160 h of chemical-looping combustion in a 10 kW reactor system with a NiO-based oxygen carrier Carl Linderholm a, *, Alberto Abad b , Tobias Mattisson a , Anders Lyngfelt a a Department of Energy and Environment, Energy Technology, Chalmers University of Technology, 41296 Go ¨ teborg, Sweden b Instituto de Carboquı´mica (CSIC), Department of Energy and Environment, Miguel Luesma Casta ´ n 4, Zaragoza 50018, Spain 1. Introduction 1.1. Chemical-looping combustion A large number of techniques for CO 2 capture have been proposed and investigated for large scale power production applications, but most of these techniques have the disadvantage of requiring huge amounts of energy for the CO 2 separation, resulting in a substantial power plant efficiency decrease. A CO 2 separation technology without such an energy penalty would obviously be of great interest. In traditional combustion the fuel is in direct contact with air. In 1987, Ishida et al. presented a novel combustion concept they called chemical-looping combustion, where the tradi- tional combustion would be divided into two gas–solid reactions: oxidation of metal by air and reduction of metal oxide by fuel. However, a similar process was patented already in 1954 by Lewis and Gilliand. Two interconnected reaction chambers, or reactors, are needed for the process, one for reduction and the other for oxidation of the metal/metal oxide particles. By circulating the particles between these reactors, a continuous system for combustion of fuel with inherent CO 2 separation is achieved, international journal of greenhouse gas control 2 (2008) 520–530 article info Article history: Received 3 August 2007 Received in revised form 10 January 2008 Accepted 3 February 2008 Published on line 2 April 2008 Keywords: Chemical-looping combustion Oxygen carrier Fluidized bed abstract Chemical-looping combustion, CLC, is a technology with inherent separation of the green- house gas CO 2 . The technique uses an oxygen carrier made up of particulate metal oxide to transfer oxygen from combustion air to fuel. In this work, an oxygen carrier consisting of 60% NiO and 40% NiAl 2 O 4 was used in a 10 kW CLC reactor system for 160 h of operation with fuel. The first 3 h of fuel operation excepted, the test series was accomplished with the same batch of oxygen carrier particles. The fuel used in the experiments was natural gas, and a fuel conversion to CO 2 of approximately 99% was accomplished. Combustion conditions were very stable during the test period, except for the operation at sub-stoichiometric conditions. It was shown that the methane fraction in the fuel reactor exit gas was dependent upon the rate of solids circulation, with higher circulation leading to more unconverted methane. The carbon monoxide fraction was found to follow the thermo- dynamical equilibrium for all investigated fuel reactor temperatures, 660–950 8C. Thermal analysis of the fuel reactor at stable conditions enabled calculation of the particle circulation which was found to be approximately 4 kg/s, MW. The loss of fines, i.e. the amount of elutriated oxygen carrier particles with diameter <45 mm, decreased during the entire test period. After 160 h of operation the fractional loss of fines was 0.00022 h 1 , corresponding to a particle life time of 4500 h. # 2008 Elsevier Ltd. All rights reserved. * Corresponding author at: Energiteknik, Ho ¨ rsalsva ¨ gen 7B, Chalmers University of Technology, 41296 Go ¨ teborg, Sweden. Tel.: +46 31 772 1443; fax: +46 31 772 3592. E-mail address: carl.linderholm@chalmers.se (C. Linderholm). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ijggc 1750-5836/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijggc.2008.02.006