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Second, the state of the equipment before the transformation Zunyi power plant # 7125MW unit was put into production in October 1991. Based on the construction funding, ideological understanding and professional standards at that time, the unit thermal control equipment was of a lower grade. The control system was a KMM single-loop control system and a DDZ-II control system. The operation monitoring instrument was a moving coil single-display meter plus an inspection instrument. The composition of ER series recorders, transmitters and actuators are still mostly domestic products with only the level of the 1970s. The following problems exist:
1. As the control system is a localized, single-loop control mode, the entire production process of the unit is divided into its own independent control and measurement system. It is neither information-sharing nor centralized and coordinated control, and it cannot optimize control. Improvement of unit efficiency;
2. Poor performance and low reliability of regulating valves and actuators, low precision of sensors and transmitters, and high failure rate, resulting in poor control quality and low reliability of the automatic control system. The automatic rate of the unit is 87.5%. The normal investment rate is only 75% and it is extremely unsuitable for power production.
3, due to the use of a large number of single-display instruments, the implementation of supervision and control of the disk, operation and maintenance personnel's workload is very large, low labor productivity;
4. After the fault and accident of the unit, there is no change in the real-time record of the monitoring data before and after the analog history record. The accident analysis can only be qualitatively inferred or cannot be inferred at all;
5, load adjustment depends entirely on manual operation, can not quickly and steadily reach the target load, it is difficult to adapt to the grid adaptability requirements of the unit;
6, conventional instruments, control devices can not communicate with MIS, production management personnel can not easily understand the real-time production information, is not conducive to production management.
Third, MAXl000 system and transformation situation (A) basic function MAXl000 system can realize DAS, CCS, SCS, FSSS and other functions. The reconstruction of #7 unit thermal control system uses two sub-function systems:
1. Data Acquisition System (DAS): Real-time collection and processing of unit operation data and equipment status, and providing monitoring means for operators to complete SOE, accident recall, and performance calculation.
2. Closed-loop control system (CCS): Complete the automatic adjustment of the operation of the furnace system, stabilize the economic coordination, and maintain the energy balance of the boiler and turbine.
In addition, the boiler auxiliary chain protection has also been set up: the chaining of auxiliary machines and dampers such as ball mills, induced draft fans, air blowers, and ball mill lubricating oil pumps can be completed.
(two) hardware system (slightly)
Fourth, the system transformation and use of effects (A) scale and scope of transformation 1, I / O configuration: 778 points 2, closed-loop control system, 19 sets of coordinated control: 3 sets of induced wind regulation: 1 sets of combustion control: 1 sets of air regulation: 1 set of water regulation: 1 set of steam temperature adjustment: 4 sets of deaerator water level: 1 set of condenser water level: 1 set of high water level: 2 sets of low water level: 2 sets of shaft seal pressure: 1 set of continuous expansion container water level: 1 set of 3, auxiliary boiler interlocking 4, external transformation range (slightly)
(II) Usage and Effects On August 5, 1998, the MAXl000 system was successfully put into operation after the #7 unit was overhauled. So far, no hardware failures and damages have occurred, and there have been no crashes. The system has measured and displayed accurate parameters, strong anti-interference, convenient operation, flexibility, excellent control performance, and good adjustment quality. Each parameter of the unit is pressed against the red line, and the load is stable. After testing, under the 15MW (125MW-110MW) load disturbance, the control quality of each control system is as follows:
* The DCS of #7 unit can not be put into operation after being put into operation. It has produced better results in reducing coal consumption, regulating load quickly and steadily, reducing steam pressure fluctuations in steam temperature, prolonging unit life, and reducing misoperation.
Economic Benefits: After coordinated control and operation, the oxygen output at the furnace outlet is effectively controlled at 4-6%, which is conducive to stable combustion, which is conducive to the exhaustion of pulverized coal and improved combustion efficiency; the main steam temperature and reheat temperature can be controlled at the rated temperature. The value (the original manual control is lower than the rated value) maintains good economic parameters; the turbine shaft seal adjusts the reliability and stability, eliminates the vacuum drop caused by the shaft seal leakage, increases the steam consumption, improves Unit efficiency. According to the cumulative amount of coal entering the furnace from December 1 to December 30, using positive balance calculations, the coal consumption of Unit #7 is reduced by 3.4 s/kwh before the transformation, and can generate 800 million kWh per year, and the coal price is RMB 150/year. In terms of ton calculation, it can save 410,000 yuan per year. In addition, DCS can reduce the number of operational centralized control personnel by 3, and can reduce wages and benefits by 70,000 yuan. The above direct economic benefit is 480,000 yuan.
Safety benefits: The unit's automatic thermal input rate is greatly improved, the misoperation caused by the operation personnel's operation amount and the difference in operation levels are reduced, the safety and reliability of the unit operation are ensured, and the unit operation condition can be reflected in real time, accurately, and concentratively. This not only reduces the burden of the operator on the supervision of the disk, but also provides equipment failure information quickly and reliably for the operating personnel. The system's historical data recollection and accident sequence recording function provide scientific basis for failure analysis and operation of the unit and failure prediction.
V. Experience in Transformation According to the experience of our factory's transformation, we believe that the DCS transformation of the old unit is necessary and feasible, but the following problems should be noted in the transformation process:
1. A complete DCS should be understood to consist of DCS software, hardware, disk devices, transmitters, measurement switches, cables, and actuators. The transformation of the old unit DCS must be combined with the actual conditions of the unit, selecting and designing from practical, reliable, technologically advanced and economical point of view. If our plant is limited by the design and installation of the unit and controllability, we can only select DAS and CCS for two functions under limited investment. On the other hand, we can't neglect the transformation of related auxiliary equipment to save investment. Transmitter cables, actuators, etc.
2, the old unit DCS transformation, the old disk table is to stay or cancel? Backup hard hand operation to stay how much appropriate? From the transformation of our plant to see, in addition to retain the water level, the main parameters of a small number of important disk tables and backup hard hand exercises, Be determined to cancel the rest of the list and hard hand exercises.
3. Strict management methods must be established for the software management of the DCS system. The software should be loaded strictly in accordance with the manufacturer's procedures.
4. DCS reconstruction should also consider relevant external environmental conditions such as power supply, grounding of control system, and environmental conditions of the equipment room. These should be completed before the DCS system is officially installed.
5. Pay special attention to the training of personnel. Thermal workers must fully participate in the design, configuration, installation and commissioning of DCS system transformation work.
Sixth, concluding remarks Zunyi Power Plant 125MW unit MAXl000. The control system has been put into operation so far, the system is stable and reliable, and the technical performance is excellent. In the unit control application (especially the boiler combustion control) shows a unique technical advantage. The long-term stable operation of the unit coordinated control indicates that the thermal control level of the Zunyi Power Plant has reached a new level. Through the promotion and application of the MAXl000 system, we have trained our team and improved our technical level. At the same time, we have provided successful experience for the retrofitting of thermal control equipment for old units.
Application of MAXl000 Distributed Control System in 125MW Unit
I. Introduction Since the 1990s, the Distributed Control System (DCS) has been widely used in domestic thermal power generating units. Because DCS can conveniently implement various functions such as DAS, CCS, and SCS, and has the characteristics of high reliability and high precision, it has become an alternative to conventional instruments and single-loop controllers. , Improve the control quality, control reliability, improve the management level and reduce the efficiency of the mainstream control system. At present, DCS has been adopted for newly-built large-capacity generating units, and the DCS transformation of old units is also inevitable. To this end, the Zunyi Power Plant adopted the MAXl000 control system to retrofit the original thermal control system of Unit #7.