Air compressor and heat utilization system

Abstract

To provide an air compressor which can be continuously operated without an operation restriction, etc., even in a situation where an ambient temperature is extremely high, while effectively utilizing characteristics including function of both heat dissipation and heat recovery.SOLUTION: An air compressor 1a comprising a compression mechanism 11 which generates compressed air by compressing supplied air includes: a heat dissipation mechanism 12 which performs a heat dissipation operation for cooling the own machine while dissipating heat generated in a compression process by heat exchange with cooling air or cooling water; a heat recovery mechanism 13 which performs a heat recovery operation for cooling the own machine while recovering heat generated in the compression process by heat exchange with service water; and a temperature detection section 14 for detecting a temperature of a fluid at which correlation with a temperature of the own machine may be generated. In a case where the temperature detected by the temperature detection section 14 exceeds a predetermined value, in the air compressor, when performing the operation for cooling the own machine, the heat recovery operation is performed with a higher priority than the heat dissipation operation.SELECTED DRAWING: Figure 2

Description

Technical Field

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

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 air compression process. Therefore, a heat dissipation mechanism for cooling the machine itself using cooling air or cooling water is provided, and by performing necessary cooling, generation of thermal stress of the machine itself due to overheating is prevented. Repeated generation of thermal stress leads to fatigue damage and creep damage of the compressor body.

[0003] However, in a situation where the ambient temperature around the air compressor is considerably high (for example, when greatly exceeding the specified operating temperature range of the air compressor), it is difficult to sufficiently lower the temperature of the machine itself only by performing the heat dissipation operation, and there is a risk of an emergency stop due to abnormal detection if left as it is. As a conventional example that can solve such problems to some extent, for example, in Patent Documents 1 and 2, an air compressor is disclosed that can suppress a temperature rise by restricting the rotational speed (operation restriction) of the compressor body when the ambient temperature is high and can prioritize continuous operation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the above-described conventional example, even in a situation where the ambient temperature is considerably high, it is possible to continue the operation itself. However, since there are operation restrictions, problems such as a decrease in the compressed air generation capacity occur. Therefore, it is desirable that such operation restrictions are not imposed as much as possible.

[0006] By the way, as an air compressor, there are models that have both a heat dissipation mechanism that can cool the machine itself by dissipating the heat generated during the compression process, and a heat recovery mechanism that can cool the machine itself by recovering the heat generated during the compression process, and can perform both heat dissipation and heat recovery according to the situation. In such an air compressor, while taking advantage of the characteristics of having both heat dissipation and heat recovery functions, it is desired that the operation can be continued without the above-described operation restrictions even in a situation where the ambient temperature is considerably high.

[0007] In view of the above problems, an object of the present invention is to provide an air compressor that can continue operation without operation restrictions such as operation restrictions even in a situation where the ambient temperature is considerably high, while taking advantage of the characteristics of having both heat dissipation and heat recovery functions, and a heat utilization system using the same.

Means for Solving the Problems

[0008] The air compressor according to the present invention is an air compressor provided with a compression mechanism that compresses supplied air to generate compressed air, and includes a heat dissipation mechanism that performs a heat dissipation operation of cooling the machine itself while dissipating the heat generated during the compression process by heat exchange with cooling air or cooling water, a heat recovery mechanism that performs a heat recovery operation of cooling the machine itself while recovering the heat generated during the compression process by heat exchange with service water, and a temperature detection unit that detects the temperature of a fluid that has a correlation with the temperature of the machine itself. When the detected temperature by the temperature detection unit exceeds a predetermined value, in performing the operation of cooling the machine itself, the heat recovery operation is given priority over the heat dissipation operation. According to this configuration, while taking advantage of the characteristics of having both heat dissipation and heat recovery functions, it is possible to continue operation without operation restrictions such as operation restrictions even in a situation where the ambient temperature is considerably high.

[0009] More specifically, as the above configuration, the service water heated in the heat recovery operation is configured to be supplied to a load facility that uses the service water. When performing an operation to cool the own device, an air compressor that determines which of the heat dissipation operation and the heat recovery operation to prioritize according to the presence or absence of demand for the service water in the load facility. When the detected temperature exceeds the predetermined value, as an operation to cool the own device, it may be configured to prioritize the heat recovery operation regardless of the presence or absence of the demand.

[0010] More specifically, as the above configuration, the service water heated in the heat recovery operation is configured to be supplied to a load facility that uses the service water. When performing an operation to cool the own device, when there is a demand for the service water in the load facility, the heat recovery operation is performed, and when there is no such demand, the heat dissipation operation is performed. An air compressor, when the detected temperature exceeds the predetermined value, as an operation to cool the own device, it may be configured to perform the heat recovery operation regardless of the presence or absence of the demand.

[0011] More specifically, as the above configuration, the load facility may be configured as a boiler facility that heats the service water to generate steam. Further, the heat utilization system according to the present invention includes the air compressor having the above configuration and the load facility. The load facility transmits a signal indicating the presence or absence of demand for the service water to the air compressor, and the air compressor determines the presence or absence of the demand based on the received signal.

Advantages of the Invention

[0012] According to the air compressor of the present invention, while taking advantage of the characteristics of having both functions of heat dissipation and heat recovery, even in a situation where the ambient temperature is considerably high, continuous operation is possible without operation restrictions or the like.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] Hereinafter, each embodiment of the present invention will be described with reference to each drawing.

[0015] 1. First Embodiment First, the first embodiment will be described. FIG. 1 is a schematic configuration diagram of a heat utilization system according to the first embodiment. As shown in this figure, the heat utilization system 1 includes an air compressor 1a and a load facility 1b.

[0016] 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 devices 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 for driving the same.

[0017] 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 own machine (air compressor 1a). In the air compressor 1a, since the temperature rises mainly due to the compression heat and frictional heat generated when the air is compressed by the compression mechanism 11, the overheating of the air compressor 1a is suppressed by performing the cooling operation. Note that "cooling the own machine" in the present application includes, in addition to the form of cooling the air compressor itself, the form of cooling the fluid existing in the air compressor (for example, lubricating oil in an oil-fed air compressor, added water in a water-added air compressor, intermediate compressed air in an oil-free air compressor, etc.).

[0018] The heat dissipation mechanism 12 is configured to perform a heat dissipation operation of cooling the own machine while dissipating the heat generated in the compression process by heat exchange with cooling air or cooling water. Among the heat dissipation mechanisms 12, the air-cooled type includes a heat exchanger between the fluid containing the compression heat and the cooling air, and the cooling air is continuously sent to the heat transfer surface of the heat exchanger by a blower fan. Among the heat dissipation mechanisms 12, the water-cooled type includes a heat exchanger between the fluid containing the compression heat and the cooling water, and the cooling water is continuously circulated to the heat transfer surface of the heat exchanger by a circulation pump. The cooling water heated up in the heat exchanger is sent to a cooling tower for heat dissipation into the air, and the cooled cooling water is returned to the heat exchanger again.

[0019] On the other hand, the heat recovery mechanism 13 is configured to perform a heat recovery operation of cooling the own machine while recovering the heat generated in the compression process by heat exchange with service water. The heat recovery mechanism 13 can receive the supply of service water, and the service water heat-recovered by heat exchange is sent to the load facility 1b. Note that the service water refers to the water used in the workplace along with the production of goods or the provision of services.

[0020] The temperature detection unit 14 is configured using a temperature sensor and is arranged so as to be able to detect the temperature of a fluid that has a correlation with the temperature of the own machine (mainly the compressor body). The fluid to be detected for temperature is classified into a fluid that affects the temperature of the own machine and a fluid that is affected by the temperature of the own machine. The fluid that affects the temperature of the own machine is typically the ambient air around the air compressor 1a. When the ambient temperature of the air compressor 1a rises, the temperature of the compressor body rises during the operation of the compression mechanism 11 under the influence. Therefore, the temperature detection unit 14 is arranged to detect the ambient temperature of the air compressor 1a (for example, the intake and exhaust temperature of the housing).

[0021] On the other hand, there are various fluids that are affected by the temperature of the own machine, and a typical one is the discharged air from the compressor body. When the temperature of the compressor body rises, the discharge temperature of the compressed air rises under the influence. Therefore, the temperature detection unit 14 is arranged to detect the discharge temperature of the compressed air from the compressor body.

[0022] When the air compressor 1a is provided with a water-cooled type heat dissipation mechanism 12, the fluid to be detected for temperature may be the cooling water sent to the cooling tower. That is, the temperature detection unit 14 is arranged to detect the forward temperature of the cooling water flowing from the heat exchanger to the cooling tower.

[0023] Also, when the air compressor 1a is an oil-fed air compressor, the fluid to be temperature-detected may be the lubricating oil discharged from the compressor body together with the compressed air. For example, the temperature detection unit 14 is arranged to detect the temperature of the lubricating oil after separation by the oil separator. Also, when the air compressor 1a is a water-added air compressor, the fluid to be temperature-detected may be the added water discharged from the compressor body together with the compressed air. For example, the temperature detection unit 14 is arranged to detect the temperature of the added water after separation by the water separator. Also, when the air compressor 1a is an oil-free air compressor, the fluid to be temperature-detected may be the cooling medium (e.g., cooling oil) circulated in the jacket of the compressor body or the electric motor. For example, the temperature detection unit 14 is arranged to detect the temperature of the cooling medium flowing out of the jacket.

[0024] The control unit 15 controls each part of the air compressor 1a so that it can exhibit normal functions. The control operations performed by the control unit 15 also include a control operation of determining the execution form of the cooling operation according to the situation at that time and making the cooling operation be performed in the determined execution form.

[0025] The load facility 1b utilizes the service water heated by the heat exchange operation in the heat recovery mechanism 13. A typical example of the load facility 1b is a boiler facility that heats service water to generate steam, but the type of the load facility 1b is not limited to this, and various production facilities may also be acceptable. In the load facility 1b, for example, in a situation where the service water tank for storing service water has already stored service water up to the upper limit amount, there is no demand for service water, and it is not necessary to supply the service water after heat recovery to the load facility 1b.

[0026] Taking such points into consideration, the load facility 1b of the present embodiment continuously transmits a demand notification signal indicating the presence or absence of water usage demand to the control unit 15 of the air compressor 1a. As a result, the control unit 15 can receive the demand notification signal, determine the presence or absence of water usage demand in the load facility 1b based on this demand notification signal, and more appropriately control the execution form of the cooling operation. Note that the control unit 15 may also determine the presence or absence of water usage demand in the load facility 1b based on information other than the demand notification signal.

[0027] Next, the determination flow of the execution form of the cooling operation performed by the control unit 15 will be described with reference to the flowchart shown in FIG. 2. Note that the determination flow is periodically repeated, for example, at a predetermined time interval.

[0028] First, the control unit 15 acquires information on the latest detected temperature T by the temperature detection unit 14 (step S1). If this detected temperature T does not exceed the predetermined value α (No in step S2), the control unit 15 causes a normal cooling operation suitable for the situation at that time to be executed (step S3).

[0029] As the process of step S3, in the example of the first embodiment, the control unit 15 recognizes the presence or absence of water usage demand in the load facility 1b based on the latest demand notification signal received from the load facility 1b. Then, when there is such demand, the control unit 15 gives priority to performing the heat recovery operation as the cooling operation, and conversely, when there is no such demand, the control unit 15 gives priority to performing the heat dissipation operation as the cooling operation. Note that when the execution form of the cooling operation is alternatively determined between the heat recovery operation and the heat dissipation operation, only the heat recovery operation is performed as the cooling operation when there is such demand, and conversely, only the heat dissipation operation is performed as the cooling operation when there is no such demand.

[0030] Regarding the specific form in which the heat recovery operation is preferentially performed as the cooling operation, typically, a form in which only the heat recovery operation is performed without the heat dissipation operation can be cited. However, the form in which the heat recovery operation is preferentially performed as the cooling operation is not limited to this, and the heat dissipation operation may be additionally performed in parallel with the heat recovery operation. For example, when mainly performing the heat recovery operation as the cooling operation, but it is difficult to obtain a sufficient cooling effect only with the heat recovery operation, the heat dissipation operation may be additionally performed.

[0031] Regarding the specific form in which the heat dissipation operation is preferentially performed as the cooling operation, typically, a form in which only the heat dissipation operation is performed without the heat recovery operation can be cited. However, the form in which the heat dissipation operation is preferentially performed as the cooling operation is not limited to this, and the heat recovery operation may be additionally performed in parallel with the heat dissipation operation. For example, when mainly performing the heat dissipation operation as the cooling operation, but it is difficult to obtain a sufficient cooling effect only with the heat dissipation operation, the heat recovery operation may be additionally performed.

[0032] On the other hand, if the detected temperature T exceeds the predetermined value α (Yes in step S2), the control unit 15 gives priority to the heat recovery operation as the cooling operation (step S3). That is, in this case, regardless of the presence or absence of the demand for the service water in the load facility 1b, the heat recovery operation is forcibly prioritized as the cooling operation. When the execution form of the cooling operation is alternatively determined from the heat recovery operation and the heat dissipation operation, only the heat recovery operation is performed as the cooling operation.

[0033] According to the above-described series of decision flows (steps S1 to S5), during normal times (under the situation where the detected temperature T does not exceed the predetermined value α), the air compressor 1a can perform a cooling operation according to the situation at that time by taking advantage of the characteristics of having both heat dissipation and heat recovery functions. In particular, in the example of the first embodiment, it is possible to perform an appropriate cooling operation considering the presence or absence of the demand for the service water in the load facility 1b at that time.

[0034] That is, when there is a demand for service water, by preferentially performing the heat recovery operation, the service water after heat recovery can be actively supplied to the load facility 1b, and it is possible to satisfy the demand for service water as much as possible. Conversely, when there is no demand for service water, by preferentially performing the heat dissipation operation, it is possible to prevent as much as possible the situation where too much service water is supplied to the load facility 1b, and it is also possible to suppress the overflow of the tank storing the service water in the load facility 1b and the like.

[0035] However, when the temperature of the fluid that has a correlation with the temperature of the own device is high (under the situation where the detected temperature T exceeds the predetermined value α), regardless of the presence or absence of the demand for service water in the load facility 1b, the heat recovery operation is preferentially performed as the cooling operation. That is, at high temperatures, in order to prevent the generation of thermal stress in the air compressor 1a due to overheating, cooling of the own device as strong as possible is required. Therefore, in this case, as the cooling operation, the heat recovery operation with a higher cooling effect than the heat dissipation operation is forcibly prioritized, so that the generation of thermal stress in the air compressor 1a is prevented as much as possible.

[0036] The heat dissipation mechanism 12 dissipates the heat generated in the compression process to the atmosphere, whether it is an air-cooled type or a water-cooled type. Therefore, when the ambient air becomes high in temperature, the cooling effect of the own device relatively decreases. On the other hand, the service water (for example, tap water or groundwater) supplied to the heat recovery mechanism 13 is lower in temperature than the ambient air unless it has stayed in a water receiving tank or piping exposed to direct sunlight for a long time, so a stronger cooling effect than that of the heat dissipation mechanism 12 can be obtained.

[0037] As described above, while making use of the characteristics of the air compressor 1a having both functions of heat dissipation and heat recovery, even in a situation where the ambient temperature is quite high, it is possible to continue operation without any operation restrictions such as restrictions on the rotational speed of the compressor. Note that the predetermined value α (the temperature corresponding to the threshold values in the normal and high temperature cases described above) is desirably set to an appropriate value so as to effectively prevent the generation of thermal stress in the air compressor 1a due to overheating while preventing the heat recovery operation from being preferentially performed unnecessarily.

[0038] Figure 3 shows a more specific configuration example of the main components related to the heat recovery operation in the first embodiment. The heat recovery mechanism 12 of the air compressor 1a shown in this figure has a heat exchanger 20, a pump 21, an accumulator 22, a first control valve 23, and a service water line L10. As other peripheral elements, it also has a buffer tank 24, a second control valve 25, a hot water outlet temperature sensor 26, and a makeup water line L20. The load facility 1b has a water supply tank 1ba and a boiler main body 1bb.

[0039] As shown in Figure 3, the service water line L10 is connected from the buffer tank 24 to the water supply tank 1ba via the pump 21, the heat exchanger 20, and the first control valve 23 in sequence. In the service water line L10, an accumulator 22 is arranged between the pump 21 and the heat exchanger 20, and a hot water outlet temperature sensor 26 is arranged between the first control valve 23 and the water supply tank 1ba.

[0040] One end of the makeup water line L20 is connected to a position P1 between the accumulator 22 and the heat exchanger 20 in the service water line L10, and the other end is connected to a 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.

[0041] 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 so that the storage amount of the service water Wa in the buffer tank 24 is within a predetermined range.

[0042] The heat exchanger 20 is configured to perform heat exchange (including indirect heat exchange through a medium) between the service water Wa supplied from the service water line L10 and the compressor mechanism 11 etc. in the own unit (air compressor 1a). Thereby, when the service water Wa is supplied to the heat exchanger 20, a heat recovery operation capable of cooling the own unit is performed.

[0043] The first control valve 23 can have its opening degree adjusted by the control unit 15 and serves to enable the adjustment of the flow rate of the service water Wa in the service water line L10. When the first control valve 23 is opened with the pump 21 operating, the service water Wa is supplied to the heat exchanger 20, a heat recovery operation for cooling the own device is performed, and the service water Wa heat-recovered in the heat exchanger 20 is supplied to the water supply tank 1ba.

[0044] The second control valve 25 can have its opening and closing controlled by the control unit 15. When the second control valve 25 is opened with the pump 21 operating, the service water Wa (service water that has not been heat-recovered) that has not passed through the heat exchanger 20 is supplied to the water supply tank 1ba.

[0045] The load facility 1b functions as a boiler facility that supplies the service water Wa stored in the water supply tank 1ba as boiler feed water to the boiler main body 1bb and heats the service water Wa in the boiler main body 1bb to generate steam. The load facility 1b monitors the storage amount of the service water Wa in the water supply tank 1ba based on, for example, the detection signal of a water level sensor (not shown). If this storage amount is below a predetermined reference value (water reduction value), a demand notification signal indicating that there is a demand for the service water Wa is transmitted to the control unit 15. If this storage amount has reached the upper limit value (full water value), a demand notification signal indicating that there is no demand for the service water Wa is transmitted to the control unit 15. The control unit 15 can receive this demand notification signal and recognize the presence or absence of the demand for the service water Wa in the load facility 1b.

[0046] 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), there is a sufficient difference in the storage amount. When the steam usage amount is large and the boiler main body 1bb is operating 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 executed in a situation where it is recognized that there is no demand for the service water Wa, overflow occurs in the water supply tank 1ba, and a situation where the service water Wa is discarded is avoided. On the other hand, when the steam usage amount is small and the boiler main body 1bb is operating 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 is operating at a low load, generally the operating rate of the production equipment is low, and the consumption flow rate of the compressed air is likely to be reduced. That is, in a situation where the operating rate of the air compressor 1a has dropped, the scene where forced cooling of the air compressor 1a is required is for a short time. Therefore, even if the heat recovery operation is executed in a situation where it is recognized that there is no demand for the service water Wa and overflow occurs in the water supply tank 1ba, it is temporary.

[0047] When the control unit 15 executes the heat recovery operation, it operates the pump 21 and controls the first control valve 23 to be in an open state. Thereby, the service water Wa is supplied to the heat exchanger 20, and the heat recovery operation is performed. Also, the degree of cooling of the own machine in the heat recovery operation can be adjusted by controlling the opening degree of the first control valve 23 to change the flow rate of the service water Wa in the heat exchanger 20. Note that the control unit 15 may control the opening degree of the first control valve 23 so that the detected temperature of the hot water outlet temperature sensor 26 becomes the target temperature (that is, the service water Wa supplied to the water supply tank 1ba is constant 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 may 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 be in an open state so that more service water Wa is supplied to the water supply tank 1ba via the makeup water line L20.

[0048] On the other hand, when the control unit 15 does not execute the heat recovery operation, it controls the first control valve 23 to be in a closed state. As a result, since the service water Wa is not supplied to the heat exchanger 20, the heat recovery operation is not executed. However, even in this case, when the cooling operation is necessary, it is possible to execute the heat dissipation operation by the heat dissipation mechanism 12. Even when 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 be in 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 be in a closed state.

[0049] As described above, the air compressor 1a is an air compressor provided with a compression mechanism 11 that compresses the supplied air to generate compressed air, and includes a heat dissipation mechanism 12 that performs a heat dissipation operation to cool the machine itself while dissipating the heat generated in the compression process by heat exchange with cooling air or cooling water, a heat recovery mechanism 13 that performs a heat recovery operation to cool the machine itself while recovering the heat generated in the compression process by heat exchange with service water, and a temperature detection unit 14 that detects the temperature of a fluid that has a correlation with the temperature of the machine itself. When the detected temperature T by the temperature detection unit 14 exceeds a predetermined value α, the air compressor 1a gives priority to the heat recovery operation over the heat dissipation operation when performing a cooling operation to cool the machine itself. Therefore, while taking advantage of the characteristics with both functions of heat dissipation and heat recovery, it is possible to continue operation without operation restrictions or the like even in a situation where the ambient temperature is considerably high.

[0050] More specifically, when performing a cooling operation to cool the air compressor 1a itself, it determines which of the heat dissipation operation and the heat recovery operation to give priority to according to the presence or absence of the demand for service water in the load facility 1b. However, when the detected temperature T exceeds the predetermined value α, it gives priority to the heat recovery operation regardless of the presence or absence of the demand as a cooling operation. That is, when performing a cooling operation, the air compressor 1a performs a heat recovery operation when the demand exists and performs a heat dissipation operation when the demand does not exist. However, when the detected temperature T exceeds the predetermined value α, it performs a heat recovery operation regardless of the presence or absence of the demand as a cooling operation.

[0051] As described above, the first embodiment has been explained. However, the specific form of the air compressor 1a is not limited to that of 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.

[0052] 2. Second Embodiment Next, the second embodiment will be described. In the following description, emphasis will be placed on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. Also in the air compressor 1a of the second 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 provided. The temperature detection unit 14 is arranged, for example, inside the housing of the air compressor 1a to detect the temperature of the outside air taken in for intake and ventilation.

[0053] FIG. 4 schematically shows the configuration of the air compressor 1a (oil-fed air compressor) according to the second embodiment. As shown in this figure, the air compressor 1a includes a compression mechanism 11, an oil separator 120, an oil cooler 130 for heat recovery, and an oil cooler 140 for heat dissipation.

[0054] The air compressor 1a also includes a first air supply line L110 that flows the compressed air discharged from the compression mechanism 11 into the oil separator 120, a second air supply line L120 connected to the gas phase part of the oil separator 120, a return oil line L130 connected to the liquid phase part of the oil separator 120 and returning lubricating oil to the compressor 110, a first bypass line L131 that bypasses the oil cooler 140 for heat dissipation in the return oil line L130, and a second bypass line L132 that bypasses the oil cooler 130 for heat recovery and the oil cooler 140 for heat dissipation in the return oil line L130. Further, an air introduction line L140 for introducing air into the compression mechanism 11 is provided.

[0055] The compressor body 111 that constitutes the compression mechanism 11 is, for example, a screw type. By driving the electric motor 112 connected to the drive shaft of the compressor body 111, outside air is inhaled and adiabatically compressed to generate compressed air Aa, which is then discharged. The compressor body 111 is oil-cooled, and by introducing lubricating oil Oa together with the intake air, cooling of the screw rotor, that is, removal of the compression heat, is performed.

[0056] A first air supply line L110 through which the compressed air Aa discharged from the compressor body 111 flows is connected to the discharge port of the compressor body 111. An oil separator 120 for separating lubricating oil from the compressed air is connected to the downstream side of the first air supply line L110.

[0057] A second air supply line L120 through which the compressed air Ab after gas-liquid separation flows is connected to the gas phase part of the oil separator 120. On the other hand, an oil return line L130 for returning the lubricating oil Oa after gas-liquid separation to the intake side of the compressor body 111 is connected to the liquid phase part of the oil separator 120. A lubricating oil temperature sensor 121 for measuring the lubricating oil temperature To of the lubricating oil Oa after gas-liquid separation is provided in the liquid phase part of the oil separator 120.

[0058] In the oil return line L130, a temperature control valve 153, an oil cooler 130 for heat recovery, and an oil cooler 140 for heat dissipation are provided in order from the upstream side.

[0059] A second bypass line L132 for bypassing the lubricating oil Oa to the oil cooler 130 for heat recovery and the oil cooler 140 for heat dissipation 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 oil cooler 130 for heat recovery 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 in the oil separator 120.

[0060] The oil cooler 130 for heat recovery is a heat exchanger for recovering the compression heat of the lubricating oil Oa flowing through the oil return line L130. A water supply line L150 for flowing the service water Wa is connected to the oil cooler 130 for heat recovery. The water supply line L150 includes a primary side line L151 through which the service water Wa before being heated by the oil cooler 130 for heat recovery flows, and a secondary side line L152 through which the service water Wa after being heated by the oil cooler 130 for heat recovery flows.

[0061] On the primary side line L151 of the water supply line L150, a pump 171, a water treatment device 172, a flow rate sensor 173, and an air cooler 180 for heat recovery (to be described in detail later) are provided in order from the upstream side. Further, on the secondary side line L152 of the water supply line L150, a flow rate adjustment valve 174 and a hot water temperature sensor 175 are provided in order from the upstream side.

[0062] The pump 171 and the flow rate adjustment valve 174 are connected to the control unit 15 and are driven by a command signal from the control unit 15. The water treatment device 172 performs processes such as removal of impurities. The water treatment device 172 includes, for example, a hard water softening device and a water supply strainer. The flow rate sensor 173 detects the flow rate of the service water Wa passing through. The flow rate of the service water Wa detected by the flow rate sensor 173 is transmitted to the control unit 15. The hot water temperature sensor 175 detects the temperature of the service water Wa after passing through the oil cooler 130 for heat recovery.

[0063] The pump 171 and the flow rate adjustment valve 174 in the present embodiment function as water flow switching means for switching between a water flow execution state and a water flow stop state with respect to the oil cooler 130 for heat recovery. Further, this water flow switching means also has a water flow rate adjustment function for adjusting the water flow rate with respect to the oil cooler 130 for heat recovery.

[0064] The service water Wa after being heated by the oil cooler 130 for heat recovery is supplied to the load facility 1b through the secondary line L152 of the service water line L150. In this way, the air compressor 1a of the present embodiment can warm the service water Wa by recovering the compression heat generated in the compressor main body 111 with the oil cooler 130 for heat recovery, and supply this warm water to the load facility 1b.

[0065] On the downstream side of the oil cooler 130 for heat recovery in the oil return line L130, a radiator oil cooler 140 is provided. The radiator oil cooler 140 includes a heat exchanger 141 (a heat exchange core composed of an assembly such as a plate fin or a fin tube), 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 through the inside of the heat exchanger 141, and the lubricating oil Oa at a temperature suitable for cooling the compressor main body 111 is generated.

[0066] Note that a mode can also be adopted in which other parts of the air compressor 1a are simultaneously cooled (for example, the control box) or ventilated (for example, the inside of 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 rotation speed equal to or higher than the minimum rotation speed.

[0067] The lubricating oil Oa that has flowed through the oil cooler 130 for heat recovery and the radiator oil cooler 140 is returned to the inside of the compressor main body 111 again through the oil return line L130.

[0068] A bypass branch portion 160 is provided between the oil cooler 130 for heat recovery and the radiator oil cooler 140 in the oil return line L130. A first bypass line L131 for bypassing the lubricating oil Oa with respect to the radiator oil cooler 140 is connected to this 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.

[0069] The bypass branch portion 160 is configured 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 communication pipe 163. The straight pipe 161 has an outlet pipe 130A of the heat recovery oil cooler 130 connected to its upstream start end, and an inlet port 151A of the bypass valve 151 connected to its downstream end. The T-shaped pipe 162 is a branching pipe incorporated in the middle of the straight pipe 161. The communication pipe 163 communicates the inlet pipe 140A of the heat dissipation oil cooler 140 with the branch port 162A of the T-shaped pipe 162. Note that the outlet pipe 130A of the heat recovery oil cooler 130 and the upstream start end of the straight pipe 161 may be connected via other piping.

[0070] When the bypass valve 151 is open, among the lubricating oil Oa that has passed through the heat recovery oil cooler 130, the first diverted flow that flows through the first bypass line L131 is supplied to the bypass valve 151 via the straight pipe 161. Therefore, in the process of passing through the bypass valve 151, it only needs to receive a relatively small frictional loss in the valve chamber. On the other hand, the second diverted flow that flows through the oil return line L130 is supplied to the heat dissipation oil cooler 140 via the T-shaped pipe 162. Therefore, it suffers a branch loss at the T-shaped pipe 162 and receives a relatively large frictional loss in the heat dissipation oil cooler 140 in the process of passing through the heat dissipation oil cooler 140. Therefore, the flow rate ratio of the lubricating oil Oa is "the first diverted flow > the second diverted flow", and most of the lubricating oil Oa will flow on the side of the first bypass line L131. Thereby, in order to prevent the lubricating oil Oa flowing back to the compressor body 111 from being excessively cooled, the purpose can be achieved inexpensively only by adjusting the pipeline resistance without providing a shut-off valve on the side of the heat dissipation oil cooler 140.

[0071] The control unit 15 performs control to switch the water passing switching means to the water passing execution state and control to switch it to the water passing stop state. In the water passing execution state, the pump 171 is operated and the flow rate adjustment valve 174 is opened. On the other hand, in the water passing stop state, the pump 171 is stopped and the flow rate adjustment valve 174 is closed.

[0072] Note that the switching determination between the water flow execution state and the water flow stop state can be made based on the water level information of the water supply tank 1ba (not shown) of the load facility 1b connected to the secondary side line L152. When the water level in the water supply tank 1ba of the load facility 1b drops to a predetermined reference value (water reduction value), the load facility 1b transmits a demand notification signal indicating that there is a demand for the service water Wa to the control unit 15. When the water level in the water supply tank 1ba rises to the upper limit value (full water value), the load facility 1b transmits a demand notification signal indicating that there is no demand for the service water Wa to the control unit 15. When the control unit 15 receives the demand notification signal indicating that there is such a demand, it determines it as the switching timing from the water flow stop state to the water flow execution state. When the control unit 15 receives the demand notification signal indicating that there is no such demand, it determines it as the switching timing from the water flow execution state to the water flow stop state.

[0073] In addition, the control unit 15 performs opening and closing control of the bypass valve 151. Specifically, when the water flow switching means is in the water flow execution state, the control unit 15 opens the bypass valve 151, and when the water flow switching means is in the water flow stop state, the control unit 15 closes the bypass valve 151.

[0074] In this way, when the service water Wa is flowed through the oil cooler 130 for heat recovery to perform heat recovery, the bypass valve 151 is configured to be opened. Therefore, most (for example, 90% or more) of the lubricating oil Oa flows through the first bypass line L131, and the oil supply amount to the oil cooler 140 for heat dissipation is small (for example, less than 10%). Since the influence of cooling in the oil cooler 140 for heat dissipation on the lubricating oil Oa after confluence is minimized, the lubricating oil Oa flowing back to the compressor body 111 is maintained within an appropriate temperature range without being excessively cooled. As a result, the required heat recovery amount can be ensured without reducing the oil supply amount to the oil cooler 130 for heat recovery.

[0075] Also, when the bypass valve 151 is opened, if the cooling water Wa supplied to the heat recovery oil cooler 130 is at a low temperature, or if the lubricating oil Oa sent out from the oil separator 120 has become too cold due to a large cooling water flow rate or other reasons, a part of the lubricating oil Oa is bypassed to the heat recovery oil cooler 130 by the temperature control valve 153. Thereby, while actively performing heat recovery in the heat recovery oil cooler 30, the lubricating oil Oa returned to the compressor body 111 can be maintained within an appropriate temperature range.

[0076] Note that the opening and closing of the bypass valve 151 may be an immediate operation accompanying the switching between the cooling water execution state and the cooling water stop state, or may be a gradual operation. In the case of an immediate operation, when the cooling water switching means is switched to the cooling water execution state, the bypass valve 151 is opened simultaneously or after a delay of about several seconds. Also, when the cooling water switching means is switched to the cooling water stop state, the bypass valve 151 is closed simultaneously or after a delay of about several seconds. In the case of a gradual operation, when the cooling water switching means is switched to the cooling water execution state and a predetermined condition (for example, the temperature condition of the cooling water, etc.) is satisfied, the bypass valve 151 is opened. Also, when the cooling water switching means is switched to the cooling water stop state and a predetermined condition (for example, the flow rate condition of the cooling water, etc.) is satisfied, the bypass valve 151 is closed.

[0077] Also, while the control unit 15 is switching the cooling water switching means to the cooling water execution state, it 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.

[0078] Also, as shown in FIG. 4, in the present embodiment, heat recovery is also performed from the compressed air Ab after gas-liquid separation by the oil separator 120. A heat recovery air cooler 180 is provided in the second air supply line L120. Also, a heat dissipation air cooler 190 is provided on the downstream side of the heat recovery air cooler 180. The compressed air Ab that has passed through the heat recovery air cooler 180 is introduced into the heat dissipation air cooler 190 and further cooled.

[0079] The air cooler 180 for heat recovery is a heat exchanger for recovering the compression heat of the compressed air Ab after gas-liquid separation flowing through the second air supply line L120. A water supply line L150 for flowing the service water Wa is connected to the air cooler 180 for heat recovery. Here, the air cooler 180 for heat recovery is provided as a heat exchanger that performs heat exchange between the service water Wa and the high-temperature fluid together with the oil cooler 130 for heat recovery to obtain warm water from the service water Wa. The water supply line L150 is configured to flow the service water Wa in series to the oil cooler 130 for heat recovery and the air cooler 180 for heat recovery.

[0080] And the pump 171 and the flow rate adjustment valve 174 as the water flow switching means are means for switching the oil cooler 130 for heat recovery and the air cooler 180 for heat recovery to the same water flow state.

[0081] The air cooler 190 for heat dissipation includes a heat exchanger 191 (a heat exchange core composed of an assembly such as a plate fin or a fin tube), 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.

[0082] Note that the cooling fan 192 of the air cooler 190 for heat dissipation and the cooling fan 142 of the oil cooler 140 for heat dissipation may be shared, and a configuration may be adopted in which one cooling fan cools the heat exchanger 191 of the air cooler 190 for heat dissipation and the heat exchanger 141 of the oil cooler 140 for heat dissipation.

[0083] The oil cooler 130 for heat dissipation and the air cooler 190 for heat dissipation may be of a water-cooled type instead of an air-cooled type. In the case of the water-cooled type, a heat exchanger between the compressed air or lubricating oil and the circulating cooling water is provided, and the circulating cooling water that has absorbed heat in the heat exchanger is radiated by a cooling tower.

[0084] <Function> The oil-fed air compressor 1a according to the second embodiment is configured to lubricate and cool the compressor mechanism 11 (compressor main body 111) of the own machine with the lubricating oil Oa circulating through the oil return line L130 including the first air supply line L110 and the first bypass line L131. The oil cooler 140 for heat dissipation, the cooling fan 142, and the fan motor 143 constitute a heat dissipation mechanism 12 that cools the compressor mechanism 11 while dissipating the compression heat by the heat exchange between the cooling air and the lubricating oil Oa. On the other hand, the oil cooler 130 for heat recovery, the pump 171, the flow rate adjustment valve 174, and the water supply line L150 constitute a heat recovery mechanism 13 that cools the compressor mechanism 11 while recovering the compression heat by the heat exchange between the water supply Wa and the lubricating oil Oa.

[0085] When the detected temperature T by the temperature detection unit 14 does not exceed the predetermined value α, the control unit 15 performs the following cooling operation. It is assumed that the cooling fan 142 is driven by the fan motor 143. When there is a demand for the water supply Wa in the load facility 1b, the control unit 15 controls to open the bypass valve 151, open the flow rate adjustment valve 174, and operate the pump 171. Thereby, in the oil cooler 130 for heat recovery, the compression heat contained in the lubricating oil Oa is recovered by the water supply Wa, and the cooled lubricating oil Oa is returned, whereby the compressor mechanism 11 of the own machine is cooled. On the other hand, when there is no demand for the water supply Wa in the load facility 1b, the control unit 15 controls to close the bypass valve 151, close the flow rate adjustment valve 174, and stop the pump 171. Thereby, in the oil cooler 140 for heat dissipation, the compression heat contained in the lubricating oil Oa is dissipated by the cooling air, and the cooled lubricating oil Oa is returned, whereby the compressor mechanism 11 of the own machine is cooled.

[0086] When the detected temperature T by the temperature detection unit 14 exceeds a predetermined value α, the control unit 15 causes the heat recovery operation to be executed regardless of the demand for the service water Wa in the load facility 1b. That is, the control unit 15 opens the flow rate adjustment valve 174 and controls to drive the pump 171. At this time, it is preferable that the control unit 15 closes the bypass valve 151. As a result, the lubricating oil Oa circulating through the compression mechanism 11 is more strongly cooled using both the heat recovery oil cooler 130 and the heat dissipation oil cooler 140. As a result, even when the ambient temperature of the air compressor 1a rises and the intake temperature becomes high, it becomes possible to prevent overheating of the compressor main body 111, and there is no need to limit the rotation speed of the electric motor 112.

[0087] 3. Third Embodiment Next, the third embodiment will be described. In the following description, emphasis will be placed on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. Also 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 provided. The temperature detection unit 14 is arranged, for example, inside the housing of the air compressor 1a to detect the temperature of the outside air taken in for intake and ventilation.

[0088] FIG. 5 schematically shows the configuration of the air compressor 1a (water-added type air compressor) according to the third embodiment. The air compressor 1a mainly includes, as components related to air compression, a compression mechanism 11, a pre-separator 204 that separates the discharged fluid from the compression mechanism 11 into gas and water, an after-cooler 205 that cools the compressed air after gas-liquid separation by the pre-separator 204, a water cooler 206 that cools the separated water after gas-liquid separation by the pre-separator 204, and a separator tank 207 to which the compressed air and the separated water after passing through each cooler 205, 206 are supplied.

[0089] The compressor body 203 that constitutes the compression mechanism 11 is, for example, of the scroll type. By driving the electric motor 208 connected to the drive shaft of the compressor body 203, outside air is inhaled and adiabatically compressed to generate compressed air Aa, which is then discharged. The compressor body 203 is of the water addition type, and by introducing the added water Wb together with the supply air, cooling of the orbiting scroll and the fixed scroll, that is, removal of the compression heat, is performed.

[0090] When the compressor body 203 is operated, outside air is sucked into the compressor body 203 from the suction passage 210 through the air filter 209. At this time, the added water Wb is injected at a set flow rate through the added water return passage 211 from the separator tank 207. Then, the compressed air Aa generated in the compressor body 203 is discharged to the pre-separator 204 while accompanied by the lubricating water Wb. A check valve 213 is provided in the discharge passage 212 from the compressor body 203 to the pre-separator 204.

[0091] Note that the water addition type compressor body 203 can also be said to be a water lubrication type or a water injection type, etc. Also, here, in the compressor body 203, the added water Wb is injected into the air suction port, but it may be provided with a water injection port other than the air suction port, and the added water Wb may be injected into this water injection port.

[0092] The pre-separator 204 receives the discharged fluid Aa (compressed air discharged together with the added water) from the compressor body 203 and separates the gas and water. That is, the discharged fluid Aa from the compressor 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. And the gas phase part of the pre-separator 204 is connected to the gas phase part of the separator tank 207 through the gas phase connection passage 214, while the liquid phase part of the pre-separator 4 is connected to the liquid phase part of the separator tank 207 through the liquid phase connection passage 215.

[0093] An aftercooler 205 is provided in the gas-phase connection passage 214 from the pre-separator 204 to the separator tank 207. The aftercooler 205 is a means for cooling the compressed air Ab after gas-liquid separation in the pre-separator 204. The aftercooler 205 acts as a heat exchanger for heat recovery that exchanges heat between the compressed air Ab and the service water Wa. In the aftercooler 205, the compressed air Ab is cooled by the service water Wa, while the service water Wa is heated by the compressed air Ab.

[0094] A water cooler 206 is provided in the liquid-phase connection passage 215 from the pre-separator 204 to the separator tank 207. The water cooler 206 is a means for cooling the separated water Wb after gas-liquid separation in the pre-separator 204. The water cooler 206 acts as a heat exchanger for heat recovery 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, while the service water Wa is heated by the separated water Wb.

[0095] The separator tank 207 receives the compressed air Ab and the separated water Wb after passing through the respective coolers 205 and 206, and performs gas-liquid separation. The compressed air Ab from the pre-separator 204 is cooled by the aftercooler 205 to achieve condensation of moisture, and the moisture is removed in the separator tank 207. Therefore, the inside of the separator tank 207 is also divided into an upper gas-phase part and a lower liquid-phase part. Note that the fluid supply from the pre-separator 204 to the separator tank 207 via the respective connection passages 214 and 215 is performed by the discharge pressure of the compressor main body 203 and the head pressure difference.

[0096] In the gas phase portion of the separator tank 207, in addition to the gas phase connection passage 214 described above, a compressed air supply passage 217 to the compressed air utilization section is connected. In the compressed air supply passage 217, a primary pressure regulating valve 218 and a check valve 219 are provided in order from the side of the separator tank 207. The primary pressure regulating valve 218 is a valve that maintains the inside of the separator tank 207 at or above a set pressure during the operation of the compressor main body 203. Here, the primary pressure regulating valve 218 is a self-operating valve that operates mechanically based on the pressure on the primary side (that is, the separator tank 207 side), but in some cases, it may be an electric valve that monitors the pressure on the primary side with a sensor and is controlled based on the detected pressure. In addition, in the present embodiment, in the gas phase portion of the separator tank 207, in addition to the safety valve 220, a bleed valve 221 for exhausting to the outside is provided. Note that the primary pressure regulating valve 218 and the check valve 219 can also be configured as an integrated valve mechanism.

[0097] In the liquid phase portion of the separator tank 207, in addition to the liquid phase connection passage 215 described above, a return passage 211 for the added water to the compressor main body 203 is connected. In the return passage 211 for the added water, an added water valve 222 and a water filter 223 are provided in order from the side of the separator tank 207. During the operation of the compressor main body 203, by opening the added water valve 222, the stored water in the separator tank 207 can be returned to the compressor main body 203 through the return passage 211 for the added water. At that time, due to the suction to the compressor main body 203 by the operation of the compressor main body 203 and the pressurization in the separator tank 207, the added water Wb can be returned from the separator tank 207 to the compressor main body 203. Further, by the primary pressure regulating valve 218, the inside of the separator tank 207 is maintained at or above the set pressure, and as will be described later, the pressure in the compressed air supply passage 217 (and thus the pressure in the separator tank 207) is maintained as desired. Therefore, while making the added water valve 222 function as an orifice, the added water Wb can be supplied to the compressor main body 203 at a set flow rate. Moreover, when supplying the added water Wb from the separator tank 207 to the compressor main body 203, contaminants can be removed by the water filter 223.

[0098] The air compressor 1a further includes a water supply passage 224 and a drain passage 225. The water supply passage 224 is a means for replenishing makeup water Wf from a water supply source such as an ion exchange device (for example, a mixed bed type pure water device or a hard water softening device) as added water Wb. In the present embodiment, the water supply passage 224 from the water supply source is branched into a first water supply passage 224A and a second water supply passage 224B. While the first water supply passage 224A is connected to the suction passage 210 to the compressor main body 203, the second water supply passage 224B is connected to the separator tank 207. A first water supply valve 226 is provided in the first water supply passage 224A, while a check valve 227 and a second water supply valve 228 are provided in the second water supply passage 224B in this order. 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.

[0099] On the other hand, the drain passage 225 is connected to the bottom of the separator tank 207. A drain valve 229 is provided in the drain passage 225, and by opening the drain valve 229, drainage from the inside of the separator tank 207 can be achieved.

[0100] In addition, a water level detector 230 is provided in the separator tank 207. The configuration of the water level detector 230 is not particularly limited, but for example, it is a float water level detector capable of detecting the water level of purified water / condensate containing no ions. Further, a pressure sensor 231 is provided downstream of the primary pressure regulating valve 218 and the check valve 219 in the compressed air supply passage 217 from the separator tank 7. By this pressure sensor 231, the discharge pressure of the compressed air Ab (the supply pressure to the compressed air utilization part) can be monitored.

[0101] In the air compressor 1a, when the operation of the compressor main body 203 is started, the compressor main body 203 sucks in air through the air filter 209, compresses it, and discharges it. The compressed air Ab discharged from the compressor main body 203 is sent from the compressed air delivery path 217 to the compressed air utilization section through the pre-separator 204, the after-cooler 205, and the separator tank 207. However, since the primary pressure regulating valve 218 is provided in the compressed air delivery path 217, when the pressure in the separator tank 207 is low immediately after the start of operation, the primary pressure regulating valve 218 is closed, and the compressed air Ab is not sent to the compressed air utilization section. When the pressure on the primary side (i.e., the separator 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 the compressed air Ab is sent to the compressed air utilization section.

[0102] 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 controlled by on-off control or inverter control. Note that the target pressure is higher than the set pressure of the primary pressure regulating valve 218. Therefore, hereafter, basically, the inside of the separator tank 207 is maintained at the target pressure.

[0103] During the operation of the compressor main body 203, by opening the water addition valve 222, the added water Wb can be injected at a set flow rate into the suction port of the compressor main body 203. 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 discharged to the pre-separator 204 in a state accompanied by the added water Wb. Then, gas-liquid separation is achieved in the pre-separator 204. The compressed air Ab after gas-liquid separation in the pre-separator 204 is cooled by the after-cooler 205, and then further gas-liquid separated in the separator tank 207, and is sent out 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, then stored in the separator tank 207, and can be supplied to the compressor main body 203 through the added water return path 211.

[0104] During the operation of the compressor body 203, the water level in the separator tank 207 is maintained at a set water level. For example, when the detected water level by the water level detector 230 exceeds the upper limit water level, the drain valve 229 is opened to lower the water level to a predetermined level. Conversely, when the detected water level by the water level detector 230 falls below the lower limit water level, the first water supply valve 226 is opened to raise the water level to a predetermined level. During the opening of the first water supply valve 226, the makeup water Wf is supplied to the separator tank 207 via the compressor body 203. During this period, the makeup water valve 222 may be closed. During the stop of the compressor body 203, the second water supply valve 228 can be opened to directly supply the makeup water Wf to the separator tank 207.

[0105] On the other hand, when the compressor body 203 stops, the air release valve 221 is opened. By opening the air release valve 221 even during the stop of the compressor body 203, reverse rotation of the compressor body 203 can be prevented. After that, when the compressor body 203 restarts, the air release valve 221 is closed.

[0106] Also, the air compressor 1a mainly includes, as components related to heat recovery, an aftercooler 205 and a water cooler 206 which are heat exchange devices for heating the service water Wa by the compression heat of the compressor body 203, an inlet passage 232 for the service water Wa to the aftercooler 205, an outlet passage 233 for the service water Wa from the water cooler 206, a return passage 234 for the service water Wa connecting the outlet passage 233 and the inlet passage 232, switching means 235 (flow control valve 236, return valve 237) for switching the liquid passage and the circulation passage described later, and a radiator 238 for cooling the circulating water in the circulation passage.

[0107] As described above, in the aftercooler 205, the compressed air Ab and the service water Wa are heat-exchanged to cool the compressed air Ab with the service water Wa while heating the service water Wa with 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 heat-exchanges the makeup water Wb (separated water in the pre-separator) and the service water Wa to cool the makeup water Wb with the service water Wa while heating the service water Wa with the makeup water Wb. The compression heat of the makeup water Wb can be used for heating the service water Wa to achieve heat recovery.

[0108] The aftercooler 205 and the water cooler 206 are sequentially passed through with service water Wa. Therefore, the aftercooler 205 and the water cooler 206 are connected by a communication path 239. And the service water Wa flows in the order of the inlet path 232, the aftercooler 205, the communication path 239, the water cooler 206, and the outlet path 233.

[0109] On the inlet path 232 from the water supply source, a pump 240, a check valve 241, and a radiator 238 are provided in order from the upstream side. By operating the pump 240, the service water Wa can be circulated through the aftercooler 205 and the water cooler 206. The radiator 238 is an air-cooled radiator, and heat exchange is performed between the service water Wa and the cooling air (ventilation by the fan 238A). For example, when the temperature of the service water at 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 by the fan 238A.

[0110] On the outlet path 233 from the water cooler 206, a flow rate adjustment valve 236 and a hot water temperature sensor 243 are provided. During the operation of the compressor body 203, by opening the flow rate adjustment valve 236 and operating the pump 240, the service water Wa can be passed through the aftercooler 205 and the water cooler 206 to recover the compression heat. In the example of this embodiment, the flow rate adjustment valve 236 is composed of an electric valve whose opening degree can be adjusted.

[0111] The outlet passage 233 upstream of the flow rate adjustment valve 236 and the inlet passage 232 upstream of the 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 point between the inlet passage 232 and the return passage 234. However, the installation of the storage tank 242 can be omitted depending on the case. Further, the storage tank 242 may be provided downstream (preferably upstream of the pump 240) rather than at the connection point with the return passage 234 within the inlet passage 232. Note that the pump 240 may be provided downstream of the connection point between the inlet passage 232 and the return passage 234, or may be provided upstream of the connection point between the communication passage 239 or the outlet passage 233 and the return passage 234.

[0112] A return valve 237 is provided in the return passage 234. In the example of the present embodiment, the return valve 237 is composed of 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 cooler 205, 206 is returned to the inlet passage 232 via the return passage 234 or sent downstream of the outlet passage 233 without passing through the return passage 234.

[0113] In the example of the present embodiment, the switching means 235 is composed of 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 either the water passage described below or the circulation path.

[0114] The water passage is realized by opening the flow rate adjustment valve 236 with the return valve 237 closed. The water passage is a path that includes the inlet passage 232, the after-cooler 205, the water cooler 206, and the outlet passage 233, and does not include the return passage 234. When the pump 240 is operated in the state of being switched to the water passage, the service water Wa from the inlet passage 232 passes through the after-cooler 205 and the water cooler 206, and is led out through the flow rate adjustment valve 236 of the outlet passage 233 (heat recovery implementation state). At this time, the storage tank 242 is appropriately supplied with water from a water supply source. In other words, while the pump 240 is operating in the water passage, makeup water from the water supply source is supplied to the inlet passage 232.

[0115] The circulation path is realized by opening the return valve 237 with the heat recovery valve 236 closed. The circulation path is a path including the inlet path 232 on the downstream side of the connection point of the return path 234, the aftercooler 205, the water cooler 206, the outlet path 233 on the upstream side of the connection point of the return path 234, and the return path 234. When the pump 240 is operated in the state of being switched to the circulation path, the service water Wa from the pump 240 is returned to the suction side of the pump 240 and circulated via the aftercooler 205, the water cooler 206, and the return path 234. At this time, by operating the radiator 238, the circulating cooling water can be cooled in the radiator 238 (heat recovery stop state). Note that there is no need for new water supply from the water supply source to the storage tank 242 while the service water Wa is being circulated in the circulation path.

[0116] In the air compressor 1a, during the operation of the compressor main body 203 (that is, during the production of the compressed air Ab), the pump 240 is operated so that the service water Wa flows through each cooler 205, 206. Thereby, the discharged fluid (compressed air Ab and added water Wb) from the compressor main body 203 can be cooled, and the service water Wa can be heated by the compression heat contained in the discharged fluid. The warm water thus produced has its flow path switched by the switching means 235 according to the presence or absence of the demand for the service water Wa in the load facility 1b. That is, when the control unit 15 receives a demand notification signal indicating that there is a demand for the service water Wa from the load facility 1b, the control unit 15 controls the switching means 235 to switch the flow path to the water passage path, and when the control unit 15 receives a demand notification signal indicating that there is no demand for the service water Wa from the load facility 1b, the control unit 15 controls the switching means 235 to switch the flow path to the circulation path.

[0117] When passing the service water Wa through each of the coolers 205 and 206 and performing heat recovery (in other words, discharging hot water to the outside), the switching means 235 is switched to the water passage. In the water passage, while closing the return valve 237, the flow rate adjustment valve 236 is opened. Also, typically, the fan 238A is stopped. In this case, the service water Wa is heated by each of the coolers 205 and 206 and sent to the load facility 1b downstream of the outlet passage 233. At this time, if the opening degree of the flow rate adjustment valve 236 is adjusted so as to maintain the detected temperature of the hot water discharge temperature sensor 243 at the target temperature, it becomes possible to supply hot water at the required temperature to the load facility 1b.

[0118] When passing the service water Wa through each of the coolers 205 and 206 and stopping heat recovery (in other words, discharging hot water to the outside), the switching means 235 is switched to the circulation passage. In the circulation passage, while closing the flow rate adjustment valve 236, the return valve 237 is opened. Also, 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 is returned to the inlet passage 232 via the return passage 234, cooled by the radiator 238, and then supplied again to each of the coolers 205 and 206. That is, while circulating the cooling water Wa through each of the coolers 205 and 206, heat is dissipated to the outside air by the radiator 238.

[0119] The radiator 238 for heat dissipation may be of a water-cooled type instead of an air-cooled type. In the case of the water-cooled type, it is provided with a heat exchanger between the circulating service water flowing through the circulation passage and the circulating cooling water, and the circulating cooling water that has absorbed heat in the heat exchanger is dissipated of heat by a cooling tower.

[0120] <Operation> The water-added air compressor 1a according to the third embodiment is configured to lubricate and cool the compressor mechanism 11 (compressor main body 203) of its own device by the added water Wb circulating through the discharge path 212, the liquid-phase connection path 215, the added water return path 211, and the suction path 210. A 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 that cools the compressor mechanism 11 while dissipating the compression heat through the heat exchange between the service water Wa and the added water Wb circulating through the circulation path and the heat exchange between the cooling air and the service water Wa. On the other hand, a water passage path not including the water cooler 206, the pump 240, the flow rate adjustment valve 236, and the return path 234 constitutes a heat recovery mechanism 13 that cools the compressor mechanism 11 while recovering the compression heat through the heat exchange between the service water Wa and the added water Wb flowing through the water passage path.

[0121] When the detected temperature T by the temperature detection unit 14 does not exceed the predetermined value α, the control unit 15 performs the following cooling operation. When there is a demand for the service water Wa in the load facility 1b, the control unit 15 opens the flow rate adjustment valve 174, closes the return valve 237, operates the pump 171, and controls to stop the radiator 238. Thereby, in the water cooler 206, the compression heat contained in the added water Wb is recovered by the continuously supplied service water Wa, and the compressor mechanism 11 of its own device is cooled by the returned cooled added water Wb. On the other hand, when there is no demand for the service water Wa in the load facility 1b, the control unit 15 closes the flow rate adjustment valve 174, opens the return valve 237, operates the pump 171, and controls to operate the radiator 238. Thereby, in the water cooler 206, the compression heat contained in the added water Wb is dissipated by the radiator 238 while being absorbed by the circulating service water Wa, and the compressor mechanism 11 of its own device is cooled by the returned cooled added water Wb.

[0122] When the detected temperature T by the temperature detection unit 14 exceeds a predetermined value α, the control unit 15 executes a heat recovery operation regardless of the demand for the service water Wa in the load facility 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 makeup water Wb circulating in the compression mechanism 11 is strongly cooled in the water cooler 206 using the service water Wa from a water supply source that is surely lower in temperature than the cooling air (outside air). Consequently, even when the ambient temperature of the air compressor 1a rises and the intake temperature becomes high, it becomes possible to prevent overheating of the compressor main body 111, and there is no need to limit the rotational speed of the electric motor 208.

[0123] 4. Fourth Embodiment Next, the fourth embodiment will be described. In the following description, emphasis will be placed 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 of 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 outside air taken in for intake and ventilation.

[0124] FIG. 6 schematically shows the configuration of the air compressor 1a (oil-free type air compressor) according to the fourth embodiment. The air compressor 1a includes a first compressor main body 311, a second compressor main body 312, an intercooler (heat dissipation air cooler) 313, an aftercooler (heat dissipation air cooler) 314, and an unloader mechanism 315.

[0125] 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 sent 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. This prevents the situation where the compression performance of the second compressor body 312 deteriorates 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 sending cooling air to this radiator with the cooling fan 313a.

[0126] 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 sent to 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. Thereby, the compressed air Ab adjusted to be below the heat-resistant 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 by the aftercooler 314 is removed by this dryer or drain separator. The aftercooler 314 is configured as an air-cooled radiator, and the compressed air Ab can be cooled by sending cooling air to this radiator with the cooling fan 314a.

[0127] The first compressor body 311 and the second compressor body 312 are connected to an electric motor 317 as a drive source via a gearbox 316. The driving force of the electric motor 317 is transmitted to each of the first compressor body 311 and the second compressor body 312 via the gearbox 316, and the first compressor body 311 and the second compressor body 312 operate.

[0128] The unloader mechanism 315 is a mechanism for switching the operating state of the air compressor 1a between a load operating state and an unload operating state (no-load operating state). For example, it is configured to include an intake valve (not shown) that opens and closes the intake line L301, and a discharge valve (not shown) that vents the second compressed air line L312 to the atmosphere. The intake valve and the discharge valve are configured to operate in conjunction with each other. When the intake valve is open, the discharge valve is closed, and when the intake valve is closed, the discharge valve is open.

[0129] In the load control for producing the compressed air Aa, Ab, the unloader mechanism 315 is controlled to open the intake valve and close the discharge valve. Also, in the unload control for not producing the compressed air Aa, Ab, the unloader mechanism 315 is controlled to close the intake valve and open the discharge valve.

[0130] Next, a configuration for performing heat recovery in the air compressor 1a will be described. The air compressor 1a includes a first heat recovery heat exchanger 351, a first shutoff valve 352, a first bypass valve 353, a second heat recovery heat exchanger 361, a second shutoff valve 362, and a second bypass valve 363.

[0131] The first heat recovery heat exchanger 351 is disposed upstream of the intercooler 313 in the first compressed air line L311. The first heat recovery heat exchanger 351 is supplied with service water Wa through a second cooling water line L331, which will be described later. The first heat recovery heat exchanger 351 performs heat exchange between the compressed air Aa flowing through the first compressed air line L311 and the service water Wa to cool the compressed air Aa.

[0132] A first bypass line L351, which is 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 from the first compressed air line L311 is referred to as a first branch portion 371, and the portion where the first bypass line L351 merges into the first compressed air line L311 is referred to as a first merge portion 372.

[0133] The first shut-off valve 352 is disposed on the upstream side of the first heat recovery heat exchanger 351 in the first compressed air line L311 and on the downstream side of the first branch portion 371 that branches into the first bypass line L351. The first shut-off valve 352 opens and closes a path from the first compressed air line L311 through the first bypass line L351 to the downstream side of the first heat recovery heat exchanger 351. The first bypass valve 353 is disposed in the first bypass line L351. The first bypass valve 353 opens and closes a path from the first compressed air line L311 through the first bypass line L351 to the downstream side of the first heat recovery heat exchanger 351.

[0134] The second heat recovery heat exchanger 361 is disposed on the upstream side of the aftercooler 314 in the second compressed air line L312. Cooling water Wa is supplied to the second heat recovery heat exchanger 361 through a first cooling water line L330, which will be described later. The second heat recovery heat exchanger 361 performs heat exchange between the compressed air Ab flowing through the second compressed air line L312 and the cooling water Wa to cool the compressed air Ab.

[0135] A second bypass line L361, which is a path through which the compressed air A2 does not pass through the second heat recovery heat exchanger 361, is provided in the second compressed air line L312. The second bypass line L361 connects the upstream side and the downstream side of the second heat recovery heat exchanger 361 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 a second branch portion 381, and the portion where the second bypass line L361 joins the second compressed air line L312 is defined as a second joining portion 382.

[0136] The second shut-off valve 362 is disposed on the upstream side of the second heat recovery heat exchanger 361 in the second compressed air line L312 and on the downstream side of the second branch portion 381 that branches into the second bypass line L361. The second shut-off valve 362 opens and closes the path of the second compressed air line L312. The second bypass valve 363 is disposed in the second bypass line L361 and opens and closes the path of the second bypass line L361.

[0137] The service water Wa supplied to the first heat recovery heat exchanger 351 and the second heat recovery heat exchanger 361 is the service water to be heated that is sent to the water supply tank 1ba of the load facility 1b. The path for supplying the service water Wa to the first heat recovery heat exchanger 351 and the second heat recovery heat exchanger 361 will be described.

[0138] The 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. The service water Wa is supplied to the first heat recovery heat exchanger 351 through a second service water line L331 that branches 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 the water supply tank 1ba via the second heat recovery heat exchanger 361. The second service water line L331 merges into the first service water line L330 at a merging portion 383 on the downstream side of the second heat recovery heat exchanger 361 after passing through the first heat recovery heat exchanger 351. In this way, the service water Wa is supplied to the first heat recovery heat exchanger 351 and the second heat recovery heat exchanger 361 in parallel connection. A flow rate sensor 333 is arranged on the upstream side of the branch portion 373 in the first service water line L330.

[0139] Regarding the control of the air compressor 1a, first, the load control and the unload control will be described. In the load control, the motor 317 is driven with the intake valve open and the exhaust valve closed in the unloader mechanism 315 to produce compressed air Ab by the first compressor main body 311 and the second compressor main body 312. In the unload control, no-load operation is performed in which the motor 317 is driven with the intake valve closed and the exhaust valve open in the unloader mechanism 315.

[0140] The control unit 15 selects load control or unload control based on the operating conditions of the first compressor body 311 and the second compressor body 312. The operating conditions are pre-set conditions. For example, they are set on the condition that the pressure in the second compressed air line L312 through which the compressed air Ab supplied from the second compressor body 312 flows or in an air tank (not shown) at the supply destination falls below the lower limit pressure. That is, when it is detected by a pressure sensor (not shown) or the like that the lower limit pressure in the air tank has been exceeded, the supply of the compressed air Ab is required. Therefore, the control unit 15 selects load control for manufacturing the compressed air Ab and sets a flag of "during load operation". On the other hand, when the upper limit pressure is exceeded, the control unit 15 selects unload control that does not manufacture the compressed air Ab and sets a flag of "during unload operation".

[0141] Regarding the water supply operation, the control unit 15 circulates the service water Wa through the first service water line L330 and the second service water line L331 based on the water flow conditions. The water flow conditions are pre-set conditions, and the flow control valve 332 and the pump are controlled according to the presence or absence of the demand for the service water Wa.

[0142] When the control unit 15 acquires information indicating that there is a demand for the service water Wa in the load facility 1b, it opens the flow control valve 332 and operates the pump, and sets a flag of "during water supply". Also, when it acquires information indicating that there is no demand for the service water Wa in the load facility 1b during water flow, it controls the flow control valve 332 to a closed state and stops the pump, and sets a flag of "during water stop".

[0143] Regarding the heat recovery operation, the control unit 15 controls the heat recovery operation triggered by satisfying all of the following three conditions. The first condition is that the flag of "during water supply" is set, the second condition is that the flag of "during load operation" is set, and the third condition is that the detected flow rate of the flow sensor 333 is "equal to or greater than a predetermined flow rate". The control unit 15 performs control to switch from a non-heat recovery path that does not perform heat recovery of the compressed air Aa and Ab to a heat recovery path that performs heat recovery of the compressed air Aa and Ab when it is "during water supply" and "during load operation" and "equal to or greater than a predetermined flow rate".

[0144] The control unit 15 opens the first shut-off valve 352 and the second shut-off valve 362 and closes the first bypass valve 353 and the second bypass valve 363. As a result, the compressed air Aa reaches the second compressor main body 312 through the first heat recovery heat exchanger 351 and the intercooler 313, and the heat recovery path through which the compressed air Ab reaches the compressed air using equipment through the second heat recovery heat exchanger 361 and the aftercooler 314 is selected. When the heat recovery path is selected, 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 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.

[0145] The conditions for stopping the heat recovery operation will be described. The control unit 15 uses, as a trigger, the satisfaction of either the condition that the "in water stop" flag is set or the condition that the "unloaded operation" flag is set and that state has continued for a predetermined time, and performs a heat recovery stop operation to switch from the non-heat recovery path to the heat recovery path.

[0146] 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 compressed air Aa passes through the first bypass line L351, reaches the second compressor main body 312 through the intercooler 313 without passing through the first heat recovery heat exchanger 351, 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, so that the non-heat recovery path is selected.

[0147] The intercooler 313 and the aftercooler 314 for heat dissipation may be of a water-cooled type instead of an air-cooled type. In the case of a water-cooled type, a heat exchanger between the compressed air and the circulating cooling water is provided, and the circulating cooling water that has absorbed heat in the heat exchanger is radiated by a cooling tower.

[0148] <Function> The oil-free air compressor 1a according to the second embodiment is configured to cool the compressor mechanism 11 (the second compressor main body 312) of its own machine by cooling the compressed air Aa flowing through the first compressed air line L311. The intercooler 313, the cooling fan 313a, and the first bypass valve 353 constitute a heat dissipation mechanism 12 that cools the subsequent-stage compressor mechanism 11 while dissipating the compression heat by the heat exchange between the cooling air and the compressed air Aa. Further, 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 cools the subsequent-stage compressor mechanism 11 while recovering the compression heat by the heat exchange between the service water Wa and the compressed air Aa.

[0149] When the detected temperature T by the temperature detection unit 14 does not exceed the predetermined value α, the control unit 15 performs the following cooling operation. When there is a demand for the service water Wa in the load facility 1b, the control unit 15 opens the first shut-off valve 352, closes the first bypass valve 353, opens the flow rate adjustment valve 332, operates the pump, and controls to stop the cooling fan 313a. Thereby, in the first heat recovery heat exchanger 351, the compression heat contained in the compressed air Aa is recovered by the service water Wa, and the compressed air Aa after heat recovery is sent out, whereby the second compressor main body 312 (the compressor mechanism 11 of its own machine) is cooled. On the other hand, when there is no demand for the service water Wa in the load facility 1b, the control unit 15 closes the first shut-off valve 352, opens the first bypass valve 353, closes the flow rate adjustment valve 332, stops the pump, and controls to operate the cooling fan 313a. Thereby, 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 compressor mechanism 11 of its own machine) is cooled.

[0150] When the detected temperature T by the temperature detection unit 14 exceeds a predetermined value α, the control unit 15 causes the heat recovery operation to be executed regardless of the demand for the service water Wa in the load facility 1b. That is, 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, the compressed air Aa discharged from the first compression main body 311 is strongly cooled in the first heat recovery heat exchanger 351 using the service water Wa from a water supply source that is surely lower in temperature than the cooling air (outside air). As a result, even when the ambient temperature of the air compressor 1a rises and the intake temperature becomes high, it becomes possible to prevent overheating of the second compressor main body 312, and there is no need to limit the rotational speed of the electric motor 317.

[0151] <Application Example> The oil-free type air compressor 1a of the fourth embodiment is configured to include jackets added to the compressor main bodies 311 and 312 and the electric motor 317, and a circulation circuit for lubricating oil for the gear box 316, and a heat dissipation oil cooler and a heat recovery oil cooler may be arranged in this circulation circuit. In this case, the heat dissipation oil cooler is an additional element constituting the heat dissipation mechanism 12, while the heat recovery oil cooler is an additional element constituting the heat recovery mechanism 13. When the detected temperature T by the temperature detection unit 14 does not exceed the predetermined value α, the control unit 15 switches between the heat recovery operation by the heat recovery oil cooler and the heat dissipation operation by the heat dissipation oil cooler according to the presence or absence of the demand for the service water Wa in the load facility 1b. Further, when the detected temperature T by the temperature detection unit 14 exceeds the predetermined value α, the control unit 15 causes the heat recovery operation by the heat recovery oil cooler to be executed regardless of the presence or absence of the demand for the service water Wa in the load facility 1b. By enabling a forced heat recovery operation for the compressor main bodies 311 and 312, when the ambient temperature of the air compressor 1a rises, it becomes possible to effectively cool not only the second compressor main body 312 but also the first compressor main body 311.

[0152] As described above, the embodiments of the present invention have been explained. However, the configuration of the present invention is not limited to the above embodiments, and various modifications 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 indicated by the scope of claims rather than the description of the above embodiments, and it is understood that all modifications belonging to the meaning and scope equivalent to the scope of claims are included.

Industrial Applicability

[0153] The present invention can be used for an air compressor and a heat utilization system having the same.

[0154] <Contribution to the Sustainable Development Goals (SDGs) led by the United Nations> The air compressor according to the present disclosure improves energy efficiency by mounting 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).

Explanation of Signs

[0155] 1 Heat utilization system 1a Air compressor 1b Load equipment 1ba Water supply tank 1bb Boiler body 11 Compression mechanism 12 Heat dissipation mechanism 13 Heat recovery mechanism 14 Temperature detection unit 15 Control unit 20 Heat exchanger 21 Pump 22 Accumulator 23 First control valve 24 Buffer tank 25 Second control valve 26 Hot water outlet temperature sensor 111 Compressor body 130 Oil cooler for heat recovery (heat recovery mechanism) 140 Oil cooler for heat dissipation (heat dissipation mechanism) 151 Bypass valve 171 Pump 174 Flow control valve 203 Compressor body 206 Water cooler (heat recovery mechanism, heat dissipation mechanism) 235 Switching means 236 Flow control valve 237 Return valve 238 Radiator (heat dissipation mechanism) 240 Pump 311 First compressor body 312 Second compressor body 313 Intercooler (heat dissipation mechanism) 332 Flow control valve 351 First heat exchanger for heat recovery (heat recovery mechanism) 352 First shut-off valve 353 First bypass valve

Claims

1. An air compressor having a compression mechanism for compressing supplied air to generate compressed air, a heat dissipation mechanism that performs a heat dissipation operation for cooling the compressor itself while dissipating heat generated during the compression process by heat exchange with cooling air or cooling water, a heat recovery mechanism that performs a heat recovery operation for cooling the compressor itself while recovering heat generated during the compression process by heat exchange with service water, and a temperature detection unit that detects the temperature of a fluid having a correlation with the temperature of the compressor itself. The air compressor, wherein when the detected temperature by the temperature detection unit exceeds a predetermined value, in performing an operation of cooling the compressor itself, the heat recovery operation is preferentially performed over the heat dissipation operation.

2. The service water heated by the heat recovery operation is configured to be supplied to a load facility that uses the service water, The air compressor according to claim 1, wherein in performing an operation of cooling the compressor itself, depending on the presence or absence of a demand for the service water in the load facility, it is determined which of the heat dissipation operation and the heat recovery operation is preferentially performed. The air compressor, wherein when the detected temperature exceeds the predetermined value, as an operation of cooling the compressor itself, the heat recovery operation is preferentially performed regardless of the presence or absence of the demand.

3. The service water heated by the heat recovery operation is configured to be supplied to a load facility that uses the service water, The air compressor according to claim 1, wherein in performing an operation of cooling the compressor itself, when there is a demand for the service water in the load facility, the heat recovery operation is performed, and when there is no such demand, the heat dissipation operation is performed. The air compressor, wherein when the detected temperature exceeds the predetermined value, as an operation of cooling the compressor itself, the heat recovery operation is performed regardless of the presence or absence of the demand.

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

5. An air compressor according to any one of claims 2 to 4, and the load facility, wherein the load facility transmits a signal indicating the presence or absence of a demand for the service water to the air compressor, and the air compressor is a heat utilization system that discriminates the presence or absence of the demand based on the received signal.

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