Alkaline leaching of coal by the mechanochemical treatment

The possibility of application of a new process GACL (Grinding and Aqueous Caustic Leaching) for the reduction of mineral components in the brown coal Nováky was tested. The simultaneous grinding and chemical leaching enable us to extract 41 % total sulphur, 95 % arsenic and to reduce the ash content to 43 %. The process proceeds at the atmospheric pressure, temperature 90oC and in diluted NaOH solutions (5 %)

Recent knowledge about the role of bacterial adhesion in coal preparation

V nadväznosti na flotáciu pyritu v uhlí sú zhrnuté súèasné poznatky o vplyve fyzikálno-chemických vlastností buneènej steny baktérie Thiobacillus ferrooxidans na jej adhéziu na povrch rôznych minerálov a uhlia. Aplikovaním modelu mikrobiálnej adhézie (kvarla, J. Chem. Soc. Faraday Trans., 89, 1993, p. 2913-2921) a vyuitím známych parametrov vstupujúcich do tohoto modelu bolo zistené, e k (reverzibilnej) adhézii T. ferrooxidans dochádza spravidla v sekundárnom minime. Pre posúdenie monosti vyuitia tohoto modelu na objasnenie selektívneho prichytenia T. ferrooxidans na pyrit je vak potrebné doplni chýbajúce údaje vstupujúce do tohoto modelu

Utilization of ferrofluids in coal preparation

The contribution deals with the possibilities of ferrofluid application as a separation medium and a selective wetting agent with the aim of desulphurization and ash content decreasing of brown coal from Slovak deposits. The influence of magnetic field induction on sulphur and ash content in the products of magneto-hydrostatic separation was observed. The adsorption of ferrofluids on the surface of coal was observed. The ferrofluids cause above all the change of magnetic properties and they increase the separability of materials under magnetic field

Technology GRAVIMELT and possibilities of their application in preparation of Slovak brown coal

The results of alkaline treatment tests on Slovak brown coal (from Nováky, Handlová and Cíge¾ localities) using the MCL procedure (Gravimelt) are presented in this paper. On the basis of conclusions of an optimal variant of the technology, the samples were pre-treated and submitted to a subsequent test at the NAOH/coal ratio = 1.0. The recovery of chemically treated coal, effectiveness of desulphurization and ash removal were assessed. This treatment procedure is less suitable for Slovak brown coal

CAPTO method application to the quality assessment of Slovak brown coal

This paper describes the principle and application of CAPTO (Controlled - atmosphere programmed - temperature oxidation) method for the sulphur content valuation in coal. The principle of CAPTO consists in mixing the coal with an inert material (WO3) and oxidation of the sample by a linear increase of temperature to 1000oC. The evolved gases (CO2, H2O, SO2 and NO2) are analyzed by infrared sensors. The method enables the determination of different sulphur forms (sulphidic, elemental, sulphate, organic aromatic and organic non-aromatic), hydrogen, carbon and humidity. The results on Americal coal Illionois No. 6 and Slovakian brown coal Nováky serve as an illustration of the CAPTO method possibility

Application of the multigravity separator Mozley in the preparation of steam coal from the Cíge¾ Colliery

The contribution presents the results of tests on a gravity separation of steam coal from the Cíge¾ Colliery. The preparation tests were carried out in a multigravity separator Mozley. The preparation conditions and the quality of obtained products are summarized in tables. The introduced results such as the ash content in washed coal (from 44 to 57%) and an ash recovery into reject (from 5 to 12%) point to the fact that the application of the Mozley separator is not advisable for the steam coal preparation from the Cíge¾ Colliery

The new knowledge on the application of the advanced clean coal technology

The results of the project ID 031 - 95 " Slovak brown coal" are presented in the paper. From the scientific knowledge point of view, the mechanic-chemical alkaline leaching, the clarification of mechanism of accompanying phenomena of MCL procedures and the influence of the radiation pre-treatment represent the priority. The study of the surface and adhesive properties will contribute to a broadening the knowledge on microbial adhesion in coal treatment. The advanced treatment procedures are not suitable for the Slovak brown coal treatment. From the physical pre-treatment procedures, the gravitation treatment in hydrocyclones without the heavy material (hydrocyclone "only" water) is perspective under condition of the innovation of coal mining aims

Selected results of the slovak coal research

The contribution gives the review of Slovak brown coal research in the last 10 years. The state and development trends of the coal research in Slovakia from the point of view of the clean coal technologies application are described. Some selected results which have been obtained at the Institute of Geotechnics of the Slovak Academy of Sciences are also introduced

A complementary study of hydrophobicity and surface charge of Thiobacillus ferrooxidans. The effect of ionic surfactants

Hydrofóbnos a náboj buneènej steny sú rozhodujúce faktory poèiatoèného tádia adhézie baktérií na tuhé povrchy. Hydrofóbnos bakteriálnych buniek sa posudzuje najmä dvoma spôsobmi. Ako prvý spôsob, umoòujúci kvalitatívne urèenie hydrofóbnosti, sa vyuíva sledovanie adsorpcie iónogénnych surfaktantov, resp. elektroforetickej pohyblivosti ktorá ju sprevádza. Druhým spôsobom semikvan-titatívneho stanovenia hydrofóbnosti buniek je testovanie ich interakcie s kvapalnými uh¾ovodíkmi v tzv. BATH teste (Bacterial Adhesion To Hydrocarbons). Stanovenie hydrofóbnosti pouitím BATH testu je vak komplikované z dôvodu spolupôsobenia elektrostatickej interakcie, ktorú môme opä odhadnú z elektroforetickej pohyblivosti buniek.Cie¾om práce bolo posúdi hydrofóbnos buniek Thiobacillus ferrooxidans oboma uvedenými spôsobmi zvlá a v kombinácii, tj. BATH test bol uskutoènený v prítomnosti surfaktantov a súèasne bola meraná elektroforetická pohyblivos buniek metódou ELS (Electrophoretic Light Scattering). V neprítomnosti surfaktantov bola zistená záporná elektroforetická pohyblivos (náboj) a silná hydro-filnos povrchu baktérií. V prítomnosti katiónaktívneho surfaktantu (CTAB) sa v dôsledku jeho postupnej adsorpcie elektroforetická pohyblivos zniovala (dokonca pri vysokých koncentráciách prechádzala do kladných hodnôt). Súèasne sa indukovala hydrofóbnos buniek. Po prekroèení urèitej CTAB koncentrácie sa vak hydrofóbnos zaèala zniova, hoci elektroforetická pohyblivos bola stále na zostupe (èo svedèí o neustávajúcom raste adsorpcie CTAB). To svedèí o adsorpcii CTAB katiónov s polárnymi skupinami orientovanými smerom k povrchu buniek a hydrofóbnymi reazcami smerom do roztoku pri nízkych koncentráciách CTAB a o opaènej orientácii pri vyej koncentrácii CTAB. Po pridaní aniónaktívneho surfaktantu (SDS) k adsorpcii nedolo, o èom svedèí iba mierne zvýenie zápornej elektroforetickej pohyblivosti a skoro vôbec neovplyvnená pôvodná hydrofilnos buniek.Na základe toho môme predpoklada, e elektrostatické interakcie ovplyvòujú hydrofilnos/hydrofóbnos buniek T. ferrooxidans BATH testom iba v malej miere

Caustic magnesite - preparation and properties

The paper presents the selected results of the thermal decomposition of natural magnesite for preparation of active MgO. At the temperature of selective decomposition of magnesite intermediate phases exhibiting enhanced reactivity and low mechanical stability are formed. Evolution of carbon dioxide is accompanied by decrepitation of active magnesia. The selective decomposition and the accompanying decrepitation of the solid may be conveniently used as a way of enriching the chemically active magnesia by simple screening. Magnesia is accumulated in the undersize fraction, whereas undecomposed calcium carbonate and silica remain in the oversize fractions