A self-coupling utilization system for low-grade waste heat from gas-fired steam boilers

Abstract

The present invention provides a self-coupling system for utilizing low-grade waste heat from a gas-fired steam boiler, comprising a water tank, a flue gas energy-saving heat exchanger, a deaerator, an electric heat pump device, a gas-fired steam boiler, and a spray heat exchanger. The water tank is used to inject softened water into the system. The exhaust gas from the gas-fired steam boiler sequentially heats the softened water and intermediate water. The heated softened water enters the deaerator and then enters the gas-fired steam boiler's water supply system. The intermediate water is heated by heat exchange in the spray heat exchanger, then passes through an intermediate water inlet pipe into the electric heat pump device to release heat and cool down. The self-coupling system for utilizing low-grade waste heat from a gas-fired steam boiler, without changing the existing water supply system, utilizes low-grade waste heat self-coupling technology to achieve efficient heat exchange between flue gas and intermediate water, fully reducing flue gas temperature and gradually increasing boiler feed water temperature. Simultaneously, secondary recovery of flue gas waste heat provides heat replenishment and capacity expansion, reducing boiler gas consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving and environmentally friendly heating, and in particular to a self-coupling utilization system for low-grade waste heat of a gas-fired steam boiler. Background Art

[0002] Natural gas is primarily composed of methane (CH4), and its combustion products contain 15-17% water vapor, which condenses at around 55°C. The latent heat of vaporization of water vapor accounts for approximately 11% of the gas's lower calorific value. The curve of natural gas utilization efficiency as a function of flue gas temperature at varying excess air coefficients shows that the lower the exhaust gas temperature, the higher the gas utilization efficiency. When the temperature is below the dew point of water vapor in the flue gas, water vapor condenses in large quantities, releasing latent heat of vaporization, and natural gas utilization efficiency increases dramatically. Therefore, the most important factor in recovering flue gas waste heat is the latent heat of vaporization of water vapor in the flue gas. The lower the exhaust gas temperature, the more waste heat can be recovered.

[0003] Under normal circumstances, the exhaust gas temperature of gas boilers is generally between 120℃ and 180℃. In general, for every 10℃ reduction in exhaust gas temperature, the loss of flue gas waste heat resources is reduced by about 1%, which correspondingly saves 2% of energy consumption and has significant economic benefits.

[0004] For gas boilers, a partition-type heat exchanger is generally used to preheat the air and heat the boiler return water to improve gas utilization efficiency. However, the low air preheating capacity and high boiler return water temperature prevent the boiler exhaust temperature from being reduced to a very low level. Existing methods use flue gas waste heat recovery devices to recover the waste heat from steam boiler exhaust and circulate and heat the softened water in the boiler softening water tank. However, as the boiler operates, this continuous circulating heating continuously increases the overall temperature of the softened water in the softening water tank, resulting in a continuous increase in the softened water temperature, which affects the reduction of the flue gas temperature. This reduces the flue gas waste heat recovery effect and makes it impossible to fully utilize the heat in the exhaust system. Summary of the Invention

[0005] In view of this, the present invention aims to propose a gas steam boiler low-grade waste heat self-coupling utilization system to solve the problem that the flue gas waste heat recovery effect of the existing gas steam boiler system cannot be fully utilized in the heat of the exhaust system.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A self-coupling utilization system for low-grade waste heat of a gas-fired steam boiler comprises a water tank, a flue gas energy-saving heat exchanger, a deaerator, an electric heat pump device, a gas-fired steam boiler and a spray heat exchanger. The water tank is used to inject softened water into the system. The exhaust smoke of the gas-fired steam boiler passes through the flue gas energy-saving heat exchanger and the spray heat exchanger for cooling in sequence, heating the softened water and intermediate water respectively. The heated softened water enters the deaerator and then enters the water supply system of the gas-fired steam boiler. The intermediate water is heated by heat exchange in the spray heat exchanger and then enters the electric heat pump device through the intermediate water inlet pipe to release heat and cool down. The cooled intermediate water is circulated to the spray heat exchanger again to absorb the waste heat of the flue gas.

[0008] Furthermore, it also includes an intermediate water heat exchanger. The boiler feed water flowing out of the deaerator flows to the intermediate water heat exchanger through the deaerator outlet pipe, and the heated boiler feed water enters the electric heat pump device for heating through the hot water outlet heat exchanger pipe; the intermediate water cooled in the electric heat pump device flows to the intermediate water heat exchanger through the intermediate water inlet heat exchanger pipe, and the intermediate water after heat exchange in the intermediate water heat exchanger flows to the spray heat exchanger through the intermediate water inlet spray tower pipe.

[0009] Furthermore, the water tank, flue gas energy-saving heat exchanger, deaerator, intermediate water heat exchanger, spray heat exchanger, electric heat pump device and gas steam boiler are divided into a softened water circulation, boiler feed water pipeline, intermediate water circulation and gas flue gas pipeline structure through pipelines, wherein:

[0010] The softened water cycle includes a water tank, which serves as the water source for the entire system. Softened water enters the system from the water tank. After absorbing heat from the flue gas in the flue gas energy-saving heat exchanger and heating up, the softened water in the water tank is combined with the steam flowing out of the gas-fired steam boiler through the boiler steam outlet pipe and the steam inlet pipe in the deaerator.

[0011] Boiler feed water pipeline, the merged water in the deaerator flows through the deaerator outlet pipe into the intermediate water heat exchanger, absorbs heat and enters the electric heat pump device, the softened water is heated again by the electric heat pump device and then enters the gas steam boiler, and the steam generated by the gas steam boiler during combustion and heating is discharged through the boiler steam outlet pipeline and steam inlet pipeline;

[0012] The intermediate water circulates. The intermediate water enters the spray heat exchanger to absorb the heat of the flue gas discharged by the flue gas energy-saving heat exchanger and heats up. The heated intermediate water enters the electric heat pump device to release heat as a low-temperature heat source. The heat is transferred to the boiler feed water through the electric heat pump device. The cooled intermediate water enters the intermediate water heat exchanger again to exchange heat with the boiler feed water. After cooling, it enters the spray heat exchanger again to absorb heat.

[0013] In the gas flue gas pipeline, the gas is burned in the gas steam boiler through the gas inlet pipe to generate flue gas, which is then discharged after heat exchange through the flue gas energy-saving heat exchanger and the spray heat exchanger.

[0014] Furthermore, in the softened water circulation, the softened water absorbs flue gas heat and heats up in the flue gas energy-saving heat exchanger, then returns to the water tank and flows to the deaerator. A water supply port is provided on the water tank, and water is supplied to the water tank through a water supply pipe.

[0015] Furthermore, the softened water flowing out of the water tank passes through the water supply pipeline of the water pump, one route is transported to the flue gas energy-saving heat exchanger through the water inlet pipe of the economizer to absorb the heat of the flue gas, and then returns to the water tank through the water outlet pipe of the economizer, and the other route flows to the deaerator through the water supply pipeline of the water pump.

[0016] Furthermore, a water supply pump is provided on the water supply pipeline of the water supply pump. Two water supply pumps are provided, which are respectively provided on the water inlet pipe of the economizer and the water supply pipeline of the water supply pump.

[0017] Furthermore, an intermediate water pump is provided on the intermediate water inlet pipe of the electric heat pump.

[0018] Furthermore, the gas steam boiler is connected to the flue gas energy-saving heat exchanger through the boiler exhaust pipe, and the flue gas energy-saving heat exchanger discharges the flue gas to the spray heat exchanger through the spray tower flue gas inlet pipe, and the flue gas is discharged after heat exchange in the spray heat exchanger.

[0019] Furthermore, the intermediate water exchanges heat with the flue gas in a countercurrent manner in the spray heat exchanger.

[0020] Furthermore, it is applied to factory energy stations and community heat exchange stations that use gas steam boilers for heating.

[0021] Compared with the existing technology, the low-grade waste heat self-coupling utilization system of the gas-fired steam boiler described in the present invention has the following advantages:

[0022] (1) The low-grade waste heat self-coupling utilization system of the gas-fired steam boiler described in the present invention is that the exhaust gas of the gas-fired steam boiler is cooled in turn by the flue gas energy-saving heat exchanger and the spray heat exchanger, and softened water and intermediate water are heated respectively. The softened water is heated in the flue gas energy-saving heat exchanger and then enters the deaerator. The boiler feed water coming out of the deaerator is heated by the electric heat pump device after absorbing heat and then enters the gas-fired steam boiler through the boiler water inlet pipe. The advantage of the electric heat pump's strong ability to recover low-temperature waste heat is utilized to fully reduce the temperature of the intermediate water and improve the utilization of flue gas waste heat.

[0023] (2) The low-grade waste heat self-coupling utilization system of the gas-fired steam boiler described in the present invention adopts the low-grade waste heat self-coupling utilization technology without changing the original water supply system, so as to realize the efficient heat exchange between the flue gas and the intermediate water, fully reduce the flue gas temperature, and gradually increase the boiler feed water temperature. At the same time, the waste heat of the gas flue gas is recovered at the second level to play the role of heat supplement and capacity expansion, reduce the gas consumption of the boiler, save energy and protect the environment, and achieve comprehensive energy utilization.

[0024] (3) The low-grade waste heat self-coupling utilization system of the gas-fired steam boiler described in the present invention adopts a high-efficiency electric heat pump, a high-efficiency intermediate water heat exchanger, and a utilization control system to fully utilize the flue gas heat and significantly reduce the flue gas temperature; increase the boiler feed water temperature, realize efficient heat exchange between the intermediate water and the boiler feed water, effectively reduce the irreversible loss of heat exchange, solve the problem that the softened water temperature of the gas-fired steam boiler system continues to rise as the operating time increases, affecting the reduction of the flue gas temperature, and realize the continuous utilization of the flue gas waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 This is a structural diagram of a gas-fired steam boiler low-grade waste heat self-coupling utilization system according to an embodiment of the present invention;

[0027] Description of reference numerals:

[0028] 1-Water tank; 2-Water supply pipeline of water pump; 3-Water supply pump; 4-Water supply pipeline of water pump; 5-Deaerator; 6-Steam inlet pipeline; 7-Spray tower flue gas inlet pipeline; 8-Spray heat exchanger; 9-Flue gas energy-saving heat exchanger; 10-Boiler exhaust pipeline; 11-Boiler steam outlet pipeline; 12-Intermediate water pump; 13-Gas steam boiler; 14-Gas inlet pipeline; 15-Intermediate water inlet pipeline for electric heat pump; 16-Intermediate water inlet pipeline for heat exchanger; 17-Intermediate water inlet pipeline for spray tower; 18-Intermediate water heat exchanger; 19-Electric heat pump device; 20-Deaerator outlet pipeline; 21-Hot water outlet pipeline for heat exchanger; 22-Boiler inlet pipeline; 23-Economizer outlet pipeline; 24-Economizer inlet pipeline; 25-Water supply pipeline. DETAILED DESCRIPTION

[0029] In order to make the technical means, objectives and effects of the present invention easier to understand, embodiments of the present invention are described in detail below with reference to specific figures.

[0030] It should be noted that all terms used in the present invention to indicate direction and position, such as "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "lateral", "longitudinal", "center", etc., are only used to explain the relative position relationship and connection status between the components in a certain specific state (as shown in the accompanying drawings). They are only for the convenience of describing the present invention, and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0031] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical connections; direct connections or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0032] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses 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 any one or more embodiments or examples.

[0033] Example 1

[0034] like Figure 1 As shown, the present invention discloses a self-coupling utilization system for low-grade waste heat of a gas-fired steam boiler, comprising a water tank 1, a flue gas energy-saving heat exchanger 9, a deaerator 5, an electric heat pump device 19, a gas-fired steam boiler 13, and a spray heat exchanger 8. The water tank 1 is used to inject softened water into the system. The exhaust smoke of the gas-fired steam boiler 13 is cooled in turn through the flue gas energy-saving heat exchanger 9 and the spray heat exchanger 8, heating the softened water and the intermediate water respectively. The heated softened water enters the deaerator 5 and then enters the water supply system of the gas-fired steam boiler 13. The intermediate water is heated by heat exchange in the spray heat exchanger 8 and then released through the electric heat pump device 19 for cooling. The cooled intermediate water is circulated to the spray heat exchanger 8 again to absorb the waste heat of the flue gas.

[0035] The gas-fired steam boiler low-grade waste heat self-coupling utilization system described in the present application is that the exhaust gas of the gas-fired steam boiler 13 is cooled in turn through the flue gas energy-saving heat exchanger 9 and the spray heat exchanger 8, and softened water and intermediate water are heated respectively. The softened water is heated in the flue gas energy-saving heat exchanger 9 and then enters the deaerator 5. The boiler feed water coming out of the deaerator 5 absorbs heat and is heated by the electric heat pump device 19, and then enters the gas-fired steam boiler 13 through the boiler water inlet pipe 22. The advantage of the electric heat pump's strong ability to recover low-temperature waste heat is utilized to fully reduce the temperature of the intermediate water and improve the utilization of flue gas waste heat.

[0036] The gas-fired steam boiler low-grade waste heat self-coupling utilization system described in the present application deeply couples and utilizes the gas-fired steam boiler 13, the electric heat pump device 19, and the heat exchanger. The intermediate water enters in reverse series, and the feed water of the gas-fired steam boiler 13 is heated and supplied in series step by step. The heat is efficiently matched and transferred, thereby realizing deep utilization of flue gas heat and improving the comprehensive utilization of energy.

[0037] The gas-fired steam boiler low-grade waste heat self-coupling utilization system described in the present application also includes an intermediate water heat exchanger 18. The boiler feed water flowing out of the deaerator 5 flows to the intermediate water heat exchanger 18 through the deaerator outlet pipe 20. The heated boiler feed water enters the electric heat pump device 19 through the hot water outlet heat exchanger pipe 21 for heating; the intermediate water cooled in the electric heat pump device 19 flows to the intermediate water heat exchanger 18 through the intermediate water inlet heat exchanger pipe 16. The intermediate water after heat exchange in the intermediate water heat exchanger 18 flows to the spray heat exchanger 8 through the intermediate water inlet spray tower pipe 17.

[0038] This arrangement enables the boiler feed water flowing out of the deaerator 5 to pass through the intermediate water heat exchanger 18 and the electric heat pump device 19 in sequence, to be heated step by step, and then enter the gas steam boiler 13. After the intermediate water is heated by the waste heat of the hand washing flue gas, it is cooled by heat exchange through the electric heat pump device 19 and the intermediate water heat exchanger 18 in sequence, thereby making full use of the flue gas heat, increasing the boiler feed water temperature, realizing efficient heat exchange between the intermediate water and the boiler feed water, effectively reducing the irreversible loss of heat exchange, and realizing the continuous utilization of the waste heat of the flue gas.

[0039] The gas-fired steam boiler low-grade waste heat self-coupling utilization system of the present invention comprises a water tank 1, a flue gas energy-saving heat exchanger 9, a deaerator 5, an intermediate water heat exchanger 18, a spray heat exchanger 8, an electric heat pump device 19, and a gas-fired steam boiler 13. The system is divided into a softened water circulation, a boiler feed water pipeline, an intermediate water circulation, and a gas flue gas pipeline structure through pipelines, wherein:

[0040] The softened water cycle includes a water tank 1, which serves as the water source for the entire system. Softened water enters the system from the water tank 1. After absorbing heat from the flue gas in the flue gas energy-saving heat exchanger 9 and heating up, the softened water is combined with steam from the gas-fired steam boiler 13 through the boiler steam outlet pipe 11 and the steam inlet pipe 6 in the deaerator 5.

[0041] The combined water in the deaerator 5 flows through the deaerator outlet pipe 20 into the intermediate water heat exchanger 18, absorbs heat, and then enters the electric heat pump device 19. The softened water is heated again by the electric heat pump device 19 and then enters the gas steam boiler 13. The steam generated by the gas steam boiler 13 during combustion and heating is discharged through the boiler steam outlet pipe 11 and the steam inlet pipe 6.

[0042] The intermediate water circulates. The intermediate water enters the spray heat exchanger 8 to absorb the heat of the flue gas discharged by the flue gas energy-saving heat exchanger 9 and heats up. The heated intermediate water enters the electric heat pump device 19 to release heat as a low-temperature heat source. The heat is transferred to the boiler feed water through the electric heat pump device 19. The cooled intermediate water enters the intermediate water heat exchanger 18 again to exchange heat with the boiler feed water. After cooling, it enters the spray heat exchanger 8 again to absorb heat.

[0043] In the gas flue gas pipeline, the gas is burned in the gas steam boiler 13 through the gas inlet pipe 14 to generate flue gas, which is then discharged after heat exchange through the flue gas energy-saving heat exchanger 9 and the spray heat exchanger 8.

[0044] The low-grade waste heat self-coupling utilization system of the gas steam boiler described in this application is based on the principle of "energy cascade utilization" and jointly adopts electric-driven heat pump technology, flue gas deep waste heat utilization heat exchange technology and other methods to meet the needs of users, and fully utilizes the advantages of electric heat pumps such as flexible adjustment, wide working range and high efficiency. The flue gas undergoes two-stage heat exchange to fully reduce the exhaust gas temperature. The electric heat pump device 19 utilizes the advantage of the electric heat pump's strong ability to recover low-temperature waste heat to fully reduce the temperature of the intermediate water. Through this coupling structure, the system realizes energy transfer and heat recovery between different media, so that the waste heat of the gas steam boiler can be fully utilized, thereby improving the overall energy efficiency of the system.

[0045] The low-grade waste heat self-coupling utilization system of the gas steam boiler described in this application can fully reduce the exhaust gas temperature and the intermediate water return temperature, realize the transfer of heat energy with a large temperature difference between the flue gas and the intermediate water, and at the same time increase the boiler feed water temperature and reduce the boiler gas consumption.

[0046] As a preferred example of the present invention, in the softened water circulation, the softened water absorbs the heat of the flue gas and heats up in the flue gas energy-saving heat exchanger 9, then returns to the water tank 1 and flows to the deaerator 5. A water supply port is provided on the water tank 1, and water is supplied to the water tank 1 through the water supply pipe 25.

[0047] This arrangement allows the softened water in the water tank 1 to always maintain a relatively stable temperature state, providing a stable softened water supply and improving the reliability of the gas-fired steam boiler low-grade waste heat self-coupling utilization system of the present invention.

[0048] As a preferred example of the present invention, the softened water flowing out of the water tank 1 passes through the water supply pipe 2 of the water pump, and is transported to the flue gas energy-saving heat exchanger 9 through the economizer water inlet pipe 24 to absorb the flue gas heat, and then returns to the water tank 1 through the economizer water outlet pipe 23, and the other way flows to the deaerator 5 through the water supply pipe 4 of the water pump.

[0049] As a preferred example of the present application, a water supply pump 3 is provided on the water supply pipeline 2 .

[0050] As an example of the present application, two water supply pumps 3 are provided, which are respectively provided on two pipelines of the water supply pipeline 2 of the water supply pump.

[0051] This arrangement ensures the reliability of water inflow from the water tank 1 into the flue gas energy-saving heat exchanger 9 and the deaerator 5, and provides a stable water inlet pressure, thereby ensuring the normal operation of the gas-steam boiler low-grade waste heat self-coupling utilization system of the present invention and improving its working effect.

[0052] As a preferred example of the present invention, an intermediate water pump 12 is provided on the intermediate water inlet electric heat pump pipe 15. This arrangement further ensures the reliability of the intermediate water supplying water to the electric heat pump device 19 to achieve heat transfer after absorbing heat, and fully realizes the heat balance and utilization of each fluid.

[0053] As a preferred example of the present invention, the gas steam boiler 13 is connected to the flue gas energy-saving heat exchanger 9 through the boiler exhaust pipe 10. The flue gas energy-saving heat exchanger 9 discharges the flue gas to the spray heat exchanger 8 through the spray tower flue gas inlet pipe 7. The flue gas is discharged after heat exchange in the spray heat exchanger 8.

[0054] This arrangement enables the low-grade waste heat self-coupling utilization system of the gas-fired steam boiler of the present invention to heat and combust the flue gas generated in the gas-fired steam boiler 13, release heat and cool it down in turn through the flue gas energy-saving heat exchanger 9 and the spray heat exchanger 8, respectively heating softened water and intermediate water, thereby realizing the transfer and utilization of the waste heat of the boiler flue gas and fully realizing the heat balance and utilization of each fluid.

[0055] As a preferred example of the present invention, the intermediate water exchanges heat with the flue gas in a countercurrent manner in the spray heat exchanger 8 .

[0056] This arrangement improves the reliability of the intermediate water absorbing the waste heat of the flue gas in the spray heat exchanger 8 and reduces the irreversible loss of heat exchange.

[0057] As a preferred example of the present invention, the low-grade waste heat self-coupling utilization system of a gas-fired steam boiler described in the present invention can be applied to places where gas-fired steam boilers are used for heating, such as factory energy stations and community heat exchange stations.

[0058] In addition, the gas steam boiler 13 and the electric heat pump device 19 in the low-grade waste heat self-coupling utilization system of the gas steam boiler described in the present invention respectively operate in accordance with the external heating demand and load as boundary conditions, and the internal heat exchange and medium circulation of the system are reasonably designed to realize the coupled operation of each module in the system.

[0059] The number and power of the electric heat pump device 19, the intermediate water heat exchanger 18, and the spray heat exchanger 8 are determined according to the heating demand.

[0060] This application sets up a gas steam boiler low-grade waste heat self-coupling utilization system with an electric heat pump device 19, a flue gas energy-saving heat exchanger 9, a spray heat exchanger 8, an intermediate water heat exchanger 18, a circulating water pump (intermediate water pump 12), and a feed water pump 3 as the core, adopts a high-efficiency electric heat pump, a high-efficiency intermediate water heat exchanger, and a utilization control system to fully utilize the flue gas heat and significantly reduce the flue gas temperature; increase the boiler feed water temperature, realize efficient heat exchange between intermediate water and boiler feed water, effectively reduce the irreversible loss of heat exchange, solve the problem that the softened water temperature continues to rise as the gas steam boiler system operates for a longer time, affecting the reduction of flue gas temperature, and realize the continuous utilization of flue gas waste heat.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A gas-fired steam boiler low-grade waste heat self-coupling utilization system, characterized in that: The system comprises a water tank (1), a flue gas energy-saving heat exchanger (9), a deaerator (5), an electric heat pump device (19), a gas steam boiler (13) and a spray heat exchanger (8), wherein the water tank (1) is used to inject softened water into the system, and the exhaust smoke of the gas steam boiler (13) is cooled by the flue gas energy-saving heat exchanger (9) and the spray heat exchanger (8) in sequence, and the softened water and the intermediate water are heated respectively. The heated softened water enters the deaerator (5) and then enters the water supply system of the gas steam boiler (13). The intermediate water is heated by heat exchange in the spray heat exchanger (8), and then enters the electric heat pump device (19) through the intermediate water inlet electric heat pump pipe (15) to release heat and cool down. The cooled intermediate water is circulated to the spray heat exchanger (8) again to absorb the waste heat of the flue gas. The gas-fired steam boiler low-grade waste heat self-coupling utilization system further comprises an intermediate water heat exchanger (18), wherein the boiler feed water flowing out of the deaerator (5) flows to the intermediate water heat exchanger (18) through the deaerator outlet pipe (20), and the heated boiler feed water enters the electric heat pump device (19) through the hot water outlet heat exchanger pipe (21) for heating; the intermediate water cooled in the electric heat pump device (19) flows to the intermediate water heat exchanger (18) through the intermediate water inlet heat exchanger pipe (16), and the intermediate water after heat exchange in the intermediate water heat exchanger (18) flows to the spray heat exchanger (8) through the intermediate water inlet spray tower pipe (17); The water tank (1), flue gas energy-saving heat exchanger (9), deaerator (5), intermediate water heat exchanger (18), spray heat exchanger (8), electric heat pump device (19) and gas steam boiler (13) are divided into a softening water circulation, boiler feed water pipeline, intermediate water circulation and gas flue gas pipeline structure through pipelines, wherein: The softened water cycle includes a water tank (1), which serves as the water source for the entire system. Softened water enters the system from the water tank (1). The softened water in the water tank (1) absorbs heat from the flue gas in the flue gas energy-saving heat exchanger (9) and is heated. The water then merges with steam flowing out of the gas-fired steam boiler (13) through the boiler steam outlet pipe (11) and the steam inlet pipe (6) in the deaerator (5). The combined water in the deaerator (5) flows through the deaerator outlet pipe (20) into the intermediate water heat exchanger (18), absorbs heat, and then enters the electric heat pump device (19). The softened water is heated again by the electric heat pump device (19) and then enters the gas steam boiler (13). The steam generated by the gas steam boiler (13) during combustion and heating is discharged through the boiler steam outlet pipe (11) and the steam inlet pipe (6); The intermediate water circulates, the intermediate water enters the spray heat exchanger (8) to absorb the heat of the flue gas discharged by the flue gas energy-saving heat exchanger (9) and heats up, the heated intermediate water enters the electric heat pump device (19) to release heat as a low-temperature heat source, and transfers the heat to the boiler feed water through the electric heat pump device (19), the cooled intermediate water enters the intermediate water heat exchanger (18) again to exchange heat with the boiler feed water, and after cooling, enters the spray heat exchanger (8) again to absorb heat; Gas flue gas pipeline, gas passes through the gas inlet pipe (14) and the gas steam boiler (13) to burn and generate flue gas, and the flue gas passes through the flue gas energy-saving heat exchanger (9) and the spray heat exchanger (8) in sequence and is then discharged; In the softened water circulation, the softened water absorbs the heat of the flue gas in the flue gas energy-saving heat exchanger (9) and is heated, and then returns to the water tank (1) and flows to the deaerator (5). A water supply port is provided on the water tank (1), and water is supplied to the water tank (1) through the water supply pipe (25); The softened water flowing out of the water tank (1) passes through the water supply pipe (2) of the water pump, is transported to the flue gas energy-saving heat exchanger (9) through the water inlet pipe (24) of the economizer, absorbs the heat of the flue gas, and then returns to the water tank (1) through the water outlet pipe (23) of the economizer. The other way is to flow to the deaerator (5) through the water supply pipe (4) of the water pump; the intermediate water exchanges heat with the flue gas in a countercurrent manner in the spray heat exchanger (8).

2. The gas-fired steam boiler low-grade waste heat self-coupling utilization system according to claim 1 is characterized in that: A water supply pump (3) is provided on the water supply pump water supply pipeline (2). Two water supply pumps (3) are provided, and are respectively provided on the economizer water inlet pipe (24) and the water supply pump water supply pipeline (4).

3. The gas-fired steam boiler low-grade waste heat self-coupling utilization system according to claim 1 is characterized in that: An intermediate water pump (12) is provided on the intermediate water inlet electric heat pump pipeline (15).

4. The gas-fired steam boiler low-grade waste heat self-coupling utilization system according to claim 1, characterized in that: The gas steam boiler (13) is connected to the flue gas energy-saving heat exchanger (9) through the boiler flue gas exhaust pipeline (10), and the flue gas energy-saving heat exchanger (9) discharges the flue gas to the spray heat exchanger (8) through the spray tower flue gas inlet pipeline (7), and the flue gas is discharged after heat exchange in the spray heat exchanger (8).

5. The gas-fired steam boiler low-grade waste heat self-coupling utilization system according to any one of claims 1 to 4, characterized in that: It is used in factory energy stations and residential heat exchange stations that use gas steam boilers for heating.

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