赤铁矿制备镁球团矿的研究与应用

 在高炉冶炼过程中,MgO有利于防止球团矿与球团矿之间、球团矿与烧结矿、块矿之间的熔融黏结、降低料层阻力损失、降低软融带的高度及提高煤气利用率。以蛇纹石作为含镁添加剂,研究其对赤铁矿球团成球性能、预热和焙烧性能的影响。冷态性能研究结果表明：随着蛇纹石质量分数增加,生球水分逐渐增加,生球的抗压强度提高,而落下强度和爆裂温度降低。预热性能研究结果表明：最佳预热温度为1 000 ℃,最佳预热时间为8 min,蛇纹石质量分数为1.40%时预热球抗压强度值最好。焙烧性能研究结果表明：最佳焙烧时间为12 min,焙烧温度以1 280 ℃为宜。工业试验表明：成品球团矿铁品位及还原度降低但是综合品位[w(TFe)＋w(MgO)]提高,还原膨胀率减小,软化开始温度升高,软化结束温度降低,球团矿的高温冶金性能得到改善。成本分析表明：镁球团矿原料成本降低。高炉应用效果表明：铁水质量得到改善,铁水合格率达到99.97%,一级品率达到75.06%,炉渣中[w(MgO)]增至8.10%,[w(Al2O3)]降低至14.72%,[w(MgO)/w(Al2O3)]上升至0.55。     

使用石灰石生产低硅碱性球团矿试验

旨在研究通过使用石灰石生产低硅碱性球团矿,掌握石灰石作为碱性熔剂对造球、焙烧及焙烧球冶金性能的影响,探索适宜的工艺措施。结果表明,经过细磨处理的石灰石对生球性能有改善作用,生球落下和抗压强度有一定程度的提高;随着石灰石配比的升高,焙烧球抗压强度逐渐降低,提高焙烧温度能改善配加石灰石的球团矿抗压强度。在研究的矿粉条件下,球团矿碱度在1.00以下时,还原膨胀率较高,不能满足入炉要求;碱度达到1.00以上时,球团矿还原膨胀率降到20%以下。     

不同含镁添加剂对球团矿工艺参数及质量的影响

 MgO对高铁低硅烧结中烧结矿的质量有不利影响,但其可以改善球团矿的冶金性能。因此,不在烧结矿而在球团矿中添加MgO,可在改善烧结矿质量的同时提高球团矿的冶金性能。不同的含镁熔剂对球团工艺参数和性能影响不同。通过试验研究了在高铁低硅条件下,白云石、蛇纹石、硼泥和镁质添加剂等4种含镁添加剂对球团造球,焙烧工艺及对球团矿物化性能和冶金性能的影响。试验结果显示,镁质添加剂对提高球团矿MgO含量、控制低硅球团矿还原膨胀率、改善球团矿还原度和熔滴性效果最好。     

球团配加镁质熔剂及新型皂土试验

为生产含MgO的镁质球团用来替代烧结矿中MgO,确保高炉造渣所需的适宜的MgO质量分数,考察了在球团生产中添加一种新型球团黏结剂(新型皂土)和一种氧化镁质熔剂(镁石粉)时,对造球焙烧及球团矿冶金性能的影响。试验结果表明,镁质球团生球落下强度有所提高,350℃时未发生爆裂。配加新型皂土可提高球团品位,降低Si O2质量分数。镁质球团的低温还原粉化指标和体积膨胀率指标均有所改善。而且,软化温度升高,软化温度区间变窄,有利于软熔带由高炉上部往下部移动,改善高炉透气性。在保证综合入炉铁料MgO质量分数不变的条件下,当烧结矿自然带入的MgO质量分数为1.2%时,球团矿中的MgO质量分数大于1.90%,可满足高炉要求。     

改善鞍钢球团矿冶金性能的研究

对带式机酸性球团矿添加含MgO添加剂的造球、焙烧和冶金性能研究表明，在带式机目前焙烧工艺制度条件下，MgO／SiO2比值在0．45～0．6时，球团矿抗压强度高于2500N／个，还原膨胀率大幅度降低；随着MgO／SiO2比值的升高，低温还原粉化率RDI＋3.15、RDI＋6.3提高；900℃还原度提高。当MgO／SiO2比值为0．45时，球团矿的综合冶金性能较好。     

球团矿还原膨胀率影响因素分析

球团矿在还原时易发生异常膨胀，这是制约其在高炉中大量使用的重要因素，为此主要研究了不同SiO₂含量、碱金属含量和焙烧温度对还原膨胀率的影响，以寻找球团矿还原膨胀率较低时的最佳成分含量以及热工制度。结果表明，球团矿还原膨胀率随SiO₂含量的升高而降低，SiO₂质量分数为5.0%时，还原膨胀率只有11.39%;SiO₂质量分数降到1.8%时，还原膨胀率则提高到了60.67%。碱金属对还原膨胀率而言为不利因素，碱金属质量分数达到1.680%时，球团矿还原膨胀率显著升高到61.08%;碱金属质量分数仅为0.045%时，球团矿还原膨胀率为13.62%。还原膨胀率随着焙烧温度的升高呈先减小后增大的趋势，当焙烧温度为1 260℃时，还原膨胀率达到最低，为11.35%。研究结果对降低球团矿还原膨胀率、保持高炉内炉料稳定和透气性具有一定意义。     

MgO添加方式对镁质球团矿的影响

 为了获得优质镁质球团矿,在添加0.7%新型复合黏结剂的条件下进行了MgO添加方式(菱镁石粉、轻烧镁粉)对造球过程、氧化焙烧及冶金性能影响的试验研究。结果表明,复合黏结剂改善了生球指标、提高了球团矿铁品位,球团矿中w(TFe+MgO)质量分数提高0.65%;当w(MgO)/w(SiO₂)为0.14～0.24时,球团矿添加菱镁石粉改善了生球落下强度、提高了球团矿还原性,MgO添加方式对抗压强度的影响很小,球团矿添加菱镁石粉、轻烧镁粉都降低了还原膨胀率,改善了低温还原粉化指标、熔滴性能。     

SG带式焙烧机镁质球团矿的生产应用

为满足高炉对镁质熔剂球团矿的质量要求,SG带式焙烧机进行轻烧镁粉、轻烧白云石及二者混合(按一定配比)添加的3种镁质熔剂添加方案工业试验。试验结果表明,添加轻烧白云石可以提高生球强度。采用轻烧镁粉和轻烧白云石按1∶3的添加方案,当该方案球团矿MgO质量分数为1.58%时,平均抗压强度为2 245 N/个,还原度为75.36%,还原膨胀率为14.37%及低温还原粉化率(RDI_+3.15)为96.79%,其综合冶金性能优于其他方案球团矿,并符合高炉对镁质熔剂球团矿的抗压强度和冶金性能要求。     

焙烧温度与球团矿强度和还原性的关系

针对首钢京唐504 m2带式焙烧机生产的球团矿抗压强度高,而还原性差的问题,通过研究不同焙烧温度下球团矿的抗压强度、还原度、还原膨胀率及其显微结构的变化,得出以下结论:随着焙烧温度从1 200℃提高到1 280℃,磁铁矿球团的抗压强度提高,而还原度明显降低,焙烧温度为1 230℃时,球团还原膨胀率最低。综合考虑,应在满足抗压强度的前提下,尽量降低焙烧温度,以改善球团矿的冶金性能。根据试验结果对带式机焙烧温度进行调整后,球团矿抗压强度控制在3 000 N/P左右,还原度提高到67.78%,还原膨胀率也控制在18%以下,取得了显著效果。     

球团矿化学成分控制现状及展望

 综述了近年来国内外高炉球团矿使用比例的现状,分析了球团矿化学成分控制以及不同化学成分对球团矿冶金性能的影响。分析表明,多数国内钢铁企业球团矿TFe的质量分数较低,SiO₂质量分数较高且差异较大。不同企业球团矿Al₂O₃和FeO的质量分数不同。应控制球团矿中SiO₂、Al₂O₃和FeO的质量分数。随着CaO和MgO质量分数的提高,球团矿抗压强度均降低。适宜质量分数的CaO有利于改善球团矿的还原膨胀性能。随着MgO质量分数的提高,球团矿的还原膨胀性和软熔滴落性能均变好。高炉炉料结构采用低MgO烧结矿、酸性球团矿和镁质球团相结合,可以充分发挥球团矿的冶炼优势,实现球团矿入炉比例的提高。MgO和CaO在球团矿焙烧过程中的作用机理,以及如何控制镁质球团中的液相含量以提高球团矿的抗压强度等需要进一步深入研究。     

MgO含量和来源对球团焙烧特性及冶金性能的影响

分别以5种不同的含镁添加剂（高镁磁铁矿、镁橄榄石、白云石、菱镁石和氧化镁粉）制备镁质球团,阐述MgO含量和来源对磁铁矿球团焙烧特性及冶金性能的影响。研究结果表明:不同的含镁添加剂对于生球的落下强度有着一定影响,其中氧化镁粉与高镁磁铁矿均能够提高球团的落下强度。相同的预热焙烧制度下,提高MgO含量会增加球团孔隙率,降低预热和焙烧球团的抗压强度,其中白云石对焙烧球团强度的不利影响最小。增加预热球团的氧化度有利于促进镁质焙烧球团固结,提高其抗压强度。在MgO来源相同的情况下,MgO含量的增加会导致球团孔隙的增减,降低了球团强度,而配加不同种类的含镁添加剂,均能不同程度改善球团的还原膨胀性、低温还原粉化性和还原性,其中配加高镁磁铁矿的球团的还原膨胀性和低温还原粉化性均优于于其他含镁球团。      

Effects of MgO Containing Additive on Low-Temperature Metallurgical Properties of Oxidized Pellet

 As a main charging form of BF (blast furnace), pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The characters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical properties are investigated such as low-temperature reduction degradation index (RDI), compressive strength (CS) and the reduction swelling index (RSI). The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can improve low-temperature metallurgical properties (RDI, RSI) of the pellets. With the increase of light burned magnesite in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2. 0% in pellets, the CS decreases slightly, but it still surpasses 2689 N, which can still meet the demand of BF.     

Effect of the firing temperature and the added MgO on the reduction swelling index of the pellet with low SiO2 content

The use of pellet with low SiO₂ content in blast furnace (BF) will reduce the slag amount as well as fuel rate and increase the productivity. In this paper, the effect of the firing temperature and the added MgO on the reduction swelling index (RSI) and the compressive strength of the reduced pellet with low SiO₂ content was investigated, and the microstructure of the fired and reduced pellets was analysed by means of the electron microscopy. It was found that the decrease of SiO₂ content will raise the RSI and reduce the compressive strength of reduced pellet. When the SiO₂ content of pellet is 4.8%, the RSI is 16.5% and compressive strength of reduced pellet is 423 N/P. When the SiO₂ content is 2.8 and 1.8% fired at 1280°C, the RSI of the reduced pellet will increase to 34.5 and 55.8% and the compressive strength is reduced to less than 200 and 80 N/P. However, if some MgO was added, the RSI and the compressive strength of the reduced pellet could be improved significantly. When pellet’s MgO content was over 1.7% and SiO₂ content was 2.8% or MgO content was 2.5% and SiO₂ content was 1.8% fired at 1280°C, the RSI of the two pellets could drop to less than 20% and the compressive strength could increase to more than 300 N/P. Then, the technical index of pellet will meet the requirement of the charging in large BF. The added MgO pellet with low SiO₂ content have been used in 5500?m³ BF in Shougang Jingtang Corporation and delivered sustainable improvement of cost reduction.     

MgO质量分数对氧化球团性能的影响

 为了改善澳洲某磁铁矿氧化球团的冶金性能,研究了MgO质量分数对其质量的影响。研究结果表明,随着MgO质量分数的提高,生球落下强度和爆裂温度提高,MgO质量分数对生球抗压强度影响较小。随着MgO质量分数提高,预热球团和焙烧球团抗压强度降低,还原度有所改善;提高MgO质量分数可以有效抑制球团的低温还原粉化和球团的还原膨胀,软化开始温度、软化结束温度和滴落温度均有所提高,软熔性能得以改善。这主要是由于提高MgO质量分数,渣相中铁酸镁和钙镁橄榄石质量分数升高,在还原过程中Mg2+与Fe2+发生晶格取代,生成FeO与MgO的固溶体,具有稳定晶格的作用,从而抑制还原膨胀和低温还原粉化。     

中关铁矿制备熔剂性球团生球性能试验

 通过增加熔剂性球团矿的入炉比例,能够改善炉料结构,降低炼铁系统能耗,并且通过“源头减量”的途径可以降低炼铁过程中污染物的排放。实现高球比冶炼的核心环节是制备熔剂性球团,而熔剂性球团质量取决于生球的性能,因此,保证生球质量是探究熔剂性球团制备工艺较为重要的环节。由于中关铁矿硅含量较低、镁含量适宜,适合作为低硅熔剂性球团的原料。以中关铁矿为原料探究熔剂性球团的制备工艺,并在此基础上分析了影响熔剂性球团生球质量的因素(粒度、时间、水分、膨润土、SiO₂含量、碱度和MgO含量)。试验结果表明,生球的抗压强度、落下强度及爆裂温度受碱度、SiO₂和MgO含量变化的影响不大;生球的抗压强度、落下强度及爆裂温度主要受造球时间、水分、黏结剂用量、铁矿粉及熔剂的理化性能影响,并在造球时间维持为12 min、水分维持为8%～9%、膨润土用量为2%时,生球抗压强度、落下强度及爆裂温度较优且满足运输与入炉要求。     

Utilization of High Sulfur Raw Materials in Iron Ore Pellets

Pyrite cinder and high sulfur magnetite were used as raw materials to produce iron ore pellets. Good qualities of green balls and fired pellets were obtained from the feed comprising 50% pyrite cinder and 50% high sulfur magnetite concentrate at a small scale. Small-scale tests were proven by pilot-scale tests. The high grade fired pellets, assaying 63.22% Fe, were analyzed, and the compressive strength of fired pellets was over 2500 N/pellet. The fired pellets possessed excellent metallurgical performances, such as reducibility index higher than 67%, reduction swelling index lower than 15% and low temperature reduction degradation index (+ 3.15 mm) higher than 1%, which can be used as the burden for blast furnace.     

w(MgO)对熔剂性球团矿冶金性能的影响

 为了研究添加高镁粉时w(MgO)对熔剂性球团矿冶金性能的影响。考察了w(MgO)为1.6%～2.4%时，其对球团矿抗压强度、RI(还原性指数)、RDI(低温还原粉化指数)和RSI(还原膨胀指数)的影响。采用光学显微镜和X射线衍射仪对球团矿微观结构和矿物组成进行了分析。结果表明，随着MgO质量分数的增加，抗压强度呈先升高后降低的趋势，w(MgO)为2.0%时，抗压强度最大，为3 533 N;随着w(MgO)由1.6%增加到2.4%，球团矿RI、RDI和RSI得到改善;w(MgO)为1.8%～2.0%时，球团矿微观形貌和矿物组成较好，赤铁矿成片结晶，球团矿强度良好。在用高镁粉和研山精粉造球时，w(MgO)控制为1.8%～2.0%，以期得到较低的还原膨胀指数和较好的冶金性能。     

添加熔剂对球团矿还原膨胀率的影响

在鞍钢现场的原料条件下,向铁精矿中添加含CaO、MgO等熔剂并研究其对原膨胀率的影响。结果表明:CaO恶化球团的还原膨胀性能,MgO能够很好地降低球团的膨胀率,并随着熔剂配比的增加而降低。当熔剂配比为1%时,镁石球团还原膨胀率指标最低,为11.83%,且比基准球团低1.2%;石灰石球团还原膨胀率指标最高,为14.93%且比基准球团高出1.93%。     

Effect of reducing MgO content on metallurgical properties of high Al2O3 sinter

As a pillar industry of a country, the iron and steel industry plays an important role in the national economy. Due to the change of raw material composition, the Al2O3 content in blast furnace slag is increasing, which increases slag viscosity and brings difficulties to blast furnace smelting. Previous studies found that adding MgO flux to sinter can effectively solve this problem. At the same time, MgO also has many impacts on the metallurgical properties of the sinter. The results show that with the mass fraction of MgO decreasing from 2.8 mass% to 2.0 mass%, the cold drum strength (TI) and reduction index (RI) of sinter increase by 3.4% (from 72.1% to 75.5%) and 3.1% (from 70.3% to 73.4%)， respectively. Besides, the temperature of soft melt zone changes from 251℃ to 233℃, leading to the enlargement of the air permeability of the blast furnace, which is helpful to strengthen the smelting of the blast furnace and improve the economic benefits of the enterprise.