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The objective is to create a large capacity (10tonnes/hour) trailer mounted dense mineral concentrator capable of independent operation (with its power generator).
A mobile gravity concentration plant for treating both alluvials and old tailing dumps is being developed.
The original flow sheet involved scrubbing, rejecting coarse gravel (at about 8 mm), a gravel sluicing stage, rejecting a coarse tail (at about 1 mm) on a sieve bend, sluicing the fines again, rejecting a second tail at about 150 um, thickening and passing over a novel type of mat to collect the ultrafines. However hydraulic tests indicated that the second sluice would have to be so wide (5 to 7 m) that it was not practical.

The second sluice has now been replaced by a prototype table based upon a dry fluidized bed separator. Fluidization is limited to concentrate and middling discharge areas. Just how wide a size range the different units will treat efficiently is yet to be determined. The sluice incorporates a jigging action which will be compared with the straight sluicing. The sluice tailing is run over a sieve bend and the undersize passed on to the second stage. As a table needs to be fed at a higher pulp density than a sluice, the flow sheet has been altered to introduce a thickening and classifying stage ahead of the table, which eliminates the second sieve bend on its tailings. The last stage is a mat shaped in the form of a cylinder which would periodically be turned through 90 degrees, the settled material being washed off the top by a row of jets and collected in a trough. The trough has been split into 3 sections (rougher and 2 scavenging sections) with a counter current cleaning pattern as in a flotation circuit. A motor and drive have been added to rotate the cylinder and add acentrifugal effect to the mat.

The parameters tested are: riffle height, spacing and inclination, sluice slope and sluice capacity. Tests have confirmed the hydraulic patterns found in the laboratory tests and indicated that the optimum unit capacity is considerably greater than the original one (32 m{3}/m width) (ie at or above the maximum rate tested in the laborat ory of 40 m{3}/m). As, in fact, there are probably little or no heavy minerals above 1 or 2 mm in size in the alluvials tested, they are being simulated by adding steel balls of 8 and 2 mm diameter to the feed. For the finer sizes the naturally occuring iron oxides (about 5%) oxidised lead minerals (about 0.5%) and gold (about 0.3 gr/t) are being used.
A mobile concentrator for heavy minerals has been developed and patented by ARMINES and is currently being manufactured and marketed under licence by the firm BROCHOT. This unit, with a nominal capacity of one tonne/hour, lends itself well to the reduction of gold prospecting samples and to the small scale mining of gold and dense minerals (cassiterite, wolframite, colombo-tantalite, etc).

The aims are as follows.
Firstly, gravimetric processing of spoil heaps. The reprocessing or processing of old European spoil heaps, the material in which has already been ground (or is to be ground with the addition of the breaker grinder module).
Secondly, mining of small deposits which on their own do not justify the installation of a large processing unit (small tonnage) and which can be upgraded in this way.
Thirdly, pilot operation of larger industrial units
The ores and processable minerals in the first instance would be gold that contrasts well in density with the associated minerals and it is hoped to extend the field of application to less dense minerals provided that their density contrasts clearly with that of their gangue, examples being smithsonite in dolomite or barytes in dolomite. The basic stages will be as follows.
The overall concept including: dimensioning and positioning the units on the line; dimensioning the requisite pumps and piping; and making provision for the addition or removal of excess water in order to keep the optimum concentration of solids circulating. These parameters for the future machine represent the overall flowsheet that has to be supplied to the manufacturer.
Preparation of detailed drawings and manufacturing drawings.
Manufacture of the unit apart from sluices and manufacture of components.
Parametrization study for sluices.
Manufacture of sluices and interchangeable sets of riffles.
Full scale tests on an alluvial gold bearing site in the Gardon valley near Alles. These tests are to make it possible to optimize the operating parameters of the prototype and to make a reliable estimate of the necessary water flow rates, hourly tonnages, performance and consumption of the unit in operation.
Study of optimum recovery of water and recycling of water with maximum removal of fine particles, and design of an additional recycling module in order to be able to use the system in conditions where water is in short supply, notably in the semiarid countries of the Lome Convention.
Study of machine performance.

The tests and analyses will enable the participants to decide on the following data: tonnage that can be processed hourly; total recovery; tenor of concentrates; hourly energy consumption; water throughput necessary without water recovery; and throughput of reusable water.

Funding Scheme

CSC - Cost-sharing contracts


Brochot SA
52 Rue Marcel Paul
93297 Tremblay-en-france

Participants (3)

Boulevard Saint-michel 60
75272 Paris
Desert and Mining Development Ltd
United Kingdom
28 Brocket Road Stanborough
AL8 7TY Welwyn Garden City
Place Du 20 Aout 7
4000 Liege