循环流化床富氧燃烧下飞灰的碳酸化

利用热天平对2种电站循环流化床飞灰富氧燃烧条件下碳酸化的特性进行了实验研究。重点探讨了温度和CO2浓度对CaO碳酸化速率的影响规律。发现温度是CaO碳酸化的重要影响因素。在500~800 ℃内，温度升高会加速碳酸化反应，包括反应速率和最终转化率。得出：富氧燃烧下CFB中的高温受热面，将是CaO发生碳酸化并结垢的主要部位。飞灰碳酸化的实验结果表明，高的CO2浓度是会加速CaO的碳酸化反应，得到更高的转化率。但是，这种影响随着温度的降低而减弱。飞灰孔隙特性也对CaO的碳酸化反应起很重要的作用。对CaO活化能的计算，采用了分区计算的方法。2种飞灰的活化能相差不大，而且产物层控制阶段的活化能都几乎是化学反应控制阶段的2倍。

Investigation on the Carbonation of Fly Ash in Oxy-fuel Fired Circulating Fluidized Bed

Two kinds of fly ashes generated in utility circulating fluidized bed (CFB) boilers were carbonated in a thermo gravimetric analyzer (TGA), and the tested conditions expected to be seen at the exit in an oxy-fuel CFB. The influence of temperature and CO2 concentrations on carbonation of CaO were investigated. It was found that higher temperature always can accelerate the carbonation of CaO at the range of 500-800℃ , and the high temperature heater zone will be easier to be deposit because of carbonation of CaO. And, more ratio of CO2 in flue gases faster carbonation of CaO, although this effect is decreasing with lower temperature. The pore structure of fly ash also plays an important role in determine the carbonation of CaO. The activation energy of carbonation of the two fly ashes was calculated. It was found the activation energy in product layer diffusion control regime is almost double that in chemical reaction control regime.