An Atlas Copco oxygen generator is helping a German biogas producer to create cleaner, more sustainable methane
Nat-Ur-Gas Solschen commissioned Bioconsruct, based in the German city of Melle, to design and build their biogas plant in 2016. Desulphurisation of biogas using oxygen produces a more sustainable energy source for the grid and reduces operating costs through improved energy efficiency by up to 50%.
The plant currently produces 1500 m3 of biogas per hour with an average methane content of 53%. The biogas is then concentrated further to a methane content of 94% in a treatment plant via membranes. The firm feeds 700 cubic metres of biomethane into the gas supply system every hour. It is sold to the Munich energy supplier BayWa.
Michael Klawitter of Nat-Ur-Gas Solschen said: “The biggest problem in the production of biogas is the resulting hydrogen sulphide.
“Firstly, it makes the filters in the treatment plant stick together. And secondly, it is converted into sulphur dioxide during combustion of the biogas and causes corrosion in fittings and motors. So, we need to try and eliminate as much hydrogen sulphide as possible from the gas.”
The company chose the biological desulphurisation method, where hydrogen sulphide is converted into elemental sulphur and water using special bacteria in the fermenter with the addition of air or oxygen. The sulphur remains in the fermentation residue and increases its fertiliser value, while the purified gas can pass through further processing stages. Atlas Copco’s trading partner D & N Drucklufttechnik, also based in Melle, planned and implemented the oxygen supply system.
“We made a conscious decision to choose desulphurisation with oxygen,” added Klawitter, “because unlike desulphurisation with ambient air, we can precisely control our O2 generator. This gives us full control over a number of factors, like explosion protection.
“We know that we have an O2 content of 95% and can dose the addition of oxygen in such a way that we are definitely always below the lower expectation limit of 2.3%.”