A Simple Guide to All-Slime Cyanidation Carbon-in-Pulp Gold Extraction: Recovering Gold with Efficiency

The following section provides a brief description of the all-slime cyanidation carbon-in-pulp gold extraction process (gold cyanide solution).

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gold cyanide solution

The ore is transported to a crude ore bunker and fed into a crusher by a feeder. The coarsely crushed ore is conveyed to a vibrating screen by a belt conveyor. The coarse ore particles are returned again to the vibrating screen through a two-stage crushing process and the undersize within the specified grinding particle size range is transported to a fine ore bin by the belt conveyor.

And then fed into a first-stage grinding mill and classifier for coarse grinding by a fine ore feeder and the belt conveyor.

The coarsely ground ore with a typical particle size of -0.074mm accounts for approximately 60%.

In the first stage, gold particles cannot be finely ground in order to achieve complete monomer dissociatio, and are not within the particle size range required by the all-slime cyanidation process. In this case, a hydrocyclone cluster for second-stage grinding is used to classify particles and ensure that the particles with a typical size of -0.074mm account for approximately 90%

The typical overflow concentration of a hydrocyclone is around 20% and the pulp concentration required for cyanide leaching and carbon adsorption is 35-45%. So the pulp needs to be concentrated by a thickener.

A trash screen is needed to remove the impurities from the pulp before concentration.

And then the treated pulp is fed into the thickener for concentration to ensure that the concentration of pulp reaches the concentration level required for leaching. That is to say, the thickener’s underflow concentration reaches the specified range of 35-45%.

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The thickener’s underflow may be pumped into a leaching tank for leaching. The overflow (clean water) from the thickener may then be returned to an elevated water tank or directly returned to the grinding and classification system feed water for reuse. Cyanide is added to a carbon-in-leach system. Then medium pressure air is pumped into the system and activated carbon is added to the system.

Then energy-efficient dual-impeller agitating tank has impellers operating at lower rotational speeds and higher linear velocities and a low-power motor. So it is more energy-efficient and can prevent the loss of gold resulting from the loss of gold-loaded carbon by avoiding the crushing of gold-loaded carbon due to the high-speed rotation of impellers.

The pre-leaching process, as well as simultaneous multi-stage leaching and adsorption process ensure that the gold-loaded carbon with a grade of 3000-4000g/t is lifted out by a carbon-lifting pump.

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The gold-loaded carbon lifted out by the carbon-in-leach system is screened and washed thoroughly and washed thoroughly and then conveyed to the desorption electrolysis shop for desorption and electrolysis. The gold in gold-loaded carbon is dissolved in liquid through desorption. In the electrolysis process, the principles of anodic and cathodic electrolysis are applied to allow gold or silver to deposit at the anode of an electrolyzer to obtain gold slime.

Normal temperature pressure desorption electrolysis systems and high-temperature pressure desorption electrolysis systems are the most common desorption electrolysis systems in China.

The operating temperature of normal temperature pressure desorption electrolysis systems is maintained at 85-95℃ and its desorption duration is kept at 28-70hoursHigh temperature pressure desorption electrolysis systems do not contain any heat exchangers. That may operate at the temperature range of 150-170℃ and the pressure of 0.35Mpa, with a desorption duration of 4-6 hours, which ensures a high desorption rate and shortened carbon cycle and helps greatly improve operating efficiency.

The barren carbon desorbed from the desorption electrolysis shop is discharged into a desorbed carbon storage tank and then fed into a picking tank for pickling. The treated barren carbon is then dehydrated and fed into an activated carbon regeneration kiln for regeneration and is finally returned to the cyanide leaching shop for recycling. The gold slime from the desorption electrolysis process contains about 30-50% gold. It is transported to the melt shop and melted using the pyrometallurgical or hydrometallurgical process to obtain gold ingots.

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Tailings from the gold cyanide solution leaching process can be treated through alkalization to reduce cyanide levels and then directly discharged to the tailings pond for sedimentation and self-purification

Alternatively, in the tailings dry discharge process, cyanide tailings are pumped into the agitation /buffer tank in the tailing shop.

And then pumped into the plate-and-frame filter press and ceramic filter for filtration using a pressure pump to achieve solid-liquid separation and ensure that the liquid is returned to the process and tailings are discharged through the dry discharge process from a central location.

The all-slime cyanidation carbon-in-pulp process is applicable to low-sulfur quartz vein-type oxidized ores, especially for raw oxidized ores with an average grade ranging from 3 to 8g/t.


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