IAO5050-1 gold refining plants model IAO

Introduction to Aqua Regia refining
The aqua regia refining process is used to refine gold alloys using a combination of acids and chemical
products. The aqua regia solution consists of a mixture of hydrochloric acid HCL and nitric acid
HNO3. The refining process can be broken down into several steps:

• Analysis of the gold to be refined
• Production of Au grains or thin strips needed for the refining process
• Refining process
• Separation and recovery of the AgCl produced in the refining process
• Precipitation of the gold in solution using chemical products
• Filter and rinsing of the gold powder
• Analysis of the refined gold
• Melting of the Au into final required shape (ingots, grains etc)

The Aqua Regia refining method
Best suited for refining gold with an initial purity of at least 600/1000. Initial purities below this value
will reduce the production capacity as well as increase process times.
Recommended maximum silver percentage: 10-12 %. Percentages above these values can reduce
production capacity as well as increase process times.

The IAO gold refining plants produced by Italimpianti Orafi can refine all gold alloys that are within
the above stated parameters or thereabouts.

For gold alloys significantly below a certain purity (in our case 600/1000) or with silver content
significantly above a certain amount (in our case 10-12 %), the inquartation process is recommended.
This refining method uses only nitric acid HNO3.

For the aqua regia refining method, the gold must be either melted into fine grains – this is normally
done using a melting furnace (our FIM model) and a grain tank (our RPG model) – or very thin strips.
Strips are best because they have a large surface area and dissolve completely when emerged in the aqua
regia solution. Grains, due to their irregular shape and size, are more difficult to dissolve and some are
often leftover in the reactor at the end of the process. On the other hand, they are very quick to
produce.

Waste products of the Aqua Regia refining method
Non-precious, heavy metals left over in the waste solutions can be treated and recovered using a water
treatment plant (our model IN/A). This unit recovers these metals by producing hydroxides that then
have to be sent to specialised companies for treatment and disposal.

Acid fume neutralisation
Fume scrubbers (our models TLF) use caustic soda or sodium hydroxide (NaOH) to neutralise the acid
fumes produced during the refining process.

The solution inside the fume scrubber must be periodically checked. If the pH falls below 10, it needs
to be reintegrated with sodium hydroxide. The formation of crystals on the bottom of tank also means
that the solution is saturate with nitrates and must be changed. The solution must be changed and
treated according to local environmental/pollution laws.

Our IN/A water treatment unit can also treat the waste solution from the scrubber.

Chemical products needed for the Aqua Regia refining method
The reagents are:

• Nitric acid HNO3 at 36 Bè
• Hydrochloric HCl at 21 Bè
• Various chemical precipitation products

Results of the Aqua Regia refining method
The IAO aqua regia refining units can guarantee a minimum purity of 999.5. Experienced workers can
achieve 999.8. It is important to point out, however, that a purity of 999.9 is only needed for those
companies that are either gold bullion dealers or have the “good delivery” certificate. In other cases,
999.5 purity is the market standard.

It is possible to achieve 999.9 by performing a double refining cycle but, as explained above, this isn’t
necessary except for particular companies.

Italimpianti Orafi does produce an electrolytic gold refining plant (model IAO/A) to produce 10-12 kg
of 999.9 gold every 24 hours.

Description of the IAO5050-1 gold refining unit
The IAO5050-1 refining plant is used to refine gold alloys using the aqua regia method as described
above.

• Refining capacity : 32-40 Kg of grains (see “The Aqau Regia refiing method”)
• Purity obtainable: 999,5/1000 ( see “Results of the Aqua Regia refining method”)

The plant is made up of:

• n.1 PPl tray where two 100 lt containers for HCl and HNO3 acids are stored.
• Polypropylene hood containing with suction fan to be connected to a fume scrubber.
  Designed to the recover any acid losses.
• n.2 100 lt polyethylene containers with cover and suction manifold
• n.2 Electrical heaters with potentiometers
• n.2 50 lt pyrex reactors with relative 1.5 m2 condensers (useful capacity of reactors : 45 lt)
• n.2 Graduated tanks for HCl and HNO3 . Acid transfer from the reactors by vacuum
• n.1 Filter unit on wheels with a compressed air diaphragm pump to transfer the solutions.
• n.1 350 lt cementation tank with stirrer, antiacid frame and service stairs.
• n.2 200 lt polyethylene tanks, fitted onto a trolley to store king waters
• n.1 Electrical board to control lighting and heaters

Technical data:

• Power supply : three-phase.
• Power : 8 Kw.
• Overall dimensions : 5000x3300x2550 mm (length-width-height).

Description of the TLF/750 fume scrubber The tower is used to neutralize fumes and remove organic substances. It is built out of polypropylene sheets. A sprayer is installed inside the tower to spray a 1000 mm thick layer of raschig rings. In order to avoid drop dragging, a second 200 mm thick layer of raschig rings has been placed upstream to the sprayer. A neutralization solution container is placed beneath the tower. The solution circulation pump has a capacity of 55 Lts/1' with a head of 6 m. The suction fan has a max capacity of 300 m3/hour. Technical data: • Power supply : three-phase. • Power : 0,95 Kw. • Overall dimensions : 1350x1050x2800 mm (length-width-height). • Loadless weight : 100 kg • Working weight : 380 kg • Capacity : 300 m3/h with 5”contact time QT PRICE TOTAL PRICE TOTAL PACKING 1 € 9.870,00 € 9.870,00 € 535,00

Price: € 50.190,00

Packing: € 1090,00

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