Energy 29 (2004) 811–821 www.elsevier.com/locate/energy Design and experimental investigation of a horizontal rotary reactor for the solar thermal production of lime Anton Meier a, , Enrico Bonaldi b , Gian Mario Cella b , Wojciech Lipinski a,c , Daniel Wuillemin a , Robert Palumbo a,d a Solar Technology Laboratory, Paul Scherrer Institute, CH-5232 Villigen, Switzerland b QualiCal Srl, Via Verdi 3, I-24121 Bergamo, Italy c Department of Mechanical and Process Engineering, ETH-Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland d Mechanical Engineering Department, Valparaiso University, Valparaiso, IN 46383, USA Abstract We designed and tested a 10-kW solar rotary kiln reactor to effect the calcination reaction: CaCO 3 ! CaO þ CO 2 . The reactor processes 1–5 mm limestone particles, producing 95% or higher purity lime with a t 60 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 tem- perature 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. # 2003 Elsevier Ltd. All rights reserved. 1. Introduction The decomposition of limestone (CaCO 3 ) for the production of lime (CaO) is an energy inten- sive process. The minimum amount of energy in the form of process heat that is required to drive the calcination reaction, CaCO 3 ! CaO þ CO 2 (1)  Corresponding author. Tel.: +41-56-310-27-88; fax: +41-56-310-31-60. E-mail address: anton.meier@psi.ch (A. Meier). 0360-5442/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0360-5442(03)00187-7