高炉使用铁焦的[火用]分析

Exergy analysis of blast furnace using iron coke

中国钢铁生产主要以高能耗和高排放的高炉-转炉长流程为主,节能减排压力较大。因此,积极研发高炉低碳炼铁技术,促进高炉工序CO减排尤为重要。铁焦是将含铁原料加入适宜的煤中,经焦化或炭化后成型的新型碳铁复合炉料,其高反应性可以显著降低热储备区温度、降低碳消耗,高炉使用适量的铁焦可实现一定程度的节能降碳。基于现场生产数据,采用[火用]分析理论,建立高炉使用铁焦的[火用]平衡模型,探索铁焦添加量对高炉物料消耗及能量利用效率的影响。结果表明,高炉使用铁焦后,炉内间接还原得到发展,碳利用率提高,炉内灰分量降低,冶炼单位生铁的碳素消耗和炉渣量均会降低,与未使用铁焦相比,高炉使用114 kg铁焦后,吨铁碳素消耗降低25.95 kg,渣量降低11.28 kg。此外,铁焦内部的金属铁仅需熔化,节省还原所需的[火用]量,焦炭和鼓风带入[火用]会显著降低,因此高炉冶炼吨铁消耗的总[火用]量降低,同时,炉内传热也得到改善,内部[火用]损失有效降低,与未使用铁焦相比,高炉使用114 kg/t铁焦后,目的[火用]效率由46.14%提高至48.87%,热力学完善度由87.46%提高到88.02%。在此条件下,高炉吨铁的内部[火用]损失降低192.63 MJ,实现节能6.57 kg(标煤)。

China′s iron and steel production is mainly based on the long process of BF-BOF with high energy consumption and high emission,which has great pressure on energy conservation and emission reduction.Therefore,it is particularly important to actively develop blast furnace low-carbon ironmaking technology and promote COemission reduction in blast furnace process.Iron coke is a new type of carbon-iron composite burden after coking or carbonization by adding iron-containing raw materials into suitable coal.Its high reactivity can significantly reduce the temperature in the heat reserve area and then reduce carbon consumption.Using proper iron coke in blast furnace can realize energy saving and carbon reduction to a certain extent.Based on the field production data,the model of iron coke used in blast furnace was established by the theory of exergy analysis,and the influence of iron coke addition on material consumption and energy utilization efficiency of blast furnace was explored.The results show that after using of iron coke in blast furnace,indirect reduction in blast furnace is developed,carbon utilization rate is improved,ash content in blast furnace is reduced,and carbon consumption per unit pig iron and slag amount are reduced.Compared with no iron coke,carbon consumption per ton iron and slag amount are reduced by 25.95 kg and 11.28 kg respectively after using 114 kg/t iron coke in blast furnace.In addition,the metallic iron in iron coke only needs to be melted,which saves the exergy amount required for reduction,and the exergy amount brought by coke and blast will be significantly reduced,so the total exergy amount consumed per ton of iron in blast furnace smelting will be reduced,at the same time,the heat transfer in the furnace will be improved,and the internal exergy loss will be effectively reduced.Compared with no iron coke,after using 114 kg iron coke in blast furnace,the target exergy efficiency increases from 46.14%to 48.87%,and the thermodynamic perfection increases from 87.46%to 88.02%.Under these conditions,the internal exergy loss per ton of iron in blast furnace is reduced by 192.63 MJ,and energy saving is achieved by 6.57 kg.