Methods to improve the waste heat utilization rate of air compressors

Abstract

This invention discloses a method for improving the waste heat utilization rate of an air compressor. The method utilizes an air source heat pump unit to recover the waste heat from the air compressor's exhaust air and a heat exchanger to recover the waste heat from the air compressor's working oil. The waste heat from the exhaust air and / or the waste heat from the working oil is supplied to a first user end through a first heating unit to provide heating or hot water for production. The waste heat from the exhaust air and / or the waste heat from the working oil is supplied to a second user end through a second heating unit to provide domestic hot water. This invention utilizes a heat pump unit to recover the waste heat from the air compressor's exhaust air and a heat exchanger to recover the oil heat, thereby improving the waste heat recovery and utilization rate of the air compressor. The second heating unit has two water tanks, one for hot water and one for cold water, reducing the impact of water replenishment on the heating needs of the second user end. This invention allows for flexible use of the waste heat from the exhaust air and the waste heat from the working oil; they can not only work independently but also work together to provide heating or heat domestic water, further improving the waste heat recovery and utilization rate of the air compressor.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, and in particular to a method for improving the utilization rate of waste heat from air compressors. Background Technology

[0002] Compressed air, as the second largest power source after electricity, is widely used in various fields. Statistics show that air compressors consume 10% of industrial energy. During operation, air compressors generate a significant amount of heat due to air compression, mechanical friction, and motor heating. According to authoritative testing, only 10% of the electrical energy consumed by an air compressor is converted into the potential energy of compressed air, while the remaining 90% is converted into heat energy (nearly 85% of which can be recovered and reused). To ensure the normal and stable operation of the air compressor and maintain its normal operating temperature, this heat is usually released into the environment, causing energy waste and environmental thermal pollution. Therefore, the recovery and rational utilization of the heat generated during air compressor operation is crucial.

[0003] Using waste heat from air compressors for domestic hot water is the most common and effective energy-saving measure. Currently, common waste heat recovery systems for air compressors utilize waste heat recovery heat exchangers to recover heat. This involves connecting the air compressor via a bypass oil or air circuit to recover the heat it carries. A water pump then sends water from an insulated hot water tank to the waste heat recovery heat exchanger for heating. After heating, the water flows back to the insulated hot water tank, and the cycle continues until all the water in the tank reaches the specified temperature. Finally, a hot water supply pump delivers the hot water from the insulated hot water tank to the user.

[0004] The aforementioned circulating heating method has the following problems in actual operation: First, when replenishing water, cold water is generally directly added to the insulated water tank. This causes the hot water in the insulated water tank to cool down again, requiring reheating until all the water in the tank is heated to the specified temperature, which takes a considerable amount of time. During this period, it is impossible to provide hot water that meets the temperature requirements at any time. Secondly, this waste heat recovery method cannot completely replace the original cooling system of the air compressor in actual operation. Most of the waste heat is lost to the external environment through the air compressor's own cooling system, resulting in low waste heat utilization rate. Therefore, how to provide hot water that meets the temperature requirements immediately and stably without affecting the stable operation of the air compressor, and how to maximize the utilization of the "free" heat from the air compressor's waste heat, has become an important technical issue in the field of air compressor waste heat recovery and utilization. Summary of the Invention

[0005] In view of this, the present invention proposes a method to improve the waste heat utilization rate of air compressors, which greatly improves the waste heat utilization rate of air compressors and enables hot water users to use hot water at any time.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The method for improving the waste heat utilization rate of air compressors according to the present invention involves using an air source heat pump unit to recover the waste heat of the exhaust air from the air compressor, using a heat exchanger to recover the waste heat of the working oil from the air compressor, and supplying the waste heat of the exhaust air and / or the waste heat of the working oil to a first user end through a first heating unit to provide heating or production hot water to the first user end; the waste heat of the exhaust air and / or the waste heat of the working oil is then supplied to a second user end through a second heating unit to provide domestic hot water to the second user end.

[0008] The first heating unit includes a circulation loop consisting of the heat pump unit, a circulating hot water supply pipe, a first user terminal, and a circulating hot water return pipe connected in sequence. The heat pump unit is an air source heat pump unit or an air source-water source hybrid heat pump unit. The hot air outlet of the air compressor is located at the air inlet of the heat pump unit.

[0009] The second heating unit includes a second user terminal, a first water tank, and a second water tank. The first water tank is connected to the water inlet of the heat exchanger via a cold water heating pipe. The water outlet of the heat exchanger is connected to the second water tank via a hot water heating pipe. The second water tank is connected to the second user terminal via a hot water supply pipe. The first water tank is connected to the hot water return pipe and the tap water pipe of the second user terminal.

[0010] The cold water heating pipe is connected to a first branch pipe at its outlet end. The first branch pipe is connected to the outlet end of the circulating hot water return pipe. The first branch pipe is equipped with a third valve and a fifth valve connected in parallel with the third valve. The hot water heating pipe is connected to the inlet end of the circulating hot water supply pipe through a second branch pipe. The second branch pipe is equipped with a fourth valve and a sixth valve connected in parallel with the fourth valve.

[0011] A hot water supply pump set is installed on the hot water supply pipeline, a cold water pump set is installed on the cold water heating pipeline, and a circulating pump set is installed on the circulating hot water return pipeline; an eleventh valve is installed at the outlet of the tap water pipeline, and a ninth valve is installed at the inlet of the cold water heating pipeline.

[0012] A first valve is installed on the cold water heating pipe located in front of the first branch pipe, and a second valve is installed on the hot water heating pipe located behind the second branch pipe; an eighth valve is installed on the circulating hot water supply pipe, and a seventh valve is installed on the circulating hot water return pipe.

[0013] The beneficial effects are: This invention changes the traditional circulating air compressor waste heat recovery system, using a heat pump unit (air source heat pump unit or composite heat pump unit with air source) to recover the waste heat of the air compressor's exhaust air, and using a heat exchanger to recover the oil heat of the air compressor, thereby improving the waste heat recovery and utilization rate of the air compressor.

[0014] The second heating unit of the present invention recovers the heat generated by the working oil of the air compressor through a heat exchanger. The second heating unit has two water tanks. Cold water enters the heat exchanger from the first water tank and flows back to the second water tank after passing through the heat exchanger. When replenishing water, it is directly added to the first water tank. The second water tank provides hot water to the second user in real time, thereby realizing the second user's ability to take out heat at any time and reducing the impact of water replenishment on the second user's heat use.

[0015] This invention utilizes a first and a second pipe to connect the cold water heating pipe, the hot water heating pipe, the circulating hot water return pipe, and the circulating hot water supply pipe. In actual operation, it can not only utilize the waste heat from the air compressor's exhaust to heat the first user end, but also directly utilize the waste heat from the air compressor's working oil to heat the first user end, improving the utilization rate of the working oil's waste heat; it can also utilize the waste heat from the air compressor's exhaust to heat domestic hot water, providing domestic hot water to the second user end, making the entire system more flexible.

[0016] Preferably, the first heating unit is connected to a water replenishment unit. The water replenishment unit includes a softened water treatment pipe connected to tap water and a third water tank. A softened water treatment device is installed on the softened water treatment pipe. The third water tank is connected to the circulating hot water return pipe via a water replenishment pipe. A water replenishment pump set is installed on the water replenishment pipe to provide water replenishment power. The replenishment water is softened water, reducing the impact of water quality on the pipes and pump set.

[0017] Preferably, the water replenishment pump group, hot water supply pump group, cold water pump group, and circulation pump group are all in pairs or more. In this invention, each pump group consists of two or more sets, which can be used as a backup for one or two pumps, ensuring the normal operation of the entire system and reducing the downtime rate caused by malfunctions.

[0018] Preferably, the bottom outlet of the second water tank is connected to the cold water heating pipe via a pipe equipped with a tenth valve. When the water temperature in the second water tank drops to a certain temperature, the tenth valve can be opened to reheat the water in the second water tank, ensuring the temperature of domestic hot water for the second user.

[0019] Preferably, a pressure regulating branch with a pressure regulating valve is provided between the circulating hot water supply pipe and the circulating hot water return pipe. The present invention can use the pressure regulating valve to balance the pressure between the return water and the supply water.

[0020] Compared to existing technologies, this invention changes the traditional circulating air compressor waste heat recovery system. It utilizes a heat pump unit (air source heat pump unit or a combined heat pump unit with an air source) to recover the waste heat from the air compressor's exhaust air, and a heat exchanger to recover the oil heat from the air compressor, thus improving the waste heat recovery and utilization rate of the air compressor. For air source heat pump units or combined heat pump units with an air source, the higher the ambient temperature, the higher the energy efficiency of the air source heat pump. The waste heat temperature of the exhaust air from the air compressor can reach over 50°C, providing the air source heat pump unit with high-temperature hot air, significantly improving its energy efficiency. This invention combines an air compressor unit and an air source heat pump unit, improving the waste heat recovery and utilization rate of the air compressor, increasing the energy efficiency of the heat pump unit, reducing its operating energy consumption, reducing environmental pollution, and lowering the operating costs for enterprises.

[0021] The second heating unit of the present invention recovers the heat generated by the working oil of the air compressor through a heat exchanger. The second heating unit has two water tanks. Cold water enters the heat exchanger from the first water tank and flows back to the second water tank after passing through the heat exchanger. When replenishing water, it is directly added to the first water tank. The second water tank provides hot water to the second user in real time, thereby realizing the second user's ability to take out heat at any time and reducing the impact of water replenishment on the second user's heat use.

[0022] This invention utilizes a first and a second pipe to connect the cold water heating pipe, the hot water heating pipe, the circulating hot water return pipe, and the circulating hot water supply pipe. In actual operation, it can not only utilize the waste heat from the air compressor's exhaust to heat the first user end, but also directly utilize the waste heat from the air compressor's working oil to heat the first user end, improving the utilization rate of the working oil's waste heat; it can also utilize the waste heat from the air compressor's exhaust to heat domestic hot water, providing domestic hot water to the second user end, making the entire system more flexible. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the pipeline of the present invention.

[0024] Figure 2 This diagram shows the operating condition where the waste heat from the air compressor's working oil and the waste heat from the hot exhaust air are both used in the second heating unit.

[0025] Figure 3 This diagram shows the operating condition where the waste heat from the air compressor's working oil and the waste heat from the hot exhaust air are both used in the first heating unit. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] It should be noted that, in the description of this invention, relational terms such as “first” and “second” are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] like Figure 1 As shown, the method for improving the waste heat utilization rate of air compressors according to the present invention utilizes an air source heat pump unit to recover the waste heat of the exhaust air from the air compressor 301, and utilizes a heat exchanger 303 to recover the waste heat of the working oil from the air compressor (a hot oil circulation loop is formed between the heat exchanger 303 and the air compressor 301 through a pipeline). The waste heat of the exhaust air (or a combination of the waste heat of the exhaust air and the waste heat of the working oil) is supplied to the first user end through the first heating unit to provide heating or hot water for production; the waste heat of the working oil (or a combination of the waste heat of the exhaust air and the waste heat of the working oil) is supplied to the second user end through the second heating unit to provide domestic hot water for the second user end.

[0030] The first heating unit includes a heat pump unit 101, a circulating hot water supply pipe 102, a first user terminal 103 (for heating or production), and a circulating hot water return pipe 104 connected in sequence to form a circulation loop. A circulation pump unit 105 is installed on the circulating hot water return pipe 104 to provide circulation power. The heat pump unit 101 is an air source heat pump unit or an air source-water source composite heat pump unit. An exhaust pipe 302 is installed at the hot air outlet of the air compressor 301, and the air outlet of the exhaust pipe 302 is directly opposite the air inlet of the heat pump unit 101. During operation, the heat pump unit 101 absorbs the cooling exhaust air from the air compressor 301 and indirectly transfers the heat of the cooling exhaust air to the softened water from the circulating hot water loop. The softened water absorbs heat and rises to 55℃~60℃, then is supplied to the first user terminal 103 via the circulating hot water supply pipe 102. The return water from the first user terminal 103 (temperature between 45℃~50℃) re-enters the heat pump unit 101 via the circulating hot water return pipe 104, thus achieving circulating heating. Because the ambient temperature at the air inlet of the heat pump unit 101 is as high as 50℃, the energy efficiency ratio and operating efficiency of the heat pump unit 101 are greatly improved, expanding the application range of air source heat pumps in northern regions and demonstrating high environmental, social, and economic benefits.

[0031] Combination Figure 1 It is understood that the second heating unit and heat exchanger 303 are combined to provide domestic hot water to the second user terminal. It includes the second user terminal, a first water tank 201 (cold water tank) and a second water tank 202 (hot water tank, the water tank has a heat insulation layer). The first water tank 201 is connected to the water channel inlet of the heat exchanger 303 through a cold water heating pipe 207 (equipped with a cold water pump group 203). The water channel outlet of the heat exchanger 303 is connected to the second water tank 202 through a hot water heating pipe 204. The second water tank 202 is connected to the second user terminal through a hot water supply pipe 205. A hot water supply pump group 206 is installed on the hot water supply pipe 205 to provide hot water to the second user terminal. The first water tank 201 is connected to the hot water return pipe and the tap water pipe of the second user terminal to realize water replenishment. An eleventh valve F11 is installed at the outlet of the tap water pipe, and a ninth valve is installed at the inlet of the cold water heating pipe 207. During operation, cold water is added to the first water tank 201. The water in the first water tank 201 enters the heat exchanger 303 through the cold water heating pipe 207, absorbing heat from the high-temperature working oil flowing through the heat exchanger 303. After absorbing the heat from the oil, the temperature of the cold water can rise to 60°C and then enter the second water tank 202 through the hot water heating pipe 204. It is then supplied to the second user end through the hot water supply pipe 205 and the hot water supply pump set 206, ensuring domestic hot water for the second user end. The second heating unit of this invention has two water tanks. Cold water enters the heat exchanger 303 from the first water tank 201, and then flows back to the second water tank 202. When replenishing water, it is directly added to the first water tank 201. The second water tank 202 provides hot water to the second user end in real time, thereby enabling the second user end to obtain heat at any time and reducing the impact of water replenishment on the second user end's heating needs.

[0032] Combination Figure 1 It can be seen that the outlet end of the cold water heating pipe 207 is also connected to the first branch pipe 401, which is connected to the outlet end of the circulating hot water return pipe 104. The first branch pipe 401 is equipped with a third valve F3 and a fifth valve F5 connected in parallel with the third valve F3. The inlet of the hot water heating pipe 204 is connected to the inlet end of the circulating hot water supply pipe 102 through the second branch pipe 402, and the second branch pipe 402 is equipped with a fourth valve F4 and a sixth valve F6 connected in parallel with the fourth valve F4. The cold water heating pipe 207 located in front of the first branch pipe 401 is equipped with a first valve F1, and the hot water heating pipe 204 located behind the second branch pipe 402 is equipped with a second valve F2. The circulating hot water supply pipe 102 is equipped with an eighth valve F8, and the circulating hot water return pipe 104 is equipped with a seventh valve F7. The present invention utilizes the first branch pipe 401 and the second branch pipe 402 to connect the cold water heating pipe 207, the hot water heating pipe 204 with the circulating hot water return pipe 104 and the circulating hot water supply pipe 102.

[0033] The working condition in which both exhaust waste heat and working oil waste heat are supplied to the first user end is as follows: When the second water tank 202 is full and the hot water temperature reaches 60℃, the heating of cold water can be stopped, and the heat of the high-temperature working oil can be used for the first user end 103 to meet the heat demand of the first user end 103. The specific working process is as follows: First valve F1, second valve F2, third valve F3, and fourth valve F4 are closed; sixth valve F6, eighth valve F8, seventh valve F7, and fifth valve F5 are opened. The outlet of the circulating hot water return pipe 104 is divided into two paths: one path directly enters the heat pump unit 101, and then enters the circulating hot water supply pipe 102 via the heat pump unit 101; the other path enters the heat exchanger 303 via the fifth valve F5. The hot water from the heat exchanger 303 enters the circulating hot water supply pipe 102 via the sixth valve F6. The hot water from the heat pump unit 101 also flows into the circulating hot water supply pipe 102, achieving simultaneous heating of the working oil waste heat and hot exhaust air waste heat of the air compressor 301. See details... Figure 3 .

[0034] During off-peak electricity hours or when rapid heat extraction is needed, the system can operate in a mode where waste heat from the exhaust fan and working oil is used to supply heat to the second user. In this mode: valves F1, F2, F3, and F4 are opened, while valves F5, F6, F7, and F8 are closed. The cold water from the first water tank 201 splits into two paths: one path enters the heat exchanger 303, and after heat exchange, flows through the hot water heating pipe 204 into the second water tank 202; the other path flows through the first branch pipe 401 (located at valve F3) into the heat pump unit 101, and after heat exchange, flows through the fourth valve F4 and the second branch pipe 402, converging into the hot water heating pipe 204. This achieves efficient heating. See details below. Figure 2 .

[0035] This invention can not only utilize the waste heat from the exhaust air of the air compressor 301 to heat the first user terminal 103, but also utilize the waste heat from the working oil of the air compressor 301 to directly heat the first user terminal 103, thereby improving the utilization rate of the waste heat from the working oil; it can also utilize the waste heat from the exhaust air of the air compressor 301 to heat domestic water and provide domestic hot water for the second user terminal, further improving the recovery and utilization rate of waste heat from the air compressor 301, achieving efficient energy utilization, reducing the consumption of electrical energy and fossil energy, and helping to reduce environmental pollution and lower the operating costs of enterprises.

[0036] Combination Figure 1 It is known that the water replenishment unit includes a softened water treatment pipe 501 connected to tap water and a third water tank 502 (which is a water replenishment tank). The softened water treatment pipe 501 is equipped with a softened water treatment device. The third water tank 502 is connected to the circulating hot water return pipe 104 through a water replenishment pipe 503, and a water replenishment pump group 504 is installed on the water replenishment pipe 503 to provide water replenishment power.

[0037] In actual installation, there are two (or more) sets of water supply pump 504, hot water supply pump 206, cold water pump 203 and circulation pump 105. Each pump set can be used as a backup to ensure the normal operation of the entire system.

[0038] As shown in the diagram, the bottom outlet of the second water tank 202 is connected to the cold water heating pipe 207 via a pipe equipped with a tenth valve F10. When the water temperature in the second water tank 202 drops to a certain level, the tenth valve F10 can be opened to reheat the water in the second water tank 202, ensuring the temperature of domestic hot water for the second user.

[0039] In actual installation, the makeup water pump set 504, hot water supply pump set 206, cold water pump set 203, and circulation pump set 105 use the same pump set. Taking the makeup water pump set 504 as an example: the makeup water pump set 504 includes a water pump, and a butterfly valve and a filter are installed on the inlet side of the water pump. A check valve and a butterfly valve are installed on its outlet side. See details... Figure 1 .

[0040] In actual installation, the circulating hot water return pipe 104 and the circulating hot water supply pipe 102 are connected by a pressure regulating branch, and a pressure regulating valve 106 is installed on the pressure regulating branch to balance the pressure between the inlet and outlet water; the first valve F1 to the eleventh valve F11 are all electric butterfly valves.

[0041] Finally, it should be emphasized that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the waste heat utilization rate of an air compressor, characterized in that: The method is to use a heat pump unit (101) to recover the waste heat of the exhaust air of the air compressor (301), and to use a heat exchanger (303) to recover the waste heat of the working oil of the air compressor. The waste heat of the exhaust air and the waste heat of the working oil are supplied to the first user end (103) through the first heating unit to provide heating or production hot water to the first user end. The waste heat of the exhaust air and the waste heat of the working oil are supplied to the second user end through the second heating unit to provide domestic hot water to the second user end. The first heating unit includes a circulation loop formed by sequentially connecting the heat pump unit (101), the circulating hot water supply pipe (102), the first user terminal (103), and the circulating hot water return pipe (104). The heat pump unit is an air source heat pump unit or an air source-water source composite heat pump unit. The hot air outlet of the air compressor (301) is located at the air inlet of the heat pump unit. The second heating unit includes a second user terminal, a first water tank (201) and a second water tank (202). The first water tank (201) is connected to the water inlet of the heat exchanger (303) through a cold water heating pipe (207). The water outlet of the heat exchanger (303) is connected to the second water tank (202) through a hot water heating pipe (204). The second water tank (202) is connected to the second user terminal through a hot water supply pipe (205). The first water tank is connected to the hot water return pipe and the tap water pipe of the second user terminal. The outlet end of the cold water heating pipe (207) is also connected to a first branch pipe (401), which is connected to the outlet end of the circulating hot water return pipe (104). The first branch pipe is equipped with a third valve (F3) and a fifth valve (F5) connected in parallel with the third valve. The inlet of the hot water heating pipe (204) is connected to the inlet end of the circulating hot water supply pipe (102) through a second branch pipe (402), and the second branch pipe (402) is equipped with a fourth valve (F4) and a sixth valve (F6) connected in parallel with the fourth valve. A hot water supply pump set (206) is installed on the hot water supply pipe (205), a cold water pump set (203) is installed on the cold water heating pipe (207), and a circulating pump set (105) is installed on the circulating hot water return pipe (104); an eleventh valve (F11) is installed at the outlet of the tap water pipe, and a ninth valve (F9) is installed at the inlet of the cold water heating pipe (207); A first valve (F1) is installed on the cold water heating pipe (207) located in front of the first branch pipe (401), and a second valve (F2) is installed on the hot water heating pipe (204) located behind the second branch pipe (402); an eighth valve (F8) is installed on the circulating hot water supply pipe (102), and a seventh valve (F7) is installed on the circulating hot water return pipe (104); The working condition where both exhaust waste heat and working oil waste heat are supplied to the first user end is as follows: When the second water tank (202) is full and the hot water temperature reaches 60℃, the heating of cold water is stopped, and the heat of the high-temperature working oil is used for the first user end (103) to meet the heat demand of the first user end (103), that is: the first valve (F1), the second valve (F2), the third valve (F3) and the fourth valve (F4) are closed, and the sixth valve (F6), the eighth valve (F8), the seventh valve (F7) and the fifth valve (F5) are opened, and the hot water return pipe is circulated. The outlet of (104) is divided into two paths. One path goes directly into the heat pump unit (101) and then into the circulating hot water supply pipeline (102) through the heat pump unit (101). The other path goes into the heat exchanger (303) through the fifth valve (F5). The hot water from the heat exchanger (303) goes into the circulating hot water supply pipeline (102) through the sixth valve (F6). The hot water from the heat pump unit (101) also flows into the circulating hot water supply pipeline (102), so as to achieve simultaneous heating of the working oil waste heat and hot exhaust waste heat of the air compressor (301). The working condition where exhaust waste heat and working oil waste heat are jointly supplied to the second user end is as follows: Open the first valve (F1), the second valve (F2), the third valve (F3) and the fourth valve (F4), and close the fifth valve (F5), the sixth valve (F6), the seventh valve (F7) and the eighth valve (F8). The cold water coming out of the first water tank (201) is divided into two paths. One path enters the heat exchanger (303), and after heat exchange, it enters the second water tank (202) through the hot water heating pipe (204). The other path enters the heat pump unit (101) through the first branch pipe (401) where the third valve (F3) is located, and after heat exchange, it merges into the hot water heating pipe (204) through the fourth valve (F4) and the second branch pipe (402).

2. The method for improving the waste heat utilization rate of an air compressor according to claim 1, characterized in that: The first heating unit is connected to the water supply unit. The water supply unit includes a softened water treatment pipe (501) connected to tap water and a third water tank (502). The softened water treatment pipe (501) is equipped with a softened water treatment device. The third water tank (502) is connected to the circulating hot water return pipe (104) through the water supply pipe. The water supply pipe is equipped with a water supply pump set (504).

3. The method for improving the waste heat utilization rate of an air compressor according to claim 2, characterized in that: The water replenishment pump group (504), hot water supply pump group (206), cold water pump group (203) and circulation pump group (105) are all in two or more groups.

4. The method for improving the waste heat utilization rate of an air compressor according to claim 1, characterized in that: The bottom outlet of the second water tank (202) is connected to the cold water heating pipe (207) via a pipe with a tenth valve (F10).

5. The method for improving the waste heat utilization rate of an air compressor according to claim 1, characterized in that: A pressure regulating branch with a pressure regulating valve (106) is provided between the circulating hot water supply pipe (102) and the circulating hot water return pipe (104).

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