燃煤电厂选择性催化还原脱硝催化剂砷中毒分析

Arsenic deactivation of honeycomb SCR catalysts in coal-fired power plants

以某燃煤电厂高温高砷(As)环境下在役蜂窝式选择性催化还原(SCR)脱硝催化剂为研究对象,在中试试验台上对其脱硝效率、氨逃逸、活性、SO_2/SO_3转化率等脱硝性能进行了检测评估,并运用X射线衍射仪(XRD)、X射线荧光光谱仪(XRF)、孔容孔径分析、扫描电镜(SEM-EDS)、电感耦合等离子-质谱仪(ICP-MS)和傅里叶变换红外光谱仪(FTIR)等对催化剂进行了理化特性表征。结果表明:该在役催化剂经过4 000 h的运行,其活性下降幅度达到30%以上,已无法满足80%脱硝效率下氨逃逸小于3mL/L的设计要求;该在役催化剂未发生因高温(415℃)引起的催化剂晶态变化或烧结团聚等;SEM-EDS、XRF以及ICP-MS检测结果表明,该在役催化剂在运行过程中As在其表面和孔道内沉积,致使其微观比表面积和孔容急剧减小,造成部分微孔及介孔的堵塞,是其活性下降的主要原因。

Taking the honeycomb selective catalytic reaction(SCR)catalysts exposed to high arsenic atmosphere in a coal-fired power plant as the research object,the denitration parameters such as the denitration efficiency,ammonia escape,activity and SO2/SO3 conversion rate were detected by bench-scale tests.Moreover,several instruments like the X-ray diffractometer(XRD),the X-ray fluorescence spectrometer(XRF),the pore volume aperture analyzer,the scanning electron microscope-energy diffraction spectrum(SEM-EDS),the inductively coupled plasma-mass spectrometer(ICP-MS)and the Fourier transform infrared spectrometer(FTIR)were employed to characterize the physical and chemical properties of the catalyst.The results show that,the activities of the catalysts dropped by more than 30%after about 4 000 hours'service,which could not meet the design requirement of ammonia escape less than 3 mL/L at 80%denitrification efficiency.No crystal change or agglomeration of the catalyst caused by high temperature(415℃)was observed.The deposition of arsenic on surface and pores of the catalysts resulted in a significant decrease of the micro specific surface area and pore volume of the catalyst,causing blocking of the pore system,thus the activity of the catalyst reduced.