I am running Cu-Zn sulphide flotation testing in a 2 L cell. Prior to this, I am grinding in a ball mill to a P80 of about 44 microns. So very fine grind of 30 minutes, at 60% solids. I add 1 kg of solids, 667 mL of water, and some lime to keep the pH high. After that I transfer the pulp right into the cell. The problem I am having is when I wash down the mill and balls. Due to the fine grind size, particles settle very quickly, and it is very hard to collect all of the solids while keeping the volume of water used at a minimum. The problem with using too much water is that I need to wait to decant the water before starting the flotation test which is not ideal as the sulphide ore can become activated and Zn will float in the Cu flotation circuit, impacting selectivity. So is it possible to keep the volume of wash water used to about 400 mL? At present I am using about a liter, which is more than double what the minimum wash water should be for this size test. What is the standard test method for grinding prior to flotation testing?
Normally, the particle size for flotation is between 20 and 150 um. Firstly, you need to know you target particle size range. Then, you need to identify properties of your sample, whether it's "hard" or "soft" material. Normally, for grinding, if you think the particles are too fine, then you need to reduce the grinding time, or reduce the number of balls you used. In my opinion, 30 minutes are too long. For me, when I do grinding, I firstly set a few minutes, and then have a look at samples to view the particle size range using our eyes, then make decisions on whether to grind more time or less time. If you can't identify the particle size range using your eyes, then you need to collect sample and do sieving.
Grinding is not a process that you can do successfully for the first time, you need to try and different materials have different grinding strategies, you can't just follow other people's work, you need to find your own way.
Hope this helps.
Dear Patrick Rankin . See the following useful RG link: Article Effects of water content on ball milling pretreatment and th...
Kindly see also the following useful links: http://www.journalssystem.com/ppmp/pdf-83724-26275?filename=Influences%20of%20operating.pdf
https://www.google.com/amp/s/www.azom.com/amp/article.aspx%3FArticleID%3D14340
https://www.sciencedirect.com/topics/engineering/ball-mills
Also check please the following useful links: https://www.sciencedirect.com/topics/chemistry/ball-mill
https://www.sciencedirect.com/topics/engineering/ball-mills
https://core.ac.uk/download/pdf/39664166.pdf
The following RG link is also very useful: https://www.sciencedirect.com/topics/engineering/grinding-medium
Lisha Dong the grind time is 30 minutes to get to the P80 of 40 microns. I tested this using a particle size analyzer and by doing sieving/cyclosizer analysis. The problem I am having is using too much water to wash the balls of after milling.
Hi,
If I understand you correctly, you want solids removal and loss reduction, not theoretical advice, correct?
I don't know the size and number (weight) of the balls. If there are many small ones (max. diameter ~1,8 cm), you can use a simple pasta filter for the ball removal, though eventually, you can remove the balls portionwise. For 2-4 cm balls, you may need to get your hands dirty (gloves, of course). You can even find a sturdy pasta filter for this case.
There are two options.
1. There is some way to remove the balls easily.
In this case, remove most of the solids (possibly into the container/bottle/flask you will put the washing slurry in). Add a portion of your planned amount of water (1/6-1/4) to the jar&balls, then cover the jar and mill it briefly for 0.5-2 minutes. Sieve/filter the sludge. Repeat the procedure. In my experience, except for very sticky solids, recovery of solid is around 95-98%.
2. If the balls cannot be easily removable, i.e., they may need to be removed by hand (with gloves on!). This case is, unfortunately, less clean.
a) The best solution is to have two jars, not necessarily of the same volume, but the balls should also move freely in the second jar. Transfer the balls to the second jar. Remove as solid as you can from the milling jar, put back the balls, then use the same procedure as in the first case. Probably, you need to use fewer water portions in the washing procedures. After a short grinding, transfer the balls to the second jar and remove the sludge from the first jar. Place the second wash load in the original vessel, suspend the solids, and pour this suspension onto the balls in the second vessel. Grind again for 0,5-2 minutes, then repeat the transfer of balls and washing of the jar in reverse. Repeat the procedures until all the washing water is over.
b) If you do not have a second milling jar, you can use a temporary vessel for the "dirty" balls. After washing, remove the balls, remove the suspension, replace the balls and repeat the washing procedure. In this case, you should reserve a small amount of water to rinse the temporary ball reservoir.
The yield of this second option is usually worse than the first, but with a bit of skill, it can be as high as 95-96%.
Since the jar size implies that you do not want to perform nanogram experiments, the missing few percent of solids will not significantly affect your flotation experiments, either in terms of weight or particle size.
Good luck,
Laszlo
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