CN116428771A - Two-stage absorption type cogeneration system based on different types of power cycles - Google Patents

Two-stage absorption type cogeneration system based on different types of power cycles Download PDF

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Publication number
CN116428771A
CN116428771A CN202211734717.XA CN202211734717A CN116428771A CN 116428771 A CN116428771 A CN 116428771A CN 202211734717 A CN202211734717 A CN 202211734717A CN 116428771 A CN116428771 A CN 116428771A
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heat
outlet
absorber
generator
inlet
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席奂
田文彪
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Xian Jiaotong University
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Xian Jiaotong University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K27/00—Plants for converting heat or fluid energy into mechanical energy, not otherwise provided for
    • F01K27/02—Plants modified to use their waste heat, other than that of exhaust, e.g. engine-friction heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
    • F01D15/10—Adaptations for driving, or combinations with, electric generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D17/00—Domestic hot-water supply systems
    • F24D17/02—Domestic hot-water supply systems using heat pumps
    • 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
    • F25B15/00—Sorption machines, plants or systems, operating continuously, e.g. absorption type
    • F25B15/02—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas
    • F25B15/06—Sorption 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
    • 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
    • F25B30/00—Heat pumps
    • F25B30/04—Heat pumps of the sorption type
    • 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
    • F25B33/00—Boilers; Analysers; Rectifiers
    • 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
    • F25B37/00—Absorbers; Adsorbers
    • 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
    • F25B39/00—Evaporators; Condensers
    • F25B39/02—Evaporators
    • 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
    • F25B39/00—Evaporators; Condensers
    • F25B39/04—Condensers
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/40—Fluid line arrangements

Abstract

The invention discloses a two-stage absorption type cogeneration system based on different types of power circulation, which utilizes the characteristics of an absorption type heat pump to carry out cascade utilization on a low-temperature waste heat source through the driving action of a high-temperature heat source. The system comprises: the system comprises a first-stage absorption heat pump, a second-stage absorption heat pump and a power circulation system. The low-temperature waste heat source firstly transfers heat to the circulating working medium through an evaporator in the power circulating system and then sequentially enters the evaporators in the second-stage absorption heat pump and the first-stage absorption heat pump. The working medium in the power cycle expands to do work after being heated by the three branches, and electric energy is output. The heat released by the first absorber is used for district heating. The invention can utilize the waste heat and low temperature in each temperature range to realize large-temperature-difference heat exchange of the waste heat source, and greatly reduce the outlet temperature, thereby improving the utilization rate of the waste heat source, meeting the electricity and heat supply requirements and reducing the consumption of fossil fuel.

Description

Two-stage absorption type cogeneration system based on different types of power cycles
Technical Field
The invention belongs to the technical field of energy, relates to the fields of absorption heat pump circulation, power circulation and cogeneration, and particularly relates to a two-stage absorption cogeneration system based on different types of power circulation.
Background
The power cycle represented by the organic rankine cycle, the organic flash cycle, the brayton cycle, the kalina cycle, and the like plays a vital role in the systems of waste heat recovery, cogeneration, renewable energy power generation, energy storage, and the like. Regardless of the field of application, the evaporator side of the power cycle has very low utilization of the heat energy of the heat source, resulting in a hot side fluid having an outlet temperature that is much higher than the inlet temperature of the cold side fluid.
The researches on power circulation mainly focus on the aspects of improvement of a system circulation form, development of important parts, optimization of key parameters, screening of working fluid and change of a heat source, and few researches consider the situation that the heat energy utilization rate of the heat source is low, and a good method is not available all the time to solve the problem that the temperature of fluid at an outlet of the heat source is too high.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a two-stage absorption type cogeneration system based on different types of power circulation so as to further improve the heat energy utilization rate of low-temperature waste heat sources such as waste heat sources and the like with the temperature not exceeding 150 ℃.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a two-stage absorption type cogeneration system based on different types of power circulation comprises an absorption type heat pump circulation system and a power circulation system; the absorption heat pump circulation system comprises a first-stage absorption heat pump and a second-stage absorption heat pump; the first-stage absorption heat pump comprises a first generator, a first condenser, a first evaporator, a first absorber and a first solution heat exchanger; the second-stage absorption heat pump comprises a second generator, a second condenser, a second evaporator, a second absorber and a second solution heat exchanger;
the circulating working medium after the power circulating system does work is divided into three branches, and a first branch flows to the first condenser; a second branch sequentially flows through the second absorber and the second condenser; the third branch flows to a third evaporator and is heated by a low-temperature waste heat source; the circulating working media of the three branches are converged, work is done and heat is released in the power circulating system, and power generation is performed;
the low-temperature waste heat source exiting the third evaporator sequentially flows through the second evaporator and the first evaporator and releases heat;
the driving heat source flows through the first generator and the second generator in sequence and releases heat.
In one embodiment, the first-stage absorption heat pump and the second-stage absorption heat pump both use lithium bromide solution as a working medium;
the liquid phase outlet of the first generator is a lithium bromide concentrated solution, is connected with the hot side inlet of the first solution heat exchanger, and is connected with the liquid phase inlet of the first absorber through the second throttle valve; the gas phase outlet of the first generator is water vapor and is connected with the hot side inlet of the first condenser, the hot side outlet of the first condenser is connected with the cold side inlet of the first evaporator through the first throttle valve, and the cold side outlet of the first evaporator is connected with the gas phase inlet of the first absorber; the hot side outlet of the first absorber is lithium bromide dilute solution, the lithium bromide dilute solution is connected with the cold side inlet of the first solution heat exchanger through the first booster pump, and the cold side outlet of the first solution heat exchanger is connected with the cold side inlet of the first generator, so that the whole absorption heat pump cycle is completed;
the liquid phase outlet of the second generator is a lithium bromide concentrated solution, is connected with the hot side inlet of the second solution heat exchanger, and is connected with the liquid phase inlet of the second absorber through a fourth throttle valve; the gas phase outlet of the second generator is water vapor, and is connected with the hot side inlet of the second condenser, the hot side outlet of the second condenser is connected with the cold side inlet of the second evaporator through a third throttle valve, and the cold side outlet of the second evaporator is connected with the gas phase inlet of the second absorber; the hot side outlet of the second absorber is lithium bromide dilute solution, the lithium bromide dilute solution is connected with the cold side inlet of the second solution heat exchanger through the second booster pump, and the cold side outlet of the second solution heat exchanger is connected with the cold side inlet of the second generator, so that the whole absorption heat pump cycle is completed.
In one embodiment, the first generator is composed of a first heat exchanger and a first two-phase separator, wherein the hot side inlet of the first heat exchanger is a hot side inlet of the first generator and is connected with the driving heat source, the cold side inlet of the first heat exchanger is a cold side inlet of the first generator, the cold side outlet of the first heat exchanger is connected with the first two-phase separator, the liquid phase outlet of the first two-phase separator is a liquid phase outlet of the first generator, and the gas phase outlet of the first two-phase separator is a gas phase outlet of the first generator;
the first absorber consists of a first heat exchanger and a first mixer, wherein a first inlet of the first mixer is a liquid phase inlet of the first absorber, a second inlet of the first mixer is a gas phase inlet of the first absorber, an outlet of the first mixer is connected with an inlet of the first heat exchanger, and a hot side outlet of the first heat exchanger is a hot side outlet of the first absorber;
the second generator consists of a second heat exchanger and a second two-phase separator, wherein a hot side inlet of the second heat exchanger is a hot side inlet of the second generator and is connected with a hot side outlet of the first heat exchanger, a cold side inlet of the second heat exchanger is a cold side inlet of the second generator, a cold side outlet of the second heat exchanger is connected with the second two-phase separator, a liquid phase outlet of the second two-phase separator is a liquid phase outlet of the second generator, and a gas phase outlet of the second generator is a gas phase outlet of the second generator;
the second absorber consists of a second heat exchanger and a second mixer, wherein a first inlet of the second mixer is a liquid phase inlet of the second absorber, a second inlet of the second mixer is a gas phase inlet of the second absorber, an outlet of the second mixer is connected with an inlet of the second heat exchanger, and a hot side outlet of the second heat exchanger is a hot side outlet of the second absorber.
In one embodiment, the first absorber is connected to a district heating network that receives heat released by the first absorber and provides domestic hot water to a hot user.
In one embodiment, the concentration of the first stage absorption heat pump is greater than the concentration of the lithium bromide solution in the second stage absorption heat pump; the flow rate of the first-stage absorption heat pump is greater than that of the lithium bromide solution in the second-stage absorption heat pump; the pressure after throttling of the second throttle valve is smaller than the pressure after throttling of the fourth throttle valve; the pressure after the first throttle valve is throttled is smaller than the pressure after the third throttle valve is throttled.
In one embodiment, working fluids exiting the first condenser, the second condenser and the third evaporator are collected into a third mixer; the third mixer and the third evaporator are all components of the power circulation system; and the outlet of the third mixer is connected with the working part of the power circulation system to provide high-temperature working medium for the working part.
In one embodiment, the third branch flows through the third evaporator when the temperature of the low temperature waste heat source is 90-150 ℃; and the low-temperature waste heat source heats the circulating working medium to a saturated gaseous state or a superheated state in the third evaporator, and the temperature is reduced to 30 ℃ after the circulating working medium exits the first evaporator.
In one embodiment, when the temperature of the low temperature waste heat source is below 90 ℃, the low temperature waste heat source directly flows into the second evaporator (15), and the third branch is omitted.
In one embodiment, the flow rate of the power cycle working medium in the third branch of the third evaporator can be adjusted for low-temperature waste heat sources with different flow rates, or the flow rate of the lithium bromide solution in the absorption heat pump cycle can be adjusted, so that the final outlet temperature of the waste heat sources is reduced to be lower.
In one embodiment, the power cycle system is an organic rankine cycle system, an organic flash cycle system, a brayton cycle system, or a kalina cycle system; and the working cycle working medium releases heat in the third condenser and is taken away by cooling water to provide hot water for a heat user.
In one embodiment, the heat released in the first condenser, or the second absorber and the second condenser, or the third evaporator is used to provide domestic hot water, depending on the change in heating and power requirements, to achieve matching and adjustment of heating and power requirements.
Compared with the prior art, the invention has the beneficial effects that:
1. by using the heat-increasing type absorption heat pump technology, high-temperature steam is used as a driving heat source, low-temperature waste heat sources (150 ℃ and below) are subjected to cascade utilization, and the outlet temperature of the waste heat sources can be reduced to 30 ℃, so that the heat source utilization rate is greatly improved.
2. The thermodynamic cycle and the absorption heat pump technology are combined, a novel cogeneration coupling system is provided, the heat energy of a heat source is efficiently converted into electric energy and the heat energy required by a heat user, and the condition of heat energy waste does not occur.
3. The two-stage absorption heat pump is adopted, so that heat exchange loss in the heat exchange process can be reduced, and the heat pump has better thermodynamic performance.
4. For the absorber in the first stage absorption heat pump, the lower temperature level of thermal energy it releases is used for district heating; for the condenser in the first stage absorption heat pump and the second absorber and condenser, the higher temperature level of thermal energy released by the condenser applies an organic Rankine cycle to generate electrical energy.
5. When the heat supply requirement is large, the heat released by the condenser in the first-stage absorption heat pump, the second absorber or the condenser or the evaporator of the organic Rankine cycle can be selectively used for heat supply, so that flexible matching and adjustment of the heat supply requirement and the power supply requirement are realized.
6. The waste heat sources in different temperature ranges or other low-temperature waste heat sources such as geothermal heat can be utilized, and an evaporator in the power cycle can be omitted when the temperature is low.
7. For waste heat sources with different flow rates, the flow rate of the circulating working medium flowing to the third branch of the power circulation evaporator can be regulated, or the flow rate of the lithium bromide solution in the absorption heat pump circulation can be regulated, so that the final outlet temperature of the waste heat source is reduced to the minimum level, and the flexible regulation and control of the system are realized.
8. The heat and power cogeneration system is suitable for different types of power cycles, such as organic Rankine cycle, organic flash evaporation cycle, brayton cycle or kalina cycle, and the like, can greatly reduce the final outlet temperature of a heat source, improve the utilization rate of the heat source and can select different power cycles according to engineering practice.
In a word, compared with the conventional power cycle, the invention can greatly improve the heat source utilization rate and the heat energy conversion rate without obviously increasing the cost, thereby bringing more power supply and heat supply benefits and having both thermal economy and environmental protection.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.
As shown in figure 1, the invention relates to a two-stage absorption type cogeneration system based on different types of power circulation, which mainly comprises an absorption type heat pump circulation system and a power circulation system. Wherein the absorption heat pump cycle system further comprises a first stage absorption heat pump and a second stage absorption heat pump. Absorption heat pumps are also known as heat pump types. In the invention, the first-stage absorption heat pump mainly comprises a first generator, a first condenser 3, a first evaporator 5, a first absorber and a first solution heat exchanger 6; the second stage absorption heat pump mainly comprises a second generator, a second condenser 13, a second evaporator 15, a second absorber and a second solution heat exchanger 16.
The circulation working medium after the power circulation system does work is divided into three branches, and the first branch flows to the first condenser 3; a second branch flows through the second absorber and the second condenser 13 in sequence; the third branch flow to the third evaporator 26 is heated by the low temperature waste heat source according to the low temperature waste heat source temperature range; the circulating working media of the three branches are converged, work is done and heat is released in the power circulating system, and power generation is performed; the low-temperature waste heat source exiting the third evaporator 26 flows through the second evaporator 15 and the first evaporator 5 in sequence and releases heat; the driving heat source sequentially flows through the first generator and the second generator and releases heat.
According to the structure, the invention combines the absorption heat pump circulation system and the power circulation system, utilizes the characteristics of the absorption heat pump, utilizes the driving heat source to perform cascade utilization on the low-temperature waste heat source, can utilize the waste heat and low-temperature heat of each temperature range, realizes large-temperature-difference heat exchange of the waste heat source, and greatly reduces the outlet temperature of the waste heat source, thereby improving the heat energy utilization rate of the heat source, meeting the power supply and heating requirements, realizing the efficient clean use of energy sources and effectively solving the problem of low heat source utilization rate.
For example, the driving heat source of the absorption heat pump can be high-temperature heat sources such as high-temperature vapor or hot water or combustion heat of combustible gas, and the high-temperature vapor generated by a boiler in a chemical plant is generally above 200 ℃, so that the driving heat source of the absorption heat pump is 230 ℃ generated by the chemical plant.
The low-temperature waste heat can be waste hot water, industrial flue gas, heat conducting oil and the like, and the low-temperature waste hot water with the temperature below 150 ℃ is used as a low-temperature heat source.
Specifically, when the temperature of the low-temperature waste heat source is 90-150 ℃, the third branch flows through the third evaporator 26; the low-temperature waste heat source heats the circulating working medium to a saturated gaseous state or a superheated state in the third evaporator 26, then sequentially enters the second evaporator 15 and the first evaporator 5, and finally the temperature can be reduced to 30 ℃ after exiting the first evaporator 5. When the temperature of the low-temperature waste heat source is below 90 ℃, the low-temperature waste heat source directly flows into the second evaporator (15), and the third branch is omitted. The low-temperature waste heat source below 90 ℃ can be replaced by a low-temperature heat source such as geothermal heat.
In the embodiment of the invention, the low-temperature waste heat source can be different heat engines such as an organic Rankine cycle, an organic flash evaporation cycle, a Brayton cycle or a kalina cycle, and the like, releases heat in a power circulation system, and meanwhile, the absorption heat pump plays a role in heating working media.
In the embodiment of the invention, the lithium bromide solution is used as a working medium in the absorption heat pump circulation system, the organic Rankine cycle heat engine is used as an example in the power circulation system, and R245fa, R134a or other environment-friendly organic matters are used as working media in the organic Rankine cycle. The absorption heat pump system takes high-temperature steam as a driving heat source to carry out cascade utilization on a low-temperature waste heat source, one part of converted heat energy is used for regional heat supply, and the other part is combined with the organic Rankine cycle system to generate electric energy. A detailed description of specific or preferred system architecture follows.
1. A first stage absorption heat pump.
In the invention, the components of the first-stage absorption heat pump mainly comprise a first generator, a first condenser 3, a first evaporator 5, a first absorber and a first solution heat exchanger 6.
As shown in fig. 1, in a first stage absorption heat pump, a heat source is first driven into a first generator and releases heat, where a dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide solution and water vapor. The liquid phase outlet of the first generator is lithium bromide concentrated solution, is connected with the hot side inlet of the first solution heat exchanger 6, and flows into the liquid phase inlet of the first absorber through the second throttle valve 7; the gas phase outlet of the first generator is superheated steam, is connected with the hot side inlet of the first condenser 3, is in a saturated liquid state, is connected with the cold side inlet of the first evaporator 5 through the first throttle valve 4, is in a saturated gas state, and is connected with the gas phase inlet of the first absorber. The hot side outlet of the first absorber is lithium bromide dilute solution, the lithium bromide dilute solution is connected with the cold side inlet of the first solution heat exchanger 6 through the first booster pump 10, and the cold side outlet of the first solution heat exchanger 6 is connected with the cold side inlet of the first generator, so that the whole absorption heat pump cycle is completed.
Further, the first heat exchanger 1 and the first two-phase separator 2 form a first generator, the hot side inlet of the first heat exchanger 1 is the hot side inlet of the first generator and is connected with the driving heat source, the cold side inlet of the first heat exchanger 1 is the cold side inlet of the first generator, the cold side outlet is connected with the inlet of the first two-phase separator 2, the liquid phase outlet of the first two-phase separator 2 is the liquid phase outlet of the first generator, and the gas phase outlet is the gas phase outlet of the first generator.
Further, the first heat exchanger 9 and the first mixer 8 form a first absorber, a first inlet of the first mixer 8 is a liquid phase inlet of the first absorber, a second inlet is a gas phase inlet of the first absorber, an outlet of the first mixer 8 is connected with an inlet of the first heat exchanger 9, and a hot side outlet of the first heat exchanger 9 is a hot side outlet of the first absorber.
Further, the first absorber is connected with a regional heating network, and the regional heating network receives heat released by the first absorber and can provide domestic hot water for a heat user.
2. A second stage absorption heat pump.
In the present invention, the constituent components of the second-stage absorption heat pump mainly include a second generator, a second condenser 13, a second evaporator 15, a second absorber, and a second solution heat exchanger 16.
The heat source is driven to release a portion of the heat in the first stage absorption heat pump into the second generator and releases heat where the dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide and water vapor. Similar to the first-stage absorption heat pump, the liquid phase outlet of the second generator is lithium bromide concentrated solution, is connected with the hot side inlet of the second solution heat exchanger 16, and the hot side outlet of the second solution heat exchanger 16 is connected with the liquid phase inlet of the second absorber through a fourth throttle valve 17; the gas phase outlet of the second generator is superheated steam, is connected with the hot side inlet of the second condenser 13, is in a saturated liquid state, is connected with the cold side inlet of the second evaporator 15 through the third throttle valve 14, is in a saturated gas state, and is connected with the gas phase inlet of the second absorber; the hot side outlet of the second absorber is lithium bromide dilute solution, and is connected with the cold side inlet of the second solution heat exchanger 16 through the second booster pump 20, and the cold side outlet of the second solution heat exchanger 16 is connected with the cold side inlet of the second generator, so that the whole absorption heat pump cycle is completed. That is, the water vapor generated in the second generator flows into the second condenser 13, the third throttle valve 14, and the second evaporator 15 in this order, and finally flows into the second absorber; the lithium bromide concentrate solution produced in the second generator passes through the second solution heat exchanger 16 and the fourth throttle valve 17, enters the second absorber and absorbs saturated water vapor from the second evaporator 15, and the formed lithium bromide dilute solution is preheated in the second solution heat exchanger 16 and finally returns to the second generator.
Compared with the first-stage absorption heat pump, the concentration and the flow rate of the lithium bromide solution in the second-stage absorption heat pump cycle are lower, and the pressure after throttling by the throttle valve is higher, so that the evaporation temperature is higher. The waste heat source enters the second evaporator 15 and then enters the first evaporator 5, so that the waste heat source can be utilized in a cascade manner by setting related parameters of the two absorption heat pump cycles to different values, heat exchange loss in a heat exchange process is reduced, and the outlet temperature is reduced to the minimum.
Further, the second heat exchanger 11 and the second two-phase separator 12 form a second generator, the second generator is composed of the second heat exchanger 11 and the second two-phase separator 12, the hot side inlet of the second heat exchanger 11 is the hot side inlet of the second generator, the hot side inlet of the second heat exchanger is connected with the hot side outlet of the first heat exchanger 1, the cold side inlet of the second heat exchanger 11 is the cold side inlet of the second generator, the cold side outlet is connected with the inlet of the second two-phase separator 12, the liquid phase outlet of the second two-phase separator 12 is the liquid phase outlet of the second generator, and the gas phase outlet is the gas phase outlet of the second generator.
Further, the second heat exchanger 19 and the second mixer 18 form a second absorber, the first inlet of the second mixer 18 is a liquid phase inlet of the second absorber, the second inlet is a gas phase inlet of the second absorber, the outlet of the second mixer 18 is connected with the inlet of the second heat exchanger 19, and the hot side outlet of the second heat exchanger 19 is a hot side outlet of the second absorber.
3. A power circulation system.
The power circulation system takes an organic Rankine cycle heat engine as an example, and the organic Rankine cycle takes R245fa, R134a or other environment-friendly organic matters as working media. The organic working medium from the working medium pump is divided into three branches, and the first branch flows to the first condenser 3 and is heated by high-temperature steam in the first condenser 3; the second branch flows to the second condenser 13 and is heated by the high-temperature steam in the second condenser 13, or flows through the second absorber and the second condenser 13 in sequence, namely is heated by the high-temperature steam in the second condenser 13, or absorbs the heat released by the second absorber firstly and is heated by the high-temperature steam in the second condenser 13; the third branch flows to the third evaporator 26 of the organic rankine cycle, i.e. the third evaporator 26 is part of the organic rankine cycle, and the working medium of the third branch is heated by the low-temperature waste heat source at the third evaporator 26. Finally, the working media in the three branches are heated and then are converged in the third mixer 21, the third mixer 21 is also a part of the organic Rankine cycle, the output working media flow into the turbine 22, namely the working part of the power circulation system, in a saturated gas state or a superheated state, and high-temperature working media are provided for the working media, and expansion work is performed on the working media to output electric energy. The exhaust gas at the outlet of the turbine 22 is connected with the hot side inlet of the third condenser 23, the hot side outlet of the third condenser 23 is in a saturated liquid state, the hot side outlet of the third condenser is pressurized by the working medium pump 24 and then is connected with the inlet of the diverter 25, and the working organic working medium releases heat in the third condenser 23 and is taken away by cooling water to provide hot water for a heat user. At the flow divider 25, the low-temperature waste heat sources with different flow rates are divided into the three branches with different flow rates according to the heat matching requirements. Alternatively, the flow of lithium bromide solution in the absorption heat pump cycle may be adjusted to lower the final outlet temperature of the waste heat source.
Based on the system, the specific implementation flow of the invention is as follows:
the invention takes water vapor at 230 ℃ as a driving heat source to heat the lithium bromide dilute solution in the first-stage and second-stage absorption heat pump generators in sequence, and the flow rates of the solution are 16kg/s and 8kg/s respectively. The component parts and the working flow of the second-stage absorption heat pump are the same as those of the first-stage absorption heat pump. Taking the first stage absorption heat pump as an example, the first heat exchanger 1 and the first two-phase separator 2 constitute a first generator, and the first heat exchanger 9 and the first mixer 8 constitute a first absorber. The heat source is first driven into the generator and emits heat where the dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide and water vapor. The lithium bromide concentrated solution enters a first solution heat exchanger 6 to preheat the lithium bromide dilute solution, and the pressure of the lithium bromide concentrated solution after heat exchange is reduced to 3kPa through the throttling action of a second throttle valve 7 and flows into an absorber; superheated steam generated in the generator enters a first condenser 3, heat is transferred to an organic working medium in the organic Rankine cycle, the steam is condensed into a saturated liquid state and then passes through a first throttle valve 4, the pressure is reduced to 3kPa, then the saturated liquid state enters a first evaporator 5, is evaporated into a saturated gaseous state by a waste heat source, and finally is introduced into an absorber. In the absorber, the concentrated lithium bromide solution absorbs water vapor and releases a large amount of heat, which is used for district heating. The outlet of the absorber is lithium bromide dilute solution, the pressure is increased to 300kPa through a booster pump, then the solution enters the first solution heat exchanger 6 to be preheated, and then the solution returns to the generator, thus completing the whole absorption heat pump cycle. In the second-stage absorption heat pump, the pressure after throttling by the throttle valve is 30kPa.
In the power circulation system, an organic Rankine cycle heat engine is taken as an embodiment, and R245fa is taken as a working medium. The organic working medium from the working medium pump is divided into three branches, the first branch flows to the first condenser 3 of the first-stage absorption heat pump, the second branch sequentially flows through the second absorber and the second condenser 13, the third branch flows to the third evaporator 26 of the organic Rankine cycle, the third branch is heated by a low-temperature waste heat source (90-150 ℃) and can be ignored for heat sources with the temperature lower than 90 ℃. After the heat is absorbed, the organic working media in the three branches are converged together through the third mixer 21, and flow into the turbine 22 in a saturated gas state or a superheated state to do expansion work to the outside, and electric energy is output. The working medium after expansion work is condensed by cooling water in the third condenser 23, and when the condensing temperature is higher, the outlet temperature of the cooling water reaches more than 50 ℃, so that hot water can be provided for a heat user. The condensed organic working medium is in a saturated liquid state, is pressurized by a working medium pump 24 and is divided into three branches with different flow rates by a flow divider 25, and enters the absorption heat pump system again, so that the whole cogeneration system is completed in a circulating way.
In summary, the invention combines the power circulation system and the two-stage absorption heat pump system by utilizing the heat increasing characteristic of the absorption heat pump, uses the vapor with higher temperature as the driving heat source, and performs cascade utilization on other low-temperature heat sources (150 ℃ and below) such as low-temperature waste heat sources or geothermal heat sources, so that the outlet temperature of the waste heat sources can be reduced to 30 ℃, the heat source utilization rate can be greatly improved, and the heat source energy can be efficiently converted into electric energy and heat energy required by heat users on the premise of not wasting heat energy. The invention adopts the two-stage absorption heat pump, can reduce heat exchange loss in the heat exchange process, reduces the temperature of the outlet of the waste heat source to be lower, and has better thermodynamic performance. And when the heat supply requirement is large, the heat released by the condenser, the second absorber or the condenser or the evaporator of the power cycle in the first-stage absorption heat pump can be selectively used for heat supply, so that the flexible matching and adjustment of the heat supply and power supply requirements are realized. The waste heat sources in different temperature ranges or other low-temperature waste heat sources such as geothermal heat can be utilized, and an evaporator in the power cycle can be omitted when the temperature of the heat source is low. Meanwhile, for waste heat sources with different flow rates, the flow rate of working medium flowing to a third branch of the power circulation evaporator can be regulated, or the flow rate of lithium bromide solution in the absorption heat pump circulation can be regulated, so that the final outlet temperature of the waste heat source is reduced to the minimum level, and the flexible regulation and control of the system are realized. In a word, compared with the conventional power cycle, the invention can greatly improve the heat source utilization rate and the heat energy conversion rate without obviously increasing the cost, thereby bringing more power supply and heat supply benefits, having both thermal economy and environmental protection, and reducing the consumption of fossil fuel.

Claims (10)

1. The two-stage absorption type cogeneration system based on different types of power circulation is characterized by comprising an absorption type heat pump circulation system and a power circulation system; the absorption heat pump circulation system comprises a first-stage absorption heat pump and a second-stage absorption heat pump; the first-stage absorption heat pump comprises a first generator, a first condenser (3), a first evaporator (5), a first absorber and a first solution heat exchanger (6); the second-stage absorption heat pump comprises a second generator, a second condenser (13), a second evaporator (15), a second absorber and a second solution heat exchanger (16);
the circulating working medium after the power circulating system does work is divided into three branches, and a first branch flows to the first condenser (3); a second branch flows through the second absorber and the second condenser (13) in sequence; the third branch flow is heated by the low-temperature waste heat source to the third evaporator (26); the circulating working media of the three branches are converged, work is done and heat is released in the power circulating system, and power generation is performed;
the low-temperature waste heat source exiting the third evaporator (26) sequentially flows through the second evaporator (15) and the first evaporator (5) and releases heat;
the driving heat source flows through the first generator and the second generator in sequence and releases heat.
2. The two-stage absorption co-generation system based on different types of power cycles according to claim 1, wherein the first stage absorption heat pump and the second stage absorption heat pump each use lithium bromide solution as a working medium;
the liquid phase outlet of the first generator is a lithium bromide concentrated solution, is connected with the hot side inlet of the first solution heat exchanger (6), and the hot side outlet of the first solution heat exchanger (6) is connected with the liquid phase inlet of the first absorber through the second throttle valve (7); the gas phase outlet of the first generator is water vapor, and is connected with the hot side inlet of the first condenser (3), the hot side outlet of the first condenser (3) is connected with the cold side inlet of the first evaporator (5) through the first throttle valve (4), and the cold side outlet of the first evaporator (5) is connected with the gas phase inlet of the first absorber; the hot side outlet of the first absorber is lithium bromide dilute solution, the lithium bromide dilute solution is connected with the cold side inlet of the first solution heat exchanger (6) through the first booster pump (10), and the cold side outlet of the first solution heat exchanger (6) is connected with the cold side inlet of the first generator to complete the whole absorption heat pump cycle;
the liquid phase outlet of the second generator is a lithium bromide concentrated solution, is connected with the hot side inlet of the second solution heat exchanger (16), and the hot side outlet of the second solution heat exchanger (16) is connected with the liquid phase inlet of the second absorber through a fourth throttle valve (17); the gas phase outlet of the second generator is water vapor, and is connected with the hot side inlet of the second condenser (13), the hot side outlet of the second condenser (13) is connected with the cold side inlet of the second evaporator (15) through a third throttle valve (14), and the cold side outlet of the second evaporator (15) is connected with the gas phase inlet of the second absorber; the hot side outlet of the second absorber is lithium bromide dilute solution, the lithium bromide dilute solution is connected with the cold side inlet of the second solution heat exchanger (16) through the second booster pump (20), and the cold side outlet of the second solution heat exchanger (16) is connected with the cold side inlet of the second generator, so that the whole absorption heat pump cycle is completed.
3. The two-stage absorption co-generation system based on different types of power cycles according to claim 2, wherein the first generator consists of a first heat exchanger (1) and a first two-phase separator (2), the hot side inlet of the first heat exchanger (1) is the hot side inlet of the first generator, the cold side inlet of the first heat exchanger (1) is the cold side inlet of the first generator, the cold side outlet is connected with the first two-phase separator (2), the liquid phase outlet of the first two-phase separator (2) is the liquid phase outlet of the first generator, and the gas phase outlet is the gas phase outlet of the first generator;
the first absorber consists of a first heat exchanger (9) and a first mixer (8), wherein a first inlet of the first mixer (8) is a liquid phase inlet of the first absorber, a second inlet is a gas phase inlet of the first absorber, an outlet of the first mixer (8) is connected with a hot side inlet of the first heat exchanger (9), and a hot side outlet of the first heat exchanger (9) is a hot side outlet of the first absorber;
the second generator consists of a second heat exchanger (11) and a second two-phase separator (12), wherein a hot side inlet of the second heat exchanger (11) is a hot side inlet of the second generator and is connected with a hot side outlet of the first heat exchanger (1), a cold side inlet of the second heat exchanger (11) is a cold side inlet of the second generator, a cold side outlet of the second heat exchanger is connected with the second two-phase separator (12), a liquid phase outlet of the second two-phase separator (12) is a liquid phase outlet of the second generator, and a gas phase outlet of the second generator is a gas phase outlet of the second generator;
the second absorber consists of a second heat exchanger (19) and a second mixer (18), wherein a first inlet of the second mixer (18) is a liquid phase inlet of the second absorber, a second inlet is a gas phase inlet of the second absorber, an outlet of the second mixer (18) is connected with a hot side inlet of the second heat exchanger (19), and a hot side outlet of the second heat exchanger (19) is a hot side outlet of the second absorber.
4. The two-stage absorption co-generation system based on different types of power cycles according to claim 2 wherein the concentration of the first stage absorption heat pump is greater than the concentration of lithium bromide solution in the second stage absorption heat pump; the flow rate of the first-stage absorption heat pump is greater than that of the lithium bromide solution in the second-stage absorption heat pump; the pressure after throttling of the second throttling valve (7) is smaller than the pressure after throttling of the fourth throttling valve (17); the pressure after the first throttling valve (4) is smaller than the pressure after the third throttling valve (14) is throttled.
5. The two-stage absorption co-generation system based on different types of power cycles according to claim 1 wherein the first absorber is connected to a district heating network that receives heat released by the first absorber and provides domestic hot water to a hot user.
6. A two-stage absorption co-generation system based on different types of power cycles according to claim 1, characterized in that the working medium exiting the first condenser (3), the second condenser (13) and the third evaporator (26) is led into a third mixer (21); the third mixer (21) and the third evaporator (26) are both components of the power circulation system; the outlet of the third mixer (21) is connected with the working part of the power circulation system to provide high-temperature working medium for the working part.
7. A two-stage absorption co-generation system based on different types of power cycles according to claim 1, wherein the third branch flows through the third evaporator (26) when the temperature of the low temperature waste heat source is 90-150 ℃; the low-temperature waste heat source heats the power circulation working medium to a saturated gaseous state or a superheated state in a third evaporator (26), and the temperature is reduced to 30 ℃ after the power circulation working medium exits the first evaporator (5); when the temperature of the low-temperature waste heat source is below 90 ℃, the low-temperature waste heat source directly flows into the second evaporator (15), and the third branch is omitted.
8. A two-stage absorption co-generation system based on different types of power cycles according to claim 1, characterized in that the flow of the circulating working fluid in the third branch to the third evaporator (26) is regulated for different flows of low temperature waste heat sources, or the flow of lithium bromide solution in the absorption heat pump cycle is regulated, so that the final outlet temperature of the waste heat sources is reduced to a lower temperature.
9. The two-stage absorption co-generation system based on different types of power cycles according to claim 1, wherein the power cycle system is an organic rankine cycle system, an organic flash cycle system, a brayton cycle system or a kalina cycle system; the working circulation working medium releases heat in the third condenser (23) and is taken away by cooling water, so that hot water is provided for a heat user.
10. A two-stage absorption co-generation system based on different types of power cycles according to claim 1, characterized in that the heat released in the first condenser (3), or the second absorber and the second condenser (13), or the third evaporator (26) is used for providing domestic hot water, according to the variation of heating and power supply requirements, achieving matching and regulation of heating and power supply requirements.
CN202211734717.XA 2022-12-30 2022-12-30 Two-stage absorption type cogeneration system based on different types of power cycles Pending CN116428771A (en)

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