Discrete element modelling of fluidised bed spray granulation

A novel discrete element spray granulation model capturing the key features of fluidised bed hydrodynamics, liquid-solid contacting and agglomeration is presented. The model computes the motion of every individual particle and droplet in the system, considering the gas phase as a continuum. Micro scale processes such as particle-particle collisions, droplet-particle coalescence and agglomeration are directly taken into account by simple closure models. Simulations of the hydrodynamic behaviour of a batch granulation process are presented to demonstrate the potential of the model for creating\ud insight into the influence of several key process conditions such as fluidisation velocity, spray rate and spray pattern on powder product characteristics

Temporary Special Measures; Accelerating de facto equality of women under article 4(1) UN Convention on the Elimination of all forms of Discrimination Against Women

Revised papers en comments that were presented at the meeting organised in Maastricht, in October 2002. The aim of the meeting was threefold: to provide input for the CEDAW Committee; stimulate the legal debate on the issue of temporary measures; and contribute towards the promotion of positive action measures in the Netherlands.bookMensenrechte

Monitoring and Implementation of Children's Rights

Effective Protection of Fundamental Rights in a pluralist worl

Comparison between a Uniaxial Compaction Tester and a Shear Tester for the Characterization of Powder Flowability

The complete characterization of powder flow properties with shear cells is a long and time-consuming process that requires specially trained operators or costly automated instruments. For these reasons, in industrial practice, the use of simpler and less extensive measurement by uniaxial compaction testers is often preferred. However, previous studies in the literature indicate that the results of the two techniques are not directly comparable due to the different stress state conditions achieved in the two testers.In this study, an experimental campaign to measure the flow function of five different powders with a ring shear tester (RST) and a uniaxial compaction tester (UCT) was performed. Different flowability results that arose for the more cohesive powders are explained by the wall friction effect in the UCT. Re-evaluation of the results accounting for the wall friction gave substantial agreement between the two experimental techniques for a calcium carbonate powder and only at low consolidation levels for the other four food powders. Phenomena other than wall friction seem to appear within these powders tested at high consolidation levels. The comparison between the results of the two techniques suggests that straightforward extrapolation of the UCT flow functions to a low consolidation condition can lead to an underestimation of powder cohesion

Analysis of the dynamics of heat transfer between a hot wire probe and gas fluidized beds

Hot wire anemometry used inside air fluidized beds of glass (175 mu m), FCC (75 mu m) and silica (85 mu m) powders (Archimedes numbers of 510, 29 and 16, respectively) allowed the measurement of the time-resolved local heat transfer coefficient. Time averages of this coefficient reproduce the same behaviour found by other authors with different experimental techniques. A stochastic model for the heat transfer rate has been developed on the basic hypothesis that heat transfer fluctuations are due to the continuous renewal of packets of solid particles along the wire. The most relevant simplifying hypothesis is that the contact time between the wire and the packet is much shorter than the characteristic heating time of the packets. With this model, probability density distributions of the heat transfer coefficient are evaluated. Comparison between experimental and theoretical results is fairly good in all experimental conditions relative to fully developed aggregative fluidization. The model is less reliable in conditions of incipient and homogeneous fluidization, where the simplifying hypotheses may not apply. Calculated values of packet to particle size ratios, lambda/d(p), are around 8 for glass, between 14 and 36 for FCC and between 17 and 32 for silica. The increasing number of particles inside a packet seems, therefore, to be correlated, on one hand, to the decreasing Archimedes number, and on the other, to an apparently reduced particle mobility of powders belonging to the Group A of the Geldart [D. Geldart, Types of gas fluidization, Powder Technol., 7 (1973) 285-292] classification. (C) 1999 Elsevier Science S.A. All rights reserved

Analysis of the dynamics of heat transfer between a hot wire probe and gas fluidized beds

Hot wire anemometry used inside air fluidized beds of glass (175 mu m), FCC (75 mu m) and silica (85 mu m) powders (Archimedes numbers of 510, 29 and 16, respectively) allowed the measurement of the time-resolved local heat transfer coefficient. Time averages of this coefficient reproduce the same behaviour found by other authors with different experimental techniques. A stochastic model for the heat transfer rate has been developed on the basic hypothesis that heat transfer fluctuations are due to the continuous renewal of packets of solid particles along the wire. The most relevant simplifying hypothesis is that the contact time between the wire and the packet is much shorter than the characteristic heating time of the packets. With this model, probability density distributions of the heat transfer coefficient are evaluated. Comparison between experimental and theoretical results is fairly good in all experimental conditions relative to fully developed aggregative fluidization. The model is less reliable in conditions of incipient and homogeneous fluidization, where the simplifying hypotheses may not apply. Calculated values of packet to particle size ratios, lambda/d(p), are around 8 for glass, between 14 and 36 for FCC and between 17 and 32 for silica. The increasing number of particles inside a packet seems, therefore, to be correlated, on one hand, to the decreasing Archimedes number, and on the other, to an apparently reduced particle mobility of powders belonging to the Group A of the Geldart [D. Geldart, Types of gas fluidization, Powder Technol., 7 (1973) 285-292] classification. (C) 1999 Elsevier Science S.A. All rights reserved

Human rights and conflicts: essays in honour of Bas de Gaay Fortman

This book examines the fate and role of human rights before, during and in the aftermath of violent conflicts. It brings together both scholars and practitioners from different parts of the world and from different disciplines, including law, anthropology, history, conflict studies, development studies and international relations. The roles of international organisations, NGOs, governments, and corporations in realising human rights are discussed. The book thus reflects the ‘de-approach’ to human rights research that has been advocated and pioneered by Bas de Gaay Fortman: de-legalise, de-Westernise, and de-State-ise, together with his instance that human rights research should not just be about norms, but as much, if not more, about the economic, political, social, and cultural aspects of the distinct environments in which these rights have to be realised

The assessment of a simple method for powder flow characterization

The complete characterization of powder flow properties with shear cells is a long and time consuming process that requires specially trained operators. For these reasons, in the industrial practice simpler and less extensive measurement by uniaxial compaction testers is often preferred. However, previous studies in the literature indicate that the results of the two techniques are not directly comparable due to different stress state conditions achieved in the two testers. In this study an experimental campaign to measure the flow function of four different powders with a ring shear tester (RST) and a uniaxial compaction tester (UCT) was performed. Different flowability results arisen for the more cohesive powders are explained with the wall friction effect in the UCT. Re-evaluation of the results accounting for the wall friction gave substantial agreement between the two experimental techniques. The major application limit of the UCT concerning the large minimum consolidation stress value that can be applied on a powder sample was confirmed. The comparison between the two techniques results suggests that straightforward extrapolation of the UCT flow functions to low consolidation condition can lead to underestimation of powder cohesion