Coal combustion characteristics in a pressurized fluidized bed

The characteristics of emission and heat transfer coefficient in a pressuri zed fluidized bed combustor are investigated. The pressure of the combustor is fixed at 6 atm. and the combustion temperatures are set to 850, 900, an d 950 degrees C. The gas velocities are 0.9, 1.1, and 1.3 m/s and the exces s air ratios are 5, 10, and 20%. The desulfurization experiment is performe d with limestone and dolomite and Ca/S mole ratios are 1, 2, and 4. The coa l used in the experiment is Cumnock coat from Australia. All experiments ar e executed at 2 m bed height. In this study, the combustion efficiency is h igher than 99.8% through the experiments. The heat transfer coefficient aff ected by gas velocity, bed temperature and coal feed rate is between 550-80 0 W/m(2) degrees C, which is higher than those of AFBC and CFBC. CO concent ration with increasing freeboard temperature decreases from 100 ppm to 20 p pm. NOx concentration in flue gas is in the range of 5-130 ppm and increase s with increasing excess air ratio. N2O concentration in flue gas decreases from 90 to 10 ppm when the bed temperature increases from 850 to 950 degre es C.