Design and experimental investigation of a horizontal rotary reactor for the solar thermal production of lime

We designed and tested a 10-kW solar rotary kiln reactor to effect the calcination reaction: CaCO3 → CaO+CO2. The reactor processes 1–5 mm limestone particles, producing 95% or higher purity lime with a t60 reactivity ranging from 14 s to 38 min. The degree of calcination and the reactivity both depend on the reactant’s decomposition temperature (1323–1423 K), residence time (3–7 min), and feed rate (10–50 g/min). The reactor’s efficiency, defined as the enthalpy of the calcination reaction at a specified temperature divided by the solar energy input, reached 20% for solar flux inputs of about 1200 kW m−2 and for quicklime production rates of about 1.3 kg/h. The solar lime reactor operated reliably for more than 100 h for a total of 24 sunny days, withstanding the thermal shocks that occur in solar applications.