John Dodds - Academia.edu (original) (raw)

Papers by John Dodds

Research paper thumbnail of Optimization of a discontinuous microfiltration-backwash process

The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995

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Research paper thumbnail of A technique for the study of the fouling of microfiltration membranes using two membranes in series

Journal of Membrane Science

This paper describes a technique for investigating the fouling of microfiltration membranes by me... more This paper describes a technique for investigating the fouling of microfiltration membranes by measuring the pressure drops across two membranes fed in series by a constant rate pump, which enables a distinction to be made between surface fouling and internal fouling of the membrane. In the case of the microfiltration of BSA solutions, the technique shows how the type of pump and the operating temperature influence membrane fouling and how protein denaturation and adsorption give rise to different types of fouling. The technique is also used to investigate the microfiltration of beer and shows how this is affected by membrane properties and the aging of beer.

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Research paper thumbnail of Computer simulation and statistical geometric model for contacts in binary random two-dimensional disk packings

EXPERIMENTAL investigation of the characteristics of multi-component packings of particles would ... more EXPERIMENTAL investigation of the characteristics of multi-component packings of particles would involve a large number of manipulations for even very few components in the mixture, and each additional component would increase this number enormously. A method of calculating the properties of such mixtures would be of interest if only as a framework within which to design experiments. One difficulty is that for this very reason a theoretical approach cannot be subjected to a thorough experimental verification. We therefore think it useful to take the problem further by comparing two previously published theoretical approaches, by a statistical geometric model1 and a computer simulation2, for calculating the contacts between disks in two-dimensional multicomponent random mixtures.

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Research paper thumbnail of An Analytical Model for Capillary Pressure–Saturation Relation for Gas–Liquid System in a Packed-Bed of Spherical Particles

Transport in Porous Media, 2009

Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid... more Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid flows in packed-bed reactors, capillary pressure gradients can have a significant influence on liquid distribution and, consequently, on the overall reactor performance. In particular, capillary pressure is important for non-uniform liquid distribution, causing liquid spreading as it flows down the packing. An analytical model for capillary pressure–saturation relation is developed for the pendular and funicular regions and the factors affecting capillary pressure in the capillary region are discussed. The present model is compared to the capillary pressure models of Grosser et al. (AIChE J., 34:1850–1860, 1988) and Attou and Ferschneider (Chem. Eng. Sci., 55:491–511, 2000) and to the experiments of Dodds and Srivastava (Part Part Syst. Charact., 23:29–39, 2006) and Dullien et al. (J. Colloid Interface Sci., 127:362–372, 1989). The non-homogeneity of real packings is considered through particle size and porosity distributions. The model is based on the assumption that the particles are covered with a liquid film, which provides hydrodynamic continuity. This makes the model more suitable for porous or rough particles than for non-porous smooth particles. The main improvements of the present model are found in the pendular region, where the liquid dispersion due to capillary pressure gradients is most significant. The model can be used to improve the hydrodynamic models (e.g., CFD and cellular automata models) for packed-bed reactors, such as trickle-bed reactors, where gas, liquid, and solid phases are present. Models for such reactors have become quite common lately (Sáez and Carbonell, AIChE J., 31:52–62, 1985; Holub et al., Chem. Eng. Sci, 47, 2343–2348, 1992; Attou et al., Chem. Eng. Sci., 54:785–802, 1999; Iliuta and Larachi, Chem. Eng. Sci., 54:5039–5045, 1999, IJCRE 3:R4, 2005; Narasimhan et al., AIChE J., 48:2459–2474, 2002), but they still lack proper terms causing liquid dispersion.

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Research paper thumbnail of The design of cyclic fixed-bed ion-exchange operations-I A predictive method applied to a simple softening cycle

Chemical Engineering Science, 1972

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Research paper thumbnail of Rheology and flow of phosphate slurries (mine tailings) in pipes

Chemical Engineering & Technology - CET, 1987

... [52] Carreiro, JASP, Dissertation, Ruhr-Univ. Bochum, 1986. [53] Ali Emesh, IT, Amenomiya, Y.... more ... [52] Carreiro, JASP, Dissertation, Ruhr-Univ. Bochum, 1986. [53] Ali Emesh, IT, Amenomiya, Y., J. Phys. Chem. 90(1986) p. 4785. ... 59, pp. 291-296. Ercolani, D., Ferreni, F., Hydrotransport 10, Ed. BHRA, Cranfield, 1979. Rambeloniaina, HV, Thesis, ULP, Strasbourg 1984. ...

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Research paper thumbnail of Sizing synthetic mixtures of latex and various colloidal suspensions by photon correlation spectrometry

Analytical Chemistry, 1986

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Research paper thumbnail of The Effect of Ultrasound on Crystallisation-Precipitation Processes: Some Examples and a New Segregation Model

Particle & Particle Systems Characterization, 2007

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Research paper thumbnail of Two Different Configurations of Flow Field-Flow Fractionation for Size Analysis of Colloids

Separation Science and Technology

Flow field-flow fractionation (F.FFF) is a technique for measuring the size of species in the col... more Flow field-flow fractionation (F.FFF) is a technique for measuring the size of species in the colloidal range (1 nm to 1 μm) which makes the use of the formation of a molecular or colloidal polarization layer at the surface of a filtering membrane. The species to be analyzed are introduced into a flow of liquid passing through a channel with porous walls (of pore size less than that of the colloids to be analyzed) which allow a certain controlled flow to pass through. The remaining fraction of the flow passes through the system, carrying the colloids to a nonspecific detector. The transit time of the colloids through the channel is found to be a function of their size and the permeation rate through the porous membrane. This chromatographic system can be calibrated by using known colloids, such as standard latex particles or fractionated polymer samples, and then used to determine the size of unknown colloids. Here we present results obtained in two different systems, an asymmetric ...

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Research paper thumbnail of An experimental study of the transport and capture of colloids in porous media by a chromatographic technique

Colloids and Surfaces A Physicochemical and Engineering Aspects

We present an experimental investigation of the transport and capture of model colloids in a well... more We present an experimental investigation of the transport and capture of model colloids in a well-defined porous medium. The experiments were performed using standard liquid chromatography equipment and involve detecting the passage of small impulses of monodisperse latex particles passing through a bed of monosize glass beads. Experiments were performed with three samples of monodisperse latex particles of diameters 226, 550 and 790 nm in carrier solutions with ionic strengths ranging from pure water up to 0.1 M at a pH of either 5.2 or 8 at flow velocities varying from 0.01 to 0.1 cm s−1. The results are presented as capture efficiency as a function of the various parameters and also in the form of Sherwood number vs Reynolds number for comparison with existing correlations of mass transfer. It is shown that capture is strongly influenced by hydrodynamics and the repulsive potential energy barrier.

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Research paper thumbnail of Laminar flow in channels with porous walls

The Chemical Engineering Journal

An analytical solution for the axial and transverse flow fields in laminar flow in porous channel... more An analytical solution for the axial and transverse flow fields in laminar flow in porous channels for both a rectangular channel with one porous wall and a porous tubular channel is presented. The solution is obtained from the Navier-Stokes equations without the simplifying assumption of constant permeation rate along the length of the duct. A dimensionless criterion for the validity of previous simplified solutions is developed which shows that the validity of the assumption of a constant permeation rate depends on the permeability of the membrane and the dimensions of the channel. Long channels with high permeability membranes can have significant departures from the constant permeation rate. The importance of these effects for the design of ultrafiltration and microfiltration modules is discussed.

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Research paper thumbnail of Co-broyage de principes actifs pharmaceutiques pour améliorer leur biodisponibilité

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Research paper thumbnail of Talc grinding in an opposed air jet mill: start-up, product quality and production rate optimization

Powder Technology, 2002

ABSTRACT We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an in... more ABSTRACT We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an inline laser granulometer. The conditions for steady state operation have been determined from continuous grinding experiments and show that overloading occurs above a critical value of feed rate classifier resulting in unstable product size distribution. For each rotation speed of the classifier, there is an optimum feed rate, which gives the finest product, thus fixing a maximum reduction ratio. A linear relation exists between this ratio and the rotation speed of the classifier. The use of liquid grinding aids have been studied and showed they can result in an increase in the production rate but can also lead to a coarser product.

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Research paper thumbnail of Chapter 8 Air Jet Milling

Handbook of Powder Technology, 2007

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Research paper thumbnail of coating active pharmaceutical substances by mechanical action

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Research paper thumbnail of Albi International Rencontres in Pharmaceutical Engineering

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Research paper thumbnail of The Effect of Ultrasound on Crystallisation-Precipitation Processes: Some Examples and a New Segregation Model

Particle & Particle Systems Characterization, 2007

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Research paper thumbnail of Generation of static electricity during fluidisation of polyethylene and its elimination by air ionisation

Powder Technology, 2003

... In order to study the influence of static electricity on the minimum fluidisation velocity (u... more ... In order to study the influence of static electricity on the minimum fluidisation velocity (u mf ... Theelectrostatic behaviour of the two products was studied in order to set the ... As low-density polyethylene has an extremely high resistivity, ohmic dissipation during contact time with the ...

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Research paper thumbnail of Symposium STP—PMF 2007, Albi France

Powder Technology, 2009

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Research paper thumbnail of Vibration induced flow in hoppers: DEM 2D polygon model

Particuology, 2008

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Research paper thumbnail of Optimization of a discontinuous microfiltration-backwash process

The Chemical Engineering Journal and the Biochemical Engineering Journal, 1995

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A technique for the study of the fouling of microfiltration membranes using two membranes in series

Journal of Membrane Science

This paper describes a technique for investigating the fouling of microfiltration membranes by me... more This paper describes a technique for investigating the fouling of microfiltration membranes by measuring the pressure drops across two membranes fed in series by a constant rate pump, which enables a distinction to be made between surface fouling and internal fouling of the membrane. In the case of the microfiltration of BSA solutions, the technique shows how the type of pump and the operating temperature influence membrane fouling and how protein denaturation and adsorption give rise to different types of fouling. The technique is also used to investigate the microfiltration of beer and shows how this is affected by membrane properties and the aging of beer.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Computer simulation and statistical geometric model for contacts in binary random two-dimensional disk packings

EXPERIMENTAL investigation of the characteristics of multi-component packings of particles would ... more EXPERIMENTAL investigation of the characteristics of multi-component packings of particles would involve a large number of manipulations for even very few components in the mixture, and each additional component would increase this number enormously. A method of calculating the properties of such mixtures would be of interest if only as a framework within which to design experiments. One difficulty is that for this very reason a theoretical approach cannot be subjected to a thorough experimental verification. We therefore think it useful to take the problem further by comparing two previously published theoretical approaches, by a statistical geometric model1 and a computer simulation2, for calculating the contacts between disks in two-dimensional multicomponent random mixtures.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An Analytical Model for Capillary Pressure–Saturation Relation for Gas–Liquid System in a Packed-Bed of Spherical Particles

Transport in Porous Media, 2009

Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid... more Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid flows in packed-bed reactors, capillary pressure gradients can have a significant influence on liquid distribution and, consequently, on the overall reactor performance. In particular, capillary pressure is important for non-uniform liquid distribution, causing liquid spreading as it flows down the packing. An analytical model for capillary pressure–saturation relation is developed for the pendular and funicular regions and the factors affecting capillary pressure in the capillary region are discussed. The present model is compared to the capillary pressure models of Grosser et al. (AIChE J., 34:1850–1860, 1988) and Attou and Ferschneider (Chem. Eng. Sci., 55:491–511, 2000) and to the experiments of Dodds and Srivastava (Part Part Syst. Charact., 23:29–39, 2006) and Dullien et al. (J. Colloid Interface Sci., 127:362–372, 1989). The non-homogeneity of real packings is considered through particle size and porosity distributions. The model is based on the assumption that the particles are covered with a liquid film, which provides hydrodynamic continuity. This makes the model more suitable for porous or rough particles than for non-porous smooth particles. The main improvements of the present model are found in the pendular region, where the liquid dispersion due to capillary pressure gradients is most significant. The model can be used to improve the hydrodynamic models (e.g., CFD and cellular automata models) for packed-bed reactors, such as trickle-bed reactors, where gas, liquid, and solid phases are present. Models for such reactors have become quite common lately (Sáez and Carbonell, AIChE J., 31:52–62, 1985; Holub et al., Chem. Eng. Sci, 47, 2343–2348, 1992; Attou et al., Chem. Eng. Sci., 54:785–802, 1999; Iliuta and Larachi, Chem. Eng. Sci., 54:5039–5045, 1999, IJCRE 3:R4, 2005; Narasimhan et al., AIChE J., 48:2459–2474, 2002), but they still lack proper terms causing liquid dispersion.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The design of cyclic fixed-bed ion-exchange operations-I A predictive method applied to a simple softening cycle

Chemical Engineering Science, 1972

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Rheology and flow of phosphate slurries (mine tailings) in pipes

Chemical Engineering & Technology - CET, 1987

... [52] Carreiro, JASP, Dissertation, Ruhr-Univ. Bochum, 1986. [53] Ali Emesh, IT, Amenomiya, Y.... more ... [52] Carreiro, JASP, Dissertation, Ruhr-Univ. Bochum, 1986. [53] Ali Emesh, IT, Amenomiya, Y., J. Phys. Chem. 90(1986) p. 4785. ... 59, pp. 291-296. Ercolani, D., Ferreni, F., Hydrotransport 10, Ed. BHRA, Cranfield, 1979. Rambeloniaina, HV, Thesis, ULP, Strasbourg 1984. ...

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Research paper thumbnail of Sizing synthetic mixtures of latex and various colloidal suspensions by photon correlation spectrometry

Analytical Chemistry, 1986

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Effect of Ultrasound on Crystallisation-Precipitation Processes: Some Examples and a New Segregation Model

Particle & Particle Systems Characterization, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Two Different Configurations of Flow Field-Flow Fractionation for Size Analysis of Colloids

Separation Science and Technology

Flow field-flow fractionation (F.FFF) is a technique for measuring the size of species in the col... more Flow field-flow fractionation (F.FFF) is a technique for measuring the size of species in the colloidal range (1 nm to 1 μm) which makes the use of the formation of a molecular or colloidal polarization layer at the surface of a filtering membrane. The species to be analyzed are introduced into a flow of liquid passing through a channel with porous walls (of pore size less than that of the colloids to be analyzed) which allow a certain controlled flow to pass through. The remaining fraction of the flow passes through the system, carrying the colloids to a nonspecific detector. The transit time of the colloids through the channel is found to be a function of their size and the permeation rate through the porous membrane. This chromatographic system can be calibrated by using known colloids, such as standard latex particles or fractionated polymer samples, and then used to determine the size of unknown colloids. Here we present results obtained in two different systems, an asymmetric ...

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Research paper thumbnail of An experimental study of the transport and capture of colloids in porous media by a chromatographic technique

Colloids and Surfaces A Physicochemical and Engineering Aspects

We present an experimental investigation of the transport and capture of model colloids in a well... more We present an experimental investigation of the transport and capture of model colloids in a well-defined porous medium. The experiments were performed using standard liquid chromatography equipment and involve detecting the passage of small impulses of monodisperse latex particles passing through a bed of monosize glass beads. Experiments were performed with three samples of monodisperse latex particles of diameters 226, 550 and 790 nm in carrier solutions with ionic strengths ranging from pure water up to 0.1 M at a pH of either 5.2 or 8 at flow velocities varying from 0.01 to 0.1 cm s−1. The results are presented as capture efficiency as a function of the various parameters and also in the form of Sherwood number vs Reynolds number for comparison with existing correlations of mass transfer. It is shown that capture is strongly influenced by hydrodynamics and the repulsive potential energy barrier.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Laminar flow in channels with porous walls

The Chemical Engineering Journal

An analytical solution for the axial and transverse flow fields in laminar flow in porous channel... more An analytical solution for the axial and transverse flow fields in laminar flow in porous channels for both a rectangular channel with one porous wall and a porous tubular channel is presented. The solution is obtained from the Navier-Stokes equations without the simplifying assumption of constant permeation rate along the length of the duct. A dimensionless criterion for the validity of previous simplified solutions is developed which shows that the validity of the assumption of a constant permeation rate depends on the permeability of the membrane and the dimensions of the channel. Long channels with high permeability membranes can have significant departures from the constant permeation rate. The importance of these effects for the design of ultrafiltration and microfiltration modules is discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Co-broyage de principes actifs pharmaceutiques pour améliorer leur biodisponibilité

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Talc grinding in an opposed air jet mill: start-up, product quality and production rate optimization

Powder Technology, 2002

ABSTRACT We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an in... more ABSTRACT We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an inline laser granulometer. The conditions for steady state operation have been determined from continuous grinding experiments and show that overloading occurs above a critical value of feed rate classifier resulting in unstable product size distribution. For each rotation speed of the classifier, there is an optimum feed rate, which gives the finest product, thus fixing a maximum reduction ratio. A linear relation exists between this ratio and the rotation speed of the classifier. The use of liquid grinding aids have been studied and showed they can result in an increase in the production rate but can also lead to a coarser product.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Chapter 8 Air Jet Milling

Handbook of Powder Technology, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of coating active pharmaceutical substances by mechanical action

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Albi International Rencontres in Pharmaceutical Engineering

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Effect of Ultrasound on Crystallisation-Precipitation Processes: Some Examples and a New Segregation Model

Particle & Particle Systems Characterization, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Generation of static electricity during fluidisation of polyethylene and its elimination by air ionisation

Powder Technology, 2003

... In order to study the influence of static electricity on the minimum fluidisation velocity (u... more ... In order to study the influence of static electricity on the minimum fluidisation velocity (u mf ... Theelectrostatic behaviour of the two products was studied in order to set the ... As low-density polyethylene has an extremely high resistivity, ohmic dissipation during contact time with the ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Symposium STP—PMF 2007, Albi France

Powder Technology, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Vibration induced flow in hoppers: DEM 2D polygon model

Particuology, 2008

Bookmarks Related papers MentionsView impact