• Energy Research

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: Fernandez Brizuela, Anabel Alejandra. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; Argentina. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; Argentina

A macro-thermogravimetric analysis (macro-TGA) was applied to analyse the non-isothermal drying of different bio-wastes (quince solid waste, grape marc and pumpkin shell from different enterprises located in San Juan Province, Argentina). The experimental data were obtained at three heating rates (5, 10 and 15 K/min) and two different initial moisture contents (30 and 50% w/w). These data were fitted using the Coats-Redfern and Sharp methods. The D2 model showed the best fitting for all experiments when using the Coats-Redfern method. It is assumed that drying occurs on the solid boundary. The predicted Ea values ranged from 43.60 to 64.50 kJ/mol for the three bio-wastes under the different experimental conditions. The Ea value slightly increases with the increase in heating rate because the wastes require more energy to undergo drying. Deff increases moderately with temperature at the beginning of the dehydration process; then, this increasing behaviour is significant due to the loss of continuous moisture channels. Otherwise, Deff increases with the initial moisture content, showing that the humidity of the samples did not reach the saturation content.

Abstract Bed collapse experiments are interpreted by a three-phase model of a gas-fluidized bed. Application of the model leads to a relationship between bed voidage in the sedimentation zone of the collapse and the properties of the emulsion and bubble phases of the bed prior to the collapse. Experimental results show that for beds of small particles fluidized under pressure the flow of gas through the emulsion phase is higher than that expected on the basis of existing theories, but it is shown that average rise velocities of bubbles may be obtained from results of bed collapse measurements.

In the search for greater efficiency and storage capacity improvements in solar energy concentration plants, a new concept for fluid transfer was proposed. This concept consists of a dense suspension of SiC particles (dp = 6.4 × 10−5 m) that is air fluidized, which allows operation at higher temperatures than the fluids currently used, such as molten salts, water, oils and air. The suspension, as a fluid, also provides energy storage. The upward flow of the SiC–air suspension inside a steel tube is achieved using a circulating fluidized bed dense regime. Concentrated solar radiation impinges the walls of the tube, increasing the temperature of the granular material up to 200–250 °C. The system in this study is part of a prototype in the PROMES Laboratory in France. Maintaining low fluidization velocities guarantees high solid fractions throughout the tube (0.28–0.45). This study simulates heat transfer between the wall and the suspension using computational fluid dynamics (CFD) (ANSYS-Fluent 14.5) for different operating conditions. The Euler–Euler model is used as the multi-phase model. The average experimental temperature in the emulsion at the exit of the heat transfer zone compares well with the temperature obtained in the CFD simulation. The global heat transfer coefficients obtained in the simulation are in good agreement with those obtained experimentally for all operating conditions. These results show that the developed simulation approach is a good representation of the real process and provides relevant information related to the movement of particles in the tube and its relation to heat transfer in the prototype.

The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles' combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature.

Spent grains from microbreweries are mostly formed by malting barley (or malt) and are suitable for a further valorization process. Transforming spent grains from waste to raw materials, for instance, in the production of nontraditional flour, requires a previous drying process. A natural convection solar dryer (NCSD) was evaluated as an alternative to a conventional electric convective dryer (CECD) for the dehydration process of local microbrewers’ spent grains. Two types of brewer’s spent grains (BSG; Golden ale and Red ale) were dried with both systems, and sustainability indices, specific energy consumption (eC), and CO2 emissions were calculated and used to assess the environmental advantages and disadvantages of the NCSD. Then, suitable models (empirical, neural networks, and computational fluid dynamics) were used to simulate both types of drying processes under different conditions. The drying times were 30–85 min (depending on the drying temperature, 363.15 K and 333.15 K) and 345–430 min (depending on the starting daytime hour at which the drying process began) for the CECD and the NCSD, respectively. However, eC and CO2 emissions for the CECD were 1.68–1.88 · 10−3 (kW h)/kg and 294.80–410.73 kg/(kW h) for the different drying temperatures. Using the NCSD, both indicators were null, considering this aspect as an environmental benefit.

Abstract The growing interest in syngas production from biomass has extended research towards solar-driven pyrolysis taking place at high temperature and heating rate, due to its high efficiency and environmental advantages. The aim of this work is to experimentally study and compare the effect of pellet size (5, 10 and 15 mm height) on product yields (liquid, char and gas), gas composition (H2, CO, CO2, CH4) and tar secondary reactions during fast solar pyrolysis of sawdust pellets (800, 1200 and 1600 °C and heating rates of 10 and 50 °C/s). Additionally, the influence of pellet height on syngas quality is analyzed by parameters such as H2/CO, CH4/H2 ratios, mechanical gas efficiency and carbon conversion efficiency, focused on methanol production. An analysis based on characteristic times and dimensionless numbers is also performed to estimate the rate-controlling phenomena. Experimental results showed that, for temperatures below 1200 °C, there were no significant differences in the gas yield for the three pellet heights. However, the gas product distribution was influenced by the pellet size even at 800 °C. A further increase in temperature emphasized the influence of the pellet height on both gas yield and gas composition. Therefore, it can be argued that, in order to improve the gas yield and the quality of the syngas, the fast pyrogasification of large particles is advisable.