Adding gas from biomass to the gas grid - SGC

Figure 15: Maximum range of delivered Wobbe index in Europe, H gasFrom these figures it can be concluded that the gas that actually is delivered to the customer showsmuch smaller variations than is allowed in the national regulations. Biogas has to be purified to> 92% methane in order to fit into the Wobbe index demands stated in DVGW 260.Conform DVGW 260 it is important that the variations in gas quality in a specific distribution grid donot vary too much. Large variations will cause problems in the combustion equipment. Variationsbetween + 0.6 / -1.4 kWh/m 3 are allowed for L gas and + 0.7 / -1.4 kWh/m 3 for H gas. Some nationalregulations are even stricter.Other demands on natural gas that is delivered to customers are:• Dewpoint at actual pressure of delivery shall be lower than the ground temperature• The gas must be free from mist, dust or liquids• Oxygen content < 3 %• Total sulphur < 120 mg/m 3• Hydrogen sulphide < 5 mg/m 3• Mercaptane sulphur < 6 mg/m 3It is important that any introduction of biogas into the natural gas grid does not change the gascomposition in a way that may affect the safe operation of the customer installation. The maximumamount of biogas that can be injected into the grid therefore has to be thoroughly calculated and notexceeded.The injection equipment has to be equipped with safety devices that shut down the biogas injectionif there is a risk that the gas composition on the grid reaches values that lie outside the designvalues for the customer installations.As an example, the maximum addition of upgraded gas from anaerobic digestion to H gas (Danishnatural gas) is presented in figure 16.page: 65