不锈钢酸洗过程中NO_x的产生机制及控制

Production mechanism and control of NO_x during acid pickling of stainless steel

为降低奥氏体不锈钢混酸(HNO3+HF)酸洗过程中产生的NOx量,利用自制的酸洗-吸收装置研究了HNO3和HF质量浓度及抑制剂和促进剂加入量对NOx生成量的影响,探讨了NOx的产生机制。结果表明,奥氏体不锈钢酸洗的优化工艺条件为:酸洗温度20~50℃,HNO3质量浓度90~110g/L,HF质量浓度40g/L,抑制剂加入量30g/L,促进剂加入量1~2g/L。抑制剂的加入降低了NOx的生成量,促进剂的加入减少了氧化皮酸洗时间,提高了酸洗效率。酸洗产生的NOx来源于两部分:一是氧化皮与酸洗液反应,约占NOx生成量的70%,二是裸露基体与酸洗液反应,约占NOx生成量的30%。

In order to reduce the amount of NOx generated during the pickling process of austenitic stainless steel with mixed acid (HNO3+HF),the effects of mass concentration of HNO3 and HF and the addition amount of inhibitor and accelerator on NOx generation was studied by using a self-made pickling-absorption device,and the mechanism of NOx generation was discussed. The results showed that the optimum pickling conditions for austenitic stainless steels are as follows:pickling temperature 20-50 ℃,HNO3 mass concentration 90-110 g/L,HF mass concentration 40 g/L,inhibitor addition 30 g/L and accelerator addition 1-2 g/L. The addition of inhibitor reduces the NOx generation,the addition of accelerator reduces the pickling time of oxide scale and improves the pickling efficiency. It is concluded that NOx generated by pickling comes from two parts:one is from the reaction of oxide scale with the pickling solution,accounting for about 70% of the NOx generation,and the other is from the reaction of exposed matrix metal with the pickling solution,accounting for about 30% of the NOx generation.