偏铝酸钠混凝同步去除脱硫废水中的Ca^(2+)和SO_(4)^(2-)  

Simultaneous removal of Ca^(2+) and SO_(4)^(2-) from desulfurization wastewater by sodium aluminate coagulation

作　　者：涂孝飞 丁胜利 孙马小璇 李伟[2] TU Xiaofei;DING Shengli;SUN Maxiaoxuan;LI Wei(Xi’an Branch of North China Electric Power Research Institute Limited Company,Xi’an 710065,China;School of Environmental and Municipal Engineering,Xi’an University of Architecture and Technology,Xi’an 710055,China)

机构地区：[1]华北电力科学研究院有限责任公司西安分公司,陕西西安710065 [2]西安建筑科技大学环境与市政工程学院,陕西西安710055

出　　处：《工业水处理》2025年第3期84-89,共6页Industrial Water Treatment

基　　金：国家自然科学基金青年基金项目(51308437);陕西省自然科学基金面上项目(2024JC-YBMS-229);华北电力科学研究院有限责任公司自有资金科技项目(KJZ2023012)。

摘　　要：经传统三联箱处理后的脱硫废水具有高碱度、高硬度和高硫酸根的特点,会使后续处理设备出现结垢、堵塞等问题。针对该难题,采用偏铝酸钠(NaAlO_(2))可与废水中的Ca^(2+)、SO_(4)^(2-)反应生成难溶性钙矾石的方法,同步高效去除Ca^(2+)、SO_(4)^(2-)。通过单因素实验考察NaAlO_(2)投加量〔n(Ca^(2+))∶n(Al^(3+))〕、搅拌速度、反应时间、反应温度等因素对NaAlO_(2)混凝同步去除脱硫废水中Ca^(2+)、SO_(4)^(2-)效果的影响,进而确定NaAlO_(2)混凝同步去除Ca^(2+)和SO_(4)^(2-)的最佳反应条件。结果表明:在室温条件下,按照n(Ca^(2+))∶n(Al^(3+))=2∶1向原水(初始溶液pH=11.9)中投加NaAlO_(2),以300 r/min搅拌30 min即可将Ca^(2+)、SO_(4)^(2-)有效去除,其去除率分别达到(95.7±0.1)%和(81.1±2.5)%。此外,研究还发现向反应系统中投加0.2 g/L水铝钙石作为晶种,可大幅缩短絮凝体的沉降时间。通过XRD、SEM分析可知,加入晶种后,柱状钙矾石晶体附着在片状晶种上,形成密实的异晶包裹体,从而有效提高了其沉降性能。与传统碳酸钠软化工艺相比,NaAlO_(2)同步去除脱硫废水中的Ca^(2+)和SO_(4)^(2-)药剂成本降低了25.97%,并且减轻了后续纳滤工艺的处理压力,是一种更为经济高效的处理工艺。The wet flue gas desulfurization(FGD)wastewater treated by traditional three-tank process is characterized by high alkalinity,high hardness,and high sulfate,which often leads to severe scaling and clogging in subsequent membrane treatment facilities.To address this challenge,sodium aluminate(NaAlO_(2))could react with Ca^(2+)and SO_(4)^(2-)in FGD wastewater to generate indissoluble ettringite precipitates for their simultaneous efficient removal.The effects of NaAlO_(2)dosage〔n(Ca^(2+))∶n(Al^(3+))〕,stirring speed,reaction time and reaction temperature on the simultaneous removal of Ca^(2+)and SO_(4)^(2-)from FGD wastewater were investigated through single-factor experiments.The optimum reaction conditions for simultaneous removal of Ca^(2+)and SO_(4)^(2-)by NaAlO_(2)were determined.The results showed that Ca^(2+)and SO_(4)^(2-)could be effectively removed by adding NaAlO_(2)to the raw water(initial solution pH=11.9)in the ratio of n(Ca^(2+))∶n(Al^(3+))=2∶1 at room temperature with stirring at 300 r/min for 30 min,and the removal rates of Ca^(2+)and SO_(4)^(2-)could reach(95.7±0.1)%and(81.1±2.5)%,respectively.Additionally,the study found that adding 0.2 g/L of hydrocalumite as a seed crystal to the system significantly shortened the settling time of flocs.XRD and SEM analyses showed that after the addition of seed crystals,the columnar ettringite crystals were attached to the hydrocalumite seeds to form dense heteroepitaxial encapsulation,which effectively improved its settling performance.Compared to the traditional sodium carbonate softening process,the use of NaAlO_(2)for the simultaneous removal of Ca^(2+)and SO_(4)^(2-)in FGD wastewater reduced the chemical cost by 25.97%and alleviated the treatment burden on subsequent nanofiltration processes.The coagulation process for simultaneous removal of Ca^(2+)and SO_(4)^(2-)was a more economical and efficient treatment approach.

关 键 词：脱硫废水 絮凝 钙离子 硫酸根离子 钙矾石 

分 类 号：X703[环境科学与工程—环境工程]