A compressed air drying system driven by jet refrigeration

Abstract

The present invention relates to the field of compressed air drying technology, and more particularly to a jet refrigeration-driven compressed air drying system. The system comprises four subsystems: an air subsystem, a jet refrigeration subsystem, a cooling water subsystem, and a lubricating oil subsystem. This system utilizes low-temperature industrial waste heat generated by an air compressor to drive a jet refrigeration cycle, which then uses the cooling energy generated by the jet refrigeration cycle to freeze-dry the compressed air, thereby producing dry compressed air.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air drying, and in particular to a compressed air drying system driven by jet refrigeration. Background Art

[0002] Compressed air is a widely used power source in many industrial sectors. To meet industrial needs, moisture must be removed from compressed air, and freeze-drying is a common method. This involves lowering the temperature to condense water vapor from the air. The widespread use of compressed air in industry has made it a major energy consumer in modern industry. The air compressors that produce compressed air (or simply, air compressors) consume significant amounts of power and generate significant heat.

[0003] Therefore, it is very meaningful to study solutions that can produce dry compressed air with relatively low energy consumption.

[0004] Currently, waste heat recovery from air compressors primarily utilizes heat from high-temperature exhaust and lubricating oil to produce hot water or as a heat source for driving absorption refrigeration. A widely adopted freeze-drying solution in the market is the conventional vapor compression refrigeration method for drying compressed air. This solution consumes a lot of energy and does not effectively recover the waste heat from the air compressor. While utilizing waste heat from the air compressor to drive absorption refrigeration to obtain cooling capacity allows for waste heat recovery from the air compressor, some issues remain. For example, when using water-lithium bromide as the working fluid, aqueous lithium bromide solution is highly corrosive to metals in the atmosphere, placing high demands on equipment and piping, and requiring a high initial investment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a compressed air drying system driven by jet refrigeration, which utilizes the low-temperature industrial waste heat generated by the air compressor to drive the jet refrigeration cycle, and utilizes the cold energy generated by the jet refrigeration cycle to freeze-dry the compressed air, thereby producing dry compressed air.

[0006] The technical solution adopted by the present invention is: a compressed air drying system driven by jet refrigeration, which includes an air compressor, a subcooler, an evaporator, a condenser, an ejector, a generator and a cooling tower, wherein:

[0007] The air outlet of the air compressor is connected to the hot air inlet of the subcooler, the hot air outlet of the subcooler is connected to the air inlet of the evaporator, and the air outlet of the evaporator is connected to the cold air inlet of the subcooler, forming an air subsystem;

[0008] The refrigerant outlet of the generator is connected to the working fluid inlet of the ejector, the ejector fluid inlet is connected to the refrigerant outlet of the evaporator, the ejector outlet is connected to the refrigerant inlet of the condenser, and the refrigerant outlet of the condenser is divided into two paths, one of which is connected to the refrigerant inlet of the generator through the first circulation pump, and the other is connected to the refrigerant inlet of the evaporator through the throttle valve, forming an ejector refrigeration subsystem;

[0009] The outlet of the cooling tower is connected to the cooling water inlet of the condenser through the second circulation pump, and the cooling water outlet of the condenser is connected to the inlet of the cooling tower to form a cooling water subsystem;

[0010] The lubricating oil outlet of the air compressor is connected to the lubricating oil inlet of the generator, and the lubricating oil outlet of the generator is connected to the lubricating oil inlet of the air compressor to form a lubricating oil subsystem.

[0011] Preferably, the air subsystem further includes an air cooler, the air outlet of the air compressor is connected to the air inlet of the air cooler, and the air outlet of the air cooler is connected to the air inlet of the subcooler.

[0012] Preferably, the lubricating oil subsystem further includes an oil cooler, the lubricating oil outlet of the oil cooler is connected to the lubricating oil inlet of the air compressor, and the lubricating oil inlet of the oil cooler is connected to the lubricating oil outlet of the generator.

[0013] Preferably, it also includes a fan for dissipating heat for the oil cooler and the air cooler.

[0014] Preferably, the air cooler, subcooler and evaporator are further provided with drain valves for discharging cooled water.

[0015] Compared with the existing technology, the present invention has the following advantages: it recovers part of the heat in the high-temperature lubricating oil when the air compressor is running to drive the jet refrigeration cycle, and then uses the cooling capacity provided by the air cooler, subcooler and evaporator to freeze-dry the compressed air. This technology not only avoids the waste of low-temperature waste heat of the air compressor, but also saves the input work of the compressor in the steam compression refrigeration required by the traditional freeze-drying technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a compressed air drying system driven by jet refrigeration according to the present invention.

[0017] As shown in the figure: 1. Air compressor; 2. Subcooler; 3. Evaporator; 4. Condenser; 5. Ejector; 6. Generator; 7. Cooling tower; 8. Air cooler; 9. Oil cooler; 10. Fan; 11. Drain valve; 12. First circulating pump; 13. Throttle valve; 14. Second circulating pump. DETAILED DESCRIPTION

[0018] The present invention is further described below through specific embodiments, but the present invention is not limited to the following specific embodiments.

[0019] like Figure 1 As shown, the present invention provides a compressed air drying system driven by jet refrigeration, which includes four subsystems: an air subsystem, a jet refrigeration subsystem, a cooling water subsystem, and a lubricating oil subsystem.

[0020] The air subsystem includes an air compressor 1, an air cooler 8, a subcooler 2, and an evaporator 3. The air inlet of air cooler 8 is connected to the air outlet of air compressor 1, which in turn is connected to the hot air inlet of subcooler 2. Air cooler 8 is also equipped with a drain valve 11. The hot air inlet of subcooler 2 is connected to the air outlet of air cooler 8, its hot air outlet is connected to the air inlet of evaporator 3, and its cold air inlet is connected to the air outlet of evaporator 3. In this specific embodiment, air compressor 1 is an oil-fired screw air compressor 1 with the following parameters: exhaust pressure 0.75 MPa, volume flow rate 3.32 m³ / min, and power 18.5 kW. Air cooler 8 uses an air-cooled heat exchanger, and subcooler 2 uses a shell-and-tube heat exchanger.

[0021] The air subsystem operates as follows: After being compressed by air compressor 1, air passes through air cooler 8, subcooler 2, evaporator 3, and subcooler 2, sequentially. The air cooler 8, subcooler 2, and evaporator 3 cool down and condense water, which is then discharged through drain valve 11. In air cooler 8, the high-temperature compressed air at the outlet of air compressor 1 undergoes a wall-to-wall heat exchange with the ambient air, causing the temperature of the high-temperature compressed air to drop. When the temperature drops below the dew point, condensate water is released. Fan 10 enhances the heat exchange process in air cooler 8. In subcooler 2, the compressed air at the outlet of air cooler 8 undergoes a wall-to-wall heat exchange with the compressed air at the outlet of evaporator 3, further lowering the temperature of the compressed air at the outlet of air cooler 8 and reducing its moisture content. Water vapor condenses and is discharged through drain valve 11. Meanwhile, the compressed air at the outlet of evaporator 3 undergoes only dry heating in subcooler 2, increasing its temperature and maintaining its moisture content. In evaporator 3, compressed air undergoes inter-wall heat exchange with the refrigerant at the outlet of throttle valve 13, causing the compressed air temperature to drop and moisture to precipitate. The moisture content of the compressed air reaches its lowest point at the outlet of evaporator 3. In this specific embodiment, outdoor air is compressed by air compressor 1 to a temperature of approximately 85°C. It is then cooled to approximately 40°C by air cooler 8, where some moisture is precipitated. It is then cooled to approximately 25.7°C by subcooler 2, where some moisture is again precipitated and flows out of drain valve 11. It is then cooled again by evaporator 3 to a pressure dew point of 7°C. Finally, it is heated to 30°C by subcooler 2 and supplied to the user.

[0022] The ejection subsystem includes a generator 6, a first circulating pump 12, an ejector 5, a condenser 4, a throttle valve 13, and an evaporator 3. The refrigerant inlet of the generator 6 is connected to the outlet of the first circulating pump 12, and the refrigerant outlet of the generator 6 is connected to the working fluid inlet of the ejector 5. The ejection fluid inlet of the ejector 5 is connected to the refrigerant outlet of the evaporator 3, and the outlet of the ejector 5 is connected to the refrigerant inlet of the condenser 4. The refrigerant outlet of the condenser 4 is respectively connected to the inlet of the first circulating pump 12 and the inlet of the throttle valve 13. The outlet of the throttle valve 13 is connected to the refrigerant inlet of the evaporator 3. In this specific embodiment, the generator 6 uses a shell and tube heat exchanger, the condenser 4 uses a plate heat exchanger, and the evaporator 3 uses a shell and tube heat exchanger.

[0023] The ejector subsystem operates as follows: The high-temperature, high-pressure refrigerant at the outlet of generator 6 enters ejector 5 as the working fluid. It is accelerated by the ejector nozzle and forms a negative pressure in the mixing chamber, thereby ejecting the low-temperature, low-pressure refrigerant at the outlet of evaporator 3. After the two are mixed, they are ejected from ejector 5 into condenser 4. In condenser 4, the refrigerant and cooling water exchange heat in a partitioned manner. The refrigerant at the outlet of condenser 4 is divided into two parts: one part is pressurized by a circulating pump and fed into generator 6; the other part enters evaporator 3 after passing through throttle valve 13. The heating required by generator 6 is provided by the high-temperature lubricating oil of air compressor 1, reducing the energy consumption of the ejector refrigeration subsystem.

[0024] In this specific embodiment: in the ejector refrigeration subsystem, the generating temperature is 75°C, the condensing temperature is 35°C, and the evaporating temperature is 5°C. Among them, the superheat degree of the generator 6 is 5°C, and the superheat degree of the evaporator 3 is 3°C. Under this working condition, the ejection coefficient of the ejector 5 is about 0.2. The refrigerant absorbs heat from the high-temperature lubricating oil in the generator 6, and after reaching the superheated state of 80°C, it enters the ejector 5 as a working fluid, and ejects the refrigerant at 8°C from the outlet of the evaporator 3. The two exchange momentum and energy in the ejector 5. The refrigerant at 60.1°C at the outlet of the ejector 5 is condensed to 35°C by the condenser 4 and divided into two streams. One stream is pressurized by the first circulating pump 12 and sent to the generator 6, and the other stream is cooled to 5°C by the throttle valve 13 and enters the evaporator 3.

[0025] The cooling water subsystem includes a cooling tower 7, a second circulating pump 14, and a condenser 4. The outlet of the cooling tower 7 is connected to the inlet of the second circulating pump 14, and its inlet is connected to the cooling water outlet of the condenser 4. The outlet of the second circulating pump 14 is connected to the cooling water inlet of the condenser 4. In this embodiment, the cooling tower 7 is a spray cooling tower 7.

[0026] The cooling water subsystem operates as follows: Cooling water at the outlet of cooling tower 7 is pressurized by a second circulating pump 14 and pumped into condenser 4, where it is then sprayed into cooling tower 7. In condenser 4, the cooling water and refrigerant undergo a wall-to-wall heat exchange process, removing excess heat from the refrigerant and ensuring the proper operation of the spray refrigeration subsystem.

[0027] In this specific embodiment, in the cooling water subsystem, considering the most unfavorable working conditions in summer, the cooling water is sprayed from the cooling tower 7 to a temperature of about 30°C, and is pressurized by the second circulation pump 14 and sent to the condenser 4, reaching 40°C at the outlet of the condenser 4.

[0028] The lubricating oil subsystem includes a fan 10, an oil cooler 9, a generator 6, and an air compressor 1. The lubricating oil outlet of the air compressor 1 is connected to the lubricating oil inlet of the generator 6, and the lubricating oil inlet of the air compressor 1 is connected to the lubricating oil outlet of the oil cooler 9. The lubricating oil outlet of the generator 6 is connected to the lubricating oil inlet of the oil cooler 9. The fan 10 cools both the oil cooler 9 and the air cooler 8. In this embodiment, the oil cooler 9 is an air-cooled heat exchanger.

[0029] The lubricating oil subsystem operates as follows: High-temperature lubricating oil from compressor 1's lubricating oil outlet passes through generator 6, oil cooler 9, and then returns to compressor 1. In generator 6, the high-temperature lubricating oil and the refrigerant undergo a wall-to-wall heat exchange, which not only meets the lubricating oil heat dissipation requirement during stable operation of compressor 1 but also recovers some of the heat from the high-temperature lubricating oil, reducing generator 6's energy consumption.

[0030] In this specific embodiment, the oil temperature at the outlet of the air compressor 1 is about 83°C, drops to about 78°C at the outlet of the generator 6, drops to 77.3°C through the oil cooler 9, and then returns to the air compressor 1.

[0031] In this specific embodiment, the outdoor meteorological parameters are: dry-bulb temperature 30°C, relative humidity 70%. The cooling capacity of evaporator 3 is 1480W, the power of the refrigerant circulation pump, i.e., first circulation pump 12, is 19.5W, and the power of the cooling water circulation pump, i.e., second circulation pump 14, is 61.9W. The refrigeration system COP is approximately 18.1.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A compressed air drying system driven by jet refrigeration, characterized in that: It includes an air compressor (1), a subcooler (2), an evaporator (3), a condenser (4), an ejector (5), a generator (6) and a cooling tower (7), wherein: The air outlet of the air compressor (1) is connected to the hot air inlet of the subcooler (2), the hot air outlet of the subcooler (2) is connected to the air inlet of the evaporator (3), and the air outlet of the evaporator (3) is connected to the cold air inlet of the subcooler (2), forming an air subsystem; The refrigerant outlet of the generator (6) is connected to the working fluid inlet of the ejector (5), the ejection fluid inlet of the ejector (5) is connected to the refrigerant outlet of the evaporator (3), the outlet of the ejector (5) is connected to the refrigerant inlet of the condenser (4), and the refrigerant outlet of the condenser (4) is divided into two paths, one of which is connected to the refrigerant inlet of the generator (6) through the first circulation pump (12), and the other is connected to the refrigerant inlet of the evaporator (3) through the throttle valve (13), forming an ejection refrigeration subsystem; The outlet of the cooling tower (7) is connected to the cooling water inlet of the condenser (4) through the second circulation pump (14), and the cooling water outlet of the condenser (4) is connected to the inlet of the cooling tower (7), forming a cooling water subsystem; The lubricating oil outlet of the air compressor (1) is connected to the lubricating oil inlet of the generator (6), and the lubricating oil outlet of the generator (6) is connected to the lubricating oil inlet of the air compressor (1), forming a lubricating oil subsystem.

2. The compressed air drying system driven by jet refrigeration according to claim 1, characterized in that: The air subsystem further comprises an air cooler (8), the air outlet of the air compressor (1) is connected to the air inlet of the air cooler (8), and the air outlet of the air cooler (8) is connected to the air inlet of the subcooler (2).

3. The compressed air drying system driven by jet refrigeration according to claim 2, characterized in that: The lubricating oil subsystem further comprises an oil cooler (9), the lubricating oil outlet of the oil cooler (9) is connected to the lubricating oil inlet of the air compressor (1), and the lubricating oil inlet of the oil cooler (9) is connected to the lubricating oil outlet of the generator (6).

4. The compressed air drying system driven by jet refrigeration according to claim 3, characterized in that: It also includes a fan (10) for dissipating heat from the oil cooler (9) and the air cooler (8).

5. The compressed air drying system driven by jet refrigeration according to claim 2, characterized in that: The air cooler (8), the subcooler (2) and the evaporator (3) are also provided with a drain valve (11) for discharging cooled water.

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