Sixteen coal samples from the No. 4 and 5 Coals of Huaibei Coalfield were collected by cutting channels downwards from two coal faces. The samples were stored immediately in plastic bags to prevent contamination and weathering. The samples were air-dried, milled and split until a representative portion of 0.5 kg was obtained. The split was then pulverized to pass 100-mesh sieve and dried for 12 hours in a desiccator. Elemental abundances of the samples were determined using an elemental analysis apparatus (Vario Elementar and Heraeus CHN-O-RAPID).
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