Gas compressor

Abstract

Provided is a gas compressor capable of preventing supercooling by a heat recovery unit and a cooler, regardless of the cooling power of the heat recovery unit.　In the present invention, an air compressor comprises: a low-pressure stage compressor body 2 for compressing air; a low-pressure stage heat recovery unit 3 for heating water using heat from the compressed air discharged from the low-pressure stage compressor body 2; an intercooler 4 for further cooling the compressed air cooled by the low-pressure stage heat recovery unit 3; and a high-pressure stage compressor body 5 for further compressing the compressed air cooled by the intercooler 4. The air compressor further includes: a compressed air temperature sensor 25 for detecting the temperature of the compressed air on the downstream side of the intercooler 4 and on the upstream side of the high-pressure stage compressor body 5; and a control device 15 for variably controlling the cooling power of the intercooler 4 on the basis of a detected value from the compressed air temperature sensor 25.

Description

Gas compressor

[0001] The present invention relates to a gas compressor.

[0002] Patent Document 1 discloses an air compressor, which is a type of gas compressor. The air compressor in one embodiment of Patent Document 1 includes a low-pressure compressor main body that compresses air (gas), a heat recovery unit that heats water (liquid) using heat from the compressed air (compressed gas) discharged from the low-pressure compressor to produce hot water, an intercooler that further cools the compressed air cooled by the heat recovery unit, and a high-pressure compressor main body that further compresses the compressed air cooled by the intercooler. The presence or absence of water supply to the heat recovery unit or the flow rate is controlled based on the usage load and / or temperature of the hot water. In other words, the cooling power of the heat recovery unit is variably controlled.

[0003] Another embodiment of the air compressor disclosed in Patent Document 1 includes a compressor main body that compresses air while injecting oil into a working chamber, an oil separator that separates oil from the compressed air discharged from the compressor main body, a heat recovery unit that generates hot water by heating water using the heat of the oil separated in the oil separator, and an oil cooler that further cools the oil cooled in the heat recovery unit and supplies the cooled oil to the compressor main body. The presence or absence of water supply to the heat recovery unit or the flow rate is controlled based on the usage load and / or temperature of the hot water. In other words, the cooling power of the heat recovery unit is variably controlled.

[0004] Japanese Patent Application Laid-Open No. 2015-038354

[0005] In one embodiment of the air compressor described in Patent Document 1, compressed air discharged from the low-pressure stage compressor body is cooled by a heat recovery unit and an intercooler. Therefore, depending on the cooling power of the heat recovery unit, the compressed air may be overcooled, resulting in the generation of condensed water. Even if a water separator is provided to separate condensed water from the compressed air, a large amount of condensed water may be generated that exceeds the capacity of the water separator. The compressed air containing condensed water may then flow into the high-pressure stage compressor body, causing corrosion inside the high-pressure stage compressor body and hindering its operation.

[0006] In another embodiment of the air compressor described in Patent Document 1, the oil separated in the oil separator is cooled in a heat recovery unit and an oil cooler. Therefore, depending on the cooling power of the heat recovery unit, the oil may be supercooled, which may then supercool the compressed air, resulting in the formation of condensed water. The oil containing the condensed water may then flow into the compressor body, causing corrosion inside the compressor body and hindering its operation.

[0007] The present invention has been made in consideration of the above circumstances, and one of its objectives is to prevent overcooling by the heat recovery device and the intercooler or oil cooler, regardless of the cooling power of the heat recovery device.

[0008] In order to solve the above problem, the configurations described in the claims are applied. The present invention includes a plurality of means for solving the above problem, and one example thereof is a gas compressor including a low-pressure stage compressor main body that compresses gas, a heat recovery unit that heats a liquid using heat from the compressed gas discharged from the low-pressure stage compressor main body, an intercooler that further cools the compressed gas cooled by the heat recovery unit, and a high-pressure stage compressor main body that further compresses the compressed gas cooled by the intercooler, the gas compressor further comprising a compressed gas temperature sensor that detects the temperature of the compressed gas downstream of the intercooler and upstream of the high-pressure stage compressor main body, and a control device that variably controls the cooling power of the intercooler based on the detected value of the compressed gas temperature sensor.

[0009] According to the present invention, it is possible to prevent overcooling by the heat recovery unit and the cooler, regardless of the cooling power of the heat recovery unit.

[0010] Problems, configurations, and effects other than those described above will become clear from the following description.

[0011] FIG. 1 is a diagram showing the configuration of an air compressor according to a first embodiment of the present invention. FIG. 2 is a flowchart showing the processing procedure of a control device according to the first embodiment of the present invention. FIG. 3 is a diagram showing the configuration of an air compressor according to a second embodiment of the present invention. FIG. 4 is a flowchart showing the processing procedure of a control device according to the second embodiment of the present invention. FIG. 5 is a diagram showing the configuration of an air compressor according to a third embodiment of the present invention. FIG. 6 is a flowchart showing the processing procedure of a control device according to the third embodiment of the present invention. FIG. 7 is a diagram showing the configuration of an air compressor according to a fourth embodiment of the present invention. FIG. 8 is a flowchart showing the processing procedure of a control device according to the fourth embodiment of the present invention.

[0012] A first embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a diagram showing the configuration of an air compressor according to this embodiment.

[0014] The air compressor (gas compressor) of this embodiment includes a low-pressure stage compressor main body 2 that takes in and compresses air (gas) through an air filter 1 or the like, a low-pressure stage heat recovery unit 3 that heats water (liquid) using the heat of the compressed air (compressed gas) discharged from the low-pressure stage compressor main body 2, an intercooler 4 that further cools the compressed air cooled in the low-pressure stage heat recovery unit 3, a high-pressure stage compressor main body 5 that further compresses the compressed air cooled in the intercooler 4, a high-pressure stage heat recovery unit 6 that heats water using the heat of the compressed air discharged from the high-pressure stage compressor main body 5, and an aftercooler 7 that further cools the compressed air cooled in the high-pressure stage heat recovery unit 6. The compressed air cooled in the aftercooler 7 is supplied to a destination where it is consumed.

[0015] The low-pressure stage compressor body 2 includes, for example, a pair of screw rotors, a plurality of bearings that rotatably support the pair of screw rotors while meshing with each other without contacting each other, a pair of timing gears that rotate the pair of screw rotors synchronously, and a casing that houses them. As the screw rotors rotate, working chambers formed in the tooth grooves of the screw rotors move and their volumes change. This causes air to be drawn in, compressed, and discharged as compressed air. The high-pressure stage compressor body 5 has a configuration substantially similar to that of the low-pressure stage compressor body 2.

[0016] The low-pressure stage compressor body 2 and the high-pressure stage compressor body 5 are configured so as not to inject liquids such as oil or water into the working chambers. Although not shown, the casing of the low-pressure stage compressor body 2 has a cooling water flow path (coolant flow path) through which cooling water (coolant) that has passed through the aftercooler 7 flows, and the casing of the high-pressure stage compressor body 5 has a cooling water flow path (coolant flow path) through which cooling water (coolant) that has passed through the intercooler 4 flows. This allows the low-pressure stage compressor body 2 and the high-pressure stage compressor body 5 to be cooled.

[0017] The low-pressure stage compressor body 2 and the high-pressure stage compressor body 5 are driven by an electric motor 9 via a speed-increasing device 8. The speed-increasing device 8 is composed of a first gear connected to the output shaft of the electric motor 9, a second gear connected to the input shaft of the low-pressure stage compressor body 2 and meshing with the first gear, a third gear connected to the input shaft of the high-pressure stage compressor body 5 and meshing with the first gear, and a gear box that houses the first gear, second gear, and third gear and stores lubricating oil.

[0018] The oil stored in the speed increasing device 8 is supplied to the bearings of the low-pressure stage compressor body 2 and the bearings of the high-pressure stage compressor body 5 via an oil line 10, and then returned to the speed increasing device 8. The oil line 10 includes a pump 11, an oil cooler 12 arranged downstream of the pump 11, and an oil filter 13 arranged downstream of the oil cooler 12.

[0019] The air compressor of this embodiment includes a user interface 14, a control device 15, a pressure sensor 16 provided downstream of the aftercooler 7, a suction throttle valve 17 provided upstream of the low-pressure stage compressor main body 2, and an air release valve (not shown) provided in a flow path (not shown) branched from the flow path downstream of the high-pressure stage compressor main body 5 and upstream of the high-pressure stage heat recovery device 6.

[0020] The user interface 14 has, for example, an operation switch, a stop switch, and a touch panel on which various settings and displays can be performed. The control device 15 has a memory for storing programs and data, and a processor for executing processing based on the programs. The control device 15 drives the electric motor 9 in response to operation of the operation switch, and stops the electric motor 9 in response to operation of the stop switch.

[0021] Furthermore, the control device 15 controls the suction throttle valve 17 and the air release valve based on the detection value of the pressure sensor 16. If the detection value of the pressure sensor 16 rises to a predetermined upper limit during load operation, the control device 15 switches the suction throttle valve 17 from an open state to a closed state, and the air release valve from a closed state to an open state. This switches the operation from load operation to no-load operation. If the detection value of the pressure sensor 16 falls to a predetermined lower limit during no-load operation, the control device 15 switches the suction throttle valve 17 from a closed state to an open state, and the air release valve from an open state to a closed state. This switches the operation from no-load operation to load operation.

[0022] Water (liquid) is supplied to and discharged from the low-pressure stage heat recovery device 3 and the high-pressure stage heat recovery device 6 via a water line 18 (liquid line), and the water is heated by heat exchange with compressed air. The hot water generated in this manner is effectively used for purposes such as preheating boiler feedwater or heat retention. In this embodiment, for example, a flow control valve 20 is controlled based on the hot water temperature detected by a hot water temperature sensor 19 to control whether or not water is supplied to the low-pressure stage heat recovery device 3 and the high-pressure stage heat recovery device 6, or the flow rate of water. In other words, the cooling power of the low-pressure stage heat recovery device 3 and the high-pressure stage heat recovery device 6 is variably controlled.

[0023] Cooling water (coolant) is supplied to and discharged from the intercooler 4 and the aftercooler 7 via a cooling water line 21 (coolant line), and the compressed air is cooled by heat exchange with the cooling water. Cooling water is supplied to and discharged from the oil cooler 12 via the cooling water line 21, and the oil cooler 12 cools the oil by heat exchange with the cooling water. The cooling water line 21 is configured to cool the cooling water discharged from the intercooler 4, the aftercooler 7, and the oil cooler 12 in a cooling tower or the like, and supply the cooled cooling water to the intercooler 4, the aftercooler 7, and the oil cooler 12.

[0024] As described above, the compressed air discharged from the low-pressure stage compressor body 2 is cooled by the low-pressure stage heat recovery device 3 and the intercooler 4. Therefore, depending on the cooling power of the low-pressure stage heat recovery device 3, the compressed air may be supercooled, resulting in the generation of condensed water. Note that although the present embodiment is provided with the water separator 22 that separates condensed water from the compressed air cooled by the intercooler 4, there is a possibility that a large amount of condensed water may be generated that exceeds the performance of the water separator 22. Then, the compressed air containing the condensed water may flow into the high-pressure stage compressor body 5, causing corrosion inside the high-pressure stage compressor body 5 and interfering with its operation.

[0025] Therefore, the air compressor of this embodiment is provided with a bypass flow path 23 that is provided in the cooling water line 21 and bypasses the intercooler 4, and a bypass valve 24 that opens and closes the bypass flow path 23, as a configuration for varying the cooling power of the intercooler 4. The air compressor also is provided with a compressed air temperature sensor 25 (compressed gas temperature sensor) that detects the temperature of the compressed air (compressed gas) downstream of the intercooler 4 and upstream of the high-pressure stage compressor main body 5, and a cooling water temperature sensor 26 (coolant temperature sensor) that detects the temperature of the cooling water (coolant) upstream of the intercooler 4.

[0026] The control device 15 variably controls the cooling power of the intercooler 4 by opening and closing the bypass valve 24 based on the detected values ​​of the compressed air temperature sensor 25 and the coolant temperature sensor 26. Details of this control will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the processing procedure of the control device 15 in this embodiment.

[0027] In step S11, the control device 15 acquires the detected value Tsh of the compressed air temperature sensor 25 and the detected value Twc of the coolant temperature sensor 26. Then, the process proceeds to step S12, where the control device 15 determines whether the difference (Tsh - Twc) between the detected value Tsh of the compressed air temperature sensor 25 and the detected value Twc of the coolant temperature sensor 26 is less than a predetermined value ΔTsmin.

[0028] The predetermined value ΔTsmin is a value that is set based on the condition that the detection value Tsh of the compressed air temperature sensor 25 becomes the condensation water generation limit temperature, calculated by assuming predetermined conditions (more specifically, the temperature and humidity of the air upstream of the low-pressure stage compressor main body 2, and the pressure of the compressed air downstream of the intercooler 4 and upstream of the high-pressure stage compressor main body 5).

[0029] If the difference (Tsh - Twc) is equal to or greater than the predetermined value ΔTsmin, the process proceeds to step S13, where the control device 15 closes the bypass valve 24. This increases the flow rate of the cooling water in the intercooler 4, thereby increasing the cooling power of the intercooler 4. On the other hand, if the difference (Tsh - Twc) is less than the predetermined value ΔTsmin, the process proceeds to step S14, where the control device 15 opens the bypass valve 24. This reduces the flow rate of the cooling water in the intercooler 4, thereby reducing the cooling power of the intercooler 4.

[0030] As described above, in this embodiment, the cooling power of the intercooler 4 is variably controlled by opening and closing the bypass valve 24 based on the detected values ​​of the compressed air temperature sensor 25 and the coolant temperature sensor 26. This makes it possible to prevent the compressed air from being overcooled by the low-pressure stage heat recovery device 3 and the intercooler 4, regardless of the cooling power of the low-pressure stage heat recovery device 3. As a result, it is possible to suppress the generation of condensed water and prevent corrosion of the high-pressure stage compressor body 5. Furthermore, it is possible to avoid suppressing the cooling power of the low-pressure stage heat recovery device 3 (in other words, suppressing the amount of heat recovery) and avoiding an increase in the size of the water separator 22.

[0031] A second embodiment of the present invention will be described with reference to the drawings.

[0032] 3 is a diagram showing the configuration of an air compressor according to this embodiment. In this embodiment, parts equivalent to those in the above embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0033] The air compressor of this embodiment is equipped with an air temperature sensor 27 (gas temperature sensor) and an air humidity sensor 28 (gas humidity sensor) that detect the temperature and humidity of the air (gas) upstream of (e.g., the surroundings) the low-pressure stage compressor main body 2, and a compressed air pressure sensor 29 (compressed gas pressure sensor) that detects the pressure of the compressed air (compressed gas) downstream of the intercooler 4 and upstream of the high-pressure stage compressor main body 5.

[0034] The control device 15 variably controls the cooling power of the intercooler 4 by opening and closing the bypass valve 24 based on the detected values ​​of the compressed air temperature sensor 25, the air temperature sensor 27, the air humidity sensor 28, and the compressed air pressure sensor 29. Details of this control will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the processing procedure of the control device in this embodiment.

[0035] In step S21, the control device 15 acquires the detection value Tsh of the compressed air temperature sensor 25, the detection value Ta of the air temperature sensor 27, the detection value Ha of the air humidity sensor 28, and the detection value Psh of the compressed air pressure sensor 29. Then, proceeding to step S22, the control device 15 calculates an upper limit temperature Tcl of the compressed air at which condensation occurs downstream of the intercooler 4 and upstream of the high-pressure stage compressor main body 5, based on the detection value Ta of the air temperature sensor 27, the detection value Ha of the air humidity sensor 28, and the detection value Psh of the compressed air pressure sensor 29. Then, proceeding to step S23, the control device 15 determines whether the detection value Tsh of the compressed air temperature sensor 25 is lower than the condensation temperature Tcl.

[0036] If the detected value Tsh of the compressed air temperature sensor 25 is equal to or higher than the condensation water generation limit temperature Tcl, the process proceeds to step S24, where the control device 15 closes the bypass valve 24. This increases the flow rate of the cooling water in the intercooler 4 and increases the cooling power of the intercooler 4. On the other hand, if the detected value Tsh of the compressed air temperature sensor 25 is lower than the condensation water generation limit temperature Tcl, the process proceeds to step S25, where the control device 15 opens the bypass valve 24. This reduces the flow rate of the cooling water in the intercooler 4 and decreases the cooling power of the intercooler 4.

[0037] As described above, in this embodiment, the cooling power of the intercooler 4 is variably controlled by opening and closing the bypass valve 24 based on the detected values ​​of the compressed air temperature sensor 25, the air temperature sensor 27, the air humidity sensor 28, and the compressed air pressure sensor 29. As a result, similar to the first embodiment, it is possible to prevent the compressed air from being overcooled by the low-pressure stage heat recovery device 3 and the intercooler 4, regardless of the cooling power of the low-pressure stage heat recovery device 3. As a result, it is possible to suppress the generation of condensed water and prevent corrosion of the high-pressure stage compressor body 5. Furthermore, it is possible to avoid suppressing the cooling power of the low-pressure stage heat recovery device 3 (in other words, suppressing the amount of heat recovery) and avoiding an increase in the size of the water separator 22.

[0038] In the first and second embodiments, the coolant line 21 is described as including the bypass flow path 23 and the bypass valve 24 as a configuration for varying the cooling power of the intercooler 4, but this is not limiting. The coolant line 21 may include, for example, an on-off valve provided downstream of the intercooler 4, a bypass flow path that bypasses the on-off valve, and a throttle provided in the bypass flow path. In this modification, the control device 15 opens the on-off valve to increase the flow rate of the coolant in the intercooler 4 and increase the cooling power of the intercooler 4, and closes the on-off valve to decrease the flow rate of the coolant in the intercooler 4 and decrease the cooling power of the intercooler 4. Even in this modification, the same effects as described above can be obtained.

[0039] In the first and second embodiments, the water line 18 is illustrated as connecting the high-pressure stage heat recovery unit 6 and the low-pressure stage heat recovery unit 3 in series in that order, but this is not limiting. The water line 18 may connect the low-pressure stage heat recovery unit 3 and the high-pressure stage heat recovery unit 6 in series in that order, or may connect them in parallel.

[0040] In the first and second embodiments, the low-pressure stage heat recovery unit 3 and the high-pressure stage heat recovery unit 6 are illustrated as being configured so that compressed air and water flow in countercurrent directions, but this is not a limitation and the compressed air and water may flow in parallel directions. The intercooler 4 and the aftercooler 7 are illustrated as being configured so that compressed air and cooling water flow in countercurrent directions, but this is not a limitation and the compressed air and cooling water may flow in parallel directions. The oil cooler 12 is illustrated as being configured so that oil and cooling water flow in countercurrent directions, but this is not a limitation and the oil and cooling water may flow in parallel directions.

[0041] A third embodiment of the present invention will be described with reference to the drawings.

[0042] 5 is a diagram showing the configuration of an air compressor according to this embodiment. In this embodiment, parts equivalent to those in the above embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0043] The air compressor of this embodiment is driven by an electric motor 9 via a speed increasing device 8 and includes a compressor main body 31 that draws in and compresses air (gas) via an air filter 1 and an intake throttle valve 17, an oil separator 32 that separates oil from the compressed air discharged from the compressor main body 31, a compressed air line 33 that supplies the compressed air separated in the oil separator 32 to a demand destination, and an oil line 34 that supplies the oil separated in the oil separator 32 to the compressor main body 31 by the pressure difference between the oil separator 32 and the compressor main body 31. The compressed air line 33 has an aftercooler 7 that cools the compressed air and a pressure sensor 16 arranged downstream of the aftercooler 7.

[0044] The compressor body 31 includes, for example, a pair of screw rotors, a plurality of bearings that rotatably support the pair of screw rotors while they are in contact with and mesh with each other, and a casing that houses them. As the screw rotors rotate, working chambers formed in the tooth grooves of the screw rotors move and their volumes change. This causes air to be drawn in, compressed, and discharged as compressed air.

[0045] The compressor body 31 is configured to inject oil from an oil line 34 into the working chamber and also supply the oil to bearings, etc. This provides cooling, sealing, lubrication, and other effects.

[0046] The oil line 34 includes a heat recovery device 35, an oil cooler 36 disposed downstream of the heat recovery device 35, a bypass line 37 bypassing the heat recovery device 35 and the oil cooler 36, a temperature control valve (three-way valve) 38 disposed at a branch point of the bypass line 37, and an oil filter 13 disposed downstream of a junction point of the bypass line 37. The temperature control valve 38 adjusts the flow rate of the heat recovery device 35 and the oil cooler 36 and the flow rate of the bypass line 37 according to the temperature of the oil. This adjusts the temperature of the oil supplied to the compressor body 31.

[0047] Water is supplied to and discharged from the heat recovery device 35 via a water line 18, and the water is heated by heat exchange with oil. The hot water thus produced is effectively used for purposes such as preheating boiler feedwater or heat retention. In this embodiment, the flow control valve 20 is controlled based on the hot water temperature detected by a hot water temperature sensor 19, for example, to control whether or not water is supplied to the heat recovery device 35, or the flow rate of the water. In other words, the cooling power of the heat recovery device 35 is variably controlled.

[0048] Cooling water is supplied to and discharged from the oil cooler 36 through a cooling water line 21, and the oil is cooled by heat exchange with the cooling water.

[0049] As described above, the oil stored in the oil separator 32 is cooled in the heat recovery device 35 and the oil cooler 36. Therefore, depending on the cooling power of the heat recovery device 35, the oil may be supercooled. Although the bypass line 37 and the temperature control valve 38 are provided in this embodiment to prevent the oil from being supercooled, this alone may not be sufficient. The oil supplied to the compressor body 31 may supercool the compressed air, causing condensed water. This may increase the amount of condensed water contained in the oil stored in the oil separator 32, and the oil containing the condensed water may flow into the compressor body 31, causing corrosion inside the compressor body 31 and interfering with its operation.

[0050] Therefore, the air compressor of this embodiment is equipped with an on-off valve 39 provided downstream of the oil cooler 36 in the cooling water line 21, a bypass flow path 40 that bypasses the on-off valve 39, and a throttle 41 (more specifically, a throttle having a smaller flow path cross section than the on-off valve 39 in its open state) provided in the bypass flow path 40, as components for varying the cooling power of the oil cooler 36. The air compressor also includes a compressed air temperature sensor 42 (compressed gas temperature sensor) that detects the temperature of the compressed air (compressed gas) downstream of the compressor body 31, and a cooling water temperature sensor 26 that detects the temperature of the cooling water upstream of the oil cooler 36.

[0051] The control device 15 variably controls the cooling power of the oil cooler 36 by opening and closing the on-off valve 39 based on the detected values ​​of the compressed air temperature sensor 42 and the cooling water temperature sensor 26. Details of this control will be explained using Fig. 6. Fig. 6 is a flowchart showing the processing procedure of the control device 15 in this embodiment.

[0052] In step S31, the control device 15 acquires the detected value To of the compressed air temperature sensor 42 and the detected value Twc of the coolant temperature sensor 26. Then, the process proceeds to step S32, where the control device 15 determines whether the difference (To-Twc) between the detected value To of the compressed air temperature sensor 42 and the detected value Twc of the coolant temperature sensor 26 is less than a predetermined value ΔTomin.

[0053] The predetermined value ΔTomin is a value that is set based on the condition that the detection value To of the compressed air temperature sensor 42 becomes the condensation water generation limit temperature, calculated by assuming predetermined conditions (specifically, the temperature and humidity of the air upstream of the compressor body 31, the pressure of the compressed air downstream of the compressor body 31, etc.).

[0054] If the difference (To-Twc) is equal to or greater than the predetermined value ΔTomin, the process proceeds to step S33, where the control device 15 opens the on-off valve 39. This increases the flow rate of the cooling water in the oil cooler 36, thereby increasing the cooling power of the oil cooler 36. On the other hand, if the difference (To-Twc) is less than the predetermined value ΔTomin, the process proceeds to step S34, where the control device 15 closes the on-off valve 39. This reduces the flow rate of the cooling water in the oil cooler 36, thereby reducing the cooling power of the oil cooler 36.

[0055] As described above, in this embodiment, the cooling power of the oil cooler 36 is variably controlled by opening and closing the on-off valve 39 based on the detected values ​​of the compressed air temperature sensor 42 and the coolant temperature sensor 26. This makes it possible to prevent the oil from being overcooled by the heat recovery device 35 and the oil cooler 36, regardless of the cooling power of the heat recovery device 35. As a result, it is possible to suppress the generation of condensed water and prevent corrosion of the compressor body 31. Furthermore, it is possible to avoid suppression of the cooling power of the heat recovery device 35 (in other words, suppression of the amount of heat recovery).

[0056] A fourth embodiment of the present invention will be described with reference to the drawings.

[0057] 7 is a diagram showing the configuration of an air compressor according to this embodiment. In this embodiment, parts equivalent to those in the above embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0058] The air compressor of this embodiment is equipped with an air temperature sensor 27 and an air humidity sensor 28 that detect the temperature and humidity of the air upstream of the compressor main body 31, and a compressed air pressure sensor 43 (compressed gas pressure sensor) that detects the pressure of the compressed air (compressed gas) downstream of the compressor main body 31.

[0059] The control device 15 variably controls the cooling power of the oil cooler 36 by opening and closing the on-off valve 39 based on the detected values ​​of the compressed air temperature sensor 42, the air temperature sensor 27, the air humidity sensor 28, and the compressed air pressure sensor 43. Details of this control will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the processing procedure of the control device 15 in this embodiment.

[0060] In step S41, the control device 15 acquires the detection value To of the compressed air temperature sensor 42, the detection value Ta of the air temperature sensor 27, the detection value Ha of the air humidity sensor 28, and the detection value Po of the compressed air pressure sensor 43. Then, in step S42, the control device 15 calculates the upper limit temperature Tcl of the compressed air at which condensation occurs downstream of the compressor main body 31 (the condensation water occurrence limit temperature) based on the detection value Ta of the air temperature sensor 27, the detection value Ha of the air humidity sensor 28, and the detection value Po of the compressed air pressure sensor 43. Then, in step S43, the control device 15 determines whether the detection value To of the compressed air temperature sensor 42 is lower than the condensation water occurrence limit temperature Tcl.

[0061] If the detection value To of the compressed air temperature sensor 42 is equal to or higher than the condensation water generation limit temperature Tcl, the process proceeds to step S44, where the control device 15 opens the on-off valve 39. This increases the flow rate of the cooling water in the oil cooler 36 and increases the cooling power of the oil cooler 36. On the other hand, if the detection value To of the compressed air temperature sensor 42 is lower than the condensation water generation limit temperature Tcl, the process proceeds to step S45, where the control device 15 closes the on-off valve 39. This reduces the flow rate of the cooling water in the oil cooler 36 and decreases the cooling power of the oil cooler 36.

[0062] As described above, in this embodiment, the cooling power of the oil cooler 36 is variably controlled by opening and closing the on-off valve 39 based on the detected values ​​of the compressed air temperature sensor 42, the air temperature sensor 27, the air humidity sensor 28, and the compressed air pressure sensor 43. As a result, similar to the third embodiment, it is possible to prevent the oil from being overcooled by the heat recovery device 35 and the oil cooler 36, regardless of the cooling power of the heat recovery device 35. As a result, it is possible to suppress the generation of condensed water and prevent corrosion of the compressor body 31. Furthermore, it is possible to avoid suppression of the cooling power of the heat recovery device 35 (in other words, suppression of the amount of heat recovery).

[0063] In the third and fourth embodiments, the cooling water line 21 is described as including the on-off valve 39, the bypass flow path 40, and the throttle 41 as components for varying the cooling power of the oil cooler 36, but this is not limiting. The cooling water line 21 may include, for example, a bypass flow path that bypasses the oil cooler 36 and a bypass valve that opens and closes the bypass flow path. In this modification, the control device 15 closes the bypass valve to increase the flow rate of the cooling water in the oil cooler 36 and increase the cooling power of the oil cooler 36, and opens the bypass valve to decrease the flow rate of the cooling water in the oil cooler 36 and decrease the cooling power of the oil cooler 36. Even in this modification, the same effects as described above can be obtained.

[0064] In the first and second embodiments, the heat recovery unit 35 is illustrated as an example in which the compressed air and water flow in countercurrent directions, but this is not limited thereto and the compressed air and water may flow in parallel directions. The aftercooler 7 is illustrated as an example in which the compressed air and cooling water flow in countercurrent directions, but this is not limited thereto and the compressed air and cooling water may flow in parallel directions. The oil cooler 36 is illustrated as an example in which the oil and cooling water flow in countercurrent directions, but this is not limited thereto and the oil and cooling water may flow in parallel directions.

[0065] In the first to fourth embodiments, the heat recovery device has been described as heating water, but this is not limiting and a liquid other than water may be heated. In addition, the intercooler, aftercooler, or oil cooler has been described as supplying or discharging cooling water through a cooling water line, but this is not limiting and a cooling liquid other than cooling water may be supplied or discharged through a cooling liquid line.

[0066] Furthermore, in the first to fourth embodiments, the compressor body has been described as being of a screw type, but the present invention is not limited to this, and may be of a scroll type, for example.

[0067] Although the present invention has been described above with reference to an air compressor that compresses air, the present invention is not limited to this. In other words, the present invention may be applied to a gas compressor that compresses a gas other than air.

[0068] 2...Low-pressure stage compressor body, 3...Low-pressure stage heat recovery device, 4...Intercooler, 5...High-pressure stage compressor body, 15...Control device, 21...Cooling water line (coolant line), 23...Bypass flow path, 24...Bypass valve, 25...Compressed air temperature sensor (compressed gas temperature sensor), 26...Cooling water temperature sensor (coolant temperature sensor), 27...Air temperature sensor (gas temperature sensor), 28...Air humidity sensor (gas humidity sensor), 29...Compressed air pressure sensor (compressed gas pressure sensor), 31...Compressor body, 32...Oil separator, 35...Heat recovery device, 36...Oil cooler, 39...Open / close valve, 40...Bypass flow path, 41...Throttle, 42...Compressed air temperature sensor (compressed gas temperature sensor), 43...Compressed air pressure sensor (compressed gas pressure sensor)

Claims

1. A gas compressor comprising a low-pressure stage compressor main body that compresses gas, a heat recovery unit that heats a liquid using the heat of the compressed gas discharged from the low-pressure stage compressor main body, an intercooler that further cools the compressed gas cooled by the heat recovery unit, and a high-pressure stage compressor main body that further compresses the compressed gas cooled by the intercooler, characterized in that the gas compressor also comprises: a compressed gas temperature sensor that detects the temperature of the compressed gas downstream of the intercooler and upstream of the high-pressure stage compressor main body, and a control device that variably controls the cooling power of the intercooler based on the detection value of the compressed gas temperature sensor.

2. A gas compressor as claimed in claim 1, comprising: a cooling liquid line for supplying and discharging cooling liquid to the intercooler; a bypass flow path provided in the cooling liquid line for bypassing the intercooler; and a bypass valve for opening and closing the bypass flow path, wherein the control device variably controls the cooling power of the intercooler by opening and closing the bypass valve based on the detection value of the compressed gas temperature sensor.

3. A gas compressor as claimed in claim 2, further comprising a coolant temperature sensor for detecting the temperature of the coolant upstream of the intercooler, and wherein the control device closes the bypass valve when the difference between the detection value of the compressed gas temperature sensor and the detection value of the coolant temperature sensor is equal to or greater than a predetermined value, and opens the bypass valve when the difference between the detection value of the compressed gas temperature sensor and the detection value of the coolant temperature sensor is less than the predetermined value.

4. A gas compressor as claimed in claim 2, comprising a gas temperature sensor and a gas humidity sensor which detect the temperature and relative humidity of the gas upstream of the low pressure stage compressor main body, and a compressed gas pressure sensor which detects the pressure of the compressed gas downstream of the intercooler and upstream of the high pressure stage compressor main body, wherein the control device calculates a condensation water generation limit temperature based on the detection values ​​of the gas temperature sensor, the gas humidity sensor and the compressed gas pressure sensor, closes the bypass valve when the detection value of the compressed gas temperature sensor is equal to or higher than the condensation water generation limit temperature, and opens the bypass valve when the detection value of the compressed gas temperature sensor is less than the condensation water generation limit temperature.

5. A gas compressor comprising a compressor body which compresses gas while injecting oil into a working chamber, an oil separator which separates oil from the compressed gas discharged from the compressor body, a heat recovery device which heats a liquid using the heat of the oil separated in the oil separator, and an oil cooler which cools the oil whose heat has been recovered in the heat recovery device and supplies it to the compressor body, characterized in that the gas compressor further comprises: a compressed gas temperature sensor which detects the temperature of the compressed gas downstream of the compressor body; and a control device which variably controls the cooling power of the oil cooler based on the detection value of the compressed gas temperature sensor.

6. A gas compressor as claimed in claim 5, further comprising: a cooling liquid line for supplying and discharging cooling liquid to and from said oil cooler; an on-off valve provided in said cooling liquid line downstream of said oil cooler; a bypass flow path for bypassing said on-off valve; and a throttle provided in said bypass flow path, wherein said control device variably controls the cooling power of said oil cooler by opening and closing said on-off valve based on the detection value of said compressed gas temperature sensor.

7. A gas compressor as described in claim 6, further comprising a coolant temperature sensor for detecting the temperature of the coolant upstream of the oil cooler, and wherein the control device opens the on-off valve when the difference between the detection value of the compressed gas temperature sensor and the detection value of the coolant temperature sensor is equal to or greater than a predetermined value, and closes the on-off valve when the difference between the detection value of the compressed gas temperature sensor and the detection value of the coolant temperature sensor is less than the predetermined value.

8. A gas compressor as claimed in claim 6, comprising a gas temperature sensor and a gas humidity sensor which detect the temperature and relative humidity of the gas upstream of the compressor body, and a compressed gas pressure sensor which detects the pressure of the compressed gas downstream of the compressor body, wherein the control device calculates a condensation water generation limit temperature based on the detection values ​​of the gas temperature sensor, the gas humidity sensor and the compressed gas pressure sensor, opens the on-off valve when the detection value of the compressed gas temperature sensor is equal to or higher than the condensation water generation limit temperature, and closes the on-off valve when the detection value of the compressed gas temperature sensor is less than the condensation water generation limit temperature.

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