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The thermochemical conversion of swine manure using chemical looping processes is an alternative for obtaining bioenergy with CO2 capture and solving environmental problems related to excess nutrients and greenhouse gas emissions. In this study, the combustion of swine manure was performed in a chemical looping with oxygen uncoupling (CLOU) unit at the 0.5 kWth scale with copper-based oxygen carrier particles supported on magnetic MnFe spinel. The effects of the fluidisation agent (CO2 or steam), air excess (7%–23%), and temperature (800–950 °C) on different parameters, namely the CO2 capture rate, combustion efficiency, and nitrogenous compound emissions, were analysed. High combustion efficiencies (95%–98%) were achieved, and tar compounds were not detected in the flue gases. Similarly, elevated CO2 capture efficiency values (82%–99%) were also achieved, which increased by increasing the temperature. Most nitrogen (ca. 93%–96%) is converted into innocuous N2. The NO concentration increased with temperature, whereas N2O and NH3 concentrations decreased.

Sorption Enhanced Chemical Looping Reforming (SE-CLR) is the integration of the sorption enhanced reforming (SER) process with the chemical looping reforming technology (CLR) to produce a highly concentrated stream of H2 without the need of using a separation unit after the reforming and at the same time capturing the CO2 produced. This process is characterized by the use of an oxygen carrier (OC) together a sorbent as a CO2 carrier. On the one hand, the thermal integration of CLR in the sorption enhanced process allows the sorbent regeneration without an external heat supply. On the other hand, the sorption of CO2 by a sorbent allows to obtain a highly concentrated hydrogen stream. In this process, three interconnected fluidized bed reactors are required.

Chemical looping combustion with oxygen uncoupling (CLOU) enables solid fuel combustion with CO capture at low cost due to the capacity of the oxygen carrier to release molecular oxygen. The present study is focused on testing the performance of a magnetic Cu-based oxygen carrier with reinforced mechanical properties owing to the addition of kaolin via the combustion of three types of biomass in a 1.5 kW continuous CLOU unit. The effect of the main operating variables on process performance parameters was studied. Complete combustion of the different biomass types was achieved. Higher CO capture efficiencies were observed at 800–950 °C compared to the previous work done with this oxygen carrier without kaolin doping. The highest value of 97.5% CO capture efficiency was obtained at 950 °C during the combustion of pine sawdust. Moreover, the oxygen carrier retained its magnetic properties without any agglomeration problems after 80 h of hot circulation operation.

La conversión termoquímica del estiércol porcino mediante tecnologías de captura de CO2 como Chemical Looping Gasification (CLG) es una opción interesante para la obtención de bioenergía [1] y también para la solución de algunos problemas ambientales relacionados con este residuo. El proceso CLG obtiene gas de síntesis (H2 y CO) por medio de la gasificación y oxidación parcial de un combustible, el cual puede ser utilizado para la producción de biocombustibles, productos químicos o hidrógeno verde. Este proceso utiliza dos reactores interconectados con un transportador de oxígeno (óxido metálico) circulando entre ellos, permitiendo la oxidación parcial del combustible sin contacto directo entre el combustible y el aire. El objetivo de este trabajo es analizar el efecto de las principales variables de operación (temperatura, agente de fluidización y relación oxígeno/combustible) en una unidad CLG de 1.5 kWt sobre la captura de CO2 y la distribución de los alquitranes y de compuestos nitrogenados (N2, NH3, NOx) para la producción de syngas en el proceso CLG.

Chemical looping combustion (CLC) is a novel technology for the combustion of fuels with inherent CO2 capture. CLC is based on the transference of oxygen from air to fuel by means of an oxygen carrier which is based on a metal oxide. CuO/Al2O3 (14 wt.% CuO) and Fe2O3/Al2O3 (20 wt.% Fe2O3) particles have been used in several CLC units with different results when methane combustion was evaluated. In order to shed light on the main processes affecting methane conversion in CLC, a mathematical model for a dual circulating fluidized bed (DCFB) system was developed to simulate the behavior of CuO/Al2O3 and Fe2O3/Al2O3 in a CLC unit. The model consists of the coupling of individual fuel and air reactor models to simulate steady state of the CLC unit. Individual models consider both the fluid dynamics of the fluidized beds at the high velocity regime and the corresponding kinetics of oxygen carrier reactions, that is, reduction in the fuel reactor and oxidation in the air reactor. The model was validated using results obtained in a 120 kWth CLC unit with CuO/Al2O3 and Fe2O3/Al2O3 particles. The validated model was used to simulate the performance of these materials in the 10 MWth CLC unit. Desing parameters of the fuel and air reactors as well as the suitable particle size of the oxygen carriers were determined in order to achieve the complete combustion of natural gas in the CLC unit as a function of the oxygen carrier properties.

El estiércol porcino o purín es un residuo compuesto por una mezcla de excrementos sólidos y líquidos, restos de alimentos y agua de limpieza de camas porcinas cuya fracción sólida se caracteriza por presentar un alto contenido en carbono (51.5% daf), nitrógeno (4.0% daf), azufre (1.1% daf) y cenizas (29%). La conversión termoquímica de este residuo carbonoso se considera una opción interesante para obtener bioenergía. Su uso en tecnologías de captura de CO2 como Chemical Looping Combustion (CLC) puede resolver algunos problemas ambientales relacionados con el exceso de nutrientes en zonas agrícolas y emisiones de gases de efecto invernadero. El objetivo de este trabajo es analizar el efectos de las principales variables de operación (temperatura, agente de fluidización y exceso de oxígeno) sobre la eficacia de combustión en una unidad CLC, la captura de CO2 y la presencia de compuestos nitrogenados (N2, NH3, NOx).

Different chemical looping processes allow burning or gasify solid fuels with inherent CO2 capture because the oxygen is transferred from air to the fuel through a metal oxide based material, which is named oxygen carrier. To improve process efficiency and CO2 capture, highly reactive synthetic materials could be used. One of the challenges of using solid fuels is the oxygen carrier separation from the ash, because loss of oxygen carrier particles is expected during ash drainage. So, their costs would have necessary the recovery of the synthetic oxygen carrier. Mn-Fe based materials show magnetic properties in the spinel phase, which could be used for a magnetic separation. When these Mn-Fe materials are used at high temperature under oxidizing or reducing atmospheres, stability of the spinel phase should be guaranteed in order to take advantage of the magnetic properties. The design of low reactive Mn-Fe based materials with magnetic properties, which can be used as a support material for other highly reactive and active phases, was the main objective of this work. In this sense, the support must have high crushing strength, low reactivity under oxidation and reduction atmospheres at high temperatures and permanent magnetism at low temperature for solids separation. Materials prepared with different Mn/(Mn + Fe) molar ratios and calcination conditions were evaluated regarding mechanical strength, inerticity and magnetic properties. A Cu-based oxygen carrier prepared on the optimal support was prepared and evaluated along 240 oxidation-reduction cycles in thermobalance (25 h experiment), exhibiting suitable mechanical and magnetic characteristics as well as high reactivity.

Chemical looping with oxygen uncoupling (CLOU) is an efficient process for solid fuel combustion with CO2 capture. This process requires a material that is capable of releasing gaseous O2 within a high temperature window. Screening was performed of reactive CuO-based oxygen carriers prepared for the CLOU process with magnetic properties for easy separation from solid fuel ashes. The effects of the CuO fraction, method of preparation (with prior preparation of the magnetic Fe-Mn support or by direct mixing of Cu, Fe and Mn oxides) and calcination conditions on oxygen carrier performance were studied. Three oxygen carriers were chosen owing to their good Cu activity, reactivity and magnetism, and were prepared by fluidized-bed granulation for evaluation in a batch fluidized bed reactor. Two of these, both with a 30% CuO content, showed similar performance throughout the process. One was prepared by physically mixing components with a Mn/Fe ratio of 1:1, and the other was prepared using a previously calcined Fe-Mn support, mixed with CuO. Both oxygen carriers showed high reactivity for gaseous oxygen release, sustained reactivity and magnetism with redox cycles, in addition to low attrition rates and no agglomeration problems.

The objective of this study was to evaluate the effect of the chemical and thermal stress on the physical and chemical stability of a CuO/Al2O3 impregnated oxygen carrier during methane chemical looping combustion at high oxygen carrier to fuel ratios to ensure low solid conversion variations. The Cu-based particles were subjected to 130 h of operation in a 0.5 kWth chemical looping combustion unit burning CH4 at steady state and unchanged conditions. Two batches of particles were used to operate the fuel and air reactor either at 800 °C or 900 °C. A full solid characterization regarding crystalline compounds, oxidation state, ASTM attrition index, crushing strength and morphology analysis was carried out in order to investigate the physical and chemical stability of the oxygen carrier. Main conclusion derived from this research work is that the low oxygen carrier conversion variation allowed reducing the chemical stress and as consequence the copper loss from particles. However, the oxygen carrier was difficult to reoxidize at 900 °C due to the formation of CuAlO2. Operating at temperatures about 800 °C and at low solid conversion variation is proposed since copper loss was limited maintaining an adequate physical stability.

Limestone Chemical Looping Combustion process (LCL-C™) patented by Alstom Power Inc. proposes the formation of a CaSO4 oxygen carrier via sulfur retention process when supplying a Ca-based sorbent together with sulfurous fuels in the fuel reactor. In the present research work, four Ca-based sorbents, three limestones and one dolomite with different physico-chemical characteristics, have been evaluated as oxygen carrier precursors during consecutive redox cycles by thermogravimetric analysis. 5% H2 and 3000 vppm H2S (N2 to balance) and 10% O2 (N2 to balance) were selected as reducing and oxidizing gases, respectively. Additionally, an anhydrite ore has also been studied for comparison purpose. Results from SEM-EDX characterization of the sorbent particles revealed the existence of three different sulfation patterns: (1) uniform distribution, (2) core–shell structure and (3) high sulfur content with high limitation to be converted into CaSO4. All sorbents exhibited high oxygen transport capacity (Roc = 13.3–20.8%), except for the material showing pattern (3) (Roc = 2.6%). Likewise, the materials presented high reactivity with rate index values ranged between 11.0 and 18.8%/min. Therefore, the Ca-based sorbents herein assessed can be considered suitable precursors for the formation of CaSO4 based oxygen carriers to be used in CLC systems burning sulfurous fuels.

The Chemical Looping with Oxygen Uncoupling (CLOU) process is a derivative technology of the Chemical Looping Combustion (CLC) process for the combustion of both renewable and non-renewable solid fuels. The present work studies the combustion and CO2 capture efficiency of burning coal or biomass using a single Cu-based oxygen carrier with magnetic properties as an oxygen carrier. The combustion of two different coals and three different biomasses was performed in a 1.5 kWth CLOU continuously operated unit for 36 h. The magnetic properties of the oxygen carrier were also studied after combustion and its separation from the ashes. Complete combustion of the fuel to CO2 and H2O was achieved in all cases. For both coals, CO2 capture efficiency increased with fuel reactor temperature, with both reaching values of 97% at 900 °C. The same increase was obtained with the biomasses. The highest CO2 capture efficiency for a biomass was obtained with pine sawdust, which achieved a value of 93%, followed by almond shell (86%) and olive stone (80%) at 900 °C. Oxygen carrier reactivity remained constant after use in the continuous unit with one small increase in the attrition jet index (AJI) value. The used particles were found to still be as magnetic as the fresh particles, and the fines were also highly magnetic. Values higher than 99% were achieved with separation from the fines reached. It was therefore proven that the elutriated oxygen carrier from the plant was still magnetic and could be easily separated from the elutriated ash.

Manganese oxides are capable of releasing molecular oxygen and regenerate in air under determined conditions. This fact makes these materials interesting for applications in different areas, such as thermochemical energy storage processes, oxygen production by chemical looping air separation (CLAS) or CO2 capture-oriented processes, namely chemical looping combustion (CLC) or chemical looping with oxygen uncoupling (CLOU). In this work, the potential to release molecular oxygen and regenerate in air of different manganese‑titanium mixed oxides with mass fractions of titanium from 0 to 50%, were evaluated in a TGA apparatus. Besides, the reactivity of the mixed oxide samples to the main fuel gases (CO, H2 and CH4) has been also evaluated. Consecutive redox cycles have been performed at different temperatures (850 and 940 °C) using nitrogen during reduction and air in oxidation. The oxygen transport capacity as well as the rate index for oxygen uncoupling and gas-solid reactions have been determined and compared to that found for other materials reported in literature. Moreover, solid phase identification in the different mixed oxide samples by XRD has been addressed in order to determine the oxygen release/regeneration mechanism. Results show a great potential of these materials as low-cost and environmentally friendly oxygen carriers.

Minerals or industrial waste materials are considered promising oxygen carriers for coal combustion through in-situ Gasification Chemical Looping Combustion (iG-CLC) process in order to maintain CO2 capture at low cost. Nevertheless, complete coal combustion to CO2 and H2O is usually not achieved and different solutions have been outlined to improve it. The aim of this work is to analyze the potential of two of these strategies: (1) using a more reactive oxygen carrier; and (2) to have two fuel reactors by feeding the coal into the carbon stripper. Coal combustion in a 50 kWth CLC unit was carried out using two oxygen carrier materials, namely Norwegian ilmenite and Tierga iron-ore. Also, an additional test was carried out feeding the coal directly into the carbon stripper of the CLC unit, in contrast with the conventional coal feeding to the fuel reactor. CO2 capture efficiency was barely affected by the type of oxygen carrier material, but slightly lower values were obtained when coal was fed to the carbon stripper. In contrast, coal combustion efficiency was enhanced by using the iron-ore material, with a potential decrease of the total oxygen demand of 40%, achieving a minimum value of total oxygen demand of 4.1%. Also, the total oxygen demand was decreased by 24% when coal was fed to the carbon stripper due to the improvement in the combustion of the volatiles in the fuel reactor. The combination of both strategies has high potential to maximize the coal combustion via iG-CLC process.

La presente invención se refiere a un soporte magnéticamente estable, estructural y químicamente a altas temperaturas en atmósferas oxidantes y reductoras, y que muestra y mantiene propiedades magnéticas a temperatura ambiente, de fórmula general (MnxFe1-x)3O4, que tiene estructura cristalina tipo espinela, y al sistema de fórmula general (MnxFe1-xMy)3O4+5/FA formado por dicho soporte y una fase activa. La presente invención además se refiere a los procedimientos de obtención de dicho soporte y de dicho sistema magnético, así como a sus usos en procesos en que dicho sistema necesita ser separado de otros materiales tras su uso en procesos industriales con atmósferas oxidantes y/o reductoras. La presente invención se engloba dentro del sector industrial y de la energía en procesos dirigidos a la mitigación del cambio climático

El Acuerdo de París fijó el objetivo de limitar en 2 ºC el incremento de temperatura media global sobre los valores preindustriales. Para tal efecto, el IPCC señala a la bioenergía con captura y almacenamiento de CO2 (BECCS en inglés) como una de las tecnologías clave para reducir el impacto del cambio climático pudiendo alcanzarse emisiones negativas de CO2. La implementación de biocombustibles en las tecnologías tradicionales de captura de CO2 implica un alto coste energético del combustible obteniendo una corriente de CO2 prácticamente puro con uno de los menores costes energéticos asociados. El proceso se basa en la utilización de un transportador de oxígeno (TO), normalmente un óxido metálico, que al transportar el oxígeno del reactor de oxidación al de reducción, evita la mezcla del oxígeno del aire y los gases de combustión, evitando de este modo la aplicación de un proceso de separación de gases. En este trabajo se evaluó en una planta piloto de 20 kW de potencia, el efecto de las principales variables de operación bajo condiciones de In situ Gasification-CLC como son la circulación de sólidos, el tipo de agente gasificante y el inventario específico de sólidos en el reactor de reducción sobre los principales parámetros de rendimiento del proceso como son la eficacia de captura de CO2 y la demanda total de oxígeno.

Bioenergy with Carbon Capture and Storage (BECCS) represents an interesting option to achieve the negative CO2 emissions needed to comply with the climate challenges set in the Paris Agreement (COP21-2015). Chemical Looping Combustion (CLC) technology has revealed as one of the CO2 capture technologies with less energy penalty and lower cost. CLC combined with biomass could become a promising BECCS technology. The objective of this work was to asses the feasibility of the CLC technology using biomass as fuel as a future BECCS technology.

Uno de los grandes retos a los que se enfrenta la sociedad actual y la futura es la lucha contra el cambio climático. El término captura y almacenamiento de CO2 (CAC) alude al conjunto de tecnologías que consiguen la separación y la captura del CO2 generado en procesos industriales y de generación eléctrica, y su posterior transporte hasta un lugar adecuado y seguro para su almacenamiento permanente. De esta manera se logra aislar el CO2 de la atmósfera durante un periodo largo de tiempo. La tecnología CLC es la opción más adecuada desde un punto de vista termodinámico para capturar el CO2 ya que se hace de forma inherente al propio proceso, lo que minimiza la pérdida de eficiencia energética respecto de una instalación sin sistema de captura. Este proceso se basa en transferir oxígeno del aire al combustible usando un transportador sólido de oxígeno, basado en un óxido metálico, que se encuentra circulando continuamente entre dos reactores de lecho fluidizado interconectados, denominados reactor de reducción y reactor de oxidación. Ello evita el contacto entre el combustible y el aire durante todo el proceso de combustión.

Chemical looping combustion allows the carbon dioxide capture by using an oxygen carrier, which transports the oxygen required for combustion from the air to the fuel. But complete combustion of a solid fuel is not achieved when low cost materials were used as oxygen carriers. Manganese‑iron mixed oxide doped with titanium has been identified as a promising oxygen carrier to improve combustion efficiency due to its oxygen uncoupling capability. The objective of this work was to assess the potential of this oxygen carrier when burning coal in a chemical looping unit. The coal combustion efficiency and carbon dioxide capture were evaluated as a function of the operating conditions both in the fuel and air reactor. Carbon dioxide capture was affected by the solids residence time in the fuel reactor. Coal combustion efficiency increased as the oxygen uncoupling capability was enhanced by using suitable operating conditions in the air reactor. Almost full coal combustion (99.4%) was achieved by setting an air reactor temperature of 880 °C, an air excess of 1.8, a fuel reactor temperature of 925 °C, and an oxygen carrier to fuel ratio >3. The oxygen carrier showed magnetic properties, allowing its re-use after being separated from ash.

Bioenergy with carbon dioxide (CO2) capture and storage (BECCS) technologies represent an interesting option to reach negative carbon emissions, which implies the removal of CO2 already emitted to the atmosphere. Chemical looping combustion (CLC) with biomass can be considered as a promising BECCS technology since CLC has low cost and energy penalty. In CLC, the oxygen needed for combustion is supplied by a solid oxygen carrier circulating between the fuel and air reactors. In the fuel reactor, the fuel is oxidized producing a CO2-concentrated stream while the oxygen carrier is reduced. In the air reactor, the oxygen carrier is regenerated with air. Chemical looping with oxygen uncoupling (CLOU) is a CLC technology that allows the combustion of solid fuels as in common combustion with air by means of an oxygen carrier that release gaseous oxygen in the fuel reactor. In the last years, several Cu-based, Mn-based, and mixed oxide oxygen (O2) carriers have been tested showing good CLOU properties. Among them, copper (Cu)-based and Cu-Manganese (Mn) mixed oxides showed high reactivity, O2 release rate, and high O2 equilibrium concentration. The aim of this work is to study the viability of biomass combustion by CLOU process. The combustion of three types of biomass (pine sawdust, olive stone, and almond shell) were studied in a continuous 1.5 kWth CLC unit. Two O2 carriers were tested: a Cu-based oxygen carrier with Magnesium, Aluminum, Oxgen (MgAl2O4) as an inert prepared by spray drying (Cu60MgAl) and a mixed Cu-Mn oxide prepared by spray granulation (Cu34Mn66). These materials are capable of releasing gaseous oxygen when they are reduced in a different range of temperatures. CO2 capture and combustion efficiency were evaluated. Two fuel reactor operation temperatures were used: 775–850 °C for Cu34Mn66 and 900–935 °C for Cu60MgAl. High CO2 capture efficiencies and 100% combustion efficiency were reached with both oxygen carriers and with all the biomasses tested. Ther

Bimetallic manganese-iron materials have been identified as suitable oxygen carriers for Chemical Looping Combustion (CLC) and Chemical Looping with Oxygen Uncoupling (CLOU) processes. These materials allow the combustion of a fuel with inherent CO2 capture according to two parallel mechanisms: reaction with lattice oxygen and oxygen uncoupling. This work is focused on the evaluation of the reactivity and physicochemical characterization of oxygen carrier particles consisting of a manganese-iron mixed oxide with manganese to iron molar ratio of 66:34 and doped with titanium (7 wt% TiO2) with the objective of determining suitable conditions to be used in CLC and CLOU processes. Particles were prepared by spray drying and the sintering procedure was optimized in order to achieve particles with high reactivity and mechanical strength. In addition, suitable magnetic properties were also sought in order to allow oxygen carrier recover and reuse in a chemical looping unit burning solid fuels. Optimum operating conditions for the fuel combustion and regeneration stages were determined in order to promote the oxygen uncoupling mechanism. Thus, temperature during the fuel combustion must be as high as possible to enhance the oxygen transference; but conditions for oxygen carrier regeneration by air must be carefully selected in order to take advantage of the oxygen uncoupling capability of this material. An oxidizing temperature interval of 1123–1173 K maximized the regeneration, while an air excess higher than 20% would be recommended in order to guarantee oxygen uncoupling capability.

Chemical Looping Combustion (CLC) with solid fuels has been widely developed by using two interconnected fluidized beds, the fuel reactor and the air reactor, with an oxygen carrier continuously circulating between them. Experience gained in this process shows that high CO2 capture values can be reached. However, complete combustion of the fuel is not achieved, with some H2, CO and CH4 as the main unconverted compounds in the combustion products from the fuel reactor. It is believed that the combustion efficiency can be increased by improving the gas-solid contact in the fuel reactor. In this work, the solids distribution in the fuel reactor was modified by using ring-type internals with the objective of enhancing the gas-solid contact. Two experimental campaigns were carried out in a 50 kWth CLC unit burning a bituminous coal with ilmenite particles in the temperature interval of 900–1000 °C. The first campaign was conducted with the original riser of the fuel reactor, which was characterized by a smooth section from bottom to top. For the second campaign, three ring-type internals were implemented in the riser in order to modify the solids distribution in the fuel reactor. The presence of the internals had a beneficial effect on the coal combustion. The major benefit was an improved oxidation of volatile matter in the form of CH4 and the full conversion of H2. As a result, the total oxygen demand decreased by 20%, from 12.2% to 9.8%, with the implementation of the internals.

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.

Alumina-supported Fe2O3 oxygen carrier material (OCM) system is among the most promising OCM systems for solid and gaseous fuel CLC. This work utilizes a comprehensive thermogravimetric and thermodynamic equilibrium approach to redox and CLOU performance, oxygen transfer capacity, reduction rate and sulfur tolerance of the Fe2O3 impregnated on Al2O3 OCM. Thermodynamic evaluations reveal that the beneficial composition range lies in a wide range of 7.5–34% molar Fe2O3 ratios. This is the range at which aluminum-rich corundum phase, i.e., (Al, Fe)2O3, remains stable throughout the oxidizing to very reducing oxygen partial pressures in fuel reactor. The experimental system in this study contains 20 mass% Fe2O3, i.e., XFe = 13.8% molar which lies well within this interval. Deep redox cycle experiments confirm the thermodynamic modeling and during the long residence time of this experiment, the sample is almost fully reduced and exhibits its thermodynamic redox oxygen capacity of close to 1.5 mass%. Extension of the deep redox cycles to 15 cycles induces no performance deterioration in terms of capacity, rate of reduction or morphological failure. The redox experiment under sour reducing gas indicates no H2S poisoning for the 20 mass% Fe2O3 supported on Al2O3 OCM. The findings that this system is not affected with the H2S content of the gas, and the prediction of the SO2 release from the fuel reactor is in good agreement with our recent reactor testing findings available in the literature.

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.

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.