Faculty Publications
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Item Artificial neural networks model for the prediction of steady state phenol biodegradation in a pulsed plate bioreactor(2008) Shetty K, K.V.; Nandennavar, S.; Srinikethan, G.Background: A recent innovation in fixed film bioreactors is the pulsed plate bioreactor (PPBR) with immobilized cells. The successful development of a theoretical model for this reactor relies on the knowledge of several parameters, which may vary with the process conditions. It may also be a time-consuming and costly task because of their nonlinear nature. Artificial neural networks (ANN) offer the potential of a generic approach to the modeling of nonlinear systems. Results: A feedforward ANN based model for the prediction of steady state percentage degradation of phenol in a PPBR by immobilized cells of Nocardia hydrocarbonoxydans (NCIM 2386) during continuous biodegradation has been developed to correlate the steady state percentage degradation with the flow rate, influent phenol concentration and vibrational velocity (amplitude x frequency). The model used two hidden layers and 53 parameters (weights and biases). The network model was then compared with a Multiple Regression Analysis (MRA) model, derived from the same training data. Further these two models were used to predict the percentage degradation of phenol for blind test data. Conclusions: The performance of the ANN model was superior to that of the MRA model and was found to be an efficient data-driven tool to predict the performance of a PPBR for phenol biodegradation. © 2008 Society of Chemical Industry.Item Solar light mediated photocatalytic degradation of phenol using Ag core - TiO2 shell (Ag@TiO2) nanoparticles in batch and fluidized bed reactor(Elsevier Ltd, 2016) Shet, A.; Shetty K, K.V.Ag@TiO2 nanoparticles were synthesised using one pot method followed by calcination at 450 °C for 3 h and were tested for their photocatalytic efficacy in degradation of phenol both in free and immobilized form under solar light irradiation through batch experiments. Ag@TiO2 nanoparticles were found to be effective in solar photocatalytic degradation of phenol. The effect of factors such as pH, initial phenol concentration and catalyst loading on phenol degradation were evaluated and these factors were found to influence the process efficiency. The optimum values of these factors were determined to maximize the phenol degradation. The efficacy of nanoparticles immobilized on cellulose acetate film was inferior to that of free nanoparticles in solar photocatalysis due to light penetration problem and diffusional limitations. The performance of fluidized bed photocatalytic reactor operated under batch with recycle mode for solar photocatalysis of phenol with immobilized Ag@TiO2 nanoparticles was evaluated for large scale application. The performance was found to be dependent on catalyst loading and the optimum is governed by active catalyst sites and light penetration limitations. The photocatalytic degradation of phenol by Ag@TiO2 nanoparticles was only marginally influenced by the presence of small traces of chloride ions. Ag@TiO2 showed a better efficacy as solar photocatalyst than as UV photocatalyst in degradation of phenol. Solar light irradiation is recommended because solar energy, a readily available form of energy can be effectively harnessed for energy efficient, environment friendly and cost effective process. The kinetics of degradation of phenol was found to follow the nth order kinetics with order, n = 2.19 for solar photocatalysis. © 2016 Elsevier Ltd.Item Design and development of TiO2 coated microflow reactor for photocatalytic partial oxidation of benzyl alcohol(Elsevier B.V., 2020) Pradhan, S.R.; Nair, V.; Giannakoudakis, D.A.; Lisovytskiy, D.; Colmenares, J.C.The synthesis of valuable organic compounds from naturally available and renewable biomass is an open field of research towards adaptation in real-life applications. Photocatalytic valorization is assumed as a potential candidate, although the lower efficiency of the traditional batch photocatalytic reactor sets some drawbacks. Recently, photocatalytic microreactors revealed as a prosperous candidate for various photocatalytic reactions, especially for selective oxidation. This area of research is challenging due to the development of the proper photocatalytic microreactor for the targeted application. Deposition of the catalyst on the internal surface of the microreactor, the sufficient utilization of the irradiation, optimization of the reaction parameters are among the most vital parameters that should be considered upon the design. Although, to obtain the most active material and tune its crucial features to maximize its catalytic performance inside the microreactors is the uppermost important part. This work introduces ultrasound-assisted TiO2 deposition on the inner walls of a perfluoroalkoxyalkane microtube under mild conditions. The deposition experiments were carried out with commercial and sol-gel synthesized TiO2. The materials were characterized by XRD, UV–vis DRS, Scanning Electron Microscopy (SEM), and nitrogen sorption. The photocatalytic activities of the TiO2 nano-engineered fluoropolymer based microreactors were evaluated for the oxidation of benzyl alcohol in flow. © 2020 The Author(s)Item Selective dehydration of 1-butanol to butenes over silica supported heteropolyacid catalysts: Mechanistic aspect(Elsevier B.V., 2021) Kella, T.; Vennathan, A.A.; Dutta, S.; Mal, S.; Shee, D.Butenes are considered as important olefinic building block to produce fuels/fuel additives and commodity chemicals. In the present investigation, selective dehydration of 1-butanol to butenes was studied in a continuous-flow fixed-bed reactor using various silica-supported heteropolyacid (HPA) catalysts such as phosphotungstic acid (PTA), silicotungstic acid (STA), phosphomolybdic acid (PMA), and silicomolybdic acid (SMA) as the solid acid catalysts. The physicochemical properties of these HPA were determined by BET, powder XRD, FTIR, NH3-TPD, and Py-FTIR. The acid strength and Brønsted/Lewis (B/L) acid ratio were increased with higher loading of HPA on silica. The nature of HPA (addenda and hetero atom) and loading of HPA are important factors for the dehydration of 1-butanol and selectivity towards butenes. PTA and STA showed superior catalytic activity than PMA and SMA. The reaction temperature and WHSV also strongly affected the butanol conversion and selectivity of butenes. The selectivity of di-n?butyl ether decreases with the rising temperature from 523 K to 623 K. The isomerization of 1-butene leading to the formation of other butene isomers depends on the HPA loading, temperature, and WHSV. The presence of molybdenum addendum atom in PMA and SMA promotes dehydrogenation and hydrogenation, leading to the formation of various light hydrocarbons. The 20PTA/SiO2 catalyst afforded 99.8% selectivity towards butenes at quantitative conversion of 1-butanol, whereas the 20STA/SiO2 catalyst gave nearly 97.0% conversion of 1-butanol and 99.9% butenes selectivity at 673 K, 37.4 h?1 of WHSV. © 2021Item 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.Item A Simplified Bubble Size Relation Compatible with the Energy Minimization Multiscale Drag Model for Studying Hydrodynamics in a 2D Gas–Solid Tapered Fluidized Bed(John Wiley and Sons Inc, 2025) Sahoo, L.K.; Sarkar, S.Gas–solid fluidized bed reactors are extensively utilized in direct reduced iron production. In practice, these reactors will have a wide particle size distribution, which is better handled by tapered fluidized beds due to their vertical velocity gradient. Herein, a simplified bubble size relation is proposed to remove implicit interdependency between the bubble size and its drag coefficient in the bubble-based energy minimization multiscale (EMMS) heterogeneous drag model. Further, the proposed drag model is coupled with the two-fluid kinetic theory of granular flow model to investigate hydrodynamics. The heterogeneous flow structure predicted by the model is similar to experiments. Further, the bulk parameters such as bed expansion ratio and bubble fraction obtained from the simulations using a simplified EMMS drag model are compared and are found to be in good agreement with the experimental findings, with mean relative deviations of 3.95% and 14.64%, respectively. The time-averaged bubble fraction and bed expansion ratio are found to increase with air velocity and decrease with taper angle, whereas a reverse trend is observed for the mean particulate fluidized area fraction. Based on the current study, the taper angle between 5° and 10° is found to be most suitable. © 2024 Wiley-VCH GmbH.Item 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.