A method and system for generating steam by cooling water with compressed air

Abstract

This invention provides a method for generating steam using compressed air cooling water. A portion of the cooling water, after absorbing waste heat from a water-cooled air compressor, is introduced into a flash tank for flash evaporation to generate low-temperature steam. The inlet water flow rate is adjustable. The remaining cooling water can be transported via three routes: one route is sent to a cooling tower; another route is directly mixed with makeup water and sent to the internal heat exchanger of the air compressor; and the third route is sent to a demineralized water treatment unit. A two-stage centrifugal steam compressor and a desuperheating buffer tank form the first-stage steam treatment unit. The low-temperature steam generated in the flash tank is sequentially processed by a series of multi-stage steam treatment units to obtain saturated steam at a set pressure and temperature, which is then used to supply steam to steam-using equipment or integrated into the on-site steam system pipeline. This invention enables the full recovery and utilization of heat from low-grade cooling water, resulting in energy conservation and environmental protection.

Description

Technical Field

[0001] This invention relates to a method and system for generating steam by cooling water with compressed air. Background Technology

[0002] In cigarette factories, the cooling water in the air compressor absorbs heat and reaches a temperature of approximately 42°C. It then enters a closed-loop cooling tower where it evaporates, dissipating the heat into the atmosphere and cooling down to below 32°C. This process wastes water resources, and over 80% of the air compressor's power consumption is converted into heat. Therefore, the current production method that relies solely on this method for cooling the circulating cooling water is costly and has low energy efficiency. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method and system for generating steam by cooling water with compressed air, which enables full recovery and utilization of the heat from low-grade thermal energy cooling water, resulting in energy conservation and environmental protection.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for generating steam by cooling water with compressed air, characterized by: A portion of the cooling water after absorbing the waste heat of the water-cooled air compressor is introduced into a flash tank to generate low-temperature water vapor. The water inlet flow rate can be adjusted according to the steam supply demand through the flash water inlet regulating valve. The remaining cooling water can be transported through three routes: one route is sent to the cooling tower, one route is directly mixed with the makeup water and sent to the heat exchanger inside the air compressor for heat exchange, and the other route is sent to the demineralized water device for treatment. A two-stage centrifugal steam compressor and a desuperheating buffer tank form the first-stage steam treatment unit. The low-temperature steam generated by the flash tank is processed sequentially by a series of multi-stage steam treatment units. When passing through each stage of the steam treatment unit, the steam is first pressurized and heated step by step by the two-stage centrifugal steam compressor to become superheated steam, and then enters the desuperheating buffer tank to obtain saturated steam by mixing with makeup water for heat exchange and desuperheating. The saturated steam with a set pressure and temperature is obtained through the final stage desuperheating buffer tank of the final stage steam treatment unit, which is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

[0005] The aforementioned method of generating steam by cooling water with compressed air is also characterized by: The water replenishment is desalinated water.

[0006] The cooling water temperature after absorbing the waste heat of the water-cooled air compressor is 42℃, and the absolute pressure inside the flash tank is 0.005MPa. Low-temperature water vapor at 32℃ is generated through flash evaporation in the flash tank.

[0007] This invention also proposes a system for generating steam by cooling water with compressed air, used to implement the above-mentioned method for generating steam by cooling water with compressed air, comprising: Two parallel return water pipelines are used to transport return water from the air compressor cooling system. One pipeline serves as the flash tank inlet pipeline and is equipped with a flash tank inlet regulating valve. The other pipeline serves as a return water bypass and is equipped with a bypass check valve. The return water bypass is divided into three pipelines downstream of the bypass check valve. The first pipeline serves as a sewage branch and is equipped with a sewage control valve, connecting to the demineralized water device. It is used to incorporate the flash liquid discharged from the flash tank and send it to the demineralized water device for treatment. The second pipeline serves as a cooling tower inlet branch and is equipped with a cooling tower inlet regulating valve. It is used to directly send the return water from the air compressor cooling system into the cooling tower for heat dissipation. After heat dissipation, it is mixed with makeup water and used as the air compressor cooling system supply water, which is sent to the internal heat exchanger of the air compressor for heat exchange with the compressed air. The third pipeline serves as a cooling tower bypass branch and is equipped with a cooling tower bypass regulating valve. It is used to directly mix with makeup water and then use it as the air compressor cooling system supply water, which is sent to the internal heat exchanger of the air compressor for heat exchange with the compressed air. The flash tank is used to receive the return water from the air compressor cooling system sent through the flash tank inlet pipe, and to flash the water to reduce the pressure and temperature to obtain low-temperature steam, which is then sent to the primary steam treatment unit. The multi-stage steam treatment unit is used to process water vapor in stages. Each stage of the steam treatment unit includes two centrifugal steam compressors and a desuperheating buffer tank. The steam is first pressurized and heated into superheated steam by the two centrifugal steam compressors, and then enters the desuperheating buffer tank to obtain saturated steam through heat exchange. The saturated steam with a set pressure and temperature is obtained by passing through the desuperheating buffer tank of the final stage of the steam treatment unit, and is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

[0008] The corresponding structural features of this system also include: The flash tank is equipped with a magnetic level gauge, pressure gauge, thermometer, conductivity meter, and safety valve. The flash tank discharges flash liquid through a flash liquid outlet pipeline connected to a flash liquid circulation pump and a flash tank outlet regulating valve. The flash liquid outlet pipeline is also connected to a sludge discharge branch. The magnetic level gauge monitors the tank level in real time to control the start / stop of the flash liquid circulation pump and the opening of the flash tank outlet regulating valve. The pressure gauge monitors the tank pressure in real time to control the opening of the flash liquid inlet regulating valve. The thermometer monitors the tank temperature in real time. The conductivity meter monitors the conductivity in real time to control the opening of the sludge discharge control valve.

[0009] A thermometer is installed upstream of the cooling tower inlet regulating valve and downstream of the flash tank outlet regulating valve and bypass check valve to monitor the liquid temperature in real time. When the temperature is higher than the set value, the cooling tower inlet regulating valve opens and the cooling tower bypass regulating valve closes. The return water from the air compressor cooling system is sent to the cooling tower for cooling via the cooling tower branch. After cooling, it is output through the cooling tower outlet pipeline with the cooling tower outlet regulating valve, mixed with the makeup water, and then sent to the internal heat exchanger of the air compressor by the air compressor system circulating water pump. When the temperature is lower than the set value, the cooling tower inlet regulating valve closes and the cooling tower bypass regulating valve opens. The return water from the air compressor cooling system is transported through the cooling tower bypass branch, directly mixed with the makeup water, and then sent to the internal heat exchanger of the air compressor by the air compressor system circulating water pump.

[0010] Compared with existing technologies, the beneficial effects of this invention are reflected in: 1. This invention uses reduced pressure flash evaporation to generate low-temperature steam from the return water of the air compressor cooling system. The low-temperature steam goes through multiple steam treatment units. In each steam treatment unit, it is first heated and pressurized by two-stage centrifugal steam compressors, and then mixed with makeup water in a desuperheating buffer tank to obtain saturated steam. After multiple compressions and desuperheating mixing, saturated steam that meets the requirements is finally generated for use by steam-using equipment, thus realizing the full recovery and utilization of the waste heat of low-grade thermal energy cooling water. 2. This invention delivers the return water from the air compressor cooling system in two paths: one path is sent to the flash tank, and the other path is mainly used to reduce or stop the operation of the cooling tower, and also serves to assist in the drainage of the flash tank. When the temperature of the return water from the air compressor cooling system is higher than the set value, it is cooled by the cooling tower before being mixed with the makeup water. When the temperature is lower than the set value, it is directly mixed with the makeup water without going through the cooling tower, thereby reducing the cooling tower's operating time and achieving significant energy saving and emission reduction effects. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0012] In the diagram, 1. Shut-off valve; 2. Sewage control valve; 3. Conductivity meter; 4. Cooling tower; 5. Cooling tower inlet regulating valve; 6. Local thermometer; 7. Remote thermometer; 8. Flash tank outlet regulating valve; 9. Check valve; 10. Local pressure gauge; 11. Flash liquid circulating water pump; 12. Safety valve; 13. Remote pressure gauge; 14. Flash tank; 15. Magnetic level gauge; 16. Cooling tower bypass regulating valve; 17. Cooling tower outlet regulating valve; 18. Butterfly valve; 19. Air compressor system circulating water pump; 20. Cooling water makeup regulating valve; 21. Internal heat exchanger of air compressor; 22. Single-stage centrifugal steam compressor; 23. Magnetic levitation motor. 24. Two-stage centrifugal steam compressor; 25. First-stage desuperheating buffer tank; 26. Buffer tank inlet regulating valve; 27. Final-stage desuperheating buffer tank; 28. Steam flow meter; 29. ​​Flash steam inlet regulating valve; 30. Bypass check valve. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Example 1 Please refer to Figure 1 The method for generating steam by cooling water with compressed air in this embodiment is as follows: A portion of the cooling water after absorbing the waste heat of the water-cooled air compressor is introduced into the flash tank 14 for flash evaporation to generate low-temperature water steam. The water inlet flow rate is adjustable according to the steam supply demand through the flash water inlet regulating valve 29. The remaining cooling water can be transported through three routes: one route is used to send it to the cooling tower 4, one route is used to directly mix it with the makeup water and then send it to the heat exchanger 21 inside the air compressor for heat exchange, and the other route is used to send it to the demineralized water device for treatment. A two-stage centrifugal steam compressor and a desuperheating buffer tank form the first-stage steam treatment unit. The low-temperature steam generated by the flash tank 14 is processed sequentially by a series of multi-stage steam treatment units. When passing through each stage of the steam treatment unit, the steam is first pressurized and heated step by step by the two-stage centrifugal steam compressor to become superheated steam, and then enters the desuperheating buffer tank to obtain saturated steam by mixing with makeup water for heat exchange and desuperheating. The saturated steam with a set pressure and temperature is obtained through the final stage desuperheating buffer tank 27 of the final stage steam treatment unit, which is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

[0015] Further: The water replenishment is desalinated water.

[0016] The cooling water temperature after absorbing the waste heat of the water-cooled air compressor is 42℃, and the absolute pressure inside flash tank 14 is 0.005MPa. Low-temperature water vapor at 32℃ is generated through flash evaporation in flash tank 14.

[0017] Example 2 The system for generating steam by cooling water with compressed air in this embodiment is used to implement the method for generating steam by cooling water with compressed air in Embodiment 1. The system includes: Two parallel return water pipelines are used to transport return water from the air compressor cooling system. One pipeline serves as the inlet pipeline for flash tank 14 and is equipped with a flash inlet regulating valve 29. The other pipeline serves as a return water bypass and is equipped with a bypass check valve 30. Downstream of the bypass check valve 30, the return water bypass is divided into three pipelines. The first pipeline serves as a sewage branch and is equipped with a sewage control valve 2, connecting to the demineralized water unit. It is used to incorporate the flash liquid discharged from flash tank 14 and send it to the demineralized water unit for treatment. The second pipeline serves as the inlet pipeline for cooling tower 4. A branch line is equipped with a cooling tower inlet regulating valve 5, which is used to directly send the return water of the air compressor cooling system into the cooling tower 4 for heat dissipation. After heat dissipation, it is mixed with the makeup water and sent as the air compressor cooling system water supply to the heat exchanger 21 inside the air compressor to exchange heat with the high-temperature compressed air (about 110°C). The third line is a bypass branch line of the cooling tower 4 and is equipped with a cooling tower bypass regulating valve 16, which is used to directly mix with the makeup water and then send as the air compressor cooling system water supply to the heat exchanger 21 inside the air compressor to exchange heat with the compressed air. Flash tank 14 is used to receive the return water from the air compressor cooling system sent through the inlet water pipe of flash tank 14 for flash evaporation, and to reduce the pressure and temperature to obtain low-temperature water vapor which is then sent to the primary steam treatment unit. The multi-stage steam treatment unit is used to process water vapor in stages. Each stage of the steam treatment unit includes two centrifugal steam compressors and a desuperheating buffer tank. The steam is first pressurized and heated into superheated steam by the two centrifugal steam compressors, and then enters the desuperheating buffer tank to obtain saturated steam through heat exchange and desuperheating. The saturated steam with a set pressure and temperature is obtained through the final desuperheating buffer tank 27 of the final stage steam treatment unit, which is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

[0018] In practice, the corresponding structural settings of the system also include: A thermometer is installed upstream of the cooling tower inlet regulating valve 5 and downstream of the flash tank outlet regulating valve 8 and bypass check valve 30 to monitor the liquid temperature in real time. When the temperature is higher than the set value, the cooling tower inlet regulating valve 5 opens and the cooling tower bypass regulating valve 16 closes. The return water from the air compressor cooling system is sent to the cooling tower 4 via the branch of the cooling tower 4 for cooling. After cooling, it is output through the outlet pipe of the cooling tower 4 with the cooling tower outlet regulating valve 17, mixed with the makeup water, and then sent to the heat exchanger 21 inside the air compressor via the air compressor system circulating water pump 19. When the temperature is lower than the set value, the cooling tower inlet regulating valve 5 closes and the cooling tower bypass regulating valve 16 opens. The return water from the air compressor cooling system is transported through the bypass branch of the cooling tower 4, directly mixed with the makeup water, and then sent to the heat exchanger 21 inside the air compressor via the air compressor system circulating water pump 19, thereby reducing the operating time of the cooling tower 4.

[0019] The flash tank 14 is equipped with a magnetic level gauge 15, a pressure gauge, a thermometer, a conductivity meter 3, and a safety valve 12. The flash tank 14 discharges flash liquid through a flash liquid outlet pipeline with a flash liquid circulation pump 11 and a flash tank outlet regulating valve 8. The flash liquid outlet pipeline is connected to the sewage branch. The magnetic level gauge 15 detects the liquid level in the tank in real time to control the start and stop of the flash liquid circulation pump 11 and the opening of the flash tank outlet regulating valve 8, so as to ensure that there is no water shortage at the inlet of the flash liquid circulation pump 11 and to ensure the flow rate control of the pump outlet, so that the liquid level fluctuation in the flash tank 14 is small. The pressure gauge detects the pressure in the tank in real time to control the opening of the flash water inlet regulating valve 29, and judges whether the water supply is excessive or insufficient by the pressure. The thermometer detects the temperature in the tank in real time. Since the salt content of the water in the cooling tower 4 in the flash tank 14 increases after flash evaporation, the conductivity meter 3 detects the conductivity in real time to control the opening of the sewage control valve 2 for appropriate sewage discharge.

[0020] The flash tank 14 is equipped with a shut-off valve 1 and a steam flow meter 28 in sequence in the pipeline for discharging low-temperature steam into the first-stage centrifugal steam compressor 22 of the primary steam treatment unit. The flow rate of the low-temperature steam is detected. The suction inlet of the first-stage centrifugal steam compressor 22 is under negative pressure, and the absolute pressure inside the flash tank 14 is about 0.005 MPa.

[0021] Each stage of the desuperheating buffer tank is equipped with a pressure gauge, a magnetic level gauge, and a temperature gauge. Water replenishment is achieved through multiple delivery routes. One of them is a cooling water supply branch with a cooling water supply regulating valve, which is connected to the air compressor inlet pipe. It is used to mix with the air compressor cooling system return water output from the bypass branch of cooling tower 4, or with the air compressor cooling system return water output from the outlet pipe of cooling tower 4 after being cooled by cooling tower 4. The air compressor inlet pipe is equipped with a pressure gauge, an upstream butterfly valve 18, an air compressor system circulating water pump 19, a pressure gauge, a check valve 9, and a downstream butterfly valve 18 in sequence. The upstream of the pressure gauge is connected to the cooling tower bypass regulating valve 16 and the downstream of the cooling tower outlet regulating valve 17, which are connected to the cooling water supply branch. Each of the other channels is equipped with a buffer tank inlet regulating valve 26, which is used to supply water to each level of the desuperheating buffer tank.

[0022] The final stage desuperheating buffer tank 27 outputs saturated steam through a saturated steam delivery pipeline equipped with a shut-off valve 1 and a pressure gauge.

[0023] The aforementioned pressure gauges include remote pressure gauges and local pressure gauges 10; the temperature gauges include remote temperature gauges and local temperature gauges 6; and the magnetic level gauges 15 include remote and basic types. All check valves 9 in the system are for preventing fluid backflow; safety valves 12 protect the tank from operating at the design pressure; shut-off valves 1 and butterfly valves 18 are for equipment maintenance, installation, and commissioning; local temperature gauges 6 and 10 provide on-site visual display; and remote temperature gauges 7 and pressure gauges are for control and remote display needs, facilitating the collection and analysis of historical data to provide analytical basis for different operating conditions.

[0024] The system works as follows: The compressed air cooling circulating water absorbs heat from the high-temperature compressed air through the heat exchanger 21 inside the air compressor, and its temperature rises to about 42°C. The cooling water at this temperature enters the flash tank 14 through the inlet regulating valve. After flash evaporation, part of the cooling water becomes low-temperature water vapor at about 32°C. The low-temperature water vapor enters the first-stage centrifugal compressor and the second-stage centrifugal compressor of the first-stage steam treatment unit and is gradually pressurized and heated. After every two stages of compression, the superheated steam is exchanged with the makeup water through the desuperheating buffer tank. After desuperheating and mixing, it enters the next stage of steam treatment unit until it is desuperheated and mixed through the final desuperheating buffer tank 27 to become the saturated steam required by the user equipment, which is used to supply heating and humidification for process air conditioning or other equipment.

[0025] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for generating steam by cooling water with compressed air, characterized in that: A portion of the cooling water after absorbing the waste heat of the water-cooled air compressor is introduced into a flash tank to generate low-temperature water vapor. The water inlet flow rate can be adjusted according to the steam supply demand through the flash water inlet regulating valve. The remaining cooling water can be transported through three routes: one route is sent to the cooling tower, one route is directly mixed with the makeup water and sent to the heat exchanger inside the air compressor for heat exchange, and the other route is sent to the demineralized water device for treatment. A two-stage centrifugal steam compressor and a desuperheating buffer tank form the first-stage steam treatment unit. The low-temperature steam generated by the flash tank is processed sequentially by a series of multi-stage steam treatment units. When passing through each stage of the steam treatment unit, the steam is first pressurized and heated step by step by the two-stage centrifugal steam compressor to become superheated steam, and then enters the desuperheating buffer tank to obtain saturated steam by mixing with makeup water for heat exchange and desuperheating. The saturated steam with a set pressure and temperature is obtained through the final stage desuperheating buffer tank of the final stage steam treatment unit, which is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

2. The method for generating steam by cooling water with compressed air according to claim 1, characterized in that: The water replenishment is desalinated water.

3. The method for generating steam by cooling water with compressed air according to claim 1, characterized in that: The cooling water temperature after absorbing the waste heat of the water-cooled air compressor is 42℃, and the absolute pressure inside the flash tank is 0.005MPa. Low-temperature water vapor at 32℃ is generated through flash evaporation in the flash tank.

4. A system for generating steam by cooling water with compressed air, characterized in that, A method for implementing the method of generating steam by cooling water with compressed air as described in any one of claims 1-3, comprising: Two parallel return water pipelines are used to transport return water from the air compressor cooling system. One pipeline serves as the flash tank inlet pipeline and is equipped with a flash tank inlet regulating valve. The other pipeline serves as a return water bypass and is equipped with a bypass check valve. The return water bypass is divided into three pipelines downstream of the bypass check valve. The first pipeline serves as a sewage branch and is equipped with a sewage control valve, connecting to the demineralized water device. It is used to incorporate the flash liquid discharged from the flash tank and send it to the demineralized water device for treatment. The second pipeline serves as a cooling tower inlet branch and is equipped with a cooling tower inlet regulating valve. It is used to directly send the return water from the air compressor cooling system into the cooling tower for heat dissipation. After heat dissipation, it is mixed with makeup water and used as the air compressor cooling system supply water, which is sent to the internal heat exchanger of the air compressor for heat exchange with the compressed air. The third pipeline serves as a cooling tower bypass branch and is equipped with a cooling tower bypass regulating valve. It is used to directly mix with makeup water and then use it as the air compressor cooling system supply water, which is sent to the internal heat exchanger of the air compressor for heat exchange with the compressed air. The flash tank is used to receive the return water from the air compressor cooling system sent through the flash tank inlet pipe, and to flash the water to reduce the pressure and temperature to obtain low-temperature steam, which is then sent to the primary steam treatment unit. The multi-stage steam treatment unit is used to process water vapor in stages. Each stage of the steam treatment unit includes two centrifugal steam compressors and a desuperheating buffer tank. The steam is first pressurized and heated into superheated steam by the two centrifugal steam compressors, and then enters the desuperheating buffer tank to obtain saturated steam through heat exchange. The saturated steam with a set pressure and temperature is obtained by passing through the desuperheating buffer tank of the final stage of the steam treatment unit, and is used to supply steam to steam-using equipment or to be connected to the on-site steam system pipeline.

5. The system for generating steam by cooling water with compressed air according to claim 4, characterized in that: The flash tank is equipped with a magnetic level gauge, pressure gauge, thermometer, conductivity meter, and safety valve. The flash tank discharges flash liquid through a flash liquid outlet pipeline connected to a flash liquid circulation pump and a flash tank outlet regulating valve. The flash liquid outlet pipeline is also connected to a sludge discharge branch. The magnetic level gauge monitors the tank level in real time to control the start / stop of the flash liquid circulation pump and the opening of the flash tank outlet regulating valve. The pressure gauge monitors the tank pressure in real time to control the opening of the flash liquid inlet regulating valve. The thermometer monitors the tank temperature in real time. The conductivity meter monitors the conductivity in real time to control the opening of the sludge discharge control valve.

6. The system for generating steam by cooling water with compressed air according to claim 4, characterized in that: A thermometer is installed upstream of the cooling tower inlet regulating valve and downstream of the flash tank outlet regulating valve and bypass check valve to monitor the liquid temperature in real time. When the temperature is higher than the set value, the cooling tower inlet regulating valve opens and the cooling tower bypass regulating valve closes. The return water from the air compressor cooling system is sent to the cooling tower for cooling via the cooling tower branch. After cooling, it is output through the cooling tower outlet pipeline with the cooling tower outlet regulating valve, mixed with the makeup water, and then sent to the internal heat exchanger of the air compressor by the air compressor system circulating water pump. When the temperature is lower than the set value, the cooling tower inlet regulating valve closes and the cooling tower bypass regulating valve opens. The return water from the air compressor cooling system is transported through the cooling tower bypass branch, directly mixed with the makeup water, and then sent to the internal heat exchanger of the air compressor by the air compressor system circulating water pump.

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