Industrial Experiments on Anthracite Combustion and NO_x Emissions with Respect to Swirling Secondary Air for a 300 MW_e Deep-Air-Staged Down-Fired Utility Boiler

A new deep-air-staging and low-NO_x technology has been introduced to a 300 MW_e anthracite- and down-fired boiler with swirl burners. Industrial experiments were performed at different outer secondary air vane angles (defined as β) (i.e., 20°, 30°, 40°, and 50°) to evaluate the environmental and economic performance for the retrofitted boiler. Furthermore, combining with the previous investigations on the inner secondary air vane angle (defined as α), the influence degrees of β and α on anthracite combustion and NO_x emissions for the retrofitted boiler were further analyzed and compared. The experimental results revealed that the main factors affecting the ignition and the flame fullness for β and α are different. Compared with α, β had a relatively greater influence on NO_x emissions for the retrofitted boiler. Compared with the orignianl boiler, a strong reducing atmosphere was formed in the primary combustion zone for the retrofitted boiler, and for the β of approximately 30°, the arithmetic mean of NO_x emissions in the whole measurement range was reduced by 1073 mg/m³ at 6% O₂. Taking consideration of the environmental and economic effects, the optimal β for the retrofitted boiler was 20°.