Factors Influencing Pressure Drop through a Dust Cake during Filtration

Three kinds of dust materials, fly ash (MMAD: 6.28 μm), limestone (MMAD: 2.53 μm) and SAE fine dust (MMAD: 3.88 μm), have been used to test the dust cake compaction and its influence on the specific dust cake resistance coefficient at filtration velocity ranging from 1 to 9 cm/sec. An accurate laser dispacement system was used to determine dust cake thickness and the amount of dust cake compaction during filtration. In the range of filtration velocity tested, dust cake compaction has been found to occur. Higher filtration velocity results in larger amount of irreversible dust cake compaction and lesser amount of elastic dust cake compaction. The experimental specific dust cake resistance coefficient, K₂, has also been found to increase with an increasing filtration velocity. For the three dusts tested, K₂ relates to filtration velocity V_f as K₂ ∞ Vⁿ_f, where n is 0.52, 0.38 and 0.43, for fly ash, limestone and SAE fine dust respectively. The theoretical K₂ values predicted by the Rudnick-Happel equation has been shown to agree better with the experimental K₂ values than those by the Kozeny-Carman equation. The maximum difference between the K₂ values predicted by the Rudnick-Happel equation and the experimental values is less than about 16%.