Study On The Co-roasting Of High-sulfur Bauxite And Bayer Process Red Mud To Separate Iron And Aluminum

High sulfur bauxite is a kind of refractory bauxite resource.Bayer process red mud is a kind of harmful high alkalinity solid waste residue in the process of producing alumina by Bayer process.The comprehensive utilization of high sulfur bauxite and Bayer red mud has always been the focus of research at home and abroad.If the problem of high sulfur content in high-sulfur bauxite can be solved and valuable metals such as iron and aluminum in high-sulfur bauxite and red mud can be recovered at the same time,the comprehensive utilization of high-sulfur bauxite and Bayer red mud will be beneficial to the development of aluminum and iron and steel industry in China and promote the effective utilization of mineral resources.In this paper,the recovery of alumina and iron oxide from high-sulfur bauxite and red mud from Bayer process was studied.Pyrite(FeS₂)from high-sulfur bauxite was used as reducing agent and NaOH and Na₂CO₃ as additives for roasting.The effects of different experimental conditions on the recovery of alumina and ferric oxide from bauxite and Bayer red mud were investigated,and the optimal experimental conditions were obtained.The main research results are as follows:(1)Calculate the thermodynamics of the reaction equations of reducing pyrite and additives NaOH and Na₂CO₃ with iron oxide and alumina in the roasting process.Pyrite and pyrite thermal decomposition products(FeS,S)can be reduced with iron oxide to produce Fe₃O₄.When the temperature is lower than 800?,the priority of reducing agents:S>FeS₂>FeS.When the temperature is higher than 800?,the reducing agent priority is FeS₂>S>FeS.The additives sodium carbonate and sodium hydroxide both convert alumina into sodium aluminate.At temperatures below 900?,sodium hydroxide is more likely to form solid sodium aluminate than sodium carbonate.(2)The experiment using sodium carbonate as additive showed that the clinker was dissolved in dilute alkali solution at the roasting temperature of 1100?and roasting time of 60 min,the roasting temperature of 80?,the roasting time of 25 min,the liquid-solid ratio of 10 m L/g,the concentration of NaOH of 18 g/L,and the solubility of Na₂CO₃ of 8 g/L.The dissolution rate of alumina in high sulfur bauxite and red mud is 92.16%.(3)The experiment with sodium carbonate and sodium hydroxide as additives showed that the mass ratio of sodium carbonate and sodium hydroxide as additives was6:4,the roasting temperature was 900?,the roasting time was 60 min,the clinker was dissolved in water solution(deionized water),the dissolution temperature was 50?,and the dissolution time was 20 min.The dissolution rate of alumina in high sulfur bauxite and red mud can reach 94.33%.(4)In the process of alkaline roasting,the increase of roasting temperature is helpful to improve the activity of reactants,promote the fo rmation of soluble sodium aluminate,and increase the dissolution rate of alumina in the clinker.However,too high temperature is easy to liquidize the material,and the densification of the material is not conducive to the dissolution of alumina.After the clinker is dissolved,the slag is mainly composed of Fe₃O₄,Ca₂Si O₄,Ca Ti O₃ and CaCO₃,and the Na₂O·Al₂O₃ in the clinker enters the solution.(5)The experiment of reducing iron oxide in Bayer red mud by using high sulfur bauxite as reducing agent shows that the main factors affecting the grade and recovery of iron concentrate are roasting temperature,roasting time and the molar ratio of iron oxide to pyrite.Under the conditions of roasting temperature 900?,roasting time 60min,molar ratio of ferric oxide to pyrite 12:1,magnetic field intensity 100 k A/m during magnetic separation and ball milling time 3 min,iron grade of 41.35%and iron recovery of 83.97% were obtained.