Biogas upgrading – Review of commercial technologies - SGC

SGC Rapport 2013:270
Figure 11 Illustration showing the separation involved during upgrading of biogas
with membranes. Image from Air Liquide.
During the separation of carbon dioxide, also water vapor, hydrogen and parts of
the oxygen are removed from the biomethane. The permeation rate through a typical
membrane (made of a glassy polymer) used in biogas applications, is mainly
depending on the size of the molecules (Baker 2004) but also on the hydrophilicity.
The relative permeation rates shown in Figure 12 are based on experiences from
the membrane manufacturer.
C3H8 CH4 N2 H2S CO2 H2O
Slow permeation Fast permeation
Figure 12 Relative permeation rate of different molecules through a membrane
produced from a glassy polymer.
On the market today, membranes produced by several manufacturer are used for
biogas upgrading, e.g. two types of polymeric (glassy polymers) hollow fibre membranes
(Air Liquide Medal TM and Evonik Sepuran®) and one carbon membrane
(manufactured by MemfoACT AS), see Figure 13. The membranes are continuously
improved to get higher selectivity, higher permeability and cheaper manufacturing.
Figure 13 Hollow fibre membrane from Evonik Sepuran to the left, from Air Liquide
Medal in the middle and carbon membrane from Memfoact to the right. Images
from Evonik Fibres, Air Liquide and Memfoact.
Svenskt Gastekniskt Center AB, Malmö – www.sgc.se 29