Bayer Process For The Production Of Dezincification In Alumina

The purity of alumina is the main factor that affects the quality of primary aluminum,and also affects the technical and economic indexes of the process.Zinc is a more electropositive element than aluminum,which will lead to the reduction of the quality of aluminum ingot during the electrolysis process.In this paper,the removal of zinc from Bayer process alumina is studied in view of the high zinc content in Yunnan bauxite and the high zinc content in the process.On the basis of reviewing and summarizing the relevant literatures at home and abroad,the dezincification process of sulfide was analyzed in depth.The behavior of S and Zn elements in alkaline solution was explored by E-pH.;thermodynamic calculation analysis of the influence of pH value on the removal of zinc sulfide,determine the process for Bayer liquor dezincification;Three kinds of zinc removal methods of sodium sulfide,two dithiocarbamate and high sulfur bauxite were studied.Experimental results show that the zinc removal with sodium sulfide-flocculation method,Na2S dosage is 0.5 g/L,the reaction time is 120 min,the reaction temperature is 60?,coagulant dosage of 0.1%,the zinc impurity in sodium aluminate solution from 70mg/L to 10mg/L;while adding ZnS seed adding sodium sulfide,can improve the removal of zinc efficiency,reduce the introduction of S2-,the best conditions for the reaction temperature 60 ?,reaction time 90min,Na2S dosage of 0.4g/L,dosage of 40mg/L ZnS seed,the sodium aluminate solution in zinc impurities decreased from 70mg/L to 15mg/L;adding sodium sulfide in the process of settlement,Na2S only with 0.5g/L concentration,can be zinc impurities in the sodium aluminate solution is reduced from 70mg/L to 7mg/L,zinc removal effect is obvious.Using two dithiocarbamate method of zinc removal,adding 0.1%in two methyl two dithiocarbamate sodium 0.8g/L,reaction time 120min,reaction temperature is 80 ?,Flocculant addition 0.1%of the conditions,sodium aluminate solution zinc impurities can be reduced to 15mg/L or less.When the addition of high sulfur bauxite in the leaching process,adding a ratio of 10%?20%,also can achieve a good effect of zinc removal,dissolution of zinc impurities from 30 mg/L to below 15 mg/L,in line with the production requirements.