Separating And Recovering Metals From Iron Tailings By Chlorination Roasting With CaCl₂

Iron tailings which are continuously generated and accumulated in recent years have become one of the main solid wastes in China.The loss of metallic elements in iron tailings not only causes a great waste of resources,but also threatens the safety of ecological environment and human health.The separation and recovery of metallic elements in iron tailings is one of the important methods for harmless and resource utilization of iron tailings.The iron tailings was collected from the mine in Guangdong Province,China.Based on the comprehensive analysis of the basic properties of iron tailings,this paper adopts the chlorination roasting process to separate and recover the heavy metals from iron tailings.Firstly,the effects of different temperatures and calcium chloride addition on the separation and removal of heavy metals from iron tailings by chlorination roasting in the different atmospheres were studied.Secondly,the composition of roasted slags and the leaching concentration of heavy metals were studied.Then the effects of different collection methods on volatiles from flue gas were compared.Finally,the recovery effect and influencing factors of heavy metal and iron in iron tailings by magnetization chlorination experiment in nitrogen atmosphere were investigated preliminarily.The main contents are as follows:?1?The effects of different temperatures and calcium chloride addition on the separation and removal of heavy metals from iron tailings by chlorination roasting in the atmosphere of air and nitrogen were studied.When the iron tailings are roasted in the air atmosphere,the volatilization rates of heavy metals are almost reach the peak when the calcium chloride addition is 10%and the temperature is 1000?.The heavy metal volatilization rates of iron tailings are Pb>Cd>Cu>Cr>Zn as a whole when the iron tailings are roasted in the nitrogen atmosphere.Pb and Cd can be nearly completely volatilized when the temperature is 1000?.The volatilization rates of Cu and Zn are greatly affected by calcium chloride addition,which can achieve a certain degree of volatilization,but there is little effect of temperature and calcium chloride addition on Cr.In the atmosphere of air and nitrogen,the method of chlorination roasting can remove Pb?Cd?Cu in iron tailings effectively.?2?The composition of roasted slags and the leaching concentration of heavy metals were studied.The main components of roasted slags obtained after chlorination roasting in air atmosphere are iron hydroxide oxide,Fe₂O₃ and SiO₂,while the main components of roasted slag obtained after chlorination roasting in nitrogen atmosphere are Fe₃O₄,Fe₂O₃ and SiO₂.With the increase of temperature,S element decreases gradually,and the mass fraction of Ca element in the roasted slags increases gradually with the increase of calcium chloride addition,but there is no presence of Cl element.The leaching concentrations of the metal elements in the roasted slags obtained in the two atmospheres are far lower than the national standard?GB 5085.3-2007?.It can be seen from this that the roasted slags in air atmosphere can be used to make building materials.Under the condition of nitrogen,the roasted slags can be further separated and recovered by magnetic separation.?3?The effects of different collection methods on Cu?Pb?Zn from flue gas under different conditions of chlorination roasting process were compared.The results show that the volatilization effect of Cu and Pb in the atmosphere of nitrogen is slightly better than that in the atmosphere of air,and it is better to use condensation method to recover volatiles,and the collection effect in the atmosphere of nitrogen is far better than that in the atmosphere of air.However,the volatilization effect of Zn in air atmosphere is better than that in nitrogen atmosphere,which is suitable to be collected by wet-washing absorption method,and the recovery effect in air atmosphere is much better than that in nitrogen atmosphere.?4?The effects of different temperatures and calcium chloride addition on the magnetization effect of iron in iron tailings were discussed.Experimental results show that:the magnetization effect is best when the calcination temperature is 1000?and the calcium chloride addition is 5%,and the recovery of iron concentrate of roasted slag is 98.29%in this case.Therefore with an N₂ flow velocity of 50 mL·min^-11 and a reaction time of 60 min,the optimal technological condition for separation and recovery of Pb,Cu,Cd,Cr,Zn and Fe in tailings by magnetization chlorination experiment in nitrogen atmosphere is that calcium chloride addition is 7.5%and the calcination temperature is 1000?.The volatilization rates of Pb,Cu,Cd,Cr and Zn are 91.97%,33.76%,99.34%,56.48%and 18.25%,respectively,and the recovery of iron concentrate is 97.65%.The results indicate that the chlorination roasting of iron tailings in the atmosphere of nitrogen not only benefits the chlorination and volatilization of Pb,Cu,Cd,Cr and other metals in iron tailings,but also realizes the synchronous magnetization of Fe without the addition of reducing agent,which provides an idea for the application of magnetization chlorination technology in the harmless and resource utilization of iron tailings.