Evaluierung des Potentials der Elektroscheidung nach Triboaufladung zur Anreicherung von Talk aus Fraktionen des Mahlwerkes Oberfeistritz der Firma Imerys Talc Austria GmbH

In this master¿s thesis, the potential of tribo-electrostatic separation to deplete chlorite from talc-rich fractions produced at the Oberfeistritz processing plant of Imerys Talc Austria GmbH was investigated systematically. To characterize mineral associations, intergrowths, and feature contrasts exploitable for efficient separation, a multidimensional feature-class analysis was carried out on three fractions from the plant¿s coarse comminution stage within a particle size range of < 500 µm. The study began with a sieve analysis, followed by determination of the chemical and mineralogical composition and the density of each size class. Chlorite, talc, and quartz were identified as the main phases, while mica and dolomite occur as accessory phases. With the exception of the < 40 µm grain-size fraction, they are present in approximately equal proportions across all grain-size classes. In addition, tests with a Frantz isodynamic separator were conducted to assess whether chlorite could also be depleted by magnetic separation. Two electrostatic separators available in the pilot plant of the Chair of Mineral Processing at Montanuniversität Leoben were used for separation in an electric field: the Hamos EMS 500 free-fall separator and the ST Equipment & Technology X2 belt-type separator. On the free-fall separator, exploratory tests with the 500/300 µm and 300/100 µm fractions were first performed to identify the most amenable size range. Subsequent tests with the 500/300 µm fraction were used to select the most promising charging-unit material. A systematic parameter study based on the Design of Experiments (DOE) then examined the effects of feed temperature, charging intensity, and feed rate on separation performance. Feed temperature and feed rate emerged as the primary influencing factors. Evaluation comprised mass distribution, loss on ignition (LOI), and product whiteness, complemented by mineralogical assessment via X-ray fluorescence analyses. The results, compiled as mass-balance tables, show clear enrichment and depletion effects. In a particularly promising test, the talc grade was nearly doubled from ~36% in the feed to ~68% in the concentrate. The concentrate mass yield was ~17%, with a talc recovery of ~30%. On the belt-type separator, a parameter study was conducted with the 100/0 µm fraction. Starting from a feed grade of 47% talc, the concentrate grade was increased to an impressive ~81% at a mass yield of ~23% and a talc recovery of ~37%. This outcome was achieved at high feed rate, ambient feed temperature, high relative humidity, and low belt speed. Additional tests with varying parameters produced lower talc grades in the concentrate but substantially higher recoveries. Applying these parameters to two further, markedly finer fractions did not yet yield comparable enrichment.