Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

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Gold heap leaching plant - Pregnant and pond water polluted and unwanted precipitation issue (7 replies)

A
Anudari
1 month ago
Anudari 1 month ago

Hello all,

I am working as a metallurgist first time after graduation in Gold processing company. But I have learned that this processing plant has many issues that needs to be solved immediately. Because the plant does not have waste pond or something, they are pouring all the useful and useless solutions that are coming from the plant into the barren pond. That is why both barren and pregnant pond was polluted to the point of precipitation. I do not if this is normal or not but even the heap leaching was polluted with black substances. I have learned that they cleaned barren pond three months ago and the barren pond is relatively cleaner than before. But now in the pregnant pond there is white precipitation which turned into shell like thing which is hard but brittle. I suspect that this is CaO or NaOH which reacted with other chemicals. Does anybody know any solution to this problem? If you know it will help me tons so give me your advice. Many thanks

J
Jorge
1 month ago
Jorge 1 month ago
1 like by Anudari

The process ponds are located on favorable site conditions and proximity to the design location for the heap leach pad. Three separate ponds comprise the process ponds, namely: the pregnant solution pond, the intermediate solution pond and the storm water pond. Two sedimentation ponds are included to prevent sediments from entering the process ponds; one for the pregnant solution pond and another for the intermediate solution pond.

The pregnant solution that percolates through the leach pad is collected in a pregnant pond where floating vertical pumps are installed. The typical design considers one pond which is called pregnant pond and collect high grade solution and the other one is an intermediate pond and receive low grade solution. All the process ponds are interconnected with spillways with the storm water pond to alleviate any overflow occurring in the pregnant solution pond and/or intermediate solution pond.

The unclarified pregnant solution is pumped to the clarifiers installed in the Merrill-Crowe Plant. Fine particles of lime or clays are usually reported in the pregnant solution. Clarifiers are three leaf pressure filters, two operating and one in standby. The clarified solution is deareated and continues the process in the Merrill-Crowe Plant.

A
Anudari
2 weeks ago
Anudari 2 weeks ago

Dear Jorge,

 

Thank you for your reply, I suspect that this participation is mainly CaCO3 and its fouling our carbonated coal. Our plant has CIC columns and coals in it become huge rocks because of the white substances. Tried to acid wash that big rock like thing but it was useless. Any suggestions?

J
Jorge
2 weeks ago
Jorge 2 weeks ago
2 likes by Anudari and David

Lime or calcium carbonate can contaminate activated carbon. The problem is the presence of big particles of lime or any material. I think, you need sediment ponds in other to a get a good pregnant solution. Other alternative is to install a screen to separate the coarse material that feeds the CIC circuit. You should review the reactivation process. and acid washing. In some cases, acid washing is performed before reactication of carbon.

 

A
Anudari
2 weeks ago
Anudari 2 weeks ago

Dear Jorge,

Thank you your advice again. This plant would operate only one more year then shift into flotation processing plant. Thus we are unable to build sediment pond and also install high level of screen. But I would definitely review the reactivation process and acid washing. I have given carbon which came after acid washing to the lab and there was about 1.14% of Ca in the coal. I was wondering about how many ppm of Ca should be in the solution so that carbon adsorption would go effectively while the Ca would not scale our activated carbon? Our Au amount is around 1.5ppm. So does Ca should be equal or less than Au concentration? Ca is also stabilizing the ph of the solution so I am confused here. I have attached the picture of the activated carbon which become hard lock like thing. I have tried to dissolve it with high concentrated HCl but it was not doing the work. Pic: Those are the just small ones big ones are almost size of a sheep.

A
Anudari
2 weeks ago
Anudari 2 weeks ago

Can you see the attached pictures now?

Carbon2
https://www.911metallurgist.com/wp-content/uploads/2022/09/Carbon2.jpg
Carbon1
https://www.911metallurgist.com/wp-content/uploads/2022/09/Carbon1.jpg
A
Anudari
2 weeks ago
Anudari 2 weeks ago

Or do you have any good recommendations for paper or book to read?

J
Jorge
2 weeks ago
Jorge 2 weeks ago
1 like by David

Activated Carbon loading capacity is influenced by the gold content in the PLS. The loading capacity can be as high as 15 to 20 kg/t. Fouling has an impact on the loading value to a significant extent. If the calcium content is high and the gold content reported in the PLS is low, the gold adsorbed in the carbon will be low.

 A screen should be installed in the column, try to review the opening, perhaps it is possible to reduce it. Try to evaluate if you can install a filter in the pumping system to separate the calcium and other coarse materials.

I think, you should use HCL to wash the carbon. Try to increase the strength. It is necessary to remove the fine carbon. If you don't do it, try to evaluate it.


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