Regeneration of granular-filter dust collectors

Use of granular filters is promising for removing dust from gases at high temperature. In addition, it is economically beneficial to remove dust from gases using charge materials in a layer. This makes it possible to capture effectively sticking, lumpy, and abrasive dust from moist gases, i.e., in those cases when use of other dust removal methods is inexpedient. Granular filters are used in removing dust from high-temperature gases in the cement industry, and preparation of rare and expensive metals. Apart from filtration, granules may fulfill the function of a heat carrier and absorbent or catalyst in combination with filtration with an absorption or catalytic process. Due to the continuous improvement of regeneration methods, granular filters are used throughout the world for cement, lime, gypsum plants, chemical enterprises, in electrical instrument manufacture, radio engineering, atomic power generation, etc. Structurally this equipment is simple, has low operational consumption, is reliable in operation and provides quite a high degree of gas cleaning. The efficiency of using granular filters in industry is governed to a considerable extent by the choice of granular layer regeneration method. Filters are shown in Fig. 1 with different methods of loose material granular regeneration. A filter with regeneration by vibration shaking and back flushing (see Fig. 1a) has a holder installed on a spring and joined to the body by means of a flexible seal. The lower part of the holder is filled with metal turnings or coarse fraction loose material granules. This part of the layer is intended for capturing the coarsest dust fractions. The upper half of the holder is filled with granules with a size of 1.5–6 mm. The thickness of the layer is normally 100–250 mm. In order to reduce loose material movement, the holder is separated into small compartments. During filtration, dusty gas passes from the bottom upwards, and during regeneration from the top downwards. Simultaneously with flushing there is vibration. During vibration, intense granule movement commences when acceleration of the induced vibrations exceeds free fall acceleration taking account of the frictional force of granules between each other and over a holder wall. Vibrators have a shaft rotation frequency of 2800 rpm and power up to 3 kW. Chemical and Petroleum Engineering, Vol. 48, Nos. 1–2, May, 2012 (Russian Original Nos. 1–2, Jan.–Feb., 2012)