First proficiency test on the siloxane content in biomethane with traceable reference values

Iris de Krom, VSL

prEN 16723 sets requirements with respect to the maximum permissible levels that exist for the injection of biomethane into the natural gas grid and for use as vehicle fuel. Siloxanes are hazardous volatile organic compounds encountered in biomethane and biogas. Currently, test methods are neither standardised nor dedicated to biomethane and lack aspects of metrological traceability.

To benchmark the results of laboratories involved in biomethane conformity assessment, a proficiency test (PT) has been set up, enabling laboratories to demonstrate their competence with respect to determining the amount-of-substance fraction of siloxanes L2, L3, D3, D4 and D5 in methane. The gas mixtures for the PT siloxanes were prepared gravimetrically in accordance with ISO 6142-1 and ISO 19229 in passivated cylinders, from a multicomponent parent gas mixture, by means of gravimetric dilution.

Given the reactive nature of the components, dedicated statistical designs were developed for the homogeneity and stability study. We present the results of these studies and the assignment of SI-traceable reference values. These reference values are compared with the consensus values computed from the laboratory results. We conclude that the design is fit-for-purpose and sets directions for a regular scheme for these challenging measurements.

Pen Profile

Iris de Krom was born on 4 August 1986 in Breda, the Netherlands. After obtaining her bachelor degree in Chemistry in 2009 at the Hogeschool Utrecht, she continued with the master study Chemistry, Molecular Design Synthesis and Catalysis, at the University of Amsterdam. In 2011 she graduated on the subject “Carbene polymers for new organic solar cells”. In the same year, she started her Ph.D. at Eindhoven University of Technology. In 2015 she successfully defended her Ph.D. thesis “2-(2′-Pyridyl)-4,6-diphenylphosphinine: synthesis, characterization, and reactivity of novel transition metal complexes based on aromatic phosphorus heterocycles”. Since 2016 she is working at VSL on research into the preparation and analysis of traceable and accurate gas mixtures containing biogas/biomethane, mercury or (semi)-volatile organic compounds (S)-VOC. This research is preformed mainly within European research projects (EMRP/EMPIR).

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