Numerical Simulation On Combustion Characteristics Of A Using Bituminite0.5MW CFR Swirl Burner With OFA

The outbreak of wide-range fog and haze phenomenon alarms us that tacklingenvironmental issues is pretty urgent. The pollutants emitted from pulverized coalboilers, such as NOx，SO2and PM, are precursor to fog and haze. At present, SO2control technology is ripe in China. However, investigation into controlling NOxisdemanding. In this study, a central fuel rich (CFR) swirl pulverized coal hot stateexperimental facility equipped with two layers of over fire air (OFA) wasnumerically studied. The results gained from the numerical study were comparedwith those of experimental study. The comparison were carried out from threeaspects, namely from four cross-sections in the primary combustion zone, threecross-sections in the OFA zone and in the central line of the furnace. It concludedthat the numerical results fit well with that of experimental study, demonstrating thatthe method for mesh generation and the selection of computational models arereasonable. Based on these conditions, numerical simulation of the swirl burner wasconducted under different lengths of primary, secondary flared ends. Theircombustion characteristics and NOxformation were simulated and analyzed. Theresearch results are listed as follows:Under different length of the primary air flared end, the pre-mixed segmentgets shorter with increasing length of the primary air flared end. It leads to the latermixing between the primary air and secondary air, making the primary air maintainlarger stiffness, the ignition point of pulverized coal move downstream as well asthe flame center, the flue gas temperature become lower, but the high temperaturezone of the flame concentrate toward the furnace center, and the NOxemission of thefurnace exit become larger.Under different length of the inner secondary air flared end, the mixingbetween the primary air and outer secondary air turns later with increasing length ofthe inner secondary air flared end. This causes the flue gas temperature to becomelower, the flame center to move downstream, and the high temperature zone of theflame concentrate toward the furnace center. On the other hand, the burnerair-staging degree is enhanced with the later mixing of the inner and outer secondaryair, making the NOxemission of the furnace exit become less.Under different length of the outer secondary air flared end, the ignition ofpulverized coal becomes earlier with increasing length of the outer secondary airflared end. This causes the flame center to move upstream, the high temperaturezone of flame to expand to the periphery, and the flue gas temperature to turn higher. The NOxemission of the furnace exit becomes less as the length of the outersecondary air flared end increases from0mm to49mm.