MODIFIED ZINCEX PROCESS - THE CLEAN, SAFE AND PROFITABLE SOLUTION TO THE ZINC SECONDARIES TREATMENT

In the Western World, zinc is mainly used in fields as Hot Dip Galvani zing (48%), Zinc-Base Alloys (13%), Brass and Bronzes (19%), Chemicals (10%) and Others (10%). The impure residues production from these ind ustrial activities, zinc secondary residues, is continuously increasin g and its treatment is each day more necessary. The zinc contained in some of these zinc secondaries such as Galvanizing ashes (64-72%), zin c oxides from the Waelz Process (48-60%), Electric Arc Furnace Dust (E AFD) (22-37%) and Cu/Zn oxides from foundries (35-50%) is a good value for processing such zinc secondaries. Pyrometallurgy and conventional zinc recovery technology are not trouble-free processes for them. Imp urities impair performance and cause environmental problems. The Modif ied Zincex Process is a hydrometallurgical process that takes advantag e of the Zincex Process long ago used in two industrial plants. The Mo dified Zincex Process is a modification and simplification of the form er process using atmospheric leaching, solvent extraction and conventi onal electrowinning, in order to resolve impurity difficulties and rec over zinc ingots SHG (99.99%). This paper deals with the main results of an experimental programme aiming at the demonstration of the suitab ility of the process to several feed materials. Waelz Oxides, Galvaniz ing ashes and EAFD coming from different European sources were tested during laboratory and continuous pilot plant campaigns. High Zinc reco very, low reagents and utilities consumption and effluents meeting EC and EPA waste regulations were confirmed. The paper also includes the main results of a feasibility study of an industrial 'base case'. A mi xed raw material and 20 000 t per year of zinc ingots production were chosen. The SHG zinc recovery from secondary raw material by means of the clean, safe and profitable Modified Zincex Process has been demons trated.