Volatile Release and Ignition Behaviors of Single Coal Particles at Different Oxygen Concentrations Under Microgravity

An experimental study on ignition and combustion of single coal particles under different O ₂ concentrations was conducted at both normal (1-g) and microgravity (μ-g) in the first time. The surface and centre temperatures of the bituminous coal particle with initial diameter of ∼ 2.0mm were measured by the monochromatic imaging technique using a short wavelength infrared (SWIR) camera and an embedded fine thermocouple respectively. Results revealed that at μ-g, ignition of the tested coal particles was homogeneous. O ₂ concentration significantly affects the shape, ignition temperature and ignition delay time of the volatile flames. A mathematical model considering thermal conduction inside the coal particle was developed to describe the ignition process of single particle, adopting the volatile matter flammability limit as the homogeneous ignition criterion. The predicted ignition temperatures were slightly lower but closer to μ-g data. And the predicted variation trends of ignition temperature and delay time under different O ₂ concentrations agreed well with the μ-g experimental results.