Department of Chemical Engineering
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Item Unraveling the kinetics, mass transfer, and multi-omics for environmentally sustainable CO2 bio-mitigation using Bacillus cereus for bioenergy feedstock production(Elsevier, 2025) Gupta, Suresh; Raghuvanshi, SmitaThis research provides a cost-competitive solution to the conflict between ever-increasing energy demand and hazardous carbon dioxide (CO2) emissions reduction from the industries. The paper outlines the use of chemolithotrophic bacteria (B. cereus SSLMC2) for the bio-mitigation of 10, 15, 20, and 25 % CO2 conducted using a 20 L bubble column bioreactor. For 10, 15, 20, and 25 % CO2 (g), the maximum biomass productivity achieved was 0.042, 0.035, 0.032, and 0.051 g L−1 h−1, respectively. The highest percentages of CO2 (g) removal achieved were 91.68, 86.83, 84.86, and 93.43 %, respectively. The effect of parameters on biomass growth and total carbon (C) assimilation was investigated to determine the correlation between the mitigation of CO2 (g) and the growth of B. cereus SSLMC2. The gas chromatography-mass spectrometry (GC-MS) examination of biomass confirmed the formation of potential products during the bio-mitigation process. The nuclear magnetic resonance (NMR) metabolomics technique identified up to 25 metabolites associated with probable bio-mitigating CO2 (g) pathways. Kinetic models such as Monod, Haldane, Powell, Webb, and Luong provided a mathematical depiction of bacterial growth dynamics. Additionally, the mass and heat transfer characteristics crucial to the bio-mitigation process were determined. By demonstrating high CO2 removal efficiencies and the production of valuable by-products, this research highlights the potential of integrating bio-based technologies into existing industrial processes.Item CFD analysis of biomass gasification using downdraft gasifier(Elsevier, 2021) Sheth, Pratik N.CFD model has been developed for the 2D axisymmetric model of an Imbert downdraft gasifier. The present Model has been validated with experimental data. The model predicts CO, hydrogen, and CO2 with precise accuracy. Producer gas composition and gasifier temperature have been studied at different equivalence ratios (ER) i.e. 0.25 to 0.60. It is noted from the observation that the rise of the equivalence ratio tends to decrease the amount of CO, hydrogen, and methane in the producer gas whereas nitrogen and CO2 excessively increased. It has also been observed that the increase of the equivalence ratio tends to increase the temperature inside the gasifier.Item Investigating effects of temperature on fuel properties of torrefied biomass for bio-energy systems(Taylor & Francis, 2018-11) Pande, JayTorrefaction of selected agro-residues (rice straw and cotton stalk) was successfully carried out on indirectly heated, batch-type fixed-bed reactor under different reactor temperatures (200–300°C) at a fixed heating rate of 10°C/min. Our preliminary results demonstrated that the rice straw, torrefied at 275°C, exhibited higher mass yield (64%) and energy yield (84%) with better fuel properties, i.e. lower moisture content (1.2%), volatile matters (54.7%), higher fixed carbon (24.8%), and higher heating value (HHV) 18.7 MJ/kg. On the other hand, cotton stalk showed a slightly lower mass yield (56.3%) and energy yield (74.4%) compared to rice star with very high HHV 22.5 MJ/kg torrefied at a relatively lower temperature of 250°C. Interestingly, the lignocellulosic composition showed a drastic increase in the lignin content of rice straw and cotton stalk, torrefied at 275°C and 250°C, respectively, which indicates good binding ability of bio-fuel leading to improved energy density. Our present work gives an insight that the torrefied rice straw and cotton stalk could be a promising biomass feedstock for bio-energy based systems such as biomass pyrolsyis and gasification.Item Improving the properties of producer gas using high temperature gasification of rice husk in a pilot scale fluidized bed gasifier (FBG)(Elsevier, 2019-01) Pandey, JayBiomass gasification is a well-studied thermo-chemical conversion route for the generating producer gas, a renewable energy carrier, for thermal and power applications as well as for bio-fuel production. High energy efficiency and clean gaseous fuel with low tar and suspended particulate matters (SPM) contents are some of the major challenges with biomass gasification. Herein, we report non-catalytic high temperature (720–855 °C) gasification of rice husk using fluidized bed gasifier (FBG). Producer gas mainly comprising of CO and H2 exhibited good higher heating value (HHV) and lower heating value (LHV) of 3.6 and 3.2 MJ/Nm3 respectively. Our experimental observations revealed that 790 °C is the optimum temperature for rice husk gasification with high carbon conversion efficiency (91.6%), thermal efficiency (75%) and high gas yield 2.7 m3/kg. High temperature gasification also resulted into reduced tar + SPM content (0.33 g/Nm3). Rice husk derived producer gas with good heating value and low tar + SPM content can be used as replacement of conventional fossil fuels for thermal applications in many processing industries.Item A mechanistic study on the reaction pathways leading to benzene and naphthalene in cellulose vapor phase cracking(Elsiever, 2014-10) Srinivas, AppariThe reaction pathways leading to aromatic hydrocarbons such as benzene and naphthalene in gas-phase reactions of multi-component mixtures derived from cellulose fast pyrolysis were studied both experimentally and numerically. A two-stage tubular reactor was used for evaluating the reaction kinetics of secondary vapor phase cracking of the nascent pyrolysates at temperature ranging from 400 to 900 °C, residence time from 0.2 to 4.3 s, and at 241 kPa. The products of alkyne and diene were identified from the primary pyrolysis of cellulose even at low temperature range 500–600 °C. These products include acetylene, propyne, propadiene, vinylacetylene, and cyclopentadiene. Experiments were also numerically validated by a detailed chemical kinetic model consisting of more than 8000 elementary step-like reactions with over 500 chemical species. Acceptable capabilities of the kinetic model in predicting concentration profiles of the products enabled us to assess reaction pathways leading to benzene and naphthalene via the alkyne and diene from primary pyrolysates of cellulose. C3 alkyne and diene are primary precursors of benzene at 650 °C, while combination of ethylene and vinylacetylene produces benzene dominantly at 850 °C. Cyclopentadiene is a prominent precursor of naphthalene. Combination of acetylene with propyne or allyl radical leads to the formation of cyclopentadiene. Furan and acrolein are likely important alkyne precursors in cellulose pyrolysis at low temperature, whereas dehydrogenations of olefins are major route to alkyne at high temperatures.Item Advances in Downdraft Biomass Gasification( Nova Science Publishers, 2010) Sheth, P.N.Item Thermo-Chemical Conversion of Jatropha Deoiled Cake: Pyrolysis vs. Gasification(IJCEA, 2015-10) Sheth, P.N.Pyrolysis and gasification of biomass is considered to be the promising alternative solutions for the increase of energy demand and environmental awareness. Pyroysis process produces a variety of chemicals by limited degradation and gasification process leads to complete breakdown of the biomass into permanent gases. By gasification, solid biomass is converted into a combustible gas mixture normally called “Producer Gas” consisting primarily of hydrogen and carbon monoxide, with lesser amounts of carbon dioxide, water, methane, higher hydrocarbons, nitrogen and particulates. Whereas the pyrolysis process produces a mainly three types of products: solid (charcoal), liquid (tar and other organics) and gaseous products. In the present study, Jatropha de-oiled cake is taken as a biomass. The pyrolysis and gasification experiments are carried out for comparing the results. The biomass is pyrolyzed in a fixed bed reactor in a Nitrogen environment as well used to produce the producer gas in a fixed bed downdraft biomass gasifier.Item Biomass gasification models for downdraft gasifier: A state-of-the-art review(Elsiever, 2015-10) Sheth, P.N.Among the different methods of energy production from biomass, gasification is considered as the most suitable option as it is a simple and economically viable process to produce thermal energy or decentralized electricity generation. Downdraft gasifiers are typically small-scale units having maximum power production capacity up to 5 MW. This feature makes it more suitable for decentralized power generation and distribution to the remote villages/islands deprived of grid electricity. Mathematical models can be helpful for the design of gasifiers, prediction of operational behavior, emissions during normal conditions, startup, shutdown, change of fuel, change of loading, and to alleviate the type of problems mentioned above. It has been observed that although many researchers have developed models of various types and degrees of complexity, reviews of these modeling and simulation studies are scarce. Largely, it is observed that the review articles reported in the literature fail to address the basic understanding of each model types and their applicability to design different gasifiers for a certain feedstock and variation of operating parameters. This review article discusses different models available for downdraft gasifiers such as thermodynamic equilibrium, kinetic, CFD, ANN and ASPEN Plus models. A comparative analysis of each model and its output is carried out. A critical analysis of the effect of different modeling parameters and finally the advantages and disadvantages of each modeling technique is outlined.Item Design of energy utilization test for a biomass cook stove: Formulation of an optimum air flow recipe(Elsiever, 2019-01-01) Sheth, P.N.Biomass is a major source of fuel in many developing countries and used in cook stoves. The water boiling test or its variants are used to evaluate the performance. The evaluation is on an average basis throughout the test and does not provide the dynamics of the energy transfer process. To provide a better insight on this transfer process, the present study demonstrates energy utilization test, which enables analysis of the performance parameters with respect to time. The WBT experimental set up is modified to measure the variation of biomass fuel consumption and water evaporation separately with time by incorporating the separate top mounted weighing balance. The new variable, weight of the water pot, variation with time is also observed along with other standard WBT variables. This new test is validated by performing several experiments. It provides insights on the time-dependent behavior of thermal efficiency and other parameters when performed at different air flow rates. Based on the test results, a new air flow recipe is developed which provides better performance and outlines the significance of energy utilization test. With the formulated recipe, the runtime has improved to nearly 85 min which is an increase of more than 30%.Item Recent progress in thermochemical techniques to produce hydrogen gas from biomass: A state of the art review(Elsiever, 2019-10-04) Sheth, P.N.The present work comprehensively covers the literature that describes the thermochemical techniques of hydrogen production from biomass. This survey highlights the current approaches, relevant methods, technologies and resources adopted for high yield hydrogen production. Prominent thermochemical methods i.e. pyrolysis, gasification, supercritical water gasification, hydrothermal upgrading followed by steam gasification, bio-oil reforming, and pyrolysis inline reforming have been discussed thoroughly in view of the current research trend and latest emerging technologies. Influences of important factors and parameters on hydrogen yield, such as biomass type, temperature, steam to biomass ratio, retention time, biomass particle size, heating rate, etc. have also been extensively studied. Catalyst is a vital integrant that has received enough attention due to its encouraging influence on hydrogen production. Literature confirms that hydrogen obtained from biomass has high-energy efficiency and potential to reduce greenhouse gases hence, it deserves versatile applications in the coming future. The study also reveals that hydrogen production through steam reforming, pyrolysis, and in-line reforming deliver a considerable amount of hydrogen from biomass with higher process efficiency. It has been identified that higher temperature, suitable steam to biomass ratio and catalyst type favor useful hydrogen yield. Nevertheless, hydrogen is not readily available in the sufficient amount and production cost is still high. Tar generation during thermochemical processing of biomass is also a concern and requires consistent efforts to minimize it.