The one thing that many people do not appreciate is that the cyanidation of gold depends on two factors the amount of cyanide AND the amount of oxygen!

Filblast was a fairly early innovation to improve the air flow so that one did not need pure oxygen or peroxide and at the time was cheaper than both. The Filblast is a high shear, pressure reactor. In the design, the reactor/feed pump relationship has been established to give a specific shear rate within the agitated cyanidation system. Basically, the required shear rate is obtained with a pressure of 400 to 500 KPa and due to the high mass transfer rate, an important part of the oxygen consuming species are oxidized during the time they are within the Filblast tank and it possible to saturate the slurry with oxygen. In this way, the high content of dissolved oxygen in the discharged slurry is available for oxidation of slower reacting oxygen consuming species present in the slurry. Other important result was the elimination of the hydrogen peroxide addition, reduction of the cyanide consumption and increased gold recovery by 8% to 10%. The others operations that installed a unit are Ragol’s Marvel Loch, JundeeNimary, Golden Star, and Blyvoor. I was involved in testing in Zimbabwe where we halved the gold extraction costs, so in my view it is very effective.

However, the largest unit I am aware of could treat 150t/h of mill feed or 3600tpd. This may be why it is no longer popular. Other factors could be that " Atomaer" the supplier only rented the filblast unit, as well as the incredible wear on the pump at the required velocity when treating abrasive ore. Oxygen lancing or peroxide may now be cheaper but at the time operating costs (including lease and maintenance charges for the Filblast and pump power costs) were about 16 cents per tonne, or about ten per cent of savings.

I used Filblast in a gold processing plant in Australia with some success using oxygen. The pump system used was simply a recycle pump in the first leach tank which recycled slurry from within the first tank. The unit needed to be rented and one could never have access to the internals of the unit.

The main problem with the unit now is that the supplier has either gone out of business or was not interested in discussions with me when I required some input for another project. If they are still in business hopefully for them they have better customer interaction. Some say the units were successful some say not - I believe it is "horses for courses" and some applications may be successful where others may not be.