| Summary: | 博士 === 國立交通大學 === 土木工程學系研究所 === 85 === Pressure drop and evaporation loss of dust cake during filtration have been st
udies in this thesis. Three kinds of dust materials, fly ash, limestone and S
AE fine dust, have been tested in a dust chamber and filtered through a Teflon
filter at filtration velocity ranging from 1 to 9 cm/sec. Dust cake porosity
and specific dust cake resistance coefficient have been investigated. It has
been found that higher filtration velocity will result in larger amount of ir
reversible dust cake compression and lesser amount of elastic dust cake compre
ssion. This leads to higher packing density or lower porosity of the dust cak
e for higher filtration velocity. The experimental specific dust cake resista
nce coefficient, K2, is also found to increase with an increasing filtration v
elocity. For the three dusts tested, K2 is found to relate to filtration velo
city Vf as K2=fV^n, where n is 0.52, 0.38 and 0.43 for fly ash,
limestone and SAE fi
ne dust respectively.The theoretical K2 values predicted by the Rudnick-Happel
equation are found to agree better with the experimental K2 values than those
by the Kozeny-Carman equation. When the dust cake porosity is larger than 0.
6, the difference between the K2 values predicted by the Rudnick-Happel equati
on and the experimental values is about 16 %, However, when the dust cake poro
sity is small than 0.6, the difference becomes larger.In another study, the ev
aporation loss of submicron, monodisperse ammonium nitrate particles during fi
lter sampling when the upstream saturation ratio is zero has also been examine
d. A theoretical model has been proposed which considers the upstream particl
e concentration, the porosity of the particle bed, particle diameter, upstream
temperature, pressure drop. According to the experimental results, upstream
particle concentration heavily influences the evaporation loss of ammonium nit
rate particles.Theoretical results agree reasonably well with the experimental
data obtained in the laboratory under well controlled conditions. Results pr
esented herein confirm that the simplified theory by Zhang and McMurry (1992)
provides a reasonable yet somewhat lower collection efficiency of volatile spe
cies during filter sampling owing to the assumptions in the downstream saturat
ion ratio and pressure drop.
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