Extraction Of Lithium Carbonate From Spodumene Ore

The lithium resources is abundant in our country, in which not only has higher value of salt lake resources, but also has a lot of high grade lithium ores.Although extracting lithium from salt lake has bright development prospects, in order to effective use of lithium mineral resources, it still is necessary to extract lithium from spodumene ore.In this paper, spodumene ore comes from Australia, Li2O grade was6.05%. Throughout the current process of extraction of lithium ore, in the lime sintering method the energy consumption is high and the lithium recovery rate is low. The chlorination roasting method was often applied to extract lithium from lithium lepidolite, its process is simple and recovery rate is high, but the furnace gas is corrosive to equipment. In sulfuric acid method, the raw materials hardly included all lithium ore, the operations was simple and the recovery rate was high.In the sodium carbonate autoclave process, its process is simple, the product purity is high, the equipment corrosion and the environmental pollution is slight. According to the characteristics of the mineral resources and the economic benefits, the process were studied in this paper, which lithium carbonate was extracted from spodumene ore by sulfuric acid method and sodium carbonate autoclave process.The details are as follows:(1)The nature spodumene roasting process of crystal conversion. The temperature, the time and the size were investigated. X-ray diffraction (XRD)analysis showed that most of a-spodumene converted to β-spodumene when masted at1050℃for30min. Owing to larger particle size of the ore sample(particle diameter was about0-3mm), which led to inadequate heat transfer, it was not appropriate to directly mast spodumene ore.(2)The β-spodumene sulfation roasting and leaching process.The results of orthogonal experiment showed the preferred condition of acidification was as follows:sulfuric acid consumption was1.4times of the theoretical value, the roasting temperature was250℃, and the masting time was30min. Meanwhile the optimal leaching conditions were as follows:liquid-olid ratio was1.85for15min at room temperature.(3)Leaching solution purification process and lithium carbonate precipitation process. Four reverse mixing washing was used to deal with leach residue, when the liquid to solid was3, the washing efficiency was more than95%. In order to reduce the Mg, Ca content,30%NaOH and300g/L Na2CO3were respectively used to deal the solution, as a result, Mg2+and Ca2+respectively reached0.0002g/L and0.0144g/L. If evaporate18.58%water,84.00%lithium carbonate would be precipitated. The mother liquor was frozen,86.12%Na2SO4·10H2O would be crystallized.(4)The β-spodumene autoclave process. The effects of different operation conditions including liquid-to-solid ratio, Na/Li ratio,agitation speed, reaction temperature and reaction time on the lithium carbonate conversion efficiencies were initially investigated, the optimal leaching conditions were as follows:the Na/Li ratio is1.25, liquid to solid ratio is4agitation speed is300r/min, the reaction temperature is225℃and time is1h, the reaction conversion efficiency can reach more than96%.(5)The β-spodumene carbonation processes. The effects of different operation conditions including temperature, liquid to solid ratio, agitation speed, gas flow rate, the aeration pipe shape and pore diameter were initially investigated. The results showed as follow:Carbonation leaching efficiency increased rapidly with time until45min, then keep steady. Meanwhile it increased with liquid to solid ratio and agitation speed, but decreased with temperature. Moreover, Compared to the straight pipe and spherical pipe, the leaching efficiency is higher by using ring pipe. When the straight tube was used, it is better that the pore size is1.5mm in the experiment.If calculate the lithium content in the filtrate, the carbonation leaching efficiency was up to72%, if plus the lotion, it would be up to88%.(6)The control steps of the carbonation process is CO2gas dissolution and lithium carbonate mass transfer process. Dynamics equation of the carbonation reaction process in the reaction medium-term was as follow: (7)The leaching solution of different lithium concentration were evaporation at90℃, the purity of the obtained lithium carbonate can reaches up to99.6%, Crystallization is mainly heterogeneous nucleation together with homogeneous nucleation.