Abstract
In this paper, micromixing is investigated in two Spinning Disk Reactors for liquids with increased viscosity. Glycerol and CMC were used as viscosity modifiers and micromixing characterization was performed by means of the Villermaux–Dushman method. For the first time, the effects of increasing the pH of the bulk solution leading to the disproportionation reaction of iodine are successfully modeled. A kinetic model is proposed to account for the presence of glycerol as a co-solvent. Micromixing efficiency decreases with increasing viscosity, yet the results are in line with the proportionality to the Kolmogorov timescale. The viscosity can be significantly increased using CMC as a viscosity modifier; however, due to the viscoelastic behavior of CMC, the effective viscosity decreases in the high shear environment inside the reactor. This leads to a much higher micromixing efficiency. It is shown that micromixing times can be estimated provided that the rheology of the liquids is known.
Highlights
Mixing efficiency plays an important role in the chemical industry, as it can affect selectivity and yield [1], the size of crystals and precipitates [2], or the molecular weight of polymers [3]
It was found that in the rotor–stator Spinning Disk Reactor (rs-SDR) the micromixing times ranged between 1×10−2 s and 1×10−4 s [13,19], which was in very good agreement with the proposed characteristic time for vorticity τω by Bałdyga and Bourne [18]
The results of fitting the reaction rate coefficient k2 as a function of ionic strength Is at different mass fractions of glycerol are shown in Fig. 4, as well as a proposed modification of the kinetic model
Summary
Mixing efficiency plays an important role in the chemical industry, as it can affect selectivity and yield [1], the size of crystals and precipitates [2], or the molecular weight of polymers [3]. In a previous publication, micromixing efficiency was studied in a rotor–stator Spinning Disk Reactor (rs-SDR) for aqueous systems [13,19]. This reactor consists of a rotating disk (rotor) enclosed by a cylindrical housing (stator), separated by only a few millimeters. It was found that in the rs-SDR the micromixing times ranged between 1×10−2 s and 1×10−4 s [13,19], which was in very good agreement with the proposed characteristic time for vorticity τω by Bałdyga and Bourne [18]
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