I would suggest you can separate chromite by gravity in most circumstances spirals, elutriators etc. cheapest options flotation would require reagents which would drive up your plant opex.

I agree thanks, a bag was put on my desk and I was asked to float it but I think gravity would be best too. I’m not sure but I think there might be Pt in this sample and now I think they meant for me to get the Pt and not the chromite.

Yes, gravity separation is the way to go in case of chromite. If there are other valuable species, e.g. PGM-containing minerals, they can be floated first and then tails go to gravity separation.

Actually chromite flotation should be similar to magnetite/ hematite ore flotation. They use amines and a reverse flotation mode.

I'll probably try PGM float than gravity separation. I believe we have the reagents available here. The grain size are coarse, the particle size needed for liberation and disassociation of the chromite is approximately 300 microns. It looks like flotation is not the way to go with this sample we've had success doing the separation using gravity and its hardness, the fines being the serpentine gangue.

The bag given to me was a pulverized sample from our chemist so I had a new batch made up which I later grounded to P80=200 um. I will try coarser I the next run. 

Based on that my advice would be to avoid flotation whenever possible, spirals will do the job well; just make sure your water circuit removes all the fines so those aren't circulated back to spirals.

When this was given to me the first thing they asked me to do was float. But I definitely agree about doing gravity if we can. Thanks for the advice on the spiral; I will make the effort to control those fines. I currently don't have assay results but just by looking at it seems to be that the slimes is mostly serpentine. That being said I think our grind is finer than it should be. I will test at a coarser size.

I am jumping in late gravity separation is the way to go. If e.g. PGMs are present you can float the tailings. This is what I would say with the limited information given.

It’s more viable to go for gravity separation may be with coarse and fine separation spirals in stages depending on granulometric analysis. Later for PGM you may try for floatation.

If eventually you do flotation, it would probably be similar to the reverse flotation of iron ore. As far as I have it, there's not much on the flotation of chromite itself.

A few years ago we used a whizzer to separate chrysotile from our a low grade nickel serpentine ore "Air separation" it was efficient, it did work and did improve our flotation but saving money where we could was important. Using air separation meant that we would have to dry the sample; also the maintenance of the machine would have been costly. Both of these would have cost a lot as we were designing for 100000 tonnes per day. We tested a hydro cyclone and found that wet separation was much more effective. I would assume the same in this situation. The hardness of the chromite seems to be higher than the gangue so we can increase the chromite concentration using a hydro cyclone by removing the fines which also has the lower density. Or a spiral, table works as good in this case. I would recommend staying away from any dry separation.

You are right. Stay away from dry process. Wet process using cyclone is good. I can test all sizes and optimize size for cyclones using age old panning plate. We too design Hydro-cyclones for such process. If you can send us few samples for testing at our end, we can design a flow sheet for you

At the 2013 CMP conference a paper was done on the Successful Recovery of Chromite Fines. It was based on Case Studies from process plants in Turkey, and there is some good advice on chromite flotation and other processing methods. I would encourage you to have a look at that paper.