Biotechnology Progress, Vol.13, No.3, 238-248, 1997
Energy-Transport in a High-Solids Aerobic Degradation Process - Mathematical-Modeling and Analysis
An energy transport model has been developed to capture the temporal and spatial changes in temperature observed within a high-solids degradation process employing forced aeration. The model components include terms for energy removed through the bulk flow of air, heat generated from microbial activity, and energy accumulated in the matrix. The heat generation component was expressed as an empirical equation developed from pilot-scale experimental oxygen depletion rate and temperature data. The model was simplified to permit a semianalytical solution using the method of characteristics. The model was validated by comparing temperature profiles simulated by the model to pilot-scale experimental profiles. The time-dependent solution of the characteristic equation was found to follow the experimental profiles well. Using the time-dependent solution, a regression analysis was performed on pilot-scale data to determine a heat generation yield of 9500 kJ/kg of O-2 consumed. The spatial-dependent solution of the characteristic equation was found to follow the experimental profiles well during the early stages of the process. Deviations were observed as temperature and time increased. These deviations were concluded to be a result of the empirical heat generation component of the model.