Combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system

Abstract

The utility model discloses a low-temperature flue gas latent heat recovery heating system of a combined cycle unit waste heat boiler, and aims to improve the energy utilization efficiency. The system is mainly composed of a gas turbine, a steam turbine, a generator, a waste heat boiler and a heat supply pipe network, and heat in flue gas is gradually recovered through a three-stage flue gas heat exchanger. Heat supply network return water is divided into two paths: one path directly enters the flue gas primary heat exchanger to recover sensible heat; and the other path recovers sensible heat and latent heat at deeper levels through the absorption heat pump I and the absorption heat pump II. In order to further improve the heat energy recovery effect, an absorption heat pump III is further added in the system, a third intermediate medium circulation loop is arranged between the absorption heat pump III and the flue gas third-stage heat exchanger, and branches of the first path of outlet water and the outlet water of the first medium circulation loop can be retreated. The system is coupled with a combined cycle unit, a new flue gas waste heat recovery heating technological process is constructed, the waste heat grade is improved, better economic benefits can be obtained, and better environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a waste heat recycling technical field, concretely relates to a combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system. BACKGROUND

[0002] The gas-steam combined cycle heating unit generally has the problem of high exhaust gas temperature, and the low-temperature waste heat (below 100 DEG C) of flue gas is huge, so reducing the exhaust gas temperature and improving the natural gas utilization efficiency is an effective means to promote energy saving and emission reduction and increase the heating capacity.

[0003] The current flue gas waste heat recovery generally uses direct heat exchange heating of the heat network return water (which is the cold source) and the flue gas (which is the heat source), such as patent application No. CN201010141597.3, an energy supply system based on gas-steam combined cycle cogeneration belongs to the energy technology field. The system uses a combination of a flue gas condensing heat exchanger, a condenser, a steam-type absorption heat pump, a high-temperature flue gas heat exchanger, and a steam-water heat exchanger on the heat source side; the heat network return water directly recovers the low-temperature flue gas condensing waste heat, high-temperature flue gas waste heat, or condensing waste heat, and simultaneously uses a steam-type absorption heat pump driven by steam extraction to recover condensing heat rejection or part of the flue gas waste heat. In winter, the user end uses a supplemental combustion hot water type absorption heat pump and a water-water heat exchanger to heat the secondary heat network water for heating, and simultaneously extracts low-grade heat from a shallow soil source, a groundwater source, or a geothermal water resource for heating; in summer, the heat network hot water at the user end uses a hot water type absorption heat pump for refrigeration, solution dehumidification air conditioning dehumidification, and domestic hot water preheating. The defect is that the high-temperature flue gas of the waste heat boiler is only exchanged with the heat network return water through two groups of heat exchangers, namely, the high-temperature flue gas heat exchanger 9 and the flue gas condensing heat exchanger 10, and the heat exchanger used by the high-temperature flue gas heat exchanger 9 and the flue gas condensing heat exchanger 10 is a plate-type or shell-and-tube heat exchanger, which is limited by the 45-60 DEG C heating return water temperature and the segment difference of the heat exchanger, so the flue gas temperature can only be reduced from 100 DEG C to about 50 DEG C, and the recovered is sensible heat, and the recovered flue gas waste heat amount is limited. After the flue gas temperature is reduced to below 50 DEG C, the latent heat of the flue gas is not recovered, the heat recovery is unreasonable, the energy cascade utilization is poor, and the flue gas below 50 DEG C is released into the atmosphere, and this part of heat accounts for about 10% of the input calculated by the low-grade heat value of natural gas.

[0004] In view of the above, how to further improve the heating capacity of the unit, it is necessary to propose a combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system to solve the above problems. UTILITY MODEL CONTENTS

[0005] The utility model is aimed at overcoming the defects in the prior art and providing a combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system.

[0006] In order to realize the above-mentioned purpose, the technical scheme of the utility model is as follows: a combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system, which comprises a gas turbine, a steam turbine, a generator, a waste heat boiler and a heating pipe network; a flue gas primary heat exchanger, a flue gas secondary heat exchanger and a flue gas tertiary heat exchanger are sequentially arranged on the flue gas discharge pipeline of the waste heat boiler.

[0007] The return water of the heat network has two paths, and the first path enters the flue gas primary heat exchanger to directly recover the sensible heat in the flue gas.

[0008] In addition, the second path passes through the absorption heat pump II and the absorption heat pump I to recover the sensible heat and latent heat in the flue gas, and the water from the first path and the second path is mixed and then sent to the heat network for water supply; a second intermediate medium circulation loop is arranged between the absorption heat pump II and the flue gas secondary heat exchanger; a first intermediate medium circulation loop is arranged between the absorption heat pump I and the flue gas primary heat exchanger.

[0009] Further, the absorption heat pump III is arranged between the flue gas tertiary heat exchanger and the third intermediate medium circulation loop, the water from the first path on the flue gas primary heat exchanger and the water from the first medium circulation loop are connected to the absorption heat pump III through branch pipes, and the water is returned to the heat network return water; and a circulating pump IV is arranged on the third intermediate medium circulation loop.

[0010] The absorption heat pump I, the absorption heat pump II and the absorption heat pump III are all driven by the steam turbine exhaust gas.

[0011] Further, the absorption heat pump II comprises a generator II, a condenser II, an evaporator II and an absorber II, the evaporator II and the flue gas secondary heat exchanger form the second intermediate medium circulation loop, and the steam turbine is connected to the generator II through one exhaust gas.

[0012] Further, the flue gas secondary heat exchanger is a low-resistance partition type flue gas / water heat exchanger, which reduces the temperature of the flue gas below the dew point and deeply recovers the sensible heat and latent heat in the flue gas; the medium circulating in the second intermediate medium circulation loop is intermediate water, and an intermediate water circulating pump II is arranged on the second intermediate medium circulation loop.

[0013] Further, the second path sequentially passes through the absorber II and the condenser II in the absorption heat pump II; and a bypass adjusting pipe is arranged on the second path at the absorption heat pump II.

[0014] Further, the heat source end of the flue gas primary heat exchanger is the high-temperature flue gas of the waste heat boiler, and the cold source end is divided into two routes, one of which is directly from the heat network return water for increasing the water temperature of the heat network, and the other is from the first intermediate medium circulation loop; the absorption heat pump I includes a generator I, a condenser I, an evaporator I, and an absorber I; the first intermediate medium circulation loop is connected to the evaporator I, and a circulating pump I is arranged on the first intermediate medium circulation loop; the second route enters the absorption heat pump I after passing through the absorption heat pump II and / or the bypass adjustment pipe, and flows out in sequence through the absorber I and the condenser I and is then sent into the heat network supply water.

[0015] Further, the absorption heat pump III includes a generator III, a condenser III, an evaporator III, and an absorber III, and the third intermediate medium circulation loop passes through the absorber III and the condenser III in the absorption heat pump III in sequence; a branch pipe of the first route outflow and the first medium circulation loop outflow on the flue gas primary heat exchanger is connected to the evaporator III, and a circulating pump III is arranged on the branch pipe.

[0016] A heating method of a waste heat boiler low-temperature flue gas latent heat recovery heating system of a combined cycle unit, including flue gas sensible heat and latent heat recovery, high-temperature flue gas generated by a gas turbine enters a waste heat boiler, and sequentially passes through a flue gas primary heat exchanger, a flue gas secondary heat exchanger, and a flue gas tertiary heat exchanger on a flue gas discharge pipeline; the flue gas primary heat exchanger directly recovers sensible heat from the high-temperature flue gas; the flue gas secondary heat exchanger is a low-resistance partition heat exchanger, which reduces the flue gas temperature below the dew point and deeply recovers the sensible heat and latent heat in the flue gas; the flue gas tertiary heat exchanger further reduces the flue gas temperature and continues to recover the remaining heat;

[0017] Two routes of heat network return water processing:

[0018] First route: the heat network return water directly enters the flue gas primary heat exchanger, recovers the sensible heat in the flue gas, increases the water temperature, and then is sent out to the heat network supply water;

[0019] Second route: the heat network return water passes through the absorption heat pump II and the absorption heat pump I to recover the sensible heat and latent heat in the flue gas. The water flow in the absorption heat pump II first passes through the absorber II and the condenser II, and then merges with the first route water flow to be sent into the heat network supply water;

[0020] Application of absorption heat pump:

[0021] The absorption heat pumps I, II, and III all use steam turbine extraction as a driving heat source;

[0022] Absorption heat pump I: a first intermediate medium circulation loop is arranged between the absorption heat pump I and the flue gas primary heat exchanger, which is used for further increasing the hot water temperature;

[0023] Absorption heat pump II: a second intermediate medium circulation loop is arranged between the absorption heat pump II and the flue gas secondary heat exchanger, and heat exchange is performed through the evaporator II to recover the heat in the flue gas;

[0024] The third intermediate medium circulation loop is arranged between the absorption heat pump III and the third flue gas heat exchanger, which functions to assist in adjusting the energy distribution in the system and to make part of the water flow back to the heat network return water, so as to optimize the overall thermal efficiency.

[0025] The regulation and control of the bypass regulation pipe:

[0026] The bypass regulation pipe arranged at the absorption heat pump II can be used to adjust the flow and temperature of the second water flow, so as to ensure stable operation and high-efficiency heat recovery of the system.

[0027] The combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system of the utility model has the advantages and beneficial effects that: the combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system of the utility model is provided with multistage flue gas heat exchangers at the tail of the waste heat boiler, the waste heat of flue gas is effectively recovered, the temperature of flue gas is reduced below the dew point, the step utilization of flue gas waste heat is effectively realized, the utilization efficiency of waste heat is improved, the sensible heat and latent heat in flue gas are deeply recovered, the thermal efficiency of the combined cycle unit is improved, when the multistage flue gas heat exchangers are used, the condensate water can absorb the acid gases such as SO2 and NOX in flue gas, and the local environmental quality can be improved. The combined cycle unit is coupled, a new flue gas waste heat recovery heating process flow is constructed, the combined cycle unit waste heat boiler ultra-low-temperature flue gas waste heat recovery heating system based on the absorption heat pump technology improves the waste heat grade, better economic benefits and environmental benefits can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is one of the combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system process flow schematic diagram of the utility model;

[0029] Figure 2 is the combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system process flow schematic diagram two of the utility model;

[0030] Figure 3 is the absorption heat pump II process flow schematic diagram in the utility model;

[0031] In the figure: 1, gas turbine; 2, steam turbine; 3, generator; 4, waste heat boiler; 5, heat supply pipe network; 6, flue gas primary heat exchanger; 7, flue gas secondary heat exchanger; 8, flue gas tertiary heat exchanger; 9, first path; 10, second path; 11, absorption heat pump I; 12, absorption heat pump II; 13, first intermediate medium circulating loop; 14, second intermediate medium circulating loop; 15, absorption heat pump III; 16, third intermediate medium circulating loop; 17, intermediate water circulating pump II; 18, bypass regulating pipe; 19, circulating pump III; 20, circulating pump I; 21, low-resistance partition flue gas / water heat exchanger; 22, main chimney; 23, generator II; 24, condenser II; 25, evaporator II; 26, absorber II; 27, circulating pump IV. DETAILED DESCRIPTION

[0032] The specific embodiments of the present application will be further described in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical scheme of the present application, and cannot be used to limit the protection scope of the present application.

[0033] A low-temperature flue gas latent heat recovery heating system for a waste heat boiler of a combined cycle unit, as shown in the figure, comprises a gas turbine 1, a steam turbine 2, a generator 3, a waste heat boiler 4, a heat supply pipe network 5, a flue gas primary heat exchanger 6, a flue gas secondary heat exchanger 7, a flue gas tertiary heat exchanger 8, a first path 9, a second path 10, an absorption heat pump I 11, an absorption heat pump II 12, a first intermediate medium circulating loop 13, a second intermediate medium circulating loop 14, an absorption heat pump III 15, a third intermediate medium circulating loop 16, an intermediate water circulating pump II 17, a bypass regulating pipe 18, a circulating pump III 19, a circulating pump I 20, a low-resistance partition flue gas / water heat exchanger 21, a main chimney 22, a generator II 23, a condenser II 24, an evaporator II 25, an absorber II 26 and a circulating pump IV 27. Figures 1-3As shown, including gas turbine 1, steam turbine 2, generator 3, waste heat boiler 4, heat supply pipe network 5; The flue gas discharge pipeline of the waste heat boiler 4 is sequentially provided with a flue gas primary heat exchanger 6, a flue gas secondary heat exchanger 7 and a flue gas tertiary heat exchanger 8; The flue gas primary heat exchanger 6 exchanges heat directly between the high-level exhaust gas of about 500 degrees Celsius of the waste heat boiler 4 and the return water of the heat supply pipe network 5, so that the sensible heat in the exhaust gas is directly transferred to the heat network, and the temperature of the flue gas after the first-level heat exchange is reduced; It can be understood that only one flue gas primary heat exchanger 6 is shown in the figure, and a plurality of flue gas primary heat exchangers 6 can be arranged in parallel or in series to form step-by-step heat exchange and cooling in actual use, and the temperature of the flue gas is reduced to about 50 degrees Celsius after passing through the flue gas primary heat exchanger 6; At this time, limited by the heating return water temperature of 45-60℃ and the section difference of the heat exchanger, the flue gas temperature can only be reduced to about 50℃, and the sensible heat in the flue gas is recovered in the flue gas primary heat exchanger 6. After the flue gas temperature is reduced to below 50 degrees, the latent heat still needs to be utilized, specifically, the flue gas secondary heat exchanger 7 is arranged, and the second intermediate medium circulation loop 14 is connected to the absorption heat pump II 12, in the embodiment, the absorption heat pump II 12 is mainly used for absorbing and utilizing the latent heat below 50 degrees Celsius in the flue gas, after passing through the flue gas secondary heat exchanger 7, the temperature of the flue gas is reduced to about 30 degrees Celsius, because the flue gas contains about 15% of water, if it is directly discharged, the wet saturated flue gas in the exhaust gas is condensed and precipitated in the diffusion process after being discharged to the atmosphere through the main chimney 22, forming a white smoke plume, in order to avoid causing visual pollution, the embodiment is provided with a flue gas tertiary heat exchanger 8, and the flue gas is slightly heated by the absorption heat pump III 15, specifically, the absorption heat pump III 15 is provided, a third intermediate medium circulation loop 16 is arranged between the absorption heat pump III 15 and the flue gas tertiary heat exchanger 8, and a circulating pump IV 27 is arranged on the third intermediate medium circulation loop 16; The first road 9 outflow, the first medium circulation loop outflow on the flue gas primary heat exchanger 6 are connected to the absorption heat pump III 15 in a branch pipe converging manner; The absorption heat pump III 15 comprises a generator III, a condenser III, an evaporator III and an absorber III, and the third intermediate medium circulation loop sequentially passes through the absorber III and the condenser III in the absorption heat pump III 15; The branch pipe of the first road 9 outflow and the first medium circulation loop outflow on the flue gas primary heat exchanger 6 is connected to the evaporator III, and a circulating pump III 19 is arranged on the branch pipe, so that the heat of the flue gas primary heat exchanger 6 is transmitted to the evaporator III through the forced backflow of the circulating pump III 19, and then the heat is sent back to the heat network return water for recycling.

[0034] And the road outflow is returned to the heat network return water. The energy of the absorption heat pump III 15 is derived from the part of the heat network water heated by the flue gas primary heat exchanger 6 and the steam turbine 2 exhaust gas to drive the absorption heat pump III 15; So as to solve the "white elimination" problem of the flue gas by less energy input.

[0035] Specifically, from the perspective of the heat supply network 5, as shown in Figure 1 , 2 , the heat network return water has two paths. The first path 9 enters the flue gas primary heat exchanger 6 to directly recover the sensible heat in the flue gas. The second path 10 passes through the absorption heat pump II 12 and the absorption heat pump I 11 to recover the sensible heat and latent heat in the flue gas, and then the combined water from the first path 9 is sent to the heat supply network. The absorption heat pump II 12 is provided with a second intermediate medium circulation loop 14 between the flue gas secondary heat exchanger 7. The absorption heat pump I 11 is provided with a first intermediate medium circulation loop 13 between the flue gas primary heat exchanger 6. It can be understood that in the first path 9, a part of the flow of the heat network return water is directly exchanged with the high-temperature flue gas. The heat network return water is directly heated by the sensible heat in the flue gas and sent to the heat supply network for heating. It can be understood that the temperature of the water entering the heat supply network can be controlled to meet the requirements by adjusting the flow and other methods. In addition, in the second path 10, a part of the flow of the heat network return water is heated from the second path 10. The working temperature of the flue gas primary heat exchanger 6 is higher than that of the flue gas secondary heat exchanger 7. The absorption heat pump II 12 is driven by the latent heat recovered from the flue gas below 50 degrees Celsius and the energy of the steam turbine 2 exhaust gas to preliminarily heat the heat network return water. After flowing out of the absorption heat pump II 12, it immediately enters the absorption heat pump I 11. The absorption heat pump I 11 uses the first intermediate medium circulation loop 13 and the steam turbine 2 exhaust gas as the driving force to perform two-stage heating on the heat network return water, thereby achieving efficient utilization of the flue gas waste heat in stages. The heat network water in the second path 10 is heated by two stages and then combined with the heat network water in the first path 9 to supply heat to the heating users.

[0036] As shown in Figure 1 , 2 , the absorption heat pump I 11, the absorption heat pump II 12, and the absorption heat pump III 15 are all driven by the steam turbine 2 exhaust gas. An adjusting valve is provided on the steam pipeline to supply steam according to the use of each absorption heat pump.

[0037] The absorption heat pump II 12 includes a generator II 23, a condenser II 24, an evaporator II 25, and an absorber II 26, as shown in Figure 2 , 3As shown, the evaporator II 25 and the flue gas secondary heat exchanger 7 form a second intermediate medium circulation loop 14; the steam turbine 2 is provided with a steam extraction connection to the generator II 23. The flue gas secondary heat exchanger 7 is a low-resistance partition flue gas / water heat exchanger 21, which reduces the flue gas temperature below the dew point, and deeply recovers the sensible heat and latent heat in the flue gas; the medium circulating in the second intermediate medium circulation loop 14 is intermediate water, and the second intermediate medium circulation loop 14 is provided with an intermediate water circulating pump II 17. The heating network return water enters the absorber II 26 and the condenser II 24 in turn, and is mixed into the heating network after being warmed. The driving steam enters the generator II 23 to release heat, and the condensed water returns to the power plant condensate recovery system.

[0038] The partition flue gas / water heat exchanger is arranged in the flue, preferably a low-resistance new partition flue gas / water heat exchanger. The intermediate water circulating pump II 17 is arranged on the return water pipeline of the partition flue gas / water heat exchanger. The low-resistance new partition flue gas / water heat exchanger is used to reduce the flue gas temperature below the dew point, and deeply recover the sensible heat and latent heat in the flue gas. After the steam from the power plant releases heat as the driving heat source of the absorption heat pump II 12 unit, the condensed water enters the power plant condensate recovery system. The absorption heat pump group warms the heat network return water, and the heated heat network return water enters the absorption heat pump I 11 to continue to be warmed, or is directly supplied as heat network supply water through the heat network circulating pump.

[0039] The heat source end of the flue gas primary heat exchanger 6 is the high-temperature flue gas of the waste heat boiler 4, and the cold source end is divided into two routes, one of which directly comes from the heat network return water to increase the heat network water temperature, and the other of which comes from the first intermediate medium circulation loop 13; the absorption heat pump I 11 includes a generator I, a condenser I, an evaporator I, and an absorber I; the first intermediate medium circulation loop 13 is connected to the evaporator I, and the first intermediate medium circulation loop 13 is provided with a circulating pump I 20; the second route 10 enters the absorption heat pump I 11 after passing through the absorption heat pump II 12 and / or the bypass adjusting pipe 18, and flows out after passing through the absorber I and the condenser I in turn, and is then sent into the heat network supply water. Thus, the second route 10 is warmed twice.

[0040] Further, the second route 10 passes through the absorber II 26 and the condenser II 24 of the absorption heat pump II 12 in turn; the bypass adjusting pipe 18 is arranged at the absorption heat pump II 12 of the second route 10. By adjusting the opening degree of the bypass adjusting pipe 18 and the opening degree of the pipeline passing through the absorption heat pump II 12, the heating proportion of the heat network water of the second route 10 can be controlled, and thus the temperature can be more accurately controlled.

[0041] The system recovers low-grade flue gas waste heat for heating, reduces the heating operation cost, and increases the heating income; the flue gas temperature is reduced below the dew point, the sensible heat and latent heat in the flue gas are deeply recovered, the condensed water simultaneously absorbs SO2, NOX and other acidic gases in the flue gas, and the local environmental quality can be improved.

[0042] The above merely describes preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system, comprising a gas turbine (1), a steam turbine (2), a generator (3), a waste heat boiler (4), and a heating pipe network (5); characterized in that, A flue gas primary heat exchanger (6), a flue gas secondary heat exchanger (7), and a flue gas tertiary heat exchanger (8) are sequentially arranged on a flue gas exhaust pipe of the waste heat boiler (4); The heat network return water is divided into two paths, a first path (9) of which enters the flue gas primary heat exchanger (6) to directly recover the sensible heat in the flue gas; A second path (10) of the heat network return water passes through the absorption heat pump II (12) and the absorption heat pump I (11) to recover the sensible heat and latent heat in the flue gas, and is combined with the water outlet of the first path (9) to be sent to the heat network water supply; the absorption heat pump II (12) is provided with a second intermediate medium circulation loop (14) between the flue gas secondary heat exchanger (7); the absorption heat pump I (11) is provided with a first intermediate medium circulation loop (13) between the flue gas primary heat exchanger (6); Further comprising an absorption heat pump III (15), the absorption heat pump III (15) is provided with a third intermediate medium circulation loop (16) between the flue gas tertiary heat exchanger (8), the water outlet of the first path (9) on the flue gas primary heat exchanger (6) and the water outlet of the first intermediate medium circulation loop are connected to the absorption heat pump III (15) through a branch pipe, and the water outlet is returned to the heat network return water; The absorption heat pump I (11), the absorption heat pump II (12), and the absorption heat pump III (15) are all driven by steam turbine (2) exhaust to provide a driving heat source.

2. The low-temperature flue gas latent heat recovery heating system for a waste heat boiler of a combined cycle unit according to claim 1, characterized in that, The absorption heat pump II (12) comprises a generator II (23), a condenser II (24), an evaporator II (25), and an absorber II (26), the evaporator II (25) and the flue gas secondary heat exchanger (7) form the second intermediate medium circulation loop (14); the steam turbine (2) is provided with one exhaust connection to the generator II (23).

3. The combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system according to claim 2, characterized in that, The flue gas secondary heat exchanger (7) is a low-resistance partition type flue gas / water heat exchanger (21), which reduces the temperature of the flue gas below the dew point, and deeply recovers the sensible heat and latent heat in the flue gas; the medium circulating in the second intermediate medium circulation loop (14) is intermediate water, and the second intermediate medium circulation loop (14) is provided with an intermediate water circulating pump II (17).

4. The combined cycle unit waste heat boiler low-temperature flue gas latent heat recovery heating system according to claim 2, characterized in that, The second path (10) sequentially passes through the absorber II (26) and the condenser II (24) in the absorption heat pump II (12); the second path (10) is provided with a bypass adjustment pipe (18) at the absorption heat pump II (12).

5. The combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system according to claim 4, characterized in that, The heat source end of the flue gas primary heat exchanger (6) is the high-temperature flue gas of the waste heat boiler (4), and the cold source end is divided into two paths, one of which directly comes from the heat network return water to increase the temperature of the heat network water, and the other of which comes from the first intermediate medium circulation loop (13); the absorption heat pump I (11) comprises a generator I, a condenser I, an evaporator I, and an absorber I; the first intermediate medium circulation loop (13) is connected to the evaporator I, and the first intermediate medium circulation loop (13) is provided with a circulating pump I (20); the second path (10) enters the absorption heat pump I (11) after passing through the absorption heat pump II (12) and / or the bypass adjustment pipe (18), and flows out after sequentially passing through the absorber I and the condenser I to be sent to the heat network water supply.

6. The combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system according to claim 1, characterized in that, The absorption heat pump III (15) comprises a generator III, a condenser III, an evaporator III, and an absorber III, and the third intermediate medium circulation loop sequentially passes through the absorber III, the condenser III in the absorption heat pump III (15); a branch pipe of water outlet of the first path (9) and water outlet of the first medium circulation loop on the flue gas primary heat exchanger (6) is connected to the evaporator III, and a circulation pump III (19) is arranged on the branch pipe.

7. The combined cycle unit waste heat boiler low temperature flue gas latent heat recovery heating system according to claim 6, characterized in that, The third intermediate medium circulation loop (16) is provided with a circulation pump IV (27).

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