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Fine Gold beneficiation issues (5 replies and 4 comments)
I am in Colombia. In the past I had the opportunity to work for KNELSON TECHNOLOGIES and I have had the opportunity to intervene in several mining operations for gold recovery.
In a very summarized way, I answer your concerns. I have to mention that my English is not very good.
I can offer professional services to solve your current problems.
1. Is it best to obtain professional GRG analysis to understand the nature of the ore that we are currently dealing with?
The GRG analysis is complementary to other required analyzes that support the base information to design the grinding circuit, volumetric classification, gravimetric concentration and leaching (if this is required). Preliminary tests such as the following should be included: Multielemental analysis: DRX, DFRXElectron microscopyGRG and GAT analysis Release analysis.Grinding tests Metallurgical runs
2. Are there labs in South America capable of providing GRG or similar service ( I have obtained a quote from one supplier, but the sample needs shipping to the US)?
In Colombia you have facilities to perform the tests mentioned above but I suggest driving some of them in Canada.
3. Are there any papers or any research regarding the suitability of hammer-mills (compared to other processes) for gold processing?
The processes of size reduction can be diverse and selecting one or the other depends on several factors. At this point it is important to note that this operation is usually carried out at an extreme grinding size (very thin), where in many cases it is not necessary. Again it is essential to characterize the mineral.
4. Are there service providers /suppliers who can help design improvements to our circuit once the ore is studied and analyzed?
Exist. This is my job from a professional point of view. I'm an engineer in mining and extractive metallurgy. My expertise focuses on extractive gold metallurgy.
5. Is there a logical or step by step process already formulated for this analysis?
It should provide a flow diagram of the process that is currently being developed in Brazil with a list of the equipment (with its technical characteristics) that intervene.
6. Is there anything logical or obvious I have omitted?
What kind of studies have you done? Mention the main results obtained
Thanks Jamie,
I like the comment on avoiding extreme grinding. We don't have recent results and as the ore has changed in nature, we will need to get new samples tested. There are two main types of ore, with one having more very fine gold.
Thanks for taking the time,
John S.
You have asked a lot of interesting questions that will take some time to consider, but one I can start off with. As to the use of hammer mills for fine crushing of the ore, I would have some issues of the mills causing a flattening of the particles which can cause loss of gold in gravity processes as the gold will not settle at the rate you expect. I would use the other crushing and grinding methods over hammer mills.
Dear Smart-Dog,
Thanks for your help, this is also my concern with the use of hammer mills, and perhaps we should get a sample of ore after the hammer mills and also after crushing using a jaw crusher and a cone crusher (which we also have set up) in the circuit.
Thanks for your help,
John S.
Hi John S,
I have designed, built and operated a similar style operation to yours. We also used hammer mills, centrifugal concentrators in Brazil (Para State) but eventually went to crushers, ball mills, flotation and a tails cyanide leach and achieved much better results.
I speak Portuguese so could be very useful to you in getting your plant set up correctly. There are plenty of good labs in Brazil.
Cheers,
Rob Riggir (rob.riggir@gmail.com)
Hi Rob,
Your experience sounds very similar to the one we are going through.
Thanks for your suggestions,
John S.
Hi John
It sounds like the orebody has a diverse characteristic as far as the gold grade and gold particle size is concerned. You need a single solution fits all approach.
Conventional crushing circuit followed by ball mill, flash flotation, gravity, cyclone, oversize to densification, leach, filtration, clarification and Merril Crowe. Flotation product may be ultra-reground and leached intensively,filtered and added to Merril Crowe feed.
I have purposefully omitted CIL and CIP. The leach requires higher than normal cyanide addition and agitation since I suspect that there are pockets of coarse grained gold particles.
Even in the best intentioned milling, gravity and flotation circuit these particles will foil and evade recovery.
Wish you well
Tony (tonyescorcio@gmail.com)
Thanks very much Tony,
It looks like you have extensive experience in this type of circuit. Thanks very much for your comments and suggestions,
Regards,
John S.
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We are a small company operating in Brazil mining quartz hosted gold from a Greenstone Belt.
I have recently started with the company, although I have been a long term follower and investor and I'm looking at all areas to try to understand the difficulties and problems and look for solutions.
...and we have had plenty of problems (and nearly closed the doors twice).
I understand that we may/will need professional assistance, but I'm looking for initial guidance to determine the best / most effective course of action.
When we started several years ago, we had a 70 kg sample analyzed by Gekko Australia, who recommended that around 90% of the ore was recoverable by only grinding down to a size of 1000 microns.
It turns out that this area of the mine was greatly overestimated for grade, and that the higher grade area of the mine (much higher -averaging from 20 g/t to 48 g/t), consisted largely of very fine gold.
It's not all fine gold, as we have also have coarse visible gold in many spectacular samples.
We have recently been using local hammer mills (the main mill being 15 tph capacity) in the last 6 months or so and we have had some spectacular bulk sample results, but this has not translated into long-term success.
I have a few main concerns/thoughts:
From these concerns, I have a few questions:
Thanks in advance for any advice received. I will try to attach some of the spectacular free gold from our deposit ...because everyone likes a pretty picture! 🙂
Regards,
John S.