氧煤燃烧熔分炉炉料沉降与传热行为数值模拟

 回转窑预还原-氧煤燃烧熔分炼铁工艺直接使用宽粒级的粉矿入炉,炉料颗粒经回转窑内煤气逆流换热和预还原后,通过沉降管到达氧煤燃烧熔分炉。为避免沉降区域内炉料颗粒冲刷炉壁、壁面堆积及气固传热不均现象,实现颗粒沉降与传热过程的耦合控制,最大限度降低炉料与熔池温度差,保证熔池熔炼稳定,达到良好的冶炼效果,利用计算流体力学-离散单元法(CFD-DEM)研究氧煤燃烧熔分炉熔池上部区域煤气流速和炉料粒径对炉料颗粒在逆流煤气作用下的沉降轨迹与传热行为的影响。数值模拟结果表明,随着煤气流速增大,炉料颗粒的沉降速度减小,煤气对小粒径炉料颗粒的作用尤为明显。煤气流速为1 m/s时,每种粒径的炉料颗粒沉降效果良好;煤气流速为2 m/s时,粒径为1.0、1.5、2.0 mm的炉料颗粒沉降效果相对较好;煤气流速为3 m/s时,粒径为1.5、2.0 mm的炉料颗粒能够顺利沉降。针对炉料颗粒传热行为,煤气流速越大,炉料粒径越小,则炉料颗粒的传热效果越好。综合炉料传热与沉降行为,粒径为1.0 mm左右的炉料颗粒在煤气流速为1和2 m/s作用下,炉料颗粒的沉降速度和传热情况均良好。

Numerical simulation of charge settlement and heat transfer behavior in oxygen coal combustion melting and separating furnace

The rotary kiln-pre-reduced oxygen coal combustion fusion iron making process uses the fine ore of wide particle size into furnace directly. After the counter current heat transfer and pre reduction of flue gas in the rotary kiln, the charge particles reach the oxygen coal combustion melting and separating furnace through the settling tube. In order to avoid the phenomena of charge particles scouring the furnace wall, wall accumulation and uneven gas-solid heat transfer in the settlement area, realize the coupling control of particle settlement and heat transfer process, minimize the temperature difference between charge and molten pool, ensure the stability of molten pool smelting and achieve good smelting effect. Computational fluid dynamics discrete element method (CFD-DEM) was used to study the effects of gas velocity and charge size on the settling trajectory and heat transfer behavior of charge particles under the action of counter current gas in the upper zone of oxygen coal combustion melting and separating furnace. The numerical simulation results show that the settling velocity of charge particles decreases with the increase of gas flow rate, and the effect of gas on small particle size is particularly obvious. The sedimentation effects of charge particles for each particle size are good when the gas velocity is 1 m/s; the sedimentation effects of charge particles with sizes of 1.0, 1.5 and 2.0 mm are relatively good when the gas velocity is 2 m/s; the charge particles with sizes of 1.5 and 2.0 mm can settle smoothly when the gas velocity is 3 m/s. For the heat transfer behavior of charge particles, the larger the gas velocity is, the smaller size of charge particles is, and the better heat transfer effect of the charge particles is. Considering the heat transfer and settlement behavior of charge, the settlement velocity and heat transfer of charge particles with particle size of about 1.0 mm are good under the action of gas velocity of 1 and 2 m/s.