The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Hermann Hofbauer - One of the best experts on this subject based on the ideXlab platform.
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Apparent Kinetics of the water gas shift reaction in biomass gasification using ash layered olivine as catalyst
Chemical Engineering Journal, 2018Co-Authors: J Kryca, Juraj Priscak, Joanna łojewska, Matthias Kuba, Hermann HofbauerAbstract:Abstract Substitution of fossil fuels for production of electricity, heat, fuels for transportation and chemicals can be realized using biomass steam gasification in a dual fluidized bed (DFB). Interaction between biomass ash and bed material in a fluidized bed leads to transformation of the bed particle due to enrichment of components from the biomass ash resulting in the development of ash layers on the bed particle surface. These ash-rich particle layers enhance the catalytic activity of the bed material regarding the water-gas-shift reaction and the reduction of tars. The water-gas-shift reaction at conditions typical for dual fluidized bed biomass gasification at a temperature of 870 °C was investigated. Diffusion and heat transfer limitations were minimized using a lab-scale experimental set-up consisting of a gas mixing section and a quartz glass reactor in which the catalyst is investigated. The following new rate expression for the water-gas-shift reaction in dual fluidized bed gasification of biomass was empirically developed, which takes ash layer formation into account: r Olivine _ ash - layer = 8 , 9 · 10 - 6 exp - 95000 RT p CO 1 , 96 p H 2 O 1 , 81 p CO 2 - 0 , 75 p H 2 - 1 , 69
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Apparent Kinetics of the catalyzed water gas shift reaction in synthetic wood gas
Chemical Engineering Journal, 2016Co-Authors: A Plaza, S Fail, J A Cortes, Karin Fottinger, N Diaz, Reinhard Rauch, Hermann HofbauerAbstract:Abstract The catalysis of the water–gas shift reaction employing two commercially available catalysts was investigated. The applied feed was a synthetic gas mixture simulating the wood gas derived from the dual fluidized bed steam gasification of biomass. A Co/Mo- and an Fe/Cr-based catalyst were compared in a differentially operated plug flow reactor. The influence of the partial pressures of all reaction partners as well as the effect of temperature were studied, allowing the formation of two power law rate models. (1) r ( Co / Mo ) = 0.044 exp - 66 R T p CO 1.28 p H 2 O 0.03 p CO 2 - 0.11 p H 2 - 0.35 1 - 1 K p CO 2 p H 2 p CO p H 2 O (2) r ( Fe / Cr ) = 300 exp - 102 R T p CO 1.37 p H 2 O 0.23 p CO 2 - 0.16 p H 2 - 0.11 1 - 1 K p CO 2 p H 2 p CO p H 2 O The CO conversion rates over both catalysts were strongly dependent on the sulfur load in the feed. The presented models were established at a constant H 2 S concentration of 100 vol.ppm db . At this sulfur load the Fe/Cr-based catalyst should be preferred to the Co/Mo-based catalyst. The partial pressure of H 2 S could not be included in the power law models because of its influence on the other coefficients of the model.
Meizhou Ding - One of the best experts on this subject based on the ideXlab platform.
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comparative investigation on thermal decomposition of powdered and pelletized biomasses thermal conversion characteristics and Apparent Kinetics
Bioresource Technology, 2020Co-Authors: Ke Zhang, Xu Li, Bin Li, Meizhou DingAbstract:Abstract In this work, the thermal degradation behaviors of two kinds of biomasses (pinewood and rice husk) with powder and pellet under three oxygen concentrations were investigated by a self-designed macro-thermogravimetric analyzer. An obvious hysteresis of thermal degradation of biomass pellets was observed under three conditions. The maximum activation energy of biomass pellets was significantly greater than that of biomass powders, while their average activation energies were almost equal based on distributed activation energy model. For the oxygen-rich combustion, the comprehensive combustion character index of powdered and pelletized biomasses ranged from 3.92 × 10−7 to 5.16 × 10−7%2·min−2·°C−3 and from 1.82 × 10−7 to 1.91 × 10−7%2·min−2·°C−3, respectively. Furthermore, the derived biochar of powdered biomass has a higher caloricity than that of pelletized biomass during combustion by TG-DSC analysis. The performances of thermal degradation observed by macro-thermogravimetric analyzer could factually reveal the influence of mass and heat transfer on the thermochemical conversion of powdered and pelletized biomasses.
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comparative investigation on thermal degradation of flue cured tobacco with different particle sizes by a macro thermogravimetric analyzer and their Apparent Kinetics based on distributed activation energy model
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Yalin Wang, Ke Zhang, Liangyuan Chen, Meizhou DingAbstract:The particle size was an important factor that can affect the thermal degradation behavior of biomass during thermochemical conversion. In this work, the thermal degradation behavior of flue-cured tobacco with different particle sizes for thermochemical conversion was investigated by a self-designed macro-thermogravimetric analyzer (macro-TGA) under inert and oxidative conditions. During pyrolysis and combustion, the thermal degradation behavior could be described by a four-stage and five-stage mass loss reaction, respectively. At the second mass loss stage, for six cut tobaccos, the mass loss rate increased with the decrease in particle size during pyrolysis and combustion. In addition, the combustion character index of cut tobaccos ranging from 3.0480 × 10−7 to 4.4825 × 10−7%2 min−2 °C−3 also increased with the decrease in particle size. Furthermore, the mass change data recorded by the macro-TGA were used to estimate the kinetic parameters, such as the Apparent activation energy and the pre-exponential factor, based on distributed activation energy model. For the thermochemical conversion of tobacco materials, it was found that the Apparent activation energy increased with the increase in conversion rate for pyrolysis reaction under inert condition, while the Apparent activation energy reached a maximum within a certain conversion rate in the middle of combustion reaction under oxidative condition. As well, the kinetic compensation effect was evaluated by the equation $$\ln A = \varphi \times E + \psi$$. The investigation on thermal degradation and Apparent Kinetics of tobacco revealed the effect of particle size on thermochemical conversion, which can provide a reference for building a more accurate cigarette combustion model.
Mohammad M Hossain - One of the best experts on this subject based on the ideXlab platform.
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Apparent Kinetics of high temperature oxidative decomposition of microalgal biomass
Bioresource Technology, 2015Co-Authors: Shaikh A Razzak, Mohammad M HossainAbstract:Abstract The oxidative thermal characteristics of two microalgae species biomass Nannochloropsis oculta and Chlorella vulgaris have been investigated. The Apparent kinetic parameters for the microalgal biomass oxidation process are estimated by fitting the experimental data to the n th order rate model. Also, the iso-conversional methods Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) were used to evaluate the Apparent activation energy. The results indicate that biomass of different microalgae strains exhibit different thermal behavior and characteristics. In addition, growth parameters and medium composition can affect the biomass productivity and composition. This would have significant impact on the thermal decomposition trend of the biomass. The kinetic modeling of the oxidation reaction with direct model fitting method shows good prediction to the experimental data. The Apparent activation energies estimated by KAS and FWO methods for N. oculta were 149.2 and 151.8 kJ/mol, respectively, while for C. vulgaris were 214.4 and 213.4 kJ/mol, respectively.
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Apparent Kinetics of nonisothermal high temperature oxidative degradation of ethylene homopolymers: effects of residual catalyst surface chemistry and structure
Journal of Polymer Research, 2013Co-Authors: Muhammad Atiqullah, Mohammad M Hossain, Syed Masiur Rahman, Khurshid Alam, Hasan A. Al-muallem, Abdulrahman F. Alharbi, Ikram Hussain, Anwar HossaenAbstract:The effects of two supported residual catalysts—one Ziegler-Natta and another metallocene—on the nonisothermal thermooxidative degradation of the resulting ethylene homopolymers were investigated using TGA experiments and kinetic modeling. The rigorous constitutive kinetic model (developed in this study), unlike the analytical Horowitz and Metzger model, fitted very well to the entire TGA curve, without distribution of activation energy E _ a , for n (overall degradation order) = 1 for both polymers. Neither n nor E _ a varied as a function of fractional weight loss of the polymer. Hence, the proposed unified molecular level concept of surface chemistry and structure of the residual catalysts held all through the degradation process. The above feature of n and E _ a also indicates the suitability of the model formulation and the effectiveness of the parameter-estimation algorithm. Random polymer chain scission, with the cleavage of the −C−C− and the −O−O− (hydroperoxide) bonds, prevailed. The types of residual catalyst surface chemistry and structure varied the bond cleavage process. The metallocene Zr residual catalyst caused more thermooxidative degradation in MetCat HomoPE than what the Ti one did in Z-N HomoPE. The rigorous constitutive model-predicted Apparent kinetic energy E _ a , and frequency factor Z also support this finding. The proposed degradation mechanism suggests that the Zr residual catalyst more (i) decreased the activation energy required to decompose the −C−C− and the −O−O− bonds, and (ii) eliminated β-hydrogen (by the carbonyl functionalities) from the polymer chains. These findings were attributed to the differences in surface chemistry and structure of the residual catalysts. Therefore, the current study presents a rigorous constitutive kinetic model that duly illustrates the influence of the characteristic surface chemistry and structure of the residual catalysts on the high temperature oxidative degradation of polyethylenes.
Edward J Anthony - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the Apparent Kinetics of air and oxy-fuel biomass combustion in a spout fluidised-bed reactor
Chemical Engineering Research & Design, 2020Co-Authors: Peter T Clough, Edward J AnthonyAbstract: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.
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investigation of the Apparent Kinetics of air and oxy fuel biomass combustion in a spouted fluidised bed reactor
Chemical Engineering Research & Design, 2020Co-Authors: Peter T Clough, Edward J AnthonyAbstract: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.
Blaž Likozar - One of the best experts on this subject based on the ideXlab platform.
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Growth, lipid extraction and thermal degradation of the microalga Chlorella vulgaris.
New biotechnology, 2012Co-Authors: Maja Sostaric, Dusan Klinar, Mihael Bricelj, Janvit Golob, Marin Berovič, Blaž LikozarAbstract:The microalga Chlorella vulgaris was cultured in a combined medium obtained by mixing standard Jaworski medium with a solution from the modified Solvay process that contained only NaHCO(3) and NH(4)Cl. Cell number, pH and nitrogen content were monitored throughout growth. Lipids were extracted from lyophilised biomass using CHCl(3)-MeOH. A combination of grinding, microwave treatment and sonication proved to give the best lipid extract yield. Freeze-dried algal biomass was also utilised for thermal degradation studies. The degradation exhibited three distinct regions - primary cell structure breakage paralleled by evaporation of water, followed by two predominant exothermic degradation processes. The latter were modelled using nth order Apparent Kinetics. The activation energies of the degradation processes were determined to be 120-126kJ/mol and 122-132kJ/mol, respectively. The degradation model may be readily applied to an assortment of thermal algal processes, especially those relating to renewable energy.
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Growth, lipid extraction and thermal degradation of the microalga Chlorella vulgaris
New Biotechnology, 2012Co-Authors: Maja Sostaric, Dusan Klinar, Mihael Bricelj, Janvit Golob, Marin Berovič, Blaž LikozarAbstract:The microalga Chlorella vulgaris was cultured in a combined medium obtained by mixing standard Jaworski medium with a solution from the modified Solvay process that contained only NaHCO3 and NH4Cl. Cell number, pH and nitrogen content were monitored throughout growth. Lipids were extracted from lyophilised biomass using CHCl3–MeOH. A combination of grinding, microwave treatment and sonication proved to give the best lipid extract yield. Freeze-dried algal biomass was also utilised for thermal degradation studies. The degradation exhibited three distinct regions – primary cell structure breakage paralleled by evaporation of water, followed by two predominant exothermic degradation processes. The latter were modelled using nth order Apparent Kinetics. The activation energies of the degradation processes were determined to be 120–126 kJ/mol and 122–132 kJ/mol, respectively. The degradation model may be readily applied to an assortment of thermal algal processes, especially those relating to renewable energy.
