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Sodium cyanide is an important chemical that has been manufactured
in Australia since the late 1980s. There are now three plants.
Sodium cyanide is also known as cyanide of sodium, cymag, hydrocyanic acid sodium salt. It is a white powder or solution in water. Liquid cyanide contains 30 per cent cyanide while the solid is 98 per cent pure in Australia (though lower grades are produced overseas).
Sodium cyanide (NaCN) is a chemical used overseas predominantly in metal
plating and chemical applications such as dyes and pharmaceuticals. In
Australia it is principally used for the gold mining industry to extract
gold from gold bearing ore using the carbon-in-leach and carbon-in-pulp
processes with 98 per cent of Australia’s gold production dependent on
it. These processes enable commercial recovery of gold at very low concentrations
(down to just 0.85gm per tonne or 0.85 ppm of soil or mine tailings). Between
300 and 500 tonnes of sodium cyanide (valued at ca. US$0.7m) is required
for each tonne of gold (valued at say $13m) produced so that cyanide represents
around 8 per cent of the value of gold produced.
Sodium cyanide is also used in nickel production as an arsenic suppressant.
 | About 90 per cent of Australia’s gold reserves are non-alluvial providing 98 per cent of production. Less than 1 per cent of Australia’s gold production does not use sodium cyanide. |
| Acid thiourea has been used as an alternative to sodium cyanide but this is unsuitable for use in soils with soluble iron and clays as typical of Australia. |
| Sodium cyanide extraction has replaced the mercury amalgam process which is environmentally harmful and less than two-thirds as efficient. |
Sodium cyanide is manufactured by the Andrussow process using ammonia, air, natural gas and caustic soda. The process reacts ammonia with natural gas and air over a platinum/rhodium catalyst to produce hydrogen cyanide gas. Typically the production of one tonne of sodium cyanide requires:
| natural gas - 36 gigajoules (940m3) |
| caustic soda - 0.95 tonnes |
| ammonia - 0.65 tonnes |
| electricity - 0.67 MW |
Ticor is believed to be using technology less demanding of ammonia.
Production at all three production centres is at around world scale using the latest technology having been established in the last ten years.
AGR
on the web
AGR is jointly owned by Wesfarmers CSBP (75%) and Coogee Chemicals (25%).
Australian Gold Reagents (AGR) manufactures sodium cyanide in liquid and dry
form at Kwinana
in Western Australia with a production capacity of about 65 000 tonnes
of sodium cyanide (on a dry weight basis). Sodium cyanide is supplied in liquid solution (30 per
cent solid) and more recently now in solid. The raw material ammonia is supplied by Wesfarmers and caustic
soda by Nufarm-Coogee.
Though more than twice the bulk of the dry form and hence more expensive
to distribute, it is generally more competitive by avoiding additional
equipment and drying costs. Liquid cyanide was considered by the West Australian
Environmental Protection Authority to be more hazardous to transport and
until 1996 in Western Australia it was required to be moved by rail. Without
railway access, some locations were for a time compelled to use the imported
dry form of cyanide.
In 1998 a A$30m expansion doubled production to 70 000
tonnes per year by plant duplication.
In September 2001, the EPA approved production of
25 000 tpa of the solid form. Prior to the AGR expansion, Orica indicated an interest to establish
a 30 000 tpa plant at Kalgoorlie (Mungari Industrial Park) (Kalgoorlie
Miner, 28 Sept. 1996 but shelved in February 1998 [together with a xanthate
plant]. It involved a $25m ammonia import terminal in Esperance.). Given
such a plant would require around 1 petajoule of gas provided by the new
Goldfields
gas line, it would (by ACTED calculations) incur a pipeline overhead
charge penalty of around $70 per tonne of cyanide compared with its competitor
AGR at Kwinana. The freight saving of regional manufacture would be further
offset by having to freight the caustic soda and ammonia to Kalgoorlie
at around $100 per tonne each (say $160 per tonne of cyanide produced).
Reflecting international scales of production and technology, quality
is equal to imports with prices at import parity.
Liquid cyanide, though cheaper to produce than solid sodium cyanide that
advantage is offset by higher transport costs, and is generally priced
by AGR to be competitive with the dry (ie. imported) form on an into store
basis. Cyanide prices in Western Australia during 1995 ranged from $1 300
per tonne to $2 800 tonne depending on form, size of packs and size of
orders. Liquid cyanide prices tend to be about $100 to $200 per tonne cheaper
than dry cyanide (ex factory dry weight basis). Offsetting that advantage
is the additional cost of freight and specialist equipment required to
receive and dispense. However, the additional transport cost has its limits
so that dry form is more economic if freighted more than about 1 000 kilometres
inland. Accordingly, the rail head near the gold producing area around
Kalgoorlie is dominated by liquid cyanide produced by AGR while more distant
locations tend to use cyanide from Australia's other two producers, ICI
and Ticor in Queensland (and some imports from overseas suppliers such
as Degussa). In other words, AGR can readily set the ex factory price to
maximise income and market share currently supplying about one-half the
West Australian market.
It was fortunate for AGR that its competition chose to establish in
Queensland - a decision that now provides a substantial local market advantage.
AGR can now expand its market with liquid (or dry) cyanide. Although its
raw materials and energy requirements are at or above international prices,
but with no other source of competitive advantage, domestic and international
transport cost savings provide a substantial advantage.
This operation was closed in April
2004 and the site sold in July 2004. Production of briquettes are 15gms, 31mm by 30mm by 11mm with a specific
gravity of 1.6 and a minimum of 98 per cent purity (0.2% water maximum).
The cyanide is packaged in 1 000 kg Intermediate Bulk Containers of plywood.
Ticor Chemical Company
Orica
Orica operates a plant at Yarwun (close to the Ticor operation) with a
production capacity of about 35 000 tpa of dry cyanide. Ammonia is road
freighted and shipped.
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