연구홍보포털

논문 초록 (Abstract)

In this study, low-grade coal with high moisture content was dried in a novel disc dryer equipped with a heating plate and rotaryblades. Raw coal was fed into the center of the disc dryer and then was transferr ed from the center of the heating plate to the outside of the plate by t he rotary blades during the drying process. According to a numerical analysis using a model ofa single solid spherical particle witho ut any porosity, the temperature of the coal particles reached that of t he heating plate within 5 mm. The analysis also showed that at a hea ting plate temperature of 150 degrees C, the moisture content of the r aw coal was lowered from 34% to below 3% within 5 min, and all of th e raw coal was dried after 10 min of drying time. Experimental studies were used to investigate the influence of the following factors on th e effectiveness of the novel disc dryer: heating plate temperature , coal feed rate, rotational speed of the rotary blades, drying environ ment, and position of thecoal on the heating plate. When the heating plate temperature was high, the moisture content of the dried coal wa s greatly decreased. However, on the basis of energy-efficiency considerations, it was recommended that the temperature of th e heating plate be maintained at 150 degrees C. Furthermore, a decrease in the coal feed rate could lower the moisture content, and a high r otational speed of the rotary blades could slightly reduce the moisture content as well. In addition, the reduction in moisture content could be remarkably enhanced by using a vacuum pump to remove the evap orated water vapor from the inside of the dryer. The position of the coal on the heating plate was also important. The temperature of the raw coal could be increased without evaporation up to a certain dista nce from the center of the dryer. However, the moisture of the raw co al began to evaporate in a region near the outside of the