Experimental Investigation on the Multistage Particle Classification in a Zigzag Air Classifier
—In most industrial solid processing operations, the separation of particles is important and designed based on the terminal settling velocity as the chief operating parameter. This settling velocity is dependent on characteristic particle properties like size, density, and shape. In this work, multi-stage separation experiments of sand and gravel have been performed using different channel velocities and mass loadings of the air. The performance has been analyzed and discussed with respect to the separation functions, and characteristic parameters as separation sharpness and product quality. Furthermore, the SMART analysis is used to evaluate different parameter configurations.
A method of comparing the performance of air classifiers
Abstract An experimental and theoretical comparison is made between a “zig-zag” air classifier and a straight-duct type. Equations are presented, based on a model already published, for the effective diffusivity of spherical particles in a turbulent air stream. The diffusivity reflects the tendency of particle species to diffuse the “wrong” way, that is to be lost. The lower the value of the effective diffusivity, the more efficient is the classifier. It is shown that the effective diffusivities are lower in the “zig-zag” classifier than in the straight-duct type especially for the “light” species. It is also shown that the effective diffusivities of “light” and “heavy” species are similar in value, indicating the mid-point as the optimum feed location. It is also shown that, at high values of the air/solids ratio, the effective diffusivities can be easily estimated by using mixtures of regular particles, or simply by feeding a single species of spherical particles. The effective diffusivities were found to be independent of the number of stages in the “zig-zag” classifier, and took values similar to freestream diffusion values. The method described represents a very simple test which could be applied to proposed designs of air classifier to enable a comparison of effectiveness to be made.
Setzmaschinen, besonders für Recyclingaufgaben : Möglichkeiten, Grenzen, Bauarten
Separation by density using jigs has been state of the art in mineral processing for a long time. Several types of jigs have been developed, each of them providing special advantages for particular applications. In the environmental field, the previous and, to a growing extent, recent applications are mostly for soil washing and building rubble recycling. Further applications are emerging La classification par densite a l'aide de bacs de lavage, un procede economique permettant une separation tres precise, a ete introduite, il y a longtemps, dans la technique de preparation de matieres premieres minerales. On a mis au point plusieurs types de machines, chacune desquelles offre des avantages pour des applications determinees. Dans le domaine de la protection de l'environnement, les applications connues jusqu'a present et qui sont devenus plus nombreuses ces derniers temps, concernent surtout le lavage de sols et le recyclage de decombres. Il se dessine encore d'autres applications