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International audience; A small-scale induction heated reactor (IHR) was specifically developed to study fast pyrolysis, here investigated as the first step of gasification process, representing some of the reaction conditions encountered in a fluidized bed reactor. First, the thermal response of the system was characterized at transient and steady state, and CFD calculations were performed to have a complete description of the temperature profiles inside the reactor. The novel device can handle a few grams of solid at temperatures up to 900 °C, allowing high heating rates (near 80 °C/s) and a uniform distribution of temperature in the sample. Secondly, the pyrolysis of a solid recovered fuel (SRF) sample was carried out at 800 °C, and the distribution and composition of reaction products were analyzed and compared with tests performed in a pilot scale fluidized bed reactor (FBR). The results obtained in the IHR showed a good reproducibility. The same main gas and tar species were measured in the IHR and FBR, with however some differences in gas and tar composition that were attributed to the extent of secondary reactions, enhanced by higher heat transfer rates and the presence of bed material in the FBR.

The present study investigates the thermochemical conversion of Solid Recovered Fuel (SRF), represented by selected “model materials”. A laboratory-scale induction heated device was specifically developed to achieve fast pyrolysis conditions close to those encountered in a fluidized bed reactor. The novel device can handle up to 5 grams of solid, allowing fast heating rates (near 70°C/s) and a homogeneous distribution of temperature all along the reactor. Pyrolysis tests of a SRF sample and four model materials (Polyethylene, Polyethylene Terephthalate, beech wood, cardboard) were performed at 800°C. The yield and composition of the produced gas for each sample were determined. Experimental results will help to elucidate the relation between the initial components of waste derived fuels and the obtained reaction products.

International audience; Woody biomass fast pyrolysis in Entrained Flow Reactor (EFR) is studied both with experiments in a lab-scale drop tube reactor (DTR) and simulations with a 1-D model. The parameters of the study are temperature (450-600 degrees C), woody biomass particle size (370-640 mu m) and gas residence time (12.6-20.6 s). The most critical phenomena affecting the bio-oil yield are considered in the model: heating of the biomass particles, slip velocity of the biomass particles varying with biomass/char properties, biomass pyrolysis and tar cracking. The analyses of all products - char, bio-oil and gas - also brought information on the advancement of the pyrolysis and cracking for the different tests. The reactor temperature and particle size were found to have a major influence on the pyrolysis product distribution. The production of bio-oil reaches a maximum of 62.4 wt.% at 500 degrees C for the 370 mm particles. The particle conversion advancement is then estimated at 94% at the reactor exit. The bio-oil yield is lower at higher temperatures for a constant particle size due to tar cracking. At 550 degrees C, increasing the particle size from 370 mm to 640 mu m induces a decrease of the bio-oil yield from 48.3 to 34.8 wt.%, which was shown to be due to incomplete pyrolysis of the particles, because of a too short residence time as well as a too long heating time of particles. The pyrolysis conditions - temperature, particle size - were not found to have any significant influence on the bio-oil properties, such as acidity.

The aim of this work is to study the air gasification of solid recovered fuel (SRF), and to compare it to the gasification of woody biomass (beech wood sawdust, and waste wood). This study focuses on the influence of several operating parameters: temperature – between 800 and 910 °C –, O2/C ratio – between 0 (pyrolysis conditions) and 0.34, and addition of steam. Experiments are performed in a bubbling fluidized bed at 1.5 bar, with a solid feeding rate of 1–3 kg/h. The yield and composition of the product gas is particularly looked at, together with the repartition of carbon into the different types of products (gas species, tar molecules). Sulphur release to the gas phase is also investigated. Temperature has mainly an influence on H2 and CO yields, which is attributed to char gasification enhancement. The addition of steam in fluidising gas induces an increase in oxygenated gas species yields (CO + CO2), related to char gasification improvement. It does not have any reforming influence on light hydrocarbon and tar, with even a slight inhibiting effect. Woody biomass and SRF show significant differences in product yields, which are qualitatively explained by the initial elemental composition and material content of each type of fuel. From a process point of view, the conversion efficiency improvement by varying the gasification conditions for SRF is limited compared to the higher efficiency obtained with woody biomass. Co-gasification of biomass – possibly waste wood – and SRF, could be a way to improve the overall efficiency, and limit pollutant content.

International audience; There are many different ways to convert biomass into liquid fuels, mostly referred to as bio-oils. This paper presents the analysis of bio-oils produced by hydrothermal liquefaction and fast pyrolysis of beech wood. Both processes have a wide panel of parameters that can be optimised influencing the oil quality. Results of the analysis show that both oils have high acidities. Iodine values indicate a high degree of unsaturations. These two qualities seem to be inversely proportional in the case of pyrolysis oils. In the case of hydrothermal conversion, additives to adjust the pH such as sodium hydroxide increase oil yields, lower its viscosity but do little to further improve the quality of the oils. For pyrolysis oils, increasing the severity does reduce acidity but at the expense of more unsaturations and a loss in yield. The results show that without extensive upgrading or refining, commercial fuel standards cannot be met. Specific norms and standards are being elaborated for pyrolysis used in specific installations. This paper shows how detailed analysis can help to optimise process parameters with an objective that goes beyond the mass or energy yield.

International audience; The properties of biochars produced in biomass pyrolysis processes highly depend on the pyrolysis conditions, specifically the pyrolysis temperature and thermal treatment duration. The higher the temperature and the duration, the more severe is the heat treatment. The present work proposes a new Heat Treatment Severity Index (HTSI) for the quantification of the heat treatment severity during the pyrolysis reaction. This metric takes into account both effects of reactor temperature and heat treatment time inside the reactor. The relevance of this HTSI is assessed through analyzing the evolution of some properties of biochars obtained after pyrolysis of 370 µm beech wood particles in an entrained flow reactor. These biochars were characterized for their chemical composition (elemental analysis), structure (Raman spectroscopy) and reactivity towards oxygen (thermogravimetric analysis). These properties were well correlated with the HTSI following remarkable mathematical relationships. This finding demonstrates the possibility to engineer biochars with controlled properties by a careful mastering of the experimental conditions of the pyrolysis process in terms of temperature and heat treatment time.

International audience; This study, performed in the context of GAYA project, focuses on the development of a simple predictive model about steam gasification of char from woodchips fast pyrolysis. A semi-empirical model was developed through experiments in a macro thermogravimetric analyzer which owns the peculiar ability of fast heating, as well as to deal with macro-size particles and higher mass loads compared to conventional TGA. The experimental results show that gasification is controlled by chemical kinetics and internal transfer phenomena. During gasification, char particles can be considered as isothermal in a given range of temperatures and particle sizes, more likely for low values. The gasification model was based on the effectiveness factor, which involves the chemical kinetics and diffusion rate. The chemical kinetics were expressed by a classical Arrhenius law, whereas empirical expressions from mathematical fitting of the experimental data were established for the diffusion coefficient and surface function. The diffusion coefficient from this work is suspected to probably include supplementary rate limiting phenomena, apart from steam porous diffusion, such as H2 inhibition and/or the decrease of temperature within char particles because of the endothermic character of gasification. The model globally predicts with accuracy the gasification rate in typical operating conditions of a fluidized bed reactor. For its simplicity and reliability, this approach can be used for the modelling of char gasification in the conditions of interest.

International audience; This work, performed in the context of Gaya project, focuses on the characterization and modelling of the effect of the pyrolysis heating rate on the steam gasification of char from woodchips. An experimental work was performed based on thermogravimetry and solid characterization of char samples prepared under different conditions. The results showed that gasification apparent reactivity increased with the increase of heating rate. The faster chemical kinetics of char prepared under high heating rate could be related to its higher catalytic inorganic content together with a more reactive carbonaceous structure. The increase of heating rate favours porosity development and the enlargement of pores, which would have a positive effect on gasification reaction rate by enhancing gas diffusion within the solid. The effect of heating rate on char gasification was included in a model previously developed, by correlating the chemical kinetics, particle density and diffusion rate to the char yield, which was selected as a suitable indicator of the heating rate. The new version of the model, considering the variability of heating rate during char formation, was validated through accurate predictions of the experimental results.

Char and soot characterization was performed for samples obtained from beech particles pyrolysis in a drop tube reactor at various temperatures and residence times. Firstly, an experimental study was performed and highlights the variation of char and soot composition and reactivity with operating conditions. A structure ordering with temperature for soot samples was also experimentally put into evidence. These variations are believed to be consequence of structural changes during char thermal annealing and soot formation process, affecting both carbonaceous matrix and mineral matter. Secondly, a semi-empirical model was developed and validated with thermogravimetry experiments. This model was then used for conversion time estimation in conditions representative of an entrained flow reactor, and shows that a complete conversion of char and soot is possible in a few seconds under severe operating conditions.

International audience; Wood particle conversion in a drop tube reactor was studied between 1000 °C and 1400 °C, both with experiments and simulations using a comprehensive model. Particular attention was paid to the influence of steam on the gasification process, and to the wood particle size. The model included a description of the different phenomena involved in biomass conversion: pyrolysis, gas phase reactions, soot formation and carbonaceous solid gasification. Satisfactory results were obtained in comparison with experiments. The addition of steam in the atmosphere influenced char, tar, soot and gas yields, especially at 1200°C and 1400°C. These changes were linked to char and soot steam gasification, and to gas phase reactions, among which hydrocarbons steam reforming and water-gas shift. At 1400°C, with 25 mol% H$_2$O and after a residence time of 4.4 s, the char seems to be completely gasified, while the soot yield still represents about 5 wt% of the initial dry biomass. Wood particle size in the range 0.35-0.80 mm was experimentally shown to have no influence on products yields for a residence time of a few seconds.

Wood sawdust gasification experiments were performed in a steam fluidized bed at 800 °C between 2 and 10 bar. An evolution of gas yields with time was measured during the tests, and especially an increase of hydrogen and carbon dioxide yields. This test duration effect was ascribed to char build-up in the bed. As tests proceed, the contribution of char steam gasification to gas yield increases, and the catalytic effect of char on hydrocarbons and tar conversion and on water–gas shift reaction is enhanced. As total pressure increases from 2 to 10 bar, hydrogen, carbon dioxide and methane yields increase by 16%, 53% and 38% respectively, whereas carbon monoxide yield decreases by 33%. The changes in gaseous yields with pressure can be partly explained by the influence of pressure on gas phase reactions (acceleration of water–gas shift kinetics and change in hydrocarbon reactions). The increase of methane yield with pressure is rather suggested to be linked to a change in secondary pyrolysis reactions scheme under high pressure.

International audience; Biomass gasification in Entrained Flow Reactor (EFR) is both studied with experiments in a drop tube reactor and modelling with a 1-D model (GASPAR). Operating conditions are chosen thanks to results of a preliminary modelling of an industrial EFR. Influence of addition of steam (0.55 g/g db), carbon dioxide (0.87 g/g db) and oxygen (Equivalent Ratio: 0-0.61) is investigated between 800 and 1400 degrees C with beech wood particles sieved between 315 and 450 mu m as feedstock. The model takes into account pyrolysis reaction, gas phase reaction with a detailed chemical scheme (176 species, 5988 reactions), char gasification by steam and CO2 and soot formation. H2O or CO2 addition has no influence on gasification product yields at 800 and 1000 degrees C, while at 1200 and 1400 degrees C the char gasification is significantly enhanced and soot formation is certainly inhibited by OH radical which reacts with soot precursors. The modification of output gas phase composition is mostly due to WGS reaction which reaches thermodynamic equilibrium from about 1200 degrees C. As expected, O-2 has a significant influence on gas and tar yields through combustion reactions. Char and soot yields decrease as ER increases. The GASPAR model allows a good prediction of gas and char and gives relevant evolution of soot and tar yields on the large majority of conditions studied.

International audience; Fast pyrolysis of wood was conducted in a drop tube furnace to study the influence of temperature (1000-1200-1400 degrees 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 degrees 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 degrees C, the drastic hydrocarbons decomposition, emphasized with temperature, leads to high yields in soot, H-2 and CO. At 1200 degrees C, no tar are detected; at 1400 degrees C only low amounts of CH4 and C2H2 still remain. Under the explored conditions, char and soot gasification with H2O and CO2, 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.

International audience; The present study investigates the thermochemical conversion of solid recovered fuel, represented by selected “model materials”. A laboratory-scale induction heated device was specifically developed to achieve gasification conditions close to those encountered in a fluidized bed reactor. The novel device can handle up to 5 grams of solid, allowing fast heating rates (near 70°C/s) and a homogeneous distribution of temperature all along the reactor. Pyrolysis tests of a SRF sample and four model materials (Polyethylene (PE), Polyethylene Terephthalate (PET), beech wood, cardboard) were performed at 800°C. The yield and composition of the produced gas for each sample were determinated. Experimental results will help to elucidate the relation between the initial components of waste derived fuels and the obtained reaction products.