Waste heat recovery system, waste heat recovery unit, and waste heat recovery method

Abstract

The invention provides a technology capable of preventing a waste heat recovery heat exchanger from being damaged. An air compressor (1) is provided with: cooling heat exchangers (103, 104) that exchange heat between cooling water and compressed air; and a cooling liquid pipe (106) through which the cooling water flows. A waste heat recovery machine (2) is provided with: waste heat recovery heat exchangers (201, 202) for exchanging heat between waste heat recovery water and compressed air; a waste heat recovery liquid pipe (211) through which the waste heat recovery water flows; branch pipes (110, 111) for connecting a coolant pipe (106) and the waste heat recovery liquid pipe (211); flow path switching three-way valves (203, 204) for opening and closing the branch pipes (110, 111); and a temperature regulator (206) for controlling the flow path switching three-way valves (203, 204) to open the branch pipes (110, 111) when the temperature of the waste heat recovery water exceeds a threshold value.

Description

Technical Field

[0001] This invention relates to waste heat recovery systems, waste heat recovery units, and waste heat recovery methods. Background Technology

[0002] A gas compressor is a device that draws in gases such as air and discharges them as compressed air or other high-pressure gases using a compression mechanism. Air compressors are particularly useful in factory production lines or work sites as an air source for machine tools, presses, blowers, etc. It is estimated that the total energy consumed by gas compressors accounts for 20-25% of the total energy consumed by a factory, and the recovery of waste heat from gas compressors is highly effective. In particular, to achieve the goal of reducing CO2 emissions due to global warming, it is predicted that the utilization of waste heat from gas compressors will receive even greater attention in the future.

[0003] A gas compressor consists of a compressor body that compresses gases such as air, a cooling system that absorbs the heat generated during compression, and a power source, namely an electric motor. Furthermore, in a gas compressor, assuming the electric motor's input power is 100%, the cooling system absorbs more than 90% of the heat, which is typically released into the outside air, resulting in a significant amount of energy being discharged into the atmosphere. While efforts are made to reduce waste heat by improving the efficiency of the compressor body and electric motor, the effect is limited to a few percent at most. Therefore, it is necessary to effectively utilize the waste heat of the gas compressor.

[0004] The prior art in this technical field is described in Patent Document 1. Patent Document 1 describes a heat recovery system, which includes a temperature sensor installed downstream of a heat recovery heat exchanger in the heat recovery liquid piping, a temperature control valve, and a temperature regulator that controls the opening and closing angle of the temperature control valve based on the temperature of the heat recovery water measured by the temperature sensor and a set recovery water temperature.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-96043 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] In the technology described in Patent Document 1, the waste heat recovery water flowing in the heat exchanger is supplied to the waste heat user as a heat source and is thus cooled. However, if the customer does not use the waste heat recovery water as a heat source, the temperature of the waste heat recovery water will rise further when it returns to the heat exchanger uncooled. Since the temperature of compressed air can reach up to approximately 170 degrees Celsius, when the temperature of the waste heat recovery water exceeds its boiling point, the internal pressure of the heat exchanger's piping increases, posing a risk of heat exchanger damage.

[0010] Therefore, the purpose of this invention is to provide a technology that can prevent damage to heat exchangers used for waste heat recovery.

[0011] Technical solutions to the problem

[0012] To address the aforementioned problems, a representative waste heat recovery system of the present invention includes a fluid machinery body capable of circulating fluid and a waste heat recovery machine for recovering waste heat from the fluid. The fluid machinery body includes a cooling heat exchanger for exchanging heat between a coolant and a fluid, and coolant piping for circulating the coolant. The waste heat recovery machine includes a waste heat recovery heat exchanger for exchanging heat between a waste heat recovery liquid and a fluid; waste heat recovery liquid piping for circulating the waste heat recovery liquid; a first bypass flow path connecting the upstream of the waste heat recovery heat exchanger of the waste heat recovery liquid piping to the upstream of the cooling heat exchanger of the coolant piping; a second bypass flow path connecting the downstream of the waste heat recovery heat exchanger of the waste heat recovery liquid piping to the downstream of the cooling heat exchanger of the coolant piping; a first valve for opening and closing the first bypass flow path; a second valve for opening and closing the second bypass flow path; and a control unit for controlling the first and second valves. The control unit controls the first and second valves to open the first and second bypass flow paths when the temperature of the waste heat recovery liquid exceeds a threshold value.

[0013] Invention Effects

[0014] According to the present invention, damage to the heat exchanger for waste heat recovery can be prevented.

[0015] Other technical issues, features, and effects not described above will become clear in the following description of the embodiments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating an example of the general structure of the waste heat recovery system of this embodiment.

[0017] Figure 2 This diagram illustrates an example of the flow path of waste heat recovery water and cooling water in the waste heat recovery system of this embodiment under normal conditions.

[0018] Figure 3 This diagram illustrates an example of the flow path of waste heat recovery water and cooling water in the waste heat recovery system of this embodiment when the temperature of the waste heat recovery water exceeds a threshold.

[0019] Figure 4 This is a flowchart illustrating an example of the control performed by the temperature controller in the waste heat recovery system of this embodiment.

[0020] Figure 5 This is a diagram illustrating an example of the temperature shift of waste heat recovery water in the waste heat recovery system of this embodiment. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, a water-cooled, encapsulated two-stage oil-free screw compressor for compressing air will be used as an example to illustrate a gas compressor.

[0022] Figure 1 This is a schematic diagram illustrating an example of the general structure of the waste heat recovery system of this embodiment.

[0023] like Figure 1 As shown, the waste heat recovery system 100 includes an air compressor 1 that compresses air and a waste heat recovery machine 2 that recovers waste heat from the compressed air discharged from the air compressor 1.

[0024] The air compressor 1 includes compressor bodies 101 and 102, heat exchangers 103 and 104 for cooling, and an oil cooler 105, all housed within a casing. While the casing is not shown in the diagram, it features a base for mounting the compressor bodies 101, 102, and other components, and a box-shaped cover consisting of multiple panels of metal or similar materials mounted on the base, providing excellent sound insulation.

[0025] The waste heat recovery unit 2 includes heat exchangers 201 and 202 and a temperature regulator 206, which are housed within a casing. The casing, which is not shown in the figure, has a base for mounting the heat exchangers 201, 202, and other equipment, and a box-shaped cover consisting of multiple panels of metal or the like that are mounted on the base to cover the heat exchangers 201, 202, and other equipment, providing excellent sound insulation.

[0026] The compressor bodies 101 and 102 each have a screw rotor consisting of a male rotor and a female rotor (not shown). Furthermore, the compressor bodies 101 and 102 are configured to be driven, for example, by a main electric motor (not shown) disposed within the housing via a transmission mechanism. Additionally, the power source for the compressor bodies 101 and 102 is not limited to an electric motor, but may also be an internal combustion engine, etc.

[0027] The compressor body 101 is a first-stage compressor body disposed upstream of the airflow, and the compressor body 102 is a second-stage compressor body disposed downstream of the airflow relative to the first-stage compressor body 101.

[0028] In this embodiment, the compressor bodies 101 and 102 are oil-free screw compressors. Therefore, unlike liquid-supply air compressors that inject liquids such as oil or water into the compression chamber, the compressor bodies 101 and 102 tend to generate heat, especially due to the heat generated during air compression. Furthermore, the compressed air is at a high temperature, making it unsuitable for use by the user. Therefore, cooling water is supplied to each part of the air compressor 1. Moreover, the air compressor 1 of this embodiment is configured, as described later, to recover the waste heat generated during air compression by the compressor bodies 101 and 102.

[0029] Waste heat recovery heat exchangers 201 and 202 exchange heat between the waste heat recovery liquid (i.e., waste heat recovery water) delivered by the heat treatment equipment 4 of the user of the waste heat generated from the compressor body 101 and 102 and the compressed air discharged from the compressor body 101 and 102.

[0030] Heat exchanger 201 is an intermediate stage waste heat recovery heat exchanger configured between the first stage compressor body 101 and the second stage compressor body 102. Heat exchanger 202 is a discharge stage waste heat recovery heat exchanger configured on the discharge side (downstream side) of the second stage compressor body 102.

[0031] The heat treatment equipment 4 cools the waste heat recovery water by exchanging heat with cold water, converting the cold water into hot water for users. However, it is not limited to this; it can also exchange heat with oil or air, and users can also use the waste heat recovery water itself.

[0032] Cooling heat exchangers 103 and 104 exchange heat between the coolant (i.e., cooling water) supplied from the cooling device 3 located outside the air compressor 1 and the compressed air discharged from the compressor body 101 and 102.

[0033] Heat exchanger 103 is a cooling heat exchanger disposed between the first-stage compressor body 101 and the second-stage compressor body 102 (hereafter referred to as an intercooler), and heat exchanger 104 is a cooling heat exchanger disposed on the discharge side of the second-stage compressor body 102 (hereafter referred to as an aftercooler).

[0034] The cooling device 3 cools the cooling water by exchanging heat with the external atmosphere or other sources of the waste heat recovery system 100.

[0035] Between the first-stage compressor body 101 and the second-stage compressor body 102, an intermediate-stage waste heat recovery heat exchanger 201 and an intercooler 103 are arranged sequentially from the upstream side. Additionally, on the discharge side of the second-stage compressor body 102, a discharge-stage waste heat recovery heat exchanger 202 and an aftercooler 104 are arranged sequentially from the upstream side. Alternatively, depending on the situation, the arrangement order of the waste heat recovery heat exchangers 201 and 202 and the intercoolers 103 and aftercoolers 104 may be reversed.

[0036] The first-stage compressor body 101, the intermediate-stage waste heat recovery heat exchanger 201, the intercooler 103, the second-stage compressor body 102, the discharge-stage waste heat recovery heat exchanger 202, and the aftercooler 104 are connected by air piping 108 through which compressed air flows.

[0037] Furthermore, the aforementioned flow path is configured such that during loaded operation (loaded operation) and unloaded operation (no-load operation), the discharged air flows through the first-stage compressor body 101, intermediate-stage waste heat recovery heat exchanger 201, intercooler 103, second-stage compressor body 102, and discharge-stage waste heat recovery heat exchanger 202. Because the check valve 109 is fully closed during unloaded operation, the air is discharged to the atmosphere through the vent pipe 107. Thus, even during (no-load operation), the discharged air also flows through heat exchangers 201 and 202, enabling waste heat recovery regardless of the operating state and improving the waste heat recovery rate.

[0038] In addition, a waste heat recovery liquid pipe 211 is provided for waste heat recovery water that flows in the waste heat recovery heat exchangers 201 and 202 to exchange heat with compressed air, and a coolant pipe 106 is provided for cooling water that flows in the intermediate cooler 103 and aftercooler 104 to exchange heat with compressed air.

[0039] Waste heat recovery liquid is transported from the heat treatment equipment 4 of the waste heat user by the operation of the circulating pump 207, and connected to the heat treatment equipment 4 through the intermediate stage waste heat recovery heat exchanger 201 and the discharge stage waste heat recovery heat exchanger 202.

[0040] In addition, downstream of the heat treatment equipment 4, which is connected to the waste heat recovery liquid piping 211, there is a temperature sensor 205 for measuring the temperature of the waste heat recovery water and a flow meter 209 for measuring the flow rate of the waste heat recovery water.

[0041] The coolant piping 106 is configured to branch from the cooling device 3 into a first coolant piping 106a, a second coolant piping 106b, and a third coolant piping 106c, and then converge and connect to the cooling device 3.

[0042] The first coolant pipe 106a connects to the cooling device 3 via the aftercooler 104. The second coolant pipe 106b connects to the cooling device 3 via the oil cooler 105, the cooling jacket installed in the housing of the second-stage compressor body 102, and the cooling jacket installed in the housing of the first-stage compressor body 101. The third coolant pipe 106c connects to the cooling device 3 via the intercooler 103.

[0043] The upstream of the intercooler 103, aftercooler 104 and oil cooler 105 of the coolant piping 106 is connected to the upstream of the intermediate stage waste heat recovery heat exchanger 201 of the waste heat recovery liquid piping 211 by a branch pipe 110 on the coolant inlet side.

[0044] In addition, the downstream of the waste heat recovery heat exchanger 202 at the discharge stage of the waste heat recovery liquid piping 211 is connected to the downstream of the intercooler 103, aftercooler 104 and oil cooler 105 of the coolant piping 106 by a branch pipe 111 on the coolant outlet side.

[0045] At the connection point between the waste heat recovery liquid pipe 211 and the branch pipe 110 on the coolant inlet side, an inlet-side flow path switching three-way valve 203 is provided to switch between the flow path starting from the upstream of the waste heat recovery liquid pipe 211 and the flow path starting from the branch pipe 110 on the coolant inlet side.

[0046] In addition, at the connection point between the waste heat recovery liquid pipe 211 and the branch pipe 111 on the coolant outlet side, an outlet side flow path switching three-way valve 204 is provided, which switches between the flow path leading to the downstream of the waste heat recovery liquid pipe 211 and the flow path leading to the branch pipe 111 on the coolant outlet side.

[0047] The upstream of the inlet-side flow path switching three-way valve 203 of the waste heat recovery liquid pipe 211 and the downstream of the outlet-side flow path switching three-way valve 204 of the waste heat recovery liquid pipe 211 are connected to the waste heat recovery liquid circulation pipe 210, and a temperature regulating valve 208 is provided to enable the waste heat recovery liquid circulation pipe 210 to open and close.

[0048] The temperature controller 206 controls the flow path switching three-way valves 203 and 204 and the temperature regulating valve 208 based on the temperature measured by the temperature sensor 205 and the set temperature.

[0049] The oil cooler 105 (not shown) is a water-cooled heat exchanger used to cool the lubricating oil that lubricates the bearings and transmission mechanisms of the compressor bodies 101 and 102. After being cooled by the oil cooler 105, the lubricating oil lubricates the bearings of the compressor bodies 101 and 102, etc., and is then stored in an oil reservoir (not shown). The lubricating oil is then guided to the oil cooler 105 by a delivery mechanism such as an oil pump (not shown) and cooled, circulating in this lubrication path.

[0050] Next, the operation of the waste heat recovery system 100 configured in this way will be explained.

[0051] Figure 1 In this process, air compressor 1 draws in air via a capacity regulating valve (not shown) located upstream of the first-stage compressor body 101, and compresses the air within the first-stage compressor body 101. The compressed, high-temperature air (e.g., around 160°C) then exchanges necessary heat in an intermediate-stage waste heat recovery heat exchanger 201, and is subsequently cooled in an intercooler 103. Here, the compressed, high-temperature air and waste heat recovery water exchange heat in the intermediate-stage waste heat recovery heat exchanger 201, and the cooled compressed air and cooling water exchanged heat in the intermediate-stage waste heat recovery heat exchanger 201 exchange heat in the intercooler 103.

[0052] Next, the air cooled in the intercooler 103 (e.g., at approximately 40°C) is compressed in the second-stage compressor body 102 to further increase its pressure. Afterward, the compressed, high-temperature air (e.g., at approximately 160°C or higher) exchanges the necessary heat again in the exhaust stage waste heat recovery heat exchanger 202, and is then cooled in the aftercooler 104. The air cooled in the aftercooler 104 (e.g., at approximately 40°C) is then delivered to the compressed air demand side.

[0053] Next, the flow paths of waste heat recovery water and cooling water in the waste heat recovery system 100 will be explained.

[0054] Figure 2 This is a diagram illustrating an example of the flow path of waste heat recovery water and cooling water in the waste heat recovery system 100 of this embodiment under normal conditions.

[0055] As shown by the dashed line, the waste heat recovery water flows into the heat treatment equipment 4 of the waste heat user due to the operation of the circulation pump 207, flows through the waste heat recovery liquid piping 211, and its temperature is measured by the temperature sensor 205. After exchanging heat with compressed air in the waste heat recovery heat exchangers 201 and 202, it flows out to the heat treatment equipment 4 of the waste heat user.

[0056] As shown by the dotted line, the cooling water flows into the cooling device 3, branches from the coolant piping 106 to the first coolant piping 106a, the second coolant piping 106b, and the second coolant piping c. After exchanging heat with compressed air in the intercooler 103 and the aftercooler 104, or exchanging heat with lubricating oil in the oil cooler 105, the water converges and flows out of the cooling device 3.

[0057] Here, without the user using heat treatment equipment 4 to exchange heat between the waste heat recovery water and cold water, the waste heat recovery water, after exchanging heat with compressed air in waste heat recovery heat exchangers 201 and 202, will not be cooled in heat treatment equipment 4. Therefore, the temperature of the waste heat recovery water circulating in waste heat recovery liquid piping 211 rises. When the temperature of the waste heat recovery water exceeds its boiling point, the internal pressure of waste heat recovery liquid piping 211 increases, posing a risk of damage to waste heat recovery heat exchangers 201 and 202.

[0058] Therefore, in this embodiment, when the temperature of the waste heat recovery water measured by the temperature sensor 205 exceeds a preset threshold, the temperature regulator 206 switches the flow path switching three-way valves 203 and 204, and opens the temperature regulating valve 208, thereby switching the flow path of the waste heat recovery water and the cooling water.

[0059] Figure 3 This diagram illustrates an example of the flow path of waste heat recovery water and cooling water in the waste heat recovery system 100 of this embodiment when the temperature of the waste heat recovery water exceeds a threshold.

[0060] If the temperature of the waste heat recovery water measured by temperature sensor 205 exceeds the threshold, temperature regulator 206 switches the flow path switching three-way valves 203 and 204, thereby allowing cooling water to flow in from the cooling equipment 3 as shown by the dotted line, and branch from the coolant pipe 106 to the first coolant pipe 106a, the second coolant pipe 106b, the second coolant pipe c, and the branch pipe 110 on the coolant inlet side.

[0061] Cooling water flowing from coolant pipe 106 into first coolant pipe 106a, second coolant pipe 106b, or second coolant pipe c undergoes heat exchange with compressed air in intercooler 103 or aftercooler 104, or with lubricating oil in oil cooler 105, before converging and flowing out of cooling equipment 3.

[0062] Cooling water flowing from the coolant pipe 106 into the coolant inlet side branch pipe 110 flows through the waste heat recovery liquid pipe 211. After exchanging heat with compressed air in the waste heat recovery heat exchangers 201 and 202, it flows out to the cooling equipment 3 via the coolant outlet side branch pipe 111 and coolant pipe 106.

[0063] Additionally, if the temperature of the waste heat recovery water measured by temperature sensor 205 exceeds the threshold, temperature regulator 206 opens temperature regulating valve 208, thereby allowing the waste heat recovery water, as shown by the dashed line, to flow into the heat treatment equipment 4 of the waste heat user, through waste heat recovery liquid piping 211, and through waste heat recovery liquid circulation piping 210, to flow out of the heat treatment equipment 4 of the waste heat user without passing through the waste heat recovery heat exchangers 201 and 202.

[0064] According to this embodiment, when the temperature of the waste heat recovery water measured by the temperature sensor 205 exceeds the threshold, the temperature regulator 206 switches the flow path switching three-way valves 203 and 204 to use the cooling water from the cooling device 3 for heat exchange with compressed air in the waste heat recovery heat exchangers 201 and 202. Therefore, it can prevent the temperature of the waste heat recovery water from rising and prevent the waste heat recovery heat exchangers from being damaged.

[0065] Figure 4 This is a flowchart illustrating an example of the control performed by the temperature regulator 206 in the waste heat recovery system 100 of this embodiment.

[0066] Figure 4 During the initial treatment, waste heat recovery water and cooling water are in the following conditions: Figure 2 The flow occurs in the normal flow path shown.

[0067] When air compressor 1 starts running, it supplies power to temperature regulator 206 and begins control.

[0068] In S302, the temperature regulator 206 acquires the temperature of the waste heat recovery water in the waste heat recovery liquid pipe 211, which is measured by the temperature sensor 205.

[0069] In S303, the temperature regulator 206 determines whether the temperature of the waste heat recovery water measured by the temperature sensor 205 exceeds 95°C. If the temperature of the waste heat recovery water exceeds 95°C in S303, the process proceeds to S304. On the other hand, if the temperature of the waste heat recovery water does not exceed 95°C in S303, the process proceeds to S314, and after a pre-set standby time under normal conditions, it returns to S302.

[0070] In S304, the temperature regulator 206 switches the inlet-side flow path switching three-way valve 203, allowing the coolant in the coolant pipe 106 to flow into the waste heat recovery liquid pipe 211 via the coolant inlet-side branch pipe 110. Simultaneously, the temperature regulator 206 switches the outlet-side flow path switching three-way valve 204, allowing the coolant after passing through the intermediate-stage waste heat recovery heat exchanger 201 and the discharge-stage waste heat recovery heat exchanger 202 to flow into the coolant outlet-side branch pipe 111.

[0071] In S305, the temperature regulator 206 opens the temperature regulating valve 208, thereby opening the waste heat recovery liquid circulation pipe 210, allowing the waste heat recovery water to circulate from the heat treatment equipment 4.

[0072] In S306, after executing S304 and S305, a pre-set standby time is set. The standby time is set to be sufficient to lower the temperature of the waste heat recovery water above 95°C.

[0073] In S307, the temperature regulator 206 again acquires the temperature of the waste heat recovery water in the waste heat recovery liquid pipe 211 as measured by the temperature sensor 205.

[0074] In step S308, the temperature regulator 206 determines whether the temperature of the waste heat recovery water, measured by the temperature sensor 205, exceeds 95°C. If the temperature of the waste heat recovery water exceeds 95°C in step S308, the process proceeds to step S310.

[0075] In S310, the temperature regulator 206 outputs a critical fault signal.

[0076] In S311, the temperature regulator 206 stops the operation of the circulating pump 207, air compressor 1 and waste heat recovery machine 2 installed in the waste heat recovery liquid piping 211, thus ending the process.

[0077] On the other hand, if the temperature of the waste heat recovery water in S308 does not exceed 95°C, it is transferred to S309.

[0078] In S309, it is determined whether the temperature of the waste heat recovery water obtained in S307 is lower than 40°C. If the temperature of the waste heat recovery water in S309 is not lower than 40°C, the process returns to S306 and waits for a preset time.

[0079] On the other hand, if the temperature of the waste heat recovery water in S309 is below 40°C, it is transferred to S312.

[0080] In S312, the temperature controller 206 switches the inlet-side flow path switching three-way valve 203 to supply waste heat recovery water from the heat treatment equipment 4 to the waste heat recovery heat exchangers 201 and 202. Simultaneously, the temperature controller 206 switches the outlet-side flow path switching three-way valve 204 to supply waste heat recovery water from the waste heat recovery heat exchangers 201 and 202 to the heat treatment equipment 4.

[0081] In S313, the temperature regulator 206 closes the temperature regulating valve 208, thereby closing the waste heat recovery liquid circulation piping 210.

[0082] In S314, after a preset standby time in normal state, return to S302.

[0083] Figure 5 This is a diagram illustrating an example of the temperature shift of waste heat recovery water in the waste heat recovery system 100 of this embodiment.

[0084] Figure 5 In the diagram, the vertical axis represents the temperature of the waste heat recovery water measured by temperature sensor 205, and the horizontal axis represents the passage of time.

[0085] If the user does not use the heat treatment equipment 4 to exchange heat between the waste heat recovery water and the cold water, the waste heat recovery water that has exchanged heat with compressed air in the waste heat recovery heat exchangers 201 and 202 will not be cooled in the heat treatment equipment 4, so the temperature of the waste heat recovery water circulating in the waste heat recovery liquid piping 211 will rise.

[0086] When the temperature of the waste heat recovery water exceeds 95℃, the temperature controller 206 performs... Figure 4 The control causes the flow path switching three-way valves 203 and 204 to switch, opening the temperature regulating valve 208.

[0087] Therefore, waste heat recovery water in Figure 3 The waste heat recovery water does not circulate through the heat exchangers 201 and 202 shown, thus preventing the temperature of the waste heat recovery water from rising and preventing damage to the waste heat recovery heat exchangers.

[0088] Subsequently, when the temperature of the waste heat recovery water measured by temperature sensor 205 is below 40°C, temperature regulator 206 switches the flow path switching three-way valves 203 and 204, and closes the temperature regulating valve 208.

[0089] Therefore, waste heat recovery water in Figure 2 The air circulates through the heat exchangers 201 and 202 shown, so it can exchange heat with compressed air in the heat exchangers 201 and 202 to recover the waste heat of the air compressor 1.

[0090] The embodiments have been described above, but the present invention is not limited to the above embodiments and includes various modifications. For example, the above embodiments are described in detail for ease of understanding of the present invention and are not limited to having all the structures described.

[0091] For example, in one embodiment, the waste heat recovery liquid piping 211 is configured to connect to the heat treatment equipment 4 via the intermediate stage waste heat recovery heat exchanger 201 and the discharge stage waste heat recovery heat exchanger 202, but this is not limited to this. That is, multiple waste heat recovery liquid piping 211 can also be provided corresponding to multiple waste heat recovery heat exchangers, and the multiple waste heat recovery liquid piping can be provided as independent passages within the housing.

[0092] Here, the multiple waste heat recovery heat exchangers can also be intermediate-stage waste heat recovery heat exchanger 201 and discharge-stage waste heat recovery heat exchanger 202. Alternatively, the multiple waste heat recovery heat exchangers can also be configured as multiple heat exchangers that connect intermediate-stage waste heat recovery heat exchanger 201 (or discharge-stage waste heat recovery heat exchanger 202) in series.

[0093] With this structure, waste heat recovery water at various temperatures can be obtained and used from multiple waste heat recovery liquid pipes. Therefore, it is possible to accommodate various equipment requiring different waste heat recovery water temperatures.

[0094] In another embodiment, the coolant piping 106 is configured to branch from the cooling device 3 into a first coolant piping 106a, a second coolant piping 106b, and a third coolant piping 106c, and then converge and connect to the cooling device 3, but is not limited thereto.

[0095] For example, multiple coolant pipes 106 can be provided corresponding to multiple cooling heat exchangers, with each coolant pipe serving as an independent passage within the housing.

[0096] Here, the multiple cooling heat exchangers can be an intercooler 103 and an aftercooler 104. Alternatively, the multiple cooling heat exchangers can also be configured as multiple heat exchangers that connect the intercooler 103 (or the aftercooler 104) in series.

[0097] In addition, in the embodiment, the flow paths of waste heat recovery water and cooling water are controlled by temperature sensor 205, temperature regulator 206, flow path switching three-way valves 203 and 204, and temperature regulating valve 208, but it is not limited to this. As long as the flow path can be controlled according to the temperature of waste heat recovery water, for example, temperature sensor 205 and temperature regulator 206 can be omitted, and a self-powered automatic temperature regulating valve that does not require auxiliary power such as air pressure, water pressure, oil pressure, or electricity can be used instead.

[0098] Furthermore, in the embodiments, the air compressor 1 can be specifically applied to a screw compressor, but the present invention is not limited thereto. That is, the embodiments use screw rotors in the compressor bodies 101 and 102, but are not limited thereto, and various forms of compression units such as centrifugal, axial flow, turbine type, scroll, reciprocating, and claw type can be used.

[0099] In addition, a single-screw rotor is used in the embodiment, but twin-screw or triple-screw rotors can also be used.

[0100] In addition, in the embodiment, the compressor bodies 101 and 102 have two stages, but are not limited to this; they can also be single-stage or have three or more stages.

[0101] In addition, in this embodiment, the air compressor 1 is an oil-free screw compressor, but it is not limited to this; it can also be a liquid-supply air compressor that injects oil or water into the compression chamber. Furthermore, it has been described that the compressed gas is air, but it is not limited to this; it can also be nitrogen, etc.

[0102] Furthermore, the temperature threshold of the waste heat recovery water used in the control of the embodiment is not limited to this.

[0103] In addition, in the embodiment, the cooling water after the temperature rises is cooled by exchanging heat with the atmosphere in the cooling device 3, but it is not limited to this, and the heat of the cooling water after the temperature rises can also be recovered and utilized.

[0104] Furthermore, a portion of the structure of one embodiment can be replaced with the structure of another embodiment, and a structure of another embodiment can be added to the structure of one embodiment. Additionally, for a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0105] Explanation of reference numerals in the attached figures

[0106] 1: Air compressor; 2: Waste heat recovery unit; 3: Cooling equipment; 4: Heat treatment equipment; 100: Waste heat recovery system; 101: First-stage compressor body; 102: Second-stage compressor body; 103: Cooling heat exchanger (intercooler); 104: Cooling heat exchanger (aftercooler); 105: Oil cooler; 106: Coolant piping; 107: Vent piping; 108: Air piping; 109: Check valve; 110: Coolant inlet. 111: Coolant outlet side branch pipe; 201: Intermediate stage waste heat recovery heat exchanger; 202: Discharge stage waste heat recovery heat exchanger; 203: Inlet side flow path switching three-way valve; 204: Outlet side flow path switching three-way valve; 205: Temperature sensor; 206: Temperature regulator; 207: Circulation pump; 208: Temperature regulating valve; 209: Flow meter; 210: Waste heat recovery liquid circulation piping; 211: Waste heat recovery liquid piping.

Claims

1. A waste heat recovery system, comprising a fluid machinery body capable of circulating fluid and a waste heat recovery machine for recovering waste heat from said fluid, characterized in that: The fluid machinery body includes: A heat exchanger for cooling that facilitates heat exchange between a coolant and the fluid; and Coolant piping for the flow of the coolant The waste heat recovery machine includes: A heat exchanger for waste heat recovery that performs heat exchange between waste heat recovery liquid and the fluid; Waste heat recovery liquid piping for circulating the waste heat recovery liquid; A first bypass flow path is provided that connects the upstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the upstream of the cooling heat exchanger in the cooling liquid piping. A second bypass flow path is provided that connects the downstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the downstream of the cooling heat exchanger in the cooling liquid piping. Open or close the first valve of the first bypass flow path; Opening and closing the second valve of the second bypass flow path; and The control unit that controls the first valve and the second valve When the temperature of the waste heat recovery liquid exceeds a threshold, the control unit controls the first valve and the second valve to open the first bypass flow path and the second bypass flow path.

2. The waste heat recovery system as described in claim 1, characterized in that: It includes a waste heat recovery liquid heat exchanger, which is located downstream of the second valve and upstream of the first valve on the waste heat recovery liquid piping, and performs heat exchange between the waste heat recovery liquid and the cooling medium.

3. The waste heat recovery system as described in claim 2, characterized in that: It includes a coolant heat exchanger, which is located downstream of the connection point of the coolant piping with the second bypass flow path and upstream of the connection point of the first bypass flow path, to perform heat exchange between the coolant and the cooling medium.

4. The waste heat recovery system as described in claim 2, characterized in that: When the temperature of the waste heat recovery liquid is lower than the second threshold, the control unit controls the first valve and the second valve to close the first bypass flow path and the second bypass flow path.

5. A waste heat recovery unit for recovering waste heat from a fluid discharged from a fluid machinery body, wherein the fluid machinery body includes a cooling heat exchanger for heat exchange between a coolant and the fluid and coolant piping for circulating the coolant, the waste heat recovery unit being characterized in that it comprises: A heat exchanger for waste heat recovery that performs heat exchange between waste heat recovery liquid and the fluid; Waste heat recovery liquid piping for circulating the waste heat recovery liquid; A first bypass flow path is provided that connects the upstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the upstream of the cooling heat exchanger in the cooling liquid piping. A second bypass flow path is provided that connects the downstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the downstream of the cooling heat exchanger in the cooling liquid piping. Open or close the first valve of the first bypass flow path; Open or close the second valve of the second bypass flow path; and The control unit that controls the first valve and the second valve When the temperature of the waste heat recovery liquid exceeds a threshold, the control unit controls the first valve and the second valve to open the first bypass flow path and the second bypass flow path.

6. The waste heat recovery unit as described in claim 5, characterized in that: It includes a waste heat recovery liquid heat exchanger, which is located downstream of the second valve and upstream of the first valve on the waste heat recovery liquid piping, and performs heat exchange between the waste heat recovery liquid and the cooling medium.

7. The waste heat recovery unit as described in claim 6, characterized in that: It includes a coolant heat exchanger, which is located downstream of the connection point of the coolant piping with the second bypass flow path and upstream of the connection point of the first bypass flow path, to perform heat exchange between the coolant and the cooling medium.

8. The waste heat recovery unit as described in claim 6, characterized in that: When the temperature of the waste heat recovery liquid is lower than the second threshold, the control unit controls the first valve and the second valve to close the first bypass flow path and the second bypass flow path.

9. A waste heat recovery method for a waste heat recovery system comprising a fluid machinery body capable of circulating fluid and a waste heat recovery machine for recovering waste heat from said fluid, characterized in that: The fluid machinery body includes: A cooling heat exchanger that facilitates heat exchange between the coolant and the fluid; and Coolant piping for the flow of the coolant The waste heat recovery machine includes: A heat exchanger for waste heat recovery that performs heat exchange between waste heat recovery liquid and the fluid; Waste heat recovery liquid piping for circulating the waste heat recovery liquid; A first bypass flow path is provided that connects the upstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the upstream of the cooling heat exchanger in the cooling liquid piping. A second bypass flow path is provided that connects the downstream of the waste heat recovery heat exchanger in the waste heat recovery liquid piping to the downstream of the cooling heat exchanger in the cooling liquid piping. Opening and closing the first valve of the first bypass flow path; and Opening and closing the second valve of the second bypass flow path, If the temperature of the waste heat recovery liquid exceeds a threshold, the first valve and the second valve are controlled to open the first bypass flow path and the second bypass flow path.

10. The waste heat recovery method as described in claim 9, characterized in that: It includes a waste heat recovery liquid heat exchanger, which is located downstream of the second valve and upstream of the first valve on the waste heat recovery liquid piping, and performs heat exchange between the waste heat recovery liquid and the cooling medium.

11. The waste heat recovery method as described in claim 10, characterized in that: It includes a coolant heat exchanger, which is located downstream of the connection point of the coolant piping with the second bypass flow path and upstream of the connection point of the first bypass flow path, to perform heat exchange between the coolant and the cooling medium.

12. The waste heat recovery method as described in claim 10, characterized in that: When the temperature of the waste heat recovery liquid is lower than the second threshold, the first valve and the second valve are controlled to close the first bypass flow path and the second bypass flow path.

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