Desarrollo y ensayo de nuevos biocombustibles para motores diesel procedentes de diversas semillas oleaginosas y de grasas vegetales usadas

Diversos cambios socioeconómicos, medioambientales y políticos han auspiciado un creciente interés hacia el desarrollo de nuevas formas de energía. Un mercado de libre competencia requiere el cese paulatino de las políticas agrarias proteccionistas y la reduccion de los excedentes agroalimentarios que las propician. Por ello, la PAC, en la UE, exige el barbecho obligatorio de un porcentaje de las tierras de cultivo, salvo que se destine a fines energéticos. El aprovechamiento de estos terrenos para producir biodíesel se erige como una medida medioambiental a la par que socioecónomica. Por otro lado, los vertidos contaminantes a los acuiferos, entre los que se encuentran los aceites usados en las cocinas, destruyen las reservas de agua. Puesto que se trata de residuos tóxicos de dificil eliminación, su conversión en biodíesel se antoja notablemente atractiva. En este sentido, en la presente Tesis Doctoral, se definen los parametros óptimos que permiten la conversion en esteres metílicos, mediante transesterificación basica, del aceite procedente de semillas oleaginosas de colza etiope y del aceite de fritura. Se observa que resulta imposible efectuar una alcohólisis basica con aceite con alto contenido de acido erucico, mientras que si su presencia se anula, la reacción se produce si dificultades. La optimización de los parámetros implicados en la elaboración del biodíesel requiere 1,26% (del peso de aceite)de KOH, 12% de metanol y una temperatura entre 10 y 50 ºC, en caso de utilizarse aceites de desecho. Respecto al aceite de colza etiope sin acido erucico, se precisan 1,48% de KOH y 16% de metanol, entre 20 y 45ºC. Los esteres resultantes precisan purificación adicional, para lo que se han de lavar con agua destilada. Las propiedades como combustible son adecuadas. Los ensayos en motores Diesel, con el biodíesel procedente de aceite usado, proporcionan resultados satisfactorios, constatandose una leve disminución del 7% de la potencia al freno, asi como un aumento del consumo específico de combustible. La viabilidad económica queda sobradamente avalada. Por ello, se recomienda la utilización de ambas alternativas como sustitutas de los combustibles fósile

An Overview of Pyrolysis as Waste Treatment to Produce Eco-Energy

The aim of this review is to understand the progress in waste material management through pyrolysis to produce eco-energy. The growing demand for energy, combined with the depletion of traditional fossil fuels and their contribution to environmental problems, has led to the search for waste-to-energy technologies in pursuit of carbon neutrality. While municipal residues are only part of the waste management problem, the impact of discarded plastics on the environment and landfills is significant. Plastics not only take centuries to decompose, but also seriously pollute the oceans. Pyrolysis is a thermochemical process that allows for the thermal decomposition of waste in the absence of oxygen. There are several types of pyrolytic reactors, including batch and continuous ones. Batch reactors are preferred to process polymeric waste, with studies highlighting the importance of optimizing parameters, i.e., type of feedstock, heating rate, and pyrolysis temperature. Moreover, the choice of reactor type can influence the yield and structure of the final compounds. Furthermore, various studies have highlighted the gas heating value obtained through waste pyrolysis and how the composition of the liquid fraction is influenced by the type of polyethylene used. Though scientific interest in pyrolysis is remarkable, as publications have increased in recent years, kinetics studies are scarce. Overall, pyrolysis is a promising technique for managing waste materials to produce energy. Ongoing research and development in this area offer significant potential for improving the sustainability of waste management systems

Compatibility studies between an indirect injection diesel injector and biodiesel with different composition: Stationary tests

Compatibility between automotive materials and biodiesel is key for engine manufacturers, since failures occur in the medium term and may significantly reduce engine useful life. There are only few studies about compatibility between biodiesel and pure materials, but all agree there is biodiesel degradation and material corrosion beyond desirable values. This manuscript shows results about the compatibility behavior of an indirect injection diesel engine injector, with different types of biodiesel (from rapeseed, soybean, coconut and palm oil). Tests were carried out by static immersion of actual injector parts inside biodiesel, at room temperature, during 1100 h. To analyze elemental composition of each injector part and potential compatibility problems, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used. Visual variations were detected in both biodiesel and metals, showing the need of a further quantification of both piece mass loss and biodiesel acid value increase. Metallic oxides on the surface were detected by X-ray photoelectron spectroscopy (XPS). After immersion tests, mass variation in alloying elements of each piece (behaving differently depending on their composition), besides biodiesel acid value differences, were found. In this sense, pieces with aluminum alloys showed the highest corrosion (mass loss) compared to those without aluminum in their structure, no matter the unsaturation degree and chain length of biodiesel. In sum, there were not conclusive results about the influence of biodiesel composition over injector materials. However, it was found that European biodiesel standard EN 14214 should include other parameters than just copper band corrosion, to determine material deterioration, provided that aluminum alloys and other metals react with biodiesel

Universal Kinetic Model to Simulate Two-Step Biodiesel Production from Vegetable Oil

To date, to simulate biodiesel production, kinetic models from different authors have been provided, each one usually applied to the use of a specific vegetable oil and experimental conditions. Models, which may include esterification, besides transesterification simulation, were validated with their own experimental conditions and raw material. Moreover, information about the intermediate reaction steps, besides catalyst concentration variation, is either rare or nonexistent. Here, in this work, a universal mathematical model comprising the chemical kinetics of a two-step (esterification and transesterification) vegetable oil-based biodiesel reaction is proposed. The proposed model is universal, as it may simulate any vegetable oil biodiesel reaction from the literature. For this purpose, a mathematical model using the software MATLAB has been designed. Using the mathematical model, the estimation of mass variation with time, of both reactants and products, as well as glyceride conversion and homogeneous catalyst concentration variation (instead of only alcohol/catalyst solution) are allowed. Moreover, analysis of the influence of some important variables affecting the reaction kinetics of biodiesel production (e.g., catalyst concentration), along with comparison and model validation with data from different authors may be carried out. In addition, Supplementary material with a collection of 290 rate constants, derived from 55 different experiments using different vegetable oils and conditions is provided

Software público, libre, abierto, gratuito, privativo y comercial para la innovación y mejora de la calidad en la docencia, investigación, gestión y asistencia

The public free software (now renamed as open software) is the basis of the open source software (OSS) project. This initiative promotes the use of open standards and platform-independent accessibility. Many OSS products are free or low cost, which allows their deployment even in the absence of large economic resources (developing countries, schools, etc.). Besides, their source code can be modified, adapted and optimized by anyone, since it is public. Nevertheless, the OSS may also have drawbacks. Thus, its development may not be as orderly and hierarchical as the privative software is, and may not have an appropriate funding. This may jeopardize the ease of use and coherence of the final product, increasing the transition, training and technical support costs. Besides, it must be taken into account that there is also commercial open software, as well as free privative software. In any case, the excellence of the software may be independent of such variables. Thus, the best strategy is the coexistence and free competition of all kinds of software. This will allow a quality improvement and an innovation enhancement, which will benefit the education, research, management and assistance at the university in particular and at the whole society in general.El software público libre es el fundamento del movimiento de software de fuente abierta (OSS). Éste puede facilitar el uso de estándares abiertos, con accesibilidad independiente de plataforma informática. El bajo coste o gratuidad de muchos productos OSS permite su implantación cuando los recursos económicos son escasos (países en desarrollo, escuelas, etc.). Además, su código se puede modificar, adaptar y mejorar por cualquiera, ya que es público. No obstante, el OSS también puede presentar inconvenientes. Así, su desarrollo puede no ser tan ordenado y jerárquico como el del software privativo y puede no tener una financiación apropiada. De este modo, puede verse comprometida la facilidad de uso y coherencia del producto final. Ello puede incrementar los costes de transición, entrenamiento y soporte técnico. Por otra parte, conviene recordar que existe software libre comercial y software privativo gratuito. En cualquier caso, la excelencia del software puede ser independiente de dichas variables. Por tanto, la mejor estrategia es la coexistencia y libre competencia de todo tipo de software. Así se puede conseguir una mejora de calidad y una potenciación de la innovación, que beneficie a la docencia, investigación, gestión y asistencia universitarias en particular, así como a la sociedad en general

Kinetic and thermodynamic behavior of co-pyrolysis of olive pomace and thermoplastic waste via thermogravimetric analysis

This work represents the first attempt to analyze kinetics, thermodynamics and reaction mechanism of olive pomace (OP) and waste plastic materials (PM) co-pyrolysis. Among PM, polypropylene (PP), polystyrene (PS), high density polypropylene (HDPE), polyvinyl chloride (PVC) and poly (ethylene terephthalate) glycol (PETG) were selected. Non-isothermal TG experiments were carried out under inert conditions at four heating rates, namely 5, 10, 20 and 40 °C/min. The kinetic triplet for raw materials and their blends was determined using Starink, Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall iso-conversional models. Pyrolysis mechanism reactions were explained by diverse models, depending on thermal degradation progress. Results shown that co-pyrolysis followed a complex multi-step reaction mechanism. A synergistic effect was detected during co-pyrolysis of OP/PM mixtures. The addition of 50 % (w/w) OP biomass to PM waste decreased the energy of activation (Ea) from 50 to 25 % for all blends, except for PVC/OP. Thermodynamic analysis reveals that adding OP generally reduces the energy barrier (ΔH), except for PS-OP, and improves energy efficiency (ΔG) by facilitating radical formation and molecular chain cleavage. As a conclusion, this study may open up new avenues for waste valorization and resource recovery. Thus, it may contribute to the transition towards a circular and sustainable economy, through zero waste goal

Kinetic and thermodynamic behavior of co-pyrolysis of olive pomace and thermoplastic waste via thermogravimetric analysis

This work represents the first attempt to analyze kinetics, thermodynamics and reaction mechanism of olive pomace (OP) and waste plastic materials (PM) co-pyrolysis. Among PM, polypropylene (PP), polystyrene (PS), high density polypropylene (HDPE), polyvinyl chloride (PVC) and poly (ethylene terephthalate) glycol (PETG) were selected. Non-isothermal TG experiments were carried out under inert conditions at four heating rates, namely 5, 10, 20 and 40 °C/min. The kinetic triplet for raw materials and their blends was determined using Starink, Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall iso-conversional models. Pyrolysis mechanism reactions were explained by diverse models, depending on thermal degradation progress. Results shown that co-pyrolysis followed a complex multi-step reaction mechanism. A synergistic effect was detected during co-pyrolysis of OP/PM mixtures. The addition of 50 % (w/w) OP biomass to PM waste decreased the energy of activation (Ea) from 50 to 25 % for all blends, except for PVC/OP. Thermodynamic analysis reveals that adding OP generally reduces the energy barrier (ΔH), except for PS-OP, and improves energy efficiency (ΔG) by facilitating radical formation and molecular chain cleavage. As a conclusion, this study may open up new avenues for waste valorization and resource recovery. Thus, it may contribute to the transition towards a circular and sustainable economy, through zero waste goal

Optimization of ultrasound-assisted liquefaction of solid digestate to produce bio-oil: Energy study and characterization

Among the possibilities for industrial waste valorization, liquefaction is gaining interest as it may provide alternative energy and high value-added products. In this context, this work focuses on the production of bio-oil through ultrasound (US)-assisted direct liquefaction. For the reaction, polyethylene glycol (PEG) and crude glycerol were selected. As this process is conducted by raising reaction temperature, US provided it, while shortening reaction time, through the cavitation phenomenon. For liquefaction reaction optimization, a response surface methodology (Box-Behnken design) was performed. As independent variables, US-amplitude, reaction time and solvent-to-biomass ratio were selected. On the other side, bio-oil yield, high calorific value (HCV) and energy consumption were chosen as dependent responses. Optimal results showed a bio-oil yield of 34.17% (reached in<20 min), HCV of 28.44 MJ/kg and energy consumption (US) of 11.477 kJ. Moreover, differences between predicted and experimental values were found to be negligible. Bio-oil was also characterized using Fourier transform infrared (FT-IR) and chromatography-mass spectrometry gas (GC–MS). Both techniques showed a profile rich in phenols and poly-oils, which can be used as precursors for industrial products, i.e. polymers. Finally, to check the impact of liquefaction on solid digestate, scanning electron microscopy (SEM) analysis was carried out. Results showed an increase in porosity, fragment and conglomerate. It may be concluded that the use of US as auxiliary energy in solid digestate liquefaction, to produce bio-oil, provides energy saving. Thus, the proposed valorization path aids consolidating the concept of circular economy through an efficient biorefinery model

Descriptive and inferential statistics as an exhaust emission comparative tool between different engine operating conditions and fuels. Application to highly oxidized biodiesel blended with primary alcohols

Despite the great electrification that vehicle fleet is expecting in the coming years, internal combustion engines still play an important role in the transport sector. New regulations for polluting emission reduction and economy decarbonization, together with lower availability of fuels from non-renewable sources, have led to the search of renewable non-polluting fuels. This is a fundamental research sector in the next decades. Biodiesel, with a long history, has proven to be a good candidate. However, diversification will be the key to success in terms of sustainable mobility, avoiding negative dependency in the future. In this context, discarded oil is key to both produce an economically affordable biodiesel and to valorize this residue. This research studies the possibility of using a binary mix of fuels, including primary alcohols (propanol and pentanol), at 10 and 20% v/v, with highly-oxidized dumped oil biodiesel. These mixtures have been tested in a diesel engine running at 1300, 1700 and 2400 rpm, under 25% and 46% engine load for each rotational speed. To check the significance and reproducibility of obtained data, polluting emissions and engine input parameters have been evaluated through descriptive and inferential statistics. Results indicate that 20% 1-propanol/biodiesel blend allows mitigating the increase in fuel consumption of biodiesel compared to fossil diesel fuel. Moreover, overall soluble organic fraction (SOF) and unburned hydrocarbon emissions are lower for biodiesel and its blends than for diesel fuel. Furthermore, the combination of the use of 10% propanol and maximum EGR valve opening can achieve a significant reduction of NOx emissions. As a final conclusion, the proposed statistical study has shown to be a reliable tool to compare emissions and input parameters from different tests, especially under intra-urban conditions. This overcomes the large data variability from emission tests