JP2015096703A - Heat recovery power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat recovery power generation system which can return cooling water at a temperature appropriate to reliability of an engine to the engine while performing heat recovery from the cooling water to the maximum.SOLUTION: A heat recovery power generation system 1 comprises: a cooling water circulation flow passage 16 through which cooling water W for cooling a water-cooling jacket 15 circulates; an exhaust gas flow passage 12 for exhausting exhaust gas G of a diesel engine 11; a heat medium circulation flow passage 21 where a heat medium M circulates through a closed loop formed by a low temperature side evaporator 5 performing heat exchange between the cooling water W and the heat medium M and evaporating the heat medium M, an expander 23 expanding the heat medium M evaporated by the low temperature side evaporator 5 and obtaining rotation driving force and a condenser 8 liquefying the heat medium M caused to be a low pressure vapor phase in the expander 23; a generator 25 receiving the rotation driving force obtained by the expander 23 and performing power generation; and a high/low heat exchange 7 performing heat exchange between the exhaust gas G flowing through the exhaust gas flow passage 12 and the cooling water W flowing through the cooling water circulation flow passage 16.

Description

  The present invention relates to a system for recovering exhaust heat from a water-cooled engine and generating electric power.

  In recent years, renewable energy has been introduced as an alternative to fossil fuels as a countermeasure against global warming, and solar power generation systems, wind power generation systems, and micro hydropower generation systems have attracted attention. Furthermore, heat is transferred from a low-temperature heat source that does not have enough heat to rotate the steam turbine to a heat cycle of a low-boiling-point heat medium (or working medium), and power generation using the heat medium is performed in this circulation cycle. Binary power generation systems are also attracting attention. As this low-temperature heat source, geothermal water used for geothermal power generation, factory exhaust heat, engine exhaust heat, and the like are used.

  As described in, for example, Patent Document 1 and Patent Document 2, a power generation system that uses engine exhaust heat as a heat source includes cooling water, exhaust gas, and air compressed by an engine supercharger. Is used as a heat source. That is, this power generation system is provided with an evaporator for exchanging heat between the cooling water and the heat medium and an evaporator for exchanging heat between the exhaust gas and the heat medium on the flow path of the heat medium. Evaporates the heat medium efficiently. In general, since the temperature of the cooling water is lower than that of the exhaust gas, the cooling water may be referred to as a low temperature side heat source and the exhaust gas may be referred to as a high temperature side heat source.

JP 2011-149332 A JP 2011-106302 A

In a power generation system that uses engine exhaust heat as a heat source, cooling water, which is a low-temperature heat source, flows through a circulation passage that passes through, for example, a water cooling jacket of the engine, and the cooling water that exchanges heat with the heat medium in the evaporator is water-cooled. Returned to the jacket. In this evaporator, it is desirable to recover more exhaust heat from the cooling water and contribute to the evaporation of the heat medium. However, on the other hand, it is necessary to avoid that the temperature of the cooling water that passes through the evaporator and is returned to the water cooling jacket is too low from the viewpoint of ensuring the reliability of the engine.
Therefore, the present invention has been made based on such a technical problem, and it is possible to return the cooling water having a temperature that can meet the reliability of the engine to the engine while maximizing the exhaust heat recovery from the cooling water. An object is to provide an exhaust heat recovery system.

The present invention made for this purpose is an exhaust heat recovery power generation system that generates power using exhaust heat from an engine, and includes a cooling water circulation passage through which cooling water for cooling the engine circulates, and an exhaust associated with the engine. A first evaporator for exchanging heat between the exhaust heat gas flow path through which the hot gas flows and the cooling water to vaporize the low boiling point heat medium, and the heat medium vaporized by the first evaporator is expanded and driven. A heat source circulation system in which the heat medium circulates in a closed circuit formed by a drive source for obtaining a force and a condenser for liquefying the low-temperature gas phase in the drive source; And a high / low heat exchanger for exchanging heat between the exhaust heat gas flowing through the exhaust heat gas flow path and the cooling water flowing through the cooling water circulation flow path.
In the high and low heat exchanger, the present invention performs heat exchange between the exhaust heat gas flowing through the exhaust heat gas flow path and the coolant flowing through the cooling water circulation flow path, thereby returning the temperature of the cooling water to the engine be able to. Therefore, the exhaust heat recovery power generation system of the present invention can ensure the reliability of the engine.
Here, as the exhaust heat gas in the present invention, at least one of engine combustion gas (exhaust gas) and air compressed by the engine supercharger can be used.

In the exhaust heat recovery power generation system of the present invention, it is preferable that the heat medium circulation flow path includes a second evaporator that performs heat exchange between the heat medium evaporated by the first evaporator and the exhaust heat gas.
By adding exhaust heat gas having a temperature higher than that of engine coolant as a heat source, the heat medium can be heated to a higher temperature while using exhaust heat from the engine without waste.

When the second evaporator is provided, the exhaust heat gas that is guided to the high and low heat exchanger and exchanges heat with the cooling water can be the one before the heat exchange with the second evaporator. However, it can also be the one after heat exchange in the second evaporator.
In the former case, the temperature of the exhaust heat gas is higher than that of the latter because heat is not exchanged in the second evaporator. Therefore, since the temperature of the cooling water can be quickly raised in the high and low heat exchanger, for example, when there is a possibility that the temperature of the cooling water is considerably lowered, the exhaust heat gas before passing through the second evaporator It is effective to use
In the latter case, the heat medium evaporated by the first evaporator is further heat-exchanged with the high-temperature exhaust heat gas in the second evaporator, so that more exhaust heat can be recovered from the engine to generate electric power. .

In the exhaust heat recovery power generation system of the present invention, it is possible to increase the value of the exhaust heat recovery system by providing a use destination that uses the exhaust heat gas flowing from the exhaust heat gas flow path.
As this usage destination, a steam boiler is used, and exhaust heat can be recovered from exhaust heat gas to obtain steam and hot water. Moreover, the exhaust heat which came out of the steam generation boiler can also be utilized as a heat source of a heat pump.

  According to the exhaust heat recovery power generation system of the present invention, heat exchange is performed between the exhaust heat gas flowing through the exhaust heat gas passage, typically between the exhaust gas and the cooling water flowing through the coolant circulation passage, in the high and low heat exchanger. By doing so, it is possible to return to the water cooling jacket after raising the temperature of the cooling water. Therefore, the exhaust heat recovery power generation system of the present invention can ensure the reliability of the engine.

It is a figure which shows schematic structure of the waste heat recovery electric power generation system in 1st Embodiment. The difference in the flow of the high temperature side heat source in the exhaust heat recovery power generation system of FIG. 1 is shown, (a) shows the case where exhaust gas is not used for heating the cooling water, and (b) shows the case where it is used. It is a figure which shows schematic structure of the waste heat recovery electric power generation system in 2nd Embodiment. It is a figure which shows schematic structure of the waste heat recovery electric power generation system in 3rd Embodiment. It is a figure which shows schematic structure of the waste heat recovery electric power generation system in 4th Embodiment.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
The exhaust heat recovery power generation system 1 according to the present embodiment includes three elements of the engine equipment 10, the heat medium circuit 20, and the condensate equipment 30, and the temperature ranges provided from the engine equipment 10 are different. The exhaust heat is recovered from the two heat sources, and power is generated by the generator 25 provided in the heat medium circuit 20. This embodiment demonstrates the example which uses the exhaust gas which is a combustion gas of an engine as exhaust heat gas.

The engine equipment 10 includes a water-cooled diesel engine 11 as a main element. As the diesel engine 11, various internal combustion engines such as a power generation engine and a marine main engine can be applied.
An exhaust gas passage 12 is connected to the diesel engine 11, and the exhaust gas G passes through the exhaust gas passage 12 and is discharged out of the system from its end. The temperature of the exhaust gas G discharged from the diesel engine 11 is about 400 ° C., for example. The exhaust gas passage 12 is incorporated in the high temperature side evaporator 6 in the middle of reaching the end, and the exhaust gas G flowing through the exhaust gas passage 12 exchanges heat with the heat medium circulating in the heat medium circuit 20. .
In the exhaust gas passage 12, a branch passage 13 a is branched downstream from the high temperature side evaporator 6. The exhaust gas G that has flowed through the exhaust gas flow path 12 can also flow from the branch portion and flow through the branch flow path 13a. However, an exhaust gas control valve V1 is provided in the branch flow path 13a, and the exhaust gas G flows through the branch flow path 13a only when the exhaust gas control valve V1 is open. The branch flow path 13a is incorporated in the high and low heat exchanger 7 downstream of the position where the exhaust gas control valve V1 is provided, and the exhaust gas G passing through the branch flow path 13a is separated from the cooling water W in the high and low heat exchanger 7. They exchange heat with each other.
In the present embodiment, upstream and downstream are specified by the direction in which the fluid flows.

The engine equipment 10 includes a cooling water circulation passage 16 that passes through the inside of a water cooling jacket 15 of the diesel engine 11. The cooling water W provided for cooling the diesel engine 11 in the water cooling jacket 15 circulates through the cooling water circulation passage 16 by the operation of the circulation pump P1 provided in the cooling water circulation passage 16. The temperature of the cooling water W provided for cooling is, for example, about 100 ° C.
The cooling water circulation channel 16 is incorporated in the low temperature side evaporator 5 downstream of the circulation pump P1, and the cooling water W passing through the cooling water circulation channel 16 exchanges heat with the heat medium circulating in the heat medium circuit 20. Is done.
The cooling water circulation passage 16 is incorporated in the high and low heat exchanger 7 downstream of the low temperature side evaporator 5, and the cooling water W passing through the cooling water circulation passage 16 mutually communicates with the exhaust gas G in the high and low heat exchanger 7. Heat exchanged.

Next, the configuration of the heat medium circuit 20 will be described.
The heat medium circuit 20 includes a heat medium circulation passage 21 that forms a closed circuit, and a circulation pump P2 for circulating the heat medium M is provided. By the circulation pump P2, the heat medium M is circulated so as to exchange heat in the high temperature side evaporator 6, the low temperature side evaporator 5, and the condenser 8.
A heat medium M having a low boiling point such as pentane (boiling point: 36.07 ° C.), chlorofluorocarbon R245fa (boiling point: 58.80 ° C.), isobutane (boiling point: −12 ° C.) circulates in the heat medium circulation passage 21. Is done.

The heat medium circulation passage 21 is incorporated in this order into the low temperature side evaporator 5 and the high temperature side evaporator 6 downstream of the circulation pump P2. Therefore, the heat medium M flowing through the heat medium circulation flow path 21 is mutually heat-exchanged with the cooling water W passing through the cooling water circulation flow path 16 in the low temperature side evaporator 5, and then the exhaust gas flow path in the high temperature side evaporator 6. Heat exchange with the exhaust gas G flowing through the cylinder 12 is performed. The heat medium M that has passed through the low-temperature side evaporator 5 and the high-temperature side evaporator 6 in order and exchanged heat flows into the downstream as steam.
The heat medium circulation flow path 21 includes an expander 23 on which the turbine is rotationally driven by the expansion force of steam downstream of the high temperature side evaporator 6. A power generator 25 is connected to the expander 23 so that power can be transmitted. When steam flows into the expander 23, power is generated by the power generator 25 and supplied to the outside via a power line (not shown). The
The heat medium circulation channel 21 is incorporated in the condenser 8 downstream of the expander 23, and the heat medium M flowing through the heat medium circulation channel 21 is cooled by circulating through the condensate facility 30 in the condenser 8. Heat is exchanged with water W to be condensed and liquefied.

Next, the condensate facility 30 includes a cooling water circulation passage 31 through which the cooling water H circulates, and a cooling tower 33 provided in the cooling water circulation passage 31.
In the process in which the cooling water H circulates in the cooling water circulation flow path 31, heat is exchanged with the heat medium M of the heat medium circuit 20 in the condenser 8, and then the cooling water 33 is cooled in the cooling tower 33. The medium M is condensed and liquefied.

Next, the operation of the exhaust heat recovery power generation system 1 having the above-described configuration will be described with reference to FIGS. 2 (a) and 2 (b). In FIG. 2, the exhaust gas before passing through the high temperature side evaporator 6 is distinguished from G1, and the exhaust gas after passing through is distinguished from G2, and the cooling water before passing through the low temperature side evaporator 5 is passed through W1. The subsequent cooling water is distinguished from W2.
The cooling water W flowing through the cooling water circulation passage 16 of the engine equipment 10 is guided to the low temperature side evaporator 5. In the low temperature side evaporator 5, the heat medium M circulating in the heat medium circuit 20 and the cooling water W are heat-exchanged, and the heat medium M is evaporated. In addition, if the temperature of the cooling water W1 led to the low temperature side evaporator 5 is about 100 ° C., the low boiling point heat medium M can be evaporated.
The heat medium M that has passed through the low temperature side evaporator 5 is then guided to the high temperature side evaporator 6. Since the exhaust gas G1 having a temperature higher than that of the cooling water W1 is guided to the high temperature side evaporator 6, the heat medium M recovers the exhaust heat of the exhaust gas G1 in the high temperature side evaporator 6 and becomes an even higher temperature. 23 to be used for power generation by the generator 25.
The heat medium M that has worked in the expander 23 is guided to the condenser 8 and condensed and liquefied by the cooling water H that circulates in the circulation flow path 31 of the condensate facility 30.
The heat medium circuit 20 generates power with the generator 25 while repeating the cycle described above by the heat medium M.

  In the process in which the heat medium M repeats the above cycle, in the engine equipment 10, the cooling water W <b> 2 obtained by evaporating and evaporating the heat medium M in the low temperature side evaporator 5 returns the cooling water circulation channel 16 toward the water cooling jacket 15. In order to ensure the reliability of the diesel engine 11, the cooling water W <b> 2 must avoid the temperature becoming too low. As an example, it is desirable that the cooling water W2 returning to the water cooling jacket 15 has a temperature of 85 ° C. or higher. On the other hand, in the low temperature side evaporator 5, it is desired in terms of the efficiency of exhaust heat recovery to increase the exhaust heat recovered from the cooling water W1. Therefore, in the present embodiment, the high and low heat exchanger 7 is provided in order to meet the conflicting requirements.

  In the high-low heat exchanger 7, the cooling water W <b> 2 that has passed through the low-temperature side evaporator 5 and the exhaust gas G <b> 2 that has passed through the high-temperature side evaporator 6 are mutually heat-exchanged. While the temperature of the cooling water W2 is less than 100 ° C., the temperature of the exhaust gas G2 is about 150 ° C. to 200 ° C., which easily exceeds 100 ° C. Therefore, when the cooling water W2 passes through the high and low heat exchanger 7 It can be returned to the water cooling jacket 15 at a temperature of 85 ° C. or higher, which is higher than before. Therefore, according to the present embodiment, even when exhaust heat recovery from the cooling water W1 is performed to the maximum in the low temperature side evaporator 5, the cooling water W2 is recovered to a temperature that can ensure the reliability of the diesel engine 11. Can be returned to the water-cooled jacket 15.

In the present embodiment, the heat exchange between the exhaust gas G1 and the cooling water W2 by the high / low heat exchanger 7 can always be performed, but can also be selectively performed by controlling the opening and closing of the exhaust gas control valve V1. For example, a temperature sensor 17 that detects the temperature of the cooling water W <b> 2 is provided in the cooling water circulation passage 16 between the high / low heat exchanger 7 and the water cooling jacket 15. Normally, the exhaust gas control valve V1 is closed as shown in FIG. 2 (a). When the temperature detected by the temperature sensor 17 is lower than 85 ° C., for example, the detection result is received and FIG. ), The exhaust gas control valve V1 is opened, and the exhaust gas G2 that has passed through the high-temperature side evaporator 6 is guided to the high-low heat exchanger 7, thereby returning the cooling water W2 to 85 ° C. or higher. If the detection result of the temperature sensor 17 is 85 ° C. or higher, the exhaust gas control valve V1 is kept closed.
As described above, if the temperature of the cooling water W2 returned to the water cooling jacket 15 is detected and the exhaust gas G2 is guided to the high-low heat exchanger 7 based on the result, it is necessary to ensure the reliability of the diesel engine 11. The temperature of the cooling water W2 can be obtained more reliably.

As described above, the exhaust heat recovery power generation system 1 of the present embodiment has the following operations and effects.
The engine equipment 10 connects the high temperature side evaporator 6 and the low temperature side evaporator 5 in series, and exhausts heat from each of the high temperature heat source (exhaust gas G) and the low temperature heat source (cooling water W) discharged from the diesel engine 11. Since it collect | recovers, it can generate electric power using the exhaust heat obtained from the diesel engine 11 efficiently.

Next, since the cooling water W2 heated using the exhaust gas G2 returns to the water cooling jacket 15, the reliability of the diesel engine 11 can be ensured.
At this time, if the exhaust gas G2 is guided to the high-low heat exchanger 7 based on the temperature of the cooling water W2 by controlling the opening and closing of the exhaust gas control valve V1, the temperature is required to ensure the reliability of the diesel engine 11. The cooling water W2 can be maintained more reliably.

Although the preferred embodiments of the present invention have been described above, several modifications will be described.
First, the exhaust heat recovery power generation system 2 shown in FIG. 3 will be described.
The exhaust heat recovery power generation system 2 is different from the exhaust heat recovery power generation system 1 in that the branch flow path 13b branches, and the branch flow path 13b is branched from the exhaust gas flow path 12 upstream of the high temperature side evaporator 6. ing. Since the other configuration of the exhaust heat recovery power generation system 2 is the same as that of the exhaust heat recovery power generation system 1, the same reference numerals as those in FIG.

The exhaust heat recovery power generation system 2 has the following actions and effects in addition to the actions and effects described above.
The exhaust heat recovery power generation system 2 guides the exhaust gas G1 before passing through the high temperature side evaporator 6 to the high and low heat exchanger 7 to exchange heat with the cooling water W2. Since the exhaust gas G1 is not heat exchanged in the high temperature side evaporator 6, the temperature is higher than the exhaust gas G2, for example, about 400 ° C. Therefore, since the temperature of the cooling water W2 can be quickly raised in the high / low heat exchanger 7, for example, when there is a possibility that the temperature of the cooling water W2 becomes considerably low, before passing through the high temperature side evaporator 6 The exhaust heat recovery power generation system 2 using the exhaust gas G1 is effective.

Next, the exhaust heat recovery power generation system 3 shown in FIG. 4 will be described.
This exhaust heat recovery power generation system 3 includes a branch flow path 13 c branched from the exhaust gas flow path 12 in addition to the configuration of the exhaust heat recovery power generation system 2. This branch flow path 13c is provided in order to use the exhaust heat from the exhaust gas G1 for purposes other than heat exchange with the heat medium M and heat exchange with the cooling water W2. A steam boiler 9 is listed as equipment that uses the exhaust heat of the exhaust gas G1. By providing the steam boiler 9, heat can be recovered from the exhaust gas G <b> 1 and steam and hot water can be obtained. Therefore, the exhaust heat recovery power generation system 3 is more effective than the exhaust heat recovery power generation system 1. be able to.

The exhaust heat recovery power generation system 3 is provided with an exhaust gas control valve V2 in the exhaust gas flow path 12 and an exhaust gas control valve V3 in the branch flow path 13c, and adjusts opening and closing together with the exhaust gas control valve V1, thereby using the exhaust gas G1. The object can be selected as follows. For example, when V1 and V2 are closed and V3 is opened, the exhaust gas G1 is used for generating steam and hot water in the steam boiler 9. When V2 is closed and V1 and V3 are opened, the exhaust gas G is used for heat exchange with the cooling water W2 in the high-low heat exchanger 7 and is also used for generating steam and hot water in the steam boiler 9. . Further, when V3 is closed and V1 and V2 are opened, the exhaust gas G1 is used for heat exchange with the heat medium M in the high temperature side evaporator 6 and heat exchange with the cooling water W2 in the high and low heat exchanger 7. To be served.
Note that the detection result of the temperature sensor 17 can be reflected in the opening and closing of the exhaust gas control valve V1.

  The steam boiler 9 applied to the exhaust heat recovery power generation system 3 can be applied to the engine equipment 10 shown in FIG. 1, as shown in FIG. The exhaust heat recovery power generation system 4 can also enjoy the functions and effects described above.

Unless departing from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.
For example, although the above-described embodiment has described an example in which the exhaust gas G of the engine is used as the high-temperature heat source (exhaust heat gas), the present invention is not limited to this. For example, air compressed by a supercharger provided in the engine can be used as a high-temperature heat source.
Moreover, although embodiment mentioned above uses the cooling tower 33 as the condensate equipment 30, if the heat medium M which passed the expander 23 can be condensed and liquefied, the means will not ask | require. For example, when the diesel engine 11 is used as a main engine for marine propulsion, seawater can be taken in and the heat medium M can be condensed.

1, 2, 3, 4 Waste heat recovery power generation system 5 Low temperature side evaporator 6 High temperature side evaporator 7 High and low heat exchanger 8 Condenser 9 Steam boiler 10 Engine equipment 11 Diesel engine 12 Exhaust gas passages 13a, 13b, 13c Branch Flow path 15 Water cooling jacket 16 Cooling water circulation path 17 Temperature sensor 20 Heat medium circuit 21 Heat medium circulation path 23 Inflator 25 Generator 30 Condensation equipment 31 Cooling water circulation path 33 Cooling towers V1, V2, V3 Exhaust gas control valve P1 , P2 Circulation pump M Heat medium G, G1, G2 Exhaust gas W, W1, W2 Cooling water

Claims (5)

An exhaust heat recovery power generation system that generates power using exhaust heat from an engine,
A cooling water circulation passage through which cooling water for cooling the engine circulates;
An exhaust gas flow path through which exhaust gas related to the engine flows;
A first evaporator that exchanges heat with the cooling water to vaporize a low boiling point heat medium, a drive source that obtains a driving force by expanding the heat medium vaporized in the first evaporator, and A heat medium circulation system in which the heat medium circulates in a closed circuit formed by a condenser that liquefies the heat medium in a low-pressure gas phase in a drive source;
A generator for generating power by receiving the driving force of the driving source;
A high and low heat exchanger for exchanging heat between the exhaust heat gas flowing through the exhaust heat gas flow path and the cooling water flowing through the cooling water circulation flow path;
An exhaust heat recovery power generation system comprising: The heat medium circulation channel is
A second evaporator that exchanges heat between the heat medium evaporated by the first evaporator and the exhaust heat gas;
The exhaust heat recovery power generation system according to claim 1. The high and low heat exchanger is
The exhaust heat gas after being heat-exchanged by the second evaporator is guided to exchange heat with the cooling water;
The exhaust heat recovery power generation system according to claim 2. The high and low heat exchanger is
The exhaust heat gas before being heat exchanged in the second evaporator is guided to exchange heat with the cooling water,
The exhaust heat recovery power generation system according to claim 2. Provided with a use destination that uses the exhaust heat gas flowing from the exhaust heat gas flow path,
The exhaust heat recovery power generation system according to any one of claims 1 to 4.

Images