Abstract
A digital image processing technique is used to investigate the ignition and combustion characteristics of an isolated coal water slurry droplet in low Re flow. Coal water slurry droplet study is useful for dilute coal suspensions based on the premise that ignitability of a spray of coal water slurry must depend on the ignition characteristic of an isolated coal water slurry droplet. A flat flame burner is used for optical accessibility and also for simulating vitiated gases as existing in boiler burners. A quartz wire of 0.175 mm diameter is chosen for low thermal conductivity and to hold the droplet above theflat flame burner. The following sequence of events is observed: (i) Water first evaporates leaving agglomerated coal particle, (ii) glowing first occurs at the leading edge of the droplet, (iii) for a droplet with diameter of the order less than I mm it was observed that the volatile combustion usually occurs away from the droplet in the wake of the combustible gases made upstream, while for droplet more than I mm, the flame is attached to the particle, (iv) combustion of coal water slurry droplet is intermittent. The ignition time and volatile combustion times are obtained. Parametric studies include the effect of drop diameter and ambient oxygen concentrations. Simplified phenomen ological type models are presented in order to determine the number of particles. interparticle spacing and density of coal water slurry droplet. Finally qualitative relations between ignition and combustion times and particle diameter are obtained and the results are then compared with experimental data.
Bhadra, Tanmoy (1998). A study of ignition and combustion characteristics of isolated coal water slurry droplet using digital image processing technique. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -B43.