World of Metallurgy ERZMETALL 68 2015 No 3158 Paul B Queneau et al Recycling Lead and Zinc in the United States smelter Clarksville TN where the CZO is washed 26 then converted to Special High Grade SHG slab by leaching electrolyte purification electrowinning and cast ing The balance of Millport s CZO is shipped to Zinc Na cional s plant in Monterrey Mexico to produce zinc metal zinc oxide and zinc sulfate 3 1 3 Fe Zn sulfate byproduct from general galvanizers When a galvanizer produces galvanized steel that fails to meet specifications the reject material can be reclaimed by acid stripping the zinc from the surface A portion of steel also dissolves lead precipitates as lead sulfate This zinc is reclaimed as hydrated sulfate from the spent strip liquor by crystallization followed by drying Initially these crystals were difficult to market Zinc to iron ratio and the particle size were variable the crystals were highly hydrated and the bulk density was low These problems have been solved Skilled processing has produced zinc iron sulphate gran ules 20 Zn 14 Fe as well as fine granular high iron sulfate 11 Zn 22 Fe Feed grade high iron product was 97 30X60 mesh free flowing monohydrate having a bulk density of 95 lb ft3 The U S feed market proved unwilling to meet the price required to compensate the producer for this high quality U S general galvanizers typically job shops processed on the order of 3 8 million tons of steel in 2014 A small portion of the steel 0 0037 processed is lost as iron to aqueous baths e g when pickling to prepare the surface for galvanizing In sulfate based operations 40 of the tonnage this aqueous iron and associated zinc are re covered for recycling as ferrous iron sulfate heptahydrate Experience has shown that multiplying the weight of the aqueous iron by five converts it to the weight of heptathy drate solid byproduct 7 to 9 Fe 5 to 7 Zn One can now estimate the quantity of zinc byproduct recovered 3 800 000 t a 0 4 0 0037 5 0 06 Zn 2000 t a of recycled zinc byproduct derived from U S sulfate based general galvanizer operations In the U S northwest this heptahydrate byproduct is typi cally shipped to Trail Teck Operations British Columbia Canada U S Midwest output is typically purchased by QC Corp Cape Girardeau Missouri for inclusion in its granulated oxysulfate micronutrient fertilizers This zinc has been included in Table 4 as Miscellaneous recycled zinc 3 1 4 Zinc recovery by smelting leaching and electro winning Table 8 summarizes the locations capacities and capa bilities of U S secondary zinc plants in 1997 All produce metallic zinc and or zinc oxide To upgrade feedstock many use milling and air separation or screening to separate Zn metallics from ZnO fines During 2013 domestic secondary zinc smelters collectively operated at about 86 of capacity In January 2015 the LME London Metal Exchange price for zinc slab was 2100 mt 0 95 lb plus premium The premium was 0 08 lb to 0 09 lb The purchase price for top dross and bottom dross was about 80 and 85 of the LME London Metal Exchange price respectively f o b the sell er Both top and bottom dross typically contain about 95 total zinc Skimmings from Special High Grade SHG zinc and from Prime Western PW zinc sold for about 50 and 60 of the LME price respectively Both skimmings typically contain about 80 to 90 total zinc 3 1 5 Horsehead Holding s Mooresboro NC Operation Horsehead s production capacity output and technology at Mooresboro are summarized in Table 7 This plant was brought on line to replace the Monaca smelter Monaca was an extraordinarily versatile but aging operation that ulti mately required replacement with up to date technology A tabulation of other U S zinc operations that have shut down in over the past 15 years includes Big River Zinc Sauget IL Eagle Zinc Hillsboro IL Meadowbrook Company Spelter WV U S Zinc s Chicago IL plant Interamerican Zinc Coldwater MI and Huron Valley Steel s zinc refinery Table 8 U S secondary zinc smelters Non EAF Dust estimated capacities 2014 and production output 2013 Company and location tons 2014 Capacity tons Technology Feedstocks 2013 production tons Horsehead Holding Monaca PA 140 000 tons con tained zinc Electrothermic 7 and Larvik 6 furnaces Distillation columns 10 Waelz ZnO calcine galvanizer diecast secondaries 125 000 tons contained zinc PW metal SSHG metal ZnO zinc powder and zinc dust U S Zinc Clarksville TN 40 000 tons ZnO Four muffle furnaces for ZnO 90 top dross balance is other secondaries 40 000 tons ZnO 32 000 tons contained Zn U S Zinc Houston TX 25 000 tons contained Zn as dust and PW Bottle retorts sweating kiln induction furnace holding furnace ISP dust column Zinc scrap skimmings dross plus 8000 st primary Zn 20 000 tons zinc dust 8000 tons PW zinc U S Zinc Millington TN 40 000 tons ZnO Four muffle furnaces 3 online One sweat furnace not operating 100 primary slab 30 000 tons ZnO 24 000 tons contained Zn Zinc Oxide LLC Dickson TN 40 000 tons ZnO projected by Jan uary 2016 30 secondaries Three muffle furnaces HG SHG remelt die cast top dross others Plans call for 4 muffle furnaces 10 000 tons ZnO each to be on line by January 2016 Capacity Capacity Utilization 244 000 tons zinc 86 Secondary zinc production Primary zinc production 177 000 tons zinc 32 000 tons of zinc Horsehead s Monaca smelter closed in April 2014

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