| Saving energy,increasing efficiency,and reducing emissions are the overall direction for technological improvement of thermal power units currently.Accurately measuring the economics of each unit on-line is of great importance for mastering the working status of equipment,analyzing equipment failures and defects,studying improvement direction,optimizing the operation method,and improving the management level.In addition,with the continuously increase in energy prices,the blending combustion of low-level coal and coal blending optimization are also the main methods for enterprises to reduce the cost of electricity generation.The key to achieve the above technical and economic goals is to measure the amount of fired coal in each unit.Hengshui power plant,one of brunches of China Guodian Corporation,built multiple units by stages which use different types of PLC(programmable controllers)respectively to measure the amount of coal in each bunker of each unit,causing many problems including less-advanced equipment performance and scattered types.What's worse,it is hard to coordinate the management and maintenance interfaces and to realize data interaction.As the increasing demand for higher accuracy of measuring coal amount,the main problem that needed to be solved is to improve the coal measuring accuracy of each unit without adding measuring equipment and changing the coal distribution methods.Electronic belt conveyor scale is equipped on the main conveyor belt for measuring the instantaneous flow rate of total coal of all units.6 sub-conveying belts are installed at the end of the main belt,and 32 coal ploughs are placed on the last belt.By controlling the operation of coal ploughs and sub-conveying belts,the coal on the main belt can get a time-sharing and on-demand distribution and be sent to 16 raw coal silos of 4 boilers.It should be summarized by the unified measurement method.The key to improving the measurement accuracy is to analyze the raw coal transport process on each belt and to count the transport time of coal after operation.In response to the above issues,the relevant main research and technical achievements include:(1)To upgrading the measuring PLC into DCS(Distributed Control System)integrally,and shifting the type as EDPF-NT PLUS.To design the overall equipment layout,engineering wiring,control logic,measurement statistics,and operation display.And the equipment platform should also be provided for accurate furnace measurements.thermodynamic calculation of pulverizing system and the analysis of flue gas composition,two methods are used for information fusion.By using real time operation data validation,the integrated heat output signal.(2)To analyze the process flow of fired coal transportation and blending,to calibrate the corresponding relationship between the measuring time of belt conveyor scale and the bunker-entering time of coal,to measure the instantaneous coal amount and Delivery delay time on each belt of the coal ploughs,belt conveyors and other equipment on site,and to design a fuzzy calculation method to realize a shift of DCS logical configuration.Finally,an accurate coal amount measurement should be achieved.After on-site calibration,the relative error of coal metering after the completion of the project is reduced from 6% to about 1%,which can meet the need for economic analysis of the unit and precise coal blending.At the same time,measurement display interface works well and the workload of equipment maintenance is significantly reduced.In particular,fuzzy calculation and statistical method for fired coal and configuration logic of engineering during the project implementation process have achieved an excellent practical result,which are worth being promoted in other similar plants. |
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