INVESTIGATION OF THE AIR GAP AND SLUG LENGTH RATIO IN SLUG FLOW PNEUMATIC CONVEYING

T. Krull1, K.C. Williams1, S. Hötte2 and M.G. Jones1

1. Centre for Bulk Solids and Particulate Technologies

The University of Newcastle, AUSTRALIA

2. Leibniz Universität Hannover, GERMANY

Abstract

There has been considerable research on the pressure drop prediction over a single full bore slug in dense phase conveying of granular material. However, in order to compute the total pressure drop contained within a pipeline, the ratio of air gap to slug length needs to be determined.

In this paper, multi-slug conveying tests were conducted on granular material and the slug length to air gap ratio was analysed. It was found that the average air gap to slug length ratio ( ) was dependant on the input parameters of air mass and solids flow rates into the system. Subsequently, was used in conjunction with a single slug pressure model to determine the total pressure drop of the slug flow pneumatic conveying system.

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EXPERIMENTAL STUDY OF DILUTE VERTICAL PNEUMATIC TRANSPORT USING PIV

Anette Mathisen, Britt Halvorsen and Morten C. Melaaen

Telemark Technological R&D centre (Tel-Tek)/Telemark University College

Porsgrunn, Norway

Abstract

Dilute vertical pneumatic transport is studied using the laser based experimental technique particle image velocimetry (PIV). PIV is a whole field technique and is used to gain a better understanding of the dilute gas/particle multiphase flow. The experimental setup is a vertical lifter. The PIV technique enables the simultaneous measurements of the axial and radial particle mean and fluctuating velocities as well as the cross-moments of the flow in the whole flow field at once. Two types of particles are used in the investigation. They are zirconium oxide (ZrO2) and glass beads both at two different size distributions. The superficial gas velocity has been varied in the experiments. The effects of superficial gas velocity, particle size and particle density on the particle mean axial velocities, particle u-rms and particle cross-moment were investigated.

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EFFECT OF ELBOW GEOMETRY ON PRESSURE DROP IN UPSTREAM STRAIGHT SECTIONS DURING DILUTE PHASE PNEUMATIC CONVEYING

Nstor Vsquez a, Karl Jacob a, Alexander Voets b

a The Dow Chemical Company, Midland, MI 48667, USA

b RWTH Aachen University, Germany

ABSTRACT

The pressure drop (P) produced by elbows during dilute phase pneumatic conveying has been the subject of various studies. Several theoretical expressions have been developed to estimate the additional P that elbows generate in comparison to straight sections. However, most of these calculations assume that the extra P produced by the elbow is generated either at the elbow or downstream of it due to the reacceleration of the solids. In this work, a number of tests were performed to measure the P produced by two types of elbows: long radius bend and blind tee, not only at the elbows and downstream, but also upstream of the elbows. The experiments were performed with two types of plastic pellets with similar size, density and shape, but different elasticity. For hard pellets, the results showed minor or no effect on P for the straight pipe section upstream of the elbows. In contrast, when conveying the soft pellets the effect of the elbow on the P was not only present at the elbow and downstream but it was also detected in the straight sections upstream of the elbow. Additional experiments were performed in order to determine how far the P increment could be detected upstream of the elbow. The results showed that the soft pellets change their particle dynamics before passing through the elbow, which affects the P in the straight section upstream.

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VALIDATION OF PARTICLE FLOW THROUGH A CONVEYOR TRANSFER HOOD VIA PARTICLE VELOCITY ANALYSIS

David B Hastie, Andrew P Grima and Peter W Wypych

Centre for Bulks Solids and Particulate Technologies,

University of Wollongong, Wollongong, NSW, 2522, Australia

Abstract

A critical factor in the design of conveyor transfers is the ability for material to flow at a velocity as close to that of the conveyor belt as possible. If particle velocity increases too much issues such as particle attrition, dust generation, chute wear and excessive noise can arise, whereas if particle velocity were to decrease, stagnation zones could develop, resulting in issues such as spillage or chute blockage. There are numerous methods available in which to analyse particle flow through a conveyor transfer, including; continuum based analytical methods, the discrete element method (DEM) and experimental analysis. This paper will detail the validation process for these three methods. The experimental investigations were performed on the conveyor transfer research facility located at the University of Wollongong, using high-speed video to capture the flow and analysis via Image Pro Plus. A continuum based analytical analysis was then used as an additional comparison and validation tool for the experimental results. Lastly, the use of DEM provided a third means of quantification and prediction of the particle velocity through the transfer hood.

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DETERMINATION OF THE STRESS DISTRIBUTION DURING THE DIE COMPACTION OF POWDERS BY NUMERICAL SIMULATION

J.-D. Prigge1 and K. Sommer1

1. Technische Universität München, Lehrstuhl für Maschinen- und Apparatekunde

Freising, GERMANY

Abstract

The alteration of the stress distribution during die compaction is analysed by numerical simulation. The Finite Element Method (FEM) is used, where a tablet is considered as elasto-plastic continuum. The Drucker-Prager Cap model is chosen as constitutive model to describe the material behavior during the compaction process. All parameters necessary to set up the material model are determined experimentally by a fully instrumented single punch compaction simulator. Furthermore a special die sensor equipped with strain gauges, which is able to measure radial stress states over the whole tablet height, is used for the measurements. A Finite Element simulation is carried out using the calibrated material model. First simulation results show good correlation with experimental data and prove the applicability of a FEM simulation to describe the compaction process.

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“MODELLING DOSATOR FILLING AND DISCHARGE OF POWDER”

O.A. Angulo, M.S.A. Bradley, R.J. Berry & R.J. Farnish

The Wolfson Centre for Bulk Solids Handling Technology,

University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.

INTRODUCTION

Dosators and other dosing mechanisms operating on generally similar principles are very widely used in the pharmaceutical industry for capsule filling, and for dosing products that are delivered to the customer in powder form such as inhalers. This is a trend that is set to increase. However a significant problem for this technology is being able to predict how accurately and reliably, new drug formulations will be dosed from these machines prior to manufacture.

This paper presents a review of the literature relating to powder dosators which considers mathematical models for predicting dosator performance, the effects of the dosator geometry and machine settings on the accuracy of the dose weight. An overview of a model based on classical powder mechanics theory that has been developed at The University of Greenwich is presented. The model uses inputs from a range of powder characterisation tests including, wall friction, bulk density, stress ratio and permeability. To validate the model it is anticipated that it will be trialled for a range of powders alongside a single shot dosator test rig.

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STUDY OF SUB-MICRON MILLING MECHANISM BY MEANS OF POPULATION BALANCE MODELING

S.L.A. Hennart1,2, V. Drouet3, W.J. Wildeboer1 and G.M.H. Meesters1,2

1. DSM Food Specialties

Delft, THE NETHERLANDS

2. Delft University of Technology

Delft, THE NETHERLANDS.

3. Ecole suprieure de Chimie Physique et Electronique (CPE Lyon)

Lyon, FRANCE

Abstract

The objective of this work was double: first to build a representative model of a grinding process and second to investigate the mechanisms of very fine grinding in a wet ball milling set-up as a function of the product properties and process parameters. The ball mill used was a Dynomill and the grinding media consisted of zirconium oxide beads. The grinded powder was a poorly watersoluble product. Laser diffraction techniques were used to analyze the particle size distributions.

During grinding the average particle diameter of a particulate product is reduced to a minimum value. These grinding experiments showed that for a specific product this minimum value is a fixed constant within the range of tested operating conditions. From literature is known that the minimum average particle diameter is a result of grinding and simultaneous agglomeration of broken particles. To better model this complex process, a dynamic population balance model was built that also enables the study of breakage mechanisms. The crystallite size as measured with X-Ray diffraction was chosen as the minimum achievable particle size by grinding. Simulations with the population balance model showed that the main grinding mechanisms are cleavage and some fracture for coarse particles (Relative particle size 1), cleavage and abrasion for intermediate particles (relative size of 0.05) and cleavage for fine particles (relative size smaller than 0.01).

The grinding mechanisms are related to the movement of the grinding media in the grinding chamber. Cleavage and abrasion of particles is characteristic from a compression force and long shear that is present in the centrifuged packed bed of grinding beads. The mechanism of grinding itself is not varying when changing the operating conditions; the packed bed is similar in the studied ranges.

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Effect of pH Variation in Wet Grinding System

S. Sakthivel, Venkatesan V. Krishnan, B. Pitchumani*

Particle Science and Technology Laboratory

Department of Chemical Engineering, Indian Institute of Technology,

New Delhi, India. Phone: +91-11-26591022

Abstract

Production of fine particles has drawn greater attention in many industries, but it was observed that difficult to get very fine particles in-spite of grinding for longer time. This was due to formation of paste and cake which retarded further size reduction. Later it was observed that importance of electrostatic stabilization in wet grinding system. In the present work, suspension stability (i.e. -potential) of nano particles was studied by measuring pH as a function of grinding time in the wet milling process. It was found that average particle size decreased with time and after a certain time the decrease is less and later it started increasing. The pH of silica suspension decreased with time. The pH variation was studied with zirconium, glass and alumina grinding media. The average particle size is decreased with increase in density of grinding media.

Keywords: suspension stability, - potential, nano particle, pH variation, attritor mill

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NUMERICAL AND EXPERIMENTAL STUDY OF PARTICLE MOTION AND CLASSIFICATION IN JET MILLING

T. Brosh, Y. Batat, H. Kalman and A. Levy

Department of Mechanical Engineering

Ben-Gurion University of the Negev

Beer-Sheva 84105, ISRAEL

Abstract

Jet mills are widely used in industries for grinding of solid materials due to many advantages they have over other mills. The jet-mill performance is affected by a combination of mainly two parallel processes: particle breakage and classification. In the present paper, three

dimensional Discrete Element Method (DEM) and CFD numerical simulations of particles motions in a given size’s jet mill were developed in order to obtain better understanding of the classification process. In parallel, experimental study of particles motion in a spiral jet mil was performed. Particles trajectories were captured as a function of particles size, air flow rate and the mill loading. The predictions of the numerical simulations were compared with the experimental data. The predictions were used to analyze the flow field characteristics and the classification process.

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WEAR RESISTANT COMPONENTS IN

MINERAL PNEUMATIC CONVEYING SYSTEMS

Bruno Zinser

Coperion Waeschle GmbH & Co. KG

Weingarten, GERMANY

Abstract

Conveying of hard, wear intensive product under pressures of 1 bar and more leads to high abrassive and erosive wear on the components of the pneumatic conveying systems. In the past the lifetime of a rotary and diverter valves for example in cement or alumina systems at 1 bar was limited. Newer developments have shown that due to improved design principles and the selection of adequate wear resistant materials, these components have a dramatical increased service time even in operation with high abrasive material. Materials have been checked in test facilities under different abrassive mineral products. Wear resistant materials have been selected due to conveying product parameters as particle size, shape and hardness and according to parameters given to the process surroundings like angle of impact etc. As the wear protection has to be used at different positions, different ways how to apply e.g. tungsten carbide has to be chosen (different welding technologies, cladding). As protection surfaces often have to be used in shock intensive places, ceramic parts have to be protected or shock resistant matrix compounds as e.g. tungsten carbide – nickel materials have to be used. The service life of diverter valves have been multiplicated by factors of 20 and more by using high end materials as ceramic and highly filled tungsten carbide instead of wear materials that have been state of the art in these components up to now. These wear protections can also be used in pipes and bends or to protect edges in process parts as illutriators and mixer inserts in silo cones. Rotary valve where these results are applied are today in operation with hard material as e.g. alumina at performances of 200 t/h. With these new technologies experiences show that rotary valves can be used now in applications that have been reserved for spiral pumps up to now. As the rotary valve can now compete with the service time, customers have recognized the big advantages due to very much lower power consumption of often less than 10 %, which refinances an exchange even of an existing spiral pump in s short period of time.

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MOTION OF COARSE PARTICLES IN A HORIZONTAL PNEUMATIC PIPE

H. Tashiro1 and Y. Tomita2

1. Kurume Institute of Technology

Kurume, Fukuoka, JAPAN

2. Kyushu Institute of Technology

Kitakyushu, JAPAN

Abstract

The horizontal pneumatic conveying of coarse particles which are continuously fed into the pipe one by one, of which the particle diameter ratio to the pipe is 0.2, is examined experimentally and numerically. It is shown that the particle conveying is possible even when the mean air velocity is smaller than the terminal settling velocity of particle as well as the case in which diameter ratio to the pipe is larger than 0.2 and that the particle velocities which were made dimensionless on the mean air velocity are almost constant independent of air velocity unlike the case in which diameter ratio is larger than 0.2, and that those dimensionless velocities are smaller than those on the case in which diameter ratio is larger than 0.2 except the case in which air velocity is small. We define the saltation velocity as the terminal settling velocity because the particle motion changes at around that velocity, except for particle with very large density. Furthermore, there is a maximum in the number of revolutions for each particle, at which air velocity is larger for

larger density particle. The numerical results of the particle velocity and number of revolution show a qualitative agreement with the experiment.

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MEASUREMENT OF DENSE-PHASE PIPE FORCES IN AN INDUSTRIAL–SIZE CONVEYING SYSTEM

Thorsten Fatho, Hans Schneider, Harald Wilms

Zeppelin Silos & Systems GmbH, Friedrichshafen, GERMANY

Abstract

Dense-phase conveying systems generate impact forces when slugs impact into a bend. The resulting pipe forces can destroy pipes, nozzles and pipe supports and need to be known for reliable design. Zeppelin has equipped a full-scale test facility with force transducers and sensors to determine slug size, velocity and impact forces. Results from conveying tests with several different polymer pellets are presented. The frequency distribution of different pipe forces is shown as well as the influence of different pipe supports.

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SILO DISCHARGE OF AN ULTRAFINE COHESIVE POWDER BY VIBRATING HOPPERS

G. Kache, D. Pötsch, A. Haack and J. Tomas

Otto-von-Guericke-University Magdeburg, Mechanical Process Engineering

Magdeburg, GERMANY

Abstract

The production of ultrafine powders requires reliable powder storage and handling equipment. The powder flow in a silo or bunker – normally driven by the force of gravity – is frequently stopped by channelling or bridging. As a solution of this serious problem, the gravity flow can be promoted using an additional energy input by mechanical vibrations. The discharge rate can be controlled by pulsating operation of the vibrating hopper. It is possible to predict necessary operating and idle periods (pulsed operation) by calculation of the discharge velocities at the annular gap of a vibrating hopper and at the outlet. To prove the calculation, experiments on the silo scale are carried out.

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PREDICTION OF FLOW MODE DURING SILO DISCHARGE AND ITS PRELIMINARY VERIFICATION

S. Ding 1, M. Jecmenica 2, G.G. Enstad 1, 2, J.Y. Ooi3 and J.M. Rotter 3

1. POSTEC dept. av TEL-TEK R&D Centre, 3917 Porsgrunn, Norway

2. Telemark University College, P. O. Box 203, Porsgrunn, Norway

3. School of Engineering and Electronics, University of Edinburgh, EH9 3JL, Scotland

Abstract

An in-house FE program was used to predict the particulate solid discharging pattern from a silo, and the effect of a double-cone insert on flow pattern during discharge. The FE predictions deployed an Eulerian approach with the assumption of a steady state flow. Such an assumption enabled investigations into effects of an insert on the granular material flow in silos; several case studies were thereby carried out. In order to check the simulation results, some

experimental tests were also carried out; comparisons were made qualitatively between the simulated results and experimental measurement for some cases.

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NUMERICAL SIMULATION STUDY UPON GRANULAR MATERIALS FLOW IN SILOS

Guoxian Xiao1,2, Delong Xu2 and S Ding3

1. Dept. of Material Sci. & Eng., Soochow Univ., Suzhou, China

2. Institute for Powder Eng., Univ. of Archi. & Tech, Xi’an, China

3. Postec dept. av Tel-Tek, Kjølnesring, Porsgrunn, Norway

Abstract

In the investigation into bulk solids flow behavior, it is more common to describe the flow phenomena on a macro-scale level, while relatively less is the effects of solid properties on its flow behavior from the view point of microcosmic scale, thus some phenomena can’t be plausibly explained. In this paper, the flow pattern of the discharging process for two-dimensional plane silos with a cone-in-cone insert is investigated by using Discrete Element Method (DEM). The placement of cone-in-cone insert with suitable location can improve the flow behaviors from funnel flow type to mass flow type during discharging. The effects of using cone-in-cone insert on the flow pattern and wall stress are analyzed in this study. Also, with the aid of liquid bridge model, the

flow of wet particles in a silo is investigated by DEM in order to gain a clear idea of the influence of liquid bridge on the flow patterns and the flow rate of bulk solid.

Keywords: Bulk solidNumerical simulationSiloInsertLiquid bridge force

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DRY COATING PROCESS USING POLYSACCHARIDES IN A PAN COATING SYSTEM

L. Bilancetti1, C. Loisel1, F. Depypere2, K. Dewettinck2, J.G. Pieters3, D. Poncelet1

1. ENITIAA - GPA, Rue de la Graudire, F-44322 Nantes Cedex 03, France;

2. Food Technology and Engineering and 3. Biosystems Engineering, Ghent University, Belgium

Abstract

Coating of inert pellets of microcrystalline cellulose with modified starches by the dry powder coating technique was investigated, as an alternative to organic- and aqueous-based coatings.

The coating process has been conducted in a Pan coater and the coating formulation is divided into two components, a powder polymer and a liquid plasticizer.

The experiments carried out have shown high coating process efficiency. The best coating results were obtained using particles smaller than 50µm and having a polygonal shape. The dry coating technique has shown a reduction of processing time compared to standard coating techniques. SEM analysis has shown uniform coating shell thickness onto pellets without presence of

coalescences in processes conducted at room temperature.

Confocal Laser Scanning Microscopy (CLSM) was used to characterize the dry coated particles in order to measure coating quality and thickness. A protocol for dry coated pellets characterization has been set up. Results obtained by CLSM have demonstrated an effective increase in coating thickness with increasing coating level.

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WATER-SOLUBLE CELLULOSE DERIVATIVES AS COATING AGENTS IN FLUIDIZED BED PROCESSING

K. Nienaltowska1, F. Depypere1, F. Ronsse2, J. Pieters2 and K. Dewettinck1

1. Food Technology and Engineering, Ghent University

Gent, BELGIUM

2. Biosystems Engineering, Ghent University

Gent, BELGIUM

Abstract

The fluidized bed coating process is characterized by a variety of input variables, which include process variables, core material properties, coating material characteristics and environmental conditions. The effectiveness of the fluidized bed coating process can be verified by the quantification of coating quality. Coating quality is strongly affected by the parameters of the fluidized bed process (e.g., inlet air temperature, coating liquid spray rate, nozzle atomization air pressure) and the properties of coating materials (e.g., chemical properties, viscosity, interaction with water, glass transition temperature).

Within this research quality of the coatings obtained from water–soluble cellulose derivatives (methylcellulose, carboxymethylcellulose and hydroxypropylcellulose) was investigated through microscopical analyses (CLSM combined with SEM). As the coating quality depends on material properties and process parameters, in the first part of the research the properties of the cellulose derivatives have been studied; a second part involved research on the influence of process parameters on the final quality of the coating.

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Dry Particle - High Impact - Coating of Biopowders

- Coating Strength of Biopowders

S. Ötles, A. Chamayou, L. Galet, O. Lecoq, J.A. Dodds

Ecole des Mines d'Albi – Carmaux, Campus Jarlard 81013 Albi, France

Abstract

The aim of this paper is to develop a fundamental knowledge on dry coating, to understand the coating strength of our bio – couples with a theoretically and experimental approach and how it is affected by the size of host particle and choose of dry particle coating equipment. For this purpose, we examine the feasibility of dry coating of two different particle size distributions of Cellets particles with Talc using a Nara Hybridizer (NHS – 0), Cyclomix and Turbula, high impact force systems that have been used successfully in the past for various applications. For a given couple host particle / guest particle it is necessary to determine suitable operating conditions in order to achieve surface modification. Particle adhesion has been also studied theoretically by van der waals approach. An experimental method based on a commercial granulometer is used to study the coating strength of the composites and allows us to study the influence of the particle size of the initial particles.

Keywords : Bio – powders, Dry coating , van der Waals, adhesion, Nara Hybridizer, Coating strength

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PERFORMANCE ANALYSIS OF A ROTARY SPREADER

Alan W. Roberts1 and Mark G. Jones

1. Emeritus Professor 2. Professor and Director, Centre for Bulk Solids and Particulate

Technologies, The University of Newcastle, NSW 2308 Australia

Abstract

The performance of a rotary spreader for distributing a bulk solid being fed into the top of a storage bin is analysed. On entering the bin, the falling bulk solid makes contact with the rotating blades and is propelled outwardly in a radial direction. The differential equations describing the motion are derived and solutions are obtained to determine the velocity and stream thickness as functions of the radial position along each blade. The influence of rotational speed and blade radius of curvature on the performance in relation to the feeding and spreading efficiency is examined.

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DETERMINATION OF THE UNDESIRED CONSOLIDATION BY MECHANICAL VIBRATIONS AT COHESIVE POWDER FLOW

A. Haack, G. Kache, S. Winkler, and J. Tomas

Otto-von-Guericke-University, Mechanical Process Engineering

Magdeburg, GERMANY

Abstract

In the industrial practice undesired compression and consolidation of cohesive powders by mechanical vibrations can be often obtained. This powder consolidation occurs at running flow promotion device with a reduced outflow at blocked discharge opening as consequence. To determine this consolidation behaviour a vibrating shear tester according to Roberts [1] and Kollmann [2] is used. At this arrangement the vibration direction and the shear direction are perpendicularly to each other. The vibrations are directly applied to the shear base. Shear tests are accomplished according to Jenike [3] in a normal stress range from 0.5 to 16 kPa with the constant shear rate 2 mm/min. The mechanical vibrations are applied between the preshear and shear steps with different intensities and operating times. The consolidation behaviour is evaluated by the increase of the shear stresses for a very cohesive limestone powder.

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INFLUENCE OF CRYSTAL PROPERTIES ON POWDER FLOW BEHAVIOUR

R. Beck1, D. Malthe-Sørenssen1, J.-P. Andreassen1,

T.O. Nysæter2, G.G. Enstad3

1: Department of Chemical Engineering, NTNU, Norway

2: Telemark University College, Norway

3: Department of POSTEC, Tel-Tek, Norway

ABSTRACT

This comparative study focuses on the effect of crystal morphology and chord length distribution on flow properties of dry material of L-glutamic acid and an aromatic amine. Polycrystalline particles with a roughly spherical shape have been identified in the industrial production of an aromatic amine derivative, where powder handling is one of the down-stream processes following crystallization. L-glutamic acid was chosen as a comparative model substance as it can also be crystallized as such spherulitic particles. For L-glutamic acid, different process conditions also yielded needle-shaped and polyhedral particles. Measured failure strength values for needleshaped and polyhedral particles were found to be lower than for the polycrystalline spherulites.

For the aromatic amine, it was possible to crystallize spherulites with different morphology and chord length distributions. Though the chord length distributions of the L-glutamic acid spherulites is lower than for the aromatic amine spherulites, the failure strength values of aromatic amine are more than four times as large, leading to the conclusion that other parameters than morphology and chord length distribution influence on the flow properties.

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MORPHOLOGY AND VISCOELASTIC BEHAVIOUR OF HPMC CAST FILMS AS MODEL FOR “QUALITY BY DESIGN” APPROACH FOR COATING CHARACTERIZATION

Giacomo Perfetti 1), K. Jansen 2), H. Wildeboer 3),G. Meesters 3)

1) NanoStructured Materials, Faculty of Applied Sciences, Delft University of Technology,

Julianalaan 136, 2628 BL Delft, The Netherlands, g.perfetti@tudelft.nl

2) Faculty of Mechanical Maritime & Materials Engineering, Mekelweg 2, Delft University of

Technology, 2628 BL Delft, The Netherlands

3) DSM Food Specialties, P.O. Box 1, 2600 MA Delft, The Netherlands

Abstract

Films based on aqueous dispersion of four molecular weight grades HydroxyPropyl MethylCellulose HPMC were cast (around 100µm) and stored until equilibration at different Temperature and Relative Humidity conditions. In this paper morphology and structure of the cast films were evaluated by X Ray Diffraction and Scanning Electron Microscope SEM. In addition, Dynamic Mechanical Thermal Analysis DMTA experiments were carried out on single HPMC cast film in order to assess viscoelastic properties of polymer cast films by detecting Dynamic Storage Modulus E’, Dynamic Loss Modulus E’’, Tan and Glass Transition over a wide temperature – frequency ranges. Magnitudes of E’, E’’ and Tan are discussed with relation to molecular weight, viscosity and coating solution’s concentration. Based on a time-temperature superposition principle, Shift Factor (aT) was obtained, which was used to get E’ and E’’ master curves. Furthermore the impact of temperature, environmental conditions and water content (through the analysis of glass transition temperature) could be investigated using the Time-Temperature Superposition principle.

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HYGIENIC DESIGN FOR COMPONENTS OF PNEUMATIC FOOD CONVEYING SYSTEMS

Bruno Zinser and Martin Stephan

Coperion Waeschle GmbH & Co. KG

Weingarten, GERMANY

Abstract

Plants for the different food applications face new demands, as the requirements for hygienic applications increase and production costs have to be decreased at the same time. Risk analysis have to be considered by the operating company to ensure that the components and the operating mode for example of a pneumatic conveying system for a baby food plant comply to the requirements. Up to now most of these plants get cleaned by using the COP-method (cleaning out of place). In this case components are manually opened, parts are removed and the plant gets flushed in the cleaning process. The removed parts get cleaned out of the main component and inserted afterwards. With the newer CIP-method (cleaning in place) plants meet the requirement that the system get cleaned with less manpower and with shorter downtimes. Cleaning in place means that the component can be cleaned without getting disassembled. Therefore the unit has to be designed according to hygienic guidelines to ensure that the component is residually free of germs and dirt. The EHEDG (European hygienic engineering design group) provides guidelines for components in hygienic operations. The EHEDG can also execute a test that ensures that a component complies with the requirements. In this test the unit gets contaminated in the first step and cleaned in a defined way in the second step. In the following analysis the EHEDG verifies with agar if there are still germs in the component. After a positive test the EHEDG provides a certificate

for CIP applications. In the recent past such tests have been successfully carried out the first time for a hygienic diverter valve and a hygienic rotary valve.

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DESCRIPTION OF THE FLOW IN THE SILO MODEL

I. Sielamowicz

Bialystok Technical University

Bialystok, POLAND

Abstract

The paper presents the mathematical description of vertical velocities and flow rate in the silo model. The analysis is based on the data obtained from the registered images of the granular material flow made by the PIV technique. In the analysis we present the comparison of experimental readings with empirical descriptions. Velocity profiles were used to this theoretical analysis to describe variation of vertical velocity from some factors. Parabolic function was proposed to describe vertical velocity of granular material in the model. The detail analysis of function parameters is conducted.

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MECHANICAL ATRITION OF SODIUM CHLORIDE PARTICLES IN A GAS-FLUIDIZED BED

V.O.P Valdo, K. Tannous

School of Chemical Engineering, UNICAMP

Campinas, Brazil

Abstract

The main proposal of this work is to investigate the mechanical attrition of sodium chloride crystals in a cold fluidized bed. A complete factorial design 23, with repetition and a central point, was applied in order to verify the influence of different variables upon the attrition rate. From the statistical analysis of the experimental design, the Pareto chart showed positively the influence of all variables studied. A first order model was proposed with suitable agreement with the experimental data.

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POPULATION BALANCE MODELING OF GRANULATION

C. Turchiuli(1,2) , T. Jimnez(1), B. Broyart(1), E.

(1) AgroParisTech, UMR 1145 Gnie Industriel Alimentaire F-

(2) Universit Paris Sud XI, IUT d’Orsay, F-91400

Abstract

Population balance equations (PBE) were combined with model particles growth in a top sprayed fluidized bed. From air

fluidized bed reactor was modelled as two perfectly mixed reactors corresponded to the “cold” wetting-active zone where particles can agglomeration. The other one included heat transfer zones where it variation occurred. The model was applied to the agglomeration of glass solution (binder) for different process conditions (air temperature (T = (QL = 2.65, 5.33, 7.75 ml/min), bi-fluid nozzle air pressure (P = 1, 2, 3 (Ch = 500, 750 g)). The discretized agglomeration kernel i,k was defined k, and g. bo, representing the kinetic rate of the size distribution variables whilst k and g did not vary.

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Characterisation of Flowability of Cohesive Powders using Indentation

Chuan Wang, Ali Hassanpour and Mojtaba Ghadiri

Institute of Particle Science and Engineering, University of Leeds, Leeds, LS2 9JT, UK

ABSTRACT

In many pharmaceutical processes such as mixing and filling process, characterisation of flowability of cohesive powders is of great industrial interest. This is particularly for the case of the dispersion in dry powder inhalers. In this paper, indentation on a powder bed is proposed for characterisation of flowability of small quantities of cohesive powders compacted to low levels of consolidation pressures. In parallel the bulk powder has been subjected to the traditional unconfined direct compression test method, in order to characterise the flowability by measuring the unconfined yield stress. It was found that the indentation hardness results can be related to the unconfined yield stress using a constraint factor (C). Simulation by the Discrete Element Method (DEM) is used as an approach to obtain an in-depth understanding of the deformation process during the indentation process and to estimate the value of the constraint factor.

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PARTICLE CHARGING IN NANOFLUIDIZATION

M.A.S. Quintanilla1, J.M. Valverde1, M. J. Espn2 and A. Castellanos1

1. Faculty of Physics. University of Seville.

Avenida Reina Mercedes s/n, 41012 Seville. SPAIN

2. Dpt. of Applied Physics II. University of Seville

Avda. Reina Mercedes s/n, 41012 Seville, SPAIN.

Abstract

Gas-fluidization of nanoparticles, providing extremely high fluid-solid contact and reaction efficiency, has become one of the most promising techniques for emerging industrial applications. Observations of uniform fluidization is usually related to the formation of porous light agglomerates due to the strong interparticle attractive forces as compared to particle weight. It is generally accepted that nanoparticle agglomerates have an average size of the order of hundreds of microns and a broad size distribution. In this work we report on measurements of agglomerates electrostatic charge by analyzing the deflection of their trajectories due to an externally applied electric field. A main result from this analysis is that nanoparticle agglomerates carry an electrostatic charge in the fluidized bed of a value of the order of 10-14C, which is comparable to the typical charge measured in pneumatic conveying of micron sized and larger particles. This high charge level acquired in fluidization is attributable to the large specific surface area of nanopowders.

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STRESS STATES AND POROSITY WITHIN HORIZONTAL SLUG BY DENSE-PHASE PNEUMATIC CONVEYING

I. Lecreps1 and K. Sommer1

1. Technische Universität München – Lehrstuhl für Maschinen- und Apparatekunde

Freising, GERMANY

Abstract

By slug-flow conveying particles are conveyed gently in form of slugs partially filling the whole cross-section of a pipeline. Unfortunately, this mode of flow is still difficult to understand and to predict. Yi and Wypych developed 2003 an iterative procedure to predict the pressure drop by horizontal slug-flow conveying. This method, involving force balances on the one hand and the empirical equation of Ergun on the other hand shows very good results. However, it involves a stress transmission coefficient from axial to radial direction, which is difficult to measure and mostly calculated from theoretical models. Thanks to a new measuring device including both stress and pressure sensors, horizontal single slugs could be investigated to determine porosity and stress states within slugs of cohensionless granular material. Each slug displays porosity much higher than the bulk porosity itself. Nevertheless, high wall shear stress and normal stress could be detected within each slug.

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INFLUENCE OF TECHNOLOGICAL PARAMETERS ON COMPRESSION AND FLOW BEHAVIOUR OF COHESIVE POWDERS

M. Stasiak12, J. Tomas1, M. Molenda2, L. Grossmann1 and P. Müller1

1. Department of Mechanical Process Engineering, Otto-von-Guericke University,

Magdeburg, GERMANY

2. Department of Physical and Technological Properties of Agricultural Materials

Institute of Agrophysics, Polish Academy of Science,

Lublin, POLAND.

Abstract

Research was conducted to examine the influences of some technological factors on properties of two powders - microcrystalline cellulose (MCC) and potato starch (PS). A low pressure range (up to 10 kPa) was applied in direct shear test to determine flowability and friction

properties. A medium pressure range (50-1000 kPa) was applied in the press shear cell to evaluate friction properties of MCC. The compression behaviour of MCC was determined in uniaxial compression tests at high pressure range (30-60 MPa).

A strong influence of consolidation time on flow function was observed. In the case of PS a strong slip stick effect was also noted. An increase in temperature from 23ºC to 40ºC resulted in a 10% increase of the internal friction angle value determined in the press shear cell in the range of preshear displacement from 0.1 to 2 m. There were no strong influences of temperature, speed of deformation and initial sample height on compression behaviour determined in uniaxial compression tests at high pressure range.

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PRELIMINARY INVESTIGATION INTO MAGNETITE POWDER’S MAGNET SHIELDING EFFECT ON DRILLING FLUID

S. Ding1, F. von Hafenbrädl1, A. Saasen2 and P.A. Amundsen2

1. POSTEC dept. av Tel-tek R&D centre, 3914 Porsgrunn, Norway

2. SPE, StatoilHydro ASA & University of Stavanger, Norway

Abstract

Magnetic contamination of the drilling fluid shields the Earth's magnetic field measured by the magnetic sensors, and might contribute significantly to errors in directional surveying of wellbores. A series of laboratory measurements were initiated to understand such a magnetic shielding effect. In the measurement, a single axis fluxgate magnetometer was immersed in a well defined magnetic drilling fluid, and the vertical component of the Earth's field inside the fluid was measured. It was found the magnet field inside the fluid damped significantly in a presence of magnetic powders. The finding of time dependency of the magnetic shielding is so far unknown to the surveying of wellbores; and could be used to illustrate how directional magnetic positioning tools give erroneous readings.

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METHODS AND EQUIPMENT OF MEASURING LOADS OF PRESSURE OF BULK MATERIALS AGAINST SILO WALL AND BOTTOM

Kamiski Mieczysaw1, and Maj Marek2

1. Institute of Civil Engineering Technical University of Wroclaw, Poland,

2. Institute of Civil Engineering Technical University of Wroclaw, Poland,

Abstract

The authors of this paper who are members of the research team in the Institute of Civil Engineering of the Technical University of Wroclaw, for more than 30 years have been carrying out researches on silos for cement, limestone powder, rape, sand, ash fly, flour, coal, gypsum (Fig. 4, 5, 6, 7), etc. They had big influence on preparing polish silo codes [1,2].

These investigations were carried out on silo batteries, free-standing silos and silo models (Fig. 10). The researches include the evaluation of value of pressure and temperature field on the silo wall as well as temperature gradient, registration of simultaneity of these loads, influences of the wall stiffness and wall inclination on pressure changes, strength and quantity of the reinforced bars, strength of concrete, thickness of the silo wall, vertical and horizontal distances between bars, value of imperfections, thickness of the silo wall, quality of lap splices, corrosion grade, etc [3 ,4, 5, 7, 8, 10, 12]. Each of these investigated parameters is a random variable. Collection of such data as pressure, temperature, coefficients mentioned above etc. is of great significance, so the authors measured these loads many times. There is the need of calculation such quantities as characteristic value of measured loads and strength parameters, material and loads coefficient partial coefficient of safety, reliability indexes etc [6, 11]. These data were subjected to statistical accounts. The data obtained from calculations can be used in designing similar silos.

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NON-INTRUSIVE MEASUREMENT OF PARTICLE TRAJECTORIES AND VELOCITIES IN PNEUMATIC CONVEYING PIPELINES USING POSITRON EMISSION PARTICLE TRACKING TECHNIQUE (PEPT)

AR Chaudhry1*, MSA Bradley2, AR Reed2

1 Portasilo Bulk Handling Systems, York, YO32 9PR, UK; formerly of The Wolfson Centre for

Bulk Solids Handling Technology.

2The Wolfson Centre for Bulk Solids Handling Technology, The Medway School of Engineering,

The University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK

In collaboration with Positron Imaging Centre, School of Physics and Astronomy, University of

Birmingham, Edgbaston, Birmingham, B15 2TT, UK.

Abstract

Computer simulations are finding increasing role in solving engineering problems. In recent years the field of pneumatic conveying has had a fair share of computer simulations and a number of researchers have developed codes to simulate two phase flow. This shift of research from experimental towards simulated work has not diminished the scope of experimental research and most of these simulations require various coefficients which need to be determined experimentally.

A number of simulations have been presented on particle motion in two phase flow but no researcher has compared the results of these simulations with experimentally measured particle trajectories. In the work reported in this paper, a PEPT technique has been applied to determine particle trajectories and velocities in horizontal lean phase conveying through a bend. This technique allows an individual tracer particle which is labelled with positron emitting radioactivity to be tracked. The information obtained consists of a history of the particle’s location in three dimensional coordinates over time, which is subsequently analysed to obtain trajectories. This work looks at a trajectory of a single particle passing through two different bends with radius to diameter ratios of 10 and 6 at different steady state lean phase conveying conditions.

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MICROMECHANICS OF ULTRAFINE PARTICLE ADHESION – ENERGY ABSORPTION AT CONTACT

Jürgen Tomas

Mechanical Process Engineering, The Otto-von-Guericke-University

Universitätsplatz 2, D – 39 106 Magdeburg, Germany

Abstract

The mechanical product behaviour of dry, ultrafine cohesive powders (d < 10 µm) is characterized by insufficient flowability and large compressibility. Consequently, a comparatively large energy input is necessary to promote the non-rapid frictional shear flow in powder handling practice. When two adhesive particles are coming in contact, the constitutive models of four stressing modes, namely by compression and detachment (tension), sliding, rolling and spinning (torsion) have to be modelled, see the previous papers of Tomas [1, 2]. Next, the consequences of elasticdissipative, elastic-plastic, frictional unloading and reloading paths of normal and tangential forces,

rolling and torsional moments are discussed with respect to energy absorption. The total energy absorption comprises contributions by elastic-dissipative hysteresis due to microslip within the contact plane and by fully developed friction work when the friction limits of displacements are exceeded during contact sliding, particle rolling or rotation. With increasing contact flattening by normal load, these friction limits, hysteresis and friction work increase. Thus, the understanding of the micromechanics of particle adhesion is essential to assess the powder product quality and to improve the process performance in particle technology.

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DIRECT MEASUREMENT OF POWDER FLAVOUR ADHESION ONTO A FOOD SURFACE USING A NOVEL ADHESION TESTER

E.Ermis, R.J.Farnish, R.J.Berry, M.S.A.Bradley

The Wolfson Centre for Bulk solids Handling Technology

The University of Greenwich

Chatham Maritime ME4 4TB Kent, UK

ABSTRACT

The firm adhesion of flavouring particles onto crisp surfaces during coating processes is a major concern in the snack production industry. Detachment of flavouring powders from products during handling and production stages can lead to substantial financial losses for the industry, in terms of variable flavour performance and extended cleaning down time of fugitive particle build-up on process equipment. Understanding the adhesion strength of applied bulk particulates used for flavouring formulations will help analysts to evaluate the efficiency of coating processes and potentially enable them to assess the adhesion strength of newly formulated flavouring powder prior to commitment to full scale plant trials.

A rapid prototype of a novel adhesion tester has been designed and constructed. The apparatus operates according to the principle of impact force acting on particles attached to the surface of the food substrate. The main component is a circular plate to which four sample holders are attached and which is subjected to vertical travel down a guide shaft.

Several flavouring powders have been tested extensively. By plotting the detachment versus impact force, the difference obtained between adhesion strength of different flavouring powders (which is a strong function of particle size) has been discussed.

Keywords: Adhesion, crisps, flavouring powder, coating, bio-powder

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AERODYNAMIC DISPERSION OF COHESIVE POWDERS: THE EFFECT OF INTERPARTICLE COHESION

G. Calvert, A. Hassanpour and M. Ghadiri

Institute of Particle Science and

Engineering, University of Leeds, Leeds, LS2 9JT, UK

Abstract

The dispersion of dry powders is important for a number of applications, including particle characterisation and Dry Powder Inhalers (DPIs). However it is difficult to disperse particle clusters due to relatively large interparticle attraction forces compared to particle weight. We report an experimental and computational approach for analysing aerodynamic dispersion of cohesive powders. The unconfined yield strength as a function of the major principal stress is measured for -lactose monohydrate and calcium carbonate to determine powder cohesion and flow

function. The powder is then dispersed using pressurised air. The dispersion efficiency is related to cohesion and disperser pressure. The computational approach investigates a single cluster of particles stuck together by van der Waals forces in a linear shear flow field. The cluster undergoes shear deformation and elongation before it disintegrates.

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FLOW IN VENDING MACHINE CANISTERS AND DOSAGE

M.Ramaioli1 and T.M.Liebling2

1. Nestl Research Centre, Lausanne, SWITZERLAND

2. Ecole Polythecnique Fdrale de Lausanne, SWITZERLAND

Abstract

The flow in a vending machine canister and dosing is studied experimentally and successfully compared with a three dimensional DEM simulation. The latter is made possible by the development of an efficient algorithm to detect the contacts between spherical grains and the dosage coil. The agreement is good, both in terms of the shape of the surface and the dosed mass. The study of the simulated canister flow highlights the presence of a shearing layer above the dosing coil and its role in conveying beads toward the exit of the canister. These beads then merge with those transported inside the coil to form the stream leaving the canister during dosage. The dosed mass decreases progressively over time. Contrary to intuition, the mass of beads conveyed by the screw is almost constant over time. The decreasing contribution of the free flow from the layer of beads above the screw is identified as the main source of the overall dose variation.

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APPLICATION OF THE THEORY OF MARKOV CHAINS TO DESCRIBE MULTI-STAGE PARTICLE BREAKAGE DUE TO FATIGUE

V. Mizonov1, H. Kalman2, H. Berthiaux3

1. Ivanovo Power Eng. State University, Ivanovo, RUSSIA

2. Ben-Gurion University of the Negev, ISRAEL

3. Ecole des Mines d’Albi – Carmaux, UMR CNRS 2392, Albi, FRANCE

Abstract

The objective of the study is to adapt the population balance model to describe the particle size distribution transformation in the process of grinding when fatigue breakdown plays an important role. The theory of Markov chains is used to build the model. The sample state of the process is presented as a two dimensional array of cells. Each column of the array describes the particle size distribution following a certain number of previous loadings. The process is controlled by the partitioned matrix of grinding consisting of matrices of grinding that follow a certain number of previous loadings and matrices controlling transitions of fractions from one loading to another. Some of results of numerical experiments demonstrating workability of the model are presented. It is shown that, if the fatigue properties are essential, the particle size distribution in the fine material can differ strongly from the one predicted by a model that does not cover these properties.

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PARTICLE BREAKAGE IN AGITATED DRYERS

C.L. Hare1, M. Ghadiri1 and R. Dennehy2

1. IPSE, University of Leeds

LS2 9JT, UK

2. GlaxoSmithKline Particle Sciences Group

Tonbridge, Kent, TN11 9AN, UK

ABSTRACT

Pharmaceutical materials dried in agitated contact dryers are prone to breakage due to shear deformation of the bed. This has negative affects on downstream processing, therefore it is of great interest to be able to understand and control the extent of breakage. In this paper the stress distribution in the dryer is analysed using the Discrete Element Method (DEM), and the simulation is validated using torque measurements on the impeller in the experimental and simulated dryers. The extent of attrition caused by the stresses present in the dryer is analysed using the attrition shear cell. By mapping the stress distribution in the dryer and relating the attrition occurring in the cell at these stresses, the attrition in the dryer is estimated.

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