CN115263476A - Control method of supercritical carbon dioxide series double-turbine power generation system - Google Patents
Control method of supercritical carbon dioxide series double-turbine power generation system Download PDFInfo
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- CN115263476A CN115263476A CN202210929044.7A CN202210929044A CN115263476A CN 115263476 A CN115263476 A CN 115263476A CN 202210929044 A CN202210929044 A CN 202210929044A CN 115263476 A CN115263476 A CN 115263476A
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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
- 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
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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
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
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Abstract
The invention discloses a control method and a control system of a supercritical carbon dioxide serial double-turbine power generation system, and belongs to the technical field of supercritical carbon dioxide cycle power generation. The system comprises a compressor, a heat regenerator, a main heat exchanger, a first-stage turbine, a second-stage turbine, a cooler, a high-pressure gas source tank, a booster pump and a balance tank. Through set up the compressor bypass between the import and the export of compressor, set up I level turbine bypass between the air inlet of I level turbine and the gas vent, set up II level turbine bypasses between the air inlet of II level turbine and the gas vent, equipment in the cooperation system has realized that the unit of supercritical carbon dioxide serial-type double turbine power generation system opens and stops, operations such as rotational speed regulation, elevating load have reduced the control degree of difficulty.
Description
Technical Field
The invention belongs to the technical field of supercritical carbon dioxide cycle power generation, and particularly relates to a control method of a supercritical carbon dioxide serial double-turbine power generation system.
Background
With the development of power generation technology, supercritical carbon dioxide as an excellent working medium replacing water vapor enters the field of many researchers due to higher cycle efficiency, more compact equipment arrangement and more economical early investment. Wherein, the double-turbine serial arrangement system can better exert the circulating advantage of the supercritical carbon dioxide.
However, in actual operation, the rotating speed control idea of the double-turbine serial arrangement is greatly different from that of a common steam unit, and the two-stage turbine back pressure control can be disturbed mutually. Meanwhile, the carbon dioxide power generation technology is still in an initial exploration stage, a plurality of small-sized test units and test platforms do not have the condition of surfing the internet, and an isolated network operation mode or load box consumption is mostly adopted, so that the difficulty of controlling the rotating speed of the turbine is improved to a certain extent.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a control method of a supercritical carbon dioxide serial double-turbine power generation system, so that the operations of unit starting and stopping, rotating speed regulation, load lifting and the like of the power generation system are realized, and the control difficulty is reduced.
The invention is realized by the following technical scheme:
a control method of a supercritical carbon dioxide serial double-turbine power generation system comprises a compressor, a heat regenerator, a main heat exchanger, a first-stage turbine, a second-stage turbine, a cooler, a high-pressure gas source tank, a booster pump and a balance tank; a compressor bypass is arranged between an inlet and an outlet of the compressor, a first-stage turbine bypass is arranged between an air inlet and an air outlet of the first-stage turbine, and a second-stage turbine bypass is arranged between an air inlet and an air outlet of the second-stage turbine; the air inlets of the first-stage turbine and the second-stage turbine are respectively provided with a quick closing valve and a main regulating valve;
the control method comprises the following steps:
before the system is started and prepared, carbon dioxide working medium enters a balance tank through a high-pressure gas source tank and a pressure pump, and then the compressor runs at low load to fill the main loop system with the carbon dioxide working medium; at the moment, the compressor bypass, the I-stage turbine bypass and the II-stage turbine bypass are all fully opened;
before the flushing rotation, the compressor bypass is gradually closed, the carbon dioxide working medium is boosted through the compressor, enters the heat regenerator for heat exchange, enters the main heat exchanger for temperature rise, enters the heat regenerator through the first-stage turbine bypass and the second-stage turbine bypass, is cooled by the cooler and finally enters the balance tank to serve as an inlet air source of the compressor;
in the process of impulse rotation, the second-stage turbine bypass is closed, and a quick closing valve and a main regulating valve of the second-stage turbine are opened at the same time, and in the process, the first-stage turbine bypass is kept fully opened; when the II-stage turbine reaches the rated rotating speed, the system is immediately connected to the grid or enters a loaded state; if the second-stage turbine bypass is not closed, completely closing the second-stage turbine bypass, and increasing the corresponding load of the load box; after the second-stage turbine bypass is completely closed, closing the first-stage turbine bypass, and simultaneously opening a quick closing valve and a main regulating valve of the first-stage turbine; in the process, a main regulating valve of the II-stage turbine is kept fully opened; when the I-stage turbine reaches the rated rotating speed, immediately connecting the grid or entering a loaded state;
the method comprises the steps that steady-state operation is carried out, a load increasing stage is carried out, a first-stage turbine and a second-stage turbine alternately operate a main regulating valve according to a theoretical load proportion, the opening degree of the main regulating valve is not smaller than 50%, meanwhile, the thermal power of a main heat exchanger is increased, the inlet pressure of a compressor is increased through a balance tank, and system parameters are improved to a supercritical state; in the load increasing process, monitoring excitation and generator parameters or alternatively adjusting corresponding loads to increase loads;
in the load reduction stage, the degree of opening of a main regulating valve is not less than 50% when the first-stage turbine and the second-stage turbine alternately operate according to the theoretical load proportion, the thermal power of a main heat exchanger is reduced, the pressure at the inlet of a compressor is reduced through a balance tank, and the back pressure of a circulating system is reduced; in the load reducing process, monitoring excitation and generator parameters or alternatively adjusting corresponding loads to reduce the loads;
when the total load of the system is less than 10% of the rated load, the system is manually opened and shut down, and at the moment, the I-stage turbine bypass, the II-stage turbine bypass and the compressor bypass are all interlocked and opened by not less than 20%.
Preferably, under the high-load accident condition, the first-stage turbine and the second-stage turbine are cut off, the main regulating valves and the air inlet valves of the first-stage turbine and the second-stage turbine are closed, meanwhile, the compressor bypass, the first-stage turbine bypass and the second-stage turbine bypass are all opened 50% quickly, and the compressor 1 is shut down in an interlocking mode.
Preferably, the outlet of the compressor is connected with the inlet of the cold side of the heat regenerator, the outlet of the cold side of the heat regenerator is connected with the inlet of the high-pressure heat exchanger of the main heat exchanger, the outlet of the high-pressure heat exchanger is connected with the air inlet of the I-stage turbine, and the I-stage turbine drives the I-stage generator; the exhaust port of the first-stage turbine is connected with the inlet of a low-pressure heat exchanger of the main heat exchanger, the outlet of the low-pressure heat exchanger is connected with the air inlet of the second-stage turbine, and the second-stage turbine drives a second-stage generator; the second-stage turbine exhaust port is connected with a hot side inlet of the heat regenerator, a hot side outlet of the heat regenerator is connected with an inlet of the cooler, an outlet of the cooler is connected with an inlet of the balance tank, an outlet of the balance tank is connected with an inlet of the compressor through a branch and connected with the booster pump through another branch, and the booster pump is connected with the high-pressure gas source tank.
Preferably, the outlets of the stage I turbine and the stage II turbine are provided with quick closing valves or check valves.
Preferably, the balance tank is connected with an emptying pipeline, and an electric valve is arranged on the emptying pipeline.
Preferably, the power sources of the stage I turbine bypass, the stage II turbine bypass and the compressor bypass are pneumatic or electric, and the action time is less than 2s.
Preferably, the inlet working pressure of the compressor is 3-8 MPa, the inlet temperature is 35-45 ℃, and the full-load outlet working pressure is 18-20 MPa.
Preferably, the maximum operating temperature of the regenerator is 450 ℃.
Preferably, the heat source of the main heat exchanger is liquid metal, molten salt, steam or flue gas, and the temperature of the carbon dioxide working medium at the outlet of the main heat exchanger is 550-650 ℃.
Preferably, the cooling medium of the cooler is water, oil or compressed air.
Compared with the prior art, the invention has the following beneficial technical effects:
by referring to the physical characteristics of carbon dioxide, the double turbines are arranged in series and have the advantages of high heat energy utilization efficiency, compact arrangement, small occupied area and the like; however, when the dual turbines are arranged in series during operation, if the rotation speed of a single turbine is controlled in a traditional mode, the first-stage turbine and the second-stage turbine interfere with each other, the stability of the system is seriously influenced, the output power fluctuation is large, and the system is particularly serious in a test platform using a load box as load consumption and an isolated network operation mode. The invention discloses a control method of a supercritical carbon dioxide serial double-turbine power generation system, which realizes the operations of unit start-stop, rotating speed regulation, load lifting and the like of the supercritical carbon dioxide serial double-turbine power generation system by arranging a compressor bypass between an inlet and an outlet of a compressor, arranging a first-stage turbine bypass between an air inlet and an air outlet of a first-stage turbine, and arranging a second-stage turbine bypass between an air inlet and an air outlet of a second-stage turbine, and matching with equipment in the system, thereby reducing the control difficulty.
Furthermore, the balance tank is connected with an emptying pipeline, an electric valve is arranged on the emptying pipeline, the inlet pressure of the compressor can be accurately controlled, and the pressure can be used as one of discharge openings for safe discharge under accident conditions.
Furthermore, the power source action time of the I-stage turbine bypass, the II-stage turbine bypass and the compressor bypass is less than 2s, the requirement of quick response can be met, and stable remote control adjustment is realized.
Drawings
FIG. 1 is a schematic diagram of a supercritical carbon dioxide tandem twin turbine system.
In the figure: 1 is the compressor, 2 is the regenerator, and 3 is main heat exchanger, and 4 are I level turbine, and 5 are II level turbine, and 6 are the cooler, and 7 are high pressure gas source jar, 8 are the force (forcing) pump, and 9 are the balance tank, and 1by is the compressor bypass, and 4by is I level turbine bypass, and 5by is II level turbine bypass.
Detailed Description
The invention will now be described in further detail with reference to the following figures and examples, which are given by way of illustration and not of limitation.
Referring to fig. 1, the supercritical carbon dioxide serial double-turbine power generation system of the present invention mainly includes a compressor 1, a heat regenerator 2, a main heat exchanger 3, a first-stage turbine 4, a second-stage turbine 5, a cooler 6, a high-pressure gas source tank 7, a booster pump 8 and a balance tank 9; a compressor bypass 1by is arranged between an inlet and an outlet of the compressor 1, a first-stage turbine bypass 4by is arranged between an air inlet and an air outlet of the first-stage turbine 4, and a second-stage turbine bypass 5by is arranged between an air inlet and an air outlet of the second-stage turbine 5; the power sources of the I-stage turbine bypass 4by, the II-stage turbine bypass 5by and the compressor bypass 1by are pneumatic or electric, and the action time is less than 2s; the air inlets of the first-stage turbine 4 and the second-stage turbine 5 are both provided with a quick-closing valve and a main regulating valve, and the outlets of the first-stage turbine 4 and the second-stage turbine 5 are provided with a quick-closing valve or a check valve.
The specific connection relation is as follows: an outlet of the compressor 1 is connected with a cold side inlet of the heat regenerator 2 through a pipeline and a valve, a cold side outlet of the heat regenerator 2 is connected with a high-pressure heat exchanger inlet of the main heat exchanger 3 through a pipeline, an outlet of the high-pressure heat exchanger is connected with an air inlet of the first-stage turbine 4 through a pipeline and a valve, and the first-stage turbine 4 drives the first-stage generator; an exhaust port of the first-stage turbine 4 is connected with an inlet of a low-pressure heat exchanger of the main heat exchanger 3, an outlet of the low-pressure heat exchanger is connected with an air inlet of the second-stage turbine 5 through a pipeline and a valve, and the second-stage turbine 5 drives a second-stage generator; the 5 gas vents of II grades of turbines are connected with 2 hot side inlet of regenerator, and 2 hot side export of regenerator is through pipeline and valve and 6 access connection of cooler, and 6 exports of cooler are through pipeline and valve and 9 access connection of surge tank, and 9 exports of surge tank are through a branch road and 1 access connection of compressor, are connected with force (forcing) pump 8 through another branch road, and force (forcing) pump 8 is connected with high-pressure air source jar 7, all is equipped with the valve on two branch roads.
In a preferred embodiment, the balancing tank 9 is connected to an evacuation line, which is provided with an electric valve.
The invention discloses a control method of a supercritical carbon dioxide series double-turbine power generation system, which comprises the following steps:
before preparation for starting, carbon dioxide working medium enters a balance tank 9 through a high-pressure gas source tank 7 and a booster pump 8. After the carbon dioxide working medium enters the balance tank 9, the compressor 1 runs under low load, and the working medium is filled in the main loop system and reaches 3.5-4 MPa. At the moment, the compressor bypass 1by, the I-stage turbine bypass 4by and the II-stage turbine bypass 5by are all in a fully open state.
Before the flushing, the compressor bypass 1by is gradually closed, namely, the carbon dioxide working medium is boosted through the compressor 1, enters the heat regenerator 2 for heat exchange and is heated by the main heat exchanger 3, enters the heat regenerator 2 through the I-stage turbine bypass 4by and the II-stage turbine bypass 5by, and finally, the carbon dioxide cold working medium cooled by the cooler 6 enters the balance tank 9 to serve as an inlet air source of the compressor 1.
In the process of impulse transfer, the second-stage turbine bypass 5by is closed preferentially, and meanwhile, the corresponding turbine, namely the second-stage turbine 5 quick-closing valve and the main regulating valve are opened, in the process, the first-stage turbine bypass 4by is kept fully opened, and when the second-stage turbine 5 reaches the rated rotating speed, the second-stage turbine should be immediately connected to the grid or enter a load state. If the stage II turbine bypass 5by is not closed, the stage II turbine bypass 5by needs to be fully closed, and corresponding load is increased. After the second-stage turbine bypass 5by is completely closed, the first-stage turbine bypass 4by is closed, corresponding turbines, namely the first-stage turbine 4 quick-closing valve and the main regulating valve, are simultaneously opened in the same way, the second-stage turbine main regulating valve is recommended to be kept fully opened in the process, and the carbon dioxide working medium is guaranteed to have the maximum through flow all the time. When the I-stage turbine 4 reaches the rated rotating speed, the I-stage turbine should be immediately connected to the grid or enter a load state.
And (3) steady-state operation, entering a load increasing stage, and alternately operating the main regulating valve by the I-stage turbine 4 and the II-stage turbine 5 according to a theoretical load proportion, wherein the opening degrees of the two stages are not less than 50%. And meanwhile, the thermal power of the main heat exchanger 3 is increased, and the inlet pressure of the compressor is increased through a balance tank 9 when necessary, so that the system parameters are improved to a supercritical state. In the process of load increase, parameters such as excitation, a generator and the like are strictly monitored or the load is increased by alternately adjusting corresponding loads.
The load reduction stage and the load increase stage are the same, the I-stage turbine 4 and the II-stage turbine 5 alternately operate the main regulating valve according to the theoretical load proportion, and the opening degrees of the two stages are not less than 50%. Meanwhile, the heat power of the main heat exchanger 3 is reduced, and the inlet pressure of the compressor is reduced through the balance tank 9 when necessary, so that the back pressure of a circulating system is reduced. In the process of reducing the load, parameters such as excitation, a generator and the like are strictly monitored or the load is reduced by alternately adjusting the corresponding load.
When the total load is less than 10% of rated load, the brake can be opened manually and stopped, and at the moment, the I-stage turbine bypass 4by, the II-stage turbine bypass 5by and the compressor bypass 1by are all interlocked and opened by not less than 20%.
The inlet pressure of the compressor 1 is maintained at 3.5-4 MPa, the inlet temperature is maintained at 35-40 ℃ through a cooler (5), and the cooling mode is water cooling or air cooling. After the carbon dioxide working medium is pressurized by the compressor 1, the pressure of the working medium reaches 18-20 MPa, and the temperature reaches 600 ℃ after the working medium is heated by the main heat exchanger 3. The maximum working temperature of the regenerator (2) is 450 ℃.
The invention will be further explained with reference to a specific embodiment:
since the supercritical carbon dioxide power generation technology at the present stage does not have the real situation of large-scale online power transmission, the present embodiment introduces a start-stop method and a control method for controlling the rotation speed of the power consumption through the load box in the supercritical carbon dioxide power generation system with the double-turbine series arrangement based on the field arrangement operation mode of the "generator-load box". I level turbine 4 coaxial coupling has I level generator, and II level turbine 5 coaxial coupling has II level generators, and I level generator and II level generators are connected a load box respectively. The load box adopted in the embodiment should meet the requirement that the minimum power division gear is less than 0.5 percent of the total load. If the requirement of the minimum power of the load box cannot be met, in a rotating speed control logic loop of the I-stage turbine 4 and the II-stage turbine 5, the precise control of the rated rotating speed is abandoned, the operating rotating speed is controlled to be +/-1%, and the rotating speed fluctuation during load adjustment is controlled to be +/-2%.
Before preparation for starting, carbon dioxide working medium enters a balance tank 9 through a high-pressure gas source tank 7 and a booster pump 8. After the carbon dioxide working medium enters the balance tank 9, the compressor 1 operates under low load, the working medium is filled in the main loop system, and the filling pressure is not lower than the minimum safe pressure of the compressor for starting by 3.5-4 MPa. At this time, the compressor bypass 1by, the stage i turbine bypass 4by, and the stage ii turbine bypass 5by are all in the fully open state. The compressor bypass 1by is also called as an anti-surge valve under the normal condition, when the compressor 1 is close to the surge interval to operate, the compressor bypass 1by automatically and forcibly opens quickly, thereby ensuring the safety of equipment and ensuring that the compressor 1 does not operate in the surge interval.
Before the flushing rotation, the compressor bypass 1by is gradually closed, namely, the carbon dioxide working medium is boosted through the compressor 1, enters the heat regenerator 2 for heat exchange, and is heated by the main heat exchanger 3. The cold working medium enters the heat regenerator 2 through the I-stage turbine bypass 4by and the II-stage turbine bypass 5by, and finally, the carbon dioxide cold working medium cooled by the cooler 6 enters the balance tank 9 to be used as an inlet air source of the compressor 1. At the moment, the working medium is in a cold state, the pressure of the compressor 1 is not recommended to be too high, the rated parameter is preferably kept at 50%, the temperature and the pressure of the main heat exchanger 3 are conveniently increased, and the cold-state impact rotation is conveniently carried out again after the protection action.
In the process of impulse conversion, the II-stage turbine 5 with lower operation parameters is started preferentially. When the outlet of the low-pressure heat exchanger 3b in the main heat exchanger 3 meets the air inlet condition, the second-stage turbine bypass 5by can be closed, and the corresponding turbine, namely the quick closing valve and the main regulating valve of the second-stage turbine 5, is opened at the same time, in the process, the first-stage turbine bypass 4by must be kept fully opened, and the carbon dioxide working medium is ensured to have the safe flow which is not lower than the protection value of the main heat exchanger 3. The switching between the stage II turbine 5 and the stage II turbine bypass 5by is carried out in two steps: firstly, according to a logical rotating speed curve, enabling the rotating speed of the II-stage turbine 5 to reach 50% of a rated rotating speed, namely a warming-up rotating speed; the warm-up time is arranged according to the shaft system in the turbine, the warm-up time is not smaller than 30min usually, and the specific warm-up time can be determined by observing parameters such as vibration, displacement and expansion difference of the turbine shaft. After warming up is finished, the second-stage turbine bypass 5by is continuously closed, the rotating speed of the second-stage turbine 5 is increased according to a rotating speed curve in logic, and the actual opening degree of the main regulating valve of the second-stage turbine 5 is kept at 50% (simulation and valve transmission test need to be carried out in advance to determine that the actual opening degree can be actually and accurately monitored and adjusted).
When the II-stage turbine 5 reaches the rated rotating speed, the corresponding load box is immediately put into operation and enters an idle state. If the II-stage turbine bypass 5by is not closed, the II-stage turbine bypass 5by needs to be closed completely, and the corresponding load of the load box is increased. It is recommended that not less than 5% of the total load of the stage II turbine 5 be present.
After the second-stage turbine bypass 5by is completely closed, the first-stage turbine bypass 4by is closed in the same way, and the first-stage turbine 4 with higher operation parameters is started. The 4-stage turbine quick-closing valve and the main regulating valve of the I stage are opened, and the 5-stage turbine main regulating valve of the II stage is suggested to be kept fully opened in the process, so that the maximum flow of the carbon dioxide working medium is ensured all the time. Similarly, when the I-stage turbine 4 reaches 50% of rated rotation speed, namely the warming-up rotation speed, the warming-up is required to be carried out for not less than 30min. After the warming-up is finished, the I-stage turbine bypass 4by is continuously closed, and the rotating speed of the I-stage turbine 4 is increased according to a rotating speed curve in the logic until the rated rotating speed is reached. The load box may then be put into a running unloaded state. If the I-stage turbine bypass 4by is not closed, the I-stage turbine bypass 4by is closed preferentially, and then the output of the compressor 1 or the pressure of the balance tank 9 is increased.
For the requirement of the warm-up rotating speed, the rotating speed of the critical area of the shaft system is determined according to the balance of the turbine shaft system. Under the non-accident working condition, the lifting load is adjusted on the basis of the minimum gear of the load box. The whole flushing process should be closely monitored for the total circulating flow.
The performance of the load box should meet the requirement that the minimum power division gear is less than 0.5 percent of the total load. If the requirement of the minimum power of the load box cannot be met, in the rotating speed control logic loops of the I-stage turbine 4 and the II-stage turbine 5, the accurate control of the rated rotating speed is abandoned, the operating rotating speed is controlled to be +/-1%, and the rotating speed fluctuation during load adjustment is controlled to be +/-2%. That is, during operation, the main regulating valve of the stage i turbine 4 not only controls the stage i turbine 4, but also controls the air intake of the stage ii turbine 5by adjusting the exhaust pressure thereof. In order to ensure the stable backpressure of the carbon dioxide circulation loop, aiming at the condition that the accuracy of the load box is not enough to meet the requirement, and comprehensively considering the power output mode of the safe pure resistance load box of the system, the main regulating valve of the II-stage turbine 5 is recommended to be kept fully opened, and the rotating speed is controlled within the range of +/-1% of the rated rotating speed.
Therefore, in the load-increasing stage, the main regulating valve needs to be alternately operated by the I-stage turbine 4 and the II-stage turbine 5 in advance according to the theoretical load proportion, the opening degrees of the two turbines are not less than 50%, and the load boxes synchronously respond. And simultaneously, the thermal power of the main heat exchanger 3 is increased, and the inlet pressure of the compressor is increased through the balance tank 9 when necessary, so that the system parameters are improved to be in a supercritical state. In the process of load increase, parameters such as excitation, a generator and the like are strictly monitored or the load of the corresponding load box is adjusted to be increased alternately.
The load reduction stage and the load increase stage are the same, the I-stage turbine 4 and the II-stage turbine 5 alternately operate the main regulating valve according to the theoretical load proportion, the opening degrees of the two stages are not less than 50%, and the load boxes synchronously respond. Meanwhile, the heat power of the main heat exchanger 3 is reduced, and the inlet pressure of the compressor is reduced through the balance tank 9 when necessary, so that the back pressure of the circulating system is reduced. In the process of reducing the load, parameters such as excitation, a generator and the like are strictly monitored or the load of the corresponding load box is adjusted to be increased alternately.
Theoretically, when the total load is less than 10% of rated load, the brake can be opened and stopped manually, at the moment, the stage I turbine bypass 4by, the stage II turbine bypass 5by and the compressor bypass 1by are all opened in an interlocking mode by not less than 20%, and the system is required to reduce the circulating pressure to a safe range as far as possible. The specific brake opening time also needs to consider the temperature change of the outlet of the main heat exchanger 3 and the influence on shafting of the I-stage turbine 4 and the II-stage turbine 5. In a full-flow circulation system, the I-stage turbine bypass 4by or the II-stage turbine bypass 5by is opened under the condition that the I-stage turbine 4 or the II-stage turbine 5 is strictly forbidden to be loaded, otherwise, the downstream heat regenerator 2, the cooler 6 and the balance tank 9 are impacted by high-pressure working media, and serious accidents such as leakage and tube explosion can occur in serious cases.
Under the high-load accident condition, the circulating system should cut off the first-stage turbine 4 and the second-stage turbine 5, when the main regulating valve and the air inlet valve of the first-stage turbine 4 and the second-stage turbine 5 are closed, the compressor bypass 1by, the first-stage turbine bypass 4by and the second-stage turbine bypass 5by must be opened 50% quickly, and the compressor 1 can be directly interlocked and shut down to cut off the system power source when necessary.
And when the unit is started in a hot state after fault recovery, the I-stage turbine 4 and the II-stage turbine 5 can be synchronously carried out, the warm-up time is properly shortened, and the fastest recovery of the running state is sought.
It should be noted that the above description is only a part of the embodiments of the present invention, and equivalent changes made to the system described in the present invention are included in the protection scope of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A control method of a supercritical carbon dioxide series double-turbine power generation system is characterized in that the system comprises a compressor (1), a heat regenerator (2), a main heat exchanger (3), a first-stage turbine (4), a second-stage turbine (5), a cooler (6), a high-pressure air source tank (7), a booster pump (8) and a balance tank (9); a compressor bypass (1 by) is arranged between an inlet and an outlet of the compressor (1), a first-stage turbine bypass (4 by) is arranged between an air inlet and an air outlet of the first-stage turbine (4), and a second-stage turbine bypass (5 by) is arranged between an air inlet and an air outlet of the second-stage turbine (5); the air inlets of the first-stage turbine (4) and the second-stage turbine (5) are respectively provided with a quick closing valve and a main regulating valve;
the control method comprises the following steps:
before the system is prepared for starting, carbon dioxide working medium enters a balance tank (9) through a high-pressure gas source tank (7) and a booster pump (8), and then the compressor (1) runs at low load to fill the main loop system with the carbon dioxide working medium; at the moment, the compressor bypass (1 by), the I-stage turbine bypass (4 by) and the II-stage turbine bypass (5 by) are all fully opened;
before the flushing, a compressor bypass (1 by) is gradually closed, a carbon dioxide working medium is boosted through the compressor (1), enters a heat regenerator (2) for heat exchange, enters a main heat exchanger (3) for temperature rise, enters the heat regenerator (2) through a first-stage turbine bypass and a second-stage turbine bypass, is cooled through a cooler (6) and enters a balance tank (9) to serve as an inlet air source of the compressor (1);
in the process of flushing and rotating, the second-stage turbine bypass (5 by) is closed, and meanwhile, a quick closing valve and a main regulating valve of the second-stage turbine (5) are opened, and in the process, the first-stage turbine bypass (4 by) is kept fully opened; when the II-stage turbine (5) reaches the rated rotating speed, the system is immediately connected to the grid or enters a loaded state; if the II-stage turbine bypass (5 by) is not closed, the II-stage turbine bypass (5 by) is closed completely, and the corresponding load of the load box is increased; after the second-stage turbine bypass (5 by) is completely closed, closing the first-stage turbine bypass (4 by), and simultaneously opening a quick closing valve and a main regulating valve of the first-stage turbine (4); the main regulating valve of the stage II turbine (5) is kept fully opened in the process; when the I-stage turbine (4) reaches the rated rotating speed, the I-stage turbine is immediately connected to the grid or enters a loaded state;
steady state operation, entering a load increasing stage, alternately operating the main regulating valve opening degree of the I-stage turbine (4) and the II-stage turbine (5) according to a theoretical load proportion to be not less than 50%, simultaneously increasing the thermal power of the main heat exchanger (3), increasing the inlet pressure of the compressor (1) through the balance tank (9), and increasing system parameters to a supercritical state; in the load increasing process, monitoring excitation and generator parameters or alternatively adjusting corresponding loads to increase loads;
in the load reduction stage, the degree of opening of a main regulating valve is not less than 50% when the first-stage turbine (4) and the second-stage turbine (5) alternately operate according to a theoretical load proportion, the thermal power of the main heat exchanger (3) is reduced, the pressure at the inlet of the compressor is reduced through a balance tank (9), and the back pressure of a circulating system is reduced; in the load reducing process, monitoring excitation and generator parameters or alternatively adjusting corresponding loads to reduce the loads;
when the total load of the system is less than 10% of rated load, the system is manually opened and shut down, and at the moment, the I-stage turbine bypass (4 by), the II-stage turbine bypass (5 by) and the compressor bypass (1 by) are all interlocked and opened by not less than 20%.
2. The control method of the supercritical carbon dioxide tandem type dual turbine power generation system according to claim 1, characterized in that under a high-load accident condition, the first-stage turbine (4) and the second-stage turbine (5) are cut off, main regulating valves and air inlet valves of the first-stage turbine (4) and the second-stage turbine (5) are closed, meanwhile, the compressor bypass (1 by), the first-stage turbine bypass (4 by) and the second-stage turbine bypass (5 by) are all opened 50% quickly, and the compressor 1 is shut down in an interlocking manner.
3. The control method of the supercritical carbon dioxide tandem type dual turbine power generation system according to claim 1, characterized in that the outlet of the compressor (1) is connected with the cold side inlet of the heat regenerator (2), the cold side outlet of the heat regenerator (2) is connected with the high pressure heat exchanger inlet of the main heat exchanger (3), the high pressure heat exchanger outlet is connected with the air inlet of the I-stage turbine (4), and the I-stage turbine (4) drives the I-stage generator; an exhaust port of the first-stage turbine (4) is connected with an inlet of a low-pressure heat exchanger of the main heat exchanger (3), an outlet of the low-pressure heat exchanger is connected with an air inlet of the second-stage turbine (5), and the second-stage turbine (5) drives a second-stage generator; the exhaust port of the II-stage turbine (5) is connected with the inlet of the hot side of the heat regenerator (2), the outlet of the hot side of the heat regenerator (2) is connected with the inlet of the cooler (6), the outlet of the cooler (6) is connected with the inlet of the balance tank (9), the outlet of the balance tank (9) is connected with the inlet of the compressor (1) through a branch and is connected with the pressure pump (8) through another branch, and the pressure pump (8) is connected with the high-pressure air source tank (7).
4. The control method of a supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, characterized in that the outlets of the stage i turbine (4) and the stage ii turbine (5) are provided with a quick-closing valve or a check valve.
5. The control method of the supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, wherein the balance tank (9) is connected to an evacuation pipe, and an electric valve is provided on the evacuation pipe.
6. The control method of the supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, wherein the power sources of the stage i turbine bypass (4 by), the stage ii turbine bypass (5 by) and the compressor bypass (1 by) are pneumatic or electric, and the operation time is < 2s.
7. The control method of the supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, wherein the inlet working pressure of the compressor (1) is 3 to 8MPa, the inlet temperature is 35 to 45 ℃, and the full-load outlet working pressure is 18 to 20MPa.
8. The control method of the supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, wherein the maximum operating temperature of the regenerator (2) is 450 ℃.
9. The control method of the supercritical carbon dioxide tandem type twin turbine power generation system according to claim 1, wherein the heat source of the main heat exchanger (3) is liquid metal, molten salt, steam or flue gas, and the temperature of the carbon dioxide working medium at the outlet of the main heat exchanger (3) is 550-650 ℃.
10. The control method of the supercritical carbon dioxide tandem twin turbine power generation system according to claim 1, wherein the cooling medium of the cooler (6) is water, oil or compressed air.
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