Chemical Engineering

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To investigate suitable model for supercritical fluid extraction of carrot seed oil, different mathematical models are selected from literature and solved using COMSOL Multiphysics software. Operating parameters such as pressure, temperature, solvent flow rate, and addition of co-solvent are varied in ranges as 200–400 bar, 50–70 °C, 5–15 g/min, and 0–10 wt\%, respectively. Solvent and solid phase mass transfer coefficients, easily accessible oil content and equilibrium constant are considered as tuning parameters to fit the model with experimental data. Oil yield is increased with pressure (400 bar) and temperature (70 °C) whereas, its value is highest at the solvent flow rate of 10 g/min, and co-solvent of 5 wt\%. Thus, these values of parameters are considered as optimum points. © 2019 Elsevier Ltd

(SoE) School of Engineering

World University root node

Selection of suitable model for the supercritical fluid extraction of carrot seed oil: A parametric study

The effects of mesophilic anaerobic co-digestion (AcoD) of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) on enhancement of biogas production were investigated under different types of sludge combinations (primary sludge PS, waste-activated sludge WAS and mixed sludge MS), varying mixing ratios of OFMSW and MS (50:50, 70:30, 80:20, 90:10, v/v) and varying total solid TS concentrations (6, 9, 12, 15%). The co-digestion of OFMSW with MS resulted in the biogas yield of 138 mL/gVS over mono-digestion of OFMSW (39 mL/gVS). Co-digestion of OFMSW + PS and OFMSW + WAS yielded biogas of 107 and 129 mL/gVS, respectively, which is less than that of OFMSW + MS (138 mL/gVS), respectively. The co-digestion of OFMSW with MS showed a 2.5 times increase in biogas yield over OFMSW digestion alone and 23% and 7% higher biogas yield than OFMSW + PS and OFMSW + WAS, respectively. The highest biogas yield of 967 mL/g VS was observed at TS concentration of 9% and OFMSW to the MS mixing ratio of 80:20, respectively. The biogas yields at different TS percentages were modelled using Gompertz and Logistic models and fitted well. [Figure not available: see fulltext.] © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Biomass Conversion and Biorefinery

Optimization of process parameters for enhanced biogas yield from anaerobic co-digestion of OFMSW and bio-solids

Large amount of food waste is generated from Indian kitchens and disposing off such a large amount possesses a great challenge in terms of environmental degradation and viable food waste processing technology. In this work, steam gasification was tested as an alternative viable technology to process the kitchen food waste. Preliminary study was carried out at low temperature on steam gasification in a fixed bed reactor to study the influence of steam flow rate (SFR) and temperature on the syngas yield, syngas composition, hydrogen yield. Performance parameters such as carbon conversion efficiency (CCE), and apparent thermal efficiency (ATE) are also calculated. Steam flow rates are varied from 0.125 mL/min to 0.75 mL/min and the temperatures are varied from 700 °C to 800 °C. The highest hydrogen yield is obtained at 0.5 mL/min SFR and 800 °C temperature and its highest value is 1.2 m3/kg. The highest value of performance parameters, CCE and ATE are found to be 63\% and 1.8. © 2020 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Low temperature steam gasification to produce hydrogen rich gas from kitchen food waste: Influence of steam flow rate and temperature

This paper reports the novel synthesis of 5′-CMP molecule-mediated pH-responsive porous supramolecular hydrogels consisting of β-FeOOH/5′-CMP core-shell type nanohybrids as building blocks. The as-synthesized hydrogels have been fully characterized in terms of the size of the core and shape/morphology along with their optical, magnetic and rheological features. Interestingly, the gelation in the self-assembly is induced by the puckering of ribose sugar in the 5′-CMP molecule enhancing the intermolecular non-covalent interactions between 5′-CMP of different nanohybrids as well as β-FeOOH in a relatively narrow pH (5.5-7; 7-8.5) and temperature (35-40 °C) range. These changes have been analyzed by IR, Raman and CD spectroscopy. The viscoelastic nature of the optimized sample is revealed by fairly high values of viscosity (5.56 × 103 cP), G′ (4 × 104 Pa), G′′ (2.3 × 102 Pa) and yield strain (8.1%) with a linear viscoelastic region up to about 4%. A decrease in viscosity with shear rate demonstrates its gel like behavior matching with that of soft supramolecular hydrogels. The mechanism of gel formation has been thoroughly analyzed. pH, temperature and mechanical force induced spontaneous transition(s) of the sol into a hydrogel and its complete reversal into the sol suggest it to be a smart material. Thus, the soft hydrogels consisting of greener components such as a pyrimidine nucleotide (5′-CMP) and β-FeOOH phase, synthesized under physiological conditions of pH (7) and temperature (37 °C) with fairly high surface area, exhibited self-healing properties, injectability, relatively higher %swelling (530), and efficient loading (217 mg g-1) and release of adsorbed methylene blue (&gt;98%; model drug) over a period of more than 3 days in aqueous PBS buffer, suggesting them to be sustainable with significant potential in biological and environmental applications. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Fulltext

New Journal of Chemistry

Environmentally benign pH-responsive cytidine-5′-monophosphate molecule-mediated akaganeite (5′-CMP-β-FeOOH) soft supramolecular hydrogels induced by the puckering of ribose sugar with efficient loading/release capabilities

Drying a droplet containing microparticles results in the deposition of particles in various patterns, including the so-called "coffee-ring" pattern. The particle deposition is dependent on the internal flow dynamics, such as the capillary flow and Marangoni vortex (MV), of the droplet. Particle migration and self-assembly on a substrate are interesting phenomena that have critical implications in many applications such as inkjet printing, coating, and many other droplet-based industrial processes. In this work, we observed the formation of bands of particles in a rotating MV during the evaporation of a water droplet containing particles. We investigated the mechanism underlying the formation of banded MV caused by capillary meniscus forces between two particles near the air-liquid interface. In particular, we show that the banded MV can be manipulated by tuning the surfactant concentration and particle concentration. Our findings would provide a new direction in understanding the particle deposition pattern of a colloidal droplet. © 2019 American Chemical Society.

Langmuir

Dynamical Clustering and Band Formation of Particles in a Marangoni Vortexing Droplet

This study evaluated the change in physical and chemical properties of sun-dried food waste, during torrefaction in a fixed bed reactor. Torrefaction was carried out at different temperatures 230 °C, 260 °C, and 290 °C, for different residence times of 15, 30, 45, 60, 75, and 90 min in a fixed bed reactor. The solid torrefied products were analyzed by elemental analysis, proximate analysis, compositional analysis, and thermogravimetric analysis (TGA), and it was found that most suitable residence time for torrefaction was 60 min as torrefaction beyond 60 min did not yield much improvement in changing the properties of kitchen food waste. Carbon content increased from 46.0 to 58.5\%, consecutively increasing higher heating value (HHV) from 16.1 to 21.9\%. Compositional analysis demonstrated that there was not much hemicellulose left in the raw food waste after cooking; however, it had cellulose in significant proportion which went through decomposition during torrefaction. Lignin was not affected much. Various process parameters such as mass yield, energy yield, and energy density were also studied, and it was found the mass and energy yield decreased by 65.0\% and 47.5\%, respectively, and energy density increased by 35\%. Van Krevelen indicated clearly that torrefied char had achieved coal characteristics. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Evaluation of the physico-chemical development of kitchen food wastes through torrefaction - a biodiversity case study

This work was focused on finding the groundnut shell (GNS) gasification performance in a fluidized bed gasifier with bubbling air as gasification medium. GNS in powder form (a mixture of different particle size as given in table 8 in the article) was gasified using naturally available river sand as bed material, top of the bed feeding, conventional charcoal as bed heating medium, and two cyclones for proper cleaning and cooling the product gas. Experiments were performed using different operating conditions such as equivalence ratio (ER) between 0.29 and 0.33, bed temperature between 650°C and 800°C, and feedstock feeding rate between 36 and 31.7 kg/h. Different parameters were evaluated to study the gasifier performance such as gas yield, cold gas efficiency, carbon conversion efficiency (CCE), and high heating value. The most suitable ER value was found to be 0.31, giving the most stable bed temperature profile at 714.4°C with 5–10\% fluctuation. Cold gas efficiency and CCE at optimal ER of 0.31 was found to be 71.8\% and 91\%, respectively. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Environmental Technology (United Kingdom)

Groundnut shell gasification performance in a fluidized bed gasifier with bubbling air as gasification medium

The flow over a stepped spillway has complex nature, and its characteristics are remarkably different from other kinds of spillways. This study conducts experimental investigations and numerical simulations on the flow behavior (velocity, concentration profile) and macroscopic features (interface position and self-aeration) of water and neutrally buoyant suspension of non-colloidal particles in a stepped spillway with uniform steps. The development of nappe, transition, and skimming flow regimes is experimentally investigated by using a flow visualization technique. The inception point related to air entrainments is identified in the experimental study. The inception point usually moves downstream and increases the length of the non-aerated region with the increase of flow rate. Results of numerical and experimental studies indicate that a vortex is formed in the triangular cavity below the pseudo-bottom line (imaginary line joining two adjacent step edges) in the stepped channel. This vortex rotates in a clockwise direction for a short time period and returns to the main flow to move downward in the channel. The velocity vector map from numerical simulation predicts the maximum velocity in the middle portion of the spillway, that is, near the pseudo-bottom line. A volume of fluid model coupled with a standard k-ε turbulence model is used in the CFD simulations to predict the location of the air-water air-suspension interface. The results are compared with experimental measurements. The calculated interface position agrees well with the experimental measurements. The migration and transport of particles are evaluated based on a diffusive flux model of shear induced particle migration. The contour map for velocity and particle concentration shows a remarkable increase in particle concentration near the air-suspension interface. © 2019, KSME & Springer.

Journal of Mechanical Science and Technology

Experimental and computational study on flow over stepped spillway

The present work is focused on experimental investigations of gas-liquid flows in T-junction splitting distributor for parallel micro-channels. The tree type T-junction splitting distributor was designed with four successive T-junctions (T1, T2, T3 and T4) that are linked in series to split a single main channel into four parallel channels. The design strategy was adopted from Adamson et al. [1], Hoang et al. [2], and modified with a combination of micro and milli channel dimensions and reduction in width of the successive blocks by a factor of 20.5 to ensure the flow uniformity in terms of constant relative lengths (Lbubble/slug/Wchannel) of bubbles/slugs in all the blocks. Experiments were performed to study the effect of Qoil (=3, 6, 8, 10, 12 and 16 ml/min) at fixed Qair (=3 ml/min) on formation dynamics of bubbles/slugs at 1st T-junction and splitting mechanisms of bubbles/slugs at the successive T-junctions, the corresponding relative lengths of bubbles/slugs and flow regimes. The results obtained from the present work showed that, followed by formation of parent gas slug at T1 the splitting of gas slug occurred at the successive T-junctions (T2, T3 and T4). Three types of splitting mechanisms were observed such as obstructed (Qoil = 3, 6, 8, 10 ml/min; 0.0023 ⩽CaBlock-I ⩽0.0050), partially obstructed (Qoil = 12 ml/min; CaBlock-I = 0.00585) and non-obstructed (Qoil = 16 ml/min; CaBlock-I = 0.0074). It was observed that asymmetry of the splitting at the successive T-junctions was reduced for Qoil ⩾10 ml/min (CaBlock-I ⩾0.0050). No splitting of bubble was observed for Qoil &gt; 16 ml/min. However, it was also found that the proposed design strategy of splitting distributor for parallel micro-channels yields an almost constant relative lengths of bubbles/slugs (flow uniformity) in all the blocks for Qoil ⩾8 ml/min. © 2018 Elsevier B.V.

Chemical Engineering Journal

Experimental characterization of gas-liquid flows in splitting distributor for parallel micro-channels

Triboelectric nanogenerators (TENGs) harvest and convert mechanical energy to electrical energy. TENGs that are transparent and flexible can be applied to various (opto-)electronic devices supporting finger- or pen-based touchscreen inputs. This paper presents a transparent, flexible TENG that harvests mechanical tapping energy (typically discarded) by simple placement on touchscreen devices. The developed TENG consists of flexible and transparent conducting electrodes (FTCE) with high transmittance (> 93%) and low sheet resistance (18.5 Ω/sq), and transparent 3D-hierarchical polydimethylsiloxane (PDMS) with porous pyramid-patterns. In this study, the developed TENG directly powered eight light-emitting diodes (LEDs) by harvesting the mechanical energy produced by tapping with a touch pen while playing a smartphone game. We also used the transparent TENG as a transparent single-electrode-based, self-powered raindrop detection sensor on a window for a smart home. Our results indicate that the proposed TENG can be used not only as an effective mechanical energy harvester for transparent, flexible, and next-generation optoelectronics devices but also as a self-powered sensor for future Internet-of-Things applications. © 2018 Elsevier Ltd