Das Projekt "Design and planning of a demonstration power station with circulating pressurized fluidized bed firing" wird vom Umweltbundesamt gefördert und von Dawid-Saar durchgeführt. Objective: Design and construction of a coal fired power plant based on a combined cycle technology successfully applied to combustion of widely varying fuels for the purpose of steam generation and power production under environmentally acceptable conditions and net efficiency of more than 40 per cent for small plants (40 MWe) and a net efficiency of more than 45 per cent for large plants (smaller than 100 MWe). General Information: For clean gaseous and liquid fuels, combined cycle power plant engineering has in the meantime be accepted. This technology is less expensive and more efficient than that of conventional power plants. If coal is to be used in combined cycle power plant, efficient fuel gas and/or flue gas cleaning is an indispensable requirement. A direct and simple procedure to burn coal under pressure and than clean the flue gases at combustion temperature and combustion pressure with directly following expansion of the flew gas in a gas turbine with high thermal efficiency is the pressurized fluidized bed combustion of coal. Within the project the design of a bubbling pressurized fluidized bed combustor and the design of a circulating pressurized fluidized bed combustor was investigated as a basic for the realisation of a demonstration plant. In the bubbling pressurized fluidized bed combustor heat release and heat transfer are simultaneously taking place in the fluidized bed. This approach is attractive for it leads to very compact solutions. However, the complex requirements resulting from combustion, emission control, heat transfer, part load operation and dynamic process also entail some disadvantages. This comprises are not so notable in the circulating fluidized bed combustion due to separation of functions. In case of bubbling pressurized fluidized bed combustor, the entire combustion air flows through the fluidized bed. With due regard to possible erosion, the fluidizing velocity is limited to 1 m/sec, resulting in a relatively large cross section of the fluidized bed and a large pressure vessel diameter. In the circulating pressurized fluidized bed combustor, the combustion reactor does not contain any immersion-typ heating surfaces. Thus, the fluidizing velocities can be increased to up 5 m/sec which reduces the vessel diameter accordingly. The fluid bed heat exchanger for the circulating pressurized fluidized bed combustor can be conceived at discretion as regards its height/diameter ratio, owing to the small particle diameter of the circulating ash, the fluidizing velocity is here below 0.3 m/sec. Erosion problems are not anticipated in contrast to bubbling pressurized combustion systems. In bubbling pressurized fluidized bed combustion, the bed temperature is given for kinetic-reaction reasons. The transfer coefficient depends on the mean particle diameter and, as a result on the fuel preparation. Thus, dimensioning of the bed heating surface also depends on the fuel and its particle size ...