Research And Application Of Coal Blending Optimization Method Based On Fly Ash Carbon Content

The carbon in fly ash is one of the most important factors which influence efficiency of boilers and combustion,economy of power plants and simultaneously the ESP and quality of coal ash for recovery.Accurate real-time measurement of the carbon in flyash and optimization of combustion and operation of boilers are not only useful for regulation of boilers but also helpful for safety and economy of boilers.For supercritical opposed-firing boilers,the carbon content in flyash used to be higher because of low rank of coals and blended coals.Obviously,it is necessary and meaningful to research the factors and reasons for increment of the carbon in flyash so as to find out methods to decrease the carbon effectively.The main content of the paper will be focused on the fly ash carbon content of a supercritical PC-fired boiler of 600MW and the main research content are as follows:(1)Combustion process and characteristics of pulverized coal were analyzed and effect of factors during operation of boilers on burning of pulverized coal were also analyzed,then based on kinetics of combustion reaction,enhancing methods for PC combustion,optimal operation and that for decreasing carbon in the flyash were also analyzed detailed.(2)For coal samples of Jincheng meager-lean coal blended with Pingdingshan bituminous coal at six different ratio,the thermo gravimetric analysis were conducted and the experimental results show that the ignition and burnout characteristics of the blended coal samples presents great differences due to the differences of quality characteristics of the component coal,and the ignition performance of the blended coal tends to be that of component coal with lower ignition temperature and the burnout performance tends to be that of coals with lower volatile content.Besides,the optimal blended ratio of the two coals are determined by method of fuzzy mathematics.(3)Coal pulverizing system is a key auxiliary system for PC-fired boilers,its operational state has significant effects on stability and safety of combustion.In order to solve problems such as lower output,larger diameter of coal particle of pulverizing system which leads to higher flyash carbon,lower efficiency of boiler,in-situ optimal experiments for the pulverizing system of a 600MW boiler unit were conducted.During the experiment,ventilation flow through the tube of mill,opening of the classifier,fineness of the pulverized coal and gas temperature at outlet of the mill were optimized and thereby,an optimal combination of the operational conditions of the pulverizing system were determined.(4)On the basis of the above mentioned experiments,optimization experiments of coal blending for a boiler of 600MW were conducted.Besides,optimization of the coal fineness and excess air were also carried out under conditions of optimal ratio of blended coal.Through the experiment,an optimal operational parameter combination were determined.