Mr. Martineztarazona et al., CHARACTERIZATION OF COMMON LIGNITE, XYLITIC LIGNITE AND PYROPISSITE VARIETIES OF LOW-RANK COALS, Fuel, 73(11), 1994, pp. 1723-1728
The chemical characteristics of the organic and mineral constituents o
f common lignite, xylitic lignite and pyropissite varieties of Spanish
low-rank coals were studied. Chemical analyses showed distinct differ
ences in the H and O contents of xylitic lignite and pyropissite: the
former is particularly rich in O and poor in H, whereas the reverse is
true for the latter. FT-i.r. spectroscopy showed that the organic mat
ter of xylitic lignite contains abundant hydroxyl and ether groups whe
reas pyropissite is rich in acid/ester and methylene groups. Mineral m
atter was characterized by X-ray diffraction and FT-i.r. spectroscopy
of low-temperature ash. The main minerals found were kaolinite and qua
rtz; illite was detected only in pyropissite. Ca is present in form of
carboxylate salts which react during low-temperature ashing with sulf
ur and nitrogen oxides, leading to formation of sulfate and nitrate ar
tefacts; these species produced the strongest peaks in the X-ray diffr
actograms and FT-i.r. spectra of all varieties. Aluminium, relatively
abundant in xylitic lignite, is probably organic in origin. In additio
n to nine major and minor inorganic elements, 13 trace elements were a
nalysed by X-ray fluorescence spectrometry. These trace elements do no
t exhibit a specific association with any of the lignite varieties and
their concentrations cannot be used as distinguishing characteristics
. In contrast, the chemical characteristics of the organic component a
llow the three coal varieties to be differentiated clearly.