A client company is proud to have started using K-curve (Kleingarn) regeneration of its hydrochloric-based pickling solutions. It carries out periodic analyzes, normally once a month. This is what is observed over two years for two of its four pickling baths:
During the first year, it follows a traditional regeneration scheme. The baths start with approximately 150 g/l of hydrochloric solution with a relatively low iron content (60-70 g/l). After exhausting the baths (50 g/l HCl) they decide to apply from that moment the Kleingarn regeneration curve and start operating in equilibrium. The graphs show that the control of the baths is not the desired, but they try to keep them around the point [HCl, 100 g/l] x [Fe, 120 g/l], slightly out of balance (halfway between saturation and optimal pickling).
There are certain interesting moments in these charts:
- When they decide to get rid of the traditional management and start applying Kleingarn, they first remove a small amount of solution (lower peak of Fe) and replace it with fresh acid (upper peak of HCl). This is observed in observations #17 and #18 of both baths.
- As the thing looks not to work well, in observation point #19 they perform a huge elimination of pickling solution and its replacement by hydrochloric. The point is [HCl, 180 g/l] x [Fe, 86 g/l] for bath 1 and of [HCl, 135 g/l] x [Fe, 120 g/l] for bath 2. Then they realize that they have placed the pickling solutions in saturation and correct both baths in the observation point #20.
The idea was a good one. The intention, excellent. But they wasted two baths for three months.