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343 p., Esta tesis doctoral se enmarca dentro de una extensa línea de investigación, que abarca el desarrollo de procesos térmicos y catalíticos para la valorización de biomasa y residuos plásticos para la obtención de combustibles líquidos, materias primas (olefinas y aromáticos) e hidrógeno. Los conocimientos adquiridos en la gasificación de biomasa y plásticos en reactores spouted bed convencionales han alentado la realización de esta tesis. Por tanto, el objetivo principal de esta tesis es avanzar en el proceso de gasificación de biomasa con vapor para la producción de gas de síntesis y la eliminación de alquitrán.El reactor de spouted bed convencional se caracteriza por tener cortos tiempo de residencia, lo cual es una excelente característica para minimizar las reacciones secundarias no deseadas en los procesos de pirolisis. Sin embargo, esto es un serio inconveniente para la gasificación, ya que los cortos tiempos de residencia dificultan las reacciones de craqueo del alquitrán. En esta tesis se propone un novedoso sistema de reacción basado en la tecnología de spouted bed, que plantea la incorporación de determinados dispositivos, como el confinador de la fuente y el tubo central, llamado spouted bed de fuente confinada. Esta combinación pretende resolver las limitaciones de los spouted bed convencionales en los procesos de gasificación. Además, se han propuesto varias estrategias primarias de eliminación de alquitrán para mejorar la eficiencia de la gasificación de biomasa con vapor. Se ha desarrollado un nuevo régimen de contacto gas-sólido basado en el reactor de spouted bed y se ha optimizado el proceso general desde el punto de vista del diseño del reactor, condiciones de operación (temperatura) y catalizadores primarios (arena, olivina, dolomita, catalizador gastado de FCC, alumina y catalizador Fe/olivina). Los resultados muestran que usando dolomita como catalizador primario se consigue disminuir el tar hasta 5.0 g Nm-3 a 850 ºC y un ratio S/B de 2.

The combination of delocalized units for the fast pyrolysis of biomass to produce bio-oil followed by centralized units for the gasification of bio-oil appears as an economically attractive option for the full-scale production of syngas because transportation of bio-oil is less costly than that of biomass. First goal of this study lies in the validation of a bio-oil feeding device made up of a line-thermostated at 60–80 °C and a non-atomizing injector cooled by water. This injector allows feeding the crude bio-oil in continuous mode into the conical spouted bed reactor without being clogged by the pyrolytic lignin in the bio-oil. The effect of gasification temperature on gas properties, tar composition, and carbon conversion efficiency were assessed in the 800–900 °C range. The results show that temperature promotes tar reduction (from 40.7 to 12.5 g/Nm3), carbon conversion efficiency (from 91.2 to 96.3 %) and gas yield (from 1.37 to 1.85 Nm3/kg on a dry basis) as temperature is increased from 800 to 900 °C. A novel aspect of this study is the detailed characterization of the tar evolution with temperature, which, to our knowledge, is an aspect that has not been approached in the literature related to raw bio-oil gasification.

In the current energy scenario, the production of heat, power and biofuels from biomass has become of major interest. Amongst diverse thermochemical routes, gasification has stood out as a key technology for the large-scale application of biomass. However, the development of biomass gasification is subjected to the efficient conversion of the biochar and the mitigation of troublesome by-products, such as tar. Syngas with high tar content can cause pipeline fouling, downstream corrosion, catalyst deactivation, as well as adverse impact on health and environment, which obstruct the commercialization of biomass gasification technologies. Since the reduction of tar formation is a key challenge in biomass gasification, a comprehensive overview is provided on the following aspects, which particularly include the definition and complementary classifications of tar, as well as possible tar formation and transformation mechanisms. Moreover, the adverse effects of tar on downstream applications, human health or environment, and tar analyzing techniques (online and off-line) are discussed. Finally, the primary tar removal strategies are summarized. In this respect, the effect of key operation parameters (temperature, ER and S/B), catalysts utilization (natural and supported metal catalysts) and the improvement of reactor design on tar formation and elimination was thoroughly analyzed.

[EN]This work pursues the validation of a new reactor for the evaluation of char gasification kinetics. This novel reactor allows continuous gas flow through the fixed bed sample and accurately monitoring the mass loss throughout the reaction. Accordingly, this thermogravimetric flow reactor has a great potential for the analysis of different thermochemical processes, such as pyrolysis and gasification of solid feedstocks. In this paper, the gasification of pine sawdust char was carried out and the effect carbon dioxide concentration (10 and 100 vol%) and temperature (800, 850 and 900 °C) have on char gasification kinetics was assessed. The experimental results were fitted to five different kinetic equations, i.e., homogeneous model (VM), shrinking core model (SCM), nth order model, random pore model (RPM) and modified random pore model (MRPM), and the best-fit parameters (frequency factor, activation energy, adjustable parameters and fitting error) were obtained for each model. The modified random pore model provides the best fit to the experimental data. The new thermogravimetric flow reactor allows obtaining rigorous kinetic results, which is clear evidence that the reactor is suitable for studying char gasification kinetics under CO2 atmosphere.

[EN] A study was carried out on the valorization of different waste plastics (HDPE, PP, PS and PE), their mixtures and biomass/HDPE mixtures by means of pyrolysis and in line oxidative steam reforming. A thermodynamic equilibrium simulation was used for determining steam reforming data, whereas previous experimental results were considered for setting the pyrolysis volatile stream composition. The adequacy of this simulation tool was validated using experimental results obtained in the pyrolysis and in line steam reforming of different plastics. The effect the most relevant process conditions, i.e., temperature, steam/plastic ratio and equivalence ratio, have on H-2 production and reaction enthalpy was evaluated. Moreover, the most suitable conditions for the oxidative steam reforming of plastics of different nature and their mixtures were determined. The results obtained are evidence of the potential interest of this novel valorization route, as H-2 productions of up to 25 wt% were obtained operating under autothermal conditions.

[EN] The performance of olivine, dolomite and gamma-alumina primary catalysts was evaluated in the continuous tar elimination process in which toluene was selected as the biomass gasification tar model compound. Iron was incorporated into these catalysts in order to improve their catalytic activity. All the experiments were performed in a continuous flow fluidized bed micro-reactor, with a steam/toluene ratio of 4 and a space velocity (GHSV) of 820 h(-1), which corresponds to a catalyst amount of 3.8 cm(3). The effect of temperature was studied using olivine in the 800-900 degrees C range, which allowed concluding that 850 degrees C was the best temperature for tar removal. The fresh and deactivated catalysts were characterized by N-2 adsorption-desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD) and temperature-programmed oxidation (TPO). Tar conversion efficiency was assessed by means of carbon conversion, H-2 yield (based on the maximum allowed by stoichiometry), gas composition and product yields, with Fe/Al2O3 leading to the highest conversion (87.6 %) and H-2 yield (38 %). Likewise, Fe/Al2O3 also provided the highest stability, as it allowed operating for long periods with high conversion values (85.9 % after 35 min on stream), although it underwent severe deactivation. The analysis of the spent catalysts revealed that deactivation occurred mainly by coke deposition on the catalyst surface and iron phase oxidation, with Fe/olivine and Fe/dolomite leading to the faster deactivation due to their poorer metal dispersion related to their reduced surface area. The TPO profiles showed that the coke deposited on the three catalysts was amorphous with a very small contribution of highly structured carbon.

343 p., Esta tesis doctoral se enmarca dentro de una extensa línea de investigación, que abarca el desarrollo de procesos térmicos y catalíticos para la valorización de biomasa y residuos plásticos para la obtención de combustibles líquidos, materias primas (olefinas y aromáticos) e hidrógeno. Los conocimientos adquiridos en la gasificación de biomasa y plásticos en reactores spouted bed convencionales han alentado la realización de esta tesis. Por tanto, el objetivo principal de esta tesis es avanzar en el proceso de gasificación de biomasa con vapor para la producción de gas de síntesis y la eliminación de alquitrán.El reactor de spouted bed convencional se caracteriza por tener cortos tiempo de residencia, lo cual es una excelente característica para minimizar las reacciones secundarias no deseadas en los procesos de pirolisis. Sin embargo, esto es un serio inconveniente para la gasificación, ya que los cortos tiempos de residencia dificultan las reacciones de craqueo del alquitrán. En esta tesis se propone un novedoso sistema de reacción basado en la tecnología de spouted bed, que plantea la incorporación de determinados dispositivos, como el confinador de la fuente y el tubo central, llamado spouted bed de fuente confinada. Esta combinación pretende resolver las limitaciones de los spouted bed convencionales en los procesos de gasificación. Además, se han propuesto varias estrategias primarias de eliminación de alquitrán para mejorar la eficiencia de la gasificación de biomasa con vapor. Se ha desarrollado un nuevo régimen de contacto gas-sólido basado en el reactor de spouted bed y se ha optimizado el proceso general desde el punto de vista del diseño del reactor, condiciones de operación (temperatura) y catalizadores primarios (arena, olivina, dolomita, catalizador gastado de FCC, alumina y catalizador Fe/olivina). Los resultados muestran que usando dolomita como catalizador primario se consigue disminuir el tar hasta 5.0 g Nm-3 a 850 ºC y un ratio S/B de 2.

This study analyzes the two-step process of biomass pyrolysis and in-line steam reforming for the production of H2. In order to evaluate the effect of the volatile composition on the commercial Ni/Al2O3 catalyst performance and stability, biomass pyrolysis step was conducted at different temperatures (500–800 °C). The analysis of the deactivated catalysts has also allowed identifying the main bio-oil compounds responsible for catalyst decay (coke precursors). Pyrolysis temperature allows modifying the composition of the volatile stream that is subsequently reformed at 600 °C. An increase in pyrolysis temperature to 800 °C improves considerably the production of both H2 and gaseous stream at the initial reaction stages, reaching values of 12.95 wt% and 2.23 Nm3 kg−1, respectively. Catalyst stability is also considerably improved when pyrolysis temperature is increased due to the lower bio-oil yield and its different composition at high temperatures. Coke was the main cause of catalyst deactivation. Besides, the nature of the coke deposited is influenced by the composition of the pyrolysis volatiles, with encapsulating coke being formed by the adsorption and subsequent condensation of all hydrocarbons (oxygenated and non-oxygenated ones) preferably at low temperatures, whereas filamentous coke is formed when the concentrations of CO and light hydrocarbons in the volatile stream are increased at 800 °C.

[EN]n recent decades, the production of H-2 from biomass, waste plastics, and their mixtures has attracted increasing attention in the literature in order to overcome the environmental problems associated with global warming and CO2 emissions caused by conventional H-2 production processes. In this regard, the strategy based on pyrolysis and in-line catalytic reforming allows for obtaining high H-2 production from a wide variety of feedstocks. In addition, it provides several advantages compared to other thermochemical routes such as steam gasification, making it suitable for its further industrial implementation. This review analyzes the fundamental aspects involving the process of pyrolysis-reforming of biomass and waste plastics. However, the optimum design of transition metal based reforming catalysts is the bottleneck in the development of the process and final H-2 production. Accordingly, this review focuses especially on the influence the catalytic materials (support, promoters, and active phase), synthesis methods, and pyrolysis-reforming conditions have on the process performance. The results reported in the literature for the steam reforming of the volatiles derived from biomass, plastic wastes, and biomass/plastics mixtures on different metal based catalysts have been compared and analyzed in terms of H-2 production.

The performance of Fe/olivine catalysts was tested in the continuous steam gasification of sawdust in a bench scale plant provided with a fountain confined conical spouted bed reactor at 850 degrees C. Olivine was used as catalyst support and loaded with 5 wt%Fe. The activity and stability of the catalyst was monitored by nitrogen adsorption-desorption, X-ray fluorescence spectroscopy, temperature programmed reduction, X-ray diffraction and X-ray photoelectron spectroscopy techniques, which were conducted before and after the runs. The fountain confined conical spouted bed performs well in the biomass steam gasification with primary catalysts. In fact, this reactor allows enhancing the gas-solid contact, and therefore the catalytic activity by avoiding the elutriation of fine catalyst particles. The uncatalysed efficiency of the gasification process, assessed based on the gas production and composition, H-2 production, tar concentration and composition, and carbon conversion efficiency, was consideraby improved on the Fe/olivine catalyst, with tar reduction being especially remarkable (to 10.4 g Nm(-3)). After 140 min on stream, catalyst deactivation was particularly evident, as tar concentration increased to 19.9 g Nm(-3) (90% of that without catalyst). However, Fe/olivine catalyst was still active for WGS and CH4 steam reforming reactions, with gas and H-2 productions being 1.35 Nm(3) kg(-1) and 5.44 wt%, respectively. Metal iron oxidation to Fe3O4 caused catalyst deactivation, as the reaction environment shifted from oxidizing to reducing conditions due to operational limitations.

[EN]The activity and stability of a 10 wt%NiO/CaO catalyst were tested in the sorption enhanced ethanol steam reforming (SEESR) in a fluidized bed reactor. The effect of temperature in the 600-750 degrees C range was analyzed and the performance of the catalyst at 700 degrees C was assessed by conducting cycles of SEESR reaction and CO2 desorption. At zero time on stream, an increase in temperature enhanced ethanol steam reforming reactions, and therefore H-2 production increased from a yield of 20.3 wt% at 600 degrees C to 22 wt% at 750 degrees C. However, high temperatures hindered the catalyst sorption performance, i.e., CO2 capture declined from 7.9 to 2.1 mmol(CO2) g(cat)(-1). In order to evaluate the catalyst performance throughout the cycles and relate it with its features, both fresh and deactivated catalysts were characterized in detail by N-2 adsorption-desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature programmed reduction (TPR) and oxidation (TPO) and transmission electron microscopy (TEM). Subsequent to 12 cycles, the catalyst CO2 capture performance was slightly lower than that of the fresh one (approximately 7%) and hardly changed in the next cycles. Furthermore, the use of the same temperature for SEESR reaction and CO2 desorption led to the highest adsorption capacity of the catalyst over multiple cycles.

[EN]This work pursues the validation of a new reactor for the evaluation of char gasification kinetics. This novel reactor allows continuous gas flow through the fixed bed sample and accurately monitoring the mass loss throughout the reaction. Accordingly, this thermogravimetric flow reactor has a great potential for the analysis of different thermochemical processes, such as pyrolysis and gasification of solid feedstocks. In this paper, the gasification of pine sawdust char was carried out and the effect carbon dioxide concentration (10 and 100 vol%) and temperature (800, 850 and 900 °C) have on char gasification kinetics was assessed. The experimental results were fitted to five different kinetic equations, i.e., homogeneous model (VM), shrinking core model (SCM), nth order model, random pore model (RPM) and modified random pore model (MRPM), and the best-fit parameters (frequency factor, activation energy, adjustable parameters and fitting error) were obtained for each model. The modified random pore model provides the best fit to the experimental data. The new thermogravimetric flow reactor allows obtaining rigorous kinetic results, which is clear evidence that the reactor is suitable for studying char gasification kinetics under CO2 atmosphere.

A Ni/Al2O3 catalyst has been modified incorporating CeO2 and MgO promoters in order to improve its performance in the steam reforming of biomass pyrolysis volatiles. Ni/Al2O3, Ni/CeO2-Al2O3 and Ni/MgO-Al2O3 catalysts have been prepared and fresh and deactivated catalysts have been characterized by N2 adsorption/ desorption, X-ray Fluorescence (XRF), Temperature Programmed Reduction (TPR), X-ray powder diffraction (XRD), Temperature Programmed Oxidation (TPO), Transmission Electron Microscopy (TEM) and a technique based on Fourier Transform Infrared Spectroscopy-Temperature Programmed Oxidation (FTIR-TPO). The results obtained revealed a similar initial activity for the three catalysts tested (conversion higher than 98%), whereas stability has been greatly improved by incorporating CeO2 as promoter, as it enhances the gasification of coke precursors. However, Ni/MgO-Al2O3 catalyst is slightly less stable than Ni/Al2O3, presumably as a result of its lower reducibility due to the formation of MgAl2O4 spinel phase. Catalysts deactivation has been associated with coke deposition, although sintering phenomenon became also evident when the Ni/CeO2-Al2O3 catalyst was tested. The coke deposited on the catalysts does not present any specific morphology, which is evidence of its amorphous structure in the three catalysts studied.

Debido al incremento en la demand a de combustibles, y al consiguiente aumento en el precio del petróleo, se plantea el uso de la biomasa como sustituto de los combustibles fósiles. La biomasa está considerada como una fuente de energía renovable y c ada vez s e está apostando más por su uso ya que contribuye a la reducción de l CO 2 de la atmó sfera. Como la biomasa proviene de fuentes naturales, se supone que todo el CO 2 que ha absorbido durante su c iclo de vida para desarrollarse es igual a la cantidad de CO 2 que se emite al utilizar la bi omasa como combustible, por lo que el ciclo de carbono es neutro. Por otro lado, la biomasa contiene un bajo contenido , casi despreciable, de sulfuros, nitrógeno y cenizas, por lo que las emisiones producidas son menores. El termino biomasa involucra toda la materia orgánica existente en la naturaleza, por lo que utilizar ésta como combustible para la obtención de electricidad es una opción muy atractiva. Ahora bien, dado que el uso masivo de la biomasa para fines energéticos puede acarrear serios problemas medioambientales, hay que tener sumo cuidado a la hora de utilizarla , como por ejemplo en las calderas de pellets. Desde el punto de vista de la contaminación obtener calor a partir de esta fuente renovable es más ecológico, pero puede llegar a originar s erios problemas de deforestación. O tro ejemplo sería el uso de cultivos energéticos para la obtención de biocombustibles. El us o de éstos supondría su escasez debido al aumento de la demanda de éstos para fines energéticos, por lo que el precio de dichos cultivos aumentaría. Por lo tanto, la solución ideal consistiría en buscar un equilibrio o el tipo de biomasa que menos repercusión tenga sobre el medio ambiente. Entre esta última opción se encuentran los residuos sólidos urbanos (RSU) . Según la ley 22/2 011, de l 28 de Julio, de residuos y suelos contaminados, l os residuos sólidos urbanos son aquellos que son generados en los hogares como consecuencia de las acti