Faculty Publications
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Item Advances in Computational Fluid Dynamics Modeling for Biomass Pyrolysis: A Review(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Kulkarni, A.; Mishra, G.; Palla, S.; Ramesh, P.; Surya, D.V.; Basak, T.Pyrolysis, a process for extracting valuable chemicals from waste materials, leverages computational fluid dynamics (CFD) to optimize reactor parameters, thereby enhancing product quality and process efficiency. This review aims to understand the application of CFD in pyrolysis. Initially, the need for pyrolysis and its role in biomass valorization are discussed, and this is followed by an elaboration of the fundamentals of CFD studies in terms of their application to the pyrolysis process. The various CFD simulations and models used to understand product formation are also explained. Pyrolysis is conducted using both conventional and microwave-assisted pyrolysis platforms. Hence, the reaction kinetics, governing model equations, and laws are discussed in the conventional pyrolysis section. In the microwave-assisted pyrolysis section, the importance of wavelength, penetration depth, and microwave conversion efficiencies on the CFD are discussed. This review provides valuable insights to academic researchers on the application of CFD in pyrolysis systems. The modeling of pyrolysis by computational fluid dynamics (CFD) is a complex process due to the implementation of multiple reaction kinetics and physics, high computational cost, and reactor design. These challenges in the modeling of the pyrolysis process are discussed in this paper. Significant solutions that have been used to overcome the challenges are also provided with potential areas of research and development in the future of CFD in pyrolysis. © 2023 by the authors.Item Preparation and characterization of CdxZn1-xS thin films by spray pyrolysis technique for photovoltaic applications(2009) Raviprakash, Y.; Bangera, K.V.; Shivakumar, G.K.CdxZn(1-x)S (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) thin films were deposited by the chemical spray pyrolysis technique using a less used combination of chemicals. Depositions were done at 573 K on cleaned glass substrates. The composition, surface morphology and structural properties of deposited films were studied using EDAX, SEM and X-ray diffraction technique. XRD studies reveal that all the films are crystalline with hexagonal (wurtzite) structure and inclusion of Cd into the structure of ZnS improved the crystallinity of the films. In the entire compositions, the (0 0 2) diffraction peak is prominent which gives lattice matching to the chalcogenide semiconductor such as CuInxGa1-xSe2 and CuIn (s1-xSex)2, which are used in photovoltaic devices. The value of lattice constant 'a' and 'c' have been observed to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm, respectively. The band gap of the thin films varied from 3.32 to 2.41 eV as composition varied from x = 0.0 to 1.0. It was observed that presence of small amount of cadmium results in marked changes in the optical band gap of ZnS. © 2009 Elsevier Ltd. All rights reserved.Item Bio-oil from microwave assisted pyrolysis of food waste-optimization using response surface methodology(Elsevier Ltd, 2019) Kadlimatti, H.M.; Raj Mohan, B.; Saidutta, M.B.Municipal solid waste (MSW) contains on an average 40% food waste and needs to be managed in an environment friendly manner. Food wastes have high energy content and offer a good potential feed stock for pyrolysis. Microwave assisted pyrolysis of food waste at different microwave power levels has been carried out in the present study. Maximum bio-oil yield of 30.24 wt.% is obtained under the optimized pyrolysis conditions of 400 °C temperature, 30 min residence time and 50 mL min-1 of nitrogen flow rate at the microwave power of 450 W. The regression model with 95% confidence level resulted in the high value of R2 = 95.4% with R2 adjusted = 91.2% indicates a very good or excellent fit of the data to the model. Main functional groups as detected by the Fourier transform infrared (FTIR) analysis are alcohols, alkenes, aromatic compounds, primary and secondary amines, carboxylic acid, esters and phenols. Oxygenated and non oxygenated compounds, nitrogenated compounds and other compounds such as phosphine, methyl-, propane, 2-fluoro-, (2-hydroxyethyl) trimethylsilyl methyl sulfide, and 1,3-bis(2-hydroxymethyl)urea have been identified by the gas chromatography/mass spectrometry (GC-MS) analysis. The heating value of the bio-oil was 23.94 MJ kg?1. © 2019 Elsevier LtdItem Evaluation of pyrolyzed areca husk as a potential adsorbent for the removal of Fe2+ ions from aqueous solutions(Academic Press, 2019) Sheeka Subramani, B.; Shrihari, S.; Manu, B.; BabuNarayan, K.S.[No abstract available]Item Magnetic behavior of polymorph composite nickel titanate nanofibers(Royal Society of Chemistry, 2021) Kumar, B.; Dhanasekhar, C.; Anandhan, S.; Kalpathy, S.K.Polymorph (spinel/ilmenite) composite nanofibers of nickel titanate (NTO) were prepared by a sol-gel assisted electrospinning process followed by pyrolysis using the styrene-acrylonitrile copolymer as a precursor at three different pyrolysis soaking temperatures (i.e. T= 773, 973, and 1173 K). The magnetic behavior of these composite NTO nanofibers was studied under isothermal and non-isothermal conditions in the temperature range of 20-300 K. The magnetic parameters such as coercivity (Hc), remanence (Mr), and saturation magnetisation (Ms) were found to be strongly dependent onT. The highestHcandMrwere observed for NTO nanofibers developed at 973 K, which have a mosaic structured morphology with spinel and ilmenite NTO crystallite sizes of ~39 nm and ~24 nm, respectively. On the other hand, the highestMsand switching field distribution were observed for mosaic structured NTO nanofibers having smaller crystallites (~13 nm and 24 nm for spinel and ilmenite NTO, respectively, with high inter-particle distance and high porosity) developed at 773 K, which are also rich in spinel NTO content. The correlation between the variation in magnetic behavior and structural/morphological features of NTO nanofibers is useful for NTO-based soft magnetic and multiferroic applications. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021.Item Understanding of synergy in non-isothermal microwave-assisted in-situ catalytic co-pyrolysis of rice husk and polystyrene waste mixtures(Elsevier Ltd, 2022) Sridevi, V.; Suriapparao, D.V.; Tukarambai, M.; Terapalli, A.; Ramesh, R.; Sankar Rao, C.S.; Gautam, R.; Moorthy, J.V.; Suresh Kumar, C.Rice husk (RH) and polystyrene (PS) wastes were converted into value-added products using microwave-assisted catalytic co-pyrolysis. The graphite susceptor (10 g) along with KOH catalyst (5 g) was mixed with the feedstock to understand the products and energy consumption. RH promoted the char yield (20–34 wt%) and gaseous yields (16–25 wt%) whereas PS enhanced the oil yield (23–70 wt%). Co-pyrolysis synergy induced an increase in gaseous yields (14–53 wt%) due to excessive cracking. The specific microwave energy consumption dramatically decreased in co-pyrolysis (5–22 kJ/g) compared to pyrolysis (56–102 kJ/g). The pyrolysis index increased (17–445) with the increase in feedstock quantity (5–50 g). The obtained oil was composed of monoaromatics (74%) and polyaromatics (18%). The char was rich in carbon content (79.5 wt%) and the gases were composed of CO (24%), H2 (12%), and CH4 (22%). © 2022 Elsevier LtdItem Effect of dry torrefaction pretreatment of the microwave-assisted catalytic pyrolysis of biomass using the machine learning approach(Elsevier Ltd, 2022) Ramesh, R.; Suriapparao, D.V.; Sankar Rao, C.S.; Sridevi, V.; Kumar, A.This study employs the Leave-One-Out cross-validation approach to build a machine-learning model using polynomial regression to predict pyro product yield through microwave-assisted pyrolysis of sawdust over KOH catalyst and graphite powder a susceptor. The determination of coefficient (R2) validates the developed models. All the developed models achieved a high prediction accuracy with R2 > 0.93, which signifies that the experimental values are in good agreement with the predicted one. The dependence of the catalyst loading and pretreatment temperature on dominating process parameters such as heating rate, pyrolysis temperature, susceptor thermal energy, and pyro products, namely bio-oil, biochar, and biogas, are explored. The yield of biochar is reduced; however, bio-oil and biogas are enhanced as the catalyst loading increased. On the other hand, increasing the temperature of pretreated sawdust decreased bio-oil and biogas yields while increasing biochar yields. Further, microwave conversion efficiency, and susceptor thermal energy increased with increased catalyst quantity and pretreatment temperatures of sawdust. It was observed that the average heating rate was increased by increasing the catalyst quantity while maintaining the same pyrolysis time until pretreatment temperatures of 150 °C were reached, after which the heating rate dropped due to the continuous microwave energy input to the system. © 2022 Elsevier LtdItem Synthesis of sustainable chemicals from waste tea powder and Polystyrene via Microwave-Assisted in-situ catalytic Co-Pyrolysis: Analysis of pyrolysis using experimental and modeling approaches(Elsevier Ltd, 2022) Suriapparao, D.V.; Sridevi, V.; Ramesh, R.; Sankar Rao, C.S.; Tukarambai, M.; Kamireddi, D.; Gautam, R.; Dharaskar, S.A.; Pritam, K.In the current study, catalytic co-pyrolysis was performed on waste tea powder (WTP) and polystyrene (PS) wastes to convert them into value-added products using KOH catalyst. The feed mixture influenced the heating rates (17–75 °C/min) and product formation. PS promoted the formation of oil and WTP enhanced the char formation. The maximum oil yield (80 wt%) was obtained at 15 g:5 g, and the maximum char yield (44 wt%) was achieved at 5 g:25 g (PS:WTP). The pyrolysis index (PI) increased with the increase in feedstock quantity. High PI was noticed at 25 g:5 g, and low PI was at 5 g:5 g (PS:WTP). Low energy consumption and low pyrolysis time enhanced the PI value. Significant interactions were noticed during co-pyrolysis. The obtained bio-oil was analyzed using GC–MS and a plausible reaction mechanism is presented. Catalyst and co-pyrolysis synergy promoted the formation of aliphatic and aromatic hydrocarbons by reducing the oxygenated products. © 2022 Elsevier LtdItem The role of solvent soaking and pretreatment temperature in microwave-assisted pyrolysis of waste tea powder: Analysis of products, synergy, pyrolysis index, and reaction mechanism(Elsevier Ltd, 2022) Talib Hamzah, H.; Sridevi, V.; Seereddi, M.; Suriapparao, D.V.; Ramesh, R.; Sankar Rao, C.S.; Gautam, R.; Kaka, F.; Pritam, K.This study focuses on microwave-assisted pyrolysis (MAP) of fresh waste tea powder and torrefied waste tea powder as feedstocks. Solvents including benzene, acetone, and ethanol were used for soaking feedstocks. The feedstock torrefaction temperature (at 150 °C) and solvents soaking enhanced the yields of char (44.2–59.8 wt%) and the oil (39.8–45.3 wt%) in MAP. Co-pyrolysis synergy induced an increase in the yield of gaseous products (4.7–20.1 wt%). The average heating rate varied in the range of 5–25 °C/min. The energy consumption in MAP of torrefied feedstock (1386 KJ) significantly decreased compared to fresh (3114 KJ). The pyrolysis index dramatically varied with the solvent soaking in the following order: ethanol (26.7) > benzene (25.6) > no solvent (10) > acetone (6). It shows that solvent soaking plays an important role in the pyrolysis process. The obtained bio-oil was composed of mono-aromatics, poly-aromatics, and oxygenated compounds. © 2022 Elsevier LtdItem The effect of torrefaction temperature and catalyst loading in Microwave-Assisted in-situ catalytic Co-Pyrolysis of torrefied biomass and plastic wastes(Elsevier Ltd, 2022) Ramesh, R.; Suriapparao, D.V.; Sankar Rao, C.S.; Sridevi, V.; Kumar, A.; Shah, M.In the current study, the effect of torrefaction temperatures (125–175 °C) and catalyst quantity (5–15 g) on co-pyrolysis of torrefied sawdust (TSD) and polystyrene (PS) are investigated to obtain value-added products. The role of torrefaction in co-pyrolysis of TSD: PS was analyzed to understand the product yields, synergy, and energy consumption. As the torrefaction temperature increases, oil yield (48.3–59.6 wt%) and char yield (24.3–29 wt%) increase while gas yield (27.4–11.4 wt%) decreases. Catalytic co-pyrolysis showed a significant level of synergy when compared to non-catalytic co-pyrolysis. For the conversion (%), a positive synergy maximum (-2.6) exists at a torrefaction temperature of 175 °C and 15 g of KOH catalyst. To develop the model, polynomial regression-based machine learning was used to predict pyrolysis product yields and energy usage variables. The developed models showed significant prediction accuracy (R2 > 0.98), suggesting the experimental values and the predicted values matched well. © 2022 Elsevier Ltd