Research On The Removal Of Flue Gas Mercury By SAPO-34 Based Modified Materials

Mercury can maintain in the environment for a long time with various chemical states.Flue gas is one of the main source of environmental mercury pollution.Mecury released to the environment can precipitation to the ground or water body and enter the food chain.Mecury could be accumulated in the organism and is hazardous to humans.Due to its strong volatility and hydrophobicity,elemental mercury is the most difficult component to get removed from flue gas.Modified materials based on SAPO-34?chabazite molecular sieves?have excellent catalytic activity in NH₃-SCR reactions.In this study,we prepared SAPO-34 based materials by ion exchange method,loading Mn,Cu and other metal elements on SAPO-34,and investigated their elemental mercury removal ability.The results show that Cu loaded SAPO-34 has Hg⁰ removal rate of25%-50%without HCl.Cu/SAPO-34 has an excellent Hg⁰ removal rate when the simulated gas contains 15 ppm HCl.The optimal removal rate can attain 97.5%with 10%copper load.Under relatively low temperature,the removal rate can also reach 80%,in the range from 100 to 250?.We also found that the chabazite structure have not been changed with the Cu load lower than 10%.But when the Cu load exceed 10%,CuO would be formed on the surface of Cu/SAPO-34.Besides,Cu/SAPO-34 shows great SO₂ and water resistance.The problems are that the removal rate of Cu/SAPO-34 is relatively low under low temperature and low HCl contents.Mn loading on SAPO-34 would promote the elementary mercury removal rate.The chabazite structure have also not been changed with the Mn load lower than 5%.But when the Mn load exceed 10%,MnO_x would be formed.The elemental mercury removal rate will decrease with the temperature increases in the range from 100 to 250?.The mercury removal rate could achieve 72.6%,The TEKRAN tests show that Mn/SAPO-34 removes elemental mercury mainly by adsorption.The adsorption process contains both physically and chemically process,due to the Hg-TPD results.Mn/SAPO-34 has great water resistance,while SO₂ would decrease its mercury removal rate.Later,we have compared three diode metal SAPO-34 based materials and found that Mn-Cu/SAPO-34 has the best elementary mercury removal rate.Ag-Mn/SAPO-34 and Pd-Mn/SAPO-34 has relatively low removal rate.