CO2 Capture. Chemical Looping Combustion (CLC)

esquema-clcThe Chemical Looping Combustion (CLC) concept is based on the transfer of oxygen from the combustion air to the fuel by means of an oxygen carrier in the form of a metal oxide, avoiding the direct contact between fuel and air.

The CLC system is made of two interconnected reactors, designated as air and fuel reactors. In the fuel reactor, the fuel gas is oxidised by a metal oxide through the chemical reaction:

CH4 (CO, H2) + MeO  →  CO2 + H2O (CO2, H2O)+ Me

The exit gas stream from the fuel reactor contains CO2 and H2O. After water condensation, almost pure CO2 can be obtained with little energy lost for component separation.

The metal or reduced oxide, Me, is further transferred into the air reactor in which it is regenerated by taking up oxygen from the air.

Me  +  ½O2  →  MeO

The flue gas leaving the air reactor contains N2 and unused O2. The total amount of heat evolved over the two reactors in CLC process is the same as for normal combustion, where the oxygen is in direct contact with the fuel.

The significant advantage compared to normal combustion is that the CO2 is not diluted with N2. As opposite to other technologies proposed for CO2 separation, this process has no significant energy penalty for the capture process, and external capture devices are avoided. Thus, the process is expected to be less costly than available technologies for CO2 separation. A conceptual process scheme is shown in the figure below.

Different metal oxides have been proposed as possible candidates for CLC process: CuO, CdO, NiO, Mn2O3, Fe2O3, and CoO. In general, these metal oxides are combined with an inert which acts as a porous support providing a higher surface area for reaction, as a binder for increasing the mechanical strength and attrition resistance, and, additionally, as an ion conductor enhancing the ion permeability in the solid.

The only drawback of the overall CLC process is that the oxygen carriers are subjected to strong chemical and thermal stresses in every cycle and the performance could be poor after enough number of cycles in use.

Research on chemical-looping combustion at ICB-CSIC:

The work includes different projects funded by ECSC, Capture of CO2 in Coal Combustion (CCCC), and by EU. In these projects we co-operate with Chalmers University of Technology in Sweden, Technical University of Vienna, BP (UK) and Alstom (France). The work is also supported by the Spanish Ministry of Education and Science.

The objectives of this research line are:

  • To develop an oxygen carrier with appropriate reduction and oxidation rates, resistant to attrition and with high durability, maintaining its chemical, structural and mechanical properties after a high number of reduction-oxidation cycles.
  • To investigate the possible designs with respect to the fluidization conditions.
  • To demonstrate and evaluate this new combustion technology in a laboratory-scale chemical-looping combustor.
  • Main achievements of this research line are:
  • To develop a Cu-based oxygen carrier without agglomeration problems and excellent properties for the CLC process.
  • To demonstrate the CLC technology a prototype of 10 kWth has been designed and built in the ICB-CSIC. This pilot plant was satisfactorily run during 200 hours burning methane and using a Cu-based oxygen carrier.




Combustion of Rechargeable Metal Fuels in Fluidized Bed Boilers (CORAL)

El proyecto CORAL explora un nuevo concepto para el almacenamiento de energía en forma de hierro metálico y su utilización en calderas de lecho fluidizado para producir calor o electricidad libre de emisiones de CO2. Este es un concepto en el que se realiza la oxidación de hierro en la caldera con aire, de forma similar a la que se realiza actualmente en la combustión de carbón. De este modo, se plantea la reconversión de calderas de combustión de carbón por calderas de oxidación de hierro. El óxido de hierro producido se reducirá con hidrógeno verde para tener un medio de almacenamiento de energía libre de emisiones de CO2. En el proyecto se demostrará el proceso hasta una escala de 1 MW. Además, se realizará el diseño del escalado del proceso a nivel industrial, así como su evaluación tecno-económica y de su impacto social y medioambiental.

The cyclic reduction/oxidation of metal oxide/metal is a promising approach for energy storage and flexible CO2-free provision of heat and power. The project explores a novel concept of metal oxidation utilising retrofitted coal-fired fluidized bed power plants. Required modifications of the steam generator, solid feeding, and extraction systems are identified. A hydrogen-based process will be used for the direct reduction of metal oxides. The reduction/oxidation process in fluidized beds is tested at various scales up to 1 MW thermal power. Various numerical models (steady-state, dynamic, and CFD models) are developed, validated by experiments, and applied to design modifications. The concept is assessed regarding electrical efficiency, economics, environmental and social impact.

Flexible chemical looping combustion for combined heat and power production from biogenic residues with negative emission (Bio-FlexCLC)

The Bio-FlexCLC project develops and demonstrates a novel flexible technology for CHP plants at TRL 5 to utilize low-value biogenic residues as feedstock for heat and power production with negative CO2 emissions. Bio-FlexCLC combines the break-through chemical-looping combustion (CLC) technology with conventional circulating fluidized bed (CFB) boilers. The concept is flexible to switch between CLC CFB modes. Bio- FlexCLC operating in CLC mode has inherent CO2 capture at a low cost and without energy penalty. Bio-FlexCLC utilizes biogenic residues and wastes, improves conversion efficiencies, achieves negative CO2 emissions, reduces SOx and NOx emissions, enhances CO2 capture efficiency at a considerably reduced cost, has flexibility towards load demand fluctuations, and the capacity to switch to CFB combustion if market conditions are not amiable for carbon capture or if there is difficulty in the operation to decreases the risk of implement.

Alberto Abad y Teresa Mendiara consiguen un nuevo proyecto de la AEI para el grupo de Combustión y Gasificación

El proyecto lleva por título: “Producción de hidrógeno con captura de CO2 mediante la mejora por absorción del reformado de múltiples combustibles con transportadores de oxígeno (HYSERLOOP)” y ha comenzado el 1 de septiembre de 2023.

Más detalles en : info proyecto

Development of Chemical Looping Gasification of microalgae for the 3rd-Generation BioFuels production (CLG-G3BioF)

CLG-G3BioF stands on the  EU’s ambitious goals for climate neutrality and a circular economy, and aims at clean and low-carbon utilization of microalgae residue with a very promising CCS technology, called Chemical Looping Gasification (CLG).  The project dedicates to the development of the third-generation biofuels (G3BioF) production through the CLG of microalgae and at the same time contributing to EU’s commitment to achieve climate neutrality in 2050. 

Project’s goals

Through the project, the applicant will progress as a scientist and gain skills of LCA, complex pilot operation, tar analysis. Together with the supervisor and the host institution, this project is ambitious for a much greener production of biofuels and the results are important to power a sustainable future.





Producción de hidrógeno con captura de CO2 mediante la mejora por absorción del reformado de múltiples combustibles con transportadores de oxígeno (HYSERLOOP)

La presente propuesta pretende la demostración y evaluación de un nuevo proceso, conocido como sorption enhanced chemical looping reforming (SE-CLR), el cual es un método avanzado con gran potencial para obtener un mayor rendimiento de H2 que los procesos alternativos. La tecnología SE CLR integra los procesos SER y CLR en un único proceso con el que es posible obtener varios productos (H2, CO2 y N2 en corrientes separadas) a partir de múltiples combustibles gaseosos o líquidos. De este modo, se obtiene una sinergia con el potencial de resolver los inconvenientes de los procesos individuales: (a) la integración térmica del proceso SE-CLR evita la necesidad de un suministro de energía externo; y (b) la absorción de CO2 permite obtener una corriente concentrada de H2, mientras que el CO2 se obtiene en una corriente separada.

Nuevo proceso de chemical looping para obtención de CO a partir de CO2 e H2 verde como ruta para la producción de biocombustibles para aviación

The main objective of this project is to evaluate and demonstrate the Chemical Looping CO2 splitting process in a continuous unit to produce CO from CO2 and green H2 as a route for aviation biofuels synthesis.
To achieve this main objective, the following specific objectives have been defined:
– To identify and develop suitable oxygen carriers for the CO2 splitting process.
– To progress in the sale-up of oxygen carriers for the CO2 splitting process.
– To demonstrate the proof-of-concept of the CO2 splitting process in a continuous unit.
– To optimize the design and operating conditions of the CO2 splitting .


Scheme of the CO2 splitting process using green H2 and CO2