Example 1
The recirculation tank 3 contains 60 m3 of hydrochloric acid at 15% having a silicon content of roughly 59 mg·L−1. The acid pickles different steel grades, e.g.: interstitial steel, medium carbon, HSLA and dual phase steels. The used pickling acid is sent by pumps to the ultrafiltration device at a flow of 17 m3·h−1. The ultrafiltration device 2 is made of 68 m2 of ceramic membrane area having a pore size of 7 nm (10 kDa Molecular Weight). A flow of 14 m3·h−1 of filtered flow containing 38 mg·L−1 of silicon is fed back inside the bath while a flow of 3 m3·h−1 of unfiltered flow containing 157 mg·L−1.
