Ignition Improvement and NO_x Reduction with Local Oxygen-Enriched Coal-fired Burner

摘要

In this paper, an experimental study on the High Temperature Air Combustion (HTAC) with local oxygen (O_2) enrichment for pulverized coal was conducted, with an 8MW model burner. A small amount of diluted O_2 stream with O_2 concentration of 25%-50% (in volume) was injected into a pre-heating chamber located at the exit of the burner. Experimental results showed that with a small amount of low O_2 concentration the flame stabilization of the burner could be significantly improved. Furthermore, the combination of local O_2 enrichment with HTAC could be also effective to reduce NO_x formation. For bituminous coal, ～50% reduction was achieved while for the low volatile coals, ～20% NO_x was reduced against the air combustion. The simulation results illustrated that high temperature zone outside the burner was enlarged and flame temperature increased with O_2 enrichment. Also, there was optimal VO_2 for NO_x reduction in OE-HATC burner. For present configuration, the optimal VO_2 ≈ 50%, at which reduction rate is largest while the production rates for fuel NO_x and thermal NO_x formations are rather weak. This study showed that with a proper burner design, and organization of oxygen enrichment, a new low-NO_x combustion technology for pulverized coal could be established.