Ohm TI  Chae JS  Lim JH  Moon SH

Vol. 19,  No. 1, pp. 30-37, Mar.  2013

Low-rank coal Fry-drying technology Pyrolysis Combustor Oil separation

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Low-rank coal with high water content (32.3 wt%) was dried by fry drying, and the fuel characteristics of the dried coal from which the oil was separated by using a high-speed centrifugal separator were analyzed. After fry drying for 6 min and 10 min, the water content decreased to 5.0 wt% and 4.2 wt% respectively. The higher calorific value (HCV) of the coal increased remarkably after fry drying, from 11,442.0 kJ/kg-wet. The oil content of the fry-dried coal was 15.0 wt% and it decreased with an increase in the reheating temperature: 9.7 wt% at 80 ℃ to 9.3 wt% at 100 ℃, and then to 8.5 wt% at 120 ℃. The recovered oil could then be reused. According to of thermogravimetric analysis (TGA), there was no difference in the weight loss patterns of the coal samples with different coal diameters at a reheating temperature of 120 ℃. This was because the amount of oil separated by the centrifugal separator was affected by the reheating temperature rather than the coal diameter. And derivative thermogravimetry (DTG) curves of raw coal before the fry-drying process, a peak is formed at 400 ℃ in which the volatile matter is gasified. In case of the fry-dried coal, the first peak is generated at 350 ℃, and the second peak is generated at 400 ℃. The first peak is caused by the oil that is replaced with the water contained in the coal during the fry-drying process. Further, the peaks of the coal samples in which the oil is separated at a reheating temperature of 80 ℃, 100 ℃, 120 ℃, respectively are smaller than that of the coal in which the oil is not separated, and this is caused by that the oil is separated by the centrifugal separator.