Research On The Decomposition Of Scheelite By Hydrochloric Acid In The Presence Of Phosphorus And Fluorine

China is one of the most important country of tungsten resources and production,ore reserves and yield have been in the first place in the world.For a long time,china depends on wolframite,it cause the depletion of wolframite.The complicate and lower grade scheelite certainly will be main tungsten resources,so it is particularly important to develop and utilize scheelite.Hydrochloric acid decompose scheelite is one of traditional industrial production methods.With the price rising of sodium hydroxide and the cost up of caustic leaching process,many tungsten smelting enterprises beginning re-picking up the technology of hydrochloric acid decomposition.However,in the process of hydrochloric acid decomposition,one part of tungsten transformed to tungstenic acid,one part of tungsten react with phosphorus and formate heteropoly acid into leaching solution at the same time.On the other side,the technology of hydrochloric acid decomposition of hydrochloric-phosphate acid and sulfuric-phosphate acid mixed system,it try to make tungsten into leaching solution by heteropoly acid as far as possible.This thesis research on the decomposition of scheelite by hydrochloric acid in the presence of phosphorus and fluorine,investigate the distribution law of the tungsten existed in leaching solution?tungstenic acid and tungsten slag,find the way that beneficial to generate tungstenic acid or phosphowolframic acid.This job is not only meaningful to traditional hydrochloric acid decomposition,but also valuable to the mixed acid leaching process aim at formate phosphowolframic acid.The mian conclusions are drawn as follows:(1)Hydrochloric acid concentration is the key factor that influent the distribution of tungsten on liquid phase and solid phase after the decomposition of scheelite.When hydrochloric acid initial concentration more than 9 mol/L,tungsten is mainly produced in the form of tungstenic acid;When hydrochloric acid initial concentration less than 8 mol/L,tungsten is mainly produced in the form of heteropoly acid.(2)At high-acid system,yield of tungstenic acid can be improved by scheelite roasting pretreatment,improve react temperature,increase react time,improve HCl addition and decrease tungsten ore size.At calcination temperature 950 ??HCl concentration 10 mol/L?reaction temperature 90 ??reaction time 90 min?rotation speed 700 r/min?HCl addition 750% and tungsten size-250/+325 mu,yield of tungstenic acid can reach 79.19%,but there are still 14.50% of tungsten exist in leaching solution.(3)At low-acid system,leaching rate of tungsten can reach 91.86% at HCl concentration 2 mol/L?reaction temperature 90 ??reaction time 120 min?HCl addition 450% and tungsten size-200/+250 mu.Therefore,for phosphorus-containing scheelite concentrate,if leached in the form of heteropoly acids,the amount of hydrochloric acid and the concentration of hydrochloric acid can be performed under low conditions,which will help improve the on-site environment.(4)In the treatment of artificial scheelite,yield of tungstenic acid can reach 99.16% at HCl concentration 3 mol/L?reaction temperature 90 ??HCl addition 300% and reaction time 90 min.With the addition of fluoroapatite and hydroxyapatite in artificial scheelite,tungsten forms phosphotungstic heteropoly acid into leaching solution,the leaching rate of tungsten keeps rising,the yield of tungstenic acid keeps decreasing.Moreover,fluoroapatite is more conducive to the entry of tungsten into the leaching solution than hydroxyapatite.For 10 g artificial scheelite,when the amount of fluoroapatite was 0.796 g,the leaching rate of tungsten reached 98.16%.Therefore,when dealing with scheelite with high phosphorus content,it is more reasonable to enhance its yield in the form of heteropoly acid.