This study is focused on the selection of the best piping arrangement for a pilot scale annular channel reactor intended for the remediation of waters and wastewaters. Two annular channel reactors ...composed of a single UV lamp and distinct piping arrangements were considered: (i) a novel reactor with tangential inlet/outlet pipes – the FluHelik reactor, and (ii) a conventional Jets reactor. These two reactors were manufactured at lab scale and characterized in terms of residence time distribution (RTD), radiant power and ability to degrade aqueous solutions spiked with a model compound – 3-amino-5-methylisoxazole (AMI) – by H2O2/UVC and UVC processes. Computational fluid dynamics (CFD) simulations were used to assess the hydrodynamics, RTD and UV radiation intensity distribution of both reactors at pilot scale. In general, experimental results at lab scale revealed quite similar RTDs, radiant powers and AMI degradation rates for both reactors. On the other hand, CFD simulations at pilot scale revealed the generation of a helical motion of fluid around the UVC lamp in the FluHelik reactor, inducing: (i) a longer contact time between fluid particles and UV light, (ii) more intense dynamics of macromixing as a result of larger velocity gradients, turbulent intensities and dispersion of RTD values around the peak, and (iii) a more homogeneous UV radiation distribution. In addition, the design of the FluHelik reactor can favor the implementation of various reactors in series, promoting its application at industrial scale. The FluHelik reactor was chosen for scaling-up. A pre-pilot scale treatment unit containing this reactor was constructed and its feasibility was proven.
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•Design of a new annular channel reactor with tangential inlet/outlet-FluHelik reactor•Generation of a helical motion of fluid around the lamp in the FluHelik reactor•Quite similar degradation rates for FluHelik and Jets reactors at lab scale•Better fluid dynamics and irradiation properties for the FluHelik at pilot scale•Easy implementation of the FluHelik reactor in series for industrial applications
Downstream processing is considered to be the bottleneck in pharmaceutical manufacturing because its development has not kept pace with upstream production. In some cases, the lack of efficient ...downstream processing capacity can seriously affect both the sustainability and profitability of a pharmaceutical product and even result in its failure. Minimising solvent and raw material consumption, as well as utilising waste, can make a significant difference towards environmentally benign and economically viable chemical production. In this work, the authors present the development and modelling of a continuous adsorption process with in situ solvent recovery for the isolation of oleuropein from olive leaves, an agricultural waste. Waste utilisation in agriculture has gained increasing attention because this economic sector is ranked as the 2nd highest global greenhouse gas emission contributor. Imprinted polymers were developed for the selective scavenging of oleuropein from olive leaf extracts using green solvents. The mild temperature-swing (25-43 degree C) process allows the continuous isolation of oleuropein at 1.75 g product per kg of adsorbent per hour with an unprecedented 99.7% purity. In situ solvent recovery was realized with a solvent-resistant nanofiltration membrane allowing 97.5% solvent recycle and 44.5% total carbon footprint reduction, while concentrating both the product stream for crystallisation and the waste stream for disposal.
The flow field in T-jets mixers is studied experimentally for different geometrical parameters using Planar Laser Induced Fluorescence (PLIF). A particular chaotic flow regime is reported for the ...first time from experimental work. It is shown that two geometrical parameters, the ratio of the mixing chamber width to the injectors’ width, and chamber's width to the chamber's depth, have an impact on the flow dynamics as important as the jets Reynolds numbers that were here studied over a range of values from 50 to 500. The values of the geometrical parameters and operation Reynolds number that mark the transitions of flow regime in the T-jets mixers are reported, and the impact of the geometry on such transitions is analyzed. The main features of the flow regimes are related with the mixing efficiency in T-jets mixers. Computational Fluid Dynamics (CFD) simulations for a particular case are shown in order to reveal the 3D flow structure of chaotic flow regime.
► Mixing in several T-jets geometry was experimentally characterized. ► The ratio of injectors to chamber widths is a critical parameter for mixing. ► The ratio of T-jets chamber depth to width is also a critical parameter for mixing. ► A new chaotic flow regime was experimentally observed in T-jets mixers. ► The 3D structure of the chaotic flow regime was numerically studied.
Efficient mixing conditions for similar fluids in T‐Jets mixers are well‐established. This paper extends the characterization of the mixing of dissimilar fluids. Planar laser‐induced fluorescence ...images were captured using fluids with a viscosity ratio between 1.2 and 3. Flow visualizations showed that the best mixing conditions are achieved when the jets are well‐balanced, and the onset of a chaotic flow regime is determined by the Reynolds number of the more viscous fluid (ReHjet > 100). Computational fluid dynamics simulations were also performed to get deeper insight into the flow field and mixing dynamics, enabling the prediction of the impingement point position. An analytical model based on jets' kinetic energy rate balance is proposed as a design tool to predict the impingement point position.
Chaotic flow regime in T‐Jets mixers can engulf the mixing of fluids with different viscosities. The Reynolds number of the more viscous fluid must be above 100, and both jets must be well‐balanced. A new analytical model based on kinetic energy rate balance is proposed to predict the impingement point position in T‐jets mixers. This model was validated from computational fluid dynamics simulations.
3D Mixing Dynamics in T‐Jet Mixers Sultan, M. Ashar; Pardilhó, Sara L.; Brito, Margarida S. C. A. ...
Chemical engineering & technology,
January 2019, 2019-01-00, 20190101, Letnik:
42, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The dynamic flow field in T‐jet mixers is characterized by means of 3D computational fluid dynamics simulations. The main goal of this work is to identify and discuss the chaotic flow regime in T‐jet ...reactors and the parameters that enable this flow regime, namely, the critical Reynolds number and design parameters of these mixers. The 3D chaotic flow regime that occurs in T‐jet mixers is described herein with unprecedented detail regarding the mixing scales, flow dynamics, and coherent structures. The mixing scales are proven to be set by the mixer dimensions. The chaotic flow regime in T‐jets is of practical interest due to its capability to promote very fast mixing, although descriptions in the literature are scarce.
Fully resolved flow dynamics in T‐jet mixers are obtained from 3D computational fluid dynamics simulations, particularly those on chaotic flow regimes that are characterized by a vortex issuing from the jet impingement point. The design and operational conditions to promote the chaotic flow regime are analyzed, and mixing scales and dynamics are assessed.
•Different pulse durations can change the jet breakup regime of a pulsed jet.•Fluid elasticity can result in the withdrawal of more fluid than the pulsed volume.•A pulsed elastic fluid can have extra ...volumes pulled from inside of a nozzle.•Gravity has no relevant effect on the breakup of a pulsed jet.
The ejection of liquids through round nozzles is a commonplace process in many industrial applications, from inkjet printing to bottling of consumer products. In this work, a Computational Fluid Dynamics model of the ejection of inelastic and elastic liquids through a round capillary tube has been developed to assess the influence of the ejection’s duration and velocity on the regimes of jet/droplet formation. Simulations have been performed at different Weissenberg and Ohnesorge numbers to further assess the impact of the fluid’s physical properties on the observed flow regimes. Several regimes have been identified: no fluid detachment, single droplet formation, and breakup into several droplets. The presence of elasticity has been observed to delay the breakup of droplets from the nozzle. More importantly, the results show that the injection time has an impact on the dynamics of droplet formation, having a crucial role on the process design of various industrial applications.
•Flow varies between rows of holes in rotor-stator mixers.•Models to predict both power and flow numbers in rotor-stator mixers are proposed.•Proposed models work for various designs of mixing ...head.•Rotor-stator gap does not have a significant impact on power and flow.
The relationship between power and flow characteristics of batch rotor-stator mixers has been studied using CFD simulations with experimental power validation. The mixer studied was the Silverson L5M batch mixer with the standard emulsor head. The size of the holes in the screen and the constriction of the base hole were changed in small increments. The MRF technique was used to model rotor rotation. A model is developed in this study which links the power and flow numbers of the mixer. Since power is easy to measure experimentally, one can use this model to predict the flow number by measuring torque. A second model is also developed which allows one to predict the flow number using solely the geometry of the mixing head. This study greatly enhances our understanding of the relationship between power, flow and mixer geometry in rotor-stator mixers.
•Mixing dynamics in opposed jets mixers is related with flow dynamics.•Effect of active mixing parameters on flow dynamics is assessed.•Active mixing is studied regarding phase displacement, ...amplitude and frequency.•Mixing is assessed from both energy dissipation and passive tracer simulation.
The flow field in a 2D T-jets mixer was simulated to study the effect of the pulsation/modulation of the jets flow rate on the dynamics of mixing. Different strategies, frequencies and amplitudes of the opposed jets flow rate modulation were tested. The modulation frequencies were set as multiples of the natural oscillation frequencies of the dynamics flow field. The natural flow frequencies are determined from the unforced flow, i.e., when the jets are not modulated. It is found that out phase modulation of the opposed jets, with frequencies close to the natural frequencies, cause resonance of the flow enhancing the order of the system, which results in a flow field with a well-defined repetitive generation of vortices. Conversely, when the pulsation frequencies were different from the natural frequencies the flow disorder was enhanced, i.e., the vortices evolution throughout the T-jets mixers is less repetitive. The impact of the jets flow rate modulation on the flow field dynamics increases with the modulation amplitude up to the extreme case where it completely drives the dynamics of the system. A design equation for the most energy efficient pulsation of the jets feed streams in opposed jets mixers is proposed.
Characterization of mixing in T-jets mixers Krupa, Kateryna; Sultan, M.Ashar; Fonte, Cláudio P ...
Chemical engineering journal (1996),
10/2012, Letnik:
207
Journal Article, Conference Proceeding
Recenzirano
The product distribution of a fast chemical reaction system was used for the characterization of micromixing in T-jets mixers; several geometries were assessed under different operational conditions ...(Reynolds number and jets flow rate ratio). The micromixing test system was the reaction between 1-naphthol and diazotized sulfanilic acid in an aqueous medium. The results obtained show that for all geometries mixing is enhanced with Reynolds number and with the operation at flow rate ratios close to unity. The geometrical parameters of T-jets mixers have a critical influence on the product distribution of the test reaction; particularly the ratio between the mixing chamber width and the inlet jet width, and also the mixing chamber depth. Micromixing is shown to be mainly related to the flow field regime observed at each geometry and operational conditions, which were previously set using Planar Laser Induced Fluorescence.
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