Interaction of blended-coal combustion process:Influence of coal rank on combustion and NOx emission characteristics

The influence of coal rank on the combustion and NOx emission characteristics are performed for four coals and their blended coals (25% ,50% and 75% ) under the out-furnace and in-furnace blending methods in this paper. The results show that these two opposite effects during the blended coal combustion,i. e. the promote function and the restrain function,are different under different types of coals. Under the out-furnace blending method,the interaction of blended coal is obvious when the volatile content of coals is widely different;especially,the burnout rate decreases ob- viously and the restrain function are found at the blending ratio of 75% . The interaction of blended coal is slight when the volatile content of coals is similar,the blended-coal burnout rate is closed to the linear principle. NOx emissions of blended coals follow the linear principle. Under the in-furnace coal blending method,the independent combustion of individual coals is enhanced as postponing the mixing time,and the blended-coal burnout rate is closed to the linear predicated value,the independent combustion of individual coals becomes stronger. For these coals with widely different volatile content,the effect of the mixing time on the burnout is significant;but for these coals with similar volatile content,the blended-coal burnout rate change is slight as postponing the mixing time. NOx emissions of blended coals decrease as postponing the mixing time.