煤气化灰水除硅方式对比与机理探讨

Comparison and mechanism analysis of silica removal way from coal gasification ash water

根据硅的存在形式,水溶液中存在的硅主要分为可溶硅和胶体硅。本研究对比分析了药剂法和电絮凝法对某煤化工公司煤气化灰水中2种形式硅的脱除效果。结果表明,对于不同形态的硅酸,NaAlO_(2)适合脱除可溶性硅,而聚合氯化铝对胶体硅的脱除效果比较理想;NaAlO_(2)和聚合氯化铝的复配药剂在投加比n(Al)/n(Si)=4时可以显著增强对可溶硅和胶体硅的去除效果,经120 min反应后,可溶硅去除率为56.1%,胶体硅去除率为66.9%,显著高于单一NaAlO_(2)对可溶硅(49.7%)和单一聚合氯化铝对胶体硅(58.8%)的去除效果,但是处理成本较高(16.65元/t)。电絮凝90 min后,胶体硅去除率为86.8%,可溶硅去除率为98.5%,总硅去除率可以达到93%,且成本为6.25元/t,显著低于药剂除硅成本。对除硅机理进行分析,电絮凝由于存在离子反应和絮凝两方面作用,从而具备同时去除可溶硅和胶体硅的能力。

Silica in aqueous solution can be divided into dissolved silica and silica colloids according to its form.In this study,two kinds of silica removal from gasification ash water of coal chemical company by chemical method and electrocoagulation were compared and analyzed.The results indicated that NaAlO_(2) was suitable for the removal of dis-solved silica and polyaluminum chloride was ideal for removing silica colloids.When n(Al)/n(Si)=4,the compound agent of NaAlO_(2) and polyaluminum chloride significantly enhanced the removal effect of dissolved silica and silica col-loids.After 120 min reaction,the removal rate of dissolved silica and silica colloids were 56.1%and 66.9%respec-tively,which was significantly higher than the removal effect of single NaAlO_(2) on dissolved silica(49.7%)and single polyaluminum chloride on silica colloids(58.8%).However,its processing cost was high(16.65 yuan/t).After 90 min of electrocoagulation,the removal rate of silica colloids and dissolved silica were 86.8%and 98.5%respectively.The total silica removal rate could reach 93%,and the cost was 6.25 yuan/t,which was significantly lower than the silica re-moval cost of pharmaceutical.The desilication mechanism showed that electroflocculation had the ability to remove both dissolved silica and silica colloids at the same time due to ionic reaction and flocculation.