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In this post you're going to see four factors influence gold heap leaching process.
This guide includes:
The influence of ore characteristics
The influence of leaching solution
The influence of spraying
The influence of the heap
So if you want to learn about factors influence gold heap leaching process, you'll love this post.
Let's dive right in!
Heap leaching method means to stack the gold raw after crushed to a certain size on the leakproof bottom pad that is made up of asphalt, concrete, plastic and other materials, spray the cyanide solution from the top to dissolve the gold. Heap leaching method has the advantages of short flow, low cost, easy to operate and quick effect, so it has been widely used in gold ore processing industry. However, the heap leaching method is affected by many factors, if not handled them properly, it will easily lead to production substandard, process accidents and other problems, thus affecting the efficiency of the plant.
Below, we will briefly describe the influencing factors of heap leaching method from the ore, leaching solution,spraying and heap leaching four aspects:
There are often other kinds of mineral components in the gold ore, such as iron ore, lead ore, antimony ore and so on.Among them, the metal group will have a certain effect on the cyanide leaching,like slowing down or accelerating the dissolution of gold.
If there is carbonaceous matter in the gold mine, it will affect the ore particles wrapped in carbon material to react with the cyanide solution, thus preventing the dissolution of gold.
Moreover, the activated carbon in the ore will adsorb the dissolved gold, thus reducing the gold leaching rate and recovery rate, which has a serious impact on the gold processing.
In order to reduce and eliminate the harmful effects of other mineral components on gold processing by heap leaching method, the saturated alkaline solution should fully spray the ore heap before cyanide leaching, so as to precipitate and decompose other harmful mineral components and keep the PH value of the solution discharged from the ore heap above 9.54, and discard the ore washing water.
At this point, heap leaching method can be used to extract the gold.
Generally, the smaller the ore size, the shorter the leaching time and the higher the leaching rate. In practice, the ore particles that have been crushed to 5~20 mm are sent to heap leached. If the content of ore fines -200 mesh exceeds 35%, the conventional heap leaching method will cause the surface of the ore heap to form a groove flow, thus reducing the leaching rate of gold.
Using a low concentration of cyanide solution, like the cyanide solution concentration is below 0.05%, the dissolution rate of gold is fast. Using the high concentration of cyanide solution, like cyanide solution is above 0.15%, the dissolution rate of gold is slow.
Therefore, it is appropriate to control the concentration of cyanide solution between 0.025% and 0.1% according to the ore composition and different leaching stages.
The dissolution rate of gold is proportional to the concentration of oxygen in the solution, and the decrease of the oxygen concentration will lead to the dissolution velocity of gold decrease.
Therefore, it is necessary to ventilate the leach solution to ensure the sufficient oxygen at any time.
When the spraying intensity is high, the relative movement between solution and ore is strengthened, which strengthens the diffusion and improves the leaching rate. But the spray intensity should not be too large, otherwise the impurities in the mineral will be leached, thus reducing the gold content in the leaching solution.
Generally, the spray intensity is controlled between 0.05~ 0.1 L /t per minute.
The ore heap has a good permeability, and the gold-containing solution can be discharged through the ore heap in time which accelerates the leaching reaction, shortens the cycle and improves the leaching rate.
Both the size of leached ore and the content of clay in ore will affect the permeability of ore pile.
The ore with good permeability can be piled higher. For the ore with poor permeability, the height of ore heap should not be too high, otherwise the permeability of ore heap will be reduced and the leaching time will be prolonged.
Generally speaking, it is advisable to keep the height of ore pile at 3~10 meters. The height of the ore pile can be determined by mineral processing test.
Although the heap leaching process is featured with short flow and quick returns, it is affected by many factors in the gold processing.In order to ensure the smooth progress of gold processing, various influencing factors must be considered comprehensively and effective measures should betaken to analyze, study and control the process of heap leaching.