Research On The Grade Improvement Of High Titanium Slag By Selective Leaching

At present,high titanium slag in China has a high impuritiescontent,such as Si,Fe,Mn,Ca and Mg,can not meet the demand of raw materials used for preparing Ti02 by chlorination process and preparing sponge titanium by Kroll method.As a result,it's necessary to improve the quality of high titanium slag.At present,there is only UGS method of improving the quality of high titanium slag in industry.However,high temperature roasting and alkali leaching and then acid leaching are necessary processes,which have disadvantages of high energy consumption and long process.In this paper,based on the systemic analysis of process mineralogy of high titanium slang,such as phase composition and occurrence state,a novel method of preparing high quality high titanium slag alkali leaching pre-desilication under oxygen-enriched condition and then acid leaching eliminating impurities was put forward.After deep study,the conclusion is as follows:(1)The phases of this high titanium slag is complex.Ti mainly exists in the form of anosovite and alittlein the form of titanium suboxide.Mg and Al are distributed in anosovite in the form of lattice substitution.Fe exists in the form of ilmenite,which is wrapped by anosovite.Si mainly exists in the form of siliceous vitreous,and a little is attached to the surface of anosovite in the form of aluminosilicate compound.S and Cr are associated with each other and gaps and exist in the holes and gaps of minerals.Ca is attached to the surface of the minerals in the form of small particles or floccus.(2)Result of thermodynamics calculation shows that,in the NaOH system under the condition of temperature ranging from 450K to 600K and oxygen enrichment,a high temperature will promote the formation of titanate and help Al and Si transfer to alkali liquor,but is bad for the oxidation of low-value Fe,Mn oxides.In the HCI system at the temperature ranging from 300K to 450K,TiO2,SiO2 and Al2O3 do not react with HCl,and a high temperature is not conducive to the dissociation of impurity oxide.(3)For the experiment of oxygen enrichment alkaline-leaching predesilication and acid-leaching removing impurity,with increase of alkaline-leaching temperature,alkali concentration,oxygen partial pressure,the removal rate of Sisignificantlyincreases.When the the granularity of raw materialsreduces,the removal rate of Si increases.With the increase of leaching temperature and acid concentration,Ti content of acid leaching product and the removal rate of Fe and Mn increases,the maximal removal rates of Si,Mn and Fe are separately 64.4%,70.3%and 95%?(4)By strengthening the condition of alkali leaching pre-desilication under oxygen enriched condition,Si can be removed in-depth and the tense phase of high titanium slang can be effectively dissolved,which provides condition for acid leaching eliminating impurities.Results indicate that:with the increase of temperature,concentration,time,liquid-solid ratio and oxygen partial pressure,the conversion rate of the product and the removal rate of A1 and Si both increase firstly and then tended to be stable after alkali leaching,but they increase with the decrease of the grain size of raw material.Improving the reaction strengthening conditions is is conducive to phases decompose of high titanium slag,the reunion,nucleation and growth of titanate.In the process ofacid-leaching,with the increase of leaching temperature,concentration and time,the conversion rate of the productincrease firstly and then tended to be stable,the maximum conversion rate is 97.9%,the maximum content of TiO2 is 99.2%,the ninimumcontent of Fe,Mg,Si are 0.01%,0.05%,0.066%,respectively.The grade and impurity content of this product are both higher than that of primary titanium dioxide in industry.