JP2015098829A - Exhaust heat recovery unit and power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust heat recovery unit and a power system capable of achieving more efficient heat recovery.SOLUTION: An exhaust heat recovery unit for recovering heat of exhaust gas discharged from an engine that burns fuel, includes: a first heat exchanger arranged in an engine exhaust pipe guiding the exhaust gas, and implementing heat exchange with the exhaust gas in the engine exhaust pipe; a second heat exchanger arranged downstream of the first heat exchanger in a flow direction of the exhaust gas, and implementing heat exchange with the exhaust gas in the engine exhaust pipe; and a short pass mechanism arranged between the first heat exchanger and the second heat exchanger, decreasing temperature of the exhaust gas, allowing short pass of the exhaust gas through a temperature range in which sulfuric acid concentration of the exhaust gas is equal to or higher than a threshold concentration.

Description

  The present invention relates to an exhaust heat recovery unit exhausted from an engine.

  Some cargo ships equipped with cargo handling are equipped with a power system that includes both an engine used as a prime mover during navigation and a boiler used as a prime mover such as a pump or crane during cargo handling.

  Some power systems including an engine and a boiler include a mechanism that uses the heat of generated exhaust gas. For example, Patent Document 1 discloses that a marine boiler and steam generated in the boiler are used as a heat source or circulating cooling water in an internal combustion engine mounted on the ship is used as a heat source to heat and evaporate seawater and condense the water vapor. Thus, a fresh water desalination apparatus for producing fresh water is described. Further, in Patent Document 2, an economizer (heat exchanger) is provided in each of an exhaust pipe for flowing exhaust gas discharged from an engine and an exhaust collecting pipe, and the exhaust gas discharged from the engine is recovered by the economizer (heat exchanger). The configuration is described. Further, Patent Document 3 describes that a sprayer for spraying water on exhaust gas and performing rapid cooling is provided in order to prevent the generation of dioxins.

Japanese Patent No. 4392469 Japanese Utility Model Publication No. 4-107463 JP 2013-76383 A

  In the power system described above, an exhaust heat recovery unit that recovers the heat of the exhaust gas with a heat exchanger can be provided to extract energy more efficiently from the energy generated by burning fuel in the engine. Here, there is room for improvement in terms of recovering heat from the exhaust gas discharged from the engine.

  The present invention solves the above-described problems, and an object thereof is to provide an exhaust heat recovery unit and a power system that can recover heat more efficiently.

  In order to achieve the above object, an exhaust heat recovery unit of the present invention is an exhaust heat recovery unit that recovers heat of exhaust gas discharged from an engine that burns fuel, and is disposed in an engine exhaust pipe that guides the exhaust gas. A first heat exchanger that exchanges heat with the exhaust gas in the engine exhaust pipe, and the exhaust gas in the engine exhaust pipe that is arranged downstream of the first heat exchanger in the flow direction of the exhaust gas. A second heat exchanger that exchanges heat with the first heat exchanger, and the first heat exchanger and the second heat exchanger, the exhaust gas is cooled, and the sulfuric acid concentration of the exhaust gas is a threshold value And a short-pass mechanism for short-passing a temperature range above the concentration.

  Moreover, it is preferable that the said Shopus mechanism reduces the said waste gas to the temperature below 20 degreeC lower than the acid dew point temperature calculated | required from the sulfur content concentration in waste gas.

  Moreover, it is preferable that the said SHOPASS mechanism reduces the sulfuric acid concentration of the said waste gas to 75% or less.

  The short path mechanism is preferably a direct contact cooler.

  Moreover, it is preferable that the short path mechanism has an air supply unit that supplies a part of the scavenged gas discharged from the supercharger to the engine exhaust pipe.

  A water supply tank for supplying water as a heat medium to the first heat exchanger and the second heat exchanger, and the short path mechanism is a water supply for spraying water from the water supply tank to the engine exhaust pipe It is preferable to have a part.

  In order to achieve the above object, a power system according to the present invention includes an engine that burns fuel, an engine exhaust pipe that guides exhaust gas discharged from the engine, and any of the above-described engines disposed in the engine exhaust pipe. The exhaust heat recovery unit according to claim 1 and a control device that controls the exhaust heat recovery unit.

  A high-sulfur fuel supply unit that supplies the engine with a high-sulfur fuel having a high sulfur content; and a low-sulfur fuel supply unit that supplies the engine with a low-sulfur fuel having a lower sulfur content than the high-sulfur fuel. And when the said high sulfur fuel is supplied to the said engine from the said high sulfur fuel supply part, it is preferable to operate the said short path mechanism.

  According to the present invention, after the exhaust gas is cooled to a predetermined state by the short path mechanism, the exhaust gas is allowed to flow into the heat exchanger, thereby suppressing the influence of corrosion due to sulfur components contained in the exhaust gas, and the exhaust gas in the heat exchanger. Heat can be recovered. Thereby, more heat can be recovered while suppressing corrosion of the apparatus.

FIG. 1 is a schematic configuration diagram illustrating a power system according to the present embodiment. FIG. 2 is a flowchart showing an example of the operation of the power system. FIG. 3 is a graph for explaining the function of the short path mechanism. FIG. 4 is a schematic configuration diagram illustrating a power system according to another embodiment. FIG. 5 is a graph for explaining the function of the short path mechanism. FIG. 6 is a schematic configuration diagram illustrating a power system according to another embodiment. FIG. 7 is a graph for explaining the function of the short path mechanism.

  Exemplary embodiments of an exhaust heat recovery unit and a power system including the exhaust heat recovery unit according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

  The power system of the present embodiment is a system that combines an engine and a boiler as a power source. The power system can be used for, for example, a ship, particularly a cargo ship that requires cargo handling. For example, in the case of a ship, an engine may be used as a power source during navigation, and a boiler may be used as a power source for devices such as pumps and cranes that are used when loading and unloading cargo at berth. The power system is not limited to a ship power source. For example, the power system can be used as a power source for equipment installed on land. The power system of the present embodiment can be suitably used for a system that uses an engine and a boiler as power sources for different purposes and basically does not use them simultaneously. Moreover, although the power system of a present Example was set as the case where an engine and a boiler were combined, you may provide only an engine.

  FIG. 1 is a schematic configuration diagram illustrating a power system according to the present embodiment. In the present embodiment, as shown in FIG. 1, the power system 1 includes an engine unit 2, a boiler unit 3, a power generation unit 4, and a steam circulation unit 5. The engine unit 2, the boiler unit 3, the power generation unit 4, and the steam circulation unit 5 share some mechanisms. For example, the steam circulation unit 5 includes a part of the mechanism of the engine unit 2 or the boiler unit 3, and supplies the generated steam to the power generation unit 4. The power system 1 includes a control device 6. The control device 6 controls the operation of each unit of the power system 1 based on the input setting, the input instruction, the result detected by the detection unit, and the like.

  The engine unit 2 includes an engine 12, a supercharger 14, an exhaust pipe (engine exhaust pipe) 15, an engine heat exchanger unit (exhaust heat recovery unit) 16, an air supply pipe 20, an air cooler 21, And a fuel supply unit 90. The engine 12 is a prime mover that rotates a drive shaft by burning fuel such as a diesel engine or a gasoline engine. When the power system 1 is installed in a ship, the engine 12 serves as a drive source during navigation of the ship. When the power system 1 is installed on a ship, the engine 12 is mainly a diesel engine.

  The supercharger 14 pressurizes air. The supercharger 14 is a so-called turbocharger that pressurizes air by obtaining energy of exhaust gas discharged to the exhaust pipe 15. The supercharger 14 supplies pressurized air to the engine 12 through the air supply pipe 20. The supercharger 14 may be a so-called supercharger that obtains the rotational force of the engine 12 and pressurizes the air. The exhaust pipe 15 is a pipe line (pipe) for guiding the exhaust gas discharged from the engine 12 and passing through the supercharger 14.

  The engine heat exchanger unit (exhaust heat recovery unit) 16 is disposed in the exhaust pipe 15 and exchanges heat with the exhaust gas flowing through the exhaust pipe 15 to recover the heat of the exhaust gas. That is, the engine heat exchanger unit 16 absorbs the heat of the exhaust gas, reduces the temperature of the exhaust gas (decreases the temperature), and exchanges heat with the exhaust gas (a low boiling point medium such as water (steam) or chlorofluorocarbon). The temperature is raised (heated). The engine heat exchanger unit 16 also exchanges heat with the fluid in the exhaust pipe 15 when the engine 12 is stopped to reduce the temperature in the exhaust pipe 15 (preventing fire caused by soot adhering around the exhaust pipe). Also equipped. The engine heat exchanger unit 16 will be described later.

  The air supply pipe 20 is connected to the engine 12 and the supercharger 14, and supplies air pressurized by the supercharger 14 to the engine 12. The air cooler (air cooler) 21 is disposed in the air supply pipe 20 and cools the pressurized air supplied from the supercharger 14 to the engine 12.

  The fuel supply unit 90 includes a low S fuel tank 92 that stores a low sulfur fuel that is a fuel having a low sulfur content, and a high S fuel that stores a high sulfur fuel that has a higher sulfur content than a low sulfur fuel. A fuel tank 94, a pipe 96 connecting the low S fuel tank 92 and the high S fuel tank and the engine 12, a control valve 98 installed in the pipe 96 between the low S fuel tank 92 and the engine 12, And a control valve 99 installed in a pipe 96 between the S fuel tank 94 and the engine 12. Here, the high sulfur fuel is residual oil, C heavy oil, or the like. Low sulfur fuel is light oil or the like. The low sulfur fuel is a fuel having a sulfur concentration in the fuel of 0.1 wt% or less. The high sulfur fuel is a fuel having a sulfur concentration in the fuel higher than 0.1 wt%. The fuel supply unit 90 supplies the low sulfur fuel in the low S fuel tank 92 to the engine 12 by opening the control valve 98 and closing the control valve 99. The fuel supply unit 90 supplies the high sulfur fuel in the high S fuel tank 94 to the engine 12 by opening the control valve 99 and closing the control valve 98. As described above, in the fuel supply unit 90, the low S fuel tank 92, the pipe 96, and the control valve 98 serve as a low S fuel supply unit, and the high S fuel tank 94, the pipe 96, and the control valve 99 serve as a high S fuel supply unit. At least one of a high sulfur fuel and a low sulfur fuel is supplied to the engine 12. The fuel supply unit 90 may include a pump for supplying fuel in the pipe 96, or may be provided in the low S fuel tank 92 or the high S fuel tank 94. Further, the fuel supply unit 90 may adjust the opening degree of the control valves 98 and 99 to mix the high sulfur fuel and the low sulfur fuel and supply them to the engine 12.

  In the present embodiment, the engine unit 2 is described as including the supercharger 14, but the engine 12 may not include the supercharger 14. That is, the engine 12 may be a naturally aspirated internal combustion engine.

  The boiler unit 3 includes a boiler 30, an exhaust pipe (boiler exhaust pipe) 32, and a boiler heat exchanger unit 34. The boiler 30 includes a furnace 42, a burner 44, an evaporation tube group 46, a water drum 48, and a first steam drum 60. The furnace 42 is a container in which each part of the boiler 30 is arranged. The exhaust pipe 32 is connected to the furnace 42. The burner 44 is disposed at a position away from the exhaust pipe 32 of the furnace 42. Air and fuel are supplied to the furnace 42, the fuel is combusted in the furnace 42, and combustion gas is generated. The evaporation tube group 46 has a plurality of heat transfer tubes, and is disposed between the burner 44 of the furnace 42 and the exhaust pipe 32. The water drum 48 is a drum that stores a heat medium, and is connected to the lower side in the vertical direction of the evaporation tube group 46. The first steam drum 60 is a drum that stores steam that is a heated heat medium, and is connected to the upper side in the vertical direction of the evaporator tube group 46. In this way, the evaporator tube group 46 is connected to the water drum 48 at the lower end in the vertical direction of the plurality of heat transfer tubes, and connected to the first steam drum 60 at the upper end in the vertical direction. The medium is in circulation. The boiler 30 burns fuel with the burner 44, and discharges the combustion gas generated by burning the fuel with the burner 44 to the exhaust pipe 32 after passing through the evaporation pipe group 46. The boiler 30 raises the temperature of the heat medium flowing inside the evaporation tube group 46 by exchanging heat between the combustion gas generated by the burner 44 and flowing toward the exhaust pipe 32 and the evaporation tube group 46. .

  The exhaust pipe 32 is a pipe that guides the exhaust gas discharged from the boiler 30. The boiler heat exchanger unit 34 is disposed in the exhaust pipe 32, exchanges heat with the exhaust gas flowing through the exhaust pipe 32, and recovers the heat of the exhaust gas. That is, the boiler heat exchanger unit 34 absorbs the heat of the exhaust gas, lowers (decreases) the temperature of the exhaust gas, and increases (heats) the temperature of the heat medium that exchanges heat with the exhaust gas. The boiler heat exchanger unit 34 will be described later.

  The power generation unit 4 includes a turbine 36 and a generator 38. The turbine 36 is rotated by being supplied with steam generated in each part of the power system 1. The turbine 36 includes a high pressure turbine 36H and a low pressure turbine 36L. The high-pressure turbine 36 </ b> H is driven by high-pressure steam supplied from the engine heat exchanger unit 16. The low pressure turbine 36L is driven by being supplied with steam having a pressure lower than that of steam supplied from the engine heat exchanger unit 16 to the high pressure turbine 36H. The low pressure turbine 36L is driven by the supply of steam generated in the boiler 30 when the boiler unit 3 is in operation. The generator 38 is provided on the same axis as the turbine 36, and can generate electricity when the turbine 36 rotates.

  The steam circulation unit 5 includes an engine heat exchanger unit 16, a boiler heat exchanger unit 34, a first steam drum 60, a second steam drum 62, a drain tank 72, a water supply line 74, and a low pressure line 78. And a high pressure line 76 and a boiler line 80. The steam circulation unit 5 includes a condenser that liquefies the steam that has passed through the turbine 36. The steam circulation unit 5 supplies the heat medium liquefied by the condenser to the drain tank 72.

  The engine heat exchanger unit 16 includes a high pressure superheater 50, a high pressure evaporator (first heat exchanger) 52, a high pressure economizer (first heat exchanger) 54, and a low pressure evaporator (first heat exchanger) 56. And a short path mechanism 102 and a low-pressure economizer (second heat exchanger) 58, which are arranged in this order from the upstream in the exhaust gas flow direction in the exhaust pipe 15. Note that the arrangement order of the high-pressure economizer 54 and the low-pressure evaporator 56 in the exhaust gas flow direction may be reversed. The high-pressure superheater 50, the high-pressure evaporator 52, the high-pressure economizer 54, the low-pressure evaporator 56, and the low-pressure economizer 58 are heat exchangers provided with heat transfer pipes and disposed in a pipe through which exhaust gas flows. Then, heat exchange is performed between the low boiling point medium such as water or steam or chlorofluorocarbon flowing in the heat transfer tube and the exhaust gas, and the temperature of the low boiling point medium such as water or steam or chlorofluorocarbon is raised. The engine heat exchanger unit 16 includes a high-pressure superheater 50, a high-pressure evaporator 52, and a high-pressure economizer 54 that recovers heat from exhaust gas discharged from the engine 12 and vaporizes low-boiling medium such as steam or chlorofluorocarbon. And a high-pressure steam circulation mechanism that supplies the generated steam to the high-pressure turbine 36H. Further, the engine heat exchanger unit 16 includes a low-pressure evaporator 56 and a low-pressure economizer 58 that recover heat from the exhaust gas discharged from the engine 12 to generate steam or chlorofluorocarbon having a lower pressure than the high-pressure steam circulation mechanism. A low-pressure steam circulation mechanism that generates a vaporized low-boiling-point medium and supplies the generated steam to the low-pressure turbine 36L.

  Each part of the high-pressure steam circulation mechanism of the engine heat exchanger unit 16 is connected by a high-pressure line 76. From the upstream side toward the high-pressure turbine 36H from the water supply line 74, the high-pressure economizer 54, the first steam drum 60, and the high-pressure evaporation. The unit 52 and the high-pressure superheater 50 are connected in this order. Here, the high-pressure line 76 includes a first high-pressure line 76a, a second high-pressure line 76b, and a third high-pressure line 76c. The first high-pressure line 76a connects a water supply line 74 described later and the first steam drum 60. The first high-pressure line 76a is provided with an on-off valve 77a and a high-pressure economizer 54 in the path. The on-off valve 77a is a valve that can be switched between open and closed, and can switch whether or not the heat medium flows through the first high-pressure line 76a that is installed. Here, the on-off valve described later has the same structure. Both ends of the second high-pressure line 76 b are connected to the first steam drum 60. The second high-pressure line 76b is provided with an on-off valve 77b and a high-pressure evaporator 52 in the path. The third high pressure line 76c has one end connected to the first steam drum 60 and the other end connected to the high pressure turbine 36H. The third high pressure line 76c is provided with an on-off valve 77c and a high pressure superheater 50 in the path. In the high-pressure steam circulation mechanism, the heat medium is sent from the water supply line 74 to the first high-pressure line 76 a where the high-pressure economizer 54 is installed, and is heated by the high-pressure economizer 54 and then supplied to the first steam drum 60. A high pressure evaporator 52 is connected to the first steam drum 60 through a second high pressure line 76b. The high-pressure evaporator 52 is connected to the first steam drum 60 at both ends by a second high-pressure line 76b. By circulating the heat medium stored in the first steam drum 60, the temperature of the high-pressure evaporator 52 is increased by exhaust gas. It becomes. The steam generated in the high-pressure evaporator 52 is supplied from the first steam drum 60 to the high-pressure superheater 50 through the third high-pressure line 76c, further heated, and then supplied to the high-pressure turbine 36H. The high pressure turbine 36H is driven by the steam supplied from the high pressure steam circulation mechanism.

  Each part of the low-pressure steam circulation mechanism of the engine heat exchanger unit 16 is connected by a low-pressure line 78. The low-pressure economizer 58, the second steam drum 62, the low-pressure evaporation from the upstream side toward the low-pressure turbine 36L from the water supply line 74. The devices are connected in the order of the devices 56. Here, the low pressure line 78 includes a first low pressure line 78a, a second low pressure line 78b, and a third low pressure line 78c. The first low-pressure line 78a connects a water supply line 74 described later and the second steam drum 62. The first low pressure line 78a is provided with an on-off valve 79a and a low pressure economizer 58 in the path. The second low pressure line 78 b is connected to the second steam drum 62 at both ends. In the second low-pressure line 78b, the low-pressure evaporator 56 is installed in the path. The third low pressure line 78c has one end connected to the second steam drum 62 and the other end connected to the low pressure turbine 36L. In the low-pressure steam circulation mechanism, the heat medium is sent from the water supply line 74 to the first low-pressure line 78 a where the low-pressure economizer 58 is installed, and is heated by the low-pressure economizer 58 and then supplied to the second steam drum 62. A low-pressure evaporator 56 is connected to the second steam drum 62 through a second low-pressure line 78b. The low-pressure evaporator 56 is connected to the second steam drum 62 at both ends by a second low-pressure line 78b. By circulating the heat medium stored in the second steam drum 62, the temperature of the low-pressure evaporator 56 is increased by exhaust gas. It becomes. The steam generated in the low-pressure evaporator 56 is supplied from the second steam drum 62 to the low-pressure turbine 36L through the third low-pressure line 78c. The low pressure turbine 36L is driven by the steam supplied from the low pressure steam circulation mechanism. Each part of the low-pressure steam circulation mechanism is disposed downstream of the corresponding part of the high-pressure steam circulation mechanism in the exhaust gas flow direction. Thereby, the temperature and pressure of the steam are lower than those of the high-pressure steam circulation mechanism.

  The first steam drum 60 is a drum that stores high-pressure steam of the engine heat exchanger unit 16, and is a drum that stores steam of the boiler unit 3. As described above, the first steam drum 60 is connected to each of the first high-pressure line 76a, the second high-pressure line 76b, and the third high-pressure line 76c, and circulates and connects the steam or liquid heat medium. Increase the temperature with the heat exchanger. The first steam drum 60 is also connected to the boiler line 80, and circulates a steam or liquid heat medium between the first steam drum 60 and the boiler line 80. The second steam drum 62 is a drum that stores the low-pressure steam of the engine heat exchanger unit 16. That is, the second steam drum 62 stores steam having a pressure lower than that of the first steam drum 60. As described above, the second steam drum 62 is connected to each of the first low pressure line 78a, the second low pressure line 78b, and the third low pressure line 78c, and circulates and connects the heat medium such as steam and liquid. Increase the temperature with the heat exchanger.

The short path mechanism 102 is disposed in the exhaust pipe 15 between the low pressure evaporator 56 and the low pressure economizer 58. The short path mechanism 102 adjusts the temperature of the exhaust gas flowing through the exhaust pipe 15 or the concentration of sulfuric acid (H ₂ SO ₄ ), and has a high corrosion rate due to corrosion caused by sulfuric acid that is an oxide of S (sulfur) component in the exhaust gas. The condition is passed for a short time and at a short distance, that is, a short pass. The short pass mechanism 102 makes a short pass by cooling or diluting the exhaust gas.

  Next, the steam circulation unit 5 supplies a heat medium to the boiler 30 using the boiler heat exchanger unit 34, the first steam drum 60, the feed water line 74, and the boiler line 80. First, the boiler heat exchanger unit 34 is a mechanism for recovering heat contained in the exhaust gas flowing through the exhaust pipe 32 (exhaust gas discharged from the boiler 30). The boiler heat exchanger unit 34 is a first boiler heat exchanger. 64 and a second boiler heat exchanger 66, which are arranged in this order from the upstream in the exhaust gas flow direction in the exhaust pipe 32. The boiler heat exchanger unit 34 supplies, to the first steam drum 60, a heat medium whose temperature has increased by recovering heat from the exhaust gas by the first boiler heat exchanger 64 and the second boiler heat exchanger 66.

  The boiler line 80 is a pipe that connects the water supply line 74, the boiler heat exchanger unit 34, the first steam drum 60, and the low-pressure turbine 36L. The boiler line 80 includes a first boiler line 80a and a second boiler line 80b. The 1st boiler line 80a has connected the water supply line 74 and the 1st steam drum 60 which are mentioned later. The first boiler line 80a is provided with an on-off valve 81a, a first boiler heat exchanger 64, and a second boiler heat exchanger 66 in the path. The second boiler line 80b is connected to the first steam drum 60 and the low pressure turbine 36L. The second boiler line 80b is provided with an on-off valve 81b in the path. In the steam circulation unit 5, the heat medium is sent from the water supply line 74 to the first boiler line 80a in which the first boiler heat exchanger 64 and the second boiler heat exchanger 66 are installed. The temperature is raised by the second boiler heat exchanger 66 and then supplied to the first steam drum 60. The first steam drum 60 heats the heat medium supplied from the first boiler line 80a by the evaporator tube group 46 of the boiler 30 to generate steam. A second boiler line 80 b is connected to the first steam drum 60. The steam stored in the first steam drum 60 is supplied from the second boiler line 80b to the low pressure turbine 36L. The low pressure turbine 36L is also driven by the steam supplied from the second boiler line 80b.

  The drain tank 72 is a tank that stores drain as a heat medium in a liquid state. After passing through the turbine 36, the drain tank 72 stores the condensed heat medium or a separately supplied heat medium.

  The water supply line 74 is connected to the drain tank 72, the high pressure line 76, the low pressure line 78 and the boiler line 80. The water supply line 74 is a pipe that supplies drain (heat medium) stored in the drain tank 72 to the high-pressure line 76, the low-pressure line 78, and the boiler line 80.

  Next, the operation of the power system 1 of the present embodiment will be described. As described above, the power system 1 has a state where the engine unit 2 is operated and a state where the boiler unit 3 is operated. The power system 1 basically stops the boiler unit 3 when the engine unit 2 is operating, and stops the engine unit 2 when the boiler unit 3 is operating. The power system 1 switches the opening and closing of each valve and switches the path of the heat medium according to the state in which the engine unit 2 is in operation and the state in which the boiler unit 3 is in operation. Below, the operation | movement at the time of operation | movement of the engine unit 2 is demonstrated.

  When the engine unit 2 is operated and the boiler unit 3 is stopped, the power system 1 closes the on-off valves 81a and 81b and opens the on-off valves 77a, 77b, 77c, and 79a. Thus, the steam circulation unit 5 supplies the heat medium supplied from the drain tank 72 to the water supply line 74 to the high pressure line 76 and the low pressure line 78. As described above, the heat medium supplied to the high-pressure line 76 passes through the first steam drum 60 and is increased in temperature and pressure by the high-pressure economizer 54, the high-pressure evaporator 52, and the high-pressure superheater 50, and then the high-pressure turbine. 36H. As described above, the heat medium supplied to the low-pressure line 78 is also supplied to the low-pressure turbine 36L after the temperature and pressure are increased by the low-pressure economizer 58 and the low-pressure evaporator 56 while passing through the second steam drum 62. .

  In addition, the steam circulation unit 5 supplies the heat medium supplied to the first steam drum 60 to the second high-pressure line 76b in which the on-off valve 77b is open, and supplies the heat medium to the second high-pressure line 76b and the high-pressure evaporator 52. Circulate.

  In the power system 1, the short path mechanism 102 of the engine heat recovery mechanism 16 disposed in the exhaust pipe 15 short-paths a predetermined state of the exhaust gas. Specifically, the short pass mechanism 102 reduces the temperature of the exhaust gas that has been heat-exchanged by the low-pressure evaporator 56 and reduced in temperature to a predetermined temperature, or reduces the sulfuric acid concentration. The exhaust gas that has passed through the short path mechanism 102 passes through the low-pressure economizer 58, is heat-exchanged by the low-pressure economizer 58, and is reduced in temperature to a predetermined temperature. The low-pressure evaporator 56 and the low-pressure economizer 58 perform heat exchange between the exhaust gas and the heat medium as described above, thereby recovering heat from the exhaust gas and increasing the temperature of the heat medium. Heat. Here, the low-pressure evaporator 56 performs heat exchange in a temperature range higher than the temperature at which the exhaust gas starts to aggregate (aggregation start temperature). That is, the low-pressure evaporator 56 does not reduce the exhaust gas below the aggregation start temperature. The low pressure economizer 58 performs heat exchange with the exhaust gas having a temperature lower than the aggregation start temperature.

  The power system 1 controls the operation of the short path mechanism 102 according to the fuel combusted by the engine 12, that is, the fuel supplied from the fuel supply unit 90. FIG. 2 is a flowchart showing an example of the operation of the power system. The control device 6 determines whether high S fuel is used, that is, whether fuel is being supplied from the high S fuel tank 94 to the engine 12. The control device 6 determines whether high S fuel is used based on the flow rate of the portion of the pipe 96 where the control valve 99 is disposed, the opening degree of the control valve 99, or various control signals. When it is determined that the high S fuel is not used (No in step S12), the control device 6 stops the short path mechanism 102 (step S14). When it is determined that the high S fuel is used (Yes in step S12), the control device 6 operates the short path mechanism 102 (step S16).

  As described above, the power system 1 recovers the heat contained in the exhaust gas discharged from the engine 12 by the engine heat exchanger unit 16 and supplies it to the turbine 36, so that it is included in the exhaust gas discharged from the engine 12. Heat can be recovered and efficiency can be further increased.

In the power system 1, the sulfur component, specifically, sulfuric acid (H ₂ SO ₄ ) is reduced to a temperature higher than the aggregation start temperature by the short path mechanism 102 in the low pressure evaporator (first heat exchanger). The exhaust gas is cooled to a predetermined temperature not higher than the aggregation start temperature or diluted to a predetermined sulfuric acid concentration. Thereby, heat can be recovered by the low pressure economizer 58 while suppressing the corrosion of the low pressure economizer 58.

Here, FIG. 3 is a graph for explaining the function of the short path mechanism. FIG. 3 shows the relationship between the temperature containing the sulfur component, that is, the exhaust gas temperature [° C.] and sulfuric acid concentration (H ₂ SO ₄ concentration) [%], and the corrosion rate [mg / cm ² / hr] in this example. The result measured for every material which gas contacts is shown. In addition, the material shown in FIG. 3 is an example, and the metal used for a heat exchanger tube or a pipe line is not limited to this.

  The short-pass mechanism 102 reduces the exhaust gas, short-passes a predetermined temperature range, and reduces it to a predetermined temperature or lower, thereby reducing the condensation start temperature at a high corrosion rate, as shown in FIG. It is possible to suppress the exhaust gas near 140 ° C. from coming into contact with the low pressure economizer 58. Furthermore, the short path mechanism 102 can perform heat exchange with the exhaust gas at a corrosion rate in a slow range, in this embodiment, 120 ° C. or lower by reducing the temperature to a predetermined temperature or lower. In the example shown in FIG. 3, the short path mechanism 102 reduces the temperature of the exhaust gas to 120 ° C. or less, but is not limited thereto. The short path mechanism 102 performs heat exchange between the exhaust gas in the range where the corrosion rate is low and the low-pressure economizer 58 by reducing the temperature to 20 ° C. or lower than the acid dew point temperature obtained from the sulfur content concentration in the exhaust gas. be able to. Here, the short path mechanism 102 can perform heat exchange more efficiently by cooling to a temperature close to a temperature 20 ° C. lower than the acid dew point temperature determined from the concentration of sulfur in the exhaust gas. The short path mechanism 120 cools from a temperature 20 ° C. lower than the acid dew point temperature determined from the sulfur content concentration in the exhaust gas to a temperature range 60 ° C. lower than the acid dew point temperature determined from the sulfur content concentration in the exhaust gas. Thus, the range in which the corrosion rate is high can be short-passed, and the exhaust gas can be caused to flow into the low pressure economizer 58 in a state in which the corrosion rate is in the low range.

  Further, the short path mechanism 102 dilutes the exhaust gas to reduce the sulfuric acid concentration, short-passes a predetermined concentration range, and reduces it to a predetermined sulfuric acid concentration or less, thereby increasing the corrosion rate as shown in FIG. Condensation start concentration, in this embodiment, 80% of exhaust gas can be prevented from coming into contact with the low pressure economizer 58. Further, the short path mechanism 102 can perform heat exchange with the exhaust gas in a range where the corrosion rate is low, in this embodiment, 75% or less, by reducing it to a predetermined concentration or less.

  As described above, the power system 1 includes the short path mechanism 102, and reduces or dilutes the exhaust gas near the acid dew point to a condition where the temperature is lower than the acid dew point and the corrosion rate is low, so that the corrosion rate near the acid dew point is obtained. Can be prevented from contacting the low-pressure economizer 58. Further, the low pressure economizer 58 can recover heat from the exhaust gas while suppressing the corrosion of the heat transfer tube or the like by recovering heat from the exhaust gas even under the condition of the acid dew point or lower.

  Here, as described above, it is preferable that the short path mechanism 102 reduces the temperature of the exhaust gas to a temperature that is 20 ° C. lower than the dew point temperature obtained from the concentration of sulfur in the exhaust gas. Thereby, a corrosion rate can be reduced more greatly and the corrosion of the low pressure economizer 58 (2nd heat exchanger) can be suppressed. It is preferable that the Shopus mechanism reduces the sulfuric acid concentration of the exhaust gas to 75% or less. Thereby, a corrosion rate can be reduced more greatly and the corrosion of the low pressure economizer 58 (2nd heat exchanger) can be suppressed.

  The power system 1 can operate the short path mechanism 120 only when necessary by switching between operation and stop of the operation of the short path mechanism 102 according to the fuel to be burned, as in the process shown in FIG. Further, more heat can be recovered from the exhaust gas while suppressing the corrosion of the low pressure economizer 58 (second heat exchanger). That is, even if the low-pressure economizer 58 reduces the temperature from the vicinity of the condensation start temperature to below the condensation start temperature, the low-pressure economizer 58 is less susceptible to corrosion or less likely to progress. During use, the low-pass ecomizer 58 can recover more heat from the exhaust gas by stopping the short path mechanism 102. As a result, the fuel utilization efficiency can be increased while suppressing corrosion of the apparatus, that is, deterioration. The power system 1 may operate the short path mechanism 102 at all times.

  Here, as the short path mechanism, before reaching the second heat exchanger, the exhaust gas that has passed through the first heat exchanger can be reduced in temperature to a predetermined condition below the acid dew point before reaching the second heat exchanger. A mechanism can be used. For example, a heat exchanger having a heat transfer tube formed with a process with high corrosion resistance, that is, a protective film or the like may be used. Here, the short path mechanism preferably uses a direct contact type cooler. By using a mechanism that directly contacts the exhaust gas with a heat medium that cools (decreases) the exhaust gas, it is possible to cool the exhaust gas while reducing the number of parts that come into contact with the exhaust gas under a fast corrosion rate.

Hereinafter, a specific example of the short path mechanism will be described with reference to FIGS. FIG. 4 is a schematic configuration diagram illustrating a power system according to another embodiment. FIG. 5 is a graph for explaining the function of the short path mechanism. FIG. 5 shows water vapor 10 vol. FIG. 6 is a state transition diagram of sulfuric acid at a sulfuric acid concentration (H ₂ SO ₄ ) [%] of a gas of% and a metal surface temperature [° C.].

  The power system 1A shown in FIG. 4 has a short path mechanism 102A. The short path mechanism 102 </ b> A is a low-pressure evaporating part of the air discharged from the supercharger 14 and supplied to the engine 12, specifically, a part of the scavenged air flowing through the air supply pipe 20 and passing through the air cooler 21. An air supply unit that supplies the exhaust pipe 15 between the vessel 56 and the low-pressure economizer 58. The short path mechanism 102 </ b> A includes a pipe 112 and a control valve 114. In the present embodiment, the pipe 112 and the control valve 114 serve as an air supply unit. The pipe 112 has one end connected to the air supply pipe 20 and the other end connected to the exhaust pipe 15 between the low-pressure evaporator 56 and the low-pressure economizer 58. The control valve 114 is disposed in the pipe 112 and adjusts the flow rate of the exhaust gas flowing through the pipe 112 by adjusting the opening degree.

  The short pass mechanism 102A supplies a part of the scavenged gas flowing through the air supply pipe 20 to a predetermined position of the exhaust pipe 15 through the pipe 112, thereby short-passing the exhaust gas to a predetermined temperature in the same manner as the short path mechanism 102A. Specifically, the short path mechanism 102A scavenges and cools the exhaust gas flowing through the exhaust pipe 15 to move the state of the exhaust gas in the direction of low temperature and low sulfuric acid concentration as shown by the arrow A in FIG. be able to. As a result, the low pressure economizer 58 can suitably recover heat while suppressing the corrosion of the low pressure economizer 58. Further, the short path mechanism 102A uses the supercharger 14 as a means for supplying air, and uses a part of the scavenging air of the supercharger 14 so that the exhaust gas is discharged only by the piping system without using a new drive source. A mechanism for performing a short pass can be realized.

FIG. 6 is a schematic configuration diagram illustrating a power system according to another embodiment. FIG. 7 is a graph for explaining the function of the short path mechanism. FIG. 7 is a graph showing the relationship between the surface temperature [° C.] and the total vapor pressure (H ₂ SO ₄ / H ₂ O) when the sulfuric acid concentration (H ₂ SO ₄ ) is each concentration.

  The power system 1B shown in FIG. 6 has a short path mechanism 102B. The short pass mechanism 102 </ b> B has a water supply unit that sprays the heat medium (water in this embodiment) stored in the drain tank 72. The short path mechanism 102B includes a storage tank 120, a supply pipe 121, a pump 122, a supply pipe 124, and a plurality of injection units 126. The storage tank 120 is a tank that stores a heat medium (water). The supply pipe 121 is a pipe that feeds the heat medium stored in the drain tank 72 to the storage tank 120. The supply pipe 124 is inserted into the exhaust pipe 15 and connected to the storage tank 120. The pump 122 sends the heat medium stored in the storage tank 120 to the supply pipe 124. The plurality of injection units 126 are arranged in a portion of the supply pipe 124 inside the exhaust pipe 15. The injection unit 126 is a member formed with a hole for injecting a heat medium, such as a spray nozzle, and injects the heat medium flowing through the supply pipe 124 into the exhaust pipe 15. The injection unit 126 is disposed in the exhaust pipe 15 between the low pressure evaporator 56 and the low pressure economizer 58.

  The short path mechanism 102 </ b> B is similar to the short path mechanism 102 by feeding the heat medium (water) stored in the storage tank 120 by the supply pipe 124 and the pump 122 and injecting it from a predetermined position of the exhaust pipe 15 from the injection unit 126. The exhaust gas is short-passed to a predetermined sulfuric acid concentration. Specifically, the short path mechanism 102B can move the state of the exhaust gas in the direction of low sulfuric acid concentration by supplying moisture to the exhaust gas flowing through the exhaust pipe 15, as indicated by an arrow B in FIG. . As a result, the low pressure economizer 58 can suitably recover heat while suppressing the corrosion of the low pressure economizer 58. Further, the short path mechanism 102B can recover more heat from the exhaust gas by reducing the sulfuric acid concentration while suppressing the temperature reduction.

  Here, the short path mechanism may be a combination of the above-described mechanisms. That is, the short path mechanism may include two mechanisms, a mechanism for cooling the exhaust gas and a mechanism for diluting. Further, the exhaust gas may be cooled and diluted by one mechanism. The engine heat exchanger unit 16 may further include a multi-stage heat exchanger. The power system 1 may not include the first boiler heat exchanger 64 and the second boiler heat exchanger 66 that recover heat from the exhaust gas of the boiler 30. Moreover, the structure of the heat exchanger arrange | positioned upstream from the short path mechanism 102 is not specifically limited, At least 1 or more heat exchanger should just be arrange | positioned. In the above embodiment, the name of the heat exchanger is an economizer, an evaporator, or a superheater. However, the heat exchanger may be a heat exchanger, and may be a heat exchanger used for a purpose other than the function of the name. Moreover, although the power system 1 of this embodiment used two types of fuel, high-sulfur fuel and low-sulfur fuel, the type of fuel is not limited, and one type or three or more types may be used.

DESCRIPTION OF SYMBOLS 1 Power system 2 Engine unit 3 Boiler unit 4 Power generation unit 5 Steam circulation unit 6 Control apparatus 12 Engine 14 Supercharger 15 Exhaust pipe 16 Engine heat exchanger unit (exhaust heat recovery unit)
20 Supply pipe 30 Boiler 32 Exhaust pipe 34 Boiler heat exchanger unit 36 Turbine 38 Generator 42 Furnace 44 Burner 46 Evaporation pipe group 48 Water drum 50 High pressure superheater 52 High pressure evaporator 54 High pressure economizer 56 Low pressure evaporator 58 Low pressure economizer 60 1 steam drum 62 2nd steam drum 64 1st boiler heat exchanger 66 2nd boiler heat exchanger 72 Drain tank 74 Water supply line 77a, 77b, 77c, 79a, 81a, 81b On-off valve 76 High pressure line 76a First high pressure line 76b Second high pressure line 76c Third high pressure line 78 Low pressure line 78a First low pressure line 78b Second low pressure line 80 Boiler line 80a First boiler line 80b Second boiler lines 102, 102A, 102B Short pass mechanism

Claims (8)

An exhaust heat recovery unit that recovers heat of exhaust gas discharged from an engine that burns fuel,
A first heat exchanger disposed in an engine exhaust pipe that guides the exhaust gas and exchanging heat with the exhaust gas in the engine exhaust pipe;
A second heat exchanger that is disposed downstream of the first heat exchanger in the flow direction of the exhaust gas and performs heat exchange with the exhaust gas in the engine exhaust pipe;
A short path mechanism that is disposed between the first heat exchanger and the second heat exchanger, reduces the temperature of the exhaust gas, and short-passes a temperature range in which the sulfuric acid concentration of the exhaust gas is equal to or higher than a threshold concentration; An exhaust heat recovery unit characterized by having.   2. The exhaust heat recovery unit according to claim 1, wherein the Shopus mechanism reduces the temperature of the exhaust gas to a temperature that is 20 ° C. lower than an acid dew point temperature obtained from a sulfur content concentration in the exhaust gas.   3. The exhaust heat recovery unit according to claim 1, wherein the Shopus mechanism reduces the sulfuric acid concentration of the exhaust gas to 75% or less.   The exhaust heat recovery unit according to any one of claims 1 to 3, wherein the short path mechanism is a direct contact type cooler.   The exhaust heat recovery unit according to claim 4, wherein the short path mechanism has an air supply unit that supplies a part of the scavenged gas discharged from the supercharger to the engine exhaust pipe. A water supply tank for supplying water as a heat medium to the first heat exchanger and the second heat exchanger;
The exhaust heat recovery unit according to claim 4, wherein the short path mechanism includes a water supply unit that sprays water from the water supply tank onto the engine exhaust pipe. An engine that burns fuel;
An engine exhaust pipe for guiding exhaust gas discharged from the engine;
The exhaust heat recovery unit according to any one of claims 1 to 6 disposed in the engine exhaust pipe,
And a controller for controlling the exhaust heat recovery unit. A high-sulfur fuel supply unit that supplies the engine with high-sulfur fuel with a high sulfur content;
A low-sulfur fuel supply unit that supplies the engine with a low-sulfur fuel having a lower sulfur content than the high-sulfur fuel,
The power system according to claim 7, wherein the control device operates the short path mechanism when the high sulfur fuel is supplied to the engine from the high sulfur fuel supply unit.

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