At the present the majority of gold is extracted from the ore by using the common and regular cyanidation process. Metallurgists have been trying to optimize the process is several ways and the Filblast Process is the results of the careful and dedicated investigation of the variables that affect the chemical recovery of gold by cyanidation. Basically, the cyanidation process comprises two operations: oxidative dissolution of gold and reductive precipitation of metallic gold from the solution. The first one is the key aspect of the process and the Filbast Process involves intense high shear mixing, high gas mass transfer and addition of oxygen at high pressure.
The process incorporates an agitated tank which can be used as the first leaching tank or as the first and intermediate leaching tank. The final arrangement depends on the complexity of the material. It has been noted that the dissolution of gold is influenced by the concentration of cyanide and oxygen with the tank size and agitation speed. These factors control the thickness of the diffusion boundary layer that governs the cyanidation rate. In this way, when the required slurry through-put exceeds the capacity of the tank, it is necessary to add other unit. The pressure in the tank is approximately 400 to 500 KPa and the final pressure can be regulated according to the level of oxidation required. The problems experienced when cyanidation is performed at high densities are solved with the Filblast process, due to the addition of oxygen tends to reduce the viscosity of the slurry by the fact that oxygen on particle surface charges with the intensely aerated, homogeneous medium. In other words, the shear effect modifies the surface of the particle and reduces the viscosity of the system around it.
The manufacturer is Atomaer Pty Ltd and the new cyanidation process has solved the problem related to small operations where the cash flow is an important aspect of the operation. The system can be used in portable plants or small gold operations. It is important to indicate that the efficiency of the process is based on the efficient mixing, oxygen dissolution and surface polishing effect. The tanks are designed considering the high levels of pressure and the material of some parts is highly resistant to abrasion and corrosion effects produced during the agitation and addition of oxygen. The smallest laboratory sized tanks has a capacity of 0.08 m3/min, and the larger unit are able to treat 17 m3/min. The operation of two or three unit is parallel is possible and designer must study the flow rate of slurry and the level of efficiency required to achieve an acceptable level of gold dissolution.