Tin-From ore to ingot
Tin-From ore to ingot
TIN: FROM ORE TO INGOT INTERNATIONAL TIN RESEARCH INSTITUTE 724 Tin: From Ore To Ingot Dredging by m m of bucket W.suctionamer dredges is an important m e t w of mining tin are, especially in South-East Asia, where it is used fim recwering alluvial ore Emm river bgds and frwn beneath artificial U s or paddocks; it is even used -to mine offshore deposits fropn the sea bed, Dredging units have now reached a considerable &gm of &velopment. The dredges themselves are huge floating processing [email protected] which move m 8 the W 8 r n digging out tin-sediments from the bed and elevating them tro the mineral processing plant on board. The gross weights of dredging units an in excess of 5000 t o m e s and the overaU length from the ladder extremity to the end of the werburden stripping chum cm be as much $s 200 metres, The sizes of the tin dredges vary, depending on such fxtm as the mount of material to be processed, the depth of operation and the mount of barren overburden above the tin-rich strata, Dredges range frum &hose handling a b u t 200 t o m s of matmid per hour from a depth of about 10 metres to large plants which cm excavate and a b u t loo0 t o ~ per s hour r e c o v d from up to 50 metres below the water level, The & g m of ccmanmatim un board the dredges varies according to the amount of accessory'heavy mineral p e n t . Initial tin concentrates usualIy have between 5 and 15% tin mined but higher percentages result when little or nu accessory heavy metal is present. ~IWSSS 2 The combination of the vibration and the flowing film of water causes the partides to become smtim, with the heavier particles of cwsiterite being carried between thc ripples to the ghm end of the table, whilst the lighter waste sands am washed down the table and off the long edge. Most tables produce three products, 8 concentrate, W g a and a ‘rniddlings’ oi mixed product, which is =-tabled. 3 Tm are r e c o v d fiom gravel pump mining is usually md first in 8, sluice b o x Ur ‘palong’, This is 8 dophg wooden trough about 2 metres wi& by 1 metre deep and 30 metres long. As the sand and slurry from the &ravel pump flow down the pdcmg, the cassiterite and other heavy minerals Elettle m the bottom, Erom h e to time the feed ia diverted and the impure concentrate mmoved for further treatment by jigs and tables 88 described already. In order to obtain tin metal fkom the concentrate, it is smelted by reduction with carbon at high temperature using 8 fluxing agent+ The impure metal & r i v d from primary smelting is purified by a series of refining cqemtions until the required grade of m m m i a l purity is obtahd. Befm smelting, however, it is often necessary to treat the mncentmtm to move the impurities they may contain, Generally speaking, the high-gtadt lXmcernES from alluvial &@m fequitc less preparation than the lm~r=gradeconcentrate# arising h m lode mines. 4 molten metal usually by bubbling compressed air through it. When both are necessary, liquating is carried out first. The refined tin, whether obtained by fire refining or electrolysis is normally remelted and cast into ingots weighing 50 kg. The brand name is generally cast into the ingot surface. There has been a rising trend in recent years for tin to be smelted in its country of origin and all major producers have their own smelters. Secondary tin: recovery and recycling In the case of tin, recycling can be broadly classified into three categories: recovery of tin metal (secondary tin), recycling of high-tin alloys and re-use of low-tin alloys. Secondary refined tin metal is unwrought tin recovered from tin scrap, tinplate scrap and residues arising from tinplating, timing, detinning and alloying processes. An important source of secondary tin is the process scrap generated by the can-making industry, for example when stamping circles from strip or sheet tinplate. The material is collected, usually as loose, unbaled scrap, and sent for recovery of the tin and the steel. Tin is also increasingly recovered from used tinplate containers in domestic refuse; these can be reclaimed by magnetic recovery plants or by consumer deposit banks. lower grade ore by improved extraction methods. They would not have deemed probable the recovery of tin from granite 750 metres below the Earth's surface, or from the sea bed 30 metres below the water line and up to 8 km out to sea, or from river beds opened up to mining by river deviation schemes. To illustrate the uncertain nature of reserves estimates, one has only to cite the detailed forecasts published periodically by the U.S. Bureau of Mines. If one goes back only a quarter of a century the quoted reserves have ranged between thee and nine million tonnes. This illustrates the fact that such estimates are subject to complex economic and geological factors, but generally represent a minimum of 20 years' foward supply at average consumption levels. As exploration continually uncovers further reserves, there will be an assured supply to meet anticipated demand in the future. Estimated Economically Recoverable World Tin Reserves Year Current state of tin reserves There has been much discussion and assessments made over many years concerning the question of mineral reserves and resources. There appear to be at least two common errors which have been perpetuated in many of the attempts to predict future resource availability. The fust relates to economic considerations and the likely changes in the cost/price ratio which can quickly make uneconomic deposits valuable; the second factor, so often discounted, is technological innovation. Improvements in both extraction and refining techniques are a continuing process and there seems little reason to doubt that mining companies will continue to develop more efficient ore recovery and smelting practices. Earlier assessments of exploitable reserves have often discounted the profitability of mining increasingly 1000s of tonnes 1965 4265' I970 P 975 I980 1985 I990 3930' w601 9100' 3060' 711Oo2 ( 1 ) Mineral Fats d Problem (1986) (2) Mineral Commodity Swnmpries (1990) (Both publkkd by U.S. Bureau of Mines) There seems little doubt that tin producing countries can look to the future with little worry about meeting demand due to heightened exploration activity and greater use of modern technology. n the demand side there are hopeful signs that lower tin prices over the last few years have encouraged consumers to halt any switch away from tin. The rise in the consumption of tin in tinplate in the USA in recent years suggests that tin consumption is recovering in this way. 5 "
Heemskirk Tin Project Highest grade undeveloped ASX-listed tin resource Annual General Meeting