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Silica Nanoparticles (SiNPs), due to its tunable properties and composition, meets the needs in specified applications. Rice Husk (RH), an agricultural waste, abundant in amorphous silica has its extensive application in various industrial products. However, the presence of impurities in RHs makes the extraction process difficult and optimum experimental conditions are needed to achieve maximum yield with specific properties for its specified applications. In this work, Rice Husk Ash (RHA) is prepared from RH by acid leaching followed by silica gel extraction from RHA via controlled pyrolysis at three temperatures (700°C, 750°C and 800°C). Pyrolyzed RHA is then dried and pulverized to get SiNPs. Characterization of SiNPs is done using UV-Vis Spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). UV-Vis Spectroscopy and XRD analysis shows that the SiNPs extracted from RHA at 750°C exhibited the highest peak at 260 nm and 2θ=26° respectively and XRD and SEM analysis show that crystallite and particle size is in close agreement with each other. The optimum temperature being 750°C, silica gel formed at a pH 6 is more stable, transparent and thicker in comparison to the silica gel formed at varied pH. Moreover, the sodium silicate sample exhibits a bright green fluorescence and the intensity of fluorescence is higher for the sodium silicate prepared at 750°C range than at any other temperature. © 2020 Scientific Publishers. All rights reserved.

World University root node

Chemical Engineering

(SoE) School of Engineering

Journal of Scientific and Industrial Research

Extraction of silica nanoparticles from Rice Husk Ash and its characterization

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 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

Three-phase segmented gas-liquid-liquid (G/L/L) flows in minichannels are important to several chemical process applications involving gas-liquid-liquid reactions. In the present work, we have investigated segmented G/L/L flows in a double T-junction minichannel, with cross-section of 0.95 mm × 1 mm, through high-speed imaging experiments and Volume-of-Fluid (VOF) simulations. The dynamics of bubble/slug formation at the 1st T-junction and importantly that of water drop/slug formation at the 2nd T-junction was simulated under different flow conditions (Caoil=2.63×10-3-1.101; Weair=4.24×10-4-2.62×10-3; Wewater=0.0431-7.14) and different surfactant concentrations (0.3 and 2 wt/wt.\%) in aqueous phase. The predicted formation mechanisms, three-phase flow regimes, and drop/bubble/slug lengths were compared quantitatively with the measurements. Different mechanisms of bubble/slug formation observed for the aforementioned range of the Caoil and Weair, and bubble/slug lengths were predicted in a satisfactory agreement with the measurements. The complex formation mechanism of water drops/slugs that was governed by viscous force exerted by continuous oil phase, inertial force exerted by water phase, interfacial tension force acting on the oil-water interface and also by incoming air bubbles/slugs; could be predicted in a satisfactory agreement with those observed in the experiments. Different three-phase flow regimes, e.g., drop-bubble, drop-slug and slug-slug, observed for different oil, air and water flow rates; and for different values of oil-water interfacial tensions are also predicted in satisfactory agreement with the measurements. The results reported in the present work help to understand the hydrodynamics of complex three-phase gas-liquid-liquid flows in minichannels, which in turn is crucial to device microreactor systems for process applications involving G/L/L flows. © 2018 Elsevier B.V.

Volume-of-fluid simulations of gas-liquid-liquid flows in minichannels

In recent years, biodiesel, as a renewable and environment-friendly fuel has emerged as one of the most investigated bio-fuel with a goal to decrease our dependence on petroleum fuels and reduce environmental pollution. The current commercial technique of biodiesel production via transesterification is constrained by high operating cost and energy requirements, long residence time and limited conversion due to equilibrium limitations. On the other hand, the process intensification using the micro-reactor technology demonstrated an excellent performance ascribed to short diffusion distance and high surface area-to-volume ratio that can lead to high heat and mass transfer rates and improved mixing compared to the conventional reactors. This review provides an overview of the current status of biodiesel production in micro-reactors. It includes various types of micro-reactors used in the production of biodiesel, factors affecting the biodiesel production (i.e., temperature, residence time, alcohol to oil molar ratio, micro-channel size, inlet mixer type, internal geometries, co-solvent, catalyst type and concentration). This review also includes the factors affecting the liquid-liquid flow patterns and application of micro-reactor technology in the purification of biodiesel. Some of the critical observations from this review are, 1) inlet mixer type, channel size, and internal channel geometry (zig-zag, omega, and tesla shaped channels) have shown a significant effect on mixing in micro-channels. 2) In case of base-catalyzed transesterification, the biodiesel yield was found to increase up to the reaction temperature of 60–65 °C. 3) Homogeneous alkaline catalyst (NaOH, KOH, CH3ONa) was preferred for the feedstock with low free fatty acid content (&lt;1 wt\%). However, an acid catalyst with high concentration, a significant amount of methanol and long reaction time were required for high free fatty acid feedstock (&gt;1 wt\%). Therefore, the current research is more focused on the investigation of heterogeneous catalysts in micro-reactors to develop an ecologically friendly process for the production of biodiesel. 4) Also, the reaction temperature and inlet mixer type had shown a significant effect on liquid-liquid flow patterns. This review also addressed the following literature gaps; a numbering-up technique to increase the throughput; catalyst development for high free fatty acid feedstock; continuous production of biodiesel in micro-reactors with in-line purification step to meet the energy demand and quality standards. © 2018 International Energy Initiative

Energy for Sustainable Development

Biodiesel production in micro-reactors: A review

Micro. -reaction/reactor technology has been used to intensify several chemical processes involving gas-liquid and liquid-liquid reactions. However, potential of intensifying gas-liquid-liquid reactions still remains unexplored. In the present work, we report experimental investigations of gas-liquid-liquid three-phase flows in microchannels. High-speed imaging experiments were performed to identify and to map flow regimes; to understand the effect of flow rates of continuous (kerosene) and dispersed phases (air and water) on the flow regimes, formation mechanisms of air bubbles/slugs and water drops/slugs and also to measure the slug lengths. In particular, the effects of different gas and liquid distributors and addition of surfactant were investigated to understand controlled generation of bubbles and drops and formation of different flow regimes in microchannels. The results presented in this manuscript will be important to device microreactor systems for catalytic reactions involving gas-liquid-liquid flows. © 2012 Elsevier B.V.