Study On Valuable Elements In Volatile Sintered Ash By Chlorination Roasting

Sintering dust comes from the sintering process of steel production and is one of the solid wastes generated by steel enterprises,which has a complex composition and contains valuable elements such as copper,lead and silver.In the hydrometallurgy treatment of sintering dust process,there are problems such as leaching residue cannot be recycled,serious pollution of treatment process,high consumption of leaching agent and tedious removal steps.In this paper,a new process of sintering dust treatment by chlorination roasting is proposed,using the chlorinating agents(CaCl₂,NaCl,KCl)contained in the sintering dust itself for chlorination roasting of the sintering dust.The thermodynamic behavior of Pb,Ag and Cu in sintering dust during roasting,the single-factor experiments of chlorinated volatile Pb,Ag and Cu and the kinetic behavior during roasting were studied,and the main conclusions are as follows:(1)The results of thermodynamic studies show that the priority order of chlorination reactions of elements with chlorinating agents is Pb>Ag>Cu.The temperature range for the reaction of chlorine containing gas and the chlorination of valuable elements is between 670.1 K and 1473 K,and the reaction becomes more violent with increasing temperature.The order of strength of chlorination reactions of chlorinating agents(CaCl₂,NaCl,KCl)with each element is CaCl₂>NaCl>KCl.C,SO₂,SiO₂,Fe₂O₃ and Mg O can all promote the chlorination reactions of chlorinating agents(CaCl₂,NaCl,KCl)with Pb O,Ag,Cu O to some extent.(2)The results of single-factor experiments showed that the roasting temperature of 1423 K,holding time of 60 min,air flow rate of 400 L/h and 4 wt.%of calcium chloride addition were the best process conditions,and the chlorinated volatilization of lead,silver and copper reached 99.48%,98.41%and 86.88%,respectively.Comparing the composition of the raw material with that of the roasted slag at different temperatures,the results showed that elements such as lead,silver and copper were chlorinated and volatilized into the gas phase during roasting,while elements such as iron,silicon and calcium could not be chlorinated and thus were retained in the residue phase,completing the efficient separation of valuable elements.(3)The kinetic results show that the apparent activation energies of chlorination of lead,silver and copper in sintering dust are 100.48 k J/mol,45.78 k J/mol and 145.3k J/mol respectively,which are all controlled by interfacial chemical reactions.In summary,the treatment of sintering dust by chlorination roasting can achieve efficient volatilization of valuable elements,and further separation and purification of soot can obtain metal products.The reduced content of K,Na and Cl in the roasted slag can be recycled as raw materials for iron making,and the main research results can provide a reference for the technology development of resource utilization of sintering dust.