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The autothermal Chemical-Looping Reforming (a-CLR) is a process where syngas is produced with two main advantages; there are captured CO 2 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 H 2 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 H 2 production was experimentally demonstrated in a continuous 1 kW th a-CLR unit. [ABSTRACT FROM AUTHOR]

One of the most important current objectives of the Chemical Looping Combustion (CLC) technology for gaseous fuels lies in scaling-up the aforementioned technology in the short term from 100 kW th to 10 MW th scale. In order to meet this challenge, the commercial availability of suitable multi ton-scale oxygen carrier materials at competitive price is needed. In this work, a Cu-based oxygen carrier prepared by the impregnation method using a commercial alumina as support, referred as Cu14γAl_Commercial, has been developed and evaluated in a 500 W th CLC pilot plant during the combustion of CH 4 at two different temperatures, i.e., 800 °C and 900 °C. The outstanding results obtained in terms of both combustion efficiency and mechanical stability have shown that the Cu14γAl_Commercial impregnated oxygen carrier can be selected to upscale CLC technology for gaseous fuels. [ABSTRACT FROM AUTHOR]

Autothermal Chemical-Looping Reforming (a-CLR) is a process which allows hydrogen production avoiding the environmental penalty of CO 2 emission typically produced in other processes. The major advantage of this technology is that the heat needed for syngas production is generated by the process itself. The heat necessary for the endothermic reactions is supplied by a Ni-based oxygen-carrier (OC) circulating between two reactors: the air reactor (AR), where the OC is oxidized by air, and the fuel reactor (FR), where the fuel is converted to syngas. Other important advantage is that this process also allows the production of pure N 2 in the AR outlet stream. A renewable fuel such as bioethanol was chosen in this work due to their increasing worldwide production and the current excess of this fuel presented by different countries. In this work, mass and heat balances were done to determine the auto-thermal conditions that maximize H 2 production, assuming that the product gas was in thermodynamic equilibrium. Three different types of bioethanol has been considered according to their ethanol purity; Dehydrated ethanol (≈100 vol.%), hydrated ethanol (≈96 vol.%), and diluted ethanol (≈52 vol.%). It has been observed that the higher H 2 production (4.62 mol of H 2 per mol of EtOH) has been obtained with the use of diluted ethanol and the surplus energy needed could be compensated by the energy save achieved during the purification of ethanol in the production process. [ABSTRACT FROM AUTHOR]

Sour gas represents about 43% of the world's natural gas reserves. The sustainable use of this fossil fuel energy entails the application of CO2 Capture and Storage (CCS) technologies. The Chemical Looping Combustion (CLC) technology can join the exploitation of the energy potential of the sour gas and the CO2 capture process in a single step without the need of a sweetening pre-treatment unit. In this work, a total of 60 h of continuous operation with sour gas and H2S concentrations up to 15 vol% has been carried out in a 500 Wth CLC unit, from which 40 corresponded to a Cu-based oxygen carrier (Cu14γAl) and 20 to a Fe-based material (Fe20γAl). This is the first time that so high H2S concentrations are present in a fuel to be burnt in a CLC process. The Cu14γAl oxygen carrier seems to be not recommendable for the combustion of sour gas because, although all the H2S is burnt to SO2, copper sulfides were formed at all combustion conditions. In contrast, the Fe20γAl oxygen carrier presented an excellent behavior with no agglomeration problems and maintaining the reactivity of the fresh material. The sour gas (CH4, H2 and H2S) was completely burnt, and neither SO2 was released in the AR nor iron sulfides were formed at usual CLC operating conditions. These tests demonstrated the possibility to use sour gas in a CLC process with 100% CO2 capture without any SO2 emissions to the atmosphere. [ABSTRACT FROM AUTHOR]

Highlights: [•] CLC of biomass (pine) was performed in a 500Wth continuous unit. [•] High carbon captures (>96%) were obtained at 880–915°C. [•] Main combustion products were CO2 and steam. Tar decreased with temperature. [•] Recirculated CO2 can be used as gasifying agent maintaining efficiency. [•] No alkali deposition from biomass ashes was observed. [ABSTRACT FROM AUTHOR]

Abstract: The interest in the use of solid fuels such as coal in Chemical Looping Combustion (CLC) is growing because of the benefits of the direct use of coal in this technology on the reduction of the costs linked to carbon dioxide capture. In CLC, the oxygen needed for the combustion is supplied by a solid oxygen carrier therefore avoiding the direct contact between fuel and air. Focusing on the use of solid fuels in the in situ Gasification Chemical Looping Combustion (iG-CLC), the oxygen carrier is mixed with the coal in the fuel reactor, where gasification of the coal and reaction of the gasification products with the oxygen carrier particles take place. In this process, the possible loss of oxygen carrier together with the ashes makes it interesting to find inexpensive materials to be used as carriers, such as natural minerals or industrial residues. In this work, an Fe-based bauxite waste is used as oxygen carrier in the combustion of different types of coal. Experiments were performed in a TGA and a batch fluidized bed (FB) using both coal and char from the corresponding coal. The influence of temperature as well as the gasifying agent composition on the performance of coal conversion in an iG-CLC process was evaluated. Tests in a thermogravimetric analyzer (TGA) revealed direct char combustion by oxygen in the bauxite waste material, but no evidences of such direct combustion were found in the experiments in the batch fluidized bed. In this case, gasification of char by H2O or CO2 was found as a necessary step in char conversion. Using steam as gasifying agent, higher char gasification rates were observed than using CO2 and in all conditions lignite presented the highest char gasification rate. At 980°C, the lignite char gasification rate in CO2 doubled the value obtained with anthracite using steam, indicating that recirculated CO2 can be fed to the fuel reactor of a CLC system if lignite is used as fuel. For the rest of the fuels, it was possible to use a mixture of H2O and CO2 as gasifying agent without decreasing the feasibility of the iG-CLC process. The bauxite waste was able to burn the gaseous products generated during the gasification of the different types of coal with high combustion efficiencies. [Copyright &y& Elsevier]

Abstract: Chemical-looping with oxygen uncoupling (CLOU) process is a chemical-looping combustion (CLC) technology that allows the combustion of solid fuels using oxygen carriers with inherent CO2 separation. The oxygen necessary for the fuel combustion is supplied by a solid oxygen carrier, which contains a metal oxide. The oxygen carrier circulates between two interconnected fluidized reactors: the fuel and the air reactor. In the CLOU process, the oxygen carrier releases gaseous oxygen in the fuel reactor which burns coal as in common combustion with air, so the CO2 generated is undiluted with N2. The reduced oxygen carrier is oxidized by air to the initial metal oxide in the air reactor, then being ready to start a new cycle. The aim of this work is to study the performance of the CLOU process using coals of different rank. Experiments were carried out in a continuously operated 1.5kWth unit. Particles prepared by spray drying containing 60wt% CuO were used as oxygen carrier. Four coals of different rank (anthracite, low volatile bituminous, medium volatile bituminous and lignite) were used as fuel. Besides, the temperature in the fuel reactor was varied between 900 and 950°C. In all the experiments there was complete combustion of the coal to CO2 and H2O, without any unburnt product. The carbon capture efficiency greatly depends on the coal rank and fuel reactor temperature. High carbon capture efficiencies were obtained for lignite and medium volatile bituminous coals. The maximum capture efficiency was 99.3% at 950°C with lignite. The analysis of the experimental results was used to evaluate the effect of the coal rank in a CLOU system when a carbon separation system is included. At 925°C, the solid inventory needed to reach 95% of CO2 capture efficiency with a carbon separation system of 90% of efficiency is 45kg/MWth using lignite, 85kg/MWth using MV bituminous, 140kg/MWth using LV bituminous and 490kg/MWth using anthracite. It must be pointed out the low solid inventories needed in the CLOU process for the different coal rank analyzed in this work. [Copyright &y& Elsevier]

Abstract: Chemical-Looping Combustion, CLC, is one of the most promising processes to capture CO2 at low cost. It is based on transferring the oxygen from air to the fuel by using a solid oxygen-carrier that circulates between two interconnected fluidized-bed reactors: the fuel- and the air-reactor. In this work, CLC with coal was investigated in a continuous 500Wth rig using ilmenite as oxygen-carrier and Colombian bituminous coal as fuel. In the fuel-reactor the oxygen-carrier is reduced by the volatile matter and coal gasification products. The effect of operating conditions such as the solids circulation rate and oxygen-carrier residence time, the coal flow feed and the steam flow as gasification agent were investigated on the combustion efficiency and extent of gasification. The influence of using CO2 as gasification agent was assessed by doing experiments with different CO2–H2O mixtures. The results obtained are valid for the scale-up of a CLC process with coal. They indicate that it is feasible to decrease the gasification agent flow to lower values than the corresponding stoichiometric for the gasification, and that some of the steam as gasification agent can be replaced by CO2 recirculated from the fuel-reactor outlet. Low circulation rate of solids improved coal conversion. [Copyright &y& Elsevier]

Abstract: Chemical-Looping Combustion, CLC, is a promising technology to capture CO2 at low cost in fossil-fuelled power plants. In CLC the oxygen from air is transferred to the fuel by a solid oxygen-carrier that circulates between two interconnected fluidized-bed reactors: the fuel- and the air-reactor. This work studies the CLC technology in a 500Wth facility fuelled with bituminous coal with ilmenite as oxygen-carrier. The effect of temperature and coal particle size on coal conversion and combustion efficiency was assessed. Char gasification and combustion of both gasification products and volatile matter were evaluated. At higher temperatures, gasification and combustion reactions are promoted. Carbon capture and combustion efficiencies grow with the temperature, with faster increase at temperatures higher than 910°C. The outgoing unburnt gases come from volatile matter that was not fully oxidized by ilmenite. Little CH4 was measured and there were neither hydrocarbons heavier than CH4 nor tars in the fuel-reactor outlet. At 870°C the char conversion was 15% and reached 82% at 950°C. The combustion efficiency in the fuel-reactor increased from 70% at 870°C to 95% at 950°C. The results show that ilmenite has good behavior as oxygen-carrier and that optimizing CLC with coal can lead to energy production with high CO2 capture. [Copyright &y& Elsevier]

Abstract: Chemical-looping combustion (CLC) is a combustion technology with inherent CO2 separation and, therefore, without energy losses. CLC is based on the transfer of oxygen from the air to the fuel by means of an oxygen carrier (OC) in the form of a metal oxide. The OC circulates between two interconnected reactors, the fuel (FR) and the air reactor (AR). To scale up the CLC process for industrial application OCs materials suitable to work at high temperatures are needed. So far, Cu-based OCs had been proved to fulfil the requirements for an OC material, although operating temperatures lower than 1073K are recommended. In this work, the behaviour of an impregnated Cu-based oxygen carrier (CuO–γAl2O3) was studied in a continuous CLC unit of 500Wth during long-term tests using methane as fuel gas and FR temperatures up to 1173K and AR temperatures up to 1223K. The behaviour of the oxygen carrier on the process performance was evaluated taking into account important aspects such as combustion efficiency, resistance to attrition, fluidization behaviour and preservation of the oxygen transport capacity and reactivity. It was found that both T FR and T AR had a great influence on the resistance to attrition of the particles. Stable operation for more than 60h was only feasible at T FR =1073K and T AR =1173K. However agglomeration or deactivation of the particles was never detected in any of the temperatures used. This is the first time that a CuO–γAl2O3 OC, prepared by a commercial manufacturing method, and used at 1073K in the FR and 1173K in the AR exhibits such a good properties: high reactivity together with high mechanical durability and absence of agglomeration. This result opens new possibilities for the application of Cu-based materials in industrial-scale CLC processes. [Copyright &y& Elsevier]

Abstract: Chemical-Looping Combustion (CLC) is an emerging technology for CO2 capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. Natural or refinery gas can be used as gaseous fuels and they may contain different amounts of sulphur compounds, such as H2S and COS. This paper presents the combustion results obtained with a Cu-based oxygen carrier using mixtures of CH4 and H2S as fuel. The influence of H2S concentration on the gas product distribution and combustion efficiency, sulphur splitting between the fuel reactor (FR) and the air reactor (AR), oxygen carrier deactivation and material agglomeration was investigated in a continuous CLC plant (500Wth). The oxygen carrier to fuel ratio, ϕ, was the main operating parameter affecting the CLC system. Complete fuel combustion were reached at 1073K working at ϕ values ≥1.5. The presence of H2S did not produce a decrease in the combustion efficiency even when working with a fuel containing 1300vppm H2S. At these conditions, the great majority of the sulphur fed into the system was released in the gas outlet of the FR as SO2, affecting to the quality of the CO2 produced. Formation of copper sulphide, Cu2S, and the subsequent reactivity loss was only detected working at low values of ϕ ≤1.5, although this fact did not produce any agglomeration problem in the fluidized beds. In addition, the oxygen carrier was fully regenerated in a H2S-free environment. It can be concluded that Cu-based oxygen carriers are adequate materials to be used in a CLC process using fuels containing H2S although quality of the CO2 produced is affected. [ABSTRACT FROM AUTHOR]

Abstract: Chemical-Looping Combustion (CLC) is an emerging technology for CO2 capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. Natural or refinery gas can be used as gaseous fuels and they may contain different amounts of light hydrocarbons. This paper presents the combustion results obtained with a Cu-based oxygen carrier using mixtures of CH4 and light hydrocarbons (LHC) (C2H6 and C3H8) as fuel. The effect on combustion efficiency of the fuel reactor temperature, solid circulation flow rate and gas composition was studied in a continuous CLC plant (500Wth). Full combustions were reached at 1073 and 1153K working at oxygen to fuel ratios, ϕ higher than 1.5 and 1.2 respectively. Unburnt hydrocarbons were never detected at any experimental conditions at the fuel reactor outlet. Carbon formation can be avoided working at 1153K or at ϕ values higher than 1.5 at 1073K. After 30h of continuous operation, the oxygen carrier exhibited an adequate behavior regarding attrition and agglomeration. It can be concluded that no special measures should be taken in a CLC process with Cu-based OC with respect to the presence of LHC in the fuel gas. [Copyright &y& Elsevier]

Chemical Looping Combustion (CLC) is one of the most promising processes for the low-cost capture of CO 2 . It is based on the transfer of oxygen from air to the fuel by means of a solid oxygen carrier that circulates between two interconnected fluidized bed reactors: the fuel reactor and the air reactor. CO 2 capture is inherent to this process since air does not become mixed with the fuel. A key issue for the large-scale development of CLC technology is the selection of oxygen carrier materials with suitable properties such as high reactivity and good fluidization. Another important feature that an oxygen carrier must fulfil is to have high resistance to attrition. For this purpose, several particle characteristics related to attrition resistance were analysed in this work on 23 oxygen carriers, both natural and synthetic, prepared by different methods and using different metal oxides. Particle crushing strength and Air Jet Index (AJI) were determined for the fresh materials, as well as the attrition rate and the corresponding particle lifetime during multi-cycle redox reactions in a continuously operated CLC unit for gaseous fuels. A comparison was made of the different methods used to evaluate attrition behaviour. The AJI-ASTM test for particles subjected to long-term CLC operation was used as a standard screening tool to evaluate the attrition behaviour of the oxygen carriers. Finally, a methodology was proposed for the selection of oxygen carriers as eligible materials for CLC scale-up based on attrition behaviour. [ABSTRACT FROM AUTHOR]

A simple model based on oxygen carrier kinetics has been developed for the in situ Gasification Chemical Looping Combustion ( i G-CLC) process. Once the kinetic parameters for different oxygen carriers and solid fuels are known, the model allows easy and fast comparison of different oxygen carrier-solid fuel pairs, which is the main purpose of the model here presented. The comparison is based on the estimation of the CO 2 capture efficiency value (η CC ) and the total oxygen demand (Ω T ) as evaluating parameters. To show the proposed procedure for the comparison, two Fe-based oxygen carriers (ilmenite and Tierga ore), and five different types of solid fuels: anthracite (Yangquan), sub-bituminous (Tremedal), two bituminous coals (Cerrejón and Taldinsky) and one biomass (olive tree pruning) have been considered. The comparison of the calculated CO 2 capture efficiency and total oxygen demand must be done including the effect of operating conditions such as temperature and solids circulation rate. A set of optimized operating conditions are given as a reference for future evaluations of different oxygen carrier-solid fuel pairs. This method is thought as a useful tool for a preliminary evaluation of new oxygen carriers for i G-CLC with different solid fuels. [ABSTRACT FROM AUTHOR]

Chemical Looping Combustion (CLC) has arisen during last years as a very promising combustion technology for power plants and industrial applications, with inherent CO 2 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 kW th to 4 MW th . 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 ( i G-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 (SO 2 , NO x , etc.) released into the atmosphere from the air reactor are no cause of concern for the environment. However, the presence of SO 2 , NO x and Hg at the exit of the fuel reactor affects CO 2 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, CO 2 capture rate, and combustion efficiency obtained in different CLC units. Solid fuel conversion is normally not complete during operation, due to the undesired loss of char. A methodology is presented to extrapolate the current information to what could be expected in a larger CLC system. CO 2 capture near 100% has been reported using a highly efficient carbon stripper, highly reactive fuels (such as lignites and biomass, etc.) or by the CLOU process. Operational experience in i G-CLC has showed that it is not possible to reach complete fuel combustion, making an additional oxygen polishing step necessary. For the further scale-up, it is essential to reduce the unburnt compounds at the fuel reactor outlet. Proposals to achieve this reduction already exist and include both improvement to the gas-oxygen carrier contact, or new design concepts based on the current scheme for i G-CLC. In addition, CLOU based on copper materials has shown that complete fuel combustion could be achieved. Main challenges for the future development and scale-up of CLC technology have been also identified. A breakthrough in the future development of CLC technology for solid fuels will come from developing long-life materials for CLOU that are easy to recover from the ash purge stream. [ABSTRACT FROM AUTHOR]

The environmental implications of mercury do not correspond only to the emissions to the atmosphere; the quality of the captured CO 2 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 CO 2 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 O 2 , NO, SO 2 and HCl in a gas containing Hg and CO 2 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 bubbling fluidized bed combustor. A lignite with high sulphur content was burned in presence of limestone. Despite high SO 2 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. [ABSTRACT FROM AUTHOR]

• The design of a pressurized FR under bubbling and turbulent regimes was performed. • Uncompleted CH 4 combustion was predicted using ilmenite as oxygen carrier. • The energy balance of the CLC system was improved at pressurized conditions. Chemical Looping Combustion (CLC) is a low-cost CO 2 capture technology highly competitive for industrial and energy applications. Up to date, CLC has been mostly developed at atmospheric pressure. Pressurized CLC may bring additional advantages due to the intensification of the process. The main objective of this work was to determine whether an increase in the operating pressure could improve the fuel conversion in CLC systems of gaseous fuels when ilmenite was used as oxygen carrier. Fluid dynamics considerations were evaluated to determine a window of suitable design parameters at pressurized conditions. A theoretical model previously validated at atmospheric pressure was modified to consider fluid dynamics and reaction kinetics at pressurized conditions, both in the bubbling and turbulent regimes, using ilmenite as oxygen carrier. The conversion of natural gas was estimated as a function of several design and operating parameters, such as the gas velocity, particle size and reacting temperature. Uncompleted combustion of natural gas was predicted at atmospheric conditions, and a limited improvement was estimated at pressurized conditions. A discussion about the required reactivity of the oxygen carrier to achieve complete combustion was performed. Furthermore, an energy analysis of a CLC system operating at atmospheric or pressurized (0.5 MPa) conditions with fuel reactor designed under the bubbling or turbulent regimes was carried out using the Aspen HYSYS process simulation software for two different applications of heat generation: production of domestic hot water and process steam. From this energy balance, it could be concluded that the energy efficiency achieved at pressurized conditions was slightly higher than that obtained at atmospheric pressure, essentially because at pressurized conditions it was possible to use the latent heat of condensation of the water generated in the fuel reactor. In addition to the results obtained in this work, a thorough assessment of technical risks and a techno-economic analysis would be required in order to make a final decision about the feasibility of operating at pressurized conditions in CLC systems. [ABSTRACT FROM AUTHOR]

Abstract: Economic benefits can be expected in the future if CO2 capture and storage are implemented in energy generation from biomass combustion. The aim of this work is to investigate the combustion of biomass in a chemical looping with oxygen uncoupling (CLOU) process with inherent CO2 separation. The performance of biomass combustion in a continuously operated 1.5kWth CLOU unit is presented. Particles prepared by spray drying containing 60wt.% CuO were used as an oxygen carrier. Milled pine wood chips were used as fuel. The work focused on the effect of fuel reactor temperature on the CO2 capture and the combustion efficiency of the CLOU process with biomass. Under CLOU operation, biomass combustion was complete to CO2 and H2O without the presence of any unburnt material, including tars. Moreover, high carbon capture efficiencies were achieved using very low oxygen carrier inventories and without a carbon separation unit. This is the first time that the CLOU concept has been demonstrated in a continuous CLC unit using biomass as fuel. [Copyright &y& Elsevier]

Highlights: [•] Several technological options to improve the performance of iG-CLC are analysed. [•] A mathematical model is developed to evaluate the performance of each option. [•] The use of a secondary fuel reactor increases the potential to reduce the oxygen demand. [•] A new iG-CLC configuration is proposed which minimises oxygen demand. [Copyright &y& Elsevier]

In order to compare potential oxygen carriers for the iG-CLC with coal a methodology was developed from resultsobtainedin a batch fluidized reactor. The methodology is based on the solidsinventory in the fuel reactor. The solids inventory values will beused for comparison purposes among different materials rather thanfor design purposes. In a companion paper, experiments with differenttypes of Fe-based oxygen carriers were presented. Based on these experimentalresults, the present paper proposes two theoretical approaches fora fast evaluation of different materials as potential oxygen carriersfor the iG-CLC process with different fuels. Themethodology is focused on the study of the gasification of the chargenerated in the process after the devolatilization of the correspondingsolid fuel and the subsequent combustion of the gasification products.Considering the results of carbon capture and combustion efficiency,the adequacy of the material can be evaluated. Four different Fe-basedmaterials are tested in this work: ilmenite, bauxite waste, a mineralbased on hematite, and a synthetic material. Based on the resultsobtained, the bauxite waste and the hematite mineral present the bestperformance for iG-CLC. As a rough estimation, aninventory around 1600 kg/MWthwill be needed using anyof the above materials to achieve carbon captures above 0.93 and combustionefficiencies of 0.99 at 1000 °C. [ABSTRACT FROM AUTHOR]

• CLC of biomass was assessed as BECCS technology using a Mn-Fe-Ti mixed oxide. • Bixbyite regeneration in AR influenced O 2 release in FR and thus oxygen demand. • Almost 100% CO 2 capture efficiency was obtained in all experiments with (Mn66Fe)-Ti7. • 3.0–3.2 air excess and AR temperature of 880 °C reduced oxygen demand to about 10%. • (Mn66Fe)-Ti7 losses in biomass ash drainage minimized due to its magnetic properties. Chemical Looping Combustion (CLC) is a promising carbon capture technology to contribute to the development of BioEnergy with Carbon Capture and Storage (BECCS) technologies. In CLC, the oxygen needed for combustion is supplied by a solid oxygen carrier. During the last years, intensive research has been conducted to identify potential oxygen carriers. Iron and manganese-based minerals allowed obtaining high CO 2 capture efficiencies, but lower values for the combustion efficiency, that is, high oxygen demand values, due to the high content of volatiles in biomass. Manganese-iron mixed oxides doped with titanium possess the capability of releasing molecular oxygen under specific conditions which would enhance volatile conversion. The objective of the present work was to evaluate the potential of one of these materials ((Mn66Fe)-Ti7) to improve the combustion efficiency of CLC with biomass in a 0.5 kW th continuous CLC unit. Almost 100% of CO 2 capture efficiency was obtained in all the experiments. Once the operational conditions for the synthetic material (Mn66Fe)-Ti7 were optimized, it was possible to reach oxygen demand values about 10% with the advantage that the (Mn66Fe)-Ti7 oxygen carrier presented magnetic properties that would facilitate its separation from biomass ashes in the fuel reactor. [ABSTRACT FROM AUTHOR]

• Manganese ores tested as low-cost oxygen carriers for biomass CLC. • Almost 100% CO 2 capture efficiency was obtained with all manganese ores. • MnSA ore reduced the oxygen demand values to about 10% • Further oxygen demand reduction of 30% recirculating part of the FR outlet flow. • No NO x emissions and low tar contents in the FR outlet gas flow. Negative Emission Technologies (NETs) should be implemented to reach the objectives set by the Paris Agreement to limit the average temperature increment to 2 °C. One of the options is the development of bioenergy with Carbon Capture and Storage (BECCS) technologies. In this sense, Chemical Looping Combustion (CLC) is one of the most efficient CO 2 Capture technologies both from economical and energy points of view. In CLC, a solid oxygen carrier is used to transfer the oxygen from air to the fuel. In this work two manganese-based ores were used as oxygen carriers to burn three different types of biomass (pine sawdust and two Spanish agricultural residues) in a 0.5 kW th CLC continuous unit. Operational conditions were varied to evaluate their effect on the CO 2 capture efficiency and the total oxygen demand of the process. Almost 100% of CO 2 capture efficiency was reached working with pine sawdust as well as with almond shells. However, high values of total oxygen demand (10–20%) were found, which led to consider further technological solutions to increase the combustion efficiency. In this respect, fuel reactor outlet recycling was evaluated as an operational solution to reduce the oxygen demand with good results (about 30% reduction in the total oxygen demand value). NO x and tar formation from the CLC system were also evaluated. There were no NO x emissions during the experimental campaign and low tar content in the fuel reactor outlet gas was reached (0.3–3.2 g/Nm3), being naphthalene the major tar compound. [ABSTRACT FROM AUTHOR]