CN114922705B - System and method for circulating split-flow repressing supercritical carbon dioxide - Google Patents
System and method for circulating split-flow repressing supercritical carbon dioxide Download PDFInfo
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- CN114922705B CN114922705B CN202210421888.0A CN202210421888A CN114922705B CN 114922705 B CN114922705 B CN 114922705B CN 202210421888 A CN202210421888 A CN 202210421888A CN 114922705 B CN114922705 B CN 114922705B
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 53
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 26
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 26
- 230000000754 repressing effect Effects 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 16
- 230000001105 regulatory effect Effects 0.000 claims description 13
- 239000002918 waste heat Substances 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 7
- 230000000087 stabilizing effect Effects 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 4
- 239000002826 coolant Substances 0.000 claims description 4
- 230000001502 supplementing effect Effects 0.000 claims description 2
- 238000004064 recycling Methods 0.000 claims 3
- 238000010438 heat treatment Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 230000000153 supplemental effect Effects 0.000 description 3
- 238000010248 power generation Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007791 liquid phase Substances 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
- 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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- 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
- F01K11/00—Plants characterised by the engines being structurally combined with boilers or condensers
- F01K11/02—Plants characterised by the engines being structurally combined with boilers or condensers the engines being turbines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- 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
- 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
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- 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
Abstract
The invention provides a split-flow repressing supercritical carbon dioxide circulating system and a method, which are reasonable in design, can conveniently adjust the total circulating flow, realize quick response and reduce the total load. The system comprises an external heat source, a shunt repressing loop, a high-voltage acting loop and a medium-voltage acting loop which are connected in parallel; the high-pressure acting loop comprises a high-pressure compressor, a cold side of a high-pressure primary heat regenerator, a cold side of a high-pressure secondary heat regenerator and a high-pressure turbine set which are connected in sequence; the medium-pressure acting loop comprises a medium-pressure compressor, a cold side of a medium-pressure heat regenerator, a three-way valve and a medium-pressure turbine set which are connected in sequence; the exhaust side of the medium-pressure turbine unit is sequentially connected with the hot side of the high-pressure primary heat regenerator and the hot side of the medium-pressure heat regenerator; the exhaust side of the high-pressure turbine unit is sequentially connected with the hot side of the high-pressure secondary heat regenerator and the three-way valve; the input end of the shunt repressurization loop is connected with the hot side outlet of the medium-pressure heat regenerator, and the output end of the shunt repressurization loop is respectively connected with the input ends of the high-pressure compressor and the medium-pressure compressor.
Description
Technical Field
The invention relates to the technical field of supercritical carbon dioxide circulating power generation, in particular to a split-flow repressing supercritical carbon dioxide circulating system and method.
Background
With the development of power generation technology, supercritical carbon dioxide as an excellent working medium for replacing water vapor has come into the field of view of many researchers due to its higher cycle efficiency, more compact equipment arrangement, and more economical early investment. The split-flow and repressed circulation mode of the main system by using the double compressors is also embodied and proved in a plurality of papers and patents.
However, in the prior art, for a small test platform only suitable for kW level, the existing split-flow repression mode is required to further realize parameters such as MW level generated power, and thus the existing common circulation mode has a plurality of unreasonable places. The existing series circulation has three problems of limitation on total flow, adverse effect of medium-pressure (re) compressor inlet temperature on compression efficiency and large fluctuation of the compressor inlet by system compressed, and cannot meet the circulation requirement of larger power level.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a split-flow repressing supercritical carbon dioxide circulating system and a method, which are reasonable in design, can conveniently adjust the total circulating flow, realize quick response and reduce the total load.
The invention is realized by the following technical scheme:
a split-flow repressing supercritical carbon dioxide circulation system comprises an external heat source, a split-flow repressing loop, a high-pressure acting loop and a medium-pressure acting loop which are connected in parallel;
the high-pressure acting loop comprises a high-pressure compressor, a cold side of a high-pressure primary heat regenerator, a cold side of a high-pressure secondary heat regenerator and a high-pressure turbine set which are connected in sequence; the medium-pressure acting loop comprises a medium-pressure compressor, a cold side of a medium-pressure heat regenerator, a three-way valve and a medium-pressure turbine set which are connected in sequence; the exhaust side of the medium-pressure turbine unit is sequentially connected with the hot side of the high-pressure primary heat regenerator and the hot side of the medium-pressure heat regenerator; the exhaust side of the high-pressure turbine unit is sequentially connected with the hot side of the high-pressure secondary heat regenerator and the three-way valve;
the input end of the split-flow repressing loop is connected with the hot side outlet of the medium-pressure heat regenerator, and the output end of the split-flow repressing loop is respectively connected with the input ends of the high-pressure compressor and the medium-pressure compressor;
the external heat source is arranged between the cold side of the high-pressure secondary heat regenerator and the high-pressure turbine unit, and between the three-way valve and the medium-pressure turbine unit.
Optionally, the three-way valve is in unidirectional conduction in both the hot side intermediate-pressure turbine set of the high-pressure secondary regenerator and the cold side intermediate-pressure turbine set of the intermediate-pressure regenerator.
Optionally, the external heat source comprises a superheater for performing primary heat exchange and a reheater for performing secondary heat exchange, and the superheater is arranged between the cold side of the high-pressure secondary regenerator and the high-pressure turbine unit; the reheater is arranged between the three-way valve and the medium-pressure turbine unit.
Optionally, the front and rear of the inlet of the high-pressure turbine unit are connected with the high-pressure inlet and outlet pipeline through the high-pressure turbine bypass, and the front and rear of the inlet of the medium-pressure turbine unit are connected with the medium-pressure inlet and outlet pipeline through the medium-pressure turbine bypass.
Optionally, the split-flow repressurization loop comprises a waste heat utilization system, a cooler, a constant pressure pump and a surge tank which are sequentially connected, and a gas supplementing source arranged on a pipeline between the cooler and the constant pressure pump.
A method for circulating split-flow repressing supercritical carbon dioxide comprises,
before the unit is started in a cold state, filling the cold state filling working medium into the whole pipeline of the split-flow repressing supercritical carbon dioxide circulating system according to any one of the above through the split-flow repressing loop;
after filling, regulating the highest pressure of the main system by the high-pressure compressor, and regulating the output of the medium-pressure compressor by the medium-pressure compressor according to the outlet pressure of the hot side of the high-pressure secondary heat regenerator; controlling inlet pressures of the high-pressure compressor and the medium-pressure compressor to be constant through the split-flow repressurization loop;
gradually raising the temperature of the system by putting an external heat source into the system; when the back pressure of an external heat source in the medium-pressure acting loop is 5-7 MPa and the outlet temperature is increased to 180 ℃, the medium-pressure turbine unit is switched from a hot standby to an operating state; after the medium-pressure turbine unit is connected with the grid, the high-pressure turbine unit is switched from a hot standby to an operating state;
gradually increasing the power of an external heat source, increasing the enthalpy value of the system, and controlling the high-pressure compressor and the medium-pressure compressor to achieve a stable working condition through the shunt repression loop by taking the temperature threshold value of the hot side outlet of the medium-pressure heat regenerator as a reference; until the parameters of the high-pressure turbine set and the medium-pressure turbine set reach a set threshold value.
Optionally, the control of the shunt repressurization loop specifically comprises,
the supplementary air source is used as a cold filling working medium air source;
regulating the pressure of the pressure stabilizing tank through the constant pressure pump, and stabilizing the inlet pressure of the high-pressure compressor and the inlet pressure of the medium-pressure compressor to be constant;
and the flow of cooling medium in the system is regulated by the waste heat utilization system and the cooler, the front temperature of the constant pressure pump is stabilized, and the temperature and the pressure of the inlet working media of the high pressure compressor and the medium pressure compressor are indirectly stabilized.
Optionally, the stable working condition is that the temperature of the inlet working medium is 35+/-3 ℃ and the pressure is 7.3+/-0.2 MPa.
Optionally, when the machine is stopped, only the output of an external heat source is required to be reduced, the total enthalpy value of the system is reduced, and the waste heat utilization system is gradually exited according to the enthalpy value change rate, or the flow of cooling medium of the cooler is regulated;
the output of the high-pressure compressor is preferentially reduced, the total flow of the system is reduced, the pressure of the hot side of the high-pressure secondary heat regenerator and the pressure of the three-way valve are tracked by adjusting the medium-pressure compressor, the pressure of the medium-pressure system is stabilized, and the loads of the high-pressure turbine unit and the medium-pressure turbine unit are gradually reduced.
Optionally, after the high-pressure turbine unit and the medium-pressure turbine unit are out of operation, the system operates through the high-pressure bypass and the medium-pressure bypass to provide a cooling source for an external heat source under an accident condition.
Compared with the prior art, the invention has the following beneficial technical effects:
according to the invention, the traditional serial connection mode of the high-pressure compressor and the medium-pressure compressor is changed into the parallel connection mode, so that the disturbance between systems is reduced; the waste heat working medium subjected to heat exchange by the high-pressure secondary heat regenerator is directly recovered by utilizing the three-way valve during operation, so that the unification and coordination of the system are realized; in the running process, the output of the medium-pressure compressor can be independently regulated to regulate the total circulation flow of the system, the output of the high-pressure compressor can be regulated, the total load is reduced by reducing the mode of rapidly reducing the air intake and exhaust quantity of the high-pressure turbine unit, and the rapid response of regulating the load is realized, so that the problem of limiting the total flow by the serial circulation is solved.
Furthermore, the method controls the parallel design to enable the high-pressure compressor and the medium-pressure compressor to operate at a lower temperature slightly higher than the liquid phase temperature, greatly improves the working efficiency of the medium-pressure compressor, indirectly improves the acting capacity of the medium-pressure turbine unit, and avoids the adverse effect of the inlet temperature of the medium-pressure (re) compressor on the compression efficiency.
Furthermore, the inlet pressure of the high-pressure compressor and the medium-pressure compressor is stabilized through the constant-pressure pump, the pressure stabilizing tank and the supplementary air source, the influence on the system caused by the change of the medium flow on the cold side of the cooler is reduced, and the problem that the inlet of the compressor is greatly influenced by the pressure fluctuation of the system is avoided.
Drawings
Fig. 1 is a process block diagram of a system according to an example of the present invention.
In the figure: the high-pressure compressor 1, the high-pressure primary regenerator 2a, the high-pressure secondary regenerator 2b, an external heat source 3, a superheater 3a, a reheater 3b, a high-pressure turbine unit 4, a high-pressure turbine bypass 4By, an intermediate-pressure compressor 5, an intermediate-pressure regenerator 6, an intermediate-pressure turbine unit 7, an intermediate-pressure turbine bypass 7By, a make-up air source 8, a cooler 9, a constant-pressure pump 10, a surge tank 11, a three-way valve 12 and a waste heat utilization system 13.
Detailed Description
The invention will now be described in further detail with reference to specific examples, which are intended to illustrate, but not to limit, the invention.
The present invention provides a split-flow repression supercritical carbon dioxide circulation system, as shown in fig. 1, comprising: a high-pressure compressor 1, a medium-pressure compressor 5, a high-pressure primary regenerator 2a, a high-pressure secondary regenerator 2b, a medium-pressure regenerator 6, an external heat source 3, a high-pressure turbine unit 4, a medium-pressure turbine unit 7, a cooler 9, a pressure-stabilizing air storage tank 11, a constant-pressure pump 10, a three-way valve 12 and a waste heat utilization system 13. The system is hooked with the pipeline through two-stage backheating, so that the total circulation flow of the system is greatly increased on the basis of ensuring the heat efficiency, and a new thought is provided for the circulation of the megawatt-level supercritical carbon dioxide. Meanwhile, the disturbance of back pressure fluctuation to the system in the operation process of the supercritical carbon dioxide unit is solved to a certain extent; thus solving the three problems of the limit of the serial circulation to the total flow, the adverse effect of the inlet temperature of the medium-pressure (re) compressor to the compression efficiency and the larger fluctuation of the inlet of the compressor by the system.
Specifically, in the above composition, the external heat source 3 includes a superheater 3a and a reheater 3b, a supplemental air source 8 is arranged on a pipeline between a cooler 9 and a constant pressure pump 10, the front and the rear of the inlet of the high pressure turbine unit 4 are connected with a high pressure inlet and outlet pipeline through a high pressure turbine bypass 4By, and the front and the rear of the inlet of the medium pressure turbine unit 7 are connected with a medium pressure inlet and outlet pipeline through a medium pressure turbine bypass 7 By.
The high-pressure compressor 1 is connected with the cold side of the high-pressure primary heat regenerator 2a through a pipeline and an outlet valve, the outlet of the cold side of the high-pressure primary heat regenerator 2a is connected with the cold side of the high-pressure secondary heat regenerator 2b through a pipeline, the outlet of the high-pressure primary heat regenerator is connected with the superheater 3a in the external heat source 3 through a valve pipeline and the air inlet side of the high-pressure turbine unit 4, and the high-pressure turbine unit 4 comprises a high-pressure turbine and a high-pressure generator set.
The exhaust side outlet of the high-pressure turbine unit 4 is connected with the hot side inlet of the high-pressure secondary heat regenerator 2b through a pipeline, and is connected into the cold side outlet pipeline of the medium-pressure heat regenerator 6 through a three-way valve 12.
The medium-pressure compressor 5 is connected with the cold side of the medium-pressure heat regenerator 6 through a pipeline and an outlet valve, the outlet is connected with the reheater 3b in the external heat source 3 through a valve pipeline and the air inlet side of the medium-pressure turbine unit 7, and the medium-pressure turbine unit 7 comprises a medium-pressure turbine and a medium-pressure generator set.
And an exhaust side outlet of the medium-pressure turbine unit 7 is respectively connected with the hot side of the high-pressure primary heat regenerator 2a and the hot side of the medium-pressure heat regenerator 6 through pipelines.
The hot side outlet of the medium-pressure heat regenerator 6 is connected with the cooler 9 through a valve pipeline by a waste heat utilization system 13. The outlet of the cooler 9 is connected with the inlet of the constant pressure pump 10 through a pipeline, and the outlet of the constant pressure pump 10 is connected with the inlets of the high pressure compressor 1 and the medium pressure compressor 5 through pipelines and the gas storage tank 6. The make-up air source 8 is connected by a pipeline to the inlet of the constant pressure pump 10.
For the high-pressure turbine unit 4, an inlet and outlet pipeline is connected through a high-pressure turbine bypass 4By before the inlet of the high-pressure turbine and after the outlet of the turbine; similarly, for the medium-pressure turbine unit 7, the inlet and outlet pipelines are connected through the medium-pressure turbine bypass 7By before the inlet of the medium-pressure turbine and after the outlet of the turbine.
In the split-flow repressurization circuit, both the high-pressure compressor 1 and the medium-pressure compressor 5 are centrifugal compressors, and the inlet pressure is maintained stable by the constant-pressure pump 10 and the surge tank 11. The constant pressure pump 10 is a high flow axial blower while ensuring a flexible and adjustable outlet baffle or the addition of a frequency converter. The surge tank 11 may be a self-operated constant pressure tank. Ensures that the high-pressure compressor 1 and the medium-pressure compressor 5 are both maintained at 6.5-7.5 MPa, and the inlet temperature is maintained at 35-40 ℃ through the cooler 9. The working medium of the carbon dioxide is pressurized by the high-pressure compressor 1 to 22-24 MPa and the working medium is pressurized by the medium-pressure compressor 5 to 16-18 MPa. After being heated by an external heat source 3, the inlet temperature of the high-pressure turbine reaches 700 ℃ before entering the high-pressure turbine set 4; before entering the medium-pressure turbine unit 7, the inlet temperature of the medium-pressure turbine should reach 600 ℃, the outlet temperature of the hot side of the high-pressure primary regenerator 2a is ensured to be 450-500 ℃, the outlet temperature of the hot side of the high-pressure secondary regenerator 2b is ensured to be 450-550 ℃, and the outlet temperature of the hot side of the medium-pressure regenerator 6 is ensured to be 500-600 ℃.
The cooling mode of the cooler 5 includes water cooling and air cooling; the external heat source 3 comprises a primary heat exchange device superheater 3a and a secondary heat exchange device reheater 3b, and the heating modes comprise coal heating, gas heating, nuclear reaction heating and photo-thermal heating.
Auxiliary steam and shaft seal gas can be used as cold sources on the cold side of the waste heat utilization system 13, and the residual heat of the working medium is recovered again.
The three-way valve 12 needs the working medium to pass through unidirectionally at the outlet side of the medium-pressure compressor 5 and the outlet side of the hot side of the high-pressure secondary heat regenerator 2 b.
The disturbance of the main system pressure distribution and circulation flow caused by the operation of the supplemental air source 8 when the system is running is reduced before the supplemental air source 8 pipeline and the main system pipeline are arranged in front of the constant pressure pump 10.
A split-flow repressing supercritical carbon dioxide circulating method operates as follows on the basis of the above system,
the carbon dioxide working medium is divided into two paths by a constant pressure pump 10 and a pressure stabilizing tank 11. One path enters the high-pressure compressor 1, is subjected to heat exchange through the high-pressure primary heat regenerator 2a and the high-pressure secondary heat regenerator 2b after being pressurized in the high-pressure compressor 1, and enters the superheater 3a of the boiler 3 for heating. The heated working medium enters the high-pressure turbine unit 4 to do work or enters the high-pressure secondary heat regenerator 2b through the high-pressure turbine bypass 4By, and after heat exchange, the working medium is converged into an outlet pipeline of the medium-pressure compressor 5 through the three-way valve 12.
The other path enters the medium-pressure compressor 5, exchanges heat through the medium-pressure heat regenerator 6 after being pressurized in the medium-pressure compressor 5, and forms medium-pressure main gas together with the working medium at the outlet of the high-pressure secondary heat regenerator 2b which is converged through the three-way valve 12. Into the boiler 3 and the reheater 3 b. The heated working medium enters the medium-pressure turbine unit 7 to do work or sequentially enters the high-pressure primary heat regenerator 2a and the medium-pressure heat regenerator 6 through the medium-pressure turbine bypass 7 By.
After the heat exchange of the medium-pressure heat regenerator 6, the enthalpy value is greatly reduced, and the heat is recovered by the waste heat utilization system 13. And finally, the working medium enters a cooler 9 to reduce the temperature, and the pressure of the working medium is balanced by a constant pressure pump 10 and a pressure stabilizing tank 11 to be used as air sources of the high pressure compressor 1 and the medium pressure compressor 5. Parameters of the high-pressure compressor 1 and the medium-pressure compressor 5 are commonly controlled by a constant-pressure pump 10 through a surge tank.
The supplementary air source 8 is used as a cold filling air source, and is matched with the constant pressure pump 10, the high pressure compressor 1 and the medium pressure compressor 5 to fill the system; meanwhile, the inlet pressure parameters of the high-pressure compressor 1 and the medium-pressure compressor 5 are ensured as a standby air source, and the intermittent operation maintains the circulating flow of the system.
The invention changes the distribution mode of the supercritical carbon dioxide diversion and re-pressure circulation system, readjusts the system structure, and realizes the multi-stage utilization of the heat of the boiler and the turbine exhaust gas on the basis of ensuring the stable operation of the system.
Claims (9)
1. The split-flow repressing supercritical carbon dioxide circulating system is characterized by comprising an external heat source (3), a split-flow repressing loop, a high-pressure acting loop and a medium-pressure acting loop which are connected in parallel;
the high-pressure acting loop comprises a high-pressure compressor (1), a cold side of a high-pressure primary heat regenerator (2 a), a cold side of a high-pressure secondary heat regenerator (2 b) and a high-pressure turbine set (4) which are connected in sequence; the medium-pressure acting loop comprises a medium-pressure compressor (5), a cold side of a medium-pressure heat regenerator (6), a three-way valve (12) and a medium-pressure turbine set (7) which are connected in sequence; the exhaust side of the medium-pressure turbine unit (7) is sequentially connected with the hot side of the high-pressure primary heat regenerator (2 a) and the hot side of the medium-pressure heat regenerator (6); the exhaust side of the high-pressure turbine unit (4) is sequentially connected with the hot side of the high-pressure secondary heat regenerator (2 b) and the three-way valve (12);
the input end of the split-flow repressing loop is connected with the hot side outlet of the medium-pressure heat regenerator (6), and the output end of the split-flow repressing loop is respectively connected with the input ends of the high-pressure compressor (1) and the medium-pressure compressor (5); the split-flow repressing loop comprises a waste heat utilization system (13), a cooler (9), a constant pressure pump (10) and a pressure stabilizing tank (11) which are sequentially connected, and a gas supplementing source (8) arranged on a pipeline between the cooler (9) and the constant pressure pump (10);
the external heat source (3) is arranged between the cold side of the high-pressure secondary regenerator (2 b) and the high-pressure turbine unit (4), and between the three-way valve (12) and the medium-pressure turbine unit (7).
2. A split-flow repressurization supercritical carbon dioxide cycle system according to claim 1, characterized in that the three-way valve (12) is on both the hot side of the high-pressure secondary regenerator (2 b) and the cold side of the medium-pressure regenerator (6) and the medium-pressure turbine (7) are on unidirectionally.
3. A split-flow repressurization supercritical carbon dioxide cycle system according to claim 1, characterized in that said external heat source (3) comprises a superheater (3 a) for primary heat exchange and a reheater (3 b) for secondary heat exchange, said superheater (3 a) being disposed between the cold side of the high-pressure secondary regenerator (2 b) and the high-pressure turbine unit (4); the reheater (3 b) is arranged between the three-way valve (12) and the medium-pressure turbine unit (7).
4. The split-flow repressurization supercritical carbon dioxide recycling system according to claim 1, wherein the front and rear of the inlet of the high-pressure turbine unit (4) are connected with the high-pressure inlet and outlet pipeline through a high-pressure turbine bypass (4 By), and the front and rear of the inlet of the medium-pressure turbine unit (7) are connected with the medium-pressure inlet and outlet pipeline through a medium-pressure turbine bypass (7 By).
5. A split-flow repressing supercritical carbon dioxide circulation method is characterized by comprising the following steps of,
before the unit is started in a cold state, filling the cold state filling working medium into the whole pipeline of the split-flow repressing supercritical carbon dioxide circulating system according to any one of claims 1-4 through the split-flow repressing loop;
after filling, the highest pressure of the main system is regulated by the high-pressure compressor (1), and the output of the medium-pressure compressor is regulated by the medium-pressure compressor (5) according to the outlet pressure of the hot side of the high-pressure secondary heat regenerator (2 b); controlling the inlet pressure of the high-pressure compressor (1) and the medium-pressure compressor (5) to be constant through the split-flow repression loop;
gradually raising the temperature of the system by putting an external heat source (3); when the back pressure of an external heat source (3) in the medium-pressure acting loop is 5-7 MPa and the outlet temperature is increased to 180 ℃, the medium-pressure turbine unit (7) is switched from a hot standby to an operating state; after the medium-pressure turbine unit (7) is connected with the grid, the high-pressure turbine unit (4) is switched from hot standby to an operating state;
gradually increasing the power of an external heat source (3), increasing the enthalpy value of the system, and controlling the inlet working media of the high-pressure compressor (1) and the medium-pressure compressor (5) to reach a stable working condition by taking the temperature threshold value of the hot side outlet of the medium-pressure heat regenerator (6) as a reference through the split-flow repressing loop; until the parameters of the high-pressure turbine unit (4) and the medium-pressure turbine unit (7) reach set thresholds.
6. A split repressurization supercritical carbon dioxide recycling method according to claim 5, wherein the control of the split repressurization loop comprises, in particular,
the cold filling working medium air source is taken as a cold filling working medium air source through a supplementary air source (8);
the pressure of the pressure stabilizing tank (11) is regulated through the constant pressure pump (10), so that the inlet pressures of the high-pressure compressor (1) and the medium-pressure compressor (5) are stabilized to be constant;
the flow of cooling medium in the system is regulated through the waste heat utilization system (13) and the cooler (9), the temperature before the constant pressure pump (10) is stabilized, and the temperature and the pressure of the working medium at the inlets of the high pressure compressor (1) and the medium pressure compressor (5) are indirectly stabilized.
7. The method for recycling split-flow repressed supercritical carbon dioxide according to claim 5 or 6, wherein the stable working condition is that the temperature of the inlet working medium is 35 ℃ +/-3 ℃ and the pressure is 7.3 MPa+/-0.2 MPa.
8. A split-flow repressurization supercritical carbon dioxide cycle method according to claim 6, characterized in that during shutdown, only the output of external heat source (3) is required to be reduced, the total enthalpy of the system is reduced, the waste heat utilization system (13) is gradually withdrawn according to the enthalpy change rate, or the flow of cooling medium in cooler (9) is regulated;
the output of the high-pressure compressor (1) is preferentially reduced, the total flow of the system is reduced, the pressure of the hot side of the high-pressure secondary heat regenerator (2 b) and the pressure of the three-way valve (12) are tracked by adjusting the medium-pressure compressor (5), the pressure of the medium-pressure system is stabilized, and the loads of the high-pressure turbine unit (4) and the medium-pressure turbine unit (7) are gradually reduced.
9. The split-flow repressurization supercritical carbon dioxide cycle method according to claim 8, wherein after the high-pressure turbine unit (4) and the medium-pressure turbine unit (7) are out of operation, the system is operated By the high-pressure turbine bypass (4 By) and the medium-pressure turbine bypass (7 By) to provide a cooling source for the external heat source (3) under accident conditions.
Priority Applications (1)
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