CN117514394A - Supercritical carbon dioxide power system and starting operation control method thereof - Google Patents
Supercritical carbon dioxide power system and starting operation control method thereof Download PDFInfo
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- CN117514394A CN117514394A CN202311558596.2A CN202311558596A CN117514394A CN 117514394 A CN117514394 A CN 117514394A CN 202311558596 A CN202311558596 A CN 202311558596A CN 117514394 A CN117514394 A CN 117514394A
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 128
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 64
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 28
- 239000002826 coolant Substances 0.000 claims description 63
- 230000001105 regulatory effect Effects 0.000 claims description 18
- 230000001276 controlling effect Effects 0.000 claims description 13
- 230000001502 supplementing effect Effects 0.000 claims description 13
- 230000008569 process Effects 0.000 abstract description 11
- 238000010248 power generation Methods 0.000 abstract description 8
- 238000001816 cooling Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
Classifications
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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
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- 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
- F01D19/00—Starting of machines or engines; Regulating, controlling, or safety means in connection therewith
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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
- 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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engine Equipment That Uses Special Cycles (AREA)
Abstract
The invention provides a supercritical carbon dioxide power system and a starting operation control method thereof, wherein the supercritical carbon dioxide power system is started primarily by taking a proper amount of gaseous carbon dioxide as a working medium, a pressure control unit and a temperature control unit are mutually matched to heat and boost the gaseous carbon dioxide to a supercritical state required by power generation of the system, meanwhile, the inlet pressure and the inlet temperature of a first compressor are monitored in real time, the working medium state in the system is controlled in real time according to the inlet pressure and the inlet temperature, excessive working medium is prevented from being filled before the starting, the working medium emission in the starting process is reduced, and the supercritical carbon dioxide power system is started stably and safely.
Description
Technical Field
The invention relates to the technical field of supercritical carbon dioxide power, in particular to a supercritical carbon dioxide power system and a starting operation control method thereof.
Background
The supercritical carbon dioxide power technology is a closed Brayton cycle technology taking supercritical carbon dioxide as a medium, and compared with the traditional steam Rankine cycle and other technologies, the technology has the advantages of high cycle efficiency, small volume, low cost, wide range of adaptive heat sources and the like, and is an emerging 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 systems typically include at least one compressor, one turbine, one regenerator, one heater, and one cooler. The supercritical carbon dioxide working medium is boosted in the compressor, enters the heater to absorb heat after the temperature is increased by the heat regenerator, enters the turbine to do work after absorbing heat, and returns to the inlet of the compressor after recycling the residual heat by the heat regenerator and the cooler to form closed circulation.
For a closed supercritical carbon dioxide power system, a certain amount of working medium needs to be filled into the system before starting. In the prior art, working medium in a power system needs to be filled to supercritical pressure before the power system is started. The density of the carbon dioxide under normal temperature and supercritical pressure conditions (normal starting working conditions) is usually 5-8 times that of the carbon dioxide under high temperature and supercritical pressure conditions (rated working conditions), which causes the requirement of filling the working mass required by the supercritical carbon dioxide power system far exceeding the rated state before starting, and the requirement of discharging a large amount of working medium to the outside in the starting process, thereby causing the waste of the working medium or the increase of the volume and the cost of the working medium storage tank.
Disclosure of Invention
Aiming at the problems that a large amount of working media are required to be charged and discharged repeatedly in the starting process of a supercritical carbon dioxide power system in the prior art, the invention aims to provide the supercritical carbon dioxide power system and a starting operation control method thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
a supercritical carbon dioxide power system comprising: the power unit comprises a first compressor, a first heat regenerator, a heater, a turbine, a cooler, a turbine bypass valve and a working medium discharge valve; the first regenerator is provided with a first hot side inlet, a first hot side outlet, a first cold side inlet and a first cold side outlet; the outlet of the first compressor, the first cold side inlet, the first cold side outlet, the heater, the turbine, the first hot side inlet, the first hot side outlet, the cooler, and the inlet of the first compressor are sequentially and cyclically connected; the input end of the turbine bypass valve is arranged on a pipeline between the heater and the turbine, the output end of the turbine bypass valve is arranged on a pipeline between the turbine and the first hot side inlet, and the turbine bypass valve is used for adjusting the inlet temperature and the inlet pressure of the turbine; the turbine bypass valve and the cooler are respectively and electrically connected with the temperature control unit, the temperature control unit controls the operation state of the cooler according to the inlet temperature of the first compressor, and the temperature control unit controls the operation state of the turbine bypass valve according to the inlet temperature of the turbine; the input end of the working medium discharge valve is connected with the outlet of the cooler or the outlet of the first compressor, and the output end of the working medium discharge valve is connected with the external atmosphere; the working medium discharge valve is electrically connected with the pressure control unit, and the pressure control unit controls the operation state of the working medium discharge valve according to the inlet pressure of the first compressor; the working medium of the internal circulation is gaseous carbon dioxide when the power unit is started.
In some embodiments, the power unit further comprises: the second heat regenerator, the second compressor and the motor are coaxially arranged, and the motor is used for driving the second compressor to run; the second heat regenerator is provided with a second hot side inlet, a second hot side outlet, a second cold side inlet and a second cold side outlet; the outlet of the turbine, the second hot side inlet, the second hot side outlet, the first hot side inlet, the first hot side outlet and the inlet of the cooler are sequentially connected; the first hot side outlet, the second compressor, the second cold side inlet, the second cold side outlet and the inlet of the heater are sequentially connected.
In some embodiments, the power unit further comprises: the working medium storage tank is used for supplementing working medium to the power unit, the outlet of the working medium storage tank is connected with the inlet of the working medium supplementing pipeline, and the outlet of the working medium supplementing pipeline is arranged on the pipeline between the cooler and the first compressor; the working medium replenishing pipeline is provided with a working medium replenishing valve, and the working medium replenishing valve is electrically connected with the pressure control unit.
In some embodiments, the cooler is provided with a coolant flow channel, and the power unit further comprises a coolant input pipeline and a coolant output pipeline, wherein the coolant input pipeline and the coolant output pipeline are respectively connected with two ends of the coolant flow channel; the coolant input pipeline is provided with a coolant regulating valve which is used for controlling the flow of the coolant flowing through the coolant flow channel; the coolant regulating valve is electrically connected with the temperature control unit.
The invention also provides a starting operation control method of the supercritical carbon dioxide power system, which is applied to the supercritical carbon dioxide power system and is characterized by comprising the following steps:
s1, filling a certain mass of gaseous carbon dioxide working medium into the power unit, and starting the first compressor, the first heat regenerator, the heater and the cooler;
s2, the pressure control unit controls the inlet pressure of the first compressor to be larger than or equal to a target pressure;
the temperature control unit controls an inlet temperature of the first compressor to a first target temperature, and the temperature control unit controls an inlet temperature of the turbine to a second target temperature; and adjusting the rotating speed of the power unit to ensure that the output power of the power unit is greater than zero, and completing the starting of the supercritical carbon dioxide power system.
In some embodiments, in the step S2, the specific step of controlling the inlet pressure of the first compressor to be greater than or equal to the target pressure by the pressure control unit is: when the inlet pressure of the first compressor is smaller than the target pressure, the pressure control unit controls the working medium discharge valve to be in a closed state, and the temperature control unit controls the inlet temperature of the first compressor to be larger than or equal to the first target temperature.
In some embodiments, in the step S2, the specific step of controlling the inlet temperature of the first compressor to the first target temperature by the temperature control unit is: reducing a coolant flow through the chiller when an inlet temperature of the first compressor is less than the first target temperature; when the inlet temperature of the first compressor is greater than the first target temperature, the coolant flow through the chiller is increased.
In the step S2, the specific step of controlling the inlet temperature of the turbine to the second target temperature by the temperature control unit is: when the inlet temperature of the turbine is smaller than the second target temperature, the temperature control unit controls the turbine bypass valve to be in an open state, and working medium at the outlet of the heater enters the first hot side inlet; when the inlet temperature of the turbine is greater than or equal to the second target temperature, the temperature control unit controls the turbine bypass valve to be in a closed state, and at the moment, working medium at the outlet of the heater enters the turbine to do work.
In some embodiments, the target pressure is 7.6MPa; the first target temperature is 33 ℃; the second target temperature is 200 ℃.
In some embodiments, in the step S1, the gaseous carbon dioxide working medium has a pressure of 2-6MPa and a mass of m 0 The method comprises the steps of carrying out a first treatment on the surface of the Setting the rated working medium mass of the power unit under the rated working condition as m 1 0.6m 1 ≤m 0 ≤1.2m 1 。
In some embodiments, the inlet pressure of the first compressor is provided with an upper limit protection value P1, the upper limit protection value P1 being 8.6-9MPa; when the inlet pressure of the first compressor exceeds the upper limit protection value P1, the pressure control unit controls the working medium discharge valve to be opened so as to discharge part of working medium and reduce the pressure in the power unit.
Compared with the prior art, the supercritical carbon dioxide power system and the starting operation control method thereof provided by the invention have the following beneficial effects:
(1) Compared with the conventional method of filling supercritical carbon dioxide working medium, the supercritical carbon dioxide power system provided by the invention is started initially by taking a proper amount of gaseous carbon dioxide as working medium, and the pressure control unit and the temperature control unit are matched with each other to raise the temperature and boost the gaseous carbon dioxide to a supercritical state required by power generation of the system, so that excessive working medium is prevented from being filled before starting, and the working medium emission in the starting process is reduced;
(2) The start operation control method provided by the invention can monitor the inlet pressure and the inlet temperature of the first compressor in real time, and control the working medium state in the system in real time according to the inlet pressure and the inlet temperature, so that the risk brought to the operation of the compressor due to the inlet of the first compressor entering the liquid phase zone can be avoided, the working medium supplementing amount in the start process is greatly reduced, and the stable start of the supercritical carbon dioxide power system is realized.
Drawings
The above features, technical features, advantages and implementation of the present invention will be further described in the following description of preferred embodiments with reference to the accompanying drawings in a clear and easily understood manner.
FIG. 1 is a schematic diagram of a supercritical carbon dioxide power system according to the present invention;
fig. 2 is a schematic structural diagram of a supercritical carbon dioxide power system according to another embodiment of the present invention.
Reference numerals illustrate:
1-a first compressor;
2-a first regenerator; 201—a first hot side inlet; 202—a first hot side outlet; 203-a first cold side inlet; 204—a first cold side outlet;
3-a heater; 4-a turbine; 5-a cooler; 6-a turbine bypass valve; 7-a working medium discharge valve; 8-a pressure control unit; 9-a temperature control unit; 10-a second compressor; 11-a motor;
12-a second regenerator; 121-a second hot side inlet; 122-a second hot side outlet; 123-second cold side inlet; 124-a second cold side outlet;
13-working medium storage tank; 14-working medium replenishing valve; 15-a coolant inlet line; 16-a coolant outlet line; 17-coolant regulating valve.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will explain the specific embodiments of the present invention with reference to the accompanying drawings. It is evident that the drawings in the following description are only examples of the invention, from which other drawings and other embodiments can be obtained by a person skilled in the art without inventive effort.
For simplicity of the drawing, only the parts relevant to the invention are schematically shown in each drawing, and they do not represent the actual structure thereof as a product. Additionally, in order to simplify the drawing for ease of understanding, components having the same structure or function in some of the drawings are shown schematically with only one of them, or only one of them is labeled. Herein, "a" means not only "only this one" but also "more than one" case.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
In this context, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, unless explicitly stated or limited otherwise; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, in the description of the present application, the terms "first," "second," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.
Example 1
As shown in fig. 1, the present invention provides a supercritical carbon dioxide power system, comprising: a power unit, a pressure control unit and a temperature control unit. Specific:
the power unit comprises a first compressor 1, a first regenerator 2, a heater 3, a turbine 4, a cooler 5, a turbine bypass valve 6 and a working medium discharge valve 7.
The first regenerator 2 comprises a hot side provided with a first hot side inlet 201 and a first hot side outlet 202 and a cold side provided with a first cold side inlet 203 and a first cold side outlet 204.
The outlet of the first compressor 1, the first cold side inlet 203, the first cold side outlet 204, the heater 3, the turbine 4, the first hot side inlet 201, the first hot side outlet 202, the cooler 5 and the inlet of the first compressor 1 are sequentially and circularly connected, when working medium at the outlet of the first compressor 1 flows into the cold side of the first regenerator 2, heat exchange occurs with the reverse flow of high-temperature working medium from the turbine 4, the waste heat of the backflow working medium is utilized to preheat and raise the temperature, the working medium flows out from the first cold side outlet 204 to the heater 3, and enters the turbine 4 to perform expansion work after being heated to a certain temperature, then flows into the hot side of the first regenerator 2 to exchange heat, and then is cooled by the cooler 5 to return to the first compressor 1 for compression.
The input end of the turbine bypass valve 6 is arranged on a pipeline between the outlet of the heater 3 and the inlet of the turbine 4, the output end of the turbine bypass valve 6 is arranged on a pipeline between the turbine 4 and the first hot side inlet 201, the turbine bypass valve 6 can be used for adjusting the inlet temperature, inlet pressure and inlet flow of the turbine 4, at the beginning of starting the power system, the turbine bypass valve 6 is firstly opened, the turbine 4 is in a shutdown state at the moment, the heater 3 heats working medium and circulates in the system, and when the inlet temperature and inlet pressure of the turbine 4 reach the starting temperature and pressure of the turbine 4, the turbine bypass valve 6 is closed again, and the turbine 4 is opened, so that stable starting of the system is realized.
And the turbine bypass valve 6 regulates the inlet flow to the turbine 4 in such a way that: when the opening degree of the turbine bypass valve 6 increases, the flow rate of the bypass increases, thereby decreasing the flow rate flowing into the turbine 4, whereas when the opening degree of the turbine bypass valve 6 decreases, the flow rate of the bypass decreases accordingly, and the flow rate flowing into the turbine 4 increases.
The turbine bypass valve 6 and the cooler 5 are electrically connected to a temperature control unit 9, respectively, the temperature control unit 9 monitors the inlet temperature of the first compressor 1 in real time and controls the operation state of the cooler 5 according to the inlet temperature of the first compressor 1, and the temperature control unit 9 controls the operation state of the turbine bypass valve 6 according to the inlet temperature of the turbine 4.
Specifically, the temperature control unit 9 controls the operation state of the cooler 5 including: the start-stop of the cooler 5 and the cooling effect of the cooler 5 are controlled, and the cooling effect of the cooler 5 is achieved by the coolant flow in the cooler 5.
The control of the operating state of the turbine bypass valve 6 by the temperature control unit 9 includes: the opening and closing and opening of the turbine bypass valve 6 are controlled.
The input end of the working medium discharge valve 7 is connected with the outlet of the cooler 5 or the outlet of the first compressor 1, the output end of the working medium discharge valve 7 is connected with the external atmosphere, and when the pressure in the power system is too high, a certain amount of working medium can be discharged to the outside through the working medium discharge valve 7.
In particular, the input end of the working substance discharge valve 7 may be in communication with the outlet of the cooler 5, with the inlet of the first compressor 1, or with the outlet of the first compressor 1.
The working medium discharge valve 7 is electrically connected with the pressure control unit 8, and the pressure control unit 8 monitors the inlet pressure of the first compressor 1 in real time and controls the operation state of the working medium discharge valve 7 according to the inlet pressure of the first compressor 1, namely, controls the opening and closing and the opening of the working medium discharge valve 7.
The working medium of the internal circulation is gaseous carbon dioxide when the power unit is started.
In some embodiments, the cooler 5 is provided with a working fluid channel and a coolant channel, the power unit further comprises a coolant input pipeline 15 and a coolant output pipeline 16, the coolant input pipeline 15 and the coolant output pipeline 16 are respectively connected with two ends of the coolant channel, and the coolant enters the coolant channel through the coolant input pipeline 15, cools the working fluid flowing through the working fluid channel, and is discharged from the coolant output pipeline 16.
Preferably, a coolant reservoir may be provided, to which the inlet of the coolant supply line 15 and the outlet of the coolant outlet line 16 are connected in each case for circulating coolant into the coolant channels.
Further, a coolant regulating valve 17 is provided on the coolant input line 15, and the coolant regulating valve 17 is used for controlling the flow of the coolant flowing through the coolant flow passage, i.e. the coolant regulating valve 17 controls the cooling effect of the cooler 5.
Preferably, the coolant control valve 17 is electrically connected to the temperature control unit 8.
When the inlet temperature of the first compressor 1 is higher, the temperature control unit 8 controls the opening of the coolant regulating valve 17 to increase, increases the flow rate of the coolant flowing into the coolant flow passage, accelerates the temperature of the cooling medium, thereby reducing the inlet temperature of the first compressor 1, and conversely, reduces the opening of the coolant regulating valve 17, and reduces the flow rate of the coolant.
In some embodiments, as shown in fig. 2, the power unit further comprises: the second regenerator 12, the second compressor 10 and the motor 11 are coaxially arranged, and the motor 11 is used for driving the second compressor 10 to operate.
The second regenerator 12 comprises a hot side provided with a second hot side inlet 121 and a second hot side outlet 122 and a cold side provided with a second cold side inlet 123 and a second cold side outlet 124.
The outlet of the turbine 4, the second hot side inlet 121, the second hot side outlet 122, the first hot side inlet 201, the first hot side outlet 202 and the inlet of the cooler 5 are sequentially connected, and the high-temperature working medium flowing out of the turbine 4 sequentially flows through the hot side of the second regenerator 12 and the hot side of the first regenerator 2, is cooled by the cooler 5, and then enters the first compressor 1 for compression.
The first hot side outlet 202, the second compressor 10, the second cold side inlet 123, the second cold side outlet 124 and the inlet of the heater 3 are sequentially connected, and a part of working medium flowing out of the first hot side outlet 202 is shunted into the second compressor 10 for compression, flows through the cold side of the second regenerator 12 and enters the heater 3 for heating. Preferably, before the heater 3 is started, the starting motor 11 drives the second compressor 10 to operate, so that the working medium flow rate when the heater 3 is started is improved, on one hand, the safety of a heat exchange surface inside the heater 3 is protected, on the other hand, the working medium flow rate flowing into the heater 3 is improved, the flow rate of a high-temperature working medium is further increased, the heat exchange effect of the heat regenerator is improved, and the system is enabled to be heated up rapidly at the initial stage of starting.
In some embodiments, the power unit further comprises: the working medium storage tank 13 and the working medium supplementing pipeline are used for supplementing working medium to the power unit, carbon dioxide is stored in the working medium storage tank 13, an outlet of the working medium storage tank 13 is connected with an inlet of the working medium supplementing pipeline, and an outlet of the working medium supplementing pipeline is arranged on a pipeline between the cooler 5 and an inlet of the first compressor.
Preferably, the output end of the working medium discharge valve 7 can be communicated with the working medium storage tank 13, and the working medium discharged out of the system is stored by the working medium storage tank 13, so that the waste caused by direct discharge is avoided.
Further, a working medium replenishment valve 14 is arranged on the working medium replenishment pipe, and the working medium replenishment valve 14 is electrically connected with the pressure control unit 8 to control the operation state of the working medium replenishment valve 14, namely, to control the opening and closing and the opening of the working medium replenishment valve 14.
When the system is started, the working medium supplementing valve 14 is always in a closed state, and working medium is not supplemented into the system. When the pressure control unit 8 monitors that the inlet pressure of the first compressor 1 is low, the working medium replenishing valve 14 can be controlled to be opened, a certain amount of working medium is input into the power unit, and the working medium enters the first compressor 1 for pressurization.
Example 2
On the basis of embodiment 1, the invention also provides a starting operation control method of the supercritical carbon dioxide power system, which is applied to the supercritical carbon dioxide power system and comprises the following steps:
s1, filling a certain mass of gaseous carbon dioxide working medium into the power unit, and starting the first compressor 1, the first heat regenerator 2, the heater 3 and the cooler 5.
S2, the pressure control unit 8 controls the inlet pressure of the first compressor 1 to be larger than or equal to the target pressure;
the temperature control unit 9 controls the inlet temperature of the first compressor 1 to a first target temperature, and the temperature control unit 9 controls the inlet temperature of the turbine 4 to a second target temperature.
And (3) regulating the rotating speed of the power unit to ensure that the output power of the power unit is greater than zero, and completing the starting of the supercritical carbon dioxide power system.
In some embodiments, in step S1, the gaseous carbon dioxide working medium has a pressure of 2-6MPa and a mass of m 0 。
Setting the rated working medium mass of the power unit under the rated working condition as m 1 0.6m 1 ≤m 0 ≤1.2m 1 。
In some embodiments, the target pressure is 7.6MPa, the first target temperature is 33 ℃, and the second target temperature is 200 ℃.
In some embodiments, in step S2, the specific steps of the pressure control unit 8 controlling the inlet pressure of the first compressor 1 to be greater than or equal to the target pressure (7.6 MPa) are:
when the inlet pressure of the first compressor 1 is smaller than the target pressure (7.6 MPa), the pressure control unit 8 controls the working substance discharge valve 7 to be in the closed state, and the temperature control unit 9 controls the inlet temperature of the first compressor 1 to be greater than or equal to the first target temperature (33 ℃).
In step S2, the specific steps of the temperature control unit 9 controlling the inlet temperature of the first compressor 1 to the first target temperature (33 ℃) are:
when the inlet temperature of the first compressor 1 is less than the first target temperature (33 c), the flow rate of the coolant through the cooler 5 is reduced, that is, the temperature control unit 9 controls the opening degree of the coolant regulating valve 17 to be reduced, and the cooling rate of the working medium is slowed down.
When the inlet temperature of the first compressor 1 is higher than the first target temperature (33 c), the flow rate of the coolant through the cooler 5 is increased, that is, the opening degree of the coolant regulating valve 17 is controlled by the temperature control unit 9 to be increased, and the cooling rate of the working medium is accelerated.
Further, in step S2, the specific step of controlling the inlet temperature of the turbine 4 to the second target temperature (200 ℃) by the temperature control unit 9 is:
when the inlet temperature of the turbine 4 is less than the second target temperature (200 ℃), the temperature control unit 9 controls the turbine bypass valve 6 to be in an open state, and at the moment, working medium at the outlet of the heater 3 enters the first hot side inlet 201 to continue circulation;
if the second regenerator 12 is provided, the working medium at the outlet of the heater 3 enters the second hot side inlet 121, flows through the hot side of the second regenerator 12 and the hot side of the first regenerator 2 in sequence, and continues to circulate.
When the inlet temperature of the turbine 4 is greater than or equal to the second target temperature (200 ℃), the temperature control unit 9 controls the turbine bypass valve 6 to be in a closed state, at this time, the working medium at the outlet of the heater 3 reaches the starting temperature of the turbine, directly enters the turbine 4 to do work, and the working medium with high temperature and low pressure after doing work enters the hot side of the first regenerator 2 or sequentially enters the hot side of the second regenerator 12 and the hot side of the first regenerator 2 to continue to participate in circulation.
In the prior art, when a supercritical carbon dioxide power system is started, working media in a pipeline are in a supercritical state, and the pressure is usually between 7.4 and 8.5 MPa. At this time, the quality of the working medium in the system is far greater than that of the working medium in the rated state, and a large amount of working medium needs to be discharged in the starting process, so that the working medium is wasted. Before the system is started, the invention is filled with gaseous carbon dioxide, the turbine 4 is closed, the turbine bypass valve 6, the first compressor 1, the first heat regenerator 2 (and the second heat regenerator 12) and the heater 3 are opened, the pressure regulating unit 8 and the temperature regulating unit 9 respectively monitor the inlet temperature and the inlet pressure of the first compressor 1 in real time, and the operation states of the turbine bypass valve 6, the working medium discharge valve 7, the coolant regulating valve 15 and the working medium replenishing valve 14 are controlled.
The gaseous carbon dioxide is pressurized and heated to a supercritical state after a period of circulation, when the inlet temperature of the turbine 4 is higher than 200 ℃, the turbine bypass valve 6 is closed, the turbine 4 is opened, the rotating speed of the power unit is regulated, the output power of the power unit is higher than zero, and the stable starting of the supercritical carbon dioxide power system is completed.
The significance of the temperature and pressure control strategy is that the inlet temperature and the inlet pressure of the first compressor 1 are not precisely controlled in the starting process, and the inlet temperature and the pressure of the first compressor 1 are allowed to change under the action of other factors (such as rotating speed, heat source outlet temperature and the like), so that the system becomes more elastic, and the working medium discharge requirement in the starting process is reduced to the greatest extent; and meanwhile, the variation ranges of the inlet pressure and the inlet temperature are specially regulated and controlled, so that the stability and the safety of the starting process are ensured.
In addition, in the starting process of the system, the inlet and outlet pressure or temperature of the first compressor 1 exceeds the limit value or other factors to cause great potential safety hazards, and the risk of working in a liquid phase interval due to the fact that the inlet temperature of the first compressor is too low can occur, the blades and the shafting of the first compressor 1 are irreversibly damaged, and therefore the supercritical carbon dioxide power generation system is stopped. The temperature control unit 9 of the present invention can ensure that the inlet temperature of the first compressor 1 is higher than the critical temperature of carbon dioxide during the system start-up process, so as to avoid the risk of liquid phase operation.
In some embodiments, the inlet pressure of the first compressor 1 is provided with an upper limit protection value P1, the upper limit protection value P1 being 8.6-9MPa.
When the pressure control unit 8 monitors that the inlet pressure of the first compressor 1 exceeds the upper limit protection value P1, the pressure control unit 8 immediately controls the working medium discharge valve 7 to be opened so as to discharge part of working medium, and the system is protected from overpressure risk.
The supercritical carbon dioxide power system and the start-up operation control method thereof provided by the invention are described in specific examples below.
Example 3
As shown in fig. 1, the working substance discharge valve 7 has an input end connected to the inlet of the first compressor 1 and an output end connected to the atmosphere.
The supercritical carbon dioxide power system starts to charge a proper amount of gaseous carbon dioxide into the power unit before starting, so that the pressure of the system is 5MPa.
During start-up, the inlet temperature of the first compressor 1 is controlled above 35 ℃.
The upper limit guard value P1 was set to 8.7MPa.
Example 4
As shown in fig. 2, the supercritical carbon dioxide power system is provided with a second compressor 10, a motor 11 and a second regenerator 12.
The input end of the working medium discharge valve 7 is communicated with the outlet of the first compressor 1, and the output end is communicated with the working medium storage tank 13.
The supercritical carbon dioxide power system starts to charge a proper amount of gaseous carbon dioxide into the power unit before starting, so that the pressure of the system is 5.5MPa.
During start-up, the inlet temperature of the first compressor 1 is controlled above 36 ℃.
The upper limit guard value P1 was set to 9MPa.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A supercritical carbon dioxide power system, comprising:
a power unit, a pressure control unit and a temperature control unit,
the power unit comprises a first compressor, a first heat regenerator, a heater, a turbine, a cooler, a turbine bypass valve and a working medium discharge valve;
the first regenerator is provided with a first hot side inlet, a first hot side outlet, a first cold side inlet and a first cold side outlet;
the outlet of the first compressor, the first cold side inlet, the first cold side outlet, the heater, the turbine, the first hot side inlet, the first hot side outlet, the cooler, and the inlet of the first compressor are sequentially and cyclically connected;
the input end of the turbine bypass valve is arranged on a pipeline between the heater and the turbine, the output end of the turbine bypass valve is arranged on a pipeline between the turbine and the first hot side inlet, and the turbine bypass valve is used for adjusting the inlet temperature and the inlet pressure of the turbine;
the turbine bypass valve and the cooler are respectively and electrically connected with the temperature control unit, the temperature control unit controls the operation state of the cooler according to the inlet temperature of the first compressor, and the temperature control unit controls the operation state of the turbine bypass valve according to the inlet temperature of the turbine;
the input end of the working medium discharge valve is connected with the outlet of the cooler or the outlet of the first compressor, and the output end of the working medium discharge valve is connected with the external atmosphere;
the working medium discharge valve is electrically connected with the pressure control unit, and the pressure control unit controls the operation state of the working medium discharge valve according to the inlet pressure of the first compressor;
the working medium of the internal circulation is gaseous carbon dioxide when the power unit is started.
2. The supercritical carbon dioxide power system according to claim 1, wherein,
the power unit further includes: the second heat regenerator, the second compressor and the motor are coaxially arranged, and the motor is used for driving the second compressor to run;
the second heat regenerator is provided with a second hot side inlet, a second hot side outlet, a second cold side inlet and a second cold side outlet;
the outlet of the turbine, the second hot side inlet, the second hot side outlet, the first hot side inlet, the first hot side outlet and the inlet of the cooler are sequentially connected;
the first hot side outlet, the second compressor, the second cold side inlet, the second cold side outlet and the inlet of the heater are sequentially connected.
3. The supercritical carbon dioxide power system according to claim 1, wherein,
the power unit further includes: a working medium storage tank and a working medium supplementing pipeline for supplementing working medium to the power unit,
the outlet of the working medium storage tank is connected with the inlet of the working medium supplementing pipeline, and the outlet of the working medium supplementing pipeline is arranged on a pipeline between the cooler and the first compressor;
the working medium replenishing pipeline is provided with a working medium replenishing valve, and the working medium replenishing valve is electrically connected with the pressure control unit.
4. The supercritical carbon dioxide power system according to claim 1, wherein,
the cooler is provided with a coolant flow passage,
the power unit further includes a coolant input line and a coolant output line,
the coolant input pipeline and the coolant output pipeline are respectively connected with two ends of the coolant flow channel;
the coolant input pipeline is provided with a coolant regulating valve which is used for controlling the flow of the coolant flowing through the coolant flow channel;
the coolant regulating valve is electrically connected with the temperature control unit.
5. A method for controlling the start-up operation of a supercritical carbon dioxide power system, applied to the supercritical carbon dioxide power system according to any one of claims 1 to 4, comprising the steps of:
s1, filling a certain mass of gaseous carbon dioxide working medium into the power unit, and starting the first compressor, the first heat regenerator, the heater and the cooler;
s2, the pressure control unit controls the inlet pressure of the first compressor to reach a target pressure;
the temperature control unit controls the inlet temperature of the first compressor to be greater than or equal to a first target temperature, and controls the inlet temperature of the turbine to be a second target temperature;
and adjusting the rotating speed of the power unit to ensure that the output power of the power unit is greater than zero, and completing the starting of the supercritical carbon dioxide power system.
6. The control method according to claim 5, wherein,
in the step S2, the specific steps of controlling the inlet pressure of the first compressor to be greater than or equal to the target pressure by the pressure control unit are as follows:
when the inlet pressure of the first compressor is smaller than the target pressure, the pressure control unit controls the working medium discharge valve to be in a closed state, and the temperature control unit controls the inlet temperature of the first compressor to be larger than or equal to the first target temperature.
7. The control method according to claim 5, wherein,
in the step S2, the specific steps of controlling the inlet temperature of the first compressor to the first target temperature by the temperature control unit are as follows:
reducing a coolant flow through the chiller when an inlet temperature of the first compressor is less than the first target temperature;
when the inlet temperature of the first compressor is greater than the first target temperature, the coolant flow through the chiller is increased.
In the step S2, the specific step of controlling the inlet temperature of the turbine to the second target temperature by the temperature control unit is:
when the inlet temperature of the turbine is smaller than the second target temperature, the temperature control unit controls the turbine bypass valve to be in an open state, and working medium at the outlet of the heater enters the first hot side inlet;
when the inlet temperature of the turbine is greater than or equal to the second target temperature, the temperature control unit controls the turbine bypass valve to be in a closed state, and at the moment, working medium at the outlet of the heater enters the turbine to do work.
8. The control method according to claim 5, wherein,
the target pressure is 7.6MPa;
the first target temperature is 33 ℃;
the second target temperature is 200 ℃.
9. The control method according to claim 5, wherein,
in the step S1, the pressure of the gaseous carbon dioxide working medium is 2-6MPa, and the mass is m 0 ；
Setting the rated working medium mass of the power unit under the rated working condition as m 1 0.6m 1 ≤m 0 ≤1.2m 1 。
10. The control method according to claim 5, characterized by further comprising:
the inlet pressure of the first compressor is provided with an upper limit protection value P1, and the upper limit protection value P1 is 8.6-9MPa;
when the inlet pressure of the first compressor exceeds the upper limit protection value P1, the pressure control unit controls the working medium discharge valve to be opened so as to discharge part of working medium and reduce the pressure in the power unit.
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