CuO-SiO₂-TiO₂ Coprecipitated Oxides for Dry-Type Simultaneous Removal of Sulfur Oxides and Nitrogen Oxides

Abstract

Metallic oxides for dry-type simultaneous removal of SO_x and NO_x were investigated. This process is based on the principle that SO_x can be removed by the sulfation of CuO in metallic oxides, and NO_x removed by the catalytic reduction with NH₃ over CuSO₄ formed. Therefore, the most important point for the practical use of this process is to develop active metallic oxides, and a method to regenerate repeatedly CuSO₄ formed to CuO. Various metallic oxides were prepared by the coprecipitation from different compositions of CuSO₄, Al₂ (SO₄) 3, Si (OC2H5) 4, TiCl4 aq. etc. with NH₃ aq. The experiments were carried out using a flow type packed bed reactor for the reduction of NO_x or the removal of SO_x and NO_x, and a thermo-balance reactor for the basic study on the removal of SO_x under atmospheric pressure at 350°C . The inlet gas was 1000ppm S-500ppm NO-500, 667ppm NH₃-5% O₂-10% H₂O-N₂. The experiments on the regeneration conditions were carried out by the reduction with NH₃/H₂O mixture, and then the oxidation with O₂/H₂O mixture.
The results obtained are as follows:
1) 30 mol% CuO-20 mol% SiO₂-50 mol % TiO₂ was found as the most preferable metallic oxides for the simultaneous removal of SO_x and NO_x, in addition to 40 mol % CuO-20 mol% Al₂O3-40 mol% TiO₂ found previously.
2) The suitable regeneration conditions are to reduce from CuSO₄ to Cu₃N with 5-20% NH₃-1.5-7.4% H₂O-N₂ at 400°C, and then to oxidize from Cu3N to CuO with 5% O₂-0-10% H₂O-N₂ at 250 to 350°C.