제철용 코크스 생산 공정에서 석탄의 용융 특성은 코크스의 강도, 반응성 등 물리적/화학적 특성에 영향을 미치는 중요한 인자이다. 본 연구에서는 일정한 전단 속도에서 점도 해석이 가능한 유동장을 형성하여 유동성의 직접적인 지표가 되는 석탄 용융 점도를 측정할 수 있는 점도 측정 장치 및 실험 방법을 개발하여 용융 석탄의 점도를 측정하였다. 점도 측정 장치는 시료의 양을 최소화하면서 end effect도 줄여줄 수 있는 점도 측정 cell, 최대로 축소된 길이의 회전자, 균일한 내부 온도를 유지할 수 있는 소형의 개폐식 원통형 전기로, 휘발분 성분을 원활히 배출시키는 후드, 토크를 측정하는 회전식 동심 실린더형 점도계로 구성되었다. 일정한 충전 밀도를 위한 충전 기구도 개발되었다. 제작된 장치를 이용하여 11개 석탄의 용융 상태의 점도를 측정하였다. 탄종에 따른 점도의 변화 경향은 Gieseler plastometer에 의한 유동도의 경향과 거의 일치하였으나 점도 측정 영역이 제한됨을 확인할 수 있었다. 또한, 석탄 입도가 증가할 수록, 충전 밀도가 증가할수록 용융 구간이 증가하며, 최저 점도는 감소함을 확인하였다.

The plasticity of coking coal is an important property influencing the strength of metallurgical coke. A molten coal viscometer with well defined flow field under a constant shear rate was designed, and the experimental procedures for reliable viscosity measurements were developed. The viscometer consists of a Searle-type concentric cylindrical cell, the rotor with the shortest possible length, a small split furnace of uniform internal temperature, and the hood for continuous vent of volatiles. The cell dimensions were determined to use the minimum possible amount of coal, while minimizing the end effect. A packing device for uniform packing of coal particles was also developed. The viscosities of 11 molten coals were determined. The trend in the minimum viscosity was in agreements with the trend in the maximum fluidity measured by Gieseler plastometer, but the viscometer showed narrower measurement range than the plastometer. The viscometer also gave the correct trends with the particle size and the packing density: the increase in coal particle size and packing density increased the plastic period and decreased the minimum viscosity.

Molten Coal Viscometer Thermoplasticity

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