600 MW机组脱硝催化剂失活机理及中试再生

Deactivation mechanism and regeneration of SCR catalyst used in 600 MW unit of coal fired power plant

针对燃用中国典型煤的2×600 MW机组电厂失活的蜂窝式催化剂,使用XRF、ICP、物理吸附仪、吡啶吸附、H_2-TPR等表征手段等对催化剂失效前后的理化性质进行表征,研究了催化剂的失效原因。结果表明,催化剂的失活是由于碱金属Na、K和碱土金属CaO等物质导致了催化剂的物理失效以及化学中毒。催化剂物理失效是由于催化剂表面碱金属颗粒的沉积造成催化剂孔道堵塞,致使活性中心被覆盖。催化剂的化学中毒是由于酸性位丧失和活性位VO_x氧化还原性质降低,进而导致NH_3的吸附过程,以及催化剂表面吸附态NH_3和NO_x物种的活化过程均受到了抑制。利用项目组开发的1 000 m^3·a^(-1)再生装置,对失效催化剂进行了中试再生,结果表明,表面和孔道内积累的中毒物质全部被去除,催化剂孔结构、酸性位数量和活性位状态均恢复至新鲜催化剂水平。实验室活性评价结果显示,再生催化剂脱硝效率相比失效催化剂在360℃提高到85%左右,与新鲜催化剂相当。再生催化剂组装为2层测试模块(每层模块含9根催化剂),历经神华四川能源公司江油电厂侧线反应器5 000 h实际烟气测试,脱硝性能良好,维持在88%左右,超过初始设计值80%,且NH_3逃逸和SO_2/SO_3转化率满足电厂工程要求。

Deactivation mechanism of commercial V2O5-WO3/TiO2 catalyst for a 2×600 MW power plant has been studied on a basis of X-ray fluorescence（XRF）, inductive coupled plasma emission spectrometer（ICP）, BET and pore structure analysis, diffuse reflectance infrared fourier transformed spectroscopy of pyridine adsorption and H2 temperature-programmed reduction experiments. Both the decrease of the specific surface area and the masking of V2O5 active sites were caused by alkali and alkaline-earth metals deposition, which could be attributed to mechanical deactivation. Besides, they both coordinated to the hydroxyl groups and active sites on catalyst surface, leading to the decreased amount of acid sites and the reducibility of active sites. After the catalysts were poisoned, the activity was significantly suppressed due to the inhibited adsorption and activation process for reactants. The regeneration on an own-developed 1 000 m^3·a^-1 pilot device led to the reversible improvement of surface acid sites and active oxygen species. The activity of the regenerated SCR catalyst was close to fresh catalyst with a NO conversion of 85% at 360 ℃. 5 000 h slip-stream flue gas test in Shenhua Sichuan Energy Jiangyou Power Plant has also been applied to validate the catalytic performance, with NOx conversion remaining stable at about 88% and no excess NH3 slip and SO2/SO3 conversion.