The unstable combustion caused by coal quality variation is a key factor affecting operation of the boiler for 600 MW unit in one power plant.Taking the said boiler as the object of study

a three-dimensional structure of the furnace has been established and a mesh being produced through Gambit software.A reasonable mathematic model has been chosed from FLUENT software and the combustion in furnace being numerically simulated under condition of burning coals with different quality.The results show that the temperature and concentration of CO in the furnace are higher as the coal quality becomes better

the phenominon of seperating pulverized coal from air being alleviated

the ignition of pulverized coal being earlier

and the fullness of flame in the furnace becoming gradually better

but the effectiveness of burners' block being decreased

the results of simulation tally comparatively well with actual operation of teh boiler.