CARBURANTS SOLAIRES

International audienc

Production d'hydrogène et de noirs de carbone par décomposition thermique de gaz naturel dans des réacteurs solaires

This doctorate deals with an attractive way for a transition toward an hydrogen-based economy via solar natural gas dissociation. In the frame of the European SOLHYCARB project, it was proposed to investigate this process extensively. At CNRS-PROMES, two indirect heating solar reactors (20 and 50 kWth) were designed, built and tested at the 1 MW solar furnace focus. They consist of graphite cavity-type receivers approaching the blackbody behavior. The reaction is carried out in tubular sections inserted in the absorber. The 20 kW solar reactor was especially suitable to study the chemical reaction and methane conversion performances depending on the experimental conditions (mainly temperature and residencetime). A temperature increase enhances the methane conversion while a residence time increase improves the dissociation of C2H2, the main by-product. The Dsmoke kinetic code was validated for the simulation of methane dissociation. The 50 kW solar reactor was operated to produce significant amounts of carbon black for determining its properties and quality in the various possible commercial applications. The software Fluent® is used for the reactor energetic optimization. A 10 MWth scale industrial plant is studied through a flowsheet (Prosim®) and an economic analysis. The solar process can be competitive with conventional methods for hydrogen production: a hydrogen production cost of 1 $/kg (reference price for reforming) is reached for a CB selling price of 1.05$/kg (possible price for specialty carbon blacks).Ce travail de thèse propose une solution intéressante pour effectuer la transition vers une économie basée sur l’hydrogène via la dissociation solaire du gaz naturel. Dans le cadre du projet européen SOLHYCARB, ce procédé a été étudié extensivement. Au laboratoire CNRS PROMES,deux réacteurs solaires à chauffage indirect (20 et 50 kWth) ont été conçus, fabriqués et testés au foyer du grand four solaire de 1 MW. Ils sont constitués d’un récepteur en graphite qui approche le comportement du corps noir. La réaction est mise en oeuvre dans des sections tubulaires insérées dans l’absorbeur. Le réacteur solaire de 20 kW a essentiellement servi à l’étude de la réaction chimique et des performances en terme deconversion du méthane en fonction des conditions expérimentales (essentiellement la température et le temps de séjour). Une augmentation de température améliore la conversion du méthane tandis que l’augmentation du temps de séjour a un rôle important dans la dissociation de C2H2, le principal sous-produit. Le code cinétique Dsmoke a pu être validé pour la simulation de la réaction de craquage du méthane. Le réacteur solaire de 50 kW a été utilisé pour produire des quantités significatives de noirs de carbone afin d’analyser leurs propriétés et leur qualité pour des applications commerciales diverses. Le logiciel Fluent® a permis une optimisation énergétique du réacteur. Un procédé solaire industriel est étudié à l’échelle 10 MWth ; un plan de circulation des fluides est réalisé sur Prosim® et une analyse économique est menée. Le procédé solaire peut être compétitif avec les méthodes conventionnelles de production d’hydrogène : un coût de production de l’hydrogène de 1 $/kg (prix de référence pour le reformage) est atteint pour un prix de vente du noir de carbone de 1.05$/kg (prix possible pour les noirs de carbone spéciaux)

DAILY FORECASTS FOR FRESNEL POWER PLANT PRODUCTION

International audienc

Utilisation de l’énergie solaire à concentration pour les procédés solaires de reformage/craquage /gazéification /métallurgie /décarbonatation

Workshop ADEME ANCRE ANRInternational audienc

Production d hydrogène et de noirs de carbone par décomposition thermique de gaz naturel dans des réacteurs solaires

Ce travail de thèse propose une solution intéressante pour effectuer la transition vers une économie basée sur l hydrogène via la dissociation solaire du gaz naturel. Dans le cadre du projet européen SOLHYCARB, ce procédé a été étudié extensivement. Au laboratoire CNRS-PROMES, deux réacteurs solaires à chauffage indirect (20 et 50 kWth) ont été conçus, fabriqués et testés au foyer du grand four solaire de 1 MW. Ils sont constitués d un récepteur en graphite qui approche le comportement du corps noir. La réaction est mise en œuvre dans des sections tubulaires insérées dans l absorbeur. Le réacteur solaire de 20 kW a essentiellement servi à l étude de la réaction chimique et des performances en terme de conversion du méthane en fonction des conditions expérimentales. Une augmentation de température améliore la conversion du méthane tandis que l augmentation du temps de séjour a un rôle important dans la dissociation de C2H2, le principal sous-produit. Le code cinétique Dsmoke a pu être validé pour la simulation de la réaction de craquage du méthane. Le réacteur solaire de 50 kW a été utilisé pour produire des quantités significatives de noirs de carbone afin d analyser leur qualité. Le logiciel Fluent® a permis une optimisation énergétique du réacteur. Un procédé solaire industriel est étudié à l échelle 10 MWth ; un plan de circulation des fluides est réalisé sur Prosim® et une analyse économique est menée. Le procédé solaire peut être compétitif avec les méthodes conventionnelles de production d hydrogène : un coût de production de l hydrogène de 1 dollards/kg est atteint pour un prix de vente du noir de carbone de 1.05 dollards/kg.This doctorate deals with an attractive way for a transition toward an hydrogen-based economy via solar natural gas dissociation. In the frame of the European SOLHYCARB project, it was proposed to investigate this process extensively. At CNRS-PROMES, two indirect heating solar reactors (20 and 50 kWth) were designed, built and tested at the 1 MW solar furnace focus. They consist of graphite cavity-type receivers approaching the blackbody behavior. The reaction is carried out in tubular sections inserted in the absorber. The 20 kW solar reactor was especially suitable to study the chemical reaction and methane conversion performances depending on the experimental conditions. A temperature increase enhances the methane conversion while a residence time increase improves the dissociation of C2H2, the main by-product. The Dsmoke kinetic code was validated for the simulation of methane dissociation. The 50 kW solar reactor was operated to produce significant amounts of carbon black for determining its quality. The software Fluent® is used for the reactor energetic optimization. A 10 MWth scale industrial plant is studied through a flowsheet (Prosim®) and an economic analysis. The solar process can be competitive with conventional methods for hydrogen production: a hydrogen production cost of 1 dollards/kg is reached for a CB selling price of 1.05 dollards/kg.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Solar chemical looping reforming of methane combined with isothermal H2O/CO2 splitting using ceria oxygen carrier for syngas production

International audienceThe chemical looping reforming of methane through the nonstoichiometric ceria redox cycle (CeO 2 /CeO 2−δ) has been experimentally investigated in a directly irradiated solar reactor to convert both solar energy and methane to syngas in the temperature range 900-1050°C. Experiments were carried out with different ce-ria shapes via two-step redox cycling composed of endothermic partial reduction of ceria with methane and complete exothermic re-oxidation of reduced ceria with H 2 O/CO 2 at the same operating temperature, thereby demonstrating the capability to operate the cycle isothermally. A parametric study considering different ceria macrostructure variants (ceria packed powder, ceria packed powder mixed with inert Al 2 O 3 particles, and ce-ria reticulated porous foam) and operating parameters (methane flow-rate, reduction temperature, or sintering temperature) was conducted in order to unravel their impact on the bed-averaged oxygen non-stoichiometry (δ), syngas yield, methane conversion, and solar reactor performance. The ceria cycling stability was also experimentally investigated to demonstrate repeatable syngas production by alternating the flow between CH 4 and H 2 O (or CO 2). A decrease in sintering temperature of the ceria foam was beneficial for increasing syngas selectivity, methane conversion, and reactor performance. Increasing both CH 4 concentration and reduction temperature enhanced δ with the maximum value up to 0.41 but concomitantly favored CH 4 cracking reaction. The ceria reticulated porous foam showed better performance in terms of effective heat transfer, due to volumetric absorption of concentrated solar radiation and uniform heating with lower solar power consumption , thereby promoting the solar-to-fuel energy conversion efficiency that reached up to 5.60%. The energy upgrade factor achieved during cycle was up to 1.19. Stable patterns in the δ and syngas yield for consecutive cycles with the ceria foam validated material performance stability

Methane Cracking for Hydrogen Production: A Review of Catalytic and Molten Media Pyrolysis

Currently, hydrogen is mainly generated by steam methane reforming, with significant CO2 emissions, thus exacerbating the greenhouse effect. This environmental concern promotes methane cracking, which represents one of the most promising alternatives for hydrogen production with theoretical zero CO/CO2 emissions. Methane cracking has been intensively investigated using metallic and carbonaceous catalysts. Recently, research has focused on methane pyrolysis in molten metals/salts to prevent both reactor coking and rapid catalyst deactivation frequently encountered in conventional pyrolysis. Another expected advantage is the heat transfer improvement due to the high heat capacity of molten media. Apart from the reaction itself that produces hydrogen and solid carbon, the energy source used in this endothermic process can also contribute to reducing environmental impacts. While most researchers used nonrenewable sources based on fossil fuel combustion or electrical heating, concentrated solar energy has not been thoroughly investigated, to date, for pyrolysis in molten media. However, it could be a promising innovative pathway to further improve hydrogen production sustainability from methane cracking. After recalling the basics of conventional catalytic methane cracking and the developed solar cracking reactors, this review delves into the most significant results of the state-of-the-art methane pyrolysis in melts (molten metals and salts) to show the advantages and the perspectives of this new path, as well as the carbon products’ characteristics and the main factors governing methane conversion

Daily forecast of solar thermal energy production for heat storage management

International audienceSolar energy offers a renewable source of power but its fluctuating nature raises concerns about the electrical grid balancing. Network regulators have to estimate the upcoming production to match supply with demand; consequently, power plant operators may be asked to provide accurate forecasts. Planning the thermal or electrical output of solar power plants is thus highly required to ensure a stable power chain supply. This paper presents a solution that couples a meteorological model with a solar power plant performance model. The power output is predicted 24 h ahead in the case of a solar Fresnel power plant. The required Direct Normal Irradiance is inferred from the global horizontal irradiance; the thermal production is evaluated from an optical and thermal model. Our approach has been validated on a 1000 m 2 Fresnel power plant, paving the way for model-based storage strategy

Autothermal Hybridization of a High-Temperature Solar Biomass Gasifier

International audienc

Co-Production of Syngas and Zinc via Combined Solar-Driven Biomass Gasification and ZnO Carbo-Thermal Reduction in a Continuously-Operated Solar Reactor

International audienc