ZINC IN METAL RECYCLING
Zinc is the fourth most valuable metal mined after iron, copper and aluminium. The zinc market currently stands at 11.6 million tonnes per annum, of which the majority, 8 million tonnes comes from newly mined metal and the balance comes from recycling. The recycling is dominated by brass and galvanising ashes.
The industry is made up of mines where zinc deposits are exploited, the ore is crushed and milled and then the zinc mineral concentrate is generally separated by physical processes. The concentrate is then shipped to an electro-refinery or smelter where the concentrate is roasted and leached and the zinc is recovered by electrowinning.
Zinc occurs throughout the world but is particularly associated with carbonate rocks and is commonly found with lead. Mines tend to be small underground operations, with the typical grade of 5% to 8% zinc.
Traditionally, Canada, Australia, the USA and Peru have dominated zinc mining however in recent years China has become by far the most important producer having a market share of almost 40% of newly mined zinc. There are few large mines in China and production is dominated by hundreds of small mines. Reliable information on the Chinese zinc mining situation is very hard to obtain.
Most concentrate is sold according to an internationally recognised standard formula that pays a fixed proportion of the zinc contained in the concentrate and a treatment fee charged by the smelters on each tonne of concentrate and which is renegotiated annually.
The conversion of zinc from concentrate to metal is also dominated by China where there has also been a tremendous growth in capacity in recent years. While the number of electro-refineries and smelters outside China would probably number less than 100, there are over 500 in China. These small operations tend to be inefficient and poorly regulated.
While metal production facilities are frequently referred to as smelters, true smelting operations have not provided a significant proportion of metal for a number of years, and production is almost entirely by electro-refining. These plants produce by-product acid, tend to be built for an indefinite life and generally draw on concentrate from several different mining operations. The acid is an important by-product provided it can be sold locally. These facilities tended to be built in industrialised areas, although with rising energy costs new electro-refineries have sought cheap long term power supply.
In common with the other major metals, zinc is traded on the London Metals Exchange or LME. The LME provides a guaranteed market for producers. The LME price forms the basis of almost all metal and concentrate pricing contracts, yet ironically very little metal changes hands at the LME price. Physical metal always trades at a premium to the quoted price and the premium will change from place to place, reflecting regional shortages and from time to time as the market swings from surplus to deficit. Generally speaking the premium is in the range US$50 to US$120 per tonne.
In order to sell to the LME, metal must meet a certain high standard of quality. Most metal achieves the LME highest quality, Special High Grade containing 99.95% zinc. Metal is produced as 25kg ingots and packaged as one tonne lots.
Galvanised car body
A little over half of zinc is used for galvanising, which is the application of a thin coating of zinc on steel. The zinc seals the steel so that corrosion cannot occur. Galvanised items are increasingly common and include car bodies, the outer shell of white goods, street furniture (lamp posts, crash barriers) and many other steel objects that are exposed to the elements.