Doppleritization of xylitic coal in the light of petrographic and chemical investigations |
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| Authors: | Marian Wagner |
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| Institution: | Institute of Fuel Materials, University of Mining and Metallurgy in Cracow, al. Mickiewicza 30, 30-059 Kraków Poland |
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| Abstract: | The paper presents the results of petrographic and chemical investigations of xylitic coal, xylite and their ash. As is known, a xylitic coal has the function of a lithotype whereas xylites are inclusions brown coals only. All these xylites were arranged according to the increasing degree of doppleritization of xylem in the sequence: common xylite, poorly, moderately and intensely doppleritized varieties, dopplerite coal. The distinctive criteria were their differentiated physical properties, which are also reflected in the variable petrographic and chemical compositions. The petrographic differences result from the replacement of textinite by ulminite and gelinite, while the differentiation of the chemical constitution is due to the increasing carbon content and the increasing number of functional groups that determine the aromatic nature of the internal structure of the coal. Infrared absorption spectroscopy, Raman spectroscopy and chemical analysis of ash have shown that the aromatization of coal and the resulting increase in the degree of order of the structural unit are due to the formation of organomineral compounds in the course of doppleritization. It appears from the investigations that the doppleritization of vegetable matter gives rise to gels that are a mixture of organo-mineral humic compounds. The process of humification leads to the formation of gel made up of humins. It follows then that there are two ways of initial coalification of plant material, both referred to as biochemical gelification. |
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