Influence of air ratio on combustion and NO_x emission characteristics of pulverized coal industrial boiler

ABSTRACT

A 46 MW pulverized coal industrial boiler with swirl burner had severe slagging and high NO_x emission during actual operation. To solve these problems, a full-scale industrial test was carried out. The flue gas temperature and the composition of exhaust gas were obtained under different ratios of secondary and separated secondary air. The results shown that reducing the ratio of secondary and separated secondary air could delay the ignition of pulverized coal and weaken the flame deflection, which was conducive to slowing down the burner slagging problem. However, it will aggravate the erosion of high temperature flue gas on the back wall, and further aggravated the furnace slagging problem. Changing the air ratio couldn’t substantially improve the problem of high exhaust temperature. Properly reducing the ratio of secondary and separated secondary air could effectively control NO_x emission. When the ratio of secondary and separated secondary air was reduced from 73:27 to 52:48, the NO_x emission was reduced by 44.8%. Reducing the ratio of secondary and separated secondary air leaded to the increase of carbon content in fly ash and slag, but the heat loss of exhaust gas was reduced and the thermal efficiency of boiler was increased.

KEYWORDS:

• Industrial pulverized coal boiler
• swirl burner
• industrial test
• slagging
• NO_x

Note

The authors declare no competing financial interest.

Acknowledgments

This work was supported by the National Key Research and Development Program of China (Grant No. 2017YFC0212502).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Key Research and Development Program of China [2017YFC0212502].