Adding gas from biomass to the gas grid - SGC

For this report the terminology ‘pipeline quality gas’ will be used throughout to indicate a gasproduced from biomass that meets the de-facto accepted local standards for natural gases.Except for the Wobbe number the de-facto quality standard for all natural gases, and theirsubstitutes, is the same. This standard is most completely described in the German publications bythe Deutsche Vereinigung des Gas- und Wasserfaches (DVGW) on ’Gasbeschaffenheit’[lit.22,23,24]. These publications describe not only natural gases, but also all gases that can replacenatural gas. Examples of these gases are synthetic natural gas, propane/air mixtures, propaneenrichedgases, addition of flue gases for calorific value mitigation and gas from coal gasification.Also the International Standard Organisation (ISO) has produced some standards on gas quality[lit.25,26,27]. The ISO standards are restricted to describing the format of the quality designation,often without giving quantitative limitations. The DVGW formulated some experience basedquantitative limits to the gas quality.Referencequality designationISO 13868ISO 13443ISO 15403quality requirementsDVGW 260DescriptionNatural gas - Quality designationNatural gas - Standard reference conditionsNatural gas - Designation of the quality of natural gas foruse as a compressed fuel for vehiclesGasbeschaffenheitTable 24: Most relevant standards on the quality of grid distributed fuel gasesThe general outline of the standard is a strict limitation of the Wobbe index range to be delivered tothe end-user and restrictions on individual component concentrations as far as necessary andpractically (technically and economically) achievable.Combustion propertiesThere are two kinds of natural gases: high calorific (group H) and low calorific (group L) gases. Thehigh calorific gases consist mainly of methane and will often contain some other hydrocarbons. Thelow calorific gases contain less methane and contain considerable amounts of nitrogen or carbondioxide. The Wobbe number W is defined by the calorific value (H) divided by the square root (√ d)from the density.HW =√ dMixtures with the same Wobbe number will have the same combustion properties. Only the flamestability requires adaptation to the combustion speed of the gases. All natural gases have nearly thesame combustion speed.page: 57