Research On Combustion Optimization Of Large CFB Boiler

Optimization of electric energy structure, improvement in quantity of power supply, increase in comprehensive resource utilization efficiency and reduction in emission of pollutants have been obtained with irreplaceable contributions made by large numbers of operated CFBBs in China. However, as a newly emerging boiler type, large capacity CFBBs still have problems in system designing, manufacturing, installing, commissioning, auxiliary machine selecting and boiler operating. Statistics show that defects such as low output, short available time, high loss of ignition and large flue gas loss exit to varying degrees in approximate60%CFBBs in China. Optimization of boiler combustion which is conducted by adjusting boiler fuel supply, parameters of air distribution and altering their control methods is a work for acquirement of most suitable combustion conditions for boilers while immediate, complete, stable and continuous combustion of fuel that entered into a boiler furnace is guaranteed as well as fulfilling requirements for load changes.In this paper, combustion optimization for220t/h,440t/h,1177t/h boilers which have been widely utilized in China is respectively carried out. Employing single factor or orthogonal experiment method, adjusting critical parameters such as mean diameter of coal particles, total air volume, fluidizing air rate, primary to secondary air rate, bed pressure and bed temperature, systematical experiments were performed. Thorough study into influence of each critical parameters on boiler combustion efficiency, unit economics and pollutants emission was conducted. Experiments indicate that optimized operating parameters corresponding to safe and stable operation of boilers and improved boiler efficiency are obtained through combustion adjusting test. Boiler efficiency is obviously improved when comparing with that before adjusting, and increased Ca to S mole ratio will greatly improve desulfuration efficiency. But in order to improve limestone utilizing efficiency, furnace temperature must be accurately controlled. Analysis on experimental results presents that trends followed by the influence of primary air ratio, total air volume and bed pressure on efficiency of CFBBs with different capacity are the same and laws discovered by these experiments apply to guiding efficient and safe operation of utility boilers with different capacity and of different type.