CN115200005A - Flue gas waste heat utilization system based on boiler system self - Google Patents
Flue gas waste heat utilization system based on boiler system self Download PDFInfo
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- CN115200005A CN115200005A CN202210549371.XA CN202210549371A CN115200005A CN 115200005 A CN115200005 A CN 115200005A CN 202210549371 A CN202210549371 A CN 202210549371A CN 115200005 A CN115200005 A CN 115200005A
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- 239000003546 flue gas Substances 0.000 title claims abstract description 112
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 111
- 239000002918 waste heat Substances 0.000 title claims abstract description 54
- 239000003245 coal Substances 0.000 claims abstract description 39
- 238000010438 heat treatment Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 61
- 239000000843 powder Substances 0.000 claims description 35
- 239000000203 mixture Substances 0.000 claims description 29
- 239000000428 dust Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims 1
- 239000007789 gas Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 12
- 239000000779 smoke Substances 0.000 description 10
- 238000002485 combustion reaction Methods 0.000 description 8
- 238000011084 recovery Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 239000002184 metal Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 2
- 239000013589 supplement Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D1/00—Feed-water heaters, i.e. economisers or like preheaters
- F22D1/16—Feed-water heaters, i.e. economisers or like preheaters with water tubes arranged otherwise than in the boiler furnace, fire tubes, or flue ways
- F22D1/18—Feed-water heaters, i.e. economisers or like preheaters with water tubes arranged otherwise than in the boiler furnace, fire tubes, or flue ways and heated indirectly
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
- F23J15/022—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material for removing solid particulate material from the gasflow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L15/00—Heating of air supplied for combustion
- F23L15/04—Arrangements of recuperators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28B—STEAM OR VAPOUR CONDENSERS
- F28B9/00—Auxiliary systems, arrangements, or devices
- F28B9/08—Auxiliary systems, arrangements, or devices for collecting and removing condensate
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Abstract
The invention belongs to the technical field of boilers, and particularly relates to a flue gas waste heat utilization system based on a boiler system. The technical scheme is as follows: a flue gas waste heat utilization system based on a boiler system comprises a boiler main body, wherein the tail part of the boiler is connected with an inlet flue, the inlet flue is connected with an air preheater, the other end of the air preheater is connected with an outlet flue, the flue gas waste heat utilization system also comprises a primary air duct and a secondary air duct, the primary air duct and the secondary air duct both pass through the air preheater, the primary air duct is connected to a coal mill, the outlet end of the coal mill is connected with the boiler main body through a pipeline, and the secondary air duct is connected to the boiler main body; and a bypass heating system is connected between the inlet flue and the outlet flue, and is connected to a pipeline between the coal mill and the boiler main body. The invention provides a flue gas waste heat utilization system which can improve the grade of energy utilization by absorbing flue gas waste heat through a boiler system.
Description
Technical Field
The invention belongs to the technical field of boilers, and particularly relates to a flue gas waste heat utilization system based on a boiler system.
Background
The exhaust gas temperature of a large-scale power station boiler is generally controlled to be about 120 ℃, and is difficult to further reduce due to various factors. With the drive of national policies on energy conservation and emission reduction, the utilization technology of the waste heat of the flue gas is endless. The flue gas waste heat utilization system can be summarized into three forms: 1) Flue gas coolers (low temperature economizers); 2) A cold air heater and a flue gas cooler; 3) Cold air heater + air preheater bypass system.
1) FIG. 2 is a system schematic diagram of a flue gas cooler (low-temperature economizer) with a heating surface arranged in a flue from an outlet of an air preheater to an inlet of a dust remover to absorb the waste heat of the flue gas at the tail of a boiler. The absorbed part of heat is used for exhausting steam of a low-pressure condensate system of the steam turbine, and the exhausted steam continues to enter the downstream of the steam turbine to do work, so that the aim of improving the efficiency of the unit is fulfilled.
2) Fig. 3 is a schematic diagram of a system of a cold air heater and a flue gas cooler, and the system consists of two systems of the cold air heater and the flue gas cooler. The cold air heater raises the temperature of the inlet cold air of the air preheater, and the temperature of the exhaust gas at the outlet of the air preheater is correspondingly raised. The flue gas cooler is arranged in a flue between an outlet of the air preheater and the smoke temperature reduction section of the cold air heater, and the waste heat of the part of flue gas with the temperature raised is utilized. The cold air heater improves the grade of tail flue gas waste heat, and compared with a single flue gas cooler system, the unit efficiency improvement range is higher.
3) FIG. 4 is a system schematic of the chilled air heater + air preheater bypass system. This system comprises cold air heater and air heater bypass system two parts, and the effect of cold air heater promotes air heater entry cold wind temperature, guarantees simultaneously that air heater outlet temperature is unchangeable, has correspondingly promoted cold junction metal wall temperature, prevents air heater's cold junction corruption and the problem of jam. The air preheater flue gas bypass consists of two-stage high-pressure and low-pressure flue gas coolers arranged in an air preheater bypass flue, and the high-pressure flue gas cooler utilizes the absorbed flue gas waste heat to heat part of high-pressure feed water so as to exhaust steam extracted by a high-pressure cylinder of the steam extruder; the low-pressure flue gas cooler utilizes the absorbed flue gas waste heat to heat part low-pressure condensed water, and then the steam is extracted from the low-pressure cylinder of the displacement steam turbine. Because the bypass smoke temperature is higher, the waste heat grade is higher, and the high-pressure cylinder exhaust steam is extruded, the utilization mode of the waste heat of the smoke of the bypass smoke is better than that of the waste heat of the smoke of the high-pressure cylinder exhaust steam in the aspect of improving the efficiency of the unit.
From the above analysis, it can be known that the three flue gas waste heat utilization systems have different energy saving effects although the system configurations are different, but have a common point: the waste heat of the flue gas acts on a steam turbine heat recovery system for exhausting steam of the steam turbine, and the grade of the energy utilization is relatively low.
The large power station boiler adopts a medium-speed mill cold primary air pulverizing system. Hot primary air at the outlet of the air preheater enters a coal mill to dry coal powder, and an air-powder mixture is formed and enters a boiler from a coal powder pipeline at the outlet of the coal mill to be combusted. In recent years, the generalized heat recovery theory is rapidly developed, and a technology of heating primary air powder at an outlet of a coal mill by using steam extracted by a steam turbine as a heat source appears. The technology of directly heating primary air powder by adopting steam extraction of a steam turbine and the technology of indirectly heating the primary air powder by a heat-conducting medium are adopted. But the heat sources are all regenerated by a steam engine.
The three flue gas waste heat utilization modes and the primary air-powder heating technology have the coupling of a boiler and a steam turbine, the operation control is complex, and the unit efficiency improvement range is limited.
Disclosure of Invention
In order to solve the above problems in the prior art, an object of the present invention is to provide a flue gas waste heat utilization system that absorbs flue gas waste heat by a boiler system itself to improve the quality of energy utilization.
The technical scheme adopted by the invention is as follows:
a flue gas waste heat utilization system based on a boiler system comprises a boiler main body, wherein the tail part of the boiler is connected with an inlet flue, the inlet flue is connected with an air preheater, the other end of the air preheater is connected with an outlet flue, the flue gas waste heat utilization system also comprises a primary air duct and a secondary air duct, the primary air duct and the secondary air duct both pass through the air preheater, the primary air duct is connected to a coal mill, the outlet end of the coal mill is connected with the boiler main body through a pipeline, and the secondary air duct is connected to the boiler main body; and a bypass heating system is connected between the inlet flue and the outlet flue, and is connected to a pipeline between the coal mill and the boiler main body.
In the invention, the flue gas waste heat is recycled to the air-powder mixture at the outlet of the coal mill, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the boiler efficiency, having higher heat grade and remarkable energy-saving effect. After the temperature of the wind-powder mixture is increased, the ignition heat is reduced, and the stable combustion capability is improved; has better effect on low volatile coal. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect on low volatile coal is better.
As a preferred scheme of the invention, the bypass heating system comprises a bypass flue, the bypass flue is connected between an inlet flue and an outlet flue, the bypass flue is connected with a flue gas heat-conducting medium heat exchanger, a heat-conducting medium air-powder mixture heater is connected on a pipeline between the coal mill and the boiler main body, and a heat-conducting medium circulating pipeline is connected between the flue gas heat-conducting medium heat exchanger and the heat-conducting medium air-powder mixture heater. The heat-conducting medium absorbs the heat of the flue gas in the flue gas heat-conducting medium heat exchanger, the temperature of the heat-conducting medium rises, the temperature of the flue gas falls, and the low-temperature flue gas returns to the outlet flue of the air preheater. The heat-conducting medium heats the air-powder mixture at the outlet of the coal mill in the heat-conducting medium air-powder mixture heat exchanger, the temperature of the heat-conducting medium is reduced, and the air-powder mixture is raised.
As a preferable scheme of the invention, the heat-conducting medium circulating pipeline is connected with a regulating oil tank and a pressurizing pump. The pressure pump can adjust the circulation rate of the heat-conducting medium, and the adjusting oil tank can supplement the heat-conducting medium to the adjusting heat-conducting medium circulation pipeline.
According to the preferable scheme of the invention, the outlet flue is also connected with a heat medium water system, the heat medium water system is respectively connected to the primary air duct and the secondary air duct, and the heat medium water system is positioned on one side, away from the air preheater, of the bypass heating system on the outlet flue. The heat medium water system reduces the exhaust gas temperature, improves the inlet air temperature of the conventional air preheater, correspondingly improves the cold end metal wall temperature, and can effectively prevent the cold end from being corroded and blocked. The heat of the heated air is recovered by the boiler system, so that the thermal efficiency of the boiler is further improved.
According to the preferable scheme of the invention, the heat medium water system comprises a flue gas cooler, the flue gas cooler is connected to the outlet flue, a water circulation pipeline is connected to the flue gas cooler, a primary air heater and a secondary air heater are connected to the water circulation pipeline in parallel, the primary air heater is connected to the primary air channel, and the secondary air heater is connected to the secondary air channel. The heat medium water absorbs the heat of the flue gas in the flue gas cooler, the temperature of the heat medium water rises, and the temperature of the flue gas falls. The hot medium water respectively heats the cold primary air and the cold secondary air in the primary air heater and the secondary air heater, the temperature of the hot medium water is reduced, and the temperature of the cold air is increased.
As a preferable scheme of the invention, an organic unit condensate system is also connected in parallel on the water circulating pipeline. The heating medium water system is also communicated and coupled with the unit condensate water system, and when the waste heat recovery capability of the boiler is insufficient due to coal type reasons, environmental reasons, operation load reasons and the like, the adjustment can be carried out through the condensate water system. When the residual heat of the flue gas is surplus, the connecting system can be used for heating condensed water, so that the residual heat of the flue gas can be transferred to a condensed water system; when the ambient temperature is lower or the low load, the cold air can be heated by the connecting system by utilizing the heat of the condensed water, so that the influence of the excessively low exhaust gas temperature on the air preheater and the dust remover is avoided.
As a preferable scheme of the invention, the tail end of the outlet flue is connected with a dust remover. The dust remover can remove dust to the flue gas, guarantees that the flue gas reaches emission standard.
As a preferred scheme of the invention, the primary air duct is connected with a temperature-adjusting air duct, one end of the temperature-adjusting air duct is connected to a section of the primary air duct before entering the air preheater, and the other end of the temperature-adjusting air duct is connected to a section of the primary air duct after extending out of the air preheater. The temperature adjusting air duct adjusts the temperature of primary air entering the coal mill by controlling the proportion of the primary air entering the air preheater.
As a preferable scheme of the invention, the bypass flue is provided with an adjusting baffle. The adjustable flue gas volume that gets into the bypass flue of adjusting the baffle, and then adjust bypass heating system's waste heat utilization quantity.
As a preferred scheme of the invention, the primary air duct is connected with a primary fan, and the secondary air duct is connected with a secondary fan.
The invention has the beneficial effects that:
1. in the invention, the flue gas waste heat is recycled to the air-powder mixture at the outlet of the coal mill, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the boiler efficiency, having higher heat grade and remarkable energy-saving effect.
2. The hot medium water respectively heats cold primary air and cold secondary air in the primary air heater and the secondary air heater, the temperature of the hot medium water is reduced, and the temperature of the cold air is increased. The heat of the heated air is recovered by the boiler system, so that the heat of the flue gas is further recovered and utilized by the boiler, and the thermal efficiency of the boiler is further improved.
3. The heat medium water system reduces the exhaust gas temperature, improves the inlet air temperature of the conventional air preheater, correspondingly improves the cold end metal wall temperature, and can effectively prevent the cold end from being corroded and blocked.
4. After the temperature of the wind-powder mixture is increased, the ignition heat is reduced, and the stable combustion capability is improved; the effect on low volatile coal is better. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect on low volatile coal is better.
5. The heating medium water system is also communicated and coupled with the unit condensate water system, and when the waste heat recovery capability of the boiler is insufficient due to coal type reasons, environmental reasons, operation load reasons and the like, the adjustment can be carried out through the condensate water system. When the residual heat of the flue gas is surplus, the connecting system can be used for heating condensed water, so that the residual heat of the flue gas can be transferred to a condensed water system; when the ambient temperature is lower or the low load, the cold air can be heated by the connecting system by utilizing the heat of the condensed water, so that the influence of the excessively low exhaust gas temperature on the air preheater and the dust remover is avoided.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a system schematic of a flue gas cooler (low temperature economizer);
FIG. 3 is a schematic diagram of a cold air heater + flue gas cooler system;
FIG. 4 is a system schematic of a chilled air heater + air preheater bypass system.
In the figure: 1-a boiler body; 2-an air preheater; 3-flue gas heat-conducting medium heat exchanger; 4-heat-conducting medium air-powder mixture heater; 5-a pressure pump; 6-adjusting an oil tank; 7-valve group; 8-a coal mill; 9-a flue gas cooler; 10-secondary air heater; 11-primary air heater; 12-a unit condensate system; 13-a secondary air fan; 14-a primary air fan; 15-a dust remover; 16-inlet flue; 17-a bypass flue; 18-an outlet flue; 19-secondary air duct; 20-primary air duct; 21-temperature adjusting air duct; 22-heating medium water system; 23-heat transfer medium circulation line; 24-a water circulation line; 25-bypass heating system.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
As shown in fig. 1, the flue gas waste heat utilization system based on the boiler system itself of the present embodiment includes a boiler main body 1, an inlet flue 16 is connected to the tail of the boiler, the inlet flue 16 is connected to an air preheater 2, the other end of the air preheater 2 is connected to an outlet flue 18, and further includes a primary air duct 20 and a secondary air duct 19, the primary air duct and the secondary air duct 19 both pass through the air preheater 2, the primary air duct 20 is connected to a coal pulverizer 8, the outlet end of the coal pulverizer 8 is connected to the boiler main body 1 through a pipeline, and the secondary air duct 19 is connected to the boiler main body 1; a bypass heating system 25 is connected between the inlet flue 16 and the outlet flue 18, and the bypass heating system 25 is connected to a pipeline between the coal mill 8 and the boiler main body 1; the primary air duct 20 is connected with a primary fan 14, and the secondary air duct 19 is connected with a secondary fan 13; the end of the outlet flue 18 is connected with a dust remover 15. The dust remover 15 can remove dust to the flue gas, guarantees that the flue gas reaches emission standard.
In the invention, the flue gas waste heat is recovered to the air-powder mixture at the outlet of the coal mill 8, and the waste heat enters the boiler system, which is equivalent to directly reducing the exhaust gas temperature, effectively improving the boiler efficiency, having higher heat grade and remarkable energy-saving effect. After the temperature of the wind-powder mixture is increased, the ignition heat is reduced, and the stable combustion capability is improved; the effect on low volatile coal is better. The temperature of the air-powder mixture is increased, the ignition is advanced, and the combustion efficiency is improved; the effect on low volatile coal is better.
Specifically, the bypass heating system 25 includes a bypass flue 17, the bypass flue 17 is connected between the inlet flue 16 and the outlet flue 18, the bypass flue 17 is connected with a flue gas heat-conducting medium heat exchanger 3, a heat-conducting medium air-powder mixture heater 4 is connected on a pipeline between the coal mill 8 and the boiler main body 1, and a heat-conducting medium circulation pipeline 23 is connected between the flue gas heat-conducting medium heat exchanger 3 and the heat-conducting medium air-powder mixture heater 4. The heat-conducting medium absorbs the heat of the flue gas in the flue gas heat-conducting medium heat exchanger 3, the temperature of the heat-conducting medium rises, the temperature of the flue gas falls, and the low-temperature flue gas returns to the outlet flue 18 of the air preheater 2. The heat-conducting medium heats the air-powder mixture at the outlet of the coal mill 8 in the heat-conducting medium air-powder mixture heat exchanger, the temperature of the heat-conducting medium is reduced, and the air-powder mixture is raised.
The heat-conducting medium circulating pipeline 23 is connected with an adjusting oil tank 6, a pressure pump 5 and a valve group 7. The booster pump 5 can adjust the circulation rate of the heat-conducting medium, and the adjusting oil tank 6 can supplement the heat-conducting medium to the adjusting heat-conducting medium circulation pipeline 23.
In order to further utilize the heat of the flue gas in the outlet flue 18, a hot water system 22 is further connected to the outlet flue 18, the hot water system 22 is respectively connected to the primary air duct 20 and the secondary air duct 19, and the hot water system 22 is located on the outlet flue 18 on the side, away from the air preheater 2, of the bypass heating system 25. The heating medium water system 22 reduces the exhaust gas temperature, improves the inlet air temperature of the conventional air preheater 2, correspondingly improves the cold end metal wall temperature, and can effectively prevent the cold end from being corroded and blocked. The heat of the heated air is recovered by the boiler system, so that the thermal efficiency of the boiler is further improved.
Specifically, the heat medium water system 22 includes a flue gas cooler 9, the flue gas cooler 9 is connected to the outlet flue 18, a water circulation pipeline 24 is connected to the flue gas cooler 9, a primary air heater 11 and a secondary air heater 10 are connected to the water circulation pipeline 24 in parallel, the primary air heater 11 is connected to the primary air duct 20, and the secondary air heater 10 is connected to the secondary air duct 19. The heat medium water absorbs the heat of the flue gas in the flue gas cooler 9, the temperature of the heat medium water rises, and the temperature of the flue gas falls. The hot medium water respectively heats the cold primary air and the cold secondary air in the primary air heater 11 and the secondary air heater 10, the temperature of the hot medium water is reduced, and the temperature of the cold air is increased.
Furthermore, the water circulation line 24 is connected in parallel with the organic condensate system 12. The heating medium water system 22 is also communicatively coupled to the unit condensate water system 12, and can be adjusted through the condensate water system when the waste heat recovery capability of the boiler is insufficient due to coal type, environmental reasons, operation load reasons, and the like. When the residual heat of the flue gas is surplus, the connecting system can be used for heating condensed water, so that the residual heat of the flue gas can be transferred to a condensed water system; when the ambient temperature is lower or the low load, the cold air can be heated by the connecting system by utilizing the heat of the condensed water, so that the influence of the excessively low exhaust gas temperature on the air preheater 2 and the dust remover 15 is avoided.
In order to adjust the temperature of the hot primary air, the primary air duct 20 is connected with a temperature adjusting air duct 21, one end of the temperature adjusting air duct 21 is connected to a section of the primary air duct 20 before entering the air preheater 2, and the other end of the temperature adjusting air duct 21 is connected to a section of the primary air duct 20 after extending out of the air preheater 2. The temperature adjusting air duct 21 adjusts the temperature of the primary air entering the coal pulverizer 8 by controlling the proportion of the primary air entering the air preheater 2.
Taking a conventional 660MW ultra supercritical boiler as an example, the inlet flue gas temperature of the air preheater 2 of the project is 370 ℃, the exhaust gas temperature is 120 ℃, the hot primary air temperature (after mixing) is 300 ℃, and the hot secondary air temperature is 345 ℃. The difference between the hot end and the hot end of the air preheater 2 is 25 ℃, and the exhaust gas temperature is difficult to further reduce. The calculated value of the boiler efficiency is 94.5 percent, and belongs to the advanced level at the present stage. The temperature of 85-90 ℃ is the temperature range with higher dust removal efficiency of the dust remover 15, so the temperature of 90 ℃ is selected as the inlet smoke temperature of the dust remover 15. Therefore, the heat released by the flue gas from 120 ℃ (outlet flue gas temperature of the air preheater 2) to 90 ℃ (inlet flue gas temperature of the dust remover 15) is the flue gas residual heat. If the existing flue gas waste heat utilization system (comprising a flue gas cooler 9 (low-temperature economizer), a cold air heater + a flue gas cooler 9, a cold air heater + an air preheater 2 bypass system) is adopted to utilize the part of waste heat, the flue gas waste heat is introduced into a steam turbine heat recovery system to exhaust steam of a steam turbine, the grade of the energy utilization is relatively low, and the efficiency improvement effect of the unit is not obvious.
The scheme is characterized in that a bypass flue 17 is arranged, the smoke content of the bypass flue 17 is 13.5%, the temperature of the bypass flue is reduced to 130 ℃ from 370 ℃, and the heat exchange quantity is 23.3MW; the heat conducting medium absorbs the heat of the flue gas in the flue gas heat conducting medium heat exchanger 3, the hot air-powder mixture is added in the heat conducting medium air-powder mixture heater 4, the air-powder mixture is heated from 75 ℃ to 185 ℃, and the absorbed heat is 23.3MW. The smoke amount in the air preheater 2 is only 86.5 percent, the inlet cold air is calculated to be 80 ℃, and the smoke exhaust temperature is calculated to be 130 ℃. The outlet temperatures of the air preheater 2 and the bypass flue 17 are equivalent and are both 130 ℃. The heating medium water type air preheater 2 realizes the first heat exchange between the flue gas and the air, and the cold air is heated from 25 ℃ to 80 ℃ in the primary air heater 11 and the secondary air heater 10. The flue gas is reduced from 130 ℃ to 90 ℃ in the fume cooler.
The heat of the flue gas of the system is completely recovered by a boiler system, namely the temperature of the flue gas is reduced to 90 ℃ from 120 ℃, the reduction amplitude reaches 30 ℃, the gain of the waste heat of the flue gas can be completely counted in the calculation of the thermal efficiency of the boiler, the thermal efficiency of the boiler is improved by about 1.5%, and the efficiency of a unit is greatly improved.
After the temperature of the wind-powder mixture is increased from 75 ℃ to 185 ℃, the ignition heat is reduced, the combustion stabilizing capability is improved, and the combustion efficiency before and after ignition is improved.
Table 1 is a filtration efficiency calculation table:
specifically, in the above embodiment, the outlet temperature of the pulverized coal heater is set to 185 ℃, and if the outlet temperature is influenced by the coal quality and the temperature is lower than 185 ℃, the heat absorbed by the air-powder mixture is reduced. Under the condition of the same waste heat quantity, the heat quantity recovered by the air-powder mixture is reduced, the redundant heat quantity is transferred to the unit condensed water system 12 through the hot water system 22, and part of the flue gas waste heat is recovered through the unit condensed water system 12.
Specially, when the ambient temperature is low or the low-load working condition is adopted, and the smoke temperature at the inlet of the dust remover 15 is lower than 90 ℃, the air is preheated by utilizing the condensate system through the communication of the heat medium water system 22 and the condensate system, so that the influence of the excessively low exhaust gas temperature on the air preheater 2 and the dust remover 15 is avoided. At the moment, the exhaust steam heat of the steam turbine is recovered as the heat input of the boiler, so that the heat energy grade is improved, and the unit efficiency is improved.
Specially, the bypass flue 17 is provided with an adjusting baffle plate, so that the amount of flue gas entering the bypass flue 17 can be adjusted through the adjusting baffle plate, and further, the waste heat utilization amount of the bypass heating system 25 is adjusted.
The invention is not limited to the above alternative embodiments, and any other various forms of products can be obtained by anyone in the light of the present invention, but any changes in shape or structure thereof, which fall within the scope of the present invention as defined in the claims, fall within the scope of the present invention.
Claims (10)
1. A flue gas waste heat utilization system based on a boiler system comprises a boiler main body (1), wherein the tail part of a boiler is connected with an inlet flue (16), the inlet flue (16) is connected with an air preheater (2), the other end of the air preheater (2) is connected with an outlet flue (18), the flue gas waste heat utilization system further comprises a primary air channel (20) and a secondary air channel (19), the primary air channel and the secondary air channel (19) both pass through the air preheater (2), the primary air channel (20) is connected to a coal pulverizer (8), the outlet end of the coal pulverizer (8) is connected with the boiler main body (1) through a pipeline, and the secondary air channel (19) is connected to the boiler main body (1); the method is characterized in that: and a bypass heating system (25) is connected between the inlet flue (16) and the outlet flue (18), and the bypass heating system (25) is connected to a pipeline between the coal mill (8) and the boiler main body (1).
2. The flue gas waste heat utilization system based on the boiler system per se according to claim 1, characterized in that: bypass heating system (25) include bypass flue (17), and bypass flue (17) are connected between inlet flue (16) and outlet flue (18), are connected with flue gas heat-conducting medium heat exchanger (3) on bypass flue (17), are connected with heat-conducting medium wind powder mixture heater (4) on the pipeline between coal pulverizer (8) and boiler main part (1), are connected with heat-conducting medium circulation pipeline (23) between flue gas heat-conducting medium heat exchanger (3) and heat-conducting medium wind powder mixture heater (4).
3. The flue gas waste heat utilization system based on the boiler system per se according to claim 2, characterized in that: the heat-conducting medium circulating pipeline (23) is connected with an adjusting oil tank (6) and a pressure pump (5).
4. The flue gas waste heat utilization system based on the boiler system per se according to claim 1, characterized in that: the outlet flue (18) is also connected with a heat medium water system (22), and the heat medium water system (22) is respectively connected to the primary air duct (20) and the secondary air duct (19).
5. The flue gas waste heat utilization system based on the boiler system per se according to claim 5, characterized in that: the heat medium water system (22) comprises a flue gas cooler (9), the flue gas cooler (9) is connected to an outlet flue (18), a water circulation pipeline (24) is connected to the flue gas cooler (9), a primary air heater (11) and a secondary air heater (10) are connected to the water circulation pipeline (24) in parallel, the primary air heater (11) is connected to a primary air duct (20), and the secondary air heater (10) is connected to a secondary air duct (19).
6. The flue gas waste heat utilization system based on the boiler system per se according to claim 5, characterized in that: the water circulation pipeline (24) is also connected with an organic unit condensed water system (12) in parallel.
7. The flue gas waste heat utilization system based on the boiler system per se according to claim 1, characterized in that: the tail end of the outlet flue (18) is connected with a dust remover (15).
8. The flue gas waste heat utilization system based on the boiler system per se according to claim 1, characterized in that: the primary air duct (20) is connected with a temperature adjusting air duct (21), one end of the temperature adjusting air duct (21) is connected to a section of the primary air duct (20) before entering the air preheater (2), and the other end of the temperature adjusting air duct (21) is connected to a section of the primary air duct (20) after extending out of the air preheater (2).
9. The flue gas waste heat utilization system based on the boiler system per se according to claim 1, characterized in that: and an adjusting baffle is arranged on the bypass flue (17).
10. The flue gas waste heat utilization system based on the boiler system per se according to any one of claims 1 to 9, characterized in that: the primary air duct (20) is connected with a primary fan (14), and the secondary air duct (19) is connected with a secondary fan (13).
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| CN202210549371.XA CN115200005A (en) | 2022-05-20 | 2022-05-20 | Flue gas waste heat utilization system based on boiler system self |
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| CN202210549371.XA CN115200005A (en) | 2022-05-20 | 2022-05-20 | Flue gas waste heat utilization system based on boiler system self |
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