A particle-tracking image pyrometer for characterizing ignition of pulverized coal particles

Abstract

In this study, a particle-tracking image pyrometer (PTIP) system, based on a high-resolution high-speed camera and a digital single lens reflex (SLR) camera, was proposed to investigate the ignition characteristics of pulverized coal particles. The goal of the PTIP system was to obtain reliable simultaneous measurements of the velocity, diameter, and temperature of individual burning particles. A modified particle-tracking velocimetry (PTV) algorithm was developed to collect the image sequences of individual particles, and it could weed out defocused particles and other odd particles by low-frequency filtration. Moreover, a template matching method was adopted to distinguish particles undergoing different combustion states (homogeneous volatile combustion or heterogeneous coal/char combustion). The experimental validation was carried out under an O2/CO2 atmosphere in an optically accessible flat flame-supported entrained flow reactor. Particles of Shenhua (SH) bituminous coal, in the size range of 70–133 μm, were combusted in the flue gas with gas temperature of 1400 K and O2 concentration of 20%. The diameter-temperature patterns of particles along their trajectories were discussed. Several criteria based on statistical analysis were adopted to divide the combustion process and obtain the ignition delay time (IDT) and devolatilization duration time (DDT).