Heat supply and air intake temperature adjusting system based on absorption heat pump for recovering flue gas waste heat

Abstract

The present application relates to gas-steam combined cycle and waste heat recovery technical field, specifically disclose a kind of based on absorption heat pump recovery flue gas waste heat's heating and intake temperature regulating system, including gas turbine, steam turbine, waste heat boiler, plate heat exchanger, absorption heat pump unit and gas-liquid heat exchanger. Gas turbine exhaust is preliminarily heat exchanged after waste heat boiler, low-temperature flue gas enters plate heat exchanger and recovers residual heat, and the waste heat is as the low-temperature heat source of absorption heat pump;Absorption heat pump is driven with the heat energy provided by steam turbine, and the grade of low-temperature waste heat is improved, and higher temperature hot water is output. The hot water is used for external heating on the one hand, and the intake air is heated through gas-liquid heat exchanger in gas turbine intake duct on the other hand, and two-way return water is combined and returned to the low-temperature side of absorption heat pump. The system recovers flue gas waste heat and improves its grade by depth, and realizes stable heating and safe regulation of gas turbine intake temperature simultaneously without consuming high-grade steam or electric energy.

Description

Technical Field

[0001] This invention relates to the field of gas-steam combined cycle and waste heat recovery technology, and in particular to a heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas. Background Technology

[0002] Gas-fired combined cycle (Gas-Steam) units play a crucial role in peak shaving within power systems due to their flexible operation and rapid response. However, in actual operation, these units often operate at 30%-70% partial load, leading to a decline in overall energy efficiency and failing to fully realize their energy-saving potential. Simultaneously, the flue gas emitted from the unit's waste heat boiler still contains a significant amount of low-grade waste heat, which, under current technology, is often directly released into the atmosphere without thorough recovery, resulting in substantial energy waste.

[0003] In existing technologies, solutions for heating the intake air of gas turbines and supplying external heat typically require consuming the high-grade heat energy (such as high-temperature steam) generated by the unit itself, failing to fully and efficiently utilize low-grade waste heat resources such as flue gas. Because the waste heat from the flue gas is of low grade, if directly used for heating or heating the intake air, its output temperature and stability cannot simultaneously meet the requirements of actual engineering projects. Especially in winter or low-temperature environments, the unit's intake air temperature can easily drop below the dew point, potentially causing corrosion and ash accumulation in critical equipment such as the compressor, threatening operational safety and equipment lifespan.

[0004] Therefore, there is an urgent need for a system that can deeply recover and improve the waste heat grade of flue gas from gas-steam combined cycle units. Under the premise of ensuring stable external heating, it can achieve safe and flexible adjustment of the inlet air temperature, thereby reducing the consumption of high-grade energy and comprehensively improving the unit's energy efficiency, economy and operational reliability. Summary of the Invention

[0005] The purpose of this invention is to provide a heating and intake air temperature regulation system based on absorption heat pump to recover waste heat from flue gas, thereby solving the above-mentioned technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: a heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas, comprising a gas turbine and a steam turbine, and: a waste heat boiler, the flue gas inlet of which is connected to the exhaust port of the gas turbine; a plate heat exchanger, the flue gas side channel of which is connected to the flue between the flue gas outlet of the waste heat boiler and the chimney, to recover the low-temperature waste heat flowing through the flue gas; and an absorption heat pump unit, comprising an evaporator and a generator, the low-temperature heat source inlet of which is connected to the plate heat exchanger. The heat medium outlet of the generator is connected to receive the waste heat from the flue gas recovered by the plate heat exchanger; the drive heat source inlet of the generator is connected to the steam turbine; the gas-liquid heat exchanger is installed in the air inlet of the gas turbine, and its hot water side inlet is connected to the hot water outlet of the condenser of the absorption heat pump unit; wherein, the hot water outlet of the condenser of the absorption heat pump unit is connected to the heat user end; the hot water side outlet of the gas-liquid heat exchanger and the return water outlet of the heat user end merge and are connected to the low temperature side loop of the absorption heat pump unit.

[0007] Furthermore, the plate heat exchanger and the absorption heat pump unit form a closed intermediate water circulation loop; after absorbing the waste heat of the flue gas in the plate heat exchanger, the intermediate water enters the evaporator of the absorption heat pump unit to release heat.

[0008] Furthermore, the intermediate water circulating in the closed intermediate water circulation loop is heated to 35°C-40°C in the plate heat exchanger before entering the evaporator of the absorption heat pump unit.

[0009] Furthermore, the heating and intake air temperature regulation system based on the absorption heat pump for recovering waste heat from flue gas also includes a steam turbine exhaust condenser. The intake port of the steam turbine exhaust condenser is connected to the exhaust port of the steam turbine, and the condensate outlet of the steam turbine exhaust condenser is connected to the feedwater inlet of the waste heat boiler.

[0010] Furthermore, the condensate formed by the steam used to drive the absorption heat pump unit after releasing heat and condensing in the generator is combined with the condensate generated by the steam turbine exhaust condenser and returned to the waste heat boiler.

[0011] Furthermore, the absorption heat pump unit is a lithium bromide absorption heat pump or an ammonia absorption heat pump.

[0012] Furthermore, a regulating valve is installed on the pipeline connecting the hot water outlet of the condenser of the absorption heat pump unit and the hot water inlet of the gas-liquid heat exchanger.

[0013] Furthermore, the flue gas recovered by the plate heat exchanger is low-temperature flue gas whose temperature has dropped to 80℃-95℃ after heat exchange in the waste heat boiler.

[0014] Furthermore, the hot water inlet at the heat user end is connected to the hot water outlet of the condenser of the absorption heat pump unit via a pipeline.

[0015] Compared with the prior art, the present invention discloses at least the following beneficial effects: This invention, after initial recovery of waste heat from gas turbine exhaust gas via a waste heat boiler, further utilizes a plate heat exchanger to recover residual heat from the low-temperature flue gas, using this low-grade waste heat as a low-temperature heat source for an absorption heat pump. The absorption heat pump, driven by heat energy provided by a steam turbine, enhances the heat grade of the low-temperature flue gas waste heat, outputting higher-temperature hot water. One path of this hot water is used for external heating, while the other path heats the intake air through a gas-liquid heat exchanger located in the gas turbine's intake duct. Finally, the two return water paths are combined and returned to the low-temperature side of the absorption heat pump, forming a cycle. This system structure allows for deep recovery and heating of low-grade flue gas waste heat, simultaneously meeting the requirements for stable heating and safe regulation of the gas turbine's intake air temperature without the need for additional high-grade steam or electricity. This significantly improves the overall energy efficiency of the gas-steam combined cycle system and effectively avoids the risks of equipment corrosion and ash accumulation caused by excessively low intake air temperatures, enhancing the safety and economy of system operation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The overall structural diagram of the heating and intake air temperature regulation system based on the recovery of waste heat from flue gas using an absorption heat pump, provided in an embodiment of the present invention; Reference numerals: 1. Gas turbine; 2. Steam turbine; 3. Steam turbine exhaust condenser; 4. Waste heat boiler; 5. Absorption heat pump unit; 6. Plate heat exchanger; 7. Chimney; 8. Heat user end; 9. Gas-liquid heat exchanger; 10. T-joint one; 11. T-joint two; 12. T-joint three; 13. T-joint four. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Reference Figure 1 As shown, this embodiment of the invention provides a heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas. The system integrates functions such as deep recovery of waste heat from flue gas, improvement of heat grade, and heat diversion and utilization. It aims to solve problems such as waste of waste heat from flue gas under partial load of gas-steam combined cycle units, competition for high-grade energy between intake air heating and external heating, and safety risks caused by low-temperature intake air in winter, so as to achieve efficient cascade utilization of energy and improve operational safety.

[0021] Specifically, such as Figure 1 As shown, the heating and intake air temperature regulation system based on the absorption heat pump for recovering waste heat from flue gas in this embodiment includes a gas turbine 1, a steam turbine 2, a steam turbine exhaust condenser 3, a waste heat boiler 4, an absorption heat pump unit 5, a plate heat exchanger 6, a chimney 7, a heat user terminal 8, a gas-liquid heat exchanger 9, and multiple tee joints.

[0022] In one specific embodiment, the inlet of the steam turbine exhaust condenser 3 is connected to the exhaust port of the steam turbine 2 via a pipeline, and its condensate outlet is connected to the feedwater inlet of the waste heat boiler 4 via a pipeline. The function of the steam turbine exhaust condenser 3 is to condense the exhaust gas from the steam turbine 2 after it has performed work into condensate, thereby completing the recovery and circulation of the working fluid on the steam side in the combined cycle.

[0023] In one specific embodiment, the plate heat exchanger 6 serves as a flue gas waste heat recovery module, with its flue gas side channel directly connected to the low-temperature flue between the tail end of the waste heat boiler 4 and the chimney 7. After the high-temperature flue gas discharged from the gas turbine 1 completes heat exchange in the waste heat boiler 4, the low-temperature flue gas, with its temperature reduced to 80℃-95℃, enters the plate heat exchanger 6, where the residual low-temperature waste heat is released.

[0024] In one specific embodiment, the driving heat source inlet of the generator of the absorption heat pump unit 5 is connected to the exhaust or extraction steam pipeline of the intermediate pressure cylinder of the steam turbine 2 via a pipeline; the low-temperature heat source inlet of the evaporator of the absorption heat pump unit 5 is connected to the heat medium outlet of the plate heat exchanger 6 via a pipeline, thereby receiving low-temperature heat from the flue gas waste heat recovery module.

[0025] In one specific embodiment, the gas-liquid heat exchanger 9 is installed in the compressor inlet of the gas turbine 1, serving as the intake preheating module of the system in this embodiment. Specifically, the gas-liquid heat exchanger 9 is directly installed in the compressor inlet of the gas turbine 1. Its hot water side inlet is connected to the hot water outlet of the condenser inside the heat pump of the absorption heat pump unit 5 via a pipeline, and its hot water side outlet is connected to the return water pipeline of the heat user terminal 8 via a pipeline, ultimately connecting together to the low-temperature side loop of the absorption heat pump unit 5 to form a complete thermodynamic cycle.

[0026] Based on the above embodiments, the absorption heat pump unit 5 is further a lithium bromide absorption heat pump, which mainly includes a generator, a condenser (hereinafter referred to as the "internal condenser of the heat pump" to distinguish it from the aforementioned steam turbine exhaust condenser 3), an evaporator, and an absorber. Medium-pressure extraction steam from the steam turbine 2 enters the generator as a driving heat source, heating the dilute lithium bromide solution to boil and generate refrigerant vapor. This refrigerant vapor condenses and releases heat in the internal condenser of the heat pump, transferring the heat to the circulating water and raising its temperature. The condensed refrigerant water enters the evaporator, evaporates under low pressure, and absorbs the waste heat from the flue gas carried by the intermediate water from the plate heat exchanger 6, thereby achieving low-temperature heat collection. In the absorber, the concentrated solution from the generator absorbs the refrigerant vapor generated in the evaporator, releasing absorbed heat to further heat the circulating water. Through this series of processes, the low-grade waste heat from the flue gas, along with some driving heat energy, is raised to a higher usable grade.

[0027] As can be seen from the above structure, the plate heat exchanger 6 and the evaporator of the absorption heat pump unit 5 form a closed intermediate water circulation loop. After absorbing waste heat from the flue gas in the plate heat exchanger 6, the intermediate water's temperature rises from 20-25℃ to 35-40℃, and then flows into the evaporator of the absorption heat pump unit 5 to release heat as a low-temperature heat source. After cooling down, it returns to the plate heat exchanger 6, forming an independent waste heat collection cycle. The gas-liquid heat exchanger 9 is a compact plate heat exchanger 6, and its air-side flow resistance is designed to be less than 100Pa to ensure that its impact on the gas turbine 1 intake system is minimized.

[0028] The system operation flow in this embodiment is as follows: The high-temperature flue gas discharged from gas turbine 1 enters waste heat boiler 4 for heat exchange, generating steam to drive steam turbine 2 to generate electricity. The cooled flue gas (approximately 80-95°C) enters plate heat exchanger 6. Inside plate heat exchanger 6, the flue gas exchanges heat with the closed-loop intermediate water, transferring heat to the intermediate water, raising its temperature from approximately 20-25°C to 35-40°C. This warm intermediate water is pumped to the evaporator of absorption heat pump unit 5 as a low-temperature heat source. Simultaneously, a portion of the medium-pressure steam extracted from steam turbine 2 is diverted via tee joint 10 and enters the generator of absorption heat pump unit 5 as a driving heat source. The condensate formed after the driving steam releases heat in the generator merges with the condensate from the main steam loop at tee joint 11 and returns to waste heat boiler 4.

[0029] Meanwhile, a portion of the steam drawn from the intermediate pressure cylinder of steam turbine 2 is split through pipelines: one part serves as a driving heat source, entering the generator of absorption heat pump unit 5 to drive the absorption heat pump cycle; the other part enters the steam turbine exhaust condenser 3 for condensation. The condensate formed after the driving steam releases heat and condenses in the generator merges with the condensate formed in the steam turbine exhaust condenser 3 and returns together to the waste heat boiler 4.

[0030] Driven by driving steam, the absorption heat pump unit 5 upgrades the low-temperature heat energy input from the evaporator, ultimately outputting high-temperature hot water with a stable temperature of around 85°C from the condenser and absorber. This high-temperature hot water is transported via pipeline to T-joint 413. At T-joint 413, the high-temperature hot water splits into two independent branches: the first branch flows into the gas-liquid heat exchanger 9 of the intake preheating module, where it exchanges heat with the low-temperature ambient air at the compressor inlet of the gas turbine 1, safely raising the intake air temperature to around 15°C, effectively avoiding condensation, corrosion, and dust accumulation problems caused by the intake air temperature being below the dew point in winter; the second branch is directly transported to the heat user end 8 to meet building heating or process heating needs. The cooled return water after heat exchange (including return water from the gas-liquid heat exchanger 9 and return water from the heat network at the heat user end 8) merges at T-joint 312 and flows back to the low-temperature side of the absorption heat pump unit 5 to re-enter the circulation.

[0031] Building upon the above embodiments, to further achieve flexible control over the preheating of the intake air, a regulating valve can be installed on the pipeline connecting the hot water outlet of the absorption heat pump unit 5 and the hot water inlet of the gas-liquid heat exchanger 9. By adjusting the opening of this valve, the flow rate of hot water entering the gas-liquid heat exchanger 9 can be controlled, thereby precisely adjusting the preheating degree of the gas turbine intake air to adapt to different ambient temperatures and unit load requirements.

[0032] In an optional embodiment, the absorption heat pump unit 5 can also employ other types of absorption heat pumps, such as ammonia-water absorption heat pumps, to adapt to different grades of driving heat sources (such as lower-pressure steam or hot water) or different application scenarios. Its core function remains the same: to utilize the driving heat source to raise the waste heat of low-grade flue gas to a temperature level suitable for heating and intake preheating.

[0033] The heating and intake air temperature control system provided in this embodiment achieves deep utilization of flue gas waste heat by organically coupling low-grade flue gas waste heat recovery, absorption heat pump heat grade enhancement, intake air preheating, and external heating, without consuming additional high-grade electricity or steam. This system not only significantly improves the overall energy efficiency of the combined cycle unit but also effectively solves the safety hazards caused by excessively low intake air temperatures in winter. Furthermore, the system has a compact structure, requires minimal modification to the original main unit system, and possesses good engineering applicability and economic efficiency.

[0034] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0035] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas, comprising a gas turbine (1) and a steam turbine (2), characterized in that, Also includes: Waste heat boiler (4), whose flue gas inlet is connected to the exhaust port of the gas turbine (1); The plate heat exchanger (6) has its flue gas side passage connected to the flue between the flue gas outlet of the waste heat boiler (4) and the chimney (7) to recover the low-temperature waste heat flowing through the flue gas. An absorption heat pump unit (5) includes an evaporator and a generator. The low-temperature heat source inlet of the evaporator is connected to the heat medium outlet of the plate heat exchanger (6) to receive the waste heat of the flue gas recovered by the plate heat exchanger (6). The drive heat source inlet of the generator is connected to the steam turbine (2). A gas-liquid heat exchanger (9) is installed in the air intake of the gas turbine (1), and its hot water side inlet is connected to the hot water outlet of the condenser of the absorption heat pump unit (5). The hot water outlet of the condenser of the absorption heat pump unit (5) is connected to the heat user terminal (8); the hot water outlet of the gas-liquid heat exchanger (9) merges with the return water outlet of the heat user terminal (8) and is then connected to the low-temperature side circuit of the absorption heat pump unit (5).

2. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 1, characterized in that, The plate heat exchanger (6) and the absorption heat pump unit (5) form a closed intermediate water circulation loop; after absorbing the waste heat of flue gas in the plate heat exchanger (6), the intermediate water enters the evaporator of the absorption heat pump unit (5) to release heat.

3. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 2, characterized in that, The intermediate water circulating in the closed intermediate water circulation loop is heated to 35°C-40°C in the plate heat exchanger (6) and then enters the evaporator of the absorption heat pump unit (5).

4. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 1, 2, or 3, characterized in that, It also includes a steam turbine exhaust condenser (3), the inlet of which is connected to the exhaust port of the steam turbine (2), and the condensate outlet of which is connected to the feedwater inlet of the waste heat boiler (4).

5. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 4, characterized in that, The condensate formed by the steam used to drive the absorption heat pump unit (5) after releasing heat and condensing in the generator, is combined with the condensate generated by the steam turbine exhaust condenser (3) and returned to the waste heat boiler (4).

6. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 5, characterized in that, The absorption heat pump unit (5) is a lithium bromide absorption heat pump or an ammonia absorption heat pump.

7. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 5, characterized in that, A regulating valve is installed on the pipeline connecting the hot water outlet of the condenser of the absorption heat pump unit (5) and the hot water inlet of the gas-liquid heat exchanger (9).

8. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 1, characterized in that, The flue gas recovered by the plate heat exchanger (6) is low-temperature flue gas whose temperature drops to 80℃-95℃ after heat exchange by the waste heat boiler (4).

9. The heating and intake air temperature regulation system based on absorption heat pump for recovering waste heat from flue gas according to claim 1, characterized in that, The hot water inlet of the heat user terminal (8) is connected to the hot water outlet of the condenser of the absorption heat pump unit (5) via a pipeline.

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