Air Classification of Talc from the Alguy Deposit
Abstract Generated abstract
This paper examines beneficiation of talc from the Alguy deposit, where talcites contain quartz and quartzite impurities concentrated mainly in coarser size fractions. The authors characterize the particle size and chemical composition of the sample, then test dry separation of the minus 3 mm material by air classification using a laboratory separator with optimized air pressure, feed rate, and cone position. A scaled experiment combining screening, air classification, grinding of tailings, and secondary classification produced a total concentrate yield of 68.7 percent with 29.70 percent MgO and 89.3 percent MgO recovery. The results indicate that air classification can produce talc concentrates meeting technical requirements for most uses, and that the separator design is suitable for laboratory studies.
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AIR CLASSIFICATION OF TALC FROM THE ALGUI DEPOSIT
S. A. BABENKO, N. T. BOLOTKINA, I. N. ZIMINA, L. M. MEDVEDEVA
(Presented by the scientific final conference of the Faculty of Chemical Technology)
The talc sample from the Algui deposit on which we carried out our investigations consisted of slightly moist, naturally compacted pieces of talcites up to 30 cm in size, with a microlayered structure; after drying they turn into a loose mass. The principal mineral is talc. Foreign impurities are grains of quartz and pieces of quartzites of various sizes. The latter are concentrated mainly in the coarse classes, \(+10\) mm and \(-10+3\) mm; the talc content here is insignificant. Chemical analysis showed that they contain MgO 1.05–3.29% (Table 1). According to mineralogical analysis,
Table 1
Particle-size and chemical compositions of the talc sample from the Algui deposit
| Classes, mm | Yield, % | Content, % | Content, % | Content, % | Content, % | Content, % | Content, % |
|---|---|---|---|---|---|---|---|
| l.o.i. | SiO₂ | Al₂O₃ | Fe₂O₃ | CaO | MgO | ||
| \(+10\) | 15.4 | 0.90 | 94.42 | — | — | 0.47 | 1.05 |
| \(-10+3\) | 6.5 | 0.90 | 94.88 | 0.24 | 0.06 | 0.30 | 3.29 |
| \(-3+1\) | 6.2 | 2.86 | 79.02 | 0.84 | 0.06 | 0.35 | 16.31 |
| \(-1+0\) | 71.9 | 4.28 | 67.30 | 0.15 | — | 0.35 | 28.05 |
| initial sample | 100 | 3.46 | 73.95 | 0.19 | 0.01 | 0.37 | 22.35 |
in the \(-3+1\) mm class talc is practically present as intergrowths with quartz, while in the \(-1\) mm class there is an insignificant amount of intergrowths. Separation of talc from quartz was carried out by air classification on a laboratory separator (Fig. 1).
The starting material (class \(-3+0\) mm) was fed by screw feeder 3, driven by electric motor 5 through reducer 4, into the separator branch pipe, from which it was thrown by the air jet into the wide part of apparatus 1, where the coarse particles fell downward and were discharged along a tray into tailings receiver 6. For better separation of coarse particles from fine ones, deflecting cone 2 is provided; its position is adjusted by bolt 7. The finely dispersed particles are carried by the air jet through the pipeline into concentrate receiver 8. A vacuum cleaner was used as the air blower.
After the optimal operating conditions of the separator had been established (air pressure, position of the baffle cone, feed rate), a scaled-up experiment was carried out on the beneficiation of talc from the Alguy deposit according to the following scheme. The initial talcites after
Fig. 1. Diagram of a laboratory installation for air classification of talc (explanation in the text)
drying were screened at a grain size of 3 mm. The undersize product was sent for air classification, as a result of which concentrate I, containing MgO 30.00% (Table 2), and tailings were obtained. The latter, after grinding in a ball mill to a grain size of 1 mm, were again subjected to air classification. Secondary classification yielded products (concentrate II), containing MgO 28.10%, and tailings—14.32%.
Table 2
Results of talc beneficiation by air classification
| Product name | Yield, % | MgO content, % | MgO recovery, % |
|---|---|---|---|
| Quartzites (class +3 mm) | 19.5 | 3.68 | 3.2 |
| Concentrate I | 57.5 | 30.00 | 75.5 |
| Concentrate II | 11.2 | 28.10 | 13.8 |
| Total concentrate | 68.7 | 29.70 | 89.3 |
| Tailings | 11.8 | 14.32 | 7.5 |
| Initial sample | 100 | 22.83 | 100 |
Thus, air classification of talc from the Alguy deposit makes it possible to obtain concentrates whose chemical composition meets the technical requirements for talc for practically all of its consumers. The proposed separator design can be used for laboratory studies on the air classification of talc.