Crushing, Screening & Conveying

Crushing, Screening & Conveying

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Cost Efficient Crushing Trial for Heap Leach (5 replies and 1 comment)

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redcastle
4 years ago
redcastle 4 years ago

I have a small gold project that I am looking at conducting a heap leach trial of around 5,000 tons, I'm looking at the most cost effective way to do the crushing with regards to mobile plant hire as I think outright purchase is unsuitable at this stage. The ore is heavily weathered and very soft , but also has high clay content. Since it's a heap leach even if I lose a bit of optimal recovery it might be worthwhile if I can save much more on machine hire

The study work I have given to me for the project suggests a 160kw Jaw Crusher with a CSS of 80mm, a 150kw Cone Crusher with a CSS of 20mm and screen with an undersize setting of 20mm. All up the P100 is 20mm and P80 listed as 8mm, in the heap leach testwork it used a P100 of 12.5mm.

As that's 3 lots of plant, and 6 heavy haulage trips all up is there a way to perhaps get away with for example 1 Large Cone crusher with a grizzly feeder or don't worry about the screening plant? I was even looking at maybe an Impact Crusher like this which is available for hire.

it has built in screening, and might be more suitable. Also does anyone have ballpark figures on what one of those large tracked cone crushers costs to hire per day? Im in Australia so any figures would be good to get an idea of what I'm looking at.

J
Jorge
4 years ago
Jorge 4 years ago

I believe you should evaluate the effect of agglomeration on gold extraction. Usually, when the clay content is high, it is important to agglomerate the ore to avoid some problems such as channeling of solution flow. If you evaluated this point, now, you should prepare a cash flow to estimate your profit. 

Q
Master Q
4 years ago
Master Q 4 years ago

Heavily weathered and very soft ore with high clay content suggests using a cone crusher would be a poor decision. You can use a cone with high clay content but would risk packing unless you flushed the chamber while crushing. This has its issues and since you don't need a cone as the ore is weathered and very soft I would go for an impact crusher for the test. Unless the ore is particularly abrasive its the cheapest option. 

S
redcastle
4 years ago
redcastle 4 years ago

Sorry I forgot to mention I have agglomeration testwork and it needed fairly high values of cement for adequate percolation, I also forgot that cone crushers can have troubles with high clay content and I'm not sure this was factored in the test study. I think a single Impact crusher setup will be simpler, cheaper and the way to go.

T
Todd H
4 years ago
Todd H 4 years ago

It does not really matter what kind of crusher you use as long as the particle size is where you need it to be - for a small test anyway.  Rental equipment varies widely in price so it would be difficult to speculate but you are likely in the couple of thousand a day range plus mod/demob costs.

Since this is a test heap I would highly recommend agglomerating especially at the crush size you are looking at.  You will need to add cement and water to the material and find a way to agglomerate it - you can do this using the CV if you have enough transfer points.  Make sure you let the material cure a few days before leaching starts.  Google belt agglomeration.

Regards

 

Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com

(unknown)
4 years ago
(unknown) 4 years ago

The amount of clay in the raw ore has a significant effect on leaching. Studies have shown that when clay is wetted by a cyanide solution, its volume expands. Its volume increase rate reaches 25-30%. This will lead to a decrease in the porosity of the mine pile and the rate of solution penetration. When the clay content is increased from 15% to 60%, the penetration rate of the solution drops from 25cm/d to 0.4cm/d, and the leaching time increases from 15d to 125d. For ore with high clay content, the solution penetration rate changes with the change of leaching time. At the 10th day of leaching, the solution penetration rate reaches the maximum value of 6L/t ore·d. Later, due to the expansion of clay minerals, the porosity of the ore pile decreased, so the solution penetration rate was reduced to 3.5-4L/t ore·d. pH value During the leaching process, the cyanide solution must maintain a certain alkalinity to prevent the decomposition of cyanide. Therefore, the pH value should be controlled between 9.5-11. If it is too high, the dissolution rate of gold will be reduced accordingly.

Mike
4 years ago

All clays do not expand on wetting, so it is important to determine the type of clay involved. And those clays that do expand do it upon wetting, whether it is a cyanide solution or just regular water. The other problem can be that some clays disintegrate upon wetting causing a large amount of suspended ultra fine material (normal called slimes). These can coat surfaces and clog pores. Again the type of clay and the clay characteristics are important, not just clay.

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