Research On The Slagging Characteristics Of Blended Coals In A Pilot-scale Furnace

A number of thermal power plants were designed to combust specific fuels. Because supply may be limited or fuels for which the plants were originally designed are now uneconomical, different fuels are now used. Hence, measures should be taken to guarantee the quality of the fuel fired in the furnace. Blending of coals can be used to satisfy the requirements of given utilities. Possible advantages for power plants include reducing fuel costs, more acceptable coals, and improving operation performance.Although the blended coals may have such advantages, the performance of blended coals may not be predicted by interpolating linearly from the performance of the parent coals. Nowadays, the use of several coals blended to satisfy power plant requirements has succeeded at some plants, whereas has caused some unexpected problems at other sites. It is uncertain how a combination of parameters from individual coals will affect power station performance. In the furnace, the interaction between the individual ash particles only happens on the depositional surface and it could be greatly nonlinearThis paper applied digital image techniques to observe the slagging characteristics of blended coals in a pilot-scale furnace. Collected deposits samples were analyzed by scanning electron microscopy linked with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD) and X-ray Fluorescence (XRF) to acquire the microstructure, chemical composition, and mineralogy. The deposit thickness of three blends was between their parent coal A (Datong) and coal B (Shan) and the time to reach stable stage decreased with the ratio of coal B. The addition of coal A in coal B could remarkably restain the growth and thickness of ash deposits.The results of XRD analysis indicated the initial layer was predominantly comprised of the crystalline minerals quartz, anorthite or albite except for coal B. All of the blends and coals contained quartz and Ca-to-Al-silicates like (Ca0.68Na0.32)(Al1.68Si0.32)Si2O8in the slag layer where iron-bearing minerals (e.g., ilvaite) were altered into an amorphous phase. The result of SEM-EDX suggested that there was an elemental disparity between coal ash and deposit.