Das Projekt "Verbesserung der Qualitaet von Biogas mit dem Ziel der Erhoehung seines Heizwertes auf Heizgasstandard" wird vom Umweltbundesamt gefördert und von Landeshauptstadt Stuttgart, Tiefbauamt durchgeführt. Objective: To construct a plant for the purification of biogas produced in a sewage treatment plant and to upgrade its calorific value. A projected 10 000 m3 of biogas will be processed daily. General Information: The biogas, which contains a high percentage of CO2, has a calorific value of 7.45 Kwh/m3. In addition, for final use H2S should be eliminated from the biogas. In order to reach the prescribed calorific value of 11.2 Kwh/m3 it may be necessary to add some hydrocarbons such as propane. The CO2 and H2S are removed in a regenerative alcanolamin process (MEA) for which the required steam of the MEA-lye is obtained from the sludge incineration plant. The condensate is conveyed back to the boiler on the sludge incineration plant. For purification the sewage gas has to go through the following process: - removal of CO2 and H2S by means of regenerative alcanolamine scrubbing; - drying, compression and absorption on activated aluminium oxide; - analysis of the CO2 content and dew point of the purified gas; - odorization with a pungent substance added by metering pump; - conditioning of the purified gas with LPG, to comply with the prescribed calorific value for fuel gas. Achievements: Experimental operation of the plant carried out from 5/9 to 11/9/1985 with the agreement of the Public Works Department and the City Gas Company was successfully completed. During this period approx. 40000 m3 purified sewage gas of natural gas quality were fed into the city's mains gas supply. The plant was thus deemed to be accepted and was transferred to the authority of the Public Works Department on 12/9/1985. Output Data of the plant were the following: Crude gas approx. 606 Nm3/h CO2 approx. 36 - 38 per cent vol. H2S approx. 270 - 320 mg/Nm3 N2 + 02 approx. 0.6 - 1.8 per cent vol. t approx. 20 deg. C. Purified gas max. 369 Nm3/h min. 128 Nm3/h. From commissioning in September 1985 until the end of 1988 3.8 million m3 of purified gas have been produced. This is equivalent to 3.7 million litres or 3.2 million kg of heating oil. The guaranteed performance of the plant is exceeded and the consumption of operating materials falls below the stated values. Despite increased output the guaranteed composition of purified gas is below the required levels. Operating costs of the main sewage plant are slightly reduced by sewage gas processing.