분류층 가스화기에서 슬래그의 점도 변화는 가스화기 운전 온도을 결정하는 중요한 요소이다. 본 논문에서는 국내 가스화 대상탄 중 결정슬래그의 거동을 보여주는 5개 탄 슬래그의 Tcv를 문헌의 경험식과 Factsage를 이용한 평형계산으로 예측하고, 각 방법의 실용성을 조사하였다. 경험식으로는 두개의 모델이 사용되었는데 각각 회분용융시험의 Th와 슬래그의 5개 주성분 농도를 이용하였다. Th를 이용한 모델은 20~100 ℃ 높은 Tcv를, 5개 주성분을 이용한 모델은 80~120 ℃ 낮은 Tcv를 예측하였다. 평형계산에서는 액상선 온도로 Tcv를 구하였다. 평형계산에 주 4 성분만을 사용하였을 경우 측정된 Tcv보다 높은 온도가 예측되었다. 액상선 온도는 부 성분의 농도에 매우 민감하여 MgO와 Na2O의 추가는 액상선 온도를 낮추어 주었다. 평형계산에서 석탄의 주성분뿐만 아니라 부성분을 모두 포함시켰을 때 측정된 Tcv에 가장 근접한 결과를 얻을 수 있었다. 또한 Cr2O3계열의 내화재가 사용되었을 경우, Tcv의 좀 더 정확한 예측을 위하여 용해 내화재의 농도도 평형계산에 포함시켜야함이 확인되었다.

The slag viscosity is an important factor determining the operation temperature of entrained flow type of gasifiers. The temperature of critical viscosity, Tcv, for 5 crystalline slags was predicted by empirical models and Fact-Sage equilibrium calculations, and the validity of each method was tested. Two empirical models were employed: one using Th from the ash fusion test, and the other using the concentrations of 5 major components. The first model using Th over-predicted Tcv by 20~100 ℃, while the model based on the slag composition under-predicted Tcv by 80~120 ℃. In the equlibrium calculations, Tcv was obtained from the liquidus temperature. When the 4-major component concentrations were used in the calculation, the predicted temperatures were higher than the observed. The liquidus temperature was very sensitive to the concentrations of minor components, and the addition of MgO and Na2O lowered the liquidus temperature. The results with 4 major and 3 minor components most closely described experimentally observed Tcv. In the case that a chromia refractory was used, it was shown that Cr2O3 concentration in the slag also needs to be included for more accurate prediction of Tcv.

Slag Viscosity Tcv Prediction FactSage

Kim SD, Coal Conversion Technologies, Mineumsa, 197-256 (1986)
Childress J, Childress R, “2004 World Gasification Survey, A Preliminary Evaluation,” Presented at 2004 Gasification Technologies Conference, Washington D.C., Oct. 4-6 (2004)
Zheng L, Weidou N, Hongtao Z, Linway M, Energy for Sustainable Development, 7, 57 (2003)
OH MS, BROOKER DD, DEPAZ EF, BRADY JJ, DECKER TR, Fuel Process. Technol., 44(1), 191 (1995)
Moon IS, Cho CB, Oh MS, Energy Engg. J., 11, 149 (2002)
Vargas S, Frandsen FJ, Dam-Johansen K, Prog. Energy Combust. Sci., 27, 273 (2001)
MOCIE Report 1996 N-CO02-P-05, Development of Fundmental Technologies for the IGCC System, Final Report, 192-226 (2000)
Decterov S, Pelton AD, “Thermodynamic Calculation of Gas/Slag/Refractory Equilibria in Coal Gasification,” in Corrosion of Materials by Molten Glass, Amer. Ceram. Soc., 91-103 (1996)
Jak E, Degterov S, Hayes PC, Pelton AD, “Thermodynamic Modelling of the System Al2O3-SiO2-CaO-FeO-Fe2O3 to Predict the Flux Requirements for Coal Ash Slags,” Fuel 77(1/2), 77-84 (1998)
Levin EM, Robbins CR, McMurdie F, Phase Diagrams for Ceramists, The American Ceramic Society (1964)
Cho CB, “Effect of Coal Composition and the Formation of Cystalline Phases on Coal Slag Viscosity,” M. S. Thesis, Hongik University, Seoul (2000)
Kim HB, Oh MS, Energy Engg. J., 13, 282 (2004)