Effect of Volatile-Char Interaction on NO Emission during Blended Coal Combustion

摘要

The utilization of blended coals has become popular in China and NOx emission from power plants has attracted extensive attention in recent years.In this paper,investigation on both NO emission and the effect of volatile-char interaction during blended coal combustion has been carried out using a tubular fixed-bed reactor.The separate combustion of volatile and char has been achieved.The effect of volatile-char interaction on the conversion of fuel-N to NO during blended coal combustion has been elucidated.In addition,the total NO emission characteristics in blended coal combustion have also been studied.Experimental results show that the NO emission process presents two peaks when the raw coal is combusted directly.The separate combustion results indicate that the interaction between volatile and char can reduce the conversion of fuel-N to NO.The influence of temperature on the conversion of fuel-N to NO is bidirectional and the NO emission would reach the maximum in the temperature range of 900-1000 °C.The NO emission process during blended coal combustion also presents obvious two peaks similar to single coals.The conversion of volatile-N to NO of blended coals has little relevance to blended ratio and oxygen concentration,while both blended ratio and oxygen concentration have significant influence on the conversion of char-N to NO.The interaction between component coals during blended coal combustion mainly occurs during the combustion process of coal char.Results in the present study are beneficial to understand the volatile-char interaction on NO formation and of crucial significance for minimizing the NO emission in blended coal fired power plants.