CN208139316U - A kind of coal unit fume afterheat utilizes and environment friendly system - Google Patents

Abstract

The utility model provides a coal-burning unit flue gas waste heat utilization and environmental protection system. The flue gas waste heat utilization system of the coal-fired unit first uses the heat energy of part of the high-temperature flue gas to heat part of the feed water in the steam turbine recovery system through the high-pressure heat exchange component, and then heats the circulating water through the low-pressure heat exchange component with the cooled flue gas. The circulating water is divided into three ways to heat the cold flue gas after desulfurization, preheat the primary and secondary air, and heat part of the condensed water. After cooling, the three paths of circulating water are combined to absorb heat through the flue gas waste heat absorber, and then return to the low-pressure heat exchange component. This system not only solves the technical problem that the heat collected by the flue gas waste heat absorber alone cannot reach the flue gas discharge temperature required to completely eliminate the chimney rain when the unit is under low load or the external environment temperature is low, but also greatly reduces the energy consumption of the air preheater. Low-temperature corrosion and ammonium bisulfate adhesion and clogging have played a very good role in energy saving and environmental protection.

Description

A coal-fired unit flue gas waste heat utilization and environmental protection system

technical field

The utility model relates to the field of environmental protection and energy saving of a coal-fired unit, in particular to a waste heat utilization and environmental protection system of a coal-fired unit.

Background technique

As my country's environmental protection continues to increase, flue gas desulfurization devices have been generally installed in the thermal power industry. Wet flue gas desulfurization (WFGD) technology has become the leading flue gas desulfurization technology at home and abroad because of its advantages such as wide application range of coal types and high desulfurization efficiency.

However, the temperature of the saturated wet flue gas after wet desulfurization is relatively low, and the moisture content is also relatively large. During the discharge process of the chimney, it is easy to condense and form liquid droplets near the chimney mouth, resulting in that the flue gas cannot be effectively lifted after being discharged from the chimney mouth. Rapidly diffuses into the atmosphere. Some of the large droplets that have not had time to spread and evaporate will fall to the ground around the chimney, forming "chimney rain".

The "chimney rain" phenomenon can cause the following hazards:

First, affect the normal life of the surrounding residents;

Second, it is not conducive to the normal growth of surrounding vegetation and crops;

Third, damage the facilities and buildings in the subsidence area and affect the normal production of the power plant.

As people pay more and more attention to the living environment, environmental issues have become more sensitive. The settlement problem of wet desulfurization "chimney rain" affects the life and production in the area near the power plant, and the long white smoke at the chimney outlet also brings obvious visual pollution. Generally, only by raising the flue gas temperature from about 50°C to above 80°C (summer) to 100°C (winter) can the effect of dry chimney emission be basically realized. At present, rotary GGH flue gas heaters or water-based flue gas heaters are mainly used to transfer the heat of the flue gas in front of the desulfurization tower to the wet flue gas behind the tower to increase the temperature of the flue gas. However, the design air preheater exhaust gas temperature of many large coal-fired units at full load is less than 120°C, and even lower than 100°C at low load, so it is difficult to heat the flue gas temperature to the required level under low load or winter conditions. Level, had to invest a large amount of high-quality high-temperature and high-pressure steam for auxiliary heating, which greatly affected the economy of the unit.

Early pre-air heaters (air heaters) were mainly designed to prevent low-temperature corrosion at the cold end of the air preheater. Since the acid dew point is generally lower than 120°C, the pre-air heater only needs to raise the air temperature to 20°C. ℃ ~ 40 ℃ can basically solve the problem of low temperature corrosion (flue gas temperature increased to 120 ℃ ~ 140 ℃, the average temperature of the cold end 70 ℃ ~ 90 ℃). However, with the widespread use of SCR denitrification devices in coal-fired power plants, the concentration of SO ₃ in the flue gas has increased significantly due to the vanadium-based catalyst, and the escape of ammonia caused by poor operation of the SCR denitrification device, the two react to form hydrogen sulfate Ammonium. The liquid temperature range of ammonium bisulfate is about 146°C to 207°C. Its formation is likely to cause the adhesion of liquid ammonium bisulfate in the low-temperature section of the air preheater, and then cause fly ash deposition and blockage. This phenomenon leads to a substantial increase in the resistance of the air preheater, which not only increases the power consumption of the induced draft fan, but also some units have to reduce the load operation because the resistance exceeds the design capacity of the induced draft fan. In order to move down and reduce the ammonium bisulfate deposition area, facilitate soot blowing and water flushing (after moving down, the flushing pressure can be reduced, and the impact on the heat exchange elements can also be reduced), it is necessary to further increase the air temperature at the inlet of the air preheater to 75 ℃～95℃, reduce the heat absorption of the air preheater, increase the exhaust gas temperature to 145℃～160℃, and make the average temperature of the cold end reach 110℃～128℃.

To increase the primary and secondary air temperature at the inlet of the air preheater, the heat source of the traditional steam heater comes from steam extraction, which consumes a lot of steam and reduces the economical efficiency of the unit. In recent years, some units have adopted water-based waste heat flue gas heaters instead of steam heating, which has better economic efficiency, but also faces the problem of insufficient waste heat to heat the primary and secondary air under low load or winter conditions. If the use of high-temperature steam is further increased, the economical efficiency of the unit will be reduced.

Utility model content

The coal-fired unit flue gas waste heat utilization and environmental protection system is characterized in that the system includes a high-pressure heat exchange component, a low-pressure heat exchange component and a flue gas waste heat absorber; part of the high-temperature flue gas is first Flow through the high-pressure heat exchange component to heat part of the high-pressure feed water in the steam turbine recuperation system, and then flow through the low-pressure heat exchange component to heat the circulating water flowing through the low-pressure heat exchange component. The circulating water is divided into three paths: one path is used to heat the cold flue gas after desulfurization, one path is used to preheat the primary air and secondary air, and the last path is used to heat part of the condensed water; the three paths of circulating water flow through after cooling The flue gas waste heat absorber before the electric precipitator of the coal-fired unit absorbs the flue gas heat, and then returns to the low-pressure heat exchange component to continue heating up.

The utility model can adjust the water volume distribution of the three-way circulation pipeline according to the operating condition of the unit, the load and the temperature and humidity of the external environment. For example, in winter, more heat is required for preheating the primary air, secondary air and heating the cold flue gas after the desulfurization tower, then reduce the amount of circulating water used to heat the condensate until it is completely closed; if it still cannot be heated to the required When the temperature is lower, further reduce the water supply of the high-pressure heat exchange component or open the regulating baffle of the branch flue to increase the flue gas flow of the branch flue. The above design increases the flexibility of the flue gas waste heat utilization system.

Optionally, an air preheater, the flue gas waste heat absorber, an electric precipitator, an induced draft fan, a wet desulfurization device and a flue gas reheater are sequentially arranged along the main flow direction of the flue gas at the tail of the boiler; The flue gas main flue before the preheater is also provided with a branch flue, and part of the high-temperature flue gas flows through the branch flue, and the high-pressure heat exchange component and the low-pressure heat exchange component are sequentially arranged in the branch flue; wherein The proportion of high-temperature flue gas flowing through the air preheater is greater than the proportion of high-temperature flue gas flowing through the branch flue.

Optionally, along the flue gas flow to the inside of the branch flue, a flow regulating baffle, an SO ₃ absorbent injection device and a shut-off door are sequentially arranged; wherein, the high-pressure heat exchange assembly and the low-pressure heat exchange assembly are sequentially arranged Arranged between the SO ₃ absorbent injection device and the shut-off door.

Optionally, the high-pressure heat exchange assembly has a heat exchange pipeline, and the part of the high-pressure feed water that flows through the heat exchange pipeline after heat exchange is heated up, and the pipeline after the final high-pressure heater merges into the main pipeline to be It is sent to the boiler for heating to generate steam.

Optionally, the low-pressure heat exchange assembly has a heat exchange pipeline, and the low-pressure circulating water flowing through the heat exchange pipeline of the low-pressure heat exchange assembly performs heat exchange with the medium-temperature flue gas that has undergone heat exchange through the high-pressure heat exchange assembly; And the three circulating water pipelines flowing out of the low-pressure heat exchange components are all provided with valves, which are used to adjust the water volume of the corresponding pipelines to meet the demand for heat in different working conditions.

Optionally, along the main flow direction of the flue gas, the high-temperature flue gas flowing through the air preheater exchanges heat with the primary air and secondary air that have been preheated by circulating water.

Optionally, the low-temperature flue gas flowing out from the outlet of the air preheater merges with the low-temperature flue gas flowing out from the branch flue, and then flows through the flue gas waste heat absorber, inside the flue gas waste heat absorber Heat exchange with the three-way circulating water merged after heat exchange, and the circulating water circulates in the pipeline under the action of the circulating water pump.

Optionally, the flue gas flowing out of the flue gas waste heat absorber is dedusted by the electrostatic precipitator, and is transported to the wet desulfurization device under the action of the induced draft fan for desulfurization, washing and dust removal, and flows through The cold flue gas from the wet desulfurization device enters the flue gas to be heated by a heater, and finally is discharged into the atmosphere through a chimney.

Optionally, along the flue gas flow direction, the branch flue includes a first pipe section and a second pipe section, the flow area of the first pipe section is larger than the flow area of the second pipe section, the SO3 absorbent injection device and The high-pressure heat exchange components are arranged on the first pipe section, and the low-pressure heat exchange assemblies are arranged on the second pipe section.

Description of drawings

Fig. 1 is a schematic structural view of waste heat utilization and environmental protection system in an embodiment of the utility model;

Fig. 2 is a partial schematic diagram of a branch flue in an embodiment of the present invention.

Wherein, the one-to-one correspondence between each component and the reference numerals in Fig. 1 to Fig. 2 is as follows:

1. Boiler, 2. SCR denitrification device, 3. Air preheater, 4. Flue gas waste heat absorber, 5. Low and low temperature electrostatic precipitator, 6. Induced fan, 7. Wet desulfurization device, 8. Flue gas reprocessing Heater, 9. Chimney, 10. Main flue gas pipe, 10a. Branch flue, 10a1. First pipe section, 10a2. Second pipe section, 11. Low-pressure heat exchange components, 12. High-pressure heat exchange components, 13. Flow adjustment Baffle plate, 14. Water-water heat exchanger, 15. Circulating water pump, 16. Front air heater, 17. SO ₃ absorbent injection device, 18. Condensate hot well, 19. Condensate pump, 20. Shaft seal Heater, 21. First low-pressure heater, 22. Second low-pressure heater, 23. Third low-pressure heater, 24. Fourth low-pressure heater, 25. Fifth low-pressure heater, 26. Deaerator, 27 . Feed water pump, 28. First high pressure heater, 29. Second high pressure heater, 30. Third high pressure heater, 31. Boiler economizer.

Detailed ways

Aiming at the technical problems of low economic performance and poor adaptability of the unit when heating the cold flue gas after the desulfurization tower and preheating the primary and secondary air in the prior art, the utility model has carried out further exploration and research, and proposes a method to improve the economical performance of the unit. Performance and adaptability of coal-fired unit flue gas waste heat utilization and environmental protection system.

In order to make those skilled in the art better understand the technical solution of the utility model, the utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a waste heat utilization and environmental protection system in an embodiment of the present invention.

It should be noted that this paper defines the flue gas flowing out of the boiler and not entering the air preheater as high-temperature flue gas.

The coal-fired unit flue gas waste heat utilization and environmental protection system in the utility model mainly includes: a boiler 1, a boiler economizer 31, an air supply system, a boiler flue gas waste heat utilization system, a steam turbine heat recovery system, and auxiliary equipment behind the furnace.

Among them, the fuel is burned in the boiler 1 to become hot flue gas, the working medium water inside the boiler 1 is heated into steam, which is transported to the steam turbine to be converted into mechanical energy, and then the mechanical energy is converted into electrical energy through the generator.

The air supply system mainly provides the boiler with the air required for fuel combustion or the air required for drying powder. The air supply system can include a primary blower and a blower, and the outside air enters the front air heater 16 and the air preheater 3 for two-stage heating after being boosted by the primary blower and the blower, and then enters the boiler. The structure and installation method of the primary fan and the blower fan can refer to the prior art, and will not be repeated here. It should be noted that, in the field, the blower for conveying secondary air is generally referred to as a blower.

The steam turbine heat recovery system may include a condensate well 18, a condensate pump 19, a low-pressure feedwater heating system, a deaerator 26, a feedwater pump 27 and a high-pressure feedwater heating system connected in sequence. The condensed water coming out of the condensed water heating well 18 is boosted by the condensed water pump 19 , enters the low-pressure feed water heating system for heating, and then flows into the deaerator 26 . In this paper, the low-pressure working medium water coming out of the condensate hot well 18 and boosted by the condensate pump 19 before the deaerator 26 is defined as condensate; Defined as condensed water.

The low-pressure feedwater heating system and the high-pressure feedwater heating system both include more than two heaters, as shown in Figure 1, in a specific boiler system, the low-pressure feedwater heating system includes five low-pressure heaters and one shaft seal heater 20 , along the condensed water flow direction are: shaft seal heater 20, first low pressure heater 21, second low pressure heater 22, third low pressure heater 23, fourth low pressure heater 24 and fifth low pressure heater 25; high pressure The feedwater heating system includes three high-pressure heaters, which are: the first high-pressure heater 28 , the second high-pressure heater 29 and the third high-pressure heater 30 along the junction water flow direction. The specific number of low-pressure heaters and high-pressure heaters can be selected according to the specific unit steam turbine heat recovery system.

In the steam turbine heat recovery system described above, part of the condensed water is separated from the pipeline behind the second low-pressure heater 22 and delivered to the water-water heat exchanger 14 for heating, and then returns to the main pipeline before the deaerator 26; After the water pump 27, part of the high-pressure feed water is separated from the pipeline and sent to the high-pressure heat exchange assembly 12 of the branch flue 10a to be heated, then returned to the main pipeline behind the third high-pressure heater 30 and sent to the boiler 1 .

The post-furnace ancillary equipment described in this article mainly includes electric dust collector, induced draft fan 6, wet desulfurization device 7 and chimney 9 and other components. Wherein the electrostatic precipitator can be a low-low temperature electrostatic precipitator 5, and the low-low temperature electrostatic precipitator 5 and the induced draft fan 6 are installed in sequence before the desulfurization device 7, after the flue gas waste heat absorber 4, and the low-low temperature electric precipitator 5 is used to collect flue gas in the dust. The induced draft fan 6 provides power for flue gas flow, and the flue gas system upstream of it is in a negative pressure operating state.

What needs to be explained is that generally electrostatic precipitators generally include three types: high-temperature electrostatic precipitators, low-temperature electrostatic precipitators, and low-low temperature electrostatic precipitators.

The wet desulfurization device 7 is used to desulfurize the flue gas, that is, to remove sulfur oxides, chlorides and fluorides in the flue gas, and to perform further cleaning and dust removal. This device is installed after the induced draft fan 6 . After passing through the desulfurization device 7, the flue gas is heated by the flue gas reheater 8, and finally discharged into the atmosphere through the chimney 9.

That is to say, the flue gas flowing out of the flue gas waste heat absorber 4 is dedusted by the electrostatic precipitator, and is transported to the wet desulfurization device 7 under the action of the induced draft fan 6 for desulfurization, washing and dust removal, and flows through the wet desulfurization device 7 The cold flue gas enters into the flue gas heater 8 to heat up, and finally is discharged into the atmosphere by the chimney.

The main function of boiler flue gas waste heat utilization system is to recover and utilize flue gas heat. The thermal energy utilization equipment along the main flow direction of flue gas at the tail of the boiler is provided with an air preheater 3 , a flue gas waste heat absorber 4 and a flue gas reheater 8 in sequence. The flue gas waste heat absorber 4 is arranged downstream of the air preheater 3 and before the low-temperature electrostatic precipitator 5 to further absorb the heat energy in the flue gas flowing out of the air preheater 3 and the branch flue 10a. When the air temperature range is approximately 85°C to 95°C, the low-temperature electrostatic precipitator 5 works better. The flue gas reheater 8 is located after the wet desulfurization unit 7 .

In the boiler flue gas waste heat utilization and environmental protection system provided by the utility model, part of the high-temperature flue gas first flows through the high-pressure heat exchange component to heat part of the high-pressure feed water in the steam turbine heat recovery system, and then flows through the low-pressure heat exchange component to heat the flowing water. The circulating water inside the low-pressure heat exchange component is divided into three paths after heating up: one path is used to heat the cold flue gas after desulfurization; one path is used to preheat the primary air and secondary air; the last path is used to heat part of the condensed water; After the three-way circulating water is cooled, it first flows through the flue gas waste heat absorber in front of the electric precipitator of the coal-fired unit to absorb the heat of the flue gas (that is, the circulating water passes through the flue gas waste heat absorber and the corresponding flue gas passing through the flue gas waste heat absorber indirectly heat exchange and temperature rise), and then return to the low-pressure heat exchange component for heat exchange and temperature rise, and so on.

The air preheater, flue gas waste heat absorber, electrostatic precipitator, induced draft fan, wet desulfurization device and flue gas reheater are arranged in sequence along the main flow direction of flue gas at the tail of the boiler. The flue gas main pipeline 10 before the air preheater also has a branch flue 10a, part of the high-temperature flue gas flows through the branch flue, and the high-pressure heat exchange assembly and the low-pressure heat exchange assembly are sequentially arranged in the branch flue. The proportion of high-temperature flue gas flowing through the air preheater is greater than the proportion of high-temperature flue gas flowing through the branch flue.

Along the flue gas flow direction, the branch flue 10a is further provided with a flow regulating baffle 13 , an SO ₃ absorbent injection device 17 , a high-pressure heat exchange assembly 12 and a low-pressure heat exchange assembly 11 . The flow regulating baffle 13 is arranged at the inlet of the branch flue 10a, and is used for regulating the flow of flue gas entering the branch flue 10a. That is to say, by adjusting the baffle opening of the flow regulating baffle 13 , the flue gas flow inside the branch flue 10 a can be adjusted.

The base absorbent is sprayed into the branch flue 10a through the SO ₃ absorbent injection device 17 to convert most of the SO ₃ gas in the flue gas into sulfate. Since most of the SO3 in the flue gas is removed, the low _- pressure heat exchange component 11 in the liquid temperature zone of ammonium bisulfate will not have the problem of ammonium bisulfate sticking and clogging.

The high-pressure heat exchange assembly 12 is arranged inside the branch flue 10 a and is located downstream of the SO ₃ absorbent injection device 17 . The high-pressure heat exchange assembly 12 has a heat exchange pipeline, and the high-pressure feed water flowing through the heat exchange pipeline of the high-pressure heat exchange assembly 12 exchanges heat with the flue gas in the branch flue 10a, that is, the heat exchange pipeline of the high-pressure heat exchange assembly 12 The high-pressure feed water is heated up after exchanging heat with the flue gas in the branch flue 10a, and then returned to the steam turbine recuperation system, wherein the high-pressure feed water can be sent back to the main outlet pipeline of the final high-pressure heater 30 to be transported to The boiler is heated to produce steam. The specific structure of the high-pressure heat exchange assembly 12 is not limited herein.

The low-pressure heat exchange assembly 11 is arranged downstream of the high-pressure heat exchange assembly 12. The low-pressure heat exchange assembly 11 has a heat exchange pipeline, and the low-pressure circulating water flowing through the heat exchange pipeline of the low-pressure heat exchange assembly 11 and the high-pressure heat exchange assembly 12 heat exchange The medium-temperature flue gas performs heat exchange; the specific structure of the low-pressure heat exchange component 11 is not limited herein. The low-pressure circulating water comes from the outlet of the flue gas waste heat absorber 4 before the low-temperature electrostatic precipitator 5 . The circulating water further heated by the low-pressure heat exchange assembly 11 is divided into three paths, that is, the outlet of the low-pressure heat exchange assembly 11 is provided with a first branch pipeline, a second branch pipeline and a third branch pipeline in parallel.

The hot circulating water in the first branch pipeline is sent to the flue gas reheater 8 behind the desulfurization tower 7 and before the chimney 9 to heat the cold flue gas after desulfurization, and heat the flue gas from a wet saturated state to an unsaturated state ;

The hot circulating water in the second branch pipeline is sent to the air preheater 16 in front of the air preheater 3 to preheat the primary air and secondary air;

The hot circulating water in the third branch pipeline is sent to the water-water heat exchanger 14 to heat part of the condensed water, which can be transferred from the main condensed water pipe between the second low-pressure heater 22 and the third low-pressure heater 23 Take water on the road, and return water from the main condensate pipeline before the deaerator 26 after the fifth low-pressure heater 25 (last-stage low-pressure heater). It should be noted that the final low-pressure heater is the last low-pressure heater in the flow direction.

The above three channels of circulating water are combined into one channel after being cooled by the above heat exchange, and are transported to the flue gas waste heat absorber 4 in front of the low-temperature electrostatic precipitator 5 under the action of the circulating water pump 15 for heating and heating, and return to the low-pressure heat exchange component to continue heating. And so on and on.

Specifically, in the above-mentioned embodiments, the low-temperature flue gas flowing out from the outlet of the air preheater 3 merges with the low-temperature flue gas flowing out from the branch flue 10a, and then flows through the flue gas waste heat absorber 4, where the flue gas waste heat absorber 4 The interior and the three-way circulating water merged after heat exchange perform heat exchange, and the circulating water circulates in the pipeline under the action of the circulating water pump.

And the three circulating water pipelines flowing out of the low-pressure heat exchange components are all provided with valves, which are used to adjust the water volume of the corresponding pipelines to meet the demand for heat in different working conditions.

This system provides a higher temperature flue gas heat source for primary air, secondary air preheating and cold flue gas reheating after the desulfurization tower, but basically does not affect the unit economy. This system can adjust the water distribution of the three-way circulation pipeline according to the operation status, load and external environment of the unit. For example, in winter, more heat is required for preheating the primary air, secondary air, and heating the cold flue gas after desulfurization, then reduce the amount of circulating water used to heat the condensate until it is completely closed; if it still cannot be heated to the required temperature , then further reduce the water supply of the high-pressure heat exchange component or open the regulating baffle of the branch flue to increase the flue gas flow of the branch flue. Similarly, in summer or under high load conditions, less heat is required to preheat the primary air, secondary air, and heat the cold flue gas after the desulfurization tower, so reduce the amount of circulating water in these two paths and increase the amount of heat used to heat the condensate The amount of circulating water in the third branch can squeeze out the steam extraction and return steam generator of the low-pressure heating system to do work, saving coal consumption. The above design increases the flexibility of the flue gas waste heat utilization system.

In the above embodiment, the flue gas in the branch flue 10a is mixed with the flue gas passing through the air preheater 3 and then passed through the flue gas waste heat absorber 4 for cooling and heat exchange, which is conducive to the full recovery and utilization of flue gas waste heat.

Moreover, a shut-off valve is provided at the outlet of the branch flue 10a for connecting or disconnecting the branch flue 10a, so that the maintenance of the branch flue 10a can be realized without stopping the machine.

In the above embodiments, part of the high-temperature flue gas may flow through the air preheater, and another part of the high-temperature flue gas may flow through the branch flue 10a.

In the above embodiments, most of the high-temperature flue gas flows through the air preheater, and the high-temperature flue gas in the air preheater further heats the primary air and secondary air that have been preheated by circulating water.

In addition, the cold flue gas of the system adopts the method of flowing forward and then countercurrent after heating the desulfurization tower by the hot circulating water, which can achieve the purpose of rapid temperature rise and protect the heat exchange tube from corrosion. Other heat exchange equipment, such as low-pressure heat exchange components 11, high-pressure heat exchange components 12, flue gas waste heat absorber 4, air pre-heater 16 and water-water heat exchanger 14 all adopt countercurrent heat exchange to enhance heat exchange effect.

Others in this embodiment also include that the pre-air heater 16 may include a primary air pre-air heater and a secondary air pre-air heater, and the primary air enters the air preheater 3 after being heated by the primary air pre-air heater. The entrance of the primary air sub-bin, and the secondary air enters the air preheater through the secondary air front air heater 3 The entrance of the secondary air sub-bin.

In addition, please refer to FIG. 2 , which is a partial schematic diagram of a branch flue in an embodiment of the present invention.

In the above-mentioned embodiments, the temperature of the flue gas decreases after heat exchange through the high-pressure heat exchange component 12, and its flow rate will inevitably decrease. , the branch flue 10a includes a first pipe section 10a1 and a second pipe section 10a2, the flow area of the first pipe section 10a1 is larger than the flow area of the second pipe section 10a2, the high-pressure heat exchange assembly 12 is arranged on the first pipe section 10a1, and the low-pressure heat exchange assembly 11 is provided In the second pipe section 10a2.

The flow area of the first pipe section 10a1 and the flow area of the second pipe section 10a2 can be set according to specific conditions, which will not be specifically introduced herein, but this does not prevent those skilled in the art from implementing the technical solution.

Through the implementation of the utility model, firstly, the cold flue gas behind the desulfurization tower 7 can be heated to above 80°C (summer) to 100°C (winter) by the flue gas reheater, so as to realize dry chimney discharge and eliminate chimney rain and long white smoke phenomenon ;

Then, the temperature of the air entering the air preheater 3 rises to 75°C-95°C, and the average temperature of the cold end of the air preheater 3 reaches 110°C-128°C. The ammonium bisulfate deposition area in the air preheater 3 is moved down and reduced, combined with soot blowing and water flushing, the increase in the resistance of the air preheater 3 can be controlled at a low level, and the air preheater 3 can be basically eliminated. Low temperature corrosion problem;

Finally, the high-pressure heater 12 of the branch flue 10a heats the feed water and the hot circulating water to heat the condensed water, which can displace more high-quality steam return steam generators in the heat recovery system and generate more electricity under the same coal consumption. It also reduces the coal consumption per unit of power supply.

Above, a system for utilization of waste heat of coal-fired unit flue gas and environmental protection provided by the utility model has been introduced in detail. In this paper, specific examples are used to illustrate the principle and implementation of the present utility model, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present utility model. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the utility model, some improvements and modifications can also be made to the utility model, and these improvements and modifications also fall into the protection of the claims of the utility model. within range.

Claims (9)

1. a kind of coal unit fume afterheat utilizes and environment friendly system, which is characterized in that the system includes high pressure heat exchange component, low Press heat-exchanging component and fume afterheat absorber；Part high-temperature flue gas flows through the high pressure heat exchange component first to heat the coal burning machine Then partial high pressure water supply in the steam turbine heat regenerative system of the utilization of group fume afterheat and environment friendly system passes through the low pressure heat exchange For component to heat the recirculated water flowed through inside the low pressure heat-exchanging component, the recirculated water after heating is divided into three tunnels：All the way to Cold flue gas after heating desulfurization, all the way to pre-add heat primary air and Secondary Air, finally all the way to heating part condensed water；This three Converge the fume afterheat absorber before first flowing through coal unit electric precipitator after the circulating water of road and absorbs flue gas heat, then Low pressure heat-exchanging component is returned to continue to heat up.

2. a kind of coal unit fume afterheat as described in claim 1 utilizes and environment friendly system, which is characterized in that along boiler tail Portion's mainstream smoke moves direction and is disposed with air preheater, the fume afterheat absorber, electric precipitator, air-introduced machine, wet process Desulfurizer and flue gas reheater；Flue gas flue collector before the air preheater is additionally provided with by-pass flue, portion High-temperature flue gas is divided to flow through the by-pass flue, the high pressure heat exchange component and low pressure heat-exchanging component are set in turn in branch's cigarette Road；The ratio for wherein flowing through the high-temperature flue gas of the air preheater is greater than the ratio for flowing through the high-temperature flue gas of the by-pass flue Example.

3. a kind of coal unit fume afterheat as claimed in claim 2 utilizes and environment friendly system, which is characterized in that along flue gas stream Flow controllable register, SO are also disposed with inside to the by-pass flue₃Sorbent injection device and shutoff door；Wherein, institute State high pressure heat exchange component, the low pressure heat-exchanging component is sequentially arranged in the SO₃Sorbent injection device and the shutoff door it Between.

4. a kind of coal unit fume afterheat as claimed in claim 2 utilizes and environment friendly system, which is characterized in that the high pressure Heat-exchanging component has heat exchanging pipe, in final stage hyperbaric heating after the partial high pressure water supply heating after flowing through the heat exchanging pipe heat exchange Pipeline after device imports main line, carries out heating generation steam to be transported to boiler.

5. a kind of coal unit fume afterheat as claimed in claim 1 or 2 utilizes and environment friendly system, which is characterized in that described Low pressure heat-exchanging component has heat exchanging pipe, flow through the low pressure recycle water of the heat exchanging pipe of the low pressure heat-exchanging component with it is excessively high The medium temperature flue gas of heat-exchanging component heat exchange is pressed to carry out heat exchange；And the three road circulating water lines flowed out by the low pressure heat-exchanging component It is provided with valve, for adjusting respective line water to meet different operating conditions to the needs of heat.

6. a kind of coal unit fume afterheat as claimed in claim 2 utilizes and environment friendly system, which is characterized in that along flue gas master Flow direction flows through the high-temperature flue gas of the air preheater and has been subjected to recirculated water preheating First air and Secondary Air progress Heat exchange.

7. a kind of coal unit fume afterheat as claimed in claim 2 utilizes and environment friendly system, which is characterized in that from the sky Air preheater exports the low-temperature flue gas of outflow and flows through more than the flue gas after converging from the low-temperature flue gas that the by-pass flue flows out Heat absorber carries out heat exchange with the three road recirculated waters converged after heat exchange inside the fume afterheat absorber, and recycles Water circulates in pipeline under the action of water circulating pump.

8. a kind of coal unit fume afterheat as claimed in claim 2 utilizes and environment friendly system, which is characterized in that through the cigarette The flue gas of gas residual heat absorber outflow is dusted through the electric precipitator, and is transported under the action of the air-introduced machine described Wet desulphurization device carries out desulfurization and cleaning dust, the cold flue gas for flowing through the wet desulphurization device enter the flue gas and add again Hot device heating, finally by smoke stack emission into atmosphere.

9. a kind of coal unit fume afterheat as claimed in claim 3 utilizes and environment friendly system, which is characterized in that along flue gas stream Dynamic direction, the by-pass flue include the first pipeline section and the second pipeline section, and the circulation area of first pipeline section is greater than described second The circulation area of pipeline section, the SO₃Sorbent injection device and high pressure heat exchange component are all set in first pipeline section, described low Pressure heat-exchanging component is set to second pipeline section.