This test method presents a procedure for the determination of siloxane species in a gaseous fuel matrix such as biogas or renewable natural gas (RNG). The method utilizes two-stage separation of siloxanes via gas chromatography coupled with ion mobility spectrometry. This approach minimizes matrix interferences and greatly increases analyte selectivity. The test method provides direct on-site analysis of gaseous fuels by transporting gaseous fuel from the sampling source to the inlet of the analyzer, which at maximum measurement frequency produces one set of siloxane concentrations per hour. The analyzer reports individual siloxane species concentrations, and determines total siloxane concentration by taking the sum of all measured species. The limit of quantitation for this method ranges from 0.5ppb to 2.3ppbv per siloxane species (expressed on a total-silicon basis), with the more massive species being correlated with higher limits of quantitation.
KeywordsGC-IMS; Biogas; Renewable Natural Gas (RNG); Siloxanes; Speciation; Silicon; Two-stage separation
This standard will provide a reliable method for on-line determination of total siloxane concentrations and siloxane speciation in gaseous fuels. Siloxanes are particularly abundant in gaseous fuels derived from landfills and wastewater treatment plants. These facilities produce a continuous supply of biogas, which can either be upgraded to RNG and injected into a natural gas pipeline or compressed and used as vehicle fuel, or combusted for electricity generation. An RNG production facility may be required to meet gas quality specifications, which could include the determination of siloxane content. Biogas electricity generation units must monitor and remove siloxanes to protect their engines, which can be damaged by the accumulation of SiO2 as a result of siloxane combustion.
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top