Adding gas from biomass to the gas grid - SGC

ParameterUnitBiogas flow (raw gas) m 3 /h 400 1,600Production of upgraded gas 10 6 m 3 /year 1.98 7.91LPG consumption 1000160 640litre/yearLPG costs k€/year 36 145Investment, propane addition k€ 17 36Investment, propane storage k€ 23 45Total investment k€ 39 81Table 18:Estimated investments and LPG consumption for LPG addition plant combined withmembrane separation [lit.15]4.5 ADAPTION TO NON NATURAL GAS GRIDSIt is not always necessary to upgrade the biogas in order to distribute it on a grid. In Revninge (DK)and Gothenburg (S) biogases are adapted for use in grids separated from the natural gas.RevningeThe biogas plant at Revninge started operating in 1990, and supplies 67 households in Revninge.For back up or for adjustment of the gas quality a mixture of natural gas and air can also supply thesmall network which is isolated from the natural gas network. An evaluation of the domestic boilersin Revninge in 1994 showed some minor corrosion problems, but the concept is in generalpromising.Instead of biogas upgrading and supply of biogas to the natural gas network, the Revninge conceptcould be a model for smaller parts of the natural gas network. For safety reasons only minorvariations of the Wobbe index can be accepted when supplying households. For separate biogasnetworks backup supply from natural gas or propane/butane is recommended.GothenburgIn Gothenburg, Sweden, another solution has been chosen. Gothenburg has an old distributionsystem for town gas and a mixture of natural gas and air is now being distributed on this grid. Themixture is 47% natural gas and 53% air, resulting in a product with a Wobbe number similar to theold town gas that was manufactured from reforming of butane. The maximum load on this system isaround 3000 m 3 /h. Biogas in Gothenburg is produced in the local treatment plant for sewage waterand is presently being used for the combined production of heat and power in a number of gasengines at the water treatment plant. Part of the biogas is compressed, cooled and transferred tothe old town gas plant, where now the mixture of natural gas and air is introduced in the town gasgrid.The biogas system has a maximum capacity of 300 m 3 /h and the maximum amount of biogas that isintroduced into the grid is limited to 30%, a figure based on tests performed with different kind ofgas equipment presently used in the town gas system. Appropriate quality of the gas on the townpage: 47