According to coal lithotypes, the bottom, parting, roof,
and 15
coal samples were collected by finely partitioning the M9 seam from
the Renjiazhuang Mining District, Ningxia, China. Conventional chemical
analysis, optical microscopy, scanning electron microscopy equipped
with energy-dispersive X-ray spectrometry, X-ray diffractometry, inductively
coupled plasma atomic emission spectrometry, inductively coupled plasma
mass spectrometry, and atomic absorption spectrophotometry techniques
were used on these samples to research the vertical variation between
geochemistry and mineralogy in the high-sulfur coal. The weighted
average content of total sulfur calculated from 15 coal samples is
3.07%, which belongs to the high-sulfur coal. However, the contents
of morphological sulfur of 15 piles are significantly different: the
contents of pyritic and organic sulfur are observed to range from
0.02 to 1.55% and from 1.88 to 3.91%. The results show that these
differences are mainly controlled by marine conditions and the contents
of organic matter and kaolinite. The mineralogy of the M9 coal is
dominated by kaolinite, followed by dolomite, and it also contains
minor amounts of illite, feldspar, pyrite, siderite, hematite, chalcopyrite,
calcite, and marcasite. Moreover, pyrite is the main sulfide in coal,
and agglomerated chalcopyrite and granular galena are partially visible.
The forms of pyrite include fine-grained, spherical, irregular block-shaped,
and clumps. Trace elements are mainly carried by pyrite and ash so
that physical coal cleaning can be applied to partially remove them,
while thalassophile elements Na, Ca, and Mg are closely related to
organic sulfur, indicating that the coal blending can be used to decrease
their contents.
