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炉顶煤气循环氧气高炉采用纯氧鼓风以及炉顶煤气循环利用工艺使得炉内煤气成分与传统高炉相比发生了改变,炉内的煤气成分主要以H2和CO为主。为了研究还原性气体H2和CO对球团矿还原行为的影响,分别用H2-N2、CO-N2、H2-CO混合气体在1173K下通过热重的方法进行试验。研究发现还原度随着混合气体中H2或CO比例的增加而增加,但是H2的还原能力明显比CO要强。在H2-CO混合气体中H2的加入有利于还原进行。用H2-CO混合气体还原得到的还原速率不能用H2-N2和CO-N2混合气体下得到的还原速率相加得到。微观结构观察发现,用H2进行还原时得到的铁结构较致密,而用CO还原时铁会破裂为许多小碎片。在用含一氧化碳的混合气体进行还原时,还原度曲线在还原后期由于碳沉积导致出现下降的趋势。还原气体中氢气的存在会加剧碳沉积现象,而氮气的存在会抑制这一现象。对还原后试样进行X射线衍射以及化学分析表明试样中的碳以碳化铁(Fe3C)和石墨形式存在。
Top gas recirculation oxygen blast furnace with pure oxygen blast furnace and top gas recycling technology makes the furnace gas composition compared with the traditional blast furnace has changed, the main gas composition of the furnace to H2 and CO-based. In order to study the effect of reductive gases H2 and CO on the reduction behavior of pellets, the experiments were carried out by thermogravimetric method at 1173K using mixed gases of H2-N2, CO-N2 and H2-CO respectively. It is found that the reduction degree increases with the increase of the proportion of H2 or CO in the mixed gas, but the reducing ability of H2 is obviously higher than that of CO. The addition of H2 in the H2-CO mixed gas facilitates the reduction. The reduction rate obtained by the reduction with a mixed gas of H2-CO can not be obtained by adding the reduction rates obtained with a mixed gas of H2-N2 and CO-N2. The microstructure observation found that the iron structure obtained by reduction with H2 is denser and the iron breaks down into many smaller fragments when reduced with CO. In the reduction with a carbon monoxide-containing gas mixture, the reduction curve tends to decrease due to carbon deposition in the late stage of reduction. The presence of hydrogen in the reducing gas can aggravate the carbon deposition, and the presence of nitrogen suppresses this phenomenon. The X-ray diffraction and chemical analysis of the reduced sample showed that the carbon in the sample exists in the form of iron carbide (Fe3C) and graphite.