Water Cyanidated Solutions

When mentioning the watering in conditions of much cold in winter, some alternatives have been proposed such as the heating of the solutions through the escapes of the diesel motors, protection against the wind, the use of ice as an insulator, protection for the waterers, underground tubing and watering by drops, the adding of salt to the lixiviant solution, etc. The aglomeration of thefines in the crushed mineral continues being the most important advance in this technology. From the first operations in heap leaching it was known that if one had a high percentage of fines, the heap leaching was impermeable and was necessary and advantageous to aglomerize or pelletize. One of the most recommendable methods is to perform the dry sifting to separate the thick from the thin.

Each fraction is sent to separated tolvas equipped with controllable feeders. On the other hand, the lime and/or cement must be stored in contiguous tolvas and must also be controllable, the same as the cyanidated solutions and/or water. The download of the aglomerator must be sifted again to remove and recirculate the fines. An interesting aspect, recently mentioned in literature, is the advantageous possibility of weakening the mineral before loading the heap leaching; treating the fines – 100# by agitation.

When mentioning the curing, in other words, the contact of the mineral with concentrated cyanide solution, followed by a period of resting, we can say that its efficiency depends in a large amount of the type of mineral. Its adavantage is the bettering of the cinetic, but it implies a higher consumption of reactives. It must be used solely with low granulometries.

In relation to the decontamination of residues and efluents, we can mention that normally the natural degradation of the cyanide in the heap leaching is pretty much complete and sufficient. Nevertheless, there are cases in which this does not occur. For example, a strong rain before it has had the necessary time for the natural degradation. For the destruction of the cyanide, there exists approximately 10 methods. The most important methods are: the use of oxigenated water, hypochlorite of sodium and the Inco process which uses SO2 + air, using copper as a cathalizer.