Frequency Conversion Energy Saving Reform Of Induced Draft Fan And Logic Optimization Of DCS After Failure

Boiler induced fan is an important auxiliary equipment in thermal power plant,because it conveys dust and high temperature flue gas,the air volume is large,the wind pressure is high,and the power consumption is huge.The reliability and economy of its operation will directly affect the economy of the power plant.The traditional fan control is the full speed operation of the motor.According to the requirements of the operation parameters,the air volume and wind speed are adjusted by adjusting the opening degree of the air valve or baffle.The opening degree of the draft fan baffle is generally kept between 70%and 80%during the operation of the unit.A considerable part of the energy is consumed on the resistance drop of the baffle,which results in the waste of electric energy,which is not conducive to the regulation of the operation index and economy of the unit.Counterwind It is an important means for power plant to reduce the power consumption of motor and to achieve the purpose of high efficiency energy saving and high efficiency operation.In view of the frequency conversion renovation project of 2 X 135MW unit boiler induced fan in the third phase of Jining Power Plant,this paper first analyzes the present situation of the equipment,and compares the power frequency operation of the induced fan with the frequency conversion operation current under different operating conditions of the unit.In this paper,the feasibility of the frequency conversion transformation project of the induced fan is studied,and the approximate economic benefit is calculated.Then,through the implementation of the whole process of the transformation of the induced fan frequency converter,the technical requirements of the transformation of the inverter and the locking between the control loops are put into effect.The connection between frequency converter and DCS system,the requirement of frequency conversion/power frequency switching,the debugging and testing process of frequency converter are analyzed and recorded.The technical difficulties and treatment methods in the process of transformation are summarized,which has accumulated experience for the same type of transformation projects.The fault trip of the induced draft fan inverter will cause the boiler RB to operate,so that the load of the generator set will be halved.In order to avoid this adverse effect,the inverter fan will automatically cut to the power frequency after the fault occurs.When the unit load is low,that is,the operating frequency of the induced draft fan inverter is low,the sudden change of the inverter fault to the power frequency operation will cause the boiler wind pressure to fluctuate greatly.If the operator fails to adjust in time,the boiler MFT will be easily caused,resulting in the generator being disassembled.The unit is unplanned to stop operation.Therefore,when the inverter inverter is cut to the power frequency operation,the DCS logic automatically reduces the opening degree of the inlet fan of the induced draft fan,and adjusts the air volume of the induced draft fan in time to stabilize the burner in the boiler.In case,the boiler wind pressure is greatly fluctuated to prevent the occurrence of boiler MFT.Based on the actual fault case,this paper further studies the cooperation relationship between the inverter running frequency and the DCS logic automatic control flap opening degree,and through the actual field test,summarizes the DCS to the inlet block when the induced draft fan inverter fails to cut the power frequency.The control relationship of the plate opening degree provides experience for the same type of engineering to improve the operational reliability of the unit.