ENERGY-TRANSPORT IN A HIGH-SOLIDS AEROBIC DEGRADATION PROCESS - MATHEMATICAL-MODELING AND ANALYSIS

An energy transport model has been developed to capture the temporal a nd spatial changes in temperature observed within a high-solids degrad ation 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 hea t generation component was expressed as an empirical equation develope d from pilot-scale experimental oxygen depletion rate and temperature data. The model was simplified to permit a semianalytical solution usi ng the method of characteristics. The model was validated by comparing temperature profiles simulated by the model to pilot-scale experiment al profiles. The time-dependent solution of the characteristic equatio n was found to follow the experimental profiles well. Using the time-d ependent solution, a regression analysis was performed on pilot-scale data to determine a heat generation yield of 9500 kJ/kg of O-2 consume d. The spatial-dependent solution of the characteristic equation was f ound to follow the experimental profiles well during the early stages of the process. Deviations were observed as temperature and time incre ased. These deviations were concluded to be a result of the empirical heat generation component of the model.