Computational fluid dynamics simulation of thermodynamic behaviour of tubular digester

Abstract

The anaerobic digesters have been widely used worldwide and followed by the environmental treatment, biogas (energy source) and biofertilizers can be produced at the same process. The plug flow digester is the most common digester system in Brazil, but it still faces great difficulties of implementation because of the low efficiency. In this context, this work proposes ways of improving the energy efficiency of such a digester. To this end, simulations were performed for this type of digester in order to analyze the thermodynamic behavior. It was possible to verify that the velocity gradient was acceptable for the studied reactor characteristics, that is, 0.054, and the average temperature reached with the heating system was 33ºC, which is considered an optimal temperature for biogas production. The simulation proved to be an important tool in scenarios using the digester model and can be of help when designing new units and in different cases of agitation. However the model used here does not evaluate the thermal changes of the digester plastic blanket due to the simplification of the simulation.