SteelNews.com Article
ThyssenKrupp Nirosta Installs Innovative Acid Recovery System at Krefeld Cold Mill
Jun. 26, 2009 ThyssenKrupp Nirosta has installed a new, enhanced technology to recycle spent mixed acid from its Krefeld cold rolling mill’s annealing and pickling lines. The new regeneration system allows valuable substances to be recovered and fed back to the processing lines.
“This innovative process delivers numerous benefits to the environment and our production operations and is also more cost efficient,” said Michael Fitzek, Environmental Officer at ThyssenKrupp Nirosta.
ThyssenKrupp Nirosta removes surface scale from annealed stainless steel in a pickling process using a mixture of hydrofluoric and nitric acid. Because the pickling liquor becomes less effective over time, the “spent acid” must be replaced with fresh acid on regular basis.
Prior to the installation of the new system, spent acid was neutralized using lime milk, the resultant sludge compacted and sent to landfill, and the waste water was fed to the sewer system. With the innovative new process developed by Andritz AG, metals and regenerated mixed acid are now recovered in a thermally driven process, with the revitalized acid fed back for re0use in the pickling process.
“That turns the line into a closed circuit,” said Gunther Hartmann, responsible project manager at ThyssenKrupp Nirosta. “The new recycling system allows us to make substantial savings, which are urgently needed in the current situation.”
The new acid regeneration system delivers a number of advantages, including the reduction of pollution due to lower volumes of wastewater and reduced nitrogen content. The new process also helps the plant reduce its need to transport acid and sludge, and also helps reduce its use of lime. The new system also helps the facility maintain consistent quality in its pickling process.
ThyssenKrupp Nirosta’s new acid recovery system at Krefeld, which started operation in April, is to reach full optimization this summer.