| 摘要 |
In purification of waste gases, esp. filtration of C particles from exhaust gases from diesel engines and domestic heating plant, the waste gas is led through a filter material contg. 30-99.8 (50-95) wt.% of Al2O3 and 70-0.2% of SiO2, or SiO2 + ZrO2, where the amt. of ZrO2 is 0.05-75 wt.% of the sum of the amts. of SiO2 + ZrO2, and the density of the material is 0.01-1.5 g/cc (0.06-0.5 g/cc). After passing through the filter, the gas flows through a gas-permeable casing of SiO2 and Al2O3 surrounding it. Pref. the filter contains 20-100% (80-100%) of Al2O3 and SiO2, with 0-10 wt.% of alkali(ne earth) oxides, oxides of Ga, In, Tl, B, Ge, Sn, Pb, P, As, Sb, Bi, Se, or Te, or oxides of the Sub-Gps., esp. FeO, Fe2O3, Fe3O4, TiO2, Cr2O3 or oxides of Mn or the rare earths. The gas is led into a chamber which is open on the inlet side, closed on the outlet side, with a gas-permeable partition between inlet and outlet. The chamber contains a fibrous filter material, resistant to high temp. The surface of the filter material pref. carries an oxidn. catalyst for removal of CO from waste gases, an oxidn. catalyst for removal of hydrocarbons, an oxidn. catalyst for removal of CO and hydrocarbons, and/or a redn. catalyst for removal of NOx. The filter material may be pre-treated with a soluble Fe cpd.
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