AUTHORS: Bruno Valentim, Paula Gonçalves, Alexandra Guedes, Luminita Georgeta Popescu, Georgeta Predeanu
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ABSTRACT: The combustion of coal generates coal combustion products (CCPs) such as boiler slag, fly ash and bottom ash that may be used in construction, manufacturing, environmental remediation, and other industries. However, these CCPs are may be in part or globally landfilled due to environmental and economic factors. The bottom ash landfilled at Ceplea Valley (Gorj county, Romania) is a matter of serious environmental concern, and its utilization may be based on the fractionation of this material since its global utilization was not possible due to the Romanian regulation. Therefore, this study aims to demonstrate that the sequential utilization of magnetic separation equipment may provide bottom ash fractions with different types and volumes volume of Fe-bearing morphotypes. For this purpose, one composite sample representative of the landfill was successively fractionated using a ferrite hand magnet, an Nd hand magnet, and a Sterns separator at 10500 Gauss and 18000 Gauss. The global sample and the magnetic fractions were then petrographically characterized via reflected light microscopy using oil immersion objectives and via scanning electron microscopy with X-ray microanalysis (SEM/EDS). As a result of the utilization of these equipment’s the petrographic results show that the Fe-rich morphotypes were almost all collected in the first step of the magnetic separation, partially baked clay is more concentrated in the intermediated steps of the process, whereas the char and the quartz concentration was strongly increased in the remaining sample. The SEM/EDS results show that after the first magnetic separation process the aluminosilicate glass and partially baked clay morphotypes only contain residual amounts of Fe. Therefore, a magnetic separation process via ferrite magnet only is enough to remove the majority of the ironrich particles from the bottom ash landfilled at Ceplea Valley. However, a further separation step with a Nd magnet or a magnetic separator at 10-11 MGauss is needed to remove the particles with minor amounts of Fe
KEYWORDS: petrography; ferrospheres; calcispheres; magnesiaspheres.
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