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A PROCESS DESIGN STUDY FOR FINELY DISSEMINATED COMPLEX SULPHIDE ORE FROM THE MOLAI AREA

Objective

THE AIM OF THE RESEARCH IS TO DEVELOP A PROCESS FOR THE TREATMENT OF COMPLEX SULPHIDE ORES FROM THE MOLAI REGION OF GREECE, WHICH ARE ALSO PARTLY OXIDIZED.
There is a finely disseminated, partially oxidized zinc lead silver sulphide ore deposit in the Molai area with reserves estimated at 2.3 million tonnes. Bulk flotation for beneficiation is considered more suitable than differential grinding.

The zinc carbonate minerals are very different to recover because of their close association with iron minerals. A new process, consisting of magnetic separation followed by flotation, to upgrade the magnetic and nonmagnetic product individually, has been developed for recovering these zinc minerals.
Laboratory grinding tests and kinetic studies of a composite sample of the Molai ore have shown that it abrades easily, to produce a relatively high quantity of slimes. To keep this quantity as low as possible, and to achieve sufficient liberation of the valuable minerals from the gangue in order to apply bulk flotation, a grinding time close to 20 minutes is appropriate.
A cleaner concentrate, suitable for conventional metallurgical treatment, has been obtained from the best laboratory bulk flotation test.

In the final bulk flotation pilot plant test, the cleaner concentrate assayed 46.92% zinc, 4.96% lead, 152 parts per million silver and 2800 parts per million cadmium, with recoveries of 79.46%, 52.54%, 62.95% and 80.97% respectively.

The aim of this project was to develop a beneficiation process for the treatment of the Molai polymetallic sulphide ore deposit.

The finely disseminated, partially oxidized zinc lead silver sulphide ore deposit had an average grade of 6.80% zinc, 1.10% lead and 28 ppm silver. Ore reserves have been estimated at 2.3 million tons.
Zinc is found mainly in sphalerite and smithsonite (monhelmite), lead in galena, cerussite and anglesite and silver in tetrahedrite, tennantite and freibergite.

The fine grained texture, the intergrowths (often between sphalerite and galena and galena and pyrite) and the numerous inclusions, particularly in sphalerite are the main reasons for the inconvenience in establishing the optimum grain size for liberating each one of the valuable minerals from the others and from the gangue.

For liberating the majority of sphalerite and galena, the required grinding size is 26 um and 12 um repectively, while for the oxidized zinc and lead minerals the above sizes become 20 um and less than 10 um. On the other hand, for liberating the majority of sphalerite and lead minerals from pyrite and gangue material, a grinding size of 60 um would be sufficient. Hence, for the beneficiation of the Molai ore, bulk flotation is considered more suitable.

Zinc carbonate (oxidized) minerals are very difficult to recover due to their close association with iron minerals. A new process, consisting of magnetic separation followed by flotation to upgrade the magnetic and the nonmagnetic product individually, has been developed for recovering these zinc minerals.

Laboratory grinding tests and kinetics study on the composite sample of the Molai ore have shown that it abrades easily, thus producing a relatively high quantity of slimes.
Also, a cleaner concentrate suitable for conventional metallurgical treatment has been obtained from a laboratory bulk flotation test and the results were well matched in the final bulk floatation pilot plant test.
THE RESEARCH IS DIVIDED INTO THREE PARTS, TO BE CARRIED OUT IN GREECE, ITALY AND FRANCE.

1.- GREECE: SAMPLING, PREPARATION OF SAMPLES, MINERALOGICAL INVESTIGATIONS, CRUSHING AND FLOTATION TESTS, AND FINALLY PILOT TESTS WITHIN THE MINE.

2.- ITALY: PLOTTING OF CHARACTERISTICS OF PURE SPECIES, PREPARATION OF NEW REAGENTS AND FLOTATION TESTS ON PURE SPECIES AND UNSORTED MINE ORE.

3.- FRANCE: QUANTITATIVE MINERALOGY, ASSESSMENT OF THE RELEASE NETWORK AND OF THE FLOTATION TESTS.

THE ECONOMIC ADVANTAGE IS BASED ON THE POTENTIAL DEVELOPMENT OF THE SULPHIDE MINING INDUSTRY IN NORTH GREECE.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Institute of Geology and Mineral Exploration
Address
70,Messogeion Street
11527 Athens
Greece

Participants (2)

Bureau de Recherches Géologiques et Minières (BRGM)
France
Address
39-43 Quai André Citroën
75739 Paris
NATIONAL RESEARCH COUNCIL OF ITALY
Italy
Address
Via Bolognola 7
00138 Roma