The co-production of Zn and synthesis gas by the combined reduction of ZnO and reforming of $CH4$ has been performed using a vortex-flow chemical reactor in a high-flux solar furnace. The reactor operating temperature ranged between 1221 and 1481 K for an input solar power of 2.3 to 4.6 kW and mean solar flux intensities of 810 to 1609 kW/m2. The performance of the reactor was determined by conducting a complete mass and energy balance for the chemical process. The chemical conversion ranged between 83–100 percent. The thermal efficiency, defined as the portion of input solar power absorbed as sensible and process heat, was in the range 11–28 percent. The exergy efficiency for the closed cycle, defined as the ratio of the maximum amount of work that the products leaving the reactor could produce if were re-combined to the input solar power, was in the range 0.3–3.1 percent. Major sources of energy loss are re-radiation heat transfer through the reactor aperture, conduction heat transfer through the reactor walls, and the quenching of the reaction products.

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