SCR烟气脱硝系统出口烟道NOx测点技术改造

燃煤电站锅炉排放的氮氧化物是大气污染的一个重要来源，控制NO_x排放已成为当前电厂的重要工作。上海漕泾电厂分别于2014年和2015年实施了超低排放改造工程，在改造后的长期运行过程中发现，1号机组选择性催化还原烟气脱硝法（SCR）装置出口NO_x浓度值与烟囱出口数据有着较大偏差。通过对SCR所在烟道流场的数值模拟发现，原有SCR进出口的测点在烟道入口NO_x浓度分布不均匀时不能准确测量出NO_x的浓度值，因此对原有的NO_x出口测点进行了技术改造，变原来的2点平均测量为网格多点测量。技术改造后发现测点NO_x与烟囱出口NO_x数据变化趋势吻合，为进一步的按需喷氨提供了基础。

Technical Transformation of NOx Measuring Point for Outlet Flue of SCR System

The nitrogen oxides emitted from coal-fired power plant boilers are an important air pollution source. Controlling NO_x emission has become an important work of power plants at present. The Shanghai Caojing power plant carried out the ultra-low emission transformation project in 2014 and 2015 respectively. In the long run after retrofitting, it was found that the NO_x data of the selective catalytic reduction (SCR) outlet were large different from that of chimney outlet in unit one. Through the numerical simulation of the flow field in the flue where SCR is located, it is found that the original measuring points at the inlet and outlet of SCR can not accurately measure the concentration value of NO_x when the concentration distribution of NO_x at the inlet of the flue is not uniform. And so, the technical transformation was made that the original two-point average NO_x measurement at the SCR outlet was changed into the multi-point measurement of the grid. Finally, it is found that the change trend of the new NO_x data coincides with the NO_x data change trend of the chimney outlet, which provides the basis for the further injection of ammonia.