Carbon dioxide conversion in an atmospheric pressure microwave plasma reactor: Improving efficiencies by enhancing afterglow quenching

Heeseon Kim, Soonho Song, Curtis Peter Tom, Fei Xie

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Microwave plasma is effective for decomposing CO2, which is a major contributor to global warming. Atmospheric pressure microwave plasma is of particular interest due to its vacuum-free configuration. Here, we investigated the CO2 conversion performance of a microwave plasma system operating at atmospheric pressure. CO2 conversion efficiency and energy efficiency were measured for various CO2 flow rates and input power levels. Lower CO2 flow and higher power yielded an enhanced CO2 conversion efficiency and lower energy efficiency. The afterglow temperature in the reactor was also measured. At a specific energy input (SEI) of 7.25 eV/molecule, a temperature of 1342 K was observed 12 cm below the gas injection nozzle. To improve the efficiencies of the plasma system, we propose an afterglow quenching method with enhanced heat transfer characteristics. This was achieved using a water-cooled quenching rod inserted into the plasma reactor to cool the afterglow gas stream, thus limiting the recombination reaction of CO to form CO2. At a SEI of 7.22 eV/molecule, CO2 conversion increased from 30.1% to 36.1% with the quenching rod; at 2.46 eV/molecule, the increment of CO2 conversion efficiency was 29 %. An energy efficiency of 28.9 % was achieved using an SEI of 1.19 eV/molecule. By tracking down the heat loss to cooling water flowing through the applicator, exhaust port, and quenching rod, we determined the energy distribution from the plasma plume to the exit gas stream. The quenching rod increased the chemical enthalpy of the product gas by reducing CO recombination.

Original languageEnglish
Pages (from-to)240-247
Number of pages8
JournalJournal of CO2 Utilization
Volume37
DOIs
Publication statusPublished - 2020 Apr

All Science Journal Classification (ASJC) codes

  • Chemical Engineering (miscellaneous)
  • Waste Management and Disposal
  • Process Chemistry and Technology

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