Heat transfer particles for solar-driven thermochemical processes

1. 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 (T 1 ) 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 (T 2 ) in the range from 500° C. to 1,200° C.;

wherein said first temperature (T 1 ) is higher than said second temperature (T 2 ); and

wherein sensible heat of said solid reactant is transferred to a solid heat transfer medium at said first temperature (T 1 ) 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 (T 2 ) 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 (T 2 ); 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.

2. The process according to claim 1 , characterized by comprising the following steps:

a) heating the solid reactant to said first temperature (T 1 );

b) reducing said solid reactant in said first reaction chamber at said first temperature (T 1 ); to release oxygen;

c) transferring the heat from said solid reactant to said solid heat transfer medium to cool said solid reactant from said first temperature (T 1 ) to said second temperature (T 2 ) in said first heat exchanger ( 3 );

d) oxidizing said solid reactant in said second reaction chamber ( 2 ) at said second temperature (T 2 );

e) transferring the heat from said solid heat transfer medium to said solid reactant in said second heat exchanger ( 4 ) to heat said solid reactant;

wherein the at least two subsequent reversible steps in the cycle comprises the above mentioned steps b) to e).

3. The process according to claim 2 , characterized in that said solid reactant is heated by means of concentrated solar radiation ( 7 ) in step a).

4. The process according to claim 2 , characterized in that, in step a), said solid heat transfer medium is heated by means of concentrated solar radiation ( 7 ), and the heat is transferred therefrom to said solid reactant.

5. The process according to claim 4 , characterized in that said heated solid heat transfer medium is stored in a store ( 6 ) before it is employed in the cycle.

6. A reactor for performing the process according to claim 1 , characterized by comprising said first reaction chamber ( 1 ) and said second reaction chamber ( 2 ) that includes the solid reactant, and said first heat exchanger ( 3 ) and said second heat exchanger ( 4 ) with solid spherical particles as heat transfer media.

7. The reactor according to claim 6 , characterized in that a first reaction takes place at said first temperature (T 1 ) in said first reaction chamber ( 1 ); and

a second reaction takes place at said second temperature (T 2 ) in said second reaction chamber ( 2 ); wherein

said first temperature (T 1 ) is higher than said second temperature (T 2 ), wherein said first heat exchanger ( 3 ) is arranged in such a way that said solid heat transfer medium contained therein takes up said sensible heat of the at least one solid reactant; and

said second heat exchanger ( 4 ) is arranged in such a way that said solid heat transfer medium contained therein releases the heat taken up in said first heat exchanger ( 3 ) to said at least one solid reactant in said second reaction chamber ( 2 ) after the reaction is complete.

8. The reactor according to claim 6 , characterized in that said first reaction chamber ( 1 ) is a reduction reactor in which said solid reactant is reduced at said first temperature (T 1 ).

9. The reactor according to claim 6 , characterized in that said second reaction chamber ( 2 ) is a cleavage reactor in which said solid reactant is oxidized at said second temperature (T 2 ).

10. The reactor according to claim 6 , characterized in that said solid reactant is a chemical compound with redox properties.

11. The reactor according to claim 6 , characterized in that said heat transfer medium is selected from the group comprising ceramics, SiO 2 , TiO 2 , Al 2 O 3 , Y 2 O 3 , ZrO 2 , Pt, W, Ta, Mo, and mixtures thereof.

12. The reactor according to claim 6 , further comprising a receiver ( 5 ) and/or one or more storage container ( 6 , 8 ) for said solid heat transfer medium.

13. The reactor according to claim 6 , characterized by being a thermochemical solar reactor.