Clean Technology, Vol.19, No.1, 30-37, March, 2013
Experimental Study on Oil Separation from Fry-dried Low-rank Coal
E-mail:
초록
본 연구에서는 함수율 32.3 wt%인 저등급 석탄을 유중증발 건조한 후 고속 원심분리 장치에서 기름을 분리하여 연료 특성을 분석하였으며, 유중증발 건조시간이 6, 10분일 때 석탄의 함수율은 각각 5.0, 4.2 wt%까지 감소하였다. 유중증발 건조 후 석탄의 고위발열량은 11,442.0 kJ/kg-wet에서 27,816.0 kJ/kg-wet로 증가하였다. 유중증발 건조한 석탄을 상온에서 원심분리 장치로 기름을 분리한 석탄의 기름 함량은 15.0 wt%이나 건조 석탄을 80, 100, 120 ℃로 재가열하여 기름을 원심분리하면 각각 9.7, 9.3, 8.5 wt%로 줄어들었으며 석탄 직경별 기름 함량차이는 미약하였다. 원심분리 장치에서 회수한 기름은 유중증발 건조용 기름으로 재사용한다. 저등급 석탄을 대상으로 열중량분석(thermogravimetric analysis, TGA)을 수행한 결과, 건조 후 120 ℃로 재가열한 석탄은 석탄입자 크기에 따른 무게변화는 거의 없었으며 이것은 원심분리 장치 성능이 석탄입자의 크기에는 영향을 받지 않기 때문이다. 또한, 미분열중량 분석(derivative thermogravimetry, DTG)을 수행한 결과에 의하면 원시료 석탄은 400 ℃에서 휘발분이 가스화되면서 피크가 나타났고 유중증발 건조한 석탄의 경우 350 ℃에서 1차 피크, 400 ℃에서 2차 피크가 발생하였다. 1차 피크는 유중증발 건조과정 중에 석탄내부의 수분과 치환된 기름 때문으로 사료되었다. 또한, 80 ℃, 100 ℃, 120 ℃로 재가열하여 기름을 분리한 석탄시료들의 피크가 기름을 분리하지 않은 석탄의 피크보다 작은 것은 원심분리 장치에 의해 기름이 일정량 분리되었기 때문이다.
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.
- Satoru S, Tetsuya D, Takuo S, Kobe Steel Eng. Reports., 53, 41 (2003)
- Sato Y, Kushiyama S, Tatsumoto K, Yamaguchi H, Fuel Process. Technol., 85(14), 1551 (2004)
- Umar DF, Usui H, Daulay B, Fuel Process. Technol., 87(11), 1007 (2006)
- Satoru S, Tetsuya D, Takuo S, Kobe Steel Eng. Reports., 56, 23 (2006)
- Ohm TI, Chae JS, Kim JE, Kim HK, Moon SH, J. Hazard. Mater., 168(1), 445 (2009)
- Ohm TI, Chae JS, Lim KS, Moon SH, J. Hazard. Mater., 178(1-3), 483 (2010)
- Ohm TI, Chae JS, Lim JH, Moon SH, J. Mech. Sci. Technol., 26, 1299 (2012)
- Farkas BE, Singh RP, Rumsey TR, J. Food Eng., 29(2), 227 (1996)
- Farid M, Butcher S, Dry. Technol., 21, 231 (2003)
- Prergrina C, Arlabosse P, Lecomte D, Rudolph V, Dry. Technol., 24, 797 (2006)
- Song H, Min L, Jun X, Sun LS, Li PS, Su S, Sun XX, Fuel, 83(10), 1307 (2004)
- Lee SJ, Chu CP, Tan RBH, Wang CH, Lee DJ, Chem. Eng. Sci., 58(9), 1687 (2003)
- Marinov SP, Gonsalvesh L, Stefanova M, Yperman J, Carleer R, Reggers G, Yurum Y, Groudeva V, Gadjanov P, Thermochim. Acta, 497(1-2), 46 (2010)
- Arenillas A, Rubiera F, Pis JJ, Cuesta MJ, Iglesas MJ, Jimenez A, Suarez-Ruiz I, J.Analy. Pyrol., 68, 371 (2003)
- Wen CY, Lee ES, Coal Conversion Technology, Addison-Wesley Publishing Company Inc., Reading, Massachusetts, 63 (1979)