Several technical points in heap leaching

Granulation: the amount of lime must reach a pH between 9.5 and 10.5. After testing, it is determined that a certain alkalinity can be achieved. A pellet can be made with a beaker plus 1000 g of mineral + lime 2 g, 4 g, 6 g + water, then Water was just immersed in the surface of the mine. After 24 hours, the pH was tested to 9.5 to 10.5. The cement is determined according to the pellets produced in the water after 24 hours in the water. The amount of sodium cyanide, because the ore itself has a moisture content of more than 10%, and the ore contains more impurities, so the concentration of sodium cyanide should be increased during granulation, and it is about 60-150 grams per ton of ore. The sodium concentration is between 0.1% and 0.5%. The concentration and concentration of sodium cyanide can be appropriately converted to determine the concentration of sodium cyanide granules, and the pH is about 11.5. The water content of the pellet is 15%-20%, and the water content of the ore itself is about 10%. The total water content is generally not more than 30%. Otherwise, the pellet is easy to disperse and soft, and the curing time is over 72 hours. If it is granulated, it will be encountered. When it rains, it is necessary to cover the ore particles to avoid gold loss, or use the side to pile and spray, because the gold is easy to leaching after granulation.

On the pile: Because the car is crushed back and forth on the heap, it is easy to compact and crush the ore. Once the heat is pressed into a large cake, it is best to use the conveyor belt on the condition. The height of the heap is currently too high, preferably 3 to 4 meters, and the leaching rate is stable and then increased.

Spray: Any pellets that have been granulated must not be washed again and the pH value should be adjusted by washing. The pH should be adjusted during granulation. Pre-spraying ore washing is absolutely impossible. After washing, mud will form and form a block. After the mud is muddy, it will be equal to no granulation. The consequences will be serious. The sodium cyanide solution cannot penetrate down during spraying, and it is easy to surface area liquid.

Sodium cyanide concentration during spraying: Due to the complexity of the ore and the cold weather, the sodium cyanide concentration during the initial spraying can be appropriately increased, which can be controlled from 0.1% to 0.08%, and the peak period is the highest (ie, the leaching gold concentration is highest). After the time), it can be reduced to 0.08% to 0.06%, and can be reduced to 0.04% to 0.02% in the later stage. The gold concentration of the precious liquid can be mastered at any time to adjust the sodium cyanide concentration.

Spraying cycle: spraying time is generally 7-8 hours a day, the maximum can not exceed 10 hours (but the amount should be reduced), generally master spray 1 stop 1 or spray 1 stop 2, during the day due to high temperature and easy to leaching, you can spray 1 stop 1, In the evening, due to the cold weather, you can spray for 30 minutes, stop for 1 hour or spray 1 stop for 2 minutes, or do not spray at night. The spraying time should not be too long, so that the heap can absorb oxygen when it is not sprayed. If the spraying time is long, it will increase the volume of the solution, so the concentration of the precious liquid will be reduced and the sodium cyanide will be wasted. The volume of the noble liquid affects the adsorption capacity of the gold-loaded charcoal.

Spraying intensity: The spray intensity is related to the spray time and the amount of spray liquid. Generally, the spray intensity is 6~20L/m2.h (6~20L/m2×hour). It is more suitable. More than 25 ~ 30L / m2.h (can be calculated by the yard area, the amount of spray per day and time). If the spray intensity is large, the volume of the noble liquid increases, and the gold concentration is diluted, which affects the adsorption amount of activated carbon (the general adsorption amount of activated carbon is 8-10 kg/t). If the volume of the noble liquid is large, the same adsorption time is due to the low gold concentration. The adsorption amount is reduced, the adsorption time is prolonged, and the workload and cost of desorption electrolysis are also affected. At the same time, the capacity of the noble liquid pool is increased. The most important thing is to reduce the concentration of gold and prolong the spray time, so the spray amount cannot be too Large, the spray cycle can not be too much per day.

Leaching of gold concentration: Generally, according to the theoretical spray gold concentration, the gold grade of the precious liquid is 5 times or more of the original ore, that is, the original ore grade is 3g/t, and the highest precious gold grade according to the normal successful heap leaching should be 15g/m3, but in actual production, due to various conditions, it is less than 5 times, but at least 2 to 3 times, especially for granulation heap leaching, adding suitable sodium cyanide solution for granulation and suitable stacking (not Compacted ore), suitable spray amount, the gold grade of the precious liquid should reach the peak period between the first and third days, reaching 6g/m3 or more, and then gradually decreasing, so the spray time is not delayed. Long, reaching below 1g/m3 is nearing the end. If the concentration of gold does not reach the expected concentration or there is no obvious peak period, or the peak period is delayed and extended, the heap leaching failure, the leaching rate will not be too high, and the laboratory test indicators are not met. This is related to the spray strength or sodium cyanide concentration, pH value, etc., should be immediately checked and analyzed, otherwise it will prolong the leaching time and reduce the leaching rate, waste sodium cyanide, which is not good for the next adsorption of activated carbon, not only increase the amount of adsorbed carbon, The impurities are adsorbed on the carbon to reduce the amount of gold adsorbed and also increase the cost of electrolysis.

The difference between the gold leaching rate and the laboratory leaching rate: if the leaching rate of the general laboratory column immersion test is 70%, the on-site leaching rate should be 60-65%, because the laboratory is performing the column immersion simulation test under ideal conditions. But the scene can not be very different, otherwise you should find the reason.