In the PRENFLO plant in Fürstenhausen, Germany, experience of materials exposure was acquired over more than 10000 operating hours. The PRENFLO process is based on the entrained-flow principle with dry fuel dust feeding. The PRENFLO development—based on the Koppers-Totzek process—received funding from the Federal Ministry of Research and Technology (BMFT) and the Commission of the European Communities (CEC). Within the operating time we elaborated two special materials programmes together with the Electric Power Research Institute (EPRI, USA). In the second materials programme KEMA (The Netherlands) was also involved to a large extent. This paper mainly describes some results from the second test series with uncooled samples.