Natural Frequency of Coal: Mathematical Model, Test, and Analysis on Influencing Factors

Table 1

Proximate analysis results of coal samples.

Type of coal	Proximate (wt%)
	Lignite	5.82	9.56	35.88	48.74
Bituminous	3.71	11.30	27.17	57.82
Anthracite	1.72	8.06	15.73	74.49

Note: M_ad: moisture content in the experimental coal sample; A_ad: ash content on an air: dried basis; V_ad: volatile matter content on an air: dried basis; FC_ad: fixed carbon content on an air-dried basis.