Search

La presente invención se refiere a un procedimiento para producir un material transportador de oxígeno mediante la mezcla de CuO y Mn3O4, preparado por granulación en lecho fluidizado. El material así obtenido presenta una elevada reactividad, alta resistencia mecánica, bajo índice de atrición y baja velocidad de atrición. Dicho material se aplica en un proceso CLOU de combustión de sólidos con captura inherente de CO2

The objective of this work was to determine suitable design parameters NORWAY and operating conditions for the complete combustion of CH4 with the impregnated Cu-based oxygen carrier developed by ICB-CSIC.

Two different oxygen-carrier materials with similar molar ratios of Mn:Fe:Al were tested in continuous chemical-looping combustion operation with different fuels, i.e., syngas (H2/CO), methane, and kerosene. One oxygen carrier was manufactured by spray drying, and the other one was a naturally occurring ore that was crushed. Experiments were conducted in a bench-scale, chemical-looping combustion reactor with continuous fuel addition and continuous circulation of oxygen-carrier particles. In fresh state, i.e., before fuel operation, both materials showed clear CLOU properties. In used state, i.e., after fuel operation, the CLOU properties of the manufactured oxygen carrier were slightly higher than before, whereas those of the natural material decreased significantly. Operation with fuel was conducted for a total of about 47 h between 850 and 950 °C, and clear differences in fuel conversion were observed. At similar oxygen-carrier-to-fuel ratios and temperatures, the manganese ore achieved a clearly higher methane conversion, whereas the manufactured material achieved a higher conversion of H2 and CO. Near-complete conversion of syngas, i.e., >99%, was reached with both materials tested. Particle circulation was indirectly measured and used to estimate solids conversion during continuous operation. The materials were characterized with ICP-SFMS, XRD, and SEM/EDX, and rate indices were calculated based on data obtained in TGA tests with different reactants. Thermodynamic equilibrium calculations were made and used to interpret results from oxygen release and TGA tests. Attrition indices and material porosity were determined for fresh and used samples of the materials used. The manganese ore exhibited a clearly lower structural integrity during redox operation compared to the manufactured material. However, the cost of producing an oxygen carrier from an ore is significantly lower than manufacturing an oxygen carrier by spray drying.

The concentration of CO2 in the atmosphere has greatly increased over the last decades, very recently exceeding 400 ppm as a consequence of the anthropogenic CO2 emissions. The use of new alternatives to reduce these emissions is therefore highly encouraged. BioEnergy and Carbon Capture and Storage (BECCS) is emerging as an interesting option for the removal of CO2 from the atmosphere, and is seen as one of the best alternatives for meeting the target set out by the United Nations Framework Convention on Climate Change (UNFCCC) in the Paris Agreement: to limit the increase in the average world temperature to 2°C above pre-industrial levels. In this context, Chemical Looping (CL) is considered to be one of the most promising CO2 capture technology due to its low economic and energy costs. The process is based on the use of an oxygen carrier to transfer the oxygen from air to the fuel, preventing the contact between them. The large-scale deployment of CL technologies could present an important advantage for future bioethanol uses. This chapter describes the current status of bioethanol use in two processes: Chemical Looping Combustion (CLC) for energy production (heat & electricity), and Chemical Looping Reforming (CLR) for syngas/H2 generation. The chapter includes the basic concepts of the technology with a focus on the use of bioethanol and potential oxygen carriers, and operational experience in continuous units. Special interest is given to the use of bioethanol in autothermal-CLR processes, where H2 can be obtained as a final product without the need for external heat input, and with high CO2 capture efficiencies and producing a pure N2 stream. In addition, the possibility of using low-grade bioethanol in the process implies important savings in energy and economic costs during the bioethanol production process.

The in-situ Gasification Chemical Looping Combustion (iG-CLC) process allows combustion with inherent CO2 capture. In this process, the oxygen for combustion is commonly supplied by a solid oxygen carrier based on a metal oxide thus avoiding direct contact between fuel and air. The oxygen carrier circulates between two reactors. In the fuel reactor, the fuel is oxidized to CO2 and H2O while the oxygen carrier is reduced. In the air reactor, the reduced oxygen carrier is regenerated in air. Ilmenite has been widely used as a low-cost oxygen carrier for the iG-CLC process, and it can be taken as a reference material. Recently, the Tierga iron ore has been identified as a promising candidate for further scale-up of the process due to the higher combustion efficiency achieved compared to the results using ilmenite. Modelling of the iG-CLC process with Tierga iron ore as oxygen carrier is a key step to determine the potential of this material. In order to model the iG-CLC process it is necessary to know the reactivity of both oxygen carrier and fuel used. In this paper, the kinetic determination for the reduction and oxidation reactions of the Tierga ore is presented. Reaction orders close to unity were obtained for the main reducing gases, i.e. H2, CO and CH4, as well as O2. The activation energy values obtained were 81.1 ± 7, 76.1 ± 6 and 257 ± 14 kJ/mol for H2, CO and CH4, respectively. The activation energy for oxidation was determined as 18.4 ± 0.5 kJ/mol. In addition, a simple method is used for a comparison of the performance of different oxygen carriers based on their kinetics.

Chemical looping combustion (CLC) processes combined with CO2 sequestration and sustainable management of biomass represent a promising BioEnergy with Carbon Capture and Storage (BECCS) technology. One of the aspects to be considered in the combustion of biomass is the formation of NOx and the possible existence of tar in the gaseous product stream. The advantage of the CLC technology compared to other CO2 capture technologies is that only fuel-N contributes to nitrogen oxides formation. Moreover, scarce information is available about tar formation in CLC. Thus, this work focuses on these two aspects and compares the results obtained when two different chemical looping combustion modes are used, namely In Situ Gasification Chemical Looping Combustion (iG-CLC) and Chemical Looping with Oxygen Uncoupling (CLOU). Important differences were observed depending on the combustion mode. In both cases most of the fuel-N appeared as N2 in the fuel reactor. However, in iG-CLC more than 94% of the nitrogen measured in the fuel reactor was N2 independently of the biomass used. These percentages under the CLOU mode were lower. In this case, low amounts of N2O were also detected, although it decreased to almost zero at 850 °C. In the air reactor, NO was found and its concentration remained below the legal limit for NOx emissions in power installations with all the types of biomass tested and operating modes. Tar species and concentrations found at the fuel reactor outlet stream were different under the two combustion modes. About 2.5–3.7 g/Nm3 total tar could be found at 980 °C burning under iG-CLC mode, mostly naphthalene. On the contrary, insignificant tar amounts were found in CLOU.

In order to limit the increase in the global average temperature to 2 °C or below, the Paris Agreement proposed the reduction of CO2 emissions throughout this century. Bioenergy with CO2 capture and storage (BECCS) technologies represent an interesting option in order to allow this goal to be metgoal, because they are able to achieve negative CO2 emissions. Chemical looping (CL) is recognized as one of the most innovative CO2 capture technologies owing to its low energy penalty. CL processes permit the utilization of renewable fuels in a nitrogen-free atmosphere, given that the required oxygen is supplied by solid oxygen carriers. The present work presents an overview of the status of development of the use of biofuels in chemical looping technologies, including chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) for the production of heat/electricity, as well as chemical looping reforming (CLR), chemical looping gasification (CLG) and chemical looping coupled with water splitting (CLWS) for syngas/H2 generation. The main milestones in the development of such processes are shown, and the future trends and opportunities for CL technology with biofuels are discussed.

Chemical Looping Combustion (CLC) is considered one of the low cost alternatives for CO2 capture for fossil fuels combustion and to reach negative emissions through biomass CLC. The cornerstone of the CLC process is the oxygen carrier performance that represents the main additional cost with respect to the conventional combustion. Manganese-based oxygen carriers are subjected to a growing interest because they are low cost, not toxic and environmentally friendly. In this work five impregnated oxygen carriers, with manganese oxide Mn3O4 or Mg6MnO8 as their active phase and three commercial supports based on zirconia and synthetic calcium aluminate, were prepared. Their behaviour for CLC was examined by TGA, batch fluidized bed reactor, TPR, SEM-EDX and XRD. After a preliminary screening two carriers (Mn-ZrM and Mn-ZrSG) were subjected to multiple redox cycles by TGA and batch fluidized bed reactor. Both showed high solids conversion by TGA under the tested conditions, appropriated resistance to fracture, rate indexes relatively high, although Mn-ZrM showed agglomeration and deactivation during batch fluidized bed tests. Reactivity in batch fluidized bed reactor of the Mn-ZrSG oxygen carrier with methane increases with temperature although suffered from significant deactivation. This was different to the results found during multiple redox cycles by TGA. There was not a clear reason for this decrease in the reactivity that likely could be due to the uncomplete oxidation in the batch fluidized bed reactor, although further investigations are needed. On the other hand, it presented high and constant reactivity with CO and H2 in all the range of temperatures tested, being suitable for iG-CLC processes of coal or biomass and syngas combustion. Agglomeration problems were not found and the attrition losses were small. Calculated lifetime was around 11,000 h, much higher than any other Mn-based material developed or tested for CLC.

Chemical-Looping Combustion (CLC) is a promising technology for performing CO2 capture in combustion processes at low cost and with lower energy consumption. Fuel conversion modelling assists in optimizing and predicting the performance of the CLC process under different operating conditions. For this work, the combustion of natural gas was modelled using a CaMnO3-type perovskite as oxygen-carrier and taking into consideration the processes of fluid dynamics and reaction kinetics involved in fuel conversion. The CLC model was validated against experimental results obtained from the 120 kWth CLC unit at the Vienna University of Technology (TUV). Good agreement between experimental and model predictions of fuel conversion was found when the temperature, pressure drop, solids circulation rate and fuel flow were varied. Model predictions showed that oxygen transfer by means of the gas–solid reaction of the fuel with the oxygen-carrier was relevant throughout the entire fuel-reactor. However, complete combustion could be only achieved under operating conditions where the process of Chemical-Looping assisted by Oxygen Uncoupling (CLaOU) became dominant, i.e. a relevant fraction of the fuel was burnt with molecular oxygen (O2) released by the oxygen-carrier. This phenomenon was improved by the design configuration of the 120 kWth CLC unit at TUV, in which oxidized particles are recirculated to the upper part of the fuel-reactor. Thus, the validated model identified the conditions at which complete combustion can be achieved, demonstrating that it is a powerful tool for the simulation and optimization of the CLC process with the CaMnO3-type material.

Materiales basados en mezclas de óxidos de metálicos como transportadores de oxígeno. La presente invención se refiere a un material transportador de oxígeno con capacidad de generar oxígeno molecular basado en una mezcla de óxidos metálicos, como por ejemplo de manganeso y titanio, y su uso para la generación de oxígeno y la combustión con captura inherente de dióxido de carbono. La invención se encuadra en el sector de las tecnologías para la captura de CO2 generado en una combustión para evitar su emisión a la atmósfera.

The transport sector is the second largest energy consumer in EU being responsible for 33% of the total energy consumption and for about 25% of the total greenhouse gas emissions, and relies on crude oils for 95% of its energy needs. Decarbonizing the transport sector to support climate and energy goals is recognized as a major challenge in the Energy Roadmap 2050). The development of biofuels from sustainable biomass feedstocks can play an important role in this regard, supporting fuel security and the EU objective of having at least 32% of transport fuels derived from renewable sources by 2030, according to the Renewable Energy Directive 2018/2001. Plant biomass is the main source of renewable materials in Earth and represents a potential source of renewable energy and biobased products. Biomass is available in high amounts at very low cost (as forest, agricultural or industrial lignocellulosic wastes and cultures) and could be a widely available and inexpensive source for energy, transportation (bio)fuels and (bio)products. Using biomass as energy source can lower EU’s external energy dependence and reduce greenhouse gas emissions. In this regard, R&I need to focus on the efficient production of advanced biofuels from renewable sources. This chapter covers the main challenges that need to be addressed in the near future for using biomass as a safe and clean source of energy. Different technologies are reviewed for the production of energy from biomass, including thermochemical, biochemical and chemical processing technologies. The biomass can be burned, transformed into a fuel gas through partial combustion, into a biogas through fermentation, into bioethanol through biochemical processes, into biodiesel, into a bio-oil or into a syngas from which chemicals and liquid fuels can be synthesized. Moreover, it is being increasingly recognized that the overall cost-effectiveness of biomass-to-biofuels pathways can increase significantly through co-production of higher

[EN] CO2 emissions to the atmosphere became an important environmental problem because of the effect on the global warming and consequently, the climate change. The climate change challenge demands a commitment of combined strategies between global institutions, governments and citizens. To reach the objectives set in the Paris Agreement (2015), greenhouse gas emissions need to be reduced. No technology is currently able to achieve the necessary reductions in greenhouse gas emissions on its own. Biomass represents an interesting alternative fuel for heat and power production as a carbon dioxide-neutral fuel. Moreover, if the CO2 generated during biomass combustion process is captured then negative-CO2 emissions would be reached and these are named bioenergy with Carbon Capture and Storage (BECCS) technologies. Chemical Looping Combustion (CLC) came up as one of the most promising CO2 capture technologies thanks to the low energy penalty of the CO2 separation and therefore, low-cost. CLC technologies are based in two interconnected fluidized bed reactors without gas mixing. The combustion takes place in the fuel reactor where the oxygen is supplied by a solid oxygen carrier, normally metal oxides. After being reduced, the oxygen carrier goes to the air reactor without gas mixing between reactors where it is oxidized again in air, and it is able for a new redox cycle starts. The main objective of this thesis is to evaluate the biomass combustion with CLC technologies (bioCLC). The research plan covers studies different at different scales, starting at lab scale, through a 1 kWth pilot plant, to the continuous operation in a 20 kWth plant to demonstrate the viability and optimizing the operation range for different low-cost oxygen carriers and different types of biomass residues. Iron based ores as well as manganese ores has been pointed as promising oxygen carriers because of their reactivity and low cost. Under In Situ Gasification Chemical Looping Combustion (iG-CLC, [ES] Las emisiones de CO2 a la atmósfera se han convertido en un importante problema ambiental debido al calentamiento global y el consecuente cambio climático. El reto del cambio climático hace necesaria la aplicación de estrategias combinadas entre instituciones, gobiernos y ciudadanos. Para alcanzar los objetivos fijados en el Acuerdo de París (2015) es necesario reducir las emisiones de gases de efecto invernadero y actualmente ninguna tecnología es capaz de alcanzar los objetivos de reducción por si sola. La biomasa representa una interesante alternativa como combustible con emisiones neutras de CO2. Así mismo, si el CO2 generado durante la combustión de biomasa es capturado para su almacenamiento, se pueden alcanzar emisiones negativas de CO2 a través de la bioenergía con captura y almacenamiento de CO2. La combustión mediante transportadores de oxígeno destaca como una de las tecnologías de captura de CO2 más prometedoras gracias a la baja penalización energética debida a la separación del CO2, y su consecuente bajo coste. La combustión mediante transportadores sólidos de oxígeno se basa en la utilización de reactores de lecho fluidizado. La combustión tiene lugar en el reactor de reducción, donde el transportador sólido de oxígeno, normalmente un óxido metálico, se reduce. Después de reducirse, el transportador de oxígeno llega al reactor de oxidación, donde se vuelve a oxidar en aire para comenzar un nuevo ciclo redox. El principal objetivo de esta tesis es evaluar el potencial de las tecnologías de combustión mediante transportadores sólidos de oxígeno con biomasa. El plan de investigación incluye estudios a diferentes escalas, comenzando a nivel de laboratorio, continuando con planta piloto de 1 kWt y finalizando con la operación en continuo de una planta de 20 kWt para demostrar la viabilidad y optimizar los rangos de operación para el uso de distintos transportadores de oxígeno. Algunos minerales basados en hierro, así como otros basados en manganeso, h

Environmental protection and specifically Climate Change, has been become a global problem not only of social responsibility but also an obstacle for economic growth and development. The 5th Assessment Report of the International Panel on Climate Change (IPCC) and the 2015 Paris Agreement conclude it is needed to reduce the Greenhouse Gasses (GHG) emissions and even to develop carbon Negative Emission Technologies (NETs) to limit the global average temperature increase to 2 ºC during the present century. The energy sector is considered as one of the major contributors to anthropogenic CO2 emissions. Capture and Storage (CCS) technologies are an interesting technological option to reduce CO2 emissions from these punctual large emitters. The combination of CCS technologies with thefact that CO2 emissions from biomass combustion are considered neutral opens the possibility to Bio-Energy with Carbon Capture and Storage (BECCS), a recently proposed alternative among NETs. BECCS development wouldcontribute to achieve Paris Agreement objectives on atmospheric GHG concentrations. Chemical Looping Combustion (CLC) has been studied during the last decades as a promising capture technology due to the low cost of CO2 capture and its low energy penaltyassociated [1]. This technology allows the combustion in a N2-free atmosphere. The oxygen is transferred to the fuel by a solid Oxygen Carrier (OC) circulating between two fluidized bed reactors. In the fuel reactor the fuel is oxidized and an almost pure CO2 stream generated. In the air reactor, the oxygen carrier is regenerated in air. The objective of this work is to analyze the feasibility of the CLC with biomass as a BECCS technology. For that purpose, three biomass residues (pine sawdust, olive stone and almond shell) were evaluated between 900-1000ºC in a continuous 500 Wth unit operating under In situ Gasification-Chemical Looping Combustion (iG-CLC) mode at Instituto de Carboquímica (ICB-CSIC, Spain) withlow-cost oxygen ca

Bioenergy and Carbon Capture and Storage (BECCS), is an interesting option to remove CO2 from the atmosphere, thus mitigating the CO2 emissions from the use of non-renewable sources, i.e., fossil fuels. BECCS has been identified as a relevant measure to achieve the target enforced by the United Nations Framework Convention on Climate Change (UNFCCC) in the Paris Agreement: To limit the increase in the average world temperature to 2ºC above pre-industrial levels. However, implementing CO2 capture in bioenergy through common technologies has the drawback of high economic and energetic costs. In this sense, the Chemical Looping Combustion (CLC) technology allows inherent CO2 capture at low cost during combustion. The benefits of CLC are based on avoiding the costly separation steps required in commercial CO2 capture processes, e.g., CO2 separation in flue gases or O2 production for oxy-fuel combustion, by the use of an oxygen carrier. The purpose of the oxygen carrier, usually a particulate metal oxide, is to transfer oxygen from air to fuel in order to avoid the direct contact between them. Thus, the oxygen carrier provides the oxygen required for combustion in the so-called fuel reactor. The oxygen carrier is later regenerated by air in the air reactor. The most common design of a CLC unit includes two fluidized bed reactors, being those mentioned fuel and air reactors with the oxygen carrier continuously circulating among them. CLC has been widely investigated for the use of gaseous fuels and coal but the interest of using biomass has recently increased considering that negative CO2 emissions would be possible. The objective of this work is to contribute to the development of biomass combustion by CLC evaluating the use of new and highly reactive Mn-based materials as oxygen carriers. Experiments were performed in a continuous 500 Wth CLC unit at Instituto de Carboquimica (ICB-CSIC), consisting of two interconnected fluidized-bed reactors. After determination of bot, This work presents an overview of the recent advances in bio-CLC technology within the key strategies arising nowadays to mitigate climate change. The Paris Agreement, the new treaty of the United Nations Framework Convention on Climate Change (UNFCCC), urges to decarbonize the world energy systems in the near future in order to limit the increase in the average world temperature to 2ºC above pre-industrial levels. To reach this goal, CO2 emissions should start to decrease by 2020 and become negative by the end of the century. Among the different options, most of the low-carbon scenarios rely on the use of BECCS (Bioenergy and Carbon Capture and Storage) as mandatory technologies to reach negative emissions. In this sense, Chemical Looping Combustion (CLC) is considered one of the most promising CCS technologies for power plants and industries because its inherent CO2 capture avoids the energetic penalty present in other competing technologies. CLC process is based on the use of a solid oxygen carrier to transfer the oxygen from air to the fuel avoiding direct contact between them. The technology has undergone a great development during last 15 years including operational experience in continuous units and oxygen carrier’s manufacture. In addition, the new Chemical Looping with Oxygen Uncoupling (CLOU) process represents a qualitative step forward in solid fuel combustion due to the use of materials with capability to release oxygen. There are several renewable energy sources that can be used in chemical looping processes, including both solid and liquid fuels. The use of biomass in CLC represents important advantages compared to conventional biomass combustion. Besides CO2 negative balance, higher thermal efficiency, NOx formation reduction and lower corrosion in heat exchangers have been reported. In addition, several renewable liquid fuels, such as bioethanol can be also used both in combustion (CLC) and reforming (CLR) processes for heat/electricity and syngas/H

Chemical Looping Combustion (CLC) using renewable solid fuels appears as an important option to reach negative carbon emissions. In this work, three types of forest and agricultural residues (pine sawdust, olive stone and almond shell) were tested between 900–980 °C in a 0.5 kWth unit with an iron ore as oxygen carrier (Tierga ore) working under In situ Gasification-Chemical Looping Combustion (iG-CLC) mode. Specific solids inventories lower than 1000 kg/MWth were tested as they were consider more representative of what can be used in a larger CLC unit. CO2 represented about 70% in the fuel reactor outlet gas stream, followed by unburnt compounds: H2, CO and CH4. CO2 capture efficiencies increased with the fuel reactor temperature achieving almost 100% of capture with the three biomasses at temperatures above 950 °C. In contrast, no clear trend with the fuel reactor temperature was observed for the total oxygen demand, achieving values about 25%. The major contribution to this value comes from the unburned volatiles with a small contribution coming from tar (≈ 1%). Regarding tar, naphthalene was the major compound found at the different operating conditions. The present results support the consideration of the CLC process with biomass (bio-CLC) as a promising Bio-Energy with Carbon Capture (BECCS) technology.

Chemical Looping Combustion (CLC) has arisen during last years as a very promising combustion technology for power plants and industrial applications, with inherent CO2 capture which reduces the energy penalty imposed on other competing technologies. The use of solid fuels in CLC has been highly developed in the last decade and currently stands at a technical readiness level (TRL) of 6. In this paper, experience gained during CLC operation in continuous units is reviewed and appraised, focusing mainly on technical and environmental issues relating to the use of solid fuels. Up to now, more than 2700 h of operational experience has been reported in 19 pilot plants ranging from 0.5 kWth to 4 MWth. When designing a CLC unit of solid fuels, the preferred configuration for the scale-up is a two circulating fluidized beds (CFB) system. Coal has been the most commonly used solid fuel in CLC, but biomass has recently emerged as a very promising option to achieve negative emissions using bioenergy with carbon dioxide capture and storage (BECCS). Mostly low cost iron and manganese materials have been used as oxygen carriers in the so called in-situ gasification CLC (iG-CLC). The development of Chemical Looping with Oxygen Uncoupling (CLOU) makes a qualitative step forward in the solid fuel combustion, due to the use of materials able to release oxygen. The performance and environmental issues of CLC of solid fuels is evaluated here. Regarding environmental aspects, the pollutant emissions (SO2, NOx, etc.) released into the atmosphere from the air reactor are no cause of concern for the environment. However, the presence of SO2, NOx and Hg at the exit of the fuel reactor affects CO2 quality, which must be taken into account during the later compression and purification stages. The effect of the main variables affecting CLC performance is evaluated for fuel conversion, CO2 capture rate, and combustion efficiency obtained in different CLC units. Solid fuel conversion is normally

Previously validated mathematical CLC models were used to simulate the process performance of CLC methane combustion using an impregnated Cu-based material and to analyse the effect of the fuel reactor design; being either a bubbling fluidized bed or a circulating fluidized bed. The CLC models considered both the fluid dynamic of the fluidized beds at the specific regime and the corresponding kinetics of oxygen carrier reduction. From the model outputs, the performance of the different systems was assessed by calculating the methane conversion in the fuel reactor. Main results highlights that the selection of a suitable particle size of the oxygen carrier and cross section area are key factors to achieve complete combustion with low solids inventory in the fuel reactor. In addition, the growing of bubbles should be limited in order to achieve high CH4 conversion with low solids inventory values, mainly in the bubbling regime with low cross section areas. Complete combustion was predicted with solids inventory in the fuel reactor of 250 kg/MWth (1 m2/MW and particle size of 0.25 mm) or 125 kg/MWth (0.2 m2/MW and a particle size of 0.15 mm) in the bubbling and turbulent regime, respectively. Considering the pressure drop related to these conditions, conclusions for the optimization design of a CLC unit using the Cu-based oxygen carrier are drawn based on the results of the modelling and simulation.

Chemical looping reforming (CLR) is a process that enables the production of syngas/H2 with CO2 capture by using oxygen carriers that prevent direct contact between the fuel and air. This work presents the experimental results obtained in a 1 kWth CLR unit using a Ni-based oxygen carrier and diesel as fuel, as a first trial for further advancement with heavier liquid fuels. The influence of the main operating conditions, such as oxygen-to-diesel molar ratio and the H2O and/or CO2 feed into the system, was analysed in both steam and dry CLR processes. In addition, the combined steam-dry CLR process enabled the production of syngas with any H2/CO molar ratio between 0.2 and 3, which resulted in a wide variety of final products during its use in Fischer-Tropsch processes. In all cases, the syngas composition was close to that given by the thermodynamic equilibrium. These results demonstrate the technical feasibility of steam, dry, and combined steam-dry reforming processes for liquid fossil fuels in a chemical looping system.

Chemical looping with oxygen uncoupling (CLOU) is a chemical looping combustion (CLC) process for the combustion of solid fuels with the use of a solid oxygen carrier that releases gaseous oxygen inside the fuel reactor. The aim of this work was to study the fate of pollutant elements present in fuel, i.e. S, N and Hg, during CLOU combustion. Experiments using lignite as fuel were carried out in a 1.5 kWth unit operating continuously for more than 35 h of coal combustion. Novel particles containing 50 wt.% CuO, 10 wt.% Fe2O3 and 40 wt.% MgAl2O4 prepared by spray drying were used as the oxygen carriers in the CLOU process. Most of the sulphur introduced with the fuel exited as SO2 at the fuel reactor outlet, although a small amount of SO2 was measured at the air reactor outlet. Most of the nitrogen present in coal was found as N2 at the outlet of the fuel reactor, although 20 wt.% of N in the coal was converted to NO. Mercury speciation was also analyzed. The major mercury species in the fuel reactor was Hg0 (g), and the Hg0 (g)/Hgtotal (g) ratio in the air reactor was 0.5.

Procedimiento de preparación de transportadores de O2, producto así obtenido y su uso. La presente invención se refiere a un procedimiento para producir un material transportador de oxígeno mediante la mezcla de CuO y Mn3O4, preparado por granulación en lecho fluidizado. El material así obtenido presenta una elevada reactividad, alta resistencia mecánica, bajo índice de atrición y baja velocidad de atrición. Dicho material se aplica en un proceso CLOU de combustión de sólidos con captura inherente de CO2.

According to the IPCC, warming of the climate system is unequivocal and this is mainly consequence of the increase in the CO2 concentration in the atmosphere. In addition, “Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history”. These emissions are mainly consequence of the burning of C-fuels, mostly fossil fuels, which result in a net increase in carbon concentration in the atmosphere, soil and oceans. In fact, the natural carbon cycle in the earth is being affected. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions. The measures considered for the reduction of CO2 emissions to the atmosphere include the improvement in the use and generation of energy, the use of nuclear energy, the boost of energy generation from renewable sources and the CO2 capture and storage (CCS).

Synthetic manganese-iron mixed oxides are considered promising materials to be used as oxygen carriers for Chemical Looping Combustion of coal with carbon dioxide capture at low cost. The aim of this work was to evaluate a manganese-iron mixed oxide material with a manganese to iron molar ratio of 0.77:0.23 as oxygen carrier for coal combustion by means of chemical looping processes, including both ex-situ and in-situ gasification of coal. The preparation method -spray drying followed by calcination- was optimized in order to produce particles with high reactivity and mechanical strength. The material was studied in two continuously operated facilities designed to burn either gaseous or solid fuels. While full combustion was achieved burning syngas, showing the feasibility of the use of this material considering the ex-situ gasification process. Coal combustion efficiency by in-situ gasification process was improved in comparison with other previously tested low-cost materials such as ilmenite and iron ore. Moreover, the oxygen carrier particles showed an interesting magnetic behavior that was able to facilitate oxygen carrier recovery from the purge ash stream. In view of these results, the manganese-iron mixed oxide as oxygen carrier is proposed as a promising candidate for use coal combustion by the chemical looping process.

Chemical looping combustion (CLC) is a low-cost CO2 capture technology with a low energy penalty. Bio-energy with CO2 capture and storage (BECCS) opens up the possibility for negative CO2 emissions involving the removal of CO2 already emitted into the atmosphere. The oxygen needed for combustion in CLC processes is supplied by a solid oxygen carrier circulating between the fuel reactor and the air reactor. In this work, the combustion of different types of biomass, such as pine sawdust, olive stones and almond shells, was studied in a continuous 1.5 kWth CLC unit. A mixed Cu-Mn oxide was used as the oxygen carrier. This material releases gaseous oxygen when reduced, resulting in Chemical looping combustion with oxygen uncoupling (CLOU). The released oxygen reacts with both the volatiles and char generated inside the fuel reactor when biomass is fed into it. The oxygen carrier is reoxidized in air inside the air reactor. High CO2 capture and 100% combustion efficiencies were achieved with this Cu-Mn oxygen carrier. The oxygen concentration inside the air reactor did not affect CO2 capture efficiency under the studied conditions.

Oxy-fuel combustion is a CO2 capture technology which consists of burning the fuel with a mix of pure oxygen and recycled flue gas, mainly composed of H2O(v) and CO2. Therefore, after steam condensation, the CO2 concentration in the flue gas may be enriched up to 95% (dry basis). Many of current researches are related to oxy-fuel pulverized coal combustion. However, circulating fluidized bed combustors can be a promising technology because in addition to other advantages, they have the possibility of carrying out the in situ desulfurization process via Ca-based sorbent added into the combustor which is highly dependent on the temperature and concentration of CO2. Because under oxy-fuel combustion the sorbent can be surrounded by CO2 concentrations ranging from 60 to 90%, the sulfation of the Ca-based sorbent can be performed at calcining (CaO solid reactant) or non-calcining conditions (CaCO3 solid reactant). A particle sulfation model has been developed to describe the limestone sulfation reaction which is carried out in two steps. The simplicity of the kinetic model permitted it to be incorporated easily in a 1.5D computational simulation model of an oxy-fuel CFB to predict the sulfur retention reached inside the boiler. The model is capable of giving important information about the oxy-coal combustion process such as longitudinal profiles of the gases (O2, CO2, H2O, SO2, etc.), char concentration distribution, combustion efficiency and sulfur retention at different operating conditions. A simulation considering the main operating variables such as temperature, sorbent reactivity, O2 concentration fed, type of coal and the use of a desulfurization unit in the recycled flue gas was carried out to determine the most influential ones. The model is considered a useful tool to optimize the oxy-fuel combustion process in circulating fluidized bed combustors.

[EN] Today there are technologies that allow CO2 capture in power plants, but these technologies consume an important amount of energy due to the need of CO2 or O2 separation of the other gases. For this reason, new technologies for CO2 capture with low energy penalty are under developing. Among them, Chemical-Looping Combustion (CLC) process is suggested among the best alternatives to reduce the economic cost of CO2 capture because CO2 separation is inherent to the process. CLC involves the use of an oxygen carrier (OC), which transfers oxygen from air to the fuel avoiding the direct contact between them. CLC system is made of two interconnected reactors, designated as air and fuel reactors. A key issue for the LC technology development is the selection of an OC which is formed by an active metal oxide and inert that acts as support. Ni-, Cu-, Fe-, Co- and Mn-based OCs supported on different inert materials, in addition to CaS/CaSO4 transformation, have been studied to be used in a CLC process. Each material has different characteristics, and so, different advantages and disadvantages.Until now, most of the OCs have been used in small installations (up to 140 kWth) and with gaseous fuels, being the main objective with these fuels the scaling up of the technology to a higher power. Moreover, the use of the CLC with solid fuels has recently gained a great interest, being this aspect the main challenge of this technolgy., [ES] Actualmente existen tecnologías que permiten la captura de CO2 en centrales de producción de energía, pero éstas consumen gran cantidad de energía, bien en el proceso de separación del CO2 o en el de producción de oxígeno. Por ello, se están desarrollando nuevas tecnologías que permitan la captura de CO2 con bajas penalizaciones energéticas. Entre éstas, la tecnología de combustión con transportadores sólidos de oxígeno (conocida por su nombre en inglés como “Chemical-Looping Combustion”, CLC) presenta un gran potencial, ya que la separación del CO2 es inherente al propio proceso de combustión. El proceso CLC está basado en la transferencia de oxígeno del aire al combustible por medio de un transportador de oxígeno en forma de óxido metálico que circula entre dos reactores interconectados entresí y no poniéndose en contacto en ningún momento el combustible con el aire. Una pieza clave del proceso es el transportador de oxígeno, el cual está formado por un óxido metálico y un inerte que actua como soporte. Entre los metales existentes, los que pueden ser utilizados como transportadores de oxígeno son Ni, Cu, Fe, Co y Mn, y además el Ca en mediante la reacción CaS/CaSO4. Cada uno de ellos presenta diferentes características y por lo tanto diferentes ventajas e inconvenientes. Hasta el momento, los transportadores sólidos de oxígeno se han utilizado principamente en plantas pequeñas (de hasta 140 kWt) y con combustibles gaseosos, siendo el reto principal con estos combustibles su escalado a plantas de mayor potencia. Además, en los útimos años ha tomado un gran auge su uso con combustibles sólidos, siendo este el gran reto de esta tecnología.

The Chemical Looping with Oxygen Uncoupling (CLOU) process is a form of Chemical Looping Combustion (CLC) technology that enables the combustion of solid fuels by means of oxygen carriers that release gaseous oxygen in the fuel reactor, i.e. with oxygen uncoupling capability. In recent years, tests have found several Cu-based, Mn-based and mixed oxide oxygen carriers with suitable properties for the CLOU process. Among them, Cu-Mn mixed oxides show high reactivity and high O2 equilibrium concentration at temperatures of interest for coal combustion. In this work, proof of concept was demonstrated by burning coal with Cu-Mn mixed oxides in a 1.5 kWth CLOU unit for the first time. The effect of fuel reactor temperature, solids circulation flow, fluidization agent in the fuel reactor (inert N2 or steam as gasifying agent), and excess air in the air reactor on combustion efficiency and CO2 capture rate was analysed. The results showed that high combustion efficiency and CO2 capture are feasible using this material at relatively low fuel reactor operating temperatures. Therefore, the developed Cu-Mn mixed oxide was a suitable material for use as an oxygen carrier for the CLOU combustion of solid fuels. Optimum operating conditions were determined for this oxygen carrier with regard to the oxygen circulation rate and air reactor conditions for the regeneration of the oxygen carrier.

Promising impregnated oxygen carriers, based on copper and iron, have been previously developed for CLC with gaseous fuels (CH4, syngas, LHC). Recently, because of its low cost and environmental compatibility, Mn-based oxygen carriers are now being considered as an attractive option for chemical-looping combustion (CLC) applications. In this work, a screening of different commercial supports in fluidizable particle size for impregnated Mn-based materials has been carried out. Different oxygen carriers have been prepared by incipient impregnation on ZrO2, and CaAl2O4, and evaluated with respect to their mechanical resistance, fuel gas reactivity and fluidization properties such as agglomeration and attrition rate. In a first step, particles showing high enough crushing strength values were selected for the reactivity investigation. The redox reactivity was evaluated through TGA experiments at suitable temperatures for the CLC process (i.e. 850-950 °C) using H2, CO and CH4. Multi cycle redox analysis and full physical and chemical characterization was also performed. In a second step, materials with high enough reactivity were prepared for fluidized bed evaluation. A batch fluidized bed installation with continuous gaseous fuel feed was used to analyze the product gas distribution during reduction and oxidation reactions at different operation temperatures, and agglomeration and attrition behavior of the selected materials. Results showed that an oxygen carrier impregnated using ZrO2 as support, had high enough reactivity and low attrition rate. Therefore, this material can be selected as a candidate for the development of CLC with syngas with promising results.

The climate change challenge demands a commitment of combined strategies between global institutions, governments, companies and citizens. In order to reach 2015 Paris Agreement, greenhouse gas emissions need to be reduced. Any single technology is currently able to achieve atmospheric greenhouse concentration values for the purpose of climate change mitigation. Also carbon sinks will be needed to further this cause as well as Carbon Capture and Storage (CCS) technologies. In this sense, biomass represents an interesting alternative fuel for heat and power production as a carbon dioxide-neutral fuel. Moreover, if the CO2 generated during biomass combustion process was captured then negative-CO2 emissions would be reached. In this way, Bio-Energy with Carbon Capture and Storage (BECCS) technologies enable energy generation while CO2 is being removed from the atmosphere., Among the different options, Chemical Looping Combustion (CLC) is considered one of the most promising second generation CCS technologies due to its negligible energy and cost penalty for CO2 capture. In this work, three types of biomass were evaluated under CLC conditions: pine sawdust, olive stone and almond shell. Combustion experiments were performed in a continuous 500 Wth CLC unit at Instituto de Carboquímica (ICB-CSIC, Spain) using a highly-reactive low-cost iron ore as oxygen carrier (Tierga ore). During the experimental campaign, the effect of fuel reactor temperature (900-980 °C) on the combustion performance was analyzed. At the highest temperature tested (980 °C) a CO2 capture efficiency of 100% was reached with all the biomasses. However, the total oxygen demand followed no clear trend with temperature and the average value was close to 25%. The high volatile content of biomass compared to coal contributed to this effect. For a correct operation with biomass, further design measures should be taken to reduce the amount of unburned compounds at the outlet of the fuel reactor. In addition, tar and NOx measurements were done. No relevant drawbacks by the use of biomass in CLC were found related with other pollutants present in the system such as tar production or NOx emissions.

Chemical looping combustion (CLC) involves the use of a solid oxygen carrier to transport the oxygen from the air to a fuel. Attention has recently been focused on oxygen carriers based on Mn-Fe mixed oxides because they are cheap materials that are able to release oxygen at high temperature, the so-called oxygen uncoupling step. The aim of this work was to assess the use of (Mn0.77Fe0.23)2O3 material as an oxygen carrier with the ability to transport oxygen both by reduction with gaseous fuels and by oxygen uncoupling, i.e. typical mechanisms in CLC and in Chemical Looping with Oxygen Uncoupling (CLOU), respectively. The particles prepared by mechanical mixing were screened to obtain particles of sufficient reactivity and mechanical strength for use in a fluidized bed reactor. The preparation methodology and calcining temperature were varied. The reactivity of one selected material was evaluated by performing redox cycles both in a TGA and a batch fluidized-bed reactor. Thus, its behaviour was assessed during both decomposition-regeneration of bixbyite phase [(Mn0.77Fe0.23)2O3] in CLOU and the reduction-oxidation of spinel phase [(Mn0.77Fe0.23)3O4] with gaseous fuels, i.e. H2, CO and CH4. Its oxygen uncoupling and re-oxidation capability was highly influenced by the reaction temperature and oxygen concentration. On the other hand, CLC redox cycles with gaseous fuels showed high reactivity with H2 and CO and high oxygen transport capacity by reduction to mangano-wüstite phase [(Mn0.77Fe0.23)O]. Good fluid-dynamic behaviour was observed for the oxygen carrier particles along the redox cycles without agglomeration problems, regardless of the operating conditions used in the batch fluidized-bed reactor. Thus, the selected material was considered a promising candidate for use in both in CLC with syngas and CLC with coal.

The environmental implications of mercury do not correspond only to the emissions to the atmosphere; the quality of the captured CO2 to be transported and sequestered has been subject of research, concerning trace quantities of heavy metals participating in mineralization and precipitation reactions in sequestration conditions. For oxycoal combustion, mercury is not an environmental issue alone but also an operational issue, particularly about where mercury could accumulate within the CO2 processing unit. Therefore, Hg removal is necessary to prevent its attack on the aluminium heat exchangers. In this work, a regenerable sorbent based on carbon supported Au nanoparticles (0.1%wt) has been used for Hg capture under oxycoal combustion atmosphere. The influence of the presence of O2, NO, SO2 and HCl in a gas containing Hg and CO2 on the sorbent as well as on the Hg oxidation (Au can act as an oxidation catalyst) has been evaluated under a simulated flue gas. The presence of either NO or HCl in the simulated flue gas led to mercury oxidation, with oxidized mercury not evolving in the gas, indicating that it is retained on the sorbent; the oxidized mercury is well stabilized on Au surfaces of the sorbent and favours the Hg-Au amalgam formation. This sorbent has been also evaluated in 3 kWth oxycoal bubling fluidized bed combustor. A lignite with high sulphur content was burned in presence of limestone. Despite high SO2 concentration that reached the Au/C sorbent, high capture efficiency was achieved and breakthrough occurred after 3.5 h and 10% breakthrough is not reached during the experiments. Bearing in mind that regeneration time can be adjusted near 1 h, two swing sorbent beds could be used to control mercury emissions under oxycoal combustion conditions.

One form of Chemical Looping Combustion (CLC) with CO2 capture as an alternative to the burning of solid fuels is the Chemical Looping with Oxygen Uncoupling (CLOU) process. The CLOU process requires metal oxides with O2 release capacity at temperatures that are suitable for solid fuel combustion, e.g. copper and manganese oxides. A Cu-Mn mixed oxide comprising 34 wt% CuO and 66 wt% Mn3O4 and prepared by fluidized bed granulation was analysed for use as an oxygen carrier for the CLOU process. TGA and batch fluidized bed reactors were used to investigate oxygen generation rates, agglomeration behaviour and oxygen carrier attrition. A medium volatile coal from South Africa and its char were used as fuel in a batch fluidized bed reactor in a temperature range of 800–930 °C. The Cu-Mn oxygen carrier showed good release O2 rate and a high rate of oxygen transfer by direct gas-solid reaction. The presence of CO as a combustion product appeared only at low oxygen carrier to coal ratios. This material has the capacity to generate O2 at lower temperatures than needed for Cu-based oxygen carriers, which suggests that this material is suitable for work at lower temperatures in a fuel reactor with complete combustion of the fuel. The low attrition rate and attrition index, together with the stable crushing strength of the particles with redox cycles, make this Cu-Mn oxygen carrier suitable for operation in a continuous CLOU unit.

The autothermal Chemical-Looping Reforming (a-CLR) is a process where syngas is produced with two main advantages; there are captured CO2 emissions and the heat required for the syngas production is generated by the process itself. A Ni-based material is used as oxygen carrier circulating between two fluidized bed reactors: the fuel and air reactors. In this work, the auto-thermal conditions in a global H2 production process, integrated by the a-CLR process and a Water Gas Shift reactor, using different liquid fossil fuels were theoretically determined. The hydrogen production per mol of carbon in the fuel was similar for all fossil fuels, taking a value of 2.2 at the optimal operating temperature (700 °C). In addition, the possibility of working at low temperature for a maximum H2 production was experimentally demonstrated in a continuous 1 kWth a-CLR unit.