高纯竖窑氮氧化物排放超标原因分析

Cause analysis for excessive emission of NO_(x) from a high-purity magnesia shaft kiln

某高纯竖窑更换脱硝催化剂3个月后出现氮氧化物排放超标的问题,为此进行了取样分析和现场测试分析,结果表明:新更换的脱硝催化剂在高纯竖窑烟气条件下运行良好,并未因中毒而快速失活。NOx超标的直接原因是GGH换热器因硫酸氢铵的缓慢沉积而逐渐腐蚀并出现穿孔,最终导致脱硝前烟气泄漏到脱硝后烟气中。“布袋除尘+GGH壳程换热升温+热风炉升温+中温SCR脱硝+GGH换热管程降温”的脱硝工艺整体上符合高纯竖窑的烟气污染物排放特点,催化剂的化学寿命可达到3年左右。

Three months after replacing the denitration catalyst in a high-purity shaft kiln,the problem of excessive NO_(x) emissions arises.This paper analyses the reasons through sampling analysis and on-site testing.The results show that the newly replaced denitration catalyst works well under the flue gas conditions in the high-purity magnesia shaft kiln,without deactivation due to catalyst damage.The direct cause of excessive NO_(x) emissions is the gradual corrosion and perforation of GGH heat exchanger due to the slow accumulation of ammonium bisulfate,which ultimately leads to the leakage of pre-denitration flue gas into the post-denitration flue gas.The denitration process of“bag filter+heat exchange and temperature rise through GGH+temperature rise through HBS+medium-temperature SCR denitration+temperature drop through GGH”generally conforms to the emission characteristics of flue gas pollutants in high-purity magnesia shaft kilns,and the chemical life of the catalyst can reach about three years.