The staged oxygen entrained flow coal-slurry gasifier has such advantages as higher carbon conversion rate· Stronger turbulent mixing inside gasifier and lower temperature near coal slurry nozzle. In this paper, the effects of secondary oxygen mass flow rate (SOMFR) on gasification performance were numerically investigated through CFD simulation. The CFD model was based on the Euler-Lagrangian method. Realizable k-ε model was used to acquire the turbulent information in the gasifier. Presumed PDF method was adopted to consider interactions between turbulence and homogeneous reactions. The characteristics of the gasification flames were analyzed as well as the flow field under different SOMFR in the staged gasifier. As SOMFR decreased, the secondary gasification flame curved up with backflow near the wall. At the same time, dome wall temperature increased as well. When SOMFR was less than 8% of the total oxygen mass flow rate, the momentum flux of the secondary oxidizer is too low to change the macro flow field. When SOMFR was larger than 8% of the total oxygen mass flow rate, the recirculation region shrank due to the entrainment of secondary flow. However, particle residence time increased, since the velocity in back-flow region increased. Particle gasification process would be benefited from this change. As SOMFR increased, the down-flow flame length decreased as well as the average temperature in the top furnace region. The result showed that the average temperature decreased by 20°C when SOMFRincreased from 2% to 16% of the total oxygen mass flow rate. At the height where secondary oxygen was introduced, the average temperature increased by 300°C as well. In all cases, the temperature flow field at the down-section of the gasifier did not change, since the oxygen-coal mass ratio was kept constant.%分级给氧气流床气化炉具有炉内混合过程强烈、喷嘴附近温度较低等优点.采用CFD数值方法研究了二次氧量变化对气化炉运行特性的影响,分析比较了不同二次给氧量下相交射流火焰特性的变化.当二次给氧量较低时,二次火焰在回流区的作用下明显向上偏斜,其射流动量不足以影响主射流产生的宏观流场.二次氧量大于总氧量的8％时,回流区在二次射流的卷吸作用下收缩,但颗粒停留时间有所增加.二次氧量为16％时,与二次氧量为2％的工况相比,气化炉上游的平均温度降低约20℃,二次射流高度处的平均温度提高约300℃.由于总的氧-煤质量比不变,二次氧量的变化对气化炉下游的影响并不显著.
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