IGNITION AND COMBUSTION OF ISOLATED AND BINARY ARRAY OF COAL PARTICLES

A digital image processing technique is employed to investigate the ig nition and combustion characteristics of isolated coal particles as we ll as the interactive combustion of a binary coal array in low Re flow . When an isolated coal particle is suddenly subjected to hot vitiated gases, the following sequence of events is observed: (i) primary hete rogeneous ignition (HI) at the leading edge of the particle, (ii) ejec tion of volatiles as jets in the direction of the convective flow, (ii i) secondary gas phase ignition of volatiles (SGI), and (iv) formation of wake flame due to combustion of volatiles with a black inner zone along with heterogeneous combustion of char. Also, for high volatile n onswelling bituminous coal (PSOC 1447, hvCb) intermittent volatiles ig nition and combustion are observed to occur during the combustion proc ess, for a few of the experiments. The experiments are then repeated f or a binary array. A group flame is formed for the binary array at clo ser interparticle spacing. Intermittent ignition does not occur for th e binary array of hvCb coal particles. Such a behavior persists even a t larger inter-particle spacing, which suggests that radiation interac tion between the particles might be occurring even though mass transfe r interactions are absent. Flame characteristics and flame merging tim es are obtained for the binary coal particle array.