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To achieve net zero carbon emissions from energy systems, biogas has become an attractive renewable resource for hydrogen production. The sorption enhanced steam reforming (SESR) process is proposed to produce high-purity hydrogen from biogas, enabled by combining the catalytic reforming reaction with the simultaneous CO2 removal by sorption in a single reactor. One of the most critical challenges in using biogas in conventional reforming processes is the presence of H2S since it may deactivate the reforming catalyst. Here we experimentally study the effect of the biogas H2S concentration on the H2 production by SESR, i.e., accounting for the presence of a CaO-based solid sorbent. This work was performed in a fixed-bed reactor using a Pd/Ni-Co hydrotalcite-like material (HT) catalyst and dolomite as CO2 sorbent. Biogas (60CH4/40CO2 vol.%) with different concentrations of H2S (150, 350, 500 and 1000 ppm) was evaluated. The catalyst did not deactivate for biogas H2S concentrations of 150 and 350 ppm during five cycles of the SESR process. However, a slight decrease in the catalyst activity was detected under higher sulfur concentrations after the third SESR cycle. Sulfur was detected in the spent catalyst and sorbent materials, with a higher proportion in the sorbent for the highest H2S concentration tested (1000 ppm). H2 yield decreased by 10.8% and 4.5% points for biogas H2S concentrations of 500 and 1000 ppm after five cycles, respectively, while H2 purity decreased by only 3 vol.% and 2 vol.% points, respectively.

The gasification process involves several reactions that occur simultaneously and are interrelated by several independent variables. Simulation tools can help us to understand the process behaviour and predict the efficiency and final composition of the products. In this work, two thermodynamic equilibrium models developed in Aspen Plus® software were assessed: a non-stoichiometric model based on the feedstock composition and on the most probable compounds expected from the results of the gasification process using minimisation of Gibbs free energy and a stoichiometric model based on a set of chemical reactions considered as the most relevant to describe the gasification process. Both models were validated with experimental data from a bubbling fluidised bed semi-pilot scale gasifier using pine kernel shells (PKS) as feedstock. The influence of temperature, stoichiometric ratio (SR) and steam to biomass ratio (SBR) were analysed. Overall, predictions of the gas composition and gasification efficiency parameters by the stoichiometric model showed better agreement to the experimental results. Our results point out the significance of an accurate description of the equilibrium composition of producer gas with the stoichiometric model for the gasification of biomass.

Energy generation from non-hazardous waste streams, which are unfeasible to be reused or recycled, can help overcome some of the problems related to fossil fuel depletion, global increase in energy demand and waste generation management under restricted landfilling. One of the main drawbacks of waste-to-energy strategies is the poor combustion properties of waste, which densification could help to circumvent. This work studies the co-pelletization of refused derived fuel (RDF) and pine sawdust (PIN) in a continuous pilot pellet mill that resembles industrial pelletization. The effect of RDF contents up to 90 wt% on a set of parameters has been assessed: pelletization energy consumption, physical properties (durability, particle and bulk densities), net calorific value and energy density of the obtained pellets. In addition, slagging, fouling and corrosion, phenomena associated with combustion, were estimated from the ash composition. Results showed that obtaining pellets with a low RDF loading (2–9 wt%) was feasible. They accomplished ISO 17225-2 solid biofuels standard for industrial use, and presented low deposition and corrosion risks. On the other hand, pellets with 30–90 wt% RDF were also manufactured and complied with the UNE-EN 15359:2012 solid recovered-fuel standard for energy recovery in incineration and co-incineration plants. All the produced pellets presented durability and net calorific value above 96.9% and 10.7 MJ/kg, respectively. Energy density higher than 10.6 GJ/m3 was obtained for pellet formulations with RDF content up to 50 wt%. It was demonstrated that the blends of RDF and PIN can provide high-quality pellets with a high load of waste material, under the same operational conditions required for PIN pelletization. It is a versatile process that can be tailored to different product requirements depending on the end-use. It promotes energy recovery and generates value out of a waste fraction with no relevant use, adding economic and environment

[EN] The increase in anthropogenic activities, as a result of industrial development, economic and demographic growth, is causing a climate change that is more noticeable today than ever before, thus leading to an increase in the global average temperature. The main factor causing the current climate change is the increase in CO2 emissions, which during the first half of 2019 reached 417.7 ppm compared to a concentration of 278 ppm in 1750. 70% of CO2 and other greenhouse gas emissions come from the combustion of fossil fuels such as coal, oil and natural gas. There are several strategies to mitigate CO2 emissions, such as the promotion of renewable energy, the replacement of fossil fuels by low-carbon fuels, the improvement of energy efficiency or the deployment of carbon capture and storage technologies. Thanks to the establishment of new environmental policies, renewable energies accounted for 26% of the global energy demand growth. Biomass is one of the main renewable sources for energy production since it is the most abundant natural resource and presents energy and environmental advantages, such as neutrality in net CO2 emissions. The main objective of this PhD dissertation is the use of biomass for the production of synthesis gas through the thermochemical process of gasification using air and steam as gasifying agents. For this purpose, several biomass samples of different origins, including woody biomass, forest, and food industry wastes were tested. One of the main biomass features is its heterogeneity; therefore, the effect of biomass thermal treatment at low temperature (torrefaction) has been studied to improve biomass handling and grinding properties, and also to increase its energetic density when combined with a pelletization process. Syngas quality, as well as the other products resultant of gasification, will depend on the operation conditions. In this work, the influence of different variables on the quantity and composition of the main product st, [ES] El aumento de las actividades antropogénicas, a raíz del desarrollo industrial y el crecimiento económico y demográfico, está provocando un cambio climático sin precedentes que se está traduciendo en un aumento de la temperatura media global del planeta. El principal causante de este calentamiento proviene de las emisiones de CO2 que, en el primer semestre de 2019, alcanzaron una concentración de 417,7 ppm frente a 278 ppm en 1750. El 70% de las emisiones de CO2 y del resto de gases de efecto invernadero, se derivan de la combustión de recursos fósiles como el petróleo, el carbón y el gas natural. Existen varias estrategias para reducir las emisiones de CO2, entre las que se encuentran el fomento de las energías renovables y el cambio a combustibles bajos en carbono, el aumento de la eficacia energética o el desarrollo de tecnologías de captura, utilización y almacenamiento de CO2. Gracias a la implementación de nuevas políticas medioambientales, en 2018 las energías renovables han supuesto un 26% del crecimiento de la demanda energética mundial. La biomasa es una de las principales fuentes renovables para la producción de energía, ya que es el recurso natural más abundante y presenta una serie de ventajas energéticas y medioambientales, como la neutralidad en las emisiones netas de CO2. El objetivo principal de esta Tesis Doctoral consiste en la utilización de biomasa para la producción de gas de síntesis, mediante el proceso termoquímico de gasificación de biomasa con aire y vapor de agua. Para ello se ha trabajado con biomasas de diferente procedencia: biomasas forestales, agrícolas y residuos obtenidos a partir de la industria alimentaria. Teniendo en cuenta que una de las principales características de la biomasa es su heterogeneidad, se ha estudiado el efecto de someter las biomasas forestales a un tratamiento térmico de torrefacción, con el fin de mejorar sus propiedades de molienda y manejabilidad, e incluso una mayor densidad energética si se combina c

This work reviews the state of the art of biomass pelletization with particular emphasis on its implementation in power generation. Biomass is a renewable feedstock with potential to supplement or partially replace fossil fuels for energy due to its neutrality with respect to CO2 emissions, the low NOx and SO2 emissions, the advantageous environmental policies that promote its use, as well as its autonomy, that may contribute to secure the energy supply. Raw (or white) biomass pellets are increasingly being used as a source of bioenergy in power plants for heat production. Torrefied (or black) pellets also have a promising future, but still need to be widely deployed. Main feedstocks and additives used in biomass pelletization research at laboratory, pilot and industrial scales are reviewed throughout the chapter. In addition, the pellet quality standards, economic costs, most meaningful markets and trade flows are also overviewed. Finally, relevant examples on the status of large scale biomass pellets firing and co-firing are reported and key conclusions from these experiences are summarized.

Multivariate analysis was used to study the influence of the biomass characteristics on the gasification process. Ten lignocellulosic biomass samples (almond shells –AS–, chestnut sawdust –CHE–, torrefied chestnut sawdust –CHET–, cocoa shells –CS–, grape pomace –GP–, olive stones –OS–, pine cone leafs –PCL–, pine sawdust –PIN–, torrefied pine sawdust –PINT–, and pine kernel shells –PKS–) were gasified in a bubbling fluidized bed gasifier under an air-steam atmosphere. Statistical analysis was applied to the variables that described the results of the gasification process, i.e., gas concentration, gas production (moles), calorific value of the product gas, energy density, and cold gas efficiency, together with the main biomass properties, such as those derived from the elemental and proximate analyses, the higher heating value (HHV), the particle density, and the elemental composition of the ashes. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were applied to the data of biomass properties and gasification parameters in order to elucidate which feedstock features had a more determinant influence on the gasification process. Both HCA and PCA revealed a clear separation of the biomass samples into two main groups on the basis of the gasification results. The results indicated that PKS, PCL, PINT, OS and PIN biomasses were characterized by high production of combustible gases, such as CO and CH4, high conversion and cold gas efficiency during gasification. This indicated that the most important biomass properties for promoting the gas production, calorific value of the product gas, gasification conversion and energy efficiency were the C and H contents and the HHV of the biomass. However, biomasses CS and GP were mainly characterized by high H2 concentration and H2/CO molar ratio in the gas product, which was mainly related to the higher H/O ratio and K2O ash content of the biomass. The H2 concentration in the product gas was negatively rela

he present study investigates the air-steam gasification of ten commercial and alternative lignocellulosic biomass fuels (pine sawdust, chestnut sawdust, torrefied pine sawdust, torrefied chestnut sawdust, almond shells, cocoa shells, grape pomace, olive stones, pine kernel shells and pine cone leafs) in order to evaluate the product gas composition and the process performance in a bubbling fluidized bed gasifier with focus on the different biomass properties. Accordingly, an effort to correlate the biomass characteristics with the gasification results has been done. Pine kernel shell (PKS) was used to test the effect of the gasification temperature (700, 800 and 900 °C), steam to air ratio in the gasifying agent (S/A = 10/90, 25/75, 50/50 and 70/30) and stoichiometric ratio (SR = 0.13 and 0.25) on the product gas composition, combustible gas (H2 + CO + CH4) production, H2/CO ratio, heating value, energy yield and cold gas efficiency of the obtained gas. Results showed that higher temperature and S/A ratio favored H2 production and gasification performance. A higher value of SR slightly affected the gas composition, but led to a higher process efficiency as a consequence of a higher biomass conversion into gaseous combustible products. All the biomass samples of different origin and characteristics were then gasified at the best experimental conditions found (900 °C, S/A = 70/30, SR = 0.25). Gasification of all the biomasses was feasible and H2 and combustible gas concentrations of 30–39 vol% and 59–78 vol% (inert gas-free basis), respectively, were obtained for the biomasses studied, with energy yields of 8–18 MJ/kgbiomass. Torrefied biomass showed similar combustible gas production than the corresponding raw biomass under the conditions studied, but it gave slightly higher H2 production and efficiency results. Possible correlations of the gasification performance parameters with biomass properties were also analyzed. The results showed positive effects of biomass

Twelve commercial and unconventional biomass fuels were evaluated in steam gasification; these include samples of hard (wood, almond, olive and pine kernel wastes) and soft (miscanthus, switchgrass, coffee, cocoa and grape wastes) biomass. Gasification tests at 700–1000 °C of biomass chars obtained from a bubbling fluidized bed reactor were performed in a TG analyzer. Steam gasification kinetics were extensively analyzed: an index of key parameters for the twelve biomasses and the correlation to biomass ash composition were developed. The random pore model (RPM) described the experimental reactivity best, with activation energies of 59–196 kJ mol−1. The study of their reactivities provided a ranking of fast-, medium- and slow-kinetics fuels. The influence of alkaline and alkaline-earth metals (AAEM) on reactivity revealed that K, Na and Mg had a positive effect while Si, P and Ca had a negative influence.

Biomass shows characteristics that makes it a promising feedstock for complementing traditional fossil fuels as main energy source. It is somewhat limited by its generally poor physical properties, but these can be enhanced by densification processes like torrefaction and pelletization. The aim of the present work is to evaluate the influence of different solid biomass additives (almond shell, cocoa shell, grape pomace, Miscanthus, olive pomace and olive stone), and parameters such as temperature, moisture content and glycerol addition upon pine sawdust, PIN, and its torrefied counterpart, PINT, pelletization performance, paying special attention to their abrasion index, higher heating value and energy density. It was observed that the addition of small quantities of lignin-rich solid additives, like grape pomace, enhances the natural binding properties of both PIN and PINT during pelletization using a bench-scale device. It was also found that a 13% overall moisture content and a glycerol addition of between 10 and 20% improve the pelletization properties of PIN and PINT, respectively, and increase their energy density when compared to the raw samples.

Investigation into clean energies has been focused on finding an alternative to fossil fuels in order to reduce global warming while at the same time satisfying the world’s energy needs. Biomass gasification is seen as a promising thermochemical conversion technology as it allows useful gaseous products to be obtained from low-energy-density solid fuels. Air–steam mixtures are the most commonly used gasification agents. The gasification performances of several biomass samples and their mixtures were compared. One softwood (pine) and one hardwood (chestnut), their torrefied counterparts, and other Spanish-based biomass wastes such as almond shell, olive stone, grape and olive pomaces or cocoa shell were tested, and their behaviors at several different stoichiometric ratios (SR) and steam/air ratios (S/A) were compared. The optimum SR was found to be in the 0.2–0.3 range for S/A = 75/25. At these conditions a syngas stream with 35% of H2 + CO and a gas yield of 2 L gas/g fuel were obtained, which represents a cold-gas efficiency of almost 50%. The torrefaction process does not significantly affect the quality of the product syngas. Some of the obtained chars were analyzed to assess their use as precursors for catalysts, combustion fuel or for agricultural purposes such as soil amendment.