Process Of Iron Powder Prepared By Reducing The Scale Microwave Heating

Mill scale with very low impurity content is an idea raw material for the production of iron products with high value-added. The output of mill scale reaches to13.5million tons since2008. However, most of them are used as ingredient in the sintering process and coolant and slugging in the steelmaking, and a few are used as reduced iron and ferromagnet which are high value-added. So it is urgent to develop products that are feasible to use mill scale. The requirement of high quality iron powder is increasing with the rapid development of automobile and home appliances. In China, however, the iron powder market is monopolized by several corporations from Sweden, Canada and Japan. Therefore, it is necessary to develop our own high-quality iron powder. Considering the excellent heating mechanism and environment friendly of microwave heating, we have proposed a process that producing reduced iron with iron reduced by fixed carbon heating by microwave.Thermodynamics analysis shows that the direct reducing is the main process, and indirect reducing is the minor process. The reduced temperature must be set above705℃to obtain zero valence iron.In this thesis, we study the effect of reducing iron in the microwave field using different reducing agent and charcoal distribution method were also studied systematically. The coal powder (ash content is9.59%) and charcoal (ash content is0.50%) were used as reducing agent which have a granularity of200mesh.1. Using different charcoal distribution method and the coal powder as reducing agent, the results are:(1), inner:the proportion of coal powder is18%, reducing temperature is1150℃, holding time is20min; The total iron content of reduced iron powder obtained T Fe=94.39%, metallization ratio η Fe=93.98%.(2), outer:inner/middle/outer=coal:mill scale:coal=10:77:13. The reducing temperature is1150℃, holding time is100min; the total iron content of reduced iron powder obtained T Fe=94.28%, metallization ratio ηFe=82.1%.(3), combine:the proportion of inner coal powder is15%, outer coal powder is3%, reducing temperature is1150℃, holding time is50min; the total iron content of reduced iron powder obtained T Fe=95.88%, metallization ratio η Fe=95.19%.Most of the impurities existed on the surface of iron powder can’t be discomposed effectively even though the reduced iron was grinded to200mesh. As to the reduced iron powder reduced by coal powder, the total iron content can only be promoted by0.5%-2.2%and reach to95%-96%after the wet magnetic separating in a200GS magnetic field.Combining the inner and outer densification of charcoal will make the most of the advantages:the fast reaction rate and short reduction time of inner, and reduce the negative effects of reducing agent on total iron of reduced iron for outer. It will also avoid the disadvantages of the two methods:the introduction of impurities in reduced iron by reducing agent for inner, and the long reduction period and high energy consumption for outer.2. Using combination distribution of wood-charcoal and the wood-charcoal as reducing agent, the results are:(1), The experimental process was optimized by response surface methodology(RSM), the proportion of total charcoal is20%, inner charcoal is13.8%,40%of CaCO3was added to outer, the reduction temperature is1118℃, holding time is43min; the results are:total iron of reduced iron T Fe=98.61%, metallization ratio η Fe=98.71%.The chemical component meets the first grade of HY100-23iron.(2) the static state experiment of3Kg level:the proportion of total charcoal is20%, inner charcoal is13.8%,40%of CaCO3was added to outer, the reduction temperature is1118℃, holding time is43min. The chemical component of products reaches the first grade of HY100-23iron.The reduced products produced by the combination distribution method have a nets-like structure with many pores. Its density is2.1g/cm3, and it can be easily smashed to produce iron powder.According to the experimental results from the staticstatical experiment of pre-production, we can estimate that the annual output of reduced iron powder is42tons/year and energy consumption is2778kw.h/t for this microwave oven,...