Devolatilization of coal of Northeastern India in Argen. Air, and Oxygen -Enriched Air under Fluidized Bed Conditions : Author
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Devolatilization is the first step in most coal conversion processes such as combustion, gasification and liquefaction. It has a significant influence on the subsequent stages of processing. Oxygen-enriched air can increase the combustion efficiency, boiler efficiency, and sulfur absorption efficiency of atmospheric fluidized bed combustion (AFBC) boilers, and other combustion systems which use coal. Devolatilization of five coals having volatile matter in the range of 31 to 41% has been studied in argon, air and oxygen-enriched air under fluidized bed conditions at 1123 K and atmospheric pressure. The experiments with oxygen-enriched air were performed using air containing 30% oxygen. The diameter of the coal particles varied between 4 and 9.5 mm. The variation of devolatilization time (tv ) with particle diameter (dv ) was expressed by the correlation, n tv = Adv , where A and n are the parameters of the correlation. The variation of mass of coal particle with time was described by an exponential correlation, ( ) ( ) 0 0 1 exp m V V V V ct D = + D D D D D D D , where c and m are the correlation parameters. The superficial gas velocity was found to have a significant effect on the rate of devolatilization. The devolatilization rate increased with the increase in the oxygen concentration in the fluidizing gas. Therefore, the parameters of the correlations were further correlated with the superficial gas velocity and oxygen concentration. The correlations developed in this study fitted the mass versus time profiles of the coal particles during devolatilization in a satisfactory manner. The same correlations were found to be appropriate for predicting devolatilization of a batch of coal particles. The correlations developed in this study will be useful for the design of fluidized bed combustors....
Supervisor: Pallab Ghosh & Paruchri Gangadhar Rao