Patent Application
20150322821
1. Field of the Invention
The present invention relates to a thermal energy recovery device that recovers exhaust heat and a start-up method of a thermal energy recovery device.
2. Description of the Related Art
Conventionally, there is a known device that recovers thermal energy generated in various facilities. As one example of this device, JP 2012-202374 describes a power generation device including a circulation flow passage in which a heater that evaporates a working medium by a heat medium, an expander that expands steam of the working medium, a condenser that condenses the steam of the working medium, and a pump that circulates the working medium are connected in series. In this power generation device, the expander includes a screw rotor, and the screw rotor is rotated by the steam of the working medium expanded in the expander. This screw rotor is connected to a power generator, and the power generator converts rotation of the screw rotor into electric power.
The power generation device of the above related art further includes a pressure sensor that detects pressure of the working medium on the inlet side of the pump, and a derivation means that detects saturated steam pressure of the working medium from a temperature of the working medium on the inlet side of the pump. This power generation device suppresses generation of cavitation in the pump by adjusting a circulation amount of the working medium in accordance with a pressure difference between the pressure detected in the pressure sensor and the saturated steam pressure derived in the derivation means.
In a case where the condenser and the pump are positioned on the upper side of the heater, the working medium in a liquid phase is accumulated in a pipe part between the heater and the pump at the time of stop of the pump, so that an amount of the working medium in a liquid phase existing on the upstream of the pump becomes short. When the pump is started up in such a state, the cavitation is generated in the pump. In the method of the above related art, the generation of the cavitation at the time of start-up of the pump is not easily avoided.
The present invention is achieved from the above viewpoint and an object thereof is to ensure an amount of a working medium in a liquid phase in a reservoir unit positioned on the upstream of a pump in a thermal energy recovery device.
A thermal energy recovery device according to the present invention includes a heater that heats a working medium by heat of a heat medium, an expander into which the working medium flowing out from the heater flows, a power recovery machine connected to the expander, a condenser positioned on the upper side of the heater, the condenser condensing the working medium flowing out from the expander by a cooling medium, a reservoir unit positioned on the upper side of the heater, the reservoir unit reserving the working medium condensed in the condenser, a pump positioned on the upper side of the heater, the pump feeding the working medium flowing out from the reservoir unit to the heater, a circulation flow passage of the working medium that connects the heater, the expander, the condenser, the reservoir unit, and the pump in the above order, and a pump control unit that controls drive of the pump, wherein the pump control unit drives the pump after the heat medium is supplied to the heater, and the cooling medium is supplied to the condenser so that the working medium is reserved in the reservoir unit.
At the time of stop of the thermal energy recovery device, supply of the heat medium to the heater and supply of the cooling medium to the condenser are stopped in general. Therefore, in a structure where the heater is arranged on the lower side of the reservoir unit, the working medium flowing out from the reservoir unit passes through the pump and is retained on the upstream side of the heater. As a result, the working medium in a liquid phase in the reservoir unit becomes short and there is a fear that cavitation is generated at the time of driving the pump.
Meanwhile, in the thermal energy recovery device according to the present invention, before the drive of the pump, that is, before start of operation of the thermal energy recovery device, the heat medium is supplied to the heater and the cooling medium is supplied to the condenser, so that a sufficient amount of the working medium is reserved in the reservoir unit. Thereby, the cavitation at the time of driving the pump can be prevented.
Preferably, the reservoir unit has a liquid level sensor that detects height of a liquid level of the working medium reserved in the reservoir unit, and the pump control unit drives the pump in a case where an amount of the working medium reserved in the reservoir unit becomes a predetermined amount or more based on a detected value of the liquid level sensor.
In the above thermal energy recovery device, the pump can be driven in a state where the amount of the working medium in the reservoir unit is surely ensured.
The pump control unit may drive the pump when a predetermined time elapses after supply of the cooling medium to the condenser is started.
In the above thermal energy recovery device, since there is no need for providing a liquid level sensor, cost can be reduced.
Preferably, a shutoff valve provided in a first flow passage of the circulation flow passage connecting the heater and the expander, a bypass flow passage that connects a second flow passage of the circulation flow passage connecting the expander and the condenser, and a part of the first flow passage on the upstream side of the shutoff valve, a bypass valve provided in the bypass flow passage, and a valve control unit that controls opening/closing of the shutoff valve and the bypass valve are provided, and the valve control unit brings the shutoff valve into a closed state and brings the bypass valve into an opened state before the drive of the pump.
In the above thermal energy recovery device, the bypass flow passage that connects the first flow passage and the second flow passage striding across the expander is provided, and before starting the drive of the pump, the working medium evaporated in the heater flows into the condenser through the first flow passage, the bypass flow passage, and the second flow passage. That is, in the above thermal energy recovery device, before starting the drive of the pump, the working medium evaporated in the heater flows into the condenser without passing through the expander. Therefore, the working medium evaporated in the heater can efficiently flow into the condenser.
Preferably, a flow passage of the circulation flow passage connecting the pump and the heater includes a bent portion connected to the pump and bent to be convex upward.
In the above thermal energy recovery device, the working medium is suppressed from flowing from the reservoir unit to the heater before the drive of the pump, so that the working medium in a liquid phase can be more promptly stored in the reservoir unit.
Preferably, the condenser and the reservoir unit are different members from each other.
In the above thermal energy recovery device, the working medium in a liquid phase is suppressed from being reserved in the condenser. Thus, pressure on the inflow side of the working medium in the condenser can be reduced, and thereby energy can be efficiently recovered in the power recovery machine.
Preferably, an on-off valve is provided in a flow passage of the circulation flow passage connecting the pump and the heater, and after the heat medium is supplied to the heater and the cooling medium is supplied to the condenser, so that the working medium is reserved in the reservoir unit, the on-off valve is opened and the pump is driven.
In the above thermal energy recovery device, by closing the on-off valve at the time of stop of the drive of the pump, the working medium is prevented from flowing to the heater before the drive of the pump, so that the working medium in a liquid phase can be more promptly stored in the reservoir unit.
Preferably, the heat medium includes at least one of supercharged air supplied to an engine, an exhaust gas discharged from the engine, and steam generated in an economizer that recovers heat from the exhaust gas.
The above thermal energy recovery device can be mounted for example on a moving body such as a vessel and a vehicle in which vibration is easily generated, and can recover thermal energy generated around an engine of the moving body.
The present invention is a start-up method of a thermal energy recovery device including a heater that heats a working medium by a heat medium, an expander into which the working medium flowing out from the heater flows, a power recovery machine connected to the expander, a condenser positioned on the upper side of the heater, the condenser condensing the working medium flowing out from the expander by a cooling medium, a reservoir unit positioned on the upper side of the heater, the reservoir unit reserving the working medium condensed in the condenser, and a pump positioned on the upper side of the heater, the pump feeding the working medium flowing out from the reservoir unit to the heater, wherein the heater, the expander, the condenser, the reservoir unit, and the pump are connected in the above order, the start-up method including a first step of supplying the heat medium to the heater, a second step of supplying the cooling medium to the condenser, so that the working medium is reserved in the reservoir unit, and a third step of driving the pump after the first step and the second step.
In the above start-up method of the thermal energy recovery device, the pump is driven after the heat medium is supplied to the heater and the cooling medium is supplied to the condenser, so that a sufficient amount of the working medium is reserved in the reservoir unit before the drive of the pump. Thus, the cavitation at the time of driving the pump can be prevented.
According to the present invention, the thermal energy recovery device capable of ensuring the amount of the working medium in a liquid phase in the reservoir unit positioned on the upstream of the pump, and the start-up method of the thermal energy recovery device are provided.
Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Note that, in the figures to be cited below, for convenience of the description, necessary major members are simplified for describing a thermal energy recovery device according to the present embodiment. Therefore, the thermal energy recovery device according to the present embodiment can include am arbitrary constituent member which is not shown in the figures to be cited in the present description.
As shown in
In the present embodiment, the thermal energy recovery device X1 is mounted on a vessel and used for recovering exhaust heat of a supercharger engine 100. It should be noted that the thermal energy recovery device X1 may be mounted for example on a vehicle or may be applied to various facilities in a factory or the like.
The supercharger engine 100 has a supercharger, an engine 130, scavenging lines 140, 150, and an exhaust line 160. The supercharger has a compressor 110, and a turbine 120 connected to the compressor 110. The supercharged air compressed in the compressor 110 is supplied to the engine 130 through the scavenging lines 140, 150. An exhaust gas from the engine 130 is fed to the turbine 120 through the exhaust line 160. The turbine 120 is driven by expansion energy of the exhaust gas, and the compressor 110 is driven by drive force of this turbine 120. In the thermal energy recovery device X1 according to the present embodiment, the heater 2 is positioned between the scavenging line 140 and the scavenging line 150, so that the exhaust heat of the supercharged air moved from the scavenging line 140 to the scavenging line 150 can be recovered.
The heater 2 has a heat medium flow passage 21 and a working medium flow passage 22. The heat medium flow passage 21 is a flow passage through which the supercharged air from the compressor 110 flows. One end of the heat medium flow passage is connected to the scavenging line 140 and the other end is connected to the scavenging line 150. The working medium flow passage 22 is a flow passage through which a working medium flows. The heater 2 evaporates the working medium by heat exchange between the supercharged air flowing through the heat medium flow passage 21 and the working medium in a liquid phase flowing through the working medium flow passage 22.
The expander 3 is positioned on the downstream side of the heater 2 in the circulation flow passage 8. The expander 3 and the working medium flow passage 22 of the heater 2 are connected to each other via the first flow passage 81 of the circulation flow passage 8. The working medium evaporated in the heater 2 flows into the expander 3 through the first flow passage 81.
In the present embodiment, a volumetric screw expander having a rotor to be driven and rotated by expansion energy of a working medium in a gas phase is used as the expander 3. It should be noted that the expander 3 is not limited to the volumetric screw expander but a centrifugal expander, scrolling expander, or the like may be used.
The power recovery machine 4 is connected to the expander 3. In the present embodiment, a power generator is used as the power recovery machine 4. This power recovery machine 4 has a rotation shaft connected to one of a pair of screw rotors of the expander 3. The power recovery machine 4 generates electric power by rotating the rotation shaft in accordance with rotation of the screw rotor. It should be noted that in addition to the power generator, a compressor or the like may be used as the power recovery machine 4.
The condenser 5 is positioned on the downstream side of the expander 3 in the circulation flow passage 8. The condenser 5 is arranged on the upper side of the heater 2 in the gravitational direction. The condenser 5 has a cooling water flow passage 51 and a working medium flow passage 52. The cooling water flow passage 51 is a flow passage through which cooling water flows. The working medium flow passage 52 is a flow passage through which the working medium flows. The working medium flow passage 52 is connected to the expander 3 via the second flow passage 82 of the circulation flow passage 8. The working medium in a gas phase flowing out from the expander 3 flows into the working medium flow passage 52 of the condenser 5 through the second flow passage 82. By heat exchange between the working medium in a gas phase flowing through the working medium flow passage 52 and the cooling water flowing through the cooling water flow passage 51, the working medium is condensed. It should be noted that although for example seawater is used as the cooling water flowing through the cooling water flow passage 51, the present invention is not limited to this. The cooling water may be any cooling medium capable of condensing the working medium in a gas phase flowing through the working medium flow passage 52.
The reservoir unit 6 is positioned on the downstream side of the condenser 5 on the third flow passage 83 of the circulation flow passage 8. The reservoir unit 6 is positioned on the lower side of the condenser 5 and arranged on the upper side of the heater 2 in the gravitational direction. The working medium flow passage 52 of the condenser 5 and the pump 7 are connected to each other via the third flow passage 83, and the reservoir unit 6 is provided in the middle of the third flow passage 83. The working medium condensed in the condenser 5 flows into the third flow passage 83 and is reserved in the reservoir unit 6 provided in the middle of the third flow passage 83.
The pump 7 is positioned on the downstream side of the reservoir unit 6 in the circulation flow passage 8. The pump 7 is positioned on the lower side of the condenser 5 and the reservoir unit 6 and positioned on the upper side of the heater 2 in the gravitational direction. The pump 7 and the working medium flow passage 22 of the heater 2 are connected to each other via the fourth flow passage 84 of the circulation flow passage 8. The working medium in a liquid phase reserved in the reservoir unit 6 flows into the pump 7 and is fed to the working medium flow passage 22 of the heater 2 at predetermined pressure by the pump 7. A centrifugal pump including an impeller as a rotor, a gear pump including a rotor of a pair of gears, or the like is used as the pump 7.
The shutoff valve 81a is provided in the first flow passage 81 of the circulation flow passage. The bypass flow passage 11 is a flow passage that connects the first flow passage 81 and the second flow passage 82 while going around the expander 3. One end of the bypass flow passage 11 is connected to a part of the first flow passage 81 on the upstream side of the shutoff valve 81a. The other end of the bypass flow passage 11 is connected to a predetermined point of the second flow passage 82. Thereby, the working medium evaporated in the heater 2 can flow into the condenser 5 through the expander 3 and can also flow into the condenser 5 not through the expander 3 but through the bypass flow passage 11.
The control unit 9 plays a role in controlling start-up in addition to control during drive of the thermal energy recovery device X1, and functionally has a pump control unit 91, a valve control unit 92, and a determination unit 93.
The determination unit 93 receives a signal from a liquid level sensor 61 provided in the reservoir unit 6 and determines whether or not the working medium in a liquid phase is sufficiently reserved in the reservoir unit 6.
The pump control unit 91 performs control of starting drive of the pump 7 in a case of receiving a determination signal from the determination unit 93.
The valve control unit 92 performs control of opening/closing a bypass valve 11a, control of opening/closing the shutoff valve 81a, and control of opening/closing an on/off valve 51a provided on the upstream of the cooling water flow passage 51 of the condenser 5.
In the control unit 9, functions of the pump control unit 91, the valve control unit 92, and the determination unit 93 are realized for example by executing programs stored in a memory by a CPU.
At the time of stop of the thermal energy recovery device X1, that is, at the time of stop of the pump 7, since the heater 2 is positioned on the lower side of the reservoir unit 6 in the gravitational direction, the working medium in a liquid phase is accumulated in the fourth flow passage 84, that is, in the part of the circulation flow passage 8 between the pump 7 and the heater 2. It should be noted that the working medium in a liquid phase accumulated in the fourth flow passage 84 includes a working medium leaking out from the reservoir unit 6 to the fourth flow passage 84 via a gap between members in the pump 7. As a result, the working medium in a liquid phase in the reservoir unit 6 becomes short. If the pump 7 is started up in a state where the working medium in a liquid phase is in short, the working medium in a gas phase intrudes into the pump 7 and there is a fear that cavitation is generated.
Thus, at the time of start-up of the thermal energy recovery device X1, the following control is performed.
Firstly, the control unit 9 repeatedly confirms whether or not the heat medium is supplied to the heat medium flow passage 21 of the heater 2 (Step Op1). This supply/non-supply of the heat medium is determined based on the rotation number of the engine 130, a temperature of the scavenging line 140, pressure of the scavenging line 140, or the like. The supply/non-supply of the heat medium may be determined based on pressure or a temperature of the working medium on the downstream side of the heater 2.
When the heat medium is supplied to the heater 2 (Yes in Step Op1), the valve control unit 92 performs the control of opening the bypass valve 11a (Step Op2) and closing the shutoff valve 81a (Step Op3). It should be noted that the shutoff valve 81a may be closed in advance. Further, the valve control unit 92 opens the on-off valve 51a, and the cooling water is supplied to the cooling water flow passage 51 (Step Op4). The working medium in a liquid phase accumulated in the fourth flow passage 84 is heated in the heater 2, and the evaporated working medium flows into the working medium flow passage 52 of the condenser 5 through the first flow passage 81, the bypass flow passage 11, and the second flow passage 82. The working medium flowing into the working medium flow passage 52 is cooled and condensed by the cooling water flowing through the cooling water flow passage 51. With such a procedure (Step Op1 to Step Op4), the working medium in a liquid phase is fed from the condenser 5 to the reservoir unit 6 positioned on the downstream of the condenser 5 before driving the pump 7.
The liquid level sensor 61 detects height of a liquid level of the working medium in a liquid phase in the reservoir unit 6 (Step Op5), and the determination unit 93 determines whether or not a sufficient amount of the working medium in a liquid phase is reserved in the reservoir unit 6 based on a detected value of the liquid level sensor 61 (Step Op6). In a case where the amount of the working medium in a liquid phase in the reservoir unit 6 is less than a predetermined amount, the height of the liquid level of the working medium is continuously or intermittently detected until the amount becomes the predetermined amount or more. The determination unit 93 determines that the predetermined amount or more of the working medium in a liquid phase is reserved in the reservoir unit 6 (Yes in Step Op6), a determination signal indicating that the reserving is completed is sent to the pump control unit 91 and the valve control unit 92.
The valve control unit 92 receiving the determination signal from the determination unit 93 performs the control of opening the shutoff valve 81a (Step Op7) and closing the bypass valve 11a (Step Op8), so that a flow passage running from the heater 2 to the condenser 5 through the expander 3 is opened. The pump control unit 91 receiving the determination signal from the determination unit 93 performs the control of starting the drive of the pump 7 (Step Op9).
When the start-up control described above is performed, the pump 7 suctions the working medium in a liquid phase from the reservoir unit 6 and feeds the working medium to the heater 2. The working medium evaporated in the heater 2 flows into the expander 3, and the expander 3 is driven by the working medium. The power generator 4 is driven by drive force of the expander 3. The working medium passing through the expander 3 is condensed in the condenser 5 and returned to the reservoir unit 6.
The structure and the actions at the time of the start-up of the thermal energy recovery device X1 according to the present embodiment are described above. At the time of the start-up of the thermal energy recovery device X1, after the heat medium is supplied to the heat medium flow passage 21 of the heater 2 and the cooling water is supplied to the cooling water flow passage 51 of the condenser 5, the pump 7 is driven. Therefore, before the drive of the pump 7, the working medium in a liquid phase accumulated in the fourth flow passage 84 can be returned to the reservoir unit 6, so that the working medium in a liquid phase is ensured in the reservoir unit 6. As a result, the working medium in a gas phase is prevented from intruding into the pump 7, so that generation of the cavitation is prevented.
In a case where the thermal energy recovery device X1 is mounted on a moving body such as a vessel, the liquid level in the reservoir unit 6 sometimes ruffles due to vibration of the moving body. However, since a sufficient amount of the working medium in a liquid phase is ensured in the reservoir unit 6, the working medium in a gas phase is prevented from intruding into the pump 7.
In the thermal energy recovery device X1 according to the present embodiment, the liquid level sensor 61 provided in the reservoir unit 6 detects the height of the liquid level of the working medium in a liquid phase, so that the working medium in a liquid phase can be surely ensured in the reservoir unit 6.
Further, before the drive of the pump 7, in accordance with the supply of the cooling water to the condenser 5, the shutoff valve 81a is closed and the bypass valve 11a is opened. By the working medium evaporated in the heater 2 flowing into the condenser 5 through the bypass valve 11a, the working medium can be efficiently condensed.
Since the condenser 5 and the reservoir unit 6 are difference members from each other, the liquefied working medium can be promptly discharged to an exterior of the condenser 5. Thereby, pressure on the inflow side of the working medium flow passage 52 of the condenser 5 can be reduced, so that power generation efficiency can be improved.
In the start-up control of the thermal energy recovery device X1, the pump drive control (Step Op9) of starting the drive of the pump 7 and the reserving control (Steps Op1 to Op8) for reserving the working medium in the reservoir unit 6 before the pump drive control are not necessarily continuously performed. For example, in a case where the supply of the heat medium is maintained for a fixed time even after stop of the thermal energy recovery device X1, by performing the reserving control after the stop so as to reserve the working medium in advance, the pump drive control can be performed at a desired timing. The same is applied to the other control actions below.
Hereinafter, modified examples of the thermal energy recovery device X1 according to the present embodiment will be described with reference to
In a modified example shown in
In a modified example shown in
In the modified example shown in
In a modified example shown in
The present embodiment described above is thought to be not restriction but only an example in all aspects. The scope of the present invention is indicated not by the above description of the embodiment but by the claims, and includes equivalent meanings to the claims and all modifications within the scope.
For example, in the actions at the time of the start-up shown in
Further, in the above embodiment, supply control of the cooling water is not necessarily performed. In a case where the cooling water is always supplied to the cooling water flow passage 51, Step Op4 is not required.
In the thermal energy recovery device X1, the shutoff valve 81a may be omitted and part of the working medium evaporated in the heater 2 may flow into the condenser 5 through the expander 3. Thereby, more electric power can be generated. In a case where a time for the reserving control of the working medium is sufficiently ensured, the entire amount of the working medium may flow into the condenser 5 through the expander 3 in a state where the bypass valve 11a is closed.
In the above embodiment, the condenser 5 and the reservoir unit 6 may be one continuous member. In this case, the liquid level sensor 61 provided in the reservoir unit 6 is provided in a downstream part of the condenser 5 functioning as the reservoir unit. It should be noted that the liquid level sensor 61 is not necessarily provided in the condenser 5 but may be provided in a part of the third flow passage 83 on the upstream side of the pump 7.
Although the control unit 9 functionally has the determination unit 93 in the present embodiment, the present invention is not limited to this. Based on the detected value of the liquid level sensor 61, an operator may instruct the pump control unit 91 and the valve control unit 92 so as to perform the control of Step Op7 to Step Op9, Step Op10.
In the thermal energy recovery device X1, the heater may be formed by a plurality of heat exchangers. In a modified example shown in
In the thermal energy recovery device X1, a heat exchanger that directly recovers heat of the exhaust gas discharged from the engine 130 as a heat medium may be provided. In such a way, the thermal energy recovery device X1 includes at least one of the supercharged air supplied to the engine 130, the exhaust gas discharged from the engine 130, and the steam generated in the economizer 200 that recovers the heat from the exhaust gas as the heat medium.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-097892 | May 2014 | JP | national |
