WO2023083242A1 - 一种以二氧化碳气体为工质的低温循环发电系统和方法 - Google Patents

一种以二氧化碳气体为工质的低温循环发电系统和方法 Download PDF

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WO2023083242A1
WO2023083242A1 PCT/CN2022/131045 CN2022131045W WO2023083242A1 WO 2023083242 A1 WO2023083242 A1 WO 2023083242A1 CN 2022131045 W CN2022131045 W CN 2022131045W WO 2023083242 A1 WO2023083242 A1 WO 2023083242A1
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low
power generation
heat exchanger
cycle power
heat
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PCT/CN2022/131045
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French (fr)
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陈光进
邓春
刘蓓
孙长宇
蔡进
李昆
汤涵
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中国石油大学(北京)
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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
    • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
    • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
    • F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
    • F01K25/103—Carbon dioxide
    • 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
    • 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
    • F01K13/00—General layout or general methods of operation of complete plants
    • 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
    • F01K13/00—General layout or general methods of operation of complete plants
    • F01K13/006—Auxiliaries or details not otherwise provided for

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  • the invention relates to the technical field of low-grade thermal energy power generation, in particular to a low-temperature cycle power generation system and method using carbon dioxide gas as a working medium.
  • the Rankine cycle the most widely used power generation method is the Rankine cycle, but there are mainly two problems in practical application.
  • the circulating medium mostly uses low-boiling point compounds, it is necessary to set up a condenser and an evaporator to make the phase change of the working fluid, which consumes more energy and has a greater heat load on the equipment.
  • a reheater is often introduced to realize the second isobaric heating process.
  • the superheated steam makes the investment cost of high temperature resistant equipment such as the superheater and the turbine higher.
  • 2-Methylimidazole belongs to imidazole compounds with a boiling point of 267°C. Because of its low toxicity, high chemical stability and low production cost, it is widely used in corrosion inhibitors, gas separation and other fields. It is often used as a ligand to synthesize zeolite imidazoles Materials (ZIFs). 2-Methylimidazole has a good absorption performance for CO 2 gas, so it can be used as an absorbent for CO 2 gas. In addition, when the temperature is high (about 80°C), the CO 2 in the solution can undergo a desorption process to realize the absorption of the absorbent. recyclable.
  • the invention utilizes low-grade thermal energy, such as solar energy, geothermal energy, and low-temperature waste heat from factories, and only needs to consume less mechanical energy for fluid transportation, which can greatly reduce the energy consumption of low-temperature power generation cycles, and has the advantages of safety, environmental protection, stable operation, and high thermal efficiency. .
  • the object of the present invention is to provide a low-temperature cycle power generation system and method using carbon dioxide gas as a working medium.
  • the low-grade cycle power generation system uses low-grade heat energy to provide heat, and the CO2 gas absorption-desorption process of 2-methylimidazole aqueous solution realizes power generation.
  • solar hot water, geothermal energy and The efficient utilization of low-grade heat sources such as factory waste heat improves the overall stability and efficiency of the system.
  • One aspect of the present invention provides a low-temperature cycle power generation system using carbon dioxide gas as a working medium.
  • the low-temperature cycle power generation system uses CO2 gas as a cycle working medium, and 2-methylimidazole aqueous solution as an absorption medium, including:
  • CO2 absorption unit first heat exchanger, circulation booster pump, CO2 desorption unit, CO2 turbine and generator;
  • the outlet of the CO absorption unit is connected to the inlet of the circulation booster pump after passing through the first heat exchanger, the outlet of the circulation booster pump is connected to the inlet of the CO desorption unit, and the CO 2.
  • the liquid outlet of the desorption unit is connected to the inlet of the CO absorption unit after passing through the first heat exchanger; the gas outlet of the CO desorption unit is connected to the inlet of the CO turbine, and the CO 2
  • the outlet of the turbine is connected to the inlet of the CO2 absorption unit, and the CO2 turbine is connected to the generator;
  • the CO2 desorption unit is provided with a heating device, and the heating device is composed of a low-grade A heat source provides heat.
  • the low-grade heat source is selected from solar hot water, geothermal or low-temperature waste heat from factories.
  • the heating device is a water heater
  • the heat source for heating water is a low-grade heat source such as solar hot water, geothermal heat, or low-temperature waste heat from a factory
  • the hot water in the heating device provides heat for the CO desorption unit through a heating coil .
  • the heating device is a solar water heater.
  • the CO 2 absorption unit is provided with an external heat collector for removing the heat of absorption of the reaction in time to stabilize the temperature of the system during the CO 2 absorption process.
  • the internal heat extraction medium of the external heat extractor is cooling water.
  • the first heat exchanger is a shell-and-tube heat exchanger; the outlet of the CO2 absorption unit is connected to the tube-side inlet of the first heat exchanger, so The tube-side outlet of the first heat exchanger is connected to the inlet of the circulating booster pump; the liquid outlet of the CO desorption unit is connected to the shell-side inlet of the first heat exchanger, and the first heat exchanger
  • the shell-side outlet of the vessel is connected with the inlet of the CO2 absorption unit.
  • the tube side of the first heat exchanger is rich liquid (2-methylimidazole aqueous solution rich in CO 2 ), and the shell side is lean liquid (also called desorption liquid); the two exchange heat here.
  • the low-temperature cycle power generation system further includes a second heat exchanger, and the shell-side outlet of the first heat exchanger passes through the second heat exchanger and connects with the CO 2 Inlet connection of the absorption unit.
  • the lean liquid passes through the first heat exchanger to exchange heat with the rich liquid and then cools down through the second heat exchanger.
  • the internal heat exchange medium of the second heat exchanger is cooling water.
  • a decompression valve is arranged on the connecting pipeline between the liquid outlet of the CO desorption unit and the first heat exchanger;
  • the lean liquid is decompressed by the pressure reducing valve, cooled by the first heat exchanger and the second heat exchanger, and then returned to the CO2 absorption unit.
  • Another aspect of the present invention provides a low-temperature cycle power generation method using CO2 as a working medium, which is performed using any of the above low-temperature cycle power generation systems.
  • the low-temperature cycle power generation method includes the following steps:
  • the 2-methylimidazole aqueous solution absorbs CO2 gas to become a rich liquid, and after the rich liquid passes through the first heat exchanger to exchange heat with the lean liquid to raise the temperature, it enters the CO2 desorption unit through boosting ;
  • the low-grade heat source supplies heat to the CO 2 desorption unit, so that CO 2 gas desorbs and escapes from the rich liquid, enters the CO 2 turbine to expand and do work, and drives the generator to generate electricity; the desorbed lean liquid Return to the CO2 absorption unit after heat exchange with the rich liquid in the first heat exchanger and cooling.
  • the operating temperature of the CO 2 absorption unit is 20-40° C., and the operating pressure is 0.2-0.3 MPa.
  • the operating temperature of the CO2 desorption unit is 80-120 ° C, and the operating pressure is 0.8-1.2 MPa; the rich liquid is boosted to 0.8-1.2 MPa by a circulating booster pump .
  • the concentration of the 2-methylimidazole aqueous solution is 30-60 wt.%.
  • the outlet pressure of the CO 2 turbine is 0.2-0.3 MPa.
  • the low-temperature cycle power generation system and method using carbon dioxide gas as a working medium use 2-methylimidazole aqueous solution to absorb CO2 at low temperature (20-40°C) and low pressure (0.2-0.3MPa), and absorb CO2 at a higher temperature ( (80 ⁇ 120°C) absorbs heat, releases high-pressure (0.8 ⁇ 1.2MPa) CO 2 gas, and generates power through turbine expansion. Since the desorption temperature of CO2 is around 80°C, solar hot water, geothermal heat or low-temperature waste heat from factories can be used as the heat source for desorption to realize low-temperature cycle power generation.
  • the system of the present invention uses CO2 as the working medium and 2-methylimidazole aqueous solution as the absorption medium, and utilizes low-grade heat sources such as solar hot water, geothermal heat, and factory waste heat to generate electricity, thereby realizing energy saving and carbon emission reduction. Because CO2 is non-toxic, non-flammable and explosive, this cycle is safer and more environmentally friendly than the existing low-temperature organic Rankine cycle, and its thermoelectric efficiency is also higher.
  • Fig. 1 is a schematic diagram of a low-temperature cycle power generation system using carbon dioxide gas as a working medium in a preferred embodiment of the present invention.
  • Fig. 2 is a schematic diagram of a carbon dioxide gas cycle power generation system driven by offshore solar energy in a preferred embodiment of the present invention.
  • the present invention provides a preferred embodiment here, as shown in Figure 1, a kind of low-temperature cycle power generation system using carbon dioxide gas as a working medium, this low-temperature cycle power generation system adopts CO Gas as a cycle working medium, 2 -methylimidazole aqueous solution
  • the absorption medium includes: CO2 absorption unit 1, first heat exchanger 2, circulation booster pump 3, CO2 desorption unit 4, second heat exchanger 5, CO2 turbine 6 and generator 7.
  • the outlet of the CO2 absorption unit 1 is connected to the inlet of the circulation booster pump 3 after passing through the first heat exchanger 2, and the outlet of the circulation booster pump 3 is connected to the inlet of the CO2 desorption unit 4 Connected, the liquid outlet of the CO desorption unit 4 is connected with the inlet of the CO absorption unit 1 after passing through the first heat exchanger 2 and the second heat exchanger 5; the gas of the CO desorption unit 4 The outlet is connected to the inlet of the CO turbine 6, the outlet of the CO turbine 6 is connected to the inlet of the CO absorption unit 1, and the CO turbine 6 is connected to the generator 7 connection; the CO 2 desorption unit 4 is provided with a heating device to provide heat for the desorption of the rich liquid therein, and the heating device is provided with heat from a low-grade heat source.
  • the low-grade heat source is selected from solar energy, geothermal heat or low-temperature waste heat from factories.
  • the CO 2 absorption unit 1 is provided with an external heat collector 11, which is used to remove the absorption heat of the reaction in time, so as to stabilize the temperature of the system during the CO 2 absorption process.
  • the internal heat extraction medium of the external heat extractor 11 is cooling water.
  • the internal heat exchange medium of the second heat exchanger 5 is also cooling water.
  • the outlet of the CO2 absorption unit 1 is connected to the tube-side inlet of the first heat exchanger 2, and the tube-side outlet of the first heat exchanger 2 is connected to the inlet of the circulating booster pump 3
  • the liquid outlet of the CO desorption unit 4 is connected with the shell side inlet of the first heat exchanger 2
  • the shell side outlet of the first heat exchanger 2 is connected with the inlet of the second heat exchanger 5
  • the outlet of the second heat exchanger 5 is connected with the inlet of the CO2 absorption unit 1. That is, the tube side of the first heat exchanger 2 is rich liquid, and the shell side is lean liquid; the two exchange heat here.
  • a decompression valve 8 is arranged on the connecting pipeline between the liquid outlet of the CO desorption unit 4 and the first heat exchanger 2; The pressure reducing valve 8 depressurizes, the first heat exchanger 2 and the second heat exchanger 5 cool down and return to the CO2 absorption unit 1.
  • the process of using the system in Figure 1 for cyclic power generation includes:
  • the 2-methylimidazole aqueous solution in the CO2 absorption unit 1 absorbs CO2 gas to become a rich liquid ( CO2 -rich absorption liquid), and the rich liquid passes through the first heat exchanger 2 and the lean
  • the liquid also known as desorption liquid
  • low-grade heat sources such as solar hot water, geothermal energy, and factory waste heat pass through The heating device of the CO2 desorption unit 4 provides heat for it.
  • the lean liquid is further cooled from the liquid outlet of the CO2 desorption unit 4 through the pressure reducing valve 8, the first heat exchanger 2 and the second heat exchanger 5, and finally sent to the CO2 absorption unit 1 for the CO2 gas absorption process.
  • the heat generated in the process is removed in time by the external heat extractor 11 to keep the temperature of the system stable.
  • the CO 2 gas enters the CO 2 turbine 6 from the gas outlet at the top of the CO 2 desorption unit 4 through the pipeline for expansion and work process, and at the same time, the generator 7 realizes the power generation demand of the circulation device.
  • the expanded CO 2 gas returns to the CO 2 absorption unit 1 to complete the low temperature power generation cycle.
  • the operating temperature of the CO 2 absorption unit 1 is 20-40° C., and the operating pressure is 0.2-0.3 MPa.
  • the operating temperature of the CO 2 desorption unit 4 is 80-120° C., and the operating pressure is 0.8-1.2 MPa.
  • the concentration of the 2-methylimidazole aqueous solution is 30-60 wt.%.
  • the outlet pressure of the CO 2 turbine 6 is 0.2-0.3 MPa.
  • the application scenario of this application example is carbon dioxide gas cycle power generation driven by offshore solar energy.
  • the gaseous cycle working fluid used is CO 2
  • the solution in CO 2 absorption unit 1 and CO 2 desorption unit 4 is 30-60wt.% 2-formazan
  • An aqueous solution of imidazole, and the internal medium of the heat exchange and heat extraction device are all seawater.
  • the circulation system of this application example includes a CO2 absorption unit 1, a first heat exchanger 2, a circulation booster pump 3, a CO2 desorption unit 4, a second heat exchanger 5, and a CO2 turbine 6.
  • Generator 7 solar water heater 10 and external heat collector 11.
  • the outlet of the CO2 absorption unit 1 is connected to the tube-side inlet of the first heat exchanger 2, and the tube-side outlet of the first heat exchanger 2 is connected to the inlet of the CO2 desorption unit 4 through the circulation booster pump 3, and the CO2 desorption unit
  • the liquid outlet of 4 is connected to the inlet of CO2 absorption unit 1 through the shell side of the first heat exchanger 2 and the second heat exchanger 5 .
  • the gas outlet of the CO2 desorption unit 4 is connected to the inlet of the CO2 turbine 6, and the CO2 turbine 6 is connected to the generator 7, and the expanded CO2 gas returns to the CO2 absorption unit 1 to complete the power cycle.
  • the outlet of the solar water heater 10 is connected to the inlet of the heating coil installed in the CO desorption unit 4 to complete its heat supply, and a valve 9 is arranged on the connecting pipeline.
  • the CO 2 absorption unit 1 is provided with an external heat extractor 11 .
  • the circulation booster pump 3 boosts the pressure of the rich liquid from 0.2 to 0.3 MPa to 0.8 to 1.2 MPa.
  • the rich liquid is heated to 80-120°C, and the absorption temperature in the CO 2 absorption unit 1 is maintained at 20-40°C.
  • the process of using the system of this application example to generate electricity based on solar energy carbon dioxide gas cycle includes:
  • the solar water heater heats the water in the internal storage tank, and the hot water is exchanged with the internal solution by the water heater through the heating coil provided by the CO2 desorption unit 4, and at the same time, the hot water after the heat exchange returns to the water heater, which is realized as the CO2 desorption unit 4 heating.
  • the rich liquid in the CO 2 desorption unit 4 is heated, CO 2 desorbs and escapes from the rich liquid, and the circulation system uses CO 2 gas as a circulating working fluid. Gaseous CO 2 enters the CO 2 turbine 6 to do work, driving the generator 7 to generate electricity.
  • the lean liquid is decompressed through the pressure reducing valve 8, the first heat exchanger 2 exchanges heat with the rich liquid, and the second heat exchanger 5 exchanges heat with seawater to return to the CO2 absorption unit 1, and the external heat extractor 11 is used to remove it in time Heat of reaction in CO2 absorption unit 1.
  • the CO 2 gas expands and returns to the CO 2 absorption unit 1, and the CO 2 gas performs gas-liquid mass transfer with the lean liquid sprayed above the CO 2 absorption unit 1 by bubbling, and the CO 2 absorption process is carried out in the absorption unit .
  • the rich liquid is boosted by the circulating booster pump 3 and returns to the CO2 desorption unit 4 to complete the power generation cycle.
  • seawater is an ideal low-temperature cold source due to its huge reserves, low temperature, and small temperature fluctuations, and the system does not need to rely on other related project construction, so the economic investment is low.
  • the solar energy-based carbon dioxide gas cycle power generation device and method provided in this application example have the same structure as the application example 1, except that the second heat exchanger 5 and the external heat extractor 11 have an internal medium of large lake water or cold air.
  • the low-temperature cycle power generation device and method provided in this application example have basically the same structure as the application example 2, except that the heat of the heating device provided in the CO2 desorption unit 4 is provided by low-temperature geothermal heat or factory waste heat.
  • the CO2 absorption unit 1 can be a CO2 absorption tank or a CO2 absorption tower
  • the CO2 desorption unit 4 can also be a CO2 desorption tank or a CO2 desorption tower
  • specific equipment can be set according to requirements.

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Abstract

一种以二氧化碳气体为工质的低温循环发电系统和方法。采用2-甲基咪唑水溶液在低温、低压下吸收CO 2，在较高温度下吸收热量，释放出高压CO 2气体，通过透平机（6）膨胀对外做功发电。

Description

一种以二氧化碳气体为工质的低温循环发电系统和方法 技术领域
本发明涉及低品位热能发电技术领域，具体涉及一种以二氧化碳气体为工质的低温循环发电系统和方法。
背景技术
目前应用最广泛的发电方法为朗肯循环，然而在实际应用中主要存在以下两个方面问题。一是由于循环介质多采用低沸点化合物，因此需要设置冷凝器、蒸发器使工质发生相变，消耗能量较多，设备热负荷较大。另一方面，为提高朗肯循环热效率，常引入再热器实现二次等压加热过程，过热水蒸汽使得过热器和透平机等耐高温设备投资费用较高。
2-甲基咪唑属于咪唑类化合物，沸点267℃，因其低毒性、高化学稳定性、生产成本低等性质被广泛应用于缓蚀剂、气体分离等领域，常作为配体合成沸石咪唑类材料(ZIFs)。2-甲基咪唑对CO 2气体有着良好的吸收性能，因此可作为CO 2气体的吸收剂，此外在温度较高时(约80℃)溶液中的CO 2可以发生解吸过程，实现吸收剂的可循环利用。本发明利用低品位热能，如太阳能、地热能以及工厂低温废热等，只需为流体输送消耗较少的机械能，能够大幅度降低低温发电循环的能耗，具有安全环保、运行稳定、热效率高等优点。
发明内容
本发明的目的在于提供一种以二氧化碳气体为工质的低温循环发电系统和方法。该低温循环发电系统利用低品位热能提供热量，2-甲基咪唑水溶液对CO 2气体的吸收-解吸过程实现发电，相比于传统的低温朗肯循环发电，可实现太阳能热水、地热能以及工厂废热等低品位热源的高效利用，整体提高系统的稳定性与高效性。
为实现上述目的，本发明采用的以下技术方案：
本发明一方面提供一种以二氧化碳气体为工质的低温循环发电系统，该低温循环发电系统采用CO 2气体作为循环工质，2-甲基咪唑水溶液为吸收介质，包括：
CO 2吸收单元、第一换热器、循环增压泵、CO 2解吸单元、CO 2透平机和发电机；
所述CO 2吸收单元的出口经过所述第一换热器之后与所述循环增压泵的入口连接，所述循环增压泵的出口与所述CO 2解吸单元的入口连接，所述CO 2解吸单元的液体出口经过所述第一换热器之后与所述CO 2吸收单元的入口连接；所述CO 2解吸单元的气体出 口与所述CO 2透平机的入口连接，所述CO 2透平机的出口与所述CO 2吸收单元的入口连接，且所述CO 2透平机与所述发电机连接；所述CO 2解吸单元设置有加热装置，所述加热装置由低品位热源提供热量。
根据本发明的低温循环发电系统，优选地，所述低品位热源选自太阳能热水、地热或工厂低温废热。例如，所述加热装置为热水器，其加热水的热源为太阳能热水、地热或工厂低温废热等低品位热源；所述加热装置中的热水通过加热盘管为所述CO 2解吸单元提供热量。当采用太阳能热水时，所述加热装置为太阳能热水器。
根据本发明的低温循环发电系统，优选地，所述CO 2吸收单元设置有外取热器，用于及时移走反应的吸收热，使CO 2吸收过程体系温度稳定。
根据本发明的低温循环发电系统，优选地，所述外取热器的内部取热介质为冷却水。
根据本发明的低温循环发电系统，优选地，所述第一换热器为管壳式换热器；所述CO 2吸收单元的出口与所述第一换热器的管程入口连接，所述第一换热器的管程出口与所述循环增压泵的入口连接；所述CO 2解吸单元的液体出口与所述第一换热器的壳程入口连接，所述第一换热器的壳程出口与所述CO 2吸收单元的入口连接。
即，所述第一换热器的管程为富液(富CO 2的2-甲基咪唑水溶液)，壳程为贫液(也称解吸液)；二者在此进行换热。
根据本发明的低温循环发电系统，优选地，所述低温循环发电系统还包括第二换热器，所述第一换热器的壳程出口经过所述第二换热器之后与所述CO 2吸收单元的入口连接。贫液经过第一换热器与富液换热降温后进一步经过所述第二换热器冷却。
根据本发明的低温循环发电系统，优选地，所述第二换热器的内部换热介质为冷却水。
根据本发明的低温循环发电系统，优选地，所述CO 2解吸单元的液体出口与所述第一换热器之间的连接管线上设置有减压阀；所述CO 2解吸单元中解析后的贫液经所述减压阀减压、第一换热器和第二换热器冷却后回到CO 2吸收单元。
本发明另一方面提供一种以CO 2为工质的低温循环发电方法，其使用以上任一低温循环发电系统进行。
进一步的，该低温循环发电方法包括以下步骤：
在所述CO 2吸收单元中2-甲基咪唑水溶液吸收CO 2气体成为富液，富液经所述第一换热器与贫液换热升温后，经升压进入所述CO 2解吸单元；
所述低品位热源为所述CO 2解吸单元供热，使得CO 2气体从富液中解吸逸出，进入 所述CO 2透平机膨胀做功，带动所述发电机发电；解吸后的贫液经所述第一换热器与富液换热冷却后回到所述CO 2吸收单元。
根据本发明的低温循环发电方法，优选地，所述CO 2吸收单元的操作温度为20～40℃，操作压力0.2～0.3MPa。
根据本发明的低温循环发电方法，优选地，所述CO 2解吸单元的操作温度为80～120℃，操作压力为0.8～1.2MPa；通过循环增压泵将富液增压至此0.8～1.2MPa。
根据本发明的低温循环发电方法，优选地，所述2-甲基咪唑水溶液的浓度为30～60wt.％。
根据本发明的低温循环发电方法，优选地，所述CO 2透平机的出口压力为0.2～0.3MPa。
本发明提供的以二氧化碳气体为工质的低温循环发电系统和方法采用2-甲基咪唑水溶液在低温(20～40℃)、低压(0.2～0.3MPa)下吸收CO 2，在较高温度(80～120℃)下吸收热量，释放出高压(0.8～1.2MPa)CO 2气体，通过透平膨胀对外做功发电。由于CO 2的解吸温度在80℃左右，因此可以利用太阳能热水、地热或工厂低温废热作为解吸的热源，实现低温位循环发电。本发明的系统以CO 2为工质，2-甲基咪唑水溶液为吸收介质，利用太阳能热水、地热和工厂废热等低品位热源来发电，实现节能和碳减排。由于CO 2无毒、不易燃易爆，该循环比现有低温有机朗肯循环更为安全环保，热电效率也更高。
附图说明
图1为本发明一优选实施例中的以二氧化碳气体为工质的低温循环发电系统示意图。
图2为本发明一优选实施例中的海上太阳能驱动的二氧化碳气体循环发电系统示意图。
附图标记说明：
1、CO 2吸收单元；
2、第一换热器；
3、循环增压泵；
4、CO 2解吸单元；
5、第二换热器；
6、CO 2透平机；
7、发电机；
8、减压阀；
9、阀门；
10、太阳能热水器；
11、外取热器。
具体实施方式
为了更清楚地说明本发明，下面结合优选实施例对本发明做进一步的说明。本领域技术人员应当理解，下面所具体描述的内容是说明性的而非限制性的，不应以此限制本发明的保护范围。
本发明在此提供一优选实施例，如图1所示，一种以二氧化碳气体为工质的低温循环发电系统，该低温循环发电系统采用CO 2气体作为循环工质，2-甲基咪唑水溶液为吸收介质，包括：CO 2吸收单元1、第一换热器2、循环增压泵3、CO 2解吸单元4、第二换热器5、CO 2透平机6和发电机7。
所述CO 2吸收单元1的出口经过所述第一换热器2之后与所述循环增压泵3的入口连接，所述循环增压泵3的出口与所述CO 2解吸单元4的入口连接，所述CO 2解吸单元4的液体出口经过所述第一换热器2和第二换热器5之后与所述CO 2吸收单元1的入口连接；所述CO 2解吸单元4的气体出口与所述CO 2透平机6的入口连接，所述CO 2透平机6的出口与所述CO 2吸收单元1的入口连接，且所述CO 2透平机6与所述发电机7连接；所述CO 2解吸单元4设置有加热装置为其中的富液解吸提供热量，所述加热装置由低品位热源提供热量。所述低品位热源选自太阳能、地热或工厂低温废热。
此外，所述CO 2吸收单元1设置有外取热器11，用于及时移走反应的吸收热，使CO 2吸收过程体系温度稳定。所述外取热器11的内部取热介质为冷却水。所述第二换热器5的内部换热介质也为冷却水。
具体的，所述CO 2吸收单元1的出口与所述第一换热器2的管程入口连接，所述第一换热器2的管程出口与所述循环增压泵3的入口连接；所述CO 2解吸单元4的液体出口与所述第一换热器2的壳程入口连接，所述第一换热器2的壳程出口与所述第二换热器5的入口连接，第二换热器5的出口与CO 2吸收单元1的入口连接。即，所述第一换热器2的管程为富液，壳程为贫液；二者在此进行换热。
进一步的，所述CO 2解吸单元4的液体出口与所述第一换热器2之间的连接管线上设置有减压阀8；所述CO 2解吸单元4中解析后的贫液经所述减压阀8减压、第一换热 器2和第二换热器5冷却后回到CO 2吸收单元1。
利用图1的系统进行循环发电的流程包括：
在2-甲基咪唑水溶液循环回路中，CO 2吸收单元1中2-甲基咪唑水溶液吸收CO 2气体成为富液(富CO 2的吸收液)，富液经第一换热器2与贫液(也称解吸液)换热升温，通过循环增压泵3被压缩升压后进入CO 2解吸单元4进行CO 2的解吸，同时低品位热源如太阳能热水、地热能以及工厂废热等通过CO 2解吸单元4的加热装置为其提供热量。贫液由CO 2解吸单元4的液体出口经减压阀8、第一换热器2与第二换热器5进一步冷却，最终输送至CO 2吸收单元1进行CO 2气体的吸收过程，吸收过程产生的热量由外取热器11及时移走保持体系温度的稳定。富液在CO 2解吸单元4中进行解吸后，CO 2气体由CO 2解吸单元4顶部气体出口经过管线进入CO 2透平机6进行膨胀做功过程，同时发电机7实现循环装置的发电需求。膨胀后的CO 2气体回到CO 2吸收单元1，完成低温发电循环。
其中，所述CO 2吸收单元1的操作温度为20～40℃，操作压力0.2～0.3MPa。所述CO 2解吸单元4的操作温度为80～120℃，操作压力为0.8～1.2MPa。所述2-甲基咪唑水溶液的浓度为30～60wt.％。CO 2透平机6的出口压力为0.2～0.3MPa。
应用例1
本应用例的应用场景为海上太阳能驱动的二氧化碳气体循环发电，采用的气态循环工质为CO 2，CO 2吸收单元1和CO 2解吸单元4内的溶液为30～60wt.％的2-甲基咪唑水溶液，所述换热及取热装置，其内部介质均为海水。
如图2所示，本应用例的循环系统包括CO 2吸收单元1、第一换热器2、循环增压泵3、CO 2解吸单元4、第二换热器5、CO 2透平机6、发电机7、太阳能热水器10以及外取热器11。
CO 2吸收单元1的出口与第一换热器2的管程进口相连，第一换热器2的管程出口通过循环增压泵3与CO 2解吸单元4的入口相连，CO 2解吸单元4的液体出口通过第一换热器2壳程以及第二换热器5与CO 2吸收单元1的进口连接。同时CO 2解吸单元4的气体出口与CO 2透平机6入口相连，CO 2透平机6与发电机7连接，膨胀后的CO 2气体回到CO 2吸收单元1，完成动力循环。太阳能热水器10出口与CO 2解吸单元4设置的加热盘管进口连接，完成为其供热，连接管路上设置有阀门9。CO 2吸收单元1设置有外取热器11。
循环增压泵3将富液由0.2～0.3MPa升压至0.8～1.2MPa。经第一换热器2以及CO 2 解吸单元4的加热盘管，富液加热到80～120℃，CO 2吸收单元1内的吸收温度维持20～40℃。
使用本应用例的系统进行基于太阳能的二氧化碳气体循环发电过程包括：
太阳能热水器加热内部储箱中的水，热水由热水器通过CO 2解吸单元4设置的加热盘管与内部溶液换热，同时换热后的热水回到热水器，实现为CO 2解吸单元4的供热。CO 2解吸单元4中的富液加热后，CO 2从富液中解吸逸出，循环系统以CO 2气体作为循环工质。气态CO 2进入CO 2透平机6做功，带动发电机7发电。贫液经减压阀8减压、第一换热器2与富液换热及第二换热器5与海水换热回到CO 2吸收单元1，外取热器11用于及时移走CO 2吸收单元1内的反应热。
CO 2气体膨胀做功后回到CO 2吸收单元1，CO 2气体通过鼓泡的方式与CO 2吸收单元1上方喷淋的贫液进行气液传质，在吸收单元中进行CO 2的吸收过程。富液被循环增压泵3升压后回到CO 2解吸单元4，完成发电循环。
此外，在本应用例中，由于海水储量巨大且温度较低、温度波动较小，是较为理想的低温冷源，且该系统无需依赖于其他相关项目建设，经济投入较低。
应用例2
本应用例提供的基于太阳能的二氧化碳气体循环发电装置及方法与应用例1的结构相同，不同之处在于所述第二换热器5和外取热器11，其内部介质为大型湖泊水或冷空气。
应用例3
本应用例提供的低温循环发电装置及方法与应用例2结构基本相同，不同之处在于CO 2解吸单元4设置的加热装置的热量由低温的地热或工厂废热提供。
在本发明以上实施例和应用例中，所述CO 2吸收单元1可以为CO 2吸收罐或CO 2吸收塔，所述CO 2解吸单元4也均可以是CO 2解吸罐或CO 2解吸塔，具体设备可根据需求设置。
显然，本发明的上述实施例仅仅是为清楚地说明本发明所作的举例，而并非是对本发明的实施方式的限定，对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动，这里无法对所有的实施方式予以穷举，凡是属于本发明的技术方案所引伸出的显而易见的变化或变动仍处于本发明的保护范围之列。

Claims (14)

  1. 一种以二氧化碳气体为工质的低温循环发电系统，其中，该低温循环发电系统采用CO 2气体作为循环工质，2-甲基咪唑水溶液为吸收介质，包括：
    CO 2吸收单元(1)、第一换热器(2)、循环增压泵(3)、CO 2解吸单元(4)、CO 2透平机(6)和发电机(7)；
    所述CO 2吸收单元(1)的出口经过所述第一换热器(2)之后与所述循环增压泵(3)的入口连接，所述循环增压泵(3)的出口与所述CO 2解吸单元(4)的入口连接，所述CO 2解吸单元(4)的液体出口经过所述第一换热器(2)之后与所述CO 2吸收单元(1)的入口连接；所述CO 2解吸单元(4)的气体出口与所述CO 2透平机(6)的入口连接，所述CO 2透平机(6)的出口与所述CO 2吸收单元(1)的入口连接，且所述CO 2透平机(6)与所述发电机(7)连接；所述CO 2解吸单元(4)设置有加热装置。
  2. 根据权利要求1所述的低温循环发电系统，其中，所述加热装置由低品位热源提供热量，所述低品位热源选自太阳能热水、地热或工厂低温废热。
  3. 根据权利要求1所述的低温循环发电系统，其中，所述CO 2吸收单元(1)设置有外取热器(11)。
  4. 根据权利要求3所述的低温循环发电系统，其中，所述外取热器(11)的内部取热介质为冷却水。
  5. 根据权利要求1所述的低温循环发电系统，其中，所述第一换热器(2)为管壳式换热器；所述CO 2吸收单元(1)的出口与所述第一换热器(2)的管程入口连接，所述第一换热器(2)的管程出口与所述循环增压泵(3)的入口连接；
    所述CO 2解吸单元(4)的液体出口与所述第一换热器(2)的壳程入口连接，所述第一换热器(2)的壳程出口与所述CO 2吸收单元(1)的入口连接。
  6. 根据权利要求5所述的低温循环发电系统，其中，所述低温循环发电系统还包括第二换热器(5)，所述第一换热器(2)的壳程出口经过所述第二换热器(5)之后与所述CO 2吸收单元(1)的入口连接。
  7. 根据权利要求6所述的低温循环发电系统，其中，所述第二换热器(5)的内部换热介质为冷却水。
  8. 根据权利要求5所述的低温循环发电系统，其中，所述CO 2解吸单元(4)的液体出口与所述第一换热器(2)之间的连接管线上设置有减压阀(8)。
  9. 一种以二氧化碳气体为工质的低温循环发电方法，其使用权利要求1-8任一项所述低温循环发电系统进行。
  10. 根据权利要求9所述的低温循环发电方法，其中，该低温循环发电方法包括以下步骤：
    在所述CO 2吸收单元(1)中2-甲基咪唑水溶液吸收CO 2气体成为富液，富液经所述第一换热器(2)与贫液换热升温后，经升压进入所述CO 2解吸单元(4)；
    使用低品位热源为所述CO 2解吸单元(4)供热，使得CO 2气体从富液中解吸逸出，进入所述CO 2透平机(6)膨胀做功，带动所述发电机(7)发电；解吸后的贫液经所述第一换热器(2)与富液换热冷却后回到所述CO 2吸收单元(1)。
  11. 根据权利要求10所述的低温循环发电方法，其中，所述CO 2吸收单元(1)的操作温度为20～40℃，操作压力0.2～0.3MPa。
  12. 根据权利要求10所述的低温循环发电方法，其中，所述CO 2解吸单元(4)的操作温度为80～120℃，操作压力为0.8～1.2MPa。
  13. 根据权利要求10所述的低温循环发电方法，其中，所述2-甲基咪唑水溶液的浓度为30～60wt.％。
  14. 根据权利要求10所述的低温循环发电方法，其中，所述CO 2透平机(6)的出口压力为0.2～0.3MPa。
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CN113882921A (zh) * 2021-11-12 2022-01-04 中国石油大学(北京) 一种以二氧化碳气体为工质的低温循环发电系统和方法

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