Experimental study on smelting reduction of carbon-bearing manganese briquettes in slag bath

The reduction of carbon-bearing manganese briquettes in a slag bath was experimentally investigated at temperatures ranging from 1550 to 1650 ℃. Both the internal temperature and the microstructure evolution of the briquettes were analyzed by differential thermal analysis, scanning electron microscopy and energy-dispersive spectrum analysis, and the smelting reduction mechanism of the carbon-bearing manganese briquettes in the slag bath was further elaborated. The results indicated that the smelting reduction of the briquettes in the slag bath could be divided into three stages, and the aggregation and growth of the metallic particles during the reduction were significantly affected by the slag temperature. Under the experimental conditions, the reduction speed at the initial stage of the carbon-bearing manganese briquettes smelting reduction was controlled by the chemical reaction, whereas the reaction speeds at both the middle and following stages were limited by gaseous diffusion.

Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The effect of metallurgical fluxes CaO and CaCO3 on the reduction rate of iron ore pellets containing carbon in nitrogen atmosphere has been studied by a weight-loss thermal balance. The experimental results showed that adding CaO or CaCO3 can promote reduction reaction as the added CaO or CaCO3 probably decrease the apparent activation energy of iron ore concentrate-carbon-CaO or CaCO3 reaction, and the reduction rate constant changes with mass percent of CaO and CaCO3. The kinetic analysis also showed that the rate-controlling step of the reaction is inner gas diffusion.

Kinetics Analyzing of Direction Reduction on Manganese Ore Pellets Containing Carbon

Using high temperature carbon tube furnace, reduction of manganese ore pellets containing carbon was investigated. The reaction was divided into two stages at five minutes after reaction, and the kinetics model of reduction process was established. The experimental results showed that, the reaction rate in the earlier stage was controlled by the chemical reactions between FeO, MnO and carbon reductant, and the activation energy was 28.85 KJ/mol. In the later stage, as the carbon reductant replaced by CO, the reaction rate was controlled by CO-diffusing in solid products, and the cor- responding activation energy was 86.56 KJ/mol. Reaction rate of the later stage was less than the earlier one.

REDUCTION BEHAVIOR OF IRON ORE PELLETS CONTAININGCARBON UNDER NON-ISOTHERMAL CONDITION

The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. The test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 573 to 1373 K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is large in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one in increasing the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about the same for various CO partial pressures or temperature-rising programs. The kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled by surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.

Influence of furnace temperature and non-uniform heat flux density on direct reduction process of newly designed carbon containing pellet

In this study,innovative ellipsoid pellet with craters on its surface was designed,and the direct reduction process was compared with ellipsoid(without craters)and sphere pellets.In addition,furnace temperature and uneven heat flux density effects on the pellet direct reduction process were also studied.The results show that ellipsoid pellet is better than that of spherical pellet on metallization ratio.However,under the condition of non-uniform heat flow,the ellipsoid pellet final metallization rate and zinc removal rate were lower.Although the heat transfer effect of ellipsoid pellet with craters was not improved significantly,the metallization rate and zinc removal rate were found improved,which will have a cumulative effect on the pellets direct reduction process in rotary hearth furnace.Under varying furnace temperature conditions,the pellet temperature was higher than that of the constant furnace temperature.After 1200 s,pellet Fe concentration increased to 123.6%,metallization rate and zinc removal rate increased to 113.7%and 102.2%,respectively.These results can provide references for the carbon-containing pellet design used in rotary hearth furnace.

含碳球团的还原性和还原冷却后的强度

在 １２７３～１５７３ Ｋ条件下研究了不同煤种、木炭和石墨与不同种类矿石制成含碳球团 的还原速度；进而讨论了温度、配碳比（Ｃ／Ｏ）、挥发分含量等因素对含碳球团还原所需时间和 金属化率的影响．通过测定含碳球团还原冷却后的强度，对影响强度因素进行了分析．还原冷 却后的强度在温度 １２７３ Ｋ时较低，配入含挥发分较高的气煤，可以使还原冷却后的强度提高， 加快反应速度．

碳还原锌浸出渣炼铁过程的热力学分析

对锌浸出渣熔池熔炼碳还原炼铁反应过程进行了热力学分析。结果表明：Zn Fe2O4和KFe3（SO4）2（OH）6受热分解的含铁产物是Fe2O3,Zn Fe2O4在300~1800 K温度范围内不能自发分解,KFe3（SO4）2（OH）6在652.25K即可分解;高pCO/pCO2、低温（但要高于炉渣熔融的温度）有利于熔体中的Fe2O3还原生成液态铁;含硫物相低温分解后的产物有金属硫酸盐K2SO4和Ca SO4,两者热分解脱硫的有利条件均是高温及低硫分压、低氧分压（但氧分压要高于硫酸盐分解生成硫化物的限值）,Ca SO4热分解脱硫比K2SO4易于进行。锌浸出渣中碱性氧化物Ca O的存在,一方面可以降低Zn2Si O4碳热还原的起始反应温度,另一方面可以提高炉渣碱度及炉渣中Ca O的活度,降低硫在铁液与炉渣中的分配平衡常数。

含碳球团铁浴熔融还原法

提出了一种新型含碳球团熔融还原法．系统研究结果表明，铁浴二次燃烧率为５０％时，预还原度可达８０％．在此条件下，工艺过程可获得低的吨铁煤耗（５３８ｋｇ）和氧耗（３９２ｍ３）以及高的煤气利用率（９５．７２％）和能量利用率（８９．１０％

提钒尾渣内配碳球团直接还原试验

在实验室条件下,对提钒尾渣压力成型工艺进行研究,考察煤粉配比、粘结剂配比、生石灰配比及成型压力等因素对提钒尾渣内配碳球团强度的影响,确定了最佳方案。结果表明,球团的强度可满足后续处理工艺的要求。并研究了配碳量、碱度、还原温度及还原时间与该种球团直接还原金属化率的关系。

含碳球团还原过程中反应分数、还原度和金属化率的关系

推导了含碳球团的反应分数、还原度和金属化率间的关系。根据这些关系处理失重试验的数据可确定含碳球团中金属Fe、FeO、Fe2O3的变化。

含碳球团—铁浴熔融还原法关键技术的应用基础研究

系统研究了以非焦煤粉和铁精矿粉为基础的含碳球团—铁浴熔融还原新流程的关键技术解决了冷团结合碳球团高温强度问题，提出了含碳球团自还原动力学模型、再氧化机理和提高球团预还原速度、抗氧化能力的技术措施和参数，研制出了具有高配碳量、高强度、高自还原速度、高预还原速度、高抗氧化能力的新型含碳球团．同时，研究了合碳球团在铁浴中熔化还原动力学参数，优化得到了控制还原速度、终还原率、熔渣中最低FeO含量、泡沫渣。

含碳铬矿球团的预还原和熔分研究

以3种典型的铬矿为原料,生产铬的质量分数为20%～40%的铁水为目标,对含碳铬矿球团在1300℃温度下还原30min,然后在1550～1600℃温度下恒温10min,进行渣金分离。考察了球团铬铁比(Cr2O3/FeO)对铁水铬含量和铬收得率的影响,试验结果表明:用南非UG2生产的铁水铬含量最高,而印度铬矿具有最少的渣量。3种铬矿的铬收得率较低,约60%～75%,其原因是由于熔分时间较短,高Al2O3和高MgO渣的熔点较高,表面张力较大,影响渣金分离。

含煤球团直接还原热失重及动力学分析

随着电炉炼钢的快速发展,作为其原料的直接还原铁的需求量日益增大,对直接还原特性和机理的研究变得越来越迫切,过去的研究主要集中在工艺条件和节能减排方面,对反应控速模型的比较相对较少。本文在950~1100℃的N2气氛下,研究了还原温度对含煤球团还原速率的影响,并结合XRD技术对还原产物的物相转换进行了分析。同时基于热重实验,应用不同控速模型方程计算了直接还原过程反应动力学参数,并与实验结果进行了对比。结果表明,温度对还原过程起着至关重要的作用,Fe3O4还原生成Fe O在950℃以下已经开始了,Fe O的还原主要发生在1000℃以上,从950~1100℃还原速率迅速增加。通过模型对比,认为还原过程由三维气相扩散控制。

含碳球团在氧化性气氛中的还原机理

根据Ｓｔｅｆａｎ流理论，研究了含碳球团在氧化性气氛中的还原机理，建立了极限抗氧化还原速度ｖＲＬ的计算式。结果表明：当还原速度大于ｖＲＬ时，还原过程不受氧化性气氛的影响。加热温度一定时，ｖＲＬ随气相中ＣＯ浓度增加和气流速度减小而降低，加热温度对ｖＲＬ的影响不大。

钢铁厂含锌铅粉尘中锌铅分离理论及实践

提出钢铁厂含锌铅粉尘中锌铅分离理论 ,并研制出一种新的火法处理工艺———铝浴法熔融还原。通过与其它还原方法的比较 ,并考察了温度、时间等工艺因素的影响 ,得到了铝浴法合理工艺参数 :温度 110 0℃ ,时间45min ,收集所得氧化锌粉含ZnO90 %以上 (最高达 92 5 2 % ) ,PbO小于 5 % ,锌挥发率和铅富集率达 90 %以上 。

厚渣层铁浴熔融还原炼铁工艺的静态模型

提出了一种两步三段式厚渣层铁浴熔融还原炼铁工艺,铁浴炉利用厚渣层保证反应器内球团矿的氧化区氧化放热与还原区还原的梯度隔离,煤气改质炉提高煤气利用率,转底炉预还原匹配整个系统能耗最低.依据物料平衡与能量平衡的原理,建立了该工艺的静态模型,依据设定的工艺流程中各个环节的生产指标,掌握了各个环节的物料消耗与能量消耗情况,并与现阶段各种炼铁工艺进行了对比,阐明了本工艺的特点与优势,为该工艺的生产实践提供了参考.

高炉瓦斯泥高效利用的实验研究

通过对攀钢高炉粉尘利用的分析研究，提出了采用含碳球团直接还原焙烧法处理高炉瓦斯泥的工艺。在本工艺条件下，得到了高质量还原矿和副产品氧化锌粉。实验研究表明，还原矿中全铁（TFe）达52％～54％、金属铁（MFe）为51％～53％、金属化率（Mη）〉95％；氧化锌粉达到：ω（ZnO）94％～96％、ω（PbO）2％～5％、ω（Fe2O3）微量。初步实现了高炉瓦斯泥的高效利用。

钒钛磁铁矿熔融还原速度研究

用铁浴法对钒钛磁铁矿在高温熔态下还原动力学进行了研究。结果表明:钒钛磁铁矿熔融还原速度有三个高峰期,而普通海南矿则只有一个高峰期,在相同条件下,钒钛磁铁矿熔融还原速度低于海南矿的还原速度;铁浴量增加,还原速度明显增高,提出了钒钛磁铁矿在有铁浴和无铁浴条件下熔融还原反应速度方程。

还原焙烧行为对冶金尘泥含碳球团结构及强度的影响

以高炉瓦斯灰和转炉污泥为原料制备含碳球团,通过还原焙烧实验,考察了焙烧温度、焙烧时间以及球团配碳量对球团微观结构及强度的影响。结果表明,升高还原温度、延长还原时间均使得球团内金属铁相连晶增加、孔隙减少且金属铁相、浮氏体及渣相连结增强,球团抗压强度提高,特别是升高温度对改善球团微观结构并提高球团抗压强度的作用最为显著,而球团配碳量的增加导致还原后的球团内部灰分及残碳增多,将铁相连晶分割成大小不一的片区,破坏了铁相聚集连续性,且球团中孔洞及脆性残碳增多,球团强度降低。因此,在控制较低球团配碳量的条件下,在还原焙烧过程中选择较高的温度及较长的时间,冶金尘泥含碳球团可获得较高的抗压强度。

内配碳对双层球团还原膨胀率的影响

分别以磁铁矿粉和赤铁矿粉为原料制备双层结构的球团,并在球团内层配加焦粉,研究不同矿种及内层不同的配碳量对球团还原膨胀性能的影响。结果表明:在相同造球工艺和焙烧制度条件下,分别以磁铁矿粉和赤铁矿粉为原料制备的内层配碳双层球团的还原膨胀性能存在明显差异;以磁铁矿粉为原料的双层球团随着内层配碳量的增加,球团的还原膨胀率(RSI)先降低后升高,配碳量1.0%(质量分数,下同)时最低,RSI为7.98%;以赤铁矿粉为原料的双层球团随着内层配碳量的增加,还原膨胀率呈降低趋势,配碳量为1.5%时最低,RSI为9.52%。从球团的显微矿相结构看出:以磁铁矿粉为原料的双层球团内层配碳量超过1.0%,球团内出现磁铁矿晶体;以赤铁矿粉为原料的双层球团内层配碳量超过1.5%,球团内出现磁铁矿晶体,球团强度开始下降且还原膨胀率升高。