Fate of Siloxane Impurities During the Combustion of Renewable Natural Gas

Abstract

The fate of siloxane impurities during the combustion of renewable natural gas has been investigated experimentally in the counter-flow configuration. These impurities were shown to decompose completely within the pre-flame and luminous regions, and to form silica layers on metal surfaces in contact with the flame environment. It was determined that first-order global decomposition reactions can describe the experimental data qualitatively. The experiments suggest that for linear siloxanes the rate of the decomposition reaction decreases as the chain length of the molecule increases. For siloxanes with the same number of silicon atoms in their structure, it was found that cyclic siloxanes decompose slower than linear ones. Volume fractions of particles within the flame were measured in-situ using the laser extinction method indicating a linear relationship between the feed concentrations of siloxanes in renewable natural gas and the corresponding volume of particles in the flue-gas.

Keywords:

• Combustion
• Deposition
• Siloxanes' oxidation kinetics
• Solid silica particles
• Volume fraction

ACKNOWLEDGMENTS

The support of the Southern California Gas Company and of the National Science Foundation is gratefully acknowledged. Also the help of Mr. Khiza Mazwi in taking the AFM images is greatly appreciated.