Effiziente Speicherung und mobile Nutzung von Biogas als flüssiges Biomethan

Abstract

A new treatment concept is intended to make biogas plants more flexible and energy-efficient and to show new marketing possibilities. This is made possible by an innovative low-temperature liquefaction unit, which separates the carbon dioxide portion as dry ice and liquefies the energetic methane at normal pressure. In the laboratory scale, the principle has been successfully implemented and optimised: An adapted multi-stage gas purification, which also works in the absence of oxygen, completely eliminates the fraction of hydrogen sulphide and other contaminants by means of iron preparations and activated carbon filters. By means of clever process control and material selection in the multi-stage heat exchanger system, the carbon dioxide can be separated as snow, thus establishing a continuous process. The resulting dry ice can be sold both energetically and materially as a by-product of gas treatment. In the final liquefaction step, in addition to an energy density of approximately 6.44 kWh per litre of liquid biomethane (based on the calorific value Hs), methane purities of up to 99.9% vol. can be achieved depending on the application case.