JP2005320938A - Exhaust heat recovery device and exhaust heat recovery method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust heat recovery device capable of increasing the output and supply/exhaust efficiency of an internal combustion engine by utilizing, without waste, steam generated by the use of exhaust heat from the internal combustion engine. <P>SOLUTION: This exhaust heat recovery device comprises the internal combustion engine 2, a main generator 3 driven by the output of the internal combustion engine 2, a supercharger 4 having a turbine 7 to which the exhaust gas of the internal combustion engine 2 is supplied through an exhaust gas passage 10, and a heat exchanger 5 to which the exhaust gas passed through the turbine 7 is supplied and generating steam by the exhaust gas. A steam passage 16 allowing the steam generated in the heat exchanger 5 to flow therein is connected to the exhaust gas passage 10 of the internal combustion engine 2 on the upstream side of the supercharger 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust heat recovery device and an exhaust heat recovery method for recovering exhaust heat of an internal combustion engine such as an engine and using it for power generation or the like.

  In recent years, cogeneration that improves energy efficiency, economic efficiency, environmental conservation, etc. by generating hot water or steam using the heat of exhaust gas discharged from internal combustion engines such as diesel engines and gas engines and using it as thermal energy The system is widespread.

  As one of such cogeneration systems, for example, Patent Document 1 discloses an engine, a main generator driven by the output of the engine, a supercharger having a turbine to which engine exhaust is supplied, There is disclosed a power generation facility that includes a boiler that is supplied with exhaust through a turbine and generates steam by heat exchange with the exhaust.

  In this technology, a steam turbine is driven using steam generated by a boiler, and an auxiliary generator is driven by the output of the steam turbine, or steam is supplied to a heat medium using device such as a water heater, thereby generating an engine. The exhaust heat is effectively used.

Japanese Patent Laid-Open No. 10-89017

  In the technique of the above-mentioned Patent Document 1, it is possible to supplement the power generation amount of the main generator by using the steam generated by the exhaust heat of the engine for power generation of the sub-generator. By providing the turbine and the sub-generator, there is a problem that the entire apparatus cannot be increased in size and complexity, and the initial cost when the equipment is introduced becomes very large. Moreover, since the steam generation by the boiler is performed with the exhaust having a relatively low temperature after passing through the supercharger, high-temperature steam cannot be generated, and the recovery efficiency of the steam turbine is not so good.

  On the other hand, when the thermal efficiency of the system is taken into consideration, it is preferable to use the steam generated in the boiler as thermal energy for hot water supply, air conditioning, etc., rather than using it for driving a steam turbine.

  However, in this case, when there is little demand for heat energy, there is a problem that excess steam is generated. This is because the steam generated by the boiler is generated according to the power generation load of the main generator regardless of the actual demand for thermal energy. Such surplus steam has to be discarded, which has caused the energy recovery efficiency to deteriorate.

  The present invention has been made in view of such circumstances, and uses steam generated by utilizing exhaust heat of the internal combustion engine without wasting it, thereby increasing the output of the internal combustion engine and using the main generator. An object of the present invention is to provide an exhaust heat recovery device and an exhaust heat recovery method capable of increasing the amount of power generation and increasing the supply / exhaust efficiency of an internal combustion engine.

  According to the first aspect of the present invention, an internal combustion engine, a main generator driven by the output of the internal combustion engine, a supercharger having a turbine to which exhaust gas of the internal combustion engine is supplied via an exhaust passage, and a turbine are passed. An exhaust heat recovery apparatus comprising a heat exchanger that is supplied with exhaust gas and generates steam by the exhaust gas, and includes a steam passage for circulating the steam generated by the heat exchanger. It is connected to the exhaust passage of the internal combustion engine on the upstream side.

  The invention according to claim 2 is the invention according to claim 1, further comprising a second steam passage for supplying steam generated by a heat exchanger to a heat medium utilization device that uses steam as heat energy, and the steam passage And a second steam passage are provided with a metering valve for adjusting the flow rate of the steam, respectively.

  The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the supercharger is constituted by a variable capacity supercharger.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, comprising a second turbine and a second generator driven by the output of the second turbine, upstream of the supercharger. The exhaust passage of the internal combustion engine is branched on the side and downstream of the connection position of the steam passage, the air-fuel mixture is supplied to the turbine of the supercharger from one of the branched exhaust passages, and the air-fuel mixture is supplied to the second turbine from the other A metering valve is provided for adjusting the supply amount of the air-fuel mixture to the second turbine in the other exhaust passage.

  The invention according to claim 5 is the invention according to any one of claims 1 to 3, further comprising a third generator driven by the output of the turbocharger turbine.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the water supplied to the heat exchanger is heated by exchanging heat with the cooling water after cooling the internal combustion engine. .

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the combustion device for burning the exhaust gas of the internal combustion engine is provided in the exhaust passage of the internal combustion engine upstream of the supercharger. It is characterized by that.

  The invention according to claim 8 supplies the exhaust gas of the internal combustion engine that drives the main generator to the turbine of the supercharger, supplies the exhaust gas that has passed through the turbine to the heat exchanger, and generates steam by the exhaust gas in the heat exchanger. In the exhaust heat recovery method, the steam generated by the heat exchanger is mixed with the exhaust of the internal combustion engine upstream of the supercharger, and the mixture of steam and exhaust is supplied to the turbocharger turbine. It was made to do.

  According to the first aspect of the present invention, the steam generated by the heat exchanger can be mixed with the exhaust gas of the internal combustion engine, and this air-fuel mixture can be supplied to the turbocharger turbine. For this reason, compared with the case where only exhaust gas is supplied, the gas flow rate to the turbine can be increased, the boost pressure for the internal combustion engine can be increased, and the output of the internal combustion engine can be increased. Therefore, even if a steam turbine or other generator driven by the turbine is not provided, the power generation amount can be increased easily and inexpensively by the main generator without wasting steam. Further, by increasing the flow rate of the gas supplied to the turbine of the supercharger, the work of supplying and exhausting can be increased, and the fuel consumption rate of the internal combustion engine can be improved.

  According to the second aspect of the invention, by adjusting the steam passage metering valve, the amount of steam flowing into the exhaust passage can be adjusted according to the load of the internal combustion engine corresponding to the power demand. By adjusting the metering valve of the two steam passages, the supply amount of steam can be adjusted according to the heat demand of the heat medium utilizing device. Therefore, it is possible to supply an appropriate amount to each of the exhaust passage side and the heat medium utilization device side without wasting steam.

  According to the invention described in claim 3, by setting the turbocharger to a variable capacity type, it is possible to obtain optimum turbocharger performance regardless of the amount of air-fuel mixture supplied to the turbine. Can be maintained.

  According to the fourth aspect of the present invention, the air-fuel mixture is supplied to both the turbine of the supercharger and the second turbine for the second generator by increasing the gas flow rate by mixing the steam and the exhaust gas. The amount of power generation can be increased by driving the second generator with the output of the second turbine. Further, by adjusting the metering valve, it is possible to supply only the surplus air-fuel mixture to the second turbine according to the amount of air-fuel mixture without degrading the performance of the supercharger.

  According to the fifth aspect of the invention, since the turbine work increases by increasing the flow rate of the gas flowing into the turbocharger turbine, the third generator is driven by the surplus power to increase the power generation amount. can do.

  According to the sixth aspect of the present invention, the heat supplied to the heat exchanger is heated by exchanging heat with the cooling water after cooling the internal combustion engine, so that the exhaust heat of the engine cooling water can be suitably recovered and energy efficiency is improved. Can be improved.

  According to the seventh aspect of the present invention, the supercharger can be operated efficiently by raising the temperature of the exhaust gas by the combustion device, and harmful components contained in the exhaust gas are combusted and removed by reburning the exhaust gas. Can do.

  According to the eighth aspect of the present invention, the steam generated by the heat exchanger is mixed with the exhaust gas of the internal combustion engine, and this mixture is supplied to the turbine of the supercharger. The gas flow rate to the internal combustion engine can be increased, the boost pressure for the internal combustion engine can be increased, and the output of the internal combustion engine can be increased. Therefore, even if a steam turbine or other generator driven by the turbine is not provided, the power generation amount can be increased easily and inexpensively by the main generator without wasting steam. It is also possible to improve the fuel consumption rate of the internal combustion engine by increasing the flow rate of the gas supplied to the turbocharger turbine.

[First Embodiment]
FIG. 1 is an overall configuration diagram showing an outline of an exhaust heat recovery apparatus 1 according to the first embodiment of the present invention. The exhaust heat recovery device 1 uses an internal combustion engine 2, a main generator 3 driven by the output of the internal combustion engine 2, a supercharger 4 that supplies compressed air to the internal combustion engine 2, and exhaust gas from the internal combustion engine 2. And a heat exchanger 5 for generating steam.

  In this embodiment, a reciprocating engine such as a diesel engine or a gas engine is used as the internal combustion engine 2. The main generator 3 is connected to the output shaft 6 of the engine 2.

  The supercharger 4 has a turbine 7 and a compressor 8, and both 7 and 8 are linked and connected via a shaft 9. The turbine 7 is disposed in the exhaust passage 10 of the engine 2, rotates by the exhaust of the engine 2, and drives the compressor 8. The compressor 8 sucks air from the intake passage 11 and generates compressed air. The generated compressed air is cooled by the cooler 12 and supplied to the combustion chamber of the engine 2.

  As the supercharger 4 of the present embodiment, a variable capacity type that can change the area of the inlet passage of the exhaust gas according to the flow rate of the exhaust gas supplied to the turbine 7 is used.

  The heat exchanger 5 is configured by an exhaust heat recovery boiler, and is disposed in the exhaust passage 10 of the engine 2 on the downstream side of the supercharger 4. Therefore, the exhaust gas that has passed through the turbine 7 is supplied to the heat exchanger 5. The exhaust gas that has passed through the heat exchanger 5 may be discharged to the outside (atmosphere) via the exhaust passage 10 or may be supplied to other devices such as an exhaust turbine.

  The heat exchanger 5 generates steam by heat exchange between the water supplied via the water supply passage 14 and the exhaust of the engine 2. A first steam passage 16 and a second steam passage 15 are connected to the heat exchanger 5, and the steam flowing through the second steam passage 15 is sent to a heat medium utilization device 17 such as a hot water supply device or an air conditioning device, where heat energy is transmitted. It has come to be used as.

  It is also possible to provide a steam turbine driven by steam instead of or in addition to the heat medium using device 17, and drive other generators, machines, and the like by this steam turbine. However, it is preferable from the viewpoint of thermal efficiency that the steam is used as heat energy by the heat medium utilization device 17 as it is.

  The downstream end of the first steam passage 16 is connected to the exhaust passage 10 of the engine 2 on the upstream side of the supercharger 4. Therefore, the steam generated in the heat exchanger 5 flows into the exhaust passage 10 via the first steam passage 16 and is mixed with the exhaust of the engine 2.

  The first steam passage 16 and the second steam passage 15 are respectively provided with a first metering valve 19 and a second metering valve 18 for adjusting the flow rate of steam.

  Cooling water that has passed through the cooler 12 is supplied from the second water supply passage 20 to the fresh water cooler 22 of the engine 2, and the cooling water passes through the fresh water cooler 22 to be heated and becomes hot water. It is discharged through the drainage passage 23. The discharged hot water is supplied to the hot water supply device 34 and the like, and is used as thermal energy.

  Further, the drainage passage 23 is branched on the way as a water supply passage 14 to the heat exchanger 5, and hot water is supplied to the heat exchanger 5.

  A third metering valve 25 is provided in the water supply passage 14, and a fourth metering valve 24 is provided downstream of the branch portion of the drainage passage 23, and the third and fourth metering valves are provided. The amount of hot water supplied to the heat exchanger 5, the hot water supply device 34, and the like is adjusted by the valves 25 and 24.

  The flow of operation of the exhaust heat recovery apparatus of the present embodiment having the above configuration will be described as follows. First, when the engine 2 is operated, the main generator 3 is driven through the output shaft 6 to generate power. Exhaust gas from the engine 2 flows through the exhaust passage 10, passes through the turbine 7 of the supercharger 4, and is then supplied to the heat exchanger 5.

  On the other hand, the hot water that has passed through the cooler 12 and the fresh water cooler 22 from the second water supply passage 20 is supplied to the hot water supply device 34 from the drainage passage 23 and passes through the water supply passage 14 branched from the drainage passage 23 to the heat exchanger 5. Then, steam is generated by heat exchange between the exhaust gas and the hot water in the heat exchanger 5.

  Thus, by using the hot water after the engine 2 is cooled, the heat energy for generating the steam is reduced, and more steam can be generated immediately.

  The steam generated in the heat exchanger 5 is supplied from the second steam passage 15 to the heat medium utilization device 17 and flows into the exhaust passage 10 from the first steam passage 16.

  Therefore, the steam that has flowed into the exhaust passage 10 is mixed with the exhaust gas, and the air-fuel mixture is supplied to the turbine 7, whereby the turbine 7 rotates and the compressor 4 is driven. Compressed air generated by driving the compressor 4 passes through the cooler 12 and is then supplied to the combustion chamber of the engine 2.

  Thus, by supplying the mixture of exhaust gas and steam to the turbine 7 of the supercharger 4, the gas flow rate to the turbine 7 is increased as compared with the case of supplying only the exhaust gas, and the turbine work is increased. To do. Thereby, the supercharging pressure with respect to the engine 2 is also increased, the output of the engine 2 is increased, and the power generation amount of the main generator 3 is increased.

  Since the 1st metering valve 19 and the 2nd metering valve 18 are provided in the 1st steam passage 16 and the 2nd steam passage 15, respectively, the heat demand of the heat carrier utilization equipment 17 by the 2nd metering valve 18 The amount of steam supplied can be adjusted according to the flow rate, and the amount of inflow into the exhaust passage 10 can be adjusted by the first metering valve 19 according to the engine load corresponding to the power demand.

  Therefore, when the heat demand in the heat medium utilization device 17 is small, most of the generated steam is mixed with the exhaust gas through the first steam passage 16 to improve the output of the engine 2 and the fuel consumption rate. On the contrary, when the heat demand is high, most of the generated steam can be supplied to the heat medium utilization device 17 through the second steam passage 15. Thereby, it can utilize without wasting steam and can improve energy efficiency.

  The first metering valve 19 and the second metering valve 18 may be interlocked so that when one flow rate is increased, the other flow rate is decreased.

  Further, since a variable capacity supercharger is used as the supercharger 4, an appropriate supercharger 4 performance can be obtained by changing the inlet passage area to the turbine 7 in accordance with the flow rate of the air-fuel mixture. Thus, the performance of the engine 2 can be maintained.

  In other words, when the heat demand is high and most of the generated steam is used for the heat medium utilization device 17, the flow area of the air-fuel mixture flowing into the turbine 7 of the supercharger 4 decreases, so the passage area flowing into the turbine 7 By reducing the flow rate, it is possible to obtain appropriate performance for both the supercharging pressure and the supercharging air flow even with a small flow rate. Conversely, when the heat demand is small, the flow rate of the air-fuel mixture flowing into the turbine 7 increases. Therefore, it is possible to obtain appropriate performance of the supercharger 4 by increasing the passage area of the turbine 7.

  In the above description, the case where the output of the engine 2 is increased by supplying the mixture of exhaust gas and steam to the turbine 7 of the supercharger 4 is described. 7 can also be set.

  In this case, as the gas flow rate to the turbine 7 increases, the expansion ratio of the turbine 7 can be designed to be smaller than the conventional one while maintaining a predetermined pressure ratio. The rate can be improved.

[Second Embodiment]
FIG. 2 is an overall configuration diagram showing an outline of the exhaust heat recovery apparatus 1 according to the second embodiment. In the present embodiment, an auxiliary generator (second generator) 26 is provided in addition to the main generator 3 driven by the output of the engine 2. The second generator 26 is a turbo generator and is linked to the second turbine 27 via a drive shaft 28.

  The exhaust passage 10 of the engine 2 is branched into two on the upstream side of the supercharger 4, and the second turbine 27 is disposed in the branched exhaust passage (second exhaust passage) 29. Therefore, the mixture of the exhaust gas and steam of the engine 2 is supplied to both the turbine 7 and the second turbine 27 of the supercharger 4, and the turbines 7 and 27 are driven simultaneously. The second generator 26 is driven by the output of the second turbine 27. After passing through the second turbine 27, the second exhaust passage 29 is joined to the exhaust passage 10 on the supercharger 4 side.

  The second exhaust passage 29 is provided with a fifth metering valve 33, and the fifth metering valve 33 can adjust the supply amount of the air-fuel mixture to the second turbine 27. Therefore, when the amount of steam generated by the heat exchanger 5 is large and the amount of the mixture of steam and exhaust exceeds the amount required by the supercharger 4, only the excess amount is adjusted to the fifth amount. It can be supplied to the second turbine 27 via the valve 33. Thereby, it is possible to increase the power generation amount by the second generator 26 while maintaining the performance of the engine 2.

  Further, in the present embodiment, a second turbine 27 and a second generator 26 are additionally provided to the exhaust heat recovery apparatus 1 (FIG. 1) of the first embodiment, and the second exhaust is provided to the exhaust passage 10. It can be configured only by connecting the passage 29.

[Third Embodiment]
FIG. 3 is an overall configuration diagram showing an outline of the exhaust heat recovery apparatus 1 according to the third embodiment. In the present embodiment, a combustion device 30 for combusting the exhaust of the engine 2 is provided in the exhaust passage 10 of the engine 2 on the upstream side of the supercharger 4, and other configurations are the same as those of the second embodiment. It is the same.

  In the case of the present embodiment, the thermal energy of the exhaust can be increased by putting fuel into the combustion device 30 and burning the exhaust flowing through the exhaust passage 10 by the combustion device 30. When the heat demand in the heat medium utilization device 17 is more than the thermal energy of the exhaust of the engine 2 corresponding to the engine load corresponding to the power demand in the main generator 3, the fuel for the combustion device 30 is adjusted. Therefore, it is possible to flexibly cope with the demand balance between the power demand and the heat demand. Moreover, the supercharger 4 can be efficiently operated by increasing the temperature of the exhaust gas by the combustion device 30.

  By recombusting the exhaust of the engine 2 with the combustion device 30, particulate matter contained in the exhaust and unburned components such as CO and HC can also be removed by combustion, and further, by causing excessive fuel combustion, NOx can be reduced and removed in a reducing atmosphere. In the case where the two-stage combustion composed of the excessive fuel combustion and the excessive air combustion is employed, NOx, particulate matter, CO, and HC can be more effectively removed.

[Fourth Embodiment]
FIG. 4 is an overall configuration diagram showing an outline of the exhaust heat recovery apparatus 1 according to the fourth embodiment. In the present embodiment, an auxiliary generator (third generator) 32 is interlocked and connected to the turbine 7 of the supercharger 4 via a drive shaft 31, and the third generator 32 is connected by the output of the turbine 7 of the supercharger 4. It comes to drive. Other configurations are the same as those of the exhaust heat recovery apparatus 1 shown in the first embodiment.

  Since the mixture of exhaust gas and steam is supplied to the turbine 7 of the supercharger 4, the turbine work is increased as compared with the case where only the exhaust gas is supplied. Therefore, the third generator 32 is driven using the surplus power of the turbine 7 so that the amount of power generation can be increased.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed in design. For example, in each of the above embodiments, the steam generated by the heat exchanger 5 is supplied to the supercharger 4 and the heat medium using device 17, but the heat medium using device 17 is omitted, Steam may be supplied only to the supercharger 4.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used as an exhaust heat recovery apparatus that efficiently generates power while recovering engine exhaust heat energy in factories, buildings, houses, and the like.

1 is an overall configuration diagram showing an outline of an exhaust heat recovery apparatus 1 according to a first embodiment of the present invention. It is a whole block diagram which shows the outline of the waste heat recovery apparatus 1 which concerns on 2nd Embodiment of this invention. It is a whole block diagram which shows the outline of the waste heat recovery apparatus 1 which concerns on 3rd Embodiment of this invention. It is a whole block diagram which shows the outline of the waste heat recovery apparatus 1 which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste heat recovery apparatus 2 Internal combustion engine 3 Main generator 4 Supercharger 5 Heat exchanger 7 Turbine 10 Exhaust path 16 2nd steam path 26 2nd generator 27 2nd turbine 29 2nd exhaust path 30 Combustion apparatus 32 3rd Generator

Claims (8)

An internal combustion engine, a main generator driven by the output of the internal combustion engine, a turbocharger having a turbine to which exhaust gas of the internal combustion engine is supplied via an exhaust passage, and exhaust gas supplied through the turbine and supplied by the exhaust gas In an exhaust heat recovery apparatus comprising a heat exchanger that generates steam,
An exhaust heat recovery apparatus comprising a steam passage for circulating steam generated by a heat exchanger, and connecting the steam passage to an exhaust passage of an internal combustion engine upstream of a supercharger.   A second steam passage is provided for supplying steam generated by the heat exchanger to a heat medium utilization device that uses steam as heat energy, and the steam flow rate and the second steam passage are respectively adjusted to adjust the flow rate of the steam. The exhaust heat recovery apparatus according to claim 1, further comprising a quantity valve.   The exhaust heat recovery apparatus according to claim 1 or 2, wherein the supercharger is constituted by a variable capacity supercharger.   A second turbine and a second generator driven by the output of the second turbine, branching the exhaust passage of the internal combustion engine upstream of the supercharger and downstream of the connection position of the steam passage; The air-fuel mixture is supplied from one of the branched exhaust passages to the turbine of the supercharger, the air-fuel mixture is supplied from the other to the second turbine, and the supply amount of the air-fuel mixture to the second turbine is adjusted to the other exhaust passage. The exhaust heat recovery apparatus according to any one of claims 1 to 3, wherein a metering valve is provided.   The exhaust heat recovery apparatus according to any one of claims 1 to 3, further comprising a third generator driven by an output of a turbocharger turbine.   The exhaust heat recovery apparatus according to any one of claims 1 to 5, wherein the heat supply to the heat exchanger is heated by exchanging heat with the cooling water after cooling the internal combustion engine.   The exhaust heat recovery device according to any one of claims 1 to 6, wherein a combustion device for combusting exhaust gas of the internal combustion engine is provided in an exhaust passage of the internal combustion engine upstream of the supercharger. Exhaust heat recovery in which exhaust gas from the internal combustion engine that drives the main generator is supplied to the turbine of the turbocharger, and exhaust gas that has passed through the turbine is supplied to the heat exchanger, and steam is generated by the exhaust gas in the heat exchanger. In the method
Waste heat characterized by mixing the steam generated by the heat exchanger with the exhaust of the internal combustion engine upstream of the supercharger and supplying the steam / exhaust gas mixture to the turbine of the supercharger Collection method.

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