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Characterization of perlites from Jastrabá and Lehôtka pod Brehmi deposits

Varga P., Lexa J., Uhlik P., Rajnoha M.

Geology, Geophysics and Environment

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2015

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Vol. 41, no. 1

146

EN

Perlite is an important industrial mineral with unique properties. It is an acid volcanic glass (rhyolitic or rhyodacitic) with a water content between 1 to 5%. The largest industrial use is in the form of expanded pearlite. This produced by rapidly heated, grinded natural perlite at 600–900°C (Barker & Santini 2006). Perlite occurrences represent economic accumulation in Slovakia. Perlite is mined at the Lehôtka pod Brehmi deposit for a long time and now is starting to open Jastrabá deposit. The aim of this paper is characterization and correlation of samples of both deposits and samples from locality Szabova skala due to their different genesis. The perlite from Lehôtka pod Brehmi deposit has been characterized by X-ray powder diffraction, IR spectroscopy and thermal analysis in the current research (Uhlík et al. 2014). Any significant differences were not identified in the content of volcanic glass, crystalline phases, or content of water. Only one differences have been observed in the macroscopically different perlite glasses (color, texture) – porosity. The macroscopically (color, texture) of different perlite glasses differences were once in porosity. The purpose of this article is to characterize the perlite sample by optical microscopy, X-ray powder diffraction and microprobe analysis. The characterization of perlitic glass is important not only for the mining company because of heterogeneity of Lehôtka pod Brehmi deposit, but also from a scientific point of view and about 30-years gap of perlite studies in the Central Slovakian Volcanic Field (Capková 1976, Kraus et al. 1980, 1985, Zuberec et al. 1980, 1983).

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Mock-up experiment for bentonite barrier testing

Stricek I., Baliak F., Uhlik P.

Górnictwo i Geoinżynieria

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2011

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R. 35, z. 2

543-548

EN

The mock-up experiment simulates vertical placement of radioactive waste in the underground repository. Relatively small model is basically a stainless steel cylinder (400 mm diameter and 600 mm height), simulating a section of gallery in which the radioactive waste will be disposed. The cylinder is equipped with a 140 mm diameter central tube, in which heating elements - simulating the heat produced by the waste - are placed. Heating temperature is 120 degrees of Celsius. The annular gap between the central tube and the outer lining is backfilled with pre-compacted bentonite blocks. Major part of blocks is made of pure bentonite from Jelsovy Potok deposit and the other from Lieskovec deposit, both milled into < 250 mim/m fraction. Some blocks contain either 5% of pyrite concentrate to simulate pyrite presence in a gallery host rock or 5% of powdered elementary iron to determine iron-bentonite interactions (iron components in gallery). In the host rock the bentonite water saturation occurs naturally. In the experimental mock-up the hydration is ensured from the external water source. Water is distributed using 23 hydration holes placed outside of the backfill block. The water chemistry is based on the composition of the original water present in the most perspective area for geological radioactive waste repository in Slovakia.

PL

Eksperyment "mock-up" symuluje pionowe ułożenie odpadów radioaktywnych w podziemnym składowisku. Stosunkowo mały model jest wykonanym ze stali nierdzewnej cylindrem o średnicy 400 mm i wysokości 600 mm. Jest on symulacją części galerii, w której odpady promieniotwórcze zostaną rozmieszczone. W centralnej części cylindra znajduje się rura o średnicy 140 mm, do której wprowadza się elementy grzejne - symulacja ciepła wytworzonego przez odpady. Temperatura grzania wynosiła 120 stopni Celsjusza. Pierścieniową szczelinę pomiędzy rurą i okładzinami zewnętrznymi wypełniono wstępnie zagęszczonymi blokami bentonitowymi. Większa część bloków jest z czystego bentonitu i pochodzi z osadów Jelsovy Potok oraz Lieskovec. Niektóre bloki zawierają albo 5% koncentratu pirytu do symulacji obecności pirytu w skale galerii lub 5% proszku żelaza w celu określenia interakcji żelazo-bentonit. W eksperymencie nawodnienie jest zapewnione z zewnętrznego źródła wody. Woda jest rozprowadzana za pomocą 23 otworów umieszczonych na zewnątrz bloku. Chemia wody bazuje na składzie oryginalnej wody obecnej w większości obszaru składowiska odpadów promieniotwórczych na Słowacji.

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Elemental and mineral inventory of tailing impoundments near Pezinok, Slovakia and possible courses of action for their remediation

Majzlan J., Brecht B., Lalinska B., Chovan M., Moravansky D., Uhlik P.

Mineralogia

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2010

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Vol. 41, iss. 1/2

55--74

EN

An effective remediation strategy for a polluted site should take the absolute amount of the pollutant(s) into account. Here, we present an elemental budget for As, Sb and Fe in two tailing impoundments of the former Sb-Au deposit near Pezinok, Slovakia. The two impoundments contain 5,740 X103 kg As, 6,360 X103 kg Sb and 50,105 X103 kg Fe. An estimated total Au content in the impoundments is 132 kg. The most abundant minerals in the tailings are quartz, illite, and chlorite. The content of carbonates in the tailings is 3.5-10.5 wt% calcite equivalent and we estimate that the carbonates are sufficiently abundant to buffer the pH at circumneutral values, up to the point when all pyrite decomposes. The possible courses of action are i) do nothing, ii) build an active barrier to capture the released As and Sb, iii) isolate the impoundments from rain and ground water and iv) use the impoundments as a source of Sb and redeposit the waste in a safer form. The simplest approach is to do nothing, which seems to be the most likely course of events, given the current economic, political and societal state of the Slovak Republic. Although this action costs nothing in the short term, it may cause significant damage to the environment, especially to the alluvial sediments and associated water resources in the long term.

4

FEM Analysis and Field Oriented Control Simulation of Bearingless Actuator

Wagner J., Maga D., Sitar J., Uhlik P., Hartansky R.

Machine Dynamics Problems

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2004

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Vol. 28, No. 4

177-184

EN

This paper deals with a bearingless rotary machine that is capable of stable controlling the levitated position of a rotor of an induction motor with a squirrel-cage type rotor under loaded conditions. This bearingless induction machine is capable to serve as an electric motor and also as a magnetic bearing for magnetically levitating and supporting the rotor of the machine. The stator has winding for rotating the rotor and winding for positional control of the rotor in a given radial position. The paper deals with the field oriented control of the bearingless induction machine. Simulations were done with parameters of designed machine based on classical induction motor with mechanical bearings. Designed machine has four-pole drive winding and additional winding to centre the rotor in the machine. Both windings are distributed in the stator slots. Power and voltage rating of the four-pole winding is 3kW/220V and of the two-pole winding for levitation is 250W/30V. Simulation results of the whole system are presented.