Flue gas waste heat recovery system

Abstract

The utility model discloses a flue gas waste heat recovery system, and belongs to the field of heat energy recovery equipment. Comprising TEG equipment, a first heat exchanger, a generator, a condenser, a second heat exchanger, an absorber, an evaporator and a cold storage tower, the hot end inlet of the TEG equipment is connected with external high-temperature flue gas, and the flue gas sequentially passes through the first heat exchanger and the generator and then is discharged to the external environment or subsequent flue gas treatment equipment; refrigerant water is introduced into a cold end inlet of the TEG equipment, the refrigerant water is obtained by liquefying refrigeration steam generated by the generator in the condenser, and the refrigerant water discharged from a cold end outlet of the TEG equipment enters the absorber to be absorbed after being treated by the evaporator. A cooling water inlet of the first heat exchanger is connected with high-temperature cooling water, the high-temperature cooling water is obtained after medium-temperature cooling water from the absorber absorbs heat in the condenser, a cooling water outlet of the first heat exchanger is connected with the absorber, and the absorber is connected with the generator through the second heat exchanger; and the evaporator and the cold storage tower form chilled water circulation.

Description

Technical Field

[0001] The utility model belongs to the field of heat energy recovery equipment, and in particular relates to a flue gas waste heat recovery system. Background Art

[0002] At present, in industries such as electricity, the temperature of flue gas discharged by waste heat boilers is still very high. If this heat energy is directly discharged into the atmosphere, it will not only waste a lot of heat energy, but also affect the utilization rate of energy. With the rapid development of the new energy industry, higher environmental protection requirements have been put forward for the utilization of flue gas waste heat. Combine high-quality coal-fired flue gas heat recovery with clean energy industry to promote the application and promotion of new energy. Flue gas waste heat has the characteristics of high temperature, large heat and large emission. Although the temperature of flue gas waste heat from different sources varies, it can reach more than 200℃ in most cases. Due to factors such as large flue gas flow, high temperature, dust and corrosive gases, it is difficult to recycle and utilize, so professional technology and equipment are required. At present, there are two ways to utilize the waste heat of flue gas from coal-fired boilers: one is the conventional heating method, that is, using the heat in the boiler flue gas to convert the heat in the flue gas into hot water, steam and other heat sources for equipment heating or production use; the other is a new power generation method, which uses the heat in the exhaust gas to convert the heat in the exhaust gas into electrical energy to rotate the turbine and generate electricity for the generator.

[0003] CN218379971U discloses a flue gas waste heat recovery device, which heats the working medium with the flue gas waste heat, makes it absorb heat, and sends it to the condenser to make it a low-temperature liquid working medium, and then sends it to the evaporator to absorb heat, thereby obtaining cooling water. This system realizes the conversion between heating mode and cooling mode, and the obtained hot water and cold water are directly connected to the user end.

[0004] CN218001553U discloses a flue gas waste heat recovery system, comprising a high-temperature flue gas heat exchanger, a desulfurization tower and a low-temperature flue gas heat exchanger connected in sequence through an air duct; the high-temperature flue gas heat exchanger is connected to a refrigerator through a first circulation pipeline, and the low-temperature flue gas heat exchanger is connected to the refrigerator through a second circulation pipeline; the refrigerator is connected to a heat pump through a third circulation pipeline, and the heat pump is connected to a heat-using device through a fourth circulation pipeline. The flue gas waste heat recovery system of the utility model effectively recovers two different grades of industrial exhaust waste heat, and realizes the full recovery and utilization of industrial exhaust waste heat.

[0005] CN218793961U discloses a negative pressure extraction desulfurization slurry flash evaporation system for recovering flue gas waste heat and condensed water, comprising: a desulfurization tower, a sprayer, a flash tank, a steam ejector and a condenser. Among them: the lower space of the desulfurization tower is connected to the sprayer, and the sprayer is arranged in the upper space in the flash tank. The top outlet of the flash tank, the steam ejector and the condenser are connected in sequence, and the water vapor generated in the flash tank is transported to the condenser for condensation. The utility model combines the existing desulfurization slurry recovery system with the steam ejector, which effectively simplifies the system and reduces the equipment cost. Moreover, the size of the connecting pipe is greatly reduced after passing through the steam ejector, making the flash tank easier to connect to the condenser. At the same time, the utility model not only realizes the utilization of the waste heat of the flue gas of the power plant, but also realizes the recovery of water resources by sucking the water vapor generated in the flash tank into the condenser for heat exchange with the external hot water supply network.

[0006] In summary, the existing flue gas waste heat recovery methods are mainly divided into two types: one is the heating method, which is to use the heat in the boiler flue gas to convert the heat in the flue gas into hot water, steam and other heat sources for equipment heating or production use; the other is the power generation method, which is to use the heat in the exhaust gas to convert the heat in the exhaust gas into electrical energy to rotate the turbine and generate electricity. Among them, the heating method is currently the most common method. In order to improve its thermal energy utilization method, the flue gas waste heat recovery system of the heating method often adopts a cascade utilization method for the flue gas waste heat. However, after the first stage of utilization, the flue gas temperature decreases and the waste heat recovery is difficult. Utility Model Content

[0007] In order to solve the shortcomings of the cascade utilization method adopted in the prior art for flue gas waste heat recovery, the utility model discloses a flue gas waste heat recovery system.

[0008] The technical solution adopted by the utility model is as follows:

[0009] A flue gas waste heat recovery system includes a TEG device, a first heat exchanger, a generator, a condenser, a second heat exchanger, an absorber, an evaporator, and a cold storage tower;

[0010] The hot end inlet of the TEG device is connected to the external high-temperature flue gas, and the hot end outlet of the TEG device is connected to the flue gas inlet of the first heat exchanger, and the flue gas outlet of the first heat exchanger is discharged to the external environment or the subsequent flue gas treatment equipment through the generator; the cooling water inlet of the first heat exchanger is connected to the high-temperature cooling water, and the high-temperature cooling water is obtained by absorbing heat from the medium-temperature cooling water from the absorber in the condenser, and the cooling water outlet of the first heat exchanger is connected to the cooling water inlet of the absorber;

[0011] The cold end inlet of the TEG device is connected to refrigerant water, and the refrigerant water is obtained by liquefying the refrigerant steam generated by the generator in the condenser. The cold end outlet of the TEG device is connected to the refrigerant inlet of the evaporator, and the refrigerant outlet of the evaporator is connected to the refrigerant inlet of the absorber;

[0012] The generator stores a dilute lithium bromide solution, and the absorber stores a concentrated lithium bromide solution; the concentrated lithium bromide solution in the absorber serves as an absorbent, and the absorber is connected to the generator via a second heat exchanger;

[0013] The chilled water inlet and the chilled water outlet of the evaporator are respectively connected to the chilled water outlet and the chilled water inlet of the cold storage tower to form a chilled water cycle.

[0014] Preferably, the generator has a cavity for storing a dilute lithium bromide solution, and the absorber has a cavity for storing a concentrated lithium bromide solution.

[0015] Preferably, the cold storage tower is connected to the user side to provide cooling for the user side.

[0016] Preferably, the chilled water returned from the user side passes through the cold storage tower and then enters the evaporator for cooling.

[0017] Preferably, the dilute solution inlet of the second heat exchanger is connected to the absorbent outlet of the absorber, the dilute solution outlet of the second heat exchanger is connected to the absorbent inlet of the generator, the concentrated solution inlet of the second heat exchanger is connected to the absorbent outlet of the generator, and the concentrated solution outlet of the second heat exchanger is connected to the absorbent inlet of the absorber.

[0018] Preferably, a solution pump is provided between the dilute solution inlet of the second heat exchanger and the absorbent outlet of the absorber.

[0019] Preferably, the condenser is provided with a cooling water inlet and outlet and a refrigerant inlet and outlet, the cooling water inlet of the condenser is connected to the cooling water outlet of the absorber, the cooling water outlet of the condenser is connected to the cooling water inlet of the first heat exchanger, the refrigerant inlet of the condenser is connected to the refrigeration steam outlet of the generator, and the refrigerant outlet of the condenser is connected to the cold end inlet of the TEG device.

[0020] Preferably, the first heat exchanger adopts smoke-water heat exchange

[0021] Preferably, the second heat exchanger is a solution heat exchanger.

[0022] Preferably, a throttle valve is provided between the cold end outlet of the TEG device and the refrigerant inlet of the evaporator.

[0023] The beneficial effects of the utility model are:

[0024] The flue gas waste heat recovery system proposed by the utility model is coupled with the TEG device. Compared with the conventional heating type flue gas waste heat recovery system, it generates electrical energy while utilizing heat energy, thereby increasing the energy utilization rate of the power plant. Compared with the flue gas waste heat recovery system that directly inputs the flue gas heat into the turbine to generate electricity, the flue gas heat energy is utilized twice, thereby realizing the cascade utilization of energy, with high energy utilization rate and low flue gas heat loss. In addition, the cooling water is circulated in the system, and the heat absorbed by the cooling water in the condenser is first released to the flue gas in the first heat exchanger to become low-temperature cooling water, and then absorbs heat in the absorber to become medium-temperature cooling water, and finally returns to the condenser to continue circulating, so that energy is fully utilized while also saving water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a flue gas waste heat recovery system shown in an embodiment of the utility model;

[0026] Among them: 1-TEG equipment, 2-throttle valve, 3-first heat exchanger (smoke-water heat exchanger), 4-generator, 5-condenser, 6-second heat exchanger (solution heat exchanger), 7-solution pump, 8-absorber, 9-evaporator, 10-cold storage tower. DETAILED DESCRIPTION

[0027] In order to make the content of the utility model more clearly understood, the utility model is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings.

[0028] See also Figure 1 In this embodiment, a flue gas waste heat recovery system is shown, which mainly includes a TEG device 1, a first heat exchanger 3, a generator 4, a condenser 5, a second heat exchanger 6, an absorber 8, an evaporator 9, and a cold storage tower 10.

[0029] Wherein, the TEG device is used to generate electric energy; the TEG includes a TEG hot end and a TEG cold end, the TEG hot end is provided with a flue gas inlet and a flue gas outlet, and the flue gas inlet and the flue gas outlet of the TEG hot end are connected inside the TEG. The flue gas inlet of the TEG hot end is connected to the outlet of the waste heat boiler, and the high-temperature flue gas discharged from the outlet of the waste heat boiler enters the TEG hot end through the flue gas inlet of the TEG hot end, and then leaves from the flue gas outlet of the TEG hot end, and then enters the first heat exchanger 3 for heat exchange. The TEG cold end is provided with a refrigerant inlet and a refrigerant outlet, and the refrigerant inlet and the refrigerant outlet of the TEG cold end are connected inside the TEG. The refrigerant inlet of the TEG cold end is connected to the condenser, and the refrigerant water discharged from the condenser enters the TEG cold end through the refrigerant inlet of the TEG cold end, leaves from the refrigerant outlet of the TEG cold end, and then enters the evaporator 9; a throttle valve 2 is provided between the refrigerant outlet of the TEG cold end and the evaporator 9, which is used to throttle and reduce the pressure of the refrigerant water discharged from the TEG cold end and then send it to the evaporator.

[0030] The first heat exchanger 3 is also called a flue gas-water heat exchanger, which is used to exchange heat between low-temperature flue gas and high-temperature cooling water. The low-temperature flue gas absorbs the heat of the high-temperature cooling water to become high-temperature flue gas, and the high-temperature cooling water releases heat to become low-temperature cooling water. The first heat exchanger is provided with a cooling water inlet, a cooling water outlet, a flue gas inlet and a flue gas outlet. The cooling water inlet and the cooling water outlet of the first heat exchanger are connected inside the first heat exchanger. Similarly, the flue gas inlet and the flue gas outlet of the first heat exchanger are connected inside the first heat exchanger. The cooling water inlet of the first heat exchanger is connected to the condenser. The high-temperature cooling water discharged from the condenser enters the first heat exchanger through the cooling water inlet of the first heat exchanger to release heat and become low-temperature cooling water, and then leaves from the cooling water outlet of the first heat exchanger, and then enters the absorber. The flue gas inlet of the first heat exchanger is connected to the hot end of the TEG. The low-temperature flue gas leaving from the flue gas outlet of the hot end of the TEG enters the first heat exchanger from the flue gas inlet of the first heat exchanger, absorbs heat and becomes high-temperature flue gas, and then leaves from the flue gas outlet of the first heat exchanger, and then enters the generator.

[0031] The generator 4 has a cavity for storing a dilute lithium bromide solution. The dilute solution absorbs the heat from the high-temperature flue gas of the first heat exchanger and precipitates refrigeration steam (water vapor) to obtain a high-temperature lithium bromide concentrated solution. The generator 4 is provided with a flue gas inlet, a flue gas outlet, an absorbent inlet, an absorbent outlet and a refrigeration steam outlet. The flue gas inlet and the flue gas outlet of the generator are connected inside the generator. Similarly, the absorbent inlet and the absorbent outlet of the generator are connected inside the generator. The flue gas inlet of the generator is connected to the first heat exchanger. The high-temperature flue gas leaving the flue gas outlet of the first heat exchanger enters the generator from the flue gas inlet of the generator and is then discharged to the outside from the flue gas outlet of the generator. The absorbent inlet of the generator is connected to the second heat exchanger. The high-temperature lithium bromide dilute solution discharged from the second heat exchanger enters the generator from the absorbent inlet of the generator. The dilute solution absorbs the heat from the high-temperature flue gas of the first heat exchanger and precipitates refrigeration steam to obtain a high-temperature lithium bromide concentrated solution, which is then discharged from the absorbent outlet of the generator and returns to the second heat exchanger for heat exchange.

[0032] The condenser 5 is used to obtain refrigerant water after the refrigeration steam from the generator releases heat, and transfers heat to the medium-temperature cooling water from the absorber 4 to obtain high-temperature cooling water; the condenser 5 is provided with a refrigerant inlet, a refrigerant outlet, a cooling water inlet and a cooling water outlet; the refrigerant inlet and the refrigerant outlet of the condenser 5 are connected inside the condenser, and similarly, the cooling water inlet and the cooling water outlet of the condenser 5 are connected inside the condenser. The refrigerant inlet of the condenser is connected to the generator, and the refrigeration steam discharged from the refrigeration steam outlet of the generator enters the condenser from the refrigerant inlet of the condenser, obtains refrigerant water after liquefaction, and then leaves from the refrigerant outlet of the condenser, and then enters the TEG cold end. The cooling water inlet of the condenser 5 is connected to the absorber, and the medium-temperature cooling water discharged from the absorber enters the condenser 5 from the cooling water inlet of the condenser 5, absorbs the heat released by the refrigeration steam to become high-temperature cooling water, and then is discharged from the cooling water outlet of the condenser 5, and then enters the first heat exchanger.

[0033] The second heat exchanger 6 is also called a solution heat exchanger, which is used to transfer the heat of the high-temperature lithium bromide concentrated solution from the generator to the low-temperature lithium bromide dilute solution from the absorber; the second heat exchanger is provided with a dilute solution inlet, a dilute solution outlet, a concentrated solution inlet and a concentrated solution outlet; the dilute solution inlet and the dilute solution outlet of the second heat exchanger 6 are connected inside the second heat exchanger, and similarly, the concentrated solution inlet and the concentrated solution outlet of the second heat exchanger 6 are connected inside the second heat exchanger. The dilute solution inlet of the second heat exchanger 6 is connected to the absorber, and the low-temperature lithium bromide dilute solution discharged from the absorber enters the second heat exchanger from the dilute solution inlet of the second heat exchanger 6 under the action of the solution pump 7, obtains a high-temperature lithium bromide dilute solution after absorbing heat, and then leaves from the dilute solution outlet of the second heat exchanger, and then continues to enter the generator from the absorbent inlet of the generator. The concentrated solution inlet of the second heat exchanger 6 is connected to the generator, and the high-temperature lithium bromide concentrated solution discharged from the absorbent outlet of the generator enters the second heat exchanger from the concentrated solution inlet of the second heat exchanger 6, and leaves from the concentrated solution outlet of the second heat exchanger after releasing heat, and then continues to enter the absorber. The lithium bromide solution forms a cycle among the absorber, the second heat exchanger, and the generator.

[0034] The absorber 8 has a cavity for storing a concentrated solution of lithium bromide LiBr, and is used to absorb the refrigeration steam from the evaporator. The heat released during the absorption process heats the low-temperature cooling water from the first heat exchanger. The absorber 8 is provided with a cooling water inlet, a cooling water outlet, an absorbent inlet, an absorbent outlet, and a refrigerant inlet. The cooling water inlet and the cooling water outlet of the absorber 8 are connected inside the absorber. Similarly, the absorbent inlet and the absorbent outlet of the absorber 8 are connected inside the absorber. The cooling water inlet of the absorber 8 is connected to the first heat exchanger, and the low-temperature cooling water discharged from the cooling water outlet of the first heat exchanger enters the absorber 8 from the cooling water inlet of the absorber 8, becomes medium-temperature cooling water after absorbing heat, and is then discharged from the cooling water outlet of the absorber 8, and then enters the condenser. The absorbent inlet of the absorber 8 is connected to the second heat exchanger, and the low-temperature lithium bromide concentrated solution discharged from the concentrated solution outlet of the second heat exchanger enters the absorber 8 from the absorbent inlet of the absorber 8. The low-temperature lithium bromide concentrated solution absorbs the refrigeration vapor and becomes a low-temperature lithium bromide dilute solution, which is then discharged from the absorbent outlet of the absorber 8 and then enters the second heat exchanger for heat exchange under the action of the solution pump 7. The refrigerant inlet of the absorber 8 is connected to the evaporator 9, and the refrigeration vapor discharged from the evaporator 9 enters the absorber from the refrigerant inlet of the absorber 8, and is absorbed by the low-temperature lithium bromide concentrated solution and becomes a low-temperature lithium bromide dilute solution.

[0035] The evaporator 9 is used to make the refrigerant water from the cold end of the TEG absorb the heat released by the chilled water from the cold storage tower, and the refrigerant water becomes refrigeration steam. The chilled water returns to the cold storage tower after releasing heat. The evaporator 9 is provided with a refrigerant inlet, a refrigerant outlet, a chilled water inlet and a chilled water outlet. The refrigerant inlet and the refrigerant outlet of the evaporator 9 are connected inside the evaporator 9. Similarly, the chilled water inlet and the chilled water outlet of the evaporator 9 are connected inside the evaporator 9. The chilled water inlet of the evaporator 9 is connected to the cold storage tower. The chilled water discharged from the cold storage tower after absorbing heat enters the evaporator 9 from the chilled water inlet of the evaporator 9, and is discharged from the chilled water outlet of the evaporator 9 after releasing heat, and returns to the cold storage tower, forming a chilled water cycle. The refrigerant inlet of the evaporator 9 is connected to the TEG cold end. The refrigerant discharged from the TEG cold end enters the evaporator 9 from the refrigerant inlet of the evaporator 9, becomes refrigeration steam after absorbing heat, and is then discharged from the refrigerant outlet of the evaporator 9, and then enters the absorber; a throttle valve 2 is provided between the refrigerant inlet of the evaporator 9 and the refrigerant outlet of the TEG cold end, which is used to throttle and reduce the pressure of the refrigerant water discharged from the TEG cold end and then send it into the evaporator.

[0036] The cold storage tower 10 is used to store chilled water. When the user needs refrigeration, the low-temperature chilled water is delivered to the user side. After absorbing heat, the chilled water returns to the cold storage tower and is then delivered to the evaporator 9 for heat release. The cold storage tower 10 is provided with a chilled water inlet and a chilled water outlet, which are respectively connected to the chilled water outlet and the chilled water inlet on the evaporator 9 to form a chilled water cycle.

[0037] The working process of the above flue gas waste heat recovery system is as follows:

[0038] (1) Flue gas process: The high-temperature flue gas generated by the waste heat boiler enters the hot end of the TEG for heat exchange, and the temperature of the high-temperature flue gas is used to maintain the high temperature of the hot end of the TEG. After heat exchange in the TEG, the high-temperature flue gas becomes low-temperature flue gas. The low-temperature flue gas leaves the hot end of the TEG and enters the first heat exchanger (flue gas water heat exchanger). The low-temperature flue gas is heated by the high-temperature cooling water from the condenser, and the temperature of the low-temperature flue gas increases and becomes high-temperature flue gas. The high-temperature flue gas leaves the first heat exchanger and enters the generator. The heat of the high-temperature flue gas is used to heat the dilute lithium bromide solution in the generator cavity to generate refrigeration steam. After passing through the generator, the temperature of the high-temperature flue gas is greatly reduced and it is discharged from the generator to the external environment or subsequent flue gas treatment equipment.

[0039] (2) Refrigerant water and absorbent process: The generator is heated by high-temperature flue gas to produce refrigerant steam. The refrigerant steam leaves the generator and enters the condenser. After heat exchange with the medium-temperature cooling water in the condenser, it becomes liquid refrigerant water. The liquid refrigerant water is discharged from the condenser and enters the TEG cold end to maintain the low temperature of the cold end. After that, the refrigerant water continues to be discharged from the TEG cold end, passes through the throttle valve and enters the evaporator. In the evaporator, it exchanges heat with the chilled water after absorbing heat from the cold storage tower. The refrigerant water absorbs the heat released by the chilled water and becomes refrigerant steam again. After leaving the evaporator, the refrigerant steam enters the absorber and is absorbed by the lithium bromide concentrated solution, completing the cycle.

[0040] The lithium bromide dilute solution in the generator is heated by high-temperature flue gas to precipitate water vapor and become a high-temperature lithium bromide concentrated solution. The high-temperature lithium bromide concentrated solution enters the second heat exchanger (solution heat exchanger), and after heat exchange, it becomes a low-temperature lithium bromide concentrated solution and enters the absorber; the lithium bromide concentrated solution in the absorber becomes a low-temperature lithium bromide dilute solution after absorbing water vapor. The low-temperature lithium bromide dilute solution enters the second heat exchanger, and after heat exchange, it becomes a high-temperature lithium bromide dilute solution and returns to the generator, completing the absorbent cycle. Through the heat exchange effect of the second heat exchanger, the heat from the high-temperature lithium bromide concentrated solution of the generator is transferred to the low-temperature lithium bromide dilute solution from the absorber.

[0041] (3) Chilled water and cooling water process:

[0042] After the medium-temperature cooling water enters the condenser, it absorbs the heat of the refrigeration steam and becomes high-temperature cooling water. After being discharged from the condenser, the high-temperature cooling water enters the first heat exchanger (smoke-water heat exchanger), becomes low-temperature cooling water after heat exchange and enters the absorber, becomes medium-temperature cooling water after absorbing heat in the absorber, and finally returns to the condenser to complete the cooling water cycle.

[0043] The chilled water is provided by the cold storage tower. After absorbing heat on the user side, the chilled water enters the evaporator to release heat, and then returns to the cold storage tower to complete the chilled water cycle.

[0044] (4) Combining the above processes, the complete workflow of the system is as follows:

[0045] After the high-temperature flue gas is discharged from the tail flue of the waste heat boiler, it enters the hot end of TEG 1. The temperature of the high-temperature flue gas is reduced to become low-temperature flue gas, and then enters the first heat exchanger, and is heated by the high-temperature cooling water from the condenser 5 to become high-temperature flue gas. The high-temperature flue gas enters the generator 4. At the same time, the high-temperature cooling water releases heat in the first heat exchanger to become low-temperature cooling water, and the low-temperature cooling water enters the absorber 8.

[0046] The dilute lithium bromide solution enters the second heat exchanger 6 at the outlet of the absorber 8 through the solution pump, absorbs the heat of the concentrated lithium bromide solution from the generator 4, enters the generator 4, and further absorbs the heat of the high-temperature flue gas. The high-temperature flue gas releases heat to become low-temperature flue gas and is discharged into the atmosphere. After absorbing heat, the dilute lithium bromide solution continuously vaporizes to generate refrigeration steam, and the refrigeration steam enters the condenser 5; the concentrated lithium bromide solution exchanges heat with the dilute lithium bromide solution in the second heat exchanger 6 and then enters the absorber 8.

[0047] In the condenser 5, the refrigeration steam releases heat and transfers the heat to the medium-temperature cooling water from the absorber 4. The refrigeration steam is cooled and condensed into liquid refrigerant water. The refrigerant water enters the cold end of TEG 1 and then enters the evaporator 9 after being reduced in pressure by the throttle valve.

[0048] In the evaporator 9, the refrigerant water is sprayed on the chilled water pipe by the evaporator pump to absorb heat and vaporize into refrigeration steam, and then enters the absorber 8. The chilled water is cooled and sent to the cold storage tower. When the user needs refrigeration, the low-temperature chilled water is sent to the user side, thereby achieving the purpose of refrigeration.

[0049] In the absorber 8, the refrigeration steam is absorbed by the concentrated lithium bromide solution from the second heat exchanger 6 and restored to a dilute lithium bromide solution. The heat released during the absorption process is absorbed by the low-temperature cooling water from the first heat exchanger. The low-temperature cooling water becomes medium-temperature cooling water and enters the condenser 5, completing a refrigeration cycle.

[0050] The temperature difference between the two ends of TEG is maintained by high-temperature flue gas and low-temperature refrigerant water respectively, which can generate electricity.

[0051] Through the above cycle, the system can produce chilled water while generating electricity through TEG elements, thus realizing the cascade utilization of flue gas waste heat.

[0052] The above examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples, and there are many variations. All variations that can be directly derived or associated with the contents disclosed by a person skilled in the art from the present invention should be considered as the protection scope of the present invention.

Claims

1. A flue gas waste heat recovery system, characterized in that: It comprises a TEG device (1), a first heat exchanger (3), a generator (4), a condenser (5), a second heat exchanger (6), an absorber (8), an evaporator (9), and a cold storage tower (10); The hot end inlet of the TEG device (1) is connected to the external high-temperature flue gas, and the hot end outlet of the TEG device (1) is connected to the flue gas inlet of the first heat exchanger (3). The flue gas outlet of the first heat exchanger (3) is discharged to the external environment or the subsequent flue gas treatment equipment through the generator; the cooling water inlet of the first heat exchanger (3) is connected to high-temperature cooling water, and the high-temperature cooling water is obtained by absorbing heat from the medium-temperature cooling water from the absorber in the condenser. The cooling water outlet of the first heat exchanger (3) is connected to the cooling water inlet of the absorber; The cold end inlet of the TEG device (1) is connected to refrigerant water, wherein the refrigerant water is obtained by liquefying the refrigerant steam generated by the generator in the condenser, and the cold end outlet of the TEG device (1) is connected to the refrigerant inlet of the evaporator, and the refrigerant outlet of the evaporator is connected to the refrigerant inlet of the absorber; The generator (4) stores a dilute lithium bromide solution, and the absorber (8) stores a concentrated lithium bromide solution; the concentrated lithium bromide solution in the absorber (8) serves as an absorbent, and the absorber (8) is connected to the generator (4) via a second heat exchanger (6); The chilled water inlet and the chilled water outlet of the evaporator (9) are respectively connected to the chilled water outlet and the chilled water inlet of the cold storage tower (10) to form a chilled water cycle.

2. A flue gas waste heat recovery system according to claim 1, characterized in that: The generator (4) has a cavity for storing a dilute lithium bromide solution, and the absorber (8) has a cavity for storing a concentrated lithium bromide solution.

3. The flue gas waste heat recovery system according to claim 1, characterized in that: The cold storage tower (10) is connected to the user side and is used to supply cold to the user side.

4. A flue gas waste heat recovery system according to claim 3, characterized in that: The chilled water returned from the user side passes through the cold storage tower (10) and then enters the evaporator (9) for cooling.

5. The flue gas waste heat recovery system according to claim 1, characterized in that: The dilute solution inlet of the second heat exchanger is connected to the absorbent outlet of the absorber, the dilute solution outlet of the second heat exchanger is connected to the absorbent inlet of the generator, the concentrated solution inlet of the second heat exchanger is connected to the absorbent outlet of the generator, and the concentrated solution outlet of the second heat exchanger is connected to the absorbent inlet of the absorber.

6. A flue gas waste heat recovery system according to claim 5, characterized in that: A solution pump is provided between the dilute solution inlet of the second heat exchanger and the absorbent outlet of the absorber.

7. The flue gas waste heat recovery system according to claim 5, characterized in that: The condenser is provided with a cooling water inlet and outlet and a refrigerant inlet and outlet, the cooling water inlet of the condenser is connected to the cooling water outlet of the absorber, the cooling water outlet of the condenser is connected to the cooling water inlet of the first heat exchanger (3), the refrigerant inlet of the condenser is connected to the refrigeration steam outlet of the generator, and the refrigerant outlet of the condenser is connected to the cold end inlet of the TEG device (1).

8. The flue gas waste heat recovery system according to claim 1, characterized in that: The first heat exchanger is a smoke-water heat exchanger.

9. A flue gas waste heat recovery system according to claim 1 or 5, characterized in that: The second heat exchanger is a solution heat exchanger.

10. The flue gas waste heat recovery system according to claim 1, characterized in that: A throttle valve is provided between the cold end outlet of the TEG device (1) and the refrigerant inlet of the evaporator.

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