gold ore beneficiation method gold cyanidation

The gold cyanide method refers to the method of extracting gold with cyanide as the leaching agent. Due to the mature technology, high leaching rate and strong applicability to ore, cyanidation method is still one of the main gold extraction methods at present. Reduce equipment weight and investment In the gold cyanidation process, every step must be controlled to ensure good economic benefits.

01 Inflate and add cyanide

After grinding, cyanide is added to the slurry to dissolve the gold and form metal complexes. The reaction formula is as follows.

4Au + 8NaCN + O2 + 2HgO → 4NaAu(CN)2 + 4NaOH

It can be seen from the above formula that oxygen is needed in the process of leaching gold, so it is necessary to inflate the leaching tank in industrial production. The aeration pressure is generally about 1kg, and the aeration volume per cubic meter of slurry is greater than 0.002m3 per minute.

02 Add protected base

In order to ensure the concentration of cyanide in the pulp, avoid environmental pollution, and prevent the production of toxic hydrogen cyanide (HCN) gas, alkali must be added to the leaching tank to maintain a high pH value of the pulp. Lime or lime milk is often used in industrial production, and sometimes NaOH is added for supplementary adjustment.

03 Keep the slurry suspended

The gold cyanidation process has certain requirements on the performance of the leaching and stirring tank. In the case of low power consumption, monomer separation in the slurry or gold particles on the exposed surface cannot be deposited in the tank, and the slurry, cyanide, lime and air must be fully mixed in the tank to reach a suspended state. The concentration of the slurry in each part of the tank should be consistent, there should be no stratification along the depth of the tank, and the particle size distribution should be uniform.

04 Maintain proper slurry concentration

When the gold ore density is 2.65~2.8, the general leach slurry concentration is 40~45%. When the density of the flotation concentrate is 3-3.5, the general leaching concentration is 30-40%. Generally, materials with fineness less than 200 mesh account for 80-95%.

05 Reduce wear and noise of moving parts

In order to reduce the wear of the agitator and increase the service life, most impellers in industrial production are lined with rubber. The selection of the transmission device should be fine to ensure high transmission efficiency and low noise.

06 Reduce carbon wear

The carbon slurry method is to add carbon to the adsorption tank to adsorb gold. If the agitation of the leaching tank is too strong, the carbon will be ground and lost. If the stirring force is weak, sediment will be produced. Therefore, while keeping the pulp in a suspended state, on the one hand, it is necessary to select carbon with high hardness for production, and on the other hand, it is necessary to reduce the speed of the impeller to reduce the loss of pulp. Carbon and stirred tank input power.

07 Determining the right capacity

At present, the processing capacity of common gold cyanide plants ranges from tens of tons to tens of thousands of tons per day. The larger the production capacity, the larger the plant area, the larger the equipment specifications and investment. Each mine owner must determine the appropriate processing plant capacity according to the actual situation.

08 Reduce equipment weight and investment

When selecting a leaching tank, on the one hand, the leaching process is required to be highly efficient and energy-saving, and at the same time, the transmission device is required to have a small footprint and light weight. When the capacity, pulp concentration and leaching time are determined, the number of leaching tanks can be determined.

However, the specification of the leaching tank should be adapted to the capacity of the plant. When constructing a 500t/d gold cyanide plant and using a φ3.5X3.5m leaching tank, it is necessary to increase the required equipment and increase investment. Therefore, only light equipment and appropriate capacity can reduce enterprise construction investment.