• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.532-539
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• 2011

The physical and chemical properties of the dried low rank coals (LRCs) before and after the surface treatment using ozone and ammonia were characterized in this study. The contents of moisture, volatiles, fixed carbon and ash consisting of dried LRCs before the surface treatment were about 2.0, 44.8, 44.9 and 8.9%, respectively. Also, it was composed of carbon of 62.66%, hydrogen of 4.33%, nitrogen of 0.94%, oxygen of 27.01% and sulfur of 0.09%. The dried LRCs was surface-treated with the various dry methods using gases such as ozone at room temperature, ammonia at $200^{\circ}C$ and then the dried LRCs before and after the surface treatment were characterized by the various analysis methods such as FT-IR, TGA, proximate and elemental analysis, caloric value, ignition test, adsorption of $H_2O$ and $NH_3-TPD$. As a result, the oxygen content increased and the calorific value, ignition temperature and the contents of carbon and hydrogen relatively decreased because the oxygen-contained functional groups were additionally generated by the surface oxidation with ozone which plays a role as an oxidant. Also, its $H_2O$ adsorption ability got higher because the hydrophilic oxygen-contained functional groups were additionally generated by the surface oxidation with ozone. On the other hand, it was confirmed that the dried LRCs after the surface treatment with $NH_3$ at $200^{\circ}C$ have the decreased oxygen content, but the increased calorific value, ignition temperature and contents of carbon and hydrogen because of the decomposition of oxygen-contained functional groups the on the surface. In addition, the $H_2O$ adsorption ability was lowered bucause the surface of the dried LRCs might be hydrophobicized by the loss of the hydrophilic oxygen-contained functional groups. It was concluded that the various physico-chemical properties of the dried LRCs can be changed by the surface treatment.