Faculty Publications
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Item Equilibrium and kinetic study for the removal of malachite green using activated carbon prepared from Borassus flabellofer male flower(2010) JagadeeshBabu, P.E.; Kumar, V.; Visvanathan, R.Activated carbon was prepared from dried Borassus flabellofer male flower and batch adsorption experiments were conducted to study its potential to remove malachite green (MG) dye. The process was further optimized by studying the operating variables like initial pH of the stock solution, activation temperature, initial dye concentration, adsorbent loading and contact time. The optimized pH and activation temperatures were found to be 7.55 and 450.C respectively, where further analysis was made using these optimal variables. Linear, Freundlich and Langmuir isotherms were studied and it was found that the Langmuir isotherms have the highest correlation coefficients compared to the others. Further, the sorption kinetics were analysed using pseudo-first-order and pseudo-second-order kinetic models. The data showed that the second-order equation was the more appropriate, which indicate that the intra-particle diffusion is the rate limiting factor. © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.Item Extruded poly(ethylene-co-octene)/fly ash composites - Value added products from an environmental pollutant(Kluwer Academic Publishers, 2012) Anandhan, S.; Sundar, S.M.; Senthil, T.; Mahendran, A.R.; Shibulal, G.S.Fly ash (FA) is a by-product generated during combustion of coal and has caused serious environmental concerns. In an effort to utilize FA beneficially, we developed composites from an ethylene-octene random copolymer (EOC) and unmodified as well as surfacemodified class-F fly ash (MFA) by twin screw extrusion. Addition of 20 wt% of MFA to EOC improves its tensile strength by 150%; also, MFA improves stress at 100% and 300% strains (M100 and M300) of EOC. Thermal stability of EOC matrix is appreciably improved by the addition of either FA or MFA, while the melting behavior is not appreciably influenced by either. Fractography study reveals an improved adhesion between the EOC and MFA particles up to a filler loading of 20%, beyond which the adhesion between EOC and MFA is weakened causing a reduction in mechanical properties. The 'flammable' nature of EOC changes to 'self extinguishing' on addition of even 10 wt% of FA or MFA, as found out from LOI study. © Springer Science+Business Media B.V. 2012.Item Reduction of carbon emission by enhancing energy efficiency of forced draft fans in thermal power plants(Acta Press journals@actapress.com, 2014) Mandi, R.P.; Yaragatti, R.Y.In this paper, various techno-economical feasible methods for reducing the carbon emission by enhancing the energy efficiency of forced draft (FD) fans in coal-fired thermal power plants based on the energy audit study conducted in 28 numbers of 210MW power plants in India are discussed. The best operating points for pressure gain, flow, pressure drop, equipment efficiency, power input and specific energy consumption are simulated by using MATLAB, and presented in this paper with case study to validate the results. Optimizing the pressure at FD fan discharge and maintaining the optimum secondary air pressure at windbox will enhance the combustion characteristics. Operational optimization and control of excess air will reduce the auxiliary power of FD fans. Optimum sizing of FD fans and motors will reduce the auxiliary power by 0.10% gross energy generation and reduce the CO2 emission by 1,600 t/year.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 InstituteItem Insitu gasification – chemical looping combustion of large coal and biomass particles: Char conversion and comminution(Elsevier Ltd, 2021) Pragadeesh, K.S.; Iyyaswami, I.; Ruben Sudhakar, D.Utilization of large solid fuel particles in fluidized bed – Chemical Looping Combustion (CLC) has the benefits of reduced energy penalty related to carbon capture. When large fuel particles (mm-sized) are used, comminution plays a vital role in the fuel conversion rate, characteristics of ash, inventory loading and thus in the effective design of CLC systems. The present work deals with the conversion of char of large fuel particles and char fragmentation phenomenon in the insitu-gasification CLC environment. Three different coals and a woody biomass in the size range of + 8–25 mm are tested at three different bed temperatures (800 to 950 °C) in a hematite-based batch CLC unit, using steam as the fluidizing/gasification agent. The char conversion time is found to increase by 60 to 170% when particle size changes from 8 to 25 mm and reduced by 42 to 86% with the increase in bed temperature. Regardless of fuel type and feed size, the inception of char fragmentation is noticed in the very first quarter of conversion indicating its significant influence on the char burnout time. 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 char conversion time and fragmentation phenomena. This study recommends the use of large particles of all fuels up to 25 mm in CLC systems without any prior size reduction, except the high-ash coals. © 2021 Elsevier LtdItem Numerical and Experimental Investigation of Thermal Barrier Effects of CNT-Reinforced Fly Ash/Alumina Coatings in Diesel Engine Pistons(American Chemical Society, 2025) Chavana, N.; Sarkar, B.; Jambagi, S.C.Fly ash (FA), an industrial byproduct from coal combustion, presents significant disposal challenges, especially in developing nations. Given its mineralogical properties, FA shows potential in thermal spray coatings. This study evaluates FA-based coatings for pistons to improve thermal management in internal combustion engines through numerical simulations, analyzing their effects on the temperature distribution, thermal stress, and combustion efficiency. FA coatings were also applied to marine-grade steel with additives (50 wt % Al2O3 and 0-2 wt % CNT) to assess high-temperature performance. Microstructural analysis revealed that 2 wt % CNT-reinforced (2CAF) coatings showed agglomeration, reducing microhardness by ?9.27% compared to 1 wt % CNT-reinforced (1CAF) coatings. The XRD analysis of 1CAF indicated ?56.51% transformation of corundum to ?-alumina, lowering thermal conductivity by ?15.40% compared to alumina/FA (AF) coatings, while 2CAF coatings showed increased conductivity due to CNT inhomogeneity. For piston applications, simulations showed an ?24.59% rise in maximum surface temperature, from 241.39 to 300.76 °C, and an ?62.06% reduction in heat flux, indicating enhanced durability and reduced cold-start emissions. Thermal cycling demonstrated that 1CAF coatings outlasted AF and 2CAF, suggesting FA-based TBCs as sustainable and economical options for enhanced engine performance and waste valorization. © 2025 American Chemical Society.Item Impact of sulfate supplement on bioleaching of iron from fly ash residue using isolated Acidithiobacillus ferrooxidans strain: A Box-Behnken process optimisation(Korean Society of Environmental Engineers, 2025) Bhaskar, S.; Apoorva, K.V.; Ashraf, S.; Shruthi, R.; Manoj, A.Fly ash, a residue from coal combustion contains significant iron content (10-40%), has potential applications in various fields. Present study investigated the impact of sulfate on bioleaching of iron from fly ash, using a novel Acidithiobacillus ferrooxidans strain. Iron dissolution obtained was 95.5 mg/L with 100 rpm shake flask speed, 3% pulp density, pH 3.0, and 5.5 g/L sulphate supplement, compared to 74.5 mg/L without sulphate over 15 days. The study employed Box-Behnken design for Design of Experiments. Variables ranged from 50 rpm – 150 rpm for shake flask speed, 2.5 – 3.5 for pH, 1% – 5% for pulp density, and 1.0 g/L – 10 g/L for sulfate concentration. In the experiment with sulfate supplement, the concentration of sulfate was treated as a variable parameter, as opposed to the pulp density, while taking into account other relevant characteristics. Iron dissolution was taken as a response. Pulp density and sulfate concentration significantly affected iron dissolution. A quadratic regression model was fit and an ANOVA was performed. According to the model, sulfate concentration has a positive linear influence with sulfate supplement, while for no sulfate supplement, shake flask speed and pulp density have a positive effect on the bioleaching of iron from fly ash. © 2025 Korean Society of Environmental Engineers.