Solid−Liquid Mass Transfer at an Oscillating Packed Bed of Raschig Rings

Abstract

Rates of solid-liquid mass transfer at an oscillating packed bed of Raschig rings contained in a wire mesh cage were studied using the diffusion-controlled dissolution of copper in an acidified dichromate technique. Variables studied were the frequency and amplitude of bed oscillation, mesh number of the screen forming the bed container, ring diameter, bed diameter, bed height, bed separation in the case of a multibed reactor, and effect of superimposed axial flow. Container mesh number and bed diameter were found to have little effect on the rate of mass transfer. The data with no net solution flow (batch reactor) were correlated by the equation Sh ) 0.76Sc 0.33 Re v 0.7 (d c /h) 0.35 . Superimposed axial laminar flow was found to increase the rate of mass transfer while turbulent flow was found to decrease the rate of mass transfer at the oscillating bed. Practical implications of the present work for designing a high space time yield reactor suitable for conducting liquid-solid heterogeneous and catalytic reactions are noticed.

Improving the rate of Cu+2 recovery from industrial wastewater using a vertical array of reciprocating perforated zinc discs

“…In addition reducing the Improving the rate of Cu +2 recovery from industrial wastewater distance between discs will decrease the free area between discs and that induced secondary flow resulting from disc oscillation inside these free regions to increase with a consequent decrease in the thickness of the hydrodynamic boundary layer and the diffusion layer in the vertical direction, this also increases the rate of mass transfer and the cementation rate. where a is constant; Vi is the vibrating velocity (V = 2fA m ), f = frequency; A m = amplitude this increase may be attributed to disc oscillation which gives rise to oscillatory flow that reduces the diffusion layer at the disc surface [16]. In addition as the perforated discs oscillate a jetting effect takes place throughout the disc holes according to Thompson and Turner [17] these jets disintegrate into turbulent eddies which decrease the diffusion layer thickness at the disc surface and increase the mass transfer coefficient.…”

Liquid–Liquid Mass Transfer Enhancement Due to T-Junction Modified with an Air Damper

“…The use of pulsation to the packed and sieve plate column resulted in average plate efficiency of 70% higher than without pulsation and reduction in the size of packed columns by over three times compared to the conventional non-pulsatile mode of operation . Pulsations were found useful in enhancing the liquid–solid mass transfer in packed bed reactors . The use of pulsating flow led to efficient emulsification and effective agglomerate dispersion .…”

Effect of fixed bed characteristics on the performance of pulsed water flow humidification-dehumidification solar desalination unit

“…Recently, it was shown that more than 20-fold increase in the mass transfer rate could be achieved by vibrating vertical electrodes along their length [23][24][25][26]. Among its applications in that field are electrochemical processing, electroplating, metal recovery from bio-leaching solutions, and more recently the manufacture of Printed Wiring Board [27][28][29][30]. In all of the above mentioned applications, generation of an oscillatory field at the solid-liquid interface is achieved by vibrating either the solid surface or the fluid surrounding it.…”

“…Although both approaches achieve the same objective, the former is more energy efficient since the energy dissipation there is mainly focused in the boundary layer adjacent to the solid-liquid interface rather than in the bulk of the fluid medium. When the power needed to vibrate the electrode was taken into consideration, Al-Taweel and Ismail [30] found that both amplitude and frequency have almost equal effect on the enhancement obtained per unit power consumed. From the above it is clear that pulsation or vibration can be considered as a good tool for enhancing the rate of mass and/or heat transfer in the humidification process.…”