CN111981458A - Control method of system under 'steam-retention mode' after secondary reheating unit boiler MFT - Google Patents
Control method of system under 'steam-retention mode' after secondary reheating unit boiler MFT Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B35/00—Control systems for steam boilers
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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
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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
- F01K13/00—General layout or general methods of operation of complete plants
- F01K13/02—Controlling, e.g. stopping or starting
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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steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating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steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines using steam of critical or overcritical pressure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
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
- F22B37/22—Drums; Headers; Accessories therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
- F22B37/48—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers
- F22B37/50—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers for draining or expelling water
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D1/00—Feed-water heaters, i.e. economisers or like preheaters
- F22D1/003—Feed-water heater systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D7/00—Auxiliary devices for promoting water circulation
- F22D7/06—Rotary devices, e.g. propellers
- F22D7/08—Arrangements of pumps, e.g. outside the boilers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22G—SUPERHEATING OF STEAM
- F22G5/00—Controlling superheat temperature
- F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22G—SUPERHEATING OF STEAM
- F22G7/00—Steam superheaters characterised by location, arrangement, or disposition
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- Combustion & Propulsion (AREA)
- Control Of Steam Boilers And Waste-Gas Boilers (AREA)
Abstract
A control method of a system under a 'steam-retention mode' behind a boiler MFT of a double reheating unit comprises the following steps; (1) defining a control target of a steam-keeping mode; (2) setting judgment conditions of automatic triggering and automatic quitting of the steam protection mode; (3) the automatic control of the high-pressure, medium-pressure and low-pressure three-stage bypass and the desuperheating water thereof in the steam-keeping mode is clearly explained; (4) the control logics of a small feed pump machine and a small induced draft fan machine in a steam-keeping mode are explained in detail; (5) further explaining the pressure control of the auxiliary steam header and the action condition of the drain valve group in the steam retention mode; (6) the supply of the shaft seal in the steam-keeping mode is preferably considered, and the control of a condensate system and an auxiliary steam system is also considered. The whole control process is changed from extensive manual control into accurate automatic adjustment. The method has great significance for realizing energy conservation and consumption reduction of the thermal power generating unit, quick recovery of accident shutdown and perfection of the automation degree of the unit.
Description
Technical Field
The invention relates to the technical field of large thermal generator sets, in particular to a control method of a system of a secondary reheating unit boiler in a steam protection mode after MFT.
Background
An ultra-supercritical 660-1000 MW secondary reheating unit (hereinafter referred to as a secondary reheating unit) is generally arranged by adopting a three-level bypass four-stage desuperheater, and is respectively a high-level bypass, a medium-level bypass and a low-level bypass. The unit is conventionally provided with 1 100% steam-driven water-feeding pump (or 2 50% steam-driven water-feeding pumps), 1 electric water-feeding pump and 2 50% steam-driven induced draft fans, and each small machine is provided with five sections of steam extraction and auxiliary steam double-path steam sources. The auxiliary steam main pipe is supplied by five pumps under normal working conditions, the secondary reheating cold section is used as a standby steam source, a machine-in-situ boiler or a starting boiler can be used for steam supply when the machine is started, and the steam source cannot be supplemented in time when the boiler is started under common accident working conditions.
For the double reheating unit provided with the steam-driven water-feeding pump and the steam-driven induced draft fan, when the boiler generates MFT (main fuel trip), the small units of the steam-driven water-feeding pump and the steam-driven induced draft fan in the conventional design are tripped due to the loss of a steam source, so that four adverse effects are caused. Firstly, the unit needs to spend more time when restarting; secondly, after the boiler MFT, the hearth cannot be swept due to tripping of the induced draft fan, and the accumulated incompletely combusted coal powder and combustible gas at the hearth, the flue, the air preheater and the like can deflagrate when the next ignition is carried out; thirdly, a large amount of high-quality hot steam is stored in a pipeline of the large-scale secondary reheating unit system, so that the waste is caused because the high-quality hot steam is not reasonably utilized; and fourthly, for a single-row or non-machine heating unit, no auxiliary steam is used in a thermal state after the MFT of the boiler, and high risk is brought to reliable supply of a shaft seal of the unit.
In the existing transformation optimization, after the unit generates MFT, most of the units utilize a secondary reheating cooling section to supply auxiliary steam, then the auxiliary steam is used for supplying a shaft seal steam source, and a steam-driven induced draft fan and a steam-driven water-feeding pump are directly tripped without speed reduction and operation maintenance treatment. The steam-driven draught fan and the steam-driven water-feeding pump are re-flushed by using a boiler starting or a near-machine steam source, so that the time for starting the machine in a hot state is increased.
Disclosure of Invention
In order to solve the adverse effects and meet the requirements of energy conservation and consumption reduction, the invention provides a control method of a system under a steam-preserving mode after a boiler of a double reheating unit is subjected to MFT, the method can reasonably utilize the heat storage of the system and provide enough auxiliary steam sources on the premise of preferentially ensuring shaft seal steam supply after the boiler is subjected to MFT so as to ensure that a feed water pump small machine and a draught fan small machine are kept running, and meanwhile, through optimization of control logic, the automation degree of the unit is improved, the operation amount of operators under accident conditions is reduced, and the safe, stable and rapid restarting of the unit is realized.
In order to achieve the purpose, the invention adopts the technical scheme that:
a control method of a system under a 'steam-retention mode' after a secondary reheating unit boiler MFT specifically comprises the following steps;
and (3) normal operation of the unit: steam at an outlet of a boiler superheater A enters an ultrahigh pressure cylinder I for acting after passing through an ultrahigh pressure main steam valve 3 and an ultrahigh pressure regulating valve 4, the steam after acting enters a primary reheater cold section D of the boiler for reheating through an ultrahigh exhaust check valve 10, the heated steam enters a high pressure cylinder II for supplying after passing through a high pressure cylinder main steam valve 18 and a high pressure cylinder regulating valve 19 from an outlet of a primary reheater B, exhaust steam enters a secondary reheater cold section E for continuous heating through a high exhaust check valve 20, the steam after secondary heating enters an intermediate pressure cylinder III for acting through an intermediate pressure cylinder main steam valve 25 and an intermediate pressure cylinder reheater regulating valve 26 from an outlet of a secondary reheater C of the boiler, and exhaust steam of the intermediate pressure cylinder III respectively enters a high back pressure condenser N forAAnd a low back pressure condenser NBThe desuperheating water of the high-pressure bypass valve 5 comes from a high-pressure water supply pump outlet main pipe pipeline, the desuperheating water of the medium-pressure bypass valve 14 comes from a middle tap of the high-pressure water supply pump and the electric pump, and the desuperheating water of the low-pressure bypass valve 27 comes from a condensed water main pipe;
after the boiler generates MFT, operating a 'steam-retention mode', directly feeding steam from a boiler superheater A into a primary reheater cold section D for heating through a high-pressure bypass 5, feeding the heated steam into a secondary reheater cold section E from an outlet of a primary reheater B of the boiler through a medium-pressure bypass valve 14, feeding the steam of the secondary reheater cold section E into an auxiliary steam header F through a secondary reheater cold section-auxiliary steam header regulating valve 42 on one hand, and preferentially feeding the steam to a main machine K shaft seal by using an auxiliary steam-to-shaft seal manual gate valve 31 and an auxiliary steam-to-shaft seal electric valve 32; on the other hand, the steam of the auxiliary steam header F supplied by the secondary reheating cooling section E is supplied to the small motor 33 of the induced draft fan through auxiliary steam to maintain that the steam-driven small motor I3000 r/min does not trip, and is supplied to the small motor H of the steam-driven water-feeding pump through the auxiliary steam to the small motor 34 of the water-feeding pump to maintain that the small motor H3000 r/min does not trip, and when the process occurs, the low-pressure bypass valve 27 is kept closed completely.
A control method of a steam-retention mode behind an MFT of a boiler of a double reheating unit comprises the following steps:
(1) when the unit normally operates in a load interval of more than 35% Pe, and a linkage button of a steam-retention mode is normally put into operation, after an MFT (field emission transform) of a boiler operates, a steam turbine-boiler-electric large linkage protection operates, a steam turbine trips, a generator trips, the boiler extinguishes fire, at the moment, the steam-retention mode is triggered, the rotating speed of a small steam feed pump H is over-reset to 3000r/min from a current rotating speed value, a recirculation regulating valve 44 of the steam feed pump is fully opened, automatic control is automatically put into operation after 90 seconds, a main feed water to an economizer inlet bypass electric door 46 of an economizer inlet and a main feed water to an economizer inlet bypass electric door 45 of the economizer are closed in an interlocking manner, a water feeding channel of the boiler is cut off, the small steam feed pump H keeps minimum flow and operates in a recirculation mode, after the steam-retention mode is triggered, a small steam-driven induced draft fan I also quickly reduces the current rotating speed, maintaining the small pneumatic draught fan I to run, and carrying out normal hearth purging;
(2) after the steam keeping mode is operated, whether three-stage bypasses of the high-pressure bypass valve 5, the medium-pressure bypass valve 14 and the low-pressure bypass valve 27 are automatically switched to the steam keeping mode control is checked, namely the high-pressure bypass valve 5 automatically controls the pressure of a primary reheating cold section, the medium-pressure bypass valve 14 automatically controls the pressure of a secondary reheating cold section, and the low-pressure bypass valve 27 is automatically and completely closed;
(3) after the standby normal of the electric water-feeding pump J is checked, the electric water-feeding pump J is started preferentially, the electric water-feeding pump J keeps running in a recirculation mode, if a unit is configured with 2 x 50% of small steam-driven water-feeding pump H, one small steam-driven water-feeding pump H is opened manually, the other small steam-driven water-feeding pump H is kept running, if the unit is a single small steam-driven water-feeding pump H, the rotating speed of 3000r/min is kept unchanged to run normally, the running electric water-feeding pump J and the small steam-driven water-feeding pump H can provide temperature reduction water for high-pressure and medium-pressure bypasses, meanwhile, in order to quickly start the unit, water can be fed into a boiler, after a period of steam-keeping mode operation, the residual steam of the system is reduced gradually, if the starting condition is not available, once the electric water-feeding pump J runs normally, the manual opening of one small steam;
(4) after the 'steam-keeping mode' is triggered, the pressure of a secondary reheating cold section is controlled by the medium-pressure bypass valve 14, at the moment, the auxiliary steam header pressure p3 of the auxiliary steam header F is supplied with steam by the secondary reheating cold section, an operator manually sets the pressure value of the auxiliary steam header F, the set range is 0.6-1.0 MPa, the pressure set value of the auxiliary steam header F is required to be smaller than the pressure value before the medium-pressure bypass valve 14, at the moment, the auxiliary steam preferentially provides a steam source for the main shaft seal K to ensure that the steam used by the main shaft seal K is normal, and meanwhile, according to the requirement of the 'steam-keeping mode', the auxiliary steam stripping supplies steam to the small steam-driven water-feeding pump H and the small steam-driven draught fan I to maintain the normal operation of 3000 r/;
(5) after the 'steam-keeping mode' is triggered for 120 seconds, whether the steam trap of the unit is correctly linked is checked, and the three hydrophobic pneumatic valves 9 and seven hydrophobic pneumatic valves 21 connected with the ultrahigh pressure cylinder I, the high pressure cylinder II and the intermediate pressure cylinder III are required to be opened according to the requirement of control logic, so that the temperature difference between the upper part and the lower part in the cylinder is prevented from being increased due to the accumulation of cooled steam in the cylinder; simultaneously, drainage on pipelines in front of each main steam valve and drainage on high-pressure, medium-pressure and low-pressure bypass pipelines are closed in a linkage manner, waste of system steam is reduced as much as possible, and finally, heat storage of the system is completely used as a steam source of a small machine and a main machine shaft seal K after tripping through automatic control of a three-stage bypass, so that the effect of a steam retention mode design is achieved;
(6) after the 'steam-keeping mode' acts, the control of each subsystem is confirmed to meet the design requirement, and the unit has the condition of hot start, the unit needs to be started as soon as possible, and when the MFT signal is reset and the ignition signal is in place, the 'steam-keeping mode' is automatically converted into the normal start mode, namely, the bypass follows.
In the steam-keeping mode, the low-pressure bypass valve 27 is automatically and fully closed, the medium-pressure bypass valve 14 automatically controls the pressure of the secondary reheating cooling section E, and the high-pressure bypass valve 5 automatically controls the pressure of the primary reheating cooling section D, so that after the boiler generates MFT, the steam-driven feed-water pump small machine H and the steam-driven induced draft fan small machine I can be quickly reduced to a lower rotating speed to maintain operation without generating trip;
the interlocking button in the steam protection mode is specifically arranged right below the original bypass control normal mode, and the automatic control of the steam protection mode can be realized only after the button is put into use.
The automatic triggering condition of the steam protection mode is as follows: automatically starting a 'steam-keeping mode' if and only if the following conditions a, b and c are simultaneously met;
a. the boiler generates MFT action;
b. the load of the unit before the MFT action is more than 35% Pe (Pe is the rated load of the unit);
c. any feed pump is running (either an electric feed pump or any steam feed pump).
The automatic exit condition of the steam protection mode is as follows:
when the MFT signal is reset and the ignition signal is started, the normal starting is automatically changed from the steam retention mode, namely the high-pressure bypass valve 5 controls the main steam pressure, the medium-pressure bypass valve 14 controls the pressure of a primary reheater, the low-pressure bypass valve 27 controls the pressure of a secondary reheater C of the boiler, and the constant value of the pressure of the secondary reheater C of the boiler controlled by the low-pressure bypass valve 27 is set by an operator.
Control of the low pressure bypass valve 27 in the "steam retention mode":
after the MFT occurs, the low pressure bypass valve 27 is closed by override (skipping the protection logic, forcibly acting) and is switched to the manual state in order to keep the low pressure bypass valve 27 fully closed, saving the stored steam of the system pipeline;
and (3) controlling the medium-pressure bypass valve 14 and the temperature-reducing water in the steam-keeping mode:
a. the low pressure by-pass valve 27 is no longer interlocked with the rapid closing of the medium pressure by-pass valve 14 after the rapid closing;
b. the pressure of the intermediate pressure bypass valve 14 is automatically controlled, and is switched to control the pressure behind the intermediate pressure bypass valve 14, namely the pressure of the secondary reheating cooling section, and the given value is the pressure point (the high limit is set according to 75% Pe load pressure) controlled by the original low pressure bypass valve 27 before the unit trips;
c. the temperature-reducing water regulating valve 16 of the middle side valve is automatically controlled, the temperature is initially set to 380 ℃, and the offset value of minus 100 ℃ to plus 50 ℃ is set;
d. the control logic of the intermediate side valve warm water stop valve 17 is kept still, namely the instruction of the intermediate side valve temperature-reducing water regulating valve 16 is more than 2 percent to open the intermediate side valve warm water stop valve 17 in a linked mode, and the intermediate side valve temperature-reducing water regulating valve is closed for 300 seconds when the time delay is less than 2 percent;
and (3) controlling the high-pressure bypass valve 5 and the desuperheating water in the steam-keeping mode:
a. the pressure of the automatic input high side is automatic and is switched to control the pressure behind the high pressure bypass valve 5, namely the pressure of the primary reheating cold section, and the given value is set as the pressure point controlled by the original medium pressure bypass valve 14 before the unit trips (the high limit is set according to 75% Pe load pressure);
b. the high-side temperature-reducing water regulating valve 7 is automatically put in, the temperature of the high-side temperature-reducing water regulating valve is initially set to 400 ℃, and a bias value of-100 ℃ to +50 ℃ is set;
c. the control logic of the high-side desuperheating water stop valve 8 is kept still: namely, the high-side temperature-reducing water regulating valve 7 instructs that the high-side temperature-reducing water stop valve 8 is opened in a way of being connected with each other by more than 2 percent, and is connected with each other by delaying for 300 seconds by less than 2 percent;
the steam feed pump small machine H is controlled in the steam keeping mode:
a. after the MFT occurs, the logic of an MFT interlocking steam tripping water supply pump small motor H is cancelled, and the auxiliary steam is interlocked and opened to a steam electric valve for a water supply pump small motor electric valve 34;
b. the H rotating speed instruction of the steam-driven water-feeding pump small machine is overridden to 3000r/min, but the remote control is not withdrawn, and the operation of an operator can be allowed after the instruction is in place, otherwise, the operation of the operator is locked;
c. the forced full-open steam feed pump recirculation regulating valve (44) is automatically controlled after delaying for 90 seconds;
d. and (3) closing the economizer inlet main water supply to the economizer inlet bypass electric door 46 and the bypass electric door 45, and unlocking the operation authority of the operator after the feedback signal is closed in place.
The small pneumatic induced draft fan I controls in the steam protection mode:
a. after the MFT occurs, the logic of a MFT interlocking steam-tripping driven small draught fan I is cancelled;
b. the auxiliary steam is interlocked and opened to the electric valve 33 of the small induced draft fan;
c. overriding the rotating speed instruction of the small motor I of the steam-driven draught fan to 3000r/min, quitting remote control, allowing an operator to operate after feeding back to the right position, and locking the operator to operate if the rotating speed instruction of the small motor I of the steam-driven draught fan is not 3000 r/min;
and the auxiliary steam header F is subjected to pressure control in the steam retention mode:
the regulating valve 42 from the secondary reheating cold section to the auxiliary steam header is automatically controlled to have two regulating states, namely a constant pressure control state and a sliding pressure control state, the sliding pressure state can be selected during normal operation, the set value of the sliding pressure state refers to the steam extraction pressure of the five sections of the steam extraction machine, the constant pressure operation state can be selected during normal start and stop, the set value is given by an operator, after the steam retention mode is triggered, the constant pressure operation is selected from the secondary reheating cold section to the auxiliary steam header pressure p3, the set value is manually set by the operator, the set range is 0.6-1.0 MPa, the temperature-reducing water regulating valve is automatically controlled, and the set value is 340 ℃ and is offset to-30- +30 ℃.
The control of the drain valve in the steam-keeping mode is as follows:
after MFT action, logic for interlocking and opening high, medium and low pressure steam traps in the original logic is not changed, considering that a steam retention mode is already triggered, in order to reduce unnecessary waste of residual steam in a system, the following automatic control drainage logic is added, and after the steam retention mode is triggered, 120 seconds of pulse signals are delayed to open or close the following drainage:
a. closing a first hydrophobic pneumatic valve 1 on a front pipeline of a main steam valve 3 of the ultra-high pressure cylinder, closing a first hydrophobic pneumatic valve 12 on a front pipeline of a main steam valve 18 of the high pressure cylinder and closing a first hydrophobic pneumatic valve 13 on a front pipeline of a main steam valve 25 of the intermediate pressure cylinder;
b. closing the front pipeline hydrophobic air-operated valve II 2 of the high-pressure bypass valve 5, closing the front pipeline hydrophobic air-operated valve I13 of the medium-pressure bypass valve 14 and closing the front pipeline hydrophobic air-operated valve II 24 of the low-pressure bypass valve 27;
c. closing a first hydrophobic pneumatic valve 11 behind the ultrahigh-discharge check valve 10 and an eighth hydrophobic pneumatic valve 22 behind the high-discharge check valve 20;
d. keeping the auxiliary steam to be supplied to a steam pipeline drainage pneumatic valve eleventh 39 opened for small machine adjustment of the water supply pump;
e. keeping the auxiliary steam to a small machine of the induced draft fan and turning on a steam pipeline drainage pneumatic valve twelve 40;
g. and (3) keeping the pipelines of the third hydrophobic air-operated valve 9 in front of the ultrahigh-discharge check valve 10 and the seventh hydrophobic air-operated valve 21 in front of the high-discharge check valve 20 to be hydrophobic and opened.
A system of a 'steam-retention mode' behind a secondary reheating unit boiler MFT;
the system comprises a boiler superheater A, wherein a steam outlet end of the boiler superheater A is connected with an ultrahigh pressure cylinder I through an ultrahigh pressure main steam valve 3 and an ultrahigh pressure regulating valve 4, and an output end of the ultrahigh pressure cylinder I is connected with a primary reheater cold section D of the boiler through an ultrahigh discharge check valve 10;
the steam output end of the boiler superheater A is connected with a primary reheater cold section D of the boiler through a high-pressure bypass 5;
connect boiler primary reheater B after the cold section D steam output of boiler primary reheater heats, boiler primary reheater B is connected with high-pressure cylinder II through high-pressure cylinder main steam valve 18 and high-pressure cylinder governing valve 19, high-pressure cylinder II exhaust steam is connected secondary reheater cold section E through high-pressure exhaust check valve 20, boiler secondary reheater C is connected to secondary reheater cold section E steam output, and boiler secondary reheater C exports and passes through intermediate pressure cylinder main steam valve 25 and intermediate pressure cylinder governing valve 26 and connect intermediate pressure cylinder III, high back pressure condenser N steam condenser III is connected respectively to intermediate pressure cylinder III exhaust steam endAAnd a low back pressure condenser NB；
The output end of the primary reheater B of the boiler is connected with the cold section E of the secondary reheater through a medium-pressure bypass valve 14.
The steam output end of the secondary reheater cold section E is connected with an auxiliary steam header F through a secondary reheating cold section-auxiliary steam header regulating valve 42, and the output end of the auxiliary steam header F is connected with a main machine shaft seal K through an auxiliary steam-to-shaft seal manual gate valve 31 and an auxiliary steam-to-shaft seal electric valve 32.
And the steam output end of the auxiliary steam header F is connected with a small pneumatic draught fan I through an auxiliary steam to small draught fan electric valve 33.
And the steam output end of the auxiliary steam header F is connected with the steam-driven feed pump small machine H through an auxiliary steam-to-feed pump small machine electric valve 34.
The exhaust end of the intermediate pressure cylinder III is connected with a high back pressure condenser N through a low pressure bypass valve 27 and a desuperheater 28 respectivelyAAnd a low back pressure condenser NB；
The desuperheater 28 is provided with a low-side desuperheating water regulating valve 29 and a low-side desuperheating water stop valve 30.
The invention has the beneficial effects that:
1) the control target of the steam-keeping mode is defined.
2) The method provides the effect required to be achieved by the steam-retaining mode, successfully realizes the speed reduction non-stop operation of a small machine of a water-feeding pump and a small machine of a draught fan after MFT of the boiler, and provides a whole set of control logic with higher automation degree and smaller regulation disturbance.
3) And setting the judgment standard of 'steam-keeping mode' automatic triggering and automatic quitting.
4) The whole control process is automatically adjusted and tracked, the operation amount of operators is reduced, the safe and quick start of the unit after MFT is realized, and the hot start time is greatly shortened.
5) The characteristics of the secondary reheating unit are fully utilized, and the flexible application of the three-level large bypass is realized. The waste of heat storage of the system is reduced, and the economical efficiency of the unit is obviously improved.
6) The supply of the shaft seal in the steam-retention mode is preferably considered, while the control of the auxiliary steam system is taken into account.
7) From the overall safety of the unit, the opening and closing actions of the drain valve group in the steam-retaining mode are optimized.
8) The whole control process is changed from extensive manual control into accurate automatic adjustment. The method has great significance for realizing energy conservation and consumption reduction of the thermal power generating unit, quick recovery of accident shutdown and perfection of the automation degree of the unit, and practice proves that the scheme is feasible and can be popularized.
Drawings
Fig. 1 is a layout diagram of a typical "steam-retention mode" process and control points of a double reheat unit.
Wherein, I is an ultrahigh pressure cylinder, II is a high pressure cylinder, III is a medium pressure cylinder (wherein the medium pressure cylinder and the medium pressure cylinder are in a combined cylinder structure), IV and V are respectively low pressure cylinders, NAHigh back pressure condenser corresponding to low pressure cylinder IV, NBA low back pressure condenser corresponding to the low pressure cylinder V; a is a boiler superheater, B is a boiler primary reheater,c is a boiler secondary reheater, D is a primary reheater cold section, E is a secondary reheater cold section, F is an auxiliary steam header, G is a shaft-added fan, H is a small steam-driven water-feeding pump, I is a small steam-driven draught fan, J is an electric water-feeding pump, and K is a main shaft seal system;
p1 is high side valve back pressure, t1 is high side valve back temperature, p2 is middle side valve back pressure, t2 is middle side valve back temperature, p3 is auxiliary steam header pressure, t3 is auxiliary steam header temperature, and t4 is temperature from a secondary reheat cooling section to the auxiliary steam header desuperheating water regulating valve back temperature;
1. 2, 9, 11, 12, 13, 21, 22, 23, 24, 39 and 40 are respectively a hydrophobic pneumatic valve, 5 is a high-pressure bypass valve, 14 is a medium-pressure bypass valve, 27 is a low-pressure bypass valve, 6, 15, 28 and 43 are desuperheaters, 7 is a high-side desuperheater water regulating valve, 8 is a high-side desuperheater water stop valve, 16 is a medium-side desuperheater water regulating valve, 17 is a medium-side desuperheater water stop valve, 29 is a low-side desuperheater water regulating valve, 30 is a low-side desuperheater water stop valve, 44 is a steam-driven feed pump recirculation regulating valve, 3 is an ultrahigh-pressure main steam valve, 4 is an ultrahigh-pressure regulating valve, 18 is a high-pressure main steam valve, 19 is a high-pressure regulating valve, 25 is a medium-pressure main steam valve, 26 is a medium-pressure electric valve, 35 is a small-driven-pump quick-closing valve, 36 is a small-induced draft fan quick-closing valve, 10 is an ultrahigh-pressure discharge valve, 20 is a high, 33 is a small electromechanical valve for auxiliary steam to an induced draft fan, 34 is a small electromechanical valve for auxiliary steam to a water feed pump, 37 is a small electromechanical valve for five pumping to a water feed pump, 38 is a small electromechanical valve for five pumping to an induced draft fan, 41 is a small electromechanical valve for five pumping to an auxiliary steam header, 42 is a secondary reheating cooling section to an auxiliary steam header regulating valve, 45 is a main water to economizer inlet bypass electric valve, and 46 is a main water to economizer inlet bypass electric valve.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a typical double reheat unit is provided with 4 cylinders, namely an ultra-high pressure cylinder (I), high and medium pressure cylinders (II and III), and two low pressure cylinders (IV and V). Steam at the outlet of the boiler superheater A enters an ultrahigh pressure cylinder I for acting after passing through an ultrahigh pressure main steam valve 3 and an ultrahigh pressure regulating valve 4,the steam after acting enters a primary reheater cold section D of the boiler for reheating through an ultrahigh-discharge check valve 10. Heated steam enters a high-pressure cylinder II from an outlet of a primary reheater B through a high-pressure cylinder main steam valve 18 and a high-pressure cylinder regulating valve 19 for supplying, exhaust steam enters a secondary reheater cold section E through a high-exhaust check valve 20 for continuous heating, the secondarily heated steam enters a medium-pressure cylinder III from an outlet of a secondary reheater C of the boiler through a medium-pressure cylinder main steam valve 25 and a medium-pressure cylinder regulating valve 26 for acting, and exhaust steam of the medium-pressure cylinder III respectively enters a high-back-pressure condenser N for actingAAnd a low back pressure condenser NBCompleting normal circulation;
under the working conditions of unit starting and accidents, steam from a boiler superheater directly enters a primary reheater cold section D for heating through a high-pressure bypass valve 5, the heated steam enters a secondary reheater cold section E from an outlet of a primary reheater B of the boiler through a medium-pressure bypass valve 14, the reheated steam enters a condenser temperature and pressure reduction device from an outlet of a secondary reheater C of the boiler through a low-pressure bypass 27 to complete the whole circulation, the temperature reduction water of the high-pressure bypass valve 5 comes from a high-pressure water feed pump outlet main pipe, the temperature reduction water of the medium-pressure bypass valve 14 comes from a high-pressure water feed pump and a middle tap of an electric pump, and the temperature reduction water of the low-pressure bypass valve 27 comes from a condensed water main pipe.
The steam source of the auxiliary steam header F is provided with a starting boiler or a machine-approaching steam, and the machine-approaching steam comprises five-extraction steam supply and steam supply from a secondary reheating cold section; the main users of the auxiliary steam include steam for a small machine H of a steam-driven water-feeding pump, steam for a small machine I of a steam-driven draught fan and steam supply for a main shaft seal. In addition, the steam sources of the small steam feed water pump H and the small steam induced draft fan I are from an auxiliary steam header and also comprise steam supply from five-section steam extraction of the machine. At the starting stage and below 30% Pe load, the steam source of the small engine is provided by auxiliary steam, and the steam source above 30% Pe load is switched to the five-extraction zone of the small engine. And the auxiliary steam for shaft seal supply supplies steam for the steam return main pipe through the shaft seal, and is finally discharged to the atmosphere through the shaft adding fan G.
As shown in fig. 1: after the machine set is normal and the net belt load is carried out, the high-pressure bypass valve 5, the medium-pressure bypass valve 14 and the low-pressure bypass valve 27 are in a normal following mode, and at the moment, the set values of the high-pressure bypass, the medium-pressure bypass and the low-pressure bypass are the sum of the current actual pressure and 0.5MPa, so that the three-stage bypasses are in automatic closing positions.
When the load of the unit reaches more than 30% Pe, the trap valves 1, 2, 9, 11, 12, 13, 21, 22, 23, 24, 39 and 40 on the system pipeline are automatically closed. At this time, the auxiliary steam header is supplied by five-section steam extraction, the electric valve 41 of the five-section steam extraction to the auxiliary steam header is fully opened, the secondary reheating cold section is used for adjusting the auxiliary steam adjusting valve 42 as a standby steam source, the pressure fixed value is manually input by an operator, and the current five-section steam extraction pressure is usually set to be less than 0.15 MPa. The water supply of the boiler is switched to the steam-driven water-feeding pump small machine H by the electric water-feeding pump J, and the electric water-feeding pump J has starting conditions as hot standby at any time. Meanwhile, the steam source of the steam-driven water-feeding pump small motor H is switched to five-section steam extraction from auxiliary steam, and it is emphasized that the auxiliary steam is kept fully opened to the water-feeding pump small motor electric valve 34 to serve as a hot standby pipeline. The steam source of the small pneumatic draught fan I is also switched to five-section steam extraction supply from auxiliary steam, and the auxiliary steam is kept fully open to the electric valve 33 of the small pneumatic draught fan and is also used as a hot standby pipeline.
When the load of the unit reaches more than 35% Pe, the button of the steam-keeping mode is put into use. At the moment, once the boiler MFT is operated, any electric feed water pump J or steam feed water pump small machine H operates, and then the steam-keeping mode is automatically triggered. After the steam-retaining mode acts, the H instruction of the steam-driven water-feeding pump small motor is over-relaxed to 3000r/min from the current value, five sections of steam are extracted to the water-feeding pump small motor electric valve 37 to be closed in a linkage mode, the auxiliary steam to the water-feeding pump small motor electric valve 34 triggers an opening instruction again, and meanwhile, the auxiliary steam to the water-feeding pump small motor electric valve front drain pneumatic valve eleventh 39 is opened in a linkage mode. Similarly, the override of the instruction of the small motor I of the steam-driven draught fan from the current instruction value is 3000r/min, five sections of steam are pumped to the small motor electric valve 38 of the draught fan to be closed in a linkage mode, the auxiliary steam is used for triggering the opening instruction again to the small motor electric valve 33 of the draught fan, and the auxiliary steam is started to the drain valve 40 in front of the small motor electric valve of the draught fan in a linkage mode.
After the 'steam-keeping mode' is triggered, the high-pressure bypass valve 5 automatically tracks the back pressure p1 of the high-side bypass valve, namely the pressure of a primary reheating cold section, the back pressure p1 of the high-side bypass valve is set according to the value of the middle-pressure bypass valve 14 before MFT, the back temperature t1 of the high-side bypass temperature-reducing water regulating valve 7 is automatically set to be 400 ℃, and the adjustment is carried out according to the offset value of minus 100 ℃ to plus 50 ℃; and the high-side desuperheating water stop valve 8 tracks the high-side desuperheating water regulating valve 7, and is connected when the instruction of the high-side desuperheating water regulating valve 7 is greater than 2%, and is connected when the instruction is less than 2% and is delayed for 300 seconds. The middle-pressure bypass valve 14 automatically tracks the back pressure p2 of the middle bypass valve after being triggered in a steam-keeping mode, namely the pressure of a secondary reheating cold section, the pressure value is set according to the value of the low-pressure bypass valve 27 before MFT, the back temperature t2 value of the middle bypass valve is automatically set by the middle bypass temperature-reducing water regulating valve 16 to be 380 ℃, and the regulation is carried out according to the offset value of minus 100 ℃ to plus 50 ℃; the middle bypass desuperheating water stop valve 17 tracks the opening degree of the high bypass desuperheating water regulating valve 7, and is connected when the instruction of the high bypass desuperheating water regulating valve 7 is greater than 2%, and is connected when the instruction is less than 2% and is delayed for 300 seconds. The low-pressure bypass valve 27 is automatically closed in a linkage manner after being triggered in the steam-keeping mode, and is automatically stopped after being closed in place, so that the low-pressure bypass valve is in a manual state.
After the steam-retaining mode is triggered, the steam turbine interlocks and closes the five-section steam extraction check valve and the five-section steam extraction electric valve due to tripping, at the moment, the auxiliary steam header pressure p3 is supplied with steam by the secondary reheating cold section, an operator manually sets the pressure p3 of the auxiliary steam header through the secondary reheating cold section auxiliary steam header adjusting valve 42, the setting range is 0.6-1.0 MPa, and the auxiliary steam header pressure is required to set the auxiliary steam header pressure p3 value to be smaller than the front pressure value p2 of the intermediate side valve. The secondary reheating cold section is used for automatic control of the auxiliary steam header temperature-reducing water regulating valve, the temperature t4 after the secondary reheating cold section is set to the auxiliary steam header temperature-reducing water regulating valve is initially set to be 340 ℃, and the adjustment is carried out according to the offset of minus 30 to plus 30 ℃.
After the 'steam-keeping mode' is triggered, the water feeding regulating valve of the deaerator is closed to 0 in an overriding mode, automatic water level regulation is recovered after 20 seconds of delay, the set value is still the set value of the original operator, the automatic lowest value of the frequency converter is set to be 30Hz, the pressure of the condensate header is tracked after 15 seconds of delay, and the pressure value is not lower than 1.8MPa and is used for ensuring the lowest pressure required by the operation of condensate fine treatment, low-side temperature reduction water and the like.
After the 'steam-keeping mode' is triggered for 120 seconds, the front drain valves 9, 21, 39 and 40 of the body drain pneumatic valve and the check valve connected with the ultrahigh pressure cylinder I, the high pressure cylinder II and the medium pressure cylinder III are required to be opened, so that the upper and lower temperature difference in the cylinder is prevented from being increased due to the fact that cooled steam is accumulated in the cylinder; and simultaneously closing the drainage valves 1, 2, 11, 12, 13, 22, 23 and 24 on the drainage pipelines in front of the main steam valves and the drainage valves on the high-pressure bypass pipelines, the middle-pressure bypass pipelines and the low-pressure bypass pipelines in an interlocking manner, reducing the waste of system steam as much as possible, and finally using all the heat storage of the system as steam sources of the small machine and the shaft seal after the trip through the automatic control of the three-stage bypass, thereby achieving the effect of the design of a 'steam-keeping mode'.
Claims (10)
1. A control method of a system under a 'steam-retention mode' behind a boiler MFT of a double reheating unit is characterized by specifically comprising the following steps of;
and (3) normal operation of the unit: steam at an outlet of a boiler superheater (A) enters an ultrahigh pressure cylinder (I) for acting after passing through an ultrahigh pressure main steam valve (3) and an ultrahigh pressure regulating valve (4), the acted steam enters a primary reheater cold section (D) of the boiler for reheating through an ultrahigh exhaust check valve (10), the heated steam enters a high pressure cylinder (II) for supplying after passing through a high pressure cylinder main steam valve (18) and a high pressure cylinder regulating valve (19) from an outlet of a primary reheater (B), exhaust steam enters a secondary reheater cold section (E) for continuous heating through a high exhaust check valve (20), the secondarily heated steam enters a medium pressure cylinder (III) for acting from an outlet of a secondary reheater (C) of the boiler through a medium pressure cylinder main steam valve (25) and a medium pressure cylinder regulating valve (26), and the exhaust steam of the medium pressure cylinder (III) respectively enters a high backpressure condenser (N) for actingA)And a low back pressure condenser (N)B)The temperature-reduced water of the high-pressure bypass valve (5) comes from a pipeline of a main pipe at the outlet of the high-pressure water-feeding pump, the temperature-reduced water of the medium-pressure bypass valve (14) comes from a middle tap of the high-pressure water-feeding pump and the electric pump, and the temperature-reduced water of the low-pressure bypass valve (27) comes from a main pipe of condensed water;
after the boiler generates MFT, operating a 'steam-retention mode', directly feeding steam from a boiler superheater (A) into a primary reheater cold section (D) through a high-pressure bypass (5) for heating, feeding the heated steam into a secondary reheater cold section (E) from an outlet of a primary reheater (B) of the boiler through a medium-pressure bypass valve (14), feeding the steam of the secondary reheater cold section (E) into an auxiliary steam header (F) through a secondary reheater cold section to an auxiliary steam header regulating valve (42), and preferentially feeding the steam to a main shaft seal (K) by using an auxiliary steam-to-shaft seal manual gate valve (31) and an auxiliary steam-to-electric valve (32); on the other hand, the steam of the auxiliary steam header F supplied by the secondary reheating cooling section (E) is supplied to the small electric valve (33) of the induced draft fan through auxiliary steam to maintain that the I3000 r/min of the small motor of the steam-driven induced draft fan does not trip, and is supplied to the small electric valve (34) of the water feed pump through the auxiliary steam to enter the small motor (H) of the steam-driven water feed pump, so that the 3000r/min of the small motor (H) of the steam-driven water feed pump does not trip, and when the process occurs, the low-pressure bypass valve (27) is kept completely closed.
2. The method for controlling the system of the double reheat unit boiler in the MFT rear steam-retention mode is characterized by comprising the following steps of:
(1) when the unit normally operates in a load interval of more than 35% Pe, and a linkage button of a steam-retention mode is normally put into operation, after the boiler MFT operates, the steam turbine-boiler-electric large linkage protection operates, the steam turbine trips, the generator trips, the boiler extinguishes fire, at the moment, the steam-retention mode is triggered, the rotating speed of a small machine (H) of a steam feed pump exceeds the current rotating speed value instruction and is 3000r/min, a recirculation regulating valve (44) of the steam feed pump is fully opened, automatic control is automatically put into operation after 90 seconds, a bypass electric door (46) from main feed water to an inlet of an economizer and a bypass electric door (45) from main feed water to the inlet of the economizer are closed in an interlocking manner, a water feeding channel of the boiler is cut off, the small machine (H) of the steam feed pump keeps minimum flow and operates in a recirculation mode, after the steam-retention mode is triggered, a small machine (I) of a steam-driven induced draft fan also quickly reduces the current rotating speed instruction, maintaining the small pneumatic draught fan (I) to run, and carrying out normal hearth purging;
(2) after the steam keeping mode is operated, whether three-stage bypasses of the high-pressure bypass valve (5), the medium-pressure bypass valve (14) and the low-pressure bypass valve (27) are automatically switched to the steam keeping mode control or not is checked, namely the high-pressure bypass valve (5) automatically controls the pressure of a primary reheating cold section, the medium-pressure bypass valve (14) automatically controls the pressure of a secondary reheating cold section, and the low-pressure bypass valve (27) is automatically closed;
(3) after the standby normal of the electric water feeding pump (J) is checked, the electric water feeding pump (J) is started preferentially, the electric water feeding pump (J) keeps operating in a recirculation mode, if the unit is configured with 2 multiplied by 50 percent small steam-driven feed-water pumps (H), one small steam-driven feed-water pump (H) is manually braked, the other small steam-driven feed-water pump (H) is kept to operate, if the steam feed pump small machine (H) is a single steam feed pump small machine, the normal operation is kept at the rotating speed of 3000r/min, the running electric feed pump (J) and the running steam feed pump small machine (H) provide the temperature reduction water for the high-pressure bypass and the medium-pressure bypass at the moment, meanwhile, in order to quickly start the boiler and feed water to the boiler, after the boiler operates in a steam-keeping mode for a period of time, the residual steam of the system is gradually reduced, and at the moment, if the boiler does not have a starting condition, once the electric water-feeding pump (J) operates normally, a small steam-feeding pump (H) can be manually braked;
(4) after the 'steam retention mode' is triggered, the pressure of a secondary reheating cold section is controlled by the medium-pressure bypass valve (14), at the moment, the auxiliary steam header pressure (p3) of the auxiliary steam header (F) is supplied with steam by the secondary reheating cold section, an operator manually sets the pressure value of the auxiliary steam header (F), the set range is 0.6-1.0 MPa, the pressure set value of the auxiliary steam header (F) is required to be smaller than the pressure value in front of the medium-pressure bypass valve (14), at the moment, the auxiliary steam preferentially provides a steam source for the main shaft seal (K), the steam consumption of the main shaft seal (K) is ensured to be normal, and meanwhile, according to the requirement of the 'steam retention mode', the auxiliary steam stripping is used for supplying a steam-driven water-feeding pump small machine (H) and a steam-driven draught fan small machine (I) to maintain 3000r/min of the;
(5) after the 'steam-keeping mode' is triggered for 120 seconds, whether the steam trap of the unit is correctly linked is checked, and the three (9) and seven (21) hydrophobic pneumatic valves connected with the ultrahigh pressure cylinder (I), the high pressure cylinder (II) and the intermediate pressure cylinder (III) are required to be opened according to the requirements of control logic, so that the temperature difference between the upper part and the lower part in the cylinder is prevented from being increased due to the accumulation of cooled steam in the cylinder; simultaneously, drainage on pipelines in front of each main steam valve and drainage on high-pressure, medium-pressure and low-pressure bypass pipelines are closed in a linkage manner, waste of system steam is reduced as much as possible, and finally, heat storage of the system is completely used as a steam source of a small machine and a main machine shaft seal (K) after tripping through automatic control of a three-stage bypass, so that the effect of a steam retention mode design is achieved;
(6) after the 'steam-keeping mode' acts, the control of each subsystem is confirmed to meet the design requirement, and the unit has the condition of hot start, the unit needs to be started as soon as possible, and when the MFT signal is reset and the ignition signal is in place, the 'steam-keeping mode' is automatically converted into the normal start mode, namely, the bypass follows.
3. The control method of the system under the 'steam-retention mode' after the boiler of the double reheat unit is MFT according to claim 2, characterized in that in the 'steam-retention mode', the low-pressure bypass valve (27) is automatically closed, the medium-pressure bypass valve (14) automatically controls the pressure of the secondary reheat cooling section (E), and the high-pressure bypass valve (5) automatically controls the pressure of the primary reheat cooling section (D), and the control mode can realize that after the boiler is subjected to MFT, the steam-driven feed water pump small machine (H) and the steam-driven induced draft fan small machine (I) are rapidly reduced to a lower rotating speed to maintain operation without machine jump;
the interlocking button in the steam protection mode is specifically arranged right below the original bypass control normal mode, and the automatic control of the steam protection mode can be realized only after the button is put into use.
4. The method for controlling the system in the secondary reheating unit boiler under the MFT steam-retention mode as claimed in claim 2, wherein the automatic triggering condition of the steam-retention mode is as follows: automatically starting a 'steam-keeping mode' if and only if the following conditions a, b and c are simultaneously met;
a. the boiler generates MFT action;
b. the load of the unit before the MFT action is more than 35% Pe (Pe is the rated load of the unit);
c. any feed pump is running (either an electric feed pump or any steam feed pump).
The automatic exit condition of the steam protection mode is as follows:
when the MFT signal is reset and the ignition signal is started, the normal starting is automatically changed from a steam-retaining mode, namely, the high-pressure bypass valve (5) controls the main steam pressure, the medium-pressure bypass valve (14) controls the pressure of a primary reheater, the low-pressure bypass valve (27) controls the pressure of a secondary reheater (C) of the boiler, and the constant value of the pressure of the current secondary reheater (C) of the boiler controlled by the low-pressure bypass valve (27) is given by an operator.
5. The method for controlling the system in the post-MFT steam-retention mode of the boiler of the double reheat unit as claimed in claim 2, wherein the control of the low pressure bypass valve (27) in the steam-retention mode is as follows:
after the MFT occurs, the low-pressure bypass valve (27) is closed in an overriding way and is switched to a manual state, so that the low-pressure bypass valve (27) is kept closed completely, and the steam storage of a system pipeline is saved;
control of the medium pressure bypass valve (14) and the desuperheating water in the 'steam-keeping mode':
a. after the low-pressure bypass valve (27) is quickly closed, the medium-pressure bypass valve (14) is not interlocked to be quickly closed;
b. the pressure automatically controlled by the automatic input medium pressure bypass valve (14) is switched to control the pressure behind the medium pressure bypass valve (14), namely the pressure of the secondary reheating cold section, and the given value is the pressure point controlled by the original low pressure bypass valve (27) before the unit trips;
c. the temperature-reducing water regulating valve (16) of the middle side valve is automatically controlled, the temperature is initially set to 380 ℃, and a bias value between-100 ℃ and +50 ℃ is set;
d. and the control logic of the middle side valve warm water stop valve (17) is kept still, namely the instruction of the middle side valve temperature-reducing water regulating valve (16) is more than 2 percent to jointly open the middle side valve warm water stop valve (17), and the connection is carried out for 300 seconds when the time delay is less than 2 percent.
6. The method for controlling the MFT post-steam-retention mode of the boiler of the double reheating unit as claimed in claim 2, wherein the control of the high-pressure bypass valve (5) and the desuperheating water in the steam-retention mode is as follows:
a. the pressure automatically input to the high side is automatically switched to control the pressure behind the high pressure bypass valve (5), namely the pressure of the primary reheating cold section, and the given value is set as the pressure point controlled by the original medium pressure bypass valve (14) before the unit trips;
b. the high-side temperature-reducing water regulating valve (7) is automatically put in, the temperature of the high-side temperature-reducing water regulating valve is initially set to 400 ℃, and the offset value of minus 100 ℃ to plus 50 ℃ is set;
c. the control logic of the high-side temperature-reducing water stop valve (8) is kept still: namely, the high-side desuperheating water regulating valve (7) instructs that the high-side desuperheating water stop valve (8) is opened in a way of linkage when the instruction is more than 2 percent and is closed in a way of delaying 300 seconds when the instruction is less than 2 percent;
the small steam feed pump (H) is controlled in the steam keeping mode:
a. after the MFT occurs, logic of an MFT interlocking steam tripping water supply pump small motor (H) is cancelled, and an auxiliary steam is interlocked to open a steam-using electric door of a water supply pump small motor electric valve (34);
b. the rotating speed of a small steam-driven water-feeding pump (H) is over-ridden and instructed to 3000r/min, but the remote control is not withdrawn, and the operation of an operator can be allowed after the instruction is in place, otherwise, the operation of the operator is locked;
c. the forced full-open steam feed pump recirculation regulating valve (44) is automatically controlled after delaying for 90 seconds;
d. and (3) closing the economizer inlet main water to the economizer inlet bypass electric door (46) and the bypass electric door (45), and unlocking the operation authority of the operator after the feedback signal is closed in place.
7. The control method of the system in the post-MFT steam-retention mode of the double reheat unit boiler as claimed in claim 2, wherein the steam-driven induced draft fan small machine (I) in the steam-retention mode controls:
a. after the MFT occurs, the logic of a MFT interlocking steam-jump driven small draught fan (I) is cancelled;
b. the auxiliary steam is interlocked and opened to the electric valve (33) of the small induced draft fan;
c. overriding the rotating speed instruction of the small steam-driven draught fan (I) to 3000r/min, quitting remote control, allowing an operator to operate after feeding back to the right position, and otherwise locking the operator to operate;
and the auxiliary steam header F is subjected to pressure control in the steam retention mode:
the regulating valve (42) from the secondary reheating cold section to the auxiliary steam header is automatically controlled to have two regulating states, namely a constant pressure control state and a sliding pressure control state, the sliding pressure state can be selected during normal operation, the set value of the sliding pressure control state refers to the steam extraction pressure of the five sections of the machine, the constant pressure operation state can be selected during normal start and stop, the set value is given by an operator, after a steam retention mode is triggered, the pressure (p3) from the secondary reheating cold section to the auxiliary steam header selects constant pressure operation, the set value is manually set by the operator, the set range is 0.6-1.0 MPa, the temperature-reducing water regulating valve is automatically controlled, the set value is 340 ℃, and the offset is-30 to +30 ℃.
8. The method for controlling the system in the secondary reheating unit boiler after MFT in the steam-keeping mode as claimed in claim 2, wherein the control of the drain valve in the steam-keeping mode is as follows:
after MFT action, logic for interlocking and opening high, medium and low pressure steam traps in the original logic is not changed, considering that a steam retention mode is already triggered, in order to reduce unnecessary waste of residual steam in a system, the following automatic control drainage logic is added, and after the steam retention mode is triggered, 120 seconds of pulse signals are delayed to open or close the following drainage:
a. closing a first hydrophobic pneumatic valve (1) on a front pipeline of a main steam valve (3) of the ultra-high pressure cylinder, closing a first hydrophobic pneumatic valve (12) in front of a high pressure main steam valve (18) and closing a first hydrophobic pneumatic valve (13) in front of a main steam valve (25) of the intermediate pressure cylinder;
b. closing a front pipeline hydrophobic air-operated valve II (2) of the high-pressure bypass valve (5), closing a front pipeline hydrophobic air-operated valve I (13) of the medium-pressure bypass valve (14) and closing a front pipeline hydrophobic air-operated valve II (24) of the low-pressure bypass valve (27);
c. closing a first hydrophobic pneumatic valve (11) behind the ultrahigh-discharge check valve (10) and an eighth hydrophobic pneumatic valve (22) behind the high-discharge check valve (20) and in a pipeline;
d. keeping the auxiliary steam to be delivered to a steam pipeline drainage pneumatic valve (39) to be opened for small machine adjustment of the water feeding pump;
e. keeping the auxiliary steam to be transferred to a small draught fan, and opening a steam pipeline drainage pneumatic valve twelve (40);
g. and (3) keeping the pipelines of the front hydrophobic pneumatic valve III (9) of the ultrahigh-discharge check valve (10) and the front hydrophobic pneumatic valve VII (21) of the high-discharge check valve (20) to be hydrophobic and opened.
9. The system under the MFT rear steam-retention mode of the boiler of the double reheating unit based on the control method of claim 1 is characterized in that;
the system comprises a boiler superheater (A), wherein a steam outlet end of the boiler superheater (A) is connected with an ultrahigh pressure cylinder (I) through an ultrahigh pressure main steam valve (3) and an ultrahigh pressure regulating valve (4), and an output end of the ultrahigh pressure cylinder (I) is connected with a primary reheater cold section (D) of the boiler through an ultrahigh discharge check valve (10);
the steam output end of the boiler superheater (A) is connected with a primary reheater cold section (D) of the boiler through a high-pressure bypass (5);
steam output end of primary reheater cold section (D) of boilerConnect boiler primary reheater (B) after heating, boiler primary reheater (B) is connected with high-pressure cylinder (II) through high-pressure cylinder main steam valve (18) and high-pressure cylinder governing valve (19), and high-pressure cylinder (II) steam extraction is connected secondary reheater cold section (E) through high-pressure check valve (20), and boiler secondary reheater cold section (E) steam output end connects boiler secondary reheater (C), and boiler secondary reheater (C) export is connected intermediate pressure cylinder (III) through intermediate pressure cylinder main steam valve (25) and intermediate pressure cylinder governing valve (26), high back pressure condenser (N) is connected respectively to intermediate pressure cylinder (III) steam extraction endA) And a low back pressure condenser (N)B)；
The output end of the primary reheater (B) of the boiler is connected with the cold section (E) of the secondary reheater through a medium-pressure bypass valve (14).
10. The system of claim 9, wherein the post-MFT "steam retention mode" of the double reheat unit boiler is characterized in that; the steam output end of the secondary reheater cold section (E) is connected with an auxiliary steam header (F) through a secondary reheating cold section-auxiliary steam header regulating valve (42), and the output end of the auxiliary steam header (F) is connected with a main machine shaft seal (K) through an auxiliary steam-to-shaft seal manual gate valve (31) and an auxiliary steam-to-shaft seal electric valve (32);
the steam output end of the auxiliary steam header (F) is connected with a small pneumatic draught fan (I) through an auxiliary steam-to-small draught fan electric valve (33);
the steam output end of the auxiliary steam header (F) is connected with the small steam-driven feed pump (H) through an electric valve (34) of the small auxiliary steam-driven feed pump;
the exhaust end of the intermediate pressure cylinder III is connected with a high back pressure condenser (N) through a low pressure bypass valve (27) and a desuperheater (28) respectivelyA) And a low back pressure condenser (N)B)；
The desuperheater (28) is provided with a low-side desuperheating water regulating valve (29) and a low-side desuperheating water stop valve (30).
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010997457.XA CN111981458A (en) | 2020-09-21 | 2020-09-21 | Control method of system under 'steam-retention mode' after secondary reheating unit boiler MFT |
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| CN202010997457.XA CN111981458A (en) | 2020-09-21 | 2020-09-21 | Control method of system under 'steam-retention mode' after secondary reheating unit boiler MFT |
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| CN112960723A (en) * | 2021-02-22 | 2021-06-15 | 西安热工研究院有限公司 | Control system for dynamically switching into deaerator heating system based on time |
| CN113606001A (en) * | 2021-07-29 | 2021-11-05 | 中国能源建设集团华东电力试验研究院有限公司 | 600MW supercritical unit bypass system and bypass temperature control method thereof |
| CN114112411A (en) * | 2021-10-30 | 2022-03-01 | 国家能源集团华北电力有限公司廊坊热电厂 | Steam turbine shaft seal system state monitoring system and method |
| CN114198804A (en) * | 2021-11-25 | 2022-03-18 | 广西电网有限责任公司电力科学研究院 | Steam extraction and heat supply system of steam turbine generator unit with secondary heating function |
| CN114253315A (en) * | 2022-03-02 | 2022-03-29 | 天津国能津能滨海热电有限公司 | Control method for reheating steam temperature of boiler, electronic equipment and storage medium |
| CN114776405A (en) * | 2022-04-11 | 2022-07-22 | 华北电力科学研究院有限责任公司 | Heat supply protection control method and device for cogeneration unit |
| CN114811562A (en) * | 2021-01-28 | 2022-07-29 | 华能北京热电有限责任公司 | Interlocking control method for boiler drum water level of gas-steam combined cycle unit |
| CN114941552A (en) * | 2022-05-13 | 2022-08-26 | 华电电力科学研究院有限公司 | Shutdown non-shutdown heat supply rapid switching control method based on large supercritical reheating type double-extraction back pressure unit |
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| CN114811562A (en) * | 2021-01-28 | 2022-07-29 | 华能北京热电有限责任公司 | Interlocking control method for boiler drum water level of gas-steam combined cycle unit |
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| CN112960723A (en) * | 2021-02-22 | 2021-06-15 | 西安热工研究院有限公司 | Control system for dynamically switching into deaerator heating system based on time |
| CN113606001A (en) * | 2021-07-29 | 2021-11-05 | 中国能源建设集团华东电力试验研究院有限公司 | 600MW supercritical unit bypass system and bypass temperature control method thereof |
| CN114112411A (en) * | 2021-10-30 | 2022-03-01 | 国家能源集团华北电力有限公司廊坊热电厂 | Steam turbine shaft seal system state monitoring system and method |
| CN114112411B (en) * | 2021-10-30 | 2023-09-08 | 国家能源集团华北电力有限公司廊坊热电厂 | Steam turbine shaft seal system state monitoring system and method |
| CN114198804B (en) * | 2021-11-25 | 2023-02-28 | 广西电网有限责任公司电力科学研究院 | Steam extraction and heat supply system of steam turbine generator unit with secondary heating function |
| CN114198804A (en) * | 2021-11-25 | 2022-03-18 | 广西电网有限责任公司电力科学研究院 | Steam extraction and heat supply system of steam turbine generator unit with secondary heating function |
| CN114253315B (en) * | 2022-03-02 | 2022-05-27 | 天津国能津能滨海热电有限公司 | Control method for reheating steam temperature of boiler, electronic equipment and storage medium |
| CN114253315A (en) * | 2022-03-02 | 2022-03-29 | 天津国能津能滨海热电有限公司 | Control method for reheating steam temperature of boiler, electronic equipment and storage medium |
| CN114776405A (en) * | 2022-04-11 | 2022-07-22 | 华北电力科学研究院有限责任公司 | Heat supply protection control method and device for cogeneration unit |
| CN114776405B (en) * | 2022-04-11 | 2024-01-26 | 华北电力科学研究院有限责任公司 | Heat supply protection control method and device for cogeneration unit |
| CN114941552A (en) * | 2022-05-13 | 2022-08-26 | 华电电力科学研究院有限公司 | Shutdown non-shutdown heat supply rapid switching control method based on large supercritical reheating type double-extraction back pressure unit |
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