A boiler energy-saving system

Abstract

This utility model relates to the field of boiler technology and discloses a boiler energy-saving system, including a boiler, a low-temperature water tank, a medium-temperature water tank, a high-temperature water tank, a gas-liquid heat exchange system, an inlet pipe, and an exhaust pipe. The gas-liquid heat exchange system includes a first heat exchanger and a second heat exchanger. Through the reasonable connection and optimization of the low-temperature, medium-temperature, and high-temperature water tanks, the water temperature is rapidly increased, improving the boiler's thermal efficiency while ensuring a stable rise in boiler water temperature, thereby reducing fuel consumption. By setting up the first and second heat exchangers, in conjunction with the medium-temperature and high-temperature water tanks, a two-stage counter-current heat exchange method is formed. This fully utilizes high-grade heat sources to improve the heat exchange efficiency of the boiler system, further enhancing energy-saving effects and solving the problem of low heat exchange efficiency and inability to improve heat recovery when using only a single-stage heat exchange method.

Description

Technical Field

[0001] This utility model relates to the field of boiler technology, and in particular to a boiler energy-saving system. Background Technology

[0002] Boilers, widely used thermal energy equipment in industrial and civil sectors, play a crucial role in the brewing industry. The brewing process requires a significant amount of heat energy to provide steam for various stages, including boiling and temperature control. However, traditional boiler systems often suffer from high energy consumption and low thermal efficiency, which not only increases production costs but also puts considerable pressure on the environment. Therefore, improving boiler thermal efficiency and reducing energy consumption has become an urgent technical challenge.

[0003] Boilers in the brewing industry typically require stable temperature control systems to ensure that water and steam temperatures are maintained within reasonable ranges during production. However, existing boiler energy-saving technologies focus primarily on improving thermal efficiency and do not adequately address the issue of temperature control stability.

[0004] Although some technologies improve heat exchange efficiency and stability by incorporating multiple water tanks and heat exchange systems, problems such as slow boiler start-up, unstable water temperature, and large fluctuations in liquid level still exist in practical applications. Therefore, how to fully utilize waste heat resources to improve thermal efficiency, ensure high energy efficiency, and guarantee stable temperature control has become a major challenge in current boiler system design. Utility Model Content

[0005] To address the aforementioned shortcomings, the purpose of this utility model is to propose a boiler energy-saving system that improves boiler thermal efficiency, shortens the time required for the boiler to reach stable operating conditions after cold start, and ensures temperature control stability, thereby meeting the high-efficiency and stable operation requirements in brewing production.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A boiler energy-saving system includes a boiler, a low-temperature water tank, a medium-temperature water tank, a high-temperature water tank, a gas-liquid heat exchange system, an inlet water pipe, and an exhaust pipe.

[0008] The water inlet pipe is connected to the low-temperature water tank. The bottom of the low-temperature water tank and the bottom of the medium-temperature water tank are connected through the water inlet pipe. The bottom of the medium-temperature water tank is not higher than the bottom of the low-temperature water tank. A medium-temperature water outlet is provided in the middle of the side of the medium-temperature water tank. The medium-temperature water outlet is connected to the high-temperature water tank through the water inlet pipe. The high-temperature water tank is connected to the boiler through the water inlet pipe.

[0009] The gas-liquid heat exchange system includes a first heat exchanger and a second heat exchanger. The two ends of the liquid channel of the first heat exchanger are connected to the medium-temperature water tank and the high-temperature water tank respectively through water inlet pipes. The two ends of the liquid channel of the second heat exchanger are connected to the high-temperature water tank and the boiler respectively through water inlet pipes. The exhaust pipe, the gas channel of the first heat exchanger, the gas channel of the second heat exchanger and the boiler are connected in sequence through an exhaust pipe.

[0010] Preferably, the system further includes a waste heat recovery heat exchanger and a waste heat circulation pump. The medium-temperature water tank is also provided with a circulation outlet and a circulation inlet. The circulation outlet is located on the side of the medium-temperature water tank, and the height of the circulation outlet is lower than that of the medium-temperature outlet. The circulation inlet is located on the top of the medium-temperature water tank. The waste heat recovery heat exchanger is provided with a low-temperature channel and a high-temperature channel. The inlet of the waste heat circulation pump is connected to the circulation outlet. The outlet of the waste heat circulation pump is connected to one end of the low-temperature channel. The other end of the low-temperature channel is connected to the circulation inlet. One end of the high-temperature channel is connected to the output port of the external waste heat supply pipeline. The other end of the high-temperature channel is connected to the return port of the external waste heat supply pipeline.

[0011] Preferably, it also includes an air preheater and an air inlet pipe. The air preheater is provided with a low-temperature air chamber and a high-temperature air chamber. One end of the low-temperature air chamber is connected to the air inlet pipe, and the other end of the low-temperature air chamber is connected to the boiler. One end of the high-temperature air chamber is connected to the exhaust pipe, and the other end of the high-temperature air chamber is connected to the boiler.

[0012] Preferably, the air preheater is a plate air preheater, and the low-temperature air chamber of the air preheater is located between the exhaust pipe and the gas channel of the gas-liquid heat exchange system.

[0013] Preferably, the system further includes a first water pump, a first flow regulating valve, and an overflow pipe. The inlet of the first water pump is connected to the medium-temperature water tank, and the outlet of the first water pump is connected to the high-temperature water tank. The first flow regulating valve is used to regulate the flow rate of liquid from the medium-temperature water tank into the high-temperature water tank, and the overflow pipe is used to return the liquid overflowing from the high-temperature water tank to the medium-temperature water tank.

[0014] Preferably, it also includes a water softener, the inlet of which is connected to the water inlet pipe, and the outlet of which is connected to the low-temperature water tank.

[0015] Preferably, the medium-temperature water tank, the high-temperature water tank, and the boiler are all equipped with thermometers.

[0016] Preferably, both the first heat exchanger and the second heat exchanger are plate heat exchangers.

[0017] Preferably, a second regulating valve and at least two third water pumps are provided between the high-temperature water tank and the boiler. The at least two third water pumps are connected in parallel. The inlet of the third water pump is connected to the high-temperature water tank, the outlet of the third water pump is connected to the second regulating valve, and the outlet of the second regulating valve is connected to the boiler.

[0018] Preferably, the system further includes a first backup pipeline, a second backup pipeline, and a second water pump. The first backup pipeline connects the water inlet pipe and the medium-temperature water tank. The inlet of the second water pump is connected to the bottom of the low-temperature water tank and the bottom of the medium-temperature water tank through the second backup pipeline. The outlet of the second water pump is connected to the inlet of the liquid channel of the gas-liquid heat exchange system through the second backup pipeline.

[0019] The technical solution provided by this utility model can include the following beneficial effects:

[0020] 1. By connecting the bottoms of the low-temperature and medium-temperature water tanks, the overall water storage capacity is increased, ensuring stable water flow. Simultaneously, since water density decreases with temperature and water is a poor conductor of heat, a temperature difference forms along the height of the water in the medium-temperature tank without external stirring or forced circulation. The water temperature gradually increases from the bottom to the top. The outlet of the medium-temperature tank is located in the middle of the side, allowing the warmer water from the upper part of the medium-temperature tank to preferentially enter the high-temperature tank under gravity. This structure solves the problems of slow initial water temperature rise during boiler startup when the overall water storage capacity is too large, slow boiler start-up in the early stages of operation, and prolonged inability to reach optimal operating conditions, resulting in low overall efficiency. Conversely, when the overall water storage capacity is too small, the liquid level and water temperature fluctuations in the boiler energy-saving system are too large and difficult to stabilize.

[0021] 2. By rationally connecting and optimizing the low-temperature, medium-temperature, and high-temperature water tanks, the water temperature can be rapidly increased, improving the boiler's thermal efficiency while ensuring a stable rise in boiler water temperature, thereby reducing fuel consumption. By setting up a first and second heat exchanger, in conjunction with the medium-temperature and high-temperature water tanks, a two-stage counter-current heat exchange method is formed. This fully utilizes high-grade heat sources to improve the heat exchange efficiency of the boiler system, further enhancing energy-saving effects and solving the problem of low heat exchange efficiency and inability to improve heat recovery when using only a single-stage heat exchange method.

[0022] 3. By using a waste heat recovery heat exchanger and a waste heat circulation pump, the water in the medium-temperature water tank is preheated with waste heat, reducing energy consumption and improving the overall thermal efficiency of the boiler system. At the same time, the design of the circulation outlet and circulation inlet positions allows the heated water to converge in the upper part of the medium-temperature water tank, forming a temperature gradient and further enhancing the comprehensive energy-saving effect of the boiler energy-saving system.

[0023] 4. An air preheater is used to recover flue gas from the boiler exhaust and heat the air about to enter the boiler, increasing the air temperature, reducing temperature fluctuations in the boiler furnace, and simultaneously reducing the boiler's fuel demand and energy consumption. The air preheater is placed at the end of the gas-liquid heat exchange system furthest from the boiler, using the high-grade heat from the boiler to heat the boiler feedwater, ensuring the boiler feedwater temperature is maintained.

[0024] 5. If one of the low-temperature water tanks or the medium-temperature water tanks or the first water pump fails, the first backup pipeline, the second backup pipeline, and the second water pump can be used in conjunction to ensure water intake for the boiler and avoid boiler shutdown caused by the failure.

[0025] 6. In the event of a malfunction in the gas-liquid heat exchange system or the high-temperature water tank, a third backup pipeline and a third water pump should be used to prevent the boiler from shutting down due to the malfunction. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of device connection according to one embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of a spare pipeline according to an embodiment of the present invention.

[0028] Figure 3 This is a diagram showing the device connections before the improvement.

[0029] The system includes: boiler 1, inlet pipe 101, exhaust pipe 102, air inlet pipe 103, low-temperature water tank 2, overflow pipe 201, first backup pipe 202, second backup pipe 203, third backup pipe 204, medium-temperature water tank 3, medium-temperature water outlet 301, circulating water outlet 302, circulating water inlet 303, high-temperature water tank 4, gas-liquid heat exchange system 5, first heat exchanger 51, second heat exchanger 52, waste heat recovery heat exchanger 6, low-temperature channel 601, high-temperature channel 602, waste heat circulation pump 61, air preheater 7, soft water device 8, second water pump 92, and third water pump 93. Detailed Implementation

[0030] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0031] In the description of this utility model, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. Furthermore, features defined with "first" and "second" may explicitly or implicitly include one or more of these features, used to distinguish and describe features, without any order or emphasis.

[0032] In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0034] The embodiments of this utility model are described below with reference to the accompanying drawings.

[0035] A boiler energy-saving system includes a boiler 1, a low-temperature water tank 2, a medium-temperature water tank 3, a high-temperature water tank 4, a gas-liquid heat exchange system 5, an inlet water pipe 101, and an exhaust pipe 102.

[0036] The water inlet pipe 101 is connected to the low-temperature water tank 2. The bottom of the low-temperature water tank 2 and the bottom of the medium-temperature water tank 3 are connected by a water inlet pipe. The bottom of the medium-temperature water tank 3 is not higher than the bottom of the low-temperature water tank 2. A medium-temperature water outlet 301 is provided in the middle of the side of the medium-temperature water tank 3. The medium-temperature water outlet 301 is connected to the high-temperature water tank 4 through a water inlet pipe. The high-temperature water tank 4 is connected to the boiler 1 through a water inlet pipe.

[0037] The gas-liquid heat exchange system 5 includes a first heat exchanger 51 and a second heat exchanger 52. The two ends of the liquid channel of the first heat exchanger 51 are connected to the medium-temperature water tank 3 and the high-temperature water tank 4 respectively through water inlet pipes. The two ends of the liquid channel of the second heat exchanger 52 are connected to the high-temperature water tank 4 and the boiler 1 respectively through water inlet pipes. The exhaust pipe 102, the gas channel of the first heat exchanger 51, the gas channel of the second heat exchanger 52 and the boiler 1 are connected in sequence through an exhaust pipe.

[0038] In a specific embodiment, the inlet pipe is used to supply water to boiler 1, the exhaust pipe is used to discharge boiler flue gas generated after combustion in boiler 1, and the gas-liquid heat exchange system 5 is used to exchange heat between the water in the inlet pipe and the boiler flue gas in the exhaust pipe. Water is injected through the inlet pipe 101 to raise the liquid level in the low-temperature water tank 2. Under the pressure provided by the liquid level difference, the water in the low-temperature water tank 2 enters the bottom of the medium-temperature water tank 3 from its bottom. When the liquid level in the medium-temperature water tank 3 is higher than the inlet pipe connected to its side center, the water enters the gas-liquid heat exchange system 5 from the side center of the medium-temperature water tank 3. The bottom connection between the low-temperature water tank 2 and the medium-temperature water tank 3 increases the overall water storage capacity and ensures stable water volume. Simultaneously, since the density of water decreases with higher temperatures and water is a poor conductor of heat, without external stirring or forced circulation, a temperature difference is formed along the height of the water in the medium-temperature water tank 3, with the water temperature gradually increasing from the bottom to the top. The outlet of the medium-temperature water tank 3 is located in the side center, and under gravity, the higher-temperature water in the upper part of the medium-temperature water tank 3 preferentially enters the high-temperature water tank 4. This structure addresses the issues of slow initial water temperature rise during boiler start-up when the overall water storage is too large, slow start-up of boiler 1 in the early stages of operation, inability to reach optimal operating conditions for a long time, and low overall efficiency; and the problem of excessive fluctuations in liquid level and water temperature in the boiler energy-saving system when the overall water storage is too small, making stable adjustment difficult.

[0039] By rationally connecting and optimizing the low-temperature water tank 2, the medium-temperature water tank 3, and the high-temperature water tank 4, the water temperature can be rapidly increased, thereby improving the thermal efficiency of boiler 1. At the same time, the water temperature of boiler 1 can be ensured to rise steadily, thereby reducing fuel consumption.

[0040] By setting up a first heat exchanger 51 and a second heat exchanger 52, and cooperating with a medium-temperature water tank 3 and a high-temperature water tank 4 to form a two-stage countercurrent heat exchange method, the heat exchange efficiency of the boiler 1 system is improved by making full use of the high-grade heat source, thereby further improving the energy-saving effect and solving the problem that the heat exchange efficiency is low and the heat recovery effect cannot be improved when only one-stage heat exchange method is used.

[0041] In one embodiment, the boiler energy-saving system uses only one heat exchanger, and the inlet water temperature of boiler 1 can only reach 60°C. After modification, by using the first heat exchanger 51 and the second heat exchanger 52 and adopting a counter-current heat exchange method, the inlet water temperature of boiler 1 can be increased to 90~95°C under the same inlet water volume.

[0042] Preferably, the system also includes a waste heat recovery heat exchanger 6 and a waste heat circulation pump 61. The medium-temperature water tank 3 is further provided with a circulation outlet 302 and a circulation inlet 303. The circulation outlet 302 is located on the side of the medium-temperature water tank 3, and the height of the circulation outlet 302 is lower than that of the medium-temperature outlet 301. The circulation inlet 303 is located at the top of the medium-temperature water tank 3. The waste heat recovery heat exchanger 6 is provided with a low-temperature channel 601 and a high-temperature channel 602. The inlet of the waste heat circulation pump 61 is connected to the circulation outlet 302, and the outlet of the waste heat circulation pump 61 is connected to one end of the low-temperature channel 601. The other end of the low-temperature channel 601 is connected to the circulation inlet 303. One end of the high-temperature channel 602 is connected to the output port of the external waste heat supply pipeline, and the other end of the high-temperature channel 602 is connected to the return port of the external waste heat supply pipeline.

[0043] In one embodiment, an external waste heat supply pipeline is connected to a heat pump system, using hot water produced in the heat pump system to heat the water in the medium-temperature water tank 3.

[0044] By using the waste heat recovery heat exchanger 6 and the waste heat circulation pump 61, the water in the medium-temperature water tank 3 is preheated with waste heat, reducing energy consumption and improving the overall thermal efficiency of the boiler 1 system. At the same time, the design of the positions of the circulation outlet 302 and the circulation inlet 303 allows the heated water to converge in the upper part of the medium-temperature water tank 3, forming a temperature gradient, which further enhances the comprehensive energy-saving effect of the boiler energy-saving system.

[0045] like Figure 3 As shown, before the modification, room temperature water was heated to 45°C in the medium temperature water tank 3 by the heat recovery heat exchanger 6, and then heated to 60°C by the gas-liquid heat exchange system 5 before entering the boiler 1. Although the waste heat was recovered and utilized, the overall thermal efficiency was not high, and the water temperature was prone to fluctuation, affecting the stability of the boiler 1.

[0046] like Figure 1 As shown, after the modification, the ambient temperature water at the bottom of the medium-temperature water tank 3, through the use of the waste heat recovery heat exchanger 6 and the waste heat circulation pump 61, and with the setting of the circulation water inlet 303 and the circulation water outlet 302, makes the water temperature flowing out of the medium-temperature water outlet 301 reach 45℃, and then is heated to 80℃ by the first heat exchanger 51 before entering the high-temperature water tank 4, and finally further heated to 90~95℃ by the second heat exchanger 52 before entering the boiler 1.

[0047] Preferably, it also includes an air preheater 7 and an air inlet pipe 103. The air preheater 7 is provided with a low-temperature air chamber and a high-temperature air chamber. One end of the low-temperature air chamber is connected to the air inlet pipe 103, and the other end of the low-temperature air chamber is connected to the boiler 1. One end of the high-temperature air chamber is connected to the exhaust pipe 102, and the other end of the high-temperature air chamber is connected to the boiler 1.

[0048] In a specific embodiment, the air intake pipe 103 is used to supply air to the boiler 1, and the air preheater 7 is used to recover the flue gas in the boiler 1 exhaust to heat the air about to enter the boiler 1, increase the air temperature, reduce the temperature fluctuation of the boiler 1 furnace, and at the same time reduce the boiler 1's fuel demand and reduce energy consumption.

[0049] Preferably, the air preheater 7 is a plate-type air preheater 7, and the low-temperature air chamber of the air preheater 7 is disposed between the exhaust pipe 102 and the gas channel of the gas-liquid heat exchange system 5.

[0050] The air preheater 7 is placed at the end of the gas-liquid heat exchange system 5 away from the boiler 1, so that the high-grade heat source from the boiler 1 is used to heat the water inlet of the boiler 1, thus ensuring the water inlet temperature of the boiler 1.

[0051] Preferably, it also includes a first water pump, a first flow regulating valve, and an overflow pipe 201. The inlet of the first water pump is connected to the medium-temperature water tank 3, and the outlet of the first water pump is connected to the high-temperature water tank 4. The first flow regulating valve is used to regulate the flow rate of liquid from the medium-temperature water tank 3 into the high-temperature water tank 4. The overflow pipe 201 is used to return the liquid overflowing from the high-temperature water tank 4 to the medium-temperature water tank 3.

[0052] By using the first water pump, the first regulating valve and the overflow pipe 201 together, the water flow and water level of each tank can be precisely controlled, ensuring the efficient and stable operation of the system.

[0053] Preferably, it also includes a water softener 8, the inlet of which is connected to the water inlet pipe 101, and the outlet of which is connected to the low-temperature water tank 2.

[0054] like Figure 2 The tap water is softened by the water softener 8 to prevent scale buildup inside the boiler energy-saving system, which would affect the overall heat exchange efficiency.

[0055] Preferably, the medium-temperature water tank 3, the high-temperature water tank 4, and the boiler 1 are all equipped with thermometers.

[0056] By observing the water temperature at various points in the boiler energy-saving system in real time using a thermometer, it is easy to monitor the operation of the boiler energy-saving system.

[0057] Preferably, both the first heat exchanger 51 and the second heat exchanger 52 are plate heat exchangers.

[0058] By increasing the heat exchange area through plate heat exchangers, heat exchange efficiency can be increased, thereby improving the recovery efficiency of boiler energy-saving systems.

[0059] Preferably, a second regulating valve and at least two third water pumps 93 are provided between the high-temperature water tank 4 and the boiler 1. The at least two third water pumps are connected in parallel. The inlet of the third water pump 93 is connected to the high-temperature water tank 4, the outlet of the third water pump is connected to the second regulating valve, and the outlet of the second regulating valve is connected to the boiler 1.

[0060] The water flow rate is adjusted by the second regulating valve to control the water intake of boiler 1. In a specific embodiment, two third water pumps 93 are set up with one on and one on standby to ensure the stable operation of the system.

[0061] Preferably, it also includes a first backup pipeline 202, a second backup pipeline 203, and a second water pump 92. The first backup pipeline 202 connects the water inlet pipe 101 and the medium-temperature water tank 3. The inlet of the second water pump 92 is connected to the bottom of the low-temperature water tank 2 and the bottom of the medium-temperature water tank 3 through the second backup pipeline 203. The outlet of the second water pump 92 is connected to the inlet of the liquid channel of the gas-liquid heat exchange system 5 through the second backup pipeline 203.

[0062] like Figure 2 As shown, with this structure, if one of the low-temperature water tank 2 and the medium-temperature water tank 3 or the first water pump fails, the first backup pipeline 202, the second backup pipeline and the second water pump 92 can be used to ensure the water intake of the boiler 1, thus avoiding the boiler 1 from shutting down due to the failure.

[0063] Preferably, it also includes a third backup pipeline 204, the inlet of the third water pump 93 is also connected to the bottom of the low temperature water tank 2 and the bottom of the medium temperature water tank 3 through the third backup pipeline 204, and the outlet of the third water pump 93 is connected to the boiler 1.

[0064] In the event of a malfunction in the gas-liquid heat exchange system 5 or the high-temperature water tank 4, the third backup pipeline 204, in conjunction with the third water pump 93, will prevent the boiler 1 from shutting down.

[0065] Other configurations and operations according to the embodiments of this utility model are known to those skilled in the art and will not be described in detail here.

[0066] In this specification, the terms "embodiment," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0067] Although embodiments of the present 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 present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A boiler energy-saving system, characterized in that: This includes boilers, low-temperature water tanks, medium-temperature water tanks, high-temperature water tanks, gas-liquid heat exchange systems, inlet pipes, and exhaust pipes; The water inlet pipe is connected to the low-temperature water tank. The bottom of the low-temperature water tank and the bottom of the medium-temperature water tank are connected through the water inlet pipe. The bottom of the medium-temperature water tank is not higher than the bottom of the low-temperature water tank. A medium-temperature water outlet is provided in the middle of the side of the medium-temperature water tank. The medium-temperature water outlet is connected to the high-temperature water tank through the water inlet pipe. The high-temperature water tank is connected to the boiler through the water inlet pipe. The gas-liquid heat exchange system includes a first heat exchanger and a second heat exchanger. The two ends of the liquid channel of the first heat exchanger are connected to the medium-temperature water tank and the high-temperature water tank respectively through water inlet pipes. The two ends of the liquid channel of the second heat exchanger are connected to the high-temperature water tank and the boiler respectively through water inlet pipes. The exhaust pipe, the gas channel of the first heat exchanger, the gas channel of the second heat exchanger and the boiler are connected in sequence through an exhaust pipe.

2. The boiler energy-saving system according to claim 1, characterized in that: It also includes a waste heat recovery heat exchanger and a waste heat circulation pump. The medium-temperature water tank is also provided with a circulation outlet and a circulation inlet. The circulation outlet is located on the side of the medium-temperature water tank, and the height of the circulation outlet is lower than that of the medium-temperature outlet. The circulation inlet is located on the top of the medium-temperature water tank. The waste heat recovery heat exchanger is provided with a low-temperature channel and a high-temperature channel. The inlet of the waste heat circulation pump is connected to the circulation outlet. The outlet of the waste heat circulation pump is connected to one end of the low-temperature channel. The other end of the low-temperature channel is connected to the circulation inlet. One end of the high-temperature channel is connected to the output port of the external waste heat supply pipeline. The other end of the high-temperature channel is connected to the return port of the external waste heat supply pipeline.

3. The boiler energy-saving system according to claim 1, characterized in that: It also includes an air preheater and an air inlet pipe. The air preheater is provided with a low-temperature air chamber and a high-temperature air chamber. One end of the low-temperature air chamber is connected to the air inlet pipe, and the other end of the low-temperature air chamber is connected to the boiler. One end of the high-temperature air chamber is connected to the exhaust pipe, and the other end of the high-temperature air chamber is connected to the boiler.

4. A boiler energy-saving system according to claim 3, characterized in that: The air preheater is a plate-type air preheater, and the low-temperature air chamber of the air preheater is located between the exhaust pipe and the gas channel of the gas-liquid heat exchange system.

5. A boiler energy-saving system according to claim 1, characterized in that: It also includes a first water pump, a first flow regulating valve, and an overflow pipe. The inlet of the first water pump is connected to the medium-temperature water tank, and the outlet of the first water pump is connected to the high-temperature water tank. The first flow regulating valve is used to regulate the flow rate of liquid from the medium-temperature water tank into the high-temperature water tank, and the overflow pipe is used to return the liquid overflowing from the high-temperature water tank to the medium-temperature water tank.

6. A boiler energy-saving system according to claim 1, characterized in that: It also includes a water softener, the inlet of which is connected to the water inlet pipe, and the outlet of which is connected to the low-temperature water tank.

7. A boiler energy-saving system according to claim 1, characterized in that: The medium-temperature water tank, the high-temperature water tank, and the boiler are all equipped with temperature gauges.

8. A boiler energy-saving system according to claim 1, characterized in that: Both the first heat exchanger and the second heat exchanger are plate heat exchangers.

9. A boiler energy-saving system according to claim 1, characterized in that: A second regulating valve and at least two third water pumps are provided between the high-temperature water tank and the boiler. The at least two third water pumps are connected in parallel. The inlet of the third water pump is connected to the high-temperature water tank, the outlet of the third water pump is connected to the second regulating valve, and the outlet of the second regulating valve is connected to the boiler.

10. The boiler energy-saving system according to claim 1, characterized in that: It also includes a first backup pipeline, a second backup pipeline, and a second water pump. The first backup pipeline connects the water inlet pipe and the medium-temperature water tank. The inlet of the second water pump is connected to the bottom of the low-temperature water tank and the bottom of the medium-temperature water tank through the second backup pipeline. The outlet of the second water pump is connected to the inlet of the liquid channel of the gas-liquid heat exchange system through the second backup pipeline.

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