BCM-Process® licensed by
DGE GmbH, Wittenberg
1) Desulphurisation
Any residual sulphur in the crude biogas needs to be removed before the actual amine wash. The biogas flows through an active carbon filter system with a special coating; the system has a very high capacity for hydrogen sulphide, which is converted into elemental sulphur and held there within the system. The spent active carbon can be spread on the fields along with the fermentation residues from the biogas plant; thus, the seperated sulphur rejoins the natural circulation.
2) Drying
Crude biogas saturated with water vapour is dried in this step. This drying process ensures that the concentrations in the amine washing solution do not change.
3) Non-pressurised amine wash – separating carbon dioxide from biogas
The non-pressurised amine washing process sends previously desulphurised and dried biogas flowing into a washing column packed with fillings. The washing solution is an aqueous amine solution that flows from top to bottom, against the biogas flow. The washing process takes place at a temperature of 40°C. The fillings in the column increase the surface area, ensuring more intensive exchange between the gas and liquid phases. Due to its own chemical composition, the amine solution is highly effective at absorbing the carbon dioxide in the biogas. Methane, on the other hand, does not react with the washing solution, and arrives as high-purity methane for extraction at the head of the column. The selectiveness of the washing solution ensures minimal methane loss at less than 0.1%.
4) Biomethane cooling and drying
After washing, the biomethane needs to be cooled down and dried again. The gas is led into a heat exchanger, where steam and amine-charged steam condense onto cooling surfaces before being led back into the washing system. The biomethane is transferred from there to a feeding facility for the natural gas supply system.
5) Regenerating the washing solution
Used amine solution containing carbon dioxide is extracted at the bottom of the column for regeneration. The aim is to expel the carbon dioxide absorbed from the solution by heating. This step in the process completely restores the amine solution’s capacity for absorbing carbon dioxide, and the regenerated washing solution can be reused.
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Gas treatment 
