Experimental study on the optimum fuel concentration of high-concentration pulverized coal flame and the effect of coal quality

High-concentration pulverized coal flame plays an important role of ignition for coal combustion system with rich-lean burners. In the presented works, a series of tests have been performed in a 1MW tangentially pulverized coal-fired furnace with rich-lean burners and in a simplified down-fired furnace to investigate the relation between the coal quality and the optimum fuel concentration (kg/kg). The results show that there is always an optimum fuel concentration corresponding to the highest furnace temperature and the shortest ignition length for each group of tests on the high-concentration pulverized coal flame, and the optimum fuel concentration generally decreases with the product of volatile content and heating value linearly as the empirical formula Copt=1.0857-0.164VQ0.6.The optimum fuel concentration also decreases when the traditional corner tangential flame is replaced by wall tangential flame. However, when the horizontal rich-lean burner is changed to vertical, it does not affect the value of optimum fuel concentration. NOx emission can be controlled much more efficiently by reducing air, when the coal concentration is in the range higher than the optimum lts can provide a meaningful guide for the efficient and safe operating of coal-fired furnace with rich-lean burners.