The invention provides a
system for reducing boiler
NOx emission by
tertiary air concentrated-diluted separation. An outlet of a
tertiary air
powder exhaust fan is connected with a
coal powder concentrated-diluted separator; a separation blade for adjusting a separation quantity of concentrated-diluted
coal powder is arranged on an inlet section of the
coal powder concentrated-diluted separator, and a concentrated coal powder
pipe and a diluted coal powder
pipe are arranged on an outlet section; the concentrated coal powder
pipe is connected with at least one layer of
hearth main
combustion area middle lower nozzles; and the diluted coal powder pipe is connected with at least one layer of
hearth main
combustion area upper nozzles. The invention further provides a method for reducing boiler
NOx emission by
tertiary air concentrated-diluted separation; tertiary air containing thin coal powder is separated as concentrated and diluted two parts of coal powder air currents; and the concentrated and diluted two parts of coal powder air currents are respectively sprayed into the middle lower part and the upper part of a
hearth main
combustion area. The concentrated coal powder current replaces one part of secondary air to form an
oxygen debt environment in the main combustion area so as to enhance the reducibility of the main combustion area; the diluted coal powder current is quickly burnt to consume
oxygen so as to enhance the reducibility of
NOx in a boiler; and the secondary air quantity reduced in the main combustion area is replenished to high-level burnt air so as to guarantee the burn-
off rate of the coal powder in the boiler.