Thanks to close cooperation guaranteed by the license agreement signed by Italy, Portugal and Romania with the Belgian company Global Water Engineering, we are able to propose processes for biogas purification.
SULFURIX™ is a maintenance free biogas scrubber system for continuous removal of hydrogen sulfide (H2S) from biogas. This is typically needed before using biogas for power generation in CHP units. The biogas is “washed” with treated water without significant chemicals consumption. Sulfur removal efficiencies of more than 95% can be reached. For ultrahigh removal efficiencies, two SULFURIX™ scrubbers can be used in series. No waste products are produced, as the sulfur is ultimately returned to the treated wastewater as sulfate.
Biogas is coming out of the anaerobic digesters saturated with water vapour. At the usual digester temperature of mesophilic anaerobic digesters of around 30°C, this means that the biogas contains about 5% water, or about 50 g/Nm³ biogas. If the temperature of the biogas subsequentely drops, some of that water will condense into liquid.
In case the biogas pipeline from the digester(s) to a biogas burner(s) is long, with many ups and downs, and/or has certain part of its trajectory under ground or in a culvert below grade, then this condensation will give rise to the build-up of water pockets, resulting in pressure fluctuations and surges which will disturb or trip the biogas reuse system.
In case the biogas is used as fuel in electrical power generators, there are limits imposed on the humidity of the biogas at the inlet of the engines (usually 70 – 80%), in order to avoid damage to the engines.
The GASODRIX™ biogas drier package unit used consists of a stainless steel biogas/refrigerant heat exchanger and a refrigerant cooling group with a compressor, a condenser, a storage tank, and an evaporator.
The biogas at typically 30 – 40°C is cooled to 5 – 10 deg C, after which ca. 60 – 70% of the water vapour (about 35 g/m³) condenses to water, which is separated from the gas in and after the heat exchanger.
The remaining moisture in the biogas is about 10 – 15 g/m³, and acceptable, considering the fact that the biogas is heated again in the biogas compressor and then cools off to ambient temperature which in subtropical and tropical climates is mostly between 15 and 35 deg C.