Study on the construction and filtration characteristics of a Triple-Layer granular bed filter

Granular bed filtration is a high-temperature dust removal technology with unique advantages. In this paper, through the fluidization tests, the densities and granule sizes of the triple-layer filter granules were optimally matched, and a triple-layer granular bed filter was constructed, which could be fluidized in layers and meet the requirement for removing ash deposited in the layers by fluidization without destroying the triple-layer structure. The whole-bed filtration tests at room and high temperatures showed that the triple-layer granular bed filter which consisted of cenosphere layer, desert yellow sand layer and 304 stainless steel shot layer had lower total pressure drop and outlet dust concentration, and higher filtration efficiency than the dual-layer granular bed filter which consisted of cenosphere layer and baozhu sand layer. The separated-bed filtration tests at high temperature found that the upper filter layer experienced the deep-bed, transition and surface filtration periods. The middle and lower filter layers didn't experience the surface filtration period and the grade filtration efficiency curves were "V" shapes, with the lowest efficiency for particles around 1.3 mu m.