【作者】 李福民；

【导师】 吕庆； 王书桓；

【作者基本信息】 东北大学 ， 钢铁冶金， 2009， 博士

【摘要】 喷吹煤粉是降低高炉冶炼成本、增强竞争力的有效技术措施,但也给高炉生产带来了一系列负面影响。作者提出了通过煤造气自风口向高炉喷吹还原气体,结合富氧进行炼铁生产的新工艺,以高炉整体炉料为对象,研究了炉料的同化过程,探讨了煤气中H₂含量对炉料的低温还原粉化、还原率、熔融滴落、成渣和焦炭变化过程的影响。研究结果表明:温度对铁矿石的低温还原粉化具有重要影响,在500℃时矿石的粉化最为严重,500～900℃区间内矿石的粉化率(RDI_-3.150随温度升高而降低;相同温度下,矿石的粉化率随煤气中H₂含量的增加而增加,随CO₂含量的增加而明显减少;相同条件下,烧结矿的低温还原粉化率明显高于球团矿和块矿,铁矿石的低温还原粉化主要是由于赤铁矿还原为磁铁矿时体积膨胀造成的。新工艺条件下矿石的还原率随着温度的升高、时间的延长而增加,两者基本上呈线性关系。相同条件下,矿石的还原率随着H₂含量增加而明显增大,H₂含量增加扩大了炉料在块状带的间接还原,对于强化高炉冶炼,降低冶炼过程能耗具有决定性作用;新工艺条件下焦炭的失碳率显著增加,导致焦炭性能恶化,对于起骨架作用的焦炭提出了更高的要求。随着H₂含量增加,炉料的滴落温度降低,滴落温度区间减小,喷吹煤气高炉能够在较低温度下进行冶炼,可以降低高炉生产过程的能耗;随着H₂含量增加,炉料滴落过程的最大负压明显降低,最大压差降低。喷吹煤气高炉内的软熔带变薄甚至可能消失,炉内的透气性改善,对高炉顺行非常有利。高炉初渣的生成与炉料的种类有关,球团和天然块矿生成由大量FeO和硅铝酸盐组成的初渣;烧结矿生成呈酸性的CaO-Al₂O₃-MgO-SiO₂初渣。球团和天然块矿的初渣在下降过程中FeO被还原,吸收CaO和MgO转变为终渣。喷吹煤气高炉由风口进入的酸性物质减少,炉料的入炉碱度大幅降低,渣量降低,没有未燃煤粉的加入,成渣过程比喷煤高炉更为合理,有利于高炉形成合理的操作炉型,强化高炉冶炼。采用合理的造渣制度可以使炉渣具有良好的冶金性能,解决渣量降低带来的问题,生产出高质量铁水。研究结果表明,高炉喷吹煤气是完全可行的。新工艺把煤粉在风口前的燃烧、气化这一复杂过程转移到炉外,使高炉冶炼功能单一化,不但可以改善冶炼条件,而且可以实现“富氢”冶炼。炉顶煤气可通过造气炉转化循环利用,降低高炉炼铁能耗,减少高炉的CO₂排放,使高炉冶炼由依赖焦炭转向普通煤,符合当前冶金行业发展方向,具有明显的优越性。更多还原

【Abstract】 Pulverized coal injection （PCI） into BFis one of effective technologies to reduce the cost and enhance competitiveness of BF process, but it brings a series of troubles to BF operation. The Bottom Oxygen Gas-Injection BF Process was put forward, which the reducing gas produced by coal in a gasifier is injected to BF from tuyeres. Whole charge assimilation of the new process was studied under the simulative conditions, the influences of H₂ content on RDI_-3.15, reduction rate, melt-dropping of iron ore, slag formation and coke transformation were determined. The conclusions are as follows:Temperature is the principal factors which influence on the low temperature reduction degradation index （RDI） of charge, the RDI_-3.15 reaches the maximum at 500℃, and it decreases as the temperature increases from 500℃to 900℃, the charge degradation finishes at 900℃. At the same condition, the RDI_-3.15 increases as the H₂ content increases, decreases with the CO₂ content increases, and the RDI_-3.15 of sinter is higher than that of pellet and crude iron ore. It is found that the mechanism of the low temperature reduction degradation is caused by volume expansion when hematite was reduced to magnetite.The reduction ratio of iron ore increases with reduction temperature and time increase, they present linear relationship. The reduction ratio of iron ore increases obviously with H₂ content of gas increasing, the indirect reduction is mainly carried out in lumpy zone of BF, and it has decisive effect to strengthen the smelting process and reducing energy consumption. The carbon loss ratio of coke increases with the H₂ ratio increases, the properties of coke is deteriorated, it has higher request to coke which act as frame in BF.When the H₂ ratio increases, the dropping temperature, maximum negative pressure and the maximum pressure drop of charge falls significantly, thus the ironmaking process could be carried out at lower temperature, the energy consumption could be reduced. The BF cohesive zone becomes thin or even disappeared, and the gas permeability of charge is improved, it is beneficial to BF smooth operation.The formation of primary slag is related to charge species. The primary slag formed by pellet and crude iron ore is composed by a large number of aluminosilicate and FeO; the primary slag formed by sinter is an acid slag system of CaO-Al₂O₃-MgO-SiO₂. In the course of primary slag descend, FeO is reduced and CaO and MgO in sinter are absorbed, then the final slag formed finally. Contrast to PCI BF process, the acidic materials entering BF tuyeres decrease sharply in the new BF technology, thus the basicity of charge loaded from furnace top decreases, the slag ratio decreases sharply; there are not unburned coal in slag, the formation of primary slag and bosh slag become well. The fluidity of BF slag was improved, it is helpful to form reasonable operating furnace profile, strengthen smelting process. Reasonable slagging system could enhance the metallurgical properties of slag, the trouble could be solved that caused by slag quantity deceases; high quality hot metal could be produced.The results reveal that the new technology is completely feasible. The complex combustion and gasification of coal in tuyeres were transferred to outside BF in the new technology, the iron-making process in BF was simplified, and rich hydrogen metallurgy was achieved. The top gas could be recycled by gasifier, the emission of CO₂ and energy consumption could be reduced, the BF process could use large number of normal coal instead of metallurgical coke. The new technology is in accordance with the needs of current metallurgical industry, it has obvious advantages.更多还原