Fluid Dynamic Efficiency and Scale-up of a Retreated Blade Impeller CSTR

Campolo, Marina; Paglianti, Alessandro; Soldati, Alfredo

doi:10.1021/ie010225y

Cited by 23 publications

(35 citation statements)

References 27 publications

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“…Thus, the efficiency of this stirrer is quite low. In fact, its power consumption is equivalent to that of an impeller with three curved blades (A=32, Campolo et al, 2002), and is much lower than that of a high-efficiency impeller. For instance, the helical ribbon impeller has a value of 160 (Tanguy et al, 1997).…”

Section: Mixing Efficiencymentioning

confidence: 99%

Numerical modeling of coupled phenomena in a mechanically stirred molten-glass bath heated by induction

Jacoutot

Fautrelle

Gagnoud

et al. 2008

Chemical Engineering Science

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A mechanically stirred molten-glass bath heated by direct induction in a cold crucible was numerically modeled. The aim of the study was to develop numerical tools to understand thermal, hydrodynamic and electromagnetic phenomena that occur in the bath. Models and coupling between these phenomena are described. This coupling and the high content of elements in the 3D mesh result in a long calculation time. The study demonstrates how to couple programs to yield the highest degree of accuracy in the shortest calculation time possible. Numerical studies are also used to characterize the fluid dynamic behavior and heat transfer in an industrial-size tank. Classical correlations commonly used to characterize stirrer efficiency and heat transfer for fluids with constant physical properties were adapted for molten glass. The power number N p and the Nusselt number Nu are used as macroscopic indicators. The results of these global studies will be useful for the operation and optimization of the vitrification facilities. ᭧

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Section: Mixing Efficiencymentioning

confidence: 99%

Numerical modeling of coupled phenomena in a mechanically stirred molten-glass bath heated by induction

Jacoutot

Fautrelle

Gagnoud

et al. 2008

Chemical Engineering Science

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“…Dynamic similarity prevails between two geometrically similar units if all corresponding forces at counterpart locations have a constant ratio (Coulson et al, 1999). Numerical simulations have been used in the scale-up of CSTRs typically used for crystallization, and these correlated well with empirical measurements (Campolo et al, 2002).…”

Section: Discussionmentioning

confidence: 78%

“…A more desirable process would be a continuously stirred tank reactor (CSTR) because installation costs are likely to be comparatively low (Gaterell et al, 2000), it would require limited additional operator training because of the use of CSTRs within the water industry (Kim and Speece, 2002;Lui, 1998), and its simple design reduces the risk of operational failures. The merits of CSTR use also include an understanding of scale-up (Campolo et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Removal of Struvite to Prevent Problems Associated with its Accumulation in Wastewater Treatment Works

Stratful¹,

Scrimshaw²,

Lester³

2004

Water Environment Research

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Deposition of struvite within the infrastructure of wastewater treatment works can cause significant operating difficulties. A laboratory-scale, two-stage, continuously stirred tank reactor was developed to remove struvite to prevent problems associated with its deposition. Before any experimental work was conducted, the mixing regime within the system was determined using a pH-tracer response method. Perfect mixing conditions were achieved once the stirring speed reached 500 rpm. Experiments were conducted examining the effects of various process parameters such as retention time, pH, recycling rate, and ammonium concentration. By increasing the hydraulic retention time, the residual magnesium concentration decreased, with the optimum conditions occurring at 125 minutes. Water Environ. Res., 76, 437 (2004).

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“…Besides, a few studies regarding the scale up of continuous reactors have been reported. For instance, Campolo et al (2002) used Nagata's correlation (Nagata, 1975 for the scale up of a CSTR from a lab scale to an industrial scale and verified the scale up of the two reactors by comparing the power number, discharge flow number, and pumping efficiency. In another study, the reaction time, heat removal capacity, and the degree of homogeneity were kept constant for the solution and bulk polymerization.…”

Section: Scale Upmentioning

confidence: 99%

Experimental and CFD investigation of the mixing of MMA emulsion polymerization in a stirred tank reactor

Roudsari¹

2021

Preprint

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Although significant advances have been achieved in emulsion polymerization in recent decades, the effect of mixing on this type of polymerization has not been fully delineated yet. In fact, mixing plays a significant role in the performance of an emulsion polymerization reaction. For instance, in case of a very low agitation rate, larger droplets are generated and phase separation, which limits the diffusion mechanism, may occur. In contrast, vigorous agitation can result in reduced nucleation of particles. Therefore, the main objective of this study is to investigate the impact of mixing parameters (e.g. impeller speed, impeller type, impeller number, and baffles) on the monomer conversion, the polymer average molecular weight, particle size and size distributions, transition glass temperature, and number of particles. To achieve this objective, the emulsion polymerization of methyl methacrylate (MMA) was carried out in a lab-scale reactor equipped with a top-entry agitator, 4 wall baffles, a U shaped cooling coil, and a temperature controller. To analyze the reactive flow inside the polymerization reactor, a novel computational fluid dynamics (CFD) model was developed. The multiple reference frames (MRF) technique, k-ε model, and mixture model approach were employed to model the impeller rotation, turbulence, and multiphase flow, respectively. The particle number density distribution within the reactor was also estimated by means of the population balance approach, which employs a discrete method to describe the nucleation and growth of the polymer particles. The experimental data and CFD results showed that the installation of the baffles enhanced the particle size and molecular weight but reduced the conversion and particle number. The number density achieved using the Rushton impeller was higher than that for the pitched blade impeller. The results revealed that the effect of the impeller speed on the characteristics of the polymer attained using the pitched-blade turbine was more prominent than that for the Rushton turbine. It was also found that the impact of the impeller speed on the polymer characteristics was much more pronounced for the double pitched-blade turbines rather than for the double Rushton turbines.

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Fluid Dynamic Efficiency and Scale-up of a Retreated Blade Impeller CSTR

Cited by 23 publications

References 27 publications

Numerical modeling of coupled phenomena in a mechanically stirred molten-glass bath heated by induction

Numerical modeling of coupled phenomena in a mechanically stirred molten-glass bath heated by induction

Removal of Struvite to Prevent Problems Associated with its Accumulation in Wastewater Treatment Works

Experimental and CFD investigation of the mixing of MMA emulsion polymerization in a stirred tank reactor

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