Flotation without the Clearing of Mud Recuperates Ultrafines
To obtain good results, with economical viability, many processes were tested in the mines of Salomongone, Amapa.
This work has the objective of showing the adopted solution ofr the recuperation of the rejects of the circuit of gravimetric separation of the mine of Salamangone in the state of Amapa, of the mines of Novo Astro S.A. controlled by the MPC Mining and Participation Company.
The mine of Salamangone shows three basic types of minerals: Alluvial/Colluvial, Saprolite and primary mineral. The Alluvial/Colluvial, Saprolite and were originally exploited by gravimetry. The gravimetric process is resumed at hydraulic dismount, breaking, grinding in bars and separation by centrifuges. The fire-assay of the rejects of the gravimetry vary from 1 to g/t. The gold contained in these rejects is extremely fine (the most part under 20 micras) and, in great part, in small laminas.
The first process which was studied for the recuperation of that gold in semi-industrial scale, was the lixiviation in pools. Pools which were re-dressed with plastic blankets and a mounted circuit of absorption were built, the stripping of carbon, including that of electrolysis.
The conclusions of that study demonstrated that, for the gold retained in the interior of the pools, the recuperation was reasonably elevated (70% to 75%) but due to the low percentage of solids in the feeding (from 5% to 10%) there was an overflow, which carried from 60% to 70% of the gold contained in the rejects. This excessive loading of gold, which was not originally expected, is due to the large amount of free-turning present in the rejects, to the excessively fine gold and at gold in laminas.
The total recuperation of that process, as originally conceived, would be perhaps the order of the 30% of the total gold contained in the rejects, which would be anti-economic. Afterwards, a variation of this process was searched for which would consist in the elimination of the existence of the overflow in the pools, so that there would not be any loss of gold. For this one would have to install large systems of thickeners, which would turn this process economically non-viable, besides causing technical problems too in the operations of the same, for incorporating in the interior of the pools all the lamas.
Due to these problems another process alternative was thought of for the recuperation of the ultrafine gold. At the beginning the process of flotation was discarded being that the same normally needs a weakening, which would also cause enormous losses in the recuperation of the process.
But at the beginnings of 1987, due to the technical and economical problems found in the lixiviation by pools, in the specific case of the Salamangone, we tried to develop a process of flotation without the need of weakening. The MPC team – Mining New Astro S.A., counting with the consolatory of the Mountain States of the United States of America, obtained a condition of appropriate technical and economical flotation for the initial pretended objectives.