Column Flotation

[PStead]

Is anyone our there still doing fundamental research on column flotation? I remember in the 80s and early 90s that all we saw in journals was column flotation, and there was a spate of conferences on the topic and books (eg Finch & Dobby).

Do we know all about them now? What about new flotation plants? Are columns now the favoured options over mechanical cells?

[Stephen Neethling]

If anything it is the other way around. Even in their traditional role as cleaner, column cells seem to be out of favour with mechanical cells (and in a few cases, Jameson Cells) being the preferred option. Of course there are a still a large number of column cells out there.

The problem with column cells is that their performance is very bad for large/dense particles.

[Greg Harbort]

Some statistics from the Australian flotation industry:

For Australian coal flotation 48% of installed flotation capacity uses Jameson Cells, 32% uses flotation columns and 20% uses mechanical flotation cells. The trend is for increases Jameson/column use.

In metalliferous flotation in Australia the story is different. Column use peaked in the mid 1990's at around 6% of installed flotation capacity and has been in gradual decline since then.

[P Stead]

The column and mechanical machine manufactuers are keeping very quiet!!

[P Stead]

It would appear that column flotation did not live up to its promise of the 80s- am I right. My original question asked if there was any active research in this area. I would love to hear the views of:

a. Machine manufacturers
b. The people who were active in research in the 80s and 90s- Finch, Dobby, Yianatos et al.

Don't be shy!!

[Mikhail Burstein]

The reason that there are less research on column flotation is probably related to the fact that it is now grown to a mature technology and there are less research comapring to the "boom" of the 80's. There are not much breakthrough fundamental papers on impellor flotation machines, too, for the same reason.

Due to the apparent simplicity of the basic design and wide use of countercurrent column separators in chemical engineering, it would be difficult to expect major technological developments other than new static sparger/aerator designs or some modifications in cell geometry.

There were several recent research papers on elementary heterocoagulation subprocesses in weakly turbulent flows as well as experimental and analytical researches of deep washed froth structures.

Only in peer-reviewed journals, on average 15-20 papers per year on theory and applications of column flotation have been published through 2002-2005, according to the ISI Web of Science search.

I would like also to mention the book "Column Flotation: Processes, Designs and Practices" by J. Rubinstein and M. Burstein published by Taylor & Francis in mid-90s (ISBN: 2881249175) in English and then translated by Rocas y Minerales into Spanish which provides a review of theory and appplications of flotation columns at that point.

[P Stead]

Thanks for your reply Mikhail. I assume from lack of response that the Finch, Dobby etcs. are out of this game now?

I assume you are Russian, Mikhail. Do you know anything of the Froth Separator, which was developed in the USSR in the 70s? Is it being used anywhere?

[Mikhail]

Regarding Froth Separator: It was actually developed in Russia and Ukraine (Prof. Malinovsky) in early 60's (not 70's) and then several systems combining countercurrent flotation (for fine classes) with "froth separation" principles (for coarse fractions).

The "froth separation" system was designed by for "coarse" coal fraction which is too large for conventional flotation (+0.5 mm) but too fine for conventional jigging or heavy-media separation. It is based on feeding the separator from the top onto deep froth layer. Obvious technical problem (or challenge) of such systems is development of industrial-size systems allowing continuous feeders not destroying the froth which would lead to immediate losses of coal in tailings. In the same time, excessive frother concentration would result in entrainment of gangue particles into concentrate.

Several types of "shelf" feeders have been developed, and the system was patented and "commercialized", but was never implemented beyond several plants processing coal, gold, silver, diamond, oxidized iron and potash ores. Recently (within the last 5 years), the new designs have been developed in Russia for forth separators used in waste water treatment (including oil/water separation, food industry wastes, etc.)

I am not in a position to reply about their current activities of Prof. Dobby and Prof. Finch , just want to mention that Dr. Glen Dobby is one of the founders of Minnovex, a company which developed patented column flotation circuits, spargers and control systems for them. Recently, the company became a part of SGS Lakefield Research.
Dr. Jim Finch is the Professor at McGill University and column flotation continues to be a part of his research area.

[ajohnston]

From what I understand the new big deal in columns is Aminpro's contact column. Low collision velocities meant low recovery probability in conventional columns, but high shear contact under pressure prior to flotation seems to help improve particle recovery by air bubbles. My personal experience with these columns is limited to a pilot plant, but it did very well.

Any one have more experience with the contact cell?

[Mikhail Burstein]

"Conctact cell" is not a new idea. Aeration prior to flotaion was tested and used in many prior designs of impellerless flotation, Jameson cell is a perfect example of widely used machine with separated "mineralization" and separation zones akin to impeller zone and the rest of the cell of impeller machine.

The goal is to create an environment where the intensity (and therefore, the internal scale) of turbulent vortices is high enough to maximize bubbvle-particle collision and low enough not to destroy the aggregates formed (at least, for the mineral to be recovered). Also, connection between the two cells should be carefully designed to minimize fines entrainment into froth by rising bubble swarm as well as fine uncoalesced bubble entrianment into tailings stream by the slurry flow.

[pamelunxen]

From what I gather most of Dobby's recent work has been directed towards his business (Minnovex) and a lot the papers coming out of McGill university (Finch & colleagues) over the last 5 or 10 years bas been directed towards fundamental modeling and/orr online control. Like Mikhail said, a lot of the kinks in the fundamental modeling for column cells have been worked out, and focus is being directed towards cameras, conductivity probes, and other online methods for measuring and controlling gas dispersion characteristics. Most recently there has been a lot of discussion on the relationships between water recovery, degree of entrainment, and froth height, although these are not specific to column flotation.

The Aminpro contact cell is a bit of a different story-- still not much progress on fundamental modeling of the contacter itself (altough the separation zone model is pretty well developed). There have been some interesting parallel developments in the chemical industry (hydrodynamic cavitation reactors), and "dissolved air flotation" is receivingng some attention as well.

The Jameson cell came before the contact cell. The main difference is that the contact cell uses forced air and the Jameson cell operates by induction.

I wonder if the decline in popularity of the column cell (if indeed there is one) is because their operation is currently misunderstood by industry, or if its because their operation was misunderstood in the 1980's and 1990's.

[ramelunxen]

The popularity of columns appears to have diminished, but in reality, as indicated by Mr Burstein, it is a mature technology and therefore receives less attention. We know that columns are good in providing a clean concentrate with little material (gangue) entrainment. Their shortcomings in recovery are dealt with in the manner the whole circuit is configured. In today's plants and future plant designs, column flotation is always an integral part of the cleaning circuit.

If you want to have a column that provides high recoveries in addition to the clean concentrate grades, you need to go to the two-stage contactor/separator technology, of which the Contact Cell is part of.

[ajohnston]

The major reason NOT to install a column would be where there is coarse native metal. There are plants here in Peru that have suffered from native copper "needle" losses in columns and others that have had gold "disc" losses. It seems that columns simply dont have the agitation, or the bubbles just dont give teh buoyancy to get these heavy particles to the concentrate.

[mikhailburstein]

The way to have "high buoyancy" bubbles is to create "double aeration" using fine bubbles from "contact cell" or injector in combination with larger bubbles from more conventional sparger. Fine mineralized bubbles can act as a "carrier" coalescing with larger "transport" bubbles.

Another option would be a combination of column flotation for fines with "froth separation" for coarse particles when coarser fraction is fed into or onto froth layer.

[scarcha]

hello, i'm graduate student in Metallurgical Civil Eng. from Universidad de Santiago de Chile, and i'm doing my tesis in Column Flotation, but i can't found some information about the spargers (design, materials, etc...) i want to know where (book, web, blog) i can find this information. I reviewd the books "Columns Flotation" (Finch and Dobb) "Flotation, science and Engineering" (K.A. Matis) but tehere not much. please if anyone can help me i really appreciate! ([e-mail])