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, CaO and NaOH 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 1200℃, 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.
Mingtao WU Dawei SHAO Qiang GUO Yongli LI Tao QI
. A new treatment process of stainless steel pickling wastewater through calcium and sodium neutralization precipitation and carbon thermal reduction[J]. The Chinese Journal of Process Engineering, 2019
, 19(5)
: 989
-996
.
DOI: 10.12034/j.issn.1009-606X.218323
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