The fragmentation of coal particles during oxy-fuel combustion in a circulating fluidized bed

摘要

The fragmentation of coal plays a significant role during combustion process in circulating fluidized-bed boilers because it accelerates combustion and influences the distribution of particle sizes in the bed. Fine char particles produced by comminution can be carried out and increase the heat loss due to incomplete carbon conversion. The main objective of this study was to determine the degree of primary and secondary fragmentation for coal particles during oxy-combustion in a circulating fluidized bed. The effects of coal type, particle size, bed temperature and oxygen concentration on the extend of primary and secondary fragmentation have been determined. Fragmentation tests were conducted in a 12-kW bench-scale oxy-CFB combustor. The experiments with one brown and two hard Polish coals were carried out in air (base case) and mixtures of O_2/CO_2 with oxygen concentrations in the range from 21% to 40%vol.