Interpretation of the full-mud cyanidation carbon-in-pulp process

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1. What is the carbon-in-pulp gold extraction process

Full-mud cyanidation carbon-in-pulp gold extraction process (Carbon in Pulp, CIP for short) is a modern mineral processing process for extracting gold from gold-bearing ores. It mainly adds sodium cyanide solution to the gold-bearing ore after crushing and grinding (to meet the particle size requirements) for stirring and leaching, so that the gold dissolves to form a gold-cyanide complex, and at the same time, activated carbon is directly added to the cyanide slurry, and the gold is recovered by the adsorption of activated carbon on the gold-cyanide complex.

This process is particularly suitable for processing low-grade, highly oxidized gold-bearing ores. Compared with the traditional cyanidation method, it is characterized by combining the two processes of leaching and adsorption in the same equipment, reducing the process links and improving production efficiency. Let's learn about the full-mud cyanidation carbon-in-pulp gold extraction process together.

2. Carbon slurry gold extraction process

The principle process of hydrogenated carbon slurry gold selection is mainly ore preparation-cyanide leaching and carbon adsorption-separation and desorption of gold-loaded carbon-gold recovery and tailings treatment.

1. Ore preparation

First, the mined gold ore is crushed, ground and other operations, the purpose of which is to reduce the ore particle size (crushed to a suitable particle size) to improve the selectivity of the ore. Generally, after crushing, the ore is fed into the ball mill to make the ore particle size reach -200 mesh, accounting for about 60%-90%. Then the slurry is fed into the stirring tank, and an appropriate amount of water is added to adjust the slurry so that the slurry concentration meets the process requirements.

2. Cyanide leaching and carbon adsorption

Cyanide leaching and carbon adsorption are slurry after slurry adjustment, which is fed into the leaching adsorption tank, and then sodium cyanide solution and sodium hydroxide solution are added to adjust the pH value of the slurry to start cyanide leaching. At the same time, activated carbon is added to the leaching and adsorption tank in a certain proportion to make the activated carbon fully contact with the slurry. Under the action of stirring, gold dissolves in the cyanide solution to form a gold-cyanide complex and is adsorbed by the activated carbon. The leaching and adsorption process is generally carried out in multiple stirring tanks connected in series to ensure sufficient leaching and adsorption time.

3. Separation and desorption of gold-loaded carbon

After the adsorption is completed, the gold-loaded carbon is separated from the slurry through a sieve. The separated gold-loaded carbon needs to be washed to remove the surface mud and impurities. The washed gold-loaded carbon enters the desorption column for desorption. Desorption usually uses high temperature, high pressure and strong alkaline desorption liquid to desorb gold from the activated carbon to form a gold-containing desorption liquid. The activated carbon after desorption can be recycled after regeneration.

4. Gold recovery

The gold-containing desorption liquid enters the electrolytic cell or displacement equipment for gold recovery. In the electrolytic cell, direct current is applied to cause gold to precipitate on the cathode; in the displacement equipment, active metals such as zinc powder are used to displace gold. After refining, the recovered gold can obtain high-purity gold products.

5. Tailings treatment

The tailings slurry after carbon adsorption still contains a certain amount of cyanide and other harmful substances, which need to be treated. Usually, bleaching powder, sulfur dioxide and other oxidants are used to oxidize the cyanide in the tailings slurry to convert it into harmless substances. The treated tailings can be landfilled or comprehensively utilized.

3. Three key points of carbon slurry gold selection

1. Selection of activated carbon

The quality of activated carbon is crucial to the effect of carbon slurry gold selection. Generally, activated carbon with high specific surface area, large porosity and good mechanical strength is selected. Commonly used activated carbon types include coconut shell activated carbon, apricot shell activated carbon, etc. Coconut shell activated carbon has high strength and adsorption performance, while apricot shell activated carbon is relatively low in cost.

According to the properties of the ore and process requirements, select the appropriate activated carbon particle size. Generally speaking, fine-grained activated carbon has a large specific surface area and fast adsorption speed, but is easy to wear and lose; coarse-grained activated carbon is the opposite.

2. Determination of reagent system

Sodium cyanide is the main leaching agent in the carbon pulp gold selection process, and its dosage needs to be reasonably adjusted according to factors such as the gold grade and mineral composition of the ore. In addition to sodium cyanide, some auxiliary agents need to be added, such as sodium hydroxide, to adjust the pH value of the slurry to keep it within the range that is conducive to gold leaching, generally around 10-11. At the same time, in order to improve the adsorption performance and selectivity of activated carbon, some special agents, such as flocculants, can also be added.

3. Control of operating parameters

Slurry concentration control:Slurry concentration is one of the important factors affecting the gold selection effect of carbon slurry. Generally speaking, the slurry concentration is more suitable at about 40%-50%. If the slurry concentration is too high, it will affect the fluidity of the slurry and the adsorption effect of the activated carbon; if the slurry concentration is too low, it will increase the processing capacity and production cost of the equipment.

Stirring intensity control:The purpose of stirring is to fully dissolve the gold in the slurry and ensure that the activated carbon is in full contact with the slurry. However, if the stirring intensity is too high, it will cause wear and breakage of the activated carbon; if the stirring intensity is too low, it will affect the adsorption effect. Therefore, the stirring intensity needs to be determined according to the actual situation.

Adsorption time control:The length of the adsorption time depends on the nature of the ore and the process requirements. Generally speaking, the adsorption time is about 8-24 hours. In actual operation, the reasonable adsorption time can be determined by regularly testing the residual gold concentration in the slurry.

The above is the introduction of gold selection by full mud cyanide carbon slurry. In actual ore dressing plants, due to the differences in the properties of gold ores, the choice of process is particularly important. It is necessary to ensure that all links are closely coordinated to achieve normal and stable operation. Therefore, it is recommended to conduct ore dressing test analysis. By analyzing and customizing a suitable gold extraction process plan, an ideal return on investment has been obtained.