| Blast furnace flue dust is a by-product captured by the gas dust removal system in the process of ironmaking,which has large output and heavy pollution.When it is directly stacked,it not only occupies the site,but also causes the valuable carbon,iron and zinc resources can not be effectively recovered.On the other hand,if it is directly returned to the iron and steel plant as the burden,the zinc which is brought in with the blast furnace gas ash will be recycled and enriched,which will cause serious damage to the blast furnace.Therefore,the premise of recycling zinc bearing blast furnace gas ash is to remove the zinc that restricts its return to the steel production process,which is called zinc iron separation.Based on the good selectivity of ammonia leaching process,this paper uses the coking waste ammonia water of iron and steel plant to realize "using waste to treat waste",and carries out the experimental research on ammonia leaching process of blast furnace gas ash.At the same time,in view of the fact that the blast furnace gas ash treatment process generally needs the pretreatment of batching and mixed pelletizing,which is easy to produce secondary pollution and high cost,this paper also makes a preliminary study on the high temperature flash reduction dezincification directly using blast furnace gas ash particles.In this paper,the basic characteristics of raw materials and the feasibility of ammonia leaching of blast furnace flue dust were analyzed from the basic properties of mineral composition,particle size distribution,micro morphology,element distribution characteristics,E-pH diagram of Zn-Fe-H2O system and species distribution diagram of Zn-NH3-H2O system;The effects of total ammonia concentration,leaching temperature,leaching time,ammonium salt type,ratio of ammonia water to ammonium salt,solid-liquid ratio,stirring speed and reverse leaching on zinc leaching rate from blast furnace flue dust were investigated by single factor variable method.In addition,high temperature flash reduction experiments of blast furnace flue dust were carried out to investigate the effects of reaction temperature and atmosphere on zinc volatilization rate and micro morphology of blast furnace flue dust.The main conclusions are as follows:(1)Zinc oxide is the main existing form of zinc in blast furnace flue dust.The smaller the particle size is,the higher the contents of zinc and TFE are,while C is mainly concentrated in large particles;After the raw material is grinded,the distribution of zinc element is more sparse and uniform.(2)After the screening and optimization of ammonia leaching process conditions,when ammonium chloride is.selected as leaching agent,the total ammonia concentration is 5mol·L-1,and the temperature is 50℃.When the leaching time is 120 min,[NH4]+/[NH3]T was 1:2,the solid-liquid ratio was 1:4,and the stirring speed was 250 r·min-1,the leaching rate of zinc reached the highest 77.2%;After the dynamic analysis,in the range of 30～60℃the apparent activation energy of ammonia leaching of blast furnace flue dust is 1.22 kJ·mol-1,and the limiting reaction is internal diffusion.(3)In the process of flash reduction dezincification of blast furnace flue dust,when the reaction atmosphere is pure nitrogen,the volatilization rate of zinc increases with the increase of temperature in the range of 1450～1650K.When the temperature is 1650K,the volatilization rate of zinc reaches 66.7%.When the reducing gas is introduced,the zinc volatilization rate gradually increases with the increase of the reaction temperature and the partial pressure of the reducing gas.When the reaction temperature is 1650K and the gas composition is 60%H2+40%N2,the volatilization rate of zinc reaches the highest,95.7%,which is 16.5%higher than the zinc leaching rate of the ammonia leaching process.At this time,the zinc in the blast furnace flue dust the content is 0.017%. |
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