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Septien S.,CEA Grenoble | Valin S.,CEA Grenoble | Dupont C.,CEA Grenoble | Peyrot M.,CEA Grenoble | Salvador S.,RAPSODEE
Fuel | Year: 2012

Fast pyrolysis of wood was conducted in a drop tube furnace to study the influence of temperature (1000-1200-1400°C) and particle size (0.35-0.80 mm) for a particle residence time of some seconds. No effect of particle size has been observed on final pyrolysis products. At 1000°C, much more gas and tar are produced than char (yield of 96% versus 4%); hydrocarbons, including light species and tar, present a considerable yield of 26%. From 1200°C, the drastic hydrocarbons decomposition, emphasized with temperature, leads to high yields in soot, H 2 and CO. At 1200°C, no tar are detected; at 1400°C only low amounts of CH 4 and C 2H 2 still remain. Under the explored conditions, char and soot gasification with H 2O and CO 2, species produced during pyrolysis, is kinetically blocked. However, even if carbonaceous solids do not seem to be considerably affected by gasification, they suffer some changes when temperature is increased. © 2012 Elsevier Ltd. All rights reserved.


Guizani C.,University of Grenoble Alpes | Haddad K.,CNRS Mulhouse Institute of Materials Science | Jeguirim M.,CNRS Mulhouse Institute of Materials Science | Colin B.,RAPSODEE | Limousy L.,CNRS Mulhouse Institute of Materials Science
Energy | Year: 2016

This investigation aims to examine the OP (olive pomace) recovery as a fuel in heat production systems. A two-steps process is proposed to adapt OP for such application. Firstly, the OP torrefaction is performed for various temperatures in order to improve the combustion properties. It is seen that, in addition to the hydrophobic character, the higher heating value of the samples increased with the torrefaction severity. Secondly, the reactivity in air of TOP (torrefied olive pomace) using thermogravimetric analyses is examined. The results show a decrease in the TOP reactivity with the increase of the torrefaction temperature. This behaviour is attributed to the degraded proportion of the three macro-components: Hemicellulose (HC), Cellulose (C), Lignin (L). A kinetic model based on the HC, C and L thermal degradation is applied to simulate the combustion of OP and TOP samples. The activation energies of the macro-components degradation and char combustion reactions are determined. In addition, the proportions of HC, C and L left in the TOP samples after the torrefaction step are extracted. This modelling part brings understanding keys on both torrefaction and combustion steps. It also provides kinetic parameters concerning OP and TOP combustion, which are necessary for combustor sizing. © 2016 Elsevier Ltd.


Guizani C.,RAPSODEE | Louisnard O.,RAPSODEE | Sanz F.J.E.,RAPSODEE | Salvador S.,RAPSODEE
Biomass and Bioenergy | Year: 2015

The present paper focuses on the gasification of thin wood particles in pure CO2 at 850 °C under high heating rate conditions (similar to fluidized bed gasifiers). The aim is to assess the potential use of CO2 as gasifying medium and to learn more about its effects on the pyrolysis as well as on the char gasification stages. Experimental and numerical modelling results provide answers on the unfolding of the whole CO2 biomass pyro-gasification process. It was found that despite the CO2 is present inside the particle during the pyrolysis stage, it has no noticeable impacts neither on the reaction rate nor on the char yield due to the relatively low temperature inside the particle. The CO2 char gasification is the rate limiting step of the global pyro-gasification reaction as its duration is near to 95% of the entire biomass conversion time. © 2015.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Jeguirim M.,CNRS Mulhouse Institute of Materials Science | Gadiou R.,CNRS Mulhouse Institute of Materials Science | Salvador S.,RAPSODEE
Fuel Processing Technology | Year: 2015

Despite the huge literature on biomass char gasification with CO2 or H2O, ambiguity still hovers over the issue of char gasification in complex atmospheres. Gas alternation gasification experiments, in which the reacting gas is changed during the reaction, were performed with CO2/H2O at 900°C for small (200μm) and large (13mm) Low Heating Rate (LHR) beech wood char particles to assess the potential influences that CO2 and H2O can have on each other during the char gasification reaction. The results showed no influence of a first gasification atmosphere on the char reactivity under the second one. The char reactivity to a specific gas at a certain conversion level was the same as if the gasification reaction was operated from the beginning with the same atmosphere composition. The purpose of this paper is to bring understanding keys to this lack of influence of previous gasification conditions on the char reactivity. Characterization of the chars throughout the conversion by measuring the total surface area and the active surface area was first performed. Then a transport limitation analysis based on the Thiele modulus was considered. It was concluded that the two gasses develop different porosities in the char, however, the Thiele modeling results and active surface area analysis indicate respectively that gasses diffuse preferentially in large macro-pores and that the concentration of active sites evolves similarly during both gasification reactions. This similarity in the diffusion mechanism as well as in the evolution of the concentration of active sites could be a plausible explanation for the only-dependent conversion reactivity observed in the gas alternation gasification experiments. © 2015 Elsevier B.V.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Salvador S.,RAPSODEE
Fuel | Year: 2014

The effect of CO2 introduction in a biomass fast pyrolysis process at 850 C was investigated. It was found that CO2 impacts the final gas yield and composition, and the char yield and properties. Introducing CO2 in the pyrolysis medium alongside nitrogen enhanced CO production as a result of homogeneous and heterogeneous reactions of CO2 with gases, tars and char. The char yield was lower compared to a reference char yield in pure nitrogen. The char obtained in a CO2-containing atmosphere has its surface area increased nearly sixfold and has a chemical composition different from that of chars obtained in N2 atmosphere. However, the reactivity of the two chars towards H2O, CO2 and O2 was almost the same. Temperature-programmed oxidation experiments on both chars - those obtained in pure nitrogen and those obtained in a CO2-containing atmosphere - revealed quite different oxidation profiles and peak temperatures. Taken together, these results tend to confirm that CO2 is impacting the biomass fast pyrolysis process. In the light of these results and of the literature findings, we propose a mechanism illustrating the role of CO2 during fast pyrolysis of biomass. © 2013 Elsevier Ltd. All rights reserved.


Guizani C.,RAPSODEE | Louisnard O.,RAPSODEE | Sanz F.J.E.,RAPSODEE | Salvador S.,RAPSODEE | Hermany D.,RAPSODEE
IREC 2014 - 5th International Renewable Energy Congress | Year: 2014

The paper focuses on the pyro-gasification of thin wood particles in pure CO2 at 850°C under high heating rate conditions (similar to fluidized bed gasifiers). The aim is to assess the potential use of CO 2 as gasifying medium and to learn more about its effects on the pyrolysis as well as on the char gasification stages. Experiments and numerical modelling provide answers on the unfolding of the CO2 biomass pyro-gasification process. © 2014 IEEE.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Salvador S.,RAPSODEE
Fuel Processing Technology | Year: 2015

The paper focuses on the gasification of biomass chars in H2O, CO2 and their mixtures. The first part is dedicated to the study of the influence of particle size and temperature in single atmosphere gasification experiments. The Thiele approach was successfully applied to assess the extent of diffusional limitations. We also studied the mixed atmosphere gasification of 0.2mm chars at various temperatures and found that the char reactivity is fairly represented by an additive law at relatively low temperatures while it is lower than the sum of the individual contributions for high temperature cases. Similarly, we assessed the effect of particle size for mixed atmosphere experiments and found that an additive law was representative of the experimental reactivities for particle sizes from 0.2 to 13mm. The present work provides useful and worthy information on the char gasification reactivity in conditions close to practical operating ones encountered in biomass gasifiers. © 2015 Elsevier B.V.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Salvador S.,RAPSODEE
Fuel | Year: 2013

Gasification reactivity of high-heating-rate chars (HHR-chars) in steam, carbon dioxide and their mixtures was investigated in a new macro-TG experimental device. The higher reactivity of the HHR-chars was highlighted by a comparison with reference chars prepared at a low heating rate (LHR-chars). It was found that the char reactivity in a mixed atmosphere of steam and carbon dioxide can be expressed as the sum of the individual reactivities obtained in single-atmosphere gasification experiments. This result was not dependent on the pyrolysis heating rate. In addition, gas-alternation gasification experiments - for both HHR-chars and LHR-chars - showed that gasifying the char with CO 2 up to 30% of conversion does not affect its reactivity to H 2O. Altogether, the results tend to indicate that the two reactant gases H2O and CO2 react on separate active sites when mixed atmospheres are used, and that CO2 does not affect the char structure to favor or inhibit the char-H2O gasification reaction. © 2013 Elsevier Ltd. All rights reserved.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Salvador S.,RAPSODEE
Comptes Rendus Chimie | Year: 2016

The catalytic properties of raw biomass chars and Ni-loaded biomass chars prepared at a high-heating-rate were assessed in the methane decomposition reaction. The raw chars exhibited a moderated catalytic activity in methane cracking while the Ni-loaded chars showed a catalytic activity 10 times higher than the raw chars. The deposited carbon was a highly ordered one as evidenced by XRD, Raman analysis and oxygen reactivity tests. The activation energy in the combustion reaction was estimated to be 300 kJ/mol. These results indicate that biomass char can be an effective low-cost and active support for metal impregnation to be used in catalytic cracking of hydrocarbons for hydrogen production. © 2015 Académie des sciences. Published by Elsevier Masson SAS.


Guizani C.,RAPSODEE | Escudero Sanz F.J.,RAPSODEE | Jeguirim M.,CNRS Mulhouse Institute of Materials Science | Gadiou R.,CNRS Mulhouse Institute of Materials Science | Salvador S.,RAPSODEE
Fuel Processing Technology | Year: 2015

Despite the huge literature on biomass char gasification with CO2 or H2O, ambiguity still hovers over the issue of char gasification in complex atmospheres. Gas alternation gasification experiments, in which the reacting gas is changed during the reaction, were performed with CO2/H2O at 900 °C for small (200 μm) and large (13 mm) Low Heating Rate (LHR) beech wood char particles to assess the potential influences that CO2 and H2O can have on each other during the char gasification reaction. The results showed no influence of a first gasification atmosphere on the char reactivity under the second one. The char reactivity to a specific gas at a certain conversion level was the same as if the gasification reaction was operated from the beginning with the same atmosphere composition. The purpose of this paper is to bring understanding keys to this lack of influence of previous gasification conditions on the char reactivity. Characterization of the chars throughout the conversion by measuring the total surface area and the active surface area was first performed. Then a transport limitation analysis based on the Thiele modulus was considered. It was concluded that the two gasses develop different porosities in the char, however, the Thiele modeling results and active surface area analysis indicate respectively that gasses diffuse preferentially in large macro-pores and that the concentration of active sites evolves similarly during both gasification reactions. This similarity in the diffusion mechanism as well as in the evolution of the concentration of active sites could be a plausible explanation for the only-dependent conversion reactivity observed in the gas alternation gasification experiments. © 2015 Elsevier B.V.

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