低温SCR脱硝催化剂失活诊断方法及对策

Diagnostic methods and countermeasures for deactivation of low temperature SCR denitration catalyst

文章针对石灰回转窑烟气170℃低温SCR脱硝工程实例,系统连续运行6个月,出现脱硝效率下降,催化剂失活现象,为找到失活原因以及解决对策,对催化剂模块进行BET比表面积、铵根质量比、SEM-EDS、XRF检测。SEM照片显示,催化剂外观没有物理性损伤;催化剂BET比表面积下降,表明附着物覆盖了晶体表面孔隙结构;催化剂铵根质量比升高,EDS和XRF检测出催化剂SO_(3)质量分数升高,推断催化剂附着物主要成分为硫铵类物质。催化剂热处理后,BET比表面积升高,证明热处理可以有效去除催化剂表面附着物。此外,文章采用950℃左右高温烟气与170℃左右的石灰回转窑烟气掺混将烟气升温至380℃,对催化剂进行连续48 h热处理。结果表明,热处理能够恢复催化剂脱硝活性,SCR脱硝系统各项指标恢复至正常运行状态,问题得到有效解决。

The article focused on the example of a 170℃low-temperature SCR denitrification project for lime rotary kiln flue gas.The system had been running continuously for 6 months,and there had been a decrease in denitrification efficiency and catalyst deactivation.In order to find the cause of deactivation and solve the problem,BET specific surface area,ammonium radical mass ratio,SEM-EDS,XRF detection were conducted on the catalyst module.SEM photos showed that there was no physical damage to the appearance of the catalyst;The decrease in BET specific surface area of the catalyst indicated that the attachment covers the pore structure of the crystal surface;The ammonium radical mass ratio in the catalyst increased,and EDS and XRF detected an increase in the mass fraction of SO_(3)content in the catalyst.It was inferred that the main component of the catalyst attachment was ammonium sulfate.After heat treatment of the catalyst,the BET specific surface area was increased,indicating that heat treatment could effectively remove surface attachments on the catalyst.Using high-temperature flue gas at around 950℃,mixed with lime rotary kiln flue gas at around 170℃,the flue gas was heated to 380℃,and the catalyst was subjected to continuous 48 hours of heat treatment.The results were indicated that heat treatment could restore the catalyst denitrification activity,and all indicators of the SCR denitrification system could be restored to normal operating conditions,effectively solving the problem.