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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. ; The authors thank the Spanish Ministry of Economy and Competitiveness (MINECO) for the funding received from the project ENE2014-56857-R) and by the European Regional Development Fund (ERDF) for the financial support. T. Mendiara thanks for the ''Ramón y Cajal'' pos t-doctoral contract awarded by MINECO. A. Pérez- Astray thanks MINECO for the FPI fellowship co-financ ed by the European Social Fund. The authors also thank PROMINDSA for providing the solid material used in this work. ; Peer reviewed

6 figures, 3 tables.-- Supplementary information available. ; 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. ; This work has been supported by the AEI/FEDER, UE ENE2016-77982-R, ENE2017-89473-R and ID2019-106441RB-I00 projects, and by the Regional Aragon Government via the T05_17R research group funding. ; Peer reviewed

Oil refining processes demand and use vast quantities of energy and thus are responsible for the emission of a great deal of CO2. In addition, hydrogen is used in oil refineries for hydrodesulfurization and hydrocraking processes. In this sense, the integration of Chemical Looping technology in an oil refinery using vacuum residues as fuel could drive to significant reductions in CO2 emissions. In this work, Chemical Looping Combustion (CLC) and Chemical Looping Reforming (CLR) experiments have been carried out in a continuously operated 1 kWth unit using a Cu- and Ni-based oxygen carrier, respectively. Diesel, synthetic and mineral lubricant oil were used as fuels as a previous step to the use of low grade residues. Regarding Chemical Looping Combustion conditions, almost 100% of combustion efficiency and full carbon capture were obtained at low oxygen carrier-to-fuel molar ratios (ϕ≥1.6). Regarding Chemical Looping Reforming conditions, a syngas containing a H2 concentration over 50 vol.% in dry basis was obtained with the additional advantage of reaching 100% CO2 capture efficiency in the process. In all cases, syngas composition obtained was close to the given by the thermodynamic equilibrium. These results provide a basis for concluding that the integration of Chemical Looping processes for heat/steam and hydrogen production in an oil refinery is feasible and could lead to significant environmental advantages. ; This work was partially supported by the Spanish Ministry for Science and Innovation (MICINN, project ENE2011-26354, ENE2014-56857-R), European Regional Development Fund (ERDF) and by the Government of Aragón (Spain, DGA ref. T06). A. Serrano also thanks the Spanish Ministry of Economy and Competitiveness for the F.P.I. fellowship. ; Peer reviewed

Intro -- 1 Einleitung -- 2 Stand des Wissens -- 3 Beschreibung der Versuchsanlage -- 4 CLC von Festbrennstoffen -- 5 CLC von Erdgas -- 6 Modellierung: CLC von Festbrennstoffen -- 7 Techno-ökonomische Diskussion -- 8 Zusammenfassung und Ausblick -- 9 Anhang -- Literatur

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.

In the in situ Gasification Chemical Looping Combustion of coal (iG-CLC), the fuel is gasified in situ in the fuel reactor and gasification products are converted to CO2 and H2O by reaction with the oxygen carrier. This work is the first study on mercury release in Chemical Looping Combustion of coal. The fraction of the mercury in coal vaporized in the fuel reactor depended mainly on the fuel reactor temperature and the coal type. In the fuel reactor, mercury was mainly emitted as Hg0 in the gas phase and the amount increased with the temperature. In the air reactor, mercury was mostly emitted as Hg2+. In a real CLC system, mercury emissions to the atmosphere will decrease compared to conventional combustion as only mercury released in the air reactor will reach the atmosphere. However, measures should be taken to reduce Hg0 in the CO2 stream before the purification and compression steps in order to avoid operational problems. ; The authors thank the Government of Aragón and La Caixa (2012-GA-LC-076 project) and the Spanish Ministry for Science and Innovation (ENE2010-19550 project) for the financial support. P. Gayán thanks CSIC for the financial support of the project 201180E102. The authors also thank to Alcoa Europe-Alúmina Española S.A. for providing the Fe-enriched sand fraction used in this work. G. Galo is acknowledged for his contribution to the experimental results. ; Peer reviewed

This work reports a detailed chemical looping investigation of strontium ferrite (SrFeO3-δ), a material with the perovskite structure type able to donate oxygen and stay in a nonstoichiometric form over a broad range of oxygen partial pressures, starting at temperatures as low as 250°C (reduction in CO, measured in TGA). SrFeO3-δ is an economically attractive, simple, but remarkably stable material that can withstand repeated phase transitions during redox cycling. Mechanical mixing and calcination of iron oxide and strontium carbonate was evaluated as an effective way to obtain pure SrFeO3-δ. In situ XRD was performed to analyse structure transformations during reduction and reoxidation. Our work reports that much deeper reduction, from SrFeO3-δ to SrO and Fe, is reversible and results in oxygen release at a chemical potential suitable for hydrogen production. Thermogravimetric experiments with different gas compositions were applied to characterize the material and evaluate its available oxygen capacity. In both TGA and in-situ XRD experiments the material was reduced below δ=0.5 followed by reoxidation either with CO2 or air, to study phase segregation and reversibility of crystal structure transitions. As revealed by in-situ XRD, even deeply reduced material regenerates at 900°C to SrFeO3 δ with a cubic structure. To investigate the catalytic behaviour of SrFeO3-δ in methane combustion, experiments were performed in a fluidized bed rig. These showed SrFeO3-δ donates O2 into the gas phase but also assists with CH4 combustion by supplying lattice oxygen. To test the material for combustion and hydrogen production, long cycling experiments in a fluidized bed rig were also performed. SrFeO3-δ showed stability over 30 redox cycles, both in experiments with a 2-step oxidation performed in CO2 followed by air, as well as a single step oxidation in CO2 alone. Finally, the influence of CO/CO2 mixtures on material performance was tested; a fast and deep reduction in elevated pCO2 makes the material susceptible to carbonation, but the process can be reversed by increasing the temperature or lowering pCO2. ; EPSRC grant no. EP/K030132/1. European Union's Horizon 2020 Marie Skłodowska–Curie grant agreement No. 659764