煤种对含煤球团还原速度的影响

研究了在１２２３～１４７３Ｋ的氮气氛中３种不同挥发分煤粉的粒度、铁精矿粉粒度、温度及碳—氧摩尔比对含煤球团还原速度的影响。发现降低煤粉或铁精矿粉粒度，提高温度或碳—氧摩尔比可提高含煤球团的还原速度，且这４种因素对还原速度的影响程度随煤种挥发分的降低而增大。分别采用以碳气化反应、气相内扩散、界面反应为控制环节而得出的表达含煤球团反应过程的速度方程处理本研究数据，发现３种速度方程（４种表达形式）均能较好地与本研究数据吻合。比较由不同速度方程计算出的速度常数而得出的含煤球团的活化能，发现对含３种不同挥发分煤的球团，以气相内扩散为控制环节的活化能均较以碳气化反应或界面反应为控制环节的活化能大，由此可推断含煤球团还原过程应由气相内扩散控制。含高挥发分煤的球团的气相内扩散活化能较含低挥发分煤的球团的活化能低，可推断前者的还原速度较快。

含煤球团的冶金特性

采用热天平装置及单个球团加热的方法,测定了含碳球团的还原速度。研究了加热温度、球团配碳量、炉气组成、添加剂、原料种类等对含碳球团的还原速度和金属化率的影响及球团的冶金特性。实验结果表明:含碳球团的软化和熔化温度较高,含碳15％以上的球团在1000～1350℃加热时,在含CO_2较高的高温炉气中也能够实现快速自还原,达到较高的金属化率。该球团的金属化率随加热温度提高而增加。研制出一种含煤25％的冷固结铁矿球团,其单个干球抗压强度已达1000N以上,有良好的冶金性能,可用于竖炉型炼铁设备作冶炼铁水的原料,还原剂焦碳也可用非焦煤代替。

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。

Effect of B2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.