Pollutant emission and attrition performance of low calorific blended coals during co-combustion in fluidized bed

Abstract

The co-combustion technology in the fluidized bed is usually used for the utilization of low-rank coals. The pollutant emission and attrition of coal particles, which are subject to bed temperature, excess air coefficient, mixture ratio and particle size, cannot be ignored. In this work, a pyrolysis-combustion-fragmentation method was presented to study the attrition and the quantitative fragmentation indexes of different coal blends, followed by the experimental investigation of the blended coal's gaseous pollutant emissions in a fluidized bed combustion reactor. As demonstrated by the experimental results, the emission of N2O decreases with increasing the bed temperature from 800 to 850 °C, while attrition rate increases with the bed temperature. Increasing the excess air coefficient is conducive to reducing CO2 and SO2. Considering the low flue gas emission and the attrition behavior, the mixed ratio of raw coal, coal gangue and coal slime at 20:60:20 may be an appropriate choice for their co-combustion in a fluidized bed reactor. The main reason for the fragmentation of blended-coal particles is the primary fragmentation. This study is useful for optimizing the condition of blended coal’s combustion in CFB boiler.