Bureau of Mines Report of Investigations , , 11 pp. Hodges, G. Recovering Platinum and Palladium at Stillwater. Metals, vol. Baglin, E. Bureau of Mines Report of Investigations , , 15 pp. Plasket, R. Hydrometallurgy, vol. Pearce, R. A New Method of Matte Refining Journal of Metals, vol. Bureau of Mines Report of Investigations , , 12 pp. Baglin 1 1. Personalised recommendations. Cite chapter How to cite? Cold dope revert is normally used to lower the temperature of the matte during conversion [ 16 , 19 ].
A number of approaches have been investigated to deal with the chrome problem. The following actions have eased chromite problem in the smelters: Deep electrode immersion operating at high power densities causes sufficient mixing which keeps the solids in suspension [ 8 , 21 ], but high power densities adversely affect the refractory life. To minimise the effect of high power input on the refractory life of the sidewall lining, the phase voltage is increased without increasing the current levels [ 19 ].
Some producers stopped recycling the converter slag to the furnaces since the converter slag has high chrome content [ 19 , 20 ]. The flux addition in the furnace was discontinued since lower CaO levels increased the solubility of the chromite in the slag [ 19 , 20 ].
The control of furnace inputs and control of furnace parameters power, furnace availability are essential in controlling chrome content [ 19 ]. Selective reduction improves the solubility of chromium in the slag [ 20 ]. Tapping out the intermediate layer intentionally [ 22 ]. Decreasing the chromium input to the smelters [ 20 ]. Another innovation able to manage chrome-rich ores is the ConRoast process. This process involves removing and capturing sulphur from the concentrate prior to smelting in a DC arc furnace.
Roasting a concentrate makes smelting more environmentally friendly; it also enables furnaces to accept any proportion of chromite, resulting in more efficient and cost-effective platinum production [ 9 , 23 ]. To prolong the service life of the refractories, sufficient cooling of the refractories is required at the cold face of the refractory wall. Copper waffle coolers are typically used in the cold face of the refractories to extract heat away from the refractories [ 24 ].
Due to high operating temperature and corrosiveness of the PGM melt, premature failure of the waffle copper coolers has been experienced in PGM smelters [ 24 ] in the upper sidewall region. Failure of waffle copper coolers causes explosions, loss of production and costs associated with furnace rebuild. The failure of waffle copper coolers was preceded by the consumption of conventional refractory bricks MgO x -CrO x which were used to form the furnace lining.
To prevent the occurrences of copper cooler failures, conventional bricks have been replaced by the graphite blocks in recent designs of PGM smelter refractory walls [ 25 ]. Graphite blocks are only applied at the hot face of the upper sidewall against the concentrate and the slag zone.
With the graphite block lining, a frozen protective skull forms at the hot face of the refractory. The formation of the protective skull is attributed to the efficient cooling of the refractory wall by waffle coolers. The frozen skull is the melt that solidified due to the surface temperature of the graphite that was lower than the liquidus temperature of the melt [ 25 ].
Graphite blocks have increased the service life of the waffle copper coolers through the formation of a protective layer.
However, high infiltration of melt is still observed at the matte-slag tidal zone. This is a challenge that still needs to be addressed; currently, conventional bricks or monolithics are used at lower sidewall of the PGM smelter refractory.
It is desired to extend the graphite blocks to the lower sidewall of the PGM smelter refractory wall against the matte zone [ 25 ]. It is envisaged that using carbon-based refractory at the hot face of the matte zone lower sidewall will improve the service life of the furnace lining in PGM smelters [ 25 ]. The PGM industry faces challenges with increasing chrome content in the feed and premature failure of refractory lining in the smelter.
Alternative ways to process the PGM have become attractive due to the challenges associated with the conventional smelting process [ 1 , 18 ]. A hydrometallurgy Kell process has been probed as an alternative to smelting PGM. The Kell process has three stages: stage 1 is the leaching of base metal sulphides in an acidic sulphate medium pressure oxidation ; stage 2 is roasting of the residue from stage 1; and stage 3 is atmospheric leaching of PGMs in a chloride media.
The leached precious metals are further treated in refineries to recover metals [ 18 ]. Other hydrometallurgical routes have been discussed in Ref. These hydrometallurgical processes have advantages over the smelting process since they reduce the operating costs drastically [ 1 ]. However, the alternative hydrometallurgical routes of processing PGMs have not yet been commercialised [ 1 ]. In this chapter, an overview of PGM processing has been presented. The conventional smelting process has challenges with high chromium feed, premature failure of refractory lining and increased operating cost associated with increasing cost of electricity in South Africa.
The Kell process is an alternative way to process a PGM concentrate, and it has a number of advantages such as less energy consumption, less energy cost, less electricity consumption, less CO 2 emissions and no restriction on chrome content of feed. Other hydrometallurgical routes have been investigated, but none has been commercialised yet.
Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Mohindar Seehra. We are IntechOpen, the world's leading publisher of Open Access books. During flotation, air is pumped through the ore-water slurry. Platinum particles chemically attach on to the oxygen and rise to the surface in a froth that is skimmed off for further refining.
Aqua regia a concoction of nitric acid and hydrochloric acid is used to dissolve platinum metal from the mineral concentrate by creating chlorine that attaches to platinum to form chloroplatinic acid. In the final step, ammonium chloride is used to convert the chloroplatinic acid to ammonium hexachloroplatinate, which can be burned to form pure platinum metal.
The good news is that not all platinum is produced from primary sources in this long and expensive process. For a metal whose annual global production is a mere tons, platinum is found in, and critical to the production of, many everyday items. Platinum's corrosion resistance and high-temperature stability make it ideal as a catalyst in chemical reactions. Catalysts speed up chemical reactions without themselves being chemically altered in the process.
Platinum is also used to catalyze nitric acid and gasoline; increasing the octane levels in fuel. In the electronics industry, platinum crucibles are used to make semiconductor crystals for lasers, while alloys are used to make magnetic disks for computer hard drives and switch contacts in automotive controls.
Demand from the medical industry is growing as platinum can be used for both its conductive properties in pacemakers' electrodes, as well as aural and retinal implants, and for its anti-cancer properties in drugs e. Below is a list of some of the many other applications for platinum:. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content.
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