BITS Faculty Publications
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Item A Review of the Unconventional Methods Used for the Demetallization of Petroleum Fractions over the Past Decade(ACS, 2015) Sande, Priya CMetals in petroleum fractions have a deleterious effect on the refining equipment and catalyst. They corrode the equipment, plug the catalyst pores, and create irregularities in the system. With reference to today’s petroleum industry, the fast depletion of light crude has created the need to process heavier crudes with much higher metal content. Hence, the need to remove traces of harmful metals and restrict their accumulation in feed stocks has become a pressing issue. In this context, we review developments over the past decade in regard to the methods of metal removal with a focus on unconventional methods, such as the use of molecularly imprinted polymers, supercritical fluids, and irradiation. Other methods of demetallization discussed include the usage of nanocatalysts, micro-organisms, and certain solvents. The removal of vanadium and nickel were reviewed most, because of the abundance of these elements in the crude.Item Fine Mesh Computational Fluid Dynamics Study on Gas-Fluidization of Geldart A Particles: Homogeneous to Bubbling Bed(ACS, 2016) Sande, Priya CGas-fluidization of Geldart A particles was simulated for a domain of lab-scale dimensions. Hydrodynamics of homogeneous regime and transition to bubbling were studied. In this context a detailed fine mesh simulation study is presented for the first time, using the state-of-the-art two-fluid model (TFM). The effect of particle density was investigated. The fine mesh simulations were analyzed for insights into bed transition from homogeneous to bubbling regime and the effect of interparticle forces (IPFs). Simulations reveal that transition to bubbling occurs over a velocity range rather than at a discrete velocity. We propose an index to quantify the effect of IPFs on bed expansion. During homogeneous expansion this IPF index was found to drop exponentially with velocity. It became negligible as bubbling ensued which is in line with the literature. The simulated average bed voidage was found comparable to the corresponding Eulerian−Lagrangian and experimental data.Item Mesh size effect on CFD simulation of gas-fluidized Geldart A particles(Elsiever, 2014) Sande, Priya C; Ray, SaumiWe investigate the effect of mesh size on CFD simulations of a lab-scale sized fluidized bed of Geldart A particles using two-fluid model (TFM), specifically for homogeneous expansion and transition to bubbling. For the first time we have shown a set of lab-scale domain size fine mesh simulations. In this context transient bed voidage profiles have been analyzed in detail. TFM follows the Eulerian–Eulerian approach which has the advantage of being less computationally expensive than Eulerian–Lagrangian approach for an engineering scale. Mesh size has a drastic effect on minimum bubbling velocity. With mesh refining, the observed minimum bubbling velocity approaches its experimental value. On reducing mesh size even up to 1 mm × 1 mm, there was no improvement in capturing homogeneous expansion. Fine mesh simulation revealed void structures and could predict the bubbling transition, though the homogeneous expansion captured was not as much as experimentally observed. Review of several simulations across all the mesh sizes studied, revealed the presence of persisting dilute regions getting triggered around experimental minimum bubbling velocity. Theses persisting dilute regions seem to signal the presence of the bubbling regime. The effect of commonly used drag laws was also studied and it was found that the Gidaspow and Syamlal O'Brien drag laws manifested the dilute region markers at 8 mm/s while for the Wen Yu drag law this value was 10 mm/s. The effect of frictional stress and wall boundary condition for both phases was qualitatively assessed. Omitting frictional stress or changing no-slip to free-slip boundary condition for gas phase had the effect of delaying minimum bubbling velocity.