湿法脱硫中石灰石溶解特性的模型及实验研究

Modeling and experimental study on limestone dissolution in wet desulphurization

在石灰石-石膏湿法烟气脱硫中,石灰石的溶解影响到浆液吸收SO2的能力及吸收塔持浆池的大小。根据传质及化学离子平衡理论,建立了石灰石的溶解模型,并通过实验对模型进行了验证,结果表明,模拟结果与实验值基本一致,模型较好地反映出石灰石的溶解过程;在浆液pH较低的情况下,通过增强搅拌强度,可以明显提高石灰石的溶解速率,而在浆液pH值较高时,增加搅拌强度对溶解速率的影响不大;定义了石灰石的溶解指数及溶解系数,溶解指数与浆液中的Ca2+浓度、pH值及气相中CO2的分压有关,溶解系数与温度有关。石灰石可以发生溶解的条件为溶解指数小于溶解系数。

The limestone dissolution affects the slurry absorbability of SO2 and the volume of the slurry pool in the wet limestone-gypsum FGD（flue gas desulphurization）.Based on theories of the mass transfer and the chemical ion balance,the model to describe the limestone dissolution is built and the experiment is carried out in this paper.Results show that modeling data are basically consistent with the experimental value and the model can perfectly describe the dissolution process.To increase the stirring intensity will obviously increase the dissolution rate in the lower pH slurry,but to increase the stirring intensity has a little influence on the rate in the higher pH slurry.The dissolution index,which is related with the Ca2＋ concentration,pH and CO2 pressure in gas phase,and dissolution coefficient which is related with temperature,are defined in this paper.The condition of limestone dissolution is that the dissolution index must be less than dissolution coefficient.