Fluidized Bed Boiler Operating Characteristics. Shandong Ultra-high Pressure Reheat Cycle

Recently, there are totally 12 sets of 135 MWe circulating fluidized bed(CFB) boiler units putting into service in Shandong. The ultra high pressure CFB boiler with reheater equipped is adopted for the very first time in china. More attentions are paid on the boiler operation characteristics because of its importance.As the examples of 135 MWe CFB boilers of Shandong, the boilers structure characteristics are introduced. The typical air distributor resistance characteristics and minimum fluidization velocity are obtained through commissioning experiment. The external hot gas generators are first time used for firing the wall of CFB boiler. Its advantage has been proved for firing the wall of large-scale capacity CFB boiler with comparing to two others.Aiming at popular problem in CFB boiler start-up process, the thesis deeply studied the start-up characteristics, put forward the key points in the start process. It can assure the start safety and economy for large CFB boiler in cold start-up process only to control well bed depth, bed grain size distribution, injection oil flow , hot gas temperature, bed temperature and method of feeding coal, bed heating-up rate, oil reducing and breaking operation, air flow no disturbance switch over in time, etc.. The variety relation of operating parameters was analyzed as well as its effect on combustion efficiency and the key points are suggested.With the comparison of the main performance parameter of two kinds of 135 MWe CFB boiler in Shandong for the very first time, it is found that the boiler adopting large clock cover type air distribution button is surpass the boiler adopting " T" shaped air distribution button in bed temperature even, slag leakproof, resistance to wear away. In maximum rating, lowest stable combustion output, boiler efficiency and pollutant exhaust the two kinds of boilers can attain design assurance value. The boiler burning bituminous coal can control fly ash carbon more easily.For higher fly ash carbon and higher platen heat-transfer coefficient in gas side of large boilers, the thesis analyzed and experimented ashing property of a few types coal carrying on the ashing test pedestal of Tsinghua University, tallied up coal ashing property and affecting factor.