Froth Flotation (Sulphide & Oxide)

Froth Flotation (Sulphide & Oxide)2017-04-04T06:57:31-04:00
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Flotation froth height test (3 replies and 3 comments)

Pabloski
3 years ago
Pabloski 3 years ago

Hi peps! Is there anybody here that has done froath height tests to give me an idea to do one at the lab?

At the moment I have a 4L transparent flotation cell available, so I was thinking of floating at different pulp heights, at differents stirring rates as well.

My main objective is to analyse the concentrate granulometry and see if different heights float different particles sizes. I could add air flow as a variable, but  for the moment height is my main target.

Any comment wil be very much appreciated, thanks.

Frank
3 years ago
Frank 3 years ago
1 like by David

I believe we discussed this topic in another forum about the concept of froth equilibrium height.  The idea of testing at different froth heights is a good one.  What we recommend in plants that have good control of the pulp level is to actually measure the grade at various heights and establishing a grade gradient versus height 0 froth height up to the FEH.  Just lower the pulp level in increments and take sample of the overflow and analyse them for grade.  You could also analyse them for particle size as well.  What you would expect is that the higher the froth height, the more coarse you would lose and the higher the grade.  The problem is that the pulp level is very hard to control in a float test unless you have a special cell that will do this.  But the concept is the same.  Establish a set of conditions like frother dosage and type, air rate and measure the FEH.  Then do flotation tests using various froth heights.  4 should do.  Just make sure that you use initial conditions that can give you a good high FEH.  This will allow you better control of each test.  If the conditions give you too low a FEH, you cannot get the precision you need.  Also make sure you perform the tests all the way to the just below the FEH because you will find that the biggest changes come when you are about 25% from the FEH.  Good luck.

Pabloski
3 years ago

That´s exactly what I had in mind. About the FEH, I didn´t get why a higher value will give me better control of the test? is it because in that way I can perform decrements starting from the FEH and lower the height from there?

I was thinking to set my FEH at standard conditions (plant conditions) and modify form there, but anyways, I will keep an eye on the FEH obtained and make sure is high enough.

Thanks for the inputs!

Aminpro
3 years ago
Aminpro 3 years ago
1 like by David

There are a few other considerations you need to look at when you are looking at froth height vs concentrate grade and screen analysis. Frank gave you some the measurement of grade gradient which would be applicable for continuous reactor. For the lab, you can do the same test but need to refresh the feed after level sampling. In all, there are other considerations:

Getting a correct level. When we (At Aminpro) want very accurate level control in the lab, we have a unique setup consisting of a water reservoir located above the cell that receives water from a main stock tank placed on the floor. The reservoir has two outlets at the same elevation: one connected to the bottom of the flotation cell and one to overflow to a water stock tank. If we ensure that the water pumped from the main stock tank to the reservoir keeps water flowing back to the stock tank, the loops is then automated. The reservoir is attached to a manual gear level positioner such that we can set its level at a desired position. As the density of the pulp is higher than that of water, the reservoir o/f pipes will always be higher than the cell. The difference can be calculated in your spare time. Then you need to adjust for air holdup…another gem to account for (hint: check the level with air and without air and estimate air holdup).

Changes in Froth Recovery (Fr): when you change the froth bed height, you are indeed changing the froth recovery and therefore the overall cell recovery from the following, where Rflot is the flotation recovery and Rc is the lab collection zone recovery Rc = (1 – exp(-kt)). Rmax. You can determine froth recovery by doing a few froth bed heights and extrapolating to zero height.

Entrainment Recovery of solids (Re): various degrees of entrainment (D.E. = Re/Rw) come into play when you change the froth bed. For one you tend to entrain more water (higher water recovery (Rw) when the bed is shallow, and with it more solids. The changes in the degree of entrainment (D.E.) are huge and well defined for industrial processes when you change air and froth depth. It closes the calculation of total cell recovery with the following expression:

Now you have the full picture….but yes, leave items 2 and 3 out and follow Frank’s notes.

Roger Amelunxen

911Met-Pabloski.pdf

 

Pabloski
3 years ago

Aminpro, first of all, many thanks for your inputs.

I really like the set up you made for level control, but I have a question... so you only control pulp level adding water? it is not better in this case to use fresh pulp? Just asking , because I think water will change solids% and probably increase entrainment and affecting the flotation... the your experience says?

Thanks

Pabloski
3 years ago

What your experience says?

David
3 years ago
David 3 years ago

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