Interaction of volatiles and char during the combustion of coal blends at high temperature and its evaluation method

The effects of blending ratios,coal types and temperature on the dynamic interaction of volatiles and char during the combustion of typical coal blends were investigated using a customized thermogravimetric analysis system at a constant high temperature. The combustion dynamic parameters were calculated according to real-time quality monitoring at a constant high temperature by this system which can approximately simulate the situation that the pulverized coal was suddenly injected into the furnace. The results show that increasing lignite blending ratio can improve the burning rate and reduce the burnout time of coal blends. Meanwhile the combustion process of volatiles and char overlaps,which is not completely independent. Simultaneously,a spherically symmetric shrinking core model was used to describe the combustion process of coal blends at high temperature. The simulated profiles and experimental profiles could be fitted well. Moreover,it could also be noted that the distinct interaction appeared during the combustion of coal blends at high temperature,and the simple weighted curves,which do not coincide with experimental profiles, could not describe the process. Consequently,an improved weighted method was proposed by changing the weight of high volatile coal to predict the combustion characteristics of coal blends based on those of single coal. This method had more practical significance than dynamic model due to its higher fitness.