Low-rank coal upgrading to optimize its utilization as fuel

Abstract

Abstract Indonesia’s coal resources and reserves are mostly categorized as low-rank coal, lignite and sub-bituminous coals. Most of them have a high content of moisture, a low calorific value, and a high tendency to low-temperature oxidation and self-combustion, making them difficult to transport over long distances. To increase the utilization of the low-rank coals, a drying treatment was carried out by heating the coal at a temperature and pressure of 160°C and 3.5 Bar respectively for about 15 minutes. Two low-rank coal samples, from South Sumatra (A coal) and South Kalimantan (B coal) were used in this research. The result indicates that the degree of dewatering of A coal is 89.00% while B coal is 95.5%. B Coal has a higher inherent moisture content which generally has more capillary water which is relatively easier to remove. The higher the degree of dewatering the higher the calorific value degree of improvement. The calorific value of the A coal increased by 27.16% and the B coal increased by 40.65%. The combustion characteristic obtained from the thermogravimetry-differential thermal analysis shows that the A and B upgraded coals have a lower tendency to spontaneous combustion than that of the raw coals.