4. Conclusions
In summary, THz technique was employed in this research to determine nine coal materials. PCA was used with the input of absorbance spectra over the whole range and PC1 scores were extracted to represent the general absorption effect in the selected range. The significant parameters to evaluate coal quality, including volatile matter and ash, indicated different trend with the increase of PC1. The PC1 dependent volatile matter revealed that anthracite and bituminous coals have clear demarcation point equaling zero of PC1 score. Moreover, 15%, which is a mark to differentiate clean and
meagre coals in China, acted as extremal point reflected in THz spectra. In addition, elemental determination was also realized by building a series of linear and non-linear models between elemental contents and PC1 scores. These results will be significant for parameters’ monitoring and elemental control in coal fields. According to this research, THz technique, combined with PCA method, should be considered as a supplementary technology for qualitative and quantitative characterization, especially on-line determination of key parameters of coal in coal industry.
Acknowledgments
We acknowledge the National Key Basic Research Program of China (Grant 2014CB744302), the Specially Founded Program on National Key Scientific Instruments and Equipment Development (Grant 2012YQ140005) and the National Natural Science Foundation of China (Grant No. 11574401) for the financial support of this work.