Das Projekt "Rueckgewinnung industrieller Abwaerme durch Nutzung des organischen Rankine-Zyklus" wird vom Umweltbundesamt gefördert und von Messerschmitt-Bölkow-Blohm durchgeführt. General Information: The recovery of industrial waste heat between 200 degrees c and 400 degrees c with an ORC engine cycle was studied both theoretically and experimentally. The objective was to identify and specify the properties of working fluids which are, at these temperatures, chemically stable and which are cheap enough to make the ORC engine economically attractive. Using test facilities which exist at m.b.b. realistic dynamic tests have been carried out to investigate the chemical stability of working fluids as a function of temperature and to compare the different types of components. The results of the tests indicated that: screw expanders can be used up to about 100 kw with r114 containing 5 per cent lubricant and up to 190 degrees c (if a degradation of 25 per cent is allowed within one year); for higher temperatures, turbines in connection with toluene are advantageous, since they allow the subsequent separation of the working fluid to the lubricant (up to 250 degrees c with 5 per cent lubricant; up to 400 degrees c without lubricant); for performances higher than 100 kw, turbines with r114 and toluene are recommended. The use of water is possible from about 300 degrees c upwards. Fluorinol 85 does not present thermodynamic properties and technical efficiency advantages compared to toluene. It has also toxicity and cost disadvantages compared to toluene. It was therefore not recommended as a working fluid. A cost sensitivity analysis was made for six ORC plants differing in the working fluid (fluorinol 85, toluene, r114), the number of expansion stages of the turbine, the supplement or not with a recuperator, the efficiency (10.9 per cent to 27.5 per cent) and the energy recovering rate (696 to 1760 kwel). The payback period for these plants was calculated to be between 2 and 10 years. The main conclusion is that, less sophisticated plants receive a higher benefit than plants with a high energetic efficiency. Three typical ORC applications in industry were also investigated. These were: a hot water source at 160 degrees c with working fluid r114 and outputs of 500, 1000 or 5000 kwel; an exhaust gas source from a ceramic kiln at 350 degrees c with working fluid fluorinol 85 and outputs of 500, 1000 or 5000 kwel; a hot air source from a sintering cooler at 350 degrees c with working fluid toluene/water and outputs of 9.3 or 12.4 mwel. The payback periods for these plants also ranged between 2 and 10 year.