Department of Chemical Engineering

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    Sustainable valorization of macroalgae residual biomass, optimization of pyrolysis parameters and life cycle assessment
    (Elsevier, 2024-04) Sangwan, Kuldip Singh; Raghuvanshi, Smita
    The major challenges for the current climate change issue are an increase in global energy demand, a limited supply of fossil fuels, and increasing carbon footprints from fossil fuels, which have necessitated the exploration of sustainable alternatives to fossil fuels. Biorefineries offer a promising path to sustainable fuel production, converting biomass into biofuels using diverse technologies. Aquatic biomass, such as macroalgae in this context, represents an abundant and renewable biomass resource that can be cultivated from water bodies without competing with traditional agricultural land. Despite this, the potential of macroalgae for biofuel production remains largely untapped, with very limited studies addressing their viability and efficiency. This study investigates the efficient conversion of unexplored macroalgae biomass through a biorefinery process that involves lipid extraction to produce biodiesel, along with the production of biochar and bio-oil from the pyrolysis of residual biomass. To improve the effectiveness and overall performance of the pyrolysis system, Response Surface Methodology (RSM) was utilized through a Box-Behnken design to systematically investigate how alterations in temperature, reaction time, and catalyst concentration influence the production of bio-oil and biochar to maximize their yields. The results showed the highest bio-oil yield achieved to be 36 %, while the highest biochar yield reached 45 %.
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    Chemical characterization of refuse derived fuel (RDF) using Py-GC/MS
    (Elsevier, 2024-05) Sheth, Pratik N.
    The conversion of municipal solid waste (MSW) to refuse-derived fuel (RDF) and its utilization as an alternative fuel in the cement industry has been an emerging trend. However, RDF is highly heterogeneous, with its complex composition changing with season and source. This work is focused on the chemical characterization of six RDF samples listed as A, B, C, D, E, and F from different locations across the country using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), thermogravimetric instrument and CHONS elemental analyzer. Qualitative and semi-quantitative results were obtained using EGA, single-shot and double-shot analysis methods. EGA has been used to derive qualitative results in correlation with TGA. FTIR analysis was carried out to understand the initial functional characterization. XRF analysis along with ICP-MS triple quad revealed the inorganic makeup of the samples. Single-shot results indicated that apart from non-hydrocarbon gases (CO2 and O2), the long-chain alkenes were most abundant, followed by alkanes, aromatic compounds, and ketones. Double-shot analysis indicated the presence of chloride and sulphur-based compounds in RDF samples as limiting components. Polystyrene contribution to LHV of RDF has been highlighted. The study can be further used to conduct compositional studies of RDF and its pyrolytic behavior in the gasifier. It will further strengthen the future gasifier models where pyrolysis is one of the critical steps. This technique will be very helpful in obtaining a better characterization of volatile and non-volatile (bio-oil and ash) fractions of the pyrolytic products.
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    Sustainable use of rice husk for the cleaner production of value-added products
    (Elsevier, 2022-02) Kuncharam, Bhanu Vardhan Reddy; Srinivas, Appari
    This paper covers a comprehensive review of the thermochemical conversion of rice husk (RH) into value-added products. RH is an organic residue and is produced in large quantities in China, India, Indonesia, and Bangladesh and appears to be a viable source for value-added products from thermochemical processes. The RH properties and operating conditions affect the quality and yield of the bio-oil, gaseous, and biochar products. The conversion techniques such as gasification, slow and fast pyrolysis, and product distribution are systematically reviewed. The literature shows that the Ni-based catalysts demonstrated high activity towards cracking of tar compounds and hydrocarbons, upgraded gas quality, and yielded high hydrogen production. Zeolite-based systems are promising catalysts for the upgradation of bio-oils. Due to the structured porosity and higher acidity, the metal-loaded zeolites catalysts have shown high removal efficiency towards the oxygenated compounds. RH ash is also used as an alternative cementitious material in the construction sector. The optimum level of cement replacement with RH ash in concrete is 15–20%, and higher compressive strength is witnessed for RH ash used concrete than conventional cement concrete. RH ash utilization for soil remediation and blended cement production are also discussed. A sustainable framework has been proposed for the utilization of RH in the chemical and construction sectors.
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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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    Chemical structures and primary pyrolysis characteristics of lignins obtained from different preparation methods
    (J-Stage, 2014) Srinivas, Appari
    This work aims at investigating correlations between primary pyrolysis characteristics of lignin and chemical structure of lignin feedstock. Three different types of lignin samples were prepared through enzymatic hydrolysis, organosolv extraction, and Klason procedure. Analysis by FT-IR and solid state 13C-NMR revealed that the lignin samples exhibited different contents of aromatic carbons, connection carbons, methoxyl carbons, and aliphatic side chains. The three lignin samples were pyrolyzed in a two-stage-tubular reactor at 650 ℃, and pyrolysis products were analyzed with gas chromatographs on-line. More than fifty compounds including inorganic gases, light hydrocarbons (LHs), aromatic hydrocarbons (AHs), phenol derivatives and light non-phenolic oxy-compounds (NPOCs) were gaschromatographically separable and quantified. The influence of the lignin structures on the pyrolysis characteristics was studied, and the correlation of product distribution and lignin chemical structures was examined. The total carbon selectivity into char and tar was increased with increasing lignin aromaticity. Methoxyl group and aliphatic substituents likely contributed for enhancing char formation, while hydrogen in lignin enhanced tar formation. Yields of LHs and NPOCs were increased with increasing aliphatic carbons of the lignin samples. AHs were formed from gas-phase recombination of LHs such as olefins, diolefines and alkynes, rather than directly from aromatic structures in the original lignin likely because of high energy required to cleavage carbon-oxygen bond existed in major structural units such as syringols or guaiacols.
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    A circular framework for the valorisation of sugar industry wastes: Review on the industrial symbiosis between sugar, construction and energy industries
    (Elsiever, 2018-12) Srinivas, Appari
    This paper provides a comprehensive review of literature on the properties of sugar industry waste, their varied uses in energy and construction sector, performance and limitations. An efficient upcycling of sugar industry waste in energy production would help the energy sector to reduce its dependency on non-renewable fossil fuels. Literature demonstrates that in the recent years there has been an increased research interest in thermochemical conversion of sugarcane bagasse to produce cleaner energy, rather than its landfilling or combustion. On the other hand, utilisation of secondary by-products from sugar industry in the production of cement, bricks, paver blocks, activated binder and other construction products helps to cut down the carbon footprint of the construction industry, while improving the properties of the final products. From the perspective of the sugar industry, such an arrangement eliminates disposal problems and creates additional revenue. Although independent research studies investigating the use of sugar industry by-products exist, few studies consider these valorisation options together to minimise waste and to create an efficient material flow chain. This study identifies various material and energy recovery pathways from published literature and connects the materials and processes to form a continuous material supply chain with minimum wastage. From the findings, a symbiotic framework has been developed with primary and secondary by-products from the sugar industry serving as source materials for energy production and sustainable construction products.
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    Multi reaction apparent kinetic scheme for the pyrolysis of large size biomass particles using macro-TGA
    (Elsiever, 2018-05-15) Sheth, P.N.
    In the present study, the pyrolysis of biomass is proposed by one step multi reaction apparent model. It is expressed as parallel production of bio-oil, gases and charcoal. Macro TGA of Jatropha de-oiled cake is performed at temperatures ranging from 350 °C to 700 °C. The volatiles released during pyrolysis exits from the top of the reactor and are cooled in a two-stage condenser followed by an ice trap. The weight reduction variation of the biomass with time, product yield and composition of non condensable gases are measured and used to develop the apparent kinetic model. The corresponding apparent kinetic parameters are estimated by minimizing the square of the error between simulated values of residual weight fraction and experimental values using non-traditional optimization technique logarithmic differential evolution (LDE). The weight reduction with time suggests that the pyrolysis of de-oiled cake is carried out in three stages. The maximum liquid yield obtained is 31.2% at 500 °C, which further decreases with an increase in temperature. The model predicted values of residual weight fractions and yield of products are matching very well with the experimental data for all reactor temperature.
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    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.
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    Magnesium Aluminate Catalyzed Pyrolysis of n-Heptane
    (IJCS, 2010) Mohanta, Hare Krishna
    The effect of magnesium oxide precursor on the activity of magnesium aluminate catalyst for the pyrolysis of n-heptane has been investigated. Magnesium oxide was prepared either from magnesium acetate, magnesium nitrate, magnesium carbonate or hydrated magnesium oxide. In each case, magnesium aluminate (containing 28 wt.% MgO) was prepared. The prepared catalysts were characterized by X-ray diffraction, surface area and pore volume measurement, thermogravimetric analysis and chemisorption of carbon dioxide. Compared to noncatalytic pyrolysis, the conversion of n-heptane increased in the presence of each of the catalysts. Depending on the salt used for the preparation of MgO, the conversion, product yields and coke deposition were different. The cracking activity increased with an increase in the total basicity of the catalyst. Magnesium aluminate prepared using magnesium oxide obtained from magnesium acetate showed the highest conversion as well as the highest yields of ethylene.