| 초록 |
Biomass is known as an important renewable alternative energy resource. Sawdust was chosen as a biomass which is suitable for domestic power plants application. By itself, sawdust dose not fluidize well and it exhibits channeling with the Geldart C powder behavior. Therefore, sand particles were added as an inert component to improve fluidization quality of sawdust The characteristic velocities of the initial fluidization velocity (Ufi), the minimum fluidization velocity (Umf), and the complete fluidization velocity (Ufc) of the mixture of sand and sawdust were determined in a fluidized bed. Umf of the mixture increases exponentially up to 14 cm/s (2.5Umf) with increasing weight fraction of sawdust. The values of Ufi and Ufc exhibit similar trends with the variation of Umf. The existing correlations to predict Umf of the binary mixtures can not be used successfully due to the peculiar fluidizing behavior of sawdust. To predict Umf of sawdust, a new correlation as a function of Reynolds and Archimedes numbers was developed. The segregation between the two components starts at the gas velocity between Ufi and Ufc. Beyond Ufc (17 cm/s), the well-mixed state of the mixture of sawdust and sand can be attained in the whole bed. |
