Study On Direct Sulfuric Acid Technology Of Medium And Low Grade Phosphorite In Jinning Area

With the increasing utilization of phosphate mining,the depleted phenomenon gradual emergence on the world’s phosphate resources,and the traditional wet-process phosphoric acid is difficult to directly use more phosphate content of impurities,there fore,how to use low grade phosphate rock in a effectively way is very important and s ignificance.In this paper,the low grade phosphate rock of Jinning phosphate rock has been used.We use phosphoric acid-sulfuric acid one-step process to preparation phosphoric acid directly.The leaching rate of phosphorus-iron-aluminum-magnesiu m,the MER value of the dilute phosphoric acid and the filter strength is the main indicator(MER value represents the sesquioxide in the acid which mainly in iron oxide,aluminum oxide,magnesium oxide with the weight ratio to phosphorus pentoxide).First of all,the dehydrate method of acid hydrolysis conditions were optimized,then the surfactant and the phosphating film formers were added in the process,finally the phosphoric acid were clarified,concentrated and a ging tests.The di rectly applicable production process to the preparation of phosphate wet-process pho sphoric acid is been developed.With the single factor and orthogonal experiments,we obtained the optimum condition for acidolysis the phosphate rock under laboratory conditions:reaction temperature is80℃;reaction time is4h;reaction liquid to solid ratio is2:1-2.5:1;SO3concentration is40g/L;stirring speed is350rad/s;back acid concentration is18%±2.Under this condition,the rate of the phosphate rock decomposition can reach94%, but the acid MER value is maintained at0.19or more higher.In order to reduce the leaching rate of iron-aluminum-magnesium in the phosp hate rock and get fewer impurities in dilute phosphoric acid,the surfactant is added in the phosphate rock acidolysis reaction process.After examine the factors of phosphorus-iron-aluminum-magnesium leaching rate and the slurry filtration strength etc,we selected the lignin sulfonic acid, sodium dodecyl sulfate and sodium citrate,the three surfactants were experiment to get the optimize amount.And we obtain the optimal adding surfactant amount when the phosphor rus-iron-aluminu m-magnesium leaching rate and the MER value of the dilute phosphoric acid were reached minimum value respectively,it’s provides the foundation of the data for subsequent active inhibitor complex.The addition of surfactant on the phosphorus-iron-aluminum-magnesium leachi ng rate and the MER value of the dilute phosphoric acid is not expected to achieve the desired effect, so considering the phosphating film technology in the application of metal film.We add phosphating film formers in phosphate rock acidolysis reaction tentatively to study the possibility of forming a micro-cell reaction to wrap the sesquioxide in phosphate rock,so we can reducing the MER value of the dilute phosp horic acid. The study found out that adding the phosphate film formers can effectively reduce the phosphorus-iron-aluminum-magnesium leaching rate, and the strength of the slurry filtration essentially has no effect.We selected nitric acid,zinc dihydrogen phosphate and hydroxylamine sulfate to experiment the optimize amount.Hydroxyla mine sulfate which is the best kind of phosphate film former,it not only make magnes ium leaching rate decreased17.01%,but also decreased the MER value in dilute phos phoric acid to0.1407,the closest target.It’s the most close to target of the experiment s.Then,we study the complex of surfactants and phosphate film former,and found out that nitric acid with hydroxylamine sulfate, nitric acid with citric acid, hydroxyla mine sulfate with citric acid is the best three group of complex type active agent.They has the best effect to reduce the iron-aluminum-magnesium leaching rat e,and can decreas the MER value in dilute phosphoric acid to0.14or less,it’s proved that we achieve the targets.Three groups of complex reactive agent has a different strength to enhance the slurry filtration strength,it can be a very good use in laboratory and industrial production.Finally,the production of dilute phosphoric acid were clarified,concentrated and a ging tests.The value of concentrated phosphoric after aging process can be reduced to about0.11,according to the production experience of DAP by Three Circles Compan y,Yuntianhua International Chemical Co.,Ltd,aging of concentrated phosphor ic acid production DAP basically reached the requirements. This process can be better used in low grade phosphate rock,and provides a new way for direct use of low grade phos phate rock.