Mineralogy and Magnetic Parameters of Burning Coal Waste Piles Materials: A Preliminary Insight

• Type: Article in International Scientific Journal
• Date: 2010

Authors

Joana Ribeiro (Author) FCUP; Helena SantOvaia (Author) FCUP; C. Gomes (Author) Other; Heloísa Ribeiro (Author) FCUP; Z. Li (Author) Other; C. Ward (Author) Other; Deolinda Flores (Author) FCUP

Journal

Title: Geochimica et Cosmochimica Acta

Vol. 74 No. 12, Supplement

ISSN: 0016-7037

Publisher: Elsevier

Indexing

ISI Web of Science

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Abstract (EN): This work describes the changes in mineralogy and magnetic parameters of the waste pile materials from burning and unburned zones in the S. Pedro da Cova, Midões and Lomba areas of the Douro Coalfield, Portugal. X-ray diffraction analysis has provided information about the mineral phases and the reactions that occurred during the combustion process, and hence been used to identify the temperatures reached. The unburned coal waste materials contain quartz, illite, mica (mainly muscovite) and in many cases pyrophyllite. Some of the burnt coal waste samples have similar mineralogy to the unburned materials, but some contain mullite and cristobalite, suggesting that higher temperatures were involved in the combustion process. Lowfield magnetic susceptibility (') and isothermal remanent magnetization (IRM) determinations were used to indicate the source of the magnetic mineralogy and the waste material contamination in burning parts of the S. Pedro da Cova and Lomba piles. In S. Pedro da Cova, the two highest values of ' (1217.60 and 556.22 x10-8 m3/kg) were found in zones where the temperature was higher than 200°C, and in Lomba the two highest values (705.84 and 211.67 x10-8 m3/kg) were found where the temperature was higher than 70°C. These temperatures were measured with a digital infrared thermometer when the samples were collected. In unburned zones ' ranges from 13.58 to 16.62 x10-8 m3/kg. The IRM values of the S. Pedro da Cova samples show that remanence saturation was achieved at a magnetic field lower than 300 mT, suggesting the presence of a low-coercivity structure, magnetite-like phase. However, in the samples from Lomba, the imparted field was insufficient to achieve remanence saturation, probably because ‘hard magnetic structures’ are also present. The ‘Index of Geo-accumulation’ at S. Pedro da Cova and Lomba shows that the samples represent a strong to very strong contamination. Here the highest ' occurs where the combustion temperature was also very high, suggesting that the burning process was the main cause of the magnetic enhancement.

Language: English

Type (Professor's evaluation): Scientific

Notes: Comunicação apresentada na conferência "Goldschmidt 2010: Earth, Energy, and the Environment"