Jul-Sept 2002 The Second Solar Lime Experimental Campaign

Oct-Dec 2002 Improving the Reactor Numerical Model

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The pictures show the first Solar Lime Pilot Reactor. The construction phase was over, as scheduled, at the end of June 2001 in order to be ready for the Solar Lime experimental campaign at the beginning of July 2001, when the "Swiss Sun" gets to its best shape...

The reactor is mainly characterized by an innovative dosing system for mass flows ranging between 25 and 500 g/min with a very high dosing accuracy and constancy. The small silo for the storage of limestone is placed on top of the reactor's aluminum structure and can be loaded with maximal 20 kg of raw material. It means that, for slow feeding conditions, long experiments could last for up to 10 hours... if only the sun would allow!

The steel rotary kiln drum is positioned horizontal to allow a more convenient and simple mechanical drive system. The characteristic slope of conventional rotary kilns, needed for the material to proceed to the exit while being burned and mixed, is given by the conical shape of the inner refractory lining itself. The revolution speed of the drum may easily be adjusted in order to control the residence time, as well as the mixing behavior, of the reactants.

According to suggestions of Refratechnik's technicians, the refractory lining has been built from two layers of different materials.
The external white layer is made of a light insulating material resistant to up to 1600°C and characterized by a very low density; the inner layer is made of a castable material with thermal resistance close to 1600°C and a very high density, similar to cement. By casting this material with the aid of a polystyrene core it was possible to easily give the desired conical shape to the inner surface.

The sunlight entrance is set on front of the reactor where a small 8 cm aperture allows the highly concentrated sunlight to radiate into the cavity reactor, i.e., on the material that has to be calcined.
The reactor works in a continuos feeding mode. The raw material enters from the rear side of the drum through a small feedinf pipe sited directly underneath the dosing system and, once it has passed through the hot calcining chamber, the finite product falls through a proper opening and is collected in a metal basket.

Most of the calcination reaction should occur near the exit of the rotating kiln because of the high temperature due to the strong direct solar radiation incident on the surface (up to 1300 °C), while the region close to the material's entrance is supposed to act as a preheating zone for the fine grained limestone particles (temperature below 800 °C).

July 7th, 2001 - The first Solar Lime Pilot Reactor is ready... the solar experiments may start.