Study On The Catalytic Characteristics Of Ce-Cu/γ-Al₂O₃ For Hg⁰ And NO Combined Control In Low Temperature Flue Gas

According to the statistics of the National Bureau of Statistics,China’s current coal consumption still occupies a major position,and coal flue gas will produce various air pollutants,among which Hg⁰ and NO_x as key pollutants have received extensive attention at home and abroad in recent years.At present,the commonly used Hg⁰ and NO combined control technology is SCR technology.The core of SCR technology is catalyst.Ce-based and Cu-based catalysts have good low temperature performance,sulfur and water resistance,andγ-Al₂O₃ as a carrier has a large specific surface area and good stability.Therefore,in this paper,Ce-Cu/γ-Al₂O₃ catalyst is selected to study the performance of joint control of Hg⁰ and NO.In this paper,Ce and Cu Modifiedγ-Al₂O₃ catalyst（Ce-Cu/Al catalyst）was prepared by equal volume impregnation method.The optimum calcination temperature and time were 500℃and 5 hours,respectively.Then,through the experimental study on the mercury removal of Ce-Cu/Al catalyst,the best formulations of Ce and Cu were selected,and the effects of operating parameters and flue gas components on the mercury removal performance of Ce-Cu/Al catalyst were investigated.The results showed that in N₂+6%O₂ atmosphere,the highest Hg⁰ removal efficiency was 73.88%at 150℃and50000h^-1 GHSV.O₂and NO promoted the mercury removal performance of 2Ce-4Cu/Al catalyst,and the Hg⁰ removal efficiency reached 90.23%in N₂+6%O₂+500ppm NO atmosphere.NH₃ will compete with Hg⁰ for adsorption,so it can inhibit the mercury removal performance of the catalyst.The addition of O₂ can alleviate the inhibition.The results show that SO₂ of 200～1000ppm can promote the mercury removal performance of the catalyst to a certain extent.When SO₂ is 600ppm,the removal efficiency of Hg⁰is the highest,reaching 85.82%.The main reason is that the inhibition of SO₂ itself and sulfate and the promotion of SO₃ and Cu SO₄ play a leading role.H₂O can inhibit the mercury removal performance of the catalyst,but the deactivation caused by H₂O is reversible.When the reaction temperature is 150℃and 200℃,the removal efficiency of Hg⁰ is 37.32%and 56.3%respectively after adding 8%H₂O.Combined with the above results,the performance and influencing factors of Ce-Cu/Al catalyst for Hg⁰ and NO removal in NH₃ atmosphere were further studied.The results showed that under the conditions of N₂+6%O₂+500ppm NH₃,reaction temperature 200℃,space velocity 50000h^-1,the Hg⁰ and no removal efficiencies of2Ce-4Cu/Al catalyst were 66.88%and 74.24%respectively.With the increase of SO₂concentration,the removal efficiency of Hg⁰ and NO increased at first and then decreased.2Ce-4Cu/Al catalyst maintained more than 70%conversion efficiency of Hg⁰ and no in 6 hours in the presence of 600ppm SO₂.The reason for the effect on NO conversion is that which one is the dominant one is the promotion of acidic SO₄^2-or the inhibition of（NH₄）₂SO₄and NH₄HSO₄.At 200℃reaction temperature,the efficiency of 8%H₂O,Hg⁰ and NO decreased by 10%,which was stable in 8 hours.Based on the experimental results and the XPS analysis results of 2Ce-4Cu/Al catalyst before and after the reaction,it is found that the conversion between 2Ce-4Cu/Al catalysts at different price is beneficial to the formation of surface lattice oxygen in the removal of Hg⁰ and NO,thus promoting the removal of Hg⁰ and NH₃-SCR.