As new feed is introduced, coarser calcines are displaced from the fluid bed, which overflow from the reactor through a fluid seal to the calcine quench tank. Off take gases are passed through a cyclone to recover calcine dust particles entrained in the gas stream. The hot gases are then passed through an evaporative gas cooler prior to dust removal in an electrostatic precipitator. The feed to the Gidji CIP circuit is the quenched calcine slurry from the roasting section, which is pumped to a 200 m3 preconditioning tank. This is the first of two tanks used for pH adjustment and preoxidation using liquid oxygen.
Liquid oxygen is added to the first five tanks in the circuit.
Carbon movement is controlled in a programmed sequence by the Yokogawa DCS, and loaded carbon is transferred in batches to Fimiston for stripping and bullion recovery. Producing gold bullion After the long process of mining, crushing, grinding, flotation and leaching, the gold bearing solution finally ends up in the adsorption tanks, where it comes into contact with granulated activated carbon. The carbon, commonly made from coconut husks, is activated by heating to 900 degrees Celsius during manufacture. Adsorption is the process whereby the activated carbon acts like a magnet, and draws the gold out of the solution. When the carbon is saturated with gold, it is referred to as loaded carbon .