工艺参数对连续流化床内铁矿粉还原效果的影响

为了研究工艺参数对连续流化床内铁矿粉还原效果的影响规律,建立了两级连续流化床内氧化铁还原及煤气氧化耦合动力学模型.R1级流化床主要为FeO的还原,采用优质煤气作为还原剂,FeO来自R2级反应器;R2级流化床主要将Fe₂O₃还原到FeO,Fe₂O₃来自预热的R3流化床反应器,还原气来自R1还原尾气.模型主要计算结果与文献吻合.并以此为模型研究了矿粉粒度、流化床内压力等参数对流化床还原效果的影响.为了取得矿粉平均金属化率不小于85%、煤气利用率不低于38%和气矿比950~1050 m3·t-1的还原效果,流化床应满足如下工艺条件:矿粉平均粒度1.5 mm以下,流化床温度780~800℃,煤气还原势不低于93%,惰性气体体积分数小于5%,R1流化床内煤气平均压力3.5×105~4.0×105 Pa,停留时间的倒数u_g/H=1.0~1.1 s-1,R1流化床矿粉平均停留时间30 min,R2流化床矿粉平均停留时间20 min. 

Influence of technical parameters on reducing efficiency of iron ore fine in continuous fluidized bed

Preheating and reduction of iron ore fine in a multi-stage continuous fluidized bed (FB), which can improve gas utilization, heat efficiency and decrease production cost of hot metal, is a development direction for ore fine reduction with gas as a reductant. Multi-stage FBs coupled with a gasifier for producing hot metal have been successfully industrialized in Southern Korea. However, progress of FBs for iron ore reduction is slow in China. The reduction fraction and utilization ratio of gas are two important parameters for the iron reduction process. The key to feasible estimation of new technologies and design of parameters in the reduction process and reactors is understanding the influence of various parameters. As a result, the coupling kinetic model of iron oxide reduction and reducing gas oxidation in two-stage FB was established to investigate the influence of technical parameters on reducing the efficiency of iron ore fine in a continuous FB. FeO, which comes from a R2 FB, is reduced in a R1 FB using qualified gas as a reducing gas. Fe₂O₃, which comes from R3 preheating of a FB, is reduced to FeO in R2 FB using off-gas from a R1 FB. The results are in a good accordance with literature data. The influence of parameters, such as the size of the ore fine and pressure in the FB, on reducing efficiency was investigated according with this model. For the reduction results to be ≥ 85% metallization ratio, ≥ 38% gas utilization rate and 950~1050 m3·t-1 ratio of gas flow to ore mass, the technological conditions are an average ore fine size less than 1.5 mm, FB temperature of 780~800℃, gas reduction potential greater than 93%, volume fraction of inert gas less than 5% average pressure of 3.5×105~4.0×105 Pa, the reciprocal of standing time u_g/H of 1.0~1.1 s-1, average retention time in R1 FB of 30 min and average retention time in R2 FB of 20 min.