Investigation on high-temperature reactions of organic compounds and its control for efficient utilization of complex wastes in the ironmaking process

在炼铁过程中，提高生产率、降低铁料还原温度是节能降耗、减少二氧化碳排放的当务之急。含碳材料的铁矿粉还原工艺是解决这一问题的有效途径之一。另一方面，废塑料通过其热解过程具有提供H_2、CO、CH_4等还原气体的潜力。利用这类气体进行铁矿石还原是减少CO_2排放的有效途径之一，其目的是了解含有还原剂颗粒的赤铁矿复合材料的还原行为，并阐明其最佳结构。采用聚乙烯和石墨作为还原剂。前者被用作有机废物的模型材料。在升温速率为0.6~3.7K/S的条件下，将复合材料加热到1427K，通过对生成气体浓度的连续分析和微观结构的观察，确定了聚乙烯对氧化铁还原的贡献，当使用赤铁矿复合材料时，聚乙烯的贡献是有限的。在复合材料中加入过量的聚乙烯几乎不起到还原剂的作用。在含聚乙烯的赤铁矿复合材料中加入石墨，还原程度较高。这是因为复合材料内部裂纹的形成增强了生成气体的直接排放，而不是对还原反应的贡献。另一方面，双层复合材料的中心层聚乙烯含量大于内部聚乙烯含量，与均质复合材料相比，双层复合材料对聚乙烯的利用更为有效。该复合材料具有双层结构，适用于转底炉和移动床的炼铁工艺。

In the ironmaking process, increasing in the production rate and lowering the reduction temperature of iron burdens are urgent issues to save energy consumption and therefore to minimize CO_2 emissions. The reduction of iron ore composite containing carbonaceous materials has been developed as one of the promising processes to cope with such problems. On the other hand, waste plastics have potentials to supply the reducing gases such as H_2, CO and CH_4 through their pyrolysis process. Utilization of such gases for the iron ore reduction process is one of effective ways to reduce the CO_2 emissions.The objectives are to understand the reduction behavior of the hematite composite with reductants particles and to clarify its optimum structure. polyethylene and graphite were used for the reductants. The former was as a model material of organic wastes. The composite was heated up to 1427K with the heating rate of 0.6-3.7K/s. The contribution of polyethylene to the reduction of iron oxide was determined by carrying out the continuous analyses of the generated gas concentrations and the microstructure observation.The contribution of polyethylene was limited when the hematite composite uniformly-mixed with the reductant was used. The addition of excess polyethylene to the composite hardly acted as reductant. The addition of graphite to the hematite composite containing polyethylene led to higher reduction degree. This is because the formation of cracks inside the composite enhanced the direct exhaust of generated gas without the contribution to the reduction reaction. On the other hand, the double-layer composite, whose polyethylene content in the center layer was larger than that in the inner, showed an effective utilization of polyethylene compared to the homogeneous composite. The composite material with the double-layer structure can be applicable to the ironmaking processes using rotary hearth furnace and moving bed.