Rapport (alle typer) - Danish Gas Technology Centre

DGC-report 13gas fired engines at CHP plants. For information on costs related to conversionof existing natural-gas fired engines to biogas operation as well as gasquality requirements etc., please refer to Section 7 and Appendix 5.Most gas turbines for gaseous fuels are developed for natural gas. If changingfrom natural gas to biogas operation, substantial modifications of bothcompressor and turbine are required. Furthermore, gas turbines are muchmore sensitive to variations in gas quality than gas engines. Therefore, gasturbine units are not foreseen as biogas consumers in the Ringkøbing-SkjernMunicipality.5.1.3 Sulphur removalIn Denmark the most common technology for sulphur removal from biogasis application of biological filters.In these filters the H 2 S is converted to solid sulphur or H 2 SO 4 by use of oxygen.The reactions are given below.H 2 S +½ O 2 H 2 O + SS + H 2 O + 1,5 O 2 H 2 SO 4Normally, 5 % of air is added to the biogas in order to supply the requiredamount of oxygen for sulphur removal. However, this is problematic if, subsequently,the biogas is supposed to be upgraded to natural gas quality,since the nitrogen content in the air makes it impossible to fulfil the requirementsto natural gas. However, it is possible to add lower amounts ofair or add pure oxygen instead of air for the sulphur removal.The main advantage of biological sulphur removal is that it is a relativecheap method for larger gas flows. Other methods are more relevant forsmaller gas flows. Some of these are described in Appendix 3 together withprices of the sulphur removal.As mentioned earlier, experiences from Revninge show that the gas grid isnot harmed by the presence of sulphur. This means that it should be possibleto do the gas cleaning at the consumers instead of by the producers. Thisallows few and large units instead of several smaller units and thereby lowersulphur removal cost. However, the approach is likely to result in an in-