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Heavy-Media Separation
Published in S. Komar Kawatra, Advanced Coal Preparation and Beyond, 2020
Organic heavy liquids are generally halogenated hydrocarbons, such as perchloroethylene, carbon tetrachloride, bromoform, and tetrabromoethane, although lower-density organic liquids, such as gasoline and benzene, are also sometimes used. The heavy liquids that are most commonly used are given in Table 4.9. These have specific gravities as high as 3.31 and have the advantages that they are stable, immiscible with water, have low viscosities, and the specific gravity of the liquid can be easily regulated by mixing the liquids in the proper proportions. Their disadvantages are that they are for the most part very toxic and quite expensive. As a result, these liquids are used exclusively for laboratory sink–float analyses and other quality-control applications, although some pilot-scale attempts have been made to develop an industrially practical separator based on true heavy liquids. One of the more successful attempts was the Otisca process, which used trichlorofluoromethane (Freon-11) as the heavy liquid (Keller, 1982). This liquid had the advantage that it was essentially nontoxic and could be easily recovered by evaporation because of its low boiling point. Because of concerns about its effect on atmospheric ozone, use of freon on an industrial scale has been heavily regulated, and it is unlikely that it would be possible to use it for coal cleaning. More recent work has been conducted using methylene chloride/tetrachloroethylene mixtures (Durney et al., 1991, 1992), which are reported to work well in the laboratory, but are toxic. However, at a plant scale, methylene chloride dissolved the pump seals, spilled all over the floor, and was not tried again.
Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Density differences can also help in the separation of minerals. In the laboratory, researchers separate crushed rock into mineral components by “floating” samples in liquids of different densities. In these heavy liquids, which are much denser than water, minerals separate as some float and others sink according to their specific gravities. In mining operations, ore minerals are often separated from valueless minerals by using gravity separation techniques that depend on density differences. This occurs in natural systems, too. Placer gold deposits form when gold from weathered rock, because of its high specific gravity, concentrates in streambeds.
A Densimetric Analysis of Flotation Concentrate from Kupferschiefer-type Copper Ore
Published in Mineral Processing and Extractive Metallurgy Review, 2021
Andrzej Luszczkiewicz, Alicja Bakalarz, Magdalena Duchnowska, Piotr Karwowski
One of the laboratory methods of analysis in the mineral processing is gravity separation of ground material in heavy liquids. This method, often referred to as densimetric analysis, makes the separation of fractions with a defined density range with very high precision possible. Laboratory tests in this analysis assume a perfect separation (Berger and Yefimov 1962). Densimetric analysis in the mineral processing is used to assess the efficiency of gravity separation processes (Das and Sarkar 2018; Majumder and Barnwal 2006; Wills and Finch 2015) as well as broadly in mineralogical studies in which heavy liquids are used to separate minerals according to density, e.g., heavy minerals from clastic materials (raw materials) (Commeau, Poppe and Commeau 1992; Gregory and Johnston 1987; Luszczkiewicz 2002; Morton 1978). Gravity separation methods in the beneficiation of non-ferrous ores are sometimes used as a process supporting the recovery of valuables from flotation by-products and tailings (Katwika et al. 2019).
Comparative study on mineralogy and beneficiation potential of western Crete iron ores
Published in Applied Earth Science, 2020
Antonios Stratakis, Evangelos Petrakis, Nikolaos Katzagiannakis, Georgios Alevizos
In the past, iron ore was mostly mined from high Fe grade (>62 wt-%) banded iron-formation (BIF) hosted-deposits mainly existing in Australia, Brazil, Canada, South Africa and the United States of America. However, the rapid increase of the exploitation of iron ores has resulted in a dramatic depletion of known high-grade deposits. This, in turn, has led mining companies to process and utilize lower-grade iron ores, in order to satisfy future demand (Zogo 2009). In light of this, there is an urgent need to improve the iron ore quality at the stage of raw material preparation. The most common approaches of upgrading iron ores are the beneficiation techniques which separate iron-bearing minerals from gangue minerals e.g. quartz (SiO2) and calcite (CaCO3) (Nomura et al. 2015). These techniques include magnetic separation (Song et al. 2002), froth flotation (Luo et al. 2016; Shrimali and Miller 2016; Yu et al. 2017) and heavy liquids separation (Alevizos et al. 2018). Reduction roasting and microwave heat treatments are also some of the techniques that have received much attention in recent years (Li et al. 2010; Rath et al. 2016). Furthermore, the beneficiation of iron ores is intimately linked to their mineralogical characteristics, intergrowth in mineral phases and the inclusions of gangue minerals. Thus, this study aims to investigate the mineralogical features of low-grade western Crete iron ores, the beneficiation potential of these ores and the effective removal of impurities associated with iron ore phases, issues that have not been extensively investigated so far.
A Detailed study of Applying Gravity Separation to Lead and Zinc Carbonate Ore for Smithsonite Concentration Using DMC
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Ali Ebtedaei, Akbar Farzanegan
According to the density of the gangue and valuable particles of this lead and zinc ore, heavy liquids of Bromoform (Tribromometan-CHBr3), Tetra-bromoethane (TBE-C2H2Br4) and Diiodomethane (methylene iodide-CH2I2) can be used in the laboratory heavy-liquid tests for the appraisal of gravity separation technique. To investigate the amenability of the ore to gravity separation, the authors collected a composite sample from the feed (coming from the ROM stockpile) to the DMC over a period of 1 week. The sink-float evaluations were done as explained in Sections 2.2.1 and 2.2.2.