1. Ph.D Theses
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Item Experimental Investigation of Coffee Husk Biodiesel as A Renewable Fuel In Compression Ignition Engine(National Institute Of Technology Karnataka Surathkal, 2023) Emma, Addisu Frinjo; A, Sathyabhama; Yadav, Ajay KumarIn the present study, coffee husk (CH) and spent coffee ground (SCG) are used for the production of biodiesel. The CH is a by-product of the coffee processing industry, and SCG is obtained after the coffee is brewed. Field Emission Gun Scanning Electron Microscope (FEG-SEM) is used to investigate the elemental composition of the CH and the SCG samples and identify the presence of different elements with their distribution and concentration. The compositional analysis indicates that the CH comprised 49.84% of carbon and 48.06% of oxygen by weight. On the other hand, it is found that the SCG had 67.72% of carbon and 26.18% of oxygen by weight. The CH is selected for further study for the production of oil due to its higher oxygen distribution than SCG. From 1Kg of CH, 250g of oil is produced. By using the transesterification process, the produced oil is converted into biodiesel. Subsequently, 700 mL of coffee husk oil methyl ester (CHOME) biodiesel was produced from 1000 mL of coffee husk oil. After characterization of obtained biodiesel, the experiments are conducted in a single-cylinder direct injection diesel engine at a constant speed by varying the loads (0%, 25%, 50%, 75%, and 100%) for different biodiesel-diesel blends (B10, B20, B30, B40, B50, B80, and B100), and the results are compared with the baseline diesel. The brake thermal efficiency (BTE) of the blends, B10, B20, B30, and B50, is reduced by 0.6, 0.7, 1.29, and 3%, respectively, compared to the regular diesel. Similarly, the brake specific energy consumption (BSEC) is increased by 0.1, 0.3, 0.44, and 0.77% for B10, B20, B30, and B50, respectively. Exhaust gas emissions are reduced for all biodiesel-diesel blends with a marginal increase in NOx emission. Compared to regular diesel, at full load, CO, HC, and smoke opacity of B30 are reduced by 13.2%, 4%, and 12%, respectively. Whereas NOx and CO2 of B30 at full load are increased by 3.8% and 8.63% respectively The viscosity of CHOME biodiesel is found to be higher than diesel; hence a preheating mechanism is set to reduce the viscosity and density of the fuel before injecting it into the combustion chamber. Preheating the neat CHOME biodiesel (B100) to 95 °C decreased its viscosity and density by 49.5% and 3.7%, respectively. Running the engine with preheated B100 reduces CO, HC, and smoke opacity by 34%, 34%, and 35%, respectively, compared to unheated regular diesel. The percentage of CO2 in the exhaust gas is increased by 45.5% for preheated B100 compared with unheated B0 at 100% load. Furthermore, the injection timing of the engine is altered to find the optimum injection timing of the biodiesel-diesel blend. The BSEC is increased by 0.53 kg/kWh and reduced by 1.4 kg/kWh for advanced and retarded injection timing, respectively. By advancing injection timing, the HC, CO, and smoke opacity were reduced by 7.4%, 36%, 5.7%, and 7%, respectively, compared to the B30 at standard injection timing.Item Experimental Studies on Intermediate Pyrolysis of Lignocellulosic Biomass Coconut Shells(National Institute of Technology Karnataka, Surathkal, 2021) D, Kiran Kumar.; Gumtapure, Veershetty.In the present scenario, the energy sectors and individual entrepreneurs can opt for a new way of producing energy using the most abundant renewable energy sources available in the form of lignocellulosic agricultural waste. Among the lignocellulosic biomass, agricultural residues, coconut shells are carbon-rich and sustainable resources. In 2016-17, global coconut production has potentially exceeded upto 22 billion nuts. India is the world's third largest producer of coconuts after Indonesia and the Philippines. The total amount of coconut shell residue in India is as high as 2887 (kt/year). If used properly, coconut shells can generate 157 MW of potential power. The literature review showed that limited research studies have been conducted on the yield of the product from coconut pyrolysis. The novelty of current work is to envisage the methodology by intermediate pyrolysis to obtain a high quality of exhaustive end products which could be used as fuel or as raw material for value added chemicals. Pyrolysis is a thermal decomposition technology which decomposes carbonaceous bio wastes into liquids, gases, and char (solid residue) in the absence of oxygen. The thermochemical conversion of agricultural waste residues coconut shell is considered in the overall study through intermediate pyrolysis process. It is a fixed bed pilot scale reactor heated externally with the help of electric heaters. In this work experiments were conducted at elevated temperature 550-575 °C, three major end products are solid (Bio-char), liquid (Bio-oil/Tar) and pyro gases. The bio-oil resulted from intermediate pyrolysis was analysed for chemical composition using, Fourier transform infrared (FT-IR) spectra and gas chromatography mass spectroscopy (GC-MS). Additionally, bio-tar was separated into saturate, aromatic resin and asphaltene (SARA) fractions by using the column chromatography with the combination of n-pentane, toluene and ethanol solvents. The SARA fractions were further characterized by FT-IR spectra, elemental analysis and nuclear magnetic resonance (NMR) analysis. Challenges in using bio-oil as drop-in fuel or as a fuel additive include high moisture content, lower heating value, and low thermal stability. Besides, the bio-oils have limited miscibility with conventional petroleum fuels due to the presence of polar compounds like alcohols and carbonyl compounds. The storage stability of bio-oils is typically low due to the presence of compounds with reactive functional groups. Therefore, the bio-oil was upgraded for better physicochemical and elemental properties prior use. Hydrodeoxygenation (HDO) has attracted considerable attention as an efficient way of removing oxygen atoms from bio-oil rich in oxygenated compounds. Although several works have reported HDO chemistry on various bio-oils, HDO chemistry has never been applied to coconut shell derived pyrolytic oil. The bio-oil was upgraded with mild thermal and catalytic hydrodeoxygenation (HDO) and compares the elemental properties of the upgraded bio-oil samples. The higher heating value (HHV) of cr-CSPO was found to be 16.46 MJ/kg. The thermal and catalytic upgrading was performed at 250 °C, 30 bar of hydrogen pressure, a reaction time of 3 h, and a stirring speed of 350 rpm. In the case of catalytic upgrading, 10% of catalysts Ru-C and Pd-C (10 wt.% of cr-CSPO) were used as the catalyst. Also, the developed activated charcoal is implemented as counter electrode in demonstrating Dye Sensitised Solar Cell (DSSC) using naturally available sensitizer. In addition, Dye Sensitised Solar Cell based current and temperature sensors were developed for highly remote optoelectronics applications. Anthocyanin dye extracted from pomegranate juice generated maximum current of 10 mA/cm2. The characteristics of the cell were performed with different optic filters wavelength ranging 400-650 nm and the maximum efficiency was developed for wavelength of 443nm.Item Thermophysical and Thermochemical Behaviour of Coal and Biomass during Chemical Looping Combustion(National Institute of Technology Karnataka, Surathkal, 2021) S, Pragadeesh K.; Regupathi, I.; D, Ruben Sudhakar.Thermal power plants burning fossil fuels are the major anthropogenic sources of carbon dioxide emissions into the atmosphere. Chemical Looping Combustion (CLC) is a promising fuel conversion technology for inherent carbon capture with a low energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC has drawbacks like loss of unconverted char and gaseous combustibles. The utilization of large solid fuel particles (in mm-sizes) potentially overcomes these problems and also reduces the energy involved in size reduction. The thermophysical and thermochemical changes involved during the conversion of these large-sized particles are large in magnitude and of greater significance. Thus, they along with the fuels’ thermochemical changes become critical inputs for the effective design of process equipment. This study is aimed at (i) gaining a qualitative understanding of the progressive thermophysical and thermochemical changes during fuel conversion and (ii) quantifying the influence of various operating parameters on the same. Thermochemical changes, namely devolatilization, char conversion, carbon transformations, and the thermophysical behaviour in terms of primary and secondary fragmentation, shrinkage, and microstructural changes are studied using single-particle experiments in fluidized bed insitu-gasification CLC conditions. Two types of Indian coals, one type of Indonesian coal and one type of carbon-neutral biomass (fuel wood), of three different sizes in the range of +8-25 mm are used in this study. Natural hematite is the oxygen carrier bed material used (in the size range of +250-425 μm), with steam as the fluidization-cum-gasification agent at 2.5 times the minimum fluidization velocity. The experiments are conducted at three different bed temperatures of 800, 875 and 950 oC. This work is comprised of six different experimental programs, viz. (i) development of a new method to determine devolatilization time in flameless FB-CLC conditions, called ‘Colour Indistinction Method (CIM)’, (ii) devolatilization and char yield experiments, (iii) experiments of primary fragmentation during devolatilization (iv) char conversion and char fragmentation (secondary) experiments, (v) char reactivity experiments using thermogravimetry, and (vi) char structural analysis using instrumental techniques. CIM is developed based on the observation of particle disappearance in the bed at the end of devolatilization and validated using standard diagnostic methods such as residual-volatile measurements and particle-centre temperature profilometry. CIM produced reliable results within the error range of -7.57 to +3.70 %. The devolatilization experiments revealed that the larger particles have a relatively lower amount of volatile release. However, increasing the bed temperature enhances the volatile release rate as well as the quantity of release (up to 12% in coals; 30% in biomass). With the decrease in sphericity (seen in flake coal particles), a maximum of 56% reduction in devolatilization time is noticed. A correlation for determining devolatilization time under the CLC environment is developed, with a coefficient of determination of 0.95. Char yield is found to be strongly influenced by operating bed temperature, but it is a weak function of particle size and shape. Shrinkage in biomass is witnessed for all sizes, with an effective reduction of 31-52% in initial particle volume. Char conversion times of fuels increase by 60 to 170% when particle size is increased by 2 to 2.5- folds, while an increase in bed temperature by 150 oC caused a reduction of 42 to 86%. It is also understood that if the fixed carbon content is higher than the ash content in fuel, intensive fragmentation occurs and brings down the char conversion time. Primary and secondary fragmentation phenomena are quantified using various indicators such as probability of fragmentation events, frequency and timing of fragmentation, number of fragments, fragmentation index and particle size distribution of fragments at different residence times. The intensity of primary fragmentation increases with the increase in particle size and bed temperature, while it decreases with the increase in compressive strength. Only a maximum of 60% of the tested particles undergo fragmentation, irrespective of fuels. High-volatile Indian coal and biomass, respectively, are the most and least susceptible fuels to primary fragmentation irrespective of particle size and bed temperature. Indian coals are found to fragment in the earlier stages of conversion, thus becoming a dominant factor in shortening the overall fuel conversion time. Unlike during devolatilization, the largest sized particles of all the tested fuels experience secondary fragmentation. Among the different bed temperatures studied, 950 oC is found to be the most favourable for char conversion and fragmentation. Regardless of fuel type and feed size, the inception of char fragmentation is noticed in the very first quarter of conversion time, indicating its substantial effect on the char conversion time, and therefore, it becomes necessary to carefully incorporate this size reduction with respect to time in the char conversion models. Percolative mode of fragmentation is noticed in the final quarter of char conversion, except for high-ash Indian coal particles. A minimum critical char size exists below which char weakening does not yield breakage, whose values vary between 4.4 and 14.2 mm, depending on fuel type and feed size. Fuel type is found to be the prime influencer of fuel conversion and comminution phenomena, followed by particle size and operating bed temperature. This study establishes that large fuel particles up to 25 mm can be used in CLC systems without any prior size reduction, except in the case of high-ash Indian coal. Isothermal char reactivity studies using TGA show that samples exhibit high reactivity if char preparation is done at low temperatures for high-volatile fuels and at high temperatures for low-volatile fuels. Peak reactivity is noticed during the initial stages of char conversion regime for all coals and in later stages for biomass samples. Char micrographs show mesoporous char formation with pore size of about 2-4 nm in all fuels, during the course of char conversion. Electron dispersive studies indicate that the high volatile Indian coal retains Ca throughout the conversion period, whereas biomass chars retain the catalytic species like K and Ca. Raman spectroscopic analyses show that graphitic carbon structures are selective towards the steam atmosphere, while defective carbon structures are relatively more selective towards CO2.Item Production of 5 - (Halomethyl) Furfurals from Cellulosic Biomass and their Synthetic Upgrading into Renewable Chemicals(National Institute of Technology Karnataka, Surathkal, 2020) Sharath, B. O.; Dutta, SaikatThe transportation fuels and most of the bulk and fine chemicals are primarily sourced from crude oil. However, the excessive use of crude oil has depleted the reserves, created a disparity between the demand and supply, and degraded the environment. In search of a renewable and preferably carbon-neutral source, biomass has found by many as a commercially-feasible replacement for fossilized carbon. The chemocatalytic valorization of biomass is of particular interest since they are fast, biomass agnostic, selective, and can potentially be integrated into the existing infrastructure. A major challenge in the chemocatalytic value addition of biomass is to develop a new generation of robust, selective, inexpensive, and environment-friendly catalysts that can selectively deconstruct the biopolymers. In this regard, the acidcatalyzed depolymerization and dehydration of biomass-derived carbohydrates (e.g., cellulose) into furanics is an elegant way of removing excessive functionalities from the carbohydrate. Biomass-derived 5-(hydroxymethyl)furfural (HMF), 5- (chloromethyl)furfural (CMF), furfural and levulinic acid (LA) have been used as renewable chemical building blocks for further value addition into fuels and specialty chemicals. In this thesis work, an improved synthesis of CMF and LA have been reported using aqueous HCl as the acid catalyst in the presence of quaternary ammonium chloride as a surface-active agent (SAA). The SAA afforded noticeably higher yields of CMF and LA compared to the control reactions. The reactions were optimized on various reaction parameters such as temperature, duration, loading of the substrate, and the loading of SAA. The SAA was successfully recovered and recycled. LA was converted into alkyl levulinates, a potential diesel additive and a renewable solvent, in the presence of phosphotungstic acid as an environment-friendly and recyclable catalyst. Alkyl levulinates were also prepared by the alcoholysis of CMF and furfuryl alcohol using HClO4-SiO2 as an inexpensive heterogeneous catalyst. A scalable and high-yielding preparation of 5-(alkoxymethyl)furfural, a novel fuel oxygenate, from CMF has also been reported.Item Application of Polyoxometalates as Efficient and Green Catalyst for Catalytic Upgrading of Cellulosic Biomass(National Institute of Technology Karnataka, Surathkal, 2020) Tiwari, Ritesh; Mal, Sib Shankar; Dutta, SaikatIn recent years, the research on the sustainable production of energy, transportation fuels, and materials has been incentivized. Non-food and preferably waste biomass has been identified as a commercially-feasible renewable alternative to fossilized carbons for producing fuels and chemicals. The chemocatalytic value addition of biomass, where the oxygen-rich biopolymers are selectively deconstructed into functionally-rich small organic molecules, is of particular interest. A new generation of robust, inexpensive, and environment-friendly catalysts are crucial for the chemocatalytic route. Over the past years, heteropolyacids (HPAs) are increasingly being used as a catalyst in the chemistry of renewables and biomass value addition. HPAs have been used in the hydrolysis and dehydration of pentose and hexose sugars in biomass into furfural and 5- (hydroxymethyl)furfural (HMF), respectively. Furfural, levulinic acid, and HMF act as renewable chemical building blocks that can be converted into commodity chemicals and materials via chemical or catalytic transformations. The proposed work is intended to explore the efficiency of various homogenous and heterogeneous HPA catalysts for the catalytic upgrading of biomass-derived chemical intermediates into value-added chemicals. HPA-based homogeneous and heterogeneous catalysts were used for the acetalization, esterification, and Baeyer-Villiger oxidation reactions of various biomass-derived chemical intermediates. The reaction conditions were optimized on various parameters such as temperature, duration, loading of reactant, and loading of catalyst. The cyclic acetals of biomass-derived furfural were prepared in high isolated yields in refluxing benzene in the presence of the phosphotungstic acid (PTA) catalyst. The PTA catalyst was successfully recovered and reused several times without significant loss in mass or activity. The esterification of saturated and unsaturated free fatty acids such as oleic acid and stearic acid were conducted in the presence of PTA catalyst as an efficient and recyclable catalyst. 2-Furanone was prepared by the selective oxidation of furfural using hydrogen peroxide as an inexpensive oxidant and PTA supported on ammonium zeolites as the catalyst. A scalable and high yielding preparation of alkyl benzoates and alkyl 2-furoates has also been reported.Item Hybrid Biological Systems for Wastewater Treatment(National Institute of Technology Karnataka, Surathkal, 2018) D S, Manu; Thalla, Arun KumarThe current trend in sustainable development deals majorly with the environmental management. There is a need for economically affordable, advanced treatment methods for the proper treatment and management of domestic wastewater containing excess nutrients (such as nitrogen and phosphorous) which otherwise may lead to eutrophication. In the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT), and dissolved oxygen (DO) on nutrients removal in a lab-scale activated sludge biofilm (AS-biofilm) reactor was monitored. Based on various trials, it was seen that ASbiofilm reactor achieved good removal efficiencies with respect to COD-92%, NH4+- N- 93%, TN- 86% and TP-52%. Further, in order to improve the quality of the treated wastewater, photocatalysis by TiO2 was investigated as a post-treatment technology, using solar and UV irradiations. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, MPN and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50% respectively. Similarly, to enhance the performance of the system in terms of nitrogen and phosphorous in addition to carbon removal integrated anaerobic/anoxic/oxic activated sludge biofilm (A2O-AS-biofilm) reactor was designed and operated by varying operating conditions such as C/N ratio, suspended biomass (X), HRT and DO. Based on various trials, it was seen that the A2O-AS-biofilm reactor achieved good removal efficiencies of COD-95.5%, TP-93.1%, NH4+-N-98% and TN-80% when the reactor maintained C/N ratio - 4, suspended biomass (X) - 3 to 3.5 g/L, HRT-10hr, and DO - 1.5 to 2.5mg/L. Applicability of soft computing techniques viz, Adaptive Neuro Fuzzy Inference System (ANFIS), Genetic Algorithm Adaptive Neuro Fuzzy Inference System (GA-ANFIS) and Particle Swarm Optimization Adaptive Neuro Fuzzy Inference System (PSO-ANFIS) to performance prediction of hybrid system was studied. ANFIS was applied on real time WWTP of 43.5 MLD capacity. ANFIS models showed better efficiency while modeling wastewater using multivariate analysis. So in the current study, in order to improve the prediction ability of ANFIS,ii hybrid models such as GA-ANFIS and PSO-ANFIS have been applied for the prediction of effluent TN, COD and TP concentration yielded from a hybrid ASbiofilm reactor. From the results, both GA-ANFIS and PSO-ANFIS proved capable to predict the effluent parameters of the reactor with varying operation conditions and can be adopted for modeling the nonlinear data.