In a circulating fluidized bed (7.8 cm - ID × 250 cm-high), flow regime of coal-air system at room temperature and coal combustion efficiency and temperature profiles have been determined.
Domestic anthracite coal having heating value of 4870 Kcal/Kg was employed. Coal particle sizes were varied 0.205 and 0.395 mm for flow regime and 0.710 mm for coal combustion studies.
The transition velocities between bubbling and turbulent beds and the transport velocities between turbulent and fast beds have been determined by means of measuring pressure fluctuations with air velocity and measuring the time of particle entrainment with air velocity, respectively.
The transition velocities between bubbling and turbulent beds and the transport velocities between turbulent and fast beds were found to be 70 and 158 cm/sec for particle size of 0.205 mm and 120 and 226 cm/sec for particle size of 0.395 mm, respectively.
In a circulating combustion system, combustion efficiency was higher in turbulent bed than that in bubbling bed. Also, combustion operations can be easily maintained at much lower bed temperature in turbulent bed than that in bubbling bed.
Combustion efficiency increased with increasing excess air for combustion of coal. The variation of bed temperature along the bed height was comparatively small in turbulent bed than in bubbling bed.
상온 및 고온 순환유동층(내경- 7.8cm × 높이-250cm)에서, 석탄-공기계의 흐름 특성과 연소효율 및 온도분포의 특성을 결정하였다. 국내 무연탄(발열량 4,870 Kcaℓ/kg)을 사용하여, 흐름 특성의 경우 입자경은 0.205mm 및 0.395mm, 연소 특성의 경우 입자경은 0.710mm로 변화시켜 사용하였다.
Bubbling 및 Turbulent bed 의 경계유속은 압력강하의 파동임계점에서, Turbulent 와 Fast bed 의 경계유속은 유동층의 소멸시간의 함수로서 결정하였다.
그 결과 Bubbling 및 Turbulent bed 의 경계유속과 Turbulent 와 Fast bed 의 경계유속은 0.205mm의 경우 각각 70cm/sec, 158cm/sec 이고, 0.395mm인 경우 각각 120cm/sec, 226cm/sec 로 결정하였다.
순환 유동층에서 연소실험 결과 Turbulent bed 의 흐름 특성인 경우가 Bubbling bed 의 경우보다 연소효율이 높고, Bed 온도가 낮은 영역에서 조업이 가능하였다. 또한 연소에 필요한 공기량보다 많은 과잉공기의 증가에 따라 연소효율도 증가하였고, Turbulent bed 에서 bed 의 층 높이에 따른 온도 변화는 bubbling bed의 경우보다 작음을 관찰하였다.
