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Carbon-neutral synfuel production via continuous solar H2O and CO2 gasification of oil palm empty fruit bunch
(2023-10-15)
Chuayboon, Srirat
;
Abanades, Stéphane
Solar gasification offers a promising carbon-neutral pathway to thermochemically convert waste biomass and solar energy into synfuel. In this study, a thermodynamic analysis of solar gasification of oil palm empty fruit bunch (EFB) with H<inf>2</inf>O and CO<inf>2</inf> gasifying agents was first performed to predict equilibrium product distribution. Subsequently, on-sun continuous solar gasification of EFB was experimentally carried out in a solar particle-fed gasifier to evaluate the influence of gasifying agent types (H<inf>2</inf>O and CO<inf>2</inf>), gasifying agent/EFB molar ratios (1.8–3.4), temperatures (1050–1350 °C), and to assess overall process feasibility and reliability. As a result, solar EFB gasification performed efficiently with both H<inf>2</inf>O and CO<inf>2</inf> gasifying agents under continuous on-sun operation. Syngas product composition and gasification reaction rate strongly depended on gasifying agent type. Increasing temperature enhanced syngas yield and quality, and changed the CO/H<inf>2</inf> mole ratio, especially in EFB + CO<inf>2</inf> gasification. A gasifying agent/EFB molar ratio of 2.6 (slight excess of gasifying agents) and a temperature of 1300 °C were shown to be optimal for continuous solar EFB gasification. The maximum total syngas yield above 76 mmol/g<inf>dry_EFB</inf>, syngas lower heating value above 22 kJ/g<inf>dry_EFB</inf>, and energy upgrade factor above 1.37 were achieved from both EFB + H<inf>2</inf>O and EFB + CO<inf>2</inf> gasification, which closely approached their theoretical equilibrium values. The maximum carbon conversion exceeding 93% and solar-to-fuel energy conversion efficiency up to 19.3% were achieved, demonstrating efficient EFB-to-synfuel conversion performance. Continuous solar EFB gasification with both H<inf>2</inf>O and CO<inf>2</inf> was thus established to be a reliable process for EFB waste biomass valorization into high-quality and carbon-neutral synfuel.
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Continuous solar-driven gasification of oil palm agricultural bio waste for high-quality syngas production
(2022-12-01)
Chuayboon, Srirat
;
Abanades, Stéphane
Empty fruit bunch (EFB) from oil palm is a solid agricultural bio-waste obtained from the edible oil process. Continuous solar-driven gasification of EFB offers a bright carbon–neutral avenue to convert both EFB bio-waste and renewable solar energy into sustainable and clean syngas. High-temperature concentrated solar heat is used to provide the reaction enthalpy, and therefore biomass waste feedstock is entirely dedicated to produce hydrogen and carbon monoxide (syngas). Solar energy is stored as a high-quality syngas and can be easily transported as a convertible and dispatchable chemical form. In this study, the performance of continuous steam gasification of EFB, fully powered by concentrated solar heat, was experimentally investigated in a solar gasification reactor. Experiments were carried out with continuous EFB biomass injection to evaluate the influence of temperature (1100–1300 °C) and biomass feeding rate (0.5–1.8 g/min). As a result, syngas yields and reactor performance were substantially enhanced by rising the EFB feeding rate and gasification temperature. An optimal EFB biomass feeding rate enabling maximum gasification performance was found to be 1.4 g/min at 1300 °C and 1.0 g/min at 1200 °C. Carbon conversion approaching 97%, energy upgrade factor of 1.38, and solar-to-fuel energy conversion efficiency up to 20% were demonstrated. Finally, the maximum syngas yield was found to be 81.1 mmol/g<inf>dry biomass</inf> at 1300 °C (with H<inf>2</inf> and CO as the main constituents), closely approaching the maximum theoretical expected value reached at thermodynamic equilibrium (85.2 mmol/g<inf>dry biomass</inf>). Combining concentrated solar energy and biomass waste gasification was shown to be a promising and sustainable pathway toward waste valorization into carbon–neutral solar fuels.
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Solar chemical looping gasification of biomass with the ZnO/Zn redox system for syngas and zinc production in a continuously-fed solar reactor
(2018-03-01)
Chuayboon, Srirat
;
Abanades, Stéphane
;
Rodat, Sylvain
The high-temperature solar-driven chemical looping gasification of lignocellulosic biomass with ZnO/Zn redox pair was investigated as a novel process producing both syngas and metallic zinc. A lab-scale solar reactor (1.5 kW) was operated for continuous combined biomass gasification and ZnO carbo-thermal reduction using solar energy as the source of high-temperature process heat. Experiments were performed at temperatures ranging from 1050 °C to 1300 °C with biomass/ZnO molar ratios from 0.5 to 1, using beech wood as a biomass feedstock. The objective of this study was to unveil the advantages and reliability of the combined process involving biomass pyro-gasification with solid ZnO as an oxidizing agent under continuous process operation for co-production of syngas and metallic Zn. The influence of temperature and reactant molar ratio on syngas production was highlighted and compared to the case of a pyrolysis process without any oxidant. Moreover, the chemical conversion of ZnO to Zn obtained by this endothermic step was also addressed, confirming pure Zn production with low recombination in the collected solid products. The evolved H<inf>2</inf> increased significantly, CO production also tended to increase slightly, while CO<inf>2</inf> and CH<inf>4</inf> decreased when increasing the temperature. The syngas yield of the combined gasification/carbo-thermal reduction (up to ∼8 mol<inf>syngas</inf>/mol<inf>biomass</inf> for a biomass/ZnO molar ratio of 0.75 at 1250 °C) was much higher in comparison with pyrolysis. The calorific value of the feedstock was solar up-graded through syngas and Zn production in the case of the biomass gasification using ZnO, whereas pyrolysis was not energetically efficient because of the energy content still remaining in the produced char. The optimal biomass/ZnO molar ratio was evidenced at 0.75 yielding maximum syngas production. The energy upgrade factor of the feedstock by the solar power input and the solar-to-fuel energy conversion efficiency were 1.17 and 19.8% respectively for a molar ratio of 0.75 at 1250 °C.
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Experimental analysis of continuous steam gasification of wood biomass for syngas production in a high-temperature particle-fed solar reactor
(2018-03-01)
Chuayboon, Srirat
;
Abanades, Stéphane
;
Rodat, Sylvain
Solar steam gasification of beech wood biomass has been performed in a novel high-temperature continuously-fed solar reactor for the thermochemical conversion of low-grade carbonaceous feedstock into transportable and storable gaseous fuels (syngas). The 1.5 kW<inf>th</inf> cavity-type solar reactor was operated in the temperature range of 1100–1300 °C. Large wood biomass particles (3–5 mm size) were continuously fed and gasified with the oxidizing agent to produce syngas, thus demonstrating the reactor suitability for large particle size processing. Operating parameters were varied in order to optimize the syngas production. The effect of steam flow-rate, carrier gas flow-rate, temperature, and biomass feeding rate on the syngas yield and reactor performances was experimentally investigated. The increase of steam flow-rate favored H<inf>2</inf>, CO<inf>2</inf> and CH<inf>4</inf> and reduced CO production. A noteworthy increase of the syngas yield with the temperature was highlighted, while the increase of carrier gas flow-rate was detrimental to the amount of syngas produced because of lowered gas residence time. The increase of biomass feeding rate (in the range of 0.8–1.8 g/min) showed noteworthy impact on the syngas composition without affecting the reactor performance, yielding high-quality syngas with a carbon conversion rate above 80%, while the total syngas yield was stable at about 70 mmol/g<inf>biomass</inf>.

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