Faculty Publications

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Continuous operation of fluidized bed bioreactor for biogenic sulfide oxidation using immobilized cells of Thiobacillus sp
(Asian Network for Scientific Information, 2007) Ravichandra, P.; Mugeraya, G.; Anupoju, G.R.; Ramakrishna, M.; Jetty, A.
In the present study, obligate autotrophic Thiobacillus sp. was isolated from aerobic sludge distillery effluent treatment plant and the experiments were conducted in a fluidized bed bioreactor for the biological oxidation of sulfide using Ca-alginate immobilized Thiobacillus sp. All the experiments were conducted in continuous mode at different sulfide loading rates 0.018, 0.02475, 0.03375, 0.03825 and 0.054 and different hydraulic retention times 5, 3.67, 2.67, 2.35 and 1.67 h by varying flow rates 2.4×10-4, 3.3×10-4, 4.5×10-4, 5.1 × 10-4 and 7.2×10-4. Sulfide conversions higher than 90% were obtained at almost all sulfide loading rates and hydraulic retention times. All the experiments were conducted at constant pH of around 6 and temperature of 30±5°C. © 2007 Asian Network for Scientific Information.
CFD modeling and simulation of catalytic pyrolysis of heavy oils in a tapered fluidized bed reactor
(Walter de Gruyter GmbH, 2025) Gowtham, C.; Kalathi, J.T.
A fluidized bed reactors (FBRs) have been widely used for catlytic cracking, combustion, gasification, pyrolysis and other applications. However, to improve the performance of FBRs, a better understanding of its flow behaviour is required, especially when multiphases are present. In this research work, we have studied the hydrodynamics and performance of FBR for the catalytic pyrolysis of heavy oil into lighter fractions using a Computational Fluid Dynamics (CFD) approach. The eight-lump kinetic model was used to model the pyrolysis of heavy oil. The effect of riser geometry on the pyrolysis was investigated using a 2D transient Eulerian and the granular flow models. The fluid flow behaviour in tapered-in and tapered-out reactors (risers) for two different tapering angles (1° and 2°), conventional cylindrical reactor and pyrolysis at two different temperatures (600°C and 700°C) are studied, and the results are compared. The yield of pyrolysis products from the cylindrical riser is validated using previous mathematical models and experimental results from the literature. The results of the present CFD model for the cylindrical riser are in concert with the experimental results reported in the literature. The yields of light olefins, ethene, propene and butene are 48 wt%, 18 wt%, 34 wt%, respectively, at 700° as higher temperature favours a better yield of pyrolysis products. The same CFD model is extended to study the tapered riser geometries, and the simulation results support that the tapered-in geometry favours the pyrolysis, resulting in the higher conversion of gas oil compared to cylindrical riser due to increased residence time of solids (catalysts) and hence better contact with the fluid phase for the reactions. © 2025 Walter de Gruyter GmbH, Berlin/Boston.
An Experimental Investigation of Slugging Phenomenon in 2D Binary Gas–Solid Tapered Fluidized Beds
(John Wiley and Sons Inc, 2025) Sahoo, L.K.; Sarkar, S.
Gas–solid fluidized beds are widely employed in metallurgical industries to produce direct reduced iron. For such practical applications, tapered fluidized beds are most suitable for handling particles with wide size distribution due to the axial velocity gradient. Herein, the slug behavior in binary tapered fluidized beds has been studied using a high-speed camera and digital image analysis method. The influence of taper angle, air velocity, and fine fraction on local parameters such as slug size, rise velocity, and aspect ratio, and bulk parameters such as slug number and its area fraction, and bed expansion ratio has been investigated. The local parameters increase with taper angle, air velocity, and fine fraction. The slug area fraction and the bed expansion ratio increase with air velocity and fine fraction. The bed expansion ratio increases while the slug area fraction decreases with taper angle. The slug number fraction, slug area fraction, and bed expansion ratio range from 0.027–0.241, 0.20–0.63, and 1.11–1.42, as taper angle, air velocity, and binary composition vary from 0°–15°, 0.20–0.35 m s?1, and 0.25–0.75, respectively. An empirical correlation is proposed for bed expansion ratio prediction. Based on the present investigation, the optimum taper angle is 5°–10°. © 2024 Wiley-VCH GmbH.
Mathematical Modeling of Fluidized Bed Magnetizing Roasting of Iron Ore Fines
(John Wiley and Sons Inc, 2025) Sahoo, L.K.; Mantripragada, V.T.; Sarkar, S.
The fluidized bed magnetizing roasting of low-grade iron ore fines is employed as a beneficiation technique in iron-making and steel-making industries. In the present work, the unreacted shrinking core reaction kinetic model is coupled with the two-fluid and kinetic theory of granular flow gas–solid flow model to simulate magnetizing roasting of hematite to magnetite in iron ore fines using a fluidized bed reactor. The model is validated with published experimental findings. Thereafter, the influence of different process parameters such as gas temperature, composition, velocity, and particle size on the reduction fraction and rate along with (Formula presented.) mass fraction and emission is studied. The reduction rate increases with gas temperature and (Formula presented.) mass fraction while it decreases with particle size. The (Formula presented.) emission increases with gas temperature, particle size, and (Formula presented.) mass fraction. However, the influence of gas velocity on these parameters is not significant. The reduction rate and time vary from 0.0010 to 0.0067 s?1 and 65 to 553 s, respectively, at a reduction fraction of 0.5. The (Formula presented.) mass fraction and emission range from 0.80 to 0.92 and from 0.63 to 4.14 g kg?1 ore, respectively. © 2024 Wiley-VCH GmbH.

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