JP7319769B2 - Exhaust heat recovery system, ship, and exhaust heat recovery device operating method - Google Patents

Description

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

Heat from hot exhaust gases discharged from a combustion device may be recovered using a heat exchanger and utilized for applications such as steam generation.

For example, in Patent Document 1, in a boiler plant including a boiler that can switch and burn gas fuel and heavy oil fuel, an economizer is used to convert combustion gas (exhaust gas) from the boiler and water supply before being supplied to the boiler. and preheating the feed water. Further, Patent Literature 1 describes adjusting the temperature of the feedwater sent to the economizer according to the type of fuel (gas fuel or heavy oil fuel) used in the boiler.

Japanese Patent No. 6219742

By the way, fuel may contain sulfur, and in this case, if the temperature of the combustion gas (exhaust gas) of the fuel is below the acid dew point, the equipment such as pipes that make up the flow path of the combustion gas will be exposed to acid. Corrosion may occur. Therefore, it is necessary to appropriately manage the temperature of the exhaust gas at the outlet of a heat exchanger (such as an economizer) for recovering heat from the exhaust gas.

Now, consider switching between a high-sulfur fuel with a relatively high sulfur content and a low-sulfur fuel with a relatively low sulfur content in a combustion device (engine, boiler, etc.).
In order to prevent acid corrosion when using high-sulfur fuel, the exhaust gas temperature at the outlet of the heat exchanger where 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 (more than the acid dew point high temperature), when switching to a low sulfur fuel, you will be operating at a temperature significantly higher than the acid dew point of the low sulfur fuel (which is lower than the acid dew point of the high sulfur fuel). It is not expected to increase the amount of waste heat recovery when sulfur fuel is used.
On the other hand, if 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 (higher temperature than the acid dew point), when switching the fuel to high sulfur fuel and using it, Operation at temperatures below the acid dew point of high sulfur fuel (higher acid dew point than low sulfur fuel) can result in acid corrosion of equipment.

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

(1) An exhaust heat recovery system according to at least one embodiment of the present invention,
a combustion device capable of 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
A control unit configured to change the pressure of the container by adjusting the degree of opening of the valve based on the signal, when receiving a signal indicating that the fuel supplied to the combustion device has been switched. and
When the fuel is the second fuel, the control unit adjusts the opening degree of the valve so that the pressure in the container becomes the second pressure, and the fuel has a sulfur content higher than that of the second fuel. When the first fuel is low, the opening of the valve is adjusted so that the pressure in the container becomes a second pressure lower than the second pressure.

The exhaust gas produced by combustion of the fuel has an acid dew point corresponding to the sulfur content of the fuel, and the higher the sulfur content of the fuel, the higher the acid dew point of the exhaust gas generated from the fuel. In addition, in order to protect equipment such as heat exchangers and pipes that make up the flow path of exhaust gas from acid corrosion, it is necessary to maintain the exhaust gas temperature in these equipment at a temperature higher than the acid dew point of the exhaust gas. .

In this regard, in the above configuration (1), when the first fuel, which is a low-sulfur fuel, is used as the fuel for the combustion device, the pressure in the container (that is, the saturation pressure) is lower than when the second fuel is used. By adjusting the degree of opening of the valve so that it becomes 1 pressure, the temperature inside the vessel (that is, the saturation temperature) is lowered, so the exhaust gas temperature at the heat exchanger outlet is increased by the amount corresponding to the decrease in the acid dew point. can be reduced, ie the amount of waste heat recovered in the heat exchanger can be increased.
Further, in the above configuration (1), when the second fuel, which is a high-sulfur fuel, is used as the fuel of the combustion device, the pressure in the container (that is, the saturation pressure) is higher than when the first fuel is used. By adjusting the degree of opening of the valve so as to maintain the pressure, the temperature inside the vessel (that is, the saturation temperature) is increased, so the exhaust gas temperature at the heat exchanger outlet is increased by the amount corresponding to the increase in the acid dew point. By doing so, equipment such as heat exchangers and piping can be protected from acid corrosion.
Therefore, according to the above configuration (1), the exhaust heat recovery amount by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the fuel type, thereby protecting the equipment from acid corrosion. However, the amount of exhaust heat recovery can be increased.

By the way, as described above, when adjusting the amount of exhaust heat recovered by the heat exchanger by adjusting the valve opening, for example, adjusting the valve opening based on the exhaust gas temperature at the heat exchange outlet may be considered. However, the exhaust gas temperature has a distribution in the plane orthogonal to the flow of the exhaust gas, and there is a possibility that the control may vary depending on the temperature detection point. Also, temperature-based control can slow control response.
On the other hand, since the pressure inside the container is almost the same regardless of the location, the detected value of the pressure inside the container is more accurate than the detected value of the exhaust gas temperature at the outlet of the heat exchanger. Also, pressure-based control tends to have a faster control response than temperature-based control.

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

(2) In some embodiments, in the configuration of (1) above,
the first pressure is 2 bar or more and 4 bar or less;
The second pressure is between 5 bar and 7 bar.

As described above, the combustion product gas (exhaust gas) of the fuel has an acid dew point corresponding to the sulfur content concentration of the fuel. For example, the acid dew point of exhaust gas derived from fuel with a sulfur concentration of 0.5% or less is about 100 ° C., and the acid dew point of exhaust gas derived from fuel with a sulfur content exceeding 0.5% is about 120 ° C. or higher. be.
According to the above 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. If a fuel with a sulfur content of 0.5% or less is used as the second fuel, and a fuel with a sulfur content of more than 0.5% is used as the second fuel, the exhaust gas is changed 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. As a result, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.

(3) In some embodiments, in the configuration of (1) above,
the first pressure is greater than or equal to 2 bar and less than 4 bar;
The second pressure is greater than or equal to 4 bar and less than or equal to 5 bar.

According to the above configuration (3), 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. If a fuel containing almost no sulfur is used as the second fuel, and a fuel with a sulfur content higher than the first fuel is used as the second fuel, the exhaust heat recovery system will exhaust the exhaust gas according to the switching of the fuel used in the combustion device. The amount of heat recovery can be adjusted appropriately. As a result, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.

(4) In some embodiments, in the configuration of any one of (1) to (3) above,
further comprising a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
The vessel contains the steam drum of the boiler.

According to the configuration of (4) above, since saturated steam and water are stored in the steam drum of the boiler, the valve opening degree is adjusted based on the pressure of this steam drum. As described in 1), the amount of exhaust heat recovered by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel. Therefore, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.
Further, according to the above configuration (4), when the demand for steam cannot be met by exhaust heat recovery from the exhaust gas of the combustion device, it is possible to further generate steam by operating the boiler. On the other hand, the configuration of the exhaust heat recovery system described above makes it possible to increase the amount of exhaust heat recovery and increase the amount of steam produced, thereby reducing the operation time of the boiler for generating steam. Thus, less fuel can be used to operate the boiler while ensuring that the demand for steam is met. Therefore, energy efficiency for steam production can be improved.

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

According to the configuration of (5) above, as described in (1) above, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion, and at the same time, the saturated steam in the vessel is transferred to the boiler. It can be effectively used for burning fuel.

(6) In some embodiments, in the configuration of any one of (1) to (5) above,
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 that can reduce the viscosity of the fuel oil by supplying steam at the second pressure to the fuel heating section.

According to the configuration of (6) above, as described in (1) above, it is possible to increase the amount of waste heat recovery while protecting the equipment from acid corrosion, and to replace the saturated steam in the container with, for example, heavy oil. It can be effectively used for heating the fuel for the purpose of heating a highly viscous fuel, such as a fuel, to lower the viscosity.

(7) In some embodiments, in any 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 heat a portion of the saturated steam flowing through the saturated steam line through heat exchange with the exhaust gas to generate the superheated steam.

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

(8) In some embodiments, in any of the above configurations (1) to (7),
The exhaust heat recovery system is
A fuel tank for storing the first fuel to be supplied to the combustion device is further provided.

According to the above configuration (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. can.

(9) A ship according to at least one embodiment of the present invention,
An exhaust heat recovery system according to any one of (1) to (7) above is provided.

In the above configuration (9), for example, when using the first fuel, which is a low-sulfur fuel, as a fuel for a combustion device such as a main engine of a ship or a power generation device, the pressure in the container is higher than when using the second fuel By adjusting the degree of opening of the valve so that the first pressure (that is, the saturation pressure) is low, the temperature (that is, the saturation temperature) in the container is lowered, so that the amount corresponding to the decrease in the acid dew point The exhaust gas temperature at the heat exchanger outlet can be lowered, that is, the amount of exhaust heat recovery in the heat exchanger can be increased.
Further, in the above configuration (9), when using the second fuel, which is a high-sulfur fuel, as the fuel for the main engine, which is the combustion device, the pressure in the container (that is, the saturation pressure) is higher than when the first fuel is used. By adjusting the degree of opening of the valve so that the second pressure is high, the temperature inside the vessel (that is, the saturation temperature) is increased, so the amount at the outlet of the heat exchanger is By increasing the exhaust gas temperature, equipment such as heat exchangers and piping can be protected from acid corrosion.
Therefore, according to the above configuration (9), the exhaust heat recovery amount by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the fuel type, thereby protecting the equipment from acid corrosion. However, the amount of exhaust heat recovery can be increased.

Further, according to the above configuration (9), the exhaust heat recovery amount is is adjusted, it is possible to suppress variation in control by the highly accurate pressure detection value, and to quickly adjust the temperature (that is, the saturation temperature) in the container.

(10) A method for operating an exhaust heat recovery device according to at least one embodiment of the present invention includes:
a combustion device capable of 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
A method of operating an exhaust heat recovery device comprising
changing the pressure of the vessel by adjusting the opening of the valve when the fuel supplied to the combustion device is switched;
In the step of changing the pressure, when the fuel is the second fuel, the degree of opening of the valve is adjusted so that the pressure in 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 of the valve is adjusted so that the pressure in the container becomes a first pressure higher than the second pressure.

In the above method (10), when the first fuel, which is a low-sulfur fuel, is used as the fuel of the combustion device, the pressure in the container (that is, the saturation pressure) is lower than when the second fuel is used. By adjusting the degree of opening of the valve, the temperature inside the container (that is, the saturation temperature) is lowered, so that the exhaust gas temperature at the heat exchanger outlet can be lowered by the amount corresponding to the lowering of the acid dew point. That is, the amount of exhaust heat recovery in the heat exchanger can be increased.
Further, in the above method (10), when the second fuel, which 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. By adjusting the degree of opening of the valve so as to maintain the pressure, the temperature inside the vessel (that is, the saturation temperature) is increased, so the exhaust gas temperature at the heat exchanger outlet is increased by the amount corresponding to the increase in the acid dew point. By doing so, equipment such as heat exchangers and piping can be protected from acid corrosion.
Therefore, according to the above method (10), the amount of exhaust heat recovered 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 above method (10), the exhaust heat recovery amount is is adjusted, it is possible to suppress variation in control by the highly accurate pressure detection value, and to quickly adjust the temperature (that is, the saturation temperature) in the container.

(11) In some embodiments, in the method of (10) above,
the first pressure is 2 bar or more and 4 bar or less;
The second pressure is between 5 bar and 7 bar.

According to the method (11) above, 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. If a fuel with a sulfur content of 0.5% or less is used as the second fuel, and a fuel with a sulfur content of more than 0.5% is used as the second fuel, the exhaust gas is changed 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. As a result, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.

(12) In some embodiments, in the method of (10) above,
the first pressure is greater than or equal to 2 bar and less than 4 bar;
The second pressure is greater than or equal to 4 bar and less than or equal to 5 bar.
According to the method (12) above, 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. If a fuel containing almost no sulfur is used as the second fuel, and a fuel with a sulfur content higher than the first fuel is used as the second fuel, the exhaust heat recovery system will exhaust the exhaust gas according to the switching of the fuel used in the combustion device. The amount of heat recovery can be adjusted appropriately. As a result, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.

(13) In some embodiments, in the method of any one of (10) to (12) above,
The exhaust heat recovery device comprises a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
The vessel of the heat recovery system includes the steam drum of the boiler.

According to the method (13) above, since saturated steam and water are stored in the steam drum of the boiler, the valve opening is adjusted based on the pressure of this steam drum. As described in 10), the amount of exhaust heat recovered by the exhaust heat recovery system can be adjusted by adjusting the valve opening according to the type of fuel. Therefore, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.
Further, according to the above method (13), when the demand for steam cannot be met by exhaust heat recovery from the exhaust gas of the combustion apparatus, it is possible to generate more steam by operating the boiler. On the other hand, the configuration of the exhaust heat recovery system described above makes it possible to increase the amount of exhaust heat recovery and increase the amount of steam produced, thereby reducing the operation time of the boiler for generating steam. Thus, less fuel can be used to operate the boiler while ensuring that the demand for steam is met. Therefore, energy efficiency for steam production can be improved.

(14) In some embodiments, in the method of any one of (10) to (13) above,
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 heat a portion of the saturated steam flowing through the saturated steam line through heat exchange with the exhaust gas to generate the superheated steam.

According to the above method (14), part of the saturated steam generated by heat exchange with exhaust gas in the heat exchanger is heat-exchanged with higher temperature exhaust gas in the superheater to generate superheated steam, Since the superheated steam is used to drive the turbine, exhaust heat from 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 equipped with the same, and an exhaust heat recovery method are provided. be.

1 is a configuration diagram of an exhaust heat recovery system according to one embodiment; FIG. 1 is a configuration diagram of an exhaust heat recovery system according to one embodiment; FIG. 1 is a configuration diagram of an exhaust heat recovery system according to one embodiment; FIG. 1 is a configuration diagram of an exhaust heat recovery system according to one embodiment; FIG.

Several embodiments of the present invention will now be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, and are merely illustrative examples. do not have.

First, the overall configuration of the 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. A saturated steam line 38 through which the saturated steam from the steam flows, and a valve 42 provided in the saturated steam line 38 are provided. The exhaust heat recovery system 1 also includes an LNG tank 4 (fuel tank) for storing LNG 5 as fuel to be supplied to the engine 3 .

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

Here, in this specification, of the first fuel and the second fuel, the first fuel having a relatively low sulfur content is sometimes referred to as a "low sulfur fuel", and the second fuel having a relatively high sulfur content The fuel is sometimes called "high sulfur fuel". The terms “low-sulfur fuel” and “high-sulfur fuel” refer to relative magnitude relationships between sulfur concentrations. That is, a "low sulfur fuel" can have a sulfur content of 0%, in which case a "high sulfur fuel" has a sulfur content greater than 0%.

In the engine 3 according to the illustrated embodiment, a fuel that does not substantially contain sulfur, such as LNG, can be used as the first fuel, and a fuel containing sulfur can be used as the second fuel, These first fuel and second fuel can be used by switching. 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 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 a boil-off gas generated by vaporization in the LNG tank 4 or as forced vaporized gas.

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

An economizer 6 is provided in the exhaust gas line 18 . The economizer 6 includes a casing 20 forming a flue that is part of the exhaust gas line 18 . Exhaust gases discharged from the engine 3 into the exhaust gas line 18 are introduced into the flue via the inlet 22 and flow through this flue towards the outlet 24 . Exhaust gas discharged from the flue through the outlet 24 may be discharged to the outside through a chimney (not shown).

The economizer 6 includes an inlet header 26, an outlet header 28, and heat transfer tubes (not shown) provided through the flue between the inlet header 26 and the outlet header 28, which are connected to the evaporator 7 ( heat exchanger). The evaporator 7 is configured to generate steam by heat exchange between water flowing through the heat transfer tubes 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.

The vessel 8 is for separating brackish water, and is designed to store saturated water and steam inside. 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 aforementioned vessel 8 includes a steam separator 10, the lower part of which is connected to the inlet header 26 of the evaporator 7 via an upstream circulation line 30a. , the upper portion of the steam separator 10 and the outlet header 28 of the evaporator 7 are connected via a downstream circulation line 30b. A pump 32 for pumping water is provided in the circulation line 30a on the upstream side.

In this specification, a series of routes for supplying water to the container 8 is called a water supply line. In this embodiment, the water supply line includes an upstream circulation line 30a, a downstream circulation line 30b, and heat transfer tubes of the evaporator 7 provided between these circulation lines 30a and 30b.

The inside of the steam separator 10 is filled with saturated steam, and condensed water (saturated water) is accumulated in the lower part. The water accumulated 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 circulation line 30a on the upstream side. 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. It's becoming

The steam separator 10 may be replenished with water from the outside through the water supply pipe 62 .

In the exemplary embodiment shown in FIGS. 2-4, the waste heat recovery device 2 includes a boiler 12 and the aforementioned vessel 8 is constituted by the steam drum 48 of the boiler 12 . That is, the steam drum 48 of the boiler 12 has a steam separation function.

The boiler 12 includes a furnace 13 equipped with burners (not shown), a steam drum 48, a water drum 50 provided below the steam drum 48 and filled with water, and connecting the steam drum 48 and the water drum 50. and an evaporator tube 51 that

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

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 via a downstream circulation line 30b. It is connected to the outlet header 28 of the vessel 7 . A pump 32 for pumping water is provided in the circulation line 30a on the upstream side.
By connecting the steam drum 48 and the inlet header 28 in this way, the relatively hot water in the steam drum 48 can reach the economizer 6 compared to, for example, connecting water from the water drum 50 to the inlet header 28 . Since it is supplied, steam can be generated more efficiently.

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

The boiler 12 is operated as described above as necessary. As will be described later, according to the present embodiment, the frequency of operating the boiler 12 (the frequency of reheating by the boiler 12) is set to can be reduced, and 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 the steam generated by the evaporator 7 (economizer 6) can cover all of the demand, there is no need to operate the boiler 12, and no fuel is supplied to the boiler 12.

In this case, the water in the water drum 50 is pumped by the pump 32 towards the inlet header 26 of the evaporator 7 . 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 steam separator, and the steam drum 48 is filled with saturated steam, and condensed water (saturated water) accumulates at the bottom. Water in steam drum 48 descends into water drum 50 via a downcomer (not shown).

On the other hand, if the steam generated by the evaporator 7 (economizer 6) cannot cover all of the demand, the evaporator 7 is used to mix the water from the water drum 50 with the exhaust gas, as in the case described above. In addition to producing steam by heat exchange, the boiler 12 is operated to produce additional steam.

In this case, fuel is supplied to the furnace 13 and burned by the burner, and the water in the boiler 12 is heated by combustion heat. When the water is heated in the boiler 12, the water rises from the lower water drum 50 through the evaporation pipe 51 to the upper steam drum 48, and part of the heated water evaporates. , the steam drum 48 separates gas and liquid.

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

A saturated steam line 38 is connected to the top of the vessel 8 (the steam separator 10 in FIG. 1 or the steam drum 48 in FIGS. 2 to 4, and the saturated steam in the vessel 8 flows into the saturated steam line 38. 2-4, regardless of whether the boiler 12 is in operation, the steam drum 48 is filled with saturated steam and water, and the saturated Saturated steam from a steam drum 48 flows through the steam line 38 .

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

In some embodiments, valve 42 may be a pressure regulating valve that operates to keep the pressure in saturated steam line 38 upstream of valve 42 constant at a set point. In this case, since the pressure of the saturated steam line 38 and the pressure of the container 8 are equivalent, the pressure of the container 8 is also constant at the above set value.
Also, in some embodiments, the valve 42 is configured to allow the pressure in the saturated steam line 38 or vessel 8 to reach a specified value based on a signal from a pressure sensor for sensing the pressure in the saturated steam line 38 or vessel 8 . It may be configured to adjust the flow rate of the saturated steam in the saturated steam line 38 so that

A condenser 44 is provided in the saturated steam line 38 downstream of the valve 42 described above. 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 off from the saturated steam line 38, and the saturated steam may be supplied to the demand destination via this branch line 40. FIG. The saturated steam supplied to the demand destination may be used, for example, to heat heavy oil used as fuel for the engine 3 or the like, or may be used as onboard general service steam.

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

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

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

A portion 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 tubes. At this time, superheated steam is generated by heat exchange between the saturated steam and the high-temperature exhaust gas flowing through the flue. The superheated steam generated in the superheater 9 is discharged from the superheater 9 via the outlet header 54, guided to the superheater outlet side line 39b, and supplied to the turbine 60 provided on the superheater outlet side line 39b. It is adapted to drive the turbine 60 .
The superheated steam that has finished work in the turbine 60 joins the saturated steam line 38 and is led to the condenser 44 .

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

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

The control device 100 receives a signal from the engine 3 or an engine control device (not shown) indicating that the fuel supplied to the engine 3 has been switched.
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. can 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 identify that the type of fuel being supplied to the engine 3 has been switched based on the above-described received signal.

Further, the control device 100 may output a signal indicating the set pressure of the valve 42 (that is, the 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 the result of measurement by the pressure sensor 64 provided in the saturated steam line 40, and adjusts the pressure of the saturated steam line 40 based on this measurement result. Also, the valve 42 may be actuated.

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

When the controller 100 receives 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, thereby changing the pressure in the container 8. It is configured.

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

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 is reduced from the second pressure to the first pressure. The set pressure of the valve 42 is changed to increase the degree of opening of the valve 42 . Also, when the first fuel (low sulfur fuel) supplied to the engine 3 is switched to the second fuel (high sulfur fuel), the valve 42 is arranged so that the pressure in the container 8 increases from the first pressure to the second pressure. is changed to reduce the opening of the valve 42.

Exhaust gas generated by combustion of fuel in the engine 3 or the like has an acid dew point corresponding to the sulfur content of the fuel, and the higher the sulfur content of the fuel, the higher the acid dew point of the exhaust gas generated from the fuel. Further, in order to protect equipment such as the exhaust gas line 18 through which the exhaust gas flows, the pipes constituting the evaporator 7 and the superheater 9 (economizer 6), etc. from acid corrosion, the exhaust gas temperature in these equipment The temperature should be maintained above the dew point.

In this regard, in the above-described embodiment, when using the first fuel, which is a low-sulfur fuel, as the fuel for the engine 3, the first By adjusting the degree of opening of the valve 42 so as to maintain the pressure, the temperature inside the container 8 (that is, the saturation temperature) is lowered. As a result, the exhaust gas temperature at the outlet of the evaporator 7 (heat exchanger) (that is, the outlet of the economizer 6) can be lowered by the amount corresponding to the decrease in acid dew point. That is, the amount of waste heat recovered in the economizer 6 including the evaporator 7 (heat exchanger) can be increased.
Moreover, by increasing the amount of exhaust heat recovery in this way, the amount of steam generated from the recovered heat can also be increased. As a result, in the configuration including the boiler 12, for example, as shown in FIGS. 12 can be reduced. That is, since the frequency of reheating using the boiler 12 can be reduced, costs such as fuel required for reheating can be reduced.

Further, in the above-described embodiment, when the second fuel, which 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 in the container 8 (that is, the saturation temperature) is raised. 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 the amount corresponding to the increase in the acid dew point, so that the exhaust gas line 18 and the evaporator 7 (economizer 6) It is possible to protect equipment such as piping that constitutes from acid corrosion.

Therefore, according to the above-described embodiment, the amount of exhaust heat recovered 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 equipment from acid corrosion. Meanwhile, the amount of waste heat recovery can be increased.

By the way, as described above, when trying to adjust the exhaust heat recovery amount by adjusting the opening of the valve 42, for example, the opening of the valve 42 based on the temperature of the exhaust gas at the outlet of the evaporator 7 (or the outlet of the economizer 6) It is also possible to adjust the However, since the exhaust gas temperature has a distribution in the plane perpendicular to the flow of the exhaust gas, there is a possibility that the control may vary depending on the temperature detection point. Also, temperature-based control can slow control response.
On the other hand, since the pressure inside the container 8 is almost the same regardless of the location, the detected value of the pressure inside the container 8 is the detected value of the exhaust gas temperature at the outlet of the evaporator 7 (or the outlet of the economizer 6). more accurate than Also, pressure-based control tends to have a faster control response than temperature-based control.

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

In the embodiment shown in FIGS. 1-4, the first fuel (low sulfur fuel) is LNG5 (liquefied natural gas) substantially free of sulfur and the second fuel (high sulfur fuel) is sulfur free. Contains fuel. The above-mentioned first pressure is set to 2 bar or more and 4 bar or less, and the above-mentioned second 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 content concentration of the fuel. For example, the acid dew point of LNG-derived exhaust gas that contains almost no sulfur content is about 100 ° C., and the acid dew point of fuel oil-derived exhaust gas with a sulfur content concentration of about 0.1% or more and 0.5% or less is 120 ° C. ~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, liquid fuel containing sulfur is used as the second fuel, 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 recovered by the exhaust heat recovery system 1 can be appropriately adjusted according to switching of the fuel (first fuel or second fuel) supplied to the engine 3 . As a result, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion.

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

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

In some embodiments, the boiler 12 includes a steam injector (not shown) configured to inject steam toward fuel combusted by a burner (not shown), the second pressure being: By injecting the steam at the second pressure from the above-described steam injection section, the pressure may be set to a pressure that allows diffusion of the fuel in the burner.

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

In some embodiments, the exhaust heat recovery system 1 further includes a fuel heating section (not shown) for heating fuel oil to reduce the viscosity of the fuel oil, and the second pressure is may be set to a pressure capable of reducing the viscosity of the fuel oil by supplying steam of the fuel oil to the fuel heating unit.

In this case, as described above, it is possible to increase the amount of exhaust heat recovery while protecting the equipment from acid corrosion. can be effectively used for heating the fuel for the purpose of reducing the

The operation of changing the opening degree of the valve 42 based on 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 can adjust the opening of the valve 42 (for example, change the set pressure of the valve 42) to change the pressure in the container 8. good.

The fuel used and the pressure of the container 8 (target pressure) are the same as in the case of 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 of the valve 42 so that the pressure in the container 8 becomes the first pressure, and 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 a second pressure higher than the first pressure.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and modes in which these modes are combined as appropriate.

As used herein, expressions such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "central", "concentric" or "coaxial", etc. express relative or absolute arrangements. represents not only such arrangement strictly, but also the state of being relatively displaced with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
Further, in this specification, expressions representing shapes such as a quadrilateral shape and a cylindrical shape not only represent shapes such as a quadrilateral shape and a cylindrical shape in a geometrically strict sense, but also within the range in which the same effect can be obtained. , a shape including an uneven portion, a chamfered portion, and the like.
Moreover, in this specification, the expressions “comprising”, “including”, or “having” one component are not exclusive expressions excluding the presence of other components.

1 Exhaust heat recovery system 2 Exhaust heat recovery device 3 Engine 4 LNG tank 6 Economizer 7 Evaporator 8 Vessel 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 line 39b Superheater outlet 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 (15)

a combustion device capable of switching between a first fuel and a second 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
When receiving a signal indicating that the fuel supplied to the combustion device has been switched between the first fuel and the second fuel , adjusting the opening of the valve based on the signal a controller configured to change the pressure of the vessel;
The first fuel is a fuel having a sulfur content lower than that of the second fuel,
When the fuel is the second fuel, the control unit adjusts the opening degree of the valve so that the pressure in the container becomes the second pressure, and when the fuel is the first fuel, 1. An exhaust heat recovery system, wherein the opening of the valve is adjusted so that the pressure of the container becomes a first pressure lower than the second pressure. the first pressure is 2 bar or more and 4 bar or less;
2. 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;
2. The exhaust heat recovery system according to claim 1, wherein the second pressure is 4 bar or more and 5 bar or less. further comprising a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
3. An exhaust heat recovery system according to claim 1 or 2, wherein the vessel comprises the steam drum of the boiler. a combustion device capable of 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
A control unit configured to change the pressure of the container by adjusting the degree of opening of the valve based on the signal, when receiving a signal indicating that the fuel supplied to the combustion device has been switched. and
When the fuel is the second fuel, the control unit adjusts the opening degree of the valve so that the pressure in the container becomes the second pressure, and the fuel has a sulfur content higher than that of the second fuel. When the first fuel is low, the opening of the valve is adjusted so that the pressure in the container becomes a first pressure lower than the second pressure,
further comprising a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
said vessel comprises said steam drum of said boiler;
the boiler includes a steam injector configured to inject steam toward the fuel combusted by the burner;
The exhaust heat recovery system, wherein the second pressure is a pressure capable of diffusing the fuel by injecting steam at the second pressure from the steam injection part. further comprising a fuel heating unit for heating the fuel oil to reduce the viscosity of the fuel oil;
3. The exhaust heat recovery system according to claim 1, wherein the second pressure is a pressure that can reduce 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 heat a portion of the saturated steam flowing through the saturated steam line through heat exchange with the exhaust gas to generate the superheated steam. waste heat recovery system. 3. The exhaust heat recovery system according to claim 1, further comprising a fuel tank for storing the first fuel supplied to the combustion device. A ship equipped with the exhaust heat recovery system according to any one of claims 1 to 8 . a combustion device capable of switching between a first fuel and a second 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
A method of operating an exhaust heat recovery device comprising
changing the pressure of the vessel by adjusting the opening of the valve when the fuel supplied to the combustion device is switched between the first fuel and the second fuel ;
The first fuel is a fuel having a sulfur content lower than that of the second fuel,
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 in the container becomes the second pressure, and the fuel is the first fuel. In some cases, the method of operating an exhaust heat recovery device is characterized by adjusting the degree of opening of the valve so that the pressure in the container becomes a first pressure lower than the second pressure. the first pressure is 2 bar or more and 4 bar or less;
11. The method of 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;
11. The method of claim 10, wherein the second pressure is 4 bar or more and 5 bar or less. The exhaust heat recovery device comprises a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
12. The method of operating an exhaust heat recovery apparatus according to claim 10, wherein the container of the exhaust heat recovery apparatus 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 heat part of the saturated steam flowing through the saturated steam line through heat exchange with the exhaust gas to generate the superheated steam. operating method of exhaust heat recovery equipment. a combustion device capable of 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 provided in the exhaust gas line for heating the water in the water supply line by heat exchange with the exhaust gas;
a valve provided in the saturated steam line for regulating the pressure of the vessel;
A method of operating an exhaust heat recovery device comprising
changing the pressure of the vessel by adjusting the opening of the valve when the fuel supplied to the combustion device is switched;
In the step of changing the pressure, when the fuel is the second fuel, the degree of opening of the valve is adjusted so that the pressure in the container becomes the second pressure, and the fuel is more sulfur than the second fuel. when the first fuel has a low concentration, adjusting the degree of opening of the valve so that the pressure in the container becomes a first pressure lower than the second pressure;
The exhaust heat recovery device comprises a boiler for generating steam,
The boiler is
a water drum for storing water;
a steam drum for storing the steam generated by the evaporation of the water;
an evaporation tube connecting the water drum and the steam drum;
the vessel of the waste heat recovery device includes the steam drum of the boiler;
the boiler includes a steam injector configured to inject steam toward the fuel combusted by the burner;
The second pressure is a pressure capable of diffusing the fuel by injecting steam at the second pressure from the steam injection part.
A method of operating an exhaust heat recovery device, characterized by:

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