Validation of a Biogas Production Model and Determination of Thermal Energy from Plug-Flow Anaerobic Digesters

摘要

A heat transfer model that predicts thermal energy requirements for plug-flow anaerobic digester operation, and a biogas production model are combined to determine heat available for beneficial uses on the farm. Both models are validated extensively against data measured over a one-year period from an anaerobic digester operating in upstate New York, and the combined models' predictions are in close agreement with measured data. An annual thermal energy requirement for a plug-flow anaerobic digester operation that has an influent manure flow rate of 60 m 3 /day was simulated. The digester consumed 18% of the total thermal energy input for its operation (maintenance heat and heat required to raise the temperature of the influent to the operating temperature), leaving theoretically 82% of the total heat for other beneficial uses. The available heat is reduced by the efficiency of heat conversion of the system used. Biogas prediction is sensitive to changes in the kinetic parameter and even more so to changes in influent total volatile solids (TVS), and the relationship is linear. A 0.01 increase in the kinetic parameter resulted in a 7.6% decrease of biogas production, and a 1 kg/m 3 increase in TVS resulted in a 9.5% increase in daily biogas production. At a flow rate of 60 m 3 /day, preheating influent manure by 1°C resulted in heat savings of 224.3 MJ/day