CN110986031B - System for avoiding water vapor condensation in gas boiler flue gas recirculation pipeline - Google Patents

System for avoiding water vapor condensation in gas boiler flue gas recirculation pipeline Download PDF

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Publication number
CN110986031B
CN110986031B CN201911235804.9A CN201911235804A CN110986031B CN 110986031 B CN110986031 B CN 110986031B CN 201911235804 A CN201911235804 A CN 201911235804A CN 110986031 B CN110986031 B CN 110986031B
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flue gas
air
water
inlet
outlet
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CN110986031A (en
Inventor
杜勇博
张井坤
胡广涛
王长安
刘艳华
车得福
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SUUN POWER Co.,Ltd.
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Xian Jiaotong University
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23CMETHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C9/00Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/06Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for completing combustion
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22STEAM GENERATION
    • F22DPREHEATING, 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
    • F22D1/00Feed-water heaters, i.e. economisers or like preheaters
    • F22D1/36Water and air preheating systems
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B15/00Sorption machines, plants or systems, operating continuously, e.g. absorption type
    • F25B15/02Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas
    • F25B15/06Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas the refrigerant being water vapour evaporated from a salt solution, e.g. lithium bromide
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00Heat pumps
    • F25B30/04Heat pumps of the sorption type
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00Adapting or protecting infrastructure or their operation
    • Y02A30/27Relating to heating, ventilation or air conditioning [HVAC] technologies
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/62Absorption based systems

Abstract

The invention discloses a system for avoiding water vapor condensation in a gas boiler flue gas recirculation pipeline, and relates to the technical field of safe operation of gas boilers. The system comprises an air preheating system, a backwater heating system, a flue gas recirculation system and an absorption heat pump flue gas waste heat utilization system. When the system operates, the temperature of the flue gas at the tail part of the boiler is reduced to about 30 ℃ through the lithium bromide absorption heat pump, and meanwhile, the backwater and part of combustion air are preheated. The preheated air and the recirculated flue gas are mixed and then sent into a hearth for combustion supporting, the temperature of the mixed gas before entering the hearth is higher than the dew point of water vapor, and condensed water cannot be generated. The invention effectively solves the problem that the pipeline and the fan are damaged due to the condensation of water vapor in the flue gas recirculation pipeline (especially in winter in the north) on the premise of ensuring that the waste heat of the flue gas is fully utilized. In addition, the water vapor in the flue gas can be recycled, and the economical efficiency and the safety of the boiler operation are improved.

Description

System for avoiding water vapor condensation in gas boiler flue gas recirculation pipeline
Technical Field
The invention belongs to the field of gas boilers, and particularly relates to a system for preventing water vapor in a gas boiler flue gas recirculation pipeline from condensing.
Background
Along with the development of natural gas mining technology and the popularization of the policy of changing coal into gas in recent years, the proportion of natural gas in primary energy consumption is increased year by year. However, the exhaust gas temperature of the existing natural gas boiler is generally higher, so that a large amount of sensible heat and latent heat in the exhaust gas are not recycled, and serious energy waste is caused. In addition to controlling NO in the combustion of natural gasxAnd a flue gas recirculation system is additionally arranged on a plurality of gas-fired boilers. In practice, the temperature of the recirculated flue gas, which is generally drawn off, is lowered after mixing with cold air, condensation of water vapour occurs in the recirculation line (especially in the northern winter), impairing the recirculationA pipeline used by circulating flue gas and a fan.
Therefore, the improvement of the tail system of the gas boiler to improve the utilization rate of the waste heat of the flue gas and avoid the condensation of the water vapor in the recirculated flue gas pipeline has important significance.
Disclosure of Invention
The invention aims to provide a system for avoiding water vapor condensation in a gas recirculation pipeline of a gas boiler, which utilizes a lithium bromide absorption heat pump to carry out cascade utilization on high-temperature flue gas waste heat to preheat partial combustion air and heat supply network backwater and simultaneously recover the water vapor in the flue gas. The preheated air and the recirculated flue gas are uniformly mixed and then are sent into a hearth for combustion supporting. The invention not only realizes the recovery of the waste heat of the flue gas, but also effectively solves the problem that the flue gas recirculation pipeline and the fan are damaged by the condensation of water vapor after the recirculation flue gas is mixed with cold air, and improves the economical efficiency and the safety of the system operation.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a system for avoiding water vapor condensation in a gas boiler flue gas recirculation pipeline comprises an air preheating system, a backwater heating system, a flue gas recirculation system and an absorption heat pump flue gas waste heat utilization system; the air preheating system comprises an induced draft fan, a flue gas-air heat exchanger, an absorber and a condenser; the backwater heating system comprises a heat supply network backwater, an absorber and a condenser; the flue gas recirculation system comprises a generator, a flue gas-air heat exchanger, an evaporator and a flue gas-air mixer; the absorption heat pump flue gas waste heat utilization system comprises a generator, an absorber, an evaporator, a condenser and a vapor compression pump;
cold air is connected with an air inlet of the flue gas-air heat exchanger through an induced draft fan, an air outlet of the flue gas-air heat exchanger is connected with an air inlet of an absorber, and an air outlet of the absorber is connected with an air inlet of a condenser; the outlet of the heat supply network water return pipeline is connected with the water return inlet of the absorber, the water return outlet of the absorber is connected with the water return inlet of the condenser, and the water return outlet of the condenser is connected with the water return inlet of the gas-fired boiler; the boiler tail flue is connected with a generator flue gas inlet, a generator flue gas outlet is connected with a flue gas inlet of a flue gas-air heat exchanger, a flue gas outlet of the flue gas-air heat exchanger is connected with a flue gas inlet of an evaporator, a flue gas outlet of the evaporator is connected with a flue gas inlet of a flue gas-air mixer, and a mixed gas outlet of the flue gas-air mixer is connected with a hearth inlet; the generator superheated steam outlet is connected with the steam compression pump inlet, the steam compression pump outlet is connected with the condenser superheated steam inlet, the condenser heat pump working medium water outlet is connected with the evaporator heat pump working medium water inlet, the evaporator refrigerant steam outlet is connected with the absorber refrigerant steam inlet, and the absorber lithium bromide dilute solution outlet is connected with the generator lithium bromide dilute solution inlet; and a generator lithium bromide concentrated solution outlet is connected with an absorber lithium bromide concentrated solution inlet for solution exchange.
The invention has the further improvement that the absorption heat pump flue gas waste heat utilization system also comprises an expansion valve, a condenser heat pump working medium water outlet is connected with an expansion valve inlet, and an expansion valve outlet is connected with an evaporator heat pump working medium water inlet.
The further improvement of the invention is that the dilute lithium bromide solution in the generator is heated and concentrated by the flue gas, and the dilute solution is changed into a concentrated solution and enters the absorber; the concentrated solution in the absorber releases absorption heat to heat backwater, and the concentrated solution is changed into a dilute solution and enters the generator; superheated steam generated in the generator is boosted by a steam compression pump and then enters a condenser, exchanges heat with return water in the condenser, is cooled to become heat pump working medium water, is reduced in pressure by an expansion valve and then enters an evaporator; then the gas is heated in the evaporator and changed into refrigerant steam, and the refrigerant steam enters the absorber to dilute the lithium bromide concentrated solution and release heat, thereby forming a cycle.
The invention has the further improvement that the tail smoke firstly enters the generator, and the smoke temperature is reduced after the lithium bromide dilute solution is heated; then the flue gas enters a flue gas-air heat exchanger to heat part of combustion air, and the temperature of the flue gas is further reduced; finally, the flue gas enters an evaporator and is cooled by the working medium water of the heat pump, the temperature of the flue gas is reduced to 30 ℃, and most of water vapor in the flue gas is condensed; after deep waste heat recovery, part of the flue gas enters a flue gas-air mixer to be uniformly mixed with preheated air and then is sent into a hearth for combustion supporting, and the rest of the flue gas is discharged into the atmosphere through a chimney.
The invention has the further improvement that the induced draft fan conveys part of combustion-supporting air to enter the flue gas-air heat exchanger to be heated by the flue gas; then enters the absorber to be further heated by the absorption heat released by the lithium bromide concentrated solution, and finally enters the condenser to be heated for the third time by the superheated steam generated by the generator.
The invention has the further improvement that the return water of the heat supply network firstly enters an absorber to be heated for the first time by the absorption heat released by the lithium bromide concentrated solution, and then enters a condenser to be heated for the second time by superheated steam and then enters a boiler.
The invention is further improved in that the temperature of the mixed gas at the outlet of the flue gas-air mixer is far greater than the dew point of water vapor, and no condensed water is generated before the mixed gas enters the hearth.
The invention has the further improvement that the invention also comprises a condensate pump, a water purifier and a water collector arranged on the evaporator, wherein the condensate water generated by cooling the flue gas in the evaporator enters the water collector through a condensate pipe, then sequentially passes through the condensate pump and the water purifier, and is softened for supplying water for the boiler heat supply network.
The invention has at least the following beneficial technical effects:
the invention provides a system for preventing water vapor in a gas boiler flue gas recirculation pipeline from condensing. When the system works, tail flue gas passes through the generator and the heat exchanger in sequence, finally enters the evaporator, then partially participates in flue gas recirculation, and the other part is discharged into the atmosphere. In the process, after the flue gas is discharged by a boiler, the cascade utilization of waste heat is realized, sensible heat and latent heat can be recycled, the temperature of the flue gas at 120 ℃ is reduced to 30 ℃ after the waste heat is recycled by a lithium bromide absorption heat pump, and simultaneously, the air is preheated and the heat supply network returns water. Heating the lithium bromide dilute solution in the generator by the flue gas, and utilizing the heat for the first time; then the cold air is heated by the heat exchanger, and the heat of the flue gas is further utilized; the temperature of the preheated air and the recirculated flue gas is far higher than the dew point of water vapor after mixing, and no condensed water is generated by the recirculated pipeline and the fan. The lithium bromide dilute solution in the generator is heated and concentrated by the flue gas, and the dilute solution is changed into a concentrated solution and enters the absorber. The whole system not only realizes deep recovery of flue gas waste heat, but also effectively solves the problem that the pipeline and the fan are damaged by condensed water generated when the flue gas is mixed with cold air in the flue gas recirculation process, and has important significance for safe and economic operation of the gas boiler.
The cold air passes through the heat exchanger, absorber and condenser in sequence, and then enters the flue gas mixer. The cold air can realize three-level preheating when the system operates, and the air is effectively preheated. Cold air (taking the lowest air temperature in certain places in winter) is preheated for the first time by absorbing the heat of the flue gas through a flue gas-air heat exchanger; the preheated air after passing through the flue gas-air heat exchanger enters an absorber to absorb heat for further preheating; the flue gas from the absorber enters a condenser to be preheated by superheated steam for three times, and then enters a flue gas mixer to be mixed with the recirculated flue gas. The concentrated solution in the absorber releases heat of absorption to heat air, and the concentrated solution becomes a dilute solution and enters the generator.
The return water of the heat supply network sequentially enters an absorber and a condenser for preheating, and then enters a gas boiler for further heating. In the whole heat supply network backwater system, the heat supply network backwater realizes secondary preheating, and the backwater temperature is effectively improved. Primary preheating: the backwater of the heat supply network enters an absorber to absorb the absorption heat released by the lithium bromide concentrated solution and is heated; secondary heating: the return water of the heat supply network after the outlet of the absorber enters a condenser and is further heated by superheated steam.
And the water collector is arranged on the evaporator, collects a large amount of condensed water in the flue gas, and is softened to be used as backwater water supplement of a heat supply network of the boiler room.
Drawings
Fig. 1 is a schematic diagram of the structure of the present invention.
Description of reference numerals:
the system comprises a generator 1, an absorber 2, an evaporator 3, a condenser 4, a flue gas-air mixer 5, a flue gas-air heat exchanger 6, a draught fan 7, a steam compression pump 8, a heat supply network backwater 9, a water collector 10, a condensate pump 11, a water purifier 12 and an expansion valve 13.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, the system for preventing water vapor from condensing in a flue gas recirculation pipeline of a gas boiler provided by the invention comprises an air preheating system, a backwater heating system, a flue gas recirculation system and an absorption heat pump flue gas waste heat utilization system.
Wherein, the cold air preheating system comprises an induced draft fan 7, a flue gas-air heat exchanger 6, an absorber 2 and a condenser 4. The return water heating system comprises a heat supply network return water 9, an absorber 2 and a condenser 4. The flue gas recirculation system comprises a generator 1, a flue gas-air heat exchanger 6, an evaporator 3 and a flue gas-air mixer 5. The absorption heat pump waste heat utilization system comprises a generator 1, an absorber 2, an evaporator 3, a condenser 4, a vapor compression pump 8 and an expansion valve 13.
The cold air is connected with an air inlet of a flue gas-air heat exchanger 6 through an induced draft fan 7, an air outlet of the flue gas-air heat exchanger 6 is connected with an air inlet of an absorber 2, and an air outlet of the absorber 2 is connected with an air inlet of a condenser 4. The return water 9 of the heating network is connected with the return water inlet of the absorber 2, the return water outlet of the absorber 2 is connected with the return water inlet of the condenser 4, and the return water outlet of the condenser 4 is connected with the return water inlet of the gas boiler. The boiler tail flue gas flue is connected with a flue gas inlet of a generator 1, a flue gas outlet of the generator 1 is connected with a flue gas inlet of a flue gas air-heat exchanger 6, a flue gas outlet of the flue gas-air heat exchanger 6 is connected with a flue gas inlet of an evaporator 3, a flue gas extraction outlet of the evaporator 3 is connected with an inlet of a flue gas-air mixer 5, and an outlet of the flue gas-air mixer 5 is connected with an inlet of a hearth. The superheated steam outlet of the generator 1 is connected with the inlet of a steam compression pump 8, the outlet of the steam compression pump is connected with a condenser 4 to enter the superheated steam inlet, the heat pump working medium water outlet of the condenser 4 is connected with the inlet of an expansion valve 13, the outlet of the expansion valve 13 is connected with the heat pump working medium water inlet of the evaporator 3, the refrigerant steam outlet of the evaporator 3 is connected with the refrigerant steam inlet of an absorber 2, and the lithium bromide dilute solution outlet of the absorber 2 is connected with the lithium bromide dilute solution inlet of the generator 1. In addition, the outlet of the generator 1 lithium bromide concentrated solution is connected with the outlet of the absorber 2 lithium bromide concentrated solution for solution exchange.
When the system is operated, flue gas with the temperature of about 120 ℃ at the tail of the boiler enters the generator 1, the dilute lithium bromide solution in the generator 1 is heated to about 108 ℃, the dilute solution is changed into a concentrated solution, and the temperature of the flue gas is reduced to about 90 ℃; then enters a heat exchanger 6 to preheat air, and the temperature is further reduced to about 81 ℃; the flue gas from the flue gas-air heat exchanger 6 enters an evaporator 3, the heat pump working medium water at 27 ℃ is heated to become refrigerant steam at 27 ℃, and the temperature of the flue gas is reduced to 30 ℃; then part of the flue gas enters a flue gas mixer 5 to be mixed with the preheated air, and the rest of the flue gas is discharged into the atmosphere through a chimney.
Cold air of-12.7 ℃ in the system (taking the lowest air temperature in winter of a certain place) is heated to 30 ℃ by flue gas for the first time through a heat exchanger 6; then the air enters an absorber 2, and the air is further heated to about 47 ℃ by the heat released by the lithium bromide concentrated solution at about 66 ℃; the air coming out of the absorber 2 enters the condenser 4 to exchange heat with superheated steam at about 104 ℃, and is finally preheated to 60 ℃. The cold air realizes three-level preheating when the air preheating system operates.
The system of the invention has the advantages that the return water 9 of the heat supply network is preheated for the second stage, and the return water is effectively preheated. The return water 9 of the heat supply network with the temperature of 50 ℃ is preheated to about 56 ℃ for the first time by absorbing the absorption heat released by the lithium bromide concentrated solution by the absorber 2; the backwater after passing through the absorber 2 enters the condenser 4 for further preheating to 61 ℃.
When the system is in operation, the lithium bromide dilute solution in the generator 1 is heated and concentrated to about 108 ℃ by the flue gas, and the dilute solution is changed into a concentrated solution and enters the absorber 2; the concentrated solution in the absorber 2 releases absorption heat to heat backwater, the temperature is reduced to about 60 ℃, and the concentrated solution is changed into a dilute solution and enters the generator 1; the 104 ℃ superheated steam generated in the generator 1 enters the condenser 4 after being boosted by the steam compression pump 8, exchanges heat with return water in the condenser 4, is cooled to be 72 ℃ heat pump working medium water, is reduced in pressure by the expansion valve 13 to be 27 ℃ and enters the evaporator 3; then the refrigerant steam which is heated by the flue gas in the evaporator 3 and becomes 27 ℃ enters the absorber 2 to dilute the lithium bromide concentrated solution and release heat, thereby forming a cycle.
The water collector 10 arranged on the evaporator 3 collects the generated condensed water, the smoke is reduced from 81 ℃ to 30 ℃, the condensed water rate reaches 79.7 percent, the condensed water amount of each cubic meter of smoke reaches 1.778kg, and then the condensed water sequentially passes through the condensed water pump 11 and the water purifier 12 and is softened to be used as the water supply of the boiler.
1Nm39.819Nm of air required for theoretical combustion of natural gas3The coefficient of excess air in combustion is taken as 1.2, and the actual generated smoke is about 12.920Nm3Therein bags2.134Nm of water vapor3At this time, the water vapor content is about 16.5%, and the dew point of the high-temperature flue gas is about 55.5 ℃. When the temperature is reduced to 30 ℃ after waste heat recovery, the condensation water rate is about 79.7 percent, and the water content in the flue gas is about 3.86 percent. 20% of the extracted flue gas and 30% of air required by preheating combustion enter a flue gas mixer to be uniformly mixed and then enter a combustor to participate in combustion. The water vapor content after mixing is changed to 2.06%, the water vapor dew point is 17.5 ℃, the gas temperature after mixing is about 36.4 ℃, the temperature after mixing is far higher than the dew point temperature, condensation can not occur in a pipeline before entering a boiler, and the problem of damage to the pipeline and a fan caused by the generation of the flue gas recirculation and cold air mixed condensate water is effectively solved.
It should be understood that this example is only for illustrating the present invention and is not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teachings of the present invention, however, these equivalents also fall within the scope of the present invention as defined by the appended claims.

Claims (8)

1. A system for avoiding water vapor condensation in a gas boiler flue gas recirculation pipeline is characterized by comprising an air preheating system, a backwater heating system, a flue gas recirculation system and an absorption heat pump flue gas waste heat utilization system; wherein the content of the first and second substances,
the air preheating system comprises an induced draft fan (7), a flue gas-air heat exchanger (6), an absorber (2) and a condenser (4); the return water heating system comprises a heat supply network return water (9), an absorber (2) and a condenser (4); the flue gas recirculation system comprises a generator (1), a flue gas-air heat exchanger (6), an evaporator (3) and a flue gas-air mixer (5); the absorption heat pump flue gas waste heat utilization system comprises a generator (1), an absorber (2), an evaporator (3), a condenser (4) and a vapor compression pump (8);
cold air is connected with an air inlet of a flue gas-air heat exchanger (6) through an induced draft fan (7), an air outlet of the flue gas-air heat exchanger (6) is connected with an air inlet of an absorber (2), and an air outlet of the absorber (2) is connected with an air inlet of a condenser (4); the pipeline outlet of the heat supply network backwater (9) is connected with the backwater inlet of the absorber (2), the backwater outlet of the absorber (2) is connected with the backwater inlet of the condenser (4), and the backwater outlet of the condenser (4) is connected with the backwater inlet of the gas boiler; the tail flue of the boiler is connected with a flue gas inlet of a generator (1), a flue gas outlet of the generator (1) is connected with a flue gas inlet of a flue gas-air heat exchanger (6), a flue gas outlet of the flue gas-air heat exchanger (6) is connected with a flue gas inlet of an evaporator (3), a flue gas outlet of the evaporator (3) is connected with a flue gas inlet of a flue gas-air mixer (5), and a mixed gas outlet of the flue gas-air mixer (5) is connected with a hearth inlet; an overheated steam outlet of the generator (1) is connected with an inlet of a steam compression pump (8), an outlet of the steam compression pump (8) is connected with an overheated steam inlet of a condenser (4), a heat pump working medium water outlet of the condenser (4) is connected with a heat pump working medium water inlet of the evaporator (3), a refrigerant steam outlet of the evaporator (3) is connected with a refrigerant steam inlet of the absorber (2), and a lithium bromide dilute solution outlet of the absorber (2) is connected with a lithium bromide dilute solution inlet of the generator (1); the outlet of the generator (1) lithium bromide concentrated solution is connected with the inlet of the absorber (2) lithium bromide concentrated solution for solution exchange.
2. The system for avoiding water vapor condensation in the flue gas recirculation pipeline of the gas-fired boiler according to claim 1, wherein the system for utilizing the waste heat of the flue gas of the absorption heat pump further comprises an expansion valve (13), the outlet of the heat pump working medium water of the condenser (4) is connected with the inlet of the expansion valve (13), and the outlet of the expansion valve (13) is connected with the inlet of the heat pump working medium water of the evaporator (3).
3. A system for avoiding condensation of water vapor in a gas boiler flue gas recirculation line according to claim 2, characterized in that the dilute lithium bromide solution in the generator (1) is heated and concentrated by the flue gas, and the dilute solution becomes a concentrated solution to enter the absorber (2); the concentrated solution in the absorber (2) releases absorption heat to heat backwater, and the concentrated solution becomes a dilute solution and enters the generator (1); superheated steam generated in the generator (1) is boosted by a steam compression pump (8) and then enters a condenser (4), exchanges heat with return water in the condenser (4), is cooled to become heat pump working medium water, and then enters an evaporator (3) after the heat pump working medium water is depressurized by an expansion valve (13); then the gas is heated in the evaporator (3) and changed into refrigerant steam, and the refrigerant steam enters the absorber (2) to dilute the lithium bromide concentrated solution and release heat, thereby forming a cycle.
4. The system for avoiding water vapor condensation in the gas boiler flue gas recirculation pipeline according to claim 1, characterized in that tail flue gas enters the generator (1) first, and the temperature of flue gas is reduced after heating the lithium bromide dilute solution; then the flue gas enters a flue gas-air heat exchanger (6) to heat part combustion air, and the temperature of the flue gas is further reduced; finally, the flue gas enters an evaporator (3) and is cooled by the working medium water of the heat pump, the temperature of the flue gas is reduced to 30 ℃, and most of water vapor in the flue gas is condensed; after deep waste heat recovery, part of the flue gas enters a flue gas-air mixer (5) to be uniformly mixed with preheated air and then is sent into a hearth for combustion supporting, and the rest of the flue gas is discharged into the atmosphere through a chimney.
5. The system for avoiding the condensation of water vapor in the gas boiler flue gas recirculation pipeline according to claim 1, characterized in that the induced draft fan (7) delivers part of the combustion air to enter the flue gas-air heat exchanger (6) first and to be heated by the flue gas; then enters an absorber (2) to be further heated by the absorption heat released by the lithium bromide concentrated solution, and finally enters a condenser (4) to be heated for the third time by the superheated steam generated by the generator (1).
6. The system for avoiding water vapor condensation in the flue gas recirculation pipeline of the gas boiler as recited in claim 1, characterized in that the return water (9) of the heat supply network firstly enters the absorber (2) to be heated by the absorption heat released by the concentrated lithium bromide solution for the first time, and then enters the condenser (4) to be heated by the superheated steam for the second time and then enters the boiler.
7. A system for avoiding condensation of water vapour in the flue gas recirculation ducts of gas boilers, according to claim 1, characterized in that the temperature of the mixed gas at the outlet of the flue gas-air mixer (5) is much higher than the dew point of the water vapour, so that no condensation water is produced before entering the furnace.
8. The system for avoiding the condensation of the water vapor in the flue gas recirculation pipeline of the gas boiler as claimed in claim 1, further comprising a condensate pump (11), a water purifier (12) and a water collector (10) installed on the evaporator (3), wherein the condensate water generated by cooling the flue gas in the evaporator (3) enters the water collector (10) through the condensate pipe, then sequentially passes through the condensate pump (11) and the water purifier (12), and is softened for supplying water for the boiler heat supply network.
CN201911235804.9A 2019-12-05 2019-12-05 System for avoiding water vapor condensation in gas boiler flue gas recirculation pipeline Active CN110986031B (en)

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CN110986031B true CN110986031B (en) 2021-01-19

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