Paper details

Title:

Pressureless Cryogenic Conversion of Biogas into Liquefied Biomethane and Solid Carbon Dioxide

Author(s):

Hofmann, J., Nachtmann, K., Falk, O., Baum, S., Fuchsz, M.

Document(s):

Abstract:

Biogas consists of about 50 to 65 Vol.-% methane CH4 and 50-35 Vol.-% carbon dioxide CO2. The calorific value of biogas is therefore significantly lower than natural gas (about 36 MJ/Nm³) with 18 to 23 MJ/ Nm³. Therefore biogas for long-term storage (weeks to months) is not suitable. In the presented treatment process biogas is largely freed from water vapor and trace gases (H2S, NH3) and transferred by a cryogenic separation process into solid carbon dioxide (dry ice) and liquid biomethane. The cryogenic pressureless separation process based on three heat exchangers: In the first step the pre-purified biogas is cleaned at 193 K (-80 °C) of H2S and NH3 residues. Subsequently, the gaseous carbon dioxide is transferred by desublimation at 123 K (-150 °C) into dry ice snow. The methane contained in the residual gas is transferred at 111 K (-162 °C) into liquid biomethane. The condensation of gaseous methane to liquid methane reduces the volume to 1/600 of its original volume and creates liquid biomethane with a calorific value of 21 MJ / liter (5,9 kWh/l). Such biomethane is long-term storable and can be used as a CO2-neutral substitute of LNG as fuel.

Keywords:

biogas, liquefaction, liquid biofuels

Topic:

Biomass Conversion Technologies for Liquid and Gaseous Fuels, Chemicals and Materials

Subtopic:

Biomethane

Event:

24th European Biomass Conference and Exhibition

Session:

3CO.4.5

Pages:

1067 - 1073

ISBN:

978-88-89407-165

Paper DOI:

10.5071/24thEUBCE2016-3CO.4.5

Price:

FREE