Carbonisation hydrothermale | EPFL Graph Search

thumb|Nanobilles de carbone issu de 6 heures de carbonisation hydrothermale de Glucose (images produite par l'Université de Tartu. La carbonisation hydrothermale (carbonisation aqueuse à température et pression élevées ; en anglais, hydrothermal carbonization ou HTC) est un procédé physicochimique de conversion de composés organiques en charbon structuré. Elle permet de transformer de la biomasse (déchet ou non) en un produit dit « biocharbon » (ou plus précisément ou ) via un processus thermochimique entretenu dans des conditions anoxiques (sans contact avec l'air, grâce à l'eau utilisée comme milieu de réaction). Ce processus imite techniquement et en quelques heures la formation de charbon brun (« coalification ») qui dans la nature se déroule sur à d'années. Ce biocharbon est présenté comme neutre en carbone. Il peut servir de combustible et être produit par une bioraffinerie. Comme pour le biochar issu de pyrolyse sèche, certains espèrent pouvoir produire un hydrochar aux v

Optimal Process Design for Power Production from Wet Waste Biomass by Hydrothermal Gasification coupled to a Solid Oxide Fuel Cell

This report presents a system analysis of the production of electricity from wet waste biomass. A system of Hydrothermal Gasification is coupled with a Hybrid Cycle composed by a SOFC and two Gas Turbines, driven in an inverted Brayton--‐Joule cycle. A thermodynamic optimization approach, based on the system energy integration, is used to analyze several configuration options. The influence of the process design on performances is discussed for the most representative scenario that highlights the key aspects of the system. Optimization results prove that a systematic system design may reaches efficiencies higher than 60%.

2011

Production of Algae for Biomaterials and Bioenergy: Closing the Nutrient Cycle and Enhancing the Light Utilisation Efficiency

Eya Nicodeme

Microalgae are small organisms that live in water and use solar energy or artificial light to grow. They are emerging to be one of the most promising long-term, sustainable sources of biomass for fuel, food, feed, and other high valuable co-products. Like any other plant, algae, when grown using sunlight consume carbon dioxide (CO2) and release oxygen (O2), but with a 5 to 10 times faster growth rate than conventional food crops. Thus, algae-based CO2 conversion is considered as a cost-effective option for CO2 capture and the mitigation of greenhouse gas emissions (GHG). Since the last decade, there have been repeated attempts to bring microalgae bioenergy and biomaterial production to an industrial level. So far, despite the enthusiastic boost towards commercialisation, the production of microalgae has been demonstrated mainly at pilot scale levels, and only a few large-scale facilities exist and produce microalgae today. There are several issues related to microalgae cultivation from either the energetic, environmental or economical point of view. Further developments are needed for algal biomass technologies to improve their cost-competitiveness and their environmental sustainability. The major bottlenecks are mainly linked to water and nutrient supply, the high energy consumption of algal processing, the high surface area requirements for cultures, and finally, the relatively low solar conversion efficiency of microalgae in highly sunny regions. Therefore, to design economically feasible algae production processes, it is necessary to close the nutrient cycle, to reach the energy balance, and to opt for a biorefinery concept where products can be valorised. This doctoral thesis aims to explore a new concept, PAWaSto, which attempts to overcome the limitations of microalgae production processes by combining different technologies to increase the energy and nutrient recoveries within the system. An urban environment was considered in the PAWaSto vision. This work focuses on four different research approaches which can be summarised as follows: (1) As low-cost water and nutrient supply source is critical to the success of microalgae production, a unique on-site sanitation system for nutrient and water recoveries (household effluents) was studied in this thesis. (2) Energy and nutrient recycling: The integration of a hydrothermal process (HT) for a fast conversion of household effluents to concentrated nutrient-rich effluents, free of pathogens, suitable for algae production was proposed. Besides, the produced energy-rich gas obtained from the HT is considered for electricity generation through a solid oxide fuel cell (SOFC). (3) The implementation of semi-transparent dye sensitised solar systems (DSCs) on the illuminated surface of an algae photobioreactor, and their effect on the algal biomass productivity was studied for the first time in this thesis. (4) Finally, for the economic viability of algal biomass production, the extraction of high-value products from wet algal biomass using green solvent was proposed, and the residual biomass generated from the extraction step was further treated through a HT process. Overall this doctoral research project studied key aspects for the integration of a biorefinery concept in urban areas contributing to the big vision of closing the materials cycles on the level of districts. A focus was put on an integrated system for efficient microalgae production, power generation, and closing the nutrient cycle.

EPFL2020

Preparation and Characterization of High-Surface-Area Bi(1-x)/3V1-xMoxO4 Catalysts

Lioubov Kiwi, Alexandre Nell

We report the successful application of a templating approach employing ordered mesoporous carbon to the synthesis of BiVO4, Bi2Mo3O12, and Bi0.85V0.55Mo0.45O4 and the performance of these materials as catalysts for the oxidation of propene to acrolein. Ordered mesoporous carbon templates were used to control the nucleation and growth of the mixed metal oxide crystals, allowing higher final surface areas to be obtained. The resulting materials were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and BET surface area analysis. The surface area of the mixed metal oxide catalysts was found to depend on the type of mesoporous silica used to prepare the carbon template and on the conditions under which the carbon template was formed. Through an appropriate choice of template, the surface areas of the mixed metal oxides exceeded 15 m(2)/g. Catalytic testing revealed that materials produced via templating in ordered mesoporous carbon had per-gram activities that were up to 85 times higher than those produced by a conventional hydrothermal synthesis and exhibited stable catalytic activities over 24 h.

American Chemical Society2014

Production of Algae for Biomaterials and Bioenergy: Closing the Nutrient Cycle and Enhancing the Light Utilisation Efficiency

Eya Nicodeme

EPFL2020