One of the last unsolved problems for stainless steel producers was the closed loop recycling of pickling waste residues. World wide, more than 1 million tonnes of hazardous and carcinogenic filter cakes are produced by the stainless steel industry every year. The conventional treatment practice for this pickling waste is neutralization and precipitation of the spent acids and dissolved metals. The remaining filter cake is usually landfilled without recovery of the valuable components entrapped.
To improve the surface characteristics of stainless steel (alloy) products, the metal is pickled with very strong acids. The acid liquor removes the unwanted oxide layer from the metal surface and partly dissolves the alloy.
|
