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Flotation of valuable minerals locked with Fe sulphide (7 replies)

9 months ago
Standartenfurer 9 months ago

Does anyone have an idea of how to float valuable minerals (Ni) locked with Fe sulphide. Recent tests have shown that liberated well sized Fe particles as well as Ni sulphide particles locked with Fe sulphide report to the tails. The question is why is well sized liberated Fe sulphides and valuable minerals locked to Fe sulphides do not report to the concentrates?

Paul Morrow
9 months ago
Paul Morrow 9 months ago

We need additional details re extent of locking, e.g.

•Particle size for the locked and liberated particles

•Grain size of the Ni locked in Fe particles

•Volumetric composition of locked particlesetc.

Marshal Meru
9 months ago
Marshal Meru 9 months ago

Additionally to the details requested by you, kindly provide the reagents suite, collectors, frother and activator if it is used and the dosage rate and your actual flotation recovery.

9 months ago
Oberfuhrer 9 months ago

Iron sulphides usually behave in the opposite fashion of what is desired of them.

The most common situation is that they are too easily recovered to the flotation concentrate and some strong chemistry is needed to be effectively depressing them to obtain a quality concentrate.

You are not providing sufficient details to be able to provide valuable suggestions. Are you dealing with marcasite, pyrite, hexagonal pyrrhotite, monoclinic pyrrhotite, other? There are no single set of conditions resulting in enhancing recovery by flotation for all of them.

One suggestion - it would be valuable to examine if the recovery of all the iron sulphides, and subsequent reprocessing to selectively recover the locked nickel minerals, is economically viable (value of nickel minerals greater than cost of recovery and reprocessing of iron sulphides).

Alan Carter
9 months ago
Alan Carter 9 months ago

You can always try a finer grind to liberate more Ni from the Fe in the ore but too fine can cause obvious problems.

An idea of the ores you're treating would be handy. Are you dealing with Pentlandite, Violorite or other Ni/Fe complexes or Fe minerals like Pyrite and Pyrrhotite? Reagents used would also help.

If it's smelter related? Issues and you want to 'reduce' the Fe/MgO ratio? You can always try to reject less MgO. I know that sounds counter productive but it's something we've been doing for a while rather than reducing our recoveries by, for example, reducing our activator usage. We find our Ni is locked to our Fe and it's hard to get one and not the other

My apologies for the above comment. I read your question and thought you were worried you were recovering too much Iron in your concentrate stream. It sounds like you're concerned with too much valuable mineral in your tailings streams which is the bane of all mine sites.

Questions stated a couple of times above still ring true though. What ores and reagents are you using and what are the reagents dosages?

Carl Jenkins
9 months ago
Carl Jenkins 9 months ago

As suggested earlier mineralogy is important. If you are dealing with pentlandite and pyrrhotite, then it is understandable, although these minerals do have rather similar flotation properties. We also need to have a better understanding of the processing flow sheet - milling environment, reagent additions, flotation time etc. to make more informed comments.

The impression is that you want to recover all of the sulphides, so you should be looking at a bulk float to recover the sulphides as composites rather than attempting full liberation.

These minerals oxidise readily, in this case, the pyrrhotite seems to be very sensitive. If this is the mineral system in your ore, then you need to understand how these minerals are formed i.e. pentlanditeexsolves at around 675 C thereafter forms, as the Ni-Fe sulphide melt cools, as lamellae intergrowths (often down to a few microns) and with nickel remaining in the pyrrhotite. So your nickel losses may be associated with lamellae intergrowths. Nonetheless, since it appears that you want to float all of the sulphides, it would seem that you have an overly oxidising flotation environment, also affected by other factors such as pH (iron oxy-hydroxide coatings), the nature of the pH regulator (calcium ions are not good for nickel flotation) plus the milling environment (mill steel balls?).

In addition, the reactivity of the pyrhhotite depends on the amount of iron deficiency - whether monoclinic or hexagonal. If you have the former, it would have magnetic properties and magnetic recovery of nickel-iron sulphide composites would be a better process option followed regrinding and flotation to separate the coarser pentlanditeparticles.

Should read mild steel balls - very reducing and produces lots of ferrous hydroxides which when oxidised to ferric, precipitate readily onto sulphide mineral surfaces.

9 months ago
Oberfuhrer 9 months ago

I would like to add to comment about bulk sulphide flotation:

Technical: once pyrrhotite has been purposely rendered hydrophobic for recovery by flotation, it then becomes quite difficult to depress it and keep it away from the final concentrate(s).

Economical: one should examine the Capex and Opex of a bulk sulphide flotation approach for the additional values recovered. With bulk flotation, the rougher-scavenger and concentrate regrind circuits will be much larger and cost more to operate. The additional equipment and reagents to then depress the pyrrhotite after the concentrate regrind would add to the costs as well. Unless the additional values recovered to concentrate(s) not only pay for these additional costs but also generate a profit, then bulk flotation would not be a viable approach.

Rahil Khan
9 months ago
Rahil Khan 9 months ago

Ni-Fe: Mineralogy. It shows that Pyrite is interlocked with Ni. PYRITE flotation chemistry is different.

Now if we target to float pyrite to avoid losses we need to follow operating parameters of PYRITE flotation. pH-Low --Acidic, Collector --Sodium IsoPropileXanthate, Frother: MIBC 

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