In order to achieve an efficient desulfurization performance of activated carbons, the presence of oxygen is indispensable.
In desulphurization, sulfur compounds, especially hydrogen sulphide, are adsorbed into the fine pores of the activated carbon after their transformation into elemental sulfur with the consumption of oxygen.
½ O2 + H2S -> S + H2O
If there is no oxygen or not a sufficient concentration, the chemical reaction and thus the desulfurization will not take place or only partially. The result is a breakthrough before the full potential of the activated carbon was exhausted.
By adding air to the biogas, the required oxygen can be supplied and optimal desulphurization can be achieved.