The Chemical Speciation Of S In Air Staged Combustion

With the development of China’s economy,environmental pollution is becoming increasingly serious,excessive emissions of nitrogen oxides and sulfur oxides have serious consequences.Air staged combustion technology is a promising technology which is implemented in the energy industry for low NO_x emissions.During achieve staged combustion of power station boiler,on the one hand,NO_x emission ssignificantly is reduced,on the other hand,it will inevitably affect the formation sulfur-containing phase of flue gas.When the boiler is working,SO₃ may cause high temperature corrosion,low temperature corrosion,SCR catalysts and air preheater jam.It is very important to study the sulfur-bearing phase and its formation mechanism in the air-staged combustion process by means of experimental research and software simulation.The thermodynamic equilibrium calculation results show that: In the reducing atmosphere,the main sulfur-containing phases are H₂S,COS,FeXSY,S₂,SO₂,HS,SO,S（g）;the main sulfur-containing phases are Fe₂（SO₄）₃,MgSO₄,FeSO₄,KAl（SO₄）₂,K₂SO₄,SO₃,SO₂,CaSO₄ in an oxidizing atmosphere;Temperature and excess air coefficient have great influence on the occurrence of S after coal combustion.The results of reaction kinetics simulation show that: in the reducing atmosphere,the main sulfur-containing phases are SO₂、COS、H₂S、S₂、SH、SO;the main sulfur-containing phases are SO₂、SO₃ in an oxidizing atmosphere;Temperature,excess air coefficient and sulfur content have great influence on the occurrence of S after coal combustion.S migration process and the migration path of different sulfur-containing phases were obtained;The process and route of S migration to SO₂ in reductive atmosphere are highlighted,and the process of SO₂ migration to SO₃ in oxidizing atmosphere is also discussed.The gas generation experimental platform of SO₃ was built and the chemical kinetic simulation of reaction process was carried out.The generation law of SO₃ were studied.The effects of reactor temperature,SO₂ content,H₂O content,NO content,CO content and O₂ content on the formation of SO₃ were discussed.The simulation results are in good agreement with the experimental results,which verifies the rationality of the model and the accuracy of the experimental results.The simulation process represents the experimental process.At the same time,the rate of formation of the reaction process was analyzed.The main generation pathway of SO₃ under different influencing factors are SO₂+O（+M）=SO₃（+M）,HOSO₂+O₂ = HO₂+SO₃ and SO₂+NO₂=NO+SO₃.The change of the main generation pathway of SO₃ was studied,and the reason of SO₃ concentration change was explained from the perspective of elementary reaction.