Process Research On Extracting Valuable Elements From Secondary Dust Of RHF

With the rapid development of China's steel industry,iron and steel enterprises currently produce hundreds of millions of tons of dust every year.In addition to high iron content,some of the dust contains Zn and alkali metal elements,the treatment of dust is very important for the protection of the environment and the secondary use of resources.At present,the method of fire treatment of dust is widely used,especially the treatment of zinc-containing dust by the rotary hearth method has been widely recognized.For the low-zinc secondary dust generated by the rotary hearth furnace,if it is not properly treated,it will not only pollute the environment,but also cause waste of metal resources.At present,there are few researches on the treatment process of secondary dust in the rotary hearth furnace.Therefore,the development and research of the process of extracting valuable elements from the secondary dust of the rotary hearth furnace is of great necessity and significance for the protection of the environment and the secondary utilization of resources.In this paper,the secondary dust generated by the rotary hearth furnace is taken as the research object,using a combination of theoretical calculations and experiments,for the purpose of separating and extracting zinc and potassium from the secondary dust of the rotary hearth furnace,and combined with the characteristics of the secondary dust of the rotary hearth furnace,there are three process has been systematically studied to provide a basis for the treatment of alkali metal and low zinc dust.First,the process of preparing basic zinc chloride by the secondary dust immersion-precipitation?precipitant NaOH?of the rotary hearth furnace.The second,the process of preparing a KCl crystal by a secondary dust of a rotary hearth furnace by adding sodium carbonate circulating leaching?circulating leachate?-evaporation crystallization.The third,the process of preparing zinc oxide by the secondary dust immersion-precipitation?precipitant Na₂CO₃?of the rotary hearth furnace.The specific research results are as follows:?1?The composition of the secondary dust of the rotary hearth furnace was analyzed by ICP,XRD and other analytical methods.The basic composition of the dust element was obtained.The main elements in the secondary dust of the rotary hearth furnace are Zn,K,Na,Cl,and a small amount of impurity elements such as Ca,Mg,Fe,etc.,and the average particle size of the dust is 5.96?m.Alkali metal is suitable for separation and extraction by means of water leaching and evaporation crystallization.Zn is suitable for separation and extraction by precipitation.?2?The process of preparing basic zinc chloride by secondary dust leaching-precipitation?precipitant NaOH?in rotary smelting furnace was studied by using water immersion-precipitation experiment and solution phase equilibrium analysis method.The influence of process conditions on the extraction of valuable elements in dust was obtained.The parameters of the water immersion process are:liquid-solid ratio 4:1,leaching time 60min;the parameters of the preparation of basic zinc chloride by water immersion liquid precipitation:NaOH addition amount is 0.42mol/L.After 100g of dust was treated,13.88g of basic zinc chloride powder having a Zn grade of 48.97%was obtained,and the total recovery of Zn in this process was 94.05%.?3?The process of adding sodium carbonate cyclic leaching experiment and solution phase equilibrium analysis method was carried out,and the process of adding sodium carbonate circulating leaching-evaporation crystallization to prepare KCl crystals was studied in the secondary dust of rotary hearth furnace,and the influence of process conditions on the extraction of valuable elements in dust was obtained.The parameters of the cyclic leaching process are:the number of cycles of leaching is one time,the amount of sodium carbonate added is 14.84g/100g dust;the parameters of KCl by evaporation crystallization are:evaporation and cooling crystallization temperature are80°C and 15°C,respectively,evaporation volume ratio is 40%.After the secondary dust of 200g rotary hearth furnace is processed by this process,16.69g of KCl mass fraction of 90.78%can be obtained,which is in line with the national agricultural potassium chloride standard crystal product,and the total recovery of Zn is 87.83%.?4?The process of preparing zinc oxide from the secondary dust-water leaching-precipitation?precipitant Na₂CO₃?of the rotary hearth furnace was studied by means of water-immersion-precipitation-calcination experiment and theoretical calculation method.The influence of process conditions on the extraction of valuable elements in dust was obtained.The parameters of water immersion are:liquid-solid ratio is 4:1,leaching time is 60min;the parameters of preparation of basic zinc carbonate by water immersion liquid precipitation are:the addition amount of sodium carbonate is 0.35mol/L and the washing can be improved by using ethanol.The parameters of the calcined basic zinc carbonate link are:calcination temperature 400°C,calcination time 2 h.After the secondary dust of100g rotary hearth furnace is treated by this process,zinc-rich slag with 30.05g of Zn content of 25.2%and ZnO with 11.75g of Zn content of 59.06%can be obtained,and the total recovery of Zn is 95.46%.?5?In this paper,for the secondary dust of the rotary hearth furnace containing both alkali metals K,Na,Cl and Zn,three different treatment processes have been developed through the combination of theory and experiment.The purity of the product obtained by the process of preparing basic zinc chloride is greatly affected by the Zn content in the dust and the impurity element,but the process is simple and the energy consumption is low,therefore,it is suitable for treating dust with less impurity elements,relatively lower alkali metal content,and Zn is mainly present in a water-soluble form.The process for preparing KCl crystals is complicated,and the energy consumption is high,but the alkali metal and Zn in the dust can be simultaneously extracted,and the overall utilization of the elements is high,and the operation is simple,so it is suitable for treating the difference between the alkali metal content and the Zn content.The process for preparing zinc oxide is complicated and has high energy consumption,but its product has high value and is suitable for treating dust with low alkali metal and impurity elements and Zn mainly in water-soluble form.