| 摘要 |
In a method for purifying biogas, components present in the biogas, such as carbon dioxide, sulfur compounds and ammonia, are separated in a plurality of different process stages. The method is characterized by low energy consumption and an increase in methane concentration of at least 10% while keeping methane losses low. In a first purifying step, carbon dioxide, hydrogen sulfide, ammonia and other organic water-soluble substances in the raw gas are removed at normal pressure or at overpressure of up to 6 bar in a wash column using fresh water, methane gas having a methane concentration of at least 65% is withdrawn at the head of the wash column. Methane and carbon dioxide dissolved in the washing water are sequentially separated from the contaminated washing water discharged from the washing stage in a first stripping column at normal pressure and subsequently in a second stripping column in a vacuum.
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