The development of renewable energy is a major challenge worldwide, due to various environmental, geopolitical and economic issues. Biomethane (upgraded biogas) to be injected into the grid is one answer. The French Energy Agency ADEME built a roadmap for biomethane in the country. The scenario predicts by 2030 a production of 30 TWh which equals to about 1400 biomethane injection plants.
According to French specifications, a number of parameters of biomethane need to be monitored before the injection into the gas grid such as Calorific Value, Wobbe Index or trace compounds (e.g. water content, ammonia, total sulfurs and mercaptans, mercury, total chloride, fluoride, etc.). Nevertheless, others trace components could be present in the gas. Thus additional measurements are necessary in order to ensure end users safety and grid integrity.
During biogas and biomethane production processes (biogas from agricultural waste, household waste or sludges from waste water treatment plants), different trace components can be found in the VOC family (Volatil Organic Compounds) such as siloxanes, terpenes, alcohols, ketones, etc.
ENGIE Lab CRIGEN has developed an efficient analytical strategy based on the use of both thermaldesorption unit (TDS) and a gas chromatograph coupled with a mass spectrometer (GC-MS). Thanks to the use of this specific detector, the analytical method enables the identification and quantification of more than a hundred components in one sample. The sampling system is used to preconcentrate trace compounds and leads to quantification limits of 1 µg/scm (ppb level in gas). It is an easy-to-use technique which matches well with constraints on site. ENGIE Lab CRIGEN has assessed the online sampling method.
As a conclusion, the use of thermaldesorption and GC-MS allows to combine an easy-to-use sampling technique and a powerful laboratory device. Thus, a global characterization of trace components of a sample can be accessed quickly in a one-shot operation. Building on this success, this strategy is now used by ENGIE LAB CRIGEN to characterize real biomethane samples on production sites.
Etienne BASSET is a research engineer at the Gas Analysis and Metering Section of ENGIE LAB CRIGEN (ENGIE) in Saint-Denis (France).
Graduate engineer in analytical chemistry (2008), he is specialized in gas quality issues through new analytical developments and uncertainties measurement.
Since 2009, he is working on gas characterization (natural gas, biogas, syngas and biomethane) through the development of new sampling and analytical methods for different applications (H2S and tetrahydrothiophene monitoring for new desulfurization processes of wet natural gas, development of new devices and methods for analyzing trace compounds in gas samples, etc.).