Flue gas gradient utilization cold and heat combined supply system

Abstract

The invention provides a flue gas gradient utilization cold and heat combined supply system, which relates to the technical field of flue gas waste heat utilization and comprises a high-temperature flue gas heat collector, a low-temperature flue gas heat collector, an absorption machine and a steam turbine, the high-temperature flue gas heat collector is communicated with the absorption machine through a first circulating heat exchange pipeline, the low-temperature flue gas heat collector is communicated with the absorption machine through a second circulating heat exchange pipeline, the steam turbine is communicated with the absorption machine, the absorption machine is communicated with user return water through a first water return pipeline, and the absorption machine is communicated with the high-temperature flue gas heat collector through a conveying pipeline. The high-temperature flue gas heat collector is communicated with user water supply through a first water supply pipeline, and the absorption machine is communicated with the user water supply through a second water supply pipeline. The flue gas gradient utilization can be achieved, cold and heat combined supply is conducted on users, and the equipment utilization rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas waste heat utilization, in particular to a flue gas cascade utilization cold and heat cogeneration system. Background Art

[0002] Boiler exhaust contains a lot of heat. Recovering this heat can significantly improve the comprehensive utilization efficiency of energy. Flue gas heat can be recovered by direct heat exchange or by using a heat pump.

[0003] Direct heat exchange is used to recover flue gas heat (for example, Chinese patent CN119065433A disclosed on December 3, 2024), and a heat exchanger is used to achieve heat exchange between high-temperature flue gas and a cold source. However, the utilization efficiency of high-temperature flue gas is low. In addition, there is a lack of consideration for the recovery of waste heat from low-temperature flue gas.

[0004] Although the use of heat pumps (such as Chinese patent CN111578301A published on December 3, 2024) can effectively recover the waste heat of low-temperature flue gas, it does not mention the utilization of high-temperature flue gas.

[0005] In addition, existing technologies all focus on heating scenarios where users have heat demand, but when the heating ends, the system cannot operate normally, which means that the utilization rate of system equipment is low, resulting in a certain degree of resource waste.

[0006] In order to improve the utilization efficiency of flue gas heat, realize not only external heating but also external cooling, meet the users' heating and cooling needs at the same time and improve equipment utilization, a flue gas cascade utilization combined heating and cooling system is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a flue gas cascade utilization combined heat and cold supply system, which can improve the utilization efficiency of flue gas heat, and at the same time realize not only external heating but also external cooling, and at the same time meet the user's cooling and heating needs and improve the equipment utilization rate;

[0008] The present invention provides a flue gas cascade utilization combined heat and cold supply system, comprising a high-temperature flue gas heat exchanger, a low-temperature flue gas heat exchanger, an absorber and a steam turbine; the high-temperature flue gas heat exchanger is connected to the absorber via a first circulation heat exchange pipeline, the low-temperature flue gas heat exchanger is connected to the absorber via a second circulation heat exchange pipeline, the steam turbine is connected to the absorber, the absorber is connected to user return water via a first return water pipeline, the absorber is connected to the high-temperature flue gas heat exchanger via a delivery pipeline, the high-temperature flue gas heat exchanger is connected to user water supply via a first water supply pipeline, and the absorber is connected to user water supply via a second water supply pipeline.

[0009] Furthermore, it also includes a radiator, and the radiator is connected to the absorption machine through a third circulation heat exchange pipeline.

[0010] Furthermore, the second circulation heat exchange pipeline includes a first branch and a second branch, and the first branch is connected to the second branch through a connecting pipeline; the third circulation heat exchange pipeline includes a third branch and a fourth branch, the third branch is connected to the first branch, and the fourth branch is connected to the second branch.

[0011] Furthermore, a first valve is provided on the first branch, and the first valve is located between the connecting pipeline and the third branch; a second valve is provided on the connecting pipeline; a third valve and a fourth valve are provided on the second branch, and the third valve is located between the connecting pipeline and the low-temperature flue gas heat exchanger, and the fourth valve is located between the connecting pipeline and the fourth branch; a fifth valve is provided on the fourth branch, and the fifth valve is located between the radiator and the second branch.

[0012] Furthermore, a valve is provided on the second water supply pipeline.

[0013] Furthermore, it also includes a desulfurization tower, the high-temperature flue gas heat exchanger is connected to the desulfurization tower through a first flue gas exhaust pipeline, and the desulfurization tower is connected to the low-temperature flue gas heat exchanger through a second flue gas exhaust pipeline.

[0014] Furthermore, the absorption machine is connected to a first condensate discharge pipe.

[0015] Furthermore, it also includes an exhaust steam heat exchanger, the exhaust steam of the steam turbine is connected to the exhaust steam heat exchanger through an exhaust steam pipeline, the exhaust steam heat exchanger is connected to a second condensate drain pipe, the exhaust steam pipeline is connected to the second condensate drain pipe, and the first condensate drain pipe is connected to the second condensate drain pipe.

[0016] Furthermore, the exhaust steam heat exchanger is connected to the user return water through a second return water pipeline, the first return water pipeline is connected to the second return water pipeline, and valves are respectively provided on the first return water pipeline and the second return water pipeline.

[0017] Furthermore, the first water return pipeline is communicated with the delivery pipeline.

[0018] The technical solution of the present invention exchanges heat with the absorption machine through the high-temperature flue gas heat exchanger and the low-temperature flue gas heat exchanger respectively, so that the system can realize the cascade utilization of flue gas. In the heating condition, the extraction steam of the steam turbine is used as the driving heat source of the absorption machine, and the user's return water enters the absorption machine for heating, and then enters the high-temperature flue gas heat exchanger after heating, and exchanges heat with the flue gas as a cold source, and is provided to the user as water supply after further heating. In the cooling condition, the absorption machine operates as a refrigerator, and the hot water flowing out of the high-temperature flue gas heat exchanger enters the absorption machine as the driving heat source of the absorption machine. The user's return water enters the absorption machine for cooling, and is provided to the user as water supply after cooling. Therefore, the system can realize the combined supply of cold and heat for users and improve the utilization rate of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a system schematic diagram of Embodiment 1 and Embodiment 2 of the present invention;

[0021] Figure 2 This is a system schematic diagram of Embodiment 3 of the present invention;

[0022] Description of reference numerals:

[0023] 1-high temperature flue gas heat exchanger; 2-desulfurization tower; 3-low temperature flue gas heat exchanger; 4-radiator; 5-absorption machine; 6-steam turbine; 7-exhaust steam heat exchanger;

[0024] 8- first cycle heat exchange pipeline;

[0025] 9-second circulation heat exchange pipeline; 901-first branch; 902-second branch; 903-connecting pipeline;

[0026] 10-first water return pipeline; 11-transmission pipeline; 12-first water supply pipeline; 13-second water supply pipeline;

[0027] 14-third circulation heat exchange pipeline; 1401-third branch; 1402-fourth branch;

[0028] 15-valve; 16-first smoke exhaust pipeline; 17-second smoke exhaust pipeline; 18-first condensate drain pipe; 19-exhaust steam pipeline; 20-second condensate drain pipe; 21-second return water pipeline; 22-user return water; 23-user water supply; 24-smoke; 25-smoke exhaust port;

[0029] V1-first valve; V2-second valve; V3-third valve; V4-fourth valve; V5-fifth valve. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] Example 1

[0034] like Figure 1As shown, the present invention provides a flue gas cascade utilization cold and heat cogeneration system, including a high-temperature flue gas heat exchanger 1, a low-temperature flue gas heat exchanger 3, an absorber 5 and a steam turbine 6; the high-temperature flue gas heat exchanger 1 is connected to the absorber 5 through a first circulation heat exchange pipeline 8, the low-temperature flue gas heat exchanger 3 is connected to the absorber 5 through a second circulation heat exchange pipeline 9, the steam turbine 6 is connected to the absorber 5, the absorber 5 is connected to the user return water 22 through a first return water pipeline 10, the absorber 5 is connected to the high-temperature flue gas heat exchanger 1 through a transmission pipeline 11, the high-temperature flue gas heat exchanger 1 is connected to the user water supply 23 through a first water supply pipeline 12, the absorber 5 is connected to the user water supply 23 through a second water supply pipeline 13, and a valve 15 is provided on the second water supply pipeline 13. A desulfurization tower 2 is also included, the high-temperature flue gas heat exchanger 1 is connected to the desulfurization tower 2 through a first exhaust pipe 16, and the desulfurization tower 2 is connected to the low-temperature flue gas heat exchanger 3 through a second exhaust pipe 17.

[0035] Specifically, Figure 1 As shown, after the high-temperature flue gas 24 is cooled by the high-temperature flue gas heat exchanger 1, it enters the desulfurization tower 2 through the first exhaust pipe 16, flows out of the desulfurization tower 2, and then enters the low-temperature flue gas heat exchanger 3 through the second exhaust pipe 17, and is further cooled before being discharged through the exhaust port 25.

[0036] In the heating condition, the absorption machine 5 operates in the heating condition, and the extraction steam of the steam turbine 6 is used as the driving heat source of the absorption machine 5, and flows out through the first condensed water discharge pipe 18 after cooling and condensing in the absorption machine 5. The user return water 22 enters the absorption machine 5 through the first return water pipeline 10 to be heated, and then enters the high-temperature flue gas heat exchanger 1 through the transmission pipeline 11 after being heated, and exchanges heat with the flue gas 24 as a cold source, and is further heated and provided to the user through the first water supply pipeline 12 as supply water.

[0037] In the refrigeration mode, the absorption machine 5 operates as a refrigeration machine. The hot water flowing out of the high-temperature flue gas heat exchanger 1 enters the absorption machine 5 through the first circulation heat exchange pipeline 8, and serves as the driving heat source of the absorption machine 5. After cooling in the absorption machine 5, it returns to the high-temperature flue gas heat exchanger 1. The user return water 22 enters the absorption machine 5 through the first return water pipeline 10 to cool down, and after cooling down, it is provided to the user as supply water through the second water supply pipeline 13.

[0038] A valve 15 is provided on the connecting pipe 903 between the steam turbine 6 and the absorption machine 5, which is opened in the heating condition. A valve 15 is provided on the delivery pipe 11 and the first water supply pipe 12, which is closed in the cooling condition and opened in the heating condition. The valve 15 on the second water supply pipe 13 is opened in the cooling condition and closed in the heating condition.

[0039] Valves 15 are respectively provided on the two branches of the first circulating heat exchange pipeline 8, and a booster pump is provided on one of the branches.

[0040] Example 2

[0041] like Figure 1 As shown, the heat exchanger 5 further includes a radiator 4, and the radiator 4 is connected to the absorption machine 5 through a third circulating heat exchange pipeline 14. The second circulating heat exchange pipeline 9 includes a first branch 901 and a second branch 902, and the first branch 901 and the second branch 902 are connected through a connecting pipeline 903; the third circulating heat exchange pipeline 14 includes a third branch 1401 and a fourth branch 1402, and the third branch 1401 is connected to the first branch 901, and the fourth branch 1402 is connected to the second branch 902. A first valve V1 is provided on the first branch 901, and the first valve V1 is located between the connecting pipeline 903 and the third branch 1401; a second valve V2 is provided on the connecting pipeline 903; a third valve V3 and a fourth valve V4 are provided on the second branch 902, and the third valve V3 is located between the connecting pipeline 903 and the low-temperature flue gas heat exchanger 3, and the fourth valve V4 is located between the connecting pipeline 903 and the fourth branch 1402; a fifth valve V5 is provided on the fourth branch 1402, and the fifth valve V5 is located between the radiator 4 and the second branch 902.

[0042] Specifically, (1) during the heating condition, the low-temperature water generated by the absorption machine 5 flows through the first valve V1 of the first branch 901 into the low-temperature flue gas heat exchanger 3. After being heated in the low-temperature flue gas heat exchanger 3, it passes through the third valve V3 and the fourth valve V4 of the second branch 902 and returns to the absorption machine 5 as a heat pump cold source. At this time, the second valve V2 and the fifth valve V5 are closed.

[0043] (2) In the refrigeration condition, the second valve V2, the third valve V3, and the fifth valve V5 are opened, and the first valve V1 and the fourth valve V4 are closed; the cold water generated by the absorption machine 5 enters the low-temperature flue gas heat exchanger 3 through the first branch 901, the connecting pipe 903, the second valve V2, the second branch 902, and the third valve V3, and after cooling the low-temperature flue gas 24, enters the radiator 4 through the first branch 901 and the third branch 1401, and after cooling and releasing heat in the radiator 4, returns to the absorption machine 5 through the fourth branch 1402 and the fifth valve V5.

[0044] Or the first valve V1, the third valve V3, the fourth valve V4, and the fifth valve V5 are opened, and the second valve V2 is closed; at this time, the water flowing out of the radiator 4 passes through the fourth branch 1402, the fifth valve V5, and the second branch 902, and a part of it enters the absorption machine 5 for heating, and the other part passes through the second branch 902, the fourth valve V4, and the third valve V3 to enter the low-temperature flue gas heat exchanger 3 for heating. After heating in the low-temperature flue gas heat exchanger 3, it passes through the first branch 901 and the first valve V1 to merge with the water flowing out of the absorption machine 5, and then returns to the radiator 4.

[0045] Or the second valve V2, the third valve V3, and the fourth valve V4 are all closed, and the first valve V1 and the fifth valve V5 are opened; the cold water generated by the absorption machine 5 enters the radiator 4 through the first branch 901 and the first valve V1, and after being cooled and released in the radiator 4, returns to the absorption machine 5 through the fourth branch 1402 and the fifth valve V5.

[0046] Through the above valve 15 combination, different valve 15 combinations correspond to different temperature requirements of the flue gas 24 at the outlet of the low-temperature flue gas heat exchanger 3 and different heat dissipation capabilities of the radiator 4 .

[0047] In the above-mentioned embodiments 1 and 2, the high-temperature flue gas heat exchanger 1 and the low-temperature flue gas heat exchanger 3 realize the step-by-step utilization matching the temperature of the flue gas 24. Under the heating condition, the user return water 22 is heated by the absorption machine 5 and the high-temperature heat exchanger in turn, and the hot water flowing out of the high-temperature flue gas heat exchanger 1 is used as the driving heat source of the absorption machine 5 under the cooling condition, thereby improving the utilization efficiency of the heat of the flue gas 24. In addition, the absorption machine 5 of the above-mentioned technical solution can realize heating and cooling for the user. Under the cooling condition, the basic stability of the final exhaust temperature is achieved by switching the radiator 4 and the first valve V1 to the fifth valve V5, thereby realizing the continuous operation of the system and improving the utilization efficiency of the equipment.

[0048] The present invention implements a cascade utilization and matching system flow of the heat of the flue gas 24, thereby improving the utilization efficiency of the flue gas 24; the absorption machine 5 can provide external heating as well as external cooling, and under different working conditions, the heat of the high-temperature flue gas 24 can be used to heat the user's return water 22, and can also be used as a heat source to drive the absorption machine 5, thereby improving the utilization rate of the equipment; through the combination of the valve 15 and the radiator 4, the exhaust temperature of the low-temperature flue gas heat exchanger 3 of the system can also be maintained at a relatively low level under the cooling working condition; the waste heat recovery of the exhaust steam of the steam turbine 6 is realized, and the user's return water 22 can be heated in series or in parallel through the absorption machine 5 and the high-temperature flue gas heat exchanger 1, thereby improving the overall energy utilization efficiency.

[0049] Example 3

[0050] like Figure 2 As shown, the absorption machine 5 is connected with a first condensed water discharge pipe 18. It also includes an exhaust steam heat exchanger 7. The exhaust steam of the steam turbine 6 is connected to the exhaust steam heat exchanger 7 through an exhaust steam pipeline 19. The exhaust steam heat exchanger 7 is connected with a second condensed water discharge pipe 20. The exhaust steam pipeline 19 is connected with the second condensed water discharge pipe 20. The first condensed water discharge pipe 18 is connected with the second condensed water discharge pipe 20. The exhaust steam heat exchanger 7 is connected with the user return water 22 through the second return water pipeline 21. The first return water pipeline 10 is connected with the second return water pipeline 21. The first return water pipeline 10 and the second return water pipeline 21 are respectively provided with valves 15. The first return water pipeline 10 is connected with the delivery pipeline 11.

[0051] Specifically, Figure 2 As shown, there are two groups of non-interconnected pipelines in the exhaust steam heat exchanger 7 and heat is exchanged in the exhaust steam heat exchanger 7. One group of pipelines connects the exhaust steam pipeline 19 of the steam turbine 6 and the second condensate discharge pipe 20. The exhaust steam of the steam turbine 6 is discharged as condensate after heat exchange in the exhaust steam heat exchanger 7; the other group of pipelines connects the user return water 22 and the second return water pipeline 21. The user return water 22 exchanges heat with the exhaust steam during the process and enters the absorption machine 5 after being heated.

[0052] Under heating conditions, the user return water 22 first enters the exhaust steam heat exchanger 7 through the second return water pipeline 21, and is heated by the exhaust steam of the steam turbine 6 and then divided into two paths, which enter the absorption machine 5 and the high-temperature flue gas heat collector 1 in parallel, and then are combined as water supply to the user through the first water supply pipeline 12 and the second water supply pipeline 13 after being heated. In the aforementioned embodiments 1 and 2, the delivery pipeline 11 is connected to the second water supply pipeline 13, but not to the user return water 22; while in this embodiment 3, the delivery pipeline 11 is connected to the second return water pipeline 21, but not to the second water supply pipeline 13.

[0053] In this embodiment, the user return water 22 is heated in stages under the heating condition, the exhaust heat of the steam turbine 6 is recovered, and the overall energy utilization efficiency of the system is improved.

[0054] Working mode and principle of the present invention:

[0055] During the heating operation, the absorption machine 5 operates under the heating operation, and the steam extraction of the steam turbine 6 is used as the driving heat source of the absorption machine 5. After cooling and condensing in the absorption machine 5, it flows out through the first condensed water discharge pipe 18. The user return water 22 enters the absorption machine 5 through the first return water pipeline 10 to be heated, and then enters the high-temperature flue gas heat exchanger 1 through the transmission pipeline 11 after heating, and exchanges heat with the flue gas 24 as a cold source. After further heating, it is provided to the user as water supply through the first water supply pipeline 12. The low-temperature water generated by the absorption machine 5 flows through the first valve V1 of the first branch 901 and enters the low-temperature flue gas heat exchanger 3. After heating in the low-temperature flue gas heat exchanger 3, it returns to the absorption machine 5 through the third valve V3 and the fourth valve V4 of the second branch 902 as a heat pump cold source. At this time, the second valve V2 and the fifth valve V5 are closed.

[0056] In the refrigeration mode, the absorption machine 5 operates as a refrigeration machine. Through the first circulation heat exchange pipeline 8, the hot water flowing out of the high-temperature flue gas heat exchanger 1 enters the absorption machine 5 as the driving heat source of the absorption machine 5, and returns to the high-temperature flue gas heat exchanger 1 after cooling in the absorption machine 5. The user return water 22 enters the absorption machine 5 through the first return water pipeline 10 to cool down, and after cooling down, it is provided to the user as water supply through the second water supply pipeline 13. The second valve V2, the third valve V3, and the fifth valve V5 are opened, and the first valve V1 and the fourth valve V4 are closed; the cold water generated by the absorption machine 5 enters the low-temperature flue gas heat exchanger 3 after passing through the first branch 901, the connecting pipeline 903 and the second valve V2, the second branch 902 and the third valve V3, and enters the radiator 4 through the first branch 901 and the third branch 1401 after cooling the low-temperature flue gas 24, and returns to the absorption machine 5 through the fourth branch 1402 and the fifth valve V5 after cooling and releasing heat in the radiator 4. Or the first valve V1, the third valve V3, the fourth valve V4, and the fifth valve V5 are open, and the second valve V2 is closed; at this time, the water flowing out of the radiator 4 passes through the fourth branch 1402, the fifth valve V5, and the second branch 902, and a part of it enters the absorber 5 for heating, and the other part passes through the second branch 902, the fourth valve V4, and the third valve V3 to enter the low-temperature flue gas heat exchanger 3 for heating, and after heating in the low-temperature flue gas heat exchanger 3, it passes through the first branch 901 and the first valve V1 to merge with the water flowing out of the absorber 5, and then returns to the radiator 4. Or the second valve V2, the third valve V3, and the fourth valve V4 are all closed, and the first valve V1 and the fifth valve V5 are opened; the cold water generated by the absorber 5 enters the radiator 4 after passing through the first branch 901 and the first valve V1, and returns to the absorber 5 through the fourth branch 1402 and the fifth valve V5 after cooling and releasing heat in the radiator 4.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Flue gas cascade utilization combined cooling and heating system, characterized in that: It includes high-temperature flue gas heat exchanger, low-temperature flue gas heat exchanger, absorption machine and steam turbine; The high-temperature flue gas heat exchanger is connected to the absorption machine through a first circulation heat exchange pipeline, the low-temperature flue gas heat exchanger is connected to the absorption machine through a second circulation heat exchange pipeline, the steam turbine is connected to the absorption machine, the absorption machine is connected to the user's return water through a first return water pipeline, the absorption machine is connected to the high-temperature flue gas heat exchanger through a transmission pipeline, the high-temperature flue gas heat exchanger is connected to the user's water supply through a first water supply pipeline, and the absorption machine is connected to the user's water supply through a second water supply pipeline.

2. The flue gas cascade utilization combined cooling and heating system according to claim 1 is characterized in that: It also includes a radiator, and the radiator is connected to the absorption machine through a third circulation heat exchange pipeline.

3. The flue gas cascade utilization combined cooling and heating system according to claim 2 is characterized in that: The second circulating heat exchange pipeline includes a first branch and a second branch, and the first branch is connected to the second branch through a connecting pipeline; The third circulation heat exchange pipeline includes a third branch and a fourth branch, the third branch is connected to the first branch, and the fourth branch is connected to the second branch.

4. The flue gas cascade utilization combined cooling and heating system according to claim 3 is characterized in that: The first branch is provided with a first valve, and the first valve is located between the connecting pipeline and the third branch; The connecting pipeline is provided with a second valve; The second branch is provided with a third valve and a fourth valve, and the third valve is located between the connecting pipeline and the low-temperature flue gas heat collector, and the fourth valve is located between the connecting pipeline and the fourth branch; The fourth branch is provided with a fifth valve, and the fifth valve is located between the radiator and the second branch.

5. The flue gas cascade utilization combined cooling and heating system according to claim 1 is characterized in that: The second water supply pipeline is provided with a valve.

6. The flue gas cascade utilization combined cooling and heating system according to claim 1 is characterized in that: It also includes a desulfurization tower, the high-temperature flue gas heat exchanger is connected to the desulfurization tower through a first flue gas exhaust pipeline, and the desulfurization tower is connected to the low-temperature flue gas heat exchanger through a second flue gas exhaust pipeline.

7. The flue gas cascade utilization combined cooling and heating system according to claim 1 is characterized in that: The absorption machine is connected with a first condensed water discharge pipe.

8. The flue gas cascade utilization combined cooling and heating system according to claim 7 is characterized in that: It also includes an exhaust steam heat exchanger, exhaust steam of the steam turbine is connected to the exhaust steam heat exchanger through an exhaust steam pipeline, the exhaust steam heat exchanger is connected to a second condensate drain pipe, the exhaust steam pipeline is connected to the second condensate drain pipe, and the first condensate drain pipe is connected to the second condensate drain pipe.

9. The flue gas cascade utilization combined cooling and heating system according to claim 8, characterized in that: The exhaust steam heat exchanger is connected to the user's return water through the second return water pipeline, the first return water pipeline is connected to the second return water pipeline, and valves are respectively provided on the first return water pipeline and the second return water pipeline.

10. The flue gas cascade utilization combined cooling and heating system according to claim 9, characterized in that: The first water return pipeline is in communication with the delivery pipeline.

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