Preparation And Dezincification Mechanism Of Zinc-Containing Sulfuric Acid Slag Oxidized Pellets

our country’s iron ore dependence on foreign countries is as high as 80%.As an iron-containing secondary resource,sulfuric acid slag has important utilization value,but it often contains a small amount of non-ferrous metals such as copper,lead,and zinc,and is a typical refractory and refractory secondary iron-containing resource.In this paper,the oxidation pellet technology is used to comprehensively utilize zinc-containing sulfuric acid slag,and the simultaneous and efficient removal of zinc in sulfuric acid slag can be achieved while preparing qualified blast furnace charges.In this paper,the mixed ore containing zinc-containing sulfuric acid slag:iron concentrate=45:55 was used as the raw material to carry out the optimization of the preparation process of sulfuric acid slag oxidation pellets and the study on the dezincification behavior,and the dezincification behavior of the pellets during the preparation of sulfuric acid slag oxidation pellets was clarified.and the mechanism of dezincification;revealed the law of zinc migration and removal during the chlorination roasting process,clarified the influence mechanism of drying and preheating on the dezincification rate of sulfuric acid slag pellets,and proposed the preparation of zinc-containing sulfuric acid slag oxidized pellets.Process improvement direction for simultaneous dezincification.The main conclusions obtained in this paper are as follows:（1）The experimental study on the preparation of zinc-containing sulfuric acid slag oxidized pellets and the optimization of simultaneous dezincification process shows that:without considering dezincification,oxidized pellets with compressive strength>2500N/piece can be prepared;under the premise of considering simultaneous dezincification,Oxidative roasting is carried out with internal fuel,and the roasted pellets have overmelting phenomenon,and the compressive strength is less than1500N/piece,and the dezincification rate is less than 70%;while the internal mixing of Ca Cl₂ 5%,the preheating temperature is 950℃,the preheating time The chlorination oxidation roasting was carried out under the conditions of 15min,roasting temperature of 1220℃and roasting time of 15min.The compressive strength of oxidized pellets containing zinc-containing sulfuric acid slag reached 2887N/piece,and the dezincification rate was as high as 98.20%.Based on the optimal system of tube furnace preheating roasting optimization,dynamic amplification tests were carried out on a simulated straight grate and the grate-kiln.The indicators of the static roasting test of the tube furnace are quite different.（2）The study on the effect of drying and preheating mode of zinc-containing sulfuric acid slag pellets on dezincification behavior shows that the chlorinating agent in the green pellets will migrate from the inside of the pellets to the outer layer with the moisture under dynamic drying conditions,resulting in The content of chlorinating agent in the middle and outer three layers is distributed in an increasing gradient;while under static drying conditions,there is no obvious migration phenomenon of the chlorinating agent in the pellet,and it is evenly distributed inside the pellet.When the chlorinating agent content is 5%,the drying method has a great influence on the compressive strength of the oxidized pellets obtained by the tube furnace roasting,but has little effect on the dezincification rate;when the chlorinating agent content is 3%,the tube furnace Compared with static drying,the dezincification rate of pellets after calcination is significantly lower than that of static drying.The effect of drying method on the dezincification rate increases,while the effect on compressive strength decreases.Under static drying,the compressive strengths of the preheated balls obtained from the static preheating of the tube furnace and the dynamic preheating of the simulated straight grate were 501N/piece and 488N/piece,respectively,and the dezincification rates were 79.41%and 26.99%,respectively.The thermal method has little effect on the compressive strength of the pellets,but has a significant effect on the dezincification rate.However,the compressive strength and dezincification rate of the preheating balls were only 368N/piece and 17.55%respectively by using a simulated straight grate for dynamic drying and preheating.（3）The theoretical study of dezincification by chlorination oxidation roasting of zinc-containing sulfuric acid residues shows that:thermodynamically,zinc oxides,sulfides and ferrites in pellets with Ca Cl₂are easily chlorinated,while iron oxides and silicon,Gangue minerals such as aluminum are difficult to be chlorinated,which is the theoretical basis for realizing the chlorination and volatilization separation of zinc-containing minerals;kinetically,in the temperature range of 850℃～1000℃,zinc-containing minerals（Zn O,Zn S and Zn Fe₂O₄）The chlorination reaction is controlled by the interfacial chemical reaction,and the apparent activation energy of the reaction is 42.07 k J/mol.The main phases in the preheated pellets of zinc-containing sulfuric acid slag are hematite and amphibole.After roasting for 5～25min,the main iron-containing phases in the pellets are hematite,and they show good recrystallization connection.This is the main reason why the pellets can obtain higher strength after chlorination oxidation roasting of zinc-containing sulfuric acid slag pellets.83figures,31 tables,103references...