Experimental Study On Synergistic Denitrification And Mercury Removal By Modified Attapulgite

Selective Catalytic Reduction?SCR?denitration is the most effective nitrogen oxide removal technology which is frequently used in coal fired power plants.With the appropriate catalyst,the Hg⁰ in the flue gas can be converted into Hg²⁺which can be removed effectively in the existing processes of dust removal and desulfurization to realize simultaneous control of mercury and NOx in the flue gas.The denitrification and mercury removal performance of Mn-Ce dual-doped catalysts was systematically studied in this thesis and the effects of O₂,NO,SO₂,space velocity and multi-flue gas conditions on the denitrification and mercury removal of catalysts were investigated.The results of the study found that the Mn-Ce-ATP catalyst can meet the actual production needs of coal-fired power plants,while being more economical and environmentally friendly.?1?The denitrification and demercuration perfeomance of Mn-ATP were investigated from different Mn loadings,reaction temperatures and flue gas conditions.The experimental datas showed that 8%Mn-ATP exhibited the highest denitrification effect at 250°C,while 8%Mn-ATP and 10%Mn-ATP exhibit the best mercury removal effect at 250°C.The appearance of SO₂ will reduce the denitrification and demercuration efficiency of Mn-ATP and the effect of SO₂ on the catalyst is irreversible.It was found by characterization that the addition of Mn reduced the specific surface area and pore volume of the catalyst.The Mn active material mainly accumulated on the surface of the catalyst in the form of particles,but the original fibrous structure of the catalyst did not change after Mn doping.As the amount of Mn doping increasing,the number of catalyst surface particles is significantly increased.The Mn was presented in the catalyst mainly in the form of MnO₂.The lattice oxygen and MnO₂ content in the catalyst with increased Mn addition are the main factors affecting the mercury removal performance of the catalyst.?2?In order to improve the sulfur resistance of Mn-ATP denitrification and demercuration,the effects of different Ce loading,reaction temperature and various flue gas conditions on the denitrification and demercuration activities of 8%Mn-Ce-ATP catalyst were investigated.It was found that the addition of 5%Ce increased the denitrification and mercury removal activity of the catalyst at 250°C.The inhibitory effect of SO₂ on the performance of the catalyst was weakened after the addition of Ce.When the SO₂ is added into the simulated flue gas,the denitration effect of the catalyst can be stabilized at about 60%,and the mercury removal effect is maintained at about 76%.It was found that NO inhibits the oxidation of Hg⁰ of the catalyst,but the presence of O₂ weakens the effect of NO on the catalyst preformance.The high space velocity(7.5×105h^-1)affects the mercury removal effect of the catalyst.Combined with the table data of BET,XRD,SEM and XPS,it was found that the addition of Ce reduced the specific surface area of the catalyst,the surface of the catalyst was smoother than Mn-ATP,and the content of O?and the proportion of Mn⁴⁺in the catalyst were improved.The main forms of Mn and Ce in the catalyst are MnO₂ and CeO₂,and MnO₂ and CeO₂ act simultaneously in the process of denitrification and demercuration.The denitrification mechanism of the catalyst is similar to that of other scholars and the demercuration mechanism basically follows the Mars-Maessen mechanism.