PhD Theses (Chemical Engineering)

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    Absorption of carbon dioxide into novel single and blended amine solvents
    (2017) Das, Bisweswar
    Over the last few decades, the increasing concentration of carbon dioxide (CO2) in the atmosphere has contributed adversely to the environment and has been a subject of worldwide attention. The capture of CO2, which is one of the main greenhouse gas (GHG), currently represents an essential step in the performance of electric power stations, petroleum refineries, chemical fertilizer plants, coal gasifiers, cement factories, and the steel industries. In the recent days, gas scrubbing using activated aqueous alkanolamine solutions is the most reliable retrofit option for post combustion CO2 capture. The present study investigates a novel activator, bis(3-aminopropyl)amine (APA), which can be an effective mode of eliminating CO2 from flue gas. The kinetics of CO2 absorption into chosen aqueous solution of APA was carried out at 303, 308, 313 and 323 K over a concentration range of 0.1-0.5 kmol m-3 and at different CO2 partial pressure. A wetted-wall column absorber was used for the kinetics measurement. The reaction mechanism of CO2 with primary and secondary amines (zwitterionic mechanism) is described and accordingly the experimentally obtained kinetic data are interpreted. A qualitative nuclear magnetic resonance [NMR (1D and 2D)] spectroscopy method has been applied to develop the reaction scheme for novel aqueous APA with CO2. The kinetic rate parameters were investigated according to the pseudo-first-order condition for CO2 absorption at each experimental condition. The values of second-order rate constant, k2-APA and reaction rate with CO2 reported in this study were higher than many existing amine activators like ethylenediamine (EDA), N-(2-aminoethyl ethanolamine (AEEA), piperazine (PZ), 2-(1-piperazinl)-ethylamine (PZEA), etc. Two blended solvents such as aqueous blend of APA with N-Methyldiethanolamine (MDEA) and 2-Amino-2-methyl-1-propanol (AMP) were considered for potential use in CO2 capture. It was observed that the enhancement factor increases significantly in comparison to single amine (aqueous MDEA) solutions when the APA concentrations increased in the blends with MDEA.
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    Absorption of CO2 by Single and Blended Amine Solvents in Various Gas–Liquid Contactors
    (2008) Paul, Subham
    In this work the absorption of CO2 into aqueous solutions of sterically hindered and blended amines is considered. A kinetic study is carried out for the reaction of CO2 into aqueous solutions of two important single sterically hindered alkanolamines, 2-piperidineethanolamine (2-PE) and 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) at 303, 313 and 323 K for a range of amine concentrations using a fabricated wetted wall column absorber. The reaction is satisfactorily described using a zwitterionic mechanism. The hydrolysis of the carbamate ion to form bicarbonate ion considered in the reaction mechanism is confirmed by 13C NMR spectroscopy. The reaction orders are found to be around 1.0 with respect to amines for both systems. The second order rate constants, k2, are obtained from the experimental results which are correlated using Arrhenius equation. Kinetics of absorption of CO2 into a new activator such as 2-(1-piperazinyl)-ethylamine (PZEA) and into the blends of PZEA and N-methyldiethanolamine (MDEA) are also carried out. The reaction of CO2 with PZEA is described by overall second order reaction. The addition of small amounts of PZEA to (MDEA + H2O) is found to be significantly enhancing the reaction rate. In order to study the effects of different physicochemical and kinetic parameter on calculated CO2 absorption rates into aqueous solutions of (2-PE + H2O),(AHPD + H2O) and (PZEA + H2O), a parametric sensitivity analysis is investigated for which a series of simulation runs are carried out. The parameters considered for the analyses are Henry’s law constant for CO2, diffusivity of CO2 into the amine solutions and the second order reaction rate constants for the absorption of CO2. The kinetic study carried out in this work should be useful for the rational design of gas treating processes employing single or blended alkanolamine solvents. Physicochemical properties of CO2 and the aqueous alkanolamine solvents needed in the kinetic study are measured in this work, extending the data in the literature for the specific single and blended amine solvents studied in this work. The diffusion coefficients and physical solubilities of N2O in the aqueous alkanolamine solutions are measured and the diffusivities and physical solubilities of CO2 in these solvents are estimated by “N2Oanalogy”. The densities and viscosities of the aqueous amine solvents are measured over a wide range of amine concentrations and temperatures. In addition, several correlations developed in this work, will allow prediction of blend properties from single amine properties for process design and research work in gas treating. Besides this kinetic analysis, a theoretical study is carried out using hollow fiber membrane contactor (HFMC) and flat sheet membrane contactor (FSMC) to compare the absorption performance of different aqueous single and blended amine solvents for the absorption of pure and as well as 20% CO2. The performance of different single and blended amine solvents is analyzed in terms of local and average absorption flux of CO2 along the length of fiber or flat membrane. The amine solvent systems considered here are the aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), 2-PE and AHPD as well as aqueous blends of (MEA + MDEA), (MEA+AMP), (DEA + MDEA), (DEA + AMP) and (PZEA + MDEA). The performance of FSMC and HFMC is also compared. The CO2 absorption flux in FSMC is found higher than that in HFMC for all high to low reacting amines.
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    Adsorption Characteristics of Activated Carbon for the Recovery of Ni (II) and Pd (II) from Synthetic Electroless Platin / Yennam Rajesh
    (2014) Rajesh, Yennam
    Among various adsobents activated carbon has been prominent for industrial applications like heavy metal removal and wastewater treatment...
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    Advanced Oxidation Processes for Theatment of Pharmaceutical Wastewater
    (2014) Giri, Ardhendu Sekhar
    Pharmaceutically active compound(PhACs) are mostly released into the environment for decades without proper treatment and toxicity assay...
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    Amine Functionalized Mch-41 for Co2 Capture
    (2014) Sravanthi, L
    The doctoral work mainly focuses on developing novel MCM-41 that will allow enhanced amine loading and demonstrate efective CO2 capture characterristics.
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    Amine functionalized ordered mesoporous silica materials and its applications towards adsorbent and membrane for CO2 capture
    (2015) Barma, Sanjib
    The main aim of this work is to study the CO2 separation using amine functionalized ordered mesoporous silica materials in adsorption based technology as well as membrane based technology. To know the inner detail of surface characteristics and the CO2 adsorption capacities of the amine-functionalized ordered mesoporous silica materials, the powder form of the materials were studied. Functionalization of the ordered mesoporous silica (MCM 48) materials with different amines was performed by using three different amines. The best result for CO2 adsorption of amine-functionalized amine was chosen for further analysis. The CO2 adsorption capacity at a particular temperature for different dosing of amine-functionalized OMS material was studied. In addition to this, the temperature effect of the amine-functionalized OMS materials which showed best CO2 adsorption capacity, were also studied. After inheriting the concept of amine-functionalized ordered mesoporous silica materials for CO2 adsorption, we analysed two different techniques to synthesize OMS materials and compared them for CO2 uptake capacity. Then the OMS materials were introduced in more energy saving membrane application. The ordered mesoporous silica membrane was successfully synthesized on porous α-alumina support. Finally, performance studies were investigated and analysed by using single and binary gas mixture (CO2/N2).
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    Antifouling and smart polymeric ultrafiltration membranes for environmental and biological separations
    (2018) Singh, Randeep
    The PhD thesis focuses on the synthesis, characterization, and applications of smart polymeric ultrafiltration membranes prepared by using phase inversion method with applications in the field of environment and biological fields. The thesis Chapter 1 discusses about the basics, properties, and problems associated with membranes. Also, the scope and objectives of the present study are reported. The methods to abstain the problem of membrane fouling are also elaborated along with state of the art. Chapter 2 discusses about the different preparation and characterization techniques used in the synthesis and analysis of the membranes. Chapter 3 of the thesis evaluates the role of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (AMPS) in the modification of polysulfone membranes for ultrafiltration. The modification of the membranes with AMPS results in better hydrophilic and antifouling nature along with improved bovine serum albumin (BSA) removal. Likewise, Chapter 4 evaluate the methoxy poly(ethylene glycol) (mPEG) effect on the hydrophilicity and antifouling nature of the Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) flat sheet polymeric membranes for humic acid (HA) removal. The study shows positive results of mPEG on the PVDF-co-HFP membrane flux and antifouling profile with better HA removal. Further, Chapter 5 investigates the role of flyash based carbon nanotubes (CNTs) on the hydrophilic and antifouling nature of polysulfone ultrafiltration membranes. The CNTs modified membranes shows better hydrophilicity and antifouling nature. In Chapter 6, Cu2O photocatalyst modified antifouling polysulfone mixed matrix membrane for ultrafiltration of protein and visible light driven photocatalytic pharmaceutical removal are discussed. The modified membranes shows improved flux profile along with antifouling and photocatalytic nature. The maximum pharmaceutical removal is shown by membrane with highest wt% of Cu2O photocatalyst under light and acidic conditions. Similarly, Chapter 7 discusses about the stimuli responsive polymer nanocomposite modified mixed matrix polysulfone ultrafiltration membrane for dye removal. The maximum dye removal is observed with modified membranes in light and basic conditions as compared to nascent membrane. Lastly, Chapter 8 presents the conclusion, summary, and scope of future work of the present thesis.
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    Binding and Destabilization of Amyloid-β Protofibrils by β-sheet Breaker Molecules: A Molecular Dynamics Simulation Study
    (2021) Kanchi, Pavan Krishna
    Alzheimer’s disease is a fatal neurodegenerative disease which affects the elderly population leading to the loss of memory and the ability to perform activities, and eventually death. There is no cure for Alzheimer’s disease at present. One of the hallmark characteristics of this disease is the presence of plaques in the brains of patients, formed mainly by the amyloid-beta peptide in the form of beta-sheets. One of the therapeutic strategies is the use of small molecules as drugs to destabilize these fibrils. In the present thesis, we employ all atom molecular dynamics simulations in order to study the destabilization of amyloid-beta protofibrils by small molecules. The extent of destabilization and the binding affinities were characterized, and the dominant interactions which influenced the binding process were identified. The first major finding of the thesis was that oligoproline chains of various lengths could break the beta-sheet structure of the protofibrils and induce the formation of random coils. The second major finding was that a peptide KLVFFP5 which was designed to exploit the properties of the self-recognition sequence of the amyloid-beta peptide KLVFF and the beta-sheet breaker amino acid proline could destabilize the amyloid protofibrils to a greater extent than the KLVFF peptide. The third major finding was that for a model of the protofibrils which is known to be a particularly difficult target for drugs, the increased presence of aromatic amino acids can enhance the binding of a known beta-sheet breaker peptide LPFFD, when it was modified by these aromatic amino acids. The fourth important finding was that THC molecules could destabilize the amyloid-beta protofibrils. We obtained insights into the destabilization of the protofibril structure by the THC molecules.
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    Bio-inspired route of metal nanoparticles synthesis and photocatalysts doping
    (2018) Chelli, Venkatanarasimha Rao
    The conventional methods of nanoparticles (NPs) synthesis are sonochemistry, laser ablation, co-precipitation, sol-gel procedures, solvothermal, chemical reduction, and photo-reduction. All these methods are chemical and energy intensive, hence, costly. Thus, a greener route of environmentally benign NPs synthesis has gained tremendous success in recent times. The bio-mediated methods are straightforward and eco-friendly and, the whole process can be carried out at room temperature and pressure. The intercellular synthesis of NPs using microbes often shows a lower synthesis rate as well as difficulty in size and shape control. Such problems can be overcome in many extents by extracting the bio-analytes in a suitable media from the living cells. After that, the particles are synthesized in this media. Faster kinetics and minimization of aggregation of particles are the main challenges of the bio- and bio-mediated processes.Sechium edule, fruits of a perennial climber, is rich in ascorbic acid (AA 294 mg/kg dry fruit). In the first part of this work, the bio-analytes were extracted in an aqueous media for the synthesis of AgNPs. The study emphasizes on the mechanism of formation of mono-crystalline AgNPs at different pH which in turn controls the kinetics and size of AgNPs. Thermodynamically facile Ag2O reduction at a higher pH (≥ 9) resulted in spherical particles of smaller sizes; however, the particles were laden with a trace of Ag2O at pH 12.5. A broad and bimodal distribution of AgNPs of different shapes and sizes were originated at a lower pH (3≤pH≤5) from Ag+ and Ag2O reductions where AA mostly exists as dehydro-AA. A single surface plasmon resonance peak at 425 nm exhibited a blue shift with the decrease in AgNPs size and increase in sphericity in the abundance of OH– ions. The hydrodynamic diameter of AgNPs was around 1.6 times greater than the dry particles from TEM micrograph at the natural pH (5.8) of the bio-extract. AgNPs were tested for the inactivation of Bacillus subtilis and Escherichia coli bacteria
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    Bio-inspired synthesis of Co3O4 and NiO nanoparticles for electrocatalytic H2O2 generation and sensing
    (2018) Das, Raj Kumar
    Environment friendly reagent Hydrogen peroxide (H2O2) has wide applications in chemical synthesis, food, clinical, biological, and environmental processes. One of the common applications of H2O2 is its use as a precursor for the hydroxyl radicals (•OH) formation in the advanced oxidation processes (AOPs) for the wastewater treatment. Therefore, H2O2 electrogeneration is usually carried out through the reduction of dissolved O2 (DO) in an acidic solution at a low cathodic potential. The present study comprises of three parts.The first part of this work is undertaken to investigate on H2O2 decomposition over a broad range of its concentration which is typically employed in water treatment. Various parameter such as pH and reaction temperature and also trace metals (Na+, Ca2+, Ni2+, Co2+, Cu2+, etc) effect H2O2 decomposition. H2O2 became essentially unstable at a higher pH in the presence of these trace metal ions except Co2+ and Ni2+ due to low catalytic effect. This work also focused on the role of common supporting electrolytes (SEs) in the electro-chemical inertness of Ti-based materials employed for the anodic (direct) oxidation coupled with H2O2 electrogeneration at the graphite cathode for the concurrent decomposition of organic contaminants. It was found that ClO4− corroded TiO2 coated Ti (TiO2–Ti) anode very fast (>60 min), and Ti4+ ions formed a yellow color complex (λmax = 380 nm) with H2O2. The influence of Cl–, NO3−, and SO42− was insignificant on the stability of TiO2–Ti. The cell current efficiency of H2O2 formation dropped sharply with ClO4− in the case of TiO2–Ti anode. The TiO2–Ti corrosion also reduced the mass transfer co-efficient of DO transport from bulk to the cathode surface because of Ti4+ adsorption on graphite cathode.
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    Bioconversion of crude glycerol to dihydroxyacetone using immobilized gluconobacter oxydans : process design, optimization and intensification
    (2017) Dikshit, Pritam Kumar
    Conversion of biodiesel derived waste/crude glycerol to higher value products is a potential way for enhancing the economy of biodiesel industry. Among several products, dihydroxyacetone (DHA) is one of the fine chemicals known to be used in pharmaceuticals and cosmetics industry. The present thesis is focused on the production of DHA from crude glycerol using immobilized Gluconoabcter oxydans cells. The immobilization support, Polyurethane foam has highly porous structure with large surface area, and cells can easily get immobilized over the surface as well as inside the pores, which results in high cell density in relatively small volume. The thesis is divided in many sections. As reported earlier, high concentration of both substrate (i.e. glycerol) and product (i.e. DHA) can inhibit cell growth and DHA biosynthesis, leading to low DHA yield and productivity. We have addressed the matter of substrate and product inhibition of free and immobilized cells in presence of both pure and biodiesel-derived crude glycerol. The experimental data were fitted to various substrate inhibition model in order to calculate the kinetic parameters. In the second step, the optimization of medium components were done using Plackett-Burman and central composite experimental design method. Most significants factors were selected from Plackett-Burman design, which were further optimized using central composite design. In the next step, optimization of the process varibales (pH, temperature and initial glycerol conc.) were carried out. The optimized medium and process variables were further used for carrying out the batch and repeated-batch experiments.
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    Biodegradation of Phenolic Compounds Using an Indigenous Mixed Microbial Culture
    (2008) Saravana, P.
    Biological treatment of wastewater containing phenolic compounds, using indigenous mixed microbial consortium, is the main theme of this thesis. Biological degradation has been advocated to be a better alternative for phenol degradation as opposed to other popular methods for wastewater treatment. Merites of biological treatment and demerites of other methods are also properly discussed in the thesis. ...
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    Bioprocess development for polyhydroxybutyrate (PHB) production from waste carob pods and its application in food packaging: A biorefinery approach
    (2020) Manikandan, N Arul
    Increasing concern on white pollution has necessitated the need for an alternate polymer possessing excellent performance. Polyhydroxybutyrate (PHB) is a highly biodegradable and sustainable polymer which is entirely sourced from microorganisms and offers tremendous potential for the green revolution. However, elevated cost incurred during its production limits its commercialization. This problem was tackled, and a cost-effective PHB production process was demonstrated by replacing various conventional techniques with emerging bioprocess technologies. A novel closed-loop biorefinery strategy was developed to utilize carob pods as the feedstock for both upstream to downstream processing of PHB. The PHB produced further resulted in a biopolymer with superior antimicrobial properties due to the intrusion of lignin-derived from the carob pods. In addition to reduction in the overall PHB production cost, achieved by using carob pods as the cheap feedstock, efforts were laid by introducing a novel wide-gap annular bioreactor for PHB fermentation and a tubular ceramic membrane assembly for its recovery. Whereas the wide-gap annular bioreactor resulted in 1.6 times higher PHB production titre than a stirred tank bioreactor, almost complete PHB recovery along with heightened throughput was attained using the novel tubular ceramic membrane assembly. By inclusion of graphene nanoplatelets to the PHB matrix, a highly durable packaging film was produced which showed a four-fold increase in shelf-life of food items like potato chips and milk product. Cost-effectiveness offered by the various novel strategies and technologies developed in the present study was further revealed by the reduced payback period and high turnover through a detailed techno-economic assessment. Thus, the closed-loop zero-waste discharge biorefinery model developed in this study based on novel waste lignocellulosic feedstock, annular bioreactor design and operation, ceramic membrane-based biomass separation and food packaging application of PHB nanocomposites demonstrated that the bioprocess is economical, sustainable and environmentally safe with potential industrial application.
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    Biosynthesis of xylitol from sugarcane bagasse : process optimization, modelling and intensification
    (2018) Tizazu, Belachew Zegale
    In the first part of this thesis, statistical optimization of process parameters for dilute acid hydrolysis of sugarcane bagasse for maximum xylose yield was reported. Prior to statistical optimization, the chemical composition of sugarcane bagasse and the effect of solid to liquid ratio on xylose yield were analysed. The process parameters considered for optimization were hydrolysis temperature, acid concentration (or acid load) and hydrolysis time. Optimum levels of these parameters were determined by Box Behnken design (BBD) method of optimization. The optimum values of the process parameters for dilute acid hydrolysis of sugarcane bagasse were investigated. The composition of monomeric sugars (xylose, glucose, and arabinose) and inhibitory products (acetic acid, furfural, and 5–HMF) in the hydrolysate has also been analyzed under optimal conditions of dilute sulfuric acid hydrolysis of sugarcane bagasse. In subsequent investigations, we addressed the kinetic and thermodynamic features of dilute acid (2% v/v H2SO4, 1:30 w/v) hydrolysis of sugarcane bagasse. Time profiles of xylose formation in range of 100°–130°C and treatment period of 0–120 min were analysed with modified biphasic Saeman model. Generation of glucose, arabinose and inhibitory products (furfural, 5–HMF and acetic acid) were also analysed. Easy–to–hydrolyse fraction of hemicellulose increased with temperature. Activation energies for hydrolysis and xylose degradation were investigated. Thermodynamic analysis (H, S, and G) revealed that xylose formation is thermodynamically more favoured than degradation. In the second part of the thesis, optimization of medium components and process parameters for xylitol production from sugarcane bagasse using C. tropicalis MTCC 184 immobilized on PU foam were investigated. Plackett–Burman design revealed that out of seven medium components, 4 medium components, viz. yeast extract, MgSO4⋅7H2O, KH2PO4 and (NH4)2SO4; as significant components. These medium components were further optimized using central composite design (CCD) method to find their optimum values. Optimization of process parameters, viz. temperature, initial pH, shaking speed and substrate (xylose) concentration, was done at the optimized values of medium components. Optimum values of these parameters for maximum xylitol yield = 0.65 g/g of xylose are: yeast extract = 5.78 g/L, (NH4)2SO4 = 3.22 g/L, KH2PO4 = 0.58 g/L, MgSO4⋅7H2O = 0.57 g/L and temperature = 29.3oC, initial pH = 6.2, shaking speed = 151 rpm and initial xylose concentration = 20.9 g/L. Medium components provide essential growth factors and utilizable potassium, phosphate, ii nitrogen, sulphur sources. Activity of xylose reductase in metabolic pathway is stabilized and augmented by Mg2+ In the third part, we addressed ultrasound–assisted xylitol production through fermentation of dilute acid (pentose–rich) hydrolysate of sugarcane bagasse using free and immobilized cells of Candida tropicalis. Sonication of fermentation mixture at optimum conditions (optimized in the second part) was carried out in ultrasound bath (37 kHz and 10% duty cycle). Time profiles of substrate and product in control (mechanical shaking) and test (mechanical shaking + sonication) fermentations were fitted to kinetic model using Genetic Algorithm (GA) optimization. Maximum xylitol yield of 0.56 g/g and 0.61 g/g of xylose was achieved in control and test fermentations, respectively, in free cells of C. tropicalis. Moreover, the xylitol yield of 0.65 g/g and 0.66 g/g of xylose was obtained in control and test experiments, respectively in immobilized cells of C. tropicalis, which essentially corresponded to 71% and 73% of the theoretical yield. Although sonication of fermentation mixture resulted in marginal (17–20%) rise in final xylitol and biomass yields, the kinetics of the fermentation showed drastic enhacement. 2.5× enhancement in xylitol productivity and 2× rise in specific uptake rate of xylose was achieved under ultrasound assisted fermentation. Comparative assessment of the parameters of kinetic model for fermentation under test and control condition revealed that sonication promoted the uptake and utilization of substrates for cell growth and increased enzyme–substrate affinity. The inhibition effect of substrate was also reduced with sonication. 10–20× enhancement in permeability of cell membrane caused faster diffusion of substrates, nutrients and metabolite products across the cell membrane, which resulted in faster xylose metabolism and enhanced kinetics of fermentation. Flow cytometry analysis of in control (mechanical shaking) and test (ultrasound–treated) fermentations was carried out. The results of flow cytometry essentially confirmed that SSC and FSC of the C. tropicalis cells remain practically unaltered after sonication. Thus, the internal complexity and morphology of the cells remain unchanged after exposure to ultrasound, or in other words, no noticeable adverse impact of sonication is seen on the yeast cells.
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    Catalytic and Non-Catalytic Co-Pyrolysis of Torrefied Bamboo Biomass and Plastic: Synergism, Kinetics and Reaction Mechanism
    (2021) Alam, Mahboob
    The depletion of fossil fuels and environmental deterioration leads researchers to search for alternative, renewable, sustainable, and eco-friendly energy resources. The lignocellulosic biomass (LCB) is one of the most promising renewable resources for the production of biofuels, due to its mass availability, eco-friendliness, and CO2 neutrality. The LCB consists majorly of hemicellulose, cellulose, lignin and minor amounts of extractives and ash. The solid biomass cannot directly be used as fuel in industrial applications, because of several drawbacks including hygroscopic nature, high moisture content, high oxygen content, low heating value, lower grindability, low bulk density, fewer compositional homogeneity and lower resistance to biological degradation. Recently, the thermochemical conversion processes such as catalytic and non-catalytic (co-)pyrolysis has increased attention to convert biomass into biofuel. The biofuel obtained from the pyrolysis of raw biomass is inferior and the process itself is inefficient due to heteropolymeric nature of the hemicellulose present in the biomass. Therefore, it was hypothesized that the selective removal of hemicellulose by wet-torrefaction would help in improving the biofuel quality as well as overall economics of the process due to extra useful product (xylose) formation in the process. Addition of plastic also improves the biofuel characteristics and mitigates the plastic pollution. Further, addition of catalyst improves the biofuel quality by forming desired products such as aromatics (BTEX). The overall aim of this thesis is to develop wet-torrefaction process to selectively remove the hemicellulose in the form of xylose and to form the hydrochar with better pyrolysis characteristics. Further, to explore the potential of various zeolite catalysts (MesoHY and HZSM-5) for the catalytic co-pyrolysis (CCP) of wet-torrefied bamboo biomass and plastic (linear low-density polyethylene, LLDPE), TGA was carried out in the temperature range of 30 to 900°C with four heating rates (5─40°C) under argon atmosphere. The kinetic parameters were determined using three models based on the isoconversional method: Kissinger-Akahira-Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman (FM) models. The reaction mechanisms for individual and mixed samples were predicted using the Criado's master plot. Initially, the co-pyrolysis of bamboo sawdust (BSD) and LLDPE was studied. A blend containing 25 wt.% BSD and 75 wt.% LLDPE (BP1:3) showed the highest synergism as compared to other blends studied. The activation energy drop (36% with respect to biomass) was the highest with this blend. The mean values of apparent activation energy (Ēα) for the decomposition of blends (BP3:1 (75 wt.% BSD and 25 wt.% LLDPE), BP1:1 (50 wt.% BSD and 50 wt.% LLDPE) and BP1:3) are determined to be 357, 371 and 143 kJ mol-1 from KAS, 368, 400 and 165 kJ mol-1 from OFW and 468, 356 and 255 kJ mol-1 from FM, respectively. The reaction follows a multistep mechanism. The decomposition of the blend BP1:3 follows a nucleation growth (A2) model in the lower conversion range and diffusion (D2) model in the higher conversion range. As a next study, the bamboo saw dust (BSD) was wet-torrefied to selectively remove hemicellulose in the form of xylose (85 wt.%) at 140°C and duration of time 30 min with formicacid:BSD 1:1 and NaCl:BSD 3:1 w/w. and solid part act as hydrochar or Torrefied biomass sawdust (TBSD). Further, the pyrolysis and co-pyrolysis behavior of TBSD, LLDPE, and their blends were studied. The blend with one part hydrochar and three parts LLDPE (TBP1:3) showed the highest positive synergism. The Ēα of co-pyrolysis of blends (TBP3:1, TBP1:1, and TBP1:3) were found to be 232, 261, 247 kJ mol-1, respectively. The Criado's master plot showed the reaction mechanism of co-pyrolysis to be multistep. For example, the blend TBP1:3 followed the trend of two-dimensional Avrami-Erofeyev model (A2) at lower conversions, diffusion-reaction model (D2) at high conversions and end with a first-order reaction. The torrefied BSD (TBSD) was catalytically co-pyrolyzed with LLDPE over HZSM-5 and MesoHY. The peak decomposition temperature of catalytic pyrolysis of LLDPE over MesoHY was reduced by 251°C than that of HZSM-5 and the enhancement can be attributed to the topology of MesoHY. The apparent activation energies (Eα) of catalytic pyrolysis (CP) of TBSD, and LLDPE were 187 and 147 kJ mol-1 over HZSM-5 from KAS model. In addition, Ēα of blends TBP3:1, TBP1:1 and TBP1:3 were 163, 135 and 133 kJ mol-1, respectively. While Ēα of blends (TBP3:1, TBP1:1, and TBP1:3) were found to be 176, 133, and 122 kJ mol-1 in presence of MesoHY, respectively. The CCP of TBP1:3 and TBP1:1 showed synergism between TBSD and LLDPE in terms of Ēα and TBP1:3 showed the highest synergism with the least Ēα over HZSM-5. A multistep mechanism was observed in both CP of individual samples and CCP of blends, as analysed by Criado’s master plot over both zeolites. For example, the CCP of TBP1:3 followed geometric (volume) contraction (R3) and first-order reaction models at low and high conversions in presence of MesoHY.
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    Cavitation Assisted Hybrid Advanced Oxidation Processes for Degradation of Recalcitrant Pollutants
    (2021) Roy, Kuldeep
    This thesis has demonstrated the efficacy of the cavitation (both ultrasonic and hydrodynamic) based hybrid advanced oxidation processes for enhanced degradation of organic pollutants. We have dealt with the pollutants from pharmaceuticals and pesticide industries. Various iron oxides were synthesized and characterized for Fenton like degradation reaction system. The process parameters and loading of additives were optimized to achieve the maximum degradation of pollutants. A kinetic model was proposed based on reaction network for homogeneous reaction system and experimental degradation profiles were analyzed vis-à-vis simulated profiles. Concurrent analysis of experiments and simulations revealed faster leaching of Fe2+ ions from surface of solid iron catalysts due to intense turbulence and shear generated in cavitating flow results in faster degradation. Results of this thesis also gives an insight into the inter-relation or inter-dependence among various design and operational parameters. Density functional theory (DFT) simulations were also performed to identify the vulnerable sites for the radical attack. DFT calculation was further employed to investigate the detailed degradation mechanism in •OH mediated oxidative degradation of pollutants. Degradation intermediates were detected through LC-MS/MS analysis which was corroboration with DFT simulations. Present work has portrayed a systematic account of complex mechanisms and interactions in cavitation-based hybrid oxidation processes and further methodology could be extended to other studies involving hybrid advanced oxidation systems.
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    CFD Modeling and Simulations of Catalytic Hydrotreatment of Bio-Oil
    (2015) Kiran, Gollakota Anjani Ravi
    The term biofuel is referred to liquid, gas, and solid fuels produced from biomass. Biofuels include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to rural sector. Biofuels include bioethanol, bio-methanol, vegetable oils, biodiesel, biogas, bio synthesis gas, bio-oil, bio-char, and bio hydrogen etc. Whereas, bio-oil refers to the synthetic fuel produced from the seeds like jatropha, karanja, corn etc., by destructive distillation or pyrolysis process at a temperature of 500oC produces both liquids and gases. Further cooling this mixture leads to a liquid form termed as bio-oil. They are also known as second generation bio fuels. These second generation bio-fuels from pyrolysis process are incompatible with the conventional fuels mainly due to the higher oxygen content, high solids, content, high viscosity, high moisture content and chemically unstable, along with higher contents of char formation. Hence upgradation of the bio-oil from the pyrolysis process is highly advisable. Among the various upgradation processes hydrodeoxygenation (HDO) process appears to be the promising technique carried in the presence of a conventional catalysts using H2 gas that is also termed as catalytic upgradation of pyrolytic oil. This Ph.D. dissertation entitled “CFD Modeling and Simulation of Catalytic Hydrotreatment of Bio-oil” deals with the modeling and simulation of lumped kinetics of the HDO process in the presence of three different catalysts, namely Pt/Al2O3, Ni-Mo/Al2O3, and Co-Mo/Al2O3. The simulations are performed using commercial computational fluid dynamics (CFD) based software, Ansys Fluent 14.5, for a wide range of pertinent conditions i.e., weight hourly space velocity ranging between , temperature ranging between and pressure values between . The numerical methodology implemented for the present simulation studies comprising Ranz –marshall, and Gunn for heat interaction,Gidaspow and Schillar Naumann for drag interaction between solid and fluid phases; kinetic theory of granular flow for solid catalyst, turbulence model for flow characteristics, and finite rate/ eddy dissipation method to study the chemical reaction kinetics are implemented and thoroughly validated with the experimental literature and good agreement is observed between two results. From the simulation studies a wide range of results in terms of volume fractions of three phases with respect to the pertinent conditions are presented. Similarly, the lumped reaction kinetics mechanism has been included in order to characterize the mass fraction of the species after the HDO process to estimate the performance of the process. Some of the key findings include that Co-Mo/Al2O3 produces the major desired species of alkanes and aromatics, phenols are higher with the Ni-Mo/Al2O3 catalyst and gaseous streams are dominating with Pt/Al2O3 catalyst. It is also observed that the hydrodeoxygenation of unprocessed bio-oil in the presence of Co-Mo/Al2O3 catalyst yields higher amounts of alkane and aromatics. The amount of LNV is found to be significant during the HDO process of bio-oil compared to HNV in the presence of three catalysts. Finally, the yields of alkanes and aromatics varying with respect to the operating parameters in the presence of catalysts follows the order Co-Mo/Al2O3 > Pt/Al2O3 > Ni-Mo/Al2O3.
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    Characterization of Mineral-Based Colloidal Microbubble and Its Subsequent Application in Separation of Fine Mineral Particles
    (2022) Ruby, Kumari
    Ionic Microbubbles are miniature gas bubbles of less than 100 μm in diameter, which are surrounded by charged ions. Fine bubbles are used in many environmental and industrial processes for solid-liquid separations. They have been used for treatment techniques, removal of pulp fiber, separation of fine particles, protein recovery, deinking of waste water, etc. The important characteristics of microbubbles are their large specific area and small buoyancy; therefore, effective dissolution of gas-phase and high adsorption rate is expected. Microbubbles are the type of bubbles, which consists of gas inside their core, they are separated from each other, so they cannot agglomerate, having a size range of micrometers, usually 1-100 micrometer. There is a lack of research to explore the characteristics of microbubbles in the presence and absence of micro-nano particles and their efficiency in removing them. This work aimed to examine the stability of microbubbles generated with surface-active agents with and without particles. The drainage kinetic study was done for the microbubbles generated in the presence of particles with and without salt for assessing the stability of the microbubble. The effects of some primary parameters on entrainment of particles of ZnO, Al2O3, etc., in a flotation column using microbubbles for enunciating the feasibility of the microparticle separation by microbubble.
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    Clarification and Concentration of Sugarcane Juiceusing Membrane Process: Study on Fouling, Cleaning, Modelling and Process Simulation
    (2021) Akhtar, Aanisha
    Membrane technology is an ever-growing field as it has several advantages over other traditional processes. Typically, membrane processes such as Ultra filtration (UF) and Forward Osmosis (FO) have several functional applications including water treatment and food processing (clarification and concentration). Among the various processes in the sugar industry, clarification and concentration of sugarcane juice suffers from several technological limitations and is thus taken up as the area of this research work. During the sugarcane juice processing (clarification, concentration) and storage following technical limitations are observed: gel formation at high concentration, browning (enzymatic) of juice, loss of vitamins and the components responsible for the juice flavour, taste change due to the thermal and chemical pre-treatment. The conventional method of sugarcane juice processing involves the pre-treatment with lime, sulphur dioxide and heat treatment above 100°C. Considering the issues as mentioned above as well as scalability and process simplicity, membrane technology can be considered to be the most viable technology for the clarification and concentration of juice. In this research, the entire work carried out was divided into four major parts as given below, • Feasibility study of the clarification of sugarcane juice by LaPO4 coated ceramic UF membrane and its fouling and cleaning analysis. • Feasibility study of the concentration of sugarcane juice by Aquaporin HFFO membrane and corresponding bottlenecks to be addressed to implement same in the industrial scale. • Development of a batch FO process mathematical model for concentration of sugarcane juice by Aquaporin HFFO membrane and its validation. • Process simulation and performance optimization of Aquaporin HFFO membrane to minimize the SEC with maximum yield. As part of the first objective, the application of the LaPO4 ceramic membrane for the clarification of sugarcane juice was explored to avoid the use of lime and to produce chemical free sugarcane juice. The effect on the polyphenol oxidase (PPO) enzyme removal efficiency, bacteria removal efficiency, permeates flux decline profile, and membrane cleaning efficiency was evaluated. Again, the result of a long terms sugarcane juice storage study revealed that the UF clarified juice could be stored in refrigerated condition for seven weeks without significant change in the quality of the juice. Moreover, the importance of the inline physical cleaning and its operating mechanism is evaluated to understand the fouling and cleaning phenomena of the ceramic membrane. As part of the second objective, the performance of a commercially available Aquaporin HFFO membrane for the concentration of sugarcane juice by adopting an appropriate UF pre-treatment technique was studied. The effect of various process parameters such as DS flow rate, DS concentration and its direction of flow (co-current, counter-current) on water and reverse solute flux in batch mode was studied. In this study NaCl is used as a draw solute. The experimental results showed that counter-current flow configuration between FS and DS were able to provide 13% high water flux than co-current flow configuration. In the case of counter-current mode batch FO operation, sugarcane juice was concentrated to a maximum of 1.6 times of initial concentration in just 12 min by using an initial DS concentration (NaCl) of 100 gL-1 (with negligible RSF). The effect of UF clarified and raw sugarcane juice on FO membrane fouling was studied. The cleaning study concluded that the fouled membrane could be regenerated easily by DI water wash for 30 min for UF clarified juice. However, regeneration of membrane for the case of raw juice was not possible with DI water wash alone, and it required 0.1 M NaOH wash. Under the third objective, modeling, validation of the batch FO process was carried out. A mathematical model of the batch FO process was developed by integrating the FO membrane module, FS and DS storage tank. The model for the FO membrane module was developed by integrating mass, momentum and membrane mass transfer equations. The unknown model parameters of FO module were estimated by minimizing the error between FO batch experimental data and model output. The estimated parameters were used to predict the performance of the model using the remaining experimental data. The developed model was able to predict experimental output within an error of 5% for permeate flux and reverse solute flux. The estimated value of model parameters such as pure water permeability (A), solute permeability (B), structural parameter (S), αf and αd were found to match the reported values in the literature. As part of the fourth objective, in process simulation of the batch FO process, three case studies were carried out viz. case I: FS and DS both are recycled, case II: FS recycle and DS in continuous mode and case III: both FS and DS were in continuous mode. From these three cases of the simulation study, it was observed that case III was more effective in terms of concentration, reverse solute flux and specific power consumption. The SEC was 78.85 W L-1 for Case III (both feed and DS in continuous mode),which was the lowest among all three cases. Again, a simulation study was carried out for the two FO modules in a series system and compared with other DS flow rates to find the optimal DS flow rate. A 60:40 DS flow-rate ratio showed the best results in low SEC, low RSF, and high concentration. Overall, the obtained results will serve as a useful solution for future use of membrane technology in sugar industries.
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    CO2 -Selective Thin-Film Polymer Composite Membranes: Improvement of Thermal Stability and Role of Amine Carriers
    (2014) Mondal, Arjit
    The overall objective of this work is to develop a simple process to separate carbon dioxide (CO2) from a fossil fuel combustion gases using thin-film composite dense polymeric membrane containing amine carrier. Main focus of this project is to improve the membrane permeability along with high CO2/N2 selectivity at elevated temperature (> 100oC) against low pressure difference ( is around 1 atm) which is essentially close to the flue gas emitting condition from thermal power plant. Poly(vinyl alcohol) (PVA) was used as basic polymeric material due to its excellent hydrophilic nature and good film-forming ability. Thermal stability of PVA has been improved by crosslinking with formaldehyde (HCHO) and polymer blending with thermally stable polymer like polyvinylpyrrolidone (PVP). The optimum degree of crosslinking of PVA with formaldehyde was 60 mole%. The PVA/PVP weight percent ratio was chosen as 1:0.2. Different combinations of single and blended amines were introduced into the polymer hydrogel to enhance the CO2 transport property through the membrane. These amines were polyethyleneimine (PEI), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), poly(allylamine) (PAA) and 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD). The synthesized dry membranes were characterized with TGA, DSC, FTIR and XRD. All the characterizations were done for active layer only which was found to be optically transparent to visible light and mechanically stable to be handled.