Design And Realization Of Boiler Automatic Control System In Hear Source Plant

Due to the increasing of energy consumption and environmental pollution,all Ministries and commissions of Beijing,Tianjin and Hebei governments vigorously implement the project of coal to gas,aiming at using new energy to alleviate traditional energy consumption such as coal and reduce environmental and atmospheric pollution.Ping Gu Heat Source Plant is also one of the key project of coal-to-gas conversion in Beijing.After its operation and commissioning,Ping Gu Heat Source Plant has solved the central heating problem of more than 21730 households.The paper designs and implements the automatic control system of boiler in Ping Gu Heat Source Plant.Two 14 MW and one 29 MW gas-fired hot water boilers and a heat exchange system are installed in the boiler room.In this paper,the gas control system,water treatment control system and heat exchanger control system in the boiler operation system of heat source plant are designed and explained respectively.Therein,the gas control system designs flammable gas alarm system which is such necessary in engineering and the linkage control system between flammable gas alarm and explosion-proof axial-flow fan;Induced draft fan starts the converter through the signal processed got from the differential transmitter by applying closed loop control principle,and then achieves the control of negative pressure in the furnace;The air-blower controls the oxygen content in the flue gas through adjusting the speed of the blower by using the frequency converter,so as to achieve the closed-loop control of the optimal value of full fuel combustion,Energy saving and emission reduction of gas system can be realized by designing frequency conversion speed regulating system of air-blower and induced draft fan.In water treatment system,Siemens S7-200 PLC,EM222 CN 8-bit output expansion module,EM235 analog input and output module,PBA program controller and timer are selected to control the time and flow of water in each process including treatment backwashing,regeneration,forward washing and operation.Through the design of water treatment core process and system configuration,the automatic control of water treatment system by PLC is further realized.In the control system of heat exchanger unit,the suitable control scheme and control algorithm are selected according to the workingprinciple of heat exchanger unit.The system adopts single chip computer AT89C51,analog processing module CD4051,conversion module AD0809A/D,and I/O module extension 8255 A to realize sampling program,digital filtering,scale conversion and linearization processing,judgment channel,over-limit alarm,Fuzzy-PID operation and water replenishment.Pump switching and circulating water pump switching functions.Through the automatic control system of heat network exchange,which is composed by the Measurement system(including flow rate,primary and secondary pipe network temperature,pressure,outdoor temperature and other state monitoring sensors and water tank level measurement sensors)and the PLC control system together,the primary network water supply flow and the primary network water supply temperature are adjusted.Finally,the heat source plant transmits data through Ethernet and 485 bus,and then collects the information of each control system into the total automatic control system of the whole project for centralized control.PingGu Heat Source Plant realized the first phase of heating on November 20,2017.After stopping heating in the following year,it was renovated twice.Finally,it delivered to Ping Gu Heating Company of Bei Jing Air Group on October 1,2018.According to the calculation,the heating area is 172,1600 m2 and the heat load is 84,340 KW.