Axial dispersion in metal foams and streamwise-periodic porous media

We present a study on the axial dispersion in metal foams and laser sintered reactors. Commercially available metal foams of 20 and 30 ppi are compared to a designed streamwise-periodic structure in terms of axial dispersion coefficients and pressure drops. Therefore tracer pulse experiments were performed and post processed by means of a deconvolution method. The Peclet number Pep based on the pore size is ranging from 5×1045×104 to 8×1058×105 which is attributed to the increased velocities due to the high porosity of the material compared to fixed bed reactors. The attained dispersion coefficients ranging from 1.3×10−41.3×10−4 to 6.7×10−3m2/s demonstrate the trend of packed beds and common packing materials and increase monotone with the Peclet number Pep. The pressure drop versus the interstitial bulk velocity follows the Forchheimer equation and can be described by the conventional Ergun model for all investigated porous media. The parameters obtained correspond to values found in literature. The results of this study show the high potential of foam reactors for catalyst driven reactions. They provide the same or even a higher surface area per volume of catalyst bed while inducing a much smaller pressure drop than corresponding fixed beds.