An experimental study on ignition of single coal particles at low oxygen concentrations
Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
An experimental study on the ignition of single coal particles at low oxygen concentrations ( <21%) was conducted using a tube furnace. The surface temperature ( ) and the center temperature ( ) of the coal particles were obtained from the images taken by an infrared camera and thermocouples respectively. The ignition processes were recorded by a high-speed camera at different values and furnace temperatures . Compared with literature experimental data obtained at a high value, the ignition delay time decreases more rapidly as increases at the low region. The responses of and to the variation of are different: decreases while remains nearly constant with increasing at a low value. In addition, is less sensitive to while the ignition temperature is more sensitive to at a low value than in air. Observations of the position of flame front evolution illustrate that the ignition of a coal particle may change from a homogeneous mode to a heterogeneous or combined ignition mode as decreases. At a low value, buoyancy plays a more significant role in sweeping away the released volatiles during the ignition process.