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RESEARCH PAPERS

# A $300kW$ Solar Chemical Pilot Plant for the Carbothermic Production of Zinc

[+] Author and Article Information
C. Wieckert1

Solar Technology Laboratory, Paul Scherrer Institute, CH-5232 Villigen, Switzerland

U. Frommherz, S. Kräupl

Solar Technology Laboratory, Paul Scherrer Institute, CH-5232 Villigen, Switzerland

E. Guillot, G. Olalde

PROMES-CNRS, F-66120 Font Romeu Odeillo, France

M. Epstein

Solar Research Unit, The Weizmann Institute of Science, IL-76100 Rehovot, Israel

S. Santén

Scanarc Plasma Technologies AB, S-81321 Hofors, Sweden

T. Osinga, A. Steinfeld

Department of Mechanical and Process Engineering, ETH Zurich, CH-8092 Zurich, Switzerland

1

Corresponding author.

J. Sol. Energy Eng 129(2), 190-196 (Mar 29, 2006) (7 pages) doi:10.1115/1.2711471 History: Received January 10, 2006; Revised March 29, 2006

## Abstract

In the framework of the EU-project SOLZINC, a 300-kW solar chemical pilot plant for the production of zinc by carbothermic reduction of ZnO was experimentally demonstrated in a beam-down solar tower concentrating facility of Cassegrain optical configuration. The solar chemical reactor, featuring two cavities, of which the upper one is functioning as the solar absorber and the lower one as the reaction chamber containing a ZnO/C packed bed, was batch-operated in the 1300–1500 K range and yielded 50 kg/h of 95%-purity Zn. The measured energy conversion efficiency, i.e., the ratio of the reaction enthalpy change to the solar power input, was 30%. Zinc finds application as a fuel for Zn/air batteries and fuel cells, and can also react with water to form high-purity hydrogen. In either case, the chemical product is ZnO, which in turn is solar-recycled to Zn. The SOLZINC process provides an efficient thermochemical route for the storage and transportation of solar energy in the form of solar fuels.

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## Figures

Figure 1

Flow diagram of the SOLZINC solar chemical pilot plant featuring the solar concentrating system, the solar reactor, the off-gas system, and the diagnostic instrumentation

Figure 2

The “beam-down” Cassegrain optical configuration of the WIS’s solar tower concentrating system, consisting of a field of heliostats that focus the sun rays onto a hyperbolical reflector at the top of the tower to re-direct sunlight to a CPC located on the ground level (28)

Figure 3

Schematic of the solar chemical reactor, featuring two cavities in series with the upper one functioning as the solar absorber and the lower one as the reaction chamber containing a ZnO∕C packed bed

Figure 4

Photograph of the 300-kW solar reactor and its peripheral components, installed under the solar tower beam-down concentrating system

Figure 5

Variation of the solar reactor temperatures during the solar experimental run C. TLP1–8 are located in the lower cavity at different heights, every 10cm (TLP1 is the top temperature, TLP9 is the bottom temperature)

Figure 6

Variation of the offgas system temperatures during the solar experimental run C. The location of thermocouples is indicated in Fig. 1

Figure 7

Off-gas flow rate, off-gas composition, and Zn production rate, as a function of time during the experimental run C of Table 1

Figure 8

Arrhenius plot for zinc production rate in quasi-stationary operation periods as a function of the temperature TLP1 (wall temperature in upper part of lower cavity)

Figure 9

Particle size distribution of Zn collected in cyclone and bag filter during test C. Shown is the volume fraction of all particles below a certain particle size

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