从铝热法制备金属铬所得铬渣中回收铬、铝工艺研究

采用在熔融碱中焙烧-水浸-碳酸化分解-浓缩结晶工艺从铝热法生产金属铬所得炉渣中回收氧化铝和铬酸钠, 探讨了铬渣粒度、碱渣比、焙烧时间以及温度等因素对铬和铝浸出率的影响。研究表明, 铬和铝的浸出率随碱渣比、焙烧时间以及焙烧温度增加而增加, 随铬渣粒度减少而增加。通过四因素三水平正交实验确定焙烧最佳浸出工艺条件为 焙烧温度 700 ℃, 焙烧时间 4 h, 粒度0.045 mm和碱矿比6∶1。所得铬盐(以重铬酸钠计)和氧化铝的纯度分别为88.5%和95.4%, 总回收率分别达到85.6%和96.4%, 钠以碳酸钠和碳酸氢钠的形式得到回收。

Recovery of Cr and Al from Chromic Residue Obtained from Preparation of Metal Chromium Using Aluminothermics Method

Chromic residue obtained from preparation of metal chromium by aluminothermic reaction, was used to recover alumina and sodium chromate by adopting a combined process consisting of roasting with molten alkali, leaching with water, carbonation decomposition, concentration and crystallization. Effects of particle size of chromic residue, alkali/residue ratio, roasting time and temperature on the recovery rate were explored. Results showed that the leaching rates of chromium and aluminum increased with an increase in the alkaliresidue ratio, roasting time and temperature, as well as a decrease in the particle size of the residue. The optimal technological conditions were obtained through orthogonal experiment L₉(3⁴), including roasting at a temperature of 700 ℃ for 4 h, with particle size of residue at 0.045 mm and alkaliresidue ratio of 6∶1. Consequently, the chromate salt (calculated in terms of sodium bichromate) and alumina were obtained with purity of 88.5% and 95.4%, at total recovery of 85.6% and 96.4%, respectively, and sodium was recovered in the form of sodium carbonate and sodium bicarbonate.