The effect of particle shape on solid entrainment in gas-solid fluidisation

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dc.contributor.advisor Du Toit, Elizabeth Louisa en
dc.contributor.coadvisor Nicol, Willie en
dc.contributor.postgraduate De Vos, Wouter Phillip en
dc.date.accessioned 2013-09-07T11:49:54Z
dc.date.available 2008-09-09 en
dc.date.available 2013-09-07T11:49:54Z
dc.date.created 2008-04-11 en
dc.date.issued 2008-09-09 en
dc.date.submitted 2008-08-28 en
dc.description Dissertation (MEng)--University of Pretoria, 2008. en
dc.description.abstract The entrainment rate of Ferrosilicone (FeSi) particles was measured in a 140 mm perspex column with air as the fluidising medium. Two different types of FeSi were used, namely atomised FeSi, which is mostly spherical in shape with smooth surfaces, and milled FeSi, which is irregular with rough surfaces. Both the FeSi mixtures had the same solid density and the similar average particle diameters ranging from 38 µm to 50 µm. The size and density of these particles put them on the border between Geldart A and Geldart B powders, similar to the high temperature Fischer-Tropsch catalyst. The atomised FeSi had a slightly higher concentration in fines (8.6% vs 1.8%), but except for the difference in particle shape, the two mixtures had otherwise very similar physical properties. A substantial difference in entrainment rate was measured between the atomised and milled FeSi, where the atomised had an entrainment rate of about six times higher than the milled FeSi throughout the range of superficial velocities tested. It was shown that the higher entrainment rate cannot be attributed only to the higher fines concentration, but that the difference in particle shape had a significant effect on the entrainment rate. Several two dimensional shape characterisation techniques were used in attempt to quantify the difference between the atomised and the milled FeSi. Of these the particle circularity managed to differentiate the best between the two particle mixtures. The circularities of the atomised and the milled FeSi were found to be 0.782 and 0.711 respectively. The measured circularity was used instead of a sphericity to adjust for the effect of particle shape on the terminal velocity of the particles. The adjusted terminal velocity was then used in the elutriation rate constant correlations to see which of the popular correlations in literature predicts the entrainment rate of the FeSi the best. All of the correlations gave a poor performance in predicting the measured entrainment rates. The two correlations that performed the best were that of Choi et al. (1999) (AARE = 72.6%) and Geldart et al. (1979) (AARE = 79%). It was concluded that single particle drag and single particle terminal velocities are not adequate to incorporate the effect of particle shape on entrainment rate. The method i by which shape affects entrainment rate therefore deserves further investigation. Further studies should also be done to develop a three dimensional shape descriptor that predicts bulk behaviour better. en
dc.description.availability unrestricted en
dc.description.department Chemical Engineering en
dc.identifier.citation a 2008 en
dc.identifier.other E1069/gm en
dc.identifier.upetdurl http://upetd.up.ac.za/thesis/available/etd-08282008-144243/ en
dc.identifier.uri http://hdl.handle.net/2263/27612
dc.language.iso en
dc.publisher University of Pretoria en_ZA
dc.rights © University of Pretoria 2008 E1069/ en
dc.subject Fischer-tropsch en
dc.subject Gas-solid fluidisation en
dc.subject Particle shape description en
dc.subject Entrainment en
dc.subject Particle shape en
dc.subject UCTD en_US
dc.title The effect of particle shape on solid entrainment in gas-solid fluidisation en
dc.type Dissertation en


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