• Energy Research

Previous studies proved the Dense Particle Suspension (DPS) - also called Upward Bubbling Fluidized Bed (UBFB) - could be used as Heat Transfer Fluid (HTF) in a single-tube solar receiver. This article describes the experiments conducted on a 16-tube, 150 kWth solar receiver using a dense gas-particle suspension (around 30% solid volume fraction) flowing upward as HTF. The receiver was part of a whole pilot setup that allowed the continuous closed-loop circulation of the SiC particles used as HTF. One hundred hours of on-sun tests were performed at the CNRS 1 MW solar furnace in Odeillo. The pilot was tested under various ranges of operating parameters: solid mass flow rate (660–1760 kg/h), input solar power (60–142 kW), and particle temperature before entering the solar receiver (40–180 °C). Steady states were reached during the experiments, with continuous circulation and constant particle temperatures. For the hottest case, the mean particle temperature reached 430 °C in the collector fluidized bed, at the receiver outlet, and it went up to 700 °C at the outlet of the hottest tube, during steady operation. A temperature difference between tubes is observed that is mainly due to the incident solar flux distribution heterogeneity. The thermal efficiency of the receiver, defined as the ratio of power transmitted to the DPS in the form of heat over solar power entering the receiver cavity, was calculated in the range 50–90% for all the experimental cases. The system transient responses to variations of the solar irradiation and of the solid mass flow rate are also reported.

Abstract Solar pyrolysis of a carbonaceous feedstock (coal, biomass and wastes) is a process in which carbon-containing feedstocks are used as chemical reactants and solar energy is supplied as high-temperature process heat. This process has the potential to produce higher calorific value products with lower CO 2 emissions than conventional pyrolysis processes. As a consequence, the intermittent solar energy is chemically stored in the form of solar fuels. Solar pyrolysis was first demonstrated in an indoor environment using a solar simulator (image furnace) for exploring the fundamental mechanisms of carbonaceous feedstock pyrolysis under severe radiative conditions (high temperatures and heating rates) in comparison to conventional pyrolysis. More recently, low-temperature solar pyrolysis has been demonstrated to be a good technology for bio-oil production. Our high-temperature solar pyrolysis process produces more combustible gas products than other processes. This paper reviews developments in the field of solar pyrolysis processing by considering fundamental mechanisms, experimental demonstrations, models and challenges.

Une utilisation alternative et durable des déchets de fumier de chameau a été étudiée dans cette étude. Les caractéristiques de dégradation par pyrolyse de la bouse de chameau ont été étudiées à l'aide d'un analyseur thermogravimétrique et comparées au comportement de décomposition par gazéification de la bouse. Les analyses de pyrolyse ont été effectuées à des vitesses de chauffage de 10, 20 et 50 K/min de la température ambiante à 1173 K sous une atmosphère inerte de N2. La cinétique pyrolytique a été estimée à l'aide de différents modèles tels que Coats-Redfern, Friedman, Distributed activation energy, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa et Starink. Les valeurs moyennes de l'énergie d'activation étaient cohérentes (162–172 kJ/mol) pour tous les modèles. La comparaison de la cinétique de pyrolyse avec la cinétique de gazéification a indiqué que la bouse de chameau nécessite plus d'énergie d'activation pour la décomposition de la pyrolyse. Les valeurs estimées de l'énergie d'activation et l'équation de Kissinger ont été utilisées pour déterminer les propriétés thermodynamiques telles que l'énergie libre de Gibbs, l'enthalpie et l'entropie. L'énergie libre de Gibbs et les valeurs d'enthalpie de la dégradation par pyrolyse étaient plus faibles que dans le cas de la décomposition par gazéification. Les détails de ces paramètres cinétiques et propriétés thermodynamiques sont vitaux pour la conception et la fabrication des réacteurs de pyrolyse. En este estudio se ha investigado una utilización alternativa y sostenible de los desechos de estiércol de camello. Las características de degradación por pirólisis del estiércol de camello se han investigado utilizando un analizador termogravimétrico y se han comparado con el comportamiento de descomposición por gasificación del estiércol. Los análisis de pirólisis se realizaron a velocidades de calentamiento de 10, 20 y 50 K/min desde temperatura ambiente hasta 1173 K en una atmósfera inerte de N2. La cinética pirolítica se estimó utilizando diferentes modelos como Coats-Redfern, Friedman, energía de activación distribuida, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa y Starink. Los valores medios de energía de activación fueron consistentes (162–172 kJ/mol) para todos los modelos. La comparación de la cinética de la pirólisis con la cinética de la gasificación indicó que el estiércol de camello requiere más energía de activación para la descomposición de la pirólisis. Los valores estimados de energía de activación y la ecuación de Kissinger se utilizaron para determinar las propiedades termodinámicas como la energía libre de Gibbs, la entalpía y la entropía. Los valores de energía libre de Gibbs y entalpía de la degradación por pirólisis fueron menores que en el caso de la descomposición por gasificación. Los detalles de estos parámetros cinéticos y propiedades termodinámicas son vitales para el diseño y la fabricación de reactores de pirólisis. An alternate and sustainable utilisation of camel dung waste has been investigated in this study. The pyrolysis degradation characteristics of camel dung have been investigated using a thermogravimetric analyser and the same has been compared with the gasification decomposition behaviour of the dung. The pyrolysis analyses were performed at heating rates of 10, 20, and 50 K/min from room temperature to 1173 K under an inert N2 atmosphere. The pyrolytic kinetics were estimated using different models such as Coats-Redfern, Friedman, Distributed activation energy, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Starink. The average activation energy values were consistent (162–172 kJ/mol) for all the models. Comparison of pyrolysis kinetics with gasification kinetics indicated that the camel dung requires more activation energy for the pyrolysis decomposition. The estimated activation energy values and the Kissinger equation were used to determine the thermodynamic properties such as Gibbs free energy, enthalpy, and entropy. The Gibbs free energy and enthalpy values of the pyrolysis degradation were lower than in the case of the gasification decomposition. The details of these kinetic parameters and thermodynamic properties are vital for the design and fabrication of pyrolysis reactors. تم التحقيق في استخدام بديل ومستدام لنفايات روث الإبل في هذه الدراسة. تم التحقيق في خصائص تحلل الانحلال الحراري لروث الإبل باستخدام محلل قياس الجاذبية الحرارية وتمت مقارنة ذلك مع سلوك تحلل التغويز للروث. تم إجراء تحليلات الانحلال الحراري بمعدلات تسخين 10 و 20 و 50 كلفن/دقيقة من درجة حرارة الغرفة إلى 1173 كلفن تحت جو N2 خامل. تم تقدير حركية الانحلال الحراري باستخدام نماذج مختلفة مثل Coats - Redfern و Friedman و Distributed activation energy و Kissinger - Akahira - Sunose و Flynn - Wall - Ozawa و Starink. كان متوسط قيم طاقة التنشيط ثابتًا (162–172 كيلو جول/مول) لجميع النماذج. تشير مقارنة حركية الانحلال الحراري مع حركية التغويز إلى أن روث الجمل يتطلب المزيد من طاقة التنشيط لتحلل الانحلال الحراري. تم استخدام قيم طاقة التنشيط المقدرة ومعادلة كيسنجر لتحديد الخصائص الديناميكية الحرارية مثل طاقة جيبس الحرة، والمحتوى الحراري، والإنتروبيا. كانت قيم طاقة جيبس الحرة والمحتوى الحراري لتحلل الانحلال الحراري أقل مما كانت عليه في حالة تحلل التغويز. تعد تفاصيل هذه المعلمات الحركية والخصائص الديناميكية الحرارية حيوية لتصميم وتصنيع مفاعلات الانحلال الحراري.

Fil: Zeng, Kuo. Centre National de la Recherche Scientifique; Francia. Processes Materials and Solar Energy Laboratory; Francia

Abstract This study presents a thermodynamic model for describing the five wastes gasification behavior with char and tar formation. Influence of variables process on the exergetic efficiency and sustainability index was considered. In order to validate, carbon monoxide release was registered and a good fit was determined. Considering the CO content in the syngas, at 850 °C, the maximum value was observed for the marc (CO mole-percentage = 17.77%) and the minimum concentration was founded for the Pistacia vera kerman’s mesocarp (CO mole-percentage = 11.37%). However, at 650 °C, the maximum CO content was observed for the Pistacia vera kerman’s exocarp (CO mole-percentage = 9.8%) and the minimum value was founded for the Pistacia vera kerman’s mesocarp (CO mole-percentage = 4.28%). Marcs has the highest exergetic efficiency, and pistachio exocarp, the lowest value. Exergetic efficiency and sustainability index decrease increasing the equivalence ratio, but, increasing the temperature; these parameters augment. Higher exergetic efficiencies are obtained via air's use than air-steam mixture's use, which is attributable to the required energy to transform water into steam. Nevertheless, its influence on the exergetic efficiency and sustainability index is not very important.

The kinetics of the steam-assisted gasification for three different agro-industrial solid wastes (sawdust, olive and plum pits) was studied by macro thermo-gravimetric analysis (macro-TGA) at different heating rates (5, 10 and 15 K/min). The progressive CO release was moreover monitored to fully identify each step of the global gasification process. A single-step kinetics modelling was applied by using the Coats-Redfern method, with both a first order model for pyrolysis and a Ginstling - Brounstein 3D-diffusion model for the gasification stages, respectively. A comparison between macro-TGA and previous TGA results for the same bio-wastes was performed. Results indicated that the reaction proceeds in three well-defined and subsequent stages, involving water evaporation [298-473 K], biomass de-volatilization [473-648 K] with the highest production of CO, and char gasification as final step. Reaction rate parameters of the Arrhenius equation were determined for both the pyrolysis and gasification steps.

Fil: Toschi, Florencia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigacion y Desarrollo en Ingenieria de Procesos, Biotecnologia y Energias Alternativas. Universidad Nacional del Comahue. Instituto de Investigacion y Desarrollo en Ingenieria de Procesos, Biotecnologia y Energias Alternativas; Argentina

Solar pyrolysis of pine sawdust, peach pit, grape stalk and grape marc was conducted in a lab-scale solar reactor for producing fuel gas from these agricultural and forestry by-products. For each type of biomass, whose lignocellulose components vary, the investigated parameters were the final temperature (in the range 800°C–2000 °C) and the heating rates (in the range 10–150 °C/s) under a constant sweep gas flow rate of 6 NL/min. The parameter influence on the pyrolysis product distribution and syngas composition was studied. The experimental results indicate that the gas yield generally increases with the temperature and heating rate for the various types of biomass residues, whereas the liquid yield progresses oppositely. Gas yield as high as 63.5wt% was obtained from pine sawdust pyrolyzed at a final temperature of 2000 °C and heating rate of 50 °C/s. This gas can be further utilized for power generation, heat or transportable fuel production.