Study On The Process Of Extracting Lithium From Spodumene And Preparing Lithium Hydroxide Monohydrat

The existing lithium extraction process of spodumene adopts the main process flow of transformation roasting,sulfation roasting,leaching and evaporation crystallization to prepare lithium hydroxide.In order to study and explore new technology and reveal the microscopic reaction mechanism of lithium extraction process of spodumene,this paper focuses on the crystal transformation of spodumene roasting process,the substitution of traditional sulfation roasting byβ-spodumene pressure leaching,and the preparation of lithium hydroxide monohydrate by thermal lithium-nitrate co-production.The main research work and results are as follows:In this paper,around the crystal transformation mechanism of spodumene roasting process,the theoretical calculation of crystal transformation was carried out by XRD,Crystal Maker Demo and Materials studio software,and the transformation rules of crystal structure and bond length and bond energy during crystal transformation were obtained.The basic law of transformation roasting of spodumene single minerals was studied.It was found that spodumene single minerals can be completely transformed after crushing to a particle size range of 48-75μm and roasting at 1000°C for 60min.The cell volume ofβ-spodumene after crystal transformation is 133.25%larger than that ofα-spodumene of natural spodumene.The activity range of Li⁺inβ-spodumene cell is larger,the electrostatic attraction of Li⁺-O^2-is smaller,and the structure of Li⁺-O^2-is unstable,which leads to Li⁺inβ-spodumene easy to break away from the bondage of O^2-.In this paper,the experimental study on pressure acid leaching of lithium fromβ-spodumene was carried out,and compared with the sulfation roasting-leaching process ofβ-spodumene.Through the single factor optimization experiment of the new technology ofβ-spodumene pressure acid leaching lithium and the analysis and characterization of the leaching residue,the results show that the acid dosage is 120%of the theoretical acid consumption,the reaction temperature is 160°C,the reaction time is 180min,the particle size D₉₀ is between 48-58μm,and the leaching rate of lithium is more than 93%.Theβ-spodumene sulfuric acid roasting-water leaching process was carried out.The results showed that the leaching rate of lithium reached more than 97%under the conditions of sulfuric acid roasting with 140%of the theoretical acid dosage,roasting temperature260°C and roasting time 35min.Comparing the direct pressure acid leaching and sulfation roasting-water leaching process,it is found that the lithium leaching rate ofβ-spodumene pressure acid leaching is about 4%lower than that of sulfation roasting process,but the pressure acid leaching method of spodumene can reduce the consumption of sulfuric acid,reduce the reaction temperature and improve the working environment.A new technical route for the preparation of lithium hydroxide monohydrate by thermal lithium-nitrate co-production was proposed.Based on the basic law of solubility changing with temperature,the metastable zone of Li OH-Na₂SO₄-H₂O ternary system was controlled by temperature,so that lithium hydroxide monohydrate was precipitated at 40°C,sodium sulfate was precipitated at 100°C,and lithium-nitrate separation was realized.The corresponding experimental research was carried out.The results show that Li OH and Na₂SO₄ can be crystallized separately by this method,and the purity of both can reach more than 80%.