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Liquid−Solid Mass Transfer at a Fixed Bed of Lessing Rings, in Relation to Electrochemical Reactor Design

“…The present Re exponent 0.46 agrees fairly well with the value of 0.5, which was predicted by the model based on the concept of a series of developing boundary layers destroyed after traversing a distance equivalent to the length of a particle . The exponent 0.46 also agrees with the experimental value obtained by different authors, who used different packing geometries at relatively high Re values ( Re > 55). , From among previous studies, the present results can be compared with the data of Delaunay et al and Mobarak et al, in view of the experimental similarity with the present work where, in the three cases, inlet and outlet calming sections were used. Also, in the three cases, the electrochemical technique was used to measure the rate of mass transfer at an entire bed operated in the flow-by regime (the flow direction is perpendicular to the current direction).…”

“…Delaunay et al reported a higher enhancement ratio ( Sh / Sh 0 = 1.13−3.33) for a fixed bed of spheres under the conditions of 0 < Re g < 30 and 15 < Re < 5000. Mobarak et al also reported a higher enhancement ratio ( Sh / Sh 0 = 1.05−3.1) for a vertical array of closely packed screens under the conditions of 1.4 < Re g < 77 and 1.1 < Re < 125. Besides the difference between the range of conditions used by previous studies and those of the present study, the difference in the packing geometry is also believed to be responsible for the higher enhancement ratio reported by Delauncy et al and Mobarak et al Although the total sphere surface used by Delaunay et al .…”

“…Studies using a single active particle embedded in an inert fixed bed and studies using flow through fixed beds (where the flow and current are parallel) were excluded from the comparison. Delaunay et al, who used a fixed bed of spheres, correlated their data for the conditions of Sc = 1039, 10 < Re < 500, and d = 0.4 cm, using the equation Mobarak et al, who used a vertical array of closely packed screens, correlated their data for the conditions of 1250 < Sc < 8270, 0.6 < Re < 124, and 0.28 < d w < 1.2 mm by the equation The wire diameter ( d w ) was used as a characteristic length in calculating Sh and Re . Comparison of eq 2 with eqs 3 and 4 shows that, for a given solution velocity, the mass-transfer coefficient obtained from eq 2 is higher than that obtained from eq 4 and lower than that obtained from eq 3.…”

“…To obviate these shortcomings, some work recently has been conducted on the performance of flow-by fixed-bed electrochemical reactors that were composed of high-porosity packing material, such as screens, Rasching rings, and cylinders. − Consistent with this trend, the objective of the present work is to examine the mass-transfer behavior of a flow-by fixed-bed electrochemical reactor packed with Lessing rings. Despite the decrease in the specific area of the bed, as a result of using large particles, the high-porosity bed offers the following advantages:…”

Electrodeposition of manganese dioxide: effect of quaternary amines

“…However, careful monitoring of appropriate surfactant concentration during electrolysis is required to achieve reproducibility. Higher concentrations may lead to irregular morphology owing to higher ohmic potential drop and electrode overvoltage [26][27][28].…”