| 摘要 |
The invention relates to a method for purifying biogas for extracting methane, where components present in biogas, such as carbon dioxide, sulfur compounds, and ammoniac are separated in a plurality of different process steps, and a system suitable for performing the method. The aim of providing a method for purifying biogas for extracting methane, characterized by low energy consumption and allowing an increase in methane content of at least 10 %, is achieved by the following characteristics: In a first purifying step, carbon dioxide, hydrogen sulfide, ammoniac, and other water-soluble organic substances present in the raw gas are removed in a washing column K1 at standard pressure or at overpressure of up to 6 bar by means of fresh water, wherein methane gas having a methane content of at least 65 % is drawn off at the head of the washing column K1. Methane and carbon dioxide dissolved in the wash water are sequentially separated from the contaminated wash water discharged from the washing stage K1, in a first stripping column K2 and subsequently in a second stripping column K3, by adding stripping air under standard pressure. An oxygenic stripping gas having fuel gas quality arises in the first stripping stage K1. The purified wash water accruing in the second stripping stage is returned to the washing stage K1. |
