KOH 첨가에 의한 석탄 및 유동사의 응집특성에 대한 실험적 연구 = Experimental study on the agglomeration characteristics of coal and silica sand by addition of KOH

다국어 초록 (Multilingual Abstract)

The agglomeration characteristics of coal and silica sand were investigated under various conditions using mixedsamples consisting of coal, silica sand, and potassium hydroxide, which is an agglomeration accelerator. The samples were prepared by either physically mixing or using aqueous solutions. The experiments using the physically mixed powder sampleswere performed with a two hour reaction time. The results showed that the number of aggregates generated increased as thereaction temperature and the total potassium content increased. The experiments using aqueous solutions were performed at 880℃, which is the operating temperature of a fluidized bed boiler, and at 980 ℃, which assumes a local hot spot. The amount ofagglomeration generated as the reaction time increased and the total potassium content increased was identified. In theexperiment performed at 880 ℃, the amount of aggregate generated clearly increased with the reaction time, and in theexperiment performed at 980 ℃, assuming a local hot spot, a large amount of aggregate was generated in a relatively short time. The aggregates became harder as the potassium content increased. When the total potassium content was less than 1.37 wt.%, theaggregates were weak at both temperatures and collapsed even with a slight impact. Additionally, the surface characteristics of thesilica sand and ash aggregates were observed by SEM-EDS analysis. The analysis revealed a large amount of potassium at thebonding sites. This result indicates that there is a high possibility of aggregation in the form of a eutectic compound when thealkali component is increased.

국문 초록 (Abstract)

본 연구에서는 석탄과 유동사 그리고 응집가속물질인 수산화칼륨(KOH)을 혼합한 시료를 이용하여 다양한 조건에서 응집특성을 파악하였다. 응집실험은 전기로에서 수행하였으며 샘플시료는 두 가지 방법으로 제작하였다. 첫 번째 방법은 수산화칼륨 분말시료를 석탄과 유동사에 물리적으로 혼합하는 방법이며 두 번째 방법은 수산화칼륨을 수용액으로 만들어 석탄과 유동사에 혼합하여 만드는 방법으로 제작하였다. 물리적으로 혼합한 분말시료 실험조건의 경우 동일 반응시간인 2시간 조건에서다양한 반응온도와 총 칼륨 함량에 따른 실험을 수행하였다. 실험 결과 반응온도 및 총 칼륨 함량이 증가할수록 응집물 발생량이 증가하는 결과를 나타내었다. 수산화칼륨 수용액을 이용한 실험 조건은 일반적인 유동층 보일러의 운전온도인 880 ℃와보일러 내 국부적인 고온 영역을 가정한 980 ℃ 조건에서 각각 수행하였다. 분말실험과 동일하게 반응시간 및 총 칼륨 함량 증가에 따라 생성되는 응집물 발생량을 파악하였다. 실험 결과 반응온도 880 ℃ 조건에서는 반응시간 증가에 따라 응집물 발생량 증가가 뚜렷하게 나타났다. 국부적인 고온 영역을 가정한 980 ℃ 조건에서는 상대적으로 짧은 시간 안에 많은 양의 응집물이 발생하는 결과를 보였다. 응집물의 굳기는 칼륨 함량이 증가할수록 점점 단단해지는 특성을 나타내었다. 총 칼륨 함량이1.37 wt.% 이하일 경우 두 반응온도 모두에서 굳기가 약해 약한 충격에도 부서지는 결과를 보였다. 추가적으로 SEM-EDS 분석을 통해 유동사 응집물과 재 응집물의 표면특성을 관찰하였다. 분석 결과 융동사 응집물과 재 응집물 내 결합 위치에서 다량의 칼륨 성분이 검출되었다. 이 결과를 통해 알칼리성분이 많아질 경우 공융화합물 형태의 응집이 발생할 가능성이 높음을 파악하였다

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