Normally the best way to deal with naturally floating carbon is by pre-flotation. This pre-flotation process is described in the papers listed below:

Removal of Organic Carbon with a Jameson Cell at Red Dog Mine Todd Smith, David Lin, Brigitte Lacouture, Greg Anderson http://is.gd/tFScmq and pre-flotation is used at the GlencoreXstrata Mount Isa Copper and Lead-Zinc Concentrators and the GlencoreXstrata McArthur River Concentrator in Australia.

Expansion of the Mount Isa Mines Copper Concentrator Phase One Cleaner Circuit Expansion Carr DC Harbort GJ Lawson V http://is.gd/fzzNH0 and

Developments in Milling Practice at the Lead/Zinc Concentrator of Mount Isa Mines Limited from 1990 Young MF, Pease JD, Johnson NW, Munro PD http://is.gd/RVlsbw

Further to your comments the treatment of Pb/Zn ores containing carbon depends on how the carbon is distributed in the ore and the surface chemistry of the carbon (actually hydrocarbon). At Mt Isa the carbon is mainly distributed as fine inter-growths around pyrite imparting natural hydrophobicity to the pyrite. A simple test is to do a flotation test without collector to see how much of each mineral type is naturally hydrophobic. One can then clean this preflotation rougher concentrate to produce a concentrate, minus entrainment, in which the minerals may be contaminated with carbon at the surface. The carbon at Mt Isa (0.5% TOC) is approaching graphitic carbon and is therefore very hydrophobic. At Century and McArthur River Mine in Australia the carbon is not as graphitic but is more like a low rank bituminous hydrocarbon. It is possible to determine this through surface analysis. This carbon adsorbs frother molecules like MIBC and very high additions of MIBC are required to get frothing (for pre-flotation). If one chooses to depress the carbon, rather than pre-flotation or reverse cleaning, for graphitic carbon the reagent naphthalene sulphonate is effective with dextrin but when the carbon is more like hydrocarbon, the reagent hydroxyl ethyl celluse (HEC) is more effective. Knowing how the carbon is dispersed in the mineral assemblage and the surface chemistry of the carbon is an important first step in diagnostics and formulating a strategy to ameliorate negative impacts. It should be noted that not all the carbon reports to a preflotation concentrate for different reasons, but the remaining carbon may still cause problems downstream. Many ores in Australia and other Pb-Zn sulphide ores globally have hydrocarbon contamination and some of these experiences are documented in the open literature. I am happy to share references of relevant publications. These publications are all available through Scopus.

Appreciate the great ideas and sharing of the experience by both of you. I'm glad to share my thoughts here as I's a key member in a team along with RTZ developing a flow scheme for complex Pb-Zn beneficiation( in India) with interfering graphitic carbon. All pre-flotation runs had to discard due to loss of Galena & Sphalerite along with the graphite concentrate- eventually carbon depression by Nigrosine was adapted as the best economical option.

There are some ways to reduce the coal impact in flotation of Cu/Pb/Zn. I have the experience of one Mexican mine that have 1.5 % of C in head and we make many works to reduce their impact in recovery and grade of the concentrates of Cu, Pb and Zn.

If you look at the case studies from Red Dog and Mt Isa and Century Mines, there were similar issues of high losses of valuable minerals in the pre-flotation concentrates. This is why the circuits were redesigned with a pre-flotation cleaning circuit with froth washing to minimise the losses of the valuable minerals and direct them back to the flotation roughers. This circuit removes the fast floating carbon.

Also the use of carbon depressant is still required in the subsequent Circuits to minimise carbon collection, normally using Dextrin or D101 (similar to Nigrosine).

The carbon will be pre washed before to feed to the mill or be classified in cyclone. We implemented a pre classification combined with pre-flotation in the overflow cyclone product.

Thanks a lot for your help. I've been reading some of the articles posted by you, and it seems like our ore is very similar to the described in the Red Dog Mine paper, but the main difference is the ore head grade, in this case we are working with an ore of 0.8% lead, 0.8% copper and 3.15% Zinc. Did you use any special type of cell for the batch kinetic flotation test used on the mathematical model?

You can also try pre-flotation coal using kerosene and frother - large consumption of reagents (it xanthate has negative effect to selectivity of sphalerite). And also you can try after treatments concentrate through the full-depression all sulfides without losing flotation activity of carbon.

Maelgwyn Mineral Services also successfully used its G-Cell for pre-flotation of graphite at TGME in South Africa. The G-Cell due to its design has extremely fast kinetics which facilitates a better separation of the graphite than other flotation techniques.

A paper describing the application entitled "application of Imhoflot G-Cell centrifugal technology can be downloaded from the website http://is.gd/78PT1J along with other papers explaining the technology.

Regarding to some comments, the best way to deal with naturally floating carbon is by pre-flotation. It should be mentioned that, the pre-flotation concentrate usually is discarded directly to tailings, however this stream contains significant amount of lead and zinc. How can we reduce lead and zinc loss to preflotation concentrate.

I operate Flotation at a lead copper zinc mine and we have found that the easiest way to deal with carbon and Graphite is with a reagent called bk257

Working with minerals containing charcoal quite content with Ag, Pb, Cu and Zn to the grinding depressants zinc sulfate, bisulphite, and sodium cyanide was added and then a naturally floatable coal flotation was performed subsequently with sparkling MIBC flotation bulk and then copper lead separation in cleaning dextrin was added to depress the fine coal with good results. In the zinc flotation is much in control the Ph mainly on the last cleaning should not exceed 11.8 this past coal begins to float.

Wouldn't we need to know first the metal and Carbon distribution size by size? Considering the slurry viscosity will be affected by grain size. Just curious!

At Campo Morado Mine Nyrstar in Mexico, we have 2 % of Argilite in the head of the mineral, and the principal problem was the amount of fine material after the mill. Their principal problem in flotation is the high amount of consumption of reagent and low grade and recovery of the concentrates. The first question is what % or amount the carbon not affect the flotation process and then We must to think in the alternative to eliminate the amount of carbon that cause any problem like high reagent consumption. Which amount of this carbon can be eliminated from the mine with the alternate mined method and what amount of carbon can be pre washed before and after the mil this system is more cheap that anyone and then thinking in pre float only in the carbon that was not eliminated, and must to ask way this carbon was not eliminated, needed moreover was very fine to be eliminated. The dextrin in the flotation process helps to depress the carbon and minimize the problem in recovery and grade of the concentrate.

Material Safety Data Sheet Bgrimm MODIFIED BIOMASS ORGANIC ACID SODIUM SALT 40%-60%

Product and company identification

Product name: DEPRESSANT BK526
Supplier: Beijing General Research Institute of Mining & Metallurgy (BGRIMM).
Mailbox Building 23, Zone 18 of ABP, No. 188, South 4th Ring Road West, Beijing, China
Website: http://is.gd/mMRaxZ
Material uses: Industrial applications
Code: BK526

It works great for depressing the carbon allowing us to do away with a pre-float.

It's understood that separation of carbon in Pb-Zn-Cu ore is either done by depression with suitable surface coatings (Nigrocene or similar chemical) or with pre flotation option, which depends upon the flotation kinematics of geological species in ore population and the quantum of carbon present. Most economic operation will vary from case to case. In the first case concentrate grade (in our plant it was pb concentrate) will suffer due to presence of Carbon to some extent and in the second case valuable mineral recovery is reduced.

My quest is to know, that anybody tried to increase or recover the lost recovery of valuable mineral in pre flotation process by installing Concentrator spirals as density difference between valuable minerals and carbon is reasonably good and seems worth taking lab scale test trials. Will thankful appreciate for sharing experience on these lines.

Could you please give some information about your plant, such as ore feed characteristics (Pb, Zn and organic carbon contents), BK526 consumption amount, BK526 addition point and required conditioning time.

My experience is with Graphitic carbon. Where we tried to depress with Nigrocene. Coal if in free form may be separated in hydrocyclone as overflow at 0.5 to 1mm size fraction. Kindly send more details to understand the grain size and free form, gangue etc.

I am also trying to understand the major property of Nigrosine and its major application in Mining. I understand the Nigrosine is the Azine dye which is used in Zinc mines and Lead also.

Several flotation methodologies like, pre graphite flotation, reverse graphite flotation are cited in literature, though could give good results with high grade ores, they failed with low grade ores containing high graphite content. Trials using different graphite depressants like nigrocene, depremin-c, Quebrecho were found not successful with low grade ores. If your ores are low grade and contains high graphite content, one way to overcome this problem is to exploit the wide differences in specific gravities between graphite and lead bearing minerals using enhanced gravity separators like MGS (MozleyMultigravity Separator) using lead rougher concentrator as feed. In India HZL Plant (Rampura-Agucha and Rajpura-Dariba) used this process in the past.

When you mention a low grade ore, would you consider a head ore grade of 0.8%Pb,0.8% Cu, and 3% Zn, would you consider it as a low grade ore?

In India HZL ore consists of approximately 2.2% Pb, 13.5% Zn and Graphitic Carbon 4%.

An ore with the head grades mentioned is low grade - and there is not much room to manoeuvre for a technical solution unless there is a substantial contribution in value from gold, silver, and indium. Can it be presumed it is disseminated and require fine grinding (i.e. P80 less than 75 um) for liberation?

One of the main challenges in dealing with graphite is its tendency to cleave easily and to smear the harder minerals during grinding. One usually ends-up with ultrafine graphite and valuable minerals responding as if they were graphite.

A potential approach would be to flash float the graphite to remove it at a size as coarse as possible and then approach the sulphide flotation conventionally. The trick would be to find a suitable process to clean the flash graphite concentrate so as to minimize the values associated with it. Many tips have been provided in the earlier posts.

Thought of sharing some of the existing literature on MGS for separation of Graphite! Please go through below links

http://is.gd/s2f35C
http://is.gd/pvBW0j

We have successful example that Cu/Pb/Zn ore use ferric sulphate instead of dichromate and cyanide as inhibitor, and then we can get better Cu and lower cost.

In Peru there is a concentrator floating carbon at beginning and then float Pb/Zn.

Kindly suggest suppliers for the above mentioned depressants (nigrocene, depremin-c, Quebrecho) and for Hubasine as well. I would like to test them.

Suppliers of Nigrosine:

Anirox Pigments Limited, Aaashiana Dyestuffs, Inc., Aakash Chemical & Dye-Stuffs, Inc., Albion Colours Ltd, Brighten Colorchem BV, Classic Dyestuffs Inc., DintexDyechem Ltd., Disha Dye Chem Pvt. Ltd., Dynasty Chemicals(Ningbo), Global Colors, Inc., Haihang Industry, Jiangsu Aolite Chemical Co.,Ltd., Krishna Industries, New Dragon Industrial, Orient Chemical, Pylam Products Company, Inc., Qingdao Double-peach Specialty Chemicals (Group) Co. Ltd., Tianjin Yadong Group, Wenzhou Huanan Chemical and Industrial Corporation

PIONERA Biopolymers are modified natural polymers from renewable sources, Pionera F-100 is able to facilitate both graphite depression and elevate zinc grades in the rougher concentrate. In addition to graphite depression, the product has been observed to reduce the silica content in Zinc concentrate.

Akzonobel is one of the suppliers of Depramin.

At Yukon Zinc they dealt with carbon in the ore and found that a reagent called BK256 worked excellent I am not completely sure of the manufacturers any more except that it was a Chinese company possibly.

My experiences with MGS in HZL as R&D HEAD: Lead concentrate slurry was fed to Mozely Cyclones to remove ultrafines. Underflow is fed to MGS.

PROBLEMS:
MGS bearings and blades got damaged. Cyclone underflow jammed. No control, no instrumentation. All manually controlled,

SOLUTION:
On investigation it was observed that heavy trash was found entrapped in pulp. Trammel screen was used to remove trash.

Flow sheet: Pb Flotation 1st stage- 2nd stage Zinc flotation. Copper NIL

YOUR CASE: NOW DISCUSSED:

Pb, Zn, Cu-Possible flow sheet advised. Bulk flotation of Pb,Cu. Then use MGS to remove graphitic Carbon. Then depress Copper using Dicromite.

Yes it is very difficult process. Lot of R&D in Lab, Pilot plant is required. Chemical depression may not work but may be tried in lab. Today we have INNOVATIVE EQUIPMENT SPIRAL NEW DESIGN which can handle very fine particles-May be tried.

MY ADVICE:
Try pre concentration of minerals at coarser size between 1mm to 0.5mm and then try spirals or MGS and then further RGBM for down line process.

I have case study of Pionera F-100 that I can share with you.