Experimental studies of single particle combustion in air and different oxy-fuel atmospheres

• Particle temperature during combustion was lower in O2/CO2 than in O2/N2 mixture.
• Greater temperature differences were observed for coal then for char particles.
• CO2 hindered volatiles release and inhibited particle swelling during combustion.
• Presence of H2O in oxy-fuel atmosphere increased temperature of combusted particle.

In this work, direct observation of char and coal single particle combustion in different gases mixtures has been performed. Investigation focused on the influence of atmosphere composition on combustion process and especially on the comparison between combustion in air-like versus oxy-fuel dry and oxy-fuel wet conditions. For these tests, particles from Pittsburgh coal and South African Coal were prepared manually to cubical shape (approximately 2 mm and 4 mg). To investigate fuel type influence on oxy-fuel combustion, some tests were also conducted for Polish lignite coal from Turów mine. Experiments were carried out in a laboratory setup consisted of an electrically heated horizontal tube operated at 1223 K with observation windows for high speed video recording (1000 frames per second). During the experiments, particle internal temperature was measured to obtain comprehensive temperature–time history profile. Results revealed that particles burned at higher temperatures in high water vapour content mixtures than in dry O2/CO2 mixture. This behaviour was attributed to lower molar specific heat of water than of CO2 and four times higher reaction rate for char–H2O gasification reaction than char–CO2 reaction. Also visible dynamic of combustion process recorded with the high speed camera differs for experiments carried with water vapour addition.