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UPGRADING OF PYRENEAN AND VALMALENCO TALCS

Objective

The objective is to obtain higher quality products, in particular talc or chlorite concentrates separated from the carbonates.
Modelization of wet micronization

A complete processing flowsheet for the manufacture of delaminated talcs was fully developed. An estimated price for a 5000 t/year delamination plant was developed.

General conclusion on treatment of talc flotation tailings
A general flowsheet could be applied on talc tailings and on talc crude ore which contain talc, chlorite, dolomite and quartz.
The different operations that must be carried out are:
- talc flotation with a frother reagent where, generally several stages are necessary
- dolomite flotation in weakly acidic media (pH=5.5) with an anionic collector
- chlorite flotation in strong acidic media (pH<3) with short chain amine or quaternary ammonium salts.
These different flotation stages have to be separated by cycloning steps. By this way collector consumption decreases with pulp thickening and the different water circuits could be separated.

Mineral processing research study of talc from Valmalenco

Six complete flow-sheets were tested including attrition, wet screening, classification, grinding and flotation.

Two of them could be adopted to suit the particle size and chemical characteristics of the required product.
The wet circuits tested permitted total recovery of talc in excess of 50%.

Acid leaching tests were performed in order to decrease the Fe2O3 content and increase the brightness of the products. Oxalic acid appears to be the best reagent for this purpose; about 15% of the iron contained in the sample can be extracted. However, the method is not economical since it requires a high temperature (80 C).
Work on the Pyrenean deposits will involve:
development of a flotation upgrading process for some types of waste, permitting separation of the chlorites (of marketable value) from the carbonates (detractive constituents);
direct upgrading of certain qualities in order to obtain, by wet micromilling, ultrafine products that can be used in the form of concentrated slurries in the paper industry;
study of the industrial application of the wet micromilling process, laboratory tested under the previous research contract, and establishment of a complete programme of pilot experiments for modelling the wet micromilling operation as designed for obtaining batches of talcose mineral optimized for incorporation in plastics;
and direct upgrading of certain qualities by heat treatment.
Particular attention will be given to the analysis of dehydroxylation mechanisms with or without fluxing agents. This has 3 main objectives: increasing the internal cohesion of the particles; making substances which combine the advantage of a high refractive index with that of great fineness for use as opacifiers; and making semifinished products for the ceramics industries. In these 3 areas, attention will be given to determining the nature and quantities of residual structural water by infrared spectrometry and proton nuclear magnetic resonance(NMR).

The other part of the project is work on the Valmalenco deposits. On the basis of the knowledge acquired under the previous contract, flotation tests will be carried out on finely milled products in order to determine the optimum operating conditions (chemical treatment, apparatus adjustement parameter, etc). The research objectives are: firstly, to obtain a talc chlorite concentrate; and secondly, to separate the talc from the chlorite.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

TALC DE LUZENAC S.A.
Address
2 Place Edouard Bouillères
09250 Luzenac
France

Participants (2)

Institut National Polytechnique de Lorraine
France
Address
Rue Du Doyen Marcel Roubault
54501 Vandoeuvre-les-nancy
NATIONAL RESEARCH COUNCIL OF ITALY
Italy
Address
Via Bolognola 7
00138 Roma