Ausmelt / Isasmelt Matte Smelting: Part Three

Ausmelt is a leading international supplier of top submerged lance (TSL) smelting technology to producers of copper, lead, tin, nickel, platinum group metals (PGMs), zinc and ferrous metals from around the world. TSL smelting technology is also used to reclaim metal values from various wastes, leaving behind an environmentally benign, compact solid. Twenty-four commercial Ausmelt furnaces have been installed in nine countries, with a further three projects ongoing.

THE LEAD SMELTING PROCESS USING AUSMELT TECHNOLOGY

Ausmelt Technology offers an efficient means of processing a wide range of primary concentrates and secondary lead materials to produce lead bullion, especially because the partial oxygen pressure (pO₂) can be readily controlled to achieve the desired process conditions.

The complete Ausmelt lead production process for primary concentrates consists of 3 process stages; (i) Smelting, (ii) Reduction and (iii) Fuming. Depending on the scale of production all 3 stages can be carried out in a single furnace as a batch operation. Alternatively, multiple, sequential furnaces can be used to enable continuous operation.

Depending upon client preference and the availability of existing furnaces it is also possible to integrate one or more Ausmelt processing stages to achieve the most efficient lead production flowsheet to best suit site requirements. Figure 1 shows a schematic flowsheet for a Multi Furnace Lead Process.

Figure 1: Schematic Flowsheet for Mutli Furnace Lead Process

The benefits and features of Ausmelt Lead Technology compared to other lead smelting technologies lie with its submerged lance operation:

• The key to this lead technology is the ability of TSL to manipulate pO₂ accurately as dictated by the metallurgy of the relevant processing stage.

• Low capital cost relative to other technologies due to simple furnace construction & peripheral system arrangement.

• Low operating cost resulting from a combination of low energy consumption, high availability, minimal maintenance requirements and low manpower needs. The process operates with very high oxygen utilisation during the Smelting stage (>95%) and can employ high levels of oxygen enrichment to minimise fuel consumption and offgas volume. The process does not require the use of expensive (and difficult to source) coke as a reductant and can utilise the lowest cost available fuel source.

• It has an excellent environmental performance due to low fugitive emissions from the well sealed, stationary reactor and can efficiently recover SO₂ in the form of sulphuric acid or gypsum from the concentrated process offgas stream.

• High degree of flexibility in terms of feed material blend that can be treated to optimise productivity and economic performance.

• Intense mixing, resulting in high reaction rates and high metal productivity per m3 of bath, hence a small plant footprint and easy to retrofit into existing operations.

• High annual plant availability due its relative simple operation, which is also well suited to remote locations. For optimum results the lead smelting process does need to be run astutely with the support of metallurgists with a good understanding of lead metallurgy. Ausmelt provides this training as part of it’s service package.

Currently Ausmelt has two reference plants processing predominantly secondary lead feed and residues sources, including Korea Zinc’s plant in South Korea and Metaleurop’s plant in Nordenham, Germany. A further four Ausmelt plants are in operation or under design for the processing of primary lead feed materials, including HZL’s lead plant in Chanderiya, India.

The technical feasibility of recovering copper, nickel and cobalt from smelting and converting slags using Ausmelt’s top-submerged lancing process has been demonstrated at the pilot-plant scale and in several commercial applications. Process conditions may be tailored to achieve the maximum economic recovery of valuable metals and to yield a product composition that is suitable for downstream processing requirements.

Strong economic justification for a slag-cleaning process exists where the contained value of metals recovered exceeds $50 per tonne of slag treated. The top-submerged lance system offers a relatively low-cost solution where this value is predominantly associated with the recovery of cobalt.

Maximizing the recovery of copper, nickel, and cobalt is critical for the economic operation of smelters treating copper, nickel, cobalt feed materials. With the current trend toward the production of higher matte grades and the adoption of continuous converting processes, effective slag cleaning is of increasing importance.

The versatility of the technology has been demonstrated for a range of processes, ranging from copper converting under highly oxidizing conditions to iron-making under highly reducing conditions.

The most recent development is the construction of a demonstration furnace (2t/h feed rate) at Whyalla in South Australian Steel and Energy project, with the production of 2.5 million t/y of pig iron as the ultimate goal. Other recent commercial applications are listed in Table 1; most of these applications include either a purpose designed, slag-cleaning furnace or a slag-cleaning process stage.