碱回收绿液除硅及应用的研究

Desilication Technology for the Green Liquor in Alkali Recovery System and Its Application

研究了二氧化碳(CO_2)法绿液除硅工艺以及除硅后的白泥应用效果。结果表明,将绿液澄清,控制总悬浮物(TSS)为60 mg/L以下,CO_2法绿液除硅的优化工艺条件为:CO_2气体流量0. 5～1 L/min,反应温度70～90℃,pH值控制在9. 8～10. 2,硫酸铝加入量1. 5 g/L。在优化工艺条件下,绿液硅含量从CO_2处理前的2. 98%降至处理后的0. 12%,除硅率可达96%。绿液钠含量(总碱)从除硅前的4. 70%降至除硅后的4. 56%,说明在保证绿液中主要成分钠含量基本不变的情况下,达到了很好的除硅效果。CO_2绿液除硅工艺简单,除硅率高,苛化后的白泥基本不含硅,产生的白泥容易洗涤,残碱量低,提高了白泥的品质。除硅后制得的白泥碳酸钙加填纸的施胶性能、强度指标等与商品PCC (沉淀碳酸钙)加填纸很接近,完全可以替代商品PCC用于纸张加填。

The dissolved silica in green liquor(GL)was precipitated by using aesation with CO 2,the optimized conditions were as follows:GL TSS,less than 60 mg/L,CO 2 gas rate 0.5~1 L/min,reactor temperature 70~90℃,pH range 9.8~10.2,Al 2(SO 4)3 dosage 1.5 g/L,silica removal reached 96%.Before desilication,GL silica content 2.98%,Na 4.70%,after desilication,GL silica content 0.12%,Na 4.56%,it showed that the total alkali content basically unchanged in GL,silica removal in GL was very efficrent.The method was very easy.The lime mud calcium carbonate had very low silica content,very easy to be washed and contained less,residue alkali it could improve the lime mud calcium carbonate quality,was beneficial to its application in papermaking.Desilication lime mud calcium carbonate could replace PCC as paper filler.