| According to those requirements of high-temperature flue gas purification technique in coal-fired combined cycle power generation, performance, characteristics and development trend of existing techniques are analyzed and problems involved are indicated. A granular-layer filtration technique for local fluidized dust-cleaning is presented basing on optimization of granular-layer filtration and dust-cleaning manners.Employing configuration of combined fluidized bed including suction hood and cell structure, a granular layer filtration device for local fluidized dust-cleaning is designed. Optimization design schemes of crucial components, amplification and fluidized dust-cleaning system are presented. Experimental data show steady filtration efficiency and bed pressure drop which do not vary with filtration period. And through adjusting the dust-cleaning cycle of the granular layer, filtration performance of the filtration device can be enhanced.Basing on fluidization theories, granular layer fluidized dust-cleaning principle is proposed and the effect of fluidization number on granular layer fluidized dust-cleaning is investigated. The results show that when fluidization number of the granular layer reaches 2.5, dust-cleaning can be completed by the granular layer within 4 seconds, and both bed height and dust content have no influence on dust-cleaning process.Granular layer filtration experiment is carried out. Influences of properties of filtration medium, flue gas, dust and dust-cleaning cycle on granular layer filtration performance are summarized. Combination of filtration medium and dust-cleaning cycle is optimized through experiment to make energy saving effect of the filtration device more salient. For example, with parameters of filtration medium size of 0.9-1.2mm, bed height of 70mm, dust cleaning cycle of 8min being applied, after flue gas with dust content of 2000mg·m-3 (normality) passes through the granular layer, the emission concentration is less than 10mg·m-3 (normality) and the bed pressure drop is 1440Pa. However, with filtration medium size of 0.45mm-0.9mm, the same filtration standard needs the bed pressure drop of as high as 3530Pa.A macroscopic mathematical model for granular-layer filtration is established. In terms of granular layer filtration mechanism, size distributions of dust particles and experimental results, impact of filtration speed on filtration performance is amended. Formulae involving filtration efficiency and bed pressure drop are deduced. Comparison of computational and experimental results testifies the feasibility of the formulae, and its reliability and accuracy in predicting relevant cases.
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