A flue gas waste heat recovery system

Abstract

This invention relates to the field of heat energy recovery technology, specifically to a flue gas waste heat recovery system, comprising: a generator having a first flue gas inlet, a first flue gas outlet, and a first refrigerant vapor outlet; a flue gas collection device connected to the first flue gas inlet; a condenser having a first refrigerant vapor inlet and a first refrigerant outlet; and an evaporator having a first refrigerant inlet, a second refrigerant vapor outlet, a chilled water inlet, and a chilled water outlet; the first refrigerant inlet and the first refrigerant outlet are connected; and a cold source user is connected between the chilled water inlet and the chilled water outlet; this application utilizes the waste heat of flue gas to heat the refrigerant, which evaporates and enters the condenser to condense, forming a low-temperature liquid refrigerant, which is then sent to the evaporator. Through the absorption of heat by the refrigerant evaporation, low-temperature chilled water is obtained; the flue gas waste heat recovery system operates in refrigeration mode, effectively utilizing the waste heat of flue gas to obtain chilled water.

Description

Technical Field

[0001] This invention relates to the field of heat energy recovery technology, and more specifically to a flue gas waste heat recovery system. Background Technology

[0002] Currently, in industrial sectors such as power generation, the flue gas from waste heat boilers still has a high temperature. If this heat is directly released into the air, it will cause a huge energy loss and reduce energy utilization. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the flue gas of the waste heat boiler is directly discharged into the air, resulting in huge energy loss. Based on the above, it is necessary to develop a system that can effectively recover the heat of the flue gas from the waste heat boiler.

[0004] To achieve the above objectives, the present invention provides a flue gas waste heat recovery system, comprising:

[0005] The generator has a cavity for storing refrigerant and is provided with a first flue gas inlet, a first flue gas outlet, a first refrigerant vapor outlet, a first absorbent inlet, and a second absorbent outlet; the first flue gas inlet is connected to the first flue gas outlet; and a flue gas collection device is connected to the first flue gas inlet.

[0006] The condenser is provided with a first refrigerant vapor inlet and a first refrigerant outlet, and the first refrigerant vapor inlet and the first refrigerant outlet are connected.

[0007] An evaporator is provided with a first refrigerant inlet, a second refrigerant vapor outlet, a chilled water inlet, and a chilled water outlet; the first refrigerant inlet is connected to the second refrigerant vapor outlet, and the chilled water inlet and chilled water outlet are connected; the first refrigerant inlet is connected to the first refrigerant outlet; a cold source user is connected between the chilled water inlet and the chilled water outlet;

[0008] The first heat exchanger is provided with a second low-temperature side inlet, a second low-temperature side outlet, a second high-temperature side inlet, and a second high-temperature side outlet; the second low-temperature side inlet and the second low-temperature side outlet are connected, and the second high-temperature side inlet and the second high-temperature side outlet are also connected.

[0009] The absorber is equipped with a second refrigerant vapor inlet, a second absorbent inlet, and a first absorbent outlet;

[0010] The second low-temperature side inlet is connected to the first absorbent outlet, the second low-temperature side outlet is connected to the first absorbent inlet, the second high-temperature side inlet is connected to the second absorbent outlet, and the second high-temperature side outlet is connected to the second absorbent inlet; the second refrigerant vapor inlet is connected to the second refrigerant vapor outlet.

[0011] Optionally, the absorber further includes a first user water inlet and a first user water outlet; the first user water inlet and the first user water outlet are connected.

[0012] The condenser is also provided with a second user water inlet and a second user water outlet; the second user water inlet and the second user water outlet are connected; the first user water inlet is connected to the second user water outlet, and the first user water outlet is connected to the second user water inlet;

[0013] A heat source user is located on the pipeline connecting the first user's water inlet and the second user's water outlet, or on the pipeline connecting the first user's water outlet and the second user's water inlet.

[0014] Optionally, it also includes:

[0015] The second heat exchanger is provided with a first low-temperature side inlet, a first low-temperature side outlet, a first high-temperature side inlet, and a first high-temperature side outlet; the first low-temperature side inlet is connected to a flue gas collection device, the first low-temperature side outlet is connected to a first flue gas inlet, and the first low-temperature side inlet is connected to the first low-temperature side outlet.

[0016] The condenser is also provided with a first cooling water inlet and a first cooling water outlet, the first cooling water inlet and the first cooling water outlet are connected, and the first cooling water inlet is connected to a first high-temperature side inlet.

[0017] The absorber is further provided with a second cooling water inlet and a second cooling water outlet, the second cooling water inlet and the second cooling water outlet are connected, the second cooling water inlet is connected to the first high temperature side outlet, and the second cooling water outlet is connected to the first cooling water inlet.

[0018] Optionally, the evaporator is further provided with a second flue gas inlet and a second flue gas outlet; the second flue gas inlet and the second flue gas outlet are connected.

[0019] The second flue gas inlet is connected to the first flue gas outlet.

[0020] Optionally, it also includes:

[0021] The first pump is connected at both ends to the second refrigerant outlet and the second refrigerant inlet of the evaporator, respectively.

[0022] Optionally, it also includes:

[0023] A throttle valve is installed between the first refrigerant inlet and the first refrigerant outlet.

[0024] Optionally, it also includes:

[0025] The second pump is located between the second low-temperature side inlet and the first absorbent outlet.

[0026] Optionally, the refrigerant is water, the first absorbent is a lithium bromide solution with a first concentration, and the second absorbent is a lithium bromide solution with a second concentration, wherein the first concentration is less than the second concentration.

[0027] Optionally, the cold source users include: cold users and refrigeration equipment;

[0028] The heat source users include: heat users and heat treatment equipment.

[0029] The technical solution of the present invention has the following advantages compared with the prior art:

[0030] 1. The flue gas waste heat recovery system provided by the present invention includes: a generator having a cavity for storing refrigerant, and having a first flue gas inlet, a first flue gas outlet, a first refrigerant vapor outlet, a first absorbent inlet, and a second absorbent outlet; the first flue gas inlet is connected to the first flue gas outlet; the first flue gas inlet is connected to a flue gas collection device; a condenser having a first refrigerant vapor inlet and a first refrigerant outlet, the first refrigerant vapor inlet and the first refrigerant outlet being connected; an evaporator having a first refrigerant inlet, a second refrigerant vapor outlet, a chilled water inlet, and a chilled water outlet; the first refrigerant inlet is connected to the second refrigerant vapor outlet, the chilled water inlet and the chilled water outlet being connected; the first refrigerant inlet is connected to the first refrigerant outlet; a cold source user is connected between the chilled water inlet and the chilled water outlet; a first heat exchanger having a second low-temperature side inlet, a second low-temperature side outlet, a second high-temperature side inlet, and a second high-temperature side outlet; the second low-temperature side outlet... The high-temperature side inlet is connected to the second low-temperature side outlet, and the second high-temperature side inlet and outlet are also connected. The absorber includes a second refrigerant vapor inlet, a second absorbent inlet, and a first absorbent outlet. The second low-temperature side inlet is connected to the first absorbent outlet, and the second low-temperature side outlet is connected to the first absorbent inlet. The second high-temperature side inlet is connected to the second absorbent outlet, and the second high-temperature side outlet is connected to the second absorbent inlet. The second refrigerant vapor inlet is connected to the second refrigerant vapor outlet. This technical solution utilizes waste heat from flue gas to heat the refrigerant. The refrigerant evaporates and enters the condenser to condense, forming a low-temperature liquid refrigerant, which is then sent to the evaporator. Through the evaporation of the refrigerant, heat is absorbed to obtain low-temperature chilled water. The evaporated refrigerant enters the absorber and, along with the second absorbent, circulates sequentially to the heat exchanger and generator, completing the refrigerant cycle. The flue gas waste heat recovery system operates in refrigeration mode, effectively utilizing the waste heat of the flue gas to obtain the chilled water needed by the cold source user.

[0031] 2. The absorber of the present invention is further provided with a first user water inlet and a first user water outlet; the first user water inlet and the first user water outlet are connected; the condenser is further provided with a second user water inlet and a second user water outlet; the second user water inlet and the second user water outlet are connected; the first user water inlet is connected to the second user water outlet, and the first user water outlet is connected to the second user water inlet; a heat source user is provided on the pipeline connecting the first user water inlet and the second user water outlet or on the pipeline connecting the first user water outlet and the second user water inlet; the technical solution of this application makes full use of the waste heat of the exhaust gas, the refrigerant is in an exothermic state in the condenser and absorber, heating the user water, and the user water recovers heat in two stages through the absorber and condenser. The flue gas waste heat recovery system can also work in heating mode, obtaining the hot water required by the heat source user, effectively improving the utilization rate of flue gas waste heat.

[0032] 3. The flue gas waste heat recovery system provided by the present invention further includes: a second heat exchanger, having a first low-temperature side inlet, a first low-temperature side outlet, a first high-temperature side inlet, and a first high-temperature side outlet; the first low-temperature side inlet is connected to a flue gas collection device, and the first low-temperature side outlet is connected to a first flue gas inlet; the first low-temperature side inlet and the first low-temperature side outlet are connected; the condenser also has a first cooling water inlet and a first cooling water outlet, the first cooling water inlet and the first cooling water outlet are connected, and the first cooling water inlet is connected to the first high-temperature side inlet; the absorber also has a second cooling water inlet and a second cooling water outlet, the second cooling water inlet and the second cooling water outlet are connected, the second cooling water inlet is connected to the first high-temperature side outlet, and the second cooling water outlet is connected to the first cooling water inlet; the technical solution of this application uses the heat recovered by the cooling water in the absorber and condenser to heat the low-temperature flue gas, which can improve the quality of the driving heat source and improve the refrigeration efficiency; at the same time, the heat recovered by the cooling water is reused, which can reduce the installation cost of cooling equipment such as cooling towers in conventional absorption chillers.

[0033] 4. The evaporator of the present invention is further provided with a second flue gas inlet and a second flue gas outlet; the second flue gas inlet and the second flue gas outlet are connected; the second flue gas inlet is connected to the first flue gas outlet; the technical solution of this application releases heat twice through the generator and the evaporator, which can effectively reduce the flue gas discharge temperature and reduce environmental damage.

[0034] 5. The flue gas waste heat recovery system provided by the present invention further includes: a first pump, with its two ends respectively connected to a second refrigerant outlet and a second refrigerant inlet provided in the evaporator; the present application uses the first pump to draw out liquid refrigerant, and in the cooling mode, sprays it back onto the chilled water pipeline, which not only makes full use of the low temperature of the liquid refrigerant to lower the temperature of the chilled water, but also accelerates the evaporation of the liquid refrigerant and accelerates the cooling of the chilled water; in the heating mode, it is sprayed back onto the flue gas pipeline, making full use of the waste heat of the flue gas, accelerating the evaporation of the liquid refrigerant, and improving the operating efficiency of the flue gas waste heat recovery system.

[0035] 6. The flue gas waste heat recovery system provided by the present invention further includes: a throttling valve, disposed between the first refrigerant inlet and the first refrigerant outlet; the technical solution of this application, by setting a throttling valve, not only regulates the flow rate of the refrigerant, but also forms a high and low pressure zone to ensure the refrigeration cycle.

[0036] 7. The flue gas waste heat recovery system provided by the present invention further includes: a second pump, disposed between the second low-temperature side inlet and the first absorbent outlet; by setting the second pump, the present application accelerates the flow of the first absorbent and the heat exchange process between the first absorbent and the second absorbent, thereby improving the operating efficiency of the entire flue gas waste heat recovery system.

[0037] 8. The refrigerant of this invention is water, the first absorbent is a lithium bromide solution with a first concentration, and the second absorbent is a lithium bromide solution with a second concentration, wherein the first concentration is less than the second concentration; the technical solution of this application specifically limits the refrigerant to water, which not only has low cost but also achieves a good cooling effect; the specific limitation of the types and concentrations of the first and second absorbents ensures the normal operation of the refrigerant cycle and the full utilization of the waste heat of the flue gas.

[0038] 9. The cold source users of the present invention include: cold users and refrigeration equipment; the heat source users include: heat users and heat treatment equipment; by defining specific cold source users and heat source users, the refrigeration mode and heating mode of the flue gas waste heat recovery system of the present application can be used not only for users, but also for the refrigeration and heating of equipment. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1This is a schematic diagram of the connection structure of the flue gas waste heat recovery system provided in the embodiment of the present invention in the cooling mode.

[0041] Figure 2 This is a schematic diagram of the connection structure of the flue gas waste heat recovery system provided in the embodiment of the present invention in heating mode.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Generator; 2. Condenser; 3. Evaporator; 4. Absorber; 5. First heat exchanger; 6. Flue gas collection device; 7. Second heat exchanger; 8. Throttling valve; 9. First pump; 10. Second pump; 11. Cold source user; 12. Heat source user. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 invention based on the specific circumstances.

[0047] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] like Figures 1 to 2The flue gas waste heat recovery system shown is used to recover waste heat from the flue gas collection device 6. It includes: a second heat exchanger 7, a generator 1, a condenser 2, a throttle valve 8, an evaporator 3 and an absorber 4 connected in sequence, and a second pump 10 and a first heat exchanger 5 connected in sequence to the absorber 4.

[0049] like Figure 1 The diagram shows the connection structure of the flue gas waste heat recovery system in cooling mode, enabling cooling in summer. The generator 1 has a cavity for storing refrigerant, specifically water. The generator 1 is equipped with a first flue gas inlet, a first flue gas outlet, a first refrigerant vapor outlet, a first absorbent inlet, and a second absorbent outlet. The first flue gas inlet is connected to the first flue gas outlet. The first flue gas inlet is connected to a flue gas collection device 6. Specifically, the first absorbent is a lithium bromide solution with a first concentration, and the second absorbent is a lithium bromide solution with a second concentration. The first concentration is less than the second concentration; that is, the lithium bromide solution with the first concentration is a dilute lithium bromide solution, and the lithium bromide solution with the second concentration is a concentrated lithium bromide solution. The flue gas collection device 6 is the tail flue of the waste heat boiler.

[0050] The condenser 2 is provided with a first refrigerant vapor inlet and a first refrigerant outlet, and the first refrigerant vapor inlet and the first refrigerant outlet are connected.

[0051] The evaporator 3 is provided with a first refrigerant inlet, a second refrigerant vapor outlet, a chilled water inlet, and a chilled water outlet; the first refrigerant inlet is connected to the second refrigerant vapor outlet, and the chilled water inlet is connected to the chilled water outlet; the first refrigerant inlet is connected to the first refrigerant outlet; a cold source user 11 is connected between the chilled water inlet and the chilled water outlet, specifically, the cold source user 11 includes: cold users and refrigeration equipment. A first pump 9, i.e., an evaporator pump, is connected and installed between the second refrigerant outlet and the second refrigerant inlet of the evaporator 3. A throttling valve 8 is located between the first refrigerant inlet and the first refrigerant outlet.

[0052] The first heat exchanger 5 is provided with a second low-temperature side inlet, a second low-temperature side outlet, a second high-temperature side inlet, and a second high-temperature side outlet; the second low-temperature side inlet and the second low-temperature side outlet are connected, and the second high-temperature side inlet and the second high-temperature side outlet are connected.

[0053] The absorber 4 is provided with a second refrigerant vapor inlet, a second absorbent inlet, and a first absorbent outlet; the second low-temperature side inlet is connected to the first absorbent outlet, the second low-temperature side outlet is connected to the first absorbent inlet, the second high-temperature side inlet is connected to the second absorbent outlet, and the second high-temperature side outlet is connected to the second absorbent inlet; the second refrigerant vapor inlet is connected to the second refrigerant vapor outlet. A second pump 10, i.e., an absorber pump, is connected between the second low-temperature side inlet and the first absorbent outlet.

[0054] The second heat exchanger 7 is provided with a first low-temperature side inlet, a first low-temperature side outlet, a first high-temperature side inlet, and a first high-temperature side outlet; the first low-temperature side inlet is connected to the flue gas collection device 6, and the first low-temperature side outlet is connected to the first flue gas inlet; the first low-temperature side inlet and the first low-temperature side outlet are connected. Specifically, the second heat exchanger 7 is a flue-water heat exchanger.

[0055] The condenser 2 is further provided with a first cooling water inlet and a first cooling water outlet, which are connected together. The first cooling water inlet is connected to a first high-temperature side inlet. The absorber 4 is further provided with a second cooling water inlet and a second cooling water outlet, which are connected together. The second cooling water inlet is connected to a first high-temperature side outlet, and the second cooling water outlet is connected to a first cooling water inlet.

[0056] like Figure 2 The diagram shows the connection structure of the flue gas waste heat recovery system in heating mode, enabling heating in winter. The absorber 4 is equipped with a first user water inlet and a first user water outlet; the first user water inlet and the first user water outlet are connected. The condenser 2 is also equipped with a second user water inlet and a second user water outlet; the second user water inlet and the second user water outlet are connected. The first user water inlet is connected to the second user water outlet, and the first user water outlet is connected to the second user water inlet. A heat source user 12 is provided on the pipeline connecting the first user water inlet and the second user water outlet, or on the pipeline connecting the first user water outlet and the second user water inlet. Specifically, the heat source user 12 includes: heat users and heat treatment equipment. The evaporator 3 is also equipped with a second flue gas inlet and a second flue gas outlet; the second flue gas inlet and the second flue gas outlet are connected; the second flue gas inlet is connected to the first flue gas outlet.

[0057] The recovery process of the flue gas waste heat recovery system described in this application is briefly described as follows: In refrigeration mode, low-temperature flue gas is discharged from the tail flue of the waste heat boiler and enters the flue-water heat exchanger. It is heated by high-temperature cooling water from condenser 2 and becomes high-temperature flue gas, which then enters generator 1. The high-temperature cooling water releases heat and becomes low-temperature cooling water, which then enters absorber 4. The dilute lithium bromide solution enters the first heat exchanger 5 through the absorber pump at the outlet of absorber 4. After absorbing heat from the concentrated lithium bromide solution from generator 1, it enters generator 1 and further absorbs heat from the flue gas. The high-temperature flue gas releases heat and becomes low-temperature flue gas, which is then discharged into the atmosphere. After the dilute lithium bromide solution absorbs heat, the refrigerant continuously vaporizes. The refrigerant vapor enters condenser 2. The concentrated lithium bromide solution releases heat to the dilute lithium bromide solution through the first heat exchanger 5 and then enters absorber 4. In condenser 2, the refrigerant vapor releases heat and transfers heat to the medium-temperature cooling water from absorber 4. After the refrigerant vapor cools down, it condenses into liquid refrigerant and, after being depressurized by throttling valve 8, enters evaporator 3. In evaporator 3, liquid refrigerant is sprayed onto the chilled water pipes by the evaporator pump, absorbing heat and vaporizing into refrigerant vapor. This vapor then enters absorber 4, where the chilled water is cooled and delivered to the users, thus achieving the purpose of refrigeration. In absorber 4, the refrigerant vapor is absorbed by the concentrated lithium bromide solution from the first heat exchanger 5, returning to a dilute lithium bromide solution. The heat released during the absorption process is absorbed by the low-temperature cooling water from the flue water heat exchanger, becoming medium-temperature cooling water, which then enters condenser 2, completing one refrigeration cycle.

[0058] In heating mode, low-temperature flue gas exits directly from the tail flue of the waste heat boiler and enters generator 1. Dilute lithium bromide solution enters the first heat exchanger 5 via the absorber pump at the outlet of absorber 4. After absorbing heat from the concentrated lithium bromide solution in generator 1, it enters generator 1 again and further absorbs heat from the flue gas. The flue gas releases heat, becoming low-temperature flue gas, and then enters evaporator 3. After the dilute lithium bromide solution absorbs heat, the refrigerant continuously vaporizes. The refrigerant vapor enters condenser 2. The concentrated lithium bromide solution releases heat to the dilute lithium bromide solution via the first heat exchanger 5 and then enters absorber 4. In condenser 2, the refrigerant vapor releases heat, transferring it to the medium-temperature user water from absorber 4. The medium-temperature user water is then sent to heat users or heat treatment equipment, thus achieving the heating purpose. After the refrigerant vapor cools down, it condenses into liquid refrigerant, which is then depressurized by throttling valve 8 and enters evaporator 3. In evaporator 3, liquid refrigerant is sprayed onto the flue gas duct by the evaporator pump, absorbing heat and vaporizing into refrigerant vapor. This vapor then enters absorber 4, where the flue gas is further cooled before being discharged into the atmosphere. In absorber 4, the refrigerant vapor is absorbed by a concentrated lithium bromide solution from the first heat exchanger 5, returning to a dilute lithium bromide solution. The heat released during the absorption process is absorbed by low-temperature user water from heat users or heat treatment equipment, becoming medium-temperature user water, which then enters condenser 2, completing one heating cycle.

[0059] As an alternative implementation, the second pump 10 is disposed between the second low-temperature side outlet and the first absorbent inlet.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A flue gas waste heat recovery system, characterized in that, include: The generator (1) has a cavity for storing refrigerant and is provided with a first flue gas inlet, a first flue gas outlet, a first refrigerant vapor outlet, a first absorbent inlet and a second absorbent outlet; the first flue gas inlet is connected to the first flue gas outlet; the first flue gas inlet is connected to a flue gas collection device (6). The condenser (2) is provided with a first refrigerant vapor inlet and a first refrigerant outlet, and the first refrigerant vapor inlet and the first refrigerant outlet are connected; The evaporator (3) is provided with a first refrigerant inlet, a second refrigerant vapor outlet, a chilled water inlet, and a chilled water outlet; the first refrigerant inlet is connected to the second refrigerant vapor outlet, and the chilled water inlet and chilled water outlet are connected; the first refrigerant inlet is connected to the first refrigerant outlet; a cold source user (11) is connected between the chilled water inlet and the chilled water outlet. The first heat exchanger (5) is provided with a second low-temperature side inlet, a second low-temperature side outlet, a second high-temperature side inlet and a second high-temperature side outlet; the second low-temperature side inlet and the second low-temperature side outlet are connected, and the second high-temperature side inlet and the second high-temperature side outlet are connected. The absorber (4) is provided with a second refrigerant vapor inlet, a second absorbent inlet and a first absorbent outlet; The second low-temperature side inlet is connected to the first absorbent outlet, the second low-temperature side outlet is connected to the first absorbent inlet, the second high-temperature side inlet is connected to the second absorbent outlet, and the second high-temperature side outlet is connected to the second absorbent inlet; the second refrigerant vapor inlet is connected to the second refrigerant vapor outlet; the absorber (4) is also provided with a first user water inlet and a first user water outlet; the first user water inlet and the first user water outlet are connected; The condenser (2) is also provided with a second user water inlet and a second user water outlet; the second user water inlet and the second user water outlet are connected; the first user water inlet is connected to the second user water outlet, and the first user water outlet is connected to the second user water inlet; A heat source user (12) is provided on the pipeline connecting the first user's water inlet and the second user's water outlet or on the pipeline connecting the first user's water outlet and the second user's water inlet. The flue gas waste heat recovery system further includes: a second heat exchanger (7), which is provided with a first low-temperature side inlet, a first low-temperature side outlet, a first high-temperature side inlet and a first high-temperature side outlet; The first low-temperature side inlet is connected to the flue gas collection device (6), and the first low-temperature side outlet is connected to the first flue gas inlet; the first low-temperature side inlet is connected to the first low-temperature side outlet; The condenser (2) is also provided with a first cooling water inlet and a first cooling water outlet, the first cooling water inlet and the first cooling water outlet are connected, and the first cooling water outlet is connected to the first high temperature side inlet; The absorber (4) is also provided with a second cooling water inlet and a second cooling water outlet. The second cooling water inlet and the second cooling water outlet are connected. The second cooling water inlet is connected to the first high-temperature side outlet, and the second cooling water outlet is connected to the first cooling water inlet.

2. The flue gas waste heat recovery system according to claim 1, characterized in that, The evaporator (3) is also provided with a second flue gas inlet and a second flue gas outlet; the second flue gas inlet and the second flue gas outlet are connected. The second flue gas inlet is connected to the first flue gas outlet.

3. The flue gas waste heat recovery system according to claim 1, characterized in that, Also includes: The first pump (9) is connected at both ends to the second refrigerant outlet and the second refrigerant inlet provided in the evaporator (3).

4. The flue gas waste heat recovery system according to claim 1, characterized in that, Also includes: A throttle valve (8) is installed between the first refrigerant inlet and the first refrigerant outlet.

5. The flue gas waste heat recovery system according to claim 1, characterized in that, Also includes: The second pump (10) is located between the second low-temperature side inlet and the first absorbent outlet.

6. The flue gas waste heat recovery system according to claim 5, characterized in that, The refrigerant is water, the first absorbent is a lithium bromide solution with a first concentration, and the second absorbent is a lithium bromide solution with a second concentration, wherein the first concentration is less than the second concentration.

7. The flue gas waste heat recovery system according to claim 1, characterized in that, The cold source users (11) include: cold users and refrigeration equipment; The heat source users (12) include: heat users and heat treatment equipment.

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