The fine ore in the ore is extremely detrimental to heap leaching. When the pile is piled up, the grain size will be deflected. When the infiltration is carried out, the powder ore moves with the liquid flow, which is easy to cause channeling, so that the leaching agent cannot uniformly percolate the heap. When the ore in the ore contains high eggs, the cyanide solution cannot be infiltrated into the heap, making the heap leaching impossible.
In order to carry out heap leaching on fine ore and cat soil, in 1978 the US Bureau of Mines developed a powder ore granulation heap leaching technology to promote the development of powder ore and cat soil heap leaching technology. At present, the technology is widely used in gold mines in other countries in the world, in addition to being widely used in the United States.
Granulation When the heap leaching of low-grade gold ore previously crushed to a fine 25mm or less, the gold silver minerals fully dissociated exposed ore crushed to 2.3 -4.5kg / t of dry ore Portland cement (ordinary silicon After mixing the acid salt cement, the mixture is wetted with water or a concentrated cyanide solution to make the water content 8% to 16%. The wetted mixture is mechanically tumbling to form a spherical pellet. After curing for more than 8 hours, it can be sent to the pile for leaching and leaching. The method of pile up and seepage is the same as the conventional heap leaching method.
A large-scale comparative test was carried out using lime or cement as a cating agent. Tests show that cement is superior to lime. Adding 2.3-4.5 k t of cement as a cating agent can produce relatively stable agglomerates with high porosity and good permeability. When leaching, the ore does not move, no channeling occurs, and leaching There is no need to add a protective base.
At present, there are two kinds of granulation methods used in production, namely, a multi-belt conveyor method and a drum granulation method. The multi-belt transport mechanism granule method is that the material is uniformly mixed with the concentrated solution, the powder ore and the cement through the mixing rod of the discharge end of each belt conveyor to make the agglomerates of the fast. The drum granulation method is to feed the ore and powder ore mixture into a rotating drum, and spray it in the drum.
The cyanide solution wets the mix to a water content of 8% to 16%. The wetted mixture is mechanically tumbling to form a spherical pellet. After curing for more than 8 hours, it can be sent to the pile for leaching and leaching. The method of pile up and seepage is the same as the conventional heap leaching method.
Production practice has proved that the granulation and solidification of fine ore by ordinary Portland cement, water or concentrated solution can significantly increase the flow rate of the proposed reagent through the heap. Compared with conventional heap leaching, granulation heap leaching has the following significant advantages:
(1) It can handle fine-grained gold ore with low-grade fine-grained gold ore and high-grade fine-grained gold ore;
(2) The fine-grained gold ore is directly granulated and heaped without classification, which eliminates the particle size segregation during the pile-up, which can greatly reduce the channeling phenomenon during the flooding, so that the leaching agent can uniformly pass through the entire heap, thereby significantly shortening the leaching. Cycle and can greatly increase the leaching rate of gold;
(3) The porosity of the agglomerates leads to good ventilation performance of the entire heap, which can increase the concentration of dissolved oxygen in the solution and accelerate the dissolution of gold;
(4) The agglomerates improve the permeability of the heap, and can appropriately increase the height of the heap, reduce the cost of pretreatment liners per unit ore and reduce the floor space;
(5) Porosity allows the residual cyanide leachate to be eluted more thoroughly after the end of the leaching.
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