| Blast furnace dust is a solid waste generated from the process of dust removal in blast furnace ironmaking. The output of blast furnace dust is about4%as much as that of iron. Its particle size is very small. The low zinc dust can directly be used in sintering, but others can not be used directly because of high zinc content. This creates a huge amount of solid waste pollution to the environment, but for now there is no widely used technology about recycling of blast furnace dust.In this thesis, the survey of blast furnace dust was carried in the north department of iron making of Tangshan Iron and Steel Group. About3kg of each dust (blast furnace gas dust and blast furnace gas mud respectively) was obtained respectively from the2#,3#blast furnace (2000m3,3200m3). The result of basic features research on the blast furnace dust showed that:the average particle size of dust is20μm which belongs to micron-size, and the fluctuation range of zinc or iron content is broad (Fe:25to50percent, Zn:0.1to7percent, C:15to25percent). The form of iron and zinc are mainly Fe2O3, Fe3O4and ZnFe2O4.The result of thermodynamics research of the reduction showed that the Fe and Zn oxide can be reduced at a low temperature. By researching the kinetics of Fe oxide particle reduction, it was found that the reduction rate of iron oxide in micron particles is much faster than that in centimeter-level balls. This effect is called "Fine reducing effect". The result of the kinetics of blast furnace dust reduction showed that the reaction is controlled by the interface reaction and the apparent activation energy is69.8kJ/mol.In this thesis, according to the "fine reduction effect", the blast furnace dust was reduced in laboratory. At a temperature of900℃-1000℃,2-4h, using pure H2as reductant to reduce10g blast furnace dust in reduction apparatus, the results (32times) show the mean metallization rate was91.02%, and the mean dezincification rate was96.14%. Sintering would not occur after reduction, Zn is enriched in volatile products.According to the result of reaction engineering research, the0.6kg/h level small-scale tests furnace is designed and manufactured. Its engineering feature is "gas-solid countercurrent continuous reactor".54times cold experiments and37times hot experiments were carried in the north department of iron making of Tangshan Iron and Steel Group, near to the TRT workshop of the1#BF. At900℃ -1000℃,10-50min, using reformed blast furnace gas reformed by shenmu carbon (reform temperature1050-1100℃) as reductant to reduce blast furnace dust, the result shows that:The best metallization rate can reach88%and the best dezincification rate can reach95%in iron-rich residual products, the ZnO content can reach83%in zinc-rich volatile products.The result of laboratory flotation shows that:the grade of carbon concentration is30.4-73.9%; the recovery is19.62-56.24%, but the simple flotation failed to achieve good Zn and Fe enrichment effect. The content of Fe is32.1-44.8%after magnetism separation. The Fe recovery ratio is6.79-90.90%, it is inversely proportional with the iron grade. When using mixture of CaO and iron-rich residual products in steelmaking, the mean Fe recovery ratio is68.3%, but no desulfurization effect. When using mixture of CaO and blast furnace gas dust in ironmaking, the mean Fe recovery ratio is93.6%, but no dephosphorization effect.In the thesis, the "fine reduction effect" was employed to recycle blast furnace dust. The iron-rich residual products and Zinc-rich products are all very valuable. The whole process does not produce secondary solid waste. The research has made an innovative exploration on recycling process for blast furnace dust. |
PDF Full Text Request