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The aim of this work is to investigate the fluidised bed gasification of several pure and blended feedstock prepared in the form of pellets: oak bark, two bark/wheat straw blends (85/15 and 50/50 wt%) and lignin residue remaining from bioethanol production. Gasification conditions were defined to be representative of dual fluidised bed ones (steam gasification at 850 °C, followed by air combustion of the char). The cold gas efficiency (77–81%), gas composition and tar content (0.9–2.3 g/kgdaf) are close for the gasification of bark and the two bark/wheat straw blends. For lignin residue, the cold gas efficiency is lower (71%), and the tar content is 9.1 g/kgdaf. The agglomeration propensity is much higher for lignin residue than for the other feedstock. This was put into evidence with in-bed temperature measurements at different levels, and confirmed with post-test size screening of the bed material particles. The 50/50 wt% bark/wheat straw blend seems to undergo defluidisation in combustion, however followed by refluidisation of the bed. These findings were also well correlated with a predictive model for defluidisation.

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.

The use of concentrated solar energy as the high-temperature heat source for the thermochemical gasification of biomass is a promising prospect for producing CO2-neutral chemical fuels (syngas). The solar process saves biomass resource because partial combustion of the feedstock is avoided, it increases the energy conversion efficiency because the calorific value of the feedstock is upgraded by the solar power input, and it also reduces the need for downstream gas cleaning and separation because the gas products are not contaminated by combustion by-products. A new concept of solar spouted bed reactor with continuous biomass injection was designed in order to enhance heat transfer in the reactor, to improve the gasification rates and gas yields by providing constant stirring of the particles, and to enable continuous operation. Thermal simulations of the prototype were performed to calculate temperature distributions and validate the reactor design at 1.5 kW scale. The reliable operation of the solar reactor based on this new design was also experimentally demonstrated under real solar irradiation using a parabolic dish concentrator. Wood particles were continuously gasified at temperatures ranging from 1100 °C to 1300 °C using either CO2 or steam as oxidizing agent. Carbon conversion rates over 94% and gas productions over 70 mmol/gbiomass were achieved. The energy contained in the biomass was upgraded thanks to the solar energy input by a factor of up to 1.21.

International audience; Solar energy is the most abundant renewable energy source on earth and its contribution in the energy mix is growing fast, especially for electricity production via photovoltaic panels and to a lesser extent for concentrated solar energy. However, concentrated solar energy can also provide high temperature heat for process applications. Solar fuels are envisioned as alternative fuels that would enable long term storage and transport of solar energy. Solar thermochemical gasification of lignocellulosic biomass has been investigated in this objective. The use of concentrated solar energy as the external heat source for the high-temperature reaction allows producing high-value syngas with both higher energy conversion efficiency and reduced cost of gas cleaning and separation, while saving biomass feedstock. A 1.5 kW(th) solar reactor was successfully tested for continuous solar driven gasification of millimetric wood particles under real solar irradiation using a parabolic dish concentrator. Investigated temperatures ranged from 1100 degrees C to 1400 degrees C. The influence of temperature, oxidizing agent nature (H2O or CO2), heating configuration (direct or indirect irradiation), on gas yield and energy conversion efficiency was investigated. The syngas yield drastically increased with the temperature for both steam and CO2 gasification, while increasing the steam content favored H-2 production over CO. Continuous biomass conversion was demonstrated with a global solar-to-fuel energy conversion efficiency of 26% at 1300 degrees C and a cold gas efficiency as high as 1.16, confirming efficient solar up-grade of the feedstock energy content.

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; The synthesis gas stemming from biomass gasification contains particles (ashes, soot, etc.), which, if not removed, can induce severe operational damage. The problem is more serious if syngas must be used for chemical synthesis as in the Fischer-Tropsch catalyst reaction or the water–gas shift. The particles contained in syngas can reduce or inhibit the catalyst effect. Moreover, for energy reasons, it is also necessary to develop a filtration process at as high a temperature as possible. To address this issue, a study to show the possibility of removing the particles from syngas with an electrostatic precipitator at high temperature (500–1000 °C) and pressure (0.1–1 MPa) was conducted. Syngas filtration tests conducted directly downstream of a gasifier demonstrated the feasibility of implementing an electrostatic precipitator to clean syngas at temperatures above 500 °C.