CN113266441B - Method and system for controlling starting operation of supercritical carbon dioxide recompression power generation system - Google Patents

Method and system for controlling starting operation of supercritical carbon dioxide recompression power generation system Download PDF

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CN113266441B
CN113266441B CN202110409642.7A CN202110409642A CN113266441B CN 113266441 B CN113266441 B CN 113266441B CN 202110409642 A CN202110409642 A CN 202110409642A CN 113266441 B CN113266441 B CN 113266441B
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compressor
unit
control valve
turbine
inlet
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CN113266441A (en
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李新宇
杜柯江
董克用
秦政
林志民
王�锋
刘惠民
王林涛
虞翔宇
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Shanghai MicroPowers Co Ltd
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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
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D17/00—Regulating or controlling by varying flow
    • F01D17/10—Final actuators
    • 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
    • F01K13/02—Controlling, e.g. stopping or starting
    • 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
    • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
    • F01K7/32—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines using steam of critical or overcritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/16—Combinations of two or more pumps ; Producing two or more separate gas flows
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/02—Surge control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/02—Surge control
    • F04D27/0253—Surge control by throttling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/58—Cooling; Heating; Diminishing heat transfer
    • F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/46—Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines

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  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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  • Combustion & Propulsion (AREA)
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  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Control Of Turbines (AREA)
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Abstract

The application provides a method and a system for controlling the starting and the operation of a supercritical carbon dioxide recompression power generation system. The power generation system comprises a first unit, a second unit, a heat exchanger set, a control valve set and a monitoring device, wherein the first unit comprises a first compressor, a first turbine and a first motor, the second unit comprises a second compressor, a second turbine and a second motor, and the heat exchanger set comprises a first regenerator, a second regenerator, a cooler and a heat source. The control valve group is arranged between the outlet end of the compressor and the inlet end of the cooler and between the outlet end and the inlet end of the turbine and used for controlling the outlet pressure of the compressor, the inlet pressure of the turbine and the flow rate. The starting operation control method is characterized in that the first unit is started to a first target rotating speed to enable the generating power of the first unit to be larger than zero, and then the second unit is started to a second target rotating speed. The application realizes the flexible and stable start of recompression closed Brayton cycle, and ensures the stable and safe operation of the system.

Description

Method and system for controlling starting and running of supercritical carbon dioxide recompression power generation system
Technical Field
The application relates to the technical field of supercritical carbon dioxide recompression power generation, in particular to a method and a system for controlling the starting and running of a supercritical carbon dioxide recompression power generation system.
Background
The supercritical carbon dioxide power generation technology is a closed Brayton cycle technology taking supercritical carbon dioxide as a medium, has the advantages of high efficiency, small volume, wide range of applicable heat sources and the like compared with the traditional steam Rankine cycle technology, and is a novel power generation technology with great potential in the fields of nuclear power generation, solar power generation, geothermal power generation, fossil fuel power generation, waste heat utilization, ship power and the like.
Supercritical carbon dioxide power generation systems have a variety of cycle configurations, with the recompression cycle being the most efficient. Typical recompression cycle systems of the current literature generally include a main compressor, a recompressor, at least one turbine, a low temperature regenerator, a high temperature regenerator, and a cooler. And a part of working medium at the hot side outlet of the low-temperature regenerator is cooled by the cooler, compressed and boosted by the main compressor and then enters the cold side channel of the low-temperature regenerator, a part of working medium flows through the secondary compressor and is boosted and then is converged at the cold side outlet of the low-temperature regenerator, two parts of working medium enter the high-temperature regenerator and a heat source for heat exchange and temperature rise after being converged at the cold side outlet of the low-temperature regenerator, and the heated working medium sequentially flows through the turbine, the high-temperature regenerator and the low-temperature regenerator to form closed recompression cycle.
Because the matching coupling of a plurality of compressors with different characteristics, turbines and high-temperature and high-pressure heat exchange equipment exists in the carbon dioxide closed circulation system, the safety problems of compressor surge, heating surface overtemperature and the like are easily caused if the control is improper in the operation process, and thus, serious accident potential is formed. The operation control of the supercritical carbon dioxide closed recompression cycle power generation system is a big difficulty of the technology.
Therefore, the invention patent application with publication number CN112343680a discloses a supercritical carbon dioxide power generation system and an operation control method thereof, wherein by means of bypass valves arranged between the first compressor, the second compressor, the first turbine and the second turbine outlet, when emergency shutdown or load reduction working conditions occur, the output power and the rotating speed of a generator set are rapidly reduced, and the operation safety of the system is guaranteed.
However, the above solution has the following disadvantages:
1. the bypass valves of the first compressor and the second compressor are arranged between the inlet and the outlet, although rapid pressure relief can be realized, in the starting or running process of the unit, a positive feedback loop can be formed when the surge of the compressor is controlled by the bypass valves, so that the temperature of fluid in the compressor is rapidly increased, the control difficulty is increased, and even potential safety hazards can be caused;
2. the scheme does not provide a control method for starting and running the unit to prevent the compressor from surging under the condition of low flow working condition or the condition that the parallel compressors are not matched properly in the starting stage.
Disclosure of Invention
In order to solve the problems in the prior art, the application provides a method and a system for controlling the starting and the operation of the supercritical carbon dioxide recompression power generation system, which can be safely and stably started.
The following first explains the start-up operation control method of the supercritical carbon dioxide recompression power generation system provided by the present application. The supercritical carbon dioxide recompression power generation system comprises a first unit, a second unit, a control valve group and a monitoring device, wherein the first unit comprises a first compressor, a first turbine and a first motor which are coaxially arranged, and the second unit comprises a second compressor and a second motor which are coaxially arranged.
The control valve group comprises: the system comprises a first control valve arranged at the outlet end of the first compressor, a second control valve arranged at the outlet end of the second compressor, a third control valve arranged at the inlet end of the first turbine and a third control valve used for controlling the inlet pressure and the flow of the first turbine.
The monitoring device is used for monitoring the first unit, the second unit and the control valve group.
The startup operation control method comprises the following steps:
s1, starting the first unit to a first target rotating speed to enable the generating power of the first unit to be larger than zero;
and S2, starting the second unit to a second target rotating speed to complete system starting.
The first unit and the second unit are started in sequence, so that a complex system formed by devices with different characteristics is decoupled, the control difficulty is reduced, and the flexible, stable and safe starting of the system is realized.
Preferably, the step S1 includes the steps of:
s11, filling a carbon dioxide working medium into a system pipeline, adjusting the inlet temperature of the first compressor to an inlet temperature design value, and adjusting the inlet pressure of the first compressor to an inlet pressure design value;
s12, enabling the first control valve, the second control valve and the third control valve to be in a fully open state, and activating the control action of the monitoring device on the inlet pressure and the inlet temperature of the first compressor;
s13, gradually closing the first control valve after the rotating speed of the first unit is increased to a first intermediate rotating speed, and starting the heat source in the process; the first intermediate rotation speed is characterized in that the flow rate of the first compressor at the rotation speed is not less than the minimum starting flow rate required by the heat source;
s14, after the temperature of the working medium at the outlet of the heat source rises to the starting temperature of the first turbine, increasing the rotating speed of the first unit to a second intermediate rotating speed, and gradually closing the third control valve; the second intermediate rotation speed is less than the first target rotation speed;
and S15, after the third control valve is fully closed, increasing the rotating speed of the first unit to the first target rotating speed, and finishing the starting process of the first unit.
Preferably, the design value of the inlet temperature is 32-40 ℃, and the design value of the inlet pressure is 7.5-8.5MPa; the control target for the inlet temperature is 90% -120% of the inlet temperature design value and the control target for the inlet pressure is 95% -110% of the inlet pressure design value.
The control of the inlet temperature and the pressure ensures that the carbon dioxide working medium is always in a supercritical state and a certain redundancy is left.
Preferably, the first turbine start-up temperature is greater than 40 ℃ and less than 150 ℃. The starting temperature of the first turbine is set for two purposes, firstly, the carbon dioxide working medium is ensured to flow through the first turbine to complete the adiabatic expansion process and still keep above the critical temperature after acting; and secondly, abnormal phenomena such as unstable working characteristics, backflow and the like of the turbine caused by over-low temperature are prevented.
Preferably, the step S2 includes the steps of:
s22, increasing the rotating speed of the second unit to a fourth intermediate rotating speed, and gradually closing the second control valve to a partial opening degree; the fourth intermediate rotation speed is less than the second target rotation speed;
and S23, increasing the rotating speed of the second unit to a second target rotating speed.
Preferably, the partial opening is 0% to 80%.
The opening degree of the second control valve needs to be determined according to the matching condition of the system, and the second control valve can be completely closed under the condition of good matching, so that the overall efficiency of the system is improved. The second control valve may also be maintained at a certain opening degree in order to allow the system to operate more stably.
Preferably, the second assembly further comprises a second turbine coaxially arranged, and the control valve group further comprises a fourth control valve arranged between an inlet end and an outlet end of the second turbine for controlling the inlet pressure and flow rate of the second turbine; the step S2 further includes the steps before the step S22:
s21, increasing the rotating speed of the second unit to a third intermediate rotating speed, and gradually closing the fourth control valve; the third intermediate rotational speed is less than the fourth intermediate rotational speed.
The application provides a supercritical carbon dioxide recompression power generation system includes first unit, second unit, heat exchanger group, valves and monitoring device, first unit includes first compressor, first turbine and the first motor of coaxial setting, the second unit includes second compressor and the second motor of coaxial setting, the heat exchanger group includes first regenerator, cooler and heat source.
In the first unit, the first motor can be set as a starting integrated motor, or a generator is additionally arranged to form a supercritical carbon dioxide generator set. And the second compressor of the second unit forms a supercritical carbon dioxide recompression loop.
The inlet end of the first compressor is communicated with the outlet end of the cooler, and the inlet end of the second compressor is communicated with the inlet end of the cooler; the first heat regenerator is provided with a first hot side channel and a first cold side channel, the inlet end of the first hot side channel is communicated with the outlet end of the first turbine, the outlet end of the first hot side channel is respectively communicated with the inlet end of the cooler and the inlet end of the second compressor, the inlet end of the first cold side channel is communicated with the outlet end of the first compressor, and the outlet end of the first cold side channel is communicated with the inlet end of the first turbine through the heat source after being converged with the outlet end of the second compressor.
When the working medium at the outlet end of the first compressor passes through the first heat regenerator, the working medium and the working medium with higher temperature from the first turbine in the first hot side channel flow in the reverse direction and perform heat exchange, after preheating is realized, the working medium flows through a high-temperature heat source to further rise to the highest circulating temperature, and the heat source is an energy source of a power generation system. The high-temperature and high-pressure working medium flows through the first turbine to complete the expansion working process. The working medium at the outlet of the first turbine enters the first heat regenerator to release heat, and then a part of the working medium is directly led to the second compressor to be compressed; the other part of working medium flows through the cooler, then enters the first compressor to be compressed, then passes through the first heat regenerator to be converged with a part of working medium directly compressed by the second compressor, and flows to a heat source to form a recompression closed Brayton cycle.
The control valve group is arranged between the outlet ends of the first compressor and the second compressor and the inlet end of the cooler and between the outlet end and the inlet end of the first turbine and is used for controlling the outlet pressure of the first compressor and the second compressor and the inlet pressure and the flow of the first turbine.
Through the control of the opening of the control valve, the pressure difference of the inlet and the outlet of the compressor can be balanced, so that the compressor is far away from a surge area in a low-flow working state in the starting process. Meanwhile, the control valve arranged between the inlet and the outlet of the turbine can control the pressure difference between the inlet and the outlet of the turbine and the flow of the turbine, so that the output torque of the turbine is reduced, and the rotating speed of the unit is easy to control.
The monitoring device controls the starting of the first unit and the second unit by adopting the starting operation control method of the supercritical carbon dioxide recompression power generation system. Under the condition of ensuring that the carbon dioxide working medium is always in a supercritical state, the first unit and the second unit are started in sequence, and the stable starting of the system can be realized.
Preferably, the second unit further comprises a second turbine coaxially arranged, and the heat exchanger group further comprises a second regenerator, wherein the second regenerator is provided with a second hot side channel and a second cold side channel, an inlet end of the second turbine is communicated with an outlet end of the first turbine, an inlet end of the second hot side channel is communicated with an outlet end of the second turbine, and an outlet end of the second hot side channel is communicated with an inlet end of the first hot side channel; the inlet end of the second cold-side channel is communicated with the outlet end of the first cold-side channel and the outlet end of the second compressor respectively, and the outlet end of the second cold-side channel is communicated with the inlet end of the first turbine through the heat source.
In the supercritical carbon dioxide recompression cycle, the heat regenerator plays a great role in improving the cycle efficiency. Due to the drastic change of the specific heat of the carbon dioxide near the critical temperature, better heat exchange efficiency can be obtained by adopting a plurality of heat regenerators.
Preferably, the control valve group comprises: the system comprises a first control valve arranged between an outlet end of the first compressor and an inlet end of the cooler, an outlet pressure used for controlling the first compressor, a second control valve arranged between an outlet end of the second compressor and an inlet end of the cooler, an outlet pressure used for controlling the second compressor, a third control valve arranged between an inlet end and an outlet end of the first turbine, an inlet pressure and a flow used for controlling the first turbine, a fourth control valve arranged between an inlet end and an outlet end of the second turbine, an inlet pressure and a flow used for controlling the second turbine.
The technical effects of this application lie in:
1. by adopting the technical scheme provided by the invention, the phenomena of compressor surge, turbine reverse flow and the like which are not beneficial to system safety can be avoided when the power generation system is started, and the safe and stable starting of the system is ensured;
2. by the technical scheme provided by the invention, the decoupling of the starting processes of the two sets of units is realized, and compared with the scheme of starting simultaneously, the scheme reduces the control difficulty of the starting process, increases the freedom degree of system control, and can freely switch between simple cycle and recompression cycle;
3. by the technical scheme provided by the invention, the starting process is optimized, and the energy consumption of the power generation system in the starting process can be reduced;
4. the control valve at the outlet of the compressor is connected to the cooler instead of being directly connected with the outlet and the inlet of the compressor, so that the temperature of working media in the compressor can be prevented from being rapidly increased when the control valve is opened, and the control process of the system is more stable;
5. after the starting is finished, a balance point can be found between the operation stability and the efficiency of the system according to the matching condition between the system operation condition and the unit by controlling the opening of the second control valve.
Drawings
The present application is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a flow chart of a process for a supercritical carbon dioxide recompression power generation system according to a first embodiment;
FIG. 2 is a process flow diagram of a supercritical carbon dioxide recompression power generation system as in example two and example three;
description of reference numerals:
1. a first unit, 2, a second unit, 3, a heat exchanger unit, 4, a control valve unit, 5, a monitoring device, 11, a first compressor, 12, a first turbine, 13, a first motor, 21, a second compressor, 22, a second turbine, 23, a second motor, 31, a first regenerator, 32, a second regenerator, 33, a cooler, 34, a heat source, 41, a first control valve, 42, a second control valve, 43, a third control valve, 44, a fourth control valve, 311, a first hot side channel, 312, a first cold side channel, 321, a second hot side channel, 322, a second cold side channel.
Detailed Description
In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will describe the embodiments of the present application with reference to the accompanying drawings. For the sake of simplicity, only the parts relevant to the present application are schematically shown in the drawings, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "a" means not only "only one of this but also a case of" more than one ".
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. In this document, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
The first embodiment is as follows: a supercritical carbon dioxide recompression power generation system.
As shown in fig. 1, the supercritical carbon dioxide recompression power generation system of the present embodiment includes a first unit 1, a second unit 2, a heat exchanger unit 3, a control valve unit 4, and a monitoring device 5; the first unit 1 comprises a first compressor 11, a first turbine 12 and a first motor 13 which are coaxially arranged; the second unit 2 comprises a second compressor 21 and a second motor 23 which are coaxially arranged; the heat exchanger group 3 comprises a first regenerator 31, a second regenerator 32, a cooler 33 and a heat source 34.
The inlet end of the first compressor 11 communicates with the outlet end of the cooler 33, and the inlet end of the second compressor 21 communicates with the inlet end of the cooler 33.
The first regenerator 31 is provided with a first hot side passage 311 and a first cold side passage 312, the second regenerator 32 is provided with a second hot side passage 321 and a second cold side passage 322, an inlet end of the second hot side passage 321 is communicated with an outlet end of the first turbine 12, an outlet end of the second hot side passage 321 is communicated with an inlet end of the first hot side passage 311, and an outlet end of the first hot side passage 311 is respectively communicated with an inlet end of the cooler 33 and an inlet end of the second compressor 21.
The inlet end of the first cold-side duct 312 communicates with the outlet end of the first compressor 11, the outlet end of the second compressor 21 merges with the outlet end of the second cold-side duct 322, and the outlet end of the second cold-side duct 322 communicates with the inlet end of the first turbine 12 through the heat source 34.
In some embodiments, the second regenerator 32 may be omitted and only the first regenerator 31 is retained, in which case the outlet end of the first turbine 12 is communicated with the inlet end of the first hot side passage 311, and the outlet end of the first cold side passage 312 is communicated with the inlet end of the first turbine 12 through the heat source 34 after being merged with the outlet end of the second compressor 21. However, because the specific heat capacity of the supercritical carbon dioxide working medium of the cold side channel of the heat regenerator is larger than that of the working medium of the hot side channel, the working medium of the cold side channel can generate smaller temperature rise only by larger temperature difference between the hot side channel and the cold side channel, so that the problem of 'pinch point' of low heat transfer efficiency is caused, and the cycle efficiency of the system is also reduced. Therefore, in practical application, two heat regenerators are additionally adopted, and thermodynamic processes such as intermediate cooling, flow splitting, recompression and the like are added to improve the system efficiency.
The recompression-closed brayton cycle of this example consists of the following processes: when the working medium at the outlet end of the first compressor 11 passes through the first cold-side passage 312 and the second cold-side passage 322, the working medium flows reversely with the working medium with higher temperature from the first turbine 12 in the first hot-side passage 311 and the second hot-side passage 321 to generate heat exchange, the waste heat of the returned working medium is used for preheating and heating, and then the working medium flows through the high-temperature heat source 34 to further heat, so that the constant-pressure heating process is completed; the high-temperature and high-pressure working medium flows through the first turbine 12 to complete the adiabatic expansion working process; the working medium at the outlet of the first turbine 12 firstly enters the second heat regenerator 32 and the first heat regenerator 31 for heat release, and then a part of the working medium is directly led to the second compressor 21 to be compressed; the other part of working medium flows through the cooler 33, then enters the first compressor 11 to be compressed, then passes through the first heat regenerator 31 and then is merged with a part of working medium directly compressed by the second compressor 21, and the processes of constant pressure heat release and adiabatic compression are completed.
The control valve group 4 includes: a first control valve 41 disposed between the outlet end of the first compressor 11 and the inlet end of the cooler 33 for controlling the outlet pressure of the first compressor 11, a second control valve 42 disposed between the outlet end of the second compressor 21 and the inlet end of the cooler 33 for controlling the outlet pressure of the second compressor 21, a third control valve 43 disposed between the inlet end and the outlet end of the first turbine 12 for controlling the inlet pressure and the flow rate of the first turbine 12.
The monitoring device 5 is used for monitoring the first unit 1, the second unit 2, the heat exchanger unit 3 and the control valve group 4. In the starting process of the system, the monitoring device 5 controls the starting of the first unit 1 and the second unit 2 by adopting the following starting operation control method of the supercritical carbon dioxide recompression power generation system, and the method specifically comprises the following steps:
s1, starting a first unit 1 to a first target rotating speed to enable the generating power of the first unit to be larger than zero;
and S2, starting the second unit 2 to a second target rotating speed to complete the starting of the system.
The first target rotating speed and the second target rotating speed are respectively the minimum rotating speeds at which the first unit 1 and the second unit 2 can stably operate. When the first unit 1 reaches the first target rotating speed, the generating power of the first unit can reach more than 30% of the rated generating power of the first unit and keep stable operation, and at the moment, the second unit 2 is started again, so that the system control difficulty can be greatly reduced.
Example two: a supercritical carbon dioxide recompression power generation system.
As shown in fig. 2, in the present embodiment, based on the first embodiment, the second unit 2 further includes a second turbine 22 coaxially disposed, and the control valve group 4 further includes a fourth control valve 44 disposed between an inlet end and an outlet end of the second turbine 22. The outlet end of the first turbine 12 is connected to the inlet end of a second turbine 22, and the outlet end of the second turbine 22 is connected to the inlet end of a second hot side passage 321.
By providing a second turbine 22, the efficiency of the system can be further improved by the incorporation of high and low pressure turbines. Similarly, a more multistage unit including a compressor and a turbine, and a plurality of regenerators may be provided, and the implementation method and operation mode thereof are similar to those of the embodiment.
Example three: a method for controlling the starting and operation of a supercritical carbon dioxide recompression power generation system.
In this embodiment, the supercritical carbon dioxide recompression power generation system described in the second embodiment is taken as an example, and the start-up operation control method of the supercritical carbon dioxide recompression power generation system provided in this application is specifically described.
As shown in FIG. 2, the operating speed ranges of the first unit 1 and the second unit 2 are 20000rpm-30000rpm, and the rated power of the system is 2MW. The startup operation control method comprises the following steps:
s1, starting the first unit 1 to a first target rotating speed of 20000rpm to enable the generating power of the first unit 1 to reach more than 30% of the rated generating power of the first unit, and specifically comprising the following steps:
s11, filling a carbon dioxide working medium into a system pipeline, adjusting the inlet temperature of the first compressor 11 to the designed inlet temperature value of 32 ℃, and adjusting the inlet pressure of the first compressor 11 to the designed inlet pressure value of 7.5Mpa;
s12, enabling the first control valve 41, the second control valve 42, the third control valve 43 and the fourth control valve 44 to be in a fully open state, and activating the control action of the monitoring device 5 on the inlet pressure and the inlet temperature of the first compressor 11; the control range of the inlet temperature is 32-36 ℃, and the control range of the inlet pressure is 7.4-9.0Mpa;
s13, gradually closing the first control valve 41 after increasing the rotating speed of the first unit 1 to a first intermediate rotating speed of 12000 rpm; during which the heat source 34 is activated; the flow rate of the first compressor 11 at the first intermediate rotation speed is greater than the minimum start-up flow rate required for the heat source 34;
s14, after the temperature of the working medium at the outlet of the heat source 34 rises to the starting temperature of the first turbine 12 of 100 ℃, increasing the rotating speed of the first unit 1 to a second intermediate rotating speed of 15000rpm, and gradually closing the third control valve 43;
s15, after the third control valve 43 is fully closed, increasing the rotating speed of the first unit 1 to a first target rotating speed of 20000rpm, and completing the starting process of the first unit 1.
S2, starting the second unit 2 to a second target rotating speed of 20000rpm, and specifically comprising the following steps:
s21, increasing the rotating speed of the second unit 2 to a third intermediate rotating speed of 12000rpm, and gradually closing the fourth control valve 44;
s22, increasing the rotating speed of the second unit 2 to a fourth intermediate rotating speed of 15000rpm, and gradually closing the second control valve 42 to 20% of opening degree;
and S23, increasing the rotating speed of the second unit 2 to a second target rotating speed of 20000rpm to complete the starting of the system.
In the starting operation control process, the inlet temperature design value can be selected within the range of 32-40 ℃, the inlet pressure design value can be selected within the range of 7.5-8.5Mpa, the selection aim is to ensure that the carbon dioxide working medium is kept in a supercritical state, namely the temperature and the pressure of the carbon dioxide working medium are above the critical point (31.2 ℃ and 7.38 Mpa), and meanwhile, the design value is made to be a lower value, so that the system efficiency is higher. The specific values depend on the system design level and the system control level.
The control ranges of the inlet pressure and the inlet temperature of the first compressor 11 by the monitoring device 5 are related to the values of the above-mentioned design values, and the monitoring device 5 can realize the above-mentioned control by controlling the cooler 33 and the first control valve 41. To balance the control difficulty and system stability, the control target for the inlet pressure may be set to 95% -110% of the design inlet pressure value and the control target for the inlet temperature may be set to 90% -120% of the design inlet temperature value.
In order to ensure the stable operation of the system, after the system is started, the second control valve 42 can be kept at a certain opening, and the specific value needs to be determined according to the design level of the system and the matching level of the system, and the preferable value is 0-80%.
The foregoing is only a preferred embodiment of the present application and the technical principles employed, and various obvious changes, rearrangements and substitutions may be made without departing from the spirit of the application. Other advantages and effects of the present application will be readily apparent to those skilled in the art from the disclosure herein. The present application is capable of other and different embodiments and its several details are capable of modifications and variations in various respects, all without departing from the spirit of the present application. The features in the above embodiments and embodiments may be combined with each other without conflict. For example, in the supercritical carbon dioxide recompression electric power generation system of the present invention, the compressor may be provided with one or more turbines, the regenerator may be provided with one or more regenerators, the cooler may be provided with one or more coolers, and the first control valve, the second control valve, the third control valve, and the fourth control valve may be provided with one or more compressors. In the above embodiments, the number of each component is one and/or two, and the operation manner of the above embodiments is similar to that of the above embodiments.

Claims (10)

1. A starting operation control method of a supercritical carbon dioxide recompression power generation system comprises a first unit, a second unit, a control valve group and a monitoring device, wherein the first unit comprises a first compressor, a first turbine and a first motor which are coaxially arranged, and the second unit comprises a second compressor and a second motor which are coaxially arranged;
the control valve group comprises: a first control valve disposed at an outlet end of the first compressor for controlling an outlet pressure of the first compressor, a second control valve disposed at an outlet end of the second compressor for controlling an outlet pressure of the second compressor, a third control valve disposed at an inlet end of the first turbine for controlling an inlet pressure and a flow rate of the first turbine;
the monitoring device is used for monitoring the first unit, the second unit and the control valve group;
the method is characterized by comprising the following steps:
s1, starting the first unit to a first target rotating speed to enable the generating power of the first unit to be larger than zero;
s2, starting the second unit to a second target rotating speed to complete the starting of the system;
wherein, the step S2 specifically includes the steps of:
s22, increasing the rotating speed of the second unit to a fourth intermediate rotating speed, and gradually closing the second control valve to a partial opening degree; the fourth intermediate rotation speed is less than the second target rotation speed;
and S23, increasing the rotating speed of the second unit to a second target rotating speed.
2. The method for controlling start-up operation of a supercritical carbon dioxide recompression power generation system as recited in claim 1, wherein said step S1 comprises the steps of:
s11, filling a carbon dioxide working medium into a system pipeline, adjusting the inlet temperature of the first compressor to an inlet temperature design value, and adjusting the inlet pressure of the first compressor to an inlet pressure design value;
s12, enabling the first control valve, the second control valve and the third control valve to be in a fully open state, and activating the control action of the monitoring device on the inlet pressure and the inlet temperature of the first compressor;
s13, gradually closing the first control valve after increasing the rotating speed of the first unit to a first intermediate rotating speed, and starting a heat source in the process; the first intermediate rotation speed is characterized in that the flow rate of the first compressor at the rotation speed is not less than the minimum starting flow rate required by the heat source;
s14, after the temperature of the working medium at the heat source outlet rises to the starting temperature of the first turbine, increasing the rotating speed of the first unit to a second intermediate rotating speed, and gradually closing the third control valve; the second intermediate rotational speed is less than the first target rotational speed;
and S15, after the third control valve is fully closed, increasing the rotating speed of the first unit to the first target rotating speed, and finishing the starting process of the first unit.
3. The method for controlling the start-up operation of a supercritical carbon dioxide recompression power generation system as recited in claim 2,
the inlet temperature design value is 32-40 ℃, and the inlet pressure design value is 7.5-8.5MPa; the control target of the inlet temperature of the first compressor is 90-120% of the inlet temperature design value, and the control target of the inlet pressure of the first compressor is 95-110% of the inlet pressure design value.
4. The method for controlling start-up operation of a supercritical carbon dioxide recompression power generation system as recited in claim 3,
the first turbine start-up temperature is greater than 40 ℃ and less than 150 ℃.
5. The method for controlling start-up operation of a supercritical carbon dioxide recompression power generation system as claimed in any one of claims 1 to 4, wherein the first control valve is provided between an outlet port of the first compressor and an inlet port of a cooler, and the second control valve is provided between an outlet port of the second compressor and an inlet port of the cooler.
6. The method for controlling start-up operation of a supercritical carbon dioxide recompression power generation system as recited in claim 5, wherein,
the partial opening degree is 0-80%.
7. The method for controlling the start-up operation of a supercritical carbon dioxide recompression power generation system as recited in claim 6,
the second set further comprises a second turbine coaxially arranged, and the control valve set further comprises a fourth control valve arranged between the inlet end and the outlet end of the second turbine and used for controlling the inlet pressure and the flow of the second turbine; said step S2 further comprises, before step S22, the step of:
s21, increasing the rotating speed of the second unit to a third intermediate rotating speed, and gradually closing the fourth control valve; the third intermediate rotational speed is less than the fourth intermediate rotational speed.
8. A supercritical carbon dioxide recompression power generation system comprises a first unit, a second unit, a heat exchanger group, a control valve group and a monitoring device, and is characterized in that,
the first unit comprises a first compressor, a first turbine and a first motor which are coaxially arranged, the second unit comprises a second compressor and a second motor which are coaxially arranged, and the heat exchanger unit comprises a first heat regenerator, a cooler and a heat source;
the inlet end of the first compressor is communicated with the outlet end of the cooler, and the inlet end of the second compressor is communicated with the inlet end of the cooler;
the first heat regenerator is provided with a first hot-side channel and a first cold-side channel, an inlet end of the first hot-side channel is communicated with an outlet end of the first turbine, an outlet end of the first hot-side channel is respectively communicated with an inlet end of the cooler and an inlet end of the second compressor, an inlet end of the first cold-side channel is communicated with an outlet end of the first compressor, and an outlet end of the first cold-side channel and an outlet end of the second compressor are communicated with an inlet end of the first turbine through the heat source after being converged;
the control valve group includes: a first control valve disposed at an outlet end of the first compressor for controlling an outlet pressure of the first compressor, a second control valve disposed at an outlet end of the second compressor for controlling an outlet pressure of the second compressor, a third control valve disposed at an inlet end of the first turbine for controlling an inlet pressure and a flow rate of the first turbine;
the monitoring device controls the start of the first unit and the second unit by using the start operation control method of the supercritical carbon dioxide recompression power generation system as set forth in any one of claims 1 to 6.
9. The supercritical carbon dioxide recompression power generation system as recited in claim 8, wherein the second bank further comprises a second turbine disposed coaxially, and the heat exchanger bank further comprises a second recuperator, wherein:
the second regenerator is provided with a second hot side channel and a second cold side channel, the inlet end of the second hot side channel is communicated with the outlet end of the second turbine, the inlet end of the second turbine is communicated with the outlet end of the first turbine, and the outlet end of the second hot side channel is communicated with the inlet end of the first hot side channel;
the inlet end of the second cold-side channel is communicated with the outlet end of the first cold-side channel and the outlet end of the second compressor respectively, and the outlet end of the second cold-side channel is communicated with the inlet end of the first turbine through the heat source.
10. The supercritical carbon dioxide recompression power generation system as recited in claim 9, wherein the set of control valves further comprises a fourth control valve disposed between the inlet and outlet ends of the second turbine.
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