Low NO x combustion and SCR flow field optimization in a low volatile coal fired boiler.

Low NO _x burner redesign and deep air staging have been carried out to optimize the poor ignition and reduce the NO _x emissions in a low volatile coal fired 330 MW _e boiler. Residual swirling flow in the tangentially-fired furnace caused flue gas velocity deviations at furnace exit, leading to flow field unevenness in the SCR (selective catalytic reduction) system and poor denitrification efficiency. Numerical simulations on the velocity field in the SCR system were carried out to determine the optimal flow deflector arrangement to improve flow field uniformity of SCR system. Full-scale experiment was performed to investigate the effect of low NO _x combustion and SCR flow field optimization. Compared with the results before the optimization, the NO _x emissions at furnace exit decreased from 550 to 650 mg/Nm³ to 330-430 mg/Nm³. The sample standard deviation of the NO _x emissions at the outlet section of SCR decreased from 34.8 mg/Nm³ to 7.8 mg/Nm³. The consumption of liquid ammonia reduced from 150 to 200 kg/h to 100-150 kg/h after optimization.
(Copyright © 2018. Published by Elsevier Ltd.)