Improved Techniques for Measuring and Validating Siloxanes present in Landfill and Digester Biogas

摘要

MKS Instruments has a Fourier Transform infrared (FTIR) analyser and novel analysis method which provides accurate on site siloxane measurements for use at landfill and digester plants for on demand or continuous siloxane measurements. This patented analysis method is capable of analyzing the presence of low level (＜0.2mg/m~3) total Si from siloxanes and employs a total siloxane number rather than speciation of the siloxanes. This paper will present results of testing performed at several landfill sites where numerous gas samples were also taken and sent to several laboratories (specializing in siloxanes detection) for analysis. While the FTIR results were very consistent, there was a large degree of variation among the laboratories even within duplicate samples. This paper will present a method by which the FTIR can be validated for response to low levels of siloxanes as well as trimethyl silanol while sampling the landfill gas (analyte recovery spikes) as well as scaling the overall FTIR response to the laboratory gas samples which are still the preferred analysis method even though there are clear issues with this type of analysis. By following this methodology, the FTIR data can be trusted to provide field-based analysis of total siloxanes as mg/ m~3 or expressed as total Si mg/ m~3.