Characteristics of the non-thermal plasma for the removal of volatile methyl siloxanes

The current study investigates the potential of non-thermal plasma (NTP) for removal of volatile methyl siloxanes (VMS) from landfill gas as it provides opportunity of removing the siloxane from the gas stream and reforming to a solid product to be extracted. The gas stream was fed through the dielectric barrier (DBD) plasma reactor, made of borosilicate tube, of diameter 6.5mm and length 120mm. Two gas streams have been explored. The control stream contained inert helium, He as the carrier gas for siloxane. The alternate stream consisted of He as the carrier gas for the test siloxane, as well as CH₄ and CO₂, maintaining gas ratios resembling LFG conditions. The total gas flowrate was maintained constant at 450 standard cm³/sec. NTP was generated at a steady rate at peak-to-peak voltage of 14 KV with the high-voltage power supply operated at 20.6 KHz frequency using positive and negative nanoseconds pulsed discharges for control conditions. Siloxane removal efficiency was ~30%, ~75%, and ~50% for L3 (linear chain), D4, and D5 (cyclic chains) respectively after 30 minutes of treatment of control gas stream, herewith generating mass deposits in the range of 12 to 14 mg. Distinct DBD discharge traits were observed between gas streams containing linear vs. cyclic siloxanes, with more instability when linear siloxanes were present. The plasma power intensity dropped from 0.0092W to 0.0034W when CH₄ and CO₂ was introduced. Siloxane removal from the mixed gas stream was evident as whitish deposits in the reactor. Removal efficiency of siloxane is under investigation.