JP6379985B2 - Heat recovery system - Google Patents

Description

  The present invention relates to a heat recovery system capable of recovering compression heat generated by an oil-free air compressor.

  Conventionally, as disclosed in FIG. 2 of Patent Document 1 below, a heat recovery heat exchanger (9) is provided in an air passage (12) from the compressor (2) to the air cooler (8), while this heat recovery is performed. There is known a heat recovery system in which the heat exchanger (9) for use can be bypassed by a bypass passage (25). In the heat recovery heat exchanger (9), the compressed air and the water flow can be heat-exchanged to cool the compressed air, while the water flow can be heated. Thus, heat recovery can be achieved by using the compression heat generated in the compressor (2) in the heat recovery heat exchanger (9) for heating the water supplied to the water supply tank (5).

JP 2012-87664 A

  When the above-described heat recovery system is applied to an oil-free compressor, the temperature of the compressed air discharged from the compressor is a high temperature close to 200 ° C., so during the stoppage of water flow to the heat recovery heat exchanger There is a risk of inconvenience. That is, if compressed air from the compressor is passed through the heat recovery heat exchanger while water flow to the heat recovery heat exchanger is stopped, the water remaining in the heat recovery heat exchanger may be boiled. Alternatively, if there is no water on the water flow side of the heat recovery heat exchanger, the water recovery state is caused, and the thermal stress in the heat recovery heat exchanger increases, which may damage the heat recovery heat exchanger.

  Therefore, if the water flow condition to the heat recovery heat exchanger is satisfied during the operation of the compressor, the compressed air from the compressor is passed through the heat recovery heat exchanger and the water flow to the heat recovery heat exchanger is passed. On the other hand, if the water flow condition to the heat recovery heat exchanger is not satisfied, it is considered that the compressed air from the compressor is controlled to pass through the bypass and to stop the water flow to the heat recovery heat exchanger. It is done.

  At that time, switching between whether the compressed air from the compressor is passed through the heat recovery heat exchanger or the bypass path is provided on the bypass valve provided in the bypass path and the inlet side of the heat recovery heat exchanger. It is assumed that switching is performed by a shutoff valve. However, at the time of this switching, if both valves are temporarily closed, there is a risk of causing problems in the compressor.

  Also, before starting water flow to the heat recovery heat exchanger, supply compressed air to the heat recovery heat exchanger, or conversely stop supplying compressed air to the heat recovery heat exchanger. If the water flow to the heat recovery heat exchanger is stopped before, there is a risk of causing inconvenience such as boiling water in the heat recovery heat exchanger as described above.

  Therefore, the problem to be solved by the present invention is an oil-free compressor heat recovery system, while preventing problems with the compressor, according to the presence or absence of water flow to the heat recovery heat exchanger, It is to switch the flow path of the compressed air. Further, preferably, it is to prevent boiling of water in the heat recovery heat exchanger and to prevent an increase in thermal stress in the heat recovery heat exchanger due to air blowing and damage caused thereby.

The present invention has been made in order to solve the above-mentioned problems, and the invention according to claim 1 is a method in which compressed air from an oil-free compressor is cooled with circulating water between a cooling tower and An air cooler that is cooled by ventilation with a fan, a heat recovery heat exchanger that is provided in an air path from the compressor to the air cooler and that heat-exchanges compressed air and water to produce hot water, and from the compressor A bypass path connecting the heat exchange inlet side air path to the heat recovery heat exchanger, a heat exchange outlet side air path from the heat recovery heat exchanger to the air cooler, and a bypass provided in the bypass path The heat exchange inlet side of the heat exchange inlet side air passage downstream of the valve and the branch portion of the bypass passage and the heat exchange outlet side air passage upstream of the joining portion of the bypass passage a shutoff valve provided only openably air passage, wherein And a controller for controlling the bypass valve and the shutoff valve, wherein the controller (i) is configured to pass the bypass when the heat recovery heat exchanger is brought into a water state during operation of the compressor. The valve is closed, the shut-off valve is opened, and (ii) when the heat recovery heat exchanger is brought into a water stop state during operation of the compressor, the bypass valve is opened, and the the shut-off valve is closed, (iii) when switching the heat recovery heat exchanger from water passing state to water flow stopped from opening the bypass valve, closing the shut-off valve, (iv) for the heat recovery when switching the heat exchanger from the water passing the stopped state to the water flow state, from open the shut-off valve, a heat recovery system characterized by closing the bypass valve.

  According to the first aspect of the present invention, when switching between the water flow state and the water flow stop state to the heat recovery heat exchanger, both the heat recovery heat exchanger and the bypass path are temporarily used. By controlling so that the compressed air flows, inconvenience due to valve operation delay can be prevented. Specifically, when switching from a heat recovery heat exchanger to a bypass path, the flow of compressed air is prevented from being blocked by opening the bypass path before blocking the heat recovery heat exchanger. it can. Conversely, when switching from the bypass path to the heat recovery heat exchanger, the flow of the compressed air can be prevented from being blocked by opening the heat recovery heat exchanger before blocking the bypass path.

Invention according to claim 2, wherein the controller, (v) when switching the heat recovery heat exchanger from water passing stopped state to the water flow state, start the water flow to the heat recovery heat exchanger from to, opening the shut-off valve, (vi) during operation of the compressor in a state in which opened the shut-off valve closes the bypass valve, passing water stopped the heat recovery heat exchanger from water passing state 2. The heat recovery system according to claim 1, wherein when switching to, the water shut-off to the heat recovery heat exchanger is stopped after the shut-off valve is closed.

  According to the second aspect of the present invention, it is possible to prevent the compressed air from flowing into the heat recovery heat exchanger while the water flow to the heat recovery heat exchanger is stopped, Water can be prevented from boiling, and an increase in thermal stress in the heat recovery heat exchanger due to emptying and damage due to the heat can be prevented.

  Furthermore, the invention described in claim 3 includes a low-stage compressor and a high-stage compressor as the compressor, an intercooler and an aftercooler as the air cooler, and the heat recovery heat exchanger. A first heat recovery heat exchanger and a second heat recovery heat exchanger, compressed air from the low stage compressor is sent to the high stage compressor through the intercooler, After further compression in the stage compressor, the first stage heat recovery heat exchanger is provided in the air path from the low stage compressor to the intercooler, and sent to the after cooler, while the high stage compression The second heat recovery heat exchanger is provided in the air path from the machine to the aftercooler, and the first heat recovery heat exchanger and the second heat recovery heat exchanger are arranged in a set order. Water is passed in series or water is passed in parallel, For the heat-recovery heat exchanger, the bypass passage, a heat recovery system according to claim 1 or claim 2, characterized in that a said bypass valve and the shut-off valve.

  According to the invention described in claim 3, the invention described in each of the above-described claims can be applied to the compressor of each stage of the two-stage oil-free compressor.

  According to the present invention, in the heat recovery system for an oil-free compressor, the flow path of the compressed air is set according to the presence or absence of water flow to the heat recovery heat exchanger while preventing problems with the compressor. Can be switched. Further, preferably, it is possible to prevent boiling of water in the heat recovery heat exchanger and to prevent an increase in thermal stress in the heat recovery heat exchanger due to air blowing and damage caused thereby.

It is the schematic which shows one Example of the heat recovery system of this invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a heat recovery system 1 according to an embodiment of the present invention.

  The heat recovery system 1 of this embodiment is applied to a two-stage oil-free air compressor. In this case, a low-stage compressor 2 and a high-stage compressor 3 are provided as compressors, and an intercooler 4 and an aftercooler 5 are provided as air coolers for cooling the compressed air from the compressors 2 and 3. The compressed air from the low stage compressor 2 is sent to the high stage compressor 3 via the intercooler 4, further compressed in the high stage compressor 3, and then sent to the after cooler 5. The compressed air after passing through the aftercooler 5 is sent to various types of equipment using compressed air via an air dryer or an air tank as required.

  The low stage compressor 2 and the high stage compressor 3 are typically driven by a motor and started and stopped in conjunction with a gear. The low stage compressor 2 sucks outside air, compresses and discharges it, and the high stage compressor 3 further compresses and discharges compressed air from the low stage compressor 2 via the intercooler 4.

  The intercooler 4 and the aftercooler 5 are indirect heat exchangers that exchange heat without mixing compressed air and cooling water, respectively. Therefore, cooling water is circulated between the cooling water passages 4a and 5a of the intercooler 4 and the aftercooler 5 with the cooling tower (cooling tower). At this time, the cooling water from the cooling tower may be passed through the intercooler 4 and then through the aftercooler 5. Conversely, after passing through the aftercooler 5, the cooling water is passed through the intercooler 4. May be. Alternatively, the cooling water from the cooling tower may be passed through the intercooler 4 and the aftercooler 5 in parallel.

  In such a two-stage oil-free air compressor, the heat recovery system 1 of the present embodiment recovers heat before passing the compressed air from the compressor 2 (3) of each stage through the air cooler 4 (5). It is configured to be able to recover the compression heat through the heat exchanger 6 (7). Specifically, the heat recovery system 1 of the present embodiment uses the compression heat generated in the compressors 2 and 3 at each stage to heat the water in the heat recovery heat exchangers 6 and 7, thereby compressing heat. Recover. As the heat recovery heat exchanger, a first heat recovery heat exchanger 6 and a second heat recovery heat exchanger 7 are provided. The first heat recovery heat exchanger 6 is provided in the first air passage 8 from the low stage compressor 2 to the intercooler 4, and the second heat recovery heat exchanger 7 is supplied from the high stage compressor 3 to the aftercooler. In the second air passage 9 to 5.

  The first heat recovery heat exchanger 6 and the second heat recovery heat exchanger 7 are indirect heat exchangers that exchange heat without mixing compressed air and water, respectively. Therefore, in the water passages of the first heat recovery heat exchanger 6 and the second heat recovery heat exchanger 7, water is supplied from a water supply source (for example, a water softener) to the water supply tank 10 via the water supply path 11. Passed. At this time, the water from the water supply source may be passed through the second heat recovery heat exchanger 7 and then through the first heat recovery heat exchanger 6 as shown in the illustrated example. Conversely, after passing through the first heat recovery heat exchanger 6, it may be passed through the second heat recovery heat exchanger 7. Alternatively, the water from the water supply source may be passed through the first heat recovery heat exchanger 6 and the second heat recovery heat exchanger 7 in parallel. In any case, in each of the heat recovery heat exchangers 6 and 7, the compressed air and water can be heat-exchanged to cool the compressed air with water, while the water can be heated with the compressed air. In addition, although the use in particular is not ask | required, the stored water in the water supply tank 10 is used, for example as water supply to a boiler.

  About each heat recovery heat exchanger 6 and 7, the inlet side and outlet side of compressed air are connected by bypass paths 12 and 13. Specifically, the first heat exchange inlet-side air passage 8a from the low stage compressor 2 to the first heat recovery heat exchanger 6 and the first heat exchanger 6 to the intercooler 4 from the first heat recovery heat exchanger 6 The heat exchange outlet side air passage 8 b is connected by the first bypass passage 12. Similarly, the second heat exchange inlet-side air passage 9a from the high stage compressor 3 to the second heat recovery heat exchanger 7 and the second heat exchange from the second heat recovery heat exchanger 7 to the aftercooler 5 are used. The outlet side air passage 9 b is connected by the second bypass passage 13.

  In each bypass passage 12, 13, bypass valves 14, 15 are provided. Specifically, the first bypass passage 12 is provided with a first bypass valve 14, while the second bypass passage 13 is provided with a second bypass valve 15.

  In the present embodiment, the heat recovery heat exchangers 6 and 7 are connected to the shutoff valves 16 in the heat exchange inlet side air passages 8a and 9a downstream of the branch portions (connection portions) to the bypass passages 12 and 13, respectively. , 17 are provided, but the shutoff valve is not provided in the heat exchange outlet side air passages 8b, 9b upstream from the junction (connection portion) with the bypass passages 12, 13. Specifically, the first shutoff valve 16 is provided in the first heat exchange inlet side air passage 8a downstream from the branch portion with the first bypass passage 12, while the first shut-off valve 16 is provided with respect to the first bypass passage 12. A shutoff valve is not provided in the upstream first heat exchange outlet side air passage 8b. Further, the second shutoff valve 17 is provided in the second heat exchange inlet side air passage 9a downstream from the branch portion with the second bypass passage 13, while the second shutoff valve 17 is provided upstream of the joining portion with the second bypass passage 13. A shutoff valve is not provided in the two heat exchange outlet side air passage 9b.

  The presence or the flow rate of water supplied to the water supply tank 10 via the water supply channel 11 can be changed. In the present embodiment, the water supply passage 11 is provided with a water supply valve 18 upstream of the heat recovery heat exchangers 6 and 7. By switching the opening and closing of the water supply valve 18, it is possible to switch the presence / absence of water flow to each heat recovery heat exchanger 6, 7 and consequently the water supply to the water supply tank 10. Further, by adjusting the opening of the water supply valve 18, it is possible to adjust the water flow rate to each heat recovery heat exchanger 6, 7, and consequently the water supply flow rate to the water supply tank 10. However, instead of or in addition to such control of the water supply valve 18, a water supply pump may be provided in the water supply path 11 to control the start / stop or rotation speed of the water supply pump.

  By the way, the use load of compressed air can be monitored by providing a pressure sensor (not shown) in an air tank (which may be a pipe line in some cases) to which compressed air is supplied from the high stage compressor 3. On the other hand, the use load of the hot water in the water supply tank 10 can be monitored by providing the water level sensor 19 in the water supply tank 10.

  Further, by providing the temperature sensor 20 downstream of the heat recovery heat exchangers 6 and 7 in the water supply path 11 to the water supply tank 10, the water supply temperature to the water supply tank 10 can be monitored. Furthermore, by providing the flow meter 21 in the water supply path 11, it is possible to monitor the flow rate of water flow to each heat recovery heat exchanger 6, 7, and consequently the water supply flow rate to the water supply tank 10. In the illustrated example, a flow meter 21 is provided immediately downstream of the water supply valve 18.

  Next, control of the heat recovery system 1 of the present embodiment will be described. A series of controls described below is executed by a controller (not shown). That is, the controller includes the compressors (more specifically, the motors) 2 and 3, the bypass valves 14 and 15, the shutoff valves 16 and 17, the water supply valve 18, the pressure sensor, the water level sensor 19, and the temperature sensor described above. 20 and a flow meter 21 and the like, and the compressors 2 and 3 and the valves 14 to 18 are controlled based on detection signals of the sensors 19 to 21.

  The controller is based on whether or not the operating conditions of the compressors 2 and 3 are satisfied, and whether or not the water flow conditions to the heat exchangers 6 and 7 for heat recovery are satisfied. 18 etc. are controlled.

  Whether or not the operating conditions of the compressors 2 and 3 are satisfied is typically determined based on the air pressure of the air tank (or pipe line) to which the compressed air from the high stage compressor 3 is supplied. Specifically, based on the detection signal of the pressure sensor, if the pressure in the air tank falls below the lower limit pressure, it is determined that the operating conditions of the compressors 2 and 3 are satisfied, while if the pressure in the air tank exceeds the upper limit pressure. It is determined that the operating conditions of the compressors 2 and 3 are not satisfied. In addition, during operation of the compressors 2 and 3, the capacity of the compressors 2 and 3 may be controlled according to the load.

  Whether or not the water flow condition to the heat exchangers 6 and 7 for heat recovery is satisfied is typically determined based on the water level in the water supply tank 10. Specifically, based on the detection signal of the water level sensor 19, if the water level in the water supply tank 10 falls below the lower limit water level, it is determined that the water flow condition is satisfied, while if the water level in the water supply tank 10 exceeds the upper limit water level, It is determined that the water flow condition is not satisfied.

  When the controller determines that the operating conditions of the compressors 2 and 3 are satisfied, the controller operates the compressors 2 and 3, while when it determines that the operating conditions of the compressors 2 and 3 are not satisfied, the controller stops the compressors 2 and 3 To do. When it is determined that the water flow condition to the heat recovery heat exchangers 6 and 7 is satisfied during the operation of the compressors 2 and 3, water is passed to the heat recovery heat exchangers 6 and 7, while the heat recovery heat If it determines with not satisfy | filling the water flow conditions to the exchangers 6 and 7, the water flow to the heat exchangers 6 and 7 for heat recovery will be stopped. During the flow of water to the heat exchangers 6 and 7 for heat recovery, the bypass valves 14 and 15 are closed and the shutoff valves 16 and 17 are opened, while the water flow to the heat exchangers 6 and 7 for heat recovery is stopped. 15 are opened and the shutoff valves 16 and 17 are closed.

  Specifically, the controller operates the compressors 2 and 3 when determining that the operating conditions of the compressors 2 and 3 are satisfied and the water flow conditions to the heat exchangers 6 and 7 for heat recovery are satisfied. At the same time, the water supply valve 18 is opened and water is passed through the heat exchangers 6 and 7 for heat recovery. Thus, compressed air is produced and supplied to the water supply tank 10 through the water supply passage 11. At this time, the shutoff valves 16 and 17 are opened while the bypass valves 14 and 15 are closed. Therefore, the compressed air from the low stage compressor 2 is sent to the intercooler 4 through the first heat recovery heat exchanger 6 without passing through the first bypass 12, and further compressed by the high stage compressor 3. After that, it is sent to the aftercooler 5 through the second heat recovery heat exchanger 7 without passing through the second bypass 13.

  The water supply to the water supply tank 10 is heat-exchanged with the heat recovery heat exchangers 6 and 7 by exchanging heat with the compressed air to cool the compressed air. If the opening degree of the water supply valve 18 is adjusted based on the temperature detected by the temperature sensor 20, the water supply temperature to the water supply tank 10 can be adjusted. When the compressed air cannot be cooled to a predetermined temperature in the heat recovery heat exchangers 6 and 7, an air cooler (intercooler 4 or after cooler) provided downstream of the heat recovery heat exchangers 6 and 7 in the compressed air flow. In 5), the compressed air at each stage is cooled to a predetermined temperature.

  On the other hand, if the controller satisfies the operating conditions of the compressors 2 and 3, but determines that the water flow conditions to the heat exchangers 6 and 7 for heat recovery are not satisfied, the controller operates the compressors 2 and 3, The water supply valve 18 is closed to stop water flow to the heat recovery heat exchangers 6 and 7. Thereby, although compressed air is manufactured, the water supply to the water supply tank 10 via the water supply path 11 is stopped. At this time, the bypass valves 14 and 15 are opened, while the shutoff valves 16 and 17 are closed. Therefore, the compressed air from the low stage compressor 2 is sent to the intercooler 4 through the first bypass 12 without passing through the first heat recovery heat exchanger 6 and further compressed by the high stage compressor 3. Then, the second heat recovery heat exchanger 7 is not passed through the second bypass passage 13 and sent to the aftercooler 5. In this case, in the air cooler (intercooler 4 or aftercooler 5), the compressed air at each stage is cooled to a predetermined temperature.

  Further, when the controller determines that the operating conditions of the compressors 2 and 3 are not satisfied, the compressors 2 and 3 regardless of whether or not the water flow conditions to the heat exchangers 6 and 7 for heat recovery are satisfied. And the water supply valve 18 is closed to stop water flow to the heat recovery heat exchangers 6 and 7. Thereby, manufacture of compressed air is stopped and the water supply to the water supply tank 10 via the water supply path 11 is also stopped. If the operating conditions of the compressors 2 and 3 are not satisfied but the water flow conditions to the heat recovery heat exchangers 6 and 7 are satisfied, the water supply tank 10 can be supplied with water from another water supply system (not shown). Good. Alternatively, since the compressors 2 and 3 are stopped, the heat recovery heat exchangers 6 and 7 cannot heat the water supply, but may supply water to the water supply tank 10 via the water supply path 11.

  By the way, when switching whether the compressed air from the compressors 2 and 3 is passed through the heat exchangers 6 and 7 for heat recovery or the bypass passages 12 and 13 is preferably controlled as follows. That is, when the compressed air from the compressors 2 and 3 passes through the bypass passages 12 and 13 while passing through the heat exchangers 6 and 7 for heat recovery, the bypass valves 14 and 15 are opened. The shut-off valves 16, 17 are preferably closed. On the contrary, when the compressed air from the compressors 2 and 3 is being passed through the bypass passages 12 and 13, when switching to pass through the heat recovery heat exchangers 6 and 7, the shut-off valves 16 and 17 are opened. The bypass valves 14 and 15 are preferably closed.

  More specifically, while the compressors 2 and 3 are in operation, the bypass valves 14 and 15 are closed and the shut-off valves 16 and 17 are opened so that the water is passed to the heat exchangers 6 and 7 for heat recovery. In some cases, when switching from the water flow state to the water flow stop state, it is preferable to first open the bypass valves 14 and 15 and then close the shutoff valves 16 and 17. Similarly, when the compressors 2 and 3 are in operation, the shutoff valves 16 and 17 are closed and the bypass valves 14 and 15 are opened and the water recovery to the heat recovery heat exchangers 6 and 7 is stopped. When switching from the water flow stop state to the water flow state, it is preferable to first open the shutoff valves 16 and 17 and then close the bypass valves 14 and 15. When switching between a water flow state and a water flow stop state for the heat exchangers 6 and 7 for heat recovery, compressed air is temporarily supplied to both the heat exchangers 6 and 7 for heat recovery and the bypass passages 12 and 13. Is controlled so that inconvenience due to valve operation delay, specifically, problems of the compressors 2 and 3 due to the blockage of the flow of compressed air can be prevented.

  Further, the compressed air from the compressors 2 and 3 is passed through the bypass passages 12 and 13 and the water recovery to the heat exchangers 6 and 7 for heat recovery is stopped. When the air is passed through the heat recovery heat exchangers 6 and 7 and the heat recovery execution state in which the water is passed to the heat recovery heat exchangers 6 and 7 is switched, the following control is preferably performed. That is, when switching from the heat recovery stop state to the heat recovery execution state, the flow of heat to the heat recovery heat exchangers 6 and 7 is started, and then the compressed air to the heat recovery heat exchangers 6 and 7 is supplied. The supply should be started. Conversely, when switching from the heat recovery execution state to the heat recovery stop state, the supply of compressed air to the heat recovery heat exchangers 6 and 7 is stopped, and then the heat recovery heat exchangers 6 and 7 are supplied. It is recommended to stop the water flow.

  More specifically, while the compressors 2 and 3 are in operation, the bypass valves 14 and 15 are opened and the shutoff valves 16 and 17 are closed to stop the water flow to the heat exchangers 6 and 7 for heat recovery. In some cases, when switching from the water flow stop state to the water flow state, the water supply valve 18 is opened and water flow to the heat exchangers 6 and 7 for heat recovery is started, and then the shutoff valves 16 and 17 are opened. preferable. In particular, it is preferable to open the water supply valve 18 and check the water flow of a predetermined flow rate or more with the flow meter 21 before opening the shutoff valves 16 and 17. This prevents the compressed air from flowing into the heat recovery heat exchangers 6 and 7 even though the water flow to the heat recovery heat exchangers 6 and 7 is stopped, and the heat recovery heat exchangers 6 and 7. It is possible to prevent boiling of the water in the inside, and to prevent an increase in thermal stress in the heat recovery heat exchangers 6 and 7 due to air blowing and damage caused thereby. For the same reason, when the compressors 2 and 3 are in operation, the bypass valves 14 and 15 are closed and the shut-off valves 16 and 17 are opened, and the water is being passed to the heat recovery heat exchangers 6 and 7. , When switching from the water flow state to the water flow stop state, the bypass valves 14 and 15 are opened, the shutoff valves 16 and 17 are closed, and then the water supply valve 18 is closed to the heat exchangers 6 and 7 for heat recovery. It is preferable to stop the water flow.

  The heat recovery system 1 of the present invention is not limited to the configuration of the above-described embodiment (including modifications), and can be changed as appropriate. For example, in the above-described embodiment, the intercooler 4 and the aftercooler 5 are of the water cooling type in which the compressed air from the compressors 2 and 3 is cooled by circulating water between the cooling tower and the intercooler 4 and the aftercooler. One or both of 5 may be air-cooled. When the intercooler 4 and / or the aftercooler 5 is air-cooled, in the air-cooled heat exchanger, the compressed air from the compressors 2 and 3 is cooled by ventilation with a fan. That is, in the air-cooled heat exchanger, indirect heat exchange may be performed without mixing the compressed air from the compressors 2 and 3 and the ventilation by the fan.

  In the above-described embodiment, an example is shown in which the boiler water supply is preheated through the water supply to the boiler water supply tank 10 through the heat recovery heat exchangers 6 and 7, but the heat recovery heat exchangers 6 and 7 are used. The use of the water passed through is not limited to this and can be changed as appropriate. In addition, the presence or absence of water flow conditions to the heat recovery heat exchangers 6 and 7 may be determined by using a signal from a hot water use facility that uses hot water after passing through the heat recovery heat exchangers 6 and 7, depending on circumstances. Good.

  Furthermore, in the said Example, the number of stages of the compressors 2 and 3 can be changed suitably. For example, a single-stage compressor may be used. In that case, in the said Example, installation of one of the two compressors 2 and 3 is abbreviate | omitted, and in connection with it, the heat exchanger 6 (7 for heat recovery) installed immediately after the compressor 2 (3). ) And the air cooler 4 (5) may be omitted. For example, in FIG. 1, the installation of the high stage compressor 3, the second heat recovery heat exchanger 7 and the aftercooler 5 can be omitted. Conversely, in FIG. 1, the number of compressors may be three or more. Accordingly, the number of sets of the compressor 2 (3), the heat recovery heat exchanger 6 (7), and the air cooler 4 (5) can be increased. That's fine. The added heat recovery heat exchanger is also provided with a bypass path, a bypass valve and a shutoff valve, and is controlled in the same manner as in the above embodiment.

1 Heat recovery system 2 Low stage compressor 3 High stage compressor 4 Intercooler (air cooler)
5 After cooler (air cooler)
6 heat exchanger for first heat recovery 7 heat exchanger for second heat recovery 8 first air path (8a: first heat exchange inlet side air path, 8b: first heat exchange outlet side air path)
9 second air passage (9a: second heat exchange inlet side air passage, 9b: second heat exchange outlet side air passage)
DESCRIPTION OF SYMBOLS 10 Water tank 11 Water supply path 12 1st bypass path 13 2nd bypass path 14 1st bypass valve 15 2nd bypass valve 16 1st shut-off valve 17 2nd shut-off valve 18 Water feed valve 19 Water level sensor 20 Temperature sensor 21 Flowmeter

Claims (3)

An air cooler that cools the compressed air from the oil-free compressor with circulating water between the cooling tower or the ventilation by a fan;
A heat exchanger for heat recovery, which is provided in an air path from the compressor to the air cooler, and produces hot water by exchanging heat between the compressed air and water;
A bypass passage connecting a heat exchange inlet side air passage from the compressor to the heat recovery heat exchanger and a heat exchange outlet side air passage from the heat recovery heat exchanger to the air cooler ;
A bypass valve provided in the bypass passage,
Of the heat exchange inlet side air passage downstream of the branching portion with the bypass passage and the heat exchange outlet side air passage upstream of the junction with the bypass passage, the heat exchange inlet side air passage a shutoff valve disposed to open and close only,
A controller for controlling the bypass valve and the shutoff valve,
The controller is
(I) During operation of the compressor, when the heat recovery heat exchanger is made to flow, the bypass valve is closed and the shut-off valve is opened.
(Ii) During operation of the compressor, when the heat recovery heat exchanger is put into a water stop state, the bypass valve is opened and the shutoff valve is closed,
(Iii) when switching the heat recovery heat exchanger from water passing state to water flow stopped from opening the bypass valve, closing the shut-off valve,
(Iv) when switching the heat recovery heat exchanger from water passing stopped state to the water flow state, heat recovery system, characterized in that the opening the shut-off valve, closing the bypass valve. The controller is
(V) when switching the heat recovery heat exchanger from water passing stopped state to the water flow state, from the start of water flow to the heat recovery heat exchanger, opening the shut-off valve,
(Vi) during operation of the compressor in a state in which opened the shut-off valve closes the bypass valve, when switching the heat recovery heat exchanger from water passing state to water flow stopped, by closing the shutoff valve The heat recovery system according to claim 1, wherein water flow to the heat recovery heat exchanger is stopped. As the compressor, comprising a low-stage compressor and a high-stage compressor,
As the air cooler, an intercooler and an aftercooler are provided,
As the heat recovery heat exchanger, it comprises a first heat recovery heat exchanger and a second heat recovery heat exchanger,
Compressed air from the low-stage compressor is sent to the high-stage compressor via the intercooler, further compressed in the high-stage compressor, and then sent to the aftercooler,
While the first heat recovery heat exchanger is provided in the air path from the low stage compressor to the intercooler, the second heat recovery is provided in the air path from the high stage compressor to the after cooler. A heat exchanger is provided,
In the first heat recovery heat exchanger and the second heat recovery heat exchanger, water is passed in series in a set order, or water is passed in parallel,
The heat recovery system according to claim 1, wherein the bypass passage, the bypass valve, and the shut-off valve are provided for each of the heat recovery heat exchangers.

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