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Albi, France

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. Source


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. Source


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. Source


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. Source


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. Source

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