湿法脱硫吸收塔结垢原因分析与防治

Cause analysis and prevention of scale formation in wet desulfurization absorption tower

某热电厂2×330 MW燃煤亚临界发电机组采用石灰石—石膏湿法烟气脱硫工艺,脱硫系统在长期运行过程中,吸收塔内烟气入口、除雾器、浆液循环泵滤网和氧化空气管道等位置出现明显结垢情况。在对不同垢样分别取样后,借助于X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱分析(EDS)、热重分析(TG)等检测方法对其元素组成、微观形貌及重要离子含量等进行表征,经分析后得出垢样形成原因与垢样在吸收塔内生成位置有较强相关性,因为生成垢样的环境是垢形成的根本原因。垢样根据结垢机理的不同大致可以分为3类:"湿-干"区域垢、结晶结垢和沉积结垢。针对不同类型结垢提出相应解决方案,指出实现脱硫过程氧化反应与pH耦合控制是解决脱硫系统运行问题的关键。

The limestone-gypsum wet flue gas desulfurization process is applied in the 2×330 MW coal-fired subcritical generator set in a thermal power plant.During the long-term operation of the desulfurization system,obvious scaling occurs at the positions of the flue gas inlet,demister,slurry circulating pump filter and oxidizing air pipeline in the absorption tower.The scale samples collected from different sampling points were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray energy spectrum analysis(EDS),thermogravimetric analysis(TG) and other methods to determine their elemental composition,microstructure and important ion content.After analysis,it was found that the cause of scale formation has a strong correlation with the formation position of the scale in the absorption tower,for the background ions concentration of the formation of scale is the root cause of fouling.Scales can be roughly classified into three categories according to the fouling mechanism,namely the "wet-dry" area scale,crystal scale and sediment scale.According to different types of scaling,the corresponding solutions are proposed.It is pointed out that the oxidation reaction and pH coupling control in the desulfurization process are the solutions to the current operation problems of the system.