Heat transfer particles for solar-driven thermochemical processes

A process for performing a chemical reaction consisting of at least two sequential reversible steps in a cycle, characterized in that

• a solid reactant is thermo-chemically reduced in a first reaction chamber (1) with uptake of heat at a first temperature (T1) in the range of from 1,000° C. to 1,400° C., and said solid reactant is subsequently oxidized in a second reaction chamber (2) with release of heat at a second temperature (T2) in the range from 500° C. to 1,200° C.;
• wherein said first temperature (T1) is higher than said second temperature (T2);
• and
• wherein sensible heat of said solid reactant is transferred to a solid heat transfer medium at said first temperature (T1) in a first heat exchanger (3) after the thermo-chemical reduction of the solid reactant in said first reaction chamber (1) is complete;
• and
• said sensible heat taken up by said solid heat transfer medium in said first heat exchanger (3) is transferred to said solid reactant at said second temperature (T2) in a second heat exchanger (4) after said solid reactant is subsequently oxidized in said second reaction chamber (2) where there is a release of heat at the second temperature (T2);
• and
• wherein to enable heat transfer from the solid reactant to the solid heat transfer medium, the surfaces of the solid reactant and the solid heat transfer medium touch each other.