In order to maintain the uniform distribution of ammonia nitrogen mole ratio and low escape amount of ammonia

conventional SCR denitrification system requires a uniform and stable NO_x concentration distribution at the inlet. However

after the transformation of the unit's flexibility

the load will be adjusted frequently

and the NO_x distribution at the inlet of SCR denitrification system will change with the combustion conditions. Then the conventional SCR denitrification system will be difficult to keep ammonia escaping amount below standard for a long time. This will pose a serious threat to the safe and reliable operation of the downstream equipments

such as air preheater

dust collector and low temperature economizer. Therefore

this study proposes a dynamic ammonia injection technology based on partition mixing. The specific scheme is as follows. Firstly

a wide-scale flue gas mixer is installed at the inlet flue of the SCR denitrification system to reduce the unevenness of the NO_x distribution. Secondly

the subsequent inlet flue of the SCR denitrification system is divided into 2 to 4 partitions and the gas components are basically evenly mixed through partition mixers. Thirdly

an automatic regulating valve is set for each partition to adjust ammonia injection amount. Finally

online NO_x measuring points are set at the outlet of each partition to adjust the ammonia injection amount of each zone in real time

which can minimize the ammonia escaping amount level. This technical transformation has been carried out on a 660 MW unit. After the transformation

the distribution uniformities of the inlet cross-section speed and ammonia nitrogen ratio are significantly improved

which significantly reduces the ammonia consumption and ensures the safe and reliable operation of the downstream equipments.