Spent pickle acid recovery and reuse
This project at a hot dip galvanising plant originally aimed to investigate the feasibility of an acid recovery process and production of an iron solution more suited for use in the waste water treatment industry in Ireland.
However as a result of the extensive investigations undertaken by Galco as part of this project, an alternative solution has been implemented which is in fact further up the waste prevention hierarchy. Increased analysis of spent pickle made Galco more aware of the chemistry of their process and they are now moving to implement simpler solutions which will improve the quality of their spent pickle.
Galco is implementing modifications to produce a spent pickle by-product which will be more acceptable for use in municipal waste water treatment plants. The steps involved will be:
• Implementing acid degreasing, replacing the current caustic degreasing system, giving reduced sludge and better pickling efficiency.
• Pickling at a higher temperature giving a lower acid solution with a higher iron content (increased energy use is compensated by reduced energy use in the degreasing step).
• Adding iron oxide to the spent pickle in a controlled reaction to boost the iron content and reduce the acid content of the pickle.
In Galco’s new plant, zinc will be practically eliminated from the spent pickle through the design of the plant equipment and layout. This is a classic case of cleaner production – i.e. do not create a waste stream in the first place. Galco has continued cleaner greener production work in other areas – water usage has been reduced throughout the plant by 36% between 2005 and 2006 (about 3000 m3) through increased controls and collection and reuse of drips and spillages.
For further details, download the Galco Steel Ltd. PDF.
