Optimizing the Combustion of Low-Quality Coal by the Wall Wind Auxiliary Combustion Method in a Tangentially Fired Utility Boiler

ABSTRACT

Adopting the low NO_x combustion technologies in tangentially fired utility boilers, burners cannot maintain flame stability, coal adaptability, or high combustion efficiency. Generally, high-temperature corrosion and slagging occurs, especially when burning low-volatile coal or anthracite. Thus, a wall wind auxiliary combustion system is developed. Here, a part of the corner secondary air is transformed into wall wind, which is then directed vertically into the furnace through the water-cooled walls, thereby optimizing the combustion organization of the corner injections downstream. Pre-modification and post-modification results are compared by simulation in a 600 MW_e boiler. The results show that wall wind prevents the injection downstream from skewing into the wall. As such, the high-temperature area near the water-cooled walls disappears and the flame center moves downwards. The combustion efficiency is also improved. The wall wind maintains oxidization near the water-cooled walls, thereby reducing the risk of high-temperature corrosion and slagging. Finally, the average NO concentration at furnace outlet is reduced by 10%. In the industrial application of this technology, the outlet steam temperature of the low temperature superheater decreases up to 20 K, and the NO_x emission at boiler outlet decreases up to 20%, which is consistent with the simulation results.

KEYWORDS:

• High-Temperature Corrosion
• Low NO_x Emission
• Low-Quality Coal
• Slagging
• Wall Wind Auxiliary Combustion System

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [No. 51761125012 and 51390493], and the National Key Research and Development Program of China [No. 2017YFB0603903].