Ceramic particles for use in a solar power tower

1. A ceramic particle for use in a solar power tower, comprising:

a sintered ceramic material formed from a mixture of a ceramic raw material and manganese oxide, the ceramic particle having a size from about 8 mesh to about 170 mesh and a bulk density of less than 3 g/cc, wherein the mixture comprises from about 1 ppmw to about 0.5 wt % manganese oxide.

2. The ceramic particle of claim 1 , wherein the ceramic raw material comprises from about 0.1 wt % to about 50 wt % silica and from about 30 wt % to about 99 wt % alumina.

3. The ceramic particle of claim 1 , wherein the mixture further comprises about 0.1 wt % to about 20 wt % FeO.

4. The ceramic particle of claim 1 , wherein the ceramic particle has a surface roughness of less than 5 μm.

5. The ceramic particle of claim 1 , wherein the manganese oxide is selected from the group consisting of MnO, Mn 2 O 3 , and MnO 2 and any mixture thereof.

6. The ceramic particle of claim 5 , wherein exposure of the ceramic particle to solar heat energy in the solar power tower reduces a Munsell Value of the ceramic particle by at least about 0.1.

7. A solar power tower comprising the ceramic particle of claim 1 .

8. A method of manufacturing ceramic particles, comprising:

preparing a slurry comprising water, a binder, a first portion of a ceramic raw material, and manganese oxide, wherein the slurry comprises from about 1 ppmw to about 0.5 wt % manganese oxide;

atomizing the slurry into droplets;

coating seeds comprising a second portion of the ceramic raw material with the droplets to form a plurality of green pellets; and

sintering the green pellets to provide a plurality of ceramic particles, wherein the sintering oxidizes a first portion of the manganese oxide from MnO to Mn 2 O 3 .

9. The method of claim 8 , wherein the ceramic raw material comprises from about 0.1 wt % to about 50 wt % silica and from about 30 wt % to about 99 wt % alumina.

10. The method of claim 8 , wherein a second portion of the manganese oxide is oxidized from MnO to Mn 2 O 3 upon being subjected to solar heat energy in a solar power tower.

11. The method of claim 8 , wherein the slurry further comprises about 0.1 wt % to about 20 wt % iron oxide.

12. The method of claim 11 , wherein the sintering oxidizes a first portion of the iron oxide from FeO to Fe 2 O 3 .

13. The method of claim 12 , wherein a second portion of the iron oxide is oxidized from FeO to Fe 2 O 3 upon being subjected to solar heat energy in a solar power tower.

14. The method of claim 8 , wherein the plurality of ceramic particles has a Munsell value of at least 6 prior to exposure to solar heat energy in a solar power tower.

15. The method of claim 14 , wherein the plurality of ceramic particles has a Munsell value of less than 6 after exposure to the solar heat energy in the solar power tower.

16. A method of manufacturing ceramic particles, comprising:

providing a slurry of ceramic raw material, a reactant and manganese oxide, wherein the mixture comprises from about 1 ppmw to about 0.5 wt % manganese oxide;

flowing the slurry through a nozzle in a gas while vibrating the slurry to form droplets;

receiving the droplets in a vessel containing a liquid having an upper surface, the liquid containing a coagulation agent;

reacting the reactant with the coagulation agent to cause coagulation of the reactant in the droplets;

transferring the droplets from the liquid;

drying the droplets to form green pellets;

sintering the green pellets in a selected temperature range to form a plurality of ceramic particles.

17. The method of claim 16 , wherein the ceramic raw material comprises from about 0.1 wt % to about 50 wt % silica and from about 30 wt % to about 99 wt % alumina.

18. The method of claim 16 , wherein a second portion of the manganese oxide is oxidized from MnO to Mn 2 O 3 upon being subjected to solar heat energy in a solar power tower.

19. The method of claim 16 , wherein the darkening component further comprises about 0.1 wt % to about 20 wt % iron oxide.

20. The method of claim 19 , wherein the sintering oxidizes a first portion of the iron oxide from FeO to Fe 2 O 3 .

21. The method of claim 20 , wherein a second portion of the iron oxide is oxidized from FeO to Fe 2 O 3 upon being subjected to solar heat energy in a solar power tower.