments, in the slip methane treatment device according to any one of (3) above,
The set temperature is 1000° C. or less.

If the combustion temperature of the combustor is too high, the material that constitutes the combustor will require high heat resistance, which will lead to high costs for the combustor. For this reason, as described in (4) above, the combustion temperature of the combustor may be set to 1000°C or less.

(5) In some embodiments, in the slip methane treatment device according to any one of (1) to (4),
The exhaust gas discharge line further includes a bypass line (e.g., the above-mentioned bypass line 34) that branches off from the exhaust gas discharge line at a position between the combustor and the gas-gas heater in the exhaust gas discharge line and joins the exhaust gas discharge line at a position between the gas-gas heater and the exhaust gas economizer in the exhaust gas discharge line.

According to the slip methane treatment device described in (5) above, by flowing exhaust gas through the bypass line, the amount of heat exchange in the gas-gas heater (the amount of heat exchange between the exhaust gas flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line) is reduced, while the amount of heat exchange in the exhaust gas economizer (the amount of heat exchange between the water supplied to the exhaust gas economizer and the exhaust gas flowing through the exhaust gas discharge line) is increased, thereby increasing the amount of heat recovered in the exhaust gas economizer. Therefore, the amount of heat recovered in the exhaust gas economizer can be changed according to the demand for energy recovered by the exhaust gas economizer.

(6) In some embodiments, in the slip methane treatment device described in (5) above,
A bypass valve (e.g., the above-mentioned bypass valve 36) provided in the bypass line;
a bypass valve controller (e.g., the bypass valve controller 38 described above) configured to control the bypass valve based on demand information relating to a demand for energy required to be recovered by the exhaust gas economizer;
It further comprises:

According to the slip methane treatment device described in (6) above, the larger the opening of the bypass valve, the larger the proportion of the flow rate of the exhaust gas that bypasses the gas-gas heater and flows through the bypass line in the flow rate of the exhaust gas discharged from the combustor. In other words, the larger the opening of the bypass valve, the smaller the amount of heat exchange in the gas-gas heater (the amount of heat exchange between the exhaust gas flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line) is, while the larger the amount of heat exchange in the exhaust gas economizer (the amount of heat exchange between the water supplied to the exhaust gas economizer and the exhaust gas flowing through the exhaust gas discharge line) is, thereby increasing the amount of heat recovered in the exhaust gas economizer. Therefore, the amount of heat recovered in the exhaust gas economizer can be changed according to the demand for energy recovered in the exhaust gas economizer.

(7) In some embodiments, in the slip methane treatment device described in (6) above,
The bypass valve control device is configured to increase an opening degree of the bypass valve as the demand indicated by the demand information increases.

According to the slip methane treatment device described in (7) above, as the demand for energy recovered by the exhaust gas economizer increases, the amount of heat recovered by the exhaust gas economizer can be increased to meet the demand.

(8) In some embodiments, in the slip methane treatment device described in (7) above,
a steam turbine driven by steam generated in the exhaust gas economizer;
a generator coupled to the steam turbine;
Further comprising:
the demand information indicates an onboard electricity demand of a ship on which the marine gas engine is mounted,
The bypass valve control device is configured to increase the opening degree of the bypass valve as the onboard electricity demand indicated by the demand information increases.

According to the slip methane treatment device described in (8) above, by increasing the amount of heat recovered in the exhaust gas economizer as the onboard electricity demand increases, the output of the generator connected to the steam turbine can be increased to meet the onboard electricity demand.

(9) A marine propulsion plant according to one embodiment of the present disclosure includes:
A slip methane treatment device according to any one of (1) to (8) above;
The marine gas engine;
a reliquefaction unit (e.g., reliquefaction unit 56 described above) for reliquefying the boil-off gas of the liquefied natural gas;
An N2 _- rich gas line (for example, the above-mentioned N2 _- rich gas line 62) for supplying N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor;
Equipped with.

Conventionally, N2 _- rich gas generated in the process of re-liquefying boil-off gas in a re-liquefaction device cannot be used as fuel for the gas engines of the main engine or auxiliary engine, so it has been incinerated by a gas combustion unit (GCU) or a dual fuel boiler (DF boiler). When a GCU is used, the energy obtained by combustion in the GCU cannot be effectively utilized, and the installation space of the GCU occupies the limited space on the ship. In addition, when a DF boiler is used, it is necessary to complete the warming of the boiler in advance, and there is a concern that extra fuel will be consumed for the warming. In addition, if the warming can is not held, it is not possible to respond immediately when the gas to be treated is generated, and it may be difficult to keep the internal pressure of the LNG tank within an appropriate range.

In contrast, according to the marine propulsion plant described in (9) above, since an N2 _- rich gas line is provided for supplying the N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor, the N2 _- rich gas can be incinerated using the combustor for combusting the slip methane. Therefore, there is no need to provide a dedicated device for incinerating the _N2- rich gas, such as a GCU or DF boiler, and space can be saved and equipment costs can be reduced.
In addition, unlike the DF boiler, the slip methane treatment device is always in operation when the gas engine is in operation as the main engine, so there is no need for preparation/standby operations like a warm boiler. In addition, by partially supplementing the fuel fed from the fuel line to the combustor for slip methane treatment with N2 _- rich gas, the fuel consumption of the entire marine propulsion plant can be reduced.

(10) A marine propulsion plant according to one embodiment of the present disclosure includes:
A slip methane treatment device according to any one of (2) to (4) above;
The marine gas engine;
a reliquefaction unit (e.g., reliquefaction unit 56 described above) for reliquefying the boil-off gas of the liquefied natural gas;
An N2 _- rich gas line (for example, the above-mentioned N2 _- rich gas line 62) for supplying N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor;
Equipped with
The _N2- rich gas from the N2 _- rich gas line is supplied to the combustor preferentially over the heating fuel from the heating fuel line.

According to the marine propulsion plant described in (10) above, the N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device is supplied to the combustor preferentially over the heating fuel, thereby making it possible to save the fuel input from the fuel line to the combustor for slip methane treatment, and thus reducing the fuel consumption of the entire marine propulsion plant.

(11) A marine propulsion plant according to an embodiment of the present disclosure,
A slip methane treatment device according to any one of (2) to (4) above;
The marine gas engine;
a reliquefaction unit (e.g., reliquefaction unit 56 described above) for reliquefying the boil-off gas of the liquefied natural gas;
An N2 _- rich gas line (for example, the above-mentioned N2 _- rich gas line 62) for supplying N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor;
An N2 _- rich gas valve (for example, the above-mentioned N2 _- rich gas valve 66) provided in the N2 _- rich gas line;
Equipped with
The combustor temperature control device is configured to control the fuel adjustment valve so as to bring the combustion temperature closer to the set temperature when the _N2 rich gas valve is open.

According to the marine propulsion plant described in (11) above, the combustor temperature control device controls the fuel adjustment valve so that the combustion temperature of the combustor approaches the set temperature when the N2 _- rich gas valve is open. Therefore, the N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device is supplied to the combustor preferentially over the heating fuel, and the combustion temperature of the combustor can be controlled to a temperature for appropriately combusting the slip methane. Therefore, the slip methane can be appropriately combusted by utilizing the N2 _- rich gas while saving the fuel input from the fuel line to the combustor for slip methane treatment. Therefore, the slip methane can be appropriately combusted while suppressing the fuel consumption in the entire marine propulsion plant.

2 Slip methane treatment device 4 Exhaust gas supply line 6 Fuel line 8 Combustor 10 Exhaust gas exhaust line 12 Gas-gas heater 14 Exhaust heat recovery device 16 Fuel adjustment valve 18 Temperature sensor 20 Combustor temperature control device 22 Exhaust gas economizer 24 Steam turbine 26, 112 Generator 28 Condenser 30 Steam line 32 Condensate line 34 Bypass line 36 Bypass valve 38 Bypass valve control device 50 Marine propulsion plant 52 LNG tank 54 Gas compressor 56 Reliquefaction device 58 Heat exchanger 60 Fuel gas line 62 _N2 rich gas line 64 Return line 66 Rich gas valve 68 Dump line 70 Dump valve 72 Discharge line 100 Marine gas engine 102 Propeller 110 Power generation gas engine

Claims (10)

A combustor;
an exhaust gas supply line for supplying exhaust gas containing slip methane discharged from a marine gas engine to the combustor;
a gas-gas heater located in the exhaust gas supply line between the marine gas engine and the combustor;
An exhaust gas economizer;
an exhaust gas discharge line for supplying the exhaust gas discharged from the combustor to the exhaust gas economizer;
A bypass line,
Equipped with
the gas-gas heater is located between the combustor and the exhaust gas economizer in the exhaust gas discharge line, and is configured to heat the exhaust gas containing the slip methane flowing through the exhaust gas supply line by heat exchange between the exhaust gas containing the slip methane flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line ;
A slip methane treatment device, wherein the bypass line branches off from the exhaust gas discharge line at a position between the combustor and the gas-gas heater in the exhaust gas discharge line, and joins the exhaust gas discharge line at a position between the gas-gas heater and the exhaust gas economizer in the exhaust gas discharge line . a fuel line for supplying heating fuel to the combustor;
a fuel regulating valve provided in the fuel line;
a combustor temperature control device configured to control a combustion temperature of the combustor by controlling the fuel metering valve;
A temperature sensor that measures a combustion temperature of the combustor;
Equipped with
The slip methane treatment device according to claim 1 , wherein the combustor temperature control device is configured to control the fuel adjustment valve based on an output of the temperature sensor so as to bring the combustion temperature of the combustor closer to a set temperature. The slip methane treatment device according to claim 2, wherein the set temperature is 537°C or higher. The slip methane treatment device according to claim 3, wherein the set temperature is 1000°C or less. a bypass valve provided in the bypass line;
A bypass valve control device configured to control the bypass valve based on demand information regarding a demand for energy to be recovered by the exhaust gas economizer;
The slip methane treatment apparatus of claim 1 further comprising: The slip methane treatment device according to claim 5 , wherein the bypass valve control device is configured to increase an opening degree of the bypass valve as the demand indicated by the demand information increases. a steam turbine driven by steam generated in the exhaust gas economizer;
a generator coupled to the steam turbine;
Further comprising:
the demand information indicates an onboard electricity demand of a ship on which the marine gas engine is mounted,
The slip methane treatment device according to claim 6 , wherein the bypass valve control device is configured to increase an opening degree of the bypass valve as the onboard electricity demand indicated by the demand information increases. a slip methane treatment device including a combustor, an exhaust gas supply line for supplying exhaust gas containing slip methane discharged from a marine gas engine to the combustor, a gas-gas heater located between the marine gas engine and the combustor in the exhaust gas supply line, an exhaust gas economizer, and an exhaust gas discharge line for supplying the exhaust gas discharged from the combustor to the exhaust gas economizer ;
The marine gas engine;
a reliquefaction unit for reliquefying the boil-off gas of the liquefied natural gas;
A _N2 -rich gas line for supplying N2 _- rich gas generated when the boil-off gas is reliquefied by the reliquefaction device to the combustor;
Equipped with
The gas-gas heater is located between the combustor and the exhaust gas economizer in the exhaust gas discharge line, and is configured to heat the exhaust gas containing the slip methane flowing through the exhaust gas supply line by heat exchange between the exhaust gas containing the slip methane flowing through the exhaust gas supply line and the exhaust gas flowing through the exhaust gas discharge line . The slip methane treatment device comprises:
a fuel line for supplying heating fuel to the combustor;
a fuel regulating valve provided in the fuel line;
a combustor temperature control device configured to control a combustion temperature of the combustor by controlling the fuel metering valve;
A temperature sensor that measures a combustion temperature of the combustor;
Equipped with
the combustor temperature control device is configured to control the fuel adjustment valve based on an output of the temperature sensor so as to bring the combustion temperature of the combustor closer to a set temperature;
9. The marine propulsion plant according to claim 8 , wherein the N2 _- rich gas from the _N2- rich gas line is supplied to the combustor in preference to the heating fuel from the fuel line. The slip methane treatment device comprises:
a fuel line for supplying heating fuel to the combustor;
a fuel regulating valve provided in the fuel line;
a combustor temperature control device configured to control a combustion temperature of the combustor by controlling the fuel metering valve;
A temperature sensor that measures a combustion temperature of the combustor;
Equipped with
the combustor temperature control device is configured to control the fuel adjustment valve based on an output of the temperature sensor so as to bring the combustion temperature of the combustor closer to a set temperature;
The marine propulsion plant further includes a N2 _- rich gas valve provided in the N2 _- rich gas line,
9. The marine propulsion plant according to claim 8 , wherein the combustor temperature control device is configured to control the fuel regulating valve so as to bring the combustion temperature of the combustor closer to the set temperature when the _N2 rich gas valve is open.

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