Effect of potassium compounds in sintering flue gas on the removal of NO and dioxin performance over V2O5–WO3/TiO2 catalyst

Abstract

Sintering is one of the most important processes in iron and steel production, which provides stable sinter for the blast furnace. However, it also produces pollutants, such as sulfur dioxide (SO2), nitrogen oxide (NOx), and dioxins, which cause serious environmental problems. With the increasing pressure of environmental protection, pollutant reduction has become one of the bottlenecks restricting the development of iron and steel enterprises. Using a vanadium–tungsten–titanium catalyst can effectively reduce NO and dioxin in the sintering flue gas, while the potassium salt contained in the flue gas will reduce the activity of the catalyst. In this study, the fresh vanadium–tungsten–titanium catalyst was deactivated by the wet impregnation method in the laboratory. Effects of three potassium salts (K2SO4, K2O, and KCl) loaded on the surface of the catalyst on its denitration and dioxin removal activities were investigated. The regeneration performance of the deactivated catalyst was studied by the water washing and acid pickling process. Results confirmed that activities of denitration and dioxin removal were reduced by different potassium salts, and the order of reduction follows the sequence: KCl>K2O>K2SO4. The deactivation mechanism of the catalyst mainly includes physical deactivation and chemical deactivation. Physical deactivation is mainly caused by the deposition of potassium salts on the surface of the catalyst, blocking its pores. Chemical deactivation mainly refers to the interaction between the potassium salts and the active component on the catalyst’s surface, which inactivates the surface’s active site, weakens its oxidation reducibility, and reduces the number of acid sites on the surface, thereby decreasing the denitration and dioxin removal activities of the catalyst. Regeneration experiment results showed that water washing could restore the denitration activity of the catalyst. Acid pickling would lead to the loss of active substances on the surface of the catalyst. However, neither water washing nor acid pickling could effectively restore the dioxin removal activity of the catalyst. Finally, the poisoning mechanism of different potassium salts on the vanadium–tungsten–titanium catalyst was proposed.

Keywords

• sintering flue gas
• denitration
• dedioxin
• v2o5−wo3/tio2 catalyst
• potassium poisoning