Characterization on hetero-homogeneous ignition of pulverized coal particle streams using CH∗ chemiluminescence and 3 color pyrometry

Abstract

Two in situ optic methods on CH∗ chemiluminescence and coal particle temperature, are newly applied to investigate the devolatilization/homogeneous and heterogeneous ignition behaviors of dispersed coal particle streams, with ambient temperature from 1200K to 1800K and oxygen mole fractions from 10% to 30%. The dispersed coal particles of 65–74μm are injected into an optical Hencken flat-flame burner by a novel de-agglomeration feeder. First, the consecutive images through multiple filters near CH∗ emission band, centered at 420 430 and 440nm, are exquisitely processed to subtract the interferences from continuum blackbody radiation of particles and soots in the CH∗ band. Then, the signal of CH∗ chemiluminescence is capable of providing a good indicator of the coal devolatilization process. Secondly, 3 color pyrometry is adopted to detect particle surface temperature and determine the heterogeneous ignition delay time. The prevalent devolatilization/homogeneous-ignition are observed at high temperatures (1500 and 1800K) with apparent CH∗ signals, whereas CH∗ emission can rarely be detected in the initial stage of 1200K case that implies a dominated heterogeneous ignition mode. The effect of oxygen concentration on devolatilization is further discussed. The particles temperatures history after injected into Hencken burner are represented by 3 color pyrometry based on a two stage principle, and thus the role of oxygen in determining particle temperature and heterogeneous ignition is finally examined.