Homogeneous ignition and volatile combustion of single solid fuel particles in air and oxy-fuel conditions

Tao Li*, Pooria Farmand, Christopher Geschwindner, Max Greifenstein, Jan Köser, Christoph Schumann, Antonio Attili, Heinz Pitsch, Andreas Dreizler, Benjamin Böhm

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The ignition and volatile combustion of single coal particles were investigated under laminar conditions. Relevant physico-chemical processes were analyzed under conventional and oxy-fuel atmospheres with varying O2 contents in experiments and simulations. An optically accessible laminar flow reactor with well-defined boundary conditions measured with PIV and quantitative OH-LIF was employed. Multi-parameter optical diagnostics were conducted, including OH-LIF, luminescence imaging, and backlight illumination. Simultaneously acquired experimental data allowed for the evaluation of particle size, ignition delay time, and volatile combustion duration for individual particles. A statistical analysis revealed the improved accuracy of OH-LIF compared to luminescence imaging regarding ignition detection. Simulations within an Eulerian–Lagrangian framework were introduced and validated against experiments. On this basis, particle temperatures, local gas temperatures, and fuel mass fraction were evaluated, providing insights into the devolatilization. Both experimental and numerical results indicated that increasing particle sizes significantly retarded homogeneous ignition and volatile consumption. When increasing the O2 content, a shorter ignition delay time and volatile combustion duration were observed experimentally, which was more significant for larger particles. High slip velocities accelerated convective transport resulting in an earlier ignition and faster volatile combustion. An atmosphere change from N2 to CO2 showed an earlier ignition and increased volatile combustion duration for larger particles, whereas the differences were insignificant for small particles. Simulation results suggested that the local heat transfer was improved by CO2, mainly due to the lower temperature sink close to particles and hence higher volatile release rates. As the initial ambient temperatures were similar, the introduction of CO2 favored homogeneous ignition and slowed down the volatile consumption.

Original languageEnglish
Article number120101
JournalFuel
Volume291
Early online date22 Jan 2021
DOIs
Publication statusPublished - 1 May 2021

Keywords

  • Bituminous coal
  • Combined experimental-numerical approach
  • Ignition and volatile flame
  • Multi-parameter laser diagnostics
  • Oxy-fuel combustion
  • Single particle combustion

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