| Recently,the strong demand of domestic Ironmaking Company for iron ore was increasing rapidly as the huge capacity of steel.However,the storage and decentralization of resource had bought those ironmaking companies to consume the import iron ores as well as to suffer the high price of ores and low profit of steel.As a response,some firms had attempted to use inferior iron ores with low price and unknown properties,of course,for lack of investigation the negative of those ores have arose in the process of sintering and ironmaking,such as unstable state of blast furnace and high cost of ironmaking.In this case,the investigation of those inferior ores is critical and meaningful to achieve the aim of smooth process and low cost.In this paper,the relationship between behavior of liquid phase and characters of iron ores was studied through sinter tests,the effect of liquid phase on the structure,minerals and properties was investigated,the formation of of liquid phase was calculated by a commercial software FactSage? 7.0,at last,above results were verified by applying those inferior iron ores in industrial production.The behavior of liquid phase was gotten by sintering inferior iron ores under certain conditions and the results were as follows.The main facts that affect the behavior of liquid phase were particle sizes,density of iron ores,chemical components of final feed and thermal process of sintering.The volume and fluidity of liquid phase were varied with the kind of iron ores.The behavior of liquid phase had taken effect on the size and number of pores as well as the bonding strength between coarse particles bonded and permeated by the liquid phase.The structure of sinter was main effected by the liquid phase behavior and ore density,in other words,pores of sinter with less number and large size were formed and large particles were well bonded and permeated by the liquid phase with well fluidity,by the way,the ore with low density was trend to form porous profile.As passages between large particles were rich,more Silicoferrite of Calcium was formed in the bonding fraction with higher temperature and oxygen during sintering.Moreover,the quantity of Silicoferrite of Calcium was affected by the component of liquid phase and sinter atmosphere.The result of sinter feeds proportion tests showed that the permeability of sinter bed was decreased when the feeds mixed more fine iron ores or showed well fluidity during sintering.The complementary advantage had taken effect on the permeability of sinter bed by using the iron ores with varieties of sizes,granulation abilities and high temperature behaviors.The empirical functions were established l to calculate the fluidity of sinter feed at setting conditions,and the result can apply to estimate the trends of fuel consumption,ISO TI,and et al.The result indicated that the reducibility of sinter,especially RDI and RI,is closely related to the usage of inferior iron ores.The sinter with high RDI was usually related to the sinter feed with well or ill fluidity,but the relation was irregular.Most results indicated that well RDI of sinter were gotten to the feed with fluidity index in range of 0.99~1.03 at 1300?.The strength of sinter decreased to the feeds mixed inferior iron ores more than 25%,and this case was more apparent to those feeds mixed coarse iron ores.The sinter factory tests indicated that the permeability of sinter bed was deteriorated to those sinter feeds mixed with 19%~32% inferior iron ore contented,and the increment of fine ore was 9%.In order to abate the unfavorable effect of inferior iron ores on the sinter process,the height of sinter bed was reduced less than 30 mm,the machine speed increased by 0.014m/min,the ignition temperature decreased by 16?,and gas pressure increased reasonably,as a result,the yield and strength of sinter had remained the same level.The unstable state of blast furnace tests was showed at the early stage of increasing inferior iron ores.To mitigate the effect,some operation had been applied,for example,5% little sinter had been replaced by big sinter,the stable flow in both center and edge had been blasting by loosen the stock of BF,at the same time,the temperature of hot air increased to 1181 ?,the oxygen increased by 0.64%,and the area of tuyere reduced,at last,the result showed that the profile of blast furnace was kept,the utilization ratio of gas increased form 45.15% to 47.51%.Comparing with the fuel consumption of using inferior ores at the early stage,the coke and coal rate had decreased by 3.09kg/t and 5.16kg/t respectively.In conclusion,it is a reasonable method to reduce the cost of ironmaking by investigating the liquid behavior of sintering iron ores. |
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