R. Medronho

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C. Michael Hall

University of Canterbury/Te Whare Wānanga o Waitaha

Athanassios Tsikliras

Aristotle University of Thessaloniki

Klaus Dodds

Royal Holloway, University of London

Armando Marques-Guedes

UNL - New University of Lisbon

Benjamin Wilson

Aalto University

Waldmir Araujo Neto

Universidade Federal do Rio de Janeiro (UFRJ)

Ian G Baird

University of Wisconsin-Madison

Sahar F Mehanna

National Institute of Oceanography and Fisheries

Maderas. Ciencia y Tecnologia

Universidad del Bio-bio

Davide Turrini

Università degli Studi di Firenze (University of Florence)

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Papers by R. Medronho

Biofilm development and ammonia removal in the nitrification of a saline wastewater

Bioresource Technology, 1998

... THE NITRIFICATION OF A SALINE WASTEWATER Morsyleide F. Rosa,' *Angela AL Furtado,Ricardo... more

Numerical simulation of hydrocyclones for cell separation

Latin American Applied Research, 2005

Numerical simulation of hydrocyclones aiming at investigating the separation of microorganisms an... more Numerical simulation of hydrocyclones aiming at investigating the separation of microorganisms and mammalian cells was performed using Computational Fluid Dynamics (CFD). The turbulence model used in the 2d- axisymmetric calculations was the Reynolds Stress Model (RSM), in order to take into account the high swirl effects that occur in this type of equipment, which induce anisotropic turbulence. The Volume of Fluid Model (VOF) was used to account for the gas/liquid interface. In all calculations, a cylindrical air core, running the whole length of the cyclone, appeared naturally as a consequence of a low pressure region that developed along the central axis. The separation of Escherichia coli, Saccharomyces cerevisiae and mammalian cells (BHK-21) using Bradley hydrocyclones was studied. According to the present work, Bradley hydrocyclones with diameters down to 10 mm cannot efficiently separate microorganisms, but the separation of mammalian cells with predicted efficiencies as high...

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Nitrification of Saline Effluents

Brazilian Journal of Chemical Engineering, 1997

ABSTRACT

Fish hook effect in centrifugal classifiers – a further analysis

International Journal of Mineral Processing, 2014

ABSTRACT

Gas holdup and flow regime in a bubble column that includes enhanced oil recovery chemicals

Journal of Petroleum Science and Engineering

Hydrocyclones as cell retention device for CHO perfusion processes in single‐use bioreactors

Biotechnology and Bioengineering

Effects of EOR chemicals and superficial gas velocity on bubble size and gas holdup of a bubble column

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles

Chemical Enhanced Oil Recovery (EOR) can boost oil extraction in offshore operations, however one... more Chemical Enhanced Oil Recovery (EOR) can boost oil extraction in offshore operations, however one of the main concerns regarding its application is how the efficiency of flotation units for treating produced water is affected. The present work thus focuses on investigating the impact of EOR chemicals on the physical properties of EOR effluents and how this can affect flotation performance parameters such as bubble size and gas holdup. Design of experiments has been used to assess the influence of polymer, surfactant and sodium chloride concentrations on bubble size and gas holdup of a laboratorial bubble column. The influence of superficial gas velocity has also been assessed together with chemicals concentrations, yet at low levels in order to avoid clusters, swarms and foam. The characterization of the synthetic effluent containing polymer, surfactant and sodium chloride has indicated that the fluid behaves as a non-Newtonian fluid, what makes separation processes in flotation cel...

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Experimental study of water droplet break up in water in oil dispersions using an apparatus that produces localized pressure drops

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles

Oil production facilities have choke/control valves to control production and protect downstream ... more Oil production facilities have choke/control valves to control production and protect downstream equipment against over pressurization. This process is responsible for droplets break up and the formation of emulsions which are difficult to treat. An experimental study of water in oil dispersion droplets break up in localized pressure drop is presented. To accomplish that, an apparatus simulating a gate valve was constructed. Droplet Size Distribution (DSD) was measured by laser light scattering. Oil physical properties were controlled and three different break up models were compared with the experimental results. All experimental maximum diameters (dmax) were above Kolmogorov length scale. The results show that dmax decreases with increase of energy dissipation rate (ε) according to the relation dmax ∝ ε−0.42. The Hinze (1955, AIChE J.1, 3, 289–295) model failed to predict the experimental results, although, it was able to adjust reasonably well those points when the original propo...

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Erratum to �Recovery of pectolytic enzymes produced by solid state culture of Aspergillus niger�

Process Biochem, 1999

Optimization of a Supersonic Ejector Coupled with a CFD Analysis

The Use of Hydrocyclones for Mammalian Cell Retention in Perfusion Bioreactors

Animal Cell Technology: From Target to Market, 2001

The Effects of Cell Separation with Hydrocyclones on the Viability of CHO Cells

Cell Technology for Cell Products, 2007

Five different hydrocyclone geometries were tested for the separation of CHO cells and presented ... more Five different hydrocyclone geometries were tested for the separation of CHO cells and presented separation efficiencies over 97%. Cell passage through the hydrocyclone did not induce apoptosis. The high separation efficiencies coupled to the low viability losses obtained in the present work confirm that hydrocyclones are suitable for animal cell retention in perfusion processes.

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Cell retention devices for suspended-cell perfusion cultures

Advances in biochemical engineering/biotechnology, 2002

Perfusion cultures of animal cells have several advantages over batch or fed-batch cultures. They... more Perfusion cultures of animal cells have several advantages over batch or fed-batch cultures. They give, for instance, higher productivities and a consistent product quality, and allow steady state operation and better cell physiology control. However, one of the main aspects limiting performance and scale-up of perfusion processes is the need for an adequate cell retention device. The devices currently in use for stirred perfusion bioreactors are continuous centrifuges, tangential flow membrane filters, dynamic filters, spin-filters, ultrasonic and dielectrophoretic separators, gravity settlers and, more recently, hydrocyclones. The advantages and disadvantages of each of these methods will be discussed.

Feed Flow Pulsation in the Separation of CHO Cells in Hydrocyclones: Effects of Pressure Drop and Pumphead Type on Separation Efficiency and Cell Viability

Proceedings of the 21st Annual Meeting of the European Society for Animal Cell Technology (ESACT), Dublin, Ireland, June 7-10, 2009, 2011

The effect of pumphead type and operating pressure on cell viability and cell separation efficien... more

CFD-Aided Design of Hollow Fibre Modules for Integrated Mammalian Cell Retention and Product Purification

Cell Technology for Cell Products, 2007

Membrane-based affinity chromatography is a powerful technique for purification protein. The use ... more

CFD Study of the Fluid and Particle Dynamics in a Spin-Filter Perfusion Bioreactor

Cells and Culture, 2010

In this work, simulations of a spin-filter bioreactor were carried out using computational fluid ... more In this work, simulations of a spin-filter bioreactor were carried out using computational fluid dynamics (CFD). Bi-directional radial exchange of fluid through the filter mesh and lateral migration were observed in the simulations. The fluid exchange might explain the observations of cell accumulation also on the internal side of the mesh. Moreover, lower cell concentrations were observed in the vicinity of the filter mesh, indicating that lateral migration could be related to the ability of spin-filters to delay clogging. The current results show that CFD modelling allows improving the current understanding of the principles that underlie spin-filter operation. The use of computational fluid dynamics could lead to a reduction in the number of experiments needed to optimize spin-filter operation and could help in the design of improved spin-filter devices.

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Rotating cylindrical filters used in perfusion cultures: CFD simulations and experiments

Biotechnology Progress, 2014

The particle and fluid dynamics in a rotating cylindrical filtration (RCF) system used for animal... more The particle and fluid dynamics in a rotating cylindrical filtration (RCF) system used for animal cell retention in perfusion processes was studied. A validated CFD model was used and the results gave numerical evidence of phenomena that had been earlier claimed, but not proven for this kind of application under turbulent and high mesh permeability conditions, such as bidirectional radial exchange flow (EF) through the filter mesh and particle (cells) lateral migration. Taylor vortices were shown to cause EF 10-100 times higher than perfusion flow, indicating that EF is the main drag source, at least in early stages of RCF operation. Particle lateral migration caused a cell concentration reduction (CCR) near the filter surface of approximately 10%, contributing significantly to cell separation in RCF systems and giving evidence that the mesh sieving effect is not the sole phenomenon underlying cell retention in RCF systems. Filter rotation rate was shown to significantly affect both EF and CCR. A higher separation efficiency (measured experimentally at 2,000-L bioreactor scale) and an enhanced CCR (predicted by the numerical simulations) were found for the same rotation rate range, indicating that there is an optimal operational space with practical consequences on RCF performance. Experimental data of a large-scale perfusion run employing the simulated RCF showed high cell viabilities for over 100 days, which is probably related to the fact that the computed shear stress level in the system was shown to be relatively low (below 20 Pa under all tested conditions).