Department of Chemical Engineering

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    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, Smita
    This 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.
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    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.
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    Investigating effects of temperature on fuel properties of torrefied biomass for bio-energy systems
    (Taylor & Francis, 2018-11) Pande, Jay
    Torrefaction 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.
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    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, Jay
    Biomass 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.
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    A mechanistic study on the reaction pathways leading to benzene and naphthalene in cellulose vapor phase cracking
    (Elsiever, 2014-10) Srinivas, Appari
    The 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.
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    Advances in Downdraft Biomass Gasification
    (‎ Nova Science Publishers, 2010) Sheth, P.N.
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    Differential Evolution Approach for Obtaining Kinetic Parameters in Nonisothermal Pyrolysis of Biomass
    (Taylor & Francis, 2009-05) Sheth, P.N.
    Pyrolysis, a first step in the biomass gasification, is the thermal decomposition of organic matter under inert atmospheric conditions, leading to the release of volatiles and formation of char. As pyrolysis is a kinetically controlled reaction, kinetic parameter estimation is very important in the design of pyrolysis reactors. In the proposed kinetic model of this study, the kinetic scheme of biomass decomposition by two competing reactions giving gaseous volatiles and solid charcoal is used. Four different models are proposed based on different possible relation of activity of biomass with normalized conversion. The corresponding kinetic parameters of the above models are estimated by minimizing the square of the error between the reported nonisothermal experimental data of thermogravimetry of hazelnut shell and simulated model predicted values of residual weight fraction using differential evolution (DE), a population-based search algorithm. Among the four different models proposed in this study, the model in which rate of change of activity of biomass with normalized conversion proposed as a function of activity itself gave the best agreement with the experimental data.
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    Experimental studies on producer gas generation from wood waste in a downdraft biomass gasifier
    (Elsiever, 2009-06) Sheth, P.N.
    A process of conversion of solid carbonaceous fuel into combustible gas by partial combustion is known as gasification. The resulting gas, known as producer gas, is more versatile in its use than the original solid biomass. In the present study, a downdraft biomass gasifier is used to carry out the gasification experiments with the waste generated while making furniture in the carpentry section of the institute’s workshop. Dalbergia sisoo, generally known as sesame wood or rose wood is mainly used in the furniture and wastage of the same is used as a biomass material in the present gasification studies. The effects of air flow rate and moisture content on biomass consumption rate and quality of the producer gas generated are studied by performing experiments. The performance of the biomass gasifier system is evaluated in terms of equivalence ratio, producer gas composition, calorific value of the producer gas, gas production rate, zone temperatures and cold gas efficiency. Material balance is carried out to examine the reliability of the results generated. The experimental results are compared with those reported in the literature.
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    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.