ISASMELT
Mineral concentrates or materials for recycling are dropped into the bath through another hole in the furnace roof or, in some cases, injected down the lance.
These feed materials react with the oxygen in the injected gas, resulting in an intensive reaction in a small volume (relative to other smelting technologies).
[4] They are designed to minimize pressure losses changing the angle from axial to tangential thus creating a strong vortex.
[16] Introducing any water to a system involving molten metals and slags can result in catastrophic explosions, such as that in the Scunthorpe Steelworks in November 1975 in which 11 men lost their lives.
[15] Following the copper slag trials of 1976–1978, MIM initiated a joint project with the CSIRO in 1978 to investigate the possibility of applying Sirosmelt lances to lead smelting.
It bought Aberfoyle's matte fuming furnace and transported it from Kalgoorlie to Mount Isa, where it was rebuilt and commissioned in 1983[16] to demonstrate the first stage of the process in continuous operation and for testing the reduction step using batches of high-lead slag.
[26] This gave the operations’ people ownership of the plant and an incentive to make it work, thus ensuring management and maintenance priority.
[15] In addition to the continuous operation of lead concentrate to produce high-lead slag, the pilot plant was used to produce lead metal from batches of the slag,[25] investigate the wear rates of the furnace's refractory lining and lances, and initial work aimed at developing a low-pressure version of the Sirosmelt lance.
[25] However, for most of the time the two furnaces were not able to operate simultaneously due to a constraint in the capacity of the baghouse used to filter the lead dust from the waste gas.
[25] A series of process improvements, particularly in the waste gas handling system, resulted in increasing the throughput of the plant from the initial design of 5 t/h to 10 t/h.
However, the oxygen originally designated for its use was diverted to the more profitable copper smelting operations, and the feed rate to the lead ISASMELT demonstration plant was severely restricted.
[28] When there was sufficient oxygen available in 1993 to increase the enrichment level to 33–35%, treatment rates of up to 36 t/h of concentrate were achieved, with residual lead in the final reduction furnace slag being in the range of 2–5%.
[7] This was demonstrated on the large scale in 1994, when 4000 t of concentrate containing 67% lead were treated at rates up to 32 t/h with lance air enriched to 27%.
In the case of the demonstration plant, the problem was caused by sticky fume that formed an insulating layer on the convection tube bundles of the waste heat boilers, significantly reducing the heat transfer rates and thus the ability of the boilers to reduce the waste gas temperature.
The problem was solved by allowing cool air to mix with the hot waste gas to lower the temperature to a level at which the baghouse could operate.
[1] In June 2017, Glencore announced that Nyrstar NV had acquired an Isasmelt licence for its new Ausmelt furnace in Port Pirie.
The design was based on MIM's 250 kg/h test work and operating experience with the lead ISASMELT pilot plant.
[35] Using enrichment of the oxygen in the lance air to 35%, the demonstration plant throughput was lifted to 48 t/h of concentrate, and the gross energy used during smelting was reduced from 25.6 GJ/t of contained copper to 4.1 GJ/t.
Agip, a subsidiary of the Italian oil company ENI, was developing the Radio Hill nickel-copper deposit near Karratha in Western Australia.
[26] MIM and representatives of Agip conducted a series of trials in which 4 tonnes of Radio Hill concentrate was smelted in the 250 kg/h test rig at Mount Isa.
[26] The Agip ISASMELT plant was designed to treat 7.5 t/h of the Radio Hill concentrate and produce 1.5 t/h of granulated matte with a combined nickel and copper content of 45% for sale.,[26][27] It was the same size as the copper ISASMELT demonstration plant (2.3 m internal diameter) and had a 5.5 Nm3/s blower to provide the lance air.
[37] The high heat transfer rate means that the Fluxflow boiler is relatively compact compared with conventional waste heat boilers and the rapid cooling of the waste gas limits the formation of sulfur trioxide ("SO3"), which in the presence of water forms sulfuric acid that can cause corrosion of cool surfaces.
[46] In the first years of operation at Mount Isa, the throughput of the ISASMELT furnace was constrained by problems with some of the ancillary equipment in the plant, including the boiler, slag granulation system and concentrate filters.
[44] MIM decided to shut down the reverberatory furnace in 1997, and the ISASMELT plant 12-month rolling mean feed rate quickly exceeded the 104 t/h design when this constraint was lifted.
[12] The new plant reached its design capacity, measured over a three-month period, six months after it started treating its first feed.
[49] Since then Sterlite decided to further expand its copper production by installing a third ISASMELT smelter and new refinery using IsaKidd technology.
[54] It initially selected flash smelting technology to replace its reverberatory furnaces, at a cost of almost US$1 billion;[14] however, one of the first actions following Grupo México's acquisition of ASARCO was to review the proposed Ilo smelter modernisation plans.
[38] Union Miniére operated a smelter at Hoboken, near Antwerpen in Belgium, that specialised in recycling scrap non-ferrous materials.
[38] A demonstration plant was designed by MIM Holdings personnel and operated for several months at the Hoboken smelter site.
[57] The Hüttenwerke Kayser smelter at Lünen in Germany installed an ISASMELT plant in 2002 to replace three blast furnaces and one Peirce-Smith converter used for smelting scrap copper.
