Viabilitat tècnica i ambiental de biocombustibles: oli de colza i estella forestal

La dependència actual dels combustibles fòssils en la majoria de sectors industrials i domèstics no és sostenible ni a curt ni a llarg termini. Això està obligant a plantejar alternatives a la majoria de sectors industrials especialment encaminades a l’estalvi energètic i la utilització d’energies renovables. A més a més en el cas dels combustibles, la Unió Europea està incentivant l’ús de biocarburants degut als compromisos assumits en el protocol de Kyoto. Els biocarburants més comuns pel cas del transport són el biodièsel i el bioetanol, que en la majoria dels casos, es produeixen a gran escala i presenten seriosos problemes ambientals i socials tal i com citen els treballs de diversos autors. En aquest escenari és interessant proposar i avaluar ambientalment altres biocarburants no presents actualment en el mercat. En aquesta tesi es proposen i s’avaluen ambientalment (mitjançant l’anàlisi del cicle de vida, ACV) dos biocombustibles, l’oli de colza pel cas del transport, comparat amb la seva conversió a biodièsel i l’estella forestal per a calefacció comparada amb el gasoil. En l’últim apartat d’aquesta tesi es realitza una caracterització de sis olis vegetals, per tal de determinar la temperatura òptima de preescalfament per ser utilitzats com a biocombustibles en motors dièsel actuals. Conjuntament amb aquesta caracterització es parametritza la densitat, viscositat i tensió superficial d’aquests olis en funció de la temperatura.La dependencia actual de los combustibles fósiles en la mayoría de sectores industriales y domésticos no es sostenible ni a corto ni a largo plazo. Esto está obligando a plantear alternativas a la mayoría de sectores industriales especialmente encaminados al ahorro energético y la utilización de energías renovables. Además en el caso de los combustibles, la Unión Europea está incentivando el uso de biocarburantes debido a los compromisos asumidos en el protocolo de Kioto. Los biocarburantes más comunes en el caso del transporte son el biodiesel y el bioetanol, que en la mayoría de los casos, se producen a gran escala y presentan serios problemas ambientales y sociales tal y como citan los trabajos de varios autores. En este escenario es interesante proponer y evaluar ambientalmente otros biocarburantes no presentes actualmente en el mercado. En esta tesis se proponen y se evalúan ambientalmente (mediante el análisis del ciclo de vida, ACV) dos biocombustibles, el aceite de colza por el caso del transporte, comparado con su conversión a biodiesel i l' forestal para calefacción comparada con el gasóleo. En el último apartado de esta tesis se realiza una caracterización de seis aceites vegetales, para determinar la temperatura óptima de precalentamiento para ser utilizados como biocombustibles en motores diesel actuales. Conjuntamente con esta caracterización se parametriza la densidad, viscosidad y tensión superficial de estos aceites en función de la temperaturaThe current dependence on fossil fuels in most industrial and domestic sectors is not sustainable in neither short nor long term. This is promoting alternatives to most industries, especially focused on saving energy and using renewable energy. Moreover, the European Union is encouraging the use of biofuels trough the commitments in the Kyoto Protocol. The most common biofuels for transport are biodiesel and bioethanol, which in most cases, are large scale produced and involve serious environmental and social problems according to several authors. In this scenario it is interesting to evaluate other alternative fuels, being environmentally friendly and not currently present in the market. This thesis presents and environmentally analyses two biofuels using life cycle assessment (LCA) methodology. One is straight vegetable rapeseed oil used for truck transport compared to rapeseed biodiesel. The other is wood chips for heating compared to diesel as heating fuel. In the last section of this PjD a characterization of six vegetable oils is performed in order to determine the optimal preheating temperature to use it as biofuel in current diesel engines. Together with this characterization, the density, the viscosity and the surface tension of different vegetable oils are parameterized for a wide range of temperature.Postprint (published version

Tècnica de grup d'experts aplicat a l'assignatura de materials

L’assignatura de Ciència i Enginyeria de Materials està integrada per continguts de diferents matèries que són difícils d’impartir alhora durant un quadrimestre. Un tema que sovint es deixa per a l’última part del curs, és el de materials ceràmics, quan ja no queda massa temps perquè l’alumnat adquireixi els coneixements necessaris. En aquest treball es resumeix una experiència d’aprenentatge actiu basada en la tècnica dels grups d’experts sobre materials ceràmics. Els punts forts de l’activitat són que permet iniciar el tema de materials ceràmics sense que l’alumnat tingui tots els coneixements previs. L’activitat es comença a meitat de curs, utilitzant poc temps de les classes expositives. Al final del quadrimestre, quan l’alumnat ja té assolits els coneixements previs per al tema de materials ceràmics, s’hi destinen dues sessions més. L’experiència d’aprenentatge actiu es basa en que, primer de tot, l’alumnat tria un material ceràmic que li resulti peculiar, amb el vist-i-plau del professorat. Durant el curs, s’estudia el material seleccionat amb l’ajuda del professorat en forma de grups d’expertesa en un material ceràmic concret. Un cop estudiats els materials, s’ha de fer una exposició oral davant altres companys/es, creant nous grups formats per un expert en cada material estudiat. En l’avaluació es tenen en compte només dos conceptes: els coneixements adquirits pel propi estudiant i pels altres experts/es. El fet que l’alumne/a sigui responsable amb un 50% de la nota dels altres fa que tingui una forta implicació a l’adquirir els coneixements. La tècnica de grups d’experts dóna la oportunitat de treballar les competències de treball en equip, capacitat de síntesi i anàlisi i comunicació oral.Postprint (published version

An eddy-current-based sensor for preventing knots in metallic wire drawing processes

During metallic wire drawing processes, the presence of knots and the failure to detect them can lead to long production interruptions, significant economic losses and a lower quality of final product. Consequently, there is a pressing need to develop methods for real-time detection and prevention of this fault. In this paper, a sensor to prevent the formation of knots during the metallic wire drawing process is presented and evaluated by means of experimental data. This fast, inexpensive, non-contact sensor is based on electromagnetic principles such as eddy current induction, magnetic reluctance variations and magnetic coupling. The proposed sensor without direct contact can detect knots in a target metallic wire by measuring the impedance variations of a calibrated sensing coil caused by either a knot or an unwound loop rising from a wire rod. The incorporation of this type of sensor into a wire-drawing machine can avoid the tightening of the knot, thereby reducing downtime and increasing the security and reliability of the process. Experiments were conducted using a scale model of the above proposed system. This allowed highlighting the sensor’s potential by carrying out an automatic, real-time knot detection during steel wire drawingPreprin

Temperature dependence of density and viscosity of vegetable oils

The straight use of vegetable oils as fuel in diesel engines entails adjusting several physical properties such as density and viscosity. By adequately heating the vegetable oil before entering the injection system, its physical parameters can reach values very close to that of diesel fuel. Consequently, by properly adjusting the temperature of vegetable oils used as fuel, it is possible to improve their combustion performance, thus avoiding premature engine aging due to incomplete burning. In this study the density and viscosity of several vegetable oils are studied within a wide variety of temperatures. The optimal range of temperatures at which each vegetable oil should operate in order to adjust its properties to those of automotive diesel and biodiesel is then found. Additionally an empirical relationship between the dependence of viscosity with density is presented. Thus, by means of the above-described relationship, through measuring the density of a given oil, its viscosity can be directly deducedPostprint (published version

An evaluation of the life cycle cost of rapeseed oil as a straight vegetable oil fuel to replace petroleum diesel in agriculture

The use of straight vegetable oil (SVO) as biofuel has been recognized as a valid substitute of diesel fuel in the agricultural sector under specific circumstances. Its direct use reduces most of the chemical processes involved when converting it into biodiesel, thus lowering harmful emissions. This study presents the economic analysis of a self-supply farming model that uses rapeseed as its fuel base. This model addresses agricultural environmental concerns and can even minimize dependence on the fluctuating costs of diesel fuel. The use of SVO in agriculture can help reduce farmers’ vulnerability to fossil fuel prices. The economic evaluation of the model proposed in this study shows clear economic benefits of introducing rapeseed to the traditional crop rotation of wheat and barley. The key factors analyzed in this model are diesel fuel price, diesel fuel grants and crop aids. The current situation in Spain favors the use of diesel fuel in agriculture rather than rapeseed SVO due to an 8% profit difference. However, results show that changes in key factors slightly affect the profit margin, calculating a difference of only 3.7% for particular factor combinations. Combined environmental-friendly agriculture supporting policies are necessary to cover this slight profit difference to promote this biofuelPostprint (published version

Environmental life cycle assessment of rapeseed straight vegetable oil as self-supply agricultural biofuel

Biofuels are nowadays considered a questionable environmental alternative to fossil fuels. In that context, this work analyses the environmental impacts when introducing rapeseed on the traditional and current wheat and barley agricultural rotation by means of a comparative life cycle assessment (LCA). The introduction of rapeseed, the correctness of its conversion to obtain straight vegetable oil and its use as self-consumption biofuel in tractors are evaluated. Life cycle assessment is used in this work to evaluate the impacts of different considered scenarios. A sensitivity analysis has also been conducted. The results presented show a modest environmental improvement (diminishment of 6 out of the 10 analyzed environmental impacts) when introducing rapeseed to local crop rotations and its partial conversion to oil to be used as fuel in existing diesel engines. Additionally, the ratio between the energy obtained and the total energy input shows moderate positive results when comparing the latter case with the current one. Results from this study can be used to support research and decision making to assess the convenience of introducing alternative fuels in agricultural exploitationsPreprin

Small-scale production of straight vegetable oil from rapeseed and its use as biofuel in the Spanish territory

Biofuels nowadays are an important topic of study. The most significant point is the availability of bioethanol or biodiesel and their production from different raw materials. It is already known that large scale production of first-generation biodiesel cannot be seen as an alternative to fossil fuels due to land requirements, competition with food, increase in fertilizer requirements and pressure on tropical forests among others. This fact does not necessarily apply to second-generation biofuels or small scale niche productions. Straight vegetable oil (SVO) can be used directly in diesel engines with minor modifications. Our proposal is a small-scale SVO production system for self-supply in agricultural machinery. In this paper a model to provide SVO to local farmers in a specific area in Catalonia (Spain) is presented. We also present a discussion about the regulations to be changed in order to make possible the incorporation of SVO as engine fuel in diesel vehicles and a comparative analysis between the emissions of tractors fed with SVO and petrodiesel. Moreover a quantitative economic analysis of modifying diesel engines and long-term operability costs are shown and a firstrun economic analysis comparing the actual crop rotation with the proposed one and some alternatives is studied.Peer ReviewedPostprint (author’s final draft