Search

The effect of filtration velocity on the filtration efficiency of a dual-layer granular bed 400°C was studied. The results showed that the bed filtration efficiency decreased from 99.87% to 99.85% as the average filtration velocity increased from 0.20 to 0.35 m/s. The effects of the filtration velocity on the efficiency of the upper and lower filtration layers were different. For the upper filtering layer, a higher filtration velocity resulted in decreased filtration efficiency, whereas the grade filtration efficiency increased with an increase in the particle size at the beginning of the test. However, toward the end of the test, it first decreased and then increased, with the critical point appearing at 0.23 μm. For the lower filtering layer, increasing the filtration velocity resulted in higher filtration efficiency. The grade filtration efficiency curve was V-shaped, with the critical points moving from 1.52, 1.45, and 1.32 μm at the beginning of the test to 1.63, 1.54, and 1.37 μm at the end of the test, respectively. In addition, the dust concentration at the outlet was maintained below 18 mg/m3. The dual-layer granular beds maintained efficient and reliable performance at high temperatures. [ABSTRACT FROM AUTHOR]

To improve the filtration efficiency of the dual-layer granular bed filter, a new method to enhance filtration with dust bipolar-charging was proposed. The characteristics of positive and negative corona discharge and dust charging at different temperatures were measured and analyzed. The filtration experiments of non-charged dust, positive charged dust, negative charged dust, and bipolar charged dust in a dual-layer granular bed filter were carried out. The results confirmed that the best filtration effect was achieved when the dust was bipolar-charged. Furthermore, because of the loose structure of dust cake formed by the charged dust, the filter regeneration cycles were prolonged. At 450 ℃, when the inlet dust concentration was 10 g/m3, and the bi-charging voltages were + 20 kV and - 14 kV, the mean outlet dust concentration in a filtering cycle was 38.1%, 46.6% and 68.2% lower than that of negative-charged, positive charged, and non-charged dust, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A triple-layer granular bed capable of stratified fluidization is constructed. • The triple-layer granular bed offers excellent filtration performance. • The upper filter layer experiences three filtration periods. • The middle and lower filter layers do not experience a surface filtration period. • The most difficult-to-filter particles exist in the middle and lower filter layers. 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 μm. [ABSTRACT FROM AUTHOR]