Time-resolved in situ measurements an d methane reforming in a nanosecond-pulsed discharge

Timothy Y. Chen, Taaresh S. Taneja, Aric C. Rousso, Suo Yang, Egemen Kolemen, Yiguang Ju

Research output: Contribution to journalConference articlepeer-review

Abstract

The plasma properties and chemical kinetics of plasma-assisted methane reforming in a He diluted nanosecond-pulsed plane-to-plane dielectric barrier discharge (ns-DBD) were studied using the combination of time-resolved in situ laser diagnostics and a 1-D numerical model. Plasma-assisted fuel reforming kinetic mechanisms were mainly evaluated based on matching reactant conversion and syngas production to steady-state measurements, which cannot describe the full range of chemistry and physics necessary to validate the model. Adding 1% CH4 to a pure He ns-DBD resulted in a faster breakdown along the rising edge of the applied voltage pulse, thereby lowering the reduced electric field (E/N), electron number density, and electron temperature. Further addition of CH4 did not continue to alter the E/N in the model. Laser absorption spectroscopy was used to measure gas temperature, C2H2, H2O, and CH2O in a CH4/CO2/He discharge to serve as validation targets for the predicted reaction pathways. CH2O was predicted within 25% of the measured value, while H2O and C2H2 were under-predicted by a factor of two and three, respectively. Path flux analysis showed that the major pathway for CH2O formation was through the reaction between CH3 and O, while C2H2 formation had multi-step pathways that relied on ions like CH3+ and C2H5+. It also revealed that CH2 is a significant intermediate for production of both CH2O and C2H2, and increased CH2 concentration could improve model predictions. The results demonstrate that the use of reaction rate constants with lower uncertainties and inclusion of He2+ are needed to improve the predictions. Varying the “equivalence ratio”, defined by the CH4 dry reforming reaction to H2 and CO, from 0.5 to 2 had a weak effect on measured product species and experimental trends were explained based on pathways extracted from the model.

Original languageEnglish (US)
Pages (from-to)6533-6540
Number of pages8
JournalProceedings of the Combustion Institute
Volume38
Issue number4
DOIs
StatePublished - 2021
Event38th International Symposium on Combustion, 2021 - Adelaide, Australia
Duration: Jan 24 2021Jan 29 2021

Bibliographical note

Funding Information:
This work was supported by ExxonMobil through its membership in the Princeton E-filliates Partnership of the Andlinger Center for Energy and the Environment. T.Y. Chen is partially supported through the Program in Plasma Science and Technology at Princeton University Fellowship. S. Yang gratefully acknowledges the faculty start-up funding from the University of Minnesota. All simulations were conducted in the Minnesota Supercomputing Institute (MSI). Y. Ju would like to acknowledge the grant support from NSF CBET 1903362 , NSF-EFRI grant for distributed chemical manufacturing, DOE DE-SC0020233 of Plasma Science Center, and DOE -NETL DE-FE0026825 .

Keywords

  • Chemical kinetics
  • Methane dry reforming
  • Non-equilibrium plasma
  • Plasma assisted fuel reforming
  • Pyrolysis

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