Ziel dieser Arbeit ist die Erhöhung von Abbauleistung und Stabilität des biologischen Abbaus von Schwefelwasserstoff (H2S) in Biotropfkörpern zur Entschwefelung von Biogas. Für die Nutzung von Biogas ist häufig eine Reduktion des H2S-Gehalts erforderlich. Üblicherweise wird H2S von aeroben Mikroorganismen bei Zugabe von Luft zum Biogas entweder direkt im Biogasreaktor oder in nachgeschalteten Biotropfkörpern zu Schwefel und Schwefelsäure oxidiert. In der Praxis auftretende Schwankungen der H2S-Konzentration sowie sinkende pH-Werte durch vermehrte Bildung von Schwefelsäure können unzureichende Abbauleistungen verursachen. Die Erhöhung der Abbauleistung wird durch Zugabe von Eisensalzen signifikant verbessert. Eine hohe Selektivität zu Schwefel und ein daraus resultierender konstanter pH-Wert sowie erhöhte Stabilität des Abbauprozesses werden bei hohen Sulfatkonzentrationen erzielt.     «

Ziel dieser Arbeit ist die Erhöhung von Abbauleistung und Stabilität des biologischen Abbaus von Schwefelwasserstoff (H2S) in Biotropfkörpern zur Entschwefelung von Biogas. Für die Nutzung von Biogas ist häufig eine Reduktion des H2S-Gehalts erforderlich. Üblicherweise wird H2S von aeroben Mikroorganismen bei Zugabe von Luft zum Biogas entweder direkt im Biogasreaktor oder in nachgeschalteten Biotropfkörpern zu Schwefel und Schwefelsäure oxidiert. In der Praxis auftretende Schwankungen der H2S-K...     »

Biogas usually contains 2,000 to 5,000 ppm hydrogen sulphide (H2S). In CHP engines biogas is converted to electrical and thermal energy. For cogeneration the reduction of H2S is necessary. In most biogas plants H2S is reduced in a biological oxidation process in which a small amount of air is directly added to the gas zone of the biogas reactor. Microorganisms located on the wall and on the surface of the liquid convert H2S into elemental sulphur and sulphuric acid. This low cost process is often very instable, shows insufficient degradation rates and may cause corrosion in the biogas reactor. Therefore biotrickling filters are increasingly used in larger plants in order to reduce H2S. Biotrickling filters are also sensitive relating to fluctuating H2S concentrations, which are often observed in biogas plants. Rapid increasing concentrations of H2S cause decreasing degradation rates. The general target of the dissertation was to enhance the performance and stability of the biological H2S degradation in biotrickling filters. To obtain this target, investigations were carried out in lab and full-scale plants. In order to scale up the process, an exemplary description of the biological degradation of H2S in biotrickling filters was developed. This description is based on cell model and Michaelis-Menten kinetics. The biological degradation of H2S is significantly enhanced by adding iron salts. During periods of increasing concentrations H2S is absorbed by ferric ions, which are reduced to ferrous ions. Most thiobacilli are able to oxidize sulphur and ferrous ions. During phases of decreasing concentrations the thiobacilli re-oxidize the formed ferrous ions. Furthermore hydrogen sulphide is stored in the biofilm by formation of iron sulphide. Thus load peaks are compensated. Thiobacilli oxidize H2S to elemental sulphur and sulphuric acid. If a sufficient quantity of oxygen is supplied, most bacteria produce sulphuric acid. Thus the pH-value decreases. Most thiobacilli are intolerant regarding fluctuations of the pH-value. In order to maintain a constant pH-value, controlling measures and the addition of alkaline solutions are required. The investigations show that sulphate concentrations of more than 30 g/l cause an increasing selectivity to elemental sulphur. Thus the pH-value remains constant without adding alkaline media. The full-scale biotrickling filter, which was developed at ATZ development centre, is well fit for the reduction of hydrogen sulphide in biogas. With a small amount of maintenance long-term stable concentrations in clean gas less than 200 ppm are achieved by adding iron salts and sulphate concentrations of more than 30 g/l in the process liquid.      «

Biogas usually contains 2,000 to 5,000 ppm hydrogen sulphide (H2S). In CHP engines biogas is converted to electrical and thermal energy. For cogeneration the reduction of H2S is necessary. In most biogas plants H2S is reduced in a biological oxidation process in which a small amount of air is directly added to the gas zone of the biogas reactor. Microorganisms located on the wall and on the surface of the liquid convert H2S into elemental sulphur and sulphuric acid. This low cost process is ofte...     »