含钙镁废渣综合利用的现状及展望

钙镁型废渣可分为氢氧化钙型、碳酸钙型,根据其中镁含量高低,又可分为高镁型和低镁型,只有高镁型废渣才需要对镁元素进行分离回收;常见的钙镁型废渣有电石渣、碱渣、皂化废渣、磷尾矿等。对钙镁型废渣充分综合利用的现状总结归纳为：氢氧化钙型废渣需通过浸取、过滤分离、浸取液碳化等主要化学物理分离步骤;碳酸钙型废渣需要经过煅烧分解、消化浸取、过滤分离、浸取液碳化等化学物理分离步骤,就可实现将钙元素以轻质碳酸钙（PCC）的形式分离出来;如果是高镁型废渣,则需要增加残渣中氢氧化镁的二氧化碳碳化、过滤分离、氨水沉淀分离或碳酸氢镁热解等化学物理步骤来实现镁元素的分离回收。展望未来,钙镁型废渣充分综合利用是一类兼具环境效益、社会效益和经济效益的循环经济项目,值得关注、重视与推广。

Present situation and prospect of comprehensive utilization of waste residue containing calcium and magnesium

Calcium magnesium type waste residue can be divided into Ca（OH）₂ type and CaCO₃ type.According to the con-tent of magnesium,it can be divided into high magnesium type and low magnesium type.Only high magnesium type waste residue needs to separate and recover magnesium.The common calcium magnesium slags are calcium carbide slag,alkali slag,saponification slag,phosphorus tailings and so on.The present situation of comprehensive utilization of Ca（OH）₂ type waste residue was summarized as follows：Ca（OH）₂ type waste residue should be separated by leaching,filtration and carboni-zation.Calcium could be separated as PCC by calcination,digestion,leaching,filtration and carbonization.If it was a high mag-nesium type waste residue,it was necessary to increase the chemical and physical steps such as CO₂ carbonization,filtration separation,ammonia precipitation separation or pyrolysis of magnesium bicarbonate to realize the separation and recovery of magnesium.Looking forward to the future,the comprehensive utilization of calcium magnesium slag would be a kind of circular economy project with environmental,social and economic benefits,which is worthy of concern,attention and promotion.