UBC Theses and Dissertations
Coal drying and comminution in a spouted bed Sun, Shang Liang
The simultaneous comminution and drying of coal in spouted beds at various temperatures and structural conditions was studied in a column with 152 mm internal diameter. Size reduction in the spouted bed occurs by three different mechanisms: impaction, shear (attrition) and crushing. The size reduction process depends on the physical parameters and the operating conditions in the spouted bed. The key parameters are the design features of the insert, the spouting velocity, the chosen feedrate and the drying temperature. The feedrate for a continuous run can be determined from the instantaneous production rates of the related semi-batch run at the same operating conditions. In this study, the operating conditions were kept constant in each run, except for the inlet gas temperature, while the grinding medium was either glass beads or a special static insert. The results show that the size reduction rate is more rapid with the special insert than with the glass beads. At elevated temperature the rate of size reduction is also more rapid than that at room temperature. The moisture content and particle size distribution of the products with various inlet gas temperatures were measured for each run. The particle size distribution of the product was dependent on the outlet gas velocity. The energy input to a spouted bed during a comminution and drying operation includes both kinetic energy and thermal energy. The kinetic energy has a direct effect, that is, it provides comminution energy to the particles, whereas the thermal energy influences the comminution of the particles due to the change in their physical properties. These two kinds of energy can complement each other and improve both the efficiency and the capacity of the comminution. The total energy equation, therefore, can provide a simple method to estimate the energy requirement for the coal comminution.
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