Faculty Publications
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Item Stimulus response experiments are conducted in four different rectangular columns having two and three spout cells. A pink-coloured polymer material is used as bed material with ambient air as the spouting fluid. A pulse input of dark blue colour polymer material is used as the stimulus, when the column is operating under steady flow conditions, and the response measured. A mathematical model 'plug flow-mixed flow in series' is used to fit the experimental data and the model parameters are evaluated.(Can Soc for Chem Eng, Mixing behaviour of solids in multiple spouted beds) Saidutta, M.B.; Murthy, D.V.R.2000Item Continuous operation of fluidized bed bioreactor for biogenic sulfide oxidation using immobilized cells of Thiobacillus sp(Asian Network for Scientific Information, 2007) Ravichandra, P.; Mugeraya, G.; Anupoju, G.R.; Ramakrishna, M.; Jetty, A.In the present study, obligate autotrophic Thiobacillus sp. was isolated from aerobic sludge distillery effluent treatment plant and the experiments were conducted in a fluidized bed bioreactor for the biological oxidation of sulfide using Ca-alginate immobilized Thiobacillus sp. All the experiments were conducted in continuous mode at different sulfide loading rates 0.018, 0.02475, 0.03375, 0.03825 and 0.054 and different hydraulic retention times 5, 3.67, 2.67, 2.35 and 1.67 h by varying flow rates 2.4×10-4, 3.3×10-4, 4.5×10-4, 5.1 × 10-4 and 7.2×10-4. Sulfide conversions higher than 90% were obtained at almost all sulfide loading rates and hydraulic retention times. All the experiments were conducted at constant pH of around 6 and temperature of 30±5°C. © 2007 Asian Network for Scientific Information.Item Biological treatment of toxic petroleum spent caustic in fluidized bed bioreactor using immobilized cells of thiobacillus RAI01(2008) Potumarthi, R.; Mugeraya, G.; Jetty, A.In the present studies, newly isolated Thiobacillus sp was used for the treatment of synthetic spent sulfide caustic in a laboratory-scale fluidized bed bioreactor. The sulfide oxidation was tested using Ca-alginate immobilized Thiobacillus sp. Initially, response surface methodology was applied for the optimization of four parameters to check the sulfide oxidation efficiency in batch mode. Further, reactor was operated in continuous mode for 51 days at different sulfide loading rates and retention times to test the sulfide oxidation and sulfate and thiosulfate formation. Sulfide conversions in the range of 90-98% were obtained at almost all sulfide loading rates and hydraulic retention times. However, increased loading rates resulted in lower sulfide oxidation capacity. All the experiments were conducted at constant pH of around 6 and temperature of 30?±?5 °C. © 2008 Humana Press.Item Biological sulfide oxidation using autotrophic Thiobacillus sp.: Evaluation of different immobilization methods and bioreactors(2009) Ravichandra, P.; Gopal, M.; Jetty, A.Aims: Evaluation of various immobilization methods and bioreactors for sulfide oxidation using Thiobacillus sp. was studied. Methods and Results: Ca-alginate, K-carrageenan and agar gel matrices (entrapment) and polyurethane foam and granular activated carbon (adsorption) efficacy was tested for the sulfide oxidation and biomass leakage using immobilized Thiobacillus sp. Maximum sulfide oxidation of 96% was achieved with alginate matrix followed by K-carrageenan (88%). Different parameters viz. alginate concentration (1%, 2%, 3%, 4% and 5%), CaCl2 concentration (1%, 2%, 3%, 4% and 5%), bead diameter (1, 2, 3, 4 and 5 mm), and curing time (1, 3, 6, 12 and 18 h) were studied for optimal immobilization conditions. Repeated batch experiments were carried out to test reusability of Ca-alginate immobilized beads for sulfide oxidation in stirred tank reactor and fluidized bed reactor (FBR) at different sulfide concentrations. Conclusions: The results proved to be promising for sulfide oxidation using Ca-alginate gel matrix immobilized Thiobacillus sp. for better sulfide oxidation with less biomass leakage. Significance and Impact of the Study: Biological sulfide oxidation is gaining more importance because of its simple operation. Present investigations will help in successful design and operation of pilot and industrial level FBR for sulfide oxidation. © 2009 The Society for Applied Microbiology.Item Minimum superficial fluid velocity in a gas-solid swirled fluidized bed(2010) Harish Kumar, S.; Murthy, D.V.R.A swirl flow is achieved in a bed of solids by passing air through multiple fluid inlets, which are tangentially located at the base of a flat-based circular column. The minimum superficial velocities needed to achieve swirling of the bed are measured experimentally under varied conditions. An empirical correlation for the minimum swirl velocity has been proposed. The results indicate that a stable swirling regime operation of the bed is possible. There exists an upper limit of static bed depth beyond which stable swirling of entire bed is not possible. The minimum swirl velocities are found to be 1.2-1.3 times the minimum fluidization velocities predicted for conventional fluidized beds. © 2010 Elsevier B.V.Item Modified PGC model and its validation by experiments for heat and moisture transfer analysis in a vertical fluidized desiccant bed(Elsevier Ltd, 2015) Ramzy K, A.; Kadoli, R.Air dehumidification in fluidized beds utilizing desiccants is an alternative for the refrigeration methods. A variety of pseudo gas controlled (PGC) model are proposed by assuming constant and varying temperature as well as water content for the solid phase to evaluate the conditions of exit air during adsorption processes. Experimental tests for moisture adsorption in silica gel fluidized bed are carried out. The modified PGC model that assumes uniform water content, varying temperature and linear porosity distributions along the bed estimates the temporal average bed water content to agree very well with the experimental data. The RMSE of the numerical results of the present model ranges from 0.2 to 6% and that obtained from the isothermal model are in the range of 6%-68%. © 2015 Elsevier Ltd. All rights reserved.Item Solar light mediated photocatalytic degradation of phenol using Ag core - TiO2 shell (Ag@TiO2) nanoparticles in batch and fluidized bed reactor(Elsevier Ltd, 2016) Shet, A.; Shetty K, K.V.Ag@TiO2 nanoparticles were synthesised using one pot method followed by calcination at 450 °C for 3 h and were tested for their photocatalytic efficacy in degradation of phenol both in free and immobilized form under solar light irradiation through batch experiments. Ag@TiO2 nanoparticles were found to be effective in solar photocatalytic degradation of phenol. The effect of factors such as pH, initial phenol concentration and catalyst loading on phenol degradation were evaluated and these factors were found to influence the process efficiency. The optimum values of these factors were determined to maximize the phenol degradation. The efficacy of nanoparticles immobilized on cellulose acetate film was inferior to that of free nanoparticles in solar photocatalysis due to light penetration problem and diffusional limitations. The performance of fluidized bed photocatalytic reactor operated under batch with recycle mode for solar photocatalysis of phenol with immobilized Ag@TiO2 nanoparticles was evaluated for large scale application. The performance was found to be dependent on catalyst loading and the optimum is governed by active catalyst sites and light penetration limitations. The photocatalytic degradation of phenol by Ag@TiO2 nanoparticles was only marginally influenced by the presence of small traces of chloride ions. Ag@TiO2 showed a better efficacy as solar photocatalyst than as UV photocatalyst in degradation of phenol. Solar light irradiation is recommended because solar energy, a readily available form of energy can be effectively harnessed for energy efficient, environment friendly and cost effective process. The kinetics of degradation of phenol was found to follow the nth order kinetics with order, n = 2.19 for solar photocatalysis. © 2016 Elsevier Ltd.Item Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion(American Chemical Society service@acs.org, 2018) Pragadeesh, K.S.; Ruben Sudhakar, D.R.Devolatilization and fragmentation are important physical phenomena occurring during solid fuel chemical looping combustion (CLC). Primary fragmentation during devolatilization strongly affects the rate of fuel conversion, emissions, and fine particulates generation in a fuel reactor of a fluidized bed CLC unit, thus forming a critical design input. The present study focuses on investigating the primary fragmentation behavior of large coal and biomass (wood) particles during the devolatilization phase of CLC. Three types of coals (two Indian coals, one Indonesian coal) and one type of Casuarina wood of three sizes in the range of 8-25 mm, at different fuel reactor bed temperatures (800, 875, and 950 °C) are studied for primary fragmentation. Iron ore with 64% Fe is used as the oxygen carrier bed material, with steam as the fluidizing medium in the fuel reactor. The fragmentation behavior is expressed in terms of the number of fragments, fragmentation index, frequency of fragmentation, and particle size distribution of fragments at different residence times of coal during devolatilization in the fuel reactor. Under the conditions of study, the number of fragments increases with an increase in particle size and temperature, for all fuels studied. Also, it is found that the number of fragments increases with the decrease in compressive strength of both coal and biomass particles. The Indian coals are found to fragment in the earlier stages of devolatilization, while the Indonesian coal and the biomass particles begin to fragment in the later stages of devolatilization. The maximum fragmentation index is found with Indian coal - IC1, which has the highest fixed carbon content among the fuels studied, and the least value is observed in biomass. Different modes of fragmentation exhibited by each fuel type is discussed. Indian coals do not show any volumetric changes as such, whereas Indonesian coal indicates some degree of volumetric expansion. © 2018 American Chemical Society.Item Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion(American Chemical Society service@acs.org, 2019) Pragadeesh, K.S.; Ruben Sudhakar, D.R.Chemical looping combustion (CLC) is one of the promising fuel conversion technologies for carbon capture with low energy penalty. Devolatilization is an important physical phenomenon occurring during solid fuel CLC. Devolatilization behavior influences fragmentation, combustion rate, emission, and particulates generation in fluidized bed CLC (FB-CLC), thus a critical input for its design. Existing visual techniques for determining devolatilization time cannot be applied in CLC conditions because of its flameless combustion nature. In the present study, a new, simple, and quick technique called "color indistinction method" (CIM) is proposed for the determination of devolatilization time (?d) in FB-CLC, where the end of devolatilization is inferred from the disappearance of fuel particle in a hot fluidized bed. Single-particle devolatilization studies in FB-CLC are conducted to determine the devolatilization time using CIM for two types of fuels, viz., coal and biomass (Casuarina equisetifolia wood), of size range 8-25 and 10-20 mm, respectively, at three different fuel reactor bed temperatures (800, 875, and 950 °C) and one fluidization velocity. The proposed technique is validated in three ways: (i) the measurement of residual volatiles present in char by thermogravimetric analysis; (ii) mass loss history of the fuel during devolatilization; and (iii) diagnostics using particle center temperature measurements. The results of CIM experiments, in terms of degree of error involved, are compared with an established flame extinction technique (FET) and a more accurate particle center temperature (PCT) method. The amount of volatiles released during devolatilization, as determined by CIM, is 91.3% for coal and 98.9% for biomass. These values compare very well with the results of the established FET, in which the volatile release is 90.7% for coal and 99.1% for biomass samples. The devolatilization times determined using CIM are in line with particle center temperature measurements with an acceptable error range of -7.57 to +3.70%. The proposed CIM is successful in establishing the devolatilization time of different fuels in CLC conditions and can also be applied in other flameless combustion conditions. © 2019 American Chemical Society.Item Study of devolatilization during chemical looping combustion of large coal and biomass particles(Elsevier B.V., 2020) Pragadeesh, K.S.; Iyyaswami, I.; Ruben Sudhakar, D.R.Chemical Looping Combustion (CLC) is one of the emerging technologies for carbon capture, with less energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC have limitations like loss of unconverted char and gaseous combustibles, which could be mitigated by use of coarser fuel particles. Devolatilization time is a critical input for the effective design of FB-CLC systems, primarily when large fuel particles are used. The present study investigates the devolatilization time and the char yield of three coals of two shapes, namely, two high ash Indian coals and a low ash Indonesian coal and a wood (Casuarina equisetifolia) in the size range of +8–25 mm, at different fuel reactor temperatures (800–950 °C) of a hematite based CLC unit. The devolatilization times of single fuel particles during CLC are determined using a visual method called ‘Color Indistinction Method’. Indonesian coal has the longest devolatilization time among the fuels, and biomass has the least. Increasing the bed temperature enhances the rate of volatile release, whereas this effect is less pronounced in larger particles. Devolatilization of Indonesian coal is found to be strongly influenced by the changes in operating conditions. With the decrease in sphericity, a maximum of 56% reduction in devolatilization time is observed for the +20–25 mm slender particles of Indonesian coals when compared to the near-round particles. The maximum average char yields at the end of the devolatilization phase for coal and biomass are about 55–76% and 16% respectively. Char yield in coal particles increases with an increase in particle size, whereas biomass particles show relatively consistent yield across all experimental conditions. Increase in bed temperature reduces the char yields of coal up to 12% and in biomass up to 30%. High volatile Indian coal is the most influenced fuel by the changes in fuels shape. A correlation for determining devolatilization time under CLC environment is presented, and it successfully fits most of the experimental values within ±20% deviation for coals (R2 = 0.95) and within ±15% deviation for biomass (R2 = 0.97). © 2020 Energy Institute