Study On The Separation Processes Of The Li～+,Mg～(2+)//CI～-—H₂O System By Crystallization Method

Crystallization technology has been Playing an importa11t role inchemistry industry in the 20th century. 1'he' theories and applicationtechnology of crystallization as well as its equipment have beendeveloped into maturity. In the exploitation of salt lake resources,crystallization serves as a leading separation process. Consequently, theworld's major salt lake companies are flourishing in a million tpa scale,utilizing this technology. The combination of the crystallizationtechnolQgy with the characteristics and geographical advantages of thesalt lakes in the Qingzang Plateau will bring the Chinese salt lakesindustr:Y into fantastic developments..This paper deals with the mutual salting-out effect among thecompOIlents of the 'Li+, Mg'+//Cl --H2O system and their separationmechanism. Concrete separation stePs are also designed. The basic idea isas follows: There exists a mutual salting-out effect between the twocompoflents-- lithium chloride and magnesium chloride in the system,which constitutes the driving force fOr separating the two componentsfrom each other. According to this, ana1yses were made for the realizingconditions fOr the salting-out operation. In addition, magnesium exclusionexperiment using the salting-out crystallization method was designed andconducted at normal temperature. The results showed that the magnesiumto lithium weight ratio could be reduced to I:l. For the sake of furthersolving the problems encountered in the salting-out experiments,comprehensive qualltative analysis was made for the salting-out effect.Based on this, discussion was made for tl1e entrainment of crystals andthe solution fOr handling this probleln. Post-processing step canpreliminarily reduce the entrainment to half The filtration al1d washingexperiment solved the problem of the lithiun1 loss caused by entrainmentin the salting-out process. In order to bring the process into practicaIappIication, researches were made for the Precipitation of IitI1ium by hotcrystaIlization and the exclusion of magl1esium by cold crystal1ization.The results showed that the exclusion of magnesium frol11 the systemcould be realized in the solar ponds' crystalIization separation. In view ofthe concentration of diluted brine and tI1e supply of fresh water in theexploitation of salt lake resources, analysis and experiInent were a1somade for the concentration-dilution of salt water by refrigeration method,in combination with the natural conditions of the Chaidam Basin.