Operational essentials of cyanide leaching
2020-08-18 17:04Introduction：Operational essentials of cyanide leaching Leaching is a complex process of chemical change. The responsibility of the leaching operator is to make all kinds of equipment in good condition by artificial control, and to make the technologic
Operational essentials of cyanide leaching
Leaching is a complex process of chemical change. The responsibility of the leaching operator is to make all kinds of equipment in good condition by artificial control, and to make the technological conditions in the most suitable condition for leaching. Finally, the leaching process was smooth and thorough.1、Strictly controlling of cyanide concentration
During leaching, the concentration of sodium cyanide is one of the main factors affecting the dissolution rate of gold. The suitable concentration of sodium cyanide is determined by experiment and production practice. The low concentration of sodium cyanide should be chosen under the condition that the leaching rate is not reduced. This is because the harmful impurities associated with gold are dissolved at the same time in the cyanidation process. The higher the concentration of sodium cyanide, the greater the amount of dissolving impurity, which not only increases the consumption of sodium cyanide, but also consumes the oxygen necessary for gold dissolution. The leaching rate of gold will not be reduced.
The control of the concentration of sodium cyanide in leaching operation depends on the types of minerals associated with gold, the kinds and contents of harmful impurities in leaching solution, the aeration stirring intensity of leaching equipment, the return of lean solution and so on. The general rule is that the concentration of sodium cyanide controlled by the cyanide leaching operation in the row ore cyanidation is lower than that in the flotation concentrate cyanidation; the harmful impurities in the cyanide ore are higher than those in the minor ones; the percolation of cyanide is higher than that of the stirring cyanide; and the return of the lean solution is large, the higher the concentration of sodium cyanide.
The following principles should be followed in controlling the concentration of sodium cyanide in leaching operation: under the premise of ensuring the dissolution efficiency of gold, the concentration of sodium cyanide should be reduced appropriately, so that the concentration of sodium cyanide in each series leaching trough is the same, or the concentration of sodium cyanide in the front is higher than that in the later one; The smaller the fluctuation range of sodium cyanide concentration is, the better it is to control the concentration fluctuation of sodium cyanide in each leaching tank, and it is better to add cyanide in multiple channels. The shorter the time interval for the determination of sodium cyanide concentration, the better. (generally two hours to detect the sodium cyanide concentration in each tank), this will be conducive to the addition of sodium cyanide according to the concentration of sodium cyanide in a timely and appropriate amount. Sodium cyanide is usually mixed with about 10% of the concentration, transported from the pipeline to each leaching slot.
2、Strictly controlling the pH value of slurry
Lime milk is generally used to adjust pH value in production, and it is added to grinding circuit. The advantages of this are: adjust pH value, carry out alkali leaching, and it is very beneficial to preprepreg concentration (accelerate slurry sedimentation). Normally, the lime milk addition points in the leaching system are replenished only. When the pH value is lower than 10, the HCN gas will be released in the solution, while the pH value is higher than 11. The cyanide will interact with the sulfide in the pulp and increase its consumption. Therefore, the pH value of leachate must also be measured regularly(generally, the concentration of calcium oxide in each tank should be measured once in two hours), and adjusted in time to ensure that the pH value of leaching solution is between 10 ~ 10.5. The traditional method is to determine the content of CaO by titration. Now the pH value can be measured directly by pH meter. It is best to use pH automatic control loop to control the amount of lime milk in conditional factories and mines.
3、Strictly controlling of pulp concentration and aeration effect
As mentioned earlier, pulp concentration and oxygen content in leachate are two important factors affecting gold dissolution rate, so they must be strictly controlled. The control of concentration is to control the concentration of ore drawing by thickener before leaching. The suitable concentration of leaching pulp for cyanidation of row ore is 40%~45%, and the suitable concentration of leaching pulp for cyanidation of flotation gold concentrate is 30%~35%.In particular, the concentration of leaching pulp must be controlled well in CIL plant. Too low concentration of pulp (less than 40%) will cause activated carbon in leaching slot to sink to the bottom of trough, and too high concentration of pulp (higher than 45%) will make activated carbon float to the surface of pulp in leaching slot, which is not conducive to adsorption operation. The air pipe inserted into the slurry is easy to be blocked by the slurry, so the operator should observe the air distribution of each tank once an hour ,so that to find if air pipe was blocked and use high pressure wind or other methods to transmit the pipe to ensure that the air filled in each tank is even.
4、In order to prevent the immersion tank from "sitting dead", the time for stopping the operation of the tank can not be too long.If the blackout time is longer, it is necessary to start the backup generator to supply the dip slot and fan to ensure the slurry stirring and aeration.
5、In order to ensure the normal operation of leaching and washing operation, the pulp should be drawn evenly and continuously, and the pulp quantity should not exceed the normal production discharge.
