Eight Process Requirements of Gold Mine Cyanidation Plant
The cyanide gold extraction process refers to the method of extracting gold with cyanide as a leaching solution. Due to the advantages of mature technology, high leaching rate, and strong applicability to ore, cyanidation is still one of the main methods of gold production. In the cyanidation process, it is necessary to control each process link in order to ensure good economic benefits. The eight process requirements for a gold mine cyanidation plant are described below.
1. Inflate and add cyanide
Cyanide is added to the milled pulp to dissolve gold to form metal complexes. Oxygen is required during the gold leaching reaction, so in industrial production it is necessary to aerate the leaching tank. The inflation pressure is generally about 2bar, and the inflation rate is more than 0.02m3 per cubic meter of pulp per minute.
2. Add the protective alkali
In order to ensure the concentration of cyanide in the pulp and prevent the loss caused by the formation of toxic hydrogen cyanide (HCN) gas, alkali must be added to the leaching tank to keep the pulp at a high pH value (10-10.5). In industrial production, lime or lime milk is often used, and sometimes NaOH is added for supplementary adjustment.
3. Keep the pulp in suspension
The cyanidation gold extraction process has certain requirements on the performance of the leaching (adsorption) stirring tank. It is required that under the condition of small power consumption, the particles in the slurry that have been separated from monomers or exposed surface gold cannot be deposited in the tank, and the slurry, cyanide, lime and air can be fully stirred and mixed in the tank to achieve a suspended state. The concentration of ore pulp in each part of the tank should be consistent, and there should be no stratification along with the depth of the tank body, and the particle size distribution should be uniform.
4. Keep the pulp concentration appropriate
When the density of gold ore treated by cyanidation is 2.65~2.8, the general leaching pulp concentration is 40~45%. When the flotation concentrate density is 3~3.5, the general leaching concentration is 30~40%. The fineness of the material is generally -200 mesh, accounting for 80~95%.
5. Reduced moving parts wear and noise
In order to reduce the wear of the agitator and increase the service life, most of the impellers in industrial production should be lined with rubber. The processing of the transmission device should be fine to ensure high transmission efficiency and low noise.
6. Reduce carbon wear
In the carbon slurry method, carbon is added to the adsorption tank to adsorb and leach gold. If the stirring force of the leaching stirring tank is too strong, the char will be crushed and lost, and the weak stirring force will cause deposition. Therefore, while maintaining the slurry in a suspended state, on the one hand, it is required to select carbon with high hardness for production, and on the other hand, reduce the speed of the impeller to reduce the loss of carbon and reduce the input power of the stirring adsorption tank.
7. Determine the right size
At present, the processing capacity of common cyanide plants ranges from tens to tens of thousands of tons per day. The larger the scale, the larger the required plant area, equipment specifications, and investment. Each mine mainly determines the appropriate plant scale according to the actual situation.
8. Reduce equipment weight and reduce investment
When choosing a leaching and stirring tank, on the one hand, the leaching should be efficient and energy-saving, and at the same time, the transmission device should occupy a small area and the weight of the equipment should be light. When the scale, pulp concentration, and leaching time are determined, the quantity can be determined. However, the specifications of the stirring tank should be adapted to the scale. If a cyanidation plant of 500t/d is built, the stirring tank of φ3.5X3.5m is still selected, which will increase the required equipment and increase the investment. Therefore, only the equipment is light and the scale is suitable, the investment in enterprise construction can be reduced.