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The No. 1 and No. 2 units are the first 300MW units that actually use the Tangential-fired anthracite burning in the country. When the auxiliary machine equipment fails to trip during operation, the RB function is not put into operation, so that the operation and operation adjustment under this working condition is very large, and various factors such as operating experience often occur due to improper parameter adjustment after the auxiliary machine trips. Affecting the stable operation of the unit, even the unit's de-listing accident occurred. Therefore, investing in RB function has positive significance for improving the unit's operational reliability.
1. RB's function and strategy RB is the abbreviation of RUNBACK, which means that when the unit's main auxiliary engine malfunction trip causes the unit's actual power to be limited, in order to adapt to the equipment's output, the control system will force the unit load to still be able to operate auxiliary equipment. Load target value, this function is called auxiliary machine fault load reduction.
The perfect RB control strategy is based on the stable investment of the coordinated control system. It should be coordinated internally (that is, the coordinated control system) to ensure the balanced transition of operating conditions; external coordination of FSSS, DEH, SCS control The system can quickly and smoothly reduce the load to the permissible range of the unit output.
Although the No. 2 unit coordination control system of Nanopower has not yet been put into operation, the DEH power is automatically stabilized, and automatic control systems such as combustion, feedwater, negative pressure, and steam temperature can also be invested for a long time. Based on this, the RB control strategy is designed. The RB function is completed by SCS, DEH, MCS, and FSSS: SCS system realizes the generation and blocking of RB instruction and related device interlocking actions after RB; DEH receives the RB instruction through RB interface and sets the target value in advance. And the load reduction rate is automatically performed; the MCS completes the adjustment of the relevant automatic system to ensure the smoothness of the RB process; the FSSS completes the function of automatically removing the powder feeder and the oil gun.
The RB project designed for Unit 2 has the following 5 items:
(1) The load is greater than 270 MW. An air preheater trips during operation of the two air preheaters.
(2) The load is greater than 270 MW, and a blower trip occurs during the operation of the two blowers.
(3) The load is more than 270MW, and a draft fan trips during the operation of the two induced draft fans.
(4) The load is more than 250MW, and a primary fan trip occurs during the operation of two primary fans.
(5) The load is more than 250MW, and the operation time of a single feed pump exceeds 2s.
Second, the RB test of Unit 2 Introduction The purpose of the RB test is to verify the rationality of the design of the control system in terms of function, logic, timing, etc.; in the normal operation of the inspection unit, if an auxiliary machine contained in the RB fails, the main heat of the unit is passed. The mutual cooperation of the work control systems reduces the unit load quickly and safely to the maximum possible value that can actually be achieved with stable operation. This is an important test of the function and performance of the automatic control system of the unit.
In 2003, after the dynamic test of induced draft fan RB was conducted in our factory, in 2004, a dynamic test of air preheater, blower, primary blower, and feed pump RB was carried out using the start-up load time after the two-cylinder unit overhaul. The test is as follows.
1. Preparations before the test (1) The unit's analog control system (MCS), combustion, feedwater, steam temperature control systems, and other auxiliary control systems have all been put into operation.
(2) The unit sequence control system (SCS, including group level, sub-group level) has been put into normal operation; the boiler furnace safety monitoring system (FSSS) has been put into operation; the DEH system has been put into operation normally.
(3) In the control system, the static test of the RB function has been completed. Based on empirical data or design data, the RB target load and the load instruction change rate have been initially set. Under the shutdown condition, according to the designed RB item, the conditions generated by RB are simulated in turn, and the FSSS and SCS systems have automatically performed related operations according to predetermined requirements. Confirm that under the RR condition, all functions have been correctly implemented according to the design requirements.
(4) The unit protection system is normally put into operation.
(5) In order to ensure smooth fuel injection during the RB test, the oil gun input test should be conducted before the test.
2. Test procedure (1) Induced draft fan RB test Before the test, the unit was operated with a 30 lMW load (100% ECR). Press the A blower trip accident button on the spot to artificially generate the RB signal. The operation process is as follows: 1 RB action alarm signal is sent out; 2#13, #15, #14, #16 are automatically shut down in 15s intervals to the powder machine, and after the powder machine is shut down, the corresponding damper is closed to 0%; 3A blower fan leaves It will be automatically forced to 100%, and the air-feeding leaves will be automatically closed by 5%. 4DEH will automatically operate at a target value of 240MW and a load reduction rate of 40MW/min. The 5th unit will operate stably after the load drops to 238MW.
Unit load reduced from 30lMW to 238MW stable operation time 78s. In the RR process, the feed water and the primary air are all normally adjusted; the main steam pressure is increased from 15 MPa to 16.58 MPa; the main parameters of the drum water level, furnace pressure, main steam temperature, and reheat steam temperature meet the unit operation requirements.
(2) Air preheater RB test Before the test, the unit operated stably with 305 MW load (100% scale ECR). Due to the frequent jamming of the air preheater, it is determined that the air preheater is not actually stopped. Artificially, the RB signal is generated by disconnecting the terminal of the “A air preparator operationâ€. The operation process is as follows: 1 RB action alarm signal is issued; 2#13, #15, #14 are automatically shut down to the powder machine at intervals of 15 seconds, and after the powder machine is shut down, the corresponding damper is closed to 0%; 3, the supply air fan leaves automatically Strong off 5%, induced draft fan stationary blade, primary windshield to maintain automatic adjustment; 4DEH automatic target value 240MW, load reduction rate 40MW/blood n action; (5) unit load stable down to 242MW.
The unit load was reduced from 305 MW to 242 MW. The stable operation time was 72 s. During the RB process, the main steam pressure is increased from 16.8 MPa to 17.8 MPa; the maximum fluctuation range of the furnace negative pressure is -17.5 to +85 lPa. The operator manually removes #10 to the powder machine, and #3 oil gun is injected; the water level of the drum is The parameters such as steam temperature and reheat steam temperature meet the unit operation requirements.
(3) Blower RB test Before the test, the unit was operated with a 30lMW load (100% ECR). Locally press B blower trip accident button to artificially generate RB signal. The operation process is as follows: 1 RB action alarm signal is issued; 2#13, #15, #14.#16 are automatically shut down to the powder machine at intervals of 15 seconds, and after the powder machine is shut down, the corresponding throttle is closed to 0%; 3A air supply The motorized leaves will be automatically opened to 100%, and the induced draft fan will automatically close at 5%. 4DEH automatically operates with a target value of 240 MW and a load reduction rate of 40 MW/min. Unit 5 operates stably after the load is reduced to 238 MW.
The unit load was reduced from 301 MW to 283 MW with stable operation time of 78 s. In the RB process, the water supply automatically and induces wind. The primary air is maintained normally; the main air pressure is increased from 15MPa to 16.58MPa; the main parameters of the drum water level, furnace pressure, main steam temperature, and reheat steam temperature meet the unit operation requirements. .
After the end of the RB, the blower A swells and the boiler MFT moves, and the first "two blowers stop." Since the blower RB has ended at the time of the MFT, and all logic and equipment are operating normally, the blower RB test is considered to be qualified. The blower surge problem needs to be solved separately.
(4) Before the test of primary fan RB test, the unit has stable operation with 300MW load (100% ECR). Due to the fear that the primary air pressure could not be maintained, the BOA and DOA oil guns were put into advance, and the A blower trip accident button was pressed on site to artificially generate the RB signal. Action over and as follows: 1 RB action alarm signal issued; 2#13.#15.#14.#16 to the powder machine automatically shut down in 6s intervals, to shut down the powder after a corresponding throttle closed to 0%; 3B once The fan baffle is automatically opened to 100%, the air-supply motorized leaves automatically override 5%, and the induced draft fan vanes remain automatic; the 4DEH automatically targets 200MW. The load-reducing rate is 40MW/min; 5th unit load is reduced to l99MW, and the operation is stable.
The unit load was reduced from 300 MW to 199 MW with a stable operation time of 93 s. During the RB process, main steam pressure increased from 16.64 MPa to 18.7 MPa. The operating personnel removed 4 sets of C-layers to the powder machine, and put #3 oil guns; the minimum air pressure was reduced to 1.3 KPa. The furnace negative pressure in the furnace was up to +964 Pa; the water level of the drums. Main steam temperature. Reheat steam temperature and other parameters meet the unit operation requirements.
(5) Steam pump rubber B test Before the test, the unit operated stably with 305 MW load (100% ECR). In order to avoid the unsafe water level caused by the pot, the electric pump was used as a hot spare to conduct the test. In the logic application, the lock pump was connected and the #2.#4 oil gun was put in advance. A small machine was turned on and off in place to artificially generate RB. signal. The operation process is as follows: 1 RB action alarm signal is issued; 2#13, #15, #14, #16.#9.#12 are automatically shut down at 6 s intervals to the powder machine, and the corresponding throttle is closed after the powder machine is shut down. %0; (3) Air-supply motorized leaves are automatically forced to close by 5%, the induced draft fan stator blades and primary air-blower baffles are kept automatic; 4DEH is automatically set to a target value of 18OMW. The load-reducing rate is 50Mw/min, and the unit load is reduced to 177MW and stabilized.
Unit load fell from 305MW to 177MW stable operation. When used 105s. During the RB process, the main steam pressure increased from 15.22 MPa to 18.1 MPa, and the water level fluctuation range of the drum was -74.39 to +50.21 mm. The operator manually removed #10.#12 to the powder machine and put it into #3 oil gun; the water level was always Automatically adjusted by B small machine. Electric pump hot spare end participate in water level adjustment; furnace pressure, main steam temperature, reheat steam temperature and other parameters meet the unit operation requirements.
Third, improve and improve the logic function of RB According to the experimental situation and system analysis, improve the RB control strategy that is not perfect, the main contents are:
(1) Air preheater RB: For the phenomenon that the vapor pressure rises rapidly during the test, the number of powder feeders will be automatically shut down and changed from 3 to 4 sets with an interval of 6 seconds; the load reduction rate is changed from 40 MW/min to 30 MW. /min.
(2) Primary fan RB: According to the analysis of the test phenomenon, the primary fan trip has a greater impact on the combustion of the furnace, causing unstable combustion, and the increase of automatic oil injection can play a stable burning role, thus increasing the automatic injection of two oil guns (#) 1.#3) Logic. In response to the rapid rise in steam pressure, the number of feeder trips was changed from 4 to 6 units with an interval of 6 s; the load reduction rate was changed from 40 MW/min to 30 MW/min.
(3) Feedwater pump RB: Increase the logic of automatically putting two oil guns (#1.#3); reduce the load rate from 50MW/Mn to 40MW/Mn. In addition, considering that the primary air pressure has a great influence on the test, the primary air baffle is added to close the 5% logic.
(4) From the water level of the drum, the water supply can be automatically tracked normally, but when the RB occurs in the feed pump, the maximum speed of the B steam pump is 5743 rpm, and only 7 rpm from the overspeed protection operation value (5750 rpm), which will almost cause the interruption of the water supply. In order to avoid overspeed tripping of a single steam pump in operation, the upper limit of the speed command of A and B small machines is set to 5650 rpm.
(5) Because DEH of Unit 2 only has 4 RB interfaces, in which RBl has been used as the boiler MFT action does not reduce the load when the machine jumps, so modify the RB working condition of the air preheater and the RB working condition of the sending and induced draft fan to share 1 RB. Interfaces (all four upper layer feeders, interval time 15s, load reduction rate 30MW/min, target value 240MW), primary fan RB. Feedwater pump RB. Each with 1 RB interface.
IV. Problems to be Solved (1) Coordinated control at the end of the input, after the RB action, the turbine is automatically derated by the DEH, but the boiler side cannot completely eliminate manual intervention. The next step is to put the RB function into the coordinated control system as a whole after putting into coordinated control.
(2) Regarding blower surge tripping problem, our plant has happened many times, and we have not yet found the root cause. We have planned to add a differential pressure transmitter to monitor its change trend, to facilitate the search for causes and to remind operators to intervene early.
V. Conclusion At present, the RB function of the domestic unit is basically realized under the coordinated control mode. Under the condition that the coordinated control mode of the Unit 2 of the nanopower unit is not put into use, the RB dynamic test is qualified, which proves that the overall control strategy is effective. In the RB automatic processing process, the interlock control is accurate, most of the automatic adjustment parameters are controlled within the alarm range, and a small number of large fluctuation parameters do not exceed the trip value conversion, reaching the power industry standard DL/T657-1998 "firepower. Power plant analog control system on-line test test requirements". At present, the above five kinds of RB functions have been put into use normally in the No. 2 unit, which has reduced the operating strength of the operating personnel and further improved the reliability and automation level of the unit operating machine.
Nayong Power Plant has an installed capacity of 8×300MW. Units 1 and 2 are produced by the three major mainframe plants in Harbin. DCS adopts the I/A series of Shanghai FOXBORO, and DEH is the DEH-IIIA produced by Xinhua Control Engineering Co., Ltd. Each boiler has 4 layers of 16 pulverized coal burners. The main auxiliary equipment includes: 2 sets of 50% capacity blades with adjustable axial flow fans; 2 sets of 50% capacity blades with adjustable axial flow induced draft fans; 2 sets of 50% capacity centrifugal primary fans; 2 sets with 50% capacity rotation Air preheater; The main water supply system consists of two sets of 50% B-MCR capacity steam-operated feed pumps (normal operation) and one 50% B-MCR capacity electric variable-speed feed pumps (startup and backup).