Study On The Recovery Of Valuable Elements From Blast Furnace And Converter Dust By Microwave Synergistic Treatment

Blast furnace dust is one of the main solid wastes in the iron and steel production process.With the increasingly strict environmental protection,blast furnace dust is also used as an important secondary resource.This paper proposes to use microwave as the heating source to carry out the reduction dezincification test,which not only shortens the heating time,but also greatly reduces the reduction time;subsequently,the potassium and sodium in the reduction residue are further separated and extracted by water leaching,and finally the obtained water leaching residue The iron is extracted by magnetic separation,and high-grade iron concentrate is obtained.The iron in the blast furnace bag ash mainly exists in the form of hematite(Fe2O3),the zinc mainly exists in the form of Zn S,Zn O and Zn Fe2O4,and the iron in the converter ESP ash mainly exists in the form of hematite and elemental iron.Zinc mainly exists in the form of Zn Fe2O4.The melting points of the two were measured.The melting point of blast furnace bag ash was 1082 ℃,and the melting point of converter dust ash exceeded1350 C.As the ratio of blast furnace ash to converter ash changed from 8:2 to 5:5,the melting point of the mixed ash gradually increased.Thermodynamic calculations show that gaseous zinc begins to appear at the cooperative treatment temperature of 850 C,the gaseous zinc reaches a higher content at 950 C,and the distribution of zinc in the slag and gas phase at 1100 C reaches equilibrium.Therefore,the microwave reduction temperature range is determined to be 950 C ～1100 C.When the ratio of blast furnace ash and converter ash is 7:3,the softening temperature of the mixed ash is 1085 C,the melting point is 1276 C,and the flow temperature exceeds 1350 C,It is higher than the required temperature for the reduction and recovery of zinc,which can meet the requirements of the experiment not to generate liquid slag and reduce ring formation.The orthogonal experiment method was used to carry out the high temperature test of the reduction and recovery of zinc metal in a microwave oven.The factors including the reduction temperature,reduction time,moisture and material height,etc.,have been investigated to affect the dezincification rate.Combined with the actual production of the enterprise,the optimized conditions are determined to be the reduction temperature of1100 C,the reduction time of 20 min,the height of the material layer 2 cm,and the moisture content of 6%.At this time,the zinc content in the reduction slag is 0.054%,and the zinc removal rate is 99.346%,which can meet the requirements of the enterprise for zinc content.The collected condensate is mainly Zn,Zn O and a small amount of volatile KCl.In order to reduce the content of potassium and sodium in the slag,a water leaching test was performed on the reduced slag to extract KCl and Na Cl from it.The leaching rate of KCl and Na Cl was explored by changing the solid-liquid ratio,water immersion temperature and stirring time,and the optimal conditions for the leaching rate of KCl and Na Cl were as follows: the solid-liquid ratio is 1:2,the water immersion temperature is 25 C,and the stirring time is 10 min.At this time,the leaching rate of KCl in the waterleaching residue was 84.07%,and the leaching rate of Na Cl was 55.82%.The main phases of the dried product of the water leaching solution are KCl and Na Cl,and the main phases of the water leaching residue are Fe,Ca Fe O3,Si O2 and soda-calcium silicate.In order to improve the grade of iron and further reduce the content of potassium and sodium in the slag,the iron and the non-magnetic part are separated by a hydromagnetic method.-After magnetic separation,92.27% of the magnetic part and 3.76% of the nonmagnetic part can be obtained.The average iron content of the magnetic part can reach62.42%,and the iron content of the non-magnetic part is 5.4%.The average concentrate yield can reach 95.91%,and the iron recovery rate can reach 92.04%.