Gas Compression System

Abstract

This gas compressor comprises: a low-pressure gas path that guides compressed gas discharged from a low-pressure stage compressor body to a high-pressure stage compressor body; a first low-pressure relief valve provided to a first low-pressure branch path that branches from a low-pressure gas path; a high-pressure gas path that guides compressed gas discharged from the high-pressure stage compressor body to a demand destination; a first high-pressure relief valve provided to a first high-pressure branch path that branches from the high-pressure gas path; and a control device. The first low-pressure branch path is provided downstream of a heat exchanger for low-pressure stage heat recovery. The first high-pressure branch path is provided downstream of a heat exchanger for high-pressure stage heat recovery. The control device opens the first low-pressure relief valve and the first high-pressure relief valve when switching from a load operation to a no-load operation.

Description

[Technical Field]

[0001] The present invention , Ga This paper relates to a compression system. [Background technology]

[0002] Patent Document 1 discloses an exhaust heat recovery system including a gas compressor having a compressor main body that compresses gas and outputs compressed gas, and an exhaust heat recovery device that recovers heat from the compressed gas. The exhaust heat recovery device includes a heat exchanger for exhaust heat recovery and an exhaust heat recovery liquid pipe through which exhaust heat recovery water flows that exchanges heat with the compressed gas in the heat exchanger. This exhaust heat recovery system includes a low-pressure stage compressor main body, a high-pressure stage compressor main body, an intermediate-stage exhaust heat recovery heat exchanger located between the low-pressure stage compressor main body and the high-pressure stage compressor main body, and a discharge-stage exhaust heat recovery heat exchanger located downstream of the high-pressure stage compressor main body.

[0003] In this exhaust heat recovery system, a vent pipe for releasing compressed gas from the gas pipe to the atmosphere during no-load operation is provided downstream of the heat exchanger for exhaust heat recovery in the discharge stage. Therefore, even during no-load operation, gas flows through the heat exchanger for intermediate stage exhaust heat recovery and the heat exchanger for discharge stage exhaust heat recovery, making it possible to recover exhaust heat regardless of the operating state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-96043 Summary of the Invention [Problem to be solved by the invention]

[0005] In the exhaust heat recovery system described in Patent Document 1, heat is exchanged between high-temperature compressed gas discharged from a gas compressor and low-temperature exhaust heat recovery fluid. However, in such an exhaust heat recovery system, when the gas compressor switches from loaded operation to unloaded operation, the temperature of the compressed gas discharged from the gas compressor becomes lower than the temperature during loaded operation, and the temperature of the exhaust heat recovery fluid also decreases. For this reason, there is a demand for technology that can suppress the decrease in temperature of the exhaust heat recovery fluid during unloaded operation.

[0006] The present invention can suppress the decrease in temperature of the exhaust heat recovery fluid during no-load operation. Naga The present invention aims to provide a gas compression system. [Means for solving the problem]

[0007] Gas Compression According to an Aspect of the Invention system a low-pressure stage compressor main body that compresses gas; an intercooler that cools the compressed gas discharged from the low-pressure stage compressor main body; a high-pressure stage compressor main body that further compresses the compressed gas cooled by the intercooler; an aftercooler that cools the compressed gas discharged from the high-pressure stage compressor main body; a low-pressure gas path that guides the compressed gas discharged from the low-pressure stage compressor main body to the high-pressure stage compressor main body through the intercooler; and a high-pressure gas path that guides the compressed gas discharged from the high-pressure stage compressor main body to a demand destination through the aftercooler. a low-pressure stage exhaust heat recovery heat exchanger that exchanges heat between the compressed gas discharged from the low-pressure stage compressor body and an exhaust heat recovery fluid, and an upstream side of the intercooler; a first low-pressure branch path branching from the low-pressure gas path; and a first low-pressure air release valve provided in the first low-pressure branch path and releasing compressed gas discharged from the low-pressure stage compressor body. a second low-pressure branch path branching from the low-pressure gas path upstream of the heat exchanger for low-pressure stage exhaust heat recovery; a second low-pressure release valve provided in the second low-pressure branch path; and a second low-pressure release valve provided in the second low-pressure branch path downstream of the heat exchanger for high-pressure stage exhaust heat recovery that exchanges heat between the compressed gas discharged from the high-pressure stage compressor body and a fluid for exhaust heat recovery, the second low-pressure branch path branching from the low-pressure gas path upstream of the aftercooler. a first high-pressure branch path branching from the high-pressure gas path; and a first high-pressure release valve provided in the first high-pressure branch path and releasing compressed gas discharged from the high-pressure stage compressor body. a second high-pressure branch path branching from the high-pressure gas path upstream of the heat exchanger for high-pressure stage exhaust heat recovery; and a second high-pressure release valve provided in the second high-pressure branch path; First low pressure air release valve , the second low pressure air release valve, The first high-pressure air release valve , and the second high-pressure air release valve and a control device for controlling the . before The control device is It is determined whether or not a disabling condition for disabling the exhaust heat recovery function during no-load operation is established, and if the disabling condition is not established,When switching the low-pressure stage compressor main body and the high-pressure stage compressor main body from load operation to no-load operation, and the second low-pressure air release valve and the second high-pressure air release valve are closed. Thus, during no-load operation, the compressed gas is released from the first low-pressure air release valve and the first high-pressure air release valve, and heat is exchanged between the compressed gas passing through the low-pressure stage heat exchanger for exhaust heat recovery and the high-pressure stage heat exchanger for exhaust heat recovery and the exhaust heat recovery fluid. If the invalid condition is met, at least the second low-pressure air release valve and the second high-pressure air release valve are opened when switching from load operation to no-load operation of the low-pressure stage compressor main body and the high-pressure stage compressor main body. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress a decrease in the temperature of the exhaust heat recovery fluid during no-load operation. Naga A gas compression system can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a gas compression system according to a first embodiment. [Figure 2] FIG. 2 is a hardware configuration diagram of the control device. [Figure 3] FIG. 3 is a flowchart showing an example of the flow of processing for valve control of the gas compression system executed by the control device according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a schematic configuration of a gas compression system according to the second embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of the flow of processing for valve control of the gas compression system executed by the control device according to the second embodiment. [Figure 6] FIG. 6 is a schematic diagram showing a schematic configuration of a gas compression system according to the third embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of processing for valve control of a gas compression system executed by a control device according to the third embodiment. [Figure 8] FIG. 8 is a schematic diagram showing a schematic configuration of a gas compression system according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A gas compressor and a gas compression system according to an embodiment of the present invention will be described with reference to the drawings.

[0011] First Embodiment A gas compressor 101 and a gas compression system 100 according to a first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing a general configuration of the gas compression system 100 according to the first embodiment.

[0012] <Gas Compression System> As shown in FIG. 1, the gas compression system 100 includes a gas compressor 101 that compresses gas and an exhaust heat recovery device 102. The gas compression system 100 is a heat recovery system that recovers exhaust heat from compressed gas generated by the gas compressor 101 using the heat recovery device 102. In this embodiment, the gas compressed by the gas compressor 101 is air, and the heat recovery fluid that absorbs heat from the compressed gas (compressed air) using the heat recovery device 102 is water. In this embodiment, an example is described in which the gas compressor 101 is an air-cooled two-stage screw compressor. The gas compression system 100 may be configured as a single unit in which the gas compressor 101 and the heat recovery device 102 are incorporated into a single housing, or the gas compressor 101 and the heat recovery device 102 may be housed in separate housings and connected to each other by piping. It should be noted that gas compressor 101 and exhaust heat recovery device 102 may be configured as a single unit by being fixed to a single base frame, without providing a housing for accommodating them.

[0013] <Gas compressor> The gas compressor 101 includes an electric motor 3 as a drive source, a low-pressure stage compressor body 1L that compresses gas, an intercooler 10 that cools the compressed air discharged from the low-pressure stage compressor body 1L with a cooling medium, a high-pressure stage compressor body 1H that further compresses the compressed air cooled by the intercooler 10, and an aftercooler 17 that cools the compressed air discharged from the high-pressure stage compressor body 1H with a cooling medium. The cooling medium used in the intercooler 10 and the aftercooler 17 is cooling air generated by a cooling fan 50.

[0014] The gas compressor 101 includes a low-pressure gas path PL that guides the compressed air discharged from the low-pressure stage compressor main body 1L to the high-pressure stage compressor main body 1H through an intercooler 10, and a high-pressure gas path PH that guides the compressed air discharged from the high-pressure stage compressor main body 1H to the air-using equipment 91, which is the demand destination, through an aftercooler 17.

[0015] The gas compressor 101 includes a first low-pressure branch path 24 branching off from the low-pressure gas path PL, and a first low-pressure air release valve 25 provided in the first low-pressure branch path 24 to release compressed air discharged from the low-pressure stage compressor main body 1L.

[0016] The gas compressor 101 includes a first high-pressure branch path 27 branching off from the high-pressure gas path PH, and a first high-pressure air release valve 28 provided in the first high-pressure branch path 27 and releasing compressed air discharged from the high-pressure stage compressor main body 1H. The system through which the compressed air flows, including the low-pressure gas path PL and the high-pressure gas path PH, is also referred to as the gas system.

[0017] The low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H have the same configuration, and therefore, hereinafter, both will be collectively referred to as the compressor body 1. The compressor body 1 has a pair of male and female screw rotors (not shown) and a casing that houses the screw rotors. The gas compressor 101 is an oil-free screw compressor in which no oil is supplied to the working chamber formed by the teeth of the screw rotor and the inner wall of the casing. The rotational force of the electric motor 3 is transmitted to the compressor body 1 via a speed increasing device 4. When the electric motor 3 is driven, the screw rotor rotates. As the screw rotor rotates, gas is sucked into the compressor body 1 and compressed.

[0018] The intake system that supplies air to the low-pressure stage compressor body 1L includes an intake filter 5 that captures foreign matter (impurities) in the air and an intake valve 6 that is provided downstream of the intake filter 5 and is capable of opening and closing the intake port of the low-pressure stage compressor body 1L. The intake valve 6 is a piston-type control valve that has a valve body that opens and closes the intake port of the low-pressure stage compressor body 1L and a valve case that houses the valve body, and operates in response to a control signal from a control device 110 (described later). The intake valve 6 may be configured to have an electromagnetic valve body, or may be configured to have an electromagnetic intake valve control valve that is provided in a flow path that guides compressed air discharged from the low-pressure stage compressor body 1L or the high-pressure stage compressor body 1H to a pressure-receiving portion of the valve body.

[0019] The low-pressure stage compressor main body 1L draws in air from the ambient atmosphere through an intake filter 5 and an intake valve 6 and compresses it. The high-pressure stage compressor main body 1H draws in the compressed air discharged from the low-pressure stage compressor main body 1L and further compresses it. The compressed air discharged from the high-pressure stage compressor main body 1H is supplied to an air-using facility 91, which is an external facility. The air-using facility 91 uses the compressed air, for example, to drive actuators of machines in a factory, to dry objects, or for cleaning, painting, etc.

[0020] The intercooler 10 and the aftercooler 17 are air-cooled heat exchangers having internal flow paths through which compressed air flows. The intercooler 10 and the aftercooler 17 cool the compressed air by exchanging heat between the cooling air (cooling medium) generated by the cooling fan 50 and the compressed air flowing through the internal flow paths.

[0021] The low-pressure gas path PL includes an air path 7 connecting the low-pressure stage compressor main body 1L and a heat exchanger 8 for low-pressure stage exhaust heat recovery (described later), an air path 9 connecting the heat exchanger 8 for low-pressure stage exhaust heat recovery and an intercooler 10, and an air path 11 connecting the intercooler 10 and the high-pressure stage compressor main body 1H. A low-pressure stage discharge temperature sensor 34 is provided in the air path 7 to detect the temperature of the compressed air generated by the low-pressure stage compressor main body 1L and output a signal indicating the detection result to the control device 110.

[0022] A first low-pressure branch path 24 is connected to the air path 9. That is, the first low-pressure branch path 24 branches off from the low-pressure gas path PL downstream of the heat exchanger 8 for low-pressure stage exhaust heat recovery and upstream of the intercooler 10. The first low-pressure branch path 24 is provided with a first low-pressure air release valve 25 that opens and closes the first low-pressure branch path 24 in response to a control signal from the control device 110, and a silencer 26 that reduces noise when compressed air is released from the first low-pressure branch path 24.

[0023] The air path 11 is provided with a condensate separator (drain separator) 12 that separates condensate (drain) from the compressed air, a high-pressure stage suction temperature sensor 35 that detects the temperature of the compressed air sucked into the high-pressure stage compressor main body 1H and outputs a signal representing the detection result to the control device 110, and a high-pressure stage suction pressure sensor 36 that detects the pressure of the compressed air sucked into the high-pressure stage compressor main body 1H and outputs a signal representing the detection result to the control device 110.

[0024] The high-pressure gas path PH includes an air path 13 that connects the high-pressure stage compressor main body 1H with a heat exchanger 14 for high-pressure stage exhaust heat recovery, which will be described later, an air path 15 that connects the heat exchanger 14 for high-pressure stage exhaust heat recovery with an aftercooler 17, and an air path 18 that connects the aftercooler 17 with air-using equipment 91. The air path 13 is provided with a high-pressure stage discharge temperature sensor 37 that detects the temperature of the compressed air generated by the high-pressure stage compressor main body 1H and outputs a signal indicating the detection result to the control device 110.

[0025] A first high-pressure branch path 27 is connected to the air path 15. That is, the first high-pressure branch path 27 branches off from the high-pressure gas path PH downstream of the heat exchanger 14 for recovering high-pressure exhaust heat and upstream of the aftercooler 17. The first high-pressure branch path 27 is provided with a first high-pressure air release valve 28 that opens and closes the first high-pressure branch path 27 in response to a control signal from the control device 110, and a silencer 29 that reduces noise when compressed air is released from the first high-pressure branch path 27.

[0026] The air path 15 is provided with a check valve 16 that allows air to flow from the high-pressure stage exhaust heat recovery heat exchanger 14 toward the aftercooler 17 and prohibits air from flowing from the aftercooler 17 to the high-pressure stage exhaust heat recovery heat exchanger 14. The air path 18 is provided with a discharge pressure sensor 38 that detects the discharge pressure of the compressed air discharged from the high-pressure stage compressor main body 1H and outputs a signal indicating the detection result to the control device 110.

[0027] The gas compressor 101 includes a control device 110 that controls the opening and closing of the electromagnetic switch 2, the intake valve 6, the first low pressure air release valve 25, and the first high pressure air release valve .

[0028] 2 is a hardware configuration diagram of the control device 110. As shown in FIG. 2, the control device 110 is configured by a computer including a processing device 111 such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or a DSP (Digital Signal Processor), a non-volatile memory 112 such as a ROM (Read Only Memory), a flash memory, or a hard disk drive, a volatile memory 113 called a RAM (Random Access Memory), an input interface 114, an output interface 115, and other peripheral circuits. The control device 110 may be configured by one computer or multiple computers. The processing device may be an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like.

[0029] The nonvolatile memory 112 stores programs capable of executing various calculations. That is, the nonvolatile memory 112 is a storage medium (storage device) capable of reading programs that realize the functions of this embodiment. The processing device 111 loads the programs stored in the nonvolatile memory 112 into the volatile memory 113 and executes the programs, and performs predetermined calculations on data acquired from the input interface 114, the nonvolatile memory 112, and the volatile memory 113 in accordance with the programs.

[0030] The control device 110 is connected to a plurality of sensors (34-39), a plurality of control valves (6, 25, 28, 33), and an input device 80. The input interface 114 converts signals input from the plurality of sensors (34-39) and the input device 80 so that they can be calculated by the processing device 111. The output interface 115 generates output signals according to the calculation results of the processing device 111, and outputs the signals to the plurality of control valves (6, 25, 28, 33) and the electromagnetic switch 2.

[0031] The multiple sensors (34-39) include a low-pressure stage discharge temperature sensor 34, a high-pressure stage suction temperature sensor 35, a high-pressure stage suction pressure sensor 36, a high-pressure stage discharge temperature sensor 37, a discharge pressure sensor 38, and a feedwater temperature sensor 39. The multiple control valves (6, 25, 28, 33) include an intake valve 6, a first low-pressure air release valve 25, a first high-pressure air release valve 28, and a feedwater valve 33. The input device 80 is an operation panel provided in the gas compressor 101, and has multiple operation units such as operation switches and touch sensors that can be operated by an operator. The multiple operation units include a start switch that switches the gas compressor 101 between operating and stopping.

[0032] In this embodiment, gas compressor 101 is a constant speed compressor that rotates at a constant rotational speed. Control device 110 controls electromagnetic switch 2 to operate electric motor 3 at a constant speed or to stop it.

[0033] The control device 110 performs loaded operation and unloaded operation of the compressor main body 1 based on the discharge pressure of the compressed air detected by the discharge pressure sensor 38. In loaded operation, the control device 110 outputs an open signal to the intake valve 6, fully opening the intake valve 6. In loaded operation, the control device 110 outputs a close signal to the first low-pressure air release valve 25 and the first high-pressure air release valve 28, fully closing the first low-pressure air release valve 25 and the first high-pressure air release valve 28. In unloaded operation, the control device 110 outputs a close signal to the intake valve 6, fully closing the intake valve 6. In unloaded operation, the control device 110 outputs an open signal to the first low-pressure air release valve 25 and the first high-pressure air release valve 28, fully opening the first low-pressure air release valve 25 and the first high-pressure air release valve 28. When the intake valve 6 is fully closed, a minute gap is formed between the valve body and valve box of the intake valve 6, and air is guided through this gap to the low-pressure stage compressor body 1L.

[0034] The gas compressor 101 includes a lubricating oil path OP through which lubricating oil flows to lubricate the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H, and an oil pump 48 and an oil cooler 20 provided in the lubricating oil path OP. The oil pump 48 draws the lubricating oil through a suction port and discharges it through a discharge port, thereby circulating the lubricating oil within the lubricating oil path OP. The oil cooler 20 cools the lubricating oil with a cooling medium. In this embodiment, the oil cooler 20 is an air-cooled heat exchanger that cools the lubricating oil using cooling air generated by a cooling fan 50 as a cooling medium.

[0035] The lubricating oil path OP includes an oil supply path 19 that guides the lubricating oil discharged from the oil pump 48 to the oil cooler 20, an oil supply path 21 that guides the lubricating oil cooled by the oil cooler 20 to the high-pressure stage compressor main body 1H, an oil supply path 22 that guides the lubricating oil discharged from the high-pressure stage compressor main body 1H to the low-pressure stage compressor main body 1L, and a return path 23 that returns the lubricating oil discharged from the low-pressure stage compressor main body 1L to the oil pump 48.

[0036] The moving parts inside the compressor body 1 and the speed increasing device 4 are lubricated by the lubricating oil in the lubricating oil path OP. The moving parts inside the compressor body 1 to be lubricated include, for example, driving parts such as bearings that support the screw rotors and synchronous gears that are installed so that a pair of male and female screw rotors can rotate synchronously with each other without contacting each other.

[0037] The lubricating oil is caused by the oil pump 48 to flow through the oil supply path 19, oil cooler 20, oil supply path 21, high-pressure stage compressor body 1H, oil supply path 22, low-pressure stage compressor body 1L, return path 23, and oil pump 48 in this order, and circulates within the lubricating oil path OP. As a result, the moving parts of the compressor body 1 and the speed increasing device 4 are lubricated by the lubricating oil.

[0038] <Waste heat recovery device> The exhaust heat recovery device 102 heats water as an exhaust heat recovery fluid using the heat of the compressed gas generated by the gas compressor 101, and supplies the heated water to a hot water usage facility 90 that demands it. The exhaust heat recovery device 102 includes a low-pressure stage exhaust heat recovery heat exchanger 8 provided in the low-pressure gas path PL, and a high-pressure stage exhaust heat recovery heat exchanger 14 provided in the high-pressure gas path PH. The exhaust heat recovery heat exchangers 8 and 14 have a high-temperature fluid flow path through which compressed air generated by the gas compressor 101 flows, and a low-temperature fluid flow path through which water supplied from a water supply source (not shown) flows. The high-temperature fluid flow path and the low-temperature fluid flow path may be arranged so that the high-temperature fluid (compressed air) and the low-temperature fluid (water) flow in opposite directions or in parallel.

[0039] The low-pressure stage exhaust heat recovery heat exchanger 8 exchanges heat between the compressed air discharged from the low-pressure stage compressor body 1L and flowing through the high-temperature fluid passage, and water as an exhaust heat recovery fluid flowing through the low-temperature fluid passage. The high-pressure stage exhaust heat recovery heat exchanger 14 exchanges heat between the compressed air discharged from the high-pressure stage compressor body 1H and flowing through the high-temperature fluid passage, and water as an exhaust heat recovery fluid flowing through the low-temperature fluid passage.

[0040] The exhaust heat recovery device 102 includes a first supply flow path 30 that supplies water from a water supply source (not shown) to the heat exchanger 8 for low-pressure stage exhaust heat recovery, a second supply flow path 31 that supplies water discharged from the heat exchanger 8 for low-pressure stage exhaust heat recovery to the heat exchanger 14 for high-pressure stage exhaust heat recovery, and a third supply flow path 32 that supplies water discharged from the heat exchanger 14 for high-pressure stage exhaust heat recovery to hot water usage equipment 90, which is external equipment. The system through which water flows, including the first supply flow path 30, the second supply flow path 31, and the third supply flow path 32, is also referred to as a water supply system.

[0041] The first supply flow path 30 is provided with a feedwater temperature sensor 39 that detects the temperature (feedwater temperature) of water supplied from a feedwater source (not shown) to the low-pressure stage exhaust heat recovery heat exchanger 8 and outputs a signal representing the detection result to the control device 110. The feedwater temperature sensor 39 is, for example, a temperature sensor that outputs a signal representing the temperature of the water (feedwater temperature) in the first supply flow path 30. Note that the feedwater temperature sensor 39 may also be a temperature sensor switch that outputs a signal representing the temperature of the water (feedwater temperature) in the first supply flow path 30 when the temperature of the water (feedwater temperature) in the first supply flow path 30 becomes equal to or higher than a predetermined temperature threshold.

[0042] The third supply flow path 32 is provided with a water supply valve 33 that adjusts the flow rate of hot water supplied from the exhaust heat recovery device 102 to the hot water usage equipment 90. The hot water usage equipment 90 is, for example, a hot water insulation equipment, a boiler feedwater preheating equipment, or the like.

[0043] <Control flow by the control device> Fig. 3 is a flowchart showing an example of the processing flow of valve control of gas compression system 100 executed by control device 110. The flowchart shown in Fig. 3 is started, for example, when the start switch of input device 80 is turned on, and is repeatedly executed at a predetermined control period.

[0044] In step S110, the control device 110 determines whether the discharge pressure Pd detected by the discharge pressure sensor 38 is equal to or greater than the no-load operation start pressure Pdu. The no-load operation start pressure Pdu is a pressure threshold value for determining to start no-load operation, and is stored in the non-volatile memory 112. Note that the no-load operation start pressure Pdu may be changeable by operating the operation unit of the input device 80.

[0045] If it is determined in step S110 that the discharge pressure Pd is equal to or greater than the no-load operation start pressure Pdu, the process proceeds to step S118. If it is determined in step S110 that the discharge pressure Pd is less than the no-load operation start pressure Pdu, the process proceeds to step S114.

[0046] In step S114, the control device 110 outputs an open signal to the intake valve 6 and outputs close signals to the first low pressure air release valve 25 and the first high pressure air release valve 28. This causes the intake valve 6 to open and the first low pressure air release valve 25 and the first high pressure air release valve 28 to close.

[0047] In step S118, the control device 110 outputs a close signal to the intake valve 6 and outputs open signals to the first low pressure air release valve 25 and the first high pressure air release valve 28. This causes the intake valve 6 to close and the first low pressure air release valve 25 and the first high pressure air release valve 28 to open.

[0048] When the valve control signal output process (the process of step S114 or step S118) ends, the process shown in the flowchart of FIG. 3 for this control cycle ends.

[0049] <Main operations of the gas compression system> 1 to 3, the main operation of the gas compression system 100 according to this embodiment will be described. The control device 110 of the gas compression system 100 performs load operation of the compressor main body 1 when supplying compressed air to an air-using facility (demand destination) 91. During load operation, the control device 110 drives the low-pressure stage compressor main body 1L and the high-pressure stage compressor main body 1H and opens the intake valve 6 (step S114). During load operation, the control device 110 closes the first low-pressure air release valve 25 and the first high-pressure air release valve 28 (step S114). As a result, outside air (air around the intake valve 6) is drawn into the low-pressure stage compressor main body 1L through the intake filter 5 and the intake valve 6. Since the intake filter 5 is provided upstream of the intake valve 6, foreign matter contained in the outside air is captured by the intake filter 5.

[0050] Air drawn into the low-pressure stage compressor body 1L is compressed to a predetermined pressure by the low-pressure stage compressor body 1L and then discharged. The temperature of the compressed air rises due to adiabatic compression by the low-pressure stage compressor body 1L, and it becomes high-temperature compressed air. The compressed air generated by the low-pressure stage compressor body 1L flows through an air path 7 into the high-temperature fluid flow path of the low-pressure stage waste heat recovery heat exchanger 8. As a result, heat is exchanged between the compressed air flowing through the high-temperature fluid flow path of the low-pressure stage waste heat recovery heat exchanger 8 and the water flowing through the low-temperature fluid flow path of the low-pressure stage waste heat recovery heat exchanger 8, and the water is heated.

[0051] The compressed air after exchanging heat with the water flows out from the high-temperature fluid flow path outlet of the heat exchanger 8 for recovering exhaust heat at the low-pressure stage, and flows into the intercooler 10 through an air path 9. The compressed air that flows into the intercooler 10 is cooled to a temperature slightly higher than the ambient air temperature by heat exchange with the cooling air. The compressed air cooled by the intercooler 10 flows into the condensed water separator 12 through an air path 11, and the condensed water is removed. The compressed air discharged from the condensed water separator 12 (compressed air from which the condensed water has been separated) is drawn into the high-pressure stage compressor main body 1H.

[0052] The compressed air drawn into the high-pressure stage compressor main body 1H is further compressed to a predetermined higher pressure by the high-pressure stage compressor main body 1H and then discharged. The temperature of the compressed air is raised again by adiabatic compression by the high-pressure stage compressor main body 1H, and it becomes high-temperature compressed air. The compressed air generated by the high-pressure stage compressor main body 1H flows through an air path 13 into the high-temperature fluid flow path of the high-pressure stage waste heat recovery heat exchanger 14. As a result, heat is exchanged between the compressed air flowing through the high-temperature fluid flow path of the high-pressure stage waste heat recovery heat exchanger 14 and the water flowing through the low-temperature fluid flow path of the high-pressure stage waste heat recovery heat exchanger 14, and the water is heated.

[0053] The compressed air after exchanging heat with water flows out from the high-temperature fluid flow path outlet of the heat exchanger 14 for recovering exhaust heat at the high-pressure stage, and flows into the aftercooler 17 through an air path 15. The compressed air that flows into the aftercooler 17 is cooled to a temperature slightly higher than the ambient air temperature through heat exchange with cooling air. The compressed air cooled by the aftercooler 17 is supplied to air-using equipment (demand destination) 91 through an air path 18.

[0054] Water supplied to the exhaust heat recovery device 102 from a water supply source (not shown) flows through a first supply flow path 30 into the low-temperature fluid flow path of the heat exchanger 8 for low-pressure stage exhaust heat recovery. The water that flows into the low-temperature fluid flow path of the heat exchanger 8 is heated by high-temperature compressed air flowing through the high-temperature fluid flow path. The water heated by the heat exchanger 8 flows through a second supply flow path 31 into the low-temperature fluid flow path of the heat exchanger 14 for high-pressure stage exhaust heat recovery. The water that flows into the low-temperature fluid flow path of the heat exchanger 14 is further heated by high-temperature compressed air flowing through the high-temperature fluid flow path. The water heated by the heat exchanger 14 is supplied to a hot water usage facility (demand destination) 90 through a third supply flow path 32.

[0055] Therefore, according to this embodiment, when compressed air generated by the gas compressor 101 passes through the heat exchangers 8 and 14 of the exhaust heat recovery device 102, heat exchange with water occurs, and exhaust heat is recovered. In other words, the heat of the compressed air generated by the gas compressor 101 can be extracted as hot water. The extracted hot water can be effectively used for various purposes, such as preheating feedwater for a boiler or for heat retention, and the fuel and electricity required to produce hot water can be reduced or eliminated compared to when hot water is produced without using the exhaust heat recovery device 102.

[0056] When the discharge pressure Pd of the gas compressor 101 increases and becomes equal to or greater than the no-load operation start pressure Pdu, the control device 110 switches the operation state from loaded operation to no-load operation. When switching the compressor main body 1 from loaded operation to no-load operation, the control device 110 closes the intake valve 6 and opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28 while continuing to operate the electric motor 3 (step S118).

[0057] When the intake valve 6 is closed, a small gap is formed between the valve body and valve element of the intake valve 6, and air is sucked into the low-pressure stage compressor body 1L through this gap. Therefore, during no-load operation, the amount of sucked air is minimized, and the first low-pressure air release valve 25 and the first high-pressure air release valve 28 are open. Therefore, during no-load operation, the compression work of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H is reduced, so the power consumption of the gas compressor 101 can be reduced compared to during loaded operation. During no-load operation, the air compression ratios of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H are lower than during loaded operation, so the temperature of the compressed air discharged from each compressor body 1 is lower than during loaded operation.

[0058] During no-load operation, the compressed air discharged from the low-pressure stage compressor main body 1L passes through the high-temperature fluid passage of the heat exchanger 8 for low-pressure stage waste heat recovery, and heats the water in the low-temperature fluid passage of the heat exchanger 8. The compressed air then flows out from the high-temperature fluid passage outlet of the heat exchanger 8 for low-pressure stage waste heat recovery. During no-load operation, the first low-pressure air release valve 25 is open, and therefore part of the compressed air flowing out of the heat exchanger 8 is released into the atmosphere through the first low-pressure branch passage 24 branching off from the air passage 9 and the silencer 26.

[0059] Any compressed air that is not completely discharged from the first low-pressure branch path 24 is sucked into the high-pressure stage compressor main body 1H. The compressed air discharged from the high-pressure stage compressor main body 1H heats the water in the low-temperature fluid path of the heat exchanger 14 while passing through the high-temperature fluid path of the heat exchanger 14 for high-pressure stage waste heat recovery. The compressed air then flows out from the high-temperature fluid path outlet of the heat exchanger 14 for high-pressure stage waste heat recovery. During no-load operation, the first high-pressure air release valve 28 is open, and therefore the compressed air that flows out of the heat exchanger 14 is released into the atmosphere through the first high-pressure branch path 27 branching off from the air path 15 and the silencer 29.

[0060] Incidentally, during no-load operation, the amount of air used in the air-using equipment 91 is small, and the pressure downstream of the check valve 16 provided in the air path 15 (i.e., discharge pressure Pd) is higher than the pressure upstream of the check valve 16. For this reason, the check valve 16 is subjected to back pressure and is in a closed state. Therefore, during no-load operation, the compressed air discharged from the high-pressure stage compressor main body 1H is released to the atmosphere through the first high-pressure branch path 27 without flowing into the aftercooler 17.

[0061] In this way, in this embodiment, when switching from load operation to no-load operation, the control device 110 opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28, thereby releasing compressed gas from the first low-pressure air release valve 25 and the first high-pressure air release valve 28 during no-load operation, while exchanging heat between the compressed air passing through the heat exchanger 8 for low-pressure stage exhaust heat recovery and the heat exchanger 14 for high-pressure stage exhaust heat recovery and the water.

[0062] The effects obtained by the gas compressor 101 and gas compression system 100 of this embodiment configured as described above will be explained in comparison with a configuration (hereinafter referred to as a comparative example) that does not include the first low-pressure branch path 24, the first low-pressure air release valve 25, and the silencer 26. In the comparative example, during no-load operation, compressed air is released to the atmosphere only via the first high-pressure air release valve 28. In contrast, in this embodiment, during no-load operation, compressed air is released to the atmosphere via the first low-pressure air release valve 25 and the first high-pressure air release valve 28.

[0063] In this embodiment, the compressed air is released into the atmosphere via the first low-pressure air release valve 25, so the pressure of the compressed air in the air path 11 between the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H (i.e., high-pressure stage suction pressure) is lower than in the comparative example. Therefore, in this embodiment, the compression ratio of the high-pressure stage compressor body 1H during no-load operation is higher than in the comparative example. As a result, in this embodiment, the temperature of the compressed air discharged from the high-pressure stage compressor body 1H (high-pressure stage discharge temperature) is higher than in the comparative example.

[0064] In this way, in this embodiment, the high-pressure stage discharge temperature can be made higher than in the comparative example, and the water flowing through the low-temperature fluid flow path of the high-pressure stage exhaust heat recovery heat exchanger 14 can be heated by compressed air with a higher temperature than in the comparative example. Therefore, in this embodiment, the temperature of the water flowing out from the high-pressure stage exhaust heat recovery heat exchanger 14 during no-load operation can be made higher than in the comparative example.

[0065] <Effects> According to the above-described embodiment, the following advantageous effects are achieved.

[0066] When switching the low-pressure stage compressor main body 1L and the high-pressure stage compressor main body 1H from load operation to no-load operation, the control device 110 opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28, thereby releasing compressed gas from the first low-pressure air release valve 25 and the first high-pressure air release valve 28 during no-load operation, and exchanging heat between the compressed air (compressed gas) passing through the heat exchanger 8 for low-pressure stage exhaust heat recovery and the heat exchanger 14 for high-pressure stage exhaust heat recovery and water (exhaust heat recovery fluid).

[0067] With this configuration, in a gas compressor 101 having multiple compressor stages, air can be released not only downstream of the high-pressure stage compressor main body 1H but also upstream of the high-pressure stage compressor main body 1H during no-load operation. This increases the compression ratio of the high-pressure stage compressor main body 1H and increases the temperature of the air compressed by the high-pressure stage compressor main body 1H. In other words, this embodiment can provide a gas compressor 101 and a gas compression system 100 that can suppress a decrease in water temperature during no-load operation. In other words, this embodiment can provide a gas compressor 101 and a gas compression system 100 that have high exhaust heat recovery efficiency during no-load operation.

[0068] Second Embodiment A gas compressor 201 and a gas compression system 200 according to a second embodiment of the present invention will be described with reference to Figures 4 and 5. Note that the same reference numerals are used to designate components that are the same as or equivalent to those described in the first embodiment, and differences will be mainly described.

[0069] 4 is a schematic diagram showing the overall configuration of a gas compression system 200 according to the second embodiment. Similar to the first embodiment, the gas compression system 200 according to the second embodiment has a function for recovering exhaust heat during no-load operation. The second embodiment differs from the first embodiment in that the exhaust heat recovery function during no-load operation can be switched between enabled and disabled.

[0070] 4, a gas compression system 200 according to the second embodiment has a similar configuration to the gas compression system 100 according to the first embodiment. Furthermore, the exhaust heat recovery device 202 of the gas compression system 200 according to the second embodiment includes a second low-pressure branch path 42 branching from the low-pressure gas path PL upstream of the heat exchanger 8 for low-pressure stage exhaust heat recovery, a second low-pressure release valve 43 provided in the second low-pressure branch path 42, a second high-pressure branch path 45 branching from the high-pressure gas path PH upstream of the heat exchanger 14 for high-pressure stage exhaust heat recovery, and a second high-pressure release valve 46 provided in the second high-pressure branch path 45. A silencer 44 is provided at a gas release portion of the second low-pressure branch path 42, and a silencer 47 is provided at a gas release portion of the second high-pressure branch path 45.

[0071] The exhaust heat recovery device 202 of the gas compression system 200 according to the second embodiment includes a differential pressure sensor 40. The differential pressure sensor 40 is provided between the first supply flow path 30 and the third supply flow path 32. The differential pressure sensor 40 detects the difference in pressure between the water pressure in the first supply flow path 30 and the water pressure in the third supply flow path 32 and outputs a signal representing the detection result to the control device 110. The differential pressure sensor 40 is provided in a pressure detection tube 41 that connects the first supply flow path 30 and the third supply flow path 32 downstream of the heat exchanger 14 for high-pressure stage exhaust heat recovery and upstream of the water feed valve 33. The differential pressure sensor 40 outputs, for example, a signal representing the detected differential pressure itself. Note that the differential pressure sensor 40 may be a differential pressure sensor switch that outputs a signal indicating that the differential pressure falls below a predetermined differential pressure threshold.

[0072] The control device 110 determines whether or not a disabling condition for disabling the exhaust heat recovery function during no-load operation is established.

[0073] The invalid conditions include the following first and second conditions, and are met when at least one of the first and second conditions is met. The invalid conditions are not met when both the first and second conditions are not met. First condition: Water is not supplied to at least one of the low-pressure stage exhaust heat recovery heat exchanger 8 and the high-pressure stage exhaust heat recovery heat exchanger 14. Second condition: The temperature (supply water temperature) Tw1 of the water supplied to at least one of the low-pressure stage exhaust heat recovery heat exchanger 8 and the high-pressure stage exhaust heat recovery heat exchanger 14 is higher than the temperature threshold value Twh.

[0074] Specifically, the control device 110 determines whether the differential pressure ΔPw detected by the differential pressure sensor 40 is equal to or less than a differential pressure threshold ΔPwl. The differential pressure ΔPw increases as the flow rate of water passing through the exhaust heat recovery heat exchangers 8, 14 increases. The differential pressure threshold ΔPwl is determined for determining whether water is being supplied to the exhaust heat recovery heat exchangers 8, 14, and is stored in advance in the non-volatile memory 112.

[0075] When the differential pressure ΔPw is equal to or less than the differential pressure threshold ΔPwl, the control device 110 determines that water is not being supplied to the heat exchangers 8, 14 for exhaust heat recovery. That is, when the differential pressure ΔPw is equal to or less than the differential pressure threshold ΔPwl, the control device 110 determines that the first condition is satisfied. When the differential pressure ΔPw is greater than the differential pressure threshold ΔPwl, the control device 110 determines that water is being supplied to the heat exchangers 8, 14 for exhaust heat recovery. That is, when the differential pressure ΔPw is greater than the differential pressure threshold ΔPwl, the control device 110 determines that the first condition is not satisfied.

[0076] The hot water usage equipment 91 may have a hot water tank and a hot water pump in the water supply system, and may circulate the water to raise the water temperature. In this hot water usage equipment 91, if low-temperature makeup water is not supplied to the water supply system for a long period of time, the temperature difference between the water and the compressed air may become very small. Furthermore, if the temperature of the compressed air drops when the system is switched from load operation to no-load operation, but the temperature of the water in the water supply system remains high, the temperature of the water may become higher than the temperature of the compressed air.

[0077] Therefore, if the water temperature is very close to the temperature of the compressed air during no-load operation, or if the water temperature exceeds the temperature of the compressed air during no-load operation, it is preferable to disable the exhaust heat recovery function.

[0078] The control device 110 determines whether the feedwater temperature Tw1 detected by the feedwater temperature sensor 39 is equal to or higher than the temperature threshold value Twh. The temperature threshold value Twh is determined in advance based on the results of experiments, etc., and is stored in the non-volatile memory 112. The temperature threshold value Twh is determined based on the temperature Td1 of the compressed air discharged from the low-pressure stage compressor main body 1L during no-load operation (hereinafter referred to as the low-pressure stage discharge temperature), and the temperature Td2 of the compressed air discharged from the high-pressure stage compressor main body 1H during no-load operation (hereinafter referred to as the high-pressure stage discharge temperature). For example, the temperature threshold value Twh is set to the minimum value of the low-pressure stage discharge temperature Td1 and the high-pressure stage discharge temperature Td2 during no-load operation.

[0079] The control device 110 determines that the second condition is satisfied when the supply water temperature Tw1 is equal to or higher than the temperature threshold value Twh, and determines that the second condition is not satisfied when the supply water temperature Tw1 is lower than the temperature threshold value Twh.

[0080] When the compressor body 1 is in load operation, the control device 110 fully opens the intake valve 6 and fully closes the first low pressure air release valve 25, the first high pressure air release valve 28, the second low pressure air release valve 43 and the second high pressure air release valve 46.

[0081] The control device 110 enables the exhaust heat recovery function during no-load operation when the disable condition is not met. The control device 110 disables the exhaust heat recovery function during no-load operation when the disable condition is met. Note that whether or not the disable condition is met may be determined after switching from load operation to no-load operation, or may be determined in advance during load operation.

[0082] Specifically, when the invalidation condition is not satisfied, the control device 110 fully opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28 and fully closes the second low-pressure air release valve 43 and the second high-pressure air release valve 46 when switching the compressor main body 1 from load operation to no-load operation. In this state, as in the first embodiment, compressed air flows into the low-pressure stage exhaust heat recovery heat exchanger 8 and the high-pressure stage exhaust heat recovery heat exchanger 14, and water is heated by the compressed air. In other words, in this state, the exhaust heat recovery function during no-load operation is enabled.

[0083] On the other hand, when the disable condition is met, the control device 110 fully opens at least the second low-pressure air release valve 43 and the second high-pressure air release valve 46 when switching the compressor body 1 from load operation to no-load operation. As a result, a portion of the compressed air discharged from the low-pressure stage compressor body 1L is released upstream of the low-pressure stage waste heat recovery heat exchanger 8. Also, the compressed air discharged from the high-pressure stage compressor body 1H is released upstream of the high-pressure stage waste heat recovery heat exchanger 14. In this state, the amount of compressed air flowing into the low-pressure stage waste heat recovery heat exchanger 8 and the high-pressure stage waste heat recovery heat exchanger 14 is significantly reduced compared to the first embodiment, and the amount of heat transferred from the compressed air to water is reduced. In other words, in this state, the waste heat recovery function during no-load operation is disabled.

[0084] Fig. 5 is a flowchart showing an example of the processing flow of valve control of gas compression system 200 executed by control device 110 according to the second embodiment. In the flowchart of Fig. 5, processing of steps S220 to S245 is executed instead of the processing of steps S114 and S118 in the flowchart of Fig. 3. The flowchart shown in Fig. 5 is started, for example, when the start switch of input device 80 is turned on, and is executed repeatedly at a predetermined control cycle.

[0085] In step S110, the control device 110 determines whether the discharge pressure Pd detected by the discharge pressure sensor 38 is equal to or greater than the no-load operation start pressure Pdu, as in the first embodiment. If it is determined in step S110 that the discharge pressure Pd is equal to or greater than the no-load operation start pressure Pdu, the process proceeds to step S225. If it is determined in step S110 that the discharge pressure Pd is less than the no-load operation start pressure Pdu, the process proceeds to step S220.

[0086] In step S220, the control device 110 outputs an open signal to the intake valve 6, and outputs close signals to the first low pressure air release valve 25, the first high pressure air release valve , the second low pressure air release valve 43 and the second high pressure air release valve .

[0087] In step S225, the control device 110 outputs a close signal to the intake valve 6, and the process proceeds to step S230.

[0088] In step S230, the control device 110 determines whether the invalid condition is met based on the detection results of the differential pressure sensor 40 and the detection results of the feedwater temperature sensor 39. In step S230, if neither the first condition nor the second condition is met, the control device 110 determines that the invalid condition is met and proceeds to step S240. In step S230, if at least one of the first condition and the second condition is met, the control device 110 determines that the invalid condition is met and proceeds to step S245.

[0089] In step S240, the control device 110 outputs an open signal to the first low-pressure air release valve 25 and the first high-pressure air release valve 28, and outputs a close signal to the second low-pressure air release valve 43 and the second high-pressure air release valve 46. As a result, the control device 110 enables the exhaust heat recovery function during no-load operation.

[0090] In step S245, the control device 110 outputs an open signal to the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46. As a result, the control device 110 disables the exhaust heat recovery function during no-load operation.

[0091] When the valve control signal output process (the process of step S220, step S240 or step S245) is completed, the process shown in the flowchart of FIG. 5 for this control cycle is completed.

[0092] 4 and 5, a description will be given of a characteristic operation of gas compression system 200 according to the second embodiment. When discharge pressure Pd of gas compressor 201 increases and becomes equal to or greater than no-load operation start pressure Pdu, control device 110 of gas compression system 200 switches the operating state from load operation to no-load operation.

[0093] When switching the compressor main body 1 from load operation to no-load operation, the control device 110 closes the intake valve 6 while continuing to operate the electric motor 3 (step S225). When water is supplied from a water supply source (not shown) to the heat exchangers 8 and 14 for exhaust heat recovery and the supply water temperature Tw1 is lower than the temperature threshold value Twh, the second low-pressure air release valve 43 and the second high-pressure air release valve 46 are maintained in a closed state (No in step S230, step S240), and the first low-pressure air release valve 25 and the first high-pressure air release valve 28 are opened. Therefore, as in the first embodiment, the exhaust heat recovery function is enabled, and a decrease in the water temperature during no-load operation can be suppressed.

[0094] When water is not supplied from a water supply source (not shown) to the heat exchangers 8 and 14 for exhaust heat recovery, or when the water supply temperature Tw1 is equal to or higher than the temperature threshold value Twh, not only the first low-pressure air release valve 25 and the first high-pressure air release valve 28 but also the second low-pressure air release valve 43 and the second high-pressure air release valve 46 are opened (Yes in step S230, step S245). As a result, compressed air is quickly released into the atmosphere, so that almost no exhaust heat recovery is performed, and the exhaust heat recovery function can be disabled.

[0095] As described above, the gas compression system 200 according to the second embodiment includes a second low-pressure air release valve 43 provided upstream of the heat exchanger 8 for recovering exhaust heat in the low-pressure stage of the gas system, a second high-pressure air release valve 46 provided upstream of the heat exchanger 14 for recovering exhaust heat in the high-pressure stage of the gas system, a differential pressure sensor 40 provided to detect whether water is being supplied to the heat exchangers 8, 14 for recovering exhaust heat, and a feed water temperature sensor 39 provided to detect that the feed water temperature has risen to a temperature close to that of the compressed air.

[0096] The control device 110 determines whether a disable condition for disabling the exhaust heat recovery function during no-load operation is established based on the detection results of the differential pressure sensor 40 and the feedwater temperature sensor 39. The control device 110 determines that the disable condition is established when the differential pressure ΔPw detected by the differential pressure sensor 40 is smaller than the differential pressure threshold ΔPwl, or when the feedwater temperature Tw1 detected by the feedwater temperature sensor 39 is higher than the temperature threshold Twh. The control device 110 determines that the disable condition is not established when the differential pressure ΔPw detected by the differential pressure sensor 40 is larger than the differential pressure threshold ΔPwl and the feedwater temperature Tw1 detected by the feedwater temperature sensor 39 is lower than the temperature threshold Twh.

[0097] When the invalidation condition is not established, the control device 110 opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28 and closes the second low-pressure air release valve 43 and the second high-pressure air release valve 46 when switching from load operation to no-load operation of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H. When the invalidation condition is established, the control device 110 opens at least the second low-pressure air release valve 43 and the second high-pressure air release valve 46 when switching from load operation to no-load operation of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H.

[0098] According to this configuration, during no-load operation, if water is not supplied to the heat exchangers 8, 14 for exhaust heat recovery, or if the supply water temperature becomes equal to or higher than the temperature of the compressed air, the second low-pressure air release valve 43 and the second high-pressure air release valve 46 are opened. This disables the exhaust heat recovery function during no-load operation. Because the flow rate of compressed air supplied to the heat exchangers 8, 14 for exhaust heat recovery is kept low, the pressure loss that occurs when the compressed air flows through the heat exchangers 8, 14 for exhaust heat recovery is kept low. In other words, when the disable condition is met during no-load operation, the pressure loss is reduced compared to when the disable condition is not met, thereby reducing the power consumption of the electric motor 3. Therefore, the gas compressor 201 and the gas compression system 200 according to the second embodiment can achieve higher energy-saving efficiency than the first embodiment.

[0099] Furthermore, in the second embodiment, if the invalidation condition is established, the control device 110 opens the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46 when switching the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H from load operation to no-load operation. Therefore, more compressed air can be released into the atmosphere more quickly than when the first low-pressure air release valve 25 and the first high-pressure air release valve 28 are closed. As a result, energy saving efficiency can be further improved.

[0100] <Third embodiment> 6 and 7, a gas compressor 301 and a gas compression system 300 according to a third embodiment of the present invention will be described. Note that the same reference numerals are used to designate components that are the same as or equivalent to those described in the second embodiment, and differences will be mainly described.

[0101] 6 is a schematic diagram showing the overall configuration of a gas compression system 300 according to the third embodiment. The gas compression system 300 according to the third embodiment has a configuration similar to that of the gas compression system 200 according to the second embodiment. Furthermore, the exhaust heat recovery device 302 of the gas compression system 300 according to the third embodiment includes a heat exchanger 49 for recovering exhaust heat from lubricating oil, which is provided in the lubricating oil path OP and exchanges heat between the lubricating oil and water. The heat exchanger 49 has a high-temperature fluid flow path through which the lubricating oil flows and a low-temperature fluid flow path through which water supplied from a water supply source (not shown) flows.

[0102] When recovering waste heat from high-temperature compressed air, such as in an oil-free air compressor, the temperature of the lubricating oil is significantly lower than the temperature of the compressed air immediately after it is discharged from each compressor body 1 during load operation. For this reason, waste heat recovery from the lubricating oil is often not actively implemented. However, the amount of decrease in lubricating oil temperature when switching from load operation to no-load operation is smaller than the amount of decrease in compressed air temperature. For this reason, during no-load operation, it is more valuable to use the lubricating oil for waste heat recovery than during load operation.

[0103] The temperature of the lubricating oil is lower than the temperature of the compressed air discharged from the low-pressure stage compressor body 1L during no-load operation and the temperature of the compressed air discharged from the high-pressure stage compressor body 1H during no-load operation. Therefore, in this embodiment, in the water supply system shown in FIG. 6, a heat exchanger 49 for lubricating oil waste heat recovery is arranged so that the lubricating oil first exchanges heat with low-temperature water immediately after the water supply source, where the water temperature is lowest. This maximizes the temperature difference between the lubricating oil and the water, thereby improving the waste heat recovery efficiency. Furthermore, the heat exchangers 49, 8, and 14 are connected in series so that the water preheated with the lubricating oil passes through the low-pressure stage waste heat recovery heat exchanger 8 and the high-pressure stage waste heat recovery heat exchanger 14 in that order. Since the heat exchanger 49 for lubricating oil waste heat recovery is arranged upstream of the heat exchangers 8 and 14 in the water supply system, the feedwater temperature can be effectively increased.

[0104] Lubricating oil pumped by oil pump 48 flows into the high-temperature fluid passage of heat exchanger 49 for recovering exhaust heat from lubricating oil and heats water, which is a low-temperature fluid. The lubricating oil flowing out from the outlet of the high-temperature fluid passage of heat exchanger 49 for recovering exhaust heat from lubricating oil passes through oil cooler 20 and is cooled by cooling air, and then supplied to the moving parts inside compressor body 1 and speed increase device 4.

[0105] Water supplied to the exhaust heat recovery device 302 from a water supply source (not shown) flows through the upstream first supply passage 30A into the low-temperature fluid passage of the heat exchanger 49 for recovering lubricating oil exhaust heat. The water flowing into the low-temperature fluid passage of the heat exchanger 49 is heated by the lubricating oil flowing through the high-temperature fluid passage. The water heated by the heat exchanger 49 flows through the downstream first supply passage 30B into the low-temperature fluid passage of the heat exchanger 8 for recovering low-pressure stage exhaust heat. The water flowing into the low-temperature fluid passage of the heat exchanger 8 is further heated by the high-temperature compressed air flowing through the high-temperature fluid passage. The water heated by the heat exchanger 8 flows through the second supply passage 31 into the low-temperature fluid passage of the heat exchanger 14 for recovering high-pressure stage exhaust heat. The water flowing into the low-temperature fluid passage of the heat exchanger 14 is further heated by the high-temperature compressed air flowing through the high-temperature fluid passage. The water heated by the heat exchanger 14 is supplied to a hot water using facility (demand destination) 90 through a third supply flow path 32.

[0106] The lubricating oil path OP includes a main path 191a upstream of the heat exchanger that guides the lubricating oil to the heat exchanger 49 for lubricating oil exhaust heat recovery, a main path 191b downstream of the heat exchanger that guides the lubricating oil from the heat exchanger 49 to the oil cooler 20, and a bypass path 192 that connects the main path 191a upstream of the heat exchanger with the main path 191b downstream of the heat exchanger. The main paths 191a and 191b form a first path that guides the lubricating oil to the oil cooler 20 via the heat exchanger 49 for lubricating oil exhaust heat recovery. The bypass path 192 forms a second path that guides the lubricating oil to the oil cooler 20, bypassing the heat exchanger 49 for lubricating oil exhaust heat recovery.

[0107] The gas compressor 301 is equipped with a path switching valve 51 that connects either the first path (main paths 191a, 191b) or the second path (bypass path 192) to the oil cooler 20. The path switching valve 51 is a three-way valve that can be switched between an active position and an inactive position. When switched to the active position, the path switching valve 51 connects the main paths 191a, 191b to the inlet path of the oil cooler 20 and blocks communication between the bypass path 192 and the inlet path of the oil cooler 20. When switched to the inactive position (bypass position), the path switching valve 51 connects the bypass path 192 to the inlet path of the oil cooler 20 and blocks communication between the main paths 191a, 191b and the inlet path of the oil cooler 20.

[0108] The path switching valve 51 is switched to an enabled position or an disabled position in response to a control signal from the control device 110. The path switching valve 51 is switched to the enabled position when an enabled signal (control signal) is input from the control device 110. The path switching valve 51 is switched to the disabled position when an disabled signal (control signal) is input from the control device 110.

[0109] Similar to the second embodiment, the control device 110 of the gas compressor 301 according to the third embodiment can switch between enabling and disabling the exhaust heat recovery function during no-load operation. Furthermore, when the disable condition is not satisfied, the control device 110 of the gas compressor 301 according to the third embodiment uses the path switching valve 51 to connect the main paths 191a, 191b to the oil cooler 20. When the disable condition is satisfied, the control device 110 of the gas compressor 301 uses the path switching valve 51 to connect the bypass path 192 to the oil cooler 20.

[0110] Figure 7 is a flowchart showing an example of the processing flow of valve control of gas compression system 300 executed by control device 110 according to the third embodiment. In the flowchart of Figure 7, processing of steps S320, S340, and S345 is executed instead of the processing of steps S220, S240, and S245 in the flowchart of Figure 5. The flowchart shown in Figure 7 is started, for example, when the start switch of input device 80 is turned on, and is repeatedly executed at a predetermined control period.

[0111] If it is determined in step S110 that the discharge pressure Pd is less than the no-load operation start pressure Pdu, the process proceeds to step S320. In step S320, similar to step S220, the control device 110 outputs an open signal to the intake valve 6 and outputs close signals to the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46. In step S320, the control device 110 also outputs an enable signal to the path switching valve 51.

[0112] If it is determined in step S230 that the disable condition is not satisfied, the process proceeds to step S340. In step S340, similar to step S240, the control device 110 outputs an open signal to the first low-pressure air release valve 25 and the first high-pressure air release valve 28, and outputs a close signal to the second low-pressure air release valve 43 and the second high-pressure air release valve 46. In step S340, the control device 110 also outputs an enable signal to the path switching valve 51. This causes the control device 110 to enable the exhaust heat recovery function during no-load operation.

[0113] If it is determined in step S230 that the disable condition is met, the process proceeds to step S345. In step S345, similar to step S245, the control device 110 outputs open signals to the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46. In step S345, the control device 110 also outputs a disable signal to the path switching valve 51. As a result, the control device 110 disables the exhaust heat recovery function during no-load operation.

[0114] As described above, the gas compression system 300 according to the third embodiment includes the heat exchanger 49 for recovering exhaust heat from lubricating oil, which exchanges heat between the lubricating oil and water, and the path switching valve 51 for connecting either the first path (main paths 191a, 191b) or the second path (bypass path 192) to the oil cooler 20. When the invalidation condition is not satisfied, the control device 110 causes the path switching valve 51 to connect the first path (main paths 191a, 191b) to the oil cooler 20 (step S340). As a result, during no-load operation, the lubricating oil passes through the heat exchanger 49 for recovering exhaust heat from lubricating oil, and the water is heated. On the other hand, when the invalidation condition is satisfied, the control device 110 causes the path switching valve 51 to connect the second path (bypass path 192) to the oil cooler 20 (step S345). As a result, when the invalid condition is met during no-load operation, the lubricating oil is guided to the oil cooler 20, bypassing the heat exchanger 49 for recovering the lubricating oil waste heat.

[0115] According to this configuration, the heat of the lubricating oil can be effectively utilized during no-load operation, and hot water at a higher temperature or in a larger amount can be supplied to the hot water usage facility (demand destination) 90. Therefore, according to the gas compressor 301 and the gas compression system 300 according to the third embodiment, the temperature of the water can be increased more efficiently than in the second embodiment.

[0116] Furthermore, when water is not supplied from a water supply source (not shown) to the heat exchangers 8 and 14 for exhaust heat recovery, or when the feedwater temperature Tw1 is equal to or higher than the temperature threshold value Twh, the lubricating oil is guided to the oil cooler 20, bypassing the heat exchanger 49 for lubricating oil exhaust heat recovery, thereby reducing the power consumption of the oil pump 48. Therefore, energy saving efficiency can be improved compared to when the lubricating oil is always supplied to the heat exchanger 49 for lubricating oil exhaust heat recovery.

[0117] <Fourth embodiment> A gas compressor 401 and a gas compression system 400 according to a fourth embodiment of the present invention will be described with reference to Fig. 8. Note that the same reference numerals are used to designate components that are the same as or equivalent to those described in the second embodiment, and differences will be mainly described.

[0118] 8 is a schematic diagram showing the overall configuration of a gas compression system 400 according to the fourth embodiment. The gas compression system 400 according to the fourth embodiment has a configuration similar to that of the gas compression system 200 according to the second embodiment. Furthermore, the exhaust heat recovery device 402 of the gas compression system 400 according to the fourth embodiment includes a drain separator 52 upstream of a first low-pressure air release valve 25 provided on a first low-pressure branch path 24 branching off from the low-pressure gas path PL. Similarly, the exhaust heat recovery device 402 includes a drain separator 53 upstream of a first high-pressure air release valve 28 provided on a first high-pressure branch path 27 branching off from the high-pressure gas path PH. This reduces the risk that when the temperature of the water supplied to each heat exchanger 8 and 14 is relatively much lower than the temperature of the compressed air, or in an environment where the relative humidity of the atmosphere is high and condensation water is more likely to be produced than in the compressed air, the condensation water produced when the compressed air is cooled in each heat exchanger 8 and 14 will spray out from the first low-pressure air release valve 25 and the first high-pressure air release valve 28 and wet the surrounding equipment, causing it to malfunction or become dirty.

[0119] The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, to combine the configurations described in the different embodiments above, or to combine the configurations described in the different modified examples below.

[0120] <Variation 1> In the first to third embodiments, the gas compressors 101, 201, and 301 have been described as constant-speed compressors. However, the present invention is not limited to this. The gas compressors 101, 201, and 301 may be variable-speed compressors that do not include the intake valve 6, that are provided with an inverter instead of the electromagnetic switch 2, and that variably control the rotation speed of the electric motor 3 by the control device 110. In this case, the rotation speed of the electric motor 3 is generally reduced to a predetermined lower limit rotation speed upon switching from load operation to no-load operation. For example, during load operation, the control device 110 closes the first low-pressure air release valve 25 and the first high-pressure air release valve 28 and controls the rotation speed of the electric motor 3 within a predetermined range based on the discharge pressure Pd. Furthermore, during no-load operation, the control device 110 controls the rotation speed of the electric motor 3 to the lower limit rotation speed and opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28. In this configuration, the amount of intake air is significantly reduced compared to load operation even without the intake valve 6. Therefore, during no-load operation, by releasing compressed air into the atmosphere through the first low-pressure air release valve 25 and the first high-pressure air release valve 28, the temperature of the water flowing through the high-pressure stage exhaust heat recovery heat exchanger 14 can be made higher than when the first low-pressure air release valve 25 is not provided.

[0121] <Variation 2> In the first to third embodiments, an example has been described in which the heat exchangers 8, 14 are connected in series in the water supply system so that water flows through the heat exchanger 8 for low-pressure stage waste heat recovery and then the heat exchanger 14 for high-pressure stage waste heat recovery. However, the method of connecting the heat exchangers 8, 14 is not limited to this. For example, in the water supply system, the heat exchangers 14, 8 may be connected in series so that water flows through the heat exchanger 14 for high-pressure stage waste heat recovery and then the heat exchanger 8 for low-pressure stage waste heat recovery.

[0122] Furthermore, in the water supply systems of the first and second embodiments, the heat exchanger 8 for low-pressure stage waste heat recovery and the heat exchanger 14 for high-pressure stage waste heat recovery may be connected in parallel downstream of a water supply source (not shown). In this case, the hot water flowing out from the low-temperature fluid passage outlet of the heat exchanger 8 for low-pressure stage waste heat recovery and the low-temperature fluid passage outlet of the heat exchanger 14 for high-pressure stage waste heat recovery may be led individually to the hot water usage facility 91, or may be joined together and then led to the hot water usage facility 91.

[0123] In the third embodiment, an example has been described in which the heat exchangers 49, 8, and 14 are connected in series in the water supply system so that water flows through the heat exchanger 49 for lubricating oil exhaust heat recovery, the heat exchanger 8 for low-pressure stage exhaust heat recovery, and the heat exchanger 14 for high-pressure stage exhaust heat recovery in that order. However, the method of connecting the heat exchangers 49, 8, and 14 is not limited to this. For example, in the water supply system, the heat exchanger 8 for low-pressure stage exhaust heat recovery and the heat exchanger 14 for high-pressure stage exhaust heat recovery may be connected in parallel downstream of the heat exchanger 49 for lubricating oil exhaust heat recovery.

[0124] <Variation 3> In the second embodiment, an example in which the invalidation conditions include the first condition and the second condition has been described, but the present invention is not limited to this. One of the first condition and the second condition may be omitted. In other words, the invalidation conditions may include at least one of the first condition and the second condition.

[0125] Furthermore, the disabling condition may include the following third condition instead of the first and second conditions: In other words, although the second embodiment has been described as an example in which the exhaust heat recovery function during no-load operation is automatically disabled, the exhaust heat recovery function during no-load operation may also be manually disabled. Third condition: An invalid operation is performed on the input device 80.

[0126] For example, the input device 80 is equipped with an invalid operation switch that can be switched between an invalid position and a valid position. When the invalid operation switch is operated to the invalid position, an invalid operation signal is input from the input device 80 to the control device 110. When the invalid operation switch is operated to the valid position, a valid operation signal is input from the input device 80 to the control device 110. When the invalid operation switch is operated to the invalid position, the control device 110 determines that the third condition is met. When the invalid operation switch is operated to the valid position, the control device 110 determines that the third condition is not met.

[0127] According to this configuration, the operator can manually disable or enable the exhaust heat recovery function during no-load operation.

[0128] The invalidation condition may include a third condition in addition to the first and second conditions. In this case, the control device 110 determines that the invalidation condition is met when at least one of the first, second, and third conditions is met. The control device 110 determines that the invalidation condition is not met when all of the first, second, and third conditions are not met.

[0129] <Variation 4> In the second and third embodiments, examples have been described in which the temperature threshold value Twh is a predetermined fixed value, but the present invention is not limited to this. For example, the temperature threshold value Twh may be increased as the temperature of the compressed air detected by the low-pressure stage discharge temperature sensor 34 and the high-pressure stage discharge temperature sensor 37 increases. This allows the temperature threshold value Twh to be set appropriately even if the temperature of the compressed gas changes with the seasons.

[0130] <Variation 5> In the second and third embodiments, examples have been described in which the temperature threshold value Twh is determined in advance through experiments or the like based on the temperature of the compressed air during no-load operation, but the present invention is not limited to this. The temperature threshold value Twh can be determined arbitrarily, and may be determined, for example, based on the temperature required by the hot water usage equipment 91. For example, the temperature threshold value Twh is a value equal to or greater than the temperature required by the hot water usage equipment 91, and is stored in advance in the non-volatile memory 112. The temperature threshold value Twh may be changeable by operating the operation unit of the input device 80.

[0131] <Variation 6> In the second and third embodiments, examples have been described in which it is determined whether water is being supplied to the heat exchangers 8, 14 for exhaust heat recovery based on the detection result of the differential pressure sensor 40, but the present invention is not limited to this. A flow rate sensor may be provided instead of the differential pressure sensor 40, and it may be determined whether water is being supplied to the heat exchangers 8, 14 for exhaust heat recovery based on the detection result of the flow rate sensor. In this case, the control device 110 determines that the first condition is met when the flow rate of water supplied to the heat exchangers 8, 14 is equal to or less than the flow rate threshold. Furthermore, the control device 110 determines that the first condition is not met when the flow rate of water supplied to the heat exchangers 8, 14 is greater than the flow rate threshold.

[0132] <Variation 7> In the first to third embodiments, an example has been described in which no-load operation is performed when the discharge pressure Pd of the gas compressor 101, 201, 301 is equal to or greater than the no-load operation start pressure Pdu, and no-load operation is performed when the discharge pressure Pd is less than the no-load operation start pressure Pdu. However, the present invention is not limited to this. For example, if an operation to forcibly perform no-load operation is performed via the input device 80 during load operation, the control device 110 may perform no-load operation even when the discharge pressure Pd is less than the no-load operation start pressure Pdu.

[0133] <Variation 8> In the first to third embodiments, an example has been described in which input device 80 is an operation panel provided in gas compressor 101, 201, 301, but the present invention is not limited to this. Input device 80 may be an external terminal device capable of transmitting signals to control device 110 from a location far away from gas compressor 101, 201, 301. The external terminal device may be a smartphone, a laptop PC, a tablet PC, or the like capable of communicating with control device 110. In this case, by operating the external terminal device serving as input device 80, an operator can start gas compression system 100, 200, 300, enable / disable the exhaust heat recovery function during no-load operation, or forcibly perform no-load operation.

[0134] <Variation 9> In the first to third embodiments, an example has been described in which the gas compressors 101, 201, 301 are two-stage screw compressors including a low-pressure stage compressor main body 1L and a high-pressure stage compressor main body 1H. However, the configuration of the gas compressors 101, 201, 301 is not limited to this. For example, a further compressor main body may be provided on the air inlet side of the low-pressure stage compressor main body 1L, a further compressor main body may be provided on the air outlet side of the high-pressure stage compressor main body 1H, or further compressor main bodies 1 may be provided on the air outlet side of the low-pressure stage compressor main body 1L and the air inlet side of the high-pressure stage compressor main body 1H.

[0135] <Modification 10> The gas compression systems 100, 200, and 300 may include multiple gas compressors 101, 201, and 301. When the gas compression system includes multiple gas compressors, the operation of each gas compressor may be controlled so that the multiple gas compressors are sequentially operated under load. The control device 110 controls the gas compressors by switching between loaded operation and unloaded operation in order to level out their operating times. In this case, when a specific gas compressor is switched from loaded operation to unloaded operation, the control device 110 opens the first low-pressure air release valve 25 and the first high-pressure air release valve 28 of the specific gas compressor, thereby recovering exhaust heat from the compressed air of the specific gas compressor.

[0136] <Variation 11> The control device 110 according to the second and third embodiments has been described as opening the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46 when switching from load operation to no-load operation of the compressor main body 1 when an invalid condition is met.

[0137] However, the present invention is not limited to this. When the invalidation condition is established, the control device 110 only needs to open at least the second low-pressure air release valve 43 and the second high-pressure air release valve 46 when switching the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H from loaded operation to unloaded operation. In other words, the control device 110 may keep the first low-pressure air release valve 25 and the first high-pressure air release valve 28 closed.

[0138] By opening at least the second low pressure air release valve 43 and the second high pressure air release valve 46 out of the first low pressure air release valve 25, the first high pressure air release valve 28, the second low pressure air release valve 43 and the second high pressure air release valve 46, it is possible to reduce pressure loss in the heat exchangers 8, 14 compared to when only the first low pressure air release valve 25 and the first high pressure air release valve 28 are opened. This makes it possible to disable the exhaust heat recovery function while reducing the power consumption of the electric motor 3.

[0139] Furthermore, when the invalidation condition is established, the control device 110 according to the second and third embodiments does not need to open the first low-pressure air release valve 25, the first high-pressure air release valve 28, the second low-pressure air release valve 43, and the second high-pressure air release valve 46 at the same timing when switching from load operation to no-load operation of the compressor body 1. For example, the control device 110 may open the second low-pressure air release valve 43 and the second high-pressure air release valve 46, and then open the first low-pressure air release valve 25 and the first high-pressure air release valve 28 at different times.

[0140] <Modification 12> The configuration of the exhaust heat recovery devices 102, 202, 302 is not limited to the examples described in the above embodiments. For example, the exhaust heat recovery device may include a flow rate adjustment device that adjusts the flow rate of water depending on the temperature of water flowing out from the high-pressure stage heat exchanger 14 for exhaust heat recovery (exhaust heat recovery outlet temperature). The flow rate adjustment device includes, for example, a temperature sensor, a temperature controller, and a temperature control valve that are provided downstream of the high-pressure stage heat exchanger 14 for exhaust heat recovery in the water supply system. The temperature sensor detects the water outlet temperature of the exhaust heat recovery device and outputs a signal representing the detection result to the temperature controller. The temperature controller controls the opening / closing angle of the temperature control valve depending on the water outlet temperature of the exhaust heat recovery device detected by the temperature sensor, thereby controlling the flow rate. The temperature controller controls the flow rate using the temperature control valve so that the water outlet temperature of the exhaust heat recovery device falls within a predetermined temperature range.

[0141] In the comparative example not provided with the first low-pressure branch path 24 and the first low-pressure air release valve 25, if this flow control device is provided, the temperature of the compressed air drops during no-load operation compared to during load operation, causing the opening / closing angle of the temperature control valve to decrease and the amount of water to be reduced. As a result, in this modified example, the amount of hot water that can be extracted from the exhaust heat recovery device during no-load operation may be significantly smaller than during load operation.

[0142] In contrast, in Modification 12, a first low-pressure branch path 24 and a first low-pressure air release valve 25 are provided. Therefore, when switching from load operation to no-load operation, not only the first high-pressure air release valve 28 but also the first low-pressure air release valve 25 are opened. This makes it possible to increase the temperature of the water flowing out of the heat exchanger 14 for high-pressure stage exhaust heat recovery during no-load operation compared to the comparative example. Because the water temperature can be increased, the amount of hot water that can be extracted from the exhaust heat recovery device can be increased compared to the comparative example. Modification 12 can provide a gas compressor and a gas compression system that can suppress a decrease in the water temperature and amount of hot water during no-load operation.

[0143] <Variation 13> In the first to third embodiments, the gas compressors 101, 201, and 301 are oil-free screw compressors equipped with a pair of male and female screw rotors. However, the present invention is not limited to this. The gas compressor may be a single-screw compressor equipped with one screw rotor. The gas compressor may also be a scroll compressor, a roots blower, a reciprocating compressor, or the like.

[0144] <Variation 14> In the first to third embodiments, an example has been shown in which the exhaust heat recovery fluid passing through the low-temperature fluid flow paths of the low-pressure stage heat exchanger 8 for exhaust heat recovery and the high-pressure stage heat exchanger 14 for exhaust heat recovery is water. However, the exhaust heat recovery fluid is not limited to water, and may be a coolant liquid containing an antifreeze component such as alcohol, or oil.

[0145] <Variation 15> In the first to third embodiments, examples have been described in which the intercooler 10, the aftercooler 17, and the oil cooler 20 are air-cooled heat exchangers that use cooling air as a cooling medium, but they may also be liquid-cooled (water-cooled) heat exchangers that use a liquid such as cooling water as a cooling medium.

[0146] <Variation 16> In the first to third embodiments, an example has been described in which the drive structure of the compressor body 1 is a structure in which the power of one electric motor 3 is transmitted to the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H via the speed-increasing device 4. However, the present invention is not limited to this. For example, the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H may each be directly connected to an independent electric motor without the speed-increasing device 4. In other words, the drive structure of the compressor body 1 may be a structure in which the power of a first electric motor is transmitted to the low-pressure stage compressor body 1L and the power of a second electric motor is transmitted to the high-pressure stage compressor body 1H.

[0147] <Variation 17> The oil pump 48 may be driven by the electric motor 3 or by an electric motor separate from the electric motor 3.

[0148] <Variation 18> In the first to third embodiments, the gas compressed by the gas compressors 101, 201, and 301 is air, and the compressed air is released into the atmosphere through the air release valve. However, the present invention is not limited to this. For example, the gas compressed by the gas compressor may be nitrogen. Furthermore, the air release valve may be connected to a gas tank having a lower pressure than the gas system, and the compressed gas may be released from the air release valve into the gas tank.

[0149] <Variation 19> The electromagnetic intake valve control valve for opening and closing the intake valve 6 shown in the first to third embodiments may be provided separately from the intake valve 6. An output signal from the control device 110 is transmitted to the intake valve control valve, and the intake valve control valve opens and closes, thereby opening and closing the intake valve 6 with a driving force due to the gas pressure (air pressure) discharged from the low-pressure stage compressor main body 1L or the high-pressure stage compressor main body 1H.

[0150] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0151] 1...Compressor body, 1H...High-pressure stage compressor body, 1L...Low-pressure stage compressor body, 2...Electromagnetic switch, 3...Electric motor, 5...Intake filter, 6...Intake valve (control valve), 7...Air path, 8...Heat exchanger for low-pressure stage waste heat recovery, 9...Air path, 10...Intercooler, 11...Air path, 12...Condensate separator, 13...Air path, 14...Heat exchanger for high-pressure stage waste heat recovery, 15...Air path, 16...Check valve, 17...Aftercooler, 18...Air path, 19...Oil supply path, 20...Oil cooler, 21...Supply Oil path, 22... oil supply path, 23... return path, 24... first low-pressure branch path, 25... first low-pressure air release valve, 27... first high-pressure branch path, 28... first high-pressure air release valve, 30... first supply flow path, 30A... upstream side first supply flow path, 30B... downstream side first supply flow path, 31... second supply flow path, 32... third supply flow path, 33... water supply valve, 34... low-pressure stage discharge temperature sensor, 35... high-pressure stage suction temperature sensor, 36... high-pressure stage suction pressure sensor, 37... high-pressure stage discharge temperature sensor, 38... discharge pressure sensor, 39... water supply temperature sensor sensor (temperature sensor), 40...differential pressure sensor, 41...pressure detection tube, 42...second low-pressure branch path, 43...second low-pressure air release valve, 44...silencer, 45...second high-pressure branch path, 46...second high-pressure air release valve, 47...silencer, 48...oil pump, 49...heat exchanger for lubricating oil exhaust heat recovery, 50...cooling fan, 51...path switching valve, 80...input device, 90...hot water using equipment (demand destination), 91...air using equipment (demand destination), 100...gas compression system, 101...gas compressor, 102...exhaust heat recovery device, 110 ...control device, 111...processing device, 112...non-volatile memory, 113...volatile memory, 114...input interface, 115...output interface, 191a...main path (first path), 191b...main path (first path), 192...bypass path (second path), 200...gas compression system, 201...gas compressor, 202...exhaust heat recovery device, 300...gas compression system, 301...gas compressor, 302...exhaust heat recovery device, OP...lubricating oil path, PL...low pressure gas path, PH...high pressure gas path

Claims

1. a low-pressure stage compressor main body that compresses gas; an intercooler that cools compressed gas discharged from the low-pressure stage compressor main body; a high-pressure stage compressor main body that further compresses the compressed gas cooled by the intercooler; an aftercooler that cools the compressed gas discharged from the high-pressure stage compressor main body; a low-pressure gas path that guides the compressed gas discharged from the low-pressure stage compressor main body to the high-pressure stage compressor main body through the intercooler; and a high-pressure gas path that guides the compressed gas discharged from the high-pressure stage compressor main body to a demand destination through the aftercooler, a first low-pressure branch path that is downstream of a low-pressure stage heat exchanger that exchanges heat between the compressed gas discharged from the low-pressure stage compressor body and a fluid for exhaust heat recovery, and that branches off from the low-pressure gas path that is upstream of the intercooler; a first low-pressure release valve provided in the first low-pressure branch path and configured to release compressed gas discharged from the low-pressure stage compressor body; a second low-pressure branch path branching from the low-pressure gas path upstream of the heat exchanger for recovering low-pressure exhaust heat; a second low-pressure air release valve provided in the second low-pressure branch path; a first high-pressure branch path that is downstream of a high-pressure stage heat exchanger that exchanges heat between the compressed gas discharged from the high-pressure stage compressor body and a fluid for exhaust heat recovery, and that branches off from the high-pressure gas path that is upstream of the aftercooler; a first high-pressure release valve provided in the first high-pressure branch path and configured to release compressed gas discharged from the high-pressure stage compressor body; a second high-pressure branch path branching from the high-pressure gas path upstream of the heat exchanger for recovering high-pressure exhaust heat; a second high-pressure air release valve provided in the second high-pressure branch path; a control device that controls the first low-pressure air release valve, the second low-pressure air release valve, the first high-pressure air release valve, and the second high-pressure air release valve; The control device determining whether a disabling condition for disabling the exhaust heat recovery function during no-load operation is established; If the invalidation condition is not established, when switching from load operation to no-load operation of the low-pressure stage compressor main body and the high-pressure stage compressor main body, the first low-pressure air release valve and the first high-pressure air release valve are opened, and the second low-pressure air release valve and the second high-pressure air release valve are closed, thereby releasing compressed gas from the first low-pressure air release valve and the first high-pressure air release valve during no-load operation, while causing heat exchange between the compressed gas passing through the low-pressure stage heat exchanger for exhaust heat recovery and the high-pressure stage heat exchanger for exhaust heat recovery and an exhaust heat recovery fluid, When the invalidation condition is satisfied, at least the second low-pressure air release valve and the second high-pressure air release valve are opened when switching the low-pressure stage compressor main body and the high-pressure stage compressor main body from load operation to no-load operation. Gas compression system.

2. 10. The gas compression system of claim 1, The invalid condition is: No exhaust heat recovery fluid is supplied to at least one of the low-pressure stage exhaust heat recovery heat exchanger and the high-pressure stage exhaust heat recovery heat exchanger; and a temperature of the exhaust heat recovery fluid supplied to at least one of the low-pressure stage heat exchanger for exhaust heat recovery and the high-pressure stage heat exchanger for exhaust heat recovery is higher than a temperature threshold. Gas compression system.

3. 10. The gas compression system of claim 1, An input device operable by an operator is provided, The invalid condition includes an invalid operation being performed by the input device. Gas compression system.

4. 10. The gas compression system of claim 1, a lubricating oil path through which lubricating oil flows to lubricate the low-pressure stage compressor body and the high-pressure stage compressor body; an oil cooler provided in the lubricating oil path to cool the lubricating oil, The lubricating oil passage includes a first passage that guides the lubricating oil to the oil cooler through a heat exchanger for lubricating oil exhaust heat recovery that exchanges heat between the lubricating oil and an exhaust heat recovery fluid, and a second passage that guides the lubricating oil to the oil cooler, bypassing the heat exchanger for lubricating oil exhaust heat recovery, a path switching valve that connects either the first path or the second path to the oil cooler; The control device When the invalidation condition is not satisfied, the path switching valve communicates the first path with the oil cooler, When the invalid condition is satisfied, the second path is communicated with the oil cooler by the path switching valve. Gas compression system.

5. 10. The gas compression system of claim 1, a heat exchanger for recovering exhaust heat from the low-pressure stage that is provided in the low-pressure gas path; a heat exchanger for recovering exhaust heat from the high-pressure stage provided in the high-pressure gas path. Gas compression system.

6. 6. The gas compression system of claim 5, a first supply flow path for supplying a waste heat recovery fluid to the low-pressure stage heat exchanger for waste heat recovery; a second supply flow path that supplies a waste heat recovery fluid discharged from the low-pressure stage heat exchanger for waste heat recovery to the high-pressure stage heat exchanger; a third supply flow path that supplies the exhaust heat recovery fluid discharged from the high-pressure stage exhaust heat recovery heat exchanger to a demand destination; a differential pressure sensor for detecting a differential pressure between the pressure of the exhaust heat recovery fluid in the first supply flow path and the pressure of the exhaust heat recovery fluid in the third supply flow path; a temperature sensor for detecting the temperature of the exhaust heat recovery fluid; The control device determining whether the invalid condition is satisfied based on the detection result of the differential pressure sensor and the detection result of the temperature sensor; If the differential pressure detected by the differential pressure sensor is smaller than a differential pressure threshold, or if the temperature detected by the temperature sensor is higher than a temperature threshold, it is determined that the invalid condition is established; If the differential pressure detected by the differential pressure sensor is greater than the differential pressure threshold and the temperature detected by the temperature sensor is lower than the temperature threshold, it is determined that the invalid condition is not established; When the invalidation condition is not satisfied, when switching from load operation of the low-pressure stage compressor main body and the high-pressure stage compressor main body to no-load operation, the first low-pressure air release valve and the first high-pressure air release valve are opened, and the second low-pressure air release valve and the second high-pressure air release valve are closed, When the invalidation condition is established, the first low-pressure air release valve, the first high-pressure air release valve, the second low-pressure air release valve, and the second high-pressure air release valve are opened when switching the low-pressure stage compressor main body and the high-pressure stage compressor main body from load operation to no-load operation. Gas compression system.

7. 7. The gas compression system of claim 6, a lubricating oil path through which lubricating oil flows to lubricate the low-pressure stage compressor body and the high-pressure stage compressor body; an oil cooler provided in the lubricating oil path to cool the lubricating oil; a heat exchanger for lubricating oil exhaust heat recovery, which is provided in the lubricating oil passage and exchanges heat between the lubricating oil and an exhaust heat recovery fluid, The lubricating oil passage includes a first passage that guides the lubricating oil to the oil cooler through the heat exchanger for lubricating oil exhaust heat recovery, and a second passage that guides the lubricating oil to the oil cooler while bypassing the heat exchanger for lubricating oil exhaust heat recovery, a path switching valve that connects either the first path or the second path to the oil cooler; The control device When the invalidation condition is not satisfied, the path switching valve communicates the first path with the oil cooler, When the invalid condition is satisfied, the second path is communicated with the oil cooler by the path switching valve. Gas compression system.

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