高炉瓦斯灰氨-碳酸铵法除锌

Removal of zinc from blast furnace dust by ammonia-ammonium carbonate

针对锌含量较高的高炉瓦斯灰无法直接返回炼铁流程循环使用的问题,采用氨-碳酸铵为浸出剂浸出含锌高炉瓦斯灰中的锌,实现了锌的脱除和高炉瓦斯灰的资源化利用。热力学计算和锌氨配位原理分析表明,通过锌氨配位浸出实现含锌瓦斯灰中锌的脱除是可行的。结果表明,最佳反应条件为氨水浓度2 mol/L、碳酸铵浓度2mol/L、温度50℃、液固比6:1、浸出时间3 h;在此条件下,锌浸出率为91%,铁的浸出率为1.15%,高炉瓦斯灰中的锌含量从9.54%降低到1.13%,铁含量由35.9%富集至47.6%。原料和终渣的物相分析表明,原料中以氧化物和硫酸盐形式存在的锌溶解浸出,终渣中残留的锌主要赋存于难溶解的锌铁尖晶石物相中,这是锌浸出率难以进一步提高的主要原因。SEM-EDS检测表明,终渣颗粒分布不均匀,表面疏松多孔,有利于高炉瓦斯灰的后续处理。

In view of the problem that the high zinc content blast furnace dust could not directly recycled to iron making process, a novel process for recovering zinc from blast furnace dust and resource utilization of dust was developed by ammonia-ammonium carbonate leaching. The thermodynamic calculation results and zinc-ammonia coordination principle show that removal of zinc from blast furnace dust by ammonia-ammonium carbonate is feasible. And the experimental results show that the optimal reaction condition is as follows: NH3 concentration 2 mol/L,(NH4)2CO3 concentration 2 mol/L, temperature 50 ℃, liquid-to-solid 6:1, leaching time 3 h. Under the optimum conditions the leaching rates of zinc and iron are 91% and 0.45%, respectively. The content of zinc decreases from 9.54% to 1.13%, and the content of iron increases from 35.9% to 47.6%. The XRD and SEM-EDS analyses of leaching residue show that the oxides and sulfates of zinc in the raw material are dissolved and leached, the zinc-iron spinel is not leached and present together with the iron oxide in the residue. This is the reason why the leaching rate of zinc is hard to be further improved. Besides, the distribution of the leaching residue particles is uneven, and the surface is loose and porous, which is beneficial to the subsequent treatment of blast furnace dust.