CN210861296U

CN210861296U - Single-pipe non-backwater long-distance heat transmission waste heat centralized heating system

Info

Publication number: CN210861296U
Application number: CN201920500085.8U
Authority: CN
Inventors: 李崇兴
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-04-15
Filing date: 2019-04-15
Publication date: 2020-06-26
Anticipated expiration: 2029-04-15

Abstract

The utility model relates to a single tube does not have defeated hot waste heat centralized heating system of return water long distance to river course water is the heat transfer medium, retrieves the flue gas waste heat of power plant, and the long-distance pipeline of big difference in height sets up pressure release hydroelectric set and utilizes potential energy electricity generation, has solved long-distance pipeline centralized heating system pipeline engineering investment big, the big problem of return water pressure water pump power consumption. The implementation of this patent has reduced a return water pipeline, has reduced pipeline and return water force (forcing) pump investment. The water pipe is provided with the pressure relief water turbine generator set for power generation, the generated power can be provided for a water source heat pump at the tail end of the system, and the operation cost of the heat supply system is reduced. The wet cold weather in south winter can be solved to this patent technique needs central heating's demand, and primary pipe network water is got from the upper reaches river course, and single tube is carried after getting into the waste heat exchanger heating of power plant after the processing, does not establish the wet return, discharges to low reaches river course lake or reservoir behind the secondary water heat transfer of the heat exchange station in the heating region and pipe network.

Description

Single-pipe non-backwater long-distance heat transmission waste heat centralized heating system

Technical Field

The utility model relates to a single tube does not have defeated hot waste heat centralized heating system of return water long distance, belongs to the heat supply field

Background

The conventional heating system consists of a heat source, a water supply and return circulating pipeline system, a radiator and accessory equipment. The power plant waste heat centralized heating is that primary water is heated to 110-. When the height difference is large, in order to reduce the deterioration of hydraulic conditions caused by high pressure in the pipe and the cost of high-pressure pipes and water pumps, a single-stage or multi-stage booster pump is required to be added on the low-end water supply (return) side. Meanwhile, the occurrence of shutdown water hammer when each stage of water pump fails is also considered. Therefore, the circulating and pressurizing water pumps of the long-distance large-altitude-difference heat supply pipeline increase the operation cost of heat supply.

In recent years, in large and medium-sized cities, in order to reduce the pollution of coal-fired heating boilers to the atmosphere, long-distance large-temperature-difference large-pipe-diameter long-distance pipeline heating projects are implemented, waste heat of large-scale cogeneration heat-generating plants far away from the cities is introduced into a city centralized heating pipe network, low-grade heat energy of the power plants is effectively utilized, the pollution emission of the heating boilers in winter is reduced, and energy conservation and emission reduction are realized. However, these projects generally face several challenges. Especially, under the condition of large height difference, a multistage high-power booster pump station is needed to pressurize and convey primary heating backwater to a power plant for continuous circular heating, the high-power water pump motor has high power consumption, the operation cost is improved, and the high-power booster pump station becomes the economic burden of an operation management unit.

Along with the improvement of living conditions, the requirement of people on comfort is also improved, the requirement of hot summer and cold winter areas in south China on heat supply is increased, and the implementation of the patent technology can provide a waste heat centralized heating system for centralized heating and long-distance heat transmission for the areas. Especially for areas with a large amount of waste heat resources such as large-scale power plants, steel mills and the like, the problem of central heating of surrounding towns is solved by using sufficient water sources by adopting the technology.

In a long-distance large-temperature-difference large-height-difference large-pipe-diameter centralized heating project implemented in a city in northern China, the difference between the elevation of a heat source power plant and the elevation of a heating urban area is 180 meters, 5-grade pressurizing pump stations are arranged for returning return water to the power plant in a primary pipe network, the total lift of a pressurizing water pump reaches 330 meters, the total lift of a circulating pump is 180 meters, the installed kilowatt of the water pump is 34000 kilowatts, the electric charge in a heating season exceeds 1 billion yuan, and the project becomes a heavy economic burden of an operation management unit. The operation cost is inevitably reduced.

Disclosure of Invention

The utility model aims at providing a single tube does not have defeated hot waste heat centralized heating system of return water long distance, characterized by to river course water is the heat transfer medium, retrieves power plant's flue gas waste heat, does not establish return water pipeline and corresponding booster pump station, and long-distance pipeline sets up pressure release hydraulic generator, and final drainage falls to initial temperature and realizes that heat energy is whole to be utilized, has solved long-distance pipeline centralized heating system once pipeline engineering investment big, the big running cost height of a return water booster pump power consumption and the many problems of potential safety hazard.

In order to achieve the above object, the present invention provides the following technical solutions:

the utility model provides a single tube does not have return water long distance heat transmission's waste heat centralized heating system, characterized by, a pipe network water is got from upper river course or reservoir, gets into power plant's waste heat exchanger after processing such as deposit, filtration and scale control, and single tube transport after the waste heat heating of power plant sets up hydroelectric set in the conduit suitable position of big difference in height, utilizes the potential energy electricity generation that the difference in height formed, with intraductal pressure release simultaneously. In the heat supply area, the temperature of water is reduced to below 50 ℃ through secondary water heat exchange with a heat supply pipe network, and the water is further reduced to 10 ℃ through a water source heat pump and then discharged to a downstream river channel.

The utility model provides a single tube does not have return water long distance defeated hot waste heat centralized heating system, including water source system, heat source system, pipe-line transportation system, pressure release power generation system, secondary heat transfer system, heat pump hoisting system. The utility model discloses a waste heat central heating system's operation is realized like this:

the water source system is characterized in that primary pipe network water is taken from an upstream river channel or a reservoir, a power plant and a heat supply area for cogeneration are in the upstream and downstream relationship of the river, and the river channel has stable natural water flow or the reservoir conveys ecological water with certain flow to the downstream through the river channel. The water source system is provided with a sedimentation tank and an adjusting tank with certain capacity, removes silt, suspended matters and partial pollutants in water and plays a role in water quantity adjustment. Before entering the heat exchanger, high-frequency electronic scale-removing and scale-preventing equipment is adopted to perform scale-preventing treatment on primary pipe network water, so that scale in the heat exchanger is prevented.

The heat source system is characterized in that the heat source is obtained from the waste heat of smoke discharged from a chimney of the power plant and the waste heat of exhaust gas of a steam turbine. When the residual heat quantity can not meet the requirement, the high-temperature air extraction of part of the steam turbine can be used for supplementing. According to the principle of temperature to the mouth, cascade utilization, set up tertiary heat exchanger:

1. the flue gas heat exchanger (steam-water heat exchange) utilizes low-temperature water (5-15 ℃, average 10 ℃) of a river channel to reduce the flue gas temperature of a boiler of a power plant from 60 ℃ (the flue gas temperature after desulfurization and denitrification) to about 20 ℃, and the primary pipe network water temperature is increased to 20-30 ℃. Meanwhile, the water vapor in the flue gas is condensed and part of pollutants in the flue gas are dissolved in water to be removed.

2. The system comprises an exhaust gas (condensed gas) heat exchanger, wherein the exhaust gas heat exchanger is connected with an air cooling island of a power plant in parallel, the air cooling island is replaced by the exhaust gas heat exchanger to operate in a heating period, and primary pipe network water heated by a flue gas heat exchanger passes through the exhaust gas heat exchanger and then is further heated.

3. When the temperature of the primary pipe network water passing through the exhaust gas heat exchanger does not meet the requirement, the exhaust gas heat exchanger enters the exhaust gas heat exchanger and is heated until the heat supply requirement is met and the exhaust gas heat exchanger enters a long-distance water conveying pipeline.

The pipeline conveying system is characterized in that the pipeline conveying system adopts a large-diameter steel pipe, and a heat insulation layer is laid outside the pipe, so that heat loss in the conveying process is reduced. The system comprises: a pressure pump, a water delivery pipeline and a drainage pipeline.

The booster pump is arranged at the outlet of the regulating reservoir and is used for ensuring the flow and the pressure of the water delivery system and overcoming the on-way resistance loss and the local resistance loss generated by the flue gas heat exchanger, the condenser heat exchanger, the air extraction heat exchanger and the water delivery pipeline.

The drainage pipeline is characterized in that primary pipe network water is subjected to multi-stage heat exchange, and is conveyed into a downstream river channel or a regulation and storage project through the drainage pipeline after the temperature of the primary pipe network water is reduced to the initial temperature, and the drainage pipeline does not need to be subjected to heat preservation treatment.

The pressure relief water turbine generator set is arranged on a water conveying pipeline with a certain pipeline fall, and primary pipe network water generates electricity through the water turbine generator set to consume potential energy, so that the pressure of the pipeline is reduced. According to the terrain and pipeline pressure conditions, a single-stage or multi-stage hydroelectric generating set can be arranged. The pressure-bearing requirement on the water delivery pipeline can be greatly reduced through the pressure-relief water turbine for power generation, the thickness of the pipe wall is reduced, and the construction cost is reduced.

The secondary heat exchange system is characterized by comprising a high-temperature heat exchanger and a medium-temperature heat exchanger. High-temperature high-pressure secondary heating water subjected to heat exchange through the high-temperature heat exchanger enters a main pipe system of the urban heat supply pipe network through a circulating pump and is conveyed to a heat exchange station of the urban heat supply pipe network for circulating heat exchange. The medium-temperature and medium-pressure secondary heating water which exchanges heat through the medium-temperature heat exchange station directly enters end users of the urban heat supply pipe network through the circulating pump to carry out circulating heat supply. After passing through the high-temperature heat exchanger and the medium-temperature heat exchanger, the primary pipe network water in the water delivery pipeline is cooled to below 50 ℃ and enters a heat pump lifting system.

The heat pump lifting system is characterized by comprising a water source heat pump and a secondary heating pipe network. The water in the primary pipe network below 50 ℃ is reduced to the initial temperature (about 10 ℃) by adopting a water source heat pump and enters a drainage pipe, and the secondary water which is increased to about 70 ℃ at the output side of the water source heat pump directly enters the end user of the urban heat supply pipe network for circular heat supply through a circulating pump.

The utility model provides a single tube does not have return water long distance defeated hot waste heat centralized heating system's advantage is:

1. the waste heat of the flue gas is recovered, and the energy conservation and emission reduction are realized

The low-temperature characteristic of the river course water in the heating season is utilized to fully recover the waste heat in the flue gas of the power plant. Although ultralow emission is realized through wet desulfurization, denitration and dust removal of the flue gas discharged from the coal-fired power plant, the content of water vapor in the flue gas is very high and is in a saturated state, so that the haze weather is still influenced to a certain extent. The temperature of the smoke which is subjected to ultralow emission is reduced to about 60 ℃, and the smoke contains a large amount of latent heat. By adopting the technology, the smoke can be discharged at 10-20 ℃, the phenomenon of white smoke emission is thoroughly eliminated, the latent heat of water vapor condensation in the smoke can be recovered, partial pollutants can be removed, and the pollution to the atmosphere is reduced.

2. Realize the single-pipe long-distance heat transmission without backwater and greatly reduce the heat transmission cost

Compared with the conventional heat supply mode, firstly, the pressure formed by the large height difference is used as the power for water delivery, the lift and the power of the pipeline booster pump station are reduced, the disadvantage of the large height difference is changed into the advantage, secondly, a water return pipeline is reduced, the pipeline investment is reduced by 50%, and thirdly, the pump station investment and the operation cost of the water return booster pump are reduced.

3. Potential energy generated by large height difference is utilized to set the hydroelectric generating set to release pressure for power generation

The pressure relief water turbine generator set is arranged at a position with a certain fall on the water conveying pipeline, potential energy is consumed through power generation of the water turbine generator set to generate economic benefits, the pressure of the pipeline is reduced, the pressure bearing requirement on the water conveying pipeline is greatly reduced, the thickness of a pipe wall is reduced, and the construction cost is reduced. The power generated by the water turbine generator set can be provided for a water source heat pump at the tail end of the system, and the running cost of the heat supply system is further reduced.

4. The primary water temperature is reduced to 10 ℃ by utilizing a water source heat pump, and the waste heat utilization of a power plant is maximized

The technology adopts the water source heat pump to reduce the final water temperature of primary pipe network water to 10 ℃, and the temperature difference of the primary water is improved to more than 100 ℃ from the traditional 60 ℃, so that the heat conveying capacity is increased, the heat transmission cost of a pipeline is greatly reduced, and the utilization rate of waste heat recovery of a power plant is improved.

5. The safety of the long-distance heat transmission central heating system is improved

Because a water return pipeline is reduced, multi-stage water return pressurizing pump stations are reduced, the pressure bearing requirement of the pipeline is reduced, the probability and the condition of failure are reduced, the low-cost operation is realized, and the economical efficiency and the safety of the long-distance heat transmission centralized heating system are improved.

The utility model provides a single tube does not have defeated hot waste heat centralized heating system of return water long distance, characterized by, this patent technique can be implemented to the wet cold climate in winter needs centralized heating's region along the line of the Yangtze river and south of the Yangtze river. The primary pipe network water is taken from an upstream river channel, lake or reservoir, enters a waste heat exchanger of a power plant after being treated by precipitation, filtration, scale prevention and the like, is heated by waste heat of the power plant and then is conveyed by a single pipe, exchanges heat with secondary water of a heat supply pipe network at a heat exchange station of a heat supply area, and is discharged to the downstream river channel, lake or reservoir after the temperature of the water is reduced to below 30 ℃. The technology can provide a cheap heat source for central heating in hot-summer and cold-winter areas.

The utility model provides a single tube does not have return water long distance heat transfer's waste heat central heating system suitable for cold in winter and hot in summer area, including water source system, heat source system, pipe-line conveying system, heating secondary heat transfer system, sluicing system. The utility model discloses a waste heat central heating system's operation is realized like this:

the water source system is characterized in that primary pipe network water of the heat supply system is taken from an upstream river channel, a lake or a reservoir (hereinafter referred to as a river channel), the combined power plant and the heat supply area are in upstream and downstream relation of the river channel, and the river channel has stable natural water flow or the reservoir delivers ecological water with a certain flow downstream. The water source system is provided with a sedimentation tank and an adjusting tank with certain capacity, removes silt, suspended matters and partial pollutants in water and plays a role in water quantity adjustment. Before entering the heat exchanger, high-frequency electronic scale-removing and scale-preventing equipment is adopted to perform scale-preventing treatment on primary pipe network water, so that scale in the heat exchanger is prevented.

The heat source system is characterized in that a heat source of the heat supply system is obtained from smoke exhausted by a chimney of a power plant and waste heat of exhaust gas of a steam turbine. According to the principle of temperature contra-aperture and cascade utilization, a secondary heat exchanger is arranged:

1. the flue gas heat exchanger (steam-water heat exchange) utilizes low-temperature water (20 ℃ on average) of a river channel to reduce the flue gas temperature of a power plant boiler from 60 ℃ (the flue gas temperature after desulfurization and denitrification) to about 30 ℃, and the primary water temperature is increased to about 30 ℃. Meanwhile, the water vapor in the flue gas is condensed and part of pollutants in the flue gas are dissolved in water to be removed.

2. The system comprises an exhaust gas (condensed gas) heat exchanger, wherein the exhaust gas heat exchanger is connected with an air cooling island of a power plant in parallel, the air cooling island is replaced by a heating period and a hot water supply working condition to operate, and primary pipe network water heated by a flue gas heat exchanger passes through the exhaust gas heat exchanger and then is further heated. Considering the heat load in southern areas, the water temperature of the primary pipe network is not too high.

The pipeline conveying system is characterized in that the pipeline conveying system of the heat supply system adopts a large-diameter steel pipe. And an insulating layer is laid outside the pipe, so that heat loss in the conveying process is reduced. The system comprises: a pressure pump, a water delivery pipeline and a drainage pipeline.

The drainage pipeline is used for conveying primary pipe network water to a downstream river channel or a regulation and storage project through the drainage pipeline after the temperature of the primary pipe network water is reduced to an initial temperature through multi-stage heat exchange.

The heating secondary heat exchange system is characterized in that the secondary heat exchange system of the heating system comprises a high-temperature heat exchanger and a medium-temperature heat exchanger. High-temperature high-pressure secondary heating water subjected to heat exchange through the high-temperature heat exchanger enters a main pipe system of the urban heat supply pipe network through a circulating pump and is conveyed to a heat exchange station of the urban heat supply pipe network for circulating heat exchange. The medium-temperature and medium-pressure secondary heating water which exchanges heat through the medium-temperature heat exchange station directly enters end users of the urban heat supply pipe network through the circulating pump to carry out circulating heat supply. The temperature of the primary pipe network water in the water delivery pipeline is reduced to below 30 ℃ after passing through the high-temperature heat exchanger and the medium-temperature heat exchanger.

The drainage pipeline is characterized in that the drainage pipeline of the centralized heating system is used for conveying primary pipeline network water which is cooled to be below 30 ℃ by a water source heat pump into a downstream river channel or a regulation and storage project.

The utility model provides a flue gas and exhaust gas waste heat of single tube does not have return water long distance heat transfer's waste heat centralized heating system make full use of power plant, through the transport of the long distance of big pipe diameter, can realize the heat supply difficult problem of low-cost solution changjiang river with south, this system can realize the operation all the year round in the abundant river network area of water yield, and non-heating season can be to city hot water supply.

The utility model provides a single tube does not have return water long distance defeated hot waste heat central heating system calls' waste heat, both can be the flue gas waste heat of combined heat and power plant, exhaust steam waste heat, the waste heat of bleeding, also can utilize the waste heat resources of trades such as steel factory, cement plant, kiln and chemical plant, provides low-priced heat source for central heating system.

The utility model provides a single tube does not have return water long distance defeated hot waste heat central heating system once pipe network water that calls both can be the water in the river course, also can be the water of urban reclaimed water system, also can be the discharge water up to standard of city and factory and mine sewage treatment plant. The drainage of reclaimed water and sewage treatment plants should add necessary treatment and disinfection processes.

Description of the drawings:

FIG. 1 is a flow of a central waste heat supply system for large-height-difference single-pipe backwater-free long-distance heat transmission

In the figure:

1. the system comprises an upstream riverway, 2, a sedimentation/regulation pool, 3, a pressure pump, 4, a high-frequency electronic scale prevention and removal device 5, a power plant chimney, 6, a flue gas heat exchanger, 7, a waste steam heat exchanger, 8, a steam turbine, 8-1, waste steam, 8-2 air exhaust, 9, an air exhaust heat exchanger, 10, a water turbine generator set, 11, a long-distance water conveying pipeline, 12, a high-temperature heat exchanger, 13, a medium-temperature heat exchanger, 14, a water source heat pump, 15, a drainage pipeline, 16 and a downstream riverway

The specific implementation mode is as follows:

the embodiment is further described with reference to fig. 1 for a project in which a heat source power plant and a heat supply area have a large height difference and a stable water source is used.

The primary pipe network water is taken from an upstream river channel 1 or a reservoir, a power plant and a heat supply area of cogeneration are in the upstream and downstream relation of a river, the river channel has stable natural water flow or the reservoir conveys ecological water with certain flow to the downstream through the river channel, and enough water can enter a long-distance heat transmission waste heat centralized heating system. Firstly, primary pipe network water is introduced into the sedimentation/filtration tank 2 to remove silt, suspended matters and partial pollutants in the water and play a role in water quantity regulation. Then the water is conveyed to the heat exchanger through a booster pump 3, and a high-frequency electronic scale removal and prevention device 4 is arranged at the outlet of the booster pump to perform scale prevention treatment on the primary pipe network water, so that scale in the heat exchanger is prevented.

The heat source of the long-distance heat transmission waste heat centralized heating system is taken from the waste heat of smoke exhaust of a chimney of a power plant and the waste heat of exhaust gas of a steam turbine. When the waste heat can not meet the requirement, the high-temperature air extraction of part of the steam turbine can be used for supplement. According to the principle of temperature to the mouth, cascade utilization, this system sets up tertiary heat exchanger altogether:

a first-stage heat exchanger: the primary pipe network water firstly enters a flue gas heat exchanger 6 (steam-water heat exchange), the temperature of the flue gas of the power plant boiler is reduced from 60 ℃ (the temperature of the flue gas after desulfurization and denitrification) to about 20 ℃ by utilizing the characteristics (5-15 ℃, average 10 ℃) of the low-temperature water of the river channel, and the temperature of the primary pipe network water is increased to about 30 ℃. At present, the smoke discharged by most coal-fired power plants is subjected to wet desulfurization, denitration and dust removal to realize ultralow emission, but the smoke is in a saturated state due to high water vapor content, so that certain influence is still exerted on haze weather. By adopting the technology, the flue gas can be discharged at 20 ℃, so that the water vapor condensation heat in the flue gas can be recovered, and part of pollutants can be removed.

A second-stage heat exchanger: the primary pipe network water enters the exhaust gas heat exchanger 7, the steam side of the exhaust gas heat exchanger 7 is connected with an air cooling island of a power plant in parallel, the air cooling island is replaced by the primary pipe network water which is heated to 30 ℃ by the flue gas heat exchanger 6 to run in the heating period, and the primary pipe network water passes through the exhaust gas heat exchanger to be further heated. For a plurality of generator sets of a large-scale power plant, a multistage series connection and cascade heating method can be adopted, and heating water can be heated to more than 80 ℃ by fully utilizing waste heat of exhaust gas.

A 3 rd stage heat exchanger: when the temperature of the primary pipe network water passing through the exhaust gas heat exchanger 7 still needs to be increased, the primary pipe network water enters the air extraction heat exchanger 9 and then is heated until the heat supply requirement is met and the primary pipe network water enters the long-distance water conveying pipeline.

Considering that the height difference between a heat source power plant and a heat supply area is large, the pipeline pressure at the middle tail end of a water pipeline is large, in order to reduce the water pressure of the pipeline, a water turbine generator set 10 is arranged at a proper position of the pipeline with the large height difference, potential energy formed by the height difference of the terrain is utilized to generate electricity, and meanwhile, the pressure in the pipeline is released and reduced. In the heat supply area, the temperature of the water is reduced to below 50 ℃ through secondary water heat exchange with a heat supply pipe network, and the water is further reduced to 10 ℃ through a water source heat pump and then discharged to a downstream river channel 16.

The pipeline conveying system adopts a large-diameter steel pipe, and a heat insulation layer is laid outside the pipe, so that heat loss in the conveying process is reduced. The pipe conveying system comprises: a booster pump 3, a water pipe 11, a pressure relief water-turbine generator set 10 and a drainage pipe 15.

The booster pump is arranged at the outlet of the regulating reservoir, and is used for ensuring the flow and pressure of a water delivery system and overcoming the on-way resistance loss and the local resistance loss generated by the flue gas heat exchanger 6, the condensed gas heat exchanger 7, the air extraction heat exchanger 9 and the water delivery pipeline 11.

The pressure relief water turbine generator set 10 is arranged on a water conveying pipeline with a certain pipeline fall, and primary pipe network water generates electricity through the water turbine generator set 10 to consume potential energy, so that the pressure of the pipeline is reduced. According to the terrain and pipeline pressure conditions, a single-stage or multi-stage hydroelectric generating set can be arranged. The pressure-bearing requirement on the water delivery pipeline can be greatly reduced through the pressure-relief water turbine for power generation, the thickness of the pipe wall is reduced, and the construction cost is reduced.

The water in the primary pipe network is subjected to multi-stage heat exchange, and is conveyed to a downstream river channel 16 or a regulation and storage project through a drainage pipeline 18 after the temperature is reduced to the initial temperature.

The secondary heat exchange system comprises a high-temperature heat exchanger 12 and a medium-temperature heat exchanger 13. The high-temperature high-pressure secondary heating water which is subjected to heat exchange through the high-temperature heat exchanger 12 enters a main pipe system of the urban heat supply pipe network through a circulating pump and is conveyed to a heat exchange station of the urban heat supply pipe network for circulating heat exchange. The medium-temperature and medium-pressure secondary heating water which exchanges heat through the medium-temperature heat exchanger 13 directly enters end users of the urban heat supply pipe network through the circulating pump to carry out circulating heat supply. After passing through the high-temperature heat exchanger 12 and the medium-temperature heat exchanger 13, the primary pipe network water in the water pipeline is cooled to below 50 ℃ and enters a heat pump lifting system.

The heat pump lifting system comprises a water source heat pump 14 and a secondary heating pipe network. The water in the primary pipe network below 50 ℃ is reduced to the initial temperature (about 10 ℃) by adopting the water source heat pump 14 and enters the drainage pipe, and the secondary water which is increased to about 70 ℃ at the output side of the water source heat pump 14 directly enters the end user of the urban heat supply pipe network for circular heat supply through the circulating pump.

The drainage pipeline 15 is used for conveying primary pipe network water which is reduced to an initial temperature (about 10 ℃) by a water source heat pump to a downstream river channel 16 or a regulation and storage project.

Claims

1. A single-pipe backwater-free long-distance heat transmission waste heat centralized heating system is characterized by comprising a water source system, a heat source system, a pipeline conveying system, a pressure relief power generation system, a secondary heat exchange system and a heat pump lifting system; the water source system takes river water as a heat exchange medium, the river water is treated by a sedimentation tank and a descaling antiscaling device and then is sent into a flue gas waste heat exchanger, an exhaust steam waste heat exchanger and a gas turbine air exhaust heat exchanger of the heat source system to be heated, the river water is conveyed for a long distance through a large-pipe-diameter steel pipe of the pipeline conveying system, is subjected to power generation by a water turbine generator set of the pressure relief power generation system and reduces the pressure of a pipeline, is conveyed to a heat exchanger of the secondary heat exchange system to exchange heat with secondary water, and is subjected to heat exchange by the heat pump lifting system to reduce the.

2. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the primary pipe network water of the water source system is taken from an upstream river channel or a reservoir, the water source system is provided with a sedimentation tank and a regulating tank with certain capacity, and high-frequency electronic scale removal and prevention equipment is adopted to perform scale prevention treatment on the primary pipe network water before the primary pipe network water enters the heat exchanger, so that scale formation in the heat exchanger is prevented.

3. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein a heat source of the heat source system is obtained from waste heat of flue gas exhausted from a chimney of a power plant, waste heat of exhaust gas of a steam turbine and high-temperature air extraction of a part of the steam turbine, and the heat source system is provided with a three-stage heat exchanger.

4. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 3, wherein the three-stage heat exchangers are respectively as follows: (1) the flue gas heat exchanger reduces the temperature of the flue gas of the power plant boiler from 60 ℃ to about 20 ℃ by using low-temperature water of a river channel, and the temperature of primary pipe network water is increased to 20-30 ℃; (2) the exhaust gas heat exchanger is connected with an air cooling island of the power plant in parallel, and primary pipe network water heated by the flue gas heat exchanger passes through the exhaust gas heat exchanger and then is further heated; (3) and the air exhaust heat exchanger heats low-temperature water at the temperature of the primary pipe network water and then enters the long-distance water conveying pipeline.

5. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the pipeline conveying system adopts a large-pipe-diameter steel pipe, and an insulating layer is laid outside the pipe; the booster pump is arranged at the outlet of the regulating reservoir and is used for ensuring the flow and pressure of the water delivery system, and the drainage pipeline is used for conveying primary pipe network water which is reduced to the initial temperature by the water source heat pump to a downstream river channel or a regulation and storage project.

6. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the pressure-relief power generation system is a water turbine generator set arranged on a water transmission pipeline with a certain pipeline fall, and primary pipe network water generates power through the water turbine generator set to consume potential energy, so that the pressure of the pipeline is reduced; according to the terrain and pipeline pressure conditions, a single-stage or multi-stage hydroelectric generating set can be arranged.

7. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the secondary heat exchange system comprises a high-temperature heat exchanger and a medium-temperature heat exchanger; high-temperature high-pressure secondary heating water subjected to heat exchange by the high-temperature heat exchanger enters a main pipe system of the urban heat supply pipe network through a circulating pump and is conveyed to a heat exchange station of the urban heat supply pipe network for circulating heat exchange; the medium-temperature and medium-pressure secondary heating water which exchanges heat through the medium-temperature heat exchange station directly enters end users of the urban heat supply pipe network through a circulating pump to carry out circulating heat supply; after passing through the high-temperature heat exchanger and the medium-temperature heat exchanger, the primary pipe network water in the water delivery pipeline is cooled to below 50 ℃ and enters a heat pump lifting system.

8. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the heat pump lifting system comprises a water source heat pump and a secondary heating pipe network; the water in the primary pipe network below 50 ℃ is reduced to the initial temperature by adopting the water source heat pump and enters the drainage pipeline, and the secondary water which is increased to about 70 ℃ at the output side of the water source heat pump directly enters the end user of the urban heat supply pipe network for circular heat supply through the circulating pump.

9. The single-pipe backwater-free long-distance heat transmission waste heat centralized heating system according to claim 1, wherein the long-distance heat transmission centralized heating system applied to the areas along the Yangtze river and in the south of the south where the winter is wet and cold comprises the following steps: the system comprises a water source system, a heat source system, a pipeline conveying system, a heating secondary heat exchange system and a water drainage system; the water source system comprises a sedimentation tank and an adjusting tank with certain volumes and high-frequency electronic descaling and antiscaling equipment; the heat source system comprises a flue gas heat exchanger and a waste gas heat exchanger; the pipeline conveying system comprises: a pressure pump, a water delivery pipeline and a drainage pipeline; the heating secondary heat exchange system comprises a high-temperature heat exchanger and a medium-temperature heat exchanger.