Effect of pressure and CO2 dilution on soot formation in laminar inverse coflow flame at conditions close to autothermal reforming

Junjun Guo, Peng Liu*, Erica Quadarella, Sreenivasa R. Gubba, Saumitra Saxena, Obulesu Chatakonda, Jeffrey W. Kloosterman, Xiaoyi He, William L. Roberts, Hong G. Im

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Autothermal reforming (ATR) is an important technology for hydrogen production from natural gas, where soot formation deserves particular attention as it may cause catalyst poisoning. The typical configuration of ATR reactors is that of an inverse diffusion flame (IDF). In this study, soot formation near ATR conditions is investigated experimentally and numerically, focusing on the effects of pressure and CO2 dilution in IDFs with pressure reaching 5 bar. The fuel stream consists of methane diluted with CO2 or N2. The mole fraction of O2 in the oxidant stream is 70%. Polycyclic aromatic hydrocarbons (PAHs) and soot volume fraction are measured by the planar laser-induced fluorescence (PLIF) and planar laser-induced incandesce (PLII) methods. High-fidelity simulations with a detailed soot aerosol model are also performed, and an empirical reactive soot inception model is proposed. A comparison of the results shows that the soot behavior is well predicted by the empirical reactive inception model but not fully captured by the physical inception model based on irreversible dimerization, demonstrating the importance of radical involvement in the soot inception process. Both measurements and predictions show a linear relationship between peak soot volume fraction and pressure, which can be explained by the linear increase of PAH molar concentration with pressure. Simulation analysis indicates that the dimer adsorption and HACA mechanism have a similar quantitative contribution to the soot growth. The CO2 shows stronger suppression effects in soot formation at the investigated pressures compared to N2. The contributions of chemical and thermal effects to soot suppression are numerically analyzed and the results indicate that the chemical effect of CO2 is mainly due to the removal of H radicals through the reaction CO2 + H→CO + OH, providing a soot suppression contribution of two times larger compared to the thermal one.

Original languageEnglish (US)
Article number112853
JournalCombustion and Flame
StatePublished - Aug 2023

Bibliographical note

Funding Information:
This work was supported by Air Products through its projects of RGC/3/4490-01-01 and RGC/3/4143-01-01 . The computational resources were provided by the KAUST Supercomputing Laboratory (KSL). PL and WR gratefully acknowledge the funding from KAUST CRG project under project number URF/1/4688-01-01 .

Publisher Copyright:
© 2023 The Combustion Institute


  • CO dilution
  • Elevated pressure
  • Inverse diffusion flame
  • Reactive inception model
  • Soot formation

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


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