双氰胺废渣制备氯化钙工艺研究

Research on Preparation Technology of Calcium Chloride from Dicyandiamide Waste Residue

现阶段双氰胺废渣主要用做水泥,附加值不高且对环境造成粉尘污染.为将双氰胺废渣高效利用,研究利用宁夏石嘴山市双氰胺废渣制备高质量工业氯化钙的工艺.通过单因素及正交实验,考察浸出温度、浸出时间、盐酸加入量及搅拌速度对双氰胺废渣中Ca^(2+)浸出的影响.结果表明,最佳浸出工艺为,浸出温度为室温(25℃),浸出时间为60 min,0.31 mol/L盐酸的加入量为100 mL,搅拌速度为750 r/min.该条件下,双氰胺废渣中Ca^(2+)的浸出率为96.22%.根据溶度积原理,将浸出液调至pH=7,Mg^(2+)大部分生成Mg(OH)_2沉淀,Fe^(3+)大部分生成Fe(OH)_3沉淀,而Ca^(2+)留在溶液中.经过滤、蒸发、结晶、高温烘干得到纯度高达94.32%的氯化钙,质量达到GB/T 26520—2011的工业氯化钙Ⅰ型产品要求.

With little added value,currently dicyandiamide wasted residue is mainly used as cement and it is easy to cause dust pollution to the environment.The article studied the preparation technology of high-quality industrial calcium chloride from dicyandiamide waste residue in Shizuishan city of Ningxia for more efficient utilization of waste residue of dicyandiamide.It studied the effect of leaching temperature,leaching time,Hydrochloric acid dosage,and stirring speed on Ca^2+leaching in dicyandiamide waste residue basing on single factor and orthogonal experiment.The result shows that,the optimum leaching process condition is when leaching temperature reaches room temperature(25℃),leaching time turns 60 min,the added amount of 0.31 mol/L hydrochloric acid becomes 100 mL,and the stirring speed turns to 750 r/min.Under such condition,the leaching ratio of Ca^2+from Hydrochloric acid dosage is 96.22%.While adjusting the leachate to pH=7 according to solubility product principle,most of Mg^2+produces Mg(OH)2 precipitation,Fe(OH)3 precipitates is produced in most of Fe^3+,and Ca^2+is kept in the solution.Calcium chloride with a purity of 94.32%is obtained by filtration,evaporation,crystallization and drying at high temperature,and its quality meets the requirement on type I products of industrial calcium chloride of GB/T 26520-2011.