250吨转炉底吹对熔池搅拌的影响研究

Research on the effect of bottom blowing on bath stirring in a 250 t converter

采用物理模拟和数值模拟,研究了某钢厂250 t转炉底吹对熔池混匀时间、气液两相区速度、熔池低速区体积、炉底剪切力和气体能量利用率的影响。结果表明,熔池混匀时间随底吹气量增大而减少,随底吹孔数增加而减少。底吹孔数为12个时,底吹气量由15 L/min增至50 L/min,熔池混匀时间降低54.8%。底吹气量不变(50 L/min),底吹孔数由12个减至3个时,混匀时间增加52.9%。底吹枪数量减少,搅拌区域减小,熔池中“死区”和“低速区”体积比分别增加4.89%和28.9%。底吹枪减至3个时,单个底枪气量增大,气液两相区最大速度由0.34 m/s增至0.64 m/s,底吹孔处炉底所受剪切力增大52%,对炉底耐材寿命不利。从数值模拟结果也可发现,底吹工况的变化影响气体在熔池中的利用效率。底吹总气量增大时,熔池动能增加,但气体能量利用率降低。底吹气量较小时,底吹孔数的变化对气体能量利用率影响较小。底吹气量较大(50 L/min)时,相比于12个底吹孔,6个和3个底吹孔的气体能量利用率分别下降18.4%和23.3%。

This work focus on the effects of bottom blowing operations on the bath mixing,plume velocities,“dead zone”volumes,shear stresses on bottom refractory and gas efficiency of the bottom blowing.It was found that the mixing time increased when bottom blowing flow rate decreased or the tuyere number decreased.The mixing time decreased 54.8%when the bottom blowing flow rate increased from 15 L/min to 50 L/min by applying 12 tuyeres.If the total bottom blowing flow rate was constant(50 L/min),the mixing time increased 52.9%,when 3 tuyeres were applied compared to that of 12 tuyeres.When the tuyere number used in the bottom blowing decreased,the volume of“dead zone”and“low-velocity zone”increased 4.89%and 28.9%,respectively.Moreover,blowing flow rate increased when the tuyere number decreased to 3 when the total flow rate was not changed.The maximum value of velocity in the liquid-gas region increased from 0.34 m/s to 0.64 m/s.As a result,strong shear stress,which was not favorable for bottom refractory,was formed in the vicinity of the bottom blowing tuyeres.The intensity of the shear stress increased 52%on the bottom refractory.Furthermore,based on the numerical analysis results,it was found that the transfer index of bottom blowing gas were affected by the blowing operations.The utilization rate of gas energy of the bottom blowing decreased although the kinetic energy increased with increasing of bottom blowing flow rate.The utilization rate of gas energy was slightly changed if the total flow rate was small.It was also found that higher utilization rate of gas energy of the bottom blowing can be obtained when more tuyeres were applied in the process based on the current model.If the bottom blowing flow rate was 50 L/min,the utilization rate of gas energy decreased 18.4%and 23.3%when the tuyere number decreased from 12 to 6 and 3,respectively.