CN-122029359-A - Waste heat recovery system, waste heat recovery unit, and waste heat recovery method

Abstract

The invention provides a technology capable of preventing damage of a heat exchanger for waste heat recovery. The air compressor 1 includes cooling heat exchangers 103 and 104 for performing heat exchange between cooling water and compressed air, and a coolant pipe 106 for circulating the cooling water, and the waste heat recovery machine 2 includes waste heat recovery heat exchangers 201 and 202 for performing heat exchange between the waste heat recovery water and the compressed air, a waste heat recovery liquid pipe 211 for circulating the waste heat recovery water, branch pipes 110 and 111 for connecting the coolant pipe 106 and the waste heat recovery liquid pipe 211, flow path switching three-way valves 203 and 204 for opening and closing the branch pipes 110 and 111, and a temperature regulator 206 for controlling the flow path switching three-way valves 203 and 204, and the temperature regulator 206 controls the flow path switching three-way valves 203 and 204 to open the branch pipes 110 and 111 when the temperature of the waste heat recovery water exceeds a threshold value.

Inventors

• KAWAMATA Takahiro
• Haruki TOMOO

Assignees

• 株式会社日立产机系统

Dates

Publication Date

20260512

Application Date

20240411

Priority Date

20231102

Claims (12)

1. 1. A waste heat recovery system comprising a fluid machine body capable of circulating a fluid and a waste heat recovery machine that recovers waste heat from the fluid, the waste heat recovery system characterized by: the fluid machine body includes: A heat exchanger for cooling which exchanges heat between a cooling liquid and the fluid, and A coolant pipe through which the coolant flows, The waste heat recovery machine includes: a heat exchanger for waste heat recovery that exchanges heat between the waste heat recovery liquid and the fluid; a waste heat recovery liquid piping for circulating the waste heat recovery liquid; a first bypass flow path that connects an upstream side of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and an upstream side of the heat exchanger for cooling of the coolant liquid pipe; A second bypass flow path connecting downstream of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and downstream of the heat exchanger for cooling of the coolant liquid pipe; A first valve that opens and closes 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 valve and the second valve, The control unit controls the first valve and the second valve to open the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid exceeds a threshold value.
2. 2. The waste heat recovery system of claim 1, wherein: The heat exchanger is provided downstream of the second valve and upstream of the first valve in the exhaust heat recovery liquid pipe, and exchanges heat between the exhaust heat recovery liquid and the cooling medium.
3. 3. The waste heat recovery system of claim 2, wherein: the cooling device includes a coolant heat exchanger that is provided downstream of a connection point with the second bypass flow path and upstream of a connection point with the first bypass flow path in the coolant pipe, and performs heat exchange between the coolant and a cooling medium.
4. 4. The waste heat recovery system of claim 2, wherein: The control unit controls the first valve and the second valve to close the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid is lower than a second threshold value.
5. 5. A waste heat recovery unit that recovers waste heat from a fluid discharged from a fluid machine body including a cooling heat exchanger that exchanges heat between a coolant and the fluid and a coolant pipe through which the coolant flows, the waste heat recovery unit comprising: a heat exchanger for waste heat recovery that exchanges heat between the waste heat recovery liquid and the fluid; a waste heat recovery liquid piping for circulating the waste heat recovery liquid; a first bypass flow path that connects an upstream side of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and an upstream side of the heat exchanger for cooling of the coolant liquid pipe; A second bypass flow path connecting downstream of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and downstream of the heat exchanger for cooling of the coolant liquid pipe; A first valve that opens and closes 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 valve and the second valve, The control unit controls the first valve and the second valve to open the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid exceeds a threshold value.
6. 6. The waste heat recovery unit of claim 5, wherein: The heat exchanger is provided downstream of the second valve and upstream of the first valve in the exhaust heat recovery liquid pipe, and exchanges heat between the exhaust heat recovery liquid and the cooling medium.
7. 7. The waste heat recovery unit of claim 6, wherein: the cooling device includes a coolant heat exchanger that is provided downstream of a connection point with the second bypass flow path and upstream of a connection point with the first bypass flow path in the coolant pipe, and performs heat exchange between the coolant and a cooling medium.
8. 8. The waste heat recovery unit of claim 6, wherein: The control unit controls the first valve and the second valve to close the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid is lower than a second threshold value.
9. 9. A waste heat recovery method of a waste heat recovery system including a fluid machine body through which a fluid can circulate and a waste heat recovery machine that recovers waste heat from the fluid, characterized by: the fluid machine body includes: A heat exchanger for cooling which exchanges heat between a cooling liquid and the fluid, and A coolant pipe through which the coolant flows, The waste heat recovery machine includes: a heat exchanger for waste heat recovery that exchanges heat between the waste heat recovery liquid and the fluid; a waste heat recovery liquid piping for circulating the waste heat recovery liquid; a first bypass flow path that connects an upstream side of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and an upstream side of the heat exchanger for cooling of the coolant liquid pipe; A second bypass flow path connecting downstream of the heat exchanger for waste heat recovery of the waste heat recovery liquid pipe and downstream of the heat exchanger for cooling of the coolant liquid pipe; A first valve for opening and closing the first bypass passage, and A second valve for opening and closing the second bypass flow path, And controlling the first valve and the second valve to open the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid exceeds a threshold value.
10. 10. The waste heat recovery method as claimed in claim 9, wherein: The heat exchanger is provided downstream of the second valve and upstream of the first valve in the exhaust heat recovery liquid pipe, and exchanges heat between the exhaust heat recovery liquid and the cooling medium.
11. 11. The waste heat recovery method as claimed in claim 10, wherein: the cooling device includes a coolant heat exchanger that is provided downstream of a connection point with the second bypass flow path and upstream of a connection point with the first bypass flow path in the coolant pipe, and performs heat exchange between the coolant and a cooling medium.
12. 12. The waste heat recovery method as claimed in claim 10, wherein: And controlling the first valve and the second valve to close the first bypass flow path and the second bypass flow path when the temperature of the exhaust heat recovery liquid is lower than a second threshold value.

Description

Waste heat recovery system, waste heat recovery unit, and waste heat recovery method Technical Field The invention relates to a waste heat recovery system, a waste heat recovery unit, and a waste heat recovery method. Background A gas compressor is known in which a gas such as air is taken in and a high-pressure gas such as compressed air is discharged by a compression mechanism. Air compressors are used in particular in factory production lines or work sites as air sources for machine tools or presses, blowers, etc. The total energy consumed by the gas compressor is considered to be 20 to 25% of the energy consumed by the whole plant, and the effect of recovering the waste heat of the gas compressor is considered to be large. In particular, in order to achieve the goal of reducing CO2 emissions caused by global warming, it is predicted that the use of waste heat from a gas compressor will be more important in the future. The gas compressor is composed of a compressor body for compressing a gas such as air, a cooling system for absorbing heat generated by compression, a motor as a power source of the compressor, and the like. In the gas compressor, when the input power of the motor is set to 100%, the amount of heat absorbed in the cooling system is 90% or more, and this heat is usually released to the outside air, and a large amount of energy is discharged to the atmosphere. In order to reduce the amount of waste heat, the efficiency of the compressor main body and the motor is promoted to be improved, but the effect is at most several, and it is required to effectively use the waste heat of the gas compressor. Patent document 1 discloses a prior art in the art. Patent document 1 describes an exhaust heat recovery system including a temperature sensor provided downstream of an exhaust heat recovery heat exchanger in an exhaust heat recovery liquid pipe, a temperature control valve, and a temperature control meter for controlling an opening/closing angle of the temperature control valve based on a temperature of exhaust heat recovery water measured by the temperature sensor and a set temperature of the recovery water. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2021-96043 Disclosure of Invention Technical problem to be solved by the invention In the technique described in patent document 1, the heat-release-heat-recovery-water flowing through the heat exchanger is supplied to the heat-release-use side and used as a heat source, and is cooled, but when the heat-release-heat-recovery-water is returned to the heat exchanger without being cooled without using the heat-release-heat-recovery-water as a heat source, the temperature of the heat-release-heat-water further increases. Since the temperature of the compressed air is up to about 170 degrees, when the temperature of the exhaust heat recovery water exceeds the boiling point, the internal pressure of the piping of the heat exchanger increases, and the heat exchanger is likely to be broken. Accordingly, an object of the present invention is to provide a technique capable of preventing breakage of a heat exchanger for waste heat recovery. Technical proposal for solving the problems In order to solve the above problems, a typical waste heat recovery system of the present invention includes a fluid machine body through which a fluid can flow, and a waste heat recovery device for recovering waste heat from the fluid, wherein the fluid machine body includes a cooling heat exchanger for performing heat exchange between a coolant and the fluid, a coolant pipe through which the coolant flows, the waste heat recovery device includes a waste heat recovery heat exchanger for performing heat exchange between the waste heat recovery liquid and the fluid, a waste heat recovery liquid pipe through which the waste heat recovery liquid flows, a first bypass flow path connecting an upstream side of the waste heat recovery heat exchanger of the waste heat recovery liquid pipe with an upstream side of the cooling heat exchanger of the coolant pipe, a second bypass flow path connecting a downstream side of the waste heat recovery heat exchanger of the waste heat recovery liquid pipe with a downstream side of the cooling heat exchanger of the coolant pipe, 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 valve and the second valve to open the first bypass flow path when a temperature of the waste heat recovery liquid exceeds a threshold value. Effects of the invention According to the present invention, breakage of the heat exchanger for waste heat recovery can be prevented. Technical problems, technical features, and technical effects other than the above will become apparent from the following description of the embodiments. Drawings Fig. 1 is a schematic diagram showing an example of the schematic configura