In an experimental project funded by the 5th Framework Programme of the European Community (EC), different measurement techniques are used to analyze in-furnace processes in a 235 MWe Circulating Fluidized Bed (CFB) boiler in Turow, Poland. The purpose of the project is to assess the insufficiently known features of large-scale CFB boilers. The furnace of the boiler has a cross-section of 21 x 10 meters and a height of 43 meters. The boiler is operated on a local brown coal. Steady state, as well as dynamic conditions, are studied. The project is unique in two respects: Firstly, several measurement ports are provided in the large CFB furnace for in-situ measurements in various locations on the furnace. Secondly, a number of measurement tech...