Liquid‐Solid Mass Transfer Behavior of a Stirred‐Tank Reactor with a Fixed Bed at Its Bottom

Abstract

The mass transfer behavior of a new batch stirred tank with a fixed bed of Raschig rings at the bottom was studied using diffusion-controlled dissolution of copper in acidified dichromate. Variables studied, amongst others, were the impeller rotation speed, Raschig ring diameter, fixed-bed height, and impeller geometry. The rate of mass transfer from the fixed bed to the solution increased with increasing impeller rotation speed, decreasing particle size, and decreasing bed height. The axial-flow turbine is more efficient in increasing the rate of mass transfer than the radial-flow turbine. The presented reactor is especially useful for conducting diffusion-controlled liquid-solid catalytic reactions involving reactants that need to be dispersed first, such as sparingly soluble solid particles.

Liquid‐to‐Particle Mass Transfer in a Structured‐Bed Minireactor

“…However, respective studies for small‐scale reactors are few 12–14 and concern different systems and operating conditions than those applied in this work. The most widely used techniques for investigating the average volumetric liquid‐solid mass transfer coefficient in three‐phase systems are the physical dissolution technique using active particles made of an organic substance 13, 15–22 and the diffusion‐controlled dissolution of copper particles 14, 23–25. Applications in small‐scale systems but with different structures and operating conditions than those used in this study have been presented by Tidona et al 14 and Fernandes Hipolito 13.…”

Liquid–solid mass transfer behaviour of a fixed bed airlift reactor

“…Abdel-Aziz et al [1] using electrochemical technique studied the mass transfer behaviour of the wall of the downcomer of a concentric tube airlift reactor with the aim of using airlift reactors for conducting diffusion controlled gas-liquid-solid electrochemical reactions and developing a heat transfer equation (by analogy) which predicts the rate of heat transfer to a cooling jacket surrounding the reactor. The present study was conducted using a technique which involves the diffusion controlled dissolution of copper in acidified dichromate [29,30], the technique has been used widely to study liquid-solid mass transfer in view of its simplicity and accuracy [31][32][33][34][35]. The technique does not suffer from the drawback of the benzoic acid technique which produces exaggerated mass transfer coefficient owing to particle attrition, the present (1) Air-lift reactor, (2) nitrogen gas cylinder, (3) pressure regulator with screwdown valve, (4) calibrated rotameter, (5) 8 mm PVC tubing, (6) non-return valve, (7) G2 sintered glass gas sparger, (8) liquid level in the air-lift reactor, (9) riser, (10) downcomer, (11) insulated stainless steel support, (12) Raschig rings fixed bed, (13) insulated stainless steel strainer, (14) baffle, (15) drain valve.…”

Effect of Suspension Pattern of Sedimentary Particles on Solid/Liquid Mass Transfer in a Mechanically Stirred Vessel

“…1−3,6−8,17−21 However, the solid/liquid mass transfer properties below N JS were not understood well except a couple of studies. 11,22 The particles stagnation on the vessel bottom or partial suspension condition below N JS is occasionally necessary to prevent the particle quality from deterioration, although it brings the decrease in productivity due to the lower mass transfer rate. Kamei et al (2008) 11 measured the apparent solid/liquid mass transfer rate below N JS with cation-exchange resin particles.…”

“…However, the actual mass transfer rate was not expressed for the regimes of the stagnation and partial suspension near the transition between them because they kept the interfacial area of solid/liquid as the total solid particle area. El-Naggar et al 22 also measured the mass transfer coefficient between the Raschig rings of 0.6 to 1.6 cm in diameter and solution. As the large size of Raschig rings remained on the bottom (a fixed bed), it was difficult to simulate the solid/liquid mass transfer rate of the partial suspension.…”