Basic Research On Molding And Reduction Reinforce-Ment Of Iron-bearing Dust From Steel Plant Based On Mechanical Activation

A large amount of gas fume was produced during iron and steel smelting process.By dust removal and gas purification of gas fume from different processes,various kinds of dust were obtained.With the increasing attention from the state and steel enterprises on environmental protection and the need of waste zero emission,it is more and more urgent to efficiently recycle the dust from steel works.Pyrormetallurgical treatment process is a well kind of method in recycling the dusts.As most dust particles gone through high temperature transmission,mutual package between particles and particles is exsited in dust.The surface activity and carbon activity of the particles is not high,which influenced its green pellet or briquette strength and high temperature reduction properties.In addition,it is not clear that the difference between the balling or pressure molding properties of different dust and their high temperature reduction behavior.In this paper,high carbon content of blast furnace dust,high alkali content of sintering dust,and high zinc content of electric arc furnace dust were studied.Firstly,on the basis of clarifying the physical,chemical and microscopic characteristics of dust,the influence law of mechanical activation on the physical and chemical activation effect of dust were studied.Secondly,the influence of activation on the dust rolling/pressure forming performance was investigated.Therefore,the suitable forming mode and its corresponding process parameters of different dusts were clarified.Thirdly,the differences and similarities of high temperature reduction and the kinetics behavior during high temperature roasting between different dusts include the activation ones were studied.The results are summarized as follows.(1)Blast furnace dust owns characterization of quick water absorption and well wettability,and its nucleation and ball forming performance are good after slightly activation.Sintering dust owns characterization of slow water absorption and strong hydrophobic,and its nucleation and ball forming performance are bad even after slightly activation.Only mechanical activation pretreatment and briquetting molding process is suitable for sintering dust.The particle size of electric arc furnace dust are all below 5 micron meters,and its CaO content is high.In consequence,it is suitable for briquetting molding process.(2)The physical activation effect such as particle size of dust mainly occurs within 30-60 min of mechanical activation.In the process of activation,reunion phenomenon is more likely to occur in sintering dust than blast furnace dust.Wet milling is helpful to delay or weaken the reunion behavior.The chemical activation effect such as grain size and dislocation density mainly occurred in the later stage of ball milling.In terms of 30 minutes' ball milling,stirring wet milling is best.(3)The reduction and dezincification ability of carbon particles in blast furnace dust is much lower than that of anthracite,which can be significantly improved by planetary dry milling activation.Due to the high activity after mechanical activation,alkali metal particles in sintering dust spontaneously migrated to the outer layer of the briquette,giving rise to over high regional concentration of alkali metal.As a result,it inhibits alkali metal volatilization and iron oxide reduction.The reduction behavior of iron oxide in sintering dust briquette during the roasting process can be significantly improved by stirring wet grinding as more than 90%of alkali metals were removed during the milling process.(4)The improvement impact of mechanical activation on dust pressure molding performance and reduction performance mainly occurred within 30-60 min of mechanical activation,which is consistent with the variation law of its average particle size,but has little relation to its chemical activation effect.(5)The difficulty of wustite reduction in electric arc furnace dust,sintering dust and blast furnace dust successively increases.The peak temperature and apparent activation energy of blast furnace dust canbon-containing briquette decreased 157K and 44%after planetary dry milling 30 minutes,respectively.The peak temperature and apparent activation energy of sintering dust canbon-containing briquette decreased 93K and 55%after stirring wet milling 30 minutes,respectively.