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Md Azharul Islam - One of the best experts on this subject based on the ideXlab platform.

  • A thermogravimetric analysis of the Combustion Kinetics of karanja (Pongamia pinnata) fruit hulls char
    Bioresource Technology, 2016
    Co-Authors: Md Azharul Islam, M. Auta, G. Kabir, Bassim H. Hameed
    Abstract:

    The Combustion characteristics of Karanj fruit hulls char (KFH-char) was investigated with thermogravimetry analysis (TGA). The TGA outlined the char Combustion thermographs at a different heating rate and isoconversional methods expressed the Combustion Kinetics. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods authenticated the char average activation energy at 62.13 and 68.53. kJ/mol respectively, enough to derive the char to burnout. However, the Coats-Redfern method verified the char Combustion via complex multi-step mechanism; the second stage mechanism has 135. kJ/mol average activation energy. The TGA thermographs and kinetic parameters revealed the adequacy of the KFH-char as fuel substrate than its precursor, Karanj fruit hulls (KFH).

  • Combustion Kinetics of hydrochar produced from hydrothermal carbonisation of karanj pongamia pinnata fruit hulls via thermogravimetric analysis
    Bioresource Technology, 2015
    Co-Authors: G. Kabir, Md Azharul Islam, Mohammad Asif, Bilal Hameed
    Abstract:

    Abstract This study examined the Combustion profile and Kinetics of hydrochar produced from hydrothermal carbonisation (HTC) of Karanj fruit hulls (KFH). The HTC-KFH hydrochar Combustion Kinetics was investigated at 5, 10, and 20 °C/min by thermogravimetric analysis. The Kinetics model, Kissinger–Akahira–Sunose revealed the Combustion Kinetics parameters for the extent of conversion from 0.1 to 0.8; the activation energy varies from 114 to 67 kJ/mol respectively. The hydrochar Combustion followed multi-steps Kinetics; the Coats–Redfern models predicted the activation energies and pre-exponential constants for the hydrochar Combustion zones. The diffusion models are the effective mechanism in the second and third zone.

Christopher R. Shaddix - One of the best experts on this subject based on the ideXlab platform.

  • the effect of bulk gas diffusivity on apparent pulverized coal char Combustion Kinetics
    Proceedings of the Combustion Institute, 2019
    Co-Authors: Christopher R. Shaddix, Cristina Gonzalotirado, Ethan S Hecht, Brian S Haynes
    Abstract:

    Abstract Apparent char kinetic rates are commonly used to predict pulverized coal char burning rates. These kinetic rates quantify the char burning rate based on the temperature of the particle and the oxygen concentration at the external particle surface, inherently neglecting the impact of variations in the internal diffusion rate and penetration of oxygen. To investigate the impact of bulk gas diffusivity on these phenomena during Zone II burning conditions, experimental measurements were performed of char particle Combustion temperature and burnout for a subbituminous coal burning in an optical entrained flow reactor with helium and nitrogen diluents. The combination of much higher thermal conductivity and mass diffusivity in the helium environments resulted in cooler char Combustion temperatures than in equivalent N2 environments. Measured char burnout was similar in the two environments for a given bulk oxygen concentration but was approximately 60% higher in helium environments for a given char Combustion temperature. To augment the experimental measurements, detailed particle simulations of the experimental conditions were conducted with the SKIPPY code. These simulations also showed a 60% higher burning rate in the helium environments for a given char particle Combustion temperature. To differentiate the effect of enhanced diffusion through the external boundary layer from the effect of enhanced diffusion through the particle, additional SKIPPY simulations were conducted under selected conditions in N2 and He environments for which the temperature and concentrations of reactants (oxygen and steam) were identical on the external char surface. Under these conditions, which yield matching apparent char burning rates, the computed char burning rate for He was 50% larger, demonstrating the potential for significant errors with the apparent Kinetics approach. However, for specific application to oxy-fuel Combustion in CO2 environments, these results suggest the error to be as low as 3% when applying apparent char burning rates from nitrogen environments.

  • determination of char Combustion Kinetics parameters comparison of point detector and imaging based particle sizing pyrometry
    Review of Scientific Instruments, 2014
    Co-Authors: Martin Schiemann, Manfred Geier, Nikita Vorobiev, Christopher R. Shaddix, Viktor Scherer
    Abstract:

    In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption Kinetics. The performance of the specialized systems is compared for two different Combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles’ burnout. The results confirm that comparable results are obtained with the two configurations, although higher lev...

  • Determination of char Combustion Kinetics parameters: Comparison of point detector and imaging-based particle-sizing pyrometry
    Review of Scientific Instruments, 2014
    Co-Authors: Matthias Schiemann, Manfred Geier, Nikita Vorobiev, Christopher R. Shaddix, Viktor Scherer
    Abstract:

    In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption Kinetics. The performance of the specialized systems is compared for two different Combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles’ burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in Kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning Kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%–30% are recommended for kinetic rate measurements on 100 μm particles.

  • Combustion Kinetics of coal chars in oxygen enriched environments
    Combustion and Flame, 2006
    Co-Authors: Jeffrey J Murphy, Christopher R. Shaddix
    Abstract:

    Oxygen-enhanced and oxygen-fired pulverized coal Combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char Combustion under these unconventional Combustion conditions. In the work reported here, the Combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A Combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320–1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir–Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for Combustion in oxygen-depleted environments.

Edward J. Anthony - One of the best experts on this subject based on the ideXlab platform.

  • investigation of the apparent Kinetics of air and oxy fuel biomass Combustion in a spouted fluidised bed reactor
    Chemical Engineering Research & Design, 2020
    Co-Authors: Peter T Clough, Edward J. Anthony
    Abstract:

    Abstract A bench-scale spouted fluidised-bed reactor was used to investigate the Combustion Kinetics of pulverised woody biomass under air and oxy-fuel atmospheres. Bed temperatures were in the range of 923−1073 K and O2 concentrations were varied from 20−35 vol%. The activation energies and apparent orders of reaction were calculated for air and oxy-fuel Combustion by means of an nth order Arrhenius equation approach. Results indicated that the apparent order of reaction for both air and oxy-fuel Combustion was approximately zero. The activation energies were calculated assuming a zero-order reaction mechanism and were averaged over all oxygen concentrations for air and oxy-fuel Combustion and found to be 18.95 kJ/mol and 26.93 kJ/mol, respectively. The rate of Combustion under oxy-fuel conditions was, on average, 37.5% higher compared to air Combustion. The shrinking core model with a reaction-controlled step was found to accurately represent the biomass Combustion reactions under both air and oxy-fuel conditions.

Zhanjun Cheng - One of the best experts on this subject based on the ideXlab platform.

Matthew A Oehlschlaeger - One of the best experts on this subject based on the ideXlab platform.

  • an experimentally validated surrogate fuel for the Combustion Kinetics of s 8 a synthetic paraffinic jet aviation fuel
    50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2012
    Co-Authors: Stephen Dooley, Frederick L Dryer, Sang Hee Won, Saeed Jahangirian, Haowei Wang, Matthew A Oehlschlaeger
    Abstract:

    A surrogate fuel designed to emulate the gas phase chemical kinetic Combustion phenomena of this target S-8 fuel is formulated in an a priori manner. The surrogate fuel is composed of n-dodecane/iso-octane and its performance is evaluated by the measurement of the same Combustion phenomena as the target fuel under identical conditions. The performance of available kinetic models for S-8 surrogates is evaluated by analysis of their computations of this experimental data. Furthermore, an experimental study evaluating the significance of weakly isomerized alkanes as important components for surrogate fuels is presented.

  • the Combustion Kinetics of a synthetic paraffinic jet aviation fuel and a fundamentally formulated experimentally validated surrogate fuel
    Combustion and Flame, 2012
    Co-Authors: Stephen Dooley, Frederick L Dryer, Sang Hee Won, Saeed Jahangirian, Haowei Wang, Matthew A Oehlschlaeger
    Abstract:

    Abstract A surrogate fuel is formulated in an a priori manner through a Combustion property matching technique to emulate the gas phase chemical kinetic Combustion phenomena of S-8 POSF 4734, an alternative aviation fuel derived from natural gas via the Fischer–Tropsch process. A fundamental concept is described which identifies n-dodecane and iso-octane as being appropriate surrogate fuel components for the non-aromatic synthetic fuels. The performance of the formulated 51.9/48.1 mole % n-dodecane/iso-octane mixture as a surrogate for the target real fuel is evaluated by the measurement of a series of Combustion phenomena exhibited by both fuels including: (1) The oxidative reactivity of stoichiometric mixtures of each fuel in O2/N2 at 12.5 atm and 500–1050 K, for a residence time of 1.8 s at a fixed carbon content of 0.3% using a variable pressure flow reactor. (2) The autoignition behavior of stoichiometric mixtures of each fuel in air at compressed conditions of 667–1223 K and ∼20 atm by the reflected shock technique. (3) The strained extinction limits of diffusion flames of each fuel at 1 atm. The performance of available kinetic models for n-dodecane/iso-octane mixtures is evaluated by analysis of their computations of this experimental data. Furthermore, the impact of oxidation Kinetics unique to the mono methylated alkanes which are the dominant molecular structure in synthetic fuels is examined by an experimental study involving the formulation of an n-decane/iso-octane mixture as a surrogate fuel for 2-methyl heptane, a proposed model molecule for such real fuel components.