Experimental Study On Extraction Process Of Valuable Elements In RHF Second Dust

In the process of iron and steel production in China,hundreds of millions of tons of dust are produced every year,most of which contain harmful metals such as Zn and Pb.If they are not handled properly,it will cause serious environmental pollution,and lead to the waste of metal resources in the dust,which will also bring a certain economic burden to the enterprises.At present,a variety of treatment methods for dust have been developed and applied in China.The RHF has achieved remarkable results in the recovery and of dust.The RHF is mostly used to treat zinc bearing dust.However,the iron and steel enterprises failed to make further effective use of the RHF second dust.Therefore,it is very important to adopt the appropriate technology to treat the RHF second dust to produce high value products,and promote the recycling of the resources.In this paper,aiming at the characteristics of the RHF second dust,in order to separate the Zn,K and Na in the dust,the process of the water leaching,adding Zn precipitant to water extract and evaporative crystallization is systematically explored.The RHF second dust were treated by this process,and zinc rich slag,KCl crystal and NaCl crystallizer could be obtained,the extraction of Zn,K and Na in the dust was achieved.The main results are as follows:?1?The analysis of the element and phase composition of the RHF second dust shows that the main elements in the dust are Zn,K,Na,Cl,and a small amount of Ca,Mg,Fe;the Zn in the dust is mostly in the form of ZnCl₂,the small part is in the form of ZnO.?2?The influence of various factors on Zn,K and Na leaching rate during the RHF second dust was studied,the factors affecting the water leaching rate of Zn,K and Na were obtained,and the best technological conditions for the RHF second dust were obtained.?3?Under the conditions of adding Zn precipitant?Na₂S,NaOH or Na₂CO₃?to the water leaching solution,the phase equilibrium of the solution system with different Zn precipitates added into the water leaching solution was theoretically analyzed.The results showed thathose Zn precipitant could transform Zn²⁺into the second slag.When Zn precipitant are used as Zn precipitant respectively,the existence form of Zn in the water leaching solution depends on the pH of the solution system after the leaching is balanced.?4?An experimental study was carried out on the addition of Zn precipitant in aqueous extracts.The results showed that NaOH and Na₂CO₃ were added to the aqueous extract respectively to achieve the precipitation of Zn.The highest precipitation rate of Zn is up to 90.29%,and the highest Zn grade of zinc rich slag is 42.02%.At the same time,more than 90%of the Ca,Mg and Fe are also precipitated into the zinc rich slag.?5?Experimental studies on the extraction of KCl and NaCl from after precipitaton treatment were carried out.The optimum evaporation conditions for the extraction of KCl and NaCl were obtained.?6?Taking the RHF second dust as the object,using the tprocess of water leaching,adding Zn precipitant to water extract and evaporative crystallization to treat it,we can produce first zinc rich slag and second zinc rich slag.At the same time,the KCl crystallizer and NaCl crystallizer can also be obtained.