Oxy-fuel circulating fluidized bed combustion (CFBC) is an alternate technology to oxy-fuel pulverized combustion (PC), which has a number of advantages that can often make it a better choice for CO2 capture. This paper presents experimental results and operating experiences from a 0.8 MWth pilot-scale, oxy-fuel-fired circulating fluidized bed. Test work demonstrated smooth transition between air-fired and oxy-fuel-fired operation and stable oxy-fuel operation with CO2 concentrations above 90% on a dry basis. Our experimental results also showed that limestone performance for sulfur removal is impacted by the combustion mode and that this impact depends on fuel characteristics as well as on combustion temperature. The test experiences showed that operating the pilot-scale unit over a long period under oxy-fuel mode led to enhanced corrosion due to higher sulfur concentrations in the flue gas. As demonstration projects of oxy-fuel CFB proceed in both Europe and North America, it is hoped that these tests can provide valuable data on the combustion characteristics, pollutant formation and operating experiences specific to this technology. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.