Design Of The Combustion Control System For Small-size Circulation Fluidized Bed Boiler

With the rapidly development of national industry, the environment pollutionand haze days problem are becoming more and more serious. So environmentalgovern without delay. Premier of the State Council Keqiang Li pointed that we shouldspeed up to adjust the energy structure, reasonable control the coal consumption,popularize the use of clean coal, accelerate the elimination of old inefficient boilerson the Executive Meeting about haze governance. This master thesis undertake theboiler company’s commissioned project in Zhejiang province about small-sizecirculation fluidized bed boiler combustion control system design. So can update theold boiler, improve the automatic control level and combustion efficiency, finallycomplete energy-saving and emission reduction.This object mainly comes from the small conventional coal boiler reconstructionproject of a Boiler Co. Ltd in Zhejiang. It aims to transform it to a circulatingfluidized bed boiler so that can increase capacity and achieve maximum energysaving. During the reconstruction, it planned to transplanted the control technology inCFBB to the reconstruction boiler, and put forward a set of control scheme for smallCFBB. This master thesis comes from safety production and energy saving, based onthe deeply study of CFBB control system, combined with signal processing, computer,process control and intelligent control technology. It proposed control requirements ofboiler combustion process and based on this put forward the design specifications forCFBB combustion control system, completed system hardware and software design.What have done and achievements obtained are as follows:Firstly, according to small-size circulation fluidized bed combustion runningprocess and based on the field test platform, carding, analyzing and researching thecombustion system control tasks, completed the small-size CFBB combustionsystem’s overall distributed control scheme.Secondly, the hardware design of small-size circulation fluidized bed boilercombustion control system is completed. Based on control requirements, selected thedistributed control system’s hardware. Also, it designed the furnace temperature,steam pressure, furnace negative pressure and flue gas oxygen content detection circuits. Simultaneously, it contains the RS485communication interface circuit andpower circuit.Thirdly, the small-size circulation fluidized bed boiler combustion controlsystem software design is completed. It mainly contains of the overall softwarearchitecture design, master/slaver chips’ software design and each function modulesoftware design. The function modules include A/D acquisition subroutine, PWMoutput subroutine, fuzzy PID control algorithm subroutine and the communicationsubroutine based on Modbus RTU protocol.Fourthly, it completed the PC monitoring interface design for the small-sizeboiler combustion control system. The monitoring interface base on MCGS touchscreen mainly include real-time parameter display, failure alarm, device control,parameter setting and real-time/history curve shows.This master thesis designed a three-tier structure and distributed control systemfor the CFBB consists of upper computer, master and slaver chips. It can provide safeand reliable control for the reconstruction boiler, improve fuel efficiency, ensure astable loading capacity, improve the automatic control level and achieve energyconservation.