A. Alvaro

Fluidization and elutriation of iron oxide particles. A study of attrition and agglomeration processes in fluidized beds

Abstract Elutriation is a way of separating particles by means of fluidodynamic forces as well as a very common method to generate solid aerosols to be used for many different purposes. In this work, a study of the elutriation of different size iron oxide particles from a fluidized bed has been carried out in order to determine the elutriation rate constants and the magnitude of the attrition and agglomeration processes in a fluidized bed of this sort of powder, which can be considered as C-type in Geldarts particle classification. The fluidized bed was formed by a mixture of sand and iron oxide particles. Sand particles were much bigger than iron oxide particles and the weight of the latter particles, which were elutriated was very small compared with the initial weight in the bed so that the weight of the bed could be considered as a constant. Theory about elutriation and its application to study the iron oxide behaviour and to determine the elutriation rate constants are presented. Experimental results showed the importance of attrition and agglomeration in iron oxide powders. The smallest iron oxide particles were not those most easily elutriated from fluidized beds of mixed size particles. These particles may be agglomerated between them or with larger sand particles. Elutriation results were compared with previous literature and it was found that a correlation similar in form to Yagi and Aochis correlation fits the experimental results quite well.

Fluid-solid mass transfer in magnetic filtration

Abstract A theoretical model for the process of magnetic filtration of paramagnetic particles suspended in water and a method for determining the kinetic parameters of the model is proposed. To validate the theory, 10 experimental runs were conducted on a cylindrical filter of 300 mm diameter, containing a concentric iron rod of 250 mm diameter and a bed of spherical iron beads of 8 mm diameter. The suspension was made from iron oxide powder particles in a size range between 2 and 30 μm. The current intensity circulating in the coil which surrounded the filter ranged from 240 to 350 A. and the suspension superficial velocity varied between 1 and 2.2 m/min. The model supposes that the filtration rate is proportional to both the particle concentration in the suspension and the fraction of the iron spheres that are not covered by the deposited paramagnetic particles. The results show that the model can adequately describe the physical phenomena occurring in the filter.

Comparative study of different fabrics in the filtration of an aerosol using more complete filtration indexes

Abstract The influence of the yarn number (or titre) of several polyester/wool fabrics on their behaviour as filter media has been studied. The main purpose of the study was to determine the relationship between their structures and their performance as filters, especially when the fluid to filter is an aerosol composed of solid particles of iron oxide of very small size (to a large extent submicron) and air at ambient temperature. The study has been accomplished by testing two nonwoven fabrics, under the same conditions as the woven fabrics, that are also appropriate for filtering applications. Three filtration indexesm δ, I F and F have been defined, in order to provide complementary information to tha given by the quality parameters already defined in the literature. This information will be very useful in quantifying the performance of filtering fabrics in solid/gas separation processes and, more importantly, to compare them mutually.

Preparation, Characterization, and Testing of Magnetic Carriers for Arsenic Removal From Water

To remove arsenic from water we are developing a research project that applies magnetic separation methods. In order to increase the removal efficiency we are using magnetic aggregates. These magnetic aggregates are iron-based and were all (except for one) prepared by us. In this paper we report the preparation steps and some of the results of the characterization and absorption tests we have performed in order to conclude about its structure and efficiency in what concerns arsenic removal.

Magnetically Stabilized and Fluidized Beds: Heat and Mass Transfer

Research and applications of magnetically stabilized and fluidized beds begun several decades ago, and have maintained their rate of interest during all these years. During last years their applications was diversified, and the application of these beds in the processing of biological materials and in environmental issues has nowadays focused the main attention within this area. In this work we present a brief review of magnetically fluidized and stabilized beds, mainly concerning their theoretical background, heat and mass transfer topics, some industrial and laboratorial setups and applications.