In stainless steel production, pickling is a treatment that is used to remove impurities, rust, and scale from the surface of the steel. In pickling stainless steel, a mixture of high concentration nitric acid and hydrofluoric acid is normally used.
Since 2016, China’s Central and Provincial Governments have closed down hundreds of steel companies that do not meet ever tougher environmental requirements. Meeting these more stringent requirements was made even harder for BDSS, as their plant is built on reclaimed land in an area known for seafood production.
BDSS is a part of BaoSteel (recently merged to Baowu), the world’s second largest steel producer and a market leader in stainless steel. BDSS has a fully integrated stainless steel plant in Fujian Province, China.
BDSS’ main challenge was to lower its high consumption of acid (especially nitric acid) and minimize waste for landfill while simultaneously reducing water consumption and improving productivity, quality and price competitiveness. In addition, BDSS did not want to increase its carbon footprint – further reducing their options for choice of supplier.
Scanacon supplied its first complete acid management system to BDSS in 2009 – including acid recovery, acid filtration and acid analysis. In 2017, Scanacon supplied a very large system with a capacity of treating 10,000 L/h of pickling acid to BDSS’ new hot annealing and pickling line. This means that 240 m3 of highly concentrated acid is being re-used, as opposed to thrown away, every day. Included was also a newly developed system for drying oxide scale to be re-used in their melting process instead of dumped to landfill.
After completing installation, start-up, training and final acceptance in early 2019, BDSS was so impressed with the result that they later the same year ordered an almost identical system for their second hot annealing and pickIing line, delivered in April 2020.
After proving all environmental, financial and other benefits with Scanacon acid management for mixed acid, discussions are now ongoing regarding a similar system for sulphuric acid and Scanacon’s latest development – the Scanacon Metal Recycling System.
Finally, reducing acid consumption and landfill handling also results in reduced environmental impact and hazardous work for BDSS employees.