CN117329532A - Multi-cold source system and method for gas steam boiler coupled double-stage heat pump - Google Patents
Multi-cold source system and method for gas steam boiler coupled double-stage heat pump Download PDFInfo
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- CN117329532A CN117329532A CN202311513501.5A CN202311513501A CN117329532A CN 117329532 A CN117329532 A CN 117329532A CN 202311513501 A CN202311513501 A CN 202311513501A CN 117329532 A CN117329532 A CN 117329532A
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- flue gas
- heat exchanger
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- stage
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- 238000000034 method Methods 0.000 title claims abstract description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 238
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 113
- 239000003546 flue gas Substances 0.000 claims abstract description 113
- 239000007789 gas Substances 0.000 claims abstract description 68
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 claims abstract description 32
- 238000010521 absorption reaction Methods 0.000 claims abstract description 20
- 239000006096 absorbing agent Substances 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000007906 compression Methods 0.000 claims description 9
- 230000008878 coupling Effects 0.000 claims description 8
- 238000010168 coupling process Methods 0.000 claims description 8
- 238000005859 coupling reaction Methods 0.000 claims description 8
- 230000006835 compression Effects 0.000 claims description 7
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 claims description 2
- 230000009977 dual effect Effects 0.000 claims 8
- 239000000779 smoke Substances 0.000 abstract description 8
- 239000002918 waste heat Substances 0.000 description 11
- 238000010586 diagram Methods 0.000 description 7
- 238000011084 recovery Methods 0.000 description 7
- 239000002028 Biomass Substances 0.000 description 3
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000008400 supply water Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000008236 heating water Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/08—Installation of heat-exchange apparatus or of means in boilers for heating air supplied for combustion
-
- 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
- F22D1/36—Water and air preheating systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B27/00—Machines, plants or systems, using particular sources of energy
- F25B27/02—Machines, plants or systems, using particular sources of energy using waste heat, e.g. from internal-combustion engines
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Air Supply (AREA)
Abstract
The invention discloses a multi-cold source system and a method for a gas steam boiler coupled with a two-stage heat pump, wherein after the heat of the flue gas of the gas steam boiler is released through two-stage flue gas-water heat exchangers, the flue gas enters a first-stage flue gas-air heat exchanger, a third-stage flue gas-water heat exchanger and a flue gas-circulating water heat exchanger which are connected in parallel to release heat, the flue gas-circulating water heat exchanger provides a heat source for a low-temperature heat pump or a lithium bromide absorption heat pump, or an air source heat pump is used for replacing the flue gas-circulating water heat exchanger and the low-temperature heat pump, and the heat of the flue gas in a parallel structure is distributed, so that the heat of the flue gas releases heat and then heats air and water. The flue gas heats the water supply through a low-temperature heat pump, an air source heat pump or a lithium bromide absorption heat pump, and the heated water supply absorbs heat through a high-temperature heat pump and a first-stage flue gas-water heat exchanger and enters the gas boiler together with air. The invention fully absorbs the latent heat of the vapor in the exhaust smoke of the gas-steam boiler, reduces the temperature of the exhaust smoke to below 30 ℃, increases the temperature of the water supply from 20 ℃ to 120-140 ℃, increases the temperature of the air from 20 ℃ to 50-90 ℃ and increases the efficiency of the boiler to above 107%.
Description
Technical Field
The invention belongs to the technical field of boilers and heat pumps, and particularly relates to a multi-cold-source system and a method for a gas-steam boiler coupled double-stage heat pump.
Background
Flue gas waste heat recovery is one of the effective ways to achieve boiler efficiency improvement. The smoke exhaust temperature of the gas boiler is generally 50-200 ℃, water vapor in the smoke is only partially condensed or is not condensed at all, a large amount of latent heat of vaporization is not utilized in the smoke, and if the water vapor in the smoke is condensed at all, 8-11% of heat of low-level heat value of fuel can be released. The water dew point of the gas flue gas is mostly 55-58 ℃, the water supply temperature of the gas steam boiler is about 20-70 ℃, the water supply quantity is far lower than that of the gas hot water boiler, and even if the water supply temperature is lower than the water dew point of the flue gas, the latent heat of the water vapor can only be partially utilized. The efficiency of the traditional steam boiler can only reach 97% under the condition of the backwater temperature of 50 ℃, the efficiency can reach 99% under the condition of the backwater temperature of 20 ℃, the heat efficiency calculated by the low-level calorific value can reach 111% at most, and a large amount of latent heat of water vapor in the smoke discharged from the gas steam boiler is not effectively utilized. The latent heat of the water vapor can be effectively utilized when the temperature of the water supply is lower than the water dew point, but the water supply amount of the steam boiler is very small, the temperature of the water supply is quickly raised to be higher than the water dew point after the water supply enters the boiler, and a system capable of transferring the latent heat of the water vapor in the flue gas of the boiler to the water supply of the boiler or the combustion air of the boiler is needed to improve the efficiency of the gas boiler.
A heat pump is a high-efficiency energy-saving device capable of fully utilizing low-grade heat energy, and has been receiving attention in recent years. The working principle of the heat pump is that heat is absorbed from a low-temperature object and released to a high-temperature object, and a large heat supply can be obtained by only consuming a small amount of work, so that low-grade heat energy which is difficult to use can be effectively utilized. The heat pump generally has a heating coefficient of 4 to 5, that is, the heat pump is capable of absorbing heat from a low-temperature heat source to transfer heat energy 4 to 5 times the energy consumed by itself to a high-temperature object. The main heat pumps in the market at present can be classified into compression heat pumps and absorption heat pumps according to the difference of refrigeration principles. At present, the heat pump is widely applied to waste heat recovery of flue gas discharged by a boiler, waste heat recovery of sewage discharged by a factory and the like. The fuel gas and the heat pump are coupled to improve the efficiency of the boiler and save natural gas by replacing the fuel gas with electricity. When the heat pump COP increases to 3-6, the system can reclaim the investment in a short period of time.
CN208253927U, which is applied by Tianjin gas thermal planning and design institute, is a gas boiler flue gas waste heat recovery system, and the heat pump is used for effectively absorbing flue gas waste heat to preheat the feed water, so that the exhaust gas temperature can be reduced. However, the system uses a spray tower to reduce the smoke temperature, the water consumption is larger, the system is also huge, and the cost and benefit problems need to be considered. The CN111156733A biomass flue gas waste heat total heat recovery type absorption-compression coupling heat pump system applied by northeast university of electric power couples the compression heat pump unit and the heating absorption heat pump unit to form a heating absorption-compression coupling heat pump module, biomass flue gas sequentially passes through the first, second and third flue gas heat exchange units to reduce the temperature from 145 ℃ to below 40 ℃, and heating hot water is heated from 45 ℃ to above 70 ℃. The invention realizes cascade utilization of the waste heat of the flue gas and improves the efficiency of the biomass boiler. However, this invention is obviously insufficient to absorb the waste heat of flue gas by using only heating water as a cold source. At present, most of gas boilers coupled with heat pumps are hot water boilers, and few cases of coupling steam boilers with heat pumps exist.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a multi-cold source system and a method for a gas steam boiler coupling two-stage heat pump, which utilize a water supply, air and a low-temperature heat pump to fully absorb the condensation heat of flue gas, so that the temperature of the flue gas is reduced to below 30 ℃, the efficiency of the boiler is improved to above 107%, and the purpose of saving energy is achieved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the method comprises the steps that after the flue gas of a gas-steam boiler is subjected to heat release through two-stage flue gas-water heat exchangers, the flue gas enters a first-stage flue gas-air heat exchanger, a third-stage flue gas-water heat exchanger and a flue gas-circulating water heat exchanger which are connected in parallel, or the flue gas enters the first-stage flue gas-air heat exchanger, the third-stage flue gas-water heat exchanger and an air source heat pump which are connected in parallel, or the first-stage flue gas-air heat exchanger, the third-stage flue gas-water heat exchanger and a lithium bromide absorption heat pump which are connected in parallel, the heat release in a parallel structure can be regulated and controlled, the flue gas heats air and water after heat release, the flue gas heats the water supply through a low-temperature heat pump, an air source heat pump or a lithium bromide absorption heat pump, the heated water supply absorbs heat through the high-temperature heat pump and the first-stage flue gas-water heat exchanger, and the absorbed air and water supply enter the gas-steam boiler.
Further, the air heated by the first-stage flue gas-air heat exchanger is heated by the second-stage flue gas-air heat exchanger, and the flow of the used flue gas is regulated and controlled.
Further, the air heated by the first-stage flue gas-air heat exchanger is heated by the second-stage flue gas-air heat exchanger and the third-stage flue gas-air heat exchanger in sequence, and the flow of the used flue gas is regulated and controlled.
Further, the air heated by the first-stage flue gas-air heat exchanger is subjected to second-stage heating by a second-stage water-air heat exchanger, and the water supply of the second-stage water-air heat exchanger is from a low-temperature heat pump.
Further, the air heated by the first-stage flue gas-air heat exchanger is heated by the second-stage water-air heat exchanger and the third-stage water-air heat exchanger in sequence, and the water supply of the third-stage water-air heat exchanger is from the high-temperature heat pump.
Based on the same inventive concept, the invention provides a multi-cold source system of a gas steam boiler coupling two-stage heat pump, which comprises a gas boiler, a first-stage flue gas-water heat exchanger and a second-stage flue gas-water heat exchanger which are sequentially connected along the flue gas flow direction, wherein a flue gas outlet of the second-stage flue gas-water heat exchanger is connected with a first-stage flue gas-air heat exchanger, a third-stage flue gas-water heat exchanger and a flue gas-circulating water heat exchanger, the flue gas-circulating water heat exchanger is connected with a low-temperature heat pump, or a flue gas outlet of the second-stage flue gas-water heat exchanger is connected with the first-stage flue gas-air heat exchanger, the third-stage flue gas-water heat exchanger and an air source heat pump; or the flue gas outlet of the second-stage flue gas-water heat exchanger is connected with the first-stage flue gas-air heat exchanger, the third-stage flue gas-water heat exchanger and the lithium bromide absorption heat pump; the second-stage flue gas-water heat exchanger is connected with a high-temperature heat pump, the low-temperature heat pump and the high-temperature heat pump adopt a compression type water source heat pump, the third-stage flue gas-water heat exchanger, the low-temperature heat pump, the high-temperature heat pump and the water side of the first-stage flue gas-water heat exchanger are communicated, and the water side outlet of the first-stage flue gas-water heat exchanger is connected with a water inlet of a gas boiler; the air side of the first-stage flue gas-air heat exchanger is communicated with a fan and a gas boiler.
Further, a second-stage flue gas-air heat exchanger is connected in parallel to the second-stage flue gas-water heat exchanger, an air side outlet of the first-stage flue gas-air heat exchanger is communicated with the gas boiler through the second-stage flue gas-air heat exchanger, and a three-way valve is arranged at flue gas side outlets of the second-stage flue gas-water heat exchanger and the second-stage flue gas-air heat exchanger.
Further, a third-stage flue gas-air heat exchanger is connected in parallel to the first-stage flue gas-water heat exchanger, an air side outlet of the first-stage flue gas-air heat exchanger is communicated with the gas boiler through the second-stage flue gas-air heat exchanger and the third-stage flue gas-air heat exchanger in sequence, and a three-way valve is arranged at flue gas side outlets of the first-stage flue gas-water heat exchanger and the third-stage flue gas-air heat exchanger.
Further, the low temperature heat pump comprises a first evaporator, a first throttle valve, a first condenser and a first compressor; the cold side outlet of the first evaporator is sequentially connected with the first compressor, the first condenser and the first throttle valve along the flow direction of the refrigerating medium, and the first throttle valve is connected with the cold side inlet of the first evaporator; the hot side of the first evaporator is connected with the cold side of the flue gas-circulating water heat exchanger, and the water side of the first condenser is connected with the water side of the high-temperature heat pump.
Further, a second-stage water-air heat exchanger is arranged between the water side of the first condenser and the water side of the high-temperature heat pump, and the air side of the first-stage flue gas-air heat exchanger is communicated with the gas boiler through the air side of the second-stage water-air heat exchanger.
Further, the high-temperature heat pump comprises a second evaporator, a second throttle valve, a second condenser and a second compressor; the cold side outlet of the second evaporator is sequentially connected with the second compressor, the second compressor and the second throttle valve along the flow direction of the refrigerating medium, the outlet of the second throttle valve is connected with the cold side inlet of the second evaporator, the hot side of the second evaporator is connected with the cold side of the second-stage flue gas-water heat exchanger, the water side inlet of the second condenser is connected with the water side outlet of the low-temperature heat pump, and the water side outlet of the second condenser is connected with the water side inlet of the first-stage flue gas-water heat exchanger.
Further, a water side outlet of the high-temperature heat pump is connected with a water side inlet of the first-stage flue gas-water heat exchanger through the third-stage water-air heat exchanger, and an air side of the first-stage flue gas-air heat exchanger is communicated with the gas boiler through an air side of the second-stage water-air heat exchanger and an air side of the third-stage water-air heat exchanger.
Further, the air source heat pump adopts a compression type heat pump, the air source heat pump comprises a third evaporator, a third throttle valve, a third condenser and a third compressor, a cold side outlet of the third evaporator is sequentially connected with a fourth compressor, the third condenser and the third throttle valve, an outlet of the third throttle valve is connected with a cold side inlet of the third evaporator, a hot side inlet of the third evaporator is connected with a flue gas outlet of the second-stage flue gas-water heat exchanger, and a hot side outlet of the third evaporator is emptied; the water side outlet of the third condenser is connected with a high-temperature heat pump.
Further, the lithium bromide absorption heat pump comprises a generator, a fourth condenser, a fourth throttle valve, a fourth evaporator, an absorber, a solution valve, a solution pump and a solution heat exchanger; the working medium outlet of the generator is connected with the working medium side of the fourth condenser, the working medium side outlet of the fourth condenser is connected with the working medium side of the fourth evaporator through a fourth throttle valve, the working medium side of the fourth evaporator is connected with the working medium inlet of the absorber, the working medium outlet of the absorber is connected with the dilute solution inlet of the solution heat exchanger, the dilute solution outlet of the solution heat exchanger is connected with the working medium inlet of the generator, a solution pump is arranged on a pipeline from the absorber to the solution heat exchanger, the generator is communicated with the solution heat exchanger, and a solution valve is arranged on a pipeline from the solution heat exchanger to the absorber; the hot side of the fourth evaporator is connected with the cold side of the flue gas-circulating water heat exchanger, the water side outlet of the third-stage flue gas-water heat exchanger enters the water side inlet of the absorber, the water side outlet of the absorber is connected with the water side inlet of the fourth condenser, and the water side outlet of the fourth condenser is connected with the high-temperature heat pump. The lithium bromide absorption heat pump is driven by high-temperature steam generated by a gas boiler or by high-temperature water or heat conducting oil.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention provides a multi-cold source system and a method for a gas steam boiler coupled with a two-stage heat pump, which utilize water supply, air and a low-temperature heat pump to fully absorb latent heat and a small amount of sensible heat of water vapor stored in flue gas. The invention adopts a parallel system, the final-stage flue gas is divided into three parts, and the three parts respectively enter a flue gas-water heat exchanger, a flue gas-air heat exchanger and a flue gas-circulating water heat exchanger, the water supply is subjected to step heating through the flue gas, the low-temperature heat pump and the high-temperature heat pump, and the reasonable distribution of the flue gas heat is realized by controlling the opening of a valve, so that the outlet temperatures of the water supply and the air are controlled, and the system is operated in the optimal state; the flue gas temperature is reduced to below 30 ℃, the water supply is increased from 20 ℃ to 120-140 ℃, the air is increased from 20 ℃ to 50-90 ℃, the boiler efficiency is increased to above 107%, and the energy saving purpose is achieved.
Furthermore, the invention realizes the cascade utilization of the waste heat of the flue gas, and the water supply is subjected to cascade heating; according to different systems, the air can be heated step by step, and two different modes of flue gas heating and water heating can be adopted.
Further, a second-stage flue gas-air heat exchanger is arranged, and air is heated twice through flue gas.
Further, a second-stage flue gas-air heat exchanger and a third-stage flue gas-air heat exchanger are arranged, and air is heated for three times through flue gas.
Further, by arranging a second-stage water-air heat exchanger, the air is heated twice through the flue gas and the water supply.
Further, by simultaneously arranging the second-stage water-air heat exchanger and the third-stage water-air heat exchanger, the air is heated for three times through the flue gas and the water supply.
Furthermore, the COP of the heat pump is maintained at 3-6, so that the system efficiency is always maintained at the optimal state, and meanwhile, as much heat is recovered as possible, electricity is used for replacing gas, so that investment recovery can be realized in a short period, and the economic benefit is remarkable.
Furthermore, the compression heat pump and the absorption heat pump can also be driven by renewable energy sources, and the flue gas waste heat is recovered in a zero-carbon mode.
Drawings
FIG. 1a is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 1b is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 1c is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 2a is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 2b is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 3 is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
FIG. 4 is a schematic diagram of a multiple cold source system of a gas steam boiler coupled two-stage heat pump.
In the figure, the solution is prepared from a solution of 1-gas steam boiler, 2-first-stage flue gas-water heat exchanger, 3-second-stage flue gas-water heat exchanger, 4-first four-way valve, 5-first-stage flue gas-air heat exchanger, 6-third-stage flue gas-water heat exchanger, 7-second four-way valve, 8-low-temperature heat pump, 81-first evaporator, 82-first throttle valve, 83-first condenser, 84-first compressor, 9-high-temperature heat pump, 91-second evaporator, 92-second throttle valve, 93-second condenser, 94-second compressor, 10-flue gas-circulating water heat exchanger, 11-fourth three-way valve, 12-second-stage flue gas-air heat exchanger, 13-third three-way valve, 14-second three-way valve, 15-third-stage flue gas-air heat exchanger, 16-first three-way valve, 17-second-stage water-air heat exchanger, 18-third-water-air heat exchanger, 19-air source, 191-third evaporator, 192-third throttle valve, 193-third condenser, 194-third condenser, fourth throttle valve, 202-fourth throttle valve, 208-fourth throttle valve, 201-fourth evaporator, fourth throttle valve, and fourth pump, and absorption pump, 204-fourth throttle valve, and the solution is absorbed by the solution.
Detailed Description
The invention is described in further detail below with reference to the attached drawing figures:
as shown in fig. 1a, the system comprises a gas steam boiler 1, each stage of flue gas-water heat exchangers, a first stage of flue gas-air heat exchanger 5, a low temperature heat pump 8, a high temperature heat pump 9, valves and connecting pipes. The low temperature heat pump 8 and the high temperature heat pump 9 both adopt compression type water source heat pumps. The flue gas outlet of the gas steam boiler 1 is connected with the flue gas side inlet of the first-stage flue gas-water heat exchanger 2, the flue gas side outlet of the first-stage flue gas-water heat exchanger 2 is connected with the flue gas side inlet of the second-stage flue gas-water heat exchanger 3, a first four-way valve 4 is arranged outside the flue gas side outlet of the second-stage flue gas-water heat exchanger 3, and a second four-way valve 7 is arranged outside the flue gas side outlet of the third-stage flue gas-water heat exchanger 6. The three outlets of the first four-way valve 4 are respectively connected with the flue gas side inlet of the third-stage flue gas-water heat exchanger 6, the flue gas side inlet of the first-stage flue gas-air heat exchanger 5 and the flue gas side inlet of the flue gas-circulating water heat exchanger 10. The flue gas side outlets of the first-stage flue gas-air heat exchanger 5, the third-stage flue gas-water heat exchanger 6 and the flue gas-circulating water heat exchanger 10 are converged by the second four-way valve 7 and then discharged to the atmosphere.
The air is heated once, and the specific process is as follows: the air side outlet of the first-stage flue gas-air heat exchanger 5 is connected with the gas steam boiler 1, air enters from the air side inlet of the first-stage flue gas-air heat exchanger 5, exchanges heat with flue gas and flows out from the air side outlet of the first-stage flue gas-air heat exchanger 5.
The step heating is realized by the water supply sequentially passing through the low-temperature flue gas, the low-temperature heat pump, the high-temperature heat pump and the high-temperature flue gas, and the specific process is as follows: the water side inlet of the third-stage flue gas-water heat exchanger 6 is connected with an external water pipe, the water side outlet of the third-stage flue gas-water heat exchanger 6 is connected with the water side inlet of the first condenser 83, the water side outlet of the first condenser 83 is connected with the water side inlet of the second condenser 93, and the water side outlet of the second condenser 93 is connected with the water side inlet of the first-stage flue gas-water heat exchanger 2.
The low-temperature heat pump 8 and the high-temperature heat pump 9 both adopt an indirect heat exchange mode, and the low-temperature heat pump 8 is taken as an example for specific explanation: the refrigerant exchanges heat with the circulating cooling water in the first evaporator 81, absorbs heat of the circulating cooling water, evaporates, and sequentially passes through the first compressor 84, the first condenser 83 and the first throttle valve 82.
One embodiment of this system is specifically described: when the temperature of the water supply is about 20 ℃, the system distributes the flue gas with the temperature close to the dew point of the flue gas water, and can distribute 60% of the flue gas to air and the water supply, wherein the air accounts for 10% and the water supply accounts for 50%. At this time, the water supply at 20℃may be heated to 50℃and the air at 20℃may be preheated to 50 ℃. The residual 40% of the flue gas waste heat is absorbed by the low-temperature heat pump, and the temperature rise of about 30 ℃ can be provided for the water supply at 50 ℃, and the COP of the low-temperature heat pump is 3.4. The high-temperature heat pump absorbs the heat of the flue gas at 130 ℃ to be reduced to be close to the acid dew point of the flue gas, and can provide about 25 ℃ of temperature rise for water supply, and the COP of the high-temperature heat pump is 5.4. The temperature of the water supply after the two heating can reach 105 ℃, and finally the temperature of the flue gas is reduced to 130 ℃ after the flue gas is heated at 230 ℃, and the water supply can finally reach about 140 ℃. The flue gas condensation heat is absorbed and utilized by the air, the water supply and the low-temperature heat pump, the temperature of the flue gas can be reduced to 30 ℃, the boiler efficiency can reach 107%, and the investment recovery can be realized in 1-2 years.
As shown in fig. 1b, a second stage flue gas-air heat exchanger 13 can be arranged on the basis of fig. 1a to realize secondary heating of air. The specific process is as follows: a third three-way valve 13 is arranged outside the flue gas side outlet of the first-stage flue gas-water heat exchanger 2, a fourth three-way valve 11 is arranged outside the flue gas side outlet of the second-stage flue gas-water heat exchanger 3, a first outlet of the third three-way valve 13 is connected with the flue gas side inlet of the second-stage flue gas-water heat exchanger 3, and a second outlet of the third three-way valve 13 is connected with the flue gas side inlet of the second-stage flue gas-air heat exchanger 12. The flue gas side outlet of the second-stage flue gas-air heat exchanger 12 and the flue gas side outlet of the second-stage flue gas-water heat exchanger 3 are converged by the fourth three-way valve 11 and then enter the inlet of the first four-way valve 4. The system needs to distribute the 130 ℃ flue gas, can distribute 30% of the flue gas to the air, and the air can be heated to 75 ℃. The rest 70% of the flue gas heat is absorbed by the high-temperature heat pump, and the temperature rise of about 15 ℃ can be provided for water supply. Finally, the temperature of the flue gas is reduced to 130 ℃ by heating the flue gas at 230 ℃, and the water supply can finally reach about 130 ℃.
As shown in fig. 1c, a third stage flue gas-air heat exchanger 15 may be provided on the basis of fig. 1b to effect three heats of air. The specific process is as follows: a second three-way valve 14 is arranged between the flue gas side outlet of the first-stage flue gas-water heat exchanger 2 and the third three-way valve 13, and a first three-way valve 16 is arranged between the flue gas outlet of the gas steam boiler 1 and the first-stage flue gas-water heat exchanger 2. The first outlet of the first three-way valve 16 is connected with the flue gas side inlet of the first-stage flue gas-water heat exchanger 2, and the second outlet of the first three-way valve 16 is connected with the flue gas side inlet of the third-stage flue gas-air heat exchanger 15. The flue gas side outlet of the third-stage flue gas-air heat exchanger 15 and the flue gas side outlet of the first-stage flue gas-water heat exchanger 2 are converged by the second three-way valve 14 and then enter the inlet of the third three-way valve 13. The system needs to distribute the flue gas at 230 ℃, can distribute 10% of the flue gas to the air, and can increase the temperature of the air from 75 ℃ to 85 ℃. The remaining 90% of the flue gas heat is used for heating the feed water, and the feed water can finally reach about 125 ℃.
As shown in fig. 2a, the liquid side does not need to be subjected to additional heat exchange enhancement treatment due to the stronger heat exchange capability of the liquid, so that the second-stage flue gas-air heat exchanger 12 can be replaced by the second-stage water-air heat exchanger 17 on the basis of fig. 1 b. The specific process is as follows: the air side inlet of the second stage water-air heat exchanger 17 is connected to the air side outlet of the first stage flue gas-air heat exchanger 5. The water side inlet of the second stage water-air heat exchanger 17 is connected to the water side outlet of the first condenser 83, and the water side outlet of the second stage water-air heat exchanger 17 is connected to the water side inlet of the second condenser 93. The air is heated twice by the flue gas and the water supply. After passing through the low temperature heat pump, the water is heated to 85 ℃, and the heat exchange capacity of the water is stronger than that of the air, so that the water can be increased by about 15 ℃ by only reducing the temperature of the water by 5 ℃. Then, the water supply at 80 ℃ is heated by a high-temperature heat pump and high-temperature flue gas at 230 ℃ and finally can be heated to about 135 ℃.
As shown in fig. 2b, a third stage water-air heat exchanger 18 may be provided on the basis of fig. 2 a. The specific process is as follows: the air side inlet of the third stage water-air heat exchanger 18 is connected to the air side outlet of the second stage water-air heat exchanger 17. The water side inlet of the third stage water-air heat exchanger 18 is connected to the water side outlet of the second condenser 93, and the water side outlet of the third stage water-air heat exchanger 18 is connected to the water side inlet of the first stage flue gas-water heat exchanger 2. As can be seen from the system of FIG. 2a, after heating by the high temperature heat pump, the feed water can be raised to 105℃and also lowered by 5℃and the air can be raised from 70℃to 90 ℃. The water supply at 100 ℃ can be heated to about 130 ℃ finally by heating the flue gas at 230 ℃.
As shown in fig. 3, the low-temperature heat pump 8 and the high-temperature heat pump 9 may be replaced by an air source heat pump 19. At this time, the flue gas exchanges heat with the refrigerating medium directly, a flue gas-circulating water heat exchanger is omitted, and the rest of the process is the same as that of fig. 1 a.
As shown in fig. 4, the low-temperature heat pump 8 and the high-temperature heat pump 9 may be replaced by a lithium bromide absorption heat pump 20. The lithium bromide absorption heat pump system comprises a generator 204, a fourth condenser 203, a fourth throttle valve 202, a fourth evaporator 201, an absorber 208, a solution valve 207, a solution pump 206 and a solution heat exchanger 205. The working medium outlet of the generator 204 is connected with the working medium side of the fourth condenser 203, the working medium side outlet of the fourth condenser 203 is connected with the working medium side of the fourth evaporator 201 through the fourth throttle valve 202, and the working medium side of the fourth evaporator 201 is connected with the working medium inlet of the absorber 208. The working medium outlet of the absorber 208 is connected with the dilute solution inlet of the solution heat exchanger 205, and the dilute solution outlet of the solution heat exchanger 205 is connected with the working medium inlet of the generator 204. A solution pump 206 is provided on the line from the absorber 208 to the solution heat exchanger 205. The generator 204 is communicated with a solution heat exchanger 205, and a solution valve 207 is arranged on a pipeline from the solution heat exchanger 205 to an absorber 208. The water side outlet of the third flue gas-water heat exchanger 6 is sequentially connected with an absorber 208 and a fourth condenser 203, and the fourth evaporator 201 also adopts an indirect heat exchange mode. The lithium bromide absorption heat pump 20 can be driven by high temperature steam generated by the gas steam boiler 1, or can be driven by other high temperature heat sources (such as high temperature water or heat conducting oil).
The invention provides a multi-cold source system and a method for coupling a gas steam boiler with a two-stage heat pump, wherein flue gas exhausted by the gas steam boiler 1 is discharged through two-stage flue gas-water heat exchangers to release heat, then enters a first-stage flue gas-air heat exchanger 5, a third-stage flue gas-water heat exchanger 6 and a flue gas-circulating water heat exchanger 10 which are connected in parallel to release heat, or enters the first-stage flue gas-air heat exchanger 5, the third-stage flue gas-water heat exchanger 6 and an air source heat pump 19 which are connected in parallel to release heat, the heat release in the parallel structure can be regulated and controlled, the flue gas releases heat to heat air and water, the flue gas is heated to supply water through a low-temperature heat pump 8 or the air source heat pump 19 or the lithium bromide absorption heat pump 20, the heated water is absorbed through a high-temperature heat pump 9 and the first-stage flue gas-water heat exchanger 2, the absorbed air and the water supply water enter the gas steam boiler 1 in a gas coupling high-low-temperature two-stage heat pump mode to fully absorb the gas steam in a mode, the flue gas is reduced to a temperature below 30 ℃, the flue gas temperature is reduced to 20 ℃ and the energy is increased to a temperature of between 20 ℃ and 50% by the energy saving the steam and the energy of the steam is increased to 50% by the energy.
Claims (14)
1. A multi-cold source method for a gas steam boiler coupled two-stage heat pump is characterized by comprising the following steps of: after the heat of the flue gas of the gas boiler (1) is released by the two-stage flue gas-water heat exchanger, the flue gas enters the parallel first-stage flue gas-air heat exchanger (5), the third-stage flue gas-water heat exchanger (6) and the flue gas-circulating water heat exchanger (10), or the flue gas enters the parallel first-stage flue gas-air heat exchanger (5), the third-stage flue gas-water heat exchanger (6) and the air source heat pump (19), or the flue gas enters the parallel first-stage flue gas-air heat exchanger (5), the third-stage flue gas-water heat exchanger (6) and the lithium bromide absorption heat pump (20), heat in the parallel structure is distributed, the flue gas releases heat, the heated air and the feed water heat, the flue gas is heated by the low-temperature heat pump (8), the air source heat pump (19) or the lithium bromide absorption heat pump (20), the heated feed water is absorbed by the high-temperature heat pump (9) and the first-stage flue gas-water heat exchanger (2), and the absorbed air and the feed water enter the gas boiler (1).
2. The multi-cold source method of a gas steam boiler coupled two-stage heat pump of claim 1, wherein: and heating the air heated by the first-stage flue gas-air heat exchanger (5) by using the second-stage flue gas-air heat exchanger, and regulating and controlling the flow of the used flue gas.
3. The multi-cold source method of a gas steam boiler coupled two-stage heat pump of claim 2, wherein: and the air heated by the first-stage flue gas-air heat exchanger (5) is heated by the second-stage flue gas-air heat exchanger and the third-stage flue gas-air heat exchanger in sequence, and the flow of the used flue gas is regulated and controlled.
4. The multi-cold source method of a gas steam boiler coupled two-stage heat pump of claim 1, wherein: and the air heated by the first-stage flue gas-air heat exchanger (5) is subjected to second-stage heating by a second-stage water-air heat exchanger (17), and the water supply of the second-stage water-air heat exchanger (17) is from a low-temperature heat pump (8).
5. The multi-cold source method of a gas steam boiler coupled two-stage heat pump of claim 4, wherein: the air heated by the first-stage flue gas-air heat exchanger (5) is sequentially heated by a second-stage water-air heat exchanger (17) and a third-stage water-air heat exchanger (18), and the water fed by the third-stage water-air heat exchanger (18) is from a high-temperature heat pump (9).
6. A multi-cold source system of a gas steam boiler coupling two-stage heat pump is characterized in that: the system comprises a gas boiler (1), a first-stage flue gas-water heat exchanger (2) and a second-stage flue gas-water heat exchanger (3) which are sequentially connected along the flue gas flow direction, wherein a flue gas outlet of the second-stage flue gas-water heat exchanger (3) is connected with a first-stage flue gas-air heat exchanger (5), a third-stage flue gas-water heat exchanger (6) and a flue gas-circulating water heat exchanger (10), the flue gas-circulating water heat exchanger (10) is connected with a low-temperature heat pump (8), or a flue gas outlet of the second-stage flue gas-water heat exchanger (3) is connected with the first-stage flue gas-air heat exchanger (5), the third-stage flue gas-water heat exchanger (6) and an air source heat pump (19); or the flue gas outlet of the second-stage flue gas-water heat exchanger (3) is connected with the first-stage flue gas-air heat exchanger (5), the third-stage flue gas-water heat exchanger (6) and the lithium bromide absorption heat pump (20); the second-stage flue gas-water heat exchanger (3) is connected with a high-temperature heat pump (9), the low-temperature heat pump (8) and the high-temperature heat pump (9) adopt a compressed water source heat pump, the third-stage flue gas-water heat exchanger (6), the low-temperature heat pump (8), the high-temperature heat pump (9) and the water side of the first-stage flue gas-water heat exchanger (2) are communicated, and the water side outlet of the first-stage flue gas-water heat exchanger (2) is connected with the water supply inlet of the gas boiler (1); the air side of the first-stage flue gas-air heat exchanger (5) is communicated with a fan and the gas boiler (1).
7. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the second-stage flue gas-water heat exchanger (3) is connected with the second-stage flue gas-air heat exchanger (12) in parallel, an air side outlet of the first-stage flue gas-air heat exchanger (5) is communicated with the gas boiler (1) through the second-stage flue gas-air heat exchanger (12), and a flue gas side outlet of the second-stage flue gas-water heat exchanger (3) and a flue gas side outlet of the second-stage flue gas-air heat exchanger (12) are provided with three-way valves.
8. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 7, wherein: the first-stage flue gas-water heat exchanger (2) is connected with the third-stage flue gas-air heat exchanger (15) in parallel, and the air side outlet of the first-stage flue gas-air heat exchanger (5) is communicated with the gas boiler (1) through the second-stage flue gas-air heat exchanger (12) and the third-stage flue gas-air heat exchanger (15), and the flue gas side outlets of the first-stage flue gas-water heat exchanger (2) and the third-stage flue gas-air heat exchanger (15) are provided with three-way valves.
9. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the low temperature heat pump (8) comprises a first evaporator (81), a first throttle valve (82), a first condenser (83) and a first compressor (84); the cold side outlet of the first evaporator (81) is sequentially connected with a first compressor (84), a first condenser (83) and a first throttle valve (82) along the flow direction of the refrigerating medium, and the first throttle valve (82) is connected with the cold side inlet of the first evaporator (81); the hot side of the first evaporator (81) is connected with the cold side of the flue gas-circulating water heat exchanger (10), and the water side of the first condenser (83) is connected with the water side of the high-temperature heat pump (9).
10. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: a second-stage water-air heat exchanger (17) is arranged between the water side of the first condenser (83) and the water side of the high-temperature heat pump (9), and the air side of the first-stage flue gas-air heat exchanger (5) is communicated with the gas boiler (1) through the air side of the second-stage water-air heat exchanger (17).
11. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the high-temperature heat pump (9) comprises a second evaporator (91), a second throttle valve (92), a second condenser (93) and a second compressor (94); the cold side outlet of the second evaporator (91) is sequentially connected with a second compressor (94), the second compressor (94) and a second throttle valve (92) along the flow direction of refrigerating medium, the outlet of the second throttle valve (92) is connected with the cold side inlet of the second evaporator (91), the hot side of the second evaporator (91) is connected with the cold side of the second-stage flue gas-water heat exchanger (3), the water side inlet of the second condenser (93) is connected with the water side outlet of the low-temperature heat pump (8), and the water side outlet of the second condenser (93) is connected with the water side inlet of the first-stage flue gas-water heat exchanger (2).
12. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the water side outlet of the high-temperature heat pump (9) is connected with the water side inlet of the first-stage flue gas-water heat exchanger (2) through the third-stage water-air heat exchanger (18), and the air side of the first-stage flue gas-air heat exchanger (5) is communicated with the gas boiler (1) through the air sides of the second-stage water-air heat exchanger (17) and the third-stage water-air heat exchanger (18).
13. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the air source heat pump (19) adopts a compression heat pump, the air source heat pump (19) comprises a third evaporator (191), a third throttle valve (192), a third condenser (193) and a fourth compressor (194), a cold side outlet of the third evaporator (191) is sequentially connected with the third compressor (194), the third condenser (193) and the third throttle valve (192), an outlet of the third throttle valve (192) is connected with a cold side inlet of the third evaporator (191), a hot side inlet of the third evaporator (191) is connected with a flue gas outlet of the second-stage flue gas-water heat exchanger (3), and a hot side outlet of the third evaporator (191) is emptied; the water side outlet of the third condenser (193) is connected with a high-temperature heat pump (9).
14. The gas steam boiler coupled dual stage heat pump multiple cold source system of claim 6, wherein: the lithium bromide absorption heat pump (20) comprises a generator (204), a fourth condenser (203), a fourth throttle valve (202), a fourth evaporator (201), an absorber (208), a solution valve (207), a solution pump (206) and a solution heat exchanger (205); the working medium outlet of the generator (204) is connected with the working medium side of the fourth condenser (203), the working medium side outlet of the fourth condenser (203) is connected with the working medium side of the fourth evaporator (201) through a fourth throttle valve (202), the working medium side of the fourth evaporator (201) is connected with the working medium inlet of the absorber (208), the working medium outlet of the absorber (208) is connected with the dilute solution inlet of the solution heat exchanger (205), the dilute solution outlet of the solution heat exchanger (205) is connected with the working medium inlet of the generator (204), a solution pump (206) is arranged on a pipeline from the absorber (208) to the solution heat exchanger (205), the generator (204) is communicated with the solution heat exchanger (205), and a solution valve (207) is arranged on a pipeline from the solution heat exchanger (205) to the absorber (208); the hot side of the fourth evaporator (201) is connected with the cold side of the flue gas-circulating water heat exchanger (10), the water side outlet of the third-stage flue gas-water heat exchanger (6) enters the water side inlet of the absorber (208), the water side outlet of the absorber (208) is connected with the water side inlet of the fourth condenser (203), the water side outlet of the fourth condenser (203) is connected with the high-temperature heat pump (9), and the lithium bromide absorption heat pump (20) is driven by high-temperature steam generated by the gas boiler (1) or driven by high-temperature water or heat conducting oil.
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| CN202311513501.5A CN117329532A (en) | 2023-11-14 | 2023-11-14 | Multi-cold source system and method for gas steam boiler coupled double-stage heat pump |
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| CN202311513501.5A CN117329532A (en) | 2023-11-14 | 2023-11-14 | Multi-cold source system and method for gas steam boiler coupled double-stage heat pump |
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