Ausmelt process

K.R. Robilliard R.W. Matusewicz and B.R. Baldock, The Ausmelt Process for Smelting Nickel Concentrates and Further Treatment of the Matte Produced CIM 33rd Conference of Metallurgists 94, Recent Developments in Non-Ferrous Pyrometallurgy Symposium, Toronto, Canada, August 21-25, 1994, (Unpaged). 

J. M. Floyd B. W. Lightfoot and W. E. Short, Application of the Ausmelt Process to Treatment of Nickel Laterite Ores , Nickel/Cobalt Laterites Seminar, Alta Metallurgical Services, Melbourne, Australia, 4-5 May, 1995, (Unpaged). 

Smelting is a proeess whereby metals, sueh as lead, iron, or eopper, are recovered from a feedstock by the ehemieal reduetion of their eompounds. These reactions occur in various processes and take place at temperatures up to 1400°C in some lead blast furnaces, and to over 1800°C in iron blast furnaces. Various types of furnace are utilized worldwide for the smelting lead. These include the blast, reverberatory and Isasmelt/Ausmelt technologies [6] (see also Chapter 16), and the QSL [7] and Kivcet [8] processes. Not all secondary lead producers use modern technology such... 

Ausmelt Dioxins and Furans , internal communication with selected parts published in J. Floyd, T.C. Hughes, R.A. Hughes, Proc. MINPREX 2000, International Congress on Mineral Processing and Extractive Metallurgy, Melbourne, Australia, 11-13 September 2000, pp. 43-48. 

A variant of this process was developed in Australia by AUSMELT in 1998 their process used a closed induction furnace but with an air feed to bum the cadmium in the furnace and recover it in the form of cadmium oxide. The process produced nickel matte which had to be sent to the nickel refiners and highly contaminated cadmium oxides that had to be sent to the producers of primary cadmium. This required a higher investment than closed furnaces and the products extracted were somewhat less effectively recyeled than the nickel-iron and cadmium metal residues. 

These commercial developments have occurred after many years of development work at Ausmelt. In excess of sixty pilot plant tests processing high, medium, and low grade sulphide concentrates, battery pastes, dusts and high grade slags have been carried out at the Ausmelt pilot facility in Dandenong, Australia. 

The superior process flexibility of the Ausmelt system emanates from the ability to accept varying feed types, to operate at varying but precisely controlled oxygen system potentials and to recover heat from the post combustion reactions to the bath via cascading splashed slag, thereby reducing the system fuel demand. The system effectively separates volatile species to fume, valuable non volatile species to metal and low value non volatiles to slag. 

The redox potential verses temperature chart for various Ausmelt technology processes is shown in Figure 2. The chart shows high, medium and low grade smelting as well as slag reduction regimes. 

With the commissioning of the third Ausmelt technology smelter at Korea Zinc in Onsan, Ausmelt technology lead smelters will process high, medium and low grade feeds for a wide range of sulphide material blends. 

In the development of each plant process design, Ausmelt uses its extensive in-house database drawn from eleven operating plants and over thirty smelters built to date incorporating Ausmelt technology. 

The general trend with plant unit operating costs is for this to increase with reduced throughput and with more than one process operation in an Ausmelt furnace. However, in some circumstances unit operating costs may actually be reduced when switching from a two furnace to a single furnace operation because of a reduced labour requirement, when this can be sustained. 

The Ausmelt system is extremely well suited for the processing of lead secondary and other materials with the minimum production of dioxins and fiirans, because of ... 

The Ausmelt system has a low rate of dust generation, typically less than 1% of the feed input. This process feature tends to concentrate volatile impurities, such as arsenic, cadmium, antimony and bismuth in the lead fume, thus providing a relatively small quantity of fume for further treatment. 

Key reasons for the selection of Ausmelt technology for lead smelting by Metaleurop, Tsumeb and Korea Zinc are the excellent environmental performance, capital and operating cost profiles and process flexibility provided in a compact high intensity smelter system. 

The Ausmelt technology plant, designed to process 120,000 tonnes per year of mixed concentrates and secondary materials to produce 90,000 tonnes of bullion, commenced operations in March 1996. After initial teething problems were overcome, the smelter is now achieving the results envisaged at the project commencement, as reported by Metaleurop (1). 

The furnace is of conventional Ausmelt design approximately 4 metres internal diameter and 10 metres high, with external water cooling on the shell, roof and offtake. The furnace uses natural gas as fuel and the Ausmelt lances are oxygen enriched to approximately 40% to optimise process efficiency. 

The main driving force for this development is the overall process improvement to be gained by removing many internal secondary recycle streams, thereby freeing the QSL smelter for primary lead smelting activities. This smelter is the third Ausmelt technology smelter installed at Korea Zinc s Onsan complex and will commence operations in the second half of... 

The fume from the process will contain significant levels of cadmium, arsenic and antimony, and will require an acid leaching process step to reduce the impurity levels to allow recycle of the fume to the Ausmelt furnace. 

A feature of the early problems of both Tsumeb and Metaleurop was the high downtime of the gas handling equipment. This contributed significantly to plant downtime, in the case of Tsumeb, centering on the operation of an evaporative gas cooler and in the case of Metaleurop, a Fluxflow waste heat boiler. In both cases, the process equipment selection occurred directly between the client and supplier without a formal review step by Ausmelt. This review has now been incorporated into Ausmelt s procedures for future projects, with a view to provide a benefit to both the client and technology supplier. 

THE QSL LEAD SLAG FUMING PROCESS USING AN AUSMELT FURNACE... 

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