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Back Pressure Vs Gforce. - (4 replies and 5 comments)
Good Day,
There is no "correct" pressure for the backpressure setting because it varies with operational conditions. If you are losing gold in the tails it could be several things:
- Your cycle is too long between cleanouts clogging riffles and leading to high tails
- You are exceeding the recommended flowrate for the unit and forcing material into the tailings
- Your backpressure is too high
Items 1 and 2 being taken care of - the simplest way to address this is to lower your backpressure 5-10% incrementally and check your tails and your conc grades as you go. What is your current backpressure set at?
Regards
Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com
Todd
We have tried cleaning the bowl out hourly, 2 hourly, 6 hourly and 8 hourly. Doesn't seem to make a difference. Catching fine gold in the tails even after 30 minutes. We have also been cleaning and testing individual rings and finding most of the course gold in the bottom 2 rings and very fine gold in the top. Something doesn't add up there. G's may need to be lifted????? Flow rate of concentrate into the bowl is about 2 ton/hr plus water which is way under what this machine can handle. Has a cyclone and we have the flow rate so the cyclone is just by washing. Not a lot of magnetite in the sample as we have a mag separator before the jig. Material size through the jig to the concentrator is 2mm and under. Back pressure has been running between 3 - 4 psi. We have tried it from nothing to max which is about 12 psi.
2 Nugget traps before the jig cells and are working brilliantly. They are catching 95% over 2mm plus a lot of very fine gold. Ratio between nugget trap and concentrator is 5:1 at this stage. Grades at the moment 0.3g/t but we think we are losing 0.2g/t at least from what is showing up in the tails.
David
Gidday
You've gone through what I would be looking at fairly comprehensively, so a left handed thing might be, have a look at your "fine gold" that is in the top rings under a microscope, just to check that it is gold, it may be a corroded pyrite or mica.
Best of luck
Andrew J
AJ
Thanks for the comment. Its deafinitely gold. We have put the tails back through the plant a couple of times and caught some of the stuff that got away the first time. Something is not quite right but we are working on it. Next step is to up the G's. At 50hz we can pull 80 G's on the top ring. Will give that a go soon. We have also added 2 inline filters with 100 mic screens to the pressure line of the concentrator. This has balance the pressure nicely so hopefully that will also make a difference also. Plant can do 40t/h so at 400 ton a day, we are losing way too much. Very frustrating.
Your concentrator is unusual. Most popular is the Knelson or similar. A Falcon will recover finer gold but all have difficulty recovering gold below 200um. You would be better off to install a tails scavenging circuit eg tails leach or flotation. I have done work on this and can advise if you are serious. Cheers
Thanks Rob. At this stage we will give our Modifications a go first. Don't want to go near any sort of chemical use at this stage. This concentrator was designed by an Aussie and made in Malaysia by GREAT who make pretty good gold wash plants. It is based on the Knelson but has unique ripples inside the rings and we are assured it will catch gold down to 30um. There are a number in the world at the moment working. We are getting some this size but for some reason our setup is wrong and we are missing a lot between 500 - 30um. I note you are in Perth. We are in Qld. David
I would be amazed if your concentrator can recover gold at 30um with a good recovery as the grains this small don't have the mass to be recovered by gravity. Scavenging flotation sounds like the the answer. Where is the operation?
I worked near Charters Towers for a while.
Rather than monitoring the back pressure you are better off "crash stopping" the machine and doing a "touch test" on the concentrate rings. Basically you shut off the water supply and after 5-10 seconds stop the machine. If the concentrate is hard packed in the rings your pressure (or flow) is too low, whereas if their isn't much material being retained or its slumping out your pressure is too high.
In general, as you increase the g-force you will need more water to counteract and keep the riffles fluidized. Have you done a GRG test to determine how much of your gold is actually recoverable with a lab centrifuge?
I've never heard of this manufacturer but there is a reason that Falcon and Knelson dominate this market.. if they promised you they could recover all of the gold down to 30 microns they were lying.
" Pretty much the same as the big Knelson"
PS: The only thing that is "pretty much the same as the big Knelson" is a Falcon & The only thing that is "pretty much the same as the big Falcon" is a Knelson
Knockoffs are knockoffs. The scrap graveyards are full of them.
Does anyone know what the right back pressure settings should be relating to a G700M Great concentrator. Pretty much the same as the big Knelson. We are losing fine gold in the tails still. Can't find anyone who know much about concentrators in general in Australia. G's are around 60 on the top ring.