不锈钢酸洗废液再生利用的工艺研究

Research on Recycling Process of Stainless Steel Pickling Liquor

不锈钢酸洗废液中含有大量可回收的硝酸、氢氟酸和铁资源,采用硫酸置换法回收其中的硝酸和氢氟酸,并通过减压蒸发、冷凝回收等过程得到再生混酸(HNO3+HF)。对硫酸置换废酸工艺进行流程模拟,研究了不同硫酸加入量、蒸发能耗对酸洗废液蒸发温度、混酸回收率的影响,结果表明:适宜的硫酸和酸洗废液加入量比为0.625∶1.000,蒸发能耗以3.4 MJ/kg酸洗废液为宜,蒸发温度为102.4℃,氢氟酸回收率为99.95%,硝酸回收率为93.11%,回收的混酸中氢氟酸、硝酸的质量分数分别为3.98%和7.51%,再生混酸可回用于不锈钢酸洗生产线。废酸经蒸发、结晶处理后得到含铁、镍、铬等重金属的盐泥,盐泥可进一步分级利用处理,分步回收其中的铁、镍、铬等金属或委外处理。

Stainless steel pickling liquor contains a large amount of recyclable nitric acid,hydrofluoric acid and iron resources.The sulfuric acid replacement method was adopted to recover nitric acid and hydrofluoric acid.A vacuum evaporation and condensation recovery system device was used to obtain regenerated HNO_3-HF mixture.The process of sulfuric acid replacement process was simulated,and the effects of different sulfuric acid addition and evaporation energy consumption on the evaporation temperature and mixed acid recovery rate of pickling liquor were analyzed.The results showed that the best ratio of sulfuric acid to picking liquor was 0.625∶1.000,and the evaporation energy consumption was 3.4 MJ/kg pickling liquor,the evaporation temperature was 102.4℃,the recovery rates of hydrofluoric acid and nitric acid were 99.95%and 93.11%respectively,and the mass fraction of hydrofluoric acid and nitric acid in the recovered mixture were 3.98%and 7.51%respectively.The regenerated mixture could be reused for stainless steel pickling process.After evaporation and crystallization,the waste acid was converted into salt mud containing heavy metals such as iron,nickel and chromium.The salt mud can be further treated and utilized to recover the iron,nickel,chromium and other metals or be disposed by external qualified units.