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

在炼铁生产过程中，提高生产率和降低炉料还原温度是降低能耗、减少CO_2排放的迫切问题。含碳铁矿石复合物的还原已被开发为科普这些问题的有前途的方法之一。另一方面，废塑料在热解过程中具有提供H_2、CO和CH_4等还原性气体的潜力。利用此类气体进行铁矿石还原过程是减少CO2排放的有效途径之一，其目的是了解含还原剂颗粒的赤铁矿复合物的还原行为并阐明其最佳结构。聚乙烯和石墨用作还原剂。前者作为有机废弃物的模型材料。以0.6-3.7K/s的升温速率将复合材料加热到1427 K。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，当采用与还原剂均匀混合的赤铁矿复合物时，聚乙烯的贡献是有限的。过量聚乙烯的加入几乎不起还原剂的作用。石墨的加入提高了赤铁矿/聚乙烯复合材料的还原度。这是因为在复合材料内部形成裂纹增强了所产生气体的直接排出，而没有对还原反应的贡献。另一方面，双层复合材料，其在中心层中的聚乙烯含量大于在内部，显示出有效的利用聚乙烯相比，均匀的复合材料。该双层结构的复合材料可适用于转底炉和移动床炼铁工艺。

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.