XRD Structure Evolution Characteristics of Tectonic Coal Under Solvent Extraction

Coal is a kind of sedimentary organic rock with the feature of microcrystalline and crystalloid structure in long-range disorderly and short-range orderly. As coalfication degree increases, coal structure grows more regular. In the coal-forming process, coal body has deformed in different degree due to the destruction of geological structures, and thus the chemical composition and microcrystalline structure of coal have been changed, which have made tectonic coal with different coal body structure formed. In order to study on change law of the microcrystalline structure of coal under geologic structure, the paper is exampled by two kinds of coal with different rank, that is gas coal and lean coal, and investigated on the differences in microcrystalline structure for coal samples with different deformed degree before and after solvent extraction. By means of X-ray diffraction (XRD), the microcrystalline structures of coal samples and their residues were measured. The results show that the solvent extraction rate appear a post relationship with the degree of coal body structure, and the contrasts of the extraction between different deformed coal samples do not alter with the change of solvent species and coal ranks. Meanwhile, under room temperature conditions, the solvent extraction is not enough to alter the contrast relationships of microcrystalline structure parameters between high and low rank coal. The value of aromatic lamellae spacing (d(002)) of lean coal is less than gas coal, and stck high (L-c) and layer numbers (N) is more than gas coal. Further study indicates that the value of d(002) decreases and La increases under the tectonic damaging effects. But the value of the diameter (L-a) does not show obvious regularity at the influence of coal ranks, solvent species and infiltration degree.