Open-close type composite flue gas waste heat recovery system and method

Abstract

This invention discloses an open-closed composite flue gas waste heat recovery system and method. The system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction. The closed heat recovery section includes a closed absorption heat pump (1) and a flue-water heat exchange chamber (3). The intermediate water absorbs the heat from the first stage of the flue gas after being sprayed by a first spray layer (61) and returns to the heat pump (1) to release heat, thereby heating the return water for heat users. The open heat recovery section includes an open absorption heat pump (2) and a flue-water heat exchange chamber (4). The absorption solution absorbs moisture after being sprayed by a second spray layer (62) and becomes a dilute solution. The dilute solution is regenerated into a concentrated solution and generates steam. The steam condenses and releases heat to heat the return water for heat users. The flue gas flows through the two chambers sequentially and is then discharged. The heat user water circuit is connected to the heating side of the two heat pumps to heat the return water for heat users and supply heat to them. This invention achieves deep recovery of waste heat from flue gas and combined water and heat supply through the cascade coupling of closed and open heat pumps, significantly reducing the temperature and humidity of exhaust gas and improving system energy efficiency and water resource recovery rate.

Description

Technical Field

[0001] This invention belongs to the field of flue gas waste heat recovery technology, specifically relating to an open-closed composite flue gas waste heat recovery system and method. Background Technology

[0002] Driven by the "dual carbon" goals, the demand for energy conservation and emission reduction in the industrial and residential heating sectors is becoming increasingly urgent. Low- and medium-temperature flue gas emitted from industrial production contains a large amount of waste heat and moisture; its clean and efficient recovery is a key approach to reducing energy consumption, carbon emissions, and resource reuse. Absorption heat pump technology, due to its ability to recover low-grade waste heat and improve its thermal energy quality, has become the mainstream technology in the field of flue gas waste heat recovery.

[0003] However, traditional flue gas waste heat recovery systems typically employ a single heat pump cycle, making it difficult to simultaneously address the dual requirements of deep recovery and grade enhancement. To solve this problem, existing technologies mainly adopt the following two approaches: (1) Closed-loop absorption heat pump cycle scheme This solution employs a closed-loop absorption heat pump, recovering waste heat from flue gas through indirect heat exchange between intermediate water and flue gas. After absorbing heat from the flue gas in the flue-water heat exchange chamber, the intermediate water releases heat into the closed-loop absorption heat pump, heating the return water for users and forming a closed-loop circulation of the intermediate water. The advantages of this solution are that the system process is closed and controllable, the heating temperature is relatively stable, and it can achieve a certain degree of quality improvement.

[0004] However, this scheme has the following drawbacks: Limited by the heat transfer temperature difference inherent in the indirect heat exchanger, the heat pump evaporation temperature decreases when recovering waste heat from the low-temperature flue gas, leading to a significant drop in the coefficient of performance (COP) and reduced economic efficiency. Under this condition, a large amount of latent heat and water resources in the flue gas cannot be effectively recovered. To achieve deep cooling, the intermediate water temperature needs to be lowered to extremely low levels, further worsening the heat pump's operating conditions and creating a contradiction between energy efficiency and depth of cooling.

[0005] (2) Open absorption heat pump cycle scheme This scheme employs an open-loop absorption heat pump, recovering waste heat and moisture from the flue gas through direct contact heat exchange between the absorption solution (such as lithium bromide solution) and the flue gas. The concentrated solution is sprayed into the flue gas solution heat exchange chamber, absorbing water vapor and releasing latent heat to become a dilute solution. This dilute solution is then heated and concentrated in an open-loop generator to regenerate into a concentrated solution and generate steam. The steam then heats the return water for heat users in an open-loop condenser. The advantage of this scheme is that direct contact heat exchange eliminates the temperature difference caused by indirect heat exchange, enabling deep recovery of latent heat and moisture from the flue gas.

[0006] However, this approach has the following drawbacks: the heating temperature and operational stability of an open-loop system are significantly affected by the flue gas conditions (temperature and humidity), making it difficult to directly meet the industrial process's demand for medium-to-high temperature heat sources or stable heating. The heat grade of a single open-loop system is relatively low, limiting its application range. Furthermore, the absorption of acidic components from the flue gas by the solution may lead to equipment corrosion problems.

[0007] Although the two approaches described above attempt to address the problem of flue gas waste heat recovery from different perspectives, both have inherent technical flaws. The closed-loop system solves the "grade improvement" problem, but at the cost of sacrificing deep recovery capabilities; the open-loop system achieves "deep recovery," but struggles to meet the demands of both grade improvement and stable heating. Neither approach achieves the engineering goal of simultaneously addressing deep recovery, efficient temperature enhancement, and combined hydrothermal recovery within the same system.

[0008] Specifically, the existing technology has the following problems: (1) The contradiction between the depth of closed-loop cycle and energy efficiency Closed-loop absorption heat pumps recover waste heat from flue gas through indirect heat exchange. However, due to the temperature difference in the indirect heat exchanger, the coefficient of performance (COP) of the heat pump decreases significantly when recovering waste heat from low-temperature flue gas. To achieve deep cooling, the evaporation temperature needs to be further reduced, leading to deterioration in energy efficiency, and a large amount of latent heat and water resources in the flue gas cannot be effectively recovered.

[0009] (2) The quality and application limitations of open circulation Although open-loop absorption heat pumps can recover waste heat and moisture from flue gas through direct contact heat exchange, their heating temperature and operational stability are greatly affected by the flue gas conditions, making it difficult to directly meet the industrial process's demand for medium- and high-temperature heat sources or stable heating, and the recovered heat grade is relatively low.

[0010] (3) High system integration difficulty Designing an efficient and compact coupled process, with the open loop serving as the "deep recycling front end" and the closed loop serving as the "quality enhancement and stable output back end," to achieve a synergistic effect of 1+1>2, while addressing the control complexity, acidic condensate treatment, and overall system corrosion prevention issues after coupling remains a technical challenge.

[0011] (4) Insufficient water resource recycling efficiency Especially in coal-fired power plants in water-scarce regions, flue gas serves as both a waste heat source and an important source of water resources. Existing technologies (particularly purely closed-loop systems) struggle to achieve large-scale water recovery economically while efficiently recovering heat energy. While open-loop systems can recover some water, they suffer from problems such as low calorific value and equipment corrosion.

[0012] (5) Inefficient use of energy grade Existing technologies fail to optimally match the heat (sensible and latent heat) of different temperature zones in flue gas with the most suitable heat pump technology, particularly failing to efficiently convert low-grade latent heat into higher-grade usable heat sources, thus limiting the efficiency of energy cascade utilization. The traditional "flue gas-water-heat pump" indirect heat exchange path involves multiple heat transfer temperature differences, resulting in significant loss of usable energy (J).

[0013] Therefore, how to achieve deep recovery of flue gas waste heat, efficient temperature increase and hydrothermal co-harvest without significantly increasing system complexity, while taking into account system energy efficiency, stability and economy, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0014] This invention aims to overcome the problems of insufficient deep recovery capacity of closed-loop flue gas waste heat recovery technology, limited heating quality of open-loop technology, high system integration difficulty, and low water resource recovery efficiency. It provides a combined open and closed-loop flue gas waste heat recovery system and method. The core of this system lies in arranging closed-loop and open-loop absorption heat pumps sequentially along the flue gas flow direction, forming a tiered utilization architecture of "closed-loop front-end recovery of sensible heat and open-loop back-end absorption of latent heat." Combined with parallel or series connection of water circuits for heat users, this achieves coordinated deep recovery and quality improvement of flue gas waste heat within a single system. The system is compact, highly energy-efficient, and integrates water and heat recovery, providing stable, economical, and efficient technical support for low-carbon transformation in high-energy-consuming industries such as industrial boilers, steel, and petrochemicals.

[0015] To address the aforementioned problems, a first aspect of the present invention provides an open-closed composite flue gas waste heat recovery system. The system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a heat user water circuit. The closed heat recovery section includes a closed absorption heat pump (1) and a flue-water heat exchange chamber (3). The intermediate water outlet of the closed absorption heat pump (1) is connected to a first spray layer (61) above the flue-water heat exchange chamber (3) to allow the intermediate water to contact the flue gas and absorb heat. The bottom of the flue-water heat exchange chamber (3) is provided with an intermediate water outlet, which is connected to the intermediate water inlet of the closed absorption heat pump (1) via a circulation drive device, forming a closed-loop intermediate water circulation circuit. The heat-absorbing intermediate water exchanges heat with the heat user return water flowing through the heating side of the closed absorption heat pump (1) via the closed absorption heat pump (1) to heat the heat user return water. The open heat recovery section includes an open absorption heat pump (2) and a flue-water heat exchange chamber (3). 4) The open absorption heat pump (2) and the flue gas solution heat exchange chamber (4) have a solution circulation loop. The solution circulation loop is connected to the second spray layer (62) above the flue gas solution heat exchange chamber (4) and is used to provide absorption solution to the flue gas solution heat exchange chamber (4). The solution is diluted after contacting the flue gas for heat exchange. The diluted solution is regenerated in the open absorption heat pump (2) and generates steam. The steam is condensed and heat exchanged with the heat user return water flowing through the heating side of the open absorption heat pump (2). The released heat is used to heat the heat user return water. The flue gas outlet of the flue gas water heat exchange chamber (3) is connected to the flue gas inlet of the flue gas solution heat exchange chamber (4) so ​​that the flue gas flows through the closed heat recovery section and the open heat recovery section in sequence and is discharged. The heat user water circuit is connected to the heating side of the closed absorption heat pump (1) and / or the heating side of the open absorption heat pump (2) and is used to heat the heat user return water to the outside.

[0016] The open / closed hybrid flue gas waste heat recovery system provided in this application is based on the core principle of constructing a tiered utilization architecture of "closed front-end sensible heat recovery and open back-end latent heat absorption" by sequentially arranging closed-loop and open-loop absorption heat pumps along the flue gas flow direction. It employs a collaborative working mode of a closed-loop intermediate water circulation loop and an open-loop solution circulation loop. After the flue gas is cooled by intermediate water spray driven by the closed-loop absorption heat pump in the flue-water heat exchange chamber, it enters the flue-solution heat exchange chamber where it is sprayed with an absorption solution driven by the open-loop absorption heat pump for deep recovery of water and latent heat. Simultaneously, the heat recovered by the closed-loop and open-loop absorption heat pumps is integrated into the user's water circuit for external heating. This significantly improves the overall energy efficiency and water resource recovery rate of the system, while deeply reducing the exhaust gas temperature and efficiently recovering the latent heat of water vapor in the flue gas.

[0017] Furthermore, the heat user water circuit includes parallel branches, and the heat user return water is divided into two paths. The first path flows through the heating side of the closed absorption heat pump (1), and the second path flows through the heating side of the open absorption heat pump (2). The two heated heat user return water paths merge and are connected to the heat user water supply pipeline.

[0018] Furthermore, the closed heat recovery section also includes a water-to-water heat exchanger (5); the intermediate water outlet at the bottom of the flue water heat exchange chamber (3) is connected to the intermediate water inlet of the water-to-water heat exchanger (5), and the intermediate water outlet of the water-to-water heat exchanger (5) is connected to the intermediate water inlet of the closed absorption heat pump (1); the first heat user return water flows sequentially through the heat side of the water-to-water heat exchanger (5) and the heating side of the closed absorption heat pump (1).

[0019] Furthermore, the heat user water circuit includes a series branch, and the heat user return water flows sequentially through the heating side of the open absorption heat pump (2) and the heating side of the closed absorption heat pump (1), and the heated heat user return water is connected to the heat user water supply pipeline.

[0020] Furthermore, the closed heat recovery section also includes a water-to-water heat exchanger (5); the intermediate water outlet at the bottom of the flue water heat exchange chamber (3) is connected to the intermediate water inlet of the water-to-water heat exchanger (5), and the intermediate water outlet of the water-to-water heat exchanger (5) is connected to the intermediate water inlet of the closed absorption heat pump (1); the heat user return water flows sequentially through the heat side of the water-to-water heat exchanger (5), the heating side of the open absorption heat pump (2), and the heating side of the closed absorption heat pump (1).

[0021] Further, the absorption solution is a concentrated solution, and the diluted solution is a dilute solution; the open absorption heat pump (2) includes a solution heat exchanger (21), an open condenser (22), and an open generator (23); the open generator (23) is used to heat and concentrate the dilute solution to regenerate the dilute solution into the concentrated solution and generate steam, the steam enters the open condenser (22) and exchanges heat with the heat user return water flowing through it; the concentrated solution of the open generator (23) The outlet is connected to the concentrated solution inlet of the solution heat exchanger (21), the concentrated solution outlet of the solution heat exchanger (21) is connected to the second spray layer (62), the dilute solution outlet at the bottom of the flue gas solution heat exchange chamber (4) is connected to the dilute solution inlet of the solution heat exchanger (21), and the dilute solution outlet of the solution heat exchanger (21) is connected to the dilute solution inlet of the open generator (23), forming the solution circulation loop; a solution driving device is provided in the solution circulation loop to drive the solution flow.

[0022] Furthermore, a baffle plate (24) is provided between the open generator (23) and the open condenser (22), and a steam passage is provided on the baffle plate (24) so ​​that the steam generated in the open generator (23) enters the open condenser (22) through the steam passage.

[0023] Furthermore, the open condenser (22) is provided with a condensate outlet at the bottom for recovering the condensate generated by steam condensation; the flue gas heat exchange chamber (3) is provided with an overflow pipe at the bottom for recovering the excess condensate generated by flue gas condensation.

[0024] Furthermore, a ventilated water-proof layer (7) is provided between the flue gas heat exchange chamber (3) and the flue gas solution heat exchange chamber (4), and a demister (8) is provided on the flue gas outlet side of the flue gas solution heat exchange chamber (4). The flue gas heat exchange chamber (3), the ventilated water-proof layer (7), the flue gas solution heat exchange chamber (4) and the demister (8) are all arranged in the same heat exchange tower.

[0025] According to another aspect of the present invention, the present invention also provides an open-closed composite flue gas waste heat recovery method, the method comprising the following steps: passing flue gas sequentially into a flue-water heat exchange chamber (3) and a flue-solution heat exchange chamber (4); in the flue-water heat exchange chamber (3), a closed-loop circulation is formed by driving intermediate water through a closed absorption heat pump (1): the intermediate water flows out from the closed absorption heat pump (1), is sprayed through a first spray layer (61), and comes into countercurrent contact with the flue gas for heat exchange, absorbs the heat of the flue gas and falls to the bottom of the flue-water heat exchange chamber (3), and then returns to the closed absorption heat pump (1) to release heat, so as to heat the heat user return water flowing through the heating side of the closed absorption heat pump (1); in the flue-solution heat exchange chamber (4), passing... The open absorption heat pump (2) drives the absorption solution to form a solution circulation: the concentrated solution is sprayed through the second spray layer (62) and comes into countercurrent contact with the flue gas cooled by the flue gas heat exchange chamber (3). After absorbing the water vapor in the flue gas, it becomes a dilute solution. The dilute solution flows out from the bottom of the flue gas heat exchange chamber (4) and is heated and concentrated in the open absorption heat pump (2) to regenerate into a concentrated solution and generate steam. The steam is condensed in the open absorption heat pump (2) with the heat user return water flowing through its heating side, and the released heat heats the heat user return water. The heat user return water heated by the closed absorption heat pump (1) and / or the open absorption heat pump (2) is supplied to the outside through the heat user water circuit.

[0026] This application provides a method for open-closed composite flue gas waste heat recovery. It constructs a tiered treatment process where flue gas flows sequentially through a closed heat recovery section and an open heat recovery section. A synergistic working mode is employed, combining a closed-loop absorption heat pump driving intermediate water spray heat exchange with an open-loop absorption heat pump driving absorption solution spray heat absorption. This allows the flue gas to release sensible heat in the closed heat recovery section before entering the open heat recovery section for further moisture removal and latent heat recovery. Simultaneously, the heat recovered from both the closed and open heat recovery sections is integrated for external heating. This achieves both tiered deep utilization of flue gas waste heat and efficient recovery of water vapor from the flue gas, resulting in improved system energy efficiency, reduced exhaust temperature, and a combined water and heat supply effect.

[0027] Further, the solution circulation specifically includes: the concentrated solution flows out from the open generator (23), is cooled by the solution heat exchanger (21), and is sprayed into the flue gas solution heat exchange chamber (4) by the second spray layer (62), comes into countercurrent contact with the flue gas, absorbs the moisture and heat in the flue gas and becomes a dilute solution; the dilute solution flows out from the bottom of the flue gas solution heat exchange chamber (4), is heated by the solution heat exchanger (21) and enters the open generator (23), is heated and concentrated by the driven heat source, is regenerated into a concentrated solution and generates steam; the regenerated concentrated solution is cooled again by the solution heat exchanger (21) and returned to the second spray layer (62) for recycling.

[0028] Furthermore, the method further includes: the steam generated in the open generator (23) enters the open condenser (22) through the steam channel provided on the baffle plate (24), and condenses after exchanging heat with the heat user return water flowing through the heating side of the open condenser (22).

[0029] Furthermore, the method also includes: recovering condensate overflowing from the bottom of the flue water heat exchange chamber (3) and / or discharged from the bottom of the open condenser (22).

[0030] Furthermore, the heat user water circuit adopts a parallel mode: the heat user return water is divided into two paths. The first path flows through the closed absorption heat pump (1) and is heated on the heating side, while the second path flows through the open absorption heat pump (2) and is heated on the heating side. The two heated heat user return water paths are combined and then supplied to the outside for heating.

[0031] Furthermore, the parallel mode also includes a preheating step: the intermediate water flowing out from the bottom of the flue water heat exchange chamber (3) is first introduced into the intermediate water side of the water-to-water heat exchanger (5) to release heat before entering the closed absorption heat pump (1); the return water of the first heat user is first introduced into the hot side of the water-to-water heat exchanger (5) before entering the heating side of the closed absorption heat pump (1) to preheat using the residual heat of the intermediate water.

[0032] Furthermore, the heat user water circuit adopts a series mode: the heat user return water flows sequentially through the heating side of the open absorption heat pump (2) and the heating side of the closed absorption heat pump (1), and is heated and then supplied to the outside.

[0033] Furthermore, the series mode also includes a preheating step: the intermediate water flowing out from the bottom of the flue water heat exchange chamber (3) is first introduced into the intermediate water side of the water-to-water heat exchanger (5) to release heat before entering the closed absorption heat pump (1); the return water of the heat user is first introduced into the hot side of the water-to-water heat exchanger (5) before entering the heating side of the open absorption heat pump (2) to preheat using the residual heat of the intermediate water.

[0034] Furthermore, the method also includes: the flue gas treated by the flue gas heat exchange chamber (4) is discharged after being demisted by the demister (8).

[0035] The above-described technical solution of the present invention has the following beneficial technical effects: 1. Achieved a tiered deep recovery of flue gas waste heat and a breakthrough in energy efficiency: By arranging closed-loop and open-loop absorption heat pumps sequentially along the flue gas flow direction, a tiered utilization architecture of "closed-loop recovery of sensible heat and open-loop absorption of latent heat" is constructed. The closed-loop section efficiently extracts the sensible heat and part of the latent heat from the first stage of the flue gas, while the open-loop section utilizes direct contact absorption of the solution to deeply recover the latent heat of water vapor in the final stage of the flue gas. This completely breaks through the contradiction between deep recovery and grade improvement in a single cycle, making the overall heat recovery efficiency and energy efficiency of the system far exceed those of traditional technologies, and the exhaust gas temperature can be reduced to an extremely low level.

[0036] 2. Significantly reduces flue gas temperature and humidity, and efficiently recovers water resources: Open-loop absorption heat pumps utilize a solution spray with strong moisture absorption capacity, maintaining a robust mass transfer driving force in low-temperature regions. This allows for the absorption and condensation of large amounts of water vapor from the flue gas, achieving efficient development of the flue gas "aerial water reservoir." Simultaneously, both flue gas condensate and steam condensate can be recycled, significantly reducing water consumption in industrial processes. This is particularly suitable for water-intensive industries such as coal-fired power plants, steel mills, and petrochemical plants in water-scarce regions.

[0037] 3. Significantly Improved System Energy Efficiency and Heating Quality: Both closed-loop and open-loop absorption heat pumps use steam or gas as the driving heat source. The heat recovered by both is integrated into the user's water circuit for external heating. The steam condensation heat generated during solution regeneration in the open-loop section can efficiently heat the user's return water, realizing the conversion of low-grade latent heat into high-grade thermal energy; the closed-loop section provides a stable medium- and high-temperature heat source. The user's water circuit adopts a flexible combination of parallel or series modes, enabling the system to output hot water that meets different temperature requirements, thereby significantly improving the overall coefficient of performance (COP).

[0038] 4. Improved system adaptability, integration, and operational stability: The water circuit for heat users can be connected in parallel, series, or with the addition of water-to-water heat exchangers, among other methods, to flexibly match load changes under different operating conditions, based on actual heating needs. The flue-water heat exchange chamber and the flue-solution heat exchange chamber are integrated into the same heat exchange tower via a ventilated and waterproof layer, resulting in a compact structure and small footprint. The open absorption heat pump is equipped with an internal solution heat exchanger to recover heat and features baffles to prevent solution entrainment, ensuring long-term stable and reliable system operation and providing an efficient, economical, and durable solution for industrial waste heat recovery. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the open-closed composite flue gas waste heat recovery system using a parallel heat user water circuit in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the open-closed composite flue gas waste heat recovery system using a series-connected heat user water circuit in an embodiment of the present invention. Figure 3 This is a schematic diagram of the internal structure of an open absorption heat pump according to an embodiment of the present invention; Figure 4 In this embodiment of the invention, a parallel hot water user circuit is used and applied. Figure 3 The diagram shows the structure of an open-loop combined flue gas waste heat recovery system for an open absorption heat pump. Figure 5 This is a schematic diagram of another internal structure of an open absorption heat pump in an embodiment of the present invention; Figure 6 A schematic diagram of the structure of the open-closed composite flue gas waste heat recovery system with an added water-to-water heat exchanger in the parallel heat user water circuit of this invention. Figure 7 This is a schematic diagram of the structure of the open-closed composite flue gas waste heat recovery system with an added water-to-water heat exchanger in the series-connected heat user water circuit of this invention. Figure 8 This is a flowchart of an open-closed composite flue gas waste heat recovery method according to an embodiment of the present invention.

[0040] Figure label: 1: Closed-loop absorption heat pump; 2: Open-loop absorption heat pump; 21: Solution heat exchanger; 22: Open-loop condenser; 23: Open-loop generator; 24: Baffle plate; 25: Flash chamber; 26: Steam / gas heater; 3: Flue gas heat exchange chamber; 4: Flue gas solution heat exchange chamber; 5: Water-to-water heat exchanger; 7: Ventilation and water barrier layer; 8: Demister; 61: First spray layer; 62: Second spray layer. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0042] To address the shortcomings of existing flue gas waste heat recovery technologies, such as insufficient deep recovery capacity in closed-loop systems, limited heating quality in open-loop systems, high system integration difficulty, and low water resource recovery efficiency, this invention proposes a combined open and closed-loop flue gas waste heat recovery system and method. This system enables tiered deep recovery of flue gas waste heat and combined hydro-heating in a single system. The invention employs a closed-loop heat recovery section and an open-loop heat recovery section arranged sequentially along the flue gas flow direction. The closed-loop heat recovery section consists of a closed-loop absorption heat pump and a flue-water heat exchange chamber forming an intermediate water closed-loop cycle. The intermediate water absorbs heat from the initial stage of the flue gas after being sprayed through a first spray layer and then returns to the heat pump to release heat, which is used to heat the return water for users. The open-loop heat recovery section consists of an open-loop absorption heat pump and a flue-water solution heat exchange chamber forming a solution cycle. The absorption solution is sprayed through a second spray layer and comes into contact with the flue gas to absorb moisture, becoming a dilute solution. This dilute solution is regenerated into a concentrated solution in the open-loop absorption heat pump, generating steam. The steam condenses and releases heat to heat the return water for users. The flue gas flows through two sections before being discharged. The heat user water circuit is connected to the heating side of the two heat pumps, and the heated return water from the heat users is used to supply heat to the outside. Using this invention, operators can achieve deep recovery of waste heat from flue gas while efficiently recovering water vapor from the flue gas, significantly reducing the exhaust temperature, improving system energy efficiency and water resource recovery rate, and providing stable, economical, and efficient technical support for low-carbon transformation in high-energy-consuming industries such as industrial boilers, steel, and petrochemicals.

[0043] The following is combined Figures 1 to 8 The present invention describes the open-closed composite flue gas waste heat recovery system and method provided by the present invention.

[0044] Figure 1 This is a schematic diagram of the open-closed composite flue gas waste heat recovery system using a parallel heat user water circuit in an embodiment of the present invention.

[0045] like Figure 1 As shown, in some embodiments, the open-closed composite flue gas waste heat recovery system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a heat user water circuit. The closed heat recovery section includes a closed absorption heat pump 1 and a flue-water heat exchange chamber 3, while the open heat recovery section includes an open absorption heat pump 2 and a flue-solution heat exchange chamber 4. The flue-water heat exchange chamber 3 and the flue-solution heat exchange chamber 4 are separated by a ventilated water-proof layer 7, and a demister 8 is provided on the flue gas outlet side of the flue-solution heat exchange chamber 4.

[0046] Flue gas enters through the flue gas inlet of the flue-water heat exchange chamber 3, where it comes into countercurrent contact with the intermediate water sprayed by the first spray layer 61, releasing initial sensible heat and some latent heat. After initial cooling, the flue gas enters the flue-solution heat exchange chamber 4 through the ventilated water-proof layer 7, where it comes into countercurrent contact with the absorbent solution sprayed by the second spray layer 62. Utilizing the strong hygroscopic properties of the solution, the moisture in the flue gas is deeply removed, and the remaining latent heat is released. Finally, after demisting by the demister 8, it is discharged in a low-temperature, low-humidity state. Through the above-described cascade heat exchange process, the system achieves deep extraction of waste heat from the flue gas and minimizes exhaust heat loss.

[0047] The intermediate water outlet of the closed-loop absorption heat pump 1 is connected to the first spray layer 61 above the flue gas heat exchange chamber 3. The intermediate water outlet at the bottom of the flue gas heat exchange chamber 3 is connected to the intermediate water inlet of the closed-loop absorption heat pump 1 through a circulation drive device (such as a circulation pump), forming a closed-loop circulation loop for the intermediate water. In this loop, the intermediate water absorbs heat from the flue gas after being sprayed by the first spray layer 61 and falls to the bottom of the flue gas heat exchange chamber 3. It then returns to the closed-loop absorption heat pump 1 via the circulation drive device. Inside the closed-loop absorption heat pump 1, the intermediate water releases heat to heat the first-stage return water flowing through its heating side. The high-efficiency heat exchange performance of the closed-loop absorption heat pump 1 ensures the stable recovery of heat from the first stage of the flue gas.

[0048] An open absorption heat pump 2 and a flue gas solution heat exchange chamber 4 have a solution circulation loop, which is connected to a second spray layer 62 above the flue gas solution heat exchange chamber 4. In this loop, the absorption solution is sprayed through the second spray layer 62 and comes into contact with the flue gas, absorbing water vapor from the flue gas and releasing absorbed heat to become a dilute solution. The dilute solution flows out from the bottom of the flue gas solution heat exchange chamber 4 and is heated and concentrated by a driven heat source in the open absorption heat pump 2, regenerating into a concentrated solution and generating steam. The regenerated concentrated solution returns to the second spray layer 62 for recycling. The generated steam exchanges heat with the second heat user return water flowing through its heating side in the open absorption heat pump 2 and condenses, efficiently transferring latent heat to the heat user return water. The open absorption heat pump 2 eliminates the heat transfer temperature difference of indirect heat exchange through direct contact heat exchange, realizing deep recovery of latent heat and moisture from the flue gas.

[0049] The heat user water circuit adopts a parallel mode: the heat user return water is divided into a first path and a second path. The first path flows through the heating side of the closed-loop absorption heat pump 1 and is heated, while the second path flows through the heating side of the open-loop absorption heat pump 2 and is heated. The heated heat user return water from both paths is combined and used as the heat user supply water for external heating. The driving heat source for both the closed-loop absorption heat pump 1 and the open-loop absorption heat pump 2 is steam or gas. The parallel heat user water circuit design allows the system to flexibly allocate flow according to actual load demand, improving overall heating capacity and operational flexibility.

[0050] Through the aforementioned structure, this system achieves the tiered synergistic utilization of stable sensible heat recovery from flue gas in the closed heat recovery section and deep recovery of latent heat and moisture from flue gas in the open heat recovery section. The heat recovered by the two heat pumps is integrated and supplied to the outside, which significantly reduces the exhaust gas temperature while greatly improving the system's energy efficiency and water resource recovery rate, achieving the comprehensive effect of deep recovery of waste heat from flue gas and combined water and heat supply.

[0051] Figure 2 This is a schematic diagram of the structure of an open-closed composite flue gas waste heat recovery system using a series-connected heat user water circuit in an embodiment of the present invention.

[0052] like Figure 2 As shown, in some embodiments, the open-closed composite flue gas waste heat recovery system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a heat user water circuit. The closed heat recovery section includes a closed absorption heat pump 1 and a flue-water heat exchange chamber 3, while the open heat recovery section includes an open absorption heat pump 2 and a flue-solution heat exchange chamber 4. The flue-water heat exchange chamber 3 and the flue-solution heat exchange chamber 4 are separated by a ventilated water-proof layer 7, and a demister 8 is provided on the flue gas outlet side of the flue-solution heat exchange chamber 4.

[0053] Flue gas enters through the flue gas inlet of the flue-water heat exchange chamber 3, where it comes into countercurrent contact with the intermediate water sprayed by the first spray layer 61, releasing initial sensible heat and some latent heat. After initial cooling, the flue gas enters the flue-solution heat exchange chamber 4 through the ventilated water-proof layer 7, where it comes into countercurrent contact with the absorbent solution sprayed by the second spray layer 62. Utilizing the strong hygroscopic properties of the solution, the moisture in the flue gas is deeply removed, and the remaining latent heat is released. Finally, after demisting by the demister 8, it is discharged in a low-temperature, low-humidity state. Through the above-described cascade heat exchange process, the system achieves deep extraction of waste heat from the flue gas and minimizes exhaust heat loss.

[0054] The intermediate water outlet of the closed-loop absorption heat pump 1 is connected to the first spray layer 61 above the flue gas heat exchange chamber 3. The intermediate water outlet at the bottom of the flue gas heat exchange chamber 3 is connected to the intermediate water inlet of the closed-loop absorption heat pump 1 through a circulation drive device (such as a circulation pump), forming a closed-loop circulation loop for the intermediate water. In this loop, the intermediate water absorbs heat from the flue gas after being sprayed by the first spray layer 61 and falls to the bottom of the flue gas heat exchange chamber 3. It then returns to the closed-loop absorption heat pump 1 via the circulation drive device, where it releases heat to heat the return water from the heat users flowing through its heating side. The high-efficiency heat exchange performance of the closed-loop absorption heat pump 1 ensures the stable recovery of heat from the first stage of the flue gas.

[0055] An open absorption heat pump 2 and a flue gas solution heat exchange chamber 4 have a solution circulation loop, which is connected to a second spray layer 62 above the flue gas solution heat exchange chamber 4. In this loop, the absorption solution is sprayed through the second spray layer 62 and comes into contact with the flue gas, absorbing water vapor from the flue gas and releasing absorbed heat to become a dilute solution. The dilute solution flows out from the bottom of the flue gas solution heat exchange chamber 4 and is heated and concentrated by a driven heat source in the open absorption heat pump 2, regenerating into a concentrated solution and generating steam. The regenerated concentrated solution returns to the second spray layer 62 for recycling. The generated steam exchanges heat with the return water of the heat user flowing through its heating side in the open absorption heat pump 2 and condenses, efficiently transferring latent heat to the heat user return water. The open absorption heat pump 2 eliminates the heat transfer temperature difference of indirect heat exchange through direct contact heat exchange, realizing deep recovery of latent heat and moisture from the flue gas.

[0056] The heat user water circuit adopts a series configuration: the heat user return water flows sequentially through the heating side of the open absorption heat pump 2 and the heating side of the closed absorption heat pump 1, and is heated in stages before being supplied to the heat user for external heating. Specifically, the heat user return water first enters the heating side of the open absorption heat pump 2, absorbing the latent heat released by steam condensation for the first stage of temperature increase; then it enters the heating side of the closed absorption heat pump 1, absorbing the sensible heat of flue gas transferred by the intermediate water for the second stage of temperature increase, and is then supplied to the outside after reaching the target heating temperature. The driving heat source for both the closed absorption heat pump 1 and the open absorption heat pump 2 is steam or gas. The series water circuit design allows the heat user return water to absorb the latent heat recovered from the open side and the sensible heat recovered from the closed side in sequence, realizing the cascade utilization of heat and further increasing the heating temperature.

[0057] Through the aforementioned structure, this system achieves the tiered synergistic utilization of stable sensible heat recovery from flue gas in the closed heat recovery section and deep recovery of latent heat and moisture from flue gas in the open heat recovery section. The heat recovered by the two heat pumps is transferred to the return water of the heat users in stages through a series water circuit. While significantly reducing the flue gas temperature, it greatly improves the system's energy efficiency, heating temperature and water resource recovery rate, achieving the comprehensive effect of deep recovery of flue gas waste heat and combined water and heat supply.

[0058] Figure 3 This is a schematic diagram of the internal structure of an open absorption heat pump according to an embodiment of the present invention.

[0059] Open absorption heat pumps can have a variety of different internal structures, and the specific structure can be arranged or designed according to the actual situation.

[0060] like Figure 3 As shown, in a specific embodiment of the present invention, the open absorption heat pump 2 includes a solution heat exchanger 21, an open condenser 22, an open generator 23, and a baffle plate 24. These components work together to achieve the circulation and regeneration of the absorption solution and the release of heat through steam condensation.

[0061] The solution heat exchanger 21 has a concentrated solution channel and a dilute solution channel for heat exchange between the concentrated and dilute solutions to recover heat during solution circulation. The open generator 23 has a drive heat source inlet (steam or gas) for heating and concentrating the dilute solution; the open condenser 22 has a heat user water channel for heat exchange and condensation of steam and heat user return water; the baffle plate 24 is located between the open generator 23 and the open condenser 22, and has a steam channel to allow steam to pass through while blocking solution droplets from being entrained.

[0062] The solution circulation and steam generation process of the open absorption heat pump 2 is as follows: The concentrated solution flows out from the concentrated solution outlet of the open generator 23 and enters the concentrated solution channel of the solution heat exchanger 21. After exchanging heat and cooling with the dilute solution flowing in the dilute solution channel, it is transported through pipelines to the second spray layer 62 above the flue gas solution heat exchange chamber 4 (e.g., ...). Figure 1 , Figure 2 As shown, the solution is used for spraying to absorb moisture from the flue gas. The dilute solution formed after absorbing moisture in the flue gas solution heat exchange chamber 4 flows out from the bottom of the chamber and enters the dilute solution channel of the solution heat exchanger 21. After exchanging heat with the concentrated solution flowing in the concentrated solution channel and heating up, it enters the open generator 23. Inside the open generator 23, the dilute solution is heated and concentrated by a driving heat source, regenerating into a concentrated solution and generating steam. The generated steam flows upward and enters the open condenser 22 through the steam channel on the baffle plate 24. Inside the open condenser 22, it exchanges heat with the return water from the heat users flowing through its heating side and condenses, releasing latent heat to heat the return water. The condensate formed after steam condensation can be discharged and recycled from the bottom of the open condenser 22.

[0063] Through the above structure, the open-loop absorption heat pump 2 achieves closed-loop regeneration of the absorption solution and efficiently transfers the latent heat released during absorption to the return water of the heat user in the form of steam condensation. The solution heat exchanger 21 effectively recovers the heat during the solution circulation process, reducing regeneration energy consumption; the baffle plate 24 effectively prevents the solution from being entrained into the condenser, ensuring the purity and heat exchange efficiency of the steam condensation. As the core component of the system, this open-loop absorption heat pump 2 provides a reliable guarantee for the deep recovery and quality improvement of the latent heat of flue gas.

[0064] Figure 4 In this embodiment of the invention, a parallel hot water user circuit is used and applied. Figure 3 The diagram shows the structure of an open-loop absorption heat pump combined open-loop flue gas waste heat recovery system.

[0065] like Figure 4 As shown, in a specific embodiment of the present invention, the open-closed composite flue gas waste heat recovery system adopts a parallel heat user water circuit and applies... Figure 3The internal structure of the open absorption heat pump 2 is shown. The system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a heat user water circuit. The closed heat recovery section includes a closed absorption heat pump 1 and a flue water heat exchange chamber 3, while the open heat recovery section includes... Figure 3 The internal structure shown includes an open absorption heat pump 2 and a flue gas solution heat exchange chamber 4.

[0066] A ventilated water-proof layer 7 is provided between the flue-water heat exchange chamber 3 and the flue-solution heat exchange chamber 4. This ventilated water-proof layer 7 spatially separates the flue-water heat exchange chamber 3 and the flue-solution heat exchange chamber 4, while allowing flue gas to pass through but preventing liquid water or solution from seeping down, ensuring independent and stable operation of the two chambers. A demister 8 is provided on the flue gas outlet side of the flue-solution heat exchange chamber 4 to capture tiny liquid droplets entrained in the treated flue gas, further reducing the moisture content of the flue gas and achieving clean emissions. To further improve system integration and reduce the footprint, the flue-water heat exchange chamber 3, the ventilated water-proof layer 7, the flue-solution heat exchange chamber 4, and the demister 8 are all arranged in the same heat exchange tower, forming a compact integrated structure that facilitates transportation, installation, and maintenance.

[0067] Flue gas enters through the flue gas inlet of the flue-water heat exchange chamber 3, where it comes into countercurrent contact with the intermediate water sprayed by the first spray layer 61, releasing initial sensible heat and some latent heat. After preliminary cooling, the flue gas enters the flue-solution heat exchange chamber 4 through the ventilated water-proof layer 7, where it comes into countercurrent contact with the absorbent solution sprayed by the second spray layer 62. Utilizing the strong hygroscopic properties of the solution, the moisture in the flue gas is deeply removed, and the remaining latent heat is released. Finally, after demisting by the demister 8, it is discharged in a low-temperature, low-humidity state. An overflow water pipe is provided at the bottom of the flue-water heat exchange chamber 3 to recover excess condensate generated by flue gas condensation. Through the above-mentioned cascade heat exchange process, the system achieves deep extraction of waste heat from the flue gas and minimizes exhaust heat loss, while significantly improving equipment integration and operational stability.

[0068] The intermediate water outlet of the closed-loop absorption heat pump 1 is connected to the first spray layer 61 above the flue gas heat exchange chamber 3. The intermediate water outlet at the bottom of the flue gas heat exchange chamber 3 is connected to the intermediate water inlet of the closed-loop absorption heat pump 1 through a circulation drive device (such as a circulation pump), forming a closed-loop circulation loop for the intermediate water. In this loop, the intermediate water absorbs heat from the flue gas after being sprayed by the first spray layer 61 and falls to the bottom of the flue gas heat exchange chamber 3. It then returns to the closed-loop absorption heat pump 1 via the circulation drive device, where it releases heat to heat the first-stage heat user return water flowing through its heating side. The high-efficiency heat exchange performance of the closed-loop absorption heat pump 1 ensures the stable recovery of heat from the first stage of the flue gas.

[0069] Open absorption heat pump 2 adopts Figure 3The internal structure shown includes a solution heat exchanger 21, an open condenser 22, an open generator 23, and a baffle plate 24. An open absorption heat pump 2 and a flue gas solution heat exchange chamber 4 have a solution circulation loop, which is connected to the second spray layer 62 above the flue gas solution heat exchange chamber 4. The solution circulation and steam generation process is as follows: a concentrated solution flows out of the open generator 23 and enters the concentrated solution channel of the solution heat exchanger 21. After heat exchange and cooling with the dilute solution flowing in the dilute solution channel, it is transported to the second spray layer 62 and sprayed into the flue gas solution heat exchange chamber 4. The concentrated solution contacts the flue gas counter-currently within the flue gas solution heat exchange chamber 4, absorbing water vapor from the flue gas and becoming a dilute solution. The dilute solution flows out from the bottom of the flue gas solution heat exchange chamber 4 and enters the dilute solution channel of the solution heat exchanger 21. After heat exchange and heating with the concentrated solution flowing in the concentrated solution channel, it enters the open generator 23. Within the open generator 23, the dilute solution... The solution is heated and concentrated by a driving heat source (steam or gas), regenerating into a concentrated solution and generating steam. The generated steam enters the open condenser 22 through the steam channel on the baffle plate 24. Inside the open condenser 22, it exchanges heat with the return water from the second heat user flowing through its heating side and condenses, releasing latent heat to heat the return water from the second heat user. The open condenser 22 has a condensate outlet at the bottom for recovering the condensate generated by steam condensation. The condensate formed after steam condensation can be discharged and recovered from the bottom of the open condenser 22. The regenerated concentrated solution then re-enters the solution heat exchanger 21 to begin the next cycle. Through the above process, the open absorption heat pump 2 achieves closed-loop regeneration of the absorption solution and efficiently transfers the latent heat released during absorption to the return water from the heat user. The solution heat exchanger 21 effectively recovers the heat during the solution circulation process, reducing regeneration energy consumption; the baffle plate 24 effectively prevents the solution from being entrained into the condenser, ensuring the purity and heat exchange efficiency of the steam condensation.

[0070] The heat user water circuit adopts a parallel mode: the heat user return water is divided into a first path and a second path. The first path flows through the heating side of the closed-loop absorption heat pump 1 and is heated, while the second path flows through the heating side of the open-loop condenser 22 of the open-loop absorption heat pump 2 and is heated. The heated heat user return water from both paths is combined and used as the heat user supply water for external heating. The driving heat source for both the closed-loop absorption heat pump 1 and the open-loop absorption heat pump 2 is steam or gas. The parallel water circuit design allows the system to flexibly allocate flow according to actual load demand, improving overall heating capacity and operational flexibility.

[0071] Through the aforementioned structure, this system achieves the tiered synergistic utilization of stable sensible heat recovery from flue gas in the closed heat recovery section and deep recovery of latent heat and moisture from flue gas in the open heat recovery section. The heat recovered by the two heat pumps is integrated and supplied to the outside, which significantly reduces the exhaust gas temperature while greatly improving the system's energy efficiency and water resource recovery rate, achieving the comprehensive effect of deep recovery of waste heat from flue gas and combined water and heat supply.

[0072] Figure 5This is a schematic diagram of another internal structure of an open absorption heat pump in an embodiment of the present invention.

[0073] Open absorption heat pumps can have a variety of different internal structures, and the specific structure can be arranged or designed according to the actual situation.

[0074] like Figure 5 As shown, in another specific embodiment of the present invention, the open absorption heat pump 2 includes a solution heat exchanger 21, an open condenser 22, a baffle plate 24, a flash chamber 25, and a steam / gas heater 26. These components work together to achieve the circulation and regeneration of the absorption solution and the release of heat from steam condensation.

[0075] The solution heat exchanger 21 has a concentrated solution channel and a dilute solution channel for heat exchange between the concentrated and dilute solutions to recover heat during solution circulation. The steam / gas heater 26 has a driving heat source inlet (steam or gas) for heating the dilute solution; the flash chamber 25 is connected to the outlet of the steam / gas heater 26 for flash separation of the heated dilute solution to produce steam and concentrated solution; the open condenser 22 has a heat user water channel for heat exchange and condensation of steam and heat user return water; the baffle plate 24 is located between the steam outlet of the flash chamber 25 and the open condenser 22, and has a steam channel to allow steam to pass through while blocking solution droplets from being entrained.

[0076] The solution circulation and steam generation process of the open absorption heat pump 2 is as follows: The concentrated solution flows out from the concentrated solution outlet of the flash evaporation chamber 25 and enters the concentrated solution channel of the solution heat exchanger 21. After exchanging heat and cooling with the dilute solution flowing in the dilute solution channel, it is transported through pipeline to the second spray layer 62 above the flue gas solution heat exchange chamber 4 (e.g., ...). Figure 1 , Figure 2 (As shown), it is used for spraying to absorb moisture from the flue gas. The dilute solution formed after absorbing moisture in the flue gas solution heat exchange chamber 4 flows out from the bottom of the flue gas solution heat exchange chamber 4 and enters the dilute solution channel of the solution heat exchanger 21. After exchanging heat with the concentrated solution flowing in the concentrated solution channel and being heated, it enters the steam / gas heater 26. In the steam / gas heater 26, the dilute solution is heated to a certain temperature by the driving heat source and then enters the flash chamber 25. In the flash chamber 25, flash separation is carried out to produce steam and concentrated solution. The generated steam flows upward and enters the open condenser 22 through the steam channel on the baffle plate 24. In the open condenser 22, it exchanges heat with the heat user return water flowing through its heating side and condenses. The released latent heat is used to heat the heat user return water. The condensate formed after the steam condenses can be discharged and recycled from the bottom of the open condenser 22. The concentrated solution separated in the flash chamber 25 then re-enters the concentrated solution channel of the solution heat exchanger 21 to start the next cycle.

[0077] Through the above structure, the open-loop absorption heat pump 2 achieves closed-loop regeneration of the absorption solution and efficiently transfers the latent heat released during absorption to the return water of the heat user in the form of steam condensation. The solution heat exchanger 21 effectively recovers the heat during the solution circulation process, reducing regeneration energy consumption; the combination of steam / gas heater 26 and flash chamber 25 replaces the traditional generator, allowing for flexible adjustment of heating intensity and flash pressure, optimizing the regeneration effect; the baffle plate 24 effectively prevents solution entrainment into the condenser, ensuring the purity and heat exchange efficiency of the steam condensation. As the core component of the system, this open-loop absorption heat pump 2 provides a reliable guarantee for the deep recovery and grade improvement of flue gas latent heat.

[0078] Figure 6 A schematic diagram of the structure of the open-closed composite flue gas waste heat recovery system with an added water-to-water heat exchanger in the parallel heat user water circuit of this invention.

[0079] like Figure 6 As shown, in some embodiments, the open-closed composite flue gas waste heat recovery system adopts a parallel heat user water circuit, and in Figure 1 A water-to-water heat exchanger 5 is added to the basic structure shown. The system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a water circuit for heat users. The closed heat recovery section includes a closed absorption heat pump 1 and a flue-to-water heat exchange chamber 3, while the open heat recovery section includes an open absorption heat pump 2 and a flue-to-solution heat exchange chamber 4. The flue-to-water heat exchange chamber 3 and the flue-to-solution heat exchange chamber 4 are separated by a ventilated water-proof layer 7, and a demister 8 is provided on the flue gas outlet side of the flue-to-solution heat exchange chamber 4.

[0080] Flue gas enters through the flue gas inlet of flue-water heat exchange chamber 3, undergoes staged heat exchange between flue-water heat exchange chamber 3 and flue-water solution heat exchange chamber 4, and is finally discharged in a low-temperature, low-humidity state after being demisted by demister 8. An overflow water pipe is provided at the bottom of flue-water heat exchange chamber 3 to recover excess condensate generated by flue gas condensation.

[0081] and Figure 1 Compared to the illustrated embodiment, this embodiment adds a water-to-water heat exchanger 5 to the intermediate water circuit of the closed-loop heat recovery section. Specifically, the intermediate water outlet at the bottom of the flue water heat exchange chamber 3 is connected to the intermediate water inlet of the water-to-water heat exchanger 5, and the intermediate water outlet of the water-to-water heat exchanger 5 is connected to the intermediate water inlet of the closed-loop absorption heat pump 1, forming an intermediate water flow path of "flue water heat exchange chamber 3 → water-to-water heat exchanger 5 → closed-loop absorption heat pump 1". In this flow path, after the intermediate water flows out from the bottom of the flue water heat exchange chamber 3, it first enters the water-to-water heat exchanger 5 to release heat, then returns to the closed-loop absorption heat pump 1 to further release heat, and then is transported back to the first spray layer 61 for spraying and heat absorption.

[0082] Figure 6 The open absorption heat pump 2 shown is Figure 1The structure shown is the same, but the internal structure of the open absorption heat pump 2 can have many different arrangements or designs. In this embodiment, its internal structure is the same as... Figure 3 The structure of the open absorption heat pump 2 given is consistent with that of the open absorption heat pump 2, which includes a solution heat exchanger 21, an open condenser 22, an open generator 23, and a baffle plate 24, forming a solution circulation loop with the flue gas solution heat exchange chamber 4. The open condenser 22 has a condensate outlet at the bottom for recovering the condensate generated by steam condensation.

[0083] The heat user water circuit adopts a parallel mode, and a water-to-water heat exchanger 5 is introduced into the first circuit for preheating. The heat user return water is divided into a first circuit and a second circuit. The second circuit flows through the heating side of the open absorption heat pump 2 and is heated. The first circuit of heat user return water flows sequentially through the heating side of the water-to-water heat exchanger 5 and the heating side of the closed absorption heat pump 1. The first circuit of heat user return water is preheated by absorbing the heat released by the intermediate water in the water-to-water heat exchanger 5, and then enters the heating side of the closed absorption heat pump 1 for further heating. The two heated heat user return water circuits are combined and used as the heat user supply water for external heating. The driving heat source for both the closed absorption heat pump 1 and the open absorption heat pump 2 is steam or gas.

[0084] This system achieves cascaded utilization of waste heat from the intermediate water by adding a water-to-water heat exchanger 5: before returning to the closed-loop absorption heat pump 1, the intermediate water releases heat in the water-to-water heat exchanger 5 to preheat the return water of the first heat user. This not only reduces the temperature of the intermediate water entering the closed-loop absorption heat pump 1, which is beneficial to its efficient operation, but also raises the temperature of the return water of the first heat user in advance. This structure further improves the matching efficiency of heat within the system and the overall energy efficiency while maintaining the flexibility of the parallel water circuit.

[0085] Figure 7 This is a schematic diagram of the structure of an open-closed composite flue gas waste heat recovery system with an added water-to-water heat exchanger in a series-connected heat user water circuit according to an embodiment of the present invention.

[0086] like Figure 7 As shown, in some embodiments, the open-closed composite flue gas waste heat recovery system adopts a series-connected heat user water circuit, and in Figure 2 A water-to-water heat exchanger 5 is added to the basic structure shown. The system includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a water circuit for heat users. The closed heat recovery section includes a closed absorption heat pump 1 and a flue-to-water heat exchange chamber 3, while the open heat recovery section includes an open absorption heat pump 2 and a flue-to-solution heat exchange chamber 4. The flue-to-water heat exchange chamber 3 and the flue-to-solution heat exchange chamber 4 are separated by a ventilated water-proof layer 7, and a demister 8 is provided on the flue gas outlet side of the flue-to-solution heat exchange chamber 4.

[0087] Flue gas enters through the flue gas inlet of the flue-water heat exchange chamber 3, undergoes staged heat exchange between the flue-water heat exchange chamber 3 and the flue-solution heat exchange chamber 4, and is finally discharged in a low-temperature, low-humidity state after being demisted by the demister 8. The bottom of the flue-water heat exchange chamber 3 is equipped with an overflow pipe for recovering excess condensate generated during flue gas condensation. The open absorption heat pump 2 internally includes a solution heat exchanger 21, an open condenser 22, an open generator 23, and a baffle plate 24. The bottom of the open condenser 22 has a condensate outlet for recovering condensate generated during steam condensation.

[0088] and Figure 2 Compared to the illustrated embodiment, this embodiment adds a water-to-water heat exchanger 5 to the intermediate water circuit of the closed-loop heat recovery section, and introduces this heat exchanger into the heat user's water circuit for preheating. Specifically, the intermediate water outlet at the bottom of the flue water heat exchange chamber 3 is connected to the intermediate water inlet of the water-to-water heat exchanger 5, and the intermediate water outlet of the water-to-water heat exchanger 5 is connected to the intermediate water inlet of the closed-loop absorption heat pump 1, forming an intermediate water flow path of "flue water heat exchange chamber 3 → water-to-water heat exchanger 5 → closed-loop absorption heat pump 1". In this flow path, after the intermediate water flows out from the bottom of the flue water heat exchange chamber 3, it first enters the water-to-water heat exchanger 5 to release heat, then returns to the closed-loop absorption heat pump 1 to further release heat, and then is transported back to the first spray layer 61 for spraying and heat absorption.

[0089] The heat user water circuit adopts a series configuration and introduces a water-to-water heat exchanger 5 for preheating: the heat user return water flows sequentially through the hot side of the water-to-water heat exchanger 5, the heating side of the open absorption heat pump 2, and the heating side of the closed absorption heat pump 1. Specifically, the heat user return water first enters the hot side of the water-to-water heat exchanger 5, absorbing the heat released by the intermediate water for preheating; the preheated heat user return water then enters the heating side of the open absorption heat pump 2, absorbing the latent heat released by steam condensation for the first stage of temperature increase; finally, it enters the heating side of the closed absorption heat pump 1, absorbing the sensible heat of the flue gas transferred by the intermediate water for the second stage of temperature increase, and after reaching the target heating temperature, it is used as the heat user supply water for external heating. The driving heat source for both the closed absorption heat pump 1 and the open absorption heat pump 2 is steam or gas.

[0090] This system, by adding a water-to-water heat exchanger 5, further achieves tiered heat utilization on the basis of a series water circuit: before returning to the closed-loop absorption heat pump 1, the intermediate water releases heat in the water-to-water heat exchanger 5 to preheat the return water of the heat users. This not only recovers the waste heat of the intermediate water and lowers the temperature of the intermediate water entering the closed-loop absorption heat pump 1 to facilitate its efficient operation, but also allows the return water of the heat users to receive an initial temperature rise before entering the open-loop absorption heat pump 2, reducing the load on the absorption heat pump 2. This structure, while maintaining the advantage of tiered heating in a series water circuit, further improves the matching efficiency of heat within the system and the overall energy efficiency.

[0091] Figure 8 This is a flowchart of an open-closed composite flue gas waste heat recovery method according to an embodiment of the present invention.

[0092] like Figure 8 As shown in the figure, an open-closed composite flue gas waste heat recovery method provided by an embodiment of the present invention mainly includes the following steps: The flue gas first enters the flue-water heat exchange chamber 3, where it comes into countercurrent contact with the intermediate water from the closed-loop absorption heat pump 1, releasing the initial sensible heat and some latent heat. The cooled flue gas then enters the flue-solution heat exchange chamber 4, where it comes into countercurrent contact with the absorption solution from the open-loop absorption heat pump 2. Utilizing the strong hygroscopic properties of the solution, the moisture in the flue gas is deeply removed, and the remaining latent heat is released. Through this stepped heat exchange process, deep recovery of waste heat from the flue gas and a significant reduction in exhaust temperature are achieved. In the closed-loop heat recovery section, the closed-loop absorption heat pump 1 drives the intermediate water to form a closed loop: the intermediate water flows out of the closed-loop absorption heat pump 1, is sprayed through the first spray layer 61 to absorb heat from the flue gas, falls to the bottom of the flue-water heat exchange chamber 3, and then returns to the closed-loop absorption heat pump 1 to release heat, heating the return water flowing through its heating side. In the open-loop heat recovery section, the open-loop absorption heat pump 2 drives the absorption solution to form a solution circulation: the concentrated solution absorbs water vapor in the flue gas through the second spray layer 62 and becomes a dilute solution; the dilute solution flows out from the bottom of the flue gas solution heat exchange chamber 4, is heated and concentrated by the driven heat source in the open-loop absorption heat pump 2, regenerated into a concentrated solution and generates steam; the generated steam exchanges heat with the return water of the heat users flowing through its heating side in the open-loop absorption heat pump 2 and condenses, releasing latent heat to heat the return water of the heat users. The heated return water of the heat users is then supplied to the outside through the heat user water circuit.

[0093] Furthermore, the solution circulation process of the open absorption heat pump 2 is as follows: the concentrated solution flows out from the open generator 23, is cooled by the solution heat exchanger 21, and is then sprayed into the flue gas solution heat exchange chamber 4 by the second spray layer 62. After countercurrent contact with the flue gas, it absorbs moisture and becomes a dilute solution. The dilute solution flows out from the bottom of the flue gas solution heat exchange chamber 4, is heated by the solution heat exchanger 21, and then enters the open generator 23. It is heated and concentrated by the driven heat source, regenerated into a concentrated solution, and generates steam. The regenerated concentrated solution is cooled again by the solution heat exchanger 21 and returned to the second spray layer 62 for recycling. The steam generated in the open generator 23 enters the open condenser 22 through the steam channel on the baffle plate 24. After exchanging heat with the heat user return water flowing through the heating side of the open condenser 22, it is condensed, and the steam condensate discharged from the open condenser 22 is recovered.

[0094] The external heating of the heat user's water circuit can be achieved using either a parallel or series connection. In the parallel connection mode, the heat user's return water is divided into two paths. The first path flows through the heating side of the closed-loop absorption heat pump 1 and is heated, while the second path flows through the heating side of the open-loop condenser 22 of the open-loop absorption heat pump 2 and is heated. The two heated return water paths are then combined for external heating. In the series connection mode, the heat user's return water flows sequentially through the heating side of the open-loop condenser 22 of the open-loop absorption heat pump 2 and the heating side of the closed-loop absorption heat pump 1, being heated step by step before being supplied to the outside. In the parallel connection mode, a preheating step can also be added: the intermediate water flowing out from the bottom of the flue water heat exchange chamber 3 is first passed through the intermediate water side of the water-to-water heat exchanger 5 to release heat before entering the closed-loop absorption heat pump 1; simultaneously, the second path of heat user return water is preheated by passing it through the hot side of the water-to-water heat exchanger 5 before entering the open-loop condenser 22. In the series mode, a preheating step can also be added: the intermediate water flowing out of the bottom of the flue water heat exchange chamber 3 is first passed into the intermediate water side of the water-to-water heat exchanger 5 to release heat, and then enters the closed absorption heat pump 1; at the same time, the return water of the heat user is first passed into the hot side of the water-to-water heat exchanger 5 for preheating before entering the open condenser 22.

[0095] In addition, the method includes a condensate recovery step: recovering the flue gas condensate overflowing from the bottom of the flue gas heat exchange chamber 3, and recovering the steam condensate discharged from the open condenser 22. Finally, the flue gas treated by the flue gas heat exchange chamber 4 is discharged after being demisted by the demister 8.

[0096] Through the above steps, this method achieves cascaded deep recovery of flue gas waste heat and combined water and heat supply, significantly improving water resource recovery rate while enhancing system energy efficiency.

[0097] For the principles, specific implementation, and beneficial effects of this open-closed composite flue gas waste heat recovery method, please refer to the preceding text and... Figures 1 to 7 The description of the system shown will not be repeated here.

[0098] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects. For example, A and / or B indicates that there are three possible relationships: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article indicates that the related objects before and after it are in an "or" relationship.

[0099] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An open-closed composite flue gas waste heat recovery system, characterized in that, It includes a closed heat recovery section and an open heat recovery section arranged sequentially along the flue gas flow direction, as well as a water circuit for heat users; The closed heat recovery section includes a closed absorption heat pump (1) and a flue gas heat exchange chamber (3); the intermediate water outlet of the closed absorption heat pump (1) is connected to the first spray layer (61) above the flue gas heat exchange chamber (3) to allow the intermediate water to contact the flue gas and absorb heat. The flue gas heat exchange chamber (3) is provided with an intermediate water outlet at the bottom, which is connected to the intermediate water inlet of the closed absorption heat pump (1) through a circulation drive device to form a closed circulation loop of intermediate water; the intermediate water after heat absorption and the heat user return water flowing through the heating side of the closed absorption heat pump (1) exchange heat through the closed absorption heat pump (1) to heat the heat user return water. The open heat recovery section includes an open absorption heat pump (2) and a flue gas solution heat exchange chamber (4); there is a solution circulation loop between the open absorption heat pump (2) and the flue gas solution heat exchange chamber (4), and the solution circulation loop is connected to the second spray layer (62) above the flue gas solution heat exchange chamber (4) to provide an absorption solution to the flue gas solution heat exchange chamber (4). The solution is diluted after contacting the flue gas for heat exchange. The diluted solution is regenerated in the open absorption heat pump (2) and generates steam. The steam is condensed and heat exchanged with the heat user return water flowing through the heating side of the open absorption heat pump (2), and the released heat is used to heat the heat user return water. The flue gas outlet of the flue-water heat exchange chamber (3) is connected to the flue gas inlet of the flue-water heat exchange chamber (4), so that the flue gas flows through the closed heat recovery section and the open heat recovery section in sequence and then is discharged. The heat user water circuit is connected to the heating side of the closed absorption heat pump (1) and / or the heating side of the open absorption heat pump (2) to heat the heat user return water to the outside.

2. The open / closed composite flue gas waste heat recovery system according to claim 1, wherein, The heat user water circuit includes parallel branches. The heat user return water is divided into two paths. The first path flows through the heating side of the closed absorption heat pump (1), and the second path flows through the heating side of the open absorption heat pump (2). The two heated heat user return water paths merge and are connected to the heat user water supply pipeline.

3. The open / closed composite flue gas waste heat recovery system according to claim 2, wherein, The closed heat recovery section also includes a water-to-water heat exchanger (5); the intermediate water outlet at the bottom of the flue water heat exchange chamber (3) is connected to the intermediate water inlet of the water-to-water heat exchanger (5), and the intermediate water outlet of the water-to-water heat exchanger (5) is connected to the intermediate water inlet of the closed absorption heat pump (1); the first heat user return water flows sequentially through the heat side of the water-to-water heat exchanger (5) and the heating side of the closed absorption heat pump (1).

4. The open / closed composite flue gas waste heat recovery system according to claim 1, wherein, The heat user water circuit includes a series branch. The heat user return water flows sequentially through the heating side of the open absorption heat pump (2) and the heating side of the closed absorption heat pump (1). The heated heat user return water is connected to the heat user water supply pipeline.

5. The open / closed composite flue gas waste heat recovery system according to claim 4, wherein, The closed heat recovery section also includes a water-to-water heat exchanger (5); the intermediate water outlet at the bottom of the flue water heat exchange chamber (3) is connected to the intermediate water inlet of the water-to-water heat exchanger (5), and the intermediate water outlet of the water-to-water heat exchanger (5) is connected to the intermediate water inlet of the closed absorption heat pump (1); the heat user return water flows sequentially through the heat side of the water-to-water heat exchanger (5), the heating side of the open absorption heat pump (2), and the heating side of the closed absorption heat pump (1).

6. The open / closed composite flue gas waste heat recovery system according to claim 1, wherein, The absorption solution is a concentrated solution, and the diluted solution is a dilute solution; the open absorption heat pump (2) includes a solution heat exchanger (21), an open condenser (22), and an open generator (23). The open generator (23) is used to heat and concentrate the dilute solution to regenerate the dilute solution into the concentrated solution and generate steam. The steam enters the open condenser (22) and exchanges heat with the heat user return water flowing through it. The concentrated solution outlet of the open generator (23) is connected to the concentrated solution inlet of the solution heat exchanger (21), the concentrated solution outlet of the solution heat exchanger (21) is connected to the second spray layer (62), the dilute solution outlet at the bottom of the flue gas solution heat exchange chamber (4) is connected to the dilute solution inlet of the solution heat exchanger (21), and the dilute solution outlet of the solution heat exchanger (21) is connected to the dilute solution inlet of the open generator (23), forming the solution circulation loop; The solution circulation loop is equipped with a solution driving device for driving the solution flow.

7. The open / closed composite flue gas waste heat recovery system according to claim 6, wherein, A baffle plate (24) is provided between the open generator (23) and the open condenser (22). A steam passage is provided on the baffle plate (24) so ​​that the steam generated in the open generator (23) enters the open condenser (22) through the steam passage.

8. The open / closed composite flue gas waste heat recovery system according to claim 6 or 7, wherein, The open condenser (22) is provided with a condensate outlet at the bottom for recovering the condensate generated by steam condensation; the flue gas heat exchange chamber (3) is provided with an overflow pipe at the bottom for recovering the excess condensate generated by flue gas condensation.

9. The open-closed composite flue gas waste heat recovery system according to any one of claims 1 to 8, wherein, A ventilated water-proof layer (7) is provided between the flue-water heat exchange chamber (3) and the flue-solution heat exchange chamber (4). A demister (8) is provided on the flue gas outlet side of the flue-solution heat exchange chamber (4). The flue-water heat exchange chamber (3), the ventilated water-proof layer (7), the flue-solution heat exchange chamber (4) and the demister (8) are all arranged in the same heat exchange tower.

10. A method for recovering waste heat from open-closed composite flue gas, characterized in that, Includes the following steps: The flue gas is sequentially introduced into the flue water heat exchange chamber (3) and the flue solution heat exchange chamber (4). In the flue gas heat exchange chamber (3), the intermediate water is driven by the closed absorption heat pump (1) to form a closed circulation: the intermediate water flows out from the closed absorption heat pump (1), is sprayed through the first spray layer (61), and comes into countercurrent contact with the flue gas for heat exchange. After absorbing the heat of the flue gas, it falls into the bottom of the flue gas heat exchange chamber (3) and then returns to the closed absorption heat pump (1) to release heat, so as to heat the heat user return water flowing through the heating side of the closed absorption heat pump (1). In the flue gas heat exchange chamber (4), the absorption solution is driven by the open absorption heat pump (2) to form a solution circulation: the concentrated solution is sprayed through the second spray layer (62) and comes into countercurrent contact with the flue gas cooled by the flue gas heat exchange chamber (3). After absorbing the water vapor in the flue gas, it becomes a dilute solution. The dilute solution flows out from the bottom of the flue gas heat exchange chamber (4) and is heated and concentrated in the open absorption heat pump (2) to regenerate into a concentrated solution and generate steam. The steam exchanges heat with the heat user return water flowing through its heating side in the open absorption heat pump (2) and condenses. The released heat heats the heat user return water. The heat user return water, heated by the closed absorption heat pump (1) and / or the open absorption heat pump (2), is supplied to the outside through the heat user water circuit.

11. The open-closed composite flue gas waste heat recovery method according to claim 10, wherein, The solution circulation specifically includes: The concentrated solution flows out from the open generator (23), is cooled by the solution heat exchanger (21), and is sprayed into the flue gas solution heat exchange chamber (4) through the second spray layer (62). It comes into countercurrent contact with the flue gas, absorbs the moisture and heat in the flue gas, and becomes a dilute solution. The dilute solution flows out from the bottom of the flue gas solution heat exchange chamber (4), is heated by the solution heat exchanger (21), and enters the open generator (23), where it is heated and concentrated by the driving heat source, regenerated into a concentrated solution and generates steam. After being regenerated, the concentrated solution is cooled again by the solution heat exchanger (21) and then returned to the second spray layer (62) for recycling.

12. The open-closed composite flue gas waste heat recovery method according to claim 11, wherein, Also includes: The steam generated in the open generator (23) enters the open condenser (22) through the steam channel provided on the baffle plate (24), and condenses after exchanging heat with the heat user return water flowing through the heating side of the open condenser (22).

13. The open-closed composite flue gas waste heat recovery method according to claim 12, wherein, It also includes: recovering condensate that overflows from the bottom of the flue water heat exchange chamber (3) and / or is discharged from the bottom of the open condenser (22).

14. The open-closed composite flue gas waste heat recovery method according to claim 10, wherein, The heat user water circuit adopts a parallel mode: the heat user return water is divided into two paths. The first path flows through a closed absorption heat pump (1) and is heated on the heating side. The second path flows through an open absorption heat pump (2) and is heated on the heating side. The two heated heat user return water paths are combined and then supplied to the outside for heating.

15. The open-closed composite flue gas waste heat recovery method according to claim 14, wherein, The parallel mode also includes a preheating step: the intermediate water flowing out from the bottom of the flue water heat exchange chamber (3) is first introduced into the intermediate water side of the water-to-water heat exchanger (5) to release heat before entering the closed absorption heat pump (1); the return water of the first heat user is first introduced into the hot side of the water-to-water heat exchanger (5) before entering the heating side of the closed absorption heat pump (1) to preheat using the residual heat of the intermediate water.

16. The open-closed composite flue gas waste heat recovery method according to claim 10, wherein, The heat user water circuit adopts a series mode: the heat user return water flows sequentially through the heating side of the open absorption heat pump (2) and the heating side of the closed absorption heat pump (1), and is heated and then supplied to the outside.

17. The open-closed composite flue gas waste heat recovery method according to claim 16, wherein, The series mode also includes a preheating step: the intermediate water flowing out from the bottom of the flue water heat exchange chamber (3) is first introduced into the intermediate water side of the water-to-water heat exchanger (5) to release heat before entering the closed absorption heat pump (1); the return water of the heat user is first introduced into the hot side of the water-to-water heat exchanger (5) before entering the heating side of the open absorption heat pump (2) to preheat using the residual heat of the intermediate water.

18. The open-closed composite flue gas waste heat recovery method according to any one of claims 10 to 16, wherein, It also includes: the flue gas treated by the flue gas heat exchange chamber (4) is discharged after being demisted by the demister (8).

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