CFD simulation for investigating the effect of coal size on tangentially coal fired boiler combustion

Boiler operation failure often caused by: local overheating on tube wall, coal combustion on super heater area or flue gas temperature exceeding 900 C before entering super heater. For increasing its reliability, boiler should be operated by avoiding the causes. The present CFD simulation was performed by varying mean coal size (35 and 74 micron) and tilting angle (0 and -5 degree). The simulation was performed by maintaining operational boiler parameter, namely: coal flow rate 155 ton/hr, air flow rate 1180 ton/hr and Primary Air: Secondary Air (PA:SA)=0.53.The study was taken on 300 MW tangentially coal fired boiler at PLTU Pacitan. Simulation result shows that selection of coal size 74 micron gives best condition or high reliability since there is no local overheating, flue gas temperature maximum is 836 and all coal burn before entering super heater. On the other hand, selection of 35-micron coal size is not recommended since it causes local overheating on lower boiler area, flue gas temperature reaching 1100 C and 0.015% coal burn on super heater area. The variation of tilting angle gives small effect on the combustion.