Chemical Looping (CLG)-based biomass gasification using a Ca sorbent is an advanced concept to produce renewable hydrogen. The limitation imposed by the carbonation balance forces the gasifier to operate below 700 ºC. This temperature implies a significant reduction in the conversion of char with steam and, therefore, a limited production of hydrogen. The unconverted char is burned in the calciner providing the energy necessary to maintain the process. Until now, the proposed solutions to generate a CO2 stream ready for sequestration in the calciner are: the use of pure oxygen from an air separation unit (ASU), or the incorporation of another Chemical Looping to transport the oxygen to the calciner. through carrier particles. In both cases, a combustion gas with CO2 and vapor is obtained, from which the vapor can be easily separated by condensation. Although some of these proposals are very attractive, there are important aspects or aspects to improve:

1. The production of hydrogen from water (water splitting) is very limited, since the gasification of char with steam below 700 ºC is very slow.

2. The processes necessary to produce CO2 ready for sequestration are extraordinarily expensive (ASU) or complex (chemical looping with an O2 carrier).

3. The precise control of the circulation of solids between reactors in CLGs is highly complex, as several processes have to be optimized simultaneously (thermal balance of the circuit, CO2 capture, tar conversion and sorbent regeneration).

4. The deactivation of the sorbent with the number of cycles is greatly penalized by the severe conditions under which calcination is generally carried out.

5. The energy penalty, resulting from working cyclically between a very endothermic calcination at a high temperature and an exothermic carbonation at a much lower temperature, is very high.

In this project, a process is proposed that improves the previous drawbacks, through a CLG in which the heat required for calcination is provided by solar thermal energy, and the char (and tar) is catalytically converted in the gasifier.

In addition, during the day CaO is used to chemically store solar energy, guaranteeing uninterrupted production of H2 during periods without solar radiation. In essence, the proposed process oxidizes biomass with steam, using solar energy and produces a concentrated H2 stream in the gasifier and a CO2 stream ready for sequestration in the calciner.

Although this project does not propose the construction of a new pilot plant to demonstrate the proposed solar CLG, it is proposed to study experimentally (in addition to theoretically) the most important aspects and challenges, using existing infrastructure in the research group. A technical and economic feasibility study will also be carried out, as well as environmental sustainability.

The research team is made up of members of Spanish and international research groups. The two Spanish research groups have extensive and proven experience in the key aspects to be developed in this project.

The project contributes to three of the challenges in the energy field of the Spanish Government, as well as to several of the specific challenges of the EU.