不锈钢酸洗废水钙钠中和沉淀与碳热还原协同处理新工艺

A new treatment process of stainless steel pickling wastewater through calcium and sodium neutralization precipitation and carbon thermal reduction

通过研究不锈钢酸洗废水体系中氟离子脱除和金属离子沉淀的规律,开发了钙钠协同沉淀新工艺,并对新工艺产生的污泥于1200℃下进行还原,细磨、磁选后得铁、铬、镍合金粉末和再生萤石矿。结果表明,该工艺实现了废水的达标排放,污泥产生量减少了14.79%,实现了铁铬镍的金属化还原,得到了再生萤石矿和金属品位93.62%的合金粉末,合金粉末中铁、铬、镍品位分别达69.31%, 7.60%和16.71%,回收率分别高达95.30%, 88.70%和97.53%。

An oxide layer is formed during stainlesssteel production and processing, which reduces the corrosion resistance of steel. At present, the common treatment for stainless steel strip surfaces is mainly pickling, using nitric and hydrofluoric acids to remove the oxide layer. After pickling, water is used to wash away the acids remaining on the surface of the stainless steel. A large number of stainless steel pickling wastewater will be produced, it contains heavy metal ions and fluoride ions and have great threat to the environment. The pickling wastewater is generally treated by lime neutralization, but the quantity of sludge is large and has difficulty in resource utilization. In this work, the law of fluorine ion removal and metal ion precipitation in stainless steel pickling wastewater system was studied, and a new process of calcium and sodium co-precipitation was developed to make the quality of wastewater achieve the standard, Ca O and Na OH were added sequentially to achieve synergistic co-precipitation of harmful ions in wastewater, the sludge production was reduced by 14.79% as well. With the optimization of sedimentation method, the composition of sludge was also changed, which was beneficial to the subsequent reduction. The sludge reducted in 1 200 ℃, realized the metallization of iron chromium nickel, metals and nonmetals were enriched in different areas, fine grinding and magnetic separation to get the regeneration of fluorite ore and alloy powder, the grade of metal was 93.62%. Grade of iron, chromium and nickel in alloy powder reached 69.31%, 7.60% and 16.71%, respectively, and their recovery rates were as high as 95.30%, 88.70% and 97.53%, respectively. The flow was short, energy consumption was low, and there did not produce secondary pollution in the new process, which had great significance to the innoxious disposal and recycle of stainless steel pickling wastewater.