Adding gas from biomass to the gas grid - SGC

Alkali metalsAt high temperatures some alkali metal components vaporize and can be transported to theappliances, some of them are vulnerable to alkali metal components. Gas turbines require a feedwithout alkali metal components.AromaticsAromatics like benzene and toluene are present in some natural gas and can induce stresscorrosion cracking in some plastic pipelines. New plastic pipeline materials are rather resistant tostress corrosion by aromatic components. Some limitation of the concentration of aromaticcomponents in the product gas can be needed.Carbon monoxideCarbon monoxide containing town gas is distributed for decennia all over the world. Properodorisation is used to reach an early warning in case of a leakage. A potential problem arises withthe increasing use of stainless steel in appliances. The nickel, if present, in the stainless steel reactsat room temperature with the carbon monoxide to form gaseous carbonyl compounds.HalogensMost chlorine and fluorine (halogens) originate from waste materials, often co-processed withbiomass. But also some biomass can contain considerable amounts of halogens. Limitations existto avoid the formation of halogen acids and other adverse halogenated products during combustion.Methane numberCurrently all reciprocal gas engines are adapted to the actual range of methane numbers in thegases to be fed to the installation. The distribution of a gas with a methane number outside thecurrent range can impose serious problems to the gas engine. Fluctuations within the actual rangereduce the averaged energy conversion efficiency of the gas engine. It is possible to have a controlsystem on the gas engine to adapt to the actual methane number. Currently most European gaseshave a methane number between 70 and 100 [lit.31]. The International Standard Organisation hasproduced a draft standard on the use of natural gas as vehicle fuel [lit.32].SiloxanesSiloxanes are large, but still volatile, organic silicium containing components present in wastestreams. On combustion they form silicium oxide building up an abrasive layer in a gas engine.Often it is possible to trace the source of the siloxanes and to stop this contamination.In Austria explicit limits are given in their standard ‘Deponiegas’ [lit.30] on chlorine and fluorineconcentrations.page: 59