关键词: 循环流化床, 石油焦, SO₂排放, 飞灰再循环, 微观结构

Abstract:

The combustion characteristics of a 410 t·h^-1 circulating fluidized bed (CFB) boiler burning the fuels of bituminous coal (BC), 70% BC+30% petroleum coke (PC) and 50% anthracite (AN) +50% PC were studied. The effects of operation parameters, including bed temperature, molar ratio of Ca to S, excess air coefficient, fly ash recirculation rate and limestone microstructure on SO₂ emission were investigated. Test results indicated that all the three kinds of fuels burned adequately in the boiler, and the bed temperature distribution was uniform. For different fuels, SO₂ emission was correspondingly related to fuel sulfur content with the same operation parameters. With increasing bed temperature, SO₂ concentration in the flue gas reduced first and then increased. There was an optimal desulfurization temperature. For burning BC only or 70% BC +30% PC, the optimal desulfurization temperature was about 850℃, while it was between 850－870℃ for burning 50% AN +50% PC, because of the different sulfur contents in the fuel. The SO₂ concentration decreased with increasing Ca/S ratio, excess air coefficient and fly ash recirculation rate. The results also showed that the microstructures of limestones including specific surface area and specific pore volume had distinct impact on their SO₂ retention. Larger specific surface area and higher specific pore volume could enhance their SO₂ capture activities to a certain extent. The optimal temperatures, Ca/S ratios and excess air coefficients for different fuels were recommended for industrial application.

Key words: 循环流化床, 石油焦, SO₂排放, 飞灰再循环, 微观结构