System for utilizing waste heat of intermediate liquid at top of desorption tower

Abstract

The invention discloses a system for utilizing waste heat of an intermediate liquid at the top of a desorption tower. The system comprises the desorption tower, a waste heat recovery device, an intermediate tower tray and a reboiler, a first material pipeline is led out from the middle tray to enter a waste heat recovery device, and enters a reboiler after being heated, so that the middle tray of the desorption tower, the waste heat recovery device and the reboiler are sequentially communicated to form a waste heat recovery heating loop; the tower top of the desorption tower enters the waste heat recovery device through a third material pipeline, and enters the tower top condenser after being cooled by the waste heat recovery device, so that the desorption tower is sequentially communicated with the waste heat recovery device and the tower top condenser to form a waste heat recovery cooling loop. According to the waste heat utilization system, on one hand, waste heat of steam at the tower top is recycled, the waste heat discharge amount of the system is reduced, on the other hand, an intermediate liquid material is heated, low-grade waste heat is used for replacing a high-temperature heat source of the reboiler at the tower bottom through the waste heat recovery device, the process steam consumption of the reboiler at the tower bottom of the desorption tower is reduced, and a large amount of steam is saved.

Description

Technical Field

[0001] The invention relates to the technical field of distillation, and in particular to a system for utilizing waste heat of an intermediate liquid at the top of a desorption tower. Background Art

[0002] CCUS is the abbreviation of Carbon Capture, Utilization and Storage, which refers to a combination of technologies used to reduce carbon dioxide emissions in the atmosphere. These technologies can be divided into several stages:

[0003] Carbon Capture: In this phase, carbon dioxide is captured from industrial processes or directly from the air. Typically, this can be achieved through methods such as chemical absorption, physical adsorption or membrane separation.

[0004] Carbon Utilization: Captured CO2 can be used as a feedstock to make chemicals, fuels or other products, or it can be used for enhanced oil recovery (EOR), which is to increase oil production by injecting CO2 into underground reservoirs.

[0005] Carbon Storage: For unused CO2, it can be stored for a long time in suitable geological formations, such as depleted oil and gas fields or deep saline aquifers. The purpose is to ensure that the CO2 is not released back into the atmosphere.

[0006] For the carbon capture stage, an absorption tower and a desorption tower are usually used, such as Figure 1 As shown, the gas rich in carbon dioxide enters from the bottom of the absorption tower, and the lean amine liquid is sprayed from top to bottom as the absorption liquid, absorbing carbon dioxide and converting it into rich amine liquid, and then transporting it to the desorption tower for desorption and circulation; the carbon dioxide gas separated at the top of the desorption tower at about 88°C is directly cooled to about 40°C by a large amount of circulating water using the top condenser for discharge. In this process, about 70% of the energy input to the bottom reboiler is taken away by the circulating cooling water at the top of the tower. This part of energy cannot be further recycled, resulting in a very low heat utilization efficiency of the conventional desorption tower. Research on energy-saving technology for desorption tower distillation should be paid attention to. The desorption tower distillation process is a continuous evaporation-condensation process. The condensation of the gas phase at the top of the tower releases latent heat, and the evaporation of the liquid phase at the bottom of the tower requires latent heat. Combined with the working principle of the heat pump, for the single-tower desorption tower distillation, the heat pump technology is obviously a very suitable energy-saving technology. The use of heat pumps in the distillation process can greatly improve energy utilization and improve economic efficiency.

[0007] In view of the above, it is necessary to propose a system for utilizing the waste heat of the intermediate liquid at the top of the desorption tower to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to overcome the defects in the prior art and provide a system for utilizing the waste heat of the intermediate liquid at the top of a desorption tower.

[0009] To achieve the above object, the technical solution of the present invention is as follows: a system for utilizing waste heat of intermediate liquid at the top of a desorption tower, comprising a desorption tower, a waste heat recovery device, an intermediate tower tray, and a reboiler; The intermediate tray is any tray in the stripping section of the desorption tower, and the material is drawn from the intermediate tray out of the No. 1 material pipeline into the waste heat recovery device, and after being heated by the waste heat recovery device, it enters the reboiler through the No. 2 material pipeline, so that the intermediate tray, the waste heat recovery device, and the reboiler of the desorption tower are connected in sequence to form a waste heat recovery heating loop; The top of the desorption tower enters the waste heat recovery device through the No. 3 material pipeline, and enters the top condenser after being cooled by the waste heat recovery device, so that the desorption tower is connected with the waste heat recovery device and the top condenser in sequence to form a waste heat recovery cooling loop.

[0010] Furthermore, the waste heat recovery device is an absorption heat pump device, which includes an absorber, a generator, a condenser, and an evaporator; The waste heat recovery heating circuit is introduced into the absorber through the No. 1 material pipeline, and flows out from the absorber through the W2 pipeline and is sent to the condenser, and after passing through the condenser, it is connected to the No. 2 material pipeline through the W3 pipeline.

[0011] Furthermore, the waste heat recovery cooling loop is connected from the No. 3 material pipeline to the W4 pipeline and leads to the evaporator, flows out through the W5 pipeline after passing through the evaporator and is connected to the tower top condenser.

[0012] Furthermore, a driving heat source is introduced into the generator through the S1 pipeline and flows out through the S2 pipeline. In actual use, the driving heat source is steam. The absorber and the generator are connected through a solution circulation loop. The solution circulation loop is transported from the absorber to the generator through a dilute solution pipeline via a solution pump, and the generator is connected to the absorber through a concentrated solution pipeline.

[0013] Furthermore, an intermediate liquid circulation pump is provided on the waste heat recovery heating circuit, the inlet of the intermediate liquid circulation pump is connected to the intermediate tower plate side, and the outlet is connected to the absorber side; a first diverter jumper is connected between the front of the intermediate liquid circulation pump and the reboiler, and a first diverter valve is provided on the first diverter jumper.

[0014] Furthermore, the No. 3 material pipeline is connected by a second diverter jumper before and after entering and exiting the waste heat recovery device, and a second diverter valve is provided on the second diverter jumper.

[0015] Furthermore, the waste heat recovery device is provided with at least one group.

[0016] Furthermore, the desorption tower is provided with multiple outflow tower plates and multiple reflux tower plates, and the multiple outflow tower plates are respectively provided with liquid outlet pipes, and the multiple liquid outlet pipes are arranged in parallel and connected to the No. 1 material pipe; the multiple reflux tower plates are respectively provided with reflux pipes, and the multiple reflux pipes are arranged in parallel and connected to the No. 2 material pipeline; in the desorption tower, the outflow tower plate is arranged on the upper side of the reflux tower plate.

[0017] Furthermore, each liquid outlet pipe is provided with a liquid outlet control valve, and each return pipe is provided with a return flow control valve; either the liquid outlet control valve or the return flow control valve is selectively opened.

[0018] The advantages and beneficial effects of the present invention are as follows: the waste heat utilization system of the desorption tower top for the intermediate liquid of the present invention, on the one hand, recovers the waste heat of the tower top steam, reduces the waste heat emission of the system, and on the other hand, heats the intermediate liquid material, and utilizes low-grade waste heat to replace the high-temperature heat source of the tower bottom reboiler through the waste heat recovery device, thereby reducing the process steam consumption of the desorption tower bottom reboiler and saving a lot of steam. Compared with the common method of directly heating the tower bottom liquid with the waste heat of the tower top steam, the waste heat is used to heat the intermediate liquid in this process design, and the temperature of the intermediate liquid is lower than that of the tower bottom liquid heat source, which is beneficial to the operation of the heat pump and effectively improves the thermal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of carbon capture of carbon dioxide by chemical absorption in the prior art; Figure 2 It is a simplified schematic diagram of a system for utilizing waste heat of an intermediate liquid at the top of a desorption tower of the present invention; Figure 3 It is a schematic diagram of the medium flow direction of the waste heat recovery device in the present invention; Figure 4 It is a specific schematic diagram of a system for utilizing waste heat of an intermediate liquid at the top of a desorption tower of the present invention; Figure 5 is a schematic diagram of a flow chart of Embodiment 2 of the present invention; In the figure: 1. Absorption tower; 2. Desorption tower; 3. Lean amine liquid; 4. Rich amine liquid; 5. Top condenser; 6. Reboiler; 7. Waste heat recovery device; 8. Intermediate tray; 9. No. 1 material pipeline; 10. No. 2 material pipeline; 11. Waste heat recovery heating circuit; 12. Waste heat recovery cooling circuit; 13. Absorber; 14. Generator; 15. Condenser; 16. Evaporator; 17. W2 pipeline; 18. W3 pipeline; 19. No. 3 material pipeline; 20. W 4 pipelines; 21, W5 pipeline; 22, S1 pipeline; 23, S2 pipeline; 24, solution circulation loop; 25, solution pump; 26, dilute solution pipeline; 27, concentrated solution pipeline; 28, intermediate liquid circulation pump; 29, first diverter jumper; 30, first diverter valve; 31, second diverter jumper; 32, second diverter valve; 33, outflow tray; 34, return tray; 35, liquid outlet pipe; 36, return pipe; 37, liquid outlet control valve; 38, return control valve. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0021] The purpose of the carbon dioxide capture process is to recover the carbon dioxide in the exhaust gas of the self-provided power plant, realize carbon dioxide capture, realize recycling value, and reduce carbon emissions. The basic process is as follows Figure 1 As shown, the chemical absorption method is used. The chemical absorption method refers to the chemical solvent reacting with CO2 to absorb carbon dioxide. When external conditions such as temperature or pressure change, the reaction is reversed, thereby achieving the purpose of carbon dioxide analysis and recycling of absorbent. Figure 1 As shown in the figure, after the flue gas is desulfurized and denitrated, the exhaust gas enters the absorption tower 1 from the bottom through the induced draft fan, and the absorption liquid is sprayed down from the top of the absorption tower 1. The flue gas and the absorption liquid react after contact in the absorption tower 1. The absorption liquid absorbs the CO2 in the flue gas and becomes a rich liquid containing a large amount of CO2. The rich liquid passes through the rich liquid pump to the desorption tower 2, and is heated to 100 to 120°C by the reboiler 6 in the desorption tower 2, so that the rich liquid decomposes and releases the CO2 absorbed in the flue gas, and finally achieves the separation and recovery of carbon dioxide. In industry, alkaline chemical absorption liquids are usually selected to absorb CO2, such as alcohol amines, potash and ammonia water. At present, the more mature chemical absorption processes are mostly based on ethanolamine aqueous solutions, such as monoethanolamine method (MEA method), diethanolamine method (DEA method) and methyldiethanolamine method (MDEA method).

[0022] Currently, it is the most widely used method for capturing CO2 in industry, but the absorption and analysis process requires continuous heat exchange, resulting in high steam energy consumption.

[0023] Embodiment 1: like Figure 2-4 As shown, a system for utilizing waste heat from the top of a desorption tower 2 for the intermediate liquid. This scheme is designed to recover the lean amine liquid 3 and the heat of the steam from the top of the desorption tower to heat the intermediate liquid, thereby achieving the purpose of reducing the steam consumption of the desorption tower. It includes a desorption tower 2, a waste heat recovery device 7, an intermediate tray 8, and a reboiler 6;

[0024] The intermediate tray 8 can be any tray in the stripping section of the desorption tower 2. In this embodiment, the intermediate liquid refers to the amine liquid on a tray near the reboiler 6 at the lower part of the desorption tower 2. A path of amine liquid is drawn from the tray, hereinafter referred to as the intermediate liquid, with a temperature of 101°C. In the original process design, the intermediate tray 8 enters the reboiler 6 after descending, and the temperature of the intermediate liquid is 101°C. In this embodiment, the feed temperature of this part is increased to reduce the steam consumption of the desorption tower. In the prior art, there is also a method of directly forcing the tower bottom liquid to circulate into the waste heat recovery device 7 for heating to realize the utilization of the waste heat at the top of the tower. On the one hand, due to the large temperature difference between the top and the bottom, it is found that the heat utilization rate of the heat pump is limited in actual use; on the other hand, the heating effect of the tower bottom before and after the tower bottom is drawn out from the tower bottom into the heat pump and then refluxed to the tower bottom is not good. The improved intermediate liquid drawn out in this embodiment is heated and sent to the tower kettle by utilizing waste heat, which can intuitively reflect the heating effect of waste heat utilization, and the temperature of the heated heat source is reduced, which is beneficial to the operation of the heat pump and effectively improves the thermal efficiency.

[0025] Specifically, Figure 1 As shown, the material No. 1 pipe 9 is drawn out from the middle tray 8 and enters the waste heat recovery device 7, and after being heated by the waste heat recovery device 7, enters the reboiler 6 through the No. 2 material pipe 10, so that the middle tray 8, the waste heat recovery device 7 and the reboiler 6 of the desorption tower 2 are connected in sequence to form a waste heat recovery heating circuit 11; this is to use the heat of the low-grade heat source absorbed in the waste heat recovery device 7 to heat the relatively high-grade heat source. In this embodiment, the No. 1 material pipe is an unheated high-grade heat source, which becomes a heated high-grade heat source after passing through the waste heat recovery device 7 and is sent out through the No. 2 material pipe 10 and converges into the reboiler 6, thereby effectively reducing the heat load of the reboiler 6, thereby reducing the steam usage in the tower bottom.

[0026] The low-grade heat source is the steam waste heat of the carbon dioxide at the top of the desorption tower 2. Specifically, the top of the desorption tower 2 enters the waste heat recovery device 7 through the No. 3 material pipeline 19. Before entering the waste heat recovery device 7, it is a low-grade heat source with a relatively high temperature. After passing through the waste heat recovery device 7, the heat in the low-grade heat source is converted into a high-grade heat source by the waste heat recovery device 7, thereby further reducing the temperature of the low-grade heat source. Specifically, the temperature of the No. 3 material pipe before entering the waste heat recovery device 7 is 86-88°C, and the temperature after flowing out is reduced to 70°C; the pipeline setting after cooling through the waste heat recovery device 7 is the same as the original design, and still enters the top condenser 5. After cooling, it drops to about 40°C. In comparison, the cooling load of the top condenser 5 is also effectively reduced. In this embodiment, the desorption tower 2 is connected with the waste heat recovery device 7 and the top condenser 5 in sequence to form a waste heat recovery cooling circuit 12.

[0027] like Figure 3 As shown, the waste heat recovery device 7 in this embodiment is an absorption heat pump device, which specifically includes an absorber 13, a generator 14, a condenser 15, and an evaporator 16; the absorber 13 and the generator 14 are connected through a solution circulation loop 24, and the solution circulation loop 24 is transported from the absorber 13 to the generator 14 through a dilute solution pipeline 26 via a solution pump 25, and the generator 14 is connected to the absorber 13 through a concentrated solution pipeline 27. The solvent is continuously circulated between the absorber 13 and the generator 14 by the solution pump 25 to form a solution circulation loop 24.

[0028] The internal working fluid of the waste heat recovery conversion system is lithium bromide solution, which is the absorbent of lithium bromide absorption refrigeration / heating unit; Physical properties of lithium bromide solution: Name: lithium bromide; Chemical formula: LiBr; Molecular weight: 86.85; Physical properties: Very easy to deliquesce. State: White cubic crystal or granular powder; Density: 3.64g / cm^3; Melting point: 560℃; Boiling point 1265℃. Solubility: Easily soluble in water, ether, ethanol, soluble in organic solvents such as methanol, acetone, ethylene glycol, slightly soluble in pyridine. Its aqueous solution has strong hygroscopicity, and the concentration of saturated lithium bromide aqueous solution at room temperature reaches 60%. The higher the concentration and the lower the temperature, the stronger the hygroscopicity.

[0029] In this embodiment, the waste heat recovery heating loop 11 is introduced into the absorber 13 by the No. 1 material pipeline 9, and flows out from the absorber 13 and is sent to the condenser 15 through the W2 pipeline 17, and is connected to the No. 2 material pipeline 10 through the W3 pipeline 18 after passing through the condenser 15. That is, the heated high-grade heat source flows through the absorber 13 and the condenser in sequence. After the secondary heating, in the embodiment, the high-grade heat source is heated from about 101°C to about 110°C. In addition, the flow direction of the low-grade heat source is that the waste heat recovery cooling loop 12 is connected to the W4 pipeline 20 from the No. 3 material pipeline 19 to the evaporator 16, and flows out through the W5 pipeline 21 after passing through the evaporator 16 and is connected to the top condenser 5. The water in the evaporator 16 evaporates and absorbs heat, so that the temperature of the low-grade heat source is reduced; and the heat is transferred to the water vapor, which is then sent to the absorber 13. In this embodiment, the initial temperature of the low-grade heat source is about 88°C, and the temperature after flowing out drops to about 70°C. Furthermore, a driving heat source is introduced into the generator 14 through the S1 pipeline 22 and flows out through the S2 pipeline 23. In actual use, the driving heat source is steam.

[0030] Furthermore, an intermediate liquid circulation pump 28 is provided on the waste heat recovery heating circuit 11, the inlet of the intermediate liquid circulation pump 28 is connected to the side of the intermediate tower plate 8, and the outlet is connected to the side of the absorber 13; the intermediate liquid is forced to circulate through the intermediate liquid circulation pump 28: it is pressurized by a booster pump and sent to the absorption heat pump component, and then enters the reboiler 6 after being heated, so as to achieve the purpose of reducing steam consumption.

[0031] like Figure 2 , 4 As shown, a first splitter jumper 29 is connected between the intermediate liquid circulation pump 28 and the reboiler 6, and a first splitter valve 30 is provided on the first splitter jumper 29. The first splitter jumper 29 can be used to adjust the flow entering the absorption heat pump assembly, and the flow is controlled by the first splitter valve 30. Similarly, the No. 3 material pipeline 19 is connected by a second diverter jumper 31 before and after entering and exiting the waste heat recovery device 7. The second diverter jumper 31 is provided with a second diverter valve 32. In actual use, if there is a problem with the waste heat recovery device 7 and maintenance is carried out, the waste heat recovery device 7 can be cut off and isolated separately, and the top gas in the system still circulates through the second diverter jumper 31; and during normal operation, the flow entering the waste heat recovery device 7 can also be controlled by the second diverter valve 32 to control the heat energy recovery amount of the waste heat recovery system; when operating under variable conditions, the design operating conditions of this heat recovery system are 108→115℃ for the bottom liquid and 101→109.93℃ for the intermediate liquid; the load adjustment range can be controlled within 20~100%.

[0032] Furthermore, the waste heat recovery device 7 may be provided with only one set of recovery devices or multiple sets in parallel according to the selected processing capacity, so as to increase the processing capacity; in this embodiment, two sets are schematically provided in parallel. Figure 4 As shown, in actual use, multiple groups of waste heat recovery devices 7 can be set up, and the effect of increasing the processing capacity can be achieved by connecting them in parallel, and a standby unit can also be formed. Figure 4 The illustrated configuration includes two groups, specifically component 1 and component 2, which can serve as backup for each other or can run simultaneously to increase processing capacity.

[0033] Driving energy, the scheme design uses 1.0MPaG saturated steam as the driving force. After condensation in the heat recovery system, it is sent to the steam condensate network of the original reboiler through condensate recovery. Process steam: 1.0MPaG saturated steam can be provided. The scheme design is based on 1.0MPaG saturated steam. The steam condensate is calculated at 120℃, and the effective enthalpy value is 544.27kcal / kg, which is 0.633MW / t steam.

[0034] Scheme design: The operating temperature of the tower bottom liquid is about 108℃, and the temperature after heating by the reboiler is about 115℃; Under the existing process conditions, the heat load of the reboiler is 1.3t steam (0.3MPaG) / t carbon dioxide. Based on the output of 1 million tons / year, the steam consumption is about 162t / h; the heat load of the analytical tower is 100.44MW; The top steam of the analytical tower: temperature 86~88℃, flow rate 168.292t / h, heat release when cooled to 70℃: 17MW; finally it needs to be cooled to 40℃.

[0035] Process principle: Recover low-grade heat energy of 20℃~70℃ and convert it into high-grade heat medium with a temperature 40℃~50℃ higher than low-grade heat. Compared with direct heating by heat exchanger, it can save 40% of steam. Energy-saving technical indicators: Rated operating system parameters: System heating capacity: 100.44MW - equivalent to 162t / h of 0.3MPaG saturated steam and 158.67t / h of 1.0MPaG saturated steam; waste heat recovery capacity is 30MW, approximately 47.39t / h, 1.0MPaG saturated steam.

[0036] Driving steam: steam 1.0MPaG saturated steam, consumption 111.28t / h, steam condensate temperature 120℃; Intermediate liquid: flow rate 4000t / h, temperature 101→109.93℃; Bottom liquid: temperature 108→115℃ (same as reboiler operation condition), flow rate is about 7580t / h; Desorption tower top steam: temperature 88→70℃, 17MW Lean amine liquid: temperature 61→56℃, heat load 14.75MW, flow rate 2674t / h, flow rate accounting for about 70.4%; Reduce circulating water consumption: 3225t / h (according to 30→38℃), and reduce cooling tower water replenishment by 45t / h on average; System consumption: about 1600kW; (This is an estimated value. The selection parameters of the tower bottom liquid can only be determined after the physical properties are determined.)

[0037] Table 1 Main operating parameters before and after energy-saving transformation

[0038] Economic benefit analysis: Table 2 Economic benefit analysis calculation table (1 million tons / year CCUS)

[0039] Embodiment 2: In order to improve the temperature control range of the waste heat utilization system, as an improvement, Figure 5As shown, a plurality of outflow trays 33 and a plurality of reflux trays 34 are provided on the desorption tower 2, and liquid outlet pipes 35 are respectively provided on the plurality of outflow trays 33, and the plurality of liquid outlet pipes 35 are arranged in parallel and connected to the No. 1 material pipe. In actual use, any one of the liquid outlet pipes 35 can be opened, and the liquid outlet pipe 35 is the liquid outlet of the middle tray 8; and at the same time, the plurality of reflux trays are respectively provided with reflux pipes 36, and the plurality of reflux pipes 36 are arranged in parallel and connected to the No. 2 material pipeline 10; the outflow tray 33 in the desorption tower 2 is arranged on the upper side of the reflux tray 34. In actual control, since the temperature after passing through the waste heat utilization system, i.e., the discharge temperature of the No. 2 material pipeline 10, will change with the change of the feed amount and the change of the flow rate entering the waste heat recovery device 7, the temperature will change. In the first implementation, no matter how much the temperature is heated, it is directly sent to the tower kettle. This may cause large fluctuations in the tower kettle temperature, which may have a greater impact on the steady state of the entire desorption tower 2. In this embodiment, in order to avoid this situation, according to the temperature monitoring of the No. 2 material pipeline 10, it is sent to an appropriate flow back to the tower plate 34. It can be understood that the temperature of the material flowing back to the tower plate 34 It is better to be closer to the temperature of the No. 2 material pipe. Furthermore, each liquid outlet pipe 35 is provided with a liquid outlet control valve 37, and each return pipe 36 is provided with a return control valve 38; the liquid outlet control valve 37 and the return control valve 38 are opened one by one; in actual use, any liquid outlet control valve 37 can be opened by remote control, and different outflow tower plates 33 can be selected to discharge liquid, so as to achieve the controllability of the temperature control range; and the material flowing out of the No. 2 material pipeline 10 is sent to the return tower plate 34 with the closest temperature, so that the waste heat of the entire desorption tower 2 can not only be effectively utilized, but also the overall operation of the system is more stable.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower, characterized in that: It comprises a desorption tower (2), a waste heat recovery device (7), an intermediate tower plate (8), and a reboiler (6); The intermediate tray (8) is any tray in the stripping section of the desorption tower (2), and the material is drawn from the intermediate tray (8) to the first material pipeline (9) to enter the waste heat recovery device (7), and after being heated by the waste heat recovery device (7), enters the reboiler (6) through the second material pipeline (10), so that the intermediate tray (8), the waste heat recovery device (7), and the reboiler (6) of the desorption tower (2) are connected in sequence to form a waste heat recovery heating circuit (11); The top of the desorption tower (2) enters the waste heat recovery device (7) through the No. 3 material pipeline (19), and enters the top condenser (5) after being cooled by the waste heat recovery device (7), so that the desorption tower (2) is connected with the waste heat recovery device (7) and the top condenser (5) in sequence to form a waste heat recovery cooling circuit (12).

2. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 1, characterized in that: The waste heat recovery device (7) is an absorption heat pump device, which comprises an absorber (13), a generator (14), a condenser (15), and an evaporator (16); The waste heat recovery heating circuit (11) is introduced into the absorber (13) through the No. 1 material pipeline (9), and flows out from the absorber (13) through the W2 pipeline (17) and is sent to the condenser (15), and after passing through the condenser (15), it is connected to the No. 2 material pipeline (10) through the W3 pipeline (18).

3. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 2, characterized in that: The waste heat recovery cooling circuit (12) is connected to the No. 3 material pipeline (19) through the W4 pipeline (20) and leads to the evaporator (16). After passing through the evaporator (16), it flows out through the W5 pipeline (21) and is connected to the tower top condenser (5).

4. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 3, characterized in that: A driving heat source is introduced into the generator (14) via the S1 pipeline (22) and flows out via the S2 pipeline (23). The absorber (13) and the generator (14) are connected via a solution circulation loop (24). The solution circulation loop (24) is transported from the absorber (13) to the generator (14) via a dilute solution pipeline (26) and a solution pump (25). The generator (14) is connected to the absorber (13) via a concentrated solution pipeline (27).

5. The system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 2, characterized in that: An intermediate liquid circulation pump (28) is provided on the waste heat recovery heating circuit (11), the inlet of the intermediate liquid circulation pump (28) is connected to the side of the intermediate tower tray (8), and the outlet is connected to the side of the absorber (13); a first flow splitter jumper (29) is connected between the front of the intermediate liquid circulation pump (28) and the reboiler (6), and a first flow splitter jumper (29) is provided on the first flow splitter jumper (29).

6. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 3, characterized in that: The third material pipeline (19) is connected before and after entering and exiting the waste heat recovery device (7) via a second flow splitter jumper (31), and a second flow splitter valve (32) is provided on the second flow splitter jumper (31).

7. The system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 1, characterized in that: The waste heat recovery device (7) is provided with at least one group.

8. The system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 1, characterized in that: The desorption tower (2) is provided with a plurality of outflow trays (33) and a plurality of reflux trays (34); the plurality of outflow trays (33) are respectively provided with liquid outlet pipes (35); the plurality of liquid outlet pipes (35) are arranged in parallel and connected to a No. 1 material pipe; the plurality of reflux trays are respectively provided with reflux pipes (36); the plurality of reflux pipes (36) are arranged in parallel and connected to a No. 2 material pipe (10); in the desorption tower (2), the outflow tray (33) is arranged on the upper side of the reflux tray (34).

9. A system for utilizing waste heat of intermediate liquid at the top of a desorption tower according to claim 8, characterized in that: Each liquid outlet pipe (35) is provided with a liquid outlet control valve (37), and each return pipe (36) is provided with a return flow control valve (38); either the liquid outlet control valve (37) or the return flow control valve (38) is selectively opened.

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