Visualization research on high efficiency and low NOx combustion technology with multiple air-staged and large angle counter flow of fuel-rich jet

Abstract

In this paper, a new technique for tangentially fired pulverized coal boiler, high efficiency and low NOx combustion technology with multiple air‐staged and large angle counter flow of fuel‐rich jet (ACCT for short), is proposed. Based on traditional air staged and rich‐lean combustion technique, a NOx reduction area is introduced through air injection between primary combustion zone and secondary combustion zone. To verify the characters of this technique, experiment with a new developed visualization method, image processing on smog tracing with fractal dimension, is carried out on a cold model of 300 MW furnace designed with this technique. The result shows, compared to injection without counter flow, the center lines of counter flow injection go deeper into the chamber and form a smaller tangential circle, which means the rotating momentum of entire vortex is feebler and the exit gyration is weaker. It also shows that with counter flow, the fractal dimensions of boundary between primary jet and front fire side air is bigger, which means more intense turbulence and better mix. As a conclusion, with fractal dimension, image processing on smog tracing method can be a quantificational, convenient and effective visualization way without disturbing the flow field, and it’s also acknowledged that ACCT has the following superiorities: high burn out rate, low NOx emission, stable burning, slagging preventing, and temp‐bias reducing.