WO2020071270A1

WO2020071270A1 - Waste heat recovery system, ship, and method for operating waste heat recovery device

Info

Publication number: WO2020071270A1
Application number: PCT/JP2019/038130
Authority: WO
Inventors: 龍太中村; 貴澄寺原; 健太高本; 浩市松下
Original assignee: 三菱重工マリンマシナリ株式会社
Priority date: 2018-10-03
Filing date: 2019-09-27
Publication date: 2020-04-09
Also published as: JP2020056551A; JP7319769B2

Abstract

This waste heat recovery system includes: a combustion device capable of using two or more types of fuels by switching therebetween; an exhaust gas line through which exhaust gas from the combustion device flows; a vessel for storing saturated water and steam; a water supply line for supplying water to the vessel; a saturated steam line through which the saturated steam from the vessel flows; a heat exchanger that is provided in the exhaust gas line and is for heating the water in the water supply line by performing heat exchange between the water and the exhaust gas; a valve that is provided in the saturated steam line and is for adjusting the pressure in the vessel; and a control unit that is configured to adjust, upon receiving a signal indicating that the fuel supplied to the combustion device has been switched, the valve aperture on the basis of the signal to change the pressure in the vessel. The control unit is configured to adjust the valve aperture so that the pressure in the vessel is a second pressure when the fuel is a second fuel and a first pressure lower than the second pressure when the fuel is a first fuel having a lower sulfur concentration than the second fuel.

Description

Exhaust heat recovery system, ship and method of operating exhaust heat recovery device

The present disclosure relates to an exhaust heat recovery system, a ship, and an operation method of an exhaust heat recovery device.

熱 In some cases, the heat of the high-temperature exhaust gas discharged from the combustion device is recovered using a heat exchanger and used for purposes such as steam generation.

For example, in Patent Document 1, in a boiler plant including a boiler capable of switching between gas fuel and heavy oil fuel for combustion, an economizer uses combustion gas (exhaust gas) from the boiler and water supply before being supplied to the boiler. It is described that the heat exchange is performed in order to preheat the feedwater. Patent Literature 1 describes that the temperature of water supplied to the above-described economizer is adjusted according to the type of fuel (gas fuel or heavy oil fuel) used in the boiler.

Japanese Patent No. 6219742

By the way, the fuel sometimes contains sulfur. In this case, if the temperature of the combustion gas (exhaust gas) of the fuel is lower than the acid dew point, the acid such as pipes constituting the flow path of the combustion gas becomes acidic. Corrosion can occur. Therefore, it is necessary to appropriately manage the temperature of the exhaust gas at the outlet of a heat exchanger (e.g., economizer) for recovering heat from the exhaust gas.

Here, it is considered that a high sulfur fuel having a relatively high sulfur concentration and a low sulfur fuel having a relatively low sulfur concentration are switched and used in a combustion device (engine, boiler, or the like).
In order to prevent acid corrosion when using a high sulfur fuel, the temperature of the exhaust gas at the outlet of the heat exchanger to which the exhaust gas from the combustion device is guided is set to a temperature based on the acid dew point of the high sulfur fuel (which is higher than the acid dew point). If the fuel is switched to low-sulfur fuel, the operation will be performed at a temperature much higher than the acid dew point of the low-sulfur fuel (lower than the high-sulfur fuel). The increase in waste heat recovery when using sulfur fuel cannot be expected.
On the other hand, when the exhaust gas temperature at the outlet of the heat exchanger is set to a temperature based on the acid dew point of the low sulfur fuel (a temperature higher than the acid dew point), when the fuel is switched to the high sulfur fuel and used, Operation at temperatures lower than the acid dew point of the high sulfur fuel (higher acid dew point than the low sulfur fuel) can occur, which can result in acid corrosion of the equipment.

In view of the above circumstances, at least one embodiment of the present invention is directed to an exhaust heat recovery system capable of increasing the amount of exhaust heat recovery while protecting equipment from acid corrosion, a ship including the same, and an exhaust heat recovery system. An object of the present invention is to provide a method of operating a recovery device.

(1) The exhaust heat recovery system according to at least one embodiment of the present invention includes:
A combustion device that can be used by switching between two or more types of fuel;
An exhaust gas line through which exhaust gas from the combustion device flows,
A container for storing saturated water and steam;
A water supply line for supplying water to the container,
A saturated steam line through which saturated steam from the vessel flows;
A heat exchanger that is provided in the exhaust gas line and heats the water in the water supply line by heat exchange with the exhaust gas,
A valve provided in the saturated steam line, for adjusting the pressure of the vessel;
When receiving a signal indicating that the fuel supplied to the combustion device has been switched, a control unit configured to change the pressure of the container by adjusting the opening degree of the valve based on the signal. And
When the fuel is the second fuel, the control unit adjusts the opening degree of the valve so that the pressure of the container becomes the second pressure, and the fuel has a sulfur concentration lower than that of the second fuel. When the first fuel is low, the opening degree of the valve is adjusted so that the pressure of the container becomes a second pressure lower than the second pressure.

(4) The exhaust gas generated by combustion of the fuel has an acid dew point corresponding to the sulfur concentration of the fuel, and the higher the sulfur concentration, the higher the acid dew point of the exhaust gas generated from the fuel. Further, in order to protect devices such as heat exchangers and pipes that constitute a flow path of exhaust gas from acid corrosion, it is necessary to maintain the temperature of the exhaust gas in these devices at a temperature higher than the acid dew point of the exhaust gas. .

In this regard, in the configuration of the above (1), when the first fuel that is a low sulfur fuel is used as the fuel for the combustion device, the pressure (that is, the saturation pressure) in the above-described container is lower than when the second fuel is used. The temperature of the exhaust gas at the outlet of the heat exchanger was reduced by the amount corresponding to the decrease in the acid dew point because the valve opening was adjusted so that the pressure became 1 and the temperature in the container (that is, the saturation temperature) was reduced. That is, the amount of exhaust heat recovered in the heat exchanger can be increased.
In the configuration (1), when the second fuel that is a high sulfur fuel is used as the fuel for the combustion device, the pressure in the above-described container (that is, the saturation pressure) is higher than when the first fuel is used. The temperature of the exhaust gas at the outlet of the heat exchanger is increased by the amount corresponding to the increase in the acid dew point because the opening degree of the valve is adjusted so as to obtain the pressure and the temperature in the container (that is, the saturation temperature) is increased. By doing so, it is possible to protect devices such as heat exchangers and pipes from acid corrosion.
Therefore, according to the above configuration (1), the amount of exhaust heat recovery by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel, thereby protecting the equipment from acid corrosion. However, the amount of exhaust heat recovery can be increased.

Incidentally, as described above, when the amount of exhaust heat recovery by the heat exchanger is to be adjusted by adjusting the valve opening, for example, the valve opening may be adjusted based on the exhaust gas temperature at the heat exchange outlet. However, the exhaust gas temperature has a distribution in a plane orthogonal to the flow of the exhaust gas, and the control may vary depending on the temperature detection point. In the control based on the temperature, the control response may be delayed.
On the other hand, since the pressure in the container is substantially the same regardless of the location, the detected value of the pressure in the container is more accurate than the detected value of the temperature of the exhaust gas at the outlet of the heat exchanger. Control based on pressure tends to have a faster control response than control based on temperature.

In this regard, according to the configuration of (1) above, the exhaust heat recovery is performed by adjusting the valve opening based on the pressure of the container storing the saturated water and steam (that is, the saturation pressure corresponding to the saturation temperature). Since the amount is adjusted, variation in control can be suppressed by a highly accurate pressure detection value, and the temperature in the container (that is, the saturation temperature) can be quickly adjusted.

(2) In some embodiments, in the configuration of the above (1),
The first pressure is not less than 2 bar and not more than 4 bar;
The second pressure is not less than 5 bar and not more than 7 bar.

As described above, the combustion product gas (exhaust gas) of the fuel has an acid dew point corresponding to the sulfur concentration of the fuel. For example, the acid dew point of an exhaust gas derived from a fuel having a sulfur concentration of 0.5% or less is about 100 ° C, and the acid dew point of an exhaust gas derived from a fuel having a sulfur concentration of more than 0.5% is about 120 ° C or more. is there.
According to the configuration (2), the valve opening is adjusted so that the first pressure is 2 bar or more and 4 bar or less and the second pressure is 5 bar or more and 7 bar or less. When a fuel having a sulfur content of 0.5% or less is used as the fuel and a fuel having a sulfur content of more than 0.5% is used as the second fuel, the fuel is discharged according to the switching of the fuel used in the combustion device. The amount of waste heat recovered by the heat recovery system can be appropriately adjusted. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

(3) In some embodiments, in the configuration of the above (1),
The first pressure is greater than or equal to 2 bar and less than 4 bar;
The second pressure is not less than 4 bar and not more than 5 bar.

According to the above configuration (3), the valve opening is adjusted such that the first pressure is 2 bar or more and less than 4 bar and the second pressure is 4 bar or more and 5 bar or less. When a fuel containing almost no sulfur content is used as the second fuel and a fuel having a sulfur content higher than the first fuel is used as the second fuel, the exhaust heat recovery system according to the switching of the fuel used in the combustion device. The amount of heat recovery can be adjusted appropriately. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

(4) In some embodiments, in any one of the above configurations (1) to (3),
Further comprising a boiler for producing steam,
The boiler is
A water drum for storing water,
A steam drum for storing steam generated by evaporation of the water,
Including an evaporator tube connecting the water drum and the steam drum,
The container includes the steam drum of the boiler.

According to the configuration (4), since the steam and the water in the saturated state are stored in the steam drum of the boiler, the valve opening is adjusted based on the pressure of the steam drum. As described in 1), the amount of exhaust heat recovery by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel. Thus, the amount of exhaust heat recovery can be increased while protecting the device from acid corrosion.
According to the configuration (4), when recovery of exhaust heat from exhaust gas from the combustion apparatus alone cannot cover the demand for steam, the steam can be further generated by operating the boiler. On the other hand, the configuration of the exhaust heat recovery system described above can increase the amount of exhaust heat recovery and the amount of steam production, so that the operating time of the boiler for generating steam can be reduced. For this reason, the fuel used for the operation of the boiler can be reduced while reliably satisfying the demand for steam. Therefore, energy efficiency for steam production can be improved.

(5) In some embodiments, in the configuration of the above (4),
The boiler includes a steam injection unit configured to inject steam toward fuel burned in a burner,
The second pressure is a pressure capable of diffusing the fuel by injecting steam at the second pressure from the steam injection unit.

According to the configuration of the above (5), as described in the above (1), the amount of exhaust heat recovery can be increased while protecting the equipment from acid corrosion, and the saturated steam in the container is removed by the boiler. It can be effectively used to burn fuel.

(6) In some embodiments, in any of the above configurations (1) to (5),
Further comprising a fuel heating unit for heating the fuel oil to reduce the viscosity of the fuel oil,
The second pressure is a pressure at which the viscosity of the fuel oil can be reduced by supplying steam at the second pressure to the fuel heating unit.

According to the configuration of the above (6), as described in the above (1), the amount of exhaust heat recovery can be increased while protecting the equipment from acid corrosion, and the saturated steam in the container is removed by, for example, heavy oil. For example, the fuel can be effectively used for heating the fuel for the purpose of lowering the viscosity by heating the fuel having high viscosity.

(7) In some embodiments, in any one of the above configurations (1) to (6),
A superheater provided upstream of the heat exchanger in the exhaust gas line,
A turbine configured to be driven by superheated steam from the superheater,
Further comprising
The superheater is configured to generate a superheated steam by heating a part of the saturated steam flowing through the saturated steam line by heat exchange with the exhaust gas.

According to the configuration of (7), a part of the saturated steam generated by heat exchange with the exhaust gas in the heat exchanger is heat-exchanged with a higher temperature exhaust gas in the superheater to generate superheated steam, Since the turbine is driven using the superheated steam, the exhaust heat of the combustion device can be effectively used.

(8) In some embodiments, in any one of the above configurations (1) to (7),
The exhaust heat recovery system,
The fuel cell system further includes a fuel tank for storing the first fuel supplied to the combustion device.

According to the configuration of (8), the gas (boil-off gas) generated by the natural heat input from the outside to the fuel tank can be used as the first fuel, so that the exhaust heat recovery system can be efficiently operated. it can.

(9) The ship according to at least one embodiment of the present invention includes:
The exhaust heat recovery system according to any one of (1) to (7) is provided.

In the configuration of the above (9), for example, when the first fuel which is a low sulfur fuel is used as a fuel for a main engine of a ship or a combustion device such as a power generator, the pressure in the above-described container is lower than when the second fuel is used. The opening degree of the valve was adjusted so that the first pressure (i.e., the saturation pressure) became low to lower the temperature in the container (i.e., the saturation temperature). The exhaust gas temperature at the heat exchanger outlet can be reduced, that is, the amount of exhaust heat recovered in the heat exchanger can be increased.
In the configuration (9), when the second fuel that is a high sulfur fuel is used as the fuel for the main engine that is the combustion device, the pressure in the container (that is, the saturation pressure) is higher than when the first fuel is used. The opening degree of the valve was adjusted so that the pressure became a high second pressure, and the temperature in the vessel (that is, the saturation temperature) was increased. Therefore, only the amount corresponding to the rise in the acid dew point at the heat exchanger outlet was increased. By raising the exhaust gas temperature, devices such as heat exchangers and pipes can be protected from acid corrosion.
Therefore, according to the above configuration (9), the amount of exhaust heat recovery by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel, thereby protecting the equipment from acid corrosion. However, the amount of exhaust heat recovery can be increased.

Further, according to the configuration of the above (9), the exhaust heat recovery amount is adjusted by adjusting the valve opening based on the pressure of the container storing the saturated water and steam (that is, the saturation pressure corresponding to the saturation temperature). , The variation in control can be suppressed by the highly accurate pressure detection value, and the temperature in the container (that is, the saturation temperature) can be quickly adjusted.

(10) The operation method of the exhaust heat recovery device according to at least one embodiment of the present invention includes:
A combustion device that can be used by switching between two or more types of fuel;
An exhaust gas line through which exhaust gas from the combustion device flows,
A container for storing saturated water and steam;
A water supply line for supplying water to the container,
A saturated steam line through which saturated steam from the vessel flows;
A heat exchanger that is provided in the exhaust gas line and heats the water in the water supply line by heat exchange with the exhaust gas,
A valve provided in the saturated steam line, for adjusting the pressure of the vessel;
An operation method of an exhaust heat recovery device including:
When the fuel supplied to the combustion device is switched, the method includes a step of changing the pressure of the container by adjusting an opening degree of the valve,
In the step of changing the pressure, when the fuel is the second fuel, the opening degree of the valve is adjusted so that the pressure of the container becomes the second pressure, and the fuel is more sulfur than the second fuel. When the first fuel has a low partial concentration, the opening degree of the valve is adjusted so that the pressure of the container becomes the first pressure higher than the second pressure.

In the method (10), when the first fuel that is a low-sulfur fuel is used as the fuel for the combustion device, the pressure (that is, the saturation pressure) in the above-described container is lower than when the second fuel is used. The temperature of the exhaust gas at the outlet of the heat exchanger is reduced by the amount corresponding to the decrease in the acid dew point because the opening degree of the valve is adjusted so as to reduce the temperature in the container (that is, the saturation temperature). That is, the amount of exhaust heat recovered in the heat exchanger can be increased.
Further, in the method (10), when the second fuel that is a high sulfur fuel is used as the fuel for the combustion device, the pressure in the container (that is, the saturation pressure) is higher than when the first fuel is used. The temperature of the exhaust gas at the outlet of the heat exchanger is increased by the amount corresponding to the increase in the acid dew point because the opening degree of the valve is adjusted so as to obtain the pressure and the temperature in the container (that is, the saturation temperature) is increased. By doing so, it is possible to protect devices such as heat exchangers and pipes from acid corrosion.
Therefore, according to the above method (10), the amount of exhaust heat recovery by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel, thereby protecting the equipment from acid corrosion. However, the amount of exhaust heat recovery can be increased.

Further, according to the method (10), the exhaust heat recovery amount is adjusted by adjusting the valve opening based on the pressure of the container storing the saturated water and steam (that is, the saturation pressure corresponding to the saturation temperature). , The variation in control can be suppressed by the highly accurate pressure detection value, and the temperature in the container (that is, the saturation temperature) can be quickly adjusted.

(11) In some embodiments, in the method of the above (10),
The first pressure is not less than 2 bar and not more than 4 bar;
The second pressure is not less than 5 bar and not more than 7 bar.

According to the above method (11), the valve opening is adjusted so that the first pressure becomes 2 bar or more and 4 bar or less and the second pressure becomes 5 bar or more and 7 bar or less. When a fuel having a sulfur concentration of 0.5% or less is used as the second fuel and a fuel having a sulfur concentration of more than 0.5% is used as the second fuel, the fuel is discharged according to the switching of the fuel used in the combustion device. The amount of waste heat recovered by the heat recovery system can be appropriately adjusted. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

(12) In some embodiments, in the method of the above (10),
The first pressure is greater than or equal to 2 bar and less than 4 bar;
The second pressure is not less than 4 bar and not more than 5 bar.
According to the method (12), the valve opening is adjusted so that the first pressure is 2 bar or more and less than 4 bar and the second pressure is 4 bar or more and 5 bar or less. When a fuel containing almost no sulfur content is used as the second fuel and a fuel having a sulfur content higher than the first fuel is used as the second fuel, the exhaust heat recovery system according to the switching of the fuel used in the combustion device. The amount of heat recovery can be adjusted appropriately. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

(13) In some embodiments, in any one of the above methods (10) to (12),
The exhaust heat recovery device includes a boiler for generating steam,
The boiler is
A water drum for storing water,
A steam drum for storing steam generated by evaporation of the water,
Including an evaporator tube connecting the water drum and the steam drum,
The container of the exhaust heat recovery device includes the steam drum of the boiler.

According to the above method (13), since steam and water in a saturated state are stored in the steam drum of the boiler, the valve opening is adjusted based on the pressure of the steam drum. As described in 10), the amount of exhaust heat recovery by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the fuel type. Thus, the amount of exhaust heat recovery can be increased while protecting the device from acid corrosion.
In addition, according to the method (13), if the demand for steam cannot be satisfied only by recovering the exhaust heat from the exhaust gas of the combustion device, the steam can be further generated by operating the boiler. On the other hand, the configuration of the exhaust heat recovery system described above can increase the amount of exhaust heat recovery and the amount of steam production, so that the operating time of the boiler for generating steam can be reduced. For this reason, the fuel used for the operation of the boiler can be reduced while reliably satisfying the demand for steam. Therefore, energy efficiency for steam production can be improved.

(14) In some embodiments, in any one of the above methods (10) to (13),
The exhaust heat recovery device,
A superheater provided upstream of the heat exchanger in the exhaust gas line,
A turbine configured to be driven by superheated steam from the superheater,
Further comprising
The superheater is configured to generate a superheated steam by heating a part of the saturated steam flowing through the saturated steam line by heat exchange with the exhaust gas.

According to the method (14), a part of the saturated steam generated by heat exchange with the exhaust gas in the heat exchanger is heat-exchanged with a higher temperature exhaust gas in the superheater to generate superheated steam, Since the turbine is driven using the superheated steam, the exhaust heat of the combustion device can be effectively used.

According to at least one embodiment of the present invention, an exhaust heat recovery system capable of increasing the amount of exhaust heat recovery while protecting equipment from acid corrosion, a ship including the same, and an exhaust heat recovery method are provided. You.

It is a lineblock diagram of an exhaust heat recovery system concerning one embodiment. It is a lineblock diagram of an exhaust heat recovery system concerning one embodiment. It is a lineblock diagram of an exhaust heat recovery system concerning one embodiment. It is a lineblock diagram of an exhaust heat recovery system concerning one embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Absent.

First, an overall configuration of an exhaust heat recovery system according to some embodiments will be described.
1 to 4 are configuration diagrams of an exhaust heat recovery system according to one embodiment. The exhaust heat recovery system 1 shown in FIGS. 1 to 4 is mounted on a ship (not shown) and recovers heat of exhaust gas from an engine 3 (combustion device) as a main engine for propulsion of the ship. And a control device 100 (control unit) for controlling the exhaust heat recovery device 2.

The exhaust heat recovery device 2 is provided in an exhaust gas line 18 through which exhaust gas from the engine 3 flows, and includes an economizer 6 for recovering heat of the exhaust gas, a container 8 for storing saturated water and steam, and a container 8. And a valve 42 provided in the saturated steam line 38. Further, the exhaust heat recovery system 1 includes an LNG tank 4 (fuel tank) for storing LNG 5 which is fuel supplied to the engine 3.

(2) The engine 3 is an engine that can be used by switching between two or more types of fuels. The engine 3 can be used by switching between a first fuel and a second fuel having a higher sulfur concentration than the first fuel.

Here, in the present specification, among the first fuel and the second fuel, the first fuel having a relatively low sulfur concentration may be referred to as “low sulfur fuel”, and the second fuel having a relatively high sulfur concentration may be referred to as a “low sulfur fuel”. Fuel is sometimes referred to as "high sulfur fuel". The terms "low-sulfur fuel" and "high-sulfur fuel" indicate the relative magnitude of the sulfur concentration. That is, the sulfur content of the “low sulfur fuel” may be 0%, in which case the “high sulfur fuel” has a sulfur content greater than 0%.

In the engine 3 according to the illustrated embodiment, a fuel substantially free of sulfur, for example, LNG can be used as the first fuel, and a fuel containing sulfur can be used as the second fuel, The first fuel and the second fuel can be switched and used. That is, in the embodiment shown in FIGS. 1 to 4, LNG 5 as the first fuel stored in the LNG tank 4 can be supplied to each cylinder of the engine 3 via the LNG supply line 14 and the second fuel Liquid fuel can be supplied to each cylinder via the liquid fuel supply line 16. Switching of the fuel supplied to the engine 3 is controlled by an engine control device (not shown).
Note that the LNG 5 may be supplied to the engine 3 as boil-off gas generated by vaporization in the LNG tank 4 or gas that has been forcibly vaporized.

燃焼 Combustion gas generated by burning fuel in the engine 3 is guided from each cylinder of the engine 3 to the exhaust gas line 18.

(4) The exhaust gas line 18 is provided with the economizer 6. The economizer 6 includes a casing 20, which forms a flue that is part of the exhaust gas line 18. Exhaust gas discharged from the engine 3 to the exhaust gas line 18 is introduced into the flue via the inlet 22 and flows toward the outlet 24 through the flue. The exhaust gas discharged from the flue via the outlet 24 may be discharged to the outside via a chimney (not shown).

The economizer 6 includes an inlet header 26, an outlet header 28, and a heat transfer tube (not shown) provided between the inlet header 26 and the outlet header 28 so as to pass through a flue. Heat exchanger). The evaporator 7 is configured to generate steam by heat exchange between water flowing through the heat transfer tube and high-temperature exhaust gas flowing through the flue.
The outlet header 28 of the evaporator 7 may be provided downstream of the inlet header 26 in the flue gas flow in the flue.

The container 8 is for performing brackish water separation, and stores saturated water and steam therein. Water (including liquid water or steam) is circulated and supplied to the container 8 via

circulation lines

30a and 30b (water supply lines).

In the exemplary embodiment shown in FIG. 1, the above-mentioned vessel 8 includes a steam separator 10, the lower part of the steam separator 10 and the inlet header 26 of the evaporator 7 being connected via an upstream circulation line 30a. The upper part of the steam separator 10 and the outlet header 28 of the evaporator 7 are connected via a circulation line 30b on the downstream side. In addition, a pump 32 for pumping water is provided in the upstream circulation line 30a.

In this specification, a series of paths for supplying water to the container 8 is referred to as a water supply line. In the present embodiment, the water supply line includes an upstream circulation line 30a, a downstream circulation line 30b, and a heat transfer tube of the evaporator 7 provided between the

circulation lines

30a and 30b.

飽和 The inside of the brackish water separator 10 is filled with saturated steam, and condensed water (saturated water) accumulates in the lower part. The water stored in the lower part of the steam separator 10 is sent to the inlet header 26 of the evaporator 7 by the pump 32 via the upstream circulation line 30a. Then, the steam generated by heat exchange with the exhaust gas in the evaporator 7 is discharged from the evaporator 7 through the outlet header 28 and introduced into the steam separator 10 through the downstream circulation line 30b. Has become.

Note that the brackish water separator 10 may be replenished with water from outside via the water supply pipe 62.

In the exemplary embodiment shown in FIGS. 2 to 4, the exhaust heat recovery apparatus 2 includes the boiler 12, and the above-described container 8 is constituted by the steam drum 48 of the boiler 12. That is, the steam drum 48 of the boiler 12 has a function of brackish water separation.

The boiler 12 includes a furnace 13 having a burner (not shown), a steam drum 48, a water drum 50 provided below the steam drum 48 and filled with water, and connects the steam drum 48 and the water drum 50. And an evaporating tube 51.

In the exemplary embodiment shown in FIGS. 2 and 3, the water drum 50 is connected to the inlet header 26 of the evaporator 7 via the upstream circulation line 30a, and the steam drum 48 is connected to the downstream circulation line. It is connected via line 30b and to the outlet header 28 of the evaporator 7. In addition, a pump 32 for pumping water is provided in the upstream circulation line 30a.

In the exemplary embodiment shown in FIG. 4, the steam drum 48 is connected to the inlet header 26 of the evaporator 7 via an upstream circulation line 30a and evaporates via a downstream circulation line 30b. It is connected to the outlet header 28 of the vessel 7. In addition, a pump 32 for pumping water is provided in the upstream circulation line 30a.
As described above, by connecting the steam drum 48 and the inlet header 28, relatively high temperature water in the steam drum 48 is supplied to the economizer 6 as compared with a case where water from the water drum 50 is connected to the inlet header 28, for example. Since it is supplied, steam can be generated more efficiently.

燃料 Fuel is supplied to the furnace 13 of the boiler 12. In the exemplary embodiment shown in FIGS. 2 to 4, the boiler 13 of the boiler 12 can be supplied with boil-off gas from the LNG tank 4 via a fuel supply line 46. In addition, as shown in FIGS. 2 to 4, for example, the fuel may be supplied via a fuel supply line 47 different from the fuel supply line 46.

The boiler 12 is operated as described above as necessary. However, as described later, according to the present embodiment, the frequency at which the boiler 12 operates (frequency of additional cooking by the boiler 12) is determined. Thus, the cost of fuel and the like can be reduced.

The operation of the exhaust heat recovery device 2 when the boiler 12 is not operated is as follows.
That is, when all of the demand can be covered by the steam generated by the evaporator 7 (economizer 6), it is not necessary to operate the boiler 12, and no fuel is supplied to the boiler 12.

In this case, the water of the water drum 50 is sent out by the pump 32 toward the inlet header 26 of the evaporator 7. Then, steam is generated by heat exchange with the exhaust gas in the evaporator 7, and this steam is discharged from the outlet header 28 of the evaporator 7 and introduced into the steam drum 48 via the downstream circulation line 30b. The steam drum 48 functions as a brackish water separator, and the steam drum 48 is filled with saturated steam and condensed water (saturated water) accumulates in a lower portion. The water in the steam drum 48 descends to the water drum 50 via a downcomer (not shown).

On the other hand, when all of the demand cannot be covered by the steam generated by the evaporator 7 (economizer 6), the water and the exhaust gas from the water drum 50 are discharged using the evaporator 7 in the same manner as described above. In addition to generating steam by heat exchange, the boiler 12 is operated to further generate steam.

In this case, the fuel is supplied to the furnace 13 and burned by the burner, and the water in the boiler 12 is heated by the combustion heat. When the water is heated in the boiler 12, the water rises from the lower water drum 50 to the upper steam drum 48 through the evaporating pipe 51, and a part of the water which has become high temperature by the heating is evaporated. The gas and liquid are separated by the steam drum 48.

The steam drum 48 or the water drum 50 is supplied with water from the outside via a water supply pipe. In the illustrated embodiment, water can be supplied to the steam drum 48 via the water supply pipe 62.

A saturated steam line 38 is connected to the vessel 8 (the steam separator 10 in FIG. 1 or the top of the steam drum 48 in FIGS. 2 to 4), and the saturated steam in the vessel 8 is connected to the saturated steam line 38. 2 to 4, the steam drum 48 stores the saturated steam and water regardless of whether the boiler 12 is operating or not. Saturated steam from a steam drum 48 flows through the steam line 38.

バルブ The saturated steam line 38 is provided with a valve 42 for adjusting the pressure of the container 8. By appropriately operating the valve 42, the pressure in the container 8, that is, the saturated vapor pressure in the container 8 can be adjusted to a specified value.

In some embodiments, the valve 42 may be a pressure regulating valve that operates such that the pressure in the saturated steam line 38 upstream of the valve 42 is constant at a set value. In this case, since the pressure of the saturated steam line 38 is equal to the pressure of the container 8, the pressure of the container 8 is also constant at the above-mentioned set value.
Further, in some embodiments, the valve 42 is configured to control the pressure in the saturated steam line 38 or the container 8 to a predetermined value based on a signal from a pressure sensor for detecting the pressure in the saturated steam line 38 or the container 8. It may be configured to adjust the flow rate of the saturated steam in the saturated steam line 38 such that

A condenser 44 is provided in the saturated steam line 38 on the downstream side of the valve 42. In the condenser 44, condensed water is generated by cooling the saturated steam flowing through the saturated steam line 38 with cooling water or the like. This condensed water is returned to the container 8 via the water supply pipe 62, for example.

As shown in FIGS. 1 to 4, a branch line 40 branches from the saturated steam line 38, and the saturated steam may be supplied to a demand destination through the branch line 40. The saturated steam supplied to the customer may be used, for example, to heat heavy oil used as a fuel for the engine 3 or the like, or may be used as shipboard chore steam.

では In the exemplary embodiment shown in FIG. 3, the exhaust heat recovery device 2 further includes a superheater 9 and a turbine 60.

In the exemplary embodiment shown in FIG. 3, the superheater 9 is provided as a part of the economizer 6. The superheater 9 is provided upstream of the evaporator 7 (heat exchanger) in the exhaust gas line 18, and has a flue between the inlet header 52, the outlet header 54, and the inlet header 52 and the outlet header 54. (A heat transfer tube (not shown) provided so as to pass through the inside of the casing 20). The outlet header 54 of the superheater 9 is provided upstream of the inlet header 52 in the exhaust gas flow in the flue.

(4) The inlet header 52 of the superheater 9 is connected to a superheater inlet side line 39a which is provided on the upstream side of the valve 42 and branched from the saturated steam line 38. The outlet header 54 of the superheater 9 is connected to a superheater outlet side line 39b which is provided downstream of the valve 42 and upstream of the condenser 44 and branched from the saturated steam line 38. Further, a turbine 60 is provided in the superheater outlet line 39b.

A part of the saturated steam flowing through the saturated steam line 38 flows into the superheater inlet side line 39a. The saturated steam in the superheater inlet side line 39a is introduced into the superheater 9 via the inlet header 52, and flows through the heat transfer tube. At this time, superheated steam is generated by heat exchange between the saturated steam and high-temperature exhaust gas flowing through the flue. The superheated steam generated by the superheater 9 is discharged from the superheater 9 via the outlet header 54, guided to the superheater outlet line 39b, and supplied to the turbine 60 provided on the superheater outlet line 39b. The turbine 60 is driven.
The superheated steam that has completed the work in the turbine 60 joins the saturated steam line 38 and is led to the condenser 44.

The generator of the turbine 60 may be connected to the rotor. In this case, electric power can be generated by driving the generator by the turbine 60.

The control device 100 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. For example, a series of processes for realizing various functions are stored in a recording medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing or arithmetic processing. Thereby, various functions are realized.

The control device 100 receives a signal indicating that the fuel supplied to the engine 3 has been switched from the engine 3 or an engine control device (not shown).
The engine 3 or the engine control device sends a signal to the control device 100 indicating that the fuel supplied to the engine 3 has been switched from the first fuel to the second fuel or from the second fuel to the first fuel. It may be. Alternatively, the engine 3 or the engine control device sends a signal indicating the type of fuel (first fuel or second fuel) currently used in the engine 3 to the control device 100 at predetermined intervals, The control device 100 may be able to specify that the type of fuel supplied to the engine 3 has been switched based on the received signal.

The control device 100 may output a signal indicating the set pressure of the valve 42 (that is, a target value of the pressure of the container 8) to the valve 42 based on the above-described signal.

Further, the control device 100 is configured to receive a signal indicating a measurement result by the pressure sensor 64 provided in the saturated steam line 40, and to adjust the pressure of the saturated steam line 40 based on the measurement result. Alternatively, the valve 42 may be operated.

Next, the operation of the exhaust heat recovery system 1 including the control device 100 according to some embodiments will be described.

When receiving a signal indicating that the fuel supplied to the engine 3 has been switched, the control device 100 adjusts the opening of the valve 42 based on the signal to change the pressure of the container 8. It is configured.

More specifically, when the fuel supplied to the engine 3 is the first fuel which is a low sulfur fuel, the control device 100 adjusts the opening degree of the valve 42 so that the pressure of the container 8 becomes the first pressure. When the fuel is the second fuel which is a high sulfur fuel, the opening degree of the valve 42 is adjusted so that the pressure of the container 8 becomes the second pressure higher than the first pressure. You.

In other words, when the fuel supplied to the engine 3 is switched from the second fuel (high sulfur fuel) to the first fuel (low sulfur fuel), the pressure in the container 8 decreases from the second pressure to the first pressure. Thus, the set pressure of the valve 42 is changed to increase the opening degree of the valve 42. Further, when switching from the first fuel (low-sulfur fuel) to the second fuel (high-sulfur fuel) supplied to the engine 3, the valve 42 increases the pressure in the container 8 from the first pressure to the second pressure. Is changed, and the opening of the valve 42 is reduced.

(4) The exhaust gas generated by the combustion of the fuel in the engine 3 or the like has an acid dew point corresponding to the sulfur concentration of the fuel. The higher the sulfur concentration, the higher the acid dew point of the exhaust gas generated from the fuel. In order to protect equipment such as the exhaust gas line 18 through which the exhaust gas flows, the evaporator 7, and the piping constituting the superheater 9 (economizer 6) from acid corrosion, the temperature of the exhaust gas in these equipment is controlled by the acid of the exhaust gas. It must be maintained at a temperature above the dew point.

In this regard, in the above-described embodiment, when the first fuel, which is a low-sulfur fuel, is used as the fuel of the engine 3, the first pressure (that is, the saturation pressure) in the container 8 is lower than when the second fuel is used. The temperature of the container 8 (that is, the saturation temperature) is reduced by adjusting the opening of the valve 42 so that the pressure becomes a pressure. Thereby, the exhaust gas temperature at the outlet of the evaporator 7 (heat exchanger) (that is, the outlet of the economizer 6) can be reduced by an amount corresponding to the decrease in the acid dew point. That is, the amount of exhaust heat recovery in the economizer 6 including the evaporator 7 (heat exchanger) can be increased.
Further, by increasing the amount of exhaust heat recovery in this way, the amount of steam generated by the recovered heat can also be increased. Thus, in a configuration including the boiler 12 as shown in FIGS. 2 to 4, for example, the amount of steam to be generated by the boiler 12 can be reduced, so that the operation time of the boiler 12 is reduced and the boiler 12 is operated. 12 can be supplied with less fuel. That is, since the frequency of reheating using the boiler 12 can be reduced, the cost of fuel and the like required for reheating can be reduced.

Further, in the above-described embodiment, when the second fuel that is a high sulfur fuel is used as the fuel for the engine 3, the pressure in the container 8 (that is, the saturation pressure) is higher than when the first fuel is used. The opening degree of the valve 42 is adjusted so that the temperature inside the container 8 (that is, the saturation temperature) is increased. As a result, the exhaust gas temperature at the outlet of the evaporator 7 (heat exchanger) (that is, the outlet of the economizer 6) is increased by an amount corresponding to the rise in the acid dew point, and the exhaust gas line 18 and the evaporator 7 (economizer 6) are increased. Can be protected from acid corrosion.

Therefore, according to the above-described embodiment, the amount of exhaust heat recovery by the exhaust heat recovery system 1 can be adjusted by adjusting the opening of the valve 42 according to the type of fuel, thereby protecting the device from acid corrosion. Meanwhile, the amount of exhaust heat recovery can be increased.

Incidentally, as described above, when the amount of exhaust heat recovery is to be adjusted by adjusting the opening of the valve 42, for example, the opening of the valve 42 is determined based on the exhaust gas temperature at the outlet of the evaporator 7 (or the outlet of the economizer 6). It is also conceivable to adjust. However, since the exhaust gas temperature has a distribution in a plane orthogonal to the flow of the exhaust gas, there is a possibility that the control may vary depending on the temperature detection point. In the control based on the temperature, the control response may be delayed.
On the other hand, since the pressure in the container 8 is almost the same regardless of the location, the detected value of the pressure in the container 8 is the detected value of the temperature of the exhaust gas at the outlet of the evaporator 7 (or the outlet of the economizer 6). More accurate than. Control based on pressure tends to have a faster control response than control based on temperature.

In this regard, according to the above-described embodiment, the exhaust heat is adjusted by adjusting the opening of the valve 42 based on the pressure of the container 8 in which the saturated water and steam are stored (that is, the saturation pressure corresponding to the saturation temperature). Since the amount of recovery is adjusted, the variation in control can be suppressed by a highly accurate pressure detection value, and the temperature in the container 8 (that is, the saturation temperature) can be quickly adjusted.

In the embodiment shown in FIGS. 1 to 4, the first fuel (low sulfur fuel) is LNG5 (liquefied natural gas) substantially free of sulfur, and the second fuel (high sulfur fuel) has low sulfur. Including fuel. And the above-mentioned 1st pressure is set to 2 bar or more and 4 bar or less, and the above-mentioned 2nd pressure is set to 5 bar or more and 7 bar or less.

As described above, the combustion product gas (exhaust gas) of the fuel has an acid dew point corresponding to the sulfur concentration of the fuel. For example, the acid dew point of an LNG-derived exhaust gas containing substantially no sulfur content is about 100 ° C., and the acid dew point of a fuel oil-derived exhaust gas having a sulfur content of about 0.1% to 0.5% is 120 ° C. It is about 150 ° C. (the higher the sulfur concentration, the higher the acid dew point of the exhaust gas tends to be).

In this regard, in the above-described embodiment, LNG is used as the first fuel, a liquid fuel containing sulfur is used as the second fuel, and the first pressure is 2 bar or more and 4 bar or less, and the second pressure is 5 bar or more and 7 bar. The opening degree of the valve 42 is adjusted as follows. Therefore, the amount of exhaust heat recovery by the exhaust heat recovery system 1 can be appropriately adjusted according to the switching of the fuel (first fuel or second fuel) supplied to the engine 3. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

では In some embodiments, the first pressure may be set between 2 bar and 4 bar and the second pressure may be set between 4 bar and 5 bar.

In this case, for example, when a fuel (for example, LNG) containing substantially no sulfur content is used as the first fuel and a fuel having a sulfur content higher than the first fuel is used as the second fuel, the fuel used in the combustion device is used. The amount of exhaust heat recovery by the exhaust heat recovery system can be appropriately adjusted in accordance with the switching of. This makes it possible to increase the amount of exhaust heat recovery while protecting the device from acid corrosion.

In some embodiments, boiler 12 includes a steam injector (not shown) configured to inject steam toward fuel combusted by a burner (not shown), wherein the second pressure is: The pressure at which the fuel of the burner can be diffused by injecting the steam of the second pressure from the above-described steam injection unit may be set.

In this case, as described above, the amount of exhaust heat recovery can be increased while protecting the equipment from acid corrosion, and the saturated steam in the steam drum 48 (vessel 8) is burned by the boiler 12 to burn fuel. Can be used effectively.

In some embodiments, the exhaust heat recovery system 1 further includes a fuel heating unit (not shown) for heating the fuel oil to reduce the viscosity of the fuel oil, wherein the second pressure is the second pressure. The pressure at which the viscosity of the fuel oil can be reduced by supplying the steam to the fuel heating unit may be set.

In this case, as described above, the exhaust heat recovery amount can be increased while protecting the device from acid corrosion, and the saturated steam in the container 8 is heated by heating a highly viscous fuel such as heavy oil, for example. It can be effectively used for heating the fuel for the purpose of lowering the fuel consumption.

The operation of changing the opening degree of the valve 42 based on the switching of the fuel supplied to the engine 3 may be performed manually without using the control device 100.
That is, when the fuel supplied to the engine 3 is switched, the operator may adjust the opening degree of the valve 42 (for example, change the set pressure of the valve 42) to change the pressure of the container 8. Good.

The used fuel and the pressure (target pressure) of the container 8 are the same as in the case of the control by the control device 100 described above.

That is, when the fuel supplied to the engine 3 is the first fuel which is a low sulfur fuel, the operator adjusts the opening degree of the valve 42 so that the pressure of the container 8 becomes the first pressure, When is the second fuel which is a high sulfur fuel, the opening of the valve 42 may be adjusted so that the pressure in the container 8 becomes the second pressure higher than the first pressure.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and includes a form in which the above-described embodiment is modified and a form in which these forms are appropriately combined.

In this specification, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial". Represents not only such an arrangement strictly, but also represents a state of being relatively displaced with a tolerance or an angle or a distance at which the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which indicate that things are in the same state, not only represent exactly the same state, but also have a tolerance or a difference to the extent that the same function is obtained. An existing state shall also be represented.
Further, in the present specification, expressions representing shapes such as a square shape and a cylindrical shape not only represent shapes such as a square shape and a cylindrical shape in a strictly geometrical sense, but also to the extent that the same effect can be obtained. , And a shape including an uneven portion and a chamfered portion.
Further, in this specification, the expression “comprising”, “including”, or “having” one component is not an exclusive expression excluding the existence of another component.

Reference Signs List 1 waste heat recovery system 2 waste heat recovery device 3 engine 4 LNG tank 6 economizer 7 evaporator 8 container 9 superheater 10 steam separator 12 boiler 13 furnace 14 LNG supply line 16 liquid fuel supply line 18 exhaust gas line 20 casing 22 inlet 24 Outlet 26 Inlet header 28 Outlet header

30a Circulation line

30b Circulation line 32 Pump 38 Saturated steam line 39a Superheater inlet side line 39b Superheater outlet side line 40 Branch line 42 Valve 44 Condenser 46 Fuel supply line 47 Fuel supply line 48 Steam Drum 50 Water drum 51 Evaporation pipe 52 Inlet header 54 Outlet header 60 Turbine 62 Water supply pipe 64 Pressure sensor 100 Control device

Claims

A combustion device that can be used by switching between two or more types of fuel;
An exhaust gas line through which exhaust gas from the combustion device flows,
A container for storing saturated water and steam;
A water supply line for supplying water to the container,
A saturated steam line through which saturated steam from the vessel flows;
A heat exchanger that is provided in the exhaust gas line and heats the water in the water supply line by heat exchange with the exhaust gas,
A valve provided in the saturated steam line, for adjusting the pressure of the vessel;
When receiving a signal indicating that the fuel supplied to the combustion device has been switched, a control unit configured to change the pressure of the container by adjusting the opening degree of the valve based on the signal. And
When the fuel is the second fuel, the control unit adjusts the opening degree of the valve so that the pressure of the container becomes the second pressure, and the fuel has a sulfur concentration lower than that of the second fuel. When the first fuel is low, the exhaust heat recovery system is configured to adjust the opening of the valve so that the pressure of the container becomes the first pressure lower than the second pressure. .
The first pressure is not less than 2 bar and not more than 4 bar;
The exhaust heat recovery system according to claim 1, wherein the second pressure is 5 bar or more and 7 bar or less.
The first pressure is greater than or equal to 2 bar and less than 4 bar;
The exhaust heat recovery system according to claim 1, wherein the second pressure is not less than 4 bar and not more than 5 bar.
Further comprising a boiler for producing steam,
The boiler is
A water drum for storing water,
A steam drum for storing steam generated by evaporation of the water,
Including an evaporator tube connecting the water drum and the steam drum,
3. The exhaust heat recovery system according to claim 1, wherein the container includes the steam drum of the boiler. 4.
The boiler includes a steam injection unit configured to inject steam toward fuel burned in a burner,
5. The exhaust heat recovery system according to claim 4, wherein the second pressure is a pressure capable of diffusing the fuel by injecting steam at the second pressure from the steam injection unit. 6.
Further comprising a fuel heating unit for heating the fuel oil to reduce the viscosity of the fuel oil,
The exhaust heat recovery according to claim 1 or 2, wherein the second pressure is a pressure capable of reducing the viscosity of the fuel oil by supplying steam at the second pressure to the fuel heating unit. system.
A superheater provided upstream of the heat exchanger in the exhaust gas line,
A turbine configured to be driven by superheated steam from the superheater,
Further comprising
3. The superheater according to claim 1, wherein the superheater is configured to generate a superheated steam by heating a part of the saturated steam flowing through the saturated steam line by exchanging heat with the exhaust gas. 4. Waste heat recovery system.
The exhaust heat recovery system according to claim 1 or 2, further comprising a fuel tank for storing the first fuel supplied to the combustion device.
A ship provided with the exhaust heat recovery system according to claim 1 or 2.
A combustion device that can be used by switching between two or more types of fuel;
An exhaust gas line through which exhaust gas from the combustion device flows,
A container for storing saturated water and steam;
A water supply line for supplying water to the container,
A saturated steam line through which saturated steam from the vessel flows;
A heat exchanger that is provided in the exhaust gas line and heats the water in the water supply line by heat exchange with the exhaust gas,
A valve provided in the saturated steam line, for adjusting the pressure of the vessel;
An operation method of an exhaust heat recovery device including:
When the fuel supplied to the combustion device is switched, the method includes a step of changing the pressure of the container by adjusting an opening degree of the valve,
In the step of changing the pressure, when the fuel is the second fuel, the opening degree of the valve is adjusted so that the pressure of the container becomes the second pressure, and the fuel is more sulfur than the second fuel. When the first fuel has a low concentration, the opening degree of the valve is adjusted so that the pressure of the container becomes the first pressure lower than the second pressure. Method.
The first pressure is not less than 2 bar and not more than 4 bar;
The method according to claim 10, wherein the second pressure is 5 bar or more and 7 bar or less.
The first pressure is greater than or equal to 2 bar and less than 4 bar;
The method according to claim 10, wherein the second pressure is not less than 4 bar and not more than 5 bar.
The exhaust heat recovery device includes a boiler for generating steam,
The boiler is
A water drum for storing water,
A steam drum for storing steam generated by evaporation of the water,
Including an evaporator tube connecting the water drum and the steam drum,
The method according to claim 10, wherein the container of the exhaust heat recovery device includes the steam drum of the boiler.
The exhaust heat recovery device,
A superheater provided upstream of the heat exchanger in the exhaust gas line,
A turbine configured to be driven by superheated steam from the superheater,
Further comprising
12. The superheater according to claim 10, wherein the superheater is configured to generate a superheated steam by heating a part of the saturated steam flowing through the saturated steam line by heat exchange with the exhaust gas. Method of operating the waste heat recovery device.