Assessment of dielectric barrier discharge non-thermal plasma for the removal of siloxanes from landfill gas*

Biogases including landfill gas (LFG) continue to be a vital renewable energy source, with a methane potential of approximately eight million tons/yr which can displace about 5% of current natural gas consumption in the electric power sector and 52% in the transportation sector. However, trace contaminant volatile methyl siloxanes (VMS) present in LFG causes deterioration of combustion engines. Conventional technologies for siloxane require periodic media replacement, is expensive and re-enters the waste cycle.  In this study, dielectric barrier discharge was applied on pure streams of D4 (octamethylcyclotetrasiloxane), L3 (octamethyltrisiloxane) and on mixtures of D4 and L3 in a tubular reactor using helium as carrier gas. The goal is to determine the experimental conditions under which the removal of siloxane as, polydimetylsiloxane (PDMS), could be optimized; PDMS is commonly used in biomedical research, medical equipment as well as in electronic sealants.  The discharge influence was explored over varying durations and flow rates, with most of the removal occurring in the first 20 minutes.  Maximum removal of ~80% for D4 and ~50 % for L3 was achieved at the highest gas flow rate of 500 sccm.  Further analysis is focused on determining kinetic rate constants for removal and PDMS generation. Preliminary operations with a pilot scale modular demonstration unit with planar electrodes has been completed that can utilize atmospheric air with other LFG components instead of helium as a discharge medium.