Zinc Scrap
Zinc Scrap Zinc brings a multitude of social and economic benefits to society. Man has discovered a wide range of uses for this versatile natural element with valuable characteristics and properties for various industrial applications.
The most important use of zinc is in protecting steel from corrosion using hot-dip galvanizing technique. The metal is used to prolong the durability of steel, which is one of the most used materials on the planet. Both zinc and steel are 100% recyclable. The zinc-steel combination has considerable economic benefits in terms of life-cycle costs. Improved air quality in several industrialized countries, with diminishing levels of sulfur dioxide (SO2), means that today zinc coatings facilitate even longer protection for steel.
Increased attention to life-cycle costing is prompting the designers, specifiers and investors to prefer zinc-coated steel in many traditional and new applications, from electricity distribution poles to safety barriers, from construction to automobiles and from farm gates to ski-lifts.
The 27th most common element in the Earth’s crust, Zinc is completely recyclable. According to estimates, at present, 70 % of the zinc produced originates from mined ores while 30 % comes from recycled or secondary zinc. The level of recycling is increasing in step with progress in zinc production technology and zinc recycling technology.
Zinc Scrap
Today, more than 80 % of the zinc available for recycling is recycled. The metal is recycled at all the stages of production and use, for example, from scrap, which arises during the manufacturing of galvanized steel sheet, from scrap generated during production and installation processes, and from end-of-life products. Given below is the pie chart that describes the percentage of recovered zinc from different products manufactured with zinc.
The life of zinc-containing products varies and may range from 10 to 15 years for household appliances or cars, to over 100 years for zinc sheet used for roofing. Street lighting columns constructed of zinc-coated steel can remain in use for 40 years or more, and transmission towers for over 70 years. All these products tend to be replaced because of obsolescence, and not because the zinc has ceased to protect the underlying steel.
The presence of zinc coating on steel does not restrict its recyclability and all types of zinc-coated products can be recycled. Zinc coated steel is recycled along with other steel scrap during the processes of steel production – the zinc volatilizes and is then recovered. According to estimates, the supply of zinc-coated steel scrap is expected to double over the coming years, as more zinc-coated vehicles enter the recycling stream.
Types / Grades of Zinc Scrap
Different grades and varieties of zinc scrap is used for recycling purposes and to recover pure zinc from the scrap. Given in the table below are some of the important grades / types of zinc scrap used in recycling – read more…
Process
The secondary zinc industry processes metal scrap for the recovery of zinc in the form of zinc oxide, zinc slabs, or zinc dust. The process of zinc recovery involves three general operations, viz. –
Pretreatment
Melting
Refining
Secondary recovery starts with the separation of zinc-containing metals from other materials, typically by magnetics, sink-float, or hand sorting.
When non-ferrous metals have been mixed in shredder scrap, zinc metal can be separated from higher-melting metals, such as such copper and aluminum, through selective melting in a sweating furnace. A sweating furnace (rotary, reverberatory, or muffle furnace) slowly heats the scrap containing zinc and other metals to approximately 419.4°C; this temperature is adequate to melt zinc, however it is still below the melting point of the remaining metals.