Constructal design of solid state fermentation bioreactors

Abstract

Constructal Design is applied to geometric optimization of an insulated wall bioreactor. The optimization of the bioreactor geometry allows that it to operate, below a certain temperature limit, without external cooling equipment. The possibility of using less equipment shows how geometric optimization can be used as a tool for the ecologically correct management of energy. For the geometric optimization, a mathematical model that represents the solid state fermentation by Aspergillus niger is validated and used to study a column fixed bed bioreactor with fixed volume. The model is solved numerically for an insulated wall bioreactor. According to Constructal Design the shape of the bioreactor is free to change subject to volume constraint and in the pursuit of better performance. The optimal ratio between the diameter and the length of the bioreactor, i.e., the ratio which corresponds to the optimal maximum temperature equal to 35 ºC, is calculated for several inlet velocities, volumetric flow rates and inlet air temperatures.