A fundamental investigation of gas/solid mass transfer in open-cell foams using a combined experimental and CFD approach

The Influence of the Washcoat Deposition Process on High Pore Density Open Cell Foams Activation for CO Catalytic Combustion

“…The usual methodology to analyze the mass transfer performances of structured catalyst is the dimensionless form In the entire span of tested flow rates, all the tested foams overcame the performances of a reference 900/2.5 square-channel honeycomb calculated at 1.4 bar and 350 • C, a temperature where the foams were assumed to be in the diffusion-limited regime considering only asymptotic contribution [35]. As already reported in [2], the mass transfer coefficients of foams increased with increasing flow rate, while the asymptotic value for honeycombs was independent of the latter. Foams with 580 µm cells exhibited higher volumetric mass transfer coefficients than 1200 µm foams at the same flow rates, due to their higher exposed surface.…”

“…From the conversions measured in the diffusional regime, the first volumetric mass transfer coefficients were calculated to provide an easy comparison with square-channel honeycombs. Then, mass transfer performances were evaluated using the dimensionless Sherwood number and compared with the correlation derived by our group combining experimental, CFD-Computational Fluid Dynamics, and literature data [2].…”

“…Sh is the Sherwood number, k m is the mass transfer coefficient, L c is the characteristic length, which accordingly to Bracconi et al [2] is the average strut diameter, D is the diffusion coefficient of CO in the gas phase, k v is the volumetric mass transfer coefficient, and S v is the surface-to-volume ratio of the foams evaluated with the model of Ambrosetti et al [1].…”

“…The geometrical properties of the tested foams after washcoat deposition are reported in Table 2. A detailed description of the procedure used for the determination of these geometrical properties is reported in Section 3.3, based on a previous work by Bracconi et al [2]. The specific surface area was calculated from the corrected cell diameter and the porosity after the deposition process calculated from the weight loading.…”

“…Moreover, the flow is not segregated, and radial mixing is allowed. These aspects yield higher pressure drops with respect to honeycombs, but at the same time higher mass transfer coefficients are obtained [2]. To enable the intensification of environmental processes and to allow the design of more compact catalytic reactors, 2 of 16 the adoption of high-PPI (pores per inch) foams is needed in order to have a comparable surface area with state-of-the-art honeycombs.…”