Air compressor and heat utilization system

Abstract

Provided is an air compressor which exhibits both functions of heat dissipation and heat recovery, and which can continue to operate without any operation restriction or the like even when the ambient temperature is very high. An air compressor provided with a compression mechanism that compresses supplied air to generate compressed air, the air compressor being provided with: a heat dissipation mechanism that performs a heat dissipation operation that dissipates heat generated during the compression process by heat exchange with cooling air or cooling water and cools the air compressor; a heat recovery mechanism that performs a heat recovery operation that recovers heat generated in the compression process and cools the air compressor by heat exchange with the use water; and a temperature detection unit that detects the temperature of the fluid associated with the temperature of the air compressor, and when the detected temperature obtained by the temperature detection unit exceeds a predetermined value, the heat recovery operation is performed preferentially than the heat dissipation operation when the air compressor is cooled.

Description

Technical Field

[0001] The present invention relates to an air compressor and a heat utilization system including the air compressor. Background Art

[0002] Conventionally, an air compressor that compresses supplied air to generate compressed air has been widely used. In such an air compressor, the temperature of the machine itself rises due to compression heat, frictional heat, etc. generated during the compression of air. Therefore, a heat dissipation mechanism for cooling the machine itself using cooling air or cooling water is provided, and by performing necessary cooling, thermal stress generation in the machine itself caused by overheating is prevented. If thermal stress is repeatedly generated, fatigue damage and creep damage of the compressor body will occur.

[0003] However, in a situation where the ambient temperature around the air compressor is quite high (for example, when it significantly exceeds the operating temperature range determined by the specifications of the air compressor), it is difficult to sufficiently lower the temperature of the machine itself only by performing the heat dissipation operation, and in this state, an emergency stop based on abnormal detection may occur. As an existing example that can somewhat eliminate such a problem, for example, Patent Documents 1 and 2 disclose an air compressor that suppresses temperature rise by restricting the rotational speed (operation restriction) of the compressor body in a high ambient temperature situation, and can preferentially continue operation.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-537423

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-525423 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] According to the above-described prior example, even in a situation where the ambient temperature is quite high, it is possible to continue operation itself, but due to the operation restriction, problems such as a decrease in the compressed air generation capacity occur. Therefore, it is preferable to minimize such operation restriction.

[0010] However, as an air compressor, there is also a type that has both a heat dissipation mechanism capable of cooling the machine itself by diffusion of heat generated during the compression process and a heat recovery mechanism capable of cooling the machine itself by recovery of heat generated during the compression process, and can execute either the heat dissipation or heat recovery operation according to the situation. In such an air compressor, it is desired to exhibit the characteristics of having both the heat dissipation and heat recovery functions, and to be able to continue operation without the above-described operation restriction even in a situation where the ambient temperature is quite high.

[0011] In view of the above problems, an object of the present invention is to provide an air compressor and a heat utilization system using the air compressor. The air compressor exhibits the characteristics of having two functions of heat dissipation and heat recovery, and can continue to operate without operation restrictions even in a situation where the ambient temperature is quite high.

[0012] Means for Solving the Problems

[0013] The air compressor of the present invention includes a compression mechanism that compresses the supplied air to generate compressed air. Among them, the air compressor includes: a heat dissipation mechanism that performs a heat dissipation operation of diffusing the heat generated during the compression process and cooling the air compressor through heat exchange with cooling air or cooling water; a heat recovery mechanism that performs a heat recovery operation of recovering the heat generated during the compression process and cooling the air compressor through heat exchange with the used water; and a temperature detection unit that detects the temperature of a fluid that has a correlation with the temperature generation of the air compressor. When the detected temperature obtained by the temperature detection unit exceeds a specified value, when performing the operation of cooling the air compressor, the heat recovery operation is preferentially performed compared to the heat dissipation operation. According to this structure, the characteristics of having two functions of heat dissipation and heat recovery can be exhibited, and even in a situation where the ambient temperature is quite high, it can continue to operate without operation restrictions and the like.

[0014] As the above structure, more specifically, it can also be set to the following structure: The air compression mechanism supplies the used water heated in the heat recovery operation to a load device that uses the used water. When performing the operation of cooling the air compressor, it is determined which one of the heat dissipation operation and the heat recovery operation is preferably performed according to the presence or absence of the demand for the used water in the load device. Among them, when the detected temperature exceeds the specified value, as the operation of cooling the air compressor, the heat recovery operation is preferentially performed regardless of the presence or absence of the demand.

[0015] As the above structure, more specifically, it can also be set to the following structure: The air compression mechanism supplies the used water heated in the heat recovery operation to a load device that uses the used water. When performing the operation of cooling the air compressor, the heat recovery operation is performed when there is a demand for the used water in the load device, and the heat dissipation operation is performed when there is no such demand. Among them, when the detected temperature exceeds the specified value, as the operation of cooling the air compressor, the heat recovery operation is performed regardless of the presence or absence of the demand.

[0016] As the above structure, more specifically, it may also be set as the following structure: The load device is a boiler device that heats the used water to generate steam. In addition, the heat utilization system of the present invention includes the air compressor having the above structure and the load device, and the load device sends a signal indicating the demand for the used water to the air compressor, and the air compressor determines the presence or absence of the demand based on the received signal.

[0017] Advantages of the Invention

[0018] According to the air compressor of the present invention, it can exhibit the characteristics of having both heat dissipation and heat recovery functions, and can continue to operate without action restrictions even under the condition of a relatively high ambient temperature. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of the heat utilization system of the first embodiment.

[0020] Figure 2 It is a flowchart related to the decision process of the execution mode of the cooling operation.

[0021] Figure 3 It is an explanatory diagram of the components related to the heat recovery operation of the first embodiment.

[0022] Figure 4 It is a schematic structural diagram of the air compressor of the second embodiment.

[0023] Figure 5 It is a schematic structural diagram of the air compressor of the third embodiment.

[0024] Figure 6 It is a schematic structural diagram of the air compressor of the fourth embodiment.

[0025] Description of Reference Numerals:

[0026] 1 Heat utilization system

[0027] 1a Air compressor

[0028] 1b Load device

[0029] 1ba Water supply tank

[0030] 1bb Boiler body

[0031] 11 Compression mechanism

[0032] 12 Heat dissipation mechanism

[0033] 13 Heat recovery mechanism

[0034] 14 Temperature detection unit

[0035] 15 Control Unit

[0036] 20 Heat Exchanger

[0037] 21 Pump

[0038] 22 Liquid Reservoir

[0039] 23 First Control Valve

[0040] 24 Buffer Tank

[0041] 25 Second Control Valve

[0042] 26 Hot Water Outlet Temperature Sensor

[0043] 111 Compressor Main Body

[0044] 130 Heat Recovery Oil Cooler (Heat Recovery Mechanism)

[0045] 140 Cooling Oil Cooler for Heat Dissipation (Heat Dissipation Mechanism)

[0046] 151 Bypass Valve

[0047] 171 Pump

[0048] 174 Flow Control Valve

[0049] 203 Compressor Main Body

[0050] 206 Water Cooler (Heat Recovery Mechanism, Heat Dissipation Mechanism)

[0051] 235 Switching Unit

[0052] 236 Flow Control Valve

[0053] 237 Return Valve

[0054] 238 Radiator (Heat Dissipation Mechanism)

[0055] 240 Pump

[0056] 311 First Compressor Main Body

[0057] 312 Second Compressor Main Body

[0058] 313 Intercooler (Heat Dissipation Mechanism)

[0059] 332 Flow Control Valve

[0060] 351 First Heat Recovery Heat Exchanger (Heat Recovery Mechanism)

[0061] 352 First Stop Valve

[0062] 353 First Bypass Valve Detailed Implementation Manner

[0063] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings.

[0064] 1. First Embodiment

[0065] First, the first embodiment will be described. Figure 1 It is a schematic structural diagram of the heat utilization system of the first embodiment. As shown in this figure, the heat utilization system 1 includes an air compressor 1a and a load device 1b.

[0066] The air compressor 1a includes a compression mechanism 11, a heat recovery mechanism 12, a heat dissipation mechanism 13, a temperature detection unit 14, and a control unit 15. The compression mechanism 11 is a mechanism that compresses the air supplied from the outside to generate compressed air and supplies the generated compressed air to various pneumatic machines and the like. The compression mechanism 11 is composed of a compressor main body (for example, a screw-type compressor main body) and an electric motor that drives the compressor main body.

[0067] The air compressor 1a has a heat dissipation mechanism 12 and a heat recovery mechanism 13 as mechanisms for performing a cooling operation to cool the machine itself (the air compressor 1a). In the air compressor 1a, the temperature rises mainly due to the compression heat, friction heat, etc. generated when the compression mechanism 11 compresses the air. Therefore, the overheating of the air compressor 1a is suppressed by performing the cooling operation. It should be noted that "cooling the machine itself" in this application means a concept that includes not only the method of cooling the air compressor itself but also the method of cooling the fluid existing in the air compressor (for example, the lubricating oil in an oil-injected air compressor, the added water in a water-added air compressor, the intermediate compressed air in an oil-free air compressor, etc.).

[0068] The heat dissipation mechanism 12 is configured to perform a heat dissipation operation of diffusing the heat generated during the compression process through heat exchange with cooling air or cooling water and cooling the machine itself. The air-cooled type in the heat dissipation mechanism 12 has a heat exchanger for the fluid containing the compression heat and the cooling air, and continuously supplies the cooling air to the heat transfer surface of the heat exchanger by a blowing fan. The water-cooled type in the heat dissipation mechanism 12 has a heat exchanger for the fluid containing the compression heat and the cooling water, and uses a circulation pump to continuously circulate the cooling water on the heat transfer surface of the heat exchanger. The cooling water heated in the heat exchanger is sent to a cooling tower for heat dissipation to the air, and the cooled cooling water returns to the heat exchanger again.

[0069] On the other hand, the heat recovery mechanism 13 is configured to perform a heat recovery operation of recovering the heat generated during the compression process through heat exchange with the service water and cooling the machine itself. The heat recovery mechanism 13 can receive the supply of the service water, and the service water heat-recovered through heat exchange is sent to the load device 1b. It should be noted that the service water refers to the water used in the enterprise site along with the production of goods or the provision of services.

[0070] The temperature detection unit 14 is composed of a temperature sensor and is configured to be able to detect the temperature of a fluid that has a correlation with the temperature generation of the present machine (mainly the compressor body). The fluid to be detected for temperature is classified into a fluid that affects the temperature of the present machine and a fluid that is affected by the temperature of the present machine. A typical fluid that affects the temperature of the present machine is the ambient air around the air compressor 1a. If the ambient temperature around the air compressor 1a rises, the temperature of the compressor body rises when the compression mechanism 11 operates due to this influence. Therefore, the temperature detection unit 14 is configured to detect the ambient temperature around the air compressor 1a (for example, the intake and exhaust temperatures of the housing).

[0071] On the other hand, there are various fluids that are affected by the temperature of the present machine. A representative one is the discharged air from the compressor body. If the temperature of the compressor body rises, the discharged temperature of the compressed air rises due to this influence. Therefore, the temperature detection unit 14 is configured to detect the discharged temperature of the compressed air from the compressor body.

[0072] In the case where the air compressor 1a is equipped with a water-cooled heat dissipation mechanism 12, the fluid to be detected for temperature can also be the cooling water supplied to the cooling tower. That is, the temperature detection unit 14 is configured to detect the supply temperature of the cooling water flowing from the heat exchanger to the cooling tower.

[0073] In addition, in the case where the air compressor 1a is an oil-injected air compressor, the fluid to be detected for temperature can also be the lubricating oil discharged from the compressor body together with the compressed air. For example, the temperature detection unit 14 is configured to detect the temperature of the lubricating oil separated by the oil separator. In addition, in the case where the air compressor 1a is a water-added air compressor, the fluid to be detected for temperature can also be the added water discharged from the compressor body together with the compressed air. For example, the temperature detection unit 14 is configured to detect the temperature of the added water separated by the water separator. In addition, in the case where the air compressor 1a is an oil-free air compressor, the fluid to be detected for temperature can also be the cooling medium (for example, cooling oil) circulating in the compressor body and the sheath of the electric motor. For example, the temperature detection unit 14 is configured to detect the temperature of the cooling medium flowing out of the sheath.

[0074] The control unit 15 controls each part of the air compressor 1a to function normally. The control actions performed by the control unit 15 also include determining the execution mode of the cooling action according to the current situation and controlling the cooling action in the determined execution mode.

[0075] The load device 1b uses the service water heated through the heat exchange operation in the heat recovery mechanism 13. As a typical example of the load device 1b, a boiler device that heats the service water to generate steam can be cited, but the type of the load device 1b is not limited thereto, and various production devices can also be used. It should be noted that in the load device 1b, for example, when the service water stored in the tank storing the service water has reached the upper limit, there is no need for the service water, and there is no need to supply the heat-recovered service water to the load device 1b.

[0076] In consideration of this, the load device 1b of the present embodiment continuously sends a demand notification signal indicating the presence or absence of the demand for the service water to the control unit 15 of the air compressor 1a. Thereby, the control unit 15 receives the demand notification signal, discriminates the presence or absence of the demand for the service water in the load device 1b based on the demand notification signal, and can more appropriately control the execution mode of the cooling operation. It should be noted that the control unit 15 can discriminate the presence or absence of the demand for the service water in the load device 1b based on information other than the demand notification signal.

[0077] Next, with reference to Figure 2 the flowchart shown, the decision process of the execution mode of the cooling operation performed by the control unit 15 will be described. It should be noted that this decision process is periodically repeated at a predetermined time interval, for example.

[0078] First, the control unit 15 acquires the information of the latest detected temperature T of the temperature detection unit 14 (step S1). And if the detected temperature T does not exceed the specified value α (No in step S2), the control unit 15 performs a normal cooling operation corresponding to the current situation (step S3).

[0079] As the processing in step S3, in the example of the first embodiment, the control unit 15 identifies the presence or absence of the demand for the service water in the load device 1b based on the latest demand notification signal received from the load device 1b. And when there is such a demand, the control unit 15 preferentially performs the heat recovery operation as the cooling operation, and conversely, when there is no such demand, the control unit 15 preferentially performs the heat dissipation operation as the cooling operation. It should be noted that when the execution mode of the cooling operation is determined by selecting either the heat recovery operation or the heat dissipation operation, when there is such a demand, only the heat recovery operation is performed as the cooling operation, and conversely, when there is no such demand, only the heat dissipation operation is performed as the cooling operation.

[0080] It should be noted that, as for the specific method of performing the heat recovery action as a cooling action, typically, there can be cited a method of performing only the heat recovery action without accompanying the heat dissipation action. However, the method of performing the heat recovery action as a cooling action is not limited to this, and the heat dissipation action can also be performed in parallel with the heat recovery action as an auxiliary. For example, the heat recovery action can also be mainly performed as the cooling action, and when it is difficult to obtain a sufficient cooling effect only by the heat recovery action, the heat dissipation action can be performed as an auxiliary.

[0081] In addition, as for the specific method of giving priority to the heat dissipation action as the cooling action, typically, there can be cited a method of performing only the heat dissipation action without accompanying the heat recovery action. However, the method of giving priority to the heat dissipation action as the cooling action is not limited to this, and the heat recovery action may be performed in parallel with the heat dissipation action as an auxiliary. For example, the heat dissipation action may be mainly performed as the cooling action, and when it is difficult to obtain a sufficient cooling effect only by the heat dissipation action, the heat recovery action may be performed as an auxiliary.

[0082] On the other hand, if the detected temperature T exceeds the predetermined value α (Yes in step S2), the control unit 15 prioritizes the heat recovery operation as the cooling operation (step S3). That is, in this case, the heat recovery operation is forcibly prioritized as the cooling operation regardless of whether there is a demand for water use in the load device 1b. It should be noted that when the execution mode of the cooling operation is determined by selecting between the heat recovery operation and the heat dissipation operation, only the heat recovery operation is performed as the cooling operation.

[0083] According to the above series of decision processes (steps S1 to S5), in normal times (when the detected temperature T does not exceed the predetermined value α), the air compressor 1a can perform cooling operations corresponding to the current situation by taking into account the characteristics of both heat dissipation and heat recovery. In particular, in the example of the first embodiment, it is possible to perform appropriate cooling operations that take into account the presence or absence of water use demand in the load device 1b at this time.

[0084] That is, by giving priority to the heat recovery operation when there is a demand for water, the water used after heat recovery can be actively supplied to the load device 1b, and the demand for water used can be met as much as possible. Conversely, by giving priority to the heat dissipation operation when there is no demand for water used, it is possible to prevent excessive supply of water used to the load device 1b, and it is also possible to suppress overflow of the water tank in the load device 1b.

[0085] However, when the temperature of the fluid that is correlated with the temperature of the unit is high (when the detected temperature T exceeds the specified value α), the heat recovery action is prioritized as the cooling action regardless of whether there is a demand for water use in the load device 1b. That is, at high temperatures, in order to prevent the generation of thermal stress in the air compressor 1a caused by overheating, the cooling of the unit is required to be as strong as possible. Therefore, in this case, as a cooling action, the heat recovery action with a higher cooling effect than the heat dissipation action is forcibly prioritized, and the generation of thermal stress in the air compressor 1a is prevented as much as possible.

[0086] The heat dissipation mechanism 12 diffuses the heat generated during the compression process into the atmosphere, regardless of whether it is an air-cooled or water-cooled type. Therefore, if the surrounding air becomes high temperature, the cooling effect of this unit is relatively reduced. On the other hand, the water used (for example, tap water, groundwater) supplied to the heat recovery mechanism 13 is lower in temperature than the surrounding air unless it is water that has been stagnant in a water tank or pipe exposed to direct sunlight for a long time, so a stronger cooling effect than the heat dissipation mechanism 12 can be obtained.

[0087] As described above, the air compressor 1a has the characteristics of having both heat dissipation and heat recovery functions, and can continue to operate without being accompanied by action restrictions such as limiting the rotation speed of the compressor even when the ambient temperature is quite high. It should be noted that the predetermined value α (a temperature corresponding to the threshold value at normal time and high temperature) is preferably set to an appropriate value so as to effectively prevent the generation of thermal stress in the air compressor 1a caused by overheating and not to give unnecessary priority to the heat recovery action.

[0088] Figure 3 A more specific structural example of the main components related to the heat recovery operation in the first embodiment is shown. The heat recovery mechanism 12 of the air compressor 1a shown in the figure has a heat exchanger 20, a pump 21, a liquid reservoir 22, a first control valve 23, and a water line L10. In addition, as other peripheral elements, there are a buffer tank 24, a second control valve 25, a hot water temperature sensor 26, and a feed water line L20. In addition, the load device 1b has a water supply tank 1ba and a boiler body 1bb.

[0089] like Figure 3 As shown, the working water line L10 is connected to the water supply tank 1ba via the pump 21, the heat exchanger 20 and the first control valve 23 from the buffer tank 24. In the working water line L10, the accumulator 22 is arranged between the pump 21 and the heat exchanger 20, and the outlet hot water temperature sensor 26 is arranged between the first control valve 23 and the water supply tank 1ba.

[0090] In addition, one end of the makeup water line L20 is connected to position P1 between the liquid reservoir 22 and the heat exchanger 20 in the service water line L10, and the other end is connected to position P2 between the hot water outlet temperature sensor 26 and the water supply tank 1ba in the service water line L10. A second regulating valve 25 is provided at an intermediate position of the makeup water line L20.

[0091] The buffer tank 24 is appropriately supplied with makeup water from the outside, and stores this makeup water as service water Wa. The supply of makeup water to the buffer tank 24 is controlled by the control unit 15 for the water level so that the storage amount of the service water Wa in the buffer tank 24 is within a specified range.

[0092] The heat exchanger 20 is configured to perform heat exchange (including indirect heat exchange via a medium) between the service water Wa supplied from the service water line L10 and the compression mechanism 11 etc. in the present machine (air compressor 1a). Thereby, when the service water Wa is supplied to the heat exchanger 20, a heat recovery operation capable of cooling the present machine is performed.

[0093] The first control valve 23 can adjust the opening degree by the control unit 15, and functions to be able to adjust the flow rate of the service water Wa in the service water line L10. When the first control valve 23 is opened in a state where the pump 21 is operating, the service water Wa is supplied to the heat exchanger 20, a heat recovery operation for cooling the present machine is performed, and the service water Wa that has undergone heat recovery in the heat exchanger 20 is supplied to the water supply tank 1ba.

[0094] The second control valve 25 can be controlled to open and close by the control unit 15. If the second control valve 25 is opened in a state where the pump 21 is operating, the service water Wa that has not passed through the heat exchanger 20 (service water Wa that has not undergone heat recovery) is supplied to the water supply tank 1ba.

[0095] It should be noted that the load device 1b supplies the service water Wa stored in the water supply tank 1ba to the boiler main body 1bb as boiler feed water, and functions as a boiler device that generates steam by heating the service water Wa in the boiler main body 1bb. The load device 1b monitors the storage amount of the service water Wa in the water supply tank 1ba based on a detection signal from a water level sensor (not shown), and if this storage amount is lower than a specified reference value (water reduction value), it sends a demand notification signal indicating the demand for the service water Wa to the control unit 15, and if this storage amount reaches the upper limit value (full water value), it sends a demand notification signal indicating no demand for the service water Wa to the control unit 15. The control unit 15 receives this demand notification signal and can recognize the demand for the service water Wa in the load device 1b.

[0096] When the water level of the service water Wa is at the reference value (water reduction value) and the upper limit value (full water value), a sufficient difference is set for the storage amount. When the steam usage is large and the boiler main body 1bb operates at a high load, the consumption flow rate of the service water Wa also increases, so the frequency of the water level reaching the upper limit value is rare. Therefore, even if the heat recovery operation is performed in a situation where there is no demand for the service water Wa, it is possible to avoid the occurrence of overflow in the water supply tank 1ba and waste the service water Wa. On the other hand, when the steam usage is small and the boiler main body 1bb operates at a low load, the consumption flow rate of the service water Wa also decreases, so the frequency of the water level reaching the upper limit value increases. However, when the boiler main body 1bb operates at a low load, the operating rate of most production equipment is low, and the consumption flow rate of compressed air is likely to decrease. That is, in a situation where the operating rate of the air compressor 1a decreases, the situation where forced cooling of the air compressor 1a is required is short-lived. Therefore, when the heat recovery operation is performed in a situation where there is no demand for the service water Wa, even if an overflow occurs in the water supply tank 1ba, it is only temporary.

[0097] When the control unit 15 performs the heat recovery operation, it operates the pump 21 and controls the first control valve 23 to an open state. Thereby, the service water Wa is supplied to the heat exchanger 20, and the heat recovery operation is performed. In addition, the cooling degree of the machine during the heat recovery operation can be adjusted by changing the flow rate of the service water Wa in the heat exchanger 20 by controlling the opening degree of the first control valve 23. It should be noted that the control unit 15 can also control the opening degree of the first control valve 23 so that the detected temperature of the hot water temperature sensor 26 becomes the target temperature (that is, the service water Wa supplied to the water supply tank 1ba is kept at the required temperature). The service water Wa used for heat exchange in the heat exchanger 20 is supplied to the water supply tank 1ba, but the water supply flow rate can be temporarily increased for the water supply tank 1ba whose storage amount has reached the lower limit value. In this case, the second control valve 25 is controlled to an open state so that the service water Wa is further supplied to the water supply tank 1ba via the makeup water line L20.

[0098] On the other hand, when the control unit 15 does not perform the heat recovery operation, it controls the first control valve 23 to a closed state. Thereby, the service water Wa is not supplied to the heat exchanger 20, so the heat recovery operation is not performed. However, even in this case, when a cooling operation is required, the heat dissipation operation of the heat dissipation mechanism 12 can be performed. It should be noted that even if the first control valve 23 is closed, the control unit 15 can supply the service water Wa that does not pass through the heat exchanger 20 to the water supply tank 1ba emergently by controlling the second control valve 25 to an open state. When the service water Wa is not supplied to the water supply tank 1ba, the control unit 15 controls both the first control valve 23 and the second control valve 25 to a closed state.

[0099] As described above, the air compressor 1a is an air compressor having a compression mechanism 11 that compresses the supplied air to generate compressed air. The air compressor 1a includes: a heat dissipation mechanism 12 that performs a heat dissipation operation of diffusing the heat generated during the compression process and cooling the air compressor through heat exchange with cooling air or cooling water; a heat recovery mechanism 13 that performs a heat recovery operation of recovering the heat generated during the compression process and cooling the machine through heat exchange with water used; and a temperature detection unit 14 that detects the temperature of a fluid having a correlation with the temperature generation of the air compressor. Further, when the detected temperature T obtained by the temperature detection unit 14 exceeds a specified value α, during the cooling operation of cooling the air compressor, the heat recovery operation is preferentially performed compared to the heat dissipation operation. Therefore, the characteristics of having both heat dissipation and heat recovery functions can be exhibited, and even in a situation where the ambient temperature is quite high, the operation can continue without accompanying operation restrictions and the like.

[0100] More specifically, when performing the cooling operation of the air compressor 1a, it is determined which of the heat dissipation operation and the heat recovery operation is preferentially performed based on the presence or absence of the demand for the water used in the load device 1b. When the detected temperature T exceeds the specified value α, as the cooling operation, the heat recovery operation is preferentially performed regardless of the presence or absence of this demand. That is, when performing the cooling operation, the heat recovery operation is performed when there is this demand, the heat dissipation operation is performed when there is no such demand, and when the detected temperature T exceeds the specified value α, as the cooling operation, the heat recovery operation is performed regardless of the presence or absence of the demand.

[0101] As described above, the first embodiment has been described, but the specific form of the air compressor 1a is not limited to the first embodiment, and various forms having both the heat dissipation mechanism 12 and the heat recovery mechanism 13 can be adopted. Hereinafter, other specific forms of the air compressor 1a will be described by taking the second to fourth embodiments as examples.

[0102] 2. Second Embodiment

[0103] Next, the second embodiment will be described. In the following description, the focus is on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. In the air compressor 1a of the second embodiment, it also includes a compression mechanism 11, a heat dissipation mechanism 12, a heat recovery mechanism 13, a temperature detection unit 14, and a control unit 15. The temperature detection unit 14 is disposed, for example, inside the housing of the air compressor 1a to detect the temperature of the external air taken in for intake and ventilation.

[0104] Figure 4Schematically shows the structure of the air compressor 1a (oil supply type air compressor) of the second embodiment. As shown in this figure, the air compressor 1a includes a compression mechanism 11, an oil separator 120, a heat recovery oil cooler 130, and a heat dissipation oil cooler 140.

[0105] In addition, the air compressor 1a includes: a first air supply line L110 that allows the compressed air ejected from the compression mechanism 11 to flow into the oil separator 120; a second air supply line L120 that is connected to the gas phase part of the oil separator 120; an oil return line L130 that is connected to the liquid phase part of the oil separator 120 and returns the lubricating oil to the compressor 110; a first bypass line L131 that bypasses the heat dissipation oil cooler 140 in the oil return line L130; and a second bypass line L132 that bypasses the heat recovery oil cooler 130 and the heat dissipation oil cooler 140 in the oil return line L130. In addition, an air introduction line L140 for introducing air into the compression mechanism 11 is provided.

[0106] The compressor main body 111 constituting the compression mechanism 11 is, for example, a screw type. By driving an electric motor 112 connected to the drive shaft of the compressor main body 111, external air is sucked in and adiabatically compressed to generate compressed air Aa, which is ejected. The compressor main body 111 is oil-cooled, and by introducing lubricating oil Oa together with the supply air, the screw rotor is cooled, that is, the compression heat is removed.

[0107] Connected to the discharge port of the compressor main body 111 is a first air supply line L110 through which the compressed air Aa ejected from the compressor main body 111 flows. Connected to the downstream side of the first air supply line L110 is an oil separator 120 that separates lubricating oil from the compressed air.

[0108] Connected to the gas phase part of the oil separator 120 is a second air supply line L120 through which the compressed air Ab after gas-liquid separation flows. On the other hand, connected to the liquid phase part of the oil separator 120 is an oil return line L130 for returning the lubricating oil Oa after gas-liquid separation to the intake side of the compressor main body 111. Provided in the liquid phase part of the oil separator 120 is a lubricating oil temperature sensor 121 for measuring the lubricating oil temperature To of the lubricating oil Oa after gas-liquid separation.

[0109] On the oil return line L130, a temperature regulating valve 153, a heat recovery oil cooler 130, and a heat dissipation oil cooler 140 are provided in sequence from the upstream side.

[0110] A second bypass line L132 that bypasses the lubricating oil Oa with respect to the heat recovery oil cooler 130 and the heat dissipation oil cooler 140 is connected to the branch port of the three-way valve that constitutes the temperature control valve 153. The temperature control valve 153 adjusts the flow rate ratio of the oil supply to the heat recovery oil cooler 130 and the oil supply to the second bypass line L132 according to the lubricating oil temperature of the lubricating oil Oa after gas-liquid separation by the oil separator 120.

[0111] The heat recovery oil cooler 130 is a heat exchanger for recovering the compression heat of the lubricating oil Oa flowing in the oil return line L130. A service water line L150 through which the service water Wa flows is connected to the heat recovery oil cooler 130. The service water line L150 includes a primary side line L151 through which the service water Wa before being heated by the heat recovery oil cooler 130 flows and a secondary side line L152 through which the service water Wa after being heated by the heat recovery oil cooler 130 flows.

[0112] A pump 171, a water treatment device 172, a flow sensor 173, and a heat recovery air cooler 180 (details will be described later) are sequentially provided in the primary side line L151 of the service water line L150 from the upstream side. In addition, a flow control valve 174 and a hot water outlet temperature sensor 175 are sequentially provided in the secondary side line L152 of the service water line L150 from the upstream side.

[0113] The pump 171 and the flow control valve 174 are connected to the control unit 15 and are driven by command signals from the control unit 15. The water treatment device 172 performs treatments such as removing impurities. The water treatment device 172 includes, for example, a hard water softening device, a water supply filter, etc. The flow sensor 173 detects the flow rate of the service water Wa passing through. The flow rate of the service water detected by the flow sensor 173 is sent to the control unit 15. The hot water outlet temperature sensor 175 detects the temperature of the service water Wa after passing through the heat recovery oil cooler 130.

[0114] The pump 171 and the flow control valve 174 of the present embodiment function as a water flow switching unit that switches between the water flow execution state and the water flow stop state for the heat recovery oil cooler 130. In addition, this water flow switching unit also has a water flow adjustment function for adjusting the water flow rate to the heat recovery oil cooler 130.

[0115] The service water Wa heated by the heat recovery oil cooler 130 is supplied to the load device 1b through the secondary side line L152 of the service water line L150. In this way, the air compressor 1a of the present embodiment can heat the service water Wa by using the heat recovery oil cooler 130 to recover the compression heat generated in the compressor main body 111 and supply the hot water to the load device 1b.

[0116] On the downstream side of the heat recovery oil cooler 130 in the oil return line L130, a heat dissipation oil cooler 140 is provided. The heat dissipation oil cooler 140 includes a heat exchanger 141 (a heat exchange core composed of an aggregate such as plate fins and finned tubes), a cooling fan 142, and a fan motor 143 for rotating the cooling fan 142. By rotating the cooling fan 142, heat exchange is performed between the air blown by the cooling fan 142 and the lubricating oil Oa flowing inside the heat exchanger 141, generating lubricating oil Oa at a temperature suitable for cooling the compressor main body 111.

[0117] It should be noted that it is also possible to adopt a method of simultaneously cooling other parts of the air compressor 1a (for example, the control tank) or performing ventilation (for example, inside the housing) by the cooling fan 142. In this case, during the operation of the compressor main body 111, the cooling fan 142 is usually controlled at a speed not lower than the minimum speed.

[0118] The lubricating oil Oa flowing through the heat recovery oil cooler 130 and the heat dissipation oil cooler 140 returns to the inside of the compressor main body 111 again through the oil return line L130.

[0119] A bypass branch portion 160 is provided between the heat recovery oil cooler 130 and the heat dissipation oil cooler 140 in the oil return line L130. A first bypass line L131 for bypassing the lubricating oil Oa with respect to the heat dissipation oil cooler 140 is connected to the bypass branch portion 160. And a bypass valve 151 for opening and closing the first bypass line L131 is provided in the first bypass line L131.

[0120] The bypass branch portion 160 is formed as a part of the oil return line L130 and the first bypass line L131, and includes a straight pipe 161, a T-shaped pipe 162, and a connecting pipe 163. The straight pipe 161 is connected to the outlet pipe 130A of the heat recovery oil cooler 130 at the upstream start end portion, and is connected to the inlet port 151A of the bypass valve 151 at the downstream terminal end portion. The T-shaped pipe 162 is a branching pipe assembled in the middle portion of the straight pipe 161. The connecting pipe 163 connects the inlet pipe 140A of the heat dissipation oil cooler 140 to the branch port 162A of the T-shaped pipe 162. It should be noted that the outlet pipe 130A of the heat recovery oil cooler 130 and the upstream start end portion of the straight pipe 161 may also be connected via other pipes.

[0121] When the bypass valve 151 is open, the first shunt flowing in the first bypass line L131 in the lubricating oil Oa that has passed through the heat recovery oil cooler 130 supplies oil to the bypass valve 151 via the straight pipe 161. Therefore, during the process of passing through the bypass valve 151, only a relatively small frictional loss is borne in the valve chamber. On the other hand, the second shunt flowing in the oil return line L130 supplies oil to the heat dissipation oil cooler 140 via the T-joint 162. Therefore, a branch loss is incurred in the T-joint 162, and a relatively large frictional loss is incurred inside the heat dissipation oil cooler 140 during the process of passing through the heat dissipation oil cooler 140. Therefore, the flow rate ratio of the lubricating oil Oa is "first shunt > second shunt", and most of the lubricating oil Oa flows on the first bypass line L131 side. Thus, when preventing the lubricating oil Oa flowing back to the compressor body 111 from being over-cooled, the purpose can be achieved inexpensively only by adjusting the pipeline resistance without installing a stop valve on the heat dissipation oil cooler 140 side.

[0122] The control unit 15 controls to switch the water passing switching unit to the water passing execution state and to switch to the water passing stop state. In the water passing execution state, the pump 171 operates and the flow rate adjustment valve 174 is open. On the other hand, in the water passing stop state, the pump 171 stops and the flow rate adjustment valve 174 is closed.

[0123] It should be noted that the switching determination between the water passing execution state and the water passing stop state can be made based on the water level information of the water supply tank 1ba (not shown) of the load device 1b connected to the secondary side line L152. When the water level in the water supply tank 1ba of the load device 1b drops to a specified reference value (water reduction value), a demand notification signal indicating the demand for the use of the service water Wa in the load device 1b is sent to the control unit 15. When the water level in the water supply tank 1ba rises to the upper limit value (full water value), a demand notification signal indicating that there is no demand for the use of the service water Wa in the load device 1b is sent to the control unit 15. The control unit 15 determines the switching timing from the water passing stop state to the water passing execution state when receiving the demand notification signal indicating the existence of such demand, and determines the switching timing from the water passing execution state to the water passing stop state when receiving the demand notification signal indicating the non-existence of such demand.

[0124] In addition, the control unit 15 controls the opening and closing of the bypass valve 151. Specifically, the control unit 15 opens the bypass valve 151 when the water passing switching unit is in the water passing execution state, and closes the bypass valve 151 when the water passing switching unit is in the water passing stop state.

[0125] Thus, since the bypass valve 151 is opened when heat recovery is performed by using the water Wa flowing to the oil cooler 130 for heat recovery, most (e.g., more than 90%) of the lubricating oil Oa flows in the first bypass line L131, and the oil supply amount to the oil cooler 140 for heat dissipation becomes small (e.g., less than 10%). The combined lubricating oil Oa minimizes the influence of cooling in the oil cooler 140 for heat dissipation. Therefore, the lubricating oil Oa returning to the compressor body 111 is not overcooled and is maintained within an appropriate temperature range. Thus, it is possible to ensure the required heat recovery amount without reducing the oil supply amount to the oil cooler 130 for heat recovery.

[0126] In addition, when the bypass valve 151 is opened and the lubricating oil Oa sent from the oil separator 120 is supercooled because the water Wa supplied to the oil cooler 130 for heat recovery is at a low temperature or the water flow rate is large, etc., a part of the lubricating oil Oa is bypassed relative to the oil cooler 130 for heat recovery by the temperature regulating valve 153. Thus, it is possible to actively perform heat recovery by using the oil cooler 30 for heat recovery while maintaining the lubricating oil Oa returning to the compressor body 111 within an appropriate temperature range.

[0127] It should be noted that the opening and closing of the bypass valve 151 can be an immediate action accompanying the switching between the water flow execution state and the water flow stop state, or a gradual action. In the case of an immediate action, the bypass valve 151 is opened simultaneously when the water flow switching unit switches to the water flow execution state, or after a delay of about several seconds. In addition, the bypass valve 151 is closed simultaneously when the water flow switching unit switches to the water flow stop state, or after a delay of about several seconds. In the case of a gradual action, the bypass valve 151 is opened when the water flow switching unit switches to the water flow execution state and satisfies a specified condition (e.g., the temperature condition of the water). In addition, the bypass valve 151 is closed when the water flow switching unit switches to the water flow stop state and satisfies a specified condition (e.g., the flow rate condition of the water).

[0128] In addition, during the process of switching the water flow switching unit to the water flow execution state, the control unit 15 adjusts the valve opening degree of the flow rate adjustment valve 174 or the driving frequency of the pump 171 so that the detected temperature of the hot water temperature sensor 175 becomes the target temperature.

[0129] In addition, as Figure 4As shown, in the present embodiment, heat recovery is also performed on the compressed air Ab that has been gas-liquid separated by the oil separator 120. An air cooler 180 for heat recovery is provided in the second air supply line L120. In addition, a radiator air cooler 190 is provided on the downstream side of the air cooler 180 for heat recovery. The compressed air Ab that has passed through the air cooler 180 for heat recovery is introduced into the radiator air cooler 190 and further cooled.

[0130] The air cooler 180 for heat recovery is a heat exchanger for recovering the compression heat of the compressed air Ab that has been gas-liquid separated and flows in the second air supply line L120. A service water line L150 through which the service water Wa flows is connected to the air cooler 180 for heat recovery. Here, the air cooler 180 for heat recovery, together with the oil cooler 130 for heat recovery, serves as a heat exchanger that exchanges heat between the service water Wa and the high-temperature fluid to obtain hot water from the service water Wa. The service water line L150 is configured to circulate the service water Wa in series with respect to the oil cooler 130 for heat recovery and the air cooler 180 for heat recovery.

[0131] Moreover, the pump 171 and the flow control valve 174, which are water flow switching units, serve as mechanisms for switching the oil cooler 130 for heat recovery and the air cooler 180 for heat recovery to the same water flow state.

[0132] The radiator air cooler 190 includes a heat exchanger 191 (a heat exchange core composed of an assembly such as plate fins and finned tubes), a cooling fan 192, and a fan motor 193 for rotating the cooling fan 192. By rotating the cooling fan 192, heat exchange is performed between the cooling air blown by the cooling fan 192 and the compressed air Ab flowing inside the heat exchanger 191, and the compressed air Ab is cooled.

[0133] It should be noted that the following structure may also be adopted, that is, the cooling fan 192 of the radiator air cooler 190 and the cooling fan 142 of the radiator oil cooler 140 are made common, and the heat exchanger 191 of the radiator air cooler 190 and the heat exchanger 141 of the radiator oil cooler 140 are cooled by one cooling fan.

[0134] The radiator oil cooler 130 and the radiator air cooler 190 may be water-cooled types instead of air-cooled types. In the case of a water-cooled type, a heat exchanger for compressed air or lubricating oil and circulating cooling water is provided, and the circulating cooling water that has absorbed heat by the heat exchanger is dissipated in a cooling tower.

[0135] <Function>

[0136] The oil-feed air compressor 1a of the second embodiment is structured such that the lubricating oil Oa circulating in the oil return line L130 including the first air supply line L110 and the first bypass line L131 lubricates and cools the compression mechanism 11 (compressor main body 111) of the machine itself. The heat dissipation oil cooler 140, the cooling fan 142, and the fan motor 143 constitute a heat dissipation mechanism 12 that diffuses the compression heat and cools the compression mechanism 11 through the heat exchange between the cooling air and the lubricating oil Oa. On the other hand, the heat recovery oil cooler 130, the pump 171, the flow rate adjustment valve 174, and the service water line L150 constitute a heat recovery mechanism 13 that recovers the compression heat and cools the compression mechanism 11 through the heat exchange between the service water Wa and the lubricating oil Oa.

[0137] When the detected temperature T obtained by the temperature detection unit 14 does not exceed the specified value α, the control unit 15 performs the next cooling operation. It should be noted that the cooling fan 142 drives the fan motor 143. When there is a demand for the service water Wa in the load device 1b, the control unit 15 controls in such a way that the bypass valve 151 is opened, the flow rate adjustment valve 174 is opened, and the pump 171 is operated. As a result, in the heat recovery oil cooler 130, the compression heat contained in the lubricating oil Oa is recovered by the service water Wa, and the cooled lubricating oil Oa is returned, thereby cooling the compression mechanism 11 of the machine itself. On the other hand, when there is no demand for the service water Wa in the load device 1b, the control unit 15 controls in such a way that the bypass valve 151 is closed, the flow rate adjustment valve 174 is closed, and the pump 171 is stopped. As a result, in the heat dissipation oil cooler 140, the compression heat contained in the lubricating oil Oa is dissipated by the cooling air, and the cooled lubricating oil Oa is returned, thereby cooling the compression mechanism 11 of the machine itself.

[0138] When the detected temperature T obtained by the temperature detection unit 14 exceeds the specified value α, the control unit 15 performs the heat recovery operation regardless of the demand for the service water Wa in the load device 1b. That is, the control unit 15 controls in such a way that the flow rate adjustment valve 174 is opened and the pump 171 is driven. At this time, the control unit 15 preferably closes the bypass valve 151. As a result, the lubricating oil Oa circulating in the compression mechanism 11 is cooled more strongly by using both the heat recovery oil cooler 130 and the heat dissipation oil cooler 140. As a result, even when the ambient temperature around the air compressor 1a rises and the intake air temperature becomes high, overheating of the compressor main body 111 can be prevented, and it is not necessary to limit the rotational speed of the electric motor 112.

[0139] 3. Third Embodiment

[0140] Next, a third embodiment will be described. In the following description, emphasis is placed on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. In the air compressor 1a of the third embodiment, a compression mechanism 11, a heat dissipation mechanism 12, a heat recovery mechanism 13, a temperature detection unit 14, and a control unit 15 are also provided. The temperature detection unit 14 is disposed, for example, inside the housing of the air compressor 1a to detect the temperature of the external air obtained for intake and ventilation. Figure 5 Schematically shows the structure of the air compressor 1a (water-added air compressor) of the third embodiment. As a main component related to air compression, the air compressor 1a includes a compression mechanism 11, a pre-separator 204 that separates gas and water from the ejected fluid from the compression mechanism 11, a post-cooler 205 that cools the compressed air separated by the pre-separator 204, a water cooler 206 that cools the separated water separated by the pre-separator 204, and a separation tank 207 that is supplied with the compressed air and separated water after passing through each cooler 205, 206.

[0141] The compressor main body 203 constituting the compression mechanism 11 is, for example, a scroll type. By driving an electric motor 208 connected to the drive shaft of the compressor main body 203, external air is sucked in, adiabatically compressed to generate compressed air Aa, and ejected. The compressor main body 203 is water-added type, and by introducing added water Wb together with the supply air, the orbiting scroll and the fixed scroll are cooled, that is, the compression heat is removed.

[0142] When the compressor main body 203 operates, external air is sucked into the compressor main body 203 from the suction path 210 via the air filter 209. At this time, the added water Wb is injected at a set flow rate via the added water return path 211 from the separation tank 207. And the compressed air Aa generated in the compressor main body 203 is ejected toward the pre-separator 204 along with the lubricating water Wb. A check valve 213 is provided in the ejection path 212 from the compressor main body 203 to the pre-separator 204.

[0143] It should be noted that the water-added compressor main body 203 can also be referred to as a water-lubricated type or a water-injection type, etc. In addition, here, the compressor main body 203 injects the added water Wb into the air suction port, but it may also have a water injection port other than the air suction port and inject the added water Wb into the water injection port.

[0144] The pre-separator 204 receives the ejected fluid Aa (compressed air ejected together with added water) from the compressor main body 203 for gas-liquid separation. That is, the ejected fluid Aa from the compressor main body 203 is separated into compressed air Ab and separated water Wb in the pre-separator 204. Along with this, the inside of the pre-separator 204 is divided into an upper gas phase part and a lower liquid phase part. Also, the gas phase part of the pre-separator 204 is connected to the gas phase part of the separation tank 207 via the gas connection passage 214. On the other hand, the liquid phase part of the pre-separator 4 is connected to the liquid phase part of the separation tank 207 via the liquid connection passage 215.

[0145] A post-cooler 205 is provided in the gas connection passage 214 from the pre-separator 204 to the separation tank 207. The post-cooler 205 is a mechanism for cooling the compressed air Ab after gas-liquid separation by the pre-separator 204. The post-cooler 205 functions as a heat recovery heat exchanger that exchanges heat between the compressed air Ab and the service water Wa. In the post-cooler 205, the compressed air Ab is cooled by the service water Wa. On the other hand, the service water Wa is heated by the compressed air Ab.

[0146] A water cooler 206 is provided in the liquid connection passage 215 from the pre-separator 204 to the separation tank 207. The water cooler 206 is a unit for cooling the separated water Wb after gas-liquid separation by the pre-separator 204. The water cooler 206 functions as a heat recovery heat exchanger that exchanges heat between the separated water Wb and the service water Wa. In the water cooler 206, the separated water Wb is cooled by the service water Wa. On the other hand, the service water Wa is heated by the separated water Wb.

[0147] The separation tank 207 receives the compressed air Ab and the separated water Wb after passing through the respective coolers 205 and 206 above for gas-liquid separation. The compressed air Ab from the pre-separator 204 is cooled by the post-cooler 205 to cause condensation of moisture, and this moisture is removed by the separation tank 207. Therefore, the inside of the separation tank 207 is also divided into an upper gas phase part and a lower liquid phase part. It should be noted that the supply of fluid from the pre-separator 204 to the separation tank 207 via the respective connection passages 214 and 215 is carried out by the ejection pressure of the compressor main body 203 and the head pressure difference.

[0148] In the gas phase portion of the separation tank 207, in addition to the aforementioned gas-phase connection passage 214, a compressed air supply passage 217 leading to the compressed air utilization section is also connected. In the compressed air supply passage 217, a primary pressure regulating valve 218 and a check valve 219 are sequentially provided from the side of the separation tank 207. The primary pressure regulating valve 218 is a valve that maintains the inside of the separation tank 207 at a set pressure or higher during the operation of the compressor main body 203. Here, the primary pressure regulating valve 218 is a self-operated valve that mechanically operates based on the pressure on the primary side (i.e., the separation tank 207 side), but depending on the situation, it can also be an electric valve that monitors the pressure on the primary side using a sensor and controls based on the detected pressure. In addition, in the present embodiment, in the gas phase portion of the separation tank 207, in addition to the safety valve 220, a bleed valve 221 for exhausting to the outside is also provided. It should be noted that the primary pressure regulating valve 218 and the check valve 219 can also be configured as an integrated valve mechanism.

[0149] In the liquid phase portion of the separation tank 207, in addition to the aforementioned liquid-phase connection passage 215, a return passage 211 for the added water leading to the compressor main body 203 is also connected. In the return passage 211 for the added water, an added water valve 222 and a water filter 223 are sequentially provided from the separation tank 207 side. During the operation of the compressor main body 203, by opening the added water valve 222, the stored water in the separation tank 207 can be returned to the compressor main body 203 via the return passage 211 for the added water. At this time, by suction into the compressor main body 203 based on the operation of the compressor main body 203 and pressurization inside the separation tank 207, the added water Wb can be returned from the separation tank 207 to the compressor main body 203. In addition, by the primary pressure regulating valve 218, the inside of the separation tank 207 is maintained at a set pressure or higher, and as will be described later, the pressure in the compressed air supply passage 217 (and thus the pressure inside the separation tank 207) is maintained as desired, so that the added water valve 222 can function as an orifice and supply the added water Wb to the compressor main body 203 at a set flow rate. And when supplying the added water Wb from the separation tank 207 to the compressor main body 203, the inclusions can be removed by the water filter 223.

[0150] The air compressor 1a also includes a water supply passage 224 and a drainage passage 225. The water supply passage 224 is a unit that replenishes makeup water Wf from a water supply source such as an ion exchange device (e.g., a mixed bed type pure water device, a hard water softening device) as added water Wb. In the present embodiment, the water supply passage 224 from the water supply source branches into a first water supply passage 224A and a second water supply passage 224B. The first water supply passage 224A is connected to the suction passage 210 leading to the compressor main body 203. On the other hand, the second water supply passage 224B is connected to the separation tank 207. And a first water supply valve 226 is provided in the first water supply passage 224A. On the other hand, a check valve 227 and a second water supply valve 228 are sequentially provided in the second water supply passage 224B. It should be noted that in the present embodiment, the first water supply valve 226 is an electromagnetic valve, and the second water supply valve 228 is a manual valve.

[0151] On the other hand, the drainage passage 225 is connected to the bottom of the separation tank 207. A drainage valve 229 is provided in the drainage passage 225. By opening the drainage valve 229, drainage from the inside of the separation tank 207 can be achieved.

[0152] In addition, a water level detector 230 is provided in the separation tank 207. The structure of the water level detector 230 is not particularly limited. For example, it is a float water level detector capable of detecting the water level of purified water and condensate without ionic substances. Also, in the compressed air delivery passage 217 from the separation tank 7, a pressure sensor 231 is provided at a position downstream of the primary pressure regulating valve 218 and the check valve 219. Through this pressure sensor 231, the ejection pressure of the compressed air Ab (the supply pressure to the compressed air utilization unit) can be monitored.

[0153] In the air compressor 1a, when the operation of the compressor main body 203 starts, the compressor main body 203 sucks in air via the air filter 209, compresses it, and ejects it. The compressed air Ab ejected from the compressor main body 203 is transported from the compressed air delivery passage 217 to the compressed air utilization unit via the pre-separator 204, the after-cooler 205, and the separation tank 207. However, since a primary pressure regulating valve 218 is provided in the compressed air delivery passage 217, in a state where the pressure inside the separation tank 207 is low, such as just after the start of operation, the primary pressure regulating valve 218 closes and does not send the compressed air Ab to the compressed air utilization unit. When the pressure on the primary side (i.e., the separation tank 207 side) of the primary pressure regulating valve 218 becomes equal to or higher than the set pressure, the primary pressure regulating valve 218 opens and sends the compressed air Ab to the compressed air utilization unit.

[0154] During the operation of the compressor main body 203, the control unit 15 controls to maintain the detected pressure of the pressure sensor 231 at the target pressure. For example, the electric motor 208 of the compressor main body 203 is subjected to on-off control or inverter control. It should be noted that the target pressure is higher than the set pressure of the primary pressure regulating valve 218. Therefore, hereafter, the separation tank 207 is basically maintained at the target pressure.

[0155] During the operation of the compressor main body 203, by opening the additive water valve 222, additive water Wb can be injected into the suction port of the compressor main body 203 at a set flow rate. Thereby, sealing, cooling, and lubrication of the compressor main body 203 can be achieved. The compressed air Aa from the compressor main body 203 is sprayed into the pre-separator 204 in a state with the additive water Wb. And gas-liquid separation is achieved in the pre-separator 204. The compressed air Ab separated by the pre-separator 204 is cooled by the after-cooler 205 and then further gas-liquid separated by the separation tank 207 and sent to the outside through the compressed air delivery path 217. On the other hand, the separated water Wb in the pre-separator 204 is cooled by the water cooler 206 and then stored in the separation tank 207 and can be supplied to the compressor main body 203 via the additive water return path 211.

[0156] During the operation of the compressor main body 203, the water level in the separation tank 207 is maintained at the set water level. For example, if the detected water level of the water level detector 230 exceeds the upper limit water level, the drain valve 229 is opened to lower the water level to the specified level. On the contrary, if the detected water level of the water level detector 230 is lower than the lower limit water level, the first water supply valve 226 is opened to raise the water level to the specified level. During the opening of the first water supply valve 226, the makeup water Wf is supplied to the separation tank 207 via the compressor main body 203. During this period, the additive water valve 222 may be closed. It should be noted that during the stop of the compressor main body 203, by opening the second water supply valve 228, the makeup water Wf can be directly supplied to the separation tank 207.

[0157] On the other hand, when the compressor main body 203 stops, the air release valve 221 is opened. By opening the air release valve 221 even during the stop of the compressor main body 203, reverse rotation of the compressor main body 203 can be prevented. After that, when the compressor main body 203 restarts, the air release valve 221 is closed.

[0158] In addition, the air compressor 1a, which is a main component related to heat recovery, includes: a post-cooler 205 and a water cooler 206, which are heat exchangers for heat recovery that use the compression heat of the compressor body 203 to heat the service water Wa; an inlet passage 232 for the service water Wa to the post-cooler 205; an outlet passage 233 for the service water Wa from the water cooler 206; a return passage 234 for the service water Wa that connects the outlet passage 233 and the inlet passage 232; a switching unit 235 (a flow control valve 236 and a return valve 237) that switches between the liquid passage and the circulation passage described later; and a radiator 238 that cools the circulating water in the circulation passage.

[0159] As described above, in the post-cooler 205, the compressed air Ab exchanges heat with the service water Wa, and the compressed air Ab is cooled by the service water Wa. On the other hand, the service water Wa is heated by the compressed air Wb. The compression heat of the compressed air Wb can be used for heating the service water Wa to achieve heat recovery. On the other hand, the water cooler 206 exchanges heat between the added water Wb (the separated water in the pre-separator) and the service water Wa, cools the added water Wb with the service water Wa, and heats the service water Wa with the added water Wb. Using the compression heat of the added water Wb for heating the service water Wa can achieve heat recovery.

[0160] The service water Wa passes through the post-cooler 205 and the water cooler 206 in sequence. Therefore, the post-cooler 205 and the water cooler 206 are connected by a connection passage 239. And the service water Wa flows in the order of the post-cooler 205, the connection passage 239, the water cooler 206, and the outlet passage 233 from the inlet passage 232.

[0161] In the inlet passage 232 from the water supply source, a pump 240, a check valve 241, and a radiator 238 are provided in sequence from the upstream side. By operating the pump 240, the service water Wa can be circulated in the post-cooler 205 and the water cooler 206. The radiator 238 is an air-cooled radiator that exchanges heat between the service water Wa and the cooling air (ventilation based on the fan 238A). For example, when the temperature of the service water on the inlet side of the radiator 238 is higher than the outside air temperature, by operating the fan 238A of the radiator 238, the service water Wa can be cooled by the ventilation of the fan 238A.

[0162] A flow control valve 236 and a hot water outlet temperature sensor 243 are provided in the outlet passage 233 from the water cooler 206. During the operation of the compressor body 203, by opening the flow control valve 236 and operating the pump 240, the service water Wa can be passed through the post-cooler 205 and the water cooler 206 to achieve the recovery of compression heat. In the example of this embodiment, the flow control valve 236 is composed of an electric valve whose opening can be adjusted.

[0163] The outlet passage 233 on the upstream side of the specific flow rate adjustment valve 236 and the inlet passage 232 on the upstream side of the specific pump 240 are connected by a return passage 234. At this time, it is preferable to provide a storage tank 242 for the service water Wa at the connection part of the inlet passage 232 and the return passage 234. However, the storage tank 242 can be omitted according to circumstances. In addition, the storage tank 242 may not be provided at the connection part of the inlet passage 232 and the return passage 234, but may be provided downstream thereof (preferably upstream of the pump 240). It should be noted that the pump 240 can be provided not only downstream of the connection part of the inlet passage 232 and the return passage 234, but also at a position upstream of the connection part of the communication passage 239 and the outlet passage 233 with the return passage 234.

[0164] A return valve 237 is provided in the return passage 234. In the example of the present embodiment, the return valve 237 is constituted by an electric valve. By selectively opening only one of the flow rate adjustment valve 236 and the return valve 237, it is possible to switch whether the service water Wa after passing through each of the coolers 205 and 206 returns to the inlet passage 232 via the return passage 234 or is conveyed downstream of the outlet passage 233 without passing through the return passage 234.

[0165] In the example of the present embodiment, the switching unit 235 is constituted by the flow rate adjustment valve 236 and the return valve 237. By switching the opening and closing of each of the flow rate adjustment valve 236 and the return valve 237, the flow path of the service water Wa can be switched to any one of the following water passing paths and circulation paths.

[0166] The water passing path is achieved by opening the flow rate adjustment valve 236 in a state where the return valve 237 is closed. The water passing path is a path including the inlet passage 232, the aftercooler 205, the water cooler 206, and the outlet passage 233 and not including the return passage 234. When the pump 240 is operated in a state switched to the water passing path, the service water Wa from the inlet passage 232 passes through the aftercooler 205 and the water cooler 206 and is discharged through the flow rate adjustment valve 236 of the outlet passage 233 (heat recovery implementation state). At this time, the service water is appropriately supplied from the water supply source to the storage tank 242. In other words, during the operation of the pump 240 in the water passing path, makeup water from the water supply source is supplied to the inlet passage 232.

[0167] The circulation path is achieved by opening the return valve 237 while closing the heat recovery valve 236. The circulation path is a path including the inlet path 232 on the downstream side of the connection part of the return path 234, the aftercooler 205, the water cooler 206, the outlet path 233 on the upstream side of the connection part of the return path 234, and the return path 234. When the pump 240 is operated in the state switched to the circulation path, the service water Wa from the pump 240 passes through the aftercooler 205, the water cooler 206, and the return path 234 and returns to the suction side of the pump 240 for circulation. At this time, by operating the radiator 238, the circulating cooling water (heat recovery stop state) can be cooled in the radiator 238. It should be noted that during the circulation of the service water Wa in the circulation path, new water supply from the water supply source to the storage tank 242 is not required.

[0168] In the air compressor 1a, during the operation of the compressor main body 203 (i.e., in the production of the compressed air Ab), the pump 240 is operated to supply the service water Wa to the coolers 205 and 206. Thereby, the ejected fluid (compressed air Ab, added water Wb) from the compressor main body 203 can be cooled, and the service water Wa can be heated using the compression heat contained in the ejected fluid. The hot water thus produced is switched in flow path by the switching unit 235 according to the presence or absence of the demand for the service water Wa in the load device 1b. That is, when the control unit 15 receives a demand notification signal indicating the demand for the service water Wa from the load device 1b, the control unit 15 controls the switching unit 235 to switch the flow path to the water passing path, and when the control unit 15 receives a demand notification signal indicating no demand for the service water Wa from the load device 1b, the control unit 15 controls the switching unit 235 to switch the flow path to the circulation path.

[0169] When supplying the service water Wa to the coolers 205 and 206, in order to implement heat recovery (in other words, to discharge hot water to the outside), the switching unit 235 is switched to the water passing path. In the water passing path, the return valve 237 is closed, and on the other hand, the flow rate adjustment valve 236 is opened. In addition, typically the fan 238A is stopped. In this case, the service water Wa is heated by the coolers 205 and 206 and sent to the load device 1b downstream of the outlet path 233. At this time, if the opening degree of the flow rate adjustment valve 236 is adjusted to maintain the detected temperature of the hot water outlet temperature sensor 243 at the target temperature, hot water at the required temperature can be supplied to the load device 1b.

[0170] In the process of supplying service water Wa to each of the coolers 205 and 206, in order to stop heat recovery (in other words, hot water discharged to the outside), the switching unit 235 is switched to the circulation path. In the circulation path, the flow control valve 236 is closed, while the return valve 237 is opened. In addition, the fan 238A of the radiator 238 is operated. In this case, the service water Wa heated by each of the coolers 205 and 206 returns to the inlet path 232 via the return path 234, and after being cooled by the radiator 238, it is supplied to each of the coolers 205 and 206 again. That is, the cooling water Wa is circulated to each of the coolers 205 and 206, and heat is dissipated to the outside air through the radiator 238.

[0171] The radiator 238 for heat dissipation may be a water-cooled type instead of an air-cooled type. In the case of the water-cooled type, a heat exchanger for the circulated service water and the circulated cooling water that flows in the circulation path is provided, and the circulated cooling water that has absorbed heat in the heat exchanger is dissipated in the cooling tower.

[0172] <Function>

[0173] The water-added air compressor 1a of the third embodiment is configured to lubricate and cool the compression mechanism 11 (compressor main body 203) of the machine by the added water Wb circulating in the injection path 212, the liquid connection path 215, the added water return path 211, and the suction path 210. The circulation path including the water cooler 206, the radiator 238, the pump 240, the return valve 237, and the return path 234 constitutes a heat dissipation mechanism 12, which diffuses the compression heat and cools the compression mechanism 11 through the heat exchange between the service water Wa and the added water Wb circulating in the circulation path, and the heat exchange between the cooling air and the service water Wa. On the other hand, the water passage path that does not include the water cooler 206, the pump 240, the flow control valve 236, and the return path 234 constitutes a heat recovery mechanism 13, which recovers the compression heat and cools the compression mechanism 11 through the heat exchange between the service water Wa and the added water Wb flowing in the water passage path.

[0174] When the detected temperature T of the temperature detection unit 14 does not exceed the specified value α, the control unit 15 performs the subsequent cooling operation. When there is a demand for the use of water Wa in the load device 1b, the control unit 15 controls to open the flow rate adjustment valve 174, close the return valve 237, operate the pump 171, and stop the radiator 238. As a result, in the water cooler 206, the compressed heat contained in the added water Wb is continuously recovered by the supplied water Wa, and the cooled added water Wb is returned, thereby cooling the compression mechanism 11 of this machine. On the other hand, when there is no demand for the use of water Wa in the load device 1b, the control unit 15 controls to close the flow rate adjustment valve 174, open the return valve 237, operate the pump 171, and operate the radiator 238. As a result, in the water cooler 206, the compressed heat contained in the added water Wb is dissipated in the radiator 238 while being absorbed by the circulated water Wa, and the cooled added water Wb is returned, thereby cooling the compression mechanism 11 of this machine.

[0175] When the detected temperature T of the temperature detection unit 14 exceeds the specified value α, the control unit 15 performs a heat recovery operation regardless of the demand for the use of water Wa in the load device 1b. That is, the control unit 15 controls to open the flow rate adjustment valve 174, close the return valve 237, operate the pump 171, and stop the radiator 238. As a result, the added water Wb circulated in the compression mechanism 11 is strongly cooled in the water cooler 206 using the water Wa from a water supply source whose temperature is reliably lower than that of the cooling air (external air). As a result, even when the ambient temperature around the air compressor 1a rises and the intake temperature becomes high, overheating of the compressor main body 111 can be prevented, and it is not necessary to limit the rotational speed of the electric motor 208.

[0176] 4. Fourth Embodiment

[0177] Next, the fourth embodiment will be described. In the following description, the focus is on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. The air compressor 1a in the fourth embodiment also includes a compression mechanism 11, a heat dissipation mechanism 12, a heat recovery mechanism 13, a temperature detection unit 14, and a control unit 15. The temperature detection unit 14 is arranged, for example, inside the housing of the air compressor 1a to detect the temperature of the external air obtained for intake and ventilation.

[0178] Figure 6 Schematically shows the structure of the air compressor 1a (oil-free air compressor) of the fourth embodiment. The air compressor 1a includes a first compressor main body 311, a second compressor main body 312, an intercooler (air cooler for heat dissipation) 313, a post-cooler (air cooler for heat dissipation) 314, and an unloading mechanism 315.

[0179] The first compressor body 311 adiabatically compresses the air supplied through the intake line L301. The compressed air Aa produced by the first compressor body 311 is transported to the second compressor body 312 through the first compressed air line L311. An intercooler 313 is arranged in the first compressed air line L311, and the compressed air Aa is cooled by the intercooler 313 before reaching the second compressor body 312. Thus, the compression performance of the second compressor body 312 is prevented from being reduced due to the high temperature of the compressed air Aa. The intercooler 313 is configured as an air-cooled radiator, and the compressed air Aa can be cooled by using a cooling fan 313a to transport cooling air to the radiator.

[0180] The second compressor body 312 further adiabatically compresses the compressed air Aa supplied through the first compressed air line L311. The compressed air Ab produced by the second compressor body 312 is transported to the external compressed air-using equipment through the second compressed air line L312. An aftercooler 314 is arranged in the second compressed air line L312, and the compressed air Ab is cooled by the aftercooler 314 before reaching the compressed air-using equipment. Thus, the compressed air Ab adjusted to a temperature lower than the heat resistance temperature of the compressed air-using equipment is supplied. A dryer or a drain separator (not shown) is arranged downstream of the aftercooler 314, and the condensed water generated in the aftercooler 314 is removed by the dryer or the drain separator. The aftercooler 314 is configured as an air-cooled radiator, and the compressed air Ab can be cooled by using a cooling fan 314a to transport cooling air to the radiator.

[0181] The first compressor body 311 and the second compressor body 312 are connected to an electric motor 317 as a driving source via a gear tank 316. The driving force of the electric motor 317 is transmitted to the first compressor body 311 and the second compressor body 312 via the gear tank 316, and the first compressor body 311 and the second compressor body 312 operate.

[0182] The unloading mechanism 315 is a mechanism for switching the operating state of the air compressor 1a to a loaded operating state or an unloaded operating state (no-load operating state), and is, for example, configured to include an intake valve (not shown) for opening and closing the intake line L301 and a purge valve (not shown) for opening the second compressed air line L312 to the atmosphere. The intake valve and the purge valve operate in conjunction, and the purge valve is closed when the intake valve is open, and on the other hand, the purge valve is opened when the intake valve is closed.

[0183] The unloading mechanism 315 is controlled in a manner that opens the intake valve and closes the exhaust valve during the loading control for manufacturing compressed air Aa and Ab. Additionally, during the unloading control when compressed air Aa and Ab are not being manufactured, it is controlled to close the intake valve and open the exhaust valve.

[0184] Next, a structure for heat recovery in the air compressor 1a will be described. The air compressor 1a includes a first heat recovery heat exchanger 351, a first shut-off valve 352, a first bypass valve 353, a second heat recovery heat exchanger 361, a second shut-off valve 362, and a second bypass valve 363.

[0185] The first heat recovery heat exchanger 351 is disposed upstream of the intercooler 313 in the first compressed air line L311. Service water Wa is supplied to the first heat recovery heat exchanger 351 through a second cooling water line L331, which will be described later. The first heat recovery heat exchanger 351 exchanges heat between the compressed air Aa flowing through the first compressed air line L311 and the service water Wa to cool the compressed air Aa.

[0186] A first bypass line L351, which provides a path for the compressed air Aa not to pass through the first heat recovery heat exchanger 351, is provided in the first compressed air line L311. The first bypass line L351 connects the upstream side and the downstream side of the first heat recovery heat exchanger 351 in the first compressed air line L311. In the following description, the portion where the first bypass line L351 branches off from the first compressed air line L311 is designated as the first branch portion 371, and the portion where the first bypass line L351 merges with the first compressed air line L311 is designated as the first merging portion 372.

[0187] The first shut-off valve 352 is disposed upstream of the first heat recovery heat exchanger 351 in the first compressed air line L311 and downstream of the first branch portion 371 where it branches off to the first bypass line L351. The first shut-off valve 352 opens and closes the path for the compressed air that reaches the downstream side of the first heat recovery heat exchanger 351 from the first compressed air line L311 through the first bypass line L351. The first bypass valve 353 is disposed in the first bypass line L351. The first bypass valve 353 opens and closes the path for the compressed air that reaches the downstream side of the first heat recovery heat exchanger 351 from the first compressed air line L311 through the first bypass line L351.

[0188] The heat exchanger 361 for the second heat recovery is arranged on the upstream side of the aftercooler 314 in the second compressed air line L312. Service water Wa is supplied to the heat exchanger 361 for the second heat recovery through the first cooling water line L330 described later. The heat exchanger 361 for the second heat recovery exchanges heat between the compressed air Ab flowing through the second compressed air line L312 and the service water Wa to cool the compressed air Ab.

[0189] A second bypass line L361, which forms a path through which the compressed air A2 does not pass through the heat exchanger 361 for the second heat recovery, is provided in the second compressed air line L312. The second bypass line L361 connects the upstream side and the downstream side of the heat exchanger 361 for the second heat recovery in the second compressed air line L312. In the following description, the portion where the second bypass line L361 branches from the second compressed air line L312 is defined as the second branch portion 381, and the portion where the second bypass line L361 merges with the second compressed air line L312 is defined as the second merging portion 382.

[0190] The second stop valve 362 is arranged on the upstream side of the heat exchanger 361 for the second heat recovery in the second compressed air line L312 and at a position downstream of the second branch portion 381 where it branches to the second bypass line L361. The path of the second compressed air line L312 is opened and closed by the second stop valve 362. The second bypass valve 363 is arranged in the second bypass line L361 to open and close the path of the second bypass line L361.

[0191] The service water Wa supplied to the heat exchanger 351 for the first heat recovery and the heat exchanger 361 for the second heat recovery is the supply water to be heated that is transported to the water supply tank 1ba of the load device 1b. The path for supplying the service water Wa to the heat exchanger 351 for the first heat recovery and the heat exchanger 361 for the second heat recovery will be described.

[0192] Service water Wa is supplied to the second heat recovery heat exchanger 361 through a first service water line L330 connected to a water supply source (not shown). A pump (not shown) is provided in the first service water line L330. Service water Wa is supplied to the first heat recovery heat exchanger 351 through a second service water line L331 branched from a branch portion 373 on the upstream side of the second heat recovery heat exchanger 361 in the first service water line L330. The first service water line L330 is connected to a water supply tank 1ba via the second heat recovery heat exchanger 361. After passing through the first heat recovery heat exchanger 351, the second service water line L331 merges with the first service water line L330 at a merging portion 383 on the downstream side of the second heat recovery heat exchanger 361. In this way, service water Wa is supplied to the first heat recovery heat exchanger 351 and the second heat recovery heat exchanger 361 in a parallel connection manner. A flow sensor 333 is disposed on the upstream side of the branch portion 373 in the first service water line L330.

[0193] Regarding the control of the air compressor 1a, first, the loading control and the unloading control will be described. In the loading control, with the intake valve open and the exhaust valve closed in the unloading mechanism 315, the motor 317 is driven, and compressed air Ab is produced by the first compressor main body 311 and the second compressor main body 312. In the unloading control, the electric motor 317 is driven for no-load operation with the intake valve closed and the exhaust valve open in the unloading mechanism 315.

[0194] The control unit 15 selects the loading control or the unloading control based on the operating conditions of the first compressor main body 311 and the second compressor main body 312. The operating conditions are pre-set conditions. For example, it is set as a condition that the pressure in the second compressed air line L312 through which the compressed air Ab supplied from the second compressor main body 312 flows and the air tank (not shown) at the supply destination is lower than the lower limit pressure. That is, when it is detected by a pressure sensor (not shown) or the like that the pressure is lower than the lower limit pressure in the air tank, compressed air Ab needs to be supplied. Therefore, the control unit 15 selects the loading control for producing compressed air Ab and sets a "loading operation in progress" flag. On the other hand, when the upper limit pressure is exceeded, the control unit 15 selects the unloading control for not producing compressed air Ab and sets an "unloading operation in progress" flag.

[0195] In addition, regarding the water supply operation, the control unit 15 causes service water Wa to flow in the first service water line L330 and the second service water line L331 based on the water passing conditions. The water passing conditions are pre-set conditions, and the flow control valve 332 and the pump are controlled according to the demand for service water Wa.

[0196] When the control unit 15 obtains information indicating a demand for using the water Wa in the load device 1b, it sets the flow rate adjustment valve 332 to the open state and operates the pump, and sets a "water supply in progress" flag. Further, when obtaining information indicating no demand for using the water Wa in the load device 1b during water supply, it controls the flow rate adjustment valve 332 to the closed state and stops the pump, and sets a "water supply stopped" flag.

[0197] Further, regarding the heat recovery operation, the control unit 15 controls the heat recovery operation triggered by all of the following three conditions being satisfied. The first condition is that the "water supply in progress" flag is set, the second condition is that the "loading operation in progress" flag is set, and the third condition is that the detected flow rate of the flow rate sensor 333 is "equal to or greater than the specified flow rate". When the control unit 15 is in the state of "water supply in progress" and "loading operation state" and "equal to or greater than the specified flow rate", it performs the following control: switching from the non-heat recovery path that does not perform heat recovery of the compressed air Aa and Ab to the heat recovery path that performs heat recovery of the compressed air Aa and Ab.

[0198] The control unit 15 sets the first stop valve 352 and the second stop valve 362 to the open state, and sets the first bypass valve 353 and the second bypass valve 363 to the closed state. Thereby, a heat recovery path is selected in which the compressed air Aa passes through the first heat recovery heat exchanger 351 and the intercooler 313 and reaches the second compressor main body 312, and the compressed air Ab passes through the second heat recovery heat exchanger 361 and the aftercooler 314 and reaches the compressed air using device. When selecting the heat recovery path, the compressed air Aa is heat recovered by the first heat recovery heat exchanger 351, and the compressed air Ab is heat recovered by the second heat recovery heat exchanger 361. During the execution of the heat recovery operation, the control unit 15 performs hot water outlet temperature constant control to change the valve opening degree of the flow rate adjustment valve 332 based on the detected temperature so that the detected temperature of the hot water outlet temperature sensor 334 becomes the target temperature.

[0199] The conditions for stopping the heat recovery operation will be described. The control unit 15 triggers a heat recovery stop operation of switching from the non-heat recovery path to the heat recovery path when either of the conditions of setting the "water supply stopped" flag or setting the "unloading operation in progress" flag and this state continuing for a specified time is satisfied.

[0200] The control unit 15 closes the first shut-off valve 352 and the second shut-off valve 362, and opens the first bypass valve 353 and the second bypass valve 363. As a result, the non-heat recovery path is selected in which the compressed air Aa passes through the first bypass line L351, does not pass through the first heat recovery heat exchanger 351, reaches the second compressor main body 312 through the intercooler 313, and the compressed air Ab passes through the second bypass line L361 and reaches the aftercooler 314 without passing through the second heat recovery heat exchanger 361.

[0201] The intercooler 313 and the aftercooler 314 for heat dissipation may be water-cooled types instead of air-cooled types. In the case of the water-cooled type, a heat exchanger for the compressed air and the circulating cooling water is provided, and the circulating cooling water after absorbing heat from the heat exchanger is dissipated in the cooling tower.

[0202] <Function>

[0203] The oil-free air compressor 1a of the second embodiment has a structure in which the compressed air Aa flowing in the first compressed air line L311 is cooled to cool the compression mechanism 11 (the second compressor main body 312) of the machine. The intercooler 313, the cooling fan 313a, and the first bypass valve 353 constitute a heat dissipation mechanism 12, which dissipates the compression heat through the heat exchange between the cooling air and the compressed air Aa and cools the compression mechanism 11 at the subsequent stage. In addition, the first heat recovery heat exchanger 351, the pump, the flow rate adjustment valve 332, the first shut-off valve 352, and the second cooling water line L332 constitute a heat recovery mechanism 13 that recovers the compression heat by using the heat exchange between the water Wa and the compressed air Aa and cools the compression mechanism 11 at the subsequent stage.

[0204] When the detected temperature T of the temperature detection unit 14 does not exceed the specified value α, the control unit 15 performs the next cooling operation. When there is a demand for using the water Wa in the load device 1b, the control unit 15 controls to open the first shut-off valve 352, close the first bypass valve 353, open the flow rate adjustment valve 332, operate the pump, and stop the cooling fan 313a. As a result, in the first heat recovery heat exchanger 351, the compression heat contained in the compressed air Aa is recovered into the water Wa, and the compressed air Aa after heat recovery is sent out, whereby the second compressor main body 312 (the compression mechanism 11 of the machine) is cooled. On the other hand, when there is no demand for using the water Wa in the load device 1b, the control unit 15 controls to close the first shut-off valve 352, open the first bypass valve 353, close the flow rate adjustment valve 332, stop the pump, and operate the cooling fan 313a. As a result, in the intercooler 313, the compression heat contained in the compressed air Aa is dissipated by the cooling air, and the compressed air Aa after heat dissipation is sent out, whereby the second compressor main body 312 (the compression mechanism 11 of the machine) is cooled.

[0205] When the detected temperature T of the temperature detection unit 14 exceeds the specified value α, the control unit 15 performs a heat recovery operation regardless of the demand for the service water Wa in the load device 1b. That is, the control unit 15 controls to open the first check valve 352, close the first bypass valve 353, open the flow adjustment valve 332, operate the pump, and stop the cooling fan 313a. As a result, the compressed air Aa ejected from the first compressor body 311 is strongly cooled by the service water Wa from a water supply source whose temperature is reliably lower than that of the cooling air (outside air) in the first heat recovery heat exchanger 351. As a result, even when the ambient temperature around the air compressor 1a rises and the intake temperature becomes high, overheating of the second compressor body 312 can be prevented, and there is no need to limit the rotational speed of the electric motor 317.

[0206] <Application Example>

[0207] The oil-free air compressor 1a of the fourth embodiment may also be configured to include a sheath attached to the compressor bodies 311 and 312 and the electric motor 317, and a lubricating oil circulation circuit for the gear tank 316, in which a heat dissipation oil cooler and a heat recovery oil cooler are arranged. In this case, the heat dissipation oil cooler becomes an additional element constituting the heat dissipation mechanism 12, while the heat recovery oil cooler becomes an additional element constituting the heat recovery mechanism 13. When the detected temperature T of the temperature detection unit 14 does not exceed the specified value α, the control unit 15 switches between the heat recovery operation of the heat recovery oil cooler and the heat dissipation operation of the heat dissipation oil cooler according to the presence or absence of the demand for the service water Wa in the load device 1b. In addition, when the detected temperature T of the temperature detection unit 14 exceeds the specified value α, the control unit 15 performs the heat recovery operation of the heat recovery oil cooler regardless of the presence or absence of the demand for the service water Wa in the load device 1b. By being able to perform a forced heat recovery operation on the compressor bodies 311 and 312, when the ambient temperature around the air compressor 1a rises, not only can the second compressor body 312 be effectively cooled, but also the first compressor body 311 can be effectively cooled.

[0208] The embodiments of the present invention have been described above, but the structure of the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the invention. That is, the above embodiments should be considered as illustrative in all respects and not restrictive. The technical scope of the present invention is not represented by the description of the above embodiments, but by the claims, and should be understood to include all changes within the meaning and scope equivalent to the claims.

[0209] Industrial Applicability

[0210] The present invention can be used in air compressors and thermal utilization systems having such air compressors.

[0211] <Contribution to the United Nations-led Sustainable Development Goals (SDGs)>

[0212] The air compressor of the present disclosure improves energy efficiency by incorporating a heat recovery mechanism and can contribute to the achievement of Goal 7, "Ensure access to affordable, reliable, sustainable and modern energy for all," of the SDGs (Sustainable Development Goals).

Claims

1. An air compressor comprising a compression mechanism for compressing supplied air to generate compressed air, wherein: The air compressor has: A heat dissipation mechanism that performs a heat dissipation action of diffusing the heat generated during the compression process through heat exchange with cooling air or cooling water and cooling the air compressor; a heat recovery mechanism that recovers heat generated during compression by heat exchange with water and performs a heat recovery action to cool the air compressor; as well as a temperature detecting unit for detecting a temperature of a fluid that is correlated with a temperature of the air compressor; When the temperature detected by the temperature detecting unit exceeds a predetermined value, the heat recovery operation is performed with priority over the heat dissipation operation when the air compressor is cooled.

2. The air compressor according to claim 1, wherein the air compressor is configured to supply the use water heated in the heat recovery operation to a load device that uses the use water, and when performing the operation of cooling the air compressor, it is determined which of the heat dissipation operation and the heat recovery operation is to be performed first according to whether there is a demand for the use water in the load device, wherein: When the detected temperature exceeds the predetermined value, the heat recovery operation is performed with priority as the operation of cooling the air compressor regardless of the presence or absence of the demand.

3. The air compressor according to claim 1, wherein the air compressor is configured to supply the use water heated in the heat recovery operation to a load device that uses the use water, and when cooling the air compressor, the heat recovery operation is performed when there is a demand for the use water in the load device, and the heat dissipation operation is performed when there is no demand, wherein: When the detected temperature exceeds the predetermined value, the heat recovery operation is performed as an operation to cool the air compressor regardless of the presence or absence of the demand.

4. The air compressor according to claim 2, wherein: The load device is a boiler device that heats the used water to generate steam.

5. A heat utilization system, wherein: The heat utilization system comprises the air compressor according to any one of claims 2 to 4 and the load device. The load device sends a signal indicating whether there is a need for water to the air compressor. The air compressor determines whether or not the demand exists based on the received signal.

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