黄铁矿在CO_(2)气氛下非等温氧化转化及动力学分析

Non-Isothermal Oxidation Transformation and Kinetics of Pyrite in CO_(2)

针对煤中常见含铁矿物黄铁矿在富氧燃烧典型气氛下转化特性,通过同步热分析结合烟气分析研究了黄铁矿在CO_(2)气氛下的转化行为.结果发现,黄铁矿在CO_(2)气氛下主要经历5个失重阶段且均为吸热过程,首先是黄铁矿颗粒表面硫脱除的起始热解段(相界面反应,n=1/2),活化能低于其在N_(2)气氛下近30 kJ/mol,为220.27 kJ/mol,随后裂解成磁黄铁矿(三维扩散,n=1/2)活化能与其在N_(2)(177.27 kJ/mol)下接近为178.1 kJ/mol;温度高于690℃,随着升温磁黄铁矿缓慢失硫,CO_(2)逐渐参与磁黄铁矿转化且释放SO_(2)和CO;820~1150℃经历双峰失重峰阶段,820~1020℃,氧化气体产物SO_(2)大量生成且在约1000℃达到体积浓度峰值;最后1020~1150℃,坩埚中残留物大量与CO_(2)持续氧化反应失重形成SO_(2)和CO,坩埚中形成复杂物相体系,铁硫化物和铁氧化物共存(或共融).CO_(2)参与黄铁矿产物转化失重阶段活化能分别为180.94 kJ/mol、229.69 kJ/mol和243.46 kJ/mol,动力学机制均为成核与生长(n=1).

To investigate the transformation behavior of pyrite under typical oxy-fuel combustion atmosphere,the transformation behavior of pyrite in CO_(2)atmosphere was studied by simultaneous thermal analysis and flue gas analysis.The results showed that the pyrolysis of pyrite can be mainly divided into five weight loss stages in CO_(2)atmosphere,all of which were endothermic processes.The activation energy of the initial pyrolysis stage(phase interface reaction,n=1/2)of sulfur removal on the surface of pyrite particles was 220.27 kJ/mol in CO_(2)atmosphere,which was about 30 kJ/mol lower than that in N_(2)atmosphere.Then,the pyrite was mainly decomposed into pyrrhotite(three-dimensional diffusion,n=1/2),and the activation energy was 178.1 kJ/mol(177.27 kJ/mol in N_(2)).When the temperature was raised above 690℃,the solid products continued to lose sulfur slowly,and CO_(2)gradually participated in the conversion of solid products to release SO_(2)and CO.At 820—1150℃,the sample experienced bimodal weight loss peak stage.At 820—1020℃,the oxidizing gas SO_(2)was generated in large quantities and reached the maximum volume concentration at about 1000℃.At the temperature between 1020—1150℃,a large amount of residue in the crucible continuously reacted with CO_(2)to generate SO_(2)and CO,and a complex phase system was formed in the crucible,in which iron sulfides and iron oxides co-existed(or formed eutectic mixtures).The activation energies of the mass loss stages of pyrite decomposition products reacting with CO_(2)are 180.94 kJ/mol,229.69 kJ/mol and 243.46 kJ/mol,respectively,and the kinetic mechanisms are nucleation and growth(n=1).