Mechanisms of droplet formation

Applied Science

Editor’s preface

ChemE/Product and Process Engineerin

Produktie van 1,1,1-tri-chloorethaan uit vinylchloride en chloor

Document uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science

The use of Stokes deformation number as a predictive tool for material exchange behaviour of granules in the 'equilibrium phase' in high shear granulation

The objective of this study was three-fold; to investigate the different mechanisms of material exchange during the equilibrium phase of the granulation process and whether these mechanisms are consistent with the mechanisms described in the growth regime map, to study how material properties and process conditions affect these exchange mechanisms, and to correlate Stokes deformation number to the exchange mechanisms. Microcrystalline cellulose (MCC), alpha-lactose, microfine cellulose (MFC), and dextrin were granulated using water as a binding agent. Once in the equilibrium phase, 5% (w/w) of the granular mass was replaced with wet tracer granules, after which the granulation process was continued. Granules were typically of a size of approximately I mm in diameter. Therefore, these granules can also be called pellets. Tracer experiments show indeed solid material exchange can take place in the equilibrium phase of the high shear granulation process. Tracer material was equally dispersed throughout the whole batch for all materials tested. However, the granulation time needed to reach this homogeneous distribution varied with material and granulation conditions. Three different mechanisms of material exchange were identified: exchange by disintegration, where granules are rapidly crushed and formed to granules again; exchange by deformation, where abraded granule fragments immediately fuse with other granules; and exchange by distribution, where there is a prolonged period over which both tracer and standard granules stay intact, followed by uncontrolled growth and exchange of material. It was found that it is possible to shift between the mechanisms by changing the process conditions, e.g., changing viscosity or amount of binder liquid. These observations indicate that by choosing the appropriate process conditions improved distribution of small amounts of insoluble materials in the granules can be obtained. A relation exists between the exchange mechanisms and the growth regime map: the disintegration mechanism resembles 'crumb behaviour', the deformation mechanism resembles 'steady growth', and the distribution mechanism resembles 'nucleation' and 'induction growth'. Unfortunately, Stokes deformation number cannot be used as a predictive tool when low viscosity binders like water are used, due to the importance of viscosity in the equation. However, this number is one of the variables of the growth regime map. Since the exchange mechanisms correspond to the granule growth mechanisms in the regime map, alternatively colour experiments might be used to reveal the granulation regime. (c) 2006 Elsevier B.V. All rights reserved

Design of a treatment protocol to improve the health of B12 deficient patients: Diagnostic tools and corrective measures to analyse and improve cellular function of vitamin B12

The design project entitled “Design of a treatment protocol to improve the health of B12 deficient patients” is carried out as an individual design project of PDEng program in Chemical Product Design. This project is commenced for the B12 Institute, Rotterdam, which aims to improve the diagnosis and treatment of patients with vitamin B12 and folate deficiency. The experience of the B12 Institute showed that the current diagnostic and treatment protocol is not sufficient to improve the health of some severe patients. This design project aims to provide knowledge beyond the classical theories of B12 deficiency, such that an extended protocol can be recommended to enhance the recovery and health of B12 deficient patients. The recommended protocol consists of diagnostic means and subsequent corrective actions. The approach of the project is divided into 4 major steps: 1. study of the biochemistry of vitamin B12 cellular metabolism; 2. generation of hypotheses on disorders related to B12 deficiency according to the biochemistry study; 3. recommendation of biomarkers/diagnostic tools; 4. recommendation of corrective actions. This report discusses the hypotheses of the vitamin B12 cellular inactivity, which extends the theory of the classical B12 deficiency. The hypotheses revolve around the failure of the B12 cellular activation due to enzymes defects and the activation cofactors deficiencies, as well as the failure of B12 co-enzymatic function due to oxidative stress. A series of vicious cycles between the overlooked causes and impacts in B12 inactivity is also described. The highlights of the hypotheses are summarized as follows: • B12 deficiency causes folate cycle block, which leads to glycine deficiency, • Glycine deficiency leads to glutathione deficiency and collagen deficiency, • Glutathione deficiency causes an elevated oxidative stress, and vice versa, • Collagen deficiency leads to intestinal bacterial dysbiosis, • Intestinal bacterial dysbiosis causes the production of bacterial toxins, including formaldehyde, • An excess of formaldehyde exacerbates oxidative stress and damages to the body, and may as well inactivate cellular B12. However, we found that the current knowledge on the mechanisms explaining a lower B12 enzyme activity may still be insufficient to explain the whole condition and issues related to B12 cellular inactivity. Finally, we designed a mini study to obtain evidence on a number of the hypotheses, especially those related to oxidative stress. New biomarkers for the extension of the diagnostic tools are explored. The new biomarkers are expected to provide better tools to explain the condition and symptoms of the patients. In addition, several supplements are recommended as corrective actions of the anticipated issues disclosed by the new biomarkers. The concepts and the results of the project are expected to provide new insights for the medical research and practice of B12 deficiency treatment, as well as to provide major improvement to the health of the patients.<br/

Fast computer simulation of open-air electrostatic spray painting

Applied Science

On the fluidization of cohesive powders: Differences and similarities between micro- and nano-sized particle gas–solid fluidization

The fluidization of cohesive powders has been extensively researched over the years. When looking at literature on the fluidization of cohesive particles, one will often find papers concerned with only micro- or only nano-sized powders. It is, however, unclear whether they should be treated differently at all. In this paper, we look at differences and similarities between cohesive powders across the size range of several nanometres to 10s of micrometres. Classification of fluidization behaviour based on particle size was found to be troublesome since cohesive powders form agglomerates and using the properties of these agglomerates introduces new problems. When looking at inter-particle forces, it is found that van der Waals forces dominate across the entire size range that is considered. Furthermore, when looking into agglomeration and modelling thereof, it was found that there is a fundamental difference between the size ranges in the way they agglomerate. Where the transition between the types of agglomeration is located is, however, unknown. Finally, how models are made and agglomerate sizes are measured is currently insufficient to accurately predict or measure their sizes consistently.ChemE/Product and Process Engineerin

Effect of vibrational modes on fluidization characteristics and solid distribution of cohesive micro- and nano-silica powders

In this study, the impact of different vibrational modes on the fluidization characteristics of cohesive micro- and nano-silica powder was examined. Fractional pressure drop, bed expansion measurements, and X-ray imaging were utilized to characterize the fluidization quality. The densities of the emulsion phase at the top and bottom of the column were quantified and compared, providing insights into the solid distribution within the fluidized bed. In the absence of vibration, neither powder could be fluidized within the considered range of superficial gas velocities. Vertical vibration was found to initiate fluidization for both powders. In contrast, elliptical vibration failed to overcome the channelling behavior when fluidizing the micro-powder. For nano-powder, combined channelling and powder compaction occurred when the bed was subjected to elliptical vibration. For the micro-powder, it was observed that bed homogeneity was independent of vertical vibration intensity but improved with increasing superficial gas velocity. For nano-powder, intensifying vertical vibration led to segregation, likely due to agglomerate densification. Furthermore, fractional pressure drop measurements proved to be a strong tool in assessing fluidization quality, providing insights that could not be attained by conventional indicators.ChemE/Product and Process EngineeringSanitary Engineerin