The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Rafael Bilbao - One of the best experts on this subject based on the ideXlab platform.
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Kinetic study of the thermal degradation of alkaline straw black liquor in nitrogen atmosphere
Chemical Engineering Journal, 2004Co-Authors: José Luis Sánchez, Rafael Bilbao, Gloria Gea, Alberto Gonzalo, Jesús ArauzoAbstract:Abstract The kinetics of Solid weight loss in the pyrolysis of straw black liquor Solids at low temperature ( Assuming a first order for the thermal decomposition rate of the Solid at a given temperature, the instantaneous kinetic constant for the same temperature diminishes as the reaction proceeds. This could be due mainly to the heterogeneity of straw black liquor Solids. Both, the pre-exponential factor and the activation energy of the Arrhenius law, seem to vary linearly with the Solid Conversion.
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A model for the prediction of the thermal degradation and ignition of wood under constant and variable heat flux
Journal of Analytical and Applied Pyrolysis, 2002Co-Authors: Rafael Bilbao, J.f. Mastral, José A. Lana, J. Ceamanos, Marı́a E. Aldea, Mónica BetránAbstract:Abstract The ignition of combustible materials is an important aspect of the processes taking place in an unwanted fire. In this work, an experimental and theoretical study of the ignition process of wood has been carried out. Experiments of both spontaneous and piloted ignition have been performed. Constant and decreasing variable heat fluxes have been tested. A mathematical model has been used to predict the time to ignition of wood for the different operating conditions used. The solution of the model provides the temperature at each point of the Solid, the local Solid Conversion and the time to ignition of the material. In general, a good agreement between experimental and theoretical results is obtained.
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The influence of the percentage of oxygen in the atmosphere on the thermal decomposition of lignocellulosic materials
Journal of Analytical and Applied Pyrolysis, 1997Co-Authors: Rafael Bilbao, J.f. Mastral, M.e. Aldea, J. CeamanosAbstract:Abstract Dynamic experiments with a heating rate of 12 °C min −1 have been carried out for different oxygen concentrations and several types of pine samples. The influence of the initial Solid weight and the sample shape on the Solid Conversion for each oxygen concentration has been analysed. A simple method is proposed to predict the Solid Conversion for different oxygen concentrations. The kinetic equations corresponding to an air atmosphere are used in this method.
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Modelling of the pyrolysis of wet wood
Journal of Analytical and Applied Pyrolysis, 1996Co-Authors: Rafael Bilbao, J.f. Mastral, J. Ceamanos, M.e. AldeaAbstract:Abstract The influence of moisture content on the thermal decomposition of wood has been analyzed. Using wood slabs, experimental results of temperature profiles and Solid Conversion for different moisture contents and heat fluxes have been obtained. A mathematical model without adjustable parameters was used to calculate the temperature at different points in the sample and the average total Solid Conversion. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.
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Kinetics and modeling of gas formation in the thermal decomposition of powdery cellulose and pine sawdust
Industrial & Engineering Chemistry Research, 1995Co-Authors: Rafael Bilbao, Jesús Arauzo, María Luisa Esteban SalvadorAbstract:The formation of different gases in the thermal decomposition of cellulose and pine sawdust has been studied. The kinetic constants of CO{sub 2} and H{sub 2} formation in cellulose decomposition have been determined from results obtained in isothermal experiments. These kinetic constants have been taken as representative of pine sawdust decomposition at T > 292 C, and values for lower temperatures have bene obtained from isothermal experiments performed with pine sawdust. For both materials, a simple model without adjustable parameters has been applied that allows one to calculate the local temperature, Solid Conversion, and yield of each gas. The results obtained in dynamic experiments with heating rates ranging between 2 and 53 C/min have been compared with the theoretical results, and an acceptable agreement has been achieved.
Jesús Arauzo - One of the best experts on this subject based on the ideXlab platform.
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Kinetics of CO2 gasification of alkaline black liquor from wheat straw. 2. Evolution of CO2 reactivity with the Solid Conversion and influence of temperature on the gasification rate
Industrial & Engineering Chemistry Research, 2005Co-Authors: Gloria Gea, José Sánchez, M.b. Murillo, Jesús ArauzoAbstract:Results obtained in recent studies have shown that black liquor (BL) gasification can be considered as an attractive recovery system. However, limited information has been published on the gasification kinetics of alkaline BL char (ABLC). Part 1 of this work (Gea, G.; Sanchez, J. L.; Murillo, M. B.; Arauzo, J. Ind. Eng. Chem. Res. 2004, 43, 3233) studied the CO 2 gasification of ABLC, specifically the influence of [CO] and [CO 2 ] on the gasification rate at different temperatures. The present work is focused on the variation of this reaction rate with Solid Conversion during the gasification process. The results obtained show that the gasification rate increases with the Solid Conversion up to a maximum value and then decreases. The effect of various factors such as pyrolysis operating conditions on this variation has also been analyzed. Furthermore, the dependence of the ABLC gasification rate on the temperature has been evaluated, and the apparent average activation energy over the range 170-234 kJ/mol has been determined for the temperature range 750-850 °C.
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Kinetic study of the thermal degradation of alkaline straw black liquor in nitrogen atmosphere
Chemical Engineering Journal, 2004Co-Authors: José Luis Sánchez, Rafael Bilbao, Gloria Gea, Alberto Gonzalo, Jesús ArauzoAbstract:Abstract The kinetics of Solid weight loss in the pyrolysis of straw black liquor Solids at low temperature ( Assuming a first order for the thermal decomposition rate of the Solid at a given temperature, the instantaneous kinetic constant for the same temperature diminishes as the reaction proceeds. This could be due mainly to the heterogeneity of straw black liquor Solids. Both, the pre-exponential factor and the activation energy of the Arrhenius law, seem to vary linearly with the Solid Conversion.
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Thermal degradation of alkaline black liquor from straw. Thermogravimetric study
Industrial & Engineering Chemistry Research, 2002Co-Authors: Gloria Gea, M.b. Murillo, Jesús ArauzoAbstract:Both pyrolysis and gasification can be considered as alternatives to conventional boilers for recovering chemicals and energy from black liquor. The present work is focused on the study of pyrolysis of alkaline black liquor from straw, and its interest is enhanced by the fact that the material used has hardly been studied before. The influence has been studied of the final pyrolysis temperature (500-900°C), the heating rate (5-30°C/min), and the addition of a determined CO concentration in the N 2 atmosphere (5-40% vol) on both the final Solid Conversion and the devolatilization rate. The results show that the thermal decomposition of the organic matter fraction of black liquor takes place at temperatures below 550°C in N 2 atmosphere. The weight loss observed at temperatures higher than 550°C is mainly due to reduction reactions of alkaline compounds by the carbon. The final Solid Conversion and the devolatilization rate are also noticeably influenced by the addition of a certain CO flow rate in N 2 atmosphere.
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Kinetics and modeling of gas formation in the thermal decomposition of powdery cellulose and pine sawdust
Industrial & Engineering Chemistry Research, 1995Co-Authors: Rafael Bilbao, Jesús Arauzo, María Luisa Esteban SalvadorAbstract:The formation of different gases in the thermal decomposition of cellulose and pine sawdust has been studied. The kinetic constants of CO{sub 2} and H{sub 2} formation in cellulose decomposition have been determined from results obtained in isothermal experiments. These kinetic constants have been taken as representative of pine sawdust decomposition at T > 292 C, and values for lower temperatures have bene obtained from isothermal experiments performed with pine sawdust. For both materials, a simple model without adjustable parameters has been applied that allows one to calculate the local temperature, Solid Conversion, and yield of each gas. The results obtained in dynamic experiments with heating rates ranging between 2 and 53 C/min have been compared with the theoretical results, and an acceptable agreement has been achieved.
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Influence of the heating rate on the temperature profiles and on the Conversion rate of powdery cellulose and pine sawdust
Journal of Analytical and Applied Pyrolysis, 1994Co-Authors: Rafael Bilbao, María Luisa Esteban Salvador, Jesús ArauzoAbstract:Abstract An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the Solid Conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the Solid bed and the average total Solid Conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.
Mikko Hupa - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Sulfided Zinc Titanate Regeneration in a Fluidized-Bed Reactor. 2. Scale-Up of the Solid Conversion Model
Industrial & Engineering Chemistry Research, 1997Co-Authors: J.t. Konttinen, C.a.p. Zevenhoven, Mikko HupaAbstract:Hot gas desulfurization with regenerable metal oxide sorbents is an essential part of the simplified integrated gasification combined cycle process which is currently being demonstrated at commercial scale. As part of a sulfur removal process development, Carbona Corporation is developing fluidized-bed reactor models for scale-up. In the first part of this work, the parameters for a uniform Conversion model were determined to describe the Conversion rate of ZnS regeneration with oxygen. A method using the uniform Conversion model for fluidized-bed application is presented in this paper. The apparent activation energy for the global reaction rate constant obtained from pilot-scale fluidized-bed tests is 200--210 kJ/mol. When using these reaction rate constants as inputs of a sensitivity analysis for a large-scale reactor model, in comparison with the rate constants reported earlier, some differences can be observed. The significance of the differences are discussed. It is stated that any zinc sulfate formed in fluidized-bed regeneration at temperatures 500--600 C will decompose, forming SO{sub 2}, at the actual regeneration temperatures of the bed (725--800 C) due to negligible O{sub 2} partial pressure.
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Modeling of sulfided zinc titanate regeneration in a fluidized-bed reactor. 1: Determination of the Solid Conversion rate model parameters
Industrial & Engineering Chemistry Research, 1997Co-Authors: J.t. Konttinen, C.a.p. Zevenhoven, K.p. Yrjas, Mikko HupaAbstract:Regenerable mixed metal oxide sorbents are prime candidates for the removal of hydrogen sulfide (a major pollutant) from the hot coal gas in the simplified integrated gasification combined cycle processes. As part of this sulfur removal process development, reactor models are needed for scale-up. It is essential for this work to apply a reliable and simple modeling correlation for the Conversion rate of zinc sulfide or oxygen in the regeneration reaction. The fit of such a model assuming uniform Conversion of the ZnS, was obtained from ambient pressure thermogravimetric analyzer test data with sulfided zinc titanate samples. An activation energy of about 140 kJ/mol was obtained for the regeneration reaction rate constant.
J.f. Mastral - One of the best experts on this subject based on the ideXlab platform.
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A model for the prediction of the thermal degradation and ignition of wood under constant and variable heat flux
Journal of Analytical and Applied Pyrolysis, 2002Co-Authors: Rafael Bilbao, J.f. Mastral, José A. Lana, J. Ceamanos, Marı́a E. Aldea, Mónica BetránAbstract:Abstract The ignition of combustible materials is an important aspect of the processes taking place in an unwanted fire. In this work, an experimental and theoretical study of the ignition process of wood has been carried out. Experiments of both spontaneous and piloted ignition have been performed. Constant and decreasing variable heat fluxes have been tested. A mathematical model has been used to predict the time to ignition of wood for the different operating conditions used. The solution of the model provides the temperature at each point of the Solid, the local Solid Conversion and the time to ignition of the material. In general, a good agreement between experimental and theoretical results is obtained.
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The influence of the percentage of oxygen in the atmosphere on the thermal decomposition of lignocellulosic materials
Journal of Analytical and Applied Pyrolysis, 1997Co-Authors: Rafael Bilbao, J.f. Mastral, M.e. Aldea, J. CeamanosAbstract:Abstract Dynamic experiments with a heating rate of 12 °C min −1 have been carried out for different oxygen concentrations and several types of pine samples. The influence of the initial Solid weight and the sample shape on the Solid Conversion for each oxygen concentration has been analysed. A simple method is proposed to predict the Solid Conversion for different oxygen concentrations. The kinetic equations corresponding to an air atmosphere are used in this method.
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Modelling of the pyrolysis of wet wood
Journal of Analytical and Applied Pyrolysis, 1996Co-Authors: Rafael Bilbao, J.f. Mastral, J. Ceamanos, M.e. AldeaAbstract:Abstract The influence of moisture content on the thermal decomposition of wood has been analyzed. Using wood slabs, experimental results of temperature profiles and Solid Conversion for different moisture contents and heat fluxes have been obtained. A mathematical model without adjustable parameters was used to calculate the temperature at different points in the sample and the average total Solid Conversion. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.
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Thermal decomposition of lignocellulosic materials: comparison of the results obtained in different experimental systems
Thermochimica Acta, 1991Co-Authors: Rafael Bilbao, M.b. Murillo, Ángela Millera, J.f. MastralAbstract:Abstract An experimental system that allows the use of large particle sizes and the simulation of different operating conditions was built to study the thermal decomposition of lignocellulosic materials. The values of Solid Conversion and of temperature obtained at different points using spherical particles of pine wood 2 cm in diameter are shown. The Conversion values are compared with those calculated from the equations obtained in a thermobalance for small particle sizes.
J. Ceamanos - One of the best experts on this subject based on the ideXlab platform.
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A model for the prediction of the thermal degradation and ignition of wood under constant and variable heat flux
Journal of Analytical and Applied Pyrolysis, 2002Co-Authors: Rafael Bilbao, J.f. Mastral, José A. Lana, J. Ceamanos, Marı́a E. Aldea, Mónica BetránAbstract:Abstract The ignition of combustible materials is an important aspect of the processes taking place in an unwanted fire. In this work, an experimental and theoretical study of the ignition process of wood has been carried out. Experiments of both spontaneous and piloted ignition have been performed. Constant and decreasing variable heat fluxes have been tested. A mathematical model has been used to predict the time to ignition of wood for the different operating conditions used. The solution of the model provides the temperature at each point of the Solid, the local Solid Conversion and the time to ignition of the material. In general, a good agreement between experimental and theoretical results is obtained.
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Modeling of the Pyrolysis of Large Samples of Polyethylene Including the Melting Process
Energy & Fuels, 2002Co-Authors: J. Ceamanos, And J. F. Mastral, F. LiesaAbstract:An experimental and theoretical study has been carried out on the thermal degradation of large samples of high density polyethylene in an inert atmosphere. The experimental results show the existence of significant longitudinal temperature profiles inside the Solid, which are basically due to its low thermal conductivity and the melting process. The polyethylene undergoes important volume variations during the experiments: expansion during the melting process and contraction due to pyrolysis. The mathematical model developed takes into account the volume variation and the melting process using the enthalpy method. The temperature profiles and the Solid Conversion are predicted, and good agreement with the experimental temperature results is obtained. Some discrepancies are observed in the case of Solid Conversion, probably due to the resistance to mass transfer of product gases in the Solid.
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The influence of the percentage of oxygen in the atmosphere on the thermal decomposition of lignocellulosic materials
Journal of Analytical and Applied Pyrolysis, 1997Co-Authors: Rafael Bilbao, J.f. Mastral, M.e. Aldea, J. CeamanosAbstract:Abstract Dynamic experiments with a heating rate of 12 °C min −1 have been carried out for different oxygen concentrations and several types of pine samples. The influence of the initial Solid weight and the sample shape on the Solid Conversion for each oxygen concentration has been analysed. A simple method is proposed to predict the Solid Conversion for different oxygen concentrations. The kinetic equations corresponding to an air atmosphere are used in this method.
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Modelling of the pyrolysis of wet wood
Journal of Analytical and Applied Pyrolysis, 1996Co-Authors: Rafael Bilbao, J.f. Mastral, J. Ceamanos, M.e. AldeaAbstract:Abstract The influence of moisture content on the thermal decomposition of wood has been analyzed. Using wood slabs, experimental results of temperature profiles and Solid Conversion for different moisture contents and heat fluxes have been obtained. A mathematical model without adjustable parameters was used to calculate the temperature at different points in the sample and the average total Solid Conversion. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.