EXPERIMENTALLY DETERMINED PARTICLE NUMBER DENSITY STATISTICS IN AN INDUSTRIAL-SCALE, PULVERIZED-COAL-FIRED BOILER

A study on the variations of particle data rate statistics and the pro bability density function (PDF) of cumulative particle number density has been completed in a full-scale, tangentially fired, 85 MW(e) pulve rized-coal-fired boiler. Variables in the tests included boiler load a nd coal type. It was observed that particle data rate fluctuations wer e greater in magnitude for small particles (<3.5 mum) and that the PDF s of particle data rate were well approximated by normal distributions . Furthermore, there were no preferential frequencies in the large (>3 .5 mum) or small particle data rate fluctuations anywhere in the boile r. The PDFs of cumulative particle number density for the small partic les were negatively skewed and, as compared to the large particle PDFs , were less sensitive to boiler location. The large particle PDFs were more negatively skewed near the walls and more Gaussian as distance f rom the wall increased. Broader distributions of cumulative particle n umber density with peaks at higher values were observed for the small particles for the coal with lower volatiles and higher ash content. Mo reover, for the large particles, a noticeable shift of the PDFs, longe r ''tails'' toward higher cumulative number densities, and a substanti al flattening of the PDF curves were observed for the same coal. The s hape of the PDF profiles did not change substantially as the boiler lo ad changed. The effect of a lighter load on the small particle PDFs wa s to slightly broaden the distribution, mostly in the direction of lar ge cumulative particle number densities. For the large particles, a sh ift toward higher cumulative particle number densities, a slightly bro adening effect, and a reduction in the maximum PDF values were observe d at lighter load.